Comparative Analysis of the Microstructural Features of 28 wt.% Cr Cast Iron Fabricated by Pulsed Plasma Deposition and Conventional Casting

NASA Astrophysics Data System (ADS)

Chabak, Yu. G.; Efremenko, V. G.; Shimizu, K.; Lekatou, A.; Pastukhova, T. V.; Azarkhov, A. Yu.; Zurnadzhy, V. I.

2018-02-01

The effect of pulsed plasma deposition (by an electrothermal axial plasma accelerator) followed by post-heat treatment on the structure and microhardness of a 28 wt.% Cr white cast iron is analyzed and discussed with respect to the microstructure of the conventionally cast monolithic counterpart. The cast iron (as deposited on a 14 wt.% Cr cast iron substrate) had a microhardness of 630-750 HV0.05; it had layered light contrast/dark contrast structure where dark contrast layers contain fine carbide network. Pulsed plasma deposition followed by heat treatment resulted in a substantial refinement of the microstructure: eutectic M7C3 coarse acicular plates in the conventional cast iron were replaced by fine M7C3, M3C2, M3C particles (Cr depleted in favor of Fe), while the initial carbide particle of 2-3 μm was reduced to 0.6 μm. Secondary dendrite arm spacing decreased from 15 to 1.3 μm, accordingly. The carbide volume fraction in the post-heat-treated coating remarkably increased with respect to the conventional counterpart resulting in a substantial increase in the coating hardness (1300-1750 HV0.05). The heat-treated coating displayed higher resistance to three-body abrasion than the as-deposited coating and similar resistance with that of the conventionally cast iron.

Experimental constraints on the sound velocities of cementite Fe3C to core pressures

NASA Astrophysics Data System (ADS)

Chen, Bin; Lai, Xiaojing; Li, Jie; Liu, Jiachao; Zhao, Jiyong; Bi, Wenli; Ercan Alp, E.; Hu, Michael Y.; Xiao, Yuming

2018-07-01

Sound velocities of cementite Fe3C have been measured up to 1.5 Mbar and at 300 K in a diamond anvil cell using the nuclear resonant inelastic X-ray scattering (NRIXS) technique. From the partial phonon density of states (pDOS) and equation of state (EOS) of Fe3C, we derived its elastic parameters including shear modulus, compressional (VP) and shear-wave (VS) velocities to core pressures. A pressure-induced spin-pairing transition in the powdered Fe3C sample was found to occur gradually between 10 and 50 GPa by the X-ray Emission Spectroscopy (XES) measurements. Following the completion of the spin-pairing transition, the VP and VS of low-spin Fe3C increased with pressure at a markedly lower rate than its high-spin counterpart. Our results suggest that the incorporation of carbon in solid iron to form iron carbide phases, Fe3C and Fe7C3, could effectively lower the VS but respectively raise the Poisson's ratio by 0.05 and 0.07 to approach the seismically observed values for the Earth's inner core. The comparison with the preliminary reference Earth model (PREM) implies that an inner core composition containing iron and its carbon-rich alloys can satisfactorily explain the observed seismic properties of the inner core.

Fe3C nanoparticle decorated Fe/N doped graphene for efficient oxygen reduction reaction electrocatalysis

NASA Astrophysics Data System (ADS)

Niu, Yanli; Huang, Xiaoqin; Hu, Weihua

2016-11-01

Oxygen reduction reaction (ORR) electrocatalysts with high activity, low cost and good durability are crucial to promote the large-scale practical application of fuel cells. Particularly, iron carbide (Fe3C) supported on nitrogen-doped carbon has recently demonstrated compelling promise for ORR electrocatalysis. In this paper, we report the facile synthesis of mesoporous Fe/N-doped graphene with encapsulated Fe3C nanoparticles (Fe3C@Fe/N-graphene) and its superior ORR catalytic activity. This hybrid material was synthesized by the spontaneous oxidative polymerization of dopamine on graphene oxide (GO) sheets in the presence of iron ion, followed by thermal annealing in Argon (Ar) atmosphere. As-prepared material shows high ORR catalytic activity with overwhelming four-electron reduction pathway, long-term durability and high methanol tolerance in alkaline media. This work reports a facile method to synthesize promising ORR electrocatalysis with multiple components and hierarchical architecture, and may offer valuable insight into the underlying mechanism of Fe3C-boosted ORR activity of Fe/N doped carbon.

Fischer–Tropsch Synthesis: Characterization Rb Promoted Iron Catalyst

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sarkar,A.; Jacobs, G.; Ji, Y.

Rubidium promoted iron Fischer-Tropsch synthesis (FTS) catalysts were prepared with two Rb/Fe atomic ratios (1.44/100 and 5/100) using rubidium nitrate and rubidium carbonate as rubidium precursors. Results of catalytic activity and deactivation studies in a CSTR revealed that rubidium promoted catalysts result in a steady conversion with a lower deactivation rate than that of the corresponding unpromoted catalyst although the initial activity of the promoted catalyst was almost half that of the unpromoted catalyst. Rubidium promotion results in lower methane production, and higher CO2, alkene and 1-alkene fraction in FTS products. M{umlt o}ssbauer spectroscopic measurements of CO activated and workingmore » catalyst samples indicated that the composition of the iron carbide phase formed after carbidization was -Fe5 C2 for both promoted and unpromoted catalysts. However, in the case of the rubidium promoted catalyst, '-Fe2.2C became the predominant carbidic phase as FTS continued and the overall catalyst composition remained carbidic in nature. In contrast, the carbide content of the unpromoted catalyst was found to decline very quickly as a function of synthesis time. Results of XANES and EXAFS measurements suggested that rubidium was present in the oxidized state and that the compound most prevalent in the active catalyst samples closely resembled that of rubidium carbonate.« less

First-principles investigations of iron-based alloys and their properties

NASA Astrophysics Data System (ADS)

Limmer, Krista Renee

Fundamental understanding of the complex interactions governing structure-property relationships in iron-based alloys is necessary to advance ferrous metallurgy. Two key components of alloy design are carbide formation and stabilization and controlling the active deformation mechanism. Following a first-principles methodology, understanding on the electronic level of these components has been gained for predictive modeling of alloys. Transition metal carbides have long played an important role in alloy design, though the complexity of their interactions with the ferrous matrix is not well understood. Bulk, surface, and interface properties of vanadium carbide, VCx, were calculated to provide insight for the carbide formation and stability. Carbon vacancy defects are shown to stabilize the bulk carbide due to increased V-V bonding in addition to localized increased V-C bond strength. The VCx (100) surface energy is minimized when carbon vacancies are at least two layers from the surface. Further, the Fe/VC interface is stabilized through maintaining stoichiometry at the Fe/VC interface. Intrinsic and unstable stacking fault energy, gammaisf and gamma usf respectively, were explicitly calculated in nonmagnetic fcc Fe-X systems for X = Al, Si, P, S, and the 3d and 4d transition elements. A parabolic relationship is observed in gamma isf across the transition metals with minimums observed for Mn and Tc in the 3d and 4d periods, respectively. Mn is the only alloying addition that was shown to decrease gamma isf in fcc Fe at the given concentration. The effect of alloying on gammausf also has a parabolic relationship, with all additions decreasing gammaisf yielding maximums for Fe and Rh.

DOE Office of Scientific and Technical Information (OSTI.GOV)

James K. Neathery; Gary Jacobs; Amitava Sarkar

In the previous reporting period, modifications were completed for integrating a continuous wax filtration system for a 4 liter slurry bubble column reactor. During the current reporting period, a shakedown of the system was completed. Several problems were encountered with the progressive cavity pump used to circulate the wax/catalyst slurry though the cross-flow filter element and reactor. During the activation of the catalyst with elevated temperature (> 270 C) the elastomer pump stator released sulfur thereby totally deactivating the iron-based catalyst. Difficulties in maintaining an acceptable leak rate from the pump seal and stator housing were also encountered. Consequently, themore » system leak rate exceeded the expected production rate of wax; therefore, no online filtration could be accomplished. Work continued regarding the characterization of ultra-fine catalyst structures. The effect of carbidation on the morphology of iron hydroxide oxide particles was the focus of the study during this reporting period. Oxidation of Fe (II) sulfate results in predominantly {gamma}-FeOOH particles which have a rod-shaped (nano-needles) crystalline structure. Carbidation of the prepared {gamma}-FeOOH with CO at atmospheric pressure produced iron carbides with spherical layered structure. HRTEM and EDS analysis revealed that carbidation of {gamma}-FeOOH particles changes the initial nano-needles morphology and generates ultrafine carbide particles with irregular spherical shape.« less

Effects of W on microstructure of as-cast 28 wt.%Cr–2.6 wt.%C–(0–10)wt.%W irons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Imurai, S.; Thanachayanont, C.; Pearce, J.T.H.

2015-01-15

Microstructures of as-cast 28 wt.%Cr–2.6 wt.%C irons containing (0–10)wt.%W with the Cr/C ratio about 10 were studied and related to their hardness. The experimental irons were cast into dry sand molds. Microstructural investigation was performed by light microscopy, X-ray diffractometry, scanning electron microscopy, transmission electron microscopy and energy-dispersive X-ray spectrometry. It was found that the irons with 1 to 10 wt.%W addition was hypereutectic containing large primary M{sub 7}C{sub 3}, whereas the reference iron without W addition was hypoeutectic. The matrix in all irons was austenite, partly transformed to martensite during cooling. The volume fractions of primary M{sub 7}C{sub 3}more » and the total carbides increased, but that of eutectic carbides decreased with increasing the W content of the irons. W addition promoted the formation of W-rich M{sub 7}C{sub 3}, M{sub 6}C and M{sub 23}C{sub 6}. At about 4 wt.%W, two eutectic carbides including M{sub 7}C{sub 3} and M{sub 6}C were observed together with primary M{sub 7}C{sub 3}. At 10 wt.%W, multiple carbides including primary M{sub 7}C{sub 3}, fish-bone M{sub 23}C{sub 6}, and M{sub 6}C were observed. M{sub x}C where x = 3 or less has not been found due possibly to the high M/C ratio in the studied irons. W distribution to all carbides has been determined increasing from ca. 0.3 to 0.8 in mass fraction as the W content in the irons was increased. W addition led to an increase in Vickers macro-hardness of the irons up to 671 kgf/(mm){sup 2} (HV30/15) obtained from the iron with 10 wt.%W. The formation of primary M{sub 7}C{sub 3} and aggregates of M{sub 6}C and M{sub 23}C{sub 6} were the main reasons for hardness increase, indicating potentially improved wear performance of the as-cast irons with W addition. - Highlights: • W addition at 1 up to 10 wt.%W to Fe–28Cr–2.6C produced “hypereutectic” structure. • W addition promoted the formation of W-rich M{sub 7}C{sub 3}, M{sub 6}C and M{sub 23}C{sub 6}. • M{sub 23}C{sub 6} has higher Fe/Cr and W/Cr atm% ratios than those in M{sub 7}C{sub 3}. • Si content and high W content over about 11 atm% are characteristics of M{sub 6}C. • Primary M{sub 7}C{sub 3} and aggregates of M{sub 6}C and M{sub 23}C{sub 6} increased the alloy macro-hardness.« less

Cascades in model steels: The effect of cementite (Fe3C) and Cr23C6 particles on short-term crystal damage

NASA Astrophysics Data System (ADS)

Henriksson, K. O. E.

2015-06-01

Ferritic stainless steel can be modeled as an iron matrix containing precipitates of cementite (Fe3C) and Cr23C6. When used in nuclear power production the steels in the vicinity of the core start to accumulate damage due to neutrons. The role of the afore-mentioned carbides in this process is not well understood. In order to clarify the situation bulk cascades created by primary recoils in model steels have been carried out in the present work. Investigated configurations consisted of bulk ferrite containing spherical particles (diameter of 4 nm) of either (1) Fe3C or (2) Cr23C6. Primary recoils were initiated at different distances from the inclusions, with recoil energies varying between 100 eV and 1 keV. Results for the number of point defects such as vacancies and antisites are presented. These findings indicate that defects are also remaining when cascades are started outside the carbide inclusions. The work uses a recently developed Abell-Brenner-Tersoff potential for the Fe-Cr-C system.

Degradation of trichloroethene with a noval ball milled Fe-C nanocomposite

DOE PAGES

Gao, Jie; Wang, Wei; Rondinone, Adam Justin; ...

2015-07-18

Nanoscale zero-valent iron (NZVI) is effective in reductively degrading dense non-aqueous phase liquids (DNAPLs), such as trichloroethene (TCE), in groundwater (i.e., dechlorination) although the NZVI technology itself still suffers from high material costs and inability to target hydrophobic contaminants in source zones. To address these problems, we developed a novel, inexpensive iron-carbon (Fe-C) nanocomposite material by simultaneously milling micron-size iron and activated carbon powder. Microscopic and X-ray diffraction (XRD) characterization of the composite material revealed that nanoparticles of Fe were dispersed in activated carbon and a new iron carbide phase was formed. Bench-scale studies showed that this material instantaneously sorbedmore » >90% of TCE from aqueous solutions and subsequently decomposed TCE into non-chlorinated products. Compared to milled Fe, Fe-C nanocomposite dechlorinated TCE at a slightly slower rate and favored the production of ethene over other TCE degradation products such as C 3-C 6 compounds. When placed in hexane-water mixture, the Fe-C nanocomposite materials are preferentially partitioned into the organic phase, indicating the ability of the composite materials to target DNAPL during remediation.« less

A Directionally Solidified Iron-chromium-aluminum-tantalum Carbide Eutectic Alloy

NASA Technical Reports Server (NTRS)

Harf, F. H.

1977-01-01

A eutectic alloy, Fe-13.6CR-3.7Al+9TaC, was directionally solidified in a high gradient furnace, producing a microstructure of alined TaC fibers in an oxidation resistant alpha-iron matrix. Tensile and stress rupture properties, thermal cycling resistance, and microstructures were evaluated. The alloy displays at 1000 C an ultimate tensile strength of 58 MPa and a 100-hour rupture life at a stress of 21 MPa. Thermal cycling to 1100 C induces faceting in the TaC fibers.

Magnetism and high magnetic-field-induced stability of alloy carbides in Fe-based materials.

PubMed

Hou, T P; Wu, K M; Liu, W M; Peet, M J; Hulme-Smith, C N; Guo, L; Zhuang, L

2018-02-14

Understanding the nature of the magnetic-field-induced precipitation behaviors represents a major step forward towards unravelling the real nature of interesting phenomena in Fe-based alloys and especially towards solving the key materials problem for the development of fusion energy. Experimental results indicate that the applied high magnetic field effectively promotes the precipitation of M 23 C 6 carbides. We build an integrated method, which breaks through the limitations of zero temperature and zero external field, to concentrate on the dependence of the stability induced by the magnetic effect, excluding the thermal effect. We investigate the intimate relationship between the external field and the origins of various magnetics structural characteristics, which are derived from the interactions among the various Wyckoff sites of iron atoms, antiparallel spin of chromium and Fe-C bond distances. The high-magnetic-field-induced exchange coupling increases with the strength of the external field, which then causes an increase in the parallel magnetic moment. The stability of the alloy carbide M 23 C 6 is more dependent on external field effects than thermal effects, whereas that of M 2 C, M 3 C and M 7 C 3 is mainly determined by thermal effects.

Microstructural Evolution of Hypoeutectic, Near-Eutectic, and Hypereutectic High-Carbon Cr-Based Hard-Facing Alloys

NASA Astrophysics Data System (ADS)

Lin, Chi-Ming; Chang, Chia-Ming; Chen, Jie-Hao; Hsieh, Chih-Chun; Wu, Weite

2009-05-01

A series of high-carbon Cr-based hard-facing alloys were successfully fabricated on a substrate of 0.45 pct C carbon steel by gas tungsten arc welding (GTAW) process using various alloy fillers with chromium and chromium carbide, CrC (Cr:C = 4:1) powders. These claddings were designed to observe hypoeutectic, near-eutectic, and hypereutectic structures with various (Cr,Fe)23C6 and (Cr,Fe)7C3 carbides at room temperature. According to X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and optical microscopy (OM), in 3.8 pct C cladding, the microstructure consisted of the primary carbides with outer shells (Cr,Fe)23C6 surrounding (Cr,Fe)7C3 cores and [ α + (Cr,Fe)23C6] eutectic structures. In 5.9 pct C cladding, the composite comprised primary (Cr,Fe)7C3 as the reinforcing phase and [α + (Cr,Fe)7C3] eutectic structures as matrix. Various morphologies of carbides were found in primary and eutectic (Cr,Fe)7C3 carbides, which included bladelike and rodlike (with a hexagonal cross section). The 5.9C cladding with great amounts of primary (Cr,Fe)7C3 carbides had the highest hardness (approximately HRC 63.9) of the all conditions.

Hollow spheres of iron carbide nanoparticles encased in graphitic layers as oxygen reduction catalysts.

PubMed

Hu, Yang; Jensen, Jens Oluf; Zhang, Wei; Cleemann, Lars N; Xing, Wei; Bjerrum, Niels J; Li, Qingfeng

2014-04-01

Nonprecious metal catalysts for the oxygen reduction reaction are the ultimate materials and the foremost subject for low-temperature fuel cells. A novel type of catalysts prepared by high-pressure pyrolysis is reported. The catalyst is featured by hollow spherical morphologies consisting of uniform iron carbide (Fe3 C) nanoparticles encased by graphitic layers, with little surface nitrogen or metallic functionalities. In acidic media the outer graphitic layers stabilize the carbide nanoparticles without depriving them of their catalytic activity towards the oxygen reduction reaction (ORR). As a result the catalyst is highly active and stable in both acid and alkaline electrolytes. The synthetic approach, the carbide-based catalyst, the structure of the catalysts, and the proposed mechanism open new avenues for the development of ORR catalysts. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structural and magnetic properties of nanocomposite iron-containing SiCxNy films

NASA Astrophysics Data System (ADS)

Pushkarev, R. V.; Fainer, N. I.; Maurya, K. K.

2017-02-01

New ferromagnetic films with composition SiCxNyFez were synthesized using chemical vapor deposition technique. Films were deposited using ferrocene, 1,1,1,3,3,3-hexamethyldisilazane (HMDS) and hydrogen gaseous mixture. Chemical and phase composition of the films were studied by FTIR, Raman spectroscopy and X-ray diffraction with grazing incidence (GI-XRD). FTIR spectra analysis confirmed the existence of Si-C and Si-N bonds. Graphite inclusions and amorphous carbon were determined by Raman spectra analysis. The surface of the SiCxNyFez films studied by SEM is covered by nanocrystallites of iron oxide Fe3O4 phase. The main purpose of GI-XRD analysis is to describe the layered structure of the films in detail. It was shown by GI-XRD study, that phase composition of the SiCxNyFez films varies from iron oxide Fe3O4 to iron silicide Fe3Si and silicon carbide SiC with the deposition temperature growing. It was established, that SiCxNyFez films are perspective for application in the spintronic field.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chakraborty, Gopa, E-mail: gopa_mjs@igcar.gov.in; Das, C.R.; Albert, S.K.

Martensitic stainless steels find extensive applications due to their optimum combination of strength, hardness and wear-resistance in tempered condition. However, this class of steels is susceptible to embrittlement during tempering if it is carried out in a specific temperature range resulting in significant reduction in toughness. Embrittlement of as-normalised AISI 410 martensitic stainless steel, subjected to tempering treatment in the temperature range of 673–923 K was studied using Charpy impact tests followed by metallurgical investigations using field emission scanning electron and transmission electron microscopes. Carbides precipitated during tempering were extracted by electrochemical dissolution of the matrix and identified by X-raymore » diffraction. Studies indicated that temper embrittlement is highest when the steel is tempered at 823 K. Mostly iron rich carbides are present in the steel subjected to tempering at low temperatures of around 723 K, whereas chromium rich carbides (M{sub 23}C{sub 6}) dominate precipitation at high temperature tempering. The range 773–823 K is the transition temperature range for the precipitates, with both Fe{sub 2}C and M{sub 23}C{sub 6} types of carbides coexisting in the material. The nucleation of Fe{sub 2}C within the martensite lath, during low temperature tempering, has a definite role in the embrittlement of this steel. Embrittlement is not observed at high temperature tempering because of precipitation of M{sub 23}C{sub 6} carbides, instead of Fe{sub 2}C, preferentially along the lath and prior austenite boundaries. Segregation of S and P, which is widely reported as one of the causes for temper embrittlement, could not be detected in the material even through Auger electron spectroscopy studies. - Highlights: • Tempering behaviour of AISI 410 steel is studied within 673–923 K temperature range. • Temperature regime of maximum embrittlement is identified as 773–848 K. • Results show that type of carbide precipitation varies with temperature of tempering. • Mostly iron rich Fe{sub 2}C carbides are present in the embrittlement temperature range. • With the precipitation of M{sub 23}C{sub 6} carbides, recovery from the embrittlement begins.« less

Solid-state reaction of iron on β-SiC

NASA Astrophysics Data System (ADS)

Kaplan, R.; Klein, P. H.; Addamiano, A.

1985-07-01

The solid-state reaction between Fe and β-SiC has been studied using Auger-electron and electron-energy-loss spectroscopies and ion sputter profiling. Fe films from submonolayer coverage to 1000 Å thickness were grown in ultrahigh vacuum, and annealed at temperatures up to 550 °C. Auger line-shape changes occurred even for initial Fe coverage at 190 °C, indicating substantial bond alteration in the SiC substrate. A 1000-Å film was largely consumed by reaction with Si and C diffused from the substrate during a 500 °C anneal, and exhibited both Fe silicide and carbide throughout most of its original volume and free C present as graphite primarily at the surface. As an aid in identifying the reaction products studied in this work, Auger line shapes were first determined for the SiLVV peak in Fe silicide and for the CKLL transition in Fe carbide.

SEM and TEM Analyses of Minerals Xifengite, Gupeiite, Fe2Si (Hapkeite?), Titanium Carbide (TiC) and Cubic Moissanite (SiC) from the Subsoil in the Alpine Foreland: Are they Cosmochemical?

NASA Astrophysics Data System (ADS)

Hiltl, M.; Bauer, F.; Ernstson, K.; Mayer, W.; Neumair, A.; Rappenglück, M. A.

2011-03-01

SEM and TEM analyses of millimeter- to centimeter-sized particles from Holocene soils reveal a multi-stoichiometric iron silicide matrix containing purest crystals of titanium carbide and cubic moissanite. A cosmochemical origin is suggested.

Iron Oxide Nanosheets and Pulse-Electrodeposited Ni-Co-S Nanoflake Arrays for High-Performance Charge Storage.

PubMed

Khani, Hadi; Wipf, David O

2017-03-01

Nanostructured nickel cobalt sulfide (Ni 4.5 Co 4.5 S 8 ) has been prepared through a single-step pulse-electrodeposition method. Iron oxide nanosheets at hollow graphite shells (Fe 3 O 4 @g-shells) were prepared from graphite-coated iron carbide/α-Fe (g-Fe 3 C/Fe) in a two-step annealing/electrochemical cycling process. Electrochemical characterization of the Ni 4.5 Co 4.5 S 8 and g-Fe 3 C/Fe materials showed that both have high specific capacities (206 mAh g -1 and 147 mAh g -1 at 1 A g -1 ) and excellent rate capabilities (∼95% and ∼83% retention at 20 A g -1 , respectively). To demonstrate the advantageous pairing of these high rate materials, a full-cell battery with supercapacitor-like power behavior was assembled with Ni 4.5 Co 4.5 S 8 and g-Fe 3 C/Fe as the positive and negative electrodes, respectively. The (Ni 4.5 Co 4.5 S 8 //g-Fe 3 C/Fe) device could be reversibly operated in a 0.0-1.6 V potential window, delivering an impressive specific energy of 89 Wh kg -1 at 1.1 kW kg -1 and a remarkable rate performance of 61 Wh kg -1 at a very high specific power of 38.5 kW kg -1 . Additionally, long-term cycling demonstrated that the asymmetric full cell assembly retained 91% of its initial specific capacity after 2500 cycles at 40 A g -1 . The performance features of this device are among the best for iron oxide/hydroxide and bimetallic sulfide based energy storage devices to date, thereby giving insight into design principles for the next generation high-energy-density devices.

Effect of hydrogen on the melting of the Fe-C system and the fate of the subducted carbon

NASA Astrophysics Data System (ADS)

Lai, X.; Chen, B.; Gao, J.; Zhu, F.

2017-12-01

The subducted oceanic crust carries significant amount of carbonates and organic carbons from the surface into the deep mantle. Through slab-mantle interactions, subducted carbons can react with metallic iron in the metal-saturated regions of the mantle and form various reduced species such as Fe carbides. The Fe-C system is found to have higher eutectic melting temperature than mantle geotherm and thus carbon by forming iron carbides may be "redox freezed" in the mantle (Rohrbach and Schmidt 2011). Hydrogen was found to be have significant effect on the melting of the Fe-light-elements systems such as the Fe-S system (Shibazaki et al., 2011). Here we report experimental results from both multi-anvil press and diamond anvil cell experiments on the melting behaviors of the Fe-C-H system. C14H12, a solid-state C-H organic compound was used as a C-H source to react with the metallic iron at high pressure and high temperature conditions. With excess C14H12, hydrogen in the FeHx alloy was totally replaced by carbon at 14.8-24.7 GPa. Conversely, with excess Fe, the existence of hydrogen is found to depress the melting temperature of the Fe-C system by at least 100 K. Hydrogen may facilitate the transport and cycling of subducted carbon in the deep mantle and contribute to formation of superdeep diamonds (Smith et al. 2016). Rohrbach, Arno, and Max W. Schmidt. "Redox freezing and melting in the Earth's deep mantle resulting from carbon-iron redox coupling." Nature 472.7342 (2011): 209. Shibazaki, Yuki, et al. "Effect of hydrogen on the melting temperature of FeS at high pressure: Implications for the core of Ganymede." Earth and Planetary Science Letters 301.1 (2011): 153-158. Smith, Evan M., et al. "Large gem diamonds from metallic liquid in Earth's deep mantle." Science 354.6318 (2016): 1403-1405.

Iron carbide encapsulated by porous carbon nitride as bifunctional electrocatalysts for oxygen reduction and evolution reactions

NASA Astrophysics Data System (ADS)

Wei, Liangqin; Sun, Hongdi; Yang, Tiantian; Deng, Shenzhen; Wu, Mingbo; Li, Zhongtao

2018-05-01

Herein, the study reports a facile and scale-up able strategy to synthesize metal organic frameworks (MOFs) Fe-7,7,8,8-Tetracyanoquinodimethane (Fe-TCNQ) as precursors to develop non-precious metal bifunctional electrocatalysts through a one-step hydrothermal route. Then, Fe3C/carbon nitride (Fe3C@CNx) core-shell structure composites are readily available through pyrolyzing Fe-TCNQ at reasonable temperature, during which hierarchical porous structures with multimodal porosity formed. Nitrogen doped porosity carbon layers can facilitate mass access to active sites and accelerate reaction. Consequently, the optimized catalyst exhibits superior oxygen reduction reaction (ORR) electrocatalytic activity and better catalytic activity for oxygen evolution reaction (OER) in alkaline medium than that of Pt/C, which can be attributed to the synergistic effect of strong coupling between Fe3C and nitrogen doped carbon shells, active sites Fe-NX, optimal level of nitrogen doping, and appropriate multimodal porosity.

DOE Office of Scientific and Technical Information (OSTI.GOV)

El-Gendy, AA; Bertino, M; Clifford, D

Attainment of magnetic order in nanoparticles at room temperature is an issue of critical importance for many different technologies. For ordinary ferromagnetic materials, a reduction in size leads to decreased magnetic anisotropy and results in superparamagnetic relaxations. If, instead, anisotropy could be enhanced at reduced particle sizes, then it would be possible to attain stable magnetic order at room temperature. Herein, we provide experimental evidence substantiating the synthesis of a cobalt iron carbide phase (CoFe2C) of nanoparticles. Structural characterization of the CoFe2C carbide phase was performed by transmission electron microscopy, electron diffraction and energy electron spectroscopy. X-ray diffraction was alsomore » performed as a complimentary analysis. Magnetic characterization of the carbide phase revealed a blocking temperature, TB, of 790K for particles with a domain size as small as 5 +/- 1 nm. The particles have magnetocrystalline anisotropy of 4.662 +/- 10 6 J/m(3), which is ten times larger than that of Co nanoparticles. Such colossal anisotropy leads to thermally stable long range magnetic order. Moreover, the thermal stability constant is much larger than that of the commonly used FePt nanoparticles. With thermal stability and colossal anisotropy, the CoFe2C nanoparticles have huge potential for enhanced magnetic data storage devices. (C) 2015 AIP Publishing LLC.« less

Growth characteristics of primary M7C3 carbide in hypereutectic Fe-Cr-C alloy.

PubMed

Liu, Sha; Zhou, Yefei; Xing, Xiaolei; Wang, Jibo; Ren, Xuejun; Yang, Qingxiang

2016-09-06

The microstructure of the hypereutectic Fe-Cr-C alloy is observed by optical microscopy (OM). The initial growth morphology, the crystallographic structure, the semi-molten morphology and the stacking faults of the primary M7C3 carbide are observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The in-suit growth process of the primary M7C3 carbide was observed by confocal laser microscope (CLM). It is found that the primary M7C3 carbide in hypereutectic Fe-Cr-C alloy is irregular polygonal shape with several hollows in the center and gaps on the edge. Some primary M7C3 carbides are formed by layers of shell or/and consist of multiple parts. In the initial growth period, the primary M7C3 carbide forms protrusion parallel to {} crystal planes. The extending and revolving protrusion forms the carbide shell. The electron backscattered diffraction (EBSD) maps show that the primary M7C3 carbide consists of multiple parts. The semi-molten M7C3 carbide contains unmelted shell and several small-scale carbides inside, which further proves that the primary M7C3 carbide is not an overall block. It is believed that the coalescence of the primary M7C3 carbides is ascribed to the growing condition of the protrusion and the gap filling process.

Growth characteristics of primary M7C3 carbide in hypereutectic Fe-Cr-C alloy

PubMed Central

Liu, Sha; Zhou, Yefei; Xing, Xiaolei; Wang, Jibo; Ren, Xuejun; Yang, Qingxiang

2016-01-01

The microstructure of the hypereutectic Fe-Cr-C alloy is observed by optical microscopy (OM). The initial growth morphology, the crystallographic structure, the semi-molten morphology and the stacking faults of the primary M7C3 carbide are observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The in-suit growth process of the primary M7C3 carbide was observed by confocal laser microscope (CLM). It is found that the primary M7C3 carbide in hypereutectic Fe-Cr-C alloy is irregular polygonal shape with several hollows in the center and gaps on the edge. Some primary M7C3 carbides are formed by layers of shell or/and consist of multiple parts. In the initial growth period, the primary M7C3 carbide forms protrusion parallel to {} crystal planes. The extending and revolving protrusion forms the carbide shell. The electron backscattered diffraction (EBSD) maps show that the primary M7C3 carbide consists of multiple parts. The semi-molten M7C3 carbide contains unmelted shell and several small-scale carbides inside, which further proves that the primary M7C3 carbide is not an overall block. It is believed that the coalescence of the primary M7C3 carbides is ascribed to the growing condition of the protrusion and the gap filling process. PMID:27596718

Precipitation of Carbides in Early Aging Stages and Their Crystallographic Orientations in Hadfield Steel Mn13

NASA Astrophysics Data System (ADS)

Ding, Zhimin; Liang, Bo; Zhao, Ruirong; Chen, Chunhuan

2015-05-01

The methods of transmission electron microscopy (TEM) and electron diffraction are used to study the carbides precipitated in Hadfield steel Mn13 during 2-h aging at 475°C. It is shown that carbides of types (Fe, Mn, Cr)23C6 and mixed (Fe, Mn, Cr)7C3 + (Fe, Mn, Cr)3C precipitate simultaneously over austenite grain boundaries. The data on precipitation of M23C- and M7C3-type carbides in a Hadfield steel after water quenching and aging are pioneer ones. Strict orientation relations of the M23C6 carbides and of the austenite matrix are determined.

Carbide-metal assemblages in a sample returned from asteroid 25143 Itokawa: Evidence for methane-rich fluids during metamorphism

NASA Astrophysics Data System (ADS)

Harries, Dennis; Langenhorst, Falko

2018-02-01

We found that the particle RA-QD02-0115 returned by the Hayabusa spacecraft from near-Earth asteroid 25143 Itokawa contains the iron carbide haxonite (Fe21.9-22.7Co0.2-0.3Ni0.2-0.8)C6 and several Fe,Ni alloys, including multi-domain tetrataenite and spinodally decomposed taenite. Ellipsoidal to nearly spherical voids occur throughout the particle and suggest the presence of a fluid phase during textural and chemical equilibration of the host rock within the parent asteroid of 25143 Itokawa. The calculated solubility of carbon in Fe,Ni metal indicates that the carbide formed at temperatures larger than 600 °C during thermal metamorphism of the LL-chondritic mineral assemblage. Haxonite formed metastably with respect to graphite and cohenite, probably due to its high degree of lattice match with neighboring taenite, a low cooling rate at peak metamorphic temperatures, and the hindered nucleation of graphite. Thermodynamic equilibrium calculations indicate that the fluid present was dry (H2O-poor) and dominated by methane. The reactive fluid most plausibly had an atomic H/C ratio of 4-5 and was derived from the reduction of macromolecular, insoluble organic matter (IOM) that initially co-accreted with water ice. The initial presence of water is a necessary assumption to provide sufficient hydrogen for the formation of methane from hydrolyzed IOM. Metallic iron was in turn partially oxidized and incorporated into the ferromagnesian silicates during the high-temperature stage of metamorphism. An exemplary bulk reaction from unequilibrated material on the left to an equilibrated assemblage on the right may be written as: 330 CH0.8O0.2(IOM) + 500 H2O(ice/g) + 681 Fe(in alloy) + 566 FeSiO3(in Opx) → 300 CH4(g) + 32 H2(g) + 5 Fe23C6(in Hx) + 566 Fe2SiO4(in Ol) (Opx = orthopyroxene, Hx = haxonite, Ol = olivine, g = fluid species). The best estimate of the fluid/rock ratio in the region of the LL parent body where RA-QD02-0115 formed is about 3 × 10-3 and corresponds to an initial ice/rock ratio of about 7 × 10-3 (both by mass).

Iron-Doped Carbon Aerogels: Novel Porous Substrates for Direct Growth of Carbon Nanotubes

DOE R&D Accomplishments Database

Steiner, S. A.; Baumann, T. F.; Kong, J.; Satcher, J. H.; Dresselhaus, M. S.

2007-02-20

We present the synthesis and characterization of Fe-doped carbon aerogels (CAs) and demonstrate the ability to grow carbon nanotubes directly on monoliths of these materials to afford novel carbon aerogel-carbon nanotube composites. Preparation of the Fe-doped CAs begins with the sol-gel polymerization of the potassium salt of 2,4-dihydroxybenzoic acid with formaldehyde, affording K{sup +}-doped gels that can then be converted to Fe{sup 2+}- or Fe{sup 3+}-doped gels through an ion exchange process, dried with supercritical CO{sub 2} and subsequently carbonized under an inert atmosphere. Analysis of the Fe-doped CAs by TEM, XRD and XPS revealed that the doped iron species are reduced during carbonization to form metallic iron and iron carbide nanoparticles. The sizes and chemical composition of the reduced Fe species were related to pyrolysis temperature as well as the type of iron salt used in the ion exchange process. Raman spectroscopy and XRD analysis further reveal that, despite the presence of the Fe species, the CA framework is not significantly graphitized during pyrolysis. The Fe-doped CAs were subsequently placed in a thermal CVD reactor and exposed to a mixture of CH{sub 4} (1000 sccm), H{sub 2} (500 sccm), and C{sub 2}H{sub 4} (20 sccm) at temperatures ranging from 600 to 800 C for 10 minutes, resulting in direct growth of carbon nanotubes on the aerogel monoliths. Carbon nanotubes grown by this method appear to be multiwalled ({approx}25 nm in diameter and up to 4 mm long) and grow through a tip-growth mechanism that pushes catalytic iron particles out of the aerogel framework. The highest yield of CNTs were grown on Fe-doped CAs pyrolyzed at 800 C treated at CVD temperatures of 700 C.

Iron rich low cost superalloys. Ph.D. Thesis. Final Report

NASA Technical Reports Server (NTRS)

Wayne, S. F.

1985-01-01

An iron-rich low-cost superalloy was developed. The alloy, when processed by conventional chill casting, has physical and mechanical properties that compare favorably with existing nickel and cobalt based superalloys while containing significantly lower amounts of strategic elements. Studies were also made on the properties of Cr(20)-Mn(10)-C(3.4)-Fe(bal.), a eutectic alloy processed by chill casting and directional solidification which produced an aligned microstructure consisting of M7C3 fibers in a gamma-Fe matrix. Thermal expansion of the M7C3 (M = Fe, Cr, Mn) carbide lattice was measured up to 800 C and found to be highly anisotropic, with the a-axis being the predominant mode of expansion. Repetitive impact sliding wear experiments performed with the Fe rich eutectic alloy showed that the directionally solidified microstructure greatly improved the alloy's wear resistance as compared to the chill cast microstructure and conventional nickel base superalloys. Studies on the molybdenum cementite phase prove that the crystal structure of the xi phase is not orthorhombic. The crystal structure of the xi phase is made up of octahedra building elements consisting of four Mo and two Fe atoms and trigonal prisms consisting of four Fe and two Mo atoms. The voids are occupied by carbon atoms. The previous chemical formula for the molybdenum cementite MoFe2C is now clearly seen to be Mo12Fe22C10.

Preparation and crystal structure of U3Fe2C5: An original uranium-iron carbide

NASA Astrophysics Data System (ADS)

Henriques, M. S.; Paixão, J. A.; Henriques, M. S. C.; Gonçalves, A. P.

2015-09-01

The U3Fe2C5 compound was prepared from the elements by arc-melting, followed by an heat-treatment in an induction furnace, at 1250 °C for 1 h and 1300 °C for 2 h. The crystal structure of this phase was determined by direct methods from single crystal X-ray diffraction data. U3Fe2C5 crystallizes in an original tetragonal crystal structure, with space group I4/mmm, a = 3.4980(3) Å and c = 19.8380(15) Å as lattice constants and two formula units per cell. This new type structure is characterized by the simultaneous presence of isolated and pairs of carbon atoms, the interatomic distances in the pairs being similar to a typical carbon-carbon double bond length found in a molecule. U3Fe2C5 is closely related to UC and UFeC2, and can be seen as build from two (distorted) UFeC2 unit cells and a UC layer.

The effects of Ni, Mo, Ti and Si on the mechanical properties of Cr free Mn steel (Fe-25Mn-5Al-2C)

NASA Technical Reports Server (NTRS)

Schuon, S. R.

1982-01-01

The FeMnAlC alloys may hold potential as Cr-free replacements for high strategic material iron base superalloys, but little is known about their intermediate temperature (650 C to 870 C) mechanical properties. The effects of alloying elements on the mechanical properties of model FeMnAlC alloys were studied. Results showed that modified FeMnAlC alloys had promising short term, intermediate temperature properties but had relatively poor stress rupture lives at 172 MPa and 788 C. Room temperature and 788 C tensile strength of FeMnAlC alloys were better than common cast stainless steels. Changes in room temperature tensile and 788 C tensile strength and ductility, and 788 C stress rupture life were correlated with changes in Ni, Mo, Ti, and Si levels due to alloying effects on interstitial carbon levels and carbide morphology. Fe-25Mn-5Al-2C had a very poor stress rupture life at 172 MPa and 788 C. Addition of carbide-forming elements improved the stress rupture life.

Elastic properties and phase transitions of Fe7C3 and new constraints on the light element budget of the Earth's inner core

NASA Astrophysics Data System (ADS)

Prescher, C.; Bykova, E.; Kupenko, I.; Glazyrin, K.; Kantor, A.; McCammon, C. A.; Mookherjee, M.; Miyajima, N.; Cerantola, V.; Nakajima, Y.; Prakapenka, V.; Rüffer, R.; Chumakov, A.; Dubrovinsky, L. S.

2013-12-01

The Earth's inner core consists mainly of iron (or iron-nickel alloy) with some amount of light element(s) whereby their nature remains controversial. Seismological data suggest that the material forming Earth's inner core (pressures over 330 GPa and temperatures above 5000 K) has an enigmatically high Poisson's ratio ~0.44, while iron or it alloys with Si, S, O, or H expected to have at appropriate thermodynamic conditions Poisson's ratio well below 0.39. We will present an experimental study on a new high pressure variant in the iron carbide system. We have synthesized and solved structure of high-pressure orthorhombic phase of o-Fe7C3, and investigated its stability and behavior at pressures over 180 GPa and temperatures above 3500 K by means of different methods including single crystal X-ray diffraction, Mössbauer spectroscopy, and nuclear resonance scattering. O-Fe7C3 is structurally stable to at least outer core conditions and demonstrates magnetic or electronic transitions at ~18 GPa and ~70 GPa. The high pressure phase of o-Fe7C3 above 70 GPa exhibits anomalous elastic properties. When extrapolated to the conditions of the Earth's inner core it shows shear wave velocities and Poisson's ratios close to the values inferred by seismological models. Our results not only support earlier works suggesting that carbon may be an important component of Earth's core, but shows that it may drastically change iron's elastic properties, thus explaining anomalous Earth's inner core elastic properties.

Characterization and in-situ formation mechanism of tungsten carbide reinforced Fe-based alloy coating by plasma cladding

NASA Astrophysics Data System (ADS)

Wang, Mi-qi; Zhou, Ze-hua; Wu, Lin-tao; Ding, Ying; Wang, Ze-hua

2018-04-01

The precursor carbonization method was first applied to prepare W-C compound powder to perform the in-situ synthesis of the WC phase in a Fe-based alloy coating. The in-situ formation mechanism during the cladding process is discussed in detail. The results reveal that fine and obtuse WC particles were successfully generated and distributed in Fe-based alloy coating via Fe/W-C compound powders. The WC particles were either surrounded by or were semi-enclosed in blocky M7C3 carbides. Moreover, net-like structures were confirmed as mixtures of M23C6 and α-Fe; these structures were transformed from M7C3. The coarse herringbone M6C carbides did not only derive from the decomposition of M7C3 but also partly originated from the chemical reaction at the α-Fe/M23C6 interface. During the cladding process, the phase evolution of the precipitated carbides was WC → M7C3 → M23C6 + M6C.

Ion probe measurements of carbon and nitrogen in iron meteorites

NASA Astrophysics Data System (ADS)

Sugiura, Naoji

1998-05-01

Carbon and nitrogen distributions in iron meteorites, their concentrations in various phases, and their isotopic compositions in certain phases were measured by secondary ion mass spectrometry (SIMS). Taenite (and its decomposition products) is the main carrier of carbon except for IAB irons where graphite and/or carbide (cohenite) may be the main carrier. Taenite is also the main carrier of nitrogen in most iron meteorites unless nitrides (carlsbergite CrN or roaldite (Fe,Ni)4N) are present. Carbon and nitrogen distributions in taenite are well correlated, unless carbides and/or nitrides are exsolved. There seem to be three types of C and N distributions within taenite. 1) These elements are enriched at the center of taenite (convex type). 2) They are enriched at the edge of taenite (concave type). 3) They are enriched near but some distance away from the edge of taenite (complex type). The case 1) is explained as equilibrium distribution of C and N in Fe-Ni alloy with M- shape nickel concentration profile. The case 2) seems to be best explained as diffusion controlled C and N distributions. In the case 3), the interior of taenite has been transformed to the a phase (kamacite or martensite). C and N were expelled from the a phase and enriched near the inner border of the remaining g phase. Such differences in the C and N distributions in taenite may reflect different cooling rates of iron meteorites. Nitrogen concentrations in taenite are quite high approaching 1 wt.% in some irons. Nitride (carlsbergite and roaldite) is present in meteorites with high nitrogen concentrations in taenite, suggesting that the nitride was formed due to supersaturation of the metallic phases with nitrogen. The same tendency is generally observed for carbon, i.e. high C concentrations in taenite correlate with the presence of carbide and/or graphite. Concentrations of C and N in kamacite are generally below detection limits. Isotopic compositions of C and N in taenite can be measured with a precision of several permil. Isotopic analysis in kamacite in most iron meteorites is not possible, because of the low concentrations. The C isotopic compositions seem to be somewhat fractionated among various phases, reflecting closure of carbon transport at low temperatures. A remarkable isotopic anomaly was observed for the Mundrabilla (IIICD anomalous) meteorite. Nitrogen isotopic compositions of taenite measured by SIMS agree very well with those of the bulk samples measured by conventional mass-spectrometry.

First principles calculations of the electronic structure and magnetic properties of Y(Fe,M)9.2 and Y(Fe,M)9.2C (M= Si, Ga, Zr)

NASA Astrophysics Data System (ADS)

Tian, Guang; Zha, Liang; Yang, Wenyun; Qiao, Guanyi; Wang, Changsheng; Yang, Yingchang; Yang, Jinbo

2018-06-01

The preferential site substitution of the Fe by Si, Ga and Zr in the Y(Fe,M)9.2 and Y(Fe,M)9.2C compounds, and the doping effects on the magnetic properties have been studied by the first-principles calculations. It is found that the doping of the Si or Zr can improve the thermodynamic stability of the 1:9 phase, while the substitution of the Fe by Ga makes it unstable. Si atom tends to enter the 3g crystal site and Zr prefers to occupy the 2e site when Y(Fe,M)9.2 and their carbides are synthesized. Although the substitution of the Fe by Si and Zr will reduce the total magnetic moments of the YFe9.2 and their carbides, the volumetric and the d-band narrowing effects caused by the doping can still modify the electron density distributions of the Fe near the Fermi level, improving the magnetic ordering temperature of the non-carbonated compound YFe9.2. The calculated magnetic ordering temperatures of Y(Fe,M)9.2C decrease with the increasing content of the doping elements M due to the stronger hybridization of the d bands in the carbides. For the rare-earth(RE) iron based intermetallics REFe9.2 with the TbCu7-type structure, it is suggested that Zr is able to stabilize the phase and enhance the magnetic ordering temperature, indicating the possible further application in the field of permanent magnets, which has not been reported before.

DOE Office of Scientific and Technical Information (OSTI.GOV)

El-Gendy, Ahmed A., E-mail: aelgendy@vcu.edu, E-mail: ecarpenter2@vcu.edu, E-mail: snkhanna@vcu.edu; Nanotechnology and Nanometrology Lab., National institute for standards; Bertino, Massimo

Attainment of magnetic order in nanoparticles at room temperature is an issue of critical importance for many different technologies. For ordinary ferromagnetic materials, a reduction in size leads to decreased magnetic anisotropy and results in superparamagnetic relaxations. If, instead, anisotropy could be enhanced at reduced particle sizes, then it would be possible to attain stable magnetic order at room temperature. Herein, we provide experimental evidence substantiating the synthesis of a cobalt iron carbide phase (CoFe{sub 2}C) of nanoparticles. Structural characterization of the CoFe{sub 2}C carbide phase was performed by transmission electron microscopy, electron diffraction and energy electron spectroscopy. X-ray diffractionmore » was also performed as a complimentary analysis. Magnetic characterization of the carbide phase revealed a blocking temperature, T{sub B}, of 790 K for particles with a domain size as small as 5 ± 1 nm. The particles have magnetocrystalline anisotropy of 4.6 ± 2 × 10{sup 6 }J/m{sup 3}, which is ten times larger than that of Co nanoparticles. Such colossal anisotropy leads to thermally stable long range magnetic order. Moreover, the thermal stability constant is much larger than that of the commonly used FePt nanoparticles. With thermal stability and colossal anisotropy, the CoFe{sub 2}C nanoparticles have huge potential for enhanced magnetic data storage devices.« less

Austenite decomposition to carbide-rich products in Fe-0.30C-6.3W

NASA Astrophysics Data System (ADS)

Hackenberg, R. E.; Granada, D. G.; Shiflet, G. J.

2002-12-01

The kinetics, morphology, and elemental distributions associated with the decomposition of austenite in Fe-0.30C-6.3W were surveyed, especially in the bay region of the time-temperature-transformation (TTT) diagram. Carbide precipitation characteristics were of particular interest. Similar to Fe-C-Mo and Fe-C-Cr alloys, grain- and twin-boundary bainite containing sheets of alloy carbides dominated the microstructure at and above the bay, while popcorn-like bainite was observed immediately below the bay. Nonequilibrium carbide-phase combinations were obtained both above and below the bay, although W partitioning to the alloy carbides was always observed. The carbon level in the remaining austenite increased with reaction time at a given temperature, which, at the later stages of reaction, helped trigger the growth of a constituent containing a high density of nonlamellar carbides. These nonequilibrium reaction-path characteristics are considered to originate from crystallographic and interfacial structure constraints affecting the nucleation of carbides at ferrite-austenite interfaces.

Equation of State of Fe3C and Implications for the Carbon Content of Earth's Core

NASA Astrophysics Data System (ADS)

Davis, A.; Brauser, N.; Thompson, E. C.; Chidester, B.; Greenberg, E.; Prakapenka, V. B.; Campbell, A.

2017-12-01

Carbon is a common component in protoplanetary cores, as represented by iron meteorites. Therefore, along with silicon, oxygen, and other light elements, it is likely to be an alloying component with iron in Earth's core. Previous studies of the densities of iron carbides have not reached the combined pressure and temperature conditions relevant to Earth's core. To better understand the geophysical implications of carbon addition to Earth's core, we report P-V-T measurements of Fe3C to pressures and temperatures exceeding 110 GPa and 2500 K, using synchrotron X-ray diffraction in a laser heated diamond anvil cell. Fitting these measurements to an equation of state and assuming 1.5% density change upon melting and a 4000 K core-mantle boundary temperature, we report a value of 6 wt% carbon necessary to match the PREM density in the outer core. This value should be considered an upper bound due to the likely presence of other light elements.

Electron Spectroscopy Studies of Iron, Iron Sulfides and Supported Iron Surfaces: Chemisorption of Simple Gases.

NASA Astrophysics Data System (ADS)

Lee, Yiu Chung

EELS was used to investigate the chemisorption of oxygen and carbon on iron. The EELS spectra of oxidized iron show characteristic features with strong enhancement of the interband transitions involving the Fe 3d band (4.6 and 7.5 eV) and moderate enhancement of the M(,2,3) transition doublet (54.4 and 58.2 eV). The changes in the electron energy loss structures with an overlayer of graphitic or carbidic carbon were investigated. The adsorption and growth of iron on Ni(100) has been studied using the combined techniques of LEED and EELS. Initially iron grows by a layer-by-layer mechanism for the first few layers. High iron coverages result in the observation of complex LEED patterns with satellites around the main (1 x 1) diffraction sports. This is due to the formation of b.c.c. Fe(110) crystallites arranged in domains with different orientations. EELS studies show the presence of three stages in the growth of iron on Ni(100): low-coverage, film-like and bulk-like. Auger and EELS were used to study the iron sulfide (FeS(,2), Fe(,7)S(,8) and FeS) surfaces. A characteristic M(,2,3) VV Auger doublet with a separation of 5.0 eV was observed on the sulfides. An assignment of the electron energy loss peaks was made based on the energy dependence of the loss peaks and previous photoemission results. The effect of argon ion bombardment was studied. Peaks with strong iron and sulfur character were observed. Heating the damaged sulfides results in reconstruction of the sulfide surfaces. The reactions of the sulfides with simple gases, such as H(,2), CO, CH(,4), C(,2)H(,4), NH(,3) and O(,2) were also studied. Using XPS, the chemisorption of SO(,2) on CaO(100) has been studied. The chemical state of sulfur has been identified as that of sulfate. The kinetics of SO(,2) chemisorption on CaO are discussed. The binding states of Fe and Na on CaO were determined to be Fe('2+) and Na('+) respectively. At low Fe or Na coverages (< 0.5 ML), there is a large increase in the rate of sulfate formation at low SO(,2) exposures (< 3 L). This increase is explained by the 'activation' of SO(,2) chemisorption sites by Fe or Na adatoms.

Crystallographic characterizations of eutectic and secondary carbides in a Fe-12Cr-2.5Mo-1.5W-3V-1.25C alloy

NASA Astrophysics Data System (ADS)

Guo, Jing; Liu, Ligang; Feng, Yunli; Liu, Sha; Ren, Xuejun; Yang, Qingxiang

2017-03-01

In this work, the morphology and structures of the eutectic and secondary carbides in a new high chromium Fe-12Cr-2.5Mo-1.5W-3V-1.25C designed for cold-rolling work roll were systematically studied. The precipitated carbides inside the grains and along the grain boundaries were investigated with optical microscope, scanning electron microscopy with energy dispersive spectroscopy, transmission electron microscopy and X-Ray diffraction. Selected area diffraction patterns have been successfully used to identify the crystal formation and lattice constants of the carbides with different alloying elements. The results show that the eutectic carbides precipitated contain MC and M2C distributed along the grain boundaries with dendrite feature. The composition and crystal structure analysis shows that the eutectic MC carbides contain VC and WC with a cubic and hexagonal crystal lattice structures respectively, while the eutectic M2C carbides predominantly contain V2C and Mo2C with orthorhombic and hexagonal crystal lattices respectively. The secondary carbides contain MC, M2C, M7C3 formed along the grain boundaries and their sizes are much larger than the eutectic carbides ones. The secondary M23C6 is much small (0.3-0.5μm) and is distributed dispersively inside the grain. Similar to the eutectic carbides, the secondary carbides also contain VC, WC, V2C, and Mo2C. M7C3 is hexagonal (Fe,Cr)7C3, while M23C6 is indexed to be in a cubic crystal form.

Crystallography of in-situ transformations of the M 7C3 carbide in the cast Fe-Cr-Ni alloy

NASA Astrophysics Data System (ADS)

Kraposhin, V. S.; Kondrat'ev, S. Yu.; Talis, A. L.; Anastasiadi, G. P.

2017-03-01

In the process of holding of the cast heat-resistant Fe-Cr-Ni (0.45C-25Cr-35Ni) alloy at 1150°C, the eutectic chromium carbide present in its structure undergoes a gradual transition M 7C3 → M 23C6. The gradual formation of domains of the M 23C6 carbide inside the particles of the M 7C3 carbide makes it possible to assume that the observed phase transition is the well-known carbide transformation of the in situ type. The mechanism of the in situ transformation of the crystal structure of the carbide from M 7C3 into M 23C6 with a change in the number of nearest metal neighbors of carbon atoms is explained within the previously developed combinatory model of polymorphic transitions in the metals.

Microstructure and abrasive wear properties of Fe-Cr-C hardfacing alloy cladding manufactured by Gas Tungsten Arc Welding (GTAW)

NASA Astrophysics Data System (ADS)

Chen, Jie-Hao; Hsieh, Chih-Chun; Hua, Pei-Shing; Chang, Chia-Ming; Lin, Chi-Ming; Wu, Paxon Ti-Yuan; Wu, Weite

2013-01-01

A series of Fe-Cr-C hardfacing alloys is deposited by gas tungsten arc welding and subjected to abrasive wear testing. Pure Fe with various amounts of CrC (Cr:C=4:1) powders are mixed as the fillers and used to deposit hardfacing alloys on low carbon steel. Depending on the various CrC additions to the alloy fillers, the claddings mainly contain hypoeutectic, near eutectic, or hypereutectic microstructures of austenite γ-Fe phase and (Cr,Fe)7C3 carbides on hardfacing alloys, respectively. When 30% CrC is added to the filler, the finest microstructure is achieved, which corresponds to the γ-Fe+(Cr,Fe)7C3 eutectic structure. With the addition of 35% and 40% CrC to the fillers, the results show that the cladding consists of the massive primary (Cr,Fe)7C3 as the reinforcing phase and interdendritic γ-Fe+(Cr,Fe)7C3 eutectics as the matrix. The (Cr,Fe)7C3 carbide-reinforced claddings have high hardness and excellent wear resistance under abrasive wear test conditions. Concerning the abrasive wear feature observable on the worn surface, the formation and fraction of massive primary (Cr,Fe)7C3 carbides predominates the wear resistance of hardfacing alloys. Abrasive particles result in continuous plastic grooves when the cladding has primary γ-Fe phase in a hypoeutectic structure.

Experimental investigation of in-situ transformations of the M 7C3 carbide in the cast Fe-Cr-Ni alloy

NASA Astrophysics Data System (ADS)

Kraposhin, V. S.; Kondrat'ev, S. Yu.; Talis, A. L.; Anastasiadi, G. P.

2017-03-01

The microstructure and the phase composition of a heat-resistant Fe-Cr-Ni alloy (0. 45C-25Cr-35Ni) has been investigated in the cast state and after annealing at 1150°C for 2-100 h. After a 2-h high-temperature annealing, the fragmentation of the crystal structure of the eutectic M 7C3 carbides into domains of 500 nm in size with a partial transition into M 23C6 carbides is observed. After a 100-h holding, the complete transition of the hexagonal M 7C3 carbides into M 23C6 with a face-centered cubic structure occurs. The carbide transition M 7C3 → M 23 can be considered to be an in situ transformation.

Influence of Solution Treatment Duration on Microstructural Features of an Industrial Forged UNS S32750/1.4410/F53 Super Duplex Stainless Steel (SDSS) Alloy

NASA Astrophysics Data System (ADS)

Cojocaru, Vasile Dănuţ; Răducanu, Doina; Angelescu, Mariana Lucia; Vintilă, Adrian Nicolae; Şerban, Nicolae; Dan, Ioan; Cojocaru, Elisabeta Mirela; Cinca, Ion

2017-08-01

The microstructural changes induced by solution treatment of an industrial forged F53 Super Duplex Stainless Steel alloy were studied, in order to emphasize how component phases are influenced by heat treatment temperature and duration. The solution treatment was done at a temperature of 1100°C, with variable holding times: 0.6 ks (10 min), 3.6 ks (60 min) and 10.8 ks (180 min). Scanning electron microscopy-electron backscattered diffraction was used as main characterization technique, to obtain and analyse data referring to microstructural features, such as: nature and morphology of constituent phases, average grain-size and grain misorientation. It was shown that in all studied cases the microstructure consisted of a mixture of about 45% δ-Fe (ferrite) and 55% γ-Fe (austenite). Besides δ-Fe and γ-Fe phases, other phases were also identified, such as τ-phase (chromium-iron carbide), σ-phase (chromium-iron) and δ-(Cr-Fe) (ferrite).

Optimizing the dual elemental thermal reactive deposition time in carbide layer formation on SUJ2 tool steel

NASA Astrophysics Data System (ADS)

Mochtar, Myrna Ariati; Putra, Wahyuaji Narottama; Mahardika, Bayu

2018-05-01

This paper presents developments contributing to the improvement of thermo-reactive deposition (TRD) process in producing hard carbide layers, on automotive components application. The problem in using FeV powder as a coating material that has been applied in the industries is it is high cost. In this study, FeCr powder coating material was mixed into FeV powder with a ratio of 35:65 weight percent. The SUJ2 steel pins components are processed at 980° C, with varying TRD time was 4,6,8 and 10 hours. Scanning Electron microscope (SEM), Electron Probe Micro Analyzer (EPMA) and X-ray diffraction (XRD) were applied to analyze the coating layers. The thickness of the carbide layer formed will increase with the longer processing time, which thickness at 4-10 hours is increase from 22.7 to 29.7 micron. The gained thickness tends to be homogeneous. Increasing the TRD process holding time results in a higher hardness of the carbide layerwith hardness at 4, 6, 8 and 10 hours is 2049, 2184, 2175 and 2343 HV. The wear rate at TRD holding time of 4-10 hours with the Ogoshi method was reduced from 5.1 × 10-4 mm3/m to 2.5 × 10-4 mm3/m. Optical microscope observations shows that substrate phases consisting of pearlite and cementite and grains that tend to enlarge with the addition of time. Carbide compounds that are formed are vanadium carbide (V8C7, V6C5, V2C) and chromium carbide (Cr3C2, Cr23C7, Cr3C7). While EDS-Linescan results show complex phase (Fe, V, Cr) xC formed. The research shows that addition of FeCr into FeV powder in TRD process in 980°C with optimum time of 10 hours processing meet the mechanical properties requirement of automotive components.

High-temperature oxidation/corrosion of iron-based superalloys

NASA Technical Reports Server (NTRS)

Lemkey, F. D.; Smeggil, J. G.; Bailey, R. S.; Schuster, J. C.; Nowotny, H.

1987-01-01

The oxidation and sulfidation of several novel iron-base superalloys were evaluated in high-temperature cyclic tests. The experimental austenitic alloys examined were modifications of NASAUT-4GA which were developed for Stirling-engine application. The weight gains and resulting surface scales were measured and analyzed. Mixed oxide scales were found to form on all specimens exposed above 871 C. The build-up of these scales led to a depletion of Mn and Cr in a zone adjacent to the oxides. In addition, the initial oxidation of the Fe-rich alloy was inhibited by a thin but tenacious Si layer which formed at the interface between oxides and the parent layer. Sulfidation tests using Na2SO4 coatings resulted in the formation of a protective spinel and alpha-Fe2O3 phases. Preferential attack of the carbide phase by hydrogen was not observed after 350 h at 871 C.

Substantiation of Epitaxial Growth of Diamond Crystals on the Surface of Carbide Fe3AlC0.66 Phase Nanoparticles

NASA Astrophysics Data System (ADS)

Dzevin, Ievgenij M.; Mekhed, Alexander A.

2017-03-01

Samples of Fe-Al-C alloys of varying composition were synthesized under high pressures and temperatures. From X-ray analysis data, only K-phase with usual for it average parameter of elemental lattice cell, a = 0.376 nm, carbide Fe3C and cubic diamond reflexes were present before and after cooling to the temperature of liquid nitrogen.

Formation of Acetylene in the Reaction of Methane with Iron Carbide Cluster Anions FeC3- under High-Temperature Conditions.

PubMed

Li, Hai-Fang; Jiang, Li-Xue; Zhao, Yan-Xia; Liu, Qing-Yu; Zhang, Ting; He, Sheng-Gui

2018-03-01

The underlying mechanism for non-oxidative methane aromatization remains controversial owing to the lack of experimental evidence for the formation of the first C-C bond. For the first time, the elementary reaction of methane with atomic clusters (FeC 3 - ) under high-temperature conditions to produce C-C coupling products has been characterized by mass spectrometry. With the elevation of temperature from 300 K to 610 K, the production of acetylene, the important intermediate proposed in a monofunctional mechanism of methane aromatization, was significantly enhanced, which can be well-rationalized by quantum chemistry calculations. This study narrows the gap between gas-phase and condensed-phase studies on methane conversion and suggests that the monofunctional mechanism probably operates in non-oxidative methane aromatization. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Simultaneous iron and nickel isotopic analyses of presolar silicon carbide grains

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trappitsch, Reto; Stephan, Thomas; Savina, Michael R.

Aside from recording stellar nucleosynthesis, a few elements in presolar grains can also provide insights into the galactic chemical evolution (GCE) of nuclides. We have studied the carbon, silicon, iron, and nickel isotopic compositions of presolar silicon carbide (SiC) grains from asymptotic giant branch (AGB) stars to better understand GCE. Since only the neutron-rich nuclides in these grains have been heavily in uenced by the parent star, the neutron-poor nuclides serve as GCE proxies. Using CHILI, a new resonance ionization mass spectrometry (RIMS) instrument, we measured 74 presolar SiC grains for all iron and nickel isotopes. With the CHARISMA instrument,more » 13 presolar SiC grains were analyzed for iron isotopes. All grains were also measured by NanoSIMS for their carbon and silicon isotopic compositions. A comparison of the measured neutron-rich isotopes with models for AGB star nucleosynthesis shows that our measurements are consistent with AGB star predictions for low-mass stars between half-solar and solar metallicity. Furthermore, our measurements give an indication on the 22Ne( ,n) 25Mg reaction rate. In terms of GCE, we nd that the GCE-dominated iron and nickel isotope ratios, 54Fe/56Fe and 60Ni/ 58Ni, correlate with their GCE-dominated counterpart in silicon, 29Si/ 28Si. The measured GCE trends include the Solar System composition, showing that the Solar System is not a special case. However, as seen in silicon and titanium, many presolar SiC grains are more evolved for iron and nickel than the Solar System. This con rms prior ndings and agrees with observations of large stellar samples that a simple age-metallicity relationship for GCE cannot explain the composition of the solar neighborhood.« less

Simultaneous iron and nickel isotopic analyses of presolar silicon carbide grains

DOE PAGES

Trappitsch, Reto; Stephan, Thomas; Savina, Michael R.; ...

2018-01-01

Aside from recording stellar nucleosynthesis, a few elements in presolar grains can also provide insights into the galactic chemical evolution (GCE) of nuclides. We have studied the carbon, silicon, iron, and nickel isotopic compositions of presolar silicon carbide (SiC) grains from asymptotic giant branch (AGB) stars to better understand GCE. Since only the neutron-rich nuclides in these grains have been heavily in uenced by the parent star, the neutron-poor nuclides serve as GCE proxies. Using CHILI, a new resonance ionization mass spectrometry (RIMS) instrument, we measured 74 presolar SiC grains for all iron and nickel isotopes. With the CHARISMA instrument,more » 13 presolar SiC grains were analyzed for iron isotopes. All grains were also measured by NanoSIMS for their carbon and silicon isotopic compositions. A comparison of the measured neutron-rich isotopes with models for AGB star nucleosynthesis shows that our measurements are consistent with AGB star predictions for low-mass stars between half-solar and solar metallicity. Furthermore, our measurements give an indication on the 22Ne( ,n) 25Mg reaction rate. In terms of GCE, we nd that the GCE-dominated iron and nickel isotope ratios, 54Fe/56Fe and 60Ni/ 58Ni, correlate with their GCE-dominated counterpart in silicon, 29Si/ 28Si. The measured GCE trends include the Solar System composition, showing that the Solar System is not a special case. However, as seen in silicon and titanium, many presolar SiC grains are more evolved for iron and nickel than the Solar System. This con rms prior ndings and agrees with observations of large stellar samples that a simple age-metallicity relationship for GCE cannot explain the composition of the solar neighborhood.« less

Kinetics of the solid-state carbothermic reduction of wessel manganese ores

NASA Astrophysics Data System (ADS)

Akdogan, Guven; Eric, R. Hurman

1995-02-01

Reduction of manganese ores from the Wessel mine of South Africa has been investigated in the temperature range 1100 °C to 1350 °C with pure graphite as the reductant under argon atmosphere. The rate and degree of reduction were found to increase with increasing temperature and decreasing particle sizes of both the ore and the graphite. The reduction was found to occur in two stages: (1) The first stage includes the rapid reduction of higher oxides of manganese and iron to MnO and FeO. The rate control appears to be mixed, both inward diffusion of CO and outward diffusion of CO2 across the porous product layer, and the reaction of carbon monoxide on the pore walls of the oxide phase play important roles. The values of effective CO-CO2 diffusivities generated by the mathematical model are in the range from 2.15 x 10-5 to 6.17 X 10-5 cm2.s-1 for different ores at 1300 °C. Apparent activation energies range from 81. 3 to 94.6 kJ/kg/mol. (2) The second stage is slower during which MnO and FeO are reduced to mixed carbide of iron and manganese. The chemical reaction between the manganous oxide and carbon dissolved in the metal phase or metal carbide seems to be the rate-controlling process The rate constant of chemical reaction between MnO and carbide on the surface of the impervious core was found to lie in the range from 1.53 x 10-8 to 1.32 x 10-7 mol . s-1 . cm-2. Apparent activation energies calculated are in the range from 102.1 to 141.7 kJ/kg/mol.

Fe3O4 nanocubes assembled on RGO nanosheets: Ultrasound induced in-situ and eco-friendly synthesis, characterization and their excellent catalytic performance for the production of liquid fuel in Fischer-tropsch synthesis.

PubMed

Abbas, Mohamed; Zhang, Juan; Lin, Ke; Chen, Jiangang

2018-04-01

In this study, Fe 3 O 4 nanocubes (NCs) decorated on RGO nanosheets (NSs) structures were successfully synthesized through an innovative and environmentally-friendly rapid sonochemical method. More importantly, iron(II) sulfate heptahydrate and GO were employed as precursors and water as reaction medium, meanwhile, NaOH within the generated free radicals from the high intensity ultrasound were sufficient as reducing and base agent in our clean synthesis. Moreover, the hydrothermal method as a conventional approach was employed to synthesize the same catalysts for the comparison with the ultrasonocation technique. The as-synthesized Fe 3 O 4 and RGO/Fe 3 O 4 NSs catalysts were exposed to industrially relevant Fischer-tropsch synthesis (FTS) conditions at various reaction temperatures (250-290 °C), and they subjected to fully characterization before and after FTS reaction using XRD, TEM, HRTEM, EDS mapping, XPS, FTIR, BET, H 2 -TPR, H 2 -TPD and CO-TPD to understand the structure-performance relationships. Notably, the catalysts produced using the sonochemical method had a better CO conversion rate [Fe 3 O 4 (80%), RGO/Fe 3 O 4 (82%)] than the hydrothermally synthesized catalysts. However, compared to the naked-Fe 3 O 4 catalysts, the sonochemically and hydrothermally synthesized RGO-supported Fe 3 O 4 catalysts had higher long chain hydrocarbon (C5+) selectivity values (72% and 67%) and C 2 -C 4 olefin/paraffin selectivity ratio (3.2 and 2) and low CH4 selectivity values (6% and 8.5%), respectively. This can be attributed to their high surface area, the degree of reducibility, and content of Hägg iron carbide (χ-Fe 5 C 2 ) as the most active phase of the FTS reaction. Proposed reaction mechanisms for the sonochemical and hydrothermal reaction synthesis of Fe 3 O 4 and RGO/Fe 3 O 4 nanoparticles are discussed. In conclusion, our developed surfactantless-sonochemical method holds promise for the eco-friendly synthesis of highly efficient catalysts materials for FTS reaction. Copyright © 2017 Elsevier B.V. All rights reserved.

Carbon isotope fractionation between Fe-carbide and diamond; a light C isotope reservoir in the deep Earth and Core?

NASA Astrophysics Data System (ADS)

Mikhail, S.; Jones, A. P.; Hunt, S. A.; Guillermier, C.; Dobson, D. P.; Tomlinson, E.; Dan, H.; Milledge, H.; Franchi, I.; Wood, I.; Beard, A.; Verchovsky, S.

2010-12-01

The largest accessible reservoir for terrestrial carbon is the mantle; however the core may yield even more. Carbon is commonly proposed as the light element (or one of) to make up the observed density deficit in the earth’s metallic core (NAKAJIMA et al., 2009). The potential isotopic effects of carbon incorporation into the core have not yet been investigated. In-situ ion probe (nanoSIMS) mapping and imaging of carbon isotope variations across rare sub-mm-scale Fe-rich carbide inclusions in mantle diamond (from Jagersfontein, South Africa) show the carbide to be significantly depleted in 13C relative to their diamond host. Distinctive textures suggest metallic liquid precipitates similar in geometry to (giant) nitrogen platelets, controlled by the octahedral symmetry of diamond, which we interpret as syngenic formation. The difference in δ13C values between the two natural phases for diamond-Fe carbide, gives an isotopic fractionation factor (ΔC) which agrees well with HPHT multi-anvil experiments (5-9 GPa and >1400°C). Our measured ΔC between Fe-carbide and diamond may only have local significance, but the measured isotopic values represent characterization of the highest PT carbide known (i.e. > minimum depth of the diamond stability field ≈ 150 km). The direction and magnitude of ΔC agrees with observations of the ΔC between cohenite-graphite in iron meteorites (DEINES and WICKMAN, 1975) and both agree with HPHT experiments, thus suggesting that carbon in the deep Earth, and particularly in the core, may be similarly fractionated (i.e. depleted in the 13C). Since metallic liquid drained from the silicate mantle to form the core during the early Earth, we can use our values as a proxy to constrain evolution of deep carbon reservoirs such as the core and bulk silicate Earth. For example, we can test the suggestion of Grady et al (2004) that the upper mantle value of δ13C ≈ -5 ‰ may not be representative of the bulk Earth, since solar system meteorites (from Mars, Vesta and the Moon) suggest a preferred value of δ13C ≈ -20 +/- 4 ‰. If we adopt this particular model, not only could we explain fractionation between a bulk silicate Earth δ13C value of -5 ‰ from an initial δ13C value of -20 ‰, but we can constrain the relative proportion of carbon in the core/mantle by using simple isotopic mass balance. Such fractionation of carbon isotopes between HPT carbides (and/or metallic iron) within the lower mantle and core would be expected immediately from the time of core formation. Therefore, isotopically light carbon reservoirs may have been present deep in the Earth throughout its history, offering an alternative explanation for light carbon (eg in diamonds) which was not formed by, and/or predated subduction of oceanic crust and organic carbon. Deines, P. and Wickman, F. E., 1975. GCA; Grady, M. M. et al. 2004. Int Journal of Astrobiology; Nakajima, Y. et al. K.-i., 2009. Physics of the Earth and Planetary Interiors.

Effect of molybdenum, vanadium, boron on mechanical properties of high chromium white cast iron in as-cast condition

NASA Astrophysics Data System (ADS)

Nurjaman, F.; Sumardi, S.; Shofi, A.; Aryati, M.; Suharno, B.

2016-02-01

In this experiment, the effect of the addition carbide forming elements on high chromium white cast iron, such as molybdenum, vanadium and boron on its mechanical properties and microstructure was investigated. The high chromium white cast iron was produced by casting process and formed in 50 mm size of grinding balls with several compositions. Characterization of these grinding balls was conducted by using some testing methods, such as: chemical and microstructure analysis, hardness, and impact test. From the results, the addition of molybdenum, vanadium, and boron on high chromium white cast iron provided a significant improvement on its hardness, but reduced its toughness. Molybdenum induced fully austenitic matrix and Mo2C formation among eutectic M7C3 carbide. Vanadium was dissolved in the matrix and carbide. While boron was played a role to form fine eutectic carbide. Grinding balls with 1.89 C-13.1 Cr-1.32 Mo-1.36 V-0.00051 B in as-cast condition had the highest hardness, which was caused by finer structure of eutectic carbide, needle like structure (upper bainite) matrix, and martensite on its carbide boundary.

Reduction of Chromite in Liquid Fe-Cr-C-Si Alloys

NASA Astrophysics Data System (ADS)

Demir, Orhan; Eric, R. Hurman

1994-08-01

The kinetics and the mechanism of the reduction of chromite in Fe-Cr-C-Si alloys were studied in the temperature range of 1534 °C to 1702 °C under an inert argon atmosphere. The rotating cylinder technique was used. The melt consisted of 10 and 20 wt Pct chromium, the carbon content varied from 2.8 wt Pct to saturation, and the silicon content varied from 0 to 2 wt Pct. The rotational speed of the chromite cylinder ranged from 100 to 1000 rpm. The initial chromium to iron ratios of the melts varied between 0.11 and 0.26. In Fe-C melts, the effect of rotational speed on the reduction of chromite was very limited. Carbon saturation (5.4 wt Pct) of the alloy caused the reduction to increase 1.5 times over the reduction observed in the unsaturated (4.87 wt Pct) alloy at a given rotational speed. The addition of chromium to the carbon-saturated Fe-C alloy increased the reduction rate. The addition of silicon to the liquid phase increased the reduction rate drastically. The reduction of chromite in Fe-Cr-C melts is hindered because of the formation of, approximately, a 1.5-mm-thick M7C3-type carbide layer around the chromite cylinders. This carbide layer did not form when silicon was present in the melt. It was found that the reduction rate is controlled by the liquid-state mass transfer of oxygen. The calculated apparent activation energies for diffusion were 102.9 and 92.9 kJ/mol of oxygen in the Si-O and C-O systems, respectively.

Recent Developments in Homogeneous Dinitrogen Reduction by Molybdenum and Iron

PubMed Central

MacLeod, K. Cory; Holland, Patrick L.

2013-01-01

The reduction of gaseous nitrogen (N2) is a challenge for industrial, biological and synthetic chemists, who want to understand the formation of ammonia (NH3) for agriculture and also want to form N-C and N-Si bonds for fine chemical synthesis. The iron-molybdenum active site of nitrogenase has inspired chemists to explore the ability of iron and molybdenum complexes to bring about transformations related to N2 reduction. This area of research has gained significant momentum, and the last two years have witnessed a number of significant advances in synthetic Fe-N2 and Mo-N2 chemistry. In addition, the identities of all atoms in the iron-molybdenum cofactor of nitrogenase have finally been elucidated, and the discovery of a carbide has generated new questions and targets for coordination chemists. This Perspective summarizes the recent work on iron and molydenum complexes, and highlights the opportunities for continued research. PMID:23787744

Friction-induced structural transformations of the carbide phase in Hadfield steel

NASA Astrophysics Data System (ADS)

Korshunov, L. G.; Sagaradze, V. V.; Chernenko, N. L.; Shabashov, V. A.

2015-08-01

Structural transformations of the carbide phase in Hadfield steel (110G13) that occur upon plastic deformation by dry sliding friction have been studied by methods of optical metallography, X-ray diffraction, and transmission electron microscopy. Deformation is shown to lead to the refinement of the particles of the carbide phase (Fe, Mn)3C to a nanosized level. The effect of the deformation-induced dissolution of (Fe, Mn)3C carbides in austenite of 110G13 (Hadfield) steel has been revealed, which manifests in the appearance of new lines belonging to austenite with an unusually large lattice parameter ( a = 0.3660-0.3680 nm) in the X-ray diffraction patterns of steel tempered to obtain a fine-lamellar carbide phase after deformation. This austenite is the result of the deformation-induced dissolution of disperse (Fe, Mn)3C particles, which leads to the local enrichment of austenite with carbon and manganese. The tempering that leads to the formation of carbide particles in 110G13 steel exerts a negative influence on the strain hardening of the steel, despite the increase in the hardness of steel upon tempering and the development of the processes of the deformation-induced dissolution of the carbide phase, which leads to the strengthening of the γ solid solution.

Microstructure and wear resistance of Al2O3-M7C3/Fe composite coatings produced by laser controlled reactive synthesis

NASA Astrophysics Data System (ADS)

Tan, Hui; Luo, Zhen; Li, Yang; Yan, Fuyu; Duan, Rui

2015-05-01

Based on the principle of thermite reaction of Al and Fe2O3 powders, the Al2O3 ceramic reinforced Fe-based composite coatings were fabricated on a steel substrate by laser controlled reactive synthesis and cladding. The effects of different additions of thermite reactants on the phase transition, microstructure evolution, microhardness and wear resistance of the composite coatings were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Vickers microhardness and block-on-ring wear test, respectively. The results show that Al2O3 ceramic and M7C3 carbide are in situ synthesized via the laser controlled reactive synthesis. The Al2O3 ceramic and M7C3 carbides prefer to distribute along the γ-Fe phase boundary continuously, which separates the γ-Fe matrix and is beneficial to the grain refinement. With the increase of thermite reactants, the amount of Al2O3 ceramic and M7C3 carbide in the composite coatings increases gradually. Moreover the cladding layer changes from dendritic structure to columnar structure and martensite structure in the heat affected zone becomes coarse. The increased thermite reactants improve the microhardness and wear resistance of the in situ composite coatings obviously and enhance the hardness of the heat affected zone, which should be ascribed to the grain refinement, ceramic and carbide precipitation and solid solution strengthening.

Formation Energies and Electronic Properties of Vanadium Carbides Found in High Strength Steel Alloys

NASA Astrophysics Data System (ADS)

Limmer, Krista; Medvedeva, Julia

2013-03-01

Carbide formation and stabilization in steels is of great interest owing to its effect on the microstructure and properties of the Fe-based alloys. The appearance of carbides with different metal/C ratios strongly depends on the carbon concentration, alloy composition as well as the heat treatment. Strong carbide-forming elements such as Ti, V, and Nb have been used in microalloyed steels; with VC showing an increased solubility in the iron matrix as compared with TiC and NbC. This allows for dissolution of the VC into the steel during heating and fine precipitation during cooling. In addition to VC, the primary vanadium carbide with cubic structure, a wide range of non-stoichiometric compositions VCy with y varying from 0.72 to 0.88, has been observed. This range includes two ordered compounds, V8C7 and V6C5. In this study, first-principles density functional theory (DFT) is employed to examine the stability of the binary carbides by calculating their formation energies. We compare the local structures (atomic coordination, bond distances and angles) and the density of states in optimized geometries of the carbides. Further, the effect of alloying additions, such as niobium and titanium, on the carbide stabilization is investigated. We determine the energetically preferable substitutional atom location in each carbide and study the impurity distribution as well as its role in the carbide formation energy and electronic structure.

Development and characterization of (Ti, Mo)C carbides reinforced Fe-based surface composite coating produced by laser cladding

NASA Astrophysics Data System (ADS)

Wang, Xinhong; Zhang, Min; Qu, Shiyao

2010-09-01

In this study, in situ multiple carbides reinforced Fe-based surface composite coatings were fabricated successfully by laser cladding a precursor mixture of graphite, ferrotitanium (Fe-Ti) and ferromolybdenum (Fe-Mo) powders. The results showed that (Ti, Mo)C particles with flower-like and cuboidal shapes were in situ formed during the solidification and most shapes of (Ti, Mo)C particles were diversiform according to different contents of Fe-Mo powder in the Fe-Ti-Mo-C system. The growth morphology of the reinforcing (Ti, Mo)C carbide has typically faceted features, indicating that the lateral growth mechanism is still predominant growth mode under rapid solidification conditions. Increasing the amount of Fe-Mo in the reactants led to a decrease of carbide size and an increase of volume fraction of carbides. The coatings had good cracking resistance when the amounts of Fe-Mo were controlled within a range of 15 wt%.

Nd2Fe14C-based magnet with better permanent magnetic properties prepared by a simple mechanochemical method

NASA Astrophysics Data System (ADS)

Geng, Hongmin; Ji, Yuan; Zhang, Jingjing; Gao, Yuchao; Yan, Yu; Wang, Wenquan; Su, Feng; Du, Xiaobo

2017-11-01

Nd2Fe14C-based magnet is prepared by a mechanochemical method, namely high-energy ball-milling Nd2Fe11Bx (x = 0-0.15) alloy in heptane (C7H16), followed by annealing to 850 °C in vacuum. Under the action of high-energy ball-milling, Nd2Fe11Bx react with heptane to form NdH2+δ, Fe-(CB), C, etc. H2 is released and Nd2Fe17, Nd2Fe17Cx (x = 0-3), Nd2Fe14C, Nd carbides and α-Fe are formed in the subsequent annealing. C amount depends on ball-milling time t. Long time ball milling or high C content suppresses the formation of 2:17 phase and favors the formation of 2:14:1 phase in the final products. Excessive ball-milling results in the quick increase of α-Fe. The maximum of magnetically hard Nd2Fe14C is obtained at t = 4 h. For Nd2Fe11 samples, there exists considerable quantity of Nd carbides and α-Fe phase appears earlier and increases rapidly with extending the ball-milling time t. The addition of B element shortens the ball-milling time of the formation of maximum Nd2Fe14C and prominently suppresses the formation of Nd carbide and α-Fe. The optimum magnetic properties, coercivity iHc of 1193.7 kA/m, remanence Mr of 580.9 kA/m, maximum magnetic energy product (BH)max of 91.7 kJ/m3 is approaching to its theoretic value of 99.2 kJ/m3 for isotropic Nd2Fe14C magnet, are obtained in Nd2Fe11B0.06 alloy ball milled for 3.5 h.

Electrical and thermal conductivity of Fe-C alloy at high pressure: implications for effects of carbon on the geodynamo of the Earth's core

NASA Astrophysics Data System (ADS)

Zhang, C.; Lin, J. F.; Liu, Y.; Feng, S.; Jin, C.; Yoshino, T.

2017-12-01

Thermal conductivity of iron alloy in the Earth's core plays a crucial role in constraining the energetics of the geodynamo and the thermal evolution of the planet. Studies on the thermal conductivity of iron reveal the importance of the effects of light elements and high temperature. Carbon has been proposed to be a candidate light element in Earth's core for its meteoritic abundance and high-pressure velocity-density profiles of iron carbides (e.g., Fe7C3). In this study, we employed four-probe van der Pauw method in a diamond anvil cell to measure the electrical resistivity of pure iron, iron carbon alloy, and iron carbides at high pressures. These studies were complimented with synchrotron X-ray diffraction and focused ion beam (FIB) analyses. Our results show significant changes in the electrical conductivity of these iron-carbon alloys that are consistent previous reports with structural and electronic transitions at high pressures, indicating that these transitions should be taken into account in evaluating the electrical and thermal conductivity at high pressure. To apply our results to understand the thermal conduction in the Earth's core, we have compared our results with literature values for the electrical and thermal conductivity of iron alloyed with light elements (C, Si) at high pressures. These comparisons permit the validity of the Wiedemann-Franz law and Matthiessen's rule for the effects of light elements on the thermal conductivity of the Earth's core. We found that an addition of a light element such as carbon has an strong effect on the reducing the thermal conductivity of Earth's core, but the magnitude of the alloying effect strongly depends on the identity of the light element and the crystal and electronic structures. Based on our results and literature values, we have modelled the electrical and thermal conductivity of iron-carbon alloy at Earth's core pressure-temperature conditions to the effects on the heat flux in the Earth's core. In this presentation, we will address how carbon as a potential light element in the Earth's core can significantly affect our view of the heat flux across the core-mantle boundary and geodynamo of our planet.

Identification of an iron permease, cFTR1, in cyanobacteria involved in the iron reduction/re-oxidation uptake pathway.

PubMed

Xu, Ning; Qiu, Guo-Wei; Lou, Wen-Jing; Li, Zheng-Ke; Jiang, Hai-Bo; Price, Neil M; Qiu, Bao-Sheng

2016-12-01

Cyanobacteria are globally important primary producers and abundant in many iron-limited aquatic environments. The ways in which they take up iron are largely unknown, but reduction of Fe 3+ is an important step in the process. Here we report a special iron permease in Synechocystis, cFTR1, that is required for Fe 3+ uptake following Fe 2+ re-oxidation. The expression of cFTR1 is induced by iron starvation, and a mutant lacking the gene is abnormally sensitive to iron starvation. The cFTR1 protein localizes to the plasma membrane and contains the iron-binding motif "REXXE". Point-directed mutagenesis of the REXXE motif results in a sensitivity to Fe-deficiency. Measurements of iron ( 55 Fe) uptake rate show that cFTR1 takes up Fe 3+ rather than Fe 2+ . The function of cFTR1 in Synechocystis could be genetically complemented by the iron permease, Ftr1p, of Saccharomyces cerevisiae, that is known to transport Fe 3+ produced by the oxidation of Fe 2+ via a multicopper oxidase. Unlike yeast Ftr1p, cyanobacterial cFTR1 probably obtains Fe 3+ primarily from the oxidation of Fe 2+ by oxygen. Growth assays show that the cFTR1 is required during oxygenic, photoautotrophic growth but not when oxygen production is inhibited during photoheterotrophic growth. In cyanobacteria, iron reduction/re-oxidation uptake pathway may represent their adaptation to oxygenated environments. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

Microstructural evolution with various Ti contents in Fe-based hardfacing alloys using a GTAW technique

NASA Astrophysics Data System (ADS)

Hsieh, Chih-Chun; Liu, Yi-Chia; Wang, Jia-Siang; Wu, Weite

2014-07-01

The aim of this study is to discuss the effect of microstructural development with different Ti contents in Fe-based hardfacing alloys. A series of Fe-Cr-C-Si-Mn-xTi alloy fillers was deposited on SS400 low carbon steel substrate using oscillating gas tungsten arc welding. The microstructure in the Fe-based hardfacing alloy without Ti content addition included: the primary γ, eutectic γ+(Fe,Cr)3C, eutectic γ+(Fe,Cr)2C and martensite. With increasing Ti contents, the microstructures showed the primary TiC carbide, γ phase and eutectic γ+(Fe,Cr,Ti)3C. The amount and size of TiC carbide in the hardfacing layers increased as the Ti content increased. However, the eutectic γ+(Fe,Cr,Ti)3C content decreased as the Ti content increased. According to the results of the hardness test, the lowest hardness value (HRC 54.93) was found with 0% wt% Ti and the highest hardness (HRC 60.29) was observed with 4.87 wt% Ti.

XPS, AES and friction studies of single-crystal silicon carbide

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1982-01-01

The surface chemistry and friction behavior of a single crystal silicon carbide surface parallel to the 0001 plane in sliding contact with iron at various temperatures to 1500 C in a vacuum of 3 x 10 nPa are investigated using X-ray photoelectron and Auger electron spectroscopy. Results show that graphite and carbide-type carbon are seen primarily on the silicon carbide surface in addition to silicon at temperatures to 800 C by both types of spectroscopy. The coefficients of friction for iron sliding against a silicon carbide surface parallel to the 0001 plane surface are found to be high at temperatures up to 800 C, with the silicon and carbide-type carbon at maximum intensity in the X-ray photoelectron spectroscopy at 800 C. The concentration of the graphite increases rapidly on the surface as the temperature is increased above 800 C, while the concentrations of the carbide-type carbon and silicon decrease rapidly and this presence of graphite is accompanied by a significant decrease in friction. Preheating the surfaces to 1500 C also gives dramatically lower coefficients of friction when reheating in the sliding temperature range of from room temperature to 1200 C, with this reduction in friction due to the graphite layer on the silicon carbide surface.

Reductive mineralization of cellulose with vanadium, iron and tungsten chlorides and access to MxOy metal oxides and MxOy/C metal oxide/carbon composites.

PubMed

Henry, Aurélien; Hesemann, Peter; Alauzun, Johan G; Boury, Bruno

2017-10-15

M x O y and M x O y /C composites (M=V, Fe and W) were obtained by mineralization of cellulose with several metal chlorides. Cellulose was used both as a templating agent and as an oxygen and a carbon source. Soluble chloride molecules (VOCl 3 and WCl 6 ) and a poorly soluble ionic chloride compound (FeCl 3 ) were chosen as metal oxide precursors. In a first time, primary metal oxide/cellulose composites were obtained via a thermal treatment by reacting urea impregnated filter paper with the corresponding metal chlorides in an autoclave at 150°C after 3days. After either pyrolysis or calcination steps of these intermediate materials, interesting metal oxides with various morphologies were obtained (V 2 O 5, V 2 O 3 , Fe 3 O 4 , WO 3, H 0.23 WO 3 ), composites (V 2 O 3 /C) as well as carbides (hexagonal W 2 C and WC, Fe 3 C) This result highlight the reductive role that can play cellulose during the pyrolysis step that allows to tune the composition of M x O y /C composites. The materials were characterized by FTIR, Raman, TGA, XRD and SEM. This study highlights that cellulose can be used for a convenient preparation of a variety of highly demanded M x O y and M x O y /C composites with original shapes and morphologies. Copyright © 2017 Elsevier Ltd. All rights reserved.

Phase formation during the carbothermic reduction of eudialyte concentrate

NASA Astrophysics Data System (ADS)

Krasikov, S. A.; Upolovnikova, A. G.; Sitnikova, O. A.; Ponomarenko, A. A.; Agafonov, S. N.; Zhidovinova, S. V.; Maiorov, D. V.

2013-07-01

The phase transformations of eudialyte concentrate during the carbothermic reduction in the temperature range 25-2000°C are studied by thermodynamic simulation, differential thermal analysis, and X-ray diffraction. As the temperature increases to 1500°C, the following phases are found to form sequentially: iron and manganese carbides, free iron, niobium carbide, iron silicides, silicon and titanium carbides, and free silicon. Strontium, yttrium, and uranium in the temperature range under study are not reduced and are retained in an oxide form, and insignificant reduction of zirconium oxides with the formation of carbide ZrC is possible only at temperatures above 1500°C.

