Thermodynamic modelling of the formation of zinc-manganese ferrite spinel in electric arc furnace dust.

PubMed

Pickles, C A

2010-07-15

Electric arc furnace dust is generated when automobile scrap, containing galvanized steel, is remelted in an electric arc furnace. This dust is considered as a hazardous waste in most countries. Zinc is a major component of the dust and can be of significant commercial value. Typically, the majority of the zinc exists as zinc oxide (ZnO) and as a zinc-manganese ferrite spinel ((Zn(x)Mn(y)Fe(1-x-y))Fe(2)O(4)). The recovery of the zinc from the dust in metal recycling and recovery processes, particularly in the hydrometallurgical extraction processes, is often hindered by the presence of the mixed ferrite spinel. However, there is a paucity of information available in the literature on the formation of this spinel. Therefore, in the present research, the equilibrium module of HSC Chemistry 6.1 was utilized to investigate the thermodynamics of the formation of the spinel and the effect of variables on the amount and the composition of the mixed ferrite spinel. It is proposed that the mixed ferrite spinel forms due to the reaction of iron-manganese particulates with both gaseous oxygen and zinc, at the high temperatures in the freeboard of the furnace above the steel melt. Based on the thermodynamic predictions, methods are proposed for minimizing the formation of the mixed ferrite spinel. 2010 Elsevier B.V. All rights reserved.

Lattice parameters and stability of the spinel compounds in relation to the ionic radii and electronegativities of constituting chemical elements.

PubMed

Brik, Mikhail G; Suchocki, Andrzej; Kamińska, Agata

2014-05-19

A thorough consideration of the relation between the lattice parameters of 185 binary and ternary spinel compounds, on one side, and ionic radii and electronegativities of the constituting ions, on the other side, allowed for establishing a simple empirical model and finding its linear equation, which links together the above-mentioned quantities. The derived equation gives good agreement between the experimental and modeled values of the lattice parameters in the considered group of spinels, with an average relative error of about 1% only. The proposed model was improved further by separate consideration of several groups of spinels, depending on the nature of the anion (oxygen, sulfur, selenium/tellurium, nitrogen). The developed approach can be efficiently used for prediction of lattice constants for new isostructural materials. In particular, the lattice constants of new hypothetic spinels ZnRE2O4, CdRE2S4, CdRE2Se4 (RE = rare earth elements) are predicted in the present Article. In addition, the upper and lower limits for the variation of the ionic radii, electronegativities, and their certain combinations were established, which can be considered as stability criteria for the spinel compounds. The findings of the present Article offer a systematic overview of the structural properties of spinels and can serve as helpful guides for synthesis of new spinel compounds.

Water-Soluble Spinel Ferrites by a Modified Polyol Process as Contrast Agents in MRI

NASA Astrophysics Data System (ADS)

Basina, Georgia; Tzitzios, Vasilis; Niarchos, Dimitris; Li, Wanfeng; Khurshid, Hafsa; Mao, Hui; Hadjipanayis, Costas; Hadjipanayis, George

2010-12-01

Magnetic nanoparticles have recently been very attractive for biomedical applications. In this study, we have synthesized ferrite nanoparticles for application as contrast agents in MRI experiments. Fe3O4 and MnFe2O4 spinel ferrites with a mean size of 11-12 nm, were prepared by a modified polyol route in commercially available polyethylene glycol with molecular weight 600 (PEG-600). The reaction takes place in the presence of water soluble and non-toxic tri-block copolymer known as Pluronic® F-127 (PEO100-PPO65-PEO100). The nanoparticles have saturation magnetization values of 52 and 68 emu/g for MnFe2O4 and Fe3O4, respectively. Both the Fe3O4, and MnFe2O4 nanoparticles make stable solutions in water known as ferrofluids. Preliminary data demonstrated the capability of these nanoparticles to induce imaging contrast in T2 weighted MRI experiments, making these materials suitable for biomedical applications such as medical MRI.

Composition of the lithospheric mantle in the northern part of Siberian craton: Constraints from peridotites in the Obnazhennaya kimberlite

NASA Astrophysics Data System (ADS)

Sun, Jing; Liu, Chuan-Zhou; Kostrovisky, Sergey I.; Wu, Fu-Yuan; Yang, Jin-Hui; Chu, Zhu-Yin; Yang, Yue-Heng; Kalashnikova, Tatiana; Fan, Sheng

2017-12-01

The character of the lithospheric mantle of the northern Siberian craton is not well established; nearly all published data are for mantle xenoliths from a single kimberlite in the center of the craton (Udachnaya). We report major elements of the whole rock, trace elements data of clinopyroxene and Re-Os isotope and PGE concentration of mantle xenoliths from the Obnazhennaya kimberlite pipe (160 Ma) in the northern part of Siberian craton. The Obnazhennaya mantle xenoliths include spinel harzburgites, spinel dunites, spinel lherzolites and spinel-garnet lherzolite. The spinel harzburgites and dunites have refractory compositions, with 0.23-1.35 wt% Al2O3, 0.41-3.11 wt% CaO and 0.00-0.09 wt% TiO2, whereas the lherzolites (both spinel- and spinel-garnet-) have more fertile compositions, containing 2.16-6.55 wt% Al2O3, 2.91-7.55 wt% CaO and 0.04-0.15 wt% TiO2. The trace element compositions and mineralogical textures of the Obnazhennaya xenoliths indicate the occurrence of metasomatic enrichments, including carbonatite melts, basaltic melts from Siberian Trap and kimberlitic melts. The spinel harzburgites and dunites have 187Os/188Os of 0.11227-0.11637, giving a TRD age of 1.6-2.2 Ga. This suggests that old cratonic mantle still existed beneath the Obnazhennaya. In contrast, both spinel and spinel-garnet lherzolites have more radiogenic 187Os/188Os ratios (0.11931-0.17627), enriched P-PGEs. But the higher Al2O3 and Os character of these lherzolites suggest that they were not juvenile mantle but the refertilized ancient mantle. Therefore, our results suggest that the cratonic mantle beneath the northern part of Siberian craton contain both ancient and reworked lithospheric mantle, and the metasomatism may not be effective at overprinting/eroding the pre-existing lithosphere.

Lunar Cordierite-Spinel Troctolite: Igneous History, and Volatiles

NASA Astrophysics Data System (ADS)

Treiman, A. H.; Gross, J.

2012-03-01

Apollo sample 15295,101 contains a cordierite spinel troctolite (Marvin et al., 1989). The cordierite is volatile-free, at least by EMP — more precise analyses are in progress. The troctolite may be a partial melt of a spinel-rich igneous cumulate.

SnS2 Thin Film Deposition by Spray Pyrolysis

NASA Astrophysics Data System (ADS)

Jaber, Abdallah Yahia; Alamri, Saleh Noaiman; Aida, Mohammed Salah

2012-06-01

Tin disulfide (SnS2) thin films have been synthesized using a simplified spray pyrolysis technique using a perfume atomizer. The films were deposited using two different solutions prepared by the dilution of SnCl2 and thiourea in distilled water and in methanol. The obtained films have a microcrystalline structure. The film deposited using methanol as the solvent is nearly stochiometric SnS2 with a spinel phase having a (001) preferential orientation. The film prepared with an aqueous solution is Sn-rich. Scanning electronic microscopy (SEM) images reveal that the film deposited with the aqueous solution is rough and is formed with large wires. However, the film deposited with methanol is dense and smooth. Conductivity measurements indicate that the aqueous solution leads to an n-type semiconductor, while methanol leads to a p-type semiconductor.

A FIB/TEM/Nanosims Study of a Wark-Lovering Rim on an Allende CAI

NASA Technical Reports Server (NTRS)

Keller, L. P.; Needham, A. W.; Messenger, S.

2014-01-01

Ca- Al-rich inclusions (CAIs) are commonly surrounded by Wark-Lovering (WL) rims - thin (approx. 50 micrometers) multilayered sequences - whose mineralogy is dominated by high temperature minerals similar to those that occur in the cores of CAIs [1]. The origins of these WL rims involved high temperature events in the early nebula such as condensation, flashheating or reaction with a nebular reservoir, or combinations of these processes. These rims formed after CAI formation but prior to accretion into their parent bodies. We have undertaken a coordinated mineralogical and isotopic study of WL rims to determine the formation conditions of the individual layers and to constrain the isotopic reservoirs they interacted with during their history. We focus here on the spinel layer, the first-formed highest- temperature layer in the WL rim sequence. Results and Discussion: We have performed mineralogical, chemical and isotopic analyses of an unusual ultrarefractory inclusion from the Allende CV3 chondrite (SHAL) consisting of an approx. 500 micrometers long single crystal of hibonite and co-existing coarsegrained perovskite. SHAL is partially surrounded by WL rim. We previously reported on the mineralogy, isotopic compositions and trace elements in SHAL [2-4]. The spinel layer in the WL rim is present only on the hibonite and terminates abruptly at the contact with the coarse perovskite. This simple observation shows that the spinel layer is not a condensate in this case (otherwise spinel would have condensed on the perovskite as well). The spinel layer appears to have formed by gas-phase corrosion of the hibonite by Mg-rich vapors such that the spinel layer grew at the expense of the hibonite. We also found that the spinel layer has the same 16Orich composition as the hibonite. The spinel layer is polycrystalline and individual crystals do not show a crystallographic relationship with the hibonite. An Al-diopside layer overlies the spinel layer, and is present on both the hibonite and perovskite. While the spinel is 16O-rich, WL-rim perovskite and pyroxene are 16O-poor. This isotopic heterogeneity likely reflects O isotopic equilibration of WL-rim perovskite and pyroxene with a planetary O isotopic reservoir after the WL rim formation. The hibonite is zoned and contains wt.% levels of Ti, Mg and Fe in contact with the Fe-bearing spinel (Sp60Hc40) in the WL rim. The Fe enrichment in spinel is likely related to the Na-Fe metasomatism that is ubiquitous in Allende. Conclusions: The petrography and microstructure of the spinel layer in a WL rim sequence shows that it formed by gas phase reactions at high temperature in the nebula. The oxygen isotopic composition of the spinel indicates that this WL rim layer formed in the same (or similar) nebular gas reservoir as the host CAI.

Suppressing Manganese Dissolution from Lithium Manganese Oxide Spinel Cathodes with Single-Layer Graphene

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

Jaber-Ansari, Laila; Puntambekar, Kanan P.; Kim, Soo

2015-06-24

Spinel-structured LiMn 2 O 4 (LMO) is a desirable cathode material for Li-ion batteries due to its low cost, abundance, and high power capability. However, LMO suffers from limited cycle life that is triggered by manganese dissolution into the electrolyte during electrochemical cycling. Here, it is shown that single-layer graphene coatings suppress manganese dissolution, thus enhancing the performance and lifetime of LMO cathodes. Relative to lithium cells with uncoated LMO cathodes, cells with graphene-coated LMO cathodes provide improved capacity retention with enhanced cycling stability. X-ray photoelectron spectroscopy reveals that graphene coatings inhibit manganese depletion from the LMO surface. Additionally, transmissionmore » electron microscopy demonstrates that a stable solid electrolyte interphase is formed on graphene, which screens the LMO from direct contact with the electrolyte. Density functional theory calculations provide two mechanisms for the role of graphene in the suppression of manganese dissolution. First, common defects in single-layer graphene are found to allow the transport of lithium while concurrently acting as barriers for manganese diffusion. Second, graphene can chemically interact with Mn 3+ at the LMO electrode surface, promoting an oxidation state change to Mn 4+ , which suppresses dissolution.« less

Structural study of Ti-doped CoFe{sub 2}O{sub 4} mixed spinel ferrite

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

Choudhary, P., E-mail: pankaj.7007@rediffmail.com; Sharma, P.; Dar, M. A.

2016-05-06

We present the results on atomic and lattice structure of the polycrystalline spinel ferrites system Co{sub 1-x} Ti{sub x}Fe{sub 2}O{sub 4} (x = 0.0, 0.25, 0.50) synthesized by following the conventional solid-state reaction route. The observed X-ray diffraction (XRD) data confirms that all the prepared samples are indexed in cubic crystal structure (space group Fd3m). Diffraction pattern showed TiO{sub 2} phase due to presence of Ti{sup +4} ions. Four Raman active phonon modes are observed for CoFe{sub 2}O{sub 4} sample existing around 295, 462, 585, 689, cm{sup −1} as Eg, T{sub 2g}(2), T{sub 2g}(3), and A{sub 1g}, respectively. With 25more » % Ti ion doping, the peak T{sub 2g}(3) disappears, while to that T{sub 2g}(1) emerges. This is an indication of presence of TiO{sub 2} phase in Co{sub 0.75}Ti{sub 0.25}Fe{sub 2}O{sub 4} and Co{sub 0.5}Ti{sub 0.5}Fe{sub 2}O{sub 4} ceramics.« less

TL and OSL properties of Mn2+-doped MgGa2O4 phosphor

NASA Astrophysics Data System (ADS)

Luchechko, A.; Zhydachevskyy, Ya; Maraba, D.; Bulur, E.; Ubizskii, S.; Kravets, O.

2018-04-01

The oxide MgGa2O4 spinel ceramics doped with Mn2+ ions was synthesized by a solid-state reaction at 1200 °C in air. The activator concentration was equal 0.05 mol% of MnO. Phase purity of the synthesized samples was analyzed by X-ray diffraction technique. This spinel ceramics show efficient green emission in the range from 470 to 550 nm with a maximum at about 505 nm under UV or X-ray excitations, which is due to Mn2+ ions. MgGa2O4: Mn2+ exhibits intense thermoluminescence (TL) and optically stimulated luminescence (OSL) after influence of ionizing radiation. Are complex nature of the TL glow curves is associated with a significant number of structural defects that are responsible for the formation of shallow and deep electron traps. In this work, time-resolved OSL characteristics of the samples exposed to beta particles are reported for the first time. A light from green LED was used for optical stimulation. Obtained TL and OSL results suggest MgGa2O4:Mn2+ as perspective material for further research and possible application in radiation dosimetry.

Degradation of lithium ion batteries employing graphite negatives and nickel-cobalt-manganese oxide + spinel manganese oxide positives: Part 2, chemical-mechanical degradation model

NASA Astrophysics Data System (ADS)

Purewal, Justin; Wang, John; Graetz, Jason; Soukiazian, Souren; Tataria, Harshad; Verbrugge, Mark W.

2014-12-01

Capacity fade is reported for 1.5 Ah Li-ion batteries containing a mixture of Li-Ni-Co-Mn oxide (NCM) + Li-Mn oxide spinel (LMO) as positive electrode material and a graphite negative electrode. The batteries were cycled at a wide range of temperatures (10 °C-46 °C) and discharge currents (0.5C-6.5C). The measured capacity losses were fit to a simple physics-based model which calculates lithium inventory loss from two related mechanisms: (1) mechanical degradation at the graphite anode particle surface caused by diffusion-induced stresses (DIS) and (2) chemical degradation caused by lithium loss to continued growth of the solid-electrolyte interphase (SEI). These two mechanisms are coupled because lithium is consumed through SEI formation on newly exposed crack surfaces. The growth of crack surface area is modeled as a fatigue phenomenon due to the cyclic stresses generated by repeated lithium insertion and de-insertion of graphite particles. This coupled chemical-mechanical degradation model is consistent with the observed capacity loss features for the NCM + LMO/graphite cells.

Reaction mechanism and thermal stability study on cathode materials for rechargeable lithium ion batteries

NASA Astrophysics Data System (ADS)

Fang, Jin

Olivine-type lithium iron phosphate has been a very promising cathode material since it was proposed by Padhi in 1997, low-cost, environmental friendly and stable structure ensure the commercialization of LiFePO 4. In LiFePO4, during charge and discharge process, Li ions are transferred between two phases, Li-poor LialphaFePO 4 and Li-rich Li1-betaFePO4, which implies a significant energy barrier for the new phase nucleation and interface growth, contrary to the fast reaction kinetics experimentally observed. The understanding of the lithiation and delithiation mechanism of this material has spurred a lot of research interests. Many theory models have been proposed to explain the reaction mechanism of LiFePO4, among them, the single phase model claims that the reaction goes through a metastable single phase, and the over potential required to form this single phase is about 30mV, so we studied the driving force to transport lithium ions between Lialpha FePO4 and Li1-betaFePO4 phases and compared the particle sizes effect. Experiment results shows that, the nano-sized (30nm) LiFePO4 has wider solid solution range, lower solid solution formation temperature and faster kinetics than normal LiFePO4 (150nm). Also a 20mV over potential was observed in both samples, either after relaxing the FePO4/LiFePO4 system to equilibrium or transport lithium from one side to the other side, the experiment result is corresponding to theoretical calculation; indicates the reaction might go through single-phase reaction mechanism. The energy and power density of lithium ion battery largely depend on cathode materials. Mn substituted LiFePO4 has a higher voltage than LiFePO4, which results a higher theoretical energy density. Safety issue is one of the most important criterions for batteries, since cathode materials need to maintain stable structure during hundreds of charge and discharge cycles and ranges of application conditions. We have reported that iron-rich compound o-Fe1-yMnyPO4 (0≤y≤0.4) is stable up to 600 °C with particle size above 100 nm particle. And in this work Mn rich olivine phase Fe1-yMnyPO4 is found to be thermally stable up to at least 450 °C with particle size down to below 50 nm, different delithiation methods result in different decomposition routes, electrochemical delithiation results in decreased thermal stability. Moisture exposure appears the most detrimental to the thermal stability of Mn-rich samples. LiNi0.5Mn1.5O4 has attracted a lot of attentions because the potential is even higher (˜ 4.7 V vs Li +/Li0). However, electrolyte decomposition is quite often observed during electrochemistry cycles due to the high voltage operation window. Spinel LiNi0.5Mn1.5O4 is known as ordered and disordered according to the distribution of cations which relates to the synthesis conditions. Mn and Ni ions distribute either randomly in 16d sites of an Fd3m-space group or ordered in 4a and 12d sites of P4332 space group. During discharge and charge processes, Li ions insert and extract from the structure with the oxidation state of Ni changing between +2 and +4 while Mn remains as Mn4+. So far the correlation between cation distribution and electrochemical performance is still unclear, mostly the disordered samples are observed to have better rate capabilities. In order to study the reaction mechanism, combined XRD and XAS are used to investigate the oxidation state of transition metals and structure change of LiNi0.5Mn1.5O4 during electrochemical cycling, disordered and ordered samples were compared and studied, and both samples show three phases transformation during charge and discharge. However, the samples suffer from severe electrolyte decomposition which has influence on the results. Good spinel samples with nice electrochemistry performance is required, pure spinel samples are obtained by using co-precipitation method, the distribution of transition metal ions can be controlled by controlling the synthesis temperature, and electrolyte plays an important role in the electrochemistry performance of spinel LiNi0.5Mn1.5O 4.

Structural transformation in nano-structured CuAl{sub x}Cr{sub x}Fe{sub 2-2x}O{sub 4} system

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

Mehta, D. K., E-mail: daxabjoshi@gmail.com; Chhantbar, M. C.; Joshi, H. H.

Polycrystalline spinel ferrite system CuAl{sub x}Cr{sub x}Fe{sub 2-2x}O{sub 4} (x=0.2, 0.6) was synthesized by solid-state reaction route. Nanoparticles of the samples have been prepared by using high energy ball milling technique with different milling durations and characterized by X-ray Diffraction and Tunneling Electron Microscope. It is observed that the structural transformation occurred from Cubic to tetragonal and particle size varied between 29 nm -14 nm with increase of milling time.

Spinel lithium manganese oxide nanoparticles: unique molten salt synthesis strategy and excellent electrochemical performances.

PubMed

Wang, Xiong; Zhu, Juanjuan; Liu, Yingjie

2009-11-01

As a promising candidate cathode material, spinel lithium manganese oxide nanoparticles were successfully synthesized through a novel molten salt synthesis route at relatively low temperature, using manganese dioxide nanowires as precursor. A variety of techniques were applied to characterize the spinel nanomaterial, including X-ray diffraction, transmission electron microscopy, field-emission scanning electron microscopy, and X-ray photoelectron spectroscopy. The average particle size of the resulting spinel nanoparticles was about 80 nm with narrow distribution. As cathode material for rechargeable lithium ion battery, the electrochemical properties were investigated. All the results show that the electrochemical performances of the homogeneous spinel nanoparticles were improved, which might be ascribed to large specific surface area, fairly narrow size distribution, and the unique synthesis strategy.

MgAl2O4 spinel refractory as containment liner for high-temperature alkali salt containing environments

DOEpatents

Peascoe-Meisner, Roberta A [Knoxville, TN; Keiser, James R [Oak Ridge, TN; Hemric, James G [Knoxville, TN; Hubbard, Camden R [Oak Ridge, TN; Gorog, J Peter [Kent, WA; Gupta, Amul [Jamestown, NY

2008-10-21

A method includes containing a high-temperature alkali salt containing environment using a refractory containment liner containing MgAl.sub.2O.sub.4 spinel. A method, includes forming a refractory brick containing MgAl.sub.2O.sub.4 spinel having an exterior chill zone defined by substantially columnar crystallization and an interior zone defined by substantially equiaxed crystallization; and removing at least a portion of the exterior chill zone from the refractory brick containing MgAl.sub.2O.sub.4 spinel by scalping the refractory brick containing MgAl.sub.2O.sub.4 spinel to define at least one outer surface having an area of substantially equiaxed crystallization. A product of manufacture includes a refractory brick containing MgAl.sub.2O.sub.4 spinel including an interior zone defined by substantially equiaxed crystallization; and at least one outer surface having an area of substantially equiaxed crystallization.

Characterization and application of the hetero-junction ZnFe2O4/TiO2 for Cr(VI) reduction under visible light

NASA Astrophysics Data System (ADS)

Rekhila, G.; Trari, M.; Bessekhouad, Y.

2017-06-01

The spinel ZnFe2O4 prepared by nitrate route is used as dispersed photons collector capable to sensitize TiO2 under visible light and to reduce Cr(VI) into trivalent state. The transport properties, optical and photo-electrochemical characterizations are correlated, to build the energetic diagram of the hetero-system ZnFe2O4/TiO2/CrO4 - solution. A gap of 1.97 eV is obtained for the spinel from the diffuse reflectance. The conduction band of ZnFe2O4 (-1.47 V SCE) favors the electrons injection into TiO2, permitting a physical separation of the charge carriers. The oxidation of oxalic acid by photoholes prevents the corrosion of the spinel. The best configuration ZnFe2O4 (75 %)/TiO2 (25 %) is used to catalyze the downhill reaction (2HCrO4 - + 3C2H4O4 + 1.5O2 + 8H+ → 2Cr3+ + 6CO2 + 11 H2O, Δ G° = -557 kcal mol-1). 60 % of Cr(VI) are reduced after 3 h of visible light illumination and the photoactivity follows a first-order kinetic with a half-life of 70 min. The water reduction competes with the HCrO4 - reduction which is the reason in the regression of the photoactivity; a hydrogen evolution rate of 24 µmol mg-1 h-1 is obtained.

Decorating unoxidized-carbon nanotubes with homogeneous Ni-Co spinel nanocrystals show superior performance for oxygen evolution/reduction reactions

NASA Astrophysics Data System (ADS)

Yang, Jun; Fujigaya, Tsuyohiko; Nakashima, Naotoshi

2017-03-01

We present a new concept for homogeneous spinel nanocrystal-coating on high crystalline pristine-carbon nanotubes (CNTs) for efficient and durable oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Oxidized CNTs have widely been used to functionalize with metal or metal oxides since the defect sites act as anchoring for metal oxide binding. However, such defects on the tubes cause the decrease in electrical conductivity and stability, leading to lower catalyst performance. In the present study, at first, pristine multi-walled carbon nanotubes (MWNTs) were wrapped by pyridine-based polybenzimidazole (PyPBI) to which uniform NixCo3-xO4 nanocrystals were homogeneously deposited by the solvothermal method without damaging the MWNTs, in which PyPBI acted as efficient anchoring sites for the deposition of spinel oxide nanocrystals with ~5 nm size. The obtained catalyst (MWNT-PyPBI-NixCo3-xO4) outperformed most state-of-the-art non-precious metal-based bifunctional catalysts; namely, for OER, the potential at 10 mA cm-2 and Tafel slope in 1 M KOH solution were 1.54 V vs. RHE and 42 mV dec-1, respectively. For ORR, the onset and half-wave potentials are 0.918 V and 0.811 V vs. RHE, respectively. Moreover, the MWNT-PyPBI-NixCo3-xO4 demonstrates an excellent durability for both ORR and OER.

Rhenium and Iridium Partitioning in Silicate and Magmatic Spinels: Implications for Planetary Magmatism and Mantles

NASA Technical Reports Server (NTRS)

Righter, K.

2001-01-01

Highly siderophile elements Re, Ru and Ir partition strongly into spinel structures with large octahedral sites. New experimental results for both magmatic and silicate spinels will be presented with a few planetary implications. Additional information is contained in the original extended abstract.

A new powder production route for transparent spinel windows: powder synthesis and window properties

NASA Astrophysics Data System (ADS)

Cook, Ronald; Kochis, Michael; Reimanis, Ivar; Kleebe, Hans-Joachim

2005-05-01

Spinel powders for the production of transparent polycrystalline ceramic windows have been produced using a number of traditional ceramic and sol-gel methods. We have demonstrated that magnesium aluminate spinel powders produced from the reaction of organo-magnesium compounds with surface modified boehmite precursors can be used to produce high quality transparent spinel parts. The new powder production method allows fine control over the starting particle size, size distribution, purity and stoichiometry. The new process involves formation of a boehmite sol-gel from the hydrolysis of aluminum alkoxides followed by surface modification of the boehmite nanoparticles using carboxylic acids. The resulting surface modified boehmite nanoparticles can then be metal exchanged at room temperature with magnesium acetylacetonate to make a precursor powder that is readily transformed into pure phase spinel.

Investigation of Synthetic Mg(1.3)V(1.7)O4 Spinel with MgO Inclusions: Case Study of a Spinel with an Apparently occupied Interstitial Site

NASA Technical Reports Server (NTRS)

Uchida, Hinako; Righter, Kevin; Lavina, Barbara; Nowell, Matthew M.; Wright, Stuart I.; Downs, Robert T.; Yang, Hexiong

2007-01-01

A magnesium vanadate spinel crystal, ideally MgV2O4, synthesized at 1 bar, 1200 C and equilibrated under FMQ + 1.3 log f(sub o2) condition, was investigated using single-crystal X-ray diffraction, electron microprobe, and electron backscatter (EBSD). The initial X-ray structure refinements gave tetrahedral and octahedral site occupancies, along with the presence of 0.053 apfu Mg at an interstitial octahedral site . Back-scattered electron (BSE) images and electron microprobe analyses revealed the existence of an Mg-rich phase in the spinel matrix, which was too small (less than or equal to 3microns) for an accurate chemical determination. The EBSD analysis combined with X-ray energy dispersive spectroscop[y (XEDS) suggested that the Mg-rich inclusions are periclase oriented coherently with the spinel matrix. The final structure refinements were optimized by subtracting the X-ray intensity contributions (approx. 9%) of periclase reflections, which eliminated the interstitial Mg. This study provides insight into possible origins of refined interstitial cations reported in the the literature for spinel, and points to the difficulty of using only X-ray diffraction data to distinguish a spinel with interstitial cations from one with coherently oriented MgO inclusions.

Morphology and composition of spinel in Pu'u 'O'o lava (1996-1998), Kilauea volcano, Hawaii

USGS Publications Warehouse

Roeder, P.L.; Thornber, C.; Poustovetov, Alexei; Grant, A.

2003-01-01

The morphology and composition of spinel in rapidly quenched Pu'u 'O'o vent and lava tube samples are described. These samples contain glass, olivine phenocrysts (3-5 vol.%) and microphenocrysts of spinel (~0.05 vol.%). The spinel surrounded by glass occurs as idiomorphic octahedra 5-50 μm in diameter and as chains of octahedra that are oriented with respect to each other. Spinel enclosed by olivine phenocrysts is sometimes rounded and does not generally form chains. The temperature before quenching was calculated from the MgO content of the glass and ranges from 1150oC to 1180oC. The oxygen fugacity before quenching was calculated by two independent methods and the log f O2 ranged from -9.2 to -9.9 (delta QFM=-1). The spinel in the Pu'u'O'o samples has a narrow range in composition with Cr/(Cr+Al)=0.61 to 0.73 and Fe2+/(Fe2++Mg) =0.46 to 0.56. The lower the calculated temperature for the samples, the higher the average Fe2+/(Fe2++Mg), Fe3+ and Ti in the spinel. Most zoned spinel crystals decrease in Cr/(Cr+Al) from core to rim and, in the chains, the Cr/(Cr+Al) is greater in the core of larger crystals than in the core of smaller crystals. The occurrence of chains and hopper crystals and the presence of Cr/(Cr+Al) zoning from core to rim of the spinel suggest diffusion-controlled growth of the crystals. Some of the spinel crystals may have grown rapidly under the turbulent conditions of the summit reservoir and in the flowing lava, and the crystals may have remained in suspension for a considerable period. The rapid growth may have caused very local (μm) gradients of Cr in the melt ahead of the spinel crystal faces. The crystals seem to have retained the Cr/(Cr+Al) ratio that developed during the original growth of the crystal, but the Fe2+/(Fe2++Mg) ratio may have equilibrated fairly rapidly with the changing melt composition due to olivine crystallization. Six of the samples were collected on the same day at various locations along a 10-km lava tube and the calculated pre-collection temperatures of the samples show a 5oC drop with distance from the vent. The average Fe2+/(Fe2++Mg) of the spinel in these samples shows a weak positive correlation with decreasing MgO in the glass of these samples. The range in Cr2O3 (0.041-0.045 wt.%) of the glass for these six samples is too small to distinguish a consistent change along the lava tube. The spinel in the Pu'u 'O'o samples shows a zoning trend in a Cr-Al-Fe3+ diagram almost directly away from the Cr apex. This compares with a zoning trend in rapidly quenched MORB samples away from Cr coupled with decreasing Fe3+. The trend away from Cr displayed by spinel in rapidly quenched samples is in marked contrast to the trend of increasing Fe3+ shown by spinel in slowly cooled lava. 

End-Member Formulation of Solid Solutions and Reactive Transport

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

Lichtner, Peter C.

2015-09-01

A model for incorporating solid solutions into reactive transport equations is presented based on an end-member representation. Reactive transport equations are solved directly for the composition and bulk concentration of the solid solution. Reactions of a solid solution with an aqueous solution are formulated in terms of an overall stoichiometric reaction corresponding to a time-varying composition and exchange reactions, equivalent to reaction end-members. Reaction rates are treated kinetically using a transition state rate law for the overall reaction and a pseudo-kinetic rate law for exchange reactions. The composition of the solid solution at the onset of precipitation is assumed tomore » correspond to the least soluble composition, equivalent to the composition at equilibrium. The stoichiometric saturation determines if the solid solution is super-saturated with respect to the aqueous solution. The method is implemented for a simple prototype batch reactor using Mathematica for a binary solid solution. Finally, the sensitivity of the results on the kinetic rate constant for a binary solid solution is investigated for reaction of an initially stoichiometric solid phase with an undersaturated aqueous solution.« less

Selection of new Kynar-based electrolytes for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Christie, Alasdair M.; Christie, Lynn; Vincent, Colin A.

New electrolyte solution compositions have been identified for use in lithium-ion batteries after gelling with an appropriate quantity of Kynar polymer. Since the Li + conducting medium is largely the liquid electrolyte component, the assessment of these solutions as suitable lithium-ion cell candidates were investigated before adding the polymer. Selected electrolyte solutions were then used in the preparation of polymer gels. The specific conductivities of Kynar-based gels were determined as a function of salt concentration and polymer concentration. Optimised self-supporting polymer films, based on mixtures of ethylene carbonate (EC), ethylmethyl carbonate (EMC) and lithium hexafluorophosphate (LiPF 6) or lithium tetrafluoroborate (LiBF 4), showed good high current density cycling performance when used as separators in coke and Li 1- xMn 2O 4 (spinel) half-cells.

Dating exhumed peridotite with spinel (U-Th)/He chronometry

NASA Astrophysics Data System (ADS)

Cooperdock, Emily H. G.; Stockli, Daniel F.

2018-05-01

The timing of cooling and exhumation of mantle peridotites in oceanic and continental settings has been challenging to determine using traditional geo- and thermochronometric techniques. Hence, the timing of the exhumation of mantle rocks to the Earth's surface at mid-ocean ridges, rifted and passive continental margins, and within continental volcanic and orogenic systems has remained largely elusive or only loosely constrained by relative age bracketing. Magmatic spinel [(Mg, Fe)(Al,Cr)2O4] is a ubiquitous primary mineral phase in mantle peridotites and is often the only primary mineral phase to survive surface weathering and serpentinization. This work explores spinel (U-Th)/He thermochronology as a novel tool to directly date the exhumation and cooling history of spinel-bearing mantle peridotite. Samples were chosen from a range of tectonic and petrologic settings, including a mid-ocean ridge abyssal peridotite (ODP Leg 209), an orogenic tectonic sliver of sub-continental mantle (Lherz massif, France), and a volcanic-rock hosted mantle xenolith (Green Knobs, NM). Spinel grains were selected based on grain size and morphology, screened for internal homogeneity using X-ray computed tomography, and air abraded to eliminate effects of alpha ejection/implantation. These case studies yield spinel He age results that are reproducible and generally in good agreement with independent age constraints. For ODP Leg 209, a spinel He age of 1.1 ± 0.3 Ma (2 SE) (n = 8) is consistent with independent U-Pb and magnetic anomaly ages for the exhumation of oceanic crust by detachment faulting along this segment of the slow-spreading ridge. Spinel from the Lherz massif yield He ages from 60-70 Ma (n = 3), which correspond well with independent thermochronometric constraints for cooling associated with Pyrenean collisional exhumation. Spinel from a mantle xenolith within a previously undated kimberlite diatreme at Green Knobs, New Mexico, generate a reproducible mean He age of 11.7 ± 1.8 Ma (2 SE) (n = 6) that appears to record young volcanism in the area or age resetting by post-emplacement re-heating or alteration. The combined results of these case studies demonstrate the viability for spinel He thermochronometry to resolve cooling histories of peridotite exhumed through tectonic and volcanic processes.

Cr diffusion in MgAl2O4 synthetic spinels: preliminary results

NASA Astrophysics Data System (ADS)

Freda, C.; Celata, B.; Andreozzi, G.; Perinelli, C.; Misiti, V.

2012-04-01

Chromian spinel is an accessory phase common in crustal and mantle rocks, including peridotites, gabbros and basalts. Spinel, it has been identified as one of the most effective, sensible, and versatile petrogenetic indicator in mafic and ultramafic rock systems due to the strict interdependence between its physico-chemical properties (chemical composition, cation configuration etc.) and genetic conditions (temperature, pressure, and chemical characteristics of the system). In particular, studies on intra- and inter-crystalline Mg-Fe2+, Cr-Al exchange demonstrated the close relationship between spinel composition and both degree of partial melting and equilibrium temperature of spinel-peridotites. Moreover, studies focused on the chemical zoning of Mg-Fe2+ and/or Cr-Al components in spinel have been used, combined with a diffusion model, to provide quantitative information on peridotites and gabbros pressure-temperature paths and on deformation mechanisms. Although these potentials, most of the experimental studies have been performed on spinels hosting a limited content of divalent iron (sensu stricto, MgAl2O4), whereas the scarce studies on Cr-Al inter-diffusion coefficient have been performed at 3-7 GPa as pressure boundary condition. In order to contribute to the understanding of processes occurring in the lithospheric mantle, we have initiated an experimental research project aiming at determining the Cr-Al inter-diffusion in spinel at 2 GPa pressure and temperature ranging from 1100 to 1250 °C. The experiments were performed in a end-loaded piston cylinder by using a 19 mm assembly and graphite-Pt double capsules. As starting materials we used synthetic Mg-Al spinel (200-300 μm in size) and Cr2O3 powder. Microanalyses of experimental charge were performed on polished carbon-coated mounts by electronic microprobe. Line elemental analyses were made perpendicular to the contact surface between Cr2O3 powder and spinel, at interval of 2 μm. By processing these preliminary data, we have estimated a diffusion coefficient of chromium (D) of 7.6·10-15 m2s-1.

Origin of coronas in metagabbros of the Adirondack mts., N. Y

USGS Publications Warehouse

Whitney, P.R.; McLelland, J.M.

1973-01-01

Metagabbros from two widely separated areas in the Adirondacks show development of coronas. In the Southern Adirondacks, these are cored by olivine which is enclosed in a shell of orthopyroxene that is partially, or completely, rimmed by symplectites consisting of clinopyroxene and spinel. Compositions of the corona phases have been determined by electron probe and are consistent with a mechanism involving three partial reactions, thus: (a) Olivine=Orthopyroxene+(Mg, Fe)++. (b) Plagioclase+(Mg, Fe)+++Ca++=Clinopyroxene+Spinel+Na+. (c) Plagioclase+(Mg, Fe)+++Na+=Spinel+more sodic plagioclase+Ca++. Reaction (a) occurs in the inner shell of the corona adjacent to olivine; reaction (b) in the outer shell; and (c) in the surrounding plagioclase, giving rise to the spinel clouding which is characteristic of the plagioclase in these rocks. Alumina and silica remain relatively immobile. These reactions, when balanced, can be generalized to account for the aluminous nature of the pyroxenes and for changing plagioclase composition. Summed together, the partial reactions are equivalent to: (d) Olivine + Anorthite = Aluminous orthopyroxene + Aluminous Clinopyroxene + Spinel (Kushiro and Yoder, 1966). In the Adirondack Highlands, coronas between olivine and plagioclase commonly have an outer shell of garnet replacing the clinopyroxene/spinel shell. The origin of the garnet can also be explained in terms of three partial reactions: (e) Orthopyroxene+Ca++=Clinopyroxene+(Mg, Fe)++. (f) Clinopyroxene+Spinel+Plagioclase+(Mg, Fe)++=Garnet+Ca+++Na+. (g) Plagioclase+(Mg, Fe)+++Na+=Spinel + more sodic plagioclase+Ca++. These occur in the inner and outer corona shell and the surrounding plagioclase, respectively, and involve the products of reactions (a)-(d). Alumina and silica are again relatively immobile. Balanced, and generalized to account for aluminous pyroxenes and variable An content of plagioclase, they are equivalent to: (h) Orthopyroxene+Anorthite+Spinel=Garnet (Green and Ringwood, 1967). Amphibole coronas about opaque oxides in rocks of both areas are the result of oxide/plagioclase reactions with addition of magnesium from coexisting olivine. Based on published experimental data, pressure and temperature at the time of corona formation were on the order of 8 kb and 800?? C for the garnet bearing coronas, with somewhat lower pressures indicated for the clinopyroxene/spinel coronas. ?? 1973 Springer-Verlag.

Exploring Lithium-Cobalt-Nickel Oxide Spinel Electrodes for ≥3.5 V Li-Ion Cells

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

Lee, Eungje; Blauwkamp, Joel; Castro, Fernando C.

2016-10-19

Recent reports have indicated that a manganese oxide spinel component, when embedded in a relatively small concentration in layered xLi2MnO3(1-x)LiMO2 (M=Ni, Mn, Co) electrode systems, can act as a stabilizer that increases their capacity, rate capability, cycle life, and first-cycle efficiency. These findings prompted us to explore the possibility of exploiting lithiated cobalt oxide spinel stabilizers by taking advantage of (1) the low mobility of cobalt ions relative to manganese and nickel ions in close-packed oxides and (2) their higher potential (~3.6 V vs. Li0) relative to manganese oxide spinels (~2.9 V vs. Li0) for the spinel-to-lithiated spinel electrochemical reaction.more » In particular, we have revisited the structural and electrochemical properties of lithiated spinels in the LiCo1-xNixO2 (0x0.2) system, first reported almost 25 years ago, by means of high-resolution (synchrotron) X-ray diffraction, transmission electron microscopy, nuclear magnetic resonance spectroscopy, electrochemical cell tests, and theoretical calculations. The results provide a deeper understanding of the complexity of intergrown layered/lithiated spinel LiCo1-xNixO2 structures, when prepared in air between 400 and 800 C, and the impact of structural variations on their electrochemical behavior. These structures, when used in low concentration, offer the possibility of improving the cycling stability, energy, and power of high energy (≥3.5 V) lithium-ion cells.« less

Exploring Lithium-Cobalt-Nickel Oxide Spinel Electrodes for ≥3.5 V Li-Ion Cells

DOE PAGES

Lee, Eungje; Blauwkamp, Joel; Castro, Fernando C.; ...

2016-10-04

Some recent reports have indicated that a manganese oxide spinel component, when embedded in a relatively small concentration in layered xLi 2MnO 3center dot(1-x)LiMO 2 (M = Ni, Mn, or Co) electrode systems, can act as a stabilizer that increases their capacity, rate capability, cycle life, and first-cycle efficiency. Our findings prompted us to explore the possibility of exploiting lithiated cobalt oxide spinel stabilizers by taking advantage of (1) the low mobility of cobalt ions relative to that of manganese and nickel ions in close-packed oxides and (2) their higher potential (similar to 3.6 V vs Li0) relative to manganesemore » oxide spinels (similar to 2.9 V vs Li0) for the spinel-to-lithiated spinel electrochemical reaction. In particular, we revisited the structural and electrochemical properties of lithiated spinels in the LiCo 1-xNi xO 2 (0 <= x <= 0.2) system, first reported almost 25 years ago, by means of high-resolution (synchrotron) X-ray diffraction, transmission electron microscopy, nuclear magnetic resonance spectroscopy, electrochemical cell tests, and theoretical calculations. These results provide a deeper understanding of the complexity of intergrown layered/lithiated spinel LiCo 1-xNi xO 2 structures when prepared in air between 400 and 800 degrees C and the impact of structural variations on their electrochemical behavior. These structures, when used in low concentrations, offer the possibility of improving the cycling stability, energy, and power of high energy (>= 3.5 V) lithium-ion cells.« less

Insertion of lattice strains into ordered LiNi0.5Mn1.5O4 spinel by mechanical stress: A comparison of perfect versus imperfect structures as a cathode for Li-ion batteries

NASA Astrophysics Data System (ADS)

Kozawa, Takahiro; Murakami, Takeshi; Naito, Makio

2016-07-01

The Ni-doped lithium manganese oxide, LiNi0.5Mn1.5O4, has received much attention as a cathode active material in high-energy lithium-ion batteries (LIBs). This active material has two different spinel structures depending on the ordering state of the Ni and Mn ions. The ordered LiNi0.5Mn1.5O4 spinel has an inferior cathode performance than the disordered phase because of its poor electronic conductivity. However, the ordered LiNi0.5Mn1.5O4 spinel possesses the potential advantage of avoiding dissolution of the Mn ion, which is an issue for the disordered spinel. The improvement of cathode performance is important for future applications. Here, we report a unique approach to improve the cathode performance of the ordered LiNi0.5Mn1.5O4 spinel. The mechanical treatment using an attrition-type mill successfully inserted lattice strains into the ordered LiNi0.5Mn1.5O4 spinel structure without a phase transformation to the disordered phase. The insertion of lattice strains by mechanical stresses provided an increased discharge capacity and a decreased charge transfer resistance. This limited crystal structure modification improved the cathode performance. The present work has the potential for application of the mechanically treated ordered LiNi0.5Mn1.5O4 spinel as a cathode for high-energy LIBs.

Synthesis of composite nanoparticles using co-precipitation of a magnetic iron-oxide shell onto core nanoparticles

NASA Astrophysics Data System (ADS)

Primc, Darinka; Belec, Blaž; Makovec, Darko

2016-03-01

Composite nanoparticles can be synthesized by coating a shell made of one material onto core nanoparticles made of another material. Here we report on a novel method for coating a magnetic iron oxide onto the surface of core nanoparticles in an aqueous suspension. The method is based on the heterogeneous nucleation of an initial product of Fe3+/Fe2+ co-precipitation on the core nanoparticles. The close control of the supersaturation of the precipitating species required for an exclusively heterogeneous nucleation and the growth of the shell were achieved by immobilizing the reactive Fe3+ ions in a nitrate complex with urea ([Fe((CO(NH2)2)6](NO3)3) and by using solid Mg(OH)2 as the precipitating reagent. The slow thermal decomposition of the complex at 60 °C homogeneously releases the reactive Fe3+ ions into the suspension of the core nanoparticles. The key stage of the process is the thermal hydrolysis of the released Fe3+ ions prior to the addition of Mg(OH)2. The thermal hydrolysis results in the formation of γ-FeOOH, exclusively at the surfaces of the core nanoparticles. After the addition of the solid hydroxide Mg(OH)2, the pH increases and at pH 5.7 the Fe2+ precipitates and reacts with the γ-FeOOH to form magnetic iron oxide with a spinel structure (spinel ferrite) at the surfaces of the core nanoparticles. The proposed low-temperature method for the synthesis of composite nanoparticles is capable of forming well-defined interfaces between the two components, important for the coupling of the different properties. The procedure is environmentally friendly, inexpensive, and appropriate for scaling up to mass production.

Nature of the lithospheric mantle beneath the Arabian Shield and genesis of Al-spinel micropods: Evidence from the mantle xenoliths of Harrat Kishb, Western Saudi Arabia

NASA Astrophysics Data System (ADS)

Ahmed, Ahmed H.; Moghazi, Abdel Kader M.; Moufti, Mohamed R.; Dawood, Yehia H.; Ali, Kamal A.

2016-01-01

The Harrat Kishb area of western Saudi Arabia is part of the Cenozoic volcanic fields in the western margin of the Arabian Shield. Numerous fresh ultramafic xenoliths are entrained in the basanite lava of Harrat Kishb, providing an opportunity to study the nature and petrogenetic processes involved in the evolution of the lithospheric mantle beneath the Arabian Shield. Based on the petrological characteristics and mineralogical compositions, the majority of the mantle xenoliths ( 92%) are peridotites (lherzolites and pyroxene-bearing harzburgites); the remaining xenoliths ( 8%) are unusual spinel-rich wehrlites containing black Al-spinel micropods. The two types of mantle xenoliths display magmatic protogranular texture. The peridotite xenoliths have high bulk-rock Mg#, high forsterite (Fo90-Fo92) and NiO (0.24-0.46 wt.%) contents of olivine, high clinopyroxene Mg# (0.91-0.93), variable spinel Cr# (0.10-0.49, atomic ratio), and approximately flat chondrite-normalized REE patterns. These features indicate that the peridotite xenoliths represent residues after variable degrees of melt extraction from fertile mantle. The estimated P (9-16 kbar) and T (877-1227 °C) as well as the oxidation state (ΔlogfO2 = - 3.38 to - 0.22) under which these peridotite xenoliths originated are consistent with formation conditions similar to most sub-arc abyssal-type peridotites worldwide. The spinel-rich wehrlite xenoliths have an unusual amount ( 30 vol.%) of Al-spinel as peculiar micropods with very minor Cr2O3 content (< 1 wt.%). Olivines of the spinel-rich wehrlites have low-average Fo (Fo81) and NiO (0.18 wt.%) contents, low-average cpx Mg# (0.79), high average cpx Al2O3 content (8.46 wt.%), and very low-average spinel Cr# (0.01). These features characterize early mantle cumulates from a picritic melt fraction produced by low degrees of partial melting of a garnet-bearing mantle source. The relatively high Na2O and Al2O3 contents of cpx suggest that the spinel-rich wehrlites are formed under high P (11-14 kbar), T (1090-1130 °C), and oxidation state (ΔlogfO2 FMQ = + 0.14 to + 0.37), which occurred slightly below the crust-mantle boundary. The REE patterns of spinel-rich wehrlites are almost similar to those of the associated peridotite xenoliths, which confirm at least a spatial genetic linkage between them. Regarding the formation of Al-spinel micropods in spinel-rich wehrlite cumulates, it is suggested that the melt-rock reaction mechanism is not the only process by which podiform chromitite is formed. Early fractionation of picritic melts produced by partial melting of a mantle source under high P-T conditions could be another mechanism. The cpx composition, not opx, as it was assumed, seems to be the main control of the size and composition of spinel concentrations.

Transparent magnesium aluminate spinel: a prospective biomaterial for esthetic orthodontic brackets.

PubMed

Krishnan, Manu; Tiwari, Brijesh; Seema, Saraswathy; Kalra, Namitha; Biswas, Papiya; Rajeswari, Kotikalapudi; Suresh, Madireddy Buchi; Johnson, Roy; Gokhale, Nitin M; Iyer, Satish R; Londhe, Sanjay; Arora, Vimal; Tripathi, Rajendra P

2014-11-01

Adult orthodontics is recently gaining popularity due to its importance in esthetics, oral and general health. However, none of the currently available alumina or zirconia based ceramic orthodontic brackets meet the esthetic demands of adult patients. Inherent hexagonal lattice structure and associated birefringence limits the visible light transmission in polycrystalline alumina and make them appear white and non transparent. Hence focus of the present study was to assess the feasibility of using magnesium aluminate (MgAl2O4) spinel; a member of the transparent ceramic family for esthetic orthodontic brackets. Transparent spinel specimens were developed from commercially available white spinel powder through colloidal shaping followed by pressureless sintering and hot isostatic pressing at optimum conditions of temperature and pressure. Samples were characterized for chemical composition, phases, density, hardness, flexural strength, fracture toughness and optical transmission. Biocompatibility was evaluated with in-vitro cell line experiments for cytotoxicity, apoptosis and genotoxicity. Results showed that transparent spinel samples had requisite physico-chemical, mechanical, optical and excellent biocompatibility for fabricating orthodontic brackets. Transparent spinel developed through this method demonstrated its possibility as a prospective biomaterial for developing esthetic orthodontic brackets.

Stretched-to-compressed-exponential crossover observed in the electrical degradation kinetics of some spinel-metallic screen-printed structures

NASA Astrophysics Data System (ADS)

Balitska, V.; Shpotyuk, O.; Brunner, M.; Hadzaman, I.

2018-02-01

Thermally-induced (170 °C) degradation-relaxation kinetics is examined in screen-printed structures composed of spinel Cu0.1Ni0.1Co1.6Mn1.2O4 ceramics with conductive Ag or Ag-Pd layered electrodes. Structural inhomogeneities due to Ag and Ag-Pd diffusants in spinel phase environment play a decisive role in non-exponential kinetics of negative relative resistance drift. If Ag migration in spinel is inhibited by Pd addition due to Ag-Pd alloy, the kinetics attains stretched exponential behavior with ∼0.58 exponent, typical for one-stage diffusion in structurally-dispersive media. Under deep Ag penetration into spinel ceramics, as for thick films with Ag-layered electrodes, the degradation kinetics drastically changes, attaining features of two-step diffusing process governed by compressed-exponential dependence with power index of ∼1.68. Crossover from stretched- to compressed-exponential kinetics in spinel-metallic structures is mapped on free energy landscape of non-barrier multi-well system under strong perturbation from equilibrium, showing transition with a character downhill scenario resulting in faster than exponential decaying.

