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Sample records for metal borides stability

  1. Ultra-fast boriding of metal surfaces for improved properties

    Science.gov (United States)

    Timur, Servet; Kartal, Guldem; Eryilmaz, Osman L.; Erdemir, Ali

    2015-02-10

    A method of ultra-fast boriding of a metal surface. The method includes the step of providing a metal component, providing a molten electrolyte having boron components therein, providing an electrochemical boriding system including an induction furnace, operating the induction furnace to establish a high temperature for the molten electrolyte, and boriding the metal surface to achieve a boride layer on the metal surface.

  2. Metal Borohydrides synthesized from metal borides and metal hydrides

    DEFF Research Database (Denmark)

    Sommer, Sanna

    2014-01-01

    and Ca(BH4)2, respectively [3,4]. An attempt to synthesize alkali and alkaline earth metal borohydrides from various borides by ball milling under high hydrogen pressure is presented here. MgB2, AlB2 and CaB6 have been milled with MHx (M = Li, Na, Mg, Ca) at p(H2) = 110 bar for 24 hours. All samples were...

  3. Metal borohydride formation from aluminium boride and metal hydrides.

    Science.gov (United States)

    Møller, Kasper T; Fogh, Alexander S; Paskevicius, Mark; Skibsted, Jørgen; Jensen, Torben R

    2016-10-05

    Metal borides are often decomposition products from metal borohydrides and thus play a role in the reverse reaction where hydrogen is absorbed. In this work, aluminium boride, AlB2, has been investigated as a boron source for the formation of borohydrides under hydrogen pressures of p(H2) = 100 or 600 bar at elevated temperatures (350 or 400 °C). The systems AlB2-MHx (M = Li, Na, Mg, Ca) have been investigated, producing LiBH4, NaBH4 and Ca(BH4)2, whereas the formation of Mg(BH4)2 was not observed at T = 400 °C and p(H2) = 600 bar. The formation of the metal borohydrides is confirmed by powder X-ray diffraction and infrared spectroscopy and the fraction of boron in AlB2 and M(BH4)x is determined quantitatively by (11)B MAS NMR. Hydrogenation for 12 h at T = 350-400 °C and p(H2) = 600 bar leads to the formation of substantial amounts of LiBH4 (38.6 mol%), NaBH4 (83.0 mol%) and Ca(BH4)2 (43.6 mol%).

  4. Interfacial phenomena in molten metals-refractory borides systems

    OpenAIRE

    Muolo, Maria Luigia; Fabbreschi, Matteo; Passerone, Alberto; Passerone, Daniele

    2006-01-01

    Non-oxide ceramics, such as carbides, nitrides and borides represent one of the fastest growing classes of new advanced materials. Among them, transition metals ceramic diborides, in particular Titanium, Zirconium and Hafnium diborides, are members of a family of materials with extremely high melting temperatures, high thermal and electrical conductivity, excellent thermal shock resistance, high hardness and chemical inertness. These materials -Ultra High Temperature Ceramics (UHTCs)- constit...

  5. Discovery of elusive structures of multifunctional transition-metal borides.

    Science.gov (United States)

    Liang, Yongcheng; Wu, Zhaobing; Yuan, Xun; Zhang, Wenqing; Zhang, Peihong

    2016-01-14

    A definitive determination of crystal structures is an important prerequisite for designing and exploiting new functional materials. Even though tungsten and molybdenum borides (TMBx) are the prototype for transition-metal light-element compounds with multiple functionalities, their elusive crystal structures have puzzled scientists for decades. Here, we discover that the long-assumed TMB2 phases with the simple hP3 structure (hP3-TMB2) are in fact a family of complex TMB3 polytypes with a nanoscale ordering along the axial direction. Compared with the energetically unfavorable and dynamically unstable hP3-TMB2 phase, the energetically more favorable and dynamically stable TMB3 polytypes explain the experimental structural parameters, mechanical properties, and X-ray diffraction (XRD) patterns better. We demonstrate that such a structural and compositional modification from the hP3-TMB2 phases to the TMB3 polytypes originates from the relief of the strong antibonding interaction between d electrons by removing one third of metal atoms systematically. These results resolve the longstanding structural mystery of this class of metal borides and uncover a hidden family of polytypic structures. Moreover, these polytypic structures provide an additional hardening mechanism by forming nanoscale interlocks that may strongly hinder the interlayer sliding movements, which promises to open a new avenue towards designing novel superhard nanocomposite materials by exploiting the coexistence of various polytypes.

  6. Synthesis of Binary Transition Metal Nitrides, Carbides and Borides from the Elements in the Laser-Heated Diamond Anvil Cell and Their Structure-Property Relations

    Directory of Open Access Journals (Sweden)

    Lkhamsuren Bayarjargal

    2011-09-01

    Full Text Available Transition metal nitrides, carbides and borides have a high potential for industrial applications as they not only have a high melting point but are generally harder and less compressible than the pure metals. Here we summarize recent advances in the synthesis of binary transition metal nitrides, carbides and borides focusing on the reaction of the elements at extreme conditions generated within the laser-heated diamond anvil cell. The current knowledge of their structures and high-pressure properties like high-(p; T stability, compressibility and hardness is described as obtained from experiments.

  7. Structural and mechanical properties of transition metal borides Nb2MB2 (M=Tc, Ru, and Os) under pressure

    Science.gov (United States)

    Li, Xiaofeng; Yan, Haiyan; Wei, Qun

    2016-10-01

    First-principle total energy calculations are employed to provide a fundamental understanding of the structural, mechanical, and electronic properties of transition metal borides Nb2MB2 (M=Tc, Ru, and Os) within the tetragonal superstructure P4/mnc structure. The mechanically and dynamically stabilities of three borides have been demonstrated by the elastic constants and phonons calculations under pressure. Among these three compounds, Nb2TcB2 exhibits the biggest bulk and Young's modulus, smallest Poission's ratio, and highest harness. Density of states of them revealed that the strong B-B, Nb-B and M-B covalent bonds are major driving forces for their high bulk and shear moduli as well as small Poisson's ratio.

  8. The structural stabilities, mechanical properties and hardness of chromium tetraboride: Compared with low-B borides

    Science.gov (United States)

    Zhong, Ming-Min; Huang, Cheng; Tian, Chun-Ling

    2016-10-01

    Using the first-principles calculations, we provide a systemic understanding of the structural features and phase stability, mechanical and electronic properties, as well as the roles of boron (B) atom arrangement in the hardness for chromium borides. The structural and relative energy searches together with formation enthalpy confirm the most stable Cr2B with an orthorhombic Fddd symmetry, CrB with an orthorhombic Cmcm symmetry, CrB2 with a hexagonal P63/mmc symmetry and chromium tetraboride (CrB4) with an orthorhombic Pnnm symmetry. The shear modulus, Young’s modulus and C44 increase with the boron content, while the Poisson’s ratio and B/G ratio have an opposite tendency. Moreover, due to higher B content, strong three-dimensional (3D) covalent B networks and lower metallic contribution, CrB4 with Pnnm symmetry has the largest hardness value (46.8 GPa), exceeding the superhard limit, indicating its superhard nature.

  9. Advancements in the search for superhard ultra-incompressible metal borides

    Energy Technology Data Exchange (ETDEWEB)

    Levine, Jonathan B.; Tolbert, Sarah H. [Department of Chemistry and Biochemistry, UCLA Los Angeles, CA (United States); California NanoSystems Institute, UCLA Los Angeles, CA (United States); Kaner, Richard B. [Department of Chemistry and Biochemistry, UCLA Los Angeles, CA (United States); California NanoSystems Institute, UCLA Los Angeles, CA (United States); Department of Materials Science and Engineering, UCLA Los Angeles, CA (United States)

    2009-11-23

    Dense transition metal borides have recently been identified as superhard materials that offer the possibility of ambient pressure synthesis compared to the conventional high pressure, high temperature approach. This feature article begins with a discussion of the relevant physical properties for this class of compounds, followed by a summary of the synthesis and properties of several transition metal borides. A strong emphasis is placed on correlating mechanical properties with electronic and atomic structure of these materials in an effort to better predict new superhard compounds. It concludes with a perspective of future research directions, highlighting some recent results and presenting several new ideas that remain to be tested. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  10. Low temperature route for the synthesis of rare earth transition metal borides and their hydrides

    Energy Technology Data Exchange (ETDEWEB)

    Kramp, S.; Febri, M.; Joubert, J.C. [CNRS UMR 5628, Saint Martin d`Heres (France)

    1997-10-01

    Synthesis of rare earth-based alloys by the ORD technique consists in the reduction of rare earth oxides in a melt of calcium under argon, and simultaneous diffusion-reaction of the just formed rare earth metal with the other elements. This method has been applied with success to numerous ternary borides containing transition metals such as the magnetic alloys Y{sub 2}Co{sub 14}B, LnCo{sub 4}B, and YCo{sub 3}B{sub 2}. By using a small excess of Ca, boride particles grow in a viscous slurry media containing unreacted (melted) Ca and nanosize CaO particles. Single phase boride alloys can be obtained at 1000{degrees}C as loose micrometer-size particles of very high crystal quality as confirmed by the sharp diffraction peaks on the corresponding X-ray diagrams. Particles can be easily recovered by gentle wishing in diluted weak acid solution, and dried under vacuum at room temperature. This rather low temperature technique is particularly adapted to the synthesis of incongruent melting phases, as well as for the alloys containing volatile rare earth elements (Sm, Yb, Tb,...).

  11. A Low Temperature Route for the Synthesis of Rare Earth Transition Metal Borides and Their Hydrides

    Science.gov (United States)

    Kramp, S.; Febri, M.; Joubert, J. C.

    1997-10-01

    Synthesis of rare earth-based alloys by the ORD technique consists in the reduction of rare earth oxides in a melt of calcium under argon, and simultaneous diffusion-reaction of the just formed rare earth metal with the other elements. This method has been applied with success to numerous ternary borides containing transition metals such as the magnetic alloys Y2Co14B, LnCo4B, and YCo3B2. By using a small excess of Ca, boride particles grow in a viscous slurry media containing unreacted (melted) Ca and nanosize CaO particles. Single phase boride alloys can be obtained at 1000°C as loose micrometer-size particles of very high crystal quality as confirmed by the sharp diffraction peaks on the corresponding X-ray diagrams. Particles can be easily recovered by gentle washing in diluted weak acid solution, and dried under vacuum at room temperature. This rather low temperature technique is particularly adapted to the synthesis of incongruent melting phases, as well as for the alloys containing volatile rare earth elements (Sm, Yb, Tb,…).

  12. Method for ultra-fast boriding

    Energy Technology Data Exchange (ETDEWEB)

    Erdemir, Ali; Sista, Vivekanand; Kahvecioglu, Ozgenur; Eryilmaz, Osman Levent

    2017-01-31

    An article of manufacture and method of forming a borided material. An electrochemical cell is used to process a substrate to deposit a plurality of borided layers on the substrate. The plurality of layers are co-deposited such that a refractory metal boride layer is disposed on a substrate and a rare earth metal boride conforming layer is disposed on the refractory metal boride layer.

  13. Prediction of new crystal structure phases in metal borides: a lithium monoboride analog to MgB2

    OpenAIRE

    Kolmogorov, Aleksey N.; Curtarolo, Stefano

    2006-01-01

    Modern compound prediction methods can efficiently screen large numbers of crystal structure phases and direct the experimental search for new materials. One of the most challenging problems in alloy theory is the identification of stable phases with a never seen prototype; such predictions do not always follow rational strategies. While performing ab initioa data mining of intermetallic compounds we made an unexpected discovery: even in such a well-studied class of systems as metal borides t...

  14. Nanosized Borides and Carbides for Electroplating. Metal-Matrix Coatings: Specifications, Performance Evaluation

    Science.gov (United States)

    Galevskiy, G. V.; Rudneva, V. V.; Galevskiy, S. G.; Il'yashchenko, D. P.; Kartsev, D. S.

    2016-04-01

    This paper summarizes experience of application of nano-sized carbides and borides of titanium and chromium, silicon carbide as components of electro-depositable coating compositions based on nickel, zinc, and chromium. Basic physical and mechanical properties of the coatings are determined. Technological and economic evaluation is completed; practicability of high-cost nano-diamonds substitution for nano-sized borides and carbides is justified.

  15. Nanosized Borides and Carbides for Electroplating. Metal-Matrix Coatings: Specifications, Performance Evaluation

    OpenAIRE

    Galevskiy, G. V.; Rudneva, V. V.; Galevskiy, S. G.; Ilyashchenko, Dmitry Pavlovich; Karthev, Dmitry Sergeevich

    2016-01-01

    This paper summarizes experience of application of nano-sized carbides and borides of titanium and chromium, silicon carbide as components of electro-depositable coating compositions based on nickel, zinc, and chromium. Basic physical and mechanical properties of the coatings are determined. Technological and economic evaluation is completed; practicability of high-cost nano-diamonds substitution for nano-sized borides and carbides is justified.

  16. Intermediate valence behavior of ternary cerium and uranium transition metal borides

    Science.gov (United States)

    Yang, K. N.; Torikachvili, M. S.; Maple, M. B.; Ku, H. C.

    1984-09-01

    Low-temperature specific heat, electrical resistivity, ac magnetic susceptibility, and dc magnetization measurements were made on ternary cerium and uranium transition metal borides with the general formula CeT3B2 (T=Co, Ru, Rh, and Ir) and UT3B2 (T=Co, Ru, and Ir). The compound CeRu3B2 was found to exhibit superconductivity below 0.68 K. The values of the electronic specific heat coefficient range from 9.7 mJ/mole-K2 for CeCo3B2 to 64 mJ/mole-K2 for UIr3B2. The electrical resistivity versus temperature curves of all of the compounds exhibit negative curvature and are reminiscent of valence fluctuation behavior. In the case of CeIr3B2, the electrical resistivity attains a maximum value at 180 K, while the dc magnetic susceptibility has a temperature dependence that is typical of intermediate valence Ce compounds, approaching a finite value at zero temperature. The electrical resistivity of the ferromagnetic compound CeRh3B2 reveals a rapid decrease in spin disorder resistivity below 120 K. The dc magnetic susceptibility of this material can be described as the sum of a constant term and a Curie-Weiss contribution with an effective magnetic moment of 1.01 µB per formula unit and a Curie-Weiss temperature of 119 K. Magnetization measurements on CeRh3B2 yield a saturation magnetic moment of 0.37 µB per formula unit and a Curie temperature of 113 K.

  17. High-temperature thermochemistry of transition metal borides, silicides and related compounds. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Klemppa, Ole J.

    2000-10-01

    Earlier this year in collaboration with Dr. Susan V. Meschel we prepared a major review paper which gives a comprehensive summary of what our laboratory has accomplished with support from DOE. This paper is No.43 in the List of Publications provided. It was presented to TMS at its National Meeting in Nashville, TN last March. A copy of the manuscript of this paper was recently mailed to DOE. It has been submitted for publication in Journal of Alloys and Compounds. This review paper summarizes our observed trends in the enthalpies of formation of TR-X and RE-X compounds (where X is a IIIB or IVB element) in their dependence of the atomic number of the transition metal (TR) and the lanthanide metal (RE). In this paper our measured enthalpies of formation for each alloy family are compared for the 3d, 4d and 5d transition metal elements. We also compare our experimental results with predicted values based on Miedema's semi-empirical model. Data are presented for the carbides, silicides, germanides and stannides in Group IVB, and for the borides and aluminides in Group IIIB. During the past year (1999-2000) we have extended our work to compounds of the 3d, 4d and 5d elements with gallium (see papers No.40, No.41, and No.45 in the List of Publications). Fig. 1 (taken from No.45) presents a systematic picture of our experimental values for the most exothermic gallide compounds formed with the transition elements. This figure is characteristic of the other systematic pictures which we have found for the two other IIIB elements which we have studied and for the four IVB elements. These figures are all presented in Ref. No.43. This paper also illustrates how the enthalpy of formation of compounds of the IIIB and IVB elements with the lanthanide elements (with the exception of Pm, Eu and Yb) depend on the atomic number of RE. Finally our results for the RE-X compounds are compared with the predictions of Gschneidner (K.A. Gschneidner, Jr., J. Less Common Metals 17, 1

  18. Precipitation of Niobium Boride Phases at the Base Metal/Weld Metal Interface in Dissimilar Weld Joints

    Science.gov (United States)

    Výrostková, Anna; Kepič, Ján; Homolová, Viera; Falat, Ladislav

    2015-07-01

    In this work, the analysis of failure mechanism in the heat affected zone is described in dissimilar weld joints between advanced martensitic steel T92 and Ni-base weld metal. The joints were treated with two different post-weld heat treatments and tested. For the creep, tensile, and Charpy impact tests, the samples with interfacially located notch were used. Moreover long term aging at 625 °C was applied before the tensile and notch toughness tests. Decohesion fractures ran along carbides at the T92 BM/WM interfaces in case of the modified PWHT, whereas type IV cracking was the prevailing failure mechanism after the classical PWHT in the creep test. In the notch tensile and Charpy impact tests, with the notch at T92 base metal/weld metal interface, fractures ran along the interface with a hard phase on the fracture surface along with the ductile dimple and brittle quasi-cleavage fracture. The phase identified as niobium boride (either NbB and/or Nb3B2) was produced during welding at the end of the solidification process. It was found in the welds regardless of the post-weld heat treatment and long-term aging.

  19. Interlayer utilization (including metal borides) for subsequent deposition of NSD films via microwave plasma CVD on 316 and 440C stainless steels

    Science.gov (United States)

    Ballinger, Jared

    . Surface boriding was implemented using the novel method of microwave plasma CVD with a mixture of hydrogen and diborane gases. On 440C bearings, dual phase boride layers of Fe2B and FeB were formed which supported adhered nanostructured diamond films. Continuity of the films was not seamless with limited regions remaining uncoated potentially corresponding to delamination of the film as evidenced by the presence of tubular structures presumably composed of sp2 bonded carbon. Surface boriding of 316 stainless steel discs was conducted at various powers and pressures to achieve temperatures ranging from 550-800 °C. The substrate boriding temperature was found to substantially influence the resultant interlayer by altering the metal boride(s) present. The lowest temperatures produced an interlayer where CrB was the single detected phase, higher temperatures yielded the presence of only Fe2B, and a combination of the two phases resulted from an intermediate boriding temperature. Compared with the more common, commercialized boriding methods, this a profound result given the problems posed by the FeB phase in addition to other advantages offered by CVD processes and microwave generated plasmas in general. Indentation testing of the boride layers revealed excellent adhesion strength for all borided interlayers, and above all, no evidence of cracking was observed for a sole Fe2B phase. As with boriding of 440C bearings, subsequent diamond deposition was achieved on these interlayers with substantially improved adhesion strength relative to diamond coated TiN interlayers. Both XRD and Raman spectroscopy confirmed a nanostructured diamond film with interfacial chromium carbides responsible for enhanced adhesion strength. Interlayers consisting solely of Fe2B have displayed an ability to support fully continuous nanostructured diamond films, yet additional study is required for consistent reproduction. This is in good agreement with initial work on pack borided high alloy steels

  20. Synthesis, characterization and investigation of thermoelectric properties of selected metal borides; Synthese, Charakterisierung und Untersuchung thermoelektrischer Eigenschaften ausgewaehlter Metallboride

    Energy Technology Data Exchange (ETDEWEB)

    Stober, Frederick

    2012-06-04

    The present work deals with the high-temperature thermoelectric properties of transition metal [eg V, Cr, Mn, Ni, Cu] and lanthanide [e.g. Sc, Y, Gd, Er, Dy]-borides. In particular, intercalation compounds of beta-rhombohedral boron, compounds of the type MB{sub 66}, dodecaborides and hexaborides were examined. In the case of intercalation compounds of beta-rhombohedral boron it was found that the incorporation of metals such as Sc, Mn or Cu result in favorable thermoelectric properties. The reason is most likely the preferred occupation of the metal position M2 instead of M4. Composites, for example, DyB{sub 66}-DyB{sub 12} show high electrical conductivities, high Seebeck effects at high temperatures due to the presence of DyB{sub 12} and low thermal conductivities as a result of the DyB{sub 66} matrix. At 1100K the composite DyB{sub 66}-DyB{sub 12} shows a ZT value of 0.55, thus exceeding the ZT of boron carbide (B{sub 13}C{sub 2}) at this temperature which is considered the best p-type boride material. A composite of ErB{sub 12}-ErB{sub 4}-ErB{sub 2} has negative Seebeck coefficients and shows a ZT value of 0.5 at 840K. Furthermore, the structure of tetragonal Scandiumdodecaboride ScB{sub 12} was solved on the basis of synchrotron data from a crystalline powder, after it has been debated for decades but never fully resolved.

  1. Rediscovering the Crystal Chemistry of Borides.

    Science.gov (United States)

    Akopov, Georgiy; Yeung, Michael T; Kaner, Richard B

    2017-03-21

    For decades, borides have been primarily studied as crystallographic oddities. With such a wide variety of structures (a quick survey of the Inorganic Crystal Structure Database counts 1253 entries for binary boron compounds!), it is surprising that the applications of borides have been quite limited despite a great deal of fundamental research. If anything, the rich crystal chemistry found in borides could well provide the right tool for almost any application. The interplay between metals and the boron results in even more varied material's properties, many of which can be tuned via chemistry. Thus, the aim of this review is to reintroduce to the scientific community the developments in boride crystal chemistry over the past 60 years. We tie structures to material properties, and furthermore, elaborate on convenient synthetic routes toward preparing borides.

  2. Synthesis, characterization and thermoelectric properties of metal borides, boron carbides and carbaborides; Synthese, Charakterisierung und thermoelektrische Eigenschaften ausgewaehlter Metallboride, Borcarbide und Carbaboride

    Energy Technology Data Exchange (ETDEWEB)

    Guersoy, Murat

    2015-07-06

    This work reports on the solid state synthesis and structural and thermoelectrical characterization of hexaborides (CaB{sub 6}, SrB{sub 6}, BaB{sub 6}, EuB{sub 6}), diboride dicarbides (CeB{sub 2}C{sub 2}, LaB{sub 2}C{sub 2}), a carbaboride (NaB{sub 5}C) and composites of boron carbide. The characterization was performed by X-ray diffraction methods and Rietveld refinements based on structure models from literature. Most of the compounds were densified by spark plasma sintering at 100 MPa. As high-temperature thermoelectric properties the Seebeck coefficients, electrical conductivities, thermal diffusivities and heat capacities were measured between room temperature and 1073 K. ZT values as high as 0.5 at 1273 K were obtained for n-type conducting EuB{sub 6}. High-temperature X-ray diffraction also confirmed its thermal stability. The solid solutions Ca{sub x}Sr{sub 1-x}B{sub 6}, Ca{sub x}Ba{sub 1-x}B{sub 6} and Sr{sub x}Ba{sub 1-x}B{sub 6} (x = 0, 0.25, 0.5, 0.75, 1) are also n-type but did not show better ZT values for the ternary compounds compared to the binaries, but for CaB{sub 6} the values of the figure of merit (ca. 0.3 at 1073 K) were significantly increased (ca. 50 %) compared to earlier investigations which is attributed to the densification process. Sodium carbaboride, NaB{sub 5}C, was found to be the first p-type thermoelectric material that crystallizes with the hexaboride-structure type. Seebeck coefficients of ca. 80 μV . K{sup -1} were obtained. Cerium diboride dicarbide, CeB{sub 2}C{sub 2}, and lanthanum diboride dicarbide, LaB{sub 2}C{sub 2}, are metallic. Both compounds were used as model compounds to develop compacting strategies for such layered borides. Densities obtained at 50 MPa were determined to be higher than 90 %. A new synthesis route using single source precursors that contain boron and carbon was developed to open the access to new metal-doped boron carbides. It was possible to obtain boron carbide, but metal-doping could not be

  3. The coloring problem in the solid-state metal boride carbide ScB{sub 2}C{sub 2}. A theoretical analysis

    Energy Technology Data Exchange (ETDEWEB)

    Lassoued, Souheila [Universite de Rennes, Ecole Nationale Superieure de Chimie, UMR 6226 CNRS (France). Inst. des Sciences Chimiques; Universite Kasdi Merbah-Ouargla (Algeria). Faculte des Mathematiques et des Sciences de la Matiere; Boucher, Benoit [Universite de Rennes, Ecole Nationale Superieure de Chimie, UMR 6226 CNRS (France). Inst. des Sciences Chimiques; Max-Planck-Institut fuer Chemische Physik Fester Stoffe, Dresden (Germany); Boutarfaia, Ahmed [Universite Kasdi Merbah-Ouargla (Algeria). Faculte des Mathematiques et des Sciences de la Matiere; Gautier, Regis; Halet, Jean-Francois [Universite de Rennes, Ecole Nationale Superieure de Chimie, UMR 6226 CNRS (France). Inst. des Sciences Chimiques

    2016-08-01

    The electronic properties of the layered ternary metal boride carbide ScB{sub 2}C{sub 2}, the structure of which consists of B/C layers made of fused five- and seven-membered rings alternating with scandium sheets, are analyzed. In particular, the respective positions of the B and C atoms (the so-called coloring problem) are tackled using density functional theory, quantum theory of atoms in molecules, and electron localizability indicator calculations. Results reveal that (i) the most stable coloring minimizes the number of B-B and C-C contacts and maximizes the number of boron atoms in the heptagons, (ii) the compound is metallic in character, and (iii) rather important covalent bonding occurs between the metallic sheets and the boron-carbon network.

  4. Combustion Front Dynamics in the Combustion Synthesis of Refractory Metal Carbides and Di-borides using Time-Resolved X-ray Diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Wong,J.; Larson, E.; Waide, P.; Frahm, R.

    2006-01-01

    A compact diffraction-reaction chamber, using a 2-inch photodiode array detector, has been employed to investigate the chemical dynamics at the combustion front of a selected series of refractory metal carbides and di-borides from their constituent element reactants as well as binary products from B4C as a reactant. These systems are denoted as (i) M + C {yields} MC; (ii) M + 2B {yields} MB{sub 2}; and (iii) 3M + B{sub 4}C {yields} 2MB{sub 2} + MC, where M = Ti, Zr, Nb, Hf or Ta. Time-resolved X-ray diffraction using intense synchrotron radiation at frame rates up to 10 frames s{sup -1} (or 100 ms frame{sup -1}) was employed. The combustion reactions were found to complete within 200-400 ms. In contrast to the Ta + C {yields} TaC combustion system studied earlier, in which a discernible intermediate sub-carbide phase was first formed, reacted further and disappeared to yield the final TaC product, no intermediate sub-carbide or sub-boride was detected in the current systems. Combustion for the Ti, Zr and Hf systems involved a liquid phase, in which the adiabatic temperatures T{sub ad} are well above the melting points of the respective reactant metals and have a typical combustion front velocity of 5-6 mm s{sup -1}. The Nb and Ta systems have lower T{sub ad}, involving no liquid phase. These are truly solid combustion systems and have a lower combustion front velocity of 1-2 mm s{sup -1}. The current study opens up a new avenue to chemical dynamics and macrokinetic investigations of high-temperature solid-state reactions.

  5. Sliding wear characteristics of Co-based overlay weld metal with dispersed boride particles; Hokabutsu ryushi bunsan kyoka Co ki nikumori kinzoku no suberi mamosei

    Energy Technology Data Exchange (ETDEWEB)

    Nishida, M.; Araki, T.; Shigekawa, Y. [Ehime University, Ehime (Japan). Faculty of Engineering; Asano, I.; Hayashi, Y. [Sumitomo Heavy Industries, Ltd., Tokyo (Japan)

    1998-05-05

    Requirements on wear resistant materials in recent years are applied not only to strength and hardness, but also to heat resistance and corrosion resistance. This paper describes fabrication of an overlay weld metal reinforced by dispersed particles, structured by a Co-based alloy (stellite No. 6) added with boride (MoB powder) using a plasma transferred arc welding process. The paper discusses the effect of MoB on wear characteristics at room temperature and elevated temperatures, as well as on seizability. When the MoB addition amount is increased to 3% by mass or more, the structure was found constituted by an eutectic structure with M2B and {beta} phases and an eutectic structure with M23C6 and {beta} phases, in addition to plate-shaped crystallized substance of CoMo2B2 which is a tetragonal system, and a matrix of {beta} Co. When S45C is used as a counterpart material, wear resistance was improved regardless of temperatures by making hardness of the overlay metal higher by HV 300 or more than that of the counterpart material. The overlay weld metal added with MoB showed high friction coefficient at room temperature, but even if the temperature is raised, it had less agglutination of S45C, and decreased at elevated temperatures. 13 refs., 16 figs., 1 tab.

  6. Gradient boride layers formed by diffusion carburizing and laser boriding

    Science.gov (United States)

    Kulka, M.; Makuch, N.; Dziarski, P.; Mikołajczak, D.; Przestacki, D.

    2015-04-01

    Laser boriding, instead of diffusion boriding, was proposed to formation of gradient borocarburized layers. The microstructure and properties of these layers were compared to those-obtained after typical diffusion borocarburizing. First method of treatment consists in diffusion carburizing and laser boriding only. In microstructure three zones are present: laser borided zone, hardened carburized zone and carburized layer without heat treatment. However, the violent decrease in the microhardness was observed below the laser borided zone. Additionally, these layers were characterized by a changeable value of mass wear intensity factor thus by a changeable abrasive wear resistance. Although at the beginning of friction the very low values of mass wear intensity factor Imw were obtained, these values increased during the next stages of friction. It can be caused by the fluctuations in the microhardness of the hardened carburized zone (HAZ). The use of through hardening after carburizing and laser boriding eliminated these fluctuations. Two zones characterized the microstructure of this layer: laser borided zone and hardened carburized zone. Mass wear intensity factor obtained a constant value for this layer and was comparable to that-obtained in case of diffusion borocarburizing and through hardening. Therefore, the diffusion boriding could be replaced by the laser boriding, when the high abrasive wear resistance is required. However, the possibilities of application of laser boriding instead of diffusion process were limited. In case of elements, which needed high fatigue strength, the substitution of diffusion boriding by laser boriding was not advisable. The surface cracks formed during laser re-melting were the reason for relatively quickly first fatigue crack. The preheating of the laser treated surface before laser beam action would prevent the surface cracks and cause the improved fatigue strength. Although the cohesion of laser borided carburized layer was

  7. Metallic alloy stability studies

    Science.gov (United States)

    Firth, G. C.

    1983-01-01

    The dimensional stability of candidate cryogenic wind tunnel model materials was investigated. Flat specimens of candidate materials were fabricated and cryo-cycled to assess relative dimensional stability. Existing 2-dimensional airfoil models as well as models in various stages of manufacture were also cryo-cycled. The tests indicate that 18 Ni maraging steel offers the greatest dimensional stability and that PH 13-8 Mo stainless steel is the most stable of the stainless steels. Dimensional stability is influenced primarily by metallurgical transformations (austenitic to martensitic) and manufacturing-induced stresses. These factors can be minimized by utilization of stable alloys, refinement of existing manufacturing techniques, and incorporation of new manufacturing technologies.

  8. Synthesis and characterization of new metal-rich borides with boron fragments; Synthese und Charakterisierung von neuartigen metallreichen Boriden mit Borfragmenten

    Energy Technology Data Exchange (ETDEWEB)

    Mbarki, Mohammed

    2016-03-30

    The present dissertation deals with the synthesis and characterization of new metal-rich borides of the Ce{sub 7}Ni{sub 5±x}Ge{sub 3±x}In{sub 6{sup -}}, Nb{sub 2}OsB{sub 2{sup -}} and NbRuB-type.The samples are synthesized by a solid state reaction route from elements using an electric arc furnace. The structural characterization of the compounds was carried out by using X-ray diffraction methods on powder samples and single crystals. The chemical composition of single-crystals was verified by EDX analyses. Moreover, the magnetic properties of suitable samples were investigated by SQUID magnetometry.The crystal structure of compounds with the nominal composition NbFe{sub 1-x}Ir{sub 6+x}B{sub 8} is successfully solved from single crystal X-ray data. The most prominent feature in this structure are one-dimensional chains along the c-axis formed by the magnetically active element iron on a site of mixed occupation with Iridium (Fe: Ir = 0.77 (2) 0.23 (2)). Thermomagnetic investigations reveal, that ferromagnetic ordering is observed below the Curie temperature (TC) of 350 K. Theoretical investigations suggest that the iron-chains are mainly responsible for the ferromagnetic ordering. In addition, the magnetocaloric effect (MCE) is calculated using isothermal magnetization measurements at several temperatures. The maximal magnetic entropy change ΔS = 0.032 J kg{sup -1} K{sup -1} is observed in the vicinity of T{sub C}. For the phases Nb{sub 6}Mn{sub 0,75(2)}Ir{sub 6,25(2)}B{sub 8} and Nb{sub 6}Co{sub 1,09(2)}Ir{sub 5,91(2)}B{sub 8} a relationship between the measured ferrimagnetic ordering and the crystal structure is found. Tiny superstructure reflections measured by Selected Area Electron Diffraction (SEAD) indicate a different crystal system for those compounds, which allows a ferrimagnetic spin arrangement within this crystal structure.In the second part of the thesis new results about the Nb{sub 2}OsB{sub 2-} and NbRuB-type borides are presented, which both

  9. Kinetics of borided gear steels

    Indian Academy of Sciences (India)

    Ibrahim Gunes

    2013-06-01

    In this study, the case properties and diffusion kinetics of GS18NiMoCr36 (GS18), GS22NiMoCr56 (GS22) and GS32NiCrMo6.4 (GS32) gear steels borided in Ekabor-II powder were investigated by conducting a series of experiments at temperatures of 1123, 1173 and 1223 K for 2, 4 and 6 h. The boride layer was characterized by optical microscopy, X-ray diffraction technique and microVickers hardness tester. X-ray diffraction analysis of boride layers on the surface of the steels revealed the existence of FeB, Fe2B, CrB and Cr2B compounds. The thickness of the boride layer increases by increasing boriding time and temperature for all steels. The hardness of the boride compounds formed on the surface of the steels GS18, GS22 and GS32 ranged from 1624 to 1905 HV0,05, 1702 to 1948 HV0,05, and 1745 to 2034 HV0,05 respectively, whereas Vickers hardness values of the untreated steels GS18, GS22 and GS32 were 335 HV0,05, 358 HV0,05 and 411 HV0,05, respectively. The activation energies (Q) of borided steels were 228.644 kJ/mol for GS18, 280.609 kJ/mol for GS22 and 294.359 kJ/mol for GS32. The growth kinetics of the boride layers forming on the GS18, GS22 and GS32 steels and the thickness of boride layers were also investigated.

  10. Microstructure and of Mechanics Microwave Boriding

    Institute of Scientific and Technical Information of China (English)

    YE Weiping; HUANG Zilin; ZHANG Qiaoxin; ZHANG Qinyi

    2008-01-01

    Microwave boriding layer microstructure of carbon steels and its diffusion mechanics were studied.The results show that the existence of microwave field in the boriding can't change the growth mechanics of boriding layer. Compared with conventional boriding,if the treatment temperature and time remain constantly,the descend rate of the boriding layer thickness with the increase of carbon content of steel is smaller.The diffusion activation energy of T8 steel is 2.6× 105 J/mol between the temperature of 750 ℃and 900 ℃ in microwave field,which is in the same order ofconventional boriding.

  11. Nanodispersed boriding of titanium alloy

    Directory of Open Access Journals (Sweden)

    Kateryna O. Kostyk

    2015-12-01

    Full Text Available The problem of improving the operational reliability of machines is becoming increasingly important due to the increased mechanical, thermal and other loads on the details. There are many surface hardening methods for machines parts which breakdown begins with surface corruption. The most promising methods are chemo-thermal treatment. Aim: The aim of this work is to study the impact of boriding on the structure and properties of titanium alloy. Materials and Methods: The material of this study is VT3-1 titanium alloy. The boriding were conducted using nanodispersed powder blend based on boric substances. Results: It is established that boriding of paste compounds allows obtaining the surface hardness within 30...29 GPa and with declining to 27...26 GPa in layer to the transition zone (with total thickness up to 110 μm owing to changes of the layer phase composition where Ti2B, TiB, TiB2 titanium borides are formed. The increasing of chemical-thermal treatment time from 15 minutes to 2 hours leads to thickening of the borated layer (30...110 µm and transition zone (30...190 µm. Conclusions: Due to usage of nanodispersed boric powder, the boriding duration is decreasing in 2...3 times. This allows saving time and electric energy. The developed optimal mode of boriding the VT3-1 titanium alloy allows obtaining the required operational characteristics and to combine the saturation of the surface layer with atomic boron and hardening.

  12. Boron-dependency of molybdenum boride electrocatalysts for the hydrogen evolution reaction

    Energy Technology Data Exchange (ETDEWEB)

    Park, Hyounmyung; Encinas, Andrew; Fokwa, Boniface P.T. [Department of Chemistry, University of California, Riverside, CA (United States); Department of Chemical and Environmental Engineering, University of California, Riverside, CA (United States); Scheifers, Jan P.; Zhang, Yuemei [Department of Chemistry, University of California, Riverside, CA (United States)

    2017-05-08

    Molybdenum-based materials have been considered as alternative catalysts to noble metals, such as platinum, for the hydrogen evolution reaction (HER). We have synthesized four binary bulk molybdenum borides Mo{sub 2}B, α-MoB, β-MoB, and MoB{sub 2} by arc-melting. All four phases were tested for their electrocatalytic activity (linear sweep voltammetry) and stability (cyclic voltammetry) with respect to the HER in acidic conditions. Three of these phases were studied for their HER activity and by X-ray photoelectron spectroscopy (XPS) for the first time; MoB{sub 2} and β-MoB show excellent activity in the same range as the recently reported α-MoB and β-Mo{sub 2}C phases, while the molybdenum richest phase Mo{sub 2}B show significantly lower HER activity, indicating a strong boron-dependency of these borides for the HER. In addition, MoB{sub 2} and β-MoB show long-term cycle stability in acidic solution. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. The Nature of the Microstructure and Interface Boundary Formation in Directionally Solidified Ceramic Boride Composites

    Science.gov (United States)

    2015-02-19

    to their oxide counterparts. In general, borides of rare-earth and d-transitional metals have outstanding refractory properties with high hardness...AFRL-AFOSR-UK-TR-2015-0021 The nature of the microstructure and interface boundary formation in directionally solidified ceramic ...microstructure and interface boundary formation in directionally solidified ceramic boride composites 5a. CONTRACT NUMBER STCU P-512 5b. GRANT NUMBER

  14. STABILITY CONSTANT OF THE TRISGLYCINATO METAL ...

    African Journals Online (AJOL)

    DR. AMINU

    Department of Pure and Industrial Chemistry,Bayero University Kano, P. M. B. 3011, Kano, ... The stability constants of iron, manganese, cobalt, and nickel complexes of glycine have been ... bidentate ligand in its coordination with metal ions.

  15. Metallic nanoshells on porphyrin-stabilized emulsions

    Science.gov (United States)

    Wang, Haorong; Song, Yujiang; Shelnutt, John A; Medforth, Craig J

    2013-10-29

    Metal nanostructures formed by photocatalytic interfacial synthesis using a porphyrin-stabilized emulsion template and the method for making the nanostructures. Catalyst-seeded emulsion droplets are employed as templates for hollow-nanoshell growth. The hollow metal nanospheres may be formed with or without inclusions of other materials.

  16. Boriding of Binary Ni-Ti Shape Memory Alloys

    Science.gov (United States)

    Ucar, Nazim; Dogan, Sule; Karakas, Mustafa Serdar; Calik, Adnan

    2016-11-01

    Boriding of binary Ni-Ti shape memory alloys was carried out in a solid medium at 1273 K for 2, 4, 6, and 8 h using the powder pack method with proprietary Ekabor-Ni powders. Characterization of the boride layer formed on the surface of alloys was done by optical microscopy and scanning electron microscopy. The presence of boride, silicide, and borosilicide phases in the boride layers was confirmed by X-ray diffraction analysis. The thickness and microhardness of the boride layers increased with increasing boriding time. Hardness profiles showed a rapid decrease in hardness moving from the boride layer to the main structure. The high hardness of the boride layer was attributed mainly to the formation of TiB2. A parabolic relationship was observed between layer thickness and boriding time, and the growth rate constant for the boriding treatment was calculated as 0.62×10-8 cm2 s-1.

  17. 纳米SiO2负载的过渡金属硼化物对AP热分解的催化作用%Catalytic Activity of Nano-silica Supported Transition-metal Borides on the Thermal Decomposition of Ammonium Perchlorate

    Institute of Scientific and Technical Information of China (English)

    李茸; 刘祥萱; 王煊军

    2012-01-01

    采用化学还原法制备纳米NiB/SiO2、CoB/SiO2、MoB/SiO2催化剂,通过热重-差热分析(TG-DTA)研究了其对AP热分解过程的催化作用.结果表明,负载过渡金属硼化物催化剂对AP分解的催化活性顺序为:CoB/SiO2>NiB/SiO2> MoB/SiO2;加入质量分数5%的CoB/SiO2使AP高温热分解峰温度降低166.2℃;SiO2载体将CoB晶型转化推迟了 110℃左右,改善了催化剂的热稳定性.%The nano-silica supported transition metal catalysts NiB/SiO2 , CoB/SiO2 , MoB/SiO2 were prepared by chemical reduction method. Their catalytic activity on the thermal decomposition of ammonium perchlorate (AP) was studied by TG-DTA. Results show that catalytic activity of nano-silica supported transition metal borides for the thermal decomposition of AP decreases in the order: CoB/SiO2 > NiB/SiO2 >MoB/SiO2. The CoB/SiO2 (mass ration of 5%) catalyst makes the high-temperature thermal decomposition temperature of AP decrease by 166. 2℃. The SiO2 carrier makes the crystal transformation temperature delay about 110℃, revealling the improvement of thermal stability of the catalyst.

  18. Boron-Based Hydrogen Storage: Ternary Borides and Beyond

    Energy Technology Data Exchange (ETDEWEB)

    Vajo, John

    2016-09-22

    DOE continues to seek reversible solid-state hydrogen materials with hydrogen densities of ³11 wt% and ³80 g/L that can deliver hydrogen and be recharged at moderate temperatures (£100 °C) and pressures (£100 bar) enabling incorporation into hydrogen storage systems suitable for transportation applications. Boron-based hydrogen storage materials have the potential to meet the density requirements given boron’s low atomic weight, high chemical valance, and versatile chemistry. However, the rates of hydrogen exchange in boron based compounds are thus far much too slow for practical applications. Although contributing to the high hydrogen densities, the high valance of boron also leads to slow rates of hydrogen exchange due to extensive boron-boron atom rearrangements during hydrogen cycling. This rearrangement often leads to multiple solid phases occurring over hydrogen release and recharge cycles. These phases must nucleate and react with each other across solid-solid phase boundaries leading to energy barriers that slow the rates of hydrogen exchange. This project sought to overcome the slow rates of hydrogen exchange in boron-based hydrogen storage materials by minimizing the number of solid phases and the boron atom rearrangement over a hydrogen release and recharge cycle. Two novel approaches were explored: 1) developing matched pairs of ternary borides and mixed-metal borohydrides that could exchange hydrogen with only one hydrogenated phase (the mixed-metal borohydride) and only one dehydrogenated phase (the ternary boride); and 2) developing boranes that could release hydrogen by being lithiated using lithium hydride with no boron-boron atom rearrangement. For the first approach, possible pairs of ternary borides and mixed-metal borohydrides based on Mg with various first row transition metals were investigated both experimentally and theoretically. In particular, the Mg/Mn ternary boride and mixed-metal borohydride were found to be a suitable pair and

  19. Silver metallization stability and reliability

    CERN Document Server

    Adams, Daniel; Mayer, James W

    2007-01-01

    Anyone involved in circuit technology will find this an absolute must-read. It's the first book to discuss the current understanding of silver metallization and its potential as a future interconnect material for integrated circuit technology.

  20. Magnesium Aluminum Borides as Explosive Materials

    Science.gov (United States)

    2011-12-20

    Figure 1). Hsia argued that compounds that do not undergo decomposition reactions are better choices for rocket propellants since the endothermic ...decomposition reaction is undesired. The endotherm for AlB2 decomposition, however, is small[13], especially when compared to the heat of combustion... exotherms for the boron carbide materials are comparable to those of Al + 2B and AlB2. 40 Figure 23. TGA of silicon borides vs . aluminum borides

  1. Characterization of AISI 4140 borided steels

    Energy Technology Data Exchange (ETDEWEB)

    Campos-Silva, I., E-mail: icampos@ipn.mx [Instituto Politecnico Nacional, Grupo Ingenieria de Superficies, SEPI-ESIME U.P. Adolfo Lopez Mateos, Zacatenco, Mexico D.F., 07738 (Mexico); Ortiz-Dominguez, M.; Lopez-Perrusquia, N.; Meneses-Amador, A. [Instituto Politecnico Nacional, Grupo Ingenieria de Superficies, SEPI-ESIME U.P. Adolfo Lopez Mateos, Zacatenco, Mexico D.F., 07738 (Mexico); Escobar-Galindo, R. [Instituto de Ciencia de Materiales de Madrid (CSIC), E-28049 Cantoblanco, Madrid (Spain); Martinez-Trinidad, J. [Instituto Politecnico Nacional, Grupo Ingenieria de Superficies, SEPI-ESIME U.P. Adolfo Lopez Mateos, Zacatenco, Mexico D.F., 07738 (Mexico)

    2010-02-01

    The present study characterizes the surface of AISI 4140 steels exposed to the paste-boriding process. The formation of Fe{sub 2}B hard coatings was obtained in the temperature range 1123-1273 K with different exposure times, using a 4 mm thick layer of boron carbide paste over the material surface. First, the growth kinetics of boride layers at the surface of AISI 4140 steels was evaluated. Second, the presence and distribution of alloying elements on the Fe{sub 2}B phase was measured using the Glow Discharge Optical Emission Spectrometry (GDOES) technique. Further, thermal residual stresses produced on the borided phase were evaluated by X-ray diffraction (XRD) analysis. The fracture toughness of the iron boride layer of the AISI 4140 borided steels was estimated using a Vickers microindentation induced-fracture testing at a constant distance of 25 {mu}m from the surface. The force criterion of fracture toughness was determined from the extent of brittle cracks, both parallel and perpendicular to the surface, originating at the tips of an indenter impression. The fracture toughness values obtained by the Palmqvist crack model are expressed in the form K{sub C}({pi}/2) > K{sub C} > K{sub C}(0) for the different applied loads and experimental parameters of the boriding process.

  2. Signs of superconductivity at 110 K on inclusions of TiB sub k boride phases into titanium matrix

    CERN Document Server

    Volkov, V V; Berzverkhij, P P; Martynets, V G; Matizen, E V

    2002-01-01

    Verification of theoretical forecasts on the possibility of the high-temperature superconductivity of the high-temperature superconductivity (HTSC) in the TiB sub k titanium borides is accomplished. It is established that the jump-like change in the temperature dependence of the electric resistance R(T) at 110 K takes place on the titanium samples, the surfaces whereof are coated with the borides diffusion layers of the TiB sub k variable in-depth composition. This proves the presence of the borides diffusion layers are applied onto the metallic titanium by means of treating its surface with the B sub 2 H sub 6 + H sub 2 gases mixture at the temperature of 610-700 deg C with the subsequent annealing in vacuum. The boride layers composition is studied through the mass-spectrometry method

  3. Electron momentum distribution and electronic response of ceramic borides

    Science.gov (United States)

    Heda, N. L.; Meena, B. S.; Mund, H. S.; Sahariya, Jagrati; Kumar, Kishor; Ahuja, B. L.

    2017-03-01

    Isotropic Compton profiles of transition metal based ceramics TaB and VB have been measured using 137Cs (661.65 keV) γ-ray Compton spectrometer. The experimental momentum densities are compared with those deduced using linear combination of atomic orbitals (LCAO) with Hartree-Fock (HF), density functional theory (DFT) with Wu-Cohen generalized gradient approximation (WCGGA) and also the hybridization of HF and DFT (namely B3PW and PBE0) schemes. It is found that LCAO-DFT-WCGGA scheme based profiles give an overall better agreement with the experimental data, for both the borides. In addition, we have computed the Mulliken's population (MP) charge transfer data, energy bands, density of states and Fermi surface topology of both the borides using full potential-linearized augmented plane wave (FP-LAPW) and LCAO methods with DFT-WCGGA scheme. Cross-overs of Fermi level by the energy bands corresponding to B-2p and valence d-states of transition metals lead to metallic character in both the compounds. Equal-valence-electron-density profiles and MP analysis suggest more ionic character of VB than that of TaB.

  4. Electron momentum distribution and electronic response of ceramic borides

    Energy Technology Data Exchange (ETDEWEB)

    Heda, N.L. [Department of Pure and Applied Physics, University of Kota, Kota 324005 (India); Meena, B.S.; Mund, H.S. [Department of Physics, Mohanlal Sukhadia University, Udaipur 313001 (India); Sahariya, Jagrati [Department of Physics, Manipal University, Jaipur 303007 (India); Kumar, Kishor [Department of Physics, Mohanlal Sukhadia University, Udaipur 313001 (India); Ahuja, B.L., E-mail: blahuja@yahoo.com [Department of Physics, Mohanlal Sukhadia University, Udaipur 313001 (India)

    2017-03-15

    Isotropic Compton profiles of transition metal based ceramics TaB and VB have been measured using {sup 137}Cs (661.65 keV) γ-ray Compton spectrometer. The experimental momentum densities are compared with those deduced using linear combination of atomic orbitals (LCAO) with Hartree-Fock (HF), density functional theory (DFT) with Wu-Cohen generalized gradient approximation (WCGGA) and also the hybridization of HF and DFT (namely B3PW and PBE0) schemes. It is found that LCAO-DFT-WCGGA scheme based profiles give an overall better agreement with the experimental data, for both the borides. In addition, we have computed the Mulliken's population (MP) charge transfer data, energy bands, density of states and Fermi surface topology of both the borides using full potential-linearized augmented plane wave (FP-LAPW) and LCAO methods with DFT-WCGGA scheme. Cross-overs of Fermi level by the energy bands corresponding to B-2p and valence d-states of transition metals lead to metallic character in both the compounds. Equal-valence-electron-density profiles and MP analysis suggest more ionic character of VB than that of TaB.

  5. Flexible amorphous metal films with high stability

    Science.gov (United States)

    Liu, M.; Cao, C. R.; Lu, Y. M.; Wang, W. H.; Bai, H. Y.

    2017-01-01

    We report the formation of amorphous Cu50Zr50 films with a large-area of more than 100 cm2. The films were fabricated by ion beam assisted deposition with a slow deposition rate at moderate temperature. The amorphous films have markedly enhanced thermal stability, excellent flexibility, and high reflectivity with atomic level smoothness. The multifunctional properties of the amorphous films are favorites in the promising applications of smart skin or wearable devices. The method of preparing highly stable amorphous metal films by tuning the deposition rate instead of deposition temperature could pave a way for exploring amorphous metal films with unique properties.

  6. Stability of bulk metallic glass structure

    Energy Technology Data Exchange (ETDEWEB)

    Jain, H.; Williams, D.B.

    2003-06-18

    The fundamental origins of the stability of the (Pd-Ni){sub 80}P{sub 20} bulk metallic glasses (BMGs), a prototype for a whole class of BMG formers, were explored. While much of the properties of their BMGs have been characterized, their glass-stability have not been explained in terms of the atomic and electronic structure. The local structure around all three constituent atoms was obtained, in a complementary way, using extended X-ray absorption fine structure (EXAFS), to probe the nearest neighbor environment of the metals, and extended energy loss fine structure (EXELFS), to investigate the environment around P. The occupied electronic structure was investigated using X-ray photoelectron spectroscopy (XPS). The (Pd-Ni){sub 80}P{sub 20} BMGs receive their stability from cumulative, and interrelated, effects of both atomic and electronic origin. The stability of the (Pd-Ni){sub 80}P{sub 20} BMGs can be explained in terms of the stability of Pd{sub 60}Ni{sub 20}P{sub 20} and Pd{sub 30}Ni{sub 50}P{sub 20}, glasses at the end of BMG formation. The atomic structure in these alloys is very similar to those of the binary phosphide crystals near x=0 and x=80, which are trigonal prisms of Pd or Ni atoms surrounding P atoms. Such structures are known to exist in dense, randomly-packed systems. The structure of the best glass former in this series, Pd{sub 40}Ni{sub 40}P{sub 20} is further described by a weighted average of those of Pd{sub 30}Ni{sub 50}P{sub 20} and Pd{sub 60}Ni{sub 20}P{sub 20}. Bonding states present only in the ternary alloys were found and point to a further stabilization of the system through a negative heat of mixing between Pd and Ni atoms. The Nagel and Tauc criterion, correlating a decrease in the density of states at the Fermi level with an increase in the glass stability, was consistent with greater stability of the Pd{sub x}Ni{sub (80-x)}P{sub 20} glasses with respect to the binary alloys of P. A valence electron concentration of 1.8 e/a, which

  7. A Crossover from High Stiffness to High Hardness: The Case of Osmium and Its Borides

    Science.gov (United States)

    Bian, Yongming; Liu, Xiaomei; Li, Anhu; Liang, Yongcheng

    2016-09-01

    Transition-metal light-element compounds are currently raising great expectations for hard and superhard materials. Using the widely attracting osmium (Os) and its borides (OsB, Os2B3 and OsB2) as prototypes, we demonstrate by first-principles calculations that heavy transition metals, which possess high stiffness but low hardness, can be converted into highly hard materials by incorporating of light elements to form compounds. Such a crossover is a manifestation that the underlying sources of high stiffness and high hardness are fundamentally different. The stiffness is related to elastic deformation that is closely associated with valence electron density, whereas the hardness depends strongly on plastic deformation that is determined by bonding nature. Therefore, the incorporation of light atoms into transition metal should be a valid pathway of designing hard and superhard materials. This strategy is in principle also applicable to other transition-metal borides, carbides, and nitrides.

  8. Flexibility and Stability of Metal Coordination Macromolecules.

    Science.gov (United States)

    Jiang, Heyan; Geng, Diya; Liu, Dapeng; Lanigan, Nicholas; Wang, Xiaosong

    2017-06-16

    The effect of chain structure on flexibility and stability of macromolecules containing weak P-Fe metal coordination bonds is studied. Migration insertion polymerization (MIP) of FpCX Fp (1) and PR2 CY PR2 (2) (Fp: CpFe(CO)2 ; CX and CY : alkyl spacers; P: phosphine; R: phenyl or isopropyl) generates P(1/2), in which the P-Fe and Fe-P bonds with opposite bonding direction are alternatively arranged in the backbone. On the other hand, P(FpCX P) synthesized from AB-type monomers (FpCX P) has P-Fe bonds arranged in the same direction. P(1/2) is more rigid and stable than P(FpCX P), which is attributed to the chain conformation resulting from the P-Fe bonding direction. In addition, the longer spacers render P(1/2) relatively flexible; the phenyl substituents, as compared with the isopropyl groups, improves the rigidity, thermal, and solution stability of P(1/2). It is therefore possible to incorporate weak metal coordination bonds into macromolecules with improved stability and adjustable flexibility for material processing. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Stability of metallic foams studied under microgravity

    Energy Technology Data Exchange (ETDEWEB)

    Wuebben, Th [University of Bremen (Germany); Stanzick, H [Fraunhofer-Institute (IFAM), Bremen (Germany); Banhart, J [Hahn-Meitner-Institute Berlin, (Germany); Odenbach, S [University of Bremen (Germany)

    2003-01-15

    Metal foams are prepared by mixing a metal powder and a gas-releasing blowing agent, by densifying the mix to a dense precursor and finally foaming by melting the powder compact. The foaming process of aluminium foams is monitored in situ by x-ray radioscopy. One observes that foam evolution is accompanied by film rupture processes which lead to foam coalescence. In order to elucidate the importance of oxides for foam stability, lead foams were manufactured from lead powders having two different oxide contents. The two foam types were generated on Earth and under weightlessness during parabolic flights. The measurements show that the main function of oxide particles is to prevent coalescence, while their influence on bulk viscosity of the melt is of secondary importance.