Surface chemistry and wear behavior of single-crystal silicon carbide sliding against iron at temperatures to 1500 C in vacuum

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1982-01-01

X-ray photoelectron and Auger electron spectroscopy analyses and morphological studies of wear and metal transfer were conducted with a single-crystal silicon carbide 0001 surface in contact with iron at various temperatures to 1500 C in a vacuum of 10 to the minus 8th power pascal. The results indicate that below 800 C, carbide-carbon and silicon are primarily seen on the silicon carbide surface. Above 800 C the graphite increases rapidly with increase in temperature. The outermost surficial layer, which consists mostly of graphite and little silicon at temperatures above 1200 C is about 2 nm thick. A thicker layer, which consists of a mixture of graphite, carbide, and silicon is approximately 100 nm thick. The closer the surface sliding temperature is to 800 C, the more the metal transfer produced. Above 800 C, there was a transfer of rough, discontinuous, and thin iron debris instead of smooth, continuous and thin iron film which was observed to transfer below 800 C. Two kinds of fracture pits were observed on the silicon carbide surface: (1) a pit with a spherical asperity; and (2) multiangular shaped pits.

Atomistic simulations of stainless steels: a many-body potential for the Fe-Cr-C system.

PubMed

Henriksson, K O E; Björkas, C; Nordlund, K

2013-11-06

Stainless steels found in real-world applications usually have some C content in the base Fe-Cr alloy, resulting in hard and dislocation-pinning carbides-Fe3C (cementite) and Cr23C6-being present in the finished steel product. The higher complexity of the steel microstructure has implications, for example, for the elastic properties and the evolution of defects such as Frenkel pairs and dislocations. This makes it necessary to re-evaluate the effects of basic radiation phenomena and not simply to rely on results obtained from purely metallic Fe-Cr alloys. In this report, an analytical interatomic potential parameterization in the Abell-Brenner-Tersoff form for the entire Fe-Cr-C system is presented to enable such calculations. The potential reproduces, for example, the lattice parameter(s), formation energies and elastic properties of the principal Fe and Cr carbides (Fe3C, Fe5C2, Fe7C3, Cr3C2, Cr7C3, Cr23C6), the Fe-Cr mixing energy curve, formation energies of simple C point defects in Fe and Cr, and the martensite lattice anisotropy, with fair to excellent agreement with empirical results. Tests of the predictive power of the potential show, for example, that Fe-Cr nanowires and bulk samples become elastically stiffer with increasing Cr and C concentrations. High-concentration nanowires also fracture at shorter relative elongations than wires made of pure Fe. Also, tests with Fe3C inclusions show that these act as obstacles for edge dislocations moving through otherwise pure Fe.

Material Analysis of Coated Siliconized Silicon Carbide (SiSiC) Honeycomb Structures for Thermochemical Hydrogen Production

PubMed Central

Neises-von Puttkamer, Martina; Simon, Heike; Schmücker, Martin; Roeb, Martin; Sattler, Christian; Pitz-Paal, Robert

2013-01-01

In the present work, thermochemical water splitting with siliconized silicon carbide (SiSiC) honeycombs coated with a zinc ferrite redox material was investigated. The small scale coated monoliths were tested in a laboratory test-rig and characterized by X-ray diffractometry (XRD) and Scanning Electron Microscopy (SEM) with corresponding micro analysis after testing in order to characterize the changes in morphology and composition. Comparison of several treated monoliths revealed the formation of various reaction products such as SiO2, zircon (ZrSiO4), iron silicide (FeSi) and hercynite (FeAl2O4) indicating the occurrence of various side reactions between the different phases of the coating as well as between the coating and the SiSiC substrate. The investigations showed that the ferrite is mainly reduced through reaction with silicon (Si), which is present in the SiSiC matrix, and silicon carbide (SiC). These results led to the formulation of a new redox mechanism for this system in which Zn-ferrite is reduced through Si forming silicon dioxide (SiO2) and through SiC forming SiO2 and carbon monoxide. A decline of hydrogen production within the first 20 cycles is suggested to be due to the growth of a silicon dioxide and zircon layer which acts as a diffusion barrier for the reacting specie. PMID:28809316

Material Analysis of Coated Siliconized Silicon Carbide (SiSiC) Honeycomb Structures for Thermochemical Hydrogen Production.

PubMed

Neises-von Puttkamer, Martina; Simon, Heike; Schmücker, Martin; Roeb, Martin; Sattler, Christian; Pitz-Paal, Robert

2013-01-31

In the present work, thermochemical water splitting with siliconized silicon carbide (SiSiC) honeycombs coated with a zinc ferrite redox material was investigated. The small scale coated monoliths were tested in a laboratory test-rig and characterized by X-ray diffractometry (XRD) and Scanning Electron Microscopy (SEM) with corresponding micro analysis after testing in order to characterize the changes in morphology and composition. Comparison of several treated monoliths revealed the formation of various reaction products such as SiO₂, zircon (ZrSiO₄), iron silicide (FeSi) and hercynite (FeAl₂O₄) indicating the occurrence of various side reactions between the different phases of the coating as well as between the coating and the SiSiC substrate. The investigations showed that the ferrite is mainly reduced through reaction with silicon (Si), which is present in the SiSiC matrix, and silicon carbide (SiC). These results led to the formulation of a new redox mechanism for this system in which Zn-ferrite is reduced through Si forming silicon dioxide (SiO₂) and through SiC forming SiO₂ and carbon monoxide. A decline of hydrogen production within the first 20 cycles is suggested to be due to the growth of a silicon dioxide and zircon layer which acts as a diffusion barrier for the reacting specie.

Iron-carbonate interaction at Earth's core-mantle boundary

NASA Astrophysics Data System (ADS)

Dorfman, S. M.; Badro, J.; Nabiei, F.; Prakapenka, V.; Gillet, P.

2015-12-01

Carbon storage and flux in the deep Earth are moderated by oxygen fugacity and interactions with iron-bearing phases. The amount of carbon stored in Earth's mantle versus the core depends on carbon-iron chemistry at the core-mantle boundary. Oxidized carbonates subducted from Earth's surface to the lowermost mantle may encounter reduced Fe0 metal from disproportionation of Fe2+ in lower mantle silicates or mixing with the core. To understand the fate of carbonates in the lowermost mantle, we have performed experiments on sandwiches of single-crystal (Ca0.6Mg0.4)CO3 dolomite and Fe foil in the laser-heated diamond anvil cell at lower mantle conditions of 49-110 GPa and 1800-2500 K. Syntheses were conducted with in situ synchrotron X-ray diffraction to identify phase assemblages. After quench to ambient conditions, samples were sectioned with a focused Ga+ ion beam for composition analysis with transmission electron microscopy. At the centers of the heated spots, iron melted and reacted completely with the carbonate to form magnesiowüstite, iron carbide, diamond, magnesium-rich carbonate and calcium carbonate. In samples heated at 49 and 64 GPa, the two carbonates exhibit a eutectoid texture. In the sample heated at 110 GPa, the carbonates form rounded ~150-nm-diameter grains with a higher modal proportion of interspersed diamonds. The presence of reduced iron in the deep lower mantle and core-mantle boundary region will promote the formation of diamonds in carbonate-bearing subducted slabs. The complete reaction of metallic iron to oxides and carbides in the presence of mantle carbonate supports the formation of these phases at the Earth's core-mantle boundary and in ultra-low velocity zones.

Atomic-Scale Design of Iron Fischer-Tropsch Catalysts: A Combined Computational Chemistry, Experimental, and Microkinetic Modeling Approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manos Mavrikakis; James A. Dumesic; Amit A. Gokhale

2006-03-03

Efforts during this second year focused on four areas: (1) continued searching and summarizing of published Fischer-Tropsch synthesis (FTS) mechanistic and kinetic studies of FTS reactions on iron catalysts; (2) investigation of CO adsorption/desorption and temperature programmed hydrogenation (TPH) of carbonaceous species after FTS on unsupported iron and alumina-supported iron catalysts; (3) activity tests of alumina-supported iron catalysts in a fixed bed reactor; (4) sequential design of experiments, for the collection of rate data in a Berty CSTR reactor, and nonlinear-regression analysis to obtain kinetic parameters. Literature sources describing mechanistic and kinetic studies of Fischer-Tropsch synthesis on iron catalysts weremore » compiled in a review. Temperature-programmed desorption/reaction methods (the latter using mass-spectrometry detection and also thermogravimetric analyzer (TGA)) were utilized to study CO adsorption/-desorption on supported and unsupported iron catalysts. Molecular and dissociative adsorptions of CO occur on iron catalysts at 25-150 C. The amounts adsorbed and bond strengths of adsorption are influenced by supports and promoters. That CO adsorbs dissociatively on polycrystalline Fe at temperatures well below those of FT reaction indicates that CO dissociation is facile and unlikely to be the rate-limiting step during FTS. Carbonaceous species formed after FT reaction for only 5 minutes at 200 C were initially hydrogenated under mild, isothermal condition (200 C and 1 atm), followed by TPH to 800 C. During the mild, isothermal hydrogenation, only about 0.1-0.2 mL of atomic carbon is apparently removed, while during TPH to 800 C multilayer equivalents of atomic, polymeric, carbidic, and graphitic carbons are removed. Rates of CO conversion on alumina-supported iron catalysts at 220-260 C and 20 atm are correlated well by a Langmuir-Hinshelwood expression, derived assuming carbon hydrogenation to CH and OH recombination to water to be rate-determining steps. In the coming year, studies will focus on quantitative determination of the rates of kinetically-relevant elementary steps on Fe catalysts with/without K and Pt promoters and at various levels of Al{sub 2}O{sub 3} support, providing a database for understanding (1) effects of promoter and support on elementary kinetic parameters and (2) for validation of computational models that incorporate effects of surface structure and promoters. Kinetic parameters will be incorporated into a microkinetics model, enabling prediction of rate without invoking assumptions, e.g. of a rate-determining step or a most-abundant surface intermediate. Calculations using periodic, self-consistent Density Functional Theory (DFT) methods were performed on two model surfaces: (1) Fe(110) with 1/4 ML subsurface carbon, and (2) Fe(110) with 1/4 ML Pt adatoms. Reaction networks for FTS on these systems were characterized in full detail by evaluating the thermodynamics and kinetics of each elementary step. We discovered that subsurface C stabilizes all the reactive intermediates, in contrast to Pt, which destabilizes most of them. A comparative study of the reactivities of the modified-Fe surfaces against pure Fe is expected to yield a more comprehensive understanding of promotion mechanisms for FTS on Fe.« less

Iron-carbide cluster thermal dynamics for catalyzed carbon nanotube growth

NASA Astrophysics Data System (ADS)

Ding, Feng; Bolton, Kim; Rosén, Arne

2004-07-01

Molecular dynamics simulations have been used to study the thermal behavior of FeN-mCm clusters where N, the total number of atoms, extends up to 2400. Comparison of the computed results with experimental data shows that the simulations yield the correct trends for the liquid-solid region of the iron-carbide phase diagram as well as the correct dependence of cluster melting point as a function of cluster size. The calculation indicates that, when carbon nanotubes (CNTs) are grown on large (>3-4 nm) catalyst particles at low temperatures (<1200 K), the catalyst particles are not completely molten. It is argued that the mechanism of CNT growth under these conditions may be governed by the surface melting of the cluster. .

Kinetic Parameters of Secondary Carbide Precipitation in High-Cr White Iron Alloyed by Mn-Ni-Mo-V Complex

NASA Astrophysics Data System (ADS)

Efremenko, V. G.; Chabak, Yu. G.; Brykov, M. N.

2013-05-01

This study presents kinetics of precipitation of secondary carbides in 14.55%Cr-Mn-Ni-Mo-V white cast iron during the destabilization heat treatment. The as-cast iron was heat treated at temperatures in the range of 800-1100 °C with soaking up to 6 h. Investigation was carried out by optical and electron microscopy, dilatometric analysis, Ms temperature measurement, and bulk hardness evaluation. TTT-curve of precipitation process of secondary carbides (M7C3, M23C6, M3C2) has been constructed in this study. It was determined that the precipitation occurs at the maximum rate at 950 °C where the process is started after 10 s and completed within 160 min further. The precipitation leads to significant increase of Ms temperature and bulk hardness; large soaking times at destabilization temperatures cause coarsening of secondary carbides and decrease in particles number, followed by decrease in hardness. The results obtained are discussed in terms of solubility of carbon in the austenite and diffusion activation of Cr atoms. The precipitation was found to consist of two stages with activation energies of 196.5 kJ/g-mole at the first stage and 47.1 kJ/g-mole at the second stage.

Cobalt-Free Permanent Magnet Alloys.

DTIC Science & Technology

1984-10-01

carbide co- UC CbC lumbium carbide M003 Uranium carbide - tho- UC 2 25ThC rium carbide ZrO2 MgO WOs Use of this Process for MnAlC As indicated in the...cobalt. Free World Cobal Consumption Estimated Breakdown by End Uses Magnetic alloys 20% Cemented carbides - 5% 30 SuPerolloy _ 15% Other steels and...would normally result in the formation of binary alloy of TbFe 2 and preventing the formation of amorphous alloy (Fe-B) contain- ing Tb. The

Iron and nickel isotope compositions of presolar silicon carbide grains from supernovae

NASA Astrophysics Data System (ADS)

Kodolányi, János; Stephan, Thomas; Trappitsch, Reto; Hoppe, Peter; Pignatari, Marco; Davis, Andrew M.; Pellin, Michael J.

2018-01-01

We report the carbon, silicon, iron, and nickel isotope compositions of twenty-five presolar SiC grains of mostly supernova (SN) origin. The iron and nickel isotope compositions were measured with the new Chicago Instrument for Laser Ionization, CHILI, which allows the analysis of all iron and nickel isotopes without the isobaric interferences that plagued previous measurements with the NanoSIMS. Despite terrestrial iron and nickel contamination, significant isotopic anomalies in 54Fe/56Fe, 57Fe/56Fe, 60Ni/58Ni, 61Ni/58Ni, 62Ni/58Ni, and 64Ni/58Ni were detected in nine SN grains (of type X). Combined multi-isotope data of three grains with the largest nickel isotope anomalies (>100‰ or <-100‰ in at least one isotope ratio, when expressed as deviation from the solar value) are compared with the predictions of two SN models, one with and one without hydrogen ingestion in the He shell prior to SN explosion. One grain's carbon-silicon-iron-nickel isotope composition is consistent with the prediction of the model without hydrogen ingestion, whereas the other two grains' isotope anomalies could not be reproduced using either SN models. The discrepancies between the measured isotope compositions and model predictions may indicate element fractionation in the SN ejecta prior to or during grain condensation, and reiterate the need for three-dimensional SN models.

Investigation on the Microstructure and Ductility-Dip Cracking Susceptibility of the Butt Weld Welded with ENiCrFe-7 Nickel-Base Alloy-Covered Electrodes

NASA Astrophysics Data System (ADS)

Qin, Renyao; Wang, Huang; He, Guo

2015-03-01

The weld metal of the ENiCrFe-7 nickel-based alloy-covered electrodes was investigated in terms of the microstructure, the grain boundary precipitation, and the ductility-dip cracking (DDC) susceptibility. Besides the dendritic gamma-Ni(Cr,Fe) phase, several types of precipitates dispersed on the austenitic matrix were observed, which were determined to be the Nb-rich MC-type carbides with "Chinese script" morphology and size of approximately 3 to 10 µm, the Mn-rich MO-type oxides with size of approximately 1 to 2 µm, and the spherical Al/Ti-rich oxides with size of less than 1 µm. The discontinuous Cr-rich M23C6-type carbides predominantly precipitate on the grain boundaries, which tend to coarsen during reheating but begin to dissolve above approximately 1273 K (1000 °C). The threshold strain for DDC at each temperature tested shows a certain degree of correlation with the grain boundary carbides. The DDC susceptibility increases sharply as the carbides coarsen in the temperature range of 973 K to 1223 K (700 °C to 950 °C). The growth and dissolution of the carbides during the welding heat cycles deteriorate the grain boundaries and increase the DDC susceptibility. The weld metal exhibits the minimum threshold strain of approximately 2.0 pct at 1323 K (1050 °C) and the DTR less than 873 K (600 °C), suggesting that the ENiCrFe-7—covered electrode has less DDC susceptibility than the ERNiCrFe-7 bare electrode but is comparable with the ERNiCrFe-7A.

Accretion and differentiation of carbon in the early Earth.

PubMed

Tingle, T N

1998-05-15

The abundance of C in carbonaceous and ordinary chondrites decreases exponentially with increasing shock pressure as inferred from the petrologic shock classification of Scott et al. [Scott, E.R.D., Keil, K., Stoffler, D., 1992. Shock metamorphism of carbonaceous chondrites. Geochim. Cosmochim. Acta 56, 4281-4293] and Stoffler et al. [Stoffler, D., Keil, K., Scott, E.R.D., 1991. Shock metamorphism of ordinary chondrites. Geochim. Cosmochim. Acta 55, 3845-3867]. This confirms the experimental results of Tyburczy et al. [Tyburczy, J.A., Frisch, B., Ahrens, T.J., 1986. Shock-induced volatile loss from a carbonaceous chondrite: implications for planetary accretion. Earth Planet. Sci. Lett. 80, 201-207] on shock-induced devolatization of the Murchison meteorite showing that carbonaceous chondrites appear to be completely devolatilized at impact velocities greater than 2 km s-1. Both of these results suggest that C incorporation would have been most efficient in the early stages of accretion, and that the primordial C content of the Earth was between 10(24) and 10(25) g C (1-10% efficiency of incorporation). This estimate agrees well with the value of 3-7 x 10(24) g C based on the atmospheric abundance of 36Ar and the chondritic C/36Ar (Marty and Jambon, 1987). Several observations suggest that C likely was incorporated into the Earth's core during accretion. (1) Graphite and carbides are commonly present in iron meteorites, and those iron meteorites with Widmanstatten patterns reflecting the slowest cooling rates (mostly Group I and IIIb) contain the highest C abundances. The C abundance-cooling rate correlation is consistent with dissolution of C into Fe-Ni liquids that segregated to form the cores of the iron meteorite parent bodies. (2) The carbon isotopic composition of graphite in iron meteorites exhibits a uniform value of -5% [Deines, P., Wickman, F.E. 1973. The isotopic composition of 'graphitic' carbon from iron meteorites and some remarks on the troilitic sulfur of iron meteorites. Geochim. Cosmochim. Acta 37, 1295-1319; Deines, P., Wickman, F.E., 1975. A contribution to the stable carbon isotope geochemistry of iron meteorites. Geochim. Cosmochim. Acta 39, 547-557] identical to the mode in the distribution found in diamonds, carbonatites and oceanic basalts [Mattey, D.P., 1987. Carbon isotopes in the mantle. Terra Cognita 7, 31-37]. (3) The room pressure solubility of C in molten iron is 4.3 wt% C. Phase equilibria confirm that the Fe-C eutectic persists to 12 GPa, and thermochemical calculations for the Fe-C-S system by Wood [Wood, B.J., 1993. Carbon in the core. Earth Planet. Sci. Lett. 117, 593-607] predict that C is soluble in Fe liquids at core pressures. The abundance of 36Ar in chondrites decreases exponentially with increasing shock pressure as observed for C. It is well known that noble gases are positively correlated and physically associated with C in meteorites [e.g. Otting, W., Zahringer J., 1967. Total carbon content and primordial rare gases in chondrites. Geochim. Cosmochim. Acta 31, 1949-1960; Reynolds, J.H., Frick, U., Niel, J.M., Phinney, D.L., 1978. Rare-gas-rich separates from carbonaceous chondrites. Geochim. Cosmochim. Acta, 42, 1775-1797]. This suggests a mechanism by which primordial He and other noble gases may have incorporated into the Earth during accretion. The abundance of He in the primordial Earth required to sustain the modern He flux for 4 Ga (assuming a planetary 3 He/4 He; Reynolds et al. [Reynolds, J.H., Frick, U., Niel, J.M., Phinney, D.L., 1978. Rare-gas-rich separates from carbonaceous chondrites. Geochim. Cosmochim. Acta 42, 1775-1797] is calculated to be > or = 10(-8) cm3 g-1. This minimum estimate is consistent with a 1-10% efficiency of noble gas retention during accretion and the observed abundance of He in carbonaceous chondrites (10(-5) to 10(-4) cm3 g-1 excluding spallogenic contributions).

Surface analysis of mixed-conducting ferrite membranes by the conversion-electron Mössbauer spectroscopy

NASA Astrophysics Data System (ADS)

Waerenborgh, J. C.; Tsipis, E. V.; Yaremchenko, A. A.; Kharton, V. V.

2011-09-01

Conversion-electron Mössbauer spectroscopy analysis of iron surface states in the dense ceramic membranes made of 57Fe-enriched SrFe 0.7Al 0.3O 3- δ perovskite, shows no traces of reductive decomposition or carbide formation in the interfacial layers after operation under air/CH 4 gradient at 1173 K, within the limits of experimental uncertainty. The predominant trivalent state of iron cations at the membrane permeate-side surface exposed to flowing dry methane provides evidence of the kinetic stabilization mechanism, which is only possible due to slow oxygen-exchange kinetics and enables long-term operation of the ferrite-based ceramic reactors for natural gas conversion. At the membrane feed-side surface exposed to air, the fractions of Fe 4+ and Fe 3+ are close to those in the powder equilibrated at atmospheric oxygen pressure, suggesting that the exchange limitations to oxygen transport are essentially localized at the partially reduced surface.

Fabrication of Iron-Containing Carbon Materials From Graphite Fluoride

NASA Technical Reports Server (NTRS)

Hung, Ching-cheh

1996-01-01

Carbon materials containing iron alloy, iron metal, iron oxide or iron halide were fabricated. Typical samples of these metals were estimated to contain 1 iron atom per 3.5 to 5 carbon atoms. Those carbon materials containing iron alloy, iron metal, and/or Fe3O4 were magnetic. The kinetics of the fabrication process were studied by exposing graphite fluoride (CF(0.68)) to FeCl3 over a 280 to 420 C temperature range. Between 280 and 295 C, FeCl3 quickly entered the structure of CF(0.68), broke the carbon-fluorine bonds, and within 10 to 30 min, completely converted it to carbon made up of graphite planes between which particles of crystalline FeF3 and noncrystalline FeCl3 were located. Longer reaction times (e.g., 28 hr) or higher reaction temperatures (e.g., 420 C) produced materials containing graphite, a FeCl3-graphite intercalation compound, FeCl2(center dot)4H2O, and FeCl2(center dot)2H2O. These products were further heat treated to produce iron-containing carbon materials. When the heating temperature was kept in the 750 to 850 C range, and the oxygen supply was kept at the optimum level, the iron halides in the carbon structure were converted to iron oxides. Raising the heat to temperatures higher than 900 C reduced such iron oxides to iron metal. The kinetics of these reactions were used to suggest processes for fabricating carbon materials containing iron alloy. Such processes were then tested experimentally. In one of the successful trial runs, commercially purchased CF(0.7) powder was used as the reactant, and NiO was added during the final heating to 1200 C as a source of both nickel and oxygen. The product thus obtained was magnetic and was confirmed to be a nickel-iron alloy in carbon.

Alumina-Forming Austenitic Stainless Steels Strengthened by Laves Phase and MC Carbide Precipitates

NASA Astrophysics Data System (ADS)

Yamamoto, Y.; Brady, M. P.; Lu, Z. P.; Liu, C. T.; Takeyama, M.; Maziasz, P. J.; Pint, B. A.

2007-11-01

Creep strengthening of Al-modified austenitic stainless steels by MC carbides or Fe2Nb Laves phase was explored. Fe-20Cr-15Ni-(0-8)Al and Fe-15Cr-20Ni-5Al base alloys (at. pct) with small additions of Nb, Mo, W, Ti, V, C, and B were cast, thermally-processed, and aged. On exposure from 650 °C to 800 °C in air and in air with 10 pct water vapor, the alloys exhibited continuous protective Al2O3 scale formation at an Al level of only 5 at. pct (2.4 wt pct). Matrices of the Fe-20Cr-15Ni-5Al base alloys consisted of γ (fcc) + α (bcc) dual phase due to the strong α-Fe stabilizing effect of the Al addition and exhibited poor creep resistance. However, adjustment of composition to the Fe-15Cr-20Ni-5Al base resulted in alloys that were single-phase γ-Fe and still capable of alumina scale formation. Alloys that relied solely on Fe2Nb Laves phase precipitates for strengthening exhibited relatively low creep resistance, while alloys that also contained MC carbide precipitates exhibited creep resistance comparable to that of commercially available heat-resistant austenitic stainless steels. Phase equilibria studies indicated that NbC precipitates in combination with Fe2Nb were of limited benefit to creep resistance due to the solution limit of NbC within the γ-Fe matrix of the alloys studied. However, when combined with other MC-type strengtheners, such as V4C3 or TiC, higher levels of creep resistance were obtained.

Effects of iron electrovalence and species on growth and astaxanthin production of Haematococcus pluvialis

NASA Astrophysics Data System (ADS)

Cai, Minggang; Li, Zhe; Qi, Anxiang

2009-05-01

To increase the cell concentration and the accumulation of astaxanthin in the cultivation of Haematococcus pluvialis, effects of different iron electrovalencies (Fe2+-EDTA and Fe3+-EDTA) and species (Fe-EDTA, Fe(OH){x/32x} and FeC6H5O7) addition on cell growth and accumulation of astaxanthin were studied. Results show that different iron electrovalencies have various effects on cell growth and astaxanthin accumulation of H. pluvialis. Compared with Fe3+-EDTA, Fe2+-EDTA stimulate more effectively the formation of astaxanthin. The maximum astaxanthin content (30.70 mg/g biomass cell) was obtained under conditions of 18 μmol/L Fe2+-EDTA, despite the lower cell density (2.3×105 cell/ml) in such condition. Fe3+-EDTA is more effective than Fe2+-EDTA in improving the cell growth. Especially, the maximal steady-state cell density, 2.9×105 cell/ml was obtained at 18 μmol/L Fe3+-EDTA addition. On the other hand, all the various species of iron (EDTA-Fe, Fe(OH){x/32x}, FeC6H5O7) are capable to improve the growth of the algae and astaxanthin production. Among the three iron species, FeC6H5O7 performed the best. Under the condition of a higher concentration (36 μmol/L) of FeC6H5O7, the cell density and astaxanthin production is 2 and 7 times higher than those of iron-limited group, respectively. The present study demonstrates that the effects of the stimulation with different iron species increased in the order of FeC6H5O7, Fe(OH){x/32x} and EDTA-Fe.

Field-emission property of self-purification SiC/SiOx coaxial nanowires synthesized via direct microwave irradiation using iron-containing catalyst

NASA Astrophysics Data System (ADS)

Zhou, Qing; Yu, Yongzhi; Huang, Shan; Meng, Jiang; Wang, Jigang

2017-07-01

SiC/SiOx coaxial nanowires were rapidly synthesized via direct microwave irradiation in low vacuum atmosphere. During the preparation process, only graphite, silicon, silicon dioxide powders were used as raw materials and iron-containing substance was employed as catalyst. Comprehensive characterizations were employed to investigate the microstructure of the products. The results showed that a great quantity of coaxial nanowires with uniform sizes and high aspect ratio had been successfully achieved. The coaxial nanowires consist of a silicon oxide (SiOx) shell and a β-phase silicon carbide (β-SiC) core that exhibited in special tube brush like. In additional, nearly all the products were achieved in the statement of pure SiC/SiOx coaxial nanowires without the existence of metallic catalyst, indicating that the self-removal of iron (Fe) catalyst should be occurred during the synthesis process. Photoluminescence (PL) spectral analysis result indicated that such novel SiC/SiOx coaxial nanowires exhibited significant blue-shift. Besides, the measurement results of field-emission (FE) demonstrated that the SiC/SiOx coaxial nanowires had ultralow turn-on field and threshold field with values of 0.2 and 2.1 V/μm, respectively. The hetero-junction structure formed between SiOx shell and SiC core, lots of emission sites, as well as clear tips of the nanowires were applied to explain the excellent FE properties.[Figure not available: see fulltext.

Substantiation of Epitaxial Growth of Diamond Crystals on the Surface of Carbide Fe3AlC0.66 Phase Nanoparticles.

PubMed

Dzevin, Ievgenij M; Mekhed, Alexander A

2017-12-01

Samples of Fe-Al-C alloys of varying composition were synthesized under high pressures and temperatures. From X-ray analysis data, only K-phase with usual for it average parameter of elemental lattice cell, a = 0.376 nm, carbide Fe 3 C and cubic diamond reflexes were present before and after cooling to the temperature of liquid nitrogen.Calculations were made of the parameters of unit cells, the enthalpy of formation of the Fe 3 AlC, Fe 3.125 Al 0.825 C 0.5 , Fe 3.5 Al 0.5 C 0.5 , Fe 3.5 Al 0.5 C, Fe 3 Al 0.66 C 0.66 , and Fe 3 AlC 0.66 unit cells and crystallographic planes were identified on which epitaxial growth of the diamond phase was possible, using density functional theory as implemented in the WIEN2k package.The possibility of epitaxial growth of diamond crystals on Fe 3 AlC 0.66 (K-phase) nanoparticles was, therefore, demonstrated. The [200] plane was established to be the most suitable plane for diamond growth, having four carbon atoms arranged in a square and a central vacancy which can be occupied by carbon during thermal-and-pressure treatment. Distances between carbon atoms in the [200] plane differ by only 5% from distances between the carbon atoms of a diamond. The electronic structure and energetic parameters of the substrate were also investigated. It was shown that the substrate with at least four intermediate layers of K-phase exhibits signs of stability such as negative enthalpy of formation and the Fermi level falling to minimum densities of states.

IN SITU Deposition of Fe-TiC Nanocomposite on Steel by Laser Cladding

NASA Astrophysics Data System (ADS)

Razavi, Mansour; Rahimipour, Mohammad Reza; Ganji, Mojdeh; Ganjali, Mansoreh; Gangali, Monireh

The possibility of deposition of Fe-TiC nanocomposite on the surface of carbon steel substrate with the laser coating method had been investigated. Mechanical milling was used for the preparation of raw materials. The mixture of milled powders was used as a coating material on the substrate steel surface and a CO2 laser was used in continuous mode for coating. Microstructural studies were performed by scanning electron microscopy. Determinations of produced phases, crystallite size and mean strain have been done by X-ray diffraction. The hardness and wear resistance of coated samples were measured. The results showed that the in situ formation of Fe-TiC nanocomposite coating using laser method is possible. This coating has been successfully used to improve the hardness and wear resistance of the substrate so that the hardness increased by about six times. Coated iron and titanium carbide crystallite sizes were in the nanometer scale.

Novel process and catalytic materials for converting CO2 and H2 containing mixtures to liquid fuels and chemicals.

PubMed

Meiri, Nora; Dinburg, Yakov; Amoyal, Meital; Koukouliev, Viatcheslav; Nehemya, Roxana Vidruk; Landau, Miron V; Herskowitz, Moti

2015-01-01

Carbon dioxide and water are renewable and the most abundant feedstocks for the production of chemicals and fungible fuels. However, the current technologies for production of hydrogen from water are not competitive. Therefore, reacting carbon dioxide with hydrogen is not economically viable in the near future. Other alternatives include natural gas, biogas or biomass for the production of carbon dioxide, hydrogen and carbon monoxide mixtures that react to yield chemicals and fungible fuels. The latter process requires a high performance catalyst that enhances the reverse water-gas-shift (RWGS) reaction and Fischer-Tropsch synthesis (FTS) to higher hydrocarbons combined with an optimal reactor system. Important aspects of a novel catalyst, based on a Fe spinel and three-reactor system developed for this purpose published in our recent paper and patent, were investigated in this study. Potassium was found to be a key promoter that improves the reaction rates of the RWGS and FTS and increases the selectivity of higher hydrocarbons while producing mostly olefins. It changed the texture of the catalyst, stabilized the Fe-Al-O spinel, thus preventing decomposition into Fe3O4 and Al2O3. Potassium also increased the content of Fe5C2 while shifting Fe in the oxide and carbide phases to a more reduced state. In addition, it increased the relative exposure of carbide iron on the catalysts surface, the CO2 adsorption and the adsorption strength. A detailed kinetic model of the RWGS, FTS and methanation reactions was developed for the Fe spinel catalyst based on extensive experimental data measured over a range of operating conditions. Significant oligomerization activity of the catalyst was found. Testing the pelletized catalyst with CO2, CO and H2 mixtures over a range of operating conditions demonstrated its high productivity to higher hydrocarbons. The composition of the liquid (C5+) was found to be a function of the potassium content and the composition of the feedstock.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jacobs, Gary; Pendyala, Venkat Ramana Rao; Martinelli, Michela

XANES K-edge spectra of potassium promoter in precipitated Fe catalysts were acquired following activation by carburization in CO and as a function of time on-stream during the course of a Fischer–Tropsch synthesis run for a 100Fe:2K catalyst by withdrawing catalysts, sealed in wax product, for analysis. CO-activated and end-of-run spectra of the catalyst were also obtained for a 100Fe:5K catalyst. Peaks representing electronic transitions and multiple scattering were observed and resembled reference spectra for potassium carbonate or potassium formate. The shift in the multiple scattering peak to higher energy was consistent with sintering of potassium promoter during the course ofmore » the reaction test. The catalyst, however, retained its carbidic state, as demonstrated by XANES and EXAFS spectra at the iron K-edge, suggesting that sintering of potassium did not adversely affect the carburization rate, which is important for preventing iron carbides from oxidizing. This method serves as a starting point for developing better understanding of the chemical state and changes in structure occurring with alkali promoter.« less

Atomic-Scale Design of Iron Fischer-Tropsch Catalysts; A Combined Computational Chemistry, Experimental, and Microkinetic Modeling Approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manos Mavrikakis; James Dumesic; Rahul Nabar

2008-09-29

This work focuses on (1) searching/summarizing published Fischer-Tropsch synthesis (FTS) mechanistic and kinetic studies of FTS reactions on iron catalysts; (2) preparation and characterization of unsupported iron catalysts with/without potassium/platinum promoters; (3) measurement of H{sub 2} and CO adsorption/dissociation kinetics on iron catalysts using transient methods; (3) analysis of the transient rate data to calculate kinetic parameters of early elementary steps in FTS; (4) construction of a microkinetic model of FTS on iron, and (5) validation of the model from collection of steady-state rate data for FTS on iron catalysts. Three unsupported iron catalysts and three alumina-supported iron catalysts weremore » prepared by non-aqueous-evaporative deposition (NED) or aqueous impregnation (AI) and characterized by chemisorption, BET, temperature-programmed reduction (TPR), extent-of-reduction, XRD, and TEM methods. These catalysts, covering a wide range of dispersions and metal loadings, are well-reduced and relatively thermally stable up to 500-600 C in H{sub 2} and thus ideal for kinetic and mechanistic studies. Kinetic parameters for CO adsorption, CO dissociation, and surface carbon hydrogenation on these catalysts were determined from temperature-programmed desorption (TPD) of CO and temperature programmed surface hydrogenation (TPSR), temperature-programmed hydrogenation (TPH), and isothermal, transient hydrogenation (ITH). A microkinetic model was constructed for the early steps in FTS on polycrystalline iron from the kinetic parameters of elementary steps determined experimentally in this work and from literature values. Steady-state rate data were collected in a Berty reactor and used for validation of the microkinetic model. These rate data were fitted to 'smart' Langmuir-Hinshelwood rate expressions derived from a sequence of elementary steps and using a combination of fitted steady-state parameters and parameters specified from the transient measurements. The results provide a platform for further development of microkinetic models of FTS on Fe and a basis for more precise modeling of FTS activity of Fe catalysts. Calculations using periodic, self-consistent Density Functional Theory (DFT) methods were performed on various realistic models of industrial, Fe-based FTS catalysts. Close-packed, most stable Fe(110) facet was analyzed and subsequently carbide formation was found to be facile leading to the choice of the FeC(110) model representing a Fe facet with a sub-surface C atom. The Pt adatom (Fe{sup Pt}(110)) was found to be the most stable model for our studies into Pt promotion and finally the role of steps was elucidated by recourse to the defected Fe(211) facet. Binding Energies(BEs), preferred adsorption sites and geometries for all FTS relevant stable species and intermediates were evaluated on each model catalyst facet. A mechanistic model (comprising of 32 elementary steps involving 19 species) was constructed and each elementary step therein was fully characterized with respect to its thermochemistry and kinetics. Kinetic calculations involved evaluation of the Minimum Energy Pathways (MEPs) and activation energies (barriers) for each step. Vibrational frequencies were evaluated for the preferred adsorption configuration of each species with the aim of evaluating entropy-changes, pre exponential factors and serving as a useful connection with experimental surface science techniques. Comparative analysis among these four facets revealed important trends in their relative behavior and roles in FTS catalysis. Overall the First Principles Calculations afforded us a new insight into FTS catalysis on Fe and modified-Fe catalysts.« less

Magnetite nano-islands on silicon-carbide with graphene

DOE PAGES

Anderson, Nathaniel A.; Zhang, Qiang; Hupalo, Myron; ...

2017-01-05

X-ray magnetic circular dichroism (XMCD) measurements of iron nano-islands grown on graphene and covered with a Au film for passivation reveal that the oxidation through defects in the Au film spontaneously leads to the formation of magnetite nano-particles (i.e, Fe 3O 4). The Fe nano-islands (20 and 75 monolayers; MLs) are grown on epitaxial graphene formed by thermally annealing 6HSiC( 0001) and subsequently covered, in the growth chamber, with nominal 20 layers of Au. Our X-ray absorption spectroscopy and XMCD measurements at applied magnetic fields show that the thin film (20 ML) is totally converted to magnetite whereas the thickermore » lm (75 ML) exhibits properties of magnetite but also those of pure metallic iron. Temperature dependence of the XMCD signal (of both samples) shows a clear transition at T V ≈ 120 K consistent with the Verwey transition of bulk magnetite. These results have implications on the synthesis of magnetite nano-crystals and also on their regular arrangements on functional substrates such as graphene.« less

Magnetite nano-islands on silicon-carbide with graphene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, Nathaniel A.; Zhang, Qiang; Hupalo, Myron

X-ray magnetic circular dichroism (XMCD) measurements of iron nano-islands grown on graphene and covered with a Au film for passivation reveal that the oxidation through defects in the Au film spontaneously leads to the formation of magnetite nano-particles (i.e, Fe 3O 4). The Fe nano-islands (20 and 75 monolayers; MLs) are grown on epitaxial graphene formed by thermally annealing 6HSiC( 0001) and subsequently covered, in the growth chamber, with nominal 20 layers of Au. Our X-ray absorption spectroscopy and XMCD measurements at applied magnetic fields show that the thin film (20 ML) is totally converted to magnetite whereas the thickermore » lm (75 ML) exhibits properties of magnetite but also those of pure metallic iron. Temperature dependence of the XMCD signal (of both samples) shows a clear transition at T V ≈ 120 K consistent with the Verwey transition of bulk magnetite. These results have implications on the synthesis of magnetite nano-crystals and also on their regular arrangements on functional substrates such as graphene.« less

Fischer–Tropsch Synthesis: XANES Spectra of Potassium in Promoted Precipitated Iron Catalysts as a Function of Time On-stream

DOE PAGES

Jacobs, Gary; Pendyala, Venkat Ramana Rao; Martinelli, Michela; ...

2017-06-06

XANES K-edge spectra of potassium promoter in precipitated Fe catalysts were acquired following activation by carburization in CO and as a function of time on-stream during the course of a Fischer–Tropsch synthesis run for a 100Fe:2K catalyst by withdrawing catalysts, sealed in wax product, for analysis. CO-activated and end-of-run spectra of the catalyst were also obtained for a 100Fe:5K catalyst. Peaks representing electronic transitions and multiple scattering were observed and resembled reference spectra for potassium carbonate or potassium formate. The shift in the multiple scattering peak to higher energy was consistent with sintering of potassium promoter during the course ofmore » the reaction test. The catalyst, however, retained its carbidic state, as demonstrated by XANES and EXAFS spectra at the iron K-edge, suggesting that sintering of potassium did not adversely affect the carburization rate, which is important for preventing iron carbides from oxidizing. This method serves as a starting point for developing better understanding of the chemical state and changes in structure occurring with alkali promoter.« less

Changes in surface chemistry of silicon carbide (0001) surface with temperature and their effect on friction

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1980-01-01

Friction studies were conducted with a silicon carbide (0001) surface contacting polycrystalline iron. The surface of silicon carbide was pretreated: (1) by bombarding it with argon ions for 30 minutes at a pressure of 1.3 pascals; (2) by heating it at 800 C for 3 hours in vacuum at a pressure of 10 to the minus eighth power pascal; or (3) by heating it at 1500 C for 3 hours in a vacuum of 10 to the minus eighth power pascal. Auger emission spectroscopy was used to determine the presence of silicon and carbon and the form of the carbon. The surfaces of silicon carbide bombarded with argon ions or preheated to 800 C revealed the main Si peak and a carbide type of C peak in the Auger spectra. The surfaces preheated to 1500 C revealed only a graphite type of C peak in the Auger spectra, and the Si peak had diminished to a barely perceptible amount. The surfaces of silicon carbide preheated to 800 C gave a 1.5 to 3 times higher coefficient of friction than did the surfaces of silicon carbide preheated to 1500 C. The coefficient of friction was lower in the 11(-2)0 direction than in the 10(-1)0 direction; that is, it was lower in the preferred crystallographic slip direction.

Phase identification in boron-containing powder metallurgy steel using EBSD in combination with EPMA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Ming-Wei, E-mail: mwwu@ntut.edu.tw; Cai, Wen-Zhang

2016-03-15

Boron (B) is extensively used to induce liquid phase sintering (LPS) in powder metallurgy (PM) steels and thereby increase the densification. The alloying elements in B-containing PM steels affect the boride phase, stability of the boride, the temperature of liquid formation, and the progress of LPS. However, the boride phase has not been systematically identified yet. The main objective of this study was to clarify the influences of alloying elements, including C, Cr, and Ni, on the boride phases using electron backscatter diffraction (EBSD) in combination with electron probe microanalysis (EPMA). Network structures consisting of ferrite, Fe{sub 2}B boride, andmore » Fe{sub 3}C carbide were extensively observed in the Fe–0.4B–0.5C steel. The portions of Fe{sub 2}B were sufficiently larger than those of Fe{sub 3}C, and Fe{sub 3}C was mostly distributed at the interfaces between ferrite and Fe{sub 2}B. Adding 1.5 wt.% Cr or 1.8 wt.% Ni to Fe–0.4B–0.5C steel completely changes the Fe{sub 2}B and Fe{sub 3}C phases to a M{sub 3}(B,C) phase, where M represents the metallic elements, including Fe, Cr, Mo, and Ni. Furthermore, Cr, Mo, B, and C atoms tend to concentrate on the M{sub 3}(B,C) phase, but Ni atoms do not. - Highlights: • Network structures consisting of ferrite, Fe{sub 2}B boride, and Fe{sub 3}C carbide were extensively observed in the Fe–0.4B–0.5C steel. • Adding 1.5 wt.% Cr or 1.8 wt.% Ni to Fe–0.4B–0.5C steel completely transforms the Fe{sub 2}B and Fe{sub 3}C phases to a M{sub 3}(B,C) phase. • Cr, Mo, B, and C atoms tend to concentrate on the M{sub 3}(B,C) phase, but Ni atoms do not.« less

Molecular and Electronic Structure of Thin Films of Protoporphyrin(IX)Fe(III)C1

DTIC Science & Technology

1991-11-10

Union Carbide). Electrical contact to the back side of the HOPG sample was made with a copper wire and conductive epoxy (Epo-tek H20E, Epoxy Technology...analysis of the contrast in STM images of copper phthalocyanine [641 and by Zheng and Tsong in their analysis of resonant tunneling via tip-localized...Electroanal. Chem. 1980, 110, 369. 71. Makinen, M.W.; Churg A.K. Iron Porphyri ns-P art One; Lever, A.B.P.; Gray, H.B., Eds.; Physical Bioinorganic

Heat treatment giving a stable high temperature micro-structure in cast austenitic stainless steel

DOEpatents

Anton, Donald L.; Lemkey, Franklin D.

1988-01-01

A novel micro-structure developed in a cast austenitic stainless steel alloy and a heat treatment thereof are disclosed. The alloy is based on a multicomponent Fe-Cr-Mn-Mo-Si-Nb-C system consisting of an austenitic iron solid solution (.gamma.) matrix reinforced by finely dispersed carbide phases and a heat treatment to produce the micro-structure. The heat treatment includes a prebraze heat treatment followed by a three stage braze cycle heat treatment.

Metal matrix composite of an iron aluminide and ceramic particles and method thereof

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneibel, Joachim H.

A metal matrix composite comprising an iron aluminide binder phase and a ceramic particulate phase such as titanium diboride, zirconium diboride, titanium carbide and tungsten carbide is made by heating a mixture of iron aluminide powder and particulates of one of the ceramics such as titanium diboride, zirconium diboride, titanium carbide and tungsten carbide in a alumina crucible at about 1450.degree. C. for about 15 minutes in an evacuated furnace and cooling the mixture to room temperature. The ceramic particulates comprise greater than 40 volume percent to about 99 volume percent of the metal matrix composite.

Metal matrix composite of an iron aluminide and ceramic particles and method thereof

DOEpatents

Schneibel, J.H.

1997-06-10

A metal matrix composite comprising an iron aluminide binder phase and a ceramic particulate phase such as titanium diboride, zirconium diboride, titanium carbide and tungsten carbide is made by heating a mixture of iron aluminide powder and particulates of one of the ceramics such as titanium diboride, zirconium diboride, titanium carbide and tungsten carbide in a alumina crucible at about 1,450 C for about 15 minutes in an evacuated furnace and cooling the mixture to room temperature. The ceramic particulates comprise greater than 40 volume percent to about 99 volume percent of the metal matrix composite.

Metal matrix composite of an iron aluminide and ceramic particles and method thereof

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneibel, J.H.

A metal matrix composite comprising an iron aluminide binder phase and a ceramic particulate phase such as titanium diboride, zirconium diboride, titanium carbide and tungsten carbide is made by heating a mixture of iron aluminide powder and particulates of one of the ceramics such as titanium diboride, zirconium diboride, titanium carbide and tungsten carbide in a alumina crucible at about 1,450 C for about 15 minutes in an evacuated furnace and cooling the mixture to room temperature. The ceramic particulates comprise greater than 40 volume percent to about 99 volume percent of the metal matrix composite.

Stress-relief cracking of a new ferritic steel

NASA Astrophysics Data System (ADS)

Nawrocki, Jesse Gerald

The mechanism of stress-relief cracking in the coarse-grained heat-affected zone (CGHAZ) of low-alloy ferritic steels was studied through a tempering study, stress-relaxation testing, and detailed microstructural characterization. A new ferritic alloy steel, HCM2S, was used as the model system. Common 2.25Cr-1 Mo steel, which is susceptible to stress-relief cracking, was used for comparison to HCM2S. The CGHAZ was simulated using Gleeble techniques. A dense distribution of small tungsten-rich carbides within the prior austenite grains induced secondary hardening in the CGHAZ of HCM2S. The CGHAZ of 2.25Cr-1 Mo steel exhibited secondary hardening due to the intragranular precipitation of many Fe-rich M3C carbides. The hardness of HCM2S was more stable at longer times and high temperatures than 2.25Cr-1 Mo steel due to the intragranular precipitation of small W and V-rich carbides. The CGHAZs of HCM2S and 2.25Cr-1 Mo steel were susceptible to stress-relief cracking between 575 and 725°C. HCM2S exhibited C-curve behavior with respect to the time to failure as a function of post-weld heat treatment (PWHT) temperature. No segregation of tramp elements to prior austenite grain boundaries was detected in HCM2S. Both intergranular and intragranular carbide precipitation controlled the stress-relief cracking behavior. The amount of intergranular failure increased with test temperature due to the increasing amounts of Fe-rich M3C carbides at the prior austenite grain boundaries. These carbides acted as cavity nucleation sites. The cavities coalesced to form microcracks along prior austenite grain boundaries. Eventually, the remaining uncracked areas could not support the load and failed by ductile rupture. The balance of intergranular and intragranular carbide precipitation resulted in the C-curve behavior. The nose of the C-curve occurred at 675°C. The intragranular regions were strong because of a dense distribution of W/Fe-rich carbides, but the prior austenite grain boundaries were weak due to a large amount of intergranular M3C carbides. A mechanism for stress-relief cracking in the CGHAZ of HCM2S has been proposed. The results of this study form a basis for heat treating and welding processing variables for HCM2S and 2.25Cr-1 Mo steel to avoid stress-relief cracking. In addition, these results can be applied to other materials to avoid microstructures susceptible to stress-relief cracking.

Carbon diffusion in solid iron as function of pressure and temperature

NASA Astrophysics Data System (ADS)

Stagno, V.; Crispin, K. L.; Fei, Y.

2012-12-01

The knowledge of carbon diffusion in metallic iron is of importance for both industrial and geological applications. In industry the diffusion properties of carbon apply to the massive production of steel through carburizing and galvanization processes at high temperature with the aim to improve the hardness and rust resistance of such materials. In geoscience the diffusion of carbon in metallic phases at high pressure and temperature is important for determining the rate of reactions and crystal growth of carbide phases likely coexisting with mantle silicates. Due to a small atomic radius, carbon is expected to dissolve by interstitial diffusion in solid metals. However, to date there are no experimental data available to understand the role that pressure plays on the mobilization of carbon through solid iron. Further, for light elements such as carbon or sulfur the activation energy is assumed to be lower than in case of lattice diffusion. However, with increasing pressure the activation volume must be taken into account to better understand diffusion processes at the atomic scale. We performed experiments using multianvil and piston cylinder devices at pressures between 1.5 and 6 GPa and temperature of 700-1200°C. Experiments were carried out using cylindrical glassy carbon sandwiched between layers of pure iron rods of known thickness enclosed in MgO capsule. Analytical techniques included FE-SEM for textural observation and accurate analyses of the interface between layers, while concentration profiles were measured using the electron microprobe with an optimized standardization procedure. Concentration profiles of carbon in iron were computed to determine the diffusion coefficients based on Fick's second law formulation assuming isotropic one dimension diffusion. Preliminary results confirm the positive temperature dependence of the diffusion coefficient for carbon widely discussed in literature. However, our results also show that a significant increase in pressure is required to affect the mobility of carbon through metallic iron by almost the same order of magnitude as cooling. The variation of the diffusion coefficient as function of temperature and pressure will be used to determine the activation energy and volume. It is known that the stability of carbide phases in the Earth's interior is mainly governed by the local Fe/C ratios. In the case of enriched mantle model, for instance, carbon in form of diamond will coexist with Fe7C3 for small amounts of metallic iron. In contrast, this would imply that at low carbon contents (<50 ppm) typical of a depleted mantle source, and at oxygen fugacity conditions lower than EMOD buffer, the transport of carbon will likely occur by diffusion through the coexisting metal phase. Results from this study will improve our understanding on the transport of carbon by diffusion at conditions of the Earth's interior and will provide new thermodynamic data to explain the fractionation of carbon by diffusion in other planetary bodies.

Effect of Discharge Time on Plasma Electrolytic Borocarbonitriding of Pure Iron

NASA Astrophysics Data System (ADS)

Jin, Xiaoyue; Wu, Jie; Wang, Bin; Yang, Xuan; Chen, Lin; Qu, Yao; Xue, Wenbin

The plasma electrolytic borocarbonitriding (PEB/C/N) process on pure iron was carried out in 25% borax solution with glycerine and carbamide additives under different discharge time at 360V. The morphology and structure of PEB/C/N hardened layers were analyzed by SEM and XRD. The hardness profiles of hardened layers were measured by microhardness test. Corrosion behavior of PEB/C/N layers was evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Their wear performance was carried out using a pin-disc friction and wear tester under dry sliding test. The PEB/C/N samples mainly consisted of α-Fe, Fe2B, Fe3C, FeN, FeB, Fe2O3 and Fe4N phases, and the Fe2B phase was the dominant phase in the boride layer. It was found that the thickness of boride layer increased with the discharge time and reached 14μm after 60min treatment. The microhardness of the boride layer was up to 2100HV, which was much higher than that of the bare pure iron (about 150HV). After PEB/C/N treatment, the corrosion resistance of pure iron was slightly improved. The friction coefficient of PEB/C/N treated pure iron decreased to 0.129 from 0.556 of pure iron substrate. The wear rate of the PEB/C/N layer after 60min under dry sliding against ZrO2 ball was only 1/10 of that of the bare pure iron. The PEB/C/N treatment is an effective way to improve the wear behavior of pure iron.

From iron coordination compounds to metal oxide nanoparticles.

PubMed

Iacob, Mihail; Racles, Carmen; Tugui, Codrin; Stiubianu, George; Bele, Adrian; Sacarescu, Liviu; Timpu, Daniel; Cazacu, Maria

2016-01-01

Various types, shapes and sizes of iron oxide nanoparticles were obtained depending on the nature of the precursor, preparation method and reaction conditions. The mixed valence trinuclear iron acetate, [Fe 2 III Fe II O(CH 3 COO) 6 (H 2 O) 3 ]·2H 2 O (FeAc1), μ 3 -oxo trinuclear iron(III) acetate, [Fe 3 O(CH 3 COO) 6 (H 2 O) 3 ]NO 3 ∙4H 2 O (FeAc2), iron furoate, [Fe 3 O(C 4 H 3 OCOO) 6 (CH 3 OH) 3 ]NO 3 ∙2CH 3 OH (FeF), iron chromium furoate, FeCr 2 O(C 4 H 3 OCOO) 6 (CH 3 OH) 3 ]NO 3 ∙2CH 3 OH (FeCrF), and an iron complex with an original macromolecular ligand (FePAZ) were used as precursors for the corresponding oxide nanoparticles. Five series of nanoparticle samples were prepared employing either a classical thermal pathway (i.e., thermal decomposition in solution, solvothermal method, dry thermal decomposition/calcination) or using a nonconventional energy source (i.e., microwave or ultrasonic treatment) to convert precursors into iron oxides. The resulting materials were structurally characterized by wide-angle X-ray diffraction and Fourier transform infrared, Raman, energy-dispersive X-ray, and X-ray fluorescence spectroscopies, as well as thermogravimetric analysis. The morphology was characterized by transmission electron microscopy, atomic force microscopy and dynamic light scattering. The parameters were varied within each route to fine tune the size and shape of the formed nanoparticles.

The influence of various cooling rates during laser alloying on nodular iron surface layer

NASA Astrophysics Data System (ADS)

Paczkowska, Marta; Makuch, Natalia; Kulka, Michał

2018-06-01

The results of research referring to modification of the nodular iron surface layer by laser alloying with cobalt were presented. The aim of this study was to analyze the possibilities of cobalt implementation into the surface layer of nodular iron in various laser heat treatment conditions (by generating different cooling rates of melted surface layer). The modified surface layer of nodular iron was analyzed with OM, SEM, TEM, XRD, EDS and Vickers microhardness tester. The modified surface layer of nodular iron after laser alloying consisted of: the alloyed zone (melted with cobalt), the transition zone and the hardened zone from solid state. The alloyed zone was characterized by higher microstructure homogeneity - in contrast to the transition and the hardened zones. All the alloyed zones contained a dendritic microstructure. Dendrites consisted of martensite needles and retained austenite. Cementite was also detected. It was stated, that due to similar dimension of iron and cobalt atoms, their mutual replacement in the crystal lattice could occur. Thus, formation of phases based on α solution: Co-Fe (44-1433) could not be excluded. Although cobalt should be mostly diluted in solid solutions (because of its content in the alloyed zone), the other newly formed phases as Co (ε-hex.), FeC and cobalt carbides: Co3C, CoC0.25 could be present in the alloyed zones as a result of unique microstructure creation during laser treatment. Pearlite grains were observed in the zone, formed using lower power density of the laser beam and its longer exposition time. Simply, such conditions resulted in the cooling rate which was lower than critical cooling rate. The alloyed zones, produced at a higher cooling rate, were characterized by better microstructure homogeneity. Dendrites were finer in this case. This could result from a greater amount of crystal nuclei appearing at higher cooling rate. Simultaneously, the increased amount of γ-Fe and Fe3C precipitates was expected in the alloyed zone formed at higher cooling rates. The hardness of nodular iron surface layer, alloyed with cobalt, was up to 4-times higher than the hardness of core material. The hardness of alloyed zones strongly depended on laser treatment conditions. In the case of lower cooling rate, lower hardness was observed due to more coarse-grained microstructure and a presence of pearlite. The hardness of the alloyed zone increased (from 850 to 950HV0.1) together with the increasing cooling rate (from 2 · 103 to nearly 9 · 103 °C/s). Laser treatment enabled a formation of surface layers on nodular iron, alloyed with cobalt. The microstructure of such a surface layer could be controlled by the laser processing parameters. High hardness and fine microstructure of the laser-alloyed nodular iron with cobalt should result in higher resistance to wear, corrosion and even (due to effect of cobalt addition) elevated temperatures during operation conditions of machine parts.

Physical and Mechanical Properties of W-Ni-Fe-Co Metal Foam Modified by Titanium Tungsten Carbide Alloying

NASA Astrophysics Data System (ADS)

Ishchenko, A. N.; Tabachenko, A. N.; Afanas'eva, S. A.; Belov, N. N.; Biryukov, Yu. A.; Burkin, V. V.; D'yachkovskii, A. S.; Rogaev, K. S.; Skosyrskii, A. B.; Yugov, N. T.

2018-02-01

The paper studies physical and mechanical properties of tungsten-nickel-iron-cobalt metal foam alloyed with titanium tungsten carbide. Test specimens are obtained by the liquid phase sintering of powder materials, including those containing tungsten nanopowders. High porosity metal foams are prepared through varying the porosity of powder specimens and the content of filling material. The penetration capability of cylinder projectiles made of new alloys is explored in this paper. It is shown that their penetration depth exceeds that of the prototype with relevant weight and size, made of tungsten-nickel-iron alloy, other factors being equal.

Effects of Pressure and Temperature on the Kinetics of Iron-magnesite Redox Reaction: Implication for the Genesis of Ultradeep Diamonds

NASA Astrophysics Data System (ADS)

Zhu, F.; Li, J.; Liu, J.; Lai, X.; Chen, B.; Meng, Y.

2016-12-01

Diamonds may be the products of redox reaction between carbonates in the subducted slabs and iron metal in the mantle [1]. Given the relatively low temperatures of the subducted slabs, however, it remains to be shown that such reaction can occur at sufficiently fast rate. To examine the influence of pressure and temperature (P-T) on the kinetics of iron-carbonate redox reaction, we performed in-situ synchrotron X-ray diffraction (XRD) experiments at the Advanced Photon Source, Argonne National Laboratory, using laser-heated diamond anvil cells. The starting material consists of an iron foil sandwiched between two magnesite pellets. Data were collected between 1050 and 1800 K at 50-100 K intervals, at seven pressures between 12 and 40 GPa, corresponding the depths where most ultradeep diamonds originated [2]. We obtained constraints on the Fe-MgCO3reaction boundary, which was located between the estimated temperatures on the surface of cold slabs near 1400 K and inside their interiors near 1000 K, and it had a similar slope as the slab geotherm [3]. Furthermore, the experiments revealed a significant effect of pressure on the extent and rate of the reaction. The XRD patterns showed that below 15 GPa the initial reaction products were iron carbides, which reacted with magnesite to form diamonds when the reaction completed in 60 minutes at 1300 to 1500 K. Above 18 GPa only iron carbides were observed in the XRD patterns even when all the iron was consumed, and iron carbides still coexisted with magnesite after 100 to 160 minutes at 1600 to 1800 K. Our results suggest that diamonds can be produced from iron-carbonate redox reaction at slab-mantle boundary conditions at the deeper part of the upper mantle, but diamond growth through this reaction is slow or kinetically hindered in the lower mantle. References[1] Palyanov, Y. N. et al. (2013). Proc. Nat. Aca. Sci., 110(51), 20408-20413. [2] Stachel, T. et al. (2005). Elements, 1(2), 73-78. [3] Eberle et al. (2002). Phys. Earth Planet. Int., 134(3), 191-202.

The material performance of HSS (high speed steel) tools and its relation with chemical composition and carbide distribution

NASA Astrophysics Data System (ADS)

Darmawan, B.; Kusman, M.; Hamdani, R. A.

2016-04-01

The study aims to compare the performance of two types of material HSS (High Speed Steel) are widely used. It also will be the chemical composition and distribution of carbide particles therein. Two types of HSS are available in the market: HSS from Germany (Bohler) and HSS from China. This research employed the pure experimental design. It consists of two stages. The first, aims to test/operate lathe machines to determine the lifetime and performance of tools based on specified wear criteria. The second, characterization of microstructure using SEM-EDS was conducted. Firstly, grinding of toolss was done so that the toolss could be used for cutting metal in the turning process. Grinding processes of the two types of toolss were done at the same geometry, that is side rake angle (12°-18°), angle of keenness (60°-68°), and side relief angle (10°-12°). Likewise, machining parameters were set in the same machining conditions. Based on the results of the tests, it is found that to reach 0.2 mm wear point, toolss made of HSS from Germany needed 24 minutes, while toolss made of HSS from China needed 8 minutes. Next, microstructure tests using SEM/EDS were done. The results of the SEM tests indicate that the carbide particles of HSS from Germany were more evenly distributed than the carbide particles of HSS from China. Carbide compounds identified in HSS from China were Cr23C6 and Fe4Mo2C. Oxide impurity of Al2O3 was also found in the material. On the other hand, in HSS from Germany, no impurity and other carbide compounds were identified, except Cr23C6 and Fe4Mo2C, also Fe4W2C, and VC or V4C3.

Fracture-tough, high hardness stainless steel and method of making same

NASA Technical Reports Server (NTRS)

Olson, Gregory B. (Inventor)

1993-01-01

A cryogenically-formed and tempered stainless steel is provided having improved fracture toughness and corrosion resistance at a given hardness level, such as, for example, of at least about Rc 60 for bearing applications. The steel consists essentially of, in weight %, about 21 to about 24% Co, about 11 to about 13% Cr, about 7 to about 9% Ni, about 0.1 to about 0.5% Mo, about 0.2 to about 0.3% V, about 0.28 to about 0.32% C, and the balance iron. The steel includes a cryogenically-formed martensitic microstructure tempered to include about 5 to about 10 volume % post-deformation retained austenite dispersed therein and M.sub.2 C-type carbides, where M is Cr, Mo, V, and/or Fe, dispersed in the microstructure.

Density functional theory study of interactions between carbon monoxide and iron tetraaza macrocyclic complexes, FeTXTAA (X = -Cl, -OH, -OCH3, -NH2, and -NO2).

PubMed

de Matos Mourão Neto, Isaias; Silva, Adilson Luís Pereira; Tanaka, Auro Atsushi; de Jesus Gomes Varela, Jaldyr

2017-02-01

This work describes a DFT level theoretical quantum study using the B3LYP functional with the Lanl2TZ(f)/6-31G* basis set to calculate parameters including the bond distances and angles, electronic configurations, interaction energies, and vibrational frequencies of FeTClTAA (iron-tetrachloro-tetraaza[14]annulene), FeTOHTAA (iron-tetrahydroxy-tetraaza[14]annulene), FeTOCH 3 TAA (iron- tetramethoxy-tetraaza[14]annulene), FeTNH 2 TAA (iron-tetraamino-tetraaza[14]annulene), and FeTNO 2 TAA (iron-tetranitro-tetraaza[14]annulene) complexes, as well as their different spin multiplicities. The calculations showed that the complexes were most stable in the triplet spin state (S = 1), while, after interaction with carbon monoxide, the singlet state was most stable. The reactivity of the complexes was evaluated using HOMO-LUMO gap calculations. Parameter correlations were performed in order to identify the best complex for back bonding (3d xz Fe → 2p x C and 3d yz Fe → 2p z C) with carbon monoxide, and the degree of back bonding increased in the order: FeTNO 2 TAA < FeTClTAA < FeTOHTAA < FeTOCH 3 TAA < FeTNH 2 TAA.

High-level ab initio predictions for the ionization energy, bond dissociation energies, and heats of formations of iron carbide (FeC) and its cation (FeC+).

PubMed

Lau, Kai-Chung; Chang, Yih-Chung; Lam, Chow-Shing; Ng, C Y

2009-12-31

The ionization energy (IE) of FeC and the 0 K bond dissociation energies (D(0)) and the heats of formation at 0 K (DeltaH(o)(f0)) and 298 K (DeltaH(o)(f298)) for FeC and FeC(+) are predicted by the single-reference wave function based CCSDTQ(Full)/CBS approach, which involves the approximation to the complete basis set (CBS) limit at the coupled cluster level up to full quadruple excitations. The zero-point vibrational energy (ZPVE) correction, the core-valence electronic corrections (up to CCSDT level), spin-orbit couplings, and relativistic effects (up to CCSDTQ level) are included in the calculations. The present calculations provide the correct symmetry predictions for the ground states of FeC and FeC(+) to be (3)Delta and (2)Delta, respectively. We have also examined the theoretical harmonic vibrational frequencies of FeC/FeC(+) at the ROHF-UCCSD(T) and UHF-UCCSD(T) levels. While the UHF-UCCSD(T) harmonic frequencies are in good agreement with the experimental measurements, the ROHF-UCCSD(T) yields significantly higher harmonic frequency predictions for FeC/FeC(+). The CCSDTQ(Full)/CBS IE(FeC) = 7.565 eV is found to compare favorably with the experimental IE value of 7.59318 +/- 0.00006 eV, suggesting that the single-reference-based coupled cluster theory is capable of providing reliable IE prediction for FeC, despite its multireference character. The CCSDTQ(Full)/CBS D(0)(Fe(+)-C) and D(0)(Fe-C) give the prediction of D(0)(Fe(+)-C) - D(0)(Fe-C) = 0.334 eV, which is consistent with the experimental determination of 0.3094 +/- 0.0001 eV. The D(0) calculations also support the experimental D(0)(Fe(+)-C) = 4.1 +/- 0.3 eV and D(0)(Fe-C) = 3.8 +/- 0.3 eV determined by the previous ion photodissociation study. The present calculations also provide the DeltaH(o)(f0)(DeltaH(o)(f298)) predictions for FeC/FeC(+). The analysis of the correction terms in these calculations shows that the core-valence and valence-valence electronic correlations beyond CCSD(T) wave function and the relativistic effects make significant contributions to the calculated thermochemical properties of FeC/FeC(+). For the experimental D(0) and DeltaH(o)(f0) values of FeC/FeC(+), which are not known to high precision, we recommend the CCSDTQ(Full)/CBS predictions [D(0)(Fe-C) = 3.778 eV, D(0)(Fe(+)-C) = 4.112 eV, DeltaH(o)(f0)(FeC) = 760.8 kJ/mol and DeltaH(o)(f0)(FeC(+)) = 1490.6 kJ/mol] based on the ZPVE corrections using the experimental vibrational frequencies of FeC and FeC(+).

From iron coordination compounds to metal oxide nanoparticles

PubMed Central

Iacob, Mihail; Racles, Carmen; Tugui, Codrin; Stiubianu, George; Bele, Adrian; Sacarescu, Liviu; Timpu, Daniel

2016-01-01

Various types, shapes and sizes of iron oxide nanoparticles were obtained depending on the nature of the precursor, preparation method and reaction conditions. The mixed valence trinuclear iron acetate, [Fe2 IIIFeIIO(CH3COO)6(H2O)3]·2H2O (FeAc1), μ3-oxo trinuclear iron(III) acetate, [Fe3O(CH3COO)6(H2O)3]NO3∙4H2O (FeAc2), iron furoate, [Fe3O(C4H3OCOO)6(CH3OH)3]NO3∙2CH3OH (FeF), iron chromium furoate, FeCr2O(C4H3OCOO)6(CH3OH)3]NO3∙2CH3OH (FeCrF), and an iron complex with an original macromolecular ligand (FePAZ) were used as precursors for the corresponding oxide nanoparticles. Five series of nanoparticle samples were prepared employing either a classical thermal pathway (i.e., thermal decomposition in solution, solvothermal method, dry thermal decomposition/calcination) or using a nonconventional energy source (i.e., microwave or ultrasonic treatment) to convert precursors into iron oxides. The resulting materials were structurally characterized by wide-angle X-ray diffraction and Fourier transform infrared, Raman, energy-dispersive X-ray, and X-ray fluorescence spectroscopies, as well as thermogravimetric analysis. The morphology was characterized by transmission electron microscopy, atomic force microscopy and dynamic light scattering. The parameters were varied within each route to fine tune the size and shape of the formed nanoparticles. PMID:28144555

Synthesis of core-shell iron nanoparticles via a new (novel) approach

NASA Astrophysics Data System (ADS)

Chaudhary, Rakesh P.; Koymen, Ali R.

2014-03-01

Carbon-encapsulated iron (Fe) nanoparticles were synthesized by a newly developed method in toluene. Transmission Electron Microscopy (TEM) and High Resolution Transmission Electron Microscopy (HRTEM) of the as prepared sample reveal that core-shell nanostructures have been formed with Fe as core and graphitic carbon as shell. Fe nanoparticles with diameter 11nm to 102 nm are encapsulated by 6-8 nm thick graphitic carbon layers. There was no iron carbide formation observed between the Fe core and the graphitic shell. The Fe nanoparticles have body centered cubic (bcc) crystal structure. The magnetic hysteresis loop of the as synthesized powder at room temperature showed a saturation magnetization of 9 Am2 kg-1. After thermal treatment crystalline order of the samples improved and hence saturation magnetization increased to 24 Am2kg-1. We foresee that the carbon-encapsulated Fe nanoparticles are biologically friendly and could have potential applications in Magnetic Resonance Imaging (MRI) and Photothermal cancer therapy.

Carbon-Coated Current Collectors for High-Power Li-Ion Secondary Batteries

DTIC Science & Technology

2012-08-29

deposition condition. Surface analysis indicates that this thin C layer does not contain interfacial Al-carbide layer. LiFePO4 electrode using this C...layer does not contain an interfacial Al-carbide layer. LiFePO4 electrode using this C-coated Al current collector exhibits higher capacity under 10 C...cathode. LiFePO4 (LFPO) was used as active materials for test, and this cathode material was purchased from Aleees company. The LFPO active layer

Iron-oxide Aerogel and Xerogel Catalyst Formulations: Characterization by 57Fe Mössbauer and XAFS Spectroscopies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huggins, F.; Bali, S; Huffman, G

2010-01-01

Iron in various iron-oxide aerogel and xerogel catalyst formulations ({ge}85% Fe{sub 2}O{sub 3}; {le}10% K, Co, Cu, or Pd) developed for possible use in Fischer-Tropsch synthesis (FTS) or the water-gas-shift (WGS) reaction has been examined by {sup 57}Fe Moessbauer spectroscopy. The seventeen samples consisted of both as-prepared and calcined aerogels and xerogels and their products after use as catalysts for FTS or the WGS reaction. Complementary XAFS spectra were obtained on the occurrence of the secondary elements in some of the same materials. A broad, slightly asymmetric, two-peak Moessbauer spectrum was obtained from the different as-prepared and calcined catalyst formulationsmore » in the majority of cases. Such spectra could only be satisfactorily fit with three quadrupole doublet components, but no systematic trends in the isomer shift and quadrupole splitting parameters and area ratios of the individual components could be discerned that reflected variations in the composition or preparation of the aerogel or xerogel materials. However, significant reductions were noted in the Moessbauer effective thickness (recoilless absorption effect per unit mass of iron) parameter, {chi}{sub eff}/g, determined at room temperature, for aerogels and xerogels compared to bulk iron oxides, reflecting the openness and lack of rigidity of the aerogel and xerogel structures. Moessbauer measurements for two aerogels over the range from 15 to 292 K confirmed the greatly diminished nature of this parameter at room temperature. Major increases in the effective thickness parameter were observed when the open structure of the aerogel or xerogel collapsed during calcination resulting in the formation of iron oxides (hematite, spinel ferrite). Similar structural changes were indicated by increases in this parameter after use of iron-oxide aerogels as catalysts for FTS or the WGS reaction, during which the iron-oxide aerogel was converted to a mixture of nonstoichiometric magnetite and the Haegg carbide, {chi}-Fe{sub 5}C{sub 2}, or nonstoichiometric magnetite, respectively.« less

Cast Iron Inoculation Enhanced by Supplementary Oxy-sulfides Forming Elements

NASA Astrophysics Data System (ADS)

Riposan, Iulian; Stan, Stelian; Uta, Valentin; Stefan, Ion

2017-09-01

Inoculation is one of the most important metallurgical treatments applied to the molten cast iron immediately prior to casting, to promote solidification without excessive eutectic undercooling, which favors carbides formation usually with undesirable graphite morphologies. The paper focused on the separate addition of an inoculant enhancer alloy [S, O, oxy-sulfides forming elements] with a conventional Ca-FeSi alloy, in the production of gray and ductile cast irons. Carbides formation tendency decreased with improved graphite characteristics as an effect of the [Ca-FeSi + Enhancer] inoculation combination, when compared to other Ca/Ca, Ba/Ca, RE-FeSi alloy treatments. Adding an inoculant enhancer greatly enhances inoculation, lowers inoculant consumption up to 50% or more and avoids the need to use more costly inoculants, such as a rare earth bearing alloy. The Inoculation Specific Factor [ISF] was developed as a means to more realistically measure inoculant treatment efficiency. It compares the ratio between the improved characteristic level and total inoculant consumption for this effect. Addition of any of the commercial inoculants plus the inoculant enhancer offered outstanding inoculation power [increased ISF] even at higher solidification cooling rates, even though the total enhancer addition was at a small fraction of the amount of commercial inoculant used.

Tuning the oxidative power of free iron-sulfur clusters.

PubMed

Lang, Sandra M; Zhou, Shaodong; Schwarz, Helmut

2017-03-15

The gas-phase reactions between a series of di-iron sulfur clusters Fe 2 S x + (x = 1-3) and the small alkenes C 2 H 4 , C 3 H 6 , and C 4 H 8 have been investigated by means of Fourier-transform ion-cyclotron resonance mass spectrometry. For all studied alkenes, the reaction efficiency is found to increase in the order Fe 2 S + < Fe 2 S 2 + < Fe 2 S 3 + . In particular, Fe 2 S + and Fe 2 S 2 + only form simple association products, whereas the sulfur-rich Fe 2 S 3 + is able to dehydrogenate propene and 2-butene via desulfurization of the cluster and formation of H 2 S. This indicates an increased propensity to induce oxidation reactions, i.e. oxidative power, of Fe 2 S 3 + that is attributed to an increased formal oxidation state of the iron atoms. Furthermore, the ability of Fe 2 S 3 + to activate and dissociate the C-H bonds of the alkenes is observed to increase with increasing size of the alkene and thus correlates with the alkene ionization energy.

One-pot synthesis of ternary zero-valent iron/phosphotungstic acid/g-C3N4 composite and its high performance for removal of arsenic(V) from water

NASA Astrophysics Data System (ADS)

Chen, Chunhua; Xu, Jia; Yang, Zhihua; Zhang, Li; Cao, Chunhua; Xu, Zhihua; Liu, Jiyan

2017-12-01

Ternary zero-valent iron/phos photungstic acid/g-C3N4 composite (Fe0@PTA/g-C3N4) was synthesized via photoreduction of iron (II) ions assisted by phosphotungstic acid (PTA) over g-C3N4 flakes. The as-prepared Fe0@PTA/g-C3N4 was investigated for removal of As(III) and As(V) species from water. The result showed that Fe0@PTA/g-C3N4 exhibited a better performance for As(V) removal than As(III) species from water, and the maximum adsorption capacity for As(V) was 70.3 mg/g, much higher than most of the reported adsorbents. As(V) removal by the Fe0@PTA/g-C3N4 adsorbent is mainly via a chemical process, synergistically occurring of reduction of As(V) and oxidation of Fe0. Moreover, the Fe0@PTA/g-C3N4 adsorbent showed effective As(V) removal from the simulated industrial wastewater and underground water. This study demonstrates that Fe0@PTA/g-C3N4 can be a potential adsorbent for As(V) removal due to its high performance, and simple one-pot synthesis process.

Effect of graphite addition into mill scale waste as a potential bipolar plates material of proton exchange membrane fuel cells

NASA Astrophysics Data System (ADS)

Khaerudini, D. S.; Prakoso, G. B.; Insiyanda, D. R.; Widodo, H.; Destyorini, F.; Indayaningsih, N.

2018-03-01

Bipolar plates (BPP) is a vital component of proton exchange membrane fuel cells (PEMFC), which supplies fuel and oxidant to reactive sites, remove reaction products, collects produced current and provide mechanical support for the cells in the stack. This work concerns the utilization of mill scale, a by-product of iron and steel formed during the hot rolling of steel, as a potential material for use as BPP in PEMFC. On the other hand, mill scale is considered a very rich in iron source having characteristic required such as for current collector in BPP and would significantly contribute to lower the overall cost of PEMFC based fuel cell systems. In this study, the iron reach source of mill scale powder, after sieving of 150 mesh, was mechanically alloyed with the carbon source containing 5, 10, and 15 wt.% graphite using a shaker mill for 3 h. The mixed powders were then pressed at 300 MPa and sintered at 900 °C for 1 h under inert gas atmosphere. The structural changes of powder particles during mechanical alloying and after sintering were studied by X-ray diffractometry, optical microscopy, scanning electron microscopy, and microhardness measurement. The details of the presence of iron, carbon, and iron carbide (Fe-C) as the products of reactions as well as sufficient mechanical strength of the sintered materials were presented in this report.

Ultra-reducing conditions in average mantle peridotites and in podiform chromitites: a thermodynamic model for moissanite (SiC) formation

NASA Astrophysics Data System (ADS)

Golubkova, Anastasia; Schmidt, Max W.; Connolly, James A. D.

2016-05-01

Natural moissanite (SiC) is reported from mantle-derived samples ranging from lithospheric mantle keel diamonds to serpentinites to podiform chromitites in ophiolites related to suprasubduction zone settings (Luobusa, Dongqiao, Semail, and Ray-Iz). To simulate ultra-reducing conditions and the formation of moissanite, we compiled thermodynamic data for alloys (Fe-Si-C and Fe-Cr), carbides (Fe3C, Fe7C3, SiC), and Fe-silicides; these data were augmented by commonly used thermodynamic data for silicates and oxides. Computed phase diagram sections then constrain the P- T- fO2 conditions of SiC stability in the upper mantle. Our results demonstrate that: Moissanite only occurs at oxygen fugacities 6.5-7.5 log units below the iron-wustite buffer; moissanite and chromite cannot stably coexist; increasing pressure does not lead to the stability of this mineral pair; and silicates that coexist with moissanite have X Mg > 0.99. At upper mantle conditions, chromite reduces to Fe-Cr alloy at fO2 values 3.7-5.3 log units above the moissanite-olivine-(ortho)pyroxene-carbon (graphite or diamond) buffer (MOOC). The occurrence of SiC in chromitites and the absence of domains with almost Fe-free silicates suggest that ultra-reducing conditions allowing for SiC are confined to grain scale microenvironments. In contrast to previous ultra-high-pressure and/or temperature hypotheses for SiC origin, we postulate a low to moderate temperature mechanism, which operates via ultra-reducing fluids. In this model, graphite-/diamond-saturated moderately reducing fluids evolve in chemical isolation from the bulk rock to ultra-reducing methane-dominated fluids by sequestering H2O into hydrous phases (serpentine, brucite, phase A). Carbon isotope compositions of moissanite are consistent with an origin of such fluids from sediments originally rich in organic compounds. Findings of SiC within rocks mostly comprised by hydrous phases (serpentine + brucite) support this model. Both the hydrous phases and the limited diffusive equilibration of SiC with most minerals in the rocks indicate temperatures below 700-800 °C. Moissanite from mantle environments is hence a mineral that does not inform on pressure but on a low to moderate temperature environment involving ultra-reduced fluids. Any mineral in equilibrium with SiC could only contain traces of Fe2+ or Cr3+.

Iron speciation in peats: Chemical and spectroscopic evidence for the co-occurrence of ferric and ferrous iron in organic complexes and mineral precipitates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhattacharyya, Amrita; Schmidt, Michael P.; Stavitski, Eli

The speciation of iron (Fe) in organic matter (OM)-rich environments under in situ variable redox conditions is largely unresolved. Peatlands provide a natural setting to study Fe–OM interactions. Utilizing chemical, spectroscopic and theoretical modeling approaches, we report the chemical forms, oxidation states and local coordination environment of naturally occurring Fe in the vertically redox-stratified Manning peatlands of western New York. In addition, we report dominant carbon, sulfur and nitrogen species that can potentially stabilize the various Fe species present in these peatlands. Our results provide clear direct and indirect evidence for the co-occurrence of ferrous (Fe 2+) and ferric (Femore » 3+) iron species in peats under both oxic and anoxic conditions. Iron is mostly present within the operationally defined organic and amorphous (i.e., short range ordered, SRO) fractions; ferric iron primarily as magnetically isolated paramagnetic Fe 3+ in Fe(III)-organic complexes, but also in mineral forms such as ferrihydrite; ferrous iron in tetrahedral coordination in Fe(II)-organic complexes with minor contribution from pyrite. All of the Fe species identified stabilize Fe(III) and/or Fe(II) in anoxic and oxic peats. Fundamental differences are also observed in the relative proportion of C, S and N functionalities of OM in oxic and anoxic peats. Aromatic C=C, ester, phenol and anomeric C (R-O-C-O-R), as well as thiol, sulfide and heterocyclic N functionalities are more prevalent in anoxic peats. Collectively, our experimental evidence suggests iron forms coordination complexes with O-, S- and N-containing functional groups of OM. We posit the co-occurrence of organic and mineral forms of Fe(II) and Fe(III) in both oxic and anoxic peat layers results from dynamic complexation and hydrolysis-precipitation reactions that occur under variable redox conditions. In conclusion, our findings aid in understanding the crucial role OM plays in determining Fe species in soils and sediments.« less

Iron speciation in peats: Chemical and spectroscopic evidence for the co-occurrence of ferric and ferrous iron in organic complexes and mineral precipitates

DOE PAGES

Bhattacharyya, Amrita; Schmidt, Michael P.; Stavitski, Eli; ...

2017-10-31

The speciation of iron (Fe) in organic matter (OM)-rich environments under in situ variable redox conditions is largely unresolved. Peatlands provide a natural setting to study Fe–OM interactions. Utilizing chemical, spectroscopic and theoretical modeling approaches, we report the chemical forms, oxidation states and local coordination environment of naturally occurring Fe in the vertically redox-stratified Manning peatlands of western New York. In addition, we report dominant carbon, sulfur and nitrogen species that can potentially stabilize the various Fe species present in these peatlands. Our results provide clear direct and indirect evidence for the co-occurrence of ferrous (Fe 2+) and ferric (Femore » 3+) iron species in peats under both oxic and anoxic conditions. Iron is mostly present within the operationally defined organic and amorphous (i.e., short range ordered, SRO) fractions; ferric iron primarily as magnetically isolated paramagnetic Fe 3+ in Fe(III)-organic complexes, but also in mineral forms such as ferrihydrite; ferrous iron in tetrahedral coordination in Fe(II)-organic complexes with minor contribution from pyrite. All of the Fe species identified stabilize Fe(III) and/or Fe(II) in anoxic and oxic peats. Fundamental differences are also observed in the relative proportion of C, S and N functionalities of OM in oxic and anoxic peats. Aromatic C=C, ester, phenol and anomeric C (R-O-C-O-R), as well as thiol, sulfide and heterocyclic N functionalities are more prevalent in anoxic peats. Collectively, our experimental evidence suggests iron forms coordination complexes with O-, S- and N-containing functional groups of OM. We posit the co-occurrence of organic and mineral forms of Fe(II) and Fe(III) in both oxic and anoxic peat layers results from dynamic complexation and hydrolysis-precipitation reactions that occur under variable redox conditions. In conclusion, our findings aid in understanding the crucial role OM plays in determining Fe species in soils and sediments.« less

Interplay of magnetism and superconductivity in the compressed Fe-ladder compound BaFe 2 Se 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ying, Jianjun; Lei, Hechang; Petrovic, Cedomir

High pressure resistance, susceptibility, and Fe K β x-ray emission spectroscopy measurements were performed on Fe-ladder compound BaFe 2 Se 3 . Pressure-induced superconductivity was observed which is similar to the previously reported superconductivity in the BaFe 2 S 3 samples. The slope of local magnetic moment versus pressure shows an anomaly across the insulator-metal transition pressure in the BaFe 2 Se 3 samples. The local magnetic moment is continuously decreasing with increasing pressure, and the superconductivity appears only when the local magnetic moment value is comparable to the one in the iron-pnictide superconductors. Our results indicate that the compressedmore » BaFe 2 C h 3 ( C h = S , Se) is a new family of iron-based superconductors. Despite the crystal structures completely different from the known iron-based superconducting materials, the magnetism in this Fe-ladder material plays a critical role in superconductivity. This behavior is similar to the other members of iron-based superconducting materials.« less

Effect of Hydrogen and Carbon on the Melting Temperature of the Core

NASA Astrophysics Data System (ADS)

Nakajima, Y.; Sakamaki, K.; Takahashi, E.; Fukai, Y.; Suzuki, T.; Funakoshi, K.

2007-12-01

The temperature of the Earth's outer core has been discussed based on the melting temperature of Fe- O-S alloys (e.g., Boehler, 1996). Although hydrogen and carbon are the possible candidates of the core component, their effects on the melting temperature of iron at high-pressures are unclear. Using a Kawai-type multi-anvil apparatus at SPring-8 synchrotron, we carried out a series of melting experiments on FeH and Fe3C up to 20 and 28 GPa, respectively. In the experiments on FeH, Fe sponge mixed with MgO was packed into a NaCl container with a hydrogen source, LiAlH4 (e.g., Fukai et al., 1989). During heating under high-pressures, hydrogenation of iron was observed by volume change. The phase boundary between ɛ'-phase (low-temperature phase) and γ-phase (high-temperature phase) of iron-hydride was determined using both cooling and heating experiments. Hydrogen concentrations in the γ-FeHx and ɛ'-FeHx were calculated based on the excess volume data from that of pure iron. It is found that γ-FeHx and ɛ'-FeHx synthesized in our experiments at pressures between 10 and 20 GPa are nearly stoichiometric FeH. Melting temperature of the γ-FeH was determined by the abrupt change in the X-ray diffraction patterns (crystalline to amorphous). The melting temperatures were determined to be 1473, 1473, 1493, 1573 and 1593 K at 10, 11.5, 15, 18 and 20 GPa, respectively. In the experiments using Fe3C, the synthesized Fe3C powder was encapsulated in a MgO container. In the diffraction sequences during heating, the peaks of Fe3C disappeared, and the new peaks identified as those of Fe7C3 were observed with halo caused by liquid. Finally, the Fe7C3 peaks disappeared, and only the halo pattern was observed. Based on these observations, the incongruent melting of Fe3C to Fe7C3 and liquid is estimated to occur at 1823 and 1923 K at 19.7 and 27.0 GPa, respectively. The liquidus temperatures of the Fe3C composition are found to be at 2098 and 2198 K at 19.5 and 26.8 GPa, respectively. The melting temperatures of Fe3C determined by our experiments are >700 K lower than that of the previous estimation based on thermodynamic calculation (Wood, 1993). Our experimental results show a possibility that the hydrogen and carbon lower the melting temperature of iron (outer core) dramatically. The melting temperatures of γ-FeH and Fe3C at 20 GPa are already 500 K lower than that of pure iron estimated by Anderson and Isaak (2000). Extrapolating our experimental melting curves for FeH and Fe3C to core pressures using Lindemann's melting law, we obtained the melting temperatures to be ~2600 and ~2900 K at the core-mantle boundary (CMB), respectively. In the presence of both hydrogen and carbon, melting temperature of the Earth's outer core could be >1500 K lower than that of the previous estimates, implying that the temperature gap at CMB could be much smaller than the current estimates.

High Chromium Cast Irons: Destabilized-Subcritical Secondary Carbide Precipitation and Its Effect on Hardness and Wear Properties

NASA Astrophysics Data System (ADS)

Guitar, María Agustina; Suárez, Sebastián; Prat, Orlando; Duarte Guigou, Martín; Gari, Valentina; Pereira, Gastón; Mücklich, Frank

2018-05-01

This work evaluates the effect of a destabilization treatment combined with a subcritical diffusion (SCD) and a subsequent quenching (Q) steps on precipitation of secondary carbides and their influence on the wear properties of HCCI (16%Cr). The destabilization of the austenite at high temperature leads to a final microstructure composed of eutectic and secondary carbides, with an M7C3 nature, embedded in a martensitic matrix. An improved wear resistance was observed in the SCD + Q samples in comparison with the Q one, which was attributed to the size of secondary carbides.

Heart cells in culture: a model of myocardial iron overload and chelation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Link, G.; Pinson, A.; Hershko, C.

1985-08-01

The effect of iron loading and chelation was studied in heart cell cultures obtained from newborn rats. Radioactive iron uptake per 2 X 10(6) cells/24 hr was 3.8% for /sup 59/Fe-transferrin, 15.8% for /sup 59/Fe-ferric ammonium citrate (FeAC) at 20 micrograms Fe/ml in 20% serum, and 37.1% for /sup 59/FeAC at 20 micrograms Fe/ml in serum-free medium. About one third of the cellular radioactive iron was in ferritin and the rest in an insoluble lysosomal fraction. Iron uptake was almost completely inhibited by reducing the incubation temperature from 37 degrees C to 10 degrees C. Intracellular concentrations of malonyldialdehyde (MDA)more » were doubled after 15 minutes of iron loading and reached maximal concentrations at 3 hours. Conversely, iron mobilization by deferoxamine at concentrations ranging from 0.025 mmol/L to 0.3 mmol/L resulted in normalization of cellular MDA concentrations, in direct proportion to the amounts of iron removed. These findings indicate that cultured myocardial cells are able to assimilate large amounts of nontransferrin iron and that iron uptake and mobilization are associated with striking changes in lipid peroxidation as manifested by the respective increase and decrease in cellular MDA concentrations.« less

What makes the T c of monolayer FeSe on SrTiO 3 so high: a sign-problem-free quantum Monte Carlo study

DOE PAGES

Li, Zi-Xiang; Wang, Fa; Yao, Hong; ...

2016-04-30

Monolayer FeSe films grown on SrTiO 3 (STO) substrate show superconducting gap-opening temperatures (T c) which are almost an order of magnitude higher than those of the bulk FeSe and are highest among all known Fe-based superconductors. Angle-resolved photoemission spectroscopy observed “replica bands” suggesting the importance of the interaction between FeSe electrons and STO phonons. These facts rejuvenated the quest for T c enhancement mechanisms in iron-based, especially iron-chalcogenide, superconductors. Here, we perform the first numerically-exact sign-problem-free quantum Monte Carlo simulations to iron-based superconductors. We (1) study the electronic pairing mechanism intrinsic to heavily electron doped FeSe films, and (2)more » examine the effects of electron–phonon interaction between FeSe and STO as well as nematic fluctuations on T c. Armed with these results, we return to the question “what makes the T c of monolayer FeSe on SrTiO 3 so high?” in the conclusion and discussions.« less

Effect of Aging Isothermal Time on the Microstructure and Room-Temperature Impact Toughness of Fe-24.8Mn-7.3Al-1.2C Austenitic Steel with κ-Carbides Precipitation

NASA Astrophysics Data System (ADS)

Feng, Yifan; Song, Renbo; Pei, Zhongzheng; Song, Renfeng; Dou, Guoyu

2018-03-01

The microstructure and impact toughness of the as-cast Fe-24.8Mn-7.3Al-1.2C austenitic steel after solution treatment and subsequent aging treatment were investigated in the present work. Research on the κ-carbides precipitation behavior was carried out by transmission electron microscope. The results show that nano-sized coherent κ-carbides were obtained in the as-solutionized steel after aging treatment, which produced precipitation hardening. After being aging treated at 550 °C for 1 h, the steel with regular hexagonal grain structure exhibited a good combination of yield strength ( 574 MPa) and room-temperature impact toughness ( 168 J). In the present steel, the typical cube-on-cube orientation relationship between austenite and κ-carbides was observed. However, due to the long aging isothermal time and high C content, the coarse intergranular κ'-carbide was formed and grew along the austenite grain boundary, which caused this orientation relationship to be destroyed and a dramatical increase of the coherency strain energy at grain boundary. Furthermore, serious embrittlement of grain boundaries caused that cleavage cracks trend to propagate along the grain boundaries. Accordingly, the room-temperature impact toughness decreased sharply. After aging isothermal time prolonging to 13 h, the Charpy V-notch impact toughness was only 5 J and fracture mode turned to fully brittle fracture accompanied with flat facets, shear cracks and well-developed secondary crack.

