Melting relations in the Fe-rich portion of the system FeFeS at 30 kb pressure

USGS Publications Warehouse

Brett, R.; Bell, P.M.

1969-01-01

The melting relations of FeFeS mixtures covering the composition range from Fe to Fe67S33 have been determined at 30 kb pressure. The phase relations are similar to those at low pressure. The eutectic has a composition of Fe72.9S27.1 and a temperature of 990??C. Solubility of S in Fe at elevated temperatures at 30 kb is of the same order of magnitude as at low pressure. Sulfur may have significantly lowered the melting point of iron in the upper mantle during the period of coalescence of metal prior to core formation in the primitive earth. ?? 1969.

[{(Mo)Mo5O21(H2O)3(SO4)}12(VO)30(H2O)20]36-: a molecular quantum spin icosidodecahedron.

PubMed

Botar, Bogdan; Kögerler, Paul; Hill, Craig L

2005-07-07

Self-assembly of aqueous solutions of molybdate and vanadate under reducing, mildly acidic conditions results in a polyoxomolybdate-based {Mo72V30} cluster compound Na8K16(VO)(H2O)5[K10 subset{(Mo)Mo5O21(H2O)3(SO4)}12(VO)30(H2O)20].150H2O, 1, a quantum spin-based Keplerate structure.

Phase stability of Keplerate-type polyoxomolybdates controlled by added cationic surfactant.

PubMed

Fan, Dawei; Hao, Jingcheng

2009-05-15

Phase stability of two nanometer-scale Keplerate-type polyoxomolybdates, (NH(4))(42)[Mo(VI)(72)Mo(V)(60)O(372)(CH(3)COO)(30)(H(2)O)(72)]300H(2)O10CH(3)COONH(4) ({Mo(132)}) and Mo(VI)(72)Fe(III)(30)O(252)L(102)ca. 180H(2)O with L=H(2)O/CH(3)COO(-)/Mo(2)O(n-)(8/9) ({Mo(72)Fe(30)}), can be easily achieved by controlling the concentration of a cationic surfactant, tetradecyltrimethylammonium bromide (TTABr), in aqueous solution. Precipitates and floccules were observed when the stoichiometric ratios of rTTA+/{Mo132} and rTTA+/{Mo72Fe30} were 40:1 and 90:1, respectively, which were determined by zeta potential measurements. The surface charge properties and structure morphologies of {Mo(132)} and {Mo(72)Fe(30)} induced by controlling cationic TTABr in aqueous solution were determined by zeta potential measurements and transmission electron microscopy (TEM) observations. {Mo(132)} and {Mo(72)Fe(30)} can self-assemble into supramolecular "Blackberry" structures and exist at compositions less than the stoichiometric ratios of rTTA+/{Mo132} and rTTA+/{Mo72Fe30} in aqueous solution. Above the 1:1 stoichiometric ratio of TTABr/{Mo(132)} or TTABr/{Mo(72)Fe(30)}, the precipitates and floccules dissolve. Dynamic laser light scattering (DLS) measurements clearly demonstrated that the R(h) values have essentially no angular dependence at excess amounts of TTABr, suggesting the presence of spherically symmetric aggregates of {Mo(132)} and {Mo(72)Fe(30)}. Bilayer-like structures in aqueous solution were also demonstrated by TEM images. The interesting phase transition observed in our model systems of {Mo(132)} and {Mo(72)Fe(30)} macroanions with high chemical stability, similar shape, and masses could provide models for the understanding of more complex polyelectrolyte solutions and self-assembled soft magnetic materials and in bioapplications for highly selective adsorbents of proteins with different molecular sizes and charges.

Mechanism of Mo-Dependent Nitrogenase

PubMed Central

Seefeldt, Lance C.; Hoffman, Brian M.; Dean, Dennis R.

2010-01-01

Nitrogen-fixing bacteria catalyze the reduction of dinitrogen (N2) to two ammonia molecules (NH3), the major contribution of fixed nitrogen into the biogeochemical nitrogen cycle. The most widely studied nitrogenase is the Mo-dependent enzyme. The reduction of N2 by this enzyme involves the transient interaction of two component proteins, designated the Fe protein and the MoFe protein, and minimally requires sixteen MgATP, eight protons, and eight electrons. The current state of knowledge on how these proteins and small molecules together effect the reduction of N2 to ammonia is reviewed. Included is a summary of the roles of the Fe protein and MgATP hydrolysis, information on the roles of the two metal clusters contained in the MoFe protein in catalysis, insights gained from recent success in trapping substrates and inhibitors at the active site metal cluster FeMo-cofactor, and finally, considerations of the mechanism of N2 reduction catalyzed by nitrogenase. PMID:19489731

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

NASA Astrophysics Data System (ADS)

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

2017-08-01

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

A Comparative Study of Hydrodeoxygenation of Furfural Over Fe/Pt(111) and Fe/Mo 2C Surfaces

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

Wan, Weiming; Jiang, Zhifeng; Chen, Jingguang G.

It is desirable to convert biomass-derived furfural to 2-methylfuran through the hydrodeoxygenation (HDO) reaction using an inexpensive catalyst with high stability. In this work, Mo 2C was used as an alternative substrate to replace precious Pt to support monolayer Fe for the HDO reaction of furfural. The HDO activity and stability of Fe/Pt(111) and Fe/Mo 2C/Mo(110) surfaces were compared. Density functional theory calculations and vibrational spectroscopy results indicated that both surfaces bonded to furfural with similar adsorption geometries and should be active toward the furfural HDO reaction. Temperature programmed desorption experiments confirmed a similar HDO activity between the two surfaces,more » with Fe/Mo 2C/Mo(110) being more thermally stable than Fe/Pt(111). As a result, the combined theoretical and experimental results demonstrated that Fe/Mo 2C should be a promising non-precious metal catalyst for the HDO reaction of furfural to produce 2-methylfuran.« less

A Comparative Study of Hydrodeoxygenation of Furfural Over Fe/Pt(111) and Fe/Mo 2C Surfaces

DOE PAGES

Wan, Weiming; Jiang, Zhifeng; Chen, Jingguang G.

2018-01-19

It is desirable to convert biomass-derived furfural to 2-methylfuran through the hydrodeoxygenation (HDO) reaction using an inexpensive catalyst with high stability. In this work, Mo 2C was used as an alternative substrate to replace precious Pt to support monolayer Fe for the HDO reaction of furfural. The HDO activity and stability of Fe/Pt(111) and Fe/Mo 2C/Mo(110) surfaces were compared. Density functional theory calculations and vibrational spectroscopy results indicated that both surfaces bonded to furfural with similar adsorption geometries and should be active toward the furfural HDO reaction. Temperature programmed desorption experiments confirmed a similar HDO activity between the two surfaces,more » with Fe/Mo 2C/Mo(110) being more thermally stable than Fe/Pt(111). As a result, the combined theoretical and experimental results demonstrated that Fe/Mo 2C should be a promising non-precious metal catalyst for the HDO reaction of furfural to produce 2-methylfuran.« less

Thermal stability of intermetallic phases in Fe-rich Fe-Cr-Ni-Mo alloys

DOE PAGES

Yang, Ying; Tan, Lizhen; Busby, Jeremy T.

2015-06-12

Understanding the stability of precipitate phases in the Fe-rich Fe-Cr-Ni-Mo alloys is critical to the alloy design and application of Mo-containing Austenitic steels. Coupled with thermodynamic modeling, stability of the chi and Laves phases in two Fe-Cr-Ni-Mo alloys were investigated at 1000, 850 and 700 °C for different annealing time. The morphologies, compositions and crystal structures of the matrix and precipitate phases were carefully examined by Scanning Electron Microscopy, Electron Probe Microanalysis, X-ray diffraction and Transmission Electron Microscopy. The two key findings resulted from this work. One is that the chi phase is stable at high temperature and transformed intomore » the Laves phase at low temperature. The other is that both the chi and Laves phases have large solubilites of Cr, Mo and Ni, among which the Mo solubility has a major role on the relative stability of the precipitate phases. The developed thermodynamic models were then applied to evaluating the Mo effect on the stability of precipitate phases in AISI 316 and NF709 alloys.« less

β-K3Fe(MoO4)2Mo2O7

PubMed Central

Souilem, Amira; Zid, Mohamed Faouzi; Driss, Ahmed

2014-01-01

The title compound, tripotassium iron(III) bis­(ortho­molyb­date) dimolybdate, was obtained by a solid-state reaction. The main structural building units are one FeO6 octa­hedron, two MoO4 tetra­hedra and one Mo2O7 dimolybdate group, all with point group symmetries m. These units are linked via corner-sharing to form ribbons parallel to [010]. The three K+ cations are located between the ribbons on mirror planes and have coordination numbers of 10 and 12. Two O atoms of one of the MoO4 tetra­hedra of the dimolybdate group are disordered over two positions in a 0.524 (11):0.476 (11) ratio. The structure of the title compound is compared briefly with that of Rb3FeMo4O15. PMID:25161509

Synthesis of MoS2-reduced graphene oxide/Fe3O4 nanocomposite for enhanced electromagnetic interference shielding effectiveness

NASA Astrophysics Data System (ADS)

Prasad, Jagdees; Singh, Ashwani Kumar; Shah, Jyoti; Kotnala, R. K.; Singh, Kedar

2018-05-01

This article presents a facile two step hydrothermal process for the synthesis of MoS2-reduced graphene oxide/Fe3O4 (MoS2-rGO/Fe3O4) nanocomposite and its application as an excellent electromagnetic interference shielding material. Characterization tools like; scanning electron microscope, transmission electron microscope, x-ray diffraction, and Raman spectroscopy were used to confirm the formation of nanocomposite and found that spherical Fe3O4 nanoparticles are well dispersed over MoS2-rGO composite with average particle size ∼25–30 nm was confirmed by TEM. Structural characterization done by XRD was found inconsistent with the known lattice parameter of MoS2 nanosheet, reduced graphene oxide and Fe3O4 nanoparticles. Electromagnetic shielding effectiveness of MoS2-rGO/Fe3O4 nanocomposite was evaluated and found to be an excellent EMI shielding material in X-band range (8.0–12.0 GHz). MoS2-rGO composite shows poor shielding capacity (SET ∼ 3.81 dB) in entire range as compared to MoS2-rGO/Fe3O4 nanocomposite (SET ∼ 8.27 dB). It is due to interfacial polarization in the presence of EM field. The result indicates that MoS2-rGO/Fe3O4 nanocomposite provide a new stage for the next generation in high-performance EM wave absorption and EMI shielding effectiveness.

β-Li0.37Na0.63Fe(MoO4)2

PubMed Central

Souilem, Amira; Zid, Mohamed Faouzi; Driss, Ahmed

2014-01-01

The title compound, lithium/sodium iron(III) bis­[ortho­molyb­date(VI)], was obtained by a solid-state reaction. The main structure units are an FeO6 octa­hedron, a distorted MoO6 octa­hedron and an MoO4 tetra­hedron sharing corners. The crystal structure is composed of infinite double MoFeO11 chains along the b-axis direction linked by corner-sharing to MoO4 tetra­hedra so as to form Fe2Mo3O19 ribbons. The cohesion between ribbons via mixed Mo—O—Fe bridges leads to layers arranged parallel to the bc plane. Adjacent layers are linked by corners shared between MoO4 tetra­hedra of one layer and FeO6 octa­hedra of the other layer. The Na+ and Li+ ions partially occupy the same general position, with a site-occupancy ratio of 0.631 (9):0.369 (1). A comparison is made with AFe(MoO4)2 (A = Li, Na, K and Cs) structures. PMID:24764805

The effect of FeF2 on the magneto-optic response in FeF2/Fe/FeF2 sandwiches

NASA Astrophysics Data System (ADS)

Pištora, J.; Lesňák, M.; Lišková, E.; Višňovský, Š.; Harward, I.; Maslankiewicz, P.; Balin, K.; Celinski, Z.; Mistrík, J.; Yamaguchi, T.; Lopusnik, R.; Vlček, J.

2010-04-01

The room temperature optical constants n and k of MBE grown FeF2 films are reported. Because of poor chemical stability, FeF2 had to be coated with a protective Au layer. Reflection spectral ellipsometry in the photon energy range between 1.3 and 5.2 eV was performed on structures with a typical profile Au(0.5 nm)/FeF2(120 nm)/Au(30 nm)/Ag(20 nm)/Fe(0.6 nm) grown on GaAs(0 0 1) substrate. The spectra of n and k in FeF2 were subsequently employed in the design of FeF2/Fe/FeF2 sandwiches considered as magneto-optic (MO) sensors for weak microwave currents. Their MO response was evaluated using reflection MO (Kerr) spectroscopy at polar magnetization. The present results may be of interest in MO studies of magnetic nanostructures with Fe/FeF2/Fe, including MO magnetometry and MO magnetic domain imaging.

Surface analysis of Fe-Co-Mo electrolytic coatings

NASA Astrophysics Data System (ADS)

Yar-Mukhamedova, G. Sh; Sakhnenko, N. D.; Ved', M. V.; Yermolenko, I. Yu; Zyubanova, S. I.

2017-06-01

Coatings Fe-Co-Mo with a composition of 47 at.% iron, 28 at.% Cobalt and 25 at.% Molybdenum were deposited from citrate electrolyte using pulse electrolysis mode. Scanning electron and atomic force microscopy have established the surface morphology and topography. It was identified the parts with a globular structure which have an average size of 0.2-0.5μm and singly located sharp grains. Within the same scan area sites with developed surface were detected the topography of which is identical to the crystal structure of cobalt with the crystallites size of 0.2-1.75μm. The parameters Ra and Rq for parts with different morphology as well as average characteristics of coatings demonstrated the low roughness of the surface. It is found that the coercive force of Fe-Co-Mo films is 7-10 Oe, which allow us to classify the Fe-Co-Mo coatings as soft magnetic materials.

AsMo7O27-bridged dinuclear sandwich-type heteropolymolybdates of Cr(III) and Fe(III): magnetism of [MM'(AsMo7O27)2]12- with MM' = FeFe, CrFe, and CrCr.

PubMed

Xu, Haisheng; Li, Lili; Liu, Bin; Xue, Ganglin; Hu, Huaiming; Fu, Feng; Wang, Jiwu

2009-11-02

Two new dinuclear sandwich-type heteropolymolybdates based on the mulitidendate inorganic fragment [AsMo(7)O(27)] and Cr(III) and Fe(III) ions, namely, the homometallic sandwich polyoxometalate (POM) (NH(4))(12)[Fe(2)(AsMo(7)O(27))(2)] x 12 H(2)O (1) and the first example of the "symmetrical" heterometallic Cr(III)-Fe(III) sandwich POM, (NH(4))(12)[FeCr(AsMo(7)O(27))(2)] x 13 H(2)O (2), were simultaneously synthesized in high yield. Their magnetic properties are thoroughly investigated together with the homometallic sandwich POM (NH(4))(12)[Cr(2)(AsMo(7)O(27))(2)] x 11 H(2)O (3). The chi(M)T values for compounds 1-3 at 300 K correspond well to the calculated spin-only values for Fe(III) (S = 5/2) and Cr(III) (S = 3/2) with g(Fe) = g(Cr) = 2. Upon cooling, the chi(M)T values decline monotonously and reach 0.14, 1.00, and 0.11 cm(3) K mol(-1) at 2.0 K for 1, 2, and 3, respectively, indicating a significant antiferromagnetic exchange between the magnetic centers with J = -2.09, -4.09, and -6.26 cm(-1), respectively, for 1, 2, and 3. The magnetic results clearly establish that compound 2 is formed by bimetallic Cr(III)-Fe(III) units and not by a mixture of the two antiferromagnetically coupled homometallic species. Their thermal properties are also characterized.

Rational synthesis of high nuclearity Mo/Fe/S clusters: the reductive coupling approach in the convenient synthesis of (Cl(4)-cat)(2)Mo(2)Fe(6)S(8)(PR(3))(6) [R = Et, (n)Pr, (n)Bu] and the new [(Cl(4)-cat)(2)Mo(2)Fe(2)S(3)O(PEt(3))(3)Cl]-1/2(Fe(PEt(3))(2)(MeCN)(4)) and (Cl(4)-cat)(2)Mo(2)Fe(3)S(5)(PEt(3))(5) clusters.

PubMed

Han, J; Koutmos, M; Ahmad, S A; Coucouvanis, D

2001-11-05

A general method for the synthesis of high nuclearity Mo/Fe/S clusters is presented and involves the reductive coupling of the (Et(4)N)(2)[(Cl(4)-cat)MoOFeS(2)Cl(2)] (I) and (Et(4)N)(2)[Fe(2)S(2)Cl(4)] (II) clusters. The reaction of I and II with Fe(PR(3))(2)Cl(2) or sodium salts of noncoordinating anions such as NaPF(6) or NaBPh(4) in the presence of PR(3) (R = Et, (n)Pr, or (n)Bu) affords (Cl(4)-cat)(2)Mo(2)Fe(6)S(8)(PR(3))(6) [R = Et (IIIa), (n)Pr (IIIb), (n)Bu (IIIc)], Fe(6)S(6)(PEt(3))(4)Cl(2) (IV) and (PF(6))[Fe(6)S(8)(P(n)Pr(3))(6)] (V) as byproducts. The isolation of (Et(4)N)[Fe(PEt(3))Cl(3)] (VI), NaCl, and SPEt(3) supports a reductive coupling mechanism. Cluster IV and V also have been synthesized by the reductive self-coupling of compound II. The reductive coupling reaction between I and II by PEt(3) and NaPF(6) in a 1:1 ratio produces the (Et(4)N)(2)[(Cl(4)-cat)Mo(L)Fe(3)S(4)Cl(3)] clusters [L = MeCN (VIIa), THF (VIIb)]. The hitherto unknown [(Cl(4)-cat)(2)Mo(2)Fe(2)S(3)O(PEt(3))(3)Cl](+) cluster (VIII) has been isolated as the 2:1 salt of the (Fe(PEt(3))(2)(MeCN)(4))(2+) cation after the reductive self-coupling reaction of I in the presence of Fe(PEt(3))(2)Cl(2). Cluster VIII crystallizes in the monoclinic space group P2(1)/c with a = 11.098(3) A, b = 22.827(6) A, c = 25.855(6) A, beta = 91.680(4) degrees, and Z = 4. The formal oxidation states of metal atoms in VIII have been assigned as Mo(III), Mo(IV), Fe(II), and Fe(III) on the basis of zero-field Mössbauer spectra. The Fe(PEt(3))(2)(MeCN)(4) cation of VIII is also synthesized independently, isolated as the BPh(4)(-) salt (IX), and has been structurally characterized. The reductive coupling of compound I also affords in low yield the new (Cl(4)-cat)(2)Mo(2)Fe(3)S(5)(PEt(3))(5) cluster (X) as a byproduct. Cluster X crystallizes in the monoclinic space group P2(1)/n with a = 14.811(3) A, b = 22.188(4) A, c = 21.864(4) A, beta = 100.124(3) degrees, and Z = 4 and the structure shows very short Mo-Fe

Metal substitution in the active site of nitrogenase MFe(7)S(9) (M = Mo(4+), V(3+), Fe(3+)).

PubMed

Lovell, Timothy; Torres, Rhonda A; Han, Wen-Ge; Liu, Tiqing; Case, David A; Noodleman, Louis

2002-11-04

The unifying view that molybdenum is the essential component in nitrogenase has changed over the past few years with the discovery of a vanadium-containing nitrogenase and an iron-only nitrogenase. The principal question that has arisen for the alternative nitrogenases concerns the structures of their corresponding cofactors and their metal-ion valence assignments and whether there are significant differences with that of the more widely known molybdenum-iron cofactor (FeMoco). Spin-polarized broken-symmetry (BS) density functional theory (DFT) calculations are used to assess which of the two possible metal-ion valence assignments (4Fe(2+)4Fe(3+) or 6Fe(2+)2Fe(3+)) for the iron-only cofactor (FeFeco) best represents the resting state. For the 6Fe(2+)2Fe(3+) oxidation state, the spin coupling pattern for several spin state alignments compatible with S = 0 were generated and assessed by energy criteria. The most likely BS spin state is composed of a 4Fe cluster with spin S(a) = (7)/(2) antiferromagnetically coupled to a 4Fe' cluster with spin S(b) = (7)/(2). This state has the lowest DFT energy for the isolated FeFeco cluster and displays calculated Mössbauer isomer shifts consistent with experiment. Although the S = 0 resting state of FeFeco has recently been proposed to have metal-ion valencies of 4Fe(2+)4Fe(3+) (derived from experimental Mössbauer isomer shifts), our isomer shift calculations for the 4Fe(2+)4Fe(3+) oxidation state are in poorer agreement with experiment. Using the Mo(4+)6Fe(2+)Fe(3+) oxidation level of the cofactor as a starting point, the structural consequences of replacement of molybdenum (Mo(4+)) with vanadium (V(3+)) or iron (Fe(3+)) in the cofactor have been investigated. The size of the cofactor cluster shows a dependency on the nature of the heterometal and increases in the order FeMoco < FeVco < FeFeco.

Turnover-Dependent Inactivation of the Nitrogenase MoFe-Protein at High pH

PubMed Central

2013-01-01

Proton uptake accompanies the reduction of all known substrates by nitrogenase. As a consequence, a higher pH should limit the availability of protons as a substrate essential for turnover, thereby increasing the proportion of more highly reduced forms of the enzyme for further study. The utility of the high-pH approach would appear to be problematic in view of the observation reported by Pham and Burgess [(1993) Biochemistry 32, 13725–13731] that the MoFe-protein undergoes irreversible protein denaturation above pH 8.65. In contrast, we found by both enzyme activity and crystallographic analyses that the MoFe-protein is stable when incubated at pH 9.5. We did observe, however, that at higher pHs and under turnover conditions, the MoFe-protein is slowly inactivated. While a normal, albeit low, level of substrate reduction occurs under these conditions, the MoFe-protein undergoes a complex transformation; initially, the enzyme is reversibly inhibited for substrate reduction at pH 9.5, yet in a second, slower process, the MoFe-protein becomes irreversibly inactivated as measured by substrate reduction activity at the optimal pH of 7.8. The final inactivated MoFe-protein has an increased hydrodynamic radius compared to that of the native MoFe-protein, yet it has a full complement of iron and molybdenum. Significantly, the modified MoFe-protein retains the ability to specifically interact with its nitrogenase partner, the Fe-protein, as judged by the support of ATP hydrolysis and by formation of a tight complex with the Fe-protein in the presence of ATP and aluminum fluoride. The turnover-dependent inactivation coupled to conformational change suggests a mechanism-based transformation that may provide a new probe of nitrogenase catalysis. PMID:24392967

Turnover-dependent inactivation of the nitrogenase MoFe-protein at high pH.

PubMed

Yang, Kun-Yun; Haynes, Chad A; Spatzal, Thomas; Rees, Douglas C; Howard, James B

2014-01-21

Proton uptake accompanies the reduction of all known substrates by nitrogenase. As a consequence, a higher pH should limit the availability of protons as a substrate essential for turnover, thereby increasing the proportion of more highly reduced forms of the enzyme for further study. The utility of the high-pH approach would appear to be problematic in view of the observation reported by Pham and Burgess [(1993) Biochemistry 32, 13725-13731] that the MoFe-protein undergoes irreversible protein denaturation above pH 8.65. In contrast, we found by both enzyme activity and crystallographic analyses that the MoFe-protein is stable when incubated at pH 9.5. We did observe, however, that at higher pHs and under turnover conditions, the MoFe-protein is slowly inactivated. While a normal, albeit low, level of substrate reduction occurs under these conditions, the MoFe-protein undergoes a complex transformation; initially, the enzyme is reversibly inhibited for substrate reduction at pH 9.5, yet in a second, slower process, the MoFe-protein becomes irreversibly inactivated as measured by substrate reduction activity at the optimal pH of 7.8. The final inactivated MoFe-protein has an increased hydrodynamic radius compared to that of the native MoFe-protein, yet it has a full complement of iron and molybdenum. Significantly, the modified MoFe-protein retains the ability to specifically interact with its nitrogenase partner, the Fe-protein, as judged by the support of ATP hydrolysis and by formation of a tight complex with the Fe-protein in the presence of ATP and aluminum fluoride. The turnover-dependent inactivation coupled to conformational change suggests a mechanism-based transformation that may provide a new probe of nitrogenase catalysis.

Perpendicular magnetic anisotropy in Mo/Co2FeAl0.5Si0.5/MgO/Mo multilayers with optimal Mo buffer layer thickness

NASA Astrophysics Data System (ADS)

Saravanan, L.; Raja, M. Manivel; Prabhu, D.; Pandiyarasan, V.; Ikeda, H.; Therese, H. A.

2018-05-01

Perpendicular Magnetic Anisotropy (PMA) was realized in as-deposited Mo(10)/Co2FeAl0.5Si0.5(CFAS)(3)/MgO(0.5)/Mo multilayer stacks with large perpendicular magnetic anisotropy energy (Keff). PMA of this multilayer is found to be strongly dependent on the thickness of the individual CFAS (tCFAS), Mo (tMo) and MgO (tMgO) layers and annealing temperatures. The interactions at the Mo/CFAS/MgO interfaces are critical to induce PMA and are tuned by the interfacial oxidation. The major contribution to PMA is due to iron oxide at the CFAS/MgO interface. X-ray diffraction (XRD) and infrared spectroscopic (FT-IR) studies further ascertain this. However, an adequate oxidation of MgO and the formation of (0 2 4) and (0 1 8) planes of α-Fe2O3 at the optimal Mo buffer layer thickness is mainly inducing PMA in Mo/CFAS/MgO/Mo stack. Microstructural changes in the films are observed by atomic force microscopy (AFM). X-ray photoelectron spectroscopy (XPS) demonstrates the oxidation of CFAS/MgO interface and the formation of Fe-O bonds confirming that the real origin of PMA in Mo/CFAS/MgO is due to hybridization of Fe (3dz2) and O (2pz) orbitals and the resulted spin-orbit interaction at their interface. The half-metallic nature CFAS with Mo layer exhibiting PMA can be a potential candidate as p-MTJs electrodes for the new generation spintronic devices.

COMPARATIVE ASSESSMENT OF THE COMPOSITION AND CHARGE STATE OF NITROGENASE FeMo-COFACTOR

PubMed Central

Harris, Travis V.; Szilagyi, Robert K.

2011-01-01

A significant limitation in our understanding of the molecular mechanism of biological nitrogen fixation is the uncertain composition of the FeMo-cofactor (FeMo-co) of nitrogenase. In this study we present a systematic, density functional theory-based evaluation of spin coupling schemes, iron oxidation states, ligand protonation states, and interstitial ligand composition using a wide range of experimental criteria. The employed functionals and basis sets were validated with molecular orbital information from X-ray absorption spectroscopic data of relevant iron-sulfur clusters. Independently from the employed level of theory, the electronic structure with the greatest number of antiferromagnetic interactions corresponds to the lowest energy state for a given charge and oxidation state distribution of the iron ions. The relative spin state energies of resting and oxidized FeMo-co already allowed the exclusion of certain iron oxidation state distributions and interstitial ligand compositions. Geometry optimized FeMo-co structures of several models further eliminated additional states and compositions, while reduction potentials indicated a strong preference for the most likely charge state of FeMo-co. Mössbauer and ENDOR parameter calculations were found to be remarkably dependent on the employed training set, density functional and basis set. Overall, we found that a more oxidized [MoIV-2FeII-5FeIII-9S2−-C4−] composition with a hydroxyl-protonated homocitrate ligand satisfies all of the available experimental criteria, and is thus favored over the currently preferred composition of [MoIV-4FeII-3FeIII-9S2−-N3−] from the literature. PMID:21545160

VTVH-MCD study of the Delta nifB Delta nifZ MoFe protein from Azotobacter vinelandii.

PubMed

Cotton, Marcia S; Rupnik, Kresimir; Broach, Robyn B; Hu, Yilin; Fay, Aaron W; Ribbe, Markus W; Hales, Brian J

2009-04-08

NifZ is a member of a series of proteins associated with the maturation of the nitrogenase MoFe protein. An MCD spectroscopic study was undertaken on the Delta nifB Delta nifZ MoFe protein generated in the absence of both NifZ and NifB (deletion of NifB generates an apo-MoFe protein lacking the FeMo cofactor). Results presented here show that, in the absence of NifZ, only one of the two P-clusters of the MoFe protein is matured to the ultimate [8Fe-7S] structure. The other P-cluster site in the protein contains a [4Fe-4S] cluster pair, representing a P-cluster precursor that is electronically identical to the analogous clusters observed in the Delta nifH MoFe protein. These results suggest that the MoFe protein is synthesized in a stepwise fashion where NifZ is specifically required for the formation of the second P-cluster.

Thermal transport properties of polycrystalline Pb2FeMoO6

NASA Astrophysics Data System (ADS)

Yuan, Xueping; Xu, Mingxiang

2018-06-01

Thermoelectric properties and specific heat of polycrystalline Pb2FeMoO6 have been systematically studied. The thermal conductivity increases monotonically with increasing of temperature, and reaches the maximum value 1.50 W m‑1 K‑1 at 350 K. The relatively low thermal conductivity is mainly attributed to the strong scattering effect of phonons at Fe/Mo sites. The negative Seebeck coefficient indicates the n-type conduction of the sample. The absolute value of S increases up to 20 μV K‑1 at 350 K. Due to the inhomogeneity resulting from Fe/Mo ions disorder, no distinct λ-type specific heat peak or anomaly typical for second-order transitions are observed.

Structures, electronic properties and reaction paths from Fe(CO)5 molecule to small Fe clusters

NASA Astrophysics Data System (ADS)

Li, Zhi; Zhao, Zhen

2018-04-01

The geometries, electrical characters and reaction paths from Fe(CO)5 molecule to small Fe clusters were investigated by using all-electron density functional theory. The results show that in the decomposition process of pentacarbonyl-iron, Fe(CO)5 molecule prefers to remove a carbon monoxide and adsorb another Fe(CO)5 molecule to produce nonacarbonyldiiron Fe2(CO)9 then Fe2(CO)9 gradually removes carbon monoxide to produce small Fe clusters. As It can be seen from the highest occupied molecule orbital-lowest unoccupied molecule orbital gap curves, the Fe(CO)n=3, and 5 and Fe2(CO)n=3, 7 and 9 intermediates have higher chemical stability than their neighbors. The local magnetic moment of the carbon monoxide is aligning anti-ferromagnetic. The effect of external magnetic field to the initial decomposition products of Fe(CO)5 can be ignored.

Molybdenum isotopes in modern marine hydrothermal Fe/Mn deposits: Implications for Archean and Paleoproterozoic Mo cycles

NASA Astrophysics Data System (ADS)

Goto, K. T.; Hein, J. R.; Shimoda, G.; Aoki, S.; Ishikawa, A.; Suzuki, K.; Gordon, G. W.; Anbar, A. D.

2016-12-01

Molybdenum isotope (δ98/95Mo) variations recorded in Archean and Paleoproterozoic Fe/Mn-rich sediments have been used to constrain ocean redox conditions at the time of deposition (Canfield et al., 2013 PNAS; Planavsky et al., 2014 Nat. Geo.; Kurzweil et al., 2015 GCA). However, except for hydrogenous Fe-Mn crusts (Siebert et al., 2003), δ98/95Mo variation of modern Fe and Mn oxide deposits has been poorly investigated. Marine hydrothermal systems are thought to be the major source of Fe and Mn in Archean and Paleoproterozoic Fe- and Mn-rich sediments. Hence, to accurately interpret Mo isotope data of those ancient sedimentary rocks, it is important to evaluate the possible influence of hydrothermally derived Mo on δ98/95Mo of modern Fe- and Mn-rich sediments. In this study, we analyzed Mo isotopic compositions of one hydrothermal Fe oxide and 15 Mn oxides from five different hydrothermal systems in the modern ocean. The Fe oxide is composed mainly of goethite, and has a δ98/95Mo of 0.7‰, which is 1.4‰ lighter than that of present-day seawater. The observed offset is similar to isotope fractionation observed during adsorption experiments of Mo on goethite (Δ98/95Mogoethite-solution = -1.4 ± 0.5%; Goldberg et al., 2009 GCA). The 15 hydrothermal Mn oxides show large variations in δ98/95Mo ranging from -1.7 to 0.5‰. However, most of the values are similar to those of modern hydrogenous Fe-Mn crusts (Siebert et al., 2003 EPSL), and fall within the range of estimated δ98/95Mo of Mn oxides precipitated from present-day seawater using the isotope offset reported from adsorption experiments (Δ98/95Mo = -2.7 ± 0.3‰; Wasylenki et al., 2008 GCA). These findings indicate that seawater is the dominant source of Mo for modern hydrothermal Fe and Mn deposits. However, the observed large variation indicates that the contribution Mo from local hydrothermal systems is not negligible. The oceanic Mo inventory during the Archean and Paleoproterozoic is thought to be

Nanostructured double-layer FeO as nanotemplate for tuning adsorption of titanyl phthalocyanine molecules

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

Lu, Shuangzan; University of Chinese Academy of Sciences, Beijing 100049; Qin, Zhihui, E-mail: zhqin@wipm.ac.cn

2014-06-23

The growth, structure of Pt(111) supported double-layer FeO and the adsorption of titanyl phthalocyanine (TiOPc) molecules with tunable site and orientation were presented. According to the atomic-resolution STM image, the structure was rationalized as (8√3 × 8√3) R30°/Pt(111) nanostructure constructed by Fe species coordinated with different number of oxygen on top of non-rotated (8 × 8) FeO /Pt(111) structure. Due to the modulation of the stacking of Fe atoms in the second layer relative to the O atoms in the second layer and the underlying layer, the interface and total dipole moment periodically vary within (8√3 × 8√3) R30°/Pt(111) structure. The resulted periodically distributed dipole-dipole interactionmore » benefits the growth of TiOPc molecules with area-selective sites and molecular orientations. Thus, this study provides a reliable method to govern the adsorption process of the polar molecules for potential applications in future functional molecular devices.« less

Nanocomposite Nd-Y-Fe-B-Mo bulk magnets prepared by injection casting technique

NASA Astrophysics Data System (ADS)

Tao, Shan; Ahmad, Zubair; Zhang, Pengyue; Yan, Mi; Zheng, Xiaomei

2017-09-01

The phase composition, magnetic and microstructural properties of Nd2Fe14B/(α-Fe, Fe3B) nanocomposite magnets produced by injection casting technique have been studied. Magnetic hysteresis loop of the Nd7Y6Fe61B22Mo4 permanent magnet demonstrates the coercivity as high as 1289 kA/m. Electron microscopy elucidates a microstructure composed of magnetically soft α-Fe, Fe3B and hard Nd2Fe14B/Y2Fe14B nanograins (20-50 nm) separated by ultra-thin grain boundary layer. The Henkel plot curve of the Nd7Y6Fe61B22Mo4 magnet yields the existence of exchange coupling interactions between soft and hard phases. Macroscopically large size sheet magnet is obtained due to high glass forming ability of the Nd7Y6Fe61B22Mo4 alloy derived from large atomic radius mismatch and negative enthalpy of alloy constituent elements. The high coercivity of the magnet is attributed to the magnetically hard phase increment, nucleation of reverse domains and the presence of thin grain boundary phase. Good magnetic properties such as remanence of 0.51 T, coercivity of 1289 kA/m and maximum energy product of 46.2 kJ/m3 are obtained in directly casted Nd7Y6Fe61B22Mo4 sheet magnets.

Fabrication of MgFe2O4/MoS2 Heterostructure Nanowires for Photoelectrochemical Catalysis.

PubMed

Fan, Weiqiang; Li, Meng; Bai, Hongye; Xu, Dongbo; Chen, Chao; Li, Chunfa; Ge, Yilin; Shi, Weidong

2016-02-16

A novel one-dimensional MgFe2O4/MoS2 heterostructure has been successfully designed and fabricated. The bare MgFe2O4 was obtained as uniform nanowires through electrospinning, and MoS2 thin film appeared on the surface of MgFe2O4 after further chemical vapor deposition. The structure of the MgFe2O4/MoS2 heterostructure was systematic investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectrometry (XPS), and Raman spectra. According to electrochemical impedance spectroscopy (EIS) results, the MgFe2O4/MoS2 heterostructure showed a lower charge-transfer resistance compared with bare MgFe2O4, which indicated that the MoS2 played an important role in the enhancement of electron/hole mobility. MgFe2O4/MoS2 heterostructure can efficiently degrade tetracycline (TC), since the superoxide free-radical can be produced by sample under illumination due to the active species trapping and electron spin resonance (ESR) measurement, and the optimal photoelectrochemical degradation rate of TC can be achieved up to 92% (radiation intensity: 47 mW/cm(2), 2 h). Taking account of its unique semiconductor band gap structure, MgFe2O4/MoS2 can also be used as an photoelectrochemical anode for hydrogen production by water splitting, and the hydrogen production rate of MgFe2O4/MoS2 was 5.8 mmol/h·m(2) (radiation intensity: 47 mW/cm(2)), which is about 1.7 times that of MgFe2O4.

Molybdenum-oxide based unique polyprotic nanoacids showing different deprotonations and related assembly processes in solution.

PubMed

Kistler, Melissa L; Liu, Tianbo; Gouzerh, Pierre; Todea, Ana Maria; Müller, Achim

2009-07-14

We report the self-assembly processes in solution of three Keplerate-type molybdenum-oxide based clusters {Mo72V30}, {Mo72Cr30} and {Mo72Fe30} (all with diameters of approximately 2.5 nm). These clusters behave as unique weak polyprotic acids owing to the external water ligands attached to the non-Mo metal centers. Whereas the Cr and Fe clusters have 30 water ligands attached at the 30 M3+ centers pointing outside, {Mo72V30} has 20 water ligands coordinated to vanadium atoms, of which only 10 are pointing outside. The self-assembly processes of the Keplerates leading to supramolecular blackberry-type structures are influenced by the effective charge densities on the cluster surfaces, which can be tuned by the pH values and solvent properties. As expected, {Mo72Cr30} and {Mo72Fe30} behave similarly in aqueous solution due to their analogous structures and in both cases the self-assembly follows the partial deprotonation of the external water ligands attached to the non-Mo metal centers. However, the M-OH2 functionalities differ not only in acidity but also lability, i.e. in different residence times of the H2O ligands. In contrast to {Mo72Cr30} and {Mo72Fe30}, the {Mo72V30} clusters carry a rather large number of negative charges so that their solution properties are different. They exist as discrete macroions in dilute aqueous solution, and form only in mixed water/organic solvent (like acetone) blackberry-type structures whose size increases with acetone content. The comparison of the properties of the clusters allows more general information about the interesting self-assembly phenomenon to be unveiled.

Harvesting visible light with MoO3 nanorods modified by Fe(iii) nanoclusters for effective photocatalytic degradation of organic pollutants.

PubMed

Alam, U; Kumar, S; Bahnemann, D; Koch, J; Tegenkamp, C; Muneer, M

2018-02-07

The photocatalytic performance of MoO 3 is limited due to its weak visible light absorption ability and quick recombination of charge carriers. In the present work, we report the facile synthesis of Fe(iii)-grafted MoO 3 nanorods using a hydrothermal method followed by an impregnation technique with the aim of enhancing the light harvesting ability and photocatalytic efficiency of MoO 3 . The prepared samples were characterized through the standard analytical techniques of XRD, SEM-EDS, TEM, XPS, UV-Vis-DRS, FT-IR, TG-DTA and PL spectrophotometry. XPS and TEM analyses reveal that Fe(iii) ions are successfully grafted onto the surface of the MoO 3 nanorod with intimate interfacial contact. The photocatalytic performances of the prepared samples were investigated by studying the degradation of methylene blue (MB), rhodamine B (RhB) and 4-nitrophenol (4-NP) under visible light irradiation. The surface-modified MoO 3 with Fe(iii) ions showed excellent photocatalytic activity towards the degradation of the above-mentioned pollutants, where Fe(iii) ions act as effective cocatalytic sites to produce hydroxyl radicals through multi-electron reduction of oxygen molecules. The improved photocatalytic activity could be ascribed to the effective separation of charge carriers and efficient production of hydroxyl radicals via the rapid capture of electrons by Fe(iii) through a well-known photoinduced interfacial charge transfer mechanism. Based on scavenger analysis study, a mechanism for the enhanced photocatalytic activity has been discussed and proposed. The concept of surface grafting onto large bandgap semiconductors with ubiquitous elements opens up a new avenue for the development of visible-light-responsive photocatalysts with excellent photocatalytic activity.

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

PubMed

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

2017-08-08

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

Processability evaluation of a Mo-containing FeCrAl alloy for seamless thin-wall tube fabrication

DOE PAGES

Sun, Zhiqian; Yamamoto, Yukinori

2017-06-10

The processability of a Mo-containing FeCrAl alloy (Fe-13Cr-5.2Al-2Mo base, in wt%), developed for accident-tolerant nuclear fuel claddings, was evaluated through a stepwise rolling process at 400 °C under two different inter-pass annealing conditions (i.e., 650 °C for 1 h and at 870 °C for 30 min). The inter-pass annealing at 870 °C easily softened the FeCrAl alloy; however, it led to the formation of coarse grains of ~200 µm. On the other hand, the FeCrAl alloy maintained elongated, deformed grains with the inter-pass annealing at 650 °C, but the annealed samples showed relatively high deformation resistance and strong texture. Importantmore » aspects concerning the processability and microstructural control of FeCrAl alloys, such as deformation inhomogeneity, texture development, and grain coarsening, were discussed. Optimized processing conditions were recommended, based on the results, to achieve desirable microstructures with balanced processability and mechanical properties.« less

Double-perovskites A 2FeMoO 6- δ (A = Ca, Sr, Ba) as anodes for solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Zhang, Leilei; Zhou, Qingjun; He, Qiang; He, Tianmin

Double-perovskites A 2FeMoO 6- δ (A = Ca, Sr, Ba) have been investigated as potential anode materials for solid oxide fuel cells (SOFCs). At room temperature, A 2FeMoO 6- δ compounds crystallize in monoclinic, tetragonal, and cubic structures for A = Ca, Sr, and Ba, respectively. A weak peak observed at around 880 cm -1 in the Raman spectra can be attributed to traces of AMoO 4. XPS has confirmed the coexistence of Fe 2+-Mo 6+ and Fe 3+-Mo 5+ electronic configurations. Moreover, a systematic shift from Fe 2+/3+-Mo 6+/5+ to Fe 2+-Mo 6+ configuration is seen with increasing A-site cation size. A 2FeMoO 6- δ samples display distinct electrical properties in H 2, which can be attributed to different degrees of degeneracy of the Fe 2+-Mo 6+ and Fe 3+-Mo 5+ configurations. Ca 2FeMoO 6- δ is unstable in a nitrogen atmosphere, while Sr 2FeMoO 6- δ and Ba 2FeMoO 6- δ are stable up to 1200 °C. The thermal expansion coefficients of Sr 2FeMoO 6- δ and Ba 2FeMoO 6- δ are very close to that of La 0.9Sr 0.1Ga 0.8Mg 0.2O 3- δ (LSGM). The performances of cells with 300 μm thick LSGM electrolyte, double-perovskite SmBaCo 2O 5+ x cathodes, and A 2FeMoO 6- δ anodes follow the sequence Ca 2FeMoO 6- δ < Ba 2FeMoO 6- δ < Sr 2FeMoO 6- δ. The maximum power densities of a cell with an Sr 2FeMoO 6- δ anode reach 831 mW cm -2 in dry H 2 and 735 mW cm -2 in commercial city gas at 850 °C, respectively.

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

NASA Astrophysics Data System (ADS)

Wang, Xinhong; Zhang, Min; Qu, Shiyao

2010-09-01

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

Antisite-disorder, magnetic and thermoelectric properties of Mo-rich Sr2Fe1-yMo1+yO6 (0 ≤y≤ 0.2) double perovskites.

PubMed

Popuri, Srinivasa R; Redpath, Debbie; Chan, Gavin; Smith, Ronald I; Cespedes, Oscar; Bos, Jan-Willem G

2015-06-21

Structure analysis using X-ray and neutron powder diffraction and elemental mapping has been used to demonstrate that nominal A-site deficient Sr(2-x)FeMoO(6-δ) (0 ≤x≤ 0.5) compositions form as Mo-rich Sr(2)Fe(1-y)Mo(1+y)O(6) (0 ≤y≤ 0.2) perovskites at high temperatures and under reducing atmospheres. These materials show a gradual transition from the Fe and Mo rock salt ordered double perovskite structure to a B-site disordered arrangement. Analysis of the fractions of B-O-B' linkages revealed a gradual increase in the number of Mo-O-Mo linkages at the expense of the ferrimagnetic (FIM) Fe-O-Mo linkages that dominate the y = 0 material. All samples contain about 10-15% antiferromagnetic (AF) Fe-O-Fe linkages, independent of the degree of B-site ordering. The magnetic susceptibility of the y = 0.2 sample is characteristic of a small domain ferrimagnet (T(c)∼ 250 K), while room temperature neutron powder diffraction demonstrated the presence of G-type AF ordering linked to the Fe-O-Fe linkages (m(Fe) = 1.25(7)μ(B)). The high temperature thermoelectric properties are characteristic of a metal with a linear temperature dependence of the Seebeck coefficient, S (for all y) and electrical resistivity ρ (y≥ 0.1). The largest thermoelectric power factor S(2)/ρ = 0.12 mW m(-1) K(-1) is observed for Sr(2)FeMoO(6) at 1000 K.

33 CFR 72.01-30 - Temporary deficiencies.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Temporary deficiencies. 72.01-30 Section 72.01-30 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY AIDS TO NAVIGATION MARINE INFORMATION Notices to Mariners § 72.01-30 Temporary deficiencies. Temporary deficiencies...

33 CFR 72.01-30 - Temporary deficiencies.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 33 Navigation and Navigable Waters 1 2011-07-01 2011-07-01 false Temporary deficiencies. 72.01-30 Section 72.01-30 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY AIDS TO NAVIGATION MARINE INFORMATION Notices to Mariners § 72.01-30 Temporary deficiencies. Temporary deficiencies...

Synthesis and characterization of sulfur-voided cubanes. Structural analogues for the MoFe(3)S(3) subunit in the nitrogenase cofactor.

PubMed

Coucouvanis, Dimitri; Han, Jaehong; Moon, Namdoo

2002-01-16

A new class of Mo/Fe/S clusters with the MoFe(3)S(3) core has been synthesized in attempts to model the FeMo-cofactor in nitrogenase. These clusters are obtained in reactions of the (Cl(4)-cat)(2)Mo(2)Fe(6)S(8)(PR(3))(6) [R = Et (I), (n)Pr (II)] clusters with CO. The new clusters include those preliminarily reported: (Cl(4)-cat)MoFe(3)S(3)(PEt(3))(2)(CO)(6) (III), (Cl(4)-cat)(O)MoFe(3)S(3)(PEt(3))(3)(CO)(5) (IV), (Cl(4)-cat)(Pyr)MoFe(3)S(3)(PEt(3))(2)(CO)(6) (VI), and (Cl(4)-cat)(Pyr)MoFe(3)S(3)(P(n)Pr(3))(3)(CO)(4) (VIII). In addition the new (Cl(4)-cat)(O)MoFe(3)S(3)(P(n)Pr(3))(3)(CO)(5) cluster (IVa), the (Cl(4)-cat)(O)MoFe(3)S(3)(PEt(3))(2)(CO)(6)cluster (V), the (Cl(4)-cat)(O)MoFe(3)S(3)(P(n)Pr(3))(2)(CO)(6) cluster (Va), the (Cl(4)-cat)(Pyr)MoFe(3)S(3)(P(n)Pr(3))(2)(CO)(6) cluster (VIa), and the (Cl(4)-cat)(P(n)Pr(3))MoFe(3)S(3)(P(n)Pr(3))(2)(CO)(6) cluster (VII) also are reported. Clusters III-VIII have been structurally and spectroscopically characterized. EPR, zero-field (57)Fe-Mössbauer spectroscopic characterizations, and magnetic susceptibility measurements have been used for a tentative assignment of the electronic and oxidation states of the MoFe(3)S(3) sulfur-voided cuboidal clusters. A structural comparison of the clusters with the MoFe(3)S(3) subunit of the FeMo-cofactor has led to the suggestion that the storage of reducing equivalents into M-M bonds, and their use in the reduction of substrates, may occur with the FeMo-cofactor, which also appears to have M-M bonding. On the basis of this argument, a possible N(2)-binding and reduction mechanism on the FeMoco-cofactor is proposed.

Investigation on microstructure and mechanical properties of Mo2FeB2 based cermets with and without PVA

NASA Astrophysics Data System (ADS)

Shen, Yupeng; Huang, Zhifu; Jian, Yongxin; Yang, Ming; Li, Kemin

2018-03-01

Mo2FeB2 based cermets with and without PVA have been investigated by x-ray diffractometry (XRD), x-ray photoelectron spectroscope (XPS) and scanning electron microscopy (SEM). The density and transverse rupture strength (TRS) of green compact, relative density, hardness (HRA), fracture toughness (KIC) and TRS of Mo2FeB2 based cermets were also measured. The results indicate that, compared with the Mo2FeB2 based cermets without PVA, the density of green compact with PVA can be improved slightly at the same pressure. However, the much higher TRS is obtained for the green compact without PVA. Meanwhile, Mo2FeB2 particles exhibit the finer and less congruity feature for Mo2FeB2 based cermets without PVA. In addition, the higher relative density, hardness, fracture toughness and TRS can be acquired for the cermets without PVA. Obviously, considering the mechanical properties and preparation period of Mo2FeB2 based cermets, no adding PVA is the optimized process of powder molding in the manufacture of Mo2FeB2 based cermets.

In-Situ Fixation of All-Inorganic Mo-Fe-S Clusters for the Highly Selective Removal of Lead(II).

PubMed

Zhang, Wentao; Shi, Shuo; Zhu, Wenxin; Yang, Chengyuan; Li, Sihang; Liu, Xinnan; Hu, Na; Huang, Lunjie; Wang, Rong; Suo, Yourui; Li, Zhonghong; Wang, Jianlong

2017-09-27

The selective adsorption by suitable substrate materials is considered one of the most economical methods. In this work, an all-inorganic bimetallic Mo-Fe-S cluster is facilely achieved through in situ chemical fixation of tetrathiomolybdate (TTM) on Fe 3 O 4 nanoparticles (NPs) at room temperature (donated as FeMoS NPs). The bimetallic building blocks on the obtained FeMoS NPs possess a monovacancy species of sulfur, endowing FeMoS NPs with a selectivity order of Zn 2+ , Mn 2+ , Ni 2+ < Cd 2+ ≪ Cu 2+ < Pb 2+ for metal-ion adsorption, a novel application for the Mo-Fe-S clusters. Particularly, with the highest selectivity for Pb 2+ (K d ≈ 10 7 ), which is about 3 × 10 3 -1 × 10 6 times higher than those for other ions and has exceeded that of a series of outstanding sorbents reported for Pb 2+ , FeMoS NPs can efficiently reduce the concentration of Pb 2+ from ∼10 ppm to an extremely low level of ∼1 ppb. This facile and rational fabrication of the Mo-Fe-S cluster with Fe 3 O 4 represents a feasible approach to cheaply develop novel and efficient materials for the selective removal of lead(II).

Large magnetoresistance in Fe3O4/molecule nanoparticles

NASA Astrophysics Data System (ADS)

Wang, S.; Yue, F. J.; Lin, L.; Shi, Y. J.; Wu, D.

2010-08-01

In this work, we successfully fabricate Fe3O4 nanoparticles self-assembled with molecules to explore a new approach of studying the molecular spintronics. Fourier transform infrared spectroscopy measurements indicate that one monolayer molecules chemically bonds to the Fe3O4 nanoparticles and the physically absorbed molecules do not exist in the samples. The magnetoresistance (MR) of molecule fully coated ~10 nm size nanoparticles is up to 7.3% at room temperature and 17.5% at 115 K under a field of 5.8 kOe. And the MR ratio is more than two times larger than that of pure Fe3O4 nanoparticles. This enhanced MR is likely arising from weak spin scattering while carriers transport through the molecules. Moreover, a very large low field magnetoresistance is also observed with ~500nm ferromagnetic Fe3O4 nanoparticles coated with acetic acid molecules. Those features open a door for the development of future spin-based molecular electronics.

Spin-Valve Effect in NiFe/MoS2/NiFe Junctions.

PubMed

Wang, Weiyi; Narayan, Awadhesh; Tang, Lei; Dolui, Kapildeb; Liu, Yanwen; Yuan, Xiang; Jin, Yibo; Wu, Yizheng; Rungger, Ivan; Sanvito, Stefano; Xiu, Faxian

2015-08-12

Two-dimensional (2D) layered transition metal dichalcogenides (TMDs) have been recently proposed as appealing candidate materials for spintronic applications owing to their distinctive atomic crystal structure and exotic physical properties arising from the large bonding anisotropy. Here we introduce the first MoS2-based spin-valves that employ monolayer MoS2 as the nonmagnetic spacer. In contrast with what is expected from the semiconducting band-structure of MoS2, the vertically sandwiched-MoS2 layers exhibit metallic behavior. This originates from their strong hybridization with the Ni and Fe atoms of the Permalloy (Py) electrode. The spin-valve effect is observed up to 240 K, with the highest magnetoresistance (MR) up to 0.73% at low temperatures. The experimental work is accompanied by the first principle electron transport calculations, which reveal an MR of ∼9% for an ideal Py/MoS2/Py junction. Our results clearly identify TMDs as a promising spacer compound in magnetic tunnel junctions and may open a new avenue for the TMDs-based spintronic applications.