  10. Stability of Metal-Rich Massive Stars

    CERN Document Server

    White, Christopher J

    2014-01-01

    We revisit the stability of very massive main-sequence stars at solar metallicity, with the goal of understanding whether pulsations set a physical upper limit to stellar mass. Models of up to 938 solar masses are constructed with the MESA code, and their radial linear stability analysed with a nonadiabatic method following that of Castor. Despite uncertainty about the effects of convection on the linear growth rate, we conclude that even if the fundamental radial mode is unstable, the growth rate will be small. Consequently the amplitude at nonlinear saturation will also be small and not dangerous to the star. We demonstrate this for our most massive model by estimating the nonlinear parametric coupling to short-wavelength g modes. Although our stellar models are hydrostatic, the structure of their outer parts suggests that optically thick, radiatively driven winds are more likely to limit the main-sequence lifetime.

  11. Reactive Boride Brazing on Low-Alloy Automotive Grade Steel

    Science.gov (United States)

    Palanisamy, B.; Upadhyaya, A.

    2011-11-01

    Brazing is a widely used process to improve the performance of steels used in automotive applications. The substrate material is often exposed to harsh conditions in these applications and may affect the service life of the component. Reactive boride brazing aims to improve the mechanical properties of the substrate material by forming a ceramic-metal composite coating in a single-step process in situ. In this study, sintered Ancor 4300 low-alloy steel is used as the substrate with chromium-rich braze and chromium-lean braze materials. The mechanical properties of the brazed samples were studied in detail using microindentation hardness measurements and the transverse rupture test. The results indicate that the brazed superlayer has a 10 times higher hardness. There was a significant improvement in the transverse rupture strength of the steel brazed with the chromium-rich boride as compared to the pure substrate material. In an effort to reduce processing time, green compacts of the substrate were also directly brazed and yielded favorable results.

  12. Simulation of the growth kinetics of boride layers formed on Fe during gas boriding in H2-BCl3 atmosphere

    Science.gov (United States)

    Kulka, M.; Makuch, N.; Pertek, A.; Małdziński, L.

    2013-03-01

    The modeling of the boriding kinetics is considered as a necessary tool to select the suitable process parameters for obtaining boride layer of an adequate thickness. Therefore, the simulation of the growth kinetics of boride layers has gained much attention for last years. The majority of the published works described the kinetics of the pack-boriding or paste-boriding. In this study, the model of growth kinetics of two-phase boride layer (FeB+Fe2B) on pure Fe was proposed for gas boriding. Displacements of the two interfaces (FeB/Fe2B and Fe2B/substrate) resulted from a difference of the arrival flux of interstitial boron atoms to one phase and the departure flux of the boron atoms from this phase to the second phase. The mass balance equations were formulated. The measurements of thickness of both zones (FeB and Fe2B), for different temperature of boriding, were used for calculations. Based on the experimental data, the parabolic growth constants AFeB and B versus the temperature of boriding were determined. The linear relationships were accepted. As a consequence, the activation energies (QFeB and Q) were calculated. The calculated values were comparable to other data derived from gas boriding. The presented model can predict the thicknesses of the FeB and Fe2B zones (XFeB and Y, respectively) formed on pure Fe during gas boriding. Additionally, the diffusion annealing after boriding was analyzed. This process was carried out in order to obtain a single-phase boride layer (Fe2B). The relationship between the reduction in FeB zone (dXFeB) and the growth in Fe2B phase (dY) was determined. The time tXFeB=0, needed for the total elimination of FeB phase in the boride layer was calculated and compared to the experimental data.

  13. Characterization of rough interfaces obtained by boriding

    Energy Technology Data Exchange (ETDEWEB)

    Campos-Silva, I. [Instituto Politecnico Nacional, SEPI-ESIME, U.P. Adolfo Lopez Mateos, Zacatenco, Mexico D.F. 07738 (Mexico)], E-mail: icampos@ipn.mx; Balankin, A.S. [Instituto Politecnico Nacional, SEPI-ESIME, U.P. Adolfo Lopez Mateos, Zacatenco, Mexico D.F. 07738 (Mexico); Sierra, A.H. [Instituto Politecnico Nacional, UPIICSA, Av. Te 950, Col Granjas, Mexico D.F. 08400 (Mexico); Lopez-Perrusquia, N. [Instituto Politecnico Nacional, SEPI-ESIME, U.P. Adolfo Lopez Mateos, Zacatenco, Mexico D.F. 07738 (Mexico); Escobar-Galindo, R. [Instituto de Ciencia de Materiales de Madrid (CSIC), Cantoblanco, Madrid E-28049 (Spain); Morales-Matamoros, D. [Instituto Mexicano del Petroleo, Eje Lazaro Cardenas Norte, Mexico D.F. 07738 (Mexico)

    2008-12-30

    This study evaluates the morphology of borided interfaces by means of the fractal theory. The boride layers were formed in the AISI M2 steel by applying the paste boriding treatment at temperatures of 1253 and 1273 K and treatment times of 2 and 6 h, while a boron carbide paste thickness of 4 or 5 mm covered the samples surface in order to produce the boron diffusion. The morphology of interfaces formed between FeB and Fe{sub 2}B layers and between Fe{sub 2}B layer and steel substrate was analyzed by the rescaled-range (R/S), root-mean-square (RMS), and Fourier power spectrum (FPS) methods. Moreover, the multi-affine spectra of roughness exponent were obtained by calculating the q-order height-height correlation functions. We found that both interfaces are multi-affine, rather than self-affine. The multi-affine spectra of roughness exponents are found to be different for FeB/Fe{sub 2}B and Fe{sub 2}B/substrate interfaces, but independent on the treatment parameters (boron carbide paste thickness, temperature, and boriding time). Furthermore, we found that the multi-affine spectra of both interfaces behave as it is expected for 'universal multi-fractals' with the Levy index {gamma} = 1, associated with the multiplicative cascades with a log-Cauchy distribution. Furthermore, our data suggest a great homogeneity of the boron diffusion field, characterized by universal fractal dimension D{sub diff} = 2.90 {+-} 0.01. These findings provide a novel insight into the nature of phase formation during the boriding treatment.

  14. Boriding of binary Ni-Ti shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ucar, Nazim; Dogan, Sule [Suleyman Demirel Univ., Isparta (Turkey). Physics Dept.; Karakas, Mustafa Serdar [Cankaya Univ., Ankara (Turkey). Materials Science and Engineering Dept.; Calik, Adnan [Suleyman Demirel Univ., Isparta (Turkey). Manufacturing Engineering Dept.

    2016-07-01

    Boriding of binary Ni-Ti shape memory alloys was carried out in a solid medium at 1273 K for 2, 4, 6, and 8 h using the powder pack method with proprietary Ekabor-Ni powders. Characterization of the boride layer formed on the surface of alloys was done by optical microscopy and scanning electron microscopy. The presence of boride, silicide, and borosilicide phases in the boride layers was confirmed by X-ray diffraction analysis. The thickness and microhardness of the boride layers increased with increasing boriding time. Hardness profiles showed a rapid decrease in hardness moving from the boride layer to the main structure. The high hardness of the boride layer was attributed mainly to the formation of TiB{sub 2}. A parabolic relationship was observed between layer thickness and boriding time, and the growth rate constant for the boriding treatment was calculated as 0.62 x 10{sup -8} cm{sup 2}s{sup -1}.

  15. Investigation of the fracture mechanics of boride composites

    Science.gov (United States)

    Kaufman, L.; Clougherty, E. V.; Nesor, H.

    1971-01-01

    Fracture energies of WC-6Co, Boride 5 (ZrB2+SiC), Boride 8(ZrB2+SiC+C) and Boride 8-M2(ZrB2+SiC+C) were measured by slow bend and impact tests of notched charpy bars. Cobalt bonded tungsten carbide exhibited impact energies of 0.76 ft-lb or 73.9 in-lb/square inch. Boride 5 and the Boride 8 exhibit impact energies one third and one quarter of that observed for WC-6Co comparing favorably with measurements for SiC and Si3N4. Slow bend-notched bar-fracture energies for WC-6Co were near 2.6 in-lb/square inch or 1/20 the impact energies. Slow bend energies for Boride 8-M2, Boride 8 and Boride 5 were 58%, 42% and 25% of the value observed for WC-6Co. Fractograph showed differences for WC-6Co where slow bend testing resulted in smooth transgranular cleavage while samples broken by impact exhibited intergranular failures. By contrast the boride fractures showed no distinction based on testing method. Fabrication studies were conducted to effect alteration of the boride composites by alloying and introduction of graphite cloth.

  16. Thermal stability of nanoscale metallic multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Ramos, A.S., E-mail: sofia.ramos@dem.uc.pt [CEMUC, Departamento de Engenharia Mecânica, Universidade de Coimbra, 3030-788 Coimbra (Portugal); Cavaleiro, A.J.; Vieira, M.T. [CEMUC, Departamento de Engenharia Mecânica, Universidade de Coimbra, 3030-788 Coimbra (Portugal); Morgiel, J. [Institute of Metallurgy and Materials Science, Polish Academy of Sciences, Reymonta 25, 30-059 Cracow (Poland); Safran, G. [Research Institute for Technical Physics and Materials Science, Hungarian Academy of Sciences, H-1121 Budapest (Hungary)

    2014-11-28

    Metallic nanolayered thin films/foils, in particular Ni/Al multilayers, have been used to promote joining. The objective of this work is to evaluate the thermal stability of nanoscale metallic multilayers with potential for joining applications. Multilayers thin films with low (Ti/Al and Ni/Ti), medium (Ni/Al) and high (Pd/Al) enthalpies of exothermic reaction were prepared by dual cathode magnetron sputtering. Their thermal stability was studied by: i) differential scanning calorimetry combined with X-ray diffraction (XRD), ii) in-situ XRD using cobalt radiation, and iii) in-situ transmission electron microscopy. It was possible to detect traces of intermetallic or amorphous phases in the as-deposited short period (bilayer thickness) multilayers, except for the Ti/Al films where no reaction products that might be formed during deposition were identified. For short periods (below 20 nm) the equilibrium phases are directly achieved upon annealing, whereas for higher periods intermediate trialuminide phases are present for Ti/Al and Ni/Al multilayers. The formation of B2-NiTi from Ni/Ti multilayers occurs without the formation of intermediate phases. On the contrary, for the Pd–Al system the formation of intermediate phases was never avoided. The viability of nanoscale multilayers as “filler” materials for joining macro or microparts/devices was demonstrated. - Highlights: • Me1 and Me2 (Me—metal) alternated nanolayers deposited by magnetron sputtering • Reactive Me1/Me2 multilayer thin films with nanometric modulation period • By heat treatment the films always evolve to the equilibrium intermetallic phase. • For some Me1–Me2 systems and periods, the formation of intermediate phases occurs. • Me1/Me2 multilayer thin films can be used as filler materials to enhance joining.

  17. Synthesis, crystal structure investigation and magnetism of the complex metal-rich boride series Cr{sub x}(Rh{sub 1-y}Ru{sub y}){sub 7-x}B{sub 3} (x=0.88-1; y=0-1) with Th{sub 7}Fe{sub 3}-type structure

    Energy Technology Data Exchange (ETDEWEB)

    Misse, Patrick R.N.; Mbarki, Mohammed [Institute of Inorganic Chemistry, RWTH Aachen University, 52066 Aachen (Germany); Fokwa, Boniface P.T., E-mail: boniface.fokwa@ac.rwth-aachen.de [Institute of Inorganic Chemistry, RWTH Aachen University, 52066 Aachen (Germany)

    2012-08-15

    Powder samples and single crystals of the new complex boride series Cr{sub x}(Rh{sub 1-y}Ru{sub y}){sub 7-x}B{sub 3} (x=0.88-1; y=0-1) have been synthesized by arc-melting the elements under purified argon atmosphere on a water-cooled copper crucible. The products, which have metallic luster, were structurally characterized by single-crystal and powder X-ray diffraction as well as EDX measurements. Within the whole solid solution range the hexagonal Th{sub 7}Fe{sub 3} structure type (space group P6{sub 3}mc, no. 186, Z=2) was identified. Single-crystal structure refinement results indicate the presence of chromium at two sites (6c and 2b) of the available three metal Wyckoff sites, with a pronounced preference for the 6c site. An unexpected Rh/Ru site preference was found in the Ru-rich region only, leading to two different magnetic behaviors in the solid solution: The Rh-rich region shows a temperature-independent (Pauli) paramagnetism whereas an additional temperature-dependent paramagnetic component is found in the Ru-rich region. - Graphical abstract: The new complex boride series Cr{sub x}(Rh{sub 1-y}Ru{sub y}){sub 7-x}B{sub 3} (x=0.88-1; y=0-1) has been synthesized by arc melting the elements under purified argon atmosphere. Beside the 3d/4d site preference within the whole solid solution, an unexpected Rh/Ru site preference was found in the Ru-rich region only, leading to two different magnetic behaviors: The Rh-rich region shows a temperature-independent (Pauli) paramagnetism whereas an additional temperature-dependent paramagnetic component is found in the Ru-rich region. Highlights: Black-Right-Pointing-Pointer Synthesis of a new boride series fulfilling Vegard Acute-Accent s rule. Black-Right-Pointing-Pointer 3d/4d site preference. Black-Right-Pointing-Pointer Unexpected Ru/Rh site preference. Black-Right-Pointing-Pointer Rh-rich region is Pauli paramagnetic. Black-Right-Pointing-Pointer Ru-rich region is Pauli and temperature-dependent paramagnetic.

  18. Univerality, Scaling, and Stability of Metallic Nanowires

    Science.gov (United States)

    Stafford, Charles

    2001-03-01

    A remarkably quantitative understanding of the electrical and mechanical properties of simple metal nanowires has been obtained within the free-electron model.^2-4 The force required to pull a gold wire apart exhibits steps of approximately 1nN, which are synchronized with steps of order G_0=2e^2/h in the wire's electrical conductance. Using a Gutzwiller sum over classical periodic orbits,(C. A. Stafford, F. Kassubek, J. Bürki, and H. Grabert, Phys. Rev. Lett. 83), 4836 (1999). we were able to explain why the characteristic size of the force steps is universal, i.e., insensitive to the size and shape of the wire, and of order \\varepsilon_F/λ_F. The statistics of conductance and shot noise in gold nanowires can also be understood quantitatively using a model of quantum-confined electrons including disorder.(J. Bürki, C. A. Stafford, X. Zotos, and D. Baeriswyl, Phys. Rev. B 60), 5000 (1999); J. Bürki and C. A. Stafford, Phys. Rev. Lett. 83, 3342 (1999). A linear stability analysis(F. Kassubek, C. A. Stafford, H. Grabert, and R. E. Goldstein, Nonlinearity 14), 167 (2001). shows that the classical instability of a long wire under surface tension can be completely suppressed by quantum effects, leading to stable cylindrical configurations whose electrical conductance is a magic number 1, 3, 5, 6,... times G_0, providing a possible theoretical explanation for the remarkable stability of long chains of gold atoms, and for the supershell structure observed in the conductance statistics of alkali metal nanowires.

  19. Boron-Based Hydrogen Storage: Ternary Borides and Beyond

    Energy Technology Data Exchange (ETDEWEB)

    Vajo, John J. [HRL Laboratories, LLC, Malibu, CA (United States)

    2016-04-28

    DOE continues to seek reversible solid-state hydrogen materials with hydrogen densities of ≥11 wt% and ≥80 g/L that can deliver hydrogen and be recharged at moderate temperatures (≤100 °C) and pressures (≤100 bar) enabling incorporation into hydrogen storage systems suitable for transportation applications. Boron-based hydrogen storage materials have the potential to meet the density requirements given boron’s low atomic weight, high chemical valance, and versatile chemistry. However, the rates of hydrogen exchange in boron-based compounds are thus far much too slow for practical applications. Although contributing to the high hydrogen densities, the high valance of boron also leads to slow rates of hydrogen exchange due to extensive boron-boron atom rearrangements during hydrogen cycling. This rearrangement often leads to multiple solid phases occurring over hydrogen release and recharge cycles. These phases must nucleate and react with each other across solid-solid phase boundaries leading to energy barriers that slow the rates of hydrogen exchange. This project sought to overcome the slow rates of hydrogen exchange in boron-based hydrogen storage materials by minimizing the number of solid phases and the boron atom rearrangement over a hydrogen release and recharge cycle. Two novel approaches were explored: 1) developing matched pairs of ternary borides and mixed-metal borohydrides that could exchange hydrogen with only one hydrogenated phase (the mixed-metal borohydride) and only one dehydrogenated phase (the ternary boride); and 2) developing boranes that could release hydrogen by being lithiated using lithium hydride with no boron-boron atom rearrangement.

  20. Metal Stabilization of Collagen and de Novo Designed Mimetic Peptides.

    Science.gov (United States)

    Parmar, Avanish S; Xu, Fei; Pike, Douglas H; Belure, Sandeep V; Hasan, Nida F; Drzewiecki, Kathryn E; Shreiber, David I; Nanda, Vikas

    2015-08-18

    We explore the design of metal binding sites to modulate triple-helix stability of collagen and collagen-mimetic peptides. Globular proteins commonly utilize metals to connect tertiary structural elements that are well separated in sequence, constraining structure and enhancing stability. It is more challenging to engineer structural metals into fibrous protein scaffolds, which lack the extensive tertiary contacts seen in globular proteins. In the collagen triple helix, the structural adjacency of the carboxy-termini of the three chains makes this region an attractive target for introducing metal binding sites. We engineered His3 sites based on structural modeling constraints into a series of designed homotrimeric and heterotrimeric peptides, assessing the capacity of metal binding to improve stability and in the case of heterotrimers, affect specificity of assembly. Notable enhancements in stability for both homo- and heteromeric systems were observed upon addition of zinc(II) and several other metal ions only when all three histidine ligands were present. Metal binding affinities were consistent with the expected Irving-Williams series for imidazole. Unlike other metals tested, copper(II) also bound to peptides lacking histidine ligands. Acetylation of the peptide N-termini prevented copper binding, indicating proline backbone amide metal-coordination at this site. Copper similarly stabilized animal extracted Type I collagen in a metal-specific fashion, highlighting the potential importance of metal homeostasis within the extracellular matrix.

  1. 硼化物陶瓷基涂层制备技术的研究进展%Research Progress of Preparation Technology on the Boride Ceramic-based Coating

    Institute of Scientific and Technical Information of China (English)

    贾成科; 张鑫; 任先京; 冀晓鹃; 彭浩然

    2012-01-01

    Boride cermet is a new cermet with many excellent properties such as high melting temperature, bulk hardness, high chemical stability, high wearable property, and good anti-causticity, which is used in the fields such as fire-resistant material, engineering cermet, nuclear industry, and space navigation. The same excellent properties of the boride ceramic based coating prepared by many kinds of techniques, which are play important roles in many fields such as ultra high-temperature components, high wearable property units,good anti-causticity parts, anti-liquid metal-causticity component, and neutron-ratiant guard etc. The preparation methods of the boride ceramic- based coating with the strongpoint and disadvantage are introduced. The advances and the application of boride ceramic- based coating, mostly including duality boride ceramic based coatings and ternary ones, are also summarized as well as the existing problems and the prospects are analyzed.%硼化物陶瓷是一种新型陶瓷材料,具有诸如高熔点、高硬度、高化学稳定性以及高耐磨、抗腐蚀性等优异的综合性能,在耐火材料、工程陶瓷、核工业、宇航等领域有着广泛应用,而通过多种工艺制备的硼化物陶瓷基涂层同样具有很好的性质和功能,这些优异的特性使得目前硼化物涂层在很多工程领域发挥着极其重要的作用,如超高温部件、高耐磨蚀性部件以及抗金属液腐蚀性的部件、中子辐射防护装置等。本文介绍了硼化物陶瓷基涂层的制备方法,指出了各种方法的优缺点,综述了硼化物陶瓷基涂层的研究进展及其涂层的应用情况,主要包括二元硼化物陶瓷基涂层、多元硼化物基金属涂层等,总结了目前该领域存在的问题,并对今后的发展前景进行了展望。

  2. The influence of density of pressed iron powder samples on the quality of boride layers

    Directory of Open Access Journals (Sweden)

    Ivanov S.

    2003-01-01

    Full Text Available In this work the influence of the density of pressed iron powder on the quality of boride layers has been analysed. Examinations were performed on pressed samples of iron powder. The used granulation was 50-100, 100-150 and 150-200 mm. The samples were pressed under pressure of 200, 400, 600, 800 and 1000 MPa. Boroning was performed in a solid mixture based on boron-carbide, and was in principle the same for all samples. The obtained boride layers varied in depth and quality (porosity, the contact with metal. It has been observed that simultaneously with boroning sintering also occurred, and this fact offers a wide application possibility in the chemical-thermal treatment for sintered materials.

  3. Microstructural evaluation of a low carbon steel submitted to boriding treatment pre and post GTAW welding; Avaliacao microestrutural de um aco de baixo carbono submetido ao tratamento de boretacao pre e pos-soldagem GTAW

    Energy Technology Data Exchange (ETDEWEB)

    Pollnow, Edilson Nunes; Osorio, Alice Goncalves, E-mail: edilson.pollnow@hotmail.com, E-mail: osorio.alice@gmail.com [Universidade Federal de Pelotas (CDTec/UFPel), Pelotas, RS (Brazil). Centro de Desenvolvimento Tecnologico; Araujo, Douglas Bezerra de, E-mail: dbaraujo@ufu.br [Universidade Federal de Uberlandia (FEMEC/UFU), Uberlandia, MG (Brazil). Faculdade de Engenharia Mecanica; Passos, Thais Andrezza dos; Souza, Daniel, E-mail: thais.andrezza.passos@gmail.com, E-mail: danielsouza@furg.br [Universidade Federal do Rio Grande (EE/FURG), Rio Grande, RS (Brazil). Escola de Engenharia

    2017-04-15

    Studies on surface engineering area are given great importance due to the improvement that surface modifications provide to materials. With a global market that has the need to provide parts and equipment with extended service life and low cost, to support stringent requests and thus maintain its high performance, surface treatments may bring what was impossible into reality. Among the surface treatments that have received attention recently, we have the thermochemical process of boriding. The boriding process consists of saturate the surface of steels and metal alloys with boron. This saturation provides an increase in the surface properties not inherent to the base metal, such as hardness, resistance to abrasion and corrosion. Although the properties of boriding steels have already been studied, the effects that the boriding process perform on the steel during or after the welding processes are not known. Hence, it is the purpose of this study to evaluate the microstructure of a low carbon steel treated with boriding before and after GTAW welding. The results indicated poor metallurgical weldability of low carbon steel with boride layer, with the presence of solidification cracks. Nonetheless, the steel welded previous to boring treatment presented a more ductile nucleus, with harder surface. Although the values of hardness within the nucleus of the steel had dropped drastically at the welded zone after the boring, the surface of this steel showed higher values of hardness due to the boriding layer. This fact should be considered when applications where wear resistance is needed. (author)

  4. Thermodynamic stability of ligand-protected metal nanoclusters

    Science.gov (United States)

    Taylor, Michael G.; Mpourmpakis, Giannis

    2017-01-01

    Despite the great advances in synthesis and structural determination of atomically precise, thiolate-protected metal nanoclusters, our understanding of the driving forces for their colloidal stabilization is very limited. Currently there is a lack of models able to describe the thermodynamic stability of these ‘magic-number’ colloidal nanoclusters as a function of their atomic-level structural characteristics. Herein, we introduce the thermodynamic stability theory, derived from first principles, which is able to address stability of thiolate-protected metal nanoclusters as a function of the number of metal core atoms and thiolates on the nanocluster shell. Surprisingly, we reveal a fine energy balance between the core cohesive energy and the shell-to-core binding energy that appears to drive nanocluster stabilization. Our theory applies to both charged and neutral systems and captures a large number of experimental observations. Importantly, it opens new avenues for accelerating the discovery of stable, atomically precise, colloidal metal nanoclusters. PMID:28685777

  5. Thermodynamic stability of ligand-protected metal nanoclusters

    Science.gov (United States)

    Taylor, Michael G.; Mpourmpakis, Giannis

    2017-07-01

    Despite the great advances in synthesis and structural determination of atomically precise, thiolate-protected metal nanoclusters, our understanding of the driving forces for their colloidal stabilization is very limited. Currently there is a lack of models able to describe the thermodynamic stability of these `magic-number' colloidal nanoclusters as a function of their atomic-level structural characteristics. Herein, we introduce the thermodynamic stability theory, derived from first principles, which is able to address stability of thiolate-protected metal nanoclusters as a function of the number of metal core atoms and thiolates on the nanocluster shell. Surprisingly, we reveal a fine energy balance between the core cohesive energy and the shell-to-core binding energy that appears to drive nanocluster stabilization. Our theory applies to both charged and neutral systems and captures a large number of experimental observations. Importantly, it opens new avenues for accelerating the discovery of stable, atomically precise, colloidal metal nanoclusters.

  6. Microstructure and properties of laser-borided 41Cr4 steel

    Science.gov (United States)

    Kulka, M.; Makuch, N.; Pertek, A.

    2013-02-01

    Laser-boriding, instead of diffusion-boriding, was applied to formation of boride layers on 41Cr4 steel. The microstructure and properties of these layers were compared to those obtained after typical diffusion-boriding. Three zones characterized the microstructure of laser-borided layer: laser-borided zone, hardened medium-carbon zone (heat affected zone) and medium-carbon substrate without heat treatment. The through-hardened laser-borided steel was also analyzed. In this case two zones characterized the microstructure: laser-borided zone and hardened medium-carbon substrate. The microstructure of laser-borided zone consisted of eutectic mixture of borides and martensite. This phase composition (especially martensite presence) was the reason for microhardness decrease at the surface in comparison with diffusion-borided steel. However, the use of laser-boriding causes the decrease in microhardness gradient between the surface and the substrate in comparison with typical diffusion-boriding process. The value of mass wear intensity factor of the hardened laser-borided layer was comparable to that obtained in case of diffusion-boriding and through-hardening. The use of laser-borided layers instead of typical diffusion-borided layers may be advantageous under conditions of high abrasive wear of mating parts. For the experimental condition used, the laser-boriding process presented worst results concerning the fatigue strength. The cracks formed on the surface during laser re-melting were the reason for relatively quick first fatigue crack. In case of elements, which require high fatigue strength, the use of modified laser processing parameters would be necessary. The better results should be obtained by increasing of tracks overlapping. Although the cohesion of laser-borided layer was sufficient, the diffusion-borided layer showed a better cohesion.

  7. Plasma metallurgical production of nanocrystalline borides and carbides

    Science.gov (United States)

    Galevsky, G. V.; Rudneva, V. V.; Cherepanov, A. N.; Galevsky, S. G.; Efimova, K. A.

    2016-09-01

    he experience in production and study of properties of nanocrystalline borides and chromium carbides, titanium, silicon was summarized. The design and features of the vertical three-jet once-through reactor with power 150 kW, used in the plasma metallurgical production, was described. The technological, thermotechnical and resource characteristics of the reactor were identified. The parameters of borides and carbides synthesis, their main characteristics in the nanodispersed state and equipment-technological scheme of production were provided. Evaluation of engineering-and-economical performance of the laboratory and industrial levels of borides and carbides production and the state corresponding to the segment of the world market was carried out.

  8. Synthesis of metallic nanoshells on porphyrin-stabilized emulsions

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Haorong (Albuquerque, NM); Song, Yujiang (Albuquerque, NM); Shelnutt, John A. (Tijeras, NM); Medforth, Craig J. (Winters, CA)

    2011-12-13

    Metal nanostructures formed by photocatalytic interfacial synthesis using a porphyrin-stabilized emulsion template and the method for making the nanostructures. Catalyst-seeded emulsion droplets are employed as templates for hollow-nanoshell growth. The hollow metal nanospheres may be formed with or without inclusions of other materials.

  9. Synthesis of metallic nanoshells on porphyrin-stabilized emulsions

    Science.gov (United States)

    Wang, Haorong [Albuquerque, NM; Song, Yujiang [Albuquerque, NM; Shelnutt, John A [Tijeras, NM; Medforth, Craig J [Winters, CA

    2011-12-13

    Metal nanostructures formed by photocatalytic interfacial synthesis using a porphyrin-stabilized emulsion template and the method for making the nanostructures. Catalyst-seeded emulsion droplets are employed as templates for hollow-nanoshell growth. The hollow metal nanospheres may be formed with or without inclusions of other materials.

  10. Improved description of metal oxide stability

    DEFF Research Database (Denmark)

    Jauho, Thomas Stenbæk; Olsen, Thomas; Bligaard, Thomas

    2015-01-01

    The renormalized adiabatic PBE (rAPBE) method has recently been shown to comprise a significant improvement over the random phase approximation (RPA) for total energy calculations of simple solids and molecules. Here we consider the formation energies of 19 group I and II metal oxides and a few...... transition-metal oxides. The mean absolute error relative to experiments is 0.21 eV and 0.38 eV per oxygen atom for rAPBE and RPA, respectively, and thus the rAPBE method greatly improves the description of metal-oxygen bonds across a wide range of oxides. The failure of the RPA can be partly attributed...... to the lack of error cancellation between the correlation energy of the oxide on the one hand and the bulk metal and oxygen molecule on the other hand, which are all separately predicted much too negative by the RPA. We ascribe the improved performance of the rAPBE to its significantly better description...

  11. Free surface stability of liquid metal plasma facing components

    Science.gov (United States)

    Fiflis, P.; Christenson, M.; Szott, M.; Kalathiparambil, K.; Ruzic, D. N.

    2016-10-01

    An outstanding concern raised over the implementation of liquid metal plasma facing components in fusion reactors is the potential for ejection of liquid metal into the fusion plasma. The influences of Rayleigh-Taylor-like and Kelvin-Helmholtz-like instabilities were experimentally observed and quantified on the thermoelectric-driven liquid-metal plasma-facing structures (TELS) chamber at the University of Illinois at Urbana-Champaign. To probe the stability boundary, plasma currents and velocities were first characterized with a flush probe array. Subsequent observations of lithium ejection under exposure in the TELS chamber exhibited a departure from previous theory based on linear perturbation analysis. The stability boundary is mapped experimentally over the range of plasma impulses of which TELS is capable to deliver, and a new theory based on a modified set of the shallow water equations is presented which accurately predicts the stability of the lithium surface under plasma exposure.

  12. Structure and Stability of Monatomic Metallic Chains

    Science.gov (United States)

    Batra, Inder P.; Sen, Prasenjit; Ciraci, S.

    2001-03-01

    We have investigated atomic and electronic structure of Au and Al monatomic chains by using first-principle plane wave method within density-functional theory. Despite their different valencies, Au and Al form planar zigzag chains with each atom having four nearest neighbors. The zigzag structure is stable against linearization and non-planar deformations. We performed an extensive charge density analysis and finite temperature calculations to reveal the origin of the unusual atomic structure in these one dimensional metallic systems. The implications of the zigzag structure on the electronic properties and the balistic electron conduction have been examined.

  13. Quantum stability and magic lengths of metal atom wires

    Science.gov (United States)

    Cui, Ping; Choi, Jin-Ho; Lan, Haiping; Cho, Jun-Hyung; Niu, Qian; Yang, Jinlong; Zhang, Zhenyu

    2016-06-01

    Metal atom wires represent an important class of nanomaterials in the development of future electronic devices and other functional applications. Using first-principles calculations within density functional theory, we carry out a systematic study of the quantum stability of freestanding atom wires consisting of prototypical metal elements with s -, s p -, and s d -valence electrons. We explore how the quantum mechanically confined motion and local bonding of the valence electrons in these different wire systems can dictate their overall structural stability and find that the formation energy of essentially all the wires oscillates with respect to their length measured by the number n of atoms contained in the wires, establishing the existence of highly preferred (or magic) lengths. Furthermore, different wire classes exhibit distinctively different oscillatory characteristics and quantum stabilities. Alkali metal wires possessing an unpaired s valence electron per atom exhibit simple damped even-odd oscillations. In contrast, Al and Ga wires containing three s2p1 valence electrons per atom generally display much larger and undamped even-odd energy oscillations due to stronger local bonding of the p orbitals. Among the noble metals, the s -dominant Ag wires behave similarly to the linear alkali metal wires, while Au and Pt wires distinctly prefer to be structurally zigzagged due to strong relativistic effects. These findings are discussed in connection with existing experiments and should also be instrumental in future experimental realization of different metal atom wires in freestanding or supported environments with desirable functionalities.

  14. Microstructure and properties of laser-borided Inconel 600-alloy

    Energy Technology Data Exchange (ETDEWEB)

    Kulka, M., E-mail: michal.kulka@put.poznan.pl; Dziarski, P.; Makuch, N.; Piasecki, A.; Miklaszewski, A.

    2013-11-01

    Nickel-based superalloys are used extensively for a variety of industrial applications involving high temperatures and aggressive environments. However, under conditions of appreciable mechanical wear (adhesive or abrasive), these materials have to be distinguished by suitable wear protection. The diffusion boronizing is the thermo-chemical treatment, which improves the tribological properties of nickel and its alloys. Nevertheless, the long duration of this process is necessary in order to obtain the layers of the thickness up to about 100 μm. Instead of the diffusion process, in this study the laser boriding is used for producing boride layer on Inconel 600-alloy. During the laser alloying, the external cylindrical surface of base material is coated by paste, including amorphous boron. Then the surface is re-melted by a laser beam. The high overlapping of multiple laser tracks (86%) causes the formation of uniform laser-alloyed layer in respect of the thickness. Laser re-melted zone, heat-affected zone and the substrate characterize the microstructure. In the re-melted zone, the three areas are observed: compact borides zone consisting of nickel, chromium and iron borides (close to the surface), zone of increased percentage of Ni–Cr–Fe-matrix (appearing in the greater distance from the surface) and zone of dominant Ni–Cr–Fe-matrix percentage (at the end of the layer). The hardness obtained is comparable to that-obtained in case of diffusion boriding. Simultaneously, the laser-borided layers are significantly thicker (about 346 or 467 μm depending on the laser power used). The significant increase in their abrasive wear resistance is observed. The wear intensity factors, as well as the relative mass loss of the laser-borided samples, are ten times smaller in comparison with untreated Inconel 600-alloy.

  15. Microstructure and properties of laser-borided Inconel 600-alloy

    Science.gov (United States)

    Kulka, M.; Dziarski, P.; Makuch, N.; Piasecki, A.; Miklaszewski, A.

    2013-11-01

    Nickel-based superalloys are used extensively for a variety of industrial applications involving high temperatures and aggressive environments. However, under conditions of appreciable mechanical wear (adhesive or abrasive), these materials have to be distinguished by suitable wear protection. The diffusion boronizing is the thermo-chemical treatment, which improves the tribological properties of nickel and its alloys. Nevertheless, the long duration of this process is necessary in order to obtain the layers of the thickness up to about 100 μm. Instead of the diffusion process, in this study the laser boriding is used for producing boride layer on Inconel 600-alloy. During the laser alloying, the external cylindrical surface of base material is coated by paste, including amorphous boron. Then the surface is re-melted by a laser beam. The high overlapping of multiple laser tracks (86%) causes the formation of uniform laser-alloyed layer in respect of the thickness. Laser re-melted zone, heat-affected zone and the substrate characterize the microstructure. In the re-melted zone, the three areas are observed: compact borides zone consisting of nickel, chromium and iron borides (close to the surface), zone of increased percentage of Ni-Cr-Fe-matrix (appearing in the greater distance from the surface) and zone of dominant Ni-Cr-Fe-matrix percentage (at the end of the layer). The hardness obtained is comparable to that-obtained in case of diffusion boriding. Simultaneously, the laser-borided layers are significantly thicker (about 346 or 467 μm depending on the laser power used). The significant increase in their abrasive wear resistance is observed. The wear intensity factors, as well as the relative mass loss of the laser-borided samples, are ten times smaller in comparison with untreated Inconel 600-alloy.

  16. Thermal stability of atomically flat metal nanofilms on metallic substrates

    Energy Technology Data Exchange (ETDEWEB)

    Calleja, F.; Hinarejos, J.J. [Departamento de Fisica de la Materia Condensada e Instituto de Ciencia de Materiales N. Cabrera, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Passeggi, M.C.G. [Laboratorio de Superficies e Interfases, INTEC (CONICET and UNL), S3000GLN Santa Fe (Argentina); Vazquez de Parga, A.L. [Departamento de Fisica de la Materia Condensada e Instituto de Ciencia de Materiales N. Cabrera, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Miranda, R. [Departamento de Fisica de la Materia Condensada e Instituto de Ciencia de Materiales N. Cabrera, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain)], E-mail: rodolfo.miranda@uam.es

    2007-10-31

    By means of variable temperature scanning tunneling microscope we studied the morphology and electronic structure of Pb films grown on Cu(1 1 1). Due to the spatial confinement of electrons, the islands display quantized energy levels. At 300 K, Pb forms 3D nanostructures with magic heights, that correspond to islands having a quantum well state (QWS) far from the Fermi energy. Below 100 K Pb grows in a quasi-layer-by-layer fashion. The QWS that develop in the films determine their total energy and, accordingly, their thermal stability. Films of particularly magic thickness are stable upon heating to 300 K.

  17. Abandoned metal mine stability risk evaluation.

    Science.gov (United States)

    Bétournay, Marc C

    2009-10-01

    The abandoned mine legacy is critical in many countries around the world, where mine cave-ins and surface subsidence disruptions are perpetual risks that can affect the population, infrastructure, historical legacies, land use, and the environment. This article establishes abandoned metal mine failure risk evaluation approaches and quantification techniques based on the Canadian mining experience. These utilize clear geomechanics considerations such as failure mechanisms, which are dependent on well-defined rock mass parameters. Quantified risk is computed using probability of failure (probabilistics using limit-equilibrium factors of safety or applicable numerical modeling factor of safety quantifications) times a consequence impact value. Semi-quantified risk can be based on failure-case-study-based empirical data used in calculating probability of failure, and personal experience can provide qualified hazard and impact consequence assessments. The article provides outlines for land use and selection of remediation measures based on risk.

  18. Governing metal-organic frameworks towards high stability.

    Science.gov (United States)

    Li, Na; Xu, Jian; Feng, Rui; Hu, Tong-Liang; Bu, Xian-He

    2016-06-30

    Metal-organic frameworks (MOFs) constructed with metal ions/clusters and organic ligands have emerged as an important family of porous materials for various applications. However, the stability of this class of materials is crucial for their practical applications, which might be improved by varying their chemical composition and/or structurally tuning them. To fabricate MOFs with high stability, several strategies for enhancing the stability of MOFs have been developed, in which the strength of metal-ligand bonds is especially considered: the use of highly charged cations and higher pKa ligands, and varying the chemical functionality of linkers. On the other hand, the regulation of their structural architectures is also investigated: interpenetrated frameworks, multi-walled frameworks, and self-strengthening of the frameworks. In addition, the surface modification can also improve the stability of the materials. In this review, we introduce and summarize these strategies from the viewpoint of structural tuning and component choosing, providing useful instructions for the further design and synthesis of MOFs with high-level stability.

  19. Stabilizing nanostructures in metals using grain and twin boundary architectures

    Science.gov (United States)

    Lu, K.

    2016-05-01

    Forming alloys with impurity elements is a routine method for modifying the properties of metals. An alternative approach involves the incorporation of interfaces into the crystalline lattice to enhance the metal's properties without changing its chemical composition. The introduction of high-density interfaces in nanostructured materials results in greatly improved strength and hardness; however, interfaces at the nanoscale show low stability. In this Review, I discuss recent developments in the stabilization of nanostructured metals by modifying the architectures of their interfaces. The amount, structure and distribution of several types of interfaces, such as high- and low-angle grain boundaries and twin boundaries, are discussed. I survey several examples of materials with nanotwinned and nanolaminated structures, as well as with gradient nanostructures, describing the techniques used to produce such samples and tracing their exceptional performances back to the nanoscale architectures of their interfaces.

  20. Corrosion behavior of boride layers evaluated by the EIS technique

    Energy Technology Data Exchange (ETDEWEB)

    Campos, I. [Instituto Politecnico Nacional. SEPI-ESIME U.P. Adolfo Lopez Mateos, Zacatenco, Mexico D.F. 07738 (Mexico)], E-mail: icampos@ipn.mx; Palomar-Pardave, M. [Universidad Autonoma Metropolitana-Azcapotzalco, Materials Department, Avenue San Pablo 180 Col. Reynosa Tamaulipas, Mexico D.F. 02200 (Mexico); Amador, A. [Tecnologico de Monterrey, Campus Ciudad de Mexico, Calle del Puente 222 Col. Ejidos de Huipulco, Mexico D.F. 14380 (Mexico); VillaVelazquez, C. [Instituto Politecnico Nacional. SEPI-ESIME U.P. Adolfo Lopez Mateos, Zacatenco, Mexico D.F. 07738 (Mexico); Hadad, J. [Tecnologico de Monterrey, Campus Ciudad de Mexico, Calle del Puente 222 Col. Ejidos de Huipulco, Mexico D.F. 14380 (Mexico)

    2007-09-30

    The corrosion behavior of boride layers at the AISI 304 steel surface is evaluated in the present study. Electrochemical impedance spectroscopy (EIS) technique was used for the evaluation of the polarization resistance at the steel surface, with the aid of AUTOLAB potentiostat. Samples were treated with boron paste thickness of 4 and 5 mm, in the range of temperatures 1123 {<=} T {<=} 1273 K and exposed time of 4 and 6 h. The electrochemical technique employed 10 mV AC with a frequency scan range from 8 kHz to 3 mHz in deaerated 0.1 M NaCl solution. Nyquist diagrams show that the highest values of corrosion resistance are present in the samples borided at the temperature of 1273 K, with treatment time of 4 h and 4 mm of boron paste thickness. The values of corrosion resistance on borided steels are compared with the porosity exhibited in the layers.

  1. Laser borided composite layer produced on austenitic 316L steel

    Science.gov (United States)

    Mikołajczak, Daria; Kulka, Michał; Makuch, Natalia

    2016-12-01

    Abstract Austenitic 316L steel is well-known for its good resistance to corrosion and oxidation. Therefore, this material is often used wherever corrosive media or high temperatures are to be expected. The main drawback of this material is very low hardness and low resistance to mechanical wear. In this study, the laser boriding was used in order to improve the wear behavior of this material. As a consequence, a composite surface layer was produced. The microstructure of laser-borided steel was characterized by only two zones: re-melted zone and base material. In the re-melted zone, a composite microstructure, consisting of hard ceramic phases (borides) and a soft austenitic matrix, was observed. A significant increase in hardness and wear resistance of such a layer was obtained.

  2. Laser borided composite layer produced on austenitic 316L steel

    Directory of Open Access Journals (Sweden)

    Mikołajczak Daria

    2016-12-01

    Full Text Available Abstract Austenitic 316L steel is well-known for its good resistance to corrosion and oxidation. Therefore, this material is often used wherever corrosive media or high temperatures are to be expected. The main drawback of this material is very low hardness and low resistance to mechanical wear. In this study, the laser boriding was used in order to improve the wear behavior of this material. As a consequence, a composite surface layer was produced. The microstructure of laser-borided steel was characterized by only two zones: re-melted zone and base material. In the re-melted zone, a composite microstructure, consisting of hard ceramic phases (borides and a soft austenitic matrix, was observed. A significant increase in hardness and wear resistance of such a layer was obtained.

  3. Increasing the Stability of Metal-Organic Frameworks

    Directory of Open Access Journals (Sweden)

    Mathieu Bosch

    2014-01-01

    Full Text Available Metal-organic frameworks (MOFs are a new category of advanced porous materials undergoing study by many researchers for their vast variety of both novel structures and potentially useful properties arising from them. Their high porosities, tunable structures, and convenient process of introducing both customizable functional groups and unsaturated metal centers have afforded excellent gas sorption and separation ability, catalytic activity, luminescent properties, and more. However, the robustness and reactivity of a given framework are largely dependent on its metal-ligand interactions, where the metal-containing clusters are often vulnerable to ligand substitution by water or other nucleophiles, meaning that the frameworks may collapse upon exposure even to moist air. Other frameworks may collapse upon thermal or vacuum treatment or simply over time. This instability limits the practical uses of many MOFs. In order to further enhance the stability of the framework, many different approaches, such as the utilization of high-valence metal ions or nitrogen-donor ligands, were recently investigated. This review details the efforts of both our research group and others to synthesize MOFs possessing drastically increased chemical and thermal stability, in addition to exemplary performance for catalysis, gas sorption, and separation.

  4. Laser borided composite layer produced on austenitic 316L steel

    OpenAIRE

    Mikołajczak Daria; Kulka Michał; Makuch Natalia

    2016-01-01

    Abstract Austenitic 316L steel is well-known for its good resistance to corrosion and oxidation. Therefore, this material is often used wherever corrosive media or high temperatures are to be expected. The main drawback of this material is very low hardness and low resistance to mechanical wear. In this study, the laser boriding was used in order to improve the wear behavior of this material. As a consequence, a composite surface layer was produced. The microstructure of laser-borided steel w...

  5. Assessing fly ash treatment: Remediation and stabilization of heavy metals

    DEFF Research Database (Denmark)

    Lima, A.T.; Ottosen, Lisbeth M.; Ribeiro, Alexandra B.

    2012-01-01

    the electrodialytic process (EDR) has been tried out before. The goal of removing heavy metals has always been the reuse of fly ash, for instance in agricultural fields (BEK). The best removal rates are here summarized and some new results have been added. MSW fly ashes are still too hazardous after treatment to even......Fly ashes from Municipal Solid Waste (MSW), straw (ST) and co-combustion of wood (CW) are here analyzed with the intent of reusing them. Two techniques are assessed, a remediation technique and a solidification/stabilization one. The removal of heavy metals from fly ashes through...

  6. Leaching of metals on stabilization of metal sludge using cement based materials

    Institute of Scientific and Technical Information of China (English)

    Carmalin Sophia A; K. Swaminathan

    2005-01-01

    Toxicity characteristic leaching procedure(TCLP) of zinc plating sludge was carried out to assess the leaching potential of the sludge and the leachates were analyzed for heavy metals. The concentration of zinc, chromium, and lead in the leachate were 371.5mg/L, 1.95 mg/L and 1.99 mg/L respectively. Solidification of zinc sludge was carried out using four different binder systems consisting of cement mortar, fly ash, clay and lime and cured for 28 d. The ratio of sludge added varied from 60% to 80% by volume. The solidified products were tested for metal fixing efficiency and physical strength. It was observed that the volume of sludge added that resulted in maximum metal stabilization was 60% for all the combinations, above which the metal fixation efficiency decreased resulting in high values of zinc in the leachate. Addition of 5% sodium silicate enhanced the chemical fixation of metals in all the binder systems. Among the four fixing agents studied, mixture of fly ash: lime, and cement mortar: lime stabilized zinc and other metals in the sludge effectively than other combinations. Addition of lime increased the stabilization of zinc whereas cement mortar increased the strength of the solidified product.

  7. Metal Cations in G-Quadruplex Folding and Stability

    Science.gov (United States)

    Bhattacharyya, Debmalya; Mirihana Arachchilage, Gayan; Basu, Soumitra

    2016-01-01

    This review is focused on the structural and physicochemical aspects of metal cation coordination to G-Quadruplexes (GQ) and their effects on GQ stability and conformation. G-quadruplex structures are non-canonical secondary structures formed by both DNA and RNA. G-quadruplexes regulate a wide range of important biochemical processes. Besides the sequence requirements, the coordination of monovalent cations in the GQ is essential for its formation and determines the stability and polymorphism of GQ structures. The nature, location, and dynamics of the cation coordination and their impact on the overall GQ stability are dependent on several factors such as the ionic radii, hydration energy, and the bonding strength to the O6 of guanines. The intracellular monovalent cation concentration and the localized ion concentrations determine the formation of GQs and can potentially dictate their regulatory roles. A wide range of biochemical and biophysical studies on an array of GQ enabling sequences have generated at a minimum the knowledge base that allows us to often predict the stability of GQs in the presence of the physiologically relevant metal ions, however, prediction of conformation of such GQs is still out of the realm. PMID:27668212

  8. Metal Cations in G-Quadruplex Folding and Stability

    Science.gov (United States)

    Bhattacharyya, Debmalya; Mirihana Arachchilage, Gayan; Basu, Soumitra

    2016-09-01

    This review is focused on the structural and physico-chemical aspects of metal cation coordination to G-Quadruplexes (GQ) and their effects on GQ stability and conformation. G-Quadruplex structures are non-canonical secondary structures formed by both DNA and RNA. G-quadruplexes regulate a wide range of important biochemical processes. Besides the sequence requirements, the coordination of monovalent cations in the GQ is essential for its formation and determines the stability and polymorphism of GQ structures. The nature, location and dynamics of the cation coordination and their impact on the overall GQ stability are dependent on several factors such as the ionic radii, hydration energy and the bonding strength to the O6 of guanines. The intracellular monovalent cation concentration and the localized ion concentrations determine the formation of GQs and can potentially dictate their regulatory roles. A wide range of biochemical and biophysical studies on an array of GQ enabling sequences have generated at a minimum the knowledge base that allows us to often predict the stability of GQs in presence of the physiologically relevant metal ions, however, prediction of conformation of such GQs is still out of the realm.

  9. Metal Cations in G-Quadruplex Folding and Stability

    Directory of Open Access Journals (Sweden)

    Debmalya Bhattacharyya

    2016-09-01

    Full Text Available This review is focused on the structural and physico-chemical aspects of metal cation coordination to G-Quadruplexes (GQ and their effects on GQ stability and conformation. G-Quadruplex structures are non-canonical secondary structures formed by both DNA and RNA. G-quadruplexes regulate a wide range of important biochemical processes. Besides the sequence requirements, the coordination of monovalent cations in the GQ is essential for its formation and determines the stability and polymorphism of GQ structures. The nature, location and dynamics of the cation coordination and their impact on the overall GQ stability are dependent on several factors such as the ionic radii, hydration energy and the bonding strength to the O6 of guanines. The intracellular monovalent cation concentration and the localized ion concentrations determine the formation of GQs and can potentially dictate their regulatory roles. A wide range of biochemical and biophysical studies on an array of GQ enabling sequences have generated at a minimum the knowledge base that allows us to often predict the stability of GQs in presence of the physiologically relevant metal ions, however, prediction of conformation of such GQs is still out of the realm.

  10. Chemical, thermal and mechanical stabilities of metal-organic frameworks

    Science.gov (United States)

    Howarth, Ashlee J.; Liu, Yangyang; Li, Peng; Li, Zhanyong; Wang, Timothy C.; Hupp, Joseph T.; Farha, Omar K.

    2016-03-01

    The construction of thousands of well-defined, porous, metal-organic framework (MOF) structures, spanning a broad range of topologies and an even broader range of pore sizes and chemical functionalities, has fuelled the exploration of many applications. Accompanying this applied focus has been a recognition of the need to engender MOFs with mechanical, thermal and/or chemical stability. Chemical stability in acidic, basic and neutral aqueous solutions is important. Advances over recent years have made it possible to design MOFs that possess different combinations of mechanical, thermal and chemical stability. Here, we review these advances and the associated design principles and synthesis strategies. We focus on how these advances may render MOFs effective as heterogeneous catalysts, both in chemically harsh condensed phases and in thermally challenging conditions relevant to gas-phase reactions. Finally, we briefly discuss future directions of study for the production of highly stable MOFs.

  11. Formation and Characterization of Hydrogen Boride Sheets Derived from MgB2 by Cation Exchange.

    Science.gov (United States)

    Nishino, Hiroaki; Fujita, Takeshi; Cuong, Nguyen Thanh; Tominaka, Satoshi; Miyauchi, Masahiro; Iimura, Soshi; Hirata, Akihiko; Umezawa, Naoto; Okada, Susumu; Nishibori, Eiji; Fujino, Asahi; Fujimori, Tomohiro; Ito, Shin-Ichi; Nakamura, Junji; Hosono, Hideo; Kondo, Takahiro

    2017-10-04

    Two-dimensional (2D) materials are promising for applications in a wide range of fields because of their unique properties. Hydrogen boride sheets, a new 2D material recently predicted from theory, exhibit intriguing electronic and mechanical properties as well as hydrogen storage capacity. Here, we report the experimental realization of 2D hydrogen boride sheets with an empirical formula of H1B1, produced by exfoliation and complete ion-exchange between protons and magnesium cations in magnesium diboride (MgB2) with an average yield of 42.3% at room temperature. The sheets feature an sp(2)-bonded boron planar structure without any long-range order. A hexagonal boron network with bridge hydrogens is suggested as the possible local structure, where the absence of long-range order was ascribed to the presence of three different anisotropic domains originating from the 2-fold symmetry of the hydrogen positions against the 6-fold symmetry of the boron networks, based on X-ray diffraction, X-ray atomic pair distribution functions, electron diffraction, transmission electron microscopy, photo absorption, core-level binding energy data, infrared absorption, electron energy loss spectroscopy, and density functional theory calculations. The established cation-exchange method for metal diboride opens new avenues for the mass production of several types of boron-based 2D materials by countercation selection and functionalization.

  12. Subminiature eddy current transducers for studying boride coatings

    Science.gov (United States)

    Dmitriev, S. F.; Ishkov, A. V.; Malikov, V. N.; Sagalakov, A. M.

    2016-07-01

    Strengthening of parts and units of machines, increased reliability and longer service life is an important task of modern mechanical engineering. The main objects of study in the work were selected steel 65G and 50HGA, wear-resistant boride coatings ternary system Fe-B-Fe n B which were investigated by scanning electron microscopy and eddy-current nondestructive methods.

  13. Microstructure and mechanical properties of Ni and Fe-base boride-dispersion-strengthened microcrystalline alloys

    Energy Technology Data Exchange (ETDEWEB)

    Wade, C.S.; Park, H.G.; Hoagland, R.G. (Ohio State Univ., Columbus (USA))

    This paper considers the relation between microstructure and mechanical properties of two Ni-base and two Fe-base Boride-Dispersion-Strengthened Microcrystalline (BDSM) alloys. In these very fine grained materials the borides were primarily Cr, Mo, and MoFe in a fcc matrix in three of the alloys, and a bcc in one of the Fe-base alloys. Strength data and resistance to stress corrosion cracking are reported and, in the latter case, extraordinary resistance to SCC in NaCl, Na{sub 2}S{sub 2}O{sub 3} and boiling MgCl{sub 2} environments was observed in every case. The fcc BDSM alloys also demonstrated excellent thermal stability in terms of strength and fracture roughness up to 1000 C. The bcc alloy suffered severe loss of toughness. The fracture mode involved ductile rupture in all alloys and they display a reasonably linear correlation between K{sub Ic} and the square root of particle spacing.

  14. Stability of Bulk Metallic Glass Structure. Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Jain, H.; Williams, D. B.