Novel Flaxseed Gum Nanocomposites Are Slow Release Iron Supplements.

PubMed

Liang, Shan; Huang, Yu; Shim, Youn Young; Ma, Xiang; Reaney, Martin J T; Wang, Yong

2018-05-23

Nanocomposites, based on iron salts and soluble flaxseed gum (FG), were prepared as potential treatments of iron deficiency anemia (IDA). FG was extracted, characterized, and formulated into iron-loading nanocomposites via ion-exchange against FeCl 3 , Fe 2 (SO 4 ) 3 , FeCl 2 , and FeSO 4 ·7H 2 O. FG-iron nanocomposites preparation condition was optimized, and physicochemical properties of the nanocomposites were investigated. In vitro release kinetics of iron in simulated gastric fluid (SGF) was also evaluated. FG heteropolysaccharide, consisting of rhamnose (33.73%), arabinose (24.35%), xylose (14.23%), glucose (4.54%), and galactose (23.15%) monosaccharides, linked together via varieties of glycosidic bonds, was a good recipient for both ferric and ferrous irons under screened conditions (i.e., 80 °C, 2 h, I/G = 1:2). Iron loaded contents in the nanocomposites prepared from FG-FeCl 3 , FG-Fe 2 (SO 4 ) 3 , FG-FeCl 2 , and FG-FeSO 4 ·7H 2 O were 25.51%, 10.36%, 5.83%, and 22.83%, respectively. Iron in these nanocomposites was mostly in a bound state, especially in FG-FeCl 3 , due to chelation forming bonds between iron and polysaccharide hydroxyl or carboxyl groups and formed stable polysaccharide-iron crystal network structures. Free iron ions were effectively removed by ethanol treatments. Because of chelation, the nanocomposites delayed iron release in SGF and the release kinetics were consistent with Korsmeyer-Peppas model. This indicates that such complexes might reduce side effects of free iron in human stomach. Altogether, this study indicates that these synthetic FG-iron nanocomposites might be developed as novel iron supplements for iron deficiency, in which FG-FeCl 3 is considered as the best option.

Increasing the cooking temperature of meat does not affect nonheme iron absorption from a phytate-rich meal in women.

PubMed

Baech, Sussi B; Hansen, Marianne; Bukhave, Klaus; Kristensen, Lars; Jensen, Mikael; Sørensen, Sven S; Purslow, Peter P; Skibsted, Leif H; Sandström, Brittmarie

2003-01-01

The effect of increasing cooking temperatures of meat on nonheme iron absorption from a composite meal was investigated. Cysteine-containing peptides may have a role in the iron absorption enhancing effect of muscle proteins. Heat treatment can change the content of sulfhydryl groups produced from cysteine and thereby affect iron absorption. Twenty-one women (25 +/- 3 y) were served a basic meal without meat and two other meals consisting of the basic meal plus 75 g of pork meat cooked at 70, 95 or 120 degrees C. The meals were extrinsically labeled with (55)Fe or (59)Fe. Iron absorption was determined from measurements of whole-body (59)Fe retention and the activity of (55)Fe and (59)Fe in blood samples. Nonheme iron absorptions were 0.9 (0.5-4.0)% (P = 0.06), 0.7 (0.4-3.9)% (P = 0.1) and 2.0 (1.3-3.1)% (P < 0.001) greater when meat cooked at 70, 95 or 120 degrees C, respectively, was added to the basic meal. Increasing the cooking temperature of meat did not impair nonheme iron absorption compared with cooking at 70 degrees C. Because the cysteine content of meat decreased with increasing cooking temperature, this argues against a specific contribution of sulfhydryl groups from cysteine residues in the promotion of nonheme iron absorption by meat proteins.

Effect of different thermal treatments on the corrosion resistance of alloy 690 tubing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crum, J.R.; Heck, K.A.; Angeliu, T.M.

1990-03-01

A comparison of the carbide precipitation characteristics and corrosion resistance of commercially produced alloy 690 steam generator tubing from various sources, with different thermal treatments, was made. Four thermal treatments within the ranges of 700--720{degree}C (1292--1328{degree}F)/5--5.75 hrs and 871--927{degree}C (1600--1700{degree}F)/10 min were compared to one another and to two as-mill annealed tubes. All tubes were characterized with respect to chemical composition, mechanical properties, and microstructure. Overall carbide precipitation was determined by etching with phosphoric acid/nital, bromine-methanol and glyceregia/oxalic etchants. Scanning transmission electron microscope analysis provided detailed chromium depletion profiles across the grain boundary and carbide composition. Nitric acid intergranular attackmore » (IGA) tests were also conducted. C-ring stress corrosion cracking (SCC) tests, with stresses above the yield strength were then conducted in 350{degree}C (662{degree}F) deaerated 1, 10, and 50% NaOH and unstressed IGA tests were conducted in a NaOH-Na{sub 2}SO{sub 4}--Fe{sub 3}O{sub 4}--Fe{sub 2}O{sub 3} environment, also at 350{degree}C (662{degree}F). 2 tabs.« less

Activity and Stability of Dispersed Multi Metallic Pt-based Catalysts for CO Tolerance in Proton Exchange Membrane Fuel Cell Anodes.

PubMed

Hassan, Ayaz; Ticianelli, Edson A

2018-01-01

Studies aiming at improving the activity and stability of dispersed W and Mo containing Pt catalysts for the CO tolerance in proton exchange membrane fuel cell (PEMFC) anodes are revised for the following catalyst systems: (1) a carbon supported PtMo electrocatalyst submitted to heat treatments; (2) Pt and PtMo nanoparticles deposited on carbon-supported molybdenum carbides (Mo2C/C); (3) ternary and quaternary materials formed by PtMoFe/C, PtMoRu/C and PtMoRuFe/C and; (4) Pt nanoparticles supported on tungsten carbide/carbon catalysts and its parallel evaluation with carbon supported PtW catalyst. The heat-treated (600 oC) Pt-Mo/C catalyst showed higher hydrogen oxidation activity in the absence and in the presence of CO and better stability, compared to all other Mo-containing catalysts. PtMoRuFe, PtMoFe, PtMoRu supported on carbon and Pt supported on Mo2C/C exhibited similar CO tolerances but better stability, as compared to as-prepared PtMo supported on carbon. Among the tungsten-based catalysts, tungsten carbide supported Pt catalyst showed reasonable performance and reliable stability in comparison to simple carbon supported PtW catalyst, though an uneven level of catalytic activity towards H2 oxidation in presence of CO is observed for the former as compared to Mo containing catalyst. However, a small dissolution of Mo, Ru, Fe and W from the anodes and their migration toward cathodes during the cell operation is observed. These results indicate that the fuel cell performance and stability has been improved but not yet totally resolved.

Atomic scale study of grain boundary segregation before carbide nucleation in Ni-Cr-Fe Alloys

NASA Astrophysics Data System (ADS)

Li, Hui; Xia, Shuang; Liu, Wenqing; Liu, Tingguang; Zhou, Bangxin

2013-08-01

Three dimensional chemical information concerning grain boundary segregation before carbide nucleation was characterized by atom probe tomography in two Ni-Cr-Fe alloys which were aged at 500 °C for 0.5 h after homogenizing treatment. B, C and Si atoms segregation at grain boundary in Alloy 690 was observed. B, C, N and P atoms segregation at grain boundary in 304 austenitic stainless steel was observed. C atoms co-segregation with Cr atoms at the grain boundaries both in Alloy 690 and 304 austenitic stainless steel was found, and its effect on the carbide nucleation was discussed. The amount of each segregated element at grain boundaries in the two Ni-Cr-Fe alloys were analyzed quantitatively. Comparison of the grain boundary segregation features of the two Ni-Cr-Fe alloys were carried out based on the experimental results. The impurity and solute atoms segregate inhomogeneously in the same grain boundary both in 304 SS and Alloy 690. The grain boundary segregation tendencies (Sav) are B (11.8 ± 1.4) > P (5.4 ± 1.4) > N (4.7 ± 0.3) > C (3.7 ± 0.4) in 304 SS, and B (6.9 ± 0.9) > C (6.7 ± 0.4) > Si (1.5 ± 0.2) in Alloy 690. Cr atoms may co-segregate with C atoms at grain boundaries before carbide nucleation at the grain boundaries both in 304 SS and Alloy 690. Ni atoms generally deplete at grain boundary both in 304 SS and Alloy 690. The literature shows that the Ni atoms may co-segregate with P atoms at grain boundaries [28], but the P atoms segregation do not leads to Ni segregation in the current study. In the current study, Fe atoms may segregate or deplete at grain boundary in Alloy 690. But Fe atoms generally deplete at grain boundary in 304 SS. B atoms have the strongest grain boundary segregation tendency both in 304 SS and Alloy 690. The grain boundary segregation tendency and Gibbs free energy of B in 304 SS is higher than in Alloy 690. C atoms are easy to segregate at grain boundaries both in 304 SS and Alloy 690. The grain boundary segregation tendency and Gibbs free energy of C in Alloy 690 is higher than in 304 SS, due to the higher bulk C concentration and the site competition of P atoms which segregate at grain boundary [29,30]. It is imply that the segregation tendency is influenced by the bulk concentration of the segregates. Si atoms slightly segregate at grain boundaries in Alloy 690, but do not segregate at grain boundaries in 304 SS. N and P atoms segregate at grain boundary in 304 SS, and their segregation Gibbs free energy are similar. N atoms may be exhausted by the TiN precipitated in the matrix and can not be observed in the grain boundary of Alloy 690 [19]. Mn atoms deplete at grain boundary in 304 SS. This phenomenon is similar to that of proton irradiation induced segregation in 304 SS [32]. B, C, N, P segregation Gibbs energies are similar both in 304 SS and Alloy 690. B and C atoms segregate at grain boundary both in Alloy 690 and 304 SS, P and N segregate at grain boundary in 304 SS. Si atoms segregate at grain boundary in Alloy 690, but do not segregate at grain boundary in 304 SS. Cr enriches at grain boundary both in Alloy 690 and 304 SS, although carbide does not nucleate. Ni and Fe may segregate, deplete or homogeneously distribute at grain boundary in Alloy 690, but they deplete at grain boundary in 304 SS. C and Cr atoms co-segregate at grain boundaries before carbide nucleation in Alloy 690 and 304 SS. Combination with other results in literatures, the evolution of Cr concentration at grain boundary should be enrichment at grain boundary before carbide nucleation, depletion at grain boundary after carbide precipitation, and healing after obvious growth of carbide. After aging treatment at 500 °C for 0.5 h, the total reduction of grain boundary free energy due to segregation is 27.489 kJ/mol for Alloy 690 and 45.207 kJ/mol for 304.

Syntheses, crystal structures, and magnetic properties of the oxalato-bridged mixed-valence complexes (FeII(bpm)3]2[FeIII2(ox)5].8H2O and FeII(bpm)3Na(H2O)2Fe(ox)(3).4H2O (bpm = 2,2'-bipyrimidine).

PubMed

Armentano, D; De Munno, G; Faus, J; Lloret, F; Julve, M

2001-02-12

The preparation and crystal structures of two oxalato-bridged FeII-FeIII mixed-valence compounds, [FeII(bpm)3]2[FeIII2(ox)5].8H2O (1) and FeII(bpm)3Na(H2O)2FeIII(ox)(3).4H2O (2) (bpm = 2,2'-bipyrimidine; ox = oxalate dianion) are reported here. Complex 1 crystallizes in the triclinic system, space group P1, with a = 10.998(2) A, b = 13.073(3) A, c = 13.308(3) A, alpha = 101.95(2) degrees, beta = 109.20(2) degrees, gamma = 99.89(2) degrees, and Z = 1. Complex 2 crystallizes in the monoclinic system, space group P2(1)/c, with a = 12.609(2) A, b = 19.670(5) A, c = 15.843(3) A, beta = 99.46(1) degrees, and Z = 4. The structure of complex 1 consists of centrosymmetric oxalato-bridged dinuclear high-spin iron(III) [Fe2(ox)5]2- anions, tris-chelated low-spin iron(II) [Fe(bpm)3]2+ cations, and lattice water molecules. The iron atoms are hexacoordinated: six oxygen atoms (iron(III)) from two bidentate and one bisbidentate oxalato ligands and six nitrogen atoms (iron(II)) from three bidentate bpm groups. The Fe(III)-O(ox) and Fe(II)-N(bpm) bond distances vary in the ranges 1.967(3)-2.099(3) and 1.967(4)-1.995(3) A, respectively. The iron(III)-iron(III) separation across the bridging oxalato is 5.449(2) A, whereas the shortest intermolecular iron(III)-iron(II) distance is 6.841(2) A. The structure of complex 2 consists of neutral heterotrinuclear Fe(bpm)2Na(H2O)2Fe(ox)3 units and water molecules of crystallization. The tris-chelated low-spin iron(II) ([Fe(bpm)3]2+) and high-spin iron(III) ([Fe(ox)3]3-) entities act as bidentate ligands (through two bpm-nitrogen and two oxalato-oxygen atoms, respectively) toward the univalent sodium cation, yielding the trinuclear (bpm)2Fe(II)-bpm-Na(I)-ox-Fe(III)(ox)2 complex. Two cis-coordinated water molecules complete the distorted octahedral surrounding of the sodium atom. The ranges of the Fe(II)-N(bpm) and Fe(III)-O(ox) bond distances [1.968(6)-1.993(5) and 1.992(6)-2.024(6) A, respectively] compare well with those observed in 1. The Na-N(bpm) bond lengths (2.548(7) and 2.677(7) A) are longer than those of Na-O(ox) (2.514(7) and 2.380(7) A) and Na-O(water) (2.334(15) and 2.356(12) A). The intramolecular Fe(II)...Fe(III) separation is 6.763(2) A, whereas the shortest intermolecular Fe(II)...Fe(II) and Fe(III)...Fe(III) distances are 8.152(2) and 8.992(2) A, respectively. Magnetic susceptibility measurements in the temperature range 2.0-290 K for 1 reveal that the high-spin iron(III) ions are antiferromagnetically coupled (J = -6.6 cm-1, the Hamiltonian being defined as H = -JS1.S2). The magnitude of the antiferromagnetic coupling through the bridging oxalato in the magneto-structurally characterized family of formula [M2(ox)5](2m-10)+ (M = Fe(III) (1), Cr(III), and Ni(II)) is analyzed and discussed by means of a simple orbital model.

Study of self-ion irradiated nanostructured ferritic alloy (NFA) and silicon carbide-nanostructured ferritic alloy (SiC-NFA) cladding materials

NASA Astrophysics Data System (ADS)

Ning, Kaijie; Bai, Xianming; Lu, Kathy

2018-07-01

Silicon carbide-nanostructured ferritic alloy (SiC-NFA) materials are expected to have the beneficial properties of each component for advanced nuclear claddings. Fabrication of pure NFA (0 vol% SiC-100 vol% NFA) and SiC-NFAs (2.5 vol% SiC-97.5 vol% NFA, 5 vol% SiC-95 vol% NFA) has been reported in our previous work. This paper is focused on the study of radiation damage in these materials under 5 MeV Fe++ ion irradiation with a dose up to ∼264 dpa. It is found that the material surfaces are damaged to high roughness with irregularly shaped ripples, which can be explained by the Bradley-Harper (B-H) model. The NFA matrix shows ion irradiation induced defect clusters and small dislocation loops, while the crystalline structure is maintained. Reaction products of Fe3Si and Cr23C6 are identified in the SiC-NFA materials, with the former having a partially crystalline structure but the latter having a fully amorphous structure upon irradiation. The different radiation damage behaviors of NFA, Fe3Si, and Cr23C6 are explained using the defect reaction rate theory.

The selective activation of a C-F bond with an auxiliary strong Lewis acid: a method to change the activation preference of C-F and C-H bonds.

PubMed

Wang, Lin; Sun, Hongjian; Li, Xiaoyan; Fuhr, Olaf; Fenske, Dieter

2016-11-15

The selective activation of the C-F bonds in substituted (2,6-difluorophenyl)phenylimines (2,6-F 2 H 3 C 6 -(C[double bond, length as m-dash]NH)-n'-R-C 6 H 4 (n' = 2, R = H (1); n' = 2, R = Me (2); n' = 4, R = tBu (3))) by Fe(PMe 3 ) 4 with an auxiliary strong Lewis acid (LiBr, LiI, or ZnCl 2 ) was explored. As a result, iron(ii) halides ((H 5 C 6 -(C[double bond, length as m-dash]NH)-2-FH 3 C 6 )FeX(PMe 3 ) 3 (X = Br (8); Cl (9)) and (n-RH 4 C 6 -(C[double bond, length as m-dash]NH)-2'-FH 3 C 6 )FeX(PMe 3 ) 3 (n = 2, R = Me, X = Br (11); n = 4, R = tBu, X = I (12))) were obtained. Under similar reaction conditions, using LiBF 4 instead of LiBr or ZnCl 2 , the reaction of (2,6-difluorophenyl)phenylimine with Fe(PMe 3 ) 4 afforded an ionic complex [(2,6-F 2 H 3 C 6 -(C[double bond, length as m-dash]NH)-H 4 C 6 )Fe(PMe 3 ) 4 ](BF 4 ) (10) via the activation of a C-H bond. The method of C-F bond activation with an auxiliary strong Lewis acid is appropriate for monofluoroarylmethanimines. Without the Lewis acid, iron(ii) hydrides ((2-RH 4 C 6 -(C[double bond, length as m-dash]NH)-2'-FH 3 C 6 )FeH(PMe 3 ) 3 (R = H (13); Me (14))) were generated from the reactions of Fe(PMe 3 ) 4 with the monofluoroarylmethanimines (2-FH 4 C 6 -(C[double bond, length as m-dash]NH)-2'-RC 6 H 4 (R = H (4); Me (5))); however, in the presence of ZnCl 2 or LiBr, iron(ii) halides ((2-RH 4 C 6 -(C[double bond, length as m-dash]NH)-H 4 C 6 )FeX(PMe 3 ) 3 (R = H, X = Cl (15); R = Me, X = Br (16))) could be obtained through the activation of a C-F bond. Furthermore, a C-F bond activation with good regioselectivity in (pentafluorophenyl)arylmethanimines (F 5 C 6 -(C[double bond, length as m-dash]NH)-2,6-Y 2 C 6 H 3 (Y = F (6); H (7))) could be realized in the presence of ZnCl 2 to produce iron(ii) chlorides ((2,6-Y 2 H 3 C 6 -(C[double bond, length as m-dash]NH)-F 4 C 6 )FeCl(PMe 3 ) 3 (Y = F (17); H (18))). This series of iron(ii) halides could be used to catalyze the hydrosilylation reaction of aldehydes. Due to the stability of iron(ii) halides to high temperature, the reaction mixture was allowed to be heated to 100 °C and the reaction could finish within 0.5 h.

The Nucleation Potency of In Situ-Formed Oxides in Liquid Iron

NASA Astrophysics Data System (ADS)

Xu, Mingqin; Wang, Lu; Lu, Wenquan; Zeng, Long; Nadendla, Hari-Babu; Wang, Yun; Li, Jun; Hu, Qiaodan; Xia, Mingxu; Li, Jianguo

2018-03-01

The nucleation potency of iron oxides was verified experimentally through nucleation undercooling of liquid iron using aerodynamic levitation technology for minimized container contaminations. Steady undercooling values were subsequently obtained from multiple melting and freezing thermal cycles, with the average undercooling values of 223 K ± 3 K and 75 K ± 6 K (223 °C ± 3 °C and 75 °C ± 6 °C) for FeO-contained liquid and Fe3O4-contained liquid, respectively. The statistical results showed a negligible difference in the sizes and numbers of particles between FeO and Fe3O4 particles, indicating that the nucleation potency difference is attributed to the nature of nucleants rather than particle size or numbers. Furthermore, high-resolution transmission electron microscopy analysis showed that the potential nucleation interfaces can be assumed as { 1 1 0}_{{δ {{-Fe}}}} //( 0 0\\bar{2})_{FeO} and { 1 1 2}_{{δ {{-Fe}}}} //(\\bar{2} 0 2 )_{{{Fe}3 {O}4 }} , based on the detected exposed crystal planes of the oxide particles. Both the interfaces have relatively large values of lattice misfit, consistent with the experimentally measured undercooling based on Turnbull's lattice matching theory.

Preparation of Fe2O3-TiO2 composite from Sukabumi iron sand through magnetic separation, pyrometallurgy, and hydrometallurgy

NASA Astrophysics Data System (ADS)

Wahyuningsih, S.; Ramelan, A. H.; Pranata, H. P.; Hanif, Q. A.; Ismoyo, Y. A.; Ichsan, K. F.

2016-11-01

Preparation of Fe2O3/TiO2 composite from Sukabumi iron sand by magnetic separation, roasting, leaching and precipitation treatment has been carried out. Magnetic separation can separate magnetic particles and non-magnetic particles of iron sand content, while the non-magnetic particles (wustite (FeO), hematite (α-Fe2O3), maghemite (γ-Fe2O3) and magnetite (Fe3O4)) was washing with oxalic acid 1 M. The result product then was roasted at 800 °C treated by sodium carbonate (Na2CO3) addition of 1:1; 2:1 and 1:2 (w/w) of iron sand to Na2CO3 weight ratio, respectively. The X-Ray Fluorescence (XRF) analysis result shown that Sukabumi iron sand have hematite (Fe2O3) and titanium dioxide (TiO2) content about 72.17% dan 14.42%. XRD analysis of roasted iron sand shown the rutile (TiO2), Hematite (Fe2O3), NaFeO2, FeO, and Na2TiO3. Leaching of roasted iron sand using sulphuric acid (H2SO4) have influenced by concentrations of the H2SO4 solution. The optimum iron sand dissolution occurred in H2SO4 9 M, which condensation product of the leachant have a weight ratio of Fe:Ti = 1:1 (w/w). Meanwhile, the settling back-filtrate result of second condensation was obtained a ratio of Fe2O3: TiO2 of 3: 1 (w/w).

Mechanical Properties and Tribological Behavior of In Situ NbC/Fe Surface Composites

NASA Astrophysics Data System (ADS)

Cai, Xiaolong; Zhong, Lisheng; Xu, Yunhua

2017-01-01

The mechanical properties and tribological behavior of the niobium carbide (NbC)-reinforced gray cast iron surface composites prepared by in situ synthesis have been investigated. Composites are comprised of a thin compound layer and followed by a deep diffusion zone on the surface of gray cast iron. The graded distributions of the hardness and elastic modulus along the depth direction of the cross section of composites form in the ranges of 6.5-20.1 and 159.3-411.2 GPa, respectively. Meanwhile, dry wear tests for composites were implemented on pin-on-disk equipment at sliding speed of 14.7 × 10-2 m/s and under 5 or 20 N, respectively. The result indicates that tribological performances of composites are considerably dependent on the volume fraction and the grain size of the NbC as well as the mechanical properties of the matrices in different areas. The surface compound layer presents the lowest coefficient of friction and wear rate, and exhibits the highest wear resistance, in comparison with diffusion zone and substrate. Furthermore, the worn morphologies observed reveal the dominant wear mechanism is abrasive wear feature in compound layer and diffusion zone.

Highly Dispersed Metal Carbide on ZIF-Derived Pyridinic-N-Doped Carbon for CO2 Enrichment and Selective Hydrogenation.

PubMed

Li, Yunhua; Cai, Xiaohu; Chen, Sijing; Zhang, Hua; Zhang, Kevin H L; Hong, Jinqing; Chen, Binghui; Kuo, Dong-Hau; Wang, Wenju

2018-03-22

Catalytic conversion of CO 2 into chemicals is a critical issue for energy and environmental research. Among such reactions, converting CO 2 into CO has been regarded as a significant foundation to generate a liquid fuels and chemicals on a large scale. In this work, zeolitic imidazolate framework-derived N-doped carbon-supported metal carbide catalysts (M/ZIF-8-C; M=Ni, Fe, Co and Cu) with highly dispersed metal carbide were prepared for selective CO 2 hydrogenation. Under the same metal loadings, catalytic activity for CO 2 hydrogenation to CO follows the order: Ni/ZIF-8-C≈Fe/ZIF-8-C>Co/ZIF-8-C>Cu/ZIF-8-C. These catalysts are composed of carbide or metal supported on pyridinic N sites within the N-doped carbon structure. ZIF-8-derived pyridinic nitrogen and carbide effect CO 2 adsorption, whereas dispersed Ni or Fe carbide and metal species serve as an active site for CO 2 hydrogenation. The supported Ni catalyst exhibits extraordinary catalytic performance, which results from high dispersion of the metal and exposure of the carbide. Based on high-sensitivity low-energy ion scattering (HS-LEIS) and line scan results, density functional theory (DFT) was used to understand reaction mechanism of selective CO 2 hydrogenation over Ni/ZIF-8-C. The product CO is derived mainly from the direct cleavage of C-O bonds in CO 2 * rather than decomposition of COOH*. The CO* desorption energy on Ni/ZIF-8-C is lower than that for further hydrogenation and dissociation. Comparison of Ni/ZIF-8-C with ZIF-8-C indicates that the combined effects of the highly dispersed metal or carbide and weak CO adsorption result in high CO selectivity for CO 2 hydrogenation. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Elevated Temperature Properties of Titanium Carbide Base Ceramals Containing Nickel or Iron

NASA Technical Reports Server (NTRS)

Cooper, A L; Colteryahn, L E

1951-01-01

Elevated-temperature properties of titanium carbide base ceramals containing nickel or iron were determined in oxidation, modulus of rupture, tensile strength, and thermal-shock resistance. These materials followed the general growth law and exhibited two stages in oxidation. The following tensile strengths were found at 2000 degrees F: 13.3 weight percent nickel, 16, 150 pounds per square inch; 11.8 weight percent iron, 12,500 pounds per square inch; unalloyed titanium carbide, 16,450 pounds per square inch. Nickel or iron additions to titanium carbide improved the thermal-shock resistance, nickel more. The path of fracture in tensile and thermal-shock specimens was found to progress approximately 50 percent intergranularly and 50 percent transgranularly.

Synthesis of Nanostructured Carbides of Titanium and Vanadium from Metal Oxides and Ferroalloys Through High-energy Mechanical Milling and Heat Treatment

NASA Astrophysics Data System (ADS)

Basu, P.; Jian, P. F.; Seong, K. Y.; Seng, G. S.; Masrom, A. K.; Hussain, Z.; Aziz, A.

2010-03-01

Carbides of Ti and V have been synthesized directly from their oxides and ferroalloys through mechanical milling and heat treatment. The powder mixtures are milled in a planetary ball mill from 15-80 hours and subsequently heat treated at 1000-1300° C for TiO2-C mixtures, at 500-550° C for V2O5-C mixtures and at 600-1000° C for (Fe-V)-C mixtures. The milled and heat treated powders are characterized by SEM, EDAX, XRD, and BET techniques. Nanostructured TiC has been successfully synthesized under suitable processing conditions. However, carbides of vanadium is unidentified even though possibilities of V2O5-C reaction are indicated with an extent of induced amorphism in the powder mixture. Density, specific surface area and particle size of the milled and heat treated mixtures are correlated with heat treatment temperatures. Similar attempts are also made to synthesize vanadium carbides from industrial grade Fe-V.

Mössbauer study of oxide films of Fe-, Sn-, Cr- doped zirconium alloys during corrosion in autoclave

NASA Astrophysics Data System (ADS)

Filippov, V. P.; Bateev, A. B.; Lauer, Yu. A.

2016-12-01

Mössbauer investigations were used to compare iron atom states in oxide films of binary Zr-Fe, ternary Zr-Fe-Cu and quaternary Zr-Fe-Cr-Sn alloys. Oxide films are received in an autoclave at a temperature of 350-360 °C and at pressure of 16.8 MPa. The corrosion process decomposes the intermetallic precipitates in alloys and forms metallic iron with inclusions of chromium atoms α-Fe(Cr), α-Fe(Cu), α-Fe 2O3 and Fe 3O4 compounds. Some iron ions are formed in divalent and in trivalent paramagnetic states. The additional doping influences on corrosion kinetics and concentration of iron compounds and phases formed in oxide films. It was shown the correlation between concentration of iron in different chemical states and corrosion resistance of alloys.

METHOD OF JOINING CARBIDES TO BASE METALS

DOEpatents

Krikorian, N.H.; Farr, J.D.; Witteman, W.G.

1962-02-13

A method is described for joining a refractory metal carbide such as UC or ZrC to a refractory metal base such as Ta or Nb. The method comprises carburizing the surface of the metal base and then sintering the base and carbide at temperatures of about 2000 deg C in a non-oxidizing atmosphere, the base and carbide being held in contact during the sintering step. To reduce the sintering temperature and time, a sintering aid such as iron, nickel, or cobait is added to the carbide, not to exceed 5 wt%. (AEC)

Infrared absorption spectra of metal carbides, nitrides and sulfides

NASA Technical Reports Server (NTRS)

Kammori, O.; Sato, K.; Kurosawa, F.

1981-01-01

The infrared absorption spectra of 12 kinds of metal carbides, 11 kinds of nitrides, and 7 kinds of sulfides, a total of 30 materials, were measured and the application of the infrared spectra of these materials to analytical chemistry was discussed. The measurements were done in the frequency (wave length) range of (1400 to 400/cm (7 to 25 mu). The carbides Al4C3, B4C, the nitrides AlN, BN, Si3N4, WB, and the sulfides Al2S3, FeS2, MnS, NiS and PbS were noted to have specific absorptions in the measured region. The sensitivity of Boron nitride was especially good and could be detected at 2 to 3 micrograms in 300 mg of potassium bromide.

Highly efficient Cu-decorated iron oxide nanocatalyst for low pressure CO 2 conversion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Halder, Avik; Kilianová, Martina; Yang, Bing

We report a nanoparticulate iron oxide based catalyst for CO2 conversion with high efficiency at low pressures and on the effect of the presence of copper on the catalyst's restructuring and its catalytic performance. In situ X-ray scattering reveals the restructuring of the catalyst at the nanometer scale. In situ X-ray absorption near edge structure (XANES) shows the evolution of the composition and oxidation state of the iron and copper components under reaction conditions along with the promotional effect of copper on the chemical transformation of the iron component. X-ray diffraction (XRD), XANES and Raman spectroscopy proved that the startingmore » nano catalyst is composed of iron oxides differing in chemical nature (alpha-Fe2O3, Fe3O4, FeO(OH)) and dimensionality, while the catalyst after CO2 conversion was identified as a mixture of alpha-Fe, Fe3C, and traces of Fe5C2. The significant increase of the rate CO2 is turned over in the presence of copper nanoparticles indicates that Cu nanoparticles activate hydrogen, which after spilling over to the neighbouring iron sites, facilitate a more efficient conversion of carbon dioxide.« less

Phase transformations during aging of a nitrogen-strengthened austenitic stainless steel

NASA Astrophysics Data System (ADS)

Ritter, Ann M.; Henry, Michael F.

1985-10-01

An analytical electron microscopy study was undertaken in order to characterize intergranular and matrix precipitation accompanying intermediate temperature aging in NITRONIC 50, a nitrogen-strengthened austenitic stainless steel. Extensive precipitation on most grain boundaries had occurred after aging for 24 hours at 675 °C. The primary intergranular phase at that time was Cr-rich M23C6, and energy dispersive spectra taken on grain boundary segments between these carbides indicated Cr-depletion and Fe- and Ni-enhancement relative to the matrix. After aging for 336 and 1008 hours at 675 °C, M6C (eta-carbide) precipitates were also present on grain boundaries. These precipitates were distinguished from M23C6 on the basis of their lattice parameters and chemistries, with M6C containing less Cr and Fe, and more Ni, Mo, and Si than M23C6. The differences in chemistry were clarified by a statistical treatment of the spectra. The statistical analysis also showed that precipitates with a range of chemistries between M23C6 and M6C coexisted with these phases on the grain boundaries. Associated with this shift in precipitate stoichiometry was an increase in the average concentration of Cr and a decrease in the average concentration of Ni at the grain boundaries. Intergranular sigma phase was also observed after times 24 hours at 675 °C, with sigma precipitating on grain boundaries containing carbides. Intragranular precipitates observed to be stable up to 1008 hours at 675 °C included Z-phase, a complex nitride which had formed during solution annealing; M7C3 carbides, which nucleated at Z-phase/austenite interfaces; M23C6 carbides, which precipitated on incoherent twin boundaries; and Cr-rich MN precipitates, which nucleated on dislocations.

Diamond and Unusual Minerals Discovered from the Chromitite in Polar Ural: A First Report

NASA Astrophysics Data System (ADS)

Yang, J.; Bai, W.; Fang, Q.; Meng, F.; Chen, S.; Zhang, Z.

2007-12-01

Ultrahigh pressure (UHP) minerals, such as diamond, coesite, and pseudomorphs of octahedral olivine, and as well as about 80 other mineral species have been recovered from podiform chromitites of the Luobusa ophiolite, southern Tibet, and a new mineral, Luobusaite (Fe0.82Si2), has been approved recently by CNMMN. The UHP minerals from Luobusa are controversial because they have not found in situ and because ophiolites are currently believed to form at shallow levels above oceanic spreading centers. More detailed study and experimental work are needed to understand the origin and significance of these unusual minerals and investigations of other ophiolites are needed to determine if such minerals occur elsewhere. For this purpose, we collected about 1500 kg of chromitite from two orebodies in an ultramafic body in the Polar Urals. Thus far, more than 60 different mineral species have been separated from these ores. The most exciting discovery is the common occurrence of diamond, a typical UHP mineral in the Luobusa chromitites. Diamonds from Ural chromitite are clear, colorless, well-developed crystals with octahedral morphology, generally 0.2-0.3 mm in size. Attached with the diamonds and perhaps also occurring as inclusions within them are many minerals as chromite, MnNiCrFe alloy, native Si and Ta, corundum, zircon, feldspar, garnet, moissanite, confirming their natural origin and suggesting a long residence time in the mantle. Other mineral group include: (1) native elements: Cr, W, Ni, Co, Si, Al and Ta; (2) carbides: SiC and WC; (3) alloys: Cr-Fe, Si-Al-Fe, Ni-Cu, Ag-Au, Ag-Sn, Fe-Si, Fe-P, and Ag-Zn-Sn; (4) oxides: NiCrFe, PbSn, REE, rutile and Si- bearing rutile, ilmenite, corundum, chromite, MgO, and SnO2; (5) silicates: kyanite, pseudomorphs of octahedral olivine, zircon, garnet, feldspar, and quartz,; (6) sulfides of Fe, Ni, Cu, Mo, Pb, Ab, AsFe, FeNi, CuZn, and CoFeNi; and (7) iron groups: native Fe, FeO, and Fe2O3. These minerals are very similar in composition and structure to those reported from the Luobusa chromitites. For examples, some spherules of native iron contain spherical inclusions of FeO, exactly like comparable grains in the Luobusa sample.

Emergent superconductivity in an iron-based honeycomb lattice initiated by pressure-driven spin-crossover.

PubMed

Wang, Yonggang; Ying, Jianjun; Zhou, Zhengyang; Sun, Junliang; Wen, Ting; Zhou, Yannan; Li, Nana; Zhang, Qian; Han, Fei; Xiao, Yuming; Chow, Paul; Yang, Wenge; Struzhkin, Viktor V; Zhao, Yusheng; Mao, Ho-Kwang

2018-05-15

The discovery of iron-based superconductors (FeSCs), with the highest transition temperature (T c ) up to 55 K, has attracted worldwide research efforts over the past ten years. So far, all these FeSCs structurally adopt FeSe-type layers with a square iron lattice and superconductivity can be generated by either chemical doping or external pressure. Herein, we report the observation of superconductivity in an iron-based honeycomb lattice via pressure-driven spin-crossover. Under compression, the layered FePX 3 (X = S, Se) simultaneously undergo large in-plane lattice collapses, abrupt spin-crossovers, and insulator-metal transitions. Superconductivity emerges in FePSe 3 along with the structural transition and vanishing of magnetic moment with a starting T c  ~ 2.5 K at 9.0 GPa and the maximum T c  ~ 5.5 K around 30 GPa. The discovery of superconductivity in iron-based honeycomb lattice provides a demonstration for the pursuit of transition-metal-based superconductors via pressure-driven spin-crossover.

Rare Examples of Fe(IV) Alkyl-Imide Migratory Insertions: Impact of Fe-C Covalency in (Me2IPr)Fe(═NAd)R2 (R = neoPe, 1-nor).

PubMed

Jacobs, Brian P; Wolczanski, Peter T; Jiang, Quan; Cundari, Thomas R; MacMillan, Samantha N

2017-09-06

The iron(IV) imide complexes, (Me 2 IPr)-R 2 Fe=NAd (R = neo Pe (3a), 1-nor (3b)) undergo migratory insertion to iron(II) amides (Me 2 IPr)RFe{NR(Ad)} (R = neo Pe (4a), 1-nor (4b)) without evidence of imidyl or free nitrene character. By increasing the field strength about iron, odd-electron reactivity was circumvented via increased covalency.

Investigation on the relationship between NbC and wear-resistance of Fe matrix composite coatings with different C contents

NASA Astrophysics Data System (ADS)

Zhao, Changchun; Zhou, Yefei; Xing, Xiaolei; Liu, Sha; Ren, Xuejun; Yang, Qingxiang

2018-05-01

The wear resistance of Fe-based composite coating is significantly related with the character of carbides and matrix, which could be strongly affected by C content in it. In this work, the Fe-based composite coatings with different C contents were prepared. The microstructure and phase structure of the coatings were analyzed by scanning electron microscope (SEM) equipped with an energy-dispersive spectroscopy (EDS) and X-ray diffractometer (XRD). The hardness and wear resistance of the coatings were determined. Then the hardness and brittleness of carbon poor niobium carbides were calculated by first principles calculation. The results show that, the phase structures of the coatings are mainly composed of NbC, γ phase (retained austenite) and α phase (martensite). With the increase of C content, the retained austenite appears and C content of martensite is increased. The hardness of the coatings are increased from HRC 22 to HRC 59. The distribution and morphology of NbC are changed with the increase of C content. The NbC precipitated in reticular grain boundary can be observed when C content is 0.4 wt.% C (C-1). NbC turn into granular and small rod morphology when C content increases to 0.8 wt.% C (C-2). The cracks and defects cannot been found on the surface of the coating when C content is 1.2 wt.% C(C-3), whose hardness is HRC 58 and wear loss is 0.27 g/N cm2 in 8 h. The flaky M7C3 carbide precipitates on the coating when C content is 1.4 wt.% C(C-4), which weaken the wear resistance of the matrix. Compared with the hardfacing coatings with different C contents, the C-3 coating processes higher hardness and wear resistance.

Impact of neutron irradiation on mechanical performance of FeCrAl alloy laser-beam weldments

NASA Astrophysics Data System (ADS)

Gussev, M. N.; Cakmak, E.; Field, K. G.

2018-06-01

Oxidation-resistant iron-chromium-aluminum (FeCrAl) alloys demonstrate better performance in Loss-of-Coolant Accidents, compared with austenitic- and zirconium-based alloys. However, further deployment of FeCrAl-based materials requires detailed characterization of their performance under irradiation; moreover, since welding is one of the key operations in fabrication of light water reactor fuel cladding, FeCrAl alloy weldment performance and properties also should be determined prior to and after irradiation. Here, advanced C35M alloy (Fe-13%Cr-5%Al) and variants with aluminum (+2%) or titanium carbide (+1%) additions were characterized after neutron irradiation in Oak Ridge National Laboratory's High Flux Isotope Reactor at 1.8-1.9 dpa in a temperature range of 195-559 °C. Specimen sets included as-received (AR) materials and specimens after controlled laser-beam welding. Tensile tests with digital image correlation (DIC), scanning electron microscopy-electron back scatter diffraction analysis, fractography, and x-ray tomography analysis were performed. DIC allowed for investigating local yield stress in the weldments, deformation hardening behavior, and plastic anisotropy. Both AR and welded material revealed a high degree of radiation-induced hardening for low-temperature irradiation; however, irradiation at high-temperatures (i.e., 559 °C) had little overall effect on the mechanical performance.

Synthesis, structural characterisation and magnetic studies of polymetallic iron phosphonate cages.

PubMed

Khanra, Sumit; Helliwell, Madeleine; Tuna, Floriana; McInnes, Eric J L; Winpenny, Richard E P

2009-08-21

Four new polymetallic iron(III) phosphonate cages have been made and structurally characterised. These are an octanuclear cage [Fe(8)O(3)(OH)(2)(O(2)C(t)Bu)(11)(PhCH(2)PO(3))(3)(py)(3)], a decanuclear cage [Fe(10)O(2)(OH)(8)(O(2)C(t)Bu)(10)(PhCH(2)PO(3))(4)(pip)(2)], a heterometallic cage [Fe(6)Li(5)(mu(3)-O)(2)((t)BuPO(3))(6)(O(2)C(t)Bu)(8)(MeOH)(2)(Py)(4)] and a tridecanuclear cage [Et(3)NH](2)[Fe(13)(mu(3)-O)(3)(mu(2)-OH)(7)((t)BuPO(3))(7)(Me(3)CCO(2))(14)(H(2)O)] (pip = piperidine, py = pyridine). Magnetic studies of the first three compounds show anti-ferromagnetic exchange between the iron(III) centers leading to diamagnetic ground states for the homometallic cages. For the heterometallic cage, the six Fe(III) centers are arranged in two triangles, and each triangle has an S = 1/2 spin ground state.

Iron Uptake in a Shelf Sea: Seasonality and Stoichiometry

NASA Astrophysics Data System (ADS)

Daniels, C. J.; Poulton, A. J.; Moore, M. M.; Birchill, A.; Mayers, K.; Lohan, M. C.

2016-02-01

Primary production by phytoplankton in shelf seas represents a significant contribution to global carbon cycling. Trace metals, such as Iron (Fe), are essential micronutrients for phytoplankton growth, and may ultimately limit primary production. The uptake of iron within natural phytoplankton communities is poorly understood. Using carrier free 55Fe, we are able to obtain novel estimates of biological uptake of Fe using trace level Fe additions that do not perturb the system. Here we present results from a study measuring the uptake of carrier free Iron (55Fe), in parallel with measurements of Carbon (14C) and Phosphorus (33P) uptake; samples were collected from the Celtic sea in spring (April 2015) and summer (July 2015), on-shelf and off-shelf, and in 2 size fractions (Total, >2µm), thus producing a novel dataset of the seasonality of macronutrient and micronutrient uptake by phytoplankton within a shelf sea. Primary production ranged from 1.0 - 2.2 mmol C m-3 d-1 in April and 0.2 - 1.5 mmol C m-3 d-1 in July, with a corresponding higher biomass in April (0.7 - 3.24 mg Chl m-3) than July (0.3 - 1.6 mg Chl m-3). Significant rates of Fe uptake were measured in all samples (e.g. 21 nmol m-3 d-1, on-shelf, April), with variable stoichiometry (e.g. Fe/C of 16 µmol/mol, and Fe/P of 0.4 mmol/mol, on-shelf, April). The results will be presented and examined in the context of the available nutrient pools, the phytoplankton community structure and the impact on biogeochemical cycling.

Changes in the state of iron atoms in Zr alloys during corrosion tests in an autoclave

NASA Astrophysics Data System (ADS)

Filippov, V. P.; Bateev, A. B.; Lauer, Yu. A.; Kargin, N. I.; Petrov, V. I.

2014-04-01

Mössbauerinvestigations were carried out on oxide films formed on specimens of zirconium alloys Zr-1.0 %wtFe-1.2 %wtSn-0.5 %wtCr subjected to corrosion in steam-water environment at a temperature of 360 °C and at a pressure of 16.8 MPa with lithium and boron additions, and on Zr-1.4 %wtFe-0.7 %wtCr corroded in steam-water environment at 350 °C and 16.8 MPa as well as in steam-water environment at 500 °C and 10 MPa. In the metal part of the samples, under the oxide film, the iron atoms are in form of intermetallic precipitates of Zr(Fe, Cr)2. The corrosion process decomposes the intermetallic precipitates and particles are formed of metallic iron with inclusions of chromium atoms -Fe(Cr), α-Fe2O3 and Fe3O4 compounds. Part of the iron ions are in divalent and part in trivalent paramagnetic states. It is proposed that some part of the iron containing oxide precipitates in the oxide film may be in the form of nanoparticles which pass from the superparamagnetic to the ferromagnetic state with decreasing temperature.

Study of AC Magnetic Properties and Core Losses of Fe/Fe3O4-epoxy Resin Soft Magnetic Composite

NASA Astrophysics Data System (ADS)

Laxminarayana, T. A.; Manna, Subhendu Kumar; Fernandes, B. G.; Venkataramani, N.

Soft Magnetic Composites (SMC) were prepared by coating of nanocrystalline Fe3O4 particles, synthesized by co-precipitation method, on atomized iron powder of particle size less than 53 μm in size using epoxy resin as a binder between iron and Fe3O4. Fe3O4 was chosen, for its high electric resistivity and suitable magnetic properties, to keep the coating layer magnetic and seek improvement to the magnetic properties of SMC. SEM images and XRD patterns were recorded in order to investigate the coatings on the surface of iron powder. A toroid was prepared by cold compaction of coated iron powder at 1050 MPa and subsequently cured at 150˚C for 1 hr in argon atmosphere. For comparison of properties, a toroid of uncoated iron powder was also compacted at 1050 MPa and annealed at 600˚C for 2 hr in argon atmosphere. The coated iron powder composite has a resistivity of greater than 200 μΩm, measured by four probe method. A comparison of Magnetic Hysteresis loops and core losses using B-H Loop tracer in the frequency range 0 to 1500 Hz on the coated and uncoated iron powder is reported.

The Fe{sup 2+}/Fe{sup 3+} ratio in natural and heat-treated iron-rich eudialytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rastsvetaeva, R. K., E-mail: rast@ns.crys.ras.ru; Aksenov, S. M.; Rozenberg, K. A.

2011-03-15

The structures of natural iron-rich eudialyte (specimen 3458 from the Khibiny massif, the Kola Peninsula) and two heat-treated samples of this mineral calcined at 700 and 800 Degree-Sign C were determined by X-ray diffraction. The trigonal unit-cell parameters (sp. gr. R3m) are as follows: a = 14.2645(1) Angstrom-Sign , c = 29.9635(5) Angstrom-Sign ; a = 14.1307(1) Angstrom-Sign , c = 30.1229(3) Angstrom-Sign ; a = 14.1921(2) Angstrom-Sign , c = 30.2417(5) Angstrom-Sign , respectively. It was found that Fe{sup 3+} ions in the calcined eudialytes, as well as impurities in the starting specimen, occupy the square-pyramidal Fe{sup 3+}(V) sites,more » whereas Fe{sup 2+} ions are in the planar-tetragonal Fe{sup 2+}(IV) sites.« less

Heat Treatment of Thixo-Formed Hypereutectic X210CrW12 Tool Steel

NASA Astrophysics Data System (ADS)

Rogal, Łukasz; Dutkiewicz, Jan

2012-12-01

Steel is a particularly challenging material to semisolid process because of the high temperatures involved and the potential for surface oxidation. Hot-rolled X210CrW12 tool steel was applied as a feedstock for thixoforming. The samples were heated up to 1525 K (1250 °C) to obtain 30 pct of the liquid phase. They were pressed in the semisolid state into a die preheated up to 473 K (200 °C) using a device based on a high-pressure die casting machine. As a result, a series of main bucket tooth thixo-casts for a mining combine was obtained. The microstructure of the thixo-cast consisted of austenite globular grains (average grain size 46 μm) surrounded by a eutectic mixture (ferrite, austenite, and M7C3 carbides). The average hardness of primary austenite grains was 470 HV0.02 and that of eutectic 551 HV0.02. The X-ray analysis confirmed the presence of 11.8 pct α-Fe, 82.4 pct γ-Fe, and 5.8 pct M7C3 carbides in the thixo-cast samples. Thermal and dilatometric effects were registered in the solid state, and the analysis of curves enabled the determination of characteristic temperatures of heat treatment: 503 K, 598 K, 693 K, 798 K, 828 K, 903 K, and 953 K (230 °C, 325 °C, 420 °C, 525 °C, 555 °C, 630 °C, 680 °C). The thixo-casts were annealed at these temperatures for 2 hours. During annealing in the temperature range 503 K to 693 K (230 °C to 420 °C), the hardness of primary globular grains continuously decreased down to 385HV0.02. The X-ray diffraction showed a slight shift of peaks responsible for the tension release. Moreover, after the treatment at 693 K (420 °C), an additional peak from precipitated carbides was observed in the X-ray diffraction. Thin plates of perlite (average hardness 820 HV0.02) with carbide precipitates appeared at the boundaries of globular grains at 798 K (525 °C). They occupied 17 pct of the grain area. Plates of martensite were found in the center of grains, while the retained austenite was observed among them (average hardness of center grains was 512 HV0.02). A nearly complete decomposition of metastable austenite was achieved after tempering at 828 K (555 °C) due to prevailing lamellar pearlite structure starting at grain boundaries and the martensite located in the center of the grains. The X-ray analysis confirmed the presence of 3.4 pct γ-Fe, 84.6 pct α-Fe, and 12 pct M7C3 carbides. The dilatometric analysis showed that the transformation of metastable austenite into martensite took place during cooling from 828 K (555 °C). The additional annealing at 523 K (250 °C) for 2 hours after heat treatment at 828 K (555 °C) caused the precipitation of carbides from the martensite. After tempering at 903 K (630 °C), the thixo-cast microstructure showed globular grains consisting mainly of thick lamellar perlite of the average hardness 555 HV0.02.

Ferroportin mediates the intestinal absorption of iron from a nanoparticulate ferritin core mimetic in mice

PubMed Central

Aslam, Mohamad F.; Frazer, David M.; Faria, Nuno; Bruggraber, Sylvaine F. A.; Wilkins, Sarah J.; Mirciov, Cornel; Powell, Jonathan J.; Anderson, Greg J.; Pereira, Dora I. A.

2014-01-01

The ferritin core is composed of fine nanoparticulate Fe3+ oxohydroxide, and we have developed a synthetic mimetic, nanoparticulate Fe3+ polyoxohydroxide (nanoFe3+). The aim of this study was to determine how dietary iron derived in this fashion is absorbed in the duodenum. Following a 4 wk run-in on an Fe-deficient diet, mice with intestinal-specific disruption of the Fpn-1 gene (Fpn-KO), or littermate wild-type (WT) controls, were supplemented with Fe2+ sulfate (FeSO4), nanoFe3+, or no added Fe for a further 4 wk. A control group was Fe sufficient throughout. Direct intestinal absorption of nanoFe3+ was investigated using isolated duodenal loops. Our data show that FeSO4 and nanoFe3+ are equally bioavailable in WT mice, and at wk 8 the mean ± sem hemoglobin increase was 18 ± 7 g/L in the FeSO4 group and 30 ± 5 g/L in the nanoFe3+ group. Oral iron failed to be utilized by Fpn-KO mice and was retained in enterocytes, irrespective of the iron source. In summary, although nanoFe3+ is taken up directly by the duodenum its homeostasis is under the normal regulatory control of dietary iron absorption, namely via ferroportin-dependent efflux from enterocytes, and thus offers potential as a novel oral iron supplement.—Aslam, M. F., Frazer, D. M., Faria, N., Bruggraber, S. F. A., Wilkins, S. J., Mirciov, C., Powell, J. J., Anderson, G. J., Pereira, D. I. A. Ferroportin mediates the intestinal absorption of iron from a nanoparticulate ferritin core mimetic in mice. PMID:24776745

Search for New Superconductors for Energy and Power Applications

DTIC Science & Technology

2014-10-21

superconductors, borides , carbides, silicides, and chalcogenides. In addition, a number of thin film systems have been explored: A15s, superlattices, arrays of...YBa2Cu3O7 Bi2Se3 Eu-Si-C ErRh4B4 Bi2Sr2CaCu2O8 (UD, OD) Sb2Se3 V-Si-C (Ga,Mn)As CuO ZrSe2 Sm-Si-C Hf(FeCo)P Y1-xCaxCrO3 Fe-Te-Se BORIDES Hf-Fe-C-P...Physics, Warsaw, Poland Table III New superconductors, discovered by UCSD MURI team. BORIDES Tc (K) Nb0.9Zr0.1B 11.2 ZrNbxB 9.0 ZrVxB 9.0

Low Temperature Synthesis of Cobalt-Chromium Carbide Nanoparticles-Doped Carbon Nanofibers.

PubMed

Yousef, Ayman; Brooks, Robert M; Abutaleb, Ahmed; Al-Deyab, Salem S; El-Newehy, Mohamed H

2018-04-01

Electrospinning has been used to synthesize cobalt-chromium carbide nanoparticles (NPs)-doped carbon nanofibers (CNFs) (Composite). Electrospun mat comprising of cobalt acetate, chromium acetate and poly(vinyl alcohol) (PVA) has been carbonized at low temperature (850 °C) for 3 h under argon atmosphere to produce the introduced composite. The process was achieved at low temperature due to the presence of cobalt as an activator. Field emission scanning electron microscope (FE-SEM), X-ray diffractometry (XRD), and transmission electron microscopy (TEM) equipped with EDX techniques were used to determine the products characteristics. The results indicated the formation of pure cobalt (Co), Cr7C3 NPs and crystalline CNFs. The Co and Cr7C3 NPs were covered with CNFs. Overall, the proposed NFs open new avenue to prepare different metals-metal carbides-carbon NFs at low temperature and short reaction time.

Modeling aqueous ferrous iron chemistry at low temperatures with application to Mars

USGS Publications Warehouse

Marion, G.M.; Catling, D.C.; Kargel, J.S.

2003-01-01

Major uncertainties exist with respect to the aqueous geochemical evolution of the Martian surface. Considering the prevailing cryogenic climates and the abundance of salts and iron minerals on Mars, any attempt at comprehensive modeling of Martian aqueous chemistry should include iron chemistry and be valid at low temperatures and high solution concentrations. The objectives of this paper were to (1) estimate ferrous iron Pitzer-equation parameters and iron mineral solubility products at low temperatures (from < 0 ??C to 25 ??C), (2) incorporate these parameters and solubility products into the FREZCHEM model, and (3) use the model to simulate the surficial aqueous geochemical evolution of Mars. Ferrous iron Pitzer-equation parameters were derived in this work or taken from the literature. Six new iron minerals [FeCl2??4H2O, FeCl2??6H2O, FeSO4??H2O, FeSO4??7H2O, FeCO3, and Fe(OH)3] were added to the FREZCHEM model bringing the total solid phases to 56. Agreement between model predictions and experimental data are fair to excellent for the ferrous systems: Fe-Cl, Fe-SO4, Fe-HCO3, H-Fe-Cl, and H-Fe-SO4. We quantified a conceptual model for the aqueous geochemical evolution of the Martian surface. The five stages of the conceptual model are: (1) carbonic acid weathering of primary ferromagnesian minerals to form an initial magnesium-iron-bicarbonate-rich solution; (2) evaporation and precipitation of carbonates, including siderite (FeCO3), with evolution of the brine to a concentrated NaCl solution; (3) ferrous/ferric iron oxidation; (4) either evaporation or freezing of the brine to dryness; and (5) surface acidification. What began as a dilute Mg-Fe-HCO3 dominated leachate representing ferromagnesian weathering evolved into an Earth-like seawater composition dominated by NaCl, and finally into a hypersaline Mg-Na-SO4-Cl brine. Weathering appears to have taken place initially under conditions that allowed solution of ferrous iron [low O2(g)], but later caused oxidation of iron [high O2(g)]. Surface acidification and/or sediment burial can account for the minor amounts of Martian surface carbonates. This model rests on a large number of assumptions and is therefore speculative. Nevertheless, the model is consistent with current understanding concerning surficial salts and minerals based on Martian meteorites, Mars lander data, and remotely-sensed spectral analyses. ?? 2003 Elsevier Ltd.

Synthesis and characterization of magnetic poly(divinyl benzene)/Fe3O4, C/Fe3O4/Fe, and C/Fe onionlike fullerene micrometer-sized particles with a narrow size distribution.

PubMed

Snovski, Ron; Grinblat, Judith; Margel, Shlomo

2011-09-06

Magnetic poly(divinyl benzene)/Fe(3)O(4) microspheres with a narrow size distribution were produced by entrapping the iron pentacarbonyl precursor within the pores of uniform porous poly(divinyl benzene) microspheres prepared in our laboratory, followed by the decomposition in a sealed cell of the entrapped Fe(CO)(5) particles at 300 °C under an inert atmosphere. Magnetic onionlike fullerene microspheres with a narrow size distribution were produced by annealing the obtained PDVB/Fe(3)O(4) particles at 500, 600, 800, and 1100 °C, respectively, under an inert atmosphere. The formation of carbon graphitic layers at low temperatures such as 500 °C is unique and probably obtained because of the presence of the magnetic iron nanoparticles. The annealing temperature allowed control of the composition, size, size distribution, crystallinity, porosity, and magnetic properties of the produced magnetic microspheres. © 2011 American Chemical Society

Manufacture of barium hexaferrite (BaO3.98Fe2O3) from iron oxide waste of grinding process by using calcination process

NASA Astrophysics Data System (ADS)

Idayanti, N.; Dedi; Kristiantoro, T.; Mulyadi, D.; Sudrajat, N.; Alam, G. F. N.

2018-03-01

The utilization of iron oxide waste of grinding process as raw materials for making barium hexaferrite has been completed by powder metallurgy method. The iron oxide waste was purified by roasting at 800 °C temperature for 3 hours. The method used varying calcination temperature at 1000, 1100, 1200, and 1250 °C for 3 hours. The starting iron oxide waste (Fe2O3) and barium carbonate (BaCO3) were prepared by mol ratio of Fe2O3:BaCO3 from the formula BaO3.98Fe2O3. Some additives such as calcium oxide (CaO), silicon dioxide (SiO2), and polyvinyl alcohol (PVA) were added after calcination process. The samples were formed at the pressure of 2 ton/cm2 and sintered at the temperature of 1250 °C for 1 hour. The formation of barium hexaferrite compounds after calcination is determined by X-Ray diffraction. The magnetic properties were observed by Permagraph-Magnet Physik with the optimum characteristic at calcination temperature of 1250 °C with the induction of remanence (Br) = 1.38 kG, coercivity (HcJ) = 4.533 kOe, product energy maximum (BHmax) = 1.086 MGOe, and density = 4.33 g/cm3.

Energy for the interface system of (Nb, Mo)C/γ-Fe

NASA Astrophysics Data System (ADS)

Zhou, Yanyuan; Wang, Zhenqiang; Zhao, Jiaying; Leng, Zhe; Niu, Zhongyi; Guo, Chunhuan; Zhang, Zhengyan; Yang, Zhigang; Yao, Chunfa; Jiang, Fengchun

2017-08-01

The interfacial energies of MC/γ-Fe and formation energies of MC carbides have been investigated using first-principles calculations based on density functional theory (DFT). Results show that the replacement of Nb by Mo in the NbC lattice is unfavorable with respect to the formation energy. However, it reduces the lattice parameter of MC and decreases the σ_{{chemical}} (interfacial chemical energy) of MC/γ-Fe, thus favoring the formation of complex (Nb, Mo)C carbide. The substitution of Nb by Mo at the interface of MC/γ-Fe system promotes the hybridizations of Mo-1NNFe and C-1NNFe (or 2NNFe) (the first or second nearest neighboring Fe atoms), which leads to a decrease in σ_{{chemical}}. The influence of bond energy is estimated using the discrete lattice plane/nearest neighbor broken bond (DLP/NNBB) model. It is found that the reduced σ_{{chemical}} is attributed to the much smaller value of e_{{{{Fe-C}}}} - e_{{{{Mo-C}}}} (the difference between Fe-C and Mo-C interactions) compared to e_{{{{Fe-C}}}} - e_{{{{Nb-C}}}} (the difference between Fe-C and Nb-C interactions). The results obtained from the analysis of the precipitates in Nb- and Nb-Mo-bearing steels are in a good agreement with the calculations.

Changing concentrations of CO, CH(4), C(5)H(8), CH(3)Br, CH(3)I, and dimethyl sulfide during the Southern Ocean Iron Enrichment Experiments.

PubMed

Wingenter, Oliver W; Haase, Karl B; Strutton, Peter; Friederich, Gernot; Meinardi, Simone; Blake, Donald R; Rowland, F Sherwood

2004-06-08

Oceanic iron (Fe) fertilization experiments have advanced the understanding of how Fe regulates biological productivity and air-sea carbon dioxide (CO(2)) exchange. However, little is known about the production and consumption of halocarbons and other gases as a result of Fe addition. Besides metabolizing inorganic carbon, marine microorganisms produce and consume many other trace gases. Several of these gases, which individually impact global climate, stratospheric ozone concentration, or local photochemistry, have not been previously quantified during an Fe-enrichment experiment. We describe results for selected dissolved trace gases including methane (CH(4)), isoprene (C(5)H(8)), methyl bromide (CH(3)Br), dimethyl sulfide, and oxygen (O(2)), which increased subsequent to Fe fertilization, and the associated decreases in concentrations of carbon monoxide (CO), methyl iodide (CH(3)I), and CO(2) observed during the Southern Ocean Iron Enrichment Experiments.

Reaction of iron with hydrogen chloride-oxygen mixtures at 550 C

NASA Technical Reports Server (NTRS)

Jacobson, N. S.

1986-01-01

The reaction of iron with 1 percent HCl/0-50 percent O2/Ar has been studied at 550 C with thermogravimetry to monitor kinetics and scanning electron microscopy to characterize product morphologies. In addition, the volatile species were identified with an atmospheric pressure sampling mass spectrometer. The reaction of 1 percent HCl/Ar produces FeCl2. The reactions of 1 percent HCl/1, 10, 50 percent O2/Ar produce Fe2O3, Fe3O4, FeCl2, and FeCl3. In each case condensed phase chlorides form at the oxide/metal interface where the oxygen potential is low. The 10 and 50 percent oxygen mixtures have kinetics in the first 3 hr similar to pure oxidation with some deviations due to iron-chloride formation. The 1 percent oxygen mixture shows enhanced reaction rates over oxidation, very likely due to the formation of a porous scale.

High purity Fe3O4 from Local Iron Sand Extraction

NASA Astrophysics Data System (ADS)

Gunanto, Y. E.; Izaak, M. P.; Jobiliong, E.; Cahyadi, L.; Adi, W. A.

2018-04-01

Indonesia has a long coastline and is rich with iron sand. The iron sand is generally rich in various elements such as iron and titanium. One of the products processing of the iron sand mineral is iron (II) (III) oxide (magnetite Fe3O4). The stages of purification process to extracting magnetite phase and discarding the other phases has been performed. Magnetite phase analysis of ironsand extraction retrieved from Indonesia have been investigated. The result of analysis element of iron sand shows that it consists of majority Fe around 65 wt%. However, there are still 17 impurities such as Ti, Al, Ce, Co, Cr, Eu, La, Mg, Mn, Na, Sc, Sm, Th, V, Yb, and Zn. After extraction process, Fe element content increases up to 94%. The iron sand powder after milling for 10 hours and separating using a magnetic separator, the iron sand powders are dissolved in acid chloride solution to form a solution of iron chloride, and this solution is sprinkled with sodium hydroxide to obtain fine powders of Fe3O4. The fine powders which formed were washed with de-mineralization water. The X-ray diffraction pattern shows that the fine powders have a single phase of Fe3O4. The analysis result shows that the sample has the chemical formula: Fe3O4 with a cubic crystal system, space group: Fd-3m and lattice parameters: a = b = c = 8.3681 (1) Å, α = β = γ = 90°. The microstructure analysis shows that the particle of Fe3O4 homogeneously shaped like spherical. The magnetic properties using vibrating sample magnetometer shows that Fe3O4 obtained have ferromagnetic behavior with soft magnetic characteristics. We concluded that this purification of iron sand had been successfully performed to obtain fine powders of Fe3O4 with high purity.

Uranyl-Peroxide Clusters Incorporating Iron Trimers and Bridging by Bisphosphonate- and Carboxylate-Containing Ligands.

PubMed

Qiu, Jie; Dong, Sining; Szymanowski, Jennifer E S; Dobrowolska, Malgorzata; Burns, Peter C

2017-04-03

A hybrid uranium-iron cage nanocluster, [(UO 2 ) 24 (FeOH) 24 (O 2 ) 24 (PO 4 ) 8 (CH(COO)(PO 3 ) 2 ) 24 ] 96- (U 24 Fe 24 ), was synthesized using bridging ligands containing bisphosphonate and carboxylate groups. U 24 Fe 24 contains six tetramers of uranyl hexagonal bipyramids and eight iron trimers, each of which consists of three corner-sharing Fe 3+ octahedra and is stabilized by in situ formed phosphate and 2,2-bis(phosphonato)acetate (C 2 P 2 ) groups. Tetramers and trimers are bridged by 24 C 2 P 2 groups into a cage cluster. Crystals of U 24 Fe 24 present a paramagnetic-like behavior. X-ray scattering showed that U 24 Fe 24 forms in the reactant solution prior to crystallization and is stable upon dissolution in water.

The structural behavior of ferric and ferrous iron in aluminosilicate glass near meta-aluminosilicate joins

NASA Astrophysics Data System (ADS)

Mysen, Bjorn O.

2006-05-01

Iron-57 resonant absorption Mössbauer spectroscopy was used to describe the redox relations and structural roles of Fe 3+ and Fe 2+ in meta-aluminosilicate glasses. Melts were formed at 1500 °C in equilibrium with air and quenched to glass in liquid H 2O with quenching rates exceeding 200 °C/s. The aluminosilicate compositions were NaAlSi 2O 6, Ca 0.5AlSi 2O 6, and Mg 0.5AlSi 2O 6. Iron oxide was added in the form of Fe 2O 3, NaFeO 2, CaFe 2O 4, and MgFe 2O 4 with total iron oxide content in the range ˜0.9 to ˜5.6 mol% as Fe 2O 3. The Mössbauer spectra, which were deconvoluted by assuming Gaussian distributions of the hyperfine field, are consistent with one absorption doublet of Fe 2+ and one of Fe 3+. From the area ratios of the Fe 2+ and Fe 3+ absorption doublets, with corrections for differences in recoil-fractions of Fe 3+ and Fe 2+, the Fe 3+/ΣFe is positively correlated with increasing total iron content and with decreasing ionization potential of the alkali and alkaline earth cation. There is a distribution of hyperfine parameters from the Mössbauer spectra of these glasses. The maximum in the isomer shift distribution function of Fe 3+, δFe 3+, ranges from about 0.25 to 0.49 mm/s (at 298 K relative to Fe metal) with the quadrupole splitting maximum, ΔFe 3+, ranging from ˜1.2 to ˜1.6 mm/s. Both δFe 3+ and δFe 2+ are negatively correlated with total iron oxide content and Fe 3+/ΣFe. The dominant oxygen coordination number Fe 3+ changes from 4 to 6 with decreasing Fe 3+/ΣFe. The distortion of the Fe 3+-O polyhedra of the quenched melts (glasses) decreases as the Fe 3+/ΣFe increases. These polyhedra do, however, coexist with lesser proportions of polyhedra with different oxygen coordination numbers. The δFe 2+ and ΔFe 2+ distribution maxima at 298 K range from ˜0.95 to 1.15 mm/s and 1.9 to 2.0 mm/s, respectively, and decrease with increasing Fe 3+/ΣFe. We suggest that these hyperfine parameter values for the most part are more consistent with Fe 2+ in a range of coordination states from 4- to 6-fold. The lower δFe 2+-values for the most oxidized melts are consistent with a larger proportion of Fe 2+ in 4-fold coordination compared with more reduced glasses and melts.

Experimental determination of activities of FeO and Fe 2O 3 components in hydrous silicic melts under oxidizing conditions

NASA Astrophysics Data System (ADS)

Gaillard, Fabrice; Pichavant, Michel; Scaillet, Bruno

2003-11-01

The critical role of iron on crystal-silicate liquid relationships and melt differentiation is mainly controlled by the redox conditions prevailing in magmas, but the presently available database merely constrains the thermodynamic properties of iron-bearing components in strongly reduced and anhydrous molten silicate where iron is in the ferrous form. This paper provides new standard states for pure ferrous (FeOliq) and ferric (Fe2O3liq) molten iron oxides and extends the experimental database towards oxidizing and water-bearing domains. Iron-iridium, iron-platinum alloys, magnetite or hematite were equilibrated with synthetic silicic liquids at high temperature and high pressure under controlled oxygen fugacity (fO2) to determine activity-composition relationships for FeOliq and Fe2O3liq. Between 1000 and 1300°C, the fO2 ranges from that in air to 3-log units below that of the nickel-nickel oxide buffer (NNO). Experiments were performed on both anhydrous and hydrous melts containing up to 6-wt.% water. Incorporation of water under reducing conditions increases the activity coefficient of FeOliq but has an opposite effect on Fe2O3liq. As calcium is added to system, the effect of water becomes weaker and is inverted for Fe2O3liq. Under oxidizing conditions, water has a negligible effect on both activities of FeOliq and Fe2O3liq. In contrast, changes in redox conditions dominate the activity coefficients of both FeOliq and Fe2O3liq, which increase significantly with increasing fO2. The present results combined with the previous work provide a specific database on the energetics of iron in silicate melts that cover most of the condition prevailing in natural magmas.

Thermomagnetic analysis of meteorites, 2: C2 chondrites

NASA Technical Reports Server (NTRS)

Watson, D. E.; Larson, E. E.; Herndon, J. M.; Rowe, M. W.

1974-01-01

Samples of all eighteen of the known C2 chondrites were analyzed thermomagnetically. For eleven of these, initial Fe3O4 content is low(generally 1%) and the J sub s-T curves are irreversible. The heating curves show variable and erratic behavior, whereas the cooling curves appear to be that of Fe3O4. The saturation moment after cooling is greater (up to 10 times larger) than it is initially. This behavior is interpreted to be the result of the production of magnetite from a thermally unstable phase--apparently FeS. Four of the remaining 7 C2 chondrites contain Fe3O4 as the only significant magnetic phase: initial magnetite contents range from 4 to 13 percent. The remaining three C2 chondrites contain iron or nickel-iron in addition to Fe3O4. These seven C2 chondrites show little evidence of the breakdown of a thermally unstable phase.

Microstructure and hydrogen induced failure mechanisms in iron-nickel weldments

NASA Astrophysics Data System (ADS)

Fenske, Jamey Alan

A recent series of inexplicable catastrophic failures of specific subsea dissimilar metal Fe-Ni butter welds has illuminated a fundamental lack of understanding of both the microstructure created along the fusion line as well as its impact on the hydrogen susceptibility of these interfaces. In order to remedy this, the present work compares and contrasts the microstructure and hydrogen-induced fracture morphology of AISI 8630-IN 625 and F22-IN 625 dissimilar metal weld interfaces as a function of post-weld heat treatment duration. A variety of techniques were used to study details of both the microstructure and fracture morphology including optical microscopy, scanning electron microscopy, secondary ion mass spectrometry, transmission electron microscopy, electron backscatter diffraction, and energy dispersive x-ray spectroscopy. For both systems, the microstructure along the weld interface consisted of a coarse grain heat-affected zone in the Fe-base metal followed by discontinuous martensitic partially-mixed zones and a continuous partially-mixed zone on the Ni-side of the fusion line. Within the partially mixed zone on the Ni-side there exists a 200 nm-wide transition zone within a 20 mum-wide planar solidification region followed by a cellular dendritic region with Nb-Mo rich carbides decorating the dendrite boundaries. The size, area fraction and composition of the discontinuous PMZ were determined to be controlled by uneven mixing in the liquid weld pool influenced by convection currents produced from the welding procedure. The virgin martensitic microstructure produced in these regions is formed as consequence of a both the local composition and the post-weld heat treatment. The local higher Ni content results in these regions being retransformed into austenite during the post-weld heat treatment and then virgin martensite while cooling to room temperature. Although there were differences in the volume of the discontinuous partially mixed-zones, the major difference in the weld metal interfaces was the presence of M 7C3 precipitates in the planar solidification region. The formation of these precipitates, which were found in what was previously referred to as the "featureless-zone," were determined to be dependent on the carbon content of the Fe-base metal and the duration of the post-weld heat treatment. A high density of these ordered 100 nm-long by 10 nm-wide needle-like precipitates were found in the AISI 8630-IN 625 weldment in the 10 hour post-weld heat treatment condition while only the initial stages of their nucleation were evident in the F22-IN 625 15 hour post-weld heat treatment specimen. The study of the fractured specimens revealed that the M7C 3 carbides play a key role in the susceptibility to hydrogen embrittlement of the Fe-Ni butter weldments. The fractures initially nucleate along the isolated Fe-base metal -- discontinuous partially mixed zone interfaces. The M7C3 carbides accumulate hydrogen and then provide a low energy fracture path between the discontinuous partially mixed zones leading to catastrophic failure. The result is a fracture morphology that alternates between flat regions produced by fracture along the discontinuous partially mixed zones and cleavage-like fracture regions produced by fracture along the ordered carbide matrix interfaces.

Complex fine-scale diffusion coating formed at low temperature on high-speed steel substrate

NASA Astrophysics Data System (ADS)

Chaus, A. S.; Pokorný, P.; Čaplovič, Ľ.; Sitkevich, M. V.; Peterka, J.

2018-04-01

A complex B-C-N diffusion coating was produced at 580 °C for 1 h on AISI M35 steel substrate and compared with a reference coating formed at 880 °C for 2.5 h. The surface and the cross-sections of the samples were subjected to detailed characterisation. The surface roughness, hardness, residual stresses and adhesion of the coatings were also evaluated together with cutting tests using drills on coated and uncoated samples while monitoring cutting force and torque. The surface of the steel treated at 580 °C revealed Fe2B, boron nitride and boron iron carbide, but FeB was noted to be absent. The 580 °C coating had the fine-scale microstructure, which resulted in the excellent adhesion and enhanced wear resistance, relative to reference samples that contained coarse borides. The results established that a complex fine-scale diffusion coating enhanced the wear resistance and reduces the cutting force and torque during drilling, thereby increasing the drill life by a factor of 2.2.

Implementation Analysis of Cutting Tool Carbide with Cast Iron Material S45 C on Universal Lathe

NASA Astrophysics Data System (ADS)

Junaidi; hestukoro, Soni; yanie, Ahmad; Jumadi; Eddy

2017-12-01

Cutting tool is the tools lathe. Cutting process tool CARBIDE with Cast Iron Material Universal Lathe which is commonly found at Analysiscutting Process by some aspects numely Cutting force, Cutting Speed, Cutting Power, Cutting Indication Power, Temperature Zone 1 and Temperatur Zone 2. Purpose of this Study was to determine how big the cutting Speed, Cutting Power, electromotor Power,Temperatur Zone 1 and Temperatur Zone 2 that drives the chisel cutting CARBIDE in the Process of tur ning Cast Iron Material. Cutting force obtained from image analysis relationship between the recommended Component Cuting Force with plane of the cut and Cutting Speed obtained from image analysis of relationships between the recommended Cutting Speed Feed rate.

Reduction and Smelting of Vanadium Titanomagnetite Metallized Pellets

NASA Astrophysics Data System (ADS)

Wang, Shuai; Chen, Mao; Guo, Yufeng; Jiang, Tao; Zhao, Baojun

2018-04-01

Reduction and smelting of the vanadium titanomagnetite metallized pellets have been experimentally investigated in this study. By using the high-temperature smelting, rapid quenching, and electron probe x-ray microanalysis (EPMA) technique, the effects of basicity, reaction time, and graphite reductant amount were investigated. The vanadium contents in iron alloys increase with increasing basicity, reaction time, and graphite amount, whereas the FeO and V2O3 concentrations in the liquid phase decrease with the increase of graphite amount and reaction time. Increasing the reaction time and reductant content promotes the reduction of titanium oxide, whereas the reduction of titanium oxides can be suppressed with increasing the slag basicity. Titanium carbide (TiC) was not observed in all the quenched samples under the present conditions. The experimental results and the FactSage calculations are also compared in the present study.

Atomistic simulations of stainless steels: a many-body potential for the Fe-Cr-C system

NASA Astrophysics Data System (ADS)

Henriksson, K. O. E.; Björkas, C.; Nordlund, K.

2013-11-01

Stainless steels found in real-world applications usually have some C content in the base Fe-Cr alloy, resulting in hard and dislocation-pinning carbides—Fe3C (cementite) and Cr23C6—being present in the finished steel product. The higher complexity of the steel microstructure has implications, for example, for the elastic properties and the evolution of defects such as Frenkel pairs and dislocations. This makes it necessary to re-evaluate the effects of basic radiation phenomena and not simply to rely on results obtained from purely metallic Fe-Cr alloys. In this report, an analytical interatomic potential parameterization in the Abell-Brenner-Tersoff form for the entire Fe-Cr-C system is presented to enable such calculations. The potential reproduces, for example, the lattice parameter(s), formation energies and elastic properties of the principal Fe and Cr carbides (Fe3C, Fe5C2, Fe7C3, Cr3C2, Cr7C3, Cr23C6), the Fe-Cr mixing energy curve, formation energies of simple C point defects in Fe and Cr, and the martensite lattice anisotropy, with fair to excellent agreement with empirical results. Tests of the predictive power of the potential show, for example, that Fe-Cr nanowires and bulk samples become elastically stiffer with increasing Cr and C concentrations. High-concentration nanowires also fracture at shorter relative elongations than wires made of pure Fe. Also, tests with Fe3C inclusions show that these act as obstacles for edge dislocations moving through otherwise pure Fe.

Microstructural evolution during quenching and partitioning of 0.2C-1.5Mn-1.3Si steels with Cr or Ni additions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pierce, Dean T.; Coughlin, D. R.; Clarke, Kester D.

Here, the influence of Cr and Ni additions and quench and partition (Q&P) processing parameters on the microstructural development, including carbide formation and austenite retention during Q&P, was studied in two steels with a base composition of 0.2C-1.5Mn-1.3Si wt.% and additions of 1.5 wt.% Cr (1.5Cr) or Ni (1.5Ni). Additions of 1.5 wt.% Cr significantly slowed the kinetics of austenite decomposition relative to the 1.5Ni alloy at all partitioning temperatures, promoting greater austenite retention, lower retained austenite carbon (C) contents, and reduced sensitivity of the retained austenite amounts to processing variables. In the 1.5Cr alloy after partitioning at 400 °Cmore » for 300 s, η-carbides were identified by transmission electron microscopy (TEM) and atom probe tomography (APT) revealed no significant enrichment of substitutional elements in the carbides. In the 1.5Ni alloy after partitioning at 450 °C for 300 s, both plate-like and globular carbides were observed by TEM. APT analysis of the globular carbides clearly revealed significant Si rejection and Mn enrichment. Mössbauer effect spectroscopy was used to quantify the amount of carbides after Q&P. In general, carbide amounts below ~0.3% of Fe were measured in both alloys after partitioning for short times (10 s), irrespective of quench or partitioning temperature, which corresponds to a relatively small portion of the bulk C. With increasing partitioning time, carbide amounts remained approximately constant or increased, depending on the alloy, quench temperature, and/or partitioning temperature.« less

Microstructural evolution during quenching and partitioning of 0.2C-1.5Mn-1.3Si steels with Cr or Ni additions

DOE PAGES

Pierce, Dean T.; Coughlin, D. R.; Clarke, Kester D.; ...

2018-03-08

Here, the influence of Cr and Ni additions and quench and partition (Q&P) processing parameters on the microstructural development, including carbide formation and austenite retention during Q&P, was studied in two steels with a base composition of 0.2C-1.5Mn-1.3Si wt.% and additions of 1.5 wt.% Cr (1.5Cr) or Ni (1.5Ni). Additions of 1.5 wt.% Cr significantly slowed the kinetics of austenite decomposition relative to the 1.5Ni alloy at all partitioning temperatures, promoting greater austenite retention, lower retained austenite carbon (C) contents, and reduced sensitivity of the retained austenite amounts to processing variables. In the 1.5Cr alloy after partitioning at 400 °Cmore » for 300 s, η-carbides were identified by transmission electron microscopy (TEM) and atom probe tomography (APT) revealed no significant enrichment of substitutional elements in the carbides. In the 1.5Ni alloy after partitioning at 450 °C for 300 s, both plate-like and globular carbides were observed by TEM. APT analysis of the globular carbides clearly revealed significant Si rejection and Mn enrichment. Mössbauer effect spectroscopy was used to quantify the amount of carbides after Q&P. In general, carbide amounts below ~0.3% of Fe were measured in both alloys after partitioning for short times (10 s), irrespective of quench or partitioning temperature, which corresponds to a relatively small portion of the bulk C. With increasing partitioning time, carbide amounts remained approximately constant or increased, depending on the alloy, quench temperature, and/or partitioning temperature.« less

Preservation of organic matter in marine sediments by inner-sphere interactions with reactive iron

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barber, Andrew; Brandes, Jay; Leri, Alessandra

Interactions between organic matter and mineral matrices are critical to the preservation of soil and sediment organic matter. In addition to clay minerals, Fe(III) oxides particles have recently been shown to be responsible for the protection and burial of a large fraction of sedimentary organic carbon (OC). Through a combination of synchrotron X-ray techniques and high-resolution images of intact sediment particles, we assessed the mechanism of interaction between OC and iron, as well as the composition of organic matter co-localized with ferric iron. We present scanning transmission x-ray microscopy images at the Fe L 3 and C K1 edges showingmore » that the organic matter co-localized with Fe(III) consists primarily of C=C, C=O and C-OH functional groups. Coupling the co-localization results to iron K-edge X-ray absorption spectroscopy fitting results allowed to quantify the relative contribution of OC-complexed Fe to the total sediment iron and reactive iron pools, showing that 25–62% of total reactive iron is directly associated to OC through inner-sphere complexation in coastal sediments, as much as four times more than in low OC deep sea sediments. Direct inner-sphere complexation between OC and iron oxides (Fe-O-C) is responsible for transferring a large quantity of reduced OC to the sedimentary sink, which could otherwise be oxidized back to CO 2.« less

Controlled Formation of Mixed Nanoscale Domains of High Capacity Fe 2O 3–FeF 3 Conversion Compounds by Direct Fluorination

DOE PAGES

Zhou, Hui; Ruther, Rose E.; Adcock, Jamie; ...

2015-02-22

In this paper, we report a direct fluorination method under fluorine gas atmosphere using a fluidized bed reactor for converting nanophase iron oxide (n-Fe 2O 3) to an electrochemically stable and higher energy density iron oxyfluoride/fluoride phase. Interestingly, no noticeable bulk iron oxyfluoride phase (FeOF) phase was observed even at fluorination temperature close to 300 °C. Instead, at fluorination temperatures below 250 °C, scanning transmission electron microscopy coupled with electron energy loss spectroscopy (STEM-EELS) and X-ray photoelectron spectroscopy (XPS) analysis showed surface fluorination with nominal composition, Fe 2O 3-xF 2x (x < 1). At fluorination temperatures of 275 °C, STEM-EELSmore » results showed porous interconnected nanodomains of FeF 3 and Fe 2O 3 coexisting within the same particle, and overall the particles become less dense after fluorination. We performed potentiometric intermittent titration and electrochemical impedance spectroscopy studies to understand the lithium diffusion (or apparent diffusion) in both the oxyfluoride and mixed phase FeF 3 + Fe 2O 3 composition, and correlate the results to their electrochemical performance. Finally and further, we analyze from a thermodynamical perspective, the observed formation of the majority fluoride phase (77% FeF 3) and the absence of the expected oxyfluoride phase based on the relative formation energies of oxide, fluoride, and oxyfluorides.« less

Thermal conversion of an iron nitride-silicon nitride precursor into a ferromagnetic nanocomposite

NASA Astrophysics Data System (ADS)

Maya, L.; Thompson, J. R.; Song, K. J.; Warmack, R. J.

1998-01-01

Iron nitride films, FeN, in a pure form and in the form of a nanocomposite in silicon nitride were prepared by reactive sputtering using iron or iron disilicide, respectively, as targets in a nitrogen plasma. Iron nitride decomposes into the elements by heating in vacuum to 800 °C. Intermediate phases such as Fe2N or Fe4N form at lower temperatures. The nanocomposites contain the iron phases as particles with an average size of ˜5 nm dispersed in the amorphous silicon nitride matrix. The magnetic properties of the nanocomposites were established. The precursor FeN-Si3N4 film is paramagnetic, while the Fe-Si3N4, obtained by heating in vacuum, is ferromagnetic and shows typical superparamagnetic behavior. These films are of interest as recording media with superior chemical and mechanical stability and may be encoded by localized heating.

Epsilon iron oxide: Origin of the high coercivity stable low Curie temperature magnetic phase found in heated archeological materials

NASA Astrophysics Data System (ADS)

López-Sánchez, J.; McIntosh, G.; Osete, M. L.; del Campo, A.; Villalaín, J. J.; Pérez, L.; Kovacheva, M.; Rodríguez de la Fuente, O.

2017-07-01

The identification of epsilon iron oxide (ɛ-Fe2O3) as the low Curie temperature high coercivity stable phase (HCSLT) carrying the remanence in heated archeological samples has been achieved in samples from two archeological sites that exhibited the clearest evidence of the presence of the HCSLT. This uncommon iron oxide has been detected by Confocal Raman Spectroscopy (CRS) and characterized by rock magnetic measurements. Large numbers of ɛ-Fe2O3 microaggregates (in CO) or isolated clusters (in HEL) could be recognized, distributed over the whole sample, and embedded within the ceramic matrix, along with hematite and pseudobrookite and with minor amounts of anatase, rutile, and maghemite. Curie temperature estimates of around 170°C for CO and 190°C for HEL are lower than for pure, synthetic ɛ-Fe2O3 (227°C). This, together with structural differences between the Raman spectra of the archeologically derived and synthetic samples, is likely due to Ti substitution in the ɛ-Fe2O3 crystal lattice. The γ-Fe2O3-ɛ-Fe2O3-α-Fe2O3 transformation series has been recognized in heated archeological samples, which may have implications in terms of their thermal history and in the factors that govern the formation of ɛ-Fe2O3.

Protection of pure iron against high-temperature oxidation using metaborate and metasilicate coatings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Husain, Z.

1993-04-01

Sodium metaborate and metasilicate coatings protect pure iron in the temperature range 800 to 1,000 C. Metaborate and metasilicate inhibit oxidation. Protective vonsenite (4 FeO [times] Fe[sub 2]O[sub 3] [times] B[sub 2]O[sub 3]) forms with metaborate, and protective fayalite (2FeO [times] SiO[sub 2]) forms with metasilicate. It is proposed that noncoherent blocking layers of these compounds effectively decrease the interface area for iron ion diffusion.

Effects of Composition and Iron Spin State on the Structural Transition of (Mg,Fe)CO3 in the Earth's Lower Mantle

NASA Astrophysics Data System (ADS)

Hsu, H.; Huang, S. C.; Wei, C. M.; Hsing, C. R.

2015-12-01

Iron-bearing magnesium carbonates (Mg,Fe)CO3 are believed the major carbon carriers in the Earth's deep lower mantle; they may play a crucial role in the Earth's deep carbon cycle. Knowledge of the physical and chemical properties of these carbonates is thus essential for our understanding of the mantle's role in global carbon cycle. Experiments have shown that (Mg,Fe)CO3 ferromagnesite (calcite structure) can be stable up to 80-100 GPa. At 45-50 GPa, ferromangsite undergoes a high-spin to low-spin transition, accompanied by a volume reduction and elastic anomalies. Starting ~100 GPa, ferromagnesite goes through a complicated structural transition. The detail of this transition and the atomic structures of high-pressure (Mg,Fe)CO3 phases are still highly debated. Experimental observations and theoretical results are inconsistent so far. In experiments, several distinct high-pressure (Mg,Fe)CO3 structures have been reported, including a P21/c phase [1] and a Pmm2 phase [2]. In theory, a C2/m phase [3] and a P-1 phase [4] have been suggested, while the Pmm2 phase is not found. One possible reason for such a discrepancy is that all available theoretical calculations so far are based on pure MgCO3, while experimental works are performed using (Mg,Fe)CO3 with high iron concentration ( > 50%). Clearly, the concentration of iron and the possible iron spin crossover can significantly affect the stability of these high-pressure (Mg,Fe)CO3 phases. Here, we use density functional theory + self-consistent Hubbard U (DFT+Usc) calculations to study this structural transition. The effects of composition and iron spin state on these (Mg,Fe)CO3 phases are also discussed. Our results can be expected to provide insightful information for better understanding the Earth's deep carbon cycle.[1] E. Boulard et al., Proc. Natl. Acad. Sci. USA 108, 5184 (2011).[2] J. Liu et al., Sci. Rep. 5, 7640 (2015). [3] A. R. Oganov et al., Earth Planet. Sci. Lett. 273, 38 (2008). [4] C. J. Pickard and R. J. Needs, Phys. Rev. B 91, 104101 (2015).

Determination of the pure silicon monocarbide content of silicon carbide and products based on silicon carbide

NASA Technical Reports Server (NTRS)

Prost, L.; Pauillac, A.

1978-01-01

Experience has shown that different methods of analysis of SiC products give different results. Methods identified as AFNOR, FEPA, and manufacturer P, currently used to detect SiC, free C, free Si, free Fe, and SiO2 are reviewed. The AFNOR method gives lower SiC content, attributed to destruction of SiC by grinding. Two products sent to independent labs for analysis by the AFNOR and FEPA methods showed somewhat different results, especially for SiC, SiO2, and Al2O3 content, whereas an X-ray analysis showed a SiC content approximately 10 points lower than by chemical methods.

Phase Transformations of an Fe-0.85 C-17.9 Mn-7.1 Al Austenitic Steel After Quenching and Annealing

NASA Astrophysics Data System (ADS)

Cheng, Wei-Chun

2014-09-01

Low-density Mn-Al steels could potentially be substitutes for commercial Ni-Cr stainless steels. However, the development of the Mn-Al stainless steels requires knowledge of the phase transformations that occur during the steel making processes. Phase transformations of an Fe-0.85 C-17.9 Mn-7.1 Al (wt.%) austenitic steel, which include spinodal decomposition, precipitation transformations, and cellular transformations, have been studied after quenching and annealing. The results show that spinodal decomposition occurs prior to the precipitation transformation in the steel after quenching and annealing at temperatures below 1023 K and that coherent fine particles of L12-type carbide precipitate homogeneously in the austenite. The cellular transformation occurs during the transformation of high-temperature austenite into lamellae of austenite, ferrite, and kappa carbide at temperatures below 1048 K. During annealing at temperatures below 923 K, the austenite decomposes into lamellar austenite, ferrite, κ-carbide, and M23C6 carbide grains for another cellular transformation. Last, when annealing at temperatures below 873 K, lamellae of ferrite and κ-carbide appear in the austenite.

Orenia metallireducens sp. nov. Strain Z6, a Novel Metal-Reducing Member of the Phylum Firmicutes from the Deep Subsurface

PubMed Central

Sanford, Robert A.; Boyanov, Maxim I.; Kemner, Kenneth M.; O'Loughlin, Edward J.; Chang, Yun-juan; Locke, Randall A.; Weber, Joseph R.; Egan, Sheila M.; Mackie, Roderick I.; Cann, Isaac; Fouke, Bruce W.