Adsorption of small inorganic molecules on a defective MoS2 monolayer.

PubMed

González, César; Biel, Blanca; Dappe, Yannick J

2017-04-05

We present a theoretical study of molecular adsorption on defects on a MoS 2 monolayer. Based on Density Functional Theory, our calculations confirm that small inorganic molecules, such as CO 2 , CO, H 2 O, NO, NO 2 , H 2 and N 2 , remain bonded to the pristine monolayer through weak van der Waals interactions, suggesting that the molecules may easily diffuse over the clean monolayer. On the other hand, the introduction of defects can lead to three different situations, depending on the defect and the molecule considered: physisorption, chemical (strong) bonding to the metallic defects, namely the Mo substitutional atoms on the S vacancies, and dissociation, that can take place spontaneously at 0 K in some specific cases or by the effect of thermal agitation in molecules such as CO 2 or NO 2 on the S vacancy. Our energetic and electronic analyses provide an explanation to such bonding possibilities, showing that in the low interacting situations, the molecules tend to adopt a planar configuration parallel to the monolayer, while a molecular rotation is favored in order to facilitate the bond formation on the reactive sites. Finally, the ab initio based Scanning Tunneling Microscopy (STM) simulations show the fingerprint of each molecule adsorbed on the most reactive site. This work opens the way to the possibility of tuning the catalytic properties of MoS 2 by controlling the creation of specific defects in the MoS 2 monolayer.

Microstructure and Room-Temperature Mechanical Properties of FeCrMoVTi x High-Entropy Alloys

NASA Astrophysics Data System (ADS)

Guo, Jun; Huang, Xuefei; Huang, Weigang

2017-07-01

FeCrMoVTi x ( x values represent the molar ratio, where x = 0, 0.5, 1.0, 1.5, and 2.0) high-entropy alloys were prepared by a vacuum arc melting method. The effects of Ti element on the microstructure and room-temperature mechanical properties of the as-cast FeCrMoVTi x alloys were investigated. The results show that the prepared alloys exhibited typical dendritic microstructure and the size of the microstructure became fine with increasing Ti content. The FeCrMoV alloy exhibited a single body-centered cubic structure (BCC1) and the alloys prepared with Ti element exhibited BCC1 + BCC2 mixed structure. The new BCC2 phase is considered as (Fe, Ti)-rich phase and was distributed in the dendrite region. With the increase of Ti content, the volume fraction of the BCC2 phase increased and its shape changed from a long strip to a network. For the FeCrMoV alloy, the fracture strength, plastic strain, and hardness reached as high as 2231 MPa, 28.2%, and 720 HV, respectively. The maximum hardness of 887 HV was obtained in the FeCrMoVTi alloy. However, the fracture strength, yield stress, and plastic strain of the alloys decreased continuously as Ti content increased. In the room-temperature compressive test, the alloys showed typical brittle fracture characteristics.

Adsorption of gas molecules on Cu impurities embedded monolayer MoS2: A first- principles study

NASA Astrophysics Data System (ADS)

Zhao, B.; Li, C. Y.; Liu, L. L.; Zhou, B.; Zhang, Q. K.; Chen, Z. Q.; Tang, Z.

2016-09-01

Adsorption of small gas molecules (O2, NO, NO2 and NH3) on transition-metal Cu atom embedded monolayer MoS2 was investigated by first-principles calculations based on the density-functional theory (DFT). The embedded Cu atom is strongly constrained on the sulfur vacancy of monolayer MoS2 with a high diffusion barrier. The stable adsorption geometry, charge transfer and electronic structures of these gas molecules on monolayer MoS2 embedded with transition-metal Cu atom are discussed in detail. It is found that the monolayer MoS2 with embedded Cu atom can effectively capture these gas molecules with high adsorption energy. The NH3 molecule acts as electron donor after adsorption, which is different from the other gas molecules (O2, NO, and NO2). The results suggest that MoS2-Cu system may be promising for future applications in gas molecules sensing and catalysis, which is similar to those of the transition-metal embedded graphene.

46 CFR 72.10-30 - Dead end corridors.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 3 2010-10-01 2010-10-01 false Dead end corridors. 72.10-30 Section 72.10-30 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) PASSENGER VESSELS CONSTRUCTION AND ARRANGEMENT Means of Escape § 72.10-30 Dead end corridors. (a) Dead end corridors, or the equivalent, more than 40...

46 CFR 72.10-30 - Dead end corridors.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 3 2013-10-01 2013-10-01 false Dead end corridors. 72.10-30 Section 72.10-30 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) PASSENGER VESSELS CONSTRUCTION AND ARRANGEMENT Means of Escape § 72.10-30 Dead end corridors. (a) Dead end corridors, or the equivalent, more than 40...

46 CFR 72.10-30 - Dead end corridors.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 3 2012-10-01 2012-10-01 false Dead end corridors. 72.10-30 Section 72.10-30 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) PASSENGER VESSELS CONSTRUCTION AND ARRANGEMENT Means of Escape § 72.10-30 Dead end corridors. (a) Dead end corridors, or the equivalent, more than 40...

46 CFR 72.10-30 - Dead end corridors.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 3 2011-10-01 2011-10-01 false Dead end corridors. 72.10-30 Section 72.10-30 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) PASSENGER VESSELS CONSTRUCTION AND ARRANGEMENT Means of Escape § 72.10-30 Dead end corridors. (a) Dead end corridors, or the equivalent, more than 40...

46 CFR 72.10-30 - Dead end corridors.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 3 2014-10-01 2014-10-01 false Dead end corridors. 72.10-30 Section 72.10-30 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) PASSENGER VESSELS CONSTRUCTION AND ARRANGEMENT Means of Escape § 72.10-30 Dead end corridors. (a) Dead end corridors, or the equivalent, more than 40...

Double perovskite Sr2FeMoO6-xNx (x=0.3, 1.0) oxynitrides with anionic ordering

NASA Astrophysics Data System (ADS)

Retuerto, M.; de la Calle, C.; Martínez-Lope, M. J.; Porcher, F.; Krezhov, K.; Menéndez, N.; Alonso, J. A.

2012-01-01

Two new oxynitride double perovskites of composition Sr2FeMoO6-xNx (x=0.3, 1.0) have been synthesized by annealing precursor powders obtained by citrate techniques in flowing ammonia at 750 °C and 650 °C, respectively. The polycrystalline samples have been characterized by chemical analysis, x-ray and neutron diffraction (NPD), Mössbauer spectroscopy and magnetic measurements. They exhibit a tetragonal structure with a=5.5959(1) Å, c=7.9024(2) Å, V=247.46(2) Å3 for Sr2FeMoO5.7N0.3; and a=5.6202(2) Å, c=7.9102(4) Å, V=249.85(2) Å3 for Sr2FeMoO5N; space group I4/m, Z=2. The nitridation process seems to extraordinarily improve the long-range Fe/Mo ordering, achieving 95% at moderate temperatures of 750 °C. The analysis of high resolution NPD data, based on the contrast existing between the scattering lengths of O and N, shows that both atoms are located at (O,N)2 anion substructure corresponding to the basal ab plane of the perovskite structure, whereas the O1 site is fully occupied by oxygen atoms. The evolution of the <Fe-O> and <Mo-O> distances suggests a shift towards a configuration close to Fe4+(3d4, S=2):Mo5+(4d1, S=1/2). The magnetic susceptibility shows a ferrimagnetic transition with a reduced saturation magnetization compared to Sr2FeMoO6, due to the different nature of the magnetic double exchange interactions through Fe-N-Mo-N-Fe paths in contrast to the stronger Fe-O-Mo-O-Fe interactions. Also, the effect observed by low-temperature NPD seems to reduce the ordered Fe moments and enhance the Mo moments, in agreement with the evolution of the oxidation states, thus decreasing the saturation magnetization.

30 CFR 7.72 - New technology.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false New technology. 7.72 Section 7.72 Mineral... MINING PRODUCTS TESTING BY APPLICANT OR THIRD PARTY Multiple-Shot Blasting Units § 7.72 New technology. MSHA may approve a blasting unit that incorporates technology for which the requirements of this...

30 CFR 7.72 - New technology.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 30 Mineral Resources 1 2013-07-01 2013-07-01 false New technology. 7.72 Section 7.72 Mineral... MINING PRODUCTS TESTING BY APPLICANT OR THIRD PARTY Multiple-Shot Blasting Units § 7.72 New technology. MSHA may approve a blasting unit that incorporates technology for which the requirements of this...

30 CFR 7.72 - New technology.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 1 2011-07-01 2011-07-01 false New technology. 7.72 Section 7.72 Mineral... MINING PRODUCTS TESTING BY APPLICANT OR THIRD PARTY Multiple-Shot Blasting Units § 7.72 New technology. MSHA may approve a blasting unit that incorporates technology for which the requirements of this...

30 CFR 7.72 - New technology.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 30 Mineral Resources 1 2012-07-01 2012-07-01 false New technology. 7.72 Section 7.72 Mineral... MINING PRODUCTS TESTING BY APPLICANT OR THIRD PARTY Multiple-Shot Blasting Units § 7.72 New technology. MSHA may approve a blasting unit that incorporates technology for which the requirements of this...

30 CFR 7.72 - New technology.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 1 2014-07-01 2014-07-01 false New technology. 7.72 Section 7.72 Mineral... MINING PRODUCTS TESTING BY APPLICANT OR THIRD PARTY Multiple-Shot Blasting Units § 7.72 New technology. MSHA may approve a blasting unit that incorporates technology for which the requirements of this...

Phase Evolution and Properties of Al2CrFeNiMo x High-Entropy Alloys Coatings by Laser Cladding

NASA Astrophysics Data System (ADS)

Wu, Wei; Jiang, Li; Jiang, Hui; Pan, Xuemin; Cao, Zhiqiang; Deng, Dewei; Wang, Tongmin; Li, Tingju

2015-10-01

A series of Al2CrFeNiMo x ( x = 0 to 2.0 at.%) high-entropy alloys coatings was synthesized on stainless steel by laser cladding. The effect of Mo content on the microstructures and mechanical properties of Al2CrFeNiMo x coatings was studied. The results show that the laser clad layer consists of the cladding zone, bonding zone, and heat-affected zone. The Al2CrFeNiMo x coatings are composed of two simple body-center cubic phases and the cladding zone is mainly composed of equiaxed grains. When the content of Mo reaches 2 at.%, a eutectic structure is found in the interdendritic regions. The surface microhardness of the Al2CrFeNiMo2 coating is 678 HV, which is about three times higher than that of the substrate (243 HV). Compared with stainless steel, the wear resistance of the coatings has been improved greatly. The wear mass loss of the Al2CrFeNiMo alloy is 9.8 mg, which is much less than that of the substrate (18.9 mg) and its wear scar width is the lowest among the Al2CrFeNiMo x coatings, indicating that the wear resistance of the Al2CrFeNiMo is the best.

Negative cooperativity in the nitrogenase Fe protein electron delivery cycle

DOE PAGES

Danyal, Karamatullah; Shaw, Sudipta; Page, Taylor R.; ...

2016-10-04

Mo-dependent nitrogenase catalyzes the biological reduction of atmospheric dinitrogen (N2) to two ammonia (NH3) molecules, through the action of two component proteins, the MoFe protein and the Fe protein. The catalytic MoFe protein is a symmetric dimer of αβ units, each of which contains one active site FeMo-co (FeMo-co; [7Fe-9S-Mo-C-homocitrate]) and an electron-carrier P cluster. Each half of the nitrogenase ternary complex, in which one Fe protein with two bound ATP molecules has bound to each MoFe protein αβ unit, undergoes an electron transfer (ET) cycle with ET from a Fe protein [4Fe-4S] cluster into its αβ unit followed bymore » the hydrolysis of the two ATP to two ADP and two Pi. The prevailing model holds that each αβ unit of the MoFe protein functions independently. We now report that the ET cycle exhibits negative cooperativity, with ET and ATP hydrolysis in one half of the ternary nitrogenase complex suppressing these processes in the other half. The observed ET, ATP hydrolysis, and Pi release behavior is captured in a global fit to a two-branch negative-cooperativity kinetic model. A possible mechanism for communication between the two halves of MoFe protein is suggested by normal mode analysis showing correlated and anti-correlated motions between the two nitrogenase αβ halves. EPR spectra furthermore show small differences between those of resting-state and singly-reduced MoFe protein that can be attributed to an intra-complex allosteric perturbation of the resting-state FeMo-co in one αβ unit by reduction of FeMo-co in the other. This work is supported as a part of the Biological and Electron Transfer and Catalysis (EFRC) program, an Energy Frontiers Research Center funded by the US Department of Energy (DOE), Office of Science (DE-SC0012518) to LCS, by National Institutes of Health (NIH) grants HL 63203 and GM 111097to BMH, and R15GM110671 to EA, and by the Division of Chemical Sciences, Geosciences, and Bio-Sciences, DOE to SR. The

Negative cooperativity in the nitrogenase Fe protein electron delivery cycle

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

Danyal, Karamatullah; Shaw, Sudipta; Page, Taylor R.

Mo-dependent nitrogenase catalyzes the biological reduction of atmospheric dinitrogen (N 2) to two ammonia (NH 3) molecules, through the action of two component proteins, the MoFe protein and the Fe protein. The catalytic MoFe protein is a symmetric dimer of αβ units, each of which contains one active site FeMo-co (FeMo-co; [7Fe-9S-Mo-C-homocitrate]) and an electron-carrier P cluster. Each half of the nitrogenase ternary complex, in which one Fe protein with two bound ATP molecules has bound to each MoFe protein αβ unit, undergoes an electron transfer (ET) cycle with ET from a Fe protein [4Fe-4S] cluster into its αβ unitmore » followed by the hydrolysis of the two ATP to two ADP and two Pi. The prevailing model holds that each αβ unit of the MoFe protein functions independently. We now report that the ET cycle exhibits negative cooperativity, with ET and ATP hydrolysis in one half of the ternary nitrogenase complex suppressing these processes in the other half. The observed ET, ATP hydrolysis, and Pi release behavior is captured in a global fit to a two-branch negative-cooperativity kinetic model. A possible mechanism for communication between the two halves of MoFe protein is suggested by normal mode analysis showing correlated and anti-correlated motions between the two nitrogenase αβ halves. EPR spectra furthermore show small differences between those of resting-state and singly-reduced MoFe protein that can be attributed to an intra-complex allosteric perturbation of the resting-state FeMo-co in one αβ unit by reduction of FeMo-co in the other. This work is supported as a part of the Biological and Electron Transfer and Catalysis (EFRC) program, an Energy Frontiers Research Center funded by the US Department of Energy (DOE), Office of Science (DE-SC0012518) to LCS, by National Institutes of Health (NIH) grants HL 63203 and GM 111097to BMH, and R15GM110671 to EA, and by the Division of Chemical Sciences, Geosciences, and Bio-Sciences, DOE to SR

Effects of Electron Beam Irradiation and Thiol Molecule Treatment on the Properties of MoS2 Field Effect Transistors

NASA Astrophysics Data System (ADS)

Choi, Barbara Yuri; Cho, Kyungjune; Pak, Jinsu; Kim, Tae-Young; Kim, Jae-Keun; Shin, Jiwon; Seo, Junseok; Chung, Seungjun; Lee, Takhee

2018-05-01

We investigated the effects of the structural defects intentionally created by electron-beam irradiation with an energy of 30 keV on the electrical properties of monolayer MoS2 field effect transistors (FETs). We observed that the created defects by electron beam irradiation on the MoS2 surface working as trap sites deteriorated the carrier mobility and carrier concentration with increasing the subthreshold swing value and shifting the threshold voltage in MoS2 FETs. The electrical properties of electron-beam irradiated MoS2 FETs were slightly improved by treating the devices with thiol-terminated molecules which presumably passivated the structural defects of MoS2. The results of this study may enhance the understanding of the electrical properties of MoS2 FETs in terms of creating and passivating defect sites.

15 CFR 30.72 - Civil penalty procedures.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 15 Commerce and Foreign Trade 1 2011-01-01 2011-01-01 false Civil penalty procedures. 30.72... CENSUS, DEPARTMENT OF COMMERCE FOREIGN TRADE REGULATIONS Penalties § 30.72 Civil penalty procedures. (a) General. Whenever a civil penalty is sought for a violation of this part, the charged party is entitled to...

New double molybdate Na9Fe(MoO4)6: Synthesis, structure, properties

NASA Astrophysics Data System (ADS)

Savina, Aleksandra A.; Solodovnikov, Sergey F.; Basovich, Olga M.; Solodovnikova, Zoya A.; Belov, Dmitry A.; Pokholok, Konstantin V.; Gudkova, Irina A.; Stefanovich, Sergey Yu.; Lazoryak, Bogdan I.; Khaikina, Elena G.

2013-09-01

A new double molybdate Na9Fe(MoO4)6 was synthesized using solid state reactions and studied with X-ray powder diffraction, second harmonic generation (SHG) technique, differential scanning calorimetry, X-ray fluorescence analysis, Mössbauer and dielectric impedance spectroscopy. Single crystals of Na9Fe(MoO4)6 were obtained and its structure was solved (the space group R3¯, a=14.8264(2), c=19.2402(3) Å, V=3662.79(9) Å3, Z=6, R=0.0132). The structure is related to that of sodium ion conductor II-Na3Fe2(AsO4)3. The basic structure units are polyhedral clusters composed of central FeО6 octahedron sharing edges with three Na(1)О6 octahedra. The clusters share common vertices with bridging МоО4 tetrahedra to form an open 3D framework where the cavities are occupied by Na(2) and Na(3) atoms. The compound melts incongruently at 904.7±0.2 K. Arrhenius type temperature dependence of electric conductivity σ has been registered in solid state (σ=6.8×10-2 S сm-1 at 800 K), thus allowing considering Na9Fe(MoO4)6 as a new sodium ion conductor.

Autonomous Filling of Grain-Boundary Cavities during Creep Loading in Fe-Mo Alloys

NASA Astrophysics Data System (ADS)

Zhang, S.; Fang, H.; Gramsma, M. E.; Kwakernaak, C.; Sloof, W. G.; Tichelaar, F. D.; Kuzmina, M.; Herbig, M.; Raabe, D.; Brück, E.; van der Zwaag, S.; van Dijk, N. H.

2016-10-01

We have investigated the autonomous repair of creep damage by site-selective precipitation in a binary Fe-Mo alloy (6.2 wt pct Mo) during constant-stress creep tests at temperatures of 813 K, 823 K, and 838 K (540 °C, 550 °C, and 565 °C). Scanning electron microscopy studies on the morphology of the creep-failed samples reveal irregularly formed deposits that show a close spatial correlation with the creep cavities, indicating the filling of creep cavities at grain boundaries by precipitation of the Fe2Mo Laves phase. Complementary transmission electron microscopy and atom probe tomography have been used to characterize the precipitation mechanism and the segregation at grain boundaries in detail.

Influence of lanthanides on spin-relaxation and spin-structure in a family of Fe 7Ln 4 single molecule magnets

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

Prodius, Denis; Mereacre, Valeriu; Singh, Prashant

A family of isostructural undecanuclear 3d–4f coordination clusters of formula [Fe III 7Ln III 4O 4(OH) 3(tea) 2(Htea) 3(Piv) 7(H 2O) 2(NO 3) 3], where Ln = Y (1), Gd (2), Tb (3), Dy (4); PivH ≡ pivalic acid and H 3tea ≡ triethanolamine, was synthesised in this paper. The central Fe7 core of the coordination cluster can be described in terms of two {Fe 4O 2} butterfly motifs sharing a common body Fe atom. The two Fe 4 mean-planes subtend a dihedral angle of ca. 72°. The Tb (3) and Dy (4) compounds show Single Molecule Magnet (SMM) behaviourmore » as confirmed by ac-susceptibility and μ-SQUID measurements. Furthermore, 57Fe Mössbauer spectra of 1–4 confirm the presence of high-spin Fe III sites. The spectra of all complexes in the high temperature range (30–300 K) show broad overlapping doublets which were assigned to the body and wing-tip pairs of metal ions within the Fe 7 core. The low temperature Mössbauer spectra show dependence on the nature of the rare-earth metal as a result of its interaction with the iron sites. Finally, we observed a transition from fast (2), to intermediate (1) and very slow (frozen) (3, 4) spin fluctuation phenomena in these compounds.« less

Influence of lanthanides on spin-relaxation and spin-structure in a family of Fe 7Ln 4 single molecule magnets

DOE PAGES

Prodius, Denis; Mereacre, Valeriu; Singh, Prashant; ...

2018-03-01

A family of isostructural undecanuclear 3d–4f coordination clusters of formula [Fe III 7Ln III 4O 4(OH) 3(tea) 2(Htea) 3(Piv) 7(H 2O) 2(NO 3) 3], where Ln = Y (1), Gd (2), Tb (3), Dy (4); PivH ≡ pivalic acid and H 3tea ≡ triethanolamine, was synthesised in this paper. The central Fe7 core of the coordination cluster can be described in terms of two {Fe 4O 2} butterfly motifs sharing a common body Fe atom. The two Fe 4 mean-planes subtend a dihedral angle of ca. 72°. The Tb (3) and Dy (4) compounds show Single Molecule Magnet (SMM) behaviourmore » as confirmed by ac-susceptibility and μ-SQUID measurements. Furthermore, 57Fe Mössbauer spectra of 1–4 confirm the presence of high-spin Fe III sites. The spectra of all complexes in the high temperature range (30–300 K) show broad overlapping doublets which were assigned to the body and wing-tip pairs of metal ions within the Fe 7 core. The low temperature Mössbauer spectra show dependence on the nature of the rare-earth metal as a result of its interaction with the iron sites. Finally, we observed a transition from fast (2), to intermediate (1) and very slow (frozen) (3, 4) spin fluctuation phenomena in these compounds.« less

Electronic structure of Fe- vs. Ru-based dye molecules

NASA Astrophysics Data System (ADS)

Johnson, Phillip S.; Cook, Peter L.; Zegkinoglou, Ioannis; García-Lastra, J. M.; Rubio, Angel; Ruther, Rose E.; Hamers, Robert J.; Himpsel, F. J.

2013-01-01

In order to explore whether Ru can be replaced by inexpensive Fe in dye molecules for solar cells, the differences in the electronic structure of Fe- and Ru-based dyes are investigated by X-ray absorption spectroscopy and first-principles calculations. Molecules with the metal in a sixfold, octahedral N cage, such as tris(bipyridines) and tris(phenanthrolines), exhibit a systematic downward shift of the N 1s-to-π* transition when Ru is replaced by Fe. This shift is explained by an extra transfer of negative charge from the metal to the N ligands in the case of Fe, which reduces the binding energy of the N 1s core level. The C 1s-to-π* transitions show the opposite trend, with an increase in the transition energy when replacing Ru by Fe. Molecules with the metal in a fourfold, planar N cage (porphyrins) exhibit a more complex behavior due to a subtle competition between the crystal field, axial ligands, and the 2+ vs. 3+ oxidation states.

30 CFR 72.520 - Diesel equipment inventory.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Diesel equipment inventory. 72.520 Section 72... HEALTH HEALTH STANDARDS FOR COAL MINES Diesel Particulate Matter-Underground Areas of Underground Coal Mines § 72.520 Diesel equipment inventory. (a) The operator of each mine that utilizes diesel equipment...

30 CFR 72.520 - Diesel equipment inventory.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Diesel equipment inventory. 72.520 Section 72... HEALTH HEALTH STANDARDS FOR COAL MINES Diesel Particulate Matter-Underground Areas of Underground Coal Mines § 72.520 Diesel equipment inventory. (a) The operator of each mine that utilizes diesel equipment...

30 CFR 72.520 - Diesel equipment inventory.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Diesel equipment inventory. 72.520 Section 72... HEALTH HEALTH STANDARDS FOR COAL MINES Diesel Particulate Matter-Underground Areas of Underground Coal Mines § 72.520 Diesel equipment inventory. (a) The operator of each mine that utilizes diesel equipment...

30 CFR 72.520 - Diesel equipment inventory.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Diesel equipment inventory. 72.520 Section 72... HEALTH HEALTH STANDARDS FOR COAL MINES Diesel Particulate Matter-Underground Areas of Underground Coal Mines § 72.520 Diesel equipment inventory. (a) The operator of each mine that utilizes diesel equipment...

30 CFR 72.520 - Diesel equipment inventory.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Diesel equipment inventory. 72.520 Section 72... HEALTH HEALTH STANDARDS FOR COAL MINES Diesel Particulate Matter-Underground Areas of Underground Coal Mines § 72.520 Diesel equipment inventory. (a) The operator of each mine that utilizes diesel equipment...

Optimizing Heat Treatment Process of Fe-13Cr-3Mo-3Ni Martensitic Stainless of Steel

NASA Astrophysics Data System (ADS)

Anwar, M. S.; Prifiharni, S.; Mabruri, E.

2017-05-01

The Fe-13Cr-3Mo-3Ni stainless steels are modified into martensitic stainless steels for steam turbine blades application. The working temperature of steam turbine was around 600 - 700 °C. The improvement properties of turbine blade material is necessary to maintain steam turbine work. The previous research revealed that it has corrosion resistance of Fe-13Cr-3Mo-3Ni which is better than 13Cr stainless steels in the chloride environment. In this work, the effect of heat treatment on microstructure and hardness of Fe-13Cr-3Mo-3Ni stainless steels has been studied. The steel was prepared by induction melting followed by hot forging. The steels were austenitized at 1000, 1050, and 1100 °C for 1 hour and were tempered at 600, 650, and 700 °C for 1 hour. The steels were then subjected to metallographic observation and hardness test of Rockwell C. The optimal heat treatment of Fe-13Cr-3Mo-3Ni was carried out austenitized in 1050 °C and tempered in 600 - 700 °C.

Stabilities of thiomolybdate complexes of iron; implications for retention of essential trace elements (Fe, Cu, Mo) in sulfidic waters.

PubMed

Helz, George R; Erickson, Britt E; Vorlicek, Trent P

2014-06-01

In aquatic ecosystems, availabilities of Fe, Mo and Cu potentially limit rates of critical biological processes, including nitrogen fixation, nitrate assimilation and N2O decomposition. During long periods in Earth's history when large parts of the ocean were sulfidic, what prevented these elements' quantitative loss from marine habitats as insoluble sulfide phases? They must have been retained by formation of soluble complexes. Identities of the key ligands are poorly known but probably include thioanions. Here, the first determinations of stability constants for Fe(2+)-[MoS4](2-) complexes in aqueous solution are reported based on measurements of pyrrhotite (hexagonal FeS) solubility under mildly alkaline conditions. Two linear complexes, [FeO(OH)MoS4](3-) and [(Fe2S2)(MoS4)2](4-), best explain the observed solubility variations. Complexes that would be consistent with cuboid cluster structures were less successful, implying that such clusters probably are minor or absent in aqueous solution under the conditions studied. The new data, together with prior data on stabilities of Cu(+)-[MoS4](2-) complexes, are used to explore computationally how competition of Fe(2+) and Cu(+) for [MoS4](2-), as well as competition of [MoS4](2-) and HS(-) for both metals would be resolved in solutions representative of sulfidic natural waters. Thiomolybdate complexes will be most important at sulfide concentrations near the [MoO4](2-)-[MoS4](2-) equivalence point. At lower sulfide concentrations, thiomolybdates are insufficiently stable to be competitive ligands in natural waters and at higher sulfide concentrations HS(-) ligands out-compete thiomolybdates.

Influence of inserted Mo layer on the thermal stability of perpendicularly magnetized Ta/Mo/Co{sub 20}Fe{sub 60}B{sub 20}/MgO/Ta films

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

Li, Minghua, E-mail: mhli@ustb.edu.cn; Department of Electrical Engineering, University of California, Los Angeles, California 90095; Lu, Jinhui

2016-04-15

We studied the thermal stability of perpendicular magnetic anisotropy (PMA) in Ta/Mo/CoFeB/MgO/Ta films with and without inserted Mo layers. In the absence of a Mo layer, the films show PMA at annealing temperatures below 300 °C. On the other hand, the insertion of a Mo layer preserves PMA at annealing temperatures of up to 500 °C; however, a higher annealing temperature leads to the collapse of PMA. X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM) were used to study the microstructure of the films to understand the deterioration of PMA. The XPS results show that the segregation ofmore » Ta is partly suppressed by inserting a Mo layer. Once inserted, Mo does not remain at the interface of Ta and CoFeB but migrates to the surface of the films. The HRTEM results show that the crystallization of the MgO (001) texture is improved owing to the higher annealing temperature of the Mo inserted sample. A smooth and clear CoFeB/MgO interface is evident. The inserted Mo layer not only helps to obtain sharper and smoother interfaces but also contributes to the crystallization after the higher annealing temperature of films.« less

Fe-MoS4: An Effective and Stable LDH-Based Adsorbent for Selective Removal of Heavy Metals.

PubMed

Jawad, Ali; Liao, Zhuwei; Zhou, Zhihua; Khan, Aimal; Wang, Ting; Ifthikar, Jerosha; Shahzad, Ajmal; Chen, Zhulei; Chen, Zhuqi

2017-08-30

It has always been a serious challenge to design efficient, selective, and stable absorbents for heavy-metal removal. Herein, we design layered double hydroxide (LDH)-based Fe-MoS 4 , a highly efficient adsorbent, for selective removal of heavy metals. We initially synthesized FeMgAl-LDH and then enriched its protective layers with MoS 4 2- anions as efficient binding sites for heavy metals. Various characterization tools, such as X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, scanning electron microscopy, energy-dispersive X-ray, X-ray photoelectron spectroscopy (XPS), CHN analysis, and inductively coupled plasma analysis, were applied to confirm structural and compositional changes during the synthesis of Fe-MoS 4 as final product. The prepared Fe-MoS 4 offered excellent attraction for heavy metals, such as Hg 2+ , Ag + , Pb 2+ , and Cu 2+ , and displayed selectivity in the order Hg 2+ ∼ Ag + > Pb 2+ > Cu 2+ > Cr 6+ > As 3+ > Ni 2+ ∼ Zn 2+ ∼ Co 2+ . The immense capacities of Hg 2+ , Ag + , and Pb 2+ (583, 565, and 346 mg/g, respectively), high distribution coefficient (K d ∼ 10 7 -10 8 ), and fast kinetics place Fe-MoS 4 on the top of materials list known for removal of such metals. The sorption kinetics and isothermal studies conducted on Hg 2+ , Ag + , Pb 2+ , and Cu 2+ suit well pseudo-second-order kinetics and Langmuir model, suggesting monolayer chemisorption mechanism through M-S linkages. XRD and FTIR studies suggested that adsorbed metals could result as coordinated complexes in LDH interlayer region. More interestingly, LDH structure offers protective space for MoS 4 2- anions to avoid oxidation under ambient environments, as confirmed by XPS studies. These features provide Fe-MoS 4 with enormous capacity, good reusability, and excellent selectivity even in the presence of huge concentration of common cations.

Multiferroicity in the generic easy-plane triangular lattice antiferromagnet RbFe(MoO4)2

NASA Astrophysics Data System (ADS)

White, J. S.; Niedermayer, Ch.; Gasparovic, G.; Broholm, C.; Park, J. M. S.; Shapiro, A. Ya.; Demianets, L. A.; Kenzelmann, M.

2013-08-01

RbFe(MoO4)2 is a quasi-two-dimensional (quasi-2D) triangular lattice antiferromagnet (TLA) that displays a zero-field magnetically driven multiferroic phase with a chiral spin structure. By inelastic neutron scattering, we determine quantitatively the spin Hamiltonian. We show that the easy-plane anisotropy is nearly 1/3 of the dominant spin exchange, making RbFe(MoO4)2 an excellent system for studying the physics of the model 2D easy-plane TLA. Our measurements demonstrate magnetic-field-induced fluctuations in this material to stabilize the generic finite-field phases of the 2D XY TLA. We further explain how Dzyaloshinskii-Moriya interactions can generate ferroelectricity only in the zero-field phase. Our conclusion is that multiferroicity in RbFe(MoO4)2, and its absence at high fields, results from the generic properties of the 2D XY TLA.

Ultrasmall Fe2O3 nanoparticles/MoS2 nanosheets composite as high-performance anode material for lithium ion batteries.

PubMed

Qu, Bin; Sun, Yue; Liu, Lianlian; Li, Chunyan; Yu, Changjian; Zhang, Xitian; Chen, Yujin

2017-02-20

Coupling ultrasmall Fe 2 O 3 particles (~4.0 nm) with the MoS 2 nanosheets is achieved by a facile method for high-performance anode material for Li-ion battery. MoS 2 nanosheets in the composite can serve as scaffolds, efficiently buffering the large volume change of Fe 2 O 3 during charge/discharge process, whereas the ultrasmall Fe 2 O 3 nanoparticles mainly provide the specific capacity. Due to bigger surface area and larger pore volume as well as strong coupling between Fe 2 O 3 particles and MoS 2 nanosheets, the composite exhibits superior electrochemical properties to MoS 2 , Fe 2 O 3 and the physical mixture Fe 2 O 3 +MoS 2 . Typically, after 140 cycles the reversible capacity of the composite does not decay, but increases from 829 mA h g -1 to 864 mA h g -1 at a high current density of 2 A g -1 . Thus, the present facile strategy could open a way for development of cost-efficient anode material with high-performance for large-scale energy conversion and storage systems.

30 CFR 72.510 - Miner health training.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Miner health training. 72.510 Section 72.510 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR COAL MINE SAFETY AND HEALTH HEALTH STANDARDS FOR COAL MINES Diesel Particulate Matter-Underground Areas of Underground Coal Mines...

30 CFR 72.510 - Miner health training.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Miner health training. 72.510 Section 72.510 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR COAL MINE SAFETY AND HEALTH HEALTH STANDARDS FOR COAL MINES Diesel Particulate Matter-Underground Areas of Underground Coal Mines...

30 CFR 72.510 - Miner health training.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Miner health training. 72.510 Section 72.510 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR COAL MINE SAFETY AND HEALTH HEALTH STANDARDS FOR COAL MINES Diesel Particulate Matter-Underground Areas of Underground Coal Mines...

30 CFR 72.510 - Miner health training.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Miner health training. 72.510 Section 72.510 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR COAL MINE SAFETY AND HEALTH HEALTH STANDARDS FOR COAL MINES Diesel Particulate Matter-Underground Areas of Underground Coal Mines...

30 CFR 72.510 - Miner health training.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Miner health training. 72.510 Section 72.510 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR COAL MINE SAFETY AND HEALTH HEALTH STANDARDS FOR COAL MINES Diesel Particulate Matter-Underground Areas of Underground Coal Mines...

Photochemical synthesis of the Fe0/C3N4/MoS2 heterostructure as a highly active and reusable photocatalyst

NASA Astrophysics Data System (ADS)

Wang, Xiu; Zhou, Zhiming; Liang, Zhiyu; Zhuang, Zanyong; Yu, Yan

2017-11-01

The Fe0/C3N4/MoS2 heterostructure was fabricated through photochemical synthesis that was free of NaBH4. Specifically, the g-C3N4/MoS2 (GCNM) composite was used as the substrate. Visible light excited the electrons from the valence band of the GCNM in the substrate, and the excited electrons reduced the Fe2+ ions in the solution nearby GCNM to Fe0 and then created the Fe0/C3N4/MoS2 heterostructure. Small Fe0 (<9 nm) dots well dispersed on the GCNM surface were obtained, because the diffusion of the Fe ions in the solution and the diffusion of the electrons on the GCNM substrate restricted the growth of Fe0 nanoparticles. The smaller size of Fe0 provided a larger number of active metal centers and improved the carrier separation efficiency. As a result, the Fe0/C3N4/MoS2 heterostructure exhibited superior catalytic properties in the redox reactions of rhodamine B, Cr(VI), Pb(II), and Cd(II). It could also be readily recycled without severe loss of catalytic performance.

Mo & Fe Influences on Nitrate Assimilation in Lake Ontario and the St Lawrence River

NASA Astrophysics Data System (ADS)

Twiss, M. R.; Salk, K.; Avolio, L. N.; Chappaz, A.; Ostrom, N. E.

2013-12-01

Lake Ontario has undergone a steady increase in nitrate since the early 1970s, a phenomenon also occurring in other large lakes. Possible causes of this increase include rising urban and agricultural runoff, atmospheric deposition, less demand for N due to effective point source P control, and trace metal-N co-limitation as observed in Lake Erie. Despite the abundance of nitrate in Lake Ontario, heterocystous cyanobacteria have been detected here setting up the paradoxical situation wherein some cyanobacteria are investing in the more costly diazotrophy whilst surrounded by a form of N that requires less energy and metal quota to assimilate. Mo and Fe are involved in reductive nitrate assimilation making it possible that reductive nitrate assimilation in Lake Ontario is limited in phytoplankton by low trace metal bioavailability. To test this hypothesis, 1-d enrcihment experiments were conducted using trace metal clean techniques in June 2013 at two coastal sites in Lake Ontario, and 4-d enrichment experiments were conducted in July 2013 on main channel waters of the St. Lawrence River, the outflow of Lake Ontario. Water was sampled from the metalimnion of Lake Ontario and from surface water of the main channel of the river. Water was enriched with the the following treatments in triplicate: control, 100 nM KH2PO4, 50 nM FeCl3, 50 nM Na2MoO4, and a mix of P, Fe & Mo. Experiments in the river showed significant effects due to P (increase in Chl-a, NO3 and SiO2 drawdown, changes in phytoplankton community, increase in photosynthetic efficiency [Fv/Fm]) but less impact of trace metals relative to control, presumably due to greater ambient trace metal bioavailability. As measured using FluoroProbe, the phytoplankton community changed very little (over 1 d) in lake waters; there was no significant change in total chl-a. However, as in the river, Fv/Fm revealed significant metal and P effects with the P, Fe & Mo mix being significantly greater than control (Fig. 1; we

Metal trafficking for nitrogen fixation: NifQ donates molybdenum to NifEN/NifH for the biosynthesis of the nitrogenase FeMo-cofactor

PubMed Central

Hernandez, Jose A.; Curatti, Leonardo; Aznar, Constantino P.; Perova, Zinaida; Britt, R. David; Rubio, Luis M.

2008-01-01

The molybdenum nitrogenase, present in a diverse group of bacteria and archea, is the major contributor to biological nitrogen fixation. The nitrogenase active site contains an iron–molybdenum cofactor (FeMo-co) composed of 7Fe, 9S, 1Mo, one unidentified light atom, and homocitrate. The nifQ gene was known to be involved in the incorporation of molybdenum into nitrogenase. Here we show direct biochemical evidence for the role of NifQ in FeMo-co biosynthesis. As-isolated NifQ was found to carry a molybdenum–iron–sulfur cluster that serves as a specific molybdenum donor for FeMo-co biosynthesis. Purified NifQ supported in vitro FeMo-co synthesis in the absence of an additional molybdenum source. The mobilization of molybdenum from NifQ required the simultaneous participation of NifH and NifEN in the in vitro FeMo-co synthesis assay, suggesting that NifQ would be the physiological molybdenum donor to a hypothetical NifEN/NifH complex. PMID:18697927

Microstructure and mechanical behavior of Zr substrates coated with FeCrAl and Mo by cold-spraying

NASA Astrophysics Data System (ADS)

Park, Dong Jun; Kim, Hyun Gil; Jung, Yang Il; Park, Jung Hwan; Yang, Jae Ho; Koo, Yang Hyun

2018-06-01

FeCrAl and Mo layers were cold-sprayed onto a Zr surface, with the Mo layer introduced between the FeCrAl coating and the Zr matrix preventing high-temperature interdiffusion. Microstructural characterization of the first-deposited Mo layer and the Zr matrix immediately below the Mo/Zr interface was performed using transmission electron microscopy, and near-interface elemental distributions were obtained using energy-dispersive X-ray spectroscopy. The deformation of the coated Mo powder induced the formation of microbands and mechanically interlocked nanoscale structures. The mechanical behavior of Zr with a coating layer was compared with those characteristic of conventional Zr samples. The coated sample showed smaller strength reduction in the test conducted at elevated temperature. The hardness and fracture morphology of the Zr matrix near the interface region were investigated to determine the effect of impacting Mo particles on the matrix microstructure. The enhanced hardness and cleavage fracture morphology of the Zr matrix immediately below the Mo/Zr interface indicated the occurrence of localized deformation owing to Mo particle impact.

High Efficient Photo-Fenton Catalyst of α-Fe2O3/MoS2 Hierarchical Nanoheterostructures: Reutilization for Supercapacitors

NASA Astrophysics Data System (ADS)

Yang, Xijia; Sun, Haiming; Zhang, Lishu; Zhao, Lijun; Lian, Jianshe; Jiang, Qing

2016-08-01

A novel three-dimensional (3D) α-Fe2O3/MoS2 hierarchical nanoheterostructure is effectively synthesized via a facile hydrothermal method. The zero-dimensional (0D) Fe2O3 nanoparticles guide the growth of two-dimensional (2D) MoS2 nanosheets and formed 3D flower-like structures, while MoS2 facilitates the good dispersion of porous Fe2O3 with abundant oxygen vacancies. This charming 3D-structure with perfect match of non-equal dimension exhibits high recyclable photo-Fenton catalytic activity for Methyl orange pollutant and nice specific capacity in reusing as supercapacitor after catalysis. The synergistic effect between Fe2O3 and MoS2, the intermediate nanointerfaces, the 3D porous structures, and the abundant oxygen vacancies both contribute to highly active catalysis, nice electrochemical performance and stable cycling. This strategy is simple, cheap, and feasible for maximizing the value of the materials, as well as eliminating the secondary pollution.

High Efficient Photo-Fenton Catalyst of α-Fe2O3/MoS2 Hierarchical Nanoheterostructures: Reutilization for Supercapacitors.

PubMed

Yang, Xijia; Sun, Haiming; Zhang, Lishu; Zhao, Lijun; Lian, Jianshe; Jiang, Qing

2016-08-16

A novel three-dimensional (3D) α-Fe2O3/MoS2 hierarchical nanoheterostructure is effectively synthesized via a facile hydrothermal method. The zero-dimensional (0D) Fe2O3 nanoparticles guide the growth of two-dimensional (2D) MoS2 nanosheets and formed 3D flower-like structures, while MoS2 facilitates the good dispersion of porous Fe2O3 with abundant oxygen vacancies. This charming 3D-structure with perfect match of non-equal dimension exhibits high recyclable photo-Fenton catalytic activity for Methyl orange pollutant and nice specific capacity in reusing as supercapacitor after catalysis. The synergistic effect between Fe2O3 and MoS2, the intermediate nanointerfaces, the 3D porous structures, and the abundant oxygen vacancies both contribute to highly active catalysis, nice electrochemical performance and stable cycling. This strategy is simple, cheap, and feasible for maximizing the value of the materials, as well as eliminating the secondary pollution.

Large low-field magnetoresistance in Fe3O4/molecule nanoparticles at room temperature

NASA Astrophysics Data System (ADS)

Yue, F. J.; Wang, S.; Lin, L.; Zhang, F. M.; Li, C. H.; Zuo, J. L.; Du, Y. W.; Wu, D.

2011-01-01

Acetic acid molecule-coated Fe3O4 nanoparticles, 450-650 nm in size, have been synthesized using a chemical solvothermal reduction method. Fourier transform infrared spectroscopy measurements confirm one monolayer acetic acid molecules chemically bond to the Fe3O4 nanoparticles. The low-field magnetoresistance (LFMR) of more than -10% at room temperature and -23% at 140 K is achieved with saturation field of less than 2 kOe. In comparison, the resistivity of cold-pressed bare Fe3O4 nanoparticles is six orders of magnitudes smaller than that of Fe3O4/molecule nanoparticles, and the LFMR ratio is one order of magnitude smaller. Our results indicate that the large LFMR in Fe3O4/molecule nanoparticles is associated with spin-polarized electrons tunnelling through molecules instead of direct nanoparticle contacts. These results suggest that magnetic oxide-molecule hybrid materials are an alternative type of materials to develop spin-based devices by a simple low-cost approach.

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

NASA Astrophysics Data System (ADS)

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

2018-03-01

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

Theoretical and experimental studies of the electronic structure of the Mo3(Micro3-0)(Micro3-OR)(Micro-OR)3(OR)6 type of triangulo metal atom cluster compound

NASA Astrophysics Data System (ADS)

Chisholm, M. H.; Cotton, F. A.; Fang, A.; Kober, E. C.

1983-09-01

The electronic structure of a Mo3(Mu sub 3-0) (Mu sub 3-OR) (Mu sub 2-OR)3(OR)6 molecule with R = H, and C3v symmetry, which serves as a model for real molecules in which R = H CH2C(CH)3 or CH(CH3)2 has been calculated by the molecular orbital method of Hall and Fenske. The calculations have been performed not only on the entire molecule, but on the Mo3(12+), Mo3O(OH)(9+) and Mo3O(OH)4(6+) fragments and the metal-metal bonding tracked through these successive stages by the ''clusters in molecules' formalism. In the full molecule, the HOMO is an e orbital that carries most of the e-type M-M bonding, while the a1-type is carried by two MO's, one of which is quite stable. The LUMO is also an e type orbital and the HOMO-LUMO gap is small (ca. 1.5 eV). It is predicted that the Mo3O(OR)10 molecules of this type will have readily accessible redox chemistry in which both oxidation and reduction steps might be slowed or irreversible judging by the character of the HOMO and LUMO of the Mo3O(OR)10 molecule. Experimental observations on Mo3O(ONe)10, Ne = CH2C(CH3)3, are in harmony with this. In addition, the absorption spectrum of Mo3O(ONe)10 has been observed and an assignment based on the calculations in proposed.

The influence of high pressure to crystalline and magnetic structure of Ba 2 FeMoO 6

NASA Astrophysics Data System (ADS)

Turchenko, V. A.; Kalanda, N. A.; Kovalev, L. V.; Yarmolich, M. V.; Petrov, A. V.; Lukin, Ye V.; Doroshkevich, A. S.; Balasoiu, M.; Lupu, N.; Savenko, B. N.

2018-03-01

The behavior of the crystalline and magnetic structure of Ba 2 FeMoO 6 compound in a wide pressure range from 0 to 4.7 GPa was studied. The crystal structure of ceramic sample was described in the framework of SG I4/mmm (No 139) and contains less 10% of anti-site defects. The change of tetragonal structure (I4/mmm) was not observed in all measured pressure range. It was shown multidirectional influence of ambient pressure onto the average interionic distances of metal-ligand in oxygen octahedrons of FeO 6 and MoO 6. For tetragonal structure of Ba 2 FeMoO 6 were determined coefficients of the linear and all-round compressibility. The influence of ambient pressure on the value of magnetic moment of iron sublattice was shown.

Microstructure and Mechanical Properties of Highly Alloyed FeCrMoVC Steel Fabricated by Spark Plasma Sintering

NASA Astrophysics Data System (ADS)

Oh, Seung-Jin; Jun, Joong-Hwan; Lee, Min-Ha; Shon, In-Jin; Lee, Seok-Jae

2018-05-01

In this study, we successfully fabricated highly alloyed FeCrMoVC specimens within 2 min by using the spark plasma sintering (SPS) method. The densities of the sintered specimens were almost identical to their theoretical values. Fine (Mo, V)-rich carbides with lamellar structure were precipitated along the grain boundaries of the as-sintered specimen, whereas relatively large carbides were formed additionally in the transgranular region during the tempering treatment. Compared with the specimen produced by a conventional casting method, the FeCrMoVC specimens from SPS showed smaller grain size with finer carbides and higher hardness values.

Contact-Engineered Electrical Properties of MoS2 Field-Effect Transistors via Selectively Deposited Thiol-Molecules.

PubMed

Cho, Kyungjune; Pak, Jinsu; Kim, Jae-Keun; Kang, Keehoon; Kim, Tae-Young; Shin, Jiwon; Choi, Barbara Yuri; Chung, Seungjun; Lee, Takhee

2018-05-01

Although 2D molybdenum disulfide (MoS 2 ) has gained much attention due to its unique electrical and optical properties, the limited electrical contact to 2D semiconductors still impedes the realization of high-performance 2D MoS 2 -based devices. In this regard, many studies have been conducted to improve the carrier-injection properties by inserting functional paths, such as graphene or hexagonal boron nitride, between the electrodes and 2D semiconductors. The reported strategies, however, require relatively time-consuming and low-yield transfer processes on sub-micrometer MoS 2 flakes. Here, a simple contact-engineering method is suggested, introducing chemically adsorbed thiol-molecules as thin tunneling barriers between the metal electrodes and MoS 2 channels. The selectively deposited thiol-molecules via the vapor-deposition process provide additional tunneling paths at the contact regions, improving the carrier-injection properties with lower activation energies in MoS 2 field-effect transistors. Additionally, by inserting thiol-molecules at the only one contact region, asymmetric carrier-injection is feasible depending on the temperature and gate bias. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

[MoS4]2- Cluster Bridges in Co-Fe Layered Double Hydroxides for Mercury Uptake from S-Hg Mixed Flue Gas.

PubMed

Xu, Haomiao; Yuan, Yong; Liao, Yong; Xie, Jiangkun; Qu, Zan; Shangguan, Wenfeng; Yan, Naiqiang

2017-09-05

[MoS 4 ] 2- clusters were bridged between CoFe layered double hydroxide (LDH) layers using the ion-exchange method. [MoS 4 ] 2- /CoFe-LDH showed excellent Hg 0 removal performance under low and high concentrations of SO 2 , highlighting the potential for such material in S-Hg mixed flue gas purification. The maximum mercury capacity was as high as 16.39 mg/g. The structure and physical-chemical properties of [MoS 4 ] 2- /CoFe-LDH composites were characterized with FT-IR, XRD, TEM&SEM, XPS, and H 2 -TPR. [MoS 4 ] 2- clusters intercalated into the CoFe-LDH layered sheets; then, we enlarged the layer-to-layer spacing (from 0.622 to 0.880 nm) and enlarged the surface area (from 41.4 m 2 /g to 112.1 m 2 /g) of the composite. During the adsorption process, the interlayer [MoS 4 ] 2- cluster was the primary active site for mercury uptake. The adsorbed mercury existed as HgS on the material surface. The absence of active oxygen results in a composite with high sulfur resistance. Due to its high efficiency and SO 2 resistance, [MoS 4 ] 2- /CoFe-LDH is a promising adsorbent for mercury uptake from S-Hg mixed flue gas.

Synthèse et étude structrale de lyonsite-type (Na0,4,Li0,6)(Fe,Li2)(MoO4)3

PubMed Central

Souilem, Amira; Zid, Mohamed Faouzi; Driss, Ahmed

2015-01-01

The new compound (Na0.4,Li0.6)(Fe,Li2)(MoO4)3 was synthesized by cooling from the melt. Its anionic framework is built up from two distinct MO6 octa­hedra, each containing disordered Li+ and Fe3+ ions in 0.6:0.4 and 0.7:0.3 ratios, and two MoO4 tetra­hedra, which link by vertex-sharing of their O atoms. These tetra­meric units are further linked by sharing edges between octa­hedra and by formation of M—O—Mo (M = Fe/Li) bridges, forming ribbons propagating in the [100] direction. The ribbons are cross-linked in both the b- and c-axis directions, giving rise to a three-dimensional framework having [100] tunnels in which the monovalent Na+/Li+ cations (0.4:0.6 ratio) lie. Bond-valence calculations are consistent with the disorder model for the cations. The structure of the title compound, which is isotypic with Li3Fe(MoO4)3 and Li3Ga(MoO4)3, is compared briefly with those of LiFeMo2O8 and Li1.6Mn2.2(MoO4)3. PMID:26090130

Spin pumping in ion-beam sputtered C o2FeAl /Mo bilayers: Interfacial Gilbert damping

NASA Astrophysics Data System (ADS)

Husain, Sajid; Kumar, Ankit; Barwal, Vineet; Behera, Nilamani; Akansel, Serkan; Svedlindh, Peter; Chaudhary, Sujeet

2018-02-01

The spin-pumping mechanism and associated interfacial Gilbert damping are demonstrated in ion-beam sputtered C o2FeAl (CFA)/Mo bilayer thin films employing ferromagnetic resonance spectroscopy. The dependence of the net spin-current transportation on Mo layer thickness, 0 to 10 nm, and the enhancement of the net effective Gilbert damping are reported. The experimental data have been analyzed using spin-pumping theory in terms of spin current pumped through the ferromagnet/nonmagnetic metal interface to deduce the real spin-mixing conductance and the spin-diffusion length, which are estimated to be 1.56 (±0.30 ) ×1019m-2 and 2.61 (±0.15 )nm , respectively. The damping constant is found to be 8.8 (±0.2 ) ×10-3 in the Mo(3.5 nm)-capped CFA(8 nm) sample corresponding to an ˜69 % enhancement of the original Gilbert damping 5.2 (±0.6 ) ×10-3 in the Al-capped CFA thin film. This is further confirmed by inserting the Cu dusting layer which reduces the spin transport across the CFA/Mo interface. The Mo layer thickness-dependent net spin-current density is found to lie in the range of 1 -4 MA m-2 , which also provides additional quantitative evidence of spin pumping in this bilayer thin-film system.