    2003-06-01

    The fundamental origins of the stability of the (Pd-Ni){sub 80}P{sub 20} bulk metallic glasses (BMGs), a prototype for a whole class of BMG formers, were explored. While much of the properties of their BMGs have been characterized, their glass-stability have not been explained in terms of the atomic and electronic structure. The local structure around all three constituent atoms was obtained, in a complementary way, using extended X-ray absorption fine structure (EXAFS), to probe the nearest neighbor environment of the metals, and extended energy loss fine structure (EXELFS), to investigate the environment around P. The occupied electronic structure was investigated using X-ray photoelectron spectroscopy (XPS). The (Pd-Ni){sub 80}P{sub 20} BMGs receive their stability from cumulative, and interrelated, effects of both atomic and electronic origin. The stability of the (Pd-Ni){sub 80}P{sub 20} BMGs can be explained in terms of the stability of Pd{sub 60}Ni{sub 20}P{sub 20} and Pd{sub 30}Ni{sub 50}P{sub 20}, glasses at the end of BMG formation. The atomic structure in these alloys is very similar to those of the binary phosphide crystals near x=0 and x=80, which are trigonal prisms of Pd or Ni atoms surrounding P atoms. Such structures are known to exist in dense, randomly-packed systems. The structure of the best glass former in this series, Pd{sub 40}Ni{sub 40}P{sub 20} is further described by a weighted average of those of Pd{sub 30}Ni{sub 50}P{sub 20} and Pd{sub 60}Ni{sub 20}P{sub 20}. Bonding states present only in the ternary alloys were found and point to a further stabilization of the system through a negative heat of mixing between Pd and Ni atoms. The Nagel and Tauc criterion, correlating a decrease in the density of states at the Fermi level with an increase in the glass stability, was consistent with greater stability of the Pd{sub x}Ni{sub 80-x}P{sub 20} glasses with respect to the binary alloys of P. A valence electron concentration of 1.8 e/a, which

  15. The Wyckoff positional order and polyhedral intergrowth in the M3B2- and M5B3-type boride precipitated in the Ni-based superalloys

    Science.gov (United States)

    Hu, X. B.; Zhu, Y. L.; Sheng, N. C.; Ma, X. L.

    2014-12-01

    Ni-based single superalloys play a crucial role in the hottest parts of jet engines. However, due to the complex geometry and macro-segregation during the solidification process, the cast defect such as stray grains is inevitable. Therefore, the transient liquid phase (TLP) bonding which can join several small single crystalline castings together is gradually believed to be an effective method for improving the yields of production of the complex components. The melting point depressant element B is always added into the interlayer filler material. Consequently, borides including the M3B2 and M5B3 phase usually precipitate during the TLP bonding process. So a comprehensive knowledge of the fine structural characteristics of the borides is very critical for an accurate evaluation of the TLP bonding process. In this work, by means of the aberration-corrected transmission electron microscopy, we show, at an atomic scale, the Wyckoff positional order phenomenon of the metal atoms in the unit cell of M3B2- and M5B3-type boride. Meanwhile, the defect along the (001) plane of the above two types of boride are determined to be the polyhedral intergrowth with complex configurations.

  16. Electrochemical Corrosion Behavior of Borided CoCrMo Alloy Immersed in Hanks' Solution

    Science.gov (United States)

    Rosas-Becerra, G.; Mejía-Caballero, I.; Martínez-Trinidad, J.; Palomar-Pardavé, M.; Romero-Romo, M.; Pérez-Pasten-Borja, R.; Campos-Silva, I.

    2017-02-01

    New results about the corrosion resistance of borided CoCrMo alloy exposed to the Hanks' solution during different days were estimated by means of the electrochemical impedance spectroscopy technique. The CoB-Co2B coating was developed on the surface of the borided alloy using the powder-pack boriding process at 1223 K during 6 h of exposure. The corrosion resistance of the borided cobalt alloy was evaluated by the fitting of suitable equivalent electrical circuits using Nyquist and Bode plots to obtain the electrochemical parameters; the results were compared with the CoCrMo (non-borided) alloy. The samples (borided and non-borided) were characterized by the scanning electron microscopy and by the energy-dispersive x-ray spectrometry techniques to determine the elemental chemical composition developed on the surface of the materials. In addition, the reaction products formed on the surface of the borided CoCrMo alloy exposed to the Hanks' solution after the tenth day of immersion were analyzed by the x-ray photoelectron spectroscopy (XPS) technique. The results showed that the corrosion resistance of the borided cobalt alloy was affected (or reduced) by the presence of B2S3 and CrPO4 clusters formed on the material's surface. Finally, the electrochemical reactions developed during the immersion of the borided cobalt alloy on the tenth day of exposure were proposed according to the XPS results.

  17. Microstructural characterization and some mechanical properties of gas-borided Inconel 600-alloy

    Energy Technology Data Exchange (ETDEWEB)

    Makuch, N.; Kulka, M., E-mail: michal.kulka@put.poznan.pl

    2014-09-30

    Graphical abstract: - Highlights: • Two-stage gas boriding was proposed to produce the boride layer on Inconel 600-alloy. • The microstructure of diffusion zone consisted of compact borides zone and borides at grain boundaries. • The identification of nickel and chromium borides required the use of a special etching solution. • The diffusion along grain boundaries was indicated as a predominant mechanism of boron diffusion. • The increased hardness and improved wear resistance of gas-borided layer were obtained. - Abstract: The excellent resistance of Ni-based alloys to corrosion and oxidation is well-known. Boriding can be applied to these alloys in order to obtain suitable wear protection. In this paper, two-stage gas boronizing in N{sub 2}–H{sub 2}–BCl{sub 3} atmosphere is proposed for the producing the boride layer on Inconel{sup ®}600-alloy. This process consists in two stages alternately repeated: saturation by boron and diffusion annealing. Such a gas boriding is applied in order to accelerate the saturation by boron and its diffusion. It turns out to be more effective because of eliminating the excess of boron, diffusing into the substrate, during the second stage. Microstructure and some mechanical properties of the produced layer are presented. Microstructural characterization is studied with using an optical microscope, scanning electron microscope, energy-dispersive x-ray microanalysis and x-ray diffraction. The diffusion zone consists of the mixture of nickel and chromium borides, occurring in the compact boride zone and in the area located beneath, at grain boundaries. The improved hardness and wear resistance characterize the layer. The formed boride layer is significantly thicker than those-obtained by the pack-boronizing or paste process at comparable temperature and time. Simultaneously, the measured depth of layer is slightly smaller than that-reported for electrolytic boriding.

  18. Facile self-assembly and stabilization of metal oxide nanoparticles.

    Science.gov (United States)

    Charbonneau, Cecile; Holliman, Peter J; Davies, Matthew L; Watson, Trystan M; Worsley, David A

    2015-03-15

    This paper describes a facile method of self-assembling different metal oxide nanoparticles into nanostructured materials via di-carboxylate linkers (oxalic acid) using TiO2 as an example. In this method, the di-carboxylate linkers react with surface hydroxyls on metal oxide nanoparticles forming covalent, ester-like bonds, which enable the binding of two metal oxide particles, one at either end of the linker and facilitates efficient self-assembly of one group of metal oxide nanoparticles homogeneously distributed onto the surface of another group. The oxalate linkers can then be removed by thermal decomposition. This approach is shown to be effective using differently-sized TiO2 nanoparticles, namely in-house synthesized 3-5nm anatase nanocrystals and Degussa P25 titania particles (mean 21nm particle size). Our data show that the application of a high temperature heat treatment (450°C for 30min), conventionally applied to achieve a stable porous structure by thermal decomposition of the linker molecules and by inducing inter-particle necking, damages the surface area of the nanostructured material. However, here we show that sintering at 300°C for 30min or by flash near infrared radiation sintering for 12s efficiently decomposes the oxalate linkers and stabilizes the nanostructure of the material whilst maintaining its high surface area. Copyright © 2013 Elsevier Inc. All rights reserved.

  19. Metal ion coordination, conditional stability constants, and solution behavior of chelating surfactant metal complexes.

    Science.gov (United States)

    Svanedal, Ida; Boija, Susanne; Almesåker, Ann; Persson, Gerd; Andersson, Fredrik; Hedenström, Erik; Bylund, Dan; Norgren, Magnus; Edlund, Håkan

    2014-04-29

    Coordination complexes of some divalent metal ions with the DTPA (diethylenetriaminepentaacetic acid)-based chelating surfactant 2-dodecyldiethylenetriaminepentaacetic acid (4-C12-DTPA) have been examined in terms of chelation and solution behavior. The headgroup of 4-C12-DTPA contains eight donor atoms that can participate in the coordination of a metal ion. Conditional stability constants for five transition metal complexes with 4-C12-DTPA were determined by competition measurements between 4-C12-DTPA and DTPA, using electrospray ionization mass spectrometry (ESI-MS). Small differences in the relative strength between the coordination complexes of DTPA and 4-C12-DTPA indicated that the hydrocarbon tail only affected the chelating ability of the headgroup to a limited extent. The coordination of Cu(2+) ions was investigated in particular, using UV-visible spectroscopy. By constructing Job's plots, it was found that 4-C12-DTPA could coordinate up to two Cu(2+) ions. Surface tension measurements and NMR diffusometry showed that the coordination of metal ions affected the solution behavior of 4-C12-DTPA, but there were no specific trends between the studied divalent metal complexes. Generally, the effects of the metal ion coordination could be linked to the neutralization of the headgroup charge of 4-C12-DTPA, and the resulting reduced electrostatic repulsions between adjacent surfactants in micelles and monolayers. The pH vs concentration plots, on the other hand, showed a distinct difference between 4-C12-DTPA complexes of the alkaline earth metals and the transition metals. This was explained by the difference in coordination between the two groups of metal ions, as predicted by the hard and soft acid and base (HSAB) theory.

  20. Characterisation of Wear Resistant Boride Layers on a Tool Steel by Activity Controlled Pack Boronising

    DEFF Research Database (Denmark)

    Fernandes, Frederico Augusto Pires; Christiansen, Thomas Lundin; Somers, Marcel A. J.

    2015-01-01

    The present work addresses the production and characterisation of iron boride layers by pack boronising of a Vanadis 6 tool steel. The boride layers were produced at 900°C for 2h using different pack compositions in order to obtain a single-phase boride layer. The layers were characterized...... by electron microscopy, glow discharge optical emission spectroscopy, X-ray diffraction, Vickers hardness tests and wear testing with a pin-on-disc tribometer. It was found that the type of boride phases (FeB and/or Fe2B) present in the treated layer can be controlled by changing the boron activity...

  1. Growth kinetics of boride layers formed on 99.0% purity nickel

    Indian Academy of Sciences (India)

    I Gunes; K Keddam; R Chegroune; M Ozcatal

    2015-08-01

    The present study reports on the kinetics of borided Nickel 201 alloy. The thermochemical treatment of boronizing was carried out in a solid medium consisting of B4C and KBF4 powders mixture at 1123, 1173 and 1223 K for 2, 4 and 6 h, respectively. The boride layer was characterized by optical microscopy, X-ray diffraction technique and micro-Vickers hardness tester. X-ray diffraction analysis revealed the existence of NiB, Ni2B, Ni3B and Ni4B3 compounds at the surface of borided Nickel 201 alloy. The thickness of the boride layer increased with an increase in the boriding time and the temperature. The hardness of the nickel borides formed on the surface of the nickel substrate ranged from 1642 to 1854 HV0.05, whereas the Vickers hardness value of the untreated nickel was 185 HV0.05. The growth kinetics of boride layers forming on the borided Nickel 201 alloy was also analysed. The boron activation energy () was estimated as equal to 203.87 kJ mol−1 for the borided Nickel 201 alloy.

  2. Dynamic Stabilization of Metal Oxide–Water Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    McBriarty, Martin E.; von Rudorff, Guido Falk; Stubbs, Joanne E.; Eng, Peter J.; Blumberger, Jochen; Rosso, Kevin M.

    2017-02-08

    The interaction of water with metal oxide surfaces plays a crucial role in the catalytic and geochemical behavior of metal oxides. In a vast majority of studies, the interfacial structure is assumed to arise from a relatively static lowest energy configuration of atoms, even at room temperature. Using hematite (α-Fe2O3) as a model oxide, we show through a direct comparison of in situ synchrotron X-ray scattering with density functional theory-based molecular dynamics simulations that the structure of the (1102) termination is dynamically stabilized by picosecond water exchange. Simulations show frequent exchanges between terminal aquo groups and adsorbed water in locations and with partial residence times consistent with experimentally determined atomic sites and fractional occupancies. Frequent water exchange occurs even for an ultrathin adsorbed water film persisting on the surface under a dry atmosphere. The resulting time-averaged interfacial structure consists of a ridged lateral arrangement of adsorbed water molecules hydrogen bonded to terminal aquo groups. Surface pKa prediction based on bond valence analysis suggests that water exchange will influence the proton-transfer reactions underlying the acid/base reactivity at the interface. Our findings provide important new insights for understanding complex interfacial chemical processes at metal oxide–water interfaces.

  3. Stability of metal-rich very massive stars

    Science.gov (United States)

    Goodman, J.; White, Christopher J.

    2016-02-01

    We revisit the stability of very massive non-rotating main-sequence stars at solar metallicity, with the goal of understanding whether radial pulsations set a physical upper limit to stellar mass. Models of up to 938 solar masses are constructed with the MESA code, and their linear stability in the fundamental mode, assumed to be the most dangerous, is analysed with a fully non-adiabatic method. Models above 100 M⊙ have extended tenuous atmospheres (`shelves') that affect the stability of the fundamental. Even when positive, this growth rate is small, in agreement with previous results. We argue that small growth rates lead to saturation at small amplitudes that are not dangerous to the star. A mechanism for saturation is demonstrated involving non-linear parametric coupling to short-wavelength g-modes and the damping of the latter by radiative diffusion. The shelves are subject to much more rapidly growing strange modes. This also agrees with previous results but is extended here to higher masses. The strange modes probably saturate via shocks rather than mode coupling but have very small amplitudes in the core, where almost all of the stellar mass resides. Although our stellar models are hydrostatic, the structure of their outer parts suggests that optically thick winds, driven by some combination of radiation pressure, transonic convection, and strange modes, are more likely than pulsation in the fundamental mode to limit the main-sequence lifetime.

  4. Critical survey of stability constants of EDTA complexes critical evaluation of equilibrium constants in solution stability constants of metal complexes

    CERN Document Server

    Anderegg, G

    2013-01-01

    Critical Survey of Stability Constants of EDTA Complexes focuses on the computations, values, and characteristics of stability constants. The book emphasizes that for a critical discussion of experimentally determined stability constants, it is important to consider the precision of the values that manifests the self-consistency of the constant, taking into consideration the random errors. The publication reviews the stability constants of metal complexes. The numerical calculations affirm the reactions and transformations of metal ions when exposed to varying conditions. The text also present

  5. Stabilization of ultrafine metal nanocatalysts on thin carbon sheets

    Science.gov (United States)

    Liu, Xiaofang; Cui, Xinrui; Liu, Yiding; Yin, Yadong

    2015-10-01

    A novel strategy was proposed to anchor ultrafine metal nanoparticles (NPs) on thin carbon sheets for highly stable and efficient heterogeneous catalysts. In this facile approach, a dense monolayer of ultrafine AuNPs was sandwiched between a silica core and a resin shell, followed by carbonization of the shell at a high temperature and then selective removal of the silica core. The shrinkage of the shells during carbonization facilitates partial embedment of the AuNPs on the carbon shell surface and provides superior stability against particle sintering during high temperature/mechanical post-treatments and catalytic reactions. It was also found that diffusion of reactants to the surface of AuNPs could be maximized by reducing the thickness of the hollow shells or simply by cracking the shells into thin carbon sheets, both significantly benefiting the catalytic efficiency. The advantages of this ultra-stable architecture together with the densely dispersed catalytic sites were demonstrated by their high stability and superior catalytic activity in reducing hydrophilic 4-nitrophenol and hydrophobic nitrobenzene.A novel strategy was proposed to anchor ultrafine metal nanoparticles (NPs) on thin carbon sheets for highly stable and efficient heterogeneous catalysts. In this facile approach, a dense monolayer of ultrafine AuNPs was sandwiched between a silica core and a resin shell, followed by carbonization of the shell at a high temperature and then selective removal of the silica core. The shrinkage of the shells during carbonization facilitates partial embedment of the AuNPs on the carbon shell surface and provides superior stability against particle sintering during high temperature/mechanical post-treatments and catalytic reactions. It was also found that diffusion of reactants to the surface of AuNPs could be maximized by reducing the thickness of the hollow shells or simply by cracking the shells into thin carbon sheets, both significantly benefiting the

  6. Stability of complex coacervate core micelles containing metal coordination polymer.

    Science.gov (United States)

    Yan, Yun; de Keizer, Arie; Cohen Stuart, Martien A; Drechsler, Markus; Besseling, Nicolaas A M

    2008-09-01

    We report on the stability of complex coacervate core micelles, i.e., C3Ms (or PIC, BIC micelles), containing metal coordination polymers. In aqueous solutions these micelles are formed between charged-neutral diblock copolymers and oppositely charged coordination polymers formed from metal ions and bisligand molecules. The influence of added salt, polymer concentration, and charge composition was investigated by using light scattering and cryo-TEM techniques. The scattering intensity decreases strongly with increasing salt concentration until a critical salt concentration beyond which no micelles exist. The critical micelle concentration increases almost exponentially with the salt concentration. From the scattering results it follows that the aggregation number decreases with the square root of the salt concentration, but the hydrodynamic radius remains constant or increases slightly. It was concluded that the density of the core decreases with increasing ionic strength. This is in agreement with theoretical predictions and is also confirmed by cryo-TEM measurements. A complete composition diagram was constructed based on the composition boundaries obtained from light scattering titrations.

  7. Dynamic Stabilization of Metal Oxide–Water Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    McBriarty, Martin E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Physical Sciences Division; von Rudorff, Guido Falk [Univ. College London (United Kingdom). Dept. of Physics and Astronomy; Stubbs, Joanne E. [Univ. of Chicago, IL (United States). Center for Advanced Radiation Sources (CARS); Eng, Peter J. [Univ. of Chicago, IL (United States). Center for Advanced Radiation Sources (CARS); Blumberger, Jochen [Univ. College London (United Kingdom). Dept. of Physics and Astronomy; Rosso, Kevin M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Physical Sciences Division

    2017-02-08

    Metal oxide growth, dissolution, and redox reactivity depend on the structure and dynamics at the interface with aqueous solution. We present the most definitive analysis to date of the hydrated naturally abundant r-cut (11$\\bar{0}$2) termination of the iron oxide hematite (α-Fe2O3). In situ synchrotron X-ray scattering analysis reveals a ridged lateral arrangement of adsorbed water molecules hydrogen bonded to terminal aquo groups. Large-scale hybrid-functional density functional theory-based molecular dynamics (DFT-MD) simulations show how this structure is dynamically stabilized by picosecond exchange between aquo groups and adsorbed water, even under nominally dry conditions. Surface pKa prediction based on bond valence analysis suggests that water exchange may influence the proton transfer reactions associated with acid/base reactivity at the interface. Our findings rectify inconsistencies between existing models and may be extended to resolving more complex electrochemical phenomena at metal oxide-water interfaces.

  8. Assessing fly ash treatment: Remediation and stabilization of heavy metals

    KAUST Repository

    Lima, A.T.

    2010-12-17

    Fly ashes from Municipal Solid Waste (MSW), straw (ST) and co-combustion of wood (CW) are here analyzed with the intent of reusing them. Two techniques are assessed, a remediation technique and a solidification/stabilization one. The removal of heavy metals from fly ashes through the electrodialytic process (EDR) has been tried out before. The goal of removing heavy metals has always been the reuse of fly ash, for instance in agricultural fields (BEK). The best removal rates are here summarized and some new results have been added. MSW fly ashes are still too hazardous after treatment to even consider application to the soil. ST ash is the only residue that gets concentrations low enough to be reused, but its fertilizing value might be questioned. An alternative reuse for the three ashes is here preliminary tested, the combination of fly ash with mortar. Fly ashes have been substituted by cement fraction or aggregate fraction. Surprisingly, better compressive strengths were obtained by replacing the aggregate fraction. CW ashes presented promising results for the substitution of aggregate in mortar and possibly in concrete. © 2010 Elsevier Ltd.

  9. Solidification/stabilization of metal polluted sediment of Krivaja river

    Directory of Open Access Journals (Sweden)

    Dalmacija Milena B.

    2012-01-01

    Full Text Available The Krivaja River is the longest natural water body (109 km that flows completely within the borders of Serbian province of Vojvodina. In the absence of national legislation, the sediment quality was assessed in accordance with the Dutch classification methodology. It was found that the river sediment is highly contaminated with copper and zinc (192 mg kg-1 and 1218 mg kg-1 respectively, and as such is an extreme risk to the environment and human health. The solidification/stabilization (S/S treatment with local clay, that has high capacity of cation exchange 70.2 meq/100 g and specific surface area of 630 m2 g-1, was employed for remediation of the contaminated sediment. The sequential extraction procedure showed that the copper and zinc have medium risk for the environment, with the percentage in the carbonate fraction of 18 and 22% respectively. The results of sequential extraction are not in full agreement with the results of pseudo-total metal concentration in the sediment, which only confirms that the total metal concentration is not sufficient to define the real danger to the environment. Based on the pseudo-total metals concentration, the sediment is of Class 4 (Dutch standards. However, judging from the results of sequential extraction, the metals show medium risk. Obviously, these results have to be taken into account in the assessment of the sediment quality, remediation procedures and sediment disposal in general. After the treatment, the proportion of these two metals in the first fraction is significantly reduced (Cu less than 2%, Zn 10% in most of samples. In order to determine the long-term behavior of S/S mixtures, leaching tests were conducted in accordance with semi-dynamic ANS diffusion test for 90 days. The results indicated that clay can effectively immobilize Cu and Zn: the cumulative leached fraction of copper in mixtures with clay was in the range from 0.001% (mixture with 80% clay to 0.15% (mixture with 10% clay, and

  10. Stability of commercial metal oxide nanoparticles in water.

    Science.gov (United States)

    Zhang, Yang; Chen, Yongsheng; Westerhoff, Paul; Hristovski, Kiril; Crittenden, John C

    2008-04-01

    The fate of commercial nanoparticles in water is of significant interest to health and regulatory authorities. This research investigated the dispersion and stability of metal oxide nanoparticles in water as well as their removal by potable water treatment processes. Commercial nanoparticles were received as powder aggregates, and in water neither ultrasound nor chemical dispersants could break them up into primary nanoparticles. Lab-synthesized hematite was prepared as a primary nanoparticle (85 nm) suspension; upon drying and 1-month storage, however, hematite formed aggregates that could not be dispersed completely as primary nanoparticles in water. This observation may explain why it is difficult to disperse dry commercial nanoparticles. Except for silica, other nanoparticles rapidly aggregated in tap water due to electric double layer (EDL) compression. The stability of silica in tap water is related to its low Hamaker constant. For all these nanoparticles, at an alum dosage of 60 mg/L, coagulation followed by sedimentation could remove 20-60% of the total nanoparticle mass. Filtration using a 0.45 microm filter was required to remove more than 90% of the nanoparticle mass.

  11. Hybridization of Metal Nanoparticles with Metal-Organic Frameworks Using Protein as Amphiphilic Stabilizer.

    Science.gov (United States)

    Mao, Hui; Zhang, Weina; Zhou, Weiqiang; Zou, Binghua; Zheng, Bing; Zhao, Shilin; Huo, Fengwei

    2017-07-26

    Here, a facile strategy is reported to efficiently hybridize metal nanoparticles (MNPs) with typical metal-organic frameworks (MOFs) of ZIF-8 (zeolitic imidazolate framework-8), which employs bovine serum albumin (BSA, a serum albumin protein derived from cows) as the amphiphilic stabilizer to increase the affinity of MNP toward MOFs. For instance, the as-synthesized PdNPs/ZIF-8 composites with diameter from 100 to 200 nm always maintain well-defined crystalline structure, and the PdNPs with small size of ∼2 nm are well-dispersed in the crystal of MOFs without serious aggregations due to the BSA stabilizer. In Suzuki cross-coupling reactions of aryl halide, the PdNPs/ZIF-8 as catalysts have exhibited high activity and satisfied reusability owing to the use of BSA stabilizer as well as the fixing of MOFs matrixes. In addition, the strategy also can be extended to synthesize other kinds of MNPs/MOFs hybrid composites with tunable particle size, which brings more opportunity for functional MOFs hybrid materials.

  12. Effect of microstructure on the wear resistance of borided Fe-Cr alloys

    Energy Technology Data Exchange (ETDEWEB)

    Dybkov, Vasyl I. [Institute of Problems of Materials Science, Kyiv (Ukraine)

    2013-07-15

    Two boride layers were found to form at the interface between reacting phases in the course of boriding of Fe-Cr alloys (10, 15, 25 and 30% Cr) and chromium steels (13 and 25% Cr) in the temperature range of 850-950 C and reaction times 3600-43200 s (1-12h). In the case of Fe-10%Cr and Fe-15%Cr alloys and 13% Cr steel, the outer boride layer bordering the boriding agent consists of the (Fe,Cr)B phase, whereas the inner boride layer adjacent to the solid substrate consists of the (Fe,Cr)2B phase. Each layer is thus a homogeneous phase (type I microstructure). In contrast, on the surface of Fe-25%Cr and Fe-30%Cr alloys and 25% Cr steel each of the two boride layers consists of two phases and has a peculiar network-platelet morphology. The outer boride layer comprises the (Fe,Cr)B and (Cr,Fe)B phases, while the inner consists of the (Fe,Cr){sub 2}B and (Cr,Fe){sub 2}B phases (type II microstructure). It is such boride layers that exhibit the highest wear resistance. (orig.)

  13. Evaluation of High Temperature Particle Erosion Resistance of Vanadium-Boride Coating

    Energy Technology Data Exchange (ETDEWEB)

    Lee, E. Y.; Kim, J. H.; Jeong, S. I. [Andong National University, Andong (Korea, Republic of); Lee, S. H.; Eum, G. W. [Corporate R and D Institute Doosan Heavy Industries and Construction Co., Changwon (Korea, Republic of)

    2015-04-15

    The components in ultra super critical (USC) steam turbine, which is under development for high efficient power generation, are encountering harsher solid particle erosion by iron oxide scales than ones in the existing steam turbines. Therefore, the currently used boride coating will not be able to hold effective protection from particle erosion in USC system and should be replaced by new particle erosion resistant coatings. One of the best protective coatings developed for USC steam turbine parts was found to be vanadium-boride (V-boride) coating which has a hardness of about 3000 HV, much higher than that of boride, 1600∼2000 HV. In order to evaluate particle erosion resistance of the various coatings such as V-boride, boride and Cr-carbide coatings at high temperature, particle erosion test equipment were designed and manufactured. In addition, erosion particle velocity was simulated using FLUENT software based on semi-implicity method for pressure linked equations revised (SIMPLER). Based on experimental results of this work, the vanadium-boride coating was found to be superior to others and to be a candidate coating to replace the boride coating.

  14. Accelerated kinetics and mechanism of growth of boride layers on titanium under isothermal and cyclic diffusion

    Science.gov (United States)

    Sarma, Biplab

    2011-12-01

    The tendency of titanium (Ti) and its alloys to wear, gall and seize during high contact stresses between sliding surfaces severely limits their applications in bearings, gears etc. One way to mitigate these problems is to modify their surfaces by applying hard and wear resistant surface coatings. Boriding, which involves solid state diffusion of boron (B) into Ti, thereby forming hard surface layers consisting of TiB2 and TiB compounds has been shown to produce extremely high wear resistant surfaces in Ti and its alloys. The growth kinetics of these layers are, however, limited by the low diffusivities of B in the high melting TiB2 and TiB compounds. On the basis of the fact that HCP metals such as Ti show enhanced (anomalous) self-diffusion near the phase transition temperature, the first hypothesis of this work has been that the diffusivity enhancement should cause rapid ingress of B atoms, thereby accelerating the growth of the hard boride layers. Isothermal boriding experiments were performed close to phase transition temperature (890, 910, and 915°C) for time periods ranging from 3 to 24 hours. It was found that indeed a much deeper growth of TiB into the Ti substrate (˜75 mum) occurred at temperatures very close to the transition temperature (910°C), compared to that obtained at 1050°C. A diffusion model based on error-function solutions of Fick's second law was developed to quantitatively illustrate the combined effects of the normal B diffusion in the TiB phase and the anomalous B diffusion in Ti phase in accelerating TiB layer growth. Furthermore, isothermal boriding experiments close to transition temperature (900°C) for a period of 71 hours resulted in coating thickness well above 100 mum, while at 1050°C, the layer growth saturated after about 24 hours of treatment time. In the second part of this work, a novel approach named "cyclic-phase-changediffusion, (CPCD)," to create deeper TiB2 and TiB coating layers on CP-Ti by cyclic thermal processing

  15. PREFACE: The 16th International Symposium on Boron, Borides and Related Materials (ISBB 2008)

    Science.gov (United States)

    Tanaka, Takaho

    2009-07-01

    This volume of Journal of Physics: Conference Series contains invited and contributed peer-reviewed papers that were presented at the 16th International Symposium on Boron, Borides and Related Materials (ISBB 2008), which was held on 7-12 September 2008, at Kunibiki Messe, Matsue, Japan. This triennial symposium has a half-century long history starting from the 1st meeting in 1959 at Asbury Park, New Jersey. We were very pleased to organize ISBB 2008, which gathered chemists, physicists, materials scientists as well as diamond and high-pressure researchers. This meeting had a strong background in the boron-related Japanese research history, which includes the discovery of superconductivity in MgB2 and development of Nd-Fe-B hard magnets and of YB66 soft X-ray monochromator. The scope of ISBB 2008 spans both basic and applied interdisciplinary research that is centered on boron, borides and related materials, and the collection of articles defines the state of the art in research on these materials. The topics are centered on: 1. Preparation of new materials (single crystals, thin films, nanostructures, ceramics, etc) under normal or extreme conditions. 2. Crystal structure and chemical bonding (new crystal structures, nonstoichiometry, defects, clusters, quantum-chemical calculations). 3. Physical and chemical properties (band structure, phonon spectra, superconductivity; optical, electrical, magnetic, emissive, mechanical properties; phase diagrams, thermodynamics, catalytic activity, etc) in a wide range of temperatures and pressures. 4. Applications and prospects (thermoelectric converters, composites, ceramics, coatings, etc) There were a few discoveries of new materials, such as nanomaterials, and developments in applications. Many contributions were related to 4f heavy Fermion systems of rare-earth borides. Exotic mechanisms of magnetism and Kondo effects have been discussed, which may indicate another direction of development of boride. Two special sessions

  16. Water-in-Supercritical CO2 Microemulsion Stabilized by a Metal Complex.

    Science.gov (United States)

    Luo, Tian; Zhang, Jianling; Tan, Xiuniang; Liu, Chengcheng; Wu, Tianbin; Li, Wei; Sang, Xinxin; Han, Buxing; Li, Zhihong; Mo, Guang; Xing, Xueqing; Wu, Zhonghua

    2016-10-17

    Herein we propose for the first time the utilization of a metal complex for forming water-in-supercritical CO2 (scCO2 ) microemulsions. The water solubility in the metal-complex-stabilized microemulsion is significantly improved compared with the conventional water-in-scCO2 microemulsions stabilized by hydrocarbons. Such a microemulsion provides a promising route for the in situ CO2 reduction catalyzed by a metal complex at the water/scCO2 interface.

  17. An Assessment of Binary Metallic Glasses: Correlations Between Structure, Glass Forming Ability and Stability (Preprint)

    Science.gov (United States)

    2011-07-01

    release; distribution unlimited. 1. Introduction It has long been suggested that metallic glass stability and glass-forming ability (GFA) are... magnetostriction of Co-Cr-Zr amorphous alloys’, Rapidly Quenched Metals, Proc. 4th International Conference on Rapidly Quenched Metals, Sendai, Japan, 861-864

  18. Effect of Fe2B boride orientation on abrasion wear resistance of Fe-B cast alloy

    Directory of Open Access Journals (Sweden)

    Da-wei Yi

    2017-07-01

    Full Text Available The microstructures and abrasion wear resistance of directional solidification Fe-B alloy have been investigated using optical microscopy, X-ray diffraction, scanning electron microscopy and laser scanning microscopy. The results show that the microstructure of as-cast Fe-B alloy consists of ferrite, pearlite and eutectic boride. After heat treatment, the microstructure is composed of boride and martensite. The plane which is perpendicular to the boride growth direction possesses the highest hardness. In two-body abrasive wear tests, the silicon carbide abrasive can cut the boride and martensite matrix synchronously, and the wear mechanism is micro cutting mechanism. The worn surface roughness and the wear weight loss both increase with the increasing contact load. Moreover, when the boride growth direction is perpendicular to the worn surface, the highest hardness plane of the boride can effectively oppose abrasion, and the martensite matrix can surround and support borides perfectly.

  19. Microstructural characterization and some mechanical properties of gas-borided Inconel 600-alloy

    Science.gov (United States)

    Makuch, N.; Kulka, M.

    2014-09-01

    The excellent resistance of Ni-based alloys to corrosion and oxidation is well-known. Boriding can be applied to these alloys in order to obtain suitable wear protection. In this paper, two-stage gas boronizing in N2-H2-BCl3 atmosphere is proposed for the producing the boride layer on Inconel®600-alloy. This process consists in two stages alternately repeated: saturation by boron and diffusion annealing. Such a gas boriding is applied in order to accelerate the saturation by boron and its diffusion. It turns out to be more effective because of eliminating the excess of boron, diffusing into the substrate, during the second stage. Microstructure and some mechanical properties of the produced layer are presented. Microstructural characterization is studied with using an optical microscope, scanning electron microscope, energy-dispersive x-ray microanalysis and x-ray diffraction. The diffusion zone consists of the mixture of nickel and chromium borides, occurring in the compact boride zone and in the area located beneath, at grain boundaries. The improved hardness and wear resistance characterize the layer. The formed boride layer is significantly thicker than those-obtained by the pack-boronizing or paste process at comparable temperature and time. Simultaneously, the measured depth of layer is slightly smaller than that-reported for electrolytic boriding.

  20. Characterisation of titanium-titanium boride composites processed by powder metallurgy techniques

    Energy Technology Data Exchange (ETDEWEB)

    Selva Kumar, M., E-mail: sel_mcet@yahoo.co.in [Department of Mechanical Engineering, Dr. Mahalingam College of Engineering and Technology, Pollachi-642003 (India); Chandrasekar, P.; Chandramohan, P. [School of Engineering, Professional Group of Institutions, Coimbatore-641662 (India); Mohanraj, M. [Department of Mechanical Engineering, Info Institute of Engineering, Coimbatore-641107 (India)

    2012-11-15

    In this work, a detailed characterisation of titanium-titanium boride composites processed by three powder metallurgy techniques, namely, hot isostatic pressing, spark plasma sintering and vacuum sintering, was conducted. Two composites with different volume percents of titanium boride reinforcement were used for the investigation. One was titanium with 20% titanium boride, and the other was titanium with 40% titanium boride (by volume). Characterisation was performed using X-ray diffraction, electron probe micro analysis - energy dispersive spectroscopy and wavelength dispersive spectroscopy, image analysis and scanning electron microscopy. The characterisation results confirm the completion of the titanium boride reaction. The results reveal the presence of titanium boride reinforcement in different morphologies such as needle-shaped whiskers, short agglomerated whiskers and fine plates. The paper also discusses how mechanical properties such as microhardness, elastic modulus and Poisson's ratio are influenced by the processing techniques as well as the volume fraction of the titanium boride reinforcement. - Highlights: Black-Right-Pointing-Pointer Ti-TiB composites were processed by HIP, SPS and vacuum sintering. Black-Right-Pointing-Pointer The completion of Ti-TiB{sub 2} reaction was confirmed by XRD, SEM and EPMA studies. Black-Right-Pointing-Pointer Hardness and elastic properties of Ti-TiB composites were discussed. Black-Right-Pointing-Pointer Processing techniques were compared with respect to their microstructure.

  1. Solubility Behavior and Phase Stability of Transition Metal Oxides in Alkaline Hydrothermal Environments

    Energy Technology Data Exchange (ETDEWEB)

    S.E. Ziemniak

    2000-05-18

    The solubility behavior of transition metal oxides in high temperature water is interpreted by recognizing three types of chemical reaction equilibria: metal oxide hydration/dehydration, metal oxide dissolution and metal ion hydroxocomplex formation. The equilibria are quantified using thermodynamic concepts and the thermochemical properties of the metal oxides/ions representative of the most common constituents of construction metal alloys, i.e., element shaving atomic numbers between Z = 22 (Ti) and Z = 30 (Zn), are summarized on the basis of metal oxide solubility studies conducted in the laboratory. Particular attention is devoted to the uncharged metal ion hydrocomplex, M{sup Z}(OH){sub Z}(aq), since its thermochemical properties define minimum solubilities of the metal oxide at a given temperature. Experimentally-extracted values of standard partial molal entropy (S{sup 0}) for the transition metal ion neutral hydroxocomplex are shown to be influenced by ligand field stabilization energies and complex symmetry.

  2. Influence of alloy ingredients on mechanical properties of ternary boride hard alloy clad materials

    Institute of Scientific and Technical Information of China (English)

    LIU Fu-tian; SONG Shi-xue; YANG Jun-ru; HUANG Wei-ling; HUANG Chuan-zhen; CHENG Xin; LI Zhao-qian

    2004-01-01

    Using Mo, B-Fe alloy and Fe powders as raw materials, and adding C, Cr and Ni ingredients, respectively, or C, Cr and Ni mixed powders, ternary boride hard alloy clad materials was prepared on Q235 steel substrate by means of in-situ reaction and vacuum liquid phase sintering technology. The influence of alloy ingredients on the mechanical properties of ternary boride hard alloy clad materials was investigated. The results indicate that a mixture of 0.8% C, 5% Cr and 2% Ni ingredients gives a ternary boride hard alloy clad material with optimal mechanical properties, such as high transverse rupture strength, high hardness and good wear resistance.

  3. Laser guided and stabilized gas metal arc welding processes (LGS-GMA)

    Science.gov (United States)

    Hermsdorf, Jörg; Barroi, Alexander; Kaierle, Stefan; Overmeyer, Ludger

    2013-05-01

    The demands of the industry are cheap and fast production of highly sophisticated parts without compromises in product quality. To realize this requirement, we have developed a laser guided and stabilized gas metal arc process (LGS-GMA welding). The new welding process is based on a gas metal arc process using low power laser radiation for stabilization. The laser stabilization of gas metal arcs welding is applied to joint welding and cladding. With only 400 W laser power and a focal spot of 1.6 mm the laser radiation is mainly interacting with the arc plasma in order to guide and stabilize it. In joint welding up to 100% increase in welding speed is possible, at equal penetration depth. The guidance effect also enables the process to weld in challenging situations like different sheet thicknesses. Used for cladding, the enhanced process stability allows low penetration depth with dilutions of only 3%. Coatings with up to 63 HRC were achieved.

  4. Microstructure and properties of laser-borided composite layers formed on commercially pure titanium

    Science.gov (United States)

    Kulka, M.; Makuch, N.; Dziarski, P.; Piasecki, A.; Miklaszewski, A.

    2014-03-01

    Laser-boriding was proposed in order to produce composite boride layers on commercially pure titanium. Three zones were observed in the microstructure: laser-borided re-melted zone (TiB, TiB2 and Tiα'-phase), heat affected zone (Tiα'-phase) and the substrate without heat treatment (Tiα-phase). The stick-like titanium borides occurred in the re-melted zone. In some areas, the tubular nature of titanium borides was visible. Among the sticks of titanium borides the needles of Tiα'-phase appeared. The high overlapping of multiple laser tracks (86%) caused the formation of uniform laser-alloyed layer in respect of the thickness. The microcracks and pores were not detected in the laser-borided composite layer. The high hardness of the re-melted zone (1250-1650 HV) was obtained. The hardness gradually decreased up to 250-300 HV in heat affected zone and up to about 200 HV in the substrate. In case of higher laser beam power used (1.95 kW), the re-melted zone was thicker and more homogeneous in respect of the microstructure and hardness. The craters obtained at the surface after the Rockwell C indentation test evidently revealed ideal cohesion of the laser-borided layer (HF1 standard). The significant increase in wear resistance of laser-borided composite layers was observed in comparison with commercially pure titanium. The lower mass wear intensity factors were obtained for laser-alloyed layers. The measurements of relative mass loss were also used in order to evaluate wear behavior of the investigated materials. The tests of laser-borided layers showed the catastrophic wear of the counter-specimens. The separated particles of counter-sample caused the accelerated wear of the laser-alloyed specimen. The longer duration of the tests, carried out without the change in a counter-specimen, caused the adhesion of counter-sample particles on the laser-borided specimen. The increased contact surface was the reason for the higher temperature and created the favourable

  5. An alternative method of gas boriding applied to the formation of borocarburized layer

    Energy Technology Data Exchange (ETDEWEB)

    Kulka, M., E-mail: michal.kulka@put.poznan.pl; Makuch, N.; Pertek, A.; Piasecki, A.

    2012-10-15

    The borocarburized layers were produced by tandem diffusion processes: carburizing followed by boriding. An alternative method of gas boriding was proposed. Two-stage gas boronizing in N{sub 2}-H{sub 2}-BCl{sub 3} atmosphere was applied to the formation of iron borides on a carburized substrate. This process consisted in two stages, which were alternately repeated: saturation by boron and diffusion annealing. The microstructure and microhardness of produced layer were compared to those-obtained in case of continuous gas boriding in H{sub 2}-BCl{sub 3} atmosphere, earlier used. The first objective of two-stage boronizing, consisting in acceleration of boron diffusion, has been efficiently implemented. Despite the lower temperature and shorter duration of boronizing, about 1.5 times larger iron borides' zone has been formed on carburized steel. Second objective, the absolute elimination of brittle FeB phase, has failed. However, the amount of FeB phase has been considerably limited. Longer diffusion annealing should provide the boride layer with single-phase microstructure, without FeB phase. - Highlights: Black-Right-Pointing-Pointer Alternative method of gas boriding in H{sub 2}-N{sub 2}-BCl{sub 3} atmosphere was proposed. Black-Right-Pointing-Pointer The process consisted in two stages: saturation by boron and diffusion annealing. Black-Right-Pointing-Pointer These stages of short duration were alternately repeated. Black-Right-Pointing-Pointer The acceleration of boron diffusion was efficiently implemented. Black-Right-Pointing-Pointer The amount of FeB phase in the boride zone was limited.

  6. Metal-dielectric interfaces in gigascale electronics thermal and electrical stability

    CERN Document Server

    He, Ming

    2012-01-01

    Metal-dielectric interfaces are ubiquitous in modern electronics. As advanced gigascale electronic devices continue to shrink, the stability of these interfaces is becoming an increasingly important issue that has a profound impact on the operational reliability of these devices. In this book, the authors present the basic science underlying  the thermal and electrical stability of metal-dielectric interfaces and its relationship to the operation of advanced interconnect systems in gigascale electronics. Interface phenomena, including chemical reactions between metals and dielectrics, metallic-atom diffusion, and ion drift, are discussed based on fundamental physical and chemical principles. Schematic diagrams are provided throughout the book to illustrate  interface phenomena and the principles that govern them. Metal-Dielectric Interfaces in Gigascale Electronics  provides a unifying approach to the diverse and sometimes contradictory test results that are reported in the literature on metal-dielectric i...

  7. Work function anisotropy and surface stability of half-metallic CrO(2)

    NARCIS (Netherlands)

    Attema, J. J.; Uijttewaal, M. A.; de Wijs, G. A.; de Groot, R. A.

    2008-01-01

    Insight in the interplay between work function and stability is important for many areas of physics. In this paper, we calculate the anisotropy in the work function and the surface stability of CrO(2), a prototype half-metal, and find an anisotropy of 3.8 eV. An earlier model for the relation betwee

  8. Work function anisotropy and surface stability of half-metallic CrO(2)

    NARCIS (Netherlands)

    Attema, J. J.; Uijttewaal, M. A.; de Wijs, G. A.; de Groot, R. A.

    Insight in the interplay between work function and stability is important for many areas of physics. In this paper, we calculate the anisotropy in the work function and the surface stability of CrO(2), a prototype half-metal, and find an anisotropy of 3.8 eV. An earlier model for the relation

  9. Resistive sensor and electromagnetic actuator for feedback stabilization of liquid metal walls in fusion reactors

    CERN Document Server

    Mirhoseini, S H M

    2016-01-01

    Liquid metal walls in fusion reactors will be subject to instabilities, turbulence, induced currents, error fields and temperature gradients that will make them locally bulge, thus entering in contact with the plasma, or deplete, hence exposing the underlying solid substrate. To prevent this, research has begun to actively stabilize static or flowing liquid metal layers by locally applying forces in feedback with thickness measurements. Here we present resistive sensors of liquid metal thickness and demonstrate jxB actuators, to locally control it.

  10. Stabilization of Heavy Metal Particles in AL2O3-W Suspensions

    Directory of Open Access Journals (Sweden)

    Kędzierska – Sar A.

    2016-09-01

    Full Text Available Ceramic – metal composites are widely used materials in a whole world. There were invented many fabrication methods for those kind of materials, but still exists some problems which need to be fixed. Stability of high density metal particles (e.g. W, Mo, Nb in ceramic-metal composite suspensions is one of crucial issues to be solved in order to obtain homogenous composite material with desired properties such as high fracture toughness, mechanical strength, hardness, wear resistance.

  11. Trends in Metal Oxide Stability for Nanorods, Nanotubes, and Surfaces

    DEFF Research Database (Denmark)

    Mowbray, Duncan; Martinez, Jose Ignacio; Vallejo, Federico Calle;

    2011-01-01

    The formation energies of nanostructures play an important role in determining their properties, including their catalytic activity. For the case of 15 different rutile and 8 different perovskite metal oxides, we used density functional theory (DFT) to calculate the formation energies of (2......,2) nanorods, (3,3) nanotubes, and the (110) and (100) surfaces. These formation energies can be described semiquantitatively (mean absolute error ≈ 0.12 eV) by the fraction of metal−oxygen bonds broken and the metal d-band and p-band centers in the bulk metal oxide....

  12. Strategies Based on Nitride Materials Chemistry to Stabilize Li Metal Anode.

    Science.gov (United States)

    Zhu, Yizhou; He, Xingfeng; Mo, Yifei

    2017-08-01

    Lithium metal battery is a promising candidate for high-energy-density energy storage. Unfortunately, the strongly reducing nature of lithium metal has been an outstanding challenge causing poor stability and low coulombic efficiency in lithium batteries. For decades, there are significant research efforts to stabilize lithium metal anode. However, such efforts are greatly impeded by the lack of knowledge about lithium-stable materials chemistry. So far, only a few materials are known to be stable against Li metal. To resolve this outstanding challenge, lithium-stable materials have been uncovered out of chemistry across the periodic table using first-principles calculations based on large materials database. It is found that most oxides, sulfides, and halides, commonly studied as protection materials, are reduced by lithium metal due to the reduction of metal cations. It is discovered that nitride anion chemistry exhibits unique stability against Li metal, which is either thermodynamically intrinsic or a result of stable passivation. The results here establish essential guidelines for selecting, designing, and discovering materials for lithium metal protection, and propose multiple novel strategies of using nitride materials and high nitrogen doping to form stable solid-electrolyte-interphase for lithium metal anode, paving the way for high-energy rechargeable lithium batteries.

  13. Changes of toxic metals during biological stabilization and their potential ecological risk assessment.

    Science.gov (United States)

    Wang, Hou-cheng; Zeng, Zheng-zhong; Zhang, He-fei; Nan, Zhong-ren

    2015-01-01

    With various disadvantages of pollution control technologies for toxic metal-contaminated soil, we mixed contaminated soil with sludge for in situ composting to stabilize toxic metals, so plants are enriched to take up the toxic metals. When simulating the above, we added toxic metal solution into sewage sludge, and then composed it with steel slag to determine inhibition of the availability of toxic metals. When toxic metals were added into sludge, the potential ecological index and geoaccumulation index of Cd became high while Zn was low. Steel slag had an inhibited availability of Cd, and when the adjunction of steel slag was 7%, the availability of Cd was lowest. Steel slag promoted the availability of Zn, and when the adjunction of steel slag was 27%, the availability of Zn was highest. Results showed that during composting, with increasing steel slag, Cd stabilizing time was reached sooner but Zn stabilizing time was slower, and the availability of all metals became lower. In the end, composting inhibited the potential ecological index of Cd, but it promoted the potential ecological index of Zn. Steel slag promoted the stability of Cd and Zn as Fe/Mn oxide-bound and residual species. Therefore, composting sludge and steel slag could be used as an effective inhibitor of Zn and Cd pollution.

  14. Thermodynamic properties and phase stability of nanocrystalline metals

    Institute of Scientific and Technical Information of China (English)

    SONG Xiaoyan; LI Lingmei; ZHANG Jiuxing

    2006-01-01

    The fundamental thermodynamic functions of enthalpy, entropy, and Gibbs free energy, as functions of the excess free volume at interfaces, temperature, and grain size, have been derived for single-phase metal nanocrystals. The model was applied to predict the thermal features of nano-grain boundaries and the characteristics of phase transformation in nanocrystalline metals, such as the transformation temperature and the critical grain size for phase transformation at a given temperature. The model predictions have been verified by experimental studies on the β-Co (→) α-Co phase transformation in nanocrystalline Co prepared by ball milling.

  15. High-internal-phase emulsions stabilized by metal-organic frameworks and derivation of ultralight metal-organic aerogels

    Science.gov (United States)

    Zhang, Bingxing; Zhang, Jianling; Liu, Chengcheng; Peng, Li; Sang, Xinxin; Han, Buxing; Ma, Xue; Luo, Tian; Tan, Xiuniang; Yang, Guanying

    2016-01-01

    To design high-internal-phase emulsion (HIPE) systems is of great interest from the viewpoints of both fundamental researches and practical applications. Here we demonstrate for the first time the utilization of metal-organic framework (MOF) for HIPE formation. By stirring the mixture of water, oil and MOF at room temperature, the HIPE stabilized by the assembly of MOF nanocrystals at oil-water interface could be formed. The MOF-stabilized HIPE provides a novel route to produce highly porous metal-organic aerogel (MOA) monolith. After removing the liquids from the MOF-stabilized HIPE, the ultralight MOA with density as low as 0.01 g·cm−3 was obtained. The HIPE approach for MOA formation has unique advantages and is versatile in producing different kinds of ultralight MOAs with tunable porosities and structures. PMID:26892258

  16. Metal hydride switchable mirrors: Factors influencing dynamic range and stability

    Energy Technology Data Exchange (ETDEWEB)

    Slack, Jonathan L.; Locke, James C.W.; Song, Seung-Wan; Ona, Jason; Richardson, Thomas J. [Lawrence Berkeley National Laboratory, Building Technologies Department, Environmental Energy Technologies Division, Berkeley, CA 94720 (United States)

    2006-03-06

    Palladium-coated magnesium-manganese-nickel films behave as gasochromic switchable mirrors, becoming transparent on exposure to dilute hydrogen, and reverting to a mirror state on exposure to air. The cycling stability of the optical switching depends upon preservation of the integrity of the Pd catalyst overlayer. Alloying between Mg and Pd causes interdiffusion of the two elements, and leads to degradation in switching speed and eventual deactivation. Incorporation of a thin niobium oxide barrier layer between the active magnesium alloy film and the Pd layer substantially improves the cycling stability of the mirror. (author)

  17. Effect of transition metal ions on the conductivity and stability of stabilized zirconia

    DEFF Research Database (Denmark)

    Lybye, D.; Mogensen, Mogens Bjerg

    2007-01-01

    the effect of co-doping with smaller transition metal ions such as Ti-, Fe- and Mn-ions. Many of the ionic radii of the transition metal ions are too small compared to the host lattice ionic radius of zirconium. Here we explore the effect of a) the small ionic radii compared to the large ionic radii...

  18. Metal-oxide-metal point contact junction detectors. [detection mechanism and mechanical stability

    Science.gov (United States)

    Baird, J.; Havemann, R. H.; Fults, R. D.

    1973-01-01

    The detection mechanism(s) and design of a mechanically stable metal-oxide-metal point contact junction detector are considered. A prototype for a mechanically stable device has been constructed and tested. A technique has been developed which accurately predicts microwave video detector and heterodyne mixer SIM (semiconductor-insulator-metal) diode performance from low dc frequency volt-ampere curves. The difference in contact potential between the two metals and geometrically induced rectification constitute the detection mechanisms.

  19. PREPARATION OF POLYMER MICROSPHERES WITH PYRIDYL GROUP AND THEIR STABILIZED GOLD METALLIC COLLOIDS

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Narrow disperse poly(ethyleneglycol dimethacrylate-co-4-vinylpyridine) (poly(EGDMA-co-4-VPy)) microspheres were prepared by distillation-precipitation copolymerization of ethyleneglycol dimethacrylate (EGDMA) and 4-vinylpyridine (4-VPy) with 2,2'-azobisisobutyronitrile (AIBN) as initiator in neat acetonitrile. The polymer microspheres containing pyridyl group were then utilized as stabilizer for gold metallic colloids with the diameter around 7 nm, which were prepared by the in situ reduction of gold chloride trihydrate with sodium borohydride through the coordination of the pyridyl group on the gel layer and surface of the microsphere with the gold metallic nano-particles. The catalytic properties of the pyridyl-functionalized microsphere-stabilized gold metallic colloids and the behavior of the stabilized-catalyst for the recycling were investigated with reduction of 4-nitrophenol to 4-aminophenol as a model reaction.

  20. Characterization and wear performance of boride phases over tool steel substrates

    Directory of Open Access Journals (Sweden)

    Edgar E Vera Cárdenas

    2016-02-01

    Full Text Available This research work was conducted to characterize boride phases, obtained from the powder-pack process, on AISI H13 and D2 steel substrates, and investigate their tribological behavior. The boriding was developed at a temperature of 1273 K with an exposure time of 8 h. X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy were conducted on the borided material to characterize the presence of the FeB, Fe2B, and CrB phases and the distribution of heavy elements on the surface of the substrates. The adherence of the boride layers was evaluated, in a qualitative form, through the Daimler-Benz Rockwell-C indentation technique. Sliding wear tests were then performed using a reciprocating wear test machine. All tests were conducted in dry conditions at room temperature. A frequency of 10 Hz and 15-mm sliding distance were used. The applied Hertzian pressure was 2.01 GPa. Scanning electron microscopy was used to observe and analyze the wear mechanisms. Additionally, the variation of the friction coefficient versus the number of cycles was obtained. Experimental results showed that the characteristic wear mechanism for the borided surface was plastic deformation and mild abrasive wear; for unborided substrates, cracking and spalling were observed.

  1. Metal lanolin fatty acid as novel thermal stabilizers for rigid poly(vinyl chloride)

    Institute of Scientific and Technical Information of China (English)

    GUO Yong; ZHENG Yuying; QIU Shangchang; ZENG Anran; LI Baoming

    2011-01-01

    The synergistic stabilization effect of different metal lanolin fatty acids as natural-based thermal stabilizers for poly(vinyl chloride)(PVC) including calcium lanolin fatty acid (Calan2), zinc lanolin fatty acid (Znlan2) and lanthanum lanolin fatty acid (Lalan3) were studied through Congo red testing, color measurements, FTIR analyses and thermal behavior in this paper. The results showed that Lalan3/Calan2/Znlan2 stabilizers exhibited more excellent thermal stabilization efficiency to PVC than Calan2/Znlan2 thermal stabilizers, and the optimal mass ratio of Lalan3/Calan2/Znlan2 was 8:9:3. At last, the effect of degradation mechanism on PVC and synergistic stabilization was also investigated by FTIR analyses and thermal behavior.