2016-01-01

ABSTRACT A novel halophilic and metal-reducing bacterium, Orenia metallireducens strain Z6, was isolated from briny groundwater extracted from a 2.02 km-deep borehole in the Illinois Basin, IL. This organism shared 96% 16S rRNA gene similarity with Orenia marismortui but demonstrated physiological properties previously unknown for this genus. In addition to exhibiting a fermentative metabolism typical of the genus Orenia, strain Z6 reduces various metal oxides [Fe(III), Mn(IV), Co(III), and Cr(VI)], using H2 as the electron donor. Strain Z6 actively reduced ferrihydrite over broad ranges of pH (6 to 9.6), salinity (0.4 to 3.5 M NaCl), and temperature (20 to 60°C). At pH 6.5, strain Z6 also reduced more crystalline iron oxides, such as lepidocrocite (γ-FeOOH), goethite (α-FeOOH), and hematite (α-Fe2O3). Analysis of X-ray absorption fine structure (XAFS) following Fe(III) reduction by strain Z6 revealed spectra from ferrous secondary mineral phases consistent with the precipitation of vivianite [Fe3(PO4)2] and siderite (FeCO3). The draft genome assembled for strain Z6 is 3.47 Mb in size and contains 3,269 protein-coding genes. Unlike the well-understood iron-reducing Shewanella and Geobacter species, this organism lacks the c-type cytochromes for typical Fe(III) reduction. Strain Z6 represents the first bacterial species in the genus Orenia (order Halanaerobiales) reported to reduce ferric iron minerals and other metal oxides. This microbe expands both the phylogenetic and physiological scopes of iron-reducing microorganisms known to inhabit the deep subsurface and suggests new mechanisms for microbial iron reduction. These distinctions from other Orenia spp. support the designation of strain Z6 as a new species, Orenia metallireducens sp. nov. IMPORTANCE A novel iron-reducing species, Orenia metallireducens sp. nov., strain Z6, was isolated from groundwater collected from a geological formation located 2.02 km below land surface in the Illinois Basin, USA. Phylogenetic, physiologic, and genomic analyses of strain Z6 found it to have unique properties for iron reducers, including (i) active microbial iron-reducing capacity under broad ranges of temperatures (20 to 60°C), pHs (6 to 9.6), and salinities (0.4 to 3.5 M NaCl), (ii) lack of c-type cytochromes typically affiliated with iron reduction in Geobacter and Shewanella species, and (iii) being the only member of the Halanaerobiales capable of reducing crystalline goethite and hematite. This study expands the scope of phylogenetic affiliations, metabolic capacities, and catalytic mechanisms for iron-reducing microbes. PMID:27565620

Relationship Between Iron Valence States of Serpentine in CM Chondrites and Their Aqueous Alteration Degrees

NASA Technical Reports Server (NTRS)

Mikouchi, T.; Zolensky, M.; Satake, W.; Le, L.

2012-01-01

The 0.6-0.7 micron absorption band observed for C-type asteroids is caused by the presence of Fe(3+) in phyllosilicates . Because Fe-bearing phyllosilicates, especially serpentine, are the most dominant product of aqueous alteration in the most abundant carbonaceous chondrites, CM chondrites, it is important to understand the crystal chemistry of serpentine in CM chondrites to better understand spectral features of C-type asteroids. CM chondrites show variable degrees of aqueous alteration, which should be related to iron valences in serpentine. It is predicted that the Fe(3+)/Sum of (Fe) ratios of serpentine in CM chondrites decrease as alteration proceeds by Si and Fe(3+) substitutions from end-member cronstedtite to serpentine, which should be apparent in the absorption intensity of the 0.6-0.7 micron band from C-type asteroids. In fact, the JAXA Hayabusa 2 target (C-type asteroid: 1993 JU3) exhibits heterogeneous spectral features (0.7 micron absorption band disappears by rotation). From these points of view, we have analyzed iron valences of matrix serpentine in several CM chondrites which span the entire observed range of aqueous alteration using Synchrotron Radiation X-ray Absorption Near-Edge Structure (SR-XANES). In this abstract we discuss the relationship between obtained Fe(3+)/Sum of (Fe) ratios and alteration degrees by adding new data to our previous studies

Utilizing Waste Thermocol Sheets and Rusted Iron Wires to Fabricate Carbon-Fe3O4 Nanocomposite Based Supercapacitors: Turning Wastes into Value-Added Materials.

PubMed

Vadiyar, Madagonda M; Liu, Xudong; Ye, Zhibin

2018-05-14

In the present work, we demonstrate the synthesis of porous activated carbon (specific surface area, 1,883 m2 g-1), Fe3O4 nanoparticles, and carbon-Fe3O4 nanocomposites using local waste thermocol sheets and rusted iron wires. The resulting carbon, Fe3O4 nanoparticles, and carbon-Fe3O4 composites are used as electrode materials for supercapacitor application. In particular, C-Fe3O4 composite electrodes exhibit a high specific capacitance of 1,375 F g-1 at 1 A g-1 and longer cyclic stability with 98 % of capacitance retention over 10,000 cycles. Subsequently, asymmetric supercapacitor, i. e., C-Fe3O4//Ni(OH)2/CNT device exhibits a high energy density of 91.1 Wh kg-1 and a remarkable cyclic stability, showing 98% of capacitance retention over 10,000 cycles. Thus, this work has important implications not only for the fabrication of low-cost electrodes for high-performance supercapacitors but also for the recycling of waste thermocol sheets and rust iron wires for value-added reuse. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Influence of carboxylic acid type on microstructure and magnetic properties of polymeric complex sol-gel driven NiFe2O4

NASA Astrophysics Data System (ADS)

Hessien, M. M.; Mostafa, Nasser Y.; Abd-Elkader, Omar H.

2016-01-01

Citric, oxalic and tartaric acids were used for synthesis of NiFe2O4 using polymeric complex precursor route. The dry precursor gels were calcined at various temperatures (400-1100 °C) for 2 h. All carboxylic acids produce iron-deficient NiFe2O4 with considerable amount of α-Fe2O3 at 400 °C. Increase in the annealing temperature caused reaction of α-Fe2O3 with iron-deficient ferrite phase. The amount of initially formed α-Fe2O3 is directly correlated with stability constant and inversely correlated with the decomposition temperature of Fe(III) carboxylate precursors. In case of tartaric acid precursor, single phase of the ferrite was obtained at 450 °C. However, in case of oxalic acid and citric acid precursors, single phase ferrite was obtained at 550 °C and 700 °C, respectively. The lattice parameters were increased with increasing annealing temperature and with decreasing the amount of α-Fe2O3. Maximum saturation magnetization (55 emu/g) was achieved using tartaric acid precursor annealed at 1100 °C.

Fe-Based Amorphous Coatings on AISI 4130 Structural Steel for Corrosion Resistance

NASA Astrophysics Data System (ADS)

Katakam, Shravana; Santhanakrishnan, S.; Dahotre, Narendra B.

2012-06-01

The current study focuses on synthesizing a novel functional coating for corrosion resistance applications, via laser surface alloying. The iron-based (Fe48Cr15Mo14Y2C15B) amorphous precursor powder is used for laser surface alloying on AISI 4130 steel substrate, with a continuous wave ytterbium Nd-YAG fiber laser. The corrosion resistance of the coatings is evaluated for different processing conditions. The microstructural evolution and the response of the microstructure to the corrosive environment is studied using x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Microstructural studies indicate the presence of face-centered cubic Fe-based dendrites intermixed within an amorphous matrix along with fine crystalline precipitates. The corrosion resistance of the coatings decrease with an increase in laser energy density, which is attributed to the precipitation and growth of chromium carbide. The enhanced corrosion resistance of the coatings processed with low energy density is attributed to the self-healing mechanism of this amorphous system.

Iron Spin Crossover in the New Hexagonal Aluminous (NAL) Phase

NASA Astrophysics Data System (ADS)

Hsu, H.

2017-12-01

The new hexagonal aluminous (NAL) phase, chemical formula AB2C6O12 (A = Na+, K+, Ca2+; B = Mg2+, Fe2+, Fe3+; C = Al3+, Si4+, Fe3+), is considered a major component ( 20 vol%) of mid-ocean ridge basalt (MORB) at lower-mantle conditions. Given that MORB can be transported back into the Earth's lower mantle via subduction, a thorough knowledge of the NAL phase is essential to fully understand the fate of subducted MORB and its role in mantle dynamics and heterogeneity. In this presentation, the complicated spin crossover of the Fe-bearing NAL phase will be discussed based on a series of first-principles calculations [1], in which the local density approximation + self-consistent Hubbard U (LDA+Usc) method was adopted. As revealed by these calculations, only the ferric iron (Fe3+) substituting Al/Si in the octahedral (C) site undergoes a crossover from the high-spin (HS) to the low-spin (LS) state at 40 GPa, while iron substituting Mg in the trigonal-prismatic (B) site remains in the HS state, regardless of its oxidation state (Fe2+ or Fe3+). The volume/elastic anomalies, iron nuclear quadrupole splittings, and crystal field spltting determined by calculations are in great agreement with experiments [2,3]. The calculations further predict that the HS-LS transition pressure of the NAL phase barely increases with temperature due to the three nearly degenerate LS states of Fe3+, suggesting that the elastic anomalies of this mineral can occur at the top lower mantle. [1] H. Hsu, Phys. Rev. B 95, 020406(R) (2017). [2] Y. Wu et al. Earth Planet. Sci. Lett. 434, 91-100 (2016). [3] S. S. Lobanov et al., J. Geophys. Res. Solid Earth 122, 3565 (2017).

Trapping a Highly Reactive Nonheme Iron Intermediate That Oxygenates Strong C-H Bonds with Stereoretention.

PubMed

Serrano-Plana, Joan; Oloo, Williamson N; Acosta-Rueda, Laura; Meier, Katlyn K; Verdejo, Begoña; García-España, Enrique; Basallote, Manuel G; Münck, Eckard; Que, Lawrence; Company, Anna; Costas, Miquel

2015-12-23

An unprecedentedly reactive iron species (2) has been generated by reaction of excess peracetic acid with a mononuclear iron complex [Fe(II)(CF3SO3)2(PyNMe3)] (1) at cryogenic temperatures, and characterized spectroscopically. Compound 2 is kinetically competent for breaking strong C-H bonds of alkanes (BDE ≈ 100 kcal·mol(-1)) through a hydrogen-atom transfer mechanism, and the transformations proceed with stereoretention and regioselectively, responding to bond strength, as well as to steric and polar effects. Bimolecular reaction rates are at least an order of magnitude faster than those of the most reactive synthetic high-valent nonheme oxoiron species described to date. EPR studies in tandem with kinetic analysis show that the 490 nm chromophore of 2 is associated with two S = 1/2 species in rapid equilibrium. The minor component 2a (∼5% iron) has g-values at 2.20, 2.19, and 1.99 characteristic of a low-spin iron(III) center, and it is assigned as [Fe(III)(OOAc)(PyNMe3)](2+), also by comparison with the EPR parameters of the structurally characterized hydroxamate analogue [Fe(III)(tBuCON(H)O)(PyNMe3)](2+) (4). The major component 2b (∼40% iron, g-values = 2.07, 2.01, 1.95) has unusual EPR parameters, and it is proposed to be [Fe(V)(O)(OAc)(PyNMe3)](2+), where the O-O bond in 2a has been broken. Consistent with this assignment, 2b undergoes exchange of its acetate ligand with CD3CO2D and very rapidly reacts with olefins to produce the corresponding cis-1,2-hydroxoacetate product. Therefore, this work constitutes the first example where a synthetic nonheme iron species responsible for stereospecific and site selective C-H hydroxylation is spectroscopically trapped, and its catalytic reactivity against C-H bonds can be directly interrogated by kinetic methods. The accumulated evidence indicates that 2 consists mainly of an extraordinarily reactive [Fe(V)(O)(OAc)(PyNMe3)](2+) (2b) species capable of hydroxylating unactivated alkyl C-H bonds with stereoretention in a rapid and site-selective manner, and that exists in fast equilibrium with its [Fe(III)(OOAc)(PyNMe3)](2+) precursor.

Simple-Cubic Carbon Frameworks with Atomically Dispersed Iron Dopants toward High-Efficiency Oxygen Reduction.

PubMed

Wang, Biwei; Wang, Xinxia; Zou, Jinxiang; Yan, Yancui; Xie, Songhai; Hu, Guangzhi; Li, Yanguang; Dong, Angang

2017-03-08

Iron and nitrogen codoped carbons (Fe-N-C) have attracted increasingly greater attention as electrocatalysts for oxygen reduction reaction (ORR). Although challenging, the synthesis of Fe-N-C catalysts with highly dispersed and fully exposed active sites is of critical importance for improving the ORR activity. Here, we report a new type of graphitic Fe-N-C catalysts featuring numerous Fe single atoms anchored on a three-dimensional simple-cubic carbon framework. The Fe-N-C catalyst, derived from self-assembled Fe 3 O 4 nanocube superlattices, was prepared by in situ ligand carbonization followed by acid etching and ammonia activation. Benefiting from its homogeneously dispersed and fully accessible active sites, highly graphitic nature, and enhanced mass transport, our Fe-N-C catalyst outperformed Pt/C and many previously reported Fe-N-C catalysts for ORR. Furthermore, when used for constructing the cathode for zinc-air batteries, our Fe-N-C catalyst exhibited current and power densities comparable to those of the state-of-the-art Pt/C catalyst.

Renewable Formate from C-H Bond Formation with CO2: Using Iron Carbonyl Clusters as Electrocatalysts.

PubMed

Loewen, Natalia D; Neelakantan, Taruna V; Berben, Louise A

2017-09-19

As a society, we are heavily dependent on nonrenewable petroleum-derived fuels and chemical feedstocks. Rapid depletion of these resources and the increasingly evident negative effects of excess atmospheric CO 2 drive our efforts to discover ways of converting excess CO 2 into energy dense chemical fuels through selective C-H bond formation and using renewable energy sources to supply electrons. In this way, a carbon-neutral fuel economy might be realized. To develop a molecular or heterogeneous catalyst for C-H bond formation with CO 2 requires a fundamental understanding of how to generate metal hydrides that selectively donate H - to CO 2 , rather than recombining with H + to liberate H 2 . Our work with a unique series of water-soluble and -stable, low-valent iron electrocatalysts offers mechanistic and thermochemical insights into formate production from CO 2 . Of particular interest are the nitride- and carbide-containing clusters: [Fe 4 N(CO) 12 ] - and its derivatives and [Fe 4 C(CO) 12 ] 2- . In both aqueous and mixed solvent conditions, [Fe 4 N(CO) 12 ] - forms a reduced hydride intermediate, [H-Fe 4 N(CO) 12 ] - , through stepwise electron and proton transfers. This hydride selectively reacts with CO 2 and generates formate with >95% efficiency. The mechanism for this transformation is supported by crystallographic, cyclic voltammetry, and spectroelectrochemical (SEC) evidence. Furthermore, installation of a proton shuttle onto [Fe 4 N(CO) 12 ] - facilitates proton transfer to the active site, successfully intercepting the hydride intermediate before it reacts with CO 2 ; only H 2 is observed in this case. In contrast, isoelectronic [Fe 4 C(CO) 12 ] 2- features a concerted proton-electron transfer mechanism to form [H-Fe 4 C(CO) 12 ] 2- , which is selective for H 2 production even in the presence of CO 2 , in both aqueous and mixed solvent systems. Higher nuclearity clusters were also studied, and all are proton reduction electrocatalysts, but none promote C-H bond formation. Thermochemical insights into the disparate reactivities of these clusters were achieved through hydricity measurements using SEC. We found that only [H-Fe 4 N(CO) 12 ] - and its derivative [H-Fe 4 N(CO) 11 (PPh 3 )] - have hydricities modest enough to avoid H 2 production but strong enough to make formate. [H-Fe 4 C(CO) 12 ] 2- is a stronger hydride donor, theoretically capable of making formate, but due to an overwhelming thermodynamic driving force and the increased electrostatic attraction between the more negative cluster and H + , only H 2 is observed experimentally. This illustrates the fundamental importance of controlling thermochemistry when designing new catalysts selective for C-H bond formation and establishes a hydricity range of 15.5-24.1 or 44-49 kcal mol -1 where C-H bond formation may be favored in water or MeCN, respectively.

Reactivity Initiated Accident Simulation to Inform Transient Testing of Candidate Advanced Cladding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, Nicholas R; Wysocki, Aaron J; Terrani, Kurt A

2016-01-01

Abstract. Advanced cladding materials with potentially enhanced accident tolerance will yield different light water reactor performance and safety characteristics than the present zirconium-based cladding alloys. These differences are due to different cladding material properties and responses to the transient, and to some extent, reactor physics, thermal, and hydraulic characteristics. Some of the differences in reactors physics characteristics will be driven by the fundamental properties (e.g., absorption in iron for an iron-based cladding) and others will be driven by design modifications necessitated by the candidate cladding materials (e.g., a larger fuel pellet to compensate for parasitic absorption). Potential changes in thermalmore » hydraulic limits after transition from the current zirconium-based cladding to the advanced materials will also affect the transient response of the integral fuel. This paper leverages three-dimensional reactor core simulation capabilities to inform on appropriate experimental test conditions for candidate advanced cladding materials in a control rod ejection event. These test conditions are using three-dimensional nodal kinetics simulations of a reactivity initiated accident (RIA) in a representative state-of-the-art pressurized water reactor with both nuclear-grade iron-chromium-aluminum (FeCrAl) and silicon carbide based (SiC-SiC) cladding materials. The effort yields boundary conditions for experimental mechanical tests, specifically peak cladding strain during the power pulse following the rod ejection. The impact of candidate cladding materials on the reactor kinetics behavior of RIA progression versus reference zirconium cladding is predominantly due to differences in: (1) fuel mass/volume/specific power density, (2) spectral effects due to parasitic neutron absorption, (3) control rod worth due to hardened (or softened) spectrum, and (4) initial conditions due to power peaking and neutron transport cross sections in the equilibrium cycle cores due to hardened (or softened) spectrum. This study shows minimal impact of SiC-based cladding configurations on the transient response versus reference zirconium-based cladding. However, the FeCrAl cladding response indicates similar energy deposition, but with significantly shorter pulses of higher magnitude. Therefore the FeCrAl-based cases have a more rapid fuel thermal expansion rate and the resultant pellet-cladding interaction occurs more rapidly.« less

Maternal iron status during pregnancy compared with neonatal iron status better predicts placental iron transporter expression in humans.

PubMed

Best, Cora M; Pressman, Eva K; Cao, Chang; Cooper, Elizabeth; Guillet, Ronnie; Yost, Olivia L; Galati, Jonathan; Kent, Tera R; O'Brien, Kimberly O

2016-10-01

The placenta richly expresses nonheme and heme Fe transport proteins. To address the impact of maternal and neonatal Fe status and hepcidin on the regulation of these proteins, mRNA expression and protein abundance of nonheme and heme Fe transport proteins were evaluated in placental tissue from 154 adolescents. Regression analyses found maternal Fe status was significantly associated with multiple placental nonheme and heme transporters, whereas neonatal Fe status was related to only 3 heme transporters. Across statistical analyses, maternal Fe status was consistently associated with the placental nonheme Fe importer transferrin receptor 1 (TfR1). Protein abundance of TfR1 was related to midgestation maternal serum ferritin (SF) (β = -0.32; P = 0.005) and serum TfR (β = 0.25; P = 0.024). Protein abundance of the heme importer, proton-coupled folate transporter, was related to neonatal SF (β = 0.30; P = 0.016) and serum TfR (β = -0.46; P < 0.0001). Neonatal SF was also related to mRNA expression of the heme exporter feline leukemia virus subgroup C receptor 1 (β = -0.30; P = 0.004). In summary, maternal Fe insufficiency during pregnancy predicts increased expression of the placental nonheme Fe transporter TfR1. Associations between placental heme Fe transporters and neonatal Fe status require further study.-Best, C. M., Pressman, E. K., Cao, C., Cooper, E., Guillet, R., Yost, O. L., Galati, J., Kent, T. R., O'Brien, K. O. Maternal iron status during pregnancy compared with neonatal iron status better predicts placental iron transporter expression in humans. © FASEB.

An iron( ii ) hydride complex of a ligand with two adjacent β-diketiminate binding sites and its reactivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gehring, Henrike; Metzinger, Ramona; Braun, Beatrice

2016-01-13

After lithiation of PYR-H2 (PYR = [(NC(Me)C(H)C(Me)NC6H3(iPr)2)2(C5H3N)]2-) – the precursor of an expanded β-diketiminato ligand system with two binding pockets – with KN(TMS)2 the reaction of the resulting potassium salt with FeBr2 led to a dinuclear iron(II) bromide complex [(PYR)Fe(μ-Br)2Fe] (1). Through treatment with KHBEt3 the bromide ligands could be replaced by hydrides to yield [PYR)Fe2(μ-H)2] (2), a distorted analogue of known β-diketiminato iron hydride complexes, as evidenced by NMR, Mößbauer and X-ray absorption spectroscopy, as well as by its reactivity: for instance, 2 reacts with the proton source lutidinium triflate via protonation of the hydride ligands to form anmore » iron(II) product [(PYR)Fe2(OTf)2] (4), while CO2 inserts into the Fe–H bonds generating the formate complex [(PYR)Fe2(μ-HCOO)2] (5); in the presence of traces of water partial hydrolysis occurs so that [(PYR)Fe2(μ-OH)(μ-HCOO)] (6) is isolated. Altogether, the iron(II) chemistry supported by the PYR2- ligand is distinctly different from the one of nickel(II), where both, the arrangement of the two binding pockets and the additional pyridyl donor led to diverging features as compared with the corresponding system based on the parent β-diketiminato ligand.« less

Comparative impacts of iron oxide nanoparticles and ferric ions on the growth of Citrus maxima.

PubMed

Hu, Jing; Guo, Huiyuan; Li, Junli; Gan, Qiuliang; Wang, Yunqiang; Xing, Baoshan

2017-02-01

The impacts of iron oxide nanoparticles (γ-Fe 2 O 3 NPs) and ferric ions (Fe 3+ ) on plant growth and molecular responses associated with the transformation and transport of Fe 2+ were poorly understood. This study comprehensively compared and evaluated the physiological and molecular changes of Citrus maxima plants as affected by different levels of γ-Fe 2 O 3 NPs and Fe 3+ . We found that γ-Fe 2 O 3 NPs could enter plant roots but no translocation from roots to shoots was observed. 20 mg/L γ-Fe 2 O 3 NPs had no impact on plant growth. 50 mg/L γ-Fe 2 O 3 NPs significantly enhanced chlorophyll content by 23.2% and root activity by 23.8% as compared with control. However, 100 mg/L γ-Fe 2 O 3 NPs notably increased MDA formation, decreased chlorophyll content and root activity. Although Fe 3+ ions could be used by plants and promoted the synthesis of chlorophyll, they appeared to be more toxic than γ-Fe 2 O 3 NPs, especially for 100 mg/L Fe 3+ . The impacts caused by γ-Fe 2 O 3 NPs and Fe 3+ were concentration-dependent. Physiological results showed that γ-Fe 2 O 3 NPs at proper concentrations had the potential to be an effective iron nanofertilizer for plant growth. RT-PCR analysis showed that γ-Fe 2 O 3 NPs had no impact on AHA gene expression. 50 mg/L γ-Fe 2 O 3 NPs and Fe 3+ significantly increased expression levels of FRO2 gene and correspondingly had a higher ferric reductase activity compared to both control and Fe(II)-EDTA exposure, thus promoting the iron transformation and enhancing the tolerance of plants to iron deficiency. Relative levels of Nramp3 gene expression exposed to γ-Fe 2 O 3 NPs and Fe 3+ were significantly lower than control, indicating that all γ-Fe 2 O 3 NPs and Fe 3+ treatments could supply iron to C. maxima seedlings. Overall, plants can modify the speciation and transport of γ-Fe 2 O 3 NPs or Fe 3+ for self-protection and development by activating many physiological and molecular processes. Copyright © 2016 Elsevier Ltd. All rights reserved.

Electrocatalysis using transition metal carbide and oxide nanocrystals

NASA Astrophysics Data System (ADS)

Regmi, Yagya N.

Carbides are one of the several families of transition metal compounds that are considered economic alternatives to catalysts based on noble metals and their compounds. Phase pure transition metal carbides of group 4-6 metals, in the first three periods, were synthesized using a common eutectic salt flux synthesis method, and their electrocatalytic activities compared under uniform electrochemical conditions. Mo2C showed highest hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) activities among the nine metal carbides investigated, but all other metal carbides also showed substantial activities. All the metal carbides showed remarkable enhancement in catalytic activities as supports, when compared to traditional graphitic carbon as platinum support. Mo2C, the most active transition metal carbide electrocatalyst, was prepared using four different synthesis routes, and the synthesis route dependent activities compared. Bifunctional Mo 2C that is HER as well as oxygen evolution reaction (OER) active, was achieved when the carbide was templated on a multiwalled carbon nanotube using carbothermic reduction method. Bimetallic carbides of Fe, Co, and Ni with Mo or W were prepared using a common carbothermic reduction method. Two different stoichiometries of bimetallic carbides were obtained for each system within a 60 °C temperature window. While the bimetallic carbides showed relatively lower electrocatalytic activities towards HER and ORR in comparison to Mo2C and WC, they revealed remarkably higher OER activities than IrO2 and RuO2, the state-of-the-art OER catalysts. Bimetallic oxides of Fe, Co, and Ni with Mo and W were also prepared using a hydrothermal synthesis method and they also revealed OER activities that are much higher than RuO2 and IrO2. Additionally, the OER activities were dependent on the degree and nature of hydration in the bimetallic oxide crystal lattice, with the completely hydrated, as synthesized, cobalt molybdate and nickel molybdate showing the highest OER activities.

The effect of oxidant addition on ferrous iron removal from multi-element acidic sulphate solutions

NASA Astrophysics Data System (ADS)

Mbedzi, Ndishavhelafhi; Ibana, Don; Dyer, Laurence; Browner, Richard

2017-01-01

This study was an investigation on the hydrolytic precipitation of iron from simulated pregnant leach solution (PLS) of nickel laterite atmospheric leaching. The effect of equilibrium pH, temperature and the addition of oxidant on total iron (ferrous (Fe (II)) and ferric (Fe (III)), aluminium and chromium removal was investigated together with the associated nickel and cobalt losses to the precipitate. Systematic variations of the experimental variables revealed ≥99% of the ferric iron can be removed from solution at conditions similar to those used in standard partial neutralisation in zinc and nickel production, pH of 2.5 and temperature less than 100 °C with minimal losses (<0.5%) of both nickel and cobalt. Temperature variation from 55 to 90 °C had no significant effect on the magnitude of Fe (III) precipitation but led to a significant increase in aluminium removal from 67% to 95% and improved the filterability of the precipitates. There was no ferrous iron precipitation even at a pH of 3.75 in the absence of an oxidant with its removal (98%) achieved by oxidative precipitation with oxygen gas at pH 3.5. Unlike Fe (III) precipitation, the operating temperature significantly affects oxidative precipitation of Fe (II). Hence, in practical application, the hydrolytic precipitation and oxidation to remove iron must be operated at 85 °C to ensure both ferrous and ferric iron are precipitated.

The reduction mechanism of a natural chromite at 1416 °C

NASA Astrophysics Data System (ADS)

Soykan, O.; Eric, R. H.; King, R. P.

1991-02-01

The behavior of a natural chromite from the Bushveld Complex, Transvaal, South Africa, during reduction at 1416 °C by graphite was studied by means of thermogravimetric analysis, X-ray diffraction (XRD) analysis, energy-dispersive X-ray analysis (EDAX), and metallographic analysis. Experimental runs were allowed to proceed up to 120 minutes, resulting in 99 pct reduction. The specific objective of this study was to delineate the reduction mechanism of chromite by graphite. Zoning was observed in partially reduced chromites with degrees of reduction of up to about 70 pct. The inner cores were rich in iron, while the outer cores were depleted of iron. Energy-dispersive X-ray analysis revealed that Fe2+ and Cr3+ ions had diffused outward, whereas Cr2+, Al3+, and Mg2+ ions had diffused inward. The following mechanism of reduction, which is based on the assumption that the composition of the spinel phase remains stoichiometric with increasing degree of reduction, is proposed, (a) Initially, Fe3+ and Fe2+ ions at the surface of the chromite particle are reduced to the metallic state. This is followed immediately by the reduction of Cr3+ ions to the divalent state, (b) Cr2+ ions diffusing toward the center of the particle reduce the Fe3+ ions in the spinel under the surface of the particle to Fe2+ at the interface between the inner and outer cores. Fe2+ ions diffuse toward the surface, where they are reduced to metallic iron, (c) After the iron has been completely reduced, Cr3+ and any Cr2+ that is present are reduced to the metallic state, leaving an iron- and chromium-free spinel, MgAl2O4.

Tribological properties of sintered polycrystalline and single crystal silicon carbide

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.; Srinivasan, M.

1982-01-01

Tribological studies and X-ray photoelectron spectroscopy analyses were conducted with sintered polycrystalline and single crystal silicon carbide surfaces in sliding contact with iron at various temperatures to 1500 C in a vacuum of 30 nPa. The results indicate that there is a significant temperature influence on both the friction properties and the surface chemistry of silicon carbide. The main contaminants on the as received sintered polycrystalline silicon carbide surfaces are adsorbed carbon, oxygen, graphite, and silicon dioxide. The surface revealed a low coefficient of friction. This is due to the presence of the graphite on the surface. At temperatures of 400 to 600 C graphite and copious amount of silicon dioxide were observed on the polycrystalline silicon carbide surface in addition to silicon carbide. At 800 C, the amount of the silicon dioxide decreased rapidly and the silicon carbide type silicon and carbon peaks were at a maximum intensity in the XPS spectra. The coefficients of friction were high in the temperature range 400 to 800 C. Small amounts of carbon and oxygen contaminants were observed on the as received single crystal silicon carbide surface below 250 C. Silicon carbide type silicon and carbon peaks were seen on the silicon carbide in addition to very small amount of graphite and silicon dioxide at temperatures of 450 to 800 C.

Microstructure and hardness of carbon and tool steel quenched with high-frequency currents

NASA Astrophysics Data System (ADS)

Fomin, Aleksandr A.; Fedoseev, Maksim E.; Palkanov, Pavel A.; Voyko, Aleksey V.; Fomina, Marina A.; Koshuro, Vladimir A.; Zakharevich, Andrey M.; Kalganova, Svetlana G.; Rodionov, Igor V.

2018-04-01

In the course of high-temperature treatment with high-frequency currents (HFC) in the range from 600 to 1300 °C, carbon and tool steels are strengthened. After the heat treatment the hardness reaches 64-70 HRC for carbon steel (carbon content 0.4-0.5%) and 68-71 HRC for tool steel 1.3343 (R6M5 steel analogue with 0.9-1.0% C content, W - 5-6 wt%, Mo - 3.5-5.3 wt%, V - 1.3-1.8 wt%, Cr - 3.8-4.3 wt%, Mn+Si - 0.5-1 wt%, Fe - balance). The resulting structure is a carbide network, and in the case of tool steel - complex carbides around a high-strength martensitic phase.

Technique Incorporating Cooling & Contraction / Expansion Analysis to Illustrate Shrinkage Tendency in Cast Irons

NASA Astrophysics Data System (ADS)

Stan, S.; Chisamera, M.; Riposan, I.; Neacsu, L.; Cojocaru, A. M.; Stan, I.

2017-06-01

With the more widespread adoption of thermal analysis testing, thermal analysis data have become an indicator of cast iron quality. The cooling curve and its first derivative display patterns that can be used to predict the characteristics of a cast iron. An experimental device was developed with a technique to simultaneously evaluate cooling curves and expansion or contraction of cast metals during solidification. Its application is illustrated with results on shrinkage tendency of ductile iron treated with FeSiMgRECa master alloy and inoculated with FeSi based alloys, as affected by mould rigidity (green sand and resin sand moulds). Undercooling at the end of solidification relative to the metastable (carbidic) equilibrium temperature and the expansion within the solidification sequence appear to have a strong influence on the susceptibility to macro - and micro - shrinkage in ductile iron castings. Green sand moulds, as less rigid moulds, encourage the formation of contraction defects, not only because of high initial expansion values, but also because of a higher cooling rate during solidification, and consequently, increased undercooling below the metastable equilibrium temperature up to the end of solidification.

Stability of iron-bearing carbonates in the deep Earth’s interior

DOE PAGES

Cerantola, Valerio; Bykova, Elena; Kupenko, Ilya; ...

2017-07-19

The presence of carbonates in inclusions in diamonds coming from depths exceeding 670 km are obvious evidence that carbonates exist in the Earth’s lower mantle. However, their range of stability, crystal structures and the thermodynamic conditions of the decarbonation processes remain poorly constrained. We investigate the behaviour of pure iron carbonate at pressures over 100 GPa and temperatures over 2,500 K using single-crystal X-ray diffraction and Mossbauer spectroscopy in laser-heated diamond anvil cells. On heating to temperatures of the Earth’s geotherm at pressures to B 50 GPa FeCO 3 partially dissociates to form various iron oxides. Furthermore, at higher pressures FeCO 3 forms two new structures— tetrairon(III) orthocarbonate Femore » $$3+\\atop{4}$$C 3O 12 and diiron(II) diiron(III) tetracarbonate Fe$$2+\\atop{2}$$ Fe$$3+\\atop{2}$$C 4 O 13, both phases containing CO 4 tetrahedra. Fe 4 C 4 O 13 is stable at conditions along the entire geotherm to depths of at least 2,500 km, thus demonstrating that self-oxidation-reduction reactions can preserve carbonates in the Earth’s lower mantle.« less

Global Identification of Genes Affecting Iron-Sulfur Cluster Biogenesis and Iron Homeostasis

PubMed Central

Hidese, Ryota; Kurihara, Tatsuo; Esaki, Nobuyoshi

2014-01-01

Iron-sulfur (Fe-S) clusters are ubiquitous cofactors that are crucial for many physiological processes in all organisms. In Escherichia coli, assembly of Fe-S clusters depends on the activity of the iron-sulfur cluster (ISC) assembly and sulfur mobilization (SUF) apparatus. However, the underlying molecular mechanisms and the mechanisms that control Fe-S cluster biogenesis and iron homeostasis are still poorly defined. In this study, we performed a global screen to identify the factors affecting Fe-S cluster biogenesis and iron homeostasis using the Keio collection, which is a library of 3,815 single-gene E. coli knockout mutants. The approach was based on radiolabeling of the cells with [2-14C]dihydrouracil, which entirely depends on the activity of an Fe-S enzyme, dihydropyrimidine dehydrogenase. We identified 49 genes affecting Fe-S cluster biogenesis and/or iron homeostasis, including 23 genes important only under microaerobic/anaerobic conditions. This study defines key proteins associated with Fe-S cluster biogenesis and iron homeostasis, which will aid further understanding of the cellular mechanisms that coordinate the processes. In addition, we applied the [2-14C]dihydrouracil-labeling method to analyze the role of amino acid residues of an Fe-S cluster assembly scaffold (IscU) as a model of the Fe-S cluster assembly apparatus. The analysis showed that Cys37, Cys63, His105, and Cys106 are essential for the function of IscU in vivo, demonstrating the potential of the method to investigate in vivo function of proteins involved in Fe-S cluster assembly. PMID:24415728

Effect of Organic Substances on the Efficiency of Fe(Ii) to Fe(Iii) Oxidation and Removal of Iron Compounds from Groundwater in the Sedimentation Process

NASA Astrophysics Data System (ADS)

Krupińska, Izabela

2017-09-01

One of the problems with iron removal from groundwater is organic matter. The article presents the experiments involved groundwater samples with a high concentration of total iron - amounting to 7.20 mgFe/dm3 and an increased amount of organic substances (TOC from 5.50 to 7.50 mgC/dm3). The water samples examined differed in terms of the value of the ratio of the TOC concentration and the concentration of total iron (D). It was concluded that with increase in the coexistence ratio of organic substances and total iron in water (D = [TOC]/[Fetot]), efficiency of Fe(II) to Fe(III) oxidization with dissolved oxygen decreased, while the oxidation time was increasing. This rule was not demonstrated for potassium manganate (VII) when used as an oxidizing agent. The application of potassium manganate (VII) for oxidation of Fe(II) ions produced the better results in terms of total iron concentration reduction in the sedimentation process than the oxidation with dissolved oxygen.

Nanoscale zerovalent iron (nZVI) at environmentally relevant concentrations induced multigenerational reproductive toxicity in Caenorhabditis elegans.

PubMed

Yang, Ying-Fei; Chen, Pei-Jen; Liao, Vivian Hsiu-Chuan

2016-05-01

Nanoscale zerovalent iron (nZVI) is widely used with large scale for environmental remediation for in situ or ex situ applications. The potential impact of nZVI on biota at environmentally relevant concentrations needs to be elucidated. In this study, the reproductive toxicities of three irons species: carboxymethyl cellulose (CMC)-stabilized nZVI, nanoscale iron oxide (nFe3O4), and ferrous ion (Fe(II)aq) in the soil-dwelling nematode Caenorhabditis elegans were examined. In addition, the generational transfer of reproductive toxicity of CMC-nZVI on C. elegans was investigated. The results showed that CMC-nZVI, nFe3O4, and Fe(II)aq did not cause significant mortality after 24 h exposure at the examined concentrations. Reproductive toxicity assays revealed that CMC-nZVI, nFe3O4, and Fe(II)aq significantly decreased offsprings in parental generation (F0) in accompany with the increased intracellular reactive oxygen species (ROS). Furthermore, the reproductive toxicity of CMC-nZVI at environmentally relevant concentrations was transferrable from the F0 to the F1 and F2 generations, but then recovered in the F3 and F4 generations. Further evidence showed that total irons were accumulated in the F0 and F1 generations of C. elegans after CMC-nZVI parental exposure. This study demonstrated that environmentally relevant concentrations of CMC-nZVI induced multigenerational reproductive toxicity which can be ascribed to its high production of ROS in F0 generation, toxicity of Fe(II)aq, and iron accumulation in C. elegans. Since nZVI is widely used for environmental remediation, considering the multigenerational toxicity, this study thus implicates a potential environmental risk of nZVI-induced nanotoxicity in the environment. Copyright © 2016 Elsevier Ltd. All rights reserved.

Iron single crystal growth from a lithium-rich melt

NASA Astrophysics Data System (ADS)

Fix, M.; Schumann, H.; Jantz, S. G.; Breitner, F. A.; Leineweber, A.; Jesche, A.

2018-03-01

α -Fe single crystals of rhombic dodecahedral habit were grown from a Li84N12Fe∼3 melt. Crystals of several millimeter along a side form at temperatures around T ≈ 800 ° C. Upon further cooling the growth competes with the formation of Fe-doped Li3N. The b.c.c. structure and good sample quality of α -Fe single crystals were confirmed by X-ray and electron diffraction as well as magnetization measurements and chemical analysis. A nitrogen concentration of 90 ppm was detected by means of carrier gas hot extraction. Scanning electron microscopy did not reveal any sign of iron nitride precipitates.

Bimetallic iron–iron and iron–zinc complexes of the redox-active ONO pincer ligand† †Electronic supplementary information (ESI) available: Complete experimental procedures and magnetic measurements and models. CCDC 1417565–1417567. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c5sc03006d Click here for additional data file. Click here for additional data file.

PubMed Central

Wong, Janice L.; Higgins, Robert F.; Bhowmick, Indrani; Cao, David Xi; Szigethy, Géza; Ziller, Joseph W.

2016-01-01

A new bimetallic platform comprising a six-coordinate Fe(ONO)2 unit bound to an (ONO)M (M = Fe, Zn) has been discovered ((ONOcat)H3 = bis(3,5-di-tert-butyl-2-phenol)amine). Reaction of Fe(ONO)2 with either (ONOcat)Fe(py)3 or with (ONOq)FeCl2 under reducing conditions led to the formation of the bimetallic complex Fe2(ONO)3, which includes unique five- and six-coordinate iron centers. Similarly, the reaction of Fe(ONO)2 with the new synthon (ONOsq˙)Zn(py)2 led to the formation of the heterobimetallic complex FeZn(ONO)3, with a six-coordinate iron center and a five-coordinate zinc center. Both bimetallic complexes were characterized by single-crystal X-ray diffraction studies, solid-state magnetic measurements, and multiple spectroscopic techniques. The magnetic data for FeZn(ONO)3 are consistent with a ground state S = 3/2 spin system, generated from a high-spin iron(ii) center that is antiferromagnetically coupled to a single (ONOsq˙)2– radical ligand. In the case of Fe2(ONO)3, the magnetic data revealed a ground state S = 7/2 spin system arising from the interactions of one high-spin iron(ii) center, one high-spin iron(iii) center, and two (ONOsq˙)2– radical ligands. PMID:28808535

The suitability of silicon carbide for photocatalytic water oxidation

NASA Astrophysics Data System (ADS)

Aslam, M.; Qamar, M. T.; Ahmed, Ikram; Rehman, Ateeq Ur; Ali, Shahid; Ismail, I. M. I.; Hameed, Abdul

2018-04-01

Silicon carbide (SiC), owing to its extraordinary chemical stability and refractory properties, is widely used in the manufacturing industry. Despite the semiconducting nature and morphology-tuned band gap, its efficacy as photocatalysts has not been thoroughly investigated. The current study reports the synthesis, characterization and the evaluation of the capability of silicon carbide for hydrogen generation from water splitting. The optical characterization of the as-synthesized powder exposed the formation of multi-wavelength absorbing entities in synthetic process. The structural analysis by XRD and the fine microstructure analysis by HRTEM revealed the cubic 3C-SiC (β-SiC) and hexagonal α-polymorphs (2H-SiC and 6H-SiC) as major and minor phases, respectively. The Mott-Schottky analysis verified the n-type nature of the material with the flat band potential of - 0.7 V. In the electrochemical evaluation, the sharp increase in the peak currents in various potential ranges, under illumination, revealed the plausible potential of the material for the oxidation of water and generation of hydrogen. The generation of hydrogen and oxygen, as a consequence of water splitting in the actual photocatalytic experiments, was observed and measured. A significant increase in the yield of hydrogen was noticed in the presence of methanol as h + scavenger, whereas a retarding effect was offered by the Fe3+ entities that served as e - scavengers. The combined effect of both methanol and Fe3+ ions in the photocatalytic process was also investigated. Besides hydrogen gas, the other evolved gasses such as methane and carbon monoxide were also measured to estimate the mechanism of the process.

Facile synthesis of highly reactive and stable Fe-doped g-C3N4 composites for peroxymonosulfate activation: A novel nonradical oxidation process.

PubMed

Feng, Yong; Liao, Changzhong; Kong, Lingjun; Wu, Deli; Liu, Yiming; Lee, Po-Heng; Shih, Kaimin

2018-07-15

Ferrous ions (Fe 2+ ) are environmentally friendly materials but show extremely inefficient persulfate activation. Polymeric graphitic carbon nitride (g-C 3 N 4 ) has recently shown potential to activate persulfates, but the process requires intense light irradiation. To overcome these drawbacks, we designed an innovative heterogeneous iron catalyst by doping Fe into g-C 3 N 4 (Fe-g-C 3 N 4 ) and used it to activate peroxymonosulfate (PMS) for degradation of pollutant phenol. The catalysts synthesized were fully characterized with various techniques, such as X-ray diffraction, Mössbauer spectroscopy, and X-ray photoelectron spectroscopy. Fe was found to be coordinated with the framework of g-C 3 N 4 . Approximately 100% degradation of phenol was achieved with Fe-g-C 3 N 4 after 20 min of reaction, whereas less than 5% degradation of phenol was achieved with Fe 2+ . Fe-g-C 3 N 4 -PMS had a wide effective pH range, and its reactivity was nearly independent of natural illumination. In contrast to the previously proposed radical mechanisms, quenching experiments revealed that nonradical oxidation contributed to the observed degradation. The OO bond in the activated PMS likely underwent heterolysis, producing high-valence iron species (Fe IV O) as the primary active species. These findings have important implications for the development of a selective heterogeneous nonradical-oxidation process. Copyright © 2018 Elsevier B.V. All rights reserved.

Modeling the active site of [NiFe] hydrogenases and the [NiFeu] subsite of the C-cluster of carbon monoxide dehydrogenases: low-spin iron(II) versus high-spin iron(II).

PubMed

Weber, Katharina; Erdem, Özlen F; Bill, Eckhard; Weyhermüller, Thomas; Lubitz, Wolfgang

2014-06-16

A series of four [S2Ni(μ-S)2FeCp*Cl] compounds with different tetradentate thiolate/thioether ligands bound to the Ni(II) ion is reported (Cp* = C5Me5). The {S2Ni(μ-S)2Fe} core of these compounds resembles structural features of the active site of [NiFe] hydrogenases. Detailed analyses of the electronic structures of these compounds by Mössbauer and electron paramagnetic resonance spectroscopy, magnetic measurements, and density functional theory calculations reveal the oxidation states Ni(II) low spin and Fe(II) high spin for the metal ions. The same electronic configurations have been suggested for the Cred1 state of the C-cluster [NiFeu] subsite in carbon monoxide dehydrogenases (CODH). The Ni-Fe distance of ∼3 Å excludes a metal-metal bond between nickel and iron, which is in agreement with the computational results. Electrochemical experiments show that iron is the redox active site in these complexes, performing a reversible one-electron oxidation. The four complexes are discussed with regard to their similarities and differences both to the [NiFe] hydrogenases and the C-cluster of Ni-containing CODH.

Maternal iron status during pregnancy compared with neonatal iron status better predicts placental iron transporter expression in humans

PubMed Central

Best, Cora M.; Pressman, Eva K.; Cao, Chang; Cooper, Elizabeth; Guillet, Ronnie; Yost, Olivia L.; Galati, Jonathan; Kent, Tera R.; O’Brien, Kimberly O.

2016-01-01

The placenta richly expresses nonheme and heme Fe transport proteins. To address the impact of maternal and neonatal Fe status and hepcidin on the regulation of these proteins, mRNA expression and protein abundance of nonheme and heme Fe transport proteins were evaluated in placental tissue from 154 adolescents. Regression analyses found maternal Fe status was significantly associated with multiple placental nonheme and heme transporters, whereas neonatal Fe status was related to only 3 heme transporters. Across statistical analyses, maternal Fe status was consistently associated with the placental nonheme Fe importer transferrin receptor 1 (TfR1). Protein abundance of TfR1 was related to midgestation maternal serum ferritin (SF) (β = −0.32; P = 0.005) and serum TfR (β = 0.25; P = 0.024). Protein abundance of the heme importer, proton-coupled folate transporter, was related to neonatal SF (β = 0.30; P = 0.016) and serum TfR (β = −0.46; P < 0.0001). Neonatal SF was also related to mRNA expression of the heme exporter feline leukemia virus subgroup C receptor 1 (β = −0.30; P = 0.004). In summary, maternal Fe insufficiency during pregnancy predicts increased expression of the placental nonheme Fe transporter TfR1. Associations between placental heme Fe transporters and neonatal Fe status require further study.—Best, C. M., Pressman, E. K., Cao, C., Cooper, E., Guillet, R., Yost, O. L., Galati, J., Kent, T. R., O’Brien, K. O. Maternal iron status during pregnancy compared with neonatal iron status better predicts placental iron transporter expression in humans. PMID:27402672

A Study of the Effect of Interrupted Quenches on a Thermomechanically Processed High Carbon Steel.

DTIC Science & Technology

1982-10-01

Martensite And Austenite Phases In Steel Using Copper Radiation ---------------------------- 38 4° J !7...34A General Equa- tion Prescribing the Extent of the Austenite- Martensite Transformation in Pure Iron-Carbon Alloys and Plain Carbon Steels ," Acta Met...relatively low temperatures, resulting in incomplete disso- lution of alloy carbides, predominantly Fe-Cr complexes. In some instances 52100 steel is

Dechlorination of polychlorinated biphenyls by iron and its oxides.

PubMed

Sun, Yifei; Liu, Xiaoyuan; Kainuma, Masashi; Wang, Wei; Takaoka, Masaki; Takeda, Nobuo

2015-10-01

The decomposition efficiency of polychlorinated biphenyls (PCBs) was determined using elemental iron (Fe) and three iron (hydr)oxides, i.e., α-Fe2O3, Fe3O4, and α-FeOOH, as catalysts. The experiments were performed using four distinct PCB congeners (PCB-209, PCB-153, and the coplanar PCB-167 and PCB-77) at temperatures ranging from 180 °C to 380 °C and under an inert, oxidizing or reducing atmosphere composed of N2, N2+O2, or N2+H2. From these three options N2 showed to provide the best reaction atmosphere. Among the iron compounds tested, Fe3O4 showed the highest activity for decomposing PCBs. The decomposition efficiencies of PCB-209, PCB-167, PCB-153, and PCB-77 by Fe3O4 in an N2 atmosphere at 230 °C were 88.5%, 82.5%, 69.9%, and 66.4%, respectively. Other inorganic chlorine (Cl) products which were measured by the amount of inorganic Cl ions represented 82.5% and 76.1% of the reaction products, showing that ring cleavage of PCBs was the main elimination process. Moreover, the dechlorination did not require a particular hydrogen donor. We used X-ray photoelectron spectroscopy to analyze the elemental distribution at the catalyst's surface. The O/Fe ratio influenced upon the decomposition efficiency of PCBs: the lower this ratio, the higher the decomposition efficiency. X-ray absorption near edge structure spectra showed that α-Fe2O3 effectively worked as a catalyst, while Fe3O4 and α-FeOOH were consumed as reactants, as their final state is different from their initial state. Finally, a decomposition pathway was postulated in which the Cl atoms in ortho-positions were more difficult to eliminate than those in the para- or meta-positions. Copyright © 2015 Elsevier Ltd. All rights reserved.

TEM investigation of ductile iron alloyed with vanadium.

PubMed

Dymek, S; Blicharski, M; Morgiel, J; Fraś, E

2010-03-01

This article presents results of the processing and microstructure evolution of ductile cast iron, modified by an addition of vanadium. The ductile iron was austenitized closed to the solidus (1095 degrees C) for 100 h, cooled down to 640 degrees C and held on at this temperature for 16 h. The heat treatment led to the dissolution of primary vanadium-rich carbides and their subsequent re-precipitation in a more dispersed form. The result of mechanical tests indicated that addition of vanadium and an appropriate heat treatment makes age hardening of ductile iron feasible. The precipitation processes as well as the effect of Si content on the alloy microstructure were examined by scanning and transmission electron microscopy. It was shown that adjacent to uniformly spread out vanadium-rich carbides with an average size of 50 nm, a dispersoid composed of extremely small approximately 1 nm precipitates was also revealed.

Effect of the carbon coating in Fe-C-TiO(2) photocatalyst on phenol decomposition under UV irradiation via photo-Fenton process.

PubMed

Tryba, Beata; Morawski, Antoni W; Inagaki, Michio; Toyoda, Masahiro

2006-08-01

Fe-C-TiO(2) photocatalysts which contained the residue carbon (0.2-3.3 mass%) were prepared from a mixture of TiO(2) and FeC(2)O(4) through the heating at 673-1173 K in Ar. These photocatalysts did not show a high adsorption of phenol, but they were active in photo-Fenton reactions during decomposition of phenol under UV irradiation with addition of H(2)O(2). It was proved that Fe(2+) governed the photoactivity of Fe-C-TiO(2) photocatalysts, it decreased with heat-treatment temperature above 773 K. For comparison, Fe-TiO(2) photocatalyst was prepared by heating TiO(2) and FeC(2)O(4) at 823 K in air for 3h. Phenol decomposition was going much slower on Fe-TiO(2) photocatalyst in comparison with Fe-C-TiO(2), of which mechanism was different, on the former phenol was decomposed by the radical reaction, on the latter through a complex reaction with iron and intermediates of phenol decomposition. Therefore carbon-coating TiO(2) was found to be advantageous for mounting iron and its application for the phenol decomposition via photo-Fenton process.

Spectroscopic, Structural, and Functional Characterization of the Alternative Low-Spin State of Horse Heart Cytochrome c

PubMed Central

Mugnol, Katia C. U.; Ando, Rômulo A.; Nagayasu, Rafael Y.; Faljoni-Alario, Adelaide; Brochsztain, Sergio; Santos, Paulo S.; Nascimento, Otaciro R.; Nantes, Iseli L.

2008-01-01

The alternative low-spin states of Fe3+ and Fe2+ cytochrome c induced by SDS or AOT/hexane reverse micelles exhibited the heme group in a less rhombic symmetry and were characterized by electron paramagnetic resonance, UV-visible, CD, magnetic CD, fluorescence, and Raman resonance. Consistent with the replacement of Met80 by another strong field ligand at the sixth heme iron coordination position, Fe3+ ALSScytc exhibited 1-nm Soret band blue shift and ɛ enhancement accompanied by disappearance of the 695-nm charge transfer band. The Raman resonance, CD, and magnetic CD spectra of Fe3+ and Fe2+ ALSScytc exhibited significant changes suggestive of alterations in the heme iron microenvironment and conformation and should not be assigned to unfold because the Trp59 fluorescence remained quenched by the neighboring heme group. ALSScytc was obtained with His33 and His26 carboxyethoxylated horse cytochrome c and with tuna cytochrome c (His33 replaced by Asn) pointing out Lys79 as the probable heme iron ligand. Fe3+ ALSScytc retained the capacity to cleave tert-butylhydroperoxide and to be reduced by dithiothreitol and diphenylacetaldehyde but not by ascorbate. Compatible with a more open heme crevice, ALSScytc exhibited a redox potential ∼200 mV lower than the wild-type protein (+220 mV) and was more susceptible to the attack of free radicals. PMID:18227133

Interfacial Phenomena in Fe/Stainless Steel-TiC Systems and the Effect of Mo

NASA Astrophysics Data System (ADS)

Kiviö, Miia; Holappa, Lauri; Yoshikawa, Takeshi; Tanaka, Toshihiro

2014-12-01

Titanium carbide is used as reinforcement particles in composites due to its hardness, wear resistance and stability. This work is a part of the study in which titanium carbides are formed in stainless steel castings in the mold to improve the wear resistance of a certain surface of the casting. Such local reinforcement is a very potential method but it is a quite demanding task requiring profound knowledge of interfacial phenomena in the system, wettability, stability, dissolution and precipitation of new phases in production of these materials. Good wetting between different constituents in the material is a key factor to attain maximal positive effects. Mo is used with TiC or Ti(C,N) reinforcement in composites to improve wettability. In this work the effect of Mo on the phenomena in Fe/stainless steel-TiC systems was examined by wetting experiments between the substrate and the alloy. Wetting was not significantly improved by adding Mo to the systems. Core-rim type carbides as well as more homogenous carbide particles were observed. Overall the carbide particles are very complex regarding to their chemistry, size and shape which aspects have to be taken into account in the development of these materials and manufacturing processes.

Fesbnd X (X = B, N) binary compounds: First-principles calculations of electronic structures, theoretic hardness and magnetic properties

NASA Astrophysics Data System (ADS)

Hui, Liangliang; Xie, Zhongjing; Li, Chunmei; Chen, Zhi-Qian

2018-04-01

The first-principles calculations are implemented to investigate the electronic structures, theoretic hardness and magnetic properties of iron borides and nitrides with four different crystal systems containing hexagonal (FeB2, ε-Fe3N), tetragonal (Fe2B, α″-Fe16N2), orthorhombic (α-FeB, θ-Fe3B, ζ-Fe2N), and cubic (zb-FeN, rs-FeN, γ‧-Fe4N, γ-Fe23B6) phase. The calculated lattice parameters using RPBE meet well with the experimental results. The cohesive energy and formation enthalpy values indicate the Fesbnd X (X = B, N) binary compounds are thermodynamically stable. Meanwhile, the h-FeB2 is most difficult phase for experimental synthesis among these interstitial compounds. Moreover, magnetic properties are discussed and show that the mean magnetic moments of o-Fe3B and c-Fe23B6 with the values of 2.227 μB and 2.256 μB per iron atom are approaching to that of pure iron (2.32 μB) while the c-Fe4N and t-Fe16N2 with the values of 2.51 and 2.48 μB are beyond that of pure α-Fe. The c-FeN phase shows nonmagnetic in zb-style while rs-type shows antiferromagnetic with a value of 2.52 μB. Furthermore, the average bonding length and Mulliken population combined with electronic structures are also analysed in this paper which provide that strong Fesbnd X and Xsbnd X covalent bonds are responsible for high hardness. Finally, the theoretic hardness of Xsbnd X, Fesbnd X and Fesbnd Fe bonds is predicted by semi empirical hardness theory.

Anodic activation of iron corrosion in clay media under water-saturated conditions at 90 degrees C: characterization of the corrosion interface.

PubMed

Schlegel, Michel L; Bataillon, Christian; Blanc, Cécile; Prêt, Dimitri; Foy, Eddy

2010-02-15

To understand the process governing iron corrosion in clay over centuries, the chemical and mineralogical properties of solids formed by free or anodically activated corrosion of iron in water-saturated clay at 90 degrees C over 4 months were probed using microscopic and spectroscopic techniques. Free corrosion led to the formation of an internal discontinuous thin (<3 microm thick) magnetite layer, an external layer of Fe-rich phyllosilicate, and a clay transformation layer containing Ca-doped siderite (Ca(0.2)Fe(0.8)CO(3)). The thickness of corroded iron equaled approximately 5-7 microm, consistent with previous studies. Anodic polarization resulted in unequally distributed corrosion, with some areas corrosion-free and others heavily corroded. Activated corrosion led to the formation of an inner magnetite layer, an intermediate Fe(2)CO(3)(OH)(2) (chukanovite) layer, an outer layer of Fe-rich 7 A-phyllosilicate, and a transformed matrix layer containing siderite (FeCO(3)). The corroded thickness was estimated to 85 microm, less than 30% of the value expected from the supplied anodic charge. The difference was accounted for by reoxidation at the anodically polarized surface of cathodically produced H(2)(g). Thus, free or anodically activated corroding conditions led to structurally similar interfaces, indicating that anodic polarization can be used to probe the long-term corrosion of iron in clay. Finally, corrosion products retained only half of Fe oxidized by anodic activation. Missing Fe probably migrated in the clay, where it could interact with radionuclides released by alteration of nuclear glass.

Microstructure and properties of Fe-based composite coating by laser cladding Fe-Ti-V-Cr-C-CeO2 powder

NASA Astrophysics Data System (ADS)

Zhang, Hui; Zou, Yong; Zou, Zengda; Wu, Dongting

2015-01-01

In situ TiC-VC reinforced Fe-based cladding layer was obtained on low carbon steel surface by laser cladding with Fe-Ti-V-Cr-C-CeO2 alloy powder. The microstructure, phases and properties of the cladding layer were investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), transmission electron microscopy (TEM), potentio-dynamic polarization and electro-chemical impedance spectroscopy (EIS). Results showed Fe-Ti-V-Cr-C-CeO2 alloy powder formed a good cladding layer without defects such as cracks and pores. The phases of the cladding layer were α-Fe, γ-Fe, TiC, VC and TiVC2. The microstructures of the cladding layer matrix were lath martensite and retained austenite. The carbides were polygonal blocks with a size of 0.5-2 μm and distributed uniformly in the cladding layer. High resolution transmission electron microscopy showed the carbide was a complex matter composed of nano TiC, VC and TiVC2. The cladding layer with a hardness of 1030 HV0.2 possessed good wear and corrosion resistance, which was about 16.85 and 9.06 times than that of the substrate respectively.

Effect of iron particle size and volume fraction on the magnetic properties of Fe/silicate glass soft magnetic composites

NASA Astrophysics Data System (ADS)

Ding, Wei; Jiang, Longtao; Liao, Yaqin; Song, Jiabin; Li, Bingqing; Wu, Gaohui

2015-03-01

Fe/silicate glass soft magnetic composites (SMC) were fabricated by powder metallurgy with 1000 MPa pressure at room temperature, and then annealed at 700 °C for 90 min. The iron particles distributed uniformly in the composites, and have been separated from each other by a continuous silicate glass insulating layer. Fe/glass interface was well bonded and a quasi-continuous layer Fe3O4 and FeO exited. Very fine crystalline phases Na12Ca3Fe2(Si6O18)2 were formed in silicate glass. Composite containing 57 vol% 75 μm iron particles demonstrated highest resistivity of 7.8×10-3 Ω m. The μm, Bs and Bt increased while Hc of Fe/silicate glass composites decreased with the increase of average size of iron particles. The composite with highest amount (82 vol%) and largest average size (140 μm) of iron particles demonstrated best μm, Bs and Bt and Hc, which were 622, 1.57 T, 1.43 T, 278 A/m, respectively. The composite containing 57 vol% 75 μm iron particles demonstrated minimum core loss of 3.5 W/kg at 50 Hz and 28.1 W/kg at 400 Hz, while the composite containing 82 vol% 140 μm iron particles exhibited maximum core loss of 5.2 W/kg at 50 Hz and 67.7 W/kg at 400 Hz.

Ba2F2Fe2+ 0.5Fe3+ S3: a two-dimensional inhomogeneous mixed valence iron compound.

PubMed

Kabbour, Houria; Cario, Laurent

2008-03-03

The structure of the new mixed valence compound Ba2F2Fe1.5S3 was solved by means of single crystal X-ray analysis. It crystallizes in an orthorhombic cell, in the Pnma space group with the cell parameters a = 12.528(3) A, b = 18.852(4) A, and c = 6.0896(12) A. The structure is formed by the alternated stacking of fluorite type [Ba2F2]2+ blocks and the newly discovered [Fe1.5S3]2- blocks. This [Fe1.5S3]2- block exhibits a mixed valence of iron with Fe(+II) located in octahedrons and Fe(+III) in tetrahedrons. Preliminary susceptibility measurements suggest a low dimensional antiferromagnetic behavior.

Oxygen and iron isotope studies of magnetite produced by magnetotactic bacteria

USGS Publications Warehouse

Mandernack, K.W.; Bazylinski, D.A.; Shanks, Wayne C.; Bullen, T.D.

1999-01-01

A series of carefully controlled laboratory studies was carried out to investigate oxygen and iron isotope fractionation during the intracellular production of magnetite (Fe3O4) by two different species of magnetotactic bacteria at temperatures between 4??and 35??C under microaerobic and anaerobic conditions. No detectable fractionation of iron isotopes in the bacterial magnetites was observed. However, oxygen isotope measurements indicated a temperature-dependent fractionation for Fe3O4 and water that is consistent with that observed for Fe3O4 produced extracellularly by thermophilic Fe3+-reducing bacteria. These results contrast with established fractionation curves estimated from either high-temperature experiments or theoretical calculations. With the fractionation curve established in this report, oxygen-18 isotope values of bacterial Fe3O4 may be useful in paleoenvironmental studies for determining the oxygen-18 isotope values of formation waters and for inferring paleotemperatures.

Electrochemical synthesis of hard-alloy compositions based on tungsten carbide and an iron triad metal

NASA Astrophysics Data System (ADS)

Kushkhov, Kh. B.; Adamokova, M. N.; Kvashin, V. A.; Kardanov, A. L.

2010-08-01

Single and cyclic voltammetry is used to study the electrode processes that occur during electrochemical synthesis of hard-alloy compositions based on tungsten carbide and an iron triad metal in tungstate and tungstate-carbonate Na2WO4-Li2WO4-Li2CO3 (5.0-22.0 wt %) melts. The conditions of bringing the electroprecipitation potentials of tungsten, carbon, and an iron triad metal into coincidence are determined.

Hydrogenation of Carbon Dioxide to Methanol Catalyzed by Iron, Cobalt, and Manganese Cyclopentadienone Complexes: Mechanistic Insights and Computational Design.

PubMed

Ge, Hongyu; Chen, Xiangyang; Yang, Xinzheng

2017-07-03

Density functional theory study of the hydrogenation of carbon dioxide to methanol catalyzed by iron, cobalt, and manganese cyclopentadienone complexes reveals a self-promoted mechanism, which features a methanol- or water-molecule-assisted proton transfer for the cleavage of H 2 . The total free energy barrier of the formation of methanol from CO 2 and H 2 catalyzed by Knölker's iron cyclopentadienone complex, [2,5-(SiMe 3 ) 2 -3,4-(CH 2 ) 4 (η 5 -C 4 COH)]Fe(CO) 2 H, is 26.0 kcal mol -1 in the methanol solvent. We also evaluated the catalytic activities of 8 other experimentally reported iron cyclopentadienone complexes and 37 iron, cobalt, and manganese cyclopentadienone complexes proposed in this study. In general, iron and manganese complexes have relatively higher catalytic activities. Among all calculated complexes, [2,5-(SiMe 3 ) 2 -3,4-CH 3 CHSCH 2 (η 5 -C 4 COH)]Fe(CO) 2 H (1 Fe-Casey-S-CH3 ) is the most active one with a total free energy barrier of 25.1 kcal mol -1 in the methanol solvent. Such a low barrier indicates that 1 Fe-Casey-S-CH3 is a very promising low-cost and high efficiency catalyst for the conversion of CO 2 and H 2 to methanol under mild conditions. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Iron Carbides and Nitrides: Ancient Materials with Novel Prospects.

PubMed

Ye, Zhantong; Zhang, Peng; Lei, Xiang; Wang, Xiaobai; Zhao, Nan; Yang, Hua

2018-02-07

Iron carbides and nitrides have aroused great interest in researchers, due to their excellent magnetic properties, good machinability and the particular catalytic activity. Based on these advantages, iron carbides and nitrides can be applied in various areas such as magnetic materials, biomedical, photo- and electrocatalysis. In contrast to their simple elemental composition, the synthesis of iron carbides and nitrides still has great challenges, particularly at the nanoscale, but it is usually beneficial to improve performance in corresponding applications. In this review, we introduce the investigations about iron carbides and nitrides, concerning their structure, synthesis strategy and various applications from magnetism to the catalysis. Furthermore, the future prospects are also discussed briefly. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Revision of iron(III)-citrate speciation in aqueous solution. Voltammetric and spectrophotometric studies.

PubMed

Vukosav, Petra; Mlakar, Marina; Tomišić, Vladislav

2012-10-01

A detailed study of iron (III)-citrate speciation in aqueous solution (θ=25°C, I(c)=0.7 mol L(-1)) was carried out by voltammetric and UV-vis spectrophotometric measurements and the obtained data were used for reconciled characterization of iron (III)-citrate complexes. Four different redox processes were registered in the voltammograms: at 0.1 V (pH=5.5) which corresponded to the reduction of iron(III)-monocitrate species (Fe:cit=1:1), at about -0.1 V (pH=5.5) that was related to the reduction of FeL(2)(5-), FeL(2)H(4-) and FeL(2)H(2)(3-) complexes, at -0.28 V (pH=5.5) which corresponded to the reduction of polynuclear iron(III)-citrate complex(es), and at -0.4V (pH=7.5) which was probably a consequence of Fe(cit)(2)(OH)(x) species reduction. Reversible redox process at -0.1 V allowed for the determination of iron(III)-citrate species and their stability constants by analyzing E(p) vs. pH and E(p) vs. [L(4-)] dependence. The UV-vis spectra recorded at varied pH revealed four different spectrally active species: FeLH (logβ=25.69), FeL(2)H(2)(3-) (log β=48.06), FeL(2)H(4-) (log β=44.60), and FeL(2)(5-) (log β=38.85). The stability constants obtained by spectrophotometry were in agreement with those determined electrochemically. The UV-vis spectra recorded at various citrate concentrations (pH=2.0) supported the results of spectrophotometric-potentiometric titration. Copyright © 2012 Elsevier B.V. All rights reserved.

Characterisation of iron inclusion during the formation of calcium sulfoaluminate phase

DOE Office of Scientific and Technical Information (OSTI.GOV)

Idrissi, M., E-mail: mari_idrissi@yahoo.f; Diouri, A.; Damidot, D.

The iron distribution among the sulfoaluminate clinker phases and its ability to enter the calcium sulfoaluminate lattice in solid solution can have a significant influence on manufacturing process and reactivity of calcium sulfoaluminate (CSA) cements. X-ray diffraction (XRD) analysis, Moessbauer spectroscopy, scanning electron microscopy (SEM) equipped with an energy dispersive X-ray analysis system (EDAX) and infrared spectroscopy were used to identify the mineralogical conditions of iron inclusion during the formation of calcium sulfoaluminate (C{sub 4}A{sub 3}S) phase from different mixtures in the CaO-Al{sub 2}O{sub 3}-Fe{sub 2}O{sub 3}-SO{sub 3} system. The mixtures, heated in a laboratory electric oven, contained stoichiometric amountsmore » of reagent grade CaCO{sub 3}, Al{sub 2}O{sub 3}, Fe{sub 2}O{sub 3} and CaSO{sub 4.2}H{sub 2}O for the synthesis of Ca{sub 4}Al{sub (6-2x)}Fe{sub 2x}SO{sub 16}, where x, comprised between 0 and 3, is the mole number of Al{sub 2}O{sub 3} substituted by Fe{sub 2}O{sub 3}. With x increasing from 0 to 1.5, both the iron content of C{sub 4}A{sub 3}S phase and the amounts of side components such as C{sub 2}F and CS increased. For x values included in the range of 1.5-3.0, at temperatures higher than 1200 {sup o}C, melting phenomena were observed and, instead of the C{sub 4}A{sub 3}S solid solution, ferritic phases and anhydrite were formed.« less

Carotenoids, but not vitamin A, improve iron uptake and ferritin synthesis by Caco-2 cells from ferrous fumarate and NaFe-EDTA.

PubMed

García-Casal, María N; Leets, Irene

2014-04-01

Due to the high prevalence of iron and vitamin A deficiencies and to the controversy about the role of vitamin A and carotenoids in iron absorption, the objectives of this study were to evaluate the following: (1) the effect of a molar excess of vitamin A as well as the role of tannic acid on iron uptake by Caco-2 cells; (2) iron uptake and ferritin synthesis in presence of carotenoids without pro-vitamin A activity: lycopene, lutein, and zeaxantin; and (3) iron uptake and ferritin synthesis from ferrous fumarate and NaFe-EDTA. Cells were incubated 1 h at 37 °C in PBS pH 5.5, containing (59) Fe and different iron compounds. Vitamin A, ferrous fumarate, β-carotene, lycopene, lutein, zeaxantin, and tannic acid were added to evaluate uptake. Ferritin synthesis was measured 24 h after uptake experiments. Vitamin A had no effect on iron uptake by Caco-2 cells, and was significantly lower from NaFe-EDTA than from ferrous fumarate (15.2 ± 2.5 compared with 52.5 ± 8.3 pmol Fe/mg cell protein, respectively). Carotenoids increase uptake up to 50% from fumarate and up to 300% from NaFe-EDTA, since absorption from this compound is low when administered alone. We conclude the following: (1) There was no effect of vitamin A on iron uptake and ferritin synthesis by Caco-2cells. (2) Carotenoids significantly increased iron uptake from ferrous fumarate and NaFe-EDTA, and were capable of partially overcoming the inhibition produced by tannic acid. (3) Iron uptake by Caco-2 cell from NaFe-EDTA was significantly lower compared to other iron compounds, although carotenoids increased and tannic acid inhibited iron uptake comparably to ferrous fumarate. © 2014 Institute of Food Technologists®

Carbide-reinforced metal matrix composite by direct metal deposition

NASA Astrophysics Data System (ADS)

Novichenko, D.; Thivillon, L.; Bertrand, Ph.; Smurov, I.

Direct metal deposition (DMD) is an automated 3D laser cladding technology with co-axial powder injection for industrial applications. The actual objective is to demonstrate the possibility to produce metal matrix composite objects in a single-step process. Powders of Fe-based alloy (16NCD13) and titanium carbide (TiC) are premixed before cladding. Volume content of the carbide-reinforced phase is varied. Relationships between the main laser cladding parameters and the geometry of the built-up objects (single track, 2D coating) are discussed. On the base of parametric study, a laser cladding process map for the deposition of individual tracks was established. Microstructure and composition of the laser-fabricated metal matrix composite objects are examined. Two different types of structures: (a) with the presence of undissolved and (b) precipitated titanium carbides are observed. Mechanism of formation of diverse precipitated titanium carbides is studied.

Characterization of a tricationic trigonal bipyramidal iron(IV) cyanide complex, with a very high reduction potential, and its iron(II) and iron(III) congeners.

PubMed

England, Jason; Farquhar, Erik R; Guo, Yisong; Cranswick, Matthew A; Ray, Kallol; Münck, Eckard; Que, Lawrence

2011-04-04

Currently, there are only a handful of synthetic S = 2 oxoiron(IV) complexes. These serve as models for the high-spin (S = 2) oxoiron(IV) species that have been postulated, and confirmed in several cases, as key intermediates in the catalytic cycles of a variety of nonheme oxygen activating enzymes. The trigonal bipyramidal complex [Fe(IV)(O)(TMG(3)tren)](2+) (1) was both the first S = 2 oxoiron(IV) model complex to be generated in high yield and the first to be crystallographically characterized. In this study, we demonstrate that the TMG(3)tren ligand is also capable of supporting a tricationic cyanoiron(IV) unit, [Fe(IV)(CN)(TMG(3)tren)](3+) (4). This complex was generated by electrolytic oxidation of the high-spin (S = 2) iron(II) complex [Fe(II)(CN)(TMG(3)tren)](+) (2), via the S = 5/2 complex [Fe(III)(CN)(TMG(3)tren)](2+) (3), the progress of which was conveniently monitored by using UV-vis spectroscopy to follow the growth of bathochromically shifting ligand-to-metal charge transfer (LMCT) bands. A combination of X-ray absorption spectroscopy (XAS), Mössbauer and NMR spectroscopies was used to establish that 4 has a S = 0 iron(IV) center. Consistent with its diamagnetic iron(IV) ground state, extended X-ray absorption fine structure (EXAFS) analysis of 4 indicated a significant contraction of the iron-donor atom bond lengths, relative to those of the crystallographically characterized complexes 2 and 3. Notably, 4 has an Fe(IV/III) reduction potential of ∼1.4 V vs Fc(+/o), the highest value yet observed for a monoiron complex. The relatively high stability of 4 (t(1/2) in CD(3)CN solution containing 0.1 M KPF(6) at 25 °C ≈ 15 min), as reflected by its high-yield accumulation via slow bulk electrolysis and amenability to (13)C NMR at -40 °C, highlights the ability of the sterically protecting, highly basic peralkylguanidyl donors of the TMG(3)tren ligand to support highly charged high-valent complexes.

Characterization of a Tricationic Trigonal Bipyramidal Iron(IV) Cyanide Complex, with a Very High Reduction Potential, and Its Iron(II) and Iron(III) Congeners

PubMed Central

England, Jason; Farquhar, Erik R.; Guo, Yisong; Cranswick, Matthew A.; Ray, Kallol

2011-01-01

Currently, there are only a handful of synthetic S = 2 oxoiron(IV) complexes. These serve as models for the high-spin (S = 2) oxoiron(IV) species that have been postulated, and confirmed in several cases, as key intermediates in the catalytic cycles of a variety of non-heme oxygen activating enzymes. The trigonal bipyramidal complex [FeIV(O)(TMG3tren)]2+ (1) was both the first S = 2 oxoiron(IV) model complex to be generated in high yield and the first to be crystallographically characterized. In this study, we demonstrate that the TMG3tren ligand is also capable of supporting a tricationic cyanoiron(IV) unit, [FeIV(CN)(TMG3tren)]3+ (4). This complex was generated by electrolytic oxidation of the high-spin (S = 2) iron(II) complex [FeII(CN)(TMG3tren)]+ (2), via the S = 5/2 complex [FeIII(CN)(TMG3tren)]2+ (3), the progress of which was conveniently monitored by using UV-Vis spectroscopy to follow the growth of bathochromically shifting LMCT bands. A combination of XAS, Mössbauer and NMR spectroscopies was used to establish that 4 has a S = 0 iron(IV) center. Consistent with its diamagnetic iron(IV) ground state, EXAFS analysis of 4 indicated a significant contraction of the iron-donor atom bond lengths, relative to those of the crystallographically characterized complexes 2 and 3. Notably, 4 has an FeIV/III reduction potential of ~1.4 V vs Fc+/o, the highest value yet observed for a monoiron complex. The relatively high stability of 4 (t1/2 in CD3CN solution containing 0.1 M KPF6 at 25 °C ≈ 15 min), as reflected by its high-yield accumulation via slow bulk electrolysis and amenability to 13C NMR at −40 °C, highlights the ability of the sterically protecting, highly basic peralkylguanidyl donors of the TMG3tren ligand to support highly charged high-valent complexes. PMID:21381646

Reduction reactions and densification during in situ TEM heating of iron oxide nanochains

NASA Astrophysics Data System (ADS)

Bonifacio, Cecile S.; Das, Gautom; Kennedy, Ian M.; van Benthem, Klaus

2017-12-01

The reduction reactions and densification of nanochains assembled from γ-Fe2O3 nanoparticles were investigated using in situ transmission electron microscopy (TEM). Morphological changes and reduction of the metal oxide nanochains were observed during in situ TEM annealing through simultaneous imaging and quantitative analysis of the near-edge fine structures of Fe L2,3 absorption edges acquired by spatially resolved electron energy loss spectroscopy. A change in the oxidation states during annealing of the iron oxide nanochains was observed with phase transformations due to continuous reduction from Fe2O3 over Fe3O4, FeO to metallic Fe. Phase transitions during the in situ heating experiments were accompanied with morphological changes in the nanochains, specifically rough-to-smooth surface transitions below 500 °C, neck formation between adjacent particles around 500 °C, and subsequent neck growth. At higher temperatures, coalescence of FeO particles was observed, representing densification.

Producing Fe-W-Co-Cr-C Alloy Cutting Tool Material Through Powder Metallurgy Route

NASA Astrophysics Data System (ADS)

Datta Banik, Bibhas; Dutta, Debasish; Ray, Siddhartha

2017-04-01

High speed steel tools can withstand high impact forces as they are tough in nature. But they cannot retain their hardness at elevated temperature i.e. their hot hardness is low. Therefore permissible cutting speed is low and tools wear out easily. Use of lubricants is essential for HSS cutting tools. On the other hand cemented carbide tools can withstand greater compressive force, but due to lower toughness the tool can break easily. Moreover the cost of the tool is comparatively high. To achieve a better machining economy, Fe-W-Co-Cr-C alloys are being used nowadays. Their toughness is as good as HSS tools and hardness is very near to carbide tools. Even, at moderate cutting speeds they can be safely used in old machines having vibration. Moreover it is much cheaper than carbide tools. This paper highlights the Manufacturing Technology of the alloy and studies the comparative tribological properties of the alloy and tungsten mono carbide.

Effect of synthesizing method on the properties of LiFePO4/C composite for rechargeable lithium-ion batteries

NASA Astrophysics Data System (ADS)

Yoon, Man-Soon; Islam, Mobinul; Park, Young Min; Ur, Soon-Chul

2013-03-01

Olivine-type LiFePO4/C cathode materials are fabricated with FePO4 powders that are pre-synthesized by two different processes from iron chloride solution. Process I is a modified precipitation method which is implemented by the pH control of a solution using NH4OH to form FePO4 precipitates at room temperature. Process II is a conventional precipitation method, of which H3PO4 (85%) solution is gradually added to a FeCl3 solution during the process to maintain a designated mole ratio. The solution is subsequently aged at 90°C in a water bath until FePO4 precipitates appear. In order to synthesize LiFePO4/C composites, each batch of FePO4 powders is then mixed with pre-milled lithium carbonate and glucose (8 wt. %) as a carbon source in a ball-mill. The structural characteristics of both LiFePO4/C composites fabricated using iron phospates from two different routes have been examined employing XRD and SEM. The modified precipitation process is considered to be a relatively simple and effective process for the preparation of LiFePO4/C composites owing to their excellent electrochemical properties and rate capabilities.

Effect of micro-scale texturing on the cutting tool performance

NASA Astrophysics Data System (ADS)

Vasumathy, D.; Meena, Anil

2018-05-01

The present study is mainly focused on the cutting performance of the micro-scale textured carbide tools while turning AISI 304 austenitic stainless steel under dry cutting environment. The texture on the rake face of the carbide tools was fabricated by laser machining. The cutting performance of the textured tools was further compared with conventional tools in terms of cutting forces, tool wear, machined surface quality and chip curl radius. SEM and EDS analyses have been also performed to better understand the tool surface characteristics. Results show that the grooves help in breaking the tool-chip contact leading to a lesser tool-chip contact area which results in reduced iron (Fe) adhesion to the tool.

Iron(II) complexes of new hexadentate 1,1,1-tris-(iminomethyl)ethane podands, and their 7-methyl-1,3,5-triazaadamantane rearrangement products.

PubMed

Diener, Sara A; Santoro, Amedeo; Kilner, Colin A; Loughrey, Jonathan J; Halcrow, Malcolm A

2012-04-07

New iron(II) podand complexes have been prepared, by condensation of 2-(aminomethyl)-2-methyl-1,3-diaminopropane with 3 equiv of a heterocyclic aldehyde in the presence of hydrated Fe[BF(4)](2) or Fe[ClO(4)](2) as templates. The 2-(aminomethyl)-2-methyl-1,3-diaminopropane is prepared in situ by deprotonation of its trihydrochloride salt. The chloride must be removed from these reactions by precipitation with silver, to avoid the formation of the alternative 2,4,6-trisubstituted-7-methyl-1,3,5-triazaadamantane condensation products, or their FeCl(2) adducts. The crystal structures of two 2,4,6-tri(pyridyl)-7-methyl-1,3,5-triazaadamantane-containing species are presented, and contain two different geometric isomers of this tricyclic ring with three equatorial, or two equatorial and one axial, pyridyl substituents. Both structures feature strong C-HX (X = Cl or F) hydrogen bonding from the aminal C-H groups in the triazaadamantane ring. Five iron(II) podand complexes were successfully obtained, all of which contain low-spin iron centres.

Synthesis Functional and Constructional Nanomaterials on a Basis Carbide Tungsten, Molybdenum and Metals of a Triad of Iron in Ionic Melts

NASA Astrophysics Data System (ADS)

Kushkhov, H. B.; Adamokova, M. N.; Kvashin, V. A.; Kardanov, A. L.

2011-04-01

Single and cyclic voltammetry is used to study the electrode processes that occur during electrochemical synthesis of hard-alloy compositions based on tungsten carbide and an iron triad metal in tungstate and tungstate-carbonate Na2WO4-Li2WO4-Li2CO3 (5.0-22.0 wt %) melts. The conditions of bringing the electroprecipitation potentials of tungsten, carbon, and an iron triad metal into coincidence are determined.

Chemical composition of Earth's core

NASA Astrophysics Data System (ADS)

Saxena, S.

2017-12-01

Many planetary scientists accept that the condensed planetesimals in the solar nebula eventually led to accretion of the earth. The details of the process have not been worked out. From the metallurgical experience, it is assumed that Earth's core may have formed by density differentiation with iron sinking to the core and the slag forming the mantle. This would be a post-accretionary process with temperature developing with self-compression. The problem with this hypothesis was recognized some time ago in that the seismic density profile of the core does not match the density of iron and requires the addition of a light element. Many elements such as Si, O, C and s have been proposed as diluents to decrease the density of a purely iron core. How and when this will be accomplished is still under discussion. Since the planetesimals (or condensates) formed in a well stirred nebula, it may be argued that a variety of condensed solids and fluids may have accreted and compressed without differentiation and the core does not necessarily contain mainly the differentiated iron. It is a matter of accumulating the condensate composition that would result in a density of 12 to 13 g/cm3 in the inner core. Therefore, we need a thermodynamic database that extends to 6000 K over the pressure range of ambient to 360 GPa. The development of such a database is currently in progress. It is a database with multicomponent solutions (C-Fe-Ni-S-Si) and all the major elements in the solar gas. Thermodynamic calculations using a preliminary dataset reveal that the solid species condensed at a temperature of 650 K and a pressure of 0.001 bar pressure, when self-compressed to various pressures and temperatures, yield densities that are appropriate for the mantle and core. Depending on H2/O of the escaping fluid, the formation of hydrous minerals, carbides, carbonates and iron melts with significant other elements have been found. Earth's core may have formed from solar condensate materials representing a range of solids avaeraging the seismic density of 13 kg/m3. Such material does not have to be Fe-Ni alloy but could be many different solids and a multielement alloy. Appropriate PVT equations of state have been used in arriving at this conclusion.

The use of ultrasmall iron(0) nanoparticles as catalysts for the selective hydrogenation of unsaturated C-C bonds.

PubMed

Kelsen, Vinciane; Wendt, Bianca; Werkmeister, Svenja; Junge, Kathrin; Beller, Matthias; Chaudret, Bruno

2013-04-28

The performance of well-defined ultrasmall iron(0) nanoparticles (NPs) as catalysts for the selective hydrogenation of unsaturated C-C and C=X bonds is reported. Monodisperse iron nanoparticles of about 2 nm size are synthesized by the decomposition of {Fe(N[Si(CH3)3]2)2}2 under dihydrogen. They are found to be active for the hydrogenation of various alkenes and alkynes under mild conditions and weakly active for C=O bond hydrogenation.

Magnetic characteristics of ultrafine Fe particles reduced from uniform iron oxide particles

NASA Astrophysics Data System (ADS)

Bridger, K.; Watts, J.; Tadros, M.; Xiao, Gang; Liou, S. H.; Chien, C. L.

1987-04-01

Uniform, cubic 0.05-μm iron oxide particles were formed by forced hydrolysis of ferric perchlorate. These particles were reduced to α-Fe by heating in hydrogen at temperatures between 300 and 500 °C. The effect of reduction temperature and various prereduction treatments on the microstructure of the iron particles will be discussed. Complete reduction to α-Fe was established by 57Fe Mössbauer spectroscopy and x-ray diffraction. Magnetic measurements on epoxy and polyurethane films containing these particles with various mass fractions gave coercivities as high as 1000 Oe. The relationship between the magnetic measurements and the microstructure will be discussed. Na2SiO3 is found to be the best coating material for the process of reducing iron oxide particles to iron.

Speciation in the Fe(III)-Cl(I)-H2O System at 298.15 K, 313.15 K, and 333.15 K (25 °C, 40 °C, and 60 °C)

NASA Astrophysics Data System (ADS)

Jamett, Nathalie E.; Hernández, Pía C.; Casas, Jesús M.; Taboada, María E.

2018-02-01

This article presents the results on speciation of ferric iron generated by the dissolution of chemical reagent hydromolysite (ferric chloride hexahydrate, FeCl3:6H2O) in water at 298.15 K, 313.15 K, and 333.15 K (25 °C, 40 °C, and 60 °C). Experiments were performed with a thermoregulated system up to the equilibrium point, as manifested by solution pH. Solution samples were analyzed in terms of concentration, pH, and electrical conductivity. Measurements of density and refractive index were obtained at different temperatures and iron concentrations. A decrease of pH was observed with the increase in the amount of dissolved iron, indicating that ferric chloride is a strong electrolyte that reacts readily with water. Experimental results were modeled using the hydrogeochemical code PHREEQC in order to obtain solution speciation. Cations and neutral and anion complexes were simultaneously present in the system at the studied conditions according to model simulations, where dominant species included Cl-, FeCl2+, FeCl2 +, FeOHCl 2 0 , and H+. A decrease in the concentration of Cl- and Fe3+ ions took place with increasing temperature due to the association of Fe-Cl species. Standard equilibrium constants for the formation of FeOHCl 2 0 obtained in this study were log Kf0 = -0.8 ± 0.01 at 298.15 K (25 °C), -0.94 ± 0.02 at 313.15 K (40 °C), and -1.03 ± 0.01 at 333.15 K (60 °C).

Synthesis of nanostructured iron oxides dispersed in carbon materials and in situ XRD study of the changes caused by thermal treatment

NASA Astrophysics Data System (ADS)

Gonçalves, Gustavo R.; Schettino, Miguel A.; Morigaki, Milton K.; Nunes, Evaristo; Cunha, Alfredo G.; Emmerich, Francisco G.; Passamani, Edson C.; Baggio-Saitovitch, Elisa; Freitas, Jair C. C.

2015-07-01

Carbon-based magnetic nanocomposites are of large interest for applications in catalysis, magnetic separation, water cleaning, and magnetic resonance imaging, among others. This work describes the synthesis of nanocomposites consisting of iron oxides dispersed into a char (obtained from the carbonization at 700 °C of a lignocellulosic precursor) and the study of the thermal transformations occurring in these materials as a consequence of heat treatments. The materials were prepared by impregnation of the char with iron nitrate in the presence of ammonium hydroxide in aqueous suspension. X-ray diffraction experiments performed using synchrotron radiation and Mössbauer spectroscopy showed that the as-prepared material was composed of amorphous Fe3+ oxides. Scanning electron microscopy images combined with energy-dispersive X-ray spectrometry indicated a homogeneous dispersion of iron oxides and of silica particles (naturally present in the lignocellulosic precursor) throughout the char. X-ray diffractograms recorded in situ during the heat treatment of the as-prepared material showed the presence of small hematite crystallites (average size 22 nm) starting from ca. 300 °C. Further heating caused a progressive growth of the hematite crystallites up to ca. 500 °C, when the conversion to magnetite (Fe3O4) started to take place. At higher temperatures, wüstite (Fe1-xO) was detected as an intermediate phase and austenitic iron (γ-Fe) became the dominant phase at temperatures from 900 °C. A steep weight loss was observed in the TG curve accompanying this last reduction stage; upon cooling, γ-Fe was converted into α-Fe (ferrite), which was the dominant phase at room temperature in this heat-treated sample.

Switching Magnetism and Superconductivity with Spin-Polarized Current in Iron-Based Superconductor.

PubMed

Choi, Seokhwan; Choi, Hyoung Joon; Ok, Jong Mok; Lee, Yeonghoon; Jang, Won-Jun; Lee, Alex Taekyung; Kuk, Young; Lee, SungBin; Heinrich, Andreas J; Cheong, Sang-Wook; Bang, Yunkyu; Johnston, Steven; Kim, Jun Sung; Lee, Jhinhwan

2017-12-01

We explore a new mechanism for switching magnetism and superconductivity in a magnetically frustrated iron-based superconductor using spin-polarized scanning tunneling microscopy (SPSTM). Our SPSTM study on single-crystal Sr_{2}VO_{3}FeAs shows that a spin-polarized tunneling current can switch the Fe-layer magnetism into a nontrivial C_{4} (2×2) order, which cannot be achieved by thermal excitation with an unpolarized current. Our tunneling spectroscopy study shows that the induced C_{4} (2×2) order has characteristics of plaquette antiferromagnetic order in the Fe layer and strongly suppresses superconductivity. Also, thermal agitation beyond the bulk Fe spin ordering temperature erases the C_{4} state. These results suggest a new possibility of switching local superconductivity by changing the symmetry of magnetic order with spin-polarized and unpolarized tunneling currents in iron-based superconductors.

Switching Magnetism and Superconductivity with Spin-Polarized Current in Iron-Based Superconductor

NASA Astrophysics Data System (ADS)

Choi, Seokhwan; Choi, Hyoung Joon; Ok, Jong Mok; Lee, Yeonghoon; Jang, Won-Jun; Lee, Alex Taekyung; Kuk, Young; Lee, SungBin; Heinrich, Andreas J.; Cheong, Sang-Wook; Bang, Yunkyu; Johnston, Steven; Kim, Jun Sung; Lee, Jhinhwan

2017-12-01

We explore a new mechanism for switching magnetism and superconductivity in a magnetically frustrated iron-based superconductor using spin-polarized scanning tunneling microscopy (SPSTM). Our SPSTM study on single-crystal Sr2VO3FeAs shows that a spin-polarized tunneling current can switch the Fe-layer magnetism into a nontrivial C4 (2 ×2 ) order, which cannot be achieved by thermal excitation with an unpolarized current. Our tunneling spectroscopy study shows that the induced C4 (2 ×2 ) order has characteristics of plaquette antiferromagnetic order in the Fe layer and strongly suppresses superconductivity. Also, thermal agitation beyond the bulk Fe spin ordering temperature erases the C4 state. These results suggest a new possibility of switching local superconductivity by changing the symmetry of magnetic order with spin-polarized and unpolarized tunneling currents in iron-based superconductors.

Occurrence of spherical ceramic debris in indentation and sliding contact

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1982-01-01

Indenting experiments were conducted with the silicon carbide (0001) surface in contact with a spherical diamond indenter in air. Sliding friction experiments were also conducted with silicon carbide in contact with iron and iron-based binary alloys at room temperature and 800 C. Fracture pits with a spherical particle and spherical wear debris were observed as a result of indenting and sliding. Spherical debris may be produced by a mechanism that involves a spherical-shaped fracture along the circular or spherical stress trajectories under the inelastic deformation zone.

