Neutron irradiation and high temperature effects on amorphous Fe-based nano-coatings on steel - A macroscopic assessment

NASA Astrophysics Data System (ADS)

Simos, N.; Zhong, Z.; Dooryhee, E.; Ghose, S.; Gill, S.; Camino, F.; Şavklıyıldız, İ.; Akdoğan, E. K.

2017-06-01

The study revealed that loss of ductility in an amorphous Fe-alloy coating on a steel substrate composite structure was essentially prevented from occurring, following radiation with modest neutron doses of ∼2 × 1018 n/cm2. At the higher neutron dose of ∼2 × 1019, macroscopic stress-strain analysis showed that the amorphous Fe-alloy nanostructured coating, while still amorphous, experienced radiation-induced embrittlement, no longer offering protection against ductility loss in the coating-substrate composite structure. Neutron irradiation in a corrosive environment revealed exemplary oxidation/corrosion resistance of the amorphous Fe-alloy coating, which is attributed to the formation of the Fe2B phase in the coating. To establish the impact of elevated temperatures on the amorphous-to-crystalline transition in the amorphous Fe-alloy, electron microscopy was carried out which confirmed the radiation-induced suppression of crystallization in the amorphous Fe-alloy nanostructured coating.

Structural Inheritance and Redox Performance of Nanoporous Electrodes from Nanocrystalline Fe85.2B10-14P0-4Cu0.8 Alloys

PubMed Central

Fu, Chaoqun; Xu, Lijun; Dan, Zhenhua; Makino, Akihiro; Hara, Nobuyoshi; Qin, Fengxiang; Chang, Hui

2017-01-01

Nanoporous electrodes have been fabricated by selectively dissolving the less noble α-Fe crystalline phase from nanocrystalline Fe85.2B14–xPxCu0.8 alloys (x= 0, 2, 4 at.%). The preferential dissolution is triggered by the weaker electrochemical stability of α-Fe nanocrystals than amorphous phase. The final nanoporous structure is mainly composed of amorphous residual phase and minor undissolved α-Fe crystals and can be predicted from initial microstructure of nanocrystalline precursor alloys. The structural inheritance is proved by the similarity of the size and outlines between nanopores formed after dealloying in 0.1 M H2SO4 and α-Fe nanocrystals precipitated after annealing of amorphous Fe85.2B14−xPxCu0.8 (x = 0, 2, 4 at.%) alloys. The Redox peak current density of the nanoporous electrodes obtained from nanocrystalline Fe85.2B10P4Cu0.8 alloys is more than one order higher than those of Fe plate electrode and its counterpart nanocrystalline alloys due to the large surface area and nearly-amorphous nature of ligaments. PMID:28594378

Fabrication of an Fe80.5Si7.5B6Nb5Cu Amorphous-Nanocrystalline Powder Core with Outstanding Soft Magnetic Properties

NASA Astrophysics Data System (ADS)

Zhang, Zongyang; Liu, Xiansong; Feng, Shuangjiu; Rehman, Khalid Mehmood Ur

2018-03-01

In this study, the melt spinning method was used to develop Fe80.5Si7.5B6Nb5Cu amorphous ribbons in the first step. Then, the Fe80.5Si7.5B6Nb5Cu amorphous-nanocrystalline core with a compact microstructure was obtained by multiple processes. The main properties of the magnetic powder core, such as micromorphology, thermal behavior, permeability, power loss and quality factor, have been analyzed. The obtained results show that an Fe80.5Si7.5B6Nb5Cu amorphous-nanocrystalline duplex core has high permeability (54.8-57), is relatively stable at different frequencies and magnetic fields, and the maximum power loss is only 313 W/kg; furthermore, it has a good quality factor.

Experimental Study of the Microstructure and Micromechanical Properties of Laser Cladded Ni-based Amorphous Composite Coatings

NASA Astrophysics Data System (ADS)

Li, Ruifeng; Zheng, Qichi; Zhu, Yanyan; Li, Zhuguo; Feng, Kai; Liu, Chuan

2018-01-01

(Ni0.6Fe0.4)65B18Si10Nb4C3 amorphous composite coating was successfully fabricated on AISI 1045 steel substrate by using laser cladding process with coaxial powder feeding equipment. The microstructure and phase distribution of the coating were investigated by using x-ray diffraction, scanning electron microscopy and transmission electron microscope. The mechanical properties of the coating were examined by using microhardness testing and nanoindentation. The experimental results indicated that the volume fraction of amorphous phase increased with the decrease in laser cladding heat input, leading to an improvement of mean microhardness and nanohardness. NbC particles in a size ranging between 150 and 1650 nm were found embedding in the amorphous composite coatings in all situations. The presence of the NbC particles can contribute to an improvement of 96.7 HV in hardness on the basis of experimental results, while theoretical prediction suggests an improvement of 92.5 HV by using Orowan-Ashby equation.

Synchronized Re-Entrant Flux Reversal of Multiple FeSiB Amorphous Wires Having the Larger Output

NASA Astrophysics Data System (ADS)

Takajo, Minoru; Yamasaki, Jiro

Technique to synchronize the re-entrant flux reversal of the multiple magnetostrictive Fe77.5Si7.5B15 amorphous wires was developed using a flux keeper of amorphous ribbons contacted to the wire ends. It is comprehended that the characteristics of the re-entrant flux takes place respectively at almost the same time in the three Fe-Si-B amorphous wires with a diameter of 65, 95μm. This phenomenon can be explained by considering the strong magnetic coupling of wires and amorphous ribbon by stray field from the each wire ends. As a result, the magnitude of the induced voltage in the sense coil is increased in proportion to the multiplication of the number of the wires.

Generalized Slater--Pauling curve and the role of metalloids in Fe-based amorphous alloys

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

Sostarich, M.

1990-05-01

A modification of the generalized Slater--Pauling curve so as to consider the concentration dependence of the number of majority-spin {ital sp} electrons per average atom is proposed for amorphous iron-metalloid alloys. In this way an improved matching of the measured magnetic moment dependence on composition is achieved for Fe alloys with B and/or P as metalloids. Comparison of theory with experiment shows that amorphous Fe-P alloys tend to be magnetically rather strong, whereas their Fe-B counterparts are weak itinerant ferromagnets in almost the entire range of compositions.

Study of Amorphous Ferrimagnet Fe0.66Er0.19B0.15 by Means of Monochromatic Circularly Polarised Source

NASA Astrophysics Data System (ADS)

Kalska, B.; Szymański, K.; Dobrzyński, L.; Satuła, D.; Wäppling, R.; Broddefalk, A.; Nordblad, P.

2002-06-01

Properties of amorphous alloy Fe0.66Er0.19B0.15 are reported. A reorientation of the Fe and Er magnetic moments during sample cooling through the compensation point in a large magnetic field is found by means of monochromatic circularly polarised radiation.

Controlling the crystallization and magnetic properties of melt-spun Pr2Fe14B/α-Fe nanocomposites by Joule heating

NASA Astrophysics Data System (ADS)

Jin, Z. Q.; Cui, B. Z.; Liu, J. P.; Ding, Y.; Wang, Z. L.; Thadhani, N. N.

2004-05-01

Pr2Fe14B/α-Fe based nanocomposites have been prepared through crystallization of melt-spun amorphous Pr7Tb1Fe85Nb0.5Zr0.5B6 ribbons by means of ac Joule heating while simultaneously monitoring room-temperature electrical resistance R. The R value shows a strong variation with respect to applied current I, and is closely related to the amorphous-to-nanocrystalline phase transformation. The curve of R versus I allows one to control the crystallization behavior during Joule heating and to identify the heat-treatment conditions for optimum magnetic properties. A coercivity of 550 kA/m and a maximum energy product of 128 kJ/m3 have been obtained upon heating the amorphous ribbons at a current of 2.0 A. These properties are around 30% higher than the values of samples prepared by conventionally (furnace) annealed amorphous ribbons.

Stability of (Fe-Tm-B) amorphous alloys: relaxation and crystallization phenomena

NASA Astrophysics Data System (ADS)

Zemčík, T.

1994-12-01

Fe-Tm-B base (TM=transition metal) amorphous alloys (metallic glasses) are thermodynamically metastable. This limits their use as otherwise favourable materials, e.g. magnetically soft, corrosion resistant and mechanically firm. By analogy of the mechanical strain-stress dependence, at a certain degree of thermal activation the amorphous structure reaches its limiting state where it changes its character and physical properties. Relaxation and early crystallization processes in amorphous alloys, starting already around 100°C, are reviewed involving subsequently stress relief, free volume shrinking, topological and chemical ordering, pre-crystallization phenomena up to partial (primary) crystallization. Two diametrically different examples are demonstrated from among the soft magnetic materials: relaxation and early crystallization processes in the Fe-Co-B metallic glasses and controlled crystallization of amorphous ribbons yielding rather modern nanocrystalline “Finemet” alloys where late relaxation and pre-crystallization phenomena overlap when forming extremely dispersive and fine-grained nanocrystals-in-amorphous-sauce structure. Mössbauer spectroscopy seems to be unique for magnetic and phase analysis of such complicated systems.

Magnetocaloric effect in amorphous and partially crystallized Fe{sub 40}Ni{sub 38}Mo{sub 4}B{sub 18} alloys

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

Thanveer, T.; Thomas, S., E-mail: senoythomas@gmail.com; Ramanujan, R. V.

A study of magnetocaloric effect in amorphous and partially crystallized Fe{sub 40}Ni{sub 38}Mo{sub 4}B{sub 18} alloys is reported. Amorphous Fe{sub 40}Ni{sub 38}Mo{sub 4}B{sub 18}, near its magnetic ordering temperature (600 K) showed a magnetic entropy change ΔS{sub M} of 1.1 J/KgK and a relative cooling power of 36 J/Kg in a field change of 10 kOe. Amorphous samples were partially crystallized by annealing at 700 K at different time intervals. Partially crystallized samples showed two distinct magnetic ordering temperature, one corresponding to the precipitated FeNi nanocrystals and the other one corresponding to the boron rich amorphous matrix. Magnetic ordering temperaturemore » of the residual amorphous matrix got shifted to the lower temperatures on increasing the annealing duration. Partially crystallised samples showed a magnetic entropy change of about 0.27 J/kgK near the magnetic ordering temperature of the amorphous matrix (540 K) in a field change of 10 kOe. The decrease in ΔS{sub M} on partial crystallisation is attributed to the biphasic magnetic nature of the sample.« less

Ferromagnetic laser-welded Fe78Si13B9 and Co71.5Fe2.5SigMn2Mo1B14ils amorphous foils

NASA Astrophysics Data System (ADS)

Pawlak, Ryszard

1997-10-01

In the paper the results of attempts at laser welding of amorphous ferromagnetic foils on the iron and cobalt base have been presented. The usefulness of this technology for making small magnetic circuits of metallic glass has been demonstrated. The action of laser radiation leading to rendering the structure amorphous and the infraction of a laser beam with an amorphous material have been discussed. Finally, the results of pulsed welding of a pack of amorphous foils and some properties of the welds formed have been discussed.

230% room-temperature magnetoresistance in CoFeB /MgO/CoFeB magnetic tunnel junctions

NASA Astrophysics Data System (ADS)

Djayaprawira, David D.; Tsunekawa, Koji; Nagai, Motonobu; Maehara, Hiroki; Yamagata, Shinji; Watanabe, Naoki; Yuasa, Shinji; Suzuki, Yoshishige; Ando, Koji

2005-02-01

Magnetoresistance (MR) ratio up to 230% at room temperature (294% at 20 K) has been observed in spin-valve-type magnetic tunnel junctions (MTJs) using MgO tunnel barrier layer fabricated on thermally oxidized Si substrates. We found that such a high MR ratio can be obtained when the MgO barrier layer was sandwiched with amorphous CoFeB ferromagnetic electrodes. Microstructure analysis revealed that the MgO layer with (001) fiber texture was realized when the MgO layer was grown on amorphous CoFeB rather than on polycrystalline CoFe. Since there have been no theoretical studies on the MTJs with a crystalline tunnel barrier and amorphous electrodes, the detailed mechanism of the huge tunneling MR effect observed in this study is not clear at the present stage. Nevertheless, the present work is of paramount importance in realizing high-density magnetoresistive random access memory and read head for ultra high-density hard-disk drives into practical use.

Fluxing purification and its effect on magnetic properties of high-Bs FeBPSiC amorphous alloy

NASA Astrophysics Data System (ADS)

Pang, Jing; Wang, Anding; Yue, Shiqiang; Kong, Fengyu; Qiu, Keqiang; Chang, Chuntao; Wang, Xinmin; Liu, Chain-Tsuan

2017-07-01

A high-Bs amorphous alloy with the base composition Fe83B11P3Si2C1 was used to study the effects of fluxing purification on amorphous forming ability and magnetic properties of the alloy prepared with raw materials in industrialization. By using fluxing purification, the surface crystallization was suppressed and fully amorphous Fe83B11P3Si2C1 ribbons with a maximum thickness of 48 μm were successfully achieved by using an industrial process and materials. The amorphous ribbons made with industrial-purified alloys exhibit excellent magnetic properties, containing high-Bs of 1.65 T, low Hc of 2.0 A/m, and high μe of 9.7 × 103 at 1 kHz. Impurities in the melting alloys exist in three forms and have different effluences on magnetic properties. The surface crystallization was triggered by the impurities which exist as high melting point inclusions serving as nuclei. Thus, fluxing purification is a feasible way for industrialization of high-Bs FeBPSiC amorphous alloys.

Irradiation and Thermal Annealing Effects in Amorphous Magnetic Alloys.

NASA Astrophysics Data System (ADS)

Fisher, David G.

Irradiation with protons, electrons, and alpha particles produces effects in amorphous magnetic alloys (Fe(,x)Ni(,80)P(,20-y)B(,y), where x was 20, 27, 34, or 40 and y was either 6 or 20) that appear analogous to effects produced by thermal annealing. The work presented in this dissertation represents an extension of work performed by Franz('(1)) and/or Donnelly.('(2)) The work of Franz, Donnelly, and this author has been a coordinated investigation into various aspects of radiation damage and thermal annealing effects in the above-mentioned amorphous alloys' magnetic properties. Upon either irradiation or thermal annealing, the Curie temperature, T(,c), is enhanced in these alloys. Also the relative permeability, (mu)(,r), is raised as much as seven-fold. Electrolytic layer removal experiments on proton-irradiated (0.25-MeV) samples conclusively demonstrate that the particle irradiation does not merely heat the sample bulk. Annealing studies performed on both irradiated and as-quenched samples suggested, via T(,c) measurement, that a structural relaxation process had taken place. The structural relaxation takes place as a result of a macroscopic heating in the case of the annealed samples and it is postulated that the structural relaxation takes place as a result of a miroscopic heating about the particle track (thermal spike mechanism) in the case of the irradiated samples. This work also presents preliminary results concerning the influence of irradiation and thermal annealing on the crystallization process in these alloys. The results of DSC and electrical resistivity (above room temperature) are presented. Using electrical resistivity as an indicator, a series of isothermal recrystallization measurements were performed using samples of 2.25-MeV proton-irradiated, 200(DEGREES)C-annealed, and as-quenched Fe(,20)Ni(,60)P(,14)B(,6). The activation energy for the onset of recrystallization is 2.0 eV for as-quenched samples and is 5.3 eV for the irradiated and thermal annealed samples. The results suggest the as-quenched state is not the ideal amorphous state. Structural relaxation resulting from either particle-irradiation or appropriate thermal annealing gives the alloys a more ideally amorphous state. References. ('(1))W. T. Franz, Ph.D. Dissertation, University of Delaware, August 1981. ('(2))T. A. Donnelly, Ph.d. Dissertation, University of Delaware, June 1982.

In situ TEM study of electron-beam radiation induced boron diffusion and effects on phase and microstructure evolution in nanostructured CoFeB/SiO2 thin film

NASA Astrophysics Data System (ADS)

Liu, B. H.; Teo, H. W.; Mo, Z. H.; Mai, Z. H.; Lam, J.; Xue, J. M.; Zhao, Y. Z.; Tan, P. K.

2017-01-01

Using in situ transmission electron microscopy (TEM), we studied boron diffusion and segregation in CoFeB/SiO2 nanostructured thin film stacks. We also investigated how these phenomena affected the phase and microstructure of CoFeB thin films under electron beam irradiation at 300 kV. A unique phase transformation was observed in CoFeB thin films under high-dose electron irradiation, from a polycrystalline Co3Fe to a unilateral amorphous phase of Co3Fe and nanocrystalline FexCo23-xB6. The unilateral amorphization of the Co3Fe film showed an electron-dose-rate sensitivity with a threshold dose rate. Detailed in situ TEM studies revealed that the unilateral amorphization of the Co3Fe film arose from boron segregation at the bottom of the Co3Fe thin film induced by radiation-enhanced diffusion of boron atoms that were displaced by electron knock-on effects. The radiation-induced nanocrystallization of FexCo23-xB6 was also found to be dose-rate sensitive with a higher electron beam current leading to earlier nucleation and more rapid grain growth. The nanocrystallization of FexCo23-xB6 occurred preferentially at the CoFeB/SiO2 interface. Kinetic studies by in situ TEM revealed the surface crystallization and diffusion-controlled nucleation and grain growth mechanisms. The radiation-enhanced atomic diffusivity and high-concentration of radiation-induced point defects at the Co3Fe/SiO2 interface enhanced the local short-range ordering of Fe, Co, and B atoms, favoring nucleation and grain growth of FexCo23-xB6 at the interface.

Microstructure, soft magnetic properties and applications of amorphous Fe-Co-Si-B-Mo-P alloy

NASA Astrophysics Data System (ADS)

Hasiak, Mariusz; Miglierini, Marcel; Łukiewski, Mirosław; Łaszcz, Amadeusz; Bujdoš, Marek

2018-05-01

DC thermomagnetic properties of Fe51Co12Si16B8Mo5P8 amorphous alloy in the as-quenched and after annealing below crystallization temperature are investigated. They are related to deviations in the microstructure as revealed by Mössbauer spectrometry. Study of AC magnetic properties, i.e. hysteresis loops, relative permeability and core losses versus maximum induction was aimed at obtaining optimal initial parameters for simulation process of a resonant transformer for a rail power supply converter. The results obtained from numerical analyses including core losses, winding losses, core mass, and dimensions were compared with the same parameters calculated for Fe-Si alloy and ferrite. Moreover, Steinmetz coefficients were also calculated for the as-quenched Fe51Co12Si16B8Mo5P8 amorphous alloy.

A novel conversion of the groundwater treatment sludge to magnetic particles for the adsorption of methylene blue.

PubMed

Zhu, Suiyi; Fang, Shuai; Huo, Mingxin; Yu, Yang; Chen, Yu; Yang, Xia; Geng, Zhi; Wang, Yi; Bian, Dejun; Huo, Hongliang

2015-07-15

Iron sludge, produced from filtration and backwash of groundwater treatment plant, has long been considered as a waste for landfill. In this study, iron sludge was reused to synthesize Fe3O4 magnetic particles (MPs) by using a novel solvothermal process. Iron sludge contained abundant amounts of silicon, iron, and aluminum and did not exhibit magnetic properties. After treatment for 4h, the amorphous Fe in iron sludge was transformed into magnetite Fe3O4, which could be easily separated from aqueous solution with a magnet. The prepared particles demonstrated the intrinsic properties of soft magnetic materials and could aggregate into a size of 1 μm. MPs treated for 10h exhibited excellent magnetic properties and a saturation magnetization value of 9 emu/g. The obtained particles presented the optimal adsorption of methylene blue under mild conditions, and the maximum adsorption capacity was 99.4 mg/g, which was higher than that of granular active carbon. The simple solvothermal method can be used to prepare Fe3O4 MPs from iron sludge, and the products could be applied to treatment of dyeing wastewater. Copyright © 2015. Published by Elsevier B.V.

Sintered magnetic cores of high Bs Fe84.3Si4B8P3Cu0.7 nano-crystalline alloy with a lamellar microstructure

NASA Astrophysics Data System (ADS)

Zhang, Yan; Sharma, Parmanand; Makino, Akihiro

2014-05-01

Fabrication of bulk cores of nano-crystalline Fe84.3Si4B8P3Cu0.7 alloy with a lamellar type of microstructure is reported. Amorphous ribbon flakes of size ˜1.0-2.0 mm were compacted in the bulk form by spark plasma sintering technique at different sintering temperatures. High density (˜96.4%) cores with a uniform nano-granular structure made from α-Fe (˜31 nm) were obtained. These cores show excellent mechanical and soft magnetic properties. The lamellar micro-structure is shown to be important in achieving significantly lower magnetic core loss than the non-oriented silicon steel sheets, commercial powder cores and even the core made of the same alloy with finer and randomly oriented powder particles.

Contrast studies of the process optimization and characterization of shielding fabric by amorphous Ni-Fe-P and Ni-P alloy

NASA Astrophysics Data System (ADS)

Yao, Kai; Wu, Xueyan; An, Zhentao

2017-01-01

A flexible shielding fabric with dense uniform coating was prepared after electrical deposition of amorphous Ni-Fe-P and Ni-P alloy on copper-coated polyethylene terephthalate (PET) fabric. The effects of coating composition and the deposition rate were discussed by the current density, temperature and pH value. The morphology, composition, and structure of coating were analyzed by SEM, EDS, and XRD characterizations. The EMI shielding effectiveness and corrosion resistance were also tested. The results fabric possesses dense, smooth, and uniform coating, when the processing conditions are 60°C, pH=1.5, and current density =8.7A/dm2. The coating fabric consists of amorphous Ni-Fe-P alloy with 16.62% P (weight percent), which has excellent of corrosion resistance. By contrast the EMI shielding effectiveness of amorphous Ni-Fe-P was better than amorphous Ni-P. The EMI shielding effectiveness of this coated fabric achieves 69.20dB-80.30dB in a broad frequency range between 300 kHz˜1.5 GHz.

Electrodeposition of amorphous Ni P coatings onto Nd Fe B permanent magnet substrates

NASA Astrophysics Data System (ADS)

Ma, C. B.; Cao, F. H.; Zhang, Z.; Zhang, J. Q.

2006-12-01

Decorative and protective Ni-P amorphous coatings were electroplated onto NdFeB permanent magnet from an ortho-phosphorous acid contained bath. The influences of the main electroplating technological parameters including current density, bath pH, bath temperature and H3PO3 on the structure and chemical composition of Ni-P coatings were investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques in conjunction with X-ray diffraction (XRD), scanning transmission electron microscopy (SEM) and X-ray energy-dispersive spectrometry (EDX). The optimized amorphous Ni-P coated NdFeB can stand for ca. 180 h against neutral 3.0 wt.% NaCl salt spray without any pitting corrosion. Meanwhile, the results also showed that large phosphorous content is the precondition for Ni-P coatings to possess the amorphous structure, but too much high phosphorous content can damage the amorphous structure due to the separation of superfluous P from Ni2P/Ni3P and the resultant formation of multi-phase coatings (such as Ni2P-P).

Structure and magnetic properties of the Nd9.5Fe84.5B6 alloy subjected to severe plastic deformation and annealing

NASA Astrophysics Data System (ADS)

Menushenkov, V. P.; Shchetinin, I. V.; Chernykh, S. V.; Savchenko, A. G.; Gorshenkov, M. V.; Zhukov, D. G.

2017-10-01

The effect of severe plastic deformation (SPD) by torsion and subsequent annealing on the structure and magnetic properties of the cast Nd9.5Fe84.5B6 alloy is studied. SPD by torsion is shown to lead to partial amorphization of the Nd2Fe14B phase and the precipitation of α-Fe; subsequent annealing results in the crystallization of the amorphous phase and the formation of a nanocomposite Nd2Fe14B/α-Fe structure. After SPD by torsion at 20 revolutions and annealing at 873 K, the (101) texture is formed; in this case, the coercive force is H c = 360 kA/m and the maximum energy product is ( BH) max = 166 kJ/m3. The residual magnetization and the squareness ratio of the hysteretic loop of the textured alloy decrease as the ambient temperature decreases.

Effect of Y addition on crystallization behavior and soft-magnetic properties of Fe78Si9B13 ribbons

NASA Astrophysics Data System (ADS)

Zhanwei, Liu; Dunbo, Yu; Kuoshe, Li; Yang, Luo; Chao, Yuan; Zilong, Wang; Liang, Sun; Kuo, Men

2017-08-01

A series of amorphous Fe-Si-B ribbons with various Y addition were prepared by melt-spinning. The effect of Y addition on crystallization behavior, thermal and magnetic properties was systematically investigated. With the increase of Y content, the initial crystallization temperature shifted to a higher temperature, indicating that the thermal stability of amorphous state in Fe-Si-B-Y ribbon is enhanced compared to that of Fe-Si-B alloy. Meanwhile, compared to the two exothermic peaks in the samples with lower Y content, a new exothermic peak was found in the ribbons with Y content higher than 1 at%, which corresponded to the decomposition of metastable Fe3B phase. Among all the alloys, Fe76.5Si9B13Y1.5 alloy exhibits optimized magnetic properties, with high saturation magnetization Ms of 187 emu/g and low coercivity HcJ of 7.6 A/m.

Enhanced magnetoimpedance and field sensitivity in microstructure controlled FeSiCuNbB ribbons

NASA Astrophysics Data System (ADS)

Sahoo, Trilochan; Chandra Mishra, Amaresh; Srinivas, V.; Nath, T. K.; Srinivas, M.; Majumdar, B.

2011-10-01

Fe73.5Si13.5Cu1Nb3B9 and Fe77.2Si11.2Cu0.8Nb3.3B7.5 nanocomposite materials consisting of nanocrystalline phase in an amorphous matrix were obtained by heat-treatment of their precursor amorphous ribbons. The influence of structural modifications induced during the heat-treatment on soft magnetic properties and magnetoimpedance (MI) effect have been studied. The structural investigations on both these ribbons revealed the presence of two phases, fine grained Fe3Si phase and a residual amorphous phase on heat-treatment. The maximum MI ratio obtained in the present study is 95% at f = 4 MHz, for the optimized heat-treated Fe77.2Si11.2Cu0.8Nb3.3B7.5 ribbon. This is ascribed to the increase in magnetic permeability and decrease in coercive force and intrinsic resistivity. Moreover, a maximum magnetic field sensitivity (ξ) of 8.3%/Oe at f = 2.5 MHz is obtained, for the optimized nanocrystalline Fe73.5Si13.5Cu1Nb3B9 ribbon. This suggests that tailoring of the nanocrystalline microstructures induced by optimum heat-treatment conditions can result in obtaining excellent combinations of the magnetic permeability and resistivity. Our results indicate that these Fe-based nanocrystalline materials can be ideally used for low magnetic field and high frequency sensor applications.

Magnetic properties of ball-milled SrFe12O19 particles consolidated by Spark-Plasma Sintering

PubMed Central

Stingaciu, Marian; Topole, Martin; McGuiness, Paul; Christensen, Mogens

2015-01-01

The room-temperature magnetic properties of ball-milled strontium hexaferrite particles consolidated by spark-plasma sintering are strongly influenced by the milling time. Scanning electron microscopy revealed the ball-milled SrFe12O19 particles to have sizes varying over several hundred nanometers. X-Ray powder-diffraction studies performed on the ball-milled particles before sintering clearly demonstrate the occurrence of a pronounced amorphization process. During sintering at 950 oC, re-crystallization takes place, even for short sintering times of only 2 minutes and transformation of the amorphous phase into a secondary phase is unavoidable. The concentration of this secondary phase increases with increasing ball-milling time. The remanence and maximum magnetization values at 1T are weakly influenced, while the coercivity drops dramatically from 2340 Oe to 1100 Oe for the consolidated sample containing the largest amount of secondary phase. PMID:26369360

Microscale Interface Synthesis of Ni-B Amorphous Nanoparticles from NiSO4 by Sodium Borohydride Reduction in Microreactor

NASA Astrophysics Data System (ADS)

Xu, Lei; Peng, Jinhui; Meng, Binfang; Li, Wei; Liu, Bingguo; Luo, Huilong

2016-09-01

Amorphous nanoparticles have attracted a large amount of interest due to their superior catalytic activity and unique selectivity. The Ni-B amorphous nanoparticles were synthesized from aqueous reduction of NiSO4 by sodium borohydride in microscale interface at room temperature. The size, morphology, elemental compositions, and the chemical composition on the surface of Ni-B amorphous nanoparticles were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). All the results showed that the synthesized particles are Ni-B amorphous nanoparticles with uniform in size distribution and having good dispersion. The mean particle diameter of Ni-B amorphous nanoparticles was around 9 nm. The present work provides an alternative synthesis route for the Ni-B amorphous nanoparticles.

Magnetic properties of the ammonolysis product of α-Fe powder containing a small amount of aluminum

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

Tsugawa, Yuta; Maubuchi, Yuji; Motohashi, Teruki

2015-02-15

Magnetite was prepared containing a small amount of aluminum and its nitride was generated through low temperature ammonolysis following reduction under hydrogen. The nitrided product was determined by XRD to be a mixture of “α″-Fe{sub 16}N{sub 2}” having a slightly deformed crystal structure from α″-Fe{sub 16}N{sub 2} and the residual α-Fe. Magnetic coercivity of the mixture was decreased from the value of 150 mT obtained for the nitride product made without aluminum, due to the precipitation of nonmagnetic amorphous alumina in the low temperature nitrided bcc (Fe{sub 1−x}Al{sub x}) with x≤0.03. The aluminum-doped nitride product in which the “α″-Fe{sub 16}N{submore » 2}” fraction was 30 at% exhibited magnetization at 1.5 T of approximately 200 Am{sup 2}kg{sup −1} at room temperature and its magnetic coercivity was 20 mT. - Graphical abstract: Magnetic iron nitride particles were separated by nonmagnetic amorphous γ-alumina. Magnetic coercivity was decreased by reducing the magnetic interaction between the particles. - Highlights: • Magnetic coercivity decreased in α”-Fe{sub 16}N{sub 2} like compound as a soft magnet. • Small amount of Al addition was effective in its preparation. • Magnetic interaction decreased between the “α”-Fe{sub 16}N{sub 2}” particles.« less

Resistivity changes of some amorphous alloys undergoing nanocrystallization

NASA Astrophysics Data System (ADS)

Barandiarán, J. M.; Fernández Barquín, L.; Sal, J. C. Gómez; Gorría, P.; Hernando, A.

1993-10-01

The electrical resistivity of amorphous alloys with compositions: Fe 73.5Nb 3Cu 1Si 13.5B 9, Fe 86Zr 7Cu 1B 6 and Co 80Nb 8B 12 has been studied in the temperature range from 300 to 1100 K, where crystallization occurs. The products of crystallization and the grain size have been studied by X-ray diffraction. In a first step, all the alloys crystallize with small grains of a few nanometers in diameter (nanocrystalline state), and the resistivity behavior at this process accounts for the difference between the amorphous and nanocrystalline phases. The nanocrystalline phases are: α-Fe-Si, α-Fe and fcc Co for the three compounds studied respectively. A second process, at which grain growth and precipitation of intermetallic compounds and borides takes place, has been found for all the alloys. The resistivity is sensitive, not only to the total transformed sample amount, but to the topological distribution of the crystalline phases, and therefore shows a more complex behavior than other well established techniques, as differential scanning calorimetry. This supplementary information given by the resistivity is also discussed.

Novel Amorphous Fe-Zr-Si(Cu) Boron-free Alloys

NASA Astrophysics Data System (ADS)

Kopcewicz, M.; Grabias, A.; Latuch, J.; Kowalczyk, M.

2010-07-01

Novel amorphous Fe80(ZrxSi20-x-y)Cuy boron-free alloys, in which boron was completely replaced by silicon as a glass forming element, have been prepared in the form of ribbons by a melt quenching technique. The X-ray diffraction and Mössbauer spectroscopy measurements revealed that the as-quenched ribbons with the composition of x = 6-10 at. % and y = 0, 1 at. % are predominantly amorphous. DSC measurements allowed the estimation of the crystallization temperatures of the amorphous alloys. The soft magnetic properties have been studied by the specialized rf-Mössbauer technique in which the spectra were recorded during an exposure of the samples to the rf field of 0 to 20 Oe at 61.8 MHz. Since the rf-collapse effect observed is very sensitive to the local anisotropy fields it was possible to evaluate the soft magnetic properties of amorphous alloys studied. The rf-Mössbauer studies were accompanied by the conventional measurements of the quasi-static hysteresis loops from which the magnetization and coercive fields were estimated. It was found that amorphous Fe-Zr-Si(Cu) alloys are magnetically very soft, comparable with those of the conventional amorphous B-containing Fe-based alloys.

Magnetic properties and crystallization kinetics of (Fe 100–xNi x) 80Nb 4Si 2B 14 metal amorphous nanocomposites

DOE PAGES

Aronhime, Natan; Zoghlin, Eli; Keylin, Vladimir; ...

2017-09-26

Fe-Ni based metal amorphous nanocomposites (MANCs) are investigated in the pseudo-binary alloys (Fe 100–xNi x) 80Nb 4Si 2B 14. To optimize the soft magnetic properties of the nanocomposites, primary and secondary crystallization kinetics must be understood. As such, primary and secondary crystallization temperatures are determined by differential scanning calorimetry, and activation energies are calculated, along with the resulting crystalline phases. Time-temperature-transformation diagrams for primary and secondary crystallization in (Fe 70Ni 30) 80Nb 4Si 2B 14 are presented. Saturation magnetization and Curie temperature are determined. In conclusion, the shape of magnetization vs. time curves for (Fe 30Ni 70) 80Nb 4Si 2Bmore » 14 at various temperatures suggest that the secondary crystal product often consumes some of the primary crystalline product.« less

The Amorphous Composition of Three Mudstone Samples from Gale Crater: Implications for Weathering and Diagenetic Processes on Mars

NASA Technical Reports Server (NTRS)

Achilles, C. N.; Downs, R. T.; Rampe, E. B.; Morris, R. V.; Bristow, T. F.; Ming, D. W.; Blake, D. F.; Vaniman, D. T.; Morrison, S. M.; Sutter, B.;

Microstructure and phase analyses of melt-spun Si-Ni base anode materials for Li-ion battery

NASA Astrophysics Data System (ADS)

Jeon, Sung Min; Song, Jong Jin; Kim, Sun-I.; Kwon, Hye Jin; Sohn, Keun Yong; Park, Won-Wook

2013-01-01

Si-based anode composite materials have been studied to improve the performance and the durability of Li-ion secondary batteries in this study. Si-Ni-Al, Si-Ni-Cu and Si-Ni-Cu-Al base alloys were designed and rapidly solidified at the cooling rate of about 106 °C/sec by optimizing the melt spinning. The ribbons were characterized using FE-SEM equipped with EDS, X-ray diffractometer and HR-TEM. The thin ribbons of Si-Ni-Al alloy consisted of nano-sized Si particles and amorphous matrix, which was regarded as an ideal microstructure for the anode material. At the wheel side of the ribbon, 20-30 nm of Si particles were formed (Zone A); whereas at the air side relatively large Si particles were distributed (Zone B). The Si-Ni-Cu alloy showed coarser Si particles than the Si-Ni-Al alloy, and its matrix consisted of NiSi2, Cu3Si and amorphous structures. Finally, the microstructure of the Si-Ni-Cu-Al alloy strips was composed of coarse Si particles, CuNi, Al4Cu9, NiSi2, and unknown phases, and the size of those Si particles were too large to be used for the anode materials.

Mössbauer and XRD study of novel quaternary Sn-Fe-Co-Ni electroplated alloy

NASA Astrophysics Data System (ADS)

Kuzmann, E.; Sziráki, L.; Stichleutner, S.; Homonnay, Z.; Lak, G. B.; El-Sharif, M.; Chisholm, C. U.

2017-11-01

Constant current electrochemical deposition technique was used to obtain quaternary alloys of Sn-Fe-Co-Ni from a gluconate electrolyte, which to date have not been reported in the literature. For the characterization of electroplated alloys, 57Fe and 119Sn Conversion Electron Mössbauer Spectroscopy (CEMS), XRD and SEM/EDAX were used. XRD revealed the amorphous character of the novel Sn-Fe-Co-Ni electrodeposited alloys. 57Fe Mössbauer spectrum of quaternary deposit with composition of 37.0 at% Sn, 38.8 at% Fe, 16.8 at% Co and 7.4 at% Ni displayed a magnetically split sextet (B = 28.9T) with broad lines typical of iron bearing ferromagnetic amorphous alloys. Magnetically split 119Sn spectra reflecting a transferred hyperfine field (B = 2.3T) were also observed. New quaternary Sn-Fe-Co-Ni alloys were successfully prepared.

The Effects of Strain-Annealing on Tuning Permeability and Lowering Losses in Fe-Ni-Based Metal Amorphous Nanocomposites

DOE PAGES

Aronhime, Natan; DeGeorge, Vincent; Keylin, Vladimir; ...

2017-07-25

Here, Fe-Ni-based metal amorphous nanocomposites with a range of compositions (Fe 100–xNi x) 80Nb 4Si 2B 14 (30 ≤ x ≤ 70) are investigated for motor and transformer applications, where it is beneficial to have tunable permeability. It is shown that strain annealing offers an effective method for tuning permeability in these alloys. For an Fe-rich alloy, permeability increased from 4000 to 16,000 with a positive magnetostriction. In a Ni-rich alloy, permeability decreased from 290 to 40 with a negative magnetostriction. Significant elongations (above 60%) are observed during strain annealing at high stress. Crystallization products have been determined in allmore » alloys heated to 480°C. γ-FeNi is formed in all alloys, while (Fe 30Ni 70) 80Nb 4Si 2B 14 also undergoes secondary crystallization at temperatures of approximately 480°C to form a phase with the Cr 23C 6-type structure and a likely composition of Fe 21Nb 2B 6. Toroidal losses have been measured for (Fe 70Ni 30) 80Nb 4Si y B 16–y (0 ≤ y ≤ 3) at various annealing temperatures. At an induction of 1 T and frequency of 400 Hz and 1 kHz, the toroidal losses obtained are W 1.0T, 400 Hz = 0.9 W/kg and W 1.0T, 1 kHz = 2.3 W/kg, respectively. These losses are lower than losses recently reported for state of the art 3.0% and 6.5% silicon steels, a Metglas Fe-based amorphous alloy, and some Fe-based nanocomposites.« less

The Effects of Strain-Annealing on Tuning Permeability and Lowering Losses in Fe-Ni-Based Metal Amorphous Nanocomposites

NASA Astrophysics Data System (ADS)

Aronhime, Natan; DeGeorge, Vincent; Keylin, Vladimir; Ohodnicki, Paul; McHenry, Michael E.

2017-11-01

Fe-Ni-based metal amorphous nanocomposites with a range of compositions (Fe100- x Ni x )80Nb4Si2B14 (30 ≤ x ≤ 70) are investigated for motor and transformer applications, where it is beneficial to have tunable permeability. It is shown that strain annealing offers an effective method for tuning permeability in these alloys. For an Fe-rich alloy, permeability increased from 4000 to 16,000 with a positive magnetostriction. In a Ni-rich alloy, permeability decreased from 290 to 40 with a negative magnetostriction. Significant elongations (above 60%) are observed during strain annealing at high stress. Crystallization products have been determined in all alloys heated to 480°C. γ-FeNi is formed in all alloys, while (Fe30Ni70)80Nb4Si2B14 also undergoes secondary crystallization at temperatures of approximately 480°C to form a phase with the Cr23C6-type structure and a likely composition of Fe21Nb2B6. Toroidal losses have been measured for (Fe70Ni30)80Nb4Si y B16- y (0 ≤ y ≤ 3) at various annealing temperatures. At an induction of 1 T and frequency of 400 Hz and 1 kHz, the toroidal losses obtained are W1.0T, 400 Hz = 0.9 W/kg and W1.0T, 1 kHz = 2.3 W/kg, respectively. These losses are lower than losses recently reported for state of the art 3.0% and 6.5% silicon steels, a Metglas Fe-based amorphous alloy, and some Fe-based nanocomposites.

The Effects of Strain-Annealing on Tuning Permeability and Lowering Losses in Fe-Ni-Based Metal Amorphous Nanocomposites

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

Aronhime, Natan; DeGeorge, Vincent; Keylin, Vladimir

Here, Fe-Ni-based metal amorphous nanocomposites with a range of compositions (Fe 100–xNi x) 80Nb 4Si 2B 14 (30 ≤ x ≤ 70) are investigated for motor and transformer applications, where it is beneficial to have tunable permeability. It is shown that strain annealing offers an effective method for tuning permeability in these alloys. For an Fe-rich alloy, permeability increased from 4000 to 16,000 with a positive magnetostriction. In a Ni-rich alloy, permeability decreased from 290 to 40 with a negative magnetostriction. Significant elongations (above 60%) are observed during strain annealing at high stress. Crystallization products have been determined in allmore » alloys heated to 480°C. γ-FeNi is formed in all alloys, while (Fe 30Ni 70) 80Nb 4Si 2B 14 also undergoes secondary crystallization at temperatures of approximately 480°C to form a phase with the Cr 23C 6-type structure and a likely composition of Fe 21Nb 2B 6. Toroidal losses have been measured for (Fe 70Ni 30) 80Nb 4Si y B 16–y (0 ≤ y ≤ 3) at various annealing temperatures. At an induction of 1 T and frequency of 400 Hz and 1 kHz, the toroidal losses obtained are W 1.0T, 400 Hz = 0.9 W/kg and W 1.0T, 1 kHz = 2.3 W/kg, respectively. These losses are lower than losses recently reported for state of the art 3.0% and 6.5% silicon steels, a Metglas Fe-based amorphous alloy, and some Fe-based nanocomposites.« less

Synthesis and characterization of bulk metallic glasses prepared by laser direct deposition

NASA Astrophysics Data System (ADS)

Ye, Xiaoyang

Fe-based and Zr-based metallic glasses have attracted extensive interest for structural applications due to their excellent glass forming ability, superior mechanical properties, unique thermal and corrosion properties. In this study, the feasibility of synthesizing metallic glasses with good ductility by laser direct deposition is explored. Both in-situ synthesis with elemental powder mixture and ex-situ synthesis with prealloyed powder are discussed. Microstructure and properties of laser direct deposited metallic glass composites are analyzed. Synthesis of Fe-Cr-Mo-W-Mn-C-Si-B metallic glass composite with a large fraction of amorphous phase was accomplished using laser direct deposition. X-ray diffraction (XRD) and transmission electron microscopy investigations revealed the existence of amorphous structure. Microstructure analyses by optical microscopy and scanning electron microscopy (SEM) indicated the periodically repeated microstructures of amorphous and crystalline phases. Partially crystallized structure brought by laser reheating and remelting during subsequent laser scans aggregated in the overlapping area between each scan. XRD analysis showed that the crystalline particle embedded in the amorphous matrix was Cr 1.07Fe18.93 phase. No significant microstructural differences were found from the first to the last layer. Microhardness of the amorphous phase (HV0.2 1591) showed a much higher value than that of the crystalline phase (HV0.2 947). Macrohardness of the top layer had a value close to the microhardness of the amorphous region. Wear resistance property of deposited layers showed a significant improvement with the increased fraction of amorphous phase. Zr65Al10Ni10Cu15 amorphous composites with a large fraction of amorphous phase were in-situ synthesized by laser direct deposition. X-ray diffraction confirmed the existence of both amorphous and crystalline phases. Laser parameters were optimized in order to increase the fraction of amorphous phase. The microstructure analysis by scanning electron microscopy revealed the deposited structure was composed of periodically repeated amorphous and crystalline phases. Overlapping regions with nanoparticles aggregated were crystallized by laser reheating and remelting processes during subsequent laser scans. Vickers microhardness of the amorphous region showed around 35% higher than that of crystalline region. Average hardness obtained by a Rockwell macrohardness tester was very close to the microhardness of the amorphous region. The compression test showed that the fracture strain of Zr65Al10Ni10Cu15 amorphous composites was enhanced from less than 2% to as high as 5.7%, compared with fully amorphous metallic glass. Differential scanning calorimetry test results further revealed the amorphous structure and glass transition temperature Tg was observed to be around 655K. In 3 mol/L NaCl solution, laser direct deposited amorphous composites exhibited distinctly improved corrosion resistance, compared with fully-crystallized samples.

Annealing induced structural changes in amorphous Co{sub 23}Fe{sub 60}B{sub 17} film on Mo buffer layer

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

Dwivedi, Jagrati, E-mail: jdwivedi.phy@gmail.com; Mishra, Ashutosh; Gupta, Ranjeeta

2016-05-23

Structural changes occurring in a thin amorphous Co{sub 23}Fe{sub 60}B{sub 17} film sandwiched between two Mo layers, as a function of thermal annealing has been studied. Thermal stability of the Co{sub 23}Fe{sub 60}B{sub 17} film is found to be significantly lower than the bulk ribbons. SIMS measurements show that during crystallization, boron which is expelled out of the crystallites, has a tendency to move towards the surface. No significant diffusion of boron in Mo buffer layer is observed. This result is in contrast with some earlier studies where it was proposed that the role of buffer layer of refractory metalmore » is to absorb boron which is expelled out of the bcc FeCo phase during crystallization.« less

Preparation, mechanical strengths, and thermal

NASA Astrophysics Data System (ADS)

Inoue, A.; Furukawa, S.; Hagiwara, M.; Masumoto, T.

1987-05-01

Ni-based amorphous wires with good bending ductility have been prepared for Ni75Si8B17 and Ni78P12B10 alloys containing 1 to 2 at. pct Al or Zr by melt spinning in rotating water. The enhancement of the wire-formation tendency by the addition of Al has been clarified to be due to the increase in the stability of the melt jet through the formation of a thin A12O3 film on the outer surface. The maximum wire diameter is about 190 to 200 μm for the Ni-Si (or P)-B-Al alloys and increases to about 250 μm for the Ni-Si-B-Al-Cr alloys containing 4 to 6 at. pct Cr. The tensile fracture strength and fracture elongation are 2730 MPa and 2.9 pct for (Ni0.75Si0.08B0.17 99Al1) wire and 2170 MPa and 2.4 pct for (Ni0.78P0.12B0.1)99Al1 wire. These wires exhibit a fatigue limit under dynamic bending strain in air with a relative humidity of 65 pct; this limit is 0.50 pct for a Ni-Si-B-Al wire, which is higher by 0.15 pct than that of a Fe75Si10B15 amorphous wire. Furthermore, the Ni-base wires do not fracture during a 180-deg bending even for a sample annealed at temperatures just below the crystallization temperature, in sharp contrast to high embrittlement tendency for Fe-base amorphous alloys. Thus, the Ni-based amorphous wires have been shown to be an attractive material similar to Fe- and Co-based amorphous wires because of its high static and dynamic strength, high ductility, high stability to thermal embrittlement, and good corrosion resistance.

Tunable Amorphous Photonic Materials with Pigmentary Colloidal Nanostructures

DOE PAGES

Han, Jinkyu; Lee, Elaine; Dudoff, Jessica K.; ...

2017-01-31

Amorphous photonic structures using pigmentary α-Fe 2O 3/SiO 2 core–shell nanoparticles are succesfully fabricated. The resulting non-iridicent brilliant colors can be manipulated by shell thickness, particle concentration, and external electrical stimuli using electrophoretic deposition process. In conclusion, fully reversible and instantaneous color changes as well as noticeable difference between transmitted and reflected colors is observed.

Thermodynamic analysis of binary Fe{sub 85}B{sub 15} to quinary Fe{sub 85}Si{sub 2}B{sub 8}P{sub 4}Cu{sub 1} alloys for primary crystallizations of α-Fe in nanocrystalline soft magnetic alloys

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

Takeuchi, A., E-mail: takeuchi@imr.tohoku.ac.jp; Zhang, Y.; Takenaka, K.

2015-05-07

Fe-based Fe{sub 85}B{sub 15}, Fe{sub 84}B{sub 15}Cu{sub 1}, Fe{sub 82}Si{sub 2}B{sub 15}Cu{sub 1}, Fe{sub 85}Si{sub 2}B{sub 12}Cu{sub 1}, and Fe{sub 85}Si{sub 2}B{sub 8}P{sub 4}Cu{sub 1} (NANOMET{sup ®}) alloys were experimental and computational analyzed to clarify the features of NANOMET that exhibits high saturation magnetic flux density (B{sub s}) nearly 1.9 T and low core loss than conventional nanocrystalline soft magnetic alloys. The X-ray diffraction analysis for ribbon specimens produced experimentally by melt spinning from melts revealed that the samples were almost formed into an amorphous single phase. Then, the as-quenched samples were analyzed with differential scanning calorimeter (DSC) experimentally for exothermicmore » enthalpies of the primary and secondary crystallizations (ΔH{sub x1} and ΔH{sub x2}) and their crystallization temperatures (T{sub x1} and T{sub x2}), respectively. The ratio ΔH{sub x1}/ΔH{sub x2} measured by DSC experimentally tended to be extremely high for the Fe{sub 85}Si{sub 2}B{sub 8}P{sub 4}Cu{sub 1} alloy, and this tendency was reproduced by the analysis with commercial software, Thermo-Calc, with database for Fe-based alloys, TCFE7 for Gibbs free energy (G) assessments. The calculations exhibit that a volume fraction (V{sub f}) of α-Fe tends to increase from 0.56 for the Fe{sub 85}B{sub 15} to 0.75 for the Fe{sub 85}Si{sub 2}B{sub 8}P{sub 4}Cu{sub 1} alloy. The computational analysis of the alloys for G of α-Fe and amorphous phases (G{sub α-Fe} and G{sub amor}) shows that a relationship G{sub α-Fe} ∼ G{sub amor} holds for the Fe{sub 85}Si{sub 2}B{sub 12}Cu{sub 1}, whereas G{sub α-Fe} < G{sub amor} for the Fe{sub 85}Si{sub 2}B{sub 8}P{sub 4}Cu{sub 1} alloy at T{sub x1} and that an extremely high V{sub f} = 0.75 was achieved for the Fe{sub 85}Si{sub 2}B{sub 8}P{sub 4}Cu{sub 1} alloy by including 2.8 at. % Si and 4.5 at. % P into α-Fe. These computational results indicate that the Fe{sub 85}Si{sub 2}B{sub 8}P{sub 4}Cu{sub 1} alloy barely forms amorphous phase, which, in turn, leads to high V{sub f} and resultant high B{sub s}.« less

Facile sonochemical synthesis of amorphous NiFe-(oxy)hydroxide nanoparticles as superior electrocatalysts for oxygen evolution reaction.

PubMed

Lee, Eunjik; Park, Ah-Hyeon; Park, Hyun-Uk; Kwon, Young-Uk

2018-01-01

In this work, we present facile synthesis of amorphous Ni/Fe mixed (oxy)hydroxide (NiFe(H)) nanoparticles (NPs) and their electrocatalytic performance for oxygen evolution reaction (OER) in alkaline media. a-NiFe(H) NPs have received lots of attention as OER electrocatalysts with many desirable properties. By using a simple sonochemical route, we prepared amorphous Ni and Fe-alkoxide (NiFe(A)) NPs whose composition can be controlled in the entire composition range (Ni 100-x Fe x , 0≤x≤1). These samples are composed of extremely small NiFe(A) NPs with Ni and Fe atoms homogeneously distributed. NiFe(A) NPs are readily converted into corresponding electrocatalytically active NiFe(H) NP by a simple electrochemical treatment. Electrochemical analysis data show that the OER activity of amorphous NiFe(H) samples follows the volcano-type trend when plotted against the Fe content. Ni 70 Fe 30 (H) sample showed the lowest overpotential of 292mV at 10mAcm -2 geo and the lowest Tafel slope of 30.4mVdec -1 , outperforming IrO x /C (326mV, 41.7mVdec -1 ). Our samples are highly durable based on the chronopotentiometry data at the current density of 10mAcm -2 geo for 2h which show that Ni 70 Fe 30 sample maintains the steady-state potential, contrary to the time-varying IrO x /C. Copyright © 2017 Elsevier B.V. All rights reserved.

Coherency strain and precipitation kinetics: crystalline and amorphous nitride formation in ternary Fe-Ti/Cr/V-Si alloys

NASA Astrophysics Data System (ADS)

Schwarz, B.; Rossi, P. J.; Straßberger, L.; Jörg, F.; Meka, S. R.; Bischoff, E.; Schacherl, R. E.; Mittemeijer, E. J.

2014-09-01

Specimens of iron-based binary Fe-Si alloy and ternary Fe-Me-Si alloys (with Me = Ti, Cr and V) were nitrided at 580 °C in a NH3/H2-gas mixture applying a nitriding potential of 0.1 atm-1/2 until nitrogen saturation in the specimens was attained. In contrast with recent observations in other Fe-Me1-Me2 alloys, no "mixed" (Me1, Me2) nitrides developed in Fe-Me-Si alloys upon nitriding: first, all Me precipitates as MeN; and thereafter, all Si precipitates as Si3N4. The MeN precipitates as crystalline, finely dispersed, nanosized platelets, obeying a Baker-Nutting orientation relationship (OR) with respect to the ferrite matrix. The Si3N4 precipitates as cubically, amorphous particles; the incoherent (part of the) MeN/α-Fe interface acts as heterogeneous nucleation site for Si3N4. The Si3N4-precipitation rate was found to be strongly dependent on the degree of coherency of the first precipitating MeN. The different, even opposite, kinetic effects observed for the various Fe-Me-Si alloys could be ascribed to the different time dependences of the coherent → incoherent transitions of the MeN particles in the different Fe-Me-Si alloys.

Mesoporous Silica Matrix as a Tool for Minimizing Dipolar Interactions in NiFe2O4 and ZnFe2O4 Nanoparticles

PubMed Central

Virumbrales, Maider; Saez-Puche, Regino; Torralvo, María José; Blanco-Gutierrez, Veronica

2017-01-01

NiFe2O4 and ZnFe2O4 nanoparticles have been prepared encased in the MCM (Mobile Composition of Matter) type matrix. Their magnetic behavior has been studied and compared with that corresponding to particles of the same composition and of a similar size (prepared and embedded in amorphous silica or as bare particles). This study has allowed elucidation of the role exerted by the matrix and interparticle interactions in the magnetic behavior of each ferrite system. Thus, very different superparamagnetic behavior has been found in ferrite particles of similar size depending on the surrounding media. Also, the obtained results clearly provide evidence of the vastly different magnetic behavior for each ferrite system. PMID:28640197

Magnetic properties of Sm2(Fe0.95M0.05)17Nx (M=Cr and Mn) anisotropic coarse powders with high coercivity

NASA Astrophysics Data System (ADS)

Ito, Mikio; Majima, Kazuhiko; Shimuta, Toru; Katsuyama, Shigeru; Nagai, Hiroshi

2002-09-01

Sm2(Fe0.95Cr0.05)17Nx and Sm2(Fe0.95Mn0.05)17Nx coarse powders 10-70 mum in size were synthesized by crushing mother alloy ingots into 32-74 mum in particle size and subsequent nitrogenation at 748 K in a flowing mixed gas of 60 vol % H2+40 vol % NH3. The effects of Cr or Mn substitution for Fe on the nitrogenation rate, magnetic properties, and microstructure of the Sm2Fe17Nx hard magnetic material were investigated. Cr and Mn substitution was quite effective for accelerating nitrogenation. When the powders were nitrogenated beyond x=3, amorphous phase formation was observed as the x value increased. The magnetic properties of the nitrogenated powders were significantly improved by Cr and Mn substitution, and these powders also possessed a satisfactory magnetic anisotropy. The maximum coercivity in this study, 0.59 MA/m, was obtained for the Sm2(Fe0.95Mn0.05)17N5.0 powder in spite of its large particle size. The high coercivity of the coarse powders was caused by a cell-like microstructure composed of fine 2-17 crystalline grains 20-30 nm in size surrounded by an amorphous phase.

Effects of annealing on the structure and magnetic properties of Fe80B20 magnetostrictive fibers.

PubMed

Zhu, Qianke; Zhang, Shuling; Geng, Guihong; Li, Qiushu; Zhang, Kewei; Zhang, Lin

2016-07-04

Fe80B20 amorphous alloys exhibit excellent soft magnetic properties, high abrasive resistance and outstanding corrosion resistance. In this work, Fe80B20 amorphous micro-fibers with HC of 3.33 Oe were firstly fabricated and the effects of annealing temperature on the structure and magnetic properties of the fibers were investigated. In this study, Fe80B20 amorphous fibers were prepared by the single roller melt-spinning method. The structures of as-spun and annealed fibers were investigated by X-ray diffractometer (XRD) (PANalytical X,Pert Power) using Cu Kα radiation. The morphology of the fibers was observed by scanning electron microscopy (SEM) (HITACHI-S4800). Differential scanning calorimetry (DSC) measurements of the fibers were performed on Mettler Toledo TGA/DSC1 device under N2 protection. Vibrating sample magnetometer (VSM, Versalab) was used to examine the magnetic properties of the fibers. The resonance behavior of the fibers was characterized by an impedance analyzer (Agilent 4294A) with a home-made copper coil. The X-ray diffusion (XRD) patterns show that the fibers remain amorphous structure until the annealing temperature reaches 500°C. The differential scanning calorimetry (DSC) results show that the crystallization temperature of the fibers is 449°C. The crystallization activation energy is calculated to be 221 kJ/mol using Kissinger formula. The scanning electron microscopy (SEM) images show that a few dendrites appear at the fiber surface after annealing. The result indicates that the coercivity HC (//) and HC (⊥) slightly increases with increasing annealing temperature until 400°C, and then dramatically increases with further increasing annealing temperature which is due to significant increase in magneto-crystalline anisotropy and magneto-elastic anisotropy. The Q value firstly increases slightly when the annealing temperature rises from room temperature (RT) to 300°C, then decreases until 400°C. Eventually, the value of Q increases to ~2000 at annealing temperature of 500°C. In this study, Fe80B20 amorphous fibers with the diameter of 60 μm were prepared by the single roller melt-spinning method and annealed at 200°C, 300°C, 400°C, and 500°C, respectively. XRD results indicate that the fiber structure remains amorphous when the annealing temperature is below 400°C. α-Fe phase and Fe3B phase appear when the annealing temperature rises to 500°C, which is above the crystallization temperature of 449°C. The recrystallization activation energy is calculated to be 221 kJ/mol. The coercivity increases with increasing annealing temperature, which attributes to the increase of total anisotropy. All the as-spun and annealed fibers exhibit good resonance behavior for magnetostrictive sensors.

Structure and soft magnetic properties of Fe-Si-B-P-Cu nanocrystalline alloys with minor Mn addition

NASA Astrophysics Data System (ADS)

Jia, Xingjie; Li, Yanhui; Wu, Licheng; Zhang, Wei

2018-05-01

Addition of minor Mn effectively improves the amorphous-forming ability and thermal stability of the Fe85Si2B8P4Cu1 alloy. With increasing the Mn content from 0 to 3 at.%, the critical thickness for amorphous formation and onset temperature of the primary crystallization increase from 14 μm and 659 K to 27 μm and 668 K, respectively. The fine nanocrystalline structure with α-Fe grains in size (D) of < 20 nm was obtained for the annealed amorphous alloys, which show excellent soft magnetic properties. The alloying of Mn reduces the coercivity (Hc) by decreasing the D value and widens the optimum annealing temperature range for obtaining low Hc, although the saturation magnetic flux density (Bs) is decreased slightly. The Fe83Mn2Si2B8P4Cu1 nanocrystalline alloy possesses fine structure with a D of ˜17.5 nm, and exhibits a high Bs of ˜1.75 T and a low Hc of ˜5.9 A/m. The mechanism related to the alloying effects on the structure and magnetic properties was discussed in term of the crystallization activation energy.

Modification of structural and magnetic properties of soft magnetic multi-component metallic glass by 80 MeV 16O6+ ion irradiation

NASA Astrophysics Data System (ADS)

Kane, S. N.; Shah, M.; Satalkar, M.; Gehlot, K.; Kulriya, P. K.; Avasthi, D. K.; Sinha, A. K.; Modak, S. S.; Ghodke, N. L.; Reddy, V. R.; Varga, L. K.

2016-07-01

Effect of 80 MeV 16O6+ ion irradiation in amorphous Fe77P8Si3C5Al2Ga1B4 alloy is reported. Electronic energy loss induced modifications in the structural and, magnetic properties were monitored by synchrotron X-ray diffraction (SXRD), Mössbauer and, magnetic measurements. Broad amorphous hump seen in SXRD patterns reveals the amorphous nature of the studied specimens. Mössbauer measurements suggest that: (a) alignment of atomic spins within ribbon plane, (b) changes in average hyperfine field suggests radiation-induced decrease in the inter atomic distance around Mössbauer (Fe) atom, (c) hyperfine field distribution confirms the presence of non-magnetic elements (e.g. - B, P, C) in the first near-neighbor shell of the Fe atom, thus reducing its magnetic moment, and (d) changes in isomer shift suggests variation in average number of the metalloid near neighbors and their distances. Minor changes in soft magnetic behavior - watt loss and, coercivity after an irradiation dose of 2 × 1013 ions/cm2 suggests prospective application of Fe77P8Si3C5Al2Ga1B4 alloy as core material in accelerators (radio frequency cavities).

Feasibility study of electrophoresis deposition of DyF3 on Nd-Fe-B particles for coercivity enhancement

NASA Astrophysics Data System (ADS)

Kim, K. M.; Kang, M. S.; Kwon, H. W.; Lee, J. G.; Yu, J. H.

2018-05-01

Feasibility of the electrophoresis deposition (EPD) technique for homogeneous and adhesive deposition of DyF3 particles on the Nd-Fe-B-type particles was studied, and coercivity enhancement in the diffusion-treated Nd-Fe-B-type particles deposited with DyF3 by EPD was investigated. HDDR-treated Nd12.5Fe80.6B6.4Ga0.3Nb0.2 particles were deposited with DyF3 particles by EPD. More homogeneous and adhesive deposition of DyF3 particles on the surface of Nd-Fe-B particles was made by the EPD with respect to conventional dip-coating, and this led to more active and homogeneous diffusion of Dy. More profound coercivity enhancement was achieved in the diffusion-treated Nd-Fe-B-type particles deposited with DyF3 by EPD compared to dip-coated particles.

Role of PO4 tetrahedron in LiFePO4 and FePO4 system.

PubMed

Zeng, Yuewu

2015-06-01

Using high resolution transmission electron microscopy with image simulation and Fourier analysis, the Li1- x FePO4 (x < 0.01), Li1- x FePO4 (x ∼ 0.5), and FePO4 particles, prepared by charging or discharging the 053048 electrochemical cells (thickness: 5 mm, width: 30 mm, height: 48 mm) and dismantled inside an Ar-filled dry box, were investigated. The high resolution images reveal: (1) the solid solution of Li1- x FePO4 (x < 0.01) contains some missing Li ions leading PO4 group distorted around M1 tunnel of the unit cell; (2) the texture of the particles of Li1- x FePO4 (x ∼0.5) has homogeneously distributed compositional domains of LiFePO4 and FePO4 resulting from spinodal decomposition which promote Li ion easily getting into the particle due to uphill diffusion, (3) the particles of FePO4 formed in charging have heavily distorted lattice and contain some isolated LiFePO4 , (4) interface between LiFePO4 and FePO4 and between amorphous and crystal region provides the lattice distortion of small polarons. © 2015 Wiley Periodicals, Inc.

Effect of Fe-Mn addition on microstructure and magnetic properties of NdFeB magnetic powders

NASA Astrophysics Data System (ADS)

Kurniawan, C.; Purba, A. S.; Setiadi, E. A.; Simbolon, S.; Warman, A.; Sebayang, P.

2018-03-01

In this paper, the effect of Fe-Mn alloy addition on microstructures and magnetic properties of NdFeB magnetic powders was investigated. Varied Fe-Mn compositions of 1, 5, and 10 wt% were mixed with commercial NdFeB type MQA powders for 15 minutes using shaker mill. The characterizations were performed by powder density, PSA, XRD, SEM, and VSM. The Fe-Mn addition increased the powder density of NdFeB/Fe-Mn powders. On the other side, particle size distribution slightly decreased as the Fe-Mn composition increases. Magnetic properties of NdFeB/Fe-Mn powders changed with the increasing of Fe-Mn content. SEM analysis showed the particle size of NdFeB/Fe-Mn powder was smaller as the Fe-Mn composition increases. It showed that NdFeB/Fe-Mn particles have different size and shape for NdFeB and Fe-Mn particles separately. The optimum magnetic properties of NdFeB/Fe-Mn powder was achieved on the 5 wt% Fe-Mn composition with remanence M r = 49.45 emu/g, coercivity H c = 2.201 kOe, and energy product, BH max = 2.15 MGOe.

Fe-based bulk amorphous alloys with iron contents as high as 82 at%

NASA Astrophysics Data System (ADS)

Li, Jin-Feng; Liu, Xue; Zhao, Shao-Fan; Ding, Hong-Yu; Yao, Ke-Fu

2015-07-01

Fe-based bulk amorphous alloys (BAAs) with high Fe contents are advantageous due to their high saturation magnetization and low cost. However, preparing Fe-based BAAs with Fe contents higher than 80 at% is difficult due to their poor glass forming abilities (GFA). In this study, an Fe81P8.5C5.5B2Si3 BAA with a diameter of 1 mm and a saturation magnetization of 1.56 T was successfully prepared using the fluxing and copper mold casting methods. In addition, by introducing a small amount of elemental Mo to the alloy, an Fe82Mo1P6.5C5.5B2Si3 BAA rod with a diameter of 1 mm, a high saturation magnetization of 1.59 T, a high yield stress of 3265 MPa, and a clear plasticity of 1.3% was prepared in the same way. The cost effectiveness and good magnetic properties of these newly-developed Fe-based BAAs with Fe contents as high as 82 at% would be advantageous and promising for industrial applications.

Thermal effect on structural and magnetic properties of Fe78B13Si9 annealed amorphous ribbons

NASA Astrophysics Data System (ADS)

Soltani, Mohamed Larbi; Touares, Abdelhay; Aboki, Tiburce A. M.; Gasser, Jean-Georges

2017-08-01

In the present work, we study the influence of thermal treatments on the magnetic properties of as-quenched and pre-crystallized Fe78Si9B13 after stress relaxation. The crystallization behavior of amorphous and treated Fe78Si9B13 ribbons was revisited. The measurements were carried out by means of Differential Scanning Calorimetry, by X-ray diffraction and by Vibrating Sample Magnetometer, Susceptometer and fluxmeter. Relaxed samples were heated in the resistivity device up to 700°C and annealed near the onset temperature about 420°C for respectively 1, 3, 5, 8 hours. In as-quenched samples, two transition points occur at about 505°C and 564°C but in relaxed sample, the transition points have been found about 552°C and 568°C. Kinetics of crystallization was deduced for all studied samples. Annealing of the as-purchased ribbon shows the occurrence of α-Fe and tetragonal Fe3B resulting from the crystallization of the remaining amorphous phase. The effects on magnetic properties were pointed out by relating the structural evolution of the samples. The magnetic measurements show that annealing change the saturation magnetization and the coercive magnetic field values, hence destroying the good magnetic properties of the material. The heat treatment shows that the crystallization has greatly altered the shape of the cycles and moved the magnetic saturation point of the samples. The effect of treatment on the magneto-crystalline anisotropy is also demonstrated.

Evolution of structural and magnetic properties of amorphous CoFeB film with thermal annealing

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

Gupta, Ranjeeta; Gupta, Ajay; Gupta, Mukul

2013-08-14

Evolution of structural and magnetic properties of amorphous Co{sub 68}Fe{sub 14}B{sub 18} thin film with thermal annealing has been studied. Initially, the film exhibits a structural relaxation as evidenced by annihilation of excess free volume and an increase in topological short range order. Annealing at 473 K results in precipitation of primary phase followed by formation of boride phase at a still higher temperature of 598 K. Iron preferentially precipitates out in the primary phase, resulting in the formation of bcc Co{sub 58}Fe{sub 41}. This suggests an affinity of Co towards B. Such affinity between Co and B is evidencedmore » even in the as-deposited film, using hard x-ray photoelectron spectroscopy (HAXPES) measurements. As-deposited film exhibits an in-plane uniaxial magnetic anisotropy which disappears at a temperature well beyond crystallization temperature, suggesting that the origin of anisotropy is mainly a chemical short range order in the system. Variation in the coercivity with thermal annealing can be understood in terms of random anisotropy model. Precise measurement of Fe self-diffusion using neutron reflectivity shows that diffusion length associated with annihilation of excess free volume in the film is about 0.5 nm. This agrees with the length scale of structural fluctuations in amorphous alloys. Secondary ion mass spectrometry measurements show that thermal annealing results in depletion of B in the region of the interface with the substrate, with associated faster Fe diffusion in this region. This faster diffusion of Fe may be a possible cause of preferential crystallization of the film in the interfacial region as seen in some earlier studies.« less

Densification behavior, nanocrystallization, and mechanical properties of spark plasma sintered Fe-based bulk amorphous alloys

NASA Astrophysics Data System (ADS)

Singh, Ashish Kumar

Fe-based amorphous alloys are gaining increasing attention due to their exceptional wear and corrosion resistance for potential structural applications. Two major challenges that are hindering the commercialization of these amorphous alloys are difficulty in processing of bulk shapes (diameter > 10 mm) and lack of ductility. Spark plasma sintering (SPS) is evolving as a promising technique for processing bulk shapes of amorphous and nanocrystalline materials. The objective of this work is to investigate densification behavior, nanocrystallization, and mechanical properties of SPS sintered Fe-based amorphous alloys of composition Fe48Cr15Mo14Y2C15B6. SPS processing was performed in three distinct temperature ranges of amorphous alloys: (a) below glass transition temperature (Tg), (b) between Tg and crystallization temperature (Tx), and (c) above Tx. Punch displacement data obtained during SPS sintering was correlated with the SPS processing parameters such as temperature, pressure, and sintering time. Powder rearrangement, plastic deformation below T g, and viscous flow of the material between Tg and Tx were observed as the main densification stages during SPS sintering. Micro-scale temperature distributions at the point of contact and macro-scale temperature distribution throughout the sample during SPS of amorphous alloys were modeled. The bulk amorphous alloys are expected to undergo structural relaxation and nanocrystallization during SPS sintering. X-ray diffraction (XRD), small angle neutron scattering (SANS), and transmission electron microscopy (TEM) was performed to investigate the evolution of nanocrystallites in SPS sintered Fe-based bulk amorphous alloys. The SANS analysis showed significant scattering for the samples sintered in the supercooled region indicating local structural and compositional changes with the profuse nucleation of nano-clusters (~4 nm). Compression tests and microhardness were performed on the samples sintered at different temperatures ranging from 570 °C to 800 °C. Maximum compression strength (1.1+/-0.2 MPa) was obtained for the samples sintered in the supercooled region. Effects of crystallization on tribological behavior of sintered samples were also investigated where crystallization resulted in increase in wear resistance. Laser surface hardening of SPS sintered amorphous samples were performed. Depending on the processing parameters, the laser surface irradiation causes structural relaxation and nanocrystallization, resulting in surface hardening.

In-situ determination of metallic variation and multi-association in single particles by combining synchrotron microprobe, sequential chemical extraction and multivariate statistical analysis.

PubMed

Zhu, Yu-Min; Zhang, Hua; Fan, Shi-Suo; Wang, Si-Jia; Xia, Yi; Shao, Li-Ming; He, Pin-Jing

2014-07-15

Due to the heterogeneity of metal distribution, it is challenging to identify the speciation, source and fate of metals in solid samples at micro scales. To overcome these challenges single particles of air pollution control residues were detected in situ by synchrotron microprobe after each step of chemical extraction and analyzed by multivariate statistical analysis. Results showed that Pb, Cu and Zn co-existed as acid soluble fractions during chemical extraction, regardless of their individual distribution as chlorides or oxides in the raw particles. Besides the forms of Fe2O3, MnO2 and FeCr2O4, Fe, Mn, Cr and Ni were closely associated with each other, mainly as reducible fractions. In addition, the two groups of metals had interrelations with the Si-containing insoluble matrix. The binding could not be directly detected by micro-X-ray diffraction (μ-XRD) and XRD, suggesting their partial existence as amorphous forms or in the solid solution. The combined method on single particles can effectively determine metallic multi-associations and various extraction behaviors that could not be identified by XRD, μ-XRD or X-ray absorption spectroscopy. The results are useful for further source identification and migration tracing of heavy metals. Copyright © 2014 Elsevier B.V. All rights reserved.

Magnetic moment arrangement in amorphous Fe 0.66Er 0.19B 0.15

NASA Astrophysics Data System (ADS)

Szymański, K.; Kalska, B.; Satuła, D.; Dobrzyński, L.; Broddefalk, A.; Wäppling, R.; Nordblad, P.

2002-11-01

Magnetization measurements and Mössbauer spectroscopy with and without a monochromatic circularly polarized Mössbauer source (MCPMS) have been performed in order to determine the magnetic properties of the amorphous alloy Fe 0.66Er 0.19B 0.15. The system is found to order ferrimagnetically at TC=330 K and to show a compensation temperature ( Tcomp) at 120 K. A reorientation of the magnetic moments of iron and erbium during sample cooling through the compensation point in magnetic field is clearly displayed in the MCPMS data. The orientation of the net magnetic moment is due to the orientation of Fe moments above Tcomp and to Er moments at low temperatures. The results are compatible with a model of predominantly antiferromagnetic Fe-Er coupling accompanied by random local anisotropy acting on the Er moments.

Corrosion behavior in high-temperature pressurized water of Zircaloy-4 joints brazed with Zr-Cu-based amorphous filler alloys

NASA Astrophysics Data System (ADS)

Lee, Jung Gu; Lee, Gyoung-Ja; Park, Jin-Ju; Lee, Min-Ku

2017-05-01

The compositional effects of ternary Zr-Cu-X (X: Al, Fe) amorphous filler alloys on galvanic corrosion susceptibility in high-temperature pressurized water were investigated for Zircaloy-4 brazed joints. Through an Al-induced microgalvanic reaction that deteriorated the overall nobility of the joint, application of the Zr-Cu-Al filler alloy caused galvanic coupling to develop readily between the Al-bearing joint and the Al-free base metal, finally leading to massive localized corrosion of the joint. Contrastingly, joints prepared with a Zr-Cu-Fe filler alloy showed excellent corrosion resistance comparable to that of the Zircaloy-4 base metal, since the Cu and Fe elements forming fine intermetallic particles with Zr did not influence the electrochemical stability of the resultant joints. The present results demonstrate that Fe is a more suitable alloying element than Al for brazing filler alloys subjected to high-temperature corrosive environments.

Abundances and distribution of minerals and elements in high-alumina coal fly ash from the Jungar Power Plant, Inner Mongolia, China

USGS Publications Warehouse

Dai, S.; Zhao, L.; Peng, S.; Chou, C.-L.; Wang, X.; Zhang, Y.; Li, D.; Sun, Y.

2010-01-01

The fly ash from the Jungar Power Plant, Inner Mongolia, China, is unique because it is highly enriched in alumina (Al2O3>50%). The fly ash mainly consists of amorphous glass and mullite and trace amounts of corundum, quartz, char, calcite, K-feldspar, clay minerals, and Fe-bearing minerals. The mullite content in fly ash is as high as 37.4% because of high boehmite and kaolinite contents in feed coal. Corundum is a characteristic mineral formed during the combustion of boehmite-rich coal.Samples from the economizer were sieved into six size fractions (<120, 120-160, 160-300, 300-360, 360-500, and >500 mesh) and separated into magnetic, mullite+corundum+quartz (MCQ) and glass phases for mineralogical and chemical analysis. The corundum content increases but amorphous glass decreases with decreasing particle size. Fractions of small particle sizes are relatively high in mullite, probably because mullite was formed from fine clay mineral particles under high-temperature combustion condition. Similarly, fine corundum crystals formed in the boiler from boehmite in feed coal. The magnetic phase consists of hematite, magnetite, magnesioferrite, and MgFeAlO4 crystals. The MCQ phase is composed of 89% mullite, 6.1% corundum, 4.5% quartz, and 0.5% K-feldspar.Overall, the fly ash from the power plant is significantly enriched in Al2O3 with an average of 51.9%, but poor in SiO2, Fe2O3, CaO, MgO, Na2O, P2O5, and As. Arsenic, TiO2, Th, Al2O3, Bi, La, Ga, Ni, and V are high in mullite, and the magnetic matter is enriched in Fe2O3, CaO, MnO, TiO2, Cs, Co, As, Cd, Ba, Ni, Sb, MgO, Zn, and V. The remaining elements are high in the glass fraction. The concentration of K2O, Na2O, P2O5, Nb, Cr, Ta, U, W, Rb, and Ni do not clearly vary with particle size, while SiO2 and Hg decrease and the remaining elements clearly increase with decreasing particle size. ?? 2009 Elsevier B.V.

Influence of ball milling on atomic structure and magnetic properties of Co{sub 40}Fe{sub 22}Ta{sub 8}B{sub 30} glassy alloy

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

Taghvaei, Amir Hossein, E-mail: Amirtaghvaei@gmail.com; Department of Materials Science and Engineering, Shiraz University of Technology, Shiraz; Stoica, Mihai

2014-06-01

The influence of ball milling on the atomic structure and magnetic properties of the Co{sub 40}Fe{sub 22}Ta{sub 8}B{sub 30} metallic glass with a high thermal stability and excellent soft magnetic properties has been investigated. After 14 h of milling, the obtained powders were found to consist mainly of an amorphous phase and a small fraction of the (Co,Fe){sub 21}Ta{sub 2}B{sub 6} nanocrystals. The changes in the reduced pair correlation functions suggest noticeable changes in the atomic structure of the amorphous upon ball milling. Furthermore, it has been shown that milling is accompanied by introduction of compressive and dilatational sites inmore » the glassy phase and increasing the fluctuation of the atomic-level hydrostatic stress without affecting the coordination number of the nearest neighbors. Ball milling has decreased the thermal stability and significantly affected the magnetic properties through increasing the saturation magnetization, Curie temperature of the amorphous phase and coercivity. - Highlights: • Ball milling affected the atomic structure of Co{sub 40}Fe{sub 22}Ta{sub 8}B{sub 30} metallic glass. • Mechanically-induced crystallization started after 4 h milling. • Milling increased the fluctuation of the atomic-level hydrostatic stress in glass. • Ball milling influenced the thermal stability and magnetic properties.« less

Fast and Universal Approach to Encapsulating Transition Bimetal Oxide Nanoparticles in Amorphous Carbon Nanotubes under an Atmospheric Environment Based on the Marangoni Effect.

PubMed

Li, Shuoyu; Liu, Yuyi; Guo, Peisheng; Wang, Chengxin

2017-09-13

Transition metal oxide nanoparticles capsuled in amorphous carbon nanotubes (ACNTs) are attractive anode materials of lithium-ion batteries (LIBs). Here, we first designed a fast and universal method with a hydromechanics conception which is called Marangoni flow to fabricate transition bimetal oxides (TBOs) in the ACNT composite with a better electrochemistry performance. Marangoni flows can produce a liquid column with several centimeters of height in a tube with one side immersed in the liquid. The key point to induce a Marangoni flow is to make a gradient of the surface tension between the surface and the inside of the solution. With our research, we control the gradient of the surface tension by controlling the viscosity of a solution. To show how our method could be generally used, we synthesize two anode materials such as (a) CoFe 2 O 4 @ACNTs, and (b) NiFe 2 O 4 @ACNTs. All of these have a similar morphology which is ∼20 μm length with a diameter of 80-100 nm for the ACNTs, and the particles (inside the ACNTs) are smaller than 5 nm. In particular, there are amorphous carbons between the nanoparticles. All of the composite materials showed an outstanding electrochemistry performance which includes a high capacity and cycling stability so that after 600 cycles the capacity changed by less than 3%.

Bulk amorphous steels based on Fe alloys

DOEpatents

Lu, ZhaoPing; Liu, Chain T.

2006-05-30

A bulk amorphous alloy has the approximate composition: Fe.sub.(100-a-b-c-d-e)Y.sub.aMn.sub.bT.sub.cM.sub.dX.sub.e wherein: T includes at least one of the group consisting of: Ni, Cu, Cr and Co; M includes at least one of the group consisting of W, Mo, Nb, Ta, Al and Ti; X includes at least one of the group consisting of Co, Ni and Cr; a is an atomic percentage, and a<5; b is an atomic percentage, and b.ltoreq.25; c is an atomic percentage, and c.ltoreq.25; d is an atomic percentage, and d.ltoreq.25; and e is an atomic percentage, and 5.ltoreq.e.ltoreq.30.

Alternating current magnetic susceptibility and heat dissipation by Mn1-xZnxFe2O4 nanoparticles for hyperthermia treatment

NASA Astrophysics Data System (ADS)

Kondo, T.; Mori, K.; Hachisu, M.; Yamazaki, T.; Okamoto, D.; Watanabe, M.; Gonda, K.; Tada, H.; Hamada, Y.; Takano, M.; Ohuchi, N.; Ichiyanagi, Y.

2015-05-01

Mn-Zn ferrite, Mn1-xZnxFe2O4 nanoparticles encapsulated in amorphous SiO2 were prepared using our original wet chemical method. X-ray diffraction patterns confirmed that the diameters of these particles were within 7-30 nm. Magnetization measurements for various sample compositions revealed that the saturation magnetization (Ms) of 7 nm particles was maximum for the x = 0.2 sample. AC magnetic susceptibility measurements were performed for Mn0.8Zn0.2Fe2O4 (x = 0.2) samples with 13-30 nm particles. The peak of the imaginary part of the magnetic susceptibility χ″ shifted to higher temperatures as the particle size increased. An AC field was found to cause the increase in temperature, with the 18 nm particles exhibiting the highest temperature increase, as expected. In addition, in vitro experiments were carried out to study the hyperthermia effects of Mn1-xZnxFe2O4 (x = 0.2, 18 nm) particles on human cancer cells.

Space Weathering Products Found on the Surfaces of the Itokawa Dust Particles: A Summary of the Initial Analysis

NASA Technical Reports Server (NTRS)

Noguchi, T.; Kimura, M.; Hashimoto, T.; Konno, M.; Nakamura, T.; Ogami, T.; Ishida, H.; Sagae, R.; Tsujimoto, S.; Tsuchiyama, A,;

Magnetization Processes in Ribbons of Soft Magnetic Amorphous Alloys

NASA Astrophysics Data System (ADS)

Skulkina, N. A.; Ivanov, O. A.; Mazeeva, A. K.; Kuznetsov, P. A.; Stepanova, E. A.; Blinova, O. V.; Mikhalitsyna, E. A.