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

NASA Astrophysics Data System (ADS)

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

2018-05-01

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

Wear and corrosion resistance of laser-cladded Fe-based composite coatings on AISI 4130 steel

NASA Astrophysics Data System (ADS)

Fan, Li; Chen, Hai-yan; Dong, Yao-hua; Dong, Li-hua; Yin, Yan-sheng

2018-06-01

The wear and corrosion resistance of Fe72.2Cr16.8Ni7.3Mo1.6Mn0.7C0.2Si1.2 and Fe77.3Cr15.8Ni3.9Mo1.1Mn0.5C0.2Si1.2 coatings laser-cladded on AISI 4130 steel were studied. The coatings possess excellent wear and corrosion resistance despite the absence of expensive yttrium, tungsten, and cobalt and very little molybdenum. The microstructure mainly consists of dendrites and eutectic phases, such as duplex (γ+α)-Fe and the Fe-Cr (Ni) solid solution, confirmed via energy dispersive spectrometry and X-ray diffraction. The cladded Fe-based coatings have lower coefficients of friction, and narrower and shallower wear tracks than the substrate without the cladding, and the main wear mechanism is mild abrasive wear. Electrochemical test results suggest that the soft Fe72.2Cr16.8Ni7.3Mo1.6Mn0.7C0.2Si1.2 coating with high Cr and Ni concentrations has high passivation resistance, low corrosion current, and positive corrosion potential, providing a better protective barrier layer to the AISI 4130 steel against corrosion.

Infrared spectra and density functional calculations for SMO2 molecules (M = Cr, Mo, W).

PubMed

Wang, Xuefeng; Andrews, Lester

2009-08-06

Infrared absorptions of the matrix isolated SMO2 (M = Cr, Mo, W) molecules were observed following laser-ablated metal atom reactions with SO2 during condensation in solid argon and neon. The symmetric and antisymmetric M-O stretching mode assignments were confirmed by appropriate S18O2 and S(16,18)O2 isotopic shifts. The much weaker Cr-S stretching mode was identified through its 34S shift. Density functional (B3LYP and BPW91) calculations were performed to obtain molecular structures and to reproduce the infrared spectra. Computed pyramidal structures for the SMO2 molecules are very similar to those for the analogous trioxides and this functional group in [MO2S(bdt)]2- complexes. Additional weaker absorptions are assigned to the (SO2)(SMO2) adducts, which are stabilized by a four-membered ring.

36 CFR 72.30 - General requirements.

Code of Federal Regulations, 2014 CFR

2014-07-01

... and Innovation § 72.30 General requirements. Applicants must have an approved Recovery Action Program on file with the appropriate NPS Regional Office prior to applying for Rehabilitation or Innovation grants. Rehabilitation and Innovation proposals must be based on priorities identified in the applicant...

36 CFR 72.30 - General requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... and Innovation § 72.30 General requirements. Applicants must have an approved Recovery Action Program on file with the appropriate NPS Regional Office prior to applying for Rehabilitation or Innovation grants. Rehabilitation and Innovation proposals must be based on priorities identified in the applicant...

36 CFR 72.30 - General requirements.

Code of Federal Regulations, 2012 CFR

2012-07-01

... and Innovation § 72.30 General requirements. Applicants must have an approved Recovery Action Program on file with the appropriate NPS Regional Office prior to applying for Rehabilitation or Innovation grants. Rehabilitation and Innovation proposals must be based on priorities identified in the applicant...

36 CFR 72.30 - General requirements.

Code of Federal Regulations, 2010 CFR

2010-07-01

... and Innovation § 72.30 General requirements. Applicants must have an approved Recovery Action Program on file with the appropriate NPS Regional Office prior to applying for Rehabilitation or Innovation grants. Rehabilitation and Innovation proposals must be based on priorities identified in the applicant...

36 CFR 72.30 - General requirements.

Code of Federal Regulations, 2013 CFR

2013-07-01

... and Innovation § 72.30 General requirements. Applicants must have an approved Recovery Action Program on file with the appropriate NPS Regional Office prior to applying for Rehabilitation or Innovation grants. Rehabilitation and Innovation proposals must be based on priorities identified in the applicant...

30 CFR 72.700 - Respiratory equipment; respirable dust.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Respiratory equipment; respirable dust. 72.700... SAFETY AND HEALTH HEALTH STANDARDS FOR COAL MINES Miscellaneous § 72.700 Respiratory equipment; respirable dust. (a) Respiratory equipment approved by NIOSH under 42 CFR part 84 shall be made available to...

New series of triple molybdates AgA{sub 3}R(MoO{sub 4}){sub 5} (A=Mg, R=Cr, Fe; A=Mn, R=Al, Cr, Fe, Sc, In) with framework structures and mobile silver ion sublattices

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

Kotova, Irina Yu.; Buryat State University, Smolin St. 24a, Ulan-Ude 670000, Buryat Republic; Solodovnikov, Sergey F.

Triple molybdates AgA{sub 3}R(MoO{sub 4}){sub 5} (A=Mg, R=Cr, Fe; A=Mn, R=Al, Cr, Fe, Sc, In) of the NaMg{sub 3}In(MoO{sub 4}){sub 5} type were synthesized and single crystals of AgMg{sub 3}R(MoO{sub 4}){sub 5} (R=Cr, Fe) were grown. In their structures, the MoO{sub 4} tetrahedra, pairs and trimers of edge-shared (Mg, R)O{sub 6} octahedra are connected by common vertices to form a 3D framework. Large framework cavities involve Ag{sup +} cations disordered on three nearby positions with CN=3+1 or 4+1. Alternating (Mg, R)O{sub 6} octahedra and MoO{sub 4} tetrahedra in the framework form quadrangular windows penetrable for Ag{sup +} at elevated temperatures.more » Above 653–673 K, the newly obtained molybdates demonstrate abrupt reduction of the activation energy to 0.4–0.6 eV. At 773 K, AgMg{sub 3}Al(MoO{sub 4}){sub 5} shows electric conductivity 2.5·10{sup −2} S/cm and E{sub a}=0.39 eV compatible with characteristics of the best ionic conductors of the NASICON type. - Graphical abstract: Triple molybdates AgA{sub 3}R(MoO{sub 4}){sub 5} (A=Mg, R=Cr, Fe; A=Mn, R=Al, Cr, Fe, Sc, In) of the NaMg{sub 3}In(MoO{sub 4}){sub 5} type were synthesized, AgMg{sub 3}R(MoO{sub 4}){sub 5} (R=Cr, Fe) were structurally characterized, ion-conductive properties of AgMg{sub 3}Al(MoO{sub 4}){sub 5} were measured. Display Omitted - Highlights: • Triple molybdates AgA{sub 3}R(MoO{sub 4}){sub 5} (A=Mg, R=Cr, Fe; A=Mn, R=Al, Cr, Fe, Sc, In) of the NaMg{sub 3}In(MoO{sub 4}){sub 5} type were synthesized. • Single crystals of AgMg{sub 3}R(MoO{sub 4}){sub 5} (R=Cr, Fe) were grown and their crystal structures were determined. • Disordering Ag{sup +} ions and penetrable framework structures of AgMg{sub 3}R(MoO{sub 4}){sub 5} (R=Cr, Fe) suggest 2D-character of silver-ion mobility. • Measured ion-conductive properties of AgMg{sub 3}Al(MoO{sub 4}){sub 5} are compatible with characteristics of the best ionic conductors of the NASICON type.« less

10 CFR 72.30 - Financial assurance and recordkeeping for decommissioning.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 10 Energy 2 2010-01-01 2010-01-01 false Financial assurance and recordkeeping for decommissioning. 72.30 Section 72.30 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED) LICENSING REQUIREMENTS FOR THE INDEPENDENT STORAGE OF SPENT NUCLEAR FUEL, HIGH-LEVEL RADIOACTIVE WASTE, AND REACTOR-RELATED GREATER THAN...

Vibrational modes in thymine molecule from an ab initio MO calculation

NASA Astrophysics Data System (ADS)

Aida, Misako; Kaneko, Motohisa; Dupuis, Michel; Ueda, Toyotoshi; Ushizawa, Koichi; Ito, Gen; Kumakura, Akiko; Tsuboi, Masamichi

1997-03-01

Ab initio self-consistent field molecular orbital (SCF MO) calculations have been made of the thymine molecule for the equilibrium geometry, harmonic force constants, vibrational frequencies, vibrational modes, infrared intensities, and Raman intensities. The results have been correlated with the observed Raman and infrared spectra of thymine crystalline powder.

Comparative studies on the room-temperature ferrielectric and ferrimagnetic Ni3TeO6-type A2FeMoO6 compounds (A = Sc, Lu)

PubMed Central

Song, Guang; Zhang, Weiyi

2016-01-01

First-principles calculations have been carried out to study the structural, electric, and magnetic properties of Ni3TeO6-type A2FeMoO6 compounds (A = Sc, Lu). Their electric and magnetic properties behave like room-temperature ferrielectric and ferrimagnetic insulators where polarization comes from the un-cancelled antiparallel dipoles of (A(1), Fe3+) and (A(2), Mo3+) ion groups, and magnetization from un-cancelled antiparallel moments of Fe3+ and Mo3+ ions. The net polarization increases with A’s ionic radius and is 7.1 and 8.7 μCcm−2 for Sc2FeMoO6 and Lu2FeMoO6, respectively. The net magnetic moment is 2 μB per formula unit. The magnetic transition temperature is estimated well above room-temperature due to the strong antiferromagnetic superexchange coupling among Fe3+ and Mo3+ spins. The estimated paraelectric to ferrielectric transition temperature is also well above room-temperature. Moreover, strong magnetoelectric coupling is also anticipated because the magnetic ions are involved both in polarization and magnetization. The fully relaxed Ni3TeO6-type A2FeMoO6 structures are free from soft-phonon modes and correspond to stable structures. As a result, Ni3TeO6-type A2FeMoO6 compounds are possible candidates for room-temperature multiferroics with large magnetization and polarization. PMID:26831406

Cathodic Electrodeposition of Ni-Mo on Semiconducting NiFe2 O4 for Photoelectrochemical Hydrogen Evolution in Alkaline Media.

PubMed

Wijten, Jochem H J; Jong, Ronald P H; Mul, Guido; Weckhuysen, Bert M

2018-04-25

Photocathodes for hydrogen evolution from water were made by electrodeposition of Ni-Mo layers on NiFe 2 O 4 substrates, deposited by spin coating on F:SnO 2 -glass. Analysis confirmed the formation of two separate layers, without significant reduction of NiFe 2 O 4 . Bare NiFe 2 O 4 was found to be unstable under alkaline conditions during (photo)electrochemistry. To improve the stability significantly, the deposition of a bifunctional Ni-Mo layer through a facile electrodeposition process was performed and the composite electrodes showed stable operation for at least 1 h. Moreover, photocurrents up to -2.1 mA cm -2 at -0.3 V vs. RHE were obtained for Ni-Mo/NiFe 2 O 4 under ambient conditions, showing that the new combination functions as both a stabilizing and catalytic layer for the photoelectrochemical evolution of hydrogen. The photoelectrochemical response of these composite electrodes decreased with increasing NiFe 2 O 4 layer thickness. Transient absorption spectroscopy showed that the lifetime of excited states is short and on the ns timescale. An increase in lifetime was observed for NiFe 2 O 4 of large layer thickness, likely explained by decreasing the defect density in the primary layer(s), as a result of repetitive annealing at elevated temperature. The photoelectrochemical and transient absorption spectroscopy results indicated that a short charge carrier lifetime limits the performance of Ni-Mo/NiFe 2 O 4 photocathodes. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Low frequency dynamics of the nitrogenase MoFe protein via femtosecond pump probe spectroscopy - Observation of a candidate promoting vibration.

PubMed

Maiuri, Margherita; Delfino, Ines; Cerullo, Giulio; Manzoni, Cristian; Pelmenschikov, Vladimir; Guo, Yisong; Wang, Hongxin; Gee, Leland B; Dapper, Christie H; Newton, William E; Cramer, Stephen P

2015-12-01

We have used femtosecond pump-probe spectroscopy (FPPS) to study the FeMo-cofactor within the nitrogenase (N2ase) MoFe protein from Azotobacter vinelandii. A sub-20-fs visible laser pulse was used to pump the sample to an excited electronic state, and a second sub-10-fs pulse was used to probe changes in transmission as a function of probe wavelength and delay time. The excited protein relaxes to the ground state with a ~1.2ps time constant. With the short laser pulse we coherently excited the vibrational modes associated with the FeMo-cofactor active site, which are then observed in the time domain. Superimposed on the relaxation dynamics, we distinguished a variety of oscillation frequencies with the strongest band peaks at ~84, 116, 189, and 226cm(-1). Comparison with data from nuclear resonance vibrational spectroscopy (NRVS) shows that the latter pair of signals comes predominantly from the FeMo-cofactor. The frequencies obtained from the FPPS experiment were interpreted with normal mode calculations using both an empirical force field (EFF) and density functional theory (DFT). The FPPS data were also compared with the first reported resonance Raman (RR) spectrum of the N2ase MoFe protein. This approach allows us to outline and assign vibrational modes having relevance to the catalytic activity of N2ase. In particular, the 226cm(-1) band is assigned as a potential 'promoting vibration' in the H-atom transfer (or proton-coupled electron transfer) processes that are an essential feature of N2ase catalysis. The results demonstrate that high-quality room-temperature solution data can be obtained on the MoFe protein by the FPPS technique and that these data provide added insight to the motions and possible operation of this protein and its catalytic prosthetic group. Copyright © 2015 Elsevier Inc. All rights reserved.

Magnetic Properties of NdFe10Mo2-N Bonded Magnet

NASA Astrophysics Data System (ADS)

Zhang, Hong-Wei; Hu, Bo-Ping; Han, Zhong-Fan; Jin, Han-Min; Fu, Quan

1997-06-01

The dependence of remanence and coercivity on the magnetizing field is studied for isotropic and anisotropic epoxy resin bonded magnets. It was found that the coercivity of the NdFe10Mo2-N bonded magnet is mainly controlled by nucleation of reversed magnetic domains. Variation of iHc with Zn content and heat treatment conditions is studied. The value of 0 iHc obtained in the best Zn-bonded condition is about 0.15 T higher than before bonding. The variation of the amount of α-Fe with processing conditions is demonstrated for anisotropic Zn-bonded magnets.

Effects of B and Mo on the magnetic properties of NdFeTi-nitrides with ThMn[sub 12]-type structure

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

Kim, Y.B.; Kim, H.T.; Kim, C.S.

1993-11-01

The alloys having nearly single phase of ThMn[sub 12]-type structure (1-12 phase) have been successfully synthesized in NdFe[sub 10.7]Ti[sub 1.3[minus]y]M[sub y] (M = B/Mo) alloy systems by substituting B or Mo up to 23% of Ti (y=0.3). After nitrification, the unit cell volume of 1--12 phase has increased by about 2--3% and a-Fe phase of 5--15 wt.% has been formed depending on the substitutional elements. The nitrides, NdFe[sub 10.7]TiB[sub 0.3]N[sub x] and Nd Fe[sub 10.7]TiMo[sub 0.3]N[sub x], were confirmed to have uniaxial anisotropy by X-ray diffractometry. The results of magnetic measurements for the nitrides have shown that B is verymore » effective for the increase of both Curie temperature and magnetization. On the other band, Mo is effective for the increase of anisotropy field, but it decreases the magnetization. The Curie temperature and magnetization of NdFe[sub 10.7]TiB[sub 0.3]N[sub x] are 560 C and 148 Am[sup 2] /kg, respectively, by about 20% and 15% higher than those of NdFe[sub 10.7]Ti[sub 1.3]N[sub x]. The anisotropy field of NdFe[sub 10.7]TiMo[sub 0.3]N[sub x] is about 7960 kA/m (100 kOe) which is about 25% higher than that of NdFe[sub 10.7]Ti[sub 1.3]N[sub x].« less

Novel "203" type of heterostructured MoS2-Fe3O4-C ternary nanohybrid: Synthesis, and enhanced microwave absorption properties

NASA Astrophysics Data System (ADS)

Yang, Erqi; Qi, Xiaosi; Xie, Ren; Bai, Zhongchen; Jiang, Yang; Qin, Shuijie; Zhong, Wei; Du, Youwei

2018-06-01

It is widely recognized that constructing multiple interface structures to enhance interface polarization is very good for the attenuation of electromagnetic (EM) wave. Here, a novel "203" type of heterostructured nanohybrid consisting of two-dimensional (2D) MoS2 nanosheets, zero-dimensional (0D) Fe3O4 nanoparticles and three-dimensional (3D) carbon layers was elaborately designed and successfully synthesized by a two-step method: Fe3O4 nanoparticles were deposited onto the surface of few-layer MoS2 nanosheets by a hydrothermal method, followed by the carbonation process by a chemical vapor deposition method. Compared to that of "20" type MoS2-Fe3O4, the as-prepared heterostructured "203" type MoS2-Fe3O4-C ternary nanohybrid exhibited remarkably enhanced EM and microwave absorption properties. And the minimum reflection loss (RL) value of the obtained MoS2-Fe3O4-C ternary nanohybrid could reach -53.03 dB at 14.4 GHz with a matching thickness of 7.86 mm. Moreover, the excellent EM wave absorption property of the as-prepared ternary nanohybrid was proved to be attributed to the quarter-wavelength matching model. Therefore, a simple and effective route was proposed to produce MoS2-based mixed-dimensional van der Waals heterostructure, which provided a new platform for the designing and production of high performance microwave absorption materials.

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

NASA Astrophysics Data System (ADS)

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

2002-12-01

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

Site specific ligand substitution in cubane-type Mo3FeS(4)(4+) clusters: kinetics and mechanism of reaction and isolation of mixed ligand Cl/SPh complexes.

PubMed

Algarra, Andrés G; Basallote, Manuel G; Fernandez-Trujillo, M J; Llusar, Rosa; Pino-Chamorro, Jose A; Sorribes, Ivan; Vicent, Cristian

2010-04-21

The synthesis, crystal structure and solution characterization of the cubane-type [Mo(3)(FeCl)S(4)(dmpe)(3)Cl(3)] (1) (dmpe = 1,2-bis(dimethylphophane-ethane)) cluster are reported and the ligand substitution processes of chloride by thiophenolate investigated. The kinetics and the intimate mechanism of these substitutions reveal that compound 1 undergoes a number of Fe and Mo site specific ligand substitution reactions in acetonitrile solutions. In particular, PhS(-) coordination at the tetrahedral Fe site proceeds in a single resolved kinetic step whereas such substitutions at the Mo sites proceed more slowly. The effect of the presence of acids in the reaction media is also investigated and reveals that an acid excess hinders substitution reactions both at the Fe and Mo sites; however, an acid-promoted solvolysis of the Fe-Cl bonds is observed. Electrospray ionization (ESI) and tandem (ESI-MS/MS) mass spectrometry allow the identification of all the reaction intermediates proposed on the basis of stopped-flow measurements. The distinctive site specific reactivity made it possible to isolate two new clusters of the Mo(3)FeS(4)(4+) family featuring mixed chlorine/thiophenolate ligands, namely Mo(3)S(4)(FeSPh)(dmpe)(3)Cl(3) (2) and [Mo(3)S(4)(FeSPh)(dmpe)(3)(SPh)(3)] (3). A detailed computational study has also been carried out to understand the details of the mechanism of substitution at the M-Cl (M = Mo and Fe) bonds as well as the solvolysis at the Fe-Cl sites, with particular emphasis on the role of acids on the substitution process. The results of the calculations are in agreement with the experimental observations, thus justifying the non-existence of an accelerating effect of acids on the thiophenolate substitution reaction, which differs from previous proposals for the Fe(4)S(4) and MoFe(3)S(4) clusters and some related compounds.

Formation of cation-anion complexes in the photochemical reaction of molybdenocene dihydrode with iron pentacarbonyl. Crystal structures of (Cp/sub 2/Mo(CO)H)/sup +/(Fe/sub 3/(CO)/sub 11/H)/sup -/ and (Cp/sub 2/Mo(CO)H)/sup +/(CoMo(CO)/sub 3/)/sup -/ (triclinic modification) (in Russian)

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

Antsyshkina, A.S.; Dikareva, L.M.; Porai-Koshits, M.A.

1985-11-01

The reaction of Cp/sub 2/MoH/sub 2/ with Fe(CO)/sub 5/ in boiling benzene under UV irradiation gives the ionic complexes (Cp/sub 2/Mo(CO)H)/sup +/(Fe/sub 3/(CO)/sub 11/H)/sup -/ (I) and (Cp/sub 2/Mo(CO)H)/sup +/(CpMo(CO)/sub 3/)/sup -/ (II), whose structures were established by x-ray diffraction analysis (Syntex P2/sub 1/ automatic diffractometer, lambda Mo K/sub ..cap alpha../, graphite monochromator, theta/2theta scan technique, full-matrix least-squares method, isotropic variant for I on the basis of 2112 reflections to % = 0.11 and anisotropic variant for II on the basis of 3770 values of hkl to R = 0.052). In complexes I and II the (CpMo(CO)H)/sup +/ fragment ismore » a tapered sandwich with an eclipsed conformation of the rings. In complex I the angle between the rings is 33.9/sup 0/, the mean Mo-C(C/sub 5/H/sub 5/) distance is 2.28(3) A, the mean Mo-C(CO) distance is 2.03(3) A, and the mean Mo-H distance is 1.78(10) A. The corresponding parameters in complex II are: 32.4/sup 0/, 2.296(7), 2.020(6), and 1.87(7) A. The anion in complex I is based on a triangular cluster of Fe atoms, in which one Fe-Fe distance is significantly shorter (2.488(5) A) than the other two (2.702(5) and 2.697(5) A). The Fe atoms forming the short bond are joined additionally by hydride (Fe-H = 2.14 A) and carbonyl (Fe-C = 1.90(3) and 1.93(3) A) Bridges. The remaining groups are terminal. A probable scheme for the process of the formation of complexes I and II has been discussed.« less

Mechanical properties of weldments in experimental Fe-12Mn-0.2Ti and Fe-12Mn-1Mo-0.2Ti alloys for cryogenic service

NASA Technical Reports Server (NTRS)

Stephens, J. R.; Witzke, W. R.; Devletian, J. H.

1981-01-01

Mechanical properties of weldments in two Fe-12Mn experimental alloys designed for cryogenic service were evaluated. Weldments were made using the GTA welding process. Tests to evaluate the weldments were conducted at -196 C and included: equivalent energy fracture toughness tests; autogenous transverse weld, notched transverse weld, and longitudinal weld tensile tests; and all-weld-metal tensile tests. The Fe-12Mn-0.2Ti and Fe-12Mn-1Mo-0.2Ti alloys proved weldable for cryogenic service, with weld metal and heat-affected zone properties comparable with those of the base metal. Optimum properties were achieved in the base alloys, weld metals, and heat-affected zones after a two-step heat treatment consisting of austenitizing at 900 C followed by tempering at 500 C. The Mo-containing alloy offered a marked improvement in cryogenic properties over those of the Mo-free alloy. Molybdenum increased the amount of retained austenite and reduced the amount of epsilon martensite observed in the microstructure of the two alloys.

Corrosion Behavior of High Nitrogen Nickel-Free Fe-16Cr-Mn-Mo-N Stainless Steels

NASA Astrophysics Data System (ADS)

Chao, K. L.; Liao, H. Y.; Shyue, J. J.; Lian, S. S.

2014-04-01

The purpose of the current study is to develop austenitic nickel-free stainless steels with lower chromium content and higher manganese and nitrogen contents. In order to prevent nickel-induced skin allergy, cobalt, manganese, and nitrogen were used to substitute nickel in the designed steel. Our results demonstrated that manganese content greater than 14 wt pct results in a structure that is in full austenite phase. The manganese content appears to increase the solubility of nitrogen; however, a lower corrosion potential was found in steel with high manganese content. Molybdenum appears to be able to increase the pitting potential. The effects of Cr, Mn, Mo, and N on corrosion behavior of Fe-16Cr-2Co-Mn-Mo-N high nitrogen stainless steels were evaluated with potentiodynamic tests and XPS surface analysis. The results reveal that anodic current and pits formation of the Fe-16Cr-2Co-Mn-Mo-N high nitrogen stainless steels were smaller than those of lower manganese and nitrogen content stainless steel.

Atomic-scale understanding of high thermal stability of the Mo/CoFeB/MgO spin injector for spin-injection in remanence.

PubMed

Tao, Bingshan; Barate, Philippe; Devaux, Xavier; Renucci, Pierre; Frougier, Julien; Djeffal, Abdelhak; Liang, Shiheng; Xu, Bo; Hehn, Michel; Jaffrès, Henri; George, Jean-Marie; Marie, Xavier; Mangin, Stéphane; Han, Xiufeng; Wang, Zhanguo; Lu, Yuan

2018-05-31

Remanent spin injection into a spin light emitting diode (spin-LED) at zero magnetic field is a prerequisite for future application of spin optoelectronics. Here, we demonstrate the remanent spin injection into GaAs based LEDs with a thermally stable Mo/CoFeB/MgO spin injector. A systematic study of magnetic properties, polarization-resolved electroluminescence (EL) and atomic-scale interfacial structures has been performed in comparison with the Ta/CoFeB/MgO spin injector. The perpendicular magnetic anisotropy (PMA) of the Mo/CoFeB/MgO injector shows more advanced thermal stability than that of the Ta/CoFeB/MgO injector and robust PMA can be maintained up to 400 °C annealing. The remanent circular polarization (PC) of EL from the Mo capped spin-LED reaches a maximum value of 10% after 300 °C annealing, and even remains at 4% after 400 °C annealing. In contrast, the Ta capped spin-LED almost completely loses the remanent PC under 400 °C annealing. Combined advanced electron microscopy and spectroscopy studies reveal that a large amount of Ta diffuses into the MgO tunneling barrier through the CoFeB layer after 400 °C annealing. However, the diffusion of Mo into CoFeB is limited and never reaches the MgO barrier. These findings afford a comprehensive perspective to use the highly thermally stable Mo/CoFeB/MgO spin injector for efficient electrical spin injection in remanence.

High-temperature properties of (La,Ca)(Fe,Mg,Mo)O3-δ perovskites as prospective electrode materials for symmetrical SOFC

NASA Astrophysics Data System (ADS)

Istomin, S. Ya.; Morozov, A. V.; Abdullayev, M. M.; Batuk, M.; Hadermann, J.; Kazakov, S. M.; Sobolev, A. V.; Presniakov, I. A.; Antipov, E. V.

2018-02-01

La1-yCayFe0.5+x(Mg,Mo)0.5-xO3-δ oxides with the orthorhombic GdFeO3-type perovskite structure have been synthesized at 1573 K. Transmission electron microscopy study for selected samples shows the coexistence of domains of perovskite phases with ordered and disordered B-cations. Mössbauer spectroscopy studies performed at 300 K and 573 K show that while compositions with low Ca-content (La0.55Ca0.45Fe0.5Mg0.2625Mo0.2375O3-δ and La0.5Ca0.5Fe0.6Mg0.175Mo0.225O3-δ) are nearly oxygen stoichiometric, La0.2Ca0.8Fe0.5Mg0.2625Mo0.2375O3-δ is oxygen deficient with δ ≈ 0.15. Oxides are stable in reducing atmosphere (Ar/H2, 8%) at 1173 K for 12 h. No additional phases have been observed at XRPD patterns of all studied perovskites and Ce1-xGdxO2-x/2 electrolyte mixtures treated at 1173-1373K, while Fe-rich compositions (x≥0.1) react with Zr1-xYxO2-x/2 electrolyte above 1273 K. Dilatometry studies reveal that all samples show rather low thermal expansion coefficients (TECs) in air of 11.4-12.7 ppm K-1. In reducing atmosphere their TECs were found to increase up to 12.1-15.4 ppm K-1 due to chemical expansion effect. High-temperature electrical conductivity measurements in air and Ar/H2 atmosphere show that the highest conductivity is observed for Fe- and Ca-rich compositions. Moderate values of electrical conductivity and TEC together with stability towards chemical interaction with typical SOFC electrolytes make novel Fe-containing perovskites promising electrode materials for symmetrical solid oxide fuel cell.

X-ray and Neutron Scattering Study of the Formation of Core–Shell-Type Polyoxometalates

DOE PAGES

Yin, Panchao; Wu, Bin; Mamontov, Eugene; ...

2016-02-05

A typical type of core-shell polyoxometalates can be obtained through the Keggin-type polyoxometalate-templated growth of a layer of spherical shell structure of {Mo 72Fe 30}. Small angle X-ray scattering is used to study the structural features and stability of the core-shell structures in aqueous solutions. Time-resolved small angle X-ray scattering is applied to monitor the synthetic reactions and a three-stage formation mechanism is proposed to describe the synthesis of the core-shell polyoxometalates based on the monitoring results. Quasi-elastic and inelastic neutron scattering are used to probe the dynamics of water molecules in the core-shell structures and two different types ofmore » water molecules, the confined and structured water, are observed. These water molecules play an important role in bridging core and shell structures and stabilizing the cluster structures. A typical type of core shell polyoxometalates can be obtained through the Keggin-type polyoxometalate-templated growth of a layer of spherical shell structure of {Mo 72Fe 30}. Small-angle X-ray scattering is used to study the structural features and stability of the core shell structures in aqueous solutions. Time-resolved small-angle X-ray scattering is applied to monitor the synthetic reactions, and a three-stage formation mechanism is proposed to describe the synthesis of the core shell polyoxometalates based on the monitoring results. New protocols have been developed by fitting the X-ray data with custom physical models, which provide more convincing, objective, and completed data interpretation. Quasi-elastic and inelastic neutron scattering are used to probe the dynamics of water molecules in the core shell structures, and two different types of water molecules, the confined and structured water, are observed. These water molecules play an important role in bridging core and shell structures and stabilizing the cluster structures.« less

Assembly of flexible CoMoO4@NiMoO4·xH2O and Fe2O3 electrodes for solid-state asymmetric supercapacitors

PubMed Central

Wang, Jing; Zhang, Leipeng; Liu, Xusong; Zhang, Xiang; Tian, Yanlong; Liu, Xiaoxu; Zhao, Jiupeng; Li, Yao

2017-01-01

In this work, CoMoO4@NiMoO4·xH2O core-shell heterostructure electrode is directly grown on carbon fabric (CF) via a feasible hydrothermal procedure with CoMoO4 nanowires (NWs) as the core and NiMoO4 nanosheets (NSs) as the shell. This core-shell heterostructure could provide fast ion and electron transfer, a large number of active sites, and good strain accommodation. As a result, the CoMoO4@NiMoO4·xH2O electrode yields high-capacitance performance with a high specific capacitance of 1582 F g−1, good cycling stability with the capacitance retention of 97.1% after 3000 cycles and good rate capability. The electrode also shows excellent mechanical flexibility. Also, a flexible Fe2O3 nanorods/CF electrode with enhanced electrochemical performance was prepared. A solid-state asymmetric supercapacitor device is successfully fabricated by using flexible CoMoO4@NiMoO4·xH2O as the positive electrode and Fe2O3 as the negative electrode. The asymmetric supercapacitor with a maximum voltage of 1.6 V demonstrates high specific energy (41.8 Wh kg−1 at 700 W kg−1), high power density (12000 W kg−1 at 26.7 Wh kg−1), and excellent cycle ability with the capacitance retention of 89.3% after 5000 cycles (at the current density of 3A g−1). PMID:28106170

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

NASA Astrophysics Data System (ADS)

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

2018-07-01

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

40 CFR 72.30 - Requirement to apply.

Code of Federal Regulations, 2010 CFR

2010-07-01

...) PERMITS REGULATION Acid Rain Permit Applications § 72.30 Requirement to apply. (a) Duty to apply. The designated representative of any source with an affected unit shall submit a complete Acid Rain permit... permit that states its Acid Rain program requirements. (b) Deadlines—(1) Phase 1. (i) The designated...

40 CFR 72.30 - Requirement to apply.

Code of Federal Regulations, 2011 CFR

2011-07-01

...) PERMITS REGULATION Acid Rain Permit Applications § 72.30 Requirement to apply. (a) Duty to apply. The designated representative of any source with an affected unit shall submit a complete Acid Rain permit... permit that states its Acid Rain program requirements. (b) Deadlines—(1) Phase 1. (i) The designated...

40 CFR 72.30 - Requirement to apply.

Code of Federal Regulations, 2012 CFR

2012-07-01

...) PERMITS REGULATION Acid Rain Permit Applications § 72.30 Requirement to apply. (a) Duty to apply. The designated representative of any source with an affected unit shall submit a complete Acid Rain permit... permit that states its Acid Rain program requirements. (b) Deadlines—(1) Phase 1. (i) The designated...

40 CFR 72.30 - Requirement to apply.

Code of Federal Regulations, 2014 CFR

2014-07-01

...) PERMITS REGULATION Acid Rain Permit Applications § 72.30 Requirement to apply. (a) Duty to apply. The designated representative of any source with an affected unit shall submit a complete Acid Rain permit... permit that states its Acid Rain program requirements. (b) Deadlines—(1) Phase 1. (i) The designated...

40 CFR 72.30 - Requirement to apply.

Code of Federal Regulations, 2013 CFR

2013-07-01

...) PERMITS REGULATION Acid Rain Permit Applications § 72.30 Requirement to apply. (a) Duty to apply. The designated representative of any source with an affected unit shall submit a complete Acid Rain permit... permit that states its Acid Rain program requirements. (b) Deadlines—(1) Phase 1. (i) The designated...

Structures, thermal expansion properties and phase transitions of Er{sub x}Fe{sub 2-x}(MoO{sub 4}){sub 3} (0.0 {le} x {le} 2.0).

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

Cheng, Y. Z.; Wu, M. M.; Peng, J.

2007-05-03

Structures, thermal expansion properties and phase transitions of Er{sub x}Fe{sub 2-x}(MoO{sub 4}){sub 3} (0.0 {le} x {le} 2.0) have been investigated by X-ray diffraction and differential thermal analysis. The partial substitution of Er{sup 3+} for Fe{sup 3+} induces pronounced decreases in the phase transition temperature from monoclinic to orthorhombic structure. Rietveld analysis of the XRD data shows that both the monoclinic and orthorhombic Fe{sub 2}(MoO{sub 4}){sub 3}, as well as the orthorhombic Er{sub x}Fe{sub 2-x}(MoO{sub 4}){sub 3} (x {le} 0.8) have positive thermal expansion coefficients. However, the linear thermal expansion coefficients of Er{sub x}Fe{sub 2-x}(MoO{sub 4}){sub 3} (x = 0.6-2.0)more » decrease with increasing content of Er{sup 3+} and for x {ge} 1.0, compounds Er{sub x}Fe{sub 2-x}(MoO{sub 4}){sub 3} show negative thermal expansion properties. Attempts for making zero thermal expansion coefficient materials result in that very low negative thermal expansion coefficient of -0.60 x 10{sup -6} C in Er{sub 1.0}Fe{sub 1.0}(MoO{sub 4}){sub 3} is observed in the temperature range of 180-400 C, and zero thermal expansion is observed in Er{sub 0.8}Fe{sub 1.2}(MoO{sub 4}){sub 3} in the temperature range of 350-450 C. In addition, anisotropic thermal expansions are found for all the orthorhombic Er{sub x}Fe{sub 2-x}(MoO{sub 4}){sub 3} compounds, with negative thermal expansion coefficients along the a axes.« less

Diversity of Chemical Bonding and Oxidation States in MS4 Molecules of Group 8 Elements.

PubMed

Huang, Wei; Jiang, Ning; Schwarz, W H Eugen; Yang, Ping; Li, Jun

2017-08-04

The geometric and electronic ground-state structures of 30 isomers of six MS 4 molecules (M=Group 8 metals Fe, Ru, Os, Hs, Sm, and Pu) have been studied by using quantum-chemical density functional theory and correlated wavefunction approaches. The MS 4 species were compared to analogous MO 4 species recently investigated (W. Huang, W.-H. Xu, W. H. E. Schwarz, J. Li, Inorg. Chem. 2016, 55, 4616). A metal oxidation state (MOS) with a high value of eight appeared in the low-spin singlet T d geometric species (Os,Hs)S 4 and (Ru,Os,Hs)O 4 , whereas a low MOS of two appeared in the high-spin septet D 2d species Fe(S 2 ) 2 and (slightly excited) metastable Fe(O 2 ) 2 . The ground states of all other molecules had intermediate MOS values, with S 2- , S 2 2- , S 2 1- (and O 2- , O 1- , O 2 2- , O 2 1- ) ligands bonded by ionic, covalent, and correlative contributions. The known tendencies toward lower MOS on going from oxides to sulfides, from Hs to Os to Ru, and from Pu to Sm, and the specific behavior of Fe, were found to arise from the different atomic orbital energies and radii of the (n-1)p core and (n-1)d and (n-2)f valence shells of the metal atoms in row n of the periodic table. The comparative results of the electronic and geometric structures of the MO 4 and MS 4 species provides insight into the periodicity of oxidation states and bonding. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of Bi doping on structural and magnetic properties of double perovskite oxides Sr2FeMoO6

NASA Astrophysics Data System (ADS)

Lan, Yaohai; Feng, Xiaomei; Zhang, Xin; Shen, Yifu; Wang, Ding

2016-08-01

A new series of double perovskite compounds Sr2 - δBixFeMoO6 have been synthesized by solid-state reaction. δ refers to the nominal doping content of Bi (δ = 0, 0.1, 0.2, 0.3, 0.4, 0.5), while the Bi content obtained by the Rietveld refinement is x = 0, 0.01, 0.05, 0.08, 0.10 and 0.12. Their crystal structure and magnetic properties are investigated. Rietveld analysis of the room temperature XRD data shows all the samples crystallize in the cubic crystal structure with the space group Fm 3 ‾ m and have no phase transition. SEM images show that substituted samples present a denser microstructure and bigger grains than Sr2FeMoO6, which is caused by a liquid sintering process due to the effumability of Bi. The unit cell volume increases with augment of Bi3+ concentration despite the smaller ionic radius Bi3+ compared with the Sr2+, which is attributed to the electronic effect. The degree of Fe/Mo order (η) increases first and then decreases to almost disappearance with augment of Bi doping, which is the result of contribution from electronic effect. Calculated saturation magnetization Ms(3) according to our phase separation likeness model matches well with the experimental ones. The observed variations of magnetoresistance (MR) are consistent with the Fe/Mo order (η) due to the internal connection with anti-site defect (ASD).

RE3Mo14O30 and RE2Mo9O19, Two Reduced Rare-Earth Molybdates with Honeycomb-Related Structures ( RE = La-Pr).

PubMed

Forbes, Scott; Kong, Tai; Cava, Robert J

2018-04-02

The previously unreported RE 3 Mo 14 O 30 and RE 2 Mo 9 O 19 phases were synthesized in vacuo from rare-earth oxides, molybdenum oxide, and molybdenum metal using halide fluxes at 875-1000 °C. Both phases adopt structures in the triclinic P1̅ space group albeit with several notable differences. The structures display an ordering of layers along the a direction of the unit cell, forming distinct honeycomb-related lattice arrangements composed of MoO 6 octahedra and vacancies. Mo-Mo bonding and clusters are present; the RE 3 Mo 14 O 30 structure contains Mo dimers and rhomboid tetramers, while the RE 2 Mo 9 O 19 structure contains rhomboid tetramers and an unusual arrangement of planar tetramers, pentamers, and hexamers. The magnetic measurements found the RE 2 Mo 9 O 19 phases to be simple paramagnets, while La 3 Mo 14 O 30 was observed to order antiferromagnetically at 18 K. Electrical resistivity measurements confirmed all of the samples to behave as nondegenerate semiconductors.

Keplerate cluster (Mo-132) mediated electrostatic assembly of nanoparticles.

PubMed

Gooch, Jonathan; Jalan, Abhishek A; Jones, Stephanie; Hine, Corey R; Alam, Rabeka; Garai, Somenath; Maye, Mathew M; Müller, Achim; Zubieta, Jon

2014-10-15

The electrostatic assembly between a series of differently charged Mo-132-type Keplerates present in the compounds (NH4)42[{(Mo(VI))Mo(VI)5O21(H2O)6}12 {Mo(V)2O4(CH3COO)}30].ca. {300 H2O+10 CH3COONH4} (Mo-132a), (NH4)72-n[{(H2O)81-n+(NH4)n} {(Mo(VI))Mo(VI)5O21(H2O)6}12 {Mo(V)2O4(SO4)}30].ca. 200 H2O (Mo-132b), and Na10(NH4)62[{(Mo(VI))Mo(VI)5O21(H2O)6}12 {Mo(V)2O4(HPO4)}30]. ca. {300H2O+2Na(+)+2NH4(+)+4H2PO4(-)} (Mo-132c) with cationic gold nanoparticles (AuNPs) was investigated for the first time. The rapid electrostatic assembly from nanoscopic entities to micron scale aggregates was observed upon precipitation, which closely matched the point of aggregate electroneutrality. Successful assembly was demonstrated using UV-vis, DLS, TEM, and zeta-potential analysis. Results indicate that the point at which precipitation occurs is related to charge balance or electroneutrality, and that counterions at both the Mo-132 and AuNP play a significant role in assembly. Copyright © 2014 Elsevier Inc. All rights reserved.

Light-driven dinitrogen reduction catalyzed by a CdS:nitrogenase MoFe protein biohybrid.

PubMed

Brown, Katherine A; Harris, Derek F; Wilker, Molly B; Rasmussen, Andrew; Khadka, Nimesh; Hamby, Hayden; Keable, Stephen; Dukovic, Gordana; Peters, John W; Seefeldt, Lance C; King, Paul W

2016-04-22

The splitting of dinitrogen (N2) and reduction to ammonia (NH3) is a kinetically complex and energetically challenging multistep reaction. In the Haber-Bosch process, N2 reduction is accomplished at high temperature and pressure, whereas N2 fixation by the enzyme nitrogenase occurs under ambient conditions using chemical energy from adenosine 5'-triphosphate (ATP) hydrolysis. We show that cadmium sulfide (CdS) nanocrystals can be used to photosensitize the nitrogenase molybdenum-iron (MoFe) protein, where light harvesting replaces ATP hydrolysis to drive the enzymatic reduction of N2 into NH3 The turnover rate was 75 per minute, 63% of the ATP-coupled reaction rate for the nitrogenase complex under optimal conditions. Inhibitors of nitrogenase (i.e., acetylene, carbon monoxide, and dihydrogen) suppressed N2 reduction. The CdS:MoFe protein biohybrids provide a photochemical model for achieving light-driven N2 reduction to NH3. Copyright © 2016, American Association for the Advancement of Science.

Light-driven dinitrogen reduction catalyzed by a CdS:nitrogenase MoFe protein biohybrid

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

Brown, K. A.; Harris, D. F.; Wilker, M. B.

The splitting of dinitrogen (N2) and reduction to ammonia (NH3) is a kinetically complex and energetically challenging multistep reaction. In the Haber-Bosch process, N2 reduction is accomplished at high temperature and pressure, whereas N2 fixation by the enzyme nitrogenase occurs under ambient conditions using chemical energy from adenosine 5'-triphosphate (ATP) hydrolysis. We show that cadmium sulfide (CdS) nanocrystals can be used to photosensitize the nitrogenase molybdenum-iron (MoFe) protein, where light harvesting replaces ATP hydrolysis to drive the enzymatic reduction of N2 into NH3. The turnover rate was 75 per minute, 63% of the ATP-coupled reaction rate for the nitrogenase complexmore » under optimal conditions. Inhibitors of nitrogenase (i.e., acetylene, carbon monoxide, and dihydrogen) suppressed N2 reduction. The CdS:MoFe protein biohybrids provide a photochemical model for achieving light-driven N2 reduction to NH3.« less

Structural investigation of MO ṡ P2O5ṡ Li2O (MO = Fe2O3 or V2O5) glass systems by FTIR spectroscopy

NASA Astrophysics Data System (ADS)

Andronache, Constantin I.; Racolta, Dania

2014-11-01

Glasses from the systems xMO ṡ(100-x )[ P2O5ṡ Li2O ] (MO = Fe2O3 or V2O5) with 0 ≤ x ≤ mol % were prepared in the same conditions and characterized by IR spectroscopy. It was established the mode in which both Fe2O3 and V2O5 influences the local structure of these glasses. The iron ions generally modify in a different way the local structure of these glasses then vanadium ions. The results shown that phosphate units are the main structural units of glass system and the iron and vanadium ions are located in the network.

Effect of MoO3 on the synthesis of boron nitride nanotubes over Fe and Ni catalysts.

PubMed

Nithya, Jeghan Shrine Maria; Pandurangan, Arumugam

2012-05-01

Synthesis of boron nitride nanotubes at reduced temperature is important for industrial manufactures. In this study boron nitride nanotubes were synthesized by thermal evaporation method using B/Fe2O3/MoO3 and B/Ni2O3/MoO3 mixtures separately with ammonia as the nitrogen source. The growth of boron nitride nanotubes occurred at 1100 degrees C, which was relatively lower than other metal oxides assisted growth processes requiring higher than 1200 degrees C. MoO3 promoted formation of B2O2 and aided boron nitride nanotubes growth at a reduced temperature. The boron nitride nanotubes with bamboo shaped, nested cone structured and straight tubes like forms were evident from the high resolution transmission electron microscopy. Metallic Fe and Ni, formed during the process, were the catalysts for the growth of boron nitride nanotubes. Their formation was established by X-ray diffraction. FT Raman showed a peak due to B-N vibration of BNNTs close to 1370 cm(-1). Hence MoO3 assisted growth of boron nitride nanotubes is advantageous, as it significantly reduced the synthesis temperature.

The effect of copper doping on martensite shear stress in porous TiNi(Mo,Fe,Cu) alloys

NASA Astrophysics Data System (ADS)

Khodorenko, V. N.; Kaftaranova, M. I.; Gunther, V. E.

2015-03-01

The properties of alloys based on porous nickel-titanium (TiNi) with copper additives have been studied. It is established that the copper doping of porous TiNi(Mo,Fe,Cu) alloys fabricated by the method of self-propagating high-temperature synthesis leads to a significant decrease in the martensite shear stress (below 30 MPa). Low values of the martensite shear stress (σmin) in copper-doped TiNi-based alloys allows medical implants of complex shapes to be manufactured for various purposes, including oral surgery. The optimum concentration of copper additives (within 3-6 at %) has been determined that ensures high performance characteristics of TiNi-based porous alloys for medical implants.

Expression of the G72/G30 gene in transgenic mice induces behavioral changes

PubMed Central

Cheng, Lijun; Hattori, Eiji; Nakajima, Akira; Woehrle, Nancy S.; Opal, Mark D.; Zhang, Chunling; Grennan, Kay; Dulawa, Stephanie C.; Tang, Ya-Ping; Gershon, Elliot S.; Liu, Chunyu

2012-01-01

The G72/G30 gene complex is a candidate gene for schizophrenia and bipolar disorder. However, G72 and G30 mRNAs are expressed at very low levels in human brain, with only rare splicing forms observed. We report here G72/G30 expression profiles and behavioral changes in a G72/G30 transgenic mouse model. A human BAC clone containing the G72/G30 genomic region was used to establish the transgenic mouse model, on which gene expression studies, Western blot and behavioral tests were performed. Relative to their minimal expression in humans, G72 and G30 mRNAs were highly expressed in the transgenic mice, and had a more complex splicing pattern. The highest G72 transcript levels were found in testis, followed by cerebral cortex, with very low or undetectable levels in other tissues. No LG72 (the long putative isoform of G72) protein was detected in the transgenic mice. Whole-genome expression profiling identified 361 genes differentially-expressed in transgenic mice compared to wild-type, including genes previously implicated in neurological and psychological disorders. Relative to wild-type mice, the transgenic mice exhibited fewer stereotypic movements in the open field test, higher baseline startle responses in the course of the prepulse inhibition test, and lower hedonic responses in the sucrose preference test. The transcriptome profile changes and multiple mouse behavioral effects suggest that the G72 gene may play a role in modulating behaviors relevant to psychiatric disorders. PMID:23337943

Cation non-stoichiometry in pulsed laser deposited Sr{sub 2+y}Fe{sub 1+x}Mo{sub 1-x}O₆ epitaxial films

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

Meyer, T. L.; Woodward, P. M., E-mail: woodward.55@osu.edu; Dixit, M.

2014-07-07

Sr₂FeMoO₆ (SFMO) films were grown on SrTiO₃ (100)- and (111)-oriented substrates via pulsed laser deposition (PLD). In order to study the fundamental characteristics of deposition, films were grown in two different PLD chambers. In chamber I, the best films were grown with a relatively long substrate-to-target distance (89 mm), high substrate temperature (850 °C), and low pressure (50 mTorr) in a 95% Ar/5% H₂ atmosphere. Although X-ray diffraction (XRD) measurements indicate these films are single phase, Rutherford Backscattering (RBS) measurements reveal considerable non-stoichiometry, corresponding to a Sr₂Fe{sub 1–x}Mo{sub 1+x}O₆ composition with x≅0.2–0.3. This level of non-stoichiometry results in inferior magneticmore » properties. In chamber II, the best films were grown with a much shorter substrate-to-target distance (38 mm), lower temperature (680 °C), and higher pressure (225 mTorr). XRD measurements show that the films are single phase, and RBS measurements indicate that they are nearly stoichiometric. The degree of ordering between Fe and Mo was dependent on both the temperature and pressure used during deposition, reaching a maximum order parameter of 85%. The saturation magnetization increases as the Fe/Mo ordering increases, reaching a maximum of 2.4 μ B/f.u. Based on prior studies of bulk samples, one would expect a higher saturation magnetization for this degree of Fe/Mo order. The presence of extra strontium oxide layers in the form of Ruddlesden-Popper intergrowths appears to be responsible for the lower than expected saturation magnetization of these films.« less

Reduced molybenum-oxide-based core-shell hybrids: "blue" electrons are delocalized on the shell.

PubMed

Todea, Ana Maria; Szakács, Julia; Konar, Sanjit; Bögge, Hartmut; Crans, Debbie C; Glaser, Thorsten; Rousselière, Hélène; Thouvenot, René; Gouzerh, Pierre; Müller, Achim

2011-06-06

The present study refers to a variety of reduced metal-oxide core-shell hybrids, which are unique with regard to their electronic structure, their geometry, and their formation. They contain spherical {Mo72Fe30} Keplerate-type shells encapsulating Keggin-type polyoxomolybdates based on very weak interactions. Studies on the encapsulation of molybdosilicate as well as on the earlier reported molybdophosphate, coupled with the use of several physical methods for the characterization led to unprecedented results (see title). Upon standing in air at room temperature, acidified aqueous solutions obtained by dissolving sodium molybdate, iron(II) chloride, acetic acid, and molybdosilicic acid led to the precipitation of monoclinic greenish crystals (1). A rhombohedral variant (2) has also been observed. Upon drying at room temperature, compound 3 with a layer structure was obtained from 1 in a solid-state reaction based on cross-linking of the shells. The compounds 1, 2, and 3 have been characterized by a combination of methods including single-crystal X-ray crystallography, magnetic studies, as well as IR, Mössbauer, (resonance) Raman, and electronic absorption spectroscopy. In connection with detailed studies of the guest-free two-electron-reduced {Mo72Fe30}-type Keplerate (4) and of the previously reported molybdophosphate-based hybrids (including 31P NMR spectroscopy results), it is unambiguously proved that 1, 2, and 3 contain non-reduced Keggin ion cores and reduced {Mo72Fe30}-type shells. The results are discussed in terms of redox considerations (the shell as well as the core can be reduced) including those related to the reduction of "molybdates" by FeII being of interdisciplinary including catalytic interest (the MoVI/MoV and FeIII/FeII couples have very close redox potentials!), while also referring to the special formation of the hybrids based on chemical Darwinism.

Exchange Interactions on the Highest-Spin Reported Molecule: the Mixed-Valence Fe42 Complex

PubMed Central

Aravena, Daniel; Venegas-Yazigi, Diego; Ruiz, Eliseo

2016-01-01

The finding of high-spin molecules that could behave as conventional magnets has been one of the main challenges in Molecular Magnetism. Here, the exchange interactions, present in the highest-spin molecule published in the literature, Fe42, have been analysed using theoretical methods based on Density Functional Theory. The system with a total spin value S = 45 is formed by 42 iron centres containing 18 high-spin FeIII ferromagnetically coupled and 24 diamagnetic low-spin FeII ions. The bridging ligands between the two paramagnetic centres are two cyanide ligands coordinated to the diamagnetic FeII cations. Calculations were performed using either small Fe4 or Fe3 models or the whole Fe42 complex, showing the presence of two different ferromagnetic couplings between the paramagnetic FeIII centres. Finally, Quantum Monte Carlo simulations for the whole system were carried out in order to compare the experimental and simulated magnetic susceptibility curves from the calculated exchange coupling constants with the experimental one. This comparison allows for the evaluation of the accuracy of different exchange-correlation functionals to reproduce such magnetic properties. PMID:27033418

Exchange Interactions on the Highest-Spin Reported Molecule: the Mixed-Valence Fe42 Complex

NASA Astrophysics Data System (ADS)

Aravena, Daniel; Venegas-Yazigi, Diego; Ruiz, Eliseo

2016-04-01

The finding of high-spin molecules that could behave as conventional magnets has been one of the main challenges in Molecular Magnetism. Here, the exchange interactions, present in the highest-spin molecule published in the literature, Fe42, have been analysed using theoretical methods based on Density Functional Theory. The system with a total spin value S = 45 is formed by 42 iron centres containing 18 high-spin FeIII ferromagnetically coupled and 24 diamagnetic low-spin FeII ions. The bridging ligands between the two paramagnetic centres are two cyanide ligands coordinated to the diamagnetic FeII cations. Calculations were performed using either small Fe4 or Fe3 models or the whole Fe42 complex, showing the presence of two different ferromagnetic couplings between the paramagnetic FeIII centres. Finally, Quantum Monte Carlo simulations for the whole system were carried out in order to compare the experimental and simulated magnetic susceptibility curves from the calculated exchange coupling constants with the experimental one. This comparison allows for the evaluation of the accuracy of different exchange-correlation functionals to reproduce such magnetic properties.