Measuring “Free” Iron Levels in Caenorhabditis Elegans Using Low-Temperature Fe(III) Electron Paramagnetic Resonance Spectroscopy

PubMed Central

Pate, Kira T.; Rangel, Natalie A.; Fraser, Brian; Clement, Matthew H. S.; Srinivasan, Chandra

2007-01-01

Oxidative stress, caused by free radicals within the body, has been associated with the process of aging and many human diseases. As free radicals, in particular superoxide, are difficult to measure, an alternative indirect method for measuring oxidative stress levels has been successfully used in E. coli and yeast. This method is based on a proposed connection between elevated superoxide levels and release of iron from solvent exposed [4Fe-4S] enzyme clusters, which eventually leads to an increase in hydroxyl radical production. In past studies using bacteria and yeast, a positive correlation was found between superoxide production or oxidative stress due to superoxide within the organism and EPR (electron paramagnetic resonance) detectable “free” iron levels. In the present study, we have developed a reliable and an efficient method for measuring “free” iron levels in C. elegans using low temperature Fe(III) EPR at g = 4.3. This method utilizes synchronized worm cultures grown on plates, which are homogenized and treated with desferrioxamine, an Fe(III) chelator, prior to packing the EPR tube. Homogenization was found not to alter “free” iron levels, while desferrioxamine treatment significantly raised these levels, indicating presence of both Fe(II) and Fe(III) in the “free” iron pool. The correlation between free radical levels and the observed “free” iron levels was examined by using heat stress and paraquat treatment. The intensity of the Fe(III) EPR signal and thus, the concentration of the “free” iron pool, varied with the treatments that altered radical levels without changing the total iron levels. This study provides the groundwork needed to uncover the correlation between oxidative stress, “free” iron levels, and longevity in C. elegans. PMID:17010298

Behavior of LiFe1-yMnyPO4/C cathode materials upon electrochemical lithium intercalation/deintercalation

NASA Astrophysics Data System (ADS)

Novikova, Svetlana; Yaroslavtsev, Sergey; Rusakov, Vyacheslav; Chekannikov, Andrey; Kulova, Tatiana; Skundin, Alexander; Yaroslavtsev, Andrey

2015-12-01

LiFe1-yMnyPO4/C (y = 0-0.3) nanocomposites are prepared by the sol-gel method, and their properties are characterized with the use of the XRD analysis, SEM, impedance spectroscopy, charge/discharge tests, and Mössbauer spectroscopy. The samples with a low manganese content, LiFe1-yMnyPO4 (y = 0.1, 0.2) are characterized by an increased conductivity. In LiFe1-yMnyPO4 (x = 0.1-0.3), electrochemical lithium deintercalation/intercalation proceeds in two stages which due to the subsequent oxidation/reduction of iron and manganese ions. The LiFe1-yMnyPO4/С (y = 0.1, 0.2) samples show enhanced charge/discharge capacity, especially, at high current density (for LiFe0.9Mn0.1PO4/C, the discharge capacity is equal to 142 and 55 mAh g-1 at a current density of 20 and 1600 mA g-1, respectively). Mn2+ ↔ Mn3+ transition in LiFe1-yMnyPO4 proceeds via the solid solutions formation under gradual changes in the potential. For LiFe0.7Mn0.3PO4, oxidation and reduction of iron ions follow the same scenario. According to the Mössbauer spectroscopy data, manganese is orderly distributed in LixFeIII1-yMnyPO4: iron contains not more than one manganese cation in its nearest neighborhood. Moreover, combination of the Mössbauer spectroscopy and X-ray analysis data indicates that, in the interval where solid solutions exist in LixFe0.7Mn0.3PO4, the regions with an inhomogeneous distribution of divalent and trivalent manganese ions are formed.

PVDF membranes containing hybrid nanoparticles for adsorbing cationic dyes: physical insights and mechanism

NASA Astrophysics Data System (ADS)

Sharma, Maya; Madras, Giridhar; Bose, Suryasarathi

2016-07-01

In this study, Fe (iron) and Ag (silver) based adsorbents were synthesized using solution combustion and in situ reduction techniques. The synthesized adsorbents were comprehensively characterized by different techniques including electron microscopy, BET, XRD, Zeta potential etc. Three chlorinated cationic dyes used were malachite green, methyl violet and pyronin Y. These dyes were adsorbed on various synthesized adsorbents [iron III oxide (Fe2O3)], iron III oxide decorated silver nanoparticles by combustion synthesis technique [Fe2O3-Ag(C)] and iron III oxide decorated silver nanoparticles using in situ reduction, [Fe2O3-Ag (S)]. The isotherm and the adsorption kinetics have been studied systematically. The kinetic data can be explained by the pseudo second order model and the adsorption equilibrium followed Langmuir isotherm. The equilibrium and kinetics results suggest that Fe2O3-Ag(S) nanoparticles showed the maximum adsorption among all the adsorbents. Hence, Polyvinylidene fluoride based membranes containing Fe2O3-Ag(S) nanoparticles were prepared via phase inversion (precipitation immersion using DMF/water) technique. The adsorption kinetics were studied in detail and it was observed that the composite membrane showed synergistic improvement in dye adsorption. Such membranes can be used for water purification.

Spark plasma sintering synthesis of Ni1-xZnxFe2O4 ferrites: Mössbauer and catalytic study

NASA Astrophysics Data System (ADS)

Velinov, Nikolay; Manova, Elina; Tsoncheva, Tanya; Estournès, Claude; Paneva, Daniela; Tenchev, Krassimir; Petkova, Vilma; Koleva, Kremena; Kunev, Boris; Mitov, Ivan

2012-08-01

Nickel-zinc ferrite nanoparticles, Ni1-xZnxFe2O4 (x = 0, 0.2, 0.5, 0.8, 1.0) were prepared by combination of chemical precipitation and spark plasma sintering (SPS) techniques and conventional thermal treatment of the obtained precursors. The phase composition and structural properties of the obtained materials were investigated by X-ray diffraction and Mössbauer spectroscopy and their catalytic activity in methanol decomposition was tested. A strong effect of reaction medium leading to the transformation of ferrites to a complex mixture of different iron containing phases was detected. A tendency of formation of Fe-carbide was found for the samples synthesized by SPS, while predominantly iron-nickel alloys ware registered in TS obtained samples. The catalytic activity and selectivity in methanol decomposition to CO and methane depended on the current phase composition of the obtained ferrites, which was formed by the influence of the reaction medium.

C Diffusion in Fe: Isotope Effects and Other Complexities

NASA Astrophysics Data System (ADS)

Watson, E. B.; Muller, T.; Trail, D.; Van Orman, J. A.; Papineau, D.

2011-12-01

Carbon is a minor but significant component of iron meteorites, and probably also of planetary cores, including that of Earth. Given the dynamical nature of core-forming processes, C diffusion in the metal phase may play a role in C equilibration between Fe-Ni metal and silicate, carbide or oxide at some stage. Despite its relevance to steel-making, C diffusion in Fe is not well characterized over the range of conditions of interest in planetary bodies, and the likelihood of an isotope mass effect on C diffusion has not been explored. The prospect of incomplete diffusive equilibration of carbon in Fe-Ni raises the possibility that carbon isotopes might be fractionated by diffusion during core formation and evolution-perhaps to an extent that could affect the C isotope ratio of the bulk silicate Earth. Here we report results of preliminary experiments addressing the isotopic mass effect on C diffusion in Fe. Initial low-pressure experiments were conducted by placing a layer of ^{13}C-enriched graphite ( 20% ^{13}C) at the end of a high-purity, polycrystalline Fe cylinder in a silica glass container. These diffusion couples were run in a piston-cylinder apparatus at 1.5 GPa and 1000-1100^{o}C for several hours, and the resulting C-uptake profiles in the Fe cylinders were measured by EPMA and SIMS. In traverses moving away from the original C-Fe interface, total carbon decreases monotonically and becomes significantly lighter, indicating that ^{12}C diffuses faster than ^{13}C. Preliminary estimates of β in the relative isotope diffusivity relation D_{1}/D_{2} = [M_{2}/M_{1}]^{β} (where D is diffusivity and M is mass of isotopes 1 and 2) suggest values as high as 0.5, corresponding to predictions for gaseous diffusion. Isotope mass effects approaching this magnitude have been observed previously for diffusion in metals, and are expected to be highest for interstitial diffusion. Such a high β value will lead to major C isotope fractionation in some partial equilibration scenarios in planets and meteorite parent bodies. Caution is warranted at this point, however, because D_{carbon} is sensitive to carbon concentration, complicating quantification of the isotope effect.

Siderophile Element Partitioning between Cohenite and Liquid in Fe-Ni-S-C System and Implications for Geochemistry of Planetary Cores and Mantles

NASA Astrophysics Data System (ADS)

Buono, A. S.; Dasgupta, R.; Walker, D.

2011-12-01

Secular cooling of terrestrial planets is known to cause crystallization of a solid inner core from metallic liquid core. Fractionation of light and siderophile elements is important during such crystallization for evolution of outer core and possible core-mantle interaction. Thus far studies focused on a pure Fe inner core in simple binary systems but the effects of possible formation of a carbide inner core component on siderophile element partitioning in a multi-component system has yet to be looked at in detail. We investigated the effects of pressure and S content on partition coefficients (D) between cohenite and liquid in the Fe-Ni-S-C system. Multi-anvil experiments were performed at 3 and 6 GPa at 1150 °C, in an Fe-rich mix containing a constant C and Ni to which S contents of 0, 5, and 14 wt.% were added. All the mixes were doped with W, Re, Os, Pt, and Co. Samples were imaged and analyzed for Fe, Ni, S, and C using an EPMA. Fe, Ni, and trace elements were analyzed using a LA-ICP-MS. All the experiments produced cohenite and Fe-Ni-C±S liquid. Compared to solid-Fe/melt Ds [1-2], cohenite/melt Ds are lower for all elements except W. The light element (S+C) content of the liquid is the dominant controlling factor in siderophile element partitioning between cohenite and liquid as it is between crystalline Fe and liquid. In the cohenite-metallic melt experiments, D Ni decreases as S+C increases. Ni is excluded from the crystallizing solid if the solid is cohenite. We also find that in the Fe-Ni-S-C system, cohenite is stabilized to higher P than in the Fe-S-C system [3-5]. Similar to the Fe-metallic liquid systems the non-metal avoidance model [6] is applicable to the Fe3C-metallic liquid system studied here. Our study has implications for both the cores of smaller planets and the mantles of larger planets. If inner core forms a cohenite layer we would predict that depletions in the outer core will be less than they might be for Fe metal crystallization. For the mantle of the earth, which is thought to become Fe-Ni metal-saturated as shallow as 250 km, the sub-system Fe-Ni + C + S becomes relevant and Fe-Ni carbide rather than metallic Fe-Ni alloy may become the crystalline phase of interest. Our study implies that because the partition coefficients between cohenite and Fe-C-S melts are significantly lower than those between Fe-metal and S-rich liquid, in the presence of cohenite and Fe-C-S melt in the mantle, the mantle budget of Ni, Co, and Pt may be dominated by Fe-C-S liquid. W, Re, and Os will also be slightly enriched in C-rich Fe-Ni liquid over cohenite if the metal sub-system of interest is S-free. [1] Chabot et al., GCA 70, 1322-1335, 2006 [2] Chabot et al., GCA 72, 4146-4158, 2008 [3] Chabot et al., Meteorit. Planet. Sci. 42, 1735-1750, 2007 [4] Stewart et al., EPSL 284, 302-309, 2009 [5] Van Orman et al., EPSL 274, 250-257, 2008 [6] Jones, J.H., Malvin, D.J., Metall Mater Trans B 21, 697-706, 1990

SufD and SufC ATPase activity are required for iron acquisition during in vivo Fe-S cluster formation on SufB.

PubMed

Saini, Avneesh; Mapolelo, Daphne T; Chahal, Harsimranjit K; Johnson, Michael K; Outten, F Wayne

2010-11-02

In vivo biogenesis of Fe-S cluster cofactors requires complex biosynthetic machinery to limit release of iron and sulfide, to protect the Fe-S cluster from oxidation, and to target the Fe-S cluster to the correct apoenzyme. The SufABCDSE pathway for Fe-S cluster assembly in Escherichia coli accomplishes these tasks under iron starvation and oxidative stress conditions that disrupt Fe-S cluster metabolism. Although SufB, SufC, and SufD are all required for in vivo Suf function, their exact roles are unclear. Here we show that SufB, SufC, and SufD, coexpressed with the SufS-SufE sulfur transfer pair, purify as two distinct complexes (SufBC(2)D and SufB(2)C(2)) that contain Fe-S clusters and FADH(2). These studies also show that SufC and SufD are required for in vivo Fe-S cluster formation on SufB. Furthermore, while SufD is dispensable for in vivo sulfur transfer, it is absolutely required for in vivo iron acquisition. Finally, we demonstrate for the first time that the ATPase activity of SufC is necessary for in vivo iron acquisition during Fe-S cluster assembly.

Orenia metallireducens sp. nov. strain Z6, a Novel Metal-reducing [member of the Phylum] Firmicute from the Deep Subsurface

DOE PAGES

Dong, Yiran; Sanford, Robert A.; Boyanov, Maxim I.; ...

2016-08-26

A novel halophilic and metal-reducing bacterium, Orenia metallireducens strain Z6, was isolated from briny groundwater extracted from a 2.02 km-deep borehole in the Illinois Basin, IL. This organism shared 96% 16S rRNA gene similarity with Orenia marismortui but demonstrated physiological properties previously unknown for this genus. In addition to exhibiting a fermentative metabolism typical of the genus Orenia, strain Z6 reduces various metal oxides [Fe(III), Mn(IV), Co(III), and Cr(VI)], using H 2 as the electron donor. Strain Z6 actively reduced ferrihydrite over broad ranges of pH (6 to 9.6), salinity (0.4 to 3.5 M NaCl), and temperature (20 to 60°C).more » At pH 6.5, strain Z6 also reduced more crystalline iron oxides, such as lepidocrocite (γ-FeOOH), goethite (α-FeOOH), and hematite (α-Fe 2O 3). Analysis of X-ray absorption fine structure (XAFS) following Fe(III) reduction by strain Z6 revealed spectra from ferrous secondary mineral phases consistent with the precipitation of vivianite [Fe 3(PO 4) 2] and siderite (FeCO 3). The draft genome assembled for strain Z6 is 3.47 Mb in size and contains 3,269 protein-coding genes. Unlike the well-understood iron-reducing Shewanella and Geobacter species, this organism lacks the c-type cytochromes for typical Fe(III) reduction. Strain Z6 represents the first bacterial species in the genus Orenia (order Halanaerobiales) reported to reduce ferric iron minerals and other metal oxides. This microbe expands both the phylogenetic and physiological scopes of iron-reducing microorganisms known to inhabit the deep subsurface and suggests new mechanisms for microbial iron reduction. In conclusion, these distinctions from other Orenia spp. support the designation of strain Z6 as a new species, Orenia metallireducens sp. nov.« less

Grain boundary character, and carbide size and spatial distribution in a ternary nickel alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, H.; Gao, M.; Harlow, D.G.

1995-06-01

A preliminary investigation of the grain boundary character and its relationship to carbide distribution in a Ni-18Cr-18Fe ternary alloy was conducted. The results showed that there was a strong preference for the formation of {Sigma}3 (44.6%) and twin-related {Sigma}9 and {Sigma}27 CSL boundaries. If the coherent {Sigma}3{sub c} twin and the twin-related boundaries are excluded, then the distribution would consist of nearly 80% random (high angle) boundaries and about 20% CSL (with {Sigma} {<=} 49) boundaries. The size and spacing of grain boundary carbides were influenced by grain boundary {Sigma}; the carbides being smaller and more closely spaced on themore » {Sigma}1, {Sigma}9 and {Sigma}27 boundaries, and none could be resolved on the coherent {Sigma}3 twin boundaries. The results could be understood, in part, in terms of the influence of grain boundary energy, but the understanding is incomplete. Further studies are in progress and will be reported.« less

Lead iron phosphate glass as a containment medium for disposal of high-level nuclear waste

DOEpatents

Boatner, Lynn A.; Sales, Brian C.

1989-01-01

Lead-iron phosphate glasses containing a high level of Fe.sub.2 O.sub.3 for use as a storage medium for high-level radioactive nuclear waste. By combining lead-iron phosphate glass with various types of simulated high-level nuclear waste, a highly corrosion resistant, homogeneous, easily processed glass can be formed. For corroding solutions at 90.degree. C., with solution pH values in the range between 5 and 9, the corrosion rate of the lead-iron phosphate nuclear waste glass is at least 10.sup.2 to 10.sup.3 times lower than the corrosion rate of a comparable borosilicate nuclear waste glass. The presence of Fe.sub.2 O.sub.3 in forming the lead-iron phosphate glass is critical. Lead-iron phosphate nuclear waste glass can be prepared at temperatures as low as 800.degree. C., since they exhibit very low melt viscosities in the 800.degree. to 1050.degree. C. temperature range. These waste-loaded glasses do not readily devitrify at temperatures as high as 550.degree. C. and are not adversely affected by large doses of gamma radiation in H.sub.2 O at 135.degree. C. The lead-iron phosphate waste glasses can be prepared with minimal modification of the technology developed for processing borosilicate glass nuclear wasteforms.

Immobilization of bacterial S-layer proteins from Caulobacter crescentus on iron oxide-based nanocomposite: synthesis and spectroscopic characterization of zincite-coated Fe₂O₃ nanoparticles.

PubMed

Habibi, Neda

2014-05-05

Zinc oxide was coated on Fe2O3 nanoparticles using sol-gel spin-coating. Caulobacter crescentus have a crystalline surface layer (S-layer), which consist of one protein or glycoprotein species. The immobilization of bacterial S-layers obtained from C. crescentus on zincite-coated nanoparticles of iron oxide was investigated. The SDS PAGE results of S-layers isolated from C. crescentus showed the weight of 50 KDa. Nanoparticles of the Fe2O3 and zinc oxide were synthesized by a sol-gel technique. Fe2O3 nanoparticles with an average size of 50 nm were successfully prepared by the proper deposition of zinc oxide onto iron oxide nanoparticles surface annealed at 450 °C. The samples were characterized by field-emission scanning electron microscope (FESEM), atomic force microscopy (AFM), powder X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR). Copyright © 2014 Elsevier B.V. All rights reserved.

The effects of redox fluctuation on iron-organic matter interactions in wet tropical soils

NASA Astrophysics Data System (ADS)

Bhattacharyya, A.; Campbell, A.; Lin, Y.; Nico, P. S.; Silver, W. L.; Pett-Ridge, J.

2016-12-01

Two-thirds of the C in the terrestrial biosphere is stored as soil organic C, and much of this is stabilized via iron (Fe) mineral-organic matter (OM) associations that are susceptible to redox effects. The rapid C cycling typical of wet tropical ecosystems- driven by ample moisture and temperature- may also be fueled by a characteristically dynamic redox environment. Yet the net result of altered tropical soil climate and fluctuating soil redox regimes on Fe-organic matter associations is poorly understood. In this study, we hypothesized that the timing of redox transitions (frequency of O2 introduction and ferrous iron (Fe2+) generation) will lead to differences in Fe (oxyhydr)oxide mineral crystallinity and C degradation rates and alter the proportion of organic C associated with iron minerals. Surface soils from a humid tropical forest in Puerto Rico were incubated for 44 days under four redox regimes: (1) static anoxic, (2) static oxic, (3) 4 days anoxic, 4 days oxic, and (4) 4 days anoxic, 8 days oxic. Replicate microcosms were harvested at multiple time points, including before and after a redox switch (oxic to anoxic or vice versa). Selective chemical extractions, bulk Fe K-edge EXAFS and STXM/NEXAFS spectromicroscopy were used to comprehensively probe treatment effects on Fe and C speciation. Static redox conditions had a significant effect on Fe2+ and dissolved organic carbon (DOC) concentrations, and prolonged anoxia promoted reductive dissolution of Fe-oxides and an increase in amorphous or short-range ordered (SRO) Fe oxides. Preferential dissolution of this less-crystalline Fe pool was more prominent during rapid redox switches from oxic to anoxic conditions, and coincided with increased DOC. Bulk Fe K-edge EXAFS spectroscopy identified Fe3+ as the dominant Fe species in all treatments and indicated O/N atoms in the first Fe co-ordination sphere and features similar to SRO Fe-oxide phases (e.g. ferrihydrite or nano-goethite) in the second co-ordination sphere. STXM/NEXAFS analyses indicated an increase in lignin-like biomolecules under static anoxic conditions, and a potential role of Fe-lignin interactions under strong reducing conditions. Our current findings highlight the necessity to explore natural redox-dynamic systems in greater detail in order to develop a better model for climate change.

Carbon dioxide hydrogenation to aromatic hydrocarbons by using an iron/iron oxide nanocatalyst.

PubMed

Wang, Hongwang; Hodgson, Jim; Shrestha, Tej B; Thapa, Prem S; Moore, David; Wu, Xiaorong; Ikenberry, Myles; Troyer, Deryl L; Wang, Donghai; Hohn, Keith L; Bossmann, Stefan H

2014-01-01

The quest for renewable and cleaner energy sources to meet the rapid population and economic growth is more urgent than ever before. Being the most abundant carbon source in the atmosphere of Earth, CO2 can be used as an inexpensive C1 building block in the synthesis of aromatic fuels for internal combustion engines. We designed a process capable of synthesizing benzene, toluene, xylenes and mesitylene from CO2 and H2 at modest temperatures (T = 380 to 540 °C) employing Fe/Fe3O4 nanoparticles as catalyst. The synthesis of the catalyst and the mechanism of CO2-hydrogenation will be discussed, as well as further applications of Fe/Fe3O4 nanoparticles in catalysis.

The CaGeO3 Ca3Fe2Ge3O12 garnet join: an experimental study

NASA Astrophysics Data System (ADS)

Iezzi, Gianluca; Boffa-Ballaran, Tiziana; McCammon, Catherine; Langenhorst, Falko

2005-06-01

Germanate garnets are often used as isostructural analogues of silicate garnets to provide insight into the crystal chemistry and symmetry of the less accessible natural garnet solid solutions. We synthesised two series of germanate garnets at 3 GPa along the joinVIIICa3VI(CaGe)IVGe3O12 VIIICa3VIFe2IVGe3O12 at 900 °C and 1,100 °C. Samples with compositions close to the CaGeO3 end-member consist of tetragonal garnet with a small amount of triclinic CaGe2O5. Samples with nominal compositions between XFe=0.4 and 1.0 consist of a mixture of tetragonal and cubic garnets; whereas, single-phase cubic garnets were obtained for compositions with XFe>1.2 (XFe gives the iron content expressed in atoms per formula unit, and varies between 0 and 2 along the join). Run products which were primarily single-phase garnet were investigated using Mössbauer spectroscopy. Spectra from samples synthesised at 1,100°C consist of one well-resolved doublet that can be assigned to Fe3+ in the octahedral site of the garnet structure. A second doublet, present primarily in samples synthesised at 900°C, can be assigned to Fe2+ at the octahedral sites of the garnet structure. The relative abundance of Fe2+ decreases with increasing iron content. Transmission electron microscopy analyses confirm this tendency and show that the garnets are essentially defect-free. The unit-cell parameters of tetragonal VIIICa3VI(CaGe)IVGe3O3 garnet decrease with increasing synthesis temperature, and the deviation from cubic symmetry becomes smaller. Cubic garnets show a linear decrease of unit-cell parameter with increasing iron content. The results are discussed in the context of iron incorporation into VIIIMg3VI(MgSi)IVSi3O3 majorite.

Engineering of Iron-Based Magnetic Activated Carbon Fabrics for Environmental Remediation

PubMed Central

Haham, Hai; Grinblat, Judith; Sougrati, Moulay-Tahar; Stievano, Lorenzo; Margel, Shlomo

2015-01-01

Magnetic Fe3O4, Fe and Fe/Pd nanoparticles embedded within the pores of activated carbon fabrics (ACF) were prepared by impregnation of the ACF in iron acetylacetanoate (Fe(acac)3) ethanol solution, followed by thermal decomposition of the embedded iron precursor at 200, 400 and 600 °C in an inert atmosphere. The effect of the annealing temperature on the chemical composition, shape, crystallinity, surface area, pore volume, and magnetic properties of the various functionalized ACF was elucidated. The Fe nanoparticles within the ACF were also doped with tinier Pd nanoparticles, by impregnation of the Fe/ACF in palladium acetate ethanol solution. The potential use of the functionalized ACF for removal of a model azo-dye, orange II, was demonstrated. This study illustrated the enhanced removal of the dye from an aqueous solution according to the following order: Fe/Pd/ACF > Fe/ACF > ACF. In addition, the enhanced activity of Fe3O4/ACF in the presence of increasing concentrations of H2O2 (Fenton catalysts) was also illustrated. PMID:28793459

Dynamics of CrO 3 –Fe 2 O 3 Catalysts during the High-Temperature Water-Gas Shift Reaction: Molecular Structures and Reactivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Keturakis, Christopher J.; Zhu, Minghui; Gibson, Emma K.

2016-06-13

A series of supported CrO 3/Fe 2O 3 catalysts were investigated for the high-temperature water-gas shift (WGS) and reverse-WGS reactions and extensively characterized using in situ and operando IR, Raman, and XAS spectroscopy during the high-temperature WGS/RWGS reactions. The in situ spectroscopy examinations reveal that the initial oxidized catalysts contain surface dioxo (O=) 2Cr 6+O 2 species and a bulk Fe 2O 3 phase containing some Cr 3+ substituted into the iron oxide bulk lattice. Operando spectroscopy studies during the high-temperature WGS/RWGS reactions show that the catalyst transforms during the reaction. The crystalline Fe 2O 3 bulk phase becomes Femore » 3O 4 ,and surface dioxo (O=) 2Cr 6+O 2 species are reduced and mostly dissolve into the iron oxide bulk lattice. Consequently, the chromium–iron oxide catalyst surface is dominated by FeO x sites, but some minor reduced surface chromia sites are also retained. The Fe 3–-xCr xO 4 solid solution stabilizes the iron oxide phase from reducing to metallic Fe0 and imparts an enhanced surface area to the catalyst. Isotopic exchange studies with C 16O 2/H 2 → C 18O 2/H 2 isotopic switch directly show that the RWGS reaction proceeds via the redox mechanism and only O* sites from the surface region of the chromium–iron oxide catalysts are involved in the RWGS reaction. The number of redox O* sites was quantitatively determined with the isotope exchange measurements under appropriate WGS conditions and demonstrated that previous methods have undercounted the number of sites by nearly 1 order of magnitude. The TOF values suggest that only the redox O* sites affiliated with iron oxide are catalytic active sites for WGS/RWGS, though a carbonate oxygen exchange mechanism was demonstrated to exist, and that chromia is only a textural promoter that increases the number of catalytic active sites without any chemical promotion effect.« less

Reactivity pathways for nitric oxide and nitrosonium with iron complexes in biologically relevant sulfur coordination spheres.

PubMed

Harrop, Todd C; Song, Datong; Lippard, Stephen J

2007-11-01

The interaction of nitric oxide (NO) with iron-sulfur cluster proteins results in the formation of dinitrosyl iron complexes (DNICs) coordinated by cysteine residues from the peptide backbone or with low molecular weight sulfur-containing molecules like glutathione. Such DNICs are among the modes available in biology to store, transport, and deliver NO to its relevant targets. In order to elucidate the fundamental chemistry underlying the formation of DNICs and to characterize possible intermediates in the process, we have investigated the interaction of NO (g) and NO(+) with iron-sulfur complexes having the formula [Fe(SR)(4)](2-), where R=(t)Bu, Ph, or benzyl, chosen to mimic sulfur-rich iron sites in biology. The reaction of NO (g) with [Fe(S(t)Bu)(4)](2-) or [Fe(SBz)(4)](2-) cleanly affords the mononitrosyl complexes (MNICs), [Fe(S(t)Bu)(3)(NO)](-) (1) and [Fe(SBz)(3)(NO)](-) (3), respectively, by ligand displacement. Mononitrosyl species of this kind were previously unknown. These complexes further react with NO (g) to generate the corresponding DNICs, [Fe(SPh)(2)(NO)(2)](-) (4) and [Fe(SBz)(2)(NO)(2)](-) (5), with concomitant reductive elimination of the coordinated thiolate donors. Reaction of [Fe(SR)(4)](2-) complexes with NO(+) proceeds by a different pathway to yield the corresponding dinitrosyl S-bridged Roussin red ester complexes, [Fe(2)(mu-S(t)Bu)(2)(NO)(4)] (2), [Fe(2)(mu-SPh)(2)(NO)(4)] (7) and [Fe(2)(mu-SBz)(2)(NO)(4)] (8). The NO/NO(+) reactivity of an Fe(II) complex with a mixed nitrogen/sulfur coordination sphere was also investigated. The DNIC and red ester species, [Fe(S-o-NH(2)C(6)H(4))(2)(NO)(2)](-) (6) and [Fe(2)(mu-S-o-NH(2)C(6)H(4))(2)(NO)(4)] (9), were generated. The structures of 8 and 9 were verified by X-ray crystallography. The MNIC complex 1 can efficiently deliver NO to iron-porphyrin complexes like [Fe(TPP)Cl], a reaction that is aided by light. Removal of the coordinated NO ligand of 1 by photolysis and addition of elemental sulfur generates higher nuclearity Fe/S clusters.

Synthesis and visible light photocatalytic properties of iron oxide–silver orthophosphate composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Febiyanto,; Eliani, Irma Vania; Riapanitra, Anung

2016-04-19

The iron oxide-silver orthophosphate composites were successfully synthesized by co-precipitation method using Fe(NO{sub 3}){sub 3}.9H{sub 2}O, AgNO{sub 3}, and Na{sub 2}HPO{sub 4}.12 H{sub 2}O, followed by calcination at 500°C for 5 hours. The Fe/Ag mole ratios of iron oxide-silver orthophosphate composites were designed at 0, 0.1, 0.2, 0.3 and 0.4. The samples were characterized using X-ray Diffraction, Diffuse Reflectance Spectroscopy, Scanning Electron Microscopy and Specific Surface Area. The photocatalytic activities were evaluated using Rhodamine B degradation under visible light irradiation. The iron oxide-silver orthophosphate composite with the Fe/Ag mole ratio of 0.2 exhibited higher photocatalytic activity compared to the puremore » Ag{sub 3}PO{sub 4} under visible light irradiation. The enhanced photocatalytic activity could be attributed to the effective separation of hole (+) and electron pairs in the iron oxide-silver orthophosphate composite.« less

AMD-like retinopathy associated with intravenous iron

PubMed Central

Song, Delu; Kanu, Levi N.; Li, Yafeng; Kelly, Kristen L.; Bhuyan, Rupak K.; Aleman, Tomas; Morgan, Jessica I. W.; Dunaief, Joshua L.

2016-01-01

Iron accumulation in the retina is associated with the development of age-related macular degeneration (AMD). IV iron is a common method to treat iron deficiency anemia in adults, and its retinal manifestations have not hitherto been identified. To assess whether IV iron formulations can be retina-toxic, we generated a mouse model for iron-induced retinal damage. Male C57BL/6J mice were randomized into groups receiving IV iron-sucrose (+Fe) or 30% sucrose (−Fe). Iron levels in neurosensory retina (NSR), retinal pigment epithelium (RPE), and choroid were assessed using immunofluorescence, quantitative PCR, and the Perls’ iron stain. Iron levels were most increased in the RPE and choroid while levels in the NSR did not differ significantly in +Fe mice compared to controls. Eyes from +Fe mice shared histological features with AMD, including Bruch’s membrane (BrM) thickening with complement C3 deposition, as well as RPE hypertrophy and vacuolization. This focal degeneration correlated with areas with high choroidal iron levels. Ultrastructural analysis provided further detail of the RPE/photoreceptor outer segment vacuolization and Bruch’s membrane thickening. Findings were correlated with a clinical case of a 43-year-old patient who developed numerous retinal drusen, the hallmark of AMD, within 11 months of IV iron therapy. Our results suggest that IV iron therapy may have the potential to induce or exacerbate a form of retinal degeneration. This retinal degeneration shares features with AMD, indicating the need for further study of AMD risk in patients receiving IV iron treatment. PMID:27565570

Iron encapsulated in 3D N-doped carbon nanotube/porous carbon hybrid from waste biomass for enhanced oxidative activity.

PubMed

Yao, Yunjin; Zhang, Jie; Wu, Guodong; Wang, Shaobin; Hu, Yi; Su, Cong; Xu, Tongwen

2017-03-01

Novel iron encapsulated in nitrogen-doped carbon nanotubes (CNTs) supported on porous carbon (Fe@N-C) 3D structured materials for degrading organic pollutants were fabricated from a renewable, low-cost biomass, melamine, and iron salt as the precursors. SEM and TEM micrographs show that iron encapsulated bamboo shaped CNTs are vertically standing on carbon sheets, and thus, a 3D hybrid was formed. The catalytic activities of the prepared samples were thoroughly evaluated by activation of peroxymonosulfate for catalytic oxidation of Orange II solutions. The influences of some reaction conditions (pH, temperature, and concentrations of reactants, peroxymonosulfate, and dye) were extensively evaluated. It was revealed that the adsorption could enrich the pollutant which was then rapidly degraded by the catalytically generated radicals, accelerating the continuous adsorption of residual pollutant. Remarkable carbon structure, introduction of CNTs, and N/Fe doping result in promoted adsorption capability and catalytic performances. Due to the simple synthetic process and cheap carbon precursor, Fe@N-C 3D hybrid can be easily scaled up and promote the development of Fenton-like catalysts.

Heterobimetallic Silver-Iron Complexes Involving Fe(CO)5 Ligands.

PubMed

Wang, Guocang; Ceylan, Yavuz S; Cundari, Thomas R; Dias, H V Rasika

2017-10-11

Iron(0) pentacarbonyl is an organometallic compound with a long history. It undergoes carbonyl displacement chemistry with various donors (L), leading to molecules of the type Fe(CO) x (L) 5-x . The work reported here illustrates that Fe(CO) 5 can also act as a ligand. The reaction between Fe(CO) 5 with the silver salts AgSbF 6 and Ag[B{3,5-(CF 3 ) 2 C 6 H 3 } 4 ] under appropriate conditions resulted in the formation of [(μ-H 2 O)AgFe(CO) 5 ] 2 [SbF 6 ] 2 and [B{3,5-(CF 3 ) 2 C 6 H 3 } 4 ]AgFe(CO) 5 , respectively, featuring heterobimetallic {Ag-Fe(CO) 5 } + fragments. The treatment of [B{3,5-(CF 3 ) 2 C 6 H 3 } 4 ]AgFe(CO) 5 with 4,4'-dimethyl-2,2'-bipyridine (Me 2 Bipy) and Fe(CO) 5 afforded a heterobimetallic [(Me 2 Bipy)AgFe(CO) 5 ][B{3,5-(CF 3 ) 2 C 6 H 3 } 4 ] species with a Ag-Fe(CO) 5 bond and a heterotrimetallic [{Fe(CO) 5 } 2 (μ-Ag)][B{3,5-(CF 3 ) 2 C 6 H 3 } 4 ] with a (CO) 5 Fe-Ag-Fe(CO) 5 core, respectively, illustrating that it is possible to manipulate the coordination sphere at silver while keeping the Ag-Fe bond intact. The chemistry of [B{3,5-(CF 3 ) 2 C 6 H 3 } 4 ]AgFe(CO) 5 with Et 2 O and PMes 3 (Mes = 2,4,6-trimethylphenyl) has also been investigated, which led to [(Et 2 O) 3 Ag][B{3,5-(CF 3 ) 2 C 6 H 3 } 4 ] and [(Mes 3 P) 2 Ag][B{3,5-(CF 3 ) 2 C 6 H 3 } 4 ] with the displacement of the Fe(CO) 5 ligand. X-ray structural and spectroscopic data of new molecules as well as results of computational analyses are presented. The Fe-Ag bond distances of these metal-only Lewis pairs range from 2.5833(4) to 2.6219(5) Å. These Ag-Fe bonds are of primarily an ionic/electrostatic nature with a modest amount of charge transfer between Ag + and Fe(CO) 5 . The ν̅(CO) bands of the molecules with Ag-Fe(CO) 5 bonds show a notable blue shift relative to those observed for free Fe(CO) 5 , indicating a significant reduction in Fe→CO back-bonding upon its coordination to silver(I).

Lipid peroxidation, antioxidant enzymes and glutathione levels in human erythrocytes exposed to colloidal iron hydroxide in vitro.

PubMed

Ferreira, A L; Machado, P E; Matsubara, L S

1999-06-01

The free form of the iron ion is one of the strongest oxidizing agents in the cellular environment. The effect of iron at different concentrations (0, 1, 5, 10, 50, and 100 microM Fe3+) on the normal human red blood cell (RBC) antioxidant system was evaluated in vitro by measuring total (GSH) and oxidized (GSSG) glutathione levels, and superoxide dismutase (SOD), catalase, glutathione peroxidase (GSH-Px) and reductase (GSH-Rd) activities. Membrane lipid peroxidation was assessed by measuring thiobarbituric acid reactive substance (TBARS). The RBC were incubated with colloidal iron hydroxide and phosphate-buffered saline, pH 7.45, at 37 degrees C, for 60 min. For each assay, the results for the control group were: a) GSH = 3.52 +/- 0.27 microM/g Hb; b) GSSG = 0.17 +/- 0.03 microM/g Hb; c) GSH-Px = 19.60 +/- 1.96 IU/g Hb; d) GSH-Rd = 3.13 +/- 0.17 IU/g Hb; e) catalase = 394.9 +/- 22.8 IU/g Hb; f) SOD = 5981 +/- 375 IU/g Hb. The addition of 1 to 100 microM Fe3+ had no effect on the parameters analyzed. No change in TBARS levels was detected at any of the iron concentrations studied. Oxidative stress, measured by GSH kinetics over time, occurs when the RBC are incubated with colloidal iron hydroxide at concentrations higher than 10 microM of Fe3+. Overall, these results show that the intact human RBC is prone to oxidative stress when exposed to Fe3+ and that the RBC has a potent antioxidant system that can minimize the potential damage caused by acute exposure to a colloidal iron hydroxide in vitro.

Interaction of γ-Fe2O3 nanoparticles with Citrus maxima leaves and the corresponding physiological effects via foliar application.

PubMed

Hu, Jing; Guo, Huiyuan; Li, Junli; Wang, Yunqiang; Xiao, Lian; Xing, Baoshan

2017-07-11

Nutrient-containing nanomaterials have been developed as fertilizers to foster plant growth and agricultural yield through root applications. However, if applied through leaves, how these nanomaterials, e.g. γ-Fe 2 O 3 nanoparticles (NPs), influence the plant growth and health are largely unknown. This study is aimed to assess the effects of foliar-applied γ-Fe 2 O 3 NPs and their ionic counterparts on plant physiology of Citrus maxima and the associated mechanisms. No significant changes of chlorophyll content and root activity were observed upon the exposure of 20-100 mg/L γ-Fe 2 O 3 NPs and Fe 3+ . In C. maxima roots, no oxidative stress occurred under all Fe treatments. In the shoots, 20 and 50 mg/L γ-Fe 2 O 3 NPs did not induce oxidative stress while 100 mg/L γ-Fe 2 O 3 NPs did. Furthermore, there was a positive correlation between the dosages of γ-Fe 2 O 3 NPs and Fe 3+ and iron accumulation in shoots. However, the accumulated iron in shoots was not translocated down to roots. We observed down-regulation of ferric-chelate reductase (FRO2) gene expression exposed to γ-Fe 2 O 3 NPs and Fe 3+ treatments. The gene expression of a Fe 2+ transporter, Nramp3, was down regulated as well under γ-Fe 2 O 3 NPs exposure. Although 100 mg/L γ-Fe 2 O 3 NPs and 20-100 mg/L Fe 3+ led to higher wax content, genes associated with wax formation (WIN1) and transport (ABCG12) were downregulated or unchanged compared to the control. Our results showed that both γ-Fe 2 O 3 NPs and Fe 3+ exposure via foliar spray had an inconsequential effect on plant growth, but γ-Fe 2 O 3 NPs can reduce nutrient loss due to their the strong adsorption ability. C. maxima plants exposed to γ-Fe 2 O 3 NPs and Fe 3+ were in iron-replete status. Moreover, the biosynthesis and transport of wax is a collaborative and multigene controlled process. This study compared the various effects of γ-Fe 2 O 3 NPs, Fe 3+ and Fe chelate and exhibited the advantages of NPs as a foliar fertilizer, laying the foundation for the future applications of nutrient-containing nanomaterials in agriculture and horticulture. Graphical abstract γ-Fe 2 O 3 NPs exposed on plants via foliar spray and genes associated with the absorption and transformation of iron, as well as wax synthesis and secretion in Citrus maxima leaves.

3D interconnected hierarchical porous N-doped carbon constructed by flake-like nanostructure with Fe/Fe3C for efficient oxygen reduction reaction and supercapacitor.

PubMed

Li, Guoning; Zhang, Jiajun; Li, Weisong; Fan, Kai; Xu, Chunjian

2018-05-17

Hierarchical porous N-doped carbon with Fe/Fe3C nanoparticles, high content of N dopants (10.51 wt%), and a 3D interconnected porous architecture constructed by flake-like nanostructure was facilely prepared by carbonization of a zeolitic imidazolate framework-8 (ZIF-8) as a self-sacrificing template and potassium ferricyanide (PF) as a multifunctional iron precursor. The unique porous structure can offer a continuous pathway for electron transfer and shorten the mass transfer pathway, which contribute to both an oxygen reduction reaction (ORR) and a supercapacitor. The influence of the carbonization temperature and iron content on the performance of ORR and supercapacitor was investigated. The as-prepared composites carbonized at 800 °C (Fe-CZIF-800-10) displayed comparable ORR activity with Pt/C in alkaline media as well as excellent long-term stability, superb methanol tolerance, and appreciable onset potential in acid media. Moreover, Fe-CZIF-800-10 exhibited excellent capacity of 246 F g-1 at a current density of 0.5 A g-1 and stability in 6 M KOH. This report provides a facile approach to prepare hierarchical porous Fe/N-doped carbon as a promising electrode material for both fuel cell and supercapacitor applications.

Studies on different iron source absorption by in situ ligated intestinal loops of broilers.

PubMed

Jia, Y F; Jiang, M M; Sun, J; Shi, R B; Liu, D S

2015-02-01

The objective of this study was to investigate the iron source absorption in the small intestine of broiler. In situ ligated intestinal loops of 70 birds were poured into one of seven solutions, including inorganic iron (FeSO4, Fe2(SO4)3), organic Fe glycine chelate (Fe-Gly(II), Fe-Gly(III)), the mixtures (FeSO4 with glycine (Fe+Gly(II)), Fe2(SO4)3 with glycine (Fe+Gly(III)), and no Fe source (control). The total volume of 3-mL solution (containing 1 mg of elemental Fe) was injected into intestinal loops, and then 120-min incubation was performed. Compared with inorganic iron groups, in which higher FeSO4 absorption than Fe2(SO4)3 was observed, supplementation with organic Fe glycine chelate significantly increased the Fe concentration in the duodenum and jejunum (P < 0.05), however, decreased DMT1 and DcytB messenger RNA (mRNA) levels (P < 0.05). Organic Fe glycine chelate (Fe-Gly(II), Fe-Gly(III)) increased serum iron concentration (SI), compared with inorganic 3 valence iron groups (Fe2(SO4)3 and Fe+Gly(III)) (P < 0.05); moreover, lower TIBC value was observed for the chelate (P < 0.05); however, mixture of inorganic iron and glycine did not have a positive role at DMT1 and DcytB mRNA levels, SI and Fe concentrations in the small intestine. Those results indicated that the absorption of organic Fe glycine chelate was more effective than that of inorganic Fe, and the orders of iron absorption in the small intestine were: Fe-Gly(II), Fe-Gly(III) > FeSO4, Fe+Gly(II) > Fe2(SO4)3, Fe+Gly(III). Additionally, the simple mixture of inorganic iron and glycine could not increase Fe absorption, and the duodenum was the main site of Fe absorption in the intestines of broilers and the ileum absorbed iron rarely.

Synthesis and Properties of Iron Oxide Particles Prepared by Hidrothermal Method

NASA Astrophysics Data System (ADS)

Saragi, T.; Santika, A. S.; Permana, B.; Syakir, N.; Kartawidjaja, M.; Risdiana

2017-05-01

Iron oxide of hematite (α-Fe2O3) has been successfully synthesized by hydrothermal method. The starting materials were Fe(NO3)3.9H2O, 2-methoxyethanol, diethanolamine and n-hexane. The optical, morphology and crystal structure were measured by UV-VIS, TEM and XRD, respectively. From UV-VIS measurement, it was found that the band-gap of sample was 4.17 eV. The morphology of particle was plate-like form. The sample which sintered at 1100°C has high quality crystal with hexagonal structure of α-Fe2O3 phase.

The role of order-disorder transitions in the quest for molecular multiferroics: structural and magnetic neutron studies of a mixed valence iron(II)-iron(III) formate framework.

PubMed

Cañadillas-Delgado, Laura; Fabelo, Oscar; Rodríguez-Velamazán, J Alberto; Lemée-Cailleau, Marie-Hélène; Mason, Sax A; Pardo, Emilio; Lloret, Francesc; Zhao, Jiong-Peng; Bu, Xian-He; Simonet, Virginie; Colin, Claire V; Rodríguez-Carvajal, Juan

2012-12-05

Neutron diffraction studies have been carried out to shed light on the unprecedented order-disorder phase transition (ca. 155 K) observed in the mixed-valence iron(II)-iron(III) formate framework compound [NH(2)(CH(3))(2)](n)[Fe(III)Fe(II)(HCOO)(6)](n). The crystal structure at 220 K was first determined from Laue diffraction data, then a second refinement at 175 K and the crystal structure determination in the low temperature phase at 45 K were done with data from the monochromatic high resolution single crystal diffractometer D19. The 45 K nuclear structure reveals that the phase transition is associated with the order-disorder of the dimethylammonium counterion that is weakly anchored in the cavities of the [Fe(III)Fe(II)(HCOO)(6)](n) framework. In the low-temperature phase, a change in space group from P31c to R3c occurs, involving a tripling of the c-axis due to the ordering of the dimethylammonium counterion. The occurrence of this nuclear phase transition is associated with an electric transition, from paraelectric to antiferroelectric. A combination of powder and single crystal neutron diffraction measurements below the magnetic order transition (ca. 37 K) has been used to determine unequivocally the magnetic structure of this Néel N-Type ferrimagnet, proving that the ferrimagnetic behavior is due to a noncompensation of the different Fe(II) and Fe(III) magnetic moments.

Function of the iron-binding chelator produced by Coriolus versicolor in lignin biodegradation.

PubMed

Wang, Lu; Yan, WenChao; Chen, JiaChuan; Huang, Feng; Gao, PeiJi

2008-03-01

An ultrafiltered low-molecular-weight preparation of chelating compounds was isolated from a wood-containing culture of the white-rot basidiomycete Coriolus versicolor. This preparation could chelate Fe3+ and reduce Fe3+ to Fe2+, demonstrating that the substance may serve as a ferric chelator, oxygen-reducing agent, and redox-cycling molecule, which would include functioning as the electron transport carrier in Fenton reaction. Lignin was treated with the iron-binding chelator and the changes in structure were investigated by 1H-NMR, 13C-NMR, difference spectrum caused by ionization under alkaline conditions and nitrobenzene oxidation. The results indicated that the iron-binding chelator could destroy the beta-O-4 bonds in etherified lignin units and insert phenolic hydroxyl groups. The low-molecular-weight chelator secreted by C. versicolor resulted in new phenolic substructures in the lignin polymer, making it susceptible to attack by laccase or manganese peroxidase. Thus, the synergic action of the iron-binding chelator and the lignocellulolytic enzymes made the substrate more accessible to degradation.

Synthetic and natural plagioclases: iron variations and its influence on VNIR reflectance spectra

NASA Astrophysics Data System (ADS)

Carli, Cristian; Orlando, Andrea; Borini, Daniele; Giuli, Gabriele; Serventi, Giovanna; Pratesi, Giovanni; Sgavetti, Maria

2017-04-01

Besides being one of the most important rock-forming phases, plagioclase (pl) is a common surface mineral in several Solar System bodies. In particular, pl is present in meteorites and lunar samples, both in lunar Highland, where it is the dominant phase, and Maria samples. Moreover, pl has been detected in Martian meteorites, as well as in HEDs. In visible and near-infrared (VNIR) reflectance spectroscopy this phase is characterized by a crystal field (C.F.) absorption band in iron-bearing samples. In particular, Burns (1993) summarized the electronic absorptions due to iron, pointing out: 1) a broad absorption around 1.25 μm related to a C.F. transition due to Fe2+ replacing Ca2+ in seven-fold coordinated sites; 2) narrow absorptions around 0.4 μm related to tetrahedrally coordinated Fe3+ ions replacing Al in the tetrahedral sites. A better understanding of the spectral properties of Fe2+-pl can be an important tool to investigate the spectral influence of pl in regolith material in which it can be mixed with variable amount of other components with variable abundance. This goal can be reached working on synthetic pl with variable FeO and An contents, which must be well characterized to be sure about the attribution of absorption bands seen in reflectance spectra, as well as working on well characterized (in term of An, iron amount and Fe2+/Fe3+) terrestrial pl. Future rover mission will have onboard hyperspectral instrument working in the VNIR with relative high spatial resolution and, so, with the possibility of measured pl crystals. For this reason, working more in detail on iron bearing plagioclase can be an important task. Here, we present our results on synthetic An90 mol% pl with different iron contents (0, 0.5 and 1.0 FeO wt%) with the aim to investigate the effects of iron substitution on the VNIR spectra of pl. Reagent-grade oxides and carbonates reactants used as starting materials were thoroughly mixed to ensure homogeneity. Each experimental charge weighed about 200 mg. All the experiments have been carried out in a Deltech vertical gas-mixing (CO - CO2) quenching furnace equipped with an oxygen fugacity probe. Temperatures were in the 1395 - 1580 ˚ C range and run duration varied from 15 min to 48 hours. The synthesis procedure envisaged two stages: 1) preparation of a glass from the starting material at high temperature (1550 or 1580 ˚ C); 2) annealing at lower T (1395 ˚ C). The produced pl were grinded and sieved at about <100 μm, VNIR reflectance and EXAFS spectra have been acquired to define the reflectance spectra and the Fe2+/Fe3+ ratio on each experiment. Moreover, the obtained products were characterized by several techniques such as optical microscopy, XRD, SEM, EMPA, to assess the pl-crystallinity and its chemical composition. Spectra collected on synthetic samples are compared with those of natural pl, and the broad 1.25gμm C.F. absorption parameters have been related to Fe2+ abundance and Fe2+/Fe3+ ratio. Reference: Burns, R.G., 1993. Mineralogical Applications of Crystal Field Theory. Cambridge University Press, 551 pp.

Hydrosilylation of aldehydes and ketones catalyzed by hydrido iron complexes bearing imine ligands.

PubMed

Zuo, Zhenyu; Sun, Hongjian; Wang, Lin; Li, Xiaoyan

2014-08-14

Two new hydrido iron complexes (2 and 4) were synthesized by the reactions of (4-methoxyphenyl)phenylketimine ((4-MeOPh)PhC=NH) with Fe(PMe3)4 or FeMe2(PMe3)4. The molecular structures of complexes 2 and 4 were confirmed by X-ray single crystal diffraction. Using hydrido iron complexes (1-4) as catalysts, the hydrosilylations of aldehydes and ketones were investigated. The four complexes were effective catalysts for this reduction reaction. Complex 1 among them is the best catalyst.

Obtaining of High Cr Content Cast Iron Materials

NASA Astrophysics Data System (ADS)

Florea, C.; Bejinariu, C.; Carcea, I.; Cimpoesu, N.; Chicet, D. L.; Savin, C.

2017-06-01

We have obtained, through the classic casting process, 3 highly chromium-based experimental alloys proposed for replacing the FC 250 classical cast iron in braking applications. Casting was carried out in an induction furnace and cast into moulds made of KALHARTZ 8500 resin casting mixture and HARTER hardener at SC RanCon SRL Iasi. It is known that the microstructure of the cast iron is a combination of martensite with a small amount of residual austenite after the heat treatment of the ingot. In the case of high-alloy chromium alloys, the performance of the material is due to the presence of M7C3 carbides distributed in the iron matrix Resistance to machining and deformation is based on alloy composition and microstructure, while abrasion resistance will depend on properties and wear conditions.

Persistent four-coordinate iron-centered radical stabilized by π-donation† †Electronic supplementary information (ESI) available: Experimental, crystallographic, computational details, and crystal data for 2, 4, 5 and 8. CCDC 1057111–1057113 and 1425703. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c5sc02601f Click here for additional data file. Click here for additional data file.

PubMed Central

Ishida, Shintaro; Hirakawa, Fumiya; Shiota, Yoshihito; Yoshizawa, Kazunari; Kanegawa, Shinji; Sato, Osamu; Nagashima, Hideo

2016-01-01

Dinuclear iron carbonyl complex 2, which contains an elongated unsupported Fe–Fe bond, was synthesized by the reaction between Fe2(CO)9 and phosphinyl radical 1. Thermal Fe–Fe bond homolysis led to the generation of a four-coordinate carbonyl-based iron-centered radical, 3, which is stabilized by π-donation. Complex 3 exhibited high reactivity toward organic radicals to form diamagnetic five-coordinate Fe(ii) complexes. PMID:28758000

Metallic impurities-silicon carbide interaction in HTGR fuel particles

NASA Astrophysics Data System (ADS)

Minato, Kazuo; Ogawa, Toru; Kashimura, Satoru; Fukuda, Kousaku; Shimizu, Michio; Tayama, Yoshinobu; Takahashi, Ishio

1990-12-01

Corrosion of the coating layers of silicon carbide (SiC) by metallic impurities was observed in irradiated Triso-coated uranium dioxide particles for high temperature gas-cooled reactors with an optical microscope and an electron probe micro-analyzer. The SiC layers were attacked from the outside of the particles. The main element observed in the corroded areas was iron, but sometimes iron and nickel were found. These elements must have been contained as impurities in the graphite matrix in which the coated particles were dispersed. Since these elements are more stable thermodynamically in the presence of SiC than in the presence of graphite at irradiation temperatures, they were transferred to the SiC layer to form more stable silicides. During fuel manufacturing processes, intensive care should be taken to prevent the fuel from being contaminated with those elements which react with SiC.

Microbial Iron Cycling in Acidic Geothermal Springs of Yellowstone National Park: Integrating Molecular Surveys, Geochemical Processes, and Isolation of Novel Fe-Active Microorganisms

PubMed Central

Kozubal, Mark A.; Macur, Richard E.; Jay, Zackary J.; Beam, Jacob P.; Malfatti, Stephanie A.; Tringe, Susannah G.; Kocar, Benjamin D.; Borch, Thomas; Inskeep, William P.

2012-01-01

Geochemical, molecular, and physiological analyses of microbial isolates were combined to study the geomicrobiology of acidic iron oxide mats in Yellowstone National Park. Nineteen sampling locations from 11 geothermal springs were studied ranging in temperature from 53 to 88°C and pH 2.4 to 3.6. All iron oxide mats exhibited high diversity of crenarchaeal sequences from the Sulfolobales, Thermoproteales, and Desulfurococcales. The predominant Sulfolobales sequences were highly similar to Metallosphaera yellowstonensis str. MK1, previously isolated from one of these sites. Other groups of archaea were consistently associated with different types of iron oxide mats, including undescribed members of the phyla Thaumarchaeota and Euryarchaeota. Bacterial sequences were dominated by relatives of Hydrogenobaculum spp. above 65–70°C, but increased in diversity below 60°C. Cultivation of relevant iron-oxidizing and iron-reducing microbial isolates included Sulfolobus str. MK3, Sulfobacillus str. MK2, Acidicaldus str. MK6, and a new candidate genus in the Sulfolobales referred to as Sulfolobales str. MK5. Strains MK3 and MK5 are capable of oxidizing ferrous iron autotrophically, while strain MK2 oxidizes iron mixotrophically. Similar rates of iron oxidation were measured for M. yellowstonensis str. MK1 and Sulfolobales str. MK5. Biomineralized phases of ferric iron varied among cultures and field sites, and included ferric oxyhydroxides, K-jarosite, goethite, hematite, and scorodite depending on geochemical conditions. Strains MK5 and MK6 are capable of reducing ferric iron under anaerobic conditions with complex carbon sources. The combination of geochemical and molecular data as well as physiological observations of isolates suggests that the community structure of acidic Fe mats is linked with Fe cycling across temperatures ranging from 53 to 88°C. PMID:22470372

Carbon dioxide hydrogenation to aromatic hydrocarbons by using an iron/iron oxide nanocatalyst

PubMed Central

Hodgson, Jim; Shrestha, Tej B; Thapa, Prem S; Moore, David; Wu, Xiaorong; Ikenberry, Myles; Troyer, Deryl L; Wang, Donghai; Hohn, Keith L

2014-01-01

Summary The quest for renewable and cleaner energy sources to meet the rapid population and economic growth is more urgent than ever before. Being the most abundant carbon source in the atmosphere of Earth, CO2 can be used as an inexpensive C1 building block in the synthesis of aromatic fuels for internal combustion engines. We designed a process capable of synthesizing benzene, toluene, xylenes and mesitylene from CO2 and H2 at modest temperatures (T = 380 to 540 °C) employing Fe/Fe3O4 nanoparticles as catalyst. The synthesis of the catalyst and the mechanism of CO2-hydrogenation will be discussed, as well as further applications of Fe/Fe3O4 nanoparticles in catalysis. PMID:24991513

Simulation of κ-Carbide Precipitation Kinetics in Aged Low-Density Fe-Mn-Al-C Steels and Its Effects on Strengthening

NASA Astrophysics Data System (ADS)

Lee, Jaeeun; Park, Siwook; Kim, Hwangsun; Park, Seong-Jun; Lee, Keunho; Kim, Mi-Young; Madakashira, Phaniraj P.; Han, Heung Nam

2018-03-01

Fe-Al-Mn-C alloy systems are low-density austenite-based steels that show excellent mechanical properties. After aging such steels at adequate temperatures for adequate time, nano-scale precipitates such as κ-carbide form, which have profound effects on the mechanical properties. Therefore, it is important to predict the amount and size of the generated κ-carbide precipitates in order to control the mechanical properties of low-density steels. In this study, the microstructure and mechanical properties of aged low-density austenitic steel were characterized. Thermo-kinetic simulations of the aging process were used to predict the size and phase fraction of κ-carbide after different aging periods, and these results were validated by comparison with experimental data derived from dark-field transmission electron microscopy images. Based on these results, models for precipitation strengthening based on different mechanisms were assessed. The measured increase in the strength of aged specimens was compared with that calculated from the models to determine the exact precipitation strengthening mechanism.

Discrimination among iron sulfide species formed in microbial cultures.

PubMed

Popa, R; Kinkle, B K

2000-10-01

A quantitative method for the study of iron sulfides precipitated in liquid cultures of bacteria is described. This method can be used to quantify and discriminate among amorphous iron sulfide (FeS(amorph)), iron monosulfide minerals such as mackinawite or greigite (FeS(min)), and iron disulfide minerals such as pyrite or marcasite (FeS(2min)) formed in liquid cultures. Degradation of iron sulfides is performed using a modified Cr(2+) reduction method with reflux distillation. The basic steps of the method are: first, separation of FeS(amorph); second, elimination of interfering species of S such as colloidal sulfur (S(c) degrees ), thiosulphate (S(2)O(3)(2-)) and polysulfides (S(x)(2-)); third, separation of FeS(min); and fourth, separation of FeS(2min). The final product is H(2)S which is determined after trapping. The efficiency of recovery is 96-99% for FeS(amorph), 76-88% for FeS(min), and >97% for FeS(2min). This method has a high reproducibility if the experimental conditions are rigorously applied and only glass conduits are used. A well ventilated fume hood must be used because of the toxicity and volatility of several reagents and products. The advantage relative to previously described methods are better resolution for iron sulfide species and use of the same bottles for both incubation of cultures and acid degradation. The method can also be used for Fe/S stoichiometry with sub-sampling and Fe analysis.

Comparison of home fortification with two iron formulations among Kenyan children: Rationale and design of a placebo-controlled non-inferiority trial.

PubMed

Teshome, Emily M; Otieno, Walter; Terwel, Sofie R; Osoti, Victor; Demir, Ayşe Y; Andango, Pauline E A; Prentice, Andrew M; Verhoef, Hans

2017-09-01

Home fortification powders containing iron and other micronutrients have been recommended by World Health Organisation to prevent iron deficiency anaemia in areas of high prevalence. There is evidence, however, that home fortification at this iron dose may cause gastrointestinal adverse events including diarrhoea. Providing a low dose of highly absorbable iron (3 mg iron as NaFeEDTA) may be safer because the decreased amount of iron in the gut lumen can possibly reduce the burden of these adverse effects whilst resulting in similar or higher amounts of absorbed iron. To show non-inferiority of home fortification with 3 mg iron as NaFeEDTA compared with 12.5 mg iron as encapsulated ferrous fumarate, with haemoglobin response as the primary outcome. 338 Kenyan children aged 12-36 months will be randomly allocated to daily home fortification with either: a) 3 mg iron as NaFeEDTA (experimental treatment), b) 12.5 mg iron as encapsulated ferrous fumarate (reference), or c) placebo. At baseline, after 30 days of intervention and within 100 days post-intervention, blood samples will be assessed for primary outcome (haemoglobin concentration), iron status markers, Plasmodium parasitaemia and inflammation markers. Urine and stool samples will be assessed for hepcidin concentrations and inflammation, respectively. Adherence will be assessed by self-reporting, sachet counts and by an electronic monitoring device. If daily home fortification with a low dose of iron (3 mg NaFeEDTA) has similar or superior efficacy to a high dose (12.5 mg ferrous fumarate) then it would be the preferred choice for treatment of iron deficiency anaemia in children.

The Iron-Iron Carbide Phase Diagram: A Practical Guide to Some Descriptive Solid State Chemistry.

ERIC Educational Resources Information Center

Long, Gary J.; Leighly, H. P., Jr.

1982-01-01

Discusses the solid state chemistry of iron and steel in terms of the iron-iron carbide phase diagram. Suggests that this is an excellent way of introducing the phase diagram (equilibrium diagram) to undergraduate students while at the same time introducing the descriptive solid state chemistry of iron and steel. (Author/JN)

Iron sand - ZnO based materials of natural origin for dye decolorization under sunlight irradiation

NASA Astrophysics Data System (ADS)

Salprima Yudha, S.; Angasa, Eka; Fitriani, Dyah; Falahudin, Aswin

2017-03-01

A mixed iron sand - ZnO materials was prepared by heating a mixture of natural iron sand and ZnO at 900 °C for 5 hours. XRD study of the sample revealed that, in the mixed iron sand - ZnO present some minor peaks that similar with XRD pattern of γ-Fe2O3 and/or Fe3O4. Observation of the sample using SEM, showed a compact morpholgy and almost homogenenous in particles size. In purpose to evaluate the ability of this materials for textile dying wastewater treatment, a study on rhodamine B decolorization was carried out as a reperesentative.

Formation of Defected Cadmium Ferrite during Hydrothermal Storage of Cadmium-Iron Hydroxides

NASA Astrophysics Data System (ADS)

Wolski, W.; Wolska, E.; Kaczmarek, J.

1994-05-01

The storage of amorphous coprecipitated Cd(OH) 2 · 2Fe(OH) 3 gel in mother liquor at 150 ± 2°C for 20 hr leads to a crystalline species which, according to X-ray analysis, is composed of cadmium hydroxide nitrate, Cd 3(OH) 5NO 3, cadmium hydroxide, βCd(OH) 2, and a strongly ferrimagnetic spinel phase. The Curie point at 270-280°C was found by thermomagnetic analysis. At that temperature the decomposition of the spinel phase and of the accompanying nonmagnetic phases takes place. IR spectra indicate that during thermomagnetic recording the liberated cadmium oxide and iron oxide form antiferromagnetic cadmium ferrite, with frequencies somewhat displaced in comparison to CdFe 2O 4 annealed at 1000°C. The results indicate that the ferrimagnetic phase (having spinel structure, a unit-cell parameter a of about 8.37 ± 0.01 Å, and a Tc point differing by more than 300°C from that of pure maghemite, γFe 2O 3) is likely to be a defected solid solution of maghemite and cadmium ferrite, of the formula Cd 2+xFe 3+1- x [Fe 3+(5+ x)/3 □ (1- x)/3 ]O 4.

Molecular structure, magnetic properties, cyclic voltammetry of the low-spin iron(III) Bis(4-ethylaniline) complex with the para-chloro substituted meso-tetraphenylporphyrin

NASA Astrophysics Data System (ADS)

Dhifaoui, Selma; Mchiri, Chadlia; Quatremare, Pierre; Marvaud, Valérie; Bujacz, Anna; Nasri, Habib

2018-02-01

In this study, the preparation of a new iron(III) hexacoordinated metalloporphyrin namely the bis(4-ethylaniline){meso-tetra(para-chlorophenyl)porphyrinato}iron(III) triflate hemi-4-ethylaniline monohydrate with the formula [FeIII(TClPP)(PhEtNH2)2]SO3CF3•1/2PhEtNH2•H2O (I) was reported. This is the first example of an iron(III) metalloporphyrin bis(primary amine) with an aryl group adjacent to the amino group. This species was characterized by elemental, spectroscopic analysis including UV-visible and IR data, cyclic voltammetry, SQUID measurements and X-ray molecular structure. The mean equatorial distance between the iron(III) and the nitrogens of the porphyrin is appropriate for a low-spin (S = 1/2) iron(III) porphyrin complex. The magnetic data confirm the low-spin state of our ferric derivative while the cyclic voltammetry indicates a shift of the half potential E1/2[Fe(III)/Fe(II)] of complex (I) toward more negative value. In the crystal of (I), the [FeIII(TClPP)(PhEtNH2)2]+ ions, the triflate counterions and the water molecules are involved in a number of O__H⋯O, N__H⋯O, C-H⋯O and C__H⋯π intermolecular interactions forming a three-dimension network.

High- T c Superconductivity in FeSe at High Pressure: Dominant Hole Carriers and Enhanced Spin Fluctuations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, J. P.; Ye, G. Z.; Shahi, P.

The importance of electron-hole interband interactions is widely acknowledged for iron-pnictide superconductors with high transition temperatures (T c). However, high-T c superconductivity without hole carriers has been suggested in FeSe single-layer films and intercalated iron-selenides, raising a fundamental question whether iron pnictides and chalcogenides have different pairing mechanisms. Here, we study the properties of electronic structure in another high-T c phase induced by pressure in bulk FeSe from magneto-transport measurements and first-principles calculations. With increasing pressure, the low-T c superconducting phase transforms into high-T c phase, where we find the normal-state Hall resistivity changes sign from negative to positive, demonstratingmore » dominant hole carriers in striking contrast to other FeSe-derived high-T c systems. Moreover, the Hall coefficient is remarkably enlarged and the magnetoresistance exhibits anomalous scaling behaviours, evidencing strongly enhanced interband spin fluctuations in the high-T c phase. These results in FeSe highlight similarities with high-T c phases of iron pnictides, constituting a step toward a unified understanding of iron-based superconductivity.« less

High- T c Superconductivity in FeSe at High Pressure: Dominant Hole Carriers and Enhanced Spin Fluctuations

DOE PAGES

Sun, J. P.; Ye, G. Z.; Shahi, P.; ...

2017-04-07

The importance of electron-hole interband interactions is widely acknowledged for iron-pnictide superconductors with high transition temperatures (T c). However, high-T c superconductivity without hole carriers has been suggested in FeSe single-layer films and intercalated iron-selenides, raising a fundamental question whether iron pnictides and chalcogenides have different pairing mechanisms. Here, we study the properties of electronic structure in another high-T c phase induced by pressure in bulk FeSe from magneto-transport measurements and first-principles calculations. With increasing pressure, the low-T c superconducting phase transforms into high-T c phase, where we find the normal-state Hall resistivity changes sign from negative to positive, demonstratingmore » dominant hole carriers in striking contrast to other FeSe-derived high-T c systems. Moreover, the Hall coefficient is remarkably enlarged and the magnetoresistance exhibits anomalous scaling behaviours, evidencing strongly enhanced interband spin fluctuations in the high-T c phase. These results in FeSe highlight similarities with high-T c phases of iron pnictides, constituting a step toward a unified understanding of iron-based superconductivity.« less

High-temperature corrosion of UNS N10003 in molten Li 2BeF 4 (FLiBe) salt

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Guiqiu; Kelleher, Brian; He, Lingfeng

2015-07-30

Here, corrosion testing of Hastelloy N in molten fluoride salt was performed in purified molten 2 7LiF-BeF 2 (66-34mol%) (FLiBe) salt at 700°C for 1000 hours, in pure nickel and graphite capsules. In the nickel capsule tests, the near-surface region of the alloy exhibited an about 200 nm porous structure, an approximately 3.5 μm chromium depleted region, and MoSi 2 precipitates. In tests performed in graphite capsules, the alloy samples gained weight due to the formation of a variety of Cr 3C 2, Cr 7C 3, Mo 2C and Cr 23C 6, carbide phases on the surface and in themore » subsurface regions of the alloy. A Cr depleted region was observed in the near-surface region where Mo thermally diffused toward either surface or grain boundary, which induced approximately 1.4 μm Ni 3Fe alloy layer in this region. The carbide containing layer extended to about 7 μm underneath the Ni 3Fe layer. The presence of graphite dramatically changes the mechanisms of corrosion attack in Hastelloy N in molten FLiBe salt. Evaluated by in terms of the depth of attack, graphite clearly accelerates corrosion, but the results appear to indicate that the formation of Cr 23C 6 phase might stabilize the Cr and mitigate its dissolution in molten FLiBe salt.« less

Iron isotope fractionation during hydrothermal ore deposition and alteration

NASA Astrophysics Data System (ADS)

Markl, Gregor; von Blanckenburg, Friedhelm; Wagner, Thomas

2006-06-01

Iron isotopes fractionate during hydrothermal processes. Therefore, the Fe isotope composition of ore-forming minerals characterizes either iron sources or fluid histories. The former potentially serves to distinguish between sedimentary, magmatic or metamorphic iron sources, and the latter allows the reconstruction of precipitation and redox processes. These processes take place during ore formation or alteration. The aim of this contribution is to investigate the suitability of this new isotope method as a probe of ore-related processes. For this purpose 51 samples of iron ores and iron mineral separates from the Schwarzwald region, southwest Germany, were analyzed for their iron isotope composition using multicollector ICP-MS. Further, the ore-forming and ore-altering processes were quantitatively modeled using reaction path calculations. The Schwarzwald mining district hosts mineralizations that formed discontinuously over almost 300 Ma of hydrothermal activity. Primary hematite, siderite and sulfides formed from mixing of meteoric fluids with deeper crustal brines. Later, these minerals were partly dissolved and oxidized, and secondary hematite, goethite and iron arsenates were precipitated. Two types of alteration products formed: (1) primary and high-temperature secondary Fe minerals formed between 120 and 300 °C, and (2) low-temperature secondary Fe minerals formed under supergene conditions (<100 °C). Measured iron isotope compositions are variable and cover a range in δ56Fe between -2.3‰ and +1.3‰. Primary hematite ( δ56Fe: -0.5‰ to +0.5‰) precipitated by mixing oxidizing surface waters with a hydrothermal fluid that contained moderately light Fe ( δ56Fe: -0.5‰) leached from the crystalline basement. Occasional input of CO 2-rich waters resulted in precipitation of isotopically light siderite ( δ56Fe: -1.4 to -0.7‰). The difference between hematite and siderite is compatible with published Fe isotope fractionation factors. The observed range in isotopic compositions can be accounted for by variable fractions of Fe precipitating from the fluid. Therefore, both fluid processes and mass balance can be inferred from Fe isotopes. Supergene weathering of siderite by oxidizing surface waters led to replacement of isotopically light primary siderite by similarly light secondary hematite and goethite, respectively. Because this replacement entails quantitative transfer of iron from precursor mineral to product, no significant isotope fractionation is produced. Hence, Fe isotopes potentially serve to identify precursors in ore alteration products. Goethites from oolitic sedimentary iron ores were also analyzed. Their compositional range appears to indicate oxidative precipitation from relatively uniform Fe dissolved in coastal water. This comprehensive iron isotope study illustrates the potential of the new technique in deciphering ore formation and alteration processes. Isotope ratios are strongly dependent on and highly characteristic of fluid and precipitation histories. Therefore, they are less suitable to provide information on Fe sources. However, it will be possible to unravel the physico-chemical processes leading to the formation, dissolution and redeposition of ores in great detail.

57Fe Mössbauer study of Lu 2Fe 3Si 5 iron silicide superconductor

DOE PAGES

Ma, Xiaoming; Ran, Sheng; Pang, Hua; ...

2015-03-28

With the advent of Fe–As based superconductivity it has become important to study how superconductivity manifests itself in details of 57Fe Mössbauer spectroscopy of conventional, Fe-bearing superconductors. The iron-based superconductor Lu 2Fe 3Si 5 has been studied by 57Fe Mössbauer spectroscopy over the temperature range from 4.4 K to room temperature with particular attention to the region close to the superconducting transition temperature (T c=6.1 K). Consistent with the two crystallographic sites for Fe in this structure, the observed spectra appear to have a pattern consisting of two doublets over the whole temperature range. Furthermore, the value of Debye temperaturemore » was estimated from temperature dependence of the isomer shift and the total spectral area and compared with the specific heat capacity data. Neither abnormal behavior of the hyperfine parameters at or near T c, nor phonon softening were observed.« less

Iron (III) hydrolysis and solubility at 25 degrees C.

PubMed

Stefánsson, Andri

2007-09-01

UV-vis spectrophotometric measurements, potentiometric titrations, and solubility measurements were performed to evaluate the hydrolysis constants for aqueous Fe(III) and the solubility of 2-line ferrihydrite over a wide concentration range (0-3 M NaClO4 and p[H+] 1.54-11.23). From these measurements, Fe3+ was found to hydrolyze to form FeOH2+, Fe2(OH)24+, Fe(OH)2+, Fe(OH)3(0), and Fe(OH)4-. The hydrolysis and solubility constants of these species were determined together with their dependence on ionic strength. The iron (III) hydrolysis constants at infinity dilution were (logbeta(1,1) to logbeta(1,4) and logbeta(2,2))-2.19 +/- 0.02, -5.76 +/- 0.06, -14.30 +/- 0.32, -21.71 +/- 0.24, and -2.92 +/- 0.02, respectively. The solubility product for 2-line ferrihydrite was (logK(s,0)) +3.50 +/- 0.20. The results have been compared with literature values.

Synthesis and reactivity of mononuclear iron models of [Fe]-hydrogenase that contain an acylmethylpyridinol ligand.

PubMed

Hu, Bowen; Chen, Dafa; Hu, Xile

2014-02-03

[Fe]-hydrogenase has a single iron-containing active site that features an acylmethylpyridinol ligand. This unique ligand environment had yet to be reproduced in synthetic models; however the synthesis and reactivity of a new class of small molecule mimics of [Fe]-hydrogenase in which a mono-iron center is ligated by an acylmethylpyridinol ligand has now been achieved. Key to the preparation of these model compounds is the successful C-O cleavage of an alkyl ether moiety to form the desired pyridinol ligand. Reaction of solvated complex [(2-CH2CO-6-HOC5H3N)Fe(CO)2(CH3CN)2](+)(BF4)(-) with thiols or thiophenols in the presence of NEt3 yielded 5-coordinate iron thiolate complexes. Further derivation produced complexes [(2-CH2CO-6-HOC5H3N)Fe(CO)2(SCH2CH2OH)] and [(2-CH2CO-6-HOC5H3N)Fe(CO)2(CH3COO)], which can be regarded as models of FeGP cofactors of [Fe]-hydrogenase extracted by 2-mercaptoethanol and acetic acid, respectively. When the derivative complexes were treated with HBF4 ⋅Et2O, the solvated complex was regenerated by protonation of the thiolate ligands. The reactivity of several models with CO, isocyanide, cyanide, and H2 was also investigated. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spectroscopic, potentiometric and theoretical studies on the binding properties of a novel tripodal polycatechol-imine ligand towards iron(III)

NASA Astrophysics Data System (ADS)

Kanungo, B. K.; Sahoo, Suban K.; Baral, Minati

2008-12-01

A novel multidentate tripodal ligand, cis, cis-1,3,5-tris[(2,3-dihydroxybenzylidene)aminomethyl]cyclohexane (TDBAC, L) containing one catechol unit in each arms of a tripodal amine, cis, cis-1,3,5-tris(aminomethyl)cyclohexane was investigated as a chelator for iron(III) through potentiometric and spectrophotometric methods in an aqueous medium of 0.1N ionic strength and 25 ± 1 °C as well as in ethanol by continuous variation method. From pH metric in water, three protonation constants characterized for the three-hydroxyl groups of the catechol units at ortho were used as input data to evaluate the stability constants of the complexes. Formation of monomeric complexes FeLH 3, FeLH 2, FeLH and FeL were depicted. In ethanol, formation of complexes FeL, Fe 2L and Fe 3L were characterized. Structures of the complexes were explained by using the experimental evidences and predicted through molecular modeling calculations. The ligand showed potential to coordinate iron(III) through three imine nitrogens and three catecholic oxygens at ortho to form a tris(iminocatecholate) type complex.

Rodolicoite and grattarolaite, intermediates in the thermal transformation of synthetic P-doped ferrihydrite

NASA Astrophysics Data System (ADS)

Pieczara, Gabriela; Borkiewicz, Olaf; Manecki, Maciej

2017-04-01

Rodolicoite FePO4 and grattarolaite Fe3PO7, naturally occurring anhydrous iron(III) phosphates have been identified in coal samples derived from Santa Barbara lignite mine, as final products of the progressive thermal conversion and oxidation of vivianite Fe32+(PO4)2•8H2O to amorphous phase [1]. In natural environment however, the conversion steps of amorphous phase into these nanominerals are extremely difficult to identify. We propose to fill this gap by utilizing the nanoparticles of synthetic P-doped ferrihydrite Fe5HO8•4H2O as a source of amorphous hydrated iron(III) phosphate. This phase, at certain conditions, undergoes thermal conversion to rodolicoite and grattarolaite. Synthetic anhydrous iron(III) phosphate analogs of berlinite AlPO4 and α- quartz, particularly rodolicoite, receive a lot of attention in mineral sciences partly because of their geologic importance and partly because of their prospective applications as raw material for lithium iron phosphate batteries LiFePO4[2]. In this case, potential presence of impurities and intermediates during thermal synthesis or oxidation steps of rodolicoite is inexpedient. Thus, the main goal of this research was to characterize the products of thermal transformation of P-doped ferrihydrite. Ferrihydrite synthesized in the presence of phosphate PO43- was used. P-ferrihydrites were synthesized by precipitation from aqueous solutions of Fe2(SO4)3 and K2HPO4 at pH 8.2. The thermal transformation experiments were carried out using ferrihydrites with various P/Fe ratios (0.00, 0.20, 0.50 and 1.00) at various heating temperatures. All samples were characterized by XRD, FTIR, SEM and differential thermal analysis prior and after the experiments. The results indicate that the presence of phosphate not only stabilizes the structure of ferrihydrite but also controls its thermal transformation to hematite α-Fe2O3 in more complex manner. Pure ferrihydrite transforms immediately to hematite at the temperature below 500˚ C. When ferrihydrite with P/Fe=0.20 and P/Fe=0.50 was annealed, the presence of tetragonal maghemite γ-Fe2O3 was detected between 650 and 700˚ C, followed by formation of hematite α-Fe2O3 at higher temperatures. Hematite is accompanied with small amounts of trigonal rodolicoite FePO4 which forms between 800 and 900˚ C. This intermediate phase is not very stable and completely vanishes in the sample of P/Fe=0.20 at temperatures above 900˚ C (transforms into hematite). In contrast, a further increase in temperature of the sample of P/Fe=0.50 causes formation of hematite associated with grattarolaite Fe3PO7. Thermal transformation of ferrihydrite containing the highest-P ratio (P/Fe=1.00) results in the formation of rodolicoite and hematite at 700˚ C, grattarolaite at 800˚ C, and a mixture of two anhydrous phosphates with hematite around 1000˚ C. This project is financed by AGH research grant no. 15.11.140.831 and partly by the Polish National Science Centre under the research project awarded by the decision no. 2015/19/N/ST10/01516. References: [1] Cipriani C, Mellini M, Pratesi G, Viti C (1997) EJM. 9, pp. 1101-1106. [2] Zhu Y, Tang S, Shi H, Hu H (2014) Ceram. Int. 40, pp. 2685-2690.

Uric acid-derived Fe3C-containing mesoporous Fe/N/C composite with high activity for oxygen reduction reaction in alkaline medium

NASA Astrophysics Data System (ADS)

Ma, Jun; Xiao, Dejian; Chen, Chang Li; Luo, Qiaomei; Yu, Yue; Zhou, Junhao; Guo, Changding; Li, Kai; Ma, Jie; Zheng, Lirong; Zuo, Xia

2018-02-01

In this work, a category of Fe3C-containing Fe/N/C mesoporous material has been fabricated by carbonizing the mixture of uric acid, Iron (Ⅲ) chloride anhydrous and carbon support (XC-72) under different pyrolysis temperature. Of all these samples, pyrolysis temperature (800 °C) becomes the most crucial factor in forming Fe3C active sites which synergizes with high content of graphitic N to catalyze oxygen reduction reaction (ORR). X-ray absorption fine structure spectroscopy (XAFS) is used to exhibit that the space structure around Fe atoms in the catalyst. This kind of catalyst possesses comparable ORR properties with commercial 20% Pt/C (onset potential is 0 V vs. Ag/AgCl in 0.1 M KOH), the average transfer electron number is 3.84 reflecting the 4-electron process. Moreover, superior stability and methanol tolerance deserve to be mentioned.

Prebiotic Polymerization: Oxidative Polymerization of 2,3 Dimercapto-1- Propanol on the Surface of Iron(III) Hydroxide Oxide

NASA Technical Reports Server (NTRS)

Weber, Arthur L.

1995-01-01

The oxidation of 2,3-dimercapto-1-propanol by ferric ions on the surface of iron(III) hydroxide oxide (Fe(OH)O) yielded polydisulfide oligomers. This polymerization occurred readily at low dithiol concentration under mild aqueous conditions. Polydisulfide polymers up to the 15-mer were synthesized from 1 mM dithiol in 5 ml water reacted with iron(III) hydroxide oxide (20 mg, 160 micromole Fe) for 3 days under anaerobic conditions at 40 C and pH 4. About 91% of the dithiol was converted to short soluble oligomers and 9% to insoluble larger oligomers that were isolated with the FE(OH)O phase. Reactions carried out at the same ratio of dithiol to FE(OH)O but at higher dithiol concentrations gave higher yields of the larger insoluble oligomers. The relationship of these results to prebiotic polymer synthesis is discussed.

Prebiotic polymerization: Oxidative polymerization of 2, 3-dimercapto-1-propanol on the surface of iron(III) hydroxide oxide

NASA Technical Reports Server (NTRS)

Weber, Arthur L.

1995-01-01

The oxidation of 2, 3-dimercapto-1-propanol by ferric ions on the surface of iron(III) hydroxide oxide (Fe(OH)O) yielded polydisulfide oligomers. This polymerization occurred readily at low dithiol concentration under mild aqueous conditions. Polydisulfide polymers up to the 15-mer were synthesized from 1 mM dithiol in 5 ml water reacted with iron(III) hydroxide oxide (20 mg, 160 micromole Fe) for 3 days under anaerobic conditions at 40 C and pH 4. About 91% of the dithiol was converted to short soluble oligomers and 9% to insoluble larger oligomers that were isolated with the Fe(OH)O phase. Reactions carried out at the same ratio of dithiol to Fe(OH)O but at higher dithiol concentrations gave higher yields of the larger insoluble oligomers. The relationship of these results to prebiotic polymer synthesis is discussed.

Equilibrium carbon and hydrogen isotope fractionation in iron

NASA Astrophysics Data System (ADS)

Schauble, E. A.

2009-12-01

Recent theoretical and experimental studies (e.g., [1-3]) have suggested that Si- and Fe-isotopic signatures can be used to characterize the compositions and conditions of segregation of metallic cores in planetary interiors. This study expands the theoretical framework to include carbon and hydrogen, which may also be alloying elements. Hydrogen (D/H) and carbon (13C/12C) fractionations in iron-rich metallic melts are estimated by modeling analogous iron-rich crystals, i.e., dhcp-FeH and η-Fe2C. C- and H-atoms in these crystals are completely coordinated by iron. The driving energy for equilibrium fractionation is assumed to come from the reduction of vibrational frequencies when heavy isotopes are substituted for light ones; vibrations are assumed to be harmonic. This treatment is crude at high temperature, and for the relatively anharmonic vibrations typical of hydrogen-bearing substances, but may provide a reasonably accurate, semi-quantitative approximation of real fractionation behavior. Vibrational frequencies of all crystals are modeled with density functional theory, using gradient-corrected functionals and ultrasoft pseudopotentials. For both carbon and hydrogen, the models suggest that the metal phase will be strongly depleted in heavy isotopes. At 2000 K, 1 atm, η-Fe2C will have 3‰ lower 13C/12C than coexisting diamond. Combining this result with previous high-temperature theoretical and experimental studies (e.g., [4]), metal-graphite fractionation is expected to be very similar, while metal-CO2 fractionation will be almost twice as large, ca. -5‰. Deuterium/hydrogen fractionations are expected to be an order of magnitude larger, with 50-70‰ lower D/H in dhcp-FeH than in coexisting H2 gas at 2000 K, and approximately 100‰ lower D/H than water vapor. These fractionations are much larger than those inferred for silicon and iron, as expected given the differences in atomic mass. References: 1. Georg et al. (2007) Nature 447:1102; 2. Rustad & Yin (2009) Nature Geoscience doi:10.1038/ngeo546; 3. Polyakov (2009) Science 323:912; 4. Polyakov & Kharlashina (1995) GCA 59:2561.

Magnetic and dielectric properties in the UHF frequency band of half-dense Ni-Zn-Co ferrites ceramics with Fe-excess and Fe-deficiency

NASA Astrophysics Data System (ADS)

Mattei, Jean-Luc; Souriou, David; Chevalier, Alexis

2018-02-01

This work investigates electromagnetic properties of half-dense ceramics with compositions Ni0.5Zn0.3Co0.2FeyO4-δ where y = 1.98 (Iron deficient, noted ID) or y = 2.3 (Iron in excess, noted IE). IE and ID materials are obtained by chemical coprecipitation route. The obtained nano-sized powders are pressed and annealed at two temperatures (800 °C, 900 °C), so has to obtain half-massive ceramics. Ferrous and ferric ions coexist in the crystalline structures, but the former in a less extend for ID ferrite. The concomitant influences of Fe2+ and Fe3+ on the dielectric and magnetic losses (ε″/ε‧ and μ″/μ‧, respectively) are considered at frequency up to 6 GHz. The permeability dispersion changes from relaxation-like to resonance-like with the decrease in ferrous ions. In reason of the relaxing-like behavior of Fe2+, and because of a relatively high amount in Fe2+, IE sample shows lower total losses (magnetic and dielectric) than ID sample. These conclusions applied for TA = 900 °C. At frequencies above 700 MHz, the total loss values (IE and ID samples) are prohibitive for antenna downsizing whatever is the firing temperature value (800 °C and 900 °C). Whereas at frequencies below 700 MHz Ni0.5Zn0.3Co0.2Fe2.3O4+δ may leads to better antenna performances than Ni0.5Zn0.3Co0.2Fe1.98O4-δ.

Mössbauer study of the firing technology of the moon-white Jun porcelain in Chinese Yuan Dynasty

NASA Astrophysics Data System (ADS)

Songhua, Chen; Zhengyao, Gao; Zhongtian, Sun; Xiande, Chen

1994-12-01

The moon-white Jun porcelain glaze contains Fe2O3, Fe3O4 and structural iron. The firing atmosphere of ancient Jun kilns was modestly reductive. The firing temperature was slightly above 1250 ‡C. The glaze color appears moon-white, and is related to the low concentration of Fe2+. The coordination numbers of Fe2+ and Fe3+ are both 4.

Enhanced activity and stability of binuclear iron (III) phthalocyanine on graphene nanosheets for electrocatalytic oxygen reduction in acid

NASA Astrophysics Data System (ADS)

Li, Tengfei; Peng, Yingxiang; Li, Kai; Zhang, Rui; Zheng, Lirong; Xia, Dingguo; Zuo, Xia

2015-10-01

Binuclear iron (III) phthalocyanine (bi-FePc) and iron (III) phthalocyanine (FePc) are synthesized in situ on graphene nanosheets (GNS) by a microwave-assisted method. TEM, ultraviolet-visible spectroscopy and Raman spectroscopy confirm that bi-FePc is supported on GNS through π-π interactions. The catalytic activity of the bi-FePc/GNS and FePc/GNS composites in the oxygen reduction reaction (ORR) is investigated by CV and RDE measurements. The bi-FePc/GNS composite shows a more positive onset potential (0.12 V vs. Hg/Hg2SO4) for the ORR than FePc/GNS (-0.02 V vs. Hg/Hg2SO4), and a four-electron mechanism similar to commercial Pt/C (0.22 V vs. Hg/Hg2SO4). Moreover, bi-FePc/GNS exhibits good stability with 100% retention after 36,000 s, while Pt/C has a retention of only 50% after the same period. Additionally, bi-FePc/GNS shows higher tolerance toward methanol than the Pt/C catalyst. XPS and X-ray absorption fine structure spectroscopy demonstrate that compared with FePc/GNS, bi-FePc/GNS possesses a higher concentration of Fe3+ and smaller skeleton radius of the phthalocyanine ring, which has a square-planar structure that evidently favors the ORR. Thus, bi-FePc/GNS is a promising candidate as a cathode catalyst in direct methanol fuel cells.

Rat liver mitochondrial dysfunction by addition of copper(II) or iron(III) ions.

PubMed

Saporito-Magriñá, Christian; Musacco-Sebio, Rosario; Acosta, Juan M; Bajicoff, Sofía; Paredes-Fleitas, Paola; Boveris, Alberto; Repetto, Marisa G

2017-01-01

Increased copper (Cu) and iron (Fe) levels in liver and brain are associated to oxidative stress and damage with increased phospholipid oxidation process. The aim of this work was to assess the toxic effects of Cu 2+ and Fe 3+ addition to rat liver mitochondria by determining mitochondrial respiration in states 3 (active respiration) and 4 (resting respiration), and phospholipid peroxidation. Both, Cu 2+ and Fe 3+ produced decreases in O 2 consumption in a concentration-dependent manner in active state 3: both ions by 42% with malate-glutamate as complex I substrate (concentration for half maximal response (C 50 ) 60μM Cu 2+ and 1.25mM Fe 3+ ), and with succinate as complex II substrate: 64-69% with C 50 of 50μM Cu 2+ and with C 50 of 1.25mM of Fe 3+ . Respiratory control decreased with Cu 2+ (C 50 50μM) and Fe 3+ (C 50 1.25-1-75mM) with both substrates. Cu 2+ produced a 2-fold increase and Fe 3+ a 5-fold increase of thiobarbituric acid-reactive substances (TBARS) content from 25μM Cu 2+ (C 50 40μM) and from 100μM Fe 3+ (C 50 1.75mM). Supplementations with Cu 2+ and Fe 3+ ions induce mitochondrial dysfunction with phospholipid peroxidation in rat liver mitochondria. Although is proved that a Fenton/Haber Weiss mechanism of oxidative damage occurs in metal-ion induced mitochondrial toxicity, slightly different responses to the metal ions suggest some differences in the mechanism of intracellular toxicity. The decreased rates of mitochondrial respiration and the alteration of mitochondrial function by phospholipid and protein oxidations lead to mitochondrial dysfunction, cellular dyshomeostasis and cell death. Copyright © 2016 Elsevier Inc. All rights reserved.

Solid Solution, Mass Transport, and Crystal Growth Studies of Cadmium Iron Selenide.