  2. THE INTERFACE OF TERNARY-BORIDE-BASED HARD CLADDING MATERIAL

    Institute of Scientific and Technical Information of China (English)

    Y.G. Wang; Z.Q. Li; D. Zhang

    2004-01-01

    The interfacial microstructure of ternary-boride-based hard cladding material (YF2) has been studied using scanning electron microanalyser (SEM), X-ray diffraction (XRD) and energy disperse spectroscopy (EDS). Results show that there are chemical reactions and elements diffusion in the interfacial zone, which make the interface bonding well and bonding strength ideal at the interface. The results gotten by studying of crack produced by Vickers indentation technique in the interfacial zone show that it is difficult to produce crack in the interface, the crack length in the cladding layer is longer than that to the interface, the crack which propagate to the interface stops at the interface rather than propagates along the interface. This suggests negligible residual stresses have developed because of thermal expansion mismatch. The bonding strength of the interface is 550MPa, which has been gotten by cutting test. The result gotten by analyzing the fracture surface shows that the fracture occurs at the side of cladding layer, which confirms that the bonding strength at the interface is higher than that in the cladding layer.

  3. Lithium boride sheet and nanotubes: structure and hydrogen storage.

    Science.gov (United States)

    Zhang, Hong; Wang, Jing; Tian, Zhi-Xue; Liu, Ying

    2015-06-07

    A new class of Li-B sheets, along with the related nanotubes, with a Li2B5 primitive cell has been designed using first-principles density functional theory. The dynamical stability of the proposed structures was confirmed by calculation of the soft phonon modes, and the calculated electronic structures show that all are metallic. The application of both the sheets and nanotubes for hydrogen storage has been investigated and it has been found that both of them can adsorb two H2 molecules around each Li atom, with an average binding energy of 0.152-0.194 eV per H2, leading to a gravimetric density of 10.6 wt%.

  4. A kinetic model for estimating the boron activation energies in the FeB and Fe{sub 2}B layers during the gas-boriding of Armco iron: Effect of boride incubation times

    Energy Technology Data Exchange (ETDEWEB)

    Keddam, M. [Laboratoire de Technologie des Matériaux, Département de Sciences des Matériaux, Faculté de Génie Mécanique et Génie des Procédés, USTHB, B.P N°32, 16111, El-Alia, Bab-Ezzouar, Algiers (Algeria); Kulka, M., E-mail: michal.kulka@put.poznan.pl [Poznan University of Technology, Institute of Materials Science and Engineering, Pl. M.Sklodowskiej-Curie 5, 60-965 Poznan (Poland); Makuch, N.; Pertek, A. [Poznan University of Technology, Institute of Materials Science and Engineering, Pl. M.Sklodowskiej-Curie 5, 60-965 Poznan (Poland); Małdziński, L. [Poznan University of Technology, Institute of Machines and Motor Vehicles, Piotrowo Street 3, 60-965 Poznan (Poland)

    2014-04-01

    Graphical abstract: - Highlights: • The mass balance equations were formulated for the FeB and Fe{sub 2}B layers grown on Fe Armco by gas-boriding. • The effect of boride incubation times was incorporated in the present model. • The boride incubation time was shorter for FeB phase. • The calculated boron activation energies in FeB and Fe{sub 2}B were respectively close to 78.03 and 120.65 kJ mol{sup −1}. • The lower activation energy in FeB phase was characteristic of gas-boriding. - Abstract: The present work deals with a simulation of the growth kinetics of boride layers grown on Armco iron substrate. The formed boride layers (FeB + Fe{sub 2}B) are obtained by the gas-boriding in the temperature range of 1073–1273 K during a time duration ranging from 80 to 240 min. The used approach solves the mass balance equations at the two growing fronts: (FeB/Fe{sub 2}B) and (Fe{sub 2}B/Fe) under certain assumptions. To consider the effect of the incubation times for the borides formation, the temperature-dependent function Φ(T) was incorporated in the model. The following input data: (the boriding temperature, the treatment time, the upper and lower values of boron concentrations in FeB and Fe{sub 2}B and the experimental parabolic growth constants) are needed to determine the boron activation energies in the FeB and Fe{sub 2}B layers. The obtained values of boron activation energies were then compared with the values available in the literature. Finally, a good agreement was obtained between the simulated values of boride layers thicknesses and the experimental ones in the temperature range of 1073–1273 K.

  5. ALLOYING-DRIVEN PHASE STABILITY IN GROUP-VB TRANSITION METALS UNDER COMPRESSION

    Energy Technology Data Exchange (ETDEWEB)

    Landa, A; Soderlind, P

    2011-04-11

    The change in phase stability of Group-VB (V, Nb, and Ta) transition metals due to pressure and alloying is explored by means of first-principles electronic-structure calculations. It is shown that under compression stabilization or destabilization of the ground-state body-centered cubic (bcc) phase of the metal is mainly dictated by the band-structure energy that correlates well with the position of the Kohn anomaly in the transverse acoustic phonon mode. The predicted position of the Kohn anomaly in V, Nb, and Ta is found to be in a good agreement with data from the inelastic x-ray or neutron scattering measurements. In the case of alloying the change in phase stability is defined by the interplay between the band-structure and Madelung energies. We show that band-structure effects determine phase stability when a particular Group-VB metal is alloyed with its nearest neighbors within the same d-transition series: the neighbor with less and more d electrons destabilize and stabilize the bcc phase, respectively. When V is alloyed with neighbors of a higher (4d- or 5d-) transition series, both electrostatic Madelung and band-structure energies stabilize the body-centered-cubic phase. The opposite effect (destabilization) happens when Nb or Ta is alloyed with neighbors of the 3d-transition series.

  6. STABILITY EVALUATION OF METAL CASK ATTACHED TO A TRANSFER PALLET DURING LONG-PERIOD SEISMIC MOTIONS

    Science.gov (United States)

    Kawaguchi, Shohei; Shirai, Koji; Kanazawa, Kenji

    Rocking behavior of unfixed body is affected by center of mass, material coefficient of restitution and so on. 2/5 scale metal cask model considering these parameter was used for seismic test to evaluate stability of grounding metal cask attached to a transfer pallet under the influence of long-period earthquake motion. The newest knowledge from seismic test indicates seismic motion with high velocity over 100 kine not always cause the raise of response velocity of metal cask because of energy consumption by cask sliding and impact deformation of concrete. And new estimation method (called "Window energy spectrum method") of earthquake response spectrum gives suitable evaluation of response energy.

  7. CATALYTIC PROPERTIES OF POLYMER-STABILIZED COLLOIDAL METAL NANOPARTICLES SYNTHESIZED BY MICROWAVE IRRADIATION

    Institute of Scientific and Technical Information of China (English)

    Wei-xia Tu; Bao-lin He; Han-fan Liu; Xue-lan Luo; Xun Liang

    2005-01-01

    Catalytic properties of polymer-stabilized colloidal metal nanoparticles synthesized by microwave irradiation were studied in the selective hydrogenation of unsaturated aldehydes, o-chloronitrobenzene and the hydrogenation of alkenes. The results show that nanosized metal particles synthesized by microwave irradiation have similar catalytic performance in selective hydrogenation of unsaturated aldehydes, better selectivity to o-chloroaniline in hydrogenation of o-chloronitrobenzene and higher catalytic activities in hydrogenation of alkenes, compared with metal clusters prepared by conventional heating. The same apparent activation energy (Ea = 29 kJ mol-1) for hydrogenation of 1-heptene catalyzed with platinum nanoparticles prepared by both heating modes implied that the reaction followed the same mechanism.

  8. Modeling of amphoteric heavy metals solubility in stabilized/solidified steel foundry dust

    OpenAIRE

    Fernández Olmo, Ignacio; Lasa Díaz, María Cristina; Lavín Castañeda, María Ángeles; Irabien Gulías, José Ángel

    2009-01-01

    The influence of pH on the leaching of metals from waste materials can be described by geochemical and empirical models. These equations may be integrated into dynamic leaching models in order to describe the longterm behavior of waste-derived forms or they can be used to predict the concentration of metals in equilibrium leaching tests at a given pH. The aim of this work is to describe the equilibrium concentration of the main metals (Zn, Pb, and Cr) contained in untreated and stabilized/sol...

  9. Nano-Disperse Borides and Carbides: Plasma Technology Production, Specific Properties, Economic Evaluation

    Science.gov (United States)

    Galevskii, G. V.; Rudneva, V. V.; Galevskii, S. G.; Tomas, K. I.; Zubkov, M. S.

    2016-04-01

    The experience of production and study on properties of nano-disperse chromium and titanium borides and carbides, and silicon carbide has been generalized. The structure and special service aspects of utilized plasma-metallurgical complex equipped with a three-jet direct-flow reactor with a capacity of 150 kW have been outlined. Processing, heat engineering and service life characteristics of the reactor are specified. The synthesis parameters of borides and carbides, as well as their basic characteristics in nano-disperse condition and their production flow diagram are outlined. Engineering and economic performance of synthesizing borides in laboratory and industrial conditions is assessed, and the respective segment of the international market as well. The work is performed at State Siberian Industrial University as a project part of the State Order of Ministry of Science and Education of the Russian Federation No. 11.1531/2014/K.

  10. Testing Single and Combinations of Amendments for Stabilization of Metals in Contrasting Extremely Contaminated Soils

    Directory of Open Access Journals (Sweden)

    Siebielec G.

    2013-04-01

    Full Text Available Metals can be stabilized by soil amendments that increase metals adsorption or alter their chemical forms. Such treatments may limit the risk related to the contamination through reduction of metal transfer to the food chain (reduction of metal uptake by plants and its availability to soil organisms and metals migration within the environment. There is a need for experiments comparing various soil amendments available at reasonable amounts under similar environmental conditions. The other question is whether all components of soil environment or soil functions are similarly protected after remediation treatment. We conducted a series of pot studies to test some traditional and novel amendments and their combinations. The treatments were tested for several highly Zn/Cd/Pb contaminated soils. Among traditional amendments composts were the most effective – they ensured plant growth, increased soil microbial activity, reduced Cd in earthworms, reduced Pb bioaccessibility and increased share of unavailable forms of Cd and Pb.

  11. Stabilization of Rocky Flats combustible residues contaminated with plutonium metal and organic solvents

    Energy Technology Data Exchange (ETDEWEB)

    Bowen, S.M.; Cisneros, M.R.; Jacobson, L.L.; Schroeder, N.C.; Ames, R.L.

    1998-09-30

    This report describes tests on a proposed flowsheet designed to stabilize combustible residues that were generated at the Rocky Flats Environmental Technology Site (RFETS) during the machining of plutonium metal. Combustible residues are essentially laboratory trash contaminated with halogenated organic solvents and plutonium metal. The proposed flowsheet, designed by RFETS, follows a glovebox procedure that includes (1) the sorting and shredding of materials, (2) a low temperature thermal desorption of solvents from the combustible materials, (3) an oxidation of plutonium metal with steam, and (4) packaging of the stabilized residues. The role of Los Alamos National Laboratory (LANL) in this study was to determine parameters for the low temperature thermal desorption and steam oxidation steps. Thermal desorption of carbon tetrachloride (CCl{sub 4}) was examined using a heated air stream on a Rocky Flats combustible residue surrogate contaminated with CCl{sub 4}. Three types of plutonium metal were oxidized with steam in a LANL glovebox to determine the effectiveness of this procedure for residue stabilization. The results from these LANL experiments are used to recommend parameters for the proposed RFETS stabilization flowsheet.

  12. Atomically Thin Ordered Alloys of Transition Metal Dichalcogenides: Stability and Band Structures

    DEFF Research Database (Denmark)

    Pandey, Mohnish; Jacobsen, Karsten Wedel; Thygesen, Kristian Sommer

    2016-01-01

    We explore the possibility of modulating the electronic band edges of the transition metal dichalcogenides (TMD) via alloying of different semiconductors within the same group (intra-group alloying). The stability of the ordered alloys is assessed from the calculated mixing enthalpy which is found...

  13. Hard Surface Layers by Pack Boriding and Gaseous Thermo-Reactive Deposition and Diffusion Treatments

    DEFF Research Database (Denmark)

    Christiansen, Thomas Lundin; Bottoli, Federico; Dahl, Kristian Vinter

    2017-01-01

    subjected to TRD (chromizing and titanizing) and boriding treatments. For the steels with low carbon content, chromizing results in surface alloying with chromium, i.e., formation of a (soft) “stainless” surface zone. Steels containing higher levels of carbon form chromium carbide (viz. Cr23C6, Cr7C3......) layers with hardnesses up to 1800 HV. Titanizing of ARNE tool steel results in a surface layer consisting of TiC with a hardness of approximately 4000 HV. Duplex treatments, where boriding is combined with subsequent (TRD) titanizing, result in formation of hard TiB2 on top of a thick layer of Fe...

  14. FORMATION OF HIGHLY RESISTANT CARBIDE AND BORIDE COATINGS BY A TWO-STAGE DEPOSITION METHOD

    Directory of Open Access Journals (Sweden)

    W. I. Sawich

    2011-01-01

    Full Text Available A study was made of the aspects of forming highly resistant coatings in the surface zone of tool steels and solid carbide inserts by a two-stage method. at the first stage of the method, pure Ta or Nb coatings were electrodeposited on samples of tool steel and solid carbide insert in a molten salt bath containing Ta and Nb fluorides. at the second stage, the electrodeposited coating of Ta (Nb was subjected to carburizing or boriding to form carbide (TaC, NbC or boride (TaB, NbB cladding layers.

  15. Investigation of long term stability in metal hydrides

    Science.gov (United States)

    Marmaro, Roger W.; Lynch, Franklin E.; Chandra, Dhanesh; Lambert, Steve; Sharma, Archana

    1991-01-01

    It is apparent from the literature and the results of this study that cyclic degradation of AB(5) type metal hydrides varies widely according to the details of how the specimens are cycled. The Rapid Cycle Apparatus (RCA) used produced less degradation in 5000 to 10000 cycles than earlier work with a Slow Cycle Apparatus (SCA) produced in 1500 cycles. Evidence is presented that the 453 K (356 F) Thermal Aging (TA) time spent in the saturated condition causes hydride degradation. But increasing the cooling (saturation) period in the RCA did not greatly increase the rate of degradation. It appears that TA type degradation is secondary at low temperatures to another degradation mechanism. If rapid cycles are less damaging than slow cycles when the saturation time is equal, the rate of hydriding/dehydriding may be an important factor. The peak temperatures in the RCA were about 30 C lower than the SCA. The difference in peak cycle temperatures (125 C in the SCA, 95 C in RCA) cannot explain the differences in degradation. TA type degradation is similar to cyclic degradation in that nickel peaks and line broadening are observed in X ray diffraction patterns after either form of degradation.

  16. Stabilization/solidification of heavy metals in sludge ceramsite and leachability affected by oxide substances.

    Science.gov (United States)

    Xu, Guoren; Zou, Jinlong; Li, Guibai

    2009-08-01

    To investigate stabilization of heavy metals in ceramsite made from wastewater treatment sludge (WWTS) and drinking water treatment sludge (DWTS), leaching tests were conducted to find out the effect of SiO2:Al2O3, acidic oxides (SiO2 and Al2O3), Fe2O3: CaO:MgO, and basic oxides (Fe2O3, CaO, and MgO) on the binding ability of heavy metals. Results show that as ratios of SiO2: Al2O3 decrease, leaching contents of Cu and Pb increase, while leaching contents of Cd and Cr first decrease and then increase; under the variation of Fe2O3:CaO:MgO (Fe2O3 contents decrease), leaching contents of Cd, Cu, and Pb increase, while leaching contents of Cr decrease. Acidic and basic oxide leaching results show that higher contents of Al2O3, Fe2O3, and MgO are advantageous to improve the stability of heavy metals, while the binding capacity for Cd, Cu, and Pb is significantly reduced at higher contents of SiO2 and CaO. The solidifying efficiencies of heavy metals are improved by crystallization, and the main compounds in ceramsite are crocoite, chrome oxide, cadmium silicate, and copper oxide. These results can be considered as a basic understanding for new technologies of stabilization of heavy metals in heavily polluted WWTS.

  17. Effects of electron doping on the stability of the metal hydride NaH

    Science.gov (United States)

    Olea-Amezcua, M. A.; Rivas-Silva, J. F.; de la Peña-Seaman, O.; Heid, R.; Bohnen, K. P.

    2017-04-01

    Alkali and alkali-earth metal hydrides have high volumetric and gravimetric hydrogen densities, but due to their high thermodynamic stability, they possess high dehydrogenation temperatures which may be reduced by transforming these compounds into less stable states/configurations. We present a systematic computational study of the electron doping effects on the stability of the alkali metal hydride NaH substituted with Mg, using the self-consistent version of the virtual crystal approximation to model the alloy Na1-x Mg x H. The phonon dispersions were studied paying special attention to the crystal stability and the correlations with the electronic structure taking into account the zero point energy contribution. We found that substitution of Na by Mg in the hydride invokes a reduction of the frequencies, leading to dynamical instabilities for Mg content of 25%. The microscopic origin of these instabilities could be related to the formation of ellipsoidal Fermi surfaces centered at the L point due to the metallization of the hydride by the Mg substitution. Applying the quasiharmonic approximation, thermodynamic properties like heat capacities, vibrational entropies and vibrational free energies as a function of temperature at zero pressure are obtained. These properties determine an upper temperature for the thermodynamic stability of the hydride, which decreases from 600 K for NaH to 300 K at 20% Mg concentration. This significant reduction of the stability range indicates that dehydrogenation could be favoured by electron doping of NaH.

  18. Effects of electron doping on the stability of the metal hydride NaH.

    Science.gov (United States)

    Olea-Amezcua, M A; Rivas-Silva, J F; de la Peña-Seaman, O; Heid, R; Bohnen, K P

    2017-04-12

    Alkali and alkali-earth metal hydrides have high volumetric and gravimetric hydrogen densities, but due to their high thermodynamic stability, they possess high dehydrogenation temperatures which may be reduced by transforming these compounds into less stable states/configurations. We present a systematic computational study of the electron doping effects on the stability of the alkali metal hydride NaH substituted with Mg, using the self-consistent version of the virtual crystal approximation to model the alloy Na1-x Mg x H. The phonon dispersions were studied paying special attention to the crystal stability and the correlations with the electronic structure taking into account the zero point energy contribution. We found that substitution of Na by Mg in the hydride invokes a reduction of the frequencies, leading to dynamical instabilities for Mg content of 25%. The microscopic origin of these instabilities could be related to the formation of ellipsoidal Fermi surfaces centered at the L point due to the metallization of the hydride by the Mg substitution. Applying the quasiharmonic approximation, thermodynamic properties like heat capacities, vibrational entropies and vibrational free energies as a function of temperature at zero pressure are obtained. These properties determine an upper temperature for the thermodynamic stability of the hydride, which decreases from 600 K for NaH to 300 K at 20% Mg concentration. This significant reduction of the stability range indicates that dehydrogenation could be favoured by electron doping of NaH.

  19. Electronic metal-support interaction enhanced oxygen reduction activity and stability of boron carbide supported platinum

    Science.gov (United States)

    Jackson, Colleen; Smith, Graham T.; Inwood, David W.; Leach, Andrew S.; Whalley, Penny S.; Callisti, Mauro; Polcar, Tomas; Russell, Andrea E.; Levecque, Pieter; Kramer, Denis

    2017-06-01

    Catalysing the reduction of oxygen in acidic media is a standing challenge. Although activity of platinum, the most active metal, can be substantially improved by alloying, alloy stability remains a concern. Here we report that platinum nanoparticles supported on graphite-rich boron carbide show a 50-100% increase in activity in acidic media and improved cycle stability compared to commercial carbon supported platinum nanoparticles. Transmission electron microscopy and x-ray absorption fine structure analysis confirm similar platinum nanoparticle shapes, sizes, lattice parameters, and cluster packing on both supports, while x-ray photoelectron and absorption spectroscopy demonstrate a change in electronic structure. This shows that purely electronic metal-support interactions can significantly improve oxygen reduction activity without inducing shape, alloying or strain effects and without compromising stability. Optimizing the electronic interaction between the catalyst and support is, therefore, a promising approach for advanced electrocatalysts where optimizing the catalytic nanoparticles themselves is constrained by other concerns.

  20. Effects of thermal treatment on mineralogy and heavy metal behavior in iron oxide stabilized air pollution control residues

    DEFF Research Database (Denmark)

    Sørensen, Mette Abildgaard; Bender-Koch, C.; Starckpoole, M. M.

    2000-01-01

    Stabilization of air pollution control residues by coprecipitation with ferrous iron and subsequent thermal treatment (at 600 and 900 °C) has been examined as a means to reduce heavy metal leaching and to improve product stability. Changes in mineralogy and metal binding were analyzed using various...

  1. Stability and heavy metal distribution of soil aggregates affected by application of apatite, lime, and charcoal.

    Science.gov (United States)

    Cui, Hongbiao; Ma, Kaiqiang; Fan, Yuchao; Peng, Xinhua; Mao, Jingdong; Zhou, Dongmei; Zhang, Zhongbin; Zhou, Jing

    2016-06-01

    Only a few studies have been reported on the stability and heavy metal distribution of soil aggregates after soil treatments to reduce the availability of heavy metals. In this study, apatite (22.3 t ha(-1)), lime (4.45 t ha(-1)), and charcoal (66.8 t ha(-1)) were applied to a heavy metal-contaminated soil for 4 years. The stability and heavy metal distribution of soil aggregates were investigated by dry and wet sieving. No significant change in the dry mean weight diameter was observed in any treatments. Compared with the control, three-amendment treatments significantly increased the wet mean weight diameter, but only charcoal treatment significantly increased the wet aggregate stability. The soil treatments increased the content of soil organic carbon, and the fraction 0.25-2 mm contained the highest content of soil organic carbon. Amendments' application slightly increased soil total Cu and Cd, but decreased the concentrations of CaCl2 -extractable Cu and Cd except for the fraction 2 and 0.25-2 mm contained the highest concentrations of CaCl2-extractable Cu and Cd, accounted for about 74.5-86.8 % of CaCl2-extractable Cu and Cd in soil. The results indicated that amendments' application increased the wet soil aggregate stability and decreased the available Cu and Cd. The distribution of available heavy metals in wet soil aggregates was not controlled by soil aggregate stability, but possibly by soil organic carbon.

  2. Mineral materials as feasible amendments to stabilize heavy metals in polluted urban soils.

    Science.gov (United States)

    Zhang, Mingkui; Pu, Jincheng

    2011-01-01

    Four minerals, agricultural limestone (AL), rock phosphate (RP), palygorskite (PG), and calcium magnesium phosphate (CMP), were evaluated by means of chemical fractions of heavy metals in soils and concentrations of heavy metals in leachates from columns to determine their ability to stabilize heavy metals in polluted urban soils. Two urban soils (calcareous soil and acidic soil) polluted with cadmium, copper, zinc and lead were selected and amended in the laboratory with the mineral materials) for 12 months. Results indicated that application of the mineral materials reduced exchangeable metals in the sequence of Pb, Cd > Cu > Zn. The reduction of exchangeable fraction of heavy metals in the soils amended with different mineral materials followed the sequence of CMP, PG > AL > RP. Reductions of heavy metals leached were based on comparison with cumulative totals of heavy metals eluted through 12 pore volumes from an untreated soil. The reductions of the metals eluted from the calcareous soil amended with the RP, AL, PG and CMP were 1.98%, 38.89%, 64.81% and 75.93% for Cd, 8.51%, 40.42%, 60.64% and 55.32% for Cu, 1.76%, 52.94%, 70.00% and 74.12% for Pb, and 28.42%, 52.74%, 64.38% and 49.66% for Zn. Those from the acidic soil amended with the CMP, PG, AL, and RP were 25.65%, 68.06%, 78.01% and 79.06% for Cd, 26.56%, 49.64%, 43.40% and 34.68% for Cu, 44.44%, 33.32%, 61.11% and 69.44% for Pb, and 18.46%, 43.77%, 41.98% and 40.68% for Zn. The CMP and PG treatments were superior to the AL and RP for stabilizing heavy metals in the polluted urban soils.

  3. Polyacrylamide-metal nanocomposites: one-pot synthesis, antibacterial properties, and thermal stability

    Energy Technology Data Exchange (ETDEWEB)

    Li, Cuiyan [Uppsala University, Department of Chemistry - Angstroem Laboratory (Sweden); Cai, Yanling [Uppsala University, Division of Nanotechnology and Functional Materials, Angstroem Laboratory (Sweden); Zhu, Yihua [East China University of Science and Technology, Key Laboratory for Ultrafine Materials of Ministry of Education (China); Ma, Mingguo [Beijing Forestry University, Institute of Biomass Chemistry and Technology, College of Materials Science and Technology (China); Zheng, Wei [University of Wisconsin-Stout, Engineering and Technology Department (United States); Zhu, Jiefang, E-mail: jiefang.zhu@kemi.uu.se [Uppsala University, Department of Chemistry - Angstroem Laboratory (Sweden)

    2013-09-15

    The incorporation of inorganic nanoparticles into polymers is a hot research spot, since it endows the nanocomposites with new or improved properties by exploiting synergistic effects. Here we report a facile one-pot synthesis of polyacrylamide (PAM)-metal (M = Au, Ag, or Pd) nanocomposites in ethylene glycol (EG). The simultaneous polymerization of the acylamide (AM) monomer and formation of metal nanoparticles lead to a homogeneous distribution of metal nanoparticles in the PAM matrix. The sizes of Au, Ag, and Pd nanoparticles are 55.50 {+-} 10.6, 14.15 {+-} 2.57, and 7.74 {+-} 1.82 nm, respectively. The reaction system only includes EG, AM monomer, and corresponding metal salt. EG acts as both the solvent and the reducing reagent. Also, no initiator for AM polymerization and no surfactant for stabilization of metal nanoparticles are used. Furthermore, this simple synthetic route does not rely on any special or expensive equipment, thus can be exploited to the synthesis of similar polymer-inorganic nanocomposites. Compared to PAM, the PAM-metal nanocomposites showed enhanced thermal stability and antibacterial properties.

  4. Polyacrylamide-metal nanocomposites: one-pot synthesis, antibacterial properties, and thermal stability

    Science.gov (United States)

    Li, Cuiyan; Cai, Yanling; Zhu, Yihua; Ma, Mingguo; Zheng, Wei; Zhu, Jiefang

    2013-09-01

    The incorporation of inorganic nanoparticles into polymers is a hot research spot, since it endows the nanocomposites with new or improved properties by exploiting synergistic effects. Here we report a facile one-pot synthesis of polyacrylamide (PAM)-metal (M = Au, Ag, or Pd) nanocomposites in ethylene glycol (EG). The simultaneous polymerization of the acylamide (AM) monomer and formation of metal nanoparticles lead to a homogeneous distribution of metal nanoparticles in the PAM matrix. The sizes of Au, Ag, and Pd nanoparticles are 55.50 ± 10.6, 14.15 ± 2.57, and 7.74 ± 1.82 nm, respectively. The reaction system only includes EG, AM monomer, and corresponding metal salt. EG acts as both the solvent and the reducing reagent. Also, no initiator for AM polymerization and no surfactant for stabilization of metal nanoparticles are used. Furthermore, this simple synthetic route does not rely on any special or expensive equipment, thus can be exploited to the synthesis of similar polymer-inorganic nanocomposites. Compared to PAM, the PAM-metal nanocomposites showed enhanced thermal stability and antibacterial properties.

  5. Imaging metal-like monoclinic phase stabilized by surface coordination effect in vanadium dioxide nanobeam

    Science.gov (United States)

    Li, Zejun; Wu, Jiajing; Hu, Zhenpeng; Lin, Yue; Chen, Qi; Guo, Yuqiao; Liu, Yuhua; Zhao, Yingcheng; Peng, Jing; Chu, Wangsheng; Wu, Changzheng; Xie, Yi

    2017-06-01

    In correlated systems, intermediate states usually appear transiently across phase transitions even at the femtosecond scale. It therefore remains an open question how to determine these intermediate states--a critical issue for understanding the origin of their correlated behaviour. Here we report a surface coordination route to successfully stabilize and directly image an intermediate state in the metal-insulator transition of vanadium dioxide. As a prototype metal-insulator transition material, we capture an unusual metal-like monoclinic phase at room temperature that has long been predicted. Coordinate bonding of L-ascorbic acid molecules with vanadium dioxide nanobeams induces charge-carrier density reorganization and stabilizes metallic monoclinic vanadium dioxide, unravelling orbital-selective Mott correlation for gap opening of the vanadium dioxide metal-insulator transition. Our study contributes to completing phase-evolution pathways in the metal-insulator transition process, and we anticipate that coordination chemistry may be a powerful tool for engineering properties of low-dimensional correlated solids.

  6. Hydrothermal synthesis of platinum-group-metal nanoparticles by using HEPES as a reductant and stabilizer.

    Science.gov (United States)

    So, Man-Ho; Ho, Chi-Ming; Chen, Rong; Che, Chi-Ming

    2010-06-01

    Platinum-group-metal (Ru, Os, Rh, Ir, Pd and Pt) nanoparticles are synthesized in an aqueous buffer solution of 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) (200 mM, pH 7.4) under hydrothermal conditions (180 degrees C). Monodispersed (monodispersity: 11-15%) metal nanoparticles were obtained with an average particle size of less than 5 nm (Ru: 1.8+/-0.2, Os: 1.6+/-0.2, Rh: 4.5+/-0.5, Ir: 2.0+/-0.3, Pd: 3.8+/-0.4, Pt: 1.9+/-0.2 nm). The size, monodispersity, and stability of the as-obtained metal nanoparticles were affected by the HEPES concentration, pH of the HEPES buffer solution, and reaction temperature. HEPES with two tertiary amines (piperazine groups) and terminal hydroxyl groups can act as a reductant and stabilizer. The HEPES molecules can bind to the surface of metal nanoparticles to prevent metal nanoparticles from aggregation. These platinum-group-metal nanoparticles could be deposited onto the surface of graphite, which catalyzed the aerobic oxidation of alcohols to aldehydes.

  7. An Evaluation of a Borided Layer Formed on Ti-6Al-4V Alloy by Means of SMAT and Low-Temperature Boriding

    OpenAIRE

    Quantong Yao; Jian Sun; Yuzhu Fu; Weiping Tong; Hui Zhang

    2016-01-01

    In this paper, a nanocrystalline surface layer without impurities was fabricated on Ti-6Al-4V alloy by means of surface mechanical attrition treatment (SMAT). The grain size in the nanocrystalline layer is about 10 nm and grain morphology displays a random crystallographic orientation distribution. Subsequently, the low-temperature boriding behaviors (at 600 °C) of the SMAT sample, including the phase composition, microstructure, micro-hardness, and brittleness, were investigated in compariso...

  8. A new strategy to stabilize oxytocin in aqueous solutions : I. The effects of divalent metal ions and citrate buffer

    NARCIS (Netherlands)

    Avanti, Christina; Amorij, Jean-Pierre; Setyaningsih, Dewi; Hawe, Andrea; Jiskoot, Wim; Visser, Jan; Kedrov, Alexej; Driessen, Arnold J. M.; Hinrichs, Wouter L. J.; Frijlink, Henderik W.

    In the current study, the effect of metal ions in combination with buffers (citrate, acetate, pH 4.5) on the stability of aqueous solutions of oxytocin was investigated. Both monovalent metal ions (Na+and K+) and divalent metal ions (Ca2+, Mg2+, and Zn2+) were tested all as chloride salts. The

  9. A new strategy to stabilize oxytocin in aqueous solutions : I. The effects of divalent metal ions and citrate buffer

    NARCIS (Netherlands)

    Avanti, Christina; Amorij, Jean-Pierre; Setyaningsih, Dewi; Hawe, Andrea; Jiskoot, Wim; Visser, Jan; Kedrov, Alexej; Driessen, Arnold J. M.; Hinrichs, Wouter L. J.; Frijlink, Henderik W.

    2011-01-01

    In the current study, the effect of metal ions in combination with buffers (citrate, acetate, pH 4.5) on the stability of aqueous solutions of oxytocin was investigated. Both monovalent metal ions (Na+and K+) and divalent metal ions (Ca2+, Mg2+, and Zn2+) were tested all as chloride salts. The effec

  10. Leaching characteristics of heavy metals during cement stabilization of fly ash from municipal solid waste incinerators

    Institute of Scientific and Technical Information of China (English)

    Shunwen LIANG; Jianguo JIANG; Yan ZHANG; Xin XU

    2008-01-01

    The leaching characteristics of heavy metals in products of cement stabilization of fly ash from a muni-cipal solid waste incinerator were investigated in this paper. The stabilization of heavy metals such as Cd, Pb, Cu, and Zn in fly ash from such incinerators was exam-ined through the national standard method in China based on the following-factors: additive quantity of cement and Na2S, curing time, and pH of leaching liquor. The results showed that as more additives were used, less heavy metals were leached except for Pb, which is sensitive to pH of the leachate, and the worse effect was observed for Cd. The mass ratio of cement to fly ash=10% is the most appropriate parameter according to the national standard method. When the hydration of cement was basically finished, stabilization of heavy metals did not vary after curing for 1 d. The mixtures of cement and fly ash had excellent adaptability to environmental pH. The pH of leachate was maintained at 7 when pH of leaching liquor varied from 3 to 11.

  11. A new strategy to stabilize oxytocin in aqueous solutions: I. The effects of divalent metal ions and citrate buffer.

    Science.gov (United States)

    Avanti, Christina; Amorij, Jean-Pierre; Setyaningsih, Dewi; Hawe, Andrea; Jiskoot, Wim; Visser, Jan; Kedrov, Alexej; Driessen, Arnold J M; Hinrichs, Wouter L J; Frijlink, Henderik W

    2011-06-01

    In the current study, the effect of metal ions in combination with buffers (citrate, acetate, pH 4.5) on the stability of aqueous solutions of oxytocin was investigated. Both monovalent metal ions (Na(+) and K(+)) and divalent metal ions (Ca(2+), Mg(2+), and Zn(2+)) were tested all as chloride salts. The effect of combinations of buffers and metal ions on the stability of aqueous oxytocin solutions was determined by RP-HPLC and HP-SEC after 4 weeks of storage at either 4°C or 55°C. Addition of sodium or potassium ions to acetate- or citrate-buffered solutions did not increase stability, nor did the addition of divalent metal ions to acetate buffer. However, the stability of aqueous oxytocin in aqueous formulations was improved in the presence of 5 and 10 mM citrate buffer in combination with at least 2 mM CaCl(2), MgCl(2), or ZnCl(2) and depended on the divalent metal ion concentration. Isothermal titration calorimetric measurements were predictive for the stabilization effects observed during the stability study. Formulations in citrate buffer that had an improved stability displayed a strong interaction between oxytocin and Ca(2+), Mg(2+), or Zn(2+), while formulations in acetate buffer did not. In conclusion, our study shows that divalent metal ions in combination with citrate buffer strongly improved the stability of oxytocin in aqueous solutions.

  12. Stabilization of ultrathin (hydroxy)oxide films on transition metal substrates for electrochemical energy conversion

    Science.gov (United States)

    Zeng, Zhenhua; Chang, Kee-Chul; Kubal, Joseph; Markovic, Nenad M.; Greeley, Jeffrey

    2017-06-01

    Design of cost-effective electrocatalysts with enhanced stability and activity is of paramount importance for the next generation of energy conversion systems, including fuel cells and electrolysers. However, electrocatalytic materials generally improve one of these properties at the expense of the other. Here, using density functional theory calculations and electrochemical surface science measurements, we explore atomic-level features of ultrathin (hydroxy)oxide films on transition metal substrates and demonstrate that these films exhibit both excellent stability and activity for electrocatalytic applications. The films adopt structures with stabilities that significantly exceed bulk Pourbaix limits, including stoichiometries not found in bulk and properties that are tunable by controlling voltage, film composition, and substrate identity. Using nickel (hydroxy)oxide/Pt(111) as an example, we further show how the films enhance activity for hydrogen evolution through a bifunctional effect. The results suggest design principles for this class of electrocatalysts with simultaneously enhanced stability and activity for energy conversion.

  13. Electrosynthesis of tantalum borides in oxygen-free and oxygen-containing fluoride melts

    DEFF Research Database (Denmark)

    Polyakova, L.P.; Polyakov, E.G.; Makarova, O.V.;

    2001-01-01

    Results of electrosynthesis of tantalum borides in fluoride and oxyfluoride melts are compared. It is shown that the single-phase X-ray-amorphous micro-layered coatings form only in the latter case. Linear and square-wave voltammetry, complemented by X-ray diffraction analysis, IR spectroscopy...

  14. Nickel boride: An improved desulphurizing agent for sulphur-rich geomacromolecules in polar and asphaltene fractions

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Schouten, S.; Pavlovic, D.; Leeuw, J.W. de

    1993-01-01

    Nickel boride, a novel desulphurizing agent, was investigated for the desulphurization of sulphur-rich geomacromolecules in polar and asphaltene fractions. It was found to be as effective as the conventional desulphurizing agent, Raney nickel, for sulphur-rich geomacromolecules in polar fractions, b

  15. Electrosynthesis of tantalum borides in oxygen-free and oxygen-containing fluoride melts

    DEFF Research Database (Denmark)

    Polyakova, L.P.; Polyakov, E.G.; Makarova, O.V.

    2001-01-01

    Results of electrosynthesis of tantalum borides in fluoride and oxyfluoride melts are compared. It is shown that the single-phase X-ray-amorphous micro-layered coatings form only in the latter case. Linear and square-wave voltammetry, complemented by X-ray diffraction analysis, IR spectroscopy...

  16. Structure of surface layers produced by non-vacuum electron beam boriding

    Energy Technology Data Exchange (ETDEWEB)

    Bataev, I.A., E-mail: ivanbataev@ngs.ru [Novosibirsk State Technical University, K. Marks 20, 630092 Novosibirsk (Russian Federation); Bataev, A.A., E-mail: bataev@adm.nstu.ru [Novosibirsk State Technical University, K. Marks 20, 630092 Novosibirsk (Russian Federation); Golkovski, M.G., E-mail: M.G.Golkovski@inp.nsk.su [Budker Institute of Nuclear Physics SB RAS, Lavrentieva prospect 11, 630090 Novosibirsk (Russian Federation); Krivizhenko, D.S., E-mail: dinylkaa@yandex.ru [Novosibirsk State Technical University, K. Marks 20, 630092 Novosibirsk (Russian Federation); Losinskaya, A.A., E-mail: anna.losinskaya@mail.ru [Novosibirsk State Technical University, K. Marks 20, 630092 Novosibirsk (Russian Federation); Lenivtseva, O.G., E-mail: lenivtseva_olga@mail.ru [Novosibirsk State Technical University, K. Marks 20, 630092 Novosibirsk (Russian Federation)

    2013-11-01

    The structure and mechanical properties of boronized layers produced on low carbon steel substrates by non-vacuum electron-beam cladding were studied. This process provides high performance and high thickness of coatings and can be used to process large workpieces. In this study, we investigated coatings obtained by one, two or three passes of the electron beam. The thickness of the coatings varied from 0.6 to 1.0 mm, and the maximum hardness achieved was 21 GPa. Structural analysis revealed the oriented growth of eutectic colonies near the primary crystals of iron borides, which was explained by the commonality of the boride phases in the primary Fe{sub 2}B and eutectic Fe{sub 2}B. The eutectic colonies formed during electron-beam cladding consisted of a continuous framework of borides crystals and segregations of α-Fe in the form of oriented fibers. Coatings produced by electron-beam cladding had higher contact-fatigue endurance than those produced by pack boriding.

  17. Ultra-Fast Boriding in High-Temperature Materials Processing Industries

    Energy Technology Data Exchange (ETDEWEB)

    None

    2008-12-01

    This factsheet describes a research project whose main objective is to further develop, optimize, scale-up, and commercialize an ultra-fast boriding (also referred to as “boronizing”) process that can provide much higher energy efficiency, productivity, and near-zero emissions in many of the high-temperature materials processing industries.

  18. Stabilization of cationic and anionic metal species in contaminated soils using sludge-derived biochar.

    Science.gov (United States)

    Fang, Shen'en; Tsang, Daniel C W; Zhou, Fengsha; Zhang, Weihua; Qiu, Rongliang

    2016-04-01

    Currently, sludge pyrolysis has been considered as a promising technology to solve disposal problem of municipal sewage sludge, recover sludge heating value, sequester carbon and replenish nutrients in farmland soils. The resultant sludge-derived biochar (SDBC) is potentially an excellent stabilizing agent for metal species. This study applied the SDBC into four soils that had been contaminated in field with cationic Pb(II) and Cd(II)/Ni(II), and anionic Cr(VI) and As(III), respectively. The performance of metal stabilization under various operational and environmental conditions was evaluated with acid batch extraction and column leaching tests. Results indicated the SDBC could effectively stabilize these metals, which was favored by elevated temperature and longer aging. Periodic temperature decrease from 45 to 4 °C resulted in the release of immobilized Cr(VI) and As(III) but not Pb(II). However, a longer aging time offset such metal remobilization. This was possibly because more Pb was strongly bound and even formed stable precipitates, as shown by XRD and sequential extraction results. With increasing time, Cr(VI) was sorbed and partly reduced to Cr(III), while immobilized As(III) was co-oxidized to As(V) as indicated by XPS spectra. Column tests revealed that adding SDBC as a separate layer was unfavorable because the concentrated Cd(II) and Ni(II) in localized positions increased the peak levels of metal release under continuous acid leaching. In contrast, uniformly mixed SDBC could effectively delay the metal breakthrough and reduce their released amounts. Yet, a long-term monitoring may be required for evaluating the potential leaching risks and bioavailability/toxicity of these immobilized and transformed species in the SDBC-amended soils.

  19. Immobilization of metals in contaminated soils using natural polymer-based stabilizers.

    Science.gov (United States)

    Tao, Xue; Li, Aimin; Yang, Hu

    2017-03-01

    Three low-cost natural polymer materials, namely, lignin (Ln), carboxymethyl cellulose, and sodium alginate, were used for soil amendment to immobilize lead and cadmium in two contaminated soil samples collected from a mining area in Nanjing, China. The remediation effects of the aforementioned natural polymers were evaluated by toxicity characteristic leaching procedure (TCLP) and sequential extractions. The stabilizers could lower the bioavailability of Pb and Cd in the contaminated soils, and the amount of the exchangeable forms of the aforementioned two metals were reduced evidently. TCLP results showed that the leaching concentrations of Pb and Cd were decreased by 5.46%-71.1% and 4.25%-49.6%, respectively, in the treated soils. The contents of the organic forms of the two metals both increased with the increase in stabilizer dose on the basis of the redistribution of metal forms by sequential extractions. These findings were due to the fact that the abundant oxygen-containing groups on the polymeric amendments were effective in chelating and immobilizing Pb and Cd, which have been further confirmed from the metal adsorptions in aqueous solutions. Moreover, Ln achieved the greatest effect among the three polymers under study because of the former's distinct three-dimensional molecular structure, showing the preferential immobilization of Pb over Cd in soils also. Thus, the above-mentioned natural polymers hold great application potentials for reducing metal ion entry into the food chain at a field scale.

  20. Processing development of 4 tantalum carbide-hafnium carbide and related carbides and borides for extreme environments

    Science.gov (United States)

    Gaballa, Osama Gaballa Bahig

    temperature, and hot-pressing pressure. Also, WC additions to Ta4HfC5 were found to improve densification and increase microhardness. The ability to process these materials at relatively low temperature would save energy and reduce cost. Boron-based hard materials are used in numerous applications such as industrial machining, armor plating, and wear-resistant coatings. It was often thought that in addition to strong bonding, super-hard materials must also possess simple crystallographic unit cells with high symmetry and a minimum number of crystal defects (e.g., diamond and cubic boron nitride (cBN)). However, one ternary boride, AlMgB14, deviates from this paradigm; AlMgB 14 has a large, orthorhombic unit cell (oI64) with multiple icosahedral boron units. TiB2 has been shown to be an effective reinforcing phase in AlMgB 14, raising hardness, wear resistance, and corrosion resistance. Thus, it was thought that adding other, similar phases (i.e., ZrB2 and HfB2) to AlMgB14 could lead to useful improvements in properties vis-à-vis pure AlMgB14. Group IV metal diborides (XB2, where X = Ti, Zr, or Hf) are hard, ultra-high temperature ceramics. These compounds have a primitive hexagonal crystal structure (hP3) with planes of graphite-like boride rings above and below planes of metal atoms. Unlike graphite, there is strong bonding between the planes, resulting in high hardness. For this study two-phase composites of 60 vol. % metal diborides with 40 vol. % AlMgB14 were produced and characterized.

  1. [Recent advance in solidification/stabilization technology for the remediation of heavy metals-contaminated soil].

    Science.gov (United States)

    Hao, Han-zhou; Chen, Tong-bin; Jin, Meng-gui; Lei, Mei; Liu, Cheng-wu; Zu, Wen-pu; Huang, Li-mi

    2011-03-01

    Remediation of heavy metals-contaminated soil is still a difficulty and a hotspot of international research projects. At present, the technologies commonly adopted for the remediation of contaminated sites mainly include excavation, solidification/stabilization (S/S), soil washing, soil vapor extraction (SVE), thermal treatment, and bioremediation. Based on the S/S technical guidelines of Unite State Environmental Protection Agency (EPA) and United Kingdom Environment Agency (EA) and the domestic and foreign patents, this paper introduced the concepts of S/S and its development status at home and abroad, and discussed its future development directions. Solidification refers to a process that binds contaminated media with a reagent, changing the media's physical properties via increasing its compressive strength, decreasing its permeability, and encapsulating the contaminants to form a solid material. Stabilization refers to the process that involves a chemical reaction which reduces the leachability of a waste, chemically immobilizes the waste and reduces its solubility, making the waste become less harmful or less mobile. S/S technology includes cement solidification, lime pozzolanic solidification, plastic materials stabilization, vitrification, and regent-based stabilization. Stabilization (or immobilization) treatment processes convert contaminants to less mobile forms through chemical or thermal interactions. In stabilization technology, the aim of adding agents is to change the soil physical and chemical properties through pH control technology, redox potential technology, precipitation techniques, adsorption technology, and ion-exchange technology that change the existing forms of heavy metals in soil, and thus, reduce the heavy metals bioavailability and mobility. This review also discussed the S/S evaluation methods, highlighted the need to enhance S/S technology in the molecular bonding, soil polymers, and formulation of China's S/S technical guidelines.

  2. Metal ion-specific thermal stability of bacterial S-Layers

    Energy Technology Data Exchange (ETDEWEB)

    Drobot, Bjoern; Raff, Johannes [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Div. Biogeochemistry; Fahmy, Karim [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Div. Biophysics

    2016-07-01

    Many bacteria are covered by a surface layer (S-layer), i.e., a para-crystalline two-dimensional array of proteins which control cell shape, act as molecular sieves and have potential applications as radionuclide-binding material for bioremediation of polluted areas. Knowledge and control of the metal-dependent stability of the purified proteins is required for their technical application. Here, we have explored by differential scanning calorimetry the thermal stability of the S-layer protein slp-B53 from Lysinibacillus sphaericus, a Gram-positive bacterium isolated from a uranium mining waste pile [1].

  3. Final Report for "Stabilization of resistive wall modes using moving metal walls"

    Energy Technology Data Exchange (ETDEWEB)

    Forest, Cary B.

    2014-02-05

    The UW experiment used a linear pinch experiment to study the stabilization of MHD by moving metal walls. The methodology of the experiment had three steps. (1) Identify and understand the no-wall MHD instability limits and character, (2) identify and understand the thin-wall MHD instabilities (re- sistive wall mode), and then (3) add the spinning wall and understand its impact on stability properties. During the duration of the grant we accomplished all 3 of these goals, discovered new physics, and completed the experiment as proposed.

  4. Polydopamine tethered enzyme/metal-organic framework composites with high stability and reusability

    Science.gov (United States)

    Wu, Xiaoling; Yang, Cheng; Ge, Jun; Liu, Zheng

    2015-11-01

    An enzyme/metal-organic framework (MOF) composite with both highly stable and easily reusable features was prepared via tethering enzyme/MOF nanocrystals with polydopamine (PDA). The micrometer-sized PDA tethered enzyme/MOF composite can be easily repeatedly used without obvious activity loss, promising for efficient enzymatic catalysis at low cost with long-term operational stability under harsh conditions.An enzyme/metal-organic framework (MOF) composite with both highly stable and easily reusable features was prepared via tethering enzyme/MOF nanocrystals with polydopamine (PDA). The micrometer-sized PDA tethered enzyme/MOF composite can be easily repeatedly used without obvious activity loss, promising for efficient enzymatic catalysis at low cost with long-term operational stability under harsh conditions. Electronic supplementary information (ESI) available: Synthesis of enzyme-MOF nanocrystals, SEM, TEM, CLSM characterization and measurements of enzymatic performances. See DOI: 10.1039/c5nr05190h

  5. Color stability, water sorption and cytotoxicity of thermoplastic acrylic resin for non metal clasp denture

    OpenAIRE

    Jang, Dae-Eun; Lee, Ji-Young; Jang, Hyun-Seon; Lee, Jang-Jae; Son, Mee-Kyoung

    2015-01-01

    PURPOSE The aim of this study was to compare the color stability, water sorption and cytotoxicity of thermoplastic acrylic resin for the non-metal clasp dentures to those of thermoplastic polyamide and conventional heat-polymerized denture base resins. MATERIALS AND METHODS Three types of denture base resin, which are conventional heat-polymerized acrylic resin (Paladent 20), thermoplastic polyamide resin (Bio Tone), thermoplastic acrylic resin (Acrytone) were used as materials for this study...

  6. Utilization of fly ash for stabilization/solidification of heavy metal contaminated soils

    Energy Technology Data Exchange (ETDEWEB)

    Dermatas, D.; Meng, X. [Stevens Inst. of Technology, Hoboken, NJ (United States)

    1995-12-01

    Pozzolanic-based stabilization/solidification (S/S) is an effective, yet economic technological alternative to immobilize heavy metals in contaminated soils and sludges. Fly ash waste materials were used along with quicklime (CaO) to immobilize lead, trivalent and hexavalent chromium present in contaminated clayey sand soils. The degree of heavy metal immobilization was evaluated using the Toxicity Characteristic Leaching Procedure (TCLP) as well as controlled extraction experiments. These leaching test results along with X-ray diffraction (XRD), scanning electron microscope and energy dispersive x-ray (SEM-EDX) analyses were also implemented to elucidate the mechanisms responsible for immobilization of the heavy metals under study. Finally, the reusability of the stabilized waste forms in construction applications was also investigated by performing unconfined compressive strength and swell tests. Results suggest that the controlling mechanism for both lead and hexavalent chromium immobilization is surface adsorption, whereas for trivalent chromium it is hydroxide precipitation. Addition of fly ash to the contaminated soils effectively reduced heavy metal leachability well below the non-hazardous regulatory limits. However, quicklime addition was necessary in order to attain satisfactory immobilization levels. Overall, fly ash addition increases the immobilization pH region for all heavy metals tested, and significantly improves the stress-strain properties of the treated solids, thus allowing their reuse as readily available construction materials. The only potential problem associated with this quicklime/fly ash treatment is the excessive formation of the pozzolanic product ettringite in the presence of sulfates. Ettringite, when brought in contact with water, may cause significant swelling and subsequent deterioration of the stabilized matrix. Addition of minimum amounts of barium hydroxide was shown to effectively eliminate ettringite formation.

  7. Hydrothermal sulfidation and floatation treatment of heavy-metal-containing sludge for recovery and stabilization.

    Science.gov (United States)

    Liang, Yan-Jie; Chai, Li-Yuan; Min, Xiao-Bo; Tang, Chong-Jian; Zhang, Hai-Jing; Ke, Yong; Xie, Xian-De

    2012-05-30

    This study focuses on the application of hydrothermal sulfidation and floatation to treat the heavy-metal-containing sludge for recovery and stabilization. After the hydrothermal sulfidation, the sulfidation percentage of zinc and lead reach up to 85.0% and 75.4%, respectively. 33.3% of Zn, 58.9% of Pb and 68.8% of Cu can be recovered from the sludge by floatation. The lower recovery of ZnS attributes to its surface and structural characteristics. To compare these characteristics, three types of synthetic metal sulfide (ZnS, PbS and CuS) were prepared and examined with XRD, SEM and TEM. The poor floatability of the finely dispersed, round shape of ZnS can be improved by crystal modification in hydrothermal condition. With increasing the temperature and reaction time, the grain size of the ZnS increased from 7.95 nm to 44.28 nm and the recovery of Zn increased to from 33.3% to 72.8%. The TCLP results indicate that all the leached heavy metal concentrations of floatation tailings are under the allowable limit. No obvious increase of heavy metal concentration was observed in continuous leaching procedure. The presence of alkaline compounds after hydrothermal sulfidation might act as mineralogical scavengers of dissolved heavy metal released by sulfide oxidation to avoid the heavy metal pollution.

  8. Stability of metal organic frameworks and interaction of small gas molecules in these materials

    Science.gov (United States)

    Tan, Kui

    The work in this dissertation combines spectroscopy ( in-situ infrared absorption and Raman), powder X-ray diffraction and DFT calculations to study the stability of metal organic frameworks materials (MOFs) in the presence of water vapor and other corrosive gases (e.g., SO 2, NO2 NO), and the interaction and competitive co-adsorption of several gases within MOFs by considering two types of prototypical MOFs: 1) a MOF with saturated metal centers based on paddlewheel secondary building units: M(bdc)(ted)0.5 [M=Cu, Zn, Ni, Co, bdc = 1,4-benzenedicarboxylate, ted = triethylenediamine], and 2) a MOF with unsaturated metal centers: M2(dobdc) [M=Mg2+, Zn2+, Ni2+, Co2+ and dobdc = 2,5-dihydroxybenzenedicarboxylate]. We find that the stability of MOFs to water vapor critically depends on their structure and the specific metal cation in the building units. For M(bdc)(ted)0.5, the metal-bdc bond is the most vulnerable for Cu(bdc)(ted)0.5, while the metal-ted bond is first attacked for the Zn and Co analogs. In contrast, Ni(bdc)(ted)0.5 remains stable under the same conditions. For M2(dobdc), or MOF-74, the weak link is the dobdc-metal bond. The water molecule is dissociatively adsorbed at the metal-oxygen group with OH adsorption directly on the metal center and H adsorption on the bridging O of the phenolate group in the dobdc linker. Other technologically important molecules besides water, such as NO, NO2, SO2, tend to poison M2(dobdc) through dissociative or molecular adsorption onto the open metal sites. A high uptake SO2 capacity was measured in M(bdc)(ted)0.5, attributed to multipoint interactions between the guest SO2 molecule and the MOF host. In the case of competitive co-adsorption between CO2 and other small molecules, we find that binding energy alone is not a good indicator of molecular site occupation within the MOF (i.e., it cannot successfully predict and evaluate the displacement of CO2 by other molecules). Instead, we show that the kinetic barrier for the

  9. Temporal stability of magic-number metal clusters: beyond the shell closing model

    Science.gov (United States)

    Desireddy, Anil; Kumar, Santosh; Guo, Jingshu; Bolan, Michael D.; Griffith, Wendell P.; Bigioni, Terry P.