2018-02-01

Using iron-based (Fe-B-Si-C; Fe-Ni-Si-B) and cobalt-based (Co-Fe-Ni-Cr-Mn-Si-B) soft magnetic alloys as examples, we have studied the dependences of the remanence measured using minor hysteresis loops on the maximum induction. The different degrees of stabilization of the 180° and 90° domain walls allows these dependences to be used to analyze the magnetization processes that occur in the rapidly quenched soft magnetic alloys. It has been established from the B r( B m) dependences that, in the ribbons of soft magnetic amorphous alloys, the processes of the rotation of the magnetization oriented perpendicular to the ribbon plane start before the end of the processes of the displacement of the walls of domains with planar magnetization. After the end of the magnetization rotation processes, the magnetization processes can be interpreted as the displacement of the domain walls with a planar magnetization accompanied by a decrease in their number and a transition to a bistable state.

Space weathering of asteroids: Lessons from Itokawa for future observations

NASA Astrophysics Data System (ADS)

Sasaki, Sho; HIroi, Takahiro

2016-07-01

Introduction Space weathering of surface silicate minerals is the main process that should control the change of brightness and color of airless silicate bodies such and the Moon, Mercury and asteroids. Spectra of S-type asteroids exhibit more overall depletion and reddening, and more weakening of absorption bands than spectra of ordinary chondrites. These spectral mismatches are explained by the space weathering, where the primary proven mechanism of such spectral change is production of nanophase metallic iron particles (npFe0) 1), which were confirmed in the amorphous rim of lunar soil grains 2,3). Vapor-deposition through at high-velocity dust particle impacts as well as implantation of intensive solar wind ions would be responsible for producing the space weathering rims bearing nano-iron particles (npFe0). Simulation experiments using nanosecond pulse laser successfully produced vapor-deposition type npFe0 to change optical properties 4,5,6). Laser experiments showed that pyroxene would be weathered less than olivine, for pyroxene, pulse laser irradiation produced melt (amorphous) droplets containing npFe0, rather than vapour deposited rim that should provide stronger optical effect trough multiple scattering of incidental light. Itokawa Observed by Remote Sensing In November 2005, Japanese Asteroid Sample Return Mission HAYABUSA spacecraft rendezvoused S-type asteroid (25143) Itokawa. Optically, the surface of Itokawa is divided into brighter (and bluer) areas and darker (and redder) areas 7,8). In rough zones, dark boulder-rich surfaces usually superpose on bright materials. The near-infrared spectrometer (NIRS) confirmed previous disk-integrated results that suggested Itokawa's spectrum closely matched a weakly weathered LL5/6 chondrite 9). Although the surface is covered with rocks and is apparently lack of fine regolith, Itokawa's surface show darkening and reddening by space weathering. Experimental results suggest rocky meteorite fragments can be weathered. The presence of opposition effect in rocky terrain of Itokawa suggested that the surface would be covered by particulate materials or porous enough to scatter light. Spectral variations were observed, that can be explained by Hapke's space weathering model, where the amount of npFe0 controls spectral reddening. As for color variation of Itokawa, we can interpret that seismic shaking caused by impacts or planetary encounters should lead to exposure of underlying relatively fresh bright area by removing weathered darker boulder-rich layer. Itokawa - Evidence from Returned Samples In 2011, HAYABUSA returned more than 1000 particulate samples of Itokawa back to the Earth. Analysis of mineral assemblies and composition of Itokawa particles supports that Itokawa has LL-chondrite composition. The most notable discoveries in Itokawa particles is amorphous space-weathering rims containing npFe0 16, 17, 18). Sometimes ion-implanted type-II layers contains vesicles, probably due mainly to trapping solar wind energetic helium with penetration depth up to a few tens µm (composite vesicular rim in 17, 18)). Large vesicles are observed as blisters on the surface of Itokawa particles. Matsumoto et al. 18) identified space weathered rims with blisters on eleven out of twenty regolith particles of Itokawa. It was confirmed that a blister corresponds to a vesicle in npFe0-bearing amorphous layer. These rims with blisters are heterogeneously distributed even in one particle. Sometimes blistered rims are observed in opposite surfaces of the same particle. This is a strong evidence of regolith mixing. So far, there is no correlation between the blister distribution and surface morphologies such as roundness of particles. A few 10 nm amorphous rim can be developed in timescale 1000 yr (based on solar flare density, Regolith mixing processes may prolong timescale of optical maturation on smooth regions of Itokawa. References 1) Hapke B., Cassidy, W. And Wells. E.: Effects of vapor-phase deposition processes on the optical, chemical, and magnetic properties of the lunar regolith, Moon, 13 (1975), 339-353 2) Keller L. P. and McKay D. S.: Science, 261 (1993), 1305-1307. 3) Pieters C. M., et al. Meteorit.: Planet. Sci., 35 (2000), 1101-1107. 4) Yamada, M., et al.: Earth Planets Space 51 (1999), 1255-1265. 5) Sasaki, S., et al.: Nature 410 (2001), 555-557. 6) Brunetto, R., et al.: Icarus 180 (1995), 546-554. 10) Brunetto, R., Loeffler, M. J., Nesvorny, D., Sasaki, S., and Strazzulla, G.: Asteroid Surface Alteration by Space Weathering Processes, in Asteroid IV, Univ. Arizona Press (2015). 11) Hirata, N., et al.: Icarus 200 (2009), 486-502. 12) Ishiguro, M.: Scattered light correction of Hayabusa/AMICA data and quantitative spectral comparisons of Itokawa, Pub. Astron. Soc. Japan, 66 (2014), 55 13) Noguchi, T., et al.: Icarus 206 (2010), 319-326. 14) Nakamura, T., et al.: Science 333 (2011), 1113-1116. 15] Tsuchiyama, A., et al.: Science 333 (2011), 1125-1128. [6) Noguchi, T., et al.: Science 333 (2011), 1121-1125. 17) Noguchi, T., et al.: Meteorit. Planet. Sci., 49 (2014), 188-214. 18) Matsumoto, T. et al. Icarus (2015) 257, 230. 19) Noble S. K. et al. (2011) Meteorit. Planet. Sci., 45 (2011), 2007.

Solubility of iron from combustion source particles in acidic media linked to iron speciation.

PubMed

Fu, Hongbo; Lin, Jun; Shang, Guangfeng; Dong, Wenbo; Grassian, Vichi H; Carmichael, Gregory R; Li, Yan; Chen, Jianmin

2012-10-16

In this study, iron solubility from six combustion source particles was investigated in acidic media. For comparison, a Chinese loess (CL) dust was also included. The solubility experiments confirmed that iron solubility was highly variable and dependent on particle sources. Under dark and light conditions, the combustion source particles dissolved faster and to a greater extent relative to CL. Oil fly ash (FA) yielded the highest soluble iron as compared to the other samples. Total iron solubility fractions measured in the dark after 12 h ranged between 2.9 and 74.1% of the initial iron content for the combustion-derived particles (Oil FA > biomass burning particles (BP) > coal FA). Ferrous iron represented the dominant soluble form of Fe in the suspensions of straw BP and corn BP, while total dissolved Fe presented mainly as ferric iron in the cases of oil FA, coal FA, and CL. Mössbauer measurements and TEM analysis revealed that Fe in oil FA was commonly presented as nanosized Fe(3)O(4) aggregates and Fe/S-rich particles. Highly labile source of Fe in corn BP could be originated from amorphous Fe form mixed internally with K-rich particles. However, Fe in coal FA was dominated by the more insoluble forms of both Fe-bearing aluminosilicate glass and Fe oxides. The data presented herein showed that iron speciation varies by source and is an important factor controlling iron solubility from these anthropogenic emissions in acidic solutions, suggesting that the variability of iron solubility from combustion-derived particles is related to the inherent character and origin of the aerosols themselves. Such information can be useful in improving our understanding on iron solubility from combustion aerosols when they undergo acidic processing during atmospheric transport.

Light scattering by dust particles (PROGRA2 experiment): size and structure effects for transparent and absorbing materials

NASA Astrophysics Data System (ADS)

Hadamcik, E.; Renard, J.-B.; Lasue, J.; Levasseur-Regourd, A. C.

2007-08-01

1- Introduction Cometary and possibly interplanetary dust particles seem to be mainly made of agglomerates of submicron and micron-sized grains. These particles are among the most primitive in our solar system. Regoliths on asteroidal and planetary surfaces seem to be loose materials produced by impinging meteorites on the surface of small bodies. Comparing their physical properties is thus fundamental to understand their evolution. To interpret remote observations of solar light scattered by dust particles and regoliths, it is necessary to use numerical and experimental simulations [1,2,3]. 2- PROGRA2 experiment PROGRA2 instruments are polarimeters; the light sources are two randomly polarized lasers (632.8 nm and 543.5 nm). Levitating particles (in microgravity or lifted by an air-draught) are studied by imaging polarimetry. Details on the instruments can be found in [4,5]. 3- Samples Two kinds of samples are studied: compact particles in the (1-400) micrometer size range and fluffy aggregates in the same size range, made from submicron and micronsized grains. The materials are transparent silica and absorbing carbon. Some deposited particles are huge agglomerates of micron-sized grains produced by random ballistic deposition of single grains [6,7] or produced by evaporation of mixtures in alcohol of fluffy aggregates of submicron-sized grains. Two samples are made of silica spheres coated by a carbonaceous black compound. Cometary analogues are mixtures of silica and amorphous carbon or Mg-Fe silicates mixed with amorphous carbon. 4- Results Phase curves and their main parameters (negative polarization at small phase angles and maximum polarization, Pmax, at 90-100° phase angle) for the different materials will be compared and related to the physical properties. For example, it is well known by numerical simulations and/or by experiments that the maximum polarization decreases when the size (submicrometer range) of the grains increases [2,8,9]. An inverse rule is found for compact grains, larger than the wavelength. Mixtures of fluffy silica and fined grained amorphous carbon or better Mg-Fe silicates with amorphous carbon are excellent cometary particles analogues (as light scattering is concerned) if they are mixed with some compact micron-sized grains [9]. Nevertheless the structure of the aggregates seems to play a major role to obtain the negative branch found on the polarimetric phase curves for comets [10]. 5- Discussion and conclusions The experiments purpose is to help to disentangle the different physical properties of dust particles that can be deduced from remote observations (cometary dust, regoliths). Differences between the main parameters influencing the variations of Pmax and the presence of a negative branch on the polarimetric phase curves for lifted and deposited particles (in huge agglomerates or not) will be discussed. Acknowledgments: Technische Universität Carolo-Wilhelmina, Braunschweig, Deutschland (Pr Blum, Dr Schräpler); University of New Mexico, Albuquerque, USA (Pr Rietmeijer); NASA Goddard Space Flight Center, Maryland, USA (Dr Nuth) References [1] A.C. Levasseur-Regourd, E. Hadamcik, JQSRT 79-80, 903 (2003) [2] J. Lasue, A.C. Levasseur-Regourd, JQSRT 100, 220 (2006) [3] J.-B. Renard et al., ASR 31, 2511 (2003) [4] J.-B. Renard et al., Appl. Opt. 91, 609 (2002) [5] E. Hadamcik et al., JQSRT 106, 74 (2007) [6] J. Blum, R. Schreapler, Phys. Rev Let 93:115031 (2004) [7] J. Blum et al., Astrophys J 652, 1768 (2006) [8] R. West, Appl. Opt. 30, 5216 (1991) [9] E. Hadamcik et al., JQSRT 100, 143 (2006) [10] E. Hadamcik et al., Icarus, in press (2007)

Formation of soft magnetic high entropy amorphous alloys composites containing in situ solid solution phase

NASA Astrophysics Data System (ADS)

Wei, Ran; Sun, Huan; Chen, Chen; Tao, Juan; Li, Fushan

2018-03-01

Fe-Co-Ni-Si-B high entropy amorphous alloys composites (HEAACs), which containing high entropy solid solution phase in amorphous matrix, show good soft magnetic properties and bending ductility even in optimal annealed state, were successfully developed by melt spinning method. The crystallization phase of the HEAACs is solid solution phase with body centered cubic (BCC) structure instead of brittle intermetallic phase. In addition, the BCC phase can transformed into face centered cubic (FCC) phase with temperature rise. Accordingly, Fe-Co-Ni-Si-B high entropy alloys (HEAs) with FCC structure and a small amount of BCC phase was prepared by copper mold casting method. The HEAs exhibit high yield strength (about 1200 MPa) and good plastic strain (about 18%). Meanwhile, soft magnetic characteristics of the HEAs are largely reserved from HEAACs. This work provides a new strategy to overcome the annealing induced brittleness of amorphous alloys and design new advanced materials with excellent comprehensive properties.

Dilution effect on the formation of amorphous phase in the laser cladded Ni-Fe-B-Si-Nb coatings after laser remelting process

NASA Astrophysics Data System (ADS)

Li, Ruifeng; Li, Zhuguo; Huang, Jian; Zhu, Yanyan

2012-08-01

Ni-Fe-B-Si-Nb coatings have been deposited on mild steel substrates using high power diode laser cladding. Scanning laser beam at high speeds was followed to remelt the surface of the coatings. Different laser cladding powers in the range of 700-1000 W were used to obtain various dilution ratios in the coating. The dilution effect on the chemical characterization, phase composition and microstructure is analyzed by energy dispersive spectroscopy, X-ray diffraction and scanning-electron microscopy. The microhardness distribution of the coatings after laser processing is also measured. The results reveal that Ni-based amorphous composite coatings have successfully been fabricated on mild steel substrate at low dilution ratio when the cladding power was 700 W, 800 W and 900 W. While at high laser power of 1000 W, no amorphous phase was found. The coatings with low dilution ratio exhibit the highest microhardness of 1200 HV0.5 due to their largest volume fraction of amorphous phase.

Sensitive bistable magnetic sensors using twisted amorphous magnetostrictive ribbons due to Matteucci effect

NASA Astrophysics Data System (ADS)

Mohri, K.; Takeuchi, S.

1982-11-01

New sensitive magnetic-field sensors are presented using twisted amorphous magnetostrictive ribbons such as Fe80B20 and Fe81-xCrxB17Si2. Sharp voltage pulses are induced between ends of the ribbon of as short as 25 mm or at the terminals of the detecting coil against external fields of as low as 1 Oe and 0.01 Hz-6 kHz. The domain nucleation field at the bistable flux reversal is very constant for 130 °C, 600 h using Fe79Cr2B17Si2, and a possible maximum operating temperature is about 180 °C. Small sized magnetic sensors without any windings for detecting rotational speed, distance, and other mechanical quantities are realized using the twisted ribbons by combining with small magnets. These sensitive and reliable magnetic sensors with digital outputs are suitable for applications in industrial robots and automobiles controlled with microcomputers.

Novel nanometer-level uniform amorphous carbon coating for boron powders by direct pyrolysis of coronene without solvent.

PubMed

Ye, ShuJun; Song, MingHui; Kumakura, Hiroaki

2015-01-30

A 3 nm coronene coating and a 4 nm amorphous carbon coating with a uniform shell-core encapsulation structure for nanosized boron (B) powders are formed by a simple process in which coronene is directly mixed with boron particles without a solvent and heated at 520 °C for 1 h or at 630 °C for 3 h in a vacuum-sealed silica tube. Coronene has a melting point lower than its decomposition temperature, which enables liquid coronene to cover B particles by liquid diffusion and penetration without the need for a solvent. The diffusion and penetration of coronene can extend to the boundaries of particles and to inside the agglomerated nanoparticles to form a complete shell-core encapsulated structure. As the temperature is increased, thermal decomposition of coronene on the B particles results in the formation of a uniform amorphous carbon coating layer. This novel and simple nanometer-level uniform amorphous carbon coating method can possibly be applied to many other powders; thus, it has potential applications in many fields at low cost.

The Effect of Ion Irradiation on Nanocrystallization and Surface Relief of a Ribbon from Fe72.5Cu1Nb2Mo1.5Si14B9 Alloy

NASA Astrophysics Data System (ADS)

Romanov, I. Yu.; Gushchina, N. V.; Ovchinnikov, V. V.; Makhinko, F. F.; Stepanov, A. V.; Medvedev, A. I.; Starodubtsev, Yu. N.; Belozerov, V. Ya.; Loginov, B. A.

2018-02-01

Using the methods of X-ray diffraction and atomic force microscopy, the process of crystallization of an amorphous Fe72.5Cu1Nb2Mo1.5Si14B9 alloy irradiated with accelerated Ar+ ions is investigated. It is found out that an irradiation by the Ar+ ions with the energy 30 keV at the ion current density 300 μA/cm2 (fluence 3.75·1015 cm-2, irradiation time 2 s, ion-beam short-duration heating up to 350°C, which is 150°C lower than the thermal crystallization threshold) results in a complete crystallization of this amorphous alloy (throughout the bulk of a 25 μm ribbon) followed by precipitation of solid solution crystals of α-Fe(Si), close in its composition to Fe80Si20, stable phase of Fe3Si, and metastable hexagonal phases. By the methods of atomic force and scanning tunneling microscopy it is shown that nanocrystallization caused by ion irradiation is accompanied by surface relief changes both on the irradiated and unirradiated sides of the Fe72.5Cu1Nb2Mo1.5Si14B9 alloy ribbon at the depth exceeding by a factor of 103 that of the physical ion penetration for this material. The data obtained, taking into account a significant temperature decrease and multiple acceleration of the crystallization process, serve an evidence of the radiation-dynamic influence of accelerated ions on the metastable amorphous medium.

Characterisation of Fe-bearing particles and colloids in the Lena River basin, NE Russia

NASA Astrophysics Data System (ADS)

Hirst, Catherine; Andersson, Per S.; Shaw, Samuel; Burke, Ian T.; Kutscher, Liselott; Murphy, Melissa J.; Maximov, Trofim; Pokrovsky, Oleg S.; Mörth, Carl-Magnus; Porcelli, Don

2017-09-01

Rivers are significant contributors of Fe to the ocean. However, the characteristics of chemically reactive Fe remain poorly constrained, especially in large Arctic rivers, which drain landscapes highly susceptible to climate change and carbon cycle alteration. The aim of this study was a detailed characterisation (size, mineralogy, and speciation) of riverine Fe-bearing particles (>0.22 μm) and colloids (1 kDa-0.22 μm) and their association with organic carbon (OC), in the Lena River and tributaries, which drain a catchment almost entirely underlain by permafrost. Samples from the main channel and tributaries representing watersheds that span a wide range in topography and lithology were taken after the spring flood in June 2013 and summer baseflow in July 2012. Fe-bearing particles were identified, using Transmission Electron Microscopy, as large (200 nm-1 μm) aggregates of smaller (20-30 nm) spherical colloids of chemically-reactive ferrihydrite. In contrast, there were also large (500 nm-1 μm) aggregates of clay (illite) particles and smaller (100-200 nm) iron oxide particles (dominantly hematite) that contain poorly reactive Fe. TEM imaging and Scanning Transmission X-ray microscopy (STXM) indicated that the ferrihydrite is present as discrete particles within networks of amorphous particulate organic carbon (POC) and attached to the surface of primary produced organic matter and clay particles. Together, these larger particles act as the main carriers of nanoscale ferrihydrite in the Lena River basin. The chemically reactive ferrihydrite accounts for on average 70 ± 15% of the total suspended Fe in the Lena River and tributaries. These observations place important constraints on Fe and OC cycling in the Lena River catchment area and Fe-bearing particle transport to the Arctic Ocean.

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.

Relationships between spray parameters, microstructures and ultrasonic cavitation erosion behavior of HVOF sprayed Fe-based amorphous/nanocrystalline coatings.

PubMed

Qiao, Lei; Wu, Yuping; Hong, Sheng; Zhang, Jianfeng; Shi, Wei; Zheng, Yugui

2017-11-01

Fe-based amorphous/nanocrystalline coatings were prepared on the AISI 321 steel substrate by the high-velocity oxygen-fuel (HVOF) thermal spraying technology. The effect of selected parameters (oxygen flow, kerosene flow and spray distance) on the cavitation erosion resistance (denoted as Rc) of the coating were investigated by using the Taguchi method. Statistical tools such as design of experiments (DOE), signal-to-noise (S/N) ratio and analysis of variance (ANOVA) were used to meet the expected objective. It was concluded that the kerosene flow had greater influence on the Rc of the coating and followed by the spray distance and the oxygen flow, respectively. The optimum spray parameters (OSP) were 963L/min for the oxygen flow, 28L/h for the kerosene flow, and 330mm for the spray distance. The Rc of the coating increased with the increase of hardness or the decrease of porosity, and the hardness had a greater influence on Rc than the porosity. The Fe-based coating deposited under the OSP exhibited the best cavitation erosion resistance in distilled water. The cracks initiated at the edge of the pores and the interfaces between the un-melted or half-melted particles, and finally leaded to the delamination of the coating. Copyright © 2017 Elsevier B.V. All rights reserved.

Microbially-accelerated consolidation of oil sands tailings. Pathway II: solid phase biogeochemistry.

PubMed

Siddique, Tariq; Kuznetsov, Petr; Kuznetsova, Alsu; Li, Carmen; Young, Rozlyn; Arocena, Joselito M; Foght, Julia M

2014-01-01

Consolidation of clay particles in aqueous tailings suspensions is a major obstacle to effective management of oil sands tailings ponds in northern Alberta, Canada. We have observed that microorganisms indigenous to the tailings ponds accelerate consolidation of mature fine tailings (MFT) during active metabolism by using two biogeochemical pathways. In Pathway I, microbes alter porewater chemistry to indirectly increase consolidation of MFT. Here, we describe Pathway II comprising significant, direct and complementary biogeochemical reactions with MFT mineral surfaces. An anaerobic microbial community comprising Bacteria (predominantly Clostridiales, Synergistaceae, and Desulfobulbaceae) and Archaea (Methanolinea/Methanoregula and Methanosaeta) transformed Fe(III) minerals in MFT to amorphous Fe(II) minerals during methanogenic metabolism of an added organic substrate. Synchrotron analyses suggested that ferrihydrite (5Fe2O3. 9H2O) and goethite (α-FeOOH) were the dominant Fe(III) minerals in MFT. The formation of amorphous iron sulfide (FeS) and possibly green rust entrapped and masked electronegative clay surfaces in amended MFT. Both Pathways I and II reduced the surface charge potential (repulsive forces) of the clay particles in MFT, which aided aggregation of clays and formation of networks of pores, as visualized using cryo-scanning electron microscopy (SEM). These reactions facilitated the egress of porewater from MFT and increased consolidation of tailings solids. These results have large-scale implications for management and reclamation of oil sands tailings ponds, a burgeoning environmental issue for the public and government regulators.

Microbially-accelerated consolidation of oil sands tailings. Pathway II: solid phase biogeochemistry

PubMed Central

Siddique, Tariq; Kuznetsov, Petr; Kuznetsova, Alsu; Li, Carmen; Young, Rozlyn; Arocena, Joselito M.; Foght, Julia M.

2014-01-01

Consolidation of clay particles in aqueous tailings suspensions is a major obstacle to effective management of oil sands tailings ponds in northern Alberta, Canada. We have observed that microorganisms indigenous to the tailings ponds accelerate consolidation of mature fine tailings (MFT) during active metabolism by using two biogeochemical pathways. In Pathway I, microbes alter porewater chemistry to indirectly increase consolidation of MFT. Here, we describe Pathway II comprising significant, direct and complementary biogeochemical reactions with MFT mineral surfaces. An anaerobic microbial community comprising Bacteria (predominantly Clostridiales, Synergistaceae, and Desulfobulbaceae) and Archaea (Methanolinea/Methanoregula and Methanosaeta) transformed FeIII minerals in MFT to amorphous FeII minerals during methanogenic metabolism of an added organic substrate. Synchrotron analyses suggested that ferrihydrite (5Fe2O3. 9H2O) and goethite (α-FeOOH) were the dominant FeIII minerals in MFT. The formation of amorphous iron sulfide (FeS) and possibly green rust entrapped and masked electronegative clay surfaces in amended MFT. Both Pathways I and II reduced the surface charge potential (repulsive forces) of the clay particles in MFT, which aided aggregation of clays and formation of networks of pores, as visualized using cryo-scanning electron microscopy (SEM). These reactions facilitated the egress of porewater from MFT and increased consolidation of tailings solids. These results have large-scale implications for management and reclamation of oil sands tailings ponds, a burgeoning environmental issue for the public and government regulators. PMID:24711806

Impact of Ion Bombardment on the Structure and Magnetic Properties of Fe78Si13B9 Amorphous Alloy

NASA Astrophysics Data System (ADS)

Wu, Yingwei; Peng, Kun

2018-06-01

Amorphous Fe78Si13B9 alloy ribbons were bombarded by ion beams with different incident angles ( θ ). The evolution of the microstructure and magnetic properties of ribbons caused by ion beam bombardment was investigated by x-ray diffraction, transmission electron microscope and vibrating sample magnetometer analysis. Low-incident-angle bombardment led to atomic migration in the short range, and high-incident-angle bombardment resulted in the crystallization of amorphous alloys. Ion bombardment induces magnetic anisotropy and affects magnetic properties. The effective magnetic anisotropy was determined by applying the law of approach to saturation, and it increased with the increase of the ion bombardment angle. The introduction of effective magnetic anisotropy will reduce the permeability and increase the relaxation frequency. Excellent high-frequency magnetic properties can be obtained by selecting suitable ion bombardment parameters.

OPTICAL AND SPECTROSCOPIC STUDIES OF Fe2O3-Bi2O3-B2O3:V2O5 GLASSES

NASA Astrophysics Data System (ADS)

Sanjay; Kishore, N.; Agarwal, A.; Dahiya, S.; Pal, Inder; Kumar, Navin

2013-11-01

The glasses of compositions xFe2O3ṡ (40 - x)Bi2O3ṡ60B2O3ṡ2V2O5 have been prepared by the standard melt-quenching technique. Amorphous nature of these samples is ascertained by XRD patterns. The presence of BO3 and BO4 units is identified by IR spectra of glass samples. The absorption edge (λcut-off) shifts toward longer wavelengths with an increase in Fe2O3 content in the glass matrix. The values of optical band gap energy for indirect allowed and forbidden transitions have been determined and it is found to decrease with increase in transition metal ions. The Urbach's energy is used to characterize the degree of disorder in amorphous solids.

The Mineralogy of Circumstellar Silicates Preserved in Cometary Dust

NASA Technical Reports Server (NTRS)

Keller, L. P.; Messenger, S.

2010-01-01

Interplanetary dust particles (IDPs) contain a record of the building blocks of the solar system including presolar grains, molecular cloud material, and materials formed in the early solar nebula. Cometary IDPs have remained relatively unaltered since their accretion because of the lack of parent body thermal and aqueous alteration. We are using coordinated transmission electron microscope (TEM) and ion microprobe studies to establish the origins of the various components within cometary IDPs. Of particular interest is the nature and abundance of presolar silicates in these particles because astronomical observations suggest that crystalline and amorphous silicates are the dominant grain types produced in young main sequence stars and evolved O-rich stars. Five circumstellar grains have been identified including three amorphous silicate grains and two polycrystalline aggregates. All of these grains are between 0.2 and 0.5 micrometers in size. The isotopic compositions of all five presolar silicate grains fall within the range of presolar oxides and silicates, having large (17)O-enrichments and normal (18)O/(16)O ratios (Group 1 grains from AGB and RG stars). The amorphous silicates are chemically heterogeneous and contain nanophase FeNi metal and FeS grains in a Mg-silicate matrix. Two of the amorphous silicate grains are aggregates with subgrains showing variable Mg/Si ratios in chemical maps. The polycrystalline grains show annealed textures (equilibrium grains boundaries, uniform Mg/Fe ratios), and consist of 50-100 nm enstatite and pyrrhotite grains with lesser forsterite. One of the polycrystalline aggregates contains a subgrain of diopside. The polycrystalline aggregates form by subsolidus annealing of amorphous precursors. The bulk compositions of the five grains span a wide range in Mg/Si ratios from 0.4 to 1.2 (avg. 0.86). The average Fe/Si (0.40) and S/Si (0.21) ratios show a much narrower range of values and are approximately 50% of their solar abundances. The latter observation may indicate a decoupling of the silicate and sulfide components in grains that condense in stellar outflows. The amorphous silicate grains described here were not extensively affected by irradiation, sputtering, or thermal processing and may represent relatively pristine circumstellar grains. They are strong candidates for the "dirty silicates" in astronomical observations of circumstellar dust shells. The polycrystalline grains were originally amorphous silicate grains that were likely annealed in the early solar nebula but the processing was not sufficient to erase their anomalous oxygen isotopic compositions.

Neutron irradiation and high temperature effects on amorphous Fe-based nano-coatings on steel – A macroscopic assessment

DOE PAGES

Simos, N.; Zhong, Z.; Dooryhee, E.; ...

2017-03-23

Here, this study revealed that loss of ductility in an amorphous Fe-alloy coating on a steel substrate composite structure was essentially prevented from occurring, following radiation with modest neutron doses of ~2 x 10 18 n/cm 2. At the higher neutron dose of ~2 x 10 19, macroscopic stress-strain analysis showed that the amorphous Fe-alloy nanostructured coating, while still amorphous, experienced radiation-induced embrittlement, no longer offering protection against ductility loss in the coating-substrate composite structure. Neutron irradiation in a corrosive environment revealed exemplary oxidation/corrosion resistance of the amorphous Fe-alloy coating, which is attributed to the formation of the Fe 2Bmore » phase in the coating. To establish the impact of elevated temperatures on the amorphous-to-crystalline transition in the amorphous Fe-alloy, electron microscopy was carried out which confirmed the radiation-induced suppression of crystallization in the amorphous Fe-alloy nanostructured coating.« less

Investigating the Effects of Low Temperature Annealing of Amorphous Corrosion Resistant Alloys.

DTIC Science & Technology

1980-11-01

Ray Diffraction.................................................... 6 Differential Scanning Calorimetry....................................... 9...17 LIST OF FIGURES Figure 1. X- Ray Diffraction Results From Fe32Ni 36Cr 4P 2 B Annealed for One Hour at...Various Temperatures (Cr Ka Radiation) ................................. 7 Figure 2. X- Ray Diffraction Results From FeU2NiaeCr14SieB Annealed for One

Tuning the Magnetic and Electronic Properties of Iron(x )Silicon(1-x) Thin Films for Spintronics

NASA Astrophysics Data System (ADS)

Karel, Julie Elizabeth

This dissertation investigated the magnetic and electronic properties of a potentially better alternative: off-stoichimetry, bcc-like FexSi 1-x thin films (0.43800 K) and theoretically predicted high spin polarization (100%). However, little work has been done on off-stoichiometry FexSi1-x thin films (0.43

Phase separation and crystallization process of amorphous Fe{sub 78}B{sub 12}Si{sub 9}Ni{sub 1} alloy

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

Mukhgalin, V. V.; Lad’yanov, V. I.

2015-08-17

The influence of the melt heat treatment on the structure and crystallization process of the rapidly quenched amorphous Fe{sub 78}B{sub 12}Si{sub 9}Ni{sub 1} alloys have been investigated by means of x-ray diffraction, DSC and TEM. Amorphous phase separation has been observed in the alloys quenched after the preliminary high temperature heat treatment of the liquid alloy (heating above 1400°C). Comparative analysis of the pair distribution functions demonstrates that this phase separation accompanied by a changes in the local atomic arrangement. It has been found that crystallization process at heating is strongly dependent on the initial amorphous phase structure - homogeneousmore » or phase separated. In the last case crystallization goes through the formation of a new metastable hexagonal phase [a=12.2849(9) Ǻ, c=7.6657(8) Ǻ]. At the same time the activation energy for crystallization (Ea) reduces from 555 to 475 kJ mole{sup −1}.« less

Structural Transformation in Fe73.5Nb3Cu1Si15.5B7 Amorphous Alloy Induced by Laser Heating

NASA Astrophysics Data System (ADS)

Nykyruy, Yu. S.; Mudry, S. I.; Kulyk, Yu. O.; Zhovneruk, S. V.

2018-03-01

The effect of continuous laser irradiation (λ = 1.06 μm) with laser power of 45 W on the structure of Fe73.5Nb3Cu1Si15.5B7 amorphous alloy has been studied using X-ray diffraction and SEM methods. The sample of the ribbon has been placed at a distance from the focal plane of the lens, so a laser beam has been defocused and the diameter of laser spot on the ribbon surface has been about 10 mm. An exposure time τ varied within interval 0.25-0.70 s. Under such conditions structural transformation processes, which depend on the exposure time, have occurred in an irradiated zone. Crystallization process has started at τ = 0.35 s with the formation of α-Fe(Si) nanocrystalline phase, while complete crystallization has occurred at τ = 0.55 s with formation of two nanocrystalline phases: α-Fe(Si) and a hexagonal H-phase.

Mössbauer and Kerr microscopy investigation of crystallization in FeCoB ribbons

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

Reddy, V. Raghavendra, E-mail: varimalla@yahoo.com, E-mail: vrreddy@csr.res.in; Hussain, Zaineb; Babu, Hari

2016-05-23

The present work reports the crystallization study of amorphous FeCoB ribbons using x-ray diffraction, {sup 57}Fe Mössbauer spectroscopy in transmission mode and magneto-optical Kerr (MOKE) microscopy. Annealing at 673 K is found to result in crystallization. From the Mossbauer measurements it is observed that the Fe magnetic moments are in the plane of sample for as-cast ribbon; α-FeCo, (Fe{sub 0.5}Co{sub 0.5}){sub 2}B and Fe{sub 2}B phases are formed after crystallization. MOKE microscopy revealed that wide 180° domain walls & narrow fingerprint domains are observed before crystallization and fine domains are observed after crystallization. The results are explained in terms ofmore » the presence of internal stresses and their annealing with thermal heat treatment.« less

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.

High Purity and Yield of Boron Nitride Nanotubes Using Amorphous Boron and a Nozzle-Type Reactor

PubMed Central

Kim, Jaewoo; Seo, Duckbong; Yoo, Jeseung; Jeong, Wanseop; Seo, Young-Soo; Kim, Jaeyong

2014-01-01

Enhancement of the production yield of boron nitride nanotubes (BNNTs) with high purity was achieved using an amorphous boron-based precursor and a nozzle-type reactor. Use of a mixture of amorphous boron and Fe decreases the milling time for the preparation of the precursor for BNNTs synthesis, as well as the Fe impurity contained in the B/Fe interdiffused precursor nanoparticles by using a simple purification process. We also explored a nozzle-type reactor that increased the production yield of BNNTs compared to a conventional flow-through reactor. By using a nozzle-type reactor with amorphous boron-based precursor, the weight of the BNNTs sample after annealing was increased as much as 2.5-times with much less impurities compared to the case for the flow-through reactor with the crystalline boron-based precursor. Under the same experimental conditions, the yield and quantity of BNNTs were estimated as much as ~70% and ~1.15 g/batch for the former, while they are ~54% and 0.78 g/batch for the latter. PMID:28788161

High Purity and Yield of Boron Nitride Nanotubes Using Amorphous Boron and a Nozzle-Type Reactor.

PubMed

Kim, Jaewoo; Seo, Duckbong; Yoo, Jeseung; Jeong, Wanseop; Seo, Young-Soo; Kim, Jaeyong

2014-08-11

Enhancement of the production yield of boron nitride nanotubes (BNNTs) with high purity was achieved using an amorphous boron-based precursor and a nozzle-type reactor. Use of a mixture of amorphous boron and Fe decreases the milling time for the preparation of the precursor for BNNTs synthesis, as well as the Fe impurity contained in the B/Fe interdiffused precursor nanoparticles by using a simple purification process. We also explored a nozzle-type reactor that increased the production yield of BNNTs compared to a conventional flow-through reactor. By using a nozzle-type reactor with amorphous boron-based precursor, the weight of the BNNTs sample after annealing was increased as much as 2.5-times with much less impurities compared to the case for the flow-through reactor with the crystalline boron-based precursor. Under the same experimental conditions, the yield and quantity of BNNTs were estimated as much as ~70% and ~1.15 g/batch for the former, while they are ~54% and 0.78 g/batch for the latter.

In situ observation of defect annihilation in Kr ion-irradiated bulk Fe/amorphous-Fe 2 Zr nanocomposite alloy

DOE PAGES

Yu, K. Y.; Fan, Z.; Chen, Y.; ...

2014-08-26

Enhanced irradiation tolerance in crystalline multilayers has received significant attention lately. However, little is known on the irradiation response of crystal/amorphous nanolayers. We report on in situ Kr ion irradiation studies of a bulk Fe 96Zr 4 nanocomposite alloy. Irradiation resulted in amorphization of Fe 2Zr and formed crystal/amorphous nanolayers. α-Fe layers exhibited drastically lower defect density and size than those in large α-Fe grains. In situ video revealed that mobile dislocation loops in α-Fe layers were confined by the crystal/amorphous interfaces and kept migrating to annihilate other defects. This study provides new insights on the design of irradiation-tolerant crystal/amorphousmore » nanocomposites.« less

Toughening Fe-based Amorphous Coatings by Reinforcement of Amorphous Carbon.

PubMed

Wang, Wei; Zhang, Cheng; Zhang, Zhi-Wei; Li, Yi-Cheng; Yasir, Muhammad; Wang, Hai-Tao; Liu, Lin

2017-06-22

Toughening of Fe-based amorphous coatings meanwhile maintaining a good corrosion resistance remains challenging. This work reports a novel approach to improve the toughness of a FeCrMoCBY amorphous coating through in-situ formation of amorphous carbon reinforcement without reducing the corrosion resistance. The Fe-based composite coating was prepared by high velocity oxy-fuel (HVOF) thermal spraying using a pre-mixed Fe-based amorphous/nylon-11 polymer feedstock powders. The nylon-11 powders were in-situ carbonized to amorphous carbon phase during thermal spraying process, which homogeneously distributed in the amorphous matrix leading to significant enhancement of toughness of the coating. The mechanical properties, including hardness, impact resistance, bending and fatigue strength, were extensively studied by using a series of mechanical testing techniques. The results revealed that the composite coating reinforced by amorphous carbon phase exhibited enhanced impact resistance and nearly twice-higher fatigue strength than that of the monolithic amorphous coating. The enhancement of impact toughness and fatigue properties is owed to the dumping effect of the soft amorphous carbon phase, which alleviated stress concentration and decreased crack propagation driving force.

Microstructure and Electrochemical Behavior of Fe-Based Amorphous Metallic Coatings Fabricated by Atmospheric Plasma Spraying

NASA Astrophysics Data System (ADS)

Zhou, Z.; Wang, L.; He, D. Y.; Wang, F. C.; Liu, Y. B.

2011-01-01

A Fe48Cr15Mo14C15B6Y2 alloy with high glass forming ability (GFA) was selected to prepare amorphous metallic coatings by atmospheric plasma spraying (APS). The as-deposited coatings present a dense layered structure and low porosity. Microstructural studies show that some nanocrystals and a fraction of yttrium oxides formed during spraying, which induced the amorphous fraction of the coatings decreasing to 69% compared with amorphous alloy ribbons of the same component. High thermal stability enables the amorphous coatings to work below 910 K without crystallization. The results of electrochemical measurement show that the coatings exhibit extremely wide passive region and relatively low passive current density in 3.5% NaCl and 1 mol/L HCl solutions, which illustrate their superior ability to resist localized corrosion. Moreover, the corrosion behavior of the amorphous coatings in 1 mol/L H2SO4 solution is similar to their performance under conditions containing chloride ions, which manifests their flexible and extensive ability to withstand aggressive environments.

Hysteresis properties of the amorphous high permeability Co66Fe3Cr3Si15B13 alloy

NASA Astrophysics Data System (ADS)

Tsepelev, V. S.; Starodubtsev, Yu. N.; Tsepeleva, N. P.

2018-04-01

The scaling law of minor loops was studied on an amorphous alloy Co66Fe3Cr3Si15B13 with a very high initial permeability (more than 150000) and low coercivity (about 0.1 A/m). An analytical expression for the coercive force in the Rayleigh region was derived. The coercive force is connected with the maximal magnetic field Hmax via the reversibility coefficient μi/ηHmax. Reversibility coefficient shows the relationship between reversible and irreversible magnetization processes. A universal dependence of magnetic losses for hysteresis Wh on the remanence Br with a power factor of 1.35 is confirmed for a wide range of magnetic fields strengths.

Alternating current magnetic susceptibility and heat dissipation by Mn{sub 1−x}Zn{sub x}Fe{sub 2}O{sub 4} nanoparticles for hyperthermia treatment

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

Kondo, T.; Mori, K.; Hachisu, M.

2015-05-07

Mn-Zn ferrite, Mn{sub 1−x}Zn{sub x}Fe{sub 2}O{sub 4} nanoparticles encapsulated in amorphous SiO{sub 2} were prepared using our original wet chemical method. X-ray diffraction patterns confirmed that the diameters of these particles were within 7–30 nm. Magnetization measurements for various sample compositions revealed that the saturation magnetization (M{sub s}) of 7 nm particles was maximum for the x = 0.2 sample. AC magnetic susceptibility measurements were performed for Mn{sub 0.8}Zn{sub 0.2}Fe{sub 2}O{sub 4} (x = 0.2) samples with 13–30 nm particles. The peak of the imaginary part of the magnetic susceptibility χ″ shifted to higher temperatures as the particle size increased. An AC field was found to causemore » the increase in temperature, with the 18 nm particles exhibiting the highest temperature increase, as expected. In addition, in vitro experiments were carried out to study the hyperthermia effects of Mn{sub 1−x}Zn{sub x}Fe{sub 2}O{sub 4} (x = 0.2, 18 nm) particles on human cancer cells.« less

Efficient Formation of Light-Absorbing Polymeric Nanoparticles from the Reaction of Soluble Fe(III) with C4 and C6 Dicarboxylic Acids.

PubMed

Tran, Ashley; Williams, Geoffrey; Younus, Shagufta; Ali, Nujhat N; Blair, Sandra L; Nizkorodov, Sergey A; Al-Abadleh, Hind A

2017-09-05

The role of transition metals in the formation and aging of secondary organic aerosol (SOA) from aliphatic and aromatic precursors in heterogeneous/multiphase reactions is not well understood. The reactivity of soluble Fe(III) toward known benzene photooxidation products that include fumaric (trans-butenedioic) and muconic (trans,trans-2,4-hexadienedioic) acids was investigated. Efficient formation of brightly colored nanoparticles was observed that are mostly rod- or irregular-shaped depending on the structure of the organic precursor. The particles were characterized for their optical properties, growth rate, elemental composition, iron content, and oxidation state. Results indicate that these particles have mass absorption coefficients on the same order as black carbon and larger than that of biomass burning aerosols. The particles are also amorphous in nature and consist of polymeric chains of Fe centers complexed to carboxylate groups. The oxidation state of Fe was found to be in between Fe(III) and Fe(II) in standard compounds. The organic reactant to iron molar ratio and pH were found to affect the particle growth rate. Control experiments using maleic acid (cis-butenedioic acid) and succinic acid (butanedioic acid) produced no particles. The formation of particles reported herein could account for new pathways that lead to SOA and brown carbon formation mediated by transition metals. In addition, the multiple chemically active components in these particles (iron, organics, and acidic groups) may have an effect on their chemical reactivity (enhanced uptake of trace gases, catalysis, and production of reactive oxygen species) and their likely poor cloud/ice nucleation properties.

Effect of milling on the plastic and the elastic stiffness of lactose particles.

PubMed

Pazesh, Samaneh; Persson, Ann-Sofie; Berggren, Jonas; Alderborn, Göran

2018-03-01

The purpose of this study was to investigate the effect of degree of disorder of a series of α-lactose monohydrate powders, prepared by milling for different time periods, on the plastic and the elastic stiffness of the particles. As references, a series of physical mixtures consisting of original crystalline particles and amorphous particles obtained by spray-drying was used. In addition, the effect of powder pre-storage humidity on the mechanical properties was investigated. For milled particles of a low degree of disorder, a decreased particle size increased the particle plastic stiffness. For milled particles of constant particle size, the plastic stiffness decreased with an increased degree of disorder while the elastic stiffness seemed nearly independent of the degree of disorder. The presence of moisture caused a recrystallisation of milled particles with low degree of disorder which increased their plastic stiffness. For the physical mixtures of crystalline and amorphous particles, similar relationships between plastic stiffness and amorphous content as for the milled powders were obtained. A reasonable explanation is that the nature of the milled particles is represented by a two-state system with crystalline and amorphous domains. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

Effect of magnetic field annealing on soft magnetic properties of Co71Fe2Si14-xB9+xMn4 amorphous alloys with low permeability

NASA Astrophysics Data System (ADS)

Fan, Xingdu; Li, Meng; Zhang, Tao; Yuan, Chenchen; Shen, Baolong

2018-05-01

The effect of transverse magnetic field annealing (TFA) on soft magnetic properties of Co71Fe2Si14-xB9+xMn4 amorphous alloys was investigated with the aim of reducing effective permeability (μe). It was revealed that the increasing B content improved thermal stability, increased saturation magnetic flux density (Bs) of as-quenched alloys, while the samples exhibited a slightly larger coercivity (Hc) when the atom percentages of Si and B were similar. Permeability decreased dramatically after TFA. The decrease of permeability mainly depended on annealing temperature and magnetic field intensity. Besides, flat hysteresis loops were obtained after TFA, Lorentz micrograph observation revealed the TFA sample exhibited denser magnetic domain walls, which confirmed it was more difficult to be saturated. The Co71Fe2Si9B14Mn4 alloy was successful prepared with low μe of 3020, low Hc of 1.7 A/m and high resistance to DC bias 6 times that of as-quenched alloy at the DC field of 300 A/m.

Changes in cluster magnetism and suppression of local superconductivity in amorphous FeCrB alloy irradiated by Ar+ ions

NASA Astrophysics Data System (ADS)

Okunev, V. D.; Samoilenko, Z. A.; Szymczak, H.; Szewczyk, A.; Szymczak, R.; Lewandowski, S. J.; Aleshkevych, P.; Malinowski, A.; Gierłowski, P.; Więckowski, J.; Wolny-Marszałek, M.; Jeżabek, M.; Varyukhin, V. N.; Antoshina, I. A.

2016-02-01

We show that сluster magnetism in ferromagnetic amorphous Fe67Cr18B15 alloy is related to the presence of large, D=150-250 Å, α-(Fe Cr) clusters responsible for basic changes in cluster magnetism, small, D=30-100 Å, α-(Fe, Cr) and Fe3B clusters and subcluster atomic α-(Fe, Cr, B) groupings, D=10-20 Å, in disordered intercluster medium. For initial sample and irradiated one (Φ=1.5×1018 ions/cm2) superconductivity exists in the cluster shells of metallic α-(Fe, Cr) phase where ferromagnetism of iron is counterbalanced by antiferromagnetism of chromium. At Φ=3×1018 ions/cm2, the internal stresses intensify and the process of iron and chromium phase separation, favorable for mesoscopic superconductivity, changes for inverse one promoting more homogeneous distribution of iron and chromium in the clusters as well as gigantic (twice as much) increase in density of the samples. As a result, in the cluster shells ferromagnetism is restored leading to the increase in magnetization of the sample and suppression of local superconductivity. For initial samples, the temperature dependence of resistivity ρ(T) T2 is determined by the electron scattering on quantum defects. In strongly inhomogeneous samples, after irradiation by fluence Φ=1.5×1018 ions/cm2, the transition to a dependence ρ(T) T1/2 is caused by the effects of weak localization. In more homogeneous samples, at Φ=3×1018 ions/cm2, a return to the dependence ρ(T) T2 is observed.

Effect of process control agent on the structural and magnetic properties of nano/amorphous Fe0.7Nb0.1Zr0.1Ti0.1 powders prepared by high energy ball milling

NASA Astrophysics Data System (ADS)

Khazaei Feizabad, Mohammad Hossein; Sharafi, Shahriar; Khayati, Gholam Reza; Ranjbar, Mohammad

2018-03-01

In this study, amorphous Fe0.7Nb0.1Zr0.1Ti0.1 alloy without metalloids was produced by mechanical alloying of pure mixture elements. Miedema's semi-empirical model was employed to predict the possibility of amorphous phase formation in proposed alloying system. The effect of Hexane as process control agent (PCA) on the structural, magnetic, morphological and thermal properties of the products was investigated. The results showed that the presence of PCA was necessary for the formation of amorphous phase as well as improved its soft magnetic properties. The PCA addition causes an increase of the saturation magnetization (about 43%) and decrease of the coercivity (about 50%). Moreover, the sample milled without PCA, showed a wide particle size distribution as well as relatively spherical geometry. While, in the presence of PCA the powders were aspherical and Polygon. In addition, the crystallization and Curie temperatures were found to be around 800 °C and 650 °C, respectively which are relatively high values for these kinds of alloys.

Phase transformation in rapidly quenched Fe-Cr-Co-Mo-Ti-Si-B alloys

NASA Astrophysics Data System (ADS)

Zhukov, D. G.; Shubakov, V. S.; Zhukova, E. Kh; Gorshenkov, M. V.

2018-03-01

The research results of phase transformations in Fe-24Cr-16Co-3Mo-0.2Ti-1Si-B alloys (with a boron content of 1 to 3% by mass) obtained by rapid quenching are presented. The structure formation regularities during the melt spinning and during the subsequent crystallization annealing in rapidly quenched bands of the Fe-Cr-Co-Mo-Ti-Si-B system alloys were studied. The changes in the phase composition of the rapidly quenched Fe-Cr-Co-Mo-Ti- Si-B system alloys after quenching at various quench rates and at different boron concentrations in the alloys are studied. It is shown that during crystallization from an amorphous state, at temperatures above 570 °C, in addition to the α-phase, the σ-phase appears first, followed by the γ-phase. Heat treatment of rapidly quenched bands to high-coercive state was carried out. A qualitative assessment of magnetic properties in a high-coercivity state was carried out. An evaluation of the level of magnetic properties in a high-coercivity state allows us to conclude that the application of a magnetic field during crystallization from an amorphous state leads to anisotropy of the magnetic properties, that is, an anisotropic effect of thermo-magnetic treatment is detected.

Ultra-soft magnetic Co-Fe-B-Si-Nb amorphous alloys for high frequency power applications

NASA Astrophysics Data System (ADS)

Ackland, Karl; Masood, Ansar; Kulkarni, Santosh; Stamenov, Plamen

2018-05-01

With the continuous shrinkage of the footprint of inductors and transformers in modern power supplies, higher flux, while still low-loss metallic replacements of traditional ferrite materials are becoming an intriguing alternative. One candidate replacement strategy is based on amorphous CoFeBSi soft-magnetic alloys, in their metallic glass form. Here the structural and magnetic properties of two different families of CoFeBSi-based soft magnetic alloys, prepared by arc-melting and subsequent melt spinning (rapid quenching) are presented, targeting potential applications at effective frequencies of 100 kHz and beyond. The nominal alloy compositions are Co67Fe4B11Si16Mo2 representing commercial Vitrovac and Co72-xFexB28-y (where B includes non-magnetic elements such as Boron, Silicon etc. x varies between 4 and 5 % and y is varied from 0 to 2 %) denoted Alloy #1 and prepared as a possible higher performance alternative, i.e. lower power loss and lower coercivity, to commercial Vitrovac. Room temperature magnetization measurements of the arc-melted alloys reveal that compared to Vitrovac, Alloy #1 already presents a ten-fold decrease in coercivity, with Hc ˜ 1.4 Am-1 and highest figure of merit of (Ms/Hc > 96). Upon melt-spinning the alloys into thin (< 30 μm) ribbons, the alloys are essentially amorphous when analyzed by XRD. Magnetization measurements of the melt-spun ribbons demonstrate that Alloy #1 possesses a coercivity of just 2 Am-1, which represents a significant improvement compared to melt-spun ribbons of Vitrovac (17 Am-1). A set of prototype transformers of approximately 10 turns of Alloy #1 ribbon exhibits systematically Hc < 10 Am-1 at 100 kHz, without a noticeable decrease in coupled flux and saturation.

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.

Bacterial nanometric amorphous Fe-based oxide: a potential lithium-ion battery anode material.

PubMed

Hashimoto, Hideki; Kobayashi, Genki; Sakuma, Ryo; Fujii, Tatsuo; Hayashi, Naoaki; Suzuki, Tomoko; Kanno, Ryoji; Takano, Mikio; Takada, Jun

2014-04-23

Amorphous Fe(3+)-based oxide nanoparticles produced by Leptothrix ochracea, aquatic bacteria living worldwide, show a potential as an Fe(3+)/Fe(0) conversion anode material for lithium-ion batteries. The presence of minor components, Si and P, in the original nanoparticles leads to a specific electrode architecture with Fe-based electrochemical centers embedded in a Si, P-based amorphous matrix.

Dose dependence of radiation damage in nano-structured amorphous SiOC/crystalline Fe composite

DOE PAGES

Su, Qing; Price, Lloyd; Shao, Lin; ...

2015-10-29

Here, through examination of radiation tolerance properties of amorphous silicon oxycarbide (SiOC) and crystalline Fe composite to averaged damage levels, from approximately 8 to 30 displacements per atom (dpa), we demonstrated that the Fe/SiOC interface and the Fe/amorphous Fe xSi yO z interface act as efficient defect sinks and promote the recombination of vacancies and interstitials. For thick Fe/SiOC multilayers, a clear Fe/SiOC interface remained and no irradiation-induced mixing was observed even after 32 dpa. For thin Fe/SiOC multilayers, an amorphous Fe xSi yO z intermixed layer was observed to form at 8 dpa, but no further layer growth wasmore » observed for higher dpa levels.« less

The XRD Amorphous Component in John Klein Drill Fines at Yellowknife Bay, Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Morris, Richard V.; Ming,, Douglas W.; Blake, David; Vaniman, David; Bish, David L; Chipera, Steve; Downs, Robert; Morrison, Shaunna; Gellert, Ralf; Campbell, Iain;

Modification of Fe-B based metallic glasses using swift heavy ions

NASA Astrophysics Data System (ADS)

Rodriguez, M. D.; Trautmann, C.; Toulemonde, M.; Afra, B.; Bierschenk, T.; Giulian, R.; Kirby, N.; Kluth, P.

2012-10-01

We report on small-angle x-ray scattering (SAXS) measurements of amorphous Fe80B20, Fe85B15, Fe81B13.5Si3.5C2, and Fe40Ni40B20 metallic alloys irradiated with 11.1 MeV/u 132Xe, 152Sm, 197Au, and 8.2 MeV/u 238U ions. SAXS experiments are nondestructive and give evidence for ion track formation including quantitative information about the size of the track radius. The measurements also indicate a cylindrical track structure with a sharp transition to the undamaged surrounding matrix material. Results are compared with calculations using an inelastic thermal spike model to deduce the critical energy loss for the track formation threshold. The damage recovery of ion tracks produced in Fe80B20 by 11.1 MeV/u 197Au ions was studied by means of isochronal annealing yielding an activation energy of 0.4 ± 0.1 eV

CM-like Interplanetary Dust Particles in Lower Stratosphere During 1989 October and 1991 June/July

NASA Technical Reports Server (NTRS)

Rietmeijer, Frans J. M.

1996-01-01

The stratospheric interplanetary dust particles L2005T12 and L2011O3 are linked to CM chondrite matrix. Particle L2005T12 is dominated by tabular grains of partially dehydrated greenalite-rich serpentine. Its amorphous matrix contains abundant smectite nanocrystals and annular Fe,Ni,S units. A uniquely stratified (partial) maghemite rim occurs only on S-rich parts of the matrix. Formation of this rim and Mg depletions in the matrix occurred during atmospheric entry heating of this particle. Particle L2011O3 has large iron sulfide and magnesiowustite grains in an amorphous low-Al, ferromagnesiosilica matrix. Hydrous crystallisation of this matrix produced ultrafine-grained smectites and disseminated iron sulfides. Atmospheric entry heating of both particles is indicated by the partial iron oxide rim, vesicular sulfides, and the scatter of matrix compositions due to loss of Mg. While many uncertainties remain, the high incidence of chondritic rough particles, which include an unknown amount of CM-like particles, in the lower stratosphere during 1984, 1989, and 1991 suggests annual variations in their abundances. The timing of lower stratospheric dust samplings is critical to collect these particles.

Inverse bilayer magnetoelectric thin film sensor

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

Yarar, E.; Piorra, A.; Quandt, E., E-mail: eq@tf.uni-kiel.de

2016-07-11

Prior investigations on magnetoelectric (ME) thin film sensors using amorphous FeCoSiB as a magnetostrictive layer and AlN as a piezoelectric layer revealed a limit of detection (LOD) in the range of a few pT/Hz{sup 1/2} in the mechanical resonance. These sensors are comprised of a Si/SiO{sub 2}/Pt/AlN/FeCoSiB layer stack, as dictated by the temperatures required for the deposition of the layers. A low temperature deposition route of very high quality AlN allows the reversal of the deposition sequence, thus allowing the amorphous FeCoSiB to be deposited on the very smooth Si substrate. As a consequence, the LOD could be enhancedmore » by almost an order of magnitude reaching 400 fT/Hz{sup 1/2} at the mechanical resonance of the sensor. Giant ME coefficients (α{sub ME}) as high as 5 kV/cm Oe were measured. Transmission electron microscopy investigations revealed highly c-axis oriented growth of the AlN starting from the Pt-AlN interface with local epitaxy.« less

Amorphization and thermal stability of aluminum-based nanoparticles prepared from the rapid cooling of nanodroplets: effect of iron addition.

PubMed

Xiao, Shifang; Li, Xiaofan; Deng, Huiqiu; Deng, Lei; Hu, Wangyu

2015-03-07

Despite an intensive investigation on bimetallic nanoparticles, little attention has been paid to their amorphization in the past few decades. The study of amorphization on a nanoscale is of considerable significance for the preparation of amorphous nanoparticles and bulk metallic glass. Herein, we pursue the amorphization process of Al-based nanoparticles with classic molecular dynamics simulations and local structural analysis techniques. By a comparative study of the amorphization of pure Al and Fe-doped Al-based nanodroplets in the course of rapid cooling, we find that Fe addition plays a very important role in the vitrification of Al-based nanodroplets. Owing to the subsurface segregated Fe atoms with their nearest neighbors tending to form relatively stable icosahedral (ICO) clusters, the Fe-centred cluster network near the surface effectively suppresses the crystallization of droplets from surface nucleation and growth as the concentration of Fe attains a certain value. The glass formation ability of nanodroplets is suggested to be enhanced by the high intrinsic inner pressure as a result of small size and surface tension, combined with the dopant-inhibited surface nucleation. In addition, the effect of the size and the added concentration of nanoparticles on amorphization and the thermal stability of the amorphous nanoparticles are discussed. Our findings reveal the amorphization mechanism in Fe-doped Al-based nanoparticles and provide a theoretical guidance for the design of amorphous materials.

Synthesis of carbon nanofibres from waste chicken fat for field electron emission applications

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

Suriani, A.B., E-mail: absuriani@yahoo.com; Department of Physics, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, Tanjung Malim, Perak 35900; Dalila, A.R.

Highlights: • Waste chicken fat is used as a starting material to produce CNFs via TCVD method. • High heating rate applied resulted in aggregation of catalyst particles. • Aggregated catalyst produced sea urchin-like CNFs with amorphous nature. • The as-grown CNFs presented a potential for field electron emission applications. - Abstract: Carbon nanofibres (CNFs) with sea urchin-like morphology were synthesised from waste chicken fat precursor via catalytic thermal chemical vapour deposition method at 750 °C. The CNFs showed amorphous structures under high-resolution transmission electron microscopy, micro-Raman spectroscopy and X-ray diffraction examination. X-ray photoelectron spectroscopy analysis confirmed that the coremore » of the sea urchin-like CNFs was composed of Fe{sub 3}C formed within the first 20 min of synthesis time. The growth of amorphous CNFs from agglomerated Fe{sub 3}C particles was favourable due to the high heating rate applied during the synthesis. Field electron emission examination of the CNFs indicated turn-on and threshold field values of 5.4 and 6.6 V μm{sup −1} at current density of 1 and 10 μA cm{sup −2}, respectively. This study demonstrates that waste chicken fat, a low-cost and readily available resource, can be used as an inexpensive carbon source for the production of CNFs with a potential application in field electron emitters.« less

An aerosol chamber investigation of the heterogeneous ice nucleating potential of refractory nanoparticles

NASA Astrophysics Data System (ADS)

Saunders, R. W.; Möhler, O.; Schnaiter, M.; Benz, S.; Wagner, R.; Saathoff, H.; Connolly, P. J.; Burgess, R.; Gallagher, M.; Wills, R.; Murray, B. J.; Plane, J. M. C.

2009-11-01

Nanoparticles of iron oxide (crystalline and amorphous), silicon oxide and magnesium oxide were investigated for their propensity to nucleate ice over the temperature range 180-250 K, using the AIDA chamber in Karlsruhe, Germany. All samples were observed to initiate ice formation via the deposition mode at threshold ice super-saturations (RHi thresh) ranging from 105% to 140% for temperatures below 220 K. Approximately 10% of amorphous Fe2O3 particles (modal diameter = 30 nm) generated in situ from a photochemical aerosol reactor, led to ice nucleation at RHi thresh = 140% at an initial chamber temperature of 182 K. Quantitative analysis using a singular hypothesis treatment provided a fitted function [ns (190 K) = 10(3.33×sice)+8.16] for the variation in ice-active surface site density (ns: m-2) with ice saturation (sice) for Fe2O3 nanoparticles. This was implemented in an aerosol-cloud model to determine a predicted deposition (mass accommodation) coefficient for water vapour on ice of 0.1 at temperatures appropriate for the upper atmosphere. Classical nucleation theory was used to determine representative contact angles (θ) for the different particle compositions. For the in situ generated Fe2O3 particles, a slight inverse temperature dependence was observed with θ = 10.5° at 182 K, decreasing to 9.0° at 200 K (compared with 10.2° and 11.4°, respectively for the SiO2 and MgO particle samples at the higher temperature). These observations indicate that such refractory nanoparticles are relatively efficient materials for the nucleation of ice under the conditions studied in the chamber which correspond to cirrus cloud formation in the upper troposphere. The results also show that Fe2O3 particles do not act as ice nuclei under conditions pertinent for tropospheric mixed phase clouds, which necessarily form above ~233 K. At the lower temperatures (<150 K) where noctilucent clouds form during summer months in the high latitude mesosphere, higher contact angles would be expected, which may reduce the effectiveness of these particles as ice nuclei in this part of the atmosphere.

An aerosol chamber investigation of the heterogeneous ice nucleating potential of refractory nanoparticles

NASA Astrophysics Data System (ADS)

Saunders, R. W.; Möhler, O.; Schnaiter, M.; Benz, S.; Wagner, R.; Saathoff, H.; Connolly, P. J.; Burgess, R.; Murray, B. J.; Gallagher, M.; Wills, R.; Plane, J. M. C.

2010-02-01

Nanoparticles of iron oxide (crystalline and amorphous), silicon oxide and magnesium oxide were investigated for their propensity to nucleate ice over the temperature range 180-250 K, using the AIDA chamber in Karlsruhe, Germany. All samples were observed to initiate ice formation via the deposition mode at threshold ice super-saturations (RHithresh) ranging from 105% to 140% for temperatures below 220 K. Approximately 10% of amorphous Fe2O3 particles (modal diameter = 30 nm) generated in situ from a photochemical aerosol reactor, led to ice nucleation at RHithresh = 140% at an initial chamber temperature of 182 K. Quantitative analysis using a singular hypothesis treatment provided a fitted function [ns(190 K)=10(3.33×sice)+8.16] for the variation in ice-active surface site density (ns:m-2) with ice saturation (sice) for Fe2O3 nanoparticles. This was implemented in an aerosol-cloud model to determine a predicted deposition (mass accommodation) coefficient for water vapour on ice of 0.1 at temperatures appropriate for the upper atmosphere. Classical nucleation theory was used to determine representative contact angles (θ) for the different particle compositions. For the in situ generated Fe2O3 particles, a slight inverse temperature dependence was observed with θ = 10.5° at 182 K, decreasing to 9.0° at 200 K (compared with 10.2° and 11.4° respectively for the SiO2 and MgO particle samples at the higher temperature). These observations indicate that such refractory nanoparticles are relatively efficient materials for the nucleation of ice under the conditions studied in the chamber which correspond to cirrus cloud formation in the upper troposphere. The results also show that Fe2O3 particles do not act as ice nuclei under conditions pertinent for tropospheric mixed phase clouds, which necessarily form above ~233 K. At the lower temperatures (<150 K) where noctilucent clouds form during summer months in the high latitude mesosphere, higher contact angles would be expected, which may reduce the effectiveness of these particles as ice nuclei in this part of the atmosphere.

RETRACTED ARTICLE: Precipitation behavior of B2-ordered aluminide

NASA Astrophysics Data System (ADS)

Han, Chang-Suk

2006-12-01

Fine dispersion of disordered phases is obtained in Ni-Al-Cr and Fe-Al-Co temary systems. A transmission electron microscope investigation has been performed on the precipitation of α-Cr in B2-ordered β-NiAl with different stoichiometry and α-Fe in B2-FeAl(Co) compound. Precipitation behavior and hardening were investigated by measuring the hardness variation. The hardness of NiAl and FeAl increases appreciably with the fine precipitation of α-Cr and α-Fe, and over-age softening occurs after prolonged aging. In the case of B2-NiAl(Cr), perfect lattice coherency is maintained at the interfaces between the α-Cr particles and the matrix during the initial stage of aging. After prolonged aging, a loss of coherency occurs by the attraction of matrix dislocations to the particle/matrix interface, followed by climbing around the particles. On the other hand, in the case of B2-FeAl(Co), the disordered α-Fe phase is present as a precipitate in the B2-FeAl(Co) matrix and has a cubic-cubic orientation with the matrix. At the early aging periods, prismatic dislocation loops formed in the B2-FeAl(Co) matrix. B2-FeAl(Co) matrix is typically hardened by the precipitation of α-Fe.

Comparison of different zeolite framework types as carriers for the oral delivery of the poorly soluble drug indomethacin.

PubMed

Karavasili, Christina; Amanatiadou, Elsa P; Kontogiannidou, Eleni; Eleftheriadis, Georgios K; Bouropoulos, Nikolaos; Pavlidou, Eleni; Kontopoulou, Ioanna; Vizirianakis, Ioannis S; Fatouros, Dimitrios G

2017-08-07

Microporous zeolites of distinct framework types, textural properties and crystal morphologies namely BEA, ZSM and NaX, have been employed as carriers to assess their effect on modulating the dissolution behavior of a BCS II model drug (indomethacin). Preparation of the loaded carriers via the incipient wetness method induced significant drug amorphization for the BEA and NaX samples, as well as high drug payloads. The stability of the amorphous drug content was retained after stressing test evaluation of the porous carriers. The dissolution profile of loaded indomethacin was evaluated in simulated gastric fluid (pH 1.2) and simulated intestinal fluids FaSSIF (fasted) and FeSSIF (fed state) conditions and was found to be dependent on the aluminosilicate ratio of the zeolites and the degree of crystalline drug content. The feasibility of the zeolitic particles as oral drug delivery systems was appraised with cytocompatibility and cellular toxicity studies in Caco-2 cultures in a time- and dose-dependent manner by means of the MTT assay and flow cytometry analysis, respectively. Intracellular accumulation of the zeolite particles was observed with no apparent cytotoxic effects at the lower concentrations tested, rendering such microporous zeolites pertinent candidates in oral drug delivery applications. Copyright © 2017 Elsevier B.V. All rights reserved.

Synthesis and magnetostrictive properties of Pr(Fe1.95B0.05)1.93 bulk nanocrystalline alloy

NASA Astrophysics Data System (ADS)

Shi, Y. G.; Hu, C. C.; Fan, J. Y.; Shi, D. N.; Lv, L. Y.; Tang, S. L.

2012-11-01

The structure, magnetic properties, and magnetostriction of Pr(Fe1.95B0.05)1.93 alloys prepared by annealing its precursor amorphous ribbons under high pressure were investigated. It was found that Pr(Fe1.95B0.05)1.93 single cubic Laves phase could be obtained only when the pressure is up to 3 GPa. The average grain size about 20 nm is found in the sample synthesized under 6 GPa. A large linear magnetostriction of 541 ppm at 3 kOe is observed in the Pr(Fe1.95B0.05)1.93 compound synthesized under 6 GPa, which is 25% larger than that under 3 GPa. The present work offers an effective method to obtain bulk nanocrystalline magnetostrictive compounds.

Mechanical contact induced transformation from the amorphous to the crystalline state in metallic glass

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1984-01-01

Friction and wear tests were conducted with 3.2- and 6.4-millimeter-diameter aluminum oxide spheres sliding, in reciprocating motion, on a Fe67Co18B14Si1 metallic foil. Crystallites with a size range of 10 to 150 nanometers were produced on the wear surface of the amorphous alloy. A strong interaction between transition metals and metalloids such as silicon and boron results in strong segregation during repeated sliding, provides preferential transition metal-metalloid clustering in the amorphous alloy, and subsequently produces the diffused honeycomb structure formed by dark grey bands and primary crystals, that is, alpha-Fe in the matrix. Large plastic flow occurs on an amorphous alloy surface with sliding and the flow film of the alloy transfers to the aluminum oxide pin surface. Multiple slip bands due to shear deformation are observed on the side of the wear track. Two distinct types of wear debris were observed as a result of sliding: an alloy wear debris, and/or powdery-whiskery oxide debris.

The discovery of silicon oxide nanoparticles in space-weathered of Apollo 15 lunar soil grains

NASA Astrophysics Data System (ADS)

Gu, Lixin; Zhang, Bin; Hu, Sen; Noguchi, Takaaki; Hidaka, Hiroshi; Lin, Yangting

2018-03-01

Space weathering is an important process on the Moon and other airless celestial bodies. The most common space weathering effects are amorphization of the top surface of soil grains and formation of nanophase iron particles (npFe) within the partially amorphous rims. Hence, space weathering significantly affects optical properties of the surface of the Moon and other airless celestial bodies. Transmission electron microscope (TEM) analysis of Apollo 15 soil grains displays npFe (≤5 nm in size) embedded in the space-weathered rim (∼60 nm in thickness) of a pyroxene grain, consistent with previous studies. In contrast, submicron-sized fragments that adhere to the pyroxene grain show distinct space weathering features. Silicon oxide nanoparticles (npSiOx) were observed with npFe in a submicron-sized Mg-Fe silicate fragment. This is the first discovery of npSiOx as a product of space weathering. The npSiOx and the coexisting npFe are ∼10-25 nm in size, significantly larger than the typical npFe in the space weathered rim of the pyroxene grain. The coexisting npSiOx and npFe were probably formed directly in micrometeorite shock-induced melt, instead of in a solar-wind generated vapor deposit or irradiated rim. This new observation will shed light on space weathering processes on the Moon and airless celestial bodies.

Investigation into the Origin of Magnetic Properties of Amorphous Metallic Alloys.

DTIC Science & Technology

1981-10-01

Luborsky, F.E., J.L. Walter, and D. LeGrand. "Cold Rolling and Annealing of Amor- phous Ribbons," IEEE Trans. Magn. Mag-12, 1976, p. 930. Reprint 8011 ...curve. Iiii) For Fe-B-Al they lie significantly below. The differences between the T, for the three different aluminium containing alloys is not

Induced anisotropy in FeCo-based nanocomposites: Early transition metal content dependence

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

Shen, S; DeGeorge, V; Ohodnicki, PR

2014-05-07

Soft magnetic nanocomposites variants of FeCo-based (HTX002) alloys (Fe65Co35)(81+x)B12Nb4-xSi2Cu1, exhibiting high inductions (up to 1.9 T), low losses, and high temperature stability are studied for high frequency inductors and current sensors. For alloys with x 0, 1, 1.5, 2, and 3, we report field induced anisotropy, K-U, after annealing at temperatures of 340-450 degrees C for 1 h in a 2 T transverse magnetic field. The anisotropy field, H-K, measured by AC permeametry on toroidal cores, and by first order reversal curves on square sections of ribbon, decreases with annealing temperature and saturates at high annealing temperatures suggesting a nanostructuremore » related anisotropy mechanism in which the amorphous phase exhibits a higher H-K than the crystalline phase. A high saturation induction nanocrystalline phase and high H-K amorphous phase were achieved by low temperature annealing resulting in a value of K-U exceeding 14 X 10(3) erg/cm(3), more than twice that reported previously for Fe-rich amorphous and nanocomposite alloys. (C) 2014 AIP Publishing LLC.« less

Ultrafine-grained mineralogy and matrix chemistry of olivine-rich chondritic interplanetary dust particles

NASA Technical Reports Server (NTRS)

Rietmeijer, F. J. M.

1989-01-01

Olivine-rich chondritic interplanetary dust particles (IDPs) are an important subset of fluffy chondritic IDPs collected in the earth's stratosphere. Particles in this subset are characterized by a matrix of nonporous, ultrafine-grained granular units. Euhedral single crystals, crystals fragments, and platey single crystals occur dispersed in the matrix. Analytical electron microscopy of granular units reveals predominant magnesium-rich olivines and FeNi-sulfides embedded in amorphous carbonaceous matrix material. The variable ratio of ultrafine-grained minerals vs. carbonaceous matrix material in granular units support variable C/Si ratios, and some fraction of sulfur is associated with carbonaceous matrix material. The high Mg/(Mg+Fe) ratios in granular units is similar to this distribution in P/Comet Halley dust. The chondritic composition of fine-grained, polycrystalline IDPs gradually breaks down into nonchondritic, and ultimately, single mineral compositions as a function of decreased particle mass. The relationship between particle mass and composition in the matrix of olivine-rich chondritic IDPs is comparable with the relationship inferred for P/Comet Halley dust.

The Use of Atomic-Force Microscopy for Studying the Crystallization Process of Amorphous Alloys

NASA Astrophysics Data System (ADS)

Elmanov, G. N.; Ivanitskaya, E. A.; Dzhumaev, P. S.; Skrytniy, V. I.

The crystallization process of amorphous alloys is accompanied by the volume changes as a result of structural phase transitions. This leads to changes in the surface topography, which was studied by atomic force microscopy (AFM). The changes of the surface topography, structure and phase composition during multistage crystallization process of the metallic glasses with composition Ni71,5Cr6,8Fe2,7B11,9Si7,1 and Ni63,4Cr7,4Fe4,3Mn0,8B15,6Si8,5 (AWS BNi2) has been investigated. The obtained results on changing of the surface topography in crystallization process are in good agreement with the data of X-ray diffraction analysis (XRD). The nature of redistribution of some alloy components in the crystallization process has been suggested.

Magnetoimpedance and magnetic properties of Co72Fe5Ni10Cr5Si7B3 amorphous ribbons in different states

NASA Astrophysics Data System (ADS)

Chlenova, A. A.; Stepanova, E. A.; Golubeva, E. V.; Lotfollahi, Z.

2017-10-01

CoFeNiCrSiB amorphous ribbons have been prepared by rapid quenching and subjected to the post preparation heat treatments in air. Structure, magnetic properties and giant magnetoimpedance (MI) characteristics were investigated. Short annealing of the sample at 380°С for 4 min leads to a useful structural relaxation and the highest MI ratio ΔZ/Z =350% for the total impedance. In as prepared state ;two-peak; MI field dependences were well correlating with effective magnetic anisotropy features. Post preparation treatment resulted in clear transformation into ;one-peak; shaped MI curve typical for the ribbons with longitudinal effective anisotropy. Corresponding decrease of the field sensitivity by the order of magnitude as a result of short heat treatments in air shows their importance.

Magnetic properties of Fe-doped NiO nanoparticles

NASA Astrophysics Data System (ADS)

Kurokawa, A.; Sakai, N.; Zhu, L.; Takeuchi, H.; Yano, S.; Yanoh, T.; Onuma, K.; Kondo, T.; Miike, K.; Miyasaka, T.; Ichiyanagi, Y.

2013-08-01

Ni1- x Fe x O ( x = 0, 0.05, 0.1) nanoparticles with several nanometers encapsulated with amorphous SiO2 were prepared by our novel preparation method. A NiO single phase structure was confirmed using the X-ray diffraction measurements. It is considered that Ni ions are replaced by Fe ions because it is observed that the lattice constant decreases. The temperature dependence behavior of the magnetization revealed that the blocking temperature, T B , shifted from 17 to 57 K as the amount of Fe ions increased, and that below T B , ferromagnetic behaviors were exhibited. The coercive force, H C , increased from 0.8 to 1.5 kOe as the amount of Fe ions increased.

Scanning transmission electron microscopy (STEM) study on surface modified CVD diamond/Si(111) film post implanted Fe-B and NiFe-B related to GMR properties

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

Purwanto, Setyo, E-mail: setyo-p@batan.go.id, E-mail: purwantosetyo@yahoo.com; Dimyati, A., E-mail: arbi-dimyati@hotmail.com; Iskandar, R.

Nanostructure investigation on the post implantation by Fe-B and NiFe-B on CVD diamond/Si(111) film have been studied by means of STEM related to their GMR phenomena. Two samples were investigated carefully, firstly sample is post NiFe-B at E=70keV and dose= 10{sup 15} ions/cm{sup 2} (denoted as A-E3D1). Secondly, is post FeB at E=20 keV and dose= 10{sup 15} ions/cm{sup 2} (denoted as B-E1D1). Based on FPP measurement at room temperature (RT) and H{sub applied} = 8 kOe, A-E3D1 sample has MR ratio almost 80% and MR ratio in B-E1D1 sample is 45%. Based on STEM-EDX investigation, there are two aspectsmore » of how MR ratio of A-E3D1 more higher than those of B-E1D1. Firstly, surface nanostructure on the top of A-E3D1 film is more grazing than on the top of B-E1D1. Analysis with Scanning Transmission Electron Microscope (STEM) equipped with Electron Energy Loss Spectroscopy (EELS) the growth of amorphous carbon layer on top of the implanted diamond film with thickness around 100 nm and only 20 nm on the no implanted sample have observed. Boron atoms were found inside the carbon amorphous layer distributed homogenously. Secondly, oxygen content at the interface between diamond film and silicon substrate in sample A-E3D1 was lower than those in B-E1D1 sample. This condition gives the resistance value in A-E3D1 lower than value in B-E1D1. This result is close to the Raman Spectroscopy data measurement which obviously suggests changes on the Raman spectrum due to implantation related to Oxygen excitation from B-E1D1 sample.« less

Earthicle: The Design of a Conceptually New Type of Particle.

PubMed

Uskoković, Vuk; Pernal, Sebastian; Wu, Victoria M

2017-01-18

The conception and the steps made in the design of a conceptually new type of composite particle, so-called "earthicle", are being described. This particle is meant to roughly mimic the layered structure of the Earth, having zerovalent iron core, silicate mantle, and a thin carbonaceous crust resembling the biosphere and its geological remnants. Particles are made in a stable colloidal form in an aqueous medium, involving chemical precipitation and pyrolysis of citric acid in the solution. The effects of various synthesis parameters were studied, including borohydride and oleate concentrations, APTES/TEOS molar ratio, chemical nature of the carbon precursors, and others. XRD analysis confirmed the predominantly zerovalent iron composition of the core, amorphous silica and crystalline iron silicate/silicide composition of the mesolayer, and the carbonaceous, amorphous graphitic composition of the surface coating. The atomically thin carbon shell was also detected as a distinct shoulder on the broad n-π* absorption resonance and the peak at ∼300 nm, a signature of sp 2 hybridized electronic orbitals and the result of the interband π-π* transition characteristic of graphitic structures. The irregularity of the shape of generally round Fe 0 particles has caused the uniformity of the silica shell to be directly proportional to the particle size. The size of the earthicles ranged from 60 to 500 nm depending on the ionic concentration of the precursors and additives. Silica layer effectively prevented the aggregation of the iron core and increased the biocompatibility of the particles. The point of zero charge first increased from the acidic to the neutral range after coating Fe 0 core with the APTES-functionalized, aminated silica shell and then restored its low value after depositing the carboxylated carbonic crust in a charge-reversal process designed to facilitate the formation of core-multishell structures. Tested on K7M2 osteosarcoma cell line and primary kidney and lung fibroblasts, cytotoxicity was cell-line dependent; however, the trend assessed in both planar and 3D cell culture with respect to the three types of particles, Fe 0 , Fe/SiO 2 , and Fe/SiO 2 /C, was general and independent of the cell line. Thus, the pronounced toxicity of Fe 0 alone became neutralized after the silica layer was coated around Fe 0 . The further addition of the carbonic layer reduced the viability as compared to Fe/SiO 2 , albeit in a statistically significant manner only for K7M2 cell line when compared against the untreated control. Cell response also varied depending on the formulation: while some formulations exhibited lethal effects on kidney fibroblasts, were harmless to lung fibroblasts, and boosted the proliferation of K7M2 osteosarcoma cells, other formulations exhibited the opposite behavior despite being similar in terms of their core/double-shell structure. Compared across three different cancerous cell lines, K7M2 osteosarcoma and U87 and E297 glioblastoma, a similar cell-line dependency in response was observed, yet the viability reduction was consistent for all Fe/SiO 2 /C particles, ranging from 80% to 85% of the untreated control. Carbon surface layer, albeit of graphitic structural nature, was of a markedly more viable character than that of nanosized graphene oxide. The viability of lung fibroblasts incubated with Fe/SiO 2 /C particles was reduced in the presence of the alternating magnetic field of 312.75 A/m and 1 MHz, while the viability reduction caused by Fe/SiO 2 /C particles in kidney fibroblasts and K7M2 cells was converted from statistically insignificant to significant, suggesting that the composite particles could be used for hyperthermia treatments, although their properties should be optimized for a more intense effect. A single-cell immunofluorescent analysis of the interaction of primary kidney fibroblasts and K7M2 osteosarcoma cells with Fe/SiO 2 /C particles demonstrated that the cell uptake and perinuclear localization may be responsible for the necrotic effects. This analysis also showed that composite Fe/SiO 2 /C particles may have the ability to cause the rupture of the cancer cell nucleus while having a harmless effect on the primary cells. Such a promising and selective anticancer activity will be investigated in more detail in future studies.

Novel solid-state synthesis of α-Fe and Fe3O4 nanoparticles embedded in a MgO matrix

NASA Astrophysics Data System (ADS)

Schneeweiss, O.; Zboril, R.; Pizurova, N.; Mashlan, M.; Petrovsky, E.; Tucek, J.

2006-01-01

Thermally induced reduction of amorphous Fe2O3 nanopowder (2-3 nm) with nanocrystalline Mg (~20 nm) under a hydrogen atmosphere is presented as a novel route to obtain α-Fe and Fe3O4 magnetic nanoparticles dispersed in a MgO matrix. The phase composition, structural and magnetic properties, size and morphology of the nanoparticles were monitored by x-ray diffraction, 57Fe Mössbauer spectroscopy at temperatures of 24-300 K, transmission electron microscopy and magnetic measurements. Spherical magnetite nanoparticles prepared at a reaction temperature of 300 °C revealed a well-defined structure, with a ratio of tetrahedral to octahedral Fe sites of 1/2 being common for the bulk material. A narrow particle size distribution (20-30 nm) and high saturation magnetization (95 ± 5 A m2 kg-1) predispose the magnetite nanoparticles to various applications, including magnetic separation processes. The Verwey transition of Fe3O4 nanocrystals was found to be decreased to about 80 K. The deeper reduction of amorphous ferric oxide at 600 °C allows α-Fe (40-50 nm) nanoparticles to be synthesized with a coercive force of about 30 mT. They have a saturation magnetization 2.2 times higher than that of synthesized magnetite nanoparticles, which corresponds well with the ratio usually found for the pure bulk phases. The magnetic properties of α-Fe nanocrystals combined with the high chemical and thermal stability of the MgO matrix makes the prepared nanocomposite useful for various magnetic applications.