Effect of mo Content on Microstructure and Properties of Laser Cladding Fe-BASED Alloy Coatings

NASA Astrophysics Data System (ADS)

Xiaoli, Ma; Kaiming, Wang; Hanguang, Fu; Jiang, Ju; Yongping, Lei; Dawei, Yi

Mo alloying Fe-based coating was fabricated on the surface of Q235 steel by using 6 kW fiber laser. The effects of Mo additions on the microstructure, microhardness and wear resistance of the cladding layer were studied by means of optical microscopy (OM), scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS), Vickers hardness tester and M-200 ring block wear tester. Research results showed that the microstructure of Mo-free cladding layer mainly consisted of matrix and eutectic structure. The matrix was martensite and retained austenite. The eutectic structure mainly consisted of M2(B,C) and M7(C,B)3 type of eutectic borocarbides. With the increase of Mo content, there was no significant change in the matrix. However, the eutectic structure was transformed from M2(B,C)- and M7(C,B)3-type borocarbides into M2(B,C)-, M7(C,B)3- and M23(C,B)6-type borocarbides. When the content of Mo is 4.0wt.%, the Mo2C-type carbide appear on the matrix, and parts of the borocarbide networks are broken. The change of microhardness of the cladding layer was not obvious with the increase of Mo content. But the increase of Mo content increases the wear resistance of the cladding layer. The wear resistance of cladding layer with 4.0wt.% Mo is 2.4 times as much as the cladding layer which is Mo-free.

Tunable properties of spin waves in magnetoelastic {NiFe}/{{Gd}}_{2}{({{MoO}}_{4})}_{3} heterostructure

NASA Astrophysics Data System (ADS)

Graczyk, Piotr; Trzaskowska, Aleksandra; Załȩski, Karol; Mróz, Bogusław

2016-07-01

Full ferroelastic and simultaneously ferroelectric materials are interesting candidates for applications in devices based on multiferroic heterostructures. They should allow for non-volatile and low-power writing of data bits in magnetoelectric random access memories. Moreover, ferroelasticity, in contrast to piezoelectric material, make magnetic information in ferromagnetic film resistant to external fields. As an example for such a system, we have studied the magnetoelastic interaction between a thin ferromagnetic layer of {{Ni}}85{{Fe}}15 with a full ferroelastic-ferroelectric gadolinium molybdate {{Gd}}2{({{MoO}}4)}3 crystal. We have investigated the influence of {{Gd}}2{({{MoO}}4)}3 spontaneous strain onto magnetic properties of thin ferromagnetic film. Particularly, we have shown by Brillouin spectroscopy, that it is possible to modulate surface spin wave frequency of {{Ni}}85{{Fe}}15 by spontaneous strain of gadolinium molybdate substrate.

Superconducting molybdenum-rhenium electrodes for single-molecule transport studies

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

Gaudenzi, R.; Island, J. O.; Bruijckere, J. de

2015-06-01

We demonstrate that electronic transport through single molecules or molecular ensembles, commonly based on gold (Au) electrodes, can be extended to superconducting electrodes by combining gold with molybdenum-rhenium (MoRe). This combination induces proximity-effect superconductivity in the gold to temperatures of at least 4.6 K and magnetic fields of 6 T, improving on previously reported aluminum based superconducting nanojunctions. As a proof of concept, we show three-terminal superconductive transport measurements through an individual Fe{sub 4} single-molecule magnet.

High pressure studies of A{sub 2}Mo{sub 3}O{sub 12} negative thermal expansion materials (A{sub 2}=Al{sub 2}, Fe{sub 2}, FeAl, AlGa)

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

Young, Lindsay; Gadient, Jennifer; Gao, Xiaodong

2016-05-15

High pressure powder X-ray diffraction studies of several A{sub 2}Mo{sub 3}O{sub 12} materials (A{sub 2}=Al{sub 2}, Fe{sub 2}, FeAl, and AlGa) were conducted up to 6–7 GPa. All materials adopted a monoclinic structure under ambient conditions, and displayed similar phase transition behavior upon compression. The initial isotropic compressibility first became anisotropic, followed by a small but distinct drop in cell volume. These patterns could be described by a distorted variant of the ambient pressure polymorph. At higher pressures, a distinct high pressure phase formed. Indexing results confirmed that all materials adopted the same high pressure phase. All changes were reversiblemore » on decompression, although some hysteresis was observed. The similarity of the high pressure cells to previously reported Ga{sub 2}Mo{sub 3}O{sub 12} suggested that this material undergoes the same sequence of transitions as all materials investigated in this paper. It was found that the transition pressures for all phase changes increased with decreasing radius of the A-site cations. - Graphical abstract: Overlay of variable pressure X-ray diffraction data of Al{sub 2}Mo{sub 3}O{sub 12} collected in a diamond anvil cell. Both subtle and discontinuous phase transitions are clearly observed. - Highlights: • The high pressure behavior of A{sub 2}Mo{sub 3}O{sub 12} (A=Al, Fe, (AlGa), (AlFe)) was studied. • All compounds undergo the same sequence of pressure-induced phase transitions. • The phase transition pressures correlate with the average size of the A-site cation. • All transitions were reversible with hysteresis. • Previously studied Ga{sub 2}Mo{sub 3}O{sub 12} undergoes the same sequence of transitions.« less

Exchange bias in zinc ferrite-FeNiMoB based metallic glass composite thin films

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

R, Lisha; P, Geetha; B, Aravind P.

2015-06-24

The Exchange bias phenomenon and methods to manipulate the bias field in a controlled manner are thrust areas in magnetism due to its sophisticated theoretical concepts as well as advanced technological utility in the field of spintronics. The Exchange bias effect is observed as a result of ferromagnetic-antiferromagnetic (FM-AFM) exchange interaction, usually observed as a loop shift on field cooling below the Neel temperature of AFM. In the present study, we have chosen zinc ferrite which is a well known antiferromagnet, and FeNiMoB based metallic glass as the ferromagnet. The films were prepared by RF sputtering technique. The thickness andmore » composition was obtained by RBS. The magnetic studies using SQUID VSM indicate exchange bias effect in the system. The effect of thermal annealing on exchange bias effect was studied. The observed exchange bias in the zinc ferrite-FeNiMoB system is not due to FM-AFM coupling but due to spin glass-ferromagnetic interaction.« less

Exchange bias in zinc ferrite-FeNiMoB based metallic glass composite thin films

NASA Astrophysics Data System (ADS)

R, Lisha; T, Hysen; P, Geetha; B, Aravind P.; Ojha, S.; Avasthi, D. K.; Ramanujan, R. V.; Anantharaman, M. R.

2015-06-01

The Exchange bias phenomenon and methods to manipulate the bias field in a controlled manner are thrust areas in magnetism due to its sophisticated theoretical concepts as well as advanced technological utility in the field of spintronics. The Exchange bias effect is observed as a result of ferromagnetic-antiferromagnetic (FM-AFM) exchange interaction, usually observed as a loop shift on field cooling below the Neel temperature of AFM. In the present study, we have chosen zinc ferrite which is a well known antiferromagnet, and FeNiMoB based metallic glass as the ferromagnet. The films were prepared by RF sputtering technique. The thickness and composition was obtained by RBS. The magnetic studies using SQUID VSM indicate exchange bias effect in the system. The effect of thermal annealing on exchange bias effect was studied. The observed exchange bias in the zinc ferrite-FeNiMoB system is not due to FM-AFM coupling but due to spin glass-ferromagnetic interaction.

Modulation of B cell regulatory molecules CD22 and CD72 in myasthenia gravis and multiple sclerosis.

PubMed

Lu, Jiayin; Li, Jing; Zhu, Tai-qing; Zhang, Longbo; Wang, Yuzhong; Tian, Fa-fa; Yang, Huan

2013-06-01

B cell activation mediated by cluster of differentiation (CD) molecules plays an important role in B cell-related autoimmune diseases. CD22 and CD72 have been demonstrated to act as B cell inhibitory receptors in many autoimmune diseases. Activated B cells are involved in the pathogenesis of myasthenia gravis (MG) by secretion of anti-acetylcholine receptor (AchR) antibodies. However, the roles of CD22 and CD72 on B cells of MG are unknown. In this study, we detected the expression of CD22 and CD72 on B cells of MG, compared to multiple sclerosis (MS) patient controls and healthy controls by flow cytometry and quantitative real-time polymerase transcription chain reaction. Our data demonstrated that aberrant expression of CD72 exists on B cells of MG and MS patients and expression level of CD72 molecule has a significantly negative correlation with anti-AchR antibody levels in MG, which suggests that CD72 may be involved in the pathogenesis of MG and MS. There were no significant differences between study patients (MG, ocular MG, generalized MG, and MS) and healthy controls.

Strain induced enhancement of magnetization in Ba{sub 2}FeMoO{sub 6} based heterostructure with (Ba{sub x}Sr{sub 1-x})TiO{sub 3}

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

Kim, Kyeong-Won; Norton, David P.; Ghosh, Siddhartha, E-mail: ghoshsid@gmail.com

2016-05-14

High quality epitaxial Ba{sub 2}FeMoO{sub 6} thin films and Ba{sub 2}FeMoO{sub 6}–(Ba{sub x}Sr{sub 1−x})TiO{sub 3} bi-layer (BL) and superlattice (SL) structures were grown via pulsed laser deposition under low oxygen pressure, and their structural, magnetic, and magneto-transport properties were examined. Superlattice and bi-layer structures were confirmed by X-ray diffraction patterns. Low temperature magnetic measurement shows that the saturation magnetization (M{sub S}) is significantly higher for SLs and almost similar or lower for BLs, when compared to phase pure Ba{sub 2}FeMoO{sub 6} thin films. The variation of the coercive field (H{sub C}) follows exact opposite trend, where BL samples have highermore » H{sub C} and SL samples have lower H{sub C} than pure Ba{sub 2}FeMoO{sub 6} thin films. Also, a significant decrease of the Curie temperature is found in both BL and SL structures compared to pure Ba{sub 2}FeMoO{sub 6} thin films. Negative magneto-resistance is seen in all the BL and SL structures as well as in pure Ba{sub 2}FeMoO{sub 6} thin films. In contrast to the magnetic properties, the magneto-transport properties do not show much variation with induced strain.« less

Mechanistic studies on the reactions of PhS(-) or [MoS(4)](2)(-) with [M(4)(SPh)(10)](2)(-) (M = Fe or Co).

PubMed

Cui, Zhen; Henderson, Richard A

2002-08-12

Kinetic studies, using stopped-flow spectrophotometry, on the reactions of [M(4)(SPh)(10)](2)(-) (M = Fe or Co) with PhS(-) to form [M(SPh)(4)](2)(-) are described, as are the reactions between [M(4)(SPh)(10)](2)(-) and [MoS(4)](2)(-) to form [S(2)MoS(2)Fe(SPh)(2)](2)(-) or [S(2)MoS(2)CoS(2)MoS(2)](2)(-). The kinetics of the reactions with PhS(-) are consistent with an initial associative substitution mechanism involving attack of PhS(-) at one of the tetrahedral M sites of [M(4)(SPh)(10)](2)(-) to form [M(4)(SPh)(11)](3)(-). Subsequent or concomitant cleavage of a micro-SPh ligand, at the same M, initiates a cascade of rapid reactions which result ultimately in the complete rupture of the cluster and formation of [M(SPh)(4)](2)(-). The kinetics of the reaction between [M(4)(SPh)(10)](2)(-) and [MoS(4)](2)(-) indicate an initial dissociative substitution mechanism at low concentrations of [MoS(4)](2)(-), in which rate-limiting dissociation of a terminal thiolate from [M(4)(SPh)(10)](2)(-) produces [M(4)(SPh)(9)](-) and the coordinatively unsaturated M site is rapidly attacked by a sulfido group of [MoS(4)](2)(-). It is proposed that subsequent chelation of the MoS(4) ligand results in cleavage of an M-micro-SPh bond, initiating a cascade of reactions which lead to the ultimate break-up of the cluster and formation of the products, [S(2)MoS(2)Fe(SPh)(2)](2)(-) or [S(2)MoS(2)CoS(2)MoS(2)](2)(-). With [Co(4)(SPh)(10)](2)(-), at higher concentrations of [MoS(4)](2)(-), a further substitution pathway is evident which exhibits a second order dependence on the concentration of [MoS(4)](2)(-). The mechanistic picture of cluster disruption which emerges from these studies rationalizes the "all or nothing" reactivity of [M(4)(SPh)(10)](2)(-).

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

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

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

2016-05-23

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

Self-Recognition Between Two Almost Identical Macroions During Their Assembly: The Effects of pH and Temperature.

PubMed

Haso, Fadi; Li, Dong; Garai, Somenath; Pigga, Joseph M; Liu, Tianbo

2015-09-14

Two Keplerate-type macroions, [Mo(VI) 72 Fe(III) 30 O252 - (CH3 COO)12 {Mo2 O7 (H2 O)}2 {H2 Mo2 O8 (H2 O)}(H2 O)91 ]⋅ca. 150 H2 O= {Mo72 Fe30 } and [{Na(H2 O)12 }⊂{Mo(VI) 72 Cr(III) 30 O252 (CH3 COO)19 - (H2 O)94 }]⋅ca. 120 H2 O={Mo72 Cr30 }, with identical size and shape but different charge density, can self-assemble into spherical "blackberry"-like structures in aqueous solution by means of electrostatic interactions. These two macroanions can self-recognize each other and self-assemble into two separate types of homogeneous blackberries in their mixed dilute aqueous solution, in which they carry -7 and -5 net charges, respectively. Either adjusting the solution pH or raising temperature is expected to make the self-recognition more difficult, by making the charge densities of the two clusters closer, or by decreasing the activation energy barrier for the blackberry formation, respectively. Amazingly, the self-recognition behavior remains, as confirmed by dynamic and static light scattering, TEM, and energy dispersive spectroscopy techniques. The results prove that the self-recognition behavior of the macroions due to the long-range electrostatic interaction is universal and can be achieved when only minimum differences exist between two types of macroanions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Coherent Fe-rich nano-scale perovskite oxide phase in epitaxial Sr2FeMoO6 films grown on cubic and scandate substrates

NASA Astrophysics Data System (ADS)

Deniz, Hakan; Preziosi, Daniele; Alexe, Marin; Hesse, Dietrich

2017-01-01

We report the growth of high-quality epitaxial Sr2FeMoO6 (SFMO) thin films on various unconventional oxide substrates, such as TbScO3, DyScO3, and Sr2Al0.3Ga0.7TaO6 (SAGT) as well as on the most commonly used one, SrTiO3 (STO), by pulsed laser deposition. The films were found to contain a foreign nano-scale phase coherently embedded inside the SFMO film matrix. Through energy dispersive X-ray spectroscopy and scanning transmission electron microscopy, we identified the foreign phase to be Sr2-xFe1+yMo1-yO6, an off-stoichiometric derivative of the SFMO compound with Fe rich content (y ≈ 0.6) and a fairly identical crystal structure to SFMO. The films on STO and SAGT exhibited very good magnetic properties with high Curie temperature values. All the samples have fairly good conducting behavior albeit the presence of a foreign phase. Despite the relatively large number of items of the foreign phase, there is no significant deterioration in the properties of the SFMO films. We discuss in detail how magneto-transport properties are affected by the foreign phase.

Experimental partitioning of Tc, Mo, Ru, and Re between solid and liquid during crystallization in Fe-Ni-S 1

NASA Astrophysics Data System (ADS)

Lazar, C.; Walker, D.; Walker, R. J.

2004-02-01

Technetium isotopes 97Tc, 98Tc and 99Tc decay to 97Mo, 98Ru and 99Ru, with half-lives of 2.6 My, 4.1 My, and 0.21 My respectively. If there were early solar system processes that resulted in significant fractionation of Tc from the daughter elements, decay of extant Tc could have led to the creation of Mo and Ru isotopic heterogeneities. To assess the potential of metallic core crystallization to fractionate these elements, we examine the partitioning behavior of Tc relative to Re, Mo and Ru in the Fe-Ni-S system between solid metal and liquid metal alloy. The experimental evidence shows that Tc behaves more like the modestly compatible siderophile element Ru than the more highly compatible siderophile element Re, and that Tc is substantially more compatible than Mo. We also demonstrate a pressure effect in the partitioning of Mo during the crystallization of Fe-Ni-S melts. For a sulfur concentration in the liquid fraction of the core of 10 wt% (16.3 at%), the Jones and Malvin (1990) parameter is -ln(1-2 × 1.09 × 0.163) ≅ 0.44, which yields: D(Re) ≅ 4.1; D(Ru) ≅ 2.3; D(Tc) ≅ 1.7; D(Mo) Lo-P ≅ 1.0;.and D(Mo) Hi-P ≅ 0.5. Our results suggest that detectable Tc-induced isotopic anomalies (≥0.1 ɛ unit) in Ru and Mo could only be produced by unrealistically extreme degrees of crystallization of metal during asteroidal core fractionation, regardless of the time scales and initial Tc abundances involved.

Methyl transfer from Fe (and Mo) to Sn: formation of (eta(5)-C(5)H(5))M(CO)(n)Sn(t)Bu(2)Me (M = Fe, n = 2; M = Mo, n = 3) complexes from photochemical irradiation of (eta(5)-C(5)H(5))M(CO)(n)Me and (t)Bu(2)SnH(2).

PubMed

Sharma, Hemant K; Arias-Ugarte, Renzo; Metta-Magana, Alejandro; Pannell, Keith H

2010-07-07

Formation of an Sn-CH(3) bond, concomitantly with an Sn-M (M = Fe, Mo), is readily achieved from the photochemical reactions of (t)Bu(2)SnH(2) with (eta(5)-C(5)H(5))M(CO)(n)Me (M = Fe, n = 2; M = Mo, n = 3) via the intermediacy of (eta(5)-C(5)H(5))M(CO)(n)Sn(t)Bu(2)H.

Raman scattering tensors in thymine molecule from an ab initio MO calculation

NASA Astrophysics Data System (ADS)

Tsuboi, Masamichi; Kumakura, Akiko; Aida, Misako; Kaneko, Motohisa; Dupuis, Michel; Ushizawa, Koichi; Ueda, Toyotoshi

1997-03-01

Ab initio SCF MO calculations have been made of the thymine molecule for the permanent polarizability and the polarizability derivatives with respect to the normal coordinates. The latter correspond to the components of the Raman tensors, and each of these tensors was brought into a visualized form by a transformation of the tensor axes into the principal system. For a comparison with such computational findings, a polarized Raman spectroscopic measurement has been made of a single crystal of thymine with 488.0 nm excitation. For most of the in-plane vibrations, calculated tensors were found to be well correlated with the observed Raman scattering anisotropy. On the basis of such correlations, discussions are given as for the polarizability oscillations caused by the atomic displacements in the molecule.

High pressure studies of A2Mo3O12 negative thermal expansion materials (A2=Al2, Fe2, FeAl, AlGa)

NASA Astrophysics Data System (ADS)

Young, Lindsay; Gadient, Jennifer; Gao, Xiaodong; Lind, Cora

2016-05-01

High pressure powder X-ray diffraction studies of several A2Mo3O12 materials (A2=Al2, Fe2, FeAl, and AlGa) were conducted up to 6-7 GPa. All materials adopted a monoclinic structure under ambient conditions, and displayed similar phase transition behavior upon compression. The initial isotropic compressibility first became anisotropic, followed by a small but distinct drop in cell volume. These patterns could be described by a distorted variant of the ambient pressure polymorph. At higher pressures, a distinct high pressure phase formed. Indexing results confirmed that all materials adopted the same high pressure phase. All changes were reversible on decompression, although some hysteresis was observed. The similarity of the high pressure cells to previously reported Ga2Mo3O12 suggested that this material undergoes the same sequence of transitions as all materials investigated in this paper. It was found that the transition pressures for all phase changes increased with decreasing radius of the A-site cations.

Selective monovalent cation association and exchange around Keplerate polyoxometalate macroanions in dilute aqueous solutions.

PubMed

Pigga, Joseph M; Teprovich, Joseph A; Flowers, Robert A; Antonio, Mark R; Liu, Tianbo

2010-06-15

The interaction between water-soluble Keplerate polyoxometalate {Mo(72)Fe(30)} macroions and small countercations is explored by laser light scattering, anomalous small-angle X-ray scattering (ASAXS), and isothermal titration calorimetry (ITC) techniques. The macroions are found to be able to select the type of associated counterions based upon the counterions' valence state and hydrated size, when multiple types of additional cations are present in solution (even among different monovalent cations). The preference goes to the cations with higher valences or smaller hydrated sizes if the valences are identical. This counterion exchange process changes the magnitude of the macroion-counterion interaction and, thus, is reflected in the dimension of the self-assembled {Mo(72)Fe(30)} blackberry supramolecular structures. The hydrophilic macroions exhibit a competitive recognition of various monovalent counterions in dilute solutions. A critical salt concentration (CSC) for each type of cation exists for the blackberry formation of {Mo(72)Fe(30)} macroions, above which the blackberry size increases significantly with the increasing total ionic strength in solution. The CSC values are much smaller for cations with higher valences and also decrease with the cations' hydrated size for various monovalent cations. The change of blackberry size corresponding to the change of ionic strength in solution is reversible.

41 CFR 102-72.30 - What are the different types of delegations related to real estate leasing?

Code of Federal Regulations, 2014 CFR

2014-01-01

... types of delegations related to real estate leasing? 102-72.30 Section 102-72.30 Public Contracts and... REGULATION REAL PROPERTY 72-DELEGATION OF AUTHORITY Delegation of Authority § 102-72.30 What are the different types of delegations related to real estate leasing? Delegations related to real estate leasing...

41 CFR 102-72.30 - What are the different types of delegations related to real estate leasing?

Code of Federal Regulations, 2011 CFR

2011-01-01

... types of delegations related to real estate leasing? 102-72.30 Section 102-72.30 Public Contracts and... REGULATION REAL PROPERTY 72-DELEGATION OF AUTHORITY Delegation of Authority § 102-72.30 What are the different types of delegations related to real estate leasing? Delegations related to real estate leasing...

41 CFR 102-72.30 - What are the different types of delegations related to real estate leasing?

Code of Federal Regulations, 2010 CFR

2010-07-01

... types of delegations related to real estate leasing? 102-72.30 Section 102-72.30 Public Contracts and... REGULATION REAL PROPERTY 72-DELEGATION OF AUTHORITY Delegation of Authority § 102-72.30 What are the different types of delegations related to real estate leasing? Delegations related to real estate leasing...

41 CFR 102-72.30 - What are the different types of delegations related to real estate leasing?

Code of Federal Regulations, 2013 CFR

2013-07-01

... types of delegations related to real estate leasing? 102-72.30 Section 102-72.30 Public Contracts and... REGULATION REAL PROPERTY 72-DELEGATION OF AUTHORITY Delegation of Authority § 102-72.30 What are the different types of delegations related to real estate leasing? Delegations related to real estate leasing...

Atom probe study of B2 order and A2 disorder of the FeCo matrix in an Fe-Co-Mo-alloy.

PubMed

Turk, C; Leitner, H; Schemmel, I; Clemens, H; Primig, S

2017-07-01

The physical and mechanical properties of intermetallic alloys can be tailored by controlling the degree of order of the solid solution by means of heat treatments. FeCo alloys with an appropriate composition exhibit an A2-disorder↔B2-order transition during continuous cooling from the disordered bcc region. The study of atomic order in intermetallic alloys by diffraction and its influence on the material properties is well established, however, investigating magnetic FeCo-based alloys by conventional methods such as X-ray diffraction is quite challenging. Thus, the imaging of ordered FeCo-nanostructures needs to be done with high resolution techniques. Transmission electron microscopy investigations of ordered FeCo domains are difficult, due to the chemical and physical similarity of Fe and Co atoms and the ferromagnetism of the samples. In this work it will be demonstrated, that the local atomic arrangement of ordered and disordered regions in an industrial Fe-Co-Mo alloy can be successfully imaged by atom probe measurements supported by field ion microscopy and transmission Kikuchi diffraction. Furthermore, a thorough atom probe parameter study will be presented and field evaporation artefacts as a function of crystallographic orientation in Fe-Co-samples will be discussed. Copyright © 2017 Elsevier Ltd. All rights reserved.

30 CFR 72.503 - Determination of emissions; filter maintenance; definition of “introduced”.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Determination of emissions; filter maintenance; definition of âintroducedâ. 72.503 Section 72.503 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION...-Underground Areas of Underground Coal Mines § 72.503 Determination of emissions; filter maintenance...

30 CFR 72.503 - Determination of emissions; filter maintenance; definition of “introduced”.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Determination of emissions; filter maintenance; definition of âintroducedâ. 72.503 Section 72.503 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION...-Underground Areas of Underground Coal Mines § 72.503 Determination of emissions; filter maintenance...

30 CFR 72.503 - Determination of emissions; filter maintenance; definition of “introduced”.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Determination of emissions; filter maintenance; definition of âintroducedâ. 72.503 Section 72.503 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION...-Underground Areas of Underground Coal Mines § 72.503 Determination of emissions; filter maintenance...

30 CFR 72.503 - Determination of emissions; filter maintenance; definition of “introduced”.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Determination of emissions; filter maintenance; definition of âintroducedâ. 72.503 Section 72.503 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION...-Underground Areas of Underground Coal Mines § 72.503 Determination of emissions; filter maintenance...

30 CFR 72.503 - Determination of emissions; filter maintenance; definition of “introduced”.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Determination of emissions; filter maintenance; definition of âintroducedâ. 72.503 Section 72.503 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION...-Underground Areas of Underground Coal Mines § 72.503 Determination of emissions; filter maintenance...

Drospirenone and levonorgestrel in combination with either 30 or 20 mcg ethinylestradiol reduce soluble adhesion molecules in Brazilian women; cross-sectional study.

PubMed

Stocco, Bianca; Fumagalli, Helen Figueiredo; Franceschini, Silvio Antônio; Martinez, Edson Zangiacomi; Marzocchi-Machado, Cleni Mara; Toloi, Maria Regina Torqueti

2012-11-01

The objective of this study was to evaluate the effect of three contraceptive pills containing ethinylestradiol (EE) (20 or 30 mcg) in combination with drospirenone (DRSP) and levonorgestrel (LNG) on plasma concentration of adhesion molecules vascular cell adhesion molecule -1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1) and E-selectin. A cross-sectional study was conducted with 72 participants (18-30 years old) distributed into three groups that used oral contraceptives containing EE 20 or 30 mcg combined with DRSP 3 mg or EE 30 mcg/LNG 150 mcg for at least 6 months. The control group was comprised of nonusers of contraceptives. Soluble VCAM-1, soluble ICAM-1 and soluble E-selectin were evaluated by enzyme-linked immunosorbent assay. Compared to the control group, a significant decrease was found in VCAM-1 and ICAM-1 concentrations with use of DRSP/20 EE and LNG/30 EE. DRSP/20 EE and LNG/30 EE induce favorable changes in endothelial function. Copyright © 2012 Elsevier Inc. All rights reserved.

Effect of Tempering Temperature on the Microstructure and Properties of Fe-2Cr-Mo-0.12C Pressure Vessel Steel

NASA Astrophysics Data System (ADS)

Wang, Qi-wen; Li, Chang-sheng; Peng, Huan; Chen, Jie; Zhang, Jian

2018-03-01

To obtain the high-temperature strength and toughness of the medium-high-temperature-pressure steel, the microstructure evolution and mechanical properties of Fe-2Cr-Mo-0.12C steel subjected to three different tempering temperatures after being normalized were investigated. The results show that the microstructure of the sample, tempered in the range 675-725 °C for 50 min, did not change dramatically, yet the martensite/austenite constituents decomposed, and the bainite lath merged together and transformed into polygonal ferrite. At the same time, the precipitate size increased with an increase in tempering temperature. With the increase in the tempering temperature from 675 to 725 °C, the impact absorbed energy of the Fe-2Cr-Mo-0.12C steel at -40 °C increased from 257 to 325 J, and the high-temperature yield strength decreased; however, the high-temperature ultimate tensile strength tempered at 700 °C was outstanding (422-571 MPa) at different tested temperatures. The variations of the properties were attributed to the decomposition of M/A constituents and the coarsening of the precipitates. Fe-2Cr-Mo-0.12C steel normalized at 930 °C and tempered at 700 °C was found to have the best combination of ductility and strength.

Hydride Conformers of the Nitrogenase FeMo-cofactor Two-Electron Reduced State E2(2H), Assigned Using Cryogenic Intra Electron Paramagnetic Resonance Cavity Photolysis.

PubMed

Lukoyanov, Dmitriy A; Khadka, Nimesh; Yang, Zhi-Yong; Dean, Dennis R; Seefeldt, Lance C; Hoffman, Brian M

2018-03-24

Early studies in which nitrogenase was freeze-trapped during enzymatic turnover revealed the presence of high-spin ( S = 3 / 2 ) electron paramagnetic resonance (EPR) signals from the active-site FeMo-cofactor (FeMo-co) in electron-reduced intermediates of the MoFe protein. Historically denoted as 1b and 1c, each of the signals is describable as a fictitious spin system, S' = 1 / 2 , with anisotropic g' tensor, 1b with g' = [4.21, 3.76, ?] and 1c with g' = [4.69, ∼3.20, ?]. A clear discrepancy between the magnetic properties of 1b and 1c and the kinetic analysis of their appearance during pre-steady-state turnover left their identities in doubt, however. We subsequently associated 1b with the state having accumulated 2[e - /H + ], denoted as E 2 (2H), and suggested that the reducing equivalents are stored on the catalytic FeMo-co cluster as an iron hydride, likely an [Fe-H-Fe] hydride bridge. Intra-EPR cavity photolysis (450 nm; temperature-independent from 4 to 12 K) of the E 2 (2H)/1b state now corroborates the identification of this state as storing two reducing equivalents as a hydride. Photolysis converts E 2 (2H)/1b to a state with the same EPR spectrum, and thus the same cofactor structure as pre-steady-state turnover 1c, but with a different active-site environment. Upon annealing of the photogenerated state at temperature T = 145 K, it relaxes back to E 2 (2H)/1b. This implies that the 1c signal comes from an E 2 (2H) hydride isomer of E 2 (2H)/1b that stores its two reducing equivalents either as a hydride bridge between a different pair of iron atoms or an Fe-H terminal hydride.

Quality of Metal Deposited Flux Cored Wire With the System Fe-C-Si-Mn-Cr-Mo-Ni-V-Co

NASA Astrophysics Data System (ADS)

Gusev, Aleksander I.; Kozyrev, Nikolay A.; Osetkovskiy, Ivan V.; Kryukov, Roman E.; Kozyreva, Olga A.

2017-10-01

Studied the effect of the introduction of vanadium and cobalt into the charge powder fused wire system Fe-C-Si-Mn-Cr-Ni-Mo-V, used in cladding assemblies and equipment parts and mechanisms operating under abrasive and abrasive shock loads. the cored wires samples were manufactured in the laboratory conditions and using appropriate powder materials and as a carbonfluoride contained material were used the dust from gas purification of aluminum production, with the following components composition, %: Al2O3 = 21-46.23; F = 18-27; Na2O = 8-15; K2O = 0.4-6; CaO = 0.7-2.3; Si2O = 0.5-2.48; Fe2O3 = 2.1-3.27; C = 12.5-30.2; MnO = 0.07-0.9; MgO = 0.06-0.9; S = 0.09-0.19; P = 0.1-0.18. Surfacing was produced on the St3 metal plates in 6 layers under the AN-26C flux by welding truck ASAW-1250. Cutting and preparation of samples for research had been implemented. The chemical composition and the hydrogen content of the weld metal were determined by modern methods. The hardness and abrasion rate of weld metal had been measured. Conducted metallographic studies of weld metal: estimated microstructure, grain size, contamination of oxide non-metallic inclusions. Metallographic studies showed that the microstructure of the surfaced layer by cored wire system Fe-C-Si-Mn-Cr-Mo-Ni-V-Co is uniform, thin dendrite branches are observed. The microstructure consists of martensite, which is formed inside the borders of the former austenite grain retained austenite present in small amounts in the form of separate islands, and thin layers of δ-ferrite, which is located on the borders of the former austenite grains. Carried out an assessment the effect of the chemical composition of the deposited metal on the hardness and wear and hydrogen content. In consequence of multivariate correlation analysis, it was determined dependence to the hardness of the deposited layer and the wear resistance of the mass fraction of the elements included in the flux-cored wires of the system Fe-C-Si-Mn-Cr-Mo

Investigation of the synthesis, activation, and isosteric heats of CO2 adsorption of the isostructural series of metal-organic frameworks M3(BTC)2 (M = Cr, Fe, Ni, Cu, Mo, Ru).

PubMed

Wade, Casey R; Dincă, Mircea

2012-07-14

The synthesis, activation, and heats of CO(2) adsorption for the known members of the M(3)(BTC)(2) (HKUST-1) isostructural series (M = Cr, Fe, Ni, Zn, Ni, Cu, Mo) were investigated to gain insight into the impact of CO(2)-metal interactions for CO(2) storage/separation applications. With the use of modified syntheses and activation procedures, improved BET surface areas were obtained for M = Ni, Mo, and Ru. The zero-coverage isosteric heats of CO(2) adsorption were measured for the Cu, Cr, Ni, Mo, and Ru analogues and gave values consistent with those reported for MOFs containing coordinatively unsaturated metal sites, but lower than for amine functionalized materials. Notably, the Ni and Ru congeners exhibited the highest CO(2) affinities in the studied series. These behaviors were attributed to the presence of residual guest molecules in the case of Ni(3)(BTC)(2)(Me(2)NH)(2)(H(2)O) and the increased charge of the dimetal secondary building unit in [Ru(3)(BTC)(2)][BTC](0.5).

Studies on hydrothermal synthesis of photolumniscent rare earth (Eu3+ & Tb3+) doped NG@FeMoO4 for enhanced visible light photodegradation of methylene blue dye

NASA Astrophysics Data System (ADS)

Singh, R.; Kumar, M.; Khajuria, H.; Sharma, S.; Sheikh, H. Nawaz

2018-02-01

FeMoO4 nanorods and their rare earth (Eu3+ and Tb3+) doped composites with nitrogen doped graphene (NG) were synthesized by facile hydrothermal method in aqueous medium. X-ray diffraction (XRD) analysis of the as-synthesized samples was done to study the phase purity and crystalline nature. FTIR and Raman Spectroscopy have been studied for investigating the bonding in nanostructures. The surface morphology of the samples was investigated with field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The photolumniscent nature of the samples was investigated by the using the fluorescence spectrophotometer. The photocatalytic degradation efficiency of the prepared pure FeMoO4 and its rare earth doped composites with nitrogen doped graphene was evaluated as function of visible light irradiation versus concentration of methylene blue (MB dye). The prepared nanocomposites show enhanced photocatalytic efficiency as compared to the bare FeMoO4 nanorods.

Ultrasonic irradiation enhanced the ability of Fluorescein-DA-Fe(III) on sonodynamic and sonocatalytic damages of DNA molecules.

PubMed

Wu, Qiong; Chen, Xia; Jia, Lizhen; Wang, Yi; Sun, Ying; Huang, Xingjun; Shen, Yuxiang; Wang, Jun

2017-11-01

The interaction of DNA with Bis [N,N-bis (carboxymethyl) aminomethyl] fluorescein-Ferrous(III) (Fluorescein-DA-Fe(III)) with dual functional (sonodynamic and sonocatalytic) activity was studied by UV-vis spectroscopy, fluorescence spectroscopy, FT-IR spectroscopy, circular dichroism (CD) spectroscopy and viscosity measurements. And then, the damage of DNA caused by Fluorescein-DA-Fe(III) under ultrasonic irradiation (US) was researched by agarose gel electrophoresis and cytotoxicity assay. Meanwhile, some influenced factors such as ultrasonic irradiation time and Fluorescein-DA-Fe(III) concentration on the damage degree of DNA molecules were also examined. As a control, for Bis [N,N-bis (carboxymethyl) aminomethyl] fluorescein (Fluorescein-DA), the same experiments were carried out. The results showed that both Fluorescein-DA-Fe(III) and Fluorescein-DA can interact with DNA molecules. Under ultrasonic irradiation, Fluorescein-DA shows sonodynamic activity, which can damage DNA molecules. While, in the presence of Fe(III) ion, the Fluorescein-DA-Fe(III) displays not only sonodynamic activity but also sonocatalytic activity under ultrasonic irradiation, which injures DNA more serious than Fluorescein-DA. The researches confirmed the dual function (sonodynamic activity and sonocatalytic activity) of Fluorescein-DA-Fe(III) and expanded the usage of Fluorescein-DA-Fe(III) as a sonosensitizer in sonodynamic therapy (SDT). Copyright © 2017 Elsevier B.V. All rights reserved.

Effect of Molybdenum on the Corrosion Behavior of High-Entropy Alloys CoCrFeNi 2 and CoCrFeNi 2 Mo 0.25 under Sodium Chloride Aqueous Conditions

DOE PAGES

Rodriguez, Alvaro A.; Tylczak, Joseph H.; Gao, Michael C.; ...

2018-01-01

The corrosion behavior of high-entropy alloys (HEAs) CoCrFeNi 2 and CoCrFeNi 2 Mo 0.25 was investigated in 3.5 wt. percent sodium chloride (NaCl) at 25°C by electrochemical methods. Their corrosion parameters were compared to those of HASTELLOY® C-276 (UNS N10276) and stainless steel 316L (UNS 31600) to assess the suitability of HEAs for potential industrial applications in NaCl simulating seawater type environments. The corrosion rates were calculated using corrosion current determined from electrochemical experiments for each of the alloys. In addition, potentiodynamic polarization measurements can indicate active, passive, and transpassive behavior of the metal as well as potential susceptibility to pittingmore » corrosion. Cyclic voltammetry (CV) can confirm the alloy susceptibility to pitting corrosion. Electrochemical impedance spectroscopy (EIS) elucidates the corrosion mechanism under studied conditions. The results of the electrochemical experiments and scanning electron microscopy (SEM) analyses of the corroded surfaces revealed general corrosion on alloy CoCrFeNi 2 Mo 0.25 and HASTELLOY C-276 and pitting corrosion on alloy CoCrFeNi 2 and stainless steel 316L.« less

Effect of Molybdenum on the Corrosion Behavior of High-Entropy Alloys CoCrFeNi 2 and CoCrFeNi 2 Mo 0.25 under Sodium Chloride Aqueous Conditions

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

Rodriguez, Alvaro A.; Tylczak, Joseph H.; Gao, Michael C.

The corrosion behavior of high-entropy alloys (HEAs) CoCrFeNi 2 and CoCrFeNi 2 Mo 0.25 was investigated in 3.5 wt. percent sodium chloride (NaCl) at 25°C by electrochemical methods. Their corrosion parameters were compared to those of HASTELLOY® C-276 (UNS N10276) and stainless steel 316L (UNS 31600) to assess the suitability of HEAs for potential industrial applications in NaCl simulating seawater type environments. The corrosion rates were calculated using corrosion current determined from electrochemical experiments for each of the alloys. In addition, potentiodynamic polarization measurements can indicate active, passive, and transpassive behavior of the metal as well as potential susceptibility to pittingmore » corrosion. Cyclic voltammetry (CV) can confirm the alloy susceptibility to pitting corrosion. Electrochemical impedance spectroscopy (EIS) elucidates the corrosion mechanism under studied conditions. The results of the electrochemical experiments and scanning electron microscopy (SEM) analyses of the corroded surfaces revealed general corrosion on alloy CoCrFeNi 2 Mo 0.25 and HASTELLOY C-276 and pitting corrosion on alloy CoCrFeNi 2 and stainless steel 316L.« less

Characteristic features of the magnetoresistance in the ferrimagnetic (Sr2FeMoO6-δ) - dielectric (SrMoO4) nanocomposite

NASA Astrophysics Data System (ADS)

Demyanov, S.; Kalanda, N.; Yarmolich, M.; Petrov, A.; Lee, S.-H.; Yu, S.-C.; Oh, S. K.; Kim, D.-H.

2018-05-01

Magnetic metal-oxide compounds with high values of magnetoresistance (MR) have attracted huge interest for spintronic applications, among which Sr2FeMoO6-δ (SFMO) has been relatively less known compared to the cobaltites and manganites, despite 100% electrons spin-polarization degree and a high Curie temperature. Here, stable fabrication and systematic analysis of nanocomposites based on SFMO with SrMoO4 dielectric sheaths are presented. SFMO-SrMoO4 nanocomposites were fabricated as follows: synthesis of the SFMO single-phase nanopowders by the modified citrate-gel technique; compaction under high pressure; thermal treatment for sheaths formation around grains. The nanocomposite is observed to exhibit a transitional behavior of conductivity from metallic, which is characteristic for the SFMO to semiconductor one in the temperature range 4 - 300K under magnetic fields up to 10T. A negative MR is observed due to the spin-polarized charge carriers tunneling through dielectric sheaths. MR value reaches 43% under 8T at 10κ. The dielectric sheaths thickness was determined to be about 10 nm by electric breakdown voltage value at current-voltage characteristics curves. The breakdown is found to be a reversible process determined by collisional ionization of dielectric atoms in strong electric field depending on knocked-out electrons from the SrMoO4. It was found that MR changes sign in electric breakdown region, revealing the giant magnetoresistive properties.

Lead discovery and in silico 3D structure modeling of tumorigenic FAM72A (p17).

PubMed

Pramanik, Subrata; Kutzner, Arne; Heese, Klaus

2015-01-01

FAM72A (p17) is a novel neuronal protein that has been linked to tumorigenic effects in non-neuronal tissue. Using state of the art in silico physicochemical analyses (e.g., I-TASSER, RaptorX, and Modeller), we determined the three-dimensional (3D) protein structure of FAM72A and further identified potential ligand-protein interactions. Our data indicate a Zn(2+)/Fe(3+)-containing 3D protein structure, based on a 3GA3_A model template, which potentially interacts with the organic molecule RSM ((2s)-2-(acetylamino)-N-methyl-4-[(R)-methylsulfinyl] butanamide). The discovery of RSM may serve as potential lead for further anti-FAM72A drug screening tests in the pharmaceutical industry because interference with FAM72A's activities via RSM-related molecules might be a novel option to influence the tumor suppressor protein p53 signaling pathways for the treatment of various types of cancers.

Structural and electrochemical properties of Fe-doped Na2Mn3-xFex(P2O7)2 cathode material for sodium ion batteries

NASA Astrophysics Data System (ADS)

Liu, Huatao; Zhao, Yanming; Zhang, Hui; Lian, Xin; Dong, Youzhong; Kuang, Quan

2017-12-01

A series of Fe-doped Na2Mn3-xFex(P2O7)2 (x = 0.0, 0.5, 1.0, 1.5 and 2.0) compounds have been successfully prepared by using sol-gel method. Rietveld refinement results indicate that single phase Na2Mn3-xFex(P2O7)2 with triclinic structure can be obtained within 0 ≤ x ≤ 2 although no Na2Fe3(P2O7)2 existing under our experimental conditions, and the cell parameters (including a, b, c and V) are decreasing with the increasing of x. Our results reveal that Na2Mn3(P2O7)2 exhibits an electrochemical activity in the voltage range of 1.5 V-4.5 V vs. Na+/Na when using as the cathode material for SIBs although it gives a limited rate capability and poor capacity retention. However, the electrochemical performance of Fe-doped Na2Mn3-xFex(P2O7)2 (0 ≤ x ≤ 2) can be improved significantly where cycle performance and rate capability can be improved significantly than that of the pristine one. Sodium ion diffusion coefficient can be increased by about two orders of magnitude with the Fe-doping content higher than x = 0.5.

Electron doping effect on structural and magnetic phase transitions in Sr{sub 2-x}Nd{sub x}FeMoO{sub 6} double perovskites

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

Azad, A.K.; Eriksson, S.-G.; Khan, Abdullah

2006-05-15

Polycrystalline Sr{sub 2-x}Nd{sub x}FeMoO{sub 6} (x=0.0, 0.1, 0.2, 0.4) materials have been synthesized by a citrate co-precipitation method and studied by neutron powder diffraction (NPD) and magnetization measurements. Rietveld analysis of the temperature-dependent NPD data shows that the compounds (x=0.0, 0.1, 0.2) crystallize in the tetragonal symmetry in the range 10-400K and converts to cubic symmetry above 450K. The unit cell volume increases with increasing Nd{sup 3+} concentration, which is an electronic effect in order to change the valence state of the B-site cations. Antisite defects at the Fe-Mo sublattice increases with the Nd{sup 3+} doping. The Curie temperature wasmore » increased from 430K for x=0 to 443K for x=0.4. The magnetic moment of the Fe-site decreases while the Mo-site moment increases with electron doping. The antiferromagnetic arrangement causes the system to show a net ferrimagnetic moment.« less

Structural features and high-temperature transport in SrFe0.7Mo0.3O3-δ

NASA Astrophysics Data System (ADS)

Merkulov, O. V.; Markov, A. A.; Patrakeev, M. V.; Leonidov, I. A.; Shalaeva, E. V.; Tyutyunnik, A. P.; Kozhevnikov, V. L.

2018-02-01

The complex oxide SrFe0.7Mo0.3O3-δ was obtained by combustion of the organometallic precursor in air followed by annealing in an argon flow at 1350 °C, and characterized with the help of X-ray and electron diffraction methods. Oxygen nonstoichiometry and electrical conductivity data were collected in the oxygen partial pressure range from 10-19 to 0.5 atm at temperatures 750-950 °C. The as-prepared single phase oxide SrFe0.7Mo0.3O3-δ with the cubic double perovskite structure (SG Fm3m) is shown to undergo a structural transition to the tetragonal double perovskite phase (SG I4mmm) in the result of reducing treatment at pO2 = 10-12 atm and 950 °C. The ordered phases are characterized by a strong anti-site disordering of iron and molybdenum and nearly zero long-range ordering parameter. The maximal concentration of n-type carriers is about four times larger than of p-type carriers in the studied limits of oxygen pressure and temperature. The mobility of p-type carriers is found to vary within 0.02-0.03 cm2 V-1 s-1 with the migration energy of about 0.4 eV, while the n-type mobility being approximately twice higher does not practically depend on temperature. Such features as good electrical conductivity, which can rise up to 40 S cm-1 in reducing conditions and a considerable amount of oxygen vacancies favorable for fast oxygen ion transport are beneficial for application of SrFe0.7Mo0.3O3-δ as anode material in SOFCs and oxygen membrane for hydrogen generation by a water splitting.

22 CFR 72.30 - Provisions in a will or advanced directive regarding disposition of remains.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 22 Foreign Relations 1 2012-04-01 2012-04-01 false Provisions in a will or advanced directive regarding disposition of remains. 72.30 Section 72.30 Foreign Relations DEPARTMENT OF STATE PROTECTION AND WELFARE OF AMERICANS, THEIR PROPERTY AND ESTATES DEATHS AND ESTATES Real Property Overseas Belonging to A...

Water vapor effect on high-temperature oxidation behavior of Fe3Al intermetallics

PubMed Central

Chevalier, Sebastian; Juzon, Pitor; Przybylski, Kazimierz; Larpin, Jean-Pierre

2009-01-01

Fe3Al intermetallics (Fe3Al, Fe3Al-Zr, Fe3Al-Zr,Mo and Fe3Al-Zr, Mo, Nb) were oxidized at 950 °C in dry and humid (11 vol% water) synthetic air. Thermogravimetric measurements showed that the oxidation rates of the tested intermetallics were lower in humid air than in dry air (especially for Fe3Al-Zr, Mo and Fe3Al-Zr, Mo, Nb). The addition of small amounts of Zr, Mo or Nb improved the kinetics compared with that of the undoped Fe3Al. Fe3Al showed massive spallation, whereas Fe3Al-Zr, Fe3Al-Zr, Mo and Fe3Al-Zr, Mo, Nb produced a flat, adherent oxide layer. The rapid transformation of transient alumina into alpha alumina may explain the decrease in the oxidation rate in humid air. PMID:27877306

10 CFR 72.30 - Financial assurance and recordkeeping for decommissioning.

Code of Federal Regulations, 2012 CFR

2012-01-01

... CLASS C WASTE License Application, Form, and Contents § 72.30 Financial assurance and recordkeeping for... plan containing information on how reasonable assurance will be provided that funds will be available.... Prepayment may be in the form of a trust, escrow account, government fund, certificate of deposit, or deposit...

Adsorption of methyl orange on mesoporous γ-Fe2O3/SiO2 nanocomposites

NASA Astrophysics Data System (ADS)

Deligeer, W.; Gao, Y. W.; Asuha, S.

2011-02-01

Mesoporous γ-Fe2O3/SiO2 nanocomposite containing 30 mol% of γ-Fe2O3 was prepared by a template-free sol-gel method, and its removal ability for methyl orange (MO) was investigated. The nanocomposite was characterized using X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscope (SEM), Fourier transform infrared (FTIR) absorption measurements, nitrogen adsorption-desorption measurements, and magnetic measurements. The synthesized γ-Fe2O3/SiO2 nanocomposite has a mesoporous structure with an average pore size of 3.5 nm and a specific surface area of 245 m2/g, and it exhibits ferrimagnetic characteristics with the maximum saturation magnetization of 20.9 emu/g. The adsorption of MO on the nanocomposite reaches the maximum adsorbed percentage of ca. 80% within a few minutes, showing that most of MO can be removed in a short time. The MO adsorption data fit well with both Langmuir and Freundlich adsorption isotherms. The maximum adsorption capacity of MO is estimated to be 476 mg/g.

30 CFR 72.630 - Drill dust control at underground areas of underground mines.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Drill dust control at underground areas of underground mines. 72.630 Section 72.630 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT... dust control at underground areas of underground mines. (a) Dust resulting from drilling in rock shall...

10 CFR 72.30 - Financial assurance and recordkeeping for decommissioning.

Code of Federal Regulations, 2013 CFR

2013-01-01

... CLASS C WASTE License Application, Form, and Contents § 72.30 Financial assurance and recordkeeping for... review and approval a decommissioning funding plan that must contain: (1) Information on how reasonable... previous cost estimate. (d) If, in surveys made under 10 CFR 20.1501(a), residual radioactivity in soils or...

10 CFR 72.30 - Financial assurance and recordkeeping for decommissioning.

Code of Federal Regulations, 2014 CFR

2014-01-01

... CLASS C WASTE License Application, Form, and Contents § 72.30 Financial assurance and recordkeeping for... review and approval a decommissioning funding plan that must contain: (1) Information on how reasonable... previous cost estimate. (d) If, in surveys made under 10 CFR 20.1501(a), residual radioactivity in soils or...

Deoxygenation of glycolaldehyde and furfural on Mo2C/Mo(100)

NASA Astrophysics Data System (ADS)

McManus, Jesse R.; Vohs, John M.

2014-12-01

The desire to produce fuels and chemicals in an energy conscious, environmentally sympathetic approach has motivated considerable research on the use of cellulosic biomass feedstocks. One of the major challenges facing the utilization of biomass is finding effective catalysts for the efficient and selective removal of oxygen from the highly-oxygenated, biomass-derived platform molecules. Herein, a study of the reaction pathways for the biomass-derived platform molecule furfural and biomass-derived sugar model compound glycolaldehyde provides insight into the mechanisms of hydrodeoxygenation (HDO) on a model molybdenum carbide catalyst, Mo2C/Mo(100). Using temperature programmed desorption (TPD) and high resolution electron energy loss spectroscopy (HREELS), it was found that the Mo2C/Mo(100) catalyst was active for selective deoxygenation of the aldehyde carbonyl by facilitating adsorption of the aldehyde in an η2(C,O) bonding configuration. Furthermore, the catalyst showed no appreciable activity for furanic ring hydrogenation, highlighting the promise of relatively inexpensive Mo2C catalysts for selective HDO chemistry.

Specific heat and related thermophysical properties of liquid Fe-Cu-Mo alloy

NASA Astrophysics Data System (ADS)

Wang, Haipeng; Luo, Bingchi; Chang, Jian; Wei, Bingbo

2007-08-01

The specific heat and related thermophysical properties of liquid Fe77.5Cu13Mo9.5 monotectic alloy were investigated by an electromagnetic levitation drop calorimeter over a wide temperature range from 1482 to 1818 K. A maximum undercooling of 221 K (0.13 T m) was achieved and the specific heat was determined as 44.71 J·mol-1·K-1. The excess specific heat, enthalpy change, entropy change and Gibbs free energy difference of this alloy were calculated on the basis of experimental results. It was found that the calculated results by traditional estimating methods can only describe the solidification process under low undercooling conditions. Only the experimental results can reflect the reality under high undercooling conditions. Meanwhile, the thermal diffusivity, thermal conductivity, and sound speed were derived from the present experimental results. Furthermore, the solidified microstructural morphology was examined, which consists of (Fe) and (Cu) phases. The calculated interface energy was applied to exploring the correlation between competitive nucleation and solidification microstructure within monotectic alloy.