    2013-02-01

    The anomalous stability of magic-number metal clusters has been associated with closed geometric and electronic shells and the opening of HOMO-LUMO gaps. Despite this enhanced stability, magic-number clusters are known to decay and react in the condensed phase to form other products. Improving our understanding of their decay mechanisms and developing strategies to control or eliminate cluster instability is a priority, to develop a more complete theory of their stability, to avoid studying mixtures of clusters produced by the decay of purified materials, and to enable technology development. Silver clusters are sufficiently reactive to facilitate the study of the ambient temporal stability of magic-number metal clusters and to begin to understand their decay mechanisms. Here, the solution phase stability of a series of silver:glutathione (Ag:SG) clusters was studied as a function of size, pH and chemical environment. Cluster stability was found to be a non-monotonic function of size. Electrophoretic separations showed that the dominant mechanism involved the redistribution of mass toward smaller sizes, where the products were almost exclusively previously known cluster sizes. Optical absorption spectra showed that the smaller clusters evolved toward the two most stable cluster sizes. The net surface charge was found to play an important role in cluster stabilization although charge screening had no effect on stability, contrary to DLVO theory. The decay mechanism was found to involve the loss of Ag+ ions and silver glutathionates. Clusters could be stabilized by the addition of Ag+ ions and destabilized by either the addition of glutathione or the removal of Ag+ ions. Clusters were also found to be most stable in near neutral pH, where they had a net negative surface charge. These results provide new mechanistic insights into the control of post-synthesis stability and chemical decay of magic-number metal clusters, which could be used to develop design principles

  10. Stability of high temperature chemical vapor deposited silicon based structures on metals for solar conversion.

    Science.gov (United States)

    Gelard, Isabelle; Chichignoud, Guy; Blanquet, Elisabeth; Xuan, Hoan Nguyen; Cruz, Ruben; Jimenez, Carmen; Sarigiannidou, Eirini; Zaidat, Kader

    2011-09-01

    Highly crystallized silicon layers were grown on metal sheets at high temperature (950 degrees C) by thermal CVD from silane. An intermediate buffer layer was mandatory to prevent interdiffusion and silicide formation but also to compensate lattice parameters and thermal expansion coefficients mismatches between metal and silicon and ideally transfer some crystalline properties (grain size, texture) from the substrate to the silicon layer. After a thermodynamic study, aluminum nitride or titanium nitride diffusion barrier layers were selected and processed by CVD. The structure and the interfaces stabilities of these silicon/nitride/metal stacks were studied by field effect gun scanning and transmission electron microscopy, X-ray diffraction, Raman and energy dispersive X-ray spectroscopy. As a result, TiN deposited by CVD appears to be an efficient material as a buffer layer between steel and silicon.

  11. A Combined Experimental and Computational Study on the Stability of Nanofluids Containing Metal Organic Frameworks.

    Science.gov (United States)

    Annapureddy, Harsha V R; Nune, Satish K; Motkuri, Radha Kishan; McGrail, B Peter; Dang, Liem X

    2015-07-23

    Computational studies on nanofluids composed of metal organic frameworks were performed using molecular modeling techniques. Grand Canonical Monte Carlo simulations were used to study the adsorption behavior of 1,1,1,3,3-pentafluoropropane (R-245fa) in a MIL-101 metal organic frameworks at various temperatures. To understand the stability of the nanofluid composed of MIL-101 particles, we performed molecular dynamics simulations to compute potentials of mean force between hypothetical MIL-101 fragments terminated with two different kinds of modulators in R-245fa and water. Our computed potentials of mean force results indicate that the metal organic frameworks particles tend to disperse better in water than in R-245fa. The reasons for this difference in dispersion were analyzed and are discussed in the paper. Our results agree with experimental results indicating that the potential models employed and modeling approaches provide good descriptions of molecular interactions and the reliabilities.

  12. Magnetic interactions as a stabilizing factor of semiquinone species of lawsone by metal complexation

    Energy Technology Data Exchange (ETDEWEB)

    Valle-Bourrouet, Grettel [Universidad de Costa Rica, Escuela de Quimica, San Jose (Costa Rica); Ugalde-Saldivar, Victor M. [Facultad de Quimica, Universidad Nacional Autonoma de Mexico, Ciudad Universitaria, C.P. 04510, Mexico, D.F. (Mexico); Gomez, Martin [Departamento de Sistemas Biologicos, Universidad Autonoma Metropolitana-Xochimilco, C.P. 04960, Mexico, D.F. (Mexico); Ortiz-Frade, Luis A. [Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, Parque Tecnologico Queretaro, Sanfandila, 76703, Pedro Escobedo, Queretaro (Mexico); Gonzalez, Ignacio [Universidad Autonoma Metropolitana - Iztapalapa, Departamento de Quimica, Area de Electroquimica, Apartado postal 55-534, 09340, Mexico, D.F. (Mexico); Frontana, Carlos, E-mail: ultrabuho@yahoo.com.m [Departamento de Quimica, Centro de Investigacion y Estudios Avanzados, Av. Instituto Politecnico Nacional No. 2508 Col. San Pedro Zacatenco, C.P. 07360, Mexico, D.F. (Mexico)

    2010-12-01

    Changes in electrochemical reactivity for lawsone anions (lawsone, 2-hydroxy-1,4-naphthoquinone, HLw) being coordinated to a series of metallic ions in dimethylsulfoxide solution were evaluated. Upon performing cyclic voltammetry experiments for metal complexes of this quinone with pyridine (Py) - structural formula M(II)(Lw{sup -}){sub 2}(Py){sub 2}; M: Co(II), Ni(II), Zn(II) - it was found that the reduction of coordinated Lw{sup -} units occurs during the first and second electron uptake in the analyzed compounds. The stability of the electrogenerated intermediates for each complex depends on the d electron configuration in each metal center and is determined by magnetic interactions with the available spins considering an octahedral conformation for all the compounds. This was evidenced by in situ spectroelectrochemical-ESR measurements in the Zn(II) complex in which due to the lack of magnetic interaction owing to its electron configuration, the structure of the coordinated anion radical species was determined. Successive reduction of the associated Lw{sup -} units leads to partial dissociation of the complex, determined by the identification of free radical dianion structures in solution. These results show some insights on how metal-lawsone complexation can modify the solution reactivity and stability of the electrogenerated radical species.

  13. Stabilization of heavy metals in MSWI fly ash using silica fume

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xinying; Chen, Quanyuan [School of Environment Science and Engineering, Donghua University, Shanghai 201620 (China); State Environmental Protection Engineering Center for Pollution Treatment and Control in Textile Industry, Donghua University, Shanghai 201620 (China); Zhou, Yasu [School of Environment Science and Engineering, Donghua University, Shanghai 201620 (China); Tyrer, Mark [Mineral Industry Research Organisation, Solihull B37 7HB (United Kingdom); Yu, Yang [School of Environment Science and Engineering, Donghua University, Shanghai 201620 (China)

    2014-12-15

    Highlights: • The stabilization of heavy metals in MSWI fly ash was investigated. • The addition of silica fume effectively reduced the leaching of Pb and Cd. • The relation of solid phase transformation and leaching behavior of heavy metals was discussed. - Abstract: The objective of this work was to investigate the feasibility and effectiveness of silica fume on stabilizing heavy metals in municipal solid waste incineration (MSWI) fly ash. In addition to compressive strength measurements, hydrated pastes were characterized by X-ray diffraction (XRD), thermal-analyses (DTA/TG), and MAS NMR ({sup 27}Al and {sup 29}Si) techniques. It was found that silica fume additions could effectively reduce the leaching of toxic heavy metals. At the addition of 20% silica fume, leaching concentrations for Cu, Pb and Zn of the hydrated paste cured for 7 days decreased from 0.32 mg/L to 0.05 mg/L, 40.99 mg/L to 4.40 mg/L, and 6.96 mg/L to 0.21 mg/L compared with the MSWI fly ash. After curing for 135 days, Cd and Pb in the leachates were not detected, while Cu and Zn concentrations decreased to 0.02 mg/L and 0.03 mg/L. The speciation of Pb and Cd by the modified version of the European Community Bureau of Reference (BCR) extractions showed that these metals converted into more stable state in hydrated pastes of MSWI fly ash in the presence of silica fume. Although exchangeable and weak-acid soluble fractions of Cu and Zn increased with hydration time, silica fume addition of 10% can satisfy the requirement of detoxification for heavy metals investigated in terms of the identification standard of hazardous waste of China.

  14. Stability evaluation of short-circuiting gas metal arc welding based on ensemble empirical mode decomposition

    Science.gov (United States)

    Huang, Yong; Wang, Kehong; Zhou, Zhilan; Zhou, Xiaoxiao; Fang, Jimi

    2017-03-01

    The arc of gas metal arc welding (GMAW) contains abundant information about its stability and droplet transition, which can be effectively characterized by extracting the arc electrical signals. In this study, ensemble empirical mode decomposition (EEMD) was used to evaluate the stability of electrical current signals. The welding electrical signals were first decomposed by EEMD, and then transformed to a Hilbert–Huang spectrum and a marginal spectrum. The marginal spectrum is an approximate distribution of amplitude with frequency of signals, and can be described by a marginal index. Analysis of various welding process parameters showed that the marginal index of current signals increased when the welding process was more stable, and vice versa. Thus EEMD combined with the marginal index can effectively uncover the stability and droplet transition of GMAW.

  15. Remote stabilization of copper paddlewheel based molecular building blocks in metal-organic frameworks

    KAUST Repository

    Gao, Wenyang

    2015-03-24

    Copper paddlewheel based molecular building blocks (MBBs) are ubiquitous and have been widely employed for the construction of highly porous metal-organic frameworks (MOFs). However, most copper paddlewheel based MOFs fail to retain their structural integrity in the presence of water. This instability is directly correlated to the plausible displacement of coordinating carboxylates in the copper paddlewheel MBB, [Cu2(O2C-)4], by the strongly coordinating water molecules. In this comprehensive study, we illustrate the chemical stability control in the rht-MOF platform via strengthening the coordinating bonds within the triangular inorganic MBB, [Cu3O(N4-x(CH)xC-)3] (x = 0, 1, or 2). Remotely, the chemical stabilization propagated into the paddlewheel MBB to afford isoreticular rht-MOFs with remarkably enhanced water/chemical stabilities compared to the prototypal rht-MOF-1. © 2015 American Chemical Society.

  16. Stability and Hydrocarbon/Fluorocarbon Sorption of a Metal-Organic Framework with Fluorinated Channels

    Directory of Open Access Journals (Sweden)

    Jijiang Xie

    2016-04-01

    Full Text Available The stabilities and hydrocarbon/fluorocarbon sorption properties of a zeolite-like metal-organic framework (MOF Zn(hfipbb with fluorinated channels has been studied. By the combination of thermogravimetric analysis (TGA and powder X-ray diffraction (PXRD measurements, we confirm that Zn(hfipbb has exceptionally high hydrothermal and thermal stabilities. The adsorption behaviors of water and methanol by Zn(hfipbb indicate that it is highly hydrophobic but with high adsorption of alcohols. Hexane and perfluorohexane adsorption measurements show that the fluorinated channels in Zn(hfipbb have high affinity with hydrocarbon and fluorocarbon. The high fluorophilic nature of the channels and the high stability of the compound suggest its potential utility in practical separation applications.

  17. A kinetic model for estimating the boron activation energies in the FeB and Fe2B layers during the gas-boriding of Armco iron: Effect of boride incubation times

    Science.gov (United States)

    Keddam, M.; Kulka, M.; Makuch, N.; Pertek, A.; Małdziński, L.

    2014-04-01

    The present work deals with a simulation of the growth kinetics of boride layers grown on Armco iron substrate. The formed boride layers (FeB + Fe2B) are obtained by the gas-boriding in the temperature range of 1073-1273 K during a time duration ranging from 80 to 240 min. The used approach solves the mass balance equations at the two growing fronts: (FeB/Fe2B) and (Fe2B/Fe) under certain assumptions. To consider the effect of the incubation times for the borides formation, the temperature-dependent function Φ(T) was incorporated in the model. The following input data: (the boriding temperature, the treatment time, the upper and lower values of boron concentrations in FeB and Fe2B and the experimental parabolic growth constants) are needed to determine the boron activation energies in the FeB and Fe2B layers. The obtained values of boron activation energies were then compared with the values available in the literature. Finally, a good agreement was obtained between the simulated values of boride layers thicknesses and the experimental ones in the temperature range of 1073-1273 K.

  18. Protective metal matrix coating with nanocomponents

    Science.gov (United States)

    Galevsky, G. V.; Rudneva, V. V.; Cherepanov, A. N.; Galevsky, S. G.; Efimova, K. A.

    2016-09-01

    Experience of nanocrystalline chromium, titanium, silicon carbides and borides components application as nickel, zinc, chromium based electrodeposited composite coating is generalized. Electrodepositing conditions are determined. Structure and physicochemical properties of coatings, namely micro-hardness, adhesion to steel base, inherent stresses, heat resistance, corrosion currents, en-during quality, and their change during isothermal annealing are studied. As is shown, nanocomponents act as metal matrix modifier. Technological and economic feasibility study to evaluate expediency of replacing high priced nano-diamonds with nanocrystalline borides and carbides is undertaken.

  19. Mineral materials as feasible amendments to stabilize heavy metals in polluted urban soils

    Institute of Scientific and Technical Information of China (English)

    Mingkui Zhang; Jincheng Pu

    2011-01-01

    Four minerals, agricultural limestone (AL), rock phosphate (RP), palygorskite (PG), and calcium magnesium phosphate (CMP), were evaluated by means of chemical fractions of heavy metals in soils and concentrations of heavy metals in leachates from columns to determine their ability to stabilize heavy metals in polluted urban soils.Two urban softs (calcareous soil and acidic soil) polluted with cadmium, copper, zinc and lead were selected and amended in the laboratory with the mineral materials) for 12 months.Results indicated that application of the mineral materials reduced exchangeable metals in the sequence of Pb, Cd > Cu > Zn.The reduction of exchangeable fraction of heavy metals in the soils amended with different mineral materials followed the sequence of CMP, PG > AL > RP.Reductions of heavy metals leached were based on comparison with cumulative totals of heavy metals eluted through 12 pore volumes from an untreated soil.The reductions of the metals eluted from the calcareous soil amended with the RP, AL, PG and CMP were 1.98%, 38.89%, 64.81% and 75.93% for Cd, 8.51%, 40.42%, 60.64% and 55.32% for Cu, 1.76%, 52.94%, 70.00% and 74.12% for Pb, and 28.42%, 52.74%, 64.38% and 49.66% for Zn.Those from the acidic soil amended with the CMP, PG, AL, and RP were 25.65%, 68.06%, 78.01% and 79.06% for Cd, 26.56%, 49.64%, 43.40% and 34.68% for Cu, 44.44%, 33.32%, 61.11% and 69.44% for Pb, and 18.46%, 43.77%, 41.98% and 40.68% for Zn.The CMP and PG treatments were superior to the AL and RP for stabilizing heavy metals in the polluted urban soils.

  20. A holistic approach to phosphate stabilization treatment of metal contaminated soil

    Directory of Open Access Journals (Sweden)

    Zupančič M.

    2013-04-01

    Full Text Available In our study we showed the importance of holistic approach to evaluation of chemical stabilization using phosphate amendments, where all aspects of chemical treatments were observed. An extensive evaluation of metal stabilization in contaminated soil and an evaluation of the leaching of phosphorus induced after treatment were performed. The soil from the former zinc smelter area in the Celje region, used in this study, was heavily polluted with Zn (34 400 ± 1500 mg kg−1, Pb (20 400 ± 1500 mg kg−1, As (950 ± 10 mg kg−1, Cu (549 ± 7 mg kg−1 and Cd (158 ± 4 mg kg−1. The results of Toxicity Characteristic Leaching Procedure showed high mobility of Zn (540 ± 25 mg L−1, Pb (12.7 ± 0.5 mg L−1 and Cd (2.9 ± 0.1 mg L−1. To immobilize metals in the soil, mixtures of soil with phosphate (variable molar ratio of hydroxyapatite and phosphoric acid were prepared with a constant molar Pb:P ratio of 1:10. Hydroxyapatite as the only source of phosphate showed a high stabilization efficiency, above all for Pb with over 97 % of primary acetic acid leachable Pb immobilized. The addition of phosphoric acid as a source of phosphate resulted in an increase in leaching of phosphorus up to 50 mg L−1 in water extracts. Lime that was also added in some stabilization mixtures increased the stabilization efficiency of phosphate and also decreased the treatment-induced phosphate leaching. To evaluate the long-term stability of immobilization, leaching of metals and phosphorus was assessed in a column experiment with synthetic precipitation that in general showed steady decrease in leachability of metals and phosphorus with quite high cumulative Zn and Cd concentrations in leachates of soil sample and extremely high (30% of total added P concentration cumulative P concentrations in leachates of mixture with highest amount of added phosphoric acid and no addition of lime.

  1. Improving the Adhesion Resistance of the Boride Coatings to AISI 316L Steel Substrate by Diffusion Annealing

    Science.gov (United States)

    Campos-Silva, I.; Bernabé-Molina, S.; Bravo-Bárcenas, D.; Martínez-Trinidad, J.; Rodríguez-Castro, G.; Meneses-Amador, A.

    2016-09-01

    In this study, new results about the practical adhesion resistance of boride coating/substrate system formed at the surface of AISI 316 L steel and improved by means of a diffusion annealing process are presented. First, the boriding of AISI 316 L steel was performed by the powder-pack method at 1173 K with different exposure times (4-8 h). The diffusion annealing process was conducted on the borided steels at 1273 K with 2 h of exposure using a diluent atmosphere of boron powder mixture. The mechanical behavior of the boride coating/substrate system developed by both treatments was established using Vickers and Berkovich tests along the depth of the boride coatings, respectively. Finally, for the entire set of experimental conditions, the scratch tests were performed with a continuously increasing normal force, in which the practical adhesion resistance of the boride coating/substrate system was represented by the critical load. The failure mechanisms developed over the surface of the scratch tracks were analyzed; the FeB-Fe2B/substrate system exhibited an adhesive mode, while the Fe2B/substrate system obtained by the diffusion annealing process showed predominantly a cohesive failure mode.

  2. Stability and activity of doped transition metal zeolites in the hydrothermal processing

    Directory of Open Access Journals (Sweden)

    Thomas François Robin

    2015-12-01

    Full Text Available This study investigates the stability and activity of HZSM-5 doped with metals such as molybdenum, nickel, copper and iron in under hydrothermal conditions used for the direct liquefaction of microalgae. Catalysts have been prepared by ion exchange techniques, and MoZSM-5 was also prepared by wet incipient impregnation for comparison. Hydrothermal liquefaction is considered as a potential route to convert microalgae into a sustainable fuel. One of the drawbacks of this process is that the bio-crude produced contains significant levels of nitrogen and oxygen compounds which have an impact on the physical and chemical propriety of the fuel. Heterogeneous catalysts have been shown to improve the quality of the bio-crude by reducing nitrogen and oxygen contents. Zeolites, such as HZSM-5, are strong candidates due to their low cost compared to noble metal catalysts but their stability and activity under hydrothermal conditions is not well understood. The stability of the catalysts has been determined under hydrothermal conditions at 350 °C. Catalysts have been characterised before and after treatment using XRD, BET physisorption and STEM microscopy. Metal leaching was determined by analysis of the water phase following hydrothermal treatment. The inserted cation following ion-exchange can influence the physical properties of HZSM-5 for example molybdenum improves the crystallinity of the zeolite. In general, metal doped zeolites were relatively stable under subcritical water. Activity of the catalysts for processing lipids, protein and microalgae has been assessed. Four feedstocks were selected: sunflower oil, soya proteins, Chlorella and P. ellipsoidea. The catalysts exhibited greater activity towards converting lipids for example MoZSM-5 enhanced the formation of aromatic compounds. NiZSM-5 and CuZSM-5 were observed to be more efficient for deoxygenation.

  3. Synthesis, morphological control, dispersion stabilization and in situ self-assembly of noble metal nanostructures using multidentate resorcinarene surfactants

    Science.gov (United States)

    Han, Sangbum

    In this dissertation, a detailed investigation on the influence of various macrocyclic resorcinarene surfactants in determining the morphology, stabilization and self-assembly of mono- and bi- metallic nanoparticles was undertaken. (Abstract shortened by ProQuest.).

  4. HIGHLY REFRACTORY CRUCIBLES OF STABILIZED ZIRCONIA FOR INDUCTION MELTING OF THE PLATINUM GROUP METALS, FABRICATED BY VIBROCASTING

    Directory of Open Access Journals (Sweden)

    V. V. Primachenko

    2012-01-01

    Full Text Available As the result of the studies at PJSC « UKRNIIO them. A.S.Berezhnogo» the technology and commercial production of crucibles from stabilized zirconia for the smelting of platinum group metals are develop

  5. Anomalous transient leaching behavior of metals solidified/stabilized by pozzolanic fly ash

    Energy Technology Data Exchange (ETDEWEB)

    Camacho, Lucy Mar [Department of Chemical Engineering, New Mexico State University, Las Cruces, NM 88003 (United States)]. E-mail: lcamacho@nmsu.edu; Munson-McGee, Stuart H. [Department of Chemical Engineering, New Mexico State University, Las Cruces, NM 88003 (United States)

    2006-09-01

    This study presents observations on the transient leaching behavior of chromium, cadmium, and aluminum that were solidified/stabilized by pozzolanic fly ash. These three metals were selected since they were present in a simulated waste stream generated by an evaporator during plutonium purification and also because the minimum solubility of these metals occurs at significantly different pHs. The transient pH behavior of the toxicity characteristic leaching procedure (TCLP) leachate showed a monotonic increase for all cases, but the equilibrium value was affected by process conditions. The transient leachate concentration behavior showed curves with one or two local maxima for some cases and curves with a monotonic increase for other cases. Data from the leaching experiments was compared to the solubility curves for the hydroxides of each metal since it was assumed that the highly alkaline conditions inside the fly ash waste would cause the metals to precipitate as hydroxides after initially dissolving in the acidic leaching solution. It was found that of the three metals, only cadmium followed the solubility curve for pure hydroxide solutions or for fly ash systems currently reported in the literature.

  6. MSWI Fly Ash Based Novel Solidification/Stabilization Matrices for Heavy Metals

    Institute of Scientific and Technical Information of China (English)

    DENG Faqing; QIAN Guangren

    2008-01-01

    The possibilities of MSWI fly ash as a major constituent of novel solidification/stabilization matrices for secure landfill were investigated by mixing MSWl fly ash with rich aluminum components,which was added as bauxite cement or metakaolinite instead,to form Friedel and Ettringite phases with high fixing capacities for heavy metals.The physical properties,heavy metals-fixing capacity,mineral phases and its vibration bands in the novel matrices were characterized by compressive strength,TCLP(toxic characteristic leaching procedure),XRD (x-ray diffraction),DTG (derivative thermogravimetry),and FTIR (fourier transform infrared spectroscopy),respectively.The Tessier's five-step sequential extraction procedure was used to analyze the fractions of chemical speciation for Pb,Cd and Zn ions.The experimental results indicate that Friedel-Ettringite based novel solidification/stabilization matrices can incorporate Pb,Cd and Zn ions effectively by physical encapsulation and chemical fixation,and it exhibits a great potential in co-landfill treatment of MSWI fly ash with some heavy metals-bearing hazardous wastes.

  7. Heavy metal bioleaching and sludge stabilization in a single-stage reactor using indigenous acidophilic heterotrophs.

    Science.gov (United States)

    Mehrotra, Akanksha; Sreekrishnan, T R

    2017-01-10

    Simultaneous sludge digestion and metal leaching (SSDML) have been reported at mesophilic temperature. It is generally perceived that while sludge stabilization is effected by heterotrophs at neutral pH, metal bioleaching is done by acidophilic autotrophs. However, little information is available on the microbial communities involved in the process. This study carried out SSDML in a single-stage reactor using sludge indigenous microorganisms and looked at the bacterial communities responsible for the process. Volatile suspended solids were reduced by more than 40%. The concentration of zinc, copper, chromium, cadmium and nickel decreased by more than 45% in the dry sludge. Acidophilic species of Alicyclobacillus genus were the dominant heterotrophs. A few heterotrophic bacteria were detected which can oxidize iron (Alicyclobacillus ferrooxydans, Alicyclobacillus ferripilum and Ferrimicrobium acidiphilum). Acidithiobacillus ferrooxidans (autotroph) was responsible for the oxidation of both iron and sulfur which lead to a change in the pH from neutral to acidic. The presence of acidophilic heterotrophs, which can oxidize either iron or sulfur, enhanced the efficiency of SSDML process with respect to sludge stabilization and metal leaching. This study shows that it is possible to carry out the SSDML in a single-stage reactor with indigenous microorganisms.

  8. Recovery of heavy metals and stabilization of spent hydrotreating catalyst using a glass-ceramic matrix.

    Science.gov (United States)

    Sun, D D; Tay, J H; Cheong, H K; Leung, D L; Qian, G

    2001-10-12

    Chemical analysis of spent Co/Mo/gamma Al(2)O(3) catalyst revealed the presence of carbon, molybdenum, sulfur, vanadium and cobalt at levels of 16.0, 10.9, 7.3, 4.6 and 4.0 wt.%, respectively. It was found that calcination at 500 degrees C provides an effective solution for the removal of carbon and sulfur and this generates the oxide form of the heavy metals. The removal of these heavy metals can be achieved through a two-stage leaching process. During the first stage, in which concentrated ammonia is used and it has been found that this process can be successful in removing as much as 83% (w/v) Mo. In a second stage, it was found that using 10% (v/v) of sulfuric acid, it was possible to account for up to 77% (w/v) Co and 4% (w/v) Mo removal. Leaching test results indicated that the vanadium present in the heated spent catalyst was almost stabilized but the molybdenum and cobalt were not. The combination of two solid wastes, ladle furnace slag (LFS) and treated residue of spent catalyst, could be used for making a high value-added anorthite glass-ceramic materials. Further leaching tests showed that ceramic glass materials provided a very effective method of Co, Mo and V heavy metals stabilization resulting in a product with a possible commercial value.

  9. Stability of alkali-metal hydrides: effects of n-type doping

    Science.gov (United States)

    Olea Amezcua, Monica Araceli; de La Peña Seaman, Omar; Rivas Silva, Juan Francisco; Heid, Rolf; Bohnen, Klaus-Peter

    Metal hydrides could be considered ideal solid-state hydrogen storage systems, they have light weight and high hydrogen volumetric densities, but the hydrogen desorption process requires excessively high temperatures due to their high stability. Efforts have been performed to improve their dehydrogenation properties, based on the introduction of defects, impurities and doping. We present a systematic study of the n-type (electronic) doping effects on the stability of two alkali-metal hydrides: Na1-xMgxH and Li1-xBexH. These systems have been studied within the framework of density functional perturbation theory, using a mixed-basis pseudopotential method and the self-consistent version of the virtual crystal approximation to model the doping. The full-phonon dispersions are analyzed for several doping content, paying special attention to the crystal stability. It is found a doping content threshold for each system, where they are close to dynamical instabilities, which are related to charge redistribution in interstitial zones. Applying the quasiharmonic approximation, the vibrational free energy, the linear thermal expansion and heat capacities are obtained for both hydrides systems and are analyzed as a function of the doping content. This work is partially supported by the VIEP-BUAP 2016 and CONACYT-México (No.221807) projects.

  10. Effects of the Electronic Doping In the Stability of the Metal Hydride NaH

    Science.gov (United States)

    Olea-Amezcua, Monica-Araceli; Rivas-Silva, Juan-Francisco; de La Peña-Seaman, Omar; Heid, Rolf; Bohnen, Klaus-Peter

    2015-03-01

    Despite metal hydrides light weight and high hydrogen volumetric densities, the Hydrogen desorption process requires excessively high temperatures due to their high stability. Attempts for improvement the hydrogenation properties have been focus on the introduction of defects, impurities and doping on the metal hydride. We present a systematic study of the electronic doping effects on the stability of a model system, NaH doped with magnesium, forming the alloying system Na1-xMgxH. We use the density functional theory (DFT) and the self-consistent version of the virtual crystal approximation (VCA) to model the doping of NaH with Mg. The evolution of the ground state structural and electronic properties is analyzed as a function of Mg-content. The full-phonon dispersion, calculated by the linear response theory (LRT) and density functional perturbation theory (DFPT), is analyzed for several Mg-concentrations, paying special attention to the crystal stability and the correlations with the electronic structure. Applying the quasiharmonic approximation (QHA), the free energy from zero-point motion is obtained, and its influence on the properties under study is analyzed. This work is partially supported by the VIEP-BUAP (OMPS-EXC14-I) and CONACYT-Mexico (No. 221807) projects.

  11. Preparation and characterization of polymer-stabilized metal nanoparticles for sensor applications

    Science.gov (United States)

    Macanás, J.; Farre, M.; Muñoz, M.; Alegret, S.; Muraviev, D. N.

    2006-05-01

    Nanomaterial-based sensing devices attract great attention of scientist and technologists due to the special properties of nano-objects, such as for example, Metal Nanoclusters (MNC), which differ from those of the bulk materials. The further development of these devices requires novel approaches to stabilize MNC and therefore, to save their unique properties. The Solid-Phase-Incorporated-Reagents (SPHINER) technique was used for in situ synthesis of Polymer-Stabilized Metal Nanoclusters (PSMNC), which were used in the construction of new composite electrodes. The size of Pt-PSMNC synthesized in polyvinyl chloride (PVC) and polysulfone stabilizing matrices was determined by Transmission Electron Microscopy (TEM) technique and appeared to be in majority of cases of 6-20 nm. The electrochemical characterization of PSMNC-based amperometric sensors has demonstrated that inclusion of Pt-MNC increases the electrical conductivity of the membrane and that the electrode performance strongly depends on both the type of polymeric matrix and the membrane preparation technique.

  12. MINE WASTE TECHNOLOGY PROGRAM; PHOSPHATE STABILIZATION OF HEAVY METALS CONTAMINATED MINE WASTE YARD SOILS, JOPLIN, MISSOURI NPL SITE

    Science.gov (United States)

    This document summarizes the results of Mine Waste Technology Project 22-Phosphate Stabilization of Heavy Metals-Contaminated Mine Waste Yard Soils. Mining, milling, and smelting of ores near Joplin, Missouri, have resulted in heavy metal contamination of the area. The Joplin s...

  13. Feasibility of biochar manufactured from organic wastes on the stabilization of heavy metals in a metal smelter contaminated soil.

    Science.gov (United States)

    Abdelhafez, Ahmed A; Li, Jianhua; Abbas, Mohamed H H

    2014-12-01

    The main objectives of the current study were to evaluate the potential effects of biochar derived from sugar cane bagasse (SC-BC) and orange peel (OP-BC) on improving the physicochemical properties of a metal smelter contaminated soil, and determining its potentiality for stabilizing Pb and As in soil. To achieve these goals, biochar was produced in a small-scale biochar producing plant, and an incubation experiment was conducted using a silt loam metal-contaminated soil treated with different application rates of biochar (0-10% w/w). The obtained results showed that, the addition of SC-BC and OP-BC increased significantly the soil aggregate stability, water-holding capacity, cation exchange capacity, organic matter and N-status in soil. SC-BC considerably decreased the solubility of Pb to values lower than the toxic regulatory level of the toxicity characteristics leaching procedure extraction (5 mg L(-1)). The rise in soil pH caused by biochar application, and the increase of soil organic matter transformed the labile Pb into less available fractions i.e. "Fe-Mn oxides" and "organic" bound fractions. On the other hand, As was desorbed from Fe-Mn oxides, which resulted in greater mobility of As in the treated soil. We concluded that SC-BC and OP-BC could be used successfully for remediating soils highly contaminated with Pb. However, considerable attention should be paid when using it in soil contaminated with As. Copyright © 2014 Elsevier Ltd. All rights reserved.

  14. Boriding kinetics of Fe2B layers formed on AISI 1045 steel

    Directory of Open Access Journals (Sweden)

    Zuno-Silva J.

    2014-01-01

    Full Text Available In the present work, a diffusion model was suggested to study the growth kinetics of Fe2B layers grown on the AISI 1045 steel by the pack-boriding treatment. The generated boride layers were analyzed by optical microscopy and X-ray diffraction analysis. The applied diffusion model is based on the principle of mass conservation at the (Fe2B/ substrate interface. It was used to estimate the boron diffusion coefficients of Fe2B in the temperature range of 1123-1273 K. A validation of the model was also made by comparing the experimental Fe2B layer thickness obtained at 1253 K for 5 h of treatment with the predicted value. Basing on our experimental results, the boron activation energy was estimated as 180 kJ mol-1 for the AISI 1045 steel.

  15. High thermal stability and sluggish crystallization kinetics of high-entropy bulk metallic glasses

    Science.gov (United States)

    Yang, M.; Liu, X. J.; Ruan, H. H.; Wu, Y.; Wang, H.; Lu, Z. P.

    2016-06-01

    Metallic glasses are metastable and their thermal stability is critical for practical applications, particularly at elevated temperatures. The conventional bulk metallic glasses (BMGs), though exhibiting high glass-forming ability (GFA), crystallize quickly when being heated to a temperature higher than their glass transition temperature. This problem may potentially be alleviated due to the recent developments of high-entropy (or multi-principle-element) bulk metallic glasses (HE-BMGs). In this work, we demonstrate that typical HE-BMGs, i.e., ZrTiHfCuNiBe and ZrTiCuNiBe, have higher kinetic stability, as compared with the benchmark glass Vitreoy1 (Zr41.2Ti13.8Cu12.5Ni10Be22.5) with a similar chemical composition. The measured activation energy for glass transition and crystallization of the HE-BMGs is nearly twice that of Vitreloy 1. Moreover, the sluggish crystallization region ΔTpl-pf, defined as the temperature span between the last exothermic crystallization peak temperature Tpl and the first crystallization exothermic peak temperature Tpf, of all the HE-BMGs is much wider than that of Vitreloy 1. In addition, high-resolution transmission electron microscopy characterization of the crystallized products at different temperatures and the continuous heating transformation diagram which is proposed to estimate the lifetime at any temperature below the melting point further confirm high thermal stability of the HE-BMGs. Surprisingly, all the HE-BMGs show a small fragility value, which contradicts with their low GFA, suggesting that the underlying diffusion mechanism in the liquid and the solid of HE-BMGs is different.

  16. Improved Photo-Induced Stability in Amorphous Metal-Oxide Based TFTs for Transparent Displays.

    Science.gov (United States)

    Koo, Sang-Mo; Ha, Tae-Jun

    2015-10-01

    In this paper, we investigate the origin of photo-induced instability in amorphous metal-oxide based thin-film transistors (oxide-TFTs) by exploring threshold voltage (Vth) shift in transfer characteristics. The combination of photo irradiation and prolonged gate bias stress enhanced the shift in Vth in amorphous hafnium-indium-zinc-oxide (a-HfIZO) TFTs. Such results stem from the extended trapped charges at the localized defect states related to oxygen vacancy which play a role in a screening effect on the electric field induced by gate voltage. We also demonstrate the chemically clean interface in oxide-TFTs by employing oxygen annealing which reduces the density of trap states, thereby resulting in improved photo-induced stability. We believe that this work stimulates the research society of transparent electronics by providing a promising approach to suppress photo-induced instability in metal-oxide TFTs.

  17. Stability of Weyl points in magnetic half-metallic Heusler compounds

    Science.gov (United States)

    Chadov, Stanislav; Wu, Shu-Chun; Felser, Claudia; Galanakis, Iosif

    2017-07-01

    We employ ab initio fully relativistic electronic structure calculations to study the stability of the Weyl points in the momentum space within the class of the half-metallic ferromagnetic full Heusler materials, by focusing on Co2TiAl as a well-established prototype compound. Here we show that both the number of the Weyl points together with their k -space coordinates can be controlled by the orientation of the magnetization. This alternative degree of freedom, which is absent in other topological materials (e.g., in Weyl semimetals), introduces functionalities that are specific for the class of half-metallic ferromagnets. Of special interest are crossing points which are preserved irrespective of any arbitrary rotation of the magnetization axis.

  18. CONSIDERATIONS REGARDING THE INFLUENCE OF METALIC IONS OF THE STABILITY OF CARBONATES FROM SOILS

    Directory of Open Access Journals (Sweden)

    D. Bulgariu

    2005-10-01

    Full Text Available The distribution of minor elements in heterogeneous mineral / aqueous solutions systems represent one of important problem, with many applications in environmental geochemistry field. Ours studies was focus on the metal ions distribution in carbonate (CaCO3 / solution systems, from applicability point of view to the estimation of formation conditions and of carbonates stability from soils. On the base of our results obtained by sequential solid / liquid extraction for 17 soil samples and theoretical modeling of CaCO3 / solution systems, and the results from literature we try to develop the McIntire prognosis models and the free Gibbs enthalpy linear correlation model, by the inclusion in calculus relations of distribution coefficients a higher number of factors which effective influenced the thermodynamics and kinetics of interphase distribution processes of metal ions. The established correlations has been used to the estimation of time evolution of carbonate / solution equilibrium under the influence of some metal ions (Cd, Zn, Cu, Pb, Bi, which appear usual as pollutants in soils. The prognosis realized on the base of the established correlations are in agreement with the theoretical modelling results and studies of case for different types of polluted soils with heavy metals.

  19. Stabilized chitosan/Fe(0)-nanoparticle beads to remove heavy metals from polluted sediments.

    Science.gov (United States)

    Liu, T; Sun, Y; Wang, Z L

    2016-01-01

    Sediment contamination by heavy metals has become a widespread problem that can affect the normal behaviors of rivers and lakes. After chitosan/Fe(0)-nanoparticles (CS-NZVI) beads were cross-linked with glutaraldehyde (GLA), their mechanical strength, stability and separation efficiency from the sediment were obviously improved. Moreover, the average aperture size of GLA-CS-NZVI beads was 20.6 μm and NZVI particles were nearly spherical in shape with a mean diameter of 40.2 nm. In addition, the pH showed an insignificant effect on the removal rates from the sediment. Due to the dissolution of metals species into aqueous solutions as an introduction of the salt, the removal rates of all heavy metals from the sediment were increased with an increase of the salinity. The competitive adsorption of heavy metals between the sediment particles and GLA-CS-NZVI beads became stronger as the sediment particles became smaller, leading to decreased removal rates. Therefore, the removal efficiency could be enhanced by optimizing experimental conditions and choosing appropriate materials for the target contaminants.

  20. Inducing half-metallicity with enhanced stability in zigzag graphene nanoribbons via fluorine passivation

    Science.gov (United States)

    Jaiswal, Neeraj K.; Tyagi, Neha; Kumar, Amit; Srivastava, Pankaj

    2017-02-01

    Half metals are the primary ingredients for the realization of novel spintronic devices. In the present work, by employing density functional theory based first-principles calculation, we predict half metallic behavior in fluorine passivated zigzag graphene nanoribbons (F-ZGNR). Four different structures have been investigated viz. one edge F passivated ZGNR (F-ZGNR-1), both edges F passivated ZGNR (F-ZGNR-2), F passivation on alternate sites in first configuration (alt-1) and F passivation on alternate sites in second configuration (alt-2). Interestingly, it is noticed that F passivation is analogous to H passivation (pristine), however, F-ZGNR are reckoned energetically more stable than pristine ones. An spin induced band gap is noticed for all F-ZGNR irrespective of their widths although its magnitude is slightly less than the pristine counterparts. With an external transverse electric field, ribbons undergo semiconducting to half metallic transformation. The observed half metallic character with enhanced stability present F-ZGNR as a better candidate than pristine ZGNR towards the realization of upcoming spintronic devices.

  1. Interfacial Stability of Li Metal-Solid Electrolyte Elucidated via in Situ Electron Microscopy.

    Science.gov (United States)

    Ma, Cheng; Cheng, Yongqiang; Yin, Kuibo; Luo, Jian; Sharafi, Asma; Sakamoto, Jeff; Li, Juchuan; More, Karren L; Dudney, Nancy J; Chi, Miaofang

    2016-11-09

    Despite their different chemistries, novel energy-storage systems, e.g., Li-air, Li-S, all-solid-state Li batteries, etc., face one critical challenge of forming a conductive and stable interface between Li metal and a solid electrolyte. An accurate understanding of the formation mechanism and the exact structure and chemistry of the rarely existing benign interfaces, such as the Li-cubic-Li7-3xAlxLa3Zr2O12 (c-LLZO) interface, is crucial for enabling the use of Li metal anodes. Due to spatial confinement and structural and chemical complications, current investigations are largely limited to theoretical calculations. Here, through an in situ formation of Li-c-LLZO interfaces inside an aberration-corrected scanning transmission electron microscope, we successfully reveal the interfacial chemical and structural progression. Upon contact with Li metal, the LLZO surface is reduced, which is accompanied by the simultaneous implantation of Li(+), resulting in a tetragonal-like LLZO interphase that stabilizes at an extremely small thickness of around five unit cells. This interphase effectively prevented further interfacial reactions without compromising the ionic conductivity. Although the cubic-to-tetragonal transition is typically undesired during LLZO synthesis, the similar structural change was found to be the likely key to the observed benign interface. These insights provide a new perspective for designing Li-solid electrolyte interfaces that can enable the use of Li metal anodes in next-generation batteries.

  2. Phase stability in heavy f-electron metals from first-principles theory

    Energy Technology Data Exchange (ETDEWEB)

    Soderlind, P

    2005-11-17

    The structural phase stability of heavy f-electron metals is studied by means of density-functional theory (DFT). These include temperature-induced transitions in plutonium metal as well as pressure-induced transitions in the trans-plutonium metals Am, Cm, Bk, and Cf. The early actinides (Th-Np) display phases that could be rather well understood from the competition of a crystal-symmetry breaking mechanism (Peierls distortion) of the 5f states and electrostatic forces, while for the trans-plutonium metals (Am-Cf) the ground-state structures are governed by 6d bonding. We show in this paper that new physics is needed to understand the phases of the actinides in the volume range of about 15-30 {angstrom}{sup 3}. At these volumes one would expect, from theoretical arguments made in the past, to encounter highly complex crystal phases due to a Peierls distortion. Here we argue that the symmetry reduction associated with spin polarization can make higher symmetry phases competitive. Taking this into account, DFT is shown to describe the well-known phase diagram of plutonium and also the recently discovered complex and intriguing high-pressure phase diagrams of Am and Cm. The theory is further applied to investigate the behaviors of Bk and Cf under compression.

  3. Improve the operational stability of the inverted organic solar cells using bilayer metal oxide structure.

    Science.gov (United States)

    Chang, Jingjing; Lin, Zhenhua; Jiang, Changyun; Zhang, Jie; Zhu, Chunxiang; Wu, Jishan

    2014-11-12

    Operational stability is a big obstacle for the application of inverted organic solar cells (OSCs), however, less talked about in the research reports. Due to photoinduced degradation of the metal oxide interlayer, which can cause shunts generation and degeneration in ZnO interlayer, a significant degradation of open circuit voltage (Voc) and fill factor (FF) has been observed by in situ periodic measurements of the device current density-voltage (J-V) curves with light illumination. By combining TiOx and ZnO to form bilayer structures on ITO, the photovoltaic performance is improved and the photoinduced degradation is reduced. It was found that the device based on ZnO/TiOx bilayer structure achieved better operational stability as compared to that with ZnO or TiOx interlayer.

  4. Fluorous Metal-Organic Frameworks with Enhanced Stability and High H2/CO2 Storage Capacities

    Science.gov (United States)

    Zhang, Da-Shuai; Chang, Ze; Li, Yi-Fan; Jiang, Zhong-Yi; Xuan, Zhi-Hong; Zhang, Ying-Hui; Li, Jian-Rong; Chen, Qiang; Hu, Tong-Liang; Bu, Xian-He

    2013-01-01

    A new class of metal-organic frameworks (MOFs) has been synthesized by ligand-functionalization strategy. Systematic studies of their adsorption properties were performed at low and high pressure. Importantly, when fluorine was introduced into the framework via the functionalization, both the framework stabilities and adsorption capacities towards H2/CO2 were enhanced significantly. This consequence can be well interpreted by theoretical studies of these MOFs structures. In addition, one of these MOFs TKL-107 was used to fabricate mixed matrix membranes, which exhibit great potential for the application of CO2 separation. PMID:24264725

  5. A Versatile Al(III) -Based Metal-Organic Framework with High Physicochemical Stability.

    Science.gov (United States)

    Wang, Zhuo-Wei; Chen, Min; Liu, Chun-Sen; Wang, Xi; Zhao, Hui; Du, Miao

    2015-11-23

    A unique Al(III) -based metal-organic framework (467-MOF) with two types of square channels has been designed and synthesized by using a flexible tricarboxylate ligand under solvothermal conditions. 467-MOF exhibits superior thermal and chemical stability and, moreover, shows high CO2 sorption selectivity over H2 , with a selectivity, based on the ideal adsorbed solution theory (IAST) of approximately 45 at 273 or 293 K. Furthermore, its solvent-dependent photoluminescence makes it an applicable sensor in the detection of nitrobenzene explosives through fluorescence quenching. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Stability and mobility of defect clusters and dislocation loops in metals

    DEFF Research Database (Denmark)

    Osetsky, Y.N.; Bacon, D.J.; Serra, A.;

    2000-01-01

    has been observed in the computer simulation of small vacancy loops in alpha-Fe. In the present paper we summarise results obtained by molecular dynamics simulations of defect clusters and small dislocation loops in alpha-Fe(bcc) and Cu(fcc). The structure and stability of vacancy and interstitial...... loops are reviewed, and the dynamics of glissile clusters assessed. The relevance and importance of these results in establishing a better understanding of the observed differences in the damage accumulation behaviour between bcc and fee metals irradiated under cascade damage conditions are pointed out...

  7. Metal Hydride Nanoparticles with Ultrahigh Structural Stability and Hydrogen Storage Activity Derived from Microencapsulated Nanoconfinement.

    Science.gov (United States)

    Zhang, Jiguang; Zhu, Yunfeng; Lin, Huaijun; Liu, Yana; Zhang, Yao; Li, Shenyang; Ma, Zhongliang; Li, Liquan

    2017-06-01

    Metal hydrides (MHs) have recently been designed for hydrogen sensors, switchable mirrors, rechargeable batteries, and other energy-storage and conversion-related applications. The demands of MHs, particular fast hydrogen absorption/desorption kinetics, have brought their sizes to nanoscale. However, the nanostructured MHs generally suffer from surface passivation and low aggregation-resisting structural stability upon absorption/desorption. This study reports a novel strategy named microencapsulated nanoconfinement to realize local synthesis of nano-MHs, which possess ultrahigh structural stability and superior desorption kinetics. Monodispersed Mg2 NiH4 single crystal nanoparticles (NPs) are in situ encapsulated on the surface of graphene sheets (GS) through facile gas-solid reactions. This well-defined MgO coating layer with a thickness of ≈3 nm efficiently separates the NPs from each other to prevent aggregation during hydrogen absorption/desorption cycles, leading to excellent thermal and mechanical stability. More interestingly, the MgO layer shows superior gas-selective permeability to prevent further oxidation of Mg2 NiH4 meanwhile accessible for hydrogen absorption/desorption. As a result, an extremely low activation energy (31.2 kJ mol(-1) ) for the dehydrogenation reaction is achieved. This study provides alternative insights into designing nanosized MHs with both excellent hydrogen storage activity and thermal/mechanical stability exempting surface modification by agents. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Polyaniline and Perfluorosulfonic Acid Co-Stabilized Metal Catalysts for Oxygen Reduction Reaction.

    Science.gov (United States)

    Ye, Bei; Cheng, Kun; Li, Wenqiang; Liu, Jing; Zhang, Jie; Mu, Shichun

    2017-06-06

    A proton (perfluorosulfonic acid, PFSA) and electron (polyaniline, PANI) conductor polymer costabilized Pt catalyst (Pt-PFSA/C@PANI) is synthesized to improve the long-term stability of polymer electrolyte membrane fuel cells (PEMFCs). The prepared catalyst not only displays comparable oxygen reduction reaction (ORR) activity, but significantly higher electrochemical stability than commercial porous carbon nanosphere supported Pt catalysts (Pt/C). This robust electrochemical property can be due to the result of PFSA and PANI. PANI as protector inhibits carbon nanospheres from corrosion of carbon supports in harsh chemical and electrochemical conditions. Meanwhile, PFSA wrapped Pt NPs (Pt@PFSA) can also anchor Pt NPs on C@PANI to avoid aggregation and detachment of Pt NPs, due to the increased metal-support interaction caused by the strong electrostatic attraction between PANI and PFSA with corresponding positive and negative charges. Significantly, after coating PANI on carbon supports (C@PANI), almost all micropores in the surface of carbon disappear, effectively avoiding the embedding of Pt nanopaticles into micropores. Furthermore, the triple-phase boundary toward ORR catalysis can be facilitated by PFSA as proton conductor (solid electrolyte). These are of benefit to increase utilization of Pt noble metals and ORR activity of our new catalysts.

  9. A facile surface chemistry route to a stabilized lithium metal anode

    Science.gov (United States)

    Liang, Xiao; Pang, Quan; Kochetkov, Ivan R.; Sempere, Marina Safont; Huang, He; Sun, Xiaoqi; Nazar, Linda F.

    2017-09-01

    Lithium metal is a highly desirable anode for lithium rechargeable batteries, having the highest theoretical specific capacity and lowest electrochemical potential of all material candidates. Its most notable problem is dendritic growth upon Li plating, which is a major safety concern and exacerbates reactivity with the electrolyte. Here we report that Li-rich composite alloy films synthesized in situ on lithium by a simple and low-cost methodology effectively prevent dendrite growth. This is attributed to the synergy of fast lithium ion migration through Li-rich ion conductive alloys coupled with an electronically insulating surface component. The protected lithium is stabilized to sustain electrodeposition over 700 cycles (1,400 h) of repeated plating/stripping at a practical current density of 2 mA cm‑2 and a 1,500 cycle-life is realized for a cell paired with a Li4Ti5O12 positive electrode. These findings open up a promising avenue to stabilize lithium metal with surface layers having targeted properties.

  10. MODIFICATION OF TRANSITION METAL CATIONS TO POLYMER- STABILIZED PLATINUM COLLOIDAL CLUSTERS IN ENANTIOSELECTIVE HYDROGENATION OF METHYL PYRUVATE

    Institute of Scientific and Technical Information of China (English)

    Xiao-ping Yan; Bao-lin He; Jie Zhang; Han-fan Liu

    2005-01-01

    Modification of transition metal cations to polymer-stabilized Pt colloidal clusters modified with cinchonidine was studied in enantioselective hydrogenation of methyl pyruvate. Compared to the enantiomeric excess (e.e.) value (71.4%)obtained without the presence of metal cations, obvious e.e. enhancement (up to 82.5%) was resulted from the addition of Zn2+ but with a certain decrease in activity. The reaction parameters in the presence of Zn2+ were also studied. It was found that the Pt colloidal catalysts in the presence of metal cations performed very differently from that in the absence of metal cations.

  11. Controlled Formation of Metal@Al₂O₃ Yolk-Shell Nanostructures with Improved Thermal Stability.

    Science.gov (United States)

    Zhang, Wei; Lin, Xi-Jie; Sun, Yong-Gang; Bin, De-Shan; Cao, An-Min; Wan, Li-Jun

    2015-12-16

    Yolk-shell structured nanomaterials have shown interesting potential in different areas due to their unique structural configurations. A successful construction of such a hybrid structure relies not only on the preparation of the core materials, but also on the capability to manipulate the outside wall. Typically, for Al2O3, it has been a tough issue in preparing it into a uniform nanoshell, making the use of Al2O3-based yolk-shell structures a challenging but long-awaited task. Here, in benefit of our success in the controlled formation of Al2O3 nanoshell, we demonstrated that yolk-shell structures with metal confined inside a hollow Al2O3 nanosphere could be successfully achieved. Different metals including Au, Pt, Pd have been demonstrated, forming a typical core@void@shell structure. We showed that the key parameters of the yolk-shell structure such as the shell thickness and the cavity size could be readily tuned. Due to the protection of a surrounding Al2O3 shell, the thermal stability of the interior metal nanoparticles could be substantially improved, resulting in promising performance for the catalytic CO oxidation as revealed by our preliminary test on Au@Al2O3.

  12. Synthesis and Characterization of Dinuclear Metal Complexes Stabilized by Tetradentate Schiff Base Ligands

    Directory of Open Access Journals (Sweden)

    Eid A. Abdalrazaq

    2010-01-01

    Full Text Available Problem statement: The synthesis, spectroscopic properties and theoretical calculations of acetylacetonimine and acetylacetanilidimine Schiff-base ligands, L1H and L2H, respectively and their dinuclear complexes of the type [M2LnCl2(H2O2], where n = 1 or 2, M = Co(II, Ni(II, Cu(II, Zn(II and Cd(II are described. Approach: The new tetradentate dianion Schiff base ligand which was used as stabilizers for the complexes were prepared by condensation of hydrazine with acetylacetone or acetylacetanilide. The dinuclear complexes of theses ligands were synthesized by treating an ethanolic solution of the prepared ligand with hydrated metal salts in molar ratio of 1:2 (L:M. Results: The ligand and their dinuclear metal complexes were characterized by CHN elemental analysis, FT-IR, UV-Vis, 1HNMR (for the ligands, conductivity, magnetic susceptibility and theoretical calculation by using MM2 modeling program. Conclusion: The reaction of these ligands in a 1:2 (L:M afford dinuclear M(II metal complexes with tetrahedral arrangement around Co(II, Zn(II and Cd(II and square planar around Ni(II and Cu(II.

  13. Investigations of the structural stability of metal hydride composites by in-situ neutron imaging

    Science.gov (United States)

    Herbrig, Kai; Pohlmann, Carsten; Gondek, Łukasz; Figiel, Henryk; Kardjilov, Nikolay; Hilger, André; Manke, Ingo; Banhart, John; Kieback, Bernd; Röntzsch, Lars

    2015-10-01

    Metal hydride composites (MHC) with expanded natural graphite (ENG) exhibiting enhanced thermal conductivity and reduced porosity compared to metal hydride powders can enable a reversible, compact and safe way for hydrogen storage. In this study, neutron imaging during cyclic hydrogenation was utilized to investigate the structural stability and the spatial-temporal hydrogen concentration of application-oriented MHC with 40 mm in diameter compared to a loose metal hydride powder. In particular, swelling and shrinking effects of a radially confined MHC which could freely expand upwards were studied. It was found that the loose powder bed was easily torn apart during dehydrogenation, which leads to increased thermal resistance within the hydride bed. In contrast, the thermal resistance between MHC and container wall was minimized since the initial gap closes during initial hydrogenation and does not reopen thereafter. Further cyclic hydrogenation caused MHC volume changes, i.e. an almost reversible swelling/shrinking (so-called ;MHC breathing;). Moreover, neutron imaging allowed for the observation of reaction fronts within the MHC and the powder bed that are governed by the heat transfer.

  14. A New Ni-Based Metallic Glass with High Thermal Stability and Hardness

    Directory of Open Access Journals (Sweden)

    Aytekin Hitit

    2015-02-01

    Full Text Available Glass forming ability (GFA, thermal stability and microhardness of Ni51−xCuxW31.6B17.4 (x = 0, 5 metallic glasses have been investigated. For each alloy, thin sheets of samples having thickness of 20 µm and 100 µm were synthesized by piston and anvil method in a vacuum arc furnace. Also, 400 µm thick samples of the alloys were synthesized by suction casting method. The samples were investigated by X-ray diffractometry (XRD and differential scanning calorimetry (DSC. Crystallization temperature of the base alloy, Ni51W31.6B17.4, is found to be 996 K and 5 at.% copper substitution for nickel increases the crystallization temperature to 1063 K, which is the highest value reported for Ni-based metallic glasses up to the present. In addition, critical casting thickness of alloy Ni51W31.6B17.4 is 100 µm and copper substitution does not have any effect on critical casting thickness of the alloys. Also, microhardness of the alloys are found to be around 1200 Hv, which is one of the highest microhardness values reported for a Ni-based metallic glass until now.