Spin-exchange interaction between transition metals and metalloids in soft-ferromagnetic metallic glasses

NASA Astrophysics Data System (ADS)

Das, Santanu; Choudhary, Kamal; Chernatynskiy, Aleksandr; Choi Yim, Haein; Bandyopadhyay, Asis K.; Mukherjee, Sundeep

2016-06-01

High-performance magnetic materials have immense industrial and scientific importance in wide-ranging electronic, electromechanical, and medical device technologies. Metallic glasses with a fully amorphous structure are particularly suited for advanced soft-magnetic applications. However, fundamental scientific understanding is lacking for the spin-exchange interaction between metal and metalloid atoms, which typically constitute a metallic glass. Using an integrated experimental and molecular dynamics approach, we demonstrate the mechanism of electron interaction between transition metals and metalloids. Spin-exchange interactions were investigated for a Fe-Co metallic glass system of composition [(Co1-x Fe x )0.75B0.2Si0.05]96Cr4. The saturation magnetization increased with higher Fe concentration, but the trend significantly deviated from simple rule of mixtures. Ab initio molecular dynamics simulation was used to identify the ferromagnetic/anti-ferromagnetic interaction between the transition metals and metalloids. The overlapping band-structure and density of states represent ‘Stoner type’ magnetization for the amorphous alloys in contrast to ‘Heisenberg type’ in crystalline iron. The enhancement of magnetization by increasing iron was attributed to the interaction between Fe 3d and B 2p bands, which was further validated by valence-band study.

Environmental application of millimeter-scale sponge iron (s-Fe(0)) particles (II): the effect of surface copper.

PubMed

Ju, Yongming; Liu, Xiaowen; Liu, Runlong; Li, Guohua; Wang, Xiaoyan; Yang, Yanyan; Wei, Dongyang; Fang, Jiande; Dionysiou, Dionysios D

2015-04-28

To enhance the catalytic reactivity of millimeter-scale particles of sponge iron (s-Fe(0)), Cu(2+) ions were deposited on the surface of s-Fe(0) using a simple direct reduction reaction, and the catalytic properties of the bimetallic system was tested for removal of rhodamine B (RhB) from an aqueous solution. The influence of Cu(0) loading, catalyst dosage, particle size, initial RhB concentration, and initial pH were investigated, and the recyclability of the catalyst was also assessed. The results demonstrate that the 3∼5 millimeter s-Fe(0) particles (s-Fe(0)(3∼5mm)) with 5wt% Cu loading gave the best results. The removal of RhB followed two-step, pseudo-first-order reaction kinetics. Cu(0)-s-Fe(0) showed excellent stability after five reuse cycles. Cu(0)-s-Fe(0) possesses great advantages compared to nanoscale zero-valent iron, iron power, and iron flakes as well as its bimetals. The surface Cu(0) apparently catalyzes the production of reactive hydrogen atoms for indirect reaction and generates Fe-Cu galvanic cells that enhance electron transfer for direct reaction. This bimetallic catalyst shows great potential for the pre-treatment of recalcitrant wastewaters. Additionally, some oxides containing iron element are selected to simulate the adsorption process. The results prove that the adsorption process of FeOOH, Fe2O3 and Fe3O4 played minor role for the removal of RhB. Copyright © 2015 Elsevier B.V. All rights reserved.

Origins of GEMS Grains

NASA Technical Reports Server (NTRS)

Messenger, S.; Walker, R. M.

2012-01-01

Interplanetary dust particles (IDPs) collected in the Earth s stratosphere contain high abundances of submicrometer amorphous silicates known as GEMS grains. From their birth as condensates in the outflows of oxygen-rich evolved stars, processing in interstellar space, and incorporation into disks around new stars, amorphous silicates predominate in most astrophysical environments. Amorphous silicates were a major building block of our Solar System and are prominent in infrared spectra of comets. Anhydrous interplanetary dust particles (IDPs) thought to derive from comets contain abundant amorphous silicates known as GEMS (glass with embedded metal and sulfides) grains. GEMS grains have been proposed to be isotopically and chemically homogenized interstellar amorphous silicate dust. We evaluated this hypothesis through coordinated chemical and isotopic analyses of GEMS grains in a suite of IDPs to constrain their origins. GEMS grains show order of magnitude variations in Mg, Fe, Ca, and S abundances. GEMS grains do not match the average element abundances inferred for ISM dust containing on average, too little Mg, Fe, and Ca, and too much S. GEMS grains have complementary compositions to the crystalline components in IDPs suggesting that they formed from the same reservoir. We did not observe any unequivocal microstructural or chemical evidence that GEMS grains experienced prolonged exposure to radiation. We identified four GEMS grains having O isotopic compositions that point to origins in red giant branch or asymptotic giant branch stars and supernovae. Based on their O isotopic compositions, we estimate that 1-6% of GEMS grains are surviving circumstellar grains. The remaining 94-99% of GEMS grains have O isotopic compositions that are indistinguishable from terrestrial materials and carbonaceous chondrites. These isotopically solar GEMS grains either formed in the Solar System or were completely homogenized in the interstellar medium (ISM). However, the chemical compositions of GEMS grains are extremely heterogeneous and seem to rule out this possibility. Based on their solar isotopic compositions and their non-solar elemental compositions we propose that most GEMS grains formed in the nebula as late-stage non-equilibrium condensates.

Distribution and variability of redox zones controlling spatial variability of arsenic in the Mississippi River Valley alluvial aquifer, southeastern Arkansas

USGS Publications Warehouse

Sharif, M.U.; Davis, R.K.; Steele, K.F.; Kim, B.; Hays, P.D.; Kresse, T.M.; Fazio, J.A.

2008-01-01

Twenty one of 118 irrigation water wells in the shallow (25-30??m thick) Mississippi River Valley alluvial aquifer in the Bayou Bartholomew watershed, southeastern Arkansas had arsenic (As) concentrations (< 0.5 to 77????g/L) exceeding 10????g/L. Sediment and groundwater samples were collected and analyzed from the sites of the highest, median, and lowest concentrations of As in groundwater in the alluvial aquifers located at Jefferson County, Arkansas. A traditional five-step sequential extraction was performed to differentiate the exchangeable, carbonate, amorphous Fe and Mn oxide, organic, and hot HNO3-leachable fraction of As and other compounds in sediments. The Chao reagent (0.25??M hydroxylamine hydrochloride in 0.25??M HCl) removes amorphous Fe and Mn oxides and oxyhydroxides (present as coatings on grains and amorphous minerals) by reductive dissolution and is a measure of reducible Fe and Mn in sediments. The hot HNO3 extraction removes mostly crystalline metal oxides and all other labile forms of As. Significant total As (20%) is complexed with amorphous Fe and Mn oxides in sediments. Arsenic abundance is not significant in carbonates or organic matter. Significant (40-70????g/kg) exchangeable As is only present at shallow depth (0-1??m below ground surface). Arsenic is positively correlated to Fe extracted by Chao reagent (r = 0.83) and hot HNO3 (r = 0.85). Arsenic extracted by Chao reagent decreases significantly with depth as compared to As extracted by hot HNO3. Fe (II)/Fe (the ratio of Fe concentration in the extracts of Chao reagent and hot HNO3) is positively correlated (r = 0.76) to As extracted from Chao reagent. Although Fe (II)/Fe increases with depth, the relative abundance of reducible Fe decreases noticeably with depth. The amount of reducible Fe, as well as As complexed to amorphous Fe and Mn oxides and oxyhydroxides decreases with depth. Possible explanations for the decrease in reducible Fe and its complexed As with depth include historic flushing of As and Fe from hydrous ferric oxides (HFO) by microbially-mediated reductive dissolution and aging of HFO to crystalline phases. Hydrogeochemical data suggests that the groundwater in the area falls in the mildly reducing (suboxic) to relatively highly reducing (anoxic) zone, and points to reductive dissolution of HFO as the dominant As release mechanism. Spatial variability of gypsum solubility and simultaneous SO42- reduction with co-precipitation of As and sulfide is an important limiting process controlling the concentration of As in groundwater in the area. ?? 2008 Elsevier B.V. All rights reserved.

Effect of fluxing treatment on the properties of Fe66Co15Mo1P7.5C5.5B2Si3 bulk metallic glass by water quenching

NASA Astrophysics Data System (ADS)

Li, Jin-Feng; Wang, Xin; Liu, Xue; Zhao, Shao-Fan; Yao, Ke-Fu

2018-01-01

The effect of fluxing treatment on the properties of Fe66Co15Mo1P7.5C5.5B2Si3bulk amorphous alloy (BAA) has been investigated. Prepared by a combination method of flux treatment and water quenching, the Fe66Co15Mo1P7.5C5.5B2Si3 BAA exhibits better glass-forming ability, thermal stability, soft magnetic properties and ductility than those of the one prepared by direct water quenching. This indicates that fluxing treatment can play a potential role in improving the properties of Fe-based BAA due to the effective elimination of the impurities within the alloy.

Importance of the Direct Contact of Amorphous Solid Particles with the Surface of Monolayers for the Transepithelial Permeation of Curcumin.

PubMed

Kimura, Shunsuke; Kasatani, Sachiha; Tanaka, Megumi; Araki, Kaeko; Enomura, Masakazu; Moriyama, Kei; Inoue, Daisuke; Furubayashi, Tomoyuki; Tanaka, Akiko; Kusamori, Kosuke; Katsumi, Hidemasa; Sakane, Toshiyasu; Yamamoto, Akira

2016-02-01

The amorphization has been generally known to improve the absorption and permeation of poorly water-soluble drugs through the enhancement of the solubility. The present study focused on the direct contact of amorphous solid particles with the surface of the membrane using curcumin as a model for water-insoluble drugs. Amorphous nanoparticles of curcumin (ANC) were prepared with antisolvent crystallization method using a microreactor. The solubility of curcumin from ANC was two orders of magnitude higher than that of crystalline curcumin (CC). However, the permeation of curcumin from the saturated solution of ANC was negligible. The transepithelial permeation of curcumin from ANC suspension was significantly increased as compared to CC suspension, while the permeation was unlikely correlated with the solubility, and the increase in the permeation was dependent on the total concentration of curcumin in ANC suspension. The absorptive transport of curcumin (from apical to basal, A to B) from ANC suspension was much higher than the secretory transport (from basal to apical, B to A). In vitro transport of curcumin through air-interface monolayers is large from ANC but negligible from CC particles. These findings suggest that the direct contact of ANC with the absorptive membrane can play an important role in the transport of curcumin from ANC suspension. The results of the study suggest that amorphous particles may be directly involved in the transepithlial permeation of curcumin.

Local melting in Al embedded with TiNi powder induced by microarea self-propagating high-temperature synthesis

NASA Astrophysics Data System (ADS)

Yamamoto, Tokujiro

2014-10-01

Microarea self-propagating high-temperature synthesis (microSHS) was ignited by the heat of mixing generated at the boundaries between an Al matrix and TiNi particles during plastic deformation at room temperature. The temperature of the boundaries was rapidly increased by microSHS; the temperature elevation resulted in local melting of the TiNi particle and the surrounding Al matrix, because the heat of mixing was localized in the vicinity of the TiNi particle although the amount of the heat of mixing was limited. Since the amount of the local melting region induced by microSHS is restricted, not only major elements (i.e. Al, Ti and Ni) but also impurities were involved in the solidification followed by local melting. As a result, ?FeNi nanoprecipitates, which have not been reported in SHS studies, were formed by inclusion of Fe, initially included as an impurity in raw materials. The formation mechanism of ?FeNi nanoprecipitates is discussed based on reference to the Al-Fe-Ni ternary alloy phase diagram. It is expected that local melting induced by microSHS is a key phenomonon for amorphization during severe plastic deformation of elemental sheets.

Availability of ferric iron for microbial reduction in bottom sediments of the freshwater tidal Potomac River

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

Lovley, D.R.; Phillips, E.J.P.

1986-10-01

The distribution of Fe(III), its availability for microbial reduction, and factors controlling Fe(III) availability were investigated in sediments from a freshwater site in the Potomac River Estuary. Fe(III) reduction in sediments incubated under anaerobic conditions and depth profiles of oxalate-extractable Fe(III) indicated that Fe(III) reduction was limited to depths of 4 cm or less, with the most intense Fe(III) reduction in the top 1 cm. In incubations of the upper 4 cm of the sediments, Fe(III) reduction was as important as methane production as a pathway for anaerobic electron flow because of the high rates of Fe(III) reduction in themore » 0- 0.5-cm interval. Most of the oxalate-extractable Fe(III) in the sediments was not reduced and persisted to a depth of at least 20 cm. The incomplete reduction was not the result of a lack of suitable electron donors. The oxalate-extractable Fe(III) that was preserved in the sediments was considered to be in a form other than amorphous Fe(III) oxyhydroxide, since synthetic amorphous Fe(III) oxyhydroxide, amorphous Fe(III) oxyhydroxide adsorbed onto clay, and amorphous Fe(III) oxyhydroxide saturated with adsorbed phosphate or fulvic acids were all readily reduced. Fe/sub 3/O/sub 4/ and the mixed Fe(III)-Fe(II) compound(s) that were produced during the reduction of amorphous Fe(III) oxyhydroxide in an enrichment culture were oxalate extractable but were not reduced, suggesting that mixed Fe(III)-Fe(II) compounds might account for the persistence of oxalate-extractable Fe(III) in the sediments.« less

Formation, reactivity and aging of amorphous ferric oxides in the presence of model and membrane bioreactor derived organics.

PubMed

Bligh, Mark W; Maheshwari, Pradeep; David Waite, T

2017-11-01

Iron salts are routinely dosed in wastewater treatment as a means of achieving effluent phosphorous concentration goals. The iron oxides that result from addition of iron salts partake in various reactions, including reductive dissolution and phosphate adsorption. The reactivity of these oxides is controlled by the conditions of formation and the processes, such as aggregation, that lead to a reduction in accessible surface sites following formation. The presence of organic compounds is expected to significantly impact these processes in a number of ways. In this study, amorphous ferric oxide (AFO) reactivity and aging was investigated following the addition of ferric iron (Fe(III)) to three solution systems: two synthetic buffered systems, either containing no organic or containing alginate, and a supernatant system containing soluble microbial products (SMPs) sourced from a membrane bioreactor (MBR). Reactivity of the Fe(III) phases in these systems at various times (1-60 min) following Fe(III) addition was quantified by determining the rate constants for ascorbate-mediated reductive dissolution over short (5 min) and long (60 min) dissolution periods and for a range (0.5-10 mM) of ascorbate concentrations. AFO particle size was monitored using dynamic light scattering during the aging and dissolution periods. In the presence of alginate, AFO particles appeared to be stabilized against aggregation. However, aging in the alginate system was remarkably similar to the inorganic system where aging is associated with aggregation. An aging mechanism involving restructuring within the alginate-AFO assemblage was proposed. In the presence of SMPs, a greater diversity of Fe(III) phases was evident with both a small labile pool of organically complexed Fe(III) and a polydisperse population of stabilized AFO particles present. The prevalence of low molecular weight organic molecules facilitated stabilization of the Fe(III) oxyhydroxides formed but subsequent aging observed in the alginate system did not occur. The reactivity of the Fe(III) in the supernatant system was maintained with little loss in reactivity over at least 24 h. The capacity of SMPs to maintain high reactivity of AFO has important implications in a reactor where Fe(III) phases encounter alternating redox conditions due to sludge recirculation, creating a cycle of reductive dissolution, oxidation and precipitation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Formation of Fe(III) oxyhydroxide colloids in freshwater and brackish seawater, with incorporation of phosphate and calcium

NASA Astrophysics Data System (ADS)

Gunnars, Anneli; Blomqvist, Sven; Johansson, Peter; Andersson, Christian

2002-03-01

The formation of Fe(III) oxyhydroxide colloids by oxidation of Fe(II) and their subsequent aggregation to larger particles were studied in laboratory experiments with natural water from a freshwater lake and a brackish coastal sea. Phosphate was incorporated in the solid phase during the course of hydrolysis of iron. The resulting precipitated amorphous Fe(III) oxyhydroxide phases were of varying composition, depending primarily on the initial dissolved Fe/P molar ratio, but with little influence by salinity or concentration of calcium ions. The lower limiting Fe/P ratio found for the solid phase suggests the formation of a basic Fe(III) phosphate compound with a stoichiometric Fe/P ratio of close to two. This implies that an Fe/P stoichiometry of ≈2 ultimately limits the capacity of precipitating Fe(III) to fix dissolved phosphate at oxic/anoxic boundaries in natural waters. In contrast to phosphorus, the uptake of calcium seemed to be controlled by sorption processes at the surface of the iron-rich particles formed. This uptake was more efficient in freshwater than in brackish water, suggesting that salinity restrains the uptake of calcium by newly formed Fe(III) oxyhydroxides in natural waters. Moreover, salinity enhanced the aggregation rate of the colloids formed. The suspensions were stabilised by the presence of organic matter, although this effect was less pronounced in seawater than in freshwater. Thus, in seawater of 6 to 33 ‰S, the removal of particles was fast (removal half time < 200 h), whereas the colloidal suspensions formed in freshwater were stable (removal half time > 900 h). Overall, oxidation of Fe(II) and removal of Fe(III) oxyhydroxide particles were much faster in seawater than in freshwater. This more rapid turnover results in lower iron availability in coastal seawater than in freshwater, making iron more likely to become a limiting element for chemical scavenging and biologic production.

Self Exchange Bias and Bi-stable Magneto-Resistance States in Amorphous TbFeCo and TbSmFeCo Thin Films

NASA Astrophysics Data System (ADS)

Ma, Chung; Li, Xiaopu; Lu, Jiwei; Poon, Joseph; Comes, Ryan; Devaraj, Arun; Spurgeon, Steven

Amorphous ferrimagetic TbFeCo and TbSmFeCo thin films are found to exhibit strong perpendicular magnetic anisotropy. Self exchange bias effect and bi-stable magneto-resistance states are observed near compensation temperature by magnetic hysteresis loop, anomalous Hall effect and transverse magneto-resistance measurements. Atom probe tomography, scanning transmission electron microscopy, and energy dispersive spectroscopy mapping have revealed two nanoscale amorphous phases with different Tb concentration distributed within the amorphous films. The observed exchange anisotropy originates from the exchange interaction between the two nanoscale amorphous phases. Exchange bias effect is used for increasing stability in spin valves and magnetic tunneling junctions. This study opens up a new platform for using amorphous ferrimagnetic thin films that require no epitaxial growth in nanodevices.. The work was supported by the Defense Threat Reduction Agency Grant and the U.S. Department of Energy.

Iron-rich (Fe1-x-yNixCoy)88Zr7B4Cu1 nanocrystalline magnetic materials for high temperature applications with minimal magnetostriction

NASA Astrophysics Data System (ADS)

Martone, Anthony; Dong, Bowen; Lan, Song; Willard, Matthew A.

2018-05-01

As inductor technology advances, greater efficiency and smaller components demand new core materials. With recent developments of nanocrystalline magnetic materials, soft magnetic properties of these cores can be greatly improved. FeCo-based nanocrystalline magnetic alloys have resulted in good soft magnetic properties and high Curie temperatures; however, magnetoelastic anisotropies persist as a main source of losses. This investigation focuses on the design of a new Fe-based (Fe,Ni,Co)88Zr7B4Cu1 alloy with reduced magnetostriction and potential for operation at elevated temperatures. The alloys have been processed by arc melting, melt spinning, and annealing in a protective atmosphere to produce nanocrystalline ribbons. These ribbons have been analyzed for structure, hysteresis, and magnetostriction using X-Ray diffraction, vibrating sample magnetometry (VSM), and a home-built magnetostriction system, respectively. In addition, Curie temperatures of the amorphous phase were analyzed to determine the best performing, high-temperature material. Our best result was found for a Fe77Ni8.25Co2.75Zr7B4Cu1 alloy with a 12 nm average crystallite size (determined from Scherrer broadening) and a 2.873 Å lattice parameter determined from the Nelson-Riley function. This nanocrystalline alloy possesses a coercivity of 10 A/m, magnetostrictive coefficient of 4.8 ppm, and amorphous phase Curie temperature of 218°C.

Physical and Microstructure Properties of MgAl2C2 Matrix Composite Coating on Titanium

NASA Astrophysics Data System (ADS)

Li, Peng

2014-12-01

This work is based on the dry sliding wear of the MgAl2C2-TiB2-FeSi composite coating deposited on a pure Ti using a laser cladding technique. Scanning electron microscope images indicate that the nanocrystals and amorphous phases are produced in such coating. X-ray diffraction result indicated that such coating mainly consists of MgAl2C2, Ti-B, Ti-Si, Fe-Al, Ti3SiC2, TiC and amorphous phases. The high resolution transmission electron microscope image indicated that the TiB nanorods were produced in the coating, which were surrounded by other fine precipitates, favoring the formation of a fine microstructure. With increase of the laser power from 0.85 kW to 1.00 kW, the micro-hardness decreased from 1350 1450 HV0.2 to 1200 1300 HV0.2. The wear volume loss of the laser clad coating was 1/7 of pure Ti.

Tribo-Mechanical Properties of HVOF Deposited Fe3Al Coatings Reinforced with TiB2 Particles for Wear-Resistant Applications

PubMed Central

Amiriyan, Mahdi; Blais, Carl; Savoie, Sylvio; Schulz, Robert; Gariépy, Mario; Alamdari, Houshang

2016-01-01

This study reveals the effect of TiB2 particles on the mechanical and tribological properties of Fe3Al-TiB2 composite coatings against an alumina counterpart. The feedstock was produced by milling Fe3Al and TiB2 powders in a high energy ball mill. The high-velocity oxy-fuel (HVOF) technique was used to deposit the feedstock powder on a steel substrate. The effect of TiB2 addition on mechanical properties and dry sliding wear rates of the coatings at sliding speeds ranging from 0.04 to 0.8 m·s−1 and loads of 3, 5 and 7 N was studied. Coatings made from unreinforced Fe3Al exhibited a relatively high wear rate. The Vickers hardness, elastic modulus and wear resistance of the coatings increased with increasing TiB2 content in the Fe3Al matrix. The wear mechanisms strongly depended on the sliding speed and the presence of TiB2 particles but were less dependent on the applied load. This study reveals the effect of TiB2 particles on the mechanical and tribological properties of Fe3Al-TiB2 composite coatings against an alumina counterpart. The feedstock was produced by milling Fe3Al and TiB2 powders in a high energy ball mill. The high-velocity oxy-fuel (HVOF) technique was used to deposit the feedstock powder on a steel substrate. The effect of TiB2 addition on mechanical properties and dry sliding wear rates of the coatings at sliding speeds ranging from 0.04 to 0.8 m·s−1 and loads of 3, 5 and 7 N was studied. Coatings made from unreinforced Fe3Al exhibited a relatively high wear rate. The Vickers hardness, elastic modulus and wear resistance of the coatings increased with increasing TiB2 content in the Fe3Al matrix. The wear mechanisms strongly depended on the sliding speed and the presence of TiB2 particles but were less dependent on the applied load. This study reveals the effect of TiB2 particles on the mechanical and tribological properties of Fe3Al-TiB2 composite coatings against an alumina counterpart. The feedstock was produced by milling Fe3Al and TiB2 powders in a high energy ball mill. The high-velocity oxy-fuel (HVOF) technique was used to deposit the feedstock powder on a steel substrate. The effect of TiB2 addition on mechanical properties and dry sliding wear rates of the coatings at sliding speeds ranging from 0.04 to 0.8 m·s−1 and loads of 3, 5 and 7 N was studied. Coatings made from unreinforced Fe3Al exhibited a relatively high wear rate. The Vickers hardness, elastic modulus and wear resistance of the coatings increased with increasing TiB2 content in the Fe3Al matrix. The wear mechanisms strongly depended on the sliding speed and the presence of TiB2 particles but were less dependent on the applied load. This study reveals the effect of TiB2 particles on the mechanical and tribological properties of Fe3Al-TiB2 composite coatings against an alumina counterpart. The feedstock was produced by milling Fe3Al and TiB2 powders in a high energy ball mill. The high-velocity oxy-fuel (HVOF) technique was used to deposit the feedstock powder on a steel substrate. The effect of TiB2 addition on mechanical properties and dry sliding wear rates of the coatings at sliding speeds ranging from 0.04 to 0.8 m·s−1 and loads of 3, 5 and 7 N was studied. Coatings made from unreinforced Fe3Al exhibited a relatively high wear rate. The Vickers hardness, elastic modulus and wear resistance of the coatings increased with increasing TiB2 content in the Fe3Al matrix. The wear mechanisms strongly depended on the sliding speed and the presence of TiB2 particles but were less dependent on the applied load. This study reveals the effect of TiB2 particles on the mechanical and tribological properties of Fe3Al-TiB2 composite coatings against an alumina counterpart. The feedstock was produced by milling Fe3Al and TiB2 powders in a high energy ball mill. The high-velocity oxy-fuel (HVOF) technique was used to deposit the feedstock powder on a steel substrate. The effect of TiB2 addition on mechanical properties and dry sliding wear rates of the coatings at sliding speeds ranging from 0.04 to 0.8 m·s−1 and loads of 3, 5 and 7 N was studied. Coatings made from unreinforced Fe3Al exhibited a relatively high wear rate. The Vickers hardness, elastic modulus and wear resistance of the coatings increased with increasing TiB2 content in the Fe3Al matrix. The wear mechanisms strongly depended on the sliding speed and the presence of TiB2 particles but were less dependent on the applied load. This study reveals the effect of TiB2 particles on the mechanical and tribological properties of Fe3Al-TiB2 composite coatings against an alumina counterpart. The feedstock was produced by milling Fe3Al and TiB2 powders in a high energy ball mill. The high-velocity oxy-fuel (HVOF) technique was used to deposit the feedstock powder on a steel substrate. The effect of TiB2 addition on mechanical properties and dry sliding wear rates of the coatings at sliding speeds ranging from 0.04 to 0.8 m·s−1 and loads of 3, 5 and 7 N was studied. Coatings made from unreinforced Fe3Al exhibited a relatively high wear rate. The Vickers hardness, elastic modulus and wear resistance of the coatings increased with increasing TiB2 content in the Fe3Al matrix. The wear mechanisms strongly depended on the sliding speed and the presence of TiB2 particles but were less dependent on the applied load. PMID:28787917

Demonstration and Analysis of Materials Processing by Ablation Plasma Ion Implantation (APII)

NASA Astrophysics Data System (ADS)

Qi, B.; Gilgenbach, R. M.; Lau, Y. Y.; Jones, M. C.; Lian, J.; Wang, L. M.; Doll, G. L.; Lazarides, A.

2001-10-01

Experiments have demonstrated laser-ablated Fe ion implantation into Si substrates. Baseline laser deposited films (0 kV) showed an amorphous Fe-Si film overlying the Si substrate with a top layer of nanocrystalline Fe. APII films exhibited an additional Fe ion-induced damage layer, extending 7.6 nm below the Si surface. The overlying Fe-Si layer and Fe top layer were amorphized by fast ions. Results were confirmed by XPS vs Ar ion etching time for depth profile of the deposited films. XPS showed primarily Fe (top layer), transitioning to roughly equal Fe/Si , then mostly Si with lower Fe (implanted region). These data clearly prove Fe ion implantation into Si, verifying the feasibility of APII as an ion acceleration and implantation process [1]. SRIM simulations predict about 20 percent deeper Fe ion penetration than data, due to:(a) Subsequent ions must pass through the Fe film deposited by earlier ions, and (b) the bias voltage has a slow rise and fall time. Theoretical research has developed the scaling laws for APII [2]. Recently, a model has successfully explained the shortening of the decay time in the high voltage pulse with the laser ablation plasma. This reduces the theoretical RC time constant, which agrees with the experimental data. * Research supported by National Science Foundation Grant CTS-9907106 [1] Appl. Phys. Lett. 78, 3785 (2001) [2] Appl. Phys. Lett. 78, 706 (2001)),

Acquisition of a Modified Suction Casting Instrument for the Fabrication of Radiation Tolerant Bulk nNanostructured Metallic Materials

DTIC Science & Technology

2015-01-13

Cu/ Nb films”, Philos. Mag., 84, 1021-1028, (2004). [23] D. H. Ryan, J. M. D. Coey, “Magnetic properties of iron-rich Fe- Zr glasses”, Phys. Rev. B...2226, (1982). [26] K. Fukamichi, R. J. Gambino, T. R. McGuire, “ Electrical resistivity and Hall effect in FeZr amorphous sputtered films”, J. Appl...fabricate several bulk nanostructured metallic materials. In particular we fabricated bulk nanostructured Fe- Zr alloys via suction casting technique. The as

Surface Properties of a Nanocrystalline Fe-Ni-Nb-B Alloy After Neutron Irradiation

NASA Astrophysics Data System (ADS)

Pavùk, Milan; Sitek, Jozef; Sedlačková, Katarína

2014-09-01

The effect of neutron radiation on the surface properties of the nanocrystalline (Fe0.25Ni0.75)81Nb7B12 alloy was studied. Firstly, amorphous (Fe0.25Ni0.75)81Nb7B12 ribbon was brought by controlled annealing to the nanocrystalline state. After annealing, the samples of the nanocrystalline ribbon were irradiated in a nuclear reactor with neutron fluences of 1×1016cm-2 and 1 × 1017cm-2 . By utilizing the magnetic force microscopy (MFM), topography and a magnetic domain structure were recorded at the surface of the ribbon-shaped samples before and after irradiation with neutrons. The results indicate that in terms of surface the nanocrystalline (Fe0.25Ni0.75)81Nb7B12 alloy is radiation-resistant up to a neutron fluence of 1 × 1017cm-2 . The changes in topography observed for both irradiated samples are discussed

Alloying Behavior and Properties of FeSiBAlNiCo x High Entropy Alloys Fabricated by Mechanical Alloying and Spark Plasma Sintering

NASA Astrophysics Data System (ADS)

Wang, Wen; Li, Boyu; Zhai, Sicheng; Xu, Juan; Niu, Zuozhe; Xu, Jing; Wang, Yan

2018-02-01

In this paper, FeSiBAlNiCo x (x = 0.2, 0.8) high-entropy alloy (HEA) powders were fabricated by mechanical alloying process, and the powders milled for 140 h were sintered by spark plasma sintering (SPS) technique. The microstructures and properties of as-milled powders and as-sintered samples were investigated. The results reveal that the final milling products (140 h) of both sample powders present the fully amorphous structure. The increased Co contents obviously enhance the glass forming ability and thermal stability of amorphous HEA powders, which are reflected by the shorter formation time of fully amorphous phase and the higher onset crystallization temperature, respectively. According to coercivity, the as-milled FeSiBAlNiCo x (x = 0.2, 0.8) powders (140 h) are the semi-hard magnetic materials. FeSiBAlNiCo0.8 HEA powders possess the highest saturation magnetization and largest remanence ratio. The SPS-ed products of both bulk HEAs are composed of body-centered cubic solid solution, and FeSi and FeB intermetallic phases. They possess the high relative density above 97% and excellent microhardness exceeding 1150 HV. The as-sintered bulks undergo the remarkable increase in saturation magnetization compared with the as-milled state. The SPS-ed FeSiBAlNiCo0.8 HEA exhibits the soft magnetic properties. The electrochemical corrosion test is carried out in 3.5% NaCl solution. The SPS-ed FeSiBAlNiCo0.2 HEA reveals the better passivity with low passive current density, and the higher pitting resistance with wide passive region.

Availability of ferric iron for microbial reduction in bottom sediments of the freshwater tidal potomac river.

PubMed

Lovley, D R; Phillips, E J

1986-10-01

The distribution of Fe(III), its availability for microbial reduction, and factors controlling Fe(III) availability were investigated in sediments from a freshwater site in the Potomac River Estuary. Fe(III) reduction in sediments incubated under anaerobic conditions and depth profiles of oxalate-extractable Fe(III) indicated that Fe(III) reduction was limited to depths of 4 cm or less, with the most intense Fe(III) reduction in the top 1 cm. In incubations of the upper 4 cm of the sediments, Fe(III) reduction was as important as methane production as a pathway for anaerobic electron flow because of the high rates of Fe(III) reduction in the 0- to 0.5-cm interval. Most of the oxalate-extractable Fe(III) in the sediments was not reduced and persisted to a depth of at least 20 cm. The incomplete reduction was not the result of a lack of suitable electron donors. The oxalate-extractable Fe(III) that was preserved in the sediments was considered to be in a form other than amorphous Fe(III) oxyhydroxide, since synthetic amorphous Fe(III) oxyhydroxide, amorphous Fe(III) oxyhydroxide adsorbed onto clay, and amorphous Fe(III) oxyhydroxide saturated with adsorbed phosphate or fulvic acids were all readily reduced. Fe(3)O(4) and the mixed Fe(III)-Fe(II) compound(s) that were produced during the reduction of amorphous Fe(III) oxyhydroxide in an enrichment culture were oxalate extractable but were not reduced, suggesting that mixed Fe(III)-Fe(II) compounds might account for the persistence of oxalate-extractable Fe(III) in the sediments. The availability of microbially reducible Fe(III) in surficial sediments demonstrates that microbial Fe(III) reduction can be important to organic matter decomposition and iron geochemistry. However, the overall extent of microbial Fe(III) reduction is governed by the inability of microorganisms to reduce most of the Fe(III) in the sediment.

Structural and magnetic properties on the Fe-B-P-Cu-W nano-crystalline alloy system

NASA Astrophysics Data System (ADS)

Zhang, Yan; Wang, Yaocen; Makino, Akihiro

2018-04-01

In the present article, the structural and soft magnetic properties of Fe-B-P-Cu alloy system with W addition have been studied as well as the annealing configurations required for magnetic softness. It is found that the substitution of B by W deteriorates the soft magnetic properties after annealing. The reason of such impact with W addition may lie in the insufficient bonding strength between W and B so that the addition of W is not effective enough to suppress grain growth against the high concentration and high crystallization tendency of Fe during annealing. The addition of 4 at.% W is also found to reduce the saturation magnetization of the nano-crystalline alloy by 14%. It is also found that the addition of P in the Fe-based alloys could help reduce the coercivity upon annealing with high heating rate. The existence of P could also help slightly increase the overall saturation magnetization by enhancing the electron transfer away from Fe in the residual amorphous structure.

Improve the catalytic activity of {alpha}-Fe{sub 2}O{sub 3} particles in decomposition of ammonium perchlorate by coating amorphous carbon on their surface

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

Zhang Yifu; Liu Xinghai, E-mail: liuxh@whu.edu.c; Nie Jiaorong

2011-02-15

Sphere- and pod-like {alpha}-Fe{sub 2}O{sub 3} particles have been selectively synthesized using NH{sub 3}.H{sub 2}O and NaOH solution to adjust the pH value of the designed synthetic system, respectively. The sphere-like {alpha}-Fe{sub 2}O{sub 3} particles with diameter about 25 nm on average were encapsulated into carbon shells to fabricate a novel core-shell composite ({alpha}-Fe{sub 2}O{sub 3}-C) through the coating experiments. The catalytic performance of the products on the thermal decomposition of ammonium perchlorate (AP) was investigated by thermal gravimetric analyzer (TG) and differential thermal analysis (DTA). The thermal decomposition temperatures of AP in the presence of pod-like {alpha}-Fe{sub 2}O{sub 3},more » sphere-like {alpha}-Fe{sub 2}O{sub 3} and {alpha}-Fe{sub 2}O{sub 3}-C are reduced by 72, 81 and 109 {sup o}C, respectively, which show that {alpha}-Fe{sub 2}O{sub 3}-C core-shell composites have higher catalytic activity than that of {alpha}-Fe{sub 2}O{sub 3}. -- Graphical abstract: The catalytic performance of pod-like {alpha}-Fe{sub 2}O{sub 3}, sphere-like {alpha}-Fe{sub 2}O{sub 3} and {alpha}-Fe{sub 2}O{sub 3}-C on the thermal decomposition of ammonium perchlorate (AP). Display Omitted Research highlights: {yields} Sphere- and pod-like {alpha}-Fe{sub 2}O{sub 3} particles have been selectively synthesized using NH{sub 3}.H{sub 2}O and NaOH solution to adjust the pH value. {yields} A novel core-shell composite ({alpha}-Fe{sub 2}O{sub 3}-C core-shell structured composite) has been successfully synthesized using sphere-like {alpha}-Fe{sub 2}O{sub 3} particles as the cores and glucose as the source of carbon. {yields} The thermal decomposition temperatures of AP in the presence of pod-like {alpha}-Fe{sub 2}O{sub 3}, sphere-like {alpha}-Fe{sub 2}O{sub 3} and {alpha}-Fe{sub 2}O{sub 3}-C are reduced by 72, 81 and 109 {sup o}C, respectively, which shows that these materials have high catalytic activity.« less

Preparation and pharmaceutical characterization of amorphous cefdinir using spray-drying and SAS-process.

PubMed

Park, Junsung; Park, Hee Jun; Cho, Wonkyung; Cha, Kwang-Ho; Kang, Young-Shin; Hwang, Sung-Joo

2010-08-30

The aim of this study was to investigate the effects of micronization and amorphorization of cefdinir on solubility and dissolution rate. The amorphous samples were prepared by spray-drying (SD) and supercritical anti-solvent (SAS) process, respectively and their amorphous natures were confirmed by DSC, PXRD and FT-IR. Thermal gravimetric analysis was performed by TGA. SEM was used to investigate the morphology of particles and the processed particle had a spherical shape, while the unprocessed crystalline particle had a needle-like shape. The mean particle size and specific surface area were measured by dynamic light scattering (DLS) and BET, respectively. The DLS result showed that the SAS-processed particle was the smallest, followed by SD and the unprocessed cefdinir. The BET result was the same as DLS result in that the SAS-processed particle had the largest surface area. Therefore, the processed cefdinir, especially the SAS-processed particle, appeared to have enhanced apparent solubility, improved intrinsic dissolution rate and better drug release when compared with SD-processed and unprocessed crystalline cefdinir due not only to its amorphous nature, but also its reduced particle size. Conclusions were that the solubility and dissolution rate of crystalline cefdinir could be improved by physically modifying the particles using SD and SAS-process. Furthermore, SAS-process was a powerful methodology for improving the solubility and dissolution rate of cefdinir. Copyright 2010 Elsevier B.V. All rights reserved.

Mössbauer and magnetic studies of surfactant mediated Ca-Mg doped ferrihydrite nanoparticles.

PubMed

Layek, Samar; Mohapatra, M; Anand, S; Verma, H C

2013-03-01

Ultrafine (2-5 nm) particles of amorphous Ca-Mg co-doped ferrihydrite have been synthesized by surfactant mediated co-precipitation method. The evolution of the amorphous ferrihydrite by Ca-Mg co-doping is quite different from our earlier investigations on individual doping of Ca and Mg. Amorphous phase of ferrihydrite for the present study has been confirmed by X-ray diffraction (XRD) and Mössbauer spectroscopy at room temperature and low temperatures (40 K and 20 K). Hematite nanoparticles with crystallite size about 8, 38 and 70 nm were obtained after annealing the as-prepared samples at 400, 600 and 800 degrees C respectively in air atmosphere. Superparamagnetism has been found in 8 nm sized hematite nanoparticles which has been confirmed from the magnetic hysteresis loop with zero remanent magnetization and coercive field and also from the superparamagnetic doublet of its room temperature Mössbauer spectrum. The magnetic properties of the 38 and 70 nm sized particles have been studied by room temperature magnetic hysteresis loop measurements and Mössbauer spectroscopy. The coercive field in these hematite nanoparticles increases with increasing particle size. Small amount of spinel MgFe2O4 phase has been detected in the 800 degrees C annealed sample.

Bioactivity of gelatin coated magnetic iron oxide nanoparticles: in vitro evaluation.

PubMed

Gaihre, Babita; Khil, Myung Seob; Kang, Hyo Kyoung; Kim, Hak Yong

2009-02-01

Current research explores formation of bone like apatite on gelatin coated magnetic iron oxide nanoparticles (GIOPs) to evaluate the bioactivity of the material. The GIOPs were soaked in simulated body fluid (SBF) and the apatite formation on the surface was investigated in regular interval of time. Fourier transform-infrared (FT-IR) and x-ray diffraction spectroscopic (XRD) analyses were done to investigate the chemical changes and field emission-scanning electron microscopic (FE-SEM) analysis was done to investigate the morphological changes occurring on the surface of the GIOPs after soaking in different time intervals. The kinetic studies of the apatite growth in SBF suggest that initially calcium and phosphorous ions were deposited to the surface of the GIOPs from the SBF leading to formation of amorphous Ca/P particles. Later, after 9 days of the incubation the amorphous particles were fused to form needle and blade like crystalline structures of bone like apatite.

Transmission Electron Microscopy of Cometary Residues from Micron-Sized Craters in the Stardust Al-Foils

NASA Technical Reports Server (NTRS)

Leroux, Hugues; Stroud, Rhonda M.; Dai, Zu Rong; Graham, Giles A.; Troadec, David; Bradley, John P.; Teslich, Nick; Borg, Janet; Kearsley, Anton T.; Horz, Friedrich

2008-01-01

We report Transmission Electron Microscopy (TEM) investigations of micro-craters that originated from hypervelocity impacts of comet 81P/Wild 2 dust particles on the aluminium foil of the Stardust collector. The craters were selected by Scanning Electron Microscopy (SEM) and then prepared by Focused Ion Beam (FIB) milling techniques in order to provide electron transparent cross-sections for TEM studies. The crater residues contain both amorphous and crystalline materials in varying proportions and compositions. The amorphous component is interpreted as resulting from shock melting during the impact and the crystalline phases as relict minerals. The latter show evidence for shock metamorphism. Based on the residue morphology and the compositional variation, the impacting particles are inferred to have been dominated by mixtures of submicron olivine, pyroxene and Fe-sulfide grains, in agreement with prior results of relatively coarse-grained mineral assemblages in the aerogel collector.

The Search for Interstellar Sulfide Grains

NASA Technical Reports Server (NTRS)

Keller, Lindsay P.; Messenger, Scott

2010-01-01

The lifecycle of sulfur in the galaxy is poorly understood. Fe-sulfide grains are abundant in early solar system materials (e.g. meteorites and comets) and S is highly depleted from the gas phase in cold, dense molecular cloud environments. In stark contrast, sulfur is essentially undepleted from the gas phase in the diffuse interstellar medium, indicating that little sulfur is incorporated into solid grains in this environment. It is widely believed that sulfur is not a component of interstellar dust grains. This is a rather puzzling observation unless Fe-sulfides are not produced in significant quantities in stellar outflows, or their lifetime in the ISM is very short due to rapid destruction. Fe sulfide grains are ubiquitous in cometary samples where they are the dominant host of sulfur. The Fe-sulfides (primarily pyrrhotite; Fe(1-x)S) are common, both as discrete 0.5-10 micron-sized grains and as fine (5-10 nm) nanophase inclusions within amorphous silicate grains. Cometary dust particles contain high abundances of well-preserved presolar silicates and organic matter and we have suggested that they should contain presolar sulfides as well. This hypothesis is supported by the observation of abundant Fe-sulfides grains in dust around pre- and post-main sequence stars inferred from astronomical spectra showing a broad 23 micron IR feature due to FeS. Fe-sulfide grains also occur as inclusions in bona fide circumstellar amorphous silicate grains and as inclusions within deuterium-rich organic matter in cometary dust samples. Our irradiation experiments show that FeS is far more resistant to radiation damage than silicates. Consequently, we expect that Fe sulfide stardust should be as abundant as silicate stardust in solar system materials.

Mechanism of molybdenum removal from the sea and its concentration in black shales: EXAFS evidence

USGS Publications Warehouse

Helz, G.R.; Miller, C.V.; Charnock, J.M.; Mosselmans, J.F.W.; Pattrick, R.A.D.; Garner, C.D.; Vaughan, D.J.

1996-01-01

Molybdenum K-edge EXAFS (extended X-ray absorption fine structure) spectra yield new structural information about the chemical environment of Mo in high-Mo black shales and sediments. Two spectral types are found. The less common one, associated with Mo ores developed in shale in China, is that of a MoS2 phase, possibly X-ray amorphous jordisite. The other, associated with Cretaceous deep sea sediments and with other black shales, is characterized by short Mo-O distances (1.69-1.71 A??), by Mo-S distances of 2.30-2.38 A??, and in some cases by second shell Mo and Fe interactions, which suggests that some Mo resides in transition metal-rich phases. EXAFS spectra of synthetic amorphous materials, prepared by scavenging Mo from HS solutions with Fe(II), FeOOH, and humic acid, suggest that the second spectral type arises from Mo present chiefly in two forms. One is a compact, Mo-Fe-S "cubane" type compound with Mo-S distances of ???2.36 A?? and Mo-Fe distances of ???2.66 A??, while the other is probably an organic form containing some Mo-O double bonds (???1.69 A??). Laboratory products, that were prepared by scavenging dissolved Mo from sulfidic solutions with humic acid, yield spectra quite similar to the second spectral type observed in shales and sediments, including unexpected indications of Mo-Fe interactions. Molybdenum L-edge spectra indicate that the mean oxidation state in the sediments and shales lies between IV and VI. This work demonstrates the merit of EXAFS for obtaining structural information on natural materials containing X-ray amorphous components which defeat conventional mineralogical characterization. The implications of these findings regarding Mo scavenging from sulfidic natural waters are considered. We introduce the concept of a geochemical switch, in which HS- transforms the marine behavior of Mo from that of a conservative element to that of a particle reactive element. The action point of the HS- switch is calculated to be, aHS- = 10-3.6 - 10-4.3. When aHS- approaches the action point, Mo becomes reactive to particles containing transition metals (e.g., Fe). We conjecture that thiols, including humic-bound thiol groups, also switch Mo behavior. In contrast to previous ideas, our model for Mo scavenging deemphasizes the role of reduction from Mo(VI) to Mo(V) as the initial step in scavenging; instead, we emphasize the ease with which Mo forms covalent bonds to transition metals and organic molecules via S bridges.

Unusual high B{sub s} for Fe-based amorphous powders produced by a gas-atomization technique

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

Yoshida, K.; Bito, M.; Kageyama, J.

2016-05-15

Fe-based alloy powders with a high Fe content of about 81 at.% were produced by a gas-atomization technique. Powders of Fe{sub 81}Si{sub 1.9}B{sub 5.7}P{sub 11.4} (at.%) alloy showed a good glass forming ability and exhibited unusual high saturation magnetic flux density of 1.57 T. The core-loss property at a frequency of 100 kHz for the compacted core made of the Fe{sub 81}Si{sub 1.9}B{sub 5.7}P{sub 11.4} powder is evaluated to be less than 500 kW/m{sup 3} under a maximum induction of 100 mT. Moreover, good DC-superposition characteristic of the core was also confirmed. These results suggest that the present Fe-based alloymore » powder is promising for low-loss magnetic-core materials and expected to contribute in miniaturization of electric parts in the near future.« less

H+-induced irradiation damage resistance in Fe- and Ni-based metallic glass

NASA Astrophysics Data System (ADS)

Zhang, Hongran; Mei, Xianxiu; Zhang, Xiaonan; Li, Xiaona; Wang, Yingmin; Sun, Jianrong; Wang, Younian

2016-05-01

In this study, use of 40-keV H+ ion for irradiating metallic glass Fe80Si7.43B12.57 and Ni62Ta38 as well as metallic tungsten (W) at fluences of 1 × 1018 and 3 × 1018 ions/cm2, respectively, was investigated. At the fluence of 1 × 1018 ions/cm2, a crystalline layer appeared in metallic glass Fe80Si7.43B12.57, with α-Fe as the major crystalline phase, coupled with a little Fe2B, Fe3B, and metastable β-Mn-type phase. Fe80Si7.43B12.57 exhibited good soft magnetic properties after irradiation. At the fluence of 3 × 1018 ions/cm2, Ni62Ta38 was found to be amorphous-based, with a little μ-NiTa and Ni3Ta phases. No significant irradiation damage phenomenon appeared in metallic glasses Fe80Si7.43B12.57 and Ni62Ta38. Blistering, flaking, and other damage occurred on the surface of metallic W, and the root-mean-square (RMS) roughness increased with the increase of fluence. Metallic glass Ni62Ta38 exhibited better resistance to H+ irradiation than Fe80Si7.43B12.57, both of which were superior to the metallic W.

Effect of iron sulfides on the space weathering of airless silicate bodies: Laboratory simulation

NASA Astrophysics Data System (ADS)

Sasaki, Sho; Hiroi, Takahiro; Okazaki, Mizuki

The spectral mismatch between S-type asteroids and ordinary chondrites is explained by the process "space weathering", which should change the optical properties of the surface of airless silicate bodies: darkening, spectral reddening, and attenuation of absorption bands in reflectance spectra. It is caused by nanophase metallic iron (nanoFe) particles within the amorphous rims, which are formed on regolith particles by high velocity dust impacts as well as irradiation of the solar wind ions. Those nanoFe particles were discovered in lunar soils, Kapoeta meteorite, and regolith grains from the surface of S-type asteroid Itokawa. Experimental studies using nano-second pulse laser confirmed that nanoFe should control the spectral darkening and reddening. In ordinary chondrites, iron sulfides, especially troilite FeS is the main sulfur-bearing mineral. TEM observation of a dust grain of Itokawa showed the presence of not only iron, but also nanophase FeS particles, which would be formed within a surface vapor-deposited thin layer (<10 to 15nm) (Noguchi et al., 2011). Among dust grains of Itokawa, one grain is composed mainly of FeS (-40 mum) with smaller olivine and pyroxene grains embedded in the FeS (Yada et al., 2014). Previously surface sulfur depletion of S-type asteroid Eros was explained by the same causes (high velocity dust impacts as well as irradiation of the solar wind ions) as space weathering (Loeffler et al. 2008), but the effect of FeS on the surface optical properties of silicate bodies has not discussed well. To examine this effect, we conducted pulse laser irradiation experiments on mixture of olivine (and pyroxene) and FeS particles with sizes typically 45-75micron, under various FeS fraction (0-20wt%). We found that addition of FeS promotes the change of optical properties in accordance with space weathering. Compared with the cases where Fe particles are mixed, darkening of 1.0 - 2.5 micron region is observed. Probably FeS nanoparticles would be formed to change the reflectance spectra. References: [1] Noguchi, T. et al. (2011) Science 333,1121., [2] Yada, T. et al. (2014) LPSC 45th, 1759., [3] Loeffler, M. J. et al. (2008) Icarus 195, 622.

Electrical and Magnetic Properties of Binary Amorphous Transition Metal Alloys.

NASA Astrophysics Data System (ADS)

Liou, Sy-Hwang

The electrical, superconductive and magnetic properties of several binary transition metal amorphous and metastable crystalline alloys, Fe(,x)Ti(,100-x) (30 (LESSTHEQ) x (LESSTHEQ) 100), Fe(,x)Zr(,100-x) (20 (LESSTHEQ) x (LESSTHEQ) 93), Fe(,x)Hf(,100-x) (20 (LESSTHEQ) x (LESSTHEQ) 100), Fe(,x)Nb(,100 -x) (22 (LESSTHEQ) x (LESSTHEQ) 85), Ni(,x)Nb(,100-x) (20 (LESSTHEQ) x (LESSTHEQ) 80), Cu(,x)Nb(,100-x) (10 (LESSTHEQ) x (LESSTHEQ) 90) were studied over a wide composition range. Films were made using a magnetron sputtering system, and the structure of the films was investigated by energy dispersive x-ray diffraction. The composition region of each amorphous alloys system was determined and found in good agreement with a model proposed by Egami and Waseda. The magnetic properties and hyperfine interactions in the films were investigated using a conventional Mossbauer spectrometer and a ('57)Co in Rh matrix source. In all Fe-early transition metal binary alloys systems, Fe does not retain its moment in the low iron concentration region and the result is that the critical concentration for magnetic order (x(,c)) is much larger than anticipated from percolation considerations. A direct comparison between crystalline alloys and their amorphous counterparts of the same composition illustrate no clear correlation between crystalline and amorphous states. Pronounced discontinuities in the magnetic properties with variation in Fe content of all Fe-early transition metal alloys at phase boundaries separating amorphous and crystalline states have been observed. This is caused by the differences in the atomic arrangement and the electronic structure between crystalline and amorphous solids. The temperature dependence of resistivity, (rho)(T), of several binary amorphous alloys of Fe-TM (where TM = Ti, Zr, Hf, Nb etc.) has been studied from 2K to 300K. The Fe-poor (x < x(,c)) samples and the Fe-rich (x > x(,c)) samples have distinctive differences in (rho)(T) at low temperature (below 30K). All the magnetic samples show a logarithmic dependence at low temperature that can be described by Kondo scattering. In addition, there is a change in slope of (rho)(T) at a temperature close to the magnetic ordering temperature, indicating a contribution attributed to magnetic ordering. Several Nb-based amorphous alloys (Fe-Nb, Ni-Nb, Cu-Nb) have also been systematically studied. The effect of the magnetic species on superconductivity is investigated. The value of superconducting transition temperature (T(,s)) increases linearly with increasing Nb concentration. (Abstract shortened with permission of author.).

Nanomineralogy in the real world: A perspective on nanoparticles in the environmental impacts of coal fire.

PubMed

Sehn, Janaína L; de Leão, Felipe B; da Boit, Kátia; Oliveira, Marcos L S; Hidalgo, Gelsa E; Sampaio, Carlos H; Silva, Luis F O

2016-03-01

Detailed geochemistry similarities between the burning coal cleaning rejects (BCCRs) and non-anthropogenic geological environments are outlined here. While no visible flames were detected, this research revealed that auto-combustion existed in the studied area for many years. The occurrence of several amorphous phases, mullite, hematite and many other Al/Fe-minerals formed by high temperature was found. Bad disposal of coal-dump wastes represents significant environmental concerns due to their potential influence on atmosphere, river sediments, soils and as well as on the surface and groundwater in the surroundings of these areas. The present work using multi-analytical techniques were performed to provide an improved understanding of the complex processes related with sulphide-rich coal waste oxidation, spontaneous combustion and newmineral creation. It recording huge numbers of rare minerals with alunite, montmorillonite, szmolnockite, halotrichite, coquimbite and copiapite at the BCCRs. The information presented the presence of abundant amorphous Si-Al-Fe-Ti as (oxy-)hydroxides and Fe-hydro/oxides with goethite and hematite with various degrees of crystallinity, containing potential hazardous elements (PHEs), such as Cu, Cr, Hf, Hg, Mo, Ni, Se, Pb, Th, U, Zr, and others. Most of the nano-particles and ultra-fine particles found in the burned coal-dump wastes are the same as those commonly associated with coal cleaning rejects, in which oxidation of sulphides plays an important impact to environment and subsequently animal and human health. Copyright © 2015 Elsevier Ltd. All rights reserved.

Development of a Tabletop Model for the Generation of Amorphous/ Microcrystalline Metal Powders

DTIC Science & Technology

1980-04-30

Voltage Characteristics for Wetting (si) and Non-wetting (AZ 4.5% Cu ) EHD Spray 2-57 28 Schematic of the Process of Electrohydrodynamic Droplet...Microscope Image of a Deposit , Fine Powders and "Matrix" Film of Fe-Ni-B-P Metallic Glass Alloy Produced by the EHD Technique 3-9 45 Selected Area...Transmission Electron Microscope Image of a Deposit , Fine Powders and "Matrix" Film of Fe-Ni-B-P Metallic Glass Alloy Produced by the EHD Technique 3-11 xi

High-capacity cathodes for lithium-ion batteries from nanostructured LiFePO4 synthesized by highly-flexible and scalable flame spray pyrolysis

NASA Astrophysics Data System (ADS)

Hamid, N. A.; Wennig, S.; Hardt, S.; Heinzel, A.; Schulz, C.; Wiggers, H.

2012-10-01

Olivine, LiFePO4 is a promising cathode material for lithium-ion batteries due to its low cost, environmental acceptability and high stability. Its low electric conductivity prevented it for a long time from being used in large-scale applications. Decreasing its particle size along with carbon coating significantly improves electronic conductivity and lithium diffusion. With respect to the controlled formation of very small particles with large specific surface, gas-phase synthesis opens an economic and flexible route towards high-quality battery materials. Amorphous FePO4 was synthesized as precursor material for LiFePO4 by flame spray pyrolysis of a solution of iron acetylacetonate and tributyl phosphate in toluene. The pristine FePO4 with a specific surface from 126-218 m2 g-1 was post-processed to LiFePO4/C composite material via a solid-state reaction using Li2CO3 and glucose. The final olivine LiFePO4/C particles still showed a large specific surface of 24 m2 g-1 and were characterized using X-ray diffraction (XRD), electron microscopy, X-ray photoelectron spectrocopy (XPS) and elemental analysis. Electrochemical investigations of the final LiFePO4/C composites show reversible capacities of more than 145 mAh g-1 (about 115 mAh g-1 with respect to the total coating mass). The material supports high drain rates at 16 C while delivering 40 mAh g-1 and causes excellent cycle stability.

Potential for microbial oxidation of ferrous iron in basaltic glass.

PubMed

Xiong, Mai Yia; Shelobolina, Evgenya S; Roden, Eric E

2015-05-01

Basaltic glass (BG) is an amorphous ferrous iron [Fe(II)]-containing material present in basaltic rocks, which are abundant on rocky planets such as Earth and Mars. Previous research has suggested that Fe(II) in BG can serve as an energy source for chemolithotrophic microbial metabolism, which has important ramifications for potential past and present microbial life on Mars. However, to date there has been no direct demonstration of microbially catalyzed oxidation of Fe(II) in BG. In this study, three different culture systems were used to investigate the potential for microbial oxidation of Fe(II) in BG, including (1) the chemolithoautotrophic Fe(II)-oxidizing, nitrate-reducing "Straub culture"; (2) the mixotrophic Fe(II)-oxidizing, nitrate-reducing organism Desulfitobacterium frappieri strain G2; and (3) indigenous microorganisms from a streambed Fe seep in Wisconsin. The BG employed consisted of clay and silt-sized particles of freshly quenched lava from the TEB flow in Kilauea, Hawaii. Soluble Fe(II) or chemically reduced NAu-2 smectite (RS) were employed as positive controls to verify Fe(II) oxidation activity in the culture systems. All three systems demonstrated oxidation of soluble Fe(II) and/or structural Fe(II) in RS, whereas no oxidation of Fe(II) in BG material was observed. The inability of the Straub culture to oxidize Fe(II) in BG was particularly surprising, as this culture can oxidize other insoluble Fe(II)-bearing minerals such as biotite, magnetite, and siderite. Although the reason for the resistance of the BG toward enzymatic oxidation remains unknown, it seems possible that the absence of distinct crystal faces or edge sites in the amorphous glass renders the material resistant to such attack. These findings have implications with regard to the idea that Fe(II)-Si-rich phases in basalt rocks could provide a basis for chemolithotrophic microbial life on Mars, specifically in neutral-pH environments where acid-promoted mineral dissolution and utilization of dissolved Fe(II) as an energy source is not likely to take place.

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

Space Weathering Effects in Lunar Soils: The Roles of Surface Exposure Time and Bulk Chemical Composition

NASA Technical Reports Server (NTRS)

Zhang, Shouliang; Keller, Lindsay P.

2011-01-01

Space weathering effects on lunar soil grains result from both radiation-damaged and deposited layers on grain surfaces. Typically, solar wind irradiation forms an amorphous layer on regolith silicate grains, and induces the formation of surficial metallic Fe in Fe-bearing minerals [1,2]. Impacts into the lunar regolith generate high temperature melts and vapor. The vapor component is largely deposited on the surfaces of lunar soil grains [3] as is a fraction of the melt [4, this work]. Both the vapor-deposits and the deposited melt typically contain nanophase Fe metal particles (npFe0) as abundant inclusions. The development of these rims and the abundance of the npFe0 in lunar regolith, and thus the optical properties, vary with the soil mineralogy and the length of time the soil grains have been exposed to space weathering effects [5]. In this study, we used the density of solar flare particle tracks in soil grains to estimate exposure times for individual grains and then perform nanometer-scale characterization of the rims using transmission electron microscopy (TEM). The work involved study of lunar soil samples with different mineralogy (mare vs. highland) and different exposure times (mature vs. immature).

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.

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

Elihn, K.; Landstroem, L.; Alm, O.

Iron nanoparticles enclosed in carbon shells were formed by laser-assisted chemical vapor decomposition of ferrocene (Fe(C{sub 5}H{sub 5}){sub 2}) vapor in Ar gas atmosphere. The particle size dependence on the total ambient gas pressure and on laser fluence of the pulsed ArF excimer laser was examined and, e.g., an effective size decrease of the iron core was observed at elevated laser fluences. Characterizations of the iron and carbon microstructures were performed by x-ray diffraction and transmission electron microscopy, while relative iron deposition rates were measured by x-ray fluorescence spectroscopy. Both {alpha}-Fe and {gamma}-Fe phases were found for the single crystallinemore » iron cores, surrounded by graphitic (inner) and amorphous (outer) carbon layers. The temperature rise of the laser-excited particles was also determined by optical spectroscopy of the emitted thermal radiation, which allowed an estimation of the iron loss of the nanoparticles due to evaporation. The estimated and measured iron losses are in good agreement.« less

Iron-Based Amorphous Metals: High-Performance Corrosion-Resistant Material Development

NASA Astrophysics Data System (ADS)

Farmer, Joseph; Choi, Jor-Shan; Saw, Cheng; Haslam, Jeffrey; Day, Dan; Hailey, Phillip; Lian, Tiangan; Rebak, Raul; Perepezko, John; Payer, Joe; Branagan, Daniel; Beardsley, Brad; D'Amato, Andy; Aprigliano, Lou

2009-06-01

An overview of the High-Performance Corrosion-Resistant Materials (HPCRM) Program, which was cosponsored by the Defense Advanced Research Projects Agency (DARPA) Defense Sciences Office (DSO) and the U.S. Department of Energy (DOE) Office of Civilian and Radioactive Waste Management (OCRWM), is discussed. Programmatic investigations have included a broad range of topics: alloy design and composition, materials synthesis, thermal stability, corrosion resistance, environmental cracking, mechanical properties, damage tolerance, radiation effects, and important potential applications. Amorphous alloys identified as SAM2X5 (Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4) and SAM1651 (Fe48Mo14Cr15Y2C15B6) have been produced as meltspun ribbons (MSRs), dropcast ingots, and thermal-spray coatings. Chromium (Cr), molybdenum (Mo), and tungsten (W) additions provided corrosion resistance, while boron (B) enabled glass formation. Earlier electrochemical studies of MSRs and ingots of these amorphous alloys demonstrated outstanding passive film stability. More recently, thermal-spray coatings of these amorphous alloys have been made and subjected to long-term salt-fog and immersion tests; good corrosion resistance has been observed during salt-fog testing. Corrosion rates were measured in situ with linear polarization, while the open-circuit corrosion potentials (OCPs) were simultaneously monitored; reasonably good performance was observed. The sensitivity of these measurements to electrolyte composition and temperature was determined. The high boron content of this particular amorphous metal makes this amorphous alloy an effective neutron absorber and suitable for criticality-control applications. In general, the corrosion resistance of such iron-based amorphous metals is maintained at operating temperatures up to the glass transition temperature. These materials are much harder than conventional stainless steel and Ni-based materials, and are proving to have excellent wear properties, sufficient to warrant their use in earth excavation, drilling, and tunnel-boring applications. Large areas have been successfully coated with these materials, with thicknesses of approximately 1 cm. The observed corrosion resistance may enable applications of importance in industries such as oil and gas production, refining, nuclear power generation, shipping, etc.

Spin-valve giant magneto-resistance film with magnetostrictive FeSiB amorphous layer and its application to strain sensors

NASA Astrophysics Data System (ADS)

Hashimoto, Y.; Yamamoto, N.; Kato, T.; Oshima, D.; Iwata, S.

2018-03-01

Giant magneto-resistance (GMR) spin-valve films with an FeSiB/CoFeB free layer were fabricated to detect applied strain in a GMR device. The magnetostriction constant of FeSiB was experimentally determined to have 32 ppm, which was one order of magnitude larger than that of CoFeB. In order to detect the strain sensitively and robustly against magnetic field fluctuation, the magnetic field modulation technique was applied to the GMR device. It was confirmed that the output voltage of the GMR device depends on the strain, and the gauge factor K = 46 was obtained by adjusting the applied DC field intensity and direction. We carried out the simulation based on a macro-spin model assuming uniaxial anisotropy, interlayer coupling between the free and pin layers, strain-induced anisotropy, and Zeeman energy, and succeeded in reproducing the experimental results. The simulation predicts that improving the magnetic properties of GMR films, especially reducing interlayer coupling, will be effective for increasing the output, i.e., the gauge factor, of the GMR strain sensors.

Metal/ceramic interface structures and segregation behavior in aluminum-based composites

DOE PAGES

Zhang, Xinming; Hu, Tao; Rufner, Jorgen F.; ...

2015-06-14

Trimodal Al alloy (AA) matrix composites consisting of ultrafine-­grained (UFG) and coarse-­ grained (CG) Al phases and micron-­sized B 4C ceramic reinforcement particles exhibit combinations of strength and ductility that render them useful for potential applications in the aerospace, defense and automotive industries. Tailoring of microstructures with specific mechanical properties requires a detailed understanding of interfacial structures to enable strong interface bonding between ceramic reinforcement and metal matrix, and thereby allow for effective load transfer. Trimodal AA metal matrix composites typically show three characteristics that are noteworthy: nanocrystalline grains in the vicinity of the B4C reinforcement particles; Mg segregation atmore » AA/B 4C interfaces; and the presence of amorphous interfacial layers separating nanocrystalline grains from B 4C particles. Interestingly, however, fundamental information related to the mechanisms responsible for these characteristics as well as information on local compositions and phases are absent in the current literature. Here in this study, we use high-­resolution transmission electron microscopy, energy-­dispersive X-­ray spectroscopy, electron energy-­loss spectroscopy, and precession assisted electron diffraction to gain fundamental insight into the mechanisms that affect the characteristics of AA/B 4C interfaces. Specifically, we determined interfacial structures, local composition and spatial distribution of the interfacial constituents. Near atomic resolution characterization revealed amorphous multilayers and a nanocrystalline region between Al phase and B 4C reinforcement particles. The amorphous multilayers consist of nonstoichiometric Al xO y, while the nanocrystalline region is comprised of MgO nanograins. The experimental results are discussed in terms of the possible underlying mechanisms at AA/B 4C interfaces.« less

Orientation of FePt nanoparticles on top of a-SiO2/Si(001), MgO(001) and sapphire(0001): effect of thermal treatments and influence of substrate and particle size.

PubMed

Schilling, Martin; Ziemann, Paul; Zhang, Zaoli; Biskupek, Johannes; Kaiser, Ute; Wiedwald, Ulf

2016-01-01

Texture formation and epitaxy of thin metal films and oriented growth of nanoparticles (NPs) on single crystal supports are of general interest for improved physical and chemical properties especially of anisotropic materials. In the case of FePt, the main focus lies on its highly anisotropic magnetic behavior and its catalytic activity, both due to the chemically ordered face-centered tetragonal (fct) L10 phase. If the c-axis of the tetragonal system can be aligned normal to the substrate plane, perpendicular magnetic recording could be achieved. Here, we study the orientation of FePt NPs and films on a-SiO2/Si(001), i.e., Si(001) with an amorphous (a-) native oxide layer on top, on MgO(001), and on sapphire(0001) substrates. For the NPs of an approximately equiatomic composition, two different sizes were chosen: "small" NPs with diameters in the range of 2-3 nm and "large" ones in the range of 5-8 nm. The 3 nm thick FePt films, deposited by pulsed laser deposition (PLD), served as reference samples. The structural properties were probed in situ, particularly texture formation and epitaxy of the specimens by reflection high-energy electron diffraction (RHEED) and, in case of 3 nm nanoparticles, additionally by high-resolution transmission electron microscopy (HRTEM) after different annealing steps between 200 and 650 °C. The L10 phase is obtained at annealing temperatures above 550 °C for films and 600 °C for nanoparticles in accordance with previous reports. On the amorphous surface of a-SiO2/Si substrates we find no preferential orientation neither for FePt films nor nanoparticles even after annealing at 630 °C. On sapphire(0001) supports, however, FePt nanoparticles exhibit a clearly preferred (111) orientation even in the as-prepared state, which can be slightly improved by annealing at 600-650 °C. This improvement depends on the size of NPs: Only the smaller NPs approach a fully developed (111) orientation. On top of MgO(001) the effect of annealing on particle orientation was found to be strongest. From a random orientation in the as-prepared state observed for both, small and large FePt NPs, annealing at 650 °C for 30 min reorients the small particles towards a cube-on-cube epitaxial orientation with a minor fraction of (111)-oriented particles. In contrast, large FePt NPs keep their as-prepared random orientation even after doubling the annealing period at 650 °C to 60 min.

Orientation of FePt nanoparticles on top of a-SiO2/Si(001), MgO(001) and sapphire(0001): effect of thermal treatments and influence of substrate and particle size

PubMed Central

Schilling, Martin; Ziemann, Paul; Zhang, Zaoli; Biskupek, Johannes; Kaiser, Ute

2016-01-01

Summary Texture formation and epitaxy of thin metal films and oriented growth of nanoparticles (NPs) on single crystal supports are of general interest for improved physical and chemical properties especially of anisotropic materials. In the case of FePt, the main focus lies on its highly anisotropic magnetic behavior and its catalytic activity, both due to the chemically ordered face-centered tetragonal (fct) L10 phase. If the c-axis of the tetragonal system can be aligned normal to the substrate plane, perpendicular magnetic recording could be achieved. Here, we study the orientation of FePt NPs and films on a-SiO2/Si(001), i.e., Si(001) with an amorphous (a-) native oxide layer on top, on MgO(001), and on sapphire(0001) substrates. For the NPs of an approximately equiatomic composition, two different sizes were chosen: “small” NPs with diameters in the range of 2–3 nm and “large” ones in the range of 5–8 nm. The 3 nm thick FePt films, deposited by pulsed laser deposition (PLD), served as reference samples. The structural properties were probed in situ, particularly texture formation and epitaxy of the specimens by reflection high-energy electron diffraction (RHEED) and, in case of 3 nm nanoparticles, additionally by high-resolution transmission electron microscopy (HRTEM) after different annealing steps between 200 and 650 °C. The L10 phase is obtained at annealing temperatures above 550 °C for films and 600 °C for nanoparticles in accordance with previous reports. On the amorphous surface of a-SiO2/Si substrates we find no preferential orientation neither for FePt films nor nanoparticles even after annealing at 630 °C. On sapphire(0001) supports, however, FePt nanoparticles exhibit a clearly preferred (111) orientation even in the as-prepared state, which can be slightly improved by annealing at 600–650 °C. This improvement depends on the size of NPs: Only the smaller NPs approach a fully developed (111) orientation. On top of MgO(001) the effect of annealing on particle orientation was found to be strongest. From a random orientation in the as-prepared state observed for both, small and large FePt NPs, annealing at 650 °C for 30 min reorients the small particles towards a cube-on-cube epitaxial orientation with a minor fraction of (111)-oriented particles. In contrast, large FePt NPs keep their as-prepared random orientation even after doubling the annealing period at 650 °C to 60 min. PMID:27335749

Effect of washing process on the magnetic properties of Nd-Fe-B nanoparticles prepared by reduction-diffusion method

NASA Astrophysics Data System (ADS)

Wang, Y.; Ahn, J.; Kim, D.; Ren, W. J.; Liu, W.; Zhang, Z. D.; Choi, C. J.

2017-10-01

Nd-Fe-B nanoparticles with a particle size below 50 nm and excellent magnetic properties were obtained via a novel route which makes use of both spray drying and reduction-diffusion processes. Uniform Nd-Fe-B particles were formed by the optimization of Ca amount as a reducing agent and additional washing by milling in ethanol media. Especially, we implemented a two-step washing process which contributed to the excellent magnetic properties with high remanence and coercivity. After the removal of CaO by novel washing process, the maximum energy product (BH)max of the particles showed 22.1 MGOe. This value is superior to those reported in reduction-diffusion process. We used Henkel plot to assume the mechanism of magnetic interactions of the Nd-Fe-B nanoparticles.

Canted spin structure and the first order magnetic transition in CoFe2O4 nanoparticles coated by amorphous silica

NASA Astrophysics Data System (ADS)

Lyubutin, I. S.; Starchikov, S. S.; Gervits, N. E.; Korotkov, N. Yu.; Dmitrieva, T. V.; Lin, Chun-Rong; Tseng, Yaw-Teng; Shih, Kun-Yauh; Lee, Jiann-Shing; Wang, Cheng-Chien

2016-10-01

The functional polymer (PMA-co-MAA) latex microspheres were used as a core template to prepare magnetic hollow spheres consisting of CoFe2O4/SiO2 composites. The spinel type crystal structure of CoFe2O4 ferrite is formed under annealing, whereas the polymer cores are completely removed after annealing at 450 °C. Magnetic and Mössbauer spectroscopy measurements reveal very interesting magnetic properties of the CoFe2O4/SiO2 hollow spheres strongly dependent on the particle size which can be tuned by the annealing temperature. In the ground state of low temperatures, the CoFe2O4 nanoparticles are in antiferromagnetic state due to the canted magnetic structure. Under heating in the applied field, the magnetic structure gradually transforms from canted to collinear, which increases the magnetization. The Mössbauer data revealed that the small size CoFe2O4/SiO2 particles (2.2-4.3 nm) do not show superparamagnetic behavior but transit from the magnetic to the paramagnetic state by a jump-like magnetic transition of the first order This effect is a specific property of the magnetic nanoparticles isolated by inert material, and can be initiated by internal pressure creating at the particle surface. The suggested method of synthesis can be modified with various bio-ligands on the silane surface, and such materials can find many applications in diagnostics and bio-separation.

Effect of Sb on physical properties and microstructures of laser nano/amorphous-composite film

NASA Astrophysics Data System (ADS)

Li, Jia-Ning; Gong, Shui-Li; Sun, Mei; Shan, Fei-Hu; Wang, Xi-Chang; Jiang, Shuai

2013-11-01

A nano/amorphous-composite film was fabricated by laser cladding (LC) of the Co-Ti-B4C-Sb mixed powders on a TA15 alloy. Such film mainly consisted of Ti-Al, Co-Ti, Co-Sb intermetallics, TiC, TiB2, TiB, and the amorphous phases. Experimental results indicated that the crystal systems of TiB2 (hexagonal)/TiC (cubic) and Sb (rhombohedral) played important role on the formation of such film. Due to the mismatch of these crystals systems and mutual immiscibility of the metallic components, Sb was not incorporated in TiB2/TiC, but formed separate nuclei during the film growth. Thus, the growth of TiB2/TiC was stopped by the Sb nucleus in such LC molten pool, so as to form the nanoscale particles.

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

Aronhime, Natan; Zoghlin, Eli; Keylin, Vladimir

Fe-Ni based metal amorphous nanocomposites (MANCs) are investigated in the pseudo-binary alloys (Fe 100–xNi x) 80Nb 4Si 2B 14. To optimize the soft magnetic properties of the nanocomposites, primary and secondary crystallization kinetics must be understood. As such, primary and secondary crystallization temperatures are determined by differential scanning calorimetry, and activation energies are calculated, along with the resulting crystalline phases. Time-temperature-transformation diagrams for primary and secondary crystallization in (Fe 70Ni 30) 80Nb 4Si 2B 14 are presented. Saturation magnetization and Curie temperature are determined. In conclusion, the shape of magnetization vs. time curves for (Fe 30Ni 70) 80Nb 4Si 2Bmore » 14 at various temperatures suggest that the secondary crystal product often consumes some of the primary crystalline product.« less

Extremely hard amorphous-crystalline hybrid steel surface produced by deformation induced cementite amorphization

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

Guo, Wei; Meng, Yifei; Zhang, Xie

Amorphous and nanograined (NG) steels are two categories of strong steels. However, over the past decade, their application has been hindered by their limited plasticity, the addition of expensive alloying elements, and processing challenges associated with producing bulk materials. Here in this work, we report that the surface of a carburized Fe-Mn-Si martensitic steel with extremely low elemental alloying additions can be economically fabricated into an amorphous-nanocrystalline hybrid structure. Atom probe tomography and nanobeam diffraction of a hard turned steel surface together with molecular dynamics (MD) simulations reveal that the original cementite surface structure experiences a size-dependent amorphization and phasemore » transformation during heavy plastic deformation. MD simulations further show that the martensite-cementite interface serves as a nucleation site for cementite amorphization, and that cementite can become disordered if further strained when the cementite particles are relatively small. These graded structures exhibit a surface hardness of ~16.2 GPa, which exceeds the value of ~8.8 GPa for the original nanocrystalline martensitic steel and most nanocrystalline steels reported before. Finally, this practical and cost-efficient approach for producing a hard surface with retained bulk ductility and toughness can provide expanded opportunities for producing an amorphous-crystalline hybrid structure in steels and other alloy systems.« less

Extremely hard amorphous-crystalline hybrid steel surface produced by deformation induced cementite amorphization

DOE PAGES

Guo, Wei; Meng, Yifei; Zhang, Xie; ...

2018-04-11

Amorphous and nanograined (NG) steels are two categories of strong steels. However, over the past decade, their application has been hindered by their limited plasticity, the addition of expensive alloying elements, and processing challenges associated with producing bulk materials. Here in this work, we report that the surface of a carburized Fe-Mn-Si martensitic steel with extremely low elemental alloying additions can be economically fabricated into an amorphous-nanocrystalline hybrid structure. Atom probe tomography and nanobeam diffraction of a hard turned steel surface together with molecular dynamics (MD) simulations reveal that the original cementite surface structure experiences a size-dependent amorphization and phasemore » transformation during heavy plastic deformation. MD simulations further show that the martensite-cementite interface serves as a nucleation site for cementite amorphization, and that cementite can become disordered if further strained when the cementite particles are relatively small. These graded structures exhibit a surface hardness of ~16.2 GPa, which exceeds the value of ~8.8 GPa for the original nanocrystalline martensitic steel and most nanocrystalline steels reported before. Finally, this practical and cost-efficient approach for producing a hard surface with retained bulk ductility and toughness can provide expanded opportunities for producing an amorphous-crystalline hybrid structure in steels and other alloy systems.« less

Corrosion resistant metallic glasses for biosensing applications

NASA Astrophysics Data System (ADS)

Sagasti, Ariane; Lopes, Ana Catarina; Lasheras, Andoni; Palomares, Verónica; Carrizo, Javier; Gutierrez, Jon; Barandiaran, J. Manuel

2018-04-01

We report the fabrication by melt spinning, the magnetic and magnetoelastic characterization and corrosion behaviour study (by potentiodynamic methods) of an Fe-based, Fe-Ni-Cr-Si-B metallic glass to be used as resonant platform for biological and chemical detection purposes. The same study has been performed in Fe-Co-Si-B (with excellent magnetoelastic properties) and Fe-Ni-B (with good corrosion properties due to the substitution of Co by Ni) composition amorphous alloys. The well-known, commercial metallic glass with high corrosion resistance Metglas 2826MB®(Fe40Ni38Mo4B18), widely used for such biological and chemical detection purposes, has been also fully characterized and used as reference. For our Fe-Ni-Cr-Si-B alloy, we have measured values of magnetization (1.22 T), magnetostriction (11.5 ppm) and ΔE effect (6.8 %) values, as well as corrosion potential (-0.25 V), current density (2.54 A/m2), and polarization resistance (56.22 Ω.cm2) that make this composition very promising for the desired biosensing applications. The obtained parameters from our exhaustive characterization are compared with the values obtained for the other different composition metallic glasses and discussed in terms of Ni and Cr content.

Experimental Investigation on Laser Impact Welding of Fe-Based Amorphous Alloys to Crystalline Copper

PubMed Central

Wang, Xiao; Luo, Yapeng; Huang, Tao; Liu, Huixia

2017-01-01

Recently, amorphous alloys have attracted many researchers’ attention for amorphous structures and excellent properties. However, the welding of amorphous alloys to traditional metals in the microscale is not easy to realize in the process with amorphous structures unchanged, which restrains the application in industry. In this paper, a new method of welding Fe-based amorphous alloys (GB1K101) to crystalline copper by laser impact welding (LIW) is investigated. A series of experiments was conducted under different laser energies, during which Fe-based amorphous alloys and crystalline copper were welded successfully by LIW. In addition, the microstructure and mechanical properties of welding joints were observed and measured, respectively. The results showed that the surface wave and springback were observed on the flyer plate after LIW. The welding interface was straight or wavy due to different plastic deformation under different laser energies. The welding interface was directly bonded tightly without visible defects. No visible element diffusion and intermetallic phases were found in the welding interface. The Fe-based amorphous alloys retained amorphous structures after LIW under the laser energy of 835 mJ. The nanoindentation hardness across the welding interface showed an increase on both sides of the welding interface. The results of the lap shearing test showed that the fracture position was on the side of copper coil. PMID:28772886

Experimental Investigation on Laser Impact Welding of Fe-Based Amorphous Alloys to Crystalline Copper.

PubMed

Wang, Xiao; Luo, Yapeng; Huang, Tao; Liu, Huixia

2017-05-12

Recently, amorphous alloys have attracted many researchers' attention for amorphous structures and excellent properties. However, the welding of amorphous alloys to traditional metals in the microscale is not easy to realize in the process with amorphous structures unchanged, which restrains the application in industry. In this paper, a new method of welding Fe-based amorphous alloys (GB1K101) to crystalline copper by laser impact welding (LIW) is investigated. A series of experiments was conducted under different laser energies, during which Fe-based amorphous alloys and crystalline copper were welded successfully by LIW. In addition, the microstructure and mechanical properties of welding joints were observed and measured, respectively. The results showed that the surface wave and springback were observed on the flyer plate after LIW. The welding interface was straight or wavy due to different plastic deformation under different laser energies. The welding interface was directly bonded tightly without visible defects. No visible element diffusion and intermetallic phases were found in the welding interface. The Fe-based amorphous alloys retained amorphous structures after LIW under the laser energy of 835 mJ. The nanoindentation hardness across the welding interface showed an increase on both sides of the welding interface. The results of the lap shearing test showed that the fracture position was on the side of copper coil.

Immobilization of pectinase onto Fe3O4@SiO2-NH2 and its activity and stability.