The soda-ash roasting of chromite ore processing residue for the reclamation of chromium

NASA Astrophysics Data System (ADS)

Antony, M. P.; Tathavadkar, V. D.; Calvert, C. C.; Jha, A.

2001-12-01

Sodium chromate is produced via the soda-ash roasting of chromite ore with sodium carbonate. After the reaction, nearly 15 pct of the chromium oxide remains unreacted and ends up in the waste stream, for landfills. In recent years, the concern over environmental pollution from hexavalent chromium (Cr6+) from the waste residue has become a major problem for the chromium chemical industry. The main purpose of this investigation is to recover chromium oxide present in the waste residue as sodium chromate. Cr2O3 in the residue is distributed between the two spinel solid solutions, Mg(Al,Cr)2O4 and γ-Fe2O3. The residue from the sodium chromate production process was analyzed both physically and chemically. The compositions of the mineral phases were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). The influence of alkali addition on the overall reaction rate is examined. The kinetics of the chromium extraction reaction resulting from the residue of the soda-ash roasting process under an oxidizing atmosphere is also investigated. It is shown that the experimental results for the roasting reaction can be best described by the Ginstling and Brounshtein (GB) equation for diffusion-controlled kinetics. The apparent activation energy for the roasting reaction was calculated to be between 85 and 90 kJ·mol-1 in the temperature range 1223 to 1473 K. The kinetics of leaching of Cr3+ ions using the aqueous phase from the process residue is also studied by treating the waste into acid solutions with different concentrations.

Fluorination Induced the Surface Segregation of High Voltage Spinel on Lithium-Rich Layered Cathodes for Enhanced Rate Capability in Lithium Ion Batteries.

PubMed

Jin, Yi-Chun; Duh, Jenq-Gong

2016-02-17

This study is aimed to explore the effect of fluoride doping and the associated structural transformation on lithium-rich layered cathode materials. The polymeric fluoride source is first adopted for synthesizing lithium intercalated oxide through a newly developed organic precipitation process. A heterostructured spinel/layered composite cathode material is obtained after appreciable fluorination and a superior rate capability is successfully achieved. The fluoride dopant amount and the surface spinel phase are evidenced and systematically examined by various structural spectroscopy and electrochemical analysis. It appears the reversible Ni(2+/4+) redox couple at high voltage regime around 4.8 V because of the formation of spinel LiNi1/2Mn3/2O4 phase. The mechanism of "layer to spinel" phase transformation is discussed in detail.

On the Oxidation State of Manganese Ions in Li-Ion Battery Electrolyte Solutions.

PubMed

Banerjee, Anjan; Shilina, Yuliya; Ziv, Baruch; Ziegelbauer, Joseph M; Luski, Shalom; Aurbach, Doron; Halalay, Ion C

2017-02-08

We demonstrate herein that Mn 3+ and not Mn 2+ , as commonly accepted, is the dominant dissolved manganese cation in LiPF 6 -based electrolyte solutions of Li-ion batteries with lithium manganate spinel positive and graphite negative electrodes chemistry. The Mn 3+ fractions in solution, derived from a combined analysis of electron paramagnetic resonance and inductively coupled plasma spectroscopy data, are ∼80% for either fully discharged (3.0 V hold) or fully charged (4.2 V hold) cells, and ∼60% for galvanostatically cycled cells. These findings agree with the average oxidation state of dissolved Mn ions determined from X-ray absorption near-edge spectroscopy data, as verified through a speciation diagram analysis. We also show that the fractions of Mn 3+ in the aprotic nonaqueous electrolyte solution are constant over the duration of our experiments and that disproportionation of Mn 3+ occurs at a very slow rate.

Method for thermal processing alumina-enriched spinel single crystals

DOEpatents

Jantzen, Carol M.

1995-01-01

A process for age-hardening alumina-rich magnesium aluminum spinel to obtain the desired combination of characteristics of hardness, clarity, flexural strength and toughness comprises selection of the time-temperature pair for isothermal heating followed by quenching. The time-temperature pair is selected from the region wherein the precipitate groups have the characteristics sought. The single crystal spinel is isothermally heated and will, if heated long enough pass from its single phase through two pre-precipitates and two metastable precipitates to a stable secondary phase precipitate within the spinel matrix. Quenching is done slowly at first to avoid thermal shock, then rapidly.

Regional Variations in Composition of Cr-spinel Xenocrysts From Kimberlite

NASA Astrophysics Data System (ADS)

Schulze, D. J.

2001-05-01

Important information on the composition of the upper mantle can be obtained by studying mantle xenocrysts in kimberlite, especially in situations in which intact mantle xenoliths are rare to absent. Spinel-group minerals are especially useful as they can coexist with garnet or represent regions of the mantle shallower than garnet-facies rocks, and chromites can exist in rocks too Al-depleted to form garnet. Xenolith studies have shown that along most typical cratonic geothermal gradients, the maximum Cr/(Cr+Al) (cr#) of spinel coexisting with garnet is 0.88. Cr-spinels with cr# > 0.88 are from Al-depleted rocks or from assemblages in which Al is partitioned into another phase (e.g., metasomatic phlogopite). Approximately 2500 Cr-spinel xenocrysts from 36 kimberlites in southern Africa and North America have been analysed (and some published data used) and evaluated, primarily in terms of cr# and Fe2/(Fe2+Mg) (fe#). Differences from pipe to pipe within and between cratons reflect variations in geologic history and fertility/depletion, only some of which can be related to mantle age. Within southern Africa, pipe average values of spinel xenocryst cr# are highest on the Kaapvaal Craton (0.80-0.89) where fe# varies from 0.36 to 0.47. Suites from the craton margin (e.g., in Lesotho) indicate a less depleted mantle (cr# = 0.75-0.80), similar to those from the Zimbabwe Craton (Orapa and Letlhakane, cr# = 0.80-0.81). Jwaneng (Kaapvaal Craton) is similar to the Zimbabwe Craton pipes (cr# = 0.83). Off-craton South African suites (Kalkput and Rietfontein) have lower cr# (0.72-0.75). Most southern African suites contain a significant population of Cr-spinel with cr# > 0.88 (including off-craton Rietfontein) except Liqhobong on the craton margin in Lesotho. Cr-spinel suites from North American kimberlites are quite different, with most suites being significantly more aluminous than African populations. Most Kirkland Lake kimberlites on the Superior Craton have a very restricted fe# (0.41-0.43) at cr# values below those from Kaapvaal and Zimbabwe Cratons (0.67-0.78). Wyoming Craton kimberlites (Sloan and Kelsey Lake) also have aluminous spinel populations (cr# = 0.70-0.76). High-Cr spinel xenocrysts (cr# > 0.88) are common in Superior Craton populations but less abundant on the Wyoming Craton. Off-craton kimberlites (on Grenville basement) in Kentucky and Pennsylvania are much more aluminous (cr# = 0.62) and have almost no xenocrysts with cr# > 0.88. The general increase in fertility (lower cr# in spinel) from craton centre to margin to off-craton is confirmed, but Cr-spinel populations from all tectonic settings in North American kimberlites appear to be less depleted on average than their equivalents in southern Africa.

Effect of cutting edge radius on surface roughness in diamond tool turning of transparent MgAl2O4 spinel ceramic

NASA Astrophysics Data System (ADS)

Yue, Xiaobin; Xu, Min; Du, Wenhao; Chu, Chong

2017-09-01

Transparent magnesium aluminate spinel (MgAl2O4) ceramic is one of an important optical materials. However, due to its pronounced hardness and brittleness, the optical machining of this material is very difficult. Diamond turning has advantages over the grinding process in flexibility and material removal rate. However, there is a lack of research that could support the use of diamond turning technology in the machining of MgAl2O4 spinel ceramic. Using brittle-ductile transition theory of brittle material machining, this work provides critical information that may help to realize ductile-regime turning of MgAl2O4 spinel ceramic. A characterization method of determination the cutting edge radius is introduced here. Suitable diamond tools were measured for sharpness and then chosen from a large number of candidate tools. The influence of rounded cutting edges on surface roughness of the MgAl2O4 spinel ceramic is also investigated. These results indicate that surface quality of MgAl2O4 spinel is relate to the radius of diamond tool's cutting edge, cutting speed, and feed rate. Sharp diamond tools (small radius of cutting edge) facilitated ductile-regime turning of MgAl2O4 spinel and shows great potential to reduce surface roughness and produce smoother final surface.

Elemental Mercury Oxidation over Fe-Ti-Mn Spinel: Performance, Mechanism, and Reaction Kinetics.

PubMed

Xiong, Shangchao; Xiao, Xin; Huang, Nan; Dang, Hao; Liao, Yong; Zou, Sijie; Yang, Shijian

2017-01-03

The design of a high-performance catalyst for Hg 0 oxidation and predicting the extent of Hg 0 oxidation are both extremely limited due to the uncertainties of the reaction mechanism and the reaction kinetics. In this work, Fe-Ti-Mn spinel was developed as a high-performance catalyst for Hg 0 oxidation, and the reaction mechanism and the reaction kinetics of Hg 0 oxidation over Fe-Ti-Mn spinel were studied. The reaction orders of Hg 0 oxidation over Fe-Ti-Mn spinel with respect to gaseous Hg 0 concentration and gaseous HCl concentration were approximately 1 and 0, respectively. Therefore, Hg 0 oxidation over Fe-Ti-Mn spinel mainly followed the Eley-Rideal mechanism (i.e., the reaction of gaseous Hg 0 with adsorbed HCl), and the rate of Hg 0 oxidation mainly depended on Cl • concentration on the surface. As H 2 O, SO 2 , and NO not only inhibited Cl • formation on the surface but also interfered with the interface reaction between gaseous Hg 0 and Cl • on the surface, Hg 0 oxidation over Fe-Ti-Mn spinel was obviously inhibited in the presence of H 2 O, SO 2 , and NO. Furthermore, the extent of Hg 0 oxidation over Fe-Ti-Mn spinel can be predicted according to the kinetic parameter k E-R , and the predicted result was consistent with the experimental result.

Amorphous lithium lanthanum titanate for solid-state microbatteries

DOE PAGES

Lee, Jungwoo Z.; Wang, Ziying; Xin, Huolin L.; ...

2016-12-16

Lithium lanthanum titanate (LLTO) is a promising solid state electrolyte for solid state batteries due to its demonstrated high bulk ionic conductivity. However, crystalline LLTO has a relatively low grain boundary conductivity, limiting the overall material conductivity. In this work, we investigate amorphous LLTO (a-LLTO) thin films grown by pulsed laser deposition (PLD). By controlling the background pressure and temperature we are able to optimize the ionic conductivity to 3 × 10 –4 S/cm and electronic conductivity to 5 × 10 –11 S/cm. XRD, TEM, and STEM/EELS analysis confirm that the films are amorphous and indicate that oxygen background gasmore » is necessary during the PLD process to decrease the oxygen vacancy concentration, decreasing the electrical conductivity. Amorphous LLTO is deposited onto high voltage LiNi 0.5Mn 1.5O 4 (LNMO) spinel cathode thin films and cycled up to 4.8 V vs. Li showing excellent capacity retention. Finally, these results demonstrate that a-LLTO has the potential to be integrated into high voltage thin film batteries.« less

Oxygen regime of Siberian alkaline-ultramafic magmas

NASA Astrophysics Data System (ADS)

Ryabchikov, Igor; Kogarko, Liya

2017-04-01

Regimes of S2 and O2 are decisive factors controlling behavior of chalcophile and siderophile elements in magmatic processes. These parameters play important role during magmagenesis and in the course of crystallization and fluid mass transfer in magma chamber. Alkaline-ultramafic magmatism in Maymecha-Kotuy Province (Polar Siberia) is represented by giant intrusive complexes as well as by volcanics and dyke rocks, which include a well-known variety - meimechites. The latter are considered primary magmas of alkaline-ultramafic plutons in the region like for instance Guli intrusive complex. Sulfur content in primitive magmas estimated from the analyses of melt inclusions in olivine megacrysts from meimechites is close to 0.1 %. fO2 values calculated using olivine+clinopyroxene+spinel and spinel+melt oxygen barometers (1, 2) are 2-3 log units above QFM buffer. The relatively high oxygen potential at the early magmatic stage of alkaline-ultramafic Guli pluton provide predominance of sulfates among other forms of sulfur in the melt. This leads to the almost complete absence of sulfides in highly magnesian rocks. The oxidizing conditions exert important effect on behavior of many ore metals. At the stage of magma generation absence of sulfides in mantle materialresults in the presence of siderophile elements in metallic form and saturation of primary magmas in respect of metallic phases at an early stage of injection of the melt into the magma chamber. Later, under favorable circumstances during magma crystallization nuggets of precious metals may be formed. During further evolution of magmatic system fO2 and activity of oxidized sulfur decrease due to intensive crystallization of magnetite during the formation of koswites, then oxygen fugacity becomes even lower as a result serpentinization at a postmagmatic stage. These serpentization processes are caused by the displacement of reactions in the aqueous phase due to cooling towards the formation of methane and other reduced components and, possibly, with their concentration in the gas phase due to boiling at lowered pressure. This leads to the appearance of late sulfides in the intergranular space of the investigated rocks. Sulfides are represented by pentlandite, monosulfide solid solution and heazlewoodite. Thermodynamic analysis of equilibria involving these minerals has shown that the oxygenpotential in the later stages is significantly reduced (up to three logarithmic units below QFM buffer at 300 ° C). The transition from an oxidizing to a reducing environment will contribute to the mobilization of many ore metals by aqueous fluids and then theirconcentrated deposition. This may be particularly important factor for gold, which is mobilized by fluid under oxidizing environment and precipitated due to the decreasing fO2. Au is present in placers on the territory of the Guli complex. Highly oxidized nature of the early phases of alkaline-ultramafic magmatic systems (high magnetite component of chrome spinel, high concentrations of ferric iron in pyroxene), and signs of the transition to a more reducing environment at a late stage (intensive crystallization of magnetite, occurrence of sulfur-deficient sulfides) can be considered as a potential prognostic signs of gold mineralization. Russian Science Foundation (grant 15-17-30019) has supported this work. 1. I. D. Ryabchikov, Oxygen potential of high-magnesium magmas. Doklady Earth Sciences 448, 149 (Jan, 2013). 2. I. D. Ryabchikov, L. N. Kogarko, A new version of the spinel-olivine-pyroxene oxybarometer and extreme redox differentiation in magmatic systems of mantle sources. Doklady Earth Sciences 430, 248 (Feb, 2010).

Partitioning of Ni, Co and V between Spinel-Structured Oxides and Silicate Melts: Importance of Spinel Composition

NASA Technical Reports Server (NTRS)

Righter, K.; Leeman, W. P.; Hervig, R. L.

2006-01-01

Partitioning of Ni, Co and V between Cr-rich spinels and basaltic melt has been studied experimentally between 1150 and 1325 C, and at controlled oxygen fugacity from the Co-CoO buffer to slightly above the hematite magnetite buffer. These new results, together with new Ni, Co and V analyses of experimental run products from Leeman [Leeman, W.P., 1974. Experimental determination of the partitioning of divalent cations between olivine and basaltic liquid, Pt. II. PhD thesis, Univ. Oregon, 231 - 337.], show that experimentally determined spinel melt partition coefficients (D) are dependent upon temperature (T), oxygen fugacity (fO2) and spinel composition. In particular, partition coefficients determined on doped systems are higher than those in natural (undoped) systems, perhaps due to changing activity coefficients over the composition range defined by the experimental data. Using our new results and published runs (n =85), we obtain a multilinear regression equation that predicts experimental D(V) values as a function of T, fO2, concentration of V in melt and spinel composition. This equation allows prediction of D(V) spinel/melt values for natural mafic liquids at relevant crystallization conditions. Similarly, D(Ni) and D(Co) values can be inferred from our experiments at redox conditions approaching the QFM buffer, temperatures of 1150 to 1250 C and spinel composition (early Cr-bearing and later Ti-magnetite) appropriate for basic magma differentiation. When coupled with major element modelling of liquid lines of descent, these values (D(Ni) sp/melt=10 and D(Co) sp/melt=5) closely reproduce the compositional variation observed in komatiite, mid-ocean ridge basalt (MORB), ocean island basalt (OIB) and basalt to rhyolite suites.

Sucrose-aided combustion synthesis of nanosized LiMn 1.99- yLi yM 0.01O 4 (M = Al 3+, Ni 2+, Cr 3+, Co 3+, y = 0.01 and 0.06) spinels . Characterization and electrochemical behavior at 25 and at 55 °C in rechargeable lithium cells

NASA Astrophysics Data System (ADS)

Amarilla, J. M.; Petrov, K.; Picó, F.; Avdeev, G.; Rojo, J. M.; Rojas, R. M.

Doubly doped LiMn 1.99- yLi yM 0.01O 4 (M = Al 3+, Ni 2+, Cr 3+, Co 3+; y = 0.01 and 0.06) spinels have been synthesized by the sucrose-aided combustion method. Combined TG/DTA and XRD studies have shown that stoichiometric single-phase spinels are formed after annealing of the samples at 700 °C for 1 h. The samples obtained are nanocrystalline materials having a narrow size-distribution and a coherent domain size between 40 and 60 nm, depending on the amount of fuel (sucrose) used in the synthesis. The influence of the Li-excess, the type of M n+-dopant cation and the amount of fuel used in the synthesis on the electrochemical behavior of the spinels in a Li-cell at room and at elevated temperature (55 °C) has been studied. At 25 °C all the spinels synthesized have a good capacity retention after 100 cycles, QRt-100 > 92%. At 55 °C the increase of the Li-excess improves the cycling performances. Rate capability studies show that the spinels retain >90% of their capacity even at 5 C rate. The synergic effect of the Li-excess and the particle size on the electrochemical properties of the spinels as cathode material has been settled. The LiMn 1.93Li 0.06M 0.01O 4, (M = Al 3+, Ni 2+) spinels, with cyclabilities >99.9% by cycle at both 25 and 55 °C, and high rate capabilities, are the ones that show the best electrochemical properties.

Determination of the spinel group end-members based on electron microprobe analyses

NASA Astrophysics Data System (ADS)

Ferracutti, Gabriela R.; Gargiulo, M. Florencia; Ganuza, M. Luján; Bjerg, Ernesto A.; Castro, Silvia M.

2015-04-01

The spinel group minerals have been the focus of many studies, not only because of their economic interest, but also due to the fact that they are very useful as petrogenetic indicators. The application End-Members Generator (EMG) allows to establish, based on electron microprobe analyses (EMPA), the 19 end-members of the spinel group: MgAl2O4 (Spinel sensu stricto, s.s.), FeAl2O4 (Hercynite), MnAl2O4 (Galaxite), ZnAl2O4 (Gahnite), MgFe2O4 (Magnesioferrite), Fe3O4 (Magnetite), MnFe2O4 (Jacobsite), ZnFe2O4 (Franklinite), NiFe2O4 (Trevorite), MgCr2O4 (Magnesiochromite), FeCr2O4 (Chromite), MnCr2O4 (Manganochromite), ZnCr2O4 (Zincochromite), NiCr2O4 (Nichromite), MgV2O4 (Magnesiocoulsonite), FeV2O4 (Coulsonite), MnV2O4 (Vuorelainenite), Mg2TiO4 (Qandilite) and Fe2TiO4 (Ulvöspinel). EMG is an application that does not require an installation process and was created with the purpose of performing calculations to obtain: cation proportions (per formula unit, p.f.u.), end-members of the spinel group, redistribution proportions for the corresponding end-members in the Magnetite prism or Ulvöspinel prism and a data validation section to check the results. EMG accepts .csv data files and the results obtained can be used to represent a given dataset with the SpinelViz program or any other 2D and/or 3D graph plotting software.

Spinel compounds as multivalent battery cathodes: A systematic evaluation based on ab initio calculations

DOE PAGES

Liu, Miao; Rong, Ziqin; Malik, Rahul; ...

2014-12-16

In this study, batteries that shuttle multivalent ions such as Mg 2+ and Ca 2+ ions are promising candidates for achieving higher energy density than available with current Li-ion technology. Finding electrode materials that reversibly store and release these multivalent cations is considered a major challenge for enabling such multivalent battery technology. In this paper, we use recent advances in high-throughput first-principles calculations to systematically evaluate the performance of compounds with the spinel structure as multivalent intercalation cathode materials, spanning a matrix of five different intercalating ions and seven transition metal redox active cations. We estimate the insertion voltage, capacity,more » thermodynamic stability of charged and discharged states, as well as the intercalating ion mobility and use these properties to evaluate promising directions. Our calculations indicate that the Mn 2O 4 spinel phase based on Mg and Ca are feasible cathode materials. In general, we find that multivalent cathodes exhibit lower voltages compared to Li cathodes; the voltages of Ca spinels are ~0.2 V higher than those of Mg compounds (versus their corresponding metals), and the voltages of Mg compounds are ~1.4 V higher than Zn compounds; consequently, Ca and Mg spinels exhibit the highest energy densities amongst all the multivalent cation species. The activation barrier for the Al³⁺ ion migration in the Mn₂O₄ spinel is very high (~1400 meV for Al 3+ in the dilute limit); thus, the use of an Al based Mn spinel intercalation cathode is unlikely. Amongst the choice of transition metals, Mn-based spinel structures rank highest when balancing all the considered properties.« less

Low-loss spinel windows for high-energy lasers

NASA Astrophysics Data System (ADS)

Kim, Woohong; Baker, Colin; Villalobos, Guillermo; Bayya, Shyam; Hunt, Michael; Sadowski, Bryan; Aggarwal, Ishwar; Sanghera, Jasbinder

2014-05-01

Ideal exit aperture windows for high-energy laser (HEL) should possess low absorption and scattering losses and be environmentally rugged and strong in order to protect the laser gain medium without compromising the light propagating through the window. Spinel is an ideal candidate for this application due to its high mechanical strength, high thermal conductivity, and excellent optical transmission between 0.2~5 μm. However, spinel ceramics fabricated with commercial powders often show inhomogeneity and suffer from absorption and scattering caused by various types of intrinsic and extrinsic impurities present in the powders. Here, we report on a convenient and economical powder purification method to significantly lower the absorption loss of transparent spinel ceramics using commercial powders. Acid washing was successfully used to reduce absorption loss in spinel ceramic fabricated using commercial powder from >20,000 ppm/cm down to 75 ppm/cm.

Cordierite-spinel troctolite, a new magnesium-rich lithology from the lunar highlands

NASA Technical Reports Server (NTRS)

Marvin, Ursula B.; Carey, J. William; Lindstrom, Marilyn M.

1989-01-01

A clast of spineltroctolite containing 8 percent cordierite (Mg2,Al4Si5O18) has been identified among the constituents of Apollo 15 regolith breccia 15295. The cordierite and associated anorthite, forsteritic olivine, and pleonaste spinel represent a new, Mg-rich lunar highlands lithology that formed by metamorphism of an igneous spinel cumulate. The cordierite-forsterite pair in the assemblage is stable at a maximum pressure of 2.5 kilobars, equivalent to a depth of 50 kilometers, or 10 kilometers above the lunar crust-mantle boundary. The occurrence of the clast indicates that spinel cumulates are a more important constituent of the lower lunar crust than has been recognized. The rarity of cordierite-spinel troctolite among lunar rock samples suggests that it is excavated only by large impact events, such as the one that formed the adjacent Imbrium Basin.

Opposite correlations between cation disordering and amorphization resistance in spinels versus pyrochlores

PubMed Central

Uberuaga, Blas Pedro; Tang, Ming; Jiang, Chao; Valdez, James A.; Smith, Roger; Wang, Yongqiang; Sickafus, Kurt E.

2015-01-01

Understanding and predicting radiation damage evolution in complex materials is crucial for developing next-generation nuclear energy sources. Here, using a combination of ion beam irradiation, transmission electron microscopy and X-ray diffraction, we show that, contrary to the behaviour observed in pyrochlores, the amorphization resistance of spinel compounds correlates directly with the energy to disorder the structure. Using a combination of atomistic simulation techniques, we ascribe this behaviour to structural defects on the cation sublattice that are present in spinel but not in pyrochlore. Specifically, because of these structural defects, there are kinetic pathways for the relaxation of disorder in spinel that are absent in pyrochlore. This leads to a direct correlation between amorphization resistance and disordering energetics in spinel, the opposite of that observed in pyrochlores. These results provide new insight into the origins of amorphization resistance in complex oxides beyond fluorite derivatives. PMID:26510750

Opposite correlations between cation disordering and amorphization resistance in spinels versus pyrochlores.

PubMed

Uberuaga, Blas Pedro; Tang, Ming; Jiang, Chao; Valdez, James A; Smith, Roger; Wang, Yongqiang; Sickafus, Kurt E

2015-10-29

Understanding and predicting radiation damage evolution in complex materials is crucial for developing next-generation nuclear energy sources. Here, using a combination of ion beam irradiation, transmission electron microscopy and X-ray diffraction, we show that, contrary to the behaviour observed in pyrochlores, the amorphization resistance of spinel compounds correlates directly with the energy to disorder the structure. Using a combination of atomistic simulation techniques, we ascribe this behaviour to structural defects on the cation sublattice that are present in spinel but not in pyrochlore. Specifically, because of these structural defects, there are kinetic pathways for the relaxation of disorder in spinel that are absent in pyrochlore. This leads to a direct correlation between amorphization resistance and disordering energetics in spinel, the opposite of that observed in pyrochlores. These results provide new insight into the origins of amorphization resistance in complex oxides beyond fluorite derivatives.

57Fe Mössbauer spectroscopy of mineral assemblages in mantle spinel lherzolites from Cenozoic alkali basalt, eastern China: Petrological applications

NASA Astrophysics Data System (ADS)

Hao, Xi-Luo; Li, Yi-Liang

2013-01-01

Mineral assemblages in spinel lherzolite xenoliths from the Cenozoic alkali basalt of eastern China were analyzed by 57Fe Mössbauer spectroscopy for Fe3+/ΣFe and distribution of Fe2+/Fe3+ in non-equivalent crystal cites. Orthopyroxene, clinopyroxene and spinel have 0.08-0.13, 0.19-0.31 and 0.13-0.23 Fe3+/ΣFe, respectively. The cation-exchange equilibrium temperatures, Fe3+ partition coefficient and oxygen fugacity of the upper mantle peridotites were calculated. The equilibrium temperatures are between 1103 K and 1405 K consistent with those reported elsewhere. The oxygen fugacities of spinel lherzolites calculated with olivine-orthopyroxene-spinel (ΔlogƒO2 from - 1.1 to 0) and clinopyroxene-olivine-orthopyroxene oxybarometers (ΔlogƒO2 from - 2.0 to 0.7) are consistent with previously reported upper mantle values.

Thermal Diffusion Fractionation of Cr and V Isotope in Silicate Melt

NASA Astrophysics Data System (ADS)

Lin, X.; Lundstrom, C.

2017-12-01

Earth's mantle is isotopically heavy relative to chondrites for V, Cr and some other siderophile elements. A possible solution is that isotopic fractionation by thermal diffusion occurs in a thermal boundary layer between solid mantle and an underlying basal magma ocean (BMO:Labrosse et al.,2007). If so, isotopically light composition might partition into the core, resulting in a complimentary isotopically heavy solid mantle. To verify how much fractionation could happen in this process, piston cylinder experiment were conducted to investigate the fractionation of Cr and V isotope ratios in partially molten silicate under an imposed temperature gradient from 1650 °C to 1350 °C at 1 GPa for 10 to 50 hours to reach a steady state isotopic profile. The temperature profile for experiments was determined by the spinel-growth method at the same pressure and temperature. Experimental runs result in 100% glass at the hot end progressing to nearly 100 % olivine at the cold end. Major and minor element concentrations of run products show systematic changes with temperature. Glass MgO contents increase and Al2O3 and CaO contents decrease by several weight percent as temperature increases across the charge. These are well modeled using IRIDIUM (Boudreau 2003) to simulate the experiments. Isotopic composition measurements of Cr and V at different temperatures are in progress, providing the first determinations of thermal diffusion isotopic sensitivity, Ω (permil isotopic fractionation per temperature offset per mass unit) for these elements. These results will be compared with previously determined Ω for network formers and modifiers and used in a BMO-based thermal diffusion model for formation of Earth's isotopically heavy mantle.

Chromium speciation in oxide-type compounds: application to minerals, gems, aqueous solutions and silicate glasses

NASA Astrophysics Data System (ADS)

Farges, François

2009-09-01

Cr K-edge XANES spectra were obtained for a variety of Cr-bearing model compounds containing Cr(II), Cr(III), Cr(IV), Cr(V) and Cr(VI), in which the Cr-site symmetry is D4h, Oh and Td. The centroid position of the pre-edge feature is a better indicator of the Cr valence than the edge position. In Cr-rich oxides, higher-energy transitions must be excluded in order to refine a robust valence for Cr. The pre-edge for chromates is not unique and varies as a function of the CrO4 2- moiety distortion, which is often related to Cr-polymerization (monochromate vs. dichromate). Both the analogy with the Mn K-pre-edge information and ab initio FEFF calculations of the pre-edge feature for Cr(III) and Cr(VI) confirm the experimental trends. This methodology is applied to the Cr K-edge pre-edge feature collected in gems (emerald, spinel and ruby), the layered minerals fuchsite and kämmererite, two Cr-bearing aqueous solutions and a set of sodo-calcic silicate glasses used for bottling sparkling white wine. In emerald and fuchsite, the Cr-site is differently distorted than its ruby or spinel counterpart. In a Cr(III)-bearing aqueous solution and sodo-calcic glass, no evidence for Cr(III) with Td and C3v symmetry is detected. However, minor amounts of chromate moieties (most likely monomeric) are detected in a glass synthesized in air. Preliminary spectra for the wine bottle glass suggest that only trace amounts of chromates might possibly be present in these glasses.

Surface protected lithium-metal-oxide electrodes

DOEpatents

Thackeray, Michael M.; Kang, Sun-Ho

2016-04-05

A lithium-metal-oxide positive electrode having a layered or spinel structure for a non-aqueous lithium electrochemical cell and battery is disclosed comprising electrode particles that are protected at the surface from undesirable effects, such as electrolyte oxidation, oxygen loss or dissolution by one or more lithium-metal-polyanionic compounds, such as a lithium-metal-phosphate or a lithium-metal-silicate material that can act as a solid electrolyte at or above the operating potential of the lithium-metal-oxide electrode. The surface protection significantly enhances the surface stability, rate capability and cycling stability of the lithium-metal-oxide electrodes, particularly when charged to high potentials.

Synthesis and characterization of Zn-Mg ferrite

NASA Astrophysics Data System (ADS)

Singh, Shailndra; Barbar, S. K.; Ram, Sahi

2018-05-01

The Zn-Mg ferrite sample of general formula Zn0.5Mg0.5Fe2O4 have been prepared by standard solid state reaction technique using high purity oxides. X-ray diffraction analysis shows the formation of a zinc-magnesium ferrite cubic phase at room temperature with space group Fd3m. FTIR spectra show two significant absorption bands first at 665.15 cm-1 corresponding to tetrahedral (A) and second band at 434 cm-1 corresponding to octahedral (B) sites of the spinel. Morphology of the sample determined by the SEM measurement and EDS analysis has confirmed the composition of atoms in the sample.

Synthetic and natural chromium-bearing spinels: an optical spectroscopy study

NASA Astrophysics Data System (ADS)

Taran, M. N.; Parisi, F.; Lenaz, D.; Vishnevskyy, A. A.

2014-09-01

Four samples of synthetic chromium-bearing spinels of (Mg, Fe2+)(Cr, Fe3+)2O4 composition and four samples of natural spinels of predominantly (Mg, Fe2+)(Al, Cr)2O4 composition were studied at ambient conditions by means of optical absorption spectroscopy. Synthetic end-member MgCr2O4 spinel was also studied at pressures up to ca. 10 GPa. In both synthetic and natural samples, chromium is present predominantly as octahedral Cr3+ seen in the spectra as two broad intense absorption bands in the visible range caused by the electronic spin-allowed 4 A 2 g → 4 T 2 g and 4 A 2 g → 4 T 1 g transitions (U- and Y-band, respectively). A distinct doublet structure of the Y-band in both synthetic and natural spinels is related to trigonal distortion of the octahedral site in the spinel structure. A small, if any, splitting of the U-band can only be resolved at curve-fitting analysis. In all synthetic high-chromium spinels, a couple of relatively narrow and weak bands of the spin-allowed transitions 4 A 2 g → 2 E g and 4 A 2 g → 2 T 1 g of Cr3+, intensified by exchange-coupled interaction between Cr3+ and Fe3+ at neighboring octahedral sites of the structure, appear at ~14,400 and ~15,100 cm-1. A vague broad band in the range from ca. 15,000 to 12,000 cm-1 in synthetic spinels is tentatively attributed to IVCr2+ + VICr3+ → IVCr3+ + VICr2+ intervalence charge-transfer transition. Iron, mainly as octahedral Fe3+, causes intense high-energy absorption edge in near UV-range (ligand-metal charge-transfer O2- → Fe3+, Fe2+ transitions). As tetrahedral Fe2+, it appears as a strong infrared absorption band at around 4,850 cm-1 caused by electronic spin-allowed 5 E → 5 T 2 transitions of IVFe2+. From the composition shift of the U-band in natural and synthetic MgCr2O4 spinels, the coefficient of local structural relaxation around Cr3+ in spinel MgAl2O4-MgCr2O4 system was evaluated as ~0.56(4), one of the lowest among (Al, Cr)O6 polyhedra known so far. The octahedral modulus of Cr3+ in MgCr2O4, derived from pressure-induced shift of the U-band of Cr3+, is ~313 (50) GPa, which is nearly the same as in natural low-chromium Mg, Al-spinel reported by Langer et al. (1997). Calculated from the results of the curve-fitting analysis, the Racah parameter B of Cr3+ in natural and synthetic MgCr2O4 spinels indicates that Cr-O-bonding in octahedral sites of MgCr2O4 has more covalent character than in the diluted natural samples. Within the uncertainty of determination in synthetic MgAl2O4 spinel, B does not much depend on pressure.

Method for thermal processing alumina-enriched spinel single crystals

DOEpatents

Jantzen, C.M.

1995-05-09

A process for age-hardening alumina-rich magnesium aluminum spinel to obtain the desired combination of characteristics of hardness, clarity, flexural strength and toughness comprises selection of the time-temperature pair for isothermal heating followed by quenching. The time-temperature pair is selected from the region wherein the precipitate groups have the characteristics sought. The single crystal spinel is isothermally heated and will, if heated long enough pass from its single phase through two pre-precipitates and two metastable precipitates to a stable secondary phase precipitate within the spinel matrix. Quenching is done slowly at first to avoid thermal shock, then rapidly. 12 figs.

Porous nanoarchitectures of spinel-type transition metal oxides for electrochemical energy storage systems.

PubMed

Park, Min-Sik; Kim, Jeonghun; Kim, Ki Jae; Lee, Jong-Won; Kim, Jung Ho; Yamauchi, Yusuke

2015-12-14

Transition metal oxides possessing two kinds of metals (denoted as AxB3-xO4, which is generally defined as a spinel structure; A, B = Co, Ni, Zn, Mn, Fe, etc.), with stoichiometric or even non-stoichiometric compositions, have recently attracted great interest in electrochemical energy storage systems (ESSs). The spinel-type transition metal oxides exhibit outstanding electrochemical activity and stability, and thus, they can play a key role in realising cost-effective and environmentally friendly ESSs. Moreover, porous nanoarchitectures can offer a large number of electrochemically active sites and, at the same time, facilitate transport of charge carriers (electrons and ions) during energy storage reactions. In the design of spinel-type transition metal oxides for energy storage applications, therefore, nanostructural engineering is one of the most essential approaches to achieving high electrochemical performance in ESSs. In this perspective, we introduce spinel-type transition metal oxides with various transition metals and present recent research advances in material design of spinel-type transition metal oxides with tunable architectures (shape, porosity, and size) and compositions on the micro- and nano-scale. Furthermore, their technological applications as electrode materials for next-generation ESSs, including metal-air batteries, lithium-ion batteries, and supercapacitors, are discussed.

Structural, dielectric and gas sensing behavior of Mn substituted spinel MFe2O4 (M=Zn, Cu, Ni, and Co) ferrite nanoparticles

NASA Astrophysics Data System (ADS)

Ranjith Kumar, E.; Siva Prasada Reddy, P.; Sarala Devi, G.; Sathiyaraj, S.

2016-01-01

Spinel ferrite (MnZnFe2O4, MnCuFe2O4, MnNiFe2O4 and MnCoFe2O4) nanoparticles have been prepared by evaporation method. The annealing temperature plays an important role on changing particle size of the spinel ferrite nanoparticles was found out by X-ray diffraction and transmission electron microscopy. The role of manganese substitution in the spinel ferrite nanoparticles were also analyzed for different annealing temperature. The substitution of Mn also creates a vital change in dielectric properties have been measured in the frequency range of 100 kHz to 5 MHz. These spinel ferrites are decomposed to α-Fe2O3 after annealing above 550 °C in air. Through the characterization of the prepared powder, the effect of annealing temperature, chemical composition and preparation technique on the microstructure, particle size and dielectric properties of the Mn substituted spinel ferrite nanoparticles are discussed. Furthermore, Conductance response of Mn substituted MFe2O4 ferrite nanoparticles were measured by exposing the materials to reducing gas like liquefied petroleum gas (LPG).

Untangling the History of Oceanic Peridotites Using Spinel Oxybarometry

NASA Astrophysics Data System (ADS)

Birner, S.; Warren, J. M.; Cottrell, E.; Davis, F. A.

2014-12-01

Comprehensive knowledge of the oxygen fugacity of the upper mantle is critical to understanding the processes associated with melt production, interaction, and extraction. Thus, it is important to understand how fO2 changes during a peridotite's thermal and petrologic history in the asthenospheric and lithospheric mantle, as metamorphic subsolidus reequilibration can result in changes to recorded fO2. A case study of Tongan forearc peridotites highlights the heterogeneity seen in mantle peridotites. We analyzed two dredges located 250 km apart along the trench: one dredge ranges in fO2 from 0.5 to 1 log unit above the QFM buffer, similar to analyses of supra-subduction zone xenoliths (e.g. Brandon and Draper, 1996; Wood and Virgo, 1989) while the other dredge ranges from QFM-0.75 to QFM+0.25 and exhibits high spinel Cr# (ranging from 0.45 to 0.75). Systematics between fO2, Ti concentration, olivine forsterite content, and Cr# within each dredge allow us to differentiate between the effects of melt extraction, melt interaction, and cooling. Because the spinel oxybarometry equation is dependent on temperature, it is important to be able to accurately determine the temperature recorded by peridotites. Though many geothermometers are available for mantle rocks, we assert that geothermometers based on Fe-Mg exchange between olivine and spinel are the most applicable to fO2 calculations, because the oxygen fugacity recorded by a mantle assemblage is primarily controlled by this exchange. Additionally, preliminary analyses of diffusion profiles across olivine-spinel grain boundaries provide insight into the cooling of peridotite in the oceanic lithosphere and its effects on oxygen fugacity. Mg-Fe exchange between olivine and spinel is controlled by the distribution coefficient, KD, which is dependent on both temperature and the proportion of Cr to other trivalent cations in spinel. We see an increase in olivine forsterite content towards the olivine-spinel interface, consistent with an increase in KD as cooling occurs. Limited data indicate that while spinel Cr# decreases as the interface is approached, no change is seen in spinel Fe3+/ΣFe ratios. As a result, the increased Fo# in olivine dominates the oxybarometry equation, resulting in higher oxygen fugacity values near the interface as cooling occurs.

Magnetic transparent conducting oxide film and method of making

DOEpatents

Windisch, Jr., Charles F.; Exarhos, Gregory J.; Sharma, Shiv K.

2004-07-13

Cobalt-nickel oxide films of nominal 100 nm thickness, and resistivity as low as 0.06 .OMEGA..multidot.cm have been deposited by spin-casting from both aqueous and organic precursor solutions followed by annealing at 450.degree. C. in air. Films deposited on sapphire substrates exhibit a refractive index of about 1.7 and are relatively transparent in the wavelength region from 0.6 to 10.0 .mu.m. They are also magnetic. The electrical and spectroscopic properties of the oxides have been studied as a function of x=Co/(Co+Ni) ratio. An increase in film resistivity was found upon substitution of other cations (e.g., Zn.sup.2+, Al.sup.3+) for Ni in the spinel structure. However, some improvement in the mechanical properties of the films resulted. On the other hand, addition of small amounts of Li decreased the resistivity. A combination of XRD, XPS, UV/Vis and Raman spectroscopy indicated that NiCo.sub.2 O.sub.4 is the primary conducting component and that the conductivity reaches a maximum at this stoichiometry. When x<0.67, NiO forms leading to an increase in resistivity; when x>0.67, the oxide was all spinel but the increased Co content lowered the conductivity. The influence of cation charge state and site occupancy in the spinel structure markedly affects calculated electron band structures and contributes to a reduction of p-type conductivity, the formation of polarons, and the reduction in population of mobile charge carriers that tend to limit transmission in the infrared.

Chromian spinels in highly altered ultramafic rocks from the Sartohay ophiolitic mélange, Xinjiang, NW China

NASA Astrophysics Data System (ADS)

Qiu, Tian; Zhu, Yongfeng

2018-06-01

The Sartohay ophiolitic mélange is located in western Junggar (Xinjiang province, NW China), which is a major component of the core part of the Central Asian Orogenic Belt (CAOB). Chromian spinels in serpentinite, talc schist, carbonate-talc schist and listwaenite in Sartohay ophiolitic mélange retain primary compositions with Cr# of 0.39-0.65, Mg# = 0.48-0.67, and Fe3+# < 0.08. Chromian spinels in deformed listwaenite were initially transformed into Fe2+-rich chromite during shearing deformation followed by Fe3+-rich chromite at shallow levels. The Cr# and Fe3+# of Fe2+-rich chromite (Cr# = 0.59-0.86, Fe3+# = 0.01-0.12, Mg# = 0.35-0.61) and Fe3+-rich chromite (Cr# = 0.85-1.00, Fe3+# = 0.17-0.38, Mg# < 0.29) increase with decrease of Mg#. We propose a model to illustrate the evolution of chromian spinels in highly altered ultramafic rocks from the Sartohay ophiolitic mélange. Chromian spinels in serpentinite and talc schist were rimmed by Cr-magnetite, which was dissolved completely during transformation from serpentinite/talc schist to listwaenite. Chromian spinels were then transformed into Fe2+-rich chromite in shear zones, which characterized by high fluid/rock ratios. This Fe2+-rich chromite and/or chromian spinels could then be transformed into Fe3+-rich chromite in oxidizing conditions at shallow levels.

Olivine and chromian spinel in primitive calc-alkaline and tholeiitic lavas from the southernmost cascade range, California: A reflection of relative fertility of the source

USGS Publications Warehouse

Clynne, M.A.; Borg, L.E.

1997-01-01

Chromian spinel and coexisting olivine phenocrysts from a geochemically diverse suite of primitive tholeiitic and calc-alkaline basalts and magnesian andesites from the Lassen region, in the southernmost Cascade Range, in California, show that the sub-arc mantle is zoned. Depleted calc-alkaline basalts and magnesian andesites erupt in the forearc region, and calc-alkaline basalts contain increasing abundances of incompatible elements toward the backarc. High-alumina olivine tholeiites erupt from the arc and backarc areas. Olivine from all these lavas displays a limited compositional range, from Fo86 to Fo91, and crystallized at high temperature, generally 1225-1275??C. Chromian spinel trapped in the olivine phenocrysts displays a large range of composition: Cr# values span the range 9-76. Excess Al in the spinel relative to that in 1-atm spinel suggests that it crystallized at elevated pressure. The phenocrysts in these lavas are in equilibrium with their host liquids. The full range of Cr# of the spinel compositions cannot be explained by differentiation or variable pressure, variations in f(O2), subsolidus equilibration or variations in degree of partial melting of a single peridotitic source. Rather, the systematic compositional differences among phenocrysts in these primitive lavas result from bulk chemical variability in their mantle sources. Correlations between spinel and host-rock compositions support the assertion that the geochemical diversity of Lassen basalts reflects the relative fertility of their mantle sources.

The effect of 0.025 Al-doped in Li4Ti5O12 material on the performance of half cell lithium ion battery

NASA Astrophysics Data System (ADS)

Priyono, Slamet; Triwibowo, Joko; Prihandoko, Bambang

2016-02-01

The effect of 0.025 Al-doped Li4Ti5O12 as anode material for Lithium Ion battery had been studied. The pure and 0.025 Al-doped Li4Ti5O12 were synthesized through solid state process in air atmosphere. Physical characteristics of all samples were observed by XRD, FTIR, and PSA. The XRD analysis revealed that the obtained particle was highly crystalline and had a face-centered cubic spinel structure. The XRD pattern also showed that the 0.025 Al-doped on the Li4Ti5O12 did not change crystal structure of Li4Ti5O12. FTIR analysis confirmed that the spinel structure in fingerprint region was unchanged when the structure was doped by 0.025 Al. However the doping of 0.025 Al increased particle size significantly. The electrochemical performance was studied by using cyclic voltammetry (CV) and charge-discharge (CD) curves. Electrochemical analysis showed that pure Li4Ti5O12 has higher capacity than 0.025 Al-doped Li4Ti5O12 had. But 0.025 Al-doped Li4Ti5O12 possesses a better cycling stability than pure Li4Ti5O12.

Preparation and study of (1 - x)CuFe2O4-xBaTiO3 (x = 0, 0.1 and 1) composite multiferroics

NASA Astrophysics Data System (ADS)

Murtaza, Tahir; Ali, Javid; Khan, M. S.

2018-07-01

The parent and mixed spinel-perovskite composite of (1 - x)CuFe2O4-xBaTiO3 (x = 0, 0.1 and 1) has been prepared by solid-state reaction method and studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), Mössbauer spectroscopy, magnetometry and P-E lope tracer. The XRD results showed the formation of single phase tetragonal spinel CuFe2O4 and tetragonal perovskite BaTiO3 at room temperature, further XRD of composite 0.1CuFe2O4-0.9BaTiO3 reflects the two crystallographic phases with 1:9 ratio. The SEM micrographs show the homogeneous and uniform formation of the samples. Through EDAX analysis, the chemical composition of the sample is found to be same as the nominal composition. The high field Mossbauer data of CuFe2O4 sample shows the ferrimagnetic ordering in the sample. The observed M-H and P-E loops of the composite 0.1CuFe2O4-0.9BaTiO3 sample show the presence of spontaneous magnetization and spontaneous electric polarization indicating the multiferroic nature of the sample.

Spinel FeCo2S4 nanoflower arrays grown on Ni foam as novel binder-free electrodes for long-cycle-life supercapacitors

NASA Astrophysics Data System (ADS)

Deng, Cuifen; Yang, Lishan; Yang, Chunming; Shen, Ping; Zhao, Liping; Wang, Zhiyu; Wang, Chunhui; Li, Junhua; Qian, Dong

2018-01-01

Spinel FeCo2S4 nanoflower arrays grown on Ni foam (FeCo2S4@Ni) have been successfully fabricated via a facile hydrothermal sulfurization of the corresponding FeCo2O4 precursor. The results of X-ray diffraction and X-ray photoelectron spectroscopy characterizations affirm that partial Co2+/Co3+ ions in Co3S4 have been substituted by Fe2+/Fe3+ ions to form FeCo2S4. The obtained FeCo2S4@Ni exhibits an ultrahigh specific capacitance (1644.07 mF cm-2 at 50 mA cm-2) and a supreme cycling stability (∼100% after 10,000 cycles at 50 mA cm-2) as binder-free electrodes for supercapacitors. The cycling stability of the fabricated product is the highest among the documented ternary metallic sulfides so far. The excellent supercapacitive performance of FeCo2S4@Ni emanates from the unique architectures of Fe2Co2S4 nanoflower arrays constituted by ultrathin nanoflakes, three-dimensional porous and conductive Ni foam, and solid skeleton of Ni foam for robust connections to the Fe2Co2S4.

Effect of MgO on Liquidus Temperatures in the ZnO-"FeO"-Al2O3-CaO-SiO2-MgO System in Equilibrium with Metallic Iron

NASA Astrophysics Data System (ADS)

Zhao, Baojun; Hayes, Peter C.; Jak, Evgueni

2011-06-01

The phase equilibria in the ZnO-"FeO"-Al2O3-CaO-SiO2-MgO system have been determined experimentally in equilibrium with metallic iron. Synthetic slags were equilibrated at a high temperature, quenched, and then the compositions of the phases in equilibrium were measured using electron probe X-ray microanalysis. Pseudoternary sections of the form ZnO-"FeO"-(Al2O3 + CaO + SiO2) for CaO/SiO2 = 0.71, (CaO + SiO2)/Al2O3 = 5 and fixed MgO concentrations of 2, 4, and 6 wt pct have been constructed. Wustite (Fe2+,Mg,Zn)O and spinel (Fe2+,Mg,Zn)O·(Al,Fe3+)2O3 are the major primary phases in the temperature and composition ranges investigated. The liquidus temperatures are increased by 140 K in the wustite primary phase field and by 70 K in the spinel primary phase field with the addition of 6 wt pct MgO in the slag. The partitioning of MgO and ZnO between the solid and liquid phases has been discussed.

Hidden Oceans? Unraveling the Structure of Hydrous Defects in the Earth's Deep Interior.

PubMed

Grüninger, Helen; Armstrong, Katherine; Greim, Dominik; Boffa-Ballaran, Tiziana; Frost, Daniel J; Senker, Jürgen

2017-08-02

High-pressure silicates making up the main proportion of the earth's interior can incorporate a significant amount of water in the form of OH defects. Generally, they are charge balanced by removing low-valent cations such as Mg 2+ . By combining high-resolution multidimensional single- and double-quantum 1 H solid-state NMR spectroscopy with density functional theory calculations, we show that, for ringwoodite (γ-Mg 2 SiO 4 ), additionally, Si 4+ vacancies are formed, even at a water content as low as 0.1 wt %. They are charge balanced by either four protons or one Mg 2+ and two protons. Surprisingly, also a significant proportion of coupled Mg and Si vacancies are present. Furthermore, all defect types feature a pronounced orientational disorder of the OH groups, which results in a significant range of OH···O bond distributions. As such, we are able to present unique insight into the defect chemistry of ringwoodite's spinel structure, which not only accounts for a potentially large fraction of the earth's entire water budget, but will also control transport properties in the mantle. We expect that our results will even impact other hydrous spinel-type materials, helping to understand properties such as ion conduction and heterogeneous catalysis.