Thermodynamic modeling and experimental validation of the Fe-Al-Ni-Cr-Mo alloy system

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

Teng, Zhenke; Zhang, F; Miller, Michael K

2012-01-01

NiAl-type precipitate-strengthened ferritic steels have been known as potential materials for the steam turbine applications. In this study, thermodynamic descriptions of the B2-NiAl type nano-scaled precipitates and body-centered-cubic (BCC) Fe matrix phase for four alloys based on the Fe-Al-Ni-Cr-Mo system were developed as a function of the alloy composition at the aging temperature. The calculated phase structure, composition, and volume fraction were validated by the experimental investigations using synchrotron X-ray diffraction and atom probe tomography. With the ability to accurately predict the key microstructural features related to the mechanical properties in a given alloy system, the established thermodynamic model inmore » the current study may significantly accelerate the alloy design process of the NiAl-strengthened ferritic steels.« less

Structural classification of RAO3( MO) n compounds ( R =Sc, In, Y, or lanthanides; A =Fe(III), Ga, Cr, or Al; M =divalent cation; n = 1-11)

NASA Astrophysics Data System (ADS)

Kimizuka, Noboru; Mohri, Takahiko

1989-01-01

A series of new compounds RAO3( MO) n ( n = 1-11) having spinel, YbFe 2O 4, or InFeO 3(ZnO) n types of structures were newly synthesized ( R =Sc, In, Y, Lu, Yb, Tm, or Er; A =Fe(III), Ga, Cr, or Al; M =Mg, Mn, Fe(II), Co, Ni, Zn, or Cd) at elevated temperatures. The conditions of synthesis and the lattice constants for these compounds are reported. The stacking sequences of the InO 1.5, (FeZn)O 2.5, and ZnO layers for InFeO 3(ZnO) 10 and the TmO 1.5, (AlZn)O 2.5, and ZnO layers for TmAlO 3(ZnO) 11 are presented, respectively. The crystal structures of the( RAO3) m( MO) n phases ( R =Sc, In, Y, or lanthanide elements; A =Fe(III), Ga, Cr, or Al; M =divalent cation elements; m and n =integer) are classified into four crystal structure types (K 2NiF 4, CaFe 2O 4, YbFe 2O 4, and spinel), based upon the constituent cations R, A, and M

Production of carbon nanotubes: Chemical vapor deposition synthesis from liquefied petroleum gas over Fe-Co-Mo tri-metallic catalyst supported on MgO

NASA Astrophysics Data System (ADS)

Setyopratomo, P.; Wulan, Praswasti P. D. K.; Sudibandriyo, M.

2016-06-01

Carbon nanotubes were produced by chemical vapor deposition method to meet the specifications for hydrogen storage. So far, the various catalyst had been studied outlining their activities, performances, and efficiencies. In this work, tri-metallic catalyst consist of Fe-Co-Mo supported on MgO was used. The catalyst was prepared by wet-impregnation method. Liquefied Petroleum Gas (LPG) was used as carbon source. The synthesis was conducted in atmospheric fixed bed reactor at reaction temperature range 750 - 850 °C for 30 minutes. The impregnation method applied in this study successfully deposed metal component on the MgO support surface. It found that the deposited metal components might partially replace Mg(OH)2 or MgO molecules in their crystal lattice. Compare to the original MgO powder; it was significant increases in pore volume and surface area has occurred during catalyst preparation stages. The size of obtained carbon nanotubes is ranging from about 10.83 nm OD/4.09 nm ID up to 21.84 nm OD/6.51 nm ID, which means that multiwall carbon nanotubes were formed during the synthesis. Yield as much as 2.35 g.CNT/g.catalyst was obtained during 30 minutes synthesis and correspond to carbon nanotubes growth rate of 0.2 μm/min. The BET surface area of the obtained carbon nanotubes is 181.13 m2/g and around 50 % of which is contributed by mesopores. Micropore with half pore width less than 1 nm contribute about 10% volume of total micro and mesopores volume of the carbon nanotubes. The existence of these micropores is very important to increase the hydrogen storage capacity of the carbon nanotubes.

New high Tc multiferroics KBiFe2O5 with narrow band gap and promising photovoltaic effect

PubMed Central

Zhang, Ganghua; Wu, Hui; Li, Guobao; Huang, Qingzhen; Yang, Chongyin; Huang, Fuqiang; Liao, Fuhui; Lin, Jianhua

2013-01-01

Intrinsic polarization of ferroelectrics (FE) helps separate photon-generated charge carriers thus enhances photovoltaic effects. However, traditional FE with transition-metal cations (M) of d0 electron in MO6 network typically has a band gap (Eg) exceeding 3.0 eV. Although a smaller Eg (2.6 eV) can be obtained in multiferroic BiFeO3, the value is still too high for optimal solar energy applications. Computational “materials genome” searches have predicted several exotic MO6 FE with Eg < 2.0 eV, all thus far unconfirmed because of synthesis difficulties. Here we report a new FE compound with MO4 tetrahedral network, KBiFe2O5, which features narrow Eg (1.6 eV), high Curie temperature (Tc ~ 780 K) and robust magnetic and photoelectric activities. The high photovoltage (8.8 V) and photocurrent density (15 μA/cm2) were obtained, which is comparable to the reported BiFeO3. This finding may open a new avenue to discovering and designing optimal FE compounds for solar energy applications. PMID:23405279

A Weakest-Link Approach for Fatigue Limit of 30CrNiMo8 Steels (Preprint)

DTIC Science & Technology

2011-03-01

34Application of a Weakest-Link Concept to the Fatigue Limit of the Bearing Steel Sae 52100 in a Bainitic Condition," Fatigue and Fracture of...AFRL-RX-WP-TP-2011-4206 A WEAKEST-LINK APPROACH FOR FATIGUE LIMIT OF 30CrNiMo8 STEELS (PREPRINT) S. Ekwaro-Osire and H.V. Kulkarni Texas...2011 4. TITLE AND SUBTITLE A WEAKEST-LINK APPROACH FOR FATIGUE LIMIT OF 30CrNiMo8 STEELS (PREPRINT) 5a. CONTRACT NUMBER In-house 5b. GRANT

Preparation of Mo-Re-C samples containing Mo7Re13C with the β-Mn-type structure by solid state reaction of planetary-ball-milled powder mixtures of Mo, Re and C, and their crystal structures and superconductivity

NASA Astrophysics Data System (ADS)

Oh-ishi, Katsuyoshi; Nagumo, Kenta; Tateishi, Kazuya; Takafumi, Ohnishi; Yoshikane, Kenta; Sugiyama, Machiko; Oka, Kengo; Kobayashi, Ryota

2017-01-01

Mo-Re-C compounds containing Mo7Re13C with the β-Mn structure were synthesized with high-melting-temperature metals Mo, Re, and C powders using a conventional solid state method with a planetary ball milling machine instead of the arc melting method. Use of the ball milling machine was necessary to obtain Mo7Re13C with the β-Mn structure using the solid state method. Almost single-phase Mo7Re13C with a trace of impurity were obtained using the synthesis method. By XRF and lattice parameter measurements on the samples, Fe element existed in the compound synthesized using the planetary ball milling machine with a pot and balls made of steel, though Fe element was not detected in the compound synthesized using a pot and balls made of tungsten carbide. The former compound containg the Fe atom did not show superconductivity but the latter compound without the Fe atom showed superconductivity at 6.1 K.

Standard Gibbs energy of formation of Mo 3Te 4 by emf measurements

NASA Astrophysics Data System (ADS)

Mallika, C.; Sreedharan, O. M.

1990-03-01

The emf of the galvanic cells Pt, Mo, MoO 2¦8 YSZ¦'FeO', Fe, Pt (I) and Pt, Fe,'FeO' ¦8 YSZ¦MoO 2, Mo 3Te 4, MoTe 2(α), C, Pt (II) were measured over the temperature ranges 837 to 1151 K and 775 to 1196 K, respectively, using 8 mass% yttria-stabilized zirconia (8 YSZ) as the solid electrolyte. From the emf values, the partial molar Gibbs energy of solution of molybdenum in Mo 3Te 4/MoTe 2(α), Δ ḠMo was found to be Δ ḠMo ± 1.19 ( kJ/mol) = -025.08 + 0.00420T(K) . Using the literature data for the Gibbs energy of formation of MoTe 2(α). the expression ΔG° f( Mo3Te4, s) ± 5.97 (kj/mol) = -253.58 + 0.09214 T( K) was derived for the range 775 to 1196 K. A third-law analysis yielded a value of -209 ± 10 kJ/mol for ΔH° f.298o of Mo 3Te 4(s).

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

NASA Astrophysics Data System (ADS)

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

2014-12-01

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

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

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

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

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

Structure and magnetism in Co/X, Fe/Si, and Fe/(FeSi) multilayers

NASA Astrophysics Data System (ADS)

Franklin, Michael Ray

Previous studies have shown that magnetic behavior in multilayers formed by repeating a bilayer unit comprised of a ferromagnetic layer and a non-magnetic spacer layer can be affected by small structural differences. For example, a macroscopic property such as giant magnetoresistance (GMR) is believed to depend significantly upon interfacial roughness. In this study, several complimentary structural probes were used to carefully characterize the structure of several sputtered multilayer systems-Co/Ag, Co/Cu, Co/Mo, Fe/Si, and Fe//[FeSi/]. X-ray diffraction (XRD) studies were used to examine the long-range structural order of the multilayers perpendicular to the plane of the layers. Transmission electron diffraction (TED) studies were used to probe the long-range order parallel to the layer plane. X-ray Absorption Fine Structure (XAFS) studies were used to determine the average local structural environment of the ferromagnetic atoms. For the Co/X systems, a simple correlation between crystal structure and saturation magnetization is discovered for the Co/Mo system. For the Fe/X systems, direct evidence of an Fe-silicide is found for the /[FeSi/] spacer layer but not for the Si spacer layer. Additionally, differences were observed in the magnetic behavior between the Fe in the nominally pure Fe layer and the Fe contained in the /[FeSi/] spacer layers.

NH3 molecule adsorption on spinel-type ZnFe2O4 surface: A DFT and experimental comparison study

NASA Astrophysics Data System (ADS)

Zou, Cong-yang; Ji, Wenchao; Shen, Zhemin; Tang, Qingli; Fan, Maohong

2018-06-01

Ammonia (NH3) is a caustic environment pollutant which contributes to haze formation and water pollution. Zinc ferrite (ZnFe2O4) exhibits good catalytic activity in NH3 removal. The density functional theory (DFT) was applied to explore the interaction mechanism of NH3 molecule adsorption on spinel-type ZnFe2O4 (1 1 0) surface with GGA-PW91 method in atomic and electronic level. The results indicated that NH3 molecule preferred to adsorb on surface Zn atom with the formation of H3Nsbnd Zn coordinate bond over ZnFe2O4 (1 1 0) surface. The H3Nsbnd Zn state was exothermic process with adsorption energy of -203.125 kJ/mol. About 0.157e were transferred from NH3 molecule to the surface which resulted in strong interaction. Higher activation degree occurred in H3Nsbnd Zn configuration with two Nsbnd H bonds elongated and NH3 structure became more flat on the surface. The PDOS change of NH3 molecule was consistent with the result of adsorption energy. It was concluded that s orbital of NH3 (N) and s, p orbitals of Zn atom overlapped at -0.619 Ha. The p orbital of NH3 (N) has interaction with d orbital of Zn atom suggesting the hybridization between them. Based on NH3 removal experimental and XPS spectra results, NH3sbnd ZnFe2O4 interaction was mainly depended on the coordination between Zn atom and NH3 molecule. The DFT calculations have deepened our understanding on NH3sbnd ZnFe2O4 interaction system.

Enhancement of spin-Seebeck effect by inserting ultra-thin Fe{sub 70}Cu{sub 30} interlayer

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

Kikuchi, D., E-mail: d.kikuchi@imr.tohoku.ac.jp; WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577; Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Sendai 980-8577

2015-02-23

We report the longitudinal spin-Seebeck effects (LSSEs) for Pt/Fe{sub 70}Cu{sub 30}/BiY{sub 2}Fe{sub 5}O{sub 12} (BiYIG) and Pt/BiYIG devices. The LSSE voltage was found to be enhanced by inserting an ultra-thin Fe{sub 70}Cu{sub 30} interlayer. This enhancement decays sharply with increasing the Fe{sub 70}Cu{sub 30} thickness, suggesting that it is not due to bulk phenomena, such as a superposition of conventional thermoelectric effects, but due to interface effects related to the Fe{sub 70}Cu{sub 30} interlayer. Combined with control experiments using Pt/Fe{sub 70}Cu{sub 30} devices, we conclude that the enhancement of the LSSE voltage in the Pt/Fe{sub 70}Cu{sub 30}/BiYIG devices is attributedmore » to the improvement of the spin-mixing conductance at the Pt/BiYIG interfaces.« less

Rates of proton transfer to Fe-S-based clusters: comparison of clusters containing {MFe(mu(2)-S)(2)}n+ and {MFe(3)(mu(3)-S)(4)}n+ (M = Fe, Mo, or W) cores.

PubMed

Bates, Katie; Garrett, Brendan; Henderson, Richard A

2007-12-24

The rates of proton transfer from [pyrH]+ (pyr = pyrrolidine) to the binuclear complexes [Fe2S2Cl4]2- and [S2MS2FeCl2]2- (M = Mo or W) are reported. The reactions were studied using stopped-flow spectrophotometry, and the rate constants for proton transfer were determined from analysis of the kinetics of the substitution reactions of these clusters with the nucleophiles Br- or PhS- in the presence of [pyrH]+. In general, Br- is a poor nucleophile for these clusters, and proton transfer occurs before Br- binds, allowing direct measure of the rate of proton transfer from [pyrH]+ to the cluster. In contrast, PhS- is a better nucleophile, and a pathway in which PhS- binds preferentially to the cluster prior to proton transfer from [pyrH]+ usually operates. For the reaction of [Fe2S2Cl4]2- with PhS- in the presence of [pyrH]+ both pathways are observed. Comparison of the results presented in this paper with analogous studies reported earlier on cuboidal Fe-S-based clusters allows discussion of the factors which affect the rates of proton transfer in synthetic clusters including the nuclearity of the cluster core, the metal composition, and the nature of the terminal ligands. The possible relevance of these findings to the protonation sites of natural Fe-S-based clusters, including FeMo-cofactor from nitrogenase, are presented.

Fast decolorization of azo methyl orange via heterogeneous Fenton and Fenton-like reactions using alginate-Fe2+/Fe3+ films as catalysts.

PubMed

Quadrado, Rafael F N; Fajardo, André R

2017-12-01

The efficiency of Fenton and Fenton-like processes can be seriously affected by the continuous loss of iron ions and by the formation of solid sludge. Here, alginate (Alg) films were synthesized to stabilize iron ions (Fe 2+ and Fe 3+ ) and to enhance their catalytic activities towards the decolorization of methyl orange via heterogeneous Fenton and Fenton-like processes. Iron ions were ionically bond to the Alg molecules resulting in a three-dimensional network with specific structural and morphological features according to the valence states of iron. Our results demonstrated that both Alg-Fe 2+ and Alg-Fe 3+ films show highlighted catalytic activity for the decolorization of MO and high decolorization rates. Reuse experiments demonstrated that both films could be employed in at least five consecutive decolorization processes without losing their catalytic efficiency or stability. Taken together, our findings reveal that the Alg-Fe 2+ and Alg-Fe 3+ films may be suitable low-cost catalysts in heterogeneous Fenton and Fenton-like processes. Copyright © 2017 Elsevier Ltd. All rights reserved.

Enhanced magnetocaloric properties and critical behavior of (Fe0.72Cr0.28)3Al alloys for near room temperature cooling

NASA Astrophysics Data System (ADS)

Sharma, V.; Maheshwar Repaka, D. V.; Chaudhary, V.; Ramanujan, R. V.

2017-04-01

Magnetic cooling is an environmentally friendly, energy efficient, thermal management technology relying on high performance magnetocaloric materials (MCM). Current research has focused on low cost, corrosion resistant, rare earth (RE) free MCMs. We report the structural and magnetocaloric properties of novel, low cost, RE free, iron based (Fe0.72Cr0.28)3Al alloys. The arc melted buttons and melt spun ribbons possessed the L21 crystal structure and B2 crystal structure, respectively. A notable enhancement of 33% in isothermal entropy change (-ΔS m) and 25% increase in relative cooling power (RCP) for the ribbons compared to the buttons can be attributed to higher structural disorder in the Fe-Cr and Fe-Al sub-lattices of the B2 structure. The critical behavior was investigated using modified Arrott plots, the Kouvel-Fisher plot and the critical isotherm technique; the critical exponents were found to correspond to the short-range order 3D Heisenberg model. The field and temperature dependent magnetization curves of (Fe0.72Cr0.28)3Al alloys revealed their soft magnetic nature with negligible hysteresis. Thus, these alloys possess promising performance attributes for near room temperature magnetic cooling applications.

Magnetostrictive GMR spin valves with composite FeGa/FeCo free layers

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

Liu, Luping; Institute of Materials Science, School of Materials Science and Engineering, Shanghai University, Shanghai 200072; Zhan, Qingfeng, E-mail: zhanqf@nimte.ac.cn, E-mail: runweili@nimte.ac.cn

2016-03-15

We have fabricated strain-sensitive spin valves on flexible substrates by utilizing the large magnetostrictive FeGa alloy to promote the strain sensitivity and the composite free layer of FeGa/FeCo to avoid the drastic reduction of giant magnetoresistance (GMR) ratio. This kind of spin valve (SV-FeGa/FeCo) displays a MR ratio about 5.9%, which is comparable to that of the conventional spin valve (SV-FeCo) with a single FeCo free layer. Different from the previously reported works on magnetostrictive spin valves, the SV-FeGa/FeCo displays an asymmetric strain dependent GMR behavior. Upon increasing the lateral strain, the MR ratio for the ascending branch decreases moremore » quickly than that for the descending branch, which is ascribed to the formation of a spiraling spin structure around the FeGa/FeCo interface under the combined influences of both magnetic field and mechanical strain. A strain sensitivity of GF = 7.2 was achieved at a magnetic bias field of -30 Oe in flexible SV-FeGa/FeCo, which is significantly larger than that of SV-FeCo.« less

Hierarchical Fe3O4@MoS2/Ag3PO4 magnetic nanocomposites: Enhanced and stable photocatalytic performance for water purification under visible light irradiation

NASA Astrophysics Data System (ADS)

Guo, Na; Li, Haiyan; Xu, Xingjian; Yu, Hongwen

2016-12-01

Novel hierarchical Fe3O4@MoS2/Ag3PO4 magnetic nanophotocatalyst with remarkable photocatalytic capability were prepared by simply depositing the Ag3PO4 onto the surface of crumpled Fe3O4@MoS2 nanosphere. The nanocomposites were characterized by XRD, TEM, HRTEM, XPS, BET, and UV-vis DRS. The outcome of the photocatalytic experiments demonstrated that Fe3O4@MoS2/Ag3PO4 with 6 wt% content of Ag3PO4 (FM/A-6%) showed the highest photocatalytic activity upon the degradation Congo red (CR) and Rhodamine B (RhB) under both visible light and simulated sunlight irradiation. In addition, FM/A-6% possessed larger specific surface area (76.56 m2/g) and excellent optical property. The possible Z-scheme charge carriers transfer mechanism for the enhanced photocatalytic properties of the FM/A-6% was also discussed. The Z-scheme charge carriers transfer mechanism established between MoS2 and Ag3PO4 facilitate the charge separation efficiency. Moreover, FM/A-6% can be separated and collected easily by external magnetic field and maintain high activity after five times photoreaction cycles. Given the remarkable photocatalytic performance and high stability of FM/A-6% nanocomposite, it is looking forward to exhibit great potential for applications in water purification.

Formation of Ultrafine Metal Particles by Gas-Evaporation VI. Bcc Metals, Fe, V, Nb, Ta, Cr, Mo and W

NASA Astrophysics Data System (ADS)

Saito, Yahachi; Mihama, Kazuhiro; Uyeda, Ryozi

1980-09-01

The crystal structures and habits of bcc metal particles have been investigated systematically by electron microscopy. The habits for the bcc structure are rhombic dodecahedra truncated by six {100} faces with various degrees of truncation from 0 to 100%. The truncation degree for Fe and V particles grown in the intermediate zone of a metal smoke is in good agreement with that for the Wulff polyhedron expected from the surface energies calculated for {110} and {100} faces. Particles of Cr, Mo and W have the A-15 type structure besides the ordinary bcc structure. The present results support the hypothesis that the A-15 type structure is stable when the particle size is small. The habits for the A-15 type structure are rhombic dodecahedra (Cr), {211} icositetrahedra (Cr and Mo) and rounded cubes (Mo and W).

Study of structural phase transitions in quinary TiNi(MoFeAg)-based alloys

NASA Astrophysics Data System (ADS)

Gunther, Victor; Marchenko, Ekaterina; Chekalkin, Timofey; Baigonakova, Gulsharat; Kang, Ji-hoon; Kim, Ji-soon; Klopotov, Anatoliy

2017-10-01

The structural phase transitions of quinary Ti50Ni49.5-X Mo0.3Fe0.2Ag X (X  =  0, 0.1, 0.2, 0.5, 1.0, and 1.5 at%) alloys prepared by vacuum-induction melting were studied by means of the four-point-probe, x-ray diffraction (XRD), and optical microscopy methods after thermal cycling. The two-stage B2 ↔ R ↔ B19‧ reversible martensitic transformation (MT) took place in all the investigated samples. It is found that the substitution of Ag for Ni in the studied alloy when C Ag  =  0-0.5 at%, reduces the T R, M s, and M f characteristic points by 20-30 K, whereas they increase by 15-35 K when the Ag content was varied from 1.0 to 1.5 at% and the B2 ↔ R ↔ B19‧ MT was realized in the high-temperature area. XRD patterns of the studied alloys recorded at the ambient temperature detected the pure Ag phase as well as Ti2Ni precipitate with a small volume fraction (up to 5%) alongside with structural lines of B2, R, and B19‧ phases.

30 CFR 72.701 - Respiratory equipment; gas, dusts, fumes, or mists.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Respiratory equipment; gas, dusts, fumes, or... LABOR COAL MINE SAFETY AND HEALTH HEALTH STANDARDS FOR COAL MINES Miscellaneous § 72.701 Respiratory equipment; gas, dusts, fumes, or mists. Respiratory equipment approved by NIOSH under 42 CFR part 84 shall...

Preparation of Mo-Re-C samples containing Mo{sub 7}Re{sub 13}C with the β-Mn-type structure by solid state reaction of planetary-ball-milled powder mixtures of Mo, Re and C, and their crystal structures and superconductivity

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

Oh-ishi, Katsuyoshi, E-mail: oh-ishi@kc.chuo-u.ac.jp; Nagumo, Kenta; Tateishi, Kazuya

Mo-Re-C compounds containing Mo{sub 7}Re{sub 13}C with the β-Mn structure were synthesized with high-melting-temperature metals Mo, Re, and C powders using a conventional solid state method with a planetary ball milling machine instead of the arc melting method. Use of the ball milling machine was necessary to obtain Mo{sub 7}Re{sub 13}C with the β-Mn structure using the solid state method. Almost single-phase Mo{sub 7}Re{sub 13}C with a trace of impurity were obtained using the synthesis method. By XRF and lattice parameter measurements on the samples, Fe element existed in the compound synthesized using the planetary ball milling machine with amore » pot and balls made of steel, though Fe element was not detected in the compound synthesized using a pot and balls made of tungsten carbide. The former compound containg the Fe atom did not show superconductivity but the latter compound without the Fe atom showed superconductivity at 6.1 K. - Graphical abstract: Temperature dependence of the magnetic susceptibility measured under 10 Oe for the superconducting PBM-T samples without Fe element and non-superconducting PBM-S with Fe element. The inset is the enlarged view of the data for the PBM-S sample.« less

The Fe-Rich Clay Microsystems in Basalt-Komatiite Lavas: Importance of Fe-Smectites for Pre-Biotic Molecule Catalysis During the Hadean Eon

NASA Astrophysics Data System (ADS)

Meunier, Alain; Petit, Sabine; Cockell, Charles S.; El Albani, Abderrazzak; Beaufort, Daniel

2010-06-01

During the Hadean to early Archean period (4.5-3.5 Ga), the surface of the Earth’s crust was predominantly composed of basalt and komatiite lavas. The conditions imposed by the chemical composition of these rocks favoured the crystallization of Fe-Mg clays rather than that of Al-rich ones (montmorillonite). Fe-Mg clays were formed inside chemical microsystems through sea weathering or hydrothermal alteration, and for the most part, through post-magmatic processes. Indeed, at the end of the cooling stage, Fe-Mg clays precipitated directly from the residual liquid which concentrated in the voids remaining in the crystal framework of the mafic-ultramafic lavas. Nontronite-celadonite and chlorite-saponite covered all the solid surfaces (crystals, glass) and are associated with tiny pyroxene and apatite crystals forming the so-called “mesostasis”. The mesostasis was scattered in the lava body as micro-settings tens of micrometres wide. Thus, every square metre of basalt or komatiite rocks was punctuated by myriads of clay-rich patches, each of them potentially behaving as a single chemical reactor which could concentrate the organics diluted in the ocean water. Considering the high catalytic potentiality of clays, and particularly those of the Fe-rich ones (electron exchangers), it is probable that large parts of the surface of the young Earth participated in the synthesis of prebiotic molecules during the Hadean to early Archean period through innumerable clay-rich micro-settings in the massive parts and the altered surfaces of komatiite and basaltic lavas. This leads us to suggest that Fe,Mg-clays should be preferred to Al-rich ones (montmorillonite) to conduct experiments for the synthesis and the polymerisation of prebiotic molecules.

Highly Enhanced Gas Adsorption Properties in Vertically Aligned MoS2 Layers.

PubMed

Cho, Soo-Yeon; Kim, Seon Joon; Lee, Youhan; Kim, Jong-Seon; Jung, Woo-Bin; Yoo, Hae-Wook; Kim, Jihan; Jung, Hee-Tae

2015-09-22

In this work, we demonstrate that gas adsorption is significantly higher in edge sites of vertically aligned MoS2 compared to that of the conventional basal plane exposed MoS2 films. To compare the effect of the alignment of MoS2 on the gas adsorption properties, we synthesized three distinct MoS2 films with different alignment directions ((1) horizontally aligned MoS2 (basal plane exposed), (2) mixture of horizontally aligned MoS2 and vertically aligned layers (basal and edge exposed), and (3) vertically aligned MoS2 (edge exposed)) by using rapid sulfurization method of CVD process. Vertically aligned MoS2 film shows about 5-fold enhanced sensitivity to NO2 gas molecules compared to horizontally aligned MoS2 film. Vertically aligned MoS2 has superior resistance variation compared to horizontally aligned MoS2 even with same surface area exposed to identical concentration of gas molecules. We found that electrical response to target gas molecules correlates directly with the density of the exposed edge sites of MoS2 due to high adsorption of gas molecules onto edge sites of vertically aligned MoS2. Density functional theory (DFT) calculations corroborate the experimental results as stronger NO2 binding energies are computed for multiple configurations near the edge sites of MoS2, which verifies that electrical response to target gas molecules (NO2) correlates directly with the density of the exposed edge sites of MoS2 due to high adsorption of gas molecules onto edge sites of vertically aligned MoS2. We believe that this observation extends to other 2D TMD materials as well as MoS2 and can be applied to significantly enhance the gas sensor performance in these materials.

Superparamagnetic behavior of Fe70Dy30 granular thin film

NASA Astrophysics Data System (ADS)

Mekala, Laxman; Muhammed Shameem P., V.; Kumar, M. Senthil

2018-04-01

In the present study, the structural and magnetic properties of the Fe70Dy30 thin films are investigated. The Fe70Dy30 thin film with a thickness of 250 Å is fabricated using a dc magnetron sputtering system. Structural and temperature dependent magnetic properties indicate the granular nature of the film. The nonsaturation of the magnetization curves even at high fields of 50 kOe and the obtained very low coercivity in the temperature range 50 - 300 K reveal that films are superparamagnetic (SPM). The decreasing blocking temperature (Tb) with increasing an external magnetic field in temperature dependent magnetization curves are exposed qualitatively.

Fe3O4-in-silica super crystal of defined interstices for single protein molecules entrapment under magnetic flux.

PubMed

Ye, Lin; Yu, Chih Hao; Jiang, PengJu; Qiu, Lin; Ng, Olivia T W; Yung, Ken K L; He, Heyong; Tsang, Shik Chi

2010-09-28

Confocal fluorescence demonstrates that single molecules of dye-labelled Cytochrome C or B5 containing paramagnetic Fe(III) can be magnetically placed into the interstices of super-crystal which is composed of three dimensional regular arrays of Fe(3)O(4) nanoparticles.

Calcined Mg-Fe layered double hydroxide as an absorber for the removal of methyl orange

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

Peng, Chao; State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070; Dai, Jing

2015-05-15

In this work, methyl orange (MO) was effectively removed from aqueous solution with the calcined product of hydrothermal synthesized Mg/Fe layered double hydroxide (Mg/Fe-LDH). The structure, composition, morphology and textural properties of the Mg/Fe-LDH before and after adsorption were characterized by X-ray diffraction, Fourier transformation infrared spectroscopy, transmission electron microscopy, nitrogen adsorption apparatus and X-ray photoelectron spectroscopy. It was confirmed that MO had been absorbed by calcined Mg/Fe-LDH which had strong interactions with MO. The adsorption of MO onto the Mg/Fe-LDH was systematically investigated by batch tests. The adsorption capacity of the Mg/Fe-LDH toward MO was found to be 194.9more » mg • g{sup −1}. Adsorption kinetics and isotherm studies revealed that the adsorption of MO onto Mg/Fe-LDH was a spontaneous and endothermic process. These results indicate that Mg/Fe-LDH is a promising material for the removal of MO.« less

Low-field magnetoresistance up to 400 K in double perovskite Sr{sub 2}FeMoO{sub 6} synthesized by a citrate route

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

Harnagea, L., E-mail: harnagealuminita@gmail.com; Jurca, B.; Physical Chemistry Department, University of Bucharest, 4-12 Bd. Elisabeta, 030018 Bucharest

2014-03-15

A wet-chemistry technique, namely the citrate route, has been used to prepare high-quality polycrystalline samples of double perovskite Sr{sub 2}FeMoO{sub 6}. We report on the evolution of magnetic and magnetoresistive properties of the synthesized samples as a function of three parameters (i) the pH of the starting solution, (ii) the decomposition temperature of the citrate precursors and (iii) the sintering conditions. The low-field magnetoresistance (LFMR) value of our best samples is as high as 5% at room temperature for an applied magnetic field of 1 kOe. Additionally, the distinguishing feature of these samples is the persistence of LFMR, with amore » reasonably large value, up to 400 K which is a crucial parameter for any practical application. Our study indicates that the enhancement of LFMR observed is due to a good compromise between the grain size distribution and their magnetic polarization. -- Graphical abstract: The microstructure (left panel) and corresponding low-field magnetoresistance of one of the Sr{sub 2}FeMoO{sub 6} samples synthesized in the course of this work. Highlights: • Samples of Sr{sub 2}FeMoO{sub 6} are prepared using a citrate route under varying conditions. • Magnetoresistive properties are improved and optimized. • Low-field magnetoresitence values as large as 5% at 300 K/1 kOe are reported. • Persistence of low-field magnetoresistance up to 400 K.« less

Temperature Driven Topological Switch in 1T'-MoTe2 and Strain Induced Nematicity in NaFeAs

NASA Astrophysics Data System (ADS)

Berger, Ayelet Denise Notis

Quasiparticle interference (QPI) is a powerful technique within Scanning Tunneling Microscopy (STM) that is used to probe the electronic bandstructure of materials. This thesis presents two examples using QPI to measure the bandstructure in materials with exotic electronic states that can be tuned via outside parameters (temperature and strain). In Part I of the thesis, we discuss the temperature dependence of Fermi Arcs in 1T'-MoTe 2, and then in Part II, the strain dependent nematic state in NaFeAs. The recent discovery of Weyl semimetals has introduced a new family of materials with topologically protected electronic properties and potential applications due to their anomalous transport effects. Even more useful is a Weyl semimetal that can be turned "on" and "off," switching between a topological and trivial state. One possible material is MoTe2, which undergoes a phase transition at 240K. This thesis consists of experiments using Scanning Tunneling Microscopy (STM) and Spectroscopy (STS) at different temperatures to visualize changes in the electronic bandstructure of MoTe2 across the topological phase transition. We show that a signature of topologically protected Fermi Arcs is present at low temperatures but disappears at room temperature, in the trivial phase. We include an in-depth discussion of how to account for thermal effects when comparing these two types of measurements. In Part II, we discuss strain induced nematicity in NaFeAs, an iron pnictide. Nematic fluctuations and spin correlations play an important role in the phase diagram of the iron pnictides, a family of unconventional superconductors. Illuminating the mechanism behind this symmetry breaking is key to understanding the superconducting state. Previous work has shown that nematicity in the iron pnictides responds strongly to applied strain [1, 2]. In this thesis, I present results from a new experimental technique, elasto-scanning tunneling microscopy (E-STM), which combines in situ strain

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

NASA Astrophysics Data System (ADS)

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

2018-01-01

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

Properties of complexes formed by Na(+), Mg(2+), and Fe(2+) binding with benzene molecules.

PubMed

Kolakkandy, Sujitha; Pratihar, Subha; Aquino, Adelia J A; Wang, Hai; Hase, William L

2014-10-09

A theoretical investigation was performed to study cation-π interactions in complexes of benzene (Bz) with cations, that is, M(z+)(Bz)n for M(z+) = Na(+), Mg(2+), Fe(2+) and n = 1-3, using MP2 theory with the 6-31+G* and 6-311++G** basis sets and the DFT/(B3LYP and B3LYP-D)/6-311++G** methods. Binding energies and structures of the complexes are reported. The splitting between the quintet and single states of the Fe(2+) complexes was found to depend on the number of benzene molecules in the complex and the complex's structure. All of the M(z+)(Bz) complexes prefer a half-sandwich geometry. A geometry with the cation sandwiched between the two benzene rings was found for the M(z+)(Bz)2 complexes, with the benzene rings either in an eclipsed or staggered conformation. An approximate cyclic structure, with the cation at its center, was found for three benzene molecules interacting with the cation. The cation-benzene binding energy is substantial and equal to 22, 108, and 151 kcal/mol for the Na(+)(Bz), Mg(2+)(Bz), and Fe(2+)(Bz) complexes, respectively. The strength of the interaction of the cation with an individual benzene molecule decreases as the number of benzene molecules bound to the cation increases; for example, it is 108 kcal/mol for Mg(2+)(Bz), but only 71 kcal/mol for Mg(2+)(Bz)3. There is a range of values for the M(z+)(Bz)n intermolecular vibrational frequencies; for example, they are ∼230-360 and ∼10-330 cm(-1) for the Mg(2+)(Bz) and Mg(2+)(Bz)3 complexes, respectively. Binding of the cation to benzene both red and blue shifts the benzene vibrational frequencies. This shifting is larger for the Mg(2+) and Fe(2+) complexes, as compared to those for Na(+), as a result of the former's stronger cation-benzene binding. The present study is an initial step to understand the possible importance of cation-π interactions for polycyclic aromatic hydrocarbon aggregation processes during soot formation.

Reduction of conductance mismatch in Fe/Al2O3/MoS2 system by tunneling-barrier thickness control

NASA Astrophysics Data System (ADS)

Hayakawa, Naoki; Muneta, Iriya; Ohashi, Takumi; Matsuura, Kentaro; Shimizu, Jun’ichi; Kakushima, Kuniyuki; Tsutsui, Kazuo; Wakabayashi, Hitoshi

2018-04-01

Molybdenum disulfide (MoS2) among two-dimensional semiconductor films is promising for spintronic devices because it has a longer spin-relaxation time with contrasting spin splitting than silicon. However, it is difficult to fabricate integrated circuits by the widely used exfoliation method. Here, we investigate the contact characteristics in the Fe/Al2O3/sputtered-MoS2 system with various thicknesses of the Al2O3 film. Current density increases with increasing thickness up to 2.5 nm because of both thermally-assisted and direct tunneling currents. On the other hand, it decreases with increasing thickness over 2.5 nm limited by direct tunneling currents. These results suggest that the Schottky barrier width can be controlled by changing thicknesses of the Al2O3 film, as supported by calculations. The reduction of conductance mismatch with this technique can lead to highly efficient spin injection from iron into the MoS2 film.

Density functional theory study of nitrogen atoms and molecules interacting with Fe(1 1 1) surfaces

NASA Astrophysics Data System (ADS)

Nosir, M. A.; Martin-Gondre, L.; Bocan, G. A.; Díez Muiño, R.

2016-09-01

We present Density functional theory (DFT) calculations for the investigation of the structural relaxation of Fe(1 1 1), as well as for the study of the interaction of nitrogen atoms and molecules with this surface. We perform spin polarized DFT calculations using VASP (Vienna Ab-initio Simulation Package) code. We use the supercell approach and up to 19 slab layers for the relaxation of the Fe(1 1 1) surface. We find a contraction of the first two interlayer distances with a relative value of Δ12 = - 7.8 % and Δ23 = - 21.7 % with respect to the bulk reference. The third interlayer distance is however expanded with a relative change of Δ34 = 9.7 % . Early experimental studies of the surface relaxation using Low Energy Electron Diffraction (LEED) and Medium Energy Ion Scattering (MEIS) showed contradictory results, even on the relaxation general trend. Our current theoretical results support the LEED conclusions and are consistent qualitatively with other recent theoretical calculations. In addition, we study the interaction energy of nitrogen atoms and molecules on the Fe(1 1 1) surface. The nitrogen atoms are adsorbed in the hollow site of the unit cell, with an adsorption energy consistent with the one found in previous studies. In addition, we find the three molecularly adsorbed states that are observed experimentally. Two of them correspond to the adsorbed molecule oriented normal to the surface and a third one corresponds to the molecule adsorbed parallel to the surface. We conclude that our results are accurate enough to be used to build a full six-dimensional potential energy surface for the N2 system.

The G72/G30 gene complex and cognitive abnormalities in schizophrenia.

PubMed

Goldberg, Terry E; Straub, Richard E; Callicott, Joseph H; Hariri, Ahmad; Mattay, Venkata S; Bigelow, Llewellyn; Coppola, Richard; Egan, Michael F; Weinberger, Daniel R

2006-09-01

A recently discovered gene complex, G72/G30 (hereafter G72, but now termed DAOA), was found to be associated with schizophrenia and with bipolar disorder, possibly because of an indirect effect on NMDA neurotransmission. In principle, if G72 increases risk for psychosis by this mechanism, it might impact with greater penetrance those cortically based cognitive and neurophysiological functions associated with NMDA signaling. We performed two independent family-based association studies (one sample contained more than 200 families and the other more than 65) of multiple SNPs in the G72 region and of multiple SNPs in the gene for D-amino acid oxidase (DAAO), which may be modulated by G72. We examined the relationship between select cognitive measures in attention, working memory, and episodic memory and a restricted set of G72 SNPs in over 600 normal controls, schizophrenic patients, and their nonpsychotic siblings using mixed model ANOVAs. We also determined genotype effects on neurophysiology measures in normal controls using the fMRI BOLD response obtained during activation procedures involving either episodic memory or working memory. There were no significant single G72 SNP associations and clinical diagnosis in either sample, though one approached significance (p=0.06). Diagnosis by genotype interaction effects for G72 SNP 10 were significant for cognitive variables assessing working memory and attention (p=0.05), and at the trend level for episodic memory, such that in the schizophrenia group an exaggerated allele load effect in the predicted directions was observed. In the fMRI paradigms, a strong effect of G72 SNP 10 genotype was observed on BOLD activation in the hippocampus during the episodic memory paradigm. Tests of association with DAAO were consistently nonsignificant. We present evidence that SNP variations in the G72 gene region increase risk of cognitive impairment in schizophrenia. SNP variations were not strongly associated with clinical diagnosis

Structural classification of RAO/sub 3/(MO)/sub n/ compounds (R = Sc, In, Y, or lanthanides; A = Fe(III), Ga, Cr, or Al; M = divalent cation; n = 1-11)

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

Kimizuka, N.; Mohri, T.

A series of new compounds (RAO/sub 3/MO)/sub n/ (n = 1-11) having spinel, YbFe/sub 2/O/sub 4/, or InFeO/sub 3/(ZnO)/sub n/ types of structures were newly synthesized (R = Sc, In, Y, Lu, Yb, Tm, or Er; A = Fe(III), Ga, Cr, or Al; M = Mg, Mn, Fe(II), Co, Ni, Zn, or Cd) at elevated temperatures. The conditions of synthesis and the lattice constants for these compounds are reported. The stacking sequences of the InO/sub 1.5/, (FeZn)O/sub 2.5/, and ZnO layers for InFeO/sub 3/(ZnO)/sub 10/ and the TmO/sub 1.5/, (AlZn)O/sub 2.5/, and ZnO layers for TmAlO/sub 3/(ZnO)/sub 11/ are presented,more » respectively. The crystal structures of the (RAO/sub 3/)/sub m/(MO)/sub n/ phases R = Sc, In, Y, or lanthanide elements; A = Fe(III), Ga, Cr, or Al; M = divalent cation elements; m and n = integer are classified into four crystal structure types (K/sub 2/NiF/sub 4/, CaFe/sub 2/O/sub 4/, YbFe/sub 2/O/sub 4/, and spinel), based upon the constituent cations R, A, and M.« less

All-atom force field for molecular dynamics simulations on organotransition metal solids and liquids. Application to M(CO)(n) (M = Cr, Fe, Ni, Mo, Ru, or W) compounds.

PubMed

Bernardes, Carlos E S; Canongia Lopes, José N; Minas da Piedade, Manuel E

2013-10-31

A previously developed OPLS-based all-atom force field for organometallic compounds was extended to a series of first-, second-, and third-row transition metals based on the study of M(CO)(n) (M = Cr, Fe, Ni, Mo, Ru, or W) complexes. For materials that are solid at ambient temperature and pressure (M = Cr, Mo, W) the validation of the force field was based on reported structural data and on the standard molar enthalpies of sublimation at 298.15 K, experimentally determined by Calvet-drop microcalorimetry using samples corresponding to a specific and well-characterized crystalline phase: Δ(sub)H(m)° = 72.6 ± 0.3 kJ·mol(–1) for Cr(CO)(6), 73.4 ± 0.3 kJ·mol(–1) for Mo(CO)(6), and 77.8 ± 0.3 kJ·mol(–1) for W(CO)(6). For liquids, where problems of polymorphism or phase mixtures are absent, critically analyzed literature data were used. The force field was able to reproduce the volumetric properties of the test set (density and unit cell volume) with an average deviations smaller than 2% and the experimentally determined enthalpies of sublimation and vaporization with an accuracy better than 2.3 kJ·mol(–1). The Lennard-Jones (12-6) potential function parameters used to calculate the repulsive and dispersion contributions of the metals within the framework of the force field were found to be transferable between chromium, iron, and nickel (first row) and between molybdenum and ruthenium (second row).

Magnetically Separable MoS2/Fe3O4/nZVI Nanocomposites for the Treatment of Wastewater Containing Cr(VI) and 4-Chlorophenol

PubMed Central

Wang, Jingkang; Wang, Ting

2017-01-01

With a large specific surface area, high reactivity, and excellent adsorption properties, nano zerovalent iron (nZVI) can degrade a wide variety of contaminants in wastewater. However, aggregation, oxidation, and separation issues greatly impede its wide application. In this study, MoS2/Fe3O4/nZVI nanocomposites were successfully synthesized by a facile step-by-step approach to overcome these problems. MoS2 nanosheets (MNs) acted as an efficient support for nZVI and enriched the organic pollutants nearby, leading to an enhanced removal efficiency. Fe3O4 nanoparticles (NPs) could not only suppress the agglomeration and restacking of MNs, but also facilitate easy separation and recovery of the nanocomposites. The synergistic effect between MNs and Fe3O4 NPs effectively enhanced the reactivity and efficiency of nZVI. In the system, Cr(VI) was reduced to Cr(III) by nZVI in the nanocomposites, and Fe2+ produced in the process was combined with H2O2 to further remove 4-Chlorophenol (4-CP) through a Fenton reaction. Furthermore, the nanocomposites could be easily separated from wastewater by a magnet and be reused for at least five consecutive runs, revealing good reusability. The results demonstrate that the novel nanocomposites are highly efficient and promising for the simultaneous removal of Cr(VI) and 4-CP in wastewater. PMID:28973986

First-principles analysis of C2H2 molecule diffusion and its dissociation process on the ferromagnetic bcc-Fe110 surface.

PubMed

Ikeda, Minoru; Yamasaki, Takahiro; Kaneta, Chioko

2010-09-29

Using the projector-augmented plane wave method, we study diffusion and dissociation processes of C(2)H(2) molecules on the ferromagnetic bcc-Fe(110) surface and investigate the formation process of graphene created by C(2)H(2) molecules. The most stable site for C(2)H(2) on the Fe surface is a hollow site and its adsorption energy is - 3.5 eV. In order to study the diffusion process of the C(2)H(2) molecule, the barrier height energies for the C atom, C(2)-dimer and CH as well as the C(2)H(2) molecule are estimated using the nudged elastic band method. The barrier height energy for C(2)H(2) is 0.71 eV and this indicates that the C(2)H(2) diffuses easily on this FM bcc-Fe(110) surface. We further investigate the two step dissociation process of C(2)H(2) on Fe. The first step is the dissociation of C(2)H(2) into C(2)H and H, and the second step is that of C(2)H into C(2) and H. Their dissociation energies are 0.9 and 1.2 eV, respectively. These energies are relatively small compared to the dissociation energy 7.5 eV of C(2)H(2) into C(2)H and H in the vacuum. Thus, the Fe surface shows catalytic effects. We further investigate the initial formation process of graphene by increasing the coverage of C(2)H(2). The formation process of the benzene molecule on the FM bcc(110) surface is also discussed. We find that there exists a critical coverage of C(2)H(2) which characterizes the beginning of the formation of the graphene.

Thermodynamic Constraints in Using AuM (M = Fe, Co, Ni, and Mo) Alloys as N₂ Dissociation Catalysts: Functionalizing a Plasmon-Active Metal.

PubMed

Martirez, John Mark P; Carter, Emily A

2016-02-23

The Haber-Bosch process for NH3 synthesis is arguably one of the greatest inventions of the 20th century, with a massive footprint in agriculture and, historically, warfare. Current catalysts for this reaction use Fe for N2 activation, conducted at high temperatures and pressures to improve conversion rate and efficiency. A recent finding shows that plasmonic metal nanoparticles can either generate highly reactive electrons and holes or induce resonant surface excitations through plasmonic decay, which catalyze dissociation and redox reactions under mild conditions. It is therefore appealing to consider AuM (M = Fe, Co, Ni, and Mo) alloys to combine the strongly plasmonic nature of Au and the catalytic nature of M metals toward N2 dissociation, which together might facilitate ammonia production. To this end, through density functional theory, we (i) explore the feasibility of forming these surface alloys, (ii) find a pathway that may stabilize/deactivate surface M substituents during fabrication, and (iii) define a complementary route to reactivate them under operational conditions. Finally, we evaluate their reactivity toward N2, as well as their ability to support a pathway for N2 dissociation with a low thermodynamic barrier. We find that AuFe possesses similar appealing qualities, including relative stability with respect to phase separation, reversibility of Fe oxidation and reduction, and reactivity toward N2. While AuMo achieves the best affinity toward N2, its strong propensity toward oxidation could greatly limit its use.

Tunable SERS signals of Rhodamine B molecules on Fe3O4@Au nanocomposite substrates controlled by magnetic field

NASA Astrophysics Data System (ADS)

Song, Hao; Fang, Rui Yang; Li, Ling

2018-02-01

In this work, we experimentally synthesized the Fe3O4@Au nanocomposites and used them as surface-enhanced Raman scattering (SERS) substrates. The Fe3O4@Au nanocomposites retained the metallic plasmon resonant effect and possessed the magnetic field controllable characteristics. The Raman spectra of Rhodamine B (RhB) probe molecules were studied under different external magnetic field. The magnitude of external magnetic field varied from 0 Gs to 700 Gs (1 Gs = 10-4 T) with intervals of 100 Gs. When the magnetic field magnitude increased, the Raman intensity of RhB probe molecules at 1356 cm-1 increased linearly. The slope of the linear fitting curves for the Raman intensity and area were 0.118/Gs and 3.700/Gs. The Raman enhancement could raise up to 7 times for RhB probe molecules when the magnetic field magnitude increased to 700 Gs. After removing the external magnetic field, the Raman peaks returned to its original intensity in several minutes. Under the external magnetic field, the Fe3O4@Au nanocomposites were concentrated, leading to the increase number of SERS "hot spots" and the surface Au density. The results show that the magnetic field controlled Fe3O4@Au nanocomposites can realize the enhanced and controllable SERS effect, which can be used in the reversible optical sensing and bio-medical applications.

Photoemission and Auger-electron spectroscopic study of the Chevrel-phase compound FexMo6S8

NASA Astrophysics Data System (ADS)

Fujimori, A.; Sekita, M.; Wada, H.

1986-05-01

The electronic structure of the Chevrel-phase compound FexMo6S8 has been studied by photoemission and Auger-electron spectroscopy. Core-level shifts suggest a large charge transfer from the Fe atoms to the Mo6S8 clusters and a small Mo-to-S charge transfer within the cluster. Line-shape asymmetry in the core levels indicates that the density of states (DOS) at the Fermi level has a finite S 3p component as well as the dominant Mo 3d character. Satellite structure and exchange splitting in the Fe core levels point to weak Fe 3d-S 3p hybridization in spite of the short Fe-S distances comparable to that in FeS. The x-ray and ultraviolet valence-band photoemission spectra and the Mo 4d partial DOS obtained by deconvoluting the Mo M4,5VV Auger spectrum are compared with existing band-structure calculations, and the Mo 4d-S 3p bonding character, the structure of the Mo 4d-derived conduction band etc., are discussed. In particular, it is shown that the conduction-band structure is sensitive to the noncubic distortion of the crystal through changes in the intercluster Mo 4d-S 3p hybridization. A pronounced final-state effect is found in the Mo M4,5N2,3V Auger spectrum and is attributed to strong 4p-4d intershell coupling.

Mechanical Properties of Nb25Mo25Ta25W25 and V20Nb20Mo20Ta20W20 Refractory High-Entropy Alloys (Preprint)

DTIC Science & Technology

2011-07-01

research seems to emphasize alloys based Approved for public release; distribution unlimited. 2 on the late transition metals such as Cr, Mn, Fe, Co, Ni ...of the Nb25Mo25Ta25W25 alloy , with larger grains at the regions experiencing slower solidification , i.e. near the surfaces not contacting with the...20-30 µm, indicating similar solidification conditions. 3.2.3 Fractography of samples deformed at room temperature The high entropy alloy

From linking of metal-oxide building blocks in a dynamic library to giant clusters with unique properties and towards adaptive chemistry.

PubMed

Müller, Achim; Gouzerh, Pierre

2012-11-21

Following Nature's lessons, today chemists can cross the boundary of the small molecule world to construct multifunctional and highly complex molecular nano-objects up to protein size and even cell-like nanosystems showing responsive sensing. Impressive examples emerge from studies of the solutions of some oxoanions of the early transition metals especially under reducing conditions which enable the controlled linking of metal-oxide building blocks. The latter are available from constitutional dynamic libraries, thus providing the option to generate multifunctional unique nanoscale molecular systems with exquisite architectures, which even opens the way towards adaptive and evolutive (Darwinian) chemistry. The present review presents the first comprehensive report of current knowledge (including synthesis aspects not discussed before) regarding the related giant metal-oxide clusters mainly of the type {Mo(57)M'(6)} (M' = Fe(III), V(IV)) (torus structure), {M(72)M'(30)} (M = Mo, M' = V(IV), Cr(III), Fe(III), Mo(V)), {M(72)Mo(60)} (M = Mo, W) (Keplerates), {Mo(154)}, {Mo(176)}, {Mo(248)} ("big wheels"), and {Mo(368)} ("blue lemon") - all having the important transferable pentagonal {(M)M(5)} groups in common. These discoveries expanded the frontiers of inorganic chemistry to the mesoscopic world, while there is probably no collection of discrete inorganic compounds which offers such a versatile chemistry and the option to study new phenomena of interdisciplinary interest. The variety of different properties of the sphere- and wheel-type metal-oxide-based clusters can directly be related to their unique architectures: The spherical Keplerate-type capsules having 20 crown-ether-type pores and tunable internal functionalities allow the investigation of confined matter as well as that of sphere-surface-supramolecular and encapsulation chemistry - including related new aspects of the biologically important hydrophobic effects - but also of nanoscale ion transport and

Thermoelectronic transport through spin-crossover single molecule Fe[(H2Bpz2)2bipy

NASA Astrophysics Data System (ADS)

Liu, N.; Zhu, L.; Yao, K. L.

2018-04-01

By means of density functional theory combined with the method of Keldysh nonequilibrium Green’s function, the thermal transport properties of high- and low-spin states of mononuclear FeII molecules with spin-crossover characteristics are studied. It is found that the high-spin molecular junction has a larger current than the low-spin one, producing thermally-induced switching effect. Furthermore, for high spin state molecule, the spin-up thermo-current is strongly blocked, thus achieving a pure thermo spin current. The enhanced Seebeck coefficient and the figure of merit value of high-spin state indicate that it is an ideal candidate for thermoelectric applications.