PubMed

Fang, Gang; Chen, Honggao; Zhang, Yunpeng; Chen, Anqing

2016-07-01

Fe3O4 magnetic nanometer particles (MNPS) with a diameter of 30-40nm and coated by ammoniated silicon dioxides were developed by sol-gel method. The X-ray diffraction (XRD) pattern indicates that the Fe3O4 is wrapped in the amorphous SiO2, and the Fourier-transform infrared spectroscopy (FT-IR) analysis confirmed the NH2 group had been successfully introduced onto the surface of Fe3O4@SiO2 nanoparticles. The main factors related to the immobilization process of pectinase onto the magnetic support were optimized by multi-factor orthogonal experiments, and the recommended combination is that 3% glutaraldehyde (coupling agent), pH=8.0, 50°C, and cross-linking time 8h. Scanning electron microscope (SEM) and FT-IR analyses confirmed that the pectinase had been immobilized onto the surface of the amino modified nanoparticles. The storage stability and reusability of the pectinase were enhanced by the immobilization that 64.4% of the total starting activity was retrieved after 7 recycling batches and only about 21.1% of the total activity was lost after 30-day storage. For the application of the immobilized pectinase, the optimal pH and temperature were 8.5 and 55°C, respectively. Copyright © 2016 Elsevier B.V. All rights reserved.

Thermal reaction of sonochemically prepared amorphous Fe/C

NASA Astrophysics Data System (ADS)

Miyatani, R.; Kobayashi, Y.; Yamada, Y.

2017-11-01

An amorphous iron/carbon mixture was prepared by sonolysis of ferrocene in diphenylmethane. Heating of the amorphous mixture at 900 or 1200 °C produced nanoparticles, which were then analyzed using Mössbauer spectroscopy, X-ray diffraction, and transmission electron microscopy. The nanoparticles obtained after heating were spherical with diameters of about 50 nm. The sample obtained after heating at 900 °C consisted of α-Fe and Fe 3C, whereas the sample obtained after heating at 1200 °C consisted of α-Fe and γ-Fe. The reaction of the mixture during the heating process was accompanied by the formation of carbon nanotubes catalyzed by the iron or iron carbide nanoparticles.

Enhanced reduction of Fe(III) oxides and methyl orange by Klebsiella oxytoca in presence of anthraquinone-2-disulfonate.

PubMed

Yu, Lei; Wang, Shi; Tang, Qing-Wen; Cao, Ming-Yue; Li, Jia; Yuan, Kun; Wang, Ping; Li, Wen-Wei

2016-05-01

Klebsiella oxytoca GS-4-08 is capable of azo dye reduction, but its quinone respiration and Fe(III) reduction abilities have not been reported so far. In this study, the abilities of this strain were reported in detail for the first time. As the biotic reduction of Fe(III) plays an important role in the biogeochemical cycles, two amorphous Fe(III) oxides were tested as the sole electron acceptor during the anaerobic respiration of strain GS-4-08. For the reduction of goethite and hematite, the biogenic Fe(II) concentrations reached 0.06 and 0.15 mM, respectively. Humic acid analog anthraquinone-2-disulfonate (AQS) was found to serve as an electron shuttle to increase the reduction of both methyl orange (MO) and amorphous Fe(III) oxides, and improve the dye tolerance of the strain. However, the formation of Fe(II) was not accelerated by biologically reduced AQS (B-AH2QS) because of the high bioavailability of soluble Fe(III). For the K. oxytoca strain, high soluble Fe(III) concentrations (above 1 mM) limit its growth and decolorization ability, while lower soluble Fe(III) concentrations produce an electron competition with MO initially, and then stimulate the decolorization after the electron couples of Fe(III)/Fe(II) are formed. With the ability to respire both soluble Fe(III) and insoluble Fe(III) oxides, this formerly known azo-reducer may be used as a promising model organism for the study of the interaction of these potentially competing processes in contaminated environments.

Submicron R2Fe14B particles

NASA Astrophysics Data System (ADS)

Koylu-Alkan, O.; Barandiaran, J. M.; Salazar, D.; Hadjipanayis, G. C.

2016-05-01

Mechanochemical synthesis of submicron R2Fe14B particles with R = Dy, Nd, Pr has been performed successfully via high energy ball milling of rare-earth oxides, iron oxide and boron oxide in the presence of a reducing agent (Ca) and a dispersant material (CaO), followed by annealing at 800 - 900 °C. In the R = Nd system, we were able to fabricate particles embedded in a CaO matrix with coercivity (Hc) of 10.3 kOe after annealing at 900 °C for 5 min. After washing off the dispersant, the Hc was decreased to below 1 kOe because of hydrogen absorption that leads to the formation of the hydrated R2Fe14BHx phase that has a lower anisotropy. Upon removal of the hydrogen the coercivity was increased to 3.3 kOe. The average size of the Nd2Fe14B particles increases from 100 nm in a sample synthesized at 800 °C to 158 nm at 900 °C. The isotropic Dy2Fe14B particles showed a higher coercivity of 21 kOe in washed samples after annealing at 900 °C for 5 min. An average size of 71 nm is measured in samples synthesized at 800 °C and 107 nm at 900 °C. Fitting the high field M(H) measurements in Nd2Fe14B to the law of approach to saturation gave values for the magnetocrystalline anisotropy for the washed sample 2.23 × 107 erg/cm3 and for the vacuum annealed sample 4.15 × 107 erg/cm3, both of which are lower than the bulk values. This would explain the lower values of Hc observed in the particles.

Thermodynamic analysis and purifying an amorphous phase of frozen crystallization centers

NASA Astrophysics Data System (ADS)

Lysov, V. I.; Tsaregradskaya, T. L.; Turkov, O. V.; Saenko, G. V.

2017-12-01

The possibility of dissolving frozen crystallization centers in amorphous alloys of the Fe-B system is considered by means of thermodynamic calculations. This can in turn improve the thermal stability of an amorphous alloy. The effect isothermal annealing has on the thermal stability of multicomponent amorphous alloys based on iron is investigated via the highly sensitive dilatometric technique, measurements of microsolidity, and electron microscopic investigations. The annealing temperature is determined empirically on the basis of the theses of the thermodynamic theory of the high temperature stability of multicomponent amorphous alloys, according to which there exists a range of temperatures that is characterized by a negative difference between the chemical potentials of phases in a heterogeneous amorphous matrix-frozen crystallization centers system. The thermodynamic condition of the possible dissolution of frozen crystallization centers is thus met. It is shown that introducing regimes of thermal processing allows us to expand the ranges of the thermal stability of iron-based amorphous alloys by 20-40 K through purifying an amorphous matrix of frozen crystallization centers. This conclusion is proved via electron microscopic investigations.

Acid-Sulfate-Weathering Activity in Shergottite Sites on Mars Recorded in Grim Glasses

NASA Technical Reports Server (NTRS)

Rao, M. N.; Nyquist, L. E.; Ross, K.; Sutton, S. R.; Schwandt, C. S.

2011-01-01

Based on mass spectrometric studies of sulfur species in Shergotty and EET79001, [1] and [2] showed that sulfates and sulfides occur in different proportions in shergottites. Sulfur speciation studies in gas-rich impact-melt (GRIM) glasses in EET79001 by the XANES method [3] showed that S K-XANES spectra in GRIM glasses from Lith A indicate that S is associated with Ca and Al presumably as sulfides/sulfates whereas the XANES spectra of amorphous sulfide globules in GRIM glasses from Lith B indicate that S is associated with Fe as FeS. In these amorphous iron sulfide globules, [4] found no Ni using FE-SEM and suggested that the globules resulting from immiscible sulfide melt may not be related to the igneous iron sulfides having approximately 1-3% Ni. Furthermore, in the amorphous iron sulfides from 507 GRIM glass, [5] determined delta(sup 34)S values ranging from +3.5%o to -3.1%o using Nano-SIMS. These values plot between the delta(sup 34)S value of +5.25%o determined in the sulfate fraction in Shergotty [6] at one extreme and the value of -1.7%o obtained for igneous sulfides in EET79001 and Shergotty [7] at the other. These results suggest that the amorphous Fe-S globules likely originated by shock reduction of secondary iron sulfate phases occurring in the regolith precursor materials during impact [7]. Sulfates in the regolith materials near the basaltic shergottite sites on Mars owe their origin to surficial acid-sulfate interactions. We examine the nature of these reactions by studying the composition of the end products in altered regolith materials. For the parent material composition, we use that of the host shergottite material in which the impact glasses are situated.

Fly ash particles spheroidization using low temperature plasma energy

NASA Astrophysics Data System (ADS)

Shekhovtsov, V. V.; Volokitin, O. G.; Kondratyuk, A. A.; Vitske, R. E.

2016-11-01

The paper presents the investigations on producing spherical particles 65-110 μm in size using the energy of low temperature plasma (LTP). These particles are based on flow ash produced by the thermal power plant in Seversk, Tomsk region, Russia. The obtained spherical particles have no defects and are characterized by a smooth exterior surface. The test bench is designed to produce these particles. With due regard for plasma temperature field distribution, it is shown that the transition of fly ash particles to a state of viscous flow occurs at 20 mm distance from the plasma jet. The X-ray phase analysis is carried out for the both original state of fly ash powders and the particles obtained. This analysis shows that fly ash contains 56.23 wt.% SiO2; 20.61 wt.% Al2O3 and 17.55 wt.% Fe2O3 phases that mostly contribute to the integral (experimental) intensity of the diffraction maximum. The LTP treatment results in a complex redistribution of the amorphous phase amount in the obtained spherical particles, including the reduction of O2Si, phase, increase of O22Al20 and Fe2O3 phases and change in Al, O density of O22Al20 chemical unit cell.

Demonstration of thin film pair distribution function analysis (tfPDF) for the study of local structure in amorphous and crystalline thin films

DOE PAGES

Jensen, K. M.Ø.; Blichfeld, A. B.; Bauers, S. R.; ...

2015-07-05

By means of normal incidence, high flux and high energy x-rays, we have obtained total scattering data for Pair Distribution Function (PDF) analysis from thin films (tf), suitable for local structure analysis. By using amorphous substrates as support for the films, the standard Rapid Acquisition PDF setup can be applied and the scattering signal from the film can be isolated from the total scattering data through subtraction of an independently measured background signal. No angular corrections to the data are needed, as would be the case for grazing incidence measurements. We illustrate the ‘tfPDF’ method through studies of as depositedmore » (i.e. amorphous) and crystalline FeSb 3 films, where the local structure analysis gives insight into the stabilization of the metastable skutterudite FeSb 3 phase. The films were prepared by depositing ultra-thin alternating layers of Fe and Sb, which interdiffuse and after annealing crystallize to form the FeSb 3 structure. The tfPDF data show that the amorphous precursor phase consists of corner-sharing FeSb 6 octahedra with motifs highly resembling the local structure in crystalline FeSb 3. Analysis of the amorphous structure allows predicting whether the final crystalline product will form the FeSb 3 phase with or without excess Sb present. The study thus illustrates how analysis of the local structure in amorphous precursor films can help to understand crystallization processes of metastable phases and opens for a range of new local structure studies of thin films.« less

Demonstration of thin film pair distribution function analysis (tfPDF) for the study of local structure in amorphous and crystalline thin films

PubMed Central

Jensen, Kirsten M. Ø.; Blichfeld, Anders B.; Bauers, Sage R.; Wood, Suzannah R.; Dooryhée, Eric; Johnson, David C.; Iversen, Bo B.; Billinge, Simon J. L.

2015-01-01

By means of normal-incidence, high-flux and high-energy X-rays, total scattering data for pair distribution function (PDF) analysis have been obtained from thin films (tf), suitable for local structure analysis. By using amorphous substrates as support for the films, the standard Rapid Acquisition PDF setup can be applied and the scattering signal from the film can be isolated from the total scattering data through subtraction of an independently measured background signal. No angular corrections to the data are needed, as would be the case for grazing incidence measurements. The ‘tfPDF’ method is illustrated through studies of as-deposited (i.e. amorphous) and crystalline FeSb3 films, where the local structure analysis gives insight into the stabilization of the metastable skutterudite FeSb3 phase. The films were prepared by depositing ultra-thin alternating layers of Fe and Sb, which interdiffuse and after annealing crystallize to form the FeSb3 structure. The tfPDF data show that the amorphous precursor phase consists of corner-sharing FeSb6 octahedra with motifs highly resembling the local structure in crystalline FeSb3. Analysis of the amorphous structure allows the prediction of whether the final crystalline product will form the FeSb3 phase with or without excess Sb present. The study thus illustrates how analysis of the local structure in amorphous precursor films can help to understand crystallization processes of metastable phases and opens for a range of new local structure studies of thin films. PMID:26306190

Nanosized amorphous (Co‚ Fe) oxide particles decorated PANI-CNT: facile synthesis‚ characterization‚ magnetic‚ electromagnetic properties and their application

NASA Astrophysics Data System (ADS)

Heydari, Farhood; Afghahi, Seyyed Salman Seyyed; Manteghian, Mehrdad; Taghizadeh, Mohammad Javad

2017-11-01

In this research (PANI/CNT) core/shell nanocomposite were synthesized via in situ chemical oxidative seeding polymerization‚ the results of SEM indicated the structure of synthesized nanocomposite. TEM‚ FTIR‚ UV-Vis‚ XRD analyses of samples showed that this nanocomposite is decorated with (Fe‚ Co) oxide nanoparticles. The VSM test of as prepared and annealed nanocomposite exhibited the saturated magnetization of 1.1 and 3.86 emu/g, respectively; the coercivity values were also - 350 and - 110 Oe, respectively. The reflection loss characteristics of (Fe‚ Co) oxide-Pani-CNT core/shell nanocomposite were also investigated with a vector network analyzer‚ in the 8.2-12.4 GHz range (X band). The maximum absorption increases with enhancement of the dispersed nanoparticles percent in polyurethane matrix from 1 to 10%. The value of the maximum reflection loss in the absorption samples with 1 and 10% of nanoparticles is - 2.14 dB at 9.33 GHz and - 7.32 dB at 11.97 GHZ, respectively.

The magnetic properties of a magnetic detector using oxidized amorphous Co 95- xFe 5(BSi) x alloys

NASA Astrophysics Data System (ADS)

Ahn, S. J.; Kim, C. K.; Kim, S. J.; Choi, D. K.; O'Handley, R. C.

2000-07-01

A comparative oxidation study of several amorphous Co 75- xFe 5(BSi) 20+ x alloys was carried out. Reentrant magnetization behavior and field-induced anisotropy which are of a critical importance for a magnetic detector were obtained after oxidation of the amorphous Co-rich ribbons. During this oxidation, the ribbons develop surface oxides which are primarily nonmagnetic borosilicate or a combination of borosilicate and magnetic oxides such CoO or FeO. Beneath this lies a 100-1000 Å thick Co-rich magnetic alloy which may be either HCP or FCC in its crystal structure. The thickness of the Co-crystallized layer is determined by the type of the surface oxides. The oxidation products such as appear to affect the reentrant magnetization behavior of Co-rich amorphous alloys significantly. We have determined the amount of metalloids (a critical concentration of B and Si) which is necessary to form a continuous layer of the most thermodynamically stable oxide, in our case borosilicate, on the surface. We also observed that there is a good correlation between reentrant magnetization and the thickness of Co layer. The best reentrant M- H loop for the magnetic detector was obtained in ribbons with a surface borate-rich borosilicate since it ensures conditions such as (1) metalloid depletion in the substrate and (2) formation of oxygen impurity faults in Co grains that are required for strong reentrant magnetization behavior.

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

Hu Qiang; Zeng Xierong; Shenzhen Key Laboratory of Special Functional Materials, Shenzhen 518060

This paper reports the observation of the clear Invar effects of (Fe{sub 71.2}B{sub 24}Y{sub 4.8}){sub 96}Nb{sub 4} bulk metallic glass. The Invar effects of (Fe{sub 71.2}B{sub 24}Y{sub 4.8}){sub 96}Nb{sub 4} alloys in different structural states are also investigated in situ through cyclic thermal dilation tests at different cyclic temperatures. The results show that these Invar effects are strengthened in the relaxation amorphous state, weakened in the nanocrystalline state, and absent in the complete crystalline state. X-ray diffraction and Moessbauer spectroscopy demonstrate that the structural influences on Invar effects can be explained by the different local atomic arrangements around Fe atomsmore » in different structural states.« less

A new nanospray drying method for the preparation of nicergoline pure nanoparticles

NASA Astrophysics Data System (ADS)

Martena, Valentina; Censi, Roberta; Hoti, Ela; Malaj, Ledjan; Di Martino, Piera

2012-06-01

Three different batches of pure nanoparticles (NPs) of nicergoline (NIC) were prepared by spray drying a water:ethanol solution by a new Nano Spray Dryer Büchi B-90. Spherical pure NPs were obtained, and several analytical techniques such as differential scanning calorimetry and X-ray powder diffractometry permitted to assess their amorphous character. A comparison of the solubility, intrinsic dissolution, and drug release of original particles and pure amorphous NPs were determined, revealing an interesting improvement of biopharmaceutical properties of amorphous NPs, due to both amorphous properties and nanosize dimensions. Since in a previous work, the high-thermodynamic stability of amorphous NIC was demonstrated, this study is addressed toward the formulation of NIC as pure amorphous NPs.

Solid state amorphization in the Al-Fe binary system during high energy milling

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

Urban, P., E-mail: purban@us.es; Montes, J. M.; Cintas, J.

2013-12-16

In the present study, mechanical alloying (MA) of Al75Fe25 elemental powders mixture was carried out in argon atmosphere, using a high energy attritor ball mill. The microstructure of the milled products at different stages of milling was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The results showed that the amorphous phase content increased by increasing the milling time, and after 50 hours the amorphization process became complete. Heating the samples resulted in the crystallization of the synthesized amorphous alloys and the appearance of the equilibrium intermetallic compounds Al{sub 5}Fe{submore » 2}.« less

Direct-write 3D printing of NdFeB bonded magnets

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

Compton, Brett Gibson; Kemp, James William; Novikov, Timofei V.

We report a method to fabricate Nd-Fe-B bonded magnets of complex shape via extrusion-based additive manufacturing (AM), also known as 3D-printing. We have successfully formulated a 3D-printable epoxy-based ink for direct-write AM with anisotropic MQA NdFeB magnet particles that can be deposited at room temperature. The new feedstocks contain up to 40 vol.% MQA anisotropic Nd-Fe-B magnet particles, and they are shown to remain uniformly dispersed in the thermoset matrix throughout the deposition process. Ring, bar, and horseshoe-type 3D magnet structures were printed and cured in air at 100°C without degrading the magnetic properties. Lastly, this study provides a newmore » pathway for fabricating Nd-Fe-B bonded magnets with complex geometry at low temperature, and presents new opportunities for fabricating multifunctional hybrid structures and devices.« less

Direct-write 3D printing of NdFeB bonded magnets

DOE PAGES

Compton, Brett Gibson; Kemp, James William; Novikov, Timofei V.; ...

2016-08-17

We report a method to fabricate Nd-Fe-B bonded magnets of complex shape via extrusion-based additive manufacturing (AM), also known as 3D-printing. We have successfully formulated a 3D-printable epoxy-based ink for direct-write AM with anisotropic MQA NdFeB magnet particles that can be deposited at room temperature. The new feedstocks contain up to 40 vol.% MQA anisotropic Nd-Fe-B magnet particles, and they are shown to remain uniformly dispersed in the thermoset matrix throughout the deposition process. Ring, bar, and horseshoe-type 3D magnet structures were printed and cured in air at 100°C without degrading the magnetic properties. Lastly, this study provides a newmore » pathway for fabricating Nd-Fe-B bonded magnets with complex geometry at low temperature, and presents new opportunities for fabricating multifunctional hybrid structures and devices.« less

Adjusting the catalytic properties of cobalt ferrite nanoparticles by pulsed laser fragmentation in water with defined energy dose.

PubMed

Waag, Friedrich; Gökce, Bilal; Kalapu, Chakrapani; Bendt, Georg; Salamon, Soma; Landers, Joachim; Hagemann, Ulrich; Heidelmann, Markus; Schulz, Stephan; Wende, Heiko; Hartmann, Nils; Behrens, Malte; Barcikowski, Stephan

2017-10-13

Highly active, structurally disordered CoFe 2 O 4 /CoO electrocatalysts are synthesized by pulsed laser fragmentation in liquid (PLFL) of a commercial CoFe 2 O 4 powder dispersed in water. A partial transformation of the CoFe 2 O 4 educt to CoO is observed and proposed to be a thermal decomposition process induced by the picosecond pulsed laser irradiation. The overpotential in the OER in aqueous alkaline media at 10 mA cm -2 is reduced by 23% compared to the educt down to 0.32 V with a Tafel slope of 71 mV dec -1 . Importantly, the catalytic activity is systematically adjustable by the number of PLFL treatment cycles. The occurrence of thermal melting and decomposition during one PLFL cycle is verified by modelling the laser beam energy distribution within the irradiated colloid volume and comparing the by single particles absorbed part to threshold energies. Thermal decomposition leads to a massive reduction in particle size and crystal transformations towards crystalline CoO and amorphous CoFe 2 O 4 . Subsequently, thermal melting forms multi-phase spherical and network-like particles. Additionally, Fe-based layered double hydroxides at higher process cycle repetitions emerge as a byproduct. The results show that PLFL is a promising method that allows modification of the structural order in oxides and thus access to catalytically interesting materials.

Synthesis and in vitro cellular interactions of superparamagnetic iron nanoparticles with a crystalline gold shell

NASA Astrophysics Data System (ADS)

Bandyopadhyay, Sulalit; Singh, Gurvinder; Sandvig, Ioanna; Sandvig, Axel; Mathieu, Roland; Anil Kumar, P.; Glomm, Wilhelm Robert

2014-10-01

Fe@Au core-shell nanoparticles (NPs) exhibit multiple functionalities enabling their effective use in applications such as medical imaging and drug delivery. In this work, a novel synthetic method was developed and optimized for the synthesis of highly stable, monodisperse Fe@Au NPs of average diameter ∼24 nm exhibiting magneto-plasmonic characteristics. Fe@Au NPs were characterized by a wide range of experimental techniques, including scanning (transmission) electron microscopy (S(T)EM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), dynamic light scattering (DLS) and UV-vis spectroscopy. The formed particles comprise an amorphous iron core with a crystalline Au shell of tunable thickness, and retain the superparamagnetic properties at room temperature after formation of a crystalline Au shell. After surface modification, PEGylated Fe@Au NPs were used for in vitro studies on olfactory ensheathing cells (OECs) and human neural stem cells (hNSCs). No adverse effects of the Fe@Au particles were observed post-labeling, both cell types retaining normal morphology, viability, proliferation, and motility. It can be concluded that no appreciable toxic effects on both cell types, coupled with multifunctionality and chemical stability make them ideal candidates for therapeutic as well as diagnostic applications.

Milling induced amorphisation and recrystallization of α-lactose monohydrate.

PubMed

Badal Tejedor, Maria; Pazesh, Samaneh; Nordgren, Niklas; Schuleit, Michael; Rutland, Mark W; Alderborn, Göran; Millqvist-Fureby, Anna

2018-02-15

Preprocessing of pharmaceutical powders is a common procedure to condition the materials for a better manufacturing performance. However, such operations may induce undesired material properties modifications when conditioning particle size through milling, for example. Modification of both surface and bulk material structure will change the material properties, thus affecting the processability of the powder. Hence it is essential to control the material transformations that occur during milling. Topographical and mechanical changes in surface properties can be a preliminary indication of further material transformations. Therefore a surface evaluation of the α-lactose monohydrate after short and prolonged milling times has been performed. Unprocessed α-lactose monohydrate and spray dried lactose were evaluated in parallel to the milled samples as reference examples of the crystalline and amorphous lactose structure. Morphological differences between unprocessed α-lactose, 1 h and 20 h milled lactose and spray dried lactose were detected from SEM and AFM images. Additionally, AFM was used to simultaneously characterize particle surface amorphicity by measuring energy dissipation. Extensive surface amorphicity was detected after 1 h of milling while prolonged milling times showed only a moderate particle surface amorphisation. Bulk material characterization performed with DSC indicated a partial amorphicity for the 1 h milled lactose and a fully amorphous thermal profile for the 20 h milled lactose. The temperature profiles however, were shifted somewhat in the comparison to the amorphous reference, particularly after extended milling, suggesting a different amorphous state compared to the spray-dried material. Water loss during milling was measured with TGA, showing lower water content for the lactose amorphized through milling compared to spray dried amorphous lactose. The combined results suggest a surface-bulk propagation of the amorphicity during milling in combination with a different amorphous structural conformation to that of the amorphous spray dried lactose. The hardened surface may be due to either surface crystallization of lactose or to formation of a low-water glass transition. Copyright © 2017 Elsevier B.V. All rights reserved.

Microstructural Evolution during the Dynamic Deformation of High Strength Navy Steels

DTIC Science & Technology

2008-05-19

phase particles (Figures 23d,e). These include carbides as well as copper precipitates that are of the order of 10 nm or less in size. These particles ...Microstructure and kinetics of martensite transformations in splat-quenched Fe and Fe-Ni alloys - I pure Fe: Acta Metallurgica 30(1982)323. 22. Y. Inokuti...and B. Cantor, Microstructure and kinetics of martensite transformations in splat-quenched Fe and Fe-Ni alloys - II Fe-Ni alloys : Acta

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.

Passivation Behavior of Fe-Based Amorphous Coatings Prepared by High-Velocity Air/Oxygen Fuel Processes

NASA Astrophysics Data System (ADS)

Ma, H. R.; Li, J. W.; Chang, C. T.; Wang, X. M.; Li, R. W.

2017-12-01

Corrosion resistance and passivation behavior of Fe63Cr8Mo3.5Ni5P10B4C4Si2.5 amorphous coatings prepared by the activated combustion high-velocity air fuel (AC-HVAF) and high-velocity oxygen fuel (HVOF) processes have been studied in detail by cyclic potentiodynamic polarization, electrochemical impedance spectroscopy, cathodic polarization and Mott-Schottky approach. The AC-HVAF coating shows higher corrosion resistance than the HVOF coating in 3.5 wt.% NaCl solution, as evidenced by its lower corrosion current density and passive current density. It is found that the superior corrosion resistance of the AC-HVAF coating is attributed to the enhanced formation of a dense passive film with less defective structure, higher pitting resistance and passivity stability, as well as stronger repassivity.

Ultrasonic assisted production of starch nanoparticles: Structural characterization and mechanism of disintegration.

PubMed

Boufi, Sami; Bel Haaj, Sihem; Magnin, Albert; Pignon, Frédéric; Impéror-Clerc, Marianne; Mortha, Gérard

2018-03-01

In this paper, the disintegration of starch (waxy and standard starch) granules into nanosized particles under the sole effect of high power ultrasonication treatment in water/isopropanol is investigated, by using wide methods of analysis. The present work aims at a fully characterization of the starch nanoparticles produced by ultrasonication, in terms of size, morphology and structural properties, and the proposition of a possible mechanism explaining the top-down generation of starch nanoparticles (SNPs) via high intensity ultrasonication. Dynamic light scattering measurements have indicated a leveling of the particle size to about 40nm after 75min of ultrasonication. The WAXD, DSC and Raman have revealed the amorphous character of the SNPs. FE-SEM. AFM observations have confirmed the size measured by DLS and suggested that SNPs exhibited 2D morphology of platelet-like shapes. This morphology is further supported by SAXS. On the basis of data collected from the different characterization techniques, a possible mechanism explaining the disintegration process of starch granules into NPs is proposed. Copyright © 2017 Elsevier B.V. All rights reserved.

Mossbauer spectroscopic studies in ferroboron

NASA Astrophysics Data System (ADS)

Yadav, Ravi Kumar; Govindaraj, R.; Amarendra, G.

2017-05-01

Mossbauer spectroscopic studies have been carried out in a detailed manner on ferroboron in order to understand the local structure and magnetic properties of the system. Evolution of the local structure and magnetic properties of the amorphous and crystalline phases and their thermal stability have been addressed in a detailed manner in this study. Role of bonding between Fe 4s and/or 4p electrons with valence electrons of boron (2s,2p) in influencing the stability and magnetic properties of Fe-B system is elucidated.

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

Determination of local order in the amorphous precursor to Ba-hexaferrite thin-film recording media

NASA Astrophysics Data System (ADS)

Snyder, J. E.; Harris, V. G.; Das, B. N.; Koon, N. C.; Sui, X.; Kryder, M. H.

1996-04-01

Ba-hexaferrite thin films for recording media applications are often fabricated by a two-step process: sputter deposition of an amorphous precursor, followed by annealing to crystallize the BaFe12O19 phase. The magnetic anisotropy of the crystalline films can be either in-plane or perpendicular, depending on the sputtering process used in the first step. However, conventional structural characterization techniques have not been able to distinguish between different as-sputtered films. Using polarization-dependent extended x-ray absorption fine structure (PD-EXAFS), we have observed anisotropic local structure around both Ba and Fe atoms in the amorphous precursor films. Comparison of the results suggests that the amorphous films consist of networks of Fe atoms surrounded by their O nearest neighbors, with Ba atoms fitting into in-between spaces as network modifiers (there might also be some minor Fe network modifying contribution). The local structural anisotropy of the amorphous films appears to determine the orientation of the fast-growing basal plane directions during annealing, and thus the directions of the c axes and the magnetic anisotropy.

The effect of milling time and sintering temperature on Mn, Ti substituted barium hexaferrite nanoparticle

NASA Astrophysics Data System (ADS)

Yustanti, Erlina; Manaf, Azwar

2018-04-01

Barium hexaferrite (BaO.6Fe2O3/BaFe12O19) is a permanent magnetic material and microwave absorbing material. The value of microwave absorption can be increased through the engineering of the material structure, while the reduction of crystallite and particle size up to nanometer results device performance improvement to be superior. In this research, the structural engineering through mechanical alloying and crystallite size reduction through high power ultrasonic irradiation will be explained. Mixing and alloying of Sigma Aldrich BaCO3, Fe2O3, MnCO3, TiO2 p.a 99% precursor material used ball mill with powder ratio of vial at 1:10. Mechanical alloying for 60 hours at 160 rpm produced amorphous material. The process of the crystalline embryo nucleation for 4 hours produced multicrystalline material at a sinter temperature of 1100°C. Phase analysis of the mechanical alloying result using x-ray diffractometer was confirmed either the formation of BaO.6Fe2-xMnx/2Tix/2O3 (x=0.5) single phase. Multicrystalline powder of BaO.6Fe2-xMnx/2Tix/2O3 (x=0.5) was obtained through 20 hours hand grinding and re-milling to bulk sample. Crystallite size reduction in the analysis was conducted through particle density variation in ultrasonic reactor and variation of the increase in ultrasonic time. Increase in milling time up to 60 hours produced fragmenting so that particle size reduction from 18.8 µm to 0.9 µm was occurred. The 12-h ultrasonic irradiation at a frequency of 20 kHz amplitude of 60 µm produced a crystallite-size reduction up to 18 nm at a 10 g/L particle density.

Mineralogical Characterization of Fe-Bearing AGB and Supernova Silicate Grains From the Queen Alexandra Range 99177 Meteorite

NASA Technical Reports Server (NTRS)

Nguyen, A. N.; Keller, L. P.; Messenger, S.; Rahman, Z.

2017-01-01

Spectroscopic observations of the circumstellar envelopes of evolved O-rich stars indicate the dust is mostly amorphous silicate with olivine-like compositions. Spectral modeling suggests these grains are Fe-rich [Mg/(Mg+Fe) 0.5], but it is not known whether the Fe is distributed within the silicate matrix or exists as metal inclusions. In contrast, the crystalline silicates are inferred to be extremely Mg-rich [Mg/(Mg+Fe) > 0.95]. The mineralogies and chemical compositions of dust in supernova (SN) remnants are not as well constrained, but abundant silicates of olivine-like and enstatite-like compositions have been fit to the infrared emission features. Silicates in the interstellar medium (ISM) are >99% amor-phous and Fe-bearing. The dearth of crystalline silicates in the ISM requires that some amorphization or destruction mechanisms process these grains.

Magnetic softening and nanocrystallization in amorphous Co-rich alloys

NASA Astrophysics Data System (ADS)

Buttino, G.; Cecchetti, A.; Poppi, M.

1997-02-01

In this work we have analyzed the changes of the magnetic properties in the Co-based Metglas 2714A (made by Allied Chem. Corp., USA) caused by isothermal heat treatments in the range of temperature from room temperature to conventional crystallization temperature Tcr = 550°C. The nominal composition of the amorphous alloy is Co 66Fe 4Ni 1B 14Si 15. The analysis is made on toroidal samples prepared by winding lengths of amorphous ribbon of about 20 cm. The magnetic properties undergo variations depending on the treatment temperature, except for the saturation magnetization which remains unchanged. For heat treatments of about half an hour around 500°C, superior soft magnetic properties are obtained. Particularly, the initial permeability reaches values up to ten times the value of permeability in the as-received sample. Analysis by the transmission electron microscopy of the sample annealed around 500°C reveals the formation of a nanocrystalline phase, with average grain size of 2 nm, embedded in a residual amorphous matrix. The occurrence of permeability increases in concomitance with the formation of the nanocrystalline phase is ascribed to a drastic reduction in the local magnetocrystalline anisotropy randomly averaged out by the exchange interactions, similar to the case of the annealed Fe-based alloys containing Cu.

Tunneling-Magnetoresistance Ratio Comparison of MgO-Based Perpendicular-Magnetic-Tunneling-Junction Spin Valve Between Top and Bottom Co2Fe6B2 Free Layer Structure.

PubMed

Lee, Du-Yeong; Lee, Seung-Eun; Shim, Tae-Hun; Park, Jea-Gun

2016-12-01

For the perpendicular-magnetic-tunneling-junction (p-MTJ) spin valve with a nanoscale-thick bottom Co2Fe6B2 free layer ex situ annealed at 400 °C, which has been used as a common p-MTJ structure, the Pt atoms of the Pt buffer layer diffused into the MgO tunneling barrier. This transformed the MgO tunneling barrier from a body-centered cubic (b.c.c) crystallized layer into a mixture of b.c.c, face-centered cubic, and amorphous layers and rapidly decreased the tunneling-magnetoresistance (TMR) ratio. The p-MTJ spin valve with a nanoscale-thick top Co2Fe6B2 free layer could prevent the Pt atoms diffusing into the MgO tunneling barrier during ex situ annealing at 400 °C because of non-necessity of a Pt buffer layer, demonstrating the TMR ratio of ~143 %.

Physical and biological studies of coal and oil fly ash.

PubMed Central

Fisher, G L; McNeill, K L; Prentice, B A; McFarland, A R

1983-01-01

Studies were performed to compare the physical and chemical characteristics and the in vitro macrophage cytotoxicity of oil and coal fly ash. Sampling methodology was developed to collect size-fractionated particulate matter from the smokestack of either a coal-fired or an oil-fired power plant. Morphological studies demonstrated particle heterogeneity, although most coal fly ash particles appeared to be spherical. Oil fly ash contained two major morphologies; nonopaque amorphous particles and opaque amorphous particles. Elemental analysis indicates that the coal ash is predominantly composed of aluminosilicate particles, while the oil ash is predominantly inorganic sulfates and carbonaceous particles. In vitro macrophage assays demonstrate that the finest coal fly ash particles are the most cytotoxic; the cytotoxicity is significantly less than that of alpha-quartz, the positive control particle. In contrast, the oil fly ash particles are more cytotoxic than quartz. The cytotoxicity of oil fly ash is due to soluble components, possibly vanadium salts. Images FIGURE 2. A FIGURE 2. B FIGURE 2. C FIGURE 2. D PMID:6641653

Amorphous salts formed from rapid dehydration of multicomponent chloride and ferric sulfate brines: Implications for Mars.

PubMed

Sklute, Elizabeth C; Rogers, A Deanne; Gregerson, Jason C; Jensen, Heidi B; Reeder, Richard J; Dyar, M Darby

2018-03-01

Salts with high hydration states have the potential to maintain high levels of relative humidity (RH) in the near subsurface of Mars, even at moderate temperatures. These conditions could promote deliquescence of lower hydrates of ferric sulfate, chlorides, and other salts. Previous work on deliquesced ferric sulfates has shown that when these materials undergo rapid dehydration, such as that which would occur upon exposure to present day Martian surface conditions, an amorphous phase forms. However, the fate of deliquesced halides or mixed ferric sulfate-bearing brines are presently unknown. Here we present results of rapid dehydration experiments on Ca-, Na-, Mg- and Fe-chloride brines and multi-component (Fe 2 (SO 4 ) 3 ± Ca, Na, Mg, Fe, Cl, HCO 3 ) brines at ∼21°C, and characterize the dehydration products using visible/near-infrared (VNIR) reflectance spectroscopy, mid-infrared attenuated total reflectance spectroscopy, and X-ray diffraction (XRD) analysis. We find that rapid dehydration of many multicomponent brines can form amorphous solids or solids with an amorphous component, and that the presence of other elements affects the persistence of the amorphous phase under RH fluctuations. Of the pure chloride brines, only Fe-chloride formed an amorphous solid. XRD patterns of the multicomponent amorphous salts show changes in position, shape, and magnitude of the characteristic diffuse scattering observed in all amorphous materials that could be used to help constrain the composition of the amorphous salt. Amorphous salts deliquesce at lower RH values compared to their crystalline counterparts, opening up the possibility of their role in potential deliquescence-related geologic phenomena such as recurring slope lineae (RSLs) or soil induration. This work suggests that a wide range of aqueous mixed salt solutions can lead to the formation of amorphous salts and are possible for Mars; detailed studies of the formation mechanisms, stability and transformation behaviors of amorphous salts are necessary to further constrain their contribution to Martian surface materials.

Amorphous salts formed from rapid dehydration of multicomponent chloride and ferric sulfate brines: Implications for Mars

NASA Astrophysics Data System (ADS)

Sklute, Elizabeth C.; Rogers, A. Deanne; Gregerson, Jason C.; Jensen, Heidi B.; Reeder, Richard J.; Dyar, M. Darby

2018-03-01

Salts with high hydration states have the potential to maintain high levels of relative humidity (RH) in the near subsurface of Mars, even at moderate temperatures. These conditions could promote deliquescence of lower hydrates of ferric sulfate, chlorides, and other salts. Previous work on deliquesced ferric sulfates has shown that when these materials undergo rapid dehydration, such as that which would occur upon exposure to present day Martian surface conditions, an amorphous phase forms. However, the fate of deliquesced halides or mixed ferric sulfate-bearing brines are presently unknown. Here we present results of rapid dehydration experiments on Ca-, Na-, Mg- and Fe-chloride brines and multicomponent (Fe2(SO4)3 ± Ca, Na, Mg, Fe, Cl, HCO3) brines at ∼21 °C, and characterize the dehydration products using visible/near-infrared (VNIR) reflectance spectroscopy, mid-infrared attenuated total reflectance spectroscopy, and X-ray diffraction (XRD) analysis. We find that rapid dehydration of many multicomponent brines can form amorphous solids or solids with an amorphous component, and that the presence of other elements affects the persistence of the amorphous phase under RH fluctuations. Of the pure chloride brines, only Fe-chloride formed an amorphous solid. XRD patterns of the multicomponent amorphous salts show changes in position, shape, and magnitude of the characteristic diffuse scattering observed in all amorphous materials that could be used to help constrain the composition of the amorphous salt. Amorphous salts deliquesce at lower RH values compared to their crystalline counterparts, opening up the possibility of their role in potential deliquescence-related geologic phenomena such as recurring slope lineae (RSLs) or soil induration. This work suggests that a wide range of aqueous mixed salt solutions can lead to the formation of amorphous salts and are possible for Mars; detailed studies of the formation mechanisms, stability and transformation behaviors of amorphous salts are necessary to further constrain their contribution to Martian surface materials.

Bending stresses and bistable behavior in Fe-rich amorphous wire

NASA Astrophysics Data System (ADS)

Vázquez, M.; Gómez Polo, C.; Velázquez, J.; Hernando, A.

1994-05-01

The aim of this work is to analyze for the first time the changes in magnetic properties of an Fe-rich amorphous wire (Fe77.5Si7.5B15) when it is submitted to bending stresses. Upon a reduction of the radius of curvature, Rc, of the wire (i.e., increasing bending stresses), the main changes in the magnetic properties are summarized as follows: (a) Bistable behavior disappears when reducing Rc below about 11 cm but it is again observed for Rc less than about 2.5 cm. This latter effect is also obtained for short wires (less than around 7 cm) which do not show spontaneous bistability. (b) For the case when bending stresses make bistability disappear, the susceptibility increases more than one order of magnitude with regards to the case of bistable wire, and parallel to the increase of susceptibility, a reduction of remanent magnetization is observed. The disappearance and later occurrence of the bistable behavior with increasing bending stresses are discussed in terms of the tensile and compressive stresses induced when the sample is bent. The possibility of having bistable wires with toroidal symmetry is also discussed owing to its interest for particular applications as pulse generators with reduced size and magnetic switches.

Effect of annealing under tensile loading on the structure of nanocrystals in the Finemet alloy

NASA Astrophysics Data System (ADS)

Ershov, N. V.; Chernenkov, Yu. P.; Fedorov, V. I.; Lukshina, V. A.; Potapov, A. P.

2014-11-01

The effect of nanocrystallization annealing under tensile loading on the structure of nanocrystals in the soft magnetic alloy Fe-Si-Nb-B-Cu (Finemet) has been investigated. It has been shown that the body-centered cubic (bcc) lattice of α-FeSi nanocrystals is extended along the direction of the application of the load upon annealing and is compressed in the transverse direction. Nanocrystals in the Finemet alloy have a higher degree of anisotropy of mechanical properties as compared to bulk crystals of α-FeSi, so that agreement between the measured and calculated values of the elongation is achieved only with a significant increase in the elastic moduli. Substantial changes in mechanical properties of the crystals with a decrease in their size to the nanometer scale are caused by the influence of the rigid amorphous matrix of the Fe(Nb)-B phase surrounding the nanocrystals.

Approach to magnetic neutron capture therapy

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

Kuznetsov, Anatoly A.; Podoynitsyn, Sergey N.; Filippov, Victor I.

2005-11-01

Purpose: The method of magnetic neutron capture therapy can be described as a combination of two methods: magnetic localization of drugs using magnetically targeted carriers and neutron capture therapy itself. Methods and Materials: In this work, we produced and tested two types of particles for such therapy. Composite ultradispersed ferro-carbon (Fe-C) and iron-boron (Fe-B) particles were formed from vapors of respective materials. Results: Two-component ultradispersed particles, containing Fe and C, were tested as magnetic adsorbent of L-boronophenylalanine and borax and were shown that borax sorption could be effective for creation of high concentration of boron atoms in the area ofmore » tumor. Kinetics of boron release into the physiologic solution demonstrate that ultradispersed Fe-B (10%) could be applied for an effective magnetic neutron capture therapy. Conclusion: Both types of the particles have high magnetization and magnetic homogeneity, allow to form stable magnetic suspensions, and have low toxicity.« less

Nanocrystalline Fe/Zr alloys: preparation by using mechanical alloying and mechanical milling processes

NASA Astrophysics Data System (ADS)

Rodríguez, V. A. Peña; Medina, J. Medina; Marcatoma, J. Quispe; Ayala, Ch. Rojas; Landauro, C. V.; Baggio-Saitovitch, E. M.; Passamani, E. C.

2011-11-01

Nanocrystalline Fe/Zr alloys have been prepared after milling for 9 h the mixture of elemental Fe and Zr powders or the arc-melting produced Fe2Zr alloy by using mechanical alloying and mechanical milling techniques, respectively. X-ray and Mössbauer results of the Fe and Zr powders, mechanically alloyed, suggest that amorphous Fe2Zr phase and \\upalpha-Fe(Zr) nanograins have been produced with relative concentrations of 91% and 9%, respectively. Conversely, the results of the mechanically milled Fe2Zr alloy indicate that nanograins of the Fe2Zr alloy have been formed, surrounded by a magnetic inter-granular phase that are simultaneously dispersed in a paramagnetic amorphous phase.

Grain boundary diffusion behaviors in hot-deformed Nd2Fe14B magnets by PrNd-Cu low eutectic alloys

NASA Astrophysics Data System (ADS)

Tang, Xu; Chen, Renjie; Li, Ming; Jin, Chaoxiang; Yin, Wenzong; Lee, Don; Yan, Aru

2018-01-01

High coercivity of hot-deformed Nd2Fe14B magnets was obtained by grain boundary diffusion. Comparable squareness and similar magnetic properties for samples diffusing from side and pole surfaces show little discrepancies if quantities of the infiltrated PrNd-Cu low eutectic alloys is enough to obtain sufficient diffusion. However, the microstructures and higher characteristic peak ratios show preferable orientation of grains near surfaces of the sample diffused from side surfaces than that from pole surfaces. Amorphous Nd-rich phases and crystal Fe-rich phases were both observed in the diffused magnets. The enhancement of coercivity is considered to be resulted from grain boundary optimization and magnetic isolation which is caused by the thickened nonmagnetic intergranular phases.

Submicron R{sub 2}Fe{sub 14}B particles

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

Koylu-Alkan, O., E-mail: ozlem@udel.edu, E-mail: hadji@udel.edu; Hadjipanayis, G. C., E-mail: ozlem@udel.edu, E-mail: hadji@udel.edu; Barandiaran, J. M.

Mechanochemical synthesis of submicron R{sub 2}Fe{sub 14}B particles with R = Dy, Nd, Pr has been performed successfully via high energy ball milling of rare-earth oxides, iron oxide and boron oxide in the presence of a reducing agent (Ca) and a dispersant material (CaO), followed by annealing at 800 - 900 °C. In the R = Nd system, we were able to fabricate particles embedded in a CaO matrix with coercivity (H{sub c}) of 10.3 kOe after annealing at 900 °C for 5 min. After washing off the dispersant, the H{sub c} was decreased to below 1 kOe because of hydrogen absorptionmore » that leads to the formation of the hydrated R{sub 2}Fe{sub 14}BH{sub x} phase that has a lower anisotropy. Upon removal of the hydrogen the coercivity was increased to 3.3 kOe. The average size of the Nd{sub 2}Fe{sub 14}B particles increases from 100 nm in a sample synthesized at 800 °C to 158 nm at 900 °C. The isotropic Dy{sub 2}Fe{sub 14}B particles showed a higher coercivity of 21 kOe in washed samples after annealing at 900 °C for 5 min. An average size of 71 nm is measured in samples synthesized at 800 °C and 107 nm at 900 °C. Fitting the high field M(H) measurements in Nd{sub 2}Fe{sub 14}B to the law of approach to saturation gave values for the magnetocrystalline anisotropy for the washed sample 2.23 × 10{sup 7} erg/cm{sup 3} and for the vacuum annealed sample 4.15 × 10{sup 7} erg/cm{sup 3}, both of which are lower than the bulk values. This would explain the lower values of H{sub c} observed in the particles.« less

Influence of Nb addition on vacancy defects and magnetic properties of the nanocrystalline Nd-Fe-B permanent magnets

NASA Astrophysics Data System (ADS)

Szwaja, Małgorzata; Gębara, Piotr; Filipecki, Jacek; Pawlik, Katarzyna; Przybył, Anna; Pawlik, Piotr; Wysłocki, Jerzy J.; Filipecka, Katarzyna

2015-05-01

In present work, influence of Nb addition on vacancy defects and magnetic properties of nanocrystalline Nd-Fe-B permanent magnets, was investigated. Samples with composition (Nd,Fe,B)100-xNbx (where x=6,7,8) were studied in as-cast state and after annealing. Samples were prepared by arc-melting with high purity of constituent elements under Ar atmosphere. Ribbons were obtained by melt-spinning technique under low pressure of Ar. Ribbon samples in as-cast state had amorphous structure and soft magnetic properties. Positron annihilation lifetime spectroscopy PALS has been applied to detection of positron - trapping voids (vacancy defects). With increase of Nb in alloy increasing of vacancy defects concentration was observed. Heat treatment of the samples was carried out at various temperatures (from 923 K to 1023 K) for 5 min, in order to obtain nanocrystalline structure. The aim of present work was to determine the influence of Nb addition and annealing conditions on the vacancy defects and magnetic properties of the Nd-Fe-B- type alloys in as-cast state and after heat treatment.

Structure and electromagnetic properties of FeSiAl particles coated by MgO

NASA Astrophysics Data System (ADS)

Zhang, Yu; Zhou, Ting-dong

2017-03-01

FeSiAl particles with a layer of MgO surface coating have excellent soft magnetic and electromagnetic properties. In order to obtain the FeSiAl/MgO composites, Mg(OH)2 sol prepared by sol-gel process was well-mixed with FeSiAl flake particles, and then treated by calcination at 823 K in vacuum. The microstructural, morphological and electromagnetic parameters of FeSiAl/MgO particles were tested. Accordingly, the electromagnetic wave reflection loss in the frequency range of 0.5-18 GHz was calculated. The results show that the surface coating increases coercivity Hc and decreases complex permittivity, leading to a good impedance matching. When the coating amount was 7.5%, reflection loss of the composite particles can reach to -33 dB.

Formation of ferric oxides from aqueous solutions: A polyhedral approach by X-ray absorption spectroscopy. I. Hydrolysis and formation of ferric gels

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

Combes, J.M.; Manceau, A.; Calas, G.

1989-03-01

X-ray absorption spectroscopy (XAS) was used to follow the evolution of local structural environments around ferric ions during the formation of ferric hydrous oxide gels from 1 M chloride and 0.1 M nitrate solutions. Fe K-XANES and EXAFS confirm that ferric ions remain 6-fold coordinated during this evolution. With increasing OH availability in the solution, Cl{sup {minus}} anions tend gradually to be exchanged for (O, OH, OH{sub 2}) ligands. Below OH/Fe = 1, no structural order is detected beyond the first coordination sphere. Above this ratio, two Fe-Fe distances at 3.05 {angstrom} and 3.44 {angstrom} are observed and correspond tomore » the presence of edge- and vertex-sharing Fe-octahedra. XAS results show that ferric gels and highly polymerized aqueous species are short-range ordered. The main contribution to disorder in the gels arises from the small size of coherently scattering domains also responsible for their X-ray amorphous character. From the initial to the final stage of hydrolysis, particles possess a nearly spherical shape with a minimum average diameter ranging from 10-30 {angstrom} for polymers formed from chloride and nitrate solutions. As polymerization proceeds, the local order extends to several tens of angstroms and the particle structures becomes progressively closer to that of akaganeite ({beta}-FeOOH) or goethite ({alpha}-FeOOH). This local structure is distinct from that of the lepidocrocite ({gamma}-FeOOH)-like structure of ferric gels precipitated after oxidation of divalent Fe solutions. The growth of the crystalline Fe-oxyhydroxides from gels takes place by the progressive long-range ordering in the ferric polymers without modifying the short-range order around Fe.« less

Relaxation of bending stresses and the reversibility of residual stresses in amorphous soft magnetic alloys

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

Kekalo, I. B.; Mogil’nikov, P. S., E-mail: pavel-mog@mail.ru

2015-06-15

The reversibility of residual bending stresses is revealed in ribbon samples of cobalt- and iron-based amorphous alloys Co{sub 69}Fe{sub 3.7}Cr{sub 3.8}Si{sub 12.5}B{sub 11} and Fe{sub 57}Co{sub 31}Si{sub 2.9}B{sub 9.1}: the ribbons that are free of applied stresses and bent under the action of residual stresses become completely or incompletely straight upon annealing at the initial temperatures. The influence of annealing on the relaxation of bending stresses is studied. Preliminary annealing is found to sharply decrease the relaxation rate of bending stresses, and the initial stage of fast relaxation of these stresses is absent. Complete straightening of preliminarily annealed ribbons ismore » shown to occur at significantly higher temperatures than that of the initial ribbons. Incomplete straightening of the ribbons is explained by the fact that bending stresses relaxation at high annealing temperatures proceeds due to both reversible anelastic deformation and viscous flow, which is a fully irreversible process. Incomplete reversibility is also caused by irreversible processes, such as the release of excess free volume and clustering (detected by small-angle X-ray scattering). The revealed differences in the relaxation processes that occur in the cobalt- and iron-based amorphous alloys are discussed in terms of different atomic diffusion mobilities in these alloys.« less

Amorphous silicon ionizing particle detectors

DOEpatents

Street, Robert A.; Mendez, Victor P.; Kaplan, Selig N.

1988-01-01

Amorphous silicon ionizing particle detectors having a hydrogenated amorphous silicon (a--Si:H) thin film deposited via plasma assisted chemical vapor deposition techniques are utilized to detect the presence, position and counting of high energy ionizing particles, such as electrons, x-rays, alpha particles, beta particles and gamma radiation.

Amorphous Slater-Pauling like behaviour in magnetic nanoparticles alloys synthesized in liquids

NASA Astrophysics Data System (ADS)

Boyer, Paul; Ménard, David; Meunier, Michel

2012-09-01

Nanoparticles of Fe, Co, Ni, and their alloys, with an average diameter of 12 nm were synthesized in liquids using a laser. Their saturation magnetization exhibited a Slater-Pauling-like behaviour with two main differences compared to that expected in bulk materials. First, the amplitude of the magnetization was found to be roughly 5 times smaller. Second, the disappearance of the ferromagnetic (FM) behaviour occurred at Ni instead of the expected Ni0.6Cu0.4. The behaviour can be explained by the presence of non-magnetic oxidized shells which reduced the fraction of ferromagnetic atoms and induce through strain an amorphous structure in the metallic core. Annealing at 500 K leads to some crystallization of the particles and thus to a partial recovery of the expected magnetization.

HST-STIS spectra and the redness of Saturn's rings

NASA Astrophysics Data System (ADS)

Cuzzi, Jeffrey N.; French, Richard G.; Hendrix, Amanda R.; Olson, Daniel M.; Roush, Ted; Vahidinia, Sanaz

2018-07-01

We have observed the main rings of Saturn with the Space Telescope Imaging Spectrometer (STIS) on the Hubble Space Telescope (HST), covering the spectral region from 180-570 nm (including for the first time the critical near-UV range 190-340 nm) with very good signal to noise ratio and a radial resolution of approximately 160-330 km. After correcting for an unexpected grating scatter problem associated with the bright, red, extended planet-ring target, we obtained complete I/F spectra for each major ring region. We have interpreted the spectra in terms of the ring particle material composition using a combination of traditional "Hapke" theory and a new correction for shadowing on the rough, re-entrant ring particle surfaces, along with a correction for the nonclassical scattering of the ring layer itself. We tested a variety of UV absorbers: iron (including nano-iron) grains, hematite, "planetary silicates", organic carbon-ring tholins of varying aromaticity, and amorphous carbon. The A and B rings can contain no more NH3 than about 10-4 by volume. We conclude that the best spectral fit for the well-known, unusually red color of the A and B rings is provided by a sub-percent mass fraction of organic tholins. It appears that the most likely regolith configuration for the A and B Rings is a heterogeneous "intimate mixture", dominated by relatively pure water ice, with some 2-40% of the grains containing roughly 5-10% tholin by volume (the amount depending on whether silicates are present), but it is hard to allow much amorphous carbon to be present in the B Ring material at least. These predictions of compositional heterogeneity can be tested by Cassini direct compositional measurements. There is some suggestion that the tholin properties differ slightly between the A and B rings. We show that tholins of this type, in the abundance we predict, would be difficult to detect at near-IR wavelengths. The C Ring particles have lower albedos, and the best fit models require a significantly higher abundance of silicates and (more importantly) "neutral" absorber which we model as amorphous carbon, plausibly representing meteoritic infall. Because of our new treatment of shadowing, our estimates of the abundance of amorphous carbon in the C Ring particles are lower (1-5% in the particle regoliths) than previously obtained. The relative abundance of silicate and carbonaceous materials in the C Ring remains uncertain due to uncertainties in how to model the C ring particle phase function.

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.

Molecular dynamic simulation study of plasma etching L10 FePt media in embedded mask patterning (EMP) process

NASA Astrophysics Data System (ADS)

Zhu, Jianxin; Quarterman, P.; Wang, Jian-Ping

2017-05-01

Plasma etching process of single-crystal L10-FePt media [H. Wang et al., Appl. Phys. Lett. 102(5) (2013)] is studied using molecular dynamic simulation. Embedded-Atom Method [M. S. Daw and M. I. Baskes, Phy. Rev. B 29, 6443 (1984); X. W. Zhou, R. A. Johnson and H. N. G. Wadley, Phy. Rev. B 69, 144113 (2004)] is used to calculate the interatomic potential within atoms in FePt alloy, and ZBL potential [J.F. Ziegler, J. P. Biersack and U. Littmark, "The Stopping and Range of Ions in Matter," Volume 1, Pergamon,1985] in comparison with conventional Lennard-Jones "12-6" potential is applied to interactions between etching gas ions and metal atoms. It is shown the post-etch structure defects can include amorphized surface layer and lattice interstitial point defects that caused by etchant ions passed through the surface layer. We show that the amorphized or damaged FePt lattice surface layer (or "magnetic dead-layer") thickness after etching increases with ion energy for Ar ion impacts, but significantly small for He ions at up to 250eV ion energy. However, we showed that He sputtering creates more interstitial defects at lower energy levels and defects are deeper below the surface compared to Ar sputtering. We also calculate the interstitial defect level and depth as dependence on ion energy for both Ar and He ions. Media magnetic property loss due to these defects is also discussed.

The properties of the nano-minerals and hazardous elements: Potential environmental impacts of Brazilian coal waste fire.

PubMed

Civeira, Matheus S; Pinheiro, Rafael N; Gredilla, Ainara; de Vallejuelo, Silvia Fdez Ortiz; Oliveira, Marcos L S; Ramos, Claudete G; Taffarel, Silvio R; Kautzmann, Rubens M; Madariaga, Juan Manuel; Silva, Luis F O

2016-02-15

Brazilian coal area (South Brazil) impacted the environment by means of a large number of coal waste piles emplaced over the old mine sites and the adjacent areas of the Criciúma, Urussanga, and Siderópolis cities. The area studied here was abandoned and after almost 30 years (smokeless visual) some companies use the actual minerals derived from burning coal cleaning rejects (BCCRs) complied in the mentioned area for industry tiles or refractory bricks. Mineralogical and geochemical similarities between the BCCRs and non-anthropogenic geological environments are outlined here. Although no visible flames were observed, this study revealed that auto-combustion existed in the studied area for many years. The presence of amorphous phases, mullite, hematite and other Fe-minerals formed by high temperature was found. There is also pyrite, Fe-sulphates (eg. jarosite) and unburnt coal present, which are useful for comparison purposes. Bad disposal of coal-dump wastes represents significant environmental concerns due to their potential influence on atmosphere, river sediments, soils and as well as on the surface and groundwater in the surroundings of these areas. The present study using advanced analytical techniques were performed to provide an improved understanding of the complex processes related with sulphide-rich coal waste oxidation, spontaneous combustion and mineral formation. It is reporting huge numbers of rare minerals with alunite, montmorillonite, szomolnokite, halotrichite, coquimbite and copiapite at the BCCRs. The data showed the presence of abundant amorphous Si-Al-Fe-Ti as (oxy-)hydroxides and Fe-hydro/oxides with goethite and hematite with various degrees of crystallinity, containing hazardous elements, such as Cu, Cr, Hf, Hg, Mo, Ni, Se, Pb, Th, U, Zr, and others. By Principal Component Analysis (PCA), the mineralogical composition was related with the range of elemental concentration of each sample. Most of the nano-minerals and ultra-fine particles found in the burned coal-dump wastes are the same as those commonly associated with coal cleaning rejects, in which oxidation of sulphides plays an important role to environment and human health. Copyright © 2015 Elsevier B.V. All rights reserved.

Composite bone cements loaded with a bioactive and ferrimagnetic glass-ceramic: Leaching, bioactivity and cytocompatibility.

PubMed

Verné, Enrica; Bruno, Matteo; Miola, Marta; Maina, Giovanni; Bianco, Carlotta; Cochis, Andrea; Rimondini, Lia

2015-08-01

In this work, composite bone cements, based on a commercial polymethylmethacrylate matrix (Palamed®) loaded with ferrimagnetic bioactive glass-ceramic particles (SC45), were produced and characterized in vitro. The ferrimagnetic bioactive glass-ceramic belongs to the system SiO2-Na2O-CaO-P2O5-FeO-Fe2O3 and contains magnetite (Fe3O4) crystals into a residual amorphous bioactive phase. Three different formulations (containing 10, 15 and 20 wt.% of glass-ceramic particles respectively) have been investigated. These materials are intended to be applied as bone fillers for the hyperthermic treatment of bone tumors. The morphological, compositional, calorimetric and mechanical properties of each formulation have been already discussed in a previous paper. The in vitro properties of the composite bone cements described in the present paper are related to iron ion leaching test (by graphite furnace atomic absorption spectrometer), bioactivity (i.e. the ability to stimulate the formation of a hydroxyapatite - HAp - layer on their surface after soaking in simulated body fluid SBF) and cytocompatibility toward human osteosarcoma cells (ATCC CRL-1427, Mg63). Morphological and chemical characterizations by scanning electron microscopy and energy dispersion spectrometry have been performed on the composite samples after each test. The iron release was negligible and all the tested samples showed the growth of HAp on their surface after 28 days of immersion in a simulated body fluid (SBF). Cells showed good viability, morphology, adhesion, density and the ability to develop bridge-like structures on all investigated samples. A synergistic effect between bioactivity and cell mineralization was also evidenced. Copyright © 2015 Elsevier B.V. All rights reserved.

Ion beam irradiation of lanthanum and thorium-doped yttrium titanates

NASA Astrophysics Data System (ADS)

Lian, J.; Zhang, F. X.; Peters, M. T.; Wang, L. M.; Ewing, R. C.

2007-05-01

Y2Ti2O7 pyrochlores doped with La have been sintered at 1373 K for 12 h with the designed compositions of the (LaxY1-x)2Ti2O7 system (x = 0, 0.08, 0.5, and 1), and the phase compositions were analyzed by X-ray diffraction. Limited amounts of La were incorporated into yttrium titanate pyrochlore structure for La-doped samples; while, the end member composition of La2Ti2O7 formed a layered perovskite structure. Ion beam-induced amorphization occurred for all compositions in the (LaxY1-x)2Ti2O7 binary under 1 MeV Kr2+ irradiation at room temperature, and the critical amorphization dose decreased with increasing amounts of La3+. The critical amorphization temperatures for Y2Ti2O7, (La0.162Y0.838)2Ti2O7 and La2Ti2O7 were determined to be ∼780, 890 and 920 K, respectively. Th4+ and Fe3+-doped yttrium titanate pyrochlores were synthesized at 1373 K by sintering Y2Ti2O7 with (ThO2 + Fe2O3). Pyrochlore structures and the chemical compositions were primarily identified by the X-ray diffraction and energy dispersive X-ray (EDX) measurements. The lattice parameter and the critical amorphization dose (1 MeV Kr2+ at room temperature) increase for yttrium titanate pyrochlores with the addition of Th. The increasing 'resistance' to amorphization with less La and greater Th and Fe contents for (Y1-xLax)2Ti2O7 and Y2Ti2O7-Fe2O3-ThO2 systems, respectively, are consistent with the changes in the average ionic radius ratio at the A-sites and B-sites. These results suggest that the addition of lanthanides and actinides (e.g., Th, U, or Pu) will affect the structural stability, as well as the radiation response behavior of the pyrochlore structure-type.

Amorphous silicon ionizing particle detectors

DOEpatents

Street, R.A.; Mendez, V.P.; Kaplan, S.N.

1988-11-15

Amorphous silicon ionizing particle detectors having a hydrogenated amorphous silicon (a--Si:H) thin film deposited via plasma assisted chemical vapor deposition techniques are utilized to detect the presence, position and counting of high energy ionizing particles, such as electrons, x-rays, alpha particles, beta particles and gamma radiation. 15 figs.

Thon rings from amorphous ice and implications of beam-induced Brownian motion in single particle electron cryo-microscopy.

PubMed

McMullan, G; Vinothkumar, K R; Henderson, R

2015-11-01

We have recorded dose-fractionated electron cryo-microscope images of thin films of pure flash-frozen amorphous ice and pre-irradiated amorphous carbon on a Falcon II direct electron detector using 300 keV electrons. We observe Thon rings [1] in both the power spectrum of the summed frames and the sum of power spectra from the individual frames. The Thon rings from amorphous carbon images are always more visible in the power spectrum of the summed frames whereas those of amorphous ice are more visible in the sum of power spectra from the individual frames. This difference indicates that while pre-irradiated carbon behaves like a solid during the exposure, amorphous ice behaves like a fluid with the individual water molecules undergoing beam-induced motion. Using the measured variation in the power spectra amplitude with number of electrons per image we deduce that water molecules are randomly displaced by a mean squared distance of ∼1.1 Å(2) for every incident 300 keV e(-)/Å(2). The induced motion leads to an optimal exposure with 300 keV electrons of 4.0 e(-)/Å(2) per image with which to observe Thon rings centred around the strong 3.7 Å scattering peak from amorphous ice. The beam-induced movement of the water molecules generates pseudo-Brownian motion of embedded macromolecules. The resulting blurring of single particle images contributes an additional term, on top of that from radiation damage, to the minimum achievable B-factor for macromolecular structure determination. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

Bending effects and temperature dependence of magnetic properties in a Fe-rich amorphous wire

NASA Astrophysics Data System (ADS)

Bordin, G.; Buttino, G.; Poppi, M.

2001-08-01

Amorphous wires with composition Fe 77.5Si 7.5B 15 exhibit a very peculiar magnetization process characterized by a single and quite large Barkhausen jump. This gives rise to a squared hysteresis loop at a critical magnetic field. The bistable behaviour, widely studied in wires with typical length of 10 cm and diameter of 125 μm, appears above a length of about 7 cm in straight wires and disappears for curvature radius within the range 2-12 cm in bent wires. In this work it is shown that bistability occurs in bent wires, whatever their curvature is, provided the wires are long enough. To this purpose spiral-shaped samples with several turns are considered. However, when the wire length is not a integer number of turns the magnetization reverses through many large Barkhausen jumps. In this condition, varying the measuring temperature can activate the energy barriers for the jumps.

Ultrafine and highly disordered Ni 2 Fe 1 nanofoams enabled highly efficient oxygen evolution reaction in alkaline electrolyte

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

Fu, Shaofang; Song, Junhua; Zhu, Chengzhou

Nickel iron hydroxides are the most promising non-noble electrocatalysts for oxygen evolution reaction (OER) in alkaline media. By in situ reduction of metal precursors, compositionally controlled three-dimensional (3D) NixFeyB nanofoams (NFs) are synthesized with high surface area and uniformly distributed bimetallic networks. The resultant ultrafine amorphous Ni2Fe1B NFs exhibit extraordinary electrocatalytic performance toward OER and overall water splitting in alkaline media. At a potential as low as 1.42 V (vs. RHE), Ni2Fe1B NFs can deliver a current density of 10 mA/cm2 and show negligible activity loss after 12 hours’ stability test. Even at large current flux of 100 mA/cm2, anmore » ultralow overpotential of 0.27 V is achieved, which is about 0.18 V more negative than benchmark RuO2. Both ex-situ Mӧssbauer spectroscopy and X-ray Absorption Spectroscopy (XAS) reveal a phase separation and transformation for the Ni2Fe1B catalyst during OER process. The evolution of oxidation state and disordered structure of Ni2Fe1B might be a key to the high catalytic performance for OER.« less

Amorphous surface layers in Ti-implanted Fe

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

Knapp, J.A.; Follstaedt, D.M.; Picraux, S.T.

1979-01-01

Implanting Ti into high-purity Fe results in an amorphous surface layer which is composed of not only Fe and Ti, but also C. Implantations were carried out at room temperature over the energy range 90 to 190 keV and fluence range 1 to 2 x 10/sup 16/ at/cm/sup 2/. The Ti-implanted Fe system has been characterized using transmission electron microscopy (TEM), ion backscattering and channeling analysis, and (d,p) nuclear reaction analysis. The amorphous layer was observed to form at the surface and grow inward with increasing Ti fluence. For an implant of 1 x 10/sup 17/ Ti/cm/sup 2/ at 180more » keV the layer thickness was 150 A, while the measured range of the implanted Ti was approx. 550 A. This difference is due to the incorporation of C into the amorphous alloy by C being deposited on the surface during implantation and subsequently diffusing into the solid. Our results indicate that C is an essential constituent of the amorphous phase for Ti concentrations less than or equal to 10 at. %. For the 1 x 10/sup 17/ Ti/cm/sup 2/ implant, the concentration of C in the amorphous phase was approx. 25 at. %, while that of Ti was only approx. 3 at. %. A higher fluence implant of 2 x 10/sup 17/ Ti/cm/sup 2/ produced an amorphous layer with a lower C concentration of approx. 10 at. % and a Ti concentration of approx. 20 at. %.« less

Exchange bias and bistable magneto-resistance states in amorphous TbFeCo thin films

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

Li, Xiaopu, E-mail: xl6ba@virginia.edu; Ma, Chung T.; Poon, S. Joseph, E-mail: sjp9x@virginia.edu

2016-01-04

Amorphous TbFeCo thin films sputter deposited at room temperature on thermally oxidized Si substrate are found to exhibit strong perpendicular magnetic anisotropy. Atom probe tomography, scanning transmission electron microscopy, and energy dispersive X-ray spectroscopy mapping have revealed two nanoscale amorphous phases with different Tb atomic percentages distributed within the amorphous film. Exchange bias accompanied by bistable magneto-resistance states has been uncovered near room temperature by magnetization and magneto-transport measurements. The exchange anisotropy originates from the exchange interaction between the ferrimagnetic and ferromagnetic components corresponding to the two amorphous phases. This study provides a platform for exchange bias and magneto-resistance switchingmore » using single-layer amorphous ferrimagnetic thin films that require no epitaxial growth.« less

Channel scaling and field-effect mobility extraction in amorphous InZnO thin film transistors

NASA Astrophysics Data System (ADS)

Lee, Sunghwan; Song, Yang; Park, Hongsik; Zaslavsky, A.; Paine, D. C.

2017-09-01

Amorphous oxide semiconductors (AOSs) based on indium oxides are of great interest for next generation ultra-high definition displays that require much smaller pixel driving elements. We describe the scaling behavior in amorphous InZnO thin film transistors (TFTs) with a significant decrease in the extracted field-effect mobility μFE with channel length L (from 39.3 to 9.9 cm2/V·s as L is reduced from 50 to 5 μm). Transmission line model measurements reveal that channel scaling leads to a significant μFE underestimation due to contact resistance (RC) at the metallization/channel interface. Therefore, we suggest a method of extracting correct μFE when the TFT performance is significantly affected by RC. The corrected μFE values are higher (45.4 cm2/V·s) and nearly independent of L. The results show the critical effect of contact resistance on μFE measurements and suggest strategies to determine accurate μFE when a TFT channel is scaled.

Changes in gene expression in the rat hippocampus following exposure to 56 fe particles and protection by berry diets

USDA-ARS?s Scientific Manuscript database

Exposing young rats to particles of high energy and charge (HZE particles), such as 56Fe, enhances indices of oxidative stress and inflammation and disrupts behavior, including spatial learning and memory. In the present study, we examined whether gene expression in the hippocampus, an area of the b...

Phosphate and phytate adsorption and precipitation on ferrihydrite surfaces

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

Wang, Xiaoming; Hu, Yongfeng; Tang, Yadong

Phosphorous (P) sorption on mineral surfaces largely controls P mobility and bioavailability, hence its pollution potential, but the sorption speciation and mechanism remain poorly understood. In this study, we have identified and quantified the speciation of both phosphate and phytate sorbed on ferrihydrite with various P loadings at pH 3–8 using differential atomic pair distribution function (d-PDF) analysis, synchrotron-based X-ray diffraction (XRD), and P and Fe K-edge X-ray absorption near edge structure (XANES) and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. With increasing P sorption loading for both phosphate and phytate, the sorption mechanism transits from bidentate-binuclear surface complexation tomore » unidentified ternary complexation and to precipitation of amorphous FePO 4 and amorphous Fe-phytate. At a given P sorption loading, phosphate precipitates more readily than phytate. Both phosphate and phytate promote ferrihydrite dissolution with phytate more intensively, but the dissolved FeIII concentration in the bulk solution is low because the majority of the released Fe III precipitate with the anions. Results also show that amorphous FePO 4 and amorphous Fe-phytate have similar PO 4 local coordination environment. In conclusion, these new insights into the P surface complexation and precipitation, and the ligand-promoted dissolution behavior improve our understanding of P fate in soils, aquatic environment and water treatment systems as mediated by mineral-water interfacial reactions.« less

Phosphate and phytate adsorption and precipitation on ferrihydrite surfaces

DOE PAGES

Wang, Xiaoming; Hu, Yongfeng; Tang, Yadong; ...

2017-09-26

Phosphorous (P) sorption on mineral surfaces largely controls P mobility and bioavailability, hence its pollution potential, but the sorption speciation and mechanism remain poorly understood. In this study, we have identified and quantified the speciation of both phosphate and phytate sorbed on ferrihydrite with various P loadings at pH 3–8 using differential atomic pair distribution function (d-PDF) analysis, synchrotron-based X-ray diffraction (XRD), and P and Fe K-edge X-ray absorption near edge structure (XANES) and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. With increasing P sorption loading for both phosphate and phytate, the sorption mechanism transits from bidentate-binuclear surface complexation tomore » unidentified ternary complexation and to precipitation of amorphous FePO 4 and amorphous Fe-phytate. At a given P sorption loading, phosphate precipitates more readily than phytate. Both phosphate and phytate promote ferrihydrite dissolution with phytate more intensively, but the dissolved FeIII concentration in the bulk solution is low because the majority of the released Fe III precipitate with the anions. Results also show that amorphous FePO 4 and amorphous Fe-phytate have similar PO 4 local coordination environment. In conclusion, these new insights into the P surface complexation and precipitation, and the ligand-promoted dissolution behavior improve our understanding of P fate in soils, aquatic environment and water treatment systems as mediated by mineral-water interfacial reactions.« less

Atomic mixing induced by swift heavy ion irradiation of Fe/Zr multilayers

NASA Astrophysics Data System (ADS)

Jaouen, C.; Michel, A.; Pacaud, J.; Dufour, C.; Bauer, Ph.; Gervais, B.

1999-01-01

The mechanism of ion induced mixing and phase change was studied for Fe/Zr multilayers, and specifically for the case of swift heavy ions giving rise to a very large electronic excitation of the target. The multilayers had a modulation of 7.6 nm and an overall composition Fe 69Zr 31. The Zr layers were amorphous whereas the Fe ones were crystalline (bcc) with a very strong (1 1 0) texture in the growth direction. The phase transformation and the composition changes were analysed using the structural and magnetic properties of the Fe component by means of a detailed analysis of the X-ray diffraction profiles and with the aid of backscattering Mössbauer spectroscopy. A complete mixing was observed at a fluence of 10 13 U/cm 2. Both phenomena, the dose dependence of the ion beam mixed amorphous non-magnetic phase and the quantitative evolution of the crystalline iron layer thickness, suggest that mixing occurs in a two-stage process. At an initial stage, an anisotropic diffusion of iron atoms in the amorphous zirconium layers takes place along the interface, while subsequent ion bombardment leads to a generalised transformation through the whole of the Fe layer. Finally, the implications of these observations are discussed in comparison to the plastic deformation phenomena reported for amorphous alloys.

Enhanced pulmonary absorption of poorly soluble itraconazole by micronized cocrystal dry powder formulations.

PubMed

Karashima, Masatoshi; Sano, Noriyasu; Yamamoto, Syunsuke; Arai, Yuta; Yamamoto, Katsuhiko; Amano, Nobuyuki; Ikeda, Yukihiro

2017-06-01

Micronized cocrystal powders and amorphous spray-dried formulations were prepared and evaluated in vivo and in vitro as pulmonary absorption enhancement formulations of poorly soluble itraconazole (ITZ). ITZ cocrystals with succinic acid (SA) or l-tartaric acid (TA) with a particle size diameter of <2μm were successfully micronized using the jet-milling system. The cocrystal crystalline morphologies observed using scanning electron microscopy (SEM) suggested particle shapes that differed from those of the crystalline or spray-dried amorphous ITZ. The micronized ITZ cocrystal powders showed better intrinsic dissolution rate (IDR) and pulmonary absorption profile in rats than that of the amorphous spray-dried formulation and crystalline ITZ with comparable particle sizes. Specifically, in rat pharmacokinetic studies following pulmonary administration, micronized ITZ-SA and ITZ-TA cocrystals showed area under the curve from 0 to 8h (AUC 0-8h ) values approximately 24- and 19-fold higher than those of the crystalline ITZ and 2.0- and 1.6-fold higher than the spray-dried ITZ amorphous values, respectively. The amorphous formulation appeared physically instable during the studies due to rapid crystallization of ITZ, which was its disadvantage compared to the crystalline formulations. Therefore, this study demonstrated that micronized cocrystals are promising formulations for enhancing the pulmonary absorption of poorly soluble compounds. Copyright © 2017 Elsevier B.V. All rights reserved.

Tunable ferromagnetic resonance behavior in Co2FeSi film by post-annealing

NASA Astrophysics Data System (ADS)

Xu, Zhan; Zhang, Zhi; Hu, Fang; Li, Xia; Liu, Peng; Liu, Er; Xu, Feng

2018-05-01

Co2FeSi film is potential in the spintronics applications, due to its low damping factor, which is reflected in the ferromagnetic resonance behavior. In this work, we demonstrate that the ferromagnetic resonance behavior in Co2FeSi film can be well engineered by post-annealing. After 450 °C post-annealing for 1 hour, the Gilbert damping factor decreases drastically from 0.039 at as-deposited state to 0.006, and the inhomogeneity contribution of ferromagnetic resonance linewidth decreases to 60.5 Oe. These decreases are ascribed to the crystallization of film from amorphous state to an ordered B2 phase. Higher annealing temperature, however, leads to the formation of the A2 phase with higher atomic disorder, instead of B2 phase, and brings about the increase of Gilbert damping.

Structural, Kinetic And Magnetic Properties Of Mechanically Alloyed Fe-Zr Powders

NASA Astrophysics Data System (ADS)

Mishra, Debabrata; Perumal, A.; Srinivasan, A.

2008-04-01

We report the study of amorphous/non-equilibrium solid solution Fe100-xZrx (x = 20 to 35) alloys by mechanical alloying process. It is observed that with increasing Zr substitution, (a) the activation energy increases, (b) the saturation magnetization and coercivity show oscillating behavior. Low temperature magnetic measurements show the presence of spin-glass like phase transition even at H = 10 kOe. The oscillating behavior of magnetic parameters is explained on the basis of variations in the average internal stress calculated using magnetic data.

Transport and magnetic properties of HITPERM alloys

NASA Astrophysics Data System (ADS)

Pekala, K.; Latuch, J.; Pekala, M.; Skorvanek, I.; Jaskiewicz, P.

2003-02-01

Nanocrystalline HITPERM alloys Fe44.6Co43.3X7.4B3.7Cu1 (X = Nb, Zr, Hf) prepared by crystallization of amorphous precursors are studied by magnetization and electrical resistivity measurements for the first time. Structural and magnetic components of the electrical resistivity are separated. The electrical resistivity of the nanocrystalline α' (FeCo) phase calculated using the Maxwell Garnett relation proves strong electron scattering on the grain boundaries. The temperature variation of the crystalline fraction during the first crystallization stage is calculated for the Hf based alloy.

Metastable Phases of Dross Particles Formed in a Molten Zinc Bath and Prediction of Soluble Aluminum During Galvannealing Processes

NASA Astrophysics Data System (ADS)

Paik, Doo-Jin; Hong, Moon-Hi; Huh, Yoon; Park, Joo Hyun; Chae, Hong-Kook; Park, Seok-Ho; Choun, Si-Youl

2012-06-01

The morphology, chemistry, and crystallographic characteristics of metastable dross particles were identified. These particles are formed during the initial stage of precipitation. The particles had aluminum concentrations of 15 to 80 mass pct, with values that decreased gradually as particle size increased. These metastable dross particles were a mixture of the crystalline phase of FeZn10, which is called the "delta phase," and the high-aluminum amorphous phase, which covered the surface of the crystalline phase. The new "meta Q" concept was proposed to predict the amount of soluble aluminum in the zinc bath by considering nucleation kinetics and particle growth. The results calculated using the "meta Q" concept were compared with the values measured by the aluminum sensor, which were taken during the same period at the commercial galvanizing line. The mean of the absolute values of the differences between the calculated and measured values was 9.7 ppm.

Following iron speciation in the early stages of magnetite magnetosome biomineralization

DOE PAGES

Firlar, Emre; Perez-Gonzalez, Teresa; Olszewska, Agata; ...

2016-02-26

Understanding magnetosome magnetite biomineralization is of fundamental interest to devising the strategies for bioinspired synthesis of magnetic materials at the nanoscale. Thus, we investigated the early stages of magnetosome formation in this work and correlated the size and emergent crystallinity of magnetosome nanoparticles with the changes in chemical environment of iron and oxygen by utilizing advanced analytical electron microscopy techniques. We observed that magnetosomes in the early stages of biomineralization with the sizes of 5–10 nm were amorphous, with a majority of iron present as Fe 3+, indicative of ferric hydroxide. The magnetosomes with intermediate sizes showed partially crystalline structuremore » with a majority of iron present as Fe 3+ and trace amounts of Fe 2+. The fully maturated magnetosomes were indexed to magnetite. Furthermore, our approach provides spatially resolved structural and chemical information of individual magnetosomes with different particle sizes, attributed to magnetosomes at different stages of biomineralization.« less

Dependency properties of the amorphous alloy Co58Ni10Fe5Si11B16 on technological parameters of spinning

NASA Astrophysics Data System (ADS)

Frolov, A. M.; Tkachev, V. V.; Fedorets, A. N.; Pustovalov, E. V.; Kraynova, G. S.; Dolzhikov, S. V.; Ilin, N. V.; Tsesarskaya, A. K.

2017-09-01

The tapes are quickly quenched onto a rotating drum. The structure of mechanical and physical properties is studied depending on the spinning parameters. An approach is proposed for the classification of obtained bands based on the statistics of the microrelief of their surfaces.

Carbon-coated CoFe-CoFe2O4 composite particles with high and dual-band electromagnetic wave absorbing properties.