NASA Astrophysics Data System (ADS)

Huang, Xuejun

Cadmium iron selenide, a semimagnetic semiconductor, has been investigated. Solid solubilities of iron in CdSe were determined at temperatures between 650^ circC and 1100^circC, using the X-ray diffraction Debye-Scherrer powder technique. The solubility limits of Fe in CdSe increase with the temperatures to reach a maximum of about 19.5 mole % FeSe_ {1.24} at 925^circ C, and then decrease with further increasing temperature. Solidification phenomena of the Cd-Fe-Se solid solutions were observed employing optical microscopy, which reveals a typical divorced, eutectic type, nonequilibrium solidification. The combination of the X-ray diffraction and the microscopic investigations yielded a pseudo-binary, eutectic type phase diagram of the Cd-Fe-Se system. Partial pressures of the major vapor species in the Cd-Fe-Se physical and the Cd-Fe-Se-Iodine chemical vapor transport systems were calculated. The partial pressure of gaseous iron species of the PVT system may be neglected compared to those of Cd and Se_2^ecies. This suggests that cadmium iron selenide crystals cannot be grown by the PVT method. For the PVT experiments, using the as-synthesized (CdSe)_ {0.90}(FeSe_{1.24})_{0.10 } source materials, crystals with compositions of 6-8 mole % FeSe_{1.24} were grown at a source temperature of 1000^ circC and a DeltaT of 12^circC. These result are contradictory to the thermodynamic predictions, and were further investigated employing specially purified source materials. Iron contents in the crystals grown in these experiments are close to zero. The transport of iron in the initial mass transport experiments may be due to the chemical impurities (most likely the metal chlorides) in the as-synthesized source materials. Mass transport experiments of the Cd-Fe-Se-Iodine CVT system were performed as a function of source temperatures, the degrees of undercooling (DeltaT), and initial iodine pressures. Promising parameters for the growth of cadmium iron selenide single crystals by the CVT method, e.g., the source temperatures of 800-850 ^circC, initial iodine pressures of 0.5-1.0 atm, and DeltaT of 10 -20^circC, were established. Mass fluxes of cadmium iron selenide were computed using a one -dimensional diffusion equation. The overall trends of the computed mass flux as a function of growth conditions are consistent with the experimental results. However, differences between the theoretical and experimental mass fluxes may be due to the uncertainties of the thermochemical data used and the approximations made in these estimations. Single crystals of cadmium iron selenide with compositions of 6.5-8.5 mole % FeSe_{1.24 } and of about 5 mm edge lengths were successfully grown from the (CdSe)_{0.90 }(FeSe_{1.24})_{0.10} source materials by the CVT method. Compositions of various portions of the bulk crystals are nearly constant along its axis within the error limits, indicating that the crystals possess reasonable compositional uniformity. The indices of the crystal surfaces were obtained by the X -ray diffraction Laue method. The (0001) and (1011) planes usually developed as the natural facets on the surfaces, and (1010) and(1120) as the cleavage planes. A promising chemical etchant for cadmium iron selenide crystals was developed, consisting of about 20 vol. % concentrated HNO_3, 60 vol. % glacial CH _3COOH, and 20 vol. % concentrated H _2SO_4 acids. Etch pit densities of the grown crystals are in the range of 5times10 ^4-rm5times10^5/cm ^2..

Evaluation of the effect of sulfate, alkalinity and disinfector on iron release of iron pipe and iron corrosion scale characteristics under water quality changing condition using response surface methodology

NASA Astrophysics Data System (ADS)

Yang, Fan; Shi, Baoyou; Zhang, Weiyu; Guo, Jianbo; Wu, Nana; Liu, Xinyuan

2018-02-01

The response surface methodology (RSM), particularly Box-Behnken design model, was used in this study to evaluate the sulfate, alkalinity and free chlorine on iron release of pipe with groundwater supply history and its iron corrosion scale characteristics under water quality changing experiment. The RSM results together with response surface contour plots indicated that the iron release of pipe section reactors was positively related with Larson Ratio and free chlorine. The thin Corrosion scales with groundwater supply history upon collection site contained Fe3O4 (18%), α-FeOOH (64%), FeCO3 (9%), β-FeOOH (8%) and γ-FeOOH (5%), besides their averaged amorphous iron oxide content was 13.6%. After the RSM water quality changing experiment, Fe3O4, amorphous iron oxide and intermediate iron products (FeCO3, Green Rust (GR)) content on scale of Cl2Rs increased, while their α-FeOOH contents decreased and β-FeOOH disappeared. The high iron released Cl2Rs receiving higher LR water (1.40-2.04) contained highest FeCO3 (20%) and amorphous iron oxide (42%), while the low iron release Cl2Rs receiving lower LR water (0.52-0.73) had higher GR(6.5%) and the amorphous iron oxide (23.7%). In high LR water (>0.73), the thin and non-protective corrosion scale containing higher amorphous iron oxide, Fe(II) derived from new produced Fe3O4 or FeCO3 or GR was easy for oxidants and sulfate ions penetration, and had higher iron release. However the same unstable corrosion scale didn’t have much iron release in low LR water (≤0.73). RSM experiment indicated that iron release of these unstable corrosion scales had close relationship with water quality (Larson Ratio and disinfectant). Optimizing the water quality of new source water and using reasonable water purification measures can help to eliminate the red water case.

Synthesis, Properties and Application of Glucose Coated Fe3O4 Nanoparticles Prepared by Co-precipitation Method

NASA Astrophysics Data System (ADS)

Sari, Ayu Y.; Eko, A. S.; Candra, K.; Hasibuan, Denny P.; Ginting, M.; Sebayang, P.; Simamora, P.

2017-07-01

Synthesis of glucose coated Fe3O4 magnetic nanoparticles have been successfully prepared with co-precipitation method. Raw material of natural iron-sand was obtained from Buaya River, Deliserdang, Indonesia. The milled iron-sand was dissolved in HCl (37 mole %), and stirred in 300 rpm at 70°C for 90 minutes. Glucose was added to the filtered powder with varied content of 0.01, 0.02, and 0.03 mole, and precipitated by NH3 (25 mole%). After drying process, the final product subsequently was glucose coated magnetite (Fe3O4) nanoparticles. The characterizations performed were true density measurement, FTIR, VSM, XRD, BET, and adsorbent performance by AAS. The FTIR analysis showed that M-O (bending) with M=Fe (stretching vibration) with υ = 570.92 and 401.19 cm-1. While glucose coated well on nanoparticle Fe3O4, proved by functional groups C=O (stretching), M-O (stretching) and C-H (bending) with υ = 1404.17, 570.92, and 2368.58 cm-1, respectively. Single phase of magnetite (Fe3O4) structure was determined from XRD analysis with cubic spinel structure and lattice parameter of 8.396 Å. The optimum conditions, obtained on the Fe3O4 nanoparticles with 0.01 mole of glucose addition, which has true density value of 4.57 g/cm3, magnetic saturation, M s = 35,41 emu/g, coercivity, H cJ = 83.58 Oe, average particle size = 12.3 nm and surface area = 124.88 m2/g. This type magnetic nanoparticles of glucose-coated Fe3O4 was capable to adsorbed 93.78 % of ion Pb. Therefore, the glucose-coated Fe3O4 nanoparticle is a potential candidate to be used as heavy metal removal from wastewater.

Effectiveness of Iron Ethylenediamine-N,N'-bis(hydroxyphenylacetic) Acid (o,o-EDDHA/Fe3+) Formulations with Different Ratios of Meso and d,l-Racemic Isomers as Iron Fertilizers.

PubMed

Alcañiz, Sara; Jordá, Juana D; Cerdán, Mar

2017-01-18

Two o,o-EDDHA/Fe 3+ formulations (meso, 93.5% w/w of meso isomer; and d,l-racemic, 91.3% w/w of d,l-racemic mixture) were prepared, and their efficacy to avoid or to relieve iron deficiency in Fe-sufficient and Fe-deficient tomato plants grown on hydroponic solution was compared with that of the current o,o-EDDHA/Fe 3+ formulations (50% of meso and d,l-racemic isomers). The effectiveness of the three o,o-EDDHA/Fe 3+ formulations was different depending on the iron nutritional status of plants. The three o,o-EDDHA/Fe 3+ formulations tested were effective in preventing iron chlorosis in healthy plants. However, the higher the meso concentration in the formulations, the higher the effectiveness in the recovery of iron chlorotic plants from iron deficiency. Accordingly, o,o-EDDHA/Fe 3+ formulations rich in meso isomer are recommended in hydroponic systems.

Zea mays Fe deficiency-related 4 (ZmFDR4) functions as an iron transporter in the plastids of monocots.

PubMed

Zhang, Xiu-Yue; Zhang, Xi; Zhang, Qi; Pan, Xiao-Xi; Yan, Luo-Chen; Ma, Xiao-Juan; Zhao, Wei-Zhong; Qi, Xiao-Ting; Yin, Li-Ping

2017-04-01

Iron (Fe)-homeostasis in the plastids is closely associated with Fe transport proteins that prevent Fe from occurring in its toxic free ionic forms. However, the number of known protein families related to Fe transport in the plastids (about five) and the function of iron in non-green plastids is limited. In the present study, we report the functional characterization of Zea mays Fe deficiency-related 4 (ZmFDR4), which was isolated from a differentially expressed clone of a cDNA library of Fe deficiency-induced maize roots. ZmFDR4 is homologous to the bacterial FliP superfamily, coexisted in both algae and terrestrial plants, and capable of restoring the normal growth of the yeast mutant fet3fet4, which possesses defective Fe uptake systems. ZmFDR4 mRNA is ubiquitous in maize and is inducible by iron deficiency in wheat. Transient expression of the 35S:ZmFDR4-eGFP fusion protein in rice protoplasts indicated that ZmFDR4 maybe localizes to the plastids envelope and thylakoid. In 35S:c-Myc-ZmFDR4 transgenic tobacco, immunohistochemistry and immunoblotting confirmed that ZmFDR4 is targeted to both the chloroplast envelope and thylakoid. Meanwhile, ultrastructure analysis indicates that ZmFDR4 promotes the density of plastids and accumulation of starch grains. Moreover, Bathophenanthroline disulfonate (BPDS) colorimetry and inductively coupled plasma mass spectrometry (ICP-MS) indicate that ZmFDR4 is related to Fe uptake by plastids and increases seed Fe content. Finally, 35S:c-Myc-ZmFDR4 transgenic tobacco show enhanced photosynthetic efficiency. Therefore, the results of the present study demonstrate that ZmFDR4 functions as an iron transporter in monocot plastids and provide insight into the process of Fe uptake by plastids. © 2017 The Authors The Plant Journal © 2017 John Wiley & Sons Ltd.

Carbon dioxide binding at a Ni/Fe center: synthesis and characterization of Ni(η1-CO2-κC) and Ni-μ-CO2-κC:κ2 O,O′-Fe† †Electronic supplementary information (ESI) available: Characterization data for 3 and 5. CCDC 1492006 and 1492007. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c6sc03450k Click here for additional data file. Click here for additional data file.

PubMed Central

Yoo, Changho

2017-01-01

The degree of CO2 activation can be tuned by incorporating a distinct electronic coordination environment at the nickel center. A mononuclear nickel carboxylate species (Ni–CO2, 3) and a dinuclear nickel–iron carboxylate species (Ni–CO2–Fe, 5) were prepared. The structure of 3 reveals a rare η1-κC binding mode of CO2, while that of 5 shows bridging CO2 binding (μ2-κC:κ2 O,O′) between the nickel and iron, presented as the first example of a nickel-μ-CO2-iron species. The structural analyses of 3 and 5 based on XRD and DFT data reveal a higher degree of CO2 activation in 5, imparted by the additional interaction with an iron ion. PMID:28616135

New Equation for Prediction of Martensite Start Temperature in High Carbon Ferrous Alloys

NASA Astrophysics Data System (ADS)

Park, Jihye; Shim, Jae-Hyeok; Lee, Seok-Jae

2018-02-01

Since previous equations fail to predict M S temperature of high carbon ferrous alloys, we first propose an equation for prediction of M S temperature of ferrous alloys containing > 2 wt pct C. The presence of carbides (Fe3C and Cr-rich M 7C3) is thermodynamically considered to estimate the C concentration in austenite. Especially, equations individually specialized for lean and high Cr alloys very accurately reproduce experimental results. The chemical driving force for martensitic transformation is quantitatively analyzed based on the calculation of T 0 temperature.

Photo-excitation of electrons in cytochrome c oxidase as a theory of the mechanism of the increase of ATP production in mitochondria by laser therapy

NASA Astrophysics Data System (ADS)

Zielke, Andrzej

2014-02-01

The hypothesis explains the molecular basis for restoring mitochondrial function by laser therapy. It also explains how laser therapy reverses both excessive oxidation (lack of NADH/FADH2) and excessive reduction (lack of O2) states of cytochrome c oxidase complex. It is proposed that photons interact with heme molecules of cytochrome c oxidase. A molecule of heme contains a porphyrin ring and an atom of iron in the center. The iron atom (Fe) can switch oxidation states back and forth between ferrous (Fe2+) and ferric (Fe3+) by accepting or releasing an electron. The porphyrin ring is a complex aromatic molecule that has 26 pi electrons which are "delocalized", spinning in the carbon rings creating a resonating electromagnetic cloud. Photons with similar wavelengths are absorbed by the cloud increasing its energy. The energy is then passed on to the centrally located atom of iron existing in a reduced state (Fe2+). The electrons on the orbits of the iron atom accept this electromagnetic energy, and change orbitals to a higher energetic level. If the energy is sufficient, electrons leave the atom entirely. If this occurs, Fe2+ become oxidized to Fe3+ releasing electrons, thus restoring electron flow and the production of ATP. At the same time, electrons freed from complex IV may have sufficient energy to be picked by NAD+/FADH and re-enter the chain at the complex I or II amplifying the flow of electrons.

Electrostatic and Structural Bases of Fe2+ Translocation through Ferritin Channels*

PubMed Central

Chandramouli, Balasubramanian; Bernacchioni, Caterina; Di Maio, Danilo; Turano, Paola; Brancato, Giuseppe

2016-01-01

Ferritin molecular cages are marvelous 24-mer supramolecular architectures that enable massive iron storage (>2000 iron atoms) within their inner cavity. This cavity is connected to the outer environment by two channels at C3 and C4 symmetry axes of the assembly. Ferritins can also be exploited as carriers for in vivo imaging and therapeutic applications, owing to their capability to effectively protect synthetic non-endogenous agents within the cage cavity and deliver them to targeted tissue cells without stimulating adverse immune responses. Recently, X-ray crystal structures of Fe2+-loaded ferritins provided important information on the pathways followed by iron ions toward the ferritin cavity and the catalytic centers within the protein. However, the specific mechanisms enabling Fe2+ uptake through wild-type and mutant ferritin channels is largely unknown. To shed light on this question, we report extensive molecular dynamics simulations, site-directed mutagenesis, and kinetic measurements that characterize the transport properties and translocation mechanism of Fe2+ through the two ferritin channels, using the wild-type bullfrog Rana catesbeiana H′ protein and some of its variants as case studies. We describe the structural features that determine Fe2+ translocation with atomistic detail, and we propose a putative mechanism for Fe2+ transport through the channel at the C3 symmetry axis, which is the only iron-permeable channel in vertebrate ferritins. Our findings have important implications for understanding how ion permeation occurs, and further how it may be controlled via purposely engineered channels for novel biomedical applications based on ferritin. PMID:27756844

Electrostatic and Structural Bases of Fe2+ Translocation through Ferritin Channels.

PubMed

Chandramouli, Balasubramanian; Bernacchioni, Caterina; Di Maio, Danilo; Turano, Paola; Brancato, Giuseppe

2016-12-02

Ferritin molecular cages are marvelous 24-mer supramolecular architectures that enable massive iron storage (>2000 iron atoms) within their inner cavity. This cavity is connected to the outer environment by two channels at C3 and C4 symmetry axes of the assembly. Ferritins can also be exploited as carriers for in vivo imaging and therapeutic applications, owing to their capability to effectively protect synthetic non-endogenous agents within the cage cavity and deliver them to targeted tissue cells without stimulating adverse immune responses. Recently, X-ray crystal structures of Fe 2+ -loaded ferritins provided important information on the pathways followed by iron ions toward the ferritin cavity and the catalytic centers within the protein. However, the specific mechanisms enabling Fe 2+ uptake through wild-type and mutant ferritin channels is largely unknown. To shed light on this question, we report extensive molecular dynamics simulations, site-directed mutagenesis, and kinetic measurements that characterize the transport properties and translocation mechanism of Fe 2+ through the two ferritin channels, using the wild-type bullfrog Rana catesbeiana H' protein and some of its variants as case studies. We describe the structural features that determine Fe 2+ translocation with atomistic detail, and we propose a putative mechanism for Fe 2+ transport through the channel at the C3 symmetry axis, which is the only iron-permeable channel in vertebrate ferritins. Our findings have important implications for understanding how ion permeation occurs, and further how it may be controlled via purposely engineered channels for novel biomedical applications based on ferritin. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Preparation of Fe3O4/Bentonite Nanocomposite from Natural Iron Sand by Co-precipitation Method for Adsorbents Materials

NASA Astrophysics Data System (ADS)

Sebayang, Perdamean; Kurniawan, Candra; Aryanto, Didik; Arief Setiadi, Eko; Tamba, Konni; Djuhana; Sudiro, Toto

2018-03-01

An adsorption method is one of the effective ways to filter the heavy metals wastes in aqueous system. In this paper, the Fe3O4/bentonite nanocomposites were successfully prepared from natural iron sand by co-precipitation method. The chemical process was carried out by dissolving and hot stirring the milled iron sand and bentonite in acid solution and precipitating it by NH4OH. The sediment was then washed using distilled water to neutralize pH and dried at 100 °C for 5 hours to produce Fe3O4/bentonite powders. The samples were characterized by XRD, FTIR, BET, TEM, VSM and AAS. All samples were composed by Fe3O4 single phase with a spinnel structure and lattice parameter of 8.373 Å. The transmittance peak of FTIR curve proved that the Fe3O4 particles and bentonite had a molecular bonding. The addition of bentonite to Fe3O4 nanoparticles generally reduced the magnetic properties of Fe3O4/bentonite nanocomposites. The optimum condition of 30 wt% bentonite resulted 105.9 m2/g in surface area, 14 nm in an average particle size and 3.2 nm in pore size. It can be used as Cu and Pb adsorbent materials.

Development and Processing of Nickel Aluminide-Carbide Alloys

NASA Technical Reports Server (NTRS)

Newport, Timothy Scott

1996-01-01

With the upper temperature limit of the Ni-based superalloys attained, a new class of materials is required. Intermetallics appear as likely candidates because of their attractive physical properties. With a relatively low density, high thermal conductivity, excellent oxidation resistance, high melting point, and simple crystal structure, nickel aluminide (NiAl) appears to be a potential candidate. However, NiAl is limited in structural applications due to its low room temperature fracture toughness and poor elevated temperature strength. One approach to improving these properties has been through the application of eutectic composites. Researchers have shown that containerless directional solidification of NiAl-based eutectic alloys can provide improvement in both the creep strength and fracture toughness. Although these systems have shown improvements in the mechanical properties, the presence of refractory metals increases the density significantly in some alloys. Lower density systems, such as the carbides, nitrides, and borides, may provide NiAl-based eutectic structure. With little or no information available on these systems, experimental investigation is required. The objective of this research was to locate and develop NiAl-carbide eutectic alloys. Exploratory arc-melts were performed in NiAl-refractory metal-C systems. Refractory metal systems investigated included Co, Cr, Fe, Hf, Mo, Nb, Ta, Ti, W, and Zr. Systems containing carbides with excellent stability (i.e.,HfC, NbC, TaC, TiC, and ZrC) produced large blocky cubic carbides in an NiAl matrix. The carbides appeared to have formed in the liquid state and were randomly distributed throughout the polycrystalline NiAl. The Co, Cr, Fe, Mo, and W systems contained NiAl dendrites with a two-phase interdendritic microconstituent present. Of these systems, the NiAl-Mo-C system had the most promising microstructure for in-situ composites. Three processing techniques were used to evaluate the NiAl-Mo-C system: arc-melting, slow cooling, and containerless directional solidification. Arc-melting provided a wide range of compositions in an economical and simple fashion. The slow cooled ingots provided larger ingots and slower cooling rates than arc-melting. Directional solidification was used to produce in-situ composites consisting of NiAl reinforced with molybdenum carbides.

Redox reactions of [FeFe]-hydrogenase models containing an internal amine and a pendant phosphine.

PubMed

Zheng, Dehua; Wang, Mei; Chen, Lin; Wang, Ning; Sun, Licheng

2014-02-03

A diiron dithiolate complex with a pendant phosphine coordinated to one of the iron centers, [(μ-SCH2)2N(CH2C6H4-o-PPh2){Fe2(CO)5}] (1), was prepared and structurally characterized. The pendant phosphine is dissociated together with a CO ligand in the presence of excess PMe3, to afford [(μ-SCH2)2N(CH2C6H4-o-PPh2){Fe(CO)2(PMe3)}2] (2). Redox reactions of 2 and related complexes were studied in detail by in situ IR spectroscopy. A series of new Fe(II)Fe(I) ([3](+) and [6](+)), Fe(II)Fe(II) ([4](2+)), and Fe(I)Fe(I) (5) complexes relevant to Hox, Hox(CO), and Hred states of the [FeFe]-hydrogenase active site were detected. Among these complexes, the molecular structures of the diferrous complex [4](2+) with the internal amine and the pendant phosphine co-coordinated to the same iron center and the triphosphine diiron complex 5 were determined by X-ray crystallography. To make a comparison, the redox reactions of an analogous complex, [(μ-SCH2)2N(CH2C6H5){Fe(CO)2(PMe3)}2] (7), were also investigated by in situ IR spectroscopy in the absence or presence of extrinsic PPh3, which has no influence on the oxidation reaction of 7. The pendant phosphine in the second coordination sphere makes the redox reaction of 2 different from that of its analogue 7.

Carbon chemistry of the Apollo 15 and 16 deep drill cores

NASA Technical Reports Server (NTRS)

Wszolek, P. C.; Burlingame, A. L.

1973-01-01

The carbon chemistry of the Apollo 15 and 16 deep drill cores is a function of the surface exposure plus the chemical and mineralogical composition of the individual samples. The depth profiles of carbide and methane yields in the Apollo 15 core show a general decline with depth and correlate with the solar wind noble gas content, percentage agglutinates, track densities, and metallic iron. All horizons examined were exposed for a considerable time on the lunar surface. The Apollo 16 core samples show that chemical and mineralogical composition plays an important role in determining the nature of carbide-like material present in the fines. The higher aluminum and calcium contents and lower iron contents of highlands material result in carbide-like material yielding less CD4 and more C2D2 (deuteroacetylene) upon DF acid dissolution.

Reaction intermediates in the catalytic Gif-type oxidation from nuclear inelastic scattering

NASA Astrophysics Data System (ADS)

Rajagopalan, S.; Asthalter, T.; Rabe, V.; Laschat, S.

2016-12-01

Nuclear inelastic scattering (NIS) of synchrotron radiation, also known as nuclear resonant vibrational spectroscopy (NRVS), has been shown to provide valuable insights into metal-centered vibrations at Mössbauer-active nuclei. We present a study of the iron-centered vibrational density of states (VDOS) during the first step of the Gif-type oxidation of cyclohexene with a novel trinuclear Fe3(μ 3-O) complex as catalyst precursor. The experiments were carried out on shock-frozen solutions for different combinations of reactants: Fe3(μ 3-O) in pyridine solution, Fe3(μ 3-O) plus Zn/acetic acid in pyridine without and with addition of either oxygen or cyclohexene, and Fe3(μ 3-O)/Zn/acetic acid/pyridine/cyclohexene (reaction mixture) for reaction times of 1 min, 5 min, and 30 min. The projected VDOS of the Fe atoms was calculated on the basis of pseudopotential density functional calculations. Two possible reaction intermediates were identified as [Fe(III)(C5H5N)2(O2CCH3)2]+ and Fe(II)(C5H5N)4(O2CCH3)2, yielding evidence that NIS (NRVS) allows to identify the presence of iron-centered intermediates also in complex reaction mixtures.

Correlation Of 2-Chlorobiphenyl Dechlorination By Fe/Pd With Iron Corrosion At Different pH

EPA Science Inventory

The rate of 2-chlorobiphenyl dechlorination by palladized iron (Fe/Pd) decreased with increasing pH until pH > 12.5. Iron corrosion potential (E_c) and current (j_c), obtained from polarization curves of a rotating disk electrode of iron, followed the Tafel e...

Microstructure and Plastic Deformation of the As-Welded Invar Fusion Zones

NASA Astrophysics Data System (ADS)

Yao, D. J.; Zhou, D. R.; Xu, P. Q.; Lu, F. G.

2017-05-01

The as-welded Invar fusion zones were fabricated between cemented carbides and carbon steel using a Fe-Ni Invar interlayer and laser welding method. Three regions in the as-welded Invar fusion zones were defined to compare microstructures, and these were characterized and confirmed by scanning electron microscopy and X-ray diffractometry. The structure and plastic deformation mechanism for initial Invar Fe-Ni alloys and the as-welded Invar fusion zones are discussed. (1) After undergoing high-temperature thermal cycles, the microstructure of the as-welded Invar fusion zones contains γ-(Fe, Ni) solid solution (nickel dissolving in γ-Fe) with a face-centered cubic (fcc) crystal structure and mixed carbides (eutectic colonies, mixed carbides between two adjacent grains). The mixed carbides exhibited larger, coarser eutectic microstructures with a decrease in welding speed and an increase in heat input. (2) The structure of the initial Invar and the as-welded Invar is face-centered cubic γ-(Fe, Ni). (3) The as-welded Invar has a larger plastic deformation than initial Invar with an increase in local strain field and dislocation density. Slip deformation is propagated along the (111) plane. This finding helps us to understand microstructure and the formation of dislocation and plastic deformation when the Invar Fe-Ni alloy undergoes a high-temperature process.

Does a higher metal oxidation state necessarily imply higher reactivity toward H-atom transfer? A computational study of C-H bond oxidation by high-valent iron-oxo and -nitrido complexes.

PubMed

Geng, Caiyun; Ye, Shengfa; Neese, Frank

2014-04-28

In this work, the reactions of C-H bond activation by two series of iron-oxo ( (Fe(IV)), (Fe(V)), (Fe(VI))) and -nitrido model complexes ( (Fe(IV)), (Fe(V)), (Fe(VI))) with a nearly identical coordination geometry but varying iron oxidation states ranging from iv to vi were comprehensively investigated using density functional theory. We found that in a distorted octahedral coordination environment, the iron-oxo species and their isoelectronic nitrido analogues feature totally different intrinsic reactivities toward C-H bond cleavage. In the case of the iron-oxo complexes, the reaction barrier monotonically decreases as the iron oxidation state increases, consistent with the gradually enhanced electrophilicity across the series. The iron-nitrido complex is less reactive than its isoelectronic iron-oxo species, and more interestingly, a counterintuitive reactivity pattern was observed, i.e. the activation barriers essentially remain constant independent of the iron oxidation states. The detailed analysis using the Polanyi principle demonstrates that the different reactivities between these two series originate from the distinct thermodynamic driving forces, more specifically, the bond dissociation energies (BDEE-Hs, E = O, N) of the nascent E-H bonds in the FeE-H products. Further decomposition of the BDEE-Hs into the electron and proton affinity components shed light on how the oxidation states modulate the BDEE-Hs of the two series.

Synthesis and electronic structure determination of N-alkyl-substituted bis(imino)pyridine iron imides exhibiting spin crossover behavior.

PubMed

Bowman, Amanda C; Milsmann, Carsten; Bill, Eckhard; Turner, Zoë R; Lobkovsky, Emil; DeBeer, Serena; Wieghardt, Karl; Chirik, Paul J

2011-11-02

Three new N-alkyl substituted bis(imino)pyridine iron imide complexes, ((iPr)PDI)FeNR ((iPr)PDI = 2,6-(2,6-(i)Pr(2)-C(6)H(3)-N═CMe)(2)C(5)H(3)N; R = 1-adamantyl ((1)Ad), cyclooctyl ((Cy)Oct), and 2-adamantyl ((2)Ad)) were synthesized by addition of the appropriate alkyl azide to the iron bis(dinitrogen) complex, ((iPr)PDI)Fe(N(2))(2). SQUID magnetic measurements on the isomeric iron imides, ((iPr)PDI)FeN(1)Ad and ((iPr)PDI)FeN(2)Ad, established spin crossover behavior with the latter example having a more complete spin transition in the experimentally accessible temperature range. X-ray diffraction on all three alkyl-substituted bis(imino)pyridine iron imides established essentially planar compounds with relatively short Fe-N(imide) bond lengths and two-electron reduction of the redox-active bis(imino)pyridine chelate. Zero- and applied-field Mössbauer spectroscopic measurements indicate diamagnetic ground states at cryogenic temperatures and established low isomer shifts consistent with highly covalent molecules. For ((iPr)PDI)FeN(2)Ad, Mössbauer spectroscopy also supports spin crossover behavior and allowed extraction of thermodynamic parameters for the S = 0 to S = 1 transition. X-ray absorption spectroscopy and computational studies were also performed to explore the electronic structure of the bis(imino)pyridine alkyl-substituted imides. An electronic structure description with a low spin ferric center (S = 1/2) antiferromagnetically coupled to an imidyl radical (S(imide) = 1/2) and a closed-shell, dianionic bis(imino)pyridine chelate (S(PDI) = 0) is favored for the S = 0 state. An iron-centered spin transition to an intermediate spin ferric ion (S(Fe) = 3/2) accounts for the S = 1 state observed at higher temperatures. Other possibilities based on the computational and experimental data are also evaluated and compared to the electronic structure of the bis(imino)pyridine iron N-aryl imide counterparts.

Rate of Iron Transfer Through the Horse Spleen Ferritin Shell Determined by the Rate of Formation of Prussian Blue and Fe-desferrioxamine Within the Ferritin Cavity

NASA Technical Reports Server (NTRS)

Zhang, Bo; Watt, Richard K.; Galvez, Natividad; Dominquez-Vera, Jose M.; Watt, Gerald D.

2005-01-01

Iron (2+ and 3+) is believed to transfer through the three-fold channels in the ferritin shell during iron deposition and release in animal ferritins. However, the rate of iron transit in and out through these channels has not been reported. The recent synthesis of [Fe(CN)(sub 6)](3-), Prussian Blue (PB) and desferrioxamine (DES) all trapped within the horse spleen ferritin (HoSF) interior makes these measurements feasible. We report the rate of Fe(2+) penetrating into the ferritin interior by adding external Fe(2+) to [Fe(CN)(sub 6)](3-) encapsulated in the HoSF interior and measuring the rate of formation of the resulting encapsulated PB. The rate at which Fe(2+) reacts with [Fe(CN)(sub 6)](3-) in the HoSF interior is much slower than the formation of free PB in solution and is proceeded by a lag period. We assume this lag period and the difference in rate represent the transfer of Fe(2+) through the HoSF protein shell. The calculated diffusion coefficient, D approx. 5.8 x 10(exp -20) square meters per second corresponds to the measured lag time of 10-20 s before PB forms within the HoSF interior. The activation energy for Fe(2+) transfer from the outside solution through the protein shell was determined to be 52.9 kJ/mol by conducting the reactions at 10 to approximately 40 C. The reaction of Fe(3+) with encapsulated [Fe(CN)6](4-) also readily forms PB in the HoSF interior, but the rate is faster than the corresponding Fe(2+) reaction. The rate for Fe(3+) transfer through the ferritin shell was confirmed by measuring the rate of the formation of Fe-DES inside HoSF and an activation energy of 58.4 kJ/mol was determined. An attempt was made to determine the rate of iron (2+ and 3+) transit out from the ferritin interior by adding excess bipyridine or DES to PB trapped within the HoSF interior. However, the reactions are slow and occur at almost identical rates for free and HoSF-encapsulated PB, indicating that the transfer of iron from the interior through the protein shell is faster than the rate-limiting step of PB dissociation. The method described in this work presents a novel way of determining the rate of transfer of iron and possibly other small molecules through the ferritin shell.

New Insight into Microbial Iron Oxidation as Revealed by the Proteomic Profile of an Obligate Iron-Oxidizing Chemolithoautotroph.

PubMed

Barco, Roman A; Emerson, David; Sylvan, Jason B; Orcutt, Beth N; Jacobson Meyers, Myrna E; Ramírez, Gustavo A; Zhong, John D; Edwards, Katrina J

2015-09-01

Microaerophilic, neutrophilic, iron-oxidizing bacteria (FeOB) grow via the oxidation of reduced Fe(II) at or near neutral pH, in the presence of oxygen, making them relevant in numerous environments with elevated Fe(II) concentrations. However, the biochemical mechanisms for Fe(II) oxidation by these neutrophilic FeOB are unknown, and genetic markers for this process are unavailable. In the ocean, microaerophilic microorganisms in the genus Mariprofundus of the class Zetaproteobacteria are the only organisms known to chemolithoautotrophically oxidize Fe and concurrently biomineralize it in the form of twisted stalks of iron oxyhydroxides. The aim of this study was to identify highly expressed proteins associated with the electron transport chain of microaerophilic, neutrophilic FeOB. To this end, Mariprofundus ferrooxydans PV-1 was cultivated, and its proteins were extracted, assayed for redox activity, and analyzed via liquid chromatography-tandem mass spectrometry for identification of peptides. The results indicate that a cytochrome c4, cbb3-type cytochrome oxidase subunits, and an outer membrane cytochrome c were among the most highly expressed proteins and suggest an involvement in the process of aerobic, neutrophilic bacterial Fe oxidation. Proteins associated with alternative complex III, phosphate transport, carbon fixation, and biofilm formation were abundant, consistent with the lifestyle of Mariprofundus. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Radiation-induced synthesis of Fe-doped TiO 2: Characterization and catalytic properties

NASA Astrophysics Data System (ADS)

Bzdon, Sylwia; Góralski, Jacek; Maniukiewicz, Waldemar; Perkowski, Jan; Rogowski, Jacek; Szadkowska-Nicze, Magdalena

2012-03-01

Fe-doped TiO 2 catalyst was prepared by wet impregnation, using TiO 2 P25 Degussa as a precursor and Fe(NO 3) 3 as a dopant, followed by irradiation with an electron beam or γ-rays. Surface properties of Fe/TiO 2 samples were examined by BET, XRD, ToF-SIMS, and TPR methods. The photocatalytic activity towards destruction of the anionic surfactant, sodium dodecylbenzenesulfonate (SDBS), in aqueous solutions was higher for the irradiated Fe/TiO 2 catalysts than for bare TiO 2 P25 or that calcined at 500 °C. The results show that irradiated catalysts exhibit a more uniform texture with high dispersion of iron species. An enhancement of the activity of irradiated Fe/TiO 2 systems can be attributed to the synergetic effects of small crystallite size and homogenous distribution of iron species including FeTiO 3 phase.

Microstructures and Surface Stabilities of {Ni-0.4C-6Ta- xCr, 0 ≤ x ≤ 50 Wt Pct} Cast Alloys at High Temperature

NASA Astrophysics Data System (ADS)

Berthod, Patrice

2018-06-01

Nickel-based cast alloys rich in chromium and reinforced by TaC carbides are potentially very interesting alloys for applications at elevated temperatures. Unfortunately, unlike cobalt-chromium and iron-chromium alloys, it is difficult to obtain exclusively TaC as primary carbides in Ni-Cr alloys. In alloys containing 30 wt pct Cr tantalum, carbides coexist with chromium carbides. The latter tend to weaken the alloy at elevated temperatures because they become rapidly spherical and then quickly lose their reinforcing effect. In this work, we attempted to stabilize TaC as a single carbide phase by testing different chromium contents in the [0, 50 wt pct] range. Six alloys containing 0.4C and 6Ta, weight contents corresponding to equivalent molar contents, were elaborated by foundry, and their as-cast microstructures were characterized. Samples of all alloys were exposed to 1127 °C and 1237 °C for 24 hours to characterize their stabilized microstructures. The surface fractions of chromium carbides and tantalum carbides were measured by image analysis, and their evolutions vs the chromium content were studied. For the chosen C and Ta contents, it appears that obtaining TaC only is possible by decreasing the chromium content to 10 wt pct. At the same time, TaC fractions are unfortunately too low because a large portion of tantalum integrates into the solid solution in the matrix. A second consequence is a critical decrease in oxidation resistance. Other possible methods to stabilize TaC as a single carbide are evocated, such as the simultaneous increase in Ta and decrease in chromium from 30 wt pct Cr.

Tribological properties and surface chemistry of silicon carbide at temperatures to 1500 C

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1981-01-01

Silicon carbide surfaces were heated to 1500 C in a vacuum and analyzed at room temperature with X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). The basic unit of the surfaces was considered as a plane of a tetrahedron of either SiC4 and CSi4 composition. AES spectra were obtained from 250-1500 C, with an analysis depth of 1 nm revealed the presence of little Si and mostly graphite. XPS analysis depth was 2 nm or less, and Si was found in the second 1 nm. Sliding friction tests with single-crystal silicon carbide in contact with iron in a vacuum were characterized by a stock-slip value. The coefficient of friction increased with increasing temperature up to 400 C, then decreased with increasing temperature from 400-600 C. Reheating surfaces to 800 C after preheating them to that temperature produced no changes in AES readings. It is concluded that the maximum density of silicon and silicon-carbide is at 800 C, and the higher the sliding temperature, the more metal that is transferred.

On the effect of the Fe(2+)/Fe(3+) redox couple on oxidation of carbon in hot H3PO4

NASA Technical Reports Server (NTRS)

Dhar, H. P.; Christner, L. G.; Kush, A. K.

1986-01-01

Oxidation studies of graphite:glassy carbon composites have been carried out at 1 and 4.7 atm. pressures in conc. H3PO4 in the presence and absence of iron ions. The concentration of the acid was varied over 85-100 wt pct, and of the iron ions over 30-300 ppm; the temperature varied over 190-210 C. Unlike the effect of Fe, which has been observed to increase the corrosion of carbon in sulphuric acid, the corrosion in phosphoric acid was observed to be slightly decreased or not at all affected. This result arises because of the catalytic reduction of the oxidized surface groups of carbon by Fe(2+) ions. The catalytic reduction is possible because under the experimental conditions the redox potential of the Fe(2+)/Fe(3+) couple is lower than the open-circuit voltage of carbon.

ATOMIC-SCALE DESIGN OF IRON FISCHER-TROPSCH CATALYSTS: A COMBINED COMPUTATIONAL CHEMISTRY, EXPERIMENTAL, AND MICROKINETIC MODELING APPROACH

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manos Mavrikakis; James A. Dumesic; Amit A. Gokhale

2005-03-22

Efforts during this first year focused on four areas: (1) searching/summarizing published FTS mechanistic and kinetic studies of FTS reactions on iron catalysts; (2) construction of mass spectrometer-TPD and Berty CSTR reactor systems; (3) preparation and characterization of unsupported iron and alumina-supported iron catalysts at various iron loadings (4) Determination of thermochemical parameters such as binding energies of reactive intermediates, heat of FTS elementary reaction steps, and kinetic parameters such as activation energies, and frequency factors of FTS elementary reaction steps on a number of model surfaces. Literature describing mechanistic and kinetic studies of Fischer-Tropsch synthesis on iron catalysts wasmore » compiled in a draft review. Construction of the mass spectrometer-TPD system is 90% complete and of a Berty CSTR reactor system 98% complete. Three unsupported iron catalysts and three alumina-supported iron catalysts were prepared by nonaqueous-evaporative deposition (NED) or aqueous impregnation (AI) and characterized by chemisorption, BET, extent-of-reduction, XRD, and TEM methods. These catalysts, covering a wide range of dispersions and metal loadings, are well-reduced and relatively thermally stable up to 500-600 C in H{sub 2}, thus ideal for kinetic and mechanistic studies. The alumina-supported iron catalysts will be used for kinetic and mechanistic studies. In the coming year, adsorption/desorption properties, rates of elementary steps, and global reaction rates will be measured for these catalysts, with and without promoters, providing a database for understanding effects of dispersion, metal loading, and support on elementary kinetic parameters and for validation of computational models that incorporate effects of surface structure and promoters. Furthermore, using state-of-the-art self-consistent Density Functional Theory (DFT) methods, we have extensively studied the thermochemistry and kinetics of various elementary steps on three different model surfaces: (1) Fe(110), (2) Fe(110) modified by subsurface C, and (3) Fe surface modified with Pt adatoms. These studies have yielded valuable insights into the reactivity of Fe surfaces for FTS, and provided accurate estimates for the effect of Fe modifiers such as subsurface C and surface Pt.« less

Switchable transport strategy to deposit active Fe/Fe3C cores into hollow microporous carbons for efficient chromium removal.

PubMed

Liu, Dong-Hai; Guo, Yue; Zhang, Lu-Hua; Li, Wen-Cui; Sun, Tao; Lu, An-Hui

2013-11-25

Magnetic hollow structures with microporous shell and highly dispersed active cores (Fe/Fe3 C nanoparticles) are rationally designed and fabricated by solution-phase switchable transport of active iron species combined with a solid-state thermolysis technique, thus allowing selective encapsulation of functional Fe/Fe3 C nanoparticles in the interior cavity. These engineered functional materials show high loading (≈54 wt%) of Fe, excellent chromium removal capability (100 mg g(-1)), fast adsorption rate (8766 mL mg(-1) h(-1)), and easy magnetic separation property (63.25 emu g(-1)). During the adsorption process, the internal highly dispersed Fe/Fe3 C nanoparticles supply a driving force for facilitating Cr(VI) diffusion inward, thus improving the adsorption rate and the adsorption capacity. At the same time, the external microporous carbon shell can also efficiently trap guest Cr(VI) ions and protect Fe/Fe3 C nanoparticles from corrosion and subsequent leaching problems. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structure and electrochemistry of proteins harboring iron-sulfur clusters of different nuclearities. Part II. [4Fe-4S] and [3Fe-4S] iron-sulfur proteins.

PubMed

Zanello, Piero

2018-06-01

In the context of the plethora of proteins harboring iron-sulfur clusters we have already reviewed structure/electrochemistry of metalloproteins expressing single types of iron-sulfur clusters (namely: {Fe(Cys) 4 }, {[Fe 2 S 2 ](Cys) 4 }, {[Fe 2 S 2 ](Cys) 3 (X)} (X = Asp, Arg, His), {[Fe 2 S 2 ](Cys) 2 (His) 2 }, {[Fe 3 S 4 ](Cys) 3 }, {[Fe 4 S 4 ](Cys) 4 } and {[Fe 4 S 4 ](S γ Cys ) 3 (nonthiolate ligand)} cores) and their synthetic analogs. More recently we are focussing on structure/electrochemistry of metalloproteins harboring iron-sulfur centres of different nuclearities. Having started such a subject with proteins harboring [4Fe-4S] and [2Fe-2S] clusters, we now depict the state of art of proteins containing [4Fe-4S] and [3Fe-4S] clusters. Copyright © 2018 Elsevier Inc. All rights reserved.

Spatially and size selective synthesis of Fe-based nanoparticles on ordered mesoporous supports as highly active and stable catalysts for ammonia decomposition.

PubMed

Lu, An-Hui; Nitz, Joerg-Joachim; Comotti, Massimiliano; Weidenthaler, Claudia; Schlichte, Klaus; Lehmann, Christian W; Terasaki, Osamu; Schüth, Ferdi

2010-10-13

Uniform and highly dispersed γ-Fe(2)O(3) nanoparticles with a diameter of ∼6 nm supported on CMK-5 carbons and C/SBA-15 composites were prepared via simple impregnation and thermal treatment. The nanostructures of these materials were characterized by XRD, Mössbauer spectroscopy, XPS, SEM, TEM, and nitrogen sorption. Due to the confinement effect of the mesoporous ordered matrices, γ-Fe(2)O(3) nanoparticles were fully immobilized within the channels of the supports. Even at high Fe-loadings (up to about 12 wt %) on CMK-5 carbon no iron species were detected on the external surface of the carbon support by XPS analysis and electron microscopy. Fe(2)O(3)/CMK-5 showed the highest ammonia decomposition activity of all previously described Fe-based catalysts in this reaction. Complete ammonia decomposition was achieved at 700 °C and space velocities as high as 60,000 cm(3) g(cat)(-1) h(-1). At a space velocity of 7500 cm(3) g(cat)(-1) h(-1), complete ammonia conversion was maintained at 600 °C for 20 h. After the reaction, the immobilized γ-Fe(2)O(3) nanoparticles were found to be converted to much smaller nanoparticles (γ-Fe(2)O(3) and a small fraction of nitride), which were still embedded within the carbon matrix. The Fe(2)O(3)/CMK-5 catalyst is much more active than the benchmark NiO/Al(2)O(3) catalyst at high space velocity, due to its highly developed mesoporosity. γ-Fe(2)O(3) nanoparticles supported on carbon-silica composites are structurally much more stable over extended periods of time but less active than those supported on carbon. TEM observation reveals that iron-based nanoparticles penetrate through the carbon layer and then are anchored on the silica walls, thus preventing them from moving and sintering. In this way, the stability of the carbon-silica catalyst is improved. Comparison with the silica supported iron oxide catalyst reveals that the presence of a thin layer of carbon is essential for increased catalytic activity.

Design and syntheses of hybrid metal-organic materials based on K3[M(C2O4)3]·3H2O [M(III)=Fe, Al, Cr] metallotectons

NASA Astrophysics Data System (ADS)

Sun, Yayong; Zong, Yingxia; Ma, Haoran; Zhang, Ao; Liu, Kang; Wang, Debao; Wang, Wenqiang; Wang, Lei

2016-05-01

By using K3[M(C2O4)3]·3H2O [M(III)=Fe, Al, Cr] (C2O42-=oxalate) metallotectons as the starting material, we have synthesized eight novel complexes with formulas [{Fe(C2O4)2(H2O)2}2]·(H-L1)2·H2O 1, [Fe(C2O4)Cl2]·(H2-L2)0.5·(L2)0.5·H2O 2, [{Fe(C2O4)1.5Cl2}2]·(H-L3)43, [Fe2(C2O4)Cl8]·(H2-L4)2·2H2O 4, K[Al(C2O4)3]·(H2-L5)·2H2O 5, K[Al(C2O4)3]·(H-L6)2·2H2O 6, K[Cr(C2O4)3]·2H2O 7, Na[Fe(C2O4)3]·(H-L6)2·2H2O 8 (with L1=4-dimethylaminopyridine, L2=2,3,5,6-tetramethylpyrazine, L3=2-aminobenzimidazole, L4=1,4-bis-(1H-imidazol-1-yl)benzene, L5=1,4-bis((2-methylimidazol-1-yl)methyl)benzene, L6=2-methylbenzimidazole). Their structures have been determined by single-crystal X-ray diffraction analyses, elemental analyses, IR spectra and thermogravimetric analyses. Compound 3 is a 2D H-bonded supramolecular architecture. Others are 3D supramolecular structures. Compound 1 shows a [Fe(C2O4)2(H2O)2]- unit and 3D antionic H-bonded framework. Compound 2 features a [Fe(C2O4)Cl2]- anion and 1D iron-oxalate-iron chain. Compound 3 features a [Fe2(C2O4)3Cl4]4- unit. Compound 4 features distinct [Fe2(C2O4)Cl8]4- units, which are mutual linked by water molecules to generated a 2D H-bonded network. Compound 5 features infinite ladder-like chains constructed by [Al(C2O4)3]3- units and K+ cations. The 1D chains are further extended into 3D antionic H-bonded framework through O-H···O H-bonds. Compounds 6-8 show 2D [KAl(C2O4)3]2- layer, [KCr(C2O4)3]2- layer and [NaFe(C2O4)3]2- layer, respectively.

Phase equilibria in the iron oxide-cobalt oxide-phosphorus oxide system

NASA Technical Reports Server (NTRS)

De Guire, Mark R.; Prasanna, T. R. S.; Kalonji, Gretchen; O'Handley, Robert C.

1987-01-01

Two novel ternary compounds are noted in the present study of 1000 C solid-state equilibria in the Fe-Co-P-O system's Fe2O3-FePO4-Co3(Po4)2-CoO region: CoFe(PO4)O, which undergoes incongruent melting at 1130 C, and Co3Fe4(PO4)6, whose incongruent melting occurs at 1080 C. The liquidus behavior-related consequences of rapidly solidified cobalt ferrite formation from cobalt ferrite-phosphate melts are discussed with a view to spinel formation. It is suggested that quenching from within the spinel-plus-liquid region may furnish an alternative to quenching a homogeneous melt.

Features of surface phase formation during case-hardening of iron- and titanium-based alloys

NASA Astrophysics Data System (ADS)

Vintaikin, B. E.; Kamynin, A. V.; Kraposhin, V. S.; Smirnov, A. E.; Terezanova, K. V.; Cherenkova, S. A.; Sheykina, V. I.

2017-11-01

The article provides a detailed analysis of formation features for surface phases in technical iron and Cr20-Ni80 alloy samples that undergo case-hardening at a temperature of 850°C for 2, 4 and 6 hours of saturation in two different environments: acetylene, and molten salt consisting of sodium tetraborate and amorphous boron. We carried out an X-ray phase analysis to determine the phase structure of surface material layers that formed as a result of the case-hardening process. We discovered that after carburising it was possible to detect Fe3C and Fe-α phases on the surface of technical iron samples, and after boriding we found FeB, Fe2B and Fe3B phases; we noted a lack of characteristic Fe-α and Fe-γ peaks on the X-ray diffraction pattern. We detected many different phases in the Cr20-Ni80 alloy after the same type of case-hardening. Titanium oxides appeared after case-hardening of titanium in air at 800°C. We provide data on surface structure of samples subjected to vacuum carburising: over a 2 to 6 hour interval, the layer thickness is a parabolic function of time. When carrying out electrolysis-free liquid boriding, increasing exposure time from 2 to 6 hours alters the thickness of the strengthened layer only slightly, so, when carrying out case-hardening, it is less efficient to increase saturation time in molten salt containing sodium tetraborate and amorphous boron.

Iron Fortified Complementary Foods Containing a Mixture of Sodium Iron EDTA with Either Ferrous Fumarate or Ferric Pyrophosphate Reduce Iron Deficiency Anemia in 12- to 36-Month-Old Children in a Malaria Endemic Setting: A Secondary Analysis of a Cluster-Randomized Controlled Trial.

PubMed

Glinz, Dominik; Wegmüller, Rita; Ouattara, Mamadou; Diakité, Victorine G; Aaron, Grant J; Hofer, Lorenz; Zimmermann, Michael B; Adiossan, Lukas G; Utzinger, Jürg; N'Goran, Eliézer K; Hurrell, Richard F

2017-07-14

Iron deficiency anemia (IDA) is a major public health problem in sub-Saharan Africa. The efficacy of iron fortification against IDA is uncertain in malaria-endemic settings. The objective of this study was to evaluate the efficacy of a complementary food (CF) fortified with sodium iron EDTA (NaFeEDTA) plus either ferrous fumarate (FeFum) or ferric pyrophosphate (FePP) to combat IDA in preschool-age children in a highly malaria endemic region. This is a secondary analysis of a nine-month cluster-randomized controlled trial conducted in south-central Côte d'Ivoire. 378 children aged 12-36 months were randomly assigned to no food intervention ( n = 125; control group), CF fortified with 2 mg NaFeEDTA plus 3.8 mg FeFum for six days/week ( n = 126; FeFum group), and CF fortified with 2 mg NaFeEDTA and 3.8 mg FePP for six days/week ( n = 127; FePP group). The outcome measures were hemoglobin (Hb), plasma ferritin (PF), iron deficiency (PF < 30 μg/L), and anemia (Hb < 11.0 g/dL). Data were analyzed with random-effect models and PF was adjusted for inflammation. The prevalence of Plasmodium falciparum infection and inflammation during the study were 44-66%, and 57-76%, respectively. There was a significant time by treatment interaction on IDA ( p = 0.028) and a borderline significant time by treatment interaction on iron deficiency with or without anemia ( p = 0.068). IDA prevalence sharply decreased in the FeFum (32.8% to 1.2%, p < 0.001) and FePP group (23.6% to 3.4%, p < 0.001). However, there was no significant time by treatment interaction on Hb or total anemia. These data indicate that, despite the high endemicity of malaria and elevated inflammation biomarkers (C-reactive protein or α-1-acid-glycoprotein), IDA was markedly reduced by provision of iron fortified CF to preschool-age children for 9 months, with no significant differences between a combination of NaFeEDTA with FeFum or NaFeEDTA with FePP. However, there was no overall effect on anemia, suggesting most of the anemia in this setting is not due to ID. This trial is registered at clinicaltrials.gov (NCT01634945).

Phosphonate removal from discharged circulating cooling water using iron-carbon micro-electrolysis.

PubMed

Zhou, Zhen; Qiao, Weimin; Lin, Yangbo; Shen, Xuelian; Hu, Dalong; Zhang, Jianqiao; Jiang, Lu-Man; Wang, Luochun

2014-01-01

Phosphonate is a commonly used corrosion and scale inhibitor for a circulating cooling water (CCW) system. Its discharge could cause eutrophication of receiving waters. The iron-carbon (Fe/C) micro-electrolysis technology was used to degrade and remove phosphonate from discharged CCW. The influences of initial pH, Fe/C ratio (FCR) and temperature on phosphonate removal were investigated in a series of batch tests and optimized by response surface methodology. The quadratic model of phosphonate removal was obtained with satisfactory degrees of fitness. The optimum conditions with total phosphorus removal efficiency of 95% were obtained at pH 7.0, FCR of 1.25, and temperature of 45 °C. The phosphonate removal mechanisms were also studied. Phosphonate removal occurred predominantly via two consecutive reactive phases: the degradation of phosphonate complexes (Ca-phosphonate) and the precipitation of Fe/C micro-electrolysis products (PO₄(3-), Ca²⁺ and Fe³⁺).

Effects of carbonate species on the kinetics of dechlorination of 1,1,1-trichloroethane by zero-valent iron.

PubMed

Agrawal, Abinash; Ferguson, William J; Gardner, Bruce O; Christ, John A; Bandstra, Joel Z; Tratnyek, Paul G

2002-10-15

The effect of precipitates on the reactivity of iron metal (Fe0) with 1,1,1-trichloroethane (TCA) was studied in batch systems designed to model groundwaters that contain dissolved carbonate species (i.e., C(IV)). At representative concentrations for high-C(IV) groundwaters (approximately 10(-2) M), the pH in batch reactors containing Fe0 was effectively buffered until most of the aqueous C(IV) precipitated. The precipitate was mainly FeCO3 (siderite) but may also have included some carbonate green rust. Exposure of the Fe0 to dissolved C(IV) accelerated reduction of TCA, and the products formed under these conditions consisted mainly of ethane and ethene, with minor amounts of several butenes. The kinetics of TCA reduction were first-order when C(IV)-enhanced corrosion predominated but showed mixed-order kinetics (zero- and first-order) in experiments performed with passivated Fe0 (i.e., before the onset of pitting corrosion and after repassivation by precipitation of FeCO3). All these data were described by fitting a Michaelis-Menten-type kinetic model and approximating the first-order rate constant as the ratio of the maximum reaction rate (Vm) and the concentration of TCA at half of the maximum rate (K(1/2)). The decrease in Vm/K(1/2) with increasing C(IV) exposure time was fit to a heuristic model assuming proportionality between changes in TCA reduction rate and changes in surface coverage with FeCO3.

Synthesis of LiFePO4/C composites based on natural iron stone using a sol gel method

NASA Astrophysics Data System (ADS)

Angela, Riyan; Islam, Humaatul; Sari, Vamellia; Latif, Chaironi; Zainuri, Mochamad; Pratapa, Suminar

2017-01-01

Synthesis of LiFePO4/C composites has been carried out using a sol gel method. The Fe precursor was made from a natural iron stone of Tanah Laut, South Kalimantan, while the other raw materials were commercial Li2CO3 powder and NH4H2PO4 powder with HCl and water as solvents. Citric acid was used as the carbon source in the synthesis. This study used a molar ratio of 1:1:2 for Li:Fe:P with variation of added citric acid of 1.5 and 2.5 g. The solutions were dried in air at 100°C. The dried powders were characterized using DSC-TGA and then calcined at 600 and 700°C under argon environment for 10 hours. The calcined powders were characterized by X-ray diffractometry (XRD), scanning electron microscopy-energy dispersive x-ray (SEM-EDX), and LCR meter. It was found that the samples contained LiFePO4 as the dominant phase and LiFeP2O7 and Fe2O3 as secondary phases. The analysis showed that the addition of citric acid influenced the electronic conductivity of the composites. A Rietveld relative weight fraction of up to 94.7% was achieved in the synthesis at temperature 600°C. The LFP/C sample exhibited electronic conductivity of 4.56×10-3 Scm-1 which was six times of that of the pure LFP.

Effect of iron ion on doxycycline photocatalytic and Fenton-based autocatatalytic decomposition.

PubMed

Bolobajev, Juri; Trapido, Marina; Goi, Anna

2016-06-01

Doxycycline plays a key role in Fe(III)-to-Fe(II) redox cycling and therefore in controlling the overall reaction rate of the Fenton-based process (H2O2/Fe(III)). This highlights the autocatalytic profile of doxycycline degradation. Ferric iron reduction in the presence of doxycycline relied on doxycycline-to-Fe(III) complex formation with an ensuing reductive release of Fe(II). The lower ratio of OH-to-contaminant in an initial H2O2/Fe(III) oxidation step than in that of classical Fenton (H2O2/Fe(II)) decreased the doxycycline degradation rate. The quantum yield of doxycycline in direct UV-C photolysis was 3.1 × 10(-3) M E(-1). In spite of doxycycline-Fe(III) complexes could produce the adverse effect on the doxycycline degradation in the UV/Fe(III) system some acceleration of the rate was observed upon irradiation of the Fe(III)-hydroxy complex. Acidic reaction media (pH 3.0) and the molar ratio of DC/Fe(III) = 2/1 favored the complex formation. Doxycycline close degradation rates and complete mineralization achieved for 120 min (Table 1) with both UV/H2O2 and UV/H2O2/Fe(III) indicated the unsubstantial role of the reduction of Fe(III) to Fe(II) in UV/H2O2/Fe(III) system efficacy. Thus, factors such as doxycycline's ability to form complexes with ferric iron and the ability of complexes to participate in a reductive pathway should be considered at a technological level in process optimization, with chemistry based on iron ion catalysis to enhance the doxycycline oxidative pathway. Copyright © 2016 Elsevier Ltd. All rights reserved.

Friction and wear with a single-crystal abrasive grit of silicon carbide in contact with iron base binary alloys in oil: Effects of alloying element and its content

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1979-01-01

Sliding friction experiments were conducted with various iron-base binary alloys (alloying elements were Ti, Cr, Mn, Ni, Rh, and W) in contact with a rider of 0.025-millimeter-radius, single-crystal silicon carbide in mineral oil. Results indicate that atomic size and content of alloying element play a dominant role in controlling the abrasive-wear and -friction properties of iron-base binary alloys. The coefficient of friction and groove height (wear volume) general alloy decrease, and the contact pressure increases in solute content. There appears to be very good correlation of the solute to iron atomic radius ratio with the decreasing rate of coefficient of friction, the decreasing rate of groove height (wear volume), and the increasing rate of contact pressure with increasing solute content C. Those rates increase as the solute to iron atomic radius ratio increases from unity.

The Acid-Base Properties, Hydrolytic Mechanism, and Susceptibility to O2 Oxidation of Fe4S4(SR)4-2 Clusters

PubMed Central

Bruice, Thomas C.; Maskiewicz, Richard; Job, Robert

1975-01-01

The iron-sulfur cluster compounds Fe4S4(SR)4-2 [where —SR = —SCH3, —S—C(CH3)3, and —S— CH2—CH(CH3)2] have been found to represent the base species of weak acids of pKa comparable to that of carboxylic acids. The acid species Fe4S4(SR)4H- is most subject to reaction with O2 and to acid-catalyzed solvolysis, while the base species Fe4S4(SR)4-2 most readily undergoes ligand exchange. The kinetics for hydrolysis of the isobutyl mercaptide cluster salt has been investigated in detail and a mechanism involving the stepwise process [Formula: see text] has been proposed. The importance of the acid-base equilibria in determining the reactivity of the iron-sulfur clusters and its possible importance as a factor in the determination of the potentials of ferredoxins and high potential iron protein are discussed. PMID:16592211

The effect of carbon distribution on deformation and cracking of Ni-16Cr-9Fe-C alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hertzberg, J.L.; Was, G.S.

1995-12-31

Constant extension rate tensile (CERT) tests and constant load tensile (CLT) tests were conducted on controlled purity Ni-16Cr-9Fe-C alloys. The amount and form of carbon were varied in order to investigate the roles of carbon in solution and as intergranular (IG) carbides in the deformation and IG cracking behavior in 360 C argon and primary water environments. Results show that the strength, ductility and creep resistance of these alloys are increased with carbon present in solid solution, while IG cracking on the fracture surface is suppressed. Alloys containing carbon in the form of IG carbides, however, exhibit reduced strength andmore » ductility relative to carbon in solution, while maintaining high IG cracking resistance with respect to carbon-free alloys. CERT results of commercial alloy 600 and controlled purity, carbon containing alloys yield comparable failure strains and IG cracking amounts. CLT comparisons with creep tests of alloy 600 suggest that alloys containing IG carbides are more susceptible to creep than those containing all carbon in solid solution.« less

Chemical leaching methods and measurements of marine labile particulate Fe

NASA Astrophysics Data System (ADS)

Revels, B. N.; John, S.

2012-12-01

Iron (Fe) is an essential nutrient for life. Yet its low solubility and concentration in the ocean limits marine phytoplankton productivity in many regions of the world. Dissolved phase Fe (<0.4μm) has traditionally been considered the most biologically accessible form, however, the particulate phase (>0.4μm) may contain an important, labile reservoir of Fe that may also be available to phytoplankton. However, concentration data alone cannot elucidate the sources of particulate Fe to the ocean and to what extent particulate iron may support phytoplankton growth. Isotopic analysis of natural particles may help to elucidate the biogeochemical cycling of Fe, though it is important to find a leaching method which accesses bioavailable Fe. Thirty-three different chemical leaches were performed on a marine sediment reference material, MESS-3. The combinations included four different acids (25% acetic acid, 0.01M HCl, 0.5M HCl, 0.1M H2SO4 at pH2), various redox conditions (0.02M hydroxylamine hydrochloride or 0.02M H2O2), three temperatures (25°C, 60°C, 90°C), and three time points (10 minutes, 2 hours, 24 hours). Leached Fe concentrations varied from 1mg/g to 35mg/g, with longer treatment times, stronger acids, and hotter temperatures generally associated with an increase in leached Fe. δ56Fe in these leaches varied from -1.0‰ to +0.2‰. Interestingly, regardless of leaching method used, there was a very similar relationship between the amount of Fe leached from the particles and the δ56Fe of this iron. Isotopically lighter δ56Fe values were associated with smaller amounts of leached Fe whereas isotopically heavier δ56Fe values were associated with larger amounts of leached Fe. Two alternate hypotheses could explain these data. Either, the particles may contain pools of isotopically light Fe that are easily accessed early in dissolution, or isotopically light Fe may be preferentially leached from the particle due to a kinetic isotope effect during dissolution. To explore the first hypothesis, we modeled dissolution of Fe from particles assuming two separate pools, labile and refractory. The model produces a good fit to the data assuming 3mg/g of a labile Fe pool with δ56Fe = -0.9‰ and a refractory Fe pool with δ56Fe = +0.1‰. If the second hypothesis is true, and there is a kinetic isotope effect during dissolution, the similar relationship between amount of Fe leached and δ56Fe for both organic and mineral acids suggests that Fe is leached from particles via proton-promoted dissolution. Several of these leaching techniques will be employed on sediment trap material from the Cariaco Basin to further investigate the relationship between δ56Fe and the labile, bioavailable fraction of iron particles. A leach or series of leaches will be chosen to provide the most useful information about the bioavailability of iron from particles, and they will be applied to filtered particle samples from portions of the US GEOTRACES A10 (North Atlantic) transect. δ56Fe values from particulate material in these regions will provide a better understanding of the sources of particulate iron to the ocean, and may help to trace how particulate iron is involved in global biogeochemical cycles.

Reactivity of tris(acetylacetonato) iron(III) with tridentate [ONO] donor Schiff base as an access to newer mixed-ligand iron(III) complexes

NASA Astrophysics Data System (ADS)

Bhattacharjee, Chira R.; Goswami, Pankaj; Pramanik, Harun A. R.; Paul, Pradip C.; Mondal, Paritosh

2011-05-01

Two new mixed-ligand iron(III) complexes, [Fe(L n)(acac)(C 2H 5OH)] incorporating coordinated ethanol from the reaction solvent were accessed from the reaction of [Fe(acac) 3] with [ONO] donor dibasic tridentate unsymmetrical Schiff base ligands derived from condensation of 2-hydroxy-1-napthaldehyde with 2-aminophenol (H 2L 1) or 2-aminobenzoic acid (H 2L 2). The thermal study (TGA-DTA) provided evidence for weakly bound ethanol which is readily substituted by neutral N-donor molecule imidazole, benzimidazole or pyridine to produce an array of newer complexes, [Fe(L n)(acac)X] ( n = 1, 2; X = Im, Bim, Py). The compounds were characterized by elemental analyses, FT-IR, UV-vis, solution electrical conductivity, FAB mass, 1H and 13C NMR spectroscopy. Room temperature magnetic susceptibility measurements ( μeff ˜ 5.8 B.M.) are consistent with spin-free octahedral iron(III) complexes. Cyclic voltammetry of ethanol complexes revealed a quasi-reversible one electron redox response (Δ Ep > 100 mV) for the Fe(III)/Fe(II) couple. Low half wave redox potential ( E1/2) values suggested easy redox susceptibility. The ground state geometries of the ethanol and imidazole complexes have been ascertained to be distorted octahedral by density functional theory using DMol3 program at BLYP/DNP level.

Mononitrosyl tris(thiolate) iron complex [Fe(NO)(SPh)3]- and dinitrosyl iron complex [(EtS)2Fe(NO)2]-: formation pathway of dinitrosyl iron complexes (DNICs) from nitrosylation of biomimetic rubredoxin [Fe(SR)4]2-/1- (R = Ph, Et).

PubMed

Lu, Tsai-Te; Chiou, Show-Jen; Chen, Chun-Yu; Liaw, Wen-Feng

2006-10-16

Nitrosylation of the biomimetic reduced- and oxidized-form rubredoxin [Fe(SR)4]2-/1- (R = Ph, Et) in a 1:1 stoichiometry led to the formation of the extremely air- and light-sensitive mononitrosyl tris(thiolate) iron complexes (MNICs) [Fe(NO)(SR)3]- along with byproducts [SR]- or (RS)2. Transformation of [Fe(NO)(SR)3]- into dinitrosyl iron complexes (DNICs) [(RS)2Fe(NO)2]- and Roussin's red ester [Fe2(mu-SR)2(NO)4] occurs rapidly under addition of 1 equiv of NO(g) and [NO]+, respectively. Obviously, the mononitrosyl tris(thiolate) complex [Fe(NO)(SR)3]- acts as an intermediate when the biomimetic oxidized- and reduced-form rubredoxin [Fe(SR)4]2-/1- exposed to NO(g) were modified to form dinitrosyl iron complexes [(RS)2Fe(NO)2]-. Presumably, NO binding to the electron-deficient [Fe(III)(SR)4]- and [Fe(III)(NO)(SR)3]- complexes triggers reductive elimination of dialkyl/diphenyl disulfide, while binding of NO radical to the reduced-form [Fe(II)(SR)4]2- induces the thiolate-ligand elimination. Protonation of [Fe(NO)(SEt)3]- yielding [Fe(NO)(SPh)3]- by adding 3 equiv of thiophenol and transformation of [Fe(NO)(SPh)3]- to [Fe(NO)(SEt)3]- in the presence of 3 equiv of [SEt]-, respectively, demonstrated that complexes [Fe(NO)(SPh)3]- and [Fe(NO)(SEt)3]- are chemically interconvertible. Mononitrosyl tris(thiolate) iron complex [Fe(NO)(SPh)3]- and dinitrosyl iron complex [(EtS)2Fe(NO)2]- were isolated and characterized by X-ray diffraction. The mean NO bond distances of 1.181(7) A (or 1.191(7) A) in complex [(EtS)2Fe(NO)2]- are nearly at the upper end of the 1.178(3)-1.160(6) A for the anionic {Fe(NO)2}9 DNICs, while the mean FeN(O) distances of 1.674(6) A (or 1.679(6) A) exactly fall in the range of 1.695(3)-1.661(4) A for the anionic {Fe(NO)2}9 DNICs.

Synthesis of carbon nanotubes via Fe-catalyzed pyrolysis of phenolic resin

NASA Astrophysics Data System (ADS)

Wang, Junkai; Deng, Xiangong; Zhang, Haijun; Zhang, Yuanzhuo; Duan, Hongjuan; Lu, Lilin; Song, Jianbo; Tian, Liang; Song, Shupeng; Zhang, Shaowei

2017-02-01

Carbon nanotubes (CNTs) with 40-100 nm in diameter and tens of micrometers in length were prepared via catalytic pyrolysis of phenol resin in Ar at 673-1273 K using ferric nitrate as a catalyst precursor. Structure and morphology of pyrolyzed resin were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. Ferric nitrate was transformed to Fe3O4 at 673 K, and to metallic Fe and FexC carbide at 873-1273 K. The optimal weight ratio of Fe catalyst to phenol resin for growing CNTs was 1.00 wt%, and the optimal temperature was 1073 K. In addition, use of a high pressure increased the yield of CNTs. Density functional theory (DFT) calculations suggest that Fe catalysts facilitate the CNTs growth by increasing the bond length and weakening the bond strength in C2H4 via donating electrons to the C atoms in it.

Characterization of magnetite (Fe3O4) minerals from natural iron sand of Bonto Kanang Village Takalar for ink powder (toner) application

NASA Astrophysics Data System (ADS)

Fahlepy, M. R.; Tiwow, V. A.; Subaer

2018-03-01

This research is about magnetite’s characterization (Fe3O4) from natural iron sands of Bonto Kanang Village, District of Takalar for ink powder (toner) application. This study aims to determine the process parameters to obtain magnetite of high purity degree and to observe its physical characteristics as a supporting toner material which synthesized through co-precipitation method. The iron sand was first separated by the magnetic technique and dissolved into HCl solution before conducting the precipitation process. Precipitation was done by dripping ammonium hydroxide (NH4OH). The precipitated powder was dried at 100°C, and then calcined at 400°C. The purity degree and magnetite mineral grain size were analyzed by XRD and SEM-EDS. The EDS elemental test before and after precipitation shown an increase of iron oxide composition from 66.70% to 87.76%. Diffractogram of XRD before and after precipitation showed Fe3O4 compounds with magnetite phase of 59% and 98%, respectively. The crystal structure iron sand powder structure before and after precipitation is cubic with each lattice parameters a = b = c = 8.384971 Å, V = 589.528423 Å3 and a = b = c = 8.386829 Å and V = 589.920291 Å3 when angle α = β = γ = 90°. SEM images (using SE and HV 20kV) showed inhomogeneous magnetite morphology. The magnetite phase percentage that obtained based on the XRD analysis gives information that magnetite precipitation has been successfully performed with high degree of purity. The material obtained can be applied as a support toner material.

Active site formation mechanism of carbon-based oxygen reduction catalysts derived from a hyperbranched iron phthalocyanine polymer.

PubMed

Hiraike, Yusuke; Saito, Makoto; Niwa, Hideharu; Kobayashi, Masaki; Harada, Yoshihisa; Oshima, Masaharu; Kim, Jaehong; Nabae, Yuta; Kakimoto, Masa-Aki

2015-01-01

Carbon-based cathode catalysts derived from a hyperbranched iron phthalocyanine polymer (HB-FePc) were characterized, and their active-site formation mechanism was studied by synchrotron-based spectroscopy. The properties of the HB-FePc catalyst are compared with those of a catalyst with high oxygen reduction reaction (ORR) activity synthesized from a mixture of iron phthalocyanine and phenolic resin (FePc/PhRs). Electrochemical measurements demonstrate that the HB-FePc catalyst does not lose its ORR activity up to 900°C, whereas that of the FePc/PhRs catalyst decreases above 700°C. Hard X-ray photoemission spectra reveal that the HB-FePc catalysts retain more nitrogen components than the FePc/PhRs catalysts between pyrolysis temperatures of 600°C and 800°C. This is because the linked structure of the HB-FePc precursor has high thermostability against nitrogen desorption. Consequently, effective doping of active nitrogen species into the sp (2) carbon network of the HB-FePc catalysts may occur up to 900°C.

Negative-Electrode Catalysts for Fe/Cr Redox Cells

NASA Technical Reports Server (NTRS)

Gahn, R. F.; Hagedorn, N.

1987-01-01

Electrodes perform more consistently and less expensive. Surfaces catalyzed by bismuth and bismuth/lead developed for application on chromium electrode in iron/chromium redox electrochemical energy storage system. NASA Fe/Cr storage system incorporates two soluble electrodes consisting of acidified solutions of iron chloride (FeC13 and FeC12) and chromium chloride (CrC13 and CrC12) oxidized and reduced in power-conversion unit to store and produce electricity. Electrolytes circulated with pumps and stored in external tanks.

Magnetic activated carbon-Fe3O4 nanocomposites--synthesis and applications in the removal of acid yellow dye 17 from water.

PubMed

Ranjithkumar, V; Hazeen, A Nizarul; Thamilselvan, M; Vairam, S

2014-07-01

In this work, synthesis of activated carbon-Fe3O4 composites using activated carbon and iron benzoate/oxalate precursors by simple pyrolytic method and its utility for the removal of acid yellow dye from water are presented. Iron carboxylates held up into the pores of carbon dissociate at their decomposition temperatures form dispersed Fe3O4 nanoparticles in carbon matrix. The composites were characterized by FTIR, PXRD, SEM, TEM, EDX and magnetization measurements. The size of the nano iron oxides are in the range of 21-33 nm formed from iron benzoate precursor and 6-11 nm from iron oxalate precursor. The oxides are magnetic and their saturation magnetization in the range of 0.08-0.16 emu/g and Coercivity (H(c)) 474-600, being lower and higher than that of bare bulk Fe3O4 are due to the nano size of oxides. Composites find application in the removal of acid yellow dye 17 from the synthetic aqueous solution at pH 5. The adsorption data are found to fit well for Langmuir adsorption isotherm. Kinetics data of adsorption of dyes indicate that the adsorption follows pseudo-second order kinetic model.

Spectrophotometric Determination of Iron(III)-Glycine Formation Constant in Aqueous Medium Using Competitive Ligand Binding

ERIC Educational Resources Information Center

Prasad, Rajendra; Prasad, Surendra

2009-01-01

The formation constant of iron(III) complex with glycine (Gly) ligand in aqueous acidic medium (0.2 M HNO[subscript 3], I = 0.2 M at 28 plus or minus 1 degree C) was determined spectrophotometrically in which a competing color reaction between Fe(III) and SCN[superscript -] was used as an indicator reaction. Under the specified conditions Fe(III)…

Synthesis of nanocrystalline α-Fe2O3 by using thermal oxidation of Fe Films

NASA Astrophysics Data System (ADS)

Fortas, G.; Saidoun, I.; Abboud, H.; Gabouze, N.; Haine, N.; Manseri, A.; Zergoug, M.; Menari, H.; Sam, S.; Cheraga, H.; Bozetine, I.

2018-03-01

α-Fe2O3 hematite films were prepared by thermal oxidation from Fe films electroplated on silicon. Electrodeposition of Fe thin films was carried out from a sulfate bath containing an ammonium chloride complexing agent. The electrochemical study was performed by cyclic voltammetry. The SEM analysis of the films obtained at a -1.3 V constant polarization shows dendritic grains in the form of islet. The DRX spectra exhibit characteristic iron peaks according to the face centered cubic (Fcc) structure. These samples were annealed. At a temperature of 650 ° C, a single iron oxide phase was well formed, with the hematite structure. The SEM photos show a well-assembled columnar structure with formation of nanowires at the surface of the deposit. The absorbance spectra reveal an absorption features in the ultraviolet range

Synthesis of nanostructured iron oxides and new magnetic ceramics using sol-gel and SPS techniques

NASA Astrophysics Data System (ADS)

Papynov, E. K.; Shichalin, O. O.; Belov, A. A.; Portnyagin, A. S.; Mayorov, V. Yu.; Gridasova, E. A.; Golub, A. V.; Nepomnyashii, A. S.; Tananaev, I. G.; Avramenko, V. A.

2017-02-01

The original way of synthesis of nanostructured iron oxides and based on them magnetic ceramics via sequential combination of sol-gel and SPS technologies has been suggested. High quality of nanostructured iron oxides is defined by porous structure (Sspec up to 47,3 n2/g) and by phase composition of mixed and individual crystal phases (γ-Fe2O3/Fe3O4 i α-Fe2O3), depending on synthesis conditions. High-temperature SPS consolidation of nanostructured hematite powder, resulting in magnetic ceramics of high mechanical strength (fracture strength 249 MPa) has been investigated. Peculiarities of change of phase composition and composite's microstructure in the range of SPS temperatures from 700 to 900 °C have been revealed. Magnetic properties have been studied and regularities of change of magnetization (Ms) and coercive force (Hc) values of the ceramics with respect to SPS sintering temperature have been described.

Structural, chemical, and isotopic microanalytical investigations of graphite from supernovae

NASA Astrophysics Data System (ADS)

Croat, T. Kevin; Bernatowicz, Thomas; Amari, Sachiko; Messenger, Scott; Stadermann, Frank J.

2003-12-01

We report the results of coordinated ion microprobe and transmission electron microscope (TEM) studies of presolar graphites from the KE3 separate (1.65-1.72 g/cm 3) of the Murchison CM2 meteorite. Isotopic analysis of individual graphites (1-12 μm) with the ion microprobe shows many to have large 18O excesses combined with large silicon isotopic anomalies, indicative of a supernova (SN) origin. Transmission electron microscopy (TEM) of ultramicrotome slices of these SN graphites revealed a high abundance (25-2400 ppm) of internal titanium carbides (TiCs), with a single graphite in some cases containing hundreds of TiCs. Isotopic compositions of individual TiCs by nanoscale resolution secondary ion mass spectrometry (NanoSIMS) confirmed their presolar origin. In addition to TiCs, composite TiC/Fe grains (TiCs with attached iron-nickel subgrains) and solitary kamacite internal grains were found. In the composite grains, the attached iron phase (kamacite [0-24 at. % Ni] or taenite [up to 60 at. % Ni]) was epitaxially grown onto one or more TiC faces. In contrast to the denser Murchison KFC1 graphites, no Zr-Ti-Mo carbides were observed. The average TiC diameters were quite variable among the SN graphites, from 30 to 232 nm, and were generally independent of the host graphite size. TiC grain morphologies ranged from euhedral to anhedral, with the grain surfaces exhibiting variable degrees of corrosion, and sometimes partially amorphous rims (3 to 15 nm thick). Partially amorphous rims of similar thickness were also observed on some solitary kamacite grains. We speculate that the rims on the internal grains are most plausibly the result of atom bombardment caused by drift of grains with respect to the ambient gas, requiring relative outflow speeds ˜100 km/s (i.e., a few percent of the SN mass outflow speed). Energy dispersive X-ray spectrometry (EDXS) of TiCs revealed significant V in solid solution, with an average V/Ti ratio over all TiCs of ˜83% of the solar value of 0.122. Significant variations about the mean V/Ti ratio were also seen among TiCs in the same graphite, likely indicating chemical equilibration with the surrounding gas over a range of temperatures. In general, the diversity in internal TiC properties suggests that TiCs formed first and had substantially diverse histories before incorporation into the graphite, implying some degree of turbulent mixing in the SN outflows. In most graphites, there is a decrease in the number density of TiCs as a function of increasing radial dis- tance, caused by either preferential depletion of TiCs from the gas or an acceleration of graphite growth with decreasing ambient temperature. In several graphites, TiCs showed a trend of larger V/Ti ratios with increasing distance from the graphite center, an indication of progressive equilibration with the surrounding gas before they were sequestered in the graphites. In all but one graphite, no trend was seen in the TiC size vs. distance from the graphite center, implying that appreciable TiC growth had effectively stopped before the graphites formed, or else that graphite growth was rapid compared to TiC growth. Taken together, the chemical variations among internal grains as well as the presence of partially amorphous rims and epitaxial Fe phases on some TiCs clearly indicate that the phase condensation sequence was TiC, followed by the iron phases (only found in some graphites) and finally graphite. Since graphite typically condenses at a higher temperature than iron at low pressures (<10 -3 bars) in a gas with C > O and otherwise solar composition, the observed condensation sequence implies a relative iron enrichment in the gas or greater supersaturation of graphite relative to iron. The TEM observations allow inferences to be made about the physical conditions in the gas from which the grains condensed. Given the TiC sizes and abundances, the gas was evidently quite dusty. From the observed TiC size range of ˜20 nm to ˜500 nm (assuming ˜1 yr growth time and T ˜ 1800°K), we infer minimum Ti number densities in the gas to be ˜7 × 10 4 to ˜2 × 10 6 atoms/cc, respectively. Although the gas composition is clearly not solar, for scale, these number densities would correspond to a pressure range of ˜0.2 μbar to ˜5.0 μbar in a gas of solar composition. They also correspond to minimum TiC grain number densities of ˜3 × 10 -4 to ˜0.2 grains/cc, assuming complete condensation of Ti in TiC. We estimate the maximum ratio of mean TiC grain separation distance in the gas to grain diameter from the Ti number densities as ˜3 × 10 5 to ˜1 × 10 6.

Consumption of galacto-oligosaccharides increases iron absorption from a micronutrient powder containing ferrous fumarate and sodium iron EDTA: a stable-isotope study in Kenyan infants.

PubMed

Paganini, Daniela; Uyoga, Mary A; Cercamondi, Colin I; Moretti, Diego; Mwasi, Edith; Schwab, Clarissa; Bechtler, Salome; Mutuku, Francis M; Galetti, Valeria; Lacroix, Christophe; Karanja, Simon; Zimmermann, Michael B

2017-10-01

Background: Whether consumption of prebiotics increases iron absorption in infants is unclear. Objective: We set out to determine whether prebiotic consumption affects iron absorption from a micronutrient powder (MNP) containing a mixture of ferrous fumarate and sodium iron EDTA (FeFum+NaFeEDTA) in Kenyan infants. Design: Infants ( n = 50; aged 6-14 mo) consumed maize porridge that was fortified with an MNP containing FeFum+NaFeEDTA and 7.5 g galacto-oligosaccharides (GOSs) (Fe+GOS group, n = 22) or the same MNP without GOSs (Fe group, n = 28) each day for 3 wk. Then, on 2 consecutive days, we fed all infants isotopically labeled maize porridge and MNP test meals containing 5 mg Fe as 57 FeFum+Na 58 FeEDTA or ferrous sulfate ( 54 FeSO 4 ). Iron absorption was measured as the erythrocyte incorporation of stable isotopes. Iron markers, fecal pH, and bacterial groups were assessed at baseline and 3 wk. Comparisons within and between groups were done with the use of mixed-effects models. Results: There was a significant group-by-compound interaction on iron absorption ( P = 0.011). The median percentages of fractional iron absorption from FeFum+NaFeEDTA and from FeSO 4 in the Fe group were 11.6% (IQR: 6.9-19.9%) and 20.3% (IQR: 14.2-25.7%), respectively, ( P < 0.001) and, in the Fe+GOS group, were 18.8% (IQR: 8.3-37.5%) and 25.5% (IQR: 15.1-37.8%), respectively ( P = 0.124). Between groups, iron absorption was greater from the FeFum+NaFeEDTA ( P = 0.047) in the Fe+GOS group but not from the FeSO 4 ( P = 0.653). The relative iron bioavailability from FeFum+NaFeEDTA compared with FeSO 4 was higher in the Fe+GOS group than in the Fe group (88% compared with 63%; P = 0.006). There was a significant time-by-group interaction on Bifidobacterium spp. ( P = 0.008) and Lactobacillus / Pediococcus / Leuconostoc spp. ( P = 0.018); Lactobacillus / Pediococcus / Leuconostoc spp. decreased in the Fe group ( P = 0.013), and there was a nonsignificant trend toward higher Bifidobacterium spp. in the Fe+GOS group ( P = 0.099). At 3 wk, iron absorption was negatively correlated with fecal pH ( P < 0.001) and positively correlated with Lactobacillus / Pediococcus / Leuconostoc spp. ( P = 0.001). Conclusion: GOS consumption by infants increased iron absorption by 62% from an MNP containing FeFum+NaFeEDTA, thereby possibly reflecting greater colonic iron absorption. This trial was registered at clinicaltrials.gov as NCT02666417. © 2017 American Society for Nutrition.

Effect of iron ions and electric field on nitrification process in the periodic reversal bio-electrocoagulation system.

PubMed

Qian, Guangsheng; Hu, Xiaomin; Li, Liang; Ye, Linlin; Lv, Weijian

2017-11-01

This study explored the nitrification mechanism of a periodic reversal bio-electrocoagulation system with Fe-C electrodes. The ammonia nitrogen removal was compared in four identical cylindrical sequencing bath reactors. Two of them were reactors with Fe-C electrodes (S1) and C-C electrodes (S2), respectively. The other two were a reactor with iron ions (S3) and a traditional SBR (S4), respectively. The results demonstrated that the effect on enhancing nitrification in S1 was the best among all four SBRs, followed by S3, S2 and S4. Iron ions increased the biomass, and electric field improved the proton transfer and enzyme activity. The dominant bacterial genera in the four SBRs were Hyphomicrobium, Thauera, Nitrobacter, Nitrosomonas, Paracoccus and Hydrogenophaga. The iron ions may increase the levels of Nitrosomonas and Nitrobacter, both of which were the main microbes of the nitrification process. This study provided a significant and meaningful understanding of nitrification in a bio-electrocoagulation system. Copyright © 2017 Elsevier Ltd. All rights reserved.

Understanding the adsorptive interactions of arsenate-iron nanoparticles with curved fullerene-like sheets in activated carbon using a quantum mechanics/molecular mechanics computational approach.

PubMed

Ha, Nguyen Ngoc; Cam, Le Minh; Ha, Nguyen Thi Thu; Goh, Bee-Min; Saunders, Martin; Jiang, Zhong-Tao; Altarawneh, Mohammednoor; Dlugogorski, Bogdan Z; El-Harbawi, Mohanad; Yin, Chun-Yang

2017-06-07

The prevalence of global arsenic groundwater contamination has driven widespread research on developing effective treatment systems including adsorption using various sorbents. The uptake of arsenic-based contaminants onto established sorbents such as activated carbon (AC) can be effectively enhanced via immobilization/impregnation of iron-based elements on the porous AC surface. Recent suggestions that AC pores structurally consist of an eclectic mix of curved fullerene-like sheets may affect the arsenic adsorption dynamics within the AC pores and is further complicated by the presence of nano-sized iron-based elements. We have therefore, attempted to shed light on the adsorptive interactions of arsenate-iron nanoparticles with curved fullerene-like sheets by using hybridized quantum mechanics/molecular mechanics (QMMM) calculations and microscopy characterization. It is found that, subsequent to optimization, chemisorption between HAsO 4 2- and the AC carbon sheet (endothermic process) is virtually non-existent - this observation is supported by experimental results. Conversely, the incorporation of iron nanoparticles (FeNPs) into the AC carbon sheet greatly facilitates chemisorption of HAsO 4 2- . Our calculation implies that iron carbide is formed at the junction between the iron and the AC interface and this tightly chemosorbed layer prevents detachment of the FeNPs on the AC surface. Other aspects including electronic structure/properties, carbon arrangement defects and rate of adsorptive interaction, which are determined using the Climbing-Image NEB method, are also discussed.

Novel Fe-oxidizing Zetaproteobacteria floating in the Chesapeake: kinetics and genomic insights into microbial Fe cycling in a stratified marine water column

NASA Astrophysics Data System (ADS)

Chiu, B.; Field, E.; Kato, S.; Mcallister, S.; Luther, G. W., III; Chan, C. S. Y.

2016-12-01

Iron-oxidizing bacteria (FeOB) are potentially important drivers in iron redox cycling, with significant effects on other major elemental cycles (e.g. C, N, P, S, As), yet the biogeochemical impacts of these microbes have been difficult to quantify. FeOB have traditionally been studied in relatively few, Fe-rich environments (groundwater seeps and hydrothermal vents), but our recent studies show that they also occur in coastal marine environments. Here we report on two Zetaproteobacteria strains, CP-5 and CP-8, isolated from the Chesapeake Bay chemocline during seasonal stratification. They represent the first known planktonic chemolithotrophic FeOB and are unusual for living in very low (micromolar) Fe(II) conditions, intermediate (brackish) salinities, and pH values (7.3-7.4) at which abiotic Fe oxidation is typically rapid. However, kinetics experiments demonstrate that CP-8 accelerates iron oxidation, relative to killed controls, and allow us to quantify the effects of microbes on iron oxidation. Ongoing work is characterizing the O2 preferences of the CP strains, specifically the lower O2 limits of FeOB activity. We obtained complete, closed genomes of both CP-5 and CP-8 genomes (2.54 and 2.30 Mbp respectively) using the PacBio RSII sequencer. Our genomic analysis of the CP strains is focused on adaptations for growth in the Chesapeake Bay chemocline, including genes for energy metabolism, and C, N, and P cycling. Initial results indicate that both strains have putative iron oxidase Cyc2 as well as Rubisco which suggests that these microbes are using energy from Fe oxidation to fix carbon, despite the availability of organics from phototrophs living higher in the water column. Our work on these Chesapeake FeOB gives us insight into how chemolithotrophic FeOB can participate in Fe redox and nutrient cycling in a stratified marine water column.

Synthesis, characterization and single crystal x-ray analysis of a complex of iron(II) bis(2,4-dimethylphenyl)dithiophosphate with 4-ethylpyridine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Sandeep; Andotra, Savit; Kaur, Mandeep

2016-09-15

Complex of iron(II) bis(2,4-dimethylphenyl)dithiophosphate with 4-ethylpyridine [((2,4- (CH{sub 3}){sub 2}C{sub 6}H{sub 3}O)2PS2)2Fe(NC{sub 5}H{sub 4}(C{sub 2}H{sub 5})-4){sub 2}] is synthesized and characterized by elemental analysis, magnetic moment, IR spectroscopy and single crystal X-ray analysis. Complex crystallizes in the monoclinic sp. gr. P2{sub 1}/n, Z = 2. Crystal structure consists of mononuclear units with Fe(II) ion chelated by four S atoms of the two diphenyldithiophosphate ligands in bidentate manner. N atoms from two 4-ethylpyridine ligands are axially coordinated to the Fe(II) atom leading to an octahedral geometry.

A Fe-C-Ca big cycle in modern carbon-intensive industries: toward emission reduction and resource utilization

PubMed Central

Sun, Yongqi; Sridhar, Seetharaman; Seetharaman, Seshadri; Wang, Hao; Liu, Lili; Wang, Xidong; Zhang, Zuotai

2016-01-01

Herein a big Fe-C-Ca cycle, clarifying the basic element flows and energy flows in modern carbon-intensive industries including the metallurgical industry and the cement industry, was proposed for the first time in the contexts of emission reduction and iron ore degradation nowadays. This big cycle was focused on three industrial elements of Fe, C and Ca and thus it mainly comprised three interdependent loops, i.e., a C-cycle, a Fe-cycle and a Ca-path. As exemplified, we started from the integrated disposal of hot steel slags, a man-made iron resource via char gasification and the employment of hematite, a natural iron resource greatly extended the application area of this idea. Accordingly, based on this concept, the theoretical potentials for energy saving, emission reduction and Fe resource recovery achieved in modern industry are estimated up to 7.66 Mt of standard coal, 63.9 Mt of CO2 and 25.2 Mt of pig iron, respectively. PMID:26923104

A Fe-C-Ca big cycle in modern carbon-intensive industries: toward emission reduction and resource utilization

NASA Astrophysics Data System (ADS)

Sun, Yongqi; Sridhar, Seetharaman; Seetharaman, Seshadri; Wang, Hao; Liu, Lili; Wang, Xidong; Zhang, Zuotai

2016-02-01

Herein a big Fe-C-Ca cycle, clarifying the basic element flows and energy flows in modern carbon-intensive industries including the metallurgical industry and the cement industry, was proposed for the first time in the contexts of emission reduction and iron ore degradation nowadays. This big cycle was focused on three industrial elements of Fe, C and Ca and thus it mainly comprised three interdependent loops, i.e., a C-cycle, a Fe-cycle and a Ca-path. As exemplified, we started from the integrated disposal of hot steel slags, a man-made iron resource via char gasification and the employment of hematite, a natural iron resource greatly extended the application area of this idea. Accordingly, based on this concept, the theoretical potentials for energy saving, emission reduction and Fe resource recovery achieved in modern industry are estimated up to 7.66 Mt of standard coal, 63.9 Mt of CO2 and 25.2 Mt of pig iron, respectively.