  15. Stabilization/solidification of battery debris & lead impacted material at Schuylkill Metals, Plant City, Florida

    Energy Technology Data Exchange (ETDEWEB)

    Anguiano, T.; Floyd, D. [ENTACT, Inc., Irving, TX (United States)

    1997-12-31

    The Schuylkill Metals facility in Plant City Florida (SMPCI) operated as a battery recycling facility for approximately 13 years. During its operation, the facility disposed of battery components in surrounding wetland areas. In March of 1991 the U.S. EPA and SMPCI entered into a Consent Decree for the remediation of the SMPCI site using stabilization/solidification and on-site disposal. In November of 1994, ENTACT began remediation at the facility and to date has successfully stabilized/solidified over 228,000 tons of lead impacted battery components and lead impacted material. The ENTACT process reduces the size of the material to be treated to ensure that complete mixing of the phosphate/cement additive is achieved thereby promoting the chemical reactions of stabilization and solidification. ENTACT has met the following performance criteria for treated material at the SMPCI site: (1) Hydraulic Conductivity less than 1x10{sup -6} cm/s, (2) Unconfined Compressive Strength greater than 50 psi, (3) Lead, Cadmium, Arsenic, Chromium TCLP Leachability below hazardous levels.

  16. Structural Stability and Performance of Noble Metal-Free SnO2-Based Gas Sensors

    Directory of Open Access Journals (Sweden)

    Antonio Tricoli

    2012-05-01

    Full Text Available The structural stability of pure SnO2 nanoparticles and highly sensitive SnO2-SiO2 nanocomposites (0–15 SiO2 wt% has been investigated for conditions relevant to their utilization as chemoresistive gas sensors. Thermal stabilization by SiO2 co-synthesis has been investigated at up to 600 °C determining regimes of crystal size stability as a function of SiO2-content. For operation up to 400 °C, thermally stable crystal sizes of ca. 24 and 11 nm were identified for SnO2 nanoparticles and 1.4 wt% SnO2-SiO2 nanocomposites, respectively. The effect of crystal growth during operation (TO = 320 °C on the sensor response to ethanol has been reported, revealing possible long-term destabilization mechanisms. In particular, crystal growth and sintering-neck formation were discussed with respect to their potential to change the sensor response and calibration. Furthermore, the effect of SiO2 cosynthesis on the cross-sensitivity to humidity of these noble metal-free SnO2-based gas sensors was assessed.

  17. A new zirconium inorganic building brick forming metal organic frameworks with exceptional stability.

    Science.gov (United States)

    Cavka, Jasmina Hafizovic; Jakobsen, Søren; Olsbye, Unni; Guillou, Nathalie; Lamberti, Carlo; Bordiga, Silvia; Lillerud, Karl Petter

    2008-10-22

    Porous crystals are strategic materials with industrial applications within petrochemistry, catalysis, gas storage, and selective separation. Their unique properties are based on the molecular-scale porous character. However, a principal limitation of zeolites and similar oxide-based materials is the relatively small size of the pores, typically in the range of medium-sized molecules, limiting their use in pharmaceutical and fine chemical applications. Metal organic frameworks (MOFs) provided a breakthrough in this respect. New MOFs appear at a high and an increasing pace, but the appearances of new, stable inorganic building bricks are rare. Here we present a new zirconium-based inorganic building brick that allows the synthesis of very high surface area MOFs with unprecedented stability. The high stability is based on the combination of strong Zr-O bonds and the ability of the inner Zr6-cluster to rearrange reversibly upon removal or addition of mu3-OH groups, without any changes in the connecting carboxylates. The weak thermal, chemical, and mechanical stability of most MOFs is probably the most important property that limits their use in large scale industrial applications. The Zr-MOFs presented in this work have the toughness needed for industrial applications; decomposition temperature above 500 degrees C and resistance to most chemicals, and they remain crystalline even after exposure to 10 tons/cm2 of external pressure.

  18. Fluidized-bed-combustion ash for the solidification and stabilization of a metal-hydroxide sludge.

    Science.gov (United States)

    Knoll, K L; Behr-Andres, C

    1998-01-01

    Fluidized-bed-combustion (FBC) ash is a by-product from a developing technology for coal-fired power plants that will economically reduce air emissions to meet requirements of the Clean Air Act. FBC ash has physical and chemical properties similar to Portland cement, but only has moderate success as a pozzolan in concrete applications due to low compressive strengths. However, FBC ash has proven effective for use as a binder for the solidification and stabilization (S/S) of metal-bearing sludges. Physical and chemical characterization procedures were used to analyze FBC ash and a metal-bearing sludge obtained from a hazardous waste treatment facility to develop 12 different S/S mix designs. The mix designs consist of four binder designs to evaluate sludge-to-binder ratios of approximately 0, 0.5, and 1. Portland cement is used as a control binder to compare unconfined compressive strengths and Toxicity Characteristic Leaching Procedure (TCLP) analyses from different ratios of the FBC ash streams: fly ash, char, and spent bed material (SBM). Compressive strengths ranging from 84 lbs per square inch (psi) to 298 psi were obtained from various mix designs containing different sludge-to-ash ratios cured for 28 days. All the mix designs passed the TCLP. Recoveries from leaching for each metal were less than 5% for most mix designs. Results of unconfined compressive strengths, TCLP, and percent recovery calculations indicate that the mix design containing approximately a 1:1 ratio of fly ash to char-and-sludge is the best mix design for the S/S of the metal-bearing sludge.

  19. Aspects of metal and silicon-based nanomaterials: Synthesis, stability and properties

    Science.gov (United States)

    Elechiguerra Joven, Jose Luis

    Metal and Si-based nanostructures have drawn increasing interest due to their potential uses in catalysis, biological sensors, and nanoelectronics among others. Therefore, in the present work, several nanostructures were produced, characterized and tested. In particular, the conventional synthesis of noble-metal nanostructures through the polyol method was modified by replacing poly-vinyl pyrrolidone PVP with poly-diallyl dimethyl ammonium chloride PDDA. As PDDA is a cationic polyelectrolyte, the initial strong electrostatic interaction between PDDA and the anionic metal precursors produce the formation of stable ion pairs, so the reactivity of the different species can be tailored and particles with different internal structure, i.e. crystallinity, can be produced. Additionally, metal nanostructures such as nanoparticles and nanowires have been proposed as building blocks for several applications in nanofabrication and nanoelectronics. However, even when atmospheric corrosion is common in metals, there is a lack of information about the stability of those nanostructures against such phenomenon. So, the atmospheric corrosion of silver nanowires and nanoparticles synthesized by the polyol method using PVP as capping agent was studied. Recently, five-fold twinned nanorods and nanowires of gold, copper and silver with pentagonal cross-sections have been synthesized by different techniques, including the polyol method. However, there is not a complete explanation of all the features presented in their electron diffraction patterns. Thus, a comprehensive study on the structure of these multi-twinned decahedral based nanorods and nanowires is presented. Another important application of noble-metal nanostructures is in the field of biology. In the present work, it has been demonstrated that silver nanoparticles undergo a size dependent interaction with HIV-1 via preferential binding to the gp120 glycoprotein knobs. Due to this interaction, silver nanoparticles inhibit the

  20. Effect of metal oxides on the stabilization of soil organic matter

    Science.gov (United States)

    Stelmach, Wioleta

    2017-04-01

    Soil organic matter (SOM) is protected from decomposition by three mechanisms: 1) biochemical stabilization through the accumulation of recalcitrant SOM compounds, 2) physical stabilization, i.e. spatial inaccessibility of SOM for microbes, and 3) chemical protection of SOM through intimate interaction with minerals and metal oxides. The latter mechanisms suggest that added organic substances (i.e. post-fermentation sludge) can be stabilized by metal oxides to increase C sequestration in soil. The aim of this study was to determine the effects of Fe2O3 - one of the dominant metal oxides in soil - on the sequestration of post-fermentation sludge C in soil by separately tracing the decomposition of sludge and of SOM to carbon dioxide (CO2). To determine changes in SOM turnover after the addition of post-fermentation sludge without/with Fe2O3, the isotopic signatures of both C sources (SOM and post-fermentation sludge) were used. Using differences in the 13C natural abundance of the soil (C3 originated, δ13C = -26) and the post-fermentation sludge (C4 originated, δ13C = -18), the CO2 fluxes arising from both C sources were tracked. Addition of post-fermentation sludge to the soil increased the CO2 production by 30% compared to soil without sludge. δ13C analysis of the total CO2 efflux revealed that post-fermentation sludge decreased SOM decomposition. Fe2O3 slightly suppressed sludge decomposition, and therefore increased C sequestration in soil. Only 30% of the post-fermentation sludge had been mineralized after one month of incubation in the soil. The collective results of my study reveal that application of post-fermentation sludge suppresses SOM decomposition, suggesting its use as a fertilizer could positively influence long-term soil quality. Finally, the success of the 13C natural abundance microcosm labeling approach in my study supports its use as an effective method of analyzing the effects of various fertilization techniques on soil nutrient retention

  1. The Effects of a High Magnetic Field on the Annealing of [(Fe0.5Co0.50.75B0.2Si0.05]96Nb4 Bulk Metallic Glass

    Directory of Open Access Journals (Sweden)

    Peng Jia

    2016-11-01

    Full Text Available In contrast with amorphous alloys, nanocrystalline soft magnetic materials show improved thermal stability and higher soft magnetic properties. The nanocrystalline soft magnetic composites are usually fabricated by partially crystallizing from parent amorphous alloys. This paper reports our experimental observation on the sequence of crystallization in metallic glass under a high magnetic field (HMF. An application of a HMF to bulk metallic glass (BMG of [(Fe0.5Co0.50.75B0.2Si0.05]96Nb4 prioritizes the precipitation of α-(Fe,Co phase separated from the subsequent precipitation of borides, (Fe,Co23B6, upon isothermal annealing at a glass transition temperature. Furthermore, it was observed that, through the annealing treatment under a HMF, a soft magnetic nanocomposite, in which only α-(Fe,Co phase uniformly distributes in amorphous matrix, was achieved for boron-bearing BMG. The promotion of the α-Fe or (Fe,Co phase and the prevention of the boride phases during the isothermal annealing process help to produce high-quality soft magnetic nanocomposite materials. The mechanism by which a HMF influences the crystallization sequence was interpreted via certain changes in Gibbs free energies for two ferromagnetic phases. This finding evidences that the annealing treatment under a HMF is suitable for enhancing the soft magnetic properties of high B content (Fe,Co-based bulk amorphous and nanocrystalline materials.

  2. Investigation of diffusion kinetics of plasma paste borided AISI 8620 steel using a mixture of B2O3 paste and B4C/SiC

    Indian Academy of Sciences (India)

    Ibrahim Gunes; Sukru Taktak; Cuma Bindal; Yilmaz Yalcin; Sukru Ulker; Yusuf Kayali

    2013-06-01

    In the present study, AISI 8620 steel was plasma paste borided by using various B2O3 paste mixture. The plasma paste boriding process was carried out in a dc plasma system at temperatures of 973, 1023 and 1073 K for 2, 5 and 7 h in a gas mixture of 70% H2 -30% Ar under a constant pressure of 10 mbar. The properties of the boride layer were evaluated by optical microscopy, X-ray diffraction, Vickers micro-hardness tester and the growth kinetics of the boride layers. X-ray diffraction analysis of boride layers on the surface of the steel revealed FeB and Fe2B phases. Depending on temperature and layer thickness, the activation energies of boron in steel were found to be 124.7 kJ/mol for 100% B2O3.

  3. Stabilization of dissolved trace metals at hydrothermal vent sites: Impact on their marine biogeochemical cycles

    Science.gov (United States)

    Sander, Sylvia G.; Powell, Zach D.; Koschinsky, Andrea; Kuzmanovski, Stefan; Kleint, Charlotte

    2014-05-01

    Hydrothermal vents have long been neglected as a significant source of several bioactive trace metals as it was assumed that elements such as Fe, Mn, and Cu etc., precipitate in extensor forming poly-metallic sulfide and oxy-hydroxy sediments in the relative vicinity of the emanation site. However, recently this paradigm has been reviewed since the stabilization of dissolved Fe and Cu from hydrothermal vents was observed [1, 2] and increased concentrations of trace metals can be traced from their hydrothermal source thousands of kilometres through the ocean basins [3]. Furthermore several independent modelling attempts have shown that not only a stabilization of dissolved hydrothermal Fe and Cu is possible [4] but also that hydrothermalism must be a significant source of Fe to be able to balance the Fe-biogeochemical cycle [5]. Here we present new data that gives further evidence of the presence of copper stabilising organic and inorganic compounds in samples characterized by hydrothermal input. We can show that there are systematic differences in copper-complexing ligands at different vent sites such as 5°S on the Mid Atlantic Ridge, Brother Volcano on the Kermadec Arc, and some shallow hydrothermal CO2 seeps in the Bay of Plenty, New Zealand and the Mediterranean Sea. Quantitative and qualitative voltammetric data convincingly indicates that inorganic sulphur and organic thiols form the majority of the strong copper-complexing ligand pool in many of these hydrothermal samples. On average, the high temperature vents had a significantly higher copper binding capacity than the diffuse vents due to higher inorganic sulphur species concentrations. References: [1] Sander, S. G., et al. 2007. Organic complexation of copper in deep-sea hydrothermal vent systems. Environmental Chemistry 4: 81-89 [2] Bennett, S. A., et al. 2008. The distribution and stabilisation of dissolved Fe in deep-sea hydrothermal plumes. Earth and Planetary Science Letters 270: 157-167. [3] Wu J

  4. Effects of modified zeolite on the removal and stabilization of heavy metals in contaminated lake sediment using BCR sequential extraction.

    Science.gov (United States)

    Wen, Jia; Yi, Yuanjie; Zeng, Guangming

    2016-08-01

    Sediment can be applied on land as a soil conditioner. However, toxic substances such as heavy metals within the sediment often lead to soil contamination if no proper management is conducted prior to land application. In order to reduce the bioavailable portion of heavy metals such as Pb, Cu, Zn and Cd, zeolite as a kind of stabilizer was investigated on the effect of metal stabilization in sediment. Zeolite was firstly modified and screened to get the best condition for removal of heavy metals. Results showed that the granulated zeolite with NaCl conditioning had the highest CEC and metal sorption. Using BCR sequential extraction, the selected modified zeolite effectively stabilized Pb, Cu, Zn and Cd in sediment to different extents. It was most suitable for Cd stabilization by reducing its acid exchangeable fraction while increasing the contents of the reducible and residual fractions. Modified zeolite also immobilized Cu, Zn and Pb in sediment by enhancing one stable fraction while decreasing the acid exchangeable fraction.

  5. Scalable process for application of stabilized lithium metal powder in Li-ion batteries

    Science.gov (United States)

    Ai, Guo; Wang, Zhihui; Zhao, Hui; Mao, Wenfeng; Fu, Yanbao; Yi, Ran; Gao, Yue; Battaglia, Vincent; Wang, Donghai; Lopatin, Sergey; Liu, Gao

    2016-03-01

    A simple solution processing method is developed to achieve a uniform and scalable stabilized lithium metal powder (SLMP) coating on a Li-ion negative electrode. A solvent and binder system for the SLMP coating is developed, including the selection of solvent, polymer binder, and optimization of polymer concentration. The optimized binder solution is a 1% concentration of polymer binder in xylene; a mixture of poly(styrene-co-butadiene) rubber (SBR) and polystyrene (PS) is chosen as the polymer binder. Results show that long-sustained, uniformly dispersed SLMP suspension can be achieved with the optimized binder solution. The uniform SLMP coating can be achieved using a simple "doctor blade" coating method, and the resulting SLMP coating can be firmly glued on the anode surface. By using SLMP to prelithiate the negative electrode, improvements in electrochemical performances are demonstrated in both graphite/NMC and SiO/NMC full cells.

  6. Two-Dimensional Transition Metal Dichalcogenide Alloys: Stability and Electronic Properties.

    Science.gov (United States)

    Komsa, Hannu-Pekka; Krasheninnikov, Arkady V

    2012-12-06

    Using density-functional theory calculations, we study the stability and electronic properties of single layers of mixed transition metal dichalcogenides (TMDs), such as MoS2xSe2(1-x), which can be referred to as two-dimensional (2D) random alloys. We demonstrate that mixed MoS2/MoSe2/MoTe2 compounds are thermodynamically stable at room temperature, so that such materials can be manufactured using chemical-vapor deposition technique or exfoliated from the bulk mixed materials. By applying the effective band structure approach, we further study the electronic structure of the mixed 2D compounds and show that general features of the band structures are similar to those of their binary constituents. The direct gap in these materials can continuously be tuned, pointing toward possible applications of 2D TMD alloys in photonics.

  7. Copper benzene tricarboxylate metal-organic framework with wide permanent mesopores stabilized by Keggin polyoxometallate ions.

    Science.gov (United States)

    Wee, Lik H; Wiktor, Christian; Turner, Stuart; Vanderlinden, Willem; Janssens, Nikki; Bajpe, Sneha R; Houthoofd, Kristof; Van Tendeloo, Gustaaf; De Feyter, Steven; Kirschhock, Christine E A; Martens, Johan A

    2012-07-04

    Porous solids with organized multiple porosity are of scientific and technological importance for broadening the application range from traditional areas of catalysis and adsorption/separation to drug release and biomedical imaging. Synthesis of crystalline porous materials offering a network of uniform micro- and mesopores remains a major scientific challenge. One strategy is based on variation of synthesis parameters of microporous networks, such as, for example, zeolites or metal-organic frameworks (MOFs). Here, we show the rational development of an hierarchical variant of the microporous cubic Cu(3)(BTC)(2) (BTC = 1,3,5-benzenetricarboxylate) HKUST-1 MOF having strictly repetitive 5 nm wide mesopores separated by uniform microporous walls in a single crystal structure. This new material coined COK-15 (COK = Centrum voor Oppervlaktechemie en Katalyse) was synthesized via a dual-templating approach. Stability was enhanced by Keggin type phosphotungstate (HPW) systematically occluded in the cavities constituting the walls between the mesopores.

  8. [Comparison of fixation effects of heavy metals between cement rotary kiln co-processing and cement solidification/stabilization].

    Science.gov (United States)

    Zhang, Jun-li; Liu, Jian-guo; Li, Cheng; Jin, Yi-ying; Nie, Yong-feng

    2008-04-01

    Both cement rotary kiln co-processing hazardous wastes and cement solidification/stabilization could dispose heavy metals by fixation. Different fixation mechanisms lead to different fixation effects. The same amount of heavy metal compounds containing As, Cd, Cr, Cu, Pb, Zn were treated by the two kinds of fixation technologies. GB leaching test, TCLP tests and sequential extraction procedures were employed to compare the fixation effects of two fixation technologies. The leached concentration and chemical species distribution of heavy metals in two grounded mortar samples were analyzed and the fixation effects of two kinds of technologies to different heavy metals were compared. The results show the fixation effect of cement rotary kiln co-processing technology is better than cement solidification/stabilization technology to As, Pb, Zn. Calcinations in cement rotary kiln and then hydration help As, Pb, Zn contained in hazardous wastes transform to more steady chemical species and effectively dispose these heavy metals compounds. Cr3+ is liable to be converted to much more toxic and more mobile Cr6+ state in cement rotary kiln. And so Cr wastes are more fit for treatment by cement solidification/stabilization technology. The work could provide a basis when choosing disposal technologies for different heavy metals and be helpful to improve the application and development of cement rotary kiln co-processing hazardous wastes.

  9. Kinetic and Thermodynamic Stabilization of Metal Complexes by Introverted Coordination in a Calix[6]azacryptand.

    Science.gov (United States)

    Inthasot, Alex; Brunetti, Emilio; Lejeune, Manuel; Menard, Nicolas; Prangé, Thierry; Fusaro, Luca; Bruylants, Gilles; Reinaud, Olivia; Luhmer, Michel; Jabin, Ivan; Colasson, Benoit

    2016-03-24

    The Huisgen thermal reaction between an organic azide and an acetylene was employed for the selective monofunctionalization of a X6 -azacryptand ligand bearing a tren coordinating unit [X6 stands for calix[6]arene and tren for tris(2-aminoethyl)amine]. Supramolecular assistance, originating from the formation of a host-guest inclusion complex between the reactants, greatly accelerates the reaction while self-inhibition affords a remarkable selectivity. The new ligand possesses a single amino-leg appended at the large rim of the calixarene core and the corresponding Zn(2+) complex was characterized both in solution and in the solid state. The coordination of Zn(2+) not only involves the tren cap but also the introverted amino-leg, which locks the metal ion in the cavity. Compared with the parent ligand deprived of the amino-leg, the affinity of the new monofunctionalized X6 tren ligand 6 for Zn(2+) is found to have a 10-fold increase in DMSO, which is a very competitive solvent, and with an enhancement of at least three orders of magnitude in CDCl3 /CD3 OD (1:1, v/v). In strong contrast with the fast binding kinetics, decoordination of Zn(2+) as well as transmetallation appeared to be very slow processes. The monofunctionalized X6 tren ligand 6 fully protects the metal ion from the external medium thanks to the combination of a cavity and a closed coordination sphere, leading to greater thermodynamic and kinetic stabilities.

  10. Surface half-metallicity and stability of zinc-blende sodium monoselenide

    Science.gov (United States)

    Tabatabaeifar, A.; Davatolhagh, S.; Moradi, M.

    2017-02-01

    The electronic structure and magnetic properties of relaxed (001) surfaces of the sp-electron half-metallic ferromagnet NaSe in the zinc-blende phase, are calculated on the basis of first principle density functional theory within the framework of self-consistent field plane wave pseudo-potential method, using the generalized gradient approximation for the exchange-correlation functional. The results of this study reveal that both Na- and Se-terminated surfaces retain the robust bulk half-metallic property. The negative value found for the bulk formation energy indicates that this material is stable against phase separation. We also obtain the surface energies and discuss their stability via the calculated bulk formation energy. The Curie temperature is estimated to be 920 K within mean field approximation, which is well above the room temperature. In the light of the above, zinc-blende NaSe appears to be a good candidate for spintronic applications as spin injection material.

  11. Synthesis and shapes of gold nanoparticles by using transition metal monosubstituted heteropolyanions as photocatalysts and stabilizers

    Institute of Scientific and Technical Information of China (English)

    Caihong NIU; Ying WU; Zhenping WANG; Zheng LI; Rong LI

    2009-01-01

    Gold nanoparticles were prepared via a simple photoreduction technique in the presence of transition metal monosubstituted Keggin heteropolyanions (PW11M, M= Cu2+, Ni2+, Zn2+, Fe3+), in which PWllM acted as reducing agent, photocatalyst and stabilizer. The results indicated that the formation rate and morphology of the nanoparticles strongly depended on the kind of transition metal substituted in heteropolyacid and the preparation conditions, such as irradiation time and propan-2-ol amount. The photoreduction rates of PWllZn and PWllFe were faster than those of PWllNi and PW 11 Cu. The shapes of the nanoparticles synthesized in the presence of PWllFe and PWllZn were nearlyuniform spheres, whereas the morphologies of the nanoparticles synthesized in the presence of PW11Ni and PW11Cu were found to contain a mixture of flat triangular/ hexagonal structures as well as spheres. Increases in the irradiation time and the propan-2-ol amount could make the morphology of nanoparticles uniform and shorten the formation time of the nanoparticles.

  12. First-principles study on structural stability of 3d transition metal alloying magnesium hydride

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A first-principles plane-wave pseudopotential method based on the density functional theory was used to investigate the energy and electronic structure of magnesium hydride (MgH2) alloyed by 3d transition metal elements. Through calculations of the negative heat formation of magnesium hydride alloyed by X (X denotes 3d transition metal) element, it is found that when a little X (not including Sc) dissolves into magnesium hydride, the structural stability of alloying systems decreases, which indicates that the dehydrogenation properties of MgH2 can be improved. After comparing the densities of states(DOS) and the charge distribution of MgH2 with or without X alloying, it is found that the improvement for the dehydrogenation properties of MgH2 alloyed by X attributes to the fact that the weakened bonding between magnesium and hydrogen is caused by the stronger interactions between X (not including Cu) and hydrogen. The calculation results of the improvement for the dehydrogenation properties of MgH2-X (X=Ti, V, Mn, Fe, Co,Ni, Cu) systems are in agreement with the experimental results. Hence, the dehydrogenation properties of MgH2 are expected to be improved by addition of Cr, Zn alloying elements.

  13. Titanium boride equation of state determined by in-situ X-ray diffraction

    OpenAIRE

    Shigeaki Ono; Takumi Kikegawa

    2016-01-01

    The equation of state (EOS) of titanium boride, TiB2, was investigated by in situ X-ray diffraction in a diamond anvil cell and multianvil high-pressure apparatus. The pressure-volume-temperature (P-V-T) data were collected at up to 111 GPa and room temperature for the diamond-anvil cell experiments and at up to 15 GPa and 1300 K for the multianvil experiments. No phase transition was observed through the entire range of experimental conditions. The pressure-volume data at room temperature we...

  14. Hydrogen segregation and its roles in structural stability and metallization: silane under pressure

    Science.gov (United States)

    Cui, Wenwen; Shi, Jingming; Liu, Hanyu; Yao, Yansun; Wang, Hui; Iitaka, Toshiaki; Ma, Yanming

    2015-08-01

    We present results from first-principles calculations on silane (SiH4) under pressure. We find that a three dimensional P-3 structure becomes the most stable phase above 241 GPa. A prominent structural feature, which separates the P-3 structure from previously observed/predicted SiH4 structures, is that a fraction of hydrogen leaves the Si-H bonding environment and forms segregated H2 units. The H2 units are sparsely populated in the system and intercalated with a polymeric Si-H framework. Calculations of enthalpy of formation suggest that the P-3 structure is against the decomposition into Si-H binaries and/or the elemental crystals. Structural stability of the P-3 structure is attributed to the electron-deficient multicenter Si-H-Si interactions when neighboring silicon atoms are linked together through a common hydrogen atom. Within the multicenter bonds, electrons are delocalized and this leads to a metallic state, possibly also a superconducting state, for SiH4. An interesting outcome of the present study is that the enthalpy sum of SiH4 (P-3 structure) and Si (fcc structure) appears to be lower than the enthalpy of disilane (Si2H6) between 200 and 300 GPa (for all previously predicted crystalline forms of Si2H6), which calls for a revisit of the stability of Si2H6 under high pressure.

  15. Recovery and stabilization of heavy metal sludge (Cu and Ni) from etching and electroplating plants by electrolysis and sintering

    Institute of Scientific and Technical Information of China (English)

    TSAI; LungChang; TSAI; FangChang

    2009-01-01

    This work dealt with the recovery and stabilization of the sludge with heavy metals (Cu and Ni) produced from etching and electroplating plants. The heavy metals in the sludge were deprived of by acid leaching, followed by precipitation with 28% NH4OH, and finally by electrolysis. In the electrolysis, the recovery percentage and purity were investigated at different electronic currency and temperature. The metal-deprived sludge was stabilized by mixing with glass powder and clay, followed by sintering at high temperature. How the ratio of glass powder to metal-deprived sludge affected final products (sludge bricks) was explored, in terms of specific gravity, absorption capacity, unconfined compressive strength, morphology, the volume shrinkage ratio and burn-up ratio. The volume shrinkage ratio and burn-up ratio of sludge bricks increased with metal-deprived sludge contents. The heavy metal remaining in sludge bricks was assessed through TCLP (toxicity characteristic leaching procedure) and by the analysis of SEM and EDX. The results from TCLP showed that the contents of leached metals were all below the regulatory criteria. This fact approved the feasibility of our method.

  16. Recovery and stabilization of heavy metal sludge (Cu and Ni) from etching and electroplating plants by electrolysis and sintering

    Institute of Scientific and Technical Information of China (English)

    TSAI LungChang; FANG HungYuan; LIN JianHung; CHEN ChingLiang; TSAI FangChang

    2009-01-01

    This work dealt with the recovery and stabilization of the sludge with heavy metals (Cu and Ni) pro-duced from etching and electroplating plants. The heavy metals in the sludge were deprived of by acid leaching, followed by precipitation with 28% NH4OH, and finally by electrolysis. In the electrolysis, the recovery percentage and purity were investigated at different electronic currency and temperature. The metal-deprived sludge was stabilized by mixing with glass powder and clay, followed by sintering at high temperature. How the ratio of glass powder to metal-deprived sludge affected final products (sludge bricks) was explored, in terms of specific gravity, absorption capacity, unconfined compressive strength, morphology, the volume shrinkage ratio and burn-up ratio. The volume shrinkage ratio and burn-up ratio of sludge bricks increased with metal-deprived sludge contents. The heavy metal re-maining in sludge bricks was assessed through TCLP (toxicity characteristic leaching procedure) and by the analysis of SEM and EDX. The results from TCLP showed that the contents of leached metals were all below the regulatory criteria. This fact approved the feasibility of our method.

  17. Crystal structures and compressibility of novel iron borides Fe{sub 2}B{sub 7} and Fe{sub x}B{sub 50} synthesized at high pressure and high temperature

    Energy Technology Data Exchange (ETDEWEB)

    Bykova, E., E-mail: elena.bykova@uni-bayreuth.de [Bavarian Research Institute of Experimental Geochemistry and Geophysics, University of Bayreuth, D-95440 Bayreuth (Germany); Laboratory of Crystallography, University of Bayreuth, D-95440 Bayreuth (Germany); Gou, H.; Bykov, M. [Laboratory of Crystallography, University of Bayreuth, D-95440 Bayreuth (Germany); Hanfland, M. [European Synchrotron Radiation Facility, BP 220, Grenoble F-38043 (France); Dubrovinsky, L. [Bavarian Research Institute of Experimental Geochemistry and Geophysics, University of Bayreuth, D-95440 Bayreuth (Germany); Dubrovinskaia, N. [Laboratory of Crystallography, University of Bayreuth, D-95440 Bayreuth (Germany)

    2015-10-15

    We present here a detailed description of the crystal structures of novel iron borides, Fe{sub 2}B{sub 7} and Fe{sub x}B{sub 50} with various iron content (x=1.01(1), 1.04(1), 1.32(1)), synthesized at high pressures and high temperatures. As revealed by high-pressure single-crystal X-ray diffraction, the structure of Fe{sub 2}B{sub 7} possesses short incompressible B–B bonds, which make it as stiff as diamond in one crystallographic direction. The volume compressibility of Fe{sub 2}B{sub 7} (the bulk modulus K{sub 0}= 259(1.8) GPa, K{sub 0}′= 4 (fixed)) is even lower than that of FeB{sub 4} and comparable with that of MnB{sub 4}, known for high bulk moduli among 3d metal borides. Fe{sub x}B{sub 50} adopts the structure of the tetragonal δ-B, in which Fe atoms occupy an interstitial position. Fe{sub x}B{sub 50} does not show considerable anisotropy in the elastic behavior. - Graphical abstract: Crystal structures of novel iron borides, Fe{sub 2}B{sub 7} and Fe{sub x}B{sub 50} (x=1.01(1), 1.04(1), 1.32(1)). - Highlights: • Novel iron borides, Fe{sub 2}B{sub 7} and Fe{sub x}B{sub 50}, were synthesized under HPHT conditions. • Fe{sub 2}B{sub 7} has a unique orthorhombic structure (space group Pbam). • Fe{sub 2}B{sub 7} possesses short incompressible B–B bonds that results in high bulk modulus. • Fe{sub x}B{sub 50} adopts the structure of the tetragonal δ-B composed of B{sub 12} icosahedra. • In Fe{sub x}B{sub 50} intraicosahedral bonds are stiffer than intericosahedral ones.

  18. Rare earth boride electron emitter materials fabrication and evaluation

    Science.gov (United States)

    Swanson, L. W.; Davis, P. R.; Gesley, M. A.

    1982-03-01

    Techniques were developed for routine preparation of single crystal rods of LaB6, CeB6 and PrB6 by arc float zone refining. Single crystal, oriented samples were prepared from these rods and mounted as cathodes for testing. Several mounting systems were used, and flat, pointed cone and truncated cone thermionic cathodes were studied. Pointed field emitters of LaB6(100) were also investigated. Variation of thermionic emitted current density and thermal stability of materials were studied as functions of rare earth element, bulk stoichiometry and crystal orientation. Life tests were performed on several different LaB6(100) cathodes. One such cathode operated for over 3000 hours at approximately 10 A/sq cm emitted current density with no serious physical degradation. Surface properties of the materials were investigated by various surface analysis techniques.

  19. Mononuclear Clusterfullerene Single-Molecule Magnet Containing Strained Fused-Pentagons Stabilized by a Nearly Linear Metal Cyanide Cluster

    DEFF Research Database (Denmark)

    Liu, Fupin; Wang, Song; Gao, Cong Li

    2017-01-01

    Fused-pentagons results in an increase of local steric strain according to the isolated pentagon rule (IPR), and for all reported non-IPR clusterfullerenes multiple (two or three) metals are required to stabilize the strained fused-pentagons, making it difficult to access the single-atom properti...

  20. A new strategy to stabilize oxytocin in aqueous solutions: I. The effects of divalent metal ions and citrate buffer

    National Research Council Canada - National Science Library

    Avanti, Christina; Amorij, Jean-Pierre; Setyaningsih, Dewi; Hawe, Anea; Jiskoot, Wim; Visser, Jan; Keov, Alexej; essen, Arnold J. M; Hinrichs, Wouter L. J; Frijlink, Henderik W

    2011-01-01

    ... (Ca2+, Mg2+, and Zn2+) were tested all as chloride salts. The effect of combinations of buffers and metal ions on the stability of aqueous oxytocin solutions was determined by RP-HPLC and HP-SEC after 4 weeks of storage at either 4°C or 55°C...

  1. Mononuclear Clusterfullerene Single-Molecule Magnet Containing Strained Fused-Pentagons Stabilized by a Nearly Linear Metal Cyanide Cluster

    DEFF Research Database (Denmark)

    Liu, Fupin; Wang, Song; Gao, Cong Li

    2017-01-01

    Fused-pentagons results in an increase of local steric strain according to the isolated pentagon rule (IPR), and for all reported non-IPR clusterfullerenes multiple (two or three) metals are required to stabilize the strained fused-pentagons, making it difficult to access the single-atom properti...... (SMM)....

  2. Hydrogen-incorporation stabilization of metallic VO2(R) phase to room temperature, displaying promising low-temperature thermoelectric effect.

    Science.gov (United States)

    Wu, Changzheng; Feng, Feng; Feng, Jun; Dai, Jun; Peng, Lele; Zhao, Jiyin; Yang, Jinlong; Si, Cheng; Wu, Ziyu; Xie, Yi

    2011-09-07

    Regulation of electron-electron correlation has been found to be a new effective way to selectively control carrier concentration, which is a crucial step toward improving thermoelectric properties. The pure electronic behavior successfully stabilized the nonambient metallic VO(2)(R) to room temperature, giving excellent thermoelectric performance among the simple oxides with wider working temperature ranges.

  3. A Highly Energetic N-Rich Zeolite-Like Metal-Organic Framework with Excellent Air Stability and Insensitivity.

    Science.gov (United States)

    Qin, Jun-Sheng; Zhang, Ji-Chuan; Zhang, Min; Du, Dong-Ying; Li, Jing; Su, Zhong-Min; Wang, Yuan-Yuan; Pang, Si-Ping; Li, Sheng-Hua; Lan, Ya-Qian

    2015-12-01

    A stable N-rich aromatic ligand is employed to prepare energetic zeolite-like metal-organic frameworks. IFMC-1 shows excellent air stability, and the lowest sensitivity toward impact, friction, and electrostatic discharge and the highest predicted heat of detonation among the reported coordination polymers, and even commercial materials (such as trinitrotoluene (TNT)).

  4. Effects of carbon on the stability and chemical performance of transition metal carbides: A density functional study

    Science.gov (United States)

    Liu, Ping; Rodriguez, José A.

    2004-03-01

    Density functional theory was employed to study the stabilities and chemical activities of transition metal carbides. Here we take the well-known Mo carbides and Ti carbides as an example. Different kinds of structures including the bulk surfaces [Mo2C(001), MoC(001), and TiC(001)] and metcars [Mo8C12 and Ti8C12] are taken into consideration. Systematic studies show that by raising the C coordination number of the metal atoms in the carbides, in general the stability of the carbides increases (metcars are an exception since they include both high-coordinated and low-coordinated metal atoms.); at the same time, the chemical activities of the carbides decrease due to a downshift of the metal d-band center (ligand effect). Considering the better catalysts those that combine high stability and moderate chemical activity, our results suggest that the catalytic potential of Mo carbide systems should decrease in the following sequence: Mo8C12>Mo2C(001) or MoC(001)>pure Mo(110). In spite of having the largest C/Mo ratio, the metcar appears as the most attractive system. Our studies also indicate that the "magic" behavior of metcars is not unique for Mo carbides. Similar behavior is also observed for Ti carbides. This implies that nanoparticles like metcar species could exhibit better performances than the corresponding bulk metal carbides as catalysts.

  5. Bio-oil Stabilization by Hydrogenation over Reduced Metal Catalysts at Low Temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Huamin; Lee, Suh-Jane; Olarte, Mariefel V.; Zacher, Alan H.

    2016-08-30

    Biomass fast pyrolysis integrated with bio-oil upgrading represents a very attractive approach for converting biomass to hydrocarbon transportation fuels. However, the thermal and chemical instability of bio-oils presents significant problems when they are being upgraded, and development of effective approaches for stabilizing bio-oils is critical to the success of the technology. Catalytic hydrogenation to remove reactive species in bio-oil has been considered as one of the most efficient ways to stabilize bio-oil. This paper provides a fundamental understanding of hydrogenation of actual bio-oils over a Ru/TiO2 catalyst under conditions relevant to practical bio-oil hydrotreating processes. Bio-oil feed stocks, bio-oils hydrogenated to different extents, and catalysts have been characterized to provide insights into the chemical and physical properties of these samples and to understand the correlation of the properties with the composition of the bio-oil and catalysts. The results indicated hydrogenation of various components of the bio-oil, including sugars, aldehydes, ketones, alkenes, aromatics, and carboxylic acids, over the Ru/TiO2 catalyst and 120 to 160oC. Hydrogenation of these species significantly changed the chemical and physical properties of the bio-oil and overall improved its thermal stability, especially by reducing the carbonyl content, which represented the content of the most reactive species (i.e., sugar, aldehydes, and ketones). The change of content of each component in response to increasing hydrogen additions suggests the following bio-oil hydrogenation reaction sequence: sugar conversion to sugar alcohols, followed by ketone and aldehyde conversion to alcohols, followed by alkene and aromatic hydrogenation, and then followed by carboxylic acid hydrogenation to alcohols. Hydrogenation of bio-oil samples with different sulfur contents or inorganic material contents suggested that sulfur poisoning of the reduced Ru metal catalysts was

  6. THERMAL STABILITY OF METAL-PITCH DEPOSITS FROM A SPRUCE THERMOMECHANICAL PULP BY USE OF A DIFFERENTIAL SCANNING CALORIMETER

    Directory of Open Access Journals (Sweden)

    Yonghao Ni

    2010-07-01

    Full Text Available Pitch-related deposition has been a significant issue in paper mills that produce wood-containing paper grades. A component analysis showed that a mill deposit sample was a mixture of wood resin, fiber, metal cations, and other inorganics. Based on the differential scanning calorimeter (DSC method, some critical parameters, including pH, metal cations, and their interactions, on the thermal stability of pitch-related deposits were studied. The valency of metal cations determined the ability of capturing pitch the formation of deposits. Trivalent Al3+ or Fe3+ ions had much stronger effects than divalent Ca2+, Mg2+, or Mn2+. It was also found that a higher pH and trivalent Al3+ or Fe3+ increased the thermal stability of deposits formed in colloidal pitch solutions.

  7. Novel borothermal process for the synthesis of nanocrystalline oxides and borides of niobium.

    Science.gov (United States)

    Jha, Menaka; Ramanujachary, Kandalam V; Lofland, Samuel E; Gupta, Govind; Ganguli, Ashok K

    2011-08-21

    A new process has been developed for the synthesis of nanocrystalline niobium oxide and niobium diboride using an amorphous niobium precursor obtained via the solvothermal route. On varying the ratio of niobium precursor to boron and the reaction conditions, pure phases of nanostructured niobium oxides (Nb(2)O(5), NbO(2)), niobium diboride (NbB(2)) and core-shell nanostructures of NbB(2)@Nb(2)O(5) could be obtained at normal pressure and low temperature of 1300 °C compared to a temperature of 1650 °C normally used. The above borothermal process involves the in situ generation of B(2)O(2) to yield either oxide or diboride. The niobium oxides and borides have been characterized in detail by XRD, HRTEM and EDX studies. The core-shell structure has been investigated by XPS depth profiling, EFTEM and EELS (especially to characterize the presence of boron and the shell thickness). The niobium diboride nanorods (with high aspect ratio) show a superconducting transition with the T(c) of 6.4 K. In the core-shell of NbB(2)@Nb(2)O(5), the superconductivity of NbB(2) is masked by the niobium oxide shell and hence no superconductivity was observed. The above methodology has the benefits of realizing both oxides and borides of niobium in nanocrystalline form, in high purity and at much lower temperatures.

  8. Phase Evolution in Boride-Based Cermets and Reaction Bonding onto Plain Low Carbon Steel Substrate

    Science.gov (United States)

    Palanisamy, B.; Upadhyaya, A.

    2012-04-01

    Reaction sinter bonding is a process that aims to bond two materials for improvement in properties through reactive sintering technique. The process has been effectively used to sinter hard materials like borides in situ which not only possess excellent oxidation resistance, good corrosion resistance but also resistant to abrasive wear. Sinter bonding is a unique surface modification process achieved through powder metallurgy and is competent with other techniques like boronizing sintering and sinter-brazing since it eliminates the additional operations of heat treatment and assembly and removes the inherent setbacks with these processes. This study focuses on identifying the phase evolution mechanism using characterization tools like x-ray diffractometry and energy dispersive spectroscopy and study of sinter bonding of the boron containing precursors (Mo-Cr-Fe-Ni-FeB-MoB) onto plain carbon steel. A microstructure containing Fe-based matrix dispersed with complex borides develops with temperature in the tape cast sheets. A fivefold increase in hardness between plain carbon steel in wrought condition and sinter bonded steel was observed. The multilayer consisted of a reaction zone adjacent to the interface and was investigated with the composition profile and hardness measurements. A model of sinter bonding between the cermet and the steel has also been proposed.

  9. Role of Metal Oxide Electron-Transport Layer Modification on the Stability of High Performing Perovskite Solar Cells.

    Science.gov (United States)

    Singh, Trilok; Singh, Jai; Miyasaka, Tsutomu

    2016-09-22

    Organic-inorganic hybrid perovskite light absorbers have recently emerged as a "holy grail" for next generation thin-film photovoltaics with excellent optoelectronics properties and low fabrication cost. In a very short span of time, we have witnessed a pronounced and unexpected progress in organic- inorganic perovskite solar cells (PSCs) with a vertical rise in power conversion efficiency from 3.8 to 22.1 %. In this manuscript we focus specifically on the recent development of metal oxide-based electron-transporting layer (ETL) modification for high performing PSCs and their stability. This review highlights various methodologies to modify existing compact/scaffold layers for improving device performance and stability. Various aspects of the ETL are discussed with different metal oxide compact layers in their relation to modification in mesoporous layers towards the design of a cell structure with high performance and stability.

  10. Formation, stability, and solubility of metal oxide nanoparticles: Surface entropy, enthalpy, and free energy of ferrihydrite

    Science.gov (United States)

    Hiemstra, Tjisse

    2015-06-01

    -line Fh, log Kso ∼ -39.5 ± 0.1. The smallest Fh particles in a suspension react according to the Ostwald-Freundlich equation (RTΔlnKso = 2/3 γA), but the suspension as a whole apparently reacts according to the Ostwald equation (RTΔlnKso = γA). This difference can be explained by the observed linear relation between the minimum (dmin) and mean (dmean) particle size (dmin = 2/3 dmean) in Fh suspensions. With best estimates for the surface entropy of goethite, hematite, and lepidocrocite, predictions show that Fh becomes thermodynamically unstable above a diameter of ∼8.0 nm at 298 K, allowing formation of nano-goethite and nano-hematite, as experienced experimentally at Ostwald ripening. More generally, one observes that metal (hydr) oxides with the highest chemical stability also have the highest mean surface Gibbs free energy, which can be considered as the scientific explanation of the empirical rule of Ostwald-Lussac. In addition, it is shown that the surface Gibbs free energies of metal (hydr) oxides increase with the mean metal coordination number of oxygen in the lattices following the order: oxides > oxyhydroxides > hydroxides.

  11. Membrane filtration studies of aquatic humic substances and their metal species: a concise overview. Part 2. Evaluation of conditional stability constants by using ultrafiltration.

    Science.gov (United States)

    Nifant'eva, T I; Shkinev, V M; Spivakov, B Y; Burba, P

    1999-02-01

    The assessment of conditional stability constants of aquatic humic substance (HS) metal complexes is overviewed with special emphasis on the application of ultrafiltration methods. Fundamentals and limitations of stability functions in the case of macromolecular and polydisperse metal-HS species in aquatic environments are critically discussed. The review summarizes the advantages and application of ultrafiltration for metal-HS complexation studies, discusses the comparibility and reliability of stability constants. The potential of ultrafiltration procedures for characterizing the lability of metal-HS species is also stressed.

  12. Ammine-Stabilized Transition-Metal Borohydrides of Iron, Cobalt, and Chromium: Synthesis and Characterization.

    Science.gov (United States)

    Roedern, Elsa; Jensen, Torben R

    2015-11-02

    Iron and cobalt borohydrides stabilized by ammonia (NH3), [Fe(NH3)6](BH4)2 and [Co(NH3)6](BH4)2, were synthesized along with a solid solution, [Co(NH3)6](BH4)(2-x)Cl(x) (x ∼ 1), and a bimetallic compound, [Fe(NH3)6](Li2(BH4)4). The compounds were prepared by new low-temperature, solvent-based synthesis methods, using dimethyl sulfide or liquid NH3, which allow for the removal of inert metal halides. The crystal structures were determined from synchrotron radiation powder X-ray diffraction (SR-PXD) data. [M(NH3)6](BH4)2 (M = Fe, Co) and [Co(NH3)6](BH4)(2-x)Cl(x) crystallize in the cubic crystal system, where the transition metals are octahedrally coordinated by NH3. Polymeric chains of lithium coordinated by four bridging BH4(-) anions are found in [Fe(NH3)6](Li2(BH4)4). The new compounds have high hydrogen densities of ∼14 wt % H2 and ∼140 g H2/L and release a mixture of hydrogen and NH3 gas at low temperatures, T < 80 °C. The decomposition mechanisms of the prepared compounds along with the composites [Fe(NH3)6](BH4)2·nNH3BH3 (n = 2, 4, 6) were studied by thermal analysis and in situ SR-PXD.

  13. Enhanced biological stabilization of heavy metals in sediment using immobilized sulfate reducing bacteria beads with inner cohesive nutrient

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xin, E-mail: hgxlixin@hnu.edu.cn [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082 (China); Dai, Lihua; Zhang, Chang; Zeng, Guangming; Liu, Yunguo [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082 (China); Zhou, Chen [Swette Center for Environmental Biotechnology, Biodesign Institute, Arizona State University (United States); Xu, Weihua; Wu, Youe; Tang, Xinquan; Liu, Wei; Lan, Shiming [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082 (China)

    2017-02-15

    Highlights: • Nutrient beads of immobilized SRB were more effective in transforming heavy metals into the more stable bound phases. • Inner cohesive nutrient effectively promoted the stabilization process of heavy metals. • The excellent removal efficiencies of Cu, Zn, Pb and Cd were 76.3%, 95.6%, 100% and 91.2%, respectively. • Easy to recycle and avoid secondary pollution. - Abstract: A series of experiments were conducted for treating heavy metals contaminated sediments sampled from Xiangjiang River, which combined polyvinyl alcohol (PVA) and immobilized sulfate reducing bacteria (SRB) into beads. The sodium lactate was served as the inner cohesive nutrient. Coupling the activity of the SRB with PVA, along with the porous structure and huge specific surface area, provided a convenient channel for the transmission of matter and protected the cells against the toxicity of metals. This paper systematically investigated the stability of Cu, Zn, Pb and Cd and its mechanisms. The results revealed the performance of leaching toxicity was lower and the removal efficiencies of Cu, Zn, Pb and Cd were 76.3%, 95.6%, 100% and 91.2%, respectively. Recycling experiments showed the beads could be reused 5 times with superbly efficiency. These results were also confirmed by continuous extraction at the optimal conditions. Furthermore, X-ray diffraction (XRD) and energy-dispersive spectra (EDS) analysis indicated the heavy metals could be transformed into stable crystal texture. The stabilization of heavy metals was attributed to the carbonyl and acyl amino groups. Results presented that immobilized bacteria with inner nutrient were potentially and practically applied to multi-heavy-metal-contamination sediment.

  14. Optimized synthesis and crystalline stability of γ-cyclodextrin metal-organic frameworks for drug adsorption.

    Science.gov (United States)

    Liu, Botao; Li, Haiyan; Xu, Xiaonan; Li, Xue; Lv, Nana; Singh, Vikramjeet; Stoddart, J Fraser; York, Peter; Xu, Xu; Gref, Ruxandra; Zhang, Jiwen

    2016-11-30

    The biocompatible and renewable cyclodextrin metal-organic frameworks (CD-MOFs) have addressed a range of opportunities in molecular storage and separation sciences. The reported protocols for their synthesis, however, were carried out at room temperature over long time periods of time (24h), producing crystals of relatively poor uniformity. In this investigation, micron sized γ-CD-MOFs were synthesized by an optimized vapor diffusion method at elevated temperature (50°C) within 6h, after which the size control, crystalline stability and drug adsorption behavior were investigated in detail. In this manner, uniform cubic γ-CD-MOF crystals were obtained when the reaction temperature was raised to 50°C with pre-addition of the reaction solvent. The size of γ-CD-MOFs was adjusted efficiently by changing the reactant concentrations, temperatures, time, γ-CD ratios to KOH and surfactant concentrations, without influencing the porosity and crystallinity of the material markedly. Varing degrees of reduction in crystallinity and change in morphology were observed when the γ-CD-MOF crystals are treated under conditions of high temperature (100°C), high humidity (92.5%) and polar solvents (e.g., MeOH and DMF). In relation to drug adsorption by γ-CD-MOFs, most of the drug molecules containing carboxyl groups showed relatively high adsorption (>5%), while low adsorption (synthesis and size control of γ-CD-MOFs, the crystalline stability and drug adsorption characteristics of γ-CD-MOF crystals have been evaluated as a fundamental requirement of a potential vehicle for drug delivery.

  15. Pulsed nanocrystalline plasma electrolytic boriding as a novel method for corrosion protection of CP-Ti (Part 1: Different frequency and duty cycle)

    Indian Academy of Sciences (India)

    M Kh Aliev; A Saboor

    2007-12-01

    Potentiodynamic polarization and electrochemical impedance spectroscopy were employed to test borided CP-Ti, treated by a relatively new method called pulsed plasma electrolytic boriding. The results show excellent corrosion resistance for modified CP-Ti. The effect of frequency and duty cycle of pulsed current was investigated. It was found that pulse frequency and duty cycle affect the size and porosity of nanocrystalline borides and by controlling these effective parameters, surface modification can render the CP-Ti material extremely corrosion resistant as a biomaterial.

  16. Direct Measurement of the Nanomechanical Stability of a Redox Protein Active Site and Its Dependence upon Metal Binding.

    Science.gov (United States)

    Giannotti, Marina I; Cabeza de Vaca, Israel; Artés, Juan M; Sanz, Fausto; Guallar, Victor; Gorostiza, Pau

    2015-09-10

    The structural basis of the low reorganization energy of cupredoxins has long been debated. These proteins reconcile a conformationally heterogeneous and exposed metal-chelating site with the highly rigid copper center required for efficient electron transfer. Here we combine single-molecule mechanical unfolding experiments with statistical analysis and computer simulations to show that the metal-binding region of apo-azurin is mechanically flexible and that high mechanical stability is imparted by copper binding. The unfolding pathway of the metal site depends on the pulling residue and suggests that partial unfolding of the metal-binding site could be facilitated by the physical interaction with certain regions of the redox protein.

  17. Functionalization of Metal-Organic Frameworks for Enhanced Stability under Humid Carbon Dioxide Capture Conditions.

    Science.gov (United States)

    Andirova, Dinara; Lei, Yu; Zhao, Xiaodan; Choi, Sunho

    2015-10-26

    Metal-organic frameworks (MOFs) have been highlighted recently as promising materials for CO2 capture. However, in practical CO2 capture processes, such as capture from flue gas or ambient air, the adsorption properties of MOFs tend to be harmed by the presence of moisture possibly because of the hydrophilic nature of the coordinatively unsaturated sites (CUSs) within their framework. In this work, the CUSs of the MOF framework are functionalized with amine-containing molecules to prevent structural degradation in a humid environment. Specifically, the framework of the magnesium dioxybenzenedicarboxylate (Mg/DOBDC) MOF was functionalized with ethylenediamine (ED) molecules to make the overall structure less hydrophilic. Structural analysis after exposure to high-temperature steam showed that the ED-functionalized Mg/DOBDC (ED-Mg/DOBDC) is more stable under humid conditions, than Mg/DOBDC, which underwent drastic structural changes. ED-Mg/DOBDC recovered its CO2 adsorption capacity and initial adsorption rate quite well as opposed to the original Mg/DOBDC, which revealed a significant reduction in its capture capacity and kinetics. These results suggest that the amine-functionalization of the CUSs is an effective way to enhance the structural stability of MOFs as well as their capture of humid CO2 .

  18. Numerical Modeling of the Stability of Face-Centered Cubic Metals with High Vacancy Concentration

    Energy Technology Data Exchange (ETDEWEB)

    Brian P. Somerday; M. I. Baskes

    1998-12-01

    The objective of this research is to assess the possibility of forming an atomically porous structure in a low-density metal, e.g., Al with vacancies up to 0.20/lattice site; and to examine the effects of hydrogen and vacancy concentration on the stability of an atomically porous structure that has been experimentally produced in nickel. The approach involves numerical modeling using the Embedded-Atom Method (EAM). High vacancy concentrations cause the Al lattice to disorder at 300K. In contrast, Ni retains the face-centered-cubic structure at 300K for vacancy concentrations up to 0.15 Vac/lattice site. Unexpectedly, the lattice with 0.15 Vac/lattice site is more stable than the lattice with 0.10 or 0.20 Vac/lattice site. The Ni systems with 0.10 and 0.15 Vac/lattice site exhibit domains consisting of uniform lattice rotations. The Ni lattice with 0.15 Vac/lattice site is more stable with an initial distribution of random vacancies compared to ordered vacancies. The equilibrium lattice structures of Ni a d Al containing vacancies and H are less ordered to structures with vacancies only at 300K.