PubMed

Guan, Zhen-Jie; Jiang, Jian-Tang; Chen, Na; Gong, Yuan-Xun; Zhen, Liang

2018-07-27

SiO 2 and TiO 2 , as conventional dielectric shells of ferromagnetic/dielectric composite particles, can protect ferromagnetic particles from aggregation and oxidation, but contribute little to electromagnetic loss. In this work, we designed nano-assembled CoFe-CoFe 2 O 4 @C composite particles, in which ferrites with high permeability were dielectric elements and carbon was introduced as protective layers, aiming for high-efficiency microwave absorption. These assembled particles with different CoFe contents were prepared through solvothermal methods and subsequent hydrogen-thermal reduction. CoFe nanoparticles were dispersed on a CoFe 2 O 4 matrix via an in situ reduction transformation from CoFe 2 O 4 to CoFe. The microstructure evolution of composite particles and corresponding electromagnetic properties tailoring were investigated. The content and size of CoFe as well as the porosity of composite particles increase gradually as the annealing temperature increases. A maximum reflection loss (RL max ) of -71.73 dB is observed at 4.78 GHz in 3.4 mm thick coating using particles annealed at 500 °C as fillers. The coating presents double-band absorbing characteristics, as broad effective absorption bandwidth with RL > 5 (ERL 5 ) and high RL max are observed in both S-C and X-K u bands. The tunability as well as the assembled characteristic of the electromagnetic property that endued from the composite structure contributes to the excellent electromagnetic wave absorbing performances.

Thermal annealing dynamics of carbon-coated LiFePO{sub 4} nanoparticles studied by in-situ analysis

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

Krumeich, Frank, E-mail: krumeich@inorg.chem.ethz.ch; Waser, Oliver; Pratsinis, Sotiris E.

The thermal behavior of core-shell carbon-coated lithium iron phosphate (LiFePO{sub 4}-C) nanoparticles made by flame spray pyrolysis (FSP) during annealing was investigated by in-situ transmission electron microscopy (TEM), in-situ X-ray powder diffraction (XRD) as well as ex-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Crystallization of the initially glassy LiFePO{sub 4}-C nanoparticles starts at quite low temperatures (T=400 °C), forming single crystals inside the confinement of the carbon shell. Upon increasing the temperature to T≥700 °C, LiFePO{sub 4} starts to diffuse through the carbon shell resulting in cavities inside the mostly intact carbon shell. By increasing the temperature further tomore » T≥800 °C, the initial core-shell morphology converts into open carbon shells (flakes and cenospheres) and bulky LiFePO{sub 4} particles (diameter in the range 300–400 nm), in agreement with ex-situ experiments. - Graphical abstract: TEM images of a typical sample area recorded at room temperature and after heating in-situ heating reveal the growth of particles and the formation of empty carbon cages. - Highlights: • LiFePO{sub 4} coated by a carbon shell is produced by flame spray pyrolysis. • The amorphous LiFePO{sub 4} starts to crystallize at 400 °C as revealed by in-situ XRD. • Crystal growth was visualized by TEM heating experiments. • The formation of empty carbon cages starts at 700 °C.« less

Microbiological and Geochemical Evidence of Fe(III) Reduction in the Rhizosphere (Root-Zone) of Wetland Plants

NASA Astrophysics Data System (ADS)

Weiss, J. V.; Megonigal, J. P.; Emerson, D.

2002-05-01

We have found that the Fe-oxide deposits (Fe-plaque) on wetland plant roots contain abundant microbes including Fe(II)-oxidizing bacteria (FeOB) (Appl. Environ. Microbiol. 1999, 65:2758-2761). In the current study, we investigated the potential for root Fe-plaque to serve as a substrate for Fe(III)-reducing bacteria (FeRB) and compared rates of Fe reduction between plaque and bulk soil. In a study at six wetland habitats located in the Mid-Atlantic region, abundances of FeRB in the rhizosphere of Typha spp. and the bulk soil were enumerated using the most probable number technique. In the rhizosphere, FeRB accounted for an average of 12% of the total cell number while in the soil they accounted for <1% of the total bacteria. We subsequently performed a sequential chemical extraction on both roots and soil to determine if FeRB abundances were driven by differences in the reducibility of Fe(III) in each environment. The roots contained a significantly higher percentage of amorphous Fe (77.4%; p<0.05 n=5 wetlands) than the bulk soil (33.8%); conversely, the soil also had significantly higher amounts of crystalline Fe (41.1%, p<0.05, n=5 wetlands) than the roots (8.1%). A significant correlation was observed between the percentage of amorphous Fe and the percentage of FeRB (r2=0.583; p<0.05). Since amorphous Fe is more readily reduced by microbes than crystalline Fe, these results suggested that the roots provide a good substrate for iron-reducing bacteria. To determine how differences in reducible Fe(III) might limit Fe reduction potential, we performed 12-day anaerobic incubations of roots and soil with Geobacter metallireducans, a common FeRB isolated from aquatic environments. Although Fe(III) reduction rates peaked at between 48 and 72 hours in both the roots and soils, the total amount of Fe(II) production in the root samples was significantly higher than that in the soil samples (350 μ moles g dry weight-1 vs. 153 μ moles g dry weight-1; p<0.05). All of these findings, including higher percentages of FeRB and amorphous Fe in the rhizosphere than in the bulk soil, support the hypothesis that the wetland plant rhizosphere is an active zone of Fe(III) reduction.

Coercivity enhancement of Dy-coated Nd-Fe-B flakes by crystallization

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

Fukunaga, H.; Sugimoto, Y.; Nakano, M.

2011-04-01

The coercivity of isotropic Dy-coated Nd-Fe-B flakes was enhanced by crystallization and simultaneous diffusion of Dy from their surfaces. Amorphous Dy-coated Nd-Fe-B flakes were crystallized by heating them to 923 K 2over a 2 min period followed by rapid cooling. During crystallization, the Dy on the surface diffused into the flakes. This low-temperature rapid annealing produced flakes with fine grains and the Dy diffusion enhanced their coercivity. The coercivity after crystallization increased with increasing Dy layer thickness, although the remanence decreased when the layer thickness exceeded 3 {mu}m. Thick coatings of over 6 {mu}m resulted in the formation of DyFe{submore » 2}, which degraded the magnetic properties of the crystallized flakes. Flakes with a 3-{mu}m-thick coating exhibited excellent magnetic properties after annealing: They had a coercivity of 1880 kA/m and a remanence of 78 emu/g. This coercivity is approximately 500 kA/m higher than that of uncoated flakes, whereas the remanence is comparable to that of uncoated flakes.« less

Study of structural and magnetic properties of melt spun Nd2Fe13.6Zr0.4B ingot and ribbon

NASA Astrophysics Data System (ADS)

Amin, Muhammad; Siddiqi, Saadat A.; Ashfaq, Ahmad; Saleem, Murtaza; Ramay, Shahid M.; Mahmood, Asif; Al-Zaghayer, Yousef S.

2015-12-01

Nd2Fe13.6Zr0.4B hard magnetic material were prepared using arc-melting technique on a water-cooled copper hearth kept under argon gas atmosphere. The prepared samples, Nd2Fe13.6Zr0.4B ingot and ribbon are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) for crystal structure determination and morphological studies, respectively. The magnetic properties of the samples have been explored using vibrating sample magnetometer (VSM). The lattice constants slightly increased due to the difference in the ionic radii of Fe and that of Zr. The bulk density decreased due to smaller molar weight and low density of Zr as compared to that of Fe. Ingot sample shows almost single crystalline phase with larger crystallite sizes whereas ribbon sample shows a mixture of amorphous and crystalline phases with smaller crystallite sizes. The crystallinity of the material was highly affected with high thermal treatments. Magnetic measurements show noticeable variation in magnetic behavior with the change in crystallite size. The sample prepared in ingot type shows soft while ribbon shows hard magnetic behavior.

Structural and Electrochemical Characterization of Pure LiFePO 4 and Nanocomposite C- LiFePO 4 Cathodes for Lithium Ion Rechargeable Batteries

DOE PAGES

Kumar, Arun; Thomas, R.; Karan, N. K.; ...

2009-01-01

Pure limore » thium iron phosphate ( LiFePO 4 ) and carbon-coated LiFePO 4 (C- LiFePO 4 ) cathode materials were synthesized for Li-ion batteries. Structural and electrochemical properties of these materials were compared. X-ray diffraction revealed orthorhombic olivine structure. Micro-Raman scattering analysis indicates amorphous carbon, and TEM micrographs show carbon coating on LiFePO 4 particles. Ex situ Raman spectrum of C- LiFePO 4 at various stages of charging and discharging showed reversibility upon electrochemical cycling. The cyclic voltammograms of LiFePO 4 and C- LiFePO 4 showed only a pair of peaks corresponding to the anodic and cathodic reactions. The first discharge capacities were 63, 43, and 13 mAh/g for C/5, C/3, and C/2, respectively for LiFePO 4 where as in case of C- LiFePO 4 that were 163, 144, 118, and 70 mAh/g for C/5, C/3, C/2, and 1C, respectively. The capacity retention of pure LiFePO 4 was 69% after 25 cycles where as that of C- LiFePO 4 was around 97% after 50 cycles. These results indicate that the capacity and the rate capability improved significantly upon carbon coating.« less

Shock wave induced phase transition in α -FePO 4

NASA Astrophysics Data System (ADS)

Joshi, K. D.; Suresh, N.; Jyoti, G.; Kulshreshtha, S. K.; Gupta, S. C.; Sikka, S. K.

Shock wave induced response of the berlinite form of FePO 4 has been investigated up to 8.5 GPa. The X-ray diffraction measurements on the shock recovered samples reveal transition to the mixture of an amorphous phase and an orthorhombic phase around 5 GPa. The proportion of the amorphous material in the recovered sample is found to decrease at higher pressure. The results are interpreted in terms of a three-level free energy diagram for the crystal to amorphous transitions.

Sm5(Fe,Ti)17 melt-spun ribbons with high coercivity

NASA Astrophysics Data System (ADS)

Saito, Tetsuji; Horita, Toru

2018-05-01

It has previously been reported that annealing of amorphous Sm5Fe17 melt-spun ribbon resulted in the formation of the Sm5Fe17 phase and the resultant Sm5Fe17 melt-spun ribbon exhibited a high coercivity. However, the annealing condition of the amorphous Sm5Fe17 melt-spun ribbon was somewhat critical and it was not easy to obtain Sm5Fe17 grains with high coercivity. In the present study, it was found that the small substitution of Ti for Fe in the Sm5Fe17 melt-spun ribbon stabilized the Sm5Fe17 phase. Annealed Sm5Fe16.7Ti0.3 melt-spun ribbon consisted of small and homogeneous Sm5(Fe,Ti)17 grains and exhibited a higher coercivity than the annealed Sm5Fe17 melt-spun ribbon.

High temperature coercive field behavior of Fe-Zr powder

NASA Astrophysics Data System (ADS)

Mishra, Debabrata; Perumal, A.; Srinivasan, A.

2009-04-01

We report the investigation of high temperature coercive field behavior of Fe80Zr20 nanocrystalline alloy powder having two-phase microstructure prepared by mechanical alloying process. Thermomagnetization measurement shows the presence of two different magnetic phase transitions corresponding to the amorphous matrix and nonequilibrium Fe(Zr) solid solution. Temperature dependent coercivity exhibits a sharp increase in its value close to the Curie temperature of the amorphous matrix. This feature is attributed to the loss of intergranular ferromagnetic exchange coupling between the nanocrystallites due to the paramagnetic nature of the amorphous matrix. The temperature dependent coercive field behavior is ascribed to the variations in both the effective anisotropy and the exchange stiffness constant with temperature.

Sub-micron magnetic patterns and local variations of adhesion force induced in non-ferromagnetic amorphous steel by femtosecond pulsed laser irradiation

NASA Astrophysics Data System (ADS)

Zhang, Huiyan; Feng, Yuping; Nieto, Daniel; García-Lecina, Eva; Mcdaniel, Clare; Díaz-Marcos, Jordi; Flores-Arias, María Teresa; Gerard M., O.'connor; Baró, Maria Dolors; Pellicer, Eva; Sort, Jordi

2016-05-01

Periodic ripple and nanoripple patterns are formed at the surface of amorphous steel after femtosecond pulsed laser irradiation (FSPLI). Formation of such ripples is accompanied with the emergence of a surface ferromagnetic behavior which is not initially present in the non-irradiated amorphous steel. The occurrence of ferromagnetic properties is associated with the laser-induced devitrification of the glassy structure to form ferromagnetic (α-Fe and Fe3C) and ferrimagnetic [(Fe,Mn)3O4 and Fe2CrO4] phases located in the ripples. The generation of magnetic structures by FSPLI turns out to be one of the fastest ways to induce magnetic patterning without the need of any shadow mask. Furthermore, local variations of the adhesion force, wettability and nanomechanical properties are also observed and compared to those of the as-cast amorphous alloy. These effects are of interest for applications (e.g., biological, magnetic recording, etc.) where both ferromagnetism and tribological/adhesion properties act synergistically to optimize material performance.

Graphene nanocomposites for electrochemical cell electrodes

DOEpatents

Zhamu, Aruna; Jang, Bor Z.; Shi, Jinjun

2015-11-19

A composite composition for electrochemical cell electrode applications, the composition comprising multiple solid particles, wherein (a) a solid particle is composed of graphene platelets dispersed in or bonded by a first matrix or binder material, wherein the graphene platelets are not obtained from graphitization of the first binder or matrix material; (b) the graphene platelets have a length or width in the range of 10 nm to 10 .mu.m; (c) the multiple solid particles are bonded by a second binder material; and (d) the first or second binder material is selected from a polymer, polymeric carbon, amorphous carbon, metal, glass, ceramic, oxide, organic material, or a combination thereof. For a lithium ion battery anode application, the first binder or matrix material is preferably amorphous carbon or polymeric carbon. Such a composite composition provides a high anode capacity and good cycling response. For a supercapacitor electrode application, the solid particles preferably have meso-scale pores therein to accommodate electrolyte.

The formation of hysteretic magnetic properties in amorphous alloys of various classes upon thermomagmetic treatment in a transverse magnetic field

NASA Astrophysics Data System (ADS)

Kekalo, I. B.; Mogil'nikov, P. S.

2016-06-01

In this paper, we have studied the effects of the thermomagnetic treatment in a transverse magnetic field (TMaT⊥) on the permeability of the amorphous alloy Co69Fe3.7Cr3.8Si12.5B11 with such a low saturation magnetostriction ( λ s 10-7) that, in the ribbons of this alloy rolled into a toroid, a sharp longitudinal magnetic texture is observed ( K sq > 0.90). It has been revealed that the permeability μ4 ( H = 4 mOe, f = 1 kHz) as a function of the annealing temperature or time of holding at a temperature is described by a curve with a maximum. This maximum is observed at a coefficient of the squareness of the hysteresis loop K sq,m in the range of 0.2 ≤ K sq,m ≤ 0.4. The regimes of the TMaT have been determined that provide optimum values of the permeability μ4 (15000) without a loss of the ductile state of the ribbons of this alloy. Based on the example of an iron-based alloy of composition Fe57Co31Si2.9B9.1 with λs = 35 × 10-6, it has been shown that the formation of the hysteretic magnetic properties upon the TMaT⊥ depends substantially on the magnitude of the magnetostriction and the Curie temperature of the amorphous alloys.

Investigation on the formation process of single-crystalline GaO x barrier in Fe/GaO x /MgO/Fe magnetic tunnel junctions

NASA Astrophysics Data System (ADS)

Krishna, N. S.; Doko, N.; Matsuo, N.; Saito, H.; Yuasa, S.

2017-11-01

We have grown Fe(0 0 1)/GaO x (0 0 1)/MgO(0 0 1)/Fe(0 0 1) magnetic tunnel junctions (MTJs) with or without in situ annealing after the deposition of GaO x layer and performed structural characterizations by focusing on the formation process of the single-crystalline GaO x . It was found that, even without the in situ annealing, the as-grown GaO x grown on the MgO was mostly single-crystalline except near the surface region (amorphous). The crystallization temperature of the amorphous region was reduced from 500 °C down to 250 °C by depositing the Fe upper electrode (poly-crystalline). It was clarified that the crystallization of the amorphous region near the Fe/GaO x interface caused the realignments of the crystal grains in the poly-crystalline Fe upper electrode, and, as a result, the fully epitaxial Fe/GaO x /MgO/Fe structure is eventually formed. All the MTJs showed high tunneling magnetoresistance ratios (about 100%) at room temperature, which was almost independent of the formation temperature of the single-crystalline GaO x .

Local Structure of the Amorphous Precursor to Ba-Hexaferrite Thin Films: An Anisotropic Octahedral Fe-O Glass Network

NASA Astrophysics Data System (ADS)

Snyder, J. E.; Harris, V. G.; Koon, N. C.; Sui, X.; Kryder, M. H.

1996-10-01

Anisotropic local structure has been observed around both the Fe and Ba ions in the amorphous precursor to Ba-hexaferrite thin films, using polarization-dependent extended x-ray-absorption fine structure. This anisotropic local structure, consisting mainly of a network of Fe-O octahedra, determines the orientation of the fast-growing basal planes during crystallization, and thus the directions of the c axes and the resulting magnetic anisotropy.

Composition-controlled active-passive transition and corrosion behavior of Fe-Cr(Mo)-Zr-B bulk amorphous steels

NASA Astrophysics Data System (ADS)

Si, Jiajia; Wu, Yidong; Wang, Tan; Liu, Yanhui; Hui, Xidong

2018-07-01

Various corrosive environments in daily life and industry have put forward high requirement on corrosion resistance of metals, especially steels. Unlike the strict demand in Cr content of crystalline stainless steels, amorphous steels (ASs) with lower Cr content can be endowed with outstanding corrosion resistance, while the intrinsic mechanism is not fully understood. Herein, we present a novel Fe92-x-y-zCrxMoyZr8Bz (6 ≤ x ≤ 40, 0 ≤ y ≤ 22, and 12 ≤ z ≤ 18) bulk amorphous steel (BAS) forming system and reveal the synergistic effect of Cr and Mo in determining the chemical stability of oxide films. It has been found the Fe92-x-zCrxZr8Bz BASs with 1 mm in diameter display a Cr-controlling active-passive transition at the Cr threshold of ∼25% in 1 M hydrochloric acid. When adding minor Mo into the BASs, the Cr threshold can be remarkably reduced by forming favorable hexavalent Mo oxides. The generation of Mo6+ is facilitated by atomic selective dissolution at the interface and can promote the passivation. In contrast, when the Cr content of the Mo-doped glasses exceeds 25%, few Mo6+ oxides would produce as the prior formation of protective passive films inhibits the further oxidation of Mo. Therefore, manipulating the active-passive transition properly is crucial to designing ASs with high stainlessness.

Reductive reactivity of iron(III) oxides in the east china sea sediments: characterization by selective extraction and kinetic dissolution.

PubMed

Chen, Liang-Jin; Zhu, Mao-Xu; Yang, Gui-Peng; Huang, Xiang-Li

2013-01-01

Reactive Fe(III) oxides in gravity-core sediments collected from the East China Sea inner shelf were quantified by using three selective extractions (acidic hydroxylamine, acidic oxalate, bicarbonate-citrate buffered sodium dithionite). Also the reactivity of Fe(III) oxides in the sediments was characterized by kinetic dissolution using ascorbic acid as reductant at pH 3.0 and 7.5 in combination with the reactive continuum model. Three parameters derived from the kinetic method: m 0 (theoretical initial amount of ascorbate-reducible Fe(III) oxides), k' (rate constant) and γ (heterogeneity of reactivity), enable a quantitative characterization of Fe(III) oxide reactivity in a standardized way. Amorphous Fe(III) oxides quantified by acidic hydroxylamine extraction were quickly consumed in the uppermost layer during early diagenesis but were not depleted over the upper 100 cm depth. The total amounts of amorphous and poorly crystalline Fe(III) oxides are highly available for efficient buffering of dissolved sulfide. As indicated by the m 0, k' and γ, the surface sediments always have the maximum content, reactivity and heterogeneity of reactive Fe(III) oxides, while the three parameters simultaneously downcore decrease, much more quickly in the upper layer than at depth. Albeit being within a small range (within one order of magnitude) of the initial rates among sediments at different depths, incongruent dissolution could result in huge discrepancies of the later dissolution rates due to differentiating heterogeneity, which cannot be revealed by selective extraction. A strong linear correlation of the m 0 at pH 3.0 with the dithionite-extractable Fe(III) suggests that the m 0 may represent Fe(III) oxide assemblages spanning amorphous and crystalline Fe(III) oxides. Maximum microbially available Fe(III) predicted by the m 0 at pH 7.5 may include both amorphous and a fraction of other less reactive Fe(III) phases.

Reductive Reactivity of Iron(III) Oxides in the East China Sea Sediments: Characterization by Selective Extraction and Kinetic Dissolution

PubMed Central

Chen, Liang-Jin; Zhu, Mao-Xu; Yang, Gui-Peng; Huang, Xiang-Li

2013-01-01

Reactive Fe(III) oxides in gravity-core sediments collected from the East China Sea inner shelf were quantified by using three selective extractions (acidic hydroxylamine, acidic oxalate, bicarbonate-citrate buffered sodium dithionite). Also the reactivity of Fe(III) oxides in the sediments was characterized by kinetic dissolution using ascorbic acid as reductant at pH 3.0 and 7.5 in combination with the reactive continuum model. Three parameters derived from the kinetic method: m 0 (theoretical initial amount of ascorbate-reducible Fe(III) oxides), k′ (rate constant) and γ (heterogeneity of reactivity), enable a quantitative characterization of Fe(III) oxide reactivity in a standardized way. Amorphous Fe(III) oxides quantified by acidic hydroxylamine extraction were quickly consumed in the uppermost layer during early diagenesis but were not depleted over the upper 100 cm depth. The total amounts of amorphous and poorly crystalline Fe(III) oxides are highly available for efficient buffering of dissolved sulfide. As indicated by the m 0, k′ and γ, the surface sediments always have the maximum content, reactivity and heterogeneity of reactive Fe(III) oxides, while the three parameters simultaneously downcore decrease, much more quickly in the upper layer than at depth. Albeit being within a small range (within one order of magnitude) of the initial rates among sediments at different depths, incongruent dissolution could result in huge discrepancies of the later dissolution rates due to differentiating heterogeneity, which cannot be revealed by selective extraction. A strong linear correlation of the m 0 at pH 3.0 with the dithionite-extractable Fe(III) suggests that the m 0 may represent Fe(III) oxide assemblages spanning amorphous and crystalline Fe(III) oxides. Maximum microbially available Fe(III) predicted by the m 0 at pH 7.5 may include both amorphous and a fraction of other less reactive Fe(III) phases. PMID:24260377

Reaction of amorphous/crystalline SiOC/Fe interfaces by thermal annealing

DOE PAGES

Su, Qing; Zhernenkov, Mikhail; Ding, Hepeng; ...

2017-06-12

The development of revolutionary new alloys and composites is crucial to meeting materials requirements for next generation nuclear reactors. The newly developed amorphous silicon oxycarbide (SiOC) and crystalline Fe composite system has shown radiation tolerance over a wide range of temperatures. To advance understanding of this new composite, we investigate the structure and thermal stability of the interface between amorphous SiOC and crystalline Fe by combining various experimental techniques and simulation methods. We show that the SiOC/Fe interface is thermally stable up to at least 400 °C. When the annealing temperature reaches 600 °C, an intermixed region forms at thismore » interface. This region appears to be a crystalline phase that forms an incoherent interface with the Fe layer. Density functional theory (DFT) Molecular dynamics (MD) is performed on the homogeneous SiFeOC phase to study the early stages of 2 formation of the intermixed layer. Both experimental and simulation results suggest this phase has the fayalite crystal structure. As a result, the physical processes involved in the formation of the intermixed region are discussed.« less

Temperature-Dependent Helium Ion-Beam Mixing in an Amorphous SiOC/Crystalline Fe Composite

DOE PAGES

Su, Qing; Price, Lloyd; Shao, Lin; ...

2016-10-31

Temperature dependent He-irradiation-induced ion-beam mixing between amorphous silicon oxycarbide (SiOC) and crystalline Fe was examined with a transmission electron microscope (TEM) and via Rutherford backscattering spectrometry (RBS). The Fe marker layer (7.2 ± 0.8 nm) was placed in between two amorphous SiOC layers (200 nm). The amount of ion-beam mixing after 298, 473, 673, 873, and 1073 K irradiation was investigated. Both TEM and RBS results showed no ion-beam mixing between Fe and SiOC after 473 and 673 K irradiation and a very trivial amount of ion-beam mixing (~2 nm) after 298 K irradiation. At irradiation temperatures higher than 873more » K, the Fe marker layer broke down and RBS could no longer be used to quantitatively examine the amount of ion mixing. The results indicate that the Fe/SiOC nanocomposite is thermally stable and tends to demix in the temperature range from 473 to 673 K. For application of this composite structure at temperatures of 873 K or higher, layer stability is a key consideration.« less

Quantification of microwave-induced amorphization of celecoxib in PVP tablets using transmission Raman spectroscopy.

PubMed

Edinger, Magnus; Knopp, Matthias Manne; Kerdoncuff, Hugo; Rantanen, Jukka; Rades, Thomas; Löbmann, Korbinian

2018-05-30

In this study, the influence of drug load on the microwave-induced amorphization of celecoxib (CCX) in polyvinylpyrrolidone (PVP) tablets was investigated using quantitative transmission Raman spectroscopy. A design of experiments (DoE) setup was applied for developing the quantitative model using two factors: drug load (10, 30, and 50% w/w) and amorphous fraction (0, 25, 50, 75 and 100%). The data was modeled using partial least-squares (PLS) regression and resulted in a robust model with a root mean-square error of prediction of 2.5%. The PLS model was used to study the amorphization kinetics of CCX-PVP tablets with different drug content (10, 20, 30, 40 and 50% w/w). For this purpose, transition Raman spectra were collected in 60 s intervals over a total microwave time of 10 min with an energy input of 1000 W. Using the quantitative model it was possible to measure the amorphous fraction of the tablets and follow the amorphization as a function of microwaving time. The relative amorphous fraction of CCX increased with increasing microwaving time and decreasing drug load, hence 90 ± 7% of the drug was amorphized in the tablets with 10% drug load whereas only 31 ± 7% of the drug was amorphized in the 50% CCX tablets. It is suggested that the degree of amorphization depends on drug loading. The likelihood of drug particles being in direct contact with the polymer PVP is a requirement for the dissolution of the drug into the polymer upon microwaving, and this is reduced with increasing drug load. This was further supported by polarized light microscopy that revealed evidence of crystalline particles and clusters in all the microwaved tablets. Copyright © 2018 Elsevier B.V. All rights reserved.

Local Structure and Anisotropy in the Amorphous Precursor= to Ba-Hexaferrite Thin Films

NASA Astrophysics Data System (ADS)

Snyder, J. E.; Harris, V. G.; Koon, N. C.; Sui, X.; Kryder, M. H.

1996-03-01

Ba-hexaferrite thin-films for recording media applications are commonly fabricated by a two-step process: sputter-deposition of an amorphous precursor, followed by annealing to crystallize the BaFe_12O_19 phase. The magnetic anisotropy of the crystalline films can be either in-plane or perpendicular, depending on the sputtering process used in the first step. However, conventional characterization techniques (x-ray diffraction and TEM) have been unable to observe any structure in the amorphous precursor films. In this study, such films are investigated by PD-EXAFS (polarization-dependent extended x-ray absorption fine structure). An anisotropic local ordered structure is observed around both Fe and Ba atoms in the "amorphous" films. This anisotropic local structure appears to determine the orientation of the fast-growing basal plane directions during crystallization, and thus the directions of the c-axes and the magnetic anisotropy. Results suggest that the structure of the amorphous films consists of networks made up of units of Fe atoms surrounded by their O nearest neighbors, that are connected together. Ba atoms appear to fit into in-between spaces as network-modifiers.

Framboidal iron oxide: Chondrite-like material from the black mat, Murray Springs, Arizona

NASA Astrophysics Data System (ADS)

Fayek, Mostafa; Anovitz, Lawrence M.; Allard, Lawrence F.; Hull, Sharon

2012-02-01

At the end of the Pleistocene a Younger Dryas "black mat" was deposited on top of the Pleistocene sediments in many parts of North America. A study of the magnetic fraction (~ 10,900 ± 50 B.P.) from the basal section of the black mat at Murray Springs, AZ revealed the presence of amorphous iron oxide framboids in a glassy iron-silica matrix. These framboids are very similar in appearance and chemistry to those reported from several types of carbonaceous chondrites. The glass contains iron, silicon, oxygen, vanadium and minor titanium, while the framboidal particles contain calcium as well. The major element chemistry of both the spherules and the glass matrix are consistent with the chemistry of material associated with meteorite impact sites and meteorites. Electron microscopy confirms that the glassy material is indeed amorphous, and also shows that what appear to be individual oxide particles are amorphous as well. The latter appears consistent with their overall morphology that, while euhedral, typically shows significant fracture. Based on these data, we argue that these particles are the product of a hypervelocity impact.

Effect of magnetic soft phase on the magnetic properties of bulk anisotropic Nd2Fe14B/α-Fe nanocomposite permanent magnets

NASA Astrophysics Data System (ADS)

Li, Yuqing; Yue, Ming; Zhao, Guoping; Zhang, Hongguo

2018-01-01

The effects of soft phase with different particle sizes and distributions on the Nd2Fe14B/α-Fe nanocomposite magnets have been studied by the micro-magnetism simulation. The calculated results show that smaller and/or scattered distribution of soft phase can benefit to the coercivity (H ci) of the nanocomposite magnets. The magnetization moment evolution during magnetic reversal is systematically analyzed. On the other hand, magnetic properties of anisotropic Nd-Fe-B/α-Fe nanocomposite magnets prepared by hot pressing and hot deformation methods also provide evidences for the calculated results.

The influence of voxel size on atom probe tomography data.

PubMed

Torres, K L; Daniil, M; Willard, M A; Thompson, G B

2011-05-01

A methodology for determining the optimal voxel size for phase thresholding in nanostructured materials was developed using an atom simulator and a model system of a fixed two-phase composition and volume fraction. The voxel size range was banded by the atom count within each voxel. Some voxel edge lengths were found to be too large, resulting in an averaging of compositional fluctuations; others were too small with concomitant decreases in the signal-to-noise ratio for phase identification. The simulated methodology was then applied to the more complex experimentally determined data set collected from a (Co(0.95)Fe(0.05))(88)Zr(6)Hf(1)B(4)Cu(1) two-phase nanocomposite alloy to validate the approach. In this alloy, Zr and Hf segregated to an intergranular amorphous phase while Fe preferentially segregated to a crystalline phase during the isothermal annealing step that promoted primary crystallization. The atom probe data analysis of the volume fraction was compared to transmission electron microscopy (TEM) dark-field imaging analysis and a lever rule analysis of the volume fraction within the amorphous and crystalline phases of the ribbon. Copyright © 2011 Elsevier B.V. All rights reserved.

Design of Inorganic Polymer Mortar from Ferricalsialic and Calsialic Slags for Indoor Humidity Control

PubMed Central

Kamseu, Elie; Lancellotti, Isabella; Sglavo, Vincenzo M.; Modolo, Luca; Leonelli, Cristina

2016-01-01

Amorphous silica and alumina of metakaolin are used to adjust the bulk composition of black (BSS) and white (WSS) steel slag to prepare alkali-activated (AAS) mortars consolidated at room temperature. The mix-design also includes also the addition of semi-crystalline matrix of river sand to the metakaolin/steel powders. The results showed that high strength of the steel slag/metakaolin mortars can be achieved with the geopolymerization process which was particularly affected by the metallic iron present into the steel slag. The corrosion of the Fe particles was found to be responsible for porosity in the range between 0.1 and 10 µm. This class of porosity dominated (~31 vol %) the pore network of B compared to W samples (~16 vol %). However, W series remained with the higher cumulative pore volume (0.18 mL/g) compared to B series, with 0.12 mL/g. The maximum flexural strength was 6.89 and 8.51 MPa for the W and B series, respectively. The fracture surface ESEM observations of AAS showed large grains covered with the matrix assuming the good adhesion bonds between the gel-like geopolymer structure mixed with alkali activated steel slag and the residual unreacted portion. The correlation between the metallic iron/Fe oxides content, the pore network development, the strength and microstructure suggested the steel slag's significant action into the strengthening mechanism of consolidated products. These products also showed an interesting adsorption/desorption behavior that suggested their use as coating material to maintain the stability of the indoor relative humidity. PMID:28773529

Design of Inorganic Polymer Mortar from Ferricalsialic and Calsialic Slags for Indoor Humidity Control.

PubMed

Kamseu, Elie; Lancellotti, Isabella; Sglavo, Vincenzo M; Modolo, Luca; Leonelli, Cristina

2016-05-24

Amorphous silica and alumina of metakaolin are used to adjust the bulk composition of black (BSS) and white (WSS) steel slag to prepare alkali-activated (AAS) mortars consolidated at room temperature. The mix-design also includes also the addition of semi-crystalline matrix of river sand to the metakaolin/steel powders. The results showed that high strength of the steel slag/metakaolin mortars can be achieved with the geopolymerization process which was particularly affected by the metallic iron present into the steel slag. The corrosion of the Fe particles was found to be responsible for porosity in the range between 0.1 and 10 µm. This class of porosity dominated (~31 vol %) the pore network of B compared to W samples (~16 vol %). However, W series remained with the higher cumulative pore volume (0.18 mL/g) compared to B series, with 0.12 mL/g. The maximum flexural strength was 6.89 and 8.51 MPa for the W and B series, respectively. The fracture surface ESEM observations of AAS showed large grains covered with the matrix assuming the good adhesion bonds between the gel-like geopolymer structure mixed with alkali activated steel slag and the residual unreacted portion. The correlation between the metallic iron/Fe oxides content, the pore network development, the strength and microstructure suggested the steel slag's significant action into the strengthening mechanism of consolidated products. These products also showed an interesting adsorption/desorption behavior that suggested their use as coating material to maintain the stability of the indoor relative humidity.

Ultra-high power capabilities in amorphous FePO4 thin films

NASA Astrophysics Data System (ADS)

Gandrud, Knut B.; Nilsen, Ola; Fjellvåg, Helmer

2016-02-01

Record breaking electrochemical properties of FePO4 have been found through investigation of the thickness dependent electrochemical properties of amorphous thin film electrodes. Atomic layer deposition was used for production of thin films of amorphous FePO4 with highly accurate thickness and topography. Electrochemical characterization of these thin film electrodes revealed that the thinner electrodes behave in a pseudocapacitive manner even at high rates of Li+ de/intercalation, which enabled specific powers above 1 MW kg-1 FePO4 to be obtained with minimal capacity loss. In addition, a self-enhancing kinetic effect was observed during cycling enabling more than 10,000 cycles at current rates approaching that of a supercapacitor (11s charge/discharge). The current findings may open for construction of ultra-high power battery electrodes that combines the energy density of batteries with the power capabilities of supercapacitors.

Direct /TEM/ observation of the catalytic oxidation of amorphous carbon by Pd particles

NASA Technical Reports Server (NTRS)

Moorhead, R. D.; Poppa, H.; Heinemann, K.

1980-01-01

The catalytic oxidation of amorphous carbon substrates by Pd particles is observed by in situ transmission electron microscopy. Various modes of selective attack of the carbon substrate in the immediate neighborhood of Pd particles are observed, which can be correlated with different degrees of particle mobility. Using amorphous substrates we have been able to demonstrate that the particle-substrate interaction is influenced by the structure of the particle. This has not previously been noted.

Influence of Weak External Magnetic Field on Amorphous and Nanocrystalline Fe-based Alloys

NASA Astrophysics Data System (ADS)

Degmová, J.; Sitek, J.

2010-07-01

Nanoperm, Hitperm and Finamet amorphous and nanocrystalline alloys were measured by Mössbauer spectrometry in a weak external magnetic field of 0.5 T. It was shown that the most sensitive parameters of Mössbauer spectra are the intensities of the 2nd and the 5th lines. Rather small changes were observed also in the case of internal magnetic field values. The spectrum of nanocrystalline Nanoperm showed the increase in A23 parameter (ratio of line intensities) from 2.4 to 3.7 and decrease of internal magnetic field from 20 to 19 T for amorphous subspectrum under the influence of magnetic field. Spectrum of nanocrystalline Finemet shown decrease in A23 parameter from 3.5 to 2.6 almost without a change in the internal magnetic field value. In the case of amorphous Nanoperm and Finemet samples, the changes are almost negligible. Hitperm alloy showed the highest sensitivity to the weak magnetic field, when the A23 parameter increased from 0.4 to 2.5 in the external magnetic fields. The A23 parameter of crystalline subspectrum increased from 2.7 to 3.8 and the value of internal magnetic field corresponding to amorphous subspectrum increased from 22 to 24 T. The behavior of nanocrystalline alloys under weak external magnetic field was analyzed within the three-level relaxation model of magnetic dynamics in an assembly of single-domain particles.

Nanosized amorphous calcium carbonate stabilized by poly(ethylene oxide)-b-poly(acrylic acid) block copolymers.

PubMed

Guillemet, Baptiste; Faatz, Michael; Gröhn, Franziska; Wegner, Gerhard; Gnanou, Yves

2006-02-14

Particles of amorphous calcium carbonate (ACC), formed in situ from calcium chloride by the slow release of carbon dioxide by alkaline hydrolysis of dimethyl carbonate in water, are stabilized against coalescence in the presence of very small amounts of double hydrophilic block copolymers (DHBCs) composed of poly(ethylene oxide) (PEO) and poly(acrylic acid) (PAA) blocks. Under optimized conditions, spherical particles of ACC with diameters less than 100 nm and narrow size distribution are obtained at a concentration of only 3 ppm of PEO-b-PAA as additive. Equivalent triblock or star DHBCs are compared to diblock copolymers. The results are interpreted assuming an interaction of the PAA blocks with the surface of the liquid droplets of the concentrated CaCO3 phase, formed by phase separation from the initially homogeneous reaction mixture. The adsorption layer of the block copolymer protects the liquid precursor of ACC from coalescence and/or coagulation.

Comparisons of carcinogenicities of nickel compounds in rats

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

Sunderman, F.W. Jr.; Maenza, R.M.

This study demonstrates marked differences in the incidences of sarcomas in Fischer rats within 2 years after a single im injection of 4 insoluble nickel-containing powders amorphous nickel monosulfide (NiS), nickel subsulfide (..cap alpha..Ni/sub 3/S/sub 2/), partially converted nickel-iron sulfide matte, and metallic nickel. The powders (<2 ..mu..m median particle diameters) were administered in penicillin suspension, and each powder was tested at 2 dosages. Whereas ..cap alpha..Ni/sub 3/S/sub 2/ was highly carcinogenic, amorphous NiS did not induce any tumors. The carcinogenic potency of partially converted nickel-iron sulfide matte was less than ..cap alpha..Ni/sub 3/S/sub 2/ but greater than Ni powder.more » No sarcomas occurred at the injection site in two groups of control rats that received im injections of penicillin or Fe powder. The observed differences in carcinogenic potencies of ..cap alpha..Ni/sub 3/S/sub 2/ and amorphous NiS may provide an experimental approach to elucidate the molecular mechanisms of nickel carcinogenesis.« less

Electromagnetic wave absorbing properties and hyperfine interactions of Fe—Cu—Nb—Si—B nanocomposites

NASA Astrophysics Data System (ADS)

Han, Man-Gui; Guo, Wei; Wu, Yan-Hui; Liu, Min; Magundappa, L. Hadimani

2014-08-01

The Fe—Cu—Nb—Si—B alloy nanocomposite containing two ferromagnetic phases (amorphous phase and nanophase phase) is obtained by properly annealing the as-prepared alloys. High resolution transmission electron microscopy (HR-TEM) images show the coexistence of these two phases. It is found that Fe—Si nanograins are surrounded by the retained amorphous ferromagnetic phase. Mössbauer spectroscopy measurements show that the nanophase is the D03-type Fe—Si phase, which is employed to find the atomic fractions of resonant 57Fe atoms in these two phases. The microwave permittivity and permeability spectra of Fe—Cu—Nb—Si—B nanocomposite are measured in the frequency range of 0.5 GHz-10 GHz. Large relative microwave permeability values are obtained. The results show that the absorber containing the nanocomposite flakes with a volume fraction of 28.59% exhibits good microwave absorption properties. The reflection loss of the absorber is less than -10 dB in a frequency band of 1.93 GHz-3.20 GHz.

Preparation of ritonavir nanosuspensions by microfluidization using polymeric stabilizers: I. A Design of Experiment approach.

PubMed

Karakucuk, Alptug; Celebi, Nevin; Teksin, Zeynep Safak

2016-12-01

The objective of this study was to prepare ritonavir (RTV) nanosuspensions, an anti-HIV protease inhibitor, to solve its poor water solubility issues. The microfluidization method with a pre-treatment step was used to obtain the nanosuspensions. Design of Experiment (DoE) approach was performed in order to understand the effect of the critical formulation parameters which were selected as polymer type (HPMC or PVP), RTV to polymer ratio, and number of passes. Interactions between the formulation variables were evaluated according to Univariate ANOVA. Particle size, particle size distribution and zeta potential were selected as dependent variables. Scanning electron microscopy, X-ray powder diffraction, and differential scanning calorimetry were performed for the in vitro characterization after lyophilization of the optimum nanosuspension formulation. The saturation solubility was examined in comparison with coarse powder, physical mixture and nanosuspension. In vitro dissolution studies were conducted using polyoxyethylene 10 lauryl ether (POE10LE) and biorelevant media (FaSSIF and FeSSIF). The results showed nanosuspensions were partially amorphous and spherically shaped with particle sizes ranging from 400 to 600nm. Moreover, 0.1-0.4 particle size distribution and about -20mV zeta potential values were obtained. The nanosuspension showed a significantly increased solubility when compared to coarse powder (3.5 fold). Coarse powder, physical mixture, nanosuspension and commercial product dissolved completely in POE10LE; however, cumulative dissolved values reached ~20% in FaSSIF for the commercial product and nanosuspension. The nanosuspension showed more than 90% drug dissolved in FeSSIF compared to the commercial product which showed ~50% in the same medium. It was determined that RTV dissolution was increased by nanosuspension formulation. We concluded that DoE approach is useful to develop nanosuspension formulation to improve solubility and dissolution rate of RTV. Copyright © 2016 Elsevier B.V. All rights reserved.

Microstructure evaluation for Dy-free Nd-Fe-B sintered magnets with high coercivity

NASA Astrophysics Data System (ADS)

Goto, R.; Matsuura, M.; Sugimoto, S.; Tezuka, N.; Une, Y.; Sagawa, M.

2012-04-01

Nd-Fe-B sintered magnets are used for motors of hybrid or electric vehicles due to their high energy products. Dy is added to Nd-Fe-B sintered magnets to work in a high temperature environment. Although the addition of Dy decreases the magnetization of Nd-Fe-B magnets, it increases coercivity; a decrease in the amount of Dy is strongly required. Recently, Nd-Fe-B sintered magnets with a grain size of 1 μm achieved high coercivity of ˜20 kOe without the addition of Dy or other heavy rare earth elements. In this paper, the microstructure of their magnets was observed and compared to magnets with a grain size of ˜3 μm. The coercivity of magnets consisting of larger particles was 17 kOe. Microstructures were observed by the scanning electron microscope and the shapes of grains and the distribution of the Nd-rich phase were evaluated. The observation was promoted in two directions. One direction is the plane perpendicular to the magnetically aligned direction (c plane side) and the other is the side parallel to the magnetically aligned direction (c axis side). For magnets consisting of smaller particles, the shapes of grains are isotropic for the c plane side and elongated for the c axis side. The angle of minor axis prefers to be parallel to magnetically aligned direction. The distribution of the Nd-rich phase for magnets was also evaluated for both magnets. The distribution of the Nd-rich phase at triple junctions for the magnets with smaller particles becomes homogeneous compared to that for magnets with larger particles. It is considered that Dy-free magnets with high coercivity were realized by the achievement of homogeneous distribution of Nd-rich phase besides decreasing grain size.

Magnetic properties and magnetization reversal mechanism of Nd-Fe-B nanoparticles synthesized by a sol-gel method

NASA Astrophysics Data System (ADS)

Rahimi, Hamed; Ghasemi, Ali; Mozaffarinia, Reza; Tavoosi, Majid

2017-12-01

Nd-Fe-B oxide powders with various pH were prepared using chloride and nitrate precursors including NdCl3·6H2O, FeCl3·6H2O, H3BO3, Nd2O3, Fe(NO3)3·9H2O, HNO3, citric acid (CA), ethylene glycol (EG) by Pechini type sol-gel method. The pH of chloride and nitrate base sols were 0 and 2.2, respectively. Mixed oxide powders were obtained by calcination and annealing the gels. These oxides by using a reduction-diffusion process under high vacuum and employing CaH2 as reducing agent at 800 °C were hated to prepare Nd2Fe14B nanoparticles. The role of pH on phase, morphologies, microstructure, and magnetic properties of the powders were investigated. The results show that with a decrease in pH, the average particle size and coercivity of Nd-Fe-B oxide powders were decreased and increased, respectively. Nd2Fe14B nanoparticles were formed successfully after reduction process. The average particle size of reduction treated products were 30 and 65 nm for powders which made of chloride and nitrate base metal salts, respectively. Final powders which made of chloride and nitrate base metal salts had a saturation magnetization of 127.7 emu/g and 122.8 emu/g while the coercivity of samples were 3.32 kOe and 1.82 kOe, respectively. The experimental results in the angular dependence of coercivity indicated that the normalized coercivity of the permanent magnets Hc(θ)/Hc(0) obeys the 1/cosθ law and intermediate between the 1/cosθ law and Stoner-Wohlfarth formula for different Nd2Fe14B magnets which made of nitrate and chloride base metal salts, respectively. Also, the results show that different Nd2Fe14B magnets which made of nitrate and chloride base metal salts had the maximum energy product of 5 and 16 MGOe, respectively. The Henkel plot showed that magnetic phases in synthesized NdFeB magnets which made of chloride and nitrate base metal salts were coupled by exchange and dipolar interactions, respectively. Different average particle size, morphology and microstructure were the reasons for variation of magnetic properties.

An amorphous FeMoS4 nanorod array toward efficient hydrogen evolution electrocatalysis under neutral conditions.

PubMed

Ren, Xiang; Wang, Weiyi; Ge, Ruixiang; Hao, Shuai; Qu, Fengli; Du, Gu; Asiri, Abdullah M; Wei, Qin; Chen, Liang; Sun, Xuping

2017-08-08

It is highly attractive to develop efficient hydrogen-evolving electrocatalysts under neutral conditions. In this communication, we report an amorphous FeMoS 4 nanorod array on carbon cloth (FeMoS 4 NRA/CC) prepared by hydrothermal treatment of an FeOOH nanorod array on carbon cloth (FeOOH NRA/CC) in (NH 4 ) 2 MoS 4 solution. As a 3D electrode for hydrogen evolution electrocatalysis, this FeMoS 4 NRA/CC demonstrates superior catalytic activity and strong long-term electrochemical durability in 1.0 M phosphate buffered saline (pH: 7). It needs an overpotential of 204 mV to drive a geometrical current density of 10 mA cm -2 , which is 450 mV less than that for FeOOH NRA/CC. Density functional theory calculations suggest that FeMoS 4 has a more favourable hydrogen adsorption free energy than FeOOH.

Carbon-coated CoFe–CoFe2O4 composite particles with high and dual-band electromagnetic wave absorbing properties

NASA Astrophysics Data System (ADS)

Guan, Zhen-Jie; Jiang, Jian-Tang; Chen, Na; Gong, Yuan-Xun; Zhen, Liang

2018-07-01

SiO2 and TiO2, as conventional dielectric shells of ferromagnetic/dielectric composite particles, can protect ferromagnetic particles from aggregation and oxidation, but contribute little to electromagnetic loss. In this work, we designed nano-assembled CoFe–CoFe2O4@C composite particles, in which ferrites with high permeability were dielectric elements and carbon was introduced as protective layers, aiming for high-efficiency microwave absorption. These assembled particles with different CoFe contents were prepared through solvothermal methods and subsequent hydrogen-thermal reduction. CoFe nanoparticles were dispersed on a CoFe2O4 matrix via an in situ reduction transformation from CoFe2O4 to CoFe. The microstructure evolution of composite particles and corresponding electromagnetic properties tailoring were investigated. The content and size of CoFe as well as the porosity of composite particles increase gradually as the annealing temperature increases. A maximum reflection loss (RL max) of –71.73 dB is observed at 4.78 GHz in 3.4 mm thick coating using particles annealed at 500 °C as fillers. The coating presents double-band absorbing characteristics, as broad effective absorption bandwidth with RL > 5 (ERL 5) and high RL max are observed in both S-C and X-Ku bands. The tunability as well as the assembled characteristic of the electromagnetic property that endued from the composite structure contributes to the excellent electromagnetic wave absorbing performances.

Gas phase condensation of superparamagnetic iron oxide-silica nanoparticles - control of the intraparticle phase distribution

NASA Astrophysics Data System (ADS)

Stötzel, C.; Kurland, H.-D.; Grabow, J.; Müller, F. A.

2015-04-01

Spherical, softly agglomerated and superparamagnetic nanoparticles (NPs) consisting of maghemite (γ-Fe2O3) and amorphous silica (SiO2) were prepared by CO2 laser co-vaporization (CoLAVA) of hematite powder (α-Fe2O3) and quartz sand (SiO2). The α-Fe2O3 portion of the homogeneous starting mixtures was gradually increased (15 mass%-95 mass%). It was found that (i) with increasing iron oxide content the NPs' morphology changes from a nanoscale SiO2 matrix with multiple γ-Fe2O3 inclusions to Janus NPs consisting of a γ-Fe2O3 and a SiO2 hemisphere to γ-Fe2O3 NPs each carrying one small SiO2 lens on its surface, (ii) the multiple γ-Fe2O3 inclusions accumulate at the NPs' inner surfaces, and (iii) all composite NPs are covered by a thin layer of amorphous SiO2. These morphological characteristics are attributed to (i) the phase segregation of iron oxide and silica within the condensed Fe2O3-SiO2 droplets, (ii) the temperature gradient within these droplets which arises during rapid cooling in the CoLAVA process, and (iii) the significantly lower surface energy of silica when compared to iron oxide. The proposed growth mechanism of these Fe2O3-SiO2 composite NPs during gas phase condensation can be transferred to other systems comprising a glass-network former and another component that is insoluble in the regarding glass. Thus, our model will facilitate the development of novel functional composite NPs for applications in biomedicine, optics, electronics, or catalysis.Spherical, softly agglomerated and superparamagnetic nanoparticles (NPs) consisting of maghemite (γ-Fe2O3) and amorphous silica (SiO2) were prepared by CO2 laser co-vaporization (CoLAVA) of hematite powder (α-Fe2O3) and quartz sand (SiO2). The α-Fe2O3 portion of the homogeneous starting mixtures was gradually increased (15 mass%-95 mass%). It was found that (i) with increasing iron oxide content the NPs' morphology changes from a nanoscale SiO2 matrix with multiple γ-Fe2O3 inclusions to Janus NPs consisting of a γ-Fe2O3 and a SiO2 hemisphere to γ-Fe2O3 NPs each carrying one small SiO2 lens on its surface, (ii) the multiple γ-Fe2O3 inclusions accumulate at the NPs' inner surfaces, and (iii) all composite NPs are covered by a thin layer of amorphous SiO2. These morphological characteristics are attributed to (i) the phase segregation of iron oxide and silica within the condensed Fe2O3-SiO2 droplets, (ii) the temperature gradient within these droplets which arises during rapid cooling in the CoLAVA process, and (iii) the significantly lower surface energy of silica when compared to iron oxide. The proposed growth mechanism of these Fe2O3-SiO2 composite NPs during gas phase condensation can be transferred to other systems comprising a glass-network former and another component that is insoluble in the regarding glass. Thus, our model will facilitate the development of novel functional composite NPs for applications in biomedicine, optics, electronics, or catalysis. Electronic supplementary information (ESI) available: Infrared absorption of the raw powders hematite and quartz (section S1), TEM investigation of the spatial distribution of the γ-Fe2O3 inclusions (section S2), particle size distributions of the Fe2O3@SiO2 nanopowder samples (section S3), ζ-potentials of aqueous dispersions of all γ-Fe2O3@SiO2 nanopowder samples (section S4), silanization of Fe2O3@SiO2 composite nanopowders with [3-(2,3-epoxypropoxy)-propyl]trimethoxysilane (section S5), and animation composed of TEM micrographs of Fe2O3@SiO2 NPs recorded at incrementally altered tilt angles (``Rotating Fe2O3@SiO2 NP.avi''). See DOI: 10.1039/c5nr00845j

A new photocatalyst of LuFeO3 for the dye degradation

NASA Astrophysics Data System (ADS)

Zhou, M.; Yang, H.; Xian, T.; Zhang, C. R.

2015-08-01

A polyacrylamide gel route was introduced to synthesize LuFeO3 particles, where the effects of calcination temperature, calcination time and chelating agent on the products were investigated. By varying the experimental conditions, several LuFeO3 samples with sphere-, ellipsoid- and worm-like morphologies and average particle sizes of 200-270 nm were prepared. The photocatalytic activity of LuFeO3 samples was evaluated by degrading rhodamine B (RhB) under simulated-sunlight irradiation, revealing that they exhibit a pronounced photocatalytic activity. The effects of p-benzoquinone (BQ), ethanol and oxalic acid (OA) on the photocatalytic efficiency were investigated. It is observed that BQ has almost no effect on the photocatalytic degradation of RhB, ethanol exhibits a substantial suppression of RhB degradation, while OA significantly enhances the photocatalytic efficiency. Hydroxyl (•OH) radicals were examined by fluorimetry using terephthalic acid as a probe molecule, and are found to be produced over the simulated-sunlight irradiated LuFeO3 particles. The addition of ethanol leads to a quenching of •OH radicals, whereas the yield of •OH radicals is highly increased on addition of OA. Based on the experimental results, •OH radicals are suggested to be the dominant active species responsible for the dye degradation, while superoxide (•O2-) radicals play a negligible role in the photocatalysis.

A study on the formation of solid state nanoscale materials using polyhedral borane compounds

NASA Astrophysics Data System (ADS)

Romero, Jennifer V.

The formation of boron containing materials using a variety of methods was explored. The pyrolysis of a metal boride precursor solution can be accomplished using a one-source method by combining TiCl4, B10H 14 and CH3CN in one reaction vessel and pyrolyzing it at temperatures above 900 °C. Amorphous dark blue colored films were obtained after the pyrolysis reactions. Well-defined spherical shaped grains or particles were observed by SEM. The amorphous films generated contained titanium, however, the determination of the boron content of the films was inconclusive. This one pot method making metal boride thin films has the advantage of being able to dictate the stoichiometry of the reactants. Another part of this work represents the first report of both the use of metal boride materials and the use of a titanium-based compound for the formation of nanotubes. This method provides a facile method for generating well-formed boron-containing carbon nanotubes in a "one-pot" process through an efficient aerosol process. The formation of metal boride corrosion resistant layers was also explored. It was shown that metallic substrates can be effectively boronized using paste mixtures containing boron carbide and borax. The formation of a Fe4B 2 iron boride phase was achieved, however, this iron boride phase does not give enough corrosion protection. The formation of a corrosion resistant metal boride coating with strong adhesion was accomplished by boronization of a thermal sprayed nickel layer on the surface of steel. Surfactants were explored as possible nanoreactors in which metal boride nanoparticles could be formed to use as nanotube growth catalyst via room temperature reaction. Different surfactants were used, but none of them successfully generated very well dispersed metal boride nanoparticles. Nanoparticles with varying shapes and sizes were generated which were highly amorphous. The carboxylic acid derivative of closo-C2B 10 cages was explored as a ligand in the hydrothermal preparation of coordination polymers with zinc salts. It was found that the stability of the cage is apparently insufficient under these conditions and cage degradation was observed. Consequently, a preliminary investigation of the preparation of dipyridyl derivatives of both the closo-C2B 10 and the closo-B12 cages was performed.

Formation of the ZnFe2O4 phase in an electric arc furnace off-gas treatment system.

PubMed

Suetens, T; Guo, M; Van Acker, K; Blanpain, B

2015-04-28

To better understand the phenomena of ZnFe2O4 spinel formation in electric arc furnace dust, the dust was characterized with particle size analysis, X-ray fluorescence (XRF), electron backscatter diffraction (EBSD), and electron probe micro-analysis (EPMA). Different ZnFe2O4 formation reaction extents were observed for iron oxide particles with different particle sizes. ZnO particles were present as both individual particles and aggregated on the surface of larger particles. Also, the slag particles found in the off-gas were shown not to react with the zinc vapor. After confirming the presence of a ZnFe2O4 formation reaction, the thermodynamic feasibility of in-process separation - a new electric arc furnace dust treatment technology - was reevaluated. The large air intake and the presence of iron oxide particles in the off-gas were included into the thermodynamic calculations. The formation of the stable ZnFe2O4 spinel phase was shown to be thermodynamically favorable in current electric arc furnace off-gas ducts conditions even before reaching the post combustion chamber. Copyright © 2015 Elsevier B.V. All rights reserved.

Composition and molecular scale structure of nanophases formed by precipitation of biotite weathering products

NASA Astrophysics Data System (ADS)

Tamrat, Wuhib Zewde; Rose, Jérôme; Grauby, Olivier; Doelsch, Emmanuel; Levard, Clément; Chaurand, Perrine; Basile-Doelsch, Isabelle

2018-05-01

Because of their large surface area and reactivity, nanometric-size soil mineral phases have a high potential for soil organic matter stabilization, contaminant sorption or soil aggregation. In the literature, Fe and Al phases have been the main targets of batch-synthesized nanomineral studies while nano-aluminosilicates (Al and Si phases) have been mainly studied in Andic soils. In the present work, we synthesized secondary nanophases of Fe, Al and Si. To simulate a system as close as possible to soil conditions, we conducted laboratory simulations of the processes of (1) biotite alteration in acidic conditions producing a Al Si Fe Mg K leachate solution and (2) the following neoformation of secondary nanophases by titrating the leachate solution to pH 4.2, 5 and 7. The morphology of the nanophases, their size, crystallinity and chemistry were characterized by TEM-EDX on single particles and their local atomic structure by EXAFS (Extended X-ray Absorption Fine Structure) at the Fe absorption K-edge. The main nanophases formed were amorphous particles 10-60 nm in size whose composition (dominated by Fe and Si) was strongly controlled by the pH conditions at the end of the titration. At pH 4.2 and pH 7, the structure of the nanophases was dominated by the polymerization of Fe, which was hindered by Al, Si, Mg and K. Conversely, at pH 5, the polymerization of Fe was counteracted by precipitation of high amounts of Si. The synthetized nanophases were estimated to be rather analogous to nanophases formed in natural biotite-bearing soils. Because of their small size and potential high surface reactivity, the adsorption capacities of these nanophases with respect to the OM should be revisited in the framework of soil C storage.

Sulfur Effect on the Space Weathering of Airless Bodies: Laboratory Simulation

NASA Astrophysics Data System (ADS)

Sasaki, S.; Okazaki, M.; Tanaka, H.; Hiroi, T.

2017-12-01

Space weathering is the main process that should control the change of brightness and color of the surface of airless silicate bodies such and the Moon, Mercury and asteroids. S-type asteroids show more overall depletion and reddening of the spectra, and more weakening of absorption bands than ordinary chondrites. Vapor-deposition through at high-velocity dust impacts as well as implantation of intensive solar wind ions may produce the space weathering rims bearing nano-iron particles (npFe0), responsible for spectral change. Simulation experiments using nanosecond pulse laser successfully produced vapor-deposition type npFe0 to change the optical properties [1]. A small (500m) asteroid Itokawa has a weathered surface, although its surface is rocky (rough terrain) or pebble-rich (smooth terrain). In 2011, HAYABUSA returned the particulate samples from the smooth terrain. The most notable discoveries in Itokawa particles are amorphous space-weathering rims containing npFe0. Sulfur and magnesium abundances suggest the presence of nanophase FeS (and MgS) in addition to npFe0 [2]. The presence of npFeS in asteroidal regolith is compatible with the observation of regolith breccia meteorites. On Mercury, MESSENGER revealed a high sulfur abundance (2wt% on average up to 4wt%), which can account for all of Fe by FeS. Both npFeS and npMgS may play an important role also on the surface of Mercury by lowering albedo. In our laboratory simulation using pulsed laser, spectral changes of olivine samples are facilitated when FeS is mixed (5-10wt%) (Fig.1). Nanophase Fe is confirmed by TEM. The darkening feature is reduced by additional heading at 150C, which would suggest the presence of volatile residue. Mixing of pure sulfur particles showed some, but not significant changes after laser irradiation. We acknowledge A. Miyake and A. Tsuchiyama at Kyoto U. for TEM observation. Ref: [1] S. Sasaki et al.: Nature 410 (2001) 555; [2] T. Noguchi et al.: Science 333 (2011) 1121 Fig. 1. Spectral change after pulse laser irradiation. The vertical axis shows normalized reflectance at 2500 nm-infrared darkening, whereas the horizontal axis shows the spectral slope of reflectance ratio of 1600 nm to 560 nm that would show reddening. Size range of fine FeS is smaller than 45 micron.

Synthesis and properties of nickel cobalt boron nanoparticles

NASA Astrophysics Data System (ADS)

Patel, J.; Pankhurst, Q. A.; Parkin, I. P.

2005-01-01

Amorphous cobalt nickel boride nanoparticles were synthesised by chemical reduction synthesis in aqueous solution. Careful control of synthesis conditions and post reaction oxidation enabled the nanoparticles to be converted into a core-shell structure comprising of an amorphous Co-Ni-B core and an outer metal oxide sheet. These particles had interesting magnetic properties including saturation magnetisations and coercivities of the order of 80 emu/g and 170 Oe respectively, making them suitable for a potential use as an exchange-pinned magnetic material.

Effect of Copper and Zirconium Addition on Properties of Fe-Co-Si-B-Nb Bulk Metallic Glasses

NASA Astrophysics Data System (ADS)

Ikram, Haris; Khalid, Fazal Ahmad; Akmal, Muhammad; Abbas, Zameer

2017-07-01

In this research work, iron-based bulk metallic glasses (BMGs) have been fabricated, characterized and compared with Fe-Si alloy. BMG alloys of composition ((Fe0.6Co0.4)0.75B0.20Si0.05)96Nb4) were synthesized by suction casting technique using chilled copper die. Effect of copper and zirconium addition on magnetic, mechanical, thermal and electrochemical behavior of ((Fe0.6Co0.4)0.75B0.20Si0.05)96Nb4 BMGs was investigated. Furthermore, effect of annealing on nano-crystallization and subsequently on magnetic and mechanical behavior was also analyzed. Amorphousness of structure was evidenced by XRD analysis and microscopic visualization, whereas nano-crystallization behavior was identified by peak broadening of XRD patterns. Magnetic properties, measured by vibrating sample magnetometer, were found to be improved for as-cast BMG alloys by copper addition and further enhanced by nano-crystallization after annealing. Mechanical properties were observed to be increased by zirconium addition while slightly declined by copper addition. Potentiodynamic polarization analysis manifested the positive role of zirconium in enhancing corrosion resistance of BMGs in acidic, basic and brine mediums. Moreover, mechanical properties and corrosion analysis results affirmed the superiority of BMG alloys over Fe-Si alloy.

CFA Films in Amorphous Substrate: Structural Phase Induction and Magnetization Dynamics

NASA Astrophysics Data System (ADS)

Correa, M. A.; Bohn, F.; Escobar, V. M.

We report a systematic study of the structural and quasi-static magnetic properties, as well as of the dynamic magnetic response through MI effect, in Co2FeAl and MgO//Co2FeAl single layers and a MgO//Co2FeAl/Ag/Co2FeAl trilayered film, all grown onto an amorphous substrate. We present a new route to induce the crystalline structure in the Co2FeAl alloy and verify that changes in the structural phase of this material leads to remarkable modifications of the magnetic anisotropy and, consequently, dynamic magnetic behavior. Considering the electrical and magnetic properties of the Co2FeAl, our results open new possibilities for technological applications of this full-Heusler alloy in rigid and flexible spintronic devices.

The effect of initial pressure on growth of FeNPs in amorphous carbon films

NASA Astrophysics Data System (ADS)

Mashayekhi, Fatemeh; Shafiekhani, Azizollah; Sebt, S. Ali; Darabi, Elham

2018-04-01

Iron nanoparticles in amorphous hydrogenated carbon films (FeNPs@a-C:H) were prepared with RF-sputtering and RFPECVD methods by acetylene gas and Fe target. In this paper, deposition and sputtering process were carried out under influence of different initial pressure gas. The morphology and roughness of surface of samples were studied by AFM technique and also TEM images show the exact size of FeNPs and encapsulated FeNPs@a-C:H. The localized surface plasmon resonance peak (LSPR) of FeNPs was studied using UV-vis absorption spectrum. The results show that the intensity and position of LSPR peak are increased by increasing initial pressure. Also, direct energy gap of samples obtained by Tauc law is decreased with respect to increasing initial pressure.

Si-FeSi2/C nanocomposite anode materials produced by two-stage high-energy mechanical milling

NASA Astrophysics Data System (ADS)

Yang, Yun Mo; Loka, Chadrasekhar; Kim, Dong Phil; Joo, Sin Yong; Moon, Sung Whan; Choi, Yi Sik; Park, Jung Han; Lee, Kee-Sun

2017-05-01

High capacity retention Silicon-based nanocomposite anode materials have been extensively explored for use in lithium-ion rechargeable batteries. Here we report the preparation of Si-FeSi2/C nanocomposite through scalable a two-stage high-energy mechanical milling process, in which nano-scale Si-FeSi2 powders are besieged by the carbon (graphite/amorphous phase) layer; and investigation of their structure, morphology and electrochemical performance. Raman analysis revealed that the carbon layer structure comprised of graphitic and amorphous phase rather than a single amorphous phase. Anodes fabricated with the Si-FeSi2/C showed excellent electrochemical behavior such as a first discharge capacity of 1082 mAh g-1 and a high capacity retention until the 30th cycle. A remarkable coulombic efficiency of 99.5% was achieved within a few cycles. Differential capacity plots of the Si-FeSi2/C anodes revealed a stable lithium reaction with Si for lithiation/delithiation. The enhanced electrochemical properties of the Si-FeSi2/C nanocomposite are mainly attributed to the nano-size Si and stable solid electrolyte interface formation and highly conductive path driven by the carbon layer.

Magnetism from Fe2O3 nanoparticles embedded in amorphous SiO2 matrix

NASA Astrophysics Data System (ADS)

Sendil Kumar, A.; Bhatnagar, Anil K.

2018-02-01

Fe2O3 nanoparticles are embedded in amorphous SiO2 matrix by coprecipitation method with varying concentrations. Conditions are optimized to get almost monodispersed Fe2O3 nanoparticles with high chemical stability. Microstructure of synthesized nanoparticles is well characterized and found that Fe2O3 is in nanocrystalline form and embedded uniformly in amorphous SiO2 matrix. Enhanced surface reactivity is found for nanoparticles which influences physical properties of the SiO2 supported Fe2O3 system due to adsorption. In oxide nanoparticles, significant number of defect sites at the surface is expected but when supported medium such as SiO2 it reduces this defect concentration. Field- and temperature-dependent magnetisation studies on these samples show superparamagnetic behaviour. Superparamagnetic behaviour is seen in all the concentration systems but the coercivity observed in the lower concentration systems is found to be anomalous compared to that of higher concentrations. The observed magnetic behaviour comes from either unsaturated bond existing due to the absence of anions at the surface of nanoparticles or reconstruction of atomic orbitals taking place at interface of Fe2O3-SiO2 system.

Preferential magnetic orientation in amorphous alloys determined by NFS and Mössbauer spectroscopy

NASA Astrophysics Data System (ADS)

Procházka, Vít; Vrba, Vlastimil; Šretrová, Pavla; Smrčka, David; Miglierini, Marcel

2016-10-01

Amorphous and nanocrystalline alloys frequently exhibit anisotropic behavior, which is a consequence of magnetic moments preferential orientation. This study reports the results obtained from a set of nuclear forward scattering experiments and transmission Mössbauer spectroscopy experiments that we have run in order to determine the degree of crystallization and the preferential orientation of magnetic moments in the material. The nuclear forward scattering of synchrotron radiation and the transmission Mössbauer spectroscopy were performed on the nanocrystalline alloy of the composition Fe79Mo8Cu1B12. The experimental data were evaluated and magnetic texture was determined. Relevance of the results was confronted with transmission Mössbauer experiments.

Fabrication and characterization of novel iodine doped hollow and mesoporous hematite (Fe2O3) particles derived from sol-gel method and their photocatalytic performances.

PubMed

Demirci, Selim; Yurddaskal, Metin; Dikici, Tuncay; Sarıoğlu, Cevat

2018-03-05

In this work, iodine (I) doped hollow and mesoporous Fe 2 O 3 photocatalyst particles were fabricated for the first time through sol-gel method. Phase structure, surface morphology, particle size, specific surface area and optical band gap of the synthesized Fe 2 O 3 photocatalysts were analyzed by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), X-ray photoelectron spectroscopy (XPS), BET surface analysis, particle size analyzer and UV-vis diffuse reflectance spectrum (UV-vis DRS), respectively. Also, electrochemical properties and photoluminescence spectra of Fe 2 O 3 particles were measured. The results illustrated that high crystalline, hollow and mesoporous Fe 2 O 3 particles were formed. The optical band gap values of the Fe 2 O 3 photocatalysts changed between 2.104 and 1.93eV. Photocatalytic efficiency of Fe 2 O 3 photocatalysts were assessed via MB solution. The photocatalytic activity results exhibited that I doping enhanced the photocatalytic efficiency. 1% mole iodine doped (I-2) Fe 2 O 3 photocatalyst had 97.723% photodegradation rate and 8.638×10 -2 min -1 kinetic constant which showed the highest photocatalytic activity within 45min. Moreover, stability and reusability experiments of Fe 2 O 3 photocatalysts were carried out. The Fe 2 O 3 photocatalysts showed outstanding stability after four sequence tests. As a result, I doped Fe 2 O 3 is a good candidate for photocatalysts. Copyright © 2017 Elsevier B.V. All rights reserved.

International Conference on Liquid and Amorphous Metals (5th) Held at Los Angeles, California on August 15-19, 1983. Abstract.

DTIC Science & Technology

1983-08-19

Wang : CORROSION RESISTANCE OF AMORPHOUS AND CRYSTALLIZED Fe-Ni-Cr-W ALLOYS " 12:25 am M4 A. Yokoyama, H. Komiyama, H. Inoue, T. Masunoto, and H.M. Kimura...ENTHALPY RELAXATION IN PdNi ALLOY GLASSES 2:30 pm N3 A.I. Taub and J.L. Walter: SCALING THE COMPOSITION DEPENDENCE OF ATOMIC TRANSPORT AND STRUCTURAL...Cnn, L.Q. Wang , Y. Obi, and K. Fukamichi: LOW- TEMPERATURE SPECIFIC HEAT OF Fe-Zr AND Ni-Zr AMORPHOUS ALLOYS 2:15 pm 02 S.J. Poon: FLUX FLOW RESISTIVITY

Space Weathering in the Fine Size Fractions of Lunar Soils: Soil Maturity Effects

NASA Technical Reports Server (NTRS)

Keller, L. P.; Wentworth, S. J.; McKay, D. S.; Taylor, L. A.; Pieters, C.; Morris, R. V.

1999-01-01

The effects of space weathering on the optical properties of lunar materials have been well documented. These effects include a reddened continuum slope, lowered albedo, and attenuated absorption features in reflectance spectra of lunar soils as compared to finely comminuted rocks from the same Apollo sites. However, the regolith processes that cause these effects are not well known, nor is the petrographic setting of the products of these processes fully understood. A Lunar Soil Characterization Consortium has been formed with the purpose of systematically integrating chemical and mineralogical data with the optical properties of lunar soils. Understanding space-weathering effects is critical in order to fully integrate the lunar sample collection with remotely-sensed data from recent robotic missions (e.g., Lunar Prospector, Clementine, and Galileo) We have shown that depositional processes (condensation of impact-derived vapors, sputter deposits, accreted impact material, e.g., splash glass, spherules, etc.) are a major factor in the modification of the optical surfaces of lunar regolith materials. In mature soils, it is the size and distribution of the nanophase metal in the soil grains that has the major effect on optical properties. In this report, we compare and contrast the space-weathering effects in an immature and a mature soil with similar elemental compositions. For this study, we analyzed <10 micron sieve fractions of two Apollo 17 soils, 79221 (mature, Is/FeO = 81) and 71061 (immature, Is/FeO = 14). Details of the sieving procedures and allocation scheme are given else where. The results of other detailed chemical, mineralogical, and spectroscopic analyses of these soil samples are reported elsewhere. A representative sample of each soil was embedded in low-viscosity epoxy, and thin sections (about 70nm thick) were obtained through ultra microtomy. The thin sections used for these analyses typically contained cross sections of up to 500 individual grains. The thin sections were studied using a JEOL 2010 transmission electron microscope (TEM) equipped with a thin window energy-dispersive X-ray (EDX) spectrometer. An individual thin section was selected from each soil, and for each grain in the section we determined (1) the elemental composition by EDX; (2) whether the grain was crystalline or glassy using electron diffraction and darkfield imaging; (3) the presence or absence of rims and accreted material; and (4) the distribution of nanophase Fe where present. Most of the categories are self-evident; however, we divide the agglutinate derived material into agglutinitic glass (glass with approximately the same composition as the bulk soil that contains nanophase Fe with or without vesicles) and agglutinate fragments, which are composed of crystalline grains and agglutinitic glass. Lithic fragments are defined as polymineralic grains with no glass. Pyroxene grains have been divided into high- and low-Ca groups. As expected, there are a number of differences in the petrography of the <10-microns fractions of 79221 and 71061 given the great difference in their respective maturities, but we focus here on two major distinctions: agglutinate content and the number of grains with micropatina. Slightly over 50% of the particles in 79221 consist of agglutinitic glass and agglutinate fragments, while the remainder are predominantly crystalline mineral grains. The agglutinic glass particles contain abundant nanophase Fe and vesicles. Angular particles are rare, with most showing smooth, rounded exteriors, Of the mineral grains analyzed thus far, over 90% of the grains have amorphous rims that contain nanophase Fe (these rims are believed to have formed by vapor deposition and irradiation effects). The nanophase Fe in these rims probably accounts for a significant fraction of the increase in Is/FeO measured in these size fractions. In addition to the rims, the majority of particles also show abundant accreted material in the form of glass splashes and spherules that also contain nanophase Fe. In stark contrast, the surfaces of the mineral grains in the 71061 sample are relatively prisitine, as only about 14% of the mineral grains in the sample exhibited amorphous rims. Furthermore, the mineral particles are more angular and show greater surface roughness than in the mature sample. Accreted material on particle surfaces is rare. Agglutinitic material is a major component of the 71061 sample; however, nanophase Fe and vesicles are not as well developed as in the 79221 sample. It is now recognized that nanophase Fe is probably the main agent in modifying the optical properties of lunar soil grains. The most important result of this study is the observation that in the fine size fractions of mature soils, nearly every grain has nanophase Fe within 100 run of the particle surface. (Additional Information contained in original)

Improving the Capacity of Sodium Ion Battery Using a Virus-Templated Nanostructured Composite Cathode

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

Moradi, M; Li, Z; Qi, JF

In this work we investigated an energy-efficient biotemplated route to synthesize nanostructured FePO4 for sodium-based batteries. Self-assembled M13 viruses and single wall carbon nanotubes (SWCNTs) have been used as a template to grow amorphous FePO4 nanoparticles at room temperature (the active composite is denoted as Bio-FePO4-CNT) to enhance the electronic conductivity of the active material. Preliminary tests demonstrate a discharge capacity as high as 166 mAh/g at C/10 rate, corresponding to composition Na0.9FePO4, which along with higher C-rate tests show this material to have the highest capacity and power performance reported for amorphous FePO4 electrodes to date.

Magnetic properties and microstructure of gas atomized MRE2(Fe, Co)14B powder with ZrC addition (MRE=Nd + Y + Dy)

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

Tang, W.; Wu, Y. Q.; Dennis, K.

2009-05-12

Gas atomization powder with Zr substitutions for the MRE and ZrC additions were systematically studied. The results show that the partial substitutions of Zr and the ZrC additions effectively improved glass formability in the alloys. Scanning electron microscopy (SEM) revealed that the as-atomized powder with a particle size of less than 32 {micro}m is predominately uniform equiaxed grains with an average grain size of 1.5 {micro}m. X-ray diffraction and differential thermal analysis measurements detected very tiny amounts of amorphous phase. After annealing at 700 C for 15 min, the SEM grain microstructure exhibits a minor change, but magnetic properties aremore » substantially improved. M versus T measurements reveal that the phase composition evolved from 2:14:1 plus a small amount of 2:17 phases to a single 2:14:1 phase during the annealing process. The sieve analysis of the powders showed a particle size distribution with 90 wt % of the powder less than 45 {micro}m. The magnetic properties of the annealed powder varied with particle size. (BH){sub max} first increases with increasing particle size from 5 {micro}m, reaches the peak value in the size range of 20-25 {micro}m, and then decreases with increasing particle size. For the 20-25 {micro}m powder sample annealed at 700 C for 15 min, the (BH){sub max} of 9.6 MG Oe at room temperature and 5.6 MG Oe at 200 C were obtained, respectively.« less

Antiferromagnetism in pressure-amorphized Fe2SiO4

USGS Publications Warehouse

Kruger, M.B.; Jeanloz, R.; Pasternak, M.P.; Taylor, R.D.; Snyder, B.S.; Stacy, A.M.; Bohlen, S.R.

1992-01-01

Amorphous Fe2SiO4 synthesized at elevated pressures exhibits a Ne??el transition at a temperature identical to that observed in the crystalline form, TN = 65 (??2) kelvin at zero pressure. This behavior contrasts sharply with observations on other disordered systems, such as spin glasses, which characteristically exhibit strong "frustration" of the spins and consequent marked suppression of the Ne??el transition.

Effect of Nano-Y2O3 on Microstructure and Crack Formation in Laser Direct-Deposited In Situ Particle-Reinforced Fe-Based Coatings

NASA Astrophysics Data System (ADS)

Yin, Guili; Chen, Suiyuan; Liu, Yuanyuan; Liang, Jing; Liu, Changsheng; Kuang, Zheng

2018-03-01

In situ hard-particle-reinforced Fe-based composite coatings were prepared on Q235 steel substrates by direct laser deposition using Fe-based alloy powders containing 2 wt.% B, 3 wt.% Si and 1-3 wt.% nano-Y2O3. The microstructures, phase compositions, hardnesses and wear resistances of the deposited coatings with different nano-Y2O3 contents were studied using metallographic microscopy, scanning electron microscopy, x-ray diffraction, transmission electron microscopy, microhardness tests and pin-on-disk abrasion tests (MMW-1A), respectively. The results showed that the appropriate addition of Y2O3 played a role in grain refinement and in decreasing the number of brittle phases and impurity elements in the grain boundaries. Consequently, the number of cracks in the laser-deposited coating also decreased. The Fe-based composite coatings were mainly composed of α-Fe, γ-Fe and in situ-produced reinforced particle phases, such as Cr23C6, Cr7C3, (Cr, Fe)7C3, Fe2B, and CrFeB. When the content of nano-Y2O3 was 2 wt.%, a Fe-based composite coating with a thickness of 4 mm that was free of cracks was obtained, and its surface hardness reached 650HV. Moreover, the wear resistance of the coating with 2 wt.% nano-Y2O3 was the best among the samples studied. The presence of nano-Y2O3 increased the solubility of Cr and Si in the solid solution, which eliminated the residual austenite region, and as a result, the phase transformation from γ-Fe to α-Fe was restrained and the transformation stress was also limited, thereby decreasing the probability of cracks in the coatings.

Systematic investigation on Cadmium-incorporation in Li₂FeSiO₄/C cathode material for lithium-ion batteries.

PubMed

Zhang, Lu-Lu; Duan, Song; Yang, Xue-Lin; Liang, Gan; Huang, Yun-Hui; Cao, Xing-Zhong; Yang, Jing; Ni, Shi-Bing; Li, Ming

2014-05-27

Cadmium-incorporated Li2FeSiO4/C composites have been successfully synthesized by a solid-state reaction assisted with refluxing. The effect and mechanism of Cd-modification on the electrochemical performance of Li2FeSiO4/C were investigated in detail by X-ray powder diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, Raman spectra, transmission electron microscopy, positron annihilation lifetime spectroscopy and Doppler broadening spectrum, and electrochemical measurements. The results show that Cd not only exists in an amorphous state of CdO on the surface of LFS particles, but also enters into the crystal lattice of LFS. Positron annihilation lifetime spectroscopy and Doppler broadening spectrum analyses verify that Cd-incorporation increases the defect concentration and the electronic conductivity of LFS, thus improve the Li(+)-ion diffusion process. Furthermore, our electrochemical measurements verify that an appropriate amount of Cd-incorporation can achieve a satisfied electrochemical performance for LFS/C cathode material.

Systematic investigation on Cadmium-incorporation in Li2FeSiO4/C cathode material for lithium-ion batteries

PubMed Central

Zhang, Lu-Lu; Duan, Song; Yang, Xue-Lin; Liang, Gan; Huang, Yun-Hui; Cao, Xing-Zhong; Yang, Jing; Ni, Shi-Bing; Li, Ming

2014-01-01

Cadmium-incorporated Li2FeSiO4/C composites have been successfully synthesized by a solid-state reaction assisted with refluxing. The effect and mechanism of Cd-modification on the electrochemical performance of Li2FeSiO4/C were investigated in detail by X-ray powder diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, Raman spectra, transmission electron microscopy, positron annihilation lifetime spectroscopy and Doppler broadening spectrum, and electrochemical measurements. The results show that Cd not only exists in an amorphous state of CdO on the surface of LFS particles, but also enters into the crystal lattice of LFS. Positron annihilation lifetime spectroscopy and Doppler broadening spectrum analyses verify that Cd-incorporation increases the defect concentration and the electronic conductivity of LFS, thus improve the Li+-ion diffusion process. Furthermore, our electrochemical measurements verify that an appropriate amount of Cd-incorporation can achieve a satisfied electrochemical performance for LFS/C cathode material. PMID:24860942

Structural and magnetic characterizations of Co2FeGa/SiO2 nanoparticles prepared via chemical route

NASA Astrophysics Data System (ADS)

Priyanka, Dhaka, Rajendra S.

2018-04-01

We report the synthesis of Co2FeGa/SiO2 nanoparticles by sol-gel method and characterization usingx-ray diffraction (XRD), transmission electron microscopy (TEM) and magnetic measurements. The Rietveld refinementsof XRD data with space group Fm-3m clearly show the formation of A2 disordersingle phase and the lattice constant isfound to be 5.738 Å. The energy-dispersive x-ray spectroscopy (EDX) confirm the elemental composition close the desired values. The value of coercivity is found to be around 283 Oe and 126 Oe, measured at 10 K and 300 K, respectively. We observed the saturation magnetization significantly lower than expected from Slater-Pauling rule. This decrease in the magnetic moment might be due to the presence of amorphous SiO2 during the synthesis process. A large content of small size SiO2 particles along with Co2FeGa nanoparticles are also found in TEM study.