Origin of sapphirine- and garnet-bearing clinopyroxenite xenoliths entrained in the Jiande basalts, SE China

NASA Astrophysics Data System (ADS)

Xiao, Yan; Zhang, Hong-Fu; Liang, Zi; Su, Ben-Xun; Zhu, Bin; Sakyi, Patrick Asamoah

2018-04-01

We present petrological and geochemical data of sapphirine- and garnet-bearing clinopyroxenite xenoliths entrained in the Jiande Cenozoic basalts, SE China, to investigate their igneous and metamorphic history, and reconstruct of the thermal-tectonic evolution of the lithospheric mantle. These xenoliths have an unusual mineral association consisting of clinopyroxene + garnet/kelyphite + spinel (±sapphirine). Clinopyroxene has high Mg# (89-93) and displays convex-upward REE pattern. Garnet, partially to completely kelyphitized, is rich in pyrope end-member. It usually includes relics of spinel, suggesting that garnet was formed at the expense of spinel. The spinel has high MgO (20.8-22.9 wt%) and Al2O3 (64.8-67.9 wt%) contents. Sapphirine, forming a rim on spinel, has homogeneous SiO2 (14.5-14.9 wt%), Al2O3 (60.9-61.7 wt%) and MgO (19.7-20.1 wt%) contents, interpreted to be of metamorphic origin. The subsolidus reaction for the formation of sapphirine is as follows: spinel + garnet = sapphirine + clinopyroxene + orthopyroxene. Thus, the earliest mineral assemblage recorded in these xenoliths was spinel + clinopyroxene. The clinopyroxene in the Jiande clinopyroxenite xenoliths has Li abundances (1.04-1.63 ppm) similar to high-P mafic cumulate but much lower than those in crustal eclogite. In addition, the clinopyroxene and garnet do not show positive Eu anomalies. Therefore, the protolith of these three clinopyroxenite xenoliths was most likely a pyroxenite, originating as clinopyroxene + spinel cumulates from mafic melts percolating through the mantle. Many reaction textures such as formation of garnet and sapphirine were developed during decompression possibly coupled with cooling and melt percolation. During this process, the earlier composition of clinopyroxene and spinel also changed. The latest P-T conditions recorded in these xenoliths were at pressure of 8-10 kbar and temperatures of 1069-1094 °C. These observations imply that these rocks have been tectonically uplifted to shallower levels. The uplift process may have been related to lithospheric thinning process accompanied by lithosphere extension and upwelling of the asthenosphere in eastern China.

Adsorption Assisted Photocatalytic Removal of Methyl Orange by MgAl2O4-Sb2S3 Composite Material.

PubMed

Muneeb, Muhammad; Ismail, Bushra; Fazal, Tanzeela; Khan, Abdur Rehman; Afzia, Mehwish

2016-01-01

The current article is about the water treatment in which colored water contaminated by methyl orange has been used for adsorption assisted photocatalysis. Coupling of photocatalysis with the traditional water treatment processes has been in practice since last couple of years for the improvement of degradation efficiencies, for example, photocatalysis coupled with ultrafilteration, adsorption, flocculation, biological methods, photolysis, membrane distillation, etc. Among all these coupling approaches, adsorption assisted photocatalysis being a very simple and highly efficient approach is suffering from few drawbacks on the account of high cost, low stability and surface area of the adsorbent support. The present study is a contribution towards improvement in this coupling approach. A low cost, highly stable spinel magnesium aluminate (MgAl2O4) material synthesized at nanoscale is used for composite formation with antimony sulphide (Sb2S3) material having high absorption coefficient in the visible light of solar spectrum. A review of recent patents shows that the field of photoctalysis is dominated by the traditional TiO2 catalyst. The modification of TiO2 by either composite formation or by doping is the main focus. Coprecipitation method is used for the synthesis of spinel in which the desired precursors in the respective molar ratios were mixed and annealing of the resulting precipitates was carried out at 800oC for 8 h. Sb2S3 was synthesized by the hydrothermal method in which the required molar solution of precursors was mixed with urea solution and the whole mixture was maintained at 105oC for 6 hrs in a Teflon lined autoclave. The resulting suspension was then annealed at 37oC for 3 hours. The composite of Sb2S3 and MgAl2O4 has been synthesized by mixing both the materials in 1:1 and heat treated in an oven at a temperature of 200oC. Peaks in X-ray diffraction pattern correspond to both the Sb2S3 and spinel phase. All the peaks corresponding to the Sb2S3 and spinel phase were found to be shifted to higher d-spacing values. This indicates the expansion of unit cells of the Sb2S3 and MgAl2O4 phases. Thermal studies show that only 3% weight loss is observed at a temperature of 200-1000oC which may be due to the loss of surface water from the sample. Surface area, pore volume and pore size obtained from N2 adsorption were 143m2/g, 0.21cc/g and 23.26Å, respectively. The removal efficiency of 0.1g catalyst for methyl orange solution of 5mg/L concentration after reaction in dark conditions for the time of one hour was calculated to be 24% owing to the adsorption. The visible light degradation efficiency of the 0.1g catalyst for 1, 5, 19, 25 and 50 mg/L concentrations of MO solutions were 97, 93, 75, 72 and 62% respectively. The dosage of the catalyst was found to have a direct relationship with the degradation efficiency. Lower pH was found suitable for the degradation owing to better interaction of catalyst surface and the adsorbed dye. Percent degradation increased with the increase in the time and temperature of reaction. The degradation kinetics followed pseudo first order rate equation; the calculated value of rate constant was 0.0102 min-1. The mechanism involves the excitation of electrons in the valence band of Sb2S3 to the conduction band by the absorption of visible and UV light. The electrons and holes participate in the surface reactions resulting in the formation of superoxide and hydroxyl radicals which degrade the targeted polluted. Lower concentration of MO solutions, acidic pH, higher catalyst dosage and greater reaction times were found suitable for the degradation efficiency.

Improving the dissolution rate of poorly water soluble drug by solid dispersion and solid solution: pros and cons.

PubMed

Chokshi, Rina J; Zia, Hossein; Sandhu, Harpreet K; Shah, Navnit H; Malick, Waseem A

2007-01-01

The solid dispersions with poloxamer 188 (P188) and solid solutions with polyvinylpyrrolidone K30 (PVPK30) were evaluated and compared in an effort to improve aqueous solubility and bioavailability of a model hydrophobic drug. All preparations were characterized by differential scanning calorimetry, powder X-ray diffraction, intrinsic dissolution rates, and contact angle measurements. Accelerated stability studies also were conducted to determine the effects of aging on the stability of various formulations. The selected solid dispersion and solid solution formulations were further evaluated in beagle dogs for in vivo testing. Solid dispersions were characterized to show that the drug retains its crystallinity and forms a two-phase system. Solid solutions were characterized to be an amorphous monophasic system with transition of crystalline drug to amorphous state. The evaluation of the intrinsic dissolution rates of various preparations indicated that the solid solutions have higher initial dissolution rates compared with solid dispersions. However, after storage at accelerated conditions, the dissolution rates of solid solutions were lower due to partial reversion to crystalline form. The drug in solid dispersion showed better bioavailability in comparison to solid solution. Therefore, considering physical stability and in vivo study results, the solid dispersion was the most suitable choice to improve dissolution rates and hence the bioavailability of the poorly water soluble drug.

Mg isotope systematics during magmatic processes: Inter-mineral fractionation in mafic to ultramafic Hawaiian xenoliths

NASA Astrophysics Data System (ADS)

Stracke, A.; Tipper, E. T.; Klemme, S.; Bizimis, M.

2018-04-01

Observed differences in Mg isotope ratios between bulk magmatic rocks are small, often on a sub per mill level. Inter-mineral differences in the 26Mg/24Mg ratio (expressed as δ26Mg) in plutonic rocks are on a similar scale, and have mostly been attributed to equilibrium isotope fractionation at magmatic temperatures. Here we report Mg isotope data on minerals in spinel peridotite and garnet pyroxenite xenoliths from the rejuvenated stage of volcanism on Oahu and Kauai, Hawaii. The new data are compared to literature data and to theoretical predictions to investigate the processes responsible for inter-mineral Mg isotope fractionation at magmatic temperatures. Theory predicts up to per mill level differences in δ26Mg between olivine and spinel at magmatic temperatures and a general decrease in Δ26Mgolivine-spinel (=δ26Mgolivine - δ26Mgspinel) with increasing temperature, but also with increasing Cr# in spinel. For peridotites with a simple petrogenetic history by melt depletion, where increasing depletion relates to increasing melting temperatures, Δ26Mgolivine-spinel should thus systematically decrease with increasing Cr# in spinel. However, most natural peridotites, including the Hawaiian spinel peridotites investigated in this study, are overprinted by variable extents of melt-rock reaction, which disturb the systematic primary temperature and compositionally related olivine-spinel Mg isotope systematics. Diffusion, subsolidus re-equilibration, or surface alteration may further affect the observed olivine-spinel Mg isotope fractionation in peridotites, making Δ26Mgolivine-spinel in peridotites a difficult-to-apply geothermometer. The available Mg isotope data on clinopyroxene and garnet suggest that this mineral pair is a more promising geothermometer, but its application is restricted to garnet-bearing igneous (garnet pyroxenites) and metamorphic rocks (eclogites). Although the observed δ26Mg variation is on a sub per mill range in bulk magmatic rocks, the clearly resolvable inter-mineral Mg isotope differences imply that crystallization or preferential melting of isotopically distinct minerals such garnet, spinel, and clinopyroxene should cause Mg isotope fractionation between bulk melt and residue. Calculated Mg isotope variations during partial mantle melting indeed predict differences between melt and residue, but these are analytically resolvable only for melting of mafic lithologies, that is, garnet pyroxenites. Contributions from garnet pyroxenite melts may thus account for some of the isotopically light δ26Mg observed in ocean island basalts and trace lithological mantle heterogeneity. Consequently, applications for high-temperature Mg isotope fractionations are promising and diverse, and recent advances in analytical precision may allow the full petrogenetic potential inherent in the sub per mill variations in δ26Mg in magmatic rocks to be exploited.

High-pressure Phase Relation In The MgAl2O4-Mg2SiO4 System

NASA Astrophysics Data System (ADS)

Kojitani, H.; Hisatomi, R.; Akaogi, M.

2005-12-01

High-pressure and high-temperature experiments indicate that high-pressure phases of oceanic basalts contain Al-rich phases. MgAl2O4 with calcium ferrite-type crystal structure is considered as a main component of such the Al-rich phases. Since the calcium ferrite-type MgAl2O4 can be synthesized at only the maximum pressure of a Kawai-type high-pressure apparatus with tungsten carbide (WC) anvils, the amount of a synthesized sample is very limited. Therefore, the crystal structure of the calcium ferrite-type MgAl2O4 has been hardly known in detail due to these difficulties in sample synthesis. In our high-pressure experiments in the MgO-Al2O3-SiO2 system, it was shown that Mg2SiO4 component could be dissolved in the MgAl2O4 calcium ferrite. In this study, we tried to synthesize a single phase MgAl2O4 calcium ferrite sample and to make the Rietveld refinement of the XRD pattern of the sample. The high-pressure phase relations in the MgAl2O4-Mg2SiO4 system were studied to know the stability field of the MgAl2O4-Mg2SiO4 calcium ferrite solid solutions. Lattice parameters-composition relation of the MgAl2O4-Mg2SiO4 calcium ferrite solid solutions was also determined. High-pressure and high-temperature experiments were performed by using a Kawai-type high-pressure apparatus at Gakushuin University. WC anvils with truncated edge length of 1.5 mm were used. Heating was made by a Re heater. Temperature was measured by a Pt/Pt-13%Rh thermocouple. Starting materials for the phase relation experiments were the mixture of MgO, Al2O3 and SiO2 with bulk compositions of MgAl2O4:Mg2SiO4 = 90:10, 78:22, 70:30 and 50:50. The starting materials were held at 21-27 GPa and 1600 °C for 3 hours and then were recovered by the quenching method. The MgAl2O4 calcium ferrite sample for the Rietveld analysis was prepared by heating MgAl2O4 spinel at 27 GPa and about 2200 °C for one hour. Powder X-ray diffraction (XRD) profiles of obtained samples were measured by using a X-ray diffractometer at Gakushuin University (RINT 2500V, Cr Kα, 45 kV, 250 mA). Composition analysis of the recovered samples was made using SEM-DES. The RIETAN-2000 program was used to perform the Rietveld refinement. The results of the high-pressure phase relation experiments show that stability field of single phase of MgAl2O4-Mg2SiO4 solid solutions spreads at lower pressure than that of pure MgAl2O4 calcium ferrite. The lowest pressure at which the calcium ferrite solid solution can be synthesized is about 23 GPa. The maximum solubility of Mg2SiO4 component is about 35%. Lattice parameters of pure MgAl2O4 calcium ferrite were determined as a = 9.9495(6) Å, b = 8.6466(5) Å, c = 2.7901(2) Å ( Pbnm space group) by the Rietveld refinement. Obtained atomic positions for calcium ferrite-type MgAl2O4 are very similar to those of CaFe2O4 calcium ferrite. Lattice parameters of MgAl2O4-Mg2SiO4 calcium ferrite solid solutions with various compositions indicate that c-axis does not change with the composition and that a- and b-axes have a linear increase and decrease trend with increasing Mg2SiO4 component, respectively.

The distribution of chromium among orthopyroxene, spinel and silicate liquid at atmospheric pressure

NASA Technical Reports Server (NTRS)

Barnes, S. J.

1986-01-01

The Cr distributions for a synthetic silicate melt equilibrated with bronzitic orthopyroxene and chromite spinel between 1334 and 1151 C over a range of oxygen fugacities between the nickel-nickel oxide and iron-wuestite buffers are studied. The occurrence, chemical composition, and structure of the orthopyroxene-silicate melt and the spinel-silicate melt are described. It is observed that the Cr content between bronzite and the melt increases with falling temperature along a given oxygen buffer and decreases with falling oxygen fugacity at a given temperature; however, the Cr content of the melt in equilibrium with spinel decreases with falling temperature and increases with lower oxygen fugacity.

Thermodynamic modeling of solid solutions between monosulfate and monochromate 3CaO Bullet Al{sub 2}O{sub 3} Bullet Ca[(CrO{sub 4}){sub x}(SO{sub 4}){sub 1-x}] Bullet nH{sub 2}O

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

Leisinger, Sabine M., E-mail: sabine.leisinger@eawag.ch; Institute of Biogeochemistry and Pollutant Dynamics, ETH, CH-8092 Zurich; Lothenbach, Barbara

2012-01-15

In hydrated cement paste AFm-phases are regarded to play an important role in the binding of the toxic contaminant chromate through isomorphic substitution with sulfate. Solid solutions formation can lower the solubility of the solids, thus reducing chromate leaching concentrations. Solid solutions between monosulfate and monochromate were synthesized and characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX) and inductive coupled plasma optical emission spectroscopy (ICP-OES). Based on the measured ion concentrations in solution total solubility products of the solid solution series were determined. For pure monochromate a logK = - 28.4more » {+-} 0.7 was determined. Results from solid and solution analysis showed that limited solid solutions exist. Based on XRD diffractograms a solid solution with a miscibility gap 0.15 < Crx < 0.85 with a dimensionless Guggenheim parameter of 2.43 was proposed.« less

Structural, Electronic, and Optical Properties of BiOX1-xYx (X, Y = F, Cl, Br, and I) Solid Solutions from DFT Calculations.

PubMed

Zhao, Zong-Yan; Liu, Qing-Lu; Dai, Wen-Wu

2016-08-23

Six BiOX1-xYx (X, Y = F, Cl, Br, and I) solid solutions have been systematically investigated by density functional theory calculations. BiOCl1-xBrx, BiOBr1-xIx, and BiOCl1-xIx solid solutions have very small bowing parameters; as such, some of their properties increase almost linearly with increasing x. For BiOF1-xYx solid solutions, the bowing parameters are very large and it is extremely difficult to fit the related calculated data by a single equation. Consequently, BiOX1-xYx (X, Y = Cl, Br, and I) solid solutions are highly miscible, while BiOF1-xYx (Y = Cl, Br, and I) solid solutions are partially miscible. In other words, BiOF1-xYx solid solutions have miscibility gaps or high miscibility temperature, resulting in phase separation and F/Y inhomogeneity. Comparison and analysis of the calculated results and the related physical-chemical properties with different halogen compositions indicates that the parameters of BiOX1-xYx solid solutions are determined by the differences of the physical-chemical properties of the two halogen compositions. In this way, the large deviation of some BiOX1-xYx solid solutions from Vegard's law observed in experiments can be explained. Moreover, the composition ratio of BiOX1-xYx solid solutions can be measured or monitored using optical measurements.

Synthesis and Electrochemical Performance of LixMn2-yCoyO4-dCld Cathode Material

DTIC Science & Technology

2016-06-13

Lithium manganese oxide spinel is a potential candidate for Li- ion battery cathodes because of its...240 mAh/g of active material, and 4) high rate charge and discharge. Keywords: Lithium and Li- ion battery , Lithium manganese oxide spinel, Spinel...demonstrate desirable traits for incorporation into lithium - ion batteries for the military. References 1. David Linden (Ed.); Handbook of Batteries

Silicon Nitride Equation of State

NASA Astrophysics Data System (ADS)

Swaminathan, Pazhayannur; Brown, Robert

2015-06-01

This report presents the development a global, multi-phase equation of state (EOS) for the ceramic silicon nitride (Si3N4) . Structural forms include amorphous silicon nitride normally used as a thin film and three crystalline polymorphs. Crystalline phases include hexagonal α-Si3N4, hexagonalβ-Si3N4, and the cubic spinel c-Si3N4. Decomposition at about 1900 °C results in a liquid silicon phase and gas phase products such as molecular nitrogen, atomic nitrogen, and atomic silicon. The silicon nitride EOS was developed using EOSPro which is a new and extended version of the PANDA II code. Both codes are valuable tools and have been used successfully for a variety of material classes. Both PANDA II and EOSPro can generate a tabular EOS that can be used in conjunction with hydrocodes. The paper describes the development efforts for the component solid phases and presents results obtained using the EOSPro phase transition model to investigate the solid-solid phase transitions in relation to the available shock data. Furthermore, the EOSPro mixture model is used to develop a model for the decomposition products and then combined with the single component solid models to study the global phase diagram. Sponsored by the NASA Goddard Space Flight Center Living With a Star program office.

Nanosized LiM YMn 2- YO 4 (M = Cr, Co and Ni) spinels synthesized by a sucrose-aided combustion method . Structural characterization and electrochemical properties

NASA Astrophysics Data System (ADS)

Amarilla, J. M.; Rojas, R. M.; Pico, F.; Pascual, L.; Petrov, K.; Kovacheva, D.; Lazarraga, M. G.; Lejona, I.; Rojo, J. M.

Spinels of composition LiM YMn 2- YO 4, M = Cr 3+, Co 3+, or Ni 2+, Y = 0.1 and 1 for the Cr and Co dopants, Y = 0.05 and 0.5 for the Ni sample, have been synthesized by a sucrose-aided combustion method. The samples as prepared require of an additional thermal treatment at 700 °C, 1 h to get stoichiometric single-phase spinels. The samples consist of aggregated particles of small size (45-50 nm) as deduced from transmission electron microscopy and X-ray powder diffraction. The electrochemical behaviour of the six spinels as cathodes in lithium cells has been analysed at 5 and 4 V under high current, 1 C rate. At 5 V the discharge capacity of LiNi 0.5Mn 1.5O 4 is higher than the one shown by LiCrMnO 4 and LiCoMnO 4, and it shows an elevated cyclability, i.e. capacity retention of 85.3% after 100 cycles. At 4 V the discharge capacity is similar for LiNi 0.05Mn 1.95O 4, LiCr 0.1Mn 1.9O 4 and LiCo 0.1Mn 1.9O 4, and all the three spinels show similar and very high cyclability, i.e. capacity retention >90% after 100 cycles. The spinels preserve their starting capacity up to currents as high as 2 C rate. The nanometric size of the samples explains the high rate capability of the synthesized spinels.

A Tale of Two Olivines: Magma Ascent in the Auckland Volcanic Field, New Zealand

NASA Astrophysics Data System (ADS)

Smid, E. R.; McGee, L. E.; Smith, I. E.; Lindsay, J. M.

2013-12-01

The Auckland Volcanic Field (AVF) is a nephelinitic to subalkali basaltic monogenetic field centered on the city of Auckland, New Zealand. Lavas are olivine-phyric, and the deposits of several volcanoes in the field contain olivine crystals with chrome spinel (Cr-spinel) inclusions. Microprobe analyses show at least two populations of olivine, categorised by their Mg# and their spinel inclusion compositions: the first has olivines that are euhedral, have compositions slightly less forsteritic than expected for whole rock Mg#, and have Cr-spinel inclusions with relatively low Cr2O3 contents of ~20%. These are interpreted as antecrysts inherited from the mantle source that yielded their host magma. The second population is characterised by olivines that are sub- to euhedral, are significantly more forsteritic than expected from their host whole rock Mg#, and have Cr-spinel inclusons with relatively high Cr2O3 contents of ~50%. These are interpreted as xenocrysts. The composition of these high Cr2O3 spinels very closely resembles the composition of spinels within olivines in dunite sampled from the Dun Mountain Ophiolite on the South Island of New Zealand. The northward extension of the Dun Mountain complex beneath the North Island is defined by the Junction Magnetic Anomaly, marking a crustal terrane boundary that underlies the Auckland Volcanic Field. These data indicate that the magmas that have risen to produce the volcanoes of the Auckland Volcanic Field have carried crystals from an underlying ultramafic crust as well as from their asthenospheric source. Euhedral olivine crystals which do not contain Cr-spinel are also present in AVF lavas and these are interpreted as true phenocrysts that crystallised directly from their host magmas. The lack of reaction textures at crystal margins suggests rapid ascent rates. A crustal origin for the xenocrysts not only has large implications for ascent rate modelling of olivines, but also for the crustal structure of the Auckland area and possible magma ascent paths under the AVF.

Petrogenesis and tectonic setting of the Bondla mafic-ultramafic complex, western India: Inferences from chromian spinel chemistry

NASA Astrophysics Data System (ADS)

Ishwar-Kumar, C.; Rajesh, V. J.; Windley, B. F.; Razakamanana, T.; Itaya, T.; Babu, E. V. S. S. K.; Sajeev, K.

2016-11-01

Crustal-scale shear/suture zones hold prime importance because they are one of the critical parameters used for paleogeographic configurations of supercontinental assemblies. The Kumta suture, located on the western margin of peninsular India, has been interpreted as the eastern extension of the Betsimisaraka suture zone of Madagascar. This suture separates the Karwar block (ca. 3200 Ma tonalite-trondhjemite-granodiorite (TTG) and amphibolite) in the west from a quartzite-dominated shelf that overlies ca. 2571 Ma quartzo-feldspathic gneisses of the Dharwar block in the east. The NW/SE-trending Bondla ultramafic-mafic complex, situated in the arc just west of the Kumta suture, comprises gabbro, troctolite, wehrlite, dunite, peridotite, pyroxenite, chromitite and chromian spinel-bearing serpentinite. In this paper, we study the chemistry of Cr-spinels in chromitites and serpentinites to help understand their paleo-tectonic environments. The Cr-spinel in Bondla chromitites and serpentinites shows variations in Cr# [Cr/(Cr + Al)] ranging from 0.54 to 0.58 and 0.56 to 0.64 respectively; also, the Mg# [Mg/(Mg + Fe)] varies from 0.56 to 0.67 and 0.41 to 0.63 respectively. The Cr-spinels in serpentinites have strong chemical zoning with distinctive ferrian chromite rims (Mg# 0.41-0.63), whereas the Cr-spinels in chromitites are generally homogeneous with only occasional weak zoning. The spinel-core crystallization temperature in the serpentinite is estimated to be above 600 °C (the spinel stability field was calculated for equilibrium with Fo90 olivine), which suggests the core composition is chemically unaltered. The Cr-spinels in all studied samples have low-Al2O3 (15-23 wt%) and moderate to high-Cr# (0.54-0.69), suggesting derivation from a supra-subduction zone arc setting. The chemistry of clinopyroxene in serpentinite indicates a wide range of crystallization temperatures from 969 °C to 1241 °C at 1.0 GPa. The calculated parental magma composition was similar to that of a modern primitive tholeiitic basalt formed by a high-degree of mantle melting. We ascribe the formation of the subduction-generated Bondla arc to the closure of the ocean that led to the formation of the Kumta suture. Thus, chromian spinel chemistry proves to be a viable indicator that helps understand the thermal conditions and tectonic derivation of the Bondla ultramafic-mafic complex against a suture zone in western India.

IR spectroscopic determination of OH defects in spinel group minerals

NASA Astrophysics Data System (ADS)

Halmer, M. M.; Libowitzky, E.; Beran, A.

2003-04-01

Previous experimental studies showed that spinel phases, likely to occur in the transition zone of the Earth's mantle, contain essential amounts of water in form of OH groups. The g-Mg_2SiO_4 phase is reported to contain 27000 wt.ppm H_2O. The corresponding IR spectrum shows very broad absorption bands centered at 3645 and 3345cm-1 with a shoulder at 3120cm-1 (Kohlstedt et al., 1996). Thus, it is evident that under high-pressure conditions the spinel structure is capable to incorporate OH groups. Up to present, hydrogen contents of spinels from upper Earth's mantle and from crustal occurrences have not been reported in the literature. It is the aim of this study to prove the presence of OH defects in spinels of naturally occurring paragenesis and to develop some ideas on the structural incorporation mode based on promising results obtained from synthetic phases. Highly disordered non-stoichiometric Verneuil-grown MgAl spinels are characterized by two significant bands centered at 3355cm-1 and 3510cm-1, which show variations in band intensities. Synthetic H_ high-temperature treated intermediate compounds in the spinel-magnesioferrite (MgFe_2O_4), spinel-hercynite (FeAl2O4) and spinel-franklinite (ZnFe2O4) system from Andreozzi et al. (2001) indicate variable behavior. Whereas some of the spectra, which may be also correlated to d-d transitions of IVFe2+ (Skogby and Halenius, 2003) show broad absorptions in the 3500-3100cm-1 range, a pure MgAl2O4 end member sample is characterized by a rather sharp mode at 3450cm-1. Naturally occurring gahnite crystals (ZnAl2O_4) show significantly broad absorption band at 3400cm-1, which resembles some of the bands of the former synthetic samples. Based on the calibration of Libowitzky and Rossman (1997) the analytical H_2O content of the natural gahnite sample was determined to 580 wt.ppm. The position of the absorption bands implies weak hydrogen bonding of the OH defects in the spinel structure. This work was partly supported by the EU through the Human Potential Program HPRN-CT-2000-0056. References: Andreozzi GB, Hålenius U, Skogby H (2001). Phys Chem Minerals, 28: 435-444. Kohlstedt DL, Keppler H, Rubie DC (1996). Contr Mineral Petrol, 123: 345-357. Libowitzky E, Rossman GR (1997). Am Mineral, 82: 1111-1115. Skogby H, Hålenius U (2003). Am Mineral, (in press)

The Petrogenesis of the Unit 7/8 and 11/12 Chrome-spinel Seams of the Rum Eastern Layered Intrusion (NW Scotland) Re-evaluated

NASA Astrophysics Data System (ADS)

O'Driscoll, B.; Daly, J. S.; Emeleus, C. H.; Donaldson, C. H.

2007-12-01

Laterally extensive (~2 mm thick) chrome-spinel seams in the Rum Layered Suite, NW Scotland, occur at the junctions of several of the coupled peridotite-troctolite macro-rhythmic units that make up the bulk of the eastern part of the intrusion. A detailed petrographic study of the rocks immediately above and below two of these seams suggests that existing models for seam formation involving early crystallisation and gravitational settling of chrome-spinel crystals from a newly emplaced body of picritic magma may be flawed. Instead, the textural relationships between minerals suggest that olivine crystallisation in the peridotite above each of the seams occurred before that of most of the chrome-spinel. Reaction textures between olivine and chrome-spinel crystals are commonly observed, with plagioclase usually occurring as thin rims between both olivine and chrome-spinel where both are in close proximity. The textural evidence suggests a significant degree of olivine crystal-shape change; it seems that many of the olivine crystals immediately above the main seams may initially have had much more complex (harrisitic) crystal shapes before modification to simpler morphologies in a crystal mush. Plagioclase occurs in the peridotite as large oikocrysts up to several cm in size. Additionally, the chrome-spinel seams occur only in those units that display extensive evidence of syn-magmatic deformation of unconsolidated cumulate in the underlying troctolite, and the seams themselves often exhibit small-scale load structures. A model suggesting in-situ crystallisation of the chrome-spinel seams is proposed, whereby mixing of an evolved interstitial liquid with a primitive picritic melt occurred approximately at the crystal mush-magma interface. The former was released from the unconsolidated troctolite mush as a response to re-mobilization and chaotic slumping, possibly triggered by emplacement of some of the hot picrite into the crystal mush pile. Significant undercooling in the picrite due to emplacement-related cooling had already produced a crystal framework comprising complex skeletal olivine crystal morphologies with very fast growth rates. It is envisaged that the significantly modified olivine textures in the peridotite immediately above both seams can be attributed to upward- moving porosity waves of the same 'mixed' interstitial melt that precipitated the chrome-spinel seams. In addition to formation of the seams at the main unit junctions, 'necklace' or 'chain-like' distributions of chrome-spinel crystals around olivine crystals in the peridotite, as well as the large plagioclase oikocrysts, argue for the presence of a mobile interstitial melt with a protracted cooling history.

Natural Occurrence of Fe2SiO4 - in Shocked Umbarger l6 Chondrite

NASA Astrophysics Data System (ADS)

Xie, Z.; Sharp, T. G.

2001-12-01

Fe2SiO4 with the spinel structure was synthesized by Ringwood [1] and inferred to be important in Earth's upper mantle [1,2], but it has not previously been found in nature. Umbarger is an L6 chondrite, which contains a series of high-pressure phases: ring-woodite, akimotoite, augite and hollandite-structured plagioclase [3-6]. Transmission electron microscopy also revealed a Fe2SiO4-spinel and stishovite assem-blage in a Fe-rich zone of a melt pocket. Phyllosili-cates and glass are also associated with the Fe2SiO4-spinel, indicating post-shock aqueous glass alteration. The Fe2SiO4-spinel grains are equant to irregular, with sizes from 100 to 400 nm. Diffraction patterns can only be indexed as a spinel structure, but the unit cell is a little large (a= 8.46 Å) relative to synthetic Fe2SiO4-spinel (a=8.234 Å [1]). EDS analyses show that the spinel has a fayalite compositon with Fe/(Fe+Mg) ratio ranging from 62% to 97%. Stishovite occurs as elongated prismatic crystals up to 1 mm long and up to 100 mm wide. The alteration products in Umbarger are phyllosilicates rich in Fe and Si, with a basal layer spacing of about 9.7 Å. Crystallization of melt veins began with akimotoite and ringwoodite at pressures up to 25 GPa and ended with augite at pressure less than 18 GPa [3, 4]. Mg2SiO4-spinel and stishovite are stable in the pres-sure range from 15 GPa to 25 GPa in the enstatite-forsterite system [7], while Fe2SiO4-spinel and stishovite is stable at lower pressure. Fe2SiO4-spinel and stishovite assemblage, like that of Akimotoite plus ringwoodite, is a sub-solidus assemblage, indicating crystallization of a supercooled liquid during rapid cooling and decompression associated with shock pres-sure release. Reference: [1] Ringwood A.E. (1958) GCA,15, 18-29. [2] Irifune T. (1993) The Island Arc, 2, 55-71. [3] Xie Z. and Sharp T. G. (2000a) LPS XXXI, 2065.pdf. [4] Xie Z. and Sharp T. G. (2000b) MAPS, 35 A172. [5] Xie Z. et al.(2001) LPS XXXII, 1805.pdf. [6] Sharp T.G. (2001) LPS XXXII, 2159.pdf. [7] Gasparik T. (1992) JGR, 97, 15181-15188.

A new lithium-rich anti-spinel in Li–O–Br system

DOE PAGES

Zhang, J.; Zhu, J.; Wang, L.; ...

2015-05-11

In spinel-type materials currently known, the divalent anions are arranged in a closed-pack lattice and cations of various valences occupy some or all of the tetrahedral and octahedral sites. We report here the first discovery of an ‘‘electronically inverted’’ antispinel. Furthermore, the new material, crystallized in a defect spinel structure, was obtained from the dehydration of Li 5Br(OH) 4 under moderate pressure and temperature conditions.

Electrochemical Performance of LixMn2-yFeyO4-zClz Synthesized Through In-Situ Glycine Nitrate Combustion

DTIC Science & Technology

2016-06-13

Aberdeen Proving Ground, MD, USA, 21005 Abstract: Lithium manganese oxide spinel is an attractive material for lithium - ion battery cathodes due to...performance allows for access to energy at extended cycling and across potential regimes. Keywords: Li- ion battery ; Lithium manganese oxide spinel...materials for lithium - ion batteries due to their affordability and low toxicity while maintaining reasonable capacity [1-3]. However, this spinel

Spinel-structured metal oxide on a substrate and method of making same by molecular beam epitaxy

DOEpatents

Chambers, Scott A.

2006-02-21

A method of making a spinel-structured metal oxide on a substrate by molecular beam epitaxy, comprising the step of supplying activated oxygen, a first metal atom flux, and at least one other metal atom flux to the surface of the substrate, wherein the metal atom fluxes are individually controlled at the substrate so as to grow the spinel-structured metal oxide on the substrate and the metal oxide is substantially in a thermodynamically stable state during the growth of the metal oxide. A particular embodiment of the present invention encompasses a method of making a spinel-structured binary ferrite, including Co ferrite, without the need of a post-growth anneal to obtain the desired equilibrium state.

Crystallographic and magnetic properties of the spinel-type ferrites ZnxCo1-xFe2O4 (0.0 ≤ x ≤ 0.75)

NASA Astrophysics Data System (ADS)

Azad, A. K.; Zakaria, A. K. M.; Jewel, Md. Yusuf; Khan, Abu Saeed; Yunus, S. M.; Kamal, I.; Datta, T. K.; Eriksson, S.-G.

2015-05-01

Ultrahigh frequencies (UHF) have applications in signal and power electronics to minimize product sizes, increase production quantity and lower manufacturing cost. In the UHF range of 300 MHz to 3 GHz, ferrimagnetic iron oxides (ferrites) are especially useful because they combine the properties of a magnetic material with that of an electrical insulator. Ferrites have much higher electrical resistivity than metallic ferromagnetic materials, resulting in minimization of the eddy current losses, and total penetration of the electromagnetic (EM) field. Hence ferrites are frequently applied as circuit elements, magnetic storage media like read/write heads, phase shifters and Faraday rotators. The electromagnetic properties of ferrites are affected by operating conditions such as field strength, temperature and frequency. The spinel system ZnxCo1-xFe2O4 (x=0.0, 0.25, 0.50 and 0.75) has been prepared by the standard solid state sintering method. X-ray and neutron powder diffraction measurements were performed at room temperature. Neutron diffraction data analysis confirms the cubic symmetry corresponding to the space group Fd3m. The distribution of three cations Zn2+, Co2+ and Fe3+ over the spinel lattice and other crystallographic parameters like lattice constant, oxygen position parameter, overall temperature factor and occupancies of different ions in different lattice sites for the samples have been determined from the analysis of neutron diffraction data. The lattice constant increases with increasing Zn content in the system. The magnetic structure was found to be ferrimagnetic for the samples with x≤0.50. Magnetization measurements show that with the increase of Zn content in the system the value of saturation magnetization first increases and then decreases. The variation of the magnetic moment with Zn substitution has been discussed in terms of the distribution of magnetic and non-magnetic ions over the A and B sub-lattices and their exchange coupling.

Single crystal structure analyses of scheelite-powellite CaW1-xMoxO4 solidsolutions and unique occurrence in Jisyakuyama skarn deposits

NASA Astrophysics Data System (ADS)

Yamashita, K.; Yoshiasa, A.; Miyazaki, H.; Tokuda, M.; Tobase, T.; Isobe, H.; Nishiyama, T.; Sugiyama, K.; Miyawaki, R.

2017-12-01

Jisyakuyama skarn deposit, Fukuchi, Fukuoka, Japan, shows a simple occurrenceformed by penetration of hot water into limestone cracks. A unique occurrence of scheelite-powellite CaW1-xMoxO4 minerals is observed in the skarn deposit. Many syntheticexperiments for scheelite-powellite solid solutions have been reported as research onfluorescent materials. In this system it is known that a complete continuous solid solution isformed even at room temperature. In this study, we have carried out the chemical analyses,crystal structural refinements and detail description of occurrence on scheelite-powelliteminerals. We have also attempted synthesis of single crystal of solid solution in a widecomposition range. The chemical compositions were determined by JEOL scanningelectron microscope and EDS, INCA system. We have performed the crystal structurerefinements of the scheelite-powellite CaW1-xMoxO4 solid solutions (x=0.0-1.0) byRIGAKU single-crystal structure analysis system RAPID. The R and S values are around0.0s and 1.03. As the result of structural refinements of natural products and many solidsolutions, we confirm that most large natural single crystals have compositions at bothendmembers, and large solid solution crystals are rare. The lattice constants, interatomicdistances and other crystallographic parameters for the solid solution change uniquely withcomposition and it was confirmed as a continuous solid solution. Single crystals of scheeliteendmember + powellite endmember + solid solution with various compositions form anaggregate in the deposit (Figure 1). Crystal shapes of powellite and scheelite arehypidiomorphic and allotriomorphic, respectively. Many solid solution crystals areaccompanied by scheelite endmember and a compositional gap is observed betweenpowellite and solid-solution crystals. The presence of several penetration solutions withsignificantly different W and Mo contents may be assumed. This research can be expectedto lead to giving restrictive conditions to elucidate the mineralization process. Figure1. Scheelite + Powellite + solid solution aggregate

Hydrated Spinel Websterite Xenoliths From Moses Rock Diatreme, Navajo Volcanic Field: Metasomatism in the Mantle Wedge of the Colorado Plateau Above the De-watering Farallon Plate

NASA Astrophysics Data System (ADS)

Schulze, D. J.; Chow, R.; Helmstaedt, H. H.

2016-12-01

Expansion and density decrease in ultramafic rocks in the mantle wedge above the subducted and dewatering Farallon Plate in the Cenozoic may have been the driving force behind uplift of the Colorado Plateau. Here we document the effects of such hydration on spinel websterites that resulted in rocks dominated by pargasitic amphibole, Mg-chlorite and Cr-magnetite/chromite. Xenoliths of spinel websterite from the Moses Rock diatreme in the Navajo Volcanic Field on the Colorado Plateau have granoblastic to mosaic porphyroclastic texture. Porphyroclasts (up to 2 cm across) of lamellar intergrowths of clinopyroxene and orthopyroxene are set in a granular matrix of sub-equal amounts of the two pyroxenes. Both pyroxenes are magnesian and aluminous, with Mg/(Mg+Fe) in the range 0.89 to 0.93 and Al2O3 contents of approximately 4.0 to 9.5 wt%. Many samples contain aluminous spinel with Al/(Al+Cr) = 0.82 to 0.94. The effects of hydration on these samples exist as partial to complete replacement of the pyroxenes by amphibole (tremolite/edenite/pargasite/magnesio-hornblende), pseudomorphing original pyroxene textures, and replacement of primary spinel by Cr-rich magnetite or chromite with Al/(Al+Cr) = 0.07 to 0.35 intergrown with, and surrounded by, clinochlore. Unusual minerals associated with replacement of primary spinel include one example with corundum + zoisite, one with secondary garnet (molar Ca:Mg:Fe = 20:40:40) and two samples with aluminous talc (5 to 7 wt% Al2O3). By analogy with Alpine peridotites and mantle xenolith suites from basalt occurrences, the spinel websterites probably existed as veins and lenses in spinel peridotite of the shallow upper mantle beneath the Colorado Plateau prior to hydration. De-watering of the subducted Farallon Plate in Cenozoic time was likely the source of water-rich fluids that caused the hydration at fairly shallow depths (within amphibole stability), as suggested for hydration of spinel peridotite xenoliths from the Buell Park and Green Knobs diatremes further south. The volume increase and density decrease accompanying hydration of the peridotites and pyroxenites were important factors in the uplift of the Colorado Plateau.

Rietveld refinement and FTIR analysis of bulk ceramic Co3-xMnxO4 compositions

NASA Astrophysics Data System (ADS)

Meena, P. L.; Kumar, Ravi; Sreenivas, K.

2013-02-01

Co3-xMnxO4 (x = 0.0, 0.6, 1.2) prepared by solid state reaction method and characterized by powder X-ray diffraction (XRD) and Fourier transform infrared (FTIR). Lattice parameters (a), oxygen parameter (u), and ionic radii of cations have been determined through Rietveld analysis. Both a and u parameters are related to expansion of octahedral site as Mn content in Co3O4. Analysis of XRD data show that Mn (x ≤ 1.2) is accommodated at the octahedral site, while retaining the cubic spinel structure. FTIR results also confirm the same and signify strong interactions due to overlapping of Co and Mn octahedra.

Heat resistant alloys as interconnect materials of reduced temperature SOFCs

NASA Astrophysics Data System (ADS)

Jian, Li; Jian, Pu; Guangyuan, Xie; Shunxu, Wang; Jianzhong, Xiao

Heat-resistant alloys, Haynes 230 and SS310, were exposed to air and humidified H 2 at 750 °C for up to 1000 h, respectively, simulating the environments in reduced temperature solid oxide fuel cells (SOFCs). The oxidized samples were characterized by using SEM, EDS and X-ray diffraction to obtain the morphology, thickness, composition and crystal structure of the oxide scales. A mechanism for the formation of metallic Ni-rich nodules on top of the oxide scale in Haynes 230 sample oxidized in humidified H 2 was established. Thermodynamic analysis confirmed that MnCr 2O 4 is the favored spinel phase, together with Cr 2O 3, in the oxide scales.

Mixed oxide solid solutions

DOEpatents

Magno, Scott; Wang, Ruiping; Derouane, Eric

2003-01-01

The present invention is a mixed oxide solid solution containing a tetravalent and a pentavalent cation that can be used as a support for a metal combustion catalyst. The invention is furthermore a combustion catalyst containing the mixed oxide solid solution and a method of making the mixed oxide solid solution. The tetravalent cation is zirconium(+4), hafnium(+4) or thorium(+4). In one embodiment, the pentavalent cation is tantalum(+5), niobium(+5) or bismuth(+5). Mixed oxide solid solutions of the present invention exhibit enhanced thermal stability, maintaining relatively high surface areas at high temperatures in the presence of water vapor.

A simple aloe vera plant-extracted microwave and conventional combustion synthesis: Morphological, optical, magnetic and catalytic properties of CoFe2O4 nanostructures

NASA Astrophysics Data System (ADS)

Manikandan, A.; Sridhar, R.; Arul Antony, S.; Ramakrishna, Seeram

2014-11-01

Nanocrystalline magnetic spinel CoFe2O4 was synthesized by a simple microwave combustion method (MCM) using ferric nitrate, cobalt nitrate and Aloe vera plant extracted solution. For the comparative study, it was also prepared by a conventional combustion method (CCM). Powder X-ray diffraction, energy dispersive X-ray and selected-area electron diffraction results indicate that the as-synthesized samples have only single-phase spinel structure with high crystallinity and without the presence of other phase impurities. The crystal structure and morphology of the powders were revealed by high resolution scanning electron microscopy and transmission electron microscopy, show that the MCM products of CoFe2O4 samples contain sphere-like nanoparticles (SNPs), whereas the CCM method of samples consist of flake-like nanoplatelets (FNPs). The band gap of the samples was determined by UV-Visible diffuse reflectance and photoluminescence spectroscopy. The magnetization (Ms) results showed a ferromagnetic behavior of the CoFe2O4 nanostructures. The Ms value of CoFe2O4-SNPs is higher i.e. 77.62 emu/g than CoFe2O4-FNPs (25.46 emu/g). The higher Ms value of the sample suggest that the MCM technique is suitable for preparing high quality nanostructures for magnetic applications. Both the samples were successfully tested as catalysts for the conversion of benzyl alcohol. The resulting spinel ferrites were highly selective for the oxidation of benzyl alcohol and exhibit important difference among their activities. It was found that CoFe2O4-SNPs catalyst show the best performance, whereby 99.5% selectivity of benzaldehyde was achieved at close to 93.2% conversion.

Mixed Metal Oxides of the Type CoxZn1-xFe2O4 as Photocatalysts for Malachite Green Degradation Under UV Light Irradiation.

PubMed

Tzvetkov, Martin; Milanova, Maria; Cherkezova-Zheleva, Zara; Spassova, Ivanka; Valcheva, Evgenia; Zaharieva, Joana; Ivan, Mitov

2017-06-01

A combination of thermal and mechanical (high energy ball milling) treatment was applied in an attempt to obtain polycrystalline mixed metal binary and ternary oxides of the type CoxZn1-xFe2O4 (x = 0; 0.25; 0.5; 0.75; 1). The synthetic procedure used successfully produced single-phased, homogeneous ZnFe2O4, CoFe2O4, and Co0.75Zn0.25Fe2O4, as well as mixed oxides, whose composition depended both on the duration of the high energy ball milling and the ratio Zn(II)/Co(II). The formation of spinel-like structures was proved by XRD, Mössbauer spectroscopy and Raman spectroscopy. For the characterization of the samples low-temperature N2 adsorption, UV/Vis spectroscopy and transmission electron microscopy were applied. The energy band gap of the samples was calculated, suggesting they are promising photocatalysts. The decomposition of the Malachite Green in model water solutions under UV-light irradiation was successfully achieved in the presence of the samples as photocatalysts. The highest rate constant was obtained for the sample synthesized at longer milling time in combination with higher Zn(II)/Co(II) ratio. The photocatalytic activity of the ternary mixed oxides was compared with the pure hematite, α-Fe2O3, and the binary ZnFe2O4 and CoFe2O4 ferrites with spinel structure that were treated in the same way. A synergetic effect of α-Fe2O3 and the spinel-like structure on the photocatalytic properties of ternary mixed metal oxides was detected.

Constraining the deformation and exhumation history of the Ronda Massif, Southern Spain

NASA Astrophysics Data System (ADS)

Myall, Jack; Donaldson, Colin

2016-04-01

The Ronda peridotite, southern Spain is comprised of four peridotite units hosted within metasedimentary units of the Betic Cordillera, Western Alps. These four areas of differing mineral facies are termed: the Garnet Mylonite , the Foliated Spinel Peridotite, the Granular Spinel Peridotite and the Foliated Plagioclase Peridotite. Whilst two of these units show a strong NE-SW foliation, the granular unit has no foliation and the Plagioclase facies shows a NW-SE foliation. The massif is separated from the metasedimentary host through a mylonite shear zone to the NW and thrust faults to the SE. The Garnets contain rims of Kelyphite which when combined with the rims of Spinel on the Plagioclase crystals illustrate the complicated exhumation of this massif. The Kelyphite shows the breakdown of garnet back to spinel and pyroxene showing the deeper high pressure high temperature mineral is under shallowing conditions whereas in contrast to this the low pressure low temperature plagioclase crystals have spinel rims showing that they have been moved into deeper conditions. The P-T-t pathway of the massif suggests slow exhumation to allow for partial recrystallisation of not only the garnets and plagioclases but of a 100m band of peridotite between the Foliated Spinel Peridotite and the Granular Spinel Peridotite facies. The tectonic model for the Ronda Peridotite that best describes the field data and subsequent lab work of this study is Mantle Core complex and slab roll back models. These models support mantle uprising during an extensional event that whereby slab roll back of the subducting lithosphere provides uplift into a void and emplacement into the crust. Further extension and final exhumation causes rotation of a mantle wedge into its present day position.

Understanding the effect of an in situ generated and integrated spinel phase on a layered Li-rich cathode material using a non-stoichiometric strategy.

PubMed

Zhang, Jicheng; Gao, Rui; Sun, Limei; Li, Zhengyao; Zhang, Heng; Hu, Zhongbo; Liu, Xiangfeng

2016-09-14

Recently, spinel-layered integrated Li-rich cathode materials have attracted great interest due to the large enhancement of their electrochemical performances. However, the modification mechanism and the effect of the integrated spinel phase on Li-rich layered cathode materials are still not very clear. Herein, we have successfully synthesized the spinel-layered integrated Li-rich cathode material using a facile non-stoichiometric strategy (NS-LNCMO). The rate capability (84 mA h g -1 vs. 28 mA h g -1 , 10 C), cycling stability (92.4% vs. 80.5%, 0.2 C), low temperature electrochemical capability (96.5 mA h g -1 vs. 59 mA h g -1 , -20 °C), initial coulomb efficiency (92% vs. 79%) and voltage fading (2.77 V vs. 3.02 V, 200 cycles@1 C) of spinel-layered integrated Li-rich cathode materials have been significantly improved compared with a pure Li-rich phase cathode. Some new insights into the effect of the integrated spinel phase on a layered Li-rich cathode have been proposed through a comparison of the structure evolution of the integrated and Li-rich only materials before and after cycling. The Li-ion diffusion coefficient of NS-LNCMO has been enlarged by about 3 times and almost does not change even after 100 cycles indicating an enhanced structure stability. The integration of the spinel phase not only enhances the structure stability of the layered Li-rich phase during charging-discharging but also expands the interslab spacing of the Li-ion diffusion layer, and elongates TM-O covalent bond lengths, which lowers the activation barrier of Li + -transportation, and alleviates the structure strain during the cycling procedure.

Enhancement of electrochemical performance by simultaneous substitution of Ni and Mn with Fe in Ni-Mn spinel cathodes for Li-ion batteries

NASA Astrophysics Data System (ADS)

Kiziltas-Yavuz, Nilüfer; Yavuz, Murat; Indris, Sylvio; Bramnik, Natalia N.; Knapp, Michael; Dolotko, Oleksandr; Das, Bijoy; Ehrenberg, Helmut; Bhaskar, Aiswarya

2016-09-01

LiNi0.5-xFe2xMn1.5-xO4 (x = 0, 0.1, 0.15, 0.2) spinel cathode materials are synthesized using citric acid-assisted sol-gel method with final calcination temperature of 1000 °C. The structure and morphology of the materials are characterized by using synchrotron and neutron powder diffraction as well as scanning electron microscopy. Different from the parent LiNi0.5Mn1.5O4 (LNMO) material, the Fe-doped spinels do not contain a rock-salt type impurity phase. However, they contain additional layered (C2/m) and spinel Fe3O4 (Fd 3 bar m) phases in small amounts. The substitution of Fe into the spinel structure has been confirmed by Mössbauer spectroscopy. The Fe-doped spinels exhibit improved cycling stability (with a C/2 charge-discharge rate) and rate capability compared to the parent LNMO at room temperature in a voltage range 3.5-5.0 V. Among all these samples, the composition LiNi0.4Fe0.2Mn1.4O4 shows the best room temperature cycling stability (capacity retention of 92% after 300 cycles) as well as the highest initial discharge capacity (134 mAh g-1). The delivered capacities at high C-rates (especially at 10C and 20C) with respect to the capacity delivered at C/2 are higher for all Fe-doped samples compared to the parent LNMO. Furthermore, Fe-doping improves the thermal stability of the Ni-Mn spinels in the delithiated state.