Wet-chemical synthesis of nanoscale iron boride, XAFS analysis and crystallisation to α-FeB.

PubMed

Rades, Steffi; Kornowski, Andreas; Weller, Horst; Albert, Barbara

2011-06-20

The reaction of lithium tetrahydridoborate and iron bromide in high boiling ether as reaction medium produces an ultrafine, pyrophoric and magnetic precipitate. X-ray and electron diffraction proved the product to be amorphous. According to X-ray absorption fine structure spectroscopy (XAFS) the precipitate has FeB structure up to nearly two coordination spheres around an iron absorber atom. Transmission electron microscopy (TEM) confirms the ultrafine powder to be nanoscale. Subsequent annealing at 450 °C causes the atoms to arrange in a more distinct FeB structure, and further thermal treatment to 1050 °C extends the local structure to the α-modification of FeB. Between 1050 °C and 1500 °C α-FeB is transformed into β-FeB. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Iron oxide nanotubes synthesized via template-based electrodeposition

NASA Astrophysics Data System (ADS)

Lim, Jin-Hee; Min, Seong-Gi; Malkinski, Leszek; Wiley, John B.

2014-04-01

Considerable effort has been invested in the development of synthetic methods for the preparation iron oxide nanostructures for applications in nanotechnology. While a variety of structures have been reported, only a few studies have focused on iron oxide nanotubes. Here, we present details on the synthesis and characterization of iron oxide nanotubes along with a proposed mechanism for FeOOH tube formation. The FeOOH nanotubes, fabricated via a template-based electrodeposition method, are found to exhibit a unique inner-surface. Heat treatment of these tubes under oxidizing or reducing atmospheres can produce either hematite (α-Fe2O3) or magnetite (Fe3O4) structures, respectively. Hematite nanotubes are composed of small nanoparticles less than 20 nm in diameter and the magnetization curves and FC-ZFC curves show superparamagnetic properties without the Morin transition. In the case of magnetite nanotubes, which consist of slightly larger nanoparticles, magnetization curves show ferromagnetism with weak coercivity at room temperature, while FC-ZFC curves exhibit the Verwey transition at 125 K.Considerable effort has been invested in the development of synthetic methods for the preparation iron oxide nanostructures for applications in nanotechnology. While a variety of structures have been reported, only a few studies have focused on iron oxide nanotubes. Here, we present details on the synthesis and characterization of iron oxide nanotubes along with a proposed mechanism for FeOOH tube formation. The FeOOH nanotubes, fabricated via a template-based electrodeposition method, are found to exhibit a unique inner-surface. Heat treatment of these tubes under oxidizing or reducing atmospheres can produce either hematite (α-Fe2O3) or magnetite (Fe3O4) structures, respectively. Hematite nanotubes are composed of small nanoparticles less than 20 nm in diameter and the magnetization curves and FC-ZFC curves show superparamagnetic properties without the Morin transition. In the case of magnetite nanotubes, which consist of slightly larger nanoparticles, magnetization curves show ferromagnetism with weak coercivity at room temperature, while FC-ZFC curves exhibit the Verwey transition at 125 K. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr06924a

Optimation and Determination of Fe-Oxinate Complex by Using High Performance Liquid Chromatography

NASA Astrophysics Data System (ADS)

Oktavia, B.; Nasra, E.; Sary, R. C.

2018-04-01

The need for iron will improve the industrial processes that require iron as its raw material. Control of industrial iron waste is very important to do. One method of iron analysis is to conduct indirect analysis of iron (III) ions by complexing with 8-Hydroxyquinoline or oxine. In this research, qualitative and quantitative tests of iron (III) ions in the form of complex with oxine. The analysis was performed using HPLC at a wavelength of 470 nm with an ODS C18 column. Three methods of analysis were performed: 1) Fe-oxinate complexes were prepared in an ethanol solvent so no need for separation anymore, (2) Fe-oxinate complexes were made in chloroform so that a solvent extraction was required before the complex was injected into the column while the third complex was formed in the column, wherein the eluent contains the oxide and the metal ions are then injected. The resulting chromatogram shows that the 3rd way provides a better chromatogram for iron analysis.

Biomineralization associated with microbial reduction of Fe3+ and oxidation of Fe2+ in solid minerals

USGS Publications Warehouse

Zhang, G.; Dong, H.; Jiang, H.; Kukkadapu, R.K.; Kim, J.; Eberl, D.; Xu, Z.

2009-01-01

Iron-reducing and oxidizing microorganisms gain energy through reduction or oxidation of iron, and by doing so play an important role in the geochemical cycling of iron. This study was undertaken to investigate mineral transformations associated with microbial reduction of Fe3+ and oxidation of Fe2+ in solid minerals. A fluid sample from the 2450 m depth of the Chinese Continental Scientific Drilling project was collected, and Fe3+-reducing and Fe2+-oxidizing microorganisms were enriched. The enrichment cultures displayed reduction of Fe3+ in nontronite and ferric citrate, and oxidation of Fe2+ in vivianite, siderite, and monosulfide (FeS). Additional experiments verified that the iron reduction and oxidation was biological. Oxidation of FeS resulted in the formation of goethite, lepidocrocite, and ferrihydrite as products. Although our molecular microbiological analyses detected Thermoan-aerobacter ethanolicus as a predominant organism in the enrichment culture, Fe3+ reduction and Fe2+ oxidation may be accomplished by a consortia of organisms. Our results have important environmental and ecological implications for iron redox cycling in solid minerals in natural environments, where iron mineral transformations may be related to the mobility and solubility of inorganic and organic contaminants.

Nonequilibrium iron oxide formation in some low-mass post-asymptotic giant branch stars

NASA Technical Reports Server (NTRS)

Rietmeijer, Frans J. M.

1992-01-01

Using experimental evidence that under highly oxidizing conditions gamma-Fe2O3 (maghemite) and Fe3O4 display refractory behavior, it is proposed that very low C/O ratios, that could be unique to evolving AGB stars, induce nonequilibrium formation of ferromagnetic iron oxide grains along with chondritic dust. The oxides are preferentially fractionated from chondritic dust in the stellar magnetic field which could account for the observed extreme iron underabundance in their photosphere. A search for the 1-2.5-micron IR absorption feature, or for diagnostic magnetite and maghemite IR absorption features, could show the validity of the model proposed.

High temperature deformation behavior, thermal stability and irradiation performance in Grade 92 steel

NASA Astrophysics Data System (ADS)

Alsagabi, Sultan

The 9Cr-2W ferritic-martensitic steel (i.e. Grade 92 steel) possesses excellent mechanical and thermophysical properties; therefore, it has been considered to suit more challenging applications where high temperature strength and creep-rupture properties are required. The high temperature deformation mechanism was investigated through a set of tensile testing at elevated temperatures. Hence, the threshold stress concept was applied to elucidate the operating high temperature deformation mechanism. It was identified as the high temperature climb of edge dislocations due to the particle-dislocation interactions and the appropriate constitutive equation was developed. In addition, the microstructural evolution at room and elevated temperatures was investigated. For instance, the microstructural evolution under loading was more pronounced and carbide precipitation showed more coarsening tendency. The growth of these carbide precipitates, by removing W and Mo from matrix, significantly deteriorates the solid solution strengthening. The MX type carbonitrides exhibited better coarsening resistance. To better understand the thermal microstructural stability, long tempering schedules up to 1000 hours was conducted at 560, 660 and 760°C after normalizing the steel. Still, the coarsening rate of M23C 6 carbides was higher than the MX-type particles. Moreover, the Laves phase particles were detected after tempering the steel for long periods before they dissolve back into the matrix at high temperature (i.e. 720°C). The influence of the tempering temperature and time was studied for Grade 92 steel via Hollomon-Jaffe parameter. Finally, the irradiation performance of Grade 92 steel was evaluated to examine the feasibility of its eventual reactor use. To that end, Grade 92 steel was irradiated with iron (Fe2+) ions to 10, 50 and 100 dpa at 30 and 500°C. Overall, the irradiated samples showed some irradiation-induced hardening which was more noticeable at 30°C. Additionally, irradiation-induced defect clusters and dislocation loops were observed and the irradiated samples did not show any bubble or void.

The melting of subducted banded iron formations

NASA Astrophysics Data System (ADS)

Kang, Nathan; Schmidt, Max W.

2017-10-01

Banded iron formations (BIF) were common shelf and ocean basin sediments 3.5-1.8 Ga ago. To understand the fate of these dense rocks upon subduction, the melting relations of carbonated BIF were determined in Fe-Ca-(Mg)-Si-C-O2 at 950-1400 °C, 6 and 10 GPa, oxidizing (fO2 = hematite-magnetite, HM) and moderately reducing (fO2 ∼CO2-graphite/diamond, CCO) conditions. Solidus temperatures under oxidizing conditions are 950-1025 °C with H2O, and 1050-1150 °C anhydrous, but 250-175 °C higher at graphite saturation (values at 6-10 GPa). The combination of Fe3+ and carbonate leads to a strong melting depression. Solidus curves are steep with 17-20 °C/GPa. Near-solidus melts are ferro-carbonatites with ∼22 wt.% FeOtot, ∼48 wt% CO2 and 1-5 wt.% SiO2 at fO2 ∼ HM and ∼49 wt.% FeOtot, ∼20 wt% CO2 and 19-25 wt.% SiO2 at fO2 ∼ CCO . At elevated subduction geotherms, as likely for the Archean, C-bearing BIF could melt out all carbonate around 6 GPa. Fe-rich carbonatites would rise but stagnate gravitationally near the slab/mantle interface until they react with the mantle through Fe-Mg exchange and partial reduction. The latter would precipitate diamond and yield Fe- and C-rich mantle domains, yet, Fe-Mg is expected to diffusively re-equilibrate over Ga time scales. We propose that the oldest subduction derived diamonds stem from BIF derived melts.

The Chemistry of Meteoric Iron

NASA Astrophysics Data System (ADS)

Self, D. E.; Plane, J. M. C.

About 120 tonnes of interplanetary dust enters the earth's atmosphere each day. Iron comprises a large fraction of this dust (12% by mass), and ablation of the particles gives rise to the layer of Fe atoms that occurs globally in the mesosphere around 85 km. Previous work in our laboratory has shown that Fe reacts rapidly with O3 to form FeO, which in turn reacts with O3, O2 and H2O to form FeO2, FeO3 and Fe(OH)2, respectively. The purpose of the present study was to determine which of these com- pounds provide stable reservoirs for iron below the atomic Fe layer, and hence form the "building blocks" of meteoric smoke particles which are implicated in phenomena lower in the atmosphere (e.g., noctilucent clouds and polar stratospheric ozone deple- tion). The reactions of these iron compounds were studied in a fast flow tube using the pulsed laser ablation of a rotating iron rod as the source of Fe atoms in the up- stream section of the tube. Iron compounds were produced by adding reactants further down the tube, and finally atomic O or H was added through a movable injector. At the downstream end of the tube, atomic Fe was detected by laser induced fluorescence at 248 nm. The following reactions were studied: FeO + O, FeO2 + O, FeO3 + O, FeO2 + O3, FeO3 + H2O, FeO3 + H, Fe(OH)2 + H, and FeOH + H. It is clear that the iron reservoir around 80 km is FeO3, which reacts very slowly with atomic O, in agreement with the requirements of a recent atmospheric model. However, Fe(OH)2 and FeO(OH), which are thermodynamically the most stable of these Fe species and eventually form from FeO3, are the likely building blocks of meteoric smoke.

Sequential structural and antiferromagnetic transitions in BaFe2Se3 under pressure

NASA Astrophysics Data System (ADS)

Zhang, Yang; Lin, Ling-Fang; Zhang, Jun-Jie; Dagotto, Elbio; Dong, Shuai

2018-01-01

The discovery of superconductivity in the two-leg ladder compound BaFe2S3 has established the 123-type iron chalcogenides as a novel and interesting subgroup of the iron-based superconductor family. However, in this 123 series, BaFe2Se3 is an exceptional member, with a magnetic order and crystalline structure different from all others. Recently, an exciting experiment reported the emergence of superconductivity in BaFe2Se3 at high pressure [J. Ying et al., Phys. Rev. B 95, 241109(R) (2017), 10.1103/PhysRevB.95.241109]. In this paper, we report a first-principles study of BaFe2Se3 . Our analysis unveils a variety of qualitative differences between BaFe2S3 and BaFe2Se3 , including in the latter an unexpected chain of transitions with increasing pressure. First, by gradually reducing the tilting angle of iron ladders, the crystalline structure smoothly transforms from P n m a to C m c m at ˜6 GPa. Second, the system becomes metallic at 10.4 GPa. Third, its unique ambient-pressure Block antiferromagnetic ground state is replaced by the more common stripe (so-called CX-type) antiferromagnetic order at ˜12 GPa, the same magnetic state as the 123-S ladder. This transition is found at a pressure very similar to the experimental superconducting transition. Finally, all magnetic moments vanish at 30 GPa. This reported theoretical diagram of the complete phase evolution is important because of the technical challenges to capture many physical properties in high-pressure experiments. The information obtained in our calculations suggests different characteristics for superconductivity in BaFe2Se3 and BaFe2S3 : in 123-S pairing occurs when magnetic moments vanish, while in 123-Se the transition region from Block- to CX-type magnetism appears to catalyze superconductivity. Finally, an additional superconducting dome above ˜30 GPa is expected to occur.

Chemical synthesis and characterization of hollow dopamine coated, pentagonal and flower shaped magnetic iron oxide nanoparticles

NASA Astrophysics Data System (ADS)

Riasat, Rabia; Kaynat, Sumbal

2018-04-01

Iron oxide nanoparticles have gained attention recently in the field of nanoscience and technology due to their unique physicochemical properties. We hereby chemically synthesized novel pentagonal flower shaped iron oxide nanoparticles by thermal decomposition of iron penta-carbonyl in a two way annealing process. Controlled oxidation by acid etching was performed for these nanoparticles. At first 13 nm core shell nanoparticles of iron oxide (Fe/Fe3O4) were synthesized at 120°C annealing temperature that act as template material. The core shell nanoparticles then converted into porous hollow core shell nanoparticles (PH Fe/ Fe3O4) in a two way annealing process of heating, first at 100°C then at 250°C and heating rate of 5°C was kept constant throughout the reaction time. X-Ray diffraction (XRD) was done for the phase confirmation of as synthesized nanoparticles. Transmission electron microscopy (TEM) and higher resolution transmission electron microscopy (HRTEM) clearly shows the flower like nanoparticles that are approx. 16 nm-18 nm in size having the 4-5 nm core of Fe and 1-2 nm of the pores in the shell while the cavity between the shell and core is about 2 nm and the shell is 4-5 nm in diameter according to the TEM micrographs. The as prepared nanoparticles were then surface functionalized by dopamine polymer to make them water dispersible. Fourier transform Infrared spectroscopy confirmed the dopamine coating on the nanoparticles and the magnetic saturation of 38 emu/g of nanoparticles was analyzed by vibrating sample magnetometer (VSM). Magnetic saturation persists in the dopamine coated nanoparticles. These nanoparticles were surface functionalized with dopamine and show dispersity in the aqueous media and can further be exploited in many nano-biotechnological applications including target specific therapeutic applications for several diseases.

Synthesis of boron nitride nanostructures from catalyst of iron compounds via thermal chemical vapor deposition technique

NASA Astrophysics Data System (ADS)

da Silva, Wellington M.; Ribeiro, Hélio; Ferreira, Tiago H.; Ladeira, Luiz O.; Sousa, Edésia M. B.

2017-05-01

For the first time, patterned growth of boron nitride nanostructures (BNNs) is achieved by thermal chemical vapor deposition (TCVD) technique at 1150 °C using a mixture of FeS/Fe2O3 catalyst supported in alumina nanostructured, boron amorphous and ammonia (NH3) as reagent gas. This innovative catalyst was synthesized in our laboratory and systematically characterized. The materials were characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The X-ray diffraction profile of the synthesized catalyst indicates the coexistence of three different crystal structures showing the presence of a cubic structure of iron oxide and iron sulfide besides the gamma alumina (γ) phase. The results show that boron nitride bamboo-like nanotubes (BNNTs) and hexagonal boron nitride (h-BN) nanosheets were successfully synthesized. Furthermore, the important contribution of this work is the manufacture of BNNs from FeS/Fe2O3 mixture.

Determination of magnetic domain state of carbon coated iron nanoparticles via 57Fe zero-external-field NMR

NASA Astrophysics Data System (ADS)

Manjunatha, M.; Kumar, Rajeev; Sahoo, Balaram; Damle, Ramakrishna; Ramesh, K. P.

2018-05-01

The magnetic domain state of carbon coated iron nanopowder (Fe@C) was studied by the internal field nuclear magnetic resonance (IFNMR) at 77 K using the spin echo technique. The structure and magnetic properties of the sample were further characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Mössbauer spectroscopy, vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA) and Raman Spectroscopy. The obtained IFNMR results of Fe@C powder were compared with that of micron sized carbonyl iron (CI) and electrolytic iron (EI) powders. The calculated critical size of the single domain iron particles in Fe@C is ∼ 16 nm. A higher enhancement in echo amplitude was observed due to better response of the domain walls of multidomain particles in comparison to the single domain particles. The echo signal of CI and EI particles exhibit a single narrow intense peak corresponding to the domain walls, whereas Fe@C exhibits two low amplitude peaks at two different frequencies: a low frequency (46.6 MHz) peak corresponds to the response of the domain walls of the multidomain particles and the other high frequency (47.2 MHz) signal (a shoulder) corresponding to the response of the magnetic nuclei inside the domain. Our results help in determining the domain state of iron-based magnetic particles using 57Fe-IFNMR.

Fe-containing nanoparticles used as effective catalysts of lignin reforming to syngas and hydrogen assisted by microwave irradiation

NASA Astrophysics Data System (ADS)

Tsodikov, M. V.; Ellert, O. G.; Nikolaev, S. A.; Arapova, O. V.; Bukhtenko, O. V.; Maksimov, Yu. V.; Kirdyankin, D. I.; Vasil'kov, A. Yu.

2018-03-01

Active iron-containing nanosized components have been formed on the lignin surface. The metal was deposited on the lignin from an ethanol solution of Fe(acac)3 and from a colloid solution of iron metal particles obtained beforehand by metal vapor synthesis. These active components are able to absorb microwave radiation and are suitable for microwave-assisted high-rate dehydrogenation and dry reforming of lignin without addition of a carbon adsorbent, as a supplementary radiation absorbing material, to the feedstock. The dependence of the solid lignin heating dynamics on the concentration of supported iron particles was investigated. The threshold Fe concentration equal to 0.5 wt.%, providing the highest rate of sample heating up to the reforming and plasma generation temperature was identified. The microstructure and magnetic properties of iron-containing nanoparticles supported on lignin were studied before and after the reforming. The Fe3O4 nanoparticles and also core-shell Fe3O4@γ-Fe-C nanostructures are formed during the reforming of lignin samples. The catalytic performance of iron-based nanoparticles toward the lignin conversion is manifested as increasing selectivity to hydrogen and syngas, which reaches 94% at the Fe concentration of 2 wt.%. It was found that with microwave irradiation under argon, hydrogen predominates in the gas. In the CO2 atmosphere, dry reforming takes place to give syngas with the CO/H2 ratio of 0.9. In both cases, the degree of hydrogen recovery from lignin reaches 90-94%. [Figure not available: see fulltext.

A Synthetic Single-Site Fe Nitrogenase: High Turnover, Freeze-Quench (57)Fe Mössbauer Data, and a Hydride Resting State.

PubMed

Del Castillo, Trevor J; Thompson, Niklas B; Peters, Jonas C

2016-04-27

The mechanisms of the few known molecular nitrogen-fixing systems, including nitrogenase enzymes, are of much interest but are not fully understood. We recently reported that Fe-N2 complexes of tetradentate P3(E) ligands (E = B, C) generate catalytic yields of NH3 under an atmosphere of N2 with acid and reductant at low temperatures. Here we show that these Fe catalysts are unexpectedly robust and retain activity after multiple reloadings. Nearly an order of magnitude improvement in yield of NH3 for each Fe catalyst has been realized (up to 64 equiv of NH3 produced per Fe for P3(B) and up to 47 equiv for P3(C)) by increasing acid/reductant loading with highly purified acid. Cyclic voltammetry shows the apparent onset of catalysis at the P3(B)Fe-N2/P3(B)Fe-N2(-) couple and controlled-potential electrolysis of P3(B)Fe(+) at -45 °C demonstrates that electrolytic N2 reduction to NH3 is feasible. Kinetic studies reveal first-order rate dependence on Fe catalyst concentration (P3(B)), consistent with a single-site catalyst model. An isostructural system (P3(Si)) is shown to be appreciably more selective for hydrogen evolution. In situ freeze-quench Mössbauer spectroscopy during turnover reveals an iron-borohydrido-hydride complex as a likely resting state of the P3(B)Fe catalyst system. We postulate that hydrogen-evolving reaction activity may prevent iron hydride formation from poisoning the P3(B)Fe system. This idea may be important to consider in the design of synthetic nitrogenases and may also have broader significance given that intermediate metal hydrides and hydrogen evolution may play a key role in biological nitrogen fixation.

Construction of an improved amperometric acrylamide biosensor based on hemoglobin immobilized onto carboxylated multi-walled carbon nanotubes/iron oxide nanoparticles/chitosan composite film.

PubMed

Batra, Bhawna; Lata, Suman; Pundir, C S

2013-11-01

A method is described for construction of an improved amperometric acrylamide biosensor based on covalent immobilization of hemoglobin (Hb) onto nanocomposite of carboxylated multi-walled carbon nanotubes (cMWCNT) and iron oxide nanoparticles (Fe3O4NPs) electrodeposited onto Au electrode through chitosan (CHIT) film. The Hb/cMWCNT-Fe3O4NP/CHIT/Au electrode was characterized by scanning electron microscopy, Fourier transform infra-red spectroscopy, electrochemical impedance spectroscopy, and differential pulse voltammetry at different stages of its construction. The biosensor was based on interaction between acrylamide and Hb, which led to decrease in the electroactivity of Hb, i.e., current generated during its reversible conversion [Fe(II)/Fe(III)]. The biosensor showed optimum response within 8 s at pH 5.0 and 30 °C. The linear working range for acrylamide was 3-90 nM, with a detection limit of 0.02 nM and sensitivity of 36.9 μA/nM/cm(2). The biosensor was evaluated and employed for determination of acrylamide in potato crisps.

Higher iron bioavailability of a human-like collagen iron complex.

PubMed

Zhu, Chenhui; Yang, Fan; Fan, Daidi; Wang, Ya; Yu, Yuanyuan

2017-07-01

Iron deficiency remains a public health problem around the world due to low iron intake and/or bioavailability. FeSO 4 , ferrous succinate, and ferrous glycinate chelate are rich in iron but have poor bioavailability. To solve the problem of iron deficiency, following previous research studies, a thiolated human-like collagen-ironcomplex supplement with a high iron content was prepared in an anaerobic workstation. In addition, cell viability tests were evaluated after conducting an MTT assay, and a quantitative analysis of the thiolated human-like collagen-iron digesta samples was performed using the SDS-PAGE method coupled with gel filtration chromatography. The iron bioavailability was assessed using Caco-2 cell monolayers and iron-deficiency anemia mice models. The results showed that (1) one mole of thiolated human-like collagen-iron possessed approximately 35.34 moles of iron; (2) thiolated human-like collagen-iron did not exhibit cytotoxity and (3) thiolated human-like collagen- iron digesta samples had higher bioavailability than other iron supplements, including FeSO 4 , ferrous succinate, ferrous glycine chelate and thiolated human-like collagen-Fe iron. Finally, the iron bioavailability was significantly enhanced by vitamin C. These results indicated that thiolated human-like collagen-iron is a promising iron supplement for use in the future.

Lactoferrin modified graphene oxide iron oxide nanocomposite for glioma-targeted drug delivery.

PubMed

Song, Meng-Meng; Xu, Huai-Liang; Liang, Jun-Xing; Xiang, Hui-Hui; Liu, Rui; Shen, Yu-Xian

2017-08-01

Targeting delivery of drugs in a specific manner represents a potential powerful technology in gliomas. Herein, we prepared a multifunctional targeted delivery system based on graphene oxide (GO) that contains a molecular bio-targeting ligand and superparamagnetic iron oxide nanoparticles on the surface of GO for magnetic targeting. Superparamagnetic Fe 3 O 4 nanoparticles was loaded on the surface of GO via chemical precipitation method to form GO@Fe 3 O 4 nanocomposites. Lactoferrin (Lf), an iron-transporting serum glycoprotein that binds to receptors overexpressed at the surface of glioma cells and vascular endothelial cell of the blood brain barrier, was chosen as the targeted ligand to construct the targeted delivery system Lf@GO@Fe 3 O 4 through EDC/NHS chemistry. With the confirmation of TEM, DLS and VSM, the resulting Lf@GO@Fe 3 O 4 had a size distribution of 200-1000nm and exhibited a superparamagnetic behavior. The nano delivery system had a high loading capacity and exhibited a pH-dependent release behavior. Compared with free DOX and DOX@GO@Fe 3 O 4 , Lf@GO@Fe 3 O 4 @DOX displayed greater intracellular delivery efficiency and stronger cytotoxicity against C6 glioma cells. The results demonstrated the potential utility of Lf conjugated GO@Fe 3 O 4 nanocomposites for therapeutic application in the treatment of gliomas. Copyright © 2017. Published by Elsevier B.V.

Repeated exposure to iron oxide nanoparticles causes testicular toxicity in mice.

PubMed

Sundarraj, Kiruthika; Manickam, Vijayprakash; Raghunath, Azhwar; Periyasamy, Madhivadhani; Viswanathan, Mangala Priya; Perumal, Ekambaram

2017-02-01

The aim of this study was to determine whether repeated exposure to iron oxide nanoparticles (Fe 2 O 3 -NPs) could be toxic to mice testis. Fe 2 O 3 -NPs (25 and 50 mg/kg) were intraperitoneally administered into mice once a week for 4 weeks. Our study showed that Fe 2 O 3 -NPs have the ability to cross the blood-testis barrier to get into the testis. The findings showed that exposure resulted in the accumulation of Fe 2 O 3 -NPs which was evidenced from the iron content and accumulation in the testis. Furthermore, 25 and 50 mg/kg Fe 2 O 3 -NPs administration increased the reactive oxygen species, lipid peroxidation, protein carbonyl content, glutathione peroxidase activity, and nitric oxide levels with a concomitant decrease in the levels of antioxidants-superoxide dismutase, catalase, glutathione, and vitamin C. Increased expression of Bax, cleaved-caspase-3, and cleaved-PARP confirms apoptosis. Serum testosterone levels increased with increased concentration of Fe 2 O 3 -NPs exposure. In addition, the histopathological lesions like vacuolization, detachment, and sloughing of germ cells were also observed in response to Fe 2 O 3 -NPs treatment. The data from our study entailed that testicular toxicity caused by Fe 2 O 3 -NPs exposure may be associated with Fe 2 O 3 -NPs accumulation leading to oxidative stress and apoptosis. Therefore, precautions should be taken in the safe use of Fe 2 O 3 -NPs to avoid complications in the fertility of males. Further research will unravel the possible molecular mechanisms on testicular toxicity of Fe 2 O 3 -NPs. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 594-608, 2017. © 2016 Wiley Periodicals, Inc.

Two-iron rubredoxin of Pseudomonas oleovorans: production, stability and characterization of the individual iron-binding domains by optical, CD and NMR spectroscopies.

PubMed

Perry, A; Lian, L Y; Scrutton, N S

2001-02-15

A minigene encoding the C-terminal domain of the 2Fe rubredoxin of Pseudomonas oleovorans was created from the parental alk G gene contained in the expression plasmid pKK223-3. The vector directed the high-level production of the C-terminal domain of this rubredoxin; a simple procedure was used to purify the recombinant domain in the 1Fe form. The 1Fe form of the C-terminal domain was readily converted into the apoprotein and cadmium forms after precipitation with trichloroacetic acid and resolubilization in the presence or absence of cadmium chloride respectively. In steady-state assays, the recombinant 1Fe C-terminal domain is redox-active and able to transfer electrons from reduced rubredoxin reductase to cytochrome c. The absorption spectrum and dichroic features of the CD spectrum for the iron- and cadmium-substituted C-terminal domain are similar to those reported for the iron- and cadmium-substituted Desulfovibrio gigas rubredoxin [Henehen, Pountney, Zerbe and Vasak (1993) Protein Sci. 2, 1756-1764]. Difference absorption spectroscopy of the cadmium-substituted C-terminal domain revealed the presence of four Gaussian-resolved maxima at 202, 225, 240 and 276 nm; from Jørgensen's electronegativity theory, the 240 nm band is attributable to a CysS-Cd(II) charge-transfer excitation. Attempts to express the N-terminal domain of the 2Fe rubredoxin directly from a minigene were unsuccessful. However, the N-terminal domain was isolated through cleavage of an engineered 2Fe rubredoxin in which a factor Xa proteolysis site had been introduced into the putative interdomain linker. The N-terminal domain is characterized by absorption spectra typical of the 1Fe rubredoxins. The domain is folded as determined by CD and NMR spectroscopies and is redox-active. However, the N-terminal domain is less stable than the isolated C-terminal domain, a finding consistent with the known properties of the full-length 2Fe and cadmium-substituted Ps. oleovorans rubredoxin.

Prion protein conversion induced by trivalent iron in vesicular trafficking.

PubMed

Choi, Bo-Ran; Lee, Jeongmin; Kim, Su Yeon; Yim, Inbeen; Kim, Eun-Hee; Woo, Hee-Jong

2013-03-15

Iron dyshomeostasis has been observed in prion diseases; however, little is known regarding the contribution of the oxidation state of iron to prion protein (PrP) conversion. In this study, PrP(C)-deficient HpL3-4 cells were exposed to divalent [Fe(II)] or trivalent [Fe(III)] iron, followed by exogenous recombinant PrP (rPrP) treatment. We then analyzed the accumulation of internalized rPrP and its biochemical properties, including its resistance to both proteinase K (PK) digestion and detergent solubility. Fe(III), but not Fe(II), induced the accumulation of internalized rPrP, which was partially converted to detergent-insoluble and PK-resistant PrP (PrP(res)). The Fe(III)-induced PrP(res) generation required an intact cell structure, and it was hindered by U18666A, an inhibitor of vesicular trafficking, but not by NH4Cl, an inhibitor of endolysosomal acidification. These observations implicated that the Fe(III)-mediated PrP(res) conversion likely occurs during endosomal vesicular trafficking rather than in the acidic environment of lysosomes. Copyright © 2013 Elsevier Inc. All rights reserved.

Iron Bioavailability from Ferric Pyrophosphate in Extruded Rice Cofortified with Zinc Sulfate Is Greater than When Cofortified with Zinc Oxide in a Human Stable Isotope Study.

PubMed

Hackl, Laura; Zimmermann, Michael B; Zeder, Christophe; Parker, Megan; Johns, Paul W; Hurrell, Richard F; Moretti, Diego

2017-03-01

Background: Extruded rice grains are often cofortified with iron and zinc. However, it is uncertain if the addition of zinc to iron-fortified rice affects iron absorption and whether this is zinc-compound specific. Objective: We investigated whether zinc, added as zinc oxide (ZnO) or zinc sulfate (ZnSO 4 ), affects human iron absorption from extruded rice fortified with ferric pyrophosphate (FePP). Methods: In 19 iron-depleted Swiss women (plasma ferritin ≤16.5 μ/L) aged between 20 and 39 y with a normal body mass index (in kg/m 2 ; 18.7-24.8), we compared iron absorption from 4 meals containing fortified extruded rice with 4 mg Fe and 3 mg Zn. Three of the meals contained extruded rice labeled with FePP ( 57 FePP): 1 ) 1 meal without added zinc ( 57 FePP-Zn), 2 ) 1 cofortified with ZnO ( 57 FePP+ZnO), and 3 ) 1 cofortified with ZnSO 4 ( 57 FePP+ZnSO 4 ). The fourth meal contained extruded rice without iron or zinc, extrinsically labeled with ferrous sulfate ( 58 FeSO 4 ) added as a solution after cooking. All 4 meals contained citric acid. Iron bioavailability was measured by isotopic iron ratios in red blood cells. We also measured relative in vitro iron solubility from 57 FePP-Zn, 57 FePP+ZnO, and 57 FePP+ZnSO 4 expressed as a fraction of FeSO 4 solubility. Results: Geometric mean fractional iron absorption (95% CI) from 57 FePP+ZnSO 4 was 4.5% (3.4%, 5.8%) and differed from 57 FePP+ZnO (2.7%; 1.8%, 4.1%) ( P < 0.03); both did not differ from 57 FePP-Zn: 4.0% (2.8%, 5.6%). Relative iron bioavailabilities compared with 58 FeSO 4 were 62%, 57%, and 38% from 57 FePP+ZnSO 4 , 57 FePP-Zn, and 57 FePP+ZnO, respectively. In vitro solubility from 57 FePP+ZnSO 4 differed from that of 57 FePP-Zn (14.3%; P < 0.02) but not from that of 57 FePP+ZnO (10.2% compared with 13.1%; P = 0.08). Conclusions: In iron-depleted women, iron absorption from FePP-fortified extruded rice cofortified with ZnSO 4 was 1.6-fold (95% CI: 1.4-, 1.9-fold) that of rice cofortified with ZnO. These findings suggest that ZnSO 4 may be the preferable zinc cofortificant for optimal iron bioavailability of iron-fortified extruded rice. This trial was registered at clinicaltrials.gov as NCT02255942. © 2017 American Society for Nutrition.

Microstructures and properties of ceramic particle-reinforced metal matrix composite layers produced by laser cladding

NASA Astrophysics Data System (ADS)

Zhang, Qingmao; He, Jingjiang; Liu, Wenjin; Zhong, Minlin

2005-01-01

Different weight ratio of titanium, zirconium, WC and Fe-based alloy powders were mixed, and cladded onto a medium carbon steel substrate using a 3kW continuous wave CO2 laser, aiming at producing Ceramic particles- reinforced metal matrix composites (MMCs) layers. The microstructures of the layers are typical hypoeutectic, and the major phases are Ni3Si2, TiSi2, Fe3C, FeNi, MC, Fe7Mo3, Fe3B, γ(residual austenite) and M(martensite). The microstructure morphologies of MMCs layers are dendrites/cells. The MC-type reinforcements are in situ synthesis Carbides which main compositions consist of transition elements Zr, Ti, W. The MC-type particles distributed within dendrite and interdendritic regions with different volume fractions for single and overlapping clad layers. The MMCs layers are dense and free of cracks with a good metallurgical bonding between the layer and substrate. The addition ratio of WC in the mixtures has the remarkable effect on the microhardness of clad layers.

Microbial Iron Oxidation in the Arctic Tundra and Its Implications for Biogeochemical Cycling

PubMed Central

Scott, Jarrod J.; Benes, Joshua; Bowden, William B.

2015-01-01

The role that neutrophilic iron-oxidizing bacteria play in the Arctic tundra is unknown. This study surveyed chemosynthetic iron-oxidizing communities at the North Slope of Alaska near Toolik Field Station (TFS) at Toolik Lake (lat 68.63, long −149.60). Microbial iron mats were common in submerged habitats with stationary or slowly flowing water, and their greatest areal extent is in coating plant stems and sediments in wet sedge meadows. Some Fe-oxidizing bacteria (FeOB) produce easily recognized sheath or stalk morphotypes that were present and dominant in all the mats we observed. The cool water temperatures (9 to 11°C) and reduced pH (5.0 to 6.6) at all sites kinetically favor microbial iron oxidation. A microbial survey of five sites based on 16S rRNA genes found a predominance of Proteobacteria, with Betaproteobacteria and members of the family Comamonadaceae being the most prevalent operational taxonomic units (OTUs). In relative abundance, clades of lithotrophic FeOB composed 5 to 10% of the communities. OTUs related to cyanobacteria and chloroplasts accounted for 3 to 25% of the communities. Oxygen profiles showed evidence for oxygenic photosynthesis at the surface of some mats, indicating the coexistence of photosynthetic and FeOB populations. The relative abundance of OTUs belonging to putative Fe-reducing bacteria (FeRB) averaged around 11% in the sampled iron mats. Mats incubated anaerobically with 10 mM acetate rapidly initiated Fe reduction, indicating that active iron cycling is likely. The prevalence of iron mats on the tundra might impact the carbon cycle through lithoautotrophic chemosynthesis, anaerobic respiration of organic carbon coupled to iron reduction, and the suppression of methanogenesis, and it potentially influences phosphorus dynamics through the adsorption of phosphorus to iron oxides. PMID:26386054

High-performing mesoporous iron oxalate anodes for lithium-ion batteries.

PubMed

Ang, Wei An; Gupta, Nutan; Prasanth, Raghavan; Madhavi, Srinivasan

2012-12-01

Mesoporous iron oxalate (FeC(2)O(4)) with two distinct morphologies, i.e., cocoon and rod, has been synthesized via a simple, scalable chimie douce precipitation method. The solvent plays a key role in determining the morphology and microstructure of iron oxalate, which are studied by field-emission scanning electron microscopy and high-resolution transmission electron microscopy. Crystallographic characterization of the materials has been carried out by X-ray diffraction and confirmed phase-pure FeC(2)O(4)·2H(2)O formation. The critical dehydration process of FeC(2)O(4)·2H(2)O resulted in anhydrous FeC(2)O(4), and its thermal properties are studied by thermogravimetric analysis. The electrochemical properties of anhydrous FeC(2)O(4) in Li/FeC(2)O(4) cells are evaluated by cyclic voltammetry, galvanostatic charge-discharge cycling, and electrochemical impedance spectroscopy. The studies showed that the initial discharge capacities of anhydrous FeC(2)O(4) cocoons and rods are 1288 and 1326 mA h g(-1), respectively, at 1C rate. Anhydrous FeC(2)O(4) cocoons exhibited stable capacity even at high C rates (11C). The electrochemical performance of anhydrous FeC(2)O(4) is found to be greatly influenced by the number of accessible reaction sites, morphology, and size effects.

Formation of nickel and copper ferrites in ceramics: a potential reaction in the reuse of iron-rich sludge incineration ash.

PubMed

Shih, Kaimin

2012-12-01

This study investigates potential solid-state reactions for the stabilization of hazardous metals when reusing the incineration ash from chemically enhanced primary treatment (CEPT) sludge to fabricate ceramic products. Nickel and copper were used as examples of hazardous metals, and the iron content in the reaction system was found to play a major role in incorporating these hazardous metals into their ferrite phases (NiFe2O4 and CuFe2O4). The results from three-hour sintering experiments on NiO + Fe2O3 and CuO + Fe2O3 systems clearly demonstrate the potential for initiating metal incorporation mechanisms using an iron-containing precursor at attainable ceramic sintering temperatures (above 750 degrees C). Both ferrite phases were examined using a prolonged leaching experiment modified from the widely used toxicity characteristic leaching procedure (TCLP) to evaluate their long-term metal leachability. The leaching results indicate that both the NiFe2O4 and the CuFe2O4 products were significantly superior to their oxide forms in immobilizing hazardous metals.

Controllable synthesis of iron oxide nanoparticles in porous NaCl matrix

NASA Astrophysics Data System (ADS)

Kurapov, Yury A.; E Litvin, Stanislav; Romanenko, Sergey M.; Didikin, Gennadii G.; Oranskaya, Elena I.

2017-03-01

The paper gives the results of studying the structure of porous condensates of Fe + NaCl composition, chemical and phase compositions and dimensions of nanoparticles produced from the vapor phase by EB-PVD. Iron nanoparticles at fast removal from the vacuum oxidize in air and possess significant sorption capacity relative to oxygen and moisture. At heating in air, reduction of porous condensate weight occurs right to the temperature of 650 °C, primarily, due to desorption of physically sorbed moisture. Final oxidation of Fe3O4 to Fe2O3 proceeds in the range of 380 °C-650 °C, due to the remaining fraction of physically adsorbed oxygen. At iron concentrations of up to 10-15 at%, condensate sorption capacity is markedly increased with increase of iron concentration, i.e. of the quantity of fine particles. Increase of condensation temperature is accompanied by increase of nanoparticle size, resulting in a considerable reduction of the total area of nanoparticle surface, and, hence of their sorption capacity. In addition to condensation temperature, the size and phase composition of nanoparticles can also be controlled by heat treatment of initial condensate, produced at low condensation temperatures. Magnetite nanoparticles can be transferred into stable colloid systems.

Iron and gallium increase iron uptake from transferrin by human melanoma cells: further examination of the ferric ammonium citrate-activated iron uptake process.

PubMed

Richardson, D R

2001-04-30

Previously we showed that preincubation of cells with ferric ammonium citrate (FAC) resulted in a marked increase in Fe uptake from both (59)Fe-transferrin (Tf) and (59)Fe-citrate (D.R. Richardson, E. Baker, J. Biol. Chem. 267 (1992) 13972-13979; D.R. Richardson, P. Ponka, Biochim. Biophys. Acta 1269 (1995) 105-114). This Fe uptake process was independent of the transferrin receptor and appeared to be activated by free radicals generated via the iron-catalysed Haber-Weiss reaction. To further understand this process, the present investigation was performed. In these experiments, cells were preincubated for 3 h at 37 degrees C with FAC or metal ion solutions and then labelled for 3 h at 37 degrees C with (59)Fe-Tf. Exposure of cells to FAC resulted in Fe uptake from (59)Fe-citrate that became saturated at an Fe concentration of 2.5 microM, while FAC-activated Fe uptake from Tf was not saturable up to 25 microM. In addition, the extent of FAC-activated Fe uptake from citrate was far greater than that from Tf. These results suggest a mechanism where FAC-activated Fe uptake from citrate may result from direct interaction with the transporter, while Fe uptake from Tf appears indirect and less efficient. Preincubation of cells with FAC at 4 degrees C instead of 37 degrees C prevented its effect at stimulating (59)Fe uptake from (59)Fe-Tf, suggesting that an active process was involved. Previous studies by others have shown that FAC can increase ferrireductase activity that may enhance (59)Fe uptake from (59)Fe-Tf. However, there was no difference in the ability of FAC-treated cells compared to controls to reduce ferricyanide to ferrocyanide, suggesting no change in oxidoreductase activity. To examine if activation of this Fe uptake mechanism could occur by incubation with a range of metal ions, cells were preincubated with either FAC, ferric chloride, ferrous sulphate, ferrous ammonium sulphate, gallium nitrate, copper chloride, zinc chloride, or cobalt chloride. Stimulation of (59)Fe uptake from Tf was shown (in order of potency) with ferric chloride, ferrous sulphate, ferrous ammonium sulphate, and gallium nitrate. The other metal ions examined decreased (59)Fe uptake from Tf. The fact that redox-active Cu(II) ion did not stimulate Fe uptake while redox-inactive Ga(III) did, suggests a mechanism of transporter activation not solely dependent on free radical generation. Indeed, the activation of Fe uptake appears dependent on the presence of the Fe atom itself or a metal ion with atomic similarities to Fe (e.g. Ga).

Synthesis and spectral characterization of trinuclear, oxo-centered, carboxylate-bridged, mixed-valence iron complexes with Schiff bases.

PubMed

Singh, Atresh Kumar; Singh, Alok Kumar

2012-10-01

Some novel trinuclear, oxo-centered, carboxylate-bridged, mixed-valence iron complexes of the general formula [Fe(3)O(OOCR)(3)(SB)(3)L(3)] (where R=C(13)H(27), C(15)H(31) or C(17)H(35,) HSB=Schiff bases and L=Ethanol) have been synthesized by the stepwise substitutions of acetate ions from μ(3)-oxo-hexa(acetato)tri(aqua)iron(II)diiron(III), first with straight chain carboxylic acids and then with Schiff bases. The complexes were characterized by elemental analyses, molecular weight determinations and spectral (electronic, infrared, FAB mass, Mössbauer and powder XRD) studies. Molar conductance measurements indicated the complexes to be non-electrolytes in nitrobenzene. Bridging nature of carboxylate and Schiff base anions in the complexes was established by their infrared spectra. Mössbauer spectroscopic studies indicated two quadrupole-split doublets due to Fe(II) and Fe(III) ions at 80, 200 and 295K, confirming the complexes are mixed-valence species. This was also supported by the observed electronic spectra of the complexes. Magnetic susceptibility measurements displayed octahedral geometry around iron in mixed-valence state and a net antiferromagnetic exchange coupling via μ-oxo atom. Trinuclear nature of the complexes was confirmed by their molecular weight determination and FAB mass spectra. A plausible structure for these complexes has been established on the basis of spectral and magnetic moment data. Copyright © 2012 Elsevier B.V. All rights reserved.

Ba2F2Fe(1.5)Se3: An Intergrowth Compound Containing Iron Selenide Layers.

PubMed

Driss, Dalel; Janod, Etienne; Corraze, Benoit; Guillot-Deudon, Catherine; Cario, Laurent

2016-03-21

The iron selenide compound Ba2F2Fe(1.5)Se3 was synthesized by a high-temperature ceramic method. The single-crystal X-ray structure determination revealed a layered-like structure built on [Ba2F2](2+) layers of the fluorite type and iron selenide layers [Fe(1.5)Se3](2-). These [Fe1.5Se3](2-) layers contain iron in two valence states, namely, Fe(II+) and Fe(III+) located in octahedral and tetrahedral sites, respectively. Magnetic measurements are consistent with a high-spin state for Fe(II+) and an intermediate-spin state for Fe(III+). Moreover, susceptibility and resistivity measurements demonstrate that Ba2F2Fe(1.5)Se3 is an antiferromagnetic insulator.

Dephytinisation with Intrinsic Wheat Phytase and Iron Fortification Significantly Increase Iron Absorption from Fonio (Digitaria exilis) Meals in West African Women

PubMed Central

Moretti, Diego; Schuth, Stephan; Egli, Ines; Zimmermann, Michael B.; Brouwer, Inge D.

2013-01-01

Low iron and high phytic acid content make fonio based meals a poor source of bioavailable iron. Phytic acid degradation in fonio porridge using whole grain cereals as phytase source and effect on iron bioavailability when added to iron fortified fonio meals were investigated. Grains, nuts and seeds collected in Mali markets were screened for phytic acid and phytase activity. We performed an iron absorption study in Beninese women (n = 16), using non-dephytinised fonio porridge (FFP) and dephytinised fonio porridge (FWFP; 75% fonio-25% wheat), each fortified with 57Fe or 58Fe labeled FeSO4. Iron absorption was quantified by measuring the erythrocyte incorporation of stable iron isotopes. Phytic acid varied from 0.39 (bambara nut) to 4.26 g/100 g DM (pumpkin seed), with oilseeds values higher than grains and nuts. Phytase activity ranged from 0.17±1.61 (fonio) to 2.9±1.3 phytase unit (PU) per g (whole wheat). Phytic acid was almost completely degraded in FWFP after 60 min of incubation (pH≈5.0, 50°C). Phytate∶iron molar ratios decreased from 23.7∶1 in FFP to 2.7∶1 in FWFP. Iron fortification further reduced phytate∶iron molar ratio to 1.9∶1 in FFP and 0.3∶1 in FWFP, respectively. Geometric mean (95% CI) iron absorption significantly increased from 2.6% (0.8–7.8) in FFP to 8.3% (3.8–17.9) in FWFP (P<0.0001). Dephytinisation of fonio porridge with intrinsic wheat phytase increased fractional iron absorption 3.2 times, suggesting it could be a possible strategy to decrease PA in cereal-based porridges. PMID:24124445

Pristine Samples of Silicon Carbide Separated From the Canyon Diablo Meteorite

NASA Astrophysics Data System (ADS)

Leung, I. S.; Winston, R.

2008-12-01

The Canyon Diablo is an iron meteorite whose collision with Earth created Meteor Crater in Arizona. In a study of a large block (53 kg) of this meteorite, Henri Moissan reported his findings of green, hexagonal crystals of silicon carbide (SiC) which was given the name moissanite the following year by George Kunz (1905). Moissan did not report finding the cubic form of SiC. Subsequently, many erroneous reports appeared when the polishing compound (synthetic SiC) was mistakenly considered by researchers as a natural mineral associated with, rather than a contaminant of many rock types. Hence, the occurrence of SiC in the Canyon Diablo remains in doubt, and any proposal to investigate this problem was discouraged and regarded as predictably unproductive. This notion hampered further work on abundant materials housed in museums. SiC grains have been found in primitive meteorites and interplanetary dust particles. Some have been identified as presolar grains. The significance of SiC in the Canyon Diablo cannot be revealed unless we have abundant data from pristine samples, enough for us to classify them into presolar or other types. We report here a simple method we used to separate SiC crystals from the meteorite. We chose samples containing a carbon nodule composed of graphite, diamond-lonsdaleite, and SiC grains in the iron matrix. We broke up the carbon nodule with a sharp tungsten carbide chisel and hammer. After removing the large metal fragments, we put a small amount of the fine black grains in a Petri dish with acetone, then swerved the dish to scatter the grains sparingly on the bottom of the dish. Under a binocular microscope, SiC crystals can be spotted easily by their adamantine luster, color (blue, green, beige, etc.), and high birefringence when placed between crossed polarizers of a petrographic microscope. We also X-rayed individual grains, and have identified several hexagonal polytype structures as well as the cubic form (3C polytype).

Synthesis, Decomposition and Characterization of Fe and Ni Sulfides and Fe and CO Nanoparticles for Aerospace Applications

NASA Technical Reports Server (NTRS)

Cowen, Jonathan E.; Hepp, Aloysius F.; Duffy, Norman V.; Jose, Melanie J.; Choi, D. B.; Brothers, Scott M.; Baird, Michael F.; Tomsik, Thomas M.; Duraj, Stan A.; Williams, Jennifer N.;

Sound Velocities of Iron-Nickel and Iron-Nickel-Silicon Alloys at High Pressure

NASA Astrophysics Data System (ADS)

Miller, R. A.; Jackson, J. M.; Sturhahn, W.; Zhao, J.; Murphy, C. A.

2014-12-01

Seismological and cosmochemical studies suggest Earth's core is primarily composed of iron with ~5 to 10 wt% nickel and some light elements [e.g. 1]. To date, the concentration of nickel and the amount and identity of light elements remain poorly constrained due in part to the difficulty of conducting experimental measurements at core conditions. The vibrational properties of a variety iron alloys paired with seismic observations can help better constrain the composition of the core. We directly measured the partial phonon density of states of bcc- and hcp-structured Fe0.9Ni0.1 and Fe0.85Ni0.1Si0.05 at high pressures. The samples were compressed using a panoramic diamond anvil cell. A subset of the experiments were conducted using neon as a pressure transmitting medium. Measurements of high statistical quality were performed with nuclear resonant inelastic x-ray scattering (NRIXS) at sector 3-ID-B of the Advanced Photon Source [2, 3, 4]. The unit cell volume of each sample was determined at each compression point with in-situ x-ray diffraction at sector 3-ID-B before and after each NRIXS measurement. The Debye, compressional, and shear sound velocities were determined from the low energy region of the partial phonon density of states paired with the volume measurements. We will present partial phonon density of states and sound velocities for Fe0.9Ni0.1 and Fe0.85Ni0.1Si0.05 at high-pressure and compare with those of pure iron. References: [1] McDonough, W.F. (2004): Compositional Model for the Earth's Core. Elsevier Ltd., Oxford. [2] Murphy, C.A., J.M. Jackson, W. Sturhahn, and B. Chen (2011): Melting and thermal pressure of hcp-Fe from the phonon density of states, Phys. Earth Planet. Int., doi:10.1016/j.pepi.2011.07.001. [3] Murphy, C.A., J.M. Jackson, W. Sturhahn, and B. Chen (2011): Grüneisen parameter of hcp-Fe to 171 GPa, Geophys. Res. Lett., doi:10.1029/2011GL049531. [4] Murphy, C.A., J.M. Jackson, and W. Sturhahn (2013): Experimental constraints on the thermodynamics and sound velocities of hcp-Fe to core pressures, J. Geophys. Res., doi:10.1002/jgrb.50166.

Hierarchical Cu precipitation in lamellated steel after multistage heat treatment

NASA Astrophysics Data System (ADS)

Liu, Qingdong; Gu, Jianfeng

2017-09-01

The hierarchical distribution of Cu-rich precipitates (CRPs) and related partitioning and segregation behaviours of solute atoms were investigated in a 1.54 Cu-3.51 Ni (wt.%) low-carbon high-strength low-alloy (HSLA) steel after multistage heat treatment by using the combination of electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and atom probe tomography (APT). Intercritical tempering at 725 °C of as-quenched lathlike martensitic structure leads to the coprecipitation of CRPs at the periphery of a carbide precipitate which is possibly in its paraequilibrium state due to distinct solute segregation at the interface. The alloyed carbide and CRPs provide constituent elements for each other and make the coprecipitation thermodynamically favourable. Meanwhile, austenite reversion occurs to form fresh secondary martensite (FSM) zone where is rich in Cu and pertinent Ni and Mn atoms, which gives rise to a different distributional morphology of CRPs with large size and high density. In addition, conventional tempering at 500 °C leads to the formation of nanoscale Cu-rich clusters in α-Fe matrix. As a consequence, three populations of CRPs are hierarchically formed around carbide precipitate, at FSM zone and in α-Fe matrix. The formation of different precipitated features can be turned by controlling diffusion pathways of related solute atoms and further to tailor mechanical properties via proper multistage heat treatments.

On the structure and radiation chemistry of iron phosphate glasses: New insights from electron spin resonance, Mössbauer, and evolved-gas mass spectroscopy

NASA Astrophysics Data System (ADS)

Griscom, D. L.; Merzbacher, C. I.; Bibler, N. E.; Imagawa, H.; Uchiyama, S.; Namiki, A.; Marasinghe, G. K.; Mesko, M.; Karabulut, M.

1998-05-01

Several vitreous forms for immobilization of plutonium and/or high-level nuclear wastes have been surveyed by electron spin resonance (ESR) to gain insights into their atomic-scale structures and to look for signs of radiolytic decomposition resulting from exposures to γ-ray doses of 30 MGy. While preliminary results are reported for Defense Waste Processing Facility (DWPF) borosilicate compositions and an experimental lanthanum-silicate glass, this paper focusses primarily on a class of glasses containing 40-75 mol% P 2O 5 and up to 40 mol% Fe 2O 3. Each of the six diverse compositions investigated displayed characteristic ESR signals (not resembling those of the iron-containing phosphorus-free glasses) comprising combinations of an extremely broad "X resonance" and a narrow "Z resonance", both centered near g=2.00 and both displaying nearly perfect Lorentzian line shapes (peak-to-peak derivative widths ˜300-600 mT and ˜30 mT, respectively, at 300 K). The X-resonance intensities in the air-melted glasses correlated linearly with Fe:P ratio up to [Fe 2O 3]/[P 2O 5] ≈ 0.6, where intensity values ˜1 spin/phosphorus were reached. Mössbauer studies showed that the [Fe 3+]/[Fe] tot ratio could be varied from 0.82 to 0.49 by raising the melting temperature in air from 1150°C to 1450°C and/or by employing mildly reducing atmospheres. The combined X + Z-resonance intensities were reduced to zero for [Fe 3+]/[Fe] tot less than ˜0.6, leaving only a much weaker spectrum attributable to Fe 3+ ions. The X and Z ESR signals of the iron phosphate glasses resemble nothing else in the literature except the correspondingly denoted signals in an iron-free amorphous peroxyborate (APB) preparation. The X and Z resonances in the latter are deemed to arise from superoxide ions (O 2-) in the borate network and in a separated Na 2O 2 phase, respectively. An asymmetric Z resonance signal attributable to interstitial O 2- species was a radiation-induced manifestation in phosphate glass of composition 50P 2O 5-20Fe 2O 3-23Li 2O-7CeO 2. Irradiated and unirradiated samples of this same glass were studied by ESR isochronal annealing and differential thermal analysis, revealing a one-for-one conversion of X to Z upon partial crystallization near 670°C and a Z → X reconversion upon partial remelting near 970°C. Heating to 1070°C in dry Ar resulted in a weight loss of ˜5 wt%, while quadrupole mass spectrometry (QMS) during ramped heating to 1550°C at a pressure of 10 -5 Pa revealed the evolution of O 2 molecules with (radiation sensitive) ion-current peaks near 1170°C and 1350-1400°C. To account for the totality of these and other results, it is suggested that air-melted iron phosphate glasses may contain macroscopic numbers of superoxide ions as an intrinsic chemical feature of their as-quenched structures. A specific four-connected phosphorus-oxygen glass network incorporating O 2- ions is proposed.

Synthesis and isolation of [Fe@Ge(10)](3-): a pentagonal prismatic Zintl ion cage encapsulating an interstitial iron atom.

PubMed

Zhou, Binbin; Denning, Mark S; Kays, Deborah L; Goicoechea, Jose M

2009-03-04

Reaction of an ethylenediamine (en) solution of the Zintl phase precursor K(4)Ge(9) with FeAr(2) (Ar = 2,6-Mes(2)C(6)H(3)) in the presence of 2,2,2-crypt (4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane) yielded the endohedral Zintl ion [Fe@Ge(10)](3-) (1) which was crystallographically characterized as a [K(2,2,2-crypt)](+) salt in [K(2,2,2-crypt)](3)[Fe@Ge(10)]*2en. This unprecedented Zintl ion exhibits a pentagonal prismatic 10-atom germanium cage with an interstitial iron atom in the central cavity. Confirmation of the existence of the cluster anion in solution was corroborated by positive and negative ion mode electrospray mass spectrometry.

Mn-Fe base and Mn-Cr-Fe base austenitic alloys

DOEpatents

Brager, Howard R.; Garner, Francis A.

1987-09-01

Manganese-iron base and manganese-chromium-iron base austenitic alloys designed to have resistance to neutron irradiation induced swelling and low activation have the following compositions (in weight percent): 20 to 40 Mn; up to about 15 Cr; about 0.4 to about 3.0 Si; an austenite stabilizing element selected from C and N, alone or in combination with each other, and in an amount effective to substantially stabilize the austenite phase, but less than about 0.7 C, and less than about 0.3 N; up to about 2.5 V; up to about 0.1 P; up to about 0.01 B; up to about 3.0 Al; up to about 0.5 Ni; up to about 2.0 W; up to about 1.0 Ti; up to about 1.0 Ta; and with the remainder of the alloy being essentially iron.

Mn-Fe base and Mn-Cr-Fe base austenitic alloys

DOEpatents

Brager, Howard R.; Garner, Francis A.

1987-01-01

Manganese-iron base and manganese-chromium-iron base austenitic alloys designed to have resistance to neutron irradiation induced swelling and low activation have the following compositions (in weight percent): 20 to 40 Mn; up to about 15 Cr; about 0.4 to about 3.0 Si; an austenite stabilizing element selected from C and N, alone or in combination with each other, and in an amount effective to substantially stabilize the austenite phase, but less than about 0.7 C, and less than about 0.3 N; up to about 2.5 V; up to about 0.1 P; up to about 0.01 B; up to about 3.0 Al; up to about 0.5 Ni; up to about 2.0 W; up to about 1.0 Ti; up to about 1.0 Ta; and with the remainder of the alloy being essentially iron.

The effect of oxygen on density of liquid iron at high pressure

NASA Astrophysics Data System (ADS)

Takubo, Y.; Terasaki, H.; Shimoyama, Y.; Urakawa, S.; Suzuki, A.; Nishida, K.; Kamuro, R.; Kishimoto, S.; Kondo, T.; Ohtani, E.; Yoshinori, K.

2012-12-01

The Earth's outer core has been thought to be composed of liquid iron alloys with 10 % of light elements, such as sulfur, carbon, silicon and oxygen. Density of liquid iron alloy is one of the key parameters to understand the composition and structure of the Earth's outer core. The effect of various light elements (e.g., S, Si, and C) on the density of liquid iron at high pressure and high temperature has been studied (Nishida et al., 2011; Tateyama et al., 2011 Sanloup et al., 2011; Terasaki et al., 2010). It was revealed that the density depression is quite different depending on dissolving light element. However the effect of oxygen on the density of liquid iron has not been investigated due to high liquidus temperature of Fe-O system, although oxygen is one of the major candidates of the light elements in the Earth's outer core (e.g., Ringwood, 1977). Oxygen could be incorporated into the core during early terrestrial evolution (Corgne et al., 2009). In this study, we have measured the density of liquid Fe-O in the pressure and temperature ranges of 2.3-3.0 GPa and 2000-2250 K using X-ray absorption method. High pressure experiment was performed using a cubic-type multi-anvil press installed at BL22XU of the SPring-8 synchrotron radiation facility in Japan. Monochromatic X-ray of 35 keV was used. Mixture of Fe and FeO powders with 0.5 wt% oxygen, which corresponds to the eutectic composition at 3 GPa (Ohtani et al., 1984) was used as a sample. The sample was inserted in a single crystal sapphire capsule. The obtained density of this study is 6.7 g/cm3 at 3 GPa and 2005 K. Compared to the density of pure liquid iron (Anderson and Ahrens, 1994) at the present experimental condition, the density of liquid Fe-O is about 5.3 % smaller than that of pure liquid iron. On the other hand, thermal expansion coefficient of liquid Fe-O shows similar value to that of liquid iron.

Preservation of Fe Isotope Proxies in the Rock Record

NASA Astrophysics Data System (ADS)

Johnson, C.; Beard, B.; Valley, J.; Valaas, E.

2005-12-01

Iron isotope variations provide powerful constraints on redox conditions and pathways involved during biogeochemical cycling of Fe in surface and near-surface environments. The relative isotopic homogeneity of igneous rocks and most bulk weathering products contrasts with the significant isotopic variations (4 per mil in 56Fe/54Fe) that accompany oxidation of Fe(II)aq, precipitation of sulfides, and reduction by bacteria. These isotopic variations often reflect intrinsic (equilibrium) Fe isotope fractionations between minerals and aqueous species whose interactions may be directly or indirectly catalyzed by bacteria. In addition, Fe isotope exchange may be limited between reactive Fe pools in low-temperature aqueous-sediment environments, fundamentally reflecting disequilibrium effects. In the absence of significant sulfide, dissimilatory Fe(III) reduction by bacteria produces relatively low 56Fe/54Fe ratios for Fe(II)aq and associated biogenic minerals such as magnetite and siderite. In contrast, Fe(II)aq that exchanges with Fe sulfides (FeS and pyrite) is relatively enriched in 56Fe/54Fe ratios. In modern and ancient environments, anoxic diagenesis tends to produce products that have low 56Fe/54Fe ratios, whereas oxidation of Fe(II)aq from hydrothermal sources tends to produce ferric Fe products that have high 56Fe/54Fe ratios. Redox cycling by bacteria tends to produce reactive ferric Fe reservoirs that have low 56Fe/54Fe ratios. Application of Fe isotopes as a proxy for redox conditions in the ancient rock record depends upon the preservation potential during metamorphism, given the fact that most Archean sedimentary sequences have been subjected to regional greenschist- to granulite-facies metamorphism. The 1.9 Ga banded iron formations (BIFs) of the Lake Superior region that are intruded by large ~1 Ga intrusions (e.g., Duluth gabbro) provide a test of the preservation potential for primary, low-temperature Fe isotope variations in sedimentary rocks. 56Fe/54Fe ratios for re-crystallized magnetite from BIFs of the Biwabik iron formation that have apparent oxygen-isotope (quartz-magnetite) temperatures between 270 and 800 oC span a significant portion of the range measured in lower-grade BIFs from South Africa and Australia. d56Fe values for Biwabik magnetite vary from -0.2 to +0.7 per mil, whereas magnetite from the Dales Gorge member of the Brockman iron formation and the Kuruman iron formation has d56Fe values that lie between -1.2 and +1.3 per mil. Iron isotope fractionations between magnetite and Fe silicates (greenalite, hedenbergite, and fayalite) in the Biwabik iron formation regularly decrease with increasing oxygen-isotope temperatures, approaching the zero fractionation expected at igneous temperatures; apparent magnetite-Fe silicate fractionations range from +0.2 per mil at 650 oC to +0.5 per mil at 300 oC, lying close to those predicted using the revised beta factors of Polyakov et al. (2005, Goldschmidt). During closed-system Fe isotope exchange during metamorphism, the overall range in d56Fe values for magnetite will remain relatively constant, although it may shift to higher d56Fe values relative to primary (low-temperature) magnetite due to the non-zero magnetite-Fe silicate fractionation factor at moderate temperature ranges. If the mineral parageneis is known, and some assumptions regarding primary mineralogy can be made, these small corrections may be made to successfully infer the original Fe isotope compositions of sedimentary minerals and rocks that have been subjected to metamorphism.

Studies on the reactivity of [Ge9]4- towards [Fe(cot)(CO)3]: synthesis and characterization of [Ge8Fe(CO)3]3- and of the anionic organometallic species [Fe(cot)(CO)3]-.

PubMed

Zhou, Binbin; Goicoechea, Jose M

2010-09-24

Reaction of cyclooctatetraene (COT) iron(II) tricarbonyl, [Fe(cot)(CO)(3)], with one equivalent of K(4)Ge(9) in ethylenediamine (en) yielded the cluster anion [Ge(8)Fe(CO)(3)](3-) which was crystallographically-characterized as a [K(2,2,2-crypt)](+) salt in [K(2,2,2-crypt)](3)[Ge(8)Fe(CO)(3)]. The chemically-reduced organometallic species [Fe(η(3)-C(8)H(8))(CO)(3)](-) was also isolated as a side-product from this reaction as [K(2,2,2-crypt)][Fe(η(3)-C(8)H(8))(CO)(3)]. Both species were further characterized by EPR and IR spectroscopy and electrospray mass spectrometry. The [Ge(8)Fe(CO)(3)](3-) cluster anion represents an unprecedented functionalized germanium Zintl anion in which the nine-atom precursor cluster has lost a vertex, which has been replaced by a transition-metal moiety.

The Effect of Nb Addition on the Microstructure and the High-Temperature Strength of Fe3Al Aluminide

NASA Astrophysics Data System (ADS)

Kratochvíl, Petr; Švec, Martin; Král, Robert; Veselý, Jozef; Lukáč, Pavel; Vlasák, Tomáš

2018-02-01

The microstructural and high-temperature mechanical properties of Fe-26Al-xNb (x = 3 and 5 at. pct) are compared. The alloys were investigated "as cast" and after hot rolling at 1473 K (1200 °C). Scanning electron microscopes equipped with EDS and EBSD were used for the microstructure and phase identification. The addition of 3 at. pct of Nb into the Fe3Al matrix leads to the formation of C14 λ—Laves phase (Fe,Al)2Nb (LP) particles spread in the Fe3Al matrix, while an eutectic with thin lamellae of LP C14 λ—Laves phase (Fe,Al)2Nb and matrix is also formed in the iron aluminide with 5 at. pct of Nb. The presence of incoherent precipitates is connected with the enhancement of the high-temperature strength and creep resistance.

Metallographic Cooling Rates of IAB Iron Meteorites

NASA Astrophysics Data System (ADS)

Meibom, A.; Haack, H.; Jensen, S. K.; Ulff-Moller, F.; Rasmussen, K. L.

1995-09-01

Non-metals can play an important role for the diffusion-controlled growth of the Widmanstatten structure in iron meteorites. The presence of P significantly changes the diffusivity and equilibrium concentration of Ni in kamacite and taenite [1,2], and the effects of P have therefore been included in metallographic cooling rate calculations for many years. The presence of C probably increases the diffusivity of Ni in taenite up to a factor of two, which is considerably smaller than the effect of P that increases the Ni diffusivity by up to a factor of 10 [3,1]. On the other hand, C partitions strongly into taenite leaving kamacite essentially C-free (<10 micrograms/g [4]) and significantly reduces the equilibrium Ni-concentration in taenite [5]. Therefore, the effect of C should be included in metallographic cooling rate calculations of C-rich iron meteorites [6]. IAB iron meteorites have much higher bulk C-concentrations than most other iron meteorites and the metallic phases of the IAB irons were probably saturated with C soon after kamacite nucleation commenced. Since C is expected to decrease the solubility of P in taenite [7] we have based our cooling rate estimate of Toluca (IAB) on the Fe-Ni-C system rather than the Fe-Ni-P system. Previous metallographic cooling rates determined for IAB irons, including the effect of P, are low (1-10 degrees C/My [8] and 30-70 degrees C/My [9]). Fractional crystallization of S-rich cores [10, 11] and impact generated melt pools [12] have been proposed as origins of the IAB iron meteorites. Since we expect melt pools near the surface to have cooled significantly faster than the core of a differentiated parent body, the metallographic cooling rates may be used to discriminate between the two models. We have performed thermodynamic calculations on the C-saturated Fe-Ni-C-system at temperatures above 400 degrees C [13]. The results agree with earlier experimental work [5] and indicate that C, to the same degree as P, reduces the Ni concentration of taenite coexisting with kamacite. We did not extend the thermodynamic calculations below 400 degrees C due to the lack of data. Therefore, our cooling rate estimates are based on taenite lamellae wider than about 10 micrometers which are largely sensitive to the cooling rate above around 400 degrees C. Our preliminary results show a slightly better match between calculated and measured Ni mid-profile-concentrations versus total-lamella-width for Toluca (IAB) using the Fe-Ni-C system than using the Fe-Ni-P system. This difference is mainly due to a lower diffusivity of Ni in taenite in the Fe-Ni-C system. The average cooling rate obtained for Toluca using the Fe-Ni-C system is approximately a factor of 5 lower than the cooling rate obtained on the basis of the Fe-Ni-P system. However, both lie in the range 1-15 degrees C/My which is consistent with cooling rate estimates based on Pu-fission tracks in silicate inclusions of Landes and Copiapo; both IAB [13]. These relatively low cooling rate is in discordance with a melt-pool origin of the IAB iron meteorites. References: [1] Dean D. C. and Goldstein J. I. (1986) Metall. Trans., 17A, 1131-1138. [2] Romig A. D. and Goldstein J. I. (1980) Metall. Trans. A, 11A, 1151-1159. [3] Wells C. and Mehl R. F. (1941) Trans. AIME, 145, 329-339. [4] Makjanic J. et al. (1988) NIMB, B30, 466-469. [5] Romig A. D. and Goldstein J. I. (1978) Metall. Trans., 9A, 1599-1609. [6] Meibom et al. (1994) Meteoritics, 29, 501. [7] Buchwald, personal communication. [8] Rasmussen K. L. (1989) Phys. Scripta, 39, 410-416. [9] Herpfer M. A. et al., GCA, 58, 1353-1365. [10] Kracher A. (1985) Proc. LPSC 15th, in JGR, 90, C689-C698. [11] McCoy T. et al. (1993) Meteoritics, 28, 552-560. [12] Choi B.-G. et al. (1995) GCA, 59, 593-612. [13] Sundman. B., Manual to Thermo-Calc, Royal Institute of Technology, Stockholm. [14] Benkheiri et al. (1979) Icarus, 40, 497-501.

Unraveling the complexity of iron oxides at high pressure and temperature: Synthesis of Fe 5O 6

DOE PAGES

Lavina, Barbara; Meng, Yue

2015-06-26

The iron-oxygen system is the most important reference of rocks’ redox state. Even as minor components, iron oxides can play a critical role in redox equilibria, which affect the speciation of the fluid phases chemical differentiation, melting, and physical properties. Until our recent finding of Fe 4O 5, iron oxides were assumed to comprise only the polymorphs of FeO, Fe 3O 4, and Fe 2O 3. Combining synthesis at high pressure and temperature with micro- diffraction mapping, we have identified yet another distinct iron oxide, Fe 5O 6. The new compound, which has an orthorhombic structure, was obtained in themore » pressure range from 10 to 20 GPa upon laser heating mixtures of iron and hematite at ~2000 K, and is recoverable to ambient conditions. The high-pressure orthorhombic iron oxides Fe 5O 6, Fe 4O 5, and h-Fe 3O 4 display similar iron coordination geometries and structural arrangements, and indeed exhibit coherent systematic behavior of crystallographic parameters and compressibility. Fe 5O 6, along with FeO and Fe 4O 5, is a candidate key minor phase of planetary interiors; as such, it is of major petrological and geo- chemical importance. Here, we are revealing an unforeseen complexity in the Fe-O system with four different compounds—FeO, Fe 5O 6, Fe 4O 5, and h-Fe 3O 4—in a narrow compositional range (0.75 < Fe/O < 1.0). New, finely spaced oxygen buffers at conditions of the Earth’s mantle can be defined.« less

Microstructures of the silicon carbide nanowires obtained by annealing the mechanically-alloyed amorphous powders

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Pengfei, E-mail: zhangpengfei1984@163.com; Li, Xinli

2015-07-15

Silicon, graphite and boron nitride powders were mechanically alloyed for 40 h in argon. The as-milled powders were annealed at 1700 °C in nitrogen for 30 min. The annealed powders are covered by a thick layer of gray–green SiC nanowires, which are 300 nm to 1000 nm in diameter and several hundred microns in length. Trace iron in the raw powders acts as a catalyst, promoting the V–L–S process. It follows that the actual substances contributing to the growth of the SiC nanowires may be silicon, graphite and the metal impurities in the raw powders. The results from HRTEM andmore » XRD reveal that the products contain both straight α/β-SiC nanowires and nodular α/β-SiC nanochains. It is interestingly found that 6H–SiC coexists with 3C–SiC in one nodular nanowire. This novel structure may introduce periodic potential field along the longitudinal direction of the nanowires, and may find applications in the highly integrated optoelectronic devices. - Graphical abstract: Display Omitted - Highlights: • SiC nanowires were prepared by annealing the mechanically alloyed amorphous powders. • SiC nanowires are 300 nm to 1000 nm in diameter and several hundred microns in length. • The products contain both straight α/β-SiC nanowires and nodular α/β-SiC nanochains. • Trace Fe in the raw powders acts as a catalyst, promoting the V–L–S process. • 6H–SiC coexists with 3C–SiC in one nodular SiC nanowire.« less

Adrenaline and triiodothyronine modify the iron handling in the freshwater air-breathing fish Anabas testudineus Bloch: role of ferric reductase in iron acquisition.

PubMed

Rejitha, V; Peter, M C Subhash

2013-01-15

The effects of in vivo adrenaline and triiodothyronine (T(3)) on ferric reductase (FR) activity, a membrane-bound enzyme that reduces Fe(III) to Fe(II) iron, were studied in the organs of climbing perch (Anabas testudineus Bloch). Adrenaline injection (10 ng g(-1)) for 30 min produced significant inhibition of FR activity in the liver and kidney and that suggests a role for this stress hormone in iron acquisition in this fish. Short-term T(3) injection (40 ng g(-1)) reduced FR activity in the gills of fed fish but not in the unfed fish. Similar reduction of FR activity was also obtained in the intestine and kidney of fed fish after T(3) injection. Feeding produced pronounced decline in FR activity in the spleen but T(3) challenge in fed and unfed fish increased its activity in this iron storing organ and that point to the sensitivity of FR system to feeding activity. The in vitro effects of Fe on FR activity in the gill explants of freshwater fish showed correlations of FR with Na(+), K(+)-ATPase and H(+)-ATPase activities. Substantial increase in the FR activity was found in the gill explants incubated with all the tested doses of Fe(II) iron (1.80, 3.59 and 7.18 μM) and Fe(III) iron (1.25, 2.51 and 5.02 μM) and this indicate that FR and Na pump activity are positively correlated. On the contrary, substantial reduction of gill H(+)-ATPase activity was found in the gill explants incubated with Fe(II) iron and Fe(III) iron indicating that perch gills may not require a high acidic microenvironment for the reduction of Fe(III) iron. Accumulation of iron in the gill explants after Fe(III) iron incubation implies a direct relationship between Fe acquisition and FR activity in this tissue. The inverse correlation between FR activity and H(+)-ATPase activity in Fe(II) or Fe(III) loaded gills and the significant positive correlations of FR activity with total [Fe] content in the Fe(III) loaded gills substantiate that FR which shows sensitivity to sodium and proton pumps, has a vital role in Fe(II) and Fe(III) iron handling in this fish. Our data also provide evidence that adrenaline, T(3) and the feeding status are the vital factors that can regulate the storage and handling of iron in fish. Copyright © 2012 Elsevier Inc. All rights reserved.

New understanding on separation of Mn and Fe from ferruginous manganese ores by the magnetic reduction roasting process

NASA Astrophysics Data System (ADS)

Liu, Bingbing; Zhang, Yuanbo; Wang, Juan; Wang, Jia; Su, Zijian; Li, Guanghui; Jiang, Tao

2018-06-01

Magnetic reduction roasting followed by magnetic separation process is reported as a simple route to realize separation of Mn and Fe from ferruginous manganese ores (Fe-Mn ores). However, the separation and recovery of Mn and Fe oxides are not very effective. This work clarified the underlying reason for the poor separation and also proposed some suggestions for the magnetic reduction process. In this work, the effect of temperature on the magnetic reduction roasting - magnetic separation of Fe-Mn ore was investigated firstly. Then the reduction behaviors of MnO2-Fe2O3 system and MnO2-Fe2O3-10 wt.%SiO2 system under 10 vol.% CO-90 vol.% CO2 at 600-1000 °C were investigated by XRD, XPS, SEM-EDS, VSM, DSC and thermodynamics analyses. Reduction and separation tests showed that higher reduction temperature was beneficial to the recovery of iron while it's not in favor of the recovery of manganese when the temperature was over 800 °C. The formation of composite oxide MnxFe3-xO4 with strong magnetism between the interface of the MnO2 and Fe2O3 particles leaded to the poor separation of iron and manganese. In addition, the formation mechanism of MnxFe3-xO4 from MnO2 and Fe2O3 as well as the interface reaction reduced under 10 vol.% CO was discussed in this study. Finally, some suggestions were recommended for the magnetic reduction roasting for utilizing the Fe-Mn ores effectively.

A facile route to modify ferrous phosphate and its use as an iron-containing resource for LiFePO4 via a polyol process.

PubMed

Li, Shaomin; Liu, Xichuan; Mi, Rui; Liu, Hao; Li, Yinchuan; Lau, Woon-min; Mei, Jun

2014-06-25

This study introduces an economical and environmentally friendly way of synthesizing LiFePO4/C to be used as cathode material in lithium ion batteries via two processes: (1) the synthesis of LiFePO4/C cathode material using a low cost divalent precursor ferrous phosphate, Fe3 (PO4)2·8H2O, as iron source in a polyol process and (2) the modification of the morphology of this precursor by varying the reaction time in a coprecipitation process. The study examines the effects of different structures and morphologies of the precursor on the structure and electrochemical performance of the as-synthesized LiFePO4/C. The LiFePO4/C shows an excellent rate capability and cycle performance, with initial discharge capacities of 153, 128, and 106 mA h g(-1) at 1 C, 5 C, and 10 C. The capacity retention is respectively 98.7%, 98.2%, and 98.7%, after 10 cycles at the corresponding rates. The capacity retention remains at 97% even after 300 cycles at the rate of 10 C. The outstanding electrochemical performance can be attributed to the improved rate of Li(+) diffusion and the excellent crystallinity of synthesized LiFePO4/C powders through the modified precursor. Therefore, this is an economical and environmentally friendly way of synthesizing LiFePO4/C to be used as cathode material in lithium ion batteries.

High-rate acidophilic ferrous iron oxidation in a biofilm airlift reactor and the role of the carrier material.

PubMed

Ebrahimi, S; Fernández Morales, F J; Kleerebezem, R; Heijnen, J J; van Loosdrecht, M C M

2005-05-20

In this study, the feasibility and engineering aspects of acidophilic ferrous iron oxidation in a continuous biofilm airlift reactor inoculated with a mixed culture of Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans bacteria were investigated. Specific attention was paid to biofilm formation, competition between both types of bacteria, ferrous iron oxidation rate, and gas liquid mass transfer limitations. The reactor was operated at a constant temperature of 30 degrees C and at pH values of 0-1.8. Startup of the reactor was performed with basalt carrier material. During the experiments the basalt was slowly removed and the ferric iron precipitates formed served as a biofilm carrier. These precipitates have highly suitable characteristics as a carrier material for the immobilization of ferrous iron-oxidizing bacteria and dense conglomerates were observed. Lowering the pH (0.6-1) resulted in dissolution of the ferric precipitates and induced granular sludge formation. The maximum ferrous iron oxidation rate achieved in this study was about 145 molFe(2+)/m(3).h at a hydraulic residence time of 0.25 h. Optimal treatment performance was obtained at a loading rate of 100 mol/m(3).h at a conversion efficiency as high as 98%. Fluorescent in situ hybridization (FISH) studies showed that when the reactor was operated at high ferrous iron conversion (>85%) for 1 month, the desirable L. ferrooxidans species could out-compete A. ferrooxidans due to the low Fe(2+) and high Fe(3+) concentrations. (c) 2005 Wiley Periodicals, Inc.

The anthropogenic influence on Iron deposition over the oceans: a 3-D global modeling

NASA Astrophysics Data System (ADS)

Myriokefalitakis, Stelios; Mihalopoulos, Nikos; Baker, Alex; Kanakidou, Maria

2014-05-01

Iron (Fe) deposition over oceans is directly linked to the marine biological productivity and consequently to atmospheric CO2 concentrations. Experimental and modeling results support that both inorganic (sulphate, ammonium and nitrate) and organic (e.g. oxalate) ligands can increase the Fe mobilization. Mineral dust deposition is considered as the most important supply of bioavailable Fe in the oceans. Although, due to the low soil soluble iron fractions, atmospheric processes which are also related to anthropogenic emissions, can convert iron to more soluble forms in the atmosphere. Recent studies also support that anthropogenic emissions of Fe from combustion sources also significantly contribute to the dissolved Fe atmospheric pool. The evaluation of the impact of humans on atmospheric soluble or bioavailable Fe deposition remains challenging, since Fe mobilization due to changes in anthropogenic emissions is largely uncertain. In the present study, the global atmospheric Fe cycle is parameterized in the 3-D chemical transport global model TM4-ECPL and the model is used to calculate the Fe deposition over the oceans. The model considers explicitly organic, sulfur and nitrogen gas-phase chemistry, aqueous-phase organic chemistry, including oxalate and all major aerosol constituents. TM4-ECPL simulates the organic and inorganic ligand-promoted mineral Fe dissolution and also aqueous-phase photochemical reactions between different forms of Fe (III/II). Primary emissions of Fe associated with dust and soluble Fe from combustion processes as well as atmospheric processing of the emitted Fe is taken into account in the model Sensitivity simulations are performed to study the impact of anthropogenic emissions on Fe deposition. For this preindustrial, present and future emission scenarios are used in the model in order to examine the response of chemical composition of iron-containing aerosols to environmental changes. The release of soluble iron associated with mineral dust and with the emissions of combustion aerosols is investigated. Model results are compared with available observations to evaluate their robustness. This work is supported by the ESF-NSRF ARISTEIA grant PANOPLY (Pollution Alters Natural Aerosol Composition: implications for Ocean Productivity, cLimate and air qualitY).

The Fe-C-O-H-N system at 6.3-7.8 GPa and 1200-1400 °C: implications for deep carbon and nitrogen cycles

NASA Astrophysics Data System (ADS)

Sokol, Alexander G.; Tomilenko, Anatoly A.; Bul'bak, Taras A.; Kruk, Alexey N.; Zaikin, Pavel A.; Sokol, Ivan A.; Seryotkin, Yurii V.; Palyanov, Yury N.

2018-06-01

Interactions in a Fe-C-O-H-N system that controls the mobility of siderophile nitrogen and carbon in the Fe0-saturated upper mantle are investigated in experiments at 6.3-7.8 GPa and 1200-1400 °C. The results show that the γ-Fe and metal melt phases equilibrated with the fluid in a system unsaturated with carbon and nitrogen are stable at 1300 °C. The interactions of Fe3C with an N-rich fluid in a graphite-saturated system produce the ɛ-Fe3N phase (space group P63/ mmc or P6322) at subsolidus conditions of 1200-1300 °C, while N-rich melts form at 1400 °C. At IW- and MMO-buffered hydrogen fugacity ( fH2), fluids vary from NH3- to H2O-rich compositions (NH3/N2 > 1 in all cases) with relatively high contents of alkanes. The fluid derived from N-poor samples contains less H2O and more carbon which mainly reside in oxygenated hydrocarbons, i.e., alcohols and esters at MMO-buffered fH2 and carboxylic acids at unbuffered fH2 conditions. In unbuffered conditions, N2 is the principal nitrogen host (NH3/N2 ≤ 0.1) in the fluid equilibrated with the metal phase. Relatively C- and N-rich fluids in equilibrium with the metal phase (γ-Fe, melt, or Fe3N) are stable at the upper mantle pressures and temperatures. According to our estimates, the metal/fluid partition coefficient of nitrogen is higher than that of carbon. Thus, nitrogen has a greater affinity for iron than carbon. The general inference is that reduced fluids can successfully transport volatiles from the metal-saturated mantle to metal-free shallow mantle domains. However, nitrogen has a higher affinity for iron and selectively accumulates in the metal phase, while highly mobile carbon resides in the fluid phase. This may be a controlling mechanism of the deep carbon and nitrogen cycles.

Reactivity of tris(acetylacetonato) iron(III) with tridentate [ONO] donor Schiff base as an access to newer mixed-ligand iron(III) complexes.

PubMed

Bhattacharjee, Chira R; Goswami, Pankaj; Pramanik, Harun A R; Paul, Pradip C; Mondal, Paritosh

2011-05-01

Two new mixed-ligand iron(III) complexes, [Fe(L(n))(acac)(C(2)H(5)OH)] incorporating coordinated ethanol from the reaction solvent were accessed from the reaction of [Fe(acac)(3)] with [ONO] donor dibasic tridentate unsymmetrical Schiff base ligands derived from condensation of 2-hydroxy-1-napthaldehyde with 2-aminophenol (H(2)L(1)) or 2-aminobenzoic acid (H(2)L(2)). The thermal study (TGA-DTA) provided evidence for weakly bound ethanol which is readily substituted by neutral N-donor molecule imidazole, benzimidazole or pyridine to produce an array of newer complexes, [Fe(L(n))(acac)X] (n=1, 2; X=Im, Bim, Py). The compounds were characterized by elemental analyses, FT-IR, UV-vis, solution electrical conductivity, FAB mass, (1)H and (13)C NMR spectroscopy. Room temperature magnetic susceptibility measurements (μ(eff)∼5.8 B.M.) are consistent with spin-free octahedral iron(III) complexes. Cyclic voltammetry of ethanol complexes revealed a quasi-reversible one electron redox response (ΔE(p)>100 mV) for the Fe(III)/Fe(II) couple. Low half wave redox potential (E(1/2)) values suggested easy redox susceptibility. The ground state geometries of the ethanol and imidazole complexes have been ascertained to be distorted octahedral by density functional theory using DMol3 program at BLYP/DNP level. Copyright © 2011 Elsevier B.V. All rights reserved.

Iron Isotope Systematics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dauphas, Nicolas; John, Seth G.; Rouxel, Olivier

Iron is a ubiquitous element with a rich (i.e., complex) chemical behavior. It possesses three oxidation states, metallic iron (Fe0), ferrous iron (Fe2+) and ferric iron (Fe3+). The distribution of these oxidation states is markedly stratified in the Earth.

Topotaxial growth of α-Fe{sub 2}O{sub 3} nanowires on iron substrate in thermal annealing method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Srivastava, Himanshu, E-mail: himsri@rrcat.gov.in; Srivastava, A. K.; Babu, Mahendra

2016-06-28

A detail cross-sectional transmission electron microscopy of as-grown α-Fe{sub 2}O{sub 3} nanowire sample, synthesized on iron substrate by thermal annealing method, was carried out to understand the mechanism of growth in this system. Iron undergoes sequential oxidation to form a layered structure of Fe/FeO/Fe{sub 3}O{sub 4}/α-Fe{sub 2}O{sub 3}. α-Fe{sub 2}O{sub 3} nanowires grow on to the top of α-Fe{sub 2}O{sub 3} layer. It was found that subsequent oxide layers grow topotaxially on the grains of iron, which results in a direct orientation relationship between the α-Fe{sub 2}O{sub 3} nanowire and the parent grain of iron. The results also showed thatmore » the grains of α-Fe{sub 2}O{sub 3} layer, which were uniquely oriented in [110] direction, undergo highly anisotropic growth to form the nanowire. This anisotropic growth occurs at a twin interface, given by (−11−1), in the α-Fe{sub 2}O{sub 3} layer. It was concluded that the growth at twin interface could be the main driving factor for such anisotropic growth. These observations are not only helpful in understanding the growth mechanism of α-Fe{sub 2}O{sub 3} nanowires, but it also demonstrates a way of patterning the nanowires by controlling the texture of iron substrate.« less

Long- and Short-Range Structure of Ferrimagnetic Iron-Chromium Maghemites.

PubMed

García-Guaderrama, Marco; Montero-Cabrera, María E; Morán, Emilio; Alario-Franco, Miguel A; Fuentes-Cobas, Luis E; Macías-Ríos, Edgar; Esparza-Ponce, Hilda E; Fuentes-Montero, María E

2015-12-07

Maghemite-like materials containing Fe(3+) and Cr(3+) in comparable amounts have been prepared by solution-combustion synthesis. The conditions of synthesis and the magnetic properties are described. These materials are ferrimagnetic and are much more stable than pure iron maghemite since their maghemite-hematite transformation takes place at about ∼ 700 °C instead of ∼ 300 °C, as usually reported. These materials were studied by synchrotron radiation X-ray diffraction (XRD) and by X-ray absorption fine structure (XAFS) of the K-absorption edge of two elements. High-resolution XRD patterns were processed by means of the Rietveld method. Thus, maghemites were studied by XAFS in both Fe and Cr K-edges to clarify the short-range structure of the investigated systems. Pre-edge decomposition and theoretical modeling of X-ray absorption near edge structure transitions were performed. The extended X-ray absorption fine structure (EXAFS) spectra were fitted considering the facts that the central atom of Fe is able to occupy octahedral and tetrahedral sites, each with a weight adjustment, while Cr occupies only octahedral sites. Interatomic distances were determined for x = 1, by fitting simultaneously both Fe and Cr K-edges average EXAFS spectra. The results showed that the cation vacancies tend to follow a regular pattern within the structure of the iron-chromium maghemite (FeCrO3).

Plasma synthesis, Mössbauer spectroscopy and X-ray diffraction studies of nanosized iron oxides

NASA Astrophysics Data System (ADS)

Paneva, Daniela; Zaharieva, Katerina; Grabis, Janis; Mitov, Ivan; Vissokov, Gheorghi

2010-06-01

In this article synthesis and study of iron oxide nanopowders are described. The synthesis of sample 1 and sample 2—iron oxides—was carried out by electric arc plasma cutting of ordinary steel. The sample 3 was prepared by evaporation of Fe2O3/FeO mixture in radio-frequency nitrogen plasma. The characterization of the as prepared iron oxide nanoproducts was achieved by means of Mössbauer spectroscopy and X-ray diffraction analysis. The presence of different phases of iron oxide with a basic phase Fe3 - xO4 (magnetite), additional Fe1 - xO (wüstite) and α or γ-Fe2O3 (hematite or maghemite) with superparamagnetic particles for sample 1 and sample 2 and Fe3 - xO4 (magnetite) for sample 3 is observed.