Air-stable nZVI formation mediated by glutamic acid: solid-state storable material exhibiting 2D chain morphology and high reactivity in aqueous environment

NASA Astrophysics Data System (ADS)

Siskova, Karolina; Tucek, Jiri; Machala, Libor; Otyepkova, Eva; Filip, Jan; Safarova, Klara; Pechousek, Jiri; Zboril, Radek

2012-03-01

We report a new chemical approach toward air-stable nanoscale zero-valent iron (nZVI). The uniformly sized (approx. 80 nm) particles, formed by the reduction of Fe(II) salt by borohydride in the presence of glutamic acid, are coated by a thin inner shell of amorphous ferric oxide/hydroxide and a secondary shell consisting of glutamic acid. The as-prepared nanoparticles stabilized by the inorganic-organic double shell create 2D chain morphologies. They are storable for several months under ambient atmosphere without the loss of Fe(0) relative content. They show one order of magnitude higher rate constant for trichlorethene decomposition compared with the pristine particles possessing only the inorganic shell as a protective layer. This is the first example of the inorganic-organic (consisting of low-molecular weight species) double-shell stabilized nanoscale zero-valent iron material being safely transportable in solid-state, storable on long-term basis under ambient conditions, environmentally acceptable for in situ applications, and extraordinarily reactive if contacted with reducible pollutants, all in one.

Fractional iron solubility of aerosol particles enhanced by biomass burning and ship emission in Shanghai, East China.

PubMed

Fu, H B; Shang, G F; Lin, J; Hu, Y J; Hu, Q Q; Guo, L; Zhang, Y C; Chen, J M

2014-05-15

In terms of understanding Fe mobilization from aerosol particles in East China, the PM2.5 particles were collected in spring at Shanghai. Combined with the backtrajectory analysis, the PM2.5/PM10 and Ca/Al ratios, a serious dust-storm episode (DSE) during the sampling was identified. The single-particle analysis showed that the major iron-bearing class is the aluminosilicate dust during DSE, while the Fe-bearing aerosols are dominated by coal fly ash, followed by a minority of iron oxides during the non-dust storm days (NDS). Chemical analyses of samples showed that the fractional Fe solubility (%FeS) is much higher during NDS than that during DSE, and a strong inverse relationship of R(2)=0.967 between %FeS and total atmospheric iron loading were found, suggested that total Fe (FeT) is not controlling soluble Fe (FeS) during the sampling. Furthermore, no relationship between FeS and any of acidic species was established, suggesting that acidic process on aerosol surfaces are not involved in the trend of iron solubility. It was thus proposed that the source-dependent composition of aerosol particles is a primary determinant for %FeS. Specially, the Al/Fe ratio is poorly correlated (R(2)=0.113) with %FeS, while the apparent relationship between %FeS and the calculated KBB(+)/Fe ratio (R(2)=0.888) and the V/Fe ratio (R(2)=0.736) were observed, reflecting that %FeS could be controlled by both biomass burning and oil ash from ship emission, rather than mineral particles and coal fly ash, although the latter two are the main contributors to the atmospheric Fe loading during the sampling. Such information can be useful improving our understanding on iron solubility on East China, which may further correlate with iron bioavailability to the ocean, as well as human health effects associated with exposure to fine Fe-rich particles in densely populated metropolis in China. Copyright © 2014 Elsevier B.V. All rights reserved.

The effect of high energy concentration source irradiation on structure and properties of Fe-based bulk metallic glass

NASA Astrophysics Data System (ADS)

Pilarczyk, Wirginia

2016-06-01

Metallic glasses exhibit metastable structure and maintain this relatively stable amorphous state within certain temperature range. High intensity laser beam was used for the surface irradiation of Fe-Co-B-Si-Nb bulk metallic glasses. The variable parameter was laser beam pulse energy. For the analysis of structure and properties of bulk metallic glasses and their surface after laser remelting the X-ray analysis, microscopic observation and test of mechanical properties were carried out. Examination of the nanostructure of amorphous materials obtained by high pressure copper mold casting method and the irradiated with the use of TITAN 80-300 HRTEM was carried out. Nanohardness and reduced Young's modulus of particular amorphous and amorphous-crystalline material zone of the laser beam were examined with the use of Hysitron TI950 Triboindenter nanoindenter and with the use of Berkovich's indenter. The XRD and microscopic analysis showed that the test material is amorphous in its structure before irradiation. Microstructure observation with electron transmission microscopy gave information about alloy crystallization in the irradiated process. Identification of given crystal phases allows to determine the kind of crystal phases created in the first place and also further changes of phase composition of alloy. The main value of the nanohardness of the surface prepared by laser beam has the order of magnitude similar to bulk metallic glasses formed by casting process irrespective of the laser beam energy used. Research results analysis showed that the area between parent material and fusion zone is characterized by extraordinarily interesting structure which is and will be the subject of further analysis in the scope of bulk metallic glasses amorphous structure and high energy concentration source. The main goal of this work is the results' presentation of structure and chosen properties of the selected bulk metallic glasses after casting process and after irradiation process employing the high energy concentration sources.

Mechanism of selenite removal by a mixed adsorbent based on Fe-Mn hydrous oxides studied using X-ray absorption spectroscopy.

PubMed

Chubar, Natalia; Gerda, Vasyl; Szlachta, Małgorzata

2014-11-18

Selenium cycling in the environment is greatly controlled by various minerals, including Mn and Fe hydrous oxides. At the same time, such hydrous oxides are the main inorganic ion exchangers suitable (on the basis of their chemical nature) to sorb (toxic) anions, separating them from water solutions. The mechanism of selenite adsorption by the new mixed adsorbent composed of a few (amorphous and crystalline) phases [maghemite, MnCO3, and X-ray amorphous Fe(III) and Mn(III) hydrous oxides] was studied by extended X-ray absorption fine structure (EXAFS) spectroscopy [supported by Fourier transform infrared (FTIR) and X-ray diffraction (XRD) data]. The complexity of the porous adsorbent, especially the presence of the amorphous phases of Fe(III) and Mn(III) hydrous oxides, is the main reason for its high selenite removal performance demonstrated by batch and column adsorption studies shown in the previous work. Selenite was bound to the material via inner-sphere complexation (via oxygen) to the adsorption sites of the amorphous Fe(III) and Mn(III) oxides. This anion was attracted via bidentate binuclear corner-sharing coordination between SeO3(2-) trigonal pyramids and both FeO6 and MnO6 octahedra; however, the adsorption sites of Fe(III) hydrous oxides played a leading role in selenite removal. The contribution of the adsorption sites of Mn(III) oxide increased as the pH decreased from 8 to 6. Because most minerals have a complex structure (they are seldom based on individual substances) of various crystallinity, this work is equally relevant to environmental science and environmental technology because it shows how various solid phases control cycling of chemical elements in the environment.

Small-Angle Neutron Scattering Studies of Magnetic Correlation Lengths in Nanoparticle Assemblies

NASA Astrophysics Data System (ADS)

Majetich, Sara

2009-03-01

Small-angle neutron scattering (SANS) measurements of ordered arrays of surfactant-coated magnetic nanoparticle reveal characteristic length scales associated with interparticle and intraparticle magnetic ordering. The high degree of uniformity in the monodisperse nanoparticle size and spacing leads to a pronounced diffraction peak and allows for a straightforward determination of these length scales [1]. There are notable differences in these length scales depending on the particle moment, which depends on the material (Fe, Co, Fe3O4) and diameter, and also on whether the metal particle core is surrounded by an oxide shell. For 8.5 nm particles containing an Fe core and thick Fe3O4 shell, evidence of a spin flop phase is seen in the magnetite shell when a field is applied , but not when the shell thickness is ˜0.5 nm [2]. 8.0 nm particles with an e-Co core and 0.75 nm CoO shell show no exchange bias effects while similar particles with a 2 nm thick shell so significant training effects below 90 K. Polarized SANS studied of 7 nm Fe3O4 nanoparticle assemblies show the ability to resolve the magnetization components in 3D. [4pt] [1] M. Sachan, C. Bonnoit, S. A. Majetich, Y. Ijiri, P. O. Mensah-Bonsu, J. A. Borchers, and J. J. Rhyne, Appl. Phys. Lett. 92, 152503 (2008). [0pt] [2] Yumi Ijiri, Christopher V. Kelly, Julie A. Borchers, James J. Rhyne, Dorothy F. Farrell, Sara A. Majetich, Appl. Phys. Lett. 86, 243102-243104 (2005). [0pt] [3] K. L. Krycka, R. Booth, J. A. Borchers, W. C. Chen, C. Conlon, T. Gentile, C. Hogg, Y. Ijiri, M. Laver, B. B. Maranville, S. A. Majetich, J. Rhyne, and S. M. Watson, Physica B (submitted).

High Resolution Transmission Electron Microscopy (HRTEM) of nanophase ferric oxides

NASA Technical Reports Server (NTRS)

Golden, D. C.; Morris, R. V.; Ming, D. W.; Lauer, H. V., Jr.

1994-01-01

Iron oxide minerals are the prime candidates for Fe(III) signatures in remotely sensed Martian surface spectra. Magnetic, Mossbauer, and reflectance spectroscopy have been carried out in the laboratory in order to understand the mineralogical nature of Martian analog ferric oxide minerals of submicron or nanometer size range. Out of the iron oxide minerals studied, nanometer sized ferric oxides are promising candidates for possible Martian spectral analogs. 'Nanophase ferric oxide (np-Ox)' is a generic term for ferric oxide/oxihydroxide particles having nanoscale (less than 10 nm) particle dimensions. Ferrihydrite, superparamagnetic particles of hematite, maghemite and goethite, and nanometer sized particles of inherently paramagnetic lepidocrocite are all examples of nanophase ferric oxides. np-Ox particles in general do not give X-ray diffraction (XRD) patterns with well defined peaks and would often be classified as X-ray amorphous. Therefore, different np-Oxs preparations should be characterized using a more sensitive technique e.g., high resolution transmission electron microscopy (HRTEM). The purpose of this study is to report the particle size, morphology and crystalline order, of five np-Ox samples by HRTEM imaging and electron diffraction (ED).

Amorphous Silica Micro Powder Additive Influence on Tensile Strength of One-Ply Particle Board

NASA Astrophysics Data System (ADS)

Pitukhin, A. V.; Kolesnikov, G. N.; Panov, N. G.; Vasilyev, S. B.

2018-03-01

The methods and results of experimental investigation on the additive influence of amorphous silica micro powder when mixed in the glue for one-ply particle board are presented in the article. Wooden particles of coniferous and hardwood species as well as glue solution based on carbamide-formaldehyde resin were used for boards manufacturing. The amorphous silica micro powder contained particles on the average 8 μm by the size and specific surface 120…400 m2/g was used in experiment. The samples were tested to determine their physical-mechanical properties. It was found that 1 % amorphous silica micro powder additive increases the breaking point of one-ply particle board under tensile stress by 143 %.

Ultra-soft magnetic properties and correlated phase analysis by {sup 57}Fe Mössbauer spectroscopy of Fe{sub 74}Cu{sub 0.8}Nb{sub 2.7}Si{sub 15.5}B{sub 7} alloy

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

Manjura Hoque, S.; Liba, S. I.; Akhter, Shireen

2016-02-15

A detailed study of magnetic softness has been performed on FINEMENT type of ribbons by investigating the BH loop with maximum applied field of 960 A/m. The ribbon with the composition of Fe{sub 74}Cu{sub 0.8}Nb{sub 2.7}Si{sub 15.5}B{sub 7} was synthesized by rapid solidification technique and the compositions volume fraction was controlled by changing the annealing condition. Detail phase analysis was performed through X-ray diffraction (XRD), Differential scanning calorimetry (DSC), Vibrating sample magnetometer (VSM) and Mössbauer spectroscopy in order to correlate the ultrasoft magnetic properties with the volume fraction of amorphous and α-Fe(Si) soft nano composites. Bright (BF) and dark fieldmore » (DF) image with selective area diffraction (SAD) patterns by the transmission electron microscopy (TEM) of the sample annealed for the optimized annealed condition at 853 K for 3 min reveals nanocrystals with an average size between 10-15 nm possessing the bcc structure which matches with the grain size revealed by the X-ray diffraction. Kinetics of crystallization of α-Fe(Si) phases has been determined by DSC curves. Extremely small coercivity of 30.9 A/m and core loss of 2.5 W/Kg for the sample annealed at 853 K for 3 min was found. Similar values for other crystalline conditions were determined by using BH loop tracer with a maximum applied field of around 960 A/m. Mössbauer spectroscopy was used to determine chemical shift, hyperfine field distribution (HFD), and peak width of different phases. The volume fractions of the relative amount of amorphous and crystalline phases are also determined by Mössbauer spectroscopy. High saturation magnetization along with ultrasoft magnetic properties exhibits very high potentials technological applications.« less

Ultra-soft magnetic properties and correlated phase analysis by 57Fe Mössbauer spectroscopy of Fe74Cu0.8Nb2.7Si15.5B7 alloy

NASA Astrophysics Data System (ADS)

Manjura Hoque, S.; Liba, S. I.; Anirban, A.; Choudhury, Shamima; Akhter, Shireen

2016-02-01

A detailed study of magnetic softness has been performed on FINEMENT type of ribbons by investigating the BH loop with maximum applied field of 960 A/m. The ribbon with the composition of Fe74Cu0.8Nb2.7Si15.5B7 was synthesized by rapid solidification technique and the compositions volume fraction was controlled by changing the annealing condition. Detail phase analysis was performed through X-ray diffraction (XRD), Differential scanning calorimetry (DSC), Vibrating sample magnetometer (VSM) and Mössbauer spectroscopy in order to correlate the ultrasoft magnetic properties with the volume fraction of amorphous and α-Fe(Si) soft nano composites. Bright (BF) and dark field (DF) image with selective area diffraction (SAD) patterns by the transmission electron microscopy (TEM) of the sample annealed for the optimized annealed condition at 853 K for 3 min reveals nanocrystals with an average size between 10-15 nm possessing the bcc structure which matches with the grain size revealed by the X-ray diffraction. Kinetics of crystallization of α-Fe(Si) phases has been determined by DSC curves. Extremely small coercivity of 30.9 A/m and core loss of 2.5 W/Kg for the sample annealed at 853 K for 3 min was found. Similar values for other crystalline conditions were determined by using BH loop tracer with a maximum applied field of around 960 A/m. Mössbauer spectroscopy was used to determine chemical shift, hyperfine field distribution (HFD), and peak width of different phases. The volume fractions of the relative amount of amorphous and crystalline phases are also determined by Mössbauer spectroscopy. High saturation magnetization along with ultrasoft magnetic properties exhibits very high potentials technological applications.

Why is it so difficult to classify Renazzo-type (CR) carbonaceous chondrites? - Implications from TEM observations of matrices for the sequences of aqueous alteration

NASA Astrophysics Data System (ADS)

Abreu, Neyda M.

2016-12-01

A number of different classifications have been proposed for the CR chondrites; this study aims at reconciling these different schemes. Mineralogy-based classification has proved particularly challenging for weakly to moderately altered CRs because incipient mineral replacement and elemental mobilization arising from aqueous alteration only affected the most susceptible primary phases, which are generally located in the matrix. Secondary matrix phases are extremely fine-grained (generally sub-micron) and heterogeneously mixed with primary nebular materials. Compositional and isotopic classification parameters are fraught with confounding factors, such as terrestrial weathering, impact processes, and variable abundance of clasts from different regions of the CR parent body or from altogether different planetary bodies. Here, detailed TEM observations from eighteen FIB sections retrieved from the matrices of nine Antarctic CR chondrites (EET 96259, GRA 95229, GRO 95577, GRO 03116, LAP 02342, LAP 04516, LAP 04720, MIL 07525, and MIL 090001) are presented, representing a range of petrologic types. Amorphous Fe-Mg silicates are found to be the dominant phase in all but the most altered CR chondrite matrices, which still retain significant amounts of these amorphous materials. Amorphous Fe-Mg silicates are mixed with phyllosilicates at the nanometer scale. The ratio of amorphous Fe-Mg silicates to phyllosilicates decreases as: (1) the size of phyllosilicates, (2) abundance of magnetite, and (3) replacement of Fe-Ni sulfides increase. Carbonates are only abundant in the most altered CR chondrite, GRO 95577. Nanophase Fe-Ni metal and tochilinite are present small abundances in most CR matrices. Based on the presence, abundance and size of phyllosilicates with respect to amorphous Fe-Mg silicates, the sub-micron features of CR chondrites have been linked to existing classification sequences, and possible reasons for inconsistencies among classification schemes are discussed.

The evolution of in-plane magnetic anisotropy in CoFeB/GaAs(001) films annealed at different temperatures

NASA Astrophysics Data System (ADS)

Tu, Hongqing; Wang, Ji; Wei, Lujun; Yuan, Yuan; Zhang, W.; You, Biao; Du, Jun

2018-05-01

A considerable in-plane uniaxial magnetic anisotropy (UMA) field (Hu ˜ 300 Oe) could be achieved when the amorphous CoFeB film was deposited on the GaAs(001) wafer by magnetron-sputtering after proper etch-annealed procedure. In order to get deep insights into the mechanism of the UMA, the film was annealed at different temperatures and the evolution of the in-plane magnetic anisotropy was investigated carefully. With increasing the annealing temperature (TA), the UMA could be maintained well when TA reached 250°C, but became very weak at 300°C. However, when TA was elevated to 400°C, another UMA (Hu ˜ 130 Oe) was built accompanied with a fourfold magnetic anisotropy with its strength of about 50 Oe. In terms of the magnetic anisotropy evolution along with TA, the anelastic strain, which is thought to be resulted from the interfacial interaction between CoFeB and GaAs, may play a dominant role in producing the enhanced UMA based on the `bond-orientational' anisotropy (BOA) model.

Spectroscopic and magnetic studies of highly dispersible superparamagnetic silica coated magnetite nanoparticles

NASA Astrophysics Data System (ADS)

Tadyszak, Krzysztof; Kertmen, Ahmet; Coy, Emerson; Andruszkiewicz, Ryszard; Milewski, Sławomir; Kardava, Irakli; Scheibe, Błażej; Jurga, Stefan; Chybczyńska, Katarzyna

2017-07-01

Superparamagnetic behavior in aqueously well dispersible magnetite core-shell Fe3O4@SiO2 nanoparticles is presented. The magnetic properties of core-shell nanoparticles were measured with use of the DC, AC magnetometry and EPR spectroscopy. Particles where characterized by HR-TEM and Raman spectroscopy, showing a crystalline magnetic core of 11.5 ± 0.12 nm and an amorphous silica shell of 22 ± 1.5 nm in thickness. The DC, AC magnetic measurements confirmed the superparamagnetic nature of nanoparticles, additionally the EPR studies performed at much higher frequency than DC, AC magnetometry (9 GHz) have confirmed the paramagnetic nature of the nanoparticles. Our results show the excellent magnetic behavior of the particles with a clear magnetite structure, which are desirable properties for environmental remediation and biomedical applications.

Antibacterial activities of amorphous cefuroxime axetil ultrafine particles prepared by high gravity antisolvent precipitation (HGAP).

PubMed

Zhao, Hong; Kang, Xu-liang; Chen, Xuan-li; Wang, Jie-xin; Le, Yuan; Shen, Zhi-gang; Chen, Jian-feng

2009-01-01

In vitro and in vivo antibacterial activities on the Staphylococcus aureus and Escherichia coli of the amorphous cefuroxime axetil (CFA) ultrafine particles prepared by HGAP method were investigated in this paper. The conventional sprayed CFA particles were studied as the control group. XRD, SEM, BET tests were performed to investigate the morphology changes of the samples before and after sterile. The in vitro dissolution test, minimal inhibitory concentrations (MIC) and the in vivo experiment on mice were explored. The results demonstrated that: (i) The structure, morphology and amorphous form of the particles could be affected during steam sterile process; (ii) CFA particles with different morphologies showed varied antibacterial activities; and (iii) the in vitro and in vivo antibacterial activities of the ultrafine particles prepared by HGAP is markedly stronger than that of the conventional sprayed amorphous particles.

The Phagocytosis and Toxicity of Amorphous Silica

PubMed Central

Costantini, Lindsey M.; Gilberti, Renée M.; Knecht, David A.

2011-01-01

Background Inhalation of crystalline silica is known to cause an inflammatory reaction and chronic exposure leads to lung fibrosis and can progress into the disease, silicosis. Cultured macrophages bind crystalline silica particles, phagocytose them, and rapidly undergo apoptotic and necrotic death. The mechanism by which particles are bound and internalized and the reason particles are toxic is unclear. Amorphous silica has been considered to be a less toxic form, but this view is controversial. We compared the uptake and toxicity of amorphous silica to crystalline silica. Methodology/Principal Findings Amorphous silica particles are phagocytosed by macrophage cells and a single internalized particle is capable of killing a cell. Fluorescent dextran is released from endo-lysosomes within two hours after silica treatment and Caspase-3 activation occurs within 4 hours. Interestingly, toxicity is specific to macrophage cell lines. Other cell types are resistant to silica particle toxicity even though they internalize the particles. The large and uniform size of the spherical, amorphous silica particles allowed us to monitor them during the uptake process. In mCherry-actin transfected macrophages, actin rings began to form 1-3 minutes after silica binding and the actin coat disassembled rapidly following particle internalization. Pre-loading cells with fluorescent dextran allowed us to visualize the fusion of phagosomes with endosomes during internalization. These markers provided two new ways to visualize and quantify particle internalization. At 37°C the rate of amorphous silica internalization was very rapid regardless of particle coating. However, at room temperature, opsonized silica is internalized much faster than non-opsonized silica. Conclusions/Significance Our results indicate that amorphous and crystalline silica are both phagocytosed and both toxic to mouse alveolar macrophage (MH-S) cells. The pathway leading to apoptosis appears to be similar in both cases. However, the result suggests a mechanistic difference between FcγRIIA receptor-mediated and non-opsonized silica particle phagocytosis. PMID:21311600

The phagocytosis and toxicity of amorphous silica.

PubMed

Costantini, Lindsey M; Gilberti, Renée M; Knecht, David A

2011-02-02

Inhalation of crystalline silica is known to cause an inflammatory reaction and chronic exposure leads to lung fibrosis and can progress into the disease, silicosis. Cultured macrophages bind crystalline silica particles, phagocytose them, and rapidly undergo apoptotic and necrotic death. The mechanism by which particles are bound and internalized and the reason particles are toxic is unclear. Amorphous silica has been considered to be a less toxic form, but this view is controversial. We compared the uptake and toxicity of amorphous silica to crystalline silica. Amorphous silica particles are phagocytosed by macrophage cells and a single internalized particle is capable of killing a cell. Fluorescent dextran is released from endo-lysosomes within two hours after silica treatment and Caspase-3 activation occurs within 4 hours. Interestingly, toxicity is specific to macrophage cell lines. Other cell types are resistant to silica particle toxicity even though they internalize the particles. The large and uniform size of the spherical, amorphous silica particles allowed us to monitor them during the uptake process. In mCherry-actin transfected macrophages, actin rings began to form 1-3 minutes after silica binding and the actin coat disassembled rapidly following particle internalization. Pre-loading cells with fluorescent dextran allowed us to visualize the fusion of phagosomes with endosomes during internalization. These markers provided two new ways to visualize and quantify particle internalization. At 37 °C the rate of amorphous silica internalization was very rapid regardless of particle coating. However, at room temperature, opsonized silica is internalized much faster than non-opsonized silica. Our results indicate that amorphous and crystalline silica are both phagocytosed and both toxic to mouse alveolar macrophage (MH-S) cells. The pathway leading to apoptosis appears to be similar in both cases. However, the result suggests a mechanistic difference between FcγRIIA receptor-mediated and non-opsonized silica particle phagocytosis.

Etude par resistivite electrique du comportement d'un alliage amorphe Fe 40Ni 38Mo 4B 18 deforme par traction

NASA Astrophysics Data System (ADS)

Hoang, Long Phan; Sacovy, Paulette; Delaplace, Jean

1983-02-01

Des rubans d'alliages amorphes Metglas du type Fe 40Ni 38Mo 4B 18 à l'état brut de trempe ont été déformés par traction à la température ambiante et l'on a suivi les variations de la résistance électrique des échantillons au cours de la déformation. Il ressort de ces essais que la déformation plastique qui est de l'ordre de 0.5% avant rupture ne se produit pas de faĉon homogène dans l'échantillon. Les mesures électriques effectuées au cours de la déformation mettent en évidence dans le domaine élastique un effet d'élastorésistance, relativement important ( K ≠ 1); elles montrent que dans le domaine plastique la déformation permanente des échantillons s'accompagne d'une diminution de la résistivité électrique du matériau. Deux hypothèses sont discutées pour expliquer cet effet inattendu, l'un qui fait appel à l'existence de volumes libres, l'autre qui suppose une cristallisation localisée du matériau sous l'effet de la contrainte.

Metallic glass coating on metals plate by adjusted explosive welding technique

NASA Astrophysics Data System (ADS)

Liu, W. D.; Liu, K. X.; Chen, Q. Y.; Wang, J. T.; Yan, H. H.; Li, X. J.

2009-09-01

Using an adjusted explosive welding technique, an aluminum plate has been coated by a Fe-based metallic glass foil in this work. Scanning electronic micrographs reveal a defect-free metallurgical bonding between the Fe-based metallic glass foil and the aluminum plate. Experimental evidence indicates that the Fe-based metallic glass foil almost retains its amorphous state and mechanical properties after the explosive welding process. Additionally, the detailed explosive welding process has been simulated by a self-developed hydro-code and the bonding mechanism has been investigated by numerical analysis. The successful welding between the Fe-based metallic glass foil and the aluminum plate provides a new way to obtain amorphous coating on general metal substrates.

Morphological, structural, and spectral characteristics of amorphous iron sulfates

PubMed Central

Sklute, E. C.; Jensen, H. B.; Rogers, A. D.; Reeder, R. J.

2018-01-01

Current or past brine hydrologic activity on Mars may provide suitable conditions for the formation of amorphous ferric sulfates. Once formed, these phases would likely be stable under current Martian conditions, particularly at low- to mid-latitudes. Therefore, we consider amorphous iron sulfates (AIS) as possible components of Martian surface materials. Laboratory AIS were created through multiple synthesis routes and characterized with total X-ray scattering, thermogravimetric analysis, scanning electron microscopy, visible/near-infrared (VNIR), thermal infrared (TIR), and Mössbauer techniques. We synthesized amorphous ferric sulfates (Fe(III)2(SO4)3 · ~ 6–8H2O) from sulfate-saturated fluids via vacuum dehydration or exposure to low relative humidity (<11%). Amorphous ferrous sulfate (Fe(II)SO4 · ~1H2O) was synthesized via vacuum dehydration of melanterite. All AIS lack structural order beyond 11 Å. The short-range (<5 Å) structural characteristics of amorphous ferric sulfates resemble all crystalline reference compounds; structural characteristics for the amorphous ferrous sulfate are similar to but distinct from both rozenite and szomolnokite. VNIR and TIR spectral data for all AIS display broad, muted features consistent with structural disorder and are spectrally distinct from all crystalline sulfates considered for comparison. Mössbauer spectra are also distinct from crystalline phase spectra available for comparison. AIS should be distinguishable from crystalline sulfates based on the position of their Fe-related absorptions in the visible range and their spectral characteristics in the TIR. In the NIR, bands associated with hydration at ~1.4 and 1.9 μm are significantly broadened, which greatly reduces their detectability in soil mixtures. AIS may contribute to the amorphous fraction of soils measured by the Curiosity rover. PMID:29675340

Characterization and determination of 28 elements in fly ashes collected in a thermal power plant in Argentina using different instrumental techniques

NASA Astrophysics Data System (ADS)

Marrero, Julieta; Polla, Griselda; Jiménez Rebagliati, Raúl; Plá, Rita; Gómez, Darío; Smichowski, Patricia

2007-02-01

Different techniques were selected for comprehensive characterization of seven samples of fly ashes collected from the electrostatic precipitator of the San Nicolás thermal power plant (Buenos Aires, Argentina). Particle size was measured using laser based particle size analyzer. X-ray diffraction powder (XRD) analysis and scanning electron microscopy (SEM) were used to characterize the mineral phase present in the matrix consisting basically of aluminosilicates and large amounts of amorphous material. The predominant crystalline phases were mullite and quartz. Major and minors elements (Al, Ca, Cl, Fe, K, Mg, Na, S, Si and Ti) were detected by energy dispersive X-ray analysis (EDAX). Trace elements (As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Se, V and Zn) content was quantified by inductively coupled plasma optical emission spectrometry (ICP OES). Different acid mixtures and digestion procedures were compared for subsequent ICP OES measurements of the dissolved samples. The digestion procedures used were: i) a mixture of FH + HNO 3 + HClO 4 (open system digestion); ii) a mixture of FH + HNO 3 (MW-assisted digestion); iii) a mixture of HF and aqua regia (MW-assisted digestion). Instrumental neutron activation analysis (INAA) was employed for the determination of As, Ba, Co, Cr, Ce, Cs, Eu, Fe, Gd, Hf, La, Lu, Rb, Sb, Sc, Sm, Ta, Tb, Th, U and Yb. The validation of the procedure was performed by the analysis of two certified materials namely, i) NIST 1633b, coal fly ash and ii) GBW07105, rock. Mean elements content spanned from 41870 μg g - 1 for Fe to 1.14 μg g - 1 for Lu. The study showed that Fe (41870 μg g - 1 ) ≫ V (1137 μg g - 1 ) > Ni (269 μg g - 1 ) > Mn (169 μg g - 1 ) are the main components. An enrichment, with respect to crustal average, in many elements was observed especially for As, V and Sb that deserve particular interest from the environmental and human health point of view.

Structural Coloration of a Colloidal Amorphous Array is Intensified by Carbon Nanolayers.

PubMed

Takeoka, Yukikazu; Iwata, Masanori; Seki, Takahiro; Nueangnoraj, Khanin; Nishihara, Hirotomo; Yoshioka, Shinya

2018-04-10

In this study, we introduce the possibility of applying a colloidal amorphous array composed of fine silica particles as a structural-color material to invisible information technology. The appearance of a thick filmlike colloidal amorphous array formed from fine silica particles is considerably influenced by incoherent light scattering across the entire visible region. Therefore, regardless of the diameter of the fine silica particles, the thick colloidal amorphous array exhibits a white color to the naked eye. When carbon is uniformly deposited in the colloidal amorphous array by a pressure-pulsed chemical vapor deposition method, incoherent light scattering in the colloidal amorphous array is suppressed. As a result, coherent light scattering due to the short-range order in the colloidal amorphous array becomes conspicuous and the array exhibits a vivid structural color. As structures, such as letters and pictures, can be drawn using this technology, the colloidal amorphous array as a structural-colored material may also be applicable for invisible information technology.

Investigation of selected structural parameters in Fe 95Si 5 amorphous alloy during crystallization process

NASA Astrophysics Data System (ADS)

Fronczyk, Adam

2007-04-01

In this study, we report on a crystallization behavior of the Fe 95Si 5 metallic glasses using a differential scanning cabrimetry (DSC), and X-ray diffraction. The paper presents the results of experimental investigation of Fe 95Si 5 amorphous alloy, subjected to the crystallizing process by the isothermal annealing. The objective of the experiment was to determine changes in the structural parameters during crystallization process of the examined alloy. Crystalline diameter and the lattice constant of the crystallizing phase were used as parameters to evaluate structural changes in material.

Electrochemical (de)lithiation of silver ferrite and composites: mechanistic insights from ex situ, in situ, and operando X-ray techniques.

PubMed

Durham, Jessica L; Brady, Alexander B; Cama, Christina A; Bock, David C; Pelliccione, Christopher J; Zhang, Qing; Ge, Mingyuan; Li, Yue Ru; Zhang, Yiman; Yan, Hanfei; Huang, Xiaojing; Chu, Yong; Takeuchi, Esther S; Takeuchi, Kenneth J; Marschilok, Amy C

2017-08-23

The structure of pristine AgFeO 2 and phase makeup of Ag 0.2 FeO 1.6 (a one-pot composite comprised of nanocrystalline stoichiometric AgFeO 2 and amorphous γ-Fe 2 O 3 phases) was investigated using synchrotron X-ray diffraction. A new stacking-fault model was proposed for AgFeO 2 powder synthesized using the co-precipitation method. The lithiation/de-lithiation mechanisms of silver ferrite, AgFeO 2 and Ag 0.2 FeO 1.6 were investigated using ex situ, in situ, and operando characterization techniques. An amorphous γ-Fe 2 O 3 component in the Ag 0.2 FeO 1.6 sample is quantified. Operando XRD of electrochemically reduced AgFeO 2 and Ag 0.2 FeO 1.6 composites demonstrated differences in the structural evolution of the nanocrystalline AgFeO 2 component. As complimentary techniques to XRD, ex situ X-ray Absorption Spectroscopy (XAS) provided insight into the short-range structure of the (de)lithiated nanocrystalline electrodes, and a novel in situ high energy X-ray fluorescence nanoprobe (HXN) mapping measurement was applied to spatially resolve the progression of discharge. Based on the results, a redox mechanism is proposed where the full reduction of Ag + to Ag 0 and partial reduction of Fe 3+ to Fe 2+ occur on reduction to 1.0 V, resulting in a Li 1+y Fe III Fe II y O 2 phase. The Li 1+y Fe III Fe II y O 2 phase can then reversibly cycle between Fe 3+ and Fe 2+ oxidation states, permitting good capacity retention over 50 cycles. In the Ag 0.2 FeO 1.6 composite, a substantial amorphous γ-Fe 2 O 3 component is observed which discharges to rock salt LiFe 2 O 3 and Fe 0 metal phase in the 3.5-1.0 V voltage range (in parallel with the AgFeO 2 mechanism), and reversibly reoxidizes to a nanocrystalline iron oxide phase.

Investigation into the morphology and structure of magnetic bentonite nanocomposites with their catalytic activity

NASA Astrophysics Data System (ADS)

Wan, Dong; Wang, Guanghua; Li, Wenbing; Wei, Xiaobi

2017-08-01

Al pillared bentonite-Fe3O4 nanocomposites (Fe3O4/Al-B) with controllable Fe3O4 particle sizes and loadings were synthesized by a simple in situ oxidation-precipitation method. The obtained samples were characterized by XRD, SEM, TEM, FTIR, XPS, VSM and N2 sorption. These results suggested that Fe3O4 was chemically anchored to the bentonite sheets via Fe-O-Si bonds, resulting in the formation of secondary pore structure. Three types of structure of Fe3O4/Al-B nanocomposites were proposed at different Fe3O4 loadings, varying from 40 to 80 wt%. The catalytic activity of the Fe3O4/Al-B nanocomposites was investigated in the heterogeneous Fenton-like oxidation of rhodamine B (RhB). The 50 nm Fe3O4/Al-B nanocomposite showed enhanced degradation of RhB over the control catalyst, benefited from its greater surface area and pore volume. The highest catalytic activity was found to be at Fe3O4 loading of 60 wt%, which was attributed to the synergistic effects between both increased surface area and formed Fe-O-Si bonds. These findings offer a better understanding on structural and morphological relationships of Fe3O4/Al-B nanocomposites with their heterogeneous Fenton-like catalytic activity.

Investigation on microstructure and mechanical properties of Mo2FeB2 based cermets with and without PVA

NASA Astrophysics Data System (ADS)

Shen, Yupeng; Huang, Zhifu; Jian, Yongxin; Yang, Ming; Li, Kemin

2018-03-01

Mo2FeB2 based cermets with and without PVA have been investigated by x-ray diffractometry (XRD), x-ray photoelectron spectroscope (XPS) and scanning electron microscopy (SEM). The density and transverse rupture strength (TRS) of green compact, relative density, hardness (HRA), fracture toughness (KIC) and TRS of Mo2FeB2 based cermets were also measured. The results indicate that, compared with the Mo2FeB2 based cermets without PVA, the density of green compact with PVA can be improved slightly at the same pressure. However, the much higher TRS is obtained for the green compact without PVA. Meanwhile, Mo2FeB2 particles exhibit the finer and less congruity feature for Mo2FeB2 based cermets without PVA. In addition, the higher relative density, hardness, fracture toughness and TRS can be acquired for the cermets without PVA. Obviously, considering the mechanical properties and preparation period of Mo2FeB2 based cermets, no adding PVA is the optimized process of powder molding in the manufacture of Mo2FeB2 based cermets.

Substrate temperature effect on the structural anisotropy in amorphous Tb-Fe films

NASA Astrophysics Data System (ADS)

Harris, V. G.; Hellman, F.; Elam, W. T.; Koon, N. C.

1993-05-01

Using extended x-ray absorption fine structures (EXAFS) measurements we have investigated the atomic environment around the Fe atom in a series of amorphous Tb0.26Fe0.74 films having different magnetic anisotropy energies owing to different deposition temperatures. The polarization properties of synchrotron radiation allowed the separate study of structure parallel and perpendicular to the sample plane. An anisotropy between these two structures was observed. Modeling results indicate this anisotropy is due to anisotropic pair correlations where the Fe-Fe pairs are statistically preferred in-plane and the Fe-Tb pairs out-of-plane. The amplitude of this anisotropy scales with both the substrate temperature and the magnetic anisotropy energy. A ≊1% in-plane compression of the Fe-Fe distance was measured between the in-plane and out-of-plane structure of the sample grown at 77 K. This sample had no detectable local chemical anisotropy suggesting that intrinsic stress plays an important role in determining its magnetic anisotropy.

Arsenic removal from water using a novel amorphous adsorbent developed from coal fly ash.

PubMed

Zhang, Kaihua; Zhang, Dongxue; Zhang, Kai

2016-01-01

A novel effective adsorbent of alumina/silica oxide hydrate (ASOH) for arsenic removal was developed through simple chemical reactions using coal fly ash. The iron-modified ASOH with enhancing adsorption activity was further developed from raw fly ash based on the in situ technique. The adsorbents were characterized by X-ray diffraction, Fourier transform infrared spectrometry, scanning electron micrograph, laser particle size and Brunauer-Emmet-Teller surface area. The results show that the adsorbents are in amorphous and porous structure, the surface areas of which are 8-12 times that of the raw ash. The acidic hydrothermal treatment acts an important role in the formation of the amorphous structure of ASOH rather than zeolite crystal. A series of adsorption experiments for arsenic on them were studied. ASOH can achieve a high removal efficiency for arsenic of 96.4% from water, which is more than 2.5 times that of the raw ash. Iron-modified ASOH can enhance the removal efficiency to reach 99.8% due to the in situ loading of iron (Fe). The condition of synthesis pH = 2-4 is better for iron-modified ASOH to adsorb arsenic from water.

Corrosion resistant amorphous metals and methods of forming corrosion resistant amorphous metals

DOEpatents

Farmer, Joseph C.; Wong, Frank M.G.; Haslam, Jeffery J.; Yang, Nancy; Lavernia, Enrique J.; Blue, Craig A.; Graeve, Olivia A.; Bayles, Robert; Perepezko, John H.; Kaufman, Larry; Schoenung, Julie; Ajdelsztajn, Leo

2014-07-15

A system for coating a surface comprises providing a source of amorphous metal, providing ceramic particles, and applying the amorphous metal and the ceramic particles to the surface by a spray. The coating comprises a composite material made of amorphous metal that contains one or more of the following elements in the specified range of composition: yttrium (.gtoreq.1 atomic %), chromium (14 to 18 atomic %), molybdenum (.gtoreq.7 atomic %), tungsten (.gtoreq.1 atomic %), boron (.ltoreq.5 atomic %), or carbon (.gtoreq.4 atomic %).

Corrosion resistant amorphous metals and methods of forming corrosion resistant amorphous metals

DOEpatents

Farmer, Joseph C [Tracy, CA; Wong, Frank M. G. [Livermore, CA; Haslam, Jeffery J [Livermore, CA; Yang, Nancy [Lafayette, CA; Lavernia, Enrique J [Davis, CA; Blue, Craig A [Knoxville, TN; Graeve, Olivia A [Reno, NV; Bayles, Robert [Annandale, VA; Perepezko, John H [Madison, WI; Kaufman, Larry [Brookline, MA; Schoenung, Julie [Davis, CA; Ajdelsztajn, Leo [Walnut Creek, CA

2009-11-17

A system for coating a surface comprises providing a source of amorphous metal, providing ceramic particles, and applying the amorphous metal and the ceramic particles to the surface by a spray. The coating comprises a composite material made of amorphous metal that contains one or more of the following elements in the specified range of composition: yttrium (.gtoreq.1 atomic %), chromium (14 to 18 atomic %), molybdenum (.gtoreq.7 atomic %), tungsten (.gtoreq.1 atomic %), boron (.ltoreq.5 atomic %), or carbon (.gtoreq.4 atomic %).

Magnetic and transport properties of Fe-based nanocrystalline materials

NASA Astrophysics Data System (ADS)

Barandiarán, J. M.

1994-01-01

Fe-rich amorphous alloys containing late transition metals like Nb, V, Zr,..., sometimes with the addition of Cu, can crystallize in ultrafine grains of a crystalline phase, a few nanometers in diameter, embedded in a disordered matrix. In such state they have shown excellent soft magnetic properties for technical applications, rising the interest for deep studies. In this paper, recent work on some Fe-Nb and Fe-Zr based alloys both in amorphous state and after several degrees of nanocrystallization is presented. The nanocrystallization process has been achieved by conventional heat treatments (about 1 h at temperatures around 400-500 °C in a controlled atmosphere furnance) as well as by Joule heating using an electrical current flowing through the sample. Magnetic measurements, electrical resistivity, x-rays diffraction and 57Fe Mössbauer spectroscopy were used in the study of the crystalline phases appearing after the thermal treatments. The basic magnetic and transport properties of the nanocrystals do not differ appreciably from their bulk values. The magnetic anisotropy, however, is very sensitive to grain size and to the intergranular magnetic coupling. The effect of such coupling is deduced from the coercivity changes at the Curie Temperature of the amorphous matrix remaining after nanocrystallization.

Influence of the chemically synthesis conditions on the microstructure and magnetic properties of the Co-Fe-B nanoparticles

NASA Astrophysics Data System (ADS)

Ababei, G.; Gaburici, M.; Budeanu, L.-C.; Grigoras, M.; Porcescu, M.; Lupu, N.; Chiriac, H.

2018-04-01

Co-Fe-B particles present a high potential for applications in microwave domain (electromagnetic shielding, toroidal transformer, etc.) due to their special soft magnetic properties like high saturation magnetization, low coercivity, large anisotropy and high magnetic permeability. However, their microwave applications are limited to about few gigahertzes due to the eddy current losses if the size of the particles is larger than few hundred of nanometers. Chemical synthesis method gives the possibility to obtain nanoparticles with diameters from few nanometers to tens of nanometers by varying the parameters of the chemical synthesis. One way to avoids the agglomeration of the particles in the utilization of the polyvinyl-pyrrolidone (PVP) which is acting as dispersant and dimensions controlling agent for nanoparticles. The aim of this paper is to study the influence of the synthesis conditions on the magnetic properties and microstructure of Co-Fe-B nanoparticles prepared by chemical reduction method in order to obtains nanoparticles with magnetic properties suitable for high frequency applications in the 0.1 ÷ 12 GHz frequency range. Co-Fe-B nanoparticles were prepared by chemical reduction of CoCl2·6H2O and FeSO4·7H2O salts in aqueous solution of sodium borohydride (NaBH4) in presence of the polyvinyl-pirrolydone (PVP). The experimental results indicate that the amount of PVP, Fe/Co ratio and the temperature of the chemical synthesis are important parameters which have to be controlled in order to obtain nanoparticles with desired dimensions, nanostructure and soft magnetic properties with suitable properties for high frequency applications.

High-Capacity and Long-Cycle Life Aqueous Rechargeable Lithium-Ion Battery with the FePO4 Anode.

PubMed

Wang, Yuesheng; Yang, Shi-Ze; You, Ya; Feng, Zimin; Zhu, Wen; Gariépy, Vincent; Xia, Jiexiang; Commarieu, Basile; Darwiche, Ali; Guerfi, Abdelbast; Zaghib, Karim

2018-02-28

Aqueous lithium-ion batteries are emerging as strong candidates for a great variety of energy storage applications because of their low cost, high-rate capability, and high safety. Exciting progress has been made in the search for anode materials with high capacity, low toxicity, and high conductivity; yet, most of the anode materials, because of their low equilibrium voltages, facilitate hydrogen evolution. Here, we show the application of olivine FePO 4 and amorphous FePO 4 ·2H 2 O as anode materials for aqueous lithium-ion batteries. Their capacities reached 163 and 82 mA h/g at a current rate of 0.2 C, respectively. The full cell with an amorphous FePO 4 ·2H 2 O anode maintained 92% capacity after 500 cycles at a current rate of 0.2 C. The acidic aqueous electrolyte in the full cells prevented cathodic oxygen evolution, while the higher equilibrium voltage of FePO 4 avoided hydrogen evolution as well, making them highly stable. A combination of in situ X-ray diffraction analyses and computational studies revealed that olivine FePO 4 still has the biphase reaction in the aqueous electrolyte and that the intercalation pathways in FePO 4 ·2H 2 O form a 2-D mesh. The low cost, high safety, and outstanding electrochemical performance make the full cells with olivine or amorphous hydrated FePO 4 anodes commercially viable configurations for aqueous lithium-ion batteries.

Aligning flaky FeSiAl particles with a two-dimensional rotating magnetic field to improve microwave-absorbing and shielding properties of composites

NASA Astrophysics Data System (ADS)

Liu, Chang; Cai, Jun; Duan, Yubing; Li, Xinghao; Zhang, Deyuan

2018-07-01

In order to enhance the microwave-absorbing and shielding properties of the composites, the flaky FeSiAl particles embedded in an epoxy polymer were aligned with a two-dimensional rotating magnetic field. The morphologies, electromagnetic (EM) characteristics, and microwave-absorbing and shielding properties of the unaligned and aligned FeSiAl/epoxy composites were investigated. The results showed that after alignment treatment, the flaky FeSiAl particles tend to orient uniformly in the rotating magnetic field, and the permittivity and permeability of the aligned composites were increased in the frequency range of 1-18 GHz compared with that of randomly distributed composites. The calculated microwave-absorbing properties indicated that the peak value of the return loss (RL) of the aligned composites can reach 8.8 dB, compared with 5.8 dB of the unaligned composites of 2.5 mm in thickness (60 wt%); and the bandwidth with RL value more than 6 dB is in a wider frequency range from 1 to 2.8 GHz. And the calculated shielding effectiveness (SE) of the aligned composites is 1.1-3 times higher than that of unaligned one in every thickness, and the maximum SE of the aligned one is 31.8 dB at 18 GHz with a thickness of 2.5 mm.

Analysis of the Glass-Forming Ability of Fe-Er Alloys, Based on Thermodynamic Modeling

NASA Astrophysics Data System (ADS)

Arutyunyan, N. A.; Zaitsev, A. I.; Dunaev, S. F.; Kalmykov, K. B.; El'nyakov, D. D.; Shaposhnikov, N. G.

2018-05-01

The Fe-Er phase diagram and thermodynamic properties of all its phases are assessed by means of self-consistent analysis. To refine the data on phase equilibria in the Fe-Er system, an investigation is performed in the 10-40 at % range of Er concentrations. The temperature-concentration dependences of the thermodynamic properties of a melt are presented using the model of ideal associated solutions. Thermodynamic parameters of each phase are obtained, and the calculated results are in agreement with available experimental data. The correlation between the thermodynamic properties of liquid Fe-Er alloys and their tendency toward amorphization are studied. It is shown that compositions of amorphous alloys prepared by melt quenching coincide with the ranges of concentration with the predominance of Fe3Er and FeEr2 associative groups that have large negative entropies of formation.

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

Paranthaman, M. Parans; Sridharan, Niyanth; List, Fred A.

The technical objective of this technical collaboration phase I proposal is to fabricate near net-shaped permanent magnets using alloy powders utilizing direct metal deposition technologies at the ORNL MDF. Direct Manufacturing using the POM laser system was used to consolidate Nd 2Fe 14B (NdFeB) magnet powders into near net-shape parts efficiently and with virtually no wasted material as part of the feasibility study. We fabricated builds based on spherical NdFeB magnet particles. The results show that despite the ability to fabricate highly reactive materials in the laser deposition process, the magnetic coercivity and remanence of the NdFeB hard magnets ismore » significantly reduced. X-ray powder diffraction in conjunction with electron microscopy showed that the material experienced a primary Nd 2Fe 17B x solidification due to the undercooling effect (>60K). Consequently the presence of alpha iron phase resulted in deterioration of the build properties. Further optimization of the processing parameters is needed to maintain the Nd 2Fe 14B phase during fabrication.« less

Environmental application of millimetre-scale sponge iron (s-Fe0) particles (IV): New insights into visible light photo-Fenton-like process with optimum dosage of H2O2 and RhB photosensitizers.

PubMed

Ju, Yongming; Yu, Yunjiang; Wang, Xiaoyan; Xiang, Mingdeng; Li, Liangzhong; Deng, Dongyang; Dionysiou, Dionysios D

2017-02-05

In this study, we firstly develop the photo-Fenton-like system with millimetric sponge iron (s-Fe 0 ), H 2 O 2 , visible light (vis, λ≥420nm) and rhodamine B (RhB), and present a comprehensive study concerning the mechanism. Thus, we investigate (1) the adsorption of RhB onto s-Fe 0 , (2) the photo-Fenton-like removal of RhB over iron oxides generated from the corrosion of s-Fe 0 , (3) the homogeneous photo-Fenton removal of RhB over Fe 2+ or Fe 3+ , (4) the Fe 3+ -RhB complexes, and (5) the photo-Fenton-like removal of tetrabromobisphenol A (TBBPA). The results show that neither the adsorption process over s-Fe 0 nor the photo-Fenton-like process over FeOOH, Fe 3 O 4 and Fe 2 O 3 , achieved efficient removal of RhB. For comparison, in homogeneous photo-Fenton process, the presence of Fe 3+ ions, rather than Fe 2+ ions, effectively eliminated RhB. Furthermore, the UV-vis spectra showing new absorbance at∼285nm indicate the complexes of RhB and Fe 3+ ions, adopting vis photons to form excited state and further eject one electron via ligand-to-metal charge-transfer to activate H 2 O 2 . Additionally, efficient TBBPA removal was obtained only in the presence of RhB. Accordingly, the s-Fe 0 - based photo-Fenton-like process assisted with dyestuff wastewater is promising for removing a series of persistent organic pollutants. Copyright © 2016 Elsevier B.V. All rights reserved.

Ambient temperature NO oxidation over Cr-based amorphous mixed oxide catalysts: effects from the second oxide components

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

Wang, Aiyong; Lin, Bo; Zhang, Hanlei

2017-01-01

Three series of Cr-based mixed oxides (Cr-Co, Cr-Fe, and Cr-Ni oxides) with high specific surface areas and amorphous textures were synthesized using a novel sol-gel method. These mixed oxides, in comparison to their pure metal oxide (CrOx, Co3O4, FeOx and NiO) counterparts, display enhanced performance for catalytic oxidation of low-concentration NO at room temperature. The best performing catalysts achieve 100% NO conversion for ~30 h of operation at a high space velocity of 45,000 ml g-1 h-1. The amorphous structure was found to be critical for these catalysts to maintain high activity and durability. Control of Cr/M (M=Co, Fe andmore » Ni) molar ratio, nitrate precursor decomposition temperature and catalyst calcination temperature was key to the synthesis of these highly active catalysts.« less

Electrochemical (de)lithiation of silver ferrite and composites: mechanistic insights from ex situ, in situ, and operando X-ray techniques

DOE PAGES

Durham, Jessica L.; Brady, Alexander B.; Cama, Christina A.; ...

2017-08-02

Here, the structure of pristine AgFeO 2 and phase makeup of Ag 0.2FeO1.6 (a one-pot composite comprised of nanocrystalline stoichiometric AgFeO 2 and amorphous γ-Fe 2O 3 phases) was investigated using synchrotron x-ray diffraction. A new stacking-fault model was proposed for AgFeO2 powder synthesized using the co-precipitation method. The lithiation/de-lithiation mechanisms of silver ferrite, AgFeO 2 and Ag 0.2FeO 1.6 were investigated using ex-situ, in-situ, and operando characterization techniques. An amorphous γ-Fe 2O 3 component in the Ag 0.2FeO 1.6 sample is quantified. Operando XRD of electrochemically reduced AgFeO 2 and Ag 0.2FeO 1.6 composites demonstrated differences in the structuralmore » evolution of the nanocrystalline AgFeO 2 component. As complimentary techniques to XRD, ex-situ x-ray Absorption Spectroscopy (XAS) provided insight into the short-range structure of the (de)lithiated nanocrystalline electrodes, and a novel in-situ high energy x-ray fluorescence nanoprobe (HXN) mapping measurement was applied to spatially resolve the progression of discharge. Based on the results, a redox mechanism is proposed where the full reduction of Ag + to Ag0 and partial reduction of Fe 3+ to Fe 2+ occur on reduction to 1.0 V, resulting in a Li 1+yFe IIIFe IIyO 2 phase. The Li 1+yFe IIIFe IIyO 2 phase can then reversibly cycle between Fe 3+ and Fe 2+ oxidation states, permitting good capacity retention over 50 cycles. In the Ag 0.2FeO 1.6 composite, a substantial amorphous γ-Fe 2O 3 component is observed which discharges to rock salt LiFe 2O 3 and Fe 0 metal phase in the 3.5 – 1.0 V voltage range (in parallel with the AgFeO 2 mechanism), and reversibly reoxidizes to a nanocrystalline iron oxide phase.« less

Electrochemical (de)lithiation of silver ferrite and composites: mechanistic insights from ex situ, in situ, and operando X-ray techniques

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

Durham, Jessica L.; Brady, Alexander B.; Cama, Christina A.

Here, the structure of pristine AgFeO 2 and phase makeup of Ag 0.2FeO1.6 (a one-pot composite comprised of nanocrystalline stoichiometric AgFeO 2 and amorphous γ-Fe 2O 3 phases) was investigated using synchrotron x-ray diffraction. A new stacking-fault model was proposed for AgFeO2 powder synthesized using the co-precipitation method. The lithiation/de-lithiation mechanisms of silver ferrite, AgFeO 2 and Ag 0.2FeO 1.6 were investigated using ex-situ, in-situ, and operando characterization techniques. An amorphous γ-Fe 2O 3 component in the Ag 0.2FeO 1.6 sample is quantified. Operando XRD of electrochemically reduced AgFeO 2 and Ag 0.2FeO 1.6 composites demonstrated differences in the structuralmore » evolution of the nanocrystalline AgFeO 2 component. As complimentary techniques to XRD, ex-situ x-ray Absorption Spectroscopy (XAS) provided insight into the short-range structure of the (de)lithiated nanocrystalline electrodes, and a novel in-situ high energy x-ray fluorescence nanoprobe (HXN) mapping measurement was applied to spatially resolve the progression of discharge. Based on the results, a redox mechanism is proposed where the full reduction of Ag + to Ag0 and partial reduction of Fe 3+ to Fe 2+ occur on reduction to 1.0 V, resulting in a Li 1+yFe IIIFe IIyO 2 phase. The Li 1+yFe IIIFe IIyO 2 phase can then reversibly cycle between Fe 3+ and Fe 2+ oxidation states, permitting good capacity retention over 50 cycles. In the Ag 0.2FeO 1.6 composite, a substantial amorphous γ-Fe 2O 3 component is observed which discharges to rock salt LiFe 2O 3 and Fe 0 metal phase in the 3.5 – 1.0 V voltage range (in parallel with the AgFeO 2 mechanism), and reversibly reoxidizes to a nanocrystalline iron oxide phase.« less

Nanocrystal dispersed amorphous alloys

NASA Technical Reports Server (NTRS)

Perepezko, John H. (Inventor); Allen, Donald R. (Inventor); Foley, James C. (Inventor)

2001-01-01

Compositions and methods for obtaining nanocrystal dispersed amorphous alloys are described. A composition includes an amorphous matrix forming element (e.g., Al or Fe); at least one transition metal element; and at least one crystallizing agent that is insoluble in the resulting amorphous matrix. During devitrification, the crystallizing agent causes the formation of a high density nanocrystal dispersion. The compositions and methods provide advantages in that materials with superior properties are provided.

Core-shell CoFe2O4@Co-Fe-Bi nanoarray: a surface-amorphization water oxidation catalyst operating at near-neutral pH.

PubMed

Ji, Xuqiang; Hao, Shuai; Qu, Fengli; Liu, Jingquan; Du, Gu; Asiri, Abdullah M; Chen, Liang; Sun, Xuping

2017-06-14

The exploration of high-performance and earth-abundant water oxidation catalysts operating under mild conditions is highly attractive and challenging. In this communication, core-shell CoFe 2 O 4 @Co-Fe-Bi nanoarray on carbon cloth (CoFe 2 O 4 @Co-Fe-Bi/CC) was successfully fabricated by in situ surface amorphization of CoFe 2 O 4 nanoarray on CC (CoFe 2 O 4 /CC). As a 3D water oxidation electrode, CoFe 2 O 4 @Co-Fe-Bi/CC shows outstanding activity with an overpotential of 460 mV to drive a geometrical catalytic current density of 10 mA cm -2 in 0.1 M potassium borate (pH 9.2). Notably, it also demonstrates superior long-term durability for at least 20 h with 96% Faradic efficiency. Density functional theory calculations indicate that the conversion from OOH* to O 2 is the rate-limiting step and the high water oxidation activity of CoFe 2 O 4 @Co-Fe-Bi/CC is associated with the lower free energy of 1.84 eV on a Co-Fe-Bi shell.

Stardust Interstellar Preliminary Examination IV: Scanning Transmission X-Ray Microscopy Analyses of Impact Features in the Stardust Interstellar Dust Collector

NASA Technical Reports Server (NTRS)

Butterworth, Anna L.; Westphal, Andrew J.; Frank, David R.; Allen, Carlton C.; Bechtel, Hans A.; Sandford, Scott A.; Tsou, Peter; Zolensky, Michael E.

2014-01-01

We report the quantitative characterization by synchrotron soft X-ray spectroscopy of 31 potential impact features in the aerogel capture medium of the Stardust Interstellar Dust Collector. Samples were analyzed in aerogel by acquiring high spatial resolution maps and high energy-resolution spectra of major rock-forming elements Mg, Al, Si, Fe, and others. We developed diagnostic screening tests to reject spacecraft secondary ejecta and terrestrial contaminants from further consideration as interstellar dust candidates. The results support an extraterrestrial origin for three interstellar candidates: I1043,1,30 (Orion) is a 3 pg particle with Mg-spinel, forsterite, and an iron-bearing phase. I1047,1,34 (Hylabrook) is a 4 pg particle comprising an olivine core surrounded by low-density, amorphous Mg-silicate and amorphous Fe, Cr, and Mn phases. I1003,1,40 (Sorok) has the track morphology of a high-speed impact, but contains no detectable residue that is convincingly distinguishable from the background aerogel. Twenty-two samples with an anthropogenic origin were rejected, including four secondary ejecta from impacts on the Stardust spacecraft aft solar panels, nine ejecta from secondary impacts on the Stardust Sample Return Capsule, and nine contaminants lacking evidence of an impact. Other samples in the collection included I1029,1,6, which contained surviving solar system impactor material. Four samples remained ambiguous: I1006,2,18, I1044,2,32, and I1092,2,38 were too dense for analysis, and we did not detect an intact projectile in I1044,3,33. We detected no radiation effects from the synchrotron soft X-ray analyses; however, we recorded the effects of synchrotron hard X-ray radiation on I1043,1,30 and I1047,1,34.

Effect of Mechanical Stresses and Annealing on the Magnetic Structure and the Magnetic Impedance of Amorphous CoFeSiBCr Microwires

NASA Astrophysics Data System (ADS)

Nematov, M. G.; Salem, M. M.; Azim, U.; Akhmat, M.; Morchenko, A. T.; Yudanov, N. A.; Panina, L. V.

2018-02-01

The structural and magnetic properties of amorphous ferromagnetic microwires can undergo significant measurements under the action of external mechanical stresses and heat treatment. The study of transformations occurring in this case is important for designing various sensors of mechanical stresses, loading, and temperature and also for inducing in the wires a certain type of magnetic anisotropy that plays a significant role in the realization of various effects in them. In this work, the influence of external stresses and annealing on the processes of the magnetization and the magnetic impedance of Co71Fe5B11Si10Cr3 microwires having a low positive magnetostriction ( 10-8) in amorphous state has been studied. The influence of external stresses leads to a sharp change in the character of the magnetization reversal curve, which was due to the change in the sign of the magnetostriction and the type of magnetic anisotropy. The amplitude of higher harmonics and the value of the magnetic impedance, respectively, are sensitive to mechanical stresses. Elastic stresses in the wires with a partial crystallization do not lead to a marked change in the magnetic properties; however, annealing can lead to a substantial increase in the axial magnetic anisotropy of the wires existing in the stressed state. The experimental results are analyzed in the framework of a magnetostriction model of induced magnetic anisotropy.

Fabrication of nano-Fe3O4 3D structure on carbon fibers as a microwave absorber and EMI shielding composite by modified EPD method

NASA Astrophysics Data System (ADS)

Gholampoor, Mahdi; Movassagh-Alanagh, Farid; Salimkhani, Hamed

2017-02-01

Recently, electromagnetic interference (EMI) shielding materials have absorbed a lot of attention due to a growing need for application in the area of electronic and wireless devices. In this study, a carbon-based EMI shielding composite was fabricated by electrophoretic deposition of Fe3O4 nano-particles on carbon fibers (CFs) as a 3D structure incorporated with an epoxy resin. Co-precipitation method was employed to synthesize Fe3O4 nano-particles. This as-synthesized Fe3O4 nano-powder was then successfully deposited on CFs using a modified multi-step electrophoretic deposition (EPD) method. The results of structural studies showed that the Fe3O4 nano-particles (25 nm) were successfully and uniformly deposited on CFs. The measured magnetic properties of as-synthesized Fe3O4 nano-powder and nano-Fe3O4/CFs composite showed that the saturation magnetization of bare Fe3O4 was decreased from Ms = 72.3 emu/g to Ms = 33.1 emu/g for nano-Fe3O4/CFs composite and also corecivity of Fe3O4 was increased from Hc = 4.9 Oe to Hc = 168 Oe for composite. The results of microwave absorption tests revealed that the reflection loss (RL) of an epoxy-based nano-Fe3O4/CFs composite are significantly influenced by layer thickness. The maximum RL value of -10.21 dB at 10.12 GHz with an effective absorption bandwidth about 2 GHz was obtained for the sample with the thickness of 2 mm. It also exhibited an EMI shielding performance of -23 dB for whole the frequency range of 8.2-12.4 GHz.

Wear behavior of the surface alloyed AISI 1020 steel with Fe-Nb-B by TIG welding technique

NASA Astrophysics Data System (ADS)

Kilinc, B.; Durmaz, M.; Abakay, E.; Sen, U.; Sen, S.

2015-03-01

Weld overlay coatings also known as hardfacing is a method which involves melting of the alloys and solidification for applied coatings. Recently hardfacing by welding has become a commonly used technique for improvement of material performance in extreme (high temperature, impact/abrasion, erosion, etc.) conditions.In the present study, the coatings were produced from a mixture of ferrous niobium, ferrous boron and iron powders in the ranges of -45µm particle size with different ratio. Fe12Nb5B3 and Fe2NbBalloys were coated on the AISI 1020 steel surface by TIG welding. The phases formed in the coated layer are Fe2B, NbB2, NbFeB and Fe0,2 Nb0,8 phases. The hardness of the presence phases are changing between 1689±85 HV0.01, and 181±7 HV0.1. Microstructural examinations were realized by optical and scanning electron microscopy. The wear and friction behaviors of Fe12Nb5B3 and Fe2NbB realized on the AISI 1020 steel were investigated by the technique of TIG welding by using ball-on-disk arrangement against alumina ball.

Monitoring the recrystallisation of amorphous xylitol using Raman spectroscopy and wide-angle X-ray scattering.

PubMed

Palomäki, Emmi; Ahvenainen, Patrik; Ehlers, Henrik; Svedström, Kirsi; Huotari, Simo; Yliruusi, Jouko

2016-07-11

In this paper we present a fast model system for monitoring the recrystallization of quench-cooled amorphous xylitol using Raman spectroscopy and wide-angle X-ray scattering. The use of these two methods enables comparison between surface and bulk crystallization. Non-ordered mesoporous silica micro-particles were added to the system in order to alter the rate of crystallization of the amorphous xylitol. Raman measurements showed that adding silica to the system increased the rate of surface crystallization, while X-ray measurements showed that the rate of bulk crystallization decreased. Using this model system it is possible to measure fast changes, which occur in minutes or within a few hours. Raman-spectroscopy and wide-angle X-ray scattering were found to be complementary techniques when assessing surface and bulk crystallization of amorphous xylitol. Copyright © 2016 Elsevier B.V. All rights reserved.

The composition of secondary amorphous phases under different environmental conditions

NASA Astrophysics Data System (ADS)

Smith, R.; Rampe, E. B.; Horgan, B. H. N.; Dehouck, E.; Morris, R. V.

2017-12-01

X-ray diffraction (XRD) patterns measured by the CheMin instrument on the Mars Science Laboratory Curiosity rover demonstrate that amorphous phases are major components ( 15-60 wt%) of all rock and soil samples in Gale Crater. The nature of these phases is not well understood and could be any combination of primary (e.g., glass) and secondary (e.g., silica, ferrihydrite) phases. Secondary amorphous phases are frequently found as weathering products in soils on Earth, but these materials remain poorly characterized. Here we study a diverse suite of terrestrial samples including: sediments from recently de-glaciated volcanoes (Oregon), modern volcanic soils (Hawaii), and volcanic paleosols (Oregon) in order to determine how formation environment, climate, and diagenesis affect the abundance and composition of amorphous phases. We combine bulk XRD mineralogy with bulk chemical compositions (XRF) to calculate the abundance and bulk composition of the amorphous materials in our samples. We then utilize scanning transmission electron microscopy (STEM) and energy dispersive x-ray spectroscopy (EDS) to study the composition of individual amorphous phases at the micrometer scale. XRD analyses of 8 samples thus far indicate that the abundance of amorphous phases are: modern soils (20-80 %) > paleosols (15-40 %) > glacial samples (15-30 %). Initial calculations suggest that the amorphous components consist primarily of SiO2, Al2O3, TiO2, FeO and Fe2O3, with minor amounts of other oxides (e.g., MgO, CaO, Na2O). Compared to their respective crystalline counterparts, calculations indicate bulk amorphous components enriched in SiO2 for the glacial sample, and depleted in SiO2 for the modern soil and paleosol samples. STEM analyses reveal that the amorphous components consist of a number of different phases. Of the two samples analyzed using STEM thus far, the secondary amorphous phases have compositions with varying ratios of SiO2, Al2O3, TiO2, and Fe-oxides, consistent with mass balance calculation results, but inconsistent with well-known amorphous phase compositions (e.g., allophane, ferrihydrite). These results show that a number of secondary amorphous phases can form within a single soil environment. Continued analysis can help determine whether compositional trends can be linked to environmental factors.

Size and shape dependence of CO adsorption sites on sapphire supported Fe microcrystals

NASA Technical Reports Server (NTRS)

Papageorgopoulos, C.; Heinemann, K.

1985-01-01

The surface structure and stoichiometry of alumina substrates, as well as the size, growth characteristics, and shape of Fe deposits on sapphire substrates have been investigated by low energy electron diffraction (LEED), Auger electron spectroscopy, electron energy loss spectroscopy, and X-ray photoemission spectroscopy (XPS), as well as work function measurements, in conjunction with transition electron microscopy observations. The substrates used in this work were the following: (1) new, clean Al2O3; (2) same surface amorphized by Ar ion bombardment; (3) same surface regenerated by 650 C annealing; (4) amorphous alumina films on Ta slab; and (5) polycrystal alumina films, obtained by heating amorphous films to 600 C. Substrate cleaning was found to be most effective in producing a reproducible surface upon oxygen RF plasma treatment. The Fe nucleation and growth process was found to depend strongly on the type of substrate surface and deposition conditions. Ar ion bombardment under beam flooding, and subsequent annealing at 650 C was found an effective means to restore the original Al2O3 (1102) surface for renewed Fe deposition.

Next-Generation Magnetic Nanocomposites: Cytotoxic and Genotoxic Effects of Coated and Uncoated Ferric Cobalt Boron (FeCoB) Nanoparticles In Vitro.

PubMed

Netzer, Katharina; Jordakieva, Galateja; Girard, Angelika M; Budinsky, Alexandra C; Pilger, Alexander; Richter, Lukas; Kataeva, Nadezhda; Schotter, Joerg; Godnic-Cvar, Jasminka; Ertl, Peter

2018-03-01

Metal nanoparticles (NPs) have unique physicochemical properties and a widespread application scope depending on their composition and surface characteristics. Potential biomedical applications and the growing diversity of novel nanocomposites highlight the need for toxicological hazard assessment of next-generation magnetic nanomaterials. Our study aimed to evaluate the cytotoxic and genotoxic properties of coated and uncoated ferric cobalt boron (FeCoB) NPs (5-15 nm particle size) in cultured normal human dermal fibroblasts. Cell proliferation was assessed via ATP bioluminescence kit, and DNA breakage and chromosomal damage were measured by alkaline comet assay and micronucleus test. Polyacryl acid-coated FeCoB NPs [polyacrylic acid (PAA)-FeCoB NPs) and uncoated FeCoB NPs inhibited cell proliferation at 10 μg/ml. DNA strand breaks were significantly increased by PAA-coated FeCoB NPs, uncoated FeCoB NPs and l-cysteine-coated FeCoB NPs (Cys-FeCoB NPs), although high concentrations (10 μg/ml) of coated NPs (Cys- and PAA-FeCoB NPs) showed significantly more DNA breakage when compared to uncoated ones. Uncoated FeCoB NPs and coated NPs (PAA-FeCoB NPs) also induced the formation of micronuclei. Additionally, PAA-coated NPs and uncoated FeCoB NPs showed a negative correlation between cell proliferation and DNA strand breaks, suggesting a common pathomechanism, possibly by oxidation-induced DNA damage. We conclude that uncoated FeCoB NPs are cytotoxic and genotoxic at in vitro conditions. Surface coating of FeCoB NPs with Cys and PAA does not prevent but rather aggravates DNA damage. Further safety assessment and a well-considered choice of surface coating are needed prior to application of FeCoB nanocomposites in biomedicine. © 2017 Nordic Association for the Publication of BCPT (former Nordic Pharmacological Society).

Fabrication of amorphous curcumin nanosuspensions using β-lactoglobulin to enhance solubility, stability, and bioavailability.

PubMed

Aditya, N P; Yang, Hanjoo; Kim, Saehoon; Ko, Sanghoon

2015-03-01

Curcumin has low aqueous stability and solubility in its native form. It also has a low bioavailability which presents a major barrier to its use in fortifying food products. The aim of this work was to reduce the size of curcumin crystals to the nanoscale and subsequently stabilize them in an amorphous form. To this end, amorphous curcumin nanosuspensions were fabricated using the antisolvent precipitation method with β-lactoglobulin (β-lg) as a stabilizer. The resulting amorphous curcumin nanosuspensions were in the size range of 150-175 nm with unimodal size distribution. The curcumin particles were amorphous and were molecularly dispersed within the β-lg as confirmed by differential scanning calorimetry (DSC) and X-ray diffraction (XRD) studies. The solubility of the amorphous curcumin nanosuspension was enhanced ∼35-fold due to the reduced size and lower crystallinity. Among the formulations, the amorphous curcumin nanosuspensions stabilized with β-lg and prepared at pH 3.4 (β-lg-cur 3.4), showed maximum aqueous stability which was >90% after 30 days. An in vitro study using Caco-2 cell lines showed a significant increase in curcumin bioavailability after stabilization with β-lg. Copyright © 2015 Elsevier B.V. All rights reserved.

Method for making fine and ultrafine spherical particles of zirconium titanate and other mixed metal oxide systems

DOEpatents

Hu, Michael Z.

2006-05-23

Disclosed is a method for making amorphous spherical particles of zirconium titanate and crystalline spherical particles of zirconium titanate comprising the steps of mixing an aqueous solution of zirconium salt and an aqueous solution of titanium salt into a mixed solution having equal moles of zirconium and titanium and having a total salt concentration in the range from 0.01 M to about 0.5 M. A stearic dispersant and an organic solvent is added to the mixed salt solution, subjecting the zirconium salt and the titanium salt in the mixed solution to a coprecipitation reaction forming a solution containing amorphous spherical particles of zirconium titanate wherein the volume ratio of the organic solvent to aqueous part is in the range from 1 to 5. The solution of amorphous spherical particles is incubated in an oven at a temperature .ltoreq.100.degree. C. for a period of time .ltoreq.24 hours converting the amorphous particles to fine or ultrafine crystalline spherical particles of zirconium titanate.

Influence of the chemical composition of rapidly quenched amorphous alloys (Ni, Fe, Cr)-B-Si on its crystallization process

NASA Astrophysics Data System (ADS)

Elmanov, G.; Dzhumaev, P.; Ivanitskaya, E.; Skrytnyi, V.; Ruslanov, A.

2016-04-01

This paper presents results of research of the structure and phase transformations during the multistage crystallization of the metallic glasses with the compositions Ni71,5Cr6,8Fe2,7B11,9Si7,1 and Ni63,4Cr7,4Fe4,3Mn0,8B15,6Si8,5 labeled as AWS BNi-2 according to American Welding Society. Differential scanning calorimetry (DSC), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray microanalysis (EDX) were used as experimental research methods. The influence of the alloys chemical composition (boron, manganese and iron) on the temperatures and the exothermic heat effects of phase transformations, as well as on the phase composition of alloys at three stages of crystallization was analyzed. We present a thermodynamic explanation of the observed heat effects. It has been shown that manganese has the main influence on the phase transformations temperatures and heat effects in these two alloys. It is also assumed that at the final crystallization stage simultaneously with the formation of phases Ni3B and β1-Ni3Si should occur the nucleation of borides of CrB type with high Cr and low Si content.

Enhanced ferrihydrite dissolution by a unicellular, planktonic cyanobacterium: a biological contribution to particulate iron bioavailability.

PubMed

Kranzler, Chana; Kessler, Nivi; Keren, Nir; Shaked, Yeala

2016-12-01

Iron (Fe) bioavailability, as determined by its sources, sinks, solubility and speciation, places severe environmental constraints on microorganisms in aquatic environments. Cyanobacteria are a widespread group of aquatic, photosynthetic microorganisms with especially high iron requirements. While iron exists predominantly in particulate form, little is known about its bioavailability to cyanobacteria. Some cyanobacteria secrete iron solubilizing ligands called siderophores, yet many environmentally relevant strains do not have this ability. This work explores the bioavailability of amorphous synthetic Fe-oxides (ferrihydrite) to the non-siderophore producing, unicellular cyanobacterium, Synechocystis sp PCC 6803. Iron uptake assays with 55 ferrihydrite established dissolution as a critical prerequisite for iron transport. Dissolution assays with the iron binding ligand, desferrioxamine B, demonstrated that Synechocystis 6803 enhances ferrihydrite dissolution, exerting siderophore-independent biological influence on ferrihydrite bioavailability. Dissolution mechanisms were studied using a range of experimental conditions; both cell-particle physical proximity and cellular electron flow were shown to be important determinants of bio-dissolution by Synechocystis 6803. Finally, the effects of ferrihydrite stability on bio-dissolution rates and cell physiology were measured, integrating biological and chemical aspects of ferrihydrite bioavailability. Collectively, these findings demonstrate that Synechocystis 6803 actively dissolves ferrihydrite, highlighting a significant biological component to mineral phase iron bioavailability in aquatic environments. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

Functional magnetic porous silica for T 1-T 2 dual-modal magnetic resonance imaging and pH-responsive drug delivery of basic drugs

NASA Astrophysics Data System (ADS)

Li, Ling; Zhang, Run; Guo, Yi; Zhang, Cheng; Zhao, Wei; Xu, Zhiping; Whittaker, Andrew K.

2016-12-01

A smart magnetic-targeting drug carrier γ-Fe2O3@p-silica comprising a γ-Fe2O3 core and porous shell has been prepared and characterized. The particles have a uniform size of about 60 nm, and a porous shell of thickness 3 nm. Abundant hydroxyl groups and a large surface area enabled the γ-Fe2O3@p-silica to be readily loaded with a large payload of the basic model drug rhodamine B (RB) (up to 73 mg g-1). Cytotoxicity assays of the γ-Fe2O3@p-silica particles indicated that the particles were biocompatible and suitable for carrying drugs. It was found that the RB was released rapidly at pH 5.5 but at pH 7.4 the rate and extent of release was greatly attenuated. The particles therefore demonstrate an excellent pH-triggered drug release. In addition, the γ-Fe2O3@p-silica particles could be tracked by magnetic resonance imaging (MRI). A clear dose-dependent contrast enhancement in both T 1-weighted and T 2-weighted MR images indicated the potential of the γ-Fe2O3@p-silica particles to act as dual-mode T 1 and T 2 MRI contrast agents.

Synthesizing skyrmion bound pairs in Fe-Gd thin films

DOE PAGES

Lee, J. C. T.; Chess, J. J.; Montoya, S. A.; ...

2016-07-11

Here, we show that properly engineered amorphous Fe-Gd alloy thin films with perpendicular magnetic anisotropy exhibit bound pairs of like-polarity, opposite helicity skyrmions at room temperature. Magnetic mirror symmetry planes present in the stripe phase, instead of chiral exchange, determine the internal skyrmion structure and the net achirality of the skyrmion phase. Our study shows that stripe domain engineering in amorphous alloy thin films may enable the creation of skyrmion phases with technologically desirable properties.

Effect of boron additions on phase formation and magnetic properties of TbCu7-type melt spun SmFe ribbons

NASA Astrophysics Data System (ADS)

Zheng, Chuanjiang; Yu, Dunbo; Li, Kuoshe; Luo, Yang; Jin, Jinling; Lu, Shuo; Li, Hongwei; Mao, Yongjun; Quan, Ningtao

2016-08-01

Melt spun ribbons of a series of SmFe12Bx (x=0.0, 0.5, 0.75, 1.0, 1.25, and 1.5) have been prepared by the melt spinning technique. Sm-Fe-B melt spun ribbons with single phase TbCu7-type structure were prepared from the SmFe12Bx (x=0.5, 0.75, and 1.0) alloys at the surface velocity around 40 m/s. The addition of boron not only inhibits the appearance of soft magnetic phase α-Fe, but also enhances the ability of amorphous formation for melt spun Sm-Fe ribbons. The concentration of boron atoms, however, exceeds the limit of the solubility (x>1.0) of Sm-Fe alloys, which does not impede the appearance of α-Fe but accelerates the formation of metastable phase Sm2Fe23B3 that is unfavorable to their magnetic properties. Moreover, it is found that the addition of boron whose concentration is 0.0≤x≤0.75 can stabilize the metastable TbCu7-type structure because of the increase of the lattice parameter ratio c/a. The magnetic properties of as-annealed SmFe12B1.0 melt spun ribbons with an energy product of 2.19MGOe, a coercivity of 2.36 kOe and a remanence of 4.8 kGs have been achieved. The microstructural characteristics of as-annealed melt spun SmFe12 and SmFe12B1.0 ribbons have been discussed as well. The following sequence of the hyperfine field H(6l)

EAG Eminent Speaker: Cold war biogeochemistry: Microbes as architects for metal attenuation

NASA Astrophysics Data System (ADS)

Küsel, K.

2012-04-01

Legacy uranium mining in the area of Ronneburg, Germany, has resulted in extensive outflow of highly heavy metal contaminated ground and upcoming mine waters. Mine water flows along a grassland into a small creek and forms iron-rich precipitates yielding rust-colored terraces at the creek bank. These iron oxyhydroxides could have been formed by iron oxidizing bacteria (FeOB) or by chemical oxidation. Precipitates may serve as important biogeochemical interfaces, because heavy metals can adsorb or co-precipitate with Fe(II) or Fe(III) minerals. Thus, microbial Fe(II) oxidation but also the reductive dissolution of iron oxides can be important processes affecting the stability of metal contaminants. Here we present a study on the potential for iron cycling processes and on indigenous bacterial communities in this acidic creek. Oxic and anoxic in vitro sediment incubations revealed iron oxidation and reduction rates of same magnitude, indicating active iron cycling regardless of pH. XRD and TEM comparing the suspended particle load of water samples with fresh creek sediment showed that amorphous particles likely formed first, then aged to become more crystalline iron oxyhydroxides, such as akaganeite and goethite. During this aging process some of the initially smooth, 50-300 nm spherical particles may have formed nano-sized needles, which could potentially provide high reactive surface area for chemical and biological reactions. Surprisingly, total and dissolved metal concentrations in creek water and sediment revealed that elements such as Mn, Si, Ni, or Zn stayed mostly in solution. Only some metals such as Cu, Cr, and U seemed to be particle-associated in the water, likely co-precipitated with or adsorbed onto freshly-precipitating minerals. Pelagic and particle-associated organisms from water as well as fresh sediments were used for 16S rRNA gene cloning and sequencing and showed that members of the Proteobacteria (mainly Betaproteobacteria and Deltaproteobacteria) dominated bacterial communities. The relative fraction of FeOB-related clones was especially high in upcoming underground water and sediment of the adjacent creek site. Up to 80% of clones in sediment microbial 16S rRNA gene clone libraries had ≥97% sequence similarity to reported FeOM or FeRM, demonstrating a strong link to function, even on RNA level. Three novel moderately acidophilic FeOM strains, Thiomonas sp. FB-Cd and FB-6 and Bordetella sp. FB-8, were isolated from pH 6.3 sediment. FB-6 is likely involved in in situ iron oxidation as it has high similarity to a RNA-derived clone from this sediment. Our results demonstrated active microbial iron cycling in heavy metal contaminated creeks, which have important implications for understanding natural attenuation.

SERS active Ag encapsulated Fe@SiO2 nanorods in electromagnetic wave absorption and crystal violet detection.