Superexchange Effects on Oxygen Reduction Activity of Edge-Sharing [Cox Mn1-x O6 ] Octahedra in Spinel Oxide.

PubMed

Zhou, Ye; Sun, Shengnan; Xi, Shibo; Duan, Yan; Sritharan, Thirumany; Du, Yonghua; Xu, Zhichuan J

2018-03-01

Mn-Co containing spinel oxides are promising, low-cost electrocatalysts for the oxygen reduction reaction (ORR). Most studies are devoted to the design of porous Mn-Co spinels or to strongly coupled hybrids (e.g., MnCo 2 O 4 /N-doped-rmGO) to maximize the mass efficiency. The lack of analyses by metal oxide intrinsic activity (activity normalized to catalysts' surface area) hinders the development of fundamental understanding of the physicochemical principles behind the catalytic activities. A systematic study on the composition dependence of ORR in ZnCo x Mn 2- x O 4 (x = 0.0-2.0) spinel is presented here with special attention to the role of edge sharing [Co x Mn 1- x O 6 ] octahedra in the spinel structure. The ORR specific activity of ZnCo x Mn 2- x O 4 spans across a potential window of 200 mV, indicating an activity difference of ≈3 orders of magnitude. The curve of composition-dependent ORR specific activity as a function of Co substitution exhibits a volcano shape with an optimum Mn/Co ratio of 0.43. It is revealed that the modulated e g occupancy of active Mn cations (0.3-0.9), as a consequence of the superexchange effect between edge sharing [CoO 6 ] and [MnO 6 ], reflects the ORR activity of edge sharing [Co x Mn 1- x O 6 ] octahedra in the ZnCo x Mn 2- x O 4 spinel oxide. These findings offer crucial insights in designing spinel oxide catalysts with fine-tuned e g occupancy for efficient catalysis. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Multi-Stage Structural Transformations in Zero-Strain Lithium Titanate Unveiled by in Situ X-ray Absorption Fingerprints

DOE PAGES

Zhang, Wei; Topsakal, Mehmet; Cama, Christina; ...

2017-10-13

Zero-strain electrodes, such as spinel lithium titanate (Li 4/3Ti 5/3O 4), are appealing for application in batteries due to their negligible volume change and extraordinary stability upon repeated charge/discharge cycles. On the other hand, this same property makes it challenging to probe their structural changes during the electrochemical reaction. In this paper, we report in situ studies of lithiation-driven structural transformations in Li 4/3Ti 5/3O 4 via a combination of X-ray absorption spectroscopy and ab initio calculations. Based on excellent agreement between computational and experimental spectra of Ti K-edge, we identified key spectral features as fingerprints for quantitative assessment ofmore » structural evolution at different length scales. Results from this study indicate that, despite the small variation in the crystal lattice during lithiation, pronounced structural transformations occur in Li 4/3Ti 5/3O 4, both locally and globally, giving rise to a multi-stage kinetic process involving mixed quasi-solid solution/macroscopic two-phase transformations over a wide range of Li concentrations. Finally, this work highlights the unique capability of combining in situ core-level spectroscopy and first-principles calculations for probing Li-ion intercalation in zero-strain electrodes, which is crucial to designing high-performance electrode materials for long-life batteries.« less

Multi-Stage Structural Transformations in Zero-Strain Lithium Titanate Unveiled by in Situ X-ray Absorption Fingerprints

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

Zhang, Wei; Topsakal, Mehmet; Cama, Christina

Zero-strain electrodes, such as spinel lithium titanate (Li 4/3Ti 5/3O 4), are appealing for application in batteries due to their negligible volume change and extraordinary stability upon repeated charge/discharge cycles. On the other hand, this same property makes it challenging to probe their structural changes during the electrochemical reaction. In this paper, we report in situ studies of lithiation-driven structural transformations in Li 4/3Ti 5/3O 4 via a combination of X-ray absorption spectroscopy and ab initio calculations. Based on excellent agreement between computational and experimental spectra of Ti K-edge, we identified key spectral features as fingerprints for quantitative assessment ofmore » structural evolution at different length scales. Results from this study indicate that, despite the small variation in the crystal lattice during lithiation, pronounced structural transformations occur in Li 4/3Ti 5/3O 4, both locally and globally, giving rise to a multi-stage kinetic process involving mixed quasi-solid solution/macroscopic two-phase transformations over a wide range of Li concentrations. Finally, this work highlights the unique capability of combining in situ core-level spectroscopy and first-principles calculations for probing Li-ion intercalation in zero-strain electrodes, which is crucial to designing high-performance electrode materials for long-life batteries.« less

First-Principles Modeling of Mn(II) Migration above and Dissolution from Li x Mn 2 O 4 (001) Surfaces

DOE PAGES

Leung, Kevin

2016-12-10

The density functional theory and ab initio molecular dynamics simulations are applied to investigate the migration of Mn(II) ions to above-surface sites on spinel Li xMn 2O 4 (001) surfaces, the subsequent Mn dissolution into the organic liquid electrolyte, and the detrimental effects on graphite anode solid electrolyte interphase (SEI) passivating films after Mn(II) ions diffuse through the separator. The dissolution mechanism proves complex; the much-quoted Hunter disproportionation of Mn(III) to form Mn(II) is far from sufficient. Key steps that facilitate Mn(II) loss include concerted liquid/solid-state motions; proton-induced weakening of Mn–O bonds forming mobile OH – surface groups; and chemicalmore » reactions of adsorbed decomposed organic fragments. Mn(II) lodged between the inorganic Li 2CO 3 and organic lithium ethylene dicarbonate (LEDC) anode SEI components facilitate electrochemical reduction and decomposition of LEDC. Our findings help inform future design of protective coatings, electrolytes, additives, and interfaces.« less

Self-diffusion of magnesium in spinel and in equilibrium melts - Constraints on flash heating of silicates

NASA Technical Reports Server (NTRS)

Sheng, Y. J.; Wasserburg, G. J.; Hutcheon, I. D.

1992-01-01

An isotopic tracer is used to measure Mg self-diffusion in spinel and coexisting melt at bulk chemical equilibrium. The diffusion coefficients were calculated from the measured isotope profiles using a model that includes the complementary diffusion of Mg-24, Mg-25, and Mg-26 in both phases with the constraint that the Mg content of each phase is constant. The activation energy and preexponential factor for Mg self-diffusion in spinel are, respectively, 384 +/- 7 kJ and 74.6 +/- 1.1 sq cm/s. These data indicate Mg diffusion in spinel is much slower than previous estimates. The activation energy for Mg self-diffusion in coexisting melt is 343 +/- 25 kJ and the preexponential factor is 7791.9 +/- 1.3 sq cm/s. These results are used to evaluate cooling rates of plagioclase-olivine inclusions (POIs) in the Allende meteorite. Given a maximum melting temperature for POIs of about 1500 C, these results show that a 1-micron radius spinel would equilibrate isotopically with a melt within about 60 min.

Compositional controls on spinel clouding and garnet formation in plagioclase of olivine metagabbros, Adirondack Mountains, New York

USGS Publications Warehouse

McLelland, J.M.; Whitney, P.R.

1980-01-01

Olivine metagabbros from the Adirondacks usually contain both clear and spinel-clouded plagioclase, as well as garnet. The latter occurs primarily as the outer rim of coronas surrounding olivine and pyroxene, and less commonly as lamellae or isolated grains within plagioclase. The formation of garnet and metamorphic spinel is dependent upon the anorthite content of the plagioclase. Plagioclase more sodic than An38??2 does not exhibit spinel clouding, and garnet rarely occurs in contact with plagioclase more albitic than An36??4. As a result of these compositional controls, the distribution of spinel and garnet mimics and visually enhances original igneous zoning in plagioclase. Most features of the arrangement of clear (unclouded) plagioclase, including the shells or moats of clear plagioclase which frequently occur inside the garnet rims of coronas, can be explained on the basis of igneous zoning. The form and distribution of the clear zones may also be affected by the metamorphic reactions which have produced the coronas, and by redistribution of plagioclase in response to local volume changes during metamorphism. ?? 1980 Springer-Verlag.

Comparative Planetary Mineralogy: Co, Ni Systematics in Chromite from Planetary Basalts

NASA Technical Reports Server (NTRS)

Karner, J. M.; Shearer, C. K.; Papike, J. J.; Righter,K.

2005-01-01

Spinel is a minor but important phase in planetary basalts because its variable composition often reflects basalt petrogenesis. For example, complicated zoning trends in spinel can give clues to melt evolution [1], and V concentrations in chromite lend insight into magma oxygen fugacity (fO2) conditions [2]. Nickel and Co are two elements that are commonly used as a measure of melt fractionation, and their partitioning between olivine and melt is fairly well understood. Less clear is their partitioning into spinel, although [3] has explored Ni and Co systematics in experimental charges. This study documents Ni and Co behavior in early crystallizing spinel (chromite) from several planetary basalts in an attempt to compare our results with [3], and also gain insight into basalt evolution on the three planets.

Analytical Description of Degradation-Relaxation Transformations in Nanoinhomogeneous Spinel Ceramics.

PubMed

Shpotyuk, O; Brunner, M; Hadzaman, I; Balitska, V; Klym, H

2016-12-01

Mathematical models of degradation-relaxation kinetics are considered for jammed thick-film systems composed of screen-printed spinel Cu 0.1 Ni 0.1 Co 1.6 Mn 1.2 O 4 and conductive Ag or Ag-Pd alloys. Structurally intrinsic nanoinhomogeneous ceramics due to Ag and Ag-Pd diffusing agents embedded in a spinel phase environment are shown to define governing kinetics of thermally induced degradation under 170 °C obeying an obvious non-exponential behavior in a negative relative resistance drift. The characteristic stretched-to-compressed exponential crossover is detected for degradation-relaxation kinetics in thick-film systems with conductive contacts made of Ag-Pd and Ag alloys. Under essential migration of a conductive phase, Ag penetrates thick-film spinel ceramics via a considerable two-step diffusing process.

UHT overprint of HP rocks? A case study from the Adula nappe complex (Central Alps, N Italy)

NASA Astrophysics Data System (ADS)

Tumiati, Simone; Zanchetta, Stefano; Malaspina, Nadia; Poli, Stefano

2014-05-01

The Adula-Cima Lunga nappe complex is located on the eastern flank of the Lepontine Dome and represents the highest of the Lower Penninic units of the Central Alps. The Adula nappe largely consists of orthogneiss and paragneiss of pre-Mesozoic origin, variably retrogressed eclogites preserved as boudins within paragneiss, minor ultramafic bodies and metasedimentary rocks of presumed Mesozoic age. The higher metamorphic conditions have been estimated for the peridotite lenses in the southern part of the nappe at pressure over 3.0 GPa and temperature of 800-850°C. Garnet lherzolite bodies crop out at three localities, from west to east: Cima di Gagnone, Alpe Arami and Mt. Duria. After the partial subduction of the European distal margin beneath the Africa-Adria margin, the HP rocks were overprinted by an upper amphibolite facies metamorphism that postdates the main phase of nappe stacking. In the southern sector of the Lepontine Dome, adjacent to the Insubric Fault, metamorphic conditions promoted extensive migmatization of both metasedimentary and metagranitoid rocks. In one single outcrop, at Monte Duria, garnet lherzolites occur in m-sized boudins hosted within partly granulitized amphibole-bearing and k-feldspar gneisses that contain also some decimeter-sized boudins of both mafic and metapelitic eclogites. This rock association is in turn embedded within the migmatitic gneisses that form most of the southern sector of the Adula nappe. Petrographic and chemical analyses indicate that garnet peridotite is composed of olivine (XMg=0.88), orthopyroxene, clinopyroxene and garnet (Py68; Cr2O3 up to 1.45 wt%) with inclusions of Cr-rich spinel (up to Cr/(Al+Cr)=0.55) surrounded by kelyphitic symplectites of opx + cpx/amph + spl. These reaction produced double coronas, one composed of opx (former ol) and one composed of cpx + opx+ spl. In one kelyphite, we observed the uncommon occurrence of ZrO2 (baddeleyite) and ZrTi2O6 (srilankite). Tiny crystals of these two Zr-bearing phases (˜1 μm) are invariably located in the opx corona after ol. The cpx + opx + spl corona (after grt) contains, instead, zircon. Baddeleyite should have formed through a reaction of the type Mg2SiO4 + ZrSiO4 = MgSiO3 + ZrO2. ZrO2 and ZrTi2O6 display a low amount of solid solution. These compositions are consistent with T below 1200°C, but an improvement of the thermodynamic model is needed in order to better constrain the T of the granulitic overprint on the basis of these Zr-bearing phases. In mafic eclogites, the HP association consists of garnet (Py40Alm37Sp20), omphacite (preserved as inclusion, containing Jd30 and Mg# 0.87), kyanite and minor quartz. Omphacite is almost always replaced by cpx (Jd5) + plag (An55) symplectites. Garnet is surrounded by plag (An33) + opx (En70) symplectites. Kyanite is replaced by plag (An84) + spinel + sapphirine. The spinel-sapphirine Fe-Mg thermometer suggests T of about 850°C due to granulite-facies overprint. We observed sapphirine associated with cpx + opx + plag also in kelyphites after garnet in clinopyroxenites. In eclogitic metapelites, kyanite is replaced by a corundum + anorthite ± spinel assemblage. A corundum-rich layer occurs between eclogites and the host gneiss. Cm-sized emerald green zoisite in this layer is replaced by anorthitic plagioclase ± cpx ± spinel ± calcite. The observed assemblages point to a diffuse granulitization of both the peridotites and the hosting HP rocks of Mt. Duria, suggesting a nearly isothermal decompression from peak-pressure conditions. The surrounding migmatitic gneiss do not display evidence of such granulitic event, having been formed at T<700°C. The mechanism and timing of emplacement of the garnet peridotite and associated HP-HT rocks in the country migmatites, and whether or not the subduction event is related to the Alpine or to an older orogenic cycle are still a matter of debate.

Spinel and plagioclase peridotites of the Nain ophiolite (Central Iran): Evidence for the incipient stage of oceanic basin formation

NASA Astrophysics Data System (ADS)

Pirnia, Tahmineh; Saccani, Emilio; Arai, Shoji

2018-06-01

The Nain ophiolites crop out along the western border of the central East Iran Microcontinent (CEIM) and consist of an ophiolitic mélange in which pargasite-bearing spinel and plagioclase mantle lherzolites are largely represented. Whole-rock and mineral chemistry data suggest that these rocks record the complex history of the asthenospheric and lithospheric mantle evolution. The spinel lherzolites have experienced low-degree ( 5%) partial melting and contain clinopyroxenes with positive Eu anomalies (Eu/Eu* = 1.10-1.48) suggesting that the partial melting occurred under oxidized conditions (fayalite-magnetite-quartz -0.8 to +1.3). The pargasite and coexisting clinopyroxene in these rocks are depleted in light rare earth elements (LREE) (mean chondrite-normalized CeN/SmN = 0.045). The depleted chemistry of this amphibole reflects metasomatism during interaction with H2O-rich subalkaline mafic melts, most likely concurrently with or after the partial melting of the spinel lherzolites. The plagioclase lherzolites were subsequently formed by the subsolidus recrystallization of spinel lherzolites under plagioclase facies conditions as a result of mantle uprising, as evidenced by: (1) the development of plagioclase rims around the spinels; (2) plagioclase + orthopyroxene exsolution textures within some clinopyroxene grains; (3) an increase in plagioclase modal content coupled with an increase in modal olivine and a decrease in modal pyroxene and pargasite; (4) coincident decreases in Al, Mg, and Ni, and increases in Cr, Ti, and Fe in spinel, as well as decreases in Al and Ca, and increases in Cr and Ti in pyroxene and pargasite; and (5) the identical whole rock compositions of the spinel and plagioclase lherzolites, which rules out a magmatic origin for the plagioclase in these units. The Nain lherzolites have similar whole-rock and mineral geochemical compositions to subcontinental peridotites that are typically representative of Iberia-type rifted continental margins and ocean-continent transition zones (OCTZ), suggesting that they formed during the early stages of the evolution of the Nain oceanic basin. This means that the Nain lherzolites represent the Triassic-Jurassic western border of the CEIM or alternatively an associated OCTZ.

PC based electrolytes with LiDFOB as an alternative salt for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Knight, Brandon M.

Lithium-ion batteries (LIBs) have been greatly sought after as a source of renewable energy storage. LIBs have a wide range of applications including but not limited portable electronic devices, electric vehicles, and power tools. As a direct result of their commercial viability an insatiable hunger for knowledge, advancement within the field of LIBs has been omnipresent for the last two decades. However, there are set backs evident within the LIB field; most notably the limitations of standard electrolyte formulations and LiPF6 lithium salt. The standard primary carbonate of ethylene carbonate (EC) has a very limited operating range due to its innate physical properties, and the LiPF6 salt is known to readily decompose to form HF which can further degrade LIB longevity. The goal of our research is to explore the use of a new primary salt LiDFOB in conjunction with a propylene carbonate based electrolyte to establish a more flexible electrolyte formulation by constructing coin cells and cycling them under various conditions to give a clear understanding of each formulation inherent performance capabilities. Our studies show that 1.2M LiDFOB in 3:7 PC/EMC + 1.5% VC is capable of performing comparably to the standard 1.2M LiPF6 in 3:7 EC/EMC at 25°C and the PC electrolyte also illustrates performance superior to the standard at 55°C. The degradation of lithium manganese spinel electrodes, including LiNi 0.5Mn1.5O4, is an area of great concern within the field of lithium ion batteries (LIBs). Manganese containing cathode materials frequently have problems associated with Mn dissolution which significantly reduces the cycle life of LIB. Thus the stability of the cathode material is paramount to the performance of Mn spinel cathode materials in LIBs. In an effort to gain a better understanding of the stability of LiNi0.5 Mn1.5O4 in common LiPF6/carbonate electrolytes, samples were stored at elevated temperature in the presence of electrolyte. Then after storage both the electrolyte solution and uncharged cathode particles were analyzed. The solid cathode particles were analyzed via scanning electron microscopy (SEM) whereas the electrolyte solution was analyzed using inductively coupled plasma mass spectroscopy (ICP-MS). The SEM analysis assists with elucidation of changes to the surfaces of the cathode particles. The ICP-MS of the electrolyte allows the determination of the extent of Mn and Ni dissolution. Samples of LiNi0.5Mn1.5O4 with different crystal surface facets were prepared to investigate the role of particle morphology in Mn and Ni dissolution. The factors affecting Mn and Ni dissolution and methods to inhibit dissolution will be discussed.

Frequency domain kinetic of positron-electron annihilation in the MgO-Al2O3 spinel-type ceramics

NASA Astrophysics Data System (ADS)

Fl'unt, Orest; Klym, Halyna; Ingram, Adam

2018-03-01

In this work, the kinetic of positron-electron annihilation in the MgO-Al2O3 spinel-type ceramics sintered at different temperatures (1100, 1200 and 1400 °C) has been calculated and analyzed in a frequency domain. The spectra of real (in-phase) and imaginary (quadrature) components of positron-electron annihilation kinetic have been obtained numerically from usual temporal characteristics using integral Fourier transform. The numerical calculations were carried out using cubic spline interpolation of the pulse characteristics of MgO-Al2O3 ceramics in time domain with following analytical calculations of integrals. The obtained spectra as real so imaginary part of MgO-Al2O3 ceramics in frequency domain almost good obey a Debye law denying correlation between elementary positron annihilation processes. Complex diagrams of frequency domain responses of as-prepared samples have a shape of semicircles with close characteristic frequencies. Some deviation on low-frequency side of the semicircles is observed confirming an availability of longer time kinetic processes. Sintering temperature dependencies of the relaxation times and characteristic frequencies of positron-electron annihilation processes have been obtained. It is shown that position of large maxima on the frequency dependencies of imaginary part corresponds to fast average relaxation lifetime representing the most intensive interaction process of positrons with small cavity traps in solids.

Improved energy storage, magnetic and electrical properties of aligned, mesoporous and high aspect ratio nanofibers of spinel-NiMn2O4

NASA Astrophysics Data System (ADS)

Bhagwan, Jai; Rani, Stuti; Sivasankaran, V.; Yadav, K. L.; Sharma, Yogesh

2017-12-01

Spinel-NiMn2O4 (NMO) nanofibers of high aspect ratio, high surface area (50 m2 g-1) and homogeneous pore size distribution are fabricated by electrospinning process and characterized by XRD, FTIR, XPS, BET, FESEM, TEM techniques. Further, multifunctional properties (energy storage properties, magnetic and electrical properties) of NMO nanofibers are also examined. High specific capacitance (Cs) of 410 (±5) F g-1 at 1 A g-1, good rate capability and high cycling stability (up to 5000 cycles) are demonstrated by NMO nanofibers. Furthermore, NMO-based solid-state symmetric supercapacitor (SSSC) shows a high Cs of 170 (±5) F g-1 at 0.5 A g-1 in potential range of 0.0V-2.0 V and exhibits excellent energy density of ∼95 W h kg-1 and power density of 1030 W Kg-1. The above storage properties i.e. high energy density and output voltage of 2.0 V are further supplemented by lighting up a red colored LED (1.8 V @ current 20 mA) at least for 5 min. The ionic diffusion coefficient of NMO based electrode is found to be ∼4.84 × 10-11 cm2 s-1. Magnetic and dielectric properties of NMO nanofibers are also examined and results are discussed.

A successful search for hidden Barbarians in the Watsonia asteroid family

NASA Astrophysics Data System (ADS)

Cellino, A.; Bagnulo, S.; Tanga, P.; Novaković, B.; Delbò, M.

2014-03-01

Barbarians, so named after the prototype of this class (234) Barbara, are a rare class of asteroids exhibiting anomalous polarimetric properties. Their very distinctive feature is that they show negative polarization at relatively large phase angles, where all `normal' asteroids show positive polarization. The origin of the Barbarian phenomenon is unclear, but it seems to be correlated with the presence of anomalous abundances of spinel, a mineral usually associated with the so-called calcium-aluminium-rich inclusions (CAIs) on meteorites. Since CAIs are samples of the oldest solid matter identified in our Solar system, Barbarians are very interesting targets for investigations. Inspired by the fact that some of the few known Barbarians are members of, or very close to, the dynamical family of Watsonia, we have checked whether this family is a major repository of Barbarians, in order to obtain some hints about their possible collisional origin. We have measured the linear polarization of a sample of nine asteroids which are members of the Watsonia family within the phase-angle range 17°-21°. We found that seven of them exhibit the peculiar Barbarian polarization signature, and we conclude that the Watsonia family is a repository of Barbarian asteroids. The new Barbarians identified in our analysis will be important to confirm the possible link between the Barbarian phenomenon and the presence of spinel on the surface.

Structural, thermodynamic, and mechanical properties of WCu solid solutions

NASA Astrophysics Data System (ADS)

Liang, C. P.; Wu, C. Y.; Fan, J. L.; Gong, H. R.

2017-11-01

Various properties of Wsbnd Cu solid solutions are systematically investigated through a combined use of first-principles calculation, cluster expansion, special quasirandom structures (SQS), and lattice dynamics. It is shown that SQS are effective to unravel the intrinsic nature of solid solutions, and that BCC and FCC W100-xCux solid solutions are energetically more stable when 0 ≤ x ≤ 70 and 70 < x ≤ 100, respectively. Calculations also reveal that the Debye model should be appropriate to derive thermodynamic properties of Wsbnd Cu, and that the coefficients of thermal expansion of W100-xCux solid solutions are much lower than those of corresponding mechanical mixtures. In addition, the G/B values of W100-xCux solid solutions reach a minimum at x = 50, which is fundamentally due to the softening of phonons as well as strong chemical bonding between W and Cu with a mainly metallic feature.

Mechanism of γ-irradiation induced phase transformations in nanocrystalline Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} ceramics

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

Jagadeesha Angadi, V.; Anupama, A.V.; Choudhary, Harish K.

The structural, infrared absorption and magnetic property transformations in nanocrystalline Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} samples irradiated with different doses (0, 15, 25 and 50 kGy) of γ-irradiation were investigated in this work and a mechanism of phase transformation/decomposition is provided based on the metastable nature of the Mn-atoms in the spinel lattice. The nano-powder sample was prepared by solution combustion route and the pellets of the sample were exposed to γ-radiation. Up to a dose of 25 kGy of γ-radiation, the sample retained the single phase cubic spinel (Fd-3m) structure, but the disorder in the sample increased. On irradiatingmore » the sample with 50 kGy γ-radiation, the spinel phase decomposed into new stable phases such as α-Fe{sub 2}O{sub 3} and ZnFe{sub 2}O{sub 4} phases along with amorphous MnO phase, leading to a change in the surface morphology of the sample. Along with the structural transformations the magnetic properties deteriorated due to breakage of the ferrimagnetic order with higher doses of γ-irradiation. Our results are important for the understanding of the stability, durability and performance of the Mn-Zn ferrite based devices used in space applications. - Graphical abstract: The nanocrystalline Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} ceramic sample transforms to crystalline α-Fe{sub 2}O{sub 3} and ZnFe{sub 2}O{sub 4} phases (and amorphous MnO phase) at a γ-irradiation dose of 50 kGy, as MnO goes out of the spinel lattice. The high energy γ-irradiation causes structural damage to the nanomaterials leading to change in morphology of the sample as seen in the SEM images. - Highlights: • Mn atoms are more unstable in the Mn-Zn ferrite spinel lattice than Zn-atoms. • Displacement of Mn atoms by γ-radiation from the lattice renders phase transformation. • In Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4}, Mn-ferrite cell transforms to crystalline α-Fe{sub 2}O{sub 3} and amorphous MnO. • The stable ZnFe{sub 2}O{sub 4} phase retains its structure even after 50 KGy γ-irradiation. • The γ-irradiation degrades the magnetic properties of Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} ceramics.« less

Effect of Acetylene Black Content in Li4Ti5O12 Xerogel Solid-State Anode Materials on Half-Cell Li-ion Batteries Performance

NASA Astrophysics Data System (ADS)

Abdurrahman, N. M.; Priyono, B.; Syahrial, A. Z.; Subhan, A.

2017-07-01

The effect of Acetylene Black (AB) additive contents in lithium titanate/Li4Ti5O12 (LTO) anode on Li-ion Batteries performance is studied in this work. The LTO active material for Li-ion batteries anode was successfully synthesized using sol-gel method to form TiO2 xerogel continued by mixing process with LiOH in ball-mill and then sintered to obtain spinel LTO. The LTO powder is characterized by X-Ray Diffraction (XRD), scanning electron microscopy-Energy Dispersive Spectroscopy (SEM-EDS), and Brunauer-Emmett-Teller (BET). The spinel LTO and TiO2 rutile were detected by XRD diffractogram. The LTO powder is in the form of agglomerates structure. This powder then was mixed with PVDF binder (10%wt) and AB additives with various amount from 10%wt (LTO2 Ac-1), 12%wt (LTO2 Ac-2), and 15%wt (LTO2 Ac-3) of total weight solid content to form electrode sheet. Half-cell coin battery was made with lithium metal foil as a counter electrode. Cyclic voltammetry (CV), Electrochemical-impedance spectroscopy (EIS), and charge discharge (CD) test used to examine the battery performance. The highest resistance value is obtained in LTO2 Ac-3 sample with 15%wt of AB. It might be caused by the formation of side reaction product on electrode surface at initial cycle due to high reactivity of LTO2 Ac-3 electrode. The highest initial capacity at CV test and CD test was obtained in LTO2 Ac-1 (10%wt AB) sample, due to the best proportion of active material content in the compound. While, in the charge-discharge test at high current rate, the best sample rate-capability performance belongs to LTO2 Ac-3 sample (15%wt AB), which still have 24.12 mAh/g of discharge capacity at 10 C with 71.34% capacity loss.

Conversion of depleted uranium hexafluoride to a solid uranium compound

DOEpatents

Rothman, Alan B.; Graczyk, Donald G.; Essling, Alice M.; Horwitz, E. Philip

2001-01-01

A process for converting UF.sub.6 to a solid uranium compound such as UO.sub.2 and CaF. The UF.sub.6 vapor form is contacted with an aqueous solution of NH.sub.4 OH at a pH greater than 7 to precipitate at least some solid uranium values as a solid leaving an aqueous solution containing NH.sub.4 OH and NH.sub.4 F and remaining uranium values. The solid uranium values are separated from the aqueous solution of NH.sub.4 OH and NH.sub.4 F and remaining uranium values which is then diluted with additional water precipitating more uranium values as a solid leaving trace quantities of uranium in a dilute aqueous solution. The dilute aqueous solution is contacted with an ion-exchange resin to remove substantially all the uranium values from the dilute aqueous solution. The dilute solution being contacted with Ca(OH).sub.2 to precipitate CaF.sub.2 leaving dilute NH.sub.4 OH.

A refractory inclusion in the Kaba CV3 chondrite - Some implications for the origin of spinel-rich objects in chondrites

NASA Technical Reports Server (NTRS)

Fegley, B., Jr.; Post, J. E.

1985-01-01

The first detailed petrographic and mineralogical study of a Ca, Al-rich inclusion (CAI) from the Kaba CV3 chondrite is reported. This 'fine-grained' CAI contains abundant small, rounded, rimmed, spinel-rich objects which have important features in common with the spinel-rich objects in other carbonaceous and ordinary chondrites. These nodules are interpreted as fractionated distillation residues of primitive dust. However, the available data do not unambiguously rule out a condensation origin for at least some of these objects. Finally, the preservation of distinct diopside-hedenbergite rims on the spinel-rich bodies and the small grain size of many minerals in the CAI matrix material both suggest that the CAI accreted cool and had a relatively cool thermal history in the Kaba parent body.

A series of spinel phase cathode materials prepared by a simple hydrothermal process for rechargeable lithium batteries

NASA Astrophysics Data System (ADS)

Liang, Yan-Yu; Bao, Shu-Juan; Li, Hu-Lin

2006-07-01

A series of spinel-structured materials have been prepared by a simple hydrothermal procedure in an aqueous medium. The new synthetic method is time and energy saving i.e., no further thermal treatment and extended grinding. The main experimental process involved the insertion of lithium into electrolytic manganese dioxide with glucose as a mild reductant in an autoclave. Both the hydrothermal temperature and the presence of glucose play the critical roles in determining the final spinel integrity. Particular electrochemical performance has also been systematically explored, and the results show that Al 3+, F - co-substituted spinels have the best combination of initial capacity and capacity retention among all these samples, exhibited the initial capacity of 115 mAh/g and maintained more than 90% of the initial value at the 50th cycle.

Upper mantle oxygen fugacity recorded by peridotite xenoliths from oceanic islands

NASA Astrophysics Data System (ADS)

Davis, F. A.; Wall, K. T.; Cottrell, E.

2017-12-01

Oxygen fugacity (fO2) in Earth's mantle is a key variable influencing mineral and fluid stability, the onset of melting, and mantle rheology; but fO2 is not uniform across mantle spatial domains. Peridotite xenoliths erupted in oceanic island basalts (OIB) potentially record fO2 of their lithospheric source - the convecting upper mantle. Many of these xenoliths have reacted with OIB as they transited the lithosphere. These xenoliths may record fO2 of the OIB source, potentially recording fO2 heterogeneity within the upper mantle. We investigate fO2heterogeneity by analyzing coexisting olivine, opx, and spinel in 41 peridotite xenoliths from islands associated with four different hotspots: Oahu (Hawaii), Savai'i (Samoa), Tubuai (Austral), and Tahiti (Society). Elevated spinel TiO2 concentrations (TiO2 >0.2 wt.%) in xenoliths from Oahu, Tubuai, and Tahiti may indicate interaction with OIB magmas [1]. Such assemblages record higher fO2 on average (QFM+0.4 to QFM+1.0) than peridotites and lavas from mid-ocean ridges (QFM-2 to QFM) [2,3,4]. This suggests that Hawaiian, Society, and Austral basalts with fO2 ≥ QFM+0.4 are more oxidized than MORB. (None of the Samoan xenoliths have spinel TiO2 >0.05 wt.%). Xenoliths with TiO2 <0.2 wt.% that have not reacted with OIB show a great degree of fO2 heterogeneity (QFM-1.5 to QFM+1.0) reflective of heterogeneity in lithospheric fO2. Although some heterogeneity may indicate spatial variability in bulk mantle chemistry, it is likely that it is partly driven by metamorphic reactions as lithosphere cools or is reheated by a mantle plume. Increased temperature causes the (Mg,Fe)Al2O4 component of spinel to dissolve into pyroxene; this concentrates the magnetite component in spinel and increases fO2 [5]. We observed evidence of this reaction at the grain-scale. Spinels in spinel-cpx symplectites and rims of equant spinels are >1 log unit more oxidized and have lower Al2O3 concentrations than interiors of the equant spinels. These results indicate that fO2 of the oceanic lithosphere is affected by subsolidus metamorphic reactions, which must be considered when relating fO2 of peridotites to fO2 of the convecting upper mantle. [1] Pearce et al. 2000, CMP; [2] Bryndzia and Wood 1990, AJS; [3] Bézos and Humler 2005, GCA; [4] Cottrell and Kelley 2011, EPSL; [5] Canil and O'Neill 1996, JPet

Stabilization of a supersaturated solution of mefenamic acid from a solid dispersion with EUDRAGIT(®) EPO.

PubMed

Kojima, Taro; Higashi, Kenjirou; Suzuki, Toyofumi; Tomono, Kazuo; Moribe, Kunikazu; Yamamoto, Keiji

2012-10-01

The stabilization mechanism of a supersaturated solution of mefenamic acid (MFA) from a solid dispersion with EUDRAGIT(®) EPO (EPO) was investigated. The solid dispersions were prepared by cryogenic grinding method. Powder X-ray diffractometry, in vitro dissolution test, in vivo oral absorption study, infrared spectroscopy, and solid- and solution-state NMR spectroscopies were used to characterize the solid dispersions. Dissolution tests in acetate buffer (pH 5.5) revealed that solid dispersion showed > 200-fold higher concentration of MFA. Supersaturated solution was stable over 1 month and exhibited improved oral bioavailability of MFA in rats, with a 7.8-fold higher area under the plasma concentration-versus-time curve. Solid-state (1)H spin-lattice relaxation time (T(1)) measurement showed that MFA was almost monomolecularly dispersed in the EPO polymer matrix. Intermolecular interaction between MFA and EPO was indicated by solid-state infrared and (13)C-T(1) measurements. Solution-state (1)H-NMR measurement demonstrated that MFA existed in monomolecular state in supersaturated solution. (1)H-T(1) and difference nuclear Overhauser effect measurements indicated that cross relaxation occurred between MFA and EPO due to the small distance between them. The formation and high stability of the supersaturated solution were attributable to the specifically formed intermolecular interactions between MFA and EPO.

Silicon nitride equation of state

NASA Astrophysics Data System (ADS)

Brown, Robert C.; Swaminathan, Pazhayannur K.

2017-01-01

This report presents the development of a global, multi-phase equation of state (EOS) for the ceramic silicon nitride (Si3N4).1 Structural forms include amorphous silicon nitride normally used as a thin film and three crystalline polymorphs. Crystalline phases include hexagonal α-Si3N4, hexagonal β-Si3N4, and the cubic spinel c-Si3N4. Decomposition at about 1900 °C results in a liquid silicon phase and gas phase products such as molecular nitrogen, atomic nitrogen, and atomic silicon. The silicon nitride EOS was developed using EOSPro which is a new and extended version of the PANDA II code. Both codes are valuable tools and have been used successfully for a variety of material classes. Both PANDA II and EOSPro can generate a tabular EOS that can be used in conjunction with hydrocodes. The paper describes the development efforts for the component solid phases and presents results obtained using the EOSPro phase transition model to investigate the solid-solid phase transitions in relation to the available shock data that have indicated a complex and slow time dependent phase change to the c-Si3N4 phase. Furthermore, the EOSPro mixture model is used to develop a model for the decomposition products; however, the need for a kinetic approach is suggested to combine with the single component solid models to simulate and further investigate the global phase coexistences.

Thermodynamics of magnesian calcite solid-solutions at 25°C and 1 atm total pressure

USGS Publications Warehouse

Busenberg, Eurybiades; Plummer, Niel

1989-01-01

The stability of magnesian calcites was reexamined, and new results are presented for 28 natural inorganic, 12 biogenic, and 32 synthetic magnesian calcites. The magnesian calcite solid-solutions were separated into two groups on the basis of differences in stoichiometric solubility and other physical and chemical properties. Group I consists of solids of mainly metamorphic and hydrothermal origin, synthetic calcites prepared at high temperatures and pressures, and synthetic solids prepared at low temperature and very low calcite supersaturations () from artificial sea water or NaClMgCl2CaCl2solutions. Group I solids are essentially binary s of CaCO2 and MgCO2, and are thought to be relatively free of structural defects. Group II solid-solutions are of either biogenic origin or are synthetic magnesian calcites and protodolomites (0–20 and ∼ 45 mole percent MgCO3) prepared at high calcite supersaturations () from NaClNa2SO4MgCl2CaCl2 or NaClMgCl2CaCl2 solutions. Group II solid-solutions are treated as massively defective solids. The defects include substitution foreign ions (Na+ and SO42−) in the magnesian calcite lattice (point defects) and dislocations (~2 · 109 cm−2). Within each group, the excess free energy of mixing, GE, is described by the mixing model , where x is the mole fraction of the end-member Ca0.5Mg0.5CO3 in the solid-solution. The values of A0and A1 for Group I and II solids were evaluated at 25°C. The equilibrium constants of all the solids are closely described by the equation ln , where KC and KD are the equilibrium constants of calcite and Ca0.5Mg0.5CO3. Group I magnesian calcites were modeled as sub-regular solid-solutions between calcite and dolomite, and between calcite and “disordered dolomite”. Both models yield almost identical equilibrium constants for these magnesian calcites. The Group II magnesian calcites were modeled as sub-regular solid-solutions between defective calcite and protodolomite. Group I and II solid-solutions differ significantly in stability. The rate of crystal growth and the chemical composition of the aqueous solutions from which the solids were formed are the main factors controlling stoichiometric solubility of the magnesian calcites and the density of crystal defects. The literature on the occurrence and behavior of magnesian calcites in sea water and other aqueous solutions is also examined.

Sustainable synthesis of monodispersed spinel nano-ferrites

EPA Science Inventory

A sustainable approach for the synthesis of various monodispersed spinel ferrite nanoparticles has been developed that occurs at water-toluene interface under both conventional and microwave hydrothermal conditions. This general synthesis procedure utilizes readily available and ...

Origin of Spinel Framboids in Calcium-Aluminum-Rich Inclusions

NASA Astrophysics Data System (ADS)

Yoshizaki, T.; Nakashima, D.; Nakamura, T.; Ishida, H.; Sakamoto, N.

2017-07-01

Mineralogical, petrological and O-isotopic study of a CV CAI suggests that spinel framboids in the CAI were originally mini-CAIs that condensed separately under different conditions and subsequently aggregated to form the inclusion.

Spinel cataclasites in 15445 and 72435 - Petrology and criteria for equilibrium

NASA Technical Reports Server (NTRS)

Baker, M. B.; Herzberg, C. T.

1980-01-01

The problem of establishing the existence of equilibrium among the coexisting phases in the rock is addressed by presenting petrographic and mineral chemistry data on a new spinel cataclasite from 15445 (clast H) and data more extensive than those previously available on two clasts in 72435. Criteria useful in reconstructing the original petrology of these and other spinel cataclasites are analyzed by considering equilibrium among the different phases, that is, the mono- or polymict nature of these cataclasized samples. Finally, the role of impact processes in disturbing the equilibria is discussed.

Single crystals of metal solid solutions

NASA Technical Reports Server (NTRS)

Miller, J. F.; Austin, A. E.; Richard, N.; Griesenauer, N. M.; Moak, D. P.; Mehrabian, M. R.; Gelles, S. H.

1974-01-01

The following definitions were sought in the research on single crystals of metal solid solutions: (1) the influence of convection and/or gravity present during crystallization on the substructure of a metal solid solution; (2) the influence of a magnetic field applied during crystallization on the substructure of a metal solid solution; and (3) requirements for a space flight experiment to verify the results. Growth conditions for the selected silver-zinc alloy system are described, along with pertinent technical and experimental details of the project.

Solid-state and solution /sup 13/C NMR in the conformational analysis of methadone-hydrochloride and related narcotic analgesics

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

Sumner, S.C.J.

1986-01-01

Solid state and solution /sup 13/C NMR have been used to study the conformations of the racemic mixtures and single enantiomers of methadone hydrochloride, alpha and beta methadol hydrochloride, and alpha and beta acetylmethadol hydrochloride. The NMR spectra acquired for the compounds as solids, and in polar and nonpolar solvents are compared, in order to determine the conformation of the molecules in solution. To determine the reliability of assigning solution conformations by comparing solution and solid state chemical shift data, three bond coupling constants measured in solution are compared with those calculated from X-ray data. The conformations of the racemicmore » mixture and plus enantiomer of methadone hydrochloride have been shown to be very similar in the solid state, where minor differences in conformation can be seen by comparing NMR spectra obtained for the solids. Also shown is that the molecules of methadone hydrochloride have conformations in polar and in nonpolar solvents which are very similar to the conformation of the molecules in the solid state.« less

MgAl{sub 2}O{sub 4}(001) based magnetic tunnel junctions made by direct sputtering of a sintered spinel target

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

Belmoubarik, Mohamed; Sukegawa, Hiroaki, E-mail: sukegawa.hiroaki@nims.go.jp; Ohkubo, Tadakatsu

We developed a fabrication process of an epitaxial MgAl{sub 2}O{sub 4} barrier for magnetic tunnel junctions (MTJs) using a direct sputtering method from an MgAl{sub 2}O{sub 4} spinel sintered target. Annealing the sputter-deposited MgAl{sub 2}O{sub 4} layer sandwiched between Fe electrodes led to the formation of a (001)-oriented cation-disorder spinel with atomically sharp interfaces and lattice-matching with the Fe electrodes. A large tunnel magnetoresistance ratio up to 245% at 297 K (436% at 3 K) was achieved in the Fe/MgAl{sub 2}O{sub 4}/Fe(001) MTJ as well as an excellent bias voltage dependence. These results indicate that the direct sputtering is an alternative methodmore » for the realization of high performance MTJs with a spinel-based tunnel barrier.« less

Amphibole and hercynite spinel in Shergotty and Zagami Magmatic water, depth of crystallization, and metasomatism

NASA Technical Reports Server (NTRS)

Treiman, A. H.

1985-01-01

Amphibole and spinel occur in the Shergotty and Zagami meteorites only in magmatic inclusions in pigeonite. The trapped magma is essentially identical to the parental magmas for Shergotty and Zagami. The amphibole is a kaersutite with minimal halogen content; by inference, it must have been hydrous. If so, the Shergotty and Zagami melts contained at least 0.2 wt pct H2O and were probably H2O-undersaturated. Pressures in excess of 1 kilobar seem necessary for the formation of amphibole. Spinel replaces magnetite in the inclusions, and olivine replaces magnetite elsewhere in the meteorites. To stabilize spinel, the melt in the inclusions must have become enriched in Al during fractionation, possibly because the small volume of the inclusions made nucleation of plagioclase unlikely. Pervasive replacement of magnetite through reduction reactions suggests that Shergotty and Zagami interacted with hydrogen-rich fluids during their cooling.

Opposite correlations between cation disordering and amorphization resistance in spinels versus pyrochlores

DOE PAGES

Uberuaga, Blas Pedro; Tang, Ming; Jiang, Chao; ...

2015-10-29

Understanding and predicting radiation damage evolution in complex materials is crucial for developing next-generation nuclear energy sources. Here, using a combination of ion beam irradiation, transmission electron microscopy and X-ray diffraction, we show that, contrary to the behaviour observed in pyrochlores, the amorphization resistance of spinel compounds correlates directly with the energy to disorder the structure. Using a combination of atomistic simulation techniques, we ascribe this behaviour to structural defects on the cation sublattice that are present in spinel but not in pyrochlore. Specifically, because of these structural defects, there are kinetic pathways for the relaxation of disorder in spinelmore » that are absent in pyrochlore. This leads to a direct correlation between amorphization resistance and disordering energetics in spinel, the opposite of that observed in pyrochlores. Furthermore, these results provide new insight into the origins of amorphization resistance in complex oxides beyond fluorite derivatives.« less

Post-irradiation examinations of THERMHET composite fuels for transmutation

NASA Astrophysics Data System (ADS)

Noirot, J.; Desgranges, L.; Chauvin, N.; Georgenthum, V.

2003-07-01

The thermal behaviour of composite targets dedicated to minor actinide transmutation was studied using THERMHET (thermal behaviour of heterogeneous fuel) irradiation in the SILOE reactor. Three inert matrix fuel designs were tested (macro-mass, jingle and microdispersion) all with a MgAl 2O 4 spinel inert matrix and around 40% weight of UO 2 to simulate minor actinide inclusions. The post-irradiation examinations led to a new interpretation of the temperature measurement by thermocouples located in the central hole of the pellets. A major change in the micro-dispersed structure was detected. The examinations enabled us to understand the behaviour of the spinel during the different stages of irradiation. They revealed an amorphisation at low temperature and then a nano re-crystallisation at high temperature of the spinel in the micro-dispersed case. These results, together with those obtained in the MATINA irradiation of an equivalent structure, show the importance of the irradiation temperature on spinel behaviour.

Zoned Cr, Fe-spinel from the La Perouse layered gabbro, Fairweather Range, Alaska

USGS Publications Warehouse

Czamanske, G.K.; Himmelberg, G.R.; Goff, F.E.

1976-01-01

Zoned spinel of unusual composition and morphology has been found in massive pyrrhotite-chalcopyrite-pent-landite ore from the La Perouse layered gabbro intrusion in the Fairweather Range, southeastern Alaska. The spinel grains show continuous zoning from cores with up to 53 wt.% Cr2O3 to rims with less than 11 wt.% Cr2O3. Their composition is exceptional because they contain less than 0.32 wt.% MgO and less than 0.10 wt.% Al2O3 and TiO2. Also notable are the concentrations of MnO and V2O3, which reach 4.73 and 4.50 wt.%, respectively, in the cores. The spinel is thought to have crystallized at low oxygen fugacity and at temperatures above 900??C, directly from a sulfide melt that separated by immiscibility from the gabbroic parental magma. ?? 1976.

Alteration of Al-rich inclusions inside amoeboid olivine aggregates in the Allende meteorite

NASA Technical Reports Server (NTRS)

Hashimoto, Akihiko; Grossman, Lawrence

1987-01-01

The primary phases of Al-rich inclusions in amoeboid olivine aggregates have undergone alteration reactions with the solar nebular gas. The simplest interpretation of the present observations is that melilite was the first primary phase to disappear with falling temperature, and was replaced by grossular + anorthite + feldspathoids, followed by fassaite; spinel was the last phase to be altered. Thermodynamic calculations suggest that Na-rich phlogopite could have formed at about 470 K and chlorite at about 328 K at a water fugacity of 0.000001, which is that of a gas of solar composition in this temperature range. The olivine around Al-rich inclusions is not serpentized, indicating the cessation of gas-solid equilibrium above 274 K.

Ab initio investigation of the thermodynamics of cation distribution and of the electronic and magnetic structures in the LiMn2O4 spinel

NASA Astrophysics Data System (ADS)

Santos-Carballal, David; Ngoepe, Phuti E.; de Leeuw, Nora H.

2018-02-01

The spinel-structured lithium manganese oxide (LiMn2O4 ) is a material currently used as cathode for secondary lithium-ion batteries, but whose properties are not yet fully understood. Here, we report a computational investigation of the inversion thermodynamics and electronic behavior of LiMn2O4 derived from spin-polarized density functional theory calculations with a Hubbard Hamiltonian and long-range dispersion corrections (DFT+U-D3). Based on the analysis of the configurational free energy, we have elucidated a partially inverse equilibrium cation distribution for the LiMn2O4 spinel. This equilibrium degree of inversion is rationalized in terms of the crystal field stabilization effects and the difference between the size of the cations. We compare the atomic charges with the oxidation numbers for each degree of inversion. We found segregation of the Mn charge once these ions occupy the tetrahedral and octahedral sites of the spinel. We have obtained the atomic projections of the electronic band structure and density of states, showing that the normal LiMn2O4 has half-metallic properties, while the fully inverse spinel is an insulator. This material is in the ferrimagnetic state for the inverse and partially inverse cation arrangement. The optimized lattice and oxygen parameters, as well as the equilibrium degree of inversion, are in agreement with the available experimental data. The partial equilibrium degree of inversion is important in the interpretation of the lithium ion migration and surface properties of the LiMn2O4 spinel.

Effect of zinc-borate glass addition on the thermal properties of the cordierite/Al2O3 composites containing nano-sized spinel crystal.

PubMed

Jo, Sinae; Kang, Seunggu

2013-11-01

Low-melting zinc-borate glass was added to the cordierite/Al2O3 composite in order to improve the sintering facility of Al2O3 and formation of nano-sized spinel crystal of high thermal conductivity. Increasing the ZnO/B2O3 ratio in the zinc-borate glass increased the ZnAl2O4 spinel and decreased the Al4B2O9 crystal peak intensities in X-ray diffraction pattern. The XRD peak intensities of the ZnAl2O4 spinel and Al4B2O9 crystals in the specimen containing 10 wt% zinc-borate glass (10G series) are higher than that of the specimen containing 5 wt% zinc-borate glass (5G series). The microstructures of most 10G series specimens had the flower-shaped crystal which was composed of 50 nm wide and 250 nm long needle-like crystals and identified as ZnAl2O4 spinel phase. The thermal conductivity of the 10G series specimen was higher than that of the 5G series in any ZnO/B2O3 ratio due to the formation of plenty of nano-sized ZnAl2O4 spinel of high thermal conductivity. Particularly, the thermal conductivity of the cordierite/Al2O3 composite containing 10 wt% zinc-borate glass of ZnO/B2O3 weight ratio = 1.5 was 3.8 W/Km which is much higher than that of the published value (3.0 W/Km).

Thermodynamic Study of Solid-Liquid Equilibrium in NaCl-NaBr-H2O System at 288.15 K

NASA Astrophysics Data System (ADS)

Li, Dan; Meng, Ling-zong; Deng, Tian-long; Guo, Ya-fei; Fu, Qing-Tao

2018-06-01

The solubility data, composition of the solid solution and refractive indices of the NaCl-NaBr-H2O system at 288.15 K were studied with the isothermal equilibrium dissolution method. The solubility diagram and refractive index diagram of this system were plotted at 288.15 K. The solubility diagram consists of two crystallization zones for solid solution Na(Cl,Br) · 2H2O and Na(Cl,Br), one invariant points cosaturated with two solid solution and two univariant solubility isothermal curves. On the basis of Pitzer and Harvie-Weare (HW) chemical models, the composition equations and solubility equilibrium constant equations of the solid solutions at 288.15 K were acquired using the solubility data, the composition of solid solutions, and binary Pitzer parameters. The solubilities calculated using the new method combining the equations are in good agreement with the experimental data.