2D Superparamagnetic Tantalum Carbide Composite MXenes for Efficient Breast-Cancer Theranostics

PubMed Central

Liu, Zhuang; Lin, Han; Zhao, Menglong; Dai, Chen; Zhang, Shengjian; Peng, Weijun; Chen, Yu

2018-01-01

Background: The emergence of two-dimensional MXenes has spurred their versatile applications in broad fields, but the exploring of novel MXene-based family members and their potential applications in theranostic nanomedicine (concurrent diagnostic imaging and therapy) have been rarely explored. In this work, we report the construction of a novel superparamagnetic MXene-based theranostic nanoplatform for efficient breast-cancer theranostics, which was based on intriguing tantalum carbide (Ta4C3) MXene and its further rational surface-superparamagnetic iron-oxide functionalization (Ta4C3-IONP-SPs composite MXenes) for efficient breast-cancer theranostic. Methods: The fabrication of ultrathin Ta4C3 nanosheets was based on an exfoliation strategy and superparamagnetic iron oxide nanoparticles were in-situ grown onto the surface of Ta4C3 MXene according to the redox reaction of MXene. Ta4C3-IONP MXenes were modified with soybean phospholipid (SP) to guarantee high stability in physiological conditions. The photothermal therapy, contrast-enhanced CT, T2-weighted magnetic resonance imaging and the high biocompatibility of these composite nanosheets have also been evaluated in vitro at cellular level and in vivo on mice breast tumor allograft tumor model. Results: The Ta component of Ta4C3-IONP-SPs exhibits high performance for contrast-enhanced CT imaging because of its high atomic number and high X-ray attenuation coefficient, and the integrated superparamagnetic IONPs act as excellent contrast agents for T2-weighted magnetic resonance imaging. Especially, these Ta4C3-IONP-SPs composite nanosheets with high photothermal-conversion efficiency (η: 32.5%) has achieved complete tumor eradication without reoccurrence, verifying their highly efficient breast-tumor photo-ablation performance. Conclusion: This work not only significantly broadens the biomedical applications of MXene-based nanoplatforms (Ta4C3 MXene) by exploring their novel family members and further functionalization strategies (magnetic functionalization in this work), but also provides a novel and efficient theranostic nanoplatform for efficient breast-cancer theranostics. PMID:29556347

A One-Step Delamination Procedure to Form Single Sheet Iron(III)-(oxy)Hydroxides

EPA Science Inventory

The dispersion of a layered iron(III)-(oxy)hydroxide intercalated with dodecanoate (oxGR_C12, Fe₃^IIIO_2.18(OH)_3.13(C₁₂H₂₃O₂)_0.56(SO₄)_0.47; derived from the corr...

The role of Ag buffer layer in Fe islands growth on Ge (111) surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fu, Tsu-Yi, E-mail: phtifu@phy.ntnu.edu.tw; Wu, Jia-Yuan; Jhou, Ming-Kuan

2015-05-07

Sub-monolayer iron atoms were deposited at room temperature on Ge (111)-c(2 × 8) substrates with and without Ag buffer layers. The behavior of Fe islands growth was investigated by using scanning tunneling microscope (STM) after different annealing temperatures. STM images show that iron atoms will cause defects and holes on substrates at room temperature. As the annealing temperature rises, iron atoms pull out germanium to form various kinds of alloyed islands. However, the silver layer can protect the Ag/Ge(111)-(√3×√3) reconstruction from forming defects. The phase diagram shows that ring, dot, and triangular defects were only found on Ge (111)-c(2 × 8) substrates. The kindsmore » of islands found in Fe/Ge system are similar to Fe/Ag/Ge system. It indicates that Ge atoms were pulled out to form islands at high annealing temperatures whether there was a Ag layer or not. But a few differences in big pyramidal or strip islands show that the silver layer affects the development of islands by changing the surface symmetry and diffusion coefficient. The structure characters of various islands are also discussed.« less

44. NORTHEAST VIEW OF IRON DESULPHERIZATION BUILDING, WITH CALCIUM CARBIDE ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

44. NORTHEAST VIEW OF IRON DESULPHERIZATION BUILDING, WITH CALCIUM CARBIDE SILO ADJACENT TO BUILDING ON RIGHT. (Jet Lowe) - U.S. Steel Duquesne Works, Blast Furnace Plant, Along Monongahela River, Duquesne, Allegheny County, PA

Magnetite solubility and phase stability in alkaline media at elevated temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ziemniak, S.E.; Jones, M.E.; Combs, K.E.S.

Magnetite, Fe{sub 3}O{sub 4}, is the dominant oxide constituent of the indigenous corrosion layers that form on iron base alloys in high purity, high temperature water. The apparent simultaneous stability of two distinct oxidation states of iron in this metal oxide is responsible for its unique solubility behavior. The present work was undertaken to extend the experimental and theoretical bases for estimating solubilities of an iron corrosion product (Fe{sub 3}O{sub 4}/Fe(OH){sub 2}) over a broader temperature range and in the presence of complexing, pH-controlling reagents. These results indicate that a surface layer of ferrous hydroxide controls magnetite solubility behavior atmore » low temperatures in much the same manner as a surface layer of nickel(II) hydroxide was previously reported to control the low temperature solubility behavior of NiO. The importance of Fe(III) ion complexes implies not only that most previously-derived thermodynamic properties of the Fe(OH){sub 3}{sup {minus}} ion are incorrect, but that magnetite phase stability probably shifts to favor a sodium ferric hydroxyphosphate compound in alkaline sodium phosphate solutions at elevated temperatures. The test methodology involved pumping alkaline solutions of known composition through a bed of Fe{sub 3}O{sub 4} granules and analyzing the emerging solution for Fe. Two pH-controlling reagents were tested: sodium phosphate and ammonia. Equilibria for the following reactions were described in thermodynamic terms: (a) Fe(OH){sub 2}/Fe{sub 3}O{sub 4} dissolution and transformation, (b) Fe(II) and Fe(III) ion hydroxocomplex formation (hydrolysis), (c) Fe(II) ion amminocomplex formation, and (d) Fe(II) and Fe(III) ion phosphatocomplex formation. 36 refs.« less

Four-Coordinate Iron(II) Diaryl Compounds with Monodentate N-Heterocyclic Carbene Ligation: Synthesis, Characterization, and Their Tetrahedral-Square Planar Isomerization in Solution.

PubMed

Liu, Yuesheng; Luo, Lun; Xiao, Jie; Wang, Lei; Song, You; Qu, Jingping; Luo, Yi; Deng, Liang

2015-05-18

The salt elimination reactions of (IPr2Me2)2FeCl2 (IPr2Me2 = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) with the corresponding aryl Grignard reagents afford [(IPr2Me2)2FeAr2] (Ar = Ph, 3; C6H4-p-Me, 4; C6H4-p-(t)Bu, 5; C6H3-3,5-(CF3)2, 6) in good yields. X-ray crystallographic studies revealed the presence of both tetrahedral and trans square planar isomers for 3 and 6 and the tetrahedral structures for 4 and 5. Magnetic susceptibility and (57)Fe Mössbauer spectrum measurements on the solid samples indicated the high-spin (S = 2) and intermediate-spin (S = 1) nature of the tetrahedral and square planar structures, respectively. Solution property studies, including solution magnetic susceptibility measurement, variable-temperature (1)H and (19)F NMR, and absorption spectroscopy, on 3-6, as well as an (57)Fe Mössbauer spectrum study on a frozen tetrahydrofuran solution of tetrahedral [(IPr2Me2)2(57)FePh2] suggest the coexistence of tetrahedral and trans square planar structures in solution phase. Density functional theory calculations on (IPr2Me2)2FePh2 disclosed that the tetrahedral and trans square planar isomers are close in energy and that the geometry isomerization can occur by spin-change-coupled geometric transformation on four-coordinate iron(II) center.

3D polymer hydrogel for high-performance atomic iron-rich catalysts for oxygen reduction in acidic media

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qiao, Zhi; Zhang, Hanguang; Karakalos, Stavros

Current platinum group metal (PGM)-free carbon nanocomposite catalysts for the oxygen reduction reaction (ORR) in acidic electrolyte often suffer from rapid degradation associated with carbon corrosion due to the use of large amount of amorphoous carbon black supports. Here, we developed a new concept of using freestanding 3D hydrogel to design support-free Fe-N-C catalysts. A 3D polyaniline (PANI)-based hydrogel was used for preparing a new type of single atomic iron site-rich catalyst, which has exhibited exceptionally enhanced activity and stability compared to conventional Fe-N-C catalysts supported on amorphous carbon blacks. The achieved performance metric on the hydrogel PANI-Fe catalysts ismore » one of the best ever reported PGM-free catalysts, reaching a half-wave potential up to 0.83 V vs. RHE and only leaving 30 mV gap with Pt/C catalysts (60 μgPt/cm2) in challenging acidic media. Remarkable ORR stability was accomplished as well on the same catalyst evidenced by using harsh potential cycling tests. The well dispersion of atomic iron into partially graphitized carbon, featured with dominance of micropores and porous network structures, is capable of accommodating increased number of active sites, strengthening local bonding among iron, nitrogen and carbon, and facilitating mass transfer. The 3D polymer hydrogel approach would be a new pathway to advance PGM-free catalysts.« less

3D polymer hydrogel for high-performance atomic iron-rich catalysts for oxygen reduction in acidic media

DOE PAGES

Qiao, Zhi; Zhang, Hanguang; Karakalos, Stavros; ...

2017-08-03

Current platinum group metal (PGM)-free carbon nanocomposite catalysts for the oxygen reduction reaction (ORR) in acidic electrolyte often suffer from rapid degradation associated with carbon corrosion due to the use of large amount of amorphoous carbon black supports. Here, we developed a new concept of using freestanding 3D hydrogel to design support-free Fe-N-C catalysts. A 3D polyaniline (PANI)-based hydrogel was used for preparing a new type of single atomic iron site-rich catalyst, which has exhibited exceptionally enhanced activity and stability compared to conventional Fe-N-C catalysts supported on amorphous carbon blacks. The achieved performance metric on the hydrogel PANI-Fe catalysts ismore » one of the best ever reported PGM-free catalysts, reaching a half-wave potential up to 0.83 V vs. RHE and only leaving 30 mV gap with Pt/C catalysts (60 μgPt/cm2) in challenging acidic media. Remarkable ORR stability was accomplished as well on the same catalyst evidenced by using harsh potential cycling tests. The well dispersion of atomic iron into partially graphitized carbon, featured with dominance of micropores and porous network structures, is capable of accommodating increased number of active sites, strengthening local bonding among iron, nitrogen and carbon, and facilitating mass transfer. The 3D polymer hydrogel approach would be a new pathway to advance PGM-free catalysts.« less

Design of Wear-Resistant Austenitic Steels for Selective Laser Melting

NASA Astrophysics Data System (ADS)

Lemke, J. N.; Casati, R.; Lecis, N.; Andrianopoli, C.; Varone, A.; Montanari, R.; Vedani, M.

2018-03-01

Type 316L stainless steel feedstock powder was modified by alloying with powders containing carbide/boride-forming elements to create improved wear-resistant austenitic alloys that can be readily processed by Selective Laser Melting. Fe-based alloys with high C, B, V, and Nb contents were thus produced, resulting in a microstructure that consisted of austenitic grains and a significant amount of hard carbides and borides. Heat treatments were performed to modify the carbide distribution and morphology. Optimal hard-phase spheroidization was achieved by annealing the proposed alloys at 1150 °C for 1 hour followed by water quenching. The total increase in hardness of samples containing 20 pct of C/B-rich alloy powder was of 82.7 pct while the wear resistance could be increased by a factor of 6.

Electronic and magnetic behaviors of B, N, and 3d transition metal substitutions in germanium carbide monolayer

NASA Astrophysics Data System (ADS)

Xu, Zhuo; Li, Yangping; Liu, Zhengtang; Liu, Shengzhong (Frank)

2018-04-01

The structural, electronic, and magnetic behaviors of two-dimensional GeC (2D-GeC) with single vacancy, substitutional B, N, and 3d transition metal atoms (Sc, Ti, V, Cr, Mn, Fe, Co, and Ni) are investigated based on the density functional theory. These impurities are tightly bonded to the surrounding atoms and found energetically more favorable at Ge sub-lattice site. In addition, the electronic band structures and magnetic properties of the doped systems indicate that (i) tunable electronic structures and magnetic moments of 2D-GeC can be obtained depending on different dopant species and sub-lattice sites, (ii) systems such as VC@Sc, VC@Fe, VC@Co, VGe@Fe, and VGe@Co are found to be half-metals, while the other systems all show semiconductor behavior. Simple models of the impurity-vacancy interaction is put forwards to illustrate the origin of the electronic structures and magnetic moments.

Mössbauer study of metallic iron and iron oxide nanoparticles having environmental purifying ability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kubuki, Shiro, E-mail: kubuki@tmu.ac.jp; Watanabe, Yuka, E-mail: kubuki@tmu.ac.jp; Akiyama, Kazuhiko, E-mail: kubuki@tmu.ac.jp

2014-10-27

A relationship between local structure and methylene blue (MB) decomposing ability of nanoparticles (NPs) of metallic iron (Fe{sup 0}) and maghemite (γ‐Fe{sub 2}O{sub 3}) was investigated by {sup 57}Fe Mössbauer spectroscopy, X-ray diffractometry and UV-visible light absorption spectroscopy. γ‐Fe{sub 2}O{sub 3} NPs were successfully prepared by mixing (NH{sub 4}){sub 2}Fe(SO{sub 4}){sub 2}⋅6H{sub 2}O (Mohr's salt) and (NH{sub 4}){sub 3}Fe(C{sub 2}O{sub 4}){sub 3}⋅3H{sub 2}O aqueous solution at 30 °C for 1 h, while those of Fe{sup 0} were obtained by the reduction of Mohr's salt with NaBH{sub 4}. From the Scherrer's equation, the smallest crystallite sizes of γ‐Fe{sub 2}O{sub 3} NPsmore » and Fe{sup 0} NPs were determined to be 9.7 and 1.5 nm, respectively. {sup 57}Fe Mössbauer spectrum of γ‐Fe{sub 2}O{sub 3} NPs consists of a relaxed sextet with isomer shift (δ) of 0.33{sub ±0.01} mm s{sup −1}, internal magnetic field (H{sub int}) of 25.8{sub ±0.5} T, and linewidth (Γ) of 0.62{sub ±0.04} mm s{sup −1}. {sup 57}Fe Mössbauer spectrum of Fe{sup 0} NP is mainly composed of a sextet having δ, Δ, and H{sub int} of 0.00{sub ±0.01} mm s{sup −1} 0.45{sub ±0.01} mm s{sup −1}, and 22.8{sub ±0.1} T, respectively. A bleaching test of the mixture of Fe{sup 0} and γ‐Fe{sub 2}O{sub 3} NPs (3:7 ratio, 100 mg) in MB aqueous solution (20 mL) for 6 h showed a remarkable decrease of MB concentration with the first-order rate constant (k{sub MB}) of 6.7 × 10{sup −1} h{sup −1}. This value is larger than that obtained for the bleaching test using bulk Fe{sup 0}+γ‐Fe{sub 2}O{sub 3} (3:7) mixture (k{sub MB} = 6.5×10{sup −3}h{sup −1}). These results prove that MB decomposing ability is enhanced by the NPs mixture of Fe{sub 0} and γ‐Fe{sub 2}O{sub 3}.« less

Genetic and biochemical effects induced by iron ore, Fe and Mn exposure in tadpoles of the bullfrog Lithobates catesbeianus.

PubMed

Veronez, Alexandra Caroline da Silva; Salla, Rômulo Victor; Baroni, Vinícius Dadalto; Barcarolli, Indianara Fernanda; Bianchini, Adalto; Dos Reis Martinez, Claudia Bueno; Chippari-Gomes, Adriana Regina

2016-05-01

For decades, the extraction of minerals has intensified in order to meet the demand of industry. Iron ore deposits are important sources of metals, such as iron (Fe) and manganese (Mn). The particulate ores can be dispersed during extraction, transport and storage, with potential to induce biological impacts. Amphibians are very sensitive to environmental stressors. Therefore, the present study aimed to assess the effects of iron ore, Fe and Mn exposure during the metamorphosis of Lithobates catesbeianus. Endpoints analyzed included morphological (biometrical and developmental analyses), whole body Fe and Mn concentration in, plasma ferritin concentration, erythrocyte DNA damage (measured through comet assay and micronucleus test) and liver activity of enzymes involved in oxidative status [glutathione S-transferase (GST) and catalase (CAT)]. Tadpoles were kept under control condition (no contaminant addition) or exposed to iron ore (3.79mg/L as fine particulate matter); Fe (nominal concentration: 0.51mg/L Fe as C10H12FeN2NaO8; Fe-EDTA); and Mn (nominal concentration: 5.23mg/L Mn as 4H2O.MnCl2) for 30 days. Virtually, no mortality was observed, except for one tadpole found dead in the iron ore treatment. However, tadpoles exposed to iron ore had longer tail than those kept under control conditions while tadpoles exposed to manganese chloride showed higher body length than control ones. Exposure to Fe and Mn induced a delay in tadpole metamorphosis, especially when these metals are presented not as a mixture (iron ore). Tadpoles exposed to iron ore had increased whole body Fe and Mn while those exposed to Fe and Mn accumulated each metal individually. Tadpoles exposed to any of the contaminants tested showed a significant increase in erythrocyte DNA damage and frequency of micronuclei. In addition, they showed higher liver GST activity respect with those kept under control conditions. Plasma ferritin concentration and liver CAT activity were higher only in tadpoles exposed to iron ore. These findings indicated that tadpoles accumulated Fe and Mn at the whole body level after exposure to the single metals or to their mixture as iron ore. In addition, they indicate that Fe and Mn accumulation can induce oxidative stress with consequent significant developmental, genotoxic and biochemical effects in L. catesbeianus tadpoles. Copyright © 2016 Elsevier B.V. All rights reserved.

The Process of Nanostructuring of Metal (Iron) Matrix in Composite Materials for Directional Control of the Mechanical Properties

PubMed Central

Zemtsova, Elena

2014-01-01

We justified theoretical and experimental bases of synthesis of new class of highly nanostructured composite nanomaterials based on metal matrix with titanium carbide nanowires as dispersed phase. A new combined method for obtaining of metal iron-based composite materials comprising the powder metallurgy processes and the surface design of the dispersed phase is considered. The following stages of material synthesis are investigated: (1) preparation of porous metal matrix; (2) surface structuring of the porous metal matrix by TiC nanowires; (3) pressing and sintering to give solid metal composite nanostructured materials based on iron with TiC nanostructures with size 1–50 nm. This material can be represented as the material type “frame in the frame” that represents iron metal frame reinforcing the frame of different chemical compositions based on TiC. Study of material functional properties showed that the mechanical properties of composite materials based on iron with TiC dispersed phase despite the presence of residual porosity are comparable to the properties of the best grades of steel containing expensive dopants and obtained by molding. This will solve the problem of developing a new generation of nanostructured metal (iron-based) materials with improved mechanical properties for the different areas of technology. PMID:24695459

The process of nanostructuring of metal (iron) matrix in composite materials for directional control of the mechanical properties.

PubMed

Zemtsova, Elena; Yurchuk, Denis; Smirnov, Vladimir

2014-01-01

We justified theoretical and experimental bases of synthesis of new class of highly nanostructured composite nanomaterials based on metal matrix with titanium carbide nanowires as dispersed phase. A new combined method for obtaining of metal iron-based composite materials comprising the powder metallurgy processes and the surface design of the dispersed phase is considered. The following stages of material synthesis are investigated: (1) preparation of porous metal matrix; (2) surface structuring of the porous metal matrix by TiC nanowires; (3) pressing and sintering to give solid metal composite nanostructured materials based on iron with TiC nanostructures with size 1-50 nm. This material can be represented as the material type "frame in the frame" that represents iron metal frame reinforcing the frame of different chemical compositions based on TiC. Study of material functional properties showed that the mechanical properties of composite materials based on iron with TiC dispersed phase despite the presence of residual porosity are comparable to the properties of the best grades of steel containing expensive dopants and obtained by molding. This will solve the problem of developing a new generation of nanostructured metal (iron-based) materials with improved mechanical properties for the different areas of technology.

The structural role and homogeneous redox equilibria of iron in peraluminous, metaluminous and peralkaline silicate melts

NASA Astrophysics Data System (ADS)

Dickenson, M. P.; Hess, P. C.

1986-02-01

The compositional dependence of the redox ratio (FeO/FeO1.5) has been experimentally determined in K2O-Al2O3-SiO2-Fe2O3-FeO (KASFF) and K2O-CaO-Al2O3-SiO2-Fe2O3-FeO (KCASFF) silicate melts. Compositions were equilibrated at 1,450° C in air, with 78 mol % SiO2. KASFF melts have from 1 to 5 mol % Fe2O3 and include both peraluminous (K2OAl2O3) compositions. KCASFF melts have 1 mol % Fe2O3 encompassing peraluminous, metaluminous (CaO+K2O>Al2O3) and peralkaline compositions. Peralkaline KASFF melts with 1 mol % Fe2O3 have low and constant values for the redox ratio, whereas in peraluminous melts the redox ratio increases with increasing (K2O/Al2O3). Increasing total iron concentration increases the redox ratio in peraluminous melts and slightly decreases the redox ratio in peralkaline melts. Substituting CaO for K2O at fixed total iron (1 mol %) increases the redox ratio in both peraluminous and metaluminous KCASFF melts; however, the redox ratio in peralkaline KCASFF melts is not affected by this exchange. These data indicate that Fe3+ is in four-fold coordination, with K+ or Ca2+ providing local charge balance. The tetrahedral ferric species is most stable in peralkaline melts and least stable in peraluminous melts, due to the competition between Al3+ and Fe3+ for charge balancing cations in the latter melt. Tetrahedral Fe3+ is also less stable when Ca2+ provides local charge balance. The data are consistent with a network modifying role for Fe2+ in the melt. The data are interpreted to reflect the effects of melt composition on the partitioning of K+ and Ca2+ and Fe3+ and Al3+ between various species in the melt. These relationships are discussed in terms of homogeneous equilibria between various iron-bearing and iron-free melt species. The results also reflect the effect of liquid composition on the exchange potentials μFe3+ Al-1 and μCa0.5K-1. The exchange potentials are relatively constant in peralkaline melts, but decrease in metaluminous and peraluminous melts as both (CaO+K2O)/(CaO+K2O+Al2O3) and K2O/CaO decrease. These qualitative observations imply that minerals exhibiting these exchanges will also be similarly affected as liquid composition changes.

Isotopically Heavy Low-Spin Iron in Ferropericlase at the Core-Mantle Boundary

NASA Astrophysics Data System (ADS)

Yang, H.; Lin, J. F.; Dauphas, N.; Bi, W.; Zhao, J.

2016-12-01

The iron isotope fractionation between metal and silicate at high pressure is of great interest for it is potentially responsible for the iron isotopic difference between the 2 main iron reservoir —the mantle and the core and therefore vital for estimating the bulk iron isotopic composition of the Earth. In 2009, Polyakov pioneered the use of NRIXS(Nuclear Resonant Inelastic X-ray Scat- tering) technique to investigate iron isotope fractionation at core-mantle boundary. This synchr- otron-based technique is excellent in that it can be applied to samples loaded in DACs with tens of um in size and one doesn't needs to put minerals together to reach isotope exchange equilib- rium. However, the NRIXS data used in Polyakov(2009) was scanned over a limited energy range and thus is not suitable for isotope fractionation at high pressure: the phonon modes shift with increasing pressure and a scanned energy range over 100meV is necessary. Recently, Shahar and co-workers(2016) used NRIXS with a wider energy scan range and DFT simulation to estimate the light element alloying effect on iron bonding environment at high pressure. They found that C or H may not be a major light element in the core considering only bridgmanite as a proxy of the mantle, but another lower mantle mineral ferropericlase was not taken into account. Here we report newly collected NRIXS data at sector-3 of the Advanced Photon Source. >95% 57Fe enriched powder ferropericlase((Fe0.25,Mg0.75)O) was loaded in 3-fold panoramic DACs us- ing Be gasket and c-BN insert as windows for X-ray fluorescence. The NRIXS spectra of ferroperic- lase were measured up to 94GPa across the spin transition zone. We found that the spin state of iron dramatically influences its force constants at high pressure. Low-spin iron force constants incr- ease 3 times faster than high-spin iron with pressure. Assuming linear relationship between force constants and pressure, this will lead to a fractionation of 0.147 (delta57Fe/54Fe) between ferrop- ericlase and iron metal at the core-mantle boundary conditions (4000K and 135GPa). The partition coefficient KD of Fe/Mg between bridgmanite and ferropericlase decreases with the spin transition of iron, therefore the ferropericlase would be a major iron carrier at the core-mantle boundary and fur- ther emphasize the results here.

Crystal structure of tricarbon­yl(μ-di­phenyl­phosphido-κ2 P:P)(methyl­diphenyl­silyl-κSi)bis(tri­phenyl­phosphane-κP)iron(II)platinum(0)(Fe—Pt)

PubMed Central

Mohamed, Ahmed Said; Jourdain, Isabelle; Knorr, Michael; Rousselin, Yoann; Kubicki, Marek M.

2015-01-01

The title compound, [FePt(C12H10P)(C13H13Si)(C18H15P)2(CO)3]·0.5CH2Cl2, represents an example of a phosphido-bridged heterobimetallic silyl complex; these are inter­esting precursors for the coordination and activation of small unsaturated organic mol­ecules. The μ2-PPh2 ligand spans the iron and platinum atoms, which are connected via a metal–metal bond of 2.7738 (4) Å. In contrast to most other complexes of the [(OC)3Fe(SiR 3)(μ-PR 2)PtL 2] family, where the iron-bound SiR 3 group is trans-arranged with respect to the μ2-PPh2 ligand, the SiPh2Me ligand is roughly collinear with the Fe–Pt vector [Si—Fe—Pt = 169.07 (3)°]. PMID:25878830

Kinetic Modelling and Experimental Studies for the Effects of Fe 2+ Ions on Xylan Hydrolysis with Dilute-Acid Pretreatment and Subsequent Enzymatic Hydrolysis

DOE PAGES

Wei, Hui; Chen, Xiaowen; Shekiro, Joseph; ...

2018-01-20

High-temperature (150-170 degrees C) pretreatment of lignocellulosic biomass with mineral acids is well established for xylan breakdown. Fe 2+ is known to be a cocatalyst of this process although kinetics of its action remains unknown. The present work addresses the effect of ferrous ion concentration on sugar yield and degradation product formation from corn stover for the entire two-step treatment, including the subsequent enzymatic cellulose hydrolysis. The feedstock was impregnated with 0.5% acid and 0.75 mM iron cocatalyst, which was found to be optimal in preliminary experiments. The detailed kinetic data of acid pretreatment, with and without iron, was satisfactorilymore » modelled with a four-step linear sequence of first-order irreversible reactions accounting for the formation of xylooligomers, xylose and furfural as intermediates to provide the values of Arrhenius activation energy. Based on this kinetic modelling, Fe 2+ turned out to accelerate all four reactions, with a significant alteration of the last two steps, that is, xylose degradation. Consistent with this model, the greatest xylan conversion occurred at the highest severity tested under 170 ⁰C/30 min with 0.75 mM Fe 2+, with a total of 8% xylan remaining in the pretreated solids, whereas the operational conditions leading to the highest xylose monomer yield, 63%, were milder, 150 degrees C with 0.75 mM Fe 2+ for 20 min. Furthermore, the subsequent enzymatic hydrolysis with the prior addition of 0.75 mM of iron(II) increased the glucose production to 56.3% from 46.3% in the control (iron-free acid). The detailed analysis indicated that conducting the process at lower temperatures yet long residence times benefits the yield of sugars. The above kinetic modelling results of Fe 2+ accelerating all four reactions are in line with our previous mechanistic research showing that the pretreatment likely targets multiple chemistries in plant cell wall polymer networks, including those represented by the C-O-C and C-H bonds in cellulose, resulting in enhanced sugar solubilization and digestibility.« less

Kinetic Modelling and Experimental Studies for the Effects of Fe 2+ Ions on Xylan Hydrolysis with Dilute-Acid Pretreatment and Subsequent Enzymatic Hydrolysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wei, Hui; Chen, Xiaowen; Shekiro, Joseph

High-temperature (150-170 degrees C) pretreatment of lignocellulosic biomass with mineral acids is well established for xylan breakdown. Fe 2+ is known to be a cocatalyst of this process although kinetics of its action remains unknown. The present work addresses the effect of ferrous ion concentration on sugar yield and degradation product formation from corn stover for the entire two-step treatment, including the subsequent enzymatic cellulose hydrolysis. The feedstock was impregnated with 0.5% acid and 0.75 mM iron cocatalyst, which was found to be optimal in preliminary experiments. The detailed kinetic data of acid pretreatment, with and without iron, was satisfactorilymore » modelled with a four-step linear sequence of first-order irreversible reactions accounting for the formation of xylooligomers, xylose and furfural as intermediates to provide the values of Arrhenius activation energy. Based on this kinetic modelling, Fe 2+ turned out to accelerate all four reactions, with a significant alteration of the last two steps, that is, xylose degradation. Consistent with this model, the greatest xylan conversion occurred at the highest severity tested under 170 ⁰C/30 min with 0.75 mM Fe 2+, with a total of 8% xylan remaining in the pretreated solids, whereas the operational conditions leading to the highest xylose monomer yield, 63%, were milder, 150 degrees C with 0.75 mM Fe 2+ for 20 min. Furthermore, the subsequent enzymatic hydrolysis with the prior addition of 0.75 mM of iron(II) increased the glucose production to 56.3% from 46.3% in the control (iron-free acid). The detailed analysis indicated that conducting the process at lower temperatures yet long residence times benefits the yield of sugars. The above kinetic modelling results of Fe 2+ accelerating all four reactions are in line with our previous mechanistic research showing that the pretreatment likely targets multiple chemistries in plant cell wall polymer networks, including those represented by the C-O-C and C-H bonds in cellulose, resulting in enhanced sugar solubilization and digestibility.« less

Solubility of copper in silicate melts as function of oxygen and sulfur fugacities, temperature, and silicate composition

NASA Astrophysics Data System (ADS)

Holzheid, A.; Lodders, K.

2001-06-01

The solubility of Cu in silicate melts coexisting with liquid Cu(Fe) metal and liquid Cu(Fe) sulfide was determined experimentally at oxygen fugacities ranging from 10 -9.1 to 10 -13.6 bar and sulfur fugacities ranging from 10 -2.5 to 10 -6.3 bar at 1300°C. An iron oxide-free silicate of anorthite-diopside eutectic composition and a synthetic MgO-rich basaltic silicate (FeO-bearing) were used in the partitioning experiments. In S-containing systems, some of the metal reacted to metal sulfide. The silicates in the four systems investigated (Fe-free and S-free; Fe-containing and S-free; Fe-free and S-containing; Fe-containing and S-containing) had different colors depending on the dissolved Cu species and the presence of iron and/or sulfur. Irrespective of the presence of sulfur, the solubility of Cu in the silicate increases with increasing oxygen fugacity and metal/silicate partition coefficients for Cu decrease. Increasing the temperature from 1300°C to 1514°C increases the Cu solubility (decreases the metal/silicate partition coefficient) at an oxygen fugacity 0.5 log units below the iron-wüstite (IW) equilibrium in the Fe-free, S-free and Fe-containing, S-free systems. We infer the presence of monovalent Cu + ("CuO 0.5") in the silicate melt on the basis of the solubility of Cu as function of oxygen fugacity. Experiments containing iron yield a formal valence of ˜0.5 for Cu at very low oxygen fugacities, which is not observed in Fe-free systems. The low formal valence is explained by redox reactions between iron and copper in the silicate melts. There is no evidence for sulfidic dissolution of Cu in the silicates but sulfur has indirect effects on Cu partitioning. Iron metal/silicate partition coefficients depend on oxygen fugacity and on sulfur fugacity. Sulfidic dissolution of iron and oxide-sulfide exchange reactions with Cu cause a small increase in Cu metal/silicate partition coefficients. We derive an activity coefficient (γ CuO 0.5) of 10 ± 1 for liquid CuO 0.5 at 1300°C for the silicate melts used here. A comparison with literature data shows that log γ CuO 0.5 increases in proportion to the mass percentages [CaO +(Al 2O 3)/2] in silicate melts. We recommend the following equations for Cu metal/silicate and sulfide/silicate partitioning for geochemical and cosmochemical modeling if silicate composition and the activity of Cu in the metal or sulfide is known: log D met/sil = -0.48 - 0.25 · log fO 2 - log γ Cu metal + 0.02 · [CaO + (Al 2O 3)/2; wt%] silicate logD sul/sil=+0.76-0.25 · logfO 2+0.25logfS 2-logγ CS 0.5,sulfide +0.02 · [CaO+Al 2O 3/2;wt%] silicate. The derived Cu metal/silicate and metal/sulfide partition coefficients are applied to core formation in the Earth and Mars. The observed Cu abundances in the Earth cannot be easily explained by simple core-mantle equilibrium, but the observed Cu abundances for Mars are consistent with core-mantle equilibrium at low pressure and temperatures.

Phosphate inhibits in vitro Fe3+ loading into transferrin by forming a soluble Fe(III)-phosphate complex: a potential non-transferrin bound iron species.

PubMed

Hilton, Robert J; Seare, Matthew C; Andros, N David; Kenealey, Zachary; Orozco, Catalina Matias; Webb, Michael; Watt, Richard K

2012-05-01

In chronic kidney diseases, NTBI can occur even when total iron levels in serum are low and transferrin is not saturated. We postulated that elevated serum phosphate concentrations, present in CKD patients, might disrupt Fe(3+) loading into apo-transferrin by forming Fe(III)-phosphate species. We report that phosphate competes with apo-transferrin for Fe(3+) by forming a soluble Fe(III)-phosphate complex. Once formed, the Fe(III)-phosphate complex is not a substrate for donating Fe(3+) to apo-transferrin. Phosphate (1-10mM) does not chelate Fe(III) from diferric transferrin under the conditions examined. Complexed forms of Fe(3+), such as iron nitrilotriacetic acid (Fe(3+)-NTA), and Fe(III)-citrate are not susceptible to this phosphate complexation reaction and efficiently deliver Fe(3+) to apo-transferrin in the presence of phosphate. This reaction suggests that citrate might play an important role in protecting against Fe(III), phosphate interactions in vivo. In contrast to the reactions of Fe(3+) and phosphate, the addition of Fe(2+) to a solution of apo-transferrin and phosphate lead to rapid oxidation and deposition of Fe(3+) into apo-transferrin. These in vitro data suggest that, in principle, elevated phosphate concentrations can influence the ability of apo-transferrin to bind iron, depending on the oxidation state of the iron. Copyright © 2012 Elsevier Inc. All rights reserved.

Catalase purification from rat liver with iron-chelated poly(hydroxyethyl methacrylate-N-methacryloyl-(l)-glutamic acid) cryogel discs.

PubMed

Göktürk, Ilgım; Perçin, Işık; Denizli, Adil

2016-08-17

In this study, iron-chelated poly(hydroxyethyl methacrylate-N-methacryloyl-(l)-glutamic acid) (PHEMAGA/Fe(3+)) cryogel discs were prepared. The PHEMAGA/Fe(3+) cryogel discs were characterized by elemental analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, swelling tests, and surface area measurements. The PHEMAGA/Fe(3+) cryogel discs had large pores ranging from 10 to 100 µm with a swelling degree of 9.36 g H2O/g cryogel. Effects of pH, temperature, initial catalase concentration, and flow rate on adsorption capacity of the PHEMAGA/Fe(3+) cryogel discs were investigated. Maximum catalase adsorption capacity (62.6 mg/g) was obtained at pH 7.0, 25°C, and 3 mg/ml initial catalase concentration. The PHEMAGA/Fe(3+) cryogel discs were also tested for the purification of catalase from rat liver. After tissue homogenization, purification of catalase was performed using the PHEMAGA/Fe(3+) cryogel discs and catalase was obtained with a yield of 54.34 and 16.67 purification fold.

Selective catalytic reduction of NOx with NH3 over iron-cerium-tungsten mixed oxide catalyst prepared by different methods

NASA Astrophysics Data System (ADS)

Xiong, Zhi-bo; Liu, Jing; Zhou, Fei; Liu, Dun-yu; Lu, Wei; Jin, Jing; Ding, Shi-fa

2017-06-01

A series of magnetic Fe0.85Ce0.10W0.05Oz catalysts were synthesized by three different methods(Co-precipitation(Fe0.85Ce0.10W0.05Oz-CP), Hydrothermal treatment assistant critic acid sol-gel method(Fe0.85Ce0.10W0.05Oz-HT) and Microwave irradiation assistant critic acid sol-gel method(Fe0.85Ce0.10W0.05Oz-MW)), and the catalytic activity was evaluated for selective catalytic reduction of NO with NH3. The catalyst was characterized by XRD, N2 adsorption-desorption, XPS, H2-TPR and NH3-TPD. Among the tested catalysts, Fe0.85Ce0.10W0.05Oz-MW shows the highest NOx conversion over per gram in unit time with NOx conversion of 60.8% at 350 °C under a high gas hourly space velocity of 1,200,000 ml/(g h). Different from Fe0.85Ce0.10W0.05Oz-CP catalyst, there exists a large of iron oxide crystallite(γ-Fe2O3 and α-Fe2O3) scattered in Fe0.85Ce0.10W0.05Oz catalysts prepared through hydrothermal treatment or microwave irradiation assistant critic acid sol-gel method, and higher iron atomic concentration on their surface. And Fe0.85Ce0.10W0.05Oz-MW shows higher surface absorbed oxygen concentration and better dispersion compared with Fe0.85Ce0.10W0.05Oz-HT catalyst. These features were favorable for the high catalytic performance of NO reduction with NH3 over Fe0.85Ce0.10W0.05Oz-MW catalyst.

Nanosiderite is effective to alleviate iron chlorosis in sensitive plants growing on calcareous soils

NASA Astrophysics Data System (ADS)

Sánchez-Alcalá, I.; del Campillo, M. C.; Barrón, V.; Torrent, J.

2012-04-01

Key words: siderite, iron chlorosis, calcareous soil, goethite, lepidocrocite Nanosized siderite (FeCO3) prepared by mixing FeSO4 and K2CO3 solutions [either alone or in presence of phosphate (siderites SID and SIDP, respectively)] was used in our experiments. The products of oxidation of siderite in a calcite suspension were goethite or a mixture of goethite and lepidocrocite when phosphate was present. These iron oxides were nanosized and acid NH4oxalate-soluble, which suggested they could be a good source of iron (Fe) for plants sensitive to Fe deficiency yellowing (chlorosis). To evaluate the effectiveness and long-term effects of suspensions of siderite mixed with calcareous soil to prevent Fe chlorosis, a pot growth experiment was carried out with five consecutive crops: chickpea (twice), peanut (twice) and strawberry. Suspensions of siderites (SID and SIDP) were mixed with 220 g of soil at the beginning of the experiment at rates of 0.24, 0.46, 0.93 and 1.40 g siderite (0.12, 0.22, 0.45, and 0.67 g Fe) kg-1 soil. A control (no Fe added) and a positive control (Fe-chelate as FeEDDHA before each cropping) were included. The concentration of chlorophyll in the youngest leaves was estimated three times for chickpea and peanut, and five times for strawberry via the SPAD value (SPAD 502 portable chlorophyll meter). The SPAD for the control plants was lower than that for Fe-fertilized plants. For all crops, times and siderite types, SPAD tended to systematically increase with increasing siderite dose, and SID and SIDP had similar effectiveness. At harvest, the SPAD for the plants fertilized with the highest siderite dose (1.40 g kg-1) did not differ significantly from that for FeEDDHA-fertilized plants. Our results suggest in summary that siderite is effective in preventing iron chlorosis and has a long-lasting effect, as the likely result of the high specific surface and high solubility of the crystalline Fe oxides resulting from its oxidation. Futhermore, siderite is readily prepared in the field, not easily leached from the soil and environmentally safe, thus constituting a good Fe fertilizer. Acknowledgments: This work was funded by the Spain's Ministerio de Ciencia e Innovación and the European Regional Development Fund (Projects AGL 2005-06691-C02-01 and AGL 2008-05053-C02-02).

Investigations on Bi{sub 25}FeO{sub 40} powders synthesized by hydrothermal and combustion-like processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Köferstein, Roberto, E-mail: roberto.koeferstein@chemie.uni-halle.de; Buttlar, Toni; Ebbinghaus, Stefan G.

2014-09-15

The syntheses of phase-pure and stoichiometric iron sillenite (Bi{sub 25}FeO{sub 40}) powders by a hydrothermal (at ambient pressure) and a combustion-like process are described. Phase-pure samples were obtained in the hydrothermal reaction at 100 °C (1), whereas the combustion-like process leads to pure Bi{sub 25}FeO{sub 40} after calcination at 750 °C for 2 h (2a). The activation energy of the crystallite growth process of hydrothermally synthesized Bi{sub 25}FeO{sub 40} was calculated as 48(9) kJ mol{sup −1}. The peritectic point was determined as 797(1) °C. The optical band gaps of the samples are between 2.70(7) eV and 2.81(6) eV. Temperature andmore » field-depending magnetization measurements (5−300 K) show a paramagnetic behaviour with a Curie constant of 55.66×10{sup −6} m{sup 3} K mol{sup −1} for sample 1 and C=57.82×10{sup −6} m{sup 3} K mol{sup −1} for sample 2a resulting in magnetic moments of µ{sub mag}=5.95(8) µ{sub B} mol{sup −1} and µ{sub mag}=6.07(4) µ{sub B} mol{sup −1}. The influence of amorphous iron-oxide as a result of non-stoichiometric Bi/Fe ratios in hydrothermal syntheses on the magnetic behaviour was additionally investigated. - Graphical abstract: Bi{sub 25}FeO{sub 40} powders were prepared by a hydrothermal method and a combustion process. The optical band gaps and the peritectic point were determined. The magnetic behaviour was investigated depending on the synthesis and the initial Bi/Fe ratios. The influence of amorphous iron-oxide on the magnetic properties was examined. - Highlights: • Two simple syntheses routes for stoichiometric Bi{sub 25}FeO{sub 40} powders using starch as polymerization agent. • Monitoring the phase evolution and crystallite growth kinetics during the syntheses. • Determination of the optical band gap and melting point. • Investigations of the magnetic behaviour of Bi{sub 25}FeO{sub 40} powders. • Influence of amorphous iron oxide and a non-stoichiometric Bi/Fe ratio on the magnetic behaviour.« less

Ferrous and ferric ion generation during iron electrocoagulation.

PubMed

Lakshmanan, Divagar; Clifford, Dennis A; Samanta, Gautam

2009-05-15

Our research on arsenate removal by iron electrocoagulation (EC) produced highly variable results, which appeared to be due to Fe2+ generation without subsequent oxidation to Fe3+. Because the environmental technology literature is contradictory with regard to the generation of ferric or ferrous ions during EC, the objective of this research was to establish the iron species generated during EC with iron anodes. Experimental results demonstrated that Fe2+, not Fe3+, was produced at the iron anode. Theoretical current efficiency was attained based on Fe2+ production with a clean iron rod, regardless of current, dissolved-oxygen (DO) level, or pH (6.5-8.5). The Fe2+ remaining after generation and mixing decreased with increasing pH and DO concentration due to rapid oxidation to Fe3+. At pH 8.5, Fe2+ was completely oxidized, which resulted in the desired Fe(OH)3(s)/ FeOOH(s), whereas, at pH 6.5 and 7.5, incomplete oxidation was observed, resulting in a mixture of soluble Fe2+ and insoluble Fe(OH)3(s)/FeOOH(s). When compared with Fe2+ chemical coagulation, a transient pH increase during EC led to faster Fe2+ oxidation. In summary, for EC in the pH 6.5-7.5 range and at low DO conditions, there is a likelihood of soluble Fe2+ species passing through a subsequentfiltration process resulting in secondary contamination and inefficient contaminant removals.

Bifunctional catalyst of graphite-encapsulated iron compound nanoparticle for magnetic carbon nanotubes growth by chemical vapor deposition

NASA Astrophysics Data System (ADS)

Saraswati, Teguh Endah; Prasiwi, Oktaviana Dewi Indah; Masykur, Abu; Anwar, Miftahul

2017-01-01

The carbon nanotube has widely taken great attractive in carbon nanomaterial research and application. One of its preparation methods is catalytic chemical vapor deposition (CCVD) using catalyst i.e. iron, nickel, etc. Generally, except the catalyst, carbon source gasses as the precursor are still required. Here, we report the use of the bifunctional material of Fe3O4/C which has an incorporated core/shell structures of carbon-encapsulated iron compound nanoparticles. The bifunctional catalyst was prepared by submerged arc discharge that simply performed using carbon and carbon/iron oxide electrodes in ethanol 50%. The prepared material was then used as a catalyst in thermal chemical vapor deposition at 800°C flown with ethanol vapor as the primer carbon source in a low-pressure condition. This catalyst might play a dual role as a catalyst and secondary carbon source for growing carbon nanotubes at the time. The synthesized products were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis. The successful formation of carbon nanotubes was assigned by the shifted X-ray diffracted peak of carbon C(002), the iron oxides of Fe3O4 and γ-Fe2O3, and the other peaks which were highly considered to the other carbon allotropes with sp2 hybridization structures. The other assignment was studied by electron microscopy which successfully observed the presence of single-wall carbon nanotubes. In addition, the as-prepared carbon nanotubes have a magnetic property which was induced by the remaining of metal catalyst inside the CNT.

Iron K-edge X-ray absorption near-edge structure spectroscopy of aerodynamically levitated silicate melts and glasses

DOE PAGES

Alderman, O. L. G.; Wilding, M. C.; Tamalonis, A.; ...

2017-01-26

Here, the local structure about Fe(II) and Fe(III) in silicate melts was investigated in-situ using iron K-edge X-ray absorption near-edge structure (XANES) spectroscopy. An aerodynamic levitation and laser heating system was used to allow access to high temperatures without contamination, and was combined with a chamber and gas mixing system to allow the iron oxidation state, Fe 3+/ΣFe, to be varied by systematic control of the atmospheric oxygen fugacity. Eleven alkali-free, mostly iron-rich and depolymerized base compositions were chosen for the experiments, including pure oxide FeO, olivines (Fe,Mg) 2SiO 4, pyroxenes (Fe,Mg)SiO 3, calcic FeO-CaSiO 3, and a calcium aluminosilicatemore » composition, where total iron content is denoted by FeO for convenience. Melt temperatures varied between 1410 and 2160 K and oxygen fugacities between FMQ – 2.3(3) to FMQ + 9.1(3) log units (uncertainties in parentheses) relative to the fayalite-magnetite-β-quartz (FMQ) buffer.« less

Understanding the Interaction between a Steel Microstructure and Hydrogen

PubMed Central

Depover, Tom; Laureys, Aurélie; Wallaert, Elien

2018-01-01

The present work provides an overview of the work on the interaction between hydrogen (H) and the steel’s microstructure. Different techniques are used to evaluate the H-induced damage phenomena. The impact of H charging on multiphase high-strength steels, i.e., high-strength low-alloy (HSLA), transformation-induced plasticity (TRIP) and dual phase (DP) is first studied. The highest hydrogen embrittlement resistance is obtained for HSLA steel due to the presence of Ti- and Nb-based precipitates. Generic Fe-C lab-cast alloys consisting of a single phase, i.e., ferrite, bainite, pearlite or martensite, and with carbon contents of approximately 0, 0.2 and 0.4 wt %, are further considered to simplify the microstructure. Finally, the addition of carbides is investigated in lab-cast Fe-C-X alloys by adding a ternary carbide forming element to the Fe-C alloys. To understand the H/material interaction, a comparison of the available H trapping sites, the H pick-up level and the H diffusivity with the H-induced mechanical degradation or H-induced cracking is correlated with a thorough microstructural analysis. PMID:29710803

Fe 3 O 4 Nanoparticles Anchored on Carbon Serve the Dual Role of Catalyst and Magnetically Recoverable Entity in the Aerobic Oxidation of Alcohols

DOE Office of Scientific and Technical Information (OSTI.GOV)

Geng, Longlong; Zheng, Bin; Wang, Xiang

2016-01-13

Carbon supported γ-Fe2O3 nanoparticle (γ-Fe2O3/C) possessing both superparamagnetism and activating molecular oxygen properties were prepared by an ammonia-assisted precipitation method. It could catalyze the selective oxidation of various benzyl alcohols with air as oxidant source, and could be easily recycled with an external magnet separation. The correlation between the intrinsic properties of γ-Fe2O3 nanoparticles and the catalytic performance was investigated with a series of characterizations. It shows that the oxidation state of γ-Fe2O3 nanoparticles were facile to be changed, which should be related to its inverse spinel type crystal structure with vacant cation sites. These γ-Fe2O3 nanoparticles should be themore » active sites and responsible for the high activity of γ-Fe2O3/C in the air oxidation of alcohols. The formation of γ-Fe2O3 nanoparticle was controlled by precipitation agent and carbon support. Using ammonia ethanol solution as precipitation agent, the hydrolysis rate of iron species could be decreased. The surface functional groups of carbon support could act as chelating sites for iron species, controlling the nucleation and growth of the γ-Fe2O3 nanoparticles in the preparation process. Dr. Xiang Wang gratefully acknowledges the US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division for the support of this work.« less

Hydrogen production from steam reforming of ethylene glycol over iron loaded on MgO

NASA Astrophysics Data System (ADS)

Chen, Mingqiang; Wang, Yishuang; Liang, Tian; Yang, Jie; Yang, Zhonglian

2017-01-01

In this study, a series of Fe-based catalysts loaded on MgO were prepared by a precipitation technique. And they were tested in hydrogen production from steam reforming of ethylene glycol (SRE), which was a representative model compound of fast bio-oil. The catalysts were characterized by XRD, SEM and H2-TPR analysis. The results showed that the crystalline phases of catalysts contained Fe2O3 (Hematite), Fe3O4 (Magnetite), Fe2MgO4 (iron magnesium oxide) and MgO, and morphology of MgO was changed from the rugby-ball like particles to spherical particles with the addition of Fe. In addition, the catalytic test results indicated that the 18%Fe/MgO catalyst exhibited the highest ethylene glycol conversion (˜99.8%) and H2 molar percent (˜77%) during at the following conditions: H2O/C molar ratio is 5˜7, the feeding rate is 14 mL/h and the reaction temperature at 600˜650°C. Furthermore, the 18%Fe/MgO catalyst can keep outstanding stability during SRE for 12 h.

Copper(I)- and copper(0)-promoted homocoupling and homocoupling-hydrodehalogenation reactions of dihalogenoclathrochelate precursors for C-C conjugated iron(II) bis-cage complexes.

PubMed

Varzatskii, Oleg A; Shul'ga, Sergey V; Belov, Alexander S; Novikov, Valentin V; Dolganov, Alexander V; Vologzhanina, Anna V; Voloshin, Yan Z

2014-12-28

Iron(II) dibromo- and diiodoclathrochelates undergo copper(I)-promoted reductive homocoupling in HMPA at 70-80 °C leading to C-C conjugated dibromo- and diiodo-bis-clathrochelates in high yields. Under the same conditions, their dichloroclathrochelate analog does not undergo the same homocoupling reaction, so the target dichloro-bis-cage product was obtained in high yield via dimerization of its heterodihalogenide iodochloromonomacrobicyclic precursor. The use of NMP as a solvent at 120-140 °C gave the mixture of bis-clathrochelates resulting from a tandem homocoupling-hydrodehalogenation reaction: the initial acetonitrile copper(I) solvato-complex at a high temperature underwent re-solvatation and disproportionation leading to Cu(II) ions and nano-copper, which promoted the hydrodehalogenation process even at room temperature. The most probable pathway of this reaction in situ includes hydrodehalogenation of the already formed dihalogeno-bis-clathrochelate via the formation of reduced anion radical intermediates. As a result, chemical transformations of the iron(II) dihalogenoclathrochelates in the presence of an acetonitrile copper(I) solvato-complex were found to depend both on the nature of halogen atoms in their ribbed chelate fragments and on reaction conditions (i.e. solvent and temperature). The C-C conjugated iron(II) dihalogeno-bis-clathrochelates easily undergo nucleophilic substitution with various N,S-nucleophiles giving ribbed-functionalized bis-cage species. These iron(II) complexes were characterized by elemental analysis, MALDI-TOF mass spectrometry, IR, UV-Vis, (1)H and (13)C NMR spectroscopy, and by X-ray diffraction; their electrochemical properties were studied by cyclic voltammetry. The isomeric shift values in (57)Fe Mössbauer spectra of such cage compounds allowed identifying them as low-spin iron(II) complexes, while those of the quadrupole splitting are the evidence for a significant TP distortion of their FeN6-coordination polyhedra. As follows from CV data, the C-C conjugated iron(II) bis-clathrochelates undergo stepwise electrochemical reduction and oxidation giving mixed-valence Fe(II)Fe(I) and Fe(II)Fe(III) bis-cage intermediates.

Effect of Heat Treatment Parameters on the Characteristics of Thin Wall Austempered Ductile Iron Casting

NASA Astrophysics Data System (ADS)

Upadhyaya, Rajat; Singh, K. K.; Kumar, Rajeev

2018-03-01

The technology of thin parts is necessary steps to designers for energy consuming equipment to choose accurate material based on material properties. Here austempering treatment process was utilized to acquire thin wall austempered ductile iron castings. The plate thickness (2-5) mm were austenitized at 900 °C for, 30 minutes took after by holding at 350°C, 400°C and 450°C inoculated by Ce-Ca-Al-S-O-FeSi,Zr-Mn-Ca-Al-Ba-FeSi and Sr-Al-Ca-FeSi at 0.2wt%,0.4wt% and 0.6wt% for 2,5 and 10 minutes for every temperature.The austempered samples are comparatively harder than the as-cast ductile iron plates. The micro hardness(HV20) also decreases with increase in austempering temperature for a given austempering time for thinner plates and also the micro hardness(HV20) is more for the samples treated at 350°C than those treated at 400°C and 450°C at 0.4wt% for a given austempering time. The yield strength and ultimate tensile strength of 2 mm thin wall austempered ductile iron are higher and ductility and impact strength are lower than that of as-cast 2 mm thin plate ductile iron inoculated by Ce-Ca-Al-S-O-FeSi compare to Zr-Mn-Ca-Al-Ba-FeSi and Sr-Al-Ca-FeSi at 0.4wt%. This may be attributed to the change in the structure change from ferrite-pearlite to austenite-bainite.

Starbon/High-Amylose Corn Starch-Supported N-Heterocyclic Carbene-Iron(III) Catalyst for Conversion of Fructose into 5-Hydroxymethylfurfural.

PubMed

Matharu, Avtar S; Ahmed, Suleiman; Almonthery, Badriya; Macquarrie, Duncan J; Lee, Yoon-Sik; Kim, Yohan

2018-02-22

Iron-N-heterocyclic carbene complexes (Fe-NHCs) have come to prominence because of their applicability in diverse catalytic reactions, ranging from C-C cross-coupling and C-X bond formation to substitution, reduction, polymerization, and dehydration reactions. The detailed synthesis, characterization, and application of novel heterogeneous Fe-NHC catalysts immobilized on mesoporous expanded high-amylose corn starch (HACS) and Starbon 350 (S350) for facile fructose conversion into 5-hydroxymethylfurfural (HMF) is reported. Both catalyst types showed good performance for the dehydration of fructose to HMF when the reaction was tested at 100 °C with varying time (10 min, 20 min, 0.5 h, 1 h, 3 h and 6 h). For Fe-NHC/S350, the highest HMF yield was 81.7 % (t=0.5 h), with a TOF of 169 h -1 , fructose conversion of 95 %, and HMF selectivity of 85.7 %, whereas for Fe-NHC/expanded HACS, the highest yield was 86 % (t=0.5 h), with a TOF of 206 h -1 , fructose conversion of 87 %, and HMF selectivity of 99 %. Iron loadings of 0.26 and 0.30 mmol g -1 were achieved for Fe-NHC/expanded starch and Fe-NHC/S350, respectively. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Geochemical and mineralogical composition of bog iron ore as a resource for prehistoric iron production - A case study of the Widawa catchment area in Eastern Silesia, Poland

NASA Astrophysics Data System (ADS)

Thelemann, Michael; Bebermeier, Wiebke; Hoelzmann, Philipp

2016-04-01

Spreading from the Near East in the declining Bronze Age from the 2nd millennium BCE onwards, the technique of iron smelting reached Eastern Silesia, Poland, in approximately the 2nd century BCE (pre-Roman Iron Age). At this time the region of the Widawa catchment area was inhabited by the Przeworsk culture. While the older moraine landscape of the study area lacks ores from geological rock formations, bog iron ores were relatively widespread and, due to their comparatively easy accessibility, were commonly exploited for early iron production. In this poster the mineralogical and elemental composition of local bog iron ore deposits and iron slag finds, as a by-product of the smelting process, are investigated. The crystalline mineralogical composition of local bog iron ores is dominated by quartz (SiO2) and goethite (α FeO(OH)), in contrast to slag samples in which fayalite (Fe2SiO4), wüstite (FeO) and quartz, with traces of goethite, represent the main minerals. Ores and slags are both characterized by notable hematite (Fe2O3), magnetite (Fe3O4) and maghemite (γ-Fe2O3) contents. Analyzed bog iron ore samples show iron contents of up to 64.9 mass% Fe2O3 (45.4 mass% Fe), whereas the iron contents of bloomery slags vary between 48.7 and 72.0 mass% FeO (37.9 and 56.0 mass% Fe). A principal component analysis of the element contents, which were quantified by portable energy-dispersive X-ray fluorescence spectrometry (p-ED-XRF), indicates local variations in the elemental composition. Our results show that bog iron ores are relatively widely distributed with spatially varying iron contents along the Widawa floodplain but present-day formation conditions (e.g. different ground-water levels) are negatively affected by modern land-use practices, such as agriculture and melioration measures.

Electrodeposition and magnetic characterization of iron and iron-silicon alloys from the ionic liquid 1-butyl-1-methylpyrrolidinium trifluoromethylsulfonate.

PubMed

Giridhar, Pulletikurthi; Weidenfeller, Bernd; El Abedin, Sherif Zein; Endres, Frank

2014-11-10

The electrodeposition of soft magnetic iron and iron-silicon alloys for magnetic measurements is presented. The preparation of these materials in 1-butyl-1-methylpyrrolidinium trifluoromethylsulfonate, [Py1,4]TfO, at 100 °C with FeCl2 and FeCl2 +SiCl4 was studied by using cyclic voltammetry. Constant-potential electrolysis was carried out to deposit either Fe or FeSi, and deposits of approximately 10 μm thicknesses were obtained. By using scanning electron microscopy and X-ray diffraction, the microstructure and crystallinity of the deposits were investigated. Grain sizes in the nanometer regime (50-80 nm) were found and the presence of iron-silicon alloys was verified. Frequency-dependent magnetic polarizations, coercive forces, and power losses of some deposits were determined by using a digital hysteresis recorder. Corresponding to the small grain sizes, the coercive forces are around 950-1150 A m(-1) and the power losses were at 6000 J m(-3), which is much higher than in commercial Fe(3.2 wt %)Si electrical steel. Below a polarization of 1.8 T, the power losses are mainly caused by domain wall movements and, above 1.8 T, by rotation of magnetic moments as well as domain wall annihilation and recreation. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ni: Fe2O3, Mg: Fe2O3 and Fe2O3 thin films gas sensor application

NASA Astrophysics Data System (ADS)

Saritas, Sevda; Kundakci, Mutlu; Coban, Omer; Tuzemen, Sebahattin; Yildirim, Muhammet

2018-07-01

Iron oxide is a widely used sensitive material for gas sensor applications. They have fascinated much attention in the field of gas sensing and detecting under atmospheric conditions and at 200 °C temperature due to their low cost in production; simplicity and fast of their use; large number of detectable gases. Iron oxide gas sensors constitute investigated for hazardous gases used in various fields. The morphological structure (particle size, pore size, etc.), optical, magnetic and electrical properties of Ni:Fe2O3, Mg:Fe2O3 and Fe2O3 thin films which grown by Spray pyrolysis (SP) have been investigated. XRD, Raman and AFM techniques have been used for structural analysis. AFM measurements have been provided very useful information about surface topography. I-V (Van der Pauw) technique has been used for response of gas sensor. These devices offer a wide variety of advantages over traditional analytical instruments such as low cost, short response time, easy manufacturing, and small size.

Structure of the catalytic sites in Fe/N/C-catalysts for O2-reduction in PEM fuel cells.

PubMed

Kramm, Ulrike I; Herranz, Juan; Larouche, Nicholas; Arruda, Thomas M; Lefèvre, Michel; Jaouen, Frédéric; Bogdanoff, Peter; Fiechter, Sebastian; Abs-Wurmbach, Irmgard; Mukerjee, Sanjeev; Dodelet, Jean-Pol

2012-09-07

Fe-based catalytic sites for the reduction of oxygen in acidic medium have been identified by (57)Fe Mössbauer spectroscopy of Fe/N/C catalysts containing 0.03 to 1.55 wt% Fe, which were prepared by impregnation of iron acetate on carbon black followed by heat-treatment in NH(3) at 950 °C. Four different Fe-species were detected at all iron concentrations: three doublets assigned to molecular FeN(4)-like sites with their ferrous ions in a low (D1), intermediate (D2) or high (D3) spin state, and two other doublets assigned to a single Fe-species (D4 and D5) consisting of surface oxidized nitride nanoparticles (Fe(x)N, with x≤ 2.1). A fifth Fe-species appears only in those catalysts with Fe-contents ≥0.27 wt%. It is characterized by a very broad singlet, which has been assigned to incomplete FeN(4)-like sites that quickly dissolve in contact with an acid. Among the five Fe-species identified in these catalysts, only D1 and D3 display catalytic activity for the oxygen reduction reaction (ORR) in the acid medium, with D3 featuring a composite structure with a protonated neighbour basic nitrogen and being by far the most active species, with an estimated turn over frequency for the ORR of 11.4 e(-) per site per s at 0.8 V vs. RHE. Moreover, all D1 sites and between 1/2 and 2/3 of the D3 sites are acid-resistant. A scheme for the mechanism of site formation upon heat-treatment is also proposed. This identification of the ORR-active sites in these catalysts is of crucial importance to design strategies to improve the catalytic activity and stability of these materials.

COMPARATIVE ASSESSMENT OF THE COMPOSITION AND CHARGE STATE OF NITROGENASE FeMo-COFACTOR

PubMed Central

Harris, Travis V.; Szilagyi, Robert K.

2011-01-01

A significant limitation in our understanding of the molecular mechanism of biological nitrogen fixation is the uncertain composition of the FeMo-cofactor (FeMo-co) of nitrogenase. In this study we present a systematic, density functional theory-based evaluation of spin coupling schemes, iron oxidation states, ligand protonation states, and interstitial ligand composition using a wide range of experimental criteria. The employed functionals and basis sets were validated with molecular orbital information from X-ray absorption spectroscopic data of relevant iron-sulfur clusters. Independently from the employed level of theory, the electronic structure with the greatest number of antiferromagnetic interactions corresponds to the lowest energy state for a given charge and oxidation state distribution of the iron ions. The relative spin state energies of resting and oxidized FeMo-co already allowed the exclusion of certain iron oxidation state distributions and interstitial ligand compositions. Geometry optimized FeMo-co structures of several models further eliminated additional states and compositions, while reduction potentials indicated a strong preference for the most likely charge state of FeMo-co. Mössbauer and ENDOR parameter calculations were found to be remarkably dependent on the employed training set, density functional and basis set. Overall, we found that a more oxidized [MoIV-2FeII-5FeIII-9S2−-C4−] composition with a hydroxyl-protonated homocitrate ligand satisfies all of the available experimental criteria, and is thus favored over the currently preferred composition of [MoIV-4FeII-3FeIII-9S2−-N3−] from the literature. PMID:21545160

Experimental and theoretical identification of the Fe(vii) oxidation state in FeO4.

PubMed

Lu, Jun-Bo; Jian, Jiwen; Huang, Wei; Lin, Hailu; Li, Jun; Zhou, Mingfei

2016-11-16

The experimentally known highest oxidation state of iron has been determined to be Fe(vi) so far. Here we report a combined matrix-isolation infrared spectroscopic and theoretical study of two interconvertible iron oxide anions: a dioxoiron peroxide complex [(η 2 -O 2 )FeO 2 ] - with a C 2v -structure and a tetroxide FeO 4 - with a D 2d tetrahedral structure, which are formed by co-condensation of laser-ablated iron atoms and electrons with O 2 /Ar mixtures at 4 K. Quantum chemistry theoretical studies indicate that the Jahn-Teller distorted tetroxide FeO 4 - anion is a d 1 species with hereto the highest iron formal oxidation state Fe(vii).

Growth of boron doped hydrogenated nanocrystalline cubic silicon carbide (3C-SiC) films by Hot Wire-CVD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pawbake, Amit; Tata Institute of Fundamental Research, Colaba, Mumbai 400 005; Mayabadi, Azam

Highlights: • Boron doped nc-3C-SiC films prepared by HW-CVD using SiH{sub 4}/CH{sub 4}/B{sub 2}H{sub 6}. • 3C-Si-C films have preferred orientation in (1 1 1) direction. • Introduction of boron into SiC matrix retard the crystallanity in the film structure. • Film large number of SiC nanocrystallites embedded in the a-Si matrix. • Band gap values, E{sub Tauc} and E{sub 04} (E{sub 04} > E{sub Tauc}) decreases with increase in B{sub 2}H{sub 6} flow rate. - Abstract: Boron doped nanocrystalline cubic silicon carbide (3C-SiC) films have been prepared by HW-CVD using silane (SiH{sub 4})/methane (CH{sub 4})/diborane (B{sub 2}H{sub 6}) gasmore » mixture. The influence of boron doping on structural, optical, morphological and electrical properties have been investigated. The formation of 3C-SiC films have been confirmed by low angle XRD, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infra-red (FTIR) spectroscopy and high resolution-transmission electron microscopy (HR-TEM) analysis whereas effective boron doping in nc-3C-SiC have been confirmed by conductivity, charge carrier activation energy, and Hall measurements. Raman spectroscopy and HR-TEM analysis revealed that introduction of boron into the SiC matrix retards the crystallanity in the film structure. The field emission scanning electron microscopy (FE-SEM) and non contact atomic force microscopy (NC-AFM) results signify that 3C-SiC film contain well resolved, large number of silicon carbide (SiC) nanocrystallites embedded in the a-Si matrix having rms surface roughness ∼1.64 nm. Hydrogen content in doped films are found smaller than that of un-doped films. Optical band gap values, E{sub Tauc} and E{sub 04} decreases with increase in B{sub 2}H{sub 6} flow rate.« less

Engineering of air-stable Fe/C/Pd composite nanoparticles for environmental remediation applications

NASA Astrophysics Data System (ADS)

Haham, Hai; Grinblat, Judith; Sougrati, Moulay-Tahar; Stievano, Lorenzo; Margel, Shlomo

2015-09-01

The present manuscript presents a convenient method for the synthesis of iron/carbon (Fe/C) nanoparticles (NPs) coated with much smaller Pd NPs for the removal of halogenated organic pollutants. For this purpose, iron oxide/polyvinylpyrrolidone (IO/PVP) NPs were first prepared by the thermal decomposition of ferrocene mixed with PVP at 350 °C under an inert atmosphere. IO,Fe/C and Fe/C NPs coated with graphitic and amorphous carbon layers were then produced by annealing the IO/PVP NPs at 500 and 600 °C, respectively, under an inert atmosphere. The effect of the annealing temperature on the chemical composition, shape, crystallinity, surface area and magnetic properties of the IO/PVP, IO,Fe/C and Fe/C NPs has been elucidated. Air-stable Fe/C/Pd NPs were produced by mixing the precursor palladium acetate with the air-stable Fe/C NPs in ethanol. The obtained Fe/C/Pd NPs demonstrated significantly higher environmental activity than the Fe/C NPs on eosin Y, a model halogenated organic pollutant. The environmental activity of the Fe/C/Pd NPs also increased with their increasing Pd content.

Nature of impurities in fertilizers containing EDDHMA/Fe(3+), EDDHSA/Fe(3+), and EDDCHA/Fe(3+) chelates.

PubMed

Alvarez-Fernández, Ana; Cremonini, Mauro A; Sierra, Miguel A; Placucci, Giuseppe; Lucena, Juan J

2002-01-16

Iron chelates derived from ethylenediaminedi(o-hydroxyphenylacetic) acid (EDDHA), ethylenediaminedi(o-hydroxy-p-methylphenylacetic) acid (EDDHMA), ethylenediaminedi(2-hydroxy-5-sulfophenylacetic) acid (EDDHSA), and ethylenediaminedi(5-carboxy-2-hydroxyphenylacetic) acid (EDDCHA) are remarkably efficient in correcting iron chlorosis in plants growing in alkaline soils. This work reports the determination of impurities in commercial samples of fertilizers containing EDDHMA/Fe(3+), EDDHSA/Fe(3+), and EDDCHA/Fe(3+). The active components (EDDHMA/Fe(3+), EDDHSA/Fe(3+), and EDDCHA/Fe(3+)) were separated easily from other compounds present in the fertilizers by HPLC. Comparison of the retention times and the UV-visible spectra of the peaks obtained from commercial EDDHSA/Fe(3+) and EDDCHA/Fe(3+) samples with those of standard solutions showed that unreacted starting materials (p-hydroxybenzenesulfonic acid and p-hydroxybenzoic acid, respectively) were always present in the commercial products. 1D and 2D NMR experiments showed that commercial fertilizers based on EDDHMA/Fe(3+) contained impurities having structures tentatively assigned to iron chelates of two isomers of EDDHMA. These findings suggest that current production processes of iron chelates used in agriculture need to be improved.

The Bradyrhizobium japonicum Ferrous Iron Transporter FeoAB Is Required for Ferric Iron Utilization in Free Living Aerobic Cells and for Symbiosis.

PubMed

Sankari, Siva; O'Brian, Mark R

2016-07-22

The bacterium Bradyrhizobium japonicum USDA110 does not synthesize siderophores for iron utilization in aerobic environments, and the mechanism of iron uptake within symbiotic soybean root nodules is unknown. An mbfA bfr double mutant defective in iron export and storage activities cannot grow aerobically in very high iron medium. Here, we found that this phenotype was suppressed by loss of function mutations in the feoAB operon encoding ferrous (Fe(2+)) iron uptake proteins. Expression of the feoAB operon genes was elevated under iron limitation, but mutants defective in either gene were unable to grow aerobically over a wide external ferric (Fe(3+)) iron (FeCl3) concentration range. Thus, FeoAB accommodates iron acquisition under iron limited and iron replete conditions. Incorporation of radiolabel from either (55)Fe(2+) or (59)Fe(3+) into cells was severely defective in the feoA and feoB strains, suggesting Fe(3+) reduction to Fe(2+) prior to traversal across the cytoplasmic membrane by FeoAB. The feoA or feoB deletion strains elicited small, ineffective nodules on soybean roots, containing few bacteria and lacking nitrogen fixation activity. A feoA(E40K) mutant contained partial iron uptake activity in culture that supported normal growth and established an effective symbiosis. The feoA(E40K) strain had partial iron uptake activity in situ within nodules and in isolated cells, indicating that FeoAB is the iron transporter in symbiosis. We conclude that FeoAB supports iron acquisition under limited conditions of soil and in the iron-rich environment of a symbiotic nodule. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Selective Removal of Iron from Low-Grade Ti Ore by Reacting with Calcium Chloride

NASA Astrophysics Data System (ADS)

Kang, Jungshin; Okabe, Toru H.

2017-02-01

Recently, titanium metal production by molten salt electrolysis using CaCl2 as molten salt and TiO2 or rutile (94 to 96 pct TiO2) as feedstock has been drawing attention. However, when a low-grade Ti ore (mainly FeTiO3) is used as feedstock, removal of iron (Fe) from the ore is indispensable. In this study, the influence of reaction temperature, reaction time, particle size of the ore, and source country for the ore on the removal of iron by selective chlorination using CaCl2 was assessed. Experimental results showed that the mass percent of iron in the ore decreased from 49.7 to 1.79 pct under certain conditions by selective removal of iron as FeCl2. As a result, high-grade CaTiO3 was produced when the ore particles smaller than 74 µm reacted with CaCl2 at 1240 K (967 °C) for 8 to 10 hours. Therefore, this study demonstrates that the removal of iron from the ore is feasible through the selective chlorination process using CaCl2 by optimizing the variables.

An XPS study of the adherence of refractory carbide, silicide, and boride RF-sputtered wear-resistant coatings. [X-ray Photoelectron Spectroscopy of steel surfaces

NASA Technical Reports Server (NTRS)

Brainard, W. A.; Wheeler, D. R.

1978-01-01

Radio frequency sputtering was used to deposit refractory carbide, silicide, and boride coatings on 440-C steel substrates. Both sputter etched and pre-oxidized substrates were used and the films were deposited with and without a substrate bias. The composition of the coatings was determined as a function of depth by X-ray photoelectron spectroscopy combined with argon ion etching. Friction and wear tests were conducted to evaluate coating adherence. In the interfacial region there was evidence that bias may produce a graded interface for some compounds. Biasing, while generally improving bulk film stoichiometry, can adversely affect adherence by removing interfacial oxide layers. Oxides of all film constituents except carbon and iron were present in all cases but the iron oxide coverage was only complete on the preoxidized substrates. The film and iron oxides were mixed in the MoSi2 and Mo2C films but layered in the Mo2B5 films. In the case of mixed oxides, preoxidation enhanced film adherence. In the layered case it did not.

Friction and wear of radiofrequency-sputtered borides, silicides, and carbides

NASA Technical Reports Server (NTRS)

Brainard, W. A.; Wheeler, D. R.

1978-01-01

The friction and wear properties of several refractory compound coatings were examined. These compounds were applied to 440 C bearing steel surfaces by radiofrequency (RF) sputtering. The refractory compounds were the titanium and molybdenum borides, the titanium and molybdenum silicides, and the titanium, molybdenum, and boron carbides. Friction testing was done with a pin-on-disk wear apparatus at loads from 0.1 to 5.0 newtons. Generally, the best wear properties were obtained when the coatings were bias sputtered onto 440 C disks that had been preoxidized. Adherence was improved because of the better bonding of the coatings to the iron oxide formed during preoxidation. As a class the carbides provided wear protection to the highest loads. Titanium boride coatings provided low friction and good wear properties to moderate loads.

An empirical approach to predicting long term behavior of metal particle based recording media

NASA Technical Reports Server (NTRS)

Hadad, Allan S.

1992-01-01

Alpha iron particles used for magnetic recording are prepared through a series of dehydration and reduction steps of alpha-Fe2O3-H2O resulting in acicular, polycrystalline, body centered cubic (bcc) alpha-Fe particles that are single magnetic domains. Since fine iron particles are pyrophoric by nature, stabilization processes had to be developed in order for iron particles to be considered as a viable recording medium for long term archival (i.e., 25+ years) information storage. The primary means of establishing stability is through passivation or controlled oxidation of the iron particle's surface. A study was undertaken to examine the degradation in magnetic properties as a function of both temperature and humidity on silicon-containing iron particles between 50-120 C and 3-89 percent relative humidity. The methodology to which experimental data was collected and analyzed leading to predictive capability is discussed.

Synthesis, chemical and biological studies on new Fe(3+)-glycosilated beta-diketo complexes for the treatment of iron deficiency.

PubMed

Arezzini, Beatrice; Ferrali, Marco; Ferrari, Erika; Frassineti, Chiara; Lazzari, Sandra; Marverti, Gaetano; Spagnolo, Ferdinando; Saladini, Monica

2008-11-01

A simple synthetic pathway to obtain glycosilated beta-diketo derivatives is proposed. These compounds show a good iron(III) affinity therefore we may suggest the use of their Fe(3+)-complexes as oral iron supplements in the treatment of anaemia. The glycosilated compounds (6-GlcH, 6-GlcOH and 6-GlcOCH(3)) are characterized by means of spectroscopic (UV, (1)H and (13)C NMR) and potentiometric techniques; they have a good water solubility, are kinetically stable in physiological condition (t(1/2)>100h) and show a low cytotoxicity also in high concentrations (IC(50)>400 microM). They are able to bind Fe(3+) ion in acid condition (pH approximately 2) forming complex species thermodynamically more stable than those of other ligands commonly used in the treatment of iron deficiency. The iron complexes show also a good kinetic stability both in acidic and physiological pH and have a good lypophilicity (logP>-0.7) that suggests an efficient gastrointestinal absorption in view of their possible use in oral therapy. In addition they demonstrate a poor affinity for competitive biological metal ion such as Ca(2+), and in particular 6-GlcOCH(3) is able to inhibit lipid peroxidation.

Cobalt and iron segregation and nitride formation from nitrogen plasma treatment of CoFeB surfaces

NASA Astrophysics Data System (ADS)

Mattson, E. C.; Michalak, D. J.; Veyan, J. F.; Chabal, Y. J.

2017-02-01

Cobalt-iron-boron (CoFeB) thin films are the industry standard for ferromagnetic layers in magnetic tunnel junction devices and are closely related to the relevant surfaces of CoFe-based catalysts. Identifying and understanding the composition of their surfaces under relevant processing conditions is therefore critical. Here we report fundamental studies on the interaction of nitrogen plasma with CoFeB surfaces using infrared spectroscopy, x-ray photoemission spectroscopy, and low energy ion scattering. We find that, upon exposure to nitrogen plasma, clean CoFeB surfaces spontaneously reorganize to form an overlayer comprised of Fe2N3 and BN, with the Co atoms moved well below the surface through a chemically driven process. Subsequent annealing to 400 °C removes nitrogen, resulting in a Fe-rich termination of the surface region.

Uranyl Coordination Polymers Incorporating η5-Cyclopentadienyliron-Functionalized η6-Phthalate Metalloligands: Syntheses, Structures and Photophysical Properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kerr, Andrew T.; Kumalah, Sayon A.; Holman, K. T.

2013-10-06

The reaction of two η5-cyclopentadienyliron(II)-functionalized terephthalate and phthalate metalloligands, namely [(η5-C5H5)FeII(η6-1,4-HO2CC6H4CO2H)][(η5-C5H5)FeII(η6-1,4-HO2CC6H4CO2)][PF6] and [(η5-C5H5)FeII(η6-1,2-HO2CC6H4CO2H)][(η5-C5H5)FeII(η6-1,2-HO2CC6H4CO2)][PF6]—hereafter [H2 CpFeTP][HCpFeTP][PF6] and [H2 CpFeP][HCpFeP][PF6], respectively—with [UO2(NO3)2]·6H2O under hydrothermal conditions yielded four new coordination polymers; (1) [(UO2)F(HCpFeTP)(PO4H2)]·2H2O, (2) [(UO2)2(CpFeTP)4]·5H2O, (3) [(UO2)2F3(H2O)(CpFeP)], and (4) [H2 CpFeP][UO2F3]. The use of metalloligands has proven to be a viable route towards the incorporation of a secondary metal center into uranyl bearing materials. Depending upon the protonation state, the iron sandwich metalloligands may vary from zwitterionic neutral or monoanionic coordinating species as observed in compounds 1–3, or a positively charged species that hydrogen bonds with anionic [UO2F3]- chains as observed in 4.more » Further, the hydrolysis of the charge balancing PF6 - anion increases the diversity of UO2 2+ coordinating species by contributing both F- and PO4 3- anions (1, 3, 4). The luminescent properties of 1–4 were also studied and revealed the absence of uranyl emission, suggestive of a possible energy transfer from the uranyl cation to the iron(II) metal center.« less

The Partial Molar Volume and Thermal Expansivity of Fe2O3 in Alkali Silicate Liquids: Evidence for the Average Coordination of Fe3+

NASA Astrophysics Data System (ADS)

Liu, Q.; Lange, R.

2003-12-01

Ferric iron is an important component in magmatic liquids, especially in those formed at subduction zones. Although it has long been known that Fe3+ occurs in four-, five- and six-fold coordination in crystalline compounds, only recently have all three Fe3+ coordination sites been confirmed in silicate glasses utilizing XANES spectroscopy at the Fe K-edge (Farges et al., 2003). Because the density of a magmatic liquid is largely determined by the geometrical packing of its network-forming cations (e.g., Si4+, Al3+, Ti4+, and Fe3+), the capacity of Fe3+ to undergo composition-induced coordination change affects the partial molar volume of the Fe2O3 component, which must be known to calculate how the ferric-ferrous ratio in magmatic liquids changes with pressure. Previous work has shown that the partial molar volume of Fe2O3 (VFe2O3) varies between calcic vs. sodic silicate melts (Mo et al., 1982; Dingwell and Brearley, 1988; Dingwell et al., 1988). The purpose of this study is to extend the data set in order to search for systematic variations in VFe2O3 with melt composition. High temperature (867-1534° C) density measurements were performed on eleven liquids in the Na2O-Fe2O3-FeO-SiO2 (NFS) system and five liquids in the K2O-Fe2O3-FeO-SiO2 (KFS) system using Pt double-bob Archimedean method. The ferric-ferrous ratio in the sodic and potassic liquids at each temperature of density measurement were calculated from the experimentally calibrated models of Lange and Carmichael (1989) and Tangeman et al. (2001) respectively. Compositions range (in mol%) from 4-18 Fe2O3, 0-3 FeO, 12-39 Na2O, 25-37 K2O, and 43-78 SiO2. Our density data are consistent with those of Dingwell et al. (1988) on similar sodic liquids. Our results indicate that for all five KFS liquids and for eight of eleven NFS liquids, the partial molar volume of the Fe2O3 component is a constant (41.57 ñ 0.14 cm3/mol) and exhibits zero thermal expansivity (similar to that for the SiO2 component). This value was obtained in a fit to a linear volume equation in which the other oxide components have the following fitted partial molar volumes (cm3/mol) at 1100° C: SiO2 = 26.85+/-0.04, Na2O = 26.57+/-0.07, K2O = 42.34+/-0.10, and FeO = 12.84+/-0.28, and the following fitted fitted partial molar thermal expansivities (10-3 cm3/mol-K): Na2O = 7.73+/-0.12, K2O = 11.99+/-0.24, and FeO = 2.88+/-1.22. For the three sodic liquids not included in this regression, the most iron-rich (18.2 mol% Fe2O3) has a value for VFe2O3 of 44.1 cm3/mole, whereas the most iron-poor (4.4 mol% Fe2O3) has a value for VFe2O3 of 37.0 cm3/mole. This trend may reflect a greater proportion of four-fold ferric iron in iron-rich liquids, which mirrors the trend of increasing ferric-ferrous ratios in sodic liquids as a function of total iron content (Lange and Carmichael, 1989). The most polymerized liquid in our data set was a sodic liquid that has a value for VFe2O3 of 45.0 cm3/mole. It thus appears that most (13 of 16) of our experimental liquids, which span a wide compositional range, lead to a VFe2O3 (41.6 cm3/mol) which is constant with composition and temperature. However, there are three important outliers that may have implications for the appropriate value to apply to magmatic liquids.

Influence of adding strong-carbide-formation elements multiply on particle-reinforced Fe-matrix composite layer produced by laser cladding

NASA Astrophysics Data System (ADS)

Ma, Mingxing; Liu, Wenjin; Zhong, Minlin; Zhang, Hongjun; Zhang, Weiming

2005-01-01

In the research hotspot of particle reinforced metal-matrix composite layer produced by laser cladding, in-situ reinforced particles obtained by adding strong-carbide-formation elements into cladding power have been attracting more attention for their unique advantage. The research has demonstrated that when adding strong-carbide-formation elements-Ti into the cladding powder of the Fe-C-Si-B separately, by optimizing the composition, better cladding coating with the characters of better strength and toughness, higher wear resistance and free of cracks. When the microstructure of cladding coating is hypoeutectic microstructure, its comprehensive performance is best. The research discovered that, compositely adding the strong-carbide-formation elements like Ti+V, Ti+Zr or V+Zr into the cladding coating is able to improve its comprehensive capability. All the cladding coatings obtained are hypoeutectic microstructure. The cladding coatings have a great deal of particulates, and its average microhardness reaches HV0.2700-1400. The research also discovered that the cladding coating obtained is of less cracking after adding the Ti+Zr.

Quality of Graphite Target for Biological/Biomedical/Environmental Applications of 14C-Accelerator Mass Spectrometry

PubMed Central

2010-01-01

Catalytic graphitization for 14C-accelerator mass spectrometry (14C-AMS) produced various forms of elemental carbon. Our high-throughput Zn reduction method (C/Fe = 1:5, 500 °C, 3 h) produced the AMS target of graphite-coated iron powder (GCIP), a mix of nongraphitic carbon and Fe3C. Crystallinity of the AMS targets of GCIP (nongraphitic carbon) was increased to turbostratic carbon by raising the C/Fe ratio from 1:5 to 1:1 and the graphitization temperature from 500 to 585 °C. The AMS target of GCIP containing turbostratic carbon had a large isotopic fractionation and a low AMS ion current. The AMS target of GCIP containing turbostratic carbon also yielded less accurate/precise 14C-AMS measurements because of the lower graphitization yield and lower thermal conductivity that were caused by the higher C/Fe ratio of 1:1. On the other hand, the AMS target of GCIP containing nongraphitic carbon had higher graphitization yield and better thermal conductivity over the AMS target of GCIP containing turbostratic carbon due to optimal surface area provided by the iron powder. Finally, graphitization yield and thermal conductivity were stronger determinants (over graphite crystallinity) for accurate/precise/high-throughput biological, biomedical, and environmental14C-AMS applications such as absorption, distribution, metabolism, elimination (ADME), and physiologically based pharmacokinetics (PBPK) of nutrients, drugs, phytochemicals, and environmental chemicals. PMID:20163100

Morphology and phase control of iron oxide polymorph nanoparticles

NASA Astrophysics Data System (ADS)

Cui, Hongtao; Wang, Li; Shi, Min; Li, Yanhong

2017-04-01

In this work, lepidocrocite (γ-FeOOH) nanobundles were prepared by a facile NH4F assisted epoxide precipitation route. The reactions between epoxide and [Fe(H2O)6]2+ promoted the hydrolysis and condensation of [Fe(H2O)6]2+, resulting in the formation of iron oxyhydroxide. After calcination of γ-FeOOH nanobundles at 400 °C, the produced α-Fe2O3 still kept the bundle morphology. Due to the unique chemistry of epoxide, the morphology and phase of iron oxide polymorph nanoparticles (goethite, akaganeite, lepidocrocite, magnetite) were well-controlled through controlling reaction conditions such as Fe2+ concentration, NH4F additive and reaction temperature. It is particularly interesting that NH4F working as phase controlling agent is able to control the phase development of iron oxyhydroxides. This phase control effect of NH4F is attributed to the promoted reaction rate of epoxide originating from the higher electronegativity of fluoride ions than chloride ions. Based on the results in this work and our other preliminary works, it is considered that this route can be used as a general strategy for controlling the morphology and phase of transition element compounds.

Synthesis and chemical characterization of the novel agronomically relevant pentadentate chelate 2-(2-((2-hydroxybenzyl)amino)ethylamino)-2-(2-hydroxyphenyl)acetic acid (DCHA).

PubMed

López-Rayo, Sandra; Hernández, Diana; Lucena, Juan J; Escudero, Rosa; Gómez-Gallego, Mar; Sierra, Miguel A

2010-07-14

Iron chelates analogous to o,o-EDDHA/Fe(3+) are the fertilizers chosen to treat iron chlorosis in plants growing on calcareous soil. The isomer o,p-EDDHA/Fe(3+) presents less stability but faster assimilation by the plant than o,o-EDDHA/Fe(3+), because only five coordinating groups are able to complex Fe(3+). The new chelating agent 2-(2-((2-hydroxybenzyl)amino)ethylamino)-2-(2-hydroxyphenyl)acetic acid (DCHA) has been synthesized to obtain an iron fertilizer with intermediate stability between o,o-EDDHA/Fe(3+) and o,p-EDDHA/Fe(3+) and with fast assimilation. Its synthesis has been done starting from phenol, N-acetylethylendiamine, glyoxylic acid, and NaOH in a three-step sequence. The purity of the DCHA chelating agent, its protonation, and Ca(2+), Mg(2+), Fe(3+), and Cu(2+) stability constants, together with its ability to maintain iron in solution in different agronomic conditions, have been determined. The results indicate that the chelate DCHA/Fe(3+) has intermediate stability between those of o,o-EDDHA/Fe(3+) and o,p-EDDHA/Fe(3+) complexes and that it is capable of maintaining the Fe(3+) in agronomic conditions. This new chelating agent may be effective in correcting iron chlorosis in plants.

Di/mono-nuclear iron(I)/(II) complexes as functional models for the 2Fe2S subunit and distal Fe moiety of the active site of [FeFe] hydrogenases: protonations, molecular structures and electrochemical properties.

PubMed

Gao, Shang; Fan, Jiangli; Sun, Shiguo; Song, Fengling; Peng, Xiaojun; Duan, Qian; Jiang, Dayong; Liang, Qingcheng

2012-10-21

Di/mono-nuclear iron(I)/(II) complexes containing conjugated and electron-withdrawing S-to-S linkers, [{(μ-S)(2)(C(4)N(2)H(2))}Fe(2)(CO)(6)] (1), [{(μ-S)(2)(C(4)N(2)H(2))}Fe(2)(CO)(5)(PMe(3))] (1P), and [{(μ-S)(2)(C(4)N(2)H(2))}Fe(CO)(2)(PMe(3))(2)] (2) were prepared as biomimetic models for the 2Fe2S subunit and distal Fe moiety of the active site of [FeFe] hydrogenases. The N atoms in the heterocyclic pyrazines of 1 and 2 were protonated in the presence of proton acid to generate one and two hydrides, [1(NH)](+) CF(3)SO(3)(-), [2(NH)](+) CF(3)SO(3)(-), and [2(NH)(2)](2+) (CF(3)SO(3)(-))(2), respectively. The protonation processes were evidenced by in situ IR and NMR spectroscopy. The molecular structures of the protonated species [1(NH)](+) CF(3)SO(3)(-) and [2(NH)(2)](2+) (CF(3)SO(3)(-))(2) together with their originating complexes and , and the mono-PMe(3) substituted diiron complex were identified by X-ray crystallography. The IR and single-crystal analysis data all suggested that the electron-withdrawing bridge, pyrazine, led to decreased electron density at the Fe centers of the model complexes, which was consistent with the electrochemical studies. The cyclic voltammograms indicated that complex exhibited a low primary reduction potential at -1.17 V vs. Fc-Fc(+) with a 270 mV positive shift compared with that of the benzene-1,2-dithiolate (bdt) bridged analogue [(μ-bdt)Fe(2)(CO)(6)]. Under the weak acid conditions, complexes 1 and 2 could electrochemically catalyze the proton reduction. More interestingly, the mononuclear ferrous complex 2 showed two catalytic peaks during the formation of hydrogen, confirming its potential as a catalyst for hydrogen production.

Structure of the catalytic sites in Fe/N/C-catalysts for O2-reduction in PEM fuel cells

PubMed Central

Kramm, Ulrike I.; Herranz, Juan; Larouche, Nicholas; Arruda, Thomas M.; Lefèvre, Michel; Jaouen, Frédéric; Bogdanoff, Peter; Fiechter, Sebastian; Abs-Wurmbach, Irmgard; Mukerjee, Sanjeev; Dodelet, Jean-Pol

2012-01-01

Fe-based catalytic sites for the reduction of oxygen in acidic medium have been identified by 57Fe Mössbauer spectroscopy of Fe/N/C catalysts containing 0.03 to 1.55 wt% Fe, which were prepared by impregnation of iron acetate on carbon black followed by heat-treatment in NH3 at 950°C. Four different Fe-species were detected at all iron concentrations: three doublets assigned to molecular FeN4-like sites with their ferrous ion in low (D1), medium (D2) or high spin state (D3), and two other doublets assigned to a single Fe-species (D4 and D5) consisting of surface oxidized nitride nanoparticles (FexN, with x≤2.1). A fifth Fe-species appears only in those catalysts with Fe-contents ≥ 0.27 wt%. It is characterized by a very broad singlet, which has been assigned to incomplete FeN4-like sites that quickly dissolve in contact with an acid. Among the five Fe-species identified in these catalysts, only D1 and D3 display catalytic activity for the oxygen reduction reaction (ORR) in the acid medium, with D3 featuring a composite structure with a protonated neighbour basic nitrogen and being by far the most active species, with an estimated turn over frequency for the ORR of 11.4 e− site−1 s−1 at 0.8V vs RHE. Moreover, all D1 sites and between 1/2 to 2/3 of the D3 sites are acid-resistant. A scheme for the mechanism of site formation upon heat-treatment is also proposed. This identification of the ORR-active sites in these catalysts is of crucial importance to design strategies to improve the catalytic activity and stability of these materials. PMID:22824866