PubMed

Senapati, Samarpita; Srivastava, Suneel Kumar; Singh, Shiv Brat; Kulkarni, Ajit R

2014-11-01

The present work is focused on the preparation of Fe nanorods by the chemical reduction of FeCl3 (aq) using NaBH4 in the presence of glycerol as template followed by annealing of the product at 500°C in the presence of H2 gas flow. Subsequently, its surface has been modified by silica followed by silver nanoparticles to form silica coated Fe (Fe@SiO2) and Ag encapsulated Fe@SiO2 nanostructure employing the Stöber method and silver mirror reaction respectively. XRD pattern of the products confirmed the formation of bcc phase of iron and fcc phase of silver, though silica remained amorphous. FESEM images established the growth of iron nanorods from the annealed product and also formation of silica and silver coating on its surface. The appearance of the characteristics bands in FTIR confirmed the presence of SiO2 on the Fe surface. Magnetic measurements at room temperature indicated the ferromagnetic behavior of as prepared iron nanorods, Fe@SiO2 and silver encapsulated Fe@SiO2 nanostructures. All the samples exhibited strong microwave absorption property in the high frequency range (10GHz), though it is superior for Ag encapsulated Fe@SiO2 (-14.7dB) compared with Fe@SiO2 (-9.7dB) nanostructures of the same thickness. The synthesized Ag encapsulated Fe@SiO2 nanostructure also exhibited the SERS phenomena, which is useful in the detection of the carcinogenic dye crystal violet (CV) upto the concentration of 10(-10)M. All these findings clearly demonstrate that the Ag encapsulated Fe@SiO2 nanostructure could efficiently be used in the environmental remediation. Copyright © 2014 Elsevier Inc. All rights reserved.

Genotoxic effects of high-energy iron particles in human lymphoblasts differing in radiation sensitivity

NASA Technical Reports Server (NTRS)

Evans, H. H.; Horng, M. F.; Evans, T. E.; Jordan, R.; Schwartz, J. L.

2001-01-01

The effects of (56)Fe particles and (137)Cs gamma radiation were compared in TK6 and WTK1 human lymphoblasts, two related cell lines which differ in TP53 status and in the ability to rejoin DNA double-strand breaks. Both cell lines were more sensitive to the cytotoxic and clastogenic effects of (56)Fe particles than to those of gamma rays. However, the mutagenicity of (56)Fe particles and gamma rays at the TK locus was the same per unit dose and was higher for gamma rays than for (56)Fe particles at isotoxic doses. The respective RBEs for TK6 and WTK1 cells were 1.5 and 1.9 for cytotoxicity and 2.5 and 1.9 for clastogenicity, but only 1 for mutagenicity. The results indicate that complex lesions induced by (56)Fe particles are repaired less efficiently than gamma-ray-induced lesions, leading to fewer colony-forming cells, a slightly higher proportion of aberrant cells at the first division, and a lower frequency of viable mutants at isotoxic doses. WTK1 cells (mutant TP53) were more resistant to the cytotoxic effects of both gamma rays and (56)Fe particles, but showed greater cytogenetic and mutagenic damage than TK6 cells (TP53(+)). A deficiency in the number of damaged TK6 cells (a) reaching the first mitosis after exposure and (b) forming viable mutants can explain these results.

Magnetic changes accompanying the thermal decomposition of nontronite /in air/ and its relevance to Martian mineralogy

NASA Technical Reports Server (NTRS)

Moskowitz, B. M.; Hargraves, R. B.

1982-01-01

It is found that the thermal treatment of nontronite in air, for long periods at 700 C or short periods at 900 C, results in the destruction of the nontronite structure, a distinct reddening in color, and a large increase in magnetic susceptibility and saturation magnetization. Measurements and calculations of the magnetic properties suggest that the magnetism is due to the presence of ultrafine particles of alpha or gamma Fe2O3. The highly magnetic thermally treated nontronite is amorphous to X-rays consistent with an ultrafine grain size. Prolonged heating results in the growth of alpha Fe2O3, while reflectivity spectra of a sample heated for 1 hr at 900 C indicate the presence of an opaque, magnetite-like phase in addition to alpha Fe2O3. It is found that the thermally treated nontronite has chemical, color, and magnetic properties similar to those found by Viking on Mars. It is concluded that these results indicate an origin for the fine grained Martian surface material by repeated impacts into an Fe-rich smectite-charged regolith (Weldon et al., 1980).

Preparation of amorphous cefuroxime axetil nanoparticles by sonoprecipitation for enhancement of bioavailability.

PubMed

Dhumal, Ravindra S; Biradar, Shailesh V; Yamamura, Shigeo; Paradkar, Anant R; York, Peter

2008-09-01

The aim of the present work was to prepare amorphous discreet nanoparticles by sonoprecipitation method for enhancing oral bioavailability of cefuroxime axetil (CA), a poorly water-soluble drug. CA nanoparticles (SONO-CA) were prepared by sonoprecipitation and compared with particles obtained by precipitation without sonication (PPT-CA) and amorphous CA obtained by spray drying. Spray drying present broad particle size distribution (PSD) with mean particle size of 10 microm and low percent yield, whereas, precipitation without sonication resulted in large amorphous aggregates with broad PSD. During sonoprecipitation, particle size and yield improve with an increase in the amplitude of sonication and lowering the operation temperature due to instantaneous supersaturation and nucleation. The overall symmetry and purity of CA molecule was maintained as confirmed by FTIR and HPLC, respectively. All the three methods resulted in the formation of amorphous CA with only sonoprecipitation resulting in uniform sized nanoparticles. Sonoprecipitated CA nanoparticles showed enhanced dissolution rate and oral bioavailability in Wistar rat due to an increased solubility attributed to combination of effects like amorphization and nanonization with increased surface area and reduced diffusion pathway.

What We Might Know About Gusev Crater if the Mars Exploration Rover Spirit Mission were Coupled with a Mars Sample Return Mission

NASA Technical Reports Server (NTRS)

Morris, Richard V.

2008-01-01

The science instruments on the Mars Exploration Rover (MER) Spirit have provided an enormous amount of chemical and mineralogical data during more than 1450 sols of exploration at Gusev crater. The Moessbauer (MB) instrument identified 10 Fe-bearing phases at Gusev Crater: olivine, pyroxene, ilmenite, chromite, and magnetite as primary igneous phases and nanophase ferric oxide (npOx), goethite, hematite, a ferric sulfate, and pyrite/marcusite as secondary phases. The Miniature Thermal Emission Spectrometer (Mini-TES) identified some of these Fe-bearing phases (olivine and pyroxene), non- Fe-bearing phases (e.g., feldspar), and an amorphous high-SiO2 phase near Home Plate. Chemical data from the Alpha Particle X-Ray Spectrometer (APXS) provided the framework for rock classification, chemical weathering/alteration, and mineralogical constraints. APXS-based mineralogical constraints include normative calculations (with Fe(3+)/FeT from MB), elemental associations, and stoichiometry (e.g., 90% SiO2 implicates opalline silica). If Spirit had cached a set of representative samples and if those samples were returned to the Earth for laboratory analysis, what value is added by Mars Sample return (MSR) over and above the mineralogical and chemical data provided by MER?

Magnetic Properties and the Giant Magnetoimpedance of Amorphous Co-Based Wires with a Carbon Coating

NASA Astrophysics Data System (ADS)

Golubeva, E. V.; Stepanova, E. A.; Balymov, K. G.; Volchkov, S. O.; Kurlyandskaya, G. V.

2018-04-01

A comparative analysis of the magnetic properties and specific features of the giant magnetoimpedance has been carried out for amorphous rapidly quenched wires with a composition of (Co0.94Fe0.06)72.5Si12.5B15 in the initial state and after the deposition of a carbon coating. The deposition of the defective graphene-like carbon layer was carried out under normal conditions during the exposure in toluene (methylbenzene). The method of the energy-dispersive X-ray spectroscopy made it possible to reliably show that after the modification in toluene, the carbon content on the surface significantly exceeds the natural amount of carbon. The deposition of the carbon coating induced changes in the distribution of the initial quenching stresses in the near-surface layer of amorphous wires. A comparative analysis of the magnetic and magnetoimpedance properties of the samples before and after exposure in the aromatic solvent confirms the occurrence of changes in the effective magnetic anisotropy as a result of this surface treatment.

Design and Characterisation of Metallic Glassy Alloys of High Neutron Shielding Capability

NASA Astrophysics Data System (ADS)

Khong, J. C.; Daisenberger, D.; Burca, G.; Kockelmann, W.; Tremsin, A. S.; Mi, J.

2016-11-01

This paper reports the design, making and characterisation of a series of Fe-based bulk metallic glass alloys with the aim of achieving the combined properties of high neutron absorption capability and sufficient glass forming ability. Synchrotron X-ray diffraction and pair distribution function methods were used to characterise the crystalline or amorphous states of the samples. Neutron transmission and macroscopic attenuation coefficients of the designed alloys were measured using energy resolved neutron imaging method and the very recently developed microchannel plate detector. The study found that the newly designed alloy (Fe48Cr15Mo14C15B6Gd2 with a glass forming ability of Ø5.8 mm) has the highest neutron absorption capability among all Fe-based bulk metallic glasses so far reported. It is a promising material for neutron shielding applications.

Design and Characterisation of Metallic Glassy Alloys of High Neutron Shielding Capability.

PubMed

Khong, J C; Daisenberger, D; Burca, G; Kockelmann, W; Tremsin, A S; Mi, J

2016-11-16

This paper reports the design, making and characterisation of a series of Fe-based bulk metallic glass alloys with the aim of achieving the combined properties of high neutron absorption capability and sufficient glass forming ability. Synchrotron X-ray diffraction and pair distribution function methods were used to characterise the crystalline or amorphous states of the samples. Neutron transmission and macroscopic attenuation coefficients of the designed alloys were measured using energy resolved neutron imaging method and the very recently developed microchannel plate detector. The study found that the newly designed alloy (Fe 48 Cr 15 Mo 14 C 15 B 6 Gd 2 with a glass forming ability of Ø5.8 mm) has the highest neutron absorption capability among all Fe-based bulk metallic glasses so far reported. It is a promising material for neutron shielding applications.

Variability of the health effects of crystalline silica: Fe speciation in industrial quartz reagents and suspended dusts—insights from XAS spectroscopy

NASA Astrophysics Data System (ADS)

Di Benedetto, Francesco; D'Acapito, Francesco; Capacci, Fabio; Fornaciai, Gabriele; Innocenti, Massimo; Montegrossi, Giordano; Oberhauser, Werner; Pardi, Luca A.; Romanelli, Maurizio

2014-03-01

We investigated the speciation of Fe in bulk and in suspended respirable quartz dusts coming from ceramic and iron-casting industrial processes via X-ray absorption spectroscopy, with the aim of contributing to a better understanding of the variability of crystalline silica toxicity. Four different bulk industrial quartz powders, nominally pure quartz samples with Fe contents below 200 ppm, and three respirable dusts filters were selected. Fe speciation was determined in all samples through a coupled study of the X-ray absorption near-edge structure and extended X-ray absorption fine structure regions, operating at the Fe-K edge. Fe speciation revealed common features at the beginning of the different production processes, whereas significant differences were observed on both respirable dusts and bulk dusts exiting from the production process. Namely, a common pollution of the raw quartz dusts by elemental Fe was evidenced and attributed to residuals of the industrial production of quartz materials. Moreover, the respirable samples indicated that reactivity occurs after the suspension of the powders in air. The gravitational selection during the particle suspension consistently allowed us to clearly discriminate between suspended and bulk dusts. On the basis of the obtained results, we provide an apparent spectroscopic discrimination between the raw materials used in the considered industrial processes, and those that are effectively inhaled by workers. In particular, an amorphous FeIII oxide, with an unsaturated coordination sphere, can be related to silica reactivity (and health consequences).

Low-Temperature Synthesis of Hierarchical Amorphous Basic Nickel Carbonate Particles for Water Oxidation Catalysis.

PubMed

Yang, Yisu; Liang, Fengli; Li, Mengran; Rufford, Thomas E; Zhou, Wei; Zhu, Zhonghua

2015-07-08

Amorphous nickel carbonate particles are catalysts for the oxygen evolution reaction (OER), which plays a critical role in the electrochemical splitting of water. The amorphous nickel carbonate particles can be prepared at a temperature as low as 60 °C by an evaporation-induced precipitation (EIP) method. The products feature hierarchical pore structures. The mass-normalized activity of the catalysts, measured at an overpotential of 0.35 V, was 55.1 A g(-1) , with a Tafel slope of only 60 mV dec(-1) . This catalytic activity is superior to the performance of crystalline NiOx particles and β-Ni(OH)2 particles, and compares favorably to state-of-the-art RuO2 catalysts. The activity of the amorphous nickel carbonate is remarkably stable during a 10 000 s chronoamperometry test. Further optimization of synthesis parameters reveals that the amorphous structure can be tuned by adjusting the H2 O/Ni ratio in the precursor mixture. These results suggest the potential application of easily prepared hierarchical basic nickel carbonate particles as cheap and robust OER catalysts with high activity. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Formation of iron disilicide on amorphous silicon

NASA Astrophysics Data System (ADS)

Erlesand, U.; Östling, M.; Bodén, K.

1991-11-01

Thin films of iron disilicide, β-FeSi 2 were formed on both amorphous silicon and on crystalline silicon. The β-phase is reported to be semiconducting with a direct band-gap of about 0.85-0.89 eV. This phase is known to form via a nucleation-controlled growth process on crystalline silicon and as a consequence a rather rough silicon/silicide interface is usually formed. In order to improve the interface a bilayer structure of amorphous silicon and iron was sequentially deposited on Czochralski <111> silicon in an e-gun evaporation system. Secondary ion mass spectrometry profiling (SIMS) and scanning electron micrographs revealed an improvement of the interface sharpness. Rutherford backscattering spectrometry (RBS) and X-ray diffractiometry showed β-FeSi 2 formation already at 525°C. It was also observed that the silicide growth was diffusion-controlled, similar to what has been reported for example in the formation of NiSi 2 for the reaction of nickel on amorphous silicon. The kinetics of the FeSi 2 formation in the temperature range 525-625°C was studied by RBS and the activation energy was found to be 1.5 ± 0.1 eV.

Tungsten solution kinetics and amorphization of nickel in mechanically alloyed Ni-W alloys

NASA Technical Reports Server (NTRS)

Aning, A. O.; Wang, Z.; Courtney, T. H.

1993-01-01

The kinetics of solution of W, and the subsequent amorphization of Ni, in mechanically alloyed Ni-W alloys has been investigated. As W is a highly abrasive material in the energy intensive devices used for mechanical alloying, we studied the above reactions in different mills. One used hardened steel balls as the grinding media, and the other Al2O3. Abrasion is common to both mills, but Fe wear debris from the hardened steel enters into solution in the Ni rich phases whereas Al2O3 debris is present as small dispersoids. The kinetics of W solution and those of subsequent amorphization do not appear strongly affected by the Fe in solution or the Al2O3 dispersoid. Tungsten dissolves in crystalline Ni in amounts in excess of the equilibrium solubility during alloying. Amorphization of the Ni phase occurs if the W content in this phase exceeds ca. 28 at. pct.

Effect of amorphous silica nanoparticles on in vitro RANKL-induced osteoclast differentiation in murine macrophages

NASA Astrophysics Data System (ADS)

Nabeshi, Hiromi; Yoshikawa, Tomoaki; Akase, Takanori; Yoshida, Tokuyuki; Tochigi, Saeko; Hirai, Toshiro; Uji, Miyuki; Ichihashi, Ko-Ichi; Yamashita, Takuya; Higashisaka, Kazuma; Morishita, Yuki; Nagano, Kazuya; Abe, Yasuhiro; Kamada, Haruhiko; Tsunoda, Shin-Ichi; Itoh, Norio; Yoshioka, Yasuo; Tsutsumi, Yasuo

2011-07-01

Amorphous silica nanoparticles (nSP) have been used as a polishing agent and/or as a remineralization promoter for teeth in the oral care field. The present study investigates the effects of nSP on osteoclast differentiation and the relationship between particle size and these effects. Our results revealed that nSP exerted higher cytotoxicity in macrophage cells compared with submicron-sized silica particles. However, tartrate-resistant acid phosphatase (TRAP) activity and the number of osteoclast cells (TRAP-positive multinucleated cells) were not changed by nSP treatment in the presence of receptor activator of nuclear factor κB ligand (RANKL) at doses that did not induce cytotoxicity by silica particles. These results indicated that nSP did not cause differentiation of osteoclasts. Collectively, the results suggested that nanosilica exerts no effect on RANKL-induced osteoclast differentiation of RAW264.7 cells, although a detailed mechanistic examination of the nSP70-mediated cytotoxic effect is needed.

Role of Coulomb blockade and spin-flip scattering in tunneling magnetoresistance of FeCo-Si-O nanogranular films

NASA Astrophysics Data System (ADS)

Kumar, Hardeep; Ghosh, Santanu; Bürger, Danilo; Li, Lin; Zhou, Shengqiang; Kabiraj, Debdulal; Avasthi, Devesh Kumar; Grötzschel, Rainer; Schmidt, Heidemarie

2011-04-01

In this work, we report the effect of FeCo atomic fraction (0.33 < x < 0.54) and temperature on the electrical, magnetic, and tunneling magnetoresistance (TMR) properties of FeCo-Si-O granular films prepared by atom beam sputtering technique. Glancing angle x-ray diffraction and TEM studies reveal that films are amorphous in nature. The dipole-dipole interactions (particle-matrix mixing) is evident from zero-field cooled and field-cooled magnetic susceptibility measurements and the presence of oxides (mainly Fe-related) is observed by x-ray photoelectron spectroscopy analysis. The presence of Fe-oxides is responsible for the observed reduction of saturation magnetization and rapid increase in coercivity below 50 K. TMR has been observed in a wide temperature range, and a maximum TMR of -4.25% at 300 K is observed for x = 0.39 at a maximum applied field of 60 kOe. The fast decay of maximum TMR at high temperatures and lower TMR values at 300 K when compared to PFeCo2/(1+PFeCo2), where PFeCo is the spin polarization of FeCo are in accordance with a theoretical model that includes spin-flip scattering processes. The temperature dependent study of TMR effect reveals a remarkably enhanced TMR at low temperatures. The TMR value varies from -2.1% at 300 K to -14.5% at 5 K for x = 0.54 and a large MR value of -18.5% at 5 K for x = 0.39 is explained on the basis of theoretical models involving Coulomb blockade effects. Qualitatively particle-matrix mixing and the presence of Fe-oxides seems to be the source of spin-flip scattering, responsible for fast decay of TMR at high temperatures. A combination of higher order tunneling (in Coulomb blockade regime) and spin-flip scattering (high temperature regime) explains the temperature dependent TMR of these films.

Preparation, characterization and in vivo evaluation of amorphous atorvastatin calcium nanoparticles using supercritical antisolvent (SAS) process.

PubMed

Kim, Min-Soo; Jin, Shun-Ji; Kim, Jeong-Soo; Park, Hee Jun; Song, Ha-Seung; Neubert, Reinhard H H; Hwang, Sung-Joo

2008-06-01

In this work, amorphous atorvastatin calcium nanoparticles were successfully prepared using the supercritical antisolvent (SAS) process. The effect of process variables on particle size and distribution of atorvastatin calcium during particle formation was investigated. Solid state characterization, solubility, intrinsic dissolution, powder dissolution studies and pharmacokinetic study in rats were performed. Spherical particles with mean particle size ranging between 152 and 863 nm were obtained by varying process parameters such as precipitation vessel pressure and temperature, drug solution concentration and feed rate ratio of CO2/drug solution. XRD, TGA, FT-IR, FT-Raman, NMR and HPLC analysis indicated that atorvastatin calcium existed as anhydrous amorphous form and no degradation occurred after SAS process. When compared with crystalline form (unprocessed drug), amorphous atorvastatin calcium nanoparticles were of better performance in solubility and intrinsic dissolution rate, resulting in higher solubility and faster dissolution rate. In addition, intrinsic dissolution rate showed a good correlation with the solubility. The dissolution rates of amorphous atorvastatin calcium nanoparticles were highly increased in comparison with unprocessed drug by the enhancement of intrinsic dissolution rate and the reduction of particle size resulting in an increased specific surface area. The absorption of atorvastatin calcium after oral administration of amorphous atorvastatin calcium nanoparticles to rats was markedly increased.

Superparamagnetic behavior of Fe-doped SnO2 nanoparticles

NASA Astrophysics Data System (ADS)

Hachisu, M.; Onuma, K.; Kondo, T.; Miike, K.; Miyasaka, T.; Mori, K.; Ichiyanagi, Y.

2014-02-01

SnO2 is an n-type semiconductor with a wide band gap of 3.62 eV, and SnO2 nanoparticles doped with magnetic ions are expected to realized new diluted magnetic semiconductors (DMSs). Realizing ferromagnetism at room temperature is important for spintronics device applications, and it is interesting that the magnetic properties of these DMS systems can be varied significantly by modifying the preparation methods or conditions. In this study, the magnetic properties of Fe-doped (3% and 5%) SnO2 nanoparticles, prepared using our novel chemical preparation method and encapsulated in amorphous SiO2, were investigated. The particle size (1.8-16.9 nm) and crystal phase were controlled by the annealing temperature. X-ray diffraction confirmed a rutile SnO2 single-phase structure for samples annealed at 1073-1373 K, and the composition was confirmed using X-ray fluorescence analysis. SQUID magnetometer measurements revealed superparamagnetic behavior of the 5%-Fe-doped sample at room temperature, although SnO2 is known to be diamagnetic. Magnetization curves at 5 K indicated that the 3%-Fe-doped has a larger magnetization than that of the 5%-Fe-doped sample. We conclude that the magnetization of the 5%-Fe-doped sample decreased at 5 K due to the superexchange interaction between the antiferromagnetic coupling in the nanoparticle system.

Design, Fabrication, Characterization and Modeling of Integrated Functional Materials

DTIC Science & Technology

2010-10-19

ribbons: A relationship between the soft magnetic properties and GMI effect has been established in Co69Fe4.5R1.5Si10B15 (R = Ni, Al , Cr) amorphous... deposition . A strain compression-relaxation mechanism has been proposed in order to explain the structure- property relationships in the CFO-PZT bilayer...being pursued. The new Laser Assisted Spray process chamber for co- deposition of QDs and polymer films is shown in Fig. 55. Fig. 55

The influence of annealing on domain wall propagation in bistable amorphous microwire with unidirectional effect

NASA Astrophysics Data System (ADS)

Onufer, Jozef; Ziman, Ján; Duranka, Peter; Kladivová, Mária

2018-07-01

The effect of gradual annealing on the domain wall mobility (velocity), nucleation, critical depinning and propagation fields in amorphous FeSiB microwires has been studied. A new experimental set-up, presented in this paper, allows measurement of average domain wall velocity for four different conditions and detection of the presence of unidirectional effect in wall propagation without manipulation of the microwire. The proposed interpretation is that a domain wall is considered as a relatively long object which can change its axial dimension due to inhomogeneity of damping forces acting on the wall during its propagation. It is demonstrated that unidirectional effect in domain wall propagation can be strongly reduced by annealing the wire at temperatures higher than 350 °C.

Wear behavior of the surface alloyed AISI 1020 steel with Fe-Nb-B by TIG welding technique

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

Kilinc, B., E-mail: bkilinc@sakarya.edu.tr; Durmaz, M.; Abakay, E.

Weld overlay coatings also known as hardfacing is a method which involves melting of the alloys and solidification for applied coatings. Recently hardfacing by welding has become a commonly used technique for improvement of material performance in extreme (high temperature, impact/abrasion, erosion, etc.) conditions.In the present study, the coatings were produced from a mixture of ferrous niobium, ferrous boron and iron powders in the ranges of -45µm particle size with different ratio. Fe{sub 12}Nb{sub 5}B{sub 3} and Fe{sub 2}NbBalloys were coated on the AISI 1020 steel surface by TIG welding. The phases formed in the coated layer are Fe{sub 2}B,more » NbB{sub 2}, NbFeB and Fe0,2 Nb{sub 0,8} phases. The hardness of the presence phases are changing between 1689±85 HV{sub 0.01}, and 181±7 HV{sub 0.1}. Microstructural examinations were realized by optical and scanning electron microscopy. The wear and friction behaviors of Fe{sub 12}Nb{sub 5}B{sub 3} and Fe2NbB realized on the AISI 1020 steel were investigated by the technique of TIG welding by using ball-on-disk arrangement against alumina ball.« less

Facile synthesis of ZnFe2O4 photocatalysts for decolourization of organic dyes under solar irradiation

PubMed Central

Behera, Arjun; Kandi, Debasmita; Majhi, Sanjit Manohar

2018-01-01

ZnFe2O4 was fabricated by a simple solution-combustion method. The structural, optical and electronic properties are investigated by XRD, TEM, FESEM, UV–vis DRS, PL, FTIR and photocurrent measurements. The photocatalytic activity of the prepared material is studied with regard to the degradation of rhodamine B (Rh B) and Congo red under solar irradiation. The kinetic study showed that the material exhibits zeroth and first order reaction kinetics for the degradation of Rh B and Congo red, respectively. The photocatalytic behaviour of ZnFe2O4 was systematically studied as a function of the activation temperature. ZnFe2O4 prepared at 500 °C showed the highest activity in degrading Rh B and Congo red. The highest activity of ZnFe2O4-500 °C correlates well with the lowest PL intensity, highest photocurrent and lowest particle size. PMID:29515956

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

Liu, Zheng; Li, Zhilin; Institute of Carbon Fibers and Composites, Beijing University of Chemical Technology, Beijing 100029

Graphical abstract: The MWCNT/Ni-B catalyst has been successfully prepared by an electroless deposition process. The Ni-B nanoparticles on the supporter are amorphous and are well-distributed. The catalytic conversion towards hydrogenation of styrene shows excellent catalytic activity of the obtained materials. Highlights: Black-Right-Pointing-Pointer A two-step treatment of MWCNTs enabled the homogeneous growth of Ni-B nanoparticles. Black-Right-Pointing-Pointer Ni-B nanoparticles were amorphous with an average size of 60 nm. Black-Right-Pointing-Pointer There were electron transfer between Ni and B. Black-Right-Pointing-Pointer The catalyst had excellent catalytic activity towards hydrogenation of styrene. -- Abstract: Nickel-boron (Ni-B) nanoparticles supported on multi-walled carbon nanotubes (MWCNTs) were successfully synthesizedmore » through an electroless deposition process using the plating bath with sodium borohydride as a reducing agent. The structural and morphological analyses using field-emission scanning electron microscopy, X-ray diffractometry and high-resolution transmission electron microscopy have shown that the Ni-B nanoparticles deposited on the sidewalls of MWCNTs are fine spheres comprised of amorphous structure with the morphologically unique fine-structure like flowers, and homogenously dispersed with a narrow particle size distribution centered at around 60 nm diameter. The catalytic activity of MWCNT/Ni-B nanoparticles was evaluated with respect to hydrogenation of styrene. The hydrogenation catalyzed by MWCNT-supported Ni-B nanoparticles has been found to make styrene selectively converted into ethylbenzene. The highest conversion reaches 99.8% under proper reaction conditions, which demonstrates the high catalytic activity of MWCNT/Ni-B nanoparticles.« less

Iron-reducing bacteria accumulate ferric oxyhydroxide nanoparticle aggregates that may support planktonic growth

PubMed Central

Luef, Birgit; Fakra, Sirine C; Csencsits, Roseann; Wrighton, Kelly C; Williams, Kenneth H; Wilkins, Michael J; Downing, Kenneth H; Long, Philip E; Comolli, Luis R; Banfield, Jillian F

2013-01-01

Iron-reducing bacteria (FeRB) play key roles in anaerobic metal and carbon cycling and carry out biogeochemical transformations that can be harnessed for environmental bioremediation. A subset of FeRB require direct contact with Fe(III)-bearing minerals for dissimilatory growth, yet these bacteria must move between mineral particles. Furthermore, they proliferate in planktonic consortia during biostimulation experiments. Thus, a key question is how such organisms can sustain growth under these conditions. Here we characterized planktonic microbial communities sampled from an aquifer in Rifle, Colorado, USA, close to the peak of iron reduction following in situ acetate amendment. Samples were cryo-plunged on site and subsequently examined using correlated two- and three-dimensional cryogenic transmission electron microscopy (cryo-TEM) and scanning transmission X-ray microscopy (STXM). The outer membranes of most cells were decorated with aggregates up to 150 nm in diameter composed of ∼3 nm wide amorphous, Fe-rich nanoparticles. Fluorescent in situ hybridization of lineage-specific probes applied to rRNA of cells subsequently imaged via cryo-TEM identified Geobacter spp., a well-studied group of FeRB. STXM results at the Fe L2,3 absorption edges indicate that nanoparticle aggregates contain a variable mixture of Fe(II)–Fe(III), and are generally enriched in Fe(III). Geobacter bemidjiensis cultivated anaerobically in the laboratory on acetate and hydrous ferric oxyhydroxides also accumulated mixed-valence nanoparticle aggregates. In field-collected samples, FeRB with a wide variety of morphologies were associated with nano-aggregates, indicating that cell surface Fe(III) accumulation may be a general mechanism by which FeRB can grow while in planktonic suspension. PMID:23038172

Iron-reducing bacteria accumulate ferric oxyhydroxide nanoparticle aggregates that may support planktonic growth

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

Luef, Birgit; Fakra, Sirine C.; Csencsits, Roseann

2013-02-04

Iron-reducing bacteria (FeRB) play key roles in anaerobic metal and carbon cycling and carry out biogeochemical transformations that can be harnessed for environmental bioremediation. A subset of FeRB require direct contact with Fe(III) bearing minerals for dissimilatory growth, yet these bacteria must move between mineral particles. Further, they proliferate in planktonic consortia during biostimulation experiments. Thus, a key question is how such organisms can sustain growth under these conditions. Here we characterized planktonic microbial communities sampled from an aquifer in Rifle, Colorado, USA close to the peak of iron reduction following in situ acetate amendment. Samples were cryo-plunged on sitemore » and subsequently examined using correlated 2- and 3- dimensional cryogenic transmission electron microscopy (cryo-TEM) and scanning transmission X-ray microscopy (STXM). Most cells had their outer membranes decorated with up to 150 nm diameter aggregates composed of a few nm wide amorphous, Fe-rich nanoparticles. Fluorescent in situ hybridization of lineage-specific probes applied to rRNA of cells subsequently imaged via cryo-TEM identified Geobacter spp., a well studied group of FeRB. STXM results at the Fe L2,3 absorption edges indicate that nanoparticle aggregates contain a variable mixture of Fe(II)-Fe(III), and are generally enriched in Fe(III). Geobacter bemidjiensis cultivated anaerobically in the laboratory on acetate and hydrous ferric oxyhydroxides also accumulated mixed valence nanoparticle aggregates. In field-collected samples, FeRB with a wide variety of morphologies were associated with nano-aggregates, indicating that cell-surface Fe(III) accumulation may be a general mechanism by which FeRB can grow while in planktonic suspension.« less

Iron-reducing bacteria accumulate ferric oxyhydroxide nanoparticle aggregates that may support planktonic growth.

PubMed

Luef, Birgit; Fakra, Sirine C; Csencsits, Roseann; Wrighton, Kelly C; Williams, Kenneth H; Wilkins, Michael J; Downing, Kenneth H; Long, Philip E; Comolli, Luis R; Banfield, Jillian F

2013-02-01

Iron-reducing bacteria (FeRB) play key roles in anaerobic metal and carbon cycling and carry out biogeochemical transformations that can be harnessed for environmental bioremediation. A subset of FeRB require direct contact with Fe(III)-bearing minerals for dissimilatory growth, yet these bacteria must move between mineral particles. Furthermore, they proliferate in planktonic consortia during biostimulation experiments. Thus, a key question is how such organisms can sustain growth under these conditions. Here we characterized planktonic microbial communities sampled from an aquifer in Rifle, Colorado, USA, close to the peak of iron reduction following in situ acetate amendment. Samples were cryo-plunged on site and subsequently examined using correlated two- and three-dimensional cryogenic transmission electron microscopy (cryo-TEM) and scanning transmission X-ray microscopy (STXM). The outer membranes of most cells were decorated with aggregates up to 150 nm in diameter composed of ∼3 nm wide amorphous, Fe-rich nanoparticles. Fluorescent in situ hybridization of lineage-specific probes applied to rRNA of cells subsequently imaged via cryo-TEM identified Geobacter spp., a well-studied group of FeRB. STXM results at the Fe L(2,3) absorption edges indicate that nanoparticle aggregates contain a variable mixture of Fe(II)-Fe(III), and are generally enriched in Fe(III). Geobacter bemidjiensis cultivated anaerobically in the laboratory on acetate and hydrous ferric oxyhydroxides also accumulated mixed-valence nanoparticle aggregates. In field-collected samples, FeRB with a wide variety of morphologies were associated with nano-aggregates, indicating that cell surface Fe(III) accumulation may be a general mechanism by which FeRB can grow while in planktonic suspension.

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.

In-plane magnetic anisotropy and coercive field dependence upon thickness of CoFeB

NASA Astrophysics Data System (ADS)

Kipgen, Lalminthang; Fulara, Himanshu; Raju, M.; Chaudhary, Sujeet

2012-09-01

The structural and magnetic properties of as-grown 5-50 nm thin ion-beam sputter deposited transition metal-metalloid Co20Fe60B20 (CFB) films are reported in this communication. A broad peak observed at 2θ∼45° in the glancing angle X-ray diffraction pattern revealed the formation of very fine nano-sized grains embedded in majority amorphous CFB matrix. Although no magnetic field is applied during deposition, the longitudinal magneto-optic Kerr effect measurements performed at 300 K in these as-grown films clearly established the presence of in-plane uniaxial magnetic anisotropy (Ku). It is argued that this observed anisotropy is strain-induced. This is supported by the observed dependence of direction of Ku on the angle between applied magnetic field and crystallographic orientation of the underlying Si(100) substrate, and increase in the coercivity with the increase of the film thickness.

N-doped amorphous carbon coated Fe3O4/SnO2 coaxial nanofibers as a binder-free self-supported electrode for lithium ion batteries.

PubMed

Xie, Wenhe; Li, Suyuan; Wang, Suiyan; Xue, Song; Liu, Zhengjiao; Jiang, Xinyu; He, Deyan

2014-11-26

N-doped amorphous carbon coated Fe3O4/SnO2 coaxial nanofibers were prepared via a facile approach. The core composite nanofibers were first made by electrospinning technology, then the shells were conformally coated using the chemical bath deposition and subsequent carbonization with polydopamine as a carbon source. When applied as a binder-free self-supported anode for lithium ion batteries, the coaxial nanofibers displayed an enhanced electrochemical storage capacity and excellent rate performance. The morphology of the interwoven nanofibers was maintained even after the rate cycle test. The superior electrochemical performance originates in the structural stability of the N-doped amorphous carbon shells formed by carbonizing polydopamine.

Monodisperse Zn-doped Fe3O4 formation and photo-Fenton activity for degradation of rhodamine B in water

NASA Astrophysics Data System (ADS)

Cen, Huoshi; Nan, Zhaodong

2018-10-01

Zn-doped Fe3O4 can be used as a catalyst in the photo-Fenton process to degrade dye molecules dissolved in water, in which cluster-shaped Zn-doped Fe3O4 (CSZnFe) was synthesized. To enhance the catalytic activity, monodisperse Zn-doped Fe3O4 (MZnFe) was facilely synthesized by a modified solvothermal method through replacement of sodium acetate by urea as a base. The particle size of MZnFe was about 9-16 nm. MZnFe exhibits a larger surface area and higher photo-Fenton catalytic activity for degradation of rhodamine B in water than CSZnFe. Additionally, MZnFe exhibits high saturation magnetization (about 80 emu/g), which is very convenient for separation of MZnFe from solution by a magnet. The growth processes for MZnFe were proposed on the basis of results from in situ calorimetry and other techniques, which indicated different formation mechanisms for MZnFe and CSZnFe.

Controlling electrodeposited ultrathin amorphous Fe hydroxides film on V-doped nickel sulfide nanowires as efficient electrocatalyst for water oxidation

NASA Astrophysics Data System (ADS)

Shang, Xiao; Yan, Kai-Li; Lu, Shan-Shan; Dong, Bin; Gao, Wen-Kun; Chi, Jing-Qi; Liu, Zi-Zhang; Chai, Yong-Ming; Liu, Chen-Guang

2017-09-01

Developing cost-effective electrocatalysts with both high activity and stability remains challenging for oxygen evolution reaction (OER) in water electrolysis. Herein, based on V-doped nickel sulfide nanowire on nickel foam (NiVS/NF), we further conduct controllable electrodeposition of Fe hydroxides film on NiVS/NF (eFe/NiVS/NF) to further improve OER performance and stability. For comparison, ultrafast chemical deposition of Fe hydroxides on NiVS/NF (uFe/NiVS/NF) is also utilized. V-doping of NiVS/NF may introduce more active sites for OER, and nanowire structure can expose abundant active sites and facilitate mass transport. Both of the two depositions generate amorphous Fe hydroxides film covering on the surface of nanowires and lead to enhanced OER activities. Furthermore, electrodeposition strategy realizes uniform Fe hydroxides film on eFe/NiVS/NF confirmed by superior OER activity of eFe/NiVS/NF than uFe/NiVS/NF with relatively enhanced stability. The OER activity of eFe/NiVS/NF depends on various electrodepositon time, and the optimal time (15 s) is obtained with maximum OER activity. Therefore, the controllable electrodeposition of Fe may provide an efficient and simple strategy to enhance the OER properties of electrocatalysts.

Effect of particle size of drug on conversion of crystals to an amorphous state in a solid dispersion with crospovidone.

PubMed

Sugamura, Yuka; Fujii, Makiko; Nakanishi, Sayaka; Suzuki, Ayako; Shibata, Yusuke; Koizumi, Naoya; Watanabe, Yoshiteru

2011-01-01

The effect of particle size on amorphization of drugs in a solid dispersion (SD) was investigated for two drugs, indomethacin (IM) and nifedipine (NP). The SD of drugs were prepared in a mixture with crospovidone by a variety of mechanical methods, and their properties investigated by particle sizing, thermal analysis, and powder X-ray diffraction. IM, which had an initial particle size of 1 µm and tends to aggregate, was forced through a sieve to break up the particles. NP, which had a large initial particle size, was jet-milled. In both cases, reduction of the particle size of the drugs enabled transition to an amorphous state below the melting point of the drug. The reduction in particle size is considered to enable increased contact between the crospovidone and drug particles, increasing interactions between the two compounds. © 2011 Pharmaceutical Society of Japan

Microchemical and Structural Evidence for Space Weathering in Soils from Asteroid Itokawa

NASA Technical Reports Server (NTRS)

Thompson, M. S.; Christoffersen, R.; Zega, T. J.

2013-01-01

The chemistry, microstructure and optical properties of grains on the surfaces of airless bodies are continu-ously modified due to their interactions predominantly with solar energetic ions and micrometeorite impacts. Collectively known as space weathering, this phenomenon results in a discrepancy between remotely sensed spectra from asteroids and those ac-quired directly from meteorites. The return of pristine samples from the asteroid Itokawa provides insight into surface processes on airless bodies and will help in correlating remote sensing data with laboratory analysis of meteorites. Samples and Methods: We examined Itokawa samples RA-QD02-0042-01 and RA-QD-02-0042-02, ultramicrotomed sec-tions of a singular grain prepared by the Hayabusa sample cura-tion team. We analyzed these slices using a 200 keV JEOL 2010F transmission electron microscope (TEM) at Arizona State Uni-versity and a 200 keV JEOL 2500SE TEM at NASA JSC. Both field emission TEMs are equipped with energy-dispersive X-ray spectrometers (EDS) and scanning TEM (STEM) detectors. Results and Discussion: TEM observations reveal that the sectioned grain predominantly consists of a single crystal of low-Ca orthopyroxene, with subsidiary smaller regions of olivine, Fe-Ni sulfide, and Fe-Ni metal. EDS-spectrum imaging and high-resolution TEM (HRTEM) show local, nanocrystalline regions of the outermost 2 to 5 nm of the pyroxene are composed of an Fe-Mg-S-rich and Si- and O-depleted layer that is underlain by a 2- to 5-nm thick amorphous zone enriched in Si. These layers occur in multiple microtome slices and have uniform thicknesses. We also observe localized 'islands' of material on the surface of the pyroxene which HRTEM imaging indicates are amorphous and EDS measurements show are compositionally heterogeneous. A 10- to 60-nm thick partially amorphous zone occurs below the compositionally distinct rim. While this this zone is associated with the compositionally heterogeneous outer layer, it also occurs as a local stand-alone feature on the exterior rim of the grain. Ar-eas of the pyroxene grain rim also exhibit a vesicular texture. The TEM data indicate a complex history of space weather-ing for samples RA-QD02-0042-01 and -02. The outermost layer of nanocrystalline material with varied composition is consistent with previously suggested [3-4] chemical and structural pro-cessing by solar wind ions, with a possible additional role for im-pact vapor deposition [3-4]. The amorphous and compositionally distinct islands on the surface of this grain, similar to lunar glasses, suggest formation through vapor deposition via micrometeor-ite impact events. In comparison, the amorphization and vesicula-tion textures are likely a product of radiation damage from the solar wind. The depth and degree of amorphization, in conjunction with model calculations, will help provide an upper limit on exposure time for these particles.

Insights to Meteorites and Impact Processes provided by Advanced EBSD Analysis

NASA Astrophysics Data System (ADS)

Palasse, Laurie; Berlin, Jana; Goran, Daniel; Tagle, Roald; Hamers, Maartje; Assis Fernandes, Vera; Deutsch, Alexander; Schulte, Peter; Salge, Tobias

2013-04-01

Electron backscatter diffraction (EBSD) is a powerful analytical technique for assessing the petrographic texture of rocks and the crystallographic orientation of minerals therein using a scanning electron microscope (SEM). Innovations in EBSD technology include colour-coded forescattered electron (FSE) images, high resolution and highly sensitive EBSD detectors, together with advanced EDS integration. It allows to accurately identify and discriminate different phases, and to investigate microstructures related to shock metamorphism. As an example, shocked carbonates and shocked quartz reveal a complex thermal history during post-shock cooling. (A) EBSD studies of calcite ejecta particles from the Chicxulub impact event, at the K-Pg boundary of El Guayal, Mexico (~520 km SW of the Chicxulub crater centre) display various microstructures [1] and spherulitic calcite ejecta particles reveal a fibre texture of elongated crystals with a preferred orientation. This indicates the presence of carbonate melts which were ejected at T>1240°C and P>40 bar from upper target lithologies and crystallized at cooling rates of ~100´s °C/s [2]. The calcite particles of El Guayal and the K/Pg boundary of La Lajilla (~1000 km W of the crater centre) show distinct microstructures represented by unoriented, equiaxed crystals with random orientation distribution. It documents recrystallization upon impact induced thermal stress at T>550°C during prolonged atmospheric transport. (B) Combined EBSD, FSE and cathodoluminescence (CL) studies of semi-amorphous shocked quartz of Chicxulub, Ries and Popigai impactites, reveal various microstructures. Colour-coded FSE imaging reveal recrystallized/deformed bands in Ries and Popigai samples indicative of planar deformation features. EBSD studies of Popigai allow to distinguish twinned Qz, α-Qz and α-cristobalite along the transition zone between shocked gneiss clast and impact melt. Recrystallized Qz grains are associated with amorphous SiO2. For Chicxulub, the brecciated impact melt rock from borehole Yaxcopoil-1 (Unit 5, 861.72 m) [3] reveals that the ballen microstructure is only semi-amorphous and cross cuts a fine grained recrystallised microstructure. (C) CB chondrite Gujba: EDS and EBSD data were acquired simultaneously to study chemical and physical interactions between preexisting metal particles and the invading silicate-rich impact melt matrix. Metal particles appear to have different thermal histories. Some of them consist of many small grains (average diameter ~10 µm), which have a similar orientation when they are surrounded by arcuate Fe,Cr-sulfides. [4]. Acknowledgements: P. Claeys, R.H. Jones, ICDP and the Museum of Natural History Berlin for providing samples. References: [1] T. Salge (2007) PhD thesis, Humboldt Universität zu Berlin, 130p. [2] A. P. Jones et al. (2000) Lect. Notes in Earth Sciences 91: 343-361. [3] M. J. Nelson et al. (2012) GCA 86: 1-20. [4]. J. Berlin et al. (2013) 44th LPSC # 2439

Occurrence of the Visible Gold and Sn-Bearing Mineral in Seafloor Hydrothermal Sulfides at Central Indian Ridge, 12.4°S

NASA Astrophysics Data System (ADS)

Choi, S. K.; Pak, S. J.; Kim, J.; Park, J. W.; Son, S. K.

2017-12-01

Sn-rich chimney fragments (up to 1,720 ppm) were recovered with ultramafic rocks from ocean core complex (OCC-4-1) of Central Indian Ridge, 12.4°S. The chimney fragments are featured by barite-free and Zn-rich (up to 50.1 wt.%) ores. The chimney fragments are mainly composed of sphalerite, isocubanite, pyrrhotite, chalcopyrite and marcasite with galena and electrum as minor minerals. The precipitation sequences of the minerals are categorized into three stages by mineral assemblage; early stage with low-temperature minerals, late stage with high-temperature minerals and seawater weathering stage with covellite, Fe-oxyhydroxides and amorphous silica. Early stage is characterized by sphalerite, intermittently showing colloform-texture, closely co-existed with anhedral marcasite and minor galena, whereas late stage is dominated by aggregates of isocubanite with chalcopyrite exsolution lamellae, pyrrhotite partially replaced by long prismatic marcasite and FeS enriched sphalerite (up to 42.69 FeS mole%). Electrums, main phase of gold mineralization, are mostly visible grains (< 3 um in diameter), occuring in sphalerite and isocubanite as inclusions and/or free gold in amorphous silica through the whole mineralization stages. On the basis of semi-quantified analysis, electrum grains are likely to have Au-rich composition. High Sn concentrations are typically observed in altered rim along the grain boundaries between sphalerite and isocubanite, going up to 5.5 wt.% in sphalerite. LA-ICP-MS mapping exhibits that Sn is preferentially incorporated into sphalerite relative to isocubanite, especially showing the highest values in boundaries between both minerals, but significantly lower in marcasite. Stoichiometry of Sn-enriched sphalerite rim seems to have a uniform ratio of atomic proportion of Cu to Sn as almost 2:1, implying that stannite micro-inclusions may result in Sn-enrichment. The LA-ICP-MS spectra also shows abrupt increase in Sn signal intensity, indicating Sn-bearing inclusions are distributed within sphalerite. Therefore, Sn-bearing mineral in sphalerite and isocubanite is likely to be fine particle of stannite in late stage and subsequently one of the possible ways to precipitate these particles could be reworking process of previously deposited Sn-bearing sulfides.

Physicochemical properties of respirable-size lunar dust

NASA Astrophysics Data System (ADS)

McKay, D. S.; Cooper, B. L.; Taylor, L. A.; James, J. T.; Thomas-Keprta, K.; Pieters, C. M.; Wentworth, S. J.; Wallace, W. T.; Lee, T. S.

2015-02-01

We separated the respirable dust and other size fractions from Apollo 14 bulk sample 14003,96 in a dry nitrogen environment. While our toxicology team performed in vivo and in vitro experiments with the respirable fraction, we studied the size distribution and shape, chemistry, mineralogy, spectroscopy, iron content and magnetic resonance of various size fractions. These represent the finest-grained lunar samples ever measured for either FMR np-Fe0 index or precise bulk chemistry, and are the first instance we know of in which SEM/TEM samples have been obtained without using liquids. The concentration of single-domain, nanophase metallic iron (np-Fe0) increases as particle size diminishes to 2 μm, confirming previous extrapolations. Size-distribution studies disclosed that the most frequent particle size was in the 0.1-0.2 μm range suggesting a relatively high surface area and therefore higher potential toxicity. Lunar dust particles are insoluble in isopropanol but slightly soluble in distilled water (~0.2 wt%/3 days). The interaction between water and lunar fines, which results in both agglomeration and partial dissolution, is observable on a macro scale over time periods of less than an hour. Most of the respirable grains were smooth amorphous glass. This suggests less toxicity than if the grains were irregular, porous, or jagged, and may account for the fact that lunar dust is less toxic than ground quartz.

Highly (002) textured large grain bcc Cr{sub 80}Mn{sub 20} seed layer on Cr{sub 50}Ti{sub 50} amorphous layer for FePt-C granular film

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

Jeon, Seong-Jae, E-mail: jsjigst@ecei.tohoku.ac.jp; Saito, Shin; Hinata, Shintaro

Effect of bcc Cr{sub 80}Mn{sub 20} seed layer and Cr{sub 50}Ti{sub 50} amorphous texture inducing layer on the heteroepitaxy system in FePt-C granular film was studied by introducing a new concept of the layered structure. The concept suggested that the large grain seed layer in which the crystallographic texture was initially formed on an amorphous layer in the layered structure can reduce the angular distribution of (002) c-axis crystal orientation in the FePt-C granular film owing to heteroepitaxial growth. Structure analysis by X-ray diffraction revealed that (1) when the substrate heating temperature was elevated from 300 °C to 500 °C, grain sizemore » in the seed layer increased from 9.8 nm to 11.6 nm, and then decreased with further increasing the substrate temperature. The reduction of the grain size over 500 °C corresponds to the crystallization of the amorphous texture inducing layer, (2) when the grain size increased from 9.8 nm to 11.6 nm, the angular distribution of the (002) orientation in the seed layer dramatically decreased from 13.7° to 4.1°. It was shown that the large grain seed layer increased the perpendicular hysteresis in FePt-C granular film.« less

One pot synthesis of exchange coupled Nd2Fe14B/alpha-Fe by pechini type sol-gel method.

PubMed

Hussain, Abid; Jadhav, Abhijit P; Baek, Yeon Kyung; Choi, Hul Jin; Lee, Jaeho; Kang, Young Soo

2013-11-01

In this work, a combination of nanoparticles of Nd2Fe14B hard magnetic phase and alpha-Fe soft magnetic phase were synthesized by one pot chemical synthesis technique using sol-gel method. A gel of Nd-Fe-B was prepared using NdCl3 x 6H2O, FeCl3 x 6H2O, H3BO3, citric acid, and ethylene glycol by pechini type sol-gel method. The gel was subsequently calcined and annealed to obtain the mixed oxide powders. The produced metal oxide particles were identified with XRD, SEM, TEM to obtain the crystal structure, shape and domain structure of them. The nanoparticles of mixed phase of Nd2Fe14B/alpha-Fe were obtained from these oxides by a process of reduction-diffusion in vacuum by employing CaH2 as reducing agent. During this process it was optimized by controlling temperature, reaction time and concentration of the reducing agent (CaH2). The phase formation of Nd2Fe14B was resulted by the direct diffusion of NdH2, Fe and B. The magnetic property of produced hard and soft phases was successfully identified with vibrating sample magnetometer (VSM). The mixed domains of the hard and soft phases were identified with selected area electron diffraction method (SAED) patterns.

Micro-Abrasion Wear Resistance of Borided 316L Stainless Steel and AISI 1018 Steel

NASA Astrophysics Data System (ADS)

Reséndiz-Calderon, C. D.; Rodríguez-Castro, G. A.; Meneses-Amador, A.; Campos-Silva, I. E.; Andraca-Adame, J.; Palomar-Pardavé, M. E.; Gallardo-Hernández, E. A.

2017-11-01

The 316L stainless steel has high corrosion resistance but low tribological performance. In different industrial sectors (biomedical, chemical, petrochemical, and nuclear engineering), improvement upon wear resistance of 316L stainless steel components using accessible and inexpensive methods is critical. The AISI 1018 steel is widely used in industry, but its tribological performance is not the best among steels. Therefore, in this study the behavior of the borided 316L stainless steel and 1018 steel is evaluated under micro-abrasion wear. The boriding was carried out at 1223 K over 6 h of exposure time, resulting in a biphase layer composed of FeB/Fe2B phases. In order to evaluate Fe2B phase with no influence from FeB phase, AISI 1018 steel samples were borided at 1273 K for over 20 min and then diffusion annealed at 1273 K over 2 h to obtain a Fe2B mono-phase layer. Micro-abrasion wear resistance was evaluated by a commercial micro-abrasion testing rig using a mix of F-1200 SiC particles with deionized water as abrasive slurry. The obtained wear rates for FeB and Fe2B phases and for the 316L stainless steel were compared. Wear resistance of 316L stainless steel increases after boriding. The wear mechanisms for both phases and for the stainless steel were identified. Also, transient conditions for rolling and grooving abrasion were determined for the FeB and Fe2B phases.

The effects of ion implantation on the tribology of perfluoropolyether-lubricated 440C stainless steel couples

NASA Technical Reports Server (NTRS)

Shogrin, Bradley; Jones, William R., Jr.; Wilbur, Paul J.; Pilar, Herrera-Fierro; Williamson, Don L.

1995-01-01

The lubricating lifetime of thin films of a perfluoropolyether (PFPE) based on hexafluoropropene oxide in the presence of ion implanted 440C stainless steel is presented. Stainless steel discs, either unimplanted or implanted with N2, C, Ti, Ti + N2, or Ti + C had a thin film of PFPE (60-400 A) applied to them reproducibly (+/- 20 percent) and uniformly (+/- 15 percent) using a device developed for this study. The lifetimes of these films were quantified by measuring the number of sliding-wear cycles required to induce an increase in the friction coefficient from an initial value characteristic of the lubricated wear couple to a final, or failure value, characteristic of an unlubricated, unimplanted couple. The tests were performed in a dry nitrogen atmosphere (less than 1 percent RH) at room temperature using a 3 N normal load with a relative sliding speed of 0.05 m/s. The lubricated lifetime of the 440C couple was increased by an order of magnitude by implanting the disc with Ti. Ranked from most to least effective, the implanted species were: Ti; Ti+C; unimplanted; N2; C approximately equals Ti+N2. The mechanism postulated to explain these results involves the formation of a passivating or reactive layer which inhibits or facilitates the production of active sites. The corresponding surface microstructures induced by ion implantation, obtained using x-ray diffraction and conversion electron Mossbauer spectroscopy, ranked from most to least effective in enhancing lubricant lifetime were: amorphous Fe-Cr-Ti; amorphous Fe-Cr-Ti-C + TiC; unimplanted; epsilon-(Fe,Cr)(sub x)N, x = 2 or 3; amorphous Fe-Cr-C approximately equals amorphous Fe-Cr-Ti-N.

Laboratory studies of refractory metal oxide smokes

NASA Technical Reports Server (NTRS)

Nuth, Joseph A.; Nelson, R. N.; Donn, Bertram

1989-01-01

Studies of the properties of refractory metal oxide smokes condensed from a gas containing various combinations of SiH4, Fe(CO)5, Al(CH3)3, TiCl4, O2 and N2O in a hydrogen carrier stream at 500 K greater than T greater than 1500 K were performed. Ultraviolet, visible and infrared spectra of pure, amorphous SiO(x), FeO(x), AlO(x) and TiO(x) smokes are discussed, as well as the spectra of various co-condensed amorphous oxides, such as FE(x)SiO(y) or Fe(x)AlO(y). Preliminary studies of the changes induced in the infrared spectra of iron-containing oxide smokes by vacuum thermal annealing suggest that such materials become increasingly opaque in the near infrared with increased processing: hydration may have the opposite effect. More work on the processing of these materials is required to confirm such a trend: this work is currently in progress. Preliminary studies of the ultraviolet spectra of amorphous Si2O3 and MgSiO(x) smokes revealed no interesting features in the region from 200 to 300 nm. Studies of the ultraviolet spectra of both amorphous, hydrated and annealed SiO(x), TiO(x), AlO(x) and FeO(x) smokes are currently in progress. Finally, data on the oxygen isotopic composition of the smokes produced in the experiments are presented, which indicate that the oxygen becomes isotopically fractionated during grain condensation. Oxygen in the grains is as much as 3 percent per amu lighter than the oxygen in the original gas stream. The authors are currently conducting experiments to understand the mechanism by which fractionation occurs.

Radio frequency shielding behaviour of silane treated Fe2O3/E-glass fibre reinforced epoxy hybrid composite

NASA Astrophysics Data System (ADS)

Arun prakash, V. R.; Rajadurai, A.

2016-10-01

In this work, radio frequency shielding behaviour of polymer (epoxy) matrixes composed of E-glass fibres and Fe2O3 fillers have been studied. The principal aim of this project is to prepare suitable shielding material for RFID application. When RFID unit is pasted on a metal plate without shielding material, the sensing distance is reduced, resulting in a less than useful RFID system. To improve RF shielding of epoxy, fibres and fillers were utilized. Magnetic behaviour of epoxy polymer composites was measured by hysteresis graphs (B-H) followed by radio frequency identifier setup. Fe2O3 particles of sizes 800, 200 and 100 nm and E-glass fibre woven mat of 600 g/m2 were used to make composites. Particle sizes of 800 nm and 200 nm were prepared by high-energy ball milling, whereas particles of 100 nm were prepared by sol-gel method. To enhance better dispersion of particles within the epoxy matrix, a surface modification process was carried out on fillers by an amino functional coupling agent called 3-Aminopropyltrimethoxysilane (APTMS). Crystalline and functional groups of siliconized Fe2O3 particles were characterized by XRD and FTIR spectroscopy analysis. Variable quantity of E-glass fibre (25, 35, and 45 vol%) was laid down along with 0.5 and 1.0 vol% of 800, 200, and 100 nm size Fe2O3 particles into the matrix, to fabricate the hybrid composites. Scanning electron microscopy and transmission electron microscopy images reveal the shape and size of Fe2O3 particles for different milling times and particle dispersion in the epoxy matrix. The maximum improved sensing distance of 45.2, 39.4 and 43.5 % was observed for low-, high-, and ultra-high radio frequency identifier setup along with shielding composite consist of epoxy, 1 vol% 200 nm Fe2O3 particles and 45 vol% of E-glass fibre.

Photoluminescence and doping mechanism of theranostic Eu3+/Fe3+ dual-doped hydroxyapatite nanoparticles.

PubMed

Chen, Min-Hua; Yoshioka, Tomohiko; Ikoma, Toshiyuki; Hanagata, Nobutaka; Lin, Feng-Huei; Tanaka, Junzo

2014-10-01

Theranostic nanoparticles currently have been regarded as an emerging concept of 'personalized medicine' with diagnostic and therapeutic dual-functions. Eu 3+ doped hydroxyapatite (HAp) has been regarded as a promising fluorescent probe for in vivo imaging applications. Additionally, substitution of Ca 2+ with Fe 3+ in HAp crystal may endow the capability of producing heat upon exposure to a magnetic field. Here we report a preliminary study of doping mechanism and photoluminescence of Eu 3+ and Fe 3+ doped HAp nanoparticles (Eu/Fe:HAp). HAp with varied concentration of Eu 3+ and Fe 3+ doping are presented as Eu(10 mol%):HAp, Eu(7 mol%)-Fe(3 mol%):HAp, Eu(5 mol%)-Fe(5 mol%):HAp, Eu(3 mol%)-Fe(7 mol%):HAp, and Fe(10 mol%):HAp in the study. The results showed that the HAp particles, in nano-size with rod-like morphology, were successfully doped with Eu 3+ and Fe 3+ , and the particles can be well suspended in cell culture medium. Photoluminescence analysis revealed that particles have prominent emissions at 536 nm, 590 nm, 615 nm, 650 nm and 695 nm upon excitation at a wavelength of 397 nm. Moreover, these Eu/Fe:HAp nanoparticles belonged to B-type carbonated HAp, which has been considered an effective biodegradable and biocompatible drug/gene carrier in biological applications.

Photoluminescence and doping mechanism of theranostic Eu3+/Fe3+ dual-doped hydroxyapatite nanoparticles

NASA Astrophysics Data System (ADS)

Chen, Min-Hua; Yoshioka, Tomohiko; Ikoma, Toshiyuki; Hanagata, Nobutaka; Lin, Feng-Huei; Tanaka, Junzo

2014-10-01

Theranostic nanoparticles currently have been regarded as an emerging concept of ‘personalized medicine’ with diagnostic and therapeutic dual-functions. Eu3+ doped hydroxyapatite (HAp) has been regarded as a promising fluorescent probe for in vivo imaging applications. Additionally, substitution of Ca2+ with Fe3+ in HAp crystal may endow the capability of producing heat upon exposure to a magnetic field. Here we report a preliminary study of doping mechanism and photoluminescence of Eu3+ and Fe3+ doped HAp nanoparticles (Eu/Fe:HAp). HAp with varied concentration of Eu3+ and Fe3+ doping are presented as Eu(10 mol%):HAp, Eu(7 mol%)-Fe(3 mol%):HAp, Eu(5 mol%)-Fe(5 mol%):HAp, Eu(3 mol%)-Fe(7 mol%):HAp, and Fe(10 mol%):HAp in the study. The results showed that the HAp particles, in nano-size with rod-like morphology, were successfully doped with Eu3+ and Fe3+, and the particles can be well suspended in cell culture medium. Photoluminescence analysis revealed that particles have prominent emissions at 536 nm, 590 nm, 615 nm, 650 nm and 695 nm upon excitation at a wavelength of 397 nm. Moreover, these Eu/Fe:HAp nanoparticles belonged to B-type carbonated HAp, which has been considered an effective biodegradable and biocompatible drug/gene carrier in biological applications.

Ambient-temperature NO oxidation over amorphous CrOx-ZrO 2 mixed oxide catalysts: Significant promoting effect of ZrO 2

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

Wang, Aiyong; Guo, Yanglong; Gao, Feng

2017-03-01

Three series of Cr-based mixed oxides (Cr-Co, Cr-Fe, and Cr-Ni oxides) with high specific surface areas and amorphous textures are synthesized using a novel sol-gel method. These mixed oxides, in comparison to their pure metal oxide (CrOx, Co3O4, FeOx and NiO) counterparts, display enhanced performance for catalytic oxidation of low-concentration NO at room temperature. Over best performing catalysts, 100% NO conversion can be maintained up to 30 h of operation at a high space velocity of 45,000 ml g-1 h-1. The amorphous structure is found to be critical for these catalysts to maintain high activity and durability. Cr/M (M=Co, Femore » and Ni) molar ratio, nitrate precursor decomposition temperature and catalyst calcination temperature are important criteria for the synthesis of the highly active catalysts. This work was supported by National Basic Research Program of China (2013CB933200), National Natural Science Foundation of China (21577035, 21577034), Commission of Science and Technology of Shanghai Municipality (15DZ1205305) and 111 Project (B08021). Aiyong Wang gratefully acknowledges the China Scholarship Council for the Joint-Training Scholarship Program with the Pacific Northwest National Laboratory (PNNL). PNNL is operated for the U.S. Department of Energy (DOE) by Battelle. FG and CHFP are supported by the U.S. DOE/Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Office.« less

Curiosity Rover's CheMin Instrument Investigates Mineralogy of Gale Crater and Implications for Diagenesis

NASA Astrophysics Data System (ADS)

Fendrich, Kim; Rampe, Elizabeth; Vaniman, David; Bish, David; Blake, David; Treiman, Allan; Ming, Doug; Morris, Richard; Bristow, Tom; Cavanagh, Patrick; Downs, Robert; Morrison, Shaunna; Chipera, Steve; Achilles, Cherie; Farmer, Jack; Sarrazin, Philippe; Crisp, Joy; Morookian, John Michael; Yen, Albert; Gellert, Ralf

2015-04-01

The Mars Science Laboratory rover Curiosity employs a suite of instruments to investigate past or present habitability of Mars, as observed at Gale crater and particularly in the lower strata of the crater's central mound, informally named Mount Sharp. The X-ray diffractometer on board, CheMin, is used to assess the quantitative mineralogy of scooped soil samples and drilled rock powders. Methods of modeling diffraction peak positions and intensities to evaluate the abundances of minerals include Rietveld refinement and FULLPAT (full-pattern fitting). Each of the samples analyzed by CheMin contains X-ray amorphous material. The amorphous component chemistry is resolved by subtracting the chemistry of the crystalline composition, as determined by X-ray diffraction data, from the bulk sample chemistry, as determined by the Alpha Particle X-ray Spectrometer (APXS). Diffraction results have been obtained on five samples thus far to include Rocknest, John Klein, Cumberland, Windjana and Confidence Hills. Soil samples collected at Rocknest, an aeolian bedform in Gale crater, were the first to be analyzed in situ by CheMin. The Rocknest mineral assemblage is basaltic (plagioclase, Fe-forsterite, augite, pigeonite) and contains amorphous material that is compositionally similar to palagonitic volcanic soils found on Earth, with the addition of sulfur and chlorine. The four drill analyses are characteristic of deposition in a variety of fluvio-lacustrine environments and exhibit evidence of low-temperature diagenesis. Both John Klein and Cumberland are part of the Sheepbed mudstone at Yellowknife Bay, where the first drilled samples were acquired as well as the first evidence of a habitable environment on Mars. Drilled three meters apart from each other, the two samples reveal basaltic minerals similar to those at Rocknest, as well as phyllosilicates, Fe-oxides/hydroxides, Ca-sulfates, Fe-sulfides, and amorphous materials. The nature and hydration of interlayer cations within the phyllosilicates differs between the two samples, which implies localized diagenesis. The Windjana sandstone at the Kimberley location differs from the Sheepbed mudstone in that it contains more pyroxene and magnetite and abundant K-feldspar, as well as phyllosilicates and amorphous material. These phases may represent potassium-rich basaltic provenance or aqueous alteration by potassium-bearing fluids. While the Confidence Hills sample is still in the preliminary stages of evaluation, major crystalline phases observed in this fine-grained sedimentary rock include plagioclase, pyroxene, K-feldspar and phyllosilicates; hematite, rare in all previous samples, is notably abundant and jarosite is present. The findings suggest localized mobilization of iron-bearing fluids and acidic conditions. The more oxidized assemblage of Confidence Hills marks the transition into the lower strata of Mount Sharp.

Amorphous or Crystalline? A Comparison of Particle Engineering Methods and Selection.

PubMed

Thakkar, Sachin G; Fathe, Kristin; Smyth, Hugh D C

2015-01-01

This review is intended to provide a critical account of the current goals and technologies of particle engineering regarding the production of crystalline and amorphous particles. The technologies discussed here cover traditional crystallization technologies, supercritical fluid technologies, spray drying, controlled solvent crystallization, and sonocrystallization. Also recent advancements in particle engineering including spray freezing into liquid, thin-film freeze-drying, PRINT technology are presented. The paper also examines the merits and limitations of these technologies with respect to their methods of characterization. Additionally a section discussing the utility of creating amorphous and crystalline formulation approaches in regards to bioavailability and utility in formulation is presented.

The role of counter ions in nano-hematite synthesis: Implications for surface area and selenium adsorption capacity.

PubMed

Lounsbury, Amanda W; Yamani, Jamila S; Johnston, Chad P; Larese-Casanova, Philip; Zimmerman, Julie B

2016-06-05

Nano metal oxides are of interest for aqueous selenium (Se) remediation, and as such, nano-hematite (nα-Fe2O3) was examined for use as a Se adsorbent. The effect of surface area on adsorption was also studied. nα-Fe2O3 particles were synthesized from Fe(NO3)3 and FeCl3 via forced hydrolysis. The resulting particles have similar sizes, morphologies, aggregate size, pore size, and PZC. The nα-Fe2O3 from FeCl3 (nα-Fe2O3-C) differs from the nα-Fe2O3 from Fe(NO3)3 (nα-Fe2O3-N) with a ∼25±2m(2)/g greater surface area. Selenite Se(IV) adsorption capacity on nα-Fe2O3 has a qmax ∼17mg/g for the freeze-dried and re-suspended nα-Fe2O3. The Δqmax for nα-Fe2O3 from Fe(NO3)3 and FeCl3 that remained in suspension was 4.6mg/g. For selenate Se(VI), the freeze-dried and re-suspended particles realize a Δqmax= 1.5mg/g for nα-Fe2O3 from Fe(NO3)3 and FeCl3. The nα-Fe2O3 from Fe(NO3)3 and FeCl3 that remained in suspension demonstrated Se(VI) Δqmax=5.4mg/g. In situ ATR-FTIR isotherm measurements completed for Se(VI) at a pH 6 suggest that Se(VI) forms primarily outer-sphere complexes with nα-Fe2O3 synthesized from both salts. Copyright © 2016 Elsevier B.V. All rights reserved.

Crystallization kinetics of Fe based amorphous alloy

NASA Astrophysics Data System (ADS)

Shanker Rao, T.; Lilly Shanker Rao, T.

2015-02-01

Differential Scanning Calorimetry(DSC) experimental data under non-isothermal conditions for Fe based Metglas 2605SA1 (wt% Fe=85-95, Si=5-10, B=1-5) metallic glass ribbons are reported and discussed. The DSC Scans performed at different heating rates showed two step crystallization processes and are interpreted in terms of different models like Kissinger, Ozawa, Boswell, Augis & Bennett and Gao & Wang. From the heating rate dependence of the onset temperature (To) and the crystallization peak temperature (Tp), the kinetic triplet, activation energy of crystallization (E), Avrami exponent (n) and the frequency factor (A) are determined. The determined E for peak I is 354.5 ± 2.5 kJ/mol and for the peak II is 348.2 ± 2.2 kJ/mol, respectively. The frequency factor for peak I is 1.1 × 1023sec-1 and for peak II is 6.1 × 1020sec-1.

Design and Characterisation of Metallic Glassy Alloys of High Neutron Shielding Capability

PubMed Central

Khong, J. C.; Daisenberger, D.; Burca, G.; Kockelmann, W.; Tremsin, A. S.; Mi, J.

2016-01-01

This paper reports the design, making and characterisation of a series of Fe-based bulk metallic glass alloys with the aim of achieving the combined properties of high neutron absorption capability and sufficient glass forming ability. Synchrotron X-ray diffraction and pair distribution function methods were used to characterise the crystalline or amorphous states of the samples. Neutron transmission and macroscopic attenuation coefficients of the designed alloys were measured using energy resolved neutron imaging method and the very recently developed microchannel plate detector. The study found that the newly designed alloy (Fe48Cr15Mo14C15B6Gd2 with a glass forming ability of Ø5.8 mm) has the highest neutron absorption capability among all Fe-based bulk metallic glasses so far reported. It is a promising material for neutron shielding applications. PMID:27848991

In vitro cytotoxicity of Fe-Cr-Nb-B magnetic nanoparticles under high frequency electromagnetic field

NASA Astrophysics Data System (ADS)

Chiriac, Horia; Petreus, Tudor; Carasevici, Eugen; Labusca, Luminita; Herea, Dumitru-Daniel; Danceanu, Camelia; Lupu, Nicoleta

2015-04-01

The heating potential, cytotoxicity, and efficiency of Fe68.2Cr11.5Nb0.3B20 magnetic nanoparticles (MNPs), as such or coated with a chitosan layer, to decrease the cell viability in a cancer cell culture model by using high frequency alternating magnetic fields (AMF) have been studied. The specific absorption rate varied from 215 W/g for chitosan-free MNPs to about 190 W/g for chitosan-coated ones, and an equilibrium temperature of 46 °C was reached when chitosan-coated MNPs were subjected to AMF. The chitosan-free Fe68.2Cr11.5Nb0.3B20 MNPs proved a good biocompatibility and low cytotoxicity in all testing conditions, while the chitosan-coated ones induced strong tumoricidal effects when a cell-particle simultaneous co-incubation approach was used. In high frequency AMF, the particle-mediated heat treatment has proved to be a critical cause for decreasing in vitro the viability of a cancer cell line.

Graphene nanosheets preparation using magnetic nanoparticle assisted liquid phase exfoliation of graphite: The coupled effect of ultrasound and wedging nanoparticles.

PubMed

Hadi, Alireza; Zahirifar, Jafar; Karimi-Sabet, Javad; Dastbaz, Abolfazl

2018-06-01

This study aims to investigate a novel technique to improve the yield of liquid phase exfoliation of graphite to graphene sheets. The method is based on the utilization of magnetic Fe 3 O 4 nanoparticles as "particle wedge" to facilitate delamination of graphitic layers. Strong shear forces resulted from the collision of Fe 3 O 4 particles with graphite particles, and intense ultrasonic waves lead to enhanced exfoliation of graphite. High quality of graphene sheets along with the ease of Fe 3 O 4 particle separation from graphene solution which arises from the magnetic nature of Fe 3 O 4 nanoparticles are the unique features of this approach. Initial graphite flakes and produced graphene sheets were characterized by various methods including field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Raman spectroscopy, atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Zeta potential analysis. Moreover, the effect of process factors comprising initial graphite concentration, Fe 3 O 4 nanoparticles concentration, sonication time, and sonication power were investigated. Results revealed that graphene preparation yield and the number of layers could be manipulated by the presence of magnetic nanoparticles. Copyright © 2018 Elsevier B.V. All rights reserved.

Key Roles of Size and Crystallinity of Nanosized Iron Hydr(oxides) Stabilized by Humic Substances in Iron Bioavailability to Plants.

PubMed

Kulikova, Natalia A; Polyakov, Alexander Yu; Lebedev, Vasily A; Abroskin, Dmitry P; Volkov, Dmitry S; Pankratov, Denis A; Klein, Olga I; Senik, Svetlana V; Sorkina, Tatiana A; Garshev, Alexey V; Veligzhanin, Alexey A; Garcia Mina, Jose M; Perminova, Irina V

2017-12-27

Availability of Fe in soil to plants is closely related to the presence of humic substances (HS). Still, the systematic data on applicability of iron-based nanomaterials stabilized with HS as a source for plant nutrition are missing. The goal of our study was to establish a connection between properties of iron-based materials stabilized by HS and their bioavailability to plants. We have prepared two samples of leonardite HS-stabilized iron-based materials with substantially different properties using the reported protocols and studied their physical chemical state in relation to iron uptake and other biological effects. We used Mössbauer spectroscopy, XRD, SAXS, and TEM to conclude on iron speciation, size, and crystallinity. One material (Fe-HA) consisted of polynuclear iron(III) (hydr)oxide complexes, so-called ferric polymers, distributed in HS matrix. These complexes are composed of predominantly amorphous small-size components (<5 nm) with inclusions of larger crystalline particles (the mean size of (11 ± 4) nm). The other material was composed of well-crystalline feroxyhyte (δ'-FeOOH) NPs with mean transverse sizes of (35 ± 20) nm stabilized by small amounts of HS. Bioavailability studies were conducted on wheat plants under conditions of iron deficiency. The uptake studies have shown that small and amorphous ferric polymers were readily translocated into the leaves on the level of Fe-EDTA, whereas relatively large and crystalline feroxyhyte NPs were mostly sorbed on the roots. The obtained data are consistent with the size exclusion limits of cell wall pores (5-20 nm). Both samples demonstrated distinct beneficial effects with respect to photosynthetic activity and lipid biosynthesis. The obtained results might be of use for production of iron-based nanomaterials stabilized by HS with the tailored iron availability to plants. They can be applied as the only source for iron nutrition as well as in combination with the other elements, for example, for industrial production of "nanofortified" macrofertilizers (NPK).

Sodium citrate functionalized reusable Fe3O4@TiO2 photocatalyst for water purification

NASA Astrophysics Data System (ADS)

Li, Wenyu; Wu, Haoyi

2017-10-01

Easy-recycle photocatalysts are new materials for water treatment technologies. In order to improve the recyclable ability, we employed Fe3O4 particles, which were functionalized by sodium citrate, to serve as a substrate core to attract the deposition of a shell of TiO2 particles. When compared to the calcining process for preparing the composite, the TiO2 distributed homogeneously on the sodium citrate treated Fe3O4, forming a mesoporous shell layer. Due to the mesoporous structure, this Fe3O4@TiO2 exhibited high photocatalytic degradation activity to Rhodamine B, and it was easily recycled using a magnetic field to recover the catalyst from solution.

Characterization of typical metal particles during haze episodes in Shanghai, China.

PubMed

Li, Rui; Yang, Xin; Fu, Hongbo; Hu, Qingqing; Zhang, Liwu; Chen, Jianmin

2017-08-01

Aerosol particles were collected during three heavy haze episodes at Shanghai in the winter of 2013. Transmission electron microscopy (TEM) coupled with energy dispersive X-ray spectroscopy was used to study the morphology and speciation of typical metal particles at a single-particle level. In addition, time-of-flight aerosol mass spectrometry (ATOFMS) was applied to identify the speciation of the Fe-containing particles. TEM analysis indicated that various metal-containing particles were hosted by sulfates, nitrates, and oxides. Fe-bearing particles mainly originated from vehicle emissions and/or steel production. Pb-, Zn-, and Sb-bearing particles were mainly contributed by anthropogenic sources. Fe-bearing particles were clustered into six groups by ATOFMS: Fe-Carbon, Fe-Inorganic, Fe-Trace metal, Fe-CN, Fe-PO 3, and Fe-NO 3 . ATOFMS data suggested that Fe-containing particles corresponded to different origins, including industrial activities, resuspension of dusts, and vehicle emissions. Fe-Carbon and Fe-CN particles displayed significant diurnal variation, and high levels were observed during the morning rush hours. Fe-Inorganic and Fe-Trace metal particle levels peaked at night. Furthermore, Fe-Carbon and Fe-PO 3 were mainly concentrated in the fine particles. Fe-CN, Fe-Inorganic, and Fe-Trace metal exhibited bimodal distribution. The mixing state of the particles revealed that all Fe-bearing particles tended to be mixed with sulfate and nitrate. The data presented herein is essential for elucidating the origin, evolution processes, and health effects of metal-bearing particles. Copyright © 2017 Elsevier Ltd. All rights reserved.

Bio-Inspired Bright Structurally Colored Colloidal Amorphous Array Enhanced by Controlling Thickness and Black Background.

PubMed

Iwata, Masanori; Teshima, Midori; Seki, Takahiro; Yoshioka, Shinya; Takeoka, Yukikazu

2017-07-01

Inspired by Steller's jay, which displays angle-independent structural colors, angle-independent structurally colored materials are created, which are composed of amorphous arrays of submicrometer-sized fine spherical silica colloidal particles. When the colloidal amorphous arrays are thick, they do not appear colorful but almost white. However, the saturation of the structural color can be increased by (i) appropriately controlling the thickness of the array and (ii) placing the black background substrate. This is similar in the case of the blue feather of Steller's jay. Based on the knowledge gained through the biomimicry of structural colored materials, colloidal amorphous arrays on the surface of a black particle as the core particle are also prepared as colorful photonic pigments. Moreover, a structural color on-off system is successfully built by controlling the background brightness of the colloidal amorphous arrays. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Effect of Spatial Heterogeneities on Nucleation Kinetics in Amorphous Aluminum Alloys

NASA Astrophysics Data System (ADS)

Shen, Ye

The mechanical property of the Al based metallic glass could be enhanced significantly by introducing the high number density of Al-fcc nanocrystals (1021 ˜1023 m-3) to the amorphous matrix through annealing treatments, which motivates the study of the nucleation kinetics for the microstructure control. With the presence of a high number density (1025 m-3) of aluminum-like medium range order (MRO), the Al-Y-Fe metallic glass is considered to be spatially heterogeneous. Combining the classical nucleation theory with the structural configuration, a MRO seeded nucleation model has been proposed and yields theoretical steady state nucleation rates consistent with the experimental results. In addition, this model satisfies all the thermodynamic and kinetic constraints to be reasonable. Compared with the Al-Y-Fe system, the primary crystallization onset temperature decreases significantly and the transient delay time (tau) is shorter in the Al-Y-Fe-Pb(In) systems because the insoluble Pb and In nanoparticles in the amorphous matrix served as extrinsic spatial heterogeneity to provide the nucleation sites for Al-fcc precipitation and the high-resolution transmission electron microscopy (HRTEM) images of the Pb-Al interface revealed a good wetting behavior between the Al and Pb nanoparticles. The study of the transient delay time (tau) could provide insight on the transport behavior during the nucleation and a more convenient approach to evaluate the delay time has been developed by measuring the Al-Y-Fe amorphous alloy glass transition temperature (Tg) shift with the increasing annealing time (tannealing) in FlashDSC. The break point in the Tg vs. log(tannealing) plot has been identified to correspond to the delay time by the TEM characterization. FlashDSC tests with different heating rates and different compositions (Al-Y-Fe-Pb and Zn-Mg-Ca-Yb amorphous alloys) further confirmed the break point and delay time relationship. The amorphous matrix composition and the enthalpy analysis indicates that there are different mechanisms leading to the Tg shift before and after the break point. Before the break point, Tg shifts solely due to the increased glass stability through a relaxation process. However, after the break point, Tg shifts to higher temperatures because of both the relaxation and the composition change effects.

Secondary mineral formation associated with respiration of nontronite, NAu-1 by iron reducing bacteria

PubMed Central

O'Reilly, S Erin; Watkins, Janet; Furukawa, Yoko

2005-01-01

Experimental batch and miscible-flow cultures were studied in order to determine the mechanistic pathways of microbial Fe(III) respiration in ferruginous smectite clay, NAu-1. The primary purpose was to resolve if alteration of smectite and release of Fe precedes microbial respiration. Alteration of NAu-1, represented by the morphological and mineralogical changes, occurred regardless of the extent of microbial Fe(III) reduction in all of our experimental systems, including those that contained heat-killed bacteria and those in which O2, rather than Fe(III), was the primary terminal electron acceptor. The solid alteration products observed under transmission electron microscopy included poorly crystalline smectite with diffuse electron diffraction signals, discrete grains of Fe-free amorphous aluminosilicate with increased Al/Si ratio, Fe-rich grains, and amorphous Si globules in the immediate vicinity of bacterial cells and extracellular polymeric substances. In reducing systems, Fe was also found as siderite. The small amount of Fe partitioned to the aqueous phase was primarily in the form of dissolved Fe(III) species even in the systems in which Fe(III) was the primary terminal electron acceptor for microbial respiration. From these observations, we conclude that microbial respiration of Fe(III) in our laboratory systems proceeded through the following: (1) alteration of NAu-1 and concurrent release of Fe(III) from the octahedral sheets of NAu-1; and (2) subsequent microbial respiration of Fe(III).

Recoil-free Fraction in Amorphous and Nanocrystalline Aluminium Based Alloys

NASA Astrophysics Data System (ADS)

Sitek, Jozef

2008-10-01

Aluminium based rapidly quenched alloys of nominal composition Al90Fe7Nb3 and Al94Fe2V4 were studied by Mössbauer spectroscopy. We have measured the recoil-free fraction and thermal shift at room and liquid nitrogen temperature. The frequency modes of atomic vibrations were determined and consequently the characteristic Debye temperature was derived. Characteristic temperature calculated from f-factor was lower than those fitted from second order Doppler shift. This indicates the presence of different frequency modes for amorphous and nanocrystalline states.

Dissolution Rates of Allophane, FE-Containing Allophane, and Hisingerite and Implications for Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Ralston, S. J.; Hausrath, E. M.; Tschauner, O.; Rampe, E. B.; Christoffersen, R.

2018-01-01

Investigations with the CheMin Xray Diffractometer (XRD) onboard the Curiosity rover in Gale Crater demonstrate that all rock and soil samples measured to date contain approximately 15-70 weight percentage X-ray amorphous materials. The diffuse scattering hump from the X-ray amorphous materials in CheMin XRD patterns can be fit with a combination of allophane, ferrihydrite, and rhyolitic and basaltic glass. Because of the iron-rich nature of Mars' surface, Fe-rich poorly-crystalline phases, such as hisingerite, may be present in addition to allophane.