Nature of the impactor at the K/T boundary: clues from Os, W and Cr isotopes.

NASA Astrophysics Data System (ADS)

Quitté, G.; Robin, E.; Capmas, F.; Levasseur, S.; Rocchia, R.; Birck, J. L.; Allègre, C. J.

2003-04-01

We measured the isotope composition of Os, W and Cr in K/T boundary sediments of three marine sites (Stevns Klint, Caravaca and Bidart) to determine the nature of the bolid that impacted the Earth 65 Myrs ago. We also analysed Ni-rich cosmic spinels, because they are thought to keep the signature of the impactor. The low REE content in spinels precludes indeed the hypothesis of a mixing with more than 10% of terrestrial material. The Os and W enrichment at the K/T boundary could be explained by a scavenging of chalcophile elements at the time of sulfide precipitation. The 187Os/186Os ratio of the K/T sediments is higher than the ratio of any kind of meteorites. On top of a possible mixing with surrounding sediments, we suggest that the boundary contained more Re in the past (lost since that time by alteration and oxidation) and that the Os isotope ratio is in fact disturbed. On each of the three sites, the boundary itself does not present any tungsten isotopic anomaly. The most likely interpretation is that the extraterrestrial material is diluted enough into the sediments so that the isotopic signature has been erased. Spinels show a small deficit of (0.34±0.9) ɛ in 182W. The large error bar precludes any clear conclusion whether or not a meteoritic signature is really present. If the spinels really carry an extraterrestrial signature as expected, their W composition is in favour of an ordinary chondrite. All K/T samples (sediments and spinels) are apparently depleted in 53Cr by about 0.5 ɛ (after renormalization of 54Cr to the terrestrial value) whereas ordinary chondrites display an excess of about 0.5 ɛ. Among meteorites, only carbonaceous chondrites present a negative value for the 53Cr/52Cr ratio relative to the terrestrial value. As more than 90% of the Cr present in spinels is of extraterrestrial origin, the Cr isotopes unambiguously show that the K/T impactor was a carbonaceous chondrite. These isotopic results also confirm the extraterrestrial origin of spinels. The W isotope composition of the spinels does not fully agree with the conclusion of a carbonaceous chondrite, but a refined measurement is required to discuss this discrepancy in more details.

Synthesis of GaN:ZnO solid solution by solution combustion method and characterization for photocatalytic application

NASA Astrophysics Data System (ADS)

Menon, Sumithra Sivadas; Anitha, R.; Gupta, Bhavana; Baskar, K.; Singh, Shubra

2016-05-01

GaN-ZnO solid solution has emerged as a successful and reproducible photocatalyst for overall water splitting by one-step photoexcitation, with a bandgap in visible region. When the solid solution is formed, some of the Zn and O ions are replaced by Ga and N ions respectively and there is a narrowing of bandgap which is hypothesized as due to Zn3d-N2p repulsion. The traditional method of synthesis of GaN-ZnO solid solution is by nitridation of the starting oxides under constant ammonia flow. Here we report a solution combustion technique for the synthesis of the solid solution at a temperature about 500 ° C in a muffle furnace with metal nitrates as precursors and urea as the fuel. The as prepared samples showed change in color with the increased concentration of ZnO in the solution. The structural, microstructural, morphological and optical properties of the samples were realized by Powder X ray diffraction, Scanning electron microscopy, Energy dispersive X ray analysis, Transmission electron microscopy and Photoluminescence. Finally the hydrogen production efficiency of the GaN-ZnO nanopowders by water splitting was found, using methanol as a scavenger. The apparent quantum yield (AQY) of 0.048% is obtained for GaN-ZnO solid solution.

Ion mobility and conductivity in the M{sub 0.5–x}Pb{sub x}Bi{sub 0.5}F{sub 2+x} (M=K, Rb) solid solutions with fluorite structure

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

Kavun, V. Ya., E-mail: kavun@ich.dvo.ru; Uvarov, N.F.; Slobodyuk, A.B.

Ionic mobility and conductivity in the K{sub 0.5–x}Pb{sub x}Bi{sub 0.5}F{sub 2+x} and Rb{sub 0.5–x}Pb{sub x}Bi{sub 0.5}F{sub 2+x} (x=0.05, 0.09) solid solutions with the fluorite structure have been investigated using the methods of {sup 19}F NMR, X-ray diffraction and impedance spectroscopy. Types of ionic motions in the fluoride sublattice of solid solutions have been established and temperature ranges of their realization have been determined (150–450 K). Diffusion of fluoride ions is a dominating type of ionic motions in the fluoride sublattice of solid solutions under study above 350 K. Due to high ionic conductivity, above 10{sup –3} S/cm at 450 K,more » these solid solutions can be used as solid electrolytes in various electrochemical devices and systems. - Graphical abstract: Temperature dependence of the concentration of mobile (2, 4) and immobile (1, 3) F ions in the K{sub 0.5–x}Pb{sub x}Bi{sub 0.5}F{sub 2+x} solid solutions. - Highlights: • Studied the ion mobility, conductivity in M{sub 0.5–x}Pb{sub x}Bi{sub 0.5}F{sub 2+x} solid solutions (M=K, Rb). • An analysis of {sup 19}F NMR spectra made it possible to identify types of ion mobility. • The main type of ion motion above 300 K in solid solutions is a diffusion of ions F{sup –}. • The ionic conductivity of the solid solutions studied more than 10{sup –3} S/cm at 450 K.« less

An added-mass partition algorithm for fluid–structure interactions of compressible fluids and nonlinear solids

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

Banks, J.W., E-mail: banksj3@rpi.edu; Henshaw, W.D., E-mail: henshw@rpi.edu; Kapila, A.K., E-mail: kapila@rpi.edu

We describe an added-mass partitioned (AMP) algorithm for solving fluid–structure interaction (FSI) problems involving inviscid compressible fluids interacting with nonlinear solids that undergo large rotations and displacements. The computational approach is a mixed Eulerian–Lagrangian scheme that makes use of deforming composite grids (DCG) to treat large changes in the geometry in an accurate, flexible, and robust manner. The current work extends the AMP algorithm developed in Banks et al. [1] for linearly elasticity to the case of nonlinear solids. To ensure stability for the case of light solids, the new AMP algorithm embeds an approximate solution of a nonlinear fluid–solidmore » Riemann (FSR) problem into the interface treatment. The solution to the FSR problem is derived and shown to be of a similar form to that derived for linear solids: the state on the interface being fundamentally an impedance-weighted average of the fluid and solid states. Numerical simulations demonstrate that the AMP algorithm is stable even for light solids when added-mass effects are large. The accuracy and stability of the AMP scheme is verified by comparison to an exact solution using the method of analytical solutions and to a semi-analytical solution that is obtained for a rotating solid disk immersed in a fluid. The scheme is applied to the simulation of a planar shock impacting a light elliptical-shaped solid, and comparisons are made between solutions of the FSI problem for a neo-Hookean solid, a linearly elastic solid, and a rigid solid. The ability of the approach to handle large deformations is demonstrated for a problem of a high-speed flow past a light, thin, and flexible solid beam.« less

Investigation of compositional segregation during unidirectional solidification of solid solution semiconducting alloys

NASA Technical Reports Server (NTRS)

Wang, J. C.

1982-01-01

Compositional segregation of solid solution semiconducting alloys in the radial direction during unidirectional solidification was investigated by calculating the effect of a curved solid liquid interface on solute concentration at the interface on the solid. The formulation is similar to that given by Coriell, Boisvert, Rehm, and Sekerka except that a more realistic cylindrical coordinate system which is moving with the interface is used. Analytical results were obtained for very small and very large values of beta with beta = VR/D, where V is the velocity of solidification, R the radius of the specimen, and D the diffusivity of solute in the liquid. For both very small and very large beta, the solute concentration at the interface in the solid C(si) approaches C(o) (original solute concentration) i.e., the deviation is minimal. The maximum deviation of C(si) from C(o) occurs for some intermediate value of beta.

Calcium-aluminum-rich inclusions recycled during formation of porphyritic chondrules from CH carbonaceous chondrites

NASA Astrophysics Data System (ADS)

Krot, Alexander N.; Nagashima, Kazuhide; van Kooten, Elishevah M. M.; Bizzarro, Martin

2017-03-01

We report on the mineralogy, petrography, and O-isotope compositions of ∼60 Ca, Al-rich inclusions (CAIs) incompletely melted during formation of porphyritic chondrules from the CH metal-rich carbonaceous chondrites and Isheyevo (CH/CB). These include (i) relict polymineralic CAIs in porphyritic chondrules, (ii) CAIs surrounded by chondrule-like igneous rims, (iii) igneous pyroxene-rich and Type C-like CAIs, and (iv) plagioclase-rich chondrules with clusters of relict spinel grains. 26Al-26Mg systematics were measured in 10 relict CAIs and 11 CAI-bearing plagioclase-rich chondrules. Based on the mineralogy, the CH CAIs incompletely melted during chondrule formation can be divided into grossite-rich (n = 13), hibonite-rich (n = 11), spinel ± melilite-rich (n = 33; these include plagioclase-rich chondrules with clusters of relict spinel grains) types. Mineralogical observations indicate that these CAIs were mixed with different proportions of ferromagnesian silicates and experienced incomplete melting and gas-melt interaction during chondrule formation. These processes resulted in partial or complete destruction of the CAI Wark-Lovering rims, replacement of melilite by Na-bearing plagioclase, and dissolution and overgrowth of nearly end-member spinel by chromium- and iron-bearing spinel. Only two relict CAIs and two CAI-bearing chondrules show resolvable excess of radiogenic 26Mg; the inferred initial 26Al/27Al ratios are (1.7 ± 1.3) × 10-6, (3.7 ± 3.1) × 10-7, (1.9 ± 0.9) × 10-6 and (4.9 ± 2.6) × 10-6. There is a large range of Δ17O among the CH CAIs incompletely melted during chondrule formation, from ∼-37‰ to ∼-5‰; the unmelted minerals in individual CAIs, however, are isotopically uniform and systematically 16O-enriched relative to the host chondrules and chondrule-like igneous rims, which have Δ17O ranging from ∼-7‰ to ∼+4‰. Most of the CH CAIs incompletely melted during chondrule formation are mineralogically and isotopically similar to the CH CAIs surrounded by Wark-Lovering rims and apparently unaffected by chondrule melting. The mineralogy and O-isotope compositions of the CH CAI-bearing chondrules are similar to those of the CH porphyritic chondrules without relict CAIs. We conclude that CH porphyritic chondrules formed by incomplete melting of isotopically diverse solid precursors, including mineralogically and isotopically unique CAIs commonly observed only in CH chondrites. Therefore, the CH porphyritic chondrules must have formed in a distinct disk region, where the CH CAIs were present at the time of chondrule formation. Because most CH CAIs avoided chondrule melting, we infer that chondrule formation was highly localized. These observations preclude formation of CH porphyritic chondrules by splashing of molten planetesimals, by impact processing of differentiated planetesimals, and by large scale nebular shocks, e.g., shocks driven by disk gravitational instabilities or by X-ray flares. Instead, they are consistent with small-scale chondrule-forming mechanisms proposed in the literature, such as nebular processing of dust balls by bow shocks and by current sheets.

Process for recovering chaotropic anions from an aqueous solution also containing other ions

DOEpatents

Rogers, Robin; Horwitz, E. Philip; Bond, Andrew H.

1999-01-01

A solid/liquid process for the separation and recovery of chaotropic anions from an aqueous solution is disclosed. The solid support comprises separation particles having surface-bonded poly(ethylene glycol) groups, whereas the aqueous solution from which the chaotropic anions are separated contains a poly(ethylene glycol) liquid/liquid biphase-forming amount of a dissolved salt (lyotrope). A solid/liquid phase admixture of separation particles containing bound chaotropic anions in such an aqueous solution is also contemplated, as is a chromatography apparatus containing that solid/liquid phase admixture.

Process for recovering chaotropic anions from an aqueous solution also containing other ions

DOEpatents

Rogers, R.; Horwitz, E.P.; Bond, A.H.

1999-03-30

A solid/liquid process for the separation and recovery of chaotropic anions from an aqueous solution is disclosed. The solid support comprises separation particles having surface-bonded poly(ethylene glycol) groups, whereas the aqueous solution from which the chaotropic anions are separated contains a poly(ethylene glycol) liquid/liquid biphase-forming amount of a dissolved salt (lyotrope). A solid/liquid phase admixture of separation particles containing bound chaotropic anions in such an aqueous solution is also contemplated, as is a chromatography apparatus containing that solid/liquid phase admixture. 19 figs.

Role of lattice distortion on diffuse phase transition temperatures in Bi0.5Na0.5TiO3-BaTiO3 [BNBTO] solid solutions

NASA Astrophysics Data System (ADS)

Pradhan, Lagen Kumar; Pandey, Rabichandra; Kumar, Sunil; Supriya, Sweety; Kar, Manoranjan

2018-04-01

Effect of lattice distortion on diffuse phase transition in BNBTO solid solutions near Morphotropic phase boundary (MPB) has been investigated. Solid solutions of (Bi0.5Na0.5)1-xBaxTiO3 (with mole % of x= 0.04, 0.05, 0.06, 0.07 and 0.08) were prepared by the planetary ball mill method in ethanol medium. Rietveld refinement technique with rhombohedral (R3c) and tetragonal (P4bm) crystal symmetry has been employed for structural as well as phase analysis of the solid solutions. Both rhombohedral and tetragonal lattice distortion (c/a) tends toward the pseudo-cubic crystal symmetry with the increase of mole fraction of Ba2+ near MPB (x= 6 mole %). Also, the average crystallite size and grain size decrease with increase of mole fraction of Ba2+ in BNT ceramic are due to larger ionic radius of Ba2+ and grain boundary pinning process in the solid solutions respectively. Additionally, depolarization temperature (Td) and maximum temperature (Tm) reduces due to the lattice distortion of both the phases in BNBTO solid solutions, which is explained extensively. Significant increase of dielectric constant has been observed near MPB composition (x=6%) in BNBTO solid solutions.

Structural characteristics and sorption properties of lithium-selective composite materials based on TiO2 and MnO2

NASA Astrophysics Data System (ADS)

Chaban, M. O.; Rozhdestvenska, L. M.; Palchyk, O. V.; Dzyazko, Y. S.; Dzyazko, O. G.

2018-04-01

A number of nanomaterials containing titanium dioxide and manganese dioxide were synthesized. The effect of synthesis conditions on structural and sorption characteristics for the selective extraction of lithium ions from solutions was studied. The ion-exchange materials were investigated with the methods of electron microscopy, thermogravimetric and X-ray analyses. During thermal synthesis phases of lithium manganese titanium spinel and TiO2 are being formed. Replacing a part of manganese with titanium ions leads to a decrease in the dissolution of Mn and to an increase in chemical stability. Composites with optimal values of selectivity and sorption rates were used to remove lithium ions from solutions with high salt background. The recovery degree of lithium ions under dynamic conditions reached 99%, the highest sorption capacity was found at pH 10.

Preparation of Sic/AIN Solid Solutions Using Organometallic Precursors

DTIC Science & Technology

1989-02-15

pyrolysis of organoaluminum and organosilicon compounds was investigated as a potential source of SiC /AUI solid solutions. Using two different co... pyrolysis methods, homogeneous mixtures of organoaluminum amides and both a vinylic polysilane and a poly- carbosilane were convertec to a preceramic ...solid that transformed to crystalline SiC /AiN solid solutions at 򒸀 C. Moreover, the liquid, polymeric , form of these precursor mixtures provides a

Cation-substituted spinel oxide and oxyfluoride cathodes for lithium ion batteries

DOEpatents

Manthiram, Arumugam; Choi, Wongchang

2014-05-13

The present invention includes compositions and methods of making cation-substituted and fluorine-substituted spinel cathode compositions by firing a LiMn.sub.2-y-zLi.sub.yM.sub.zO.sub.4 oxide with NH.sub.4HF.sub.2 at low temperatures of between about 300 and 700.degree. C. for 2 to 8 hours and a .eta. of more than 0 and less than about 0.50, mixed two-phase compositions consisting of a spinel cathode and a layered oxide cathode, and coupling them with unmodified or surface modified graphite anodes in lithium ion cells.

Flexure Strength and Optical Transparency of Magnesium-Aluminate Spinel (MgAlO4): Influence of Polishing and Glass Coating

DTIC Science & Technology

2016-12-01

resulting from the addition of a sodium aluminosilicate ( SiO2 -BaO- Na2O-B2O3-Al2O3) glass coating on coarse-grained transparent spinel having 3...MgAlO4): Influence of Polishing and Glass Coating by Steve M Kilczewski, Robert J Pavlacka, Jeffrey J Swab, Jane W Adams, and Jared C Wright...Magnesium–Aluminate Spinel (MgAlO4): Influence of Polishing and Glass Coating by Steve M Kilczewski and Jared C Wright TKC Global, Herndon, VA

Dielectric and impedance study of praseodymium substituted Mg-based spinel ferrites

NASA Astrophysics Data System (ADS)

Farid, Hafiz Muhammad Tahir; Ahmad, Ishtiaq; Ali, Irshad; Ramay, Shahid M.; Mahmood, Asif; Murtaza, G.

2017-07-01

Spinel ferrites with nominal composition MgPryFe2-yO4 (y = 0.00, 0.025, 0.05, 0.075, 0.10) were prepared by sol-gel method. Temperature dependent DC electrical conductivity and drift mobility were found in good agreement with each other, reflecting semiconducting behavior. The dielectric properties of all the samples as a function of frequency (1 MHz-3 GHz) were measured at room temperature. The dielectric constant and complex dielectric constant of these samples decreased with the increase of praseodymium concentration. In the present spinel ferrite, Cole-Cole plots were used to separate the grain and grain boundary's effects. The substitution of praseodymium ions in Mg-based spinel ferrites leads to a remarkable rise of grain boundary's resistance as compared to the grain's resistance. As both AC conductivity and Cole-Cole plots are the functions of concentration, they reveal the dominant contribution of grain boundaries in the conduction mechanism. AC activation energy was lower than dc activation energy. Temperature dependence normalized AC susceptibility of spinel ferrites reveals that MgFe2O4 exhibits multi domain (MD) structure with high Curie temperature while on substitution of praseodymium, MD to SD transitions occurs. The low values of conductivity and low dielectric loss make these materials best candidate for high frequency application.

Spinel and orthopyroxene exsolved from clinopyroxene in the Haladala pluton in the middle Tianshan (Xinjiang, China)

NASA Astrophysics Data System (ADS)

Zhu, Yongfeng; Chen, Jing; Xue, Yunxin; Feng, Wanyi; Jiang, Jiuyang

2017-12-01

The Haladala pluton, consisting of troctolite, olivine gabbro and gabbro with zircon SHRIMP U-Pb age of 309 ± 2 Ma (MSWD = 0.72), intruded the Devonian-Carboniferous arc segments in the middle Tianshan. Amphibole, coexisting with magnetite, amphibole, and phlogopite, crystallized in a magma chamber at depth of 20 km (6.9-7.4 kbar, 934-943 °C) based on various thermobaramoters. Two kinds of exsolution textures (spinel rods in clinopyroxene, orthopyroxene lamellae in clinopyroxene) occur in troctolite and olivine gabbro. We describe oriented spinel rods and orthopyroxene lamellae exsolved from the host clinopyroxene based on optical and high-resolution transmission electron microscope (HRTEM) observations. The spinel rods (100) are parallel to their host clinopyroxene (010). Orthopyroxene lamellae (010) are coherent and strictly parallel to their host clinopyroxene (010). Exsolution of spinel rods from the host clinopyroxene is controlled by the reaction of (Ca0.5M2+ 0.5)Fe3+[AlSiO6]in clinopyroxene → (Ca0.86-0.17M2+ 0.14-0.17)(M2 + 1.00-0.96Al0-0.04)[Al0.17-0.10Si1.83-1.90O6] + Fe3O4 + O2.

Challenges and approaches for high-voltage spinel lithium-ion batteries.

PubMed

Kim, Jung-Hyun; Pieczonka, Nicholas P W; Yang, Li

2014-07-21

Lithium-ion (Li-ion) batteries have been developed for electric vehicle (EV) applications, owing to their high energy density. Recent research and development efforts have been devoted to finding the next generation of cathode materials for Li-ion batteries to extend the driving distance of EVs and lower their cost. LiNi(0.5)Mn(1.5)O(4) (LNMO) high-voltage spinel is a promising candidate for a next-generation cathode material based on its high operating voltage (4.75 V vs. Li), potentially low material cost, and excellent rate capability. Over the last decade, much research effort has focused on achieving a fundamental understanding of the structure-property relationship in LNMO materials. Recent studies, however, demonstrated that the most critical barrier for the commercialization of high-voltage spinel Li-ion batteries is electrolyte decomposition and concurrent degradative reactions at electrode/electrolyte interfaces, which results in poor cycle life for LNMO/graphite full cells. Despite scattered reports addressing these processes in high-voltage spinel full cells, they have not been consolidated into a systematic review article. With this perspective, emphasis is placed herein on describing the challenges and the various approaches to mitigate electrolyte decomposition and other degradative reactions in high-voltage spinel cathodes in full cells. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Formation of Boundary Clinopyroxenes and Associated Glass Veins in Type B1 CAIs

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

Paque, J M; Beckett, J R; Ishii, H A

2008-05-18

We used focused ion beam thin section preparation and scanning transmission electron microscopy (FIB/STEM) to examine the interfacial region between spinel and host melilite for three spinel grains, two from the mantle and one from the core of an Allende type B1 inclusion, and a second pair of spinel grains from a type B1 inclusion from the Leoville carbonaceous chondrite. The compositions of boundary clinopyroxenes decorating spinel surfaces are generally consistent with those of coarser clinopyroxenes from the same region of the inclusion, suggesting little movement of spinels between mantle and core regions after the formation of boundary clinopyroxenes. Themore » host melilite displays no anomalous compositions near the interface, and anorthite or other late-stage minerals are not observed, suggesting that crystallization of residual liquid was not responsible for the formation of boundary clinopyroxenes. Allende spinels display either direct spinel-melilite contact or an intervening boundary clinopyroxene between the two phases. In the core, boundary clinopyroxene is mantled by a thin (1-2 {micro}m thick) layer of normally zoned (X{sub Ak} increasing away from the melilite-clinopyroxene contact) melilite with X{sub Ak} matching that of the host melilite at the melilite-melilite contact. In the mantle, X{sub Ak} near boundary spinels is constant. Spinels in a Leoville type B1 inclusion are more complex with boundary clinopyroxene, as observed in Allende, but also variable amounts of glass ({approx}1 {micro}m width), secondary calcite, perovskite, and an unknown Mg-, Al-, OH-rich and Ca-, Si-poor crystalline phase that may be a layered double hydrate. Glass compositions are consistent to first order with a precursor consisting mostly of Mg-carpholite or sudoite with some aluminous diopside. One possible scenario of formation for the glass veins is that open system alteration of melilite produced a porous, hydrated aggregate of Mg-carpholite or sudoite + aluminous diopside that was shock melted and quenched to a glass. The unknown crystalline phase may be a shocked remnant of the precursor phase assemblage but is more likely to have formed later by alteration of the glass. Calcite appears to be an opportunistic fracture filling that postdated all major shock events. Boundary clinopyroxenes probably share a common origin with coarser-grained pyroxenes from the same region of the inclusion. In the mantle, these crystals may represent clinopyroxene crystallized in Ti-rich liquids caused by the direct dissolution of perovskite and an associated Sc-Zr-rich phase or as a reaction product between dissolving perovskite and liquid (i.e., indirect dissolution of perovskite). In the core, any perovskite and associated Ti-enriched liquids that may have originally been present disappeared before the growth of boundary clinopyroxene.« less

The Homestead kimberlite, central Montana, USA: Mineralogy, xenocrysts, and upper-mantle xenoliths

USGS Publications Warehouse

Carter, Hearn B.

2004-01-01

The Homestead kimberlite was emplaced in lower Cretaceous marine shale and siltstone in the Grassrange area of central Montana. The Grassrange area includes aillikite, alnoite, carbonatite, kimberlite, and monchiquite and is situated within the Archean Wyoming craton. The kimberlite contains 25-30 modal% olivine as xenocrysts and phenocrysts in a matrix of phlogopite, monticellite, diopside, serpentine, chlorite, hydrous Ca-Al-Na silicates, perovskite, and spinel. The rock is kimberlite based on mineralogy, the presence of atoll-textured groundmass spinels, and kimberlitic core-rim zoning of groundmass spinels and groundmass phlogopites. Garnet xenocrysts are mainly Cr-pyropes, of which 2-12% are G10 compositions, crustal almandines are rare and eclogitic garnets are absent. Spinel xenocrysts have MgO and Cr2O3 contents ranging into the diamond inclusion field. Mg-ilmenite xenocrysts contain 7-11 wt.% MgO and 0.8-1.9 wt.% Cr2O3, with (Fe+3/Fetot) from 0.17-0.31. Olivine is the only obvious megacryst mineral present. One microdiamond was recovered from caustic fusion of a 45-kg sample. Upper-mantle xenoliths up to 70 cm size are abundant and are some of the largest known garnet peridotite xenoliths in North America. The xenolith suite is dominated by dunites, and harzburgites containing garnet and/or spinel. Granulites are rare and eclogites are absent. Among 153 xenoliths, 7% are lherzolites, 61% are harzburgites, 31% are dunites, and 1% are orthopyroxenites. Three of 30 peridotite xenoliths that were analysed are low-Ca garnet-spinel harzburgites containing G10 garnets. Xenolith textures are mainly coarse granular, and only 5% are porphyroclastic. Xenolith modal mineralogy and mineral compositions indicate ancient major-element depletion as observed in other Wyoming craton xenolith assemblages, followed by younger enrichment events evidenced by tectonized or undeformed veins of orthopyroxenite, clinopyroxenite, websterite, and the presence of phlogopite-bearing veins and disseminated phlogopite. Phlogopite-bearing veins may represent kimberlite-related addition and/or earlier K-metasomatism. Xenolith thermobarometry using published two-pyroxene and Al-in-opx methods suggest that garnet-spinel peridotites are derived from 1180 to 1390 ??C and 3.6 to 4.7 GPa, close to the diamond-graphite boundary and above a 38 mW/m2 shield geotherm. Low-Ca garnet-spinel harzburgites with G10 garnets fall in about the same T and P range. Most spinel peridotites with assumed 2.0 GPa pressure are in the same T range, possibly indicating heating of the shallow mantle. Four of 79 Cr diopside xenocrysts have P-T estimates in the diamond stability field using published single-pyroxene P-T calculation methods.

Étude par diffraction des rayons X de la nitruration plasma d'un acier 304L Influence sur l'oxydation à 1000 ^{circ}C

NASA Astrophysics Data System (ADS)

Marot, L.; Buscail, H.; Straboni, A.; Riffard, F.; Caudron, E.; Cueff, R.

2002-07-01

This work presents the influence of various nitridation parameters on the 304L steel oxidation at 1000 ^{circ}C, in air under atmospheric pressure. Nitridation temperatures were ranging between 300 ^{circ}C and 430 ^{circ}C with exposure times lasting from 2 to 8 hours. At 300 and 430 ^{circ}C, the nitridation treatment leads to the solid solution surface formation γ-N without any nitride formation. After oxidation at 1000 ^{circ}C of blank specimens, X ray diffraction reveals the FeCr2O4 spinel formation. This oxide does not act as a good diffusion barrier. With nitrogen treated specimens, the higher the nitridation temperature is and the longer the exposure time is, better is the oxidation behaviour at 1000 ^{circ}C. We then observe that the Cr{1,3}Fe{0,7}O3 oxide is more present in the oxide sale from the very beginning of the oxidation test which is correlated to a final lower mass gain. Cette étude porte sur l'influence des paramètres de nitruration plasma sur l'oxydation de l'acier 304L à 1000 ^{circ}C, sous air, à la pression atmosphérique. Les températures employées lors de la nitruration ont été de 300 ^{circ}C et 430 ^{circ}C pour des durées de nitruration variant entre 2 et 8 heures. A 300 et 430 ^{circ}C, la nitruration conduit à la formation d'une solution solide γ-N en surface sans provoquer la formation de nitrures. Après oxydation à 1000 ^{circ}C du 304L non nitruré, la diffraction des rayons X révèle la formation d'une couche de type spinelle FeCr2O4 qui ne semble pas jouer le rôle de barrière de diffusion. Pour les échantillons préalablement nitrurés, plus la température de nitruration est élevée et plus la durée du traitement est longue, meilleur est le comportement en oxydation. Nous observons alors l'oxyde Cr{1,3}Fe{0,7}O3 en proportion importante dès le début de l'oxydation et une prise de masse finale plus faible.

Synthesis of Zn1- x Co x Al2O4 Spinel Nanoparticles by Liquid-Feed Flame Spray Pyrolysis: Ceramic Pigments Application

NASA Astrophysics Data System (ADS)

Betancur Granados, Natalia; Yi, Eongyu; Laine, Richard M.; Restrepo Baena, Oscar Jaime

2016-01-01

Zn1- x Co x Al2O4 ( x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) spinel nanoparticles were synthesized by a liquid-feed flame spray pyrolysis (LF-FSP) method by combusting metallorganic precursor solutions to produce nanopowders with precise composition control. The precursor solutions were aerosolized into a methane/oxygen flame where it was combusted in an oxygen-rich environment to result in nanopowders at a single step. The nanopowders were analyzed by x-ray diffraction, Fourier transform infrared spectroscopy, colorimetry, field emission scanning electron microscopy, transmission electron microscopy, and BET (Brunauer-Emmett-Teller) N2 adsorption. Results show formation of spherical nanopowders with specific surface areas of 42 m2/g to 50 m2/g, which correspond to average particle sizes of 26 nm to 31 nm. Single-phase materials were obtained with a high control of composition, which indicates that LF-FSP is an excellent method to produce mixed-metal oxides for applications in which powder homogeneity is crucial. The products were evaluated for ceramic pigment application, where the ratio of Zn to Co was gradually changed to observe the color change in the structure with the increase of cobalt concentration. The resulting pigments were calcined at 1200°C, which aimed to identify the color stability after a high-temperature process, whereby the colors were measured using the color space CIE L*a*b* under standardized light, D65. Finally, the powders were tested for ceramic decoration using transparent glazes and ceramic bodies. The application was carried out at 1250°C to evaluate the color performance after a decoration process.

Microwave hydrothermal-assisted preparation of novel spinel-NiFe2O4/natural mineral composites as microwave catalysts for degradation of aquatic organic pollutants.

PubMed

Shen, Manli; Fu, Lu; Tang, Jianhua; Liu, Mingyu; Song, Youtao; Tian, Fangyuan; Zhao, Zhigang; Zhang, Zhaohong; Dionysiou, Dionysios D

2018-05-15

In this study, novel spinel-NiFe 2 O 4 /natural mineral (sepiolite, diatomite and kaolinite) composites were developed using microwave (MW) hydrothermal method, and applied in MW-induced catalytic degradation (NiFe 2 O 4 /natural mineral/MW) of organic pollutants such as sodium dodecyl benzene sulfonate (SDBS), azo fuchsine (AF), methyl parathion (MP), and crystal violet (CVL) in solution. Catalytic activities of three NiFe 2 O 4 /natural mineral composites were compared. The effects of material synthesis process parameters such as molar ratios of NiFe 2 O 4 and natural mineral, and pH of precursor solutions for synthesizing catalysts, and degradation parameters such as MW irradiation time and catalyst reuse cycles were also investigated. The principle on NiFe 2 O 4 /natural mineral/MW degradation was provided. The results reveal that organic pollutants in wastewater can be removed completely using NiFe 2 O 4 /natural mineral/MW within minutes. NiFe 2 O 4 /sepiolite shows higher catalytic activity than the others. The calculated degradation rate constants are 1.865, 0.672, 0.472, and 0.329 min -1 for SDBS, AF, MP, and CVL, respectively, using NiFe 2 O 4 /sepiolite/MW system. The performance of NiFe 2 O 4 /natural mineral can be maintained for three reuse cycles. Active species OH, O 2 - , and h + play main roles in NiFe 2 O 4 /sepiolite/MW degradation. Hence, NiFe 2 O 4 /sepiolite/MW technology with rapid and cost-effective degradation, magnetic separation, and no secondary pollution, demonstrates to be promising in treating organic contaminants in wastewater. Copyright © 2018 Elsevier B.V. All rights reserved.

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

Rai, R.N., E-mail: rn_rai@yahoo.co.in; Kant, Shiva; Reddi, R.S.B.

Urea is an attractive material for frequency conversion of high power lasers to UV (for wavelength down to 190 nm), but its usage is hindered due to its hygroscopic nature, though there is no alternative organic NLO crystal which could be transparent up to 190 nm. The hygroscopic character of urea has been modified by making the solid solution (UCNB) of urea (U) and p-chloronitrobenzene (CNB). The formation of the solid solution of CNB in U is explained on the basis of phase diagram, powder XRD, FTIR, elemental analysis and single crystal XRD studies. The solubility of U, CNB andmore » UCNB in ethanol solution is evaluated at different temperatures. Transparent single crystals of UCNB are grown from its saturated solution in ethanol. Optical properties e.g., second harmonic generation (SHG), refractive index and the band gap for UCNB crystal were measured and their values were compared with the parent compounds. Besides modification in hygroscopic nature, UCNB has also shown the higher SHG signal and mechanical hardness in comparison to urea crystal. - Highlights: • The hygroscopic character of urea was modified by making the solid solution • Solid solution formation is support by elemental, powder- and single crystal XRD • Crystal of solid solution has higher SHG signal and mechanical stability. • Refractive index and band gap of solid solution crystal have determined.« less

Dissolution of aragonite-strontianite solid solutions in nonstoichiometric Sr (HCO3)2-Ca (HCO3)2-CO2-H2O solutions

USGS Publications Warehouse

Plummer, Niel; Busenberg, E.; Glynn, P.D.; Blum, A.E.

1992-01-01

Synthetic strontianite-aragonite solid-solution minerals were dissolved in CO2-saturated non-stoichiometric solutions of Sr(HCO3)2 and Ca(HCO3)2 at 25??C. The results show that none of the dissolution reactions reach thermodynamic equilibrium. Congruent dissolution in Ca(HCO3)2 solutions either attains or closely approaches stoichiometric saturation with respect to the dissolving solid. In Sr(HCO3)2 solutions the reactions usually become incongruent, precipitating a Sr-rich phase before reaching stoichiometric saturation. Dissolution of mechanical mixtures of solids approaches stoichiometric saturation with respect to the least stable solid in the mixture. Surface uptake from subsaturated bulk solutions was observed in the initial minutes of dissolution. This surficial phase is 0-10 atomic layers thick in Sr(HCO3)2 solutions and 0-4 layers thick in Ca(HCO3)2 solutions, and subsequently dissolves and/or recrystallizes, usually within 6 min of reaction. The initial transient surface precipitation (recrystallization) process is followed by congruent dissolution of the original solid which proceeds to stoichiometric saturation, or until the precipitation of a more stable Sr-rich solid. The compositions of secondary precipitates do not correspond to thermodynamic equilibrium or stoichiometric saturation states. X-ray photoelectron spectroscopy (XPS) measurements indicate the formation of solid solutions on surfaces of aragonite and strontianite single crystals immersed in Sr(HCO3)2 and Ca(HCO3)2 solutions, respectively. In Sr(HCO3)2 solutions, the XPS signal from the outer ~ 60 A?? on aragonite indicates a composition of 16 mol% SrCO3 after only 2 min of contact, and 14-18 mol% SrCO3 after 3 weeks of contact. The strontianite surface averages approximately 22 mol% CaCO3 after 2 min of contact with Ca(HCO3)2 solution, and is 34-39 mol% CaCO3 after 3 weeks of contact. XPS analysis suggests the surface composition is zoned with somewhat greater enrichment in the outer ~25 A?? (as much as 26 mol% SrCO3 on aragonite and 44 mol% CaCO3 on strontianite). The results indicate rapid formation of a solid-solution surface phase from subsaturated aqueous solutions. The surface phase continually adjusts in composition in response to changes in composition of the bulk fluid as net dissolution proceeds. Dissolution rates of the endmembers are greatly reduced in nonstoichiometric solutions relative to dissolution rates observed in stoichiometric solutions. All solids dissolve more slowly in solutions spiked with the least soluble component ((Sr(HCO3)2)) than in solutions spiked with the more soluble component (Ca(HCO3)2), an effect that becomes increasingly significant as stoichiometric saturation is approached. It is proposed that the formation of a non-stoichiometric surface reactive zone significantly decreases dissolution rates. ?? 1992.

Precipitation in Al–Mg solid solution prepared by solidification under high pressure

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

Jie, J.C., E-mail: jiejc@dlut.edu.cn; School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001; Wang, H.W.

2014-01-15

The precipitation in Al–Mg solid solution containing 21.6 at.% Mg prepared by solidification under 2 GPa was investigated. The results show that the γ-Al{sub 12}Mg{sub 17} phase is formed and the β′ phase cannot be observed in the solid solution during ageing process. The precipitation of γ and β phases takes place in a non-uniform manner during heating process, i.e. the γ and β phases are first formed in the interdendritic region, which is caused by the inhomogeneous distribution of Mg atoms in the solid solution solidified under high pressure. Peak splitting of X-ray diffraction patterns of Al(Mg) solid solutionmore » appears, and then disappears when the samples are aged at 423 K for different times, due to the non-uniform precipitation in Al–Mg solid solution. The direct transformation from the γ to β phase is observed after ageing at 423 K for 24 h. It is considered that the β phase is formed through a peritectoid reaction of α + γ → β which needs the diffusion of Mg atoms across the interface of α/γ phases. - Highlights: • The γ phase is formed and the β′ phase is be observed in Al(Mg) solid solution. • Peak splitting of XRD pattern of Al(Mg) solid solution appears during aged at 150 °C. • The β phase is formed through a peritectoid reaction of α + γ → β.« less

New structure of high-pressure body-centered orthorhombic Fe 2SiO 4

DOE PAGES

Yamanaka, Takamitsu; Kyono, Atsushi; Nakamoto, Yuki; ...

2015-08-01

Here, a structural change in Fe 2SiO 4 spinel and the structure of a new high pressure phase are determined by Rietveld 26 profile fitting of x-ray diffraction data up to 64 GPa at ambient temperature. The compression curve of the spinel is discontinuous at approximately 20 GPa. Fe Kβ x-ray emission measurements at high pressure show that the transition from a high spin (HS) to an intermediate spin (IS) state begins at 17 GPa in the spinel phase. The IS electronic state is gradually enhanced with pressure, which results in an isostructural phase transition. A transition from the cubic spinel structure to a body centered orthorhombic phase (I-Fe 2SiO 4) with space group Imma and Z=4 was observed at approximately 34 GPa. The structure of I-Fe 2SiO 4 has two crystallographically distinct FeO 6 octahedra, which are arranged in layers parallel to (101) and (011) and are very similar to the layers of FeO 6 octahedra that constitute the spinel structure. Silicon also exists in six-fold coordination in I-Fe 2SiO 4. The transformation to the new high-pressure phase is reversible under decompression at ambient temperature. A Martensitic transformation of each slab of the spinel structure with translation vector [more » $$\\vec{1/8}$$ $$\\vec{1/8}$$ $$\\vec{1/8}$$] generates the I-Fe 2SiO 4 structure. Laser heating of I-Fe 2SiO 4 at 1500 K results in a decomposition of the material to rhombohedral FeO and SiO 2 stishovite.« less

Pt-Doped NiFe₂O₄ Spinel as a Highly Efficient Catalyst for H₂ Selective Catalytic Reduction of NO at Room Temperature.

PubMed

Sun, Wei; Qiao, Kai; Liu, Ji-Yuan; Cao, Li-Mei; Gong, Xue-Qing; Yang, Ji

2016-04-11

H2 selective catalytic reduction (H2-SCR) has been proposed as a promising technology for controlling NOx emission because hydrogen is clean and does not emit greenhouse gases. We demonstrate that Pt doped into a nickel ferrite spinel structure can afford a high catalytic activity of H2-SCR. A superior NO conversion of 96% can be achieved by employing a novel NiFe1.95Pt0.05O4 spinel-type catalyst at 60 °C. This novel catalyst is different from traditional H2-SCR catalysts, which focus on the role of metallic Pt species and neglect the effect of oxidized Pt states in the reduction of NO. The obtained Raman and XPS spectra indicate that Pt in the spinel lattice has different valence states with Pt(2+) occupying the tetrahedral sites and Pt(4+) residing in the octahedral ones. These oxidation states of Pt enhance the back-donation process, and the lack of filling electrons of the 5d band causes Pt to more readily hybridize with the 5σ orbital of the NO molecule, especially for octahedral Pt(4+), which enhances the NO chemisorption on the Pt sites. We also performed DFT calculations to confirm the enhancement of adsorption of NO onto Pt sites when doped into the Ni-Fe spinel structure. The prepared Pt/Ni-Fe catalysts indicate that increasing the dispersity of Pt on the surfaces of the individual Ni-Fe spinel-type catalysts can efficiently promote the H2-SCR activity. Our demonstration provides new insight into designing advanced catalysts for H2-SCR.

Manufacturing process scale-up of optical grade transparent spinel ceramic at ArmorLine Corporation

NASA Astrophysics Data System (ADS)

Spilman, Joseph; Voyles, John; Nick, Joseph; Shaffer, Lawrence

2013-06-01

While transparent Spinel ceramic's mechanical and optical characteristics are ideal for many Ultraviolet (UV), visible, Short-Wave Infrared (SWIR), Mid-Wave Infrared (MWIR), and multispectral sensor window applications, commercial adoption of the material has been hampered because the material has historically been available in relatively small sizes (one square foot per window or less), low volumes, unreliable supply, and with unreliable quality. Recent efforts, most notably by Technology Assessment and Transfer (TA and T), have scaled-up manufacturing processes and demonstrated the capability to produce larger windows on the order of two square feet, but with limited output not suitable for production type programs. ArmorLine Corporation licensed the hot-pressed Spinel manufacturing know-how of TA and T in 2009 with the goal of building the world's first dedicated full-scale Spinel production facility, enabling the supply of a reliable and sufficient volume of large Transparent Armor and Optical Grade Spinel plates. With over $20 million of private investment by J.F. Lehman and Company, ArmorLine has installed and commissioned the largest vacuum hot press in the world, the largest high-temperature/high-pressure hot isostatic press in the world, and supporting manufacturing processes within 75,000 square feet of manufacturing space. ArmorLine's equipment is capable of producing window blanks as large as 50" x 30" and the facility is capable of producing substantial volumes of material with its Lean configuration and 24/7 operation. Initial production capability was achieved in 2012. ArmorLine will discuss the challenges that were encountered during scale-up of the manufacturing processes, ArmorLine Optical Grade Spinel optical performance, and provide an overview of the facility and its capabilities.

Petrology of spinel lherzolite xenoliths from Youkou volcano, Adamawa Massif, Cameroon Volcanic Line: mineralogical and geochemical fingerprints of sub-rift mantle processes

NASA Astrophysics Data System (ADS)

Njombie, Merlin Patrick Wagsong; Temdjim, Robert; Foley, Stephen F.

2018-02-01

The basaltic maar of Youkou, situated in the Adamawa Volcanic Massif in the eastern branch of the continental segment of the Cameroon Volcanic Line, contains mantle-derived xenoliths of various types in pyroclastites. Spinel-bearing lherzolite xenoliths from the Youkou volcano generally exhibit protogranular textures with olivine (Fo89.4-90.5), enstatite (En89 - 91Fs8.7-9.8Wo0.82-1.13), clinopyroxene, spinel (Cr#Sp = 9.4-13.8), and in some cases amphibole (Mg# = 88.5-89.1). Mineral equilibration temperatures in the lherzolite xenoliths have been estimated from three-two pyroxene thermometers and range between 835 and 937 °C at pressures of 10-18 kbar, consistent with shallow mantle depths of around 32-58 km. Trends displayed by bulk-rock MgO correlate with Al2O3, indicating that the xenoliths are refractory mantle residues after partial melting. The degree of partial melting estimated from spinel compositions is less than 10%: evidences for much higher degrees of depletion are preserved in one sample, but overprinted by refertilization in others. Trace element compositions of the xenoliths are enriched in highly incompatible elements (LREE, Sr, Ba, and U), indicating that the spinel lherzolites underwent later cryptic metasomatic enrichment induced by plume-related hydrous silicate melts. The extreme fertility (Al2O3 = 6.07-6.56 wt% in clinopyroxene) and the low CaO/Al2O3 ratios in the spinel lherzolites suggest that they could not be a simple residue of partial melting of primitive mantle and must have experienced refertilization processes driven by the infiltration of carbonatite or carbonated silicate melts.

Unique atom hyper-kagome order in Na4Ir3O8 and in low-symmetry spinel modifications.

PubMed

Talanov, V M; Shirokov, V B; Talanov, M V

2015-05-01

Group-theoretical and thermodynamic methods of the Landau theory of phase transitions are used to investigate the hyper-kagome atomic order in structures of ordered spinels and a spinel-like Na4Ir3O8 crystal. The formation of an atom hyper-kagome sublattice in Na4Ir3O8 is described theoretically on the basis of the archetype (hypothetical parent structure/phase) concept. The archetype structure of Na4Ir3O8 has a spinel-like structure (space group Fd\\bar 3m) and composition [Na1/2Ir3/2](16d)[Na3/2](16c)O(32e)4. The critical order parameter which induces hypothetical phase transition has been stated. It is shown that the derived structure of Na4Ir3O8 is formed as a result of the displacements of Na, Ir and O atoms, and ordering of Na, Ir and O atoms, ordering dxy, dxz, dyz orbitals as well. Ordering of all atoms takes place according to the type 1:3. Ir and Na atoms form an intriguing atom order: a network of corner-shared Ir triangles called a hyper-kagome lattice. The Ir atoms form nanoclusters which are named decagons. The existence of hyper-kagome lattices in six types of ordered spinel structures is predicted theoretically. The structure mechanisms of the formation of the predicted hyper-kagome atom order in some ordered spinel phases are established. For a number of cases typical diagrams of possible crystal phase states are built in the framework of the Landau theory of phase transitions. Thermodynamical conditions of hyper-kagome order formation are discussed by means of these diagrams. The proposed theory is in accordance with experimental data.

Low temperature processed MnCo2O4 and MnCo1.8Fe0.2O4 as effective protective coatings for solid oxide fuel cell interconnects at 750 °C

NASA Astrophysics Data System (ADS)

Molin, S.; Jasinski, P.; Mikkelsen, L.; Zhang, W.; Chen, M.; Hendriksen, P. V.

2016-12-01

In this study two materials, MnCo2O4 and MnCo1.8Fe0.2O4 are studied as potential protective coatings for Solid Oxide Fuel Cell interconnects working at 750 °C. First powder fabrication by a modified Pechini method is described followed by a description of the coating procedure. The protective action of the coating applied on Crofer 22 APU is evaluated by following the area specific resistance (ASR) of the scale/coating for 5500 h including several thermal cycles. The coating is prepared by brush painting and has a porous structure after deposition. Post mortem microstructural characterization performed on the coated samples shows good protection against chromium diffusion from the chromia scale ensured by a formation of a dense reaction layer. This study shows, that even without high temperature sintering and/or reactive sintering it is possible to fabricate protective coatings based on MnCo spinels.

Near Infrared-Emitting Cr3+/Eu3+ Co-doped Zinc Gallogermanate Persistence Luminescent Nanoparticles for Cell Imaging

NASA Astrophysics Data System (ADS)

Wang, Qiaoqiao; Zhang, Shuyun; Li, Zhiwei; Zhu, Qi

2018-02-01

Near infrared (NIR)-emitting persistent luminescent nanoparticles have been developed as potential agents for bioimaging. However, synthesizing uniform nanoparticles with long afterglow for long-term imaging is lacking. Here, we demonstrated the synthesis of spinel structured Zn3Ga2Ge2O10:Cr3+ (ZGGO:Cr3+) and Zn3Ga2Ge2O10:Cr3+,Eu3+ (ZGGO:Cr3+,Eu3+) nanoparticles by a sol-gel method in combination with a subsequent reducing atmosphere-free calcination. The samples were investigated via detailed characterizations by combined techniques of XRD, TEM, STEM, selected area electron diffraction, photoluminescence excitation (PLE)/photoluminescence (PL) spectroscopy, and temperature-dependent PL analysis. The single-crystalline nanoparticles are homogeneous solid solution, possessing uniform cubic shape and lateral size of 80-100 nm. Upon UV excitation at 273 nm, ZGGO:Cr3+,Eu3+ exhibited a NIR emission band at 697 nm (2E → 4A2 transition of distorted Cr3+ ions in gallogermanate), in the absence of Eu3+ emission. NIR persistent luminescence of the sample can last longer than 7200 s and still hold intense intensity. Eu3+ incorporation increased the persistent luminescence intensity and the afterglow time of ZGGO:Cr3+, but it did not significantly affect the thermal stability. The obtained ZGGO:Cr3+,Eu3+-NH2 nanoparticles possessed an excellent imaging capacity for cells in vitro.

Enhanced photocatalytic degradation of 2-propanol over macroporous GaN/ZnO solid solution prepared by a novel sol-gel method

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

Wang, Lizhong; Ouyang, Shuxin; Ren, Bofan

2015-10-01

Macroporous GaN/ZnO solid solution photocatalyst is synthesized through a novel sol-gel method under mild conditions. The performance of as-synthesized solid solution photocatalyst is evaluated for decomposition of gaseous 2-propanol (IPA). It is found that due to enhancement in both the adsorption to gaseous IPA and the absorbance to visible light, the porous GaN/ZnO solid solution exhibits a good photocatalytic performance for IPA decomposition. Moreover, the mechanism for photocatalytic degradation IPA over porous GaN/ZnO solid solution is also investigated in comparison with those for the two end materials ZnO and GaN. The trapping effects with different scavengers prove that both themore » photoexcited electrons and holes affect the IPA photodegradation process, simultaneously.« less

Synthesis of GaN:ZnO solid solution by solution combustion method and characterization for photocatalytic application

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

Menon, Sumithra Sivadas; Anitha, R.; Baskar, K.