  19. Relative edge energy in the stability of transition metal nanoclusters of different motifs.

    Science.gov (United States)

    Zhao, X J; Xue, X L; Guo, Z X; Li, S F

    2016-07-07

    When a structure is reduced to a nanometer scale, the proportion of the edge atoms increases significantly, which can play a crucial role in determining both their geometric and electronic properties, as demonstrated by the recently established generalized Wulff construction principle [S. F. Li, et al., Phys. Rev. Lett., 2013, 111, 115501]. Consequently, it is of great interest to clarify quantitatively the role of the edge atoms that dominate the motifs of these nanostructures. In principle, establishing an effective method valid for determining the absolute value of the surface energy and particularly the edge energy for a given nanostructure is expected to resolve such a problem. However, hitherto, it is difficult to obtain the absolute edge energy of transition metal clusters, particularly when their sizes approach the nanometer regime. In this paper, taking Ru nanoclusters as a prototypical example, our first-principles calculations introduce the concept of relative edge energy (REE), reflecting the net edge atom effect over the surface (facet) atom effect, which is fairly powerful to quasi-quantitatively estimate the critical size at which the crossover occurs between different configurations of a given motif, such as from an icosahedron to an fcc nanocrystal. By contrast, the bulk effect should be re-considered to rationalize the power of the REE in predicting the relative stability of larger nanostructures between different motifs, such as fcc-like and hcp-like nanocrystals.

  20. Facile synthesis of glucoamylase embedded metal-organic frameworks (glucoamylase-MOF) with enhanced stability.

    Science.gov (United States)

    Nadar, Shamraja S; Rathod, Virendra K

    2017-02-01

    The self-assembled glucoamylase metal-organic framework (glucoamylase-MOF) was synthesized by facile one-step method within 20min by simply mixing aqueous solution of 2-methylimidazole (160mM), glucoamylase (5mg/mL) and zinc acetate (40mM) at room temperature (28±2°C). The prepared glucoamylase-MOF was characterized by using FT-IR, confocal scanning laser microscopy, XRD and SEM. The robustness and thermal stability of glucoamylase embedded MOF was evaluated in terms of half-life (in the range of 60-80°C) which showed 6 folds increment as against free form. Further, in Michaelis-Menten kinetics studies, glucoamylase entrapped MOF exhibited higher Km value and lower Vmax value as compared to native enzyme. Moreover, the immobilized glucoamylase exhibited up to 57% of residual activity after six consecutive cycles of reuse, whereas it retained 91% of residual activity till 25days of storage. Finally, the conformational changes occurred after the encapsulation of glucoamylase in the interior of MOF, which was analyzed by using FT-IR data analysis tools.

  1. Thermoelastic Stability Analysis of Solidification of Pure Metals on a Coated Planar Mold of Finite Thickness

    Science.gov (United States)

    Demir, Mehmet Hakan; Yigit, Faruk

    2016-12-01

    A theoretical model for investigating the thermoelastic instability/mechanism during pure metal solidification on a coated mold of finite thickness is developed. This study extends the previous theoretical works on growth instability during solidification process by investigating the effects of an added coating layer. Mold coating is one of the most important factors controlling the heat transfer rate, and hence it has a very important role on the solidification rate and the development of microstructure. In this model, thermal and mechanical problems are coupled through the pressure-dependent contact resistances at mold/coating and coating/shell interfaces. The thermal diffusivities of solidified shell, coating, and mold materials are assumed to be zero. This assumption provides us to solve heat transfer problem analytically. A linear perturbation method is used to simplify complexity of the modeled solidification problem, and governing equations are solved numerically using a variable step variable order predictor-corrector algorithm. The effects of coating layer thickness and coupling rates at shell/coating and coating/mold interfaces are investigated in detail. The results show that coating thickness has destabilizing effect on the growth instability when the coupling rates are small. However, when these coupling rates are increased individually or together, the destabilizing effect of coating thickness turns to be stabilizing. On the other hand, coupling rates have generally destabilizing effects on the process, but an increase in the thickness of coating leads to diminishing coupling rates effect in some cases.

  2. A Combined Experimental and Computational Study on the Stability of Nanofluids Containing Metal Organic Frameworks

    Energy Technology Data Exchange (ETDEWEB)

    Annapureddy, Harsha Vardhan Reddy [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Nune, Satish K. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Motkuri, Radha K. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); McGrail, B. Peter [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Dang, Liem X. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-01-08

    Computational studies on nanofluids composed of metal organic frameworks (MOFs) were performed using molecular modeling techniques. Grand Canonical Monte Carlo (GCMC) simulations were used to study adsorption behavior of 1,1,1,3,3-pentafluoropropane (R-245fa) in a MIL-101 MOF at various temperatures. To understand the stability of the nanofluid composed of MIL-101 particles, we performed molecular dynamics simulations to compute potentials of mean force between hypothetical MIL-101 fragments terminated with two different kinds of modulators in R-245fa and water. Our computed potentials of mean force results indicate that the MOF particles tend to disperse better in water than in R-245fa. The reasons for this observation were analyzed and discussed. Our results agree with experimental results indicating that the employed potential models and modeling approaches provide good description of molecular interactions and the reliabilities. Work performed by LXD was supported by the U.S. Department of Energy (DOE), Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences. Work performed by HVRA, SKN, RKM, and PBM was supported by the Office of Energy Efficiency and Renewable Energy, Geothermal Technologies Program. Pacific Northwest National Laboratory is a multiprogram national laboratory operated for DOE by Battelle.

  3. High internal ionic liquid phase emulsion stabilized by metal-organic frameworks.

    Science.gov (United States)

    Li, Zhihao; Zhang, Jianling; Luo, Tian; Tan, Xiuniang; Liu, Chengcheng; Sang, Xinxin; Ma, Xue; Han, Buxing; Yang, Guanying

    2016-11-04

    The emulsification of metal-organic frameworks (MOFs) for the two immiscible phases of water and ionic liquid (IL) was investigated for the first time. It was found that Ni-BDC (BDC = 1,4-dicarboxybenzene) can emulsify water and ILs and favor the formation of high internal phase emulsions (HIPEs) under certain experimental conditions. The microstructures of the HIPEs were characterized by confocal laser scanning microscopy using a fluorescent dye Rhodamine B, which proves that the HIPEs are the IL-in-water type. Further results reveal that the HIPE forms during the IL-in-water to water-in-IL emulsion inversion. The possibilities of the HIPE formation by other MOFs (Cu-BDC and Zn-BDC) were explored and the mechanism for HIPE formation was discussed. The MOF-stabilized HIPE was applied to the in situ synthesis of a MOF/polymer composite by HIPE polymerization. The macroporous MOF/polyacrylamide network and MOF/polystyrene microspheres were obtained from the HIPEs, respectively.

  4. STABILITY OF BETACYANIN PIGMENTS FROM RED PURPLE PITAYA FRUIT (Hylocereus polyrhizus : INFLUENCE OF PH, TEMPERATURE, METAL IONS AND ASCORBIC ACID

    Directory of Open Access Journals (Sweden)

    Tang, C.S Tang, C.S

    2010-06-01

    Full Text Available Betacyanin pigments from red-purple pitaya fruit (Hylocereus polyrhizus could be an attractive source of red colourant for food application. This paper presents results on the extraction of betacyanin pigments from pitaya fruits grown locally in Malaysia. Both the flesh of the fruit and its mesocarp were investigated and it was found that the flesh had higher pigment contents compared to its peel component. The concentration of betacyanins expressed as betanin equivalents per 100 g of flesh and peel were 10.1 ± 0.6 mg and 6.7 ± 0.2 mg, respectively when 80% methanol was used.  The stability of betacyanin pigments were investigated at different pH, temperature and in presence of different concentrations of metal ions (Cu2+ and Fe2+ and ascorbic acid. The results showed that the pigment was most stable at pH range between 5 and 6. However, it forfeited its stability to the heat induced at elevated temperatures. Metal ions (Cu2+ and Fe2+ proved to be capable of accelerating betacyanin degradation, with Cu2+ exhibiting the greatest effect. By contrast, supplementation with ascorbic acid could enhance the pigment stability against the detrimental effects caused by pH, temperature and metal ions. Nevertheless, if the concentration of ascorbic acid exceeds 0.7 %, it may change its role from pigment stabilizer to become a pro-oxidant.    Keywords: Betacyanin, pigments, pitaya fruit, Hylocereus polyrhizus, ascorbic acid

  5. Metal organic frameworks/macroporous carbon composites with enhanced stability properties and good electrocatalytic ability for ascorbic acid and hemoglobin.

    Science.gov (United States)

    Zhang, Yufan; Nsabimana, Anaclet; Zhu, Liande; Bo, Xiangjie; Han, Ce; Li, Mian; Guo, Liping

    2014-11-01

    The thermal, water and electrochemical stability of Cu-based metal organic frameworks (Cu-MOFs) confined in macroporous carbon (MPC) hybrids has been investigated. Thermogravimetric analyses, X-Ray diffraction, scanning electron microscopy, and cyclic voltammetry were employed to confirm the stability of pure Cu-MOFs, MPC, and Cu-MOFs-MPC. As compared to pure Cu-MOFs, the porous composite materials of MPC and Cu-MOFs interact and seem to form new materials having homogenous structure and chemistry, which show structural stability in aqueous media and electrochemical stability in phosphate buffer solution (PBS pH 7.4). The detection of ascorbic acid and hemoglobin is performed as an electrochemical probe, indicating Cu-MOFs-MPC holds great promise for the design of electrochemical sensors.

  6. Plants grown on sewage sludge in South China and its relevance to sludge stabilization and metal removal

    Institute of Scientific and Technical Information of China (English)

    SAMAKE Moussa; WU Qi-Tang; MO Ce-hui; MOREL Jean-Louis

    2003-01-01

    The production of sewage sludge in China has been increasing sharply in order to treat 40% of the municipal sewage in 2005 as planned by central government. The main sludge disposal method is landfill owing to heavy metal contamination, but it presents an attractive potential for agricultural land application. Experiments were carried out to study the simultaneous metal removal and sludge stabilization by plants. The sludge samples were collected from Datansha Wastewater Treatment Plant of Guangzhou, it contained excessive Cu and Zn compared with the Chinese National Standard for Agricultural Use of Sewage Sludge. Plants growing on sludge beds were investigated to follow their growth and metal uptake. 30 sludge plants were identified during 1 year's observation. A Zn high-accumulating and high growth rate plant(Alocasia macrorrhiza) was selected and grown on sludge beds in plots. The water, organic matter, heavy metals and nutrients contents, the E. coli number and the cress seed germination index were monitored for the sludge samples collected monthly. The plant growth parameters and its heavy metals contents were also determined. The sewage sludge treated by plants could be stabilized at about 5 months, the E. coli number was significantly decreased and the cress seed germination index attained 100%. Crop on sludge could ameliorate the sludge drying. The experiments are continuing to find out the appropriate plant combination for simultaneous sludge stabilization and metal removal for an acceptable period. Comparisons between the proposed processes and other methods for treating produced sludge such as composting, chemical and bacterial leaching were discussed.

  7. Thermal stability analysis of eccentrically stiffened Sigmoid-FGM plate with metal–ceramic–metal layers based on FSDT

    Directory of Open Access Journals (Sweden)

    Pham Hong Cong

    2016-12-01

    Full Text Available This paper researches the thermal stability of eccentrically stiffened plates made of functionally graded materials (FGM with metal–ceramic–metal layers subjected to thermal load. The equilibrium and compatibility equations for the plates are derived by using the first-order shear deformation theory of plates, taking into account both the geometrical nonlinearity in the von Karman sense and initial geometrical imperfections with Pasternak type elastic foundations. By applying Galerkin method and using stress function, effects of material and geometrical properties, elastic foundations, temperature-dependent material properties, and stiffeners on the thermal stability of the eccentrically stiffened S-FGM plates in thermal environment are analyzed and discussed.

  8. In situ stabilization of heavy metals in multiple-metal contaminated paddy soil using different steel slag-based silicon fertilizer.

    Science.gov (United States)

    Ning, Dongfeng; Liang, Yongchao; Song, Alin; Duan, Aiwang; Liu, Zhandong

    2016-12-01

    Steel slag has been widely used as amendment and silicon fertilizer to alleviate the mobility and bioavailability of heavy metals in soil. The objective of this study was to evaluate the influence of particle size, composition, and application rate of slag on metal immobilization in acidic soil, metals uptake by rice and rice growth. The results indicated that application of slag increased soil pH, plant-available silicon concentrations in soil, and decreased the bioavailability of metals compared with control treatment, whereas pulverous slag (S1) was more effective than granular slag (S2 and S3). The acid-extractable fraction of Cd in the spiked soil was significantly decreased with application of S1 at rates of 1 and 3 %, acid-extractable fractions of Cu and Zn were decreased when treated at 3 %. Use of S1 at both rates resulted in significantly lower Cd, Cu, and Zn concentrations in rice tissues than in controls by 82.6-92.9, 88.4-95.6, and 67.4-81.4 %, respectively. However, use of pulverous slag at 1 % significantly promotes rice growth, restricted rice growth when treated at 3 %. Thus, the results explained that reduced particle size and suitable application rate of slag could be beneficial to rice growth and metals stabilization.

  9. Co-Immobilization of Enzymes and Magnetic Nanoparticles by Metal-Nucleotide Hydrogelnanofibers for Improving Stability and Recycling

    Directory of Open Access Journals (Sweden)

    Chunfang Li

    2017-01-01

    Full Text Available In this paper we report a facile method for preparing co-immobilized enzyme and magnetic nanoparticles (MNPs using metal coordinated hydrogel nanofibers. Candida rugosa lipase (CRL was selected as guest protein. For good aqueous dispersity, low price and other unique properties, citric acid-modified magnetic iron oxide nanoparticles (CA-Fe3O4 NPs have been widely used for immobilizing enzymes. As a result, the relative activity of CA-Fe3O4@Zn/AMP nanofiber-immobilized CRL increased by 8-fold at pH 10.0 and nearly 1-fold in a 50 °C water bath after 30 min, compared to free CRL. Moreover, the immobilized CRL had excellent long-term storage stability (nearly 80% releative activity after storage for 13 days. This work indicated that metal-nucleotide nanofibers could efficiently co-immobilize enzymes and MNPs simultaneously, and improve the stability of biocatalysts.

  10. Titanium boride equation of state determined by in-situ X-ray diffraction.

    Science.gov (United States)

    Ono, Shigeaki; Kikegawa, Takumi

    2016-12-01

    The equation of state (EOS) of titanium boride, TiB2, was investigated by in situ X-ray diffraction in a diamond anvil cell and multianvil high-pressure apparatus. The pressure-volume-temperature (P-V-T) data were collected at up to 111 GPa and room temperature for the diamond-anvil cell experiments and at up to 15 GPa and 1300 K for the multianvil experiments. No phase transition was observed through the entire range of experimental conditions. The pressure-volume data at room temperature were fitted using a Vinet EOS to obtain the isothermal bulk modulus, BT0 = 256.7 GPa, and its pressure derivative, B' T0 = 3.83. When fitting a thermal EOS using the P-V-T data for the multianvil experiments, we find that [Formula: see text] = 0.095 (GPa/K) and α 0 = 2.49 × 10(-5) K(-1).

  11. Relative edge energy in the stability of transition metal nanoclusters of different motifs

    Science.gov (United States)

    Zhao, X. J.; Xue, X. L.; Guo, Z. X.; Li, S. F.

    2016-06-01

    When a structure is reduced to a nanometer scale, the proportion of the lowly-coordinated edge atoms increases significantly, which can play a crucial role in determining both their geometric and electronic properties, as demonstrated by the recently established generalized Wulff construction principle [S. F. Li, et al., Phys. Rev. Lett., 2013, 111, 115501]. Consequently, it is of great interest to clarify quantitatively the role of the edge atoms that dominate the motifs of these nanostructures. In principle, establishing an effective method valid for determining the absolute value of the surface energy and particularly the edge energy for a given nanostructure is expected to resolve such a problem. However, hitherto, it is difficult to obtain the absolute edge energy of transition metal clusters, particularly when their sizes approach the nanometer regime. In this paper, taking Ru nanoclusters as a prototypical example, our first-principles calculations introduce the concept of relative edge energy (REE), reflecting the net edge atom effect over the surface (facet) atom effect, which is fairly powerful to quasi-quantitatively estimate the critical size at which the crossover occurs between different configurations of a given motif, such as from an icosahedron to an fcc nanocrystal. By contrast, the bulk effect should be re-considered to rationalize the power of the REE in predicting the relative stability of larger nanostructures between different motifs, such as fcc-like and hcp-like nanocrystals.When a structure is reduced to a nanometer scale, the proportion of the lowly-coordinated edge atoms increases significantly, which can play a crucial role in determining both their geometric and electronic properties, as demonstrated by the recently established generalized Wulff construction principle [S. F. Li, et al., Phys. Rev. Lett., 2013, 111, 115501]. Consequently, it is of great interest to clarify quantitatively the role of the edge atoms that dominate the

  12. Metal–Organic Frameworks Stabilize Mono(phosphine)–Metal Complexes for Broad-Scope Catalytic Reactions

    Energy Technology Data Exchange (ETDEWEB)

    Sawano, Takahiro; Lin, Zekai; Boures, Dean; An, Bing; Wang, Cheng; Lin, Wenbin (UC); (Xiamen)

    2016-08-10

    Mono(phosphine)–M (M–PR3; M = Rh and Ir) complexes selectively prepared by postsynthetic metalation of a porous triarylphosphine-based metal–organic framework (MOF) exhibited excellent activity in the hydrosilylation of ketones and alkenes, the hydrogenation of alkenes, and the C–H borylation of arenes. The recyclable and reusable MOF catalysts significantly outperformed their homogeneous counterparts, presumably via stabilizing M–PR3 intermediates by preventing deleterious disproportionation reactions/ligand exchanges in the catalytic cycles.

  13. Gaseous Hydrogenation and Its Effect on Thermal Stability of Mg63Ni22Pr15 Metallic Glass

    Institute of Scientific and Technical Information of China (English)

    DU Yu-Lei; DENG Yan-Hui; XU Feng; CHEN Guang; CHEN Guo-Liang; ZHANG Qing-An

    2006-01-01

    Mg6sNi22Pr15 metallic glasses are produced by a single roller melt-spinning technique. The hydrogen absorption and desorption capacities are respectively 0.38 and 0.14 wt. % at 313 K obtained by pressure-composition isotherm.The amorphous structure is found to be retained after gaseous hydrogenation. The glass transition temperature,the onset crystallization temperature, and the crystallization temperature of the hydrogenated Mg63Ni22Pr15metallic glass are 550, 570 and 577K, respectively, much higher than the corresponding values of 440, 470and 499K of the as-quenched sample. This means that dramatic enhancement of thermal stability occurs in Mg63Ni22Pr15 metallic glass due to hydrogenation.

  14. Stabilization

    Directory of Open Access Journals (Sweden)

    Muhammad H. Al-Malack

    2016-07-01

    Full Text Available Fuel oil flyash (FFA produced in power and water desalination plants firing crude oils in the Kingdom of Saudi Arabia is being disposed in landfills, which increases the burden on the environment, therefore, FFA utilization must be encouraged. In the current research, the effect of adding FFA on the engineering properties of two indigenous soils, namely sand and marl, was investigated. FFA was added at concentrations of 5%, 10% and 15% to both soils with and without the addition of Portland cement. Mixtures of the stabilized soils were thoroughly evaluated using compaction, California Bearing Ratio (CBR, unconfined compressive strength (USC and durability tests. Results of these tests indicated that stabilized sand mixtures could not attain the ACI strength requirements. However, marl was found to satisfy the ACI strength requirement when only 5% of FFA was added together with 5% of cement. When the FFA was increased to 10% and 15%, the mixture’s strength was found to decrease to values below the ACI requirements. Results of the Toxicity Characteristics Leaching Procedure (TCLP, which was performed on samples that passed the ACI requirements, indicated that FFA must be cautiously used in soil stabilization.

  15. Metal-coupled folding as the driving force for the extreme stability of Rad50 zinc hook dimer assembly

    Science.gov (United States)

    Kochańczyk, Tomasz; Nowakowski, Michał; Wojewska, Dominika; Kocyła, Anna; Ejchart, Andrzej; Koźmiński, Wiktor; Krężel, Artur

    2016-11-01

    The binding of metal ions at the interface of protein complexes presents a unique and poorly understood mechanism of molecular assembly. A remarkable example is the Rad50 zinc hook domain, which is highly conserved and facilitates the Zn2+-mediated homodimerization of Rad50 proteins. Here, we present a detailed analysis of the structural and thermodynamic effects governing the formation and stability (logK12 = 20.74) of this evolutionarily conserved protein assembly. We have dissected the determinants of the stability contributed by the small β-hairpin of the domain surrounding the zinc binding motif and the coiled-coiled regions using peptides of various lengths from 4 to 45 amino acid residues, alanine substitutions and peptide bond-to-ester perturbations. In the studied series of peptides, an >650 000-fold increase of the formation constant of the dimeric complex arises from favorable enthalpy because of the increased acidity of the cysteine thiols in metal-free form and the structural properties of the dimer. The dependence of the enthalpy on the domain fragment length is partially compensated by the entropic penalty of domain folding, indicating enthalpy-entropy compensation. This study facilitates understanding of the metal-mediated protein-protein interactions in which the metal ion is critical for the tight association of protein subunits.

  16. Stabilization of Metal-Loaded Ion-Exchange Resin with a Porous Silica Supporter Through Thermal Treatment

    Energy Technology Data Exchange (ETDEWEB)

    Kim, I-T. Park, H-S.; Yoo, J-H.; Kim, J-H.

    2003-02-25

    A new ion exchanger with porous silica as a supporting material and diphosphonic acid as a functional chelating group has been developed at ANL for the effective removal of transition metals and actinide ions from very acidic radioactive liquid wastes. The applicability of this resin for the treatment of low- and/or intermediate-level aqueous waste from nuclear power plants (NPP) has not been reported in scientific literature, but is under study now in Korea. The major radioisotopes in NPP radioactive liquid waste are Cs and Co in neutral pH ranges. This study on the thermal stabilization of metal-loaded waste resin has been carried out in parallel with the sorption experiment. Thermal treatment of metal (Co, Cs or U) loaded resin was accomplished to see the possibility of enhancing the safety and stability of the final product during transportation and disposal. In this paper, characteristics of the metal-loaded resins before and after heat treatment at three different thermal conditions were investigated and compared with each other to see the effectiveness of the thermal treatment method.

  17. Solidification/stabilization of toxic metals in calcium aluminate cement matrices.

    Science.gov (United States)

    Navarro-Blasco, I; Duran, A; Sirera, R; Fernández, J M; Alvarez, J I

    2013-09-15

    The ability of calcium aluminate cement (CAC) to encapsulate toxic metals (Pb, Zn and Cu) was assessed under two curing conditions. Changes in the consistency and in the setting time were found upon the addition of the nitrates of the target metals. Both Pb and Cu caused a delay in CAC hydration, while Zn accelerated the stiffening of the mortar. Compressive strengths of the metal-doped mortars, when initially cured at 60 °C/100% RH, were comparable with that of the free-metal mortar. Three different pore size distribution patterns were identified and related to the compounds identified by XRD and SEM. Sorbent capacities of CAC for the toxic metals were excellent: a total uptake was achieved for up to 3 wt.% loading of the three metals. In this way, CAC mortars were perfectly able to encapsulate the toxic metals, allowing the use of CAC for waste management as proved by the leaching tests.

  18. A Modulator-Induced Defect-Formation Strategy to Hierarchically Porous Metal-Organic Frameworks with High Stability.

    Science.gov (United States)

    Cai, Guorui; Jiang, Hai-Long

    2017-01-09

    The pore size enlargement and structural stability have been recognized as two crucial targets, which are rarely achieved together, in the development of metal-organic frameworks (MOFs). Herein, we have developed a versatile modulator-induced defect-formation strategy, in the presence of monocarboxylic acid as a modulator and an insufficient amount of organic ligand, successfully realizing the controllable synthesis of hierarchically porous MOFs (HP-MOFs) with high stability and tailorable pore characters. Remarkably, the integration of high stability and large mesoporous property enables these HP-MOFs to be important porous platforms for applications involving large molecules, especially in catalysis. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Improved electrochemical performance of micro-sized SiO-based composite anode by prelithiation of stabilized lithium metal powder

    Science.gov (United States)

    Pan, Qingrui; Zuo, Pengjian; Mu, Tiansheng; Du, Chunyu; Cheng, Xinqun; Ma, Yulin; Gao, Yunzhi; Yin, Geping

    2017-04-01

    The micro-sized SiO-based composite anode material (d-SiO/G/C) for lithium-ion batteries (LIBs) is achieved via the disproportionation reaction of SiO followed by a pitch pyrolysis reaction. The d-SiO/G/C composite exhibits an initial reversible capacity of 905 mAh g-1 and excellent cycling stability. The initial Coulombic efficiency of the d-SiO/G/C composite can be significantly improved from 68.1% to 98.5% by the prelithiation of the composite anode using stabilized lithium metal powders (SLMP), which counteracts the irreversible capacity loss caused by the solid electrolyte interphase (SEI) formation and irreversible conversion reaction during the first lithiation. The micro-sized d-SiO/G/C composite anode with SLMP prelithiation maintains an excellent cycling stability, suggesting its great potential in practical application for high specific energy lithium ion batteries.

  20. Stabilization of heavy metals in municipal sewage sludge by freeze-thaw treatment with a blend of diatomite, FeSO4, and Ca(OH)2.

    Science.gov (United States)

    Wang, Jing; Fu, Rongbing; Xu, Zhen

    2017-08-01

    In this work, the effects of diatomite with 15% FeSO4•7H2O and 7.5% Ca(OH)2 on sludge stabilization were investigated using batch leaching tests. The influence of cell rupture caused by freezing and thawing on stabilization was also evaluated. The results indicated that the optimal diatomite percentage was 2%. Cell rupture by freezing and thawing reduced heavy metal leachability, followed by cell death and decrease of organic groups. The concentration of heavy metals in sludge leachate increased after cell rupture, indicating that the heavy metal leachability was reduced after freezing and thawings. Moreover, the stabilization effects were generally improved after freezing and thawing. As compared with the stabilization of the original sludge, the unstable fractions decreased and the residual fractions of the heavy metals increased in the stabilized sludge after cell rupture. This study developed a method to stabilize heavy metals in municipal sewage sludge. Diatomite combined with FeSO4·7H2O and Ca(OH)2 improved the treatment of sewage sludge contaminated by heavy metals. Cell lysis by freeze-thaw treatment reduced the risk of leaching heavy metals caused by cell death and decreased major organic groups in the sludge.

  1. Trace Metals in Groundwater & Vadose Zone Calcite: In Situ Containment & Stabilization of 90Strontium & Other Divalent Metals & Radionuclides at Arid West DOE Sites

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Robert W.; Fujita, Yoshiko; Ferris, F. Grant; Cosgrove, Donna M.; Colwell, Rick S.

    2004-06-01

    Radionuclide and metal contaminants such as 90Sr are present beneath U.S. Department of Energy (DOE) lands in both the groundwater (e.g., 100-N area at Hanford, WA) and vadose zone (e.g., Idaho Nuclear Technology and Engineering Center (INTEC) at the Idaho National Engineering and Environmental Laboratory). In situ containment and stabilization of these contaminants is a cost-effective treatment strategy. However, implementing in situ containment and stabilization approaches requires definition of the mechanisms that control contaminant sequestration. We are investigating the in situ immobilization of radionuclides or contaminant metals (e.g., 90Sr) by their facilitated co-precipitation with calcium carbonate in groundwater and vadose zone systems. Our facilitated approach, shown schematically in Figure 1, relies upon the hydrolysis of introduced urea to cause the acceleration of calcium carbonate precipitation (and trace metal co-precipitation) by increasing pH and alkalinity. Subsurface urea hydrolysis is catalyzed by the urease enzyme, which may be either introduced with the urea or produced in situ by ubiquitous subsurface urea hydrolyzing microorganisms. Because the precipitation process tends to be irreversible and many western aquifers are saturated with respect to calcite, the co-precipitated metals and radionuclides will be effectively removed from the aqueous phase over the long-term. Another advantage of the ureolysis approach is that the ammonium ions produced by the reaction can exchange with radionuclides sorbed to subsurface minerals, thereby enhancing the availability of the radionuclides for re-capture in a more stable solid phase (co-precipitation rather than adsorption).

  2. Trace Metals in Groundwater & the Vadose Zone Calcite: In Situ Containment & Stabilization of Strontium-90 & Other Divalent Metals & Radionuclides at Arid West DOE

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Robert W.

    2004-12-01

    Radionuclide and metal contaminants such as strontium-90 are present beneath U.S. Department of Energy (DOE) lands in both the groundwater (e.g., 100-N area at Hanford, WA) and vadose zone (e.g., Idaho Nuclear Technology and Engineering Center at the Idaho National Engineering and Environmental Laboratory). In situ containment and stabilization of these contaminants is a cost-effective treatment strategy. However, implementing in situ containment and stabilization approaches requires definition of the mechanisms that control contaminant sequestration. We are investigating the in situ immobilization of radionuclides or contaminant metals (e.g., strontium-90) by their facilitated co-precipitation with calcium carbonate in groundwater and vadose zone systems. Our facilitated approach, shown schematically in Figure 1, relies upon the hydrolysis of introduced urea to cause the acceleration of calcium carbonate precipitation (and trace metal co-precipitation) by increasing pH and alkalinity. Subsurface urea hydrolysis is catalyzed by the urease enzyme, which may be either introduced with the urea or produced in situ by ubiquitous subsurface urea hydrolyzing microorganisms. Because the precipitation process tends to be irreversible and many western aquifers are saturated with respect to calcite, the co-precipitated metals and radionuclides will be effectively removed from the aqueous phase over the long-term. Another advantage of the ureolysis approach is that the ammonium ions produced by the reaction can exchange with radionuclides sorbed to subsurface minerals, thereby enhancing the availability of the radionuclides for re-capture in a more stable solid phase (co-precipitation rather than adsorption).

  3. Trace Metals in Groundwater & Vadose Zone Calcite: In Situ Containment & Stabilization of Stronthium-90 & Other Divalent Metals & Radionuclides at Arid West DOE

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Robert W.

    2005-06-01

    Radionuclide and metal contaminants such as strontium-90 are present beneath U.S. Department of Energy (DOE) lands in both the groundwater (e.g., 100-N area at Hanford, WA) and vadose zone (e.g., Idaho Nuclear Technology and Engineering Center [INTEC] at the Idaho National Laboratory [INL]). In situ containment and stabilization of these contaminants is a cost-effective treatment strategy. However, implementing in situ containment and stabilization approaches requires definition of the mechanisms that control contaminant sequestration. We are investigating the in situ immobilization of radionuclides or contaminant metals (e.g., strontium-90) by their facilitated co-precipitation with calcium carbonate (primarily calcite) in groundwater and vadose zone systems. Our facilitated approach relies upon the hydrolysis of introduced urea to cause the acceleration of calcium carbonate precipitation (and trace metal co-precipitation) by (a) increasing pH and alkalinity and (b) liberating cations from the aquifer matrix by cation exchange reactions. Subsurface urea hydrolysis is catalyzed by the urease enzyme, which is produced in situ by native urea hydrolyzing microorganisms. Because the precipitation process tends to be irreversible and many western aquifers are saturated with respect to calcite, the co-precipitated metals and radionuclides will be effectively removed from the aqueous phase over the long term. We are currently conducting field based activities at both the INL Vadose Zone Research Park (VZRP), an uncontaminated surrogate site for the strontium-90 contaminated vadose zone at INTEC and at the strontium-90 contaminated aquifer of 100-N area of the Hanford site.

  4. Microstructural Characterization and Wear Behavior of Nano-Boride Dispersed Coating on AISI 304 Stainless Steel by Hybrid High Velocity Oxy-Fuel Spraying Laser Surface Melting

    Science.gov (United States)

    Sharma, Prashant; Majumdar, Jyotsna Dutta

    2015-07-01

    The current study concerns the detailed microstructural characterization and investigation of wear behavior of nano-boride dispersed coating developed on AISI 304 stainless steel by high velocity oxy-fuel spray deposition of nickel-based alloy and subsequent laser melting. There is a significant refinement and homogenization of microstructure with improvement in microhardness due to laser surface melting (1200 VHN as compared to 945 VHN of as-sprayed and 250 VHN of as-received substrate). The high temperature phase stability of the as-coated and laser melted surface has been studied by differential scanning calorimeter followed by detailed phase analysis at room and elevated temperature. There is a significant improvement in wear resistance of laser melted surface as compared to as-sprayed and the as-received one due to increased hardness and reduced coefficient of friction. The mechanism of wear has been investigated in details. Corrosion resistance of the coating in a 3.56 wt pct NaCl solution is significantly improved (4.43 E-2 mm/year as compared to 5 E-1 mm/year of as-sprayed and 1.66 mm/year of as-received substrate) due to laser surface melting as compared to as-sprayed surface.

  5. Metal Fluoride Inhibition of a P-type H+ Pump: STABILIZATION OF THE PHOSPHOENZYME INTERMEDIATE CONTRIBUTES TO POST-TRANSLATIONAL PUMP ACTIVATION

    National Research Council Canada - National Science Library

    Pedersen, Jesper Torbøl; Falhof, Janus; Ekberg, Kira; Buch-Pedersen, Morten Jeppe; Palmgren, Michael

    2015-01-01

    .... In contrast to findings for other P-type ATPases, inhibition of the plasma membrane H(+)-ATPase by metal fluorides was partly reversible, and the stability of the inhibition varied with the activation state...

  6. Influence of Metal Transfer Stability and Shielding Gas Composition on CO and CO2 Emissions during Short-circuiting MIG/MAG Welding

    National Research Council Canada - National Science Library

    Meneses, Valter Alves de; Leal, Valdemar Silva; Scotti, Américo

    2016-01-01

    Several studies have demonstrated the influence of parameters and shielding gas on metal transfer stability or on the generation of fumes in MIG/MAG welding, but little or nothing has been discussed...

  7. Metal-dependent SpoIIE oligomerization stabilizes FtsZ during asymmetric division in Bacillus subtilis

    Science.gov (United States)

    Król, Ewa; de Sousa Borges, Anabela; Kopacz, Malgorzata

    2017-01-01

    SpoIIE is a bifunctional protein involved in asymmetric septum formation and in activation of the forespore compartment-specific transcription factor σF through dephosphorylation of SpoIIAA-P. The phosphatase activity of SpoIIE requires Mn2+ as a metal cofactor. Here, we show that the presence of a metal cofactor also influences SpoIIE oligomerization and asymmetric septum formation. Absence of Mn2+ from sporulation medium results in a delay of the formation of polar FtsZ-rings, similar to a spoIIE null mutant. We purified the entire cytoplasmic part of the SpoIIE protein, and show that the protein copurifies with bound metals. Metal binding both stimulates SpoIIE oligomerization, and results in the formation of larger oligomeric structures. The presence of SpoIIE oligomers reduces FtsZ GTP hydrolysis activity and stabilizes FtsZ polymers in a light scattering assay. Combined, these results indicate that metal binding is not just required for SpoIIE phosphatase activity but also is important for SpoIIE's role in asymmetric septum formation. PMID:28358838

  8. Computational-Experimental Processing of Boride/Carbide Composites by Reactive Infusion of Hf Alloy Melts into B4C

    Science.gov (United States)

    2015-09-16

    elements from the Hf family (i.e., Hf, Ti and Zr ) into a capillary to understand the effects of surface tension and viscosity during processing of melts...project primarily investigated computationally the infusion of liquid elements from the Hf family (i.e., Hf, Ti and Zr ) into a capillary to understand the... effects of surface tension and viscosity during processing of melts with a packed bed of B4C to form boride-carbide precipitates. Although the

  9. Field Deployment for In-situ Metal and Radionuclide Stabilization by Microbial Metabolites

    Energy Technology Data Exchange (ETDEWEB)

    Turick, C. E.; Knox, A. S.; Dixon, K. L.; Roseberry, R. J.; Kritzas, Y. G

    2005-09-26

    A novel biotechnology is reported here that was demonstrated at SRS that facilitates metal and actinide immobilization by incorporating the physiology and ecology of indigenous bacteria. This technology is based on our previous work with pyomelanin-producing bacteria isolated from SRS soils. Through tyrosine supplementation, overproduction of pyomelanin was achieved, which lead ultimately to metal and actinide immobilization, both in-vitro and in-situ. Pyomelanin is a recalcitrant microbial pigment and a humic type compound in the class of melanin pigments. Pyomelanin has electron shuttling and metal chelation capabilities and thus accelerates the bacterial reduction and/or immobilization of metals. Pyomelanin is produced outside the cell and either diffuses away or attaches to the cell surface. In either case, the reduced pyomelanin is capable of transferring electrons to metals as well as chelating metals. Because of its recalcitrance and redox cycling properties, pyomelanin molecules can be used over and over again for metal transformation. When produced in excess, pyomelanin produced by one bacterial species can be used by other species for metal reduction, thereby extending the utility of pyomelanin and further accelerating metal immobilization rates. Soils contaminated with Ni and U were the focus of this study in order to develop in-situ, metal bioimmobilization technologies. We have demonstrated pyomelanin production in soil from the Tims Branch area of SRS as a result of tyrosine amendments. These results were documented in laboratory soil column studies and field deployment studies. The amended soils demonstrated increased redox behavior and sequestration capacity of U and transition metals following pyomelanin production. Treatments incorporating tyrosine and lactate demonstrated the highest levels of pyomelanin production. In order to determine the potential use of this technology at other areas of SRS, pyomelanin producing bacteria were also quantified

  10. Solubility of ion and trace metals from stabilized sewage sludge by fly ash and alkaline mine tailing

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hongling; SUN Lina; SUN Tieheng

    2008-01-01

    Stabilized sewage sludge (SS) by fly ash (FA) and alkaline mine tailing as artificial soil,to be applied on the ecological rehabilitation at mining junkyards,offers a potentially viable utilization of the industrial by-product,as well as solves the shortage of soil resource in the mine area.An incubation experiment with different ratios of SS and FA was conducted to evaluate the solubility of ions and trace elements from stabilized sewage sludge.Results showed that fly ash offset a decrease in pH value of sewage sludge.The pH of (C) treatment (FA:SS=1:1) was stable and tended to neutrality.The SO42- and Cl- concentrations of the solution in the mixture were significantly decreased in the stabilized sewage sludge by alkaline fly ash and mine tailing,compared to the single SS treatment.Stabilized sewage sludge by FA weakened the nitrification of total nitrogen from SS when the proportion of FA in the mixture was more than 50%.The Cr,Ni,and Cu concentrations in the solution were gradually decreased and achieved a stable level after 22 days,for all treatments over the duration of the incubation.Moreover stabilized sewage sludge by fly ash and/or mine tailing notably decreased the trace metal solubility.The final Cr,Cu,and Ni concentrations in the solution for all mixtures of treatments were lower than 2.5,15,and 50 μg/L,respectively.

  11. Influence of Metal Transfer Stability and Shielding Gas Composition on CO and CO2 Emissions during Short-circuiting MIG/MAG Welding

    OpenAIRE

    Valter Alves de Meneses; Valdemar Silva Leal; Américo Scotti

    2016-01-01

    Abstract: Several studies have demonstrated the influence of parameters and shielding gas on metal transfer stability or on the generation of fumes in MIG/MAG welding, but little or nothing has been discussed regarding the emission of toxic and asphyxiating gases, particularly as it pertains to parameterization of the process. The purpose of this study was to analyze and evaluate the effect of manufacturing aspects of welding processes (short-circuit metal transfer stability and shielding gas...

  12. Trace Metals in Groundwater & Vadose Zone Calcite: In Situ Containment & Stabilization of Stronthium-90 & Other Divalent Metals & Radionuclides at Arid West DOE

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Robert W

    2003-06-01

    Radionuclide and metal contaminants such as strontium-90 are present beneath U.S. Department of Energy (DOE) lands in both the groundwater (e.g., 100-N area at Hanford, WA) and vadose zone (e.g., Idaho Nuclear Technology and Engineering Center at the Idaho National Engineering and Environmental Laboratory). In situ containment and stabilization of these contaminants is a cost-effective treatment strategy. However, implementing in situ containment and stabilization approaches requires definition of the mechanisms that control contaminant sequestration. We are investigating the in situ immobilization of radionuclides or contaminant metals (e.g., strontium-90) by their facilitated co-precipitation with calcium carbonate in groundwater and vadose zone systems. Our facilitated approach, shown schematically in Figure 1, relies upon the hydrolysis of introduced urea to cause the acceleration of calcium carbonate precipitation (and trace metal co-precipitation) by increasing pH and alkalinity. Subsurface urea hydrolysis is catalyzed by the urease enzyme, which may be either introduced with the urea or produced in situ by ubiquitous subsurface urea hydrolyzing microorganisms. Because the precipitation process tends to be irreversible and many western aquifers are saturated with respect to calcite, the co-precipitated metals and radionuclides will be effectively removed from the aqueous phase over the long-term. Another advantage of the ureolysis approach is that the ammonium ions produced by the reaction can exchange with radionuclides sorbed to subsurface minerals, thereby enhancing the availability of the radionuclides for recapture in a more stable solid phase (co-precipitation rather than adsorption). Our specific research objectives include: * Elucidation of the mechanisms and rates for the release of sorbed trace metals and their subsequent sequestration by co-precipitation in calcite induced by urea hydrolysis. * Evaluation at the field scale of the influence of

  13. Solidification/stabilization of toxic metals in calcium aluminate cement matrices

    Energy Technology Data Exchange (ETDEWEB)

    Navarro-Blasco, I.; Duran, A.; Sirera, R.; Fernández, J.M.; Alvarez, J.I., E-mail: jalvarez@unav.es

    2013-09-15

    Highlights: • Reliable encapsulation and effective sorption of Pb, Zn and Cu on CAC was proved. • Cu and Pb were fully retained in the CAC mortar, while Zn was retained in 99.99%. •A maximum sorption capacity ca. 60 mg/g CAC was attained for Cu. • Three different PSD patterns were established as a function of XRD phase assemblage. • Some metal-loaded mortars achieved suitable mechanical strengths for landfilling. -- Abstract: The ability of calcium aluminate cement (CAC) to encapsulate toxic metals (Pb, Zn and Cu) was assessed under two curing conditions. Changes in the consistency and in the setting time were found upon the addition of the nitrates of the target metals. Both Pb and Cu caused a delay in CAC hydration, while Zn accelerated the stiffening of the mortar. Compressive strengths of the metal-doped mortars, when initially cured at 60 °C/100% RH, were comparable with that of the free-metal mortar. Three different pore size distribution patterns were identified and related to the compounds identified by XRD and SEM. Sorbent capacities of CAC for the toxic metals were excellent: a total uptake was achieved for up to 3 wt.% loading of the three metals. In this way, CAC mortars were perfectly able to encapsulate the toxic metals, allowing the use of CAC for waste management as proved by the leaching tests.

  14. A Sr2+-metal-organic framework with high chemical stability: synthesis, crystal structure and photoluminescence property.

    Science.gov (United States)

    Jia, Yan-Yuan; Liu, Xiao-Ting; Wang, Wen-He; Zhang, Li-Zhu; Zhang, Ying-Hui; Bu, Xian-He

    2017-01-13

    Metal-organic frameworks (MOFs) are typically built by assembly of metal centres and organic linkers, and have emerged as promising crystalline materials in a variety of fields. However, the stability of MOFs is a key limitation for their practical applications. Herein, we report a novel Sr 2+: -MOF [Sr4(Tdada)2(H2O)3(DMF)2] (denoted as NKU- 105: , NKU = Nankai University; H4Tdada = 5,5'-((thiophene-2,5-dicar bonyl)bis(azanediyl))diisophthalic acid; DMF = N,N-dimethylformamide) featuring an open square channel of about 6 Å along the c-axis. Notably, NKU- 105: exhibits much outstanding chemical stability against common organic solvents, boiling water, acids and bases, relative to most MOF materials. Furthermore, NKU- 105: is an environment-friendly luminescent material with a bright cyan emission.This article is part of the themed issue 'Coordination polymers and metal-organic frameworks: materials by design'.

  15. Stabilization of Li Metal Anode in DMSO-Based Electrolytes via Optimization of Salt-Solvent Coordination for Li-O 2 Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Bin [Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland WA 99354 USA; Xu, Wu [Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland WA 99354 USA; Yan, Pengfei [Environmental and Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland WA 99354 USA; Kim, Sun Tai [Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland WA 99354 USA; Department of Energy Engineering, School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology, Ulsan 689-798 South Korea; Engelhard, Mark H. [Environmental and Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland WA 99354 USA; Sun, Xiuliang [Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland WA 99354 USA; Mei, Donghai [Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland WA 99354 USA; Cho, Jaephil [Department of Energy Engineering, School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology, Ulsan 689-798 South Korea; Wang, Chong-Min [Environmental and Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland WA 99354 USA; Zhang, Ji-Guang [Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland WA 99354 USA

    2017-03-08

    The conventional DMSO-based electrolyte (1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in DMSO) is unstable against the Li metal anode and therefore cannot be used directly in practical Li-O2 batteries. Here, we demonstrate that a highly concentrated electrolyte based on LiTFSI in DMSO (with a molar ratio of 1:3) can greatly improve the stability of the Li metal anode against DMSO and significantly improve the cycling stability of Li-O2 batteries. This highly concentrated electrolyte contains no free DMSO solvent molecules, but only complexes of (TFSI–)a-Li+-(DMSO)b (where a + b = 4), and thus enhances their stability with Li metal anodes. In addition, such salt-solvent complexes have higher Gibbs activation energy barriers than the free DMSO solvent molecules, indicating improved stability of the electrolyte against the attack of superoxide radical anions. Therefore, the stability of this highly concentrated electrolyte at both Li metal anodes and carbon-based air electrodes has been greatly enhanced, resulting in improved cyclic stability of Li-O2 batteries. The fundamental stability of the electrolyte with free-solvent against the chemical and electrochemical reactions can also be used to enhance the stability of other electrochemical systems.

  16. Stability

    Directory of Open Access Journals (Sweden)

    Nada S. Abdelwahab

    2017-05-01

    Full Text Available The present work concerns with the development of stability indicating the RP-HPLC method for simultaneous determination of guaifenesin (GUF and pseudoephedrine hydrochloride (PSH in the presence of guaifenesin related substance (Guaiacol. GUC, and in the presence of syrup excepients with minimum sample pre-treatment. In the developed RP-HPLC method efficient chromatographic separation was achieved for GUF, PSH, GUC and syrup excepients using ODS column as a stationary phase and methanol: water (50:50, v/v, pH = 4 with orthophosphoric acid as a mobile phase with a flow rate of 1 mL min−1 and UV detection at 210 nm. The chromatographic run time was approximately 10 min. Calibration curves were drawn relating the integrated area under peak to the corresponding concentrations of PSH, GUF and GUC in the range of 1–8, 1–20, 0.4–8 μg mL−1, respectively. The developed method has been validated and met the requirements delineated by ICH guidelines with respect to linearity, accuracy, precision, specificity and robustness. The validated method was successfully applied for determination of the studied drugs in triaminic chest congestion® syrup; moreover its results were statistically compared with those obtained by the official method and no significant difference was found between them.

  17. Radical bonding: structure and stability of bis(phenalenyl) complexes of divalent metals from across the periodic table.

    Science.gov (United States)

    Craciun, Smaranda; Donald, Kelling J

    2009-07-06

    We examine the bonding possibilities of the bis(phenalenyl) MP(2) sandwich complexes of the divalent metals M = Be, Mg, Ca, Sr, Ba, Zn, Cd, and Hg, at the B3LYP level of theory. The outcome is an extraordinarily diverse class of low symmetry bis(phenalenyl)metal complexes in which bonding preferences and binding enthalpies differ dramatically. The lowest energy group 2 metal MP(2) complexes include an intriguing eta(1),eta(3) BeP(2) structure, and bent eta(6),eta(6) systems for M = Ca, Sr, and Ba. The group 12 bis(phenalenyl) complexes are thermodynamically unstable eta(1),eta(1) slip-sandwich structures. To better understand changes in the structural preferences going from the (eta(6),eta(6)) group 2 to the (eta(1),eta(1)) group 12 complexes, we explored the bonding in the bis(phenalenyl) complexes of transition metals with stable +2 oxidations states between Ca and Zn in period 4. The computed binding enthalpies are large and negative for nearly all of the minimum energy bis(phenalenyl) complexes of the group 2 and the transition metals; they are tiny for MgP(2), and are quite positive for the group 12 systems. The structural preferences and stability of the complexes is a subtle negotiation of several influences: the (un)availability of (n - 1)d and np, orbitals for bonding, the cost of the rehybridization at carbon sites in the phenalenyl rings in preparation for bonding to the metals, and the (P---P) interaction between the phenalenyl radicals.

  18. Electron-band theory inspired design of magnesium-precious metal bulk metallic glasses with high thermal stability and extended ductility.

    Science.gov (United States)

    Laws, Kevin J; Shamlaye, Karl F; Granata, Davide; Koloadin, Leah S; Löffler, Jörg F

    2017-06-13

    Magnesium-based bulk metallic glasses (BMGs) exhibit high specific strengths and excellent glass-forming ability compared to other metallic systems, making them suitable candidates for next-generation materials. However, current Mg-based BMGs tend to exhibit low thermal stability and are prone to structural relaxation and brittle failure. This study presents a range of new magnesium-precious metal-based BMGs from the ternary Mg-Ag-Ca, Mg-Ag-Yb, Mg-Pd-Ca and Mg-Pd-Yb alloy systems with Mg content greater than 67 at.%. These alloys were designed for high ductility by utilising atomic bond-band theory and a topological efficient atomic packing model. BMGs from the Mg-Pd-Ca alloy system exhibit high glass-forming ability with critical casting sizes of up to 3 mm in diameter, the highest glass transition temperatures (>200 °C) of any reported Mg-based BMG to date, and sustained compressive ductility. Alloys from the Mg-Pd-Yb family exhibit critical casting sizes of up to 4 mm in diameter, and the highest compressive plastic (1.59%) and total (3.78%) strain to failure of any so far reported Mg-based glass. The methods and theoretical approaches presented here demonstrate a significant step forward in the ongoing development of this extraordinary class of materials.

  19. Biomimetic PEG-catecholates for stabile antifouling coatings on metal surfaces: applications on TiO2 and stainless steel.

    Science.gov (United States)

    Khalil, Faiza; Franzmann, Elisa; Ramcke, Julian; Dakischew, Olga; Lips, Katrin S; Reinhardt, Alexander; Heisig, Peter; Maison, Wolfgang

    2014-05-01

    Trimeric catecholates have been designed for the stable immobilization of effector molecules on metal surfaces. The design of these catecholates followed a biomimetic approach and was inspired by natural multivalent metal binders, such as mussel adhesion proteins (MAPs) and siderophores. Three catecholates have been conjugated to central scaffolds based on adamantyl or trisalkylmethyl core structures. The resulting triscatecholates have been immobilized on TiO2 and stainless steel. In a proof of concept study we have demonstrated the high stability of the resulting nanolayers at neutral and slightly acidic pH. Furthermore, polyethylene glycol (PEG) conjugates of our triscatecholates have been synthesized and were immobilized on TiO2 and stainless steel. The PEG coated surfaces showed excellent antifouling properties upon exposure to human blood and bacteria as demonstrated by fluorescence microscopy, ellipsometry and a bacterial assay with Staphylococcus epidermidis. In addition, our PEG-triscatecholates showed no cytotoxicity against bone-marrow stem cells on TiO2.

  20. First-principles study on stability of transition metal solutes in aluminum by analyzing the underlying forces

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Wei; Xu, Yichun; Li, Xiangyan; Wu, Xuebang, E-mail: xbwu@issp.ac.cn; Liu, C. S., E-mail: csliu@issp.ac.cn [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, P.O. Box 1129, Hefei 230031 (China); Liang, Yunfeng [Environment and Resource System Engineering, Kyoto University, Kyoto 615-8540 (Japan); Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, P.O. Box 1129, Hefei 230031 (China); Wang, Zhiguang [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)

    2015-05-07

    Although there have been some investigations on behaviors of solutes in metals under strain, the underlying mechanism of how strain changes the stability of a solute is still unknown. To gain such knowledge, first-principles calculations are performed on substitution energy of transition metal solutes in fcc Al host under rhombohedral strain (RS). Our results show that under RS, substitution energy decreases linearly with the increase of outermost d radius r{sub d} of the solute due to Pauli repulsion. The screened Coulomb interaction increases or decreases the substitution energy of a solute on condition that its Pauling electronegativity scale ϕ{sub P} is less or greater than that of Al under RS. This paper verifies a linear relation of substitution energy change versus r{sub d} and ϕ{sub P} under RS, which might be instructive for composition design of long life alloys serving in high stress condition.

  1. Seasonal variability of heavy metal content and its chemical speciation in excess sludge by vermi-stabilization

    Science.gov (United States)

    Mu, H.; Zhao, Y. X.; Li, Y.; Zhang, X. D.; Hua, D. L.; Zhao, C. H.

    2017-01-01

    Vermifiltration system has been reported to enhance sludge degradation and relieve the potential risks of heavy metals, whereas few studies focus on the seasonal variability of heavy metal content and its chemical speciation in excess sludge by vermi-stabilization. The results of this study showed that total contents of Zn, Pb, Cr and the treatment efficiency of vermifilter were higher in summer and lower in winter due to the temperature effect. While Cu was observed to not be dependent on season. Further investigation using a five-step fractionation procedure to evaluate the main chemical speciations of metals in the sludge showed that there were similar variations in the five fractions (F1-F5) between each season, which indicated that the chemical speciation of heavy metals were most affected by vermifiltration technique than seasonal factor. The transformations among the five fractions suggested that the vermifiltration significantly reduced the mobility and bioavailability of Zn and Pb due to their increased stable fractions and decreased unstable fractions. The higher stable fraction of Cu led to the stable morphology in sludge, which favoured the insignificant variations with seasons.

  2. Direct space representation of metallicity and structural stability in SiO solids

    Energy Technology Data Exchange (ETDEWEB)

    Jenkins, Samantha [Department of Informatics and Mathematics, University of Trollhaettan/Uddevalla, PO Box 957, 461 29 Trollhaettan (Sweden)

    2002-11-04

    First principles calculations are performed on possible structures of silicon monoxide solids. The chemical character of all of the bonding interactions is systematically quantified in real space. It is found that the most stable SiO structure possesses the highest number of inequivalent bond paths. This process reveals a novel metallic Si-Si interaction and provides an explanation for the origin of the unexpectedly high conductivity in thin silicon oxide layers. In this paper a new measure for quantifying metallic character (in direct space) present in a bond has been introduced. Furthermore it has been possible to determine the directional properties of this metallic character in real space using the charge density. This finding is very important for future complementary metal oxide semiconductor technology.

  3. Green synthesis of metal nanoparticles: biodegradable polymers and enzymes in stabilization and surface functionalization

    Science.gov (United States)

    Current breakthroughs in green nanotechnology are capable to transform many of the existing processes and products that enhance environmental quality, reduce pollution, and conserve natural and non-renewable resources. Noteworthy, successful use of metal nanoparticles and 10 nano...

  4. Green synthesis of metal nanoparticles: biodegradable polymers and enzymes in stabilization and surface functionalization

    Science.gov (United States)

    Current breakthroughs in green nanotechnology are capable to transform many of the existing processes and products that enhance environmental quality, reduce pollution, and conserve natural and non-renewable resources. Noteworthy, successful use of metal nanoparticles and 10 nano...

  5. Glass-to-metal bonding process improves stability and performance of semiconductor devices

    Science.gov (United States)

    Trent, R. L.