Lithium potential variations for metastable materials: case study of nanocrystalline and amorphous LiFePO4.

PubMed

Zhu, Changbao; Mu, Xiaoke; Popovic, Jelena; Weichert, Katja; van Aken, Peter A; Yu, Yan; Maier, Joachim

2014-09-10

Much attention has been paid to metastable materials in the lithium battery field, especially to nanocrystalline and amorphous materials. Nonetheless, fundamental issues such as lithium potential variations have not been pertinently addressed. Using LiFePO4 as a model system, we inspect such lithium potential variations for various lithium storage modes and evaluate them thermodynamically. The conclusions of this work are essential for an adequate understanding of the behavior of electrode materials and even helpful in the search for new energy materials.

Effect of mechanical activation on jell boronizing treatment of the AISI 4140

NASA Astrophysics Data System (ADS)

Yılmaz, S. O.; Karataş, S.

2013-06-01

The article presents the effect of mechanical activation on the growth kinetics of boride layer of boronized AISI 4140 steel. The samples were boronized by ferroboron + (SiO2-Na2O) powders for 873-1173 K temperature and 2, 4, 6 and 8 h times, respectively. The morphology and types of borides formed on the surface of AISI 4140 steel substrate were analyzed. Layer growth kinetics were analyzed by measuring the extent of penetration of FeB and Fe2B sublayers as function of treatment time and temperature in the range of 873-1173 K. High diffusivity was obtained by creating a large number of defects through mechanical activation in the form of nanometer sized crystalline particles through the repeated fracturing and cold-welding of the powder particles, and a depth of 100 μm was found in the specimen borided by the 2 h MA powders, for 4 h and 1073 K, where 2000-2350 HV were measured. Consequently, the application conditions of boronizing were improved by usage of mechanical activation. The preferred Fe2B boride without FeB could be formed in the boride layer under 973 K boronizing temperature by mechanically activated by ferroboron + sodium silicate powder mixture due to the decrease of the activation energy.

EFFECT OF PRE-ALLOYING CONDITION ON THE BULK AMORPHOUS ALLOY ND(60)FE(30)AL(10).

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

OCONNOR,A.S.; LEWIS,L.H.; MCCALLUM,R.W.

Bulk metallic glasses are materials that require only modest cooling rates to obtain amorphous solids directly from the melt. Nd{sub 60}Fe{sub 30}Al{sub 10} has been reported to be a ferromagnetic bulk metallic glass that exhibits high coercivity, a combination unlike conventional Nd-based amorphous magnetic alloys. To clarify the relationship between short-range order and high coercivity in glassy Nd{sub 60}Fe{sub 30}Al{sub 10}, experiments were performed to verify the existence of a homogeneous liquid state prior to rapid solidification. Alloys were prepared by various pre-alloying routes and then melt-spun. Arc-melted alloys were prepared for melt spinning using three different protocols involving: (1)more » alloying all three elements at once, (2) forming a Nd-Fe alloy which was subsequently alloyed with Al, and (3) forming a Fe-Al alloy for subsequent alloying with Nd. XRD, DTA, and magnetic measurement data from the resultant ribbons indicate significant differences in both the glassy fraction and the crystalline phase present in the as-spun material. These observed differences are attributed to the presence of highly stable nanoscopic aluminide-and/or silicide-phases, or motes, present in the melt prior to solidification. These motes would affect the short-range order and coercivity of the resultant glassy state and are anticipated to provide heterogeneous nucleation sites for crystallization.« less

Preservation of amorphous ultrafine material: A proposed proxy for slip during recent earthquakes on active faults

NASA Astrophysics Data System (ADS)

Hirono, Tetsuro; Asayama, Satoru; Kaneki, Shunya; Ito, Akihiro

2016-11-01

The criteria for designating an “Active Fault” not only are important for understanding regional tectonics, but also are a paramount issue for assessing the earthquake risk of faults that are near important structures such as nuclear power plants. Here we propose a proxy, based on the preservation of amorphous ultrafine particles, to assess fault activity within the last millennium. X-ray diffraction data and electron microscope observations of samples from an active fault demonstrated the preservation of large amounts of amorphous ultrafine particles in two slip zones that last ruptured in 1596 and 1999, respectively. A chemical kinetic evaluation of the dissolution process indicated that such particles could survive for centuries, which is consistent with the observations. Thus, preservation of amorphous ultrafine particles in a fault may be valuable for assessing the fault’s latest activity, aiding efforts to evaluate faults that may damage critical facilities in tectonically active zones.

Ethylene glycol assisted spray pyrolysis for the synthesis of hollow BaFe12O19 spheres

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

Xu, X; Park, J; Hong, YK

2015-04-01

Hollow spherical BaFe12O19 particles were synthesized by spray pyrolysis from a solution containing ethylene glycol (EG) and precursors at 1000 degrees C. The effects of EG concentration on particle morphology, crystallinity and magnetic properties were investigated. The hollow spherical particles were found to consist of primary particles, and higher EG concentration led to a bigger primary particle size. EG concentration did not show much effect on the hollow particle size. Better crystallinity and higher magnetic coercivity were obtained with higher EG concentration, which is attributed to further crystallization with the heat produced from EG combustion. Saturation magnetization (emu/g) decreased withmore » increasing EG concentration due to residual carbon from EG incomplete combustion, contributing as a non-magnetic phase to the particles. Published by Elsevier B.V.« less

Innovative soft magnetic multilayers with enhanced in-plane anisotropy and ferromagnetic resonance frequency for integrated RF passive devices

NASA Astrophysics Data System (ADS)

Falub, Claudiu V.; Bless, Martin; Hida, Rachid; MeduÅa, Mojmír; Ammann, Arnold

2018-04-01

We present an innovative, economical method for manufacturing soft magnetic materials that may pave the way for integrated thin film magnetic cores with dramatically improved properties. Soft magnetic multilayered thin films based on the Fe-28%Co20%B (at.%) and Co-4.5%Ta4%Zr (at.%) amorphous alloys are deposited on 8" bare Si and Si/200nm-thermal-SiO2 wafers in an industrial, high-throughput Evatec LLS EVO II magnetron sputtering system. The multilayers consist of stacks of alternating 80-nm-thick ferromagnetic layers and 4-nm-thick Al2O3 dielectric interlayers. Since in our dynamic sputter system the substrate cage rotates continuously, such that the substrates face different targets alternatively, each ferromagnetic sublayer in the multilayer consists of a fine structure comprising alternating CoTaZr and FeCoB nanolayers with very sharp interfaces. We adjust the thickness of these individual nanolayers between 0.5 and 1.5 nm by changing the cage rotation speed and the power of each gun, which is an excellent mode to engineer new, composite ferromagnetic materials. Using X-ray reflectometry (XRR) we reveal that the interfaces between the FeCoB and CoTaZr nanolayers are perfectly smooth with roughness of 0.2-0.3 nm. Kerr magnetometry and B-H looper measurements for the as-deposited samples show that the coercivity of these thin films is very low, 0.2-0.3 Oe, and gradually scales up with the thickness of FeCoB nanolayers, i.e. with the increase of the overall Fe content from 0 % (e.g. CoTaZr-based multilayers) to 52 % (e.g. FeCoB-based multilayers). We explain this trend in the random anisotropy model, based on considerations of grain size growth, as revealed by glancing angle X-ray diffraction (GAXRD), but also because of the increase of magnetostriction with the increase of Fe content as shown by B-H looper measurements performed on strained wafers. The unexpected enhancement of the in-plane anisotropy field from 18.3 Oe and 25.8 Oe for the conventional CoTaZr- and FeCoB-based multilayers, respectively, up to ˜48 Oe for the nanostructured multilayers with FeCoB/CoTaZr nano-bilayers is explained based on interface anisotropy contribution. These novel soft magnetic multilayers, with enhanced in-plane anisotropy, allow operation at higher frequencies, as revealed by broadband (between 100 MHz and 10 GHz) RF measurements that exhibit a classical Landau-Lifschitz-Gilbert (LLG) behavior.

HIGHWAY INFRASTRUCTURE FOCUS AREA NEXT-GENERATION INFRASTRUCTURE MATERIALS VOLUME I - TECHNICAL PROPOSAL & MANAGEMENTENHANCEMENT OF TRANSPORTATION INFRASTRUCTURE WITH IRON-BASED AMORPHOUS-METAL AND CERAMIC COATINGS

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

Farmer, J C

2007-12-04

The infrastructure for transportation in the United States allows for a high level of mobility and freight activity for the current population of 300 million residents, and several million business establishments. According to a Department of Transportation study, more than 230 million motor vehicles, ships, airplanes, and railroads cars were used on 6.4 million kilometers (4 million miles) of highways, railroads, airports, and waterways in 1998. Pipelines and storage tanks were considered to be part of this deteriorating infrastructure. The annual direct cost of corrosion in the infrastructure category was estimated to be approximately $22.6 billion in 1998. There weremore » 583,000 bridges in the United States in 1998. Of this total, 200,000 bridges were steel, 235,000 were conventional reinforced concrete, 108,000 bridges were constructed using pre-stressed concrete, and the balance was made using other materials of construction. Approximately 15 percent of the bridges accounted for at this point in time were structurally deficient, primarily due to corrosion of steel and steel reinforcement. Iron-based amorphous metals, including SAM2X5 (Fe{sub 49.7}Cr{sub 17.7}Mn{sub 1.9}Mo{sub 7.4}W{sub 1.6}B{sub 15.2}C{sub 3.8}Si{sub 2.4}) and SAM1651 (Fe{sub 48}Mo{sub 14}Cr{sub 15}Y{sub 2}C{sub 15}B{sub 6}) have been developed, and have very good corrosion resistance. These materials have been prepared as a melt-spun ribbons, as well as gas atomized powders and thermal-spray coatings. During electrochemical testing in several environments, including seawater at 90 C, the passive film stabilities of these materials were found to be comparable to that of more expensive high-performance alloys, based on electrochemical measurements of the passive film breakdown potential and general corrosion rates. These materials also performed very well in standard salt fog tests. Chromium (Cr), molybdenum (Mo) and tungsten (W) provided corrosion resistance, and boron (B) enabled glass formation. The high boron content of this particular amorphous metal made it an effective neutron absorber, and suitable for criticality control applications. These amorphous alloys appear to maintain their corrosion resistance up to the glass transition temperature. Visionary research is proposed to extend the application of corrosion-resistant iron-based amorphous metal coatings, and variants of these coatings, to protection of the Nation's transportation infrastructure. Specific objectives of the proposed work are: (1) fabrication of appropriate test samples for evaluation of concept; (2) collection of production and test data for coated steel reinforcement bars, enabling systematic comparison of various coating options, based upon performance and economic considerations; and (3) construction and testing of concrete structures with coated steel reinforcement bars, thereby demonstrating the value of amorphous-metal coatings. The benefits of ceramic coatings as thermal barriers will also be addressed.« less

Amorphous solid dispersion of cyclosporine A prepared with fine droplet drying process: Physicochemical and pharmacokinetic characterization.

PubMed

Suzuki, Hiroki; Moritani, Tatsuru; Morinaga, Tadahiko; Seto, Yoshiki; Sato, Hideyuki; Onoue, Satomi

2017-03-15

The present study aimed to develop an amorphous solid dispersion (ASD) of cyclosporine A (CsA) by a fine droplet drying (FDD) process for improvement in oral absorption of CsA. CsA and hydroxypropyl cellulose-SSL were dissolved in 1,4-dioxane, and the solution was powdered by the FDD process to obtain the ASD formulation of CsA (ASD/CsA). The ASD/CsA was characterized in terms of morphology, particle size distribution, crystallinity, dissolution behavior, physicochemical stability, and pharmacokinetic behavior in rats. The ASD/CsA was obtained in the form of uniform spherical particles, and the span factor was calculated to be ca. 0.4. CsA in the formulation existed in an amorphous state. The ASD/CsA exhibited a higher dissolution behavior of CsA than amorphous CsA, whereas storage of the ASD/CsA under accelerated conditions led to impairment in the dissolution behavior. The constant release of CsA from non-aged ASD/CsA was observed during dissolution testing. After oral administration of CsA samples (10mg-CsA/kg) in rats, the ASD/CsA showed a high and sustained plasma concentration of CsA as evidenced by a 18-fold increase in the oral bioavailability of CsA compared with amorphous CsA. From these findings, the FDD process might be an efficacious option for the ASD formulation of CsA with enhanced biopharmaceutics properties. Copyright © 2017 Elsevier B.V. All rights reserved.

Soft magnetic properties of nanocrystalline FeRuGaSi-Hf alloy films and head characteristics for the embedded thin film tape head

NASA Astrophysics Data System (ADS)

Ohmori, H.; Shoji, M.; Kobayashi, T.; Yamamoto, T.; Sugiyama, Y.; Hayashi, K.; Hono, K.

1996-04-01

The Hf-added FeRuGaSi alloy film has an amorphous structure in the as-deposited state and becomes nanocrystalline after annealing. Due to this structure change from crystalline to amorphous by the addition of Hf, soft magnetic degradation of the film deposited on the slant grooved substrate, which is necessary for the sophisticated embedded thin film (ETF) head structure, is greatly suppressed and the undesirable film stress is relieved. The FeRuGaSi-Hf alloy film has higher resistivity and permeability at high frequencies than those of sendust film, and the read/write characteristics of this alloy film show better performance than sendust film.

Mössbauer and X-ray Diffraction Investigations of Sn-containing Binary and Ternary Electrodeposited Alloys from a Gluconate Bath

NASA Astrophysics Data System (ADS)

Kuzmann, E.; Stichleutner, S.; Doyle, O.; Chisholm, C. U.; El-Sharif, M.; Homonnay, Z.; Vértes, A.

2005-04-01

Constant current technique was applied to electrodeposit tin-containing coatings such as tin-cobalt (Sn-Co), tin-iron (Sn-Fe) and a novel tin-cobalt-iron (Sn-Co-Fe) from a gluconate bath. The effect of plating parameters (current density, deposition time at an electrolyte temperature of 60°C and pH=7.0) on phase composition, crystal structure and magnetic anisotropy of alloy deposits has been investigated mainly by 57Fe CEMS, 119Sn CEMS and transmission Mössbauer Spectroscopy as well as XRD. 57Fe and 119Sn CEM spectra and XRD reflect that the dominant phases of the deposits are orthorhombic Co3Sn2, tetragonal FeSn2 or amorphous Fe-Sn and amorphous Sn-Co-Fe in Sn-Co, Sn-Fe and Sn-Co-Fe coatings, respectively. Furthermore, the relative area of the 2nd and 5th lines of the sextets representing the magnetic iron containing phases decreases continuously with increasing current density in all Fe-containing deposits. At the same time, no essential change in the magnetic anisotropy can be found with the plating time. 119Sn spectra reveal the presence of small amount of β-Sn besides the main phases in Sn-Fe and in the Sn-Co coatings. Magnetically split 119Sn spectra reflecting transferred hyperfine field were observed in the case of Co-Sn-Fe coatings.

Computer Simulation of Fracture in Aerogels

NASA Technical Reports Server (NTRS)

Good, Brian S.

2006-01-01

Aerogels are of interest to the aerospace community primarily for their thermal properties, notably their low thermal conductivities. While the gels are typically fragile, recent advances in the application of conformal polymer layers to these gels has made them potentially useful as lightweight structural materials as well. In this work, we investigate the strength and fracture behavior of silica aerogels using a molecular statics-based computer simulation technique. The gels' structure is simulated via a Diffusion Limited Cluster Aggregation (DLCA) algorithm, which produces fractal structures representing experimentally observed aggregates of so-called secondary particles, themselves composed of amorphous silica primary particles an order of magnitude smaller. We have performed multi-length-scale simulations of fracture in silica aerogels, in which the interaction b e e n two secondary particles is assumed to be described by a Morse pair potential parameterized such that the potential range is much smaller than the secondary particle size. These Morse parameters are obtained by atomistic simulation of models of the experimentally-observed amorphous silica "bridges," with the fracture behavior of these bridges modeled via molecular statics using a Morse/Coulomb potential for silica. We consider the energetics of the fracture, and compare qualitative features of low-and high-density gel fracture.

Comparing Wild 2 Particles to Chondrites and IDPS

NASA Technical Reports Server (NTRS)

Zolensky, Michael; Nakamura-Messenger, Keiko; Rietmeijer, Frans; Leroux, Hugues; Mikouchi, Takashi; Ohsumi, Kazumasa; Simon, Steven; Grossman, Lawrence; Stephan, Thomas; Weisberg, Michael;

Fe and O EELS Studies of Ion Irradiated Murchison CM2 Carbonaceous Chondrite Matrix

NASA Technical Reports Server (NTRS)

Keller, L. P.; Christofferson, R.; Dukes, C. A.; Baragiola, R. A.; Rahman, Z.

2015-01-01

Introduction: The physical and chemical response of hydrated carbonaceous chondrite materials to space weathering processes is poorly understood. Improving this understanding is a key part of establishing how regoliths on primitive carbonaceous asteroids respond to space weathering processes, knowledge that supports future sample return missions (Hayabusa 2 and OSIRISREx) that are targeting objects of this type. We previously reported on He+ irradiation of Murchison matrix and showed that the irradiation resulted in amorphization of the matrix phyllosilicates, loss of OH, and surface vesiculation. Here, we report electron energy-loss spectroscopy (EELS) measurements of the irradiated material with emphasis on the Fe and O speciation. Sample and Methods: A polished thin section of the Murchison CM2 carbonaceous chondrite was irradiated with 4 kilovolts He(+) (normal incidence) to a total dose of 1 x 10(exp 18) He(+) per square centimeter. We extracted thin sections from both irradiated and unirradiated regions in matrix using focused ion beam (FIB) techniques with electron beam deposition for the protective carbon strap to minimize surface damage artifacts from the FIB milling. The FIB sections were analyzed using a JEOL 2500SE scanning and transmission electron microscope (STEM) equipped with a Gatan Tridiem imaging filter. EELS spectra were collected from 50 nanometer diameter regions with an energy resolution of 0.7 electronvolts FWHM at the zero loss. EELS spectra were collected at low electron doses to minimize possible artifacts from electron-beam irradiation damage. Results and Discussion: Fe L (sub 2,3) EELS spectra from matrix phyllosilicates in CM chondrites show mixed Fe(2+)/Fe(3+) oxidation states with Fe(3+)/Sigma Fe approximately 0.5. Fe L(sub 2,3) spectra from the irradiated/ amorphized matrix phyllosilicates show higher Fe(2+)/Fe(3+) ratios compared to spectra obtained from pristine material at depths beyond the implantation/amorphization layer. We also obtained O Ka spectra from phyllosilicates in both regions of the sample. The O Ka spectra show a pre-edge feature at approximately 530.5 electronvolts that is related to O 2p states hybridized with Fe 3d states. The intensity ratio of the O Ka pre-edge peak relative to the main part of the O Ka edge (that results from transitions of O 1s to 2p states) is lower in the irradiated layer compared to the pristine material and may reflect the loss of O (as OH) as was observed by IR spectroscopy. Conclusions: In addition to amorphization and OH loss, EELS spectra of He(+) irradiated matrix phyllosilicates in Murchison show that some of the Fe(3+) is reduced to Fe(2+). Spectral deconvolution is underway to extract quantitative ratios from the EELS spectra.

Characterization of terrestrial hydrothermal alteration products with Mars analog instrumentation: Implications for current and future rover investigations

NASA Astrophysics Data System (ADS)

Black, Sarah R.; Hynek, Brian M.

2018-06-01

Interpretation of Martian geology relies heavily on our understanding of terrestrial analog deposits and our ability to obtain comprehensive and accurate mineralogical compositions. Many previous studies of terrestrial hydrothermal deposits relied on limited datasets and/or did not use instruments analogous to those deployed on Mars. We analyzed 100 hydrothermally altered basalts from Costa Rica, Nicaragua, and Iceland with Mars analog Visible to Short Wave Infrared (VSWIR) spectroscopy, X-ray Diffraction (XRD), and Raman laser spectrometry. Alteration mineralogy consisted of amorphous and crystalline SiO2 (cristobalite, tridymite, quartz), Ca/Al/Fe/Mg-sulfates (gypsum, anhydrite, alunite, jarosite, hexahydrite, alunogen), Fe-, Ti-, and Mg-oxides/hydroxides (hematite, goethite, anatase/brookite, brucite), elemental sulfur, and phyllosilicates (montmorillonite, kaolinite). Results indicate VSWIR is best suited for identification of X-ray amorphous materials such as hydrated SiO2 and phyllosilicates, while XRD is best utilized for highly ordered crystalline materials such as sulfates, crystalline SiO2 polymorphs, elemental sulfur, and Mg-hydroxides identification. Surprisingly, XRD had the lowest identification rates for Fe-oxides/hydroxides (42% compared to 61% and 75% for VNIR and Raman, respectively), and nearly equal identification rates as VSWIR for kaolinite (76% for VSWIR, 71% for XRD). Identification of phyllosilicates in XRD, while possible, is not as effective as VSWIR without extensive sample preparation. Our observed identification rates may be attributed to the relative abundance of materials-Fe-oxides/hydroxides being present as surface coatings, the presence of large amounts of kaolinite in some samples, and an increased particle size for kaolinite relative to other clays. Elemental sulfur and Fe- and Ti-oxides/hydroxides were more readily identified with Raman. With NASA's current focus on habitability, hydrothermally altered areas-which we know to host a wide range of microbial life here on Earth-are of high interest and it is likely that future rovers will encounter similar mineral assemblages. Therefore, future rovers would benefit from using a combination of these methods and expanding the VSWIR sampling range to the full 300-2500 nm to conduct a comprehensive mineralogical investigation.

Facile hydrothermal synthesis of Fe3O4@cellulose aerogel nanocomposite and its application in Fenton-like degradation of Rhodamine B.

PubMed

Jiao, Yue; Wan, Caichao; Bao, Wenhui; Gao, He; Liang, Daxin; Li, Jian

2018-06-01

A magnetic cellulose aerogel-supported Fe 3 O 4 nanoparticles composite was designed as a highly efficient and eco-friendly catalyst for Fenton-like degradation of Rhodamine B (RhB). The composite (coded as Fe 3 O 4 @CA) was formed by embedding well-dispersed Fe 3 O 4 nanoparticles into the 3D structure of cellulose aerogels by virtue of a facile and cheap hydrothermal method. Comparative studies indicate that the RhB decolorization ratio is much higher in co-presence of Fe 3 O 4 and H 2 O 2 than that in presence of Fe 3 O 4 or H 2 O 2 only, revealing that the Fe 3 O 4 @CA-catalyzed Fenton-like reaction governed the RhB decolorization process. It was also found that almost 100% RhB removal was achieved in the Fenton-like system. Moreover, the composite exhibited higher catalytic activity than that of the individual Fe 3 O 4 particles. In addition, the Fe 3 O 4 @CA catalyst retained ∼97% of its ability to degrade RhB after the six successive degradation experiments, suggesting its excellent reusability. All these merits indicate that the green and low-cost catalyst with strong magnetic responsiveness possesses good potential for H 2 O 2 -driven Fenton-like treatment of organic dyestuff wastewater. Copyright © 2018 Elsevier Ltd. All rights reserved.

Magnetoconductive maghemite core/polyaniline shell nanoparticles: Physico-chemical and biological assessment.

PubMed

Anna, Zasońska Beata; Patrycja, Bober; Petr, Jošt; Petrovský, Eduard; Pavel, Boštík; Daniel, Horák

2016-05-01

Nanoparticles of various compositions are increasingly being used in many areas of medicine. The aim of this study was to develop nanoparticles, which would possess both magnetic and conductive properties and, thus improve their suitability for a wider range of biomedical applications. Namely, it would enable both the particle manipulation and imaging using their magnetic properties and simultaneous stimulation of electro-sensitive cell types using their magnetic properties, which can be used in tissue therapy, engineering and as biosensors. Maghemite (γ-Fe2O3) particles were prepared by the co-precipitation of Fe(2+) and Fe(3+) salts with ammonium hydroxide, followed by the controlled oxidation with NaOCl. The polyaniline (PANI) shell on the γ-Fe2O3 nanoparticles was obtained by the polymerization of aniline hydrochloride with ammonium peroxydisulfate in an aqueous solution of poly(N-vinylpyrrolidone) at two reaction temperatures (0 and 25 °C). The resulting γ-Fe2O3&PANI particles were characterized by both the light and transmission electron microscopies, dynamic light scattering, magnetic measurements, UV-vis and energy dispersive X-ray (EDAX) spectroscopy. The size of the starting γ-Fe2O3 particles was 11 nm, that increased to 25 nm after the modification with PANI. The incubation of both the γ-Fe2O3 and γ-Fe2O3&PANI nanoparticles with the human neuroblastoma derived SH-SY5Y cells for 8 days showed neither significant decrease in the cell viability, nor detectable changes in the cell morphology. This indicates, that the particles have no detectable cytotoxicity in cell culture and represent a promising tool for further use in biomedical applications. Copyright © 2016 Elsevier B.V. All rights reserved.

Amorphous salts formed from rapid dehydration of multicomponent chloride and ferric sulfate brines: Implications for Mars

PubMed Central

Sklute, Elizabeth C.; Rogers, A. Deanne; Gregerson, Jason C.; Jensen, Heidi B.; Reeder, Richard J.; Dyar, M. Darby

2018-01-01

Salts with high hydration states have the potential to maintain high levels of relative humidity (RH) in the near subsurface of Mars, even at moderate temperatures. These conditions could promote deliquescence of lower hydrates of ferric sulfate, chlorides, and other salts. Previous work on deliquesced ferric sulfates has shown that when these materials undergo rapid dehydration, such as that which would occur upon exposure to present day Martian surface conditions, an amorphous phase forms. However, the fate of deliquesced halides or mixed ferric sulfate-bearing brines are presently unknown. Here we present results of rapid dehydration experiments on Ca–, Na–, Mg– and Fe–chloride brines and multi-component (Fe2 (SO4)3 ± Ca, Na, Mg, Fe, Cl, HCO3) brines at ∼21°C, and characterize the dehydration products using visible/near-infrared (VNIR) reflectance spectroscopy, mid-infrared attenuated total reflectance spectroscopy, and X-ray diffraction (XRD) analysis. We find that rapid dehydration of many multicomponent brines can form amorphous solids or solids with an amorphous component, and that the presence of other elements affects the persistence of the amorphous phase under RH fluctuations. Of the pure chloride brines, only Fe–chloride formed an amorphous solid. XRD patterns of the multicomponent amorphous salts show changes in position, shape, and magnitude of the characteristic diffuse scattering observed in all amorphous materials that could be used to help constrain the composition of the amorphous salt. Amorphous salts deliquesce at lower RH values compared to their crystalline counterparts, opening up the possibility of their role in potential deliquescence-related geologic phenomena such as recurring slope lineae (RSLs) or soil induration. This work suggests that a wide range of aqueous mixed salt solutions can lead to the formation of amorphous salts and are possible for Mars; detailed studies of the formation mechanisms, stability and transformation behaviors of amorphous salts are necessary to further constrain their contribution to Martian surface materials. PMID:29670302

Synthesis of triaxial LiFePO4 nanowire with a VGCF core column and a carbon shell through the electrospinning method.

PubMed

Hosono, Eiji; Wang, Yonggang; Kida, Noriyuki; Enomoto, Masaya; Kojima, Norimichi; Okubo, Masashi; Matsuda, Hirofumi; Saito, Yoshiyasu; Kudo, Tetsuichi; Honma, Itaru; Zhou, Haoshen

2010-01-01

A triaxial LiFePO4 nanowire with a multi wall carbon nanotube (VGCF:Vapor-grown carbon fiber) core column and an outer shell of amorphous carbon was successfully synthesized through the electrospinning method. The carbon nanotube core oriented in the direction of the wire played an important role in the conduction of electrons during the charge-discharge process, whereas the outer amorphous carbon shell suppressed the oxidation of Fe2+. An electrode with uniformly dispersed carbon and active materials was easily fabricated via a single process by heating after the electrospinning method is applied. Mossbauer spectroscopy for the nanowire showed a broadening of the line width, indicating a disordered coordination environment of the Fe ion near the surface. The electrospinning method was proven to be suitable for the fabrication of a triaxial nanostructure.

Synthesis and characterization of Fe(III)-silicate precipitation tubes

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

Parmar, K.; Pramanik, A.K.; Bandyopadhya, N.R.

2010-09-15

Fe(III)-silicate precipitation tubes synthesized through 'silica garden' route have been characterized using a number of analytical techniques including X-ray diffraction, infrared spectroscopy, atomic force microscopy, scanning and transmission electron microscopy. These tubes are brittle and amorphous and are hierarchically built from smaller tubes of 5-10 nm diameters. They remain amorphous at least up to 650 {sup o}C. Crystobalite and hematite are the major phases present in Fe(III)-silicate tubes heated at 850 {sup o}C. Morphology and chemical compositions at the external and internal walls of these tubes are remarkably different. These tubes are porous with high BET surface area of 291.2more » m{sup 2}/g. Fe(III)-silicate tubes contain significant amount of physically and chemically bound moisture. They show promise as an adsorbent for Pb(II), Zn(II), and Cr(III) in aqueous medium.« less

Effects of Chloride and Sulfate Salts on the Inhibition or Promotion of Sucrose Crystallization in Initially Amorphous Sucrose-Salt Blends.

PubMed

Thorat, Alpana A; Forny, Laurent; Meunier, Vincent; Taylor, Lynne S; Mauer, Lisa J

2017-12-27

The effects of salts on the stability of amorphous sucrose and its crystallization in different environments were investigated. Chloride (LiCl, NaCl, KCl, MgCl 2 , CaCl 2 , CuCl 2 , FeCl 2 , FeCl 3 , and AlCl 3 ) and sulfate salts with the same cations (Na 2 SO 4 , K 2 SO 4 , MgSO 4 , CuSO 4 , Fe(II)SO 4 , and Fe(III)SO 4 ) were studied. Samples (sucrose controls and sucrose:salt 1:0.1 molar ratios) were lyophilized, stored in controlled temperature and relative humidity (RH) conditions, and monitored for one month using X-ray diffraction. Samples were also analyzed by differential scanning calorimetry, microscopy, and moisture sorption techniques. All lyophiles were initially amorphous, but during storage the presence of a salt had a variable impact on sucrose crystallization. While all samples remained amorphous when stored at 11 and 23% RH at 25 °C, increasing the RH to 33 and 40% RH resulted in variations in crystallization onset times. The recrystallization time generally followed the order monovalent cations < sucrose < divalent cations < trivalent cations. The presence of a salt typically increased water sorption as compared to sucrose alone when stored at the same RH; however, anticrystallization effects were observed for sucrose combined with salts containing di- and trivalent cations in spite of the increased water content. The cation valency and hydration number played a major role in dictating the impact of the added salt on sucrose crystallization.

Amorphous calcium carbonate particles form coral skeletons

NASA Astrophysics Data System (ADS)

Mass, Tali; Giuffre, Anthony J.; Sun, Chang-Yu; Stifler, Cayla A.; Frazier, Matthew J.; Neder, Maayan; Tamura, Nobumichi; Stan, Camelia V.; Marcus, Matthew A.; Gilbert, Pupa U. P. A.

2017-09-01

Do corals form their skeletons by precipitation from solution or by attachment of amorphous precursor particles as observed in other minerals and biominerals? The classical model assumes precipitation in contrast with observed “vital effects,” that is, deviations from elemental and isotopic compositions at thermodynamic equilibrium. Here, we show direct spectromicroscopy evidence in Stylophora pistillata corals that two amorphous precursors exist, one hydrated and one anhydrous amorphous calcium carbonate (ACC); that these are formed in the tissue as 400-nm particles; and that they attach to the surface of coral skeletons, remain amorphous for hours, and finally, crystallize into aragonite (CaCO3). We show in both coral and synthetic aragonite spherulites that crystal growth by attachment of ACC particles is more than 100 times faster than ion-by-ion growth from solution. Fast growth provides a distinct physiological advantage to corals in the rigors of the reef, a crowded and fiercely competitive ecosystem. Corals are affected by warming-induced bleaching and postmortem dissolution, but the finding here that ACC particles are formed inside tissue may make coral skeleton formation less susceptible to ocean acidification than previously assumed. If this is how other corals form their skeletons, perhaps this is how a few corals survived past CO2 increases, such as the Paleocene-Eocene Thermal Maximum that occurred 56 Mya.

Amorphous calcium carbonate particles form coral skeletons.

PubMed

Mass, Tali; Giuffre, Anthony J; Sun, Chang-Yu; Stifler, Cayla A; Frazier, Matthew J; Neder, Maayan; Tamura, Nobumichi; Stan, Camelia V; Marcus, Matthew A; Gilbert, Pupa U P A

2017-09-12

Do corals form their skeletons by precipitation from solution or by attachment of amorphous precursor particles as observed in other minerals and biominerals? The classical model assumes precipitation in contrast with observed "vital effects," that is, deviations from elemental and isotopic compositions at thermodynamic equilibrium. Here, we show direct spectromicroscopy evidence in Stylophora pistillata corals that two amorphous precursors exist, one hydrated and one anhydrous amorphous calcium carbonate (ACC); that these are formed in the tissue as 400-nm particles; and that they attach to the surface of coral skeletons, remain amorphous for hours, and finally, crystallize into aragonite (CaCO 3 ). We show in both coral and synthetic aragonite spherulites that crystal growth by attachment of ACC particles is more than 100 times faster than ion-by-ion growth from solution. Fast growth provides a distinct physiological advantage to corals in the rigors of the reef, a crowded and fiercely competitive ecosystem. Corals are affected by warming-induced bleaching and postmortem dissolution, but the finding here that ACC particles are formed inside tissue may make coral skeleton formation less susceptible to ocean acidification than previously assumed. If this is how other corals form their skeletons, perhaps this is how a few corals survived past CO 2 increases, such as the Paleocene-Eocene Thermal Maximum that occurred 56 Mya.

Amorphous calcium carbonate particles form coral skeletons

PubMed Central

Mass, Tali; Giuffre, Anthony J.; Sun, Chang-Yu; Stifler, Cayla A.; Frazier, Matthew J.; Neder, Maayan; Tamura, Nobumichi; Stan, Camelia V.; Marcus, Matthew A.

2017-01-01

Do corals form their skeletons by precipitation from solution or by attachment of amorphous precursor particles as observed in other minerals and biominerals? The classical model assumes precipitation in contrast with observed “vital effects,” that is, deviations from elemental and isotopic compositions at thermodynamic equilibrium. Here, we show direct spectromicroscopy evidence in Stylophora pistillata corals that two amorphous precursors exist, one hydrated and one anhydrous amorphous calcium carbonate (ACC); that these are formed in the tissue as 400-nm particles; and that they attach to the surface of coral skeletons, remain amorphous for hours, and finally, crystallize into aragonite (CaCO3). We show in both coral and synthetic aragonite spherulites that crystal growth by attachment of ACC particles is more than 100 times faster than ion-by-ion growth from solution. Fast growth provides a distinct physiological advantage to corals in the rigors of the reef, a crowded and fiercely competitive ecosystem. Corals are affected by warming-induced bleaching and postmortem dissolution, but the finding here that ACC particles are formed inside tissue may make coral skeleton formation less susceptible to ocean acidification than previously assumed. If this is how other corals form their skeletons, perhaps this is how a few corals survived past CO2 increases, such as the Paleocene–Eocene Thermal Maximum that occurred 56 Mya. PMID:28847944

Prebiotic carbon in clays from Orgueil and Ivuna (CI), and Tagish Lake (C2 ungrouped) meteorites

NASA Astrophysics Data System (ADS)

Garvie, Laurence A. J.; Buseck, Peter R.

Transmission electron microscopic (TEM) and electron energy-loss spectroscopic (EELS) study of the Ivuna and Orgueil (CI), and Tagish Lake (C2 ungrouped) carbonaceous chondrite meteorites shows two types of C-clay assemblages. The first is coarser-grained (to 1 μm) clay flakes that show an intense O K edge from the silicate together with a prominent C K edge, but without discrete C particles. Nitrogen is common in some clay flakes. Individual Orgueil and Tagish Lake meteorite clay flakes contain up to 6 and 8 at% C, respectively. The C K-edge spectra from the clays show fine structure revealing aromatic, aliphatic, carboxylic, and carbonate C. The EELS data shows that this C is intercalated with the clay flakes. The second C-clay association occurs as poorly crystalline to amorphous material occurring as nanometer aggregates of C, clay, and Fe-O-rich material. Some aggregates are dominated by carbonaceous particles that are structurally and chemically similar to the acid insoluble organic matter. The C K-edge shape from this C resembles that of amorphous C, but lacking the distinct peaks corresponding to aliphatic, carboxylic, and carbonate C groups. Nanodiamonds are locally abundant in some carbonaceous particles. The abundance of C in the clays suggest that molecular speciation in the carbonaceous chondrites is partly determined by the effects of aqueous processing on the meteorite parent bodies, and that clays played an important role. This intricate C-clay association lends credence to the proposal that minerals were important in the prebiotic chemical evolution of the early solar system.

Magnetic and magnetothermal studies of iron boride (FeB) nanoparticles

NASA Astrophysics Data System (ADS)

Hamayun, M. Asif; Abramchuk, Mykola; Alnasir, Hisham; Khan, Mohsin; Pak, Chongin; Lenhert, Steven; Ghazanfari, Lida; Shatruk, Michael; Manzoor, Sadia

2018-04-01

We report magnetic and magnetothermal properties of iron boride (FeB) nanoparticles prepared by surfactant-assisted ball milling of arc-melted bulk ingots of this binary alloy. Size-dependent magnetic properties were used to identify the transition to the single domain limit and calculate the anisotropy and exchange stiffness constants for this system. Extended milling is seen to produce coercivity enhancement and exchange bias of up to 270 Ôe at room temperature. The magnetothermal properties were investigated by measuring the response of single domain FeB nanoparticles to externally applied ac magnetic fields. All investigated particle sizes show a significant heating response, demonstrating their potential as candidates for magnetically induced hyperthermia. FeB nanoparticles were encapsulated into lipophilic domains of liposomes as evidenced by TEM. Exposure of HeLa cells to these liposomes did not affect cell viability, suggesting the biocompatibility of these new magnetic nanomaterials.

Transmission electron microscope analyses of alteration phases in martian meteorite MIL 090032

NASA Astrophysics Data System (ADS)

Hallis, L. J.; Ishii, H. A.; Bradley, J. P.; Taylor, G. J.

2014-06-01

The nakhlite group of martian meteorites found in the Antarctic contain varying abundances of both martian and terrestrial secondary alteration phases. The aim of this study was to use transmission electron microscopy (TEM) to compare martian and terrestrial alteration embodied within a single nakhlite martian meteorite find - MIL 090032. Martian alteration veins in MIL 090032 are composed of poorly ordered Fe-smectite phyllosilicate. This poorly-ordered smectite appears to be equivalent to the nanocrystalline phyllosilicate/hydrated amorphous gel phase previously described in the martian alteration veins of other nakhlites. Chemical differences in this nanocrystalline phyllosilicate between different nakhlites imply localised alteration, which occurred close to the martian surface in MIL 090032. Both structurally and compositionally the nakhlite nanocrystalline phyllosilicate shows similarities to the amorphous/poorly ordered phase recently discovered in martian soil by the Mars Curiosity Rover at Rocknest, Gale Crater. Terrestrially derived alteration phases in MIL 090032 include jarosite and gypsum, amorphous silicates, and Fe-oxides and hydroxides. Similarities between the mineralogy and chemistry of the MIL 090032 terrestrial and martian alteration phases suggest the alteration conditions on Mars were similar to those in the Antarctic. At both sites a small amount of fluid at low temperatures infiltrated the rock and became acidic as a result of the conversion of Fe2+ to Fe3+ under oxidising conditions.

Efficient gradient-based Monte Carlo simulation of materials: Applications to amorphous Si and Fe and Ni clusters

NASA Astrophysics Data System (ADS)

Limbu, Dil; Biswas, Parthapratim

We present a simple and efficient Monte-Carlo (MC) simulation of Iron (Fe) and Nickel (Ni) clusters with N =5-100 and amorphous Silicon (a-Si) starting from a random configuration. Using Sutton-Chen and Finnis-Sinclair potentials for Ni (in fcc lattice) and Fe (in bcc lattice), and Stillinger-Weber potential for a-Si, respectively, the total energy of the system is optimized by employing MC moves that include both the stochastic nature of MC simulations and the gradient of the potential function. For both iron and nickel clusters, the energy of the configurations is found to be very close to the values listed in the Cambridge Cluster Database, whereas the maximum force on each cluster is found to be much lower than the corresponding value obtained from the optimized structural configurations reported in the database. An extension of the method to model the amorphous state of Si is presented and the results are compared with experimental data and those obtained from other simulation methods. The work is partially supported by the NSF under Grant Number DMR 1507166.

Hydrothermal synthesis of Ni 2FeBO 5 in near-supercritical PWR coolant and possible effects of neutron-induced 10B fission in fuel crud

NASA Astrophysics Data System (ADS)

Sawicki, Jerzy A.

2011-08-01

The hydrothermal synthesis of a nickel-iron oxyborate, Ni 2FeBO 5, known as bonaccordite, was investigated at pressures and temperatures that might occur at the surface of high-power fuel rods in PWR cores and in supercritical water reactors, especially during localized departures from nucleate boiling and dry-outs. The tests were performed using aqueous mixtures of nickel and iron oxides with boric acid or boron oxide, and as a function of lithium hydroxide addition, temperature and time of heating. At subcritical temperatures nickel ferrite NiFe 2O 4 was always the primary reaction product. High yield of Ni 2FeBO 5 synthesis started near critical water temperature and was strongly promoted by additions of LiOH up to Li/Fe and Li/B molar ratios in a range 0.1-1. The synthesis of bonaccordite was also promoted by other alkalis such as NaOH and KOH. The bonaccordite particles were likely formed by dissolution and re-crystallization by means of an intermediate nickel ferrite phase. It is postulated that the formation of Ni 2FeBO 5 in deposits of borated nickel and iron oxides on PWR fuel cladding can be accelerated by lithium produced in thermal neutron capture 10B(n,α) 7Li reactions. The process may also be aided in the reactor core by kinetic energy of α-particles and 7Li ions dissipated in the crud layer.

Crystallization of MgFe2O4 from a glass in the system K2O/B2O3/MgO/P2O5/Fe2O3

NASA Astrophysics Data System (ADS)

El Shabrawy, Samha; Bocker, Christian; Rüssel, Christian

2016-10-01

Spherical magnetic Mg-Fe-O nanoparticles were successfully prepared by the crystallization of glass in the system K2O/B2O3/MgO/P2O5/Fe2O3. The magnetic glass ceramics were prepared by melting the raw materials using the conventional melt quenching technique followed by a thermal treatment at temperatures in the range 560-700 °C for a time ranging from 2 to 8 h. The studies of the X-ray diffraction, electron microscopy and FTIR spectra confirmed the precipitation of finely dispersed spherical (Mg, Fe) based spinel nanoparticles with a minor quantity of hematite (α-Fe2O3) in the glass matrix. The average size of the magnetic nano crystals increases slightly with temperature and time from 9 to 15 nm as determined by the line broadening from the XRD patterns. XRD studies show that annealing the glass samples for long periods of time at temperature ≥604 °C results in an increase of the precipitated hematite concentration, dissolution of the spinel phase and the formation of magnesium di-borate phase (Mg2B2O5). For electron microscopy, the particles were extracted by two methods; (i) replica extraction technique and (ii) dissolution of the glass matrix by diluted acetic acid. An agglomeration of the nano crystals to larger particles (25-35 nm) was observed.

Germanium and Tin Based Anode Materials for Lithium-Ion Batteries

NASA Astrophysics Data System (ADS)

Ji, Dongsheng

The discovery of safe anode materials with high energy density for lithium-ion batteries has always been a significant topic. Group IV elements have been under intensive study for their high capability of alloying with lithium. Batteries with graphite and tin based anode material have already been applied in cell phones and vehicles. In order to apply group IV elements, their dramatic volume change during lithiation and delithiation processes is the key point to work on. Reducing the particle size is the most common method to buffer the volume expansion. This strategy has been applied on both germanium and tin based materials. Germanium based anode material has been made by two different synthesis methods. The amorphous Ge-C-Ti composite material was made by ball milling method and performed much better than other germanium alloy including Ge-Mg, Ge-Fe and Ge-Fe.Germanium sphere nano particles with diameter of around 50 nm have been made by solution method. After ball milled with graphite, the resulted product performed stable capacity over 500 mAh˙g-1 for more than 20 cycles. Ball milled graphite in the composite plays an important role of buffering volume change and stabilizing germanium. Sn-Fe alloy is one of the feasible solutions to stabilize tin. Sn 2Fe-C composite has been made by ball milling method. After optimizations of the ratio of precursors, reaction time, milling balls and electrolyte additives, the electrochemistry performance was improved. The anode performed 420 mAh˙ -1 at 1.0 mA/cm2 and maintained its structure after cycling at 2.0 mA/cm2. At 0.3 mA/cm2 cycling rate, the anode performed 978 mAh/cm3 after 500 cycles, which still exceeds the theoretical capacity of graphite.

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.

Navicula sp. Sulfated Polysaccharide Gels Induced by Fe(III): Rheology and Microstructure

PubMed Central

Fimbres-Olivarría, Diana; López-Elías, José Antonio; Carvajal-Millán, Elizabeth; Márquez-Escalante, Jorge Alberto; Martínez-Córdova, Luis Rafael; Miranda-Baeza, Anselmo; Enríquez-Ocaña, Fernando; Valdéz-Holguín, José Eduardo; Brown-Bojórquez, Francisco

2016-01-01

A sulfated polysaccharide extracted from Navicula sp. presented a yield of 4.4 (% w/w dry biomass basis). Analysis of the polysaccharide using gas chromatography showed that this polysaccharide contained glucose (29%), galactose (21%), rhamnose (10%), xylose (5%) and mannose (4%). This polysaccharide presented an average molecular weight of 107 kDa. Scanning electron microscopy (SEM) micrographs showed that the lyophilized Navicula sp. polysaccharide is an amorphous solid with particles of irregular shapes and sharp angles. The polysaccharide at 1% (w/v) solution in water formed gels in the presence of 0.4% (w/v) FeCl3, showing elastic and viscous moduli of 1 and 0.7 Pa, respectively. SEM analysis performed on the lyophilized gel showed a compact pore structure, with a pore size of approximately 150 nm. Very few studies on the gelation of sulfated polysaccharides using trivalent ions exist in the literature, and, to the best of our knowledge, this study is the first to describe the gelation of sulfated polysaccharides extracted from Navicula sp. PMID:27483255

Navicula sp. Sulfated Polysaccharide Gels Induced by Fe(III): Rheology and Microstructure.

PubMed

Fimbres-Olivarría, Diana; López-Elías, José Antonio; Carvajal-Millán, Elizabeth; Márquez-Escalante, Jorge Alberto; Martínez-Córdova, Luis Rafael; Miranda-Baeza, Anselmo; Enríquez-Ocaña, Fernando; Valdéz-Holguín, José Eduardo; Brown-Bojórquez, Francisco

2016-07-30

A sulfated polysaccharide extracted from Navicula sp. presented a yield of 4.4 (% w/w dry biomass basis). Analysis of the polysaccharide using gas chromatography showed that this polysaccharide contained glucose (29%), galactose (21%), rhamnose (10%), xylose (5%) and mannose (4%). This polysaccharide presented an average molecular weight of 107 kDa. Scanning electron microscopy (SEM) micrographs showed that the lyophilized Navicula sp. polysaccharide is an amorphous solid with particles of irregular shapes and sharp angles. The polysaccharide at 1% (w/v) solution in water formed gels in the presence of 0.4% (w/v) FeCl₃, showing elastic and viscous moduli of 1 and 0.7 Pa, respectively. SEM analysis performed on the lyophilized gel showed a compact pore structure, with a pore size of approximately 150 nm. Very few studies on the gelation of sulfated polysaccharides using trivalent ions exist in the literature, and, to the best of our knowledge, this study is the first to describe the gelation of sulfated polysaccharides extracted from Navicula sp.

To enhance the efficiency of a power supply circuit by the use of Fe-P-B-Nb-type ultralow loss glassy metal core

NASA Astrophysics Data System (ADS)

Matsumoto, H.; Urata, A.; Yamada, Y.; Makino, A.

2009-04-01

The inductor in a power supply is required to be capable of dealing satisfactorily with the high-current supply and to improve the power loss characteristic. A novel glassy metal powder with a chemical composition Fe77P7B13Nb3 features both a high saturated magnetic flux density of 1.3 T and a low coercive force of 2.0 A/m, which has a stable amorphous structure suitable for glassy metal composite cores. Hence there is no magnetic saturation even under a high-current supply, and it is confirmed to have significantly low magnetic loss resulting from the low coercive force. As a result of using the glassy metal alloy Fe77P7B13Nb3 powder in an inductor core, we have achieved improvement in power supply efficiency by up to roughly 2.0%. Moreover, the reduction in the standby power requirement by the improvement in the power supply efficiency in the low load current case, where the core loss occupies a high ratio in the entire loss, can be expected. Additionally, heat generation in a core is suppressed by using the low loss powder, and it becomes easy to design a temperature rise in the entire power supply circuit.

Heteroatom (P, B, or S) incorporated NiFe-based nanocubes as efficient electrocatalysts for the oxygen evolution reaction

DOE PAGES

Xuan, Cuijuan; Wang, Jie; Xia, Weiwei; ...

2018-03-21

Exploring low-cost and highly efficient electrocatalysts toward the oxygen evolution reaction (OER) is of significant importance, although facing great challenges for sustainable energy systems. In this study, amorphous NiFe-based porous nanocubes (Ni–Fe–O–P, Ni–Fe–O–B, and Ni–Fe–O–S) are successfully synthesized via simple and cost-effective one-step calcination of Ni–Fe based metal–organic frameworks (MOFs) and heteroatom containing molecules. The resulting three materials maintain a well-defined porous nanocube morphology with heteroatoms uniformly distributed in the structure. The unique porous structure can effectively provide more active sites and shorten the mass transport distance. Additionally, the introduction of P, B or S can tune the electronic structure,more » which is favorable for accelerating the charge transfer, and may lead to the formation of the higher average oxidative valence of Ni species during the OER process. Benefiting from the above desirable properties, all three materials exhibit excellent OER electrocatalytic activities and outstanding long-term stability in a home-made zinc air battery. Lastly, this work not only provides a general approach for the synthesis of highly efficient electrocatalysts based on earth-abundant elements but also highlights the potential prospects of MOFs in energy conversion and storage devices.« less

Heteroatom (P, B, or S) incorporated NiFe-based nanocubes as efficient electrocatalysts for the oxygen evolution reaction

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

Xuan, Cuijuan; Wang, Jie; Xia, Weiwei

Exploring low-cost and highly efficient electrocatalysts toward the oxygen evolution reaction (OER) is of significant importance, although facing great challenges for sustainable energy systems. In this study, amorphous NiFe-based porous nanocubes (Ni–Fe–O–P, Ni–Fe–O–B, and Ni–Fe–O–S) are successfully synthesized via simple and cost-effective one-step calcination of Ni–Fe based metal–organic frameworks (MOFs) and heteroatom containing molecules. The resulting three materials maintain a well-defined porous nanocube morphology with heteroatoms uniformly distributed in the structure. The unique porous structure can effectively provide more active sites and shorten the mass transport distance. Additionally, the introduction of P, B or S can tune the electronic structure,more » which is favorable for accelerating the charge transfer, and may lead to the formation of the higher average oxidative valence of Ni species during the OER process. Benefiting from the above desirable properties, all three materials exhibit excellent OER electrocatalytic activities and outstanding long-term stability in a home-made zinc air battery. Lastly, this work not only provides a general approach for the synthesis of highly efficient electrocatalysts based on earth-abundant elements but also highlights the potential prospects of MOFs in energy conversion and storage devices.« less

Octahedron Fe3O4 particles supported on 3D MWCNT/graphene foam: In-situ method and application as a comprehensive microwave absorption material

NASA Astrophysics Data System (ADS)

Shi, Luolin; Zhao, Yan; Li, Ye; Han, Xiao; Zhang, Tong

2017-09-01

In this work, we used in-situ method to directly prepare a novel structure consisting of well-distributed octahedron Fe3O4 particles, porous graphene foam (GF) and fibrous multiwalled carbon nanotube (MWCNT): started with an intense stir to anchor Fe3+ on the surfaces of graphene oxide and oxided MWCNT, followed by solvothermal reaction to synthesize 3D lightweight Fe3O4/MWCNT/GF hybrids with high performance microwave absorption (MA). The maximum Reflection Loss (RL) value of -35.30 dB and 9.01 GHz bandwidth with RL below -10 dB detected with the thickness of 3.0 mm are achieved by Fe3O4/MWCNT/GF with an ultralow bulk density of 5.0 mg cm-3, of which the Specific Microwave Absorption Performance is much higher than most available MA materials reported. Impedance matching, high loss characteristic, interfacial polarization and polarization relaxation significantly improve MA properties, which serves as a guide for fabricating comprehensive MA materials enjoying numerous advantages of high RL value, broad bandwidth, low density and thin thickness.

Degradation of high energetic and insensitive munitions compounds by Fe/Cu bimetal reduction.

PubMed

Koutsospyros, Agamemnon; Pavlov, Julius; Fawcett, Jacqueline; Strickland, David; Smolinski, Benjamin; Braida, Washington

2012-06-15

A reductive technology based on a completely mixed two-phase reactor (bimetallic particles and aqueous stream) was developed for the treatment of aqueous effluents contaminated with nitramines and nitro-substituted energetic materials. Experimental degradation studies were performed using solutions of three high energetics (RDX, HMX, TNT) and three insensitive-munitions components (NTO, NQ, DNAN). The study shows that, on laboratory scale, these energetic compounds are easily degraded in solution by suspensions of bimetallic particles (Fe/Ni and Fe/Cu) prepared by electro-less deposition. The type of bimetal pair (Fe/Cu or Fe/Ni) does not appear to affect the degradation kinetics of RDX, HMX, and TNT. The degradation of all components followed apparent first-order kinetics. The half-lives of all compounds except NTO were under 10 min. Additional parameters affecting the degradation processes were solids loading and initial pH. Copyright © 2012 Elsevier B.V. All rights reserved.

Transmission X-ray Diffraction (XRD) Patterns Relevant to the MSL Chemin Amorphous Component: Sulfates And Silicates

NASA Technical Reports Server (NTRS)

Morris, R. V.; Rampe, E. B.; Graff, T. G.; Archer, P. D., Jr.; Le, L.; Ming, D. W.; Sutter, B.

2015-01-01

The Mars Science Laboratory (MSL) CheMin instrument on the Curiosity rover is a transmission X-ray diffractometer (Co-Kalpha radiation source and a approx.5deg to approx.52deg 2theta range) where the analyzed powder samples are constrained to have discrete particle diameters <150 microns by a sieve. To date, diffraction patterns have been obtained for one basaltic soil (Rocknest (RN)) and four drill fines of coherent rock (John Klein (JK), Cumberland (CB), Windjana (WJ), and Confidence Hills (CH)). The CheMin instrument has detected and quantified the abundance of both primary igneous (e.g., feldspar, olivine, and pyroxene) and secondary (e.g., Ca-sulfates, hematite, akaganeite, and Fe-saponite) minerals. The diffraction patterns of all CheMin samples are also characterized by a broad diffraction band centered near 30deg 2theta and by increasing diffraction intensity (scattering continuum) from approx.15deg to approx.5deg, the 2theta minimum. Both the broad band and the scattering continuum are attributed to the presence of an XRD amorphous component. Estimates of amorphous component abundance, based on the XRD data itself and on mass-balance calculations using APXS data crystalline component chemistry derived from XRD data, martian meteorites, and/or stoichiometry [e.g., 6-9], range from approx.20 wt.% to approx.50 wt.% of bulk sample. The APXSbased calculations show that the amorphous component is rich in volatile elements (esp. SO3) and is not simply primary basaltic glass, which was used as a surrogate to model the broad band in the RN CheMin pattern. For RN, the entire volatile inventory (except minor anhydrite) is assigned to the amorphous component because no volatile-bearing crystalline phases were reported within detection limits [2]. For JK and CB, Fesaponite, basanite, and akaganeite are volatile-bearing crystalline components. Here we report transmission XRD patterns for sulfate and silicate phases relevant to interpretation of MSL-CheMin XRD amorphous components.

Laboratory Experiments to Study Spherical, Iron Oxide Concretion Growth Without Solid Nuclei: Implications for Understanding Meridiani "Blueberries"

NASA Astrophysics Data System (ADS)

Ormö, J.; Souza-Egipsy, V.; Chan, M. A.; Park, A. J.; Stich, M.; Komatsu, G.

2006-03-01

Spherical hematite concretions can form without a nucleus. Self-organized zones of super-saturated solution cause spherical precipitates of amorphous iron-hydroxide. Diffusion of Fe ions towards the outer perimeter of the amorphous sphere forms a rind, which then grows inwards.

In-situ ductile metal/bulk metallic glass matrix composites formed by chemical partitioning

DOEpatents

Kim, Choong Paul; Hays, Charles C.; Johnson, William L.

2004-03-23

A composite metal object comprises ductile crystalline metal particles in an amorphous metal matrix. An alloy is heated above its liquidus temperature. Upon cooling from the high temperature melt, the alloy chemically partitions, forming dendrites in the melt. Upon cooling the remaining liquid below the glass transition temperature it freezes to the amorphous state, producing a two-phase microstructure containing crystalline particles in an amorphous metal matrix. The ductile metal particles have a size in the range of from 0.1 to 15 micrometers and spacing in the range of from 0.1 to 20 micrometers. Preferably, the particle size is in the range of from 0.5 to 8 micrometers and spacing is in the range of from 1 to 10 micrometers. The volume proportion of particles is in the range of from 5 to 50% and preferably 15 to 35%. Differential cooling can produce oriented dendrites of ductile metal phase in an amorphous matrix. Examples are given in the Zr--Ti--Cu--Ni--Be alloy bulk glass forming system with added niobium.

In-situ ductile metal/bulk metallic glass matrix composites formed by chemical partitioning

DOEpatents

Kim, Choong Paul [Northridge, CA; Hays, Charles C [Pasadena, CA; Johnson, William L [Pasadena, CA

2007-07-17

A composite metal object comprises ductile crystalline metal particles in an amorphous metal matrix. An alloy is heated above its liquidus temperature. Upon cooling from the high temperature melt, the alloy chemically partitions, forming dendrites in the melt. Upon cooling the remaining liquid below the glass transition temperature it freezes to the amorphous state, producing a two-phase microstructure containing crystalline particles in an amorphous metal matrix. The ductile metal particles have a size in the range of from 0.1 to 15 micrometers and spacing in the range of from 0.1 to 20 micrometers. Preferably, the particle size is in the range of from 0.5 to 8 micrometers and spacing is in the range of from 1 to 10 micrometers. The volume proportion of particles is in the range of from 5 to 50% and preferably 15 to 35%. Differential cooling can produce oriented dendrites of ductile metal phase in an amorphous matrix. Examples are given in the Zr--Ti--Cu--Ni--Be alloy bulk glass forming system with added niobium.

Synthesis of u-channelled spherical Fex(CoyNi1-y)100-x Janus colloidal particles with excellent electromagnetic wave absorption performance.

PubMed

Li, Hao; Cao, Zhenming; Lin, Jiayao; Zhao, Hui; Jiang, Qiaorong; Jiang, Zhiyuan; Liao, Honggang; Kuang, Qin; Xie, Zhaoxiong

2018-01-25

Due to their distinctive structure, inherently anisotropic properties and broad applications, Janus colloidal particles have attracted tremendous attention and it is significant to synthesize high yield Janus colloidal particles in a cost-effective and reliable way. On the other hand, due to the expanded electromagnetic interference problems, it is highly desired to develop excellent electromagnetic wave absorbing materials with an ultra-wide absorption bandwidth for practical application. Herein, a confined liquid-solid redox reaction strategy has been developed to fabricate a series of Fe x (Co y Ni 1-y ) 100-x ternary alloy particles. The as-prepared particles are in the form of u-channelled noncentrosymmetric spheres, one kind of Janus colloidal particles which have been rarely observed. Due to the combination and synergy effects of multi-magnetic metals, the polycrystalline structure and their specific morphology, the as-prepared particles possess multiple magnetic resonance and multiple dielectric relaxation processes, and therefore show excellent electromagnetic wave absorption performances. In particular, the strongest reflection loss (RL) of the Fe 15 (Co 0.2 Ni 0.8 ) 85 Janus colloidal particles is up to -36.9 dB with a thickness of 2.5 mm, and the effective absorption (RL < -10 dB) bandwidth can reach 9.2 GHz (8-17.2 GHz) with a thickness of 2 mm. Such a wide bandwidth has barely been reported for magnetic metal alloys under a single thickness. These results suggest that the Fe x (Co y Ni 1-y ) 100-x Janus particles could be a promising candidate for highly efficient electromagnetic wave absorbing materials for practical application.

Brazing Inconel 625 Using Two Ni/(Fe)-Based Amorphous Filler Foils

NASA Astrophysics Data System (ADS)

Chen, Wen-Shiang; Shiue, Ren-Kae

2012-07-01

For MBF-51 filler, the brazed joint consists of interfacial grain boundary borides, coarse Nb6Ni16Si7, and Ni/Cr-rich matrix. In contrast, the VZ-2106 brazed joint is composed of interfacial Nb6Ni16Si7 precipitates as well as grain boundary borides, coarse Nb6Ni16Si7, and Ni/Cr/Fe-rich matrix. The maximum tensile strength of 443 MPa is obtained from the MBF-51 brazed specimen. The tensile strengths of VZ-2106 brazed joints are approximately 300 MPa. Both amorphous filler foils demonstrate potential in brazing IN-625 substrate.

Synthesis and electrochemical performances of amorphous carbon-coated Sn Sb particles as anode material for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Wang, Zhong; Tian, Wenhuai; Liu, Xiaohe; Yang, Rong; Li, Xingguo

2007-12-01

The amorphous carbon coating on the Sn-Sb particles was prepared from aqueous glucose solutions using a hydrothermal method. Because the outer layer carbon of composite materials is loose cotton-like and porous-like, it can accommodate the expansion and contraction of active materials to maintain the stability of the structure, and hinder effectively the aggregation of nano-sized alloy particles. The as-prepared composite materials show much improved electrochemical performances as anode materials for lithium-ion batteries compared with Sn-Sb alloy and carbon alone. This amorphous carbon-coated Sn-Sb particle is extremely promising anode materials for lithium secondary batteries and has a high potentiality in the future use.

Flux pinning and inhomogeneity in magnetic nanoparticle doped MgB2/Fe wires

NASA Astrophysics Data System (ADS)

Novosel, Nikolina; Pajić, Damir; Mustapić, Mislav; Babić, Emil; Shcherbakov, Andrey; Horvat, Joseph; Skoko, Željko; Zadro, Krešo

2010-06-01

The effects of magnetic nanoparticle doping on superconductivity of MgB2/Fe wires have been investigated. Fe2B and SiO2-coated Fe2B particles with average diameters 80 and 150 nm, respectively, were used as dopands. MgB2 wires with different nanoparticle contents (0, 3, 7.5, 12 wt.%) were sintered at temperature 750°C. The magnetoresistivity and critical current density Jc of wires were measured in the temperature range 2-40 K in magnetic field B <= 16 T. Both transport and magnetic Jc were determined. Superconducting transition temperature Tc of doped wires decreases quite rapidly with doping level (~ 0.5 K per wt.%). This results in the reduction of the irreversibility fields Birr(T) and critical current densities Jc(B,T) in doped samples (both at low (5 K) and high temperatures (20 K)). Common scaling of Jc(B,T) curves for doped and undoped wires indicates that the main mechanism of flux pinning is the same in both types of samples. Rather curved Kramer's plots for Jc of doped wires imply considerable inhomogeneity.

Uranium(VI) Scavenging by Amorphous Iron Phosphate Encrusting Sphaerotilus natans Filaments.

PubMed

Seder-Colomina, Marina; Morin, Guillaume; Brest, Jessica; Ona-Nguema, Georges; Gordien, Nilka; Pernelle, Jean-Jacques; Banerjee, Dipanjan; Mathon, Olivier; Esposito, Giovanni; van Hullebusch, Eric D

2015-12-15

U(VI) sorption to iron oxyhydroxides, precipitation of phosphate minerals, as well as biosorption on bacterial biomass are among the most reported processes able to scavenge U(VI) under oxidizing conditions. Although phosphates significantly influence bacterially mediated as well as iron oxyhydroxide mediated scavenging of uranium, the sorption or coprecipitation of U(VI) with poorly crystalline nanosized iron phosphates has been scarcely documented, especially in the presence of microorganisms. Here we show that dissolved U(VI) can be bound to amorphous iron phosphate during their deposition on Sphaerotilus natans filamentous bacteria. Uranium LIII-edge EXAFS analysis reveals that the adsorbed uranyl ions share an equatorial oxygen atom with a phosphate tetrahedron of the amorphous iron phosphate, with a characteristic U-P distance of 3.6 Å. In addition, the uranyl ions are connected to FeO6 octahedra with U-Fe distances at ~3.4 Å and at ~4.0 Å. The shortest U-Fe distance corresponds to a bidentate edge-sharing complex often reported for uranyl adsorption onto iron oxyhydroxides, whereas the longest U-Fe and U-P distances can be interpreted as a bidentate corner-sharing complex, in which two adjacent equatorial oxygen atoms are shared with the vertices of a FeO6 octahedron and of a phosphate tetrahedron. Furthermore, based on these sorption reactions, we demonstrate the ability of an attached S. natans biofilm to remove uranium from solution without any filtration step.

Novel Fe-based nanocrystalline powder cores with excellent magnetic properties produced using gas-atomized powder

NASA Astrophysics Data System (ADS)

Chang, Liang; Xie, Lei; Liu, Min; Li, Qiang; Dong, Yaqiang; Chang, Chuntao; Wang, Xin-Min; Inoue, Akihisa

2018-04-01

FeSiBPNbCu nanocrystalline powder cores (NPCs) with excellent magnetic properties were fabricated by cold-compaction of the gas-atomized amorphous powder. Upon annealing at the optimum temperature, the NPCs showed excellent magnetic properties, including high initial permeability of 88, high frequency stability up to 1 MHz with a constant value of 85, low core loss of 265 mW/cm3 at 100 kHz for Bm = 0.05 T, and superior DC-bias permeability of 60% at a bias field of 100 Oe. The excellent magnetic properties of the present NPCs could be attributed to the ultrafine α-Fe(Si) phase precipitated in the amorphous matrix and the use of gas-atomized powder coated with a uniform insulation layer.

Preservation of amorphous ultrafine material: A proposed proxy for slip during recent earthquakes on active faults

PubMed Central

Hirono, Tetsuro; Asayama, Satoru; Kaneki, Shunya; Ito, Akihiro

2016-01-01

The criteria for designating an “Active Fault” not only are important for understanding regional tectonics, but also are a paramount issue for assessing the earthquake risk of faults that are near important structures such as nuclear power plants. Here we propose a proxy, based on the preservation of amorphous ultrafine particles, to assess fault activity within the last millennium. X-ray diffraction data and electron microscope observations of samples from an active fault demonstrated the preservation of large amounts of amorphous ultrafine particles in two slip zones that last ruptured in 1596 and 1999, respectively. A chemical kinetic evaluation of the dissolution process indicated that such particles could survive for centuries, which is consistent with the observations. Thus, preservation of amorphous ultrafine particles in a fault may be valuable for assessing the fault’s latest activity, aiding efforts to evaluate faults that may damage critical facilities in tectonically active zones. PMID:27827413

Iron and silicon isotope behaviour accompanying weathering in Icelandic soils, and the implications for iron export from peatlands

NASA Astrophysics Data System (ADS)

Opfergelt, S.; Williams, H. M.; Cornelis, J. T.; Guicharnaud, R. A.; Georg, R. B.; Siebert, C.; Gislason, S. R.; Halliday, A. N.; Burton, K. W.

2017-11-01

Incipient warming of peatlands at high latitudes is expected to modify soil drainage and hence the redox conditions, which has implications for Fe export from soils. This study uses Fe isotopes to assess the processes controlling Fe export in a range of Icelandic soils including peat soils derived from the same parent basalt, where Fe isotope variations principally reflect differences in weathering and drainage. In poorly weathered, well-drained soils (non-peat soils), the limited Fe isotope fractionation in soil solutions relative to the bulk soil (Δ57Fesolution-soil = -0.11 ± 0.12‰) is attributed to proton-promoted mineral dissolution. In the more weathered poorly drained soils (peat soils), the soil solutions are usually lighter than the bulk soil (Δ57Fesolution-soil = -0.41 ± 0.32‰), which indicates that Fe has been mobilised by reductive mineral dissolution and/or ligand-controlled dissolution. The results highlight the presence of Fe-organic complexes in solution in anoxic conditions. An additional constraint on soil weathering is provided by Si isotopes. The Si isotope composition of the soil solutions relative to the soil (Δ30Sisolution-soil = 0.92 ± 0.26‰) generally reflects the incorporation of light Si isotopes in secondary aluminosilicates. Under anoxic conditions in peat soils, the largest Si isotope fractionation in soil solutions relative to the bulk soil is observed (Δ30Sisolution-soil = 1.63 ± 0.40‰) and attributed to the cumulative contribution of secondary clay minerals and amorphous silica precipitation. Si supersaturation in solution with respect to amorphous silica is reached upon freezing when Al availability to form aluminosilicates is limited by the affinity of Al for metal-organic complexes. Therefore, the precipitation of amorphous silica in peat soils indirectly supports the formation of metal-organic complexes in poorly drained soils. These observations highlight that in a scenario of decreasing soil drainage with warming high latitude peatlands, Fe export from soils as Fe-organic complexes will increase, which in turn has implications for Fe transport in rivers, and ultimately the delivery of Fe to the oceans.

Amorphous surface layer versus transient amorphous precursor phase in bone - A case study investigated by solid-state NMR spectroscopy.

PubMed

Von Euw, Stanislas; Ajili, Widad; Chan-Chang, Tsou-Hsi-Camille; Delices, Annette; Laurent, Guillaume; Babonneau, Florence; Nassif, Nadine; Azaïs, Thierry

2017-09-01

The presence of an amorphous surface layer that coats a crystalline core has been proposed for many biominerals, including bone mineral. In parallel, transient amorphous precursor phases have been proposed in various biomineralization processes, including bone biomineralization. Here we propose a methodology to investigate the origin of these amorphous environments taking the bone tissue as a key example. This study relies on the investigation of a bone tissue sample and its comparison with synthetic calcium phosphate samples, including a stoichiometric apatite, an amorphous calcium phosphate sample, and two different biomimetic apatites. To reveal if the amorphous environments in bone originate from an amorphous surface layer or a transient amorphous precursor phase, a combined solid-state nuclear magnetic resonance (NMR) experiment has been used. The latter consists of a double cross polarization 1 H→ 31 P→ 1 H pulse sequence followed by a 1 H magnetization exchange pulse sequence. The presence of an amorphous surface layer has been investigated through the study of the biomimetic apatites; while the presence of a transient amorphous precursor phase in the form of amorphous calcium phosphate particles has been mimicked with the help of a physical mixture of stoichiometric apatite and amorphous calcium phosphate. The NMR results show that the amorphous and the crystalline environments detected in our bone tissue sample belong to the same particle. The presence of an amorphous surface layer that coats the apatitic core of bone apatite particles has been unambiguously confirmed, and it is certain that this amorphous surface layer has strong implication on bone tissue biogenesis and regeneration. Questions still persist on the structural organization of bone and biomimetic apatites. The existing model proposes a core/shell structure, with an amorphous surface layer coating a crystalline bulk. The accuracy of this model is still debated because amorphous calcium phosphate (ACP) environments could also arise from a transient amorphous precursor phase of apatite. Here, we provide an NMR spectroscopy methodology to reveal the origin of these ACP environments in bone mineral or in biomimetic apatite. The 1 H magnetization exchange between protons arising from amorphous and crystalline domains shows unambiguously that an ACP layer coats the apatitic crystalline core of bone et biomimetic apatite platelets. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Enhancement of oxidation resistance via a self-healing boron carbide coating on diamond particles

PubMed Central

Sun, Youhong; Meng, Qingnan; Qian, Ming; Liu, Baochang; Gao, Ke; Ma, Yinlong; Wen, Mao; Zheng, Weitao

2016-01-01

A boron carbide coating was applied to diamond particles by heating the particles in a powder mixture consisting of H3BO3, B and Mg. The composition, bond state and coverage fraction of the boron carbide coating on the diamond particles were investigated. The boron carbide coating prefers to grow on the diamond (100) surface than on the diamond (111) surface. A stoichiometric B4C coating completely covered the diamond particle after maintaining the raw mixture at 1200 °C for 2 h. The contribution of the boron carbide coating to the oxidation resistance enhancement of the diamond particles was investigated. During annealing of the coated diamond in air, the priory formed B2O3, which exhibits a self-healing property, as an oxygen barrier layer, which protected the diamond from oxidation. The formation temperature of B2O3 is dependent on the amorphous boron carbide content. The coating on the diamond provided effective protection of the diamond against oxidation by heating in air at 1000 °C for 1 h. Furthermore, the presence of the boron carbide coating also contributed to the maintenance of the static compressive strength during the annealing of diamond in air. PMID:26831205

Enhancement of oxidation resistance via a self-healing boron carbide coating on diamond particles.

PubMed

Sun, Youhong; Meng, Qingnan; Qian, Ming; Liu, Baochang; Gao, Ke; Ma, Yinlong; Wen, Mao; Zheng, Weitao

2016-02-02

A boron carbide coating was applied to diamond particles by heating the particles in a powder mixture consisting of H3BO3, B and Mg. The composition, bond state and coverage fraction of the boron carbide coating on the diamond particles were investigated. The boron carbide coating prefers to grow on the diamond (100) surface than on the diamond (111) surface. A stoichiometric B4C coating completely covered the diamond particle after maintaining the raw mixture at 1200 °C for 2 h. The contribution of the boron carbide coating to the oxidation resistance enhancement of the diamond particles was investigated. During annealing of the coated diamond in air, the priory formed B2O3, which exhibits a self-healing property, as an oxygen barrier layer, which protected the diamond from oxidation. The formation temperature of B2O3 is dependent on the amorphous boron carbide content. The coating on the diamond provided effective protection of the diamond against oxidation by heating in air at 1000 °C for 1 h. Furthermore, the presence of the boron carbide coating also contributed to the maintenance of the static compressive strength during the annealing of diamond in air.

Self-Assembly of Magnetic Nanoparticles at the Surface and Within Block Copolymer Films

NASA Astrophysics Data System (ADS)

Xu, Chen; Ohno, Kohji; Composto, Russell

2007-03-01

We investigate the self-assembly of magnetic Fe3O4 nanoparticles in thin films of a symmetric block copolymer of poly(styrene-b-methyl methacrylate), PS-b-PMMA (75 kg/mol). The Fe3O4 nanoparticles (4nm) are grafted by poly(methyl methacrylate) (PMMA) (2.7 kg/mol) brushes to improve their compatibility. The weight percent of Fe3O4 in PS-b-PMMA is 1, 4 and 10. The Fe3O4 reside at the intermaterial dividing surface and also form small disk-like aggregates within the PMMA phase. The addition of Fe3O4 slows down the transition from perpendicular to parallel lamellae morphology at the surface and slowing down increases as weight percent Fe3O4 increases. Using cross-sectional TEM, nanoparticles are found to be rejected from the parallel lamellae and gather preferentially within the perpendicular lamellae. These studies demonstrate that the Fe3O4 particles influence thin film morphology and visa versa. Because of widespread interest in nanodevices, this study shows that arrays of functional nanoparticles can be formed using block copolymer templates.

Liquid coated melt-spun Nd-Fe-B powders for bonded magnets

NASA Astrophysics Data System (ADS)

Li, D.; Gaiffi, S.; Kirk, D.; Young, K.; Herchenroeder, J.; Berwald, T.

1999-04-01

The liquid coating (LC) has been employed to apply epoxy and lubricant over the surface of rapidly solidified Nd-Fe-B powder particles. The LC led to an improvement of physical and magnetic properties for the powders and magnets compared to the dry blending and the encapsulation methods. The LC powders have excellent flowability and can be used for bonded magnets requiring very close tolerances; further bonded magnets made using this powder posses higher strength.

SU-F-T-662: Feasibility Study of Fe3O4/TaOx Nano Particles as a Radiosensitizer for Radiation Therapy

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

Ahn, S; Lee, N; Shin, S

Purpose: To investigate the feasibility of using multifunctional Fe{sub 3}O{sub 4}/TaOx(core / shell) nano particles developed for CT and MRI contrast agent as dose enhancing radiosensitizers. Methods: Firstly, to verify the imaging detectability of Fe{sub 3}O{sub 4}/TaOx nano particles, in-vivo tests were conducted. Approximately 600 mg/kg of 19 nm diameter Fe{sub 3}O{sub 4}/TaOx nano particles dispersed in phosphate buffered saline(PBS) were injected to ten nude Balb/c mice through the tail vein. Difference between pre- and post-injection images was analyzed by computing the pixel histogram and correlation coefficient factor using MATLAB in the user defined ROI. Secondly, to quantify the potentialmore » therapeutic enhancement with nano materials, DER (Dose Enhancement Ratio) and number of SER (Secondary Electron Ratio) were computed using TOPAS(ver.2.0 P-03) MC simulation. Results: In CT, MRI imaging, the aorta, the blood vessel, and the liver were clearly visualized after intravenous injection of Fe{sub 3}O{sub 4}/TaOx nano particles. There was large different between pre and post-injection images of Histogram data and Coefficients of correlation factor in CT and MR are 0.006, 0.060, respectively. When 70 MeV protons were irradiated for a Gold, Tantalum, TaOx, Fe{sub 3}O{sub 4}/TaOx, Fe{sub 3}O{sub 4} nano particle, DER was 2.59, 2.41, 1.68, 1.54 and 1.36 respectively. Similarly, SER increment was 2.31, 2.15, 1.56, 1.46, and 1.27 for Gold, Tantalum, TaOx, Fe{sub 3}O{sub 4}/TaOx, Fe{sub 3}O{sub 4} nano particle, respectively. Conclusion: Fe{sub 3}O{sub 4}/TaOx nano particles have potential as a multifunctional agent which enhances the accuracy in cancer detection through visualization of developed tumor lesion and increases the therapeutic effect in proton therapy. The dose enhancement with Fe{sub 3}O{sub 4}/TaOx was estimated as half of the Gold. However, tumor targeting such as combined with magnetic field may overcome the low DER. This research was supported by the NRF funded by the Ministry of Science, ICT & Future Planning (2012M3A9B6055201 and 2012R1A1A2042414), Samsung Medical Center grant[GFO1130081].« less

Attempt to form hydride and amorphous particles, and introduction of a new evaporation method

NASA Astrophysics Data System (ADS)

Yatsuya, S.; Yamauchi, K.; Kamakura, T.; Yanagida, A.; Wakayama, H.; Mihama, K.

1985-06-01

Al and TiH 2 particles of fcc structure can be produced in an atmosphere of gaseous H 2 at reduced pressure. Al particles with definite habit are obtained, which has been never observed in the ordinary gas evaporation technique using a HV system. The habit of TiH 2 particles grown in the intermediate zone of the smoke is determined to be a dodecahedron. The growth is considered as the result of the martensite transformation from the bcc structure initially formed to the fcc structure accompanying a slight modification of the characteristic habit as observed for Ti particles. For the preparation of amorphous particles, first, the quenching rate of a particle, {dT}/{dt} was estimated to be more than {10 4°C }/{s}. Ultrafine particles of Pd 80Si 20 chosen as a test sample did not show the amorphous structure, but the crystalline. Application of the sputtering method as a new evaporation source in the gas evaporation technique is attempted. With the sputtering method, W particles with definite habits are produced.

Authigenesis/Diagenesis of the Murray Formation Mudstone in Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Ming, D. W.; Rampe, E. B.; Grotzinger, J. P.; Hurowitz, J. A.; Morris, R. V.; Yen, A. S.; Blake, D. B.; Geller, R.; Sutter, B.

2016-01-01

The Mars Science Laboratory rover Curiosity has been exploring sedimentary deposits in Gale crater since August, 2012. The rover has traversed up section through approximately 150 m of sedimentary rocks deposited in fluvial, deltaic, and lacustrine environments (Bradbury group and overlying Mount Sharp group). The Murray formation lies at the base of the Mt. Sharp group and has been interpreted to be a finely laminated mudstone likely deposited in a subaqueous lacustrine environment. Four drill samples from several elevations in the Murray fm have been acquired by the rover's sampling system and delivered to the CheMin XRD instrument. The lower section of the Murray fm contains 2:1 phyllosilicate(s), hematite, jarosite, XRD amorphous materials, and primary basaltic minerals. Further up section, the Murray fm contains magnetite, cristobalite, tridymite, abundant Si-rich XRD amorphous materials along with plagioclase and K-feldspars. Murray formation materials appear to have been altered under an open hydrologic system based on the bulk chemistry of these materials measured by the Alpha Particle X-ray Spectrometer (APXS). The 2:1 phyllosilicate only occurs in the lowermost section of the Murray fm and may be detrital or formed during authigenesis of Murray fm materials, similar to the Fe-saponite and magnetite detected in a mudstone in the Yellowknife Bay fm near Curiosity's landing site (stratigraphically at the base of the Bradbury group). The occurrence of jarosite and hematite in the lower section indicates an acidic diagenetic event. These phases may have formed via several acidic alteration mechanisms, including (1) oxidative weathering of mafic igneous rocks containing sulfides; (2) sulfuric acid weathering of Fe-bearing phases; and (3) near-neutral pH subsurface solutions rich in Fe2(+) that were rapidly oxidized to Fe3(+), which produced excess acidity. The transition from abundant hematite in the lowermost Murray fm to magnetite moving up section may indicate changes in lake chemistry, i.e., variable redox conditions, possibly during authigenesis or subsequent diagenetic events. Tridymite, a high temperature mineral, (and possibly cristobalite) is detrital, potentially deposited in a lake from a distal silicic volcanic rock source or from crustal materials present prior to the Gale Crater impact event. Abundant Si-rich XRD amorphous materials in the upper sections of the Murray fm may be detrital or an aqueous alteration product of primary igneous phases and phyllosilicates. Curiosity's science team is still deciphering the authigenesis and diagenetic events that formed the Murray fm. The mineralogy and geochemistry of the formation suggest a complicated history with several (many?) episodes of aqueous alteration under a variety of environmental conditions.