2016-05-23

GaN-ZnO solid solution has emerged as a successful and reproducible photocatalyst for overall water splitting by one-step photoexcitation, with a bandgap in visible region. When the solid solution is formed, some of the Zn and O ions are replaced by Ga and N ions respectively and there is a narrowing of bandgap which is hypothesized as due to Zn3d-N2p repulsion. The traditional method of synthesis of GaN-ZnO solid solution is by nitridation of the starting oxides under constant ammonia flow. Here we report a solution combustion technique for the synthesis of the solid solution at a temperature about 500 °more » C in a muffle furnace with metal nitrates as precursors and urea as the fuel. The as prepared samples showed change in color with the increased concentration of ZnO in the solution. The structural, microstructural, morphological and optical properties of the samples were realized by Powder X ray diffraction, Scanning electron microscopy, Energy dispersive X ray analysis, Transmission electron microscopy and Photoluminescence. Finally the hydrogen production efficiency of the GaN-ZnO nanopowders by water splitting was found, using methanol as a scavenger. The apparent quantum yield (AQY) of 0.048% is obtained for GaN-ZnO solid solution.« less

Development of Ni-Ferrite-Based PVDF Nanomultiferroics

NASA Astrophysics Data System (ADS)

Behera, C.; Choudhary, R. N. P.; Das, Piyush R.

2017-10-01

Thin-film polyvinylidene fluoride (PVDF)-spinel ferrite nanocomposites with 0-3 connectivity and varying composition, i.e., (1 - x)PVDF- xNiFe2O4 ( x = 0.05, 0.1, 0.15), have been fabricated by a solution-casting route. The basic crystal data and microstructure of the composite samples were obtained by x-ray powder diffraction analysis and scanning electron microscopy, respectively. Preliminary structural analysis showed the presence of polymeric electroactive β-phase of PVDF (matrix) and spinel ferrite (filler) phase in the composites. The composites were found to be flexible with high relative dielectric constant ( ɛ r) and low loss tangent (tan δ). Detailed studies of their electrical characteristics using complex impedance spectroscopy showed the contributions of bulk (grains) and grain boundaries in the resistive and capacitive properties of the composites. Study of the frequency-dependent electrical conductivity at different temperatures showed that Jonscher's power law could be used to interpret the transport properties of the composites. Important experimental data and results obtained from magnetic as well ferroelectric hysteresis loops and the first-order magnetoelectric coefficient suggest the suitability of some of these composites for fabrication of multifunctional devices. The low electrical conductivity, high dielectric constant, and low loss tangent suggest that such composites could be used in capacitor devices.

Exploring hardness enhancement in superhard tungsten tetraboride-based solid solutions using radial X-ray diffraction

DOE PAGES

Xie, Miao; Mohammadi, Reza; Turner, Christopher L.; ...

2015-07-29

In this paper, we explore the hardening mechanisms in WB4-based solid solutions upon addition of Ta, Mn, and Cr using in situ radial X-ray diffraction techniques under nonhydrostatic pressure. By examining the lattice-supported differential strain, we provide insights into the mechanism for hardness increase in binary solid solutions at low dopant concentrations. Speculations on the combined effects of electronic structure and atomic size in ternary WB 4 solid solutions containing Ta with Mn or Cr are also included to understand the extremely high hardness of these materials.

Ion mobility and transport properties of bismuth fluoride-containing solid solutions with tysonite-type structure

NASA Astrophysics Data System (ADS)

Kavun, V. Ya.; Uvarov, N. F.; Slobodyuk, A. B.; Merkulov, E. B.; Polyantsev, M. M.

2018-07-01

The ion mobility and conductivity of solid solutions with tysonite-type structure obtained by doping bismuth trifluoride with lead (II) fluoride, and zirconium and bismuth oxides have been studied using 19F NMR, X-ray diffraction analysis, and impedance spectroscopy. The types of ionic motions in the fluoride sublattice of the synthesized solid solutions in the temperature range 150-450 K have been determined and the energy of their activation has been estimated. Due to high ionic conductivity, above 10-2 S/cm at 570 K, these solid solutions can be considered as superionic conductors.

Solid-solution CrCoCuFeNi high-entropy alloy thin films synthesized by sputter deposition

DOE PAGES

An, Zhinan; Jia, Haoling; Wu, Yueying; ...

2015-05-04

The concept of high configurational entropy requires that the high-entropy alloys (HEAs) yield single-phase solid solutions. However, phase separations are quite common in bulk HEAs. A five-element alloy, CrCoCuFeNi, was deposited via radio frequency magnetron sputtering and confirmed to be a single-phase solid solution through the high-energy synchrotron X-ray diffraction, energy-dispersive spectroscopy, wavelength-dispersive spectroscopy, and transmission electron microscopy. The formation of the solid-solution phase is presumed to be due to the high cooling rate of the sputter-deposition process.

X-ray diffraction and Mössbauer spectroscopy studies of LiFe 0.5Ti 1.5O 4 - A new primitive cubic ordered spinel

NASA Astrophysics Data System (ADS)

Avdeev, Georgi; Petrov, Kostadin; Mitov, Ivan

2007-12-01

LiFe 0.5Ti 1.5O 4 was synthesized by solid-state reaction carried out at 900 °C in flowing argon atmosphere, followed by rapid quenching of the reaction product to room temperature. The compound has been characterized by X-ray powder diffraction (XRD) and 57Fe Mössbauer effect spectroscopy (MES). It crystallizes in the space group P4 332, a = 8.4048(1) Å. Results from Rietveld structural refinement indicated 1:3 cation ordering on the octahedral sites: Li occupies the octahedral (4 b) sites, Ti occupies the octahedral (12 d) sites, while the tetrahedral (8 c) sites have mixed (Fe/Li) occupancy. A small, about 5%, inversion of Fe on the (4 b) sites has been detected. The MES data is consistent with cation distribution and oxidation state of Fe, determined from the structural data. The title compound is thermally unstable in air atmosphere. At 800 °C it transforms to a mixture of two Fe 3+ containing phases - a face centred cubic spinel Li (1+ y)/2 Fe (5-3 y)/2 Ti yO 4 and a Li ( z-1)/2 Fe (7-3 z)/2 Ti zO 5 - pseudobrookite. The major product of thermal treatment at 1000 °C is a ramsdellite type lithium titanium iron(III) oxide, accompanied by traces of rutile and pseudobrookite.

Refractory materials in comet samples

NASA Astrophysics Data System (ADS)

Joswiak, D. J.; Brownlee, D. E.; Nguyen, A. N.; Messenger, S.

2017-08-01

Transmission electron microscope examination of more than 250 fragments, >1 μm from comet Wild 2 and a giant cluster interplanetary dust particle (GCP) of probable cometary origin has revealed four new calcium-aluminum-rich inclusions (CAIs), an amoeboid olivine aggregate (AOA), and an additional AOA or Al-rich chondrule (ARC) object. All of the CAIs have concentric mineral structures and are composed of spinel + anorthite cores surrounded by Al,Ti clinopyroxenes and are similar to two previous CAIs discovered in Wild 2. All of the cometary refractory objects are of moderate refractory character. The mineral assemblages, textures, and bulk compositions of the comet CAIs are similar to nodules in fine-grained, spinel-rich inclusions (FGIs) found in primitive chondrites and like the nodules may be nebular condensates that were altered via solid-gas reactions in the solar nebula. Oxygen isotopes collected on one Wild 2 CAI also match FGIs. The lack of the most refractory inclusions in the comet samples may reflect the higher abundances of small moderately refractory CAI nodules that were produced in the nebula and the small sample sizes collected. In the comet samples, approximately 2-3% of all fragments larger than 1 μm, by number, are CAIs and nearly 50% of all bulbous Stardust tracks contain at least one CAI. We estimate that 0.5 volume % of Wild 2 material and 1 volume % of GCP is in the form of CAIs. ARCs and AOAs account for <1% of the Wild 2 and GCP grains by number.

A photochemical proposal for the preparation of ZnAl{sub 2}O{sub 4} and MgAl{sub 2}O{sub 4} thin films from β-diketonate complex precursors

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

Cabello, G., E-mail: gerardocabelloguzman@hotmail.com; Lillo, L.; Caro, C.

2016-05-15

Highlights: • ZnAl{sub 2}O{sub 4} and MgAl{sub 2}O{sub 4} thin films were prepared by photo-chemical method. • The Zn(II), Mg(II) and Al(III) β-diketonate complexes were used as precursors. • The photochemical reaction was monitored by UV–vis and FT-IR spectroscopy. • The results reveal spinel oxide formation and the generation of intermediate products. - Abstract: ZnAl{sub 2}O{sub 4} and MgAl{sub 2}O{sub 4} thin films were grown on Si(100) and quartz plate substrates using a photochemical method in the solid phase with thin films of β-diketonate complexes as the precursors. The films were deposited by spin-coating and subsequently photolyzed at room temperaturemore » using 254 nm UV light. The photolysis of these films results in the deposition of metal oxide thin films and fragmentation of the ligands from the coordination sphere of the complexes. The obtained samples were post-annealed at different temperatures (350–1100 °C) for 2 h and characterized by FT-Infrared spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force miscroscopy (AFM), and UV–vis spectroscopy. The results indicate the formation of spinel-type structures and other phases. These characteristics determined the quality of the films, which were obtained from the photodeposition of ternary metal oxides.« less

Detecting structural variances of Co 3O 4 catalysts by controlling beam-induced sample alterations in the vacuum of a transmission electron microscope

DOE PAGES

Kisielowski, C.; Frei, H.; Specht, P.; ...

2016-11-02

This article summarizes core aspects of beam-sample interactions in research that aims at exploiting the ability to detect single atoms at atomic resolution by mid-voltage transmission electron microscopy. Investigating the atomic structure of catalytic Co 3O 4 nanocrystals underscores how indispensable it is to rigorously control electron dose rates and total doses to understand native material properties on this scale. We apply in-line holography with variable dose rates to achieve this goal. Genuine object structures can be maintained if dose rates below ~100 e/Å 2s are used and the contrast required for detection of single atoms is generated by capturing largemore » image series. Threshold doses for the detection of single atoms are estimated. An increase of electron dose rates and total doses to common values for high resolution imaging of solids stimulates object excitations that restructure surfaces, interfaces, and defects and cause grain reorientation or growth. We observe a variety of previously unknown atom configurations in surface proximity of the Co 3O 4 spinel structure. These are hidden behind broadened diffraction patterns in reciprocal space but become visible in real space by solving the phase problem. Finallly, an exposure of the Co 3O 4 spinel structure to water vapor or other gases induces drastic structure alterations that can be captured in this manner.« less

Formation mechanisms of Fe3−xSnxO4 by a chemical vapor transport (CVT) process

PubMed Central

Su, Zijian; Zhang, Yuanbo; Liu, Bingbing; Chen, Yingming; Li, Guanghui; Jiang, Tao

2017-01-01

Our former study reported that Fe-Sn spinel (Fe3−xSnxO4) was easily formed when SnO2 and Fe3O4 were roasted under CO-CO2 atmosphere at 900–1100 °C. However, the formation procedure is still unclear and there is a lack of theoretical research on the formation mechanism of the Fe-Sn spinel. In this work, the reaction mechanisms between SnO2 and Fe3O4 under CO-CO2 atmosphere were determined using XRD, VSM, SEM-EDS, XPS, etc. The results indicated that the formation of Fe3−xSnxO4 could be divided into four steps: reduction of SnO2 to solid phase SnO, volatilization of gaseous SnO, adsorption of gaseous SnO on the surface of Fe3O4, and redox reaction between SnO and Fe3O4. During the roasting process, part of Fe3+ in Fe3O4 was reduced to Fe2+ by gaseous SnO, and meanwhile Sn2+ was oxidized to Sn4+ and entered into Fe3−xSnxO4. The reaction between SnO2 and Fe3O4 could be summarized as Fe3O4 + xSnO(g) → Fe3−xSnxO4 (x = 0–1.0). PMID:28262673

Conformal ALON® and spinel windows

NASA Astrophysics Data System (ADS)

Goldman, Lee M.; Smith, Mark; Ramisetty, Mohan; Jha, Santosh; Sastri, Suri

2017-05-01

The requirements for modern aircraft based reconnaissance systems are driving the need for conformal windows for future sensor systems. However, limitations on optical systems and the ability to produce windows in complex geometries currently limit the geometry of existing windows and window assemblies to faceted assemblies of flat windows. ALON consists primarily of aluminum and oxygen, similar to that of alumina, with a small amount of nitrogen added to help stabilize the cubic gamma-AlON phase. ALON's chemical similarity to alumina, translates into a robust manufacturing process. This ease of processing has allowed Surmet to produce ALON windows and domes in a wide variety of geometries and sizes. Spinel (MgAl2O4) contains equal molar amounts of MgO and Al2O3, and is a cubic material, that transmits further into the Infrared than ALON. Spinel is produced via powder processing techniques similar to those used to produce ALON. Surmet is now applying the lessons learned with ALON to produce conformal spinel windows and domes as well.

Process for growing a film epitaxially upon an oxide surface and structures formed with the process

DOEpatents

McKee, Rodney Allen; Walker, Frederick Joseph

1998-01-01

A process and structure wherein a film comprised of a perovskite or a spinel is built epitaxially upon a surface, such as an alkaline earth oxide surface, involves the epitaxial build up of alternating constituent metal oxide planes of the perovskite or spinel. The first layer of metal oxide built upon the surface includes a metal element which provides a small cation in the crystalline structure of the perovskite or spinel, and the second layer of metal oxide built upon the surface includes a metal element which provides a large cation in the crystalline structure of the perovskite or spinel. The layering sequence involved in the film build up reduces problems which would otherwise result from the interfacial electrostatics at the first atomic layers, and these oxides can be stabilized as commensurate thin films at a unit cell thickness or grown with high crystal quality to thicknesses of 0.5-0.7 .mu.m for optical device applications.

Process for growing a film epitaxially upon an oxide surface and structures formed with the process

DOEpatents

McKee, Rodney A.; Walker, Frederick J.

1995-01-01

A process and structure wherein a film comprised of a perovskite or a spinel is built epitaxially upon a surface, such as an alkaline earth oxide surface, involves the epitaxial build up of alternating constituent metal oxide planes of the perovskite or spinel. The first layer of metal oxide built upon the surface includes a metal element which provides a small cation in the crystalline structure of the perovskite or spinel, and the second layer of metal oxide built upon the surface includes a metal element which provides a large cation in the crystalline structure of the perovskite or spinel. The layering sequence involved in the film build up reduces problems which would otherwise result from the interfacial electrostatics at the first atomic layers, and these oxides can be stabilized as commensurate thin films at a unit cell thickness or grown with high crystal quality to thicknesses of 0.5-0.7 .mu.m for optical device applications.

Probing optical band gaps at the nanoscale in NiFe₂O₄ and CoFe₂O₄ epitaxial films by high resolution electron energy loss spectroscopy

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

Dileep, K.; Loukya, B.; Datta, R., E-mail: ranjan@jncasr.ac.in

2014-09-14

Nanoscale optical band gap variations in epitaxial thin films of two different spinel ferrites, i.e., NiFe₂O₄ (NFO) and CoFe₂O₄ (CFO), have been investigated by spatially resolved high resolution electron energy loss spectroscopy. Experimentally, both NFO and CFO show indirect/direct band gaps around 1.52 eV/2.74 and 2.3 eV, and 1.3 eV/2.31 eV, respectively, for the ideal inverse spinel configuration with considerable standard deviation in the band gap values for CFO due to various levels of deviation from the ideal inverse spinel structure. Direct probing of the regions in both the systems with tetrahedral A site cation vacancy, which is distinct frommore » the ideal inverse spinel configuration, shows significantly smaller band gap values. The experimental results are supported by the density functional theory based modified Becke-Johnson exchange correlation potential calculated band gap values for the different cation configurations.« less

The effect of Cr substitution on the structural, electronic and magnetic properties of pulsed laser deposited NiFe2O4 thin films

NASA Astrophysics Data System (ADS)

Panwar, Kalpana; Tiwari, Shailja; Bapna, Komal; Heda, N. L.; Choudhary, R. J.; Phase, D. M.; Ahuja, B. L.

2017-01-01

We have studied the structural, electronic and magnetic properties of pulsed laser deposited thin films of Ni1-xCrxFe2O4 (x=0.02 and 0.05) on Si (111) and Si (100) substrates. The films reveal single phase, polycrystalline structure with larger grain size on Si (111) substrate than that on Si (100) substrate. Contrary to the expected inverse spinel structure, x-ray photoemission (XPS) studies reveal the mixed spinel structure. XPS results suggest that Ni and Fe ions exist in 2+ and 3+ states, respectively, and they exist in tetrahedral as well as octahedral sites. The deviation from the inverse spinel leads to modified magnetic properties. It is observed that saturation magnetization drastically drops compared to the expected saturation value for inverse spinel structure. Strain in the films and lattice distortion produced by the Cr doping also appear to influence the magnetic properties.

RHEED oscillations in spinel ferrite epitaxial films grown by conventional planar magnetron sputtering

NASA Astrophysics Data System (ADS)

Ojima, T.; Tainosho, T.; Sharmin, S.; Yanagihara, H.

2018-04-01

Real-time in situ reflection high energy electron diffraction (RHEED) observations of Fe3O4, γ-Fe2O3, and (Co,Fe)3O4 films on MgO(001) substrates grown by a conventional planar magnetron sputtering was studied. The change in periodical intensity of the specular reflection spot in the RHEED images of three different spinel ferrite compounds grown by two different sputtering systems was examined. The oscillation period was found to correspond to the 1/4 unit cell of each spinel ferrite, similar to that observed in molecular beam epitaxy (MBE) and pulsed laser deposition (PLD) experiments. This suggests that the layer-by-layer growth of spinel ferrite (001) films is general in most physical vapor deposition (PVD) processes. The surfaces of the films were as flat as the surface of the substrate, consistent with the observed layer-by-layer growth process. The observed RHEED oscillation indicates that even a conventional sputtering method can be used to control film thickness during atomic layer depositions.

Modelling solid solutions with cluster expansion, special quasirandom structures, and thermodynamic approaches

NASA Astrophysics Data System (ADS)

Saltas, V.; Horlait, D.; Sgourou, E. N.; Vallianatos, F.; Chroneos, A.

2017-12-01

Modelling solid solutions is fundamental in understanding the properties of numerous materials which are important for a range of applications in various fields including nanoelectronics and energy materials such as fuel cells, nuclear materials, and batteries, as the systematic understanding throughout the composition range of solid solutions for a range of conditions can be challenging from an experimental viewpoint. The main motivation of this review is to contribute to the discussion in the community of the applicability of methods that constitute the investigation of solid solutions computationally tractable. This is important as computational modelling is required to calculate numerous defect properties and to act synergistically with experiment to understand these materials. This review will examine in detail two examples: silicon germanium alloys and MAX phase solid solutions. Silicon germanium alloys are technologically important in nanoelectronic devices and are also relevant considering the recent advances in ternary and quaternary groups IV and III-V semiconductor alloys. MAX phase solid solutions display a palette of ceramic and metallic properties and it is anticipated that via their tuning they can have applications ranging from nuclear to aerospace industries as well as being precursors for particular MXenes. In the final part, a brief summary assesses the limitations and possibilities of the methodologies discussed, whereas there is discussion on the future directions and examples of solid solution systems that should prove fruitful to consider.

Subsolidus cooling of mid-ocean ridge peridotites and implications for the oxygen fugacity of the oceanic upper mantle

NASA Astrophysics Data System (ADS)

Birner, S.; Davis, F. A.; Cottrell, E.; Warren, J. M.; Kelley, K. A.

2017-12-01

Peridotites dredged from mid-ocean ridges provide a window into the chemistry of Earth's upper mantle. At equilibrium, mineral assemblages within peridotite record intrinsic properties, including oxygen fugacity (fO2). During cooling below the solidus, however, reactions affect the chemical compositions and modal abundances of minerals, directly affecting the fO2 recorded by these mineral assemblages. The slow kinetics of subsolidus diffusion also prevent full re-equilibration of peridotite during cooling, and different reactions have different closure temperatures. As a result, peridotites measured at the surface record neither equilibrium nor asthenospheric conditions. In order to quantify the effect of subsolidus diffusion on fO2, we analyzed minerals from abyssal peridotites dredged from the Southwest Indian Ridge (SWIR), which we then used as a basis for modeling potential subsolidus reactions. We first examined exchange reactions where no modal changes occur. We considered both Fe-Mg exchange between olivine and spinel [1] and Al-Cr exchange between orthopyroxene and spinel [2], and combined these models with spinel oxybarometry [3] to determine the effect of these reactions on fO2. Our results indicate that as peridotites cool from 1300°C to 900°C, these exchange processes together increase recorded fO2 by 0.3 log units relative to the approach in which compositional changes are not considered. Some reactions additionally change mineral modal abundances during cooling, in particular the Tschermak exchange in orthopyroxene [2], which consumes olivine and Al-rich orthopyroxene and produces spinel and Al-poor orthopyroxene as temperature decreases. Depending on partitioning of Fe3+ between phases, this reaction may dilute the concentration of Fe3+ in spinel and decrease recorded fO2 as temperature decreases. Preliminary results suggest that the magnitude of this effect is strongly sensitive to both initial spinel mode and partitioning of Fe3+ between orthopyroxene and spinel. Finally, we compare the fO2 recorded by SWIR peridotites to the fO2 recorded by basalts, projected to source conditions. [1] Li et al., 1995; [2] Voigt and von der Handt, 2011; [3] Davis et al., 2017

New structure of high-pressure body-centered orthorhombic Fe 2 SiO 4

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

Yamanaka, Takamitsu; Kyono, Atsushi; Nakamoto, Yuki

2015-08-01

A structural change in Fe2SiO4 spinel (ringwoodite) has been found by synchrotron powder diffraction study and the structure of a new high-pressure phase was determined by Monte-Carlo simulation method and Rietveld profile fitting of X-ray diffraction data up to 64 GPa at ambient temperature. A transition from the cubic spinel structure to a body centered orthorhombic phase (I-Fe2SiO4) with space group Imma and Z = 4 was observed at approximately 34 GPa. The structure of I-Fe2SiO4 has two crystallographically independent FeO6 octahedra. Iron resides in two different sites of sixfold coordination: Fe1 and Fe2, which are arranged in layers parallelmore » to (101) and (011) and are very similar to the layers of FeO6 octahedra in the spinel structure. Silicon is located in the sixfold coordination in I-Fe2SiO4. The transformation to the new high-pressure phase is reversible under decompression at ambient temperature. A martensitic transformation of each slab of the spinel structure with translation vector Embedded Image generates the I-Fe2SiO4 structure. Laser heating of I-Fe2SiO4 at 1500 K results in a decomposition of the material to rhombohedral FeO and SiO2 stishovite. FeKβ X-ray emission measurements at high pressure up to 65 GPa show that the transition from a high spin (HS) to an intermediate spin (IS) state begins at 17 GPa in the spinel phase. The IS electron spin state is gradually enhanced with pressure. The Fe2+ ion at the octahedral site changes the ion radius under compression at the low spin, which results in the changes of the lattice parameter and the deformation of the octahedra of the spinel structure. The compression curve of the lattice parameter of the spinel is discontinuous at ~20 GPa. The spin transition induces an isostructural change.« less

Quench-age method for the fabrication of niobium-aluminum superconductors

DOEpatents

Pickus, Milton R.; Ciardella, Robert L.

1978-01-01

A flexible Nb.sub.3 Al superconducting wire is fabricated from a niobium-aluminum composite wire by heating to form a solid solution which is retained at room temperature as a metastable solid solution by quenching. The metastable solid solution is then transformed to the stable superconducting A-15 phase by low temperature aging. The transformation induced by aging can be controlled to yield either a multifilamentary or a solid A-15 core surrounded by ductile niobium.

Cation-substituted spinel oxide and oxyfluoride cathodes for lithium ion batteries

DOEpatents

Manthiram, Arumugam; Choi, Wonchang

2010-05-18

The present invention includes compositions and methods of making cation-substituted and fluorine-substituted spinel cathode compositions by firing a LiMn_2-y-zLi_yM_zO₄ oxide with NH₄HF₂ at low temperatures of between about 300 and 700.degree. C. for 2 to 8 hours and a .eta. of more than 0 and less than about 0.50, mixed two-phase compositions consisting of a spinel cathode and a layered oxide cathode, and coupling them with unmodified or surface modified graphite anodes in lithium ion cells.

Magneto-structural correlation in Co0.8Cu0.2Cr2O4 cubic spinel

NASA Astrophysics Data System (ADS)

Kumar, Ram; Rayaprol, S.; Siruguri, V.; Xiao, Y.; Ji, W.; Pal, D.

2018-05-01

Neutron and X-ray diffraction, magnetic susceptibility, and specific heat measurements have been used to investigate the magneto-structural phase transitions in 20% Cu substituted multiferroic CoCr2O4 spinel. The Jahn-Teller active Cu2+ ion in the tetrahedral A-site of the spinel configuration induces the Jahn-Teller distortion slightly above the Néel temperature. In this compound, we observe a Jahn-Teller distortion of the crystal structure at 90 K. It was further observed that the high temperature cubic (Fd 3 ‾ m) structure coexists with the low temperature orthorhombic (Fddd) structure till the lowest temperature of measurement.

Correlation of Solid State and Solution Coordination Numbers with Infrared Spectroscopy in Five-, Six-, and Eight-Coordinate Transition Metal Complexes of DOTAM.

PubMed

Nagata, Maika K C T; Brauchle, Paul S; Wang, Sen; Briggs, Sarah K; Hong, Young Soo; Laorenza, Daniel W; Lee, Andrea G; Westmoreland, T David

2016-08-16

Three new DOTAM (1,4,7,10-tetrakis(acetamido)-1,4,7,10-tetraazacyclododecane) complexes have been synthesized and characterized by X-ray crystallography: [Co(DOTAM)]Cl 2 •3H 2 O, [Ni(DOTAM)]Cl 2 •4H 2 O, and [Cu(DOTAM)](ClO 4 ) 2 •H 2 O. Solid state and solution IR spectroscopic features for a series of [M(DOTAM)] 2+ complexes (M=Mn, Co, Cu, Ni, Ca, Zn) correlate with solid state and solution coordination numbers. [Co(DOTAM)] 2+ , [Ni(DOTAM)] 2+ , and [Zn(DOTAM)] 2+ are demonstrated to be six-coordinate in both the solid state and in solution, while [Mn(DOTAM)] 2+ and [Ca(DOTAM)] 2+ are eight-coordinate in the solid state and remain so in solution. [Cu(DOTAM)] 2+ , which is five-coordinate by X-ray crystallography, is shown to increase its coordination number in solution to six-coordinate.

Structural, electrical and magnetic properties of Sc3+ doped Mn-Zn ferrite nanoparticles

NASA Astrophysics Data System (ADS)

Angadi, V. Jagdeesha; Choudhury, Leema; Sadhana, K.; Liu, Hsiang-Lin; Sandhya, R.; Matteppanavar, Shidaling; Rudraswamy, B.; Pattar, Vinayak; Anavekar, R. V.; Praveena, K.

2017-02-01

Sc3+ doped Mn0.5Zn0.5ScyFe2-yO4 (y=0.00, 0.01, 0.03 and 0.05) nanoparticles were synthesized by solution combustion method using mixture of fuels were reported for the first time. The mixture of fuels plays an important role in obtaining nano crystalline, single phase present without any heat treatment. X-ray diffraction (XRD) results confirm the formation of the single-phase ferrites which crystallize in cubic spinel structure. The Fourier transform infrared spectra (FTIR) exhibit two prominent bands around 360 cm-1 and 540 cm-1 which are characteristic feature of spinel ferrite. The transmission electron microscope (TEM) micrographs revealed the nanoparticles to be nearly spherical in shape and of fairly uniform size. The room temperature impedance spectra (IS) and vibrating sample magnetometry (VSM) measurements were carried out in order to study the effect of doping (Sc3+) on the characteristic properties of Mn-Zn ferrites. Further, the frequency dependent dielectric constant and dielectric loss were found to decrease with increasing multiple Sc3+ concentration. Nyquist plot in the complex impedance spectra suggest the existence of multiple electrical responses. Magnetic measurements reveals that saturation magnetization (Ms), remnant magnetization (Mr), magnetic moment (ηB) and magnetic particle size (Dm) increase with Sc3+ ion concentration up to x=0.03 and then decrease. The values of spin canting angle (αY-K) and the magnetic particle size (Dm) are found to be in the range of 68-75° and 10-19 nm respectively with Sc3+ concentration. The room temperature Mössbauer spectra were fitted with two sextets corresponding to ions at tetrahedral (A-) and octahedral (B-) sites confirms the spinel lattice. The ferromagnetic resonance (FMR) spectra's has shown that high concentration of scandium doping leads to an increase in dipolar interaction and decrease in super exchange interaction.

Solid/liquid interfacial free energies in binary systems

NASA Technical Reports Server (NTRS)

Nason, D.; Tiller, W. A.

1973-01-01

Description of a semiquantitative technique for predicting the segregation characteristics of smooth interfaces between binary solid and liquid solutions in terms of readily available thermodynamic parameters of the bulk solutions. A lattice-liquid interfacial model and a pair-bonded regular solution model are employed in the treatment with an accommodation for liquid interfacial entropy. The method is used to calculate the interfacial segregation and the free energy of segregation for solid-liquid interfaces between binary solutions for the (111) boundary of fcc crystals. The zone of compositional transition across the interface is shown to be on the order of a few atomic layers in width, being moderately narrower for ideal solutions. The free energy of the segregated interface depends primarily upon the solid composition and the heats of fusion of the component atoms, the composition difference of the solutions, and the difference of the heats of mixing of the solutions.

Interfacial Tension in the CaO-Al2O3-SiO2-(MgO) Liquid Slag-Solid Oxide Systems

NASA Astrophysics Data System (ADS)

Abdeyazdan, Hamed; Monaghan, Brian J.; Longbottom, Raymond J.; Rhamdhani, M. Akbar; Dogan, Neslihan; Chapman, Michael W.

2017-08-01

Interfacial phenomenon is critical in metal processing and refining. While it is known to be important, there are little data available for key oxide systems in the literature. In this study, the interfacial tension ( σ LS) of liquid slag on solid oxides (alumina, spinel, and calcium aluminate), for a range of slags in the CaO-Al2O3-SiO2-(MgO) system at 1773 K (1500 °C), has been evaluated. The results show that basic ladle-type slags exhibit lower σ LS with oxide phases examined compared to that of acid tundish-type slags. Also, within the slag types (acid and base), σ LS was observed to decrease with increasing slag basicity. A correlation between σ LS and slag structure was observed, i.e., σ LS was found to decrease linearly with increasing of slag optical basicity (Λ) and decrease logarithmically with decreasing of slag viscosity from acid to base slags. This indicated a higher σ LS as the ions in the slag become larger and more complex. Through a work of adhesion ( W) analysis, it was shown that basic ladle slags with lower σ LS result in a greater W, i.e., form a stronger bond with the solid oxide phases examined. This indicates that all other factors being equal, the efficiency of inclusion removal from steel of inclusions of similar phase to these solid oxides would be greater.

77 FR 16679 - Emergency Planning and Notification; Emergency Planning and List of Extremely Hazardous...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-22

...The U.S. Environmental Protection Agency (EPA or the Agency) is taking final action to revise the manner for applying the threshold planning quantities (TPQs) for those extremely hazardous substances (EHSs) that are non-reactive solid chemicals in solution. This revision allows facilities subject to the Emergency Planning requirements that have a non-reactive solid EHS in solution, to first multiply the amount of the solid chemical in solution on-site by 0.2 before determining if this quantity equals or exceeds the lower published TPQ. This change is based on data that shows less potential for non-reactive solid chemicals in solution to remain airborne and dispersed beyond a facility's fence line in the event of an accidental release. Previously, EPA assumed that 100% of non-reactive solid chemicals in solution could become airborne and dispersed beyond the fenceline in the event of an accidental release.

Fe-Mg substitution in aluminate spinels: effects on elastic properties investigated by Brillouin scattering

NASA Astrophysics Data System (ADS)

Bruschini, Enrico; Speziale, Sergio; Bosi, Ferdinando; Andreozzi, Giovanni B.

2018-03-01

We investigated by a multi-analytical approach (Brillouin scattering, X-ray diffraction and electron microprobe) the dependence of the elastic properties on the chemical composition of six spinels in the series (Mg1-x ,Fe x )Al2O4 (0 ≤ x ≤ 0.5). With the exception of C 12, all the elastic moduli (C 11, C 44, K S0 and G) are insensitive to chemical composition for low iron concentration, while they decrease linearly for higher Fe2+ content. Only C 12 shows a continuous linear increase with increasing Fe2+ across the whole compositional range under investigation. The high cation disorder showed by the sample with x = 0.202 has little or no influence on the elastic parameters. The range 0.202 < x < 0.388 bounds the percolation threshold (p c) for nearest neighbor interaction of Fe in the cation sublattices of the spinel structure. Below x = 0.202, the iron atoms are diluted in the system and far from each other, and the elastic moduli are nearly constant. Above x = 0.388, Fe atoms form extended interconnected clusters and show a cooperative behavior thus affecting the single-crystal elastic moduli. The elastic anisotropy largely increases with the introduction of Fe2+ in substitution of magnesium in spinel. This behavior is different with respect to other spinels containing transition metals such as Mn2+ and Co2+.

Columnar-Structured Mg-Al-Spinel Thermal Barrier Coatings (TBCs) by Suspension Plasma Spraying (SPS)

NASA Astrophysics Data System (ADS)

Schlegel, N.; Ebert, S.; Mauer, G.; Vaßen, R.

2015-01-01

The suspension plasma spraying (SPS) process has been developed to permit the feeding of sub-micrometer-sized powder into the plasma plume. In contrast to electron beam-physical vapor deposition and plasma spray-physical vapor deposition, SPS enables the cost-efficient deposition of columnar-structured coatings. Due to their strain tolerance, these coatings play an important role in the field of thermal barrier coatings (TBCs). In addition to the cost-efficient process, attention was turned to the TBC material. Nowadays, yttria partially stabilized zirconia (YSZ) is used as standard TBC material. However, its long-term application at temperatures higher than 1200 °C is problematic. At these high temperatures, phase transitions and sintering effects lead to the degradation of the TBC system. To overcome those deficits of YSZ, Mg-Al-spinel was chosen as TBC material. Even though it has a lower melting point (~2135 °C) and a higher thermal conductivity (~2.5 W/m/K) than YSZ, Mg-Al-spinel provides phase stability at high temperatures in contrast to YSZ. The Mg-Al-spinel deposition by SPS resulted in columnar-structured coatings, which have been tested for their thermal cycling lifetime. Furthermore, the influence of substrate cooling during the spraying process on thermal cycling behavior, phase composition, and stoichiometry of the Mg-Al-spinel has been investigated.

Enhanced magneto-optical and photo-catalytic properties of transition metal cobalt (Co2+ ions) doped spinel MgFe2O4 ferrite nanocomposites

NASA Astrophysics Data System (ADS)

Abraham, A. Godlyn; Manikandan, A.; Manikandan, E.; Vadivel, S.; Jaganathan, S. K.; Baykal, A.; Renganathan, P. Sri

2018-04-01

In this study, spinel magnesium cobalt ferrite (CoxMg1-xFe2O4: x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) nanocomposites were synthesized successfully by modified sol-gel combustion method. Magnesium nitrate, cobalt nitrate and iron nitrate were used as the source of divalent (Mg2+ and Co2+) and trivalent (Fe3+) cations, respectively and urea were used as the reducing (fuel) agent. The effects of cobalt ions on morphology, structural, optical, magnetic and photo-catalytic properties of spinel CoxMg1-xFe2O4 nanocomposites were investigated. Various characterization methods, including X-ray powder diffraction (XRD), high resolution scanning electron microscope (HR-SEM), transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transforms infrared (FT-IR) spectroscopy, vibrating sample magnetometer (VSM) and photo-catalytic degradation (PCD) activity were used to study the phase purity, microstructure, particle size, elemental composition, functional group determination, band gap calculation, magnetic properties and degradation efficiency of nanoparticles, respectively. The observed results showed that the final products consists cubic spinel phase with sphere-like nanoparticles morphologies. Furthermore, spinel Co0.6Mg0.4Fe2O4 nanocomposite showed highest PCD efficiency (98.55%) than other composition of ferrite nanoparticles.

Symplectite in spinel lherzolite xenoliths from the Little Hungarian Plain, Western Hungary: A key for understanding the complex history of the upper mantle of the Pannonian Basin

NASA Astrophysics Data System (ADS)

Falus, György; Szabó, Csaba; Kovács, István; Zajacz, Zoltán; Halter, Werner

2007-03-01

Two spinel lherzolite xenoliths from Hungary that contain pyroxene-spinel symplectites have been studied using EPMA, Laser ablation ICP-MS and universal stage. Based on their geochemical and structural characteristics, the xenoliths represent two different domains of the shallow subcontinental lithospheric mantle beneath the Pannonian Basin. The occurrence of symplectites is attributed to the former presence and subsequent breakdown of garnets due to significant pressure decrease related to lithospheric thinning. This implies that both mantle domains were once part of the garnet lherzolitic upper mantle and had a similar history during the major extension that formed the Pannonian Basin. Garnet breakdown resulted in distinct geochemical characteristics in the adjacent clinopyroxene crystals in both xenoliths. This is manifested by enrichment in HREE, Y, Zr and Hf towards the clinopyroxene porphyroclast rims and also in the neoblasts with respect to porphyroclast core compositions. This geochemical feature, together with the development and preservation of the texturally very sensitive symplectites, enables us to determine the relative timing of mantle processes. Our results indicate that garnets had been metastable in the spinel lherzolite environment and their breakdown to pyroxene and spinel is one of the latest processes that took place within the upper mantle before the xenoliths were brought to the surface.

Photoelectrochemical and theoretical investigations of spinel type ferrites (MxFe3-xO4) for water splitting: a mini-review

NASA Astrophysics Data System (ADS)

Taffa, Dereje H.; Dillert, Ralf; Ulpe, Anna C.; Bauerfeind, Katharina C. L.; Bredow, Thomas; Bahnemann, Detlef W.; Wark, Michael

2017-01-01

Solar-assisted water splitting using photoelectrochemical cells (PECs) is one of the promising pathways for the production of hydrogen for renewable energy storage. The nature of the semiconductor material is the primary factor that controls the overall energy conversion efficiency. Finding semiconductor materials with appropriate semiconducting properties (stability, efficient charge separation and transport, abundant, visible light absorption) is still a challenge for developing materials for solar water splitting. Owing to the suitable bandgap for visible light harvesting and the abundance of iron-based oxide semiconductors, they are promising candidates for PECs and have received much research attention. Spinel ferrites are subclasses of iron oxides derived from the classical magnetite (FeIIFe2IIIO4) in which the FeII is replaced by one (some cases two) additional divalent metals. They are generally denoted as MxFe3-xO4 (M=Ca, Mg, Zn, Co, Ni, Mn, and so on) and mostly crystallize in spinel or inverse spinel structures. In this mini review, we present the current state of research in spinel ferrites as photoelectrode materials for PECs application. Strategies to improve energy conversion efficiency (nanostructuring, surface modification, and heterostructuring) will be presented. Furthermore, theoretical findings related to the electronic structure, bandgap, and magnetic properties will be presented and compared with experimental results.

System and process for dissolution of solids

DOEpatents

Liezers, Martin; Farmer, III, Orville T.

2017-10-10

A system and process are disclosed for dissolution of solids and "difficult-to-dissolve" solids. A solid sample may be ablated in an ablation device to generate nanoscale particles. Nanoparticles may then swept into a coupled plasma device operating at atmospheric pressure where the solid nanoparticles are atomized. The plasma exhaust may be delivered directly into an aqueous fluid to form a solution containing the atomized and dissolved solids. The composition of the resulting solution reflects the composition of the original solid sample.

Photoluminescent properties of Eu-doped ZnLiNbO4

NASA Astrophysics Data System (ADS)

Huang, Meng-Hsi; Lin, Ming-Hong; Fang, Te-Hua; Chang, Chia-Wei

2018-04-01

In this study, fluorescent Eu3+-doped ZnLiNbO4 materials were prepared via a vibrating milled solid-state reaction method. The objective was to develop new fluorescent oxide materials and study their fluorescent properties. The ZnLiNbO4 tetragonal spinel structure was formed with a single phase at a sintering temperature of 800 °C and with a regular shape at 1000 °C. The main exciton band was at 466 nm (7F0 → 5D2), and the main emission band was at 615 nm (5D0 → 7F2), which was an orange–red light band. The emission intensity was approximately 5% when the doping concentration reached 7%. The decay time was 2.96 ms.

Analytical solution for the transient wave propagation of a buried cylindrical P-wave line source in a semi-infinite elastic medium with a fluid surface layer

NASA Astrophysics Data System (ADS)

Shan, Zhendong; Ling, Daosheng

2018-02-01

This article develops an analytical solution for the transient wave propagation of a cylindrical P-wave line source in a semi-infinite elastic solid with a fluid layer. The analytical solution is presented in a simple closed form in which each term represents a transient physical wave. The Scholte equation is derived, through which the Scholte wave velocity can be determined. The Scholte wave is the wave that propagates along the interface between the fluid and solid. To develop the analytical solution, the wave fields in the fluid and solid are defined, their analytical solutions in the Laplace domain are derived using the boundary and interface conditions, and the solutions are then decomposed into series form according to the power series expansion method. Each item of the series solution has a clear physical meaning and represents a transient wave path. Finally, by applying Cagniard's method and the convolution theorem, the analytical solutions are transformed into the time domain. Numerical examples are provided to illustrate some interesting features in the fluid layer, the interface and the semi-infinite solid. When the P-wave velocity in the fluid is higher than that in the solid, two head waves in the solid, one head wave in the fluid and a Scholte wave at the interface are observed for the cylindrical P-wave line source.

Solid lipid nanoparticles suspension versus commercial solutions for dermal delivery of minoxidil.

PubMed

Padois, Karine; Cantiéni, Céline; Bertholle, Valérie; Bardel, Claire; Pirot, Fabrice; Falson, Françoise

2011-09-15

Solid lipid nanoparticles have been reported as possible carrier for skin drug delivery. Solid lipid nanoparticles are produced from biocompatible and biodegradable lipids. Solid lipid nanoparticles made of semi-synthetic triglycerides stabilized with a mixture of polysorbate and sorbitan oleate were loaded with 5% of minoxidil. The prepared systems were characterized for particle size, pH and drug content. Ex vivo skin penetration studies were performed using Franz-type glass diffusion cells and pig ear skin. Ex vivo skin corrosion studies were realized with a method derived from the Corrositex(®) test. Solid lipid nanoparticles suspensions were compared to commercial solutions in terms of skin penetration and skin corrosion. Solid lipid nanoparticles suspensions have been shown as efficient as commercial solutions for skin penetration; and were non-corrosive while commercial solutions presented a corrosive potential. Solid lipid nanoparticles suspensions would constitute a promising formulation for hair loss treatment. Copyright © 2011 Elsevier B.V. All rights reserved.

Volatile-rich komatiitic and picritic melt inclusions in Cr-spinel beach sand from Gorgona Island, Colombia

NASA Astrophysics Data System (ADS)

Shimizu, K.; Shimizu, N.; Suzuki, K.; Tatsumi, Y.; Komiya, T.; Maruyama, S.

2007-12-01

Volatile content of komatiite is a key to constrain thermal evolution of the deep Earth. We report volatile contents with major and trace element compositions of melt inclusions (MIs) in chromian spinel (Cr-spinel) from beach sands of Gorgona Island, Colombia. Gorgona Island is ~90 Ma volcanic island, where picrites and the world-youngest komatiites occur. As Cr-spinel is dense and rigid oxide mineral that crystallizes only at early stages of crystallization, it is considered to be a superior container for retaining primitive melt, even including volatiles. Volatile (H2O, CO2, S, F and Cl) and trace element (K2O, Sr, Y, Zr, Nb, Ba, La, Ce, Sm, Dy, Yb) compositions of ~80 MIs were analyzed by SIMS (Cameca-1280 and 3f, respectively) at WHOI. MIs in the Cr-spinel from Gorgona Is. are classified into three types by their host Cr-spinel compositions such as low-Ti (P-type), high-Ti with high-Cr# (BK-type) and high-Ti with low-Cr# (K-type). MIs of P-type, BK-type and K-type are mostly in compositional ranges of picrite, high TiO2 komatiite (some basalt) and low TiO2 komatiite in Gorgona Island, respectively. Water content of P-type MIs is variable, ranging from 0.05 to 0.9 wt%, whereas those of BK and K-type MIs are limited (< 0.1 wt%). On the other hand, CO2 contents of BK-type and K- type MIs are highly scattered (40 to 4200 ppm), whereas that of P-type is relatively constant at ~200 ppm. All MIs with high CO2 content (>500 ppm) do not contain (shrinkage) bubbles and many of them are low in K2O. H2O/K2O, CO2/K2O, S/K2O and F/K2O ratios are positively correlated with Y/Sr ratios, indicating degassing trends of melt at crystallization, magma mixing and/or assimilation. Undegassed H2O/K2O, CO2/K2O, S/K2O and F/K2O ratios of komatiitic (picritic) melt are estimated to be ~10 (~40), ~80 (n.d.), ~7(~3) and ~1(~0.5), respectively, which are much higher than those estimated for the depleted source mantle of the MORB [1.6, 0.7, 1.6 and 0.2, respectively; Salters, V. & Stracke, A. (2004), Composition of the depleted mantle. Geochem. Geophys. Geosys. 5 (2003GC000597)]. The results suggest that Gorgona komatiite and picrite magmas were derived from volatile-rich sources. CO2 degassing might also have contributed to eruption of high-density magmas to the surface. In addition, H2O, S, F and Cl contents in MIs in olivine from a picrite were identical to those of P-type MIs in Cr-spinel, but CO2 in olivine-hosted MIs were considerably lower (~50 ppm) than those in Cr-spinel. This indicates that entrapment pressure for MIs in Cr-spinel is likely to be greater than that for MIs in olivine. Therefore, in order to evaluate the volatile contents of undegassed magmas from oceanic islands, melt inclusions in Cr-spinel beach sand could be very useful.

Investigation of passive films on nickel Alloy 690 in lead-containing environments

NASA Astrophysics Data System (ADS)

Peng, B.; Lu, B. T.; Luo, J. L.; Lu, Y. C.; Ma, H. Y.

2008-09-01

Passive films formed on Alloy UNS N06690 were investigated in simulated crevice chemistries. It was found the role of lead in corrosion processes is strongly dependent on the pH value of the testing solutions. At pH 1.5 the effect of lead is narrowly noticeable; while at pH 12.7, lead has a significant influence on the electrochemical performance of alloy UNS N06690. The lead alters the surface morphologies at both pH and account for higher hydroxide content in the surface film at pH 12.7. The lead incorporation hinders the formation of spinel oxides during the passivation in alkaline solution. Nanoindentation tests indicate a significant lead-induced degradation in the mechanical properties of passive films. The passivation degradation is attributed to detrimental effects of lead via interrupting the dehydration process and hindering the formation of protective layers on the alloy surface.

Oceanization of the lithospheric mantle: the study case of the spinel peridotites from Monte Maggiore (Corsica, France).

NASA Astrophysics Data System (ADS)

Piccardo, G. B.

2009-04-01

The Monte Maggiore peridotite body, cropping out within the Alpine Corsica metamorphic belt, is an ophiolite massif derived from the more internal setting of the Jurassic Ligurian Tethys basin. It is mostly composed by spinel and plagioclase peridotites that are cut by MORB gabbroic dykes. The spinel peridotites, similarly to other ophiolitic peridotites from the Internal Ligurides, have been considered, on the basis of their low abundance of fusible components, low Si and high Mg contents, as refractory residua after MORB-type partial melting related to the formation of the Jurassic basin (e.g. Rampone et al., 1997). Recent studies (e.g. Müntener & Piccardo 2003; Rampone et al. 2008) have evidenced that these depleted spinel peridotites show diffuse melt-rock interaction micro-textures and contrasting bulk vs. mineral chemistry features which cannot be simply reconciled with partial melting. Accordingly, these peridotites have been recognized as reactive peridotites, formed by interaction of pristine peridotites with melts percolating by porous flow. Geochemical data have evidenced the depleted MORB signature of the percolating melts. Recent field studies at Monte Maggiore (Piccardo, 2007; Piccardo & Guarnieri, 2009), have revealed: 1) the presence and local abundance of pyroxenite-bearing, cpx-rich spinel lherzolites and 2) the replacement relationships of the reactive peridotites on the pyroxenite-bearing lherzolite rock-types. The pyroxenite-veined spinel lherzolites record a composite history of subsolidus evolution under lithospheric P-T conditions, thus indicating their provenance from the sub-continental lithospheric mantle. Accordingly, the pristine sub-continental mantle protoliths were infiltrated by MORB melts and transformed by melt-rock interaction to reactive spinel peridotites and refertilized by melt impregnation to plagioclase-enriched peridotites. Available isotopic data on the Mt. Maggiore spinel and plagioclase peridotites and gabbroic rocks (Rampone, 2004; Rampone et al., 2008; 2009) provide reliable geochronological informations (i.e. Sm-Nd cpx-plg-wr isochron ages and Sm-Nd model ages) and evidence that the whole mafic and ultramafic rocks show an overall Sm/Nd isotopic homogeneity. Cpx-plg-wr data from gabbroic dykes define internal isochrones yielding Jurassic ages (162+/-10 Ma and 159+/-15 Ma, respectively). The plg-cpx(-wr) isochrons for impregnated plagioclase peridotites yields age of 155+/-6 Ma. The initial ɛNd values (8.9-9.7) are indicative of a MORB affinity. Calculated DM model ages for both spinel and plagioclase peridotites point to a Late Jurassic age (150 Ma). Isotope ratios of cpx from spinel and plagioclase peridotites conform to the linear array defined by overall gabbroic rocks. The isotopic evidence from the melt-percolated, reactive and impregnated peridotites indicates that the pristine lithospheric mantle protoliths were isotopically homogenized by the melt-rock interaction during percolation/impregnation processes which erased any pre-existing isotopic signature. Moreover, the overall Sm/Nd isotopic homogeneity indicates that the asthenospheric mantle sources of the infiltrating melts were isotopically homogeneous. Accordingly, it is plausible that percolation and intrusion were operated by similar and coeval Late Jurassic MORB-type melts. In conclusion, petrologic and isotopic data allow to recognize that the extending sub-continental lithospheric mantle was infiltrated by Late Jurassic MORB melts, formed by asthenospheric decompression-induced partial melting during continental extension and rifting. Melt-peridotite interaction modified the compositional features of the lithospheric mantle and caused its isotopic resetting. Accordingly, the sub-continental lithospheric mantle underwent an "oceanization" process (i.e. isotope resetting to "oceanic" MORB signatures) during Late Jurassic times operated by asthenospheric MORB melts. Depending on the melt composition, the lithospheric level and the mode of melt-rock interaction, fertile peridotites from the sub-continental lithospheric mantle were transformed, concomitantly, to depleted spinel peridotites and refertilized plagioclase peridotites.