Molecules based on M(v) (M=Mo, W) and Ni(II) ions: a new class of trigonal bipyramidal cluster and confirmation of SMM behavior for the pentadecanuclear molecule {NiII[NiII(tmphen)(MeOH)]6[Ni(H2O)3]2[micro-CN]30[WV(CN)3]6}.

PubMed

Hilfiger, Matthew G; Zhao, Hanhua; Prosvirin, Andrey; Wernsdorfer, Wolfgang; Dunbar, Kim R

2009-07-14

The preparation, single crystal X-ray crystallography, and magnetic properties are reported for four new clusters based on [M'V(CN)8]3- octacyanometallates (M'=Mo, W). Reactions of [M'V(CN)8]3- with mononuclear NiII ions in the presence of the tmphen blocking ligand (tmphen=3,4,7,8-tetramethyl-1,10-phenanthroline) in a 2:3:6 ratio, respectively, lead to the formation of the trigonal bipyramidal clusters [NiII(tmphen)2]3[M'V(CN)8]2. Analogous reactions with the same starting materials performed in a 2:3:2 ratio, respectively, produce pentadecanuclear clusters of the type {NiII[NiII(tmphen)(MeOH)]6[Ni(H2O)3]2[micro-CN]30[WV(CN)3]6}. The W2Ni3 (1) and Mo2Ni3(2) pentanuclear clusters and the W6Ni9 (3) and Mo6Ni9 (4) pentadecanuclear molecules are isostructural to each other and crystallize in the space groups P2(1)/c and R3 respectively. Magnetic measurements indicate that the ground states for the trigonal bipyamidal clusters are S=4 as a consequence of ferromagnetic coupling with JW-Ni=9.5 cm(-1), JMo-Ni=10 cm(-1). The pentadecanuclear clusters exhibit ferromagnetic coupling as well, which leads to S=12 ground states (JW-Ni=12 cm(-1), JMo-Ni=12.2 cm(-1)). Reduced magnetization studies on the W-Ni analogues support the conclusion that they exhibit a negative axial anisotropy term; the fits give D values of -0.24 cm(-1) for the W2Ni3 cluster and D=-0.04 cm(-1)for the W6Ni9 cluster. AC susceptibility measurements indicate the beginning of an out-of-phase signal for the W2Ni3 and the W6Ni9 compounds, but detailed low temperature studies on small crystals by the microSQUID technique indicate that only the pentadecanuclear cluster exhibits hysteresis in accord with SMM behavior. Neither Mo cluster reveals any evidence for slow paramagnetic relaxation at low temperatures.

Luminescence and magnetic properties of novel nanoparticle-sheathed 3D Micro-Architectures of Fe0.5R0.5(MoO4)1.5:Ln3+ (R = Gd3+, La3+), (Ln = Eu, Tb, Dy) for bifunctional application

NASA Astrophysics Data System (ADS)

Krishnan, Rajagopalan; Thirumalai, Jagannathan; Kathiravan, Arunkumar

2015-01-01

For the first time, we report the successful synthesis of novel nanoparticle-sheathed bipyramid-like and almond-like Fe0.5R0.5(MoO4)1.5:Ln3+ (R = Gd3+, La3+), (Ln = Eu, Tb, Dy) 3D hierarchical microstructures through a simple disodium ethylenediaminetetraacetic acid (Na2EDTA) facilitated hydrothermal method. Interestingly, time-dependent experiments confirm that the assembly-disassembly process is responsible for the formation of self-aggregated 3D architectures via Ostwald ripening phenomena. The resultant products are characterized by x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), photoluminescence (PL), and magnetic measurements. The growth and formation mechanisms of the self-assembled 3D micro structures are discussed in detail. To confirm the presence of all the elements in the microstructure, the energy loss induced by the K, L shell electron ionization is observed in order to map the Fe, Gd, Mo, O, and Eu components. The photo luminescence properties of Fe0.5R0.5(MoO4)1.5 doped with Eu3+, Tb3+, Dy3+ are investigated. The room temperature and low temperature magnetic properties suggest that the interaction between the local-fields introduced by the magnetic Fe3+ ions and the R3+ (La, Gd) ions in the dodecahedral sites determine the magnetism in Fe0.5R0.5(MoO4)1.5:Eu3+. This work provides a new approach to synthesizing the novel Fe0.5R0.5(MoO4)1.5:Ln3+ for bi-functional magnetic and luminescence applications.

Surface topography and electrical properties in Sr2FeMoO6 films studied at cryogenic temperatures

NASA Astrophysics Data System (ADS)

Angervo, I.; Saloaro, M.; Mäkelä, J.; Lehtiö, J.-P.; Huhtinen, H.; Paturi, P.

2018-03-01

Pulsed laser deposited Sr2FeMoO6 thin films were investigated for the first time with scanning tunneling microscopy and spectroscopy. The results confirm atomic scale layer growth, with step-terrace structure corresponding to a single lattice cell scale. The spectroscopy research reveals a distribution of local electrical properties linked to structural deformation in the initial thin film layers at the film substrate interface. Significant hole structure giving rise to electrically distinctive regions in thinner film also seems to set a thickness limit for the thinnest films to be used in applications.

La Doped Disorder in LaxCa2-xFeMoO6 Ferrimagnet: Magnetic and Thermoelectric Study

NASA Astrophysics Data System (ADS)

Muthuselvam, I. Panneer; Bhowmik, R. N.; Poddar, Asok

2011-06-01

We report the magnetic and thermo-electric properties of LaxCa2-xFeMoO6 (x = 0 to 0.8) ferrimagnet. The ferromagnetic ordering temperature (TC) changes with increasing La doping. The band structure modification due to La doping in double perovskite structure was understood by correlating the electrical conductivity and thermoelectric power (S). S(T) curve of different samples was fitted with the proposed equation S(T) = S0+S1T+S3/2T3/2+S3T4 and each term has been interpreted in this paper.

The Synthesis and Characterization of Aromatic Hybrid Anderson–Evans POMs and their Serum Albumin Interactions: The Shift from Polar to Hydrophobic Interactions

PubMed Central

Al-Sayed, Emir; Blazevic, Amir; Roller, Alexander; Rompel, Annette

2015-01-01

Four aromatic hybrid Anderson polyoxomolybdates with Fe3+ or Mn3+ as the central heteroatom have been synthesized by using a pre-functionalization protocol and characterized by using single-crystal X-ray diffraction, FTIR, ESI-MS, 1H NMR spectroscopy, and elemental analysis. Structural analysis revealed the formation of (TBA)3[FeMo6O18{(OCH2)3CNHCOC6H5}2]⋅3.5 ACN (TBA-FeMo6-bzn; TBA=tetrabutylammonium, ACN=acetonitrile, bzn=TRIS-benzoic acid alkanolamide, TRIS–R=(HOCH2)3C–R)), (TBA)3[FeMo6O18{(OCH2)3CNHCOC8H7}2]⋅2.5 ACN (TBA-FeMo6-cin; cin=TRIS-cinnamic acid alkanolamide), (TBA)3[MnMo6O18{(OCH2)3CNHCOC6H5}2]⋅3.5 ACN (TBA-MnMo6-bzn), and (TBA)3[MnMo6O18{(OCH2)3CNHCOC8H7}2]⋅2.5 ACN (TBA-MnMo6-cin). To make these four compounds applicable in biological systems, an ion exchange was performed that gave the water-soluble (up to 80 mm) sodium salts Na3[FeMo6O18{(OCH2)3CNHCOC6H5}2] (Na-FeMo6-bzn), Na3[FeMo6O18{(OCH2)3CNHCOC8H7}2] (Na-FeMo6-cin), Na3[MnMo6O18{(OCH2)3CNHCOC6H5}2] (Na-MnMo6-bzn), and Na3[MnMo6O18{(OCH2)3CNHCOC8H7}2] (Na-MnMo6-cin). The hydrolytic stability of the sodium salts was examined by applying ESI-MS in the pH range of 4 to 9. Sodium dodecylsulfate–polyacrylamide gel electrophoresis (SDS-PAGE) showed that human and bovine serum albumin (HSA and BSA) remain intact in solutions that contain up to 100 equivalents of the sodium salts over more than 4 d at 20 °C. Tryptophan (Trp) fluorescence quenching was applied to study the interactions between the sodium salts and HSA and BSA at pH 5.5 and 7.4. The quenching constants were extracted by using Stern–Volmer analysis, which suggested the formation of a 1:1 POM–protein complex in all samples. It is suggested that the aromatic hybrid POM approaches subdomain IIA of HSA and exhibits hydrophobic interactions with its hydrophobic tails, whereas the Anderson core is stabilized through electrostatic interactions with polar amino acid side chains from, for example

Molecular characterization of human xanthine oxidoreductase: the enzyme is grossly deficient in molybdenum and substantially deficient in iron-sulphur centres

PubMed Central

2005-01-01

XOR (xanthine oxidoreductase) purified from human milk was shown to contain 0.04 atom of Mo and 0.09 molecule of molybdopterin/subunit. On the basis of UV/visible and CD spectra, the human enzyme was approx. 30% deficient in iron-sulphur centres. Mo(V) EPR showed the presence of a weak rapid signal corresponding to the enzyme of low xanthine oxidase activity and a slow signal indicating a significant content of desulpho-form. Resulphuration experiments, together with calculations based on enzymic activity and Mo content, led to an estimate of 50–60% desulpho-form. Fe/S EPR showed, in addition to the well-known Fe/S I and Fe/S II species, the presence of a third Fe/S signal, named Fe/S III, which appears to replace partially Fe/S I. Comparison is made with similarly prepared bovine milk XOR, which has approx. 15-fold higher enzymic activity and Mo content. Taken along with evidence of low Mo content in the milk of other mammals, these findings add further support to the idea that XOR protein plays a physiological role in milk (e.g. in secretion) equal in importance to its catalytic function as an enzyme. PMID:15679468

Anti-site defected MoS2 sheet for catalytic application

NASA Astrophysics Data System (ADS)

Sharma, Archana; Husain, Mushahid; Khan, Mohd. Shahid

2018-04-01

To prevent harmful and poisonous CO gas molecules, catalysts are needed for converting them into benign substances. Density functional theory (DFT) calculations have been used to investigate CO oxidation on the surface of MoS2 monolayer with Mo atom embedded at S-vacancy site (anti-site defect). The stronger interaction between Mo metal with O2 molecule as compared with CO molecule suggests high catalytic activity. The complete oxidation of CO is studied in a two-step procedure using Langmuir-Hinshelwood (LH) and Eley-Rideal (ER) mechanisms with a low overall energy barrier of 0.35 eV. Creation of anti-site defect makes the surface of MoS2 nanosheet catalytically active for the CO oxidation to take place.

30 CFR 241.72 - How will the Office of Hearings and Appeals conduct the hearing on the record?

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 2 2010-07-01 2010-07-01 false How will the Office of Hearings and Appeals conduct the hearing on the record? 241.72 Section 241.72 Mineral Resources MINERALS MANAGEMENT SERVICE, DEPARTMENT OF THE INTERIOR MINERALS REVENUE MANAGEMENT PENALTIES Penalties for Federal and Indian Oil and Gas Leases General Provisions § 241.72 How...

The Azotobacter vinelandii NifEN complex contains two identical [4Fe-4S] clusters.

PubMed

Goodwin, P J; Agar, J N; Roll, J T; Roberts, G P; Johnson, M K; Dean, D R

1998-07-21

The nifE and nifN gene products from Azotobacter vinelandii form an alpha2beta2 tetramer (NifEN complex) that is required for the biosynthesis of the nitrogenase FeMo cofactor. In the current model for NifEN complex organization and function, the complex is structurally analogous to the nitrogenase MoFe protein and provides an assembly site for a portion of FeMo cofactor biosynthesis. In this work, gene fusion and immobilized metal-affinity chromatography strategies were used to elevate the in vivo production of the NifEN complex and to facilitate its rapid and efficient purification. The NifEN complex produced and purified in this way exhibits an FeMo cofactor biosynthetic activity similar to that previously described for the NifEN complex purified by traditional chromatography methods. UV-visible, EPR, variable-temperature magnetic circular dichroism, and resonance Raman spectroscopies were used to show that the NifEN complex contains two identical [4Fe-4S]2+ clusters. These clusters have a predominantly S = 1/2 ground state in the reduced form, exhibit a reduction potential of -350 mV, and are likely to be coordinated entirely by cysteinyl residues on the basis of spectroscopic properties and sequence comparisons. A model is proposed where each NifEN complex [4Fe-4S] cluster is bridged between a NifE-NifN subunit interface at a position analogous to that occupied by the P clusters in the nitrogenase MoFe protein. In contrast to the MoFe protein P clusters, the NifEN complex [4Fe-4S] clusters are proposed to be asymmetrically coordinated to the NifEN complex where NifE cysteines-37, -62, and -124 and NifN cysteine-44 are the coordinating ligands. On the basis of a homology model of the three-dimensional structure of the NifEN complex, the [4Fe-4S] cluster sites are likely to be remote from the proposed FeMo cofactor assembly site and are unlikely to become incorporated into the FeMo cofactor during its assembly.

Tellurite‐Squarate Driven Assembly of a New Family of Nanoscale Clusters Based on (Mo2O2S2)2+

PubMed Central

Purcell, Jamie W.; Miras, Haralampos N.; Long, De‐Liang; Markopoulou, Panagiota

2017-01-01

Abstract The preparation and characterization of a new family of four polyoxothiometalate (POTM) clusters are reported, with varying size and complexity, based upon the dimeric [Mo2O2S2(H2O)6]2+ cation with the general formula (NMe4)aKb[(Mo2O2S2)c(TeO4)d(C4O4)e(OH)f] where a,b,c,d,e,f={1,7,14,2,4,10}=1, {Mo28Te2}; {2,26,36,12,10,48}=2, {Mo72Te12}; {0,11,15,3,3,21}=3, {Mo30Te3}; {2,6,12,2,4,16}=4, {Mo24Te2}. The incorporation of tellurite anions allowed the fine tuning of the templating and bridging of the available building blocks, leading to new topologies of increased complexity. The structural diversity of this family of compounds ranges from the highly symmetrical cross‐shaped {Mo24Te2} to the stacked ring structure of {Mo72Te12}, which is the largest tellurium‐containing POTM cluster reported so far. Also a detailed experimental analysis revealed that the pH isolation window extends from acidic to basic values. ESI‐MS analyses not only confirmed the stability of this family in solution but also revealed the stability of the observed virtual building blocks. PMID:28548217

Au/NiFe/M(Au, MoS2, graphene) trilayer magnetoplasmonics DNA-hybridized sensors with high record of sensitivity

NASA Astrophysics Data System (ADS)

Faridi, Ehsan; Moradi, Maryam; Ansari, Narges; Ghasemi, Amir Hossein Baradaran; Afshar, Amir; Mohseni, Seyed Majid

2017-12-01

The demonstration of biosensors based on the surface plasmon effect holds promise for future high-sensitive electrodeless biodetection. The combination of magnetic effects with surface plasmon waves brings additional freedom to improve sensitivity and signal selectivity. Stacking biosensors with two-dimensional (2-D) materials, e.g., graphene (Gr) and MoS2, can influence plasmon waves and facilitate surface physiochemical properties as additional versatility aspects. We demonstrate magnetoplasmonic biosensors through the detuning of surface plasmon oscillation modes affected by magnetic effect via the presence of the NiFe (Py) layer and different light absorbers of Gr, MoS2, and Au ultrathin layers in three stacks of Au/Py/M(MoS2, Gr, Au) trilayers. We found minimum reflection, resonance angle shift, and transverse magneto-optical Kerr effect (TMOKE) responses of all sensors in the presence of the ss-DNA monolayer. Very few changes of ˜5×10-7 in the ss-DNA's refractive index result in valuable TMOKE response. We found that the presence of three-layer Gr and two-layer MoS2 on top of the Au/Py bilayer can dramatically increase the sensitivity by nine and four times, respectively, than the conventional Au/Co/Au trilayer. Our results show the highest reported DNA sensitivity based on the coupling of light with 2-D materials in magnetoplasmonic devices.

Reactivity of Cubane-Type [(OC)(3)MFe(3)S(4)(SR)(3)](3-) Clusters (M = Mo, W): Interconversion with Cuboidal [Fe(3)S(4)](0) Clusters and Electron Transfer.

PubMed

Raebiger, James W.; Crawford, Charles A.; Zhou, Jian; Holm, R. H.

1997-03-12

The title clusters, several examples of which have been reported earlier, have been prepared by two different methods and subjected to structural and reactivity studies. The compounds (Et(4)N)(3)[(OC)(3)MFe(3)S(4)(Smes)(3)].MeCN (M = Mo/W) are isomorphous and crystallize in monoclinic space group P2(1)/n with a = 13.412(1)/13.297(1) Å, b = 19.0380(1)/18.9376(3) Å, c = 26.4210(1)/26.2949(1) Å, beta = 97.87(1)/97.549(1) degrees, and Z = 4. The clusters contain long M-S (2.62/2.59 Å) and M-Fe (3.22/3.19 Å) bonds, consistent with the reported structure of [(OC)(3)MoFe(3)S(4)(SEt)(3)](3-) (3). Reaction of [(OC)(3)MoFe(3)S(4)(LS(3))](3-) (7) with CO in the presence of NaPF(6) affords cuboidal [Fe(3)S(4)(LS(3))](3-) (9), also prepared in this laboratory by another route as a synthetic analogue of protein-bound [Fe(3)S(4)](0) clusters. The clusters [Fe(3)S(4)(SR)(3)](3-) (R = mes, Et), of limited stability, were generated by the same reaction. Treatment of 9 with [M(CO)(3)(MeCN)(3)] affords 7 and its M = W analogue. The clusters [(OC)(3)MFe(3)S(4)(SR)(3)](3-) form a four-member electron transfer series in which the 3- cluster can be once reduced (4-) and twice oxidized (2-, 1-) to afford clusters of the indicated charges. The correct assignment of redox couple to potential in the redox series of six clusters is presented, correcting an earlier misassignment of the redox series of 3. Carbonyl stretching frequencies are shown to be sensitive to cluster oxidation state, showing that the M sites and Fe(3)S(4) fragments are electronically coupled despite the long bond distances. (LS(3) = 1,3,5-tris((4,6-dimethyl-3-mercaptophenyl)thio)-2,4,6-tris(p-tolylthio)benzenate(3-); mes = mesityl.)

Mechanical properties and structural features of novel Fe-based bulk metallic glasses with unprecedented plasticity

PubMed Central

Yang, Weiming; Liu, Haishun; Zhao, Yucheng; Inoue, Akihisa; Jiang, Kemin; Huo, Juntao; Ling, Haibo; Li, Qiang; Shen, Baolong

2014-01-01

Fe-based bulk metallic glasses (BMGs) have attracted great attention due to their unique magnetic and mechanical properties, but few applications have been materialized because of their brittleness at room temperature. Here we report a new Fe50Ni30P13C7 BMG which exhibits unprecedented compressive plasticity (>20%) at room temperature without final fracture. The mechanism of unprecedented plasticity for this new Fe-based BMG was also investigated. It was discovered that the ductile Fe50Ni30P13C7 BMG is composed of unique clusters mainly linked by less directional metal-metal bonds which are inclined to accommodate shear strain and absorbed energy in the front of crack tip. This conclusion was further verified by the X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy experiments of Fe80-xNixP13C7 (x = 0, 10, 20, 30) and Fe72-xNixB20Si4Nb4 (x = 0, 7.2, 14.4, 21.6, 28.8) glassy systems. The results also indicate a strong correlation between the p-d hybridization and plasticity, verifying that the transition from brittle to ductile induced by Ni addition is due to the change of bonding characteristics in atomic configurations. Thus, we can design the plasticity of Fe-based BMGs and open up a new possible pathway for manufacturing BMGs with high strength and plasticity. PMID:25167887

NO-sensing performance of vacancy defective monolayer MoS2 predicted by density function theory

NASA Astrophysics Data System (ADS)

Li, Feifei; Shi, Changmin

2018-03-01

Using density functional theory (DFT), we predict the NO-sensing performance of monolayer MoS2 (MoS2-MLs) with and without MoS3-vacancy/S-vacancy defects. Our theoretical results demonstrate that MoS3- and S-vacancy defective MoS2-MLs show stronger chemisorption and greater electron transfer effects than pure MoS2-MLs. The charge transfer analysis showed pure and defective MoS2-MLs all act as donors. Both MoS3-vacancy and S-vacancy defects induce dramatic changes of electronic properties of MoS2-MLs, which have direct relationship with gas sensing performance. In addition, S-vacancy defect leads to more electrons transfer to NO molecule than MoS3-vacancy defect. The H2O molecule urges more electrons transfer from MoS3- or S-vacancy defective MoS2-MLs to NO molecule. We believe that this calculation results will provide some information for future experiment.

Fe-Cr-Mo based ODS alloys via spark plasma sintering: A combinational characterization study by TEM and APT

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

Y. Q. Wu; K. N. Allahar; J. Burns

2013-08-01

Nanoscale oxides play an important role in oxide dispersion strengthened (ODS) alloys for improved high temperature creep resistance and enhanced radiation damage tolerance. In this study, transmission electron microscopy (TEM) and atom probe tomography (APT) were combined to investigate two novel Fe-16Cr-3Mo (wt.%) based ODS alloys. Spark plasma sintering (SPS) was used to consolidate the ODS alloys from powders that were milled with 0.5 wt.% Y2O3 powder only or with Y2O3 powder and 1 wt.% Ti. TEM characterization revealed that both alloys have a bimodal structure of nanometer-size (~ 100 – 500 nm) and micron-size grains with nanostructured oxide precipitatesmore » formed along and close to grain boundaries with diameters ranging from five to tens of nanometers. APT provides further quantitative analyses of the oxide precipitates, and also reveals Mo segregation at grain boundaries next to oxide precipitates. The alloys with and without Ti are compared based on their microstructures.« less

Reactivity of cyclopentadienyl transition metal(ii) complexes with borate ligands: structural characterization of the toluene-activated molybdenum complex [Cp*Mo(CO)2(η3-CH2C6H5)].

PubMed

Ramalakshmi, Rongala; Maheswari, K; Sharmila, Dudekula; Paul, Anamika; Roisnel, Thierry; Halet, Jean-François; Ghosh, Sundargopal

2016-10-18

Reactions of cyclopentadienyl transition-metal halide complexes [Cp*Mo(CO) 3 Cl], 1, and [CpFe(CO) 2 I], 2, (Cp = C 5 H 5 ; Cp* = η 5 -C 5 Me 5 ) with borate ligands are reported. Treatment of 1 with [NaBt 2 ] (Bt 2 = dihydrobis(2-mercapto-benzothiazolyl)borate) in toluene yielded [Cp*Mo(CO) 2 (C 7 H 4 S 2 N)], 3, and [Cp*Mo(CO) 2 (η 3 -CH 2 C 6 H 5 )], 4, with a selective binding of toluene through C-H activation followed by orthometallation. Note that compound 4 is a structurally characterized toluene-activated molecule in which the metal is in η 3 -coordination mode. Under similar reaction conditions, [NaPy 2 ] (Py 2 = dihydrobis(2-mercaptopyridyl)borate) produced only the mercaptopyridyl molybdenum complex [Cp*Mo(CO) 2 (C 5 H 4 SN)], 5, in good yield. On the other hand, when compound 2 was treated individually with [NaBt] (Bt = trihydro(2-mercapto-benzothiazolyl)borate) and [NaPy 2 ] in THF, formation of the η 1 -coordinated complexes [CpFe(CO) 2 (C 7 H 4 S 2 N)], 6, and [CpFe(CO) 2 (C 5 H 4 SN)], 7, was observed. The solid-state molecular structures of compounds 3, 4, 6, and 7 have been established by single-crystal X-ray crystallographic analyses.

Anti-site defected MoS2 sheet-based single electron transistor as a gas sensor

NASA Astrophysics Data System (ADS)

Sharma, Archana; Husain, Mushahid; Srivastava, Anurag; Khan, Mohd. Shahid

2018-05-01

To prevent harmful and poisonous CO gas molecules, catalysts are needed for converting them into benign substances. Density functional theory (DFT) calculations have been used to study the adsorption of CO and CO2 gas molecules on the surface of MoS2 monolayer with Mo atom embedded at S-vacancy site (MoS). The strong interaction between Mo metal with pristine MoS2 sheet suggests its strong binding nature. Doping Mo into MoS2 sheet enhances CO and CO2 adsorption strength. The sensing response of MoS-doped MoS2 system to CO and CO2 gas molecules is obtained in the single electron transistor (SET) environment by varying bias voltage. Doping reduces charging energy of the device which results in fast switching of the device from OFF to ON state.

Photoinduced charge transfer from vacuum-deposited molecules to single-layer transition metal dichalcogenides

NASA Astrophysics Data System (ADS)

Osada, Kazuki; Tanaka, Masatoshi; Ohno, Shinya; Suzuki, Takanori

2016-06-01

Variations of photoluminescence (PL) and Raman spectra of single-layer MoS2, MoSe2, WS2, and WSe2 due to the vacuum deposition of C60 or copper phthalocyanine (CuPc) molecules have been investigated. PL spectra are decomposed into two competitive components, an exciton and a charged exciton (trion), depending on carrier density. The variation of PL spectra is interpreted in terms of charge transfer across the interfaces between transition metal dichalcogenides (TMDs) and dopant molecules. We find that deposited C60 molecules inject photoexcited electrons into MoS2, MoSe2, and WS2 or holes into WSe2. CuPc molecules also inject electrons into MoS2, MoSe2, and WS2, while holes are depleted from WSe2 to CuPc. We then propose a band alignment between TMDs and dopant molecules. Peak shifts of Raman spectra and doped carrier density estimated using a three-level model also support the band alignment. We thus demonstrate photoinduced charge transfer from dopant molecules to single-layer TMDs.

Ultra-thin L1{sub 0}-FePt for perpendicular anisotropy L1{sub 0}-FePt/Ag/[Co/Pd]{sub 30} pseudo spin valves

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

Ho, Pin; Chow, Gan Moog; Chen, Jing-Sheng, E-mail: msecj@nus.edu.sg

2014-05-07

Perpendicular anisotropy L1{sub 0}-FePt/Ag/[Co/Pd]{sub 30} pseudo spin valves (PSVs) with ultra-thin L1{sub 0}-FePt alloy free layer possessing high anisotropy and thermal stability have been fabricated and studied. The thickness of the L1{sub 0}-FePt layer was varied between 2 and 4 nm. The PSV became increasingly decoupled with reduced L1{sub 0}-FePt thickness due to the larger difference between the coercivity of the L1{sub 0}-FePt and [Co/Pd]{sub 30} films. The PSV with an ultra-thin L1{sub 0}-FePt free layer of 2 nm displayed a high K{sub u} of 2.21 × 10{sup 7} ergs/cm{sup 3}, high thermal stability of 84 and a largest giant magnetoresistance of 0.54%.

A [4Fe-4S]-Fe(CO)(CN)-l-cysteine intermediate is the first organometallic precursor in [FeFe] hydrogenase H-cluster bioassembly

NASA Astrophysics Data System (ADS)

Rao, Guodong; Tao, Lizhi; Suess, Daniel L. M.; Britt, R. David

2018-05-01

Biosynthesis of the [FeFe] hydrogenase active site (the 'H-cluster') requires the interplay of multiple proteins and small molecules. Among them, the radical S-adenosylmethionine enzyme HydG, a tyrosine lyase, has been proposed to generate a complex that contains an Fe(CO)2(CN) moiety that is eventually incorporated into the H-cluster. Here we describe the characterization of an intermediate in the HydG reaction: a [4Fe-4S][(Cys)Fe(CO)(CN)] species, 'Complex A', in which a CO, a CN- and a cysteine (Cys) molecule bind to the unique 'dangler' Fe site of the auxiliary [5Fe-4S] cluster of HydG. The identification of this intermediate—the first organometallic precursor to the H-cluster—validates the previously hypothesized HydG reaction cycle and provides a basis for elucidating the biosynthetic origin of other moieties of the H-cluster.

A bifunctional luminescent Tb(III)-metal-organic framework by a tetracarboxylate ligand for highly selective detection of Fe3+ cation and Cr2O72- anion

NASA Astrophysics Data System (ADS)

Yu, Li; Wang, Chao; Hu, Chang-Jiang; Dong, Wen-Wen; Wu, Ya-Pan; Li, Dong-Sheng; Zhao, Jun

2018-06-01

Reaction of Tb3+ ions with p-terphenyl-3,3″,5,5″-tetracarboxylic acid (H4ptptc) in a mixed solvent system has afforded a new metal-organic framework formulated as [Tb2(ptptc)1.5(H2O)2]n (1). Compound 1 displays a 3D (5,6,8)-connected framework with fascinating one-dimensional triangle open channels. The luminescence explorations demonstrated that 1 exhibits highly selective and sensitive response to Fe3+ in DMF solution and biological system through luminescence quenching effects. In addition, 1 also shows high detection for the Cr2O72-, making it a promising dual functional materials for detecting Fe3+ cation and Cr2O72- anion with high sensitivity and selectivity.

Metastable gamma-Iron Nickel Nanostructures for Magnetic Refrigeration Near Room Temperature

NASA Astrophysics Data System (ADS)

Ucar, Huseyin

250 J/kg at 5 T, with peak temperatures 363 K and 333 K, respectively. The RCFW H M for the Fe70Ni30 is higher than the previously reported Nanoperm (Fe70Ni 30)89Zr7B4 type alloy and on the same order of magnitude with other Fe-based alloys. The maximum magnetic entropy change values observed for the Fe70Ni30 and the Fe 72Ni28 are 0.65 and 0.5 Jkg--1K --1, respectively, at a field of 5 T. These are smaller than those of rare earth magnetic refrigerants showing first order transformation behavior. The larger RCFW H M value results mainly from the width of the magnetic entropy curve in these types of materials. In a follow up study, nanocrystalline powders of (Fe70Ni 30)100--xMox (x=1 to x=4) were produced by high energy (SPEX) mechanical alloying. Increasing the Mo content was found to stabilize the FCC phase in mechanically alloyed nanopowders. The TC of the alloys was lowered with Mo additions, without decreasing the Refrigeration Capacity (RC), due to the additional temperature broadening of the magnetic entropy change. Based on the previous study on the role of disorder, the additional temperature broadening was attributed to the increased positional disorder introduced by the Mo additions into the gammaFeNi system. Alloy with (Fe70Ni 30)96Mo4 composition was observed to have RCFW H M of 432 J/kg at 5T which is comparable to other prominent magnetic refrigerants operating near room temperatures. The economic viability of these rare-earth-free alloys, along with respectable magnetocaloric properties and potential for scalable production, make them good candidates for magnetic refrigeration applications.

Au/NiFe/M(Au, MoS2, graphene) trilayer magnetoplasmonics DNA-hybridized sensors with high record of sensitivity.

PubMed

Faridi, Ehsan; Moradi, Maryam; Ansari, Narges; Baradaran Ghasemi, Amir Hossein; Afshar, Amir; Mohseni Armaki, Seyed Majid

2017-12-01

The demonstration of biosensors based on the surface plasmon effect holds promise for future high-sensitive electrodeless biodetection. The combination of magnetic effects with surface plasmon waves brings additional freedom to improve sensitivity and signal selectivity. Stacking biosensors with two-dimensional (2-D) materials, e.g., graphene (Gr) and MoS2, can influence plasmon waves and facilitate surface physiochemical properties as additional versatility aspects. We demonstrate magnetoplasmonic biosensors through the detuning of surface plasmon oscillation modes affected by magnetic effect via the presence of the NiFe (Py) layer and different light absorbers of Gr, MoS2, and Au ultrathin layers in three stacks of Au/Py/M(MoS2, Gr, Au) trilayers. We found minimum reflection, resonance angle shift, and transverse magneto-optical Kerr effect (TMOKE) responses of all sensors in the presence of the ss-DNA monolayer. Very few changes of ∼5×10-7 in the ss-DNA's refractive index result in valuable TMOKE response. We found that the presence of three-layer Gr and two-layer MoS2 on top of the Au/Py bilayer can dramatically increase the sensitivity by nine and four times, respectively, than the conventional Au/Co/Au trilayer. Our results show the highest reported DNA sensitivity based on the coupling of light with 2-D materials in magnetoplasmonic devices. (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

Structure and tribological behavior of Pb-Ti/MoS2 nanoscaled multilayer films deposited by magnetron sputtering method

NASA Astrophysics Data System (ADS)

Li, Hao; Xie, Mingling; Zhang, Guangan; Fan, Xiaoqiang; Li, Xia; Zhu, Minhao; Wang, Liping

2018-03-01

The Pb-Ti/MoS2 nanoscaled multilayer films with different bilayer period were deposited by unbalanced magnetron sputtering system. The morphology, microstructure, mechanical and tribological properties of the films were investigated. It was found that the film changed from multilayer structure to composite structure as the bilayer period decreased from 25 nm to 6 nm, due to the diffusion effect. The multilayer film showed a pronounced (002) diffraction peak, the growth of the MoS2 platelets below the interface were affected by Pb and Ti, and the c-axis of MoS2 platelets were inclined to the substrate at an angle of -30° to 30°. The hardness of the film ranged from 5.9 to 7.2 GPa depending on the bilayer period. The tribological behavior of the films was performed under vacuum, and the friction coefficient were typically below 0.25. Furthermore, the nanoscale multilayer film with a bilayer period of 20 nm exhibits much better mechanical and tribological properties than pure MoS2. The result indicates that the nanoscale multilayer is a design methodology for developing high basal plane oriented and vacuum solid lubricating MoS2 based materials.

High-Performance Few-layer Mo-doped ReSe2 Nanosheet Photodetectors

PubMed Central

Yang, Shengxue; Tongay, Sefaattin; Yue, Qu; Li, Yongtao; Li, Bo; Lu, Fangyuan

2014-01-01

Transition metal dichalcogenides (TMDCs) have recently been the focus of extensive research activity owing to their fascinating physical properties. As a new member of TMDCs, Mo doped ReSe2 (Mo:ReSe2) is an octahedral structure semiconductor being optically biaxial and highly anisotropic, different from most of hexagonal layered TMDCs with optically uniaxial and relatively high crystal symmetry. We investigated the effects of physisorption of gas molecule on the few-layer Mo:ReSe2 nanosheet based photodetectors. We compared the photoresponse of the as-exfoliated device with annealed device both in air or ammonia (NH3) environment. After annealing at sub-decomposition temperatures, the Mo:ReSe2 photodetectors show a better photoresponsivity (~55.5 A/W) and higher EQE (10893%) in NH3 than in air. By theoretical investigation, we conclude that the physisorption of NH3 molecule on Mo:ReSe2 monolayer can cause the charge transfer between NH3 molecule and Mo:ReSe2 monolayer, increasing the n-type carrier density of Mo:ReSe2 monolayer. The prompt photoswitching, high photoresponsivity and different sensitivity to surrounding environment from the few-layer anisotropic Mo:ReSe2 can be used to design multifunctional optoelectronic and sensing devices. PMID:24962077

An ab initio MO study on the hydrolysis of methyl chloride with explicit consideration of 13 water molecules

NASA Astrophysics Data System (ADS)

Yamataka, Hiroshi; Aida, Misako

1998-06-01

Ab initio MO calculations (HF/3-21G, HF/6-31G, HF/6-31+G* and MP2/6-31+G*) were carried out on the hydrolysis of CH 3Cl in which up to 13 water solvent molecules were explicitly considered. For n⩾3, three important stationary points ( cmp1, TS, and cmp2) were detected in the course of the reaction. The calculations for the n=13 system at the HF/6-31+G* level reproduced the experimental activation enthalpy and the secondary deuterium kinetic isotope effect. The two reacting bond lengths in the transition state are 1.975 Å (O-C) and 2.500 Å (C-Cl), and CH 3Cl is surrounded by 13 water molecules without any apparent vacant space. The proton transfer from the attacking water to the water cluster occurs after TS is reached.

Disorder induced magnetism and electrical conduction in La doped Ca2FeMoO6 double perovskite

NASA Astrophysics Data System (ADS)

Poddar, Asok; Bhowmik, R. N.; Muthuselvam, I. Panneer

2010-11-01

We report the magnetism and electrical transport properties of La doped Ca2FeMoO6 double perovskite. Reduction in magnetic moment, nonmonotonic variation in magnetic ordering temperature (TC), increasing magnetic hardness, low temperature resistivity upturn, and loss of metallic conductivity are some of the major changes that we observed due to La doping induced disorder in double perovskite structure. The increase in magnetic disorder in La doped samples and its effect on TC is more consistent with the mean field theory. The modification in electronic band structure due to La doping is understood by establishing a correlation between the temperature dependence of electrical conductivity and thermoelectric power.

Structure and magnetic properties of Fe12X clusters

NASA Astrophysics Data System (ADS)

Gutsev, G. L.; Johnson, L. E.; Belay, K. G.; Weatherford, C. A.; Gutsev, L. G.; Ramachandran, B. R.

2014-02-01

The electronic and geometrical structures of a Fe12X family of binary clusters Fe12Al, Fe12Sc, Fe12Ti, Fe12V, Fe12Cr, Fe12Mn, Fe12Co, Fe12Ni, Fe12Cu, Fe12Zn, Fe12Y, Fe12Zr, Fe12Nb, Fe12Mo, Fe12Tc, Fe12Ru, Fe12Rh, Fe12Pd, Fe12Ag, Fe12Cd, and Fe12Gd are studied using density functional theory within generalized gradient approximation. It is found that the geometrical structures corresponding to the lowest total energy states found for the Fe12X clusters possess icosahedral shape with the substituent atom occupying the central or a surface site. The only exception presents Fe12Nb where a squeezed cage structure is the energetically most favorable. The substitution of an atom in the Fe13 cluster results in the decrease of its total spin magnetic moment of 44 μB, except for Fe12Mn and Fe12Gd. The Fe12X clusters are more stable than the parent Fe13 cluster when X = Al, Sc, Ti, V, Co, Y, Zr, Nb, Mo, Tc, Ru, and Rh.

The effects of oxygen pressure on disordering and magneto-transport properties of Ba{sub 2}FeMoO{sub 6} thin films grown via pulsed laser deposition

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

Kim, Kyeong-Won; Mhin, Sungwook; Jones, Jacob L.

2015-07-21

Epitaxial Ba{sub 2}FeMoO{sub 6} thin films were grown via pulsed laser deposition under low oxygen pressure and their structural, chemical, and magnetic properties were examined, focusing on the effects of oxygen pressure. The chemical disorder, off-stoichiometry in B site cations (Fe and Mo) increased with increasing oxygen pressure and thus magnetic properties were degraded. Interestingly, in contrast, negative magneto-resistance, which is the characteristics of this double perovskite material, was enhanced with increasing oxygen pressure. It is believed that phase segregation of highly disordered thin films is responsible for the increased magneto-resistance of thin films grown at high oxygen pressure. Themore » anomalous Hall effect, which behaves hole-like, was also observed due to spin-polarized itinerant electrons under low magnetic field below 1 T and the ordinary electron-like Hall effect was dominant at higher magnetic fields.« less

Continuous Reductive Amination of Biomass-Derived Molecules over Carbonized Filter Paper-Supported FeNi Alloy.

PubMed

Chieffi, Gianpaolo; Braun, Max; Esposito, Davide

2015-11-01

This paper reports the continuous reductive amination of different molecules, including biomass-related compounds, over carbon-supported FeNi nanoparticles obtained on the basis of inexpensive and abundant metal precursors and cellulose. A biorefinery case study for the preparation of pyrrolidones via acid-catalyzed hydrolysis of glucose followed by reductive amination of the obtained levulinic acid is described. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fe(+) chemical ionization of peptides.

PubMed

Speir, J P; Gorman, G S; Amster, I J

1993-02-01

Laser-desorbed peptide neutral molecules were allowed to react with Fe(+) in a Fourier transform mass spectrometer, using the technique of laser desorption/chemical ionization. The Fe(+) ions are formed by laser ablation of a steel target, as well as by dissociative charge-exchange ionization of ferrocene with Ne(+). Prior to reaction with laser-desorbed peptide molecules, Fe(+) ions undergo 20-100 thermalizin collisions with xenon to reduce the population of excited-state metal ion species. The Fe(+) ions that have not experienced thermalizing collisions undergo charge exchange with peptide molecules. Iron ions that undergo thermalizing collisions before they are allowed to react with peptides are found to undergo charge exchange and to form adduct species [M + Fe(+)] and fragment ions that result from the loss of small, stable molecules, such as H2O, CO, and CO2, from the metal ion-peptide complex.

Magnetic coupling of Fe-porphyrin molecules adsorbed on clean and c(2×2) oxygen-reconstructed Co(100) investigated by spin-polarized photoemission spectroscopy

NASA Astrophysics Data System (ADS)

Weber, A. P.; Caruso, A. N.; Vescovo, E.; Ali, Md. E.; Tarafder, K.; Janjua, S. Z.; Sadowski, J. T.; Oppeneer, P. M.

2013-05-01

The spin-polarized electronic structure of iron octaethylporphyrin (FeOEP) molecules adsorbed on a pristine and on a c(2×2) oxygen-reconstructed Co(100) surface has been analyzed by means of spin-polarized photoemission spectroscopy (SPPES) and first-principles density functional theory with the on-site Coulomb repulsion U term (DFT+U) calculations with and without Van der Waals corrections. The aim is to examine the magnetic exchange mechanism between the FeOEP molecules and the Co(100) substrate in the presence or absence of the oxygen mediator. The results demonstrate that the magnetic coupling from the ferromagnetic substrate to the adsorbed FeOEP molecules is ferromagnetic, whereas, the coupling is antiferromagnetic for the FeOEP on the c(2×2)O/Co(100) system. Spin-resolved partial densities of states extracted from ab initio DFT+U modeling are in fairly good comparison with the electronic spectral densities seen in angle-integrated SPPES energy dispersion curves for submonolayer coverages of FeOEP. Through combined analysis of these spectra and theoretical results, we determine that hybridization of 2p orbitals of N and O with Co 3d orbitals facilitates indirect magnetic exchange interactions between Fe and Co, whereas, a direct Fe-Co interaction involving the Fe dz2 orbital is also found for FeOEP on Co. It is observed through SPPES that the spin polarization of the photoemission-visible molecular overlayers decreases to zero as coverage is increased beyond the submonolayer regime, indicating that only interfacial magnetic coupling is at work. Microspot low-energy electron diffraction and low-energy electron microscopy were performed to characterize the physical order of the molecular coverage, revealing that FeOEP structural domains are orders of magnitude greater in size on c(2×2)O/Co(100) than on clean Co(100), which coincides with reduced scattering from the disorder and sharper features seen in SPPES.

Diversity of Chemical Bonding and Oxidation States in MS 4 Molecules of Group 8 Elements

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

Huang, Wei; Jiang, Ning; Schwarz, W. H. Eugen

The geometric and electronic ground-state structures of six MS 4 molecules (M = group-8 metals Fe, Ru, Os, Hs, Sm, and Pu) have been studied by using quantum-chemical density-functional and correlated wave-function approaches. The MS 4 species are compared to analogous MO 4 species recently investi-gated (Inorg. Chem. 2016, 55: 4616). Metal oxidation state (MOS) of high value VIII appears in low- spin singlet Td geometric species (Os,Hs)S 4 and (Ru,Os,Hs)O 4, whereas low MOS=II appears in high- spin septet D 2d species Fe(S 2) 2 and (slightly excited) metastable Fe(O 2) 2. The ground states of all other moleculesmore » have intermediate MOS values, containing S 2-, S 2 2-, S2 1- (and resp. O 2--, O 1-, O 2 2-, O 2 1-) ligands, bonded by ionic, covalent and correlative contributions.« less

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

NASA Technical Reports Server (NTRS)

Schuon, S. R.

1982-01-01

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

Magnetostructural coupling behavior at the ferromagnetic transition in double-perovskite S r2FeMo O6

NASA Astrophysics Data System (ADS)

Yang, Dexin; Harrison, Richard J.; Schiemer, Jason A.; Lampronti, Giulio I.; Liu, Xueyin; Zhang, Fenghua; Ding, Hao; Liu, Yan'gai; Carpenter, Michael A.

2016-01-01

The ordered double-perovskite S r2FeMo O6 (SFMO) possesses remarkable room-temperature low-field colossal magnetoresistivity and transport properties which are related, at least in part, to combined structural and magnetic instabilities that are responsible for a cubic-tetragonal phase transition near 420 K. A formal strain analysis combined with measurements of elastic properties from resonant ultrasound spectroscopy reveal a system with weak biquadratic coupling between two order parameters belonging to Γ4+ and m Γ4+ of parent space group F m 3 ¯m . The observed softening of the shear modulus by ˜50% is due to the classical effects of strain/order parameter coupling at an improper ferroelastic (Γ4+) transition which is second order in character, while the ferromagnetic order parameter (m Γ4+ ) couples only with volume strain. The influence of a third order parameter, for ordering of Fe and Mo on crystallographic B sites, is to change the strength of coupling between the Γ4+ order parameter and the tetragonal shear strain due to the influence of changes in local strain heterogeneity at a unit cell scale. High anelastic loss below the transition point reveals the presence of mobile ferroelastic twin walls which become pinned by oxygen vacancies in a temperature interval near 340 K. The twin walls must be both ferroelastic and ferromagnetic, but due to the weak coupling between the magnetic and structural order parameters it should be possible to pull them apart with a weak magnetic field. These insights into the role of strain coupling and relaxational effects in a system with only weak coupling between three order parameters allow rationalization and prediction of how static and dynamic properties of the material might be tuned in thin film form by choice of strain contrast with a substrate.

Microwave synthesis of molybdenum doped LiFePO4/C and its electrochemical studies.

PubMed

Naik, Amol; P, Sajan C

2016-05-10

A Mo-doped LiFePO4 composite was prepared successfully from an iron carbonyl complex by adopting a facile and rapid microwave assisted solid state method. The evolution of gases from the iron precursor produces a highly porous product. The formation and substitution of Mo in LiFePO4 were confirmed by X-ray diffraction; surface analysis was carried out by scanning electron microscopy, field emission scanning electron microscopy, and transmission electron microscopy. The electrochemical properties of the substituted LiFePO4 were examined by cyclic voltammetry, electrochemical impedance spectroscopy and by recording charge-discharge cycles. It was observed that the as prepared composites consisted of a single phase orthorhombic olivine-type structure, where Mo(6+) was successfully introduced into the M2(Fe) sites. Incorporation of supervalent Mo(6+) introduced Li(+) ion vacancies in LiFePO4. The synthesized material facilitated lithium ion diffusion during charging/discharging due to the charge compensation effect and porosity. The battery performance studies showed that LiMo0.05Fe0.095PO4 exhibited a maximum capacity of 169.7 mA h g(-1) at 0.1 C current density, with admirable stability retention. Even at higher current densities, the retention of the specific capacity was exceptional.

Phase composition and fine structure of 0.18C-1Cr-3Ni-1Mo-Fe steel after plasma-electrolytic treatment

NASA Astrophysics Data System (ADS)

Popova, Natalya; Bayatanova, Lyayla; Nikonenko, Elena; Skakov, Mazhyn; Kozlov, Eduard

2017-01-01

The paper presents the transmission electron microscopy (TEM) investigation of 0.18C-1Cr-3Mn-1Mo- Fe steel specimens to study phase transitions and modification of fine structure after plasma-electrolytic treatment (carbonitriding at 850°C during 5 min). TEM investigations involve two points: on the specimen surface and at ˜40 µm distance from it. The experiments show that the structure in the original state is a mixture consisting of ferrite and perlite grains. Carbonitriding results in a considerable modification of the quality and quantity of steel structure. Thus, on the surface, α-phase is represented by lamellar martensite, while at ˜40 µm depth - by massive and lamellar martensite tempered at low and high temperatures. Moreover, on the subsurface of the martensite plates' boundaries retained austenite layers are observed, while inside plates the particles of alloyed cementite, carbonitrides of M23(C,N)6, M2C0.61N0.39, M6,2C3,5N0,3, M(C,N)2, Cr12Fe32Mo7Ni7 types, and β-graphite are present. In the specimen at the depth of ˜40 µm, retained austenite layers are observed on the boundaries of martensite laths and plates, while inside plates only the particles of alloyed cementite and M23(C,N)6 carbonitride are formed.

Magnetic Properties of Hard Magnetic Alloy Fe - 28% Cr - 13.4% Co - 2% Mo - 0.5% Si

NASA Astrophysics Data System (ADS)

Vompe, T. A.; Milyaev, I. M.; Yusupov, V. S.

2017-01-01

The method of regression analysis is used to obtain equations describing the dependences of magnetic hysteresis properties of magnetically hard powder alloy Fe - 28% Cr - 13.4% Co - 2% Mo - 0.5% Si on regimes of thermomagnetic treatment (the temperatures of the start of the treatment and the rates of cooling in magnetic field). The determined treatment modes make it possible to obtain in an alloy with a coercive force H c up to 40 kA/m, a residual induction B r up to 1.2 T, and a maximum energy product ( BH)max up to 25 kJ/m3. The alloy may find application in the production of rotors of synchronous hysteresis-reluctance motors.

22 CFR 72.30 - Provisions in a will or advanced directive regarding disposition of remains.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 22 Foreign Relations 1 2010-04-01 2010-04-01 false Provisions in a will or advanced directive... Decreased United States Citizen Or National § 72.30 Provisions in a will or advanced directive regarding disposition of remains. United States state law regarding advance directives, deaths and estates include...

Fabrication of CaFe2O4 nanofibers via electrospinning method with enhanced visible light photocatalytic activity

NASA Astrophysics Data System (ADS)

Wang, Jianmin; Wang, Yunan; Liu, Yinglei; Li, Song; Cao, Feng; Qin, Gaowu

CaFe2O4 nanofibers with diameters of about 130nm have been fabricated via a facile electrospinning method. The structures, morphologies and optical properties of the obtained CaF2O4 nanofibers have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-Visible UV-Vis diffuse reflectance spectrum. The photocatalytic activities of the CaFe2O4 nanofibers are evaluated by the photo-degradation of Methyl orange (MO). The results show that the CaFe2O4 nanofibers (72%) exhibit much higher photocatalytic performance than the CaFe2O4 powders (27%) prepared by conventional method under visible light irradiation. The enhanced photocatalytic performance of CaFe2O4 nanofibers could be attributed to the large surface area, high photogenerated charge carriers density and low charge transfer resistance, as revealed by photoelectrochemical measurement. And fundamentally, it could be attributed to the decreased particle size and the fibrous nanostructure. This work not only provides an efficient way to improve the photocatalytic activity of CaFe2O4, but also provides a new method for preparing materials with nanofibrous structure.

A water stable europium coordination polymer as fluorescent sensor for detecting Fe3+, CrO42-, and Cr2O72- ions

NASA Astrophysics Data System (ADS)

Chen, Chen; Zhang, Xiaolei; Gao, Peng; Hu, Ming

2018-02-01

A europium coordination polymer constructed by the 4‧-(4-carboxyphenyl)- 2,2‧:6‧,2″-terpyridine ligand (HL), namely, [EuL(CH3COO)Cl]n (1), has been prepared by the solvothermal method. Compound 1 was structurally characterized by the elemental analysis, FT-IR, powder X-ray diffractions (PXRD), thermogravimetric (TG) analysis, and single-crystal X-ray diffraction. Complex 1 displays a novel linear chain structure, which further extends to the 3D supramolecular structure via π···π and hydrogen bonds interactions. The luminescent properties of 1 were investigated in detail, which exhibit the fluorescent sensing for detecting Fe3+, CrO42-, and Cr2O72- ions in aqueous solution, respectively. In addition, 1 shows high sensitive and selective sensing for CrO42- and Cr2O72- anions with the great quenching efficiency. Furthermore, the luminescent sensing mechanisms of differentiating analytes are explored in detail. It is worth noting that there exists the weak interaction between Fe3+ ions and carboxylate oxygen atoms of CH3COO- groups through XPS characterization, resulting in the high quenching effect of 1.

Micronutrients (B, Co, Cu, Fe, Mn, Mo, and Zn) content in made tea (Camellia sinensis L.) and tea infusion with health prospect: A critical review.