Role of the chemical substitution on the luminescence properties of solid solutions Ca{sub (1−x)}Cd{sub (x)}WO{sub 4} (0 ≤ x ≤1)

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

Taoufyq, A.; Laboratoire Matériaux et Environnement LME, Faculté des Sciences, Université Ibn Zohr, BP 8106, Cité Dakhla, Agadir; CEA, DEN, Département d'Etudes des Réacteurs, Service de Physique Expérimentale, Laboratoire Dosimétrie Capteurs Instrumentation, 13108 Saint-Paul-lez-Durance

2015-10-15

Highlights: • Luminescence can be modified by chemical substitution in solid solutions Ca{sub 1−x}Cd{sub x}WO{sub 4}. • The various emission spectra (charge transfer) were obtained under X-ray excitation. • Scheelite or wolframite solid solutions presented two types of emission spectra. • A luminescence component depended on cadmium substitution in each solid solution. • A component was only characteristic of oxyanion symmetry in each solid solution. - Abstract: We have investigated the chemical substitution effects on the luminescence properties under X-ray excitation of the solid solutions Ca{sub (1−x)}Cd{sub (x)}WO{sub 4} with 0 ≤ x ≤ 1. Two types of wide spectralmore » bands, associated with scheelite-type or wolframite-type solid solutions, have been observed at room temperature. We decomposed each spectral band into several spectral components characterized by energies and intensities varying with composition x. One Gaussian component was characterized by an energy decreasing regularly with the composition x, while the other Gaussian component was only related to the tetrahedral or octahedral configurations of tungstate groups WO{sub 4}{sup 2−} or WO{sub 6}{sup 6−}. The luminescence intensities exhibited minimum values in the composition range x < 0.5 corresponding to scheelite-type structures, then, they regularly increased for cadmium compositions x > 0.5 corresponding to wolframite-type structures.« less

Ultrathin spinel membrane-encapsulated layered lithium-rich cathode material for advanced Li-ion batteries.

PubMed

Wu, Feng; Li, Ning; Su, Yuefeng; Zhang, Linjing; Bao, Liying; Wang, Jing; Chen, Lai; Zheng, Yu; Dai, Liqin; Peng, Jingyuan; Chen, Shi

2014-06-11

Lack of high-performance cathode materials has become a technological bottleneck for the commercial development of advanced Li-ion batteries. We have proposed a biomimetic design and versatile synthesis of ultrathin spinel membrane-encapsulated layered lithium-rich cathode, a modification by nanocoating. The ultrathin spinel membrane is attributed to the superior high reversible capacity (over 290 mAh g(-1)), outstanding rate capability, and excellent cycling ability of this cathode, and even the stubborn illnesses of the layered lithium-rich cathode, such as voltage decay and thermal instability, are found to be relieved as well. This cathode is feasible to construct high-energy and high-power Li-ion batteries.

All-spinel oxide Josephson junctions for high-efficiency spin filtering.

PubMed

Mesoraca, S; Knudde, S; Leitao, D C; Cardoso, S; Blamire, M G

2018-01-10

Obtaining high efficiency spin filtering at room temperature using spinel ferromagnetic tunnel barriers has been hampered by the formation of antiphase boundaries due to their difference in lattice parameters between barrier and electrodes. In this work we demonstrate the use of LiTi 2 O 4 thin films as electrodes in an all-spinel oxide CoFe 2 O 4 -based spin filter devices. These structures show nearly perfect epitaxy maintained throughout the structure and so minimise the potential for APBs formation. The LiTi 2 O 4 in these devices is superconducting and so measurements at low temperature have been used to explore details of the tunnelling and Josephson junction behaviour.

Eutectics as improved pharmaceutical materials: design, properties and characterization.

PubMed

Cherukuvada, Suryanarayan; Nangia, Ashwini

2014-01-28

Eutectics are a long known class of multi-component solids with important and useful applications in daily life. In comparison to other multi-component crystalline solids, such as salts, solid solutions, molecular complexes and cocrystals, eutectics are less studied in terms of molecular structure organization and bonding interactions. Classically, a eutectic is defined based on its low melting point compared to the individual components. In this article, we attempt to define eutectics not just based on thermal methods but from a structural organization view point, and discuss their microstructures and properties as organic materials vis-a-vis solid solutions and cocrystals. The X-ray crystal structure of a cocrystal is different from that of the individual components whereas the unit cell of a solid solution is similar to that of one of the components. Eutectics are closer to the latter species in that their crystalline arrangement is similar to the parent components but they are different with respect to the structural integrity. A solid solution possesses structural homogeneity throughout the structure (single phase) but a eutectic is a heterogeneous ensemble of individual components whose crystal structures are like discontinuous solid solutions (phase separated). Thus, a eutectic may be better defined as a conglomerate of solid solutions. A structural analysis of cocrystals, solid solutions and eutectics has led to an understanding that materials with strong adhesive (hetero) interactions between the unlike components will lead to cocrystals whereas those having stronger cohesive (homo/self) interactions will more often give rise to solid solutions (for similar structures of components) and eutectics (for different structures of components). We demonstrate that the same crystal engineering principles which have been profitably utilized for cocrystal design in the past decade can now be applied to make eutectics as novel composite materials, illustrated by stable eutectics of the hygroscopic salt of the anti-tuberculosis drug ethambutol as a case study. A current gap in the characterization of eutectic microstructure may be fulfilled through pair distribution function (PDF) analysis of X-ray diffraction data, which could be a rapid signature technique to differentiate eutectics from their components.

Solution and solid trinitrotoluene (TNT) photochemistry: persistence of TNT-like ultraviolet (UV) resonance Raman bands.

PubMed

Gares, Katie L; Bykov, Sergei V; Godugu, Bhaskar; Asher, Sanford A

2014-01-01

We examined the 229 nm deep-ultraviolet resonance Raman (DUVRR) spectra of solution and solid-state trinitrotoluene (TNT) and its solution and solid-state photochemistry. Although TNT photodegrades with a solution quantum yield of ϕ ∼ 0.015, the initial photoproducts show DUVRR spectra extraordinarily similar to pure TNT, due to the similar photoproduct enhancement of the -NO2 stretching vibrations. This results in TNT-like DUVRR spectra even after complete TNT photolysis. These ultraviolet resonance Raman spectral bands enable DUVRR of trace as well as DUVRR standoff TNT detection. We determined the structure of various initial TNT photoproducts by using liquid chromatography-mass spectrometry and tandem mass spectrometry. Similar TNT DUVRR spectra and photoproducts are observed in the solution and solid states.

NEUTRALIZATIONS OF HIGH ALUMINUM LOW URANIUM USED NUCLEAR FUEL SOLUTIONS CONTAINING GADOLINIUM AS A NEUTRON POISON

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

Taylor-Pashow, K.

2011-06-08

H-Canyon will begin dissolving High Aluminum - Low Uranium (High Al/Low U) Used Nuclear Fuel (UNF) following approval by DOE which is anticipated in CY2011. High Al/Low U is an aluminum/enriched uranium UNF with small quantities of uranium relative to aluminum. The maximum enrichment level expected is 93% {sup 235}U. The High Al/Low U UNF will be dissolved in H-Canyon in a nitric acid/mercury/gadolinium solution. The resulting solution will be neutralized and transferred to Tank 39H in the Tank Farm. To confirm that the solution generated could be poisoned with Gd, neutralized, and discarded to the Savannah River Site (SRS)more » high level waste (HLW) system without undue nuclear safety concerns the caustic precipitation of simulant solutions was examined. Experiments were performed with three simulant solutions representative of the H-Canyon estimated concentrations in the final solutions after dissolution. The maximum U, Gd, and Al concentration were selected for testing from the range of solution compositions provided. Simulants were prepared in three different nitric acid concentrations, ranging from 0.5 to 1.5 M. The simulant solutions were neutralized to four different endpoints: (1) just before a solid phase was formed (pH 3.5-4), (2) the point where a solid phase was obtained, (3) 0.8 M free hydroxide, and (4) 1.2 M free hydroxide, using 50 wt % sodium hydroxide (NaOH). The settling behavior of the neutralized solutions was found to be slower compared to previous studies, with settling continuing over a one week period. Due to the high concentration of Al in these solutions, precipitation of solids was observed immediately upon addition of NaOH. Precipitation continued as additional NaOH was added, reaching a point where the mixture becomes almost completely solid due to the large amount of precipitate. As additional NaOH was added, some of the precipitate began to redissolve, and the solutions neutralized to the final two endpoints mixed easily and had expected densities of typical neutralized waste. Based on particle size and scanning electron microscopy analyses, the neutralized solids were found to be homogeneous and less than 20 microns in size. The majority of solids were less than 4 microns in size. Compared to previous studies, a larger percentage of the Gd was found to precipitate in the partially neutralized solutions (at pH 3.5-4). In addition the Gd:U mass ratio was found to be at least 1.0 in all of the solids obtained after partial or full neutralization. The hydrogen to U (H:U) molar ratios for two accident scenarios were also determined. The first was for transient neutralization and agitator failure. Experimentally this scenario was determined by measuring the H:U ratio of the settled solids. The minimum H:U molar ratio for solids from fully neutralized solutions was 388:1. The second accident scenario is for the solids drying out in an unagitiated pump box. Experimentally, this scenario was determined by measuring the H:U molar ratio in centrifuged solids. The minimum H:U atom ratios for centrifuged precipitated solids was 250:1. It was determined previously that a 30:1 H:Pu atom ratio was sufficient for a 1:1 Gd:Pu mass ratio. Assuming a 1:1 equivalence with {sup 239}Pu, the results of these experiments show Gd is a viable poison for neutralizing U/Gd solutions with the tested compositions.« less

An investigation of manganese based electrode materials for use in lithium ion batteries

NASA Astrophysics Data System (ADS)

Sengupta, Surajit

Lithium-based batteries are potential candidates to provide maximum volumetric and gravimetric energy density. One of the most attractive candidates as a cathode material for secondary lithium ion battery systems is the spinel LiMn 2O4 because it is environmentally friendly, less expensive and is capable of providing high energy density as compared to other cathode materials that are currently available. One problem associated with the spinel structure is capacity fading during multiple cycles of charge and discharge operations. This behaviour is due in part to the structural distortion during deep charge and discharge where nearly 100% of the lithium is extracted and inserted inside the spinel structure. Capacity fading can also be caused by dissolution of manganese ions in the electrolyte phase. A solution based method has been adapted for the synthesis of lithium manganese oxide, and chromium and cobalt doped mixed oxide materials using polyvinyl alcohol (PVA) as a chelating agent. It has been found from TGA/DSC analysis that at around 220°C the synthesis reaction is completed. The precursor powders obtained were annealed at different temperatures and times in the range of 250°C to 600°C and from 2 to 8 hours respectively to obtain pure spinel oxides. From X-ray analysis it has been observed that the crystallite size can be controlled in the range of approximately 6 nm to 32 nm depending on the annealing time and the temperature. The morphology of the synthesized materials consisted of submicron sized particles agglomerated with micropores inside the network structure. To observe the effect of physical properties on battery performance cyclic chronopotentiometric evaluation was conducted. It has been found with these synthesized materials that there is an increase in the 1st discharge capacity with an increase in the annealing time and the temperature at both 1C and C/5 rates. This increase is more significant when the annealing temperature is 600°C as compared to that at 250°C. This implies that an increase in particle size may improve the initial discharge capacity. It was observed that at the discharge rate of 1C, the material annealed at 600°C for 8 hours showed the best performance with respect to an average initial discharge capacity, energy density and capacity retention. However, it was found that the initial discharge capacity, the energy density and the capacity retention are poor for highly crystalline, micron sized lithium manganese oxide cathode material. (Abstract shortened by UMI.)

Inorganic ion sorbents

DOEpatents

Teter, David M.; Brady, Patrick V.; Krumhansl, James L.

2006-10-17

A process and medium for decontamination of water containing anionic species including arsenic and chromium, wherein compounds comprising divalent and trivalent metal oxides and sulfides are used to form surface complexes with contaminants under pH conditions within the range of potable water. In one embodiment natural and synthetic spinels and spinel-like materials are used as the sorbent substance.

A novel multi-functional magnetic Fe-Ti-V spinel catalyst for elemental mercury capture and callback from flue gas.

PubMed

Yang, Shijian; Guo, Yongfu; Yan, Naiqiang; Wu, Daqing; He, Hongping; Xie, Jiangkun; Qu, Zan; Yang, Chen; Jia, Jinping

2010-11-28

A novel magnetic Fe-Ti-V spinel catalyst showed an excellent performance for elemental mercury capture at 100 °C, and the formed HgO can be catalytically decomposed by the catalyst at 300 °C to reclaim elemental mercury and regenerate the catalyst.

Spinel from Apollo 12 Olivine Mare Basalts: Chemical Systematics of Selected Major, Minor, and Trace Elements

NASA Technical Reports Server (NTRS)

Papike, J. J.; Karner, J. M.; Shearer, C. K.; Spilde, M. N.

2002-01-01

Spinels from Apollo 12 Olivine basalts have been studied by Electron and Ion microprobe techniques. The zoning trends of major, minor and trace elements provide new insights into the conditions under which planetary basalts form. Additional information is contained in the original extended abstract.

Reduced grain boundary energies in rare-earth doped MgAl 2O 4 spinel and consequent grain growth inhibition

DOE PAGES

Hasan, Md M.; Dholabhai, Pratik P.; Dey, Sanchita; ...

2017-05-15

In this paper, grain growth inhibition in MgAl 2O 4 spinel nanostructure was achieved by grain boundary (GB) segregation of rare-earth dopants. Microcalorimetric measurements showed that dense spinel compacts doped with 3 mol% of R 2O 3 (R = Y, Gd, and La) had decreased GB energies as compared to the undoped spinel, representing reduction in the driving force for grain growth. Segregation energies of the three dopants to the Σ3 (111) GB were calculated by atomistic simulation. The dopants with higher ionic radius tend to segregate more strongly to GBs. The GB energies were calculated from atomistic simulation and,more » consistent with experiments, a systematic reduction in GB energy with dopant ionic size was found. Finally, high temperature grain growth experiments revealed a significant reduction of grain growth in the doped nanostructures as compared to the undoped one, which was attributed to increased metastability or possibly also a GB dragging originated from the dopant segregation.« less

Spinel formation for stabilizing simulated nickel-laden sludge with aluminum-rich ceramic precursors.

PubMed

Shih, Kaimin; White, Tim; Leckie, James O

2006-08-15

The feasibility of stabilizing nickel-laden sludge from commonly available Al-rich ceramic precursors was investigated and accomplished with high nickel incorporation efficiency. To simulate the process, nickel oxide was mixed alternatively with gamma-alumina, corundum, kaolinite, and mullite and was sintered from 800 to 1480 degrees C. The nickel aluminate spinel (NiAl2O4) was confirmed as the stabilization phase for nickel and crystallized with efficiencies greater than 90% for all precursors above 1250 degrees C and 3-h sintering. The nickel-incorporation reaction pathways with these precursors were identified, and the microstructure and spinel yield were investigated as a function of sintering temperature with fixed sintering time. This study has demonstrated a promising process for forming nickel spinel to stabilize nickel-laden sludge from a wide range of inexpensive ceramic precursors, which may provide an avenue for economically blending waste metal sludges via the building industry processes to reduce the environmental hazards of toxic metals. The correlation of product textures and nickel incorporation efficiencies through selection of different precursors also provides the option of tailoring property-specific products.

Coupled ferroelectric polarization and magnetization in spinel FeCr2S4

PubMed Central

Lin, L.; Zhu, H. X.; Jiang, X. M.; Wang, K. F.; Dong, S.; Yan, Z. B.; Yang, Z. R.; Wan, J. G.; Liu, J.-M.

2014-01-01

One of the core issues for multiferroicity is the strongly coupled ferroelectric polarization and magnetization, while so far most multiferroics have antiferromagnetic order with nearly zero magnetization. Magnetic spinel compounds with ferrimagnetic order may be alternative candidates offering large magnetization when ferroelectricity can be activated simultaneously. In this work, we investigate the ferroelectricity and magnetism of spinel FeCr2S4 in which the Fe2+ sublattice and Cr3+ sublattice are coupled in antiparallel alignment. Well defined ferroelectric transitions below the Fe2+ orbital ordering termperature Too = 8.5 K are demonstrated. The ferroelectric polarization has two components. One component arises mainly from the noncollinear conical spin order associated with the spin-orbit coupling, which is thus magnetic field sensitive. The other is probably attributed to the Jahn-Teller distortion induced lattice symmetry breaking, occuring below the orbital ordering of Fe2+. Furthermore, the coupled ferroelectric polarization and magnetization in response to magnetic field are observed. The present work suggests that spinel FeCr2S4 is a multiferroic offering both ferroelectricity and ferrimagnetism with large net magnetization. PMID:25284432

Semiconducting-metallic transition of singlecrystalline ferromagnetic Hf-doped CuCr2Se4 spinels

NASA Astrophysics Data System (ADS)

Maciążek, E.; Malicka, E.; Gągor, A.; Stokłosa, Z.; Groń, T.; Sawicki, B.; Duda, H.; Gudwański, A.

2017-09-01

Chalcogenide spinels show a variety of physical properties and are very good candidates for electronic and high-frequency applications. We report the measurements of magnetic susceptibility, magnetic isotherm, electrical conductivity, thermoelectric power and calculations of the superexchange and double-exchange integrals made for singlecrystalline Cu[CrxHfy]Se4 spinels. The results showed a ferromagnetic order of magnetic moments below the Curie temperatures of 390 K and, an increase in the splitting of the zero-field cooled and field cooled susceptibilities with increasing Hf-content below the room temperature suggesting a slight spin-frustration and a rapid transition from semiconducting to metallic state at room temperature. A quantitative evaluation of the exchange Hamiltonian showed that the total hopping integral rapidly decreased and the bandwidth of the 3d t2g band due to Cr3+ and Cr4+ ions strongly narrowed from 0.76 eV for y = 0 to 0.28 eV for y = 0.14. The narrowing of this band appears to be responsible for semiconducting properties of the Hf-doped CuCr2Se4 spinels below the room temperature.

Effect of Zn-doping on structural and magnetic properties of copper ferrite nanoparticles

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

Gautam, Nisha; Thirupathi, Gadipelly; Singh, Rajender

2016-05-23

The nanoparticles of CuFe{sub 2}O{sub 4} (CF) and Cu{sub 0.8}Zn{sub 0.2}Fe{sub 2}O{sub 4} (CZF) were synthesized using co-precipitation method to study the effect of Zn doping in Cu-ferrite. The X-ray diffraction (XRD) patterns were well fitted with two-phase structure using Rietveld analysis as Fd-3 m space group (spinel system) and C12/c1 space group (monoclinic system CuO-phase). The average crystallite size of the CF and CZF nanoparticles for spinel structure are 6 and 7 nm respectively. The spinel phase fraction is increased from 56% to 71% with Zn-doping of 20% in CF. The transmission electron micrograph analysis showed the narrow size distribution formore » CZF nanoparticles. The magnetization plots as a function of magnetic field (M (H)) of CF and CZF nanoparticles indicate superparamagnetic behavior. The magnetization is increased with Zn-doping in CF. The stable spinel Cu-ferrite can be obtained with Zn-doping in CF.« less

Dipole defects in MgAl2O4 spinel crystals

NASA Astrophysics Data System (ADS)

Ayres, F.; de Souza, S. S.; Blak, A. R.

In order to study defects of dipole origin in normal and inverse spinel structures, Thermally Stimulated Depolarisation Current (TSDC) measurements have been carried out in MgAl2O4 spinel crystals doped with Fe, Cr, Mn and Co. The TSDC spectrum of the as-received sample labelled R shows two bands at 160K and 290K. Temperatures above 700K destroy the 290K band and γ-irradiation up to 1,500kGy restores the peak. In another sample labelled UC, the 290K band, of dipole origin, is only detected after γ-irradiation. The dipole origin of the 160K band has already been verified. This band is affected neither by γ-irradiation nor by thermal treatment. The reduction of the 290K band is observed when heating the samples between 350K and 480K for three minutes at each temperature. The correlation between the thermal reduction of the 290K band and the study of V-centres in MgAl2O4 spinels indicates the possible attribution of the band to V-type centres.

Study on the energy band structure and photoelectrochemical performances of spinel Li{sub 4}Ti{sub 5}O{sub 12}

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

Ge, Hao; Tian, Hui; Song, Hua

2015-01-15

Highlights: • Spinel Li{sub 4}Ti{sub 5}O{sub 12} possesses more positive potential of valence band and wider band gap than TiO{sub 2}. • Spinel Li{sub 4}Ti{sub 5}O{sub 12} displays typical n-type semiconductor characteristic and excellent UV-excitateded photocatalysis activity. • Our preliminary study will open new perspectives in investigation of other lithium-based compounds for new photocatalysts. - Abstract: Energy band structure, photoelectrochemical performances and photocatalysis activity of spinel Li{sub 4}Ti{sub 5}O{sub 12} are investigated for the first time in this paper. Li{sub 4}Ti{sub 5}O{sub 12} possesses more positive valence band potential and wider band gap than TiO{sub 2} due to its valencemore » band consisting of Li{sub 1s} and Ti{sub 3d} orbitals mixed with O{sub 2p}. Li{sub 4}Ti{sub 5}O{sub 12} shows typical photocatalysis material characteristics and excellent photocatlytic activity under UV irradiation.« less

Cations in Octahedral Sites: A Descriptor for Oxygen Electrocatalysis on Transition-Metal Spinels

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

Wei, Chao; Feng, Zhenxing; Scherer, Günther G.

2017-04-10

Exploring efficient and low-cost electrocatalysts for the oxygen-reduction reaction (ORR) and oxygen-evolution reaction (OER) is critical for developing renewable energy technologies such as fuel cells, metal–air batteries, and water electrolyzers. A rational design of a catalyst can be guided by identifying descriptors that determine its activity. Here, a descriptor study on the ORR/OER of spinel oxides is presented. With a series of MnCo2O4, the Mn in octahedral sites is identified as an active site. This finding is then applied to successfully explain the ORR/OER activities of other transition-metal spinels, including MnxCo3-xO4 (x = 2, 2.5, 3), LixMn2O4 (x = 0.7,more » 1), XCo2O4 (X = Co, Ni, Zn), and XFe2O4 (X = Mn, Co, Ni). A general principle is concluded that the eg occupancy of the active cation in the octahedral site is the activity descriptor for the ORR/OER of spinels, consolidating the role of electron orbital filling in metal oxide catalysis.« less

Mineralogy and origin of coarse-grained segregations in the pyrometallurgical Zn-Pb slags from Katowice-Wełnowiec (Poland)

NASA Astrophysics Data System (ADS)

Warchulski, R.; Gawęda, A.; Janeczek, J.; Kądziołka-Gaweł, M.

2016-10-01

The unique among pyrometallurgical slags, coarse-grained (up to 2.5 cm) segregations (up to 40 cm long) rimmed by "aplitic" border zones occur within holocrystalline historical Zn-smelting slag in Katowice, S Poland. Slag surrounding the segregations consists of olivine, spinel series, melilite, clinopyroxene, leucite, nepheline and sulphides. Ca-olivines, kalsilite and mica compositionally similar to oxykinoshitalite occur in border zones in addition to olivine, spinel series and melilite. Miarolitic and massive pegmatite-like segregations are built of subhedral crystals of melilite, leucite, spinel series, clinopyroxene and hematite. Melilite, clinopyroxenes and spinels in the segregations are enriched in Zn relatively to original slag and to fine-grained border zones. The segregations originated as a result of crystallization from residual melt rich in volatiles (presumably CO2). The volatile-rich melt was separated during fractional crystallization of molten slag under the cover of the overlying hot (ca. 1250 °C) vesicular slag, preventing the escape of volatiles. That unique slag system is analogous to natural magmatic systems.

An X-ray absorption spectroscopy study of the inversion degree in zinc ferrite nanocrystals dispersed on a highly porous silica aerogel matrix.

PubMed

Carta, D; Marras, C; Loche, D; Mountjoy, G; Ahmed, S I; Corrias, A

2013-02-07

The structural properties of zinc ferrite nanoparticles with spinel structure dispersed in a highly porous SiO(2) aerogel matrix were compared with a bulk zinc ferrite sample. In particular, the details of the cation distribution between the octahedral (B) and tetrahedral (A) sites of the spinel structure were determined using X-ray absorption spectroscopy. The analysis of both the X-ray absorption near edge structure and the extended X-ray absorption fine structure indicates that the degree of inversion of the zinc ferrite spinel structures varies with particle size. In particular, in the bulk microcrystalline sample, Zn(2+) ions are at the tetrahedral sites and trivalent Fe(3+) ions occupy octahedral sites (normal spinel). When particle size decreases, Zn(2+) ions are transferred to octahedral sites and the degree of inversion is found to increase as the nanoparticle size decreases. This is the first time that a variation of the degree of inversion with particle size is observed in ferrite nanoparticles grown within an aerogel matrix.

Preparation of Layered-Spinel Microsphere/Reduced Graphene Oxide Cathode Materials for Ultrafast Charge-Discharge Lithium-Ion Batteries.

PubMed

Luo, Dong; Fang, Shaohua; Yang, Li; Hirano, Shin-Ichi

2017-12-22

Although Li-rich layered oxides (LLOs) have the highest capacity of any cathodes used, the rate capability of LLOs falls short of meeting the requirements of electric vehicles and smart grids. Herein, a layered-spinel microsphere/reduced graphene oxide heterostructured cathode (LS@rGO) is prepared in situ. This cathode is composed of a spinel phase, two layered structures, and a small amount of reduced graphene oxide (1.08 wt % of carbon). The assembly delivers a considerable charge capacity (145 mA h g -1 ) at an ultrahigh charge- discharge rate of 60 C (12 A g -1 ). The rate capability of LS@rGO is influenced by the introduced spinel phase and rGO. X-ray absorption and X-ray photoelectron spectroscopy data indicate that Cr ions move from octahedral lattice sites to tetrahedral lattice sites, and that Mn ions do not participate in the oxidation reaction during the initial charge process. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Process for recovering pertechnetate ions from an aqueous solution also containing other ions

DOEpatents

Rogers, Robin; Horwitz, E. Philip; Bond, Andrew H.

1997-01-01

A solid/liquid process for the separation and recovery of TcO.sub.4.sup.-1 ions from an aqueous solution is disclosed. The solid support comprises separation particles having surface-bonded poly(ethylene glycol) groups; whereas the aqueous solution from which the TcO.sub.4.sup.-1 ions are separated contains a poly(ethylene glycol) liquid/liquid biphase-forming amount of a dissolved salt. A solid/liquid phase admixture of separation particles containing bound TcO.sub.4.sup.-1 ions in such an aqueous solution that is free from MoO.sub.4.sup.-2 ions is also contemplated, as is a chromatography apparatus containing that solid/liquid phase admixture.

Operando identification of the point of [Mn- 2]O- 4 spinel formation during gamma-MnO 2 discharge within batteries

DOE PAGES

Gallaway, Joshua W.; Hertzberg, Benjamin J.; Zhong, Zhong; ...

2016-05-07

The rechargeability of γ-MnO 2 cathodes in alkaline batteries is limited by the formation of the [Mn 2]O 4 spinels ZnMn 2O 4 (hetaerolite) and Mn 3O 4 (hausmannite). However, the time and formation mechanisms of these spinels are not well understood. Here we directly observe γ-MnO 2 discharge at a range of reaction extents distributed across a thick porous electrode. Coupled with a battery model, this reveals that spinel formation occurs at a precise and predictable point in the reaction, regardless of reaction rate. Observation is accomplished by energy dispersive X-ray diffraction (EDXRD) using photons of high energy andmore » high flux, which penetrate the cell and provide diffraction data as a function of location and time. After insertion of 0.79 protons per γ-MnO 2 the α-MnOOH phase forms rapidly. α-MnOOH is the precursor to spinel, which closely follows. ZnMn 2O 4 and Mn 3O 4 form at the same discharge depth, by the same mechanism. The results show the final discharge product, Mn 3O 4 or Mn(OH) 2, is not an intrinsic property of γ-MnO 2. While several studies have identified Mn(OH) 2 as the final γ-MnO 2 discharge product, we observe direct conversion to Mn 3O 4 with no Mn(OH) 2.« less

Experimental investigation of the reaction between corundum xenocrysts and alkaline basaltic host magma: Constraints on magma residence times of basalt-hosted sapphires

NASA Astrophysics Data System (ADS)

Baldwin, L. C.; Ballhaus, C.

2018-03-01

Megacrystic sapphires (Fe-Ti-rich corundum) of up to 5 cm in size are well known from alkaline mafic rocks from intra-continental rift-related magmatic fields. There is no doubt that these sapphires represent xenocrysts that were trapped from their original lithology by ascending basaltic magmas carrying them to the Earth's surface. Most studies about basalt-hosted sapphires address the question about the origin of the sapphires, but there is hardly any information available about the time the sapphires resided inside the carrier melt. Sapphires are in reaction relationship with basalt and produce spinel coronas at the sapphire-basalt interface, spatially separating the mutually incompatible phases from one another. Assuming isothermal and isobaric conditions of spinel rim formation, the rim-thickness should be a function of the reaction time with the basaltic melt. In this paper, we report time-series experiments aimed at investigating the kinetics of spinel rim formation due to igneous corrosion of corundum. Therefore, we reacted corundum fragments with alkaline basalt powder at 1250 °C and 1GPa, using a Piston Cylinder Apparatus. The width of the spinel rim was used to estimate a residence time. Extrapolating the experimentally derived reaction rates to the thickness of natural spinel rims as described from the Siebengebirge Volcanic Field, Germany, and from Changle, China, we estimated residence times in the order of a few weeks to months.

H2S-Modified Fe-Ti Spinel: A Recyclable Magnetic Sorbent for Recovering Gaseous Elemental Mercury from Flue Gas as a Co-Benefit of Wet Electrostatic Precipitators.

PubMed

Zou, Sijie; Liao, Yong; Xiong, Shangchao; Huang, Nan; Geng, Yang; Yang, Shijian

2017-03-21

The nonrecyclability of the sorbents used to capture Hg 0 from flue gas causes a high operation cost and the potential risk of exposure to Hg. The installation of wet electrostatic precipitators (WESPs) in coal-fired plants makes possible the recovery of spent sorbents for recycling and the centralized control of Hg pollution. In this work, a H 2 S-modified Fe-Ti spinel was developed as a recyclable magnetic sorbent to recover Hg 0 from flue gas as a co-benefit of the WESP. Although the Fe-Ti spinel exhibited poor Hg 0 capture activity in the temperature range of flue gas downstream of flue gas desulfurization, the H 2 S-modified Fe-Ti spinel exhibited excellent Hg 0 capture performance with an average adsorption rate of 1.92 μg g -1 min -1 at 60 °C and a capacity of 0.69 mg g -1 (5% of the breakthrough threshold) due to the presence of S 2 2- on its surface. The five cycles of Hg 0 capture, Hg 0 recovery, and sorbent regeneration demonstrated that the ability of the modified Fe-Ti spinel to capture Hg 0 did not degrade remarkably. Meanwhile, the ultralow concentration of Hg 0 in flue gas was increased to a high concentration of Hg 0 , which facilitated the centralized control of Hg pollution.

LEACHING OF TITANIUM FROM MONOSODIUM TITANATE AND MODIFIED MST

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

Taylor-Pashow, K.; Fondeur, F.; Fink, S.

2012-08-01

Analysis of a fouled coalescer and pre-filters from Actinide Removal Process/Modular Caustic Side Solvent Extraction Unit (ARP/MCU) operations showed evidence of Ti containing solids. Based on these results a series of tests were planned to examine the extent of Ti leaching from monosodium titanate (MST) and modified monosodium titanate (mMST) in various solutions. The solutions tested included a series of salt solutions with varying free hydroxide concentrations, two sodium hydroxide concentrations, 9 wt % and 15 wt %, nitric and oxalic acid solutions. Overall, the amount of Ti leached from the MST and mMST was much greater in the acidmore » solutions compared to the sodium hydroxide or salt solutions, which is consistent with the expected trend. The leaching data also showed that increasing hydroxide concentration, whether pure NaOH solution used for filter cleaning in ARP or the waste salt solution, increased the amount of Ti leached from both the MST and mMST. For the respective nominal contact times with the MST solids - for filter cleaning or the normal filter operation, the dissolved Ti concentrations are comparable suggesting either cause may contribute to the increased Ti fouling on the MCU coalescers. Tests showed that Ti containing solids could be precipitated from solution after the addition of scrub acid and a decrease in temperature similar to expected in MCU operations. FTIR analysis of these solids showed some similarity to the solids observed on the fouled coalescer and pre-filters. Although only a cursory study, this information suggests that the practice of increasing free hydroxide in feed solutions to MCU as a mitigation to aluminosilicate formation may be offset by the impact of formation of Ti solids in the overall process. Additional consideration of this finding from MCU and SWPF operation is warranted.« less

The Record of Meteorite Infall During the Jurassic as Derived from Chrome-Spinel Grains

NASA Astrophysics Data System (ADS)

Caplan, C.; Huss, G. R.; Schmitz, B.; Nagashima, K.

2017-12-01

We study sediment-dispersed chrome-spinels in the stratigraphic record to determine how the types and amounts of meteorites falling to Earth have changed over time. The parent meteorite type of chrome-spinel grains can be determined using characteristic elemental and O-isotope compositions. In this study, we present data on grains from the Jurassic period ( 160 Ma). The Jurassic was chosen because of the possibility of discovering remnants from the breakup of the Baptistina asteroid family estimated to have occurred 160 Ma (+30, -20 Myr) (Bottke et al., 2007). Chrome-spinel grains derived from 400 kg of condensed limestone near Carcabuey, Spain were measured for their chemical compositions by electron microprobe, and their O-isotope compositions were measured by ion microprobe at the University of Hawai'i. Initial results show that 43% of the grains come from ordinary chondrites (OCs) and 18% from known types of achondrites. The remaining grains are extraterrestrial, as shown by their O-isotopes, but have not yet been classified. Some may represent material that is not currently falling on Earth. Meteorites falling on Earth today are 90.6% OCs and 7.1% achondrites. The Jurassic samples show a lower percentage of chrome-spinels from OCs (even though OCs are chrome-spinel rich). Other time periods also show meteorite abundances that are different than today. About 466 Ma there was an overwhelming influx of L-chondritic material (>99% of infalling material), due to the breakup of the L-chondrite parent body (Schmitz et al., 2001). One million years prior to the breakup, 56% of the infalling meteorites were OCs and 44% were achondrites (Heck et al., 2017). A new study suggests that 80% of the material falling in the Early Cretaceous (145-133 Ma) were from OCs and 10% were from achondrites (Schmitz et al., 2017). With just a few windows into Earth's past, we are already seeing significant changes in the mixture of materials that have fallen to Earth throughout time.

Fe2SiO4-rich spinel as mineral in a shocked meteorite - constraints on P-T conditions during shock

NASA Astrophysics Data System (ADS)

Tschauner, O.; Ma, C.; Asimow, P. D.; Kostandova, N.

2008-12-01

We report the occurrence of a spinel phase (Fe0.8, Mg0.2)2(Si0.9, Fe0.1)O4 in veins of the L4 chondrite Laundry West, Nullarbor, Australia. While Fe2SiO4-rich spinel has been reported from the Umbarger meteorite earlier (Xie et al. Am .Min. 87, 1257, 2002), the present study is the first to present complete structural and chemical information. We collected powder diffraction, EBSD, and EMP data, all confirming structure and chemistry of this new mineral, the Fe-endmember analog of Mg2SiO4 ringwoodite. The observation of this spinel phase, which forms at pressures of a few GPa under static conditions, in a shocked meteorite is a contribution to a finer shock metamorphic scale. The vicinity of these FeSi-spinel grains to melted (Fe,Ni)S in combination with modeling of shock reverberation in a FeS-silicate system allows for estimating a lower limit of the peak shock pressure and temperature: The fayalite-spinel P-T phase boundary and the melting curve of (Fe,Ni)S determine a fixed point in P-T space of 5-6 GPa and 1500 - 1600 K. However, the bulk shock pressure (and temperature) was lower and can be calculated by impedance match. Acknowledgements: We dedicate this work to our friend and collaborator Thomas J. Ahrens. We are particularly grateful to Dr. Zhongwu Wang, CHESS, for providing beamtime and support at station B2. This work was supported by NNSA Cooperative Agreement DOE-FC88-01NV14049 and NASA/Goddard grants under awards NNG04GP57G and NNG04GI07G. Participation by NK was supported by the Caltech SURF program and in particular by Mr. and Mrs. Robert E. Anderson.

Structural, magnetic, optical, dielectric, electrical and modulus spectroscopic characteristics of ZnFe2O4 spinel ferrite nanoparticles synthesized via honey-mediated sol-gel combustion method

NASA Astrophysics Data System (ADS)

Yadav, Raghvendra Singh; Kuřitka, Ivo; Vilcakova, Jarmila; Urbánek, Pavel; Machovsky, Michal; Masař, Milan; Holek, Martin

2017-11-01

This paper reports a honey-mediated green synthesis of ZnFe2O4 spinel ferrite nanoparticles and the effect of further annealing on structural, magnetic, optical, dielectric and electrical properties. X-ray diffraction study confirmed the well formation of ZnFe2O4 spinel ferrite crystal structure. Raman and Fourier transform infrared spectroscopy confirmed the formation of spinel ferrite crystal structure. The scanning electron microscopy study revealed the formation of spherical morphology at lower annealing temperature with achieved particle size 30-60 nm, whereas, octahedral like morphology at higher annealing temperature with particle size 50-400 nm. Magnetization measurements were carried out using a vibrating sample magnetometer at room temperature. The estimated magnetic parameter such as saturation magnetization (Ms), remanence (Mr) and coercivity (Hc) showed variation in value with nano-crystallite size. The highest saturation magnetization (Ms) was 12.81 emu/g for as-synthesized ZnFe2O4 spinel ferrite nanoparticles, whereas, highest coercivity (Hc) was 25.77 Oe for ZnFe2O4 nanoparticles annealed at high temperature 1000 °C. UV-Visible reflectance spectroscopy showed the band gap variation from 1.90 eV to 2.14 eV with the increase of annealing temperature. The dielectric constant and dielectric loss were decreased with frequency showing the normal behavior of spinel ferrites. The variation in conductivity is explained in terms of the variation in microstructure and variation in the mobility of charge carriers associated with the cation redistribution induced by annealing or grain size. The modulus and impedance spectroscopy study revealed the influence of bulk grain and the grain boundary on the electrical resistance and capacitance of ZnFe2O4 nanoparticles. The results presented in this work are helpful for green synthesis of well-controlled size, morphology and physical properties of ZnFe2O4 nanoparticles.

H Diffusion in Olivine and Pyroxene from Peridotite Xenoliths and a Hawaiian Magma Speedometer

NASA Technical Reports Server (NTRS)

Peslier, A. H.; Bizimis, M.

2014-01-01

Hydrogen is present as a trace element in olivine and pyroxene and its content distribution in the mantle results from melting and metasomatic processes. Here we examine how these H contents can be disturbed during decompression. Hydrogen was analyzed by FTIR in olivine and pyroxene of spinel peridotite xenoliths from Salt Lake Crater (SLC) nephelinites which are part of the rejuvenated volcanism at Oahu (Hawaii) [1,2]. H mobility in pyroxene resulting from spinel exsolution during mantle upwelling Most pyroxenes in SLC peridotites exhibit exsolutions, characterized by spinel inclusions. Pyroxene edges where no exsolution are present have less H then their core near the spinel. Given that H does not enter spinel [3], subsolidus requilibration may have concentrated H in the pyroxene adjacent to the spinel exsolution during mantle upwelling. H diffusion in olivine during xenolith transport by its host magma and host magma ascent rates Olivines have lower water contents at the edge and near fractures compared to at their core, while the concentrations of all other chemical elements appear homogeneous. This suggests that some of the initial water has diffused out of the olivine. Water loss from the olivine is thought to occur during host-magma ascent and xenolith transport to the surface [4-6]. Diffusion modeling matches best the data when the initial water content used is that measured at the core of the olivines, implying that mantle water contents are preserved at the core of the olivines. The 3225 cm(sup -1) OH band at times varies independantly of other OH bands, suggesting uneven H distribution in olivine defects likely acquired during mantle metasomatism just prior to eruption and unequilibrated. Diffusion times (1-48 hrs) combined with depths of peridotite equilibration or of magma start of degassing allow to calculate ascent rates for the host nephelinite of 0.1 to 27 m/s.

Structure of oxides prepared by decomposition of layered double Mg–Al and Ni–Al hydroxides

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

Cherepanova, Svetlana V.; Novosibirsk State University, Novosibirsk; Leont’eva, Natalya N., E-mail: n_n_leonteva@list.ru

2015-05-15

Abstracts: Thermal decomposition of Mg–Al and Ni–Al layered double hydroxides LDH at temperatures lower than 800 °C leads to the formation of oxides with different structures. Mg–Al oxide has a very defective structure and consists of octahedral layers as in periclase MgO and mixed octahedral–tetrahedral layers as in spinel MgAl{sub 2}O{sub 4}. Mixed Ni–Al oxide has a sandwich-like structure, consisting of a core with Al-doped NiO-like structure and some surface layers with spinel NiAl{sub 2}O{sub 4} structure epitaxial connected with the core. Suggested models were verified by simulation of X-ray diffraction patterns using DIFFaX code, as well as HRTEM, IR-,more » UV-spectroscopies, and XPS. - Graphical abstract: In the Mg–Al layered double hydroxide Al{sup 3+} ions migrate into interlayers during decomposition. The Mg–Al oxide represents sequence of octahedral and octahedral–tetrahedral spinel layers with vacancies. The Ni–Al oxide has a sandwich-like structure with NiO-like core and surface spinel layers as a result of migration of Al{sup 3+} ions on the surface. The models explain the presence and absence of “memory effect” for the Mg–Al and Ni–Al oxides, respectively. - Highlights: • We study products of Mg(Ni)–Al LDH decomposition by calcination at 500(400)–800 °C. • In Mg–Al/Ni–Al LDH Al ions migrate into interlayers/on the surface during decomposition. • Mg–Al oxide represents sequence of periclase- and spinel-like layers with vacancies. • Ni–Al oxide has a sandwich-like structure with NiO-like core and surface spinel layers. • The models explain the presence/absence of “memory effect” for Mg–Al/Ni–Al oxides.« less

Solid lithium ion conducting electrolytes and methods of preparation

DOEpatents

Narula, Chaitanya K; Daniel, Claus

2013-05-28

A composition comprised of nanoparticles of lithium ion conducting solid oxide material, wherein the solid oxide material is comprised of lithium ions, and at least one type of metal ion selected from pentavalent metal ions and trivalent lanthanide metal ions. Solution methods useful for synthesizing these solid oxide materials, as well as precursor solutions and components thereof, are also described. The solid oxide materials are incorporated as electrolytes into lithium ion batteries.

Solid lithium ion conducting electrolytes and methods of preparation

DOEpatents

Narula, Chaitanya K.; Daniel, Claus

2015-11-19

A composition comprised of nanoparticles of lithium ion conducting solid oxide material, wherein the solid oxide material is comprised of lithium ions, and at least one type of metal ion selected from pentavalent metal ions and trivalent lanthanide metal ions. Solution methods useful for synthesizing these solid oxide materials, as well as precursor solutions and components thereof, are also described. The solid oxide materials are incorporated as electrolytes into lithium ion batteries.

INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Simple formula for the thermal conductivity of a quaternary solid solution

NASA Astrophysics Data System (ADS)

Nakwaski, W.

1988-11-01

An analysis is made of the thermal conductivity of quaternary solid solutions (alloys) allowing for their disordered structure on the basis of a phenomenological analysis proposed by Abeles. This method is applied to a quaternary solid solution In1 - xGaxAsyP1 - y. A simple analytic expression is derived for the thermal conductivity of this material.

Lattice Parameter Behavior with Different Nd and O Concentrations in (U 1-yNd y)O 2±x Solid Solution

DOE PAGES

Lee, Seung Min; Knight, Travis W.; Voit, Stwart L.; ...

2016-02-02

The solid solution of (U1-yFPy)O- 2±x, has the same fluorite structure as UO 2±x lambda, and the lattice parameter is affected by dissolved fission product and oxygen concentrations. We investigated the relation between the lattice parameter and the concentrations of neodymium and oxygen in the fluorite structure of (U 1-yNd y)O 2±x using X-ray diffraction. Moreover, the lattice parameter behavior in the (U 1-yNd y)O 2±x, solid solution shows a linear change as a function of the oxygen-to-metal ratio and solubility of neodymium. The lattice parameter depends on the radii of ions forming the fluorite structure and also can bemore » expressed by a particular rule (modified Vegard's law). Furthermore, the numerical analyses of the lattice parameters for the stoichiometric and nonstoichionietric solid solutions were conducted, and the lattice parameter model for the (U1-yNdy)O 2±x, solid solution was assessed. There is a very linear relationship between the lattice parameter and the Nd and O concentration for the stoichiometry and nonstoichiometry of the (U 1-yNd y)O 2±x solid solution was verified.« less

First Ti-XANES analyses of refractory inclusions from Murchison

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

Simon, S.B.; Sutton, S.R.; Grossman, L.

2009-03-23

Ti valence in refractory phases is an important recorder of redox conditions in the early solar nebula. We report the valence of Ti in pyroxene, spinel and hibonite in spinel-hibonite and spinel-pyroxene inclusions and in a coarse hibonite grain. A system of solar composition is so reducing that Ti{sup 3+} and Ti{sup 4+} can coexist, making the valence of Ti a valuable indicator of f{sub O2} conditions during formation of nebular materials. The Ti{sup 3+}/Ti{sup 4+} ratios observed in the Ti-rich phases fassaite and rhoenite in coarse-grained refractory inclusions from CV3 chondrites have been shown to be quantitatively consistent withmore » formation in a gas of solar composition (log f{sub O2} = IW-6.8), but these are the only objects in chondrites for which this is the case. Here, we report the valence of Ti in various phases in refractory inclusions from the Murchison CM2 chondrite. The second-highest temperature, major-element-bearing phase predicted to condense from a gas of solar composition, hibonite (ideally CaAl{sub 12}O{sub 19}), can contain significant amounts of Ti, but the hibonite structure can have oxygen vacancies, so calculation of Ti valence from stoichiometry of electron probe analyses is not recommended for hibonite. To date, the only reported measurement of Ti valence in meteoritic hibonite was done by electron spin resonance, on coarse crystals from a Murchison hibonite-perovskite-melilite inclusion. Spinel and most of the pyroxene in CM inclusions contain too little Ti for derivation of Ti{sup 3+}/Ti{sup 4+} ratios from electron probe analyses. X-ray absorption near edge spectroscopy (XANES), however, allows determination of Ti valence in relatively Ti-poor phases. In the present work, we apply synchrotron microXANES to a large hibonite grain from Murchison and to spinel-hibonite (sp-hib) and spinel-pyroxene (sp-pyx) inclusions from Murchison, refractory materials whose Ti{sup 3+}/Ti{sup 4+} ratios have not been previously measured. Analysis of these samples allows comparison of Ti valence of (1) pyroxene in sp-pyx inclusions with that of fassaite; (2) spinel in hibonite-bearing with that of hibonite-free inclusions; and (3) hibonite in sp-hib inclusions with that of large, single grains and the previously analyzed sample.« less

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

Bruce S. Kang

The objective of this project was to understand and improve high-temperature structural properties of metal-silicide intermetallic alloys. Through research collaboration between the research team at West Virginia University (WVU) and Dr. J.H. Schneibel at Oak Ridge National Laboratory (ORNL), molybdenum silicide alloys were developed at ORNL and evaluated at WVU through atomistic modeling analyses, thermo-mechanical tests, and metallurgical studies. In this study, molybdenum-based alloys were ductilized by dispersing MgAl2O4 or MgO spinel particles. The addition of spinel particles is hypothesized to getter impurities such as oxygen and nitrogen from the alloy matrix with the result of ductility improvement. The introductionmore » of fine dispersions has also been postulated to improve ductility by acting as a dislocation source or reducing dislocation pile-ups at grain boundaries. The spinel particles, on the other hand, can also act as local notches or crack initiation sites, which is detrimental to the alloy mechanical properties. Optimization of material processing condition is important to develop the desirable molybdenum alloys with sufficient room-temperature ductility. Atomistic analyses were conducted to further understand the mechanism of ductility improvement of the molybdenum alloys and the results showed that trace amount of residual oxygen may be responsible for the brittle behavior of the as-cast Mo alloys. For the alloys studied, uniaxial tensile tests were conducted at different loading rates, and at room and elevated temperatures. Thermal cycling effect on the mechanical properties was also studied. Tensile tests for specimens subjected to either ten or twenty thermal cycles were conducted. For each test, a follow-up detailed fractography and microstructural analysis were carried out. The test results were correlated to the size, density, distribution of the spinel particles and processing time. Thermal expansion tests were carried out using thermo-mechanical analyzer (TMA). Results showed that the coefficient of thermal expansion (CTE) value decreases with the addition of spinel and silicide particles. Thermo-cycling tests showed that molybdenum alloy with 6% wt of spinel (MgAl2O4) developed microcracks which were caused by thermal expansion mismatch between the spinel particles and molybdenum matrix, as well as the processing conditions. Detailed post-mortem studies of microstructures and segregation of impurities to the oxide dispersion/Mo interfaces were conducted using x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS).« less

The phase relations in the In 2O 3Fe 2ZnO 4ZnO system at 1350°C

NASA Astrophysics Data System (ADS)

Nakamura, Masaki; Kimizuka, Noboru; Mohri, Takahiko

1990-05-01

The phase relations in the In 2O 3Fe 2ZnO 4ZnO system at 1350°C are determined by means of a classical quenching method. There are a series of homologous solid solutions, In 1.28Fe 0.72O 3(ZnO)InFeO 3(ZnO), In 1.69Fe 0.31O 3(ZnO) 2InFeO 3(ZnO) 2In 0.85Fe 1.15O 3(ZnO) 2, In 2O 3(ZnO) 3InFeO 3(ZnO) 3In 0.78Fe 1.22O 3(ZnO) 3, In 2O 3(ZnO) 4InFeO 3(ZnO) 4In 0.62Fe 1.38O 3(ZnO) 4, In 2O 3(ZnO) 5InFeO 3(ZnO) 5In 0.67Fe 1.33O 3(ZnO) 5, In 2O 3(ZnO) 6InFeO 3(ZnO) 6In 0.60Fe 1.40O 3(ZnO) 6, In 2O 3(ZnO) 7InFeO 3(ZnO) 7In 0.51Fe 1.49O 3(ZnO) 7, In 2O 3(ZnO) 8InFeO 3(ZnO) 8In 1- xFe 1+ xO 3(ZnO) 8 (0.44 ≦ x ≦ 0.64), In 2O 3(ZnO) 9InFeO 3(ZnO) 9In 0.20Fe 1.80O 3(ZnO) 9, In 2O 3(ZnO) 10InFeO 3(ZnO) 10In 1- xFe 1+ xO 3(ZnO) 10 (0.74 ≦ x ≦ 0.89), In 2O 3(ZnO) 11InFeO 3(ZnO) 11In 1- xFe 1+ xO 3(ZnO) 11 (0.60 ≦ x < 1.00), and In 2O 3(ZnO) 13InFeO 3(ZnO) 13Fe 2O 3(ZnO) 13 having the layered structures with space group R overline3m (m = odd) or {P6 3}/{mmc} (m = even) for m in the InFeO 3(ZnO) m. We conclude that there are a series of homologous phases, (Fe 2O 3)(ZnO) m (m ≧ 12) , in the binary ZnOFe 2O 3 system. The lattice constants for these solid solutions are presented as a hexagonal crystal system. It is also concluded that the crystal structures for each solid solution consist of three kinds of layers which are stacked perpendicular to the c-axis in the hexagonal crystal system. In 1+ xFe 1- xO 3(ZnO) m (0 ≦ x ≦ 1) is composed of the InO 1.5, (In xFe 1- xZn)O 2.5, and ZnO layers, and In 1- xFe 1+ xO 3(ZnO) m (0 ≦ x ≦ 1) is composed of (In 1- xFe x)O 1.5, (FeZn)O 2.5, and ZnO layers, respectively. The solid solution range between Fe 2ZnO 4 and In xFe 2- xZnO 4 ( x = 0.40 ± 0.02) with a spinel structure is observed.