PubMed

Karak, Tanmoy; Kutu, Funso Raphael; Nath, Jyoti Rani; Sonar, Indira; Paul, Ranjit Kumar; Boruah, Romesh Kumar; Sanyal, Sandip; Sabhapondit, Santanu; Dutta, Amrit Kumar

2017-09-22

Tea (Camellia sinensis L.) is a perennial acidophilic crop, and known to be a nonalcoholic stimulating beverage that is most widely consumed after water. The aim of this review paper is to provide a detailed documentation of selected micronutrient contents, viz. boron (B), cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), and zinc (Zn) in made tea and tea infusion. Available data from the literature were used to calculate human health aspect associated with the consumption of tea infusion. A wide range of micronutrients reported in both made tea and tea infusion could be the major sources of micronutrients for human. The content of B, Co, Cu, Fe, Mn, Mo, and Zn in made tea are ranged from 3.04 to 58.44 μg g -1 , below detectable limit (BDL) to 122.4 μg g -1 , BDL to 602 μg g -1 , 0.275 to 13,040 μg g -1 , 0.004 to 15,866 μg g -1 , 0.04 to 570.80 μg g -1 and 0.01 to 1120 μg g -1 , respectively. Only 3.2 μg L -1 to 7.25 mg L -1 , 0.01 μg L -1 to 7 mg L -1 , 3.80 μg L -1 to 6.13 mg L -1 , 135.59 μg L -1 -11.05 mg L -1 , 0.05 μg L -1 to 1980.34 mg L -1 , 0.012 to 3.78 μg L -1 , and 1.12 μg L -1 to 2.32 μg L -1 of B, Co, Cu, Fe, Mn, Mo, and Zn, respectively, are found in tea infusion which are lower than the prescribed limit of micronutrients in drinking water by World Health Organization. Furthermore, micronutrient contents in tea infusion depend on infusion procedure as well as on the instrument used for analysis. The proportion of micronutrients found in different tea types are 1.0-88.9% for B, 10-60% for Co, 2.0-97.8% for Cu, 67.8-89.9% for Fe, 71.0-87.4% for Mn, 13.3-34% for Mo, and 34.9-83% for Zn. From the results, it can also be concluded that consumption of three cups of tea infusion per day does not have any adverse effect on human health with respect to the referred micronutrients rather got beneficial effects to human.

Ferroelectric FET for nonvolatile memory application with two-dimensional MoSe2 channels

NASA Astrophysics Data System (ADS)

Wang, Xudong; Liu, Chunsen; Chen, Yan; Wu, Guangjian; Yan, Xiao; Huang, Hai; Wang, Peng; Tian, Bobo; Hong, Zhenchen; Wang, Yutao; Sun, Shuo; Shen, Hong; Lin, Tie; Hu, Weida; Tang, Minghua; Zhou, Peng; Wang, Jianlu; Sun, Jinglan; Meng, Xiangjian; Chu, Junhao; Li, Zheng

2017-06-01

Graphene and other two-dimensional materials have received considerable attention regarding their potential applications in nano-electronics. Here, we report top-gate nonvolatile memory field-effect transistors (FETs) with different layers of MoSe2 nanosheets channel gated by ferroelectric film. The conventional gate dielectric of FETs was replaced by a ferroelectric thin film that provides a ferroelectric polarization electric field, and therefore defined as an Fe-FET where the poly (vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) was used as the gate dielectric. Among the devices with MoSe2 channels of different thicknesses, the device with a single layer of MoSe2 exhibited a large hysteresis of electronic transport with an over 105 write/erase ratio, and displayed excellent retention and endurance performance. The possible mechanism of the device’s good properties was qualitatively analyzed using band theory. Additionally, a comprehensive study comparing the memory properties of MoSe2 channels of different thicknesses is presented. Increasing the numbers of MoSe2 layers was found to cause a reduced memory window. However, MoSe2 thickness of 5 nm yielded a write/erase ratio of more than 103. The results indicate that, based on a Fe-FET structure, the combination of two-dimensional semiconductors and organic ferroelectric gate dielectrics shows good promise for future applications in nonvolatile ferroelectric memory.

Enhanced decolorization of methyl orange in aqueous solution using iron-carbon micro-electrolysis activation of sodium persulfate.

PubMed

Li, Peng; Liu, Zhipeng; Wang, Xuegang; Guo, Yadan; Wang, Lizhang

2017-08-01

Reactivity of sodium persulfate (PS) in the decolorization of methyl orange (MO) in aqueous solution using an iron-carbon micro-electrolysis (ICE) method was investigated. The effects of sodium persulfate doses, pH, Fe-to-C mass ratios, initial MO concentration as well as the reaction temperature were comprehensively studied in batch experiments. The ICE-PS coupled process was more suitable for wide ranges of pH, initial MO concentration and reaction temperature, accompanied by the reduction of Fe compared ICE. The MO removal efficiency improved substantially by ICE-PS technique, 76.03% for ICE and 91.27% for ICE-PS at experimental conditions of pH 3.0, Fe-to-C mass ratio 3:1, PS addition 10 mM and initial MO concentration 0.61 mM. Furthermore, the biodegradability index (BI) dramatically increased from 0.26 to 0.65. The binary hydroxyl and sulfate radicals that non-selectively degrade MO to the derivatives with small molecules are ascribed to ICE-PS method as detected by the UV-vis spectra. The PS activation resource was Fe 2+ through the hydroxyl radical quenching reaction by the additive tert-butanol (TBA). This study provides an in-depth theoretical understanding of the development and wide commercial application of the ICE technology to refractory industrial dye wastewater treatment. Copyright © 2017 Elsevier Ltd. All rights reserved.

A New CuO-Fe2 O3 -Mesocarbon Microbeads Conversion Anode in a High-Performance Lithium-Ion Battery with a Li1.35 Ni0.48 Fe0.1 Mn1.72 O4 Spinel Cathode.

PubMed

Di Lecce, Daniele; Verrelli, Roberta; Campanella, Daniele; Marangon, Vittorio; Hassoun, Jusef

2017-04-10

A ternary CuO-Fe 2 O 3 -mesocarbon microbeads (MCMB) conversion anode was characterized and combined with a high-voltage Li 1.35 Ni 0.48 Fe 0.1 Mn 1.72 O 4 spinel cathode in a lithium-ion battery of relevant performance in terms of cycling stability and rate capability. The CuO-Fe 2 O 3 -MCMB composite was prepared by using high-energy milling, a low-cost pathway that leads to a crystalline structure and homogeneous submicrometrical morphology as revealed by XRD and electron microscopy. The anode reversibly exchanges lithium ions through the conversion reactions of CuO and Fe 2 O 3 and by insertion into the MCMB carbon. Electrochemical tests, including impedance spectroscopy, revealed a conductive electrode/electrolyte interface that enabled the anode to achieve a reversible capacity value higher than 500 mAh g -1 when cycled at a current of 120 mA g -1 . The remarkable stability of the CuO-Fe 2 O 3 -MCMB electrode and the suitable characteristics in terms of delivered capacity and voltage-profile retention allowed its use in an efficient full lithium-ion cell with a high-voltage Li 1.35 Ni 0.48 Fe 0.1 Mn 1.72 O 4 cathode. The cell had a working voltage of 3.6 V and delivered a capacity of 110 mAh g cathode -1 with a Coulombic efficiency above 99 % after 100 cycles at 148 mA g cathode -1 . This relevant performances, rarely achieved by lithium-ion systems that use the conversion reaction, are the result of an excellent cell balance in terms of negative-to-positive ratio, favored by the anode composition and electrochemical features. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhanced interlayer exchange coupling in antiferromagnetically coupled ultrathin (Co70Fe30/Pd) multilayers

NASA Astrophysics Data System (ADS)

Meng, Zhaoliang; Qiu, Jinjun; Han, Guchang; Teo, Kie Leong

2015-12-01

We report the studies of magnetization reversal and magnetic interlayer coupling in synthetic antiferromagnetic (SAF) [Pd/Co70Fe30]9/Ru(tRu)/Pd(tPd)/[Co70Fe30/Pd]9 structure as functions of inserted Pd layer (tPd) and Ru layer (tRu) thicknesses. We found the exchange coupling field (Hex) and perpendicular magnetic anisotropy (PMA) can be controlled by both the tPd and tRu, The Hex shows a Ruderman-Kittel-Kasuya-Yosida-type oscillatory decay dependence on tRu and a maximum interlayer coupling strength Jex = 0.522 erg/cm2 is achieved at tPd + tRu ≈ 0.8 nm in the as-deposited sample. As it is known that a high post-annealing stability of SAF structure is required for magnetic random access memory applications, the dependence of Hex and PMA on the post-annealing temperature (Ta) is also investigated. We found that both high PMA of the top Co70Fe30/Pd multilayer is maintained and Hex is enhanced with increasing Ta up to 350 °C for tRu > 0.7 nm in our SAF structure.

Enhanced field emission performance of NiMoO4 nanosheets by tuning the phase

NASA Astrophysics Data System (ADS)

Bankar, Prashant K.; Ratha, Satyajit; More, Mahendra A.; Late, Dattatray J.; Rout, Chandra Sekhar

2017-10-01

In this paper we report, large scale synthesis of α and β-NiMoO4 by a facile hydrothermal method and we observed that urea plays important role on the growth of β-NiMoO4 nanosheets. We have also carried out field emission (FE) investigations of α and β-NiMoO4 at a base pressure of ∼1 × 10-8 mbar. The obtained turn-on field at emission current density of 1 μA/cm2 for β-NiMoO4 nanosheets and α -NiMoO4 is 1.3 V/μm and 2.2 V/μm respectively were observed. The maximum field emission current density of 1.006 mA/cm2at an applied electric field of 2.7 V/μm was achieved for β-NiMoO4 nanosheets. Furthermore, we found that the β-NiMoO4 nanosheets possess good field emission performance compared to α-NiMoO4. The results indicate that NiMoO4can be used as a promising material in FE applications with possibility of tuning field emission performance by controlling the phase.

Siderophile trace element diffusion in Fe-Ni alloys

NASA Astrophysics Data System (ADS)

Watson, Heather C.; Watson, E. Bruce

2003-09-01

Experiments were performed in a piston cylinder apparatus to characterize the diffusion behavior of the siderophile elements, Mo, Cu, Pd, Au, and Re in solid Fe-Ni alloy (90 wt.% Fe, 10 wt.% Ni). All experiments were conducted at 1 GPa and temperatures ranging from 1175 to 1400 °C. Activation energies of all elements fall between 270 kJ/mol (Cu) and 360 kJ/mol (Mo). Mo, Cu, Pd, and Au all show similar diffusivities at the same conditions, but the diffusivity of Re was consistently close to an order of magnitude lower. Initial experiments on other refractory elements (Os, Pt, and Ir) indicate that their diffusivities are close to or slightly lower than that of Re.

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

NASA Astrophysics Data System (ADS)

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

2017-03-01

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

Bio-dissolution of Ni, V and Mo from spent petroleum catalyst using iron oxidizing bacteria.

PubMed

Pradhan, Debabrata; Kim, Dong J; Roychaudhury, Gautam; Lee, Seoung W

2010-01-01

Bioleaching studies of spent petroleum catalyst containing Ni, V and Mo were carried out using iron oxidizing bacteria. Various leaching parameters such as Fe(II) concentration, pulp density, pH, temperature and particle size were studied to evaluate their effects on the leaching efficiency as well as the kinetics of dissolution. The percentage of leaching of Ni and V were higher than Mo. The leaching process followed a diffusion controlled model and the product layer was observed to be impervious due to formation of ammonium jarosite (NH(4))Fe(3)(SO(4))(2)(OH)(6). Apart from this, the lower leaching efficiency of Mo was due to a hydrophobic coating of elemental sulfur over Mo matrix in the spent catalyst. The diffusivities of the attacking species for Ni, V and Mo were also calculated.

Assessing potential release tendency of As, Mo and W in the tributary sediments of the Three Gorges Reservoir, China.

PubMed

Gao, Li; Gao, Bo; Peng, Wenqi; Xu, Dongyu; Yin, Shuhua

2018-01-01

As the largest man-made reservoir in China, the Three Gorges Reservoir (TGR) has significant influence on national drinking water safety. The geochemical behavior of trace elements at the sediment-water interface (SWI) is still unknown. The mobilization characteristics of trace elements (As, Mo and W)-determined by diffusive gradients in thin films (DGT)-were studied to quantitatively calculate the release trends in the SWI in three typical tributaries and the mainstream of the TGR in the summer. The results showed that concentrations of DGT-labile As, Mo and W in the overlying water and sediment cores showed significant variations in the ranges of 0.05-50.90, 0.30-1.63 and 0.01-0.42μgL -1 , respectively. The apparent net diffusive fluxes were significantly positive in most sampling sites (77.8% for As, 88.8% for Mo and 66.6% for W), suggesting that the sediment was the source of these three elements. It was noteworthy that the maximum net diffusive fluxes of As and W were found in the upstream of Meixi tributary, which may be attributed to anthropogenic activities. In addition, As, Mo and W may be incorporated in Fe and Mn oxyhydroxides and these three elements simultaneously remobilized with Fe and Mn. Copyright © 2017 Elsevier Inc. All rights reserved.

Fe-doped graphene nanosheet as an adsorption platform of harmful gas molecules (CO, CO2, SO2 and H2S), and the co-adsorption in O2 environments

NASA Astrophysics Data System (ADS)

Cortés-Arriagada, Diego; Villegas-Escobar, Nery; Ortega, Daniela E.

2018-01-01

The adsorption of pollutant gases (CO, CO2, SO2 and H2S) onto Fe-doped graphene nanosheets (FeG) is studied on the basis of density functional theory calculations at the PBE/Def2-SVP level of theory. The most stable adsorption configurations, binding characteristics, electronic properties and stability at room temperature of the FeG-Gas interactions is fully analyzed. The gas molecules are chemisorbed onto FeG with adsorption energies in the range of 0.54-1.8 eV, with an enhanced adsorption strength compared to intrinsic graphene. The stability of the FeG-Gas interactions is dominated by Lewis-acid-base interactions, and its strength is sorted as SO2 > CO > H2S > CO2. The adsorption stability is also retained at room temperature (300 K). Due to the strong interaction of SO2, CO, and H2S, FeG could catalyze or activate these gas molecules, suggesting the possibility of FeG as a catalyst substrate. The electron acceptor/donor character of CO, CO2, SO2 and H2S molecules when adsorbed onto FeG causes charge transfer processes that are responsible for the change in conductance of FeG; thus, the response of the HOMO-LUMO gap of FeG under gas adsorption could be useful for sensing applications. Furthermore, the analysis of the co-adsorption in O2 environments shows that the CO2 interaction turns unstable onto FeG, while the sensing response towards H2S is suppressed. Finally, these results give new insights into the emerging applications of Fe-doped graphene in gas capture/filtration devices, solid-state gas sensors or as a catalyst substrate.

Normal and grazing incidence pulsed laser deposition of nanostructured MoSx hydrogen evolution catalysts from a MoS2 target

NASA Astrophysics Data System (ADS)

Fominski, V. Yu.; Romanov, R. I.; Fominski, D. V.; Dzhumaev, P. S.; Troyan, I. A.

2018-06-01

Pulsed laser ablation of a MoS2 target causes enhanced splashing of the material. So, for MoSx films obtained by pulsed laser deposition (PLD) in the conventional normal incidence (NI) configuration, their typical morphology is characterized by an underlying granular structure with an overlayer of widely dispersed spherical Mo and MoSx particles possessing micro-, sub-micro- and nanometer sizes. We investigated the possibility of using high surface roughness, which occurs due to particle deposition, as a support with a large exposed surface area for thin MoSx catalytic layers for the hydrogen evolution reaction (HER). For comparison, the HER performance of MoSx layers formed by grazing incidence (GI) PLD was studied. During GI-PLD, a substrate was placed along the direction of laser plume transport and few large particles loaded the substrate. The local structure and composition of thin MoSx layers formed by the deposition of the vapor component of the laser plume were varied by changing the pressure of the buffer gas (argon, Ar). In the case of NI-PLD, an increase in Ar pressure caused the formation of quasi-amorphous MoSx (x ≥ 2) films that possessed highly active catalytic sites on the edges of the layered MoS2 nanophase. At the same time, a decrease in the deposition rate of the MoSx film appeared due to the scattering of the vapor flux by Ar molecules during flux transport from the target to the substrate. This effect prevented uniform deposition of the MoSx catalytic film on the surface of most particles, whose deposition rate was independent of Ar pressure. The scattered vapor flux containing Mo and S atoms was a dominant source for MoSx film growth during GI-PLD. The thickness and composition distribution of the MoSx film on the substrate depended on both the pressure of the buffer gas and the distance from the target. For 1.0-2.5 cm from the target, the deposition rate was quite sufficient to form S-enriched quasi-amorphous MoSx (2.5 < x < 6) catalytic

Measurement and Estimation of the 99Mo Production Yield by 100Mo(n,2n)99Mo

NASA Astrophysics Data System (ADS)

Minato, Futoshi; Tsukada, Kazuaki; Sato, Nozomi; Watanabe, Satoshi; Saeki, Hideya; Kawabata, Masako; Hashimoto, Shintaro; Nagai, Yasuki

2017-11-01

We, for the first time, measured the yield of 99Mo, the mother nuclide of 99mTc used in nuclear medicine diagnostic procedures, produced by the 100Mo(n,2n)99Mo reaction with accelerator neutrons. The neutrons with a continuous energy spectrum from the thermal energy up to about 40 MeV were provided by the C(d,n) reaction with 40 MeV deuteron beams. It was proved that the 99Mo yield agrees with that estimated by using the latest data on neutrons from the C(d,n) reaction and the evaluated cross section of the 100Mo(n,2n)99Mo reaction given in the Japanese Evaluated Nuclear Data Library. On the basis of the agreement, a systematic calculation was carried out to search for an optimum condition that enables us to produce as much 99Mo as possible with a good 99Mo/100Mo value from an economical point of view. The calculated 99Mo yield from a 150 g 100MoO3 sample indicated that about 30% of the demand for 99Mo in Japan can be met with a single accelerator capable of 40 MeV, 2 mA deuteron beams. Here, by referring to an existing 18F-fluorodeoxyglucose (FDG) distribution system we assumed that 99mTc radiopharmaceuticals formed after separating 99mTc from 99Mo can be delivered to hospitals from a radiopharmaceutical company within 6 h. The elution of 99mTc from 99Mo twice a day would meet about 50% of the demand for 99Mo.

Controlling n-type doping in MoO 3

DOE PAGES

Peelaers, H.; Chabinyc, M. L.; Van de Walle, C. G.

2017-02-27

Here, we study the electronic properties of native defects and intentional dopant impurities in MoO 3, a widely used transparent conductor. Using first-principles hybrid functional calculations, we show that electron polarons can be self-trapped, but they can also bind to defects; thus, they play an important role in understanding the properties of doped MoO 3. Our calculations show that oxygen vacancies can cause unintentional n-type doping in MoO 3. Mo vacancies are unlikely to form. Tc and Re impurities on the Mo site and halogens (F, Cl, and Br) on the O site all act as shallow donors but trapmore » electron polarons. Fe, Ru, and Os impurities are amphoteric and will compensate n-type MoO 3. Mn dopants are also amphoteric, and they show interesting magnetic properties. These results support the design of doping approaches that optimally exploit functionality.« less

Development of a wear-resistant flux cored wire of Fe-C-Si-Mn-Cr-Ni-Mo-V system for deposit welding of mining equipment parts

NASA Astrophysics Data System (ADS)

Osetkovsky, I. V.; Kozyrev, N. A.; Kryukov, R. E.; Usoltsev, A. A.; Gusev, A. I.

2017-09-01

The effect of introduction of cobalt in the charge of the flux cored wire of Fe-C-Si-Mn-Cr-Ni-Mo-V system operating under abrasive and abrasive-shock loads is studied. In the laboratory conditions samples of flux cored wires were made, deposition was performed, the effect of cobalt on the hardness and the degree of wear was evaluated, metallographic studies were carried out. The influence of cobalt introduced into the charge of the flux cored wire of Fe-C-Si-Mn-Cr-Ni-Mo-V system on the structure, nature of nonmetallic inclusions, hardness and wear resistance of the weld metal was studied. In the laboratory conditions samples flux cored wire were made using appropriate powdered materials. As a carbon-fluorine-containing material dust from gas cleaning units of aluminum production was used. In the course of the study the chemical composition of the weld metal was determined, metallographic analysis was performed, mechanical properties were determined. As a result of the metallographic analysis the size of the former austenite grain, martensite dispersion in the structure of the weld metal, the level of contamination with its nonmetallic inclusions were established.

Highly ordered molecular rotor matrix on a nanopatterned template: titanyl phthalocyanine molecules on FeO/Pt(111).

PubMed

Lu, Shuangzan; Huang, Min; Qin, Zhihui; Yu, Yinghui; Guo, Qinmin; Cao, Gengyu

2018-08-03

Molecular rotors, motors and gears play important roles in artificial molecular machines, in which rotor and motor matrices are highly desirable for large-scale bottom-up fabrication of molecular machines. Here we demonstrate the fabrication of a highly ordered molecular rotor matrix by depositing nonplanar dipolar titanyl phthalocyanine (TiOPc, C 32 H 16 N 8 OTi) molecules on a Moiré patterned dipolar FeO/Pt(111) substrate. TiOPc molecules with O atoms pointing outwards from the substrate (upward) or towards the substrate (downward) are alternatively adsorbed on the fcc sites by strong lateral confinement. The adsorbed molecules, i.e. two kinds of molecular rotors, show different scanning tunneling microscopy images, thermal stabilities and rotational characteristics. Density functional theory calculations clarify that TiOPc molecules anchoring upwards with high adsorption energies correspond to low-rotational-rate rotors, while those anchoring downwards with low adsorption energies correspond to high-rotational-rate rotors. A robust rotor matrix fully occupied by low-rate rotors is fabricated by depositing molecules on the substrate at elevated temperature. Such a paradigm opens up a promising route to fabricate functional molecular rotor matrices, driven motor matrices and even gear groups on solid substrates.

{Mo96La8} eggshell ring and self-assembly to {Mo132} Keplerate through Mo-blue intermediate, involved in UV-photolysis of [Mo7O24](6-)/carboxylic acid system at pH 4.

PubMed

Yamase, Toshihiro; Kumagai, Shun; Prokop, Petra V; Ishikawa, Eri; Tomsa, Adrian-Raul

2010-10-18

The prolonged UV-photolysis of aqueous solutions containing [Mo(7)O(24)](6-) and C(2)H(5)CO(2)H (as electron donor) at pH 3.9-4.1 generates the carboxylate-coordinated {Mo(132)} Keplerate (1a) isolated as a formamidinium/ammonium-mixed salt, [HC(NH(2))(2)](26)(NH(4))(28)[Mo(V)(60)Mo(VI)(72)O(372)(H(2)O)(48)(C(2)H(5)CO(2))(36)((i)C(3)H(7)CO(2))(6)]·16H(2)O (1), through the Mo-blue intermediate (2). The coordination of 2 to La(3+) gives rise to the formation of the chain structure of the C(2)-symmetric {Mo(96)La(8)} eggshell rings, formulated by H(22)[Mo(V)(20)Mo(VI)(76)O(301)(H(2)O)(29){La(H(2)O)(6)}(2)]{La(H(2)O)(5)}(6)]·54.5H(2)O (3). The eggshell-ring geometry results from the insertion of [Mo(VI)(2)O(7)(H(2)O)](2-) (spacer) into the equator outer ring of the wheel-shaped Mo-blue, and 10 {(Mo(VI))(Mo(VI)(5))} pentagonal subunits alternately above and below the equator outer ring are connected by eight La(3+) and two {Mo(VI)(2)} linkers within two inner rings. The neighboring eggshell rings are linked through two Mo-O-Mo bonds formed by dehydrative condensation between the {Mo(VI)(2)} linkers to result in the chain structure. Together with the results of the elemental analysis and IR, electronic absorption, (13)C NMR, and ESI-MS spectra for 2, the ring profile analysis of 3 let us identify 2 with a carbolylate-coordinated Mo-blue ring of high nuclearity. The Mo(VI)→Mo(V) photoreductive change of 2 to the 60-electron reduced Keplerate in the presence of C(2)H(5)CO(2)H involves both degradation of the outer ring and splitting of the binuclear linkers, which leads to the formation of [(Mo(VI))Mo(VI)(5)O(21)(H(2)O)(4)(carboxylate)](7-) pentagonal subunits and [Mo(V)(2)O(4)(carboxylate)](+)/[Mo(V)O(2)(carboxylate)(1/2)](0.5+)-mixed linkers for 1.

Ferromagnetic resonance study of the non-stoichiometric double perovskite Sr2Fe1+xMo1-xO6

NASA Astrophysics Data System (ADS)

Medina, J. De La Torre; Piraux, L.; Soto, T. E.; Morales, R.; Navarro, O.

2018-02-01

In this work we report a ferromagnetic resonance study on the magnetic properties of double perovskite compounds fab-ricated by solid state reaction. Based on a mean field approach, along with morphological considerations, we accurately determined the saturation magnetization of the non-stoichiometric double perovskite Sr2Fe1+xMo1-xO6. Our approach has revealed a direct in-fluence of composition on the overall magnetic behavior of these materials, providing complementary experimental evidence that corroborates previous theoretical findings. The understanding of the influence of composition is of paramount importance for the design of ferromagnetic oxides with tunable magnetic and magneto-transport behavior.

Heterometal cubane-type MFe(3)S(4) clusters (M = Mo, V) trigonally symmetrized with hydrotris(pyrazolyl)borate(1-) and tris(pyrazolyl)methanesulfonate(1-) capping ligands.

PubMed

Fomitchev, Dmitry V; McLauchlan, Craig C; Holm, R H

2002-02-25

A series of heterometal cubane-type clusters containing [VFe(3)S(4)](2+) and [MoFe(3)S(4)](3+,2+) cores has been prepared. Ligand substitution of [(DMF)(3)VFe(3)S(4)Cl(3)](-) affords [(Tpms)VFe(3)S(4)L(3)](2)(-) (L = Cl(-) (8), EtS(-) (9), p-MeC(6)H(4)S(-), p-MeC(6)H(4)O(-)). A new procedure for the preparation of molybdenum single cubanes is introduced by the reaction of recently reported [(Tp)MoS(S(4))](-) with FeCl(2)/NaSEt to afford [(Tp)MoFe(3)S(4)Cl(3)](-) (1, 75% yield). This procedure is more efficient that the existing multistep synthesis of single cubanes, which generally affords clusters of mirror symmetry. Also prepared were [(Tp)MoFe(3)S(4)L(3)](-) (L = EtS(-) (2), p-MeC(6)H(4)S(-)). Reduction of 1 with borohydride gives [(Tp)MoFe(3)S(4)Cl(3)](2-) (5, 67%). Owing to the nature of the heterometal ligand, all clusters have idealized trigonal symmetry, reflected in their (1)H NMR spectra. Trigonal structures are demonstrated by crystallography of (Bu(4)N)[1,2], (Bu(4)N)(2)[5] x MeCN, and (Me(4)N)(2)[8,9]. The availability of 1 and 5 allows the first comparison of structures and (57)Fe isomer shifts of [MoFe(3)S(4)](3+,2+) in a constant ligand environment. Small increases in most bond distances indicate that an antibonding electron is added in the reduction of 1. Collective synthetic and electrochemical results from this and other studies demonstrate the existence of the series of oxidation states [VFe(3)S(4)](3+,2+,1+) and [MoFe(3)S(4)](4+,3+,2+) whose relative stabilities within a given series are strongly ligand dependent. Isomer shifts indicate that the reduction of 1 largely affects the Fe(3) subcluster and are consistent with the formal descriptions [MoFe(3+)(2)Fe(2+)S(4)](3+) (1) and [MoFe(3+)Fe(2+)(2)S(4)](2+) (5). Reaction of 1 with excess Li(2)S in acetonitrile affords the double cubane [[(Tp)MoFe(3)S(4)Cl(2)](2)(mu(2)(-)S)](2)(-), whose sulfide-bridged structure is supported by two sequential reductions separated by 290 mV, in analogy with

Cold cathode emission studies on topographically modified few layer and single layer MoS2 films

NASA Astrophysics Data System (ADS)

Gaur, Anand P. S.; Sahoo, Satyaprakash; Mendoza, Frank; Rivera, Adriana M.; Kumar, Mohit; Dash, Saroj P.; Morell, Gerardo; Katiyar, Ram S.

2016-01-01

Nanostructured materials, such as carbon nanotubes, are excellent cold cathode emitters. Here, we report comparative field emission (FE) studies on topographically tailored few layer MoS2 films consisting of ⟨0001⟩ plane perpendicular (⊥) to c-axis (i.e., edge terminated vertically aligned) along with planar few layer and monolayer (1L) MoS2 films. FE measurements exhibited lower turn-on field Eto (defined as required applied electric field to emit current density of 10 μA/cm2) ˜4.5 V/μm and higher current density ˜1 mA/cm2, for edge terminated vertically aligned (ETVA) MoS2 films. However, Eto magnitude for planar few layer and 1L MoS2 films increased further to 5.7 and 11 V/μm, respectively, with one order decrease in emission current density. The observed differences in emission behavior, particularly for ETVA MoS2 is attributed to the high value of geometrical field enhancement factor (β), found to be ˜1064, resulting from the large confinement of localized electric field at edge exposed nanograins. Emission behavior of planar few layers and 1L MoS2 films are explained under a two step emission mechanism. Our studies suggest that with further tailoring the microstructure of ultra thin ETVA MoS2 films would result in elegant FE properties.

Modulating the magnetic behavior of Fe(II)-MOF-74 by the high electron affinity of the guest molecule.

PubMed

Han, Sungmin; Kim, Heejin; Kim, Jaehoon; Jung, Yousung

2015-07-14

As a new class of magnetic materials, metal-organic framework (MOF) has received a significant attention due to their functionality and porosity that can provide diverse magnetic phenomena by utilizing host-guest chemistry. For Fe-MOF-74, we here find using density functional calculations that the O2 and C2H4 adsorptions result in the ferromagnetic (FM) and antiferromagnetic (AFM) orderings along the 1D chain of an hexagonal MOF framework, respectively, while their adsorption energies, pi-complexation, and geometrical changes are all similar upon binding. We reveal that this different magnetism behavior is attributed to the different electronic effects, where the adsorbed O2 greatly withdraws a minor spin electron from the Fe centers. The latter significant back donation opens a new channel for superexchange interactions that can enhance the FM coupling between Fe centers, where the strength of calculated intrachain FM coupling constrant (Jin) in O2 adsorbed Fe-MOF-74 is more than 10 times enhanced compared to bare Fe-MOF-74. This prediction suggests a possibility for the conceptual usage of Fe-MOF-74 as a gas sensor based on its magnetic changes caused by the adsorbed gases. Furthermore, the suggested mechanism might be used to control the magnetic properties of MOFs using the guest molecules, although concrete strategies to enhance such magnetic interactions to be used in practical applications would require further significant investigation.

Fluorescence quenching by TEMPO: a sub-30 A single-molecule ruler.

PubMed

Zhu, Peizhi; Clamme, Jean-Pierre; Deniz, Ashok A

2005-11-01

A series of DNA molecules labeled with 5-carboxytetramethylrhodamine (5-TAMRA) and the small nitroxide radical TEMPO were synthesized and tested to investigate whether the intramolecular quenching efficiency can be used to measure short intramolecular distances in small ensemble and single-molecule experiments. In combination with distance calculations using molecular mechanics modeling, the experimental results from steady-state ensemble fluorescence and fluorescence correlation spectroscopy measurements both show an exponential decrease in the quenching rate constant with the dye-quencher distance in the 10-30 A range. The results demonstrate that TEMPO-5-TAMRA fluorescence quenching is a promising method to measure short distance changes within single biomolecules.

Fluorescence Quenching by TEMPO: A Sub-30 Å Single-Molecule Ruler

PubMed Central

Zhu, Peizhi; Clamme, Jean-Pierre; Deniz, Ashok A.

2005-01-01

A series of DNA molecules labeled with 5-carboxytetramethylrhodamine (5-TAMRA) and the small nitroxide radical TEMPO were synthesized and tested to investigate whether the intramolecular quenching efficiency can be used to measure short intramolecular distances in small ensemble and single-molecule experiments. In combination with distance calculations using molecular mechanics modeling, the experimental results from steady-state ensemble fluorescence and fluorescence correlation spectroscopy measurements both show an exponential decrease in the quenching rate constant with the dye-quencher distance in the 10–30 Å range. The results demonstrate that TEMPO-5-TAMRA fluorescence quenching is a promising method to measure short distance changes within single biomolecules. PMID:16199509

Heterogeneous Fenton-like discoloration of methyl orange using Fe3O4/MWCNTs as catalyst: kinetics and Fenton-like mechanism

NASA Astrophysics Data System (ADS)

Xu, Huan-Yan; Wang, Yuan; Shi, Tian-Nuo; Zhao, Hang; Tan, Qu; Zhao, Bo-Chao; He, Xiu-Lan; Qi, Shu-Yan

2018-03-01

The kinetics and Fenton-like mechanism are two challenging tasks for heterogeneous Fenton-like catalytic oxidation of organic pollutants. In this study, three kinetic models were used for the kinetic studies of Fe3O4/MWCNTs-H2O2 Fenton-like reaction for MO degradation. The results indicated that this reaction followed the first-order kinetic model. The relationship of reaction rate constant and temperature followed the Arrhenius equation. The activation energy and frequency factor of this system were calculated as 8.2 kJ·mol-1 and 2.72 s-1, respectively. The quantifications of Fe ions dissolution and •OH radicals generation confirmed that the homogeneous and heterogeneous catalyses were involved in Fe3O4/MWCNTs-H2O2 Fenton-like reaction. The reaction rate constant was closely related with Fe ions dissolution and •OH radicals generation. Fe3O4/MWCNTs nanocomposites had typical ferromagnetic property and could be easily separated from solution by an external magnet after being used. Furthermore, Fe3O4/MWCNTs nanocomposites exhibited good stability and recyclability. Finally, the Fenton-like mechanisms on homogeneous and heterogeneous catalyses were described.

Biogeochemical Cycling of Fe, S, C, N, and Mo in the 3.2 Ga ocean: Constraints from DXCL-DP Black Shales from Pilbara, Western Australia

NASA Astrophysics Data System (ADS)

Yamaguchi, K. E.; Naraoka, H.; Ikehara, M.; Ito, T.; Kiyokawa, S.

2014-12-01

Records of geochemical cycling of bio-essential, redox-sensitive elements have keys to decipher mysteries of the co-evolution of Earth and life. To obtain insight into biogeochemical cycling of those elements and early evolution of microbial biosphere from high-quality samples, we drilled through Mesoarchean strata in coastal Pilbara (Dixon Island-Cleaverville Drilling Project, see Yamaguchi et al., 2009; Kiyokawa et al., 2012), and obtained 3.2 Ga old drillcores (CL1, CL2, and DX) of sulfide-rich black shales in the Cleaverville Group, Pilbara Supergroup. We conducted a systematic geochemical study involving sequential extractions of Fe, S, C, and N for phase-dependent contents (e.g., pyrite-Fe, reactive-Fe, highly reactive-Fe, unreactive-Fe, pyrite-S, sulfate-S, organic-S, elemental-S, Corg, Ccarb, Norg, and Nclay) and their stable isotope compositions, micro FT-IR and laser Raman spectroscopy for extracted kerogen, in addition to major and trace (redox-sensitive; e.g., Mo) element analysis, for >100 samples. Here we integrate our recent multidisciplinary investigations into the redox state of ocean and nature of microbial biosphere in the ocean 3.2 Ga ago. All of the obtained data are very difficult to explain only by geochemical processes in strictly anoxic environments, where both atmosphere and oceans were completely anoxic, like an environment before the inferred "Great Oxidation Event" when pO2 was lower than 0.00001 PAL (e.g., Holland, 1994). Our extensive data set consistently suggests that oxygenic photosynthesis, bacterial sulfate reduction, and microbially mediated redox-cycling of nitrogen, possibly involving denitrification and N2-fixation, are very likely to have been operating, and may be used as a strong evidence for at least local and temporal existence of oxidized environment as far back as 3.2 Ga ago. Modern-style biogeochemical cycling of Fe, S, C, N, and Mo has been operating since then. The atmosphere-hydrosphere system 3.2 Ga ago would have

Molecular adsorption properties of CO and H2O on Au-, Cu-, and AuxCuy-doped MoS2 monolayer

NASA Astrophysics Data System (ADS)

Kadioglu, Yelda; Gökoğlu, Gökhan; Üzengi Aktürk, Olcay

2017-12-01

In this study, we investigate the adsorption properties of Au, Cu, and AuxCuy nanoclusters on MoS2 sheet and the interactions of the adsorbed systems with CO and H2O molecules by using first principles calculations. Results indicate that Au, Cu, or AuxCuy strongly binds to MoS2 monolayer resulting in enhanced chemical activity and sensitivity toward CO and H2O molecules compared to bare MoS2 monolayer. Although both CO and H2O molecules bind weakly to pristine MoS2 monolayer, CO strongly binds to MoS2 sheet in the presence of Au, Cu atoms or AuxCuy clusters. Semiconductor MoS2 monolayer turns into metal upon Au or Cu adsorption. AuxCuy nanocluster adsorption decreases the band gap of MoS2 monolayer acting as a n-type dopant. AuxCuy-doped MoS2 systems have improved adsorption properties for CO and H2O molecules, so the conclusions provided in this study can be useful as a guide for next generation device modeling.

Reconstruction of early Cambrian ocean chemistry from Mo isotopes

NASA Astrophysics Data System (ADS)

Wen, Hanjie; Fan, Haifeng; Zhang, Yuxu; Cloquet, Christophe; Carignan, Jean

2015-09-01

The Neoproterozoic-Cambrian transition was a key time interval in the history of the Earth, especially for variations in oceanic and atmospheric chemical composition. However, two conflicting views exist concerning the nature of ocean chemistry across the Precambrian-Cambrian boundary. Abundant geochemical evidence suggests that oceanic basins were fully oxygenated by the late Ediacaran, while other studies provide seemingly conflicting evidence for anoxic deep waters, with ferruginous conditions [Fe(II)-enriched] persisting into the Cambrian. Here, two early Cambrian sedimentary platform and shelf-slope sections in South China were investigated to trace early Cambrian ocean chemistry from Mo isotopes. The results reveal that early Cambrian sediments deposited under oxic to anoxic/euxinic conditions have δ98/95Mo values ranging from -0.28‰ to 2.29‰, which suggests that early Cambrian seawater may have had δ98/95Mo values of at least 2.29‰, similar to modern oceans. The heaviest and relatively homogeneous δ98/95Mo values were recorded in siltstone samples formed under completely oxic conditions, which is considered that Mn oxide-free shuttling was responsible for such heavy δ98/95Mo value. Further, combined with Fe species data and the accumulation extent of Mo and U, the variation of δ98/95Mo values in the two studied sections demonstrate a redox-stratified ocean with completely oxic shallow water and predominantly anoxic (even euxinic) deeper water having developed early on, which eventually became completely oxygenated. This suggests that oceanic circulation at the time became reorganized, and such changes in oceanic chemistry may have been responsible for triggering the "Cambrian Explosion" of biological diversity.

Experimental investigation of the influence of Mo contained in stainless steel on Cs chemisorption behavior

NASA Astrophysics Data System (ADS)

Di Lemma, F. G.; Nakajima, K.; Yamashita, S.; Osaka, M.

2017-02-01

Chemisorption phenomena can affect fission products (FP) retention in a nuclear reactor vessel during a severe accident (SA). Detailed information on the FP chemisorbed deposits, especially for Cs, are important for a rational decommissioning of the reactor following a SA, as for the Fukushima Daiichi Power Station. Moreover the retention of Cs will influence the source term assessment and thus improved models for this phenomenon are needed in SA codes. This paper describes the influence on Cs chemisorption of molybdenum contained in stainless steel (SS) type 316. In our experiments it was observed that Cs-Mo deposits (CsFe(MoO4)3, Cs2MoO4) were formed together with CsFeSiO4, which is the predominant compound formed by chemisorption. The Cs-Mo deposits were found to revaporize from the SS sample at 1000 °C, and thus could contribute to the source term. On the other hand, CsFeSiO4 will be probably retained in the reactor during a SA due to its stability.

MoSi2-Base Composites

NASA Technical Reports Server (NTRS)

Hebsur, Mohan G.

2003-01-01

Addition of 30 to 50 vol% of Si3N4 particulate to MoSi2 eliminated its low temperature catastrophic failure, improved room temperature fracture toughness and the creep resistance. The hybrid composite SCS-6/MoSi2-Si3N4 did not show any matrix cracking and exhibited excellent mechanical and environmental properties. Hi-Nicalon continuous fiber reinforced MoSi2-Si3N4 also showed good strength and toughness. A new MoSi2-base composite containing in-situ whisker-type (Beta)Si3N4 grains in a MoSi2 matrix is also described.

Effect of Quenching Process on Microstructures and Mechanical Properties of Fe-0.9Mn-0.5Cr-2.4Ni-0.5Mo-C Steel

NASA Astrophysics Data System (ADS)

Chen, Jie; Li, Changsheng; Jin, Xin; Chen, Liqing; Fang, Lei

2018-03-01

To develop an appropriate quenching process to produce Fe-0.9Mn-0.5Cr-2.4Ni-0.5Mo-C steel, the microstructures and mechanical properties of this steel were investigated under the direct quenching and tempering (DQT) and the direct quenching, reheated quenching and tempering (DQQT) heat treatment processes. The microstructure of the DQQT specimen was basically tempered sorbite with spherical precipitates, while quite a bit of tempered martensite was in the DQT specimen with dispersive nanoscaled precipitates. The yield strengths of the DQT and DQQT specimens were 1154 and 955 MPa, respectively. The yield strength of the DQT specimen was higher than that of the DQQT specimen because of its finer grain size, higher density of dislocations and dispersed precipitates. The DQQT specimen had spherical precipitates, which hindered the propagation of the crack. Moreover, the high-angle grain boundaries in the DQQT specimen took a higher proportion. Therefore, the Charpy impact values of DQT and DQQT specimens at - 60 °C were 38 and 75 J, respectively. Consequently, the mechanical properties of the Fe-0.9Mn-0.5Cr-2.4Ni-0.5Mo-C steel, which met the standard of 1000 MPa grade steel plate for hydropower station, were acquired by the DQQT process.

Molybdenum-carbon bond dissociation energies in Mo(CO) sub 6

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

Ganske, J.A.; Rosenfeld, R.N.

1990-05-17

The pressure dependence of the recombination rate constants for Mo(CO){sub n} (n = 3,4 and 5) with CO has been studied by time-resolved infrared laser absorption spectroscopy. These data, in conjunction with an RRKM model for unimolecular decay of the activated molecules (Mo(CO){sub 6})*, (Mo(CO){sub 5})*, and (Mo(CO){sub 4})*, have allowed the determination of the bond dissociation energies for several of the Mo-C bonds in Mo(CO){sub 6}. The first Mo-C bond dissociation energies for Mo(CO){sub 6}, Mo(CO){sub 5}, and Mo(CO){sub 4} are found to be DH{degree}((CO){sub 5}Mo{hor ellipsis}CO) = 35 {plus minus} 5 kcal/mol, DH{degree}((CO){sub 4}Mo{hor ellipsis}CO) = 27 {plusmore » minus} 5 kcal/mol, and DH{degree}((CO){sub 3}Mo{hor ellipsis}CO) = 31 {plus minus} 5 kcal/mol.« less

40 CFR 141.72 - Disinfection.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 23 2014-07-01 2014-07-01 false Disinfection. 141.72 Section 141.72... PRIMARY DRINKING WATER REGULATIONS Filtration and Disinfection § 141.72 Disinfection. A public water... disinfection treatment specified in paragraph (a) of this section beginning December 30, 1991, unless the State...

40 CFR 141.72 - Disinfection.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 24 2012-07-01 2012-07-01 false Disinfection. 141.72 Section 141.72... PRIMARY DRINKING WATER REGULATIONS Filtration and Disinfection § 141.72 Disinfection. A public water... disinfection treatment specified in paragraph (a) of this section beginning December 30, 1991, unless the State...

Purification and some properties of Fe protein of nitrogenase from. Anabaena cylindrica

NASA Astrophysics Data System (ADS)

Du, Daixian; Lin, Huimin; He, Zhenrong; Dai, Lingfen; Xin, Wusheng; Li, Shanghao

1990-12-01

The Fe protein of Anabaena cylindrica was first separated and purified by chromatography through DEAE-cellulose columns then by gel electrophoresis. The specific activity was up to 142.46 nmol C2H4/mg protein · min. It was homogeneous as shown by 1) a single band in the gel electrophorogram; 2) absence of Mo and tryptophan; 3) content of about 3.4 atoms of Fe per mole protein. The molecular weight of the Fe protein of A. cylindrica was about 61,000 daltons as estimated by SDS-gel electrophoresis and calculated from the amino acid composition. The residues of aspartate and glutamate were about 2.6 times that of arginine and lysine in the Fe protein. Crossing Fe protein of A. cylindrica with Mo-Fe protein of Azotobacter vinelandii gave positive result. The reciprocal crossing also showed activity.

Fe/Co doped molybdenum diselenide: a promising two-dimensional intermediate-band photovoltaic material.

PubMed

Zhang, Jiajia; He, Haiyan; Pan, Bicai

2015-05-15

An intermediate-band (IB) photovoltaic material is an important candidate in developing the new-generation solar cell. In this paper, we propose that the Fe-doped or the Co-doped MoSe2 just meets the required features in IB photovoltaic materials. Our calculations demonstrate that when the concentration of the doped element reaches 11.11%, the doped MoSe2 shows a high absorptivity for both infrared and visible light, where the photovoltaic efficiency of the doped MoSe2 is as high as 56%, approaching the upper limit of photovoltaic efficiency of IB materials. So, the Fe- or Co-doped MoSe2 is a promising two-dimensional photovoltaic material.

The C9orf72 repeat expansion disrupts nucleocytoplasmic transport.

PubMed

Zhang, Ke; Donnelly, Christopher J; Haeusler, Aaron R; Grima, Jonathan C; Machamer, James B; Steinwald, Peter; Daley, Elizabeth L; Miller, Sean J; Cunningham, Kathleen M; Vidensky, Svetlana; Gupta, Saksham; Thomas, Michael A; Hong, Ingie; Chiu, Shu-Ling; Huganir, Richard L; Ostrow, Lyle W; Matunis, Michael J; Wang, Jiou; Sattler, Rita; Lloyd, Thomas E; Rothstein, Jeffrey D

2015-09-03

The hexanucleotide repeat expansion (HRE) GGGGCC (G4C2) in C9orf72 is the most common cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Recent studies support an HRE RNA gain-of-function mechanism of neurotoxicity, and we previously identified protein interactors for the G4C2 RNA including RanGAP1. A candidate-based genetic screen in Drosophila expressing 30 G4C2 repeats identified RanGAP (Drosophila orthologue of human RanGAP1), a key regulator of nucleocytoplasmic transport, as a potent suppressor of neurodegeneration. Enhancing nuclear import or suppressing nuclear export of proteins also suppresses neurodegeneration. RanGAP physically interacts with HRE RNA and is mislocalized in HRE-expressing flies, neurons from C9orf72 ALS patient-derived induced pluripotent stem cells (iPSC-derived neurons), and in C9orf72 ALS patient brain tissue. Nuclear import is impaired as a result of HRE expression in the fly model and in C9orf72 iPSC-derived neurons, and these deficits are rescued by small molecules and antisense oligonucleotides targeting the HRE G-quadruplexes. Nucleocytoplasmic transport defects may be a fundamental pathway for ALS and FTD that is amenable to pharmacotherapeutic intervention.

Ethylene response factor AtERF72 negatively regulates Arabidopsis thaliana response to iron deficiency.

PubMed

Liu, Wei; Li, Qiwei; Wang, Yi; Wu, Ting; Yang, Yafei; Zhang, Xinzhong; Han, Zhenhai; Xu, Xuefeng

2017-09-23

Ethylene regulates the plant's response to stress caused by iron (Fe) deficiency. However, specific roles of ERF proteins in response to Fe deficiency remain poorly understood. Here, we investigated the role of ERF72 in response to iron deficiency in Arabidopsis thaliana. In this study, the levels of the ethylene response factor AtERF72 increased in leaves and roots induced under the iron deficient conditions. erf72 mutant plants showed increased growth compared to wild type (WT) when grown in iron deficient medium for 5 d. erf72 mutants had increased root H + velocity and the ferric reductase activity, and increase in the expression of the iron deficiency response genes iron-regulated transporter 1 (IRT1) and H + -ATPase (HA2) levels in iron deficient conditions. Compared to WT plants, erf72 mutants retained healthy chloroplast structure with significantly higher Fe and Mg content, and decreased chlorophyll degradation gene pheophorbide a oxygenase (PAO) and chlorophyllase (CLH1) expression when grown in iron deficient media. Yeast one-hybrid analysis showed that ERF72 could directly bind to the promoter regions of iron deficiency responses genes IRT1, HA2 and CLH1. Based on our results, we suggest that ethylene released from plants under iron deficiency stress can activate the expression of ERF72, which responds to iron deficiency in the negative regulation. Copyright © 2017 Elsevier Inc. All rights reserved.

CD30 antigen in embryonal carcinoma and embryogenesis and release of the soluble molecule.

PubMed Central

Latza, U.; Foss, H. D.; Dürkop, H.; Eitelbach, F.; Dieckmann, K. P.; Loy, V.; Unger, M.; Pizzolo, G.; Stein, H.

1995-01-01

The expression, serological detection, and possible functional role of the CD30 antigen in Hodgkin's disease and anaplastic large cell lymphoma is well documented. In embryonal carcinoma (EC), the expression of this cytokine receptor has been demonstrated only by immunohistology. Because the CD30 monoclonal antibody Ki-1 was found to cross-react with an unrelated molecule, we examined by in situ hybridization testicular germ cell neoplasms for the presence of CD30-specific transcripts. CD30 mRNA was detectable in the tumor cells of 9 of 9 cases of EC or mixed germ cell tumors with an EC component but in no other nonlymphoid tumors. Thus, the CD30 transcript expression pattern proved to be identical to the immunostaining pattern seen with the CD30-specific monoclonal antibody Ber-H2. By Northern blot analysis, CD30 transcripts could be demonstrated in the EC cell line Tera-2. Employing a highly sensitive second generation sandwich enzyme-linked immunosorbent assay, we could detect the soluble CD30 molecule in 8 of 8 sera from patients with a diagnosis of EC but not in 8 of 10 sera from patients with other testicular germ cell tumors. In fetal tissue, no CD30-expressing germ cells or epithelial cells could be observed. Thus, the cellularly expressed CD30 marker for testicular neoplasms of EC type. Moreover, the serum levels of soluble CD30 antigen seem to be a promising parameter for monitoring patients with EC. Images Figure 1 Figure 2 PMID:7856755

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

USGS Publications Warehouse

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

1996-01-01

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

Substrate channel in nitrogenase revealed by a molecular dynamics approach.

PubMed

Smith, Dayle; Danyal, Karamatullah; Raugei, Simone; Seefeldt, Lance C

2014-04-15

Mo-dependent nitrogenase catalyzes the biological reduction of N2 to two NH3 molecules at FeMo-cofactor buried deep inside the MoFe protein. Access of substrates, such as N2, to the active site is likely restricted by the surrounding protein, requiring substrate channels that lead from the surface to the active site. Earlier studies on crystallographic structures of the MoFe protein have suggested three putative substrate channels. Here, we have utilized submicrosecond atomistic molecular dynamics simulations to allow the nitrogenase MoFe protein to explore its conformational space in an aqueous solution at physiological ionic strength, revealing a putative substrate channel. The viability of this observed channel was tested by examining the free energy of passage of N2 from the surface through the channel to FeMo-cofactor, resulting in the discovery of a very low energy barrier. These studies point to a viable substrate channel in nitrogenase that appears during thermal motions of the protein in an aqueous environment and that approaches a face of FeMo-cofactor earlier implicated in substrate binding.

Chemistry of one-dimensional metallic edge states in MoS2 nanoclusters

NASA Astrophysics Data System (ADS)

Lauritsen, J. V.; Nyberg, M.; Vang, R. T.; Bollinger, M. V.; Clausen, B. S.; Topsøe, H.; Jacobsen, K. W.; Lægsgaard, E.; Nørskov, J. K.; Besenbacher, F.

2003-03-01

Nanostructures often have unusual properties that are linked to their small size. We report here on extraordinary chemical properties associated with the edges of two-dimensional MoS2 nanoclusters, which we show to be able to hydrogenate and break up thiophene (C4H4S) molecules. By combining atomically resolved scanning tunnelling microscopy images of single-layer MoS2 nanoclusters and density functional theory calculations of the reaction energetics, we show that the chemistry of the MoS2 nanoclusters can be associated with one-dimensional metallic states located at the perimeter of the otherwise insulating nanoclusters. The new chemistry identified in this work has significant implications for an important catalytic reaction, since MoS2 nanoclusters constitute the basis of hydrotreating catalysts used to clean up sulfur-containing molecules from oil products in the hydrodesulfurization process.

Experimental evidence for Mo isotope fractionation between metal and silicate liquids

NASA Astrophysics Data System (ADS)

Hin, Remco C.; Burkhardt, Christoph; Schmidt, Max W.; Bourdon, Bernard; Kleine, Thorsten

2013-10-01

Stable isotope fractionation of siderophile elements may inform on the conditions and chemical consequences of core-mantle differentiation in planetary objects. The extent to which Mo isotopes fractionate during such metal-silicate segregation, however, is so far unexplored. We have therefore investigated equilibrium fractionation of Mo isotopes between liquid metal and liquid silicate to evaluate the potential of Mo isotopes as a new tool to study core formation. We have performed experiments at 1400 and 1600 °C in a centrifuging piston cylinder. Tin was used to lower the melting temperature of the Fe-based metal alloys to <1400 °C, while variable Fe-oxide contents were used to vary oxygen fugacity in graphite and MgO capsules. Isotopic analyses were performed using a double spike technique. In experiments performed at 1400 °C, the 98Mo/95Mo ratio of silicate is 0.19±0.03‰ (95% confidence interval) heavier than that of metal. This fractionation is not significantly affected by the presence or absence of carbon. Molybdenum isotope fractionation is furthermore independent of oxygen fugacity in the range IW -1.79 to IW +0.47, which are plausible values for core formation. Experiments at 1600 °C show that, at equilibrium, the 98Mo/95Mo ratio of silicate is 0.12±0.02‰ heavier than that of metal and that the presence or absence of Sn does not affect this fractionation. Equilibrium Mo isotope fractionation between liquid metal and liquid silicate as a function of temperature can therefore be described as ΔMoMetal-Silicate98/95=-4.70(±0.59)×105/T2. Our experiments show that Mo isotope fractionation may be resolvable up to metal-silicate equilibration temperatures of about 2500 °C, rendering Mo isotopes a novel tool to investigate the conditions of core formation in objects ranging from planetesimals to Earth sized bodies.