Revisiting HgCl 2: A solution- and solid-state 199Hg NMR and ZORA-DFT computational study

NASA Astrophysics Data System (ADS)

Taylor, R. E.; Carver, Colin T.; Larsen, Ross E.; Dmitrenko, Olga; Bai, Shi; Dybowski, C.

2009-07-01

The 199Hg chemical-shift tensor of solid HgCl 2 was determined from spectra of polycrystalline materials, using static and magic-angle spinning (MAS) techniques at multiple spinning frequencies and field strengths. The chemical-shift tensor of solid HgCl 2 is axially symmetric ( η = 0) within experimental error. The 199Hg chemical-shift anisotropy (CSA) of HgCl 2 in a frozen solution in dimethylsulfoxide (DMSO) is significantly smaller than that of the solid, implying that the local electronic structure in the solid is different from that of the material in solution. The experimental chemical-shift results (solution and solid state) are compared with those predicted by density functional theory (DFT) calculations using the zeroth-order regular approximation (ZORA) to account for relativistic effects. 199Hg spin-lattice relaxation of HgCl 2 dissolved in DMSO is dominated by a CSA mechanism, but a second contribution to relaxation arises from ligand exchange. Relaxation in the solid state is independent of temperature, suggesting relaxation by paramagnetic impurities or defects.

The behavior of mineral inclusions during host decomposition. A SEM-STEM study of rutile inclusions at a natural propagating corundum-spinel interface.

NASA Astrophysics Data System (ADS)

Baldwin, Lisa; Li, Chen; Habler, Gerlinde; Abart, Rainer

2017-04-01

When two neighbor phases are not in chemical equilibrium, they may react and produce a reaction rim at their interface, separating the mutually incompatible phases. At constant P-T-X conditions, such a reaction will continue until one of the reactants is completely consumed. Reaction rim growth involves transfer of chemical components across the growing rim by long-range diffusion and localized interface reactions on either side of the growing rim. Consequently, the thickness of the reaction rim will be a function of time. Yet, in order to quantify and interpret such corona structures and to define a reaction rate law, the kinetics and mechanism of rim formation must be well constrained. In particular, the coupling between long-range diffusion, and interface reaction must be known. In this contribution we focus on potential complexities associated with interface reactions. Many natural minerals contain inclusions of other phases, which in turn may influence the reaction interface propagation kinetics during host phase decomposition (Ashby et al. 1969), as a propagating reaction interface dissipates more free energy when bypassing a mineral inclusion, resulting in a locally decelerated reaction rate. Here, we report results of a SEM-STEM study of the interface between natural rutile-bearing corundum and a polycrystalline ferromagnesio-aluminate spinel that grew topotactically with respect to the corundum precursor as a consequence of its reaction with FeO and MgO from basaltic melt. Electron Backscatter Diffraction (EBSD) crystal orientation imaging revealed that the spinel rim is polycrystalline and exhibits (111) twinning that is parallel to the corundum (0001) plane. The rutile inclusions in corundum are elongated perpendicular to the corundum [0001] axis and are randomly oriented in the (0001) plane. Furthermore, they follow an oscillatory grain size distribution zonation with grain sizes being either a few tens of nanometers, or about 500 to 800 nanometers in the elongated axis. The behavior of the rutile inclusions as they are encountered by the propagating corundum-spinel reaction interface strongly depends on the inclusion size. The nano-inclusions are incorporated into the spinel rim, where -after a recrystallization and coarsening step at the reaction interface- they have a size of > 1 micrometer. There, rutiles form inclusions within spinel grains or accumulate at grain- or twin boundaries within the spinel reaction rim. In contrast, larger inclusions in corundum are collected at the reaction interface, leaving behind a largely rutile-free spinel rim. From our investigations, we conclude that the inclusion size plays an important role in the effective mechanisms of interface propagation during precursor phase decomposition. Contrastingly, the reactive interface orientation with respect to certain crystallographic planes of corundum seems not to influence the inclusion behavior.

Thermobarometry for spinel lherzolite xenoliths in alkali basalts

NASA Astrophysics Data System (ADS)

Ozawa, Kazuhito; Youbi, Nasrrddine; Boumehdi, Moulay Ahmed; Nagahara, Hiroko

2016-04-01

Application of geothermobarometers to peridotite xenoliths has been providing very useful information on thermal and chemical structure of lithospheric or asthenospheric mantle at the time of almost instantaneous sampling by the host magmas, based on which various thermal (e.g., McKenzie et al., 2005), chemical (e.g., Griffin et al., 2003), and rheological (e.g., Ave Lallemant et al., 1980) models of lithosphere have been constructed. Geothermobarometry for garnet or plagioclase-bearing lithologies provide accurate pressure estimation, but this is not the case for the spinel peridotites, which are frequently sampled from Phanerozoic provinces in various tectonic environments (Nixon and Davies, 1987). There are several geobarometers proposed for spinel lherzolite, such as single pyroxene geothermobarometer (Mercier, 1980) and geothermobarometer based on Ca exchange between olivine and clinopyroxene (Köhler and Brey, 1990), but they have essential problems and it is usually believed that appropriated barometers do not exist for spinel lherzolites (O'Reilly et al., 1997; Medaris et al., 1999). It is thus imperative to develop reliable barometry for spinel peridotite xenoliths. We have developed barometry for spinel peridotite xenoliths by exploiting small differences in pressure dependence in relevant reactions, whose calibration was made through careful evaluation of volume changes of the reactions. This is augmented with higher levels of care in application of barometer by choosing mineral domains and their chemical components that are in equilibrium as close as possible. This is necessary because such barometry is very sensitive to changes in chemical composition induced by transient state of the system possibly owing to pressure and temperature changes as well as chemical modification, forming chemical heterogeneity or zoning frequently reported from various mantle xenoliths (Smith, 1999). Thus very carful treatment of heterogeneity, which might be trivial for geothermobarometry based on reactions with large and distinct volume changes, is necessary. Specification of mineral domains and their components representing the thermal state of the mantle just before xenolith extraction is one of the major tasks for the establishment of reliable geothermobarometry for spinel lherzolite xenoliths. Systematic variations of such mineralogical information among xenoliths transported by a single volcanic eruption guarantees proper estimation of a mantle geotherm. For the development of such geobarometry, it is important to choose appropriate xenolith locality, where previous studies provide enough information and where many xenolith samples are available for extending a range of derivation depth. Spinel lherzolite xenoliths in alkali basalts from Bou Ibalhatene maars in the Middle Atlas in Morocco are suitable study target. Geochemical, geochronological, petrological, and rheological aspects of the spinel lherzolite xenoliths have been studied (Raffone et al. 2009; El Messbahi et al., 2015; Witting et al., 2010; El Azzouzi et al., 2010), which show that they represent fragments of the lithospheric mantle formed and modified since 1.7Ga before their extraction from Miocene to recent. We have pinpointed portions of minerals in the xenolith samples and their components representing condition just before their entrapment in magmas, on which appropriate geothermobarometers are applied and detected ~0.5GPa pressure difference (1.5-2.0GPa) for ~100°C variation in temperatures (950-1050°C).

Magnetism and Solid Solution Effects in NiAI (40% AI) Alloys

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

Liu, Chain T; Fu, Chong Long; Chisholm, Matthew F

2007-01-01

The solid solution effects of ternary additions of transition elements in intermetallic Ni-40% Al were investigated by both experimental studies and theoretical calculations. Co solute atoms when sitting at Ni sublattice sites do not affect the lattice parameter and hardening behavior of Ni-40Al. On the other hand, Fe, Mn, and Cr solutes, which are mainly on Al sublattice sites, substantially expand the lattice parameter and produce an unusual solid solution softening effect. First-principles calculations predict that these solute atoms with large unfilled d-band electrons develop large magnetic moments and effectively expand the lattice parameter when occupying Al sublattice sites. Themore » theoretical predictions were verified by both electron loss-energy spectroscopy (EELS) analyses and magnetic susceptibility measurements. The observed softening behavior can be explained quantitatively by the replacement of Ni anti-site defects (potent hardeners) by Fe, Mn, and Cr anti-site defects with smaller atom size mismatch between solute and Al atoms. This study has led to the identification of magnetic interaction as an important physical parameter affecting the solid solution hardening in intermetallic alloys containing transition elements.« less

Research on the synergistic doped effects and the catalysis properties of Cu2+ and Zn2+ co-doped CeO2 solid solutions

NASA Astrophysics Data System (ADS)

Zhang, Guofang; Li, Yiming; Hou, Zhonghui; Xv, Jianyi; Wang, Qingchun; Zhang, Yanghuan

2018-08-01

The Cu2+ and Zn2+ co-doped CeO2-based solid solutions were synthesized via hydrothermal method. The microstructure and the spectra features of the solid solutions were characterized systematically. The XRD results showed that the dopants were incorporated into the CeO2 lattice to form Ce1-xCu0.5xZn0.5xO2 solid solutions when x was lower than 0.14. The cell parameters and the crystalline size decreased linearly, and the lattice strain gradually increased with increasing the doping level. The TEM patterns showed that the particle size in the solid solution was lower than 10 nm which is in accordance with the XRD results. The ICP analysis indicated that the real doped content in the solid solution was close to the nominal proportion. XPS proved that the Ce3+ component was increased by doping. The Raman and PL spectra indicated that the lattice distortion and the oxygen vacancies also increased following the same trend. At the same time, the synergistic effects of two ions co-doped solid solutions were studied by comparing them with that of single ions doped samples. The catalysis effects of Cu2+ and Zn2+ co-doped CeO2-based solid solutions on the hydrogen storage electrochemical and kinetic properties of Mg2Ni alloys were detected. The electrochemistry properties of the Mg2Ni-Ni-5 wt% Ce1-xCu0.5xZn0.5xO2 composites indicated that the doped catalysts could provide better optimizations to improve the maximum discharge capacities and the discharge potentials. On the other hand, the charge transfer abilities on the surface and diffusion rate of H atoms in the bulk of alloys also got improved. The DSC measurements showed that the hydrogen desorption activation of the hydrogenated composites with Ce0.88Cu0.06Zn0.06O2 solid solutions decreased to 77.03 kJ mol-1, while that of the composites with pure CeO2 was 97.62 kJ mol-1. The catalysis effect was enhanced by the doped content increase that means that the catalysis mechanism had close links to the oxygen vacancy concentration and the lattice defects in the solid solutions. On the other hand, the doped Cu2+ and Zn2+ ions could also play an important role in the catalytic process.

Interaction of coal-derived synthesis gas impurities with solid oxide fuel cell metallic components

NASA Astrophysics Data System (ADS)

Marina, Olga A.; Pederson, Larry R.; Coyle, Christopher A.; Edwards, Danny J.; Chou, Yeong-Shyung; Cramer, Carolyn N.

Oxidation-resistant alloys find use as interconnect materials, heat exchangers, and gas supply tubing in solid oxide fuel cell (SOFC) systems, especially when operated at temperatures below ∼800 °C. If fueled with synthesis gas derived from coal or biomass, such metallic components could be exposed to impurities contained in those fuel sources. In this study, coupons of ferritic stainless steels Crofer 22 APU and SS 441, austenitic nickel-chromium superalloy Inconel 600, and an alumina-forming high nickel alloy alumel were exposed to synthesis gas containing ≤2 ppm phosphorus, arsenic and antimony, and reaction products were tested. Crofer 22 APU coupons coated with a (Mn,Co) 3O 4 protective layer were also evaluated. Phosphorus was found to be the most reactive. On Crofer 22 APU, the (Mn,Cr) 3O 4 passivation layer reacted to form an Mn-P-O product, predicted to be manganese phosphate from thermochemical calculations, and Cr 2O 3. On SS 441, reaction of phosphorus with (Mn,Cr) 3O 4 led to the formation of manganese phosphate as well as an Fe-P product, predicted from thermochemical calculations to be Fe 3P. Minimal interactions with antimony or arsenic in synthesis gas were limited to Fe-Sb and Fe-As solid solution formation. Though not intended for use on the anode side, a (Mn,Co) 3O 4 spinel coating on Crofer 22 APU reacted with phosphorus in synthesis gas to produce products consistent with Mn 3(PO 4) 2 and Co 2P. A thin Cr 2O 3 passivation layer on Inconel 600 did not prevent the formation of nickel phosphides and arsenides and of iron phosphides and arsenides, though no reaction with Cr 2O 3 was apparent. On alumel, an Al 2O 3 passivation layer rich in Ni did not prevent the formation of nickel phosphides, arsenides, and antimonides, though no reaction with Al 2O 3 occurred. This work shows that unprotected metallic components of an SOFC stack and system can provide a sink for P, As and Sb impurities that may be present in fuel gases, and thus complicate experimental studies of impurity interactions with the anode.

Inorganic ion sorbent method

DOEpatents

Teter, David M [Edgewood, NM; Brady, Patrick V [Albuquerque, NM; Krumhansl, James L [Albuquerque, NM

2007-07-17

A process and medium for decontamination of water containing anionic species including arsenic and chromium, wherein compounds comprising divalent and trivalent metal oxides and sulfides are used to form surface complexes with contaminants under pH conditions within the range of potable water. In one embodiment natural and synthetic spinels and spinel-like materials are used as the sorbent substance.

Subsurface Optical Microscopy of Coarse Grain Spinels. Phase 1

DTIC Science & Technology

2013-12-01

A 456 nm LED line bar illuminated in figure 15 and a Xenon fiber optic bar illuminator is shown for figure 16. The optical in situ or subsurface ... imaging of coarse grain spinels and AlONs is optically more complex than expected. An overhead view of the side illumination field is shown in figure 20

Observation and manipulation of magnetic domains in sol gel derived thin films of spinel ferrites

NASA Astrophysics Data System (ADS)

Datar, Ashwini A.; Mathe, Vikas L.

2017-12-01

Thin films of spinel ferrites, namely zinc substituted nickel, cobalt ferrite, and manganese substituted cobalt ferrite, were synthesized using sol-gel derived spin-coating techniques. The films were characterized using x-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared spectroscopy and Raman spectroscopy techniques for the analysis of structural, morphological and vibrational band transition properties, which confirm the spinel phase formation of the films. The magnetic force microscopy (MFM) technique was used to observe the magnetic domain structure present in the synthesized films. Further, the films were subjected to an external DC magnetic field of 2 kG to orient the magnetic domains and analyzed using an ex situ MFM technique.

Structural and optical properties of NiFe2O4 synthesized via green technology

NASA Astrophysics Data System (ADS)

Patel, S.; Saleem, M.; Varshney, Dinesh

2018-05-01

The nanoparticles of NiFe2O4 were successfully synthesized via green technology using banana peel extract as the catalyst as well as the medium for reaction technique is reported. Analysis of X-ray diffraction spectrum revealed the cubic structure for the prepared spinel ferrite samples crystallized into cubic spinel structure with the space group Fd3m. The Retvield refinement was carried out which obeyed the results obtained from the XRD spectrum analysis of the sample. Raman spectrum provided confirmation for the spinel structure formation and five active Raman modes were observed. Since the optical band-gap value shows inverse response to the crystallite size, The UV-Vis spectrum study confirmed dual but reduced band-gap value.

Ion irradiation-induced crystal structure changes in inverse spinel MgIn 2O 4

DOE PAGES

Tang, Ming; Valdez, James A.; Wang, Yongqiang; ...

2016-07-29

We performed 400 keV Ne and 200 keV He ion irradiations on fully inverse MgIn 2O 4 samples at cryogenic temperature (~ 77 K), in order to examine the influence of radiation-induced cation disordering on crystal structure. In the case of MgIn 2O 4 samples irradiated with Ne ions to a peak displacement damage dose of 4 displacements per atom (dpa), a spinel-to-rocksalt phase transformation was observed. Conversely, for MgIn 2O 4 samples irradiated with He ions to a peak displacement damage dose of 5 dpa, the only observed structural effect involved cation rearrangements from an inverse to a “random”more » spinel structure.« less

Coupling between crystal structure and magnetism in transition-metal oxides

NASA Astrophysics Data System (ADS)

Barton, Phillip Thomas

Transition-metal oxides exhibit a fascinating array of phenomena ranging from superconductivity to negative thermal expansion to catalysis. This dissertation focuses on magnetism, which is integral to engineering applications such as data storage, electric motors/generators, and transformers. The investigative approach follows structure-property relationships from materials science and draws on intuition from solid-state chemistry. The interplay between crystal structure and magnetic properties is studied experimentally in order to enhance the understanding of magnetostructural coupling mechanisms and provide insight into avenues for tuning behavior. A combination of diffraction and physical property measurements were used to study structural and magnetic phase transitions as a function of chemical composition, temperature, and magnetic field. The systems examined are of importance in Li-ion battery electrochemistry, condensed-matter physics, solid-state chemistry, and p-type transparent conducting oxides. The materials were prepared by solid-state reaction of powder reagents at high temperatures for periods lasting tens of hours. The first project discussed is of a solid solution between NiO, a correlated insulator, and LiNiO2, a layered battery cathode. Despite the deceptive structural and compositional simplicity of this system, a complete understanding of its complex magnetic properties has remained elusive. This study shows that nanoscale domains of chemical order form at intermediate compositions, creating interfaces between antiferromagnetism and ferrimagnetism that give rise to magnetic exchange bias. A simple model of the magnetism is presented along with a comprehensive phase diagram. The second set of investigations focus on the Ge-Co-O system where the spin-orbit coupling of Co(II) plays a significant role. GeCo2O 4 is reported to exhibit unusual magnetic behavior that arises from Ising spin in its spinel crystal structure. Studies by variable-temperature synchrotron X-ray diffraction reveal a magnetostructural transition and capacitance measurements show evidence for magnetodielectric behavior. The above work uncovered a Co10Ge3O16 phase that had a known structure but whose physical properties were largely uncharacterized. This project examined its metamagnetic properties using detailed magnetometry experiments. Upon the application of a magnetic field, this material goes through a first-order phase transition from a noncollinear antiferromagnet to an unknown ferrimagnetic state. Lastly, this thesis explored the chemical dilution of magnetism in some perovskite and delafossite solid solutions. In the perovskite structure, compositions intermediate to the endmembers SrRuO3, a ferromagnetic metal, and LaRhO3, a diamagnetic semiconductor, were investigated. While the magnetism of this system is poised between localized and itinerant behavior, a compositionally-driven metal to insulator transition, revealed by electrical resistivity measurements, did not strongly impact the magnetic properties. Instead, both octahedral tilting and magnetic dilution had strong effects, and comparison of this characterization to Sr1-- x CaxRuO3 reinforces the important role of structural distortions in determining magnetic ground state. The final materials studied were of composition CuAl1-- xCrxO2 (0 < x < 1) in the delafossite structure. The primary interest was the geometric frustration of antiferromagnetism in CuCrO 2 and significant short-range correlations were observed above TN. The analysis found that reducing the number of degenerate states through Al substitution did not enhance magnetic ordering because of the weakening of magnetic exchange.

Process for recovering pertechnetate ions from an aqueous solution also containing other ions

DOEpatents

Rogers, R.; Horwitz, E.P.; Bond, A.H.

1997-02-18

A solid/liquid process for the separation and recovery of TcO{sub 4}{sup {minus}1} ions from an aqueous solution is disclosed. The solid support comprises separation particles having surface-bonded poly(ethylene glycol) groups; whereas the aqueous solution from which the TcO{sub 4}{sup {minus}1} ions are separated contains a poly(ethylene glycol) liquid/liquid biphase-forming amount of a dissolved salt. A solid/liquid phase admixture of separation particles containing bound TcO{sub 4}{sup {minus}1} ions in such an aqueous solution that is free from MoO{sub 4}{sup {minus}2} ions is also contemplated, as is a chromatography apparatus containing that solid/liquid phase admixture. 15 figs.

Structure, morphology, and cathode performance of Li 1- x[Ni 0.5Mn 1.5]O 4 prepared by coprecipitation with oxalic acid

NASA Astrophysics Data System (ADS)

Liu, Dongqiang; Han, Jiantao; Goodenough, John B.

The cathode materials Li 1- x[Ni 0.5Mn 1.5]O 4 prepared by coprecipitation from acetate solution by oxalic acid and annealing at 900 °C in air had the preferred disordered Ni and Mn on the 16d octahedral sites of a spinel F d 3 bar m structure. The coprecipitation method provides better crystallinity than the F d 3 bar m phase previously obtained by quenching from the melt. Polycrystalline octahedral-shaped particles with smooth surfaces contained trace amounts of a Li yNi 1- yO impurity that introduced some Mn(III) into the spinel phase. Half-cells cycled at 0.2 C rate between 3.5 and 4.8 V versus Li exhibited a flat voltage V ≈ 4.7 V with a small step at x ≈ 0.5 and a capacity at room temperature of 130 mAh g -1 that showed no fade after 50 cycles. A small capacity fade was initiated with a cut-off voltage ≥4.9 V; a significant capacity loss between 2 and 5 C cycling rates was reversible to 134 mAh g -1 on returning to 0.1 C after 50 cycles at 10 C between 3.5 and 5.0 V.

Synthesis of magnetic nickel spinel ferrite nanospheres by a reverse emulsion-assisted hydrothermal process

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

Zhang Jilin; Shi Jianxin, E-mail: chemshijx@163.co; Gong Menglian

2009-08-15

Nickel ferrite nanospheres were successfully synthesized by a reverse emulsion-assisted hydrothermal method. The reverse emulsion was composed of water, cetyltrimethyl ammonium bromide, polyoxyethylene(10)nonyl phenyl ether, iso-amyl alcohol and hexane. During the hydrothermal process, beta-FeO(OH) and Ni{sub 0.75}Fe{sub 0.25}(CO{sub 3}){sub 0.125}(OH){sub 2}.0.38H{sub 2}O (INCHH) nanorods formed first and then transformed into nickel spinel ferrite nanospheres. The phase transformation mechanism is proposed based on the results of X-ray powder diffraction, transmission electron microscopy and energy-dispersive X-ray spectroscopy, etc. Nickel ferrite may form at the end of the INCHH nanorods or from the solution accompanied by the dissolution of beta-FeO(OH) and INCHH nanorods.more » The X-ray photoelectron spectroscopy analysis shows that a few Fe{sup 3+} ions have been reduced to Fe{sup 2+} ions during the formation of nickel ferrite. The maximum magnetization of the nickel ferrite nanospheres obtained after hydrothermal reaction for 30 h is 55.01 emu/g, which is close to that of bulk NiFe{sub 2}O{sub 4}. - Graphical abstract: Nickel ferrite nanospheres were obtained through a reverse emulsion-assisted hydrothermal process. The phase transformation as a function of reaction time was studied based on the XRD, TEM and EDS analyses.« less

Effect of Ce-substitution on structural, morphological, magnetic and DC electrical resistivity of Co-ferrite materials

NASA Astrophysics Data System (ADS)

Mammo, Tulu Wegayehu; Murali, N.; Sileshi, Yonatan Mulushoa; Arunamani, T.

2018-02-01

Partially substituted spinel structured CoFe2-xCexO4 (x = 0, 0.03, 0.06, and 0.09) samples have been synthesized using the sol-gel autocombustion route. Stoichiometric amounts of metal nitrates and citric acid were mixed in double distilled water to get homogeneously mixed solutions which were then heated to burn and result in samples for the next two-step annealing procedures. Structural and phase characterization using powder X-ray diffraction (XRD) has been carried out; and a pure spinel structured samples with lattice parameters increasing with the increase of Ce concentration levels have been obtained. The lattice parameters were calculated to be in the range of 8.42774-8.4744 Å. Field emission scanning electron microscopy (FESEM) microstructure characterizations revealed clear grain structures of the so synthesized samples with grain sizes decreasing with Ce. Fourier transform Infrared (FT-IR) characterization measured in the wave number ranges of 400-4000 cm-1 showed the cation vibrations and stretching at characteristic frequency of 668-418 cm-1. The DC resistivity measurements confirmed a decrease in the resistivity of the samples with the increase of Ce concentration and with the increase of temperature in all of the samples synthesized. Room temperature vibrating sample magnetometer measurement revealed the magnetic properties of the samples with decreasing magnetic parameters as Ce concentration increases.

Development of a ceramic membrane from a lithian spinel, Li1+xMyMn2-yO4 (M=trivalent or tetravalent cations) for a Li ion-selective electrode

NASA Astrophysics Data System (ADS)

Yoon, H.; Venugopal, N.; Rim, T.; Yang, B.; Chung, K.; Ko, T.

2010-12-01

Recently a few lithium containing ceramics are reported as promising cathodes for application in lithium batteries. Among them, a spinel-type lithium manganate (LM) exhibits an exceptionally high ion selectivity at room temperature. Thus, LM could have a great potential as an ion selective membrane material for screening interfering ions from lithium ion for the determination of lithium ion in salt solution. In this study, we developed an ion-selective electrode based on LM as a membrane material and investigated its lithium ion selectivity by varying the content of M in composition. A sol-gel process was successfully applied for preparing LM films without resorting to calcination at a high temperature. The LM thin film-type membranes exhibit a high selectivity for Li ion over other cations, a wide operation detection range of 10-5 ~ 10-2 M, and a fast response time less than 60 s. Furthermore, our result demonstrates a linear potentiometric response over a wide range of lithium concentration, which is compared to that of a lithium ion-selective electrode based on an ionophore. Acknowledgements: This research was supported by a grant from the Development of Technology for Extraction of Resources Dissolved in Sea Water Program funded by Ministry of Land Transport and Maritime Affairs in Korean Government (2010).

Design and analysis of novel photocatalytic materials

NASA Astrophysics Data System (ADS)

Boppana, Venkata Bharat Ram

The development of sustainable sources of energy to decrease our dependence on non-renewable fossil fuels and the reduction of emissions causing global warming are important technological challenges of the 21st century. Production of solar fuels by photocatalysis is one potential route to reduce the impact of those problems. The most widely applied photocatalyst is TiO2 because it is stable, non-toxic and inexpensive. Still, it cannot utilize the solar spectrum efficiently as its band gap is 3.2 eV thus able to absorb only 3% of sun light. This thesis therefore explores multiple avenues towards improving the light absorption capability of semiconductor materials without loss in activity. To achieve this objective, the valence band hybridization method of band gap reduction was utilized. This technique is based on introducing new orbitals at the top of valence band of the semiconductor that can then hybridize with existing orbitals. The hybridization then raises the maximum of the valence band thereby reducing the band gap. This technique has the added advantage of increasing the mobility of oxidizing holes in the now dispersed valence band. In practice, this can be achieved by introducing N 2p or Sn 5s orbitals in the valence band of an oxide. We initially designed novel zinc gallium oxy-nitrides, with the spinel structure and band gaps in the visible region of the solar spectrum, by nitridation of a zinc gallate precursor produced by sol-gel synthesis. These spinel oxy-nitrides have band gaps of 2.5 to 2.7 eV, surface areas of 16 to 36 m 2/g, and nitrogen content less than 1.5%. They are active towards degradation of organic molecules in visible light. Density functional theory calculations show that this band gap reduction in part is associated with hybridization between the dopant N 2p states with Zn 3d orbitals at the top of the valence band. While spinel oxy-nitrides are produced under nitridation at 550°C, at higher temperatures they are consumed to form wurzitic oxy-nitrides. The wurzite materials also have band gaps less than 3 eV but their surface areas are 2 to 5 m2/g. The thesis explores in detail the changes associated with the gallium coordination as the spinel zinc gallate precursor transforms into the spinel oxy-nitride at 550°C, and further changes into the wurzite oxy-nitride at 850°C are studied through X-ray diffraction, ultraviolet-visible diffuse reflectance spectroscopy, neutron powder diffraction, X-ray absorption spectroscopy and other techniques. We believe that the protocol developed in this thesis opens an avenue for the synthesis of semiconductors having the spinel crystal structure and band gaps engineered to the visible region with potential applications for opto-electronic devices and photocatalytic processes. Though these spinel oxynitrides are interesting, they suffer from vacancies and low surface areas from the high temperature nitridation step. This could be overcome by synthesizing photocatalysts hydrothermally. We proceeded to explore the interactions of Sn2+ 5s orbitals with O 2p orbitals towards hybridizing the valence band. This led to the development of novel visible-light-active Sn2+ - TiO2 and SnOx -- ZnGa2O4 materials. The former catalysts are prepared from the reaction of titanium butoxide and several tin precursors at 80°C in aqueous solutions. Samples synthesized with SnCl2 have lower band gaps (red-shifted to the visible region) with respect to anatase TiO2. The catalysts are isostructural with anatase TiO2 even at the highest loadings of Sn2+. When the precursor is changed to SnCl4, rutile is the predominant phase obtained but no reduction in the band gap is observed. The experiments also indicate the presence of chlorine in the samples, also influencing the optical and catalytic properties as confirmed by comparison to materials prepared using bromide precursors. These catalysts are photocatalytically active for the degradation of organic molecules with rates higher than the standard (P25 TiO2) and also evidenced from the generation of hydroxyl radicals using visible light. This protocol could be extended to incorporate Sn2+ 5s orbitals into other oxide semiconductors to prepare photocatalysts with interesting electronic properties.

Influence of carbonate ion in the crystallization medium on the formation and chemical composition of CaHA-SrHA solid solutions

NASA Astrophysics Data System (ADS)

Nikolaev, Anton; Kuz'mina, Maria; Frank-Kamenetskaya, Olga; Zorina, Maina

2015-06-01

The study of the influence of carbonate ions in a solution to Sr-distribution in system «solution-crystal» and to ion substitutions and the non-stoichiometry of formed CaHA-SrHA solid solutions was carried out. The CaHA-SrHA solid solutions were synthesized by precipitation from aqueous solutions with the atomic C/P ratio equal to 0, 0.05 and 0.1 at T = 90 °C. Resulting precipitates were studied using various methods including X-ray powder diffraction, infrared spectroscopy and different chemical analyses. The results of the study have shown that in the range of values of (Ca + Sr)/P in the water solution from 40% to 85%, the presence of carbonate ions (C/P = 0.05-0.1) promotes the incorporation of strontium in the apatite. Crystalline apatite solid solutions formed from water solutions of such composition are more defective compared to apatites that are mainly calcium or strontium. They are characterized by a smaller size coherence scattering domain length along [0 0 1] direction and a greater number of carbonate ions, water molecules and vacancies at the Ca-sites.

The migration mechanism of transition metal ions in LiNi 0.5 Mn 1.5O 4

DOE PAGES

Xu, Gui-Liang; Qin, Yan; Ren, Yang; ...

2015-05-12

The migration of transition metal ions in the oxygen framework was recently proposed to be responsible for the continuous loss of average working potential of high energy density layered–layered composite cathodes for lithium-ion batteries. The potential migration pathway in a model material, LiNi 0.5 Mn 1.5O 4 spinel, was investigated using in situ high-energy X-ray diffraction and in situ neutron diffraction during the solid state synthesis process. It was found that the migration of transition metal ions among octahedral sites is possible by using tetrahedral vacancies as intermediate sites. It was also suggested that the number of electrons in 3dmore » orbitals has a significant impact on their mobility in the hosting oxygen framework.« less

ZrB 2-HfB 2 solid solutions as electrode materials for hydrogen reaction in acidic and basic solutions

DOE PAGES

Sitler, Steven J.; Raja, Krishnan S.; Charit, Indrajit

2016-11-09

Spark plasma sintered transition metal diborides such as HfB 2, ZrB 2 and their solid solutions were investigated as electrode materials for electrochemical hydrogen evolutions reactions (HER) in 1 M H 2SO 4 and 1 M NaOH electrolytes. HfB 2 and ZrB 2 formed complete solid solutions when mixed in 1:1, 1:4, and 4:1 ratios and they were stable in both electrolytes. The HER kinetics of the diborides were slower in the basic solution than in the acidic solutions. The Tafel slopes in 1 M H 2SO 4 were in the range of 0.15 - 0.18 V/decade except for puremore » HfB 2 which showed a Tafel slope of 0.38 V/decade. In 1 M NaOH the Tafel slopes were in the range of 0.12 - 0.27 V/decade. The composition of Hf xZr 1-xB 2 solid solutions with x = 0.2 - 0.8, influenced the exchange current densities, overpotentials and Tafel slopes of the HER. As a result, the EIS data were fitted with a porous film equivalent circuit model in order to better understand the HER behavior. In addition, modeling calculations, using density functional theory approach, were carried out to estimate the density of states and band structure of the boride solid solutions.« less

Calculation of open and closed system elastic coefficients for multicomponent solids

NASA Astrophysics Data System (ADS)

Mishin, Y.

2015-06-01

Thermodynamic equilibrium in multicomponent solids subject to mechanical stresses is a complex nonlinear problem whose exact solution requires extensive computations. A few decades ago, Larché and Cahn proposed a linearized solution of the mechanochemical equilibrium problem by introducing the concept of open system elastic coefficients [Acta Metall. 21, 1051 (1973), 10.1016/0001-6160(73)90021-7]. Using the Ni-Al solid solution as a model system, we demonstrate that open system elastic coefficients can be readily computed by semigrand canonical Monte Carlo simulations in conjunction with the shape fluctuation approach. Such coefficients can be derived from a single simulation run, together with other thermodynamic properties needed for prediction of compositional fields in solid solutions containing defects. The proposed calculation approach enables streamlined solutions of mechanochemical equilibrium problems in complex alloys. Second order corrections to the linear theory are extended to multicomponent systems.

Local Structure and Short-Range Order in a NiCoCr Solid Solution Alloy

DOE PAGES

Zhang, F. X.; Zhao, Shijun; Jin, Ke; ...

2017-05-19

Multi-element solid solution alloys are intrinsically disordered on the atomic scale, and many of their advanced properties originate from the unique local structural characteristics. We measured the local structure of a NiCoCr solid solution alloy with X-ray/neutron total scattering and extended X-ray absorption fine structure (EXAFS) techniques. The atomic pair distribution function analysis (PDF) did not exhibit distinct structural distortion. But, EXAFS analysis suggested that the Cr atoms are favorably bonded with Ni and Co in the solid solution alloys. This short-range order (SRO) plays a role in the distinct low values of electrical and thermal conductivities in Ni-based solidmore » solution alloys when Cr is incorporated. Both the long-range and local structures of the NiCoCr alloy upon Ni ion irradiation were studied and an irradiation-induced enhancement of SRO was found.« less

Life prediction of coated and uncoated metallic interconnect for solid oxide fuel cell applications

NASA Astrophysics Data System (ADS)

Liu, W. N.; Sun, X.; Stephens, E.; Khaleel, M. A.

In this paper, we present an integrated experimental and modeling methodology in predicting the life of coated and uncoated metallic interconnect (IC) for solid oxide fuel cell (SOFC) applications. The ultimate goal is to provide cell designer and manufacture with a predictive methodology such that the life of the IC system can be managed and optimized through different coating thickness to meet the overall cell designed life. Crofer 22 APU is used as the example IC material system. The life of coated and uncoated Crofer 22 APU under isothermal cooling was predicted by comparing the predicted interfacial strength and the interfacial stresses induced by the cooling process from the operating temperature to room temperature, together with the measured oxide scale growth kinetics. It was found that the interfacial strength between the oxide scale and the Crofer 22 APU substrate decreases with the growth of the oxide scale, and that the interfacial strength for the oxide scale/spinel coating interface is much higher than that of the oxide scale/Crofer 22 APU substrate interface. As expected, the predicted life of the coated Crofer 22 APU is significantly longer than that of the uncoated Crofer 22 APU.

First-Principles Modeling of the Initial Stages of Organic Solvent Decomposition on Li xMn 2O 4 (100) Surfaces [First principles modeling of Mn(II) migration to and dissolution from Li xMn 2O 4 (100) surfaces

DOE PAGES

Leung, Kevin

2012-04-13

Density functional theory and ab initio molecular dynamics simulations are applied to investigate the migration of Mn(II) ions to above-surface sites on spinel Li xMn 2O 4 (100) surfaces, the subsequent Mn dissolution into the organic liquid electrolyte, and the detrimental effects on anode solid electrolyte interphase (SEI) passivating films after Mn(II) ions diffuse through the separator. The dissolution mechanism proves complex; the much-quoted Hunter disproportionation of Mn(III) to form Mn(II) is necessary but far from sufficient. Key steps that facilitate Mn(II) ion migration include concerted liquid/solid-state motions, proton-induced weakening of Mn-O bonds forming mobile OH - surface groups; andmore » chemical reactions of adsorbed decomposed organic fragments. Mn(II) lodged between the inorganic Li 2CO 3 and organic lithium ethylene dicarbonate (LEDC) anode SEI component facilitates electrochemical reduction and decomposition of LEDC. These findings help inform future design of protective coatings, electrolytes, additives, and interfaces.« less

LiMn2O4–yBryNanoparticles Synthesized by a Room Temperature Solid-State Coordination Method

PubMed Central

2009-01-01

LiMn2O4–yBrynanoparticles were synthesized successfully for the first time by a room temperature solid-state coordination method. X-ray diffractometry patterns indicated that the LiMn2O4–yBrypowders were well-crystallized pure spinel phase. Transmission electron microscopy images showed that the LiMn2O4–yBrypowders consisted of small and uniform nanosized particles. Synthesis conditions such as the calcination temperature and the content of Br−were investigated to optimize the ideal condition for preparing LiMn2O4–yBrywith the best electrochemical performances. The optimized synthesis condition was found in this work; the calcination temperature is 800 °C and the content of Br−is 0.05. The initial discharge capacity of LiMn2O3.95Br0.05obtained from the optimized synthesis condition was 134 mAh/g, which is far higher than that of pure LiMn2O4, indicating introduction of Br−in LiMn2O4is quite effective in improving the initial discharge capacity. PMID:20628635

Experimental evidence for the magnetic moment directions of Cr2+ and Cr3+ cations in the spinel ferrites Cux1Crx2Fe3-x1-x2O4

NASA Astrophysics Data System (ADS)

Zhang, X. Y.; Xu, J.; Li, Z. Z.; Qi, W. H.; Tang, G. D.; Shang, Z. F.; Ji, D. H.; Lang, L. L.

2014-08-01

(A)[B]2O4 spinel ferrite samples with the composition Cux1Crx2Fe3-x1-x2O4 (0.0≤x1≤0.284 and 1.04≥x2≥0.656) were prepared by a chemical co-precipitation method. X-ray diffraction patterns indicated that the samples had a single-phase cubic spinel structure. It is interesting that the saturation magnetization of the samples increased when Cu2+ or Cu3+ (with 1 or 2μB of magnetic moment) substituted for Cr2+ or Cr3+ (with 4 or 3μB), which cannot be obviously explained if the magnetic moments of Cr2+ and Cr3+ cations are assumed to be parallel to those of the Fe and Cu cations. However, with the assumption that the magnetic moments of Cr2+ and Cr3+ cations are antiparallel to the Fe and Cu cation moments in spinel ferrites, the dependence on the Cu doping level of the sample magnetic moments at 10 K was fitted successfully, using the quantum-mechanical potential barrier model earlier proposed by our group. Using the cation distributions obtained in the fitting process, the experimental observation that the magnetic moment of the samples increased with increasing Cu doping level was explained. This work therefore provides experimental evidence that the magnetic moments of the Cr2+ and Cr3+ cations are antiparallel to those of the Fe and Cu cations in spinel ferrites.

Ten Windows Into the Meteorite Flux to Earth During the Past 500 Million Years

NASA Astrophysics Data System (ADS)

Schmitz, B.

2017-12-01

Almost nothing is known about the variations through deep time in the types of meteorites arriving at Earth. In an ongoing project we are searching ancient sediments from ten different time periods through the Phanerozoic for relict extraterrestrial spinel grains from micrometeorites (Schmitz, 2013). Samples, 300-1500 kg large, of slowly formed pelagic limestone are dissolved in acids leaving a residue of extraterrestrial spinels. The time periods studied include the middle Cambrian, Ordovician before and after the breakup of the L-chondrite parent body, late Silurian, late Devonian, middle Jurassic, early and late Cretaceous, early Paleocene and late Eocene. The approach builds on complex methodological considerations and a thorough understanding also of the spinel fraction in recent meteorites is necessary. In order to obtain some insights into the changes in the meteorite flux carefully calibrated analyses of the isotopic and elemental composition of the recovered spinel grains as well as consistent data treatment is required for the different time windows. Our results indicate that the background meteorite flux has changed significantly through the Phanerozoic. The results so far suggest that there may have been a gradual long-term (on the order of hundred million years) turnover in the meteorite flux from dominance of achondrites in the early Phanerozoic to ordinary chondrites in the late Phanerozoic interrupted by short-term (a few million years) meteorite cascades from single asteroid breakup events. This scenario may change, however, as results from additional time windows emerge. B. Schmitz (2013) Extraterrestrial spinels and the astronomical perspective on Earth's geological record and evolution of life: Chemie der Erde 73:117-145.

Structure and Electrical Properties of Mn-Cu-O Spinels

NASA Astrophysics Data System (ADS)

Bobruk, M.; Durczak, K.; Dąbek, J.; Brylewski, T.

2017-04-01

The study presents the results of structural and electrical conductivity investigations of a Cu1.3Mn1.7O4 spinel obtained using EDTA gel processes. An amorphous gel was synthesized and calcinated for 5 h in air at temperatures of 673, 773, 873, and 973 K. When calcinating the gel at temperatures below 973 K, the obtained powders consisted of two phases—the regular Cu1.5Mn1.5O4 spinel and manganese(III) oxide. At 973 K, Mn2O3 was no longer observed, but a new Mn3O4 phase appeared in addition to the Cu1.5Mn1.5O4 spinel. Green bodies prepared from these powders were sintered for 2 h in air at 1393 K. The obtained sinters had a porosity of around 12% and were composed predominantly of the spinel phase, with minor amounts of Mn3O4 and, in the case of three of four sinters—CuO. Electrical conductivity measurements were taken over the temperature range of 300-1073 K. A change in the character of conductivity of the studied sinters was observed in the range of 400-430 K, and it was associated with an increase in activation energy from 0.20 to 0.56 eV. The electrical conductivity of the studied sinters ranged from 74.8 to 88.4 S cm-1, which makes the Cu1.3Mn1.7O4 material suitable for application as a protective-conducting coating in IT-SOFC ferritic stainless steel interconnects.

Melts of garnet lherzolite: experiments, models and comparison to melts of pyroxenite and carbonated lherzolite

USGS Publications Warehouse

Grove, Timothy L.; Holbig, Eva S.; Barr, Jay A.; Till, Christy B.; Krawczynski, Michael J.

2013-01-01

Phase equilibrium experiments on a compositionally modified olivine leucitite from the Tibetan plateau have been carried out from 2.2 to 2.8 GPa and 1,380–1,480 °C. The experiments-produced liquids multiply saturated with spinel and garnet lherzolite phase assemblages (olivine, orthopyroxene, clinopyroxene and spinel ± garnet) under nominally anhydrous conditions. These SiO2-undersaturated liquids and published experimental data are utilized to develop a predictive model for garnet lherzolite melting of compositionally variable mantle under anhydrous conditions over the pressure range of 1.9–6 GPa. The model estimates the major element compositions of garnet-saturated melts for a range of mantle lherzolite compositions and predicts the conditions of the spinel to garnet lherzolite phase transition for natural peridotite compositions at above-solidus temperatures and pressures. We compare our predicted garnet lherzolite melts to those of pyroxenite and carbonated lherzolite and develop criteria for distinguishing among melts of these different source types. We also use the model in conjunction with a published predictive model for plagioclase and spinel lherzolite to characterize the differences in major element composition for melts in the plagioclase, spinel and garnet facies and develop tests to distinguish between melts of these three lherzolite facies based on major elements. The model is applied to understand the source materials and conditions of melting for high-K lavas erupted in the Tibetan plateau, basanite–nephelinite lavas erupted early in the evolution of Kilauea volcano, Hawaii, as well as younger tholeiitic to alkali lavas from Kilauea.

Growth, intermixing, and surface phase formation for zinc tin oxide nanolaminates produced by atomic layer deposition

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

Hägglund, Carl, E-mail: carl.hagglund@angstrom.uu.se; Grehl, Thomas; Brongersma, Hidde H.

2016-03-15

A broad and expanding range of materials can be produced by atomic layer deposition at relatively low temperatures, including both oxides and metals. For many applications of interest, however, it is desirable to grow more tailored and complex materials such as semiconductors with a certain doping, mixed oxides, and metallic alloys. How well such mixed materials can be accomplished with atomic layer deposition requires knowledge of the conditions under which the resulting films will be mixed, solid solutions, or laminated. The growth and lamination of zinc oxide and tin oxide is studied here by means of the extremely surface sensitivemore » technique of low energy ion scattering, combined with bulk composition and thickness determination, and x-ray diffraction. At the low temperatures used for deposition (150 °C), there is little evidence for atomic scale mixing even with the smallest possible bilayer period, and instead a morphology with small ZnO inclusions in a SnO{sub x} matrix is deduced. Postannealing of such laminates above 400 °C however produces a stable surface phase with a 30% increased density. From the surface stoichiometry, this is likely the inverted spinel of zinc stannate, Zn{sub 2}SnO{sub 4}. Annealing to 800 °C results in films containing crystalline Zn{sub 2}SnO{sub 4}, or multilayered films of crystalline ZnO, Zn{sub 2}SnO{sub 4}, and SnO{sub 2} phases, depending on the bilayer period.« less

Surface Defects Enhanced Visible Light Photocatalytic H2 Production for Zn-Cd-S Solid Solution.

PubMed

Zhang, Xiaoyan; Zhao, Zhao; Zhang, Wanwan; Zhang, Guoqiang; Qu, Dan; Miao, Xiang; Sun, Shaorui; Sun, Zaicheng

2016-02-10

In order to investigate the defect effect on photocatalytic performance of the visible light photocatalyst, Zn-Cd-S solid solution with surface defects is prepared in the hydrazine hydrate. X-ray photoelectron spectra and photoluminescence results confirm the existence of defects, such as sulfur vacancies, interstitial metal, and Zn and Cd in the low valence state on the top surface of solid solutions. The surface defects can be effectively removed by treating with sulfur vapor. The solid solution with surface defect exhibits a narrower band gap, wider light absorption range, and better photocatalytic perfomance. The optimized solid solution with defects exhibits 571 μmol h(-1) for 50 mg photocatalyst without loading Pt as cocatalyst under visible light irradiation, which is fourfold better than that of sulfur vapor treated samples. The wavelength dependence of photocatalytic activity discloses that the enhancement happens at each wavelength within the whole absorption range. The theoretical calculation shows that the surface defects induce the conduction band minimum and valence band maximum shift downward and upward, respectively. This constructs a type I junction between bulk and surface of solid solution, which promotes the migration of photogenerated charges toward the surface of nanostructure and leads to enhanced photocatalytic activity. Thus a new method to construct highly efficient visible light photocatalysts is opened. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Stabilized antiferroelectricity in xBiScO3-(1-x)NaNbO3 lead-free ceramics with established double hysteresis loops

NASA Astrophysics Data System (ADS)

Gao, Lisheng; Guo, Hanzheng; Zhang, Shujun; Randall, Clive A.

2018-02-01

We previously reported various solid solution systems that demonstrated the stabilized antiferroelectric (P) phases in NaNbO3 through lowering the tolerance factor. However, all those reported modifications were achieved by adding A2+B4+O3 type solid solutions. A lead-free antiferroelectric (AFE) solid solution xBiScO3-(1-x)NaNbO3 was rationalized by adopting the tolerance factor design rule. Specifically, adding BiScO3 was found to effectively stabilize the AFE phase without changing the crystal symmetry of NaNbO3. Microstructure and electron zone axis diffraction patterns from transmission electron microscopy revealed the stabilized AFE (P) phase in this solid solution. Besides, the electric-field-induced polarization with a double-hysteresis loop was observed. The present results pointed out that the strategy could also be applied while adding A3+B3+O3 type solid solutions. In addition, it expanded the compositional design that can be applied to antiferroelectric materials.

Inorganic ion sorbents and methods for using the same

DOEpatents

Teter, David M [Edgewood, NM; Brady, Patrick V [Albuquerque, NM; Krumhansl, James L [Albuquerque, NM

2006-07-11

A process and medium for decontamination of water containing anionic species including arsenic and chromium, wherein compounds comprising divalent and trivalent metal oxides and sulfides are used to form surface complexes with contaminants under pH conditions within the range of potable water. In one embodiment natural and synthetic spinels and spinel-like materials are used as the sorbent substance.

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

Wang, Li-Fang; Ou, Chin-Ching; Striebel, Kathryn A.

The goal of this research was to measure Mn dissolution from a thin porous spinel LiMn{sub 2}O{sub 4} electrode by rotating ring-disk collection experiments. The amount of Mn dissolution from the spinel LiMn{sub 2}O{sub 4} electrode under various conditions was detected by potential step chronoamperometry. The concentration of dissolved Mn was found to increase with increasing cycle numbers and elevated temperature. The dissolved Mn was not dependent on disk rotation speed, which indicated that the Mn dissolution from the disk was under reaction control. The in situ monitoring of Mn dissolution from the spinel was carried out under various conditions.more » The ring currents exhibited maxima corresponding to the end-of-charge (EOC) and end-of-discharge (EOD), with the largest peak at EOC. The results suggest that the dissolution of Mn from spinel LiMn{sub 2}O{sub 4} occurs during charge/discharge cycling, especially in a charged state (at >4.1 V) and in a discharged state (at <3.1 V). The largest peak at EOC demonstrated that Mn dissolution took place mainly at the top of charge. At elevated temperatures, the ring cathodic currents were larger due to the increase of Mn dissolution rate.« less