Deconvolution of trace element (As, Cr, Mo, Th, U) sources and pathways to surface waters of a gold mining-influenced watershed.

PubMed

Grosbois, C; Schäfer, J; Bril, H; Blanc, G; Bossy, A

2009-03-01

The Upper Isle River (SW France) drains the second most productive gold-mining district of France. A high resolution survey during one hydrological year of As, Cl(-), Cr, Fe, Mn, Mo, SO(4)(2-), Th and U dissolved concentrations in surface water aimed to better understand pathways of trace element export to the river system downstream from the mining district. Dissolved concentrations of As (up to 35000 ng/L) and Mo (up to 292 ng/L) were about 3-fold higher than the regional dissolved background and showed a negative logarithmic relation with discharge. Dissolved concentrations of Cr (up to 483 ng/L), Th (up to 48 ng/L) and U (up to 184 ng/L) increased with discharge. Geochemical relationships between molar ratios in surface water, geochemical background as well as rain- and groundwater data were combined. The contrasting behavior of distinct element groups was explained by a scenario involving three seasonal components: (i) The high flow component is poorly concentrated in As and Mo but highly concentrated in Cr, Th, U. This has been attributed to diffuse sources such as water-soil interactions, atmospheric inputs, bedrock and bed sediment weathering. Although this component probably also includes a contribution by weathering of sulfide veins, this signal is masked by dilution. (ii) One low flow component presents high SO(4)(2-), Fe, As and Mo and moderate Cr, Th and U concentrations. This component has been attributed to point sources such as mine gallery effluents, mining waste weathering and groundwater inputs from natural and/or mining-induced sulfide oxidation in the ore deposit. (iii) A second low flow component showing high As plus Mo concentrations associated with very low SO(4)(2-), Fe, Cr, Th and U concentrations, probably reflects trace element scavenging by ferric oxyhydroxide formation in the adjacent aquifer. This is supported by the decrease of Fe, Cr, Th and U in surface waters. Flux estimates suggest contrasting element-specific impacts on annual

Local configurations and atomic intermixing in as-quenched and annealed Fe1-xCrx and Fe1-xMox ribbons

NASA Astrophysics Data System (ADS)

Stanciu, A. E.; Greculeasa, S. G.; Bartha, C.; Schinteie, G.; Palade, P.; Kuncser, A.; Leca, A.; Filoti, G.; Birsan, A.; Crisan, O.; Kuncser, V.

2018-04-01

Local atomic configuration, phase composition and atomic intermixing in Fe-rich Fe1-xCrx and Fe1-xMox ribbons (x = 0.05, 0.10, 0.15), of potential interest for high-temperature applications and nuclear devices, are investigated in this study in relation to specific processing and annealing routes. The Fe-based thin ribbons have been prepared by induction melting, followed by melt spinning and further annealed in He at temperatures up to 1250 °C. The complex structural, compositional and atomic configuration characterisation has been performed by means of X-ray diffraction (XRD), transmission Mössbauer spectroscopy and differential scanning calorimetry (TG-DSC). The XRD analysis indicates the formation of the desired solid solutions with body-centred cubic (bcc) structure in the as-quenched state. The Mössbauer spectroscopy results have been analysed in terms of the two-shell model. The distribution of Cr/Mo atoms in the first two coordination spheres is not homogeneous, especially after annealing, as supported by the short-range order parameters. In addition, high-temperature annealing treatments give rise to oxidation of Fe (to haematite, maghemite and magnetite) at the surface of the ribbons. Fe1-xCrx alloys are structurally more stable than the Mo counterpart under annealing at 700 °C. Annealing at 1250 °C in He enhances drastically the Cr clustering around Fe nuclei.

Pressure effect on Fe3+/FeT in silicate melts and applications to magma redox, particularly in magma oceans

NASA Astrophysics Data System (ADS)

Zhang, H.; Hirschmann, M. M.

2014-12-01

The proportions of Fe3+ and Fe2+ in magmas reflect the redox conditions of their origin and influence the chemical and physical properties of natural silicate liquids, but the relationship between Fe3+/FeT and oxygen fugacity depends on pressure owing to different molar volumes and compressibilities of Fe3+ and Fe2+ in silicates. An important case where the effect of pressure effect may be important is in magma oceans, where well mixed (and therefore potentially uniform Fe3+/FeT) experiencses a wide range of pressures, and therefore can impart different ƒO2 at different depths, influencing magma ocean degassing and early atmospheres, as well as chemical gradients within magma oceans. To investigate the effect of pressure on magmatic Fe3+/FeT we conducted high pressure expeirments on ƒO2-buffered andestic liquids. Quenched glasses were analyzed by Mössbauer spectroscopy. To verify the accuracy of Mössbauer determinations of Fe3+/FeT in glasses, we also conducted low temperature Mössbauer studies to determine differences in the recoilless fraction (ƒ) of Fe2+ and Fe3. These indicate that room temperature Mössbauer determinations of on Fe3+/FeT glasses are systematically high by 4% compared to recoilless-fraction corrected ratios. Up to 7 GPa, pressure decreases Fe3+/FeT, at fixed ƒO2 relative to metal-oxide buffers, meaning that an isochemical magma will become more reduced with decreasing pressure. Consequently, for small planetary bodies such as the Moon or Mercury, atmospheres overlying their MO will be highly reducing, consisting chiefly of H2 and CO. The same may also be true for Mars. The trend may reverse at higher pressure, as is the case for solid peridotite, and so for Earth, Venus, and possibly Mars, more oxidized atmospheres above MO are possible. Diamond anvil experiments are underway to examine this hypothesis.

Compatibility studies on Mo-coating systems for nuclear fuel cladding applications

NASA Astrophysics Data System (ADS)

Koh, Huan Chin; Hosemann, Peter; Glaeser, Andreas M.; Cionea, Cristian

2017-12-01

To improve the safety factor of nuclear power plants in accident scenarios, molybdenum (Mo), with its high-temperature strength, is proposed as a potential fuel-cladding candidate. However, Mo undergoes rapid oxidation and sublimation at elevated temperatures in oxygen-rich environments. Thus, it is necessary to coat Mo with a protective layer. The diffusional interactions in two systems, namely, Zircaloy-2 (Zr2) on a Mo tube, and iron-chromium-aluminum (FeCrAl) on a Mo rod, were studied by aging coated Mo substrates in high vacuum at temperatures ranging from 650 °C to 1000° for 1000 h. The specimens were characterized using scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS) and nanoindentation. In both systems, pores in the coating increased in size and number with increasing temperature over time, and cracks were also observed; intermetallic phases formed between the Mo and its coatings.

Control of Fe(III) site occupancy on the rate and extent of microbial reduction of Fe(III) in nontronite

USGS Publications Warehouse

Jaisi, Deb P.; Kukkadapu, R.K.; Eberl, D.D.; Dong, H.

2005-01-01

A quantitative study was performed to understand how Fe(III) site occupancy controls Fe(III) bioreduction in nontronite by Shewanella putrefaciens CN32. NAu-1 and NAu-2 were nontronites and contained Fe(III) in different structural sites with 16 and 23% total iron (w/w), respectively, with almost all iron as Fe(III). Mo??ssbauer spectroscopy showed that Fe(III) was present in the octahedral site in NAu-1 (with a small amount of goethite), but in both the tetrahedral and the octahedral sites in NAu-2. Mo??ssbauer data further showed that the octahedral Fe(III) in NAu-2 existed in at least two environments- trans (M1) and cis (M2) sites. The microbial Fe(III) reduction in NAu-1 and NAu-2 was studied in batch cultures at a nontronite concentration of 5 mg/mL in bicarbonate buffer with lactate as the electron donor. The unreduced and bioreduced nontronites were characterized by X-ray diffraction (XRD), Mo??ssbauer spectroscopy, and transmission electron microscopy (TEM). In the presence of an electron shuttle, anthraquinone-2,6-disulfonate (AQDS), the extent of bioreduction was 11%-16% for NAu-1 but 28%-32% for NAu-2. The extent of reduction in the absence of AQDS was only 5%-7% for NAu-1 but 14%-18% for NAu-2. The control experiments with heat killed cells and without cells did not show any appreciable reduction (<2%). The extent of reduction in experiments performed with a dialysis membrane to separate cells from clays (without AQDS) was 2%-3% for NAu-1 but 5%-7% for NAu-2, suggesting that cells probably released an electron shuttling compound and/or Fe(III) chelator. The reduction rate was also faster in NAu-2 than that in NAu-1. Mo??ssbauer data of the bioreduced nontronite materials indicated that the Fe(III) reduction in NAu-1 was mostly from the presence of goethite, whereas the reduction in NAu-2 was due to the presence of the tetrahedral and trans-octahedral Fe(III) in the structure. The measured aqueous Fe(II) was negligible. As a result of bioreduction, the

Oxidation of Sulfonamides in Aqueous Solution by UV-TiO2-Fe(VI).

PubMed

Ma, Yan; Zhang, Kejia; Li, Cong; Zhang, Tuqiao; Gao, Naiyun

2015-01-01

The photocatalytic degradation of sulfonamides in aqueous TiO2 suspension under UV irradiation has been investigated using potassium ferrate as electron acceptors. The results showed that the stability of Fe(VI) is dependent on pH significantly, and the stability reduces obviously in the presence of UV-TiO2. The experiments indicated that Fe(VI) could effectively scavenge the conduction band electrons from the surface of TiO2. The photocatalytic oxidation of sulfonamides with Fe(VI) was found to be much faster than that without Fe(VI). The SD, SM, and SMX concentration was greatly reduced by 89.2%, 83.4%, and 82.0%, respectively, after 10 min with UV-TiO2-Fe(VI), comparing to 65.2%, 66.0%, and 71.9%, respectively, with Fe(VI) only in the dark and 71.3%, 72.7%, and 76.0%, respectively, with UV-TiO2. The pH value of solution significantly influenced the sulfonamides degradation in UV-TiO2-Fe(VI) system. The degradation amount of sulfonamides after 10 min was a maximum at pH 7. The intermediate products of sulfonamides oxidation by UV-TiO2-Fe(VI) were analysed by LC-HESI-MS-MS and the results suggested that a majority of sulfonamides turned into large-molecule products without complete mineralization.

Oxidation of Sulfonamides in Aqueous Solution by UV-TiO2-Fe(VI)

PubMed Central

Ma, Yan; Zhang, Kejia; Li, Cong; Zhang, Tuqiao; Gao, Naiyun

2015-01-01

The photocatalytic degradation of sulfonamides in aqueous TiO2 suspension under UV irradiation has been investigated using potassium ferrate as electron acceptors. The results showed that the stability of Fe(VI) is dependent on pH significantly, and the stability reduces obviously in the presence of UV-TiO2. The experiments indicated that Fe(VI) could effectively scavenge the conduction band electrons from the surface of TiO2. The photocatalytic oxidation of sulfonamides with Fe(VI) was found to be much faster than that without Fe(VI). The SD, SM, and SMX concentration was greatly reduced by 89.2%, 83.4%, and 82.0%, respectively, after 10 min with UV-TiO2-Fe(VI), comparing to 65.2%, 66.0%, and 71.9%, respectively, with Fe(VI) only in the dark and 71.3%, 72.7%, and 76.0%, respectively, with UV-TiO2. The pH value of solution significantly influenced the sulfonamides degradation in UV-TiO2-Fe(VI) system. The degradation amount of sulfonamides after 10 min was a maximum at pH 7. The intermediate products of sulfonamides oxidation by UV-TiO2-Fe(VI) were analysed by LC-HESI-MS-MS and the results suggested that a majority of sulfonamides turned into large-molecule products without complete mineralization. PMID:26347888

Improved electrochemical performances of binder-free CoMoO4 nanoplate arrays@Ni foam electrode using redox additive electrolyte

NASA Astrophysics Data System (ADS)

Veerasubramani, Ganesh Kumar; Krishnamoorthy, Karthikeyan; Kim, Sang Jae

2016-02-01

Herein, we are successfully prepared cobalt molybdate (CoMoO4) grown on nickel foam as a binder free electrode by hydrothermal approach for supercapacitors and improved their electrochemical performances using potassium ferricyanide (K3Fe(CN)6) as redox additive. The formation of CoMoO4 on Ni foam with high crystallinity is confirmed using XRD, Raman, and XPS measurements. The nanoplate arrays (NPAs) of CoMoO4 are uniformly grown on Ni foam which is confirmed by FE-SEM analysis. The prepared binder-free CoMoO4 NPAs achieved maximum areal capacity of 227 μAh cm-2 with KOH electrolyte at 2.5 mA cm-2. This achieved areal capacity is further improved about three times using the addition of K3Fe(CN)6 as redox additive. The increased electrochemical performances of CoMoO4 NPAs on Ni foam electrode via redox additive are discussed in detail and the mechanism has been explored. Moreover, the assembled CoMoO4 NPAs on Ni foam//activated carbon asymmetric supercapacitor device with an extended operating voltage window of 1.5 V exhibits an excellent performances such as high energy density and cyclic stability. The overall performances of binder-free CoMoO4 NPAs on Ni foam with redox additives suggesting their potential use as positive electrode material for high performance supercapacitors.

Photodecomposition of Mo(CO)/sub 6/ adsorbed on Si(100)

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

Creighton, J.R.

1986-01-15

The photochemical properties of Mo(CO)/sub 6/ adsorbed on Si(100) were investigated using temperature programmed desorption (TPD) and Auger spectroscopy. TPD experiments indicate that Mo(CO)/sub 6/ physisorbs on silicon and desorbs at 210--230 K. At 150 K, KrF laser radiation (248 nm) partially decomposes the adsorbed Mo(CO)/sub 6/ releasing gas-phase CO in the process and TPD experiments after irradiation show that additional CO desorbs at 335 K. However, Auger analysis indicates that one CO molecule per molybdenum atom dissociates, leaving the molybdenum overlayer heavily contaminated with carbon and oxygen. The cross section for photodecomposition was measured to be 5 +- 3more » x 10/sup -17/ cm/sup 2/. Decomposition of the excited molecule must compete strongly with energy relaxation to account for the magnitude of this cross section.« less

Growth behavior of carbon nanotubes on multilayered metal catalyst film (Al/Fe/Mo) in chemical vapor deposition

NASA Astrophysics Data System (ADS)

Cui, H.; Eres, G.; Howe, J. Y.; Puretzky, A.; Varela, M.; Geohegan, D. B.; Lowndes, D. H.

2003-03-01

The temperature- and time- dependences of carbon nanotube (CNT) growth by chemical vapor deposition are studied using a multilayered Al/Fe/Mo catalyst on silicon substrates. Within the 600 - 1100 ^oC temperature range in these studies, narrower temperature ranges were determined for the growth of aligned multi-walled carbon nanotubes (MWCNTs) and single-walled carbon nanotubes (SWCNTs). Aligned MWCNT growth is favored at lower temperatures ( ˜700 ^oC). At 900 ^oC, in contrast to earlier work, double-walled carbon nanotubes (DWCNTs) are found more abundant than SWCNTs. At further elevated temperature, highly defective carbon structures are produced. Defects also are found to accumulate faster than the ordered graphitic structure if the growth of CNTs is extended to long growth durations. Atomic force microscopy, field emission scanning electron microscopy, high resolution transmission electron microscopy, and Raman spectroscopy are used to characterize the catalyst and various types of CNTs.

Molecules coating magnetic nanoparticles for oil-field applications

NASA Astrophysics Data System (ADS)

Zuluaga, Sebastian; Manchanda, Priyanka; Pantelides, Sokrates

Magnetic nanoparticles have recently attracted significant attention in scientific and industrial communities due to their use in the fields of catalysis, spintronics, biomedical applications, and oil recovery and reservoir characterization. However, these nanoparticles have to be protected with a coating layer of molecules that prevents the nanoparticles from oxidation, which is known to occur in air, and from agglomeration into larger nanoparticles. Therefore, the binding of the molecules to the nanoparticles is critical before a large scale implementation can be done. Here we report results of density functional theory calculations on several molecules (methylamine, acetic acid, boronic acid, ethyl phosphate, and ethyl trihydroxysilane) and magnetic nanoparticles (Fe3O4, NiFe2O4, and Fe3C). We focus on two main points: 1) the bond strength between the organic molecule and the nano particle, and 2) how, H2O and H+ in the oil well may facilitate the desorption of the molecules. The results show that H+ and H2O molecules facilitate the desorption of molecules reducing the bond strength by several eV. On the other hand, the results allow us to identify and design molecules that exhibit the best performance in protecting each nanoparticle. Supported by a Grant from the Petroleum Institute, Abu Dhabi.

In-situ Raman and X-ray photoelectron spectroscopic studies on the pitting corrosion of modified 9Cr-1Mo steel in neutral chloride solution

NASA Astrophysics Data System (ADS)

Ramya, S.; Nanda Gopala Krishna, D.; Mudali, U. Kamachi

2018-01-01

In-situ Raman and X-ray photoelectron spectroscopic studies were performed for the identification of native and corroded surface oxide layers of modified 9Cr-1Mo steel. The Raman data obtained for native oxide layer of modified 9Cr-1Mo steel revealed that it was mainly composed of oxides of Fe and Cr. The presence of alloying element Mo was found to be less significant in the native oxide film. The oxides of Cr were dominant at the surface and were found to be decreasing closer to metal/oxide layer interface. The changes in the chemical composition of the native films upon in-situ pitting during potentiostatic polarization experiment were characterized by in-situ Raman analysis. The corrosion products of potentiostatically polarized modified 9Cr-1Mo steel was composed of dominant Fe (III) phases viz., γ- Fe2O3, α and γ - FeOOH along with the oxides of chromium. The results from Raman analysis were corroborated with the XPS experiments on as received and pitted samples of modified 9Cr-1Mo steel specimens. It was observed that the oxides of Cr and Mo contributed for the stability of the surface layer by forming Cr2O3 and MoO3. Also, the study attempted to find out the intermediate corrosion products inside the metastable pits to account for the pseudo passive behavior of modified 9Cr-1Mo steel in 0.1 M NaCl solution.

MnMoO4 nanolayers : Synthesis characterizations and electrochemical detection of QA

NASA Astrophysics Data System (ADS)

Muthamizh, S.; Kumar, S. Praveen; Munusamy, S.; Narayanan, V.

2018-04-01

MnMoO4 nanolayers were prepared by precipitation method. The MnMoO4 nanolayers were synthesized by using commercially available (CH3COO)2Mn.4H2O and Na2WO4.2H2O. The XRD pattern reveals that the synthesized MnMoO4 has monoclinic structure. In addition, lattice parameter values were also calculated using XRD data. The Raman analysis confirm the presence of Mo-O in MnMoO4 nanolayers. DRS-UV analysis shows that MnMoO4 has a band gap of 2.59 eV. FE-SEM and HR-TEM analysis along with EDAX confirms the material morphology in stacked layers like structure in nano scale. Synthesized nanolayers were utilized for the detection of biomolecule quercetin (QA).

41 CFR 105-72.302 - Payment.

Code of Federal Regulations, 2010 CFR

2010-07-01

... NON-PROFIT ORGANIZATIONS 72.30-Post-Award Requirements/Financial and Program Management § 105-72.302..., and (ii) Financial management systems that meet the standards for fund control and accountability as... 41 Public Contracts and Property Management 3 2010-07-01 2010-07-01 false Payment. 105-72.302...

Measuring FeO variation using astronomical spectroscopic observations

NASA Astrophysics Data System (ADS)

Unterguggenberger, Stefanie; Noll, Stefan; Feng, Wuhu; Plane, John M. C.; Kausch, Wolfgang; Kimeswenger, Stefan; Jones, Amy; Moehler, Sabine

2017-03-01

Airglow emission lines of OH, O2, O and Na are commonly used to probe the MLT (mesosphere-lower thermosphere) region of the atmosphere. Furthermore, molecules like electronically excited NO, NiO and FeO emit a (pseudo-) continuum. These continua are harder to investigate than atomic emission lines. So far, limb-sounding from space and a small number of ground-based low-to-medium resolution spectra have been used to measure FeO emission in the MLT. In this study the medium-to-high resolution echelle spectrograph X-shooter at the Very Large Telescope (VLT) in the Chilean Atacama Desert (24°37' S, 70°24' W; 2635 m) is used to study the FeO pseudo-continuum in the range from 0.5 to 0.72 µm based on 3662 spectra. Variations of the FeO spectrum itself, as well as the diurnal and seasonal behaviour of the FeO and Na emission intensities, are reported. These airglow emissions are linked by their common origin, meteoric ablation, and they share O3 as a common reactant. Major differences are found in the main emission peak of the FeO airglow spectrum between 0.58 and 0.61 µm, compared with a theoretical spectrum. The FeO and Na airglow intensities exhibit a similar nocturnal variation and a semi-annual seasonal variation with equinoctial maxima. This is satisfactorily reproduced by a whole atmosphere chemistry climate model, if the quantum yields for the reactions of Fe and Na with O3 are 13 ± 3 and 11 ± 2 % respectively. However, a comparison between the modelled O3 in the upper mesosphere and measurements of O3 made with the SABER satellite instrument suggests that these quantum yields may be a factor of ˜ 2 smaller.

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

NASA Astrophysics Data System (ADS)

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

2018-05-01

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

Giant Faraday Rotation through Ultrasmall Fe0 n Clusters in Superparamagnetic FeO-SiO2 Vitreous Films.

PubMed

Nakatsuka, Yuko; Pollok, Kilian; Wieduwilt, Torsten; Langenhorst, Falko; Schmidt, Markus A; Fujita, Koji; Murai, Shunsuke; Tanaka, Katsuhisa; Wondraczek, Lothar

2017-04-01

Magnetooptical (MO) glasses and, in particular, Faraday rotators are becoming key components in lasers and optical information processing, light switching, coding, filtering, and sensing. The common design of such Faraday rotator materials follows a simple path: high Faraday rotation is achieved by maximizing the concentration of paramagnetic ion species in a given matrix material. However, this approach has reached its limits in terms of MO performance; hence, glass-based materials can presently not be used efficiently in thin film MO applications. Here, a novel strategy which overcomes this limitation is demonstrated. Using vitreous films of x FeO·(100 - x )SiO 2 , unusually large Faraday rotation has been obtained, beating the performance of any other glassy material by up to two orders of magnitude. It is shown that this is due to the incorporation of small, ferromagnetic clusters of atomic iron which are generated in line during laser deposition and rapid condensation of the thin film, generating superparamagnetism. The size of these clusters underbids the present record of metallic Fe incorporation and experimental verification in glass matrices.

Experimental determination of the Mo isotope fractionation factor between metal and silicate liquids

NASA Astrophysics Data System (ADS)

Hin, R. C.; Burkhardt, C.; Schmidt, M. W.; Bourdon, B.

2011-12-01

The conditions and chemical consequences of core formation have mainly been reconstructed from experimentally determined element partition coefficients between metal and silicate liquids. However, first order questions such as the mode of core formation or the nature of the light element(s) in the Earth's core are still debated [1]. In addition, the geocentric design of most experimental studies leaves the conditions of core formation on other terrestrial planets and asteroids even more uncertain than for Earth. Through mass spectrometry, records of mass-dependent stable isotope fractionation during high-temperature processes such as metal-silicate segregation are detectable. Stable isotope fractionation may thus yield additional constrains on core formation conditions and its consequences for the chemical evolution of planetary objects. Experimental investigations of equilibrium mass-dependent stable isotope fractionation have shown that Si isotopes fractionate between metal and silicate liquids at temperatures of 1800°C and pressures of 1 GPa, while Fe isotopes leave no resolvable traces of core formation processes [2,3]. Molybdenum is a refractory and siderophile trace element in the Earth, and thus much less prone to complications arising from mass balancing core and mantle and from potential volatile behaviour than other elements. To determine equilibrium mass-dependent Mo isotope fractionation during metal-silicate segregation, we have designed piston cylinder experiments with a basaltic silicate composition and an iron based metal with ~8 wt% Mo, using both graphite and MgO capsules. Metal and silicate phases are completely segregated by the use of a centrifuging piston cylinder at ETH Zurich, thus preventing analysis of mixed metal and silicate signatures. Molybdenum isotope compositions were measured using a Nu Instruments 1700 MC-ICP-MS at ETH Zurich. To ensure an accurate correction of analytical mass fractionation a 100Mo-97Mo double spike was admixed

Chemistry and temperature-assisted dehydrogenation of C60H30 molecules on TiO2(110) surfaces

NASA Astrophysics Data System (ADS)

Sánchez-Sánchez, Carlos; Martínez, José Ignacio; Lanzilotto, Valeria; Biddau, Giulio; Gómez-Lor, Berta; Pérez, Rubén; Floreano, Luca; López, María Francisca; Martín-Gago, José Ángel

2013-10-01

The thermal induced on-surface chemistry of large polycyclic aromatic hydrocarbons (PAHs) deposited on dielectric substrates is very rich and complex. We evidence temperature-assisted (cyclo)dehydrogenation reactions for C60H30 molecules and the subsequent bottom-up formation of assembled nanostructures, such as nanodomes, on the TiO2(110) surface. To this aim we have deposited, under ultra-high vacuum, a submonolayer coverage of C60H30 and studied, by a combination of experimental techniques (STM, XPS and NEXAFS) and theoretical methods, the different chemical on-surface interaction stages induced by the increasing temperature. We show that room temperature adsorbed molecules exhibit a weak interaction and freely diffuse on the surface, as previously reported for other aromatics. Nevertheless, a slight annealing induces a transition from this (meta)stable configuration into chemisorbed molecules. This adsorbate-surface interaction deforms the C60H30 molecular structure and quenches surface diffusion. Higher annealing temperatures lead to partial dehydrogenation, in which the molecule loses some of the hydrogen atoms and LUMO levels spread in the gap inducing a net total energy gain. Further annealing, up to around 750 K, leads to complete dehydrogenation. At these temperatures the fully dehydrogenated molecules link between them in a bottom-up coupling, forming nanodomes or fullerene-like monodisperse species readily on the dielectric surface. This work opens the door to the use of on-surface chemistry to generate new bottom-up tailored structures directly on high-K dielectric surfaces.The thermal induced on-surface chemistry of large polycyclic aromatic hydrocarbons (PAHs) deposited on dielectric substrates is very rich and complex. We evidence temperature-assisted (cyclo)dehydrogenation reactions for C60H30 molecules and the subsequent bottom-up formation of assembled nanostructures, such as nanodomes, on the TiO2(110) surface. To this aim we have deposited

Albumin adsorption on CoCrMo alloy surfaces

NASA Astrophysics Data System (ADS)

Yan, Yu; Yang, Hongjuan; Su, Yanjing; Qiao, Lijie

2015-12-01

Proteins can adsorb on the surface of artificial joints immediately after being implanted. Although research studying protein adsorption on medical material surfaces has been carried out, the mechanism of the proteins’ adsorption which affects the corrosion behaviour of such materials still lacks in situ observation at the micro level. The adsorption of bovine serum albumin (BSA) on CoCrMo alloy surfaces was studied in situ by AFM and SKPFM as a function of pH and the charge of CoCrMo alloy surfaces. Results showed that when the specimens were uncharged, hydrophobic interaction could govern the process of the adsorption rather than electrostatic interaction, and BSA molecules tended to adsorb on the surfaces forming a monolayer in the side-on model. Results also showed that adsorbed BSA molecules could promote the corrosion process for CoCrMo alloys. When the surface was positively charged, the electrostatic interaction played a leading role in the adsorption process. The maximum adsorption occurred at the isoelectric point (pH 4.7) of BSA.

High levels of the soluble form of CD30 molecule in rheumatoid arthritis (RA) are expression of CD30+ T cell involvement in the inflamed joints.

PubMed Central

Gerli, R; Muscat, C; Bistoni, O; Falini, B; Tomassini, C; Agea, E; Tognellini, R; Biagini, P; Bertotto, A

1995-01-01

The CD30 is a surface molecule expressed by Th2-type lymphokine-producing T cells upon activation. CD30-expressing activated T cells release a soluble form of the molecule, which can be detectable both in vitro and in vivo. In the present study, high levels of soluble CD30 were found in peripheral blood and synovial fluid from patients with RA. However, CD30+ CD3+ cells, either CD4+ or CD8+, were significantly present in synovial fluid, but not in peripheral blood, of RA patients. Serum values of soluble CD30 were higher in active than inactive RA patients and directly correlated with rheumatoid factor serum titres. These data strongly support an involvement of CD30+ T cells in the immune processes of rheumatoid synovitis, and may suggest a relationship between Th2-type cytokine-secreting T cells and the pathological response in RA. PMID:8536371

MoMa: From Molecules to Man: Space Research Applied to the improvement of the Quality of Life of the Ageing Population on Earth. Evolution of a project

NASA Astrophysics Data System (ADS)

Zambito, Anna Maria; Curcio, Francesco; Meli, Antonella; Saverio Ambesi-Impiombato, Francesco

The "MoMa" project: "From Molecules to Man: Space Research Applied to the improvement of the Quality of Life of the Ageing Population on Earth started June 16 2006 and finished right on schedule June 25 2009, has been the biggest of the three projects funded by ASI in the sector "Medicine and Biotechnology. In the last years the scientific community had formed a national chain of biomedical spatial research with different research areas. MoMa responds to the necessity of unification in ASI of the two areas "Radiobiology and Protection" and "Cellular and Molecular Biotechnology" in a line of joint research: "Biotechnological Applications" were the interests of all groups would be combined and unified in a goal of social relevance. MoMa is the largest project ever developed in the biomedical area in Italy, the idea was born thinking about the phenomenon of acceleration of the aging process observed in space, and already described in literature, and the aim of studying the effects of the space environment at cellular, molecular and human organism level. "MoMa" was divided into three primary areas of study: Molecules, Cells and Man with an industrial area alongside. This allowed to optimize the work and information flows within the scientific research more similar and more culturally homogeneous and allowed a perfect industrial integration in a project of great scientific importance. Within three scientific areas 10 scientific lines in total are identified, each of them coordinated by a subcontractor. The rapid and efficient exchange of information between different areas of science and the development of industrial applications in various areas of interest have been assured by a strong work of Scientific Coordination of System Engineering and Quality Control. After three years of intense and coordinated activities within the MoMa project, the objectives achieved are very significant not only as regards the scientific results and the important hardware produced but

Efficient spin filter and spin valve in a single-molecule magnet Fe{sub 4} between two graphene electrodes

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

Zu, Feng-Xia; School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074; Gao, Guo-Ying

2015-12-21

We propose a magnetic molecular junction consisting of a single-molecule magnet Fe{sub 4} connected two graphene electrodes and investigate transport properties, using the nonequilibrium Green's function method in combination with spin-polarized density-functional theory. The results show that the device can be used as a nearly perfect spin filter with efficiency approaching 100%. Our calculations provide crucial microscopic information how the four iron cores of the chemical structure are responsible for the spin-resolved transmissions. Moreover, it is also found that the device behaves as a highly efficient spin valve, which is an excellent candidate for spintronics of molecular devices. The ideamore » of combining single-molecule magnets with graphene provides a direction in designing a new class of molecular spintronic devices.« less

The El Teniente porphyry Cu-Mo deposit from a hydrothermal rutile perspective

NASA Astrophysics Data System (ADS)

Rabbia, Osvaldo M.; Hernández, Laura B.; French, David H.; King, Robert W.; Ayers, John C.

2009-11-01

Mineralogical, textural, and chemical analyses (EPMA and PIXE) of hydrothermal rutile in the El Teniente porphyry Cu-Mo deposit help to better constrain ore formation processes. Rutile formed from igneous Ti-rich phases (sphene, biotite, Ti-magnetite, and ilmenite) by re-equilibration and/or breakdown under hydrothermal conditions at temperatures ranging between 400°C and 700°C. Most rutile nucleate and grow at the original textural position of its Ti-rich igneous parent mineral phase. The distribution of Mo content in rutile indicates that low-temperature (˜400-550°C), Mo-poor rutile (5.4 ± 1.1 ppm) is dominantly in the Mo-rich mafic wallrocks (high-grade ore), while high-temperature (˜550-700°C), Mo-rich rutile (186 ± 20 ppm) is found in the Mo-poor felsic porphyries (low-grade ore). Rutile from late dacite ring dikes is a notable exception to this distribution pattern. The Sb content in rutile from the high-temperature potassic core of the deposit to its low-temperature propylitic fringe remains relatively constant (35 ± 3 ppm). Temperature and Mo content of the hydrothermal fluids in addition to Mo/Ti ratio, modal abundance and stability of Ti-rich parental phases are key factors constraining Mo content and provenance in high-temperature (≥550°C) rutile. The initial Mo content of parent mineral phases is controlled by melt composition and oxygen fugacity as well as timing and efficiency of fluid-melt separation. Enhanced reduction of SO2-rich fluids and sulfide deposition in the Fe-rich mafic wallrocks influences the low-temperature (≤550°C) rutile chemistry. The data are consistent with a model of fluid circulation of hot (>550°C), oxidized (ƒO2 ≥ NNO + 1.3), SO2-rich and Mo-bearing fluids, likely exsolved from deeper crystallizing parts of the porphyry system and fluxed through the upper dacite porphyries and related structures, with metal deposition dominantly in the Fe-rich mafic wallrocks.

Sonocatalytic performance of magnetically separable CuS/CoFe2O4 nanohybrid for efficient degradation of organic dyes.

PubMed

Siadatnasab, Firouzeh; Farhadi, Saeed; Khataee, Alireza

2018-06-01

The sonocatalytic activity of the magnetic CuS/CoFe 2 O 4 (CuS/CFO) nanohybrid was studied through the H 2 O 2 -assisted system for degradation of water soluble organic pollutants such as methylene blue (MB), rhodamine B (RhB) and methyl orange (MO). The CuS/CFO nanohybrid was fabricated at 200 °C by hydrothermal method. X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) equipped with energy dispersive X-ray microanalysis (EDX), Fourier-transform infrared spectroscopy (FT-IR), UV-Vis spectroscopy, magnetic measurements, and Brunauere-Emmette-Teller (BET) were employed for the characterizing the structure and morphology of the so-synthesized nanohybrid. Compared with sonolysis/H 2 O 2 , the higher degradation of MB (25 mg/L) was achieved via sonocatalytic process. The degradation efficiency of sonolysis/H 2 O 2 , sonocatalysis using CuS/H 2 O 2 , CFO/H 2 O 2 and CuS/CFO/H 2 O 2 systems was 6%, 62%, 23% and 100% within reaction time of 30 min for MB, respectively. The integration of H 2 O 2 and catalyst dosage intensified the sonocatalytic degradation of MB. On the other hand, adding a hydroxyl radical (OH) scavenger (tert-butyl alcohol) and a hole scavenger (disodium ethylenediaminetetraacetate) decreased the degradation efficiency from 100% to 35% and 72% within 30 min, indicating the OH radicals as prominent oxidizing agent of this process. Furthermore, the magnetic property of the sample helped for easier separation of the nanohybrid, made it recyclable with a negligible decline in the performance even after four consecutive runs. Copyright © 2018 Elsevier B.V. All rights reserved.

Additive patterning of ion-beam-sputtered non-conformal Ni80Fe20 and Co70Fe30 magnetic films

NASA Astrophysics Data System (ADS)

Redondo, C.; Moralejo, S.; Castaño, F.; Lee, W.; Nielsch, K.; Ross, C. A.; Castaño, F. J.

2006-04-01

Additive patterning processes of magnetic films grown using an ion-beam sputter (IBS) system designed to produce non-conformal films are described. The effects of the ion-gun beam current and Ar pressure on the sputtering rates and roughness of Ni80Fe20 and Co70Fe30 magnetic thin films are investigated using atomic-force microscopy (AFM) and the films' magnetic properties are measured using spatially resolved magneto-optical magnetometry. By tailoring the plasma solid angle, non-conformal film growth allows for simple additive patterning down to lateral dimensions ranging from a few microns to the deep-submicron regime, using templates defined by photolithography or electron-beam lithography, and shadow masks created using templated self-assembly. The magnetization reversal exhibited by patterned sub-200 nm nanodisc arrays with different lateral edge-roughness will be discussed.

30 CFR 256.72 - Compensatory payments as production.

Code of Federal Regulations, 2014 CFR

2014-07-01

... INTERIOR OFFSHORE LEASING OF SULPHUR OR OIL AND GAS IN THE OUTER CONTINENTAL SHELF Assignments, Transfers, and Extensions § 256.72 Compensatory payments as production. If an oil and gas lessee makes compensatory payments and if the lease is not being maintained in force by other production of oil or gas in...

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

NASA Astrophysics Data System (ADS)

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

2015-07-01

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

Nonvolatile ferroelectric memory based on PbTiO3 gated single-layer MoS2 field-effect transistor

NASA Astrophysics Data System (ADS)

Shin, Hyun Wook; Son, Jong Yeog

2018-01-01

We fabricated ferroelectric non-volatile random access memory (FeRAM) based on a field effect transistor (FET) consisting of a monolayer MoS2 channel and a ferroelectric PbTiO3 (PTO) thin film of gate insulator. An epitaxial PTO thin film was deposited on a Nb-doped SrTiO3 (Nb:STO) substrate via pulsed laser deposition. A monolayer MoS2 sheet was exfoliated from a bulk crystal and transferred to the surface of the PTO/Nb:STO. Structural and surface properties of the PTO thin film were characterized by X-ray diffraction and atomic force microscopy, respectively. Raman spectroscopy analysis was performed to identify the single-layer MoS2 sheet on the PTO/Nb:STO. We obtained mobility value (327 cm2/V·s) of the MoS2 channel at room temperature. The MoS2-PTO FeRAM FET showed a wide memory window with 17 kΩ of resistance variation which was attributed to high remnant polarization of the epitaxially grown PTO thin film. According to the fatigue resistance test for the FeRAM FET, however, the resistance states gradually varied during the switching cycles of 109. [Figure not available: see fulltext.

Charge-controlled switchable CO adsorption on FeN4 cluster embedded in graphene

NASA Astrophysics Data System (ADS)

Omidvar, Akbar

2018-02-01

Electrical charging of an FeN4 cluster embedded in graphene (FeN4G) is proposed as an approach for electrocatalytically switchable carbon monoxide (CO) adsorption. Using density functional theory (DFT), we found that the CO molecule is strongly adsorbed on the uncharged FeN4G cluster. Our results show that the adsorption energy of a CO molecule on the FeN4G cluster is dramatically decreased by introducing extra electrons into the cluster. Once the charges are removed, the CO molecule is spontaneously adsorbed on the FeN4G absorbent. In the framework of frontier molecular orbital (FMO) analysis, the enhanced sensitivity and reactivity of the FeN4G cluster towards the CO molecule can be interpreted in terms of interaction between the HOMO of CO molecule and the LUMO of FeN4G cluster. Therefore, this approach promises both facile reversibility and tunable kinetics without the need of specific catalysts. Our study indicates that the FeN4G nanomaterial is an excellent absorbent for controllable and reversible capture and release of the CO.

Vector MO magnetometry for mapping microwave currents

NASA Astrophysics Data System (ADS)

Višňovský, Š.; Lišková-Jakubisová, E.; Harward, I.; Celinski, Z.

2018-05-01

Magneto-optic (MO) effects in magnetic multilayers (MML) can be employed in non-invasive 2D mapping of microwave (mw) radiation on the surface of semiconductor chips. A typical sensor configuration consists of Fe nanolayers sandwiched with dielectrics on a thin Si substrate transparent to mw radiation. To extend the observation bandwidth, Δf, up to 100 GHz range the sensor works at ferromagnetic resonance (FMR) frequency in applied magnetic flux density, Bappl. The mw currents excite the precession of magnetization, M, in magnetic nanolayers proportional to their amplitude. The MO component reflected on the sensor surface is proportional to the amplitude of M component, M⊥. The laser source operates at the wavelength of 410 nm. Its plane of incidence is oriented perpendicular to the M⊥ plane. M⊥ oscillates between polar and transverse configurations. A substantial improvement of MO figure of merit takes place in aperiodic MML. More favorable Δf vs. Bappl dependence and MO response can potentially be achieved in MML imbedding hexagonal ferrite or Co nanolayers with in-plane magnetic anisotropy.

Nano-domain states of strontium ferrites SrFe{sub 1−y}M{sub y}O{sub 2.5+x} (M=V, Mo; y≤0.1; x≤0.2)

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

Ancharova, Uliana V., E-mail: ancharova@gmail.com; Cherepanova, Svetlana V., E-mail: svch@catalysis.ru; Novosibirsk State University, Pirogova st., 2, Novosibirsk 630090

Series of the oxygen-deficient strontium ferrites SrFe{sub 1−y}M{sub y}O{sub 2.5+x} (M=V, Mo, y<0.1; x<0.2) substituted with high-charged cations have been investigated by HRTEM and synchrotron radiation XRD. For artificial lowering of x, all the compounds were treated and quenched in vacuum from 950 °C, which led to the formation of the vacancy-ordered brownmillerite phase at local order. Depending on y, the substituted strontium ferrites have three differently disordered nano-domain states. At y≤0.03 there are twinned lamellar 1D nano-domain structures. At 0.04≤y≤0.05 and 0.06≤y≤0.08 the intergrown 3D nano-domain structures with two different types of disorder are formed. The higher the y,more » the lower the domain size. Disordering phenomena of the 3D nano-domain states were examined with local structure simulations followed by the Debye calculation of XRD patterns. - Graphical abstract: Evolution of nano-domain structure with an increase in the substitution degree y in strontium ferrites SrFe{sub 1−y}M{sub y}O{sub 2.5+x} (M=V, Mo; y≤0.1; x≤0.2): an increase in y decreases the average size of domains and increases the degree of disorder, thus producing the lamellar (1D) or 3D nano-domains. - Highlights: • Two major nanodomain states were found for SrFe{sub 1−y}M{sub y}O{sub 2.5+x} (M=V, Mo, y<0.1; x<0.2). • Both contain vacancy-ordered orthorhombic domains intergrown with cubic matrix. • First (y≤0.03) shows orthorhombic and second (0.04≤y≤0.08) – cubic XRD patterns. • First contains 1D twinned lamellar domains with low-angle boundaries and deformations. • Second contains intergrown isotropic in 3D domains perpendicular oriented in matrix.« less

Exploring the Molecular Growth of Two Gigantic Half‐Closed Polyoxometalate Clusters {Mo180} and {Mo130Ce6}

PubMed Central

Xuan, Weimin; Pow, Robert; Long, De‐Liang

2017-01-01

Abstract Understanding the process of the self‐assembly of gigantic polyoxometalates and their subsequent molecular growth, by the addition of capping moieties onto the oxo‐frameworks, is critical for the development of the designed assembly of complex high‐nuclearity cluster species, yet such processes remain far from being understood. Herein we describe the molecular growth from {Mo150} and {Mo120Ce6} to afford two half‐closed gigantic molybdenum blue clusters {Mo180} (1) and {Mo130Ce6} (2), respectively. Compound 1 features a hat‐shaped structure with the parent wheel‐shaped {Mo150} being capped by a {Mo30} unit on one side. Similarly, 2 exhibits an elliptical lanthanide‐doped wheel {Mo120Ce6} that is sealed by a {Mo10} unit on one side. Moreover, the observation of the parent uncapped {Mo150} and {Mo120Ce6} clusters as minor products during the synthesis of 1 and 2 strongly suggests that the molecular growth process can be initialized from {Mo150} and {Mo120Ce6} in solution, respectively. PMID:28508585

Cracking process of Fe-26Cr-1Mo during low cycle corrosion fatigue

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

Wang, J.Q.; Li, J.; Wang, Z.F.

1994-12-01

The corrosion fatigue (CF) life has been divided classically into the initiation'' and propagation'' periods. Usually, the crack initiation process dominates the component lifetime under the low cycle CF condition because the crack propagates rapidly one initiated. Despite much work done on the research of the CF crack initiation mechanisms, however, a full understanding of crack initiation is still lacking. There are some limitations in explaining the CF crack initiation in an aqueous solution using the above four mechanisms individually. And, it is difficult to conduct experiments in which one mechanism along can be examined. Although CF is complicated, itmore » is possible to reproduce a specific experiment condition which will have the dominant factor affecting the CF crack initiation. Once the cracks initiate on the smooth metal surface, their coalescence, micropropagation and macropropagation will take place successively. The initiated cracks propagate first in the range of several grains, and the behavior of the microcrack propagation is different from that of macrocrack propagation. For Fe-26Cr-1Mo ferritic stainless steel, the fundamental research work of straining electrode has been done by many investigators, but the observation of the material surface at different deformation processes has not been reported. In the present study, the detailed observation of the cracking process of the material has been carried out in low cycle CF.« less

Novel low-cost Fenton-like layered Fe-titanate catalyst: preparation, characterization and application for degradation of organic colorants.

PubMed

Chen, Yongzhou; Li, Nian; Zhang, Ye; Zhang, Lide

2014-05-15

Novel low-cost layered Fe-titanate catalyst for photo-Fenton degradation of organic contaminants was successfully developed by ion exchange of Fe(3+) with Na(+) layered nano Na-titanates which was prepared by alkali hydrothermal method. The as prepared materials were characterized by powder X-ray diffraction analysis (XRD), field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectrometer (EDX). The catalytic activity of the Fe-titanate catalyst was evaluated by the decolorization of three different dyes (rhodamine 6G (R6G), methyl blue (MB), and methyl orange (MO)) under UV irradiation at room temperature. Effect of several important factors such as Fe loading in the catalyst, initial solution pH, catalyst dosage, H2O2 amount, and reaction time was systematically studied. It was found that the decolorization was very efficient for all three dyes. The efficiency reached 98% for R6G, 98.5% for MB, and 97% for MO, respectively, under optimal conditions. The oxidation process was quick, and only 15 min is needed for all three dyes. Moreover, the Fe-titanate catalyst could be used in a wider and near neutral pH range compared with classic Fenton systems which need to be operated at around pH 3.0. Kinetic analysis results showed that the oxidation kinetics was accurately represented by pseudo-first-order model. More importantly, the catalyst was very stable and could be reused for at least four cycles when operated under near neutral pH. The Fe leaching from the catalyst measured was almost negligible, which not only demonstrated the stability of the catalyst, but also avoided the formation of secondary Fe pollution. Therefore, the reported Fe-titanates are promising nanomaterials which can be used as Fenton like catalyst for the degradation of organic contaminant in wastewater. Crown Copyright © 2014. Published by Elsevier Inc. All rights reserved.

The controlled relay of multiple protons required at the active site of nitrogenase.

PubMed

Dance, Ian

2012-07-07

The enzyme nitrogenase, when reducing natural and unnatural substrates, requires large numbers of protons per chemical catalytic cycle. The active face of the catalytic site (the FeMo-cofactor, FeMo-co) is situated in a protein domain which is largely hydrophobic and anhydrous, and incapable of serial provision of multiple protons. Through detailed analysis of the high quality protein crystal structures available the characteristics of a chain of water molecules leading from the protein surface to a key sulfur atom (S3B) of FeMo-co are described. The first half of the water chain from the surface inwards is branched, slightly variable, and able to accommodate exogenous small molecules: this is dubbed the proton bay. The second half, from the proton bay to S3B, is comprised of a single chain of eight hydrogen bonded water molecules. This section is strictly conserved, and is intimately involved in hydrogen bonds with homocitrate, an essential component that chelates Mo. This is the proton wire, and a detailed Grotthuss mechanism for serial translocation of protons through this proton wire to S3B is proposed. This controlled serial proton relay from the protein surface to S3B is an essential component of the intramolecular hydrogenation paradigm for the complete chemical mechanisms of nitrogenase. Each proton reaching S3B, instigated by electron transfer to FeMo-co, becomes a hydrogen atom that migrates to other components of the active face of FeMo-co and to bound substrates and intermediates, allowing subsequent multiple proton transfers along the proton wire. Experiments to test the proposed mechanism of proton supply are suggested. The water chain in nitrogenase is comparable with the purported proton pumping pathway of cytochrome c oxidase.

Ambient dose equivalent and effective dose from scattered x-ray spectra in mammography for Mo/Mo, Mo/Rh and W/Rh anode/filter combinations.

PubMed

Künzel, R; Herdade, S B; Costa, P R; Terini, R A; Levenhagen, R S

2006-04-21

In this study, scattered x-ray distributions were produced by irradiating a tissue equivalent phantom under clinical mammographic conditions by using Mo/Mo, Mo/Rh and W/Rh anode/filter combinations, for 25 and 30 kV tube voltages. Energy spectra of the scattered x-rays have been measured with a Cd(0.9)Zn(0.1)Te (CZT) detector for scattering angles between 30 degrees and 165 degrees . Measurement and correction processes have been evaluated through the comparison between the values of the half-value layer (HVL) and air kerma calculated from the corrected spectra and measured with an ionization chamber in a nonclinical x-ray system with a W/Mo anode/filter combination. The shape of the corrected x-ray spectra measured in the nonclinical system was also compared with those calculated using semi-empirical models published in the literature. Scattered x-ray spectra measured in the clinical x-ray system have been characterized through the calculation of HVL and mean photon energy. Values of the air kerma, ambient dose equivalent and effective dose have been evaluated through the corrected x-ray spectra. Mean conversion coefficients relating the air kerma to the ambient dose equivalent and to the effective dose from the scattered beams for Mo/Mo, Mo/Rh and W/Rh anode/filter combinations were also evaluated. Results show that for the scattered radiation beams the ambient dose equivalent provides an overestimate of the effective dose by a factor of about 5 in the mammography energy range. These results can be used in the control of the dose limits around a clinical unit and in the calculation of more realistic protective shielding barriers in mammography.

Bulk amorphous steels based on Fe alloys

DOEpatents

Lu, ZhaoPing; Liu, Chain T.

2006-05-30

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

Towards intrinsic MoS{sub 2} devices for high performance arsenite sensing

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

Li, Peng, E-mail: pengli@mail.tsinghua.edu.cn, E-mail: dzzhang@upc.edu.cn; Zhang, Dongzhi, E-mail: pengli@mail.tsinghua.edu.cn, E-mail: dzzhang@upc.edu.cn; Sun, Yan'e

2016-08-08

Molybdenum disulphide (MoS{sub 2}) is one of the most attractive two dimensional materials other than graphene, and the exceptional properties make it a promising candidate for bio/chemical sensing. Nevertheless, intrinsic properties and sensing performances of MoS{sub 2} are easily masked by the presence of the Schottky barrier (SB) at source/drain electrodes, and its impact on MoS{sub 2} sensors remains unclear. Here, we systematically investigated the influence of the SB on MoS{sub 2} sensors, revealing the sensing mechanism of intrinsic MoS{sub 2}. By utilizing a small work function metal, Ti, to reduce the SB, excellent electrical properties of this 2D materialmore » were yielded with 2–3 times enhanced sensitivity. We experimentally demonstrated that the sensitivity of MoS{sub 2} is superior to that of graphene. Intrinsic MoS{sub 2} was able to realize rapid detection of arsenite down to 0.1 ppb without the influence of large SB, which is two-fold lower than the World Health Organization (WHO) tolerance level and better than the detection limit of recently reported arsenite sensors. Additionally, accurately discriminating target molecules is a great challenge for sensors based on 2D materials. This work demonstrates MoS{sub 2} sensors encapsulated with ionophore film which only allows certain types of molecules to selectively permeate through it. As a result, multiplex ion detection with superb selectivity was realized. Our results show prominent advantages of intrinsic MoS{sub 2} as a sensing material.« less

EFFECT OF PRE-ALLOYING CONDITION ON THE BULK AMORPHOUS ALLOY ND(60)FE(30)AL(10).

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

OCONNOR,A.S.; LEWIS,L.H.; MCCALLUM,R.W.

Bulk metallic glasses are materials that require only modest cooling rates to obtain amorphous solids directly from the melt. Nd{sub 60}Fe{sub 30}Al{sub 10} has been reported to be a ferromagnetic bulk metallic glass that exhibits high coercivity, a combination unlike conventional Nd-based amorphous magnetic alloys. To clarify the relationship between short-range order and high coercivity in glassy Nd{sub 60}Fe{sub 30}Al{sub 10}, experiments were performed to verify the existence of a homogeneous liquid state prior to rapid solidification. Alloys were prepared by various pre-alloying routes and then melt-spun. Arc-melted alloys were prepared for melt spinning using three different protocols involving: (1)more » alloying all three elements at once, (2) forming a Nd-Fe alloy which was subsequently alloyed with Al, and (3) forming a Fe-Al alloy for subsequent alloying with Nd. XRD, DTA, and magnetic measurement data from the resultant ribbons indicate significant differences in both the glassy fraction and the crystalline phase present in the as-spun material. These observed differences are attributed to the presence of highly stable nanoscopic aluminide-and/or silicide-phases, or motes, present in the melt prior to solidification. These motes would affect the short-range order and coercivity of the resultant glassy state and are anticipated to provide heterogeneous nucleation sites for crystallization.« less

A single-molecule diode