    1970-01-01

    Anodic bonding of glass coverslips to photodiodes and photovoltaic devices eliminates the need for adhesive. The process requires relatively low temperatures /less than 560 degrees C/ and the metals and glass remain solid throughout the bonding process.

  6. Stabilization of Heavy Metal Particles in AL2O3-W Suspensions

    National Research Council Canada - National Science Library

    A. Kędzierska – Sar; P. Falkowski; M. Szafran

    2016-01-01

    Ceramic – metal composites are widely used materials in a whole world. There were invented many fabrication methods for those kind of materials, but still exists some problems which need to be fixed...

  7. Stabilization effects of third element on CaCu5 type derivatives of rare-earth transition-metal intermetallics

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Part of the results of the key project "Search for novel rare-earth functional materials" supported by the National Natural Science Foundation of China is reviewed. In combination with reports in literature, the effects of the third element M on the formation and stability of La2(Co, M)17, R(Fe, M)12 and R3(Fe, M)29 intermetallic compounds are discussed by considering mixing enthalpy of M with rare-earth, Fe and Co, and atomic radius, electronegativity and electronic configurations, etc. It is concluded that the mixing en thalpy and atomic radius dominate the preferential sites and the minimum amount of M required to stabilize a structure, which ultimately affect the magnetic properties of a compound prominently. This review should provide some heuristic hints for exploiting novel rare-earth transition metal functional materials and for improving their performance.

  8. Bio-inspired stabilization of sulfenyl iodide RS-I in a Zr(IV)-based metal-organic framework.

    Science.gov (United States)

    Yee, Ka-Kit; Wong, Yan-Lung; Xu, Zhengtao

    2016-03-28

    A Zr(IV)-based metal-organic framework (MOF) appended with free-standing thiol (-SH) groups was found to react readily with I2 molecules to form sulfenyl iodide (S-I) units. In contrast to its solution chemistry of facile disproportionation into disulfide and I2, the sulfenyl iodide (SI) function, anchored onto the rigid MOF grid and thus prevented from approaching one another to undergo the dismutation reaction, exhibits distinct stability even at elevated temperatures (e.g., 90 °C). On a conceptual plane, this simple and effective solid host also captures the spatial confinement observed for the complex biomacromolecular scaffolds involved in iodine thyroid chemistry, wherein the spatial isolation and consequent stabilization of sulfenyl/selenenyl iodides are exerted by means of the protein scaffolds.

  9. Thermodynamics of formation of the insulin hexamer: metal-stabilized proton-coupled assembly of quaternary structure.

    Science.gov (United States)

    Carpenter, Margaret C; Wilcox, Dean E

    2014-03-01

    The thermodynamics of formation of the insulin hexamer, which is stabilized by two Zn(2+) ions, were quantified by isothermal titration calorimetry (ITC). Because the insulin monomer is unstable to aggregation (fibrillation) during ITC measurements, an original method involving EDTA chelation of Zn(2+) from the hexamer was employed. The two metal ions are chelated sequentially, reflecting stepwise Zn(2+) binding and stabilization of the quaternary structure. Analysis of the ITC data reveals that two to three H(+) bind to the hexamer upon its formation at pH 7.4, which is both enthalpically and entropically favored. The former is due to Zn(2+) coordination to His residues from three subunits, and the latter is associated with desolvation that accompanies the protonation and the packing of the subunits in the hexamer.

  10. Hydrogen evolution activity and electrochemical stability of selected transition metal carbides in concentrated phosphoric acid

    DEFF Research Database (Denmark)

    Tomás García, Antonio Luis; Jensen, Jens Oluf; Bjerrum, Niels J.

    2014-01-01

    Alternative catalysts based on carbides of Group 5 (niobium and tantalum) and 6 (chromium, molybdenum and tungsten) metals were prepared as films on the metallic substrates. The electrochemical activities of these carbide electrodes towards the hydrogen evolution reaction (HER) in concentrated......, attributable to the different electronic structures. Tungsten carbide among the studied electrode samples exhibited the highest HER activity. Upon anodic potential scans in the presence of oxygen, chromium, tantalum and tungsten carbides displayed passivation due to the formation of stable surface layers...

  11. An analysis of harmful factors to storage stability of the reduced metallic fuel produced by the advanced spent fuel management process

    Energy Technology Data Exchange (ETDEWEB)

    Ju, J. S.; You, G. S.; Cho, I. J.; Kook, D. H.; Lee, J. C.; Seo, G. S.; Lee, E. P.; Seo, H. S. [Korea Atomic Energy Research Institute, Taejeon (Korea)

    2002-03-01

    This study was performed for the selection of alloying elements to make the metallic fuel alloys having a good stability to oxidation. Harmful factors on oxidation were also analyzed. Several basic properties such as microstructure, immiscibility, thermal and fission product effects were surveyed. The oxidation properties of metal uranium and uranium alloys were also studied. The results from this study are applicable to the selection of the alloying elements to stabilize the reduced uranium metal in the 2nd year research in phase 2, and also do an important role to increase the storage temperature. 29 refs., 37 figs., 5 tabs. (Author)

  12. Study of corrosion protection. 3. ; Stabilization of interface between polymer and metal

    Energy Technology Data Exchange (ETDEWEB)

    Tsutsumi, A.; Yamabe, H. (Nisshin Steel Co. Ltd., Tokyo (Japan))

    1993-12-20

    The interface between carboxyl group of poly (acrylic acid) (PAA) and metals with different IEPS (isoelectric point of surface) values such as Cu, Fe and Al was studied. The main difference in XPS (X-ray photoelectron spectroscopy) spectra for each metal was observed in shift of the binding energy of a 0(1s) peak from carboxyl group, suggesting the strong ionic interaction between surfaces of every metal and carboxyl group. The difference revealed by SSIMS (static secondary ion mass spectrometry) was detection of COOCu[sup +], COOFe[sup +] and COOAl[sup +] ions from the metal surfaces treated with PAA, suggesting formation of a chemical bond as a result of the strong ionic interaction between surfaces of every metal and carboxyl group. Results obtained by RA-FTIR (reflection-absorption Fourier transform infrared spectroscopy) were in good agreement with those by XPS and SSIMS. As a result, PAA treatment used for epoxide resin/PAA/metal joint systems was effective in improving a joint durability. 7 refs., 12 figs., 2 tabs.

  13. Changes in speciation and leaching behaviors of heavy metals in dredged sediment solidified/stabilized with various materials.

    Science.gov (United States)

    Bao, Jianping; Wang, Liang; Xiao, Man

    2016-05-01

    Solidification/stabilization (S/S) of sediments is frequently used to treat contaminants in dredged sediments. In this study, sediment collected from the Pearl River Delta (China) was solidified/stabilized with three different kinds of functional materials: cement, lime and bentonite. Lime primarily acted via induced increases in pH, while cements stabilization occurred through their silicate-based systems and the main function of bentonite was adsorption. The speciation and leaching behaviors of specific heavy metals before and after S/S were analyzed and the results showed that the residual speciation of Cd, Cr, Ni, Pb and Zn increased in all treatments except for Cu, as the exchangeable speciation, carbonate-bound speciation and Fe-Mn-oxide-bound speciation of Cu (all of which could be stabilized) were less than 2 % of the total amount. Pb leaching only decreased when pH increased, while the mobility of Cr and Ni only decreased in response to the silicate-based systems. The leached portion of the Fe-Mn-oxide-bound speciation followed the order Zn > Cu > Ni/Cd > Pb > Cr. The leached portion of organic-matter-bound species was less than 4 % for Cd, Cr, Ni and Pb, but 35.1 % and 20.6 % for Cu and Zn, respectively.

  14. Evaluation of metal oxide and carbonate nanoparticle stability in soybean oil: Implications for controlled release of alkalinity during subsurface remediation

    Science.gov (United States)

    Ramsburg, C. A.; Leach, O. I.; Sebik, J.; Muller, K.

    2011-12-01

    Traditional methods for adjusting groundwater pH rely on injection of aqueous solutes and therefore, amendment distribution is reliant upon aqueous phase flow and transport. This reliance can limit mixing and sustention of amendments within the treatment zone. Oil-in-water emulsions offer an alternative for amendment delivery - one that has potential to enhance control of the distribution and release of buffering agents within the subsurface. Focus here is placed on using metal oxide and carbonate nanoparticles to release alkalinity from soybean oil, a common dispersed phase within emulsions designed to support remediation activities. Batch reactor systems were employed to examine the influence of dispersed phase composition on particle stability and solubility. The stability of uncoated MgO and CaCO3 particles in unmodified soybean oil was explored in a series of sedimentation studies conducted at solid loadings of 0.05, 0.1, and 0.2% mass. Three nominal sizes of MgO particles were examined (20, 50, and 100 nm) and one CaCO3 particle size (60 nm). Results from sedimentation studies conducted over four hours suggest that the viscosity of the soybean oil imparts a kinetic stability, for all sizes of the uncoated MgO and CaCO3 nanoparticles, which is sufficient time for particle encapsulation within oil-in-water emulsions. Based upon these results, the sedimentation of the 50 nm and 100 nm MgO, and 60 nm CaCO3 particles was assessed over longer durations (≥72 hr). Results from these stability tests suggest that the 50 nm and 100 nm MgO particles have greater kinetic stability than the 60 nm CaCO3. Batch studies were also used to assess the influence of n-butanol, a co-solvent hypothesized to aid in controlling the rate of alkalinity release, on phase behavior and metal (Mg2+ and Ca2+) solubility. Phase behavior studies suggest that n-butanol has a limited region of miscibility within the soybean oil-water system. Use of n-butanol and water within this region of

  15. Evaluation of the Effect of Temperature on the Stability of Metal ...

    African Journals Online (AJOL)

    Michael Horsfall

    application as thermal stabilizers for poly(vinyl chloride) (Owen ... greases, cosmetics, textiles (Egbuchunam et al.,. 2005). ... “Snake gourd” is a cucurbitaceous vegetable that is cultivated ... Information on the industrial utilization of seed oil of.

  16. Effect of thermal stabilizers (Ba/Cd/Zn metal salts carboxylate and ...

    African Journals Online (AJOL)

    DSC tests and the TG measurements performed in this work, ... a thermogravimeter (TG), Mettler TA 3000 instruments. ... measurement of the degree or the level of stabilisation of ...... main elementary events of degradation and stabilization of ...

  17. Ternary borides Nb7Fe3B8 and Ta7Fe3B8 with Kagome-type iron framework.

    Science.gov (United States)

    Zheng, Qiang; Gumeniuk, Roman; Borrmann, Horst; Schnelle, Walter; Tsirlin, Alexander A; Rosner, Helge; Burkhardt, Ulrich; Reissner, Michael; Grin, Yuri; Leithe-Jasper, Andreas

    2016-06-21

    Two new ternary borides TM7Fe3B8 (TM = Nb, Ta) were synthesized by high-temperature thermal treatment of samples obtained by arc-melting. This new type of structure with space group P6/mmm, comprises TM slabs containing isolated planar hexagonal [B6] rings and iron centered TM columns in a Kagome type of arrangement. Chemical bonding analysis in Nb7Fe3B8 by means of the electron localizability approach reveals two-center interactions forming the Kagome net of Fe and embedded B, while weaker multicenter bonding present between this net and Nb atoms. Magnetic susceptibility measurements reveal antiferromagnetic order below TN = 240 K for Nb7Fe3B8 and TN = 265 K for Ta7Fe3B8. Small remnant magnetization below 0.01μB per f.u. is observed in the antiferromagnetic state. The bulk nature of the magnetic transistions was confirmed by the hyperfine splitting of the Mössbauer spectra, the sizable anomalies in the specific heat capacity, and the kinks in the resistivity curves. The high-field paramagnetic susceptibilities fitted by the Curie-Weiss law show effective paramagnetic moments μeff≈ 3.1μB/Fe in both compounds. The temperature dependence of the electrical resistivity also reveals metallic character of both compounds. Density functional calculations corroborate the metallic behaviour of both compounds and demonstrate the formation of a sizable local magnetic moment on the Fe-sites. They indicate the presence of both antiferro- and ferrromagnetic interactions.

  18. Rescaling metal molybdate nanostructures with biopolymer for energy storage having high capacitance with robust cycle stability.

    Science.gov (United States)

    Minakshi, Manickam; Barmi, Maryam J; Jones, Robert T

    2017-03-14

    Hybrid capacitors can replace or complement batteries, while storing energy through ion adsorption and fast surface redox reactions. There is a growing demand in developing nanostructured materials as electrodes for hybrid systems that can enhance the specific capacitance by ion desolvation in the nanopores. Here, we demonstrate that rescaling the pore diameter with the aid of biopolymer at an optimal level during the synthesis of metal molybdate leads to high capacitance 124 F g(-1) giving robust capacitance retention of 80% over 2000 cycles for a constructed device (activated carbon vs. metal molybdate). The presence of biopolymer (l-glutamic acid) in the metal molybdate acts as a complexing agent of the metal ion while enhancing the mass transport and hence it's improved electrochemical performance. However, XPS and other elemental analyses illustrated no evidence for N doping but traces of other surface functional groups (i.e. C and O) could be present on the molybdate surface. The biopolymer synthetic approach has the advantage of yielding nanostructured material with a relatively narrow pore size distribution controlled by l-glutamic acid. This study will provide a generic route to rescale other metal molybdate, phosphate or oxide counterparts and be an added value to the database.

  19. Preparation of iron boride-silica core-shell nanoparticles with soft ferromagnetic properties.

    Science.gov (United States)

    Saiyasombat, C; Petchsang, N; Tang, I M; Hodak, J H

    2008-02-27

    A one-pot aqueous chemical synthesis for silica-passivated ferromagnetic nanoparticles is presented. The average size of these particles is 84 ± 20 nm. The x-ray and electron diffraction experiments revealed that the nanoparticles are mainly composed of polycrystalline iron boride. The broad x-ray diffraction peak leads to an average crystallite size of 1.8 nm, which is much smaller than the overall size of the particles, and is consistent with the polycrystalline nature of the samples. Mössbauer spectroscopy and magnetization experiments were used to establish the room temperature magnetic properties as well as the chemical nature of the particles. Fe(2)B dominates the composition of the nanoparticles, having a hyperfine field broadly distributed in the 10-33 T range. Alpha iron, the second ferromagnetic material identified in the particles, amounts to 4.6% of the composition. Finally, a paramagnetic phase accounting for approximately 14.6% of the material of the particles was also detected. These nanoparticles contain a core with soft ferromagnetic properties surrounded by a passivating silica layer, and are suitable for magnetically targeted drug delivery and electromagnetic induction heating applications.

  20. Titanium boride equation of state determined by in-situ X-ray diffraction

    Directory of Open Access Journals (Sweden)

    Shigeaki Ono

    2016-12-01

    Full Text Available The equation of state (EOS of titanium boride, TiB2, was investigated by in situ X-ray diffraction in a diamond anvil cell and multianvil high-pressure apparatus. The pressure-volume-temperature (P-V-T data were collected at up to 111 GPa and room temperature for the diamond-anvil cell experiments and at up to 15 GPa and 1300 K for the multianvil experiments. No phase transition was observed through the entire range of experimental conditions. The pressure-volume data at room temperature were fitted using a Vinet EOS to obtain the isothermal bulk modulus, BT0 = 256.7 GPa, and its pressure derivative, B’T0 = 3.83. When fitting a thermal EOS using the P-V-T data for the multianvil experiments, we find that (∂BT/∂TV = 0.095 (GPa/K and α0 = 2.49 × 10−5 K−1.

  1. Metallic corrosion processes reactivation sustained by iron-reducing bacteria: Implication on long-term stability of protective layers

    Science.gov (United States)

    Esnault, L.; Jullien, M.; Mustin, C.; Bildstein, O.; Libert, M.

    In deep geological environments foreseen for the disposal of radioactive waste, metallic containers will undergo anaerobic corrosion. In this context, the formation of corrosion products such as magnetite may reduce the rate of corrosion processes through the formation of a protective layer. This study aims at determining the direct impact of iron-reducing bacteria (IRB) activity on the stability of corrosion protective layers. Batch experiments investigating iron corrosion processes including the formation of secondary magnetite and its subsequent alteration in the presence of IRB show the bacteria ability to use structural Fe(III) for respiration which leads to the sustainment of a high corrosion rate. With the bio-reduction of corrosion products such as magnetite, and H 2 as electron donor, IRB promote the reactivation of corrosion processes in corrosive environments by altering the protective layer. This phenomenon could have a major impact on the long-term stability of metallic compounds involved in multi-barrier system for high-level radioactive waste containment.

  2. Effect of Au Content on Thermal Stability and Mechanical Properties of Au-Cu-Ag-Si Bulk Metallic Glasses

    Science.gov (United States)

    Guo, H.; Zhang, W.; Chen, M. W.; Saotome, Y.; Fukuhara, M.; Inoue, A.

    2011-06-01

    The thermal stability, glass-forming ability (GFA), and mechanical and electrical properties of Au-based Au x Si17Cu75.5- x Ag7.5 ( x = 40 to 75.5 at. pct) metallic glasses were investigated. The glass transition temperature ( T g ) and crystallization temperature ( T x ) decreased with increasing Au content. The ultralow T g values below 373 K (100 °C) were obtained for alloys with x = 55 to 75.5. The alloys with x = 45 to 70 exhibited a high stabilization of supercooled liquid and a high GFA, and the supercooled liquid region and critical sample diameter for glass formation were in the range of 31 K to 50 K and 2 to 5 mm, respectively. The compressive fracture strength ( σ c,f ), Young's modulus ( E), and Vicker's hardness ( H v ) of the bulk metallic glasses (BMGs) decreased with increasing Au content. A linear correlation between Au concentration and the characteristic temperature, i.e., T g and T x , and mechanical properties, i.e., σ c,f , E, and H v , as well as electrical resistivity can be found in the BMGs, which will be helpful for the composition design of the desirable Au-based BMGs with tunable physical properties.

  3. MHD Stability Analysis and Flow Controls of Liquid Metal Free Surface Film Flows as Fusion Reactor PFCs

    Science.gov (United States)

    Zhang, Xiujie; Pan, Chuanjie; Xu, Zengyu

    2016-12-01

    Numerical and experimental investigation results on the magnetohydrodynamics (MHD) film flows along flat and curved bottom surfaces are summarized in this study. A simplified modeling has been developed to study the liquid metal MHD film state, which has been validated by the existing experimental results. Numerical results on how the inlet velocity (V), the chute width (W) and the inlet film thickness (d0) affect the MHD film flow state are obtained. MHD stability analysis results are also provided in this study. The results show that strong magnetic fields make the stable V decrease several times compared to the case with no magnetic field, especially small radial magnetic fields (Bn) will have a significant impact on the MHD film flow state. Based on the above numerical and MHD stability analysis results flow control methods are proposed for flat and curved MHD film flows. For curved film flow we firstly proposed a new multi-layers MHD film flow system with a solid metal mesh to get the stable MHD film flows along the curved bottom surface. Experiments on flat and curved MHD film flows are also carried out and some firstly observed results are achieved. supported by the National Magnetic Confinement Fusion Science Program of China (Nos. 2014GB125003 and 2013GB114002), National Natural Science Foundation of China (No. 11105044)

  4. Multiple Electron Charge Transfer Chemistries for Electrochemical Energy Storage Systems: The Metal Boride and Metal Air Battery

    Science.gov (United States)

    Stuart, Jessica F.

    The primary focus of this work has been to develop high-energy capacity batteries capable of undergoing multiple electron charge transfer redox reactions to address the growing demand for improved electrical energy storage systems that can be applied to a range of applications. As the levels of carbon dioxide (CO2) increase in the Earth's atmosphere, the effects on climate change become increasingly apparent. According to the Energy Information Administration (EIA), the U.S. electric power sector is responsible for the release of 2,039 million metric tons of CO2 annually, equating to 39% of total U.S. energy-related CO2 emissions. Both nationally and abroad, there are numerous issues associated with the generation and use of electricity aside from the overwhelming dependence on fossil fuels and the subsequent carbon emissions, including reliability of the grid and the utilization of renewable energies. Renewable energy makes up a relatively small portion of total energy contributions worldwide, accounting for only 13% of the 3,955 billion kilowatt-hours of electricity produced each year, as reported by the EIA. As the demand to reduce our dependence on fossils fuels and transition to renewable energy sources increases, cost effective large-scale electrical energy storage must be established for renewable energy to become a sustainable option for the future. A high capacity energy storage system capable of leveling the intermittent nature of energy sources such as solar, wind, and water into the electric grid and provide electricity at times of high demand will facilitate this transition. In 2008, the Licht Group presented the highest volumetric energy capacity battery, the vanadium diboride (VB2) air battery, exceedingly proficient in transferring eleven electrons per molecule. This body of work focuses on new developments to this early battery such as fundamentally understanding the net discharge mechanism of the system, evaluation of the properties and performance of nanoscopic anodic materials in addition to the previously developed macroscopic system, as well as the exploration of a high-energy capacity TiB 2/VB2 composite anode. However, the greatest challenge to this room temperature VB2 primary battery is to develop a means to electrochemically recharge the anodic material (how to reinsert the eleven electrons per molecule that are removed during the battery's discharge). Rechargeable batteries, such as the new molten air battery presented in this thesis, offer a high intrinsic capacity mode for energy storage and overcome problems such as the need for higher energy capacity, cost-effective batteries for a range of electronic, transportation, and large-scale power storage devices. Molten air batteries presented and discussed in this work are viable systems that provide a means to electrochemically recharge the VB2-air battery and deliver large-scale energy storage due to their scalability, location flexibility, construction from readily available resources, and offer increased energy storage capacity for the electric grid. One example is the VB2 molten air battery, which discharges according to: VB 2 + 11/4 O2 → 1/ 2 V2O5 + B2O3 (1). Previously, our group has shown that carbon dioxide can be captured from atmospheric air concentrations at solar efficiencies as high as 50%, and that carbon dioxide emissions associated with the production of several commodities can be electrochemically avoided in by the Solar Thermal Electrochemical Process (STEP). Utilizing this process, the carbon molten air battery relies on carbon dioxide directly from the air: Charging: CO2 (g) → C (solid) + O2 (g) (2) Discharging: C (solid) + O2 (g) → CO2 (g) (3). More specifically, in a molten carbonate electrolyte containing added oxide, such as lithium carbonate with lithium oxide, the four-electron charging reaction, Equation 2, approaches 100% faradic efficiency and can be described as the following two equations: O2- (dissolved) + CO2 (g) → CO 32- (molten) (2a) CO32- (molten) ?→ C (solid) + O2 (g) + O2- (dissolved) (2b). Thus, powered by the oxidation of carbon formed directly from the CO 2 in our earth's atmosphere, the carbon molten air battery is a viable system to provide large-scale energy storage. These batteries are rechargeable and have amongst the highest intrinsic battery storage capacities available. The electron charge transfer chemistry is demonstrated through three examples. These examples utilize iron, carbon, and vanadium diboride as reactive materials, each containing intrinsic volumetric energy capacities of 10,000 Wh/L for Fe to Fe (III), 19,000 Wh/L for C to CO2, and 27,000 Wh/L for VB2 to B2O3 and V2O 5, compared to 6,200 Wh/L for the lithium air battery.

  5. Remote Stabilization of Copper Paddlewheel Based Molecular Building Blocks in Metal-Organic Frameworks

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Wen-Yang; Cai, Rong; Pham, Tony; Forrest, Katherine A.; Hogan, Adam; Nugent, Patrick; Williams, Kia; Wojtas, Lukasz; Luebke, Ryan; Weseli; #324; ski, Lukasz J.; Zaworotko, Michael J.; Space, Brian; Chen, Yu-Sheng; Eddaoudi, Mohamed; Shi, Xiaodong; Ma, Shengqian (KAUST); (UC); (USF); (WVU)

    2015-08-21

    Copper paddlewheel based molecular building blocks (MBBs) are ubiquitous and have been widely employed for the construction of highly porous metal–organic frameworks (MOFs). However, most copper paddlewheel based MOFs fail to retain their structural integrity in the presence of water. This instability is directly correlated to the plausible displacement of coordinating carboxylates in the copper paddlewheel MBB, [Cu₂(O₂C-)₄], by the strongly coordinating water molecules. In this comprehensive study, we illustrate the chemical stability control in the rht-MOF platform via strengthening the coordinating bonds within the triangular inorganic MBB, [Cu₃O(N4–x(CH)xC-)₃] (x = 0, 1, or 2). Remotely, the chemical stabilization propagated into the paddlewheel MBB to afford isoreticular rht-MOFs with remarkably enhanced water/chemical stabilities compared to the prototypal rht-MOF-1.

  6. Polarographic Determination of Composition and Thermodynamic Stability Constant of a Complex Metal Ion.

    Science.gov (United States)

    Marin, Dolores; Mendicuti, Francisco

    1988-01-01

    Describes a laboratory experiment designed to encourage laboratory cooperation among individual undergraduate students or groups. Notes each student contributes results individually and the exchange of data is essential to obtain final results. Uses the polarographic method for determining complex metal ions. (MVL)

  7. La2@C72 : Metal-Mediated Stabilization of a Carbon Cage

    NARCIS (Netherlands)

    Stevenson, S.; Burbank, P.; Harich, K.; Dorn, H.C.; Loosdrecht, P.H.M. van; Vries, M.S. de; Salem, J.R.; Kiang, C.-H.; Johnson, R.D.; Bethune, D.S.

    1998-01-01

    In this study, we report production, isolation, and characterization for the relatively small endohedral metallofullerene, La2@C72. As described, La2@C72 is readily isolated from conventional electric-arc-generated carbon/metal soot. This new species was purified by HPLC chromatography and

  8. A Highly Efficient and Self-Stabilizing Metallic-Glass Catalyst for Electrochemical Hydrogen Generation.

    Science.gov (United States)

    Hu, Yuan Chao; Wang, Yi Zhi; Su, Rui; Cao, Cheng Rong; Li, Fan; Sun, Chun Wen; Yang, Yong; Guan, Peng Fei; Ding, Da Wei; Wang, Zhong Lin; Wang, Wei Hua

    2016-12-01

    A multicomponent metallic glass (MG) with highly efficient and anomalous durability for catalyzing water splitting is reported. The outstanding performance of the MG catalyst contributed by self-optimized active sites originates from the intrinsic chemical heterogeneity and selective dealloying on the disordered surface; thus, a new mechanism for improving the durability of catalysts is uncovered.

  9. Computational and experimental investigation for new transition metal selenides and sulfides: The importance of experimental verification for stability

    Science.gov (United States)

    Narayan, Awadhesh; Bhutani, Ankita; Rubeck, Samantha; Eckstein, James N.; Shoemaker, Daniel P.; Wagner, Lucas K.

    2016-07-01

    Expanding the library of known inorganic materials with functional electronic or magnetic behavior is a long-standing goal in condensed matter physics and materials science. Recently, the transition metal chalcogenides including selenium and sulfur have been of interest because of their correlated-electron properties, as seen in the iron-based superconductors and the transition metal dichalcogenides. However, the chalcogenide chemical space is less explored than that of oxides, and there is an open question of whether there may be new materials heretofore undiscovered. We perform a systematic combined theoretical and experimental search over ternary phase diagrams that are empty in the Inorganic Crystal Structure Database containing cations, transition metals, and one of selenium or sulfur. In these 27 ternary systems, we use a probabilistic model to reduce the likelihood of false negative predictions, which results in a list of 24 candidate materials. We then conduct a variety of synthesis experiments to check the candidate materials for stability. While the prediction method did obtain previously unknown compositions that are predicted stable within density functional theory, none of the candidate materials formed in our experiments. We come to the conclusion that these phase diagrams are "empty" in the case of bulk synthesis, but it remains a possibility that alternate synthesis routes may produce some of these phases.

  10. Integrating EDDS-enhanced washing with low-cost stabilization of metal-contaminated soil from an e-waste recycling site.

    Science.gov (United States)

    Beiyuan, Jingzi; Tsang, Daniel C W; Ok, Yong Sik; Zhang, Weihua; Yang, Xin; Baek, Kitae; Li, Xiang-Dong

    2016-09-01

    While chelant-enhanced soil washing has been widely studied for metal extraction from contaminated soils, there are concerns about destabilization and leaching of residual metals after remediation. This study integrated 2-h soil washing enhanced by biodegradable ethylenediaminedisuccinic acid (EDDS) and 2-month stabilization using agricultural waste product (soybean stover biochar pyrolyzed at 300 and 700 °C), industrial by-product (coal fly ash (CFA)), and their mixture. After integration with 2-month stabilization, the leachability and mobility of residual metals (Cu, Zn, and Pb) in the field-contaminated soil were significantly reduced, especially for Cu, in comparison with 2-h EDDS washing alone. This suggested that the metals destabilized by EDDS-washing could be immobilized by subsequent stabilization with biochar and CFA. Moreover, when the remediation performance was evaluated for phytoavailability and bioaccessibility, prior EDDS washing helped to achieve a greater reduction in the bioavailable fraction of metals than sole stabilization treatment. This was probably because the weakly-bound metals were first removed by EDDS washing before stabilization. Both individual and combined applications of biochar and CFA showed comparable effectiveness regardless of the difference in material properties, possibly due to the high level of amendments (150 ton ha(-1)). Based on the mobility and bioaccessibility results, the estimated human health risk (primarily resulting from Pb) could be mitigated to an acceptable level in water consumption pathway or reduced by half in soil ingestion pathway. These results suggest that an integration of EDDS washing with soil stabilization can alleviate post-remediation impacts of residual metals in the treated soil. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Recovery of Metals and Stabilization of Arsenic from (Bio-)Leaching Operations by Engineered Biological Processes

    NARCIS (Netherlands)

    Gonzalez Contreras, P.A.; weghuis, M.O.; Weijma, J.; Buisman, C.J.N.

    2013-01-01

    This paper focuses on the application of biotechnological stabilization of arsenic from (bio-) leaching operations. One of the latest applications of the Thioteq technology is arsenic immobilization. The Thioteq-scorodite biorecovery reactor is an aerobic system to immobilise arsenic in bio-scorodit

  12. Quantitative characterization of the colloidal stability of metallic nanoparticles using UV-vis absorbance spectroscopy.

    Science.gov (United States)

    Ray, Tyler R; Lettiere, Bethany; de Rutte, Joseph; Pennathur, Sumita

    2015-03-31

    Plasmonic nanoparticles are used in a wide variety of applications over a broad array of fields including medicine, energy, and environmental chemistry. The continued successful development of this material class requires the accurate characterization of nanoparticle stability for a variety of solution-based conditions. Although many characterization methods exists, there is an absence of a unified, quantitative means for assessing the colloidal stability of plasmonic nanoparticles. We present the particle instability parameter (PIP) as a robust, quantitative, and generalizable characterization technique based on UV-vis absorbance spectroscopy to characterize colloidal instability. We validate PIP performance with both traditional and alternative characterization methods by measuring gold nanorod instability in response to different salt (NaCl) concentrations. We further measure gold nanorod stability as a function of solution pH, salt, and buffer (type and concentration), nanoparticle concentration, and concentration of free surfactant. Finally, these results are contextualized within the literature on gold nanorod stability to establish a standardized methodology for colloidal instability assessment.

  13. The effect of metal-buffer bilayer drain/source electrodes on the operational stability of the organic field effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Karimi-Alavijeh, H.R., E-mail: h.karimi@eng.ui.ac.ir [Department of Electrical Engineering, University of Isfahan, Isfahan (Iran, Islamic Republic of); Ehsani, A. [Department of Electrical and Avionics Engineering, Malek-Ashtar University of Technology, Isfahan (Iran, Islamic Republic of)

    2015-09-01

    In this paper, we have investigated experimentally the effect of different drain/source (D/S) electrodes and charge injection buffer layers on the electrical properties and operational stability of a stilbene organic field effect transistor (OFET). The results show that the organic buffer layer of copper phthalocyanine (CuPc) considerably improves the electrical properties of the transistors, but has a negligible effect on their temporal behavior. On the other hand, inorganic metal-oxide buffer layer of molybdenum oxide (MoO{sub 3}) drastically changes both the electrical properties and operational stability. The functionalities of this metal-oxide tightly depend on the properties of the D/S metallic electrodes. OFETs with Al/MoO{sub 3} as the bilayer D/S electrodes have the best electrical properties: field effect mobility μ{sub eff} = 0.32 cm{sup 2} V{sup −1} s{sup −1} and threshold voltage V{sub TH} = − 5 V and the transistors with Ag/MoO{sub 3} have the longest operational stability. It was concluded that the chemical stability of the metal/metal-oxide or metal/organic interfaces of the bilayer D/S electrodes determine the operational stability of the OFETs. - Highlights: • The effect of buffer layers on the performance of the stilbene OFETs has been investigated. • Inorganic buffer layer improved the electrical and temporal behaviors simultaneously. • Organic buffer layer only changes the electrical properties. • Chemical stability of the interfaces determines the operational stability of the transistor.

  14. Post-Plasma SiOx Coatings of Metal and Metal Oxide Nanoparticles for Enhanced Thermal Stability and Tunable Photoactivity Applications

    Directory of Open Access Journals (Sweden)

    Patrick Post

    2016-05-01

    Full Text Available The plasma-based aerosol process developed for the direct coating of particles in gases with silicon oxide in a continuous chemical vapor deposition (CVD process is presented. It is shown that non-thermal plasma filaments induced in a dielectric barrier discharge (DBD at atmospheric pressure trigger post-DBD gas phase reactions. DBD operating conditions are first scanned to produce ozone and dinitrogen pentoxide. In the selected conditions, these plasma species react with gaseous tetraethyl orthosilicate (TEOS precursor downstream of the DBD. The gaseous intermediates then condense on the surface of nanoparticles and self-reactions lead to homogeneous solid SiOx coatings, with thickness from nanometer to micrometer. This confirms the interest of post-DBD injection of the organo-silicon precursor to achieve stable production of actives species with subsequent controlled thickness of SiOx coatings. SiOx coatings of spherical and agglomerated metal and metal oxide nanoparticles (Pt, CuO, TiO2 are achieved. In the selected DBD operating conditions, the thickness of homogeneous nanometer sized coatings of spherical nanoparticles depends on the reaction duration and on the precursor concentration. For agglomerates, operating conditions can be tuned to cover preferentially the interparticle contact zones between primary particles, shifting the sintering of platinum agglomerates to much higher temperatures than the usual sintering temperature. Potential applications for enhanced thermal stability and tunable photoactivity of coated agglomerates are presented.

  15. Post-Plasma SiOx Coatings of Metal and Metal Oxide Nanoparticles for Enhanced Thermal Stability and Tunable Photoactivity Applications.

    Science.gov (United States)

    Post, Patrick; Jidenko, Nicolas; Weber, Alfred P; Borra, Jean-Pascal

    2016-05-13

    The plasma-based aerosol process developed for the direct coating of particles in gases with silicon oxide in a continuous chemical vapor deposition (CVD) process is presented. It is shown that non-thermal plasma filaments induced in a dielectric barrier discharge (DBD) at atmospheric pressure trigger post-DBD gas phase reactions. DBD operating conditions are first scanned to produce ozone and dinitrogen pentoxide. In the selected conditions, these plasma species react with gaseous tetraethyl orthosilicate (TEOS) precursor downstream of the DBD. The gaseous intermediates then condense on the surface of nanoparticles and self-reactions lead to homogeneous solid SiOx coatings, with thickness from nanometer to micrometer. This confirms the interest of post-DBD injection of the organo-silicon precursor to achieve stable production of actives species with subsequent controlled thickness of SiOx coatings. SiOx coatings of spherical and agglomerated metal and metal oxide nanoparticles (Pt, CuO, TiO₂) are achieved. In the selected DBD operating conditions, the thickness of homogeneous nanometer sized coatings of spherical nanoparticles depends on the reaction duration and on the precursor concentration. For agglomerates, operating conditions can be tuned to cover preferentially the interparticle contact zones between primary particles, shifting the sintering of platinum agglomerates to much higher temperatures than the usual sintering temperature. Potential applications for enhanced thermal stability and tunable photoactivity of coated agglomerates are presented.

  16. Structure, bonding and energetics of N-heterocyclic carbene (NHC) stabilized low oxidation state group 2 (Be, Mg, Ca, Sr and Ba) metal complexes: A theoretical study

    Indian Academy of Sciences (India)

    Ashim Baishya; V Rao Mundlapati; Sharanappa Nembenna; Himansu S Biswal

    2014-11-01

    A series of N-heterocyclic carbene stabilized low oxidation state group 2 metal halide and hydrides with metal-metal bonds ([L(X) M-M(X) L]; L = NHC ((CHNH)2C:), M = Be, Mg, Ca, Sr and Ba, and X = Cl or H) has been studied by computational methods. The main objective of this study is to predict whether it is possible to stabilize neutral ligated low oxidation state alkaline-earth metal complexes with metal-metal bonds. The homolytic metal-metal Bond Dissociation Energy (BDE) calculation, Natural Bond Orbital (NBO) and Energy Decomposition Analyses (EDA) on density functional theory (DFT) optimized [L(X)M-M(X)L] complexes revealed that they are as stable as their -diketiminate, guanidinate and -diimine counterparts. The optimized structures of the complexes are in trans-linear geometries. The bond order analyses such as Wiberg Bond Indices (WBI) and Fuzzi Bond Order (FBO) confirm the existence of single bond between two metal atoms, and it is covalent in nature.

  17. Effect of heavy metals on the stabilization of mercury(II) by DTCR in desulfurization solutions

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Jiaai; Lu, Rongjie; Sun, Mingyang; Baig, Shams Ali; Tang, Tingmei; Cheng, Lihua [Department of Environmental Engineering, Zhejiang University, Hangzhou 310058 (China); Xu, Xinhua, E-mail: xuxinhua@zju.edu.cn [Department of Environmental Engineering, Zhejiang University, Hangzhou 310058 (China)

    2012-05-30

    Highlights: Black-Right-Pointing-Pointer The interference of heavy metals on Hg{sup 2+} removal by DTCR was first investigated. Black-Right-Pointing-Pointer Mechanism of the decrease in the participating performance over Hg{sup 2+} was analyzed. Black-Right-Pointing-Pointer Optimal DTCR dosage was determined in the coexistence of Cu{sup 2+} or Pb{sup 2+} with Hg{sup 2+}. Black-Right-Pointing-Pointer Effect of pH value on the interference of Hg{sup 2+} removal rate was studied. Black-Right-Pointing-Pointer The equilibrium constant of Cu{sup 2+} and Hg{sup 2+} with DTCR was obtained. - Abstract: Several heavy metals, including Cu{sup 2+}, Ni{sup 2+}, Pb{sup 2+}, and Zn{sup 2+}, were investigated in simulated desulfurization solutions to evaluate their interferences with Hg{sup 2+} during the reaction with dithiocarbamate type chelating resin (DTCR). Appropriate DTCR dosage and the effect of pH were also explored with respect to restoration of high Hg{sup 2+} precipitation efficiency and reduction of mercury concentrations. The experimental results suggested that increasing heavy metal concentration inhibited Hg{sup 2+} precipitation efficiency to a considerable extent and the inhibition order of the four heavy metals was Cu{sup 2+} > Ni{sup 2+} > Pb{sup 2+} > Zn{sup 2+}. However, the coordination ability was closely related to the configuration and the orbital hybridization of each metal. In the cases of Cu{sup 2+} and Pb{sup 2+}, increased DTCR dosage was beneficial to Hg{sup 2+} precipitation, which could lay the foundation of practical applications of DTCR dosage for industrial wastewater treatment. The enhanced Hg{sup 2+} precipitation performance seen for increasing pH might have come from the deprotonation of sulfur atoms on the DTCR functional groups and the formation of metal hydroxides (M(OH){sub 2}, M = Cu, Pb, Hg).

  18. Investigations on the conditional kinetic and thermodynamic stability of aquatic humic substance-metal complexes by means of EDTA exchange, ultrafiltration and atomic spectrometry.

    Science.gov (United States)

    Van den Bergh, J; Jakubowski, B; Burba, P

    2001-09-13

    The conditional metal availability and the kinetic stability of humic substance-metal species in humic-rich waters (e.g. bog water) was characterized by means of EDTA exchange. For this purpose a combined procedure consisting of time-controlled ligand exchange by EDTA, species differentiation by a fast single-stage tangential-flow ultrafiltration (TF-UF) technique (cut-off 1 kDa) and sensitive atomic spectrometry methods (e.g. AAS, ICP-OES, TXRF) was developed. The kinetics and the yield of the EDTA exchange served as operational parameters for assessing the kinetic stability and EDTA availability of HS-metal species, respectively. Considerable fractions of natural HS-metal species studied were shown to be EDTA-inert (e.g. 31% of the total Fe, 44% of the total Al) even after long reaction times (48 h), in contrast to artificial ones formed in solutions of isolated HS. Moreover, the conditional thermodynamic stability of HS-metal complexes formed by successive loading of an aquatic reference HS (HO14) with a number of heavy metal ions (e.g. Cr(III), Cu(II), Fe(III), Mn(II), Zn(II)) was also evaluated discriminating the free metal concentrations by means of TF-UF. In addition, from the loading isotherms obtained conditional complexation capacities could be derived for the studied HS exhibiting the order Fe(III)>Cu(II)>Cr(III)>Co(II)>Mn(II).

  19. Dichlorostannylene complexes of group 10 metals, a unique bonding mode stabilized by bridging 2-pyridyldiphenylphosphine ligands

    NARCIS (Netherlands)

    Cabon, Y.; Kleijn, H.; Siegler, M. A.; Spek, A.L.; Klein Gebbink, R.J.M.; Deelman, B.J.

    2010-01-01

    The reaction of tin dichloride with catalytically-relevant group 10 metal precursors [M(Cl)(X)(2-PyPPh2)2] (M = Ni, Pd, Pt; 2-PyPPh2 = 2-pyridyldiphenylphosphine; X = Cl, Me) provides easy access to unprecedented cationic dichlorostannylene complexes [M(X)(2-PyPPh2)2(SnCl2)]+ where the M–Sn bond is

  20. Direct generation of oxygen-stabilized radicals by H• transfer from transition metal hydrides.

    Science.gov (United States)

    Kuo, Jonathan L; Hartung, John; Han, Arthur; Norton, Jack R

    2015-01-28

    Transition-metal hydrides generate α-alkoxy radicals by H• transfer to enol ethers. We have measured the rate constant for transfer from CpCr(CO)3H to n-butyl vinyl ether and have examined the chemistry of radicals generated by such transfers. Radicals from appropriate substrates undergo 5-exo cyclization, with higher diastereoselectivity than the analogous all-carbon radicals. From such radicals it is straightforward to make substituted tetrahydrofurans.

  1. Easy Access to Metallic Copper Nanoparticles with High Activity and Stability for CO Oxidation.

    Science.gov (United States)

    Gonçalves, Renato V; Wojcieszak, Robert; Wender, Heberton; Sato B Dias, Carlos; Vono, Lucas L R; Eberhardt, Dario; Teixeira, Sergio R; Rossi, Liane M

    2015-04-22

    Copper catalysts are very promising, affordable alternatives for noble metals in CO oxidation; however, the nature of the active species remains unclear and differs throughout previous reports. Here, we report the preparation of 8 nm copper nanoparticles (Cu NPs), with high metallic content, directly deposited onto the surface of silica nanopowders by magnetron sputtering deposition. The as-prepared Cu/SiO2 contains 85% Cu0 and 15% Cu2+ and was enriched in the Cu0 phase by H2 soft pretreatment (96% Cu0 and 4% Cu2+) or further oxidized after treatment with O2 (33% Cu0 and 67% Cu2+). These catalysts were studied in the catalytic oxidation of CO under dry and humid conditions. Higher activity was observed for the sample previously reduced with H2, suggesting that the presence of Cu-metal species enhances CO oxidation performance. Inversely, a poorer performance was observed for the sample previously oxidized with O2. The presence of water vapor caused only a small increase in the temperature require for the reaction to reach 100% conversion. Under dry conditions, the Cu NP catalyst was able to maintain full conversion for up to 45 h at 350 °C, but it deactivated with time on stream in the presence of water vapor.

  2. Selection of a mineral binder with potentialities for the stabilization/solidification of aluminum metal

    Energy Technology Data Exchange (ETDEWEB)

    Cau Dit Coumes, C., E-mail: celine.cau-dit-coumes@cea.fr [Commissariat à l’Energie Atomique et aux Energies Alternatives, CEA/DEN/MAR/DTCD/SPDE, BP17171, 30207 Bagnols-sur-Cèze cedex (France); Lambertin, D.; Lahalle, H.; Antonucci, P. [Commissariat à l’Energie Atomique et aux Energies Alternatives, CEA/DEN/MAR/DTCD/SPDE, BP17171, 30207 Bagnols-sur-Cèze cedex (France); Cannes, C.; Delpech, S. [Institut de Physique Nucléaire, CNRS, Univ. Paris-Sud 11, 91406 Orsay Cedex (France)

    2014-10-15

    Highlights: • Binders capable of reducing the pore solution pH compared with Portland cements are reviewed. • The binders are then tested against aluminum corrosion. • Corrosion of aluminum metal is minimal with magnesium phosphate cement. • The H{sub 2} release can be reduced still further by adding LiNO{sub 3} to the mixing solution. • Electrochemical characterizations show that aluminum tends to a passive state. - Abstract: In a strongly alkaline medium, such as that encountered in conventional cementitious materials based on Portland cement, aluminum metal is corroded, with continued production of hydrogen. In order to develop a mineral matrix having enhanced compatibility with aluminum, a literature review was first undertaken to identify binders capable of reducing the pore solution pH compared with Portland cement. An experimental study was then carried out to measure the hydrogen production resulting from corrosion of aluminum metal rods encapsulated in the different selected cement pastes. The best results were achieved with magnesium phosphate cement, which released very little hydrogen over the duration of the study. This production could be reduced still further by adding a corrosion inhibitor (lithium nitrate) to the mixing solution. Open circuit potential measurement and Electrochemical Impedance Spectroscopy of aluminum electrode encapsulated in two pastes based on Portland cement and magnesium phosphate cement showed different redox behaviors. In the Portland cement paste, the electrochemical data confirmed the corrosion of aluminum whereas this latter tended to a passive state in the magnesium phosphate binder.

  3. Thermal stability of tungsten-titanium diffusion barriers for silver metallization

    Energy Technology Data Exchange (ETDEWEB)

    Bhagat, S.K. [School of Materials, Arizona State University, Tempe, Arizona (United States); Theodore, N.D. [School of Materials, Arizona State University, Tempe, Arizona (United States); Wireless and Packaging Systems Laboratory, Freescale Semiconductor Inc., Tempe, Arizona (United States); Alford, T.L. [School of Materials, Arizona State University, Tempe, Arizona (United States)], E-mail: alford@asu.edu

    2008-09-01

    Tungsten-titanium thin films have been extensively applied as barrier layers for aluminum and copper metallization. The present work investigated the feasibility of tungsten-titanium barrier layers for silver metallization. Reactive sputtered W-Ti was deposited on a Si wafer followed by an Ag thin film on top. The resulting samples were annealed in vacuum at temperatures up to 700 deg. C. These were then characterized using X-ray diffractometry, Rutherford backscattering spectrometry, secondary ion mass spectroscopy, transmission electron microscopy, scanning electron microscopy and four point probe analysis. The analyses showed that the samples were stable up to 600 deg. C. Secondary ion mass spectroscopy showed that above 600 deg. C, agglomeration of silver film started. Si started moving into the tungsten-titanium film above 600 deg. C. Movement of Si resulted in local Si voiding as indicated by transmission electron microscopy. At Si/W-Ti interface, silicide formation occurred. Silver agglomerated completely at 700 deg. C. These results showed that W-Ti was an effective barrier layer for silver metallization for process temperatures below 600 deg. C.

  4. Antioxidant study of quercetin and their metal complex and determination of stability constant by spectrophotometry method.

    Science.gov (United States)

    Ravichandran, R; Rajendran, M; Devapiriam, D

    2014-03-01

    Quercetin found chelate cadmium ions, scavenge free radicals produced by cadmium. Hence new complex, quercetin with cadmium was synthesised, and the synthesised complex structures were determined by UV-vis spectrophotometry, infrared spectroscopy, thermogravimetry and differential thermal analysis techniques (UV-vis, IR, TGA and DTA). The equilibrium stability constants of quercetin-cadmium complex were determined by Job's method. The determined stability constant value of quercetin-cadminum complex at pH 4.4 is 2.27×10(6) and at pH 7.4 is 7.80×10(6). It was found that the quercetin and cadmium ion form 1:1 complex in both pH 4.4 and pH 7.4. The structure of the compounds was elucidated on the basis of obtained results. Furthermore, the antioxidant activity of the free quercetin and quercetin-cadmium complexes were determined by DPPH and ABTS assays.

  5. Humidity versus photo-stability of metal halide perovskite films in a polymer matrix.

    Science.gov (United States)

    Manshor, Nurul Ain; Wali, Qamar; Wong, Ka Kan; Muzakir, Saifful Kamaluddin; Fakharuddin, Azhar; Schmidt-Mende, Lukas; Jose, Rajan

    2016-08-21

    Despite the high efficiency of over 21% reported for emerging thin film perovskite solar cells, one of the key issues prior to their commercial deployment is to attain their long term stability under ambient and outdoor conditions. The instability in perovskite is widely conceived to be humidity induced due to the water solubility of its initial precursors, which leads to decomposition of the perovskite crystal structure; however, we note that humidity alone is not the major degradation factor and it is rather the photon dose in combination with humidity exposure that triggers the instability. In our experiment, which is designed to decouple the effect of humidity and light on perovskite degradation, we investigate the shelf-lifetime of CH3NH3PbI3 films in the dark and under illumination under high humidity conditions (Rel. H. > 70%). We note minor degradation in perovskite films stored in a humid dark environment whereas upon exposure to light, the films undergo drastic degradation, primarily owing to the reactive TiO2/perovskite interface and also the surface defects of TiO2. To enhance its air-stability, we incorporate CH3NH3PbI3 perovskite in a polymer (poly-vinylpyrrolidone, PVP) matrix which retained its optical and structural characteristics in the dark for ∼2000 h and ∼800 h in room light soaking, significantly higher than a pristine perovskite film, which degraded completely in 600 h in the dark and in less than 100 h when exposed to light. We attribute the superior stability of PVP incorporated perovskite films to the improved structural stability of CH3NH3PbI3 and also to the improved TiO2/perovskite interface upon incorporating a polymer matrix. Charge injection from the polymer embedded perovskite films has also been confirmed by fabricating solar cells using them, thereby providing a promising future research pathway for stable and efficient perovskite solar cells.

  6. Metal-Induced Stabilization and Activation of Plasmid Replication Initiator RepB

    Science.gov (United States)

    Ruiz-Masó, José A.; Bordanaba-Ruiseco, Lorena; Sanz, Marta; Menéndez, Margarita; del Solar, Gloria

    2016-01-01

    Initiation of plasmid rolling circle replication (RCR) is catalyzed by a plasmid-encoded Rep protein that performs a Tyr- and metal-dependent site-specific cleavage of one DNA strand within the double-strand origin (dso) of replication. The crystal structure of RepB, the initiator protein of the streptococcal plasmid pMV158, constitutes the first example of a Rep protein structure from RCR plasmids. It forms a toroidal homohexameric ring where each RepB protomer consists of two domains: the C-terminal domain involved in oligomerization and the N-terminal domain containing the DNA-binding and endonuclease activities. Binding of Mn2+ to the active site is essential for the catalytic activity of RepB. In this work, we have studied the effects of metal binding on the structure and thermostability of full-length hexameric RepB and each of its separate domains by using different biophysical approaches. The analysis of the temperature-induced changes in RepB shows that the first thermal transition, which occurs at a range of temperatures physiologically relevant for the pMV158 pneumococcal host, represents an irreversible conformational change that affects the secondary and tertiary structure of the protein, which becomes prone to self-associate. This transition, which is also shown to result in loss of DNA binding capacity and catalytic activity of RepB, is confined to its N-terminal domain. Mn2+ protects the protein from undergoing this detrimental conformational change and the observed protection correlates well with the high-affinity binding of the cation to the active site, as substituting one of the metal-ligands at this site impairs both the protein affinity for Mn2+and the Mn2+-driven thermostabilization effect. The level of catalytic activity of the protein, especially in the case of full-length RepB, cannot be explained based only on the high-affinity binding of Mn2+ at the active site and suggests the existence of additional, lower-affinity metal binding site

  7. Solvent and stabilizer free growth of Ag and Pd nanoparticles using metallic salts/cyclotriphosphazenes mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Díaz Valenzuela, C. [Departamento de Química, Facultad de Química, Universidad de Chile, La Palmeras 3425, Nuñoa, Casilla 653, Santiago de Chile (Chile); Valenzuela, M.L., E-mail: mlvalenzuela@unab.cl [Universidad Andres Bello, Departamento de Ciencias Química, Facultad de Ciencias Exactas, Av. Republica 275, Santiago (Chile); Caceres, S.; Diaz, R. [Departamento de Química, Facultad de Química, Universidad de Chile, La Palmeras 3425, Nuñoa, Casilla 653, Santiago de Chile (Chile); O' Dwyer, C. [Applied Nanoscience Group, Department of Chemistry, University College Cork, Cork (Ireland); Micro and Nanoelectronics Centre, Tyndall National Institute, Lee Maltings, Cork (Ireland)

    2013-12-16

    Cyclotriphosphazene is used as a sacrificial solid-state template to synthesize a range of Ag and Pd nanoparticles with diverse geometries by thermal treatment using MLn/N{sub 3}P{sub 3}(O{sub 2}C{sub 12}H{sub 8}){sub 3} mixtures. The Pd and Ag nanoparticles are synthesized by solid-state pyrolysis of AgPPh{sub 3}[CF{sub 3}SO{sub 3}]/N{sub 3}P{sub 3}(O{sub 2}C{sub 12}H{sub 8}){sub 3} and PdCl{sub 2}/N{sub 3}P{sub 3}(O{sub 2}C{sub 12}H{sub 8}){sub 3} mixtures with molar relationships of 1:1, 1:5 and 1:10 respectively, in air and at 800 °C. The morphology of the as-prepared nanoparticles is found to depend on the molar ratio of the precursor mixture, the preparation method and of the nature of the metal. Ag and Pd, microcrystals were thermally grown on Si from the respective 1:1 precursors while that metal foams were grown from 1:5 ratios precursors on SiO{sub 2} wafers. High resolution transmission electron microscopy investigations reveal in most cases small crystals of Pd. HRSTEM measurements indicate that the formation of the Pd and Ag nanoparticles occurs through a phase demixing and dewetting mechanism. This approach has potential to be a useful and facile method to prepare metallic nanoparticles without requiring solutions or surfactants for application in electronic, catalytic and sensor materials and devices. - Highlights: • Pyrolysis MLn/N{sub 3}P{sub 3}(O{sub 2}C{sub 12}H{sub 8}){sub 3} mixtures under air, give Pd and Ag nanoparticles. • AgPPh{sub 3}[CF{sub 3}SO{sub 3}] and PdCl{sub 2} in molar ratios 1:1 and 1:5 were used. • Metal foams were obtained from 1:5 ratios when deposited on SiO{sub 2.} • Using crucible supporting in 1:1 metal/trimer <2 nm Pd nanoparticles were obtained. • The probable mechanism involves a dewetting, nucleation and ripening crystallization.

  8. High mobility and high stability glassy metal-oxynitride materials and devices

    Science.gov (United States)

    Lee, Eunha; Kim, Taeho; Benayad, Anass; Hur, Jihyun; Park, Gyeong-Su; Jeon, Sanghun

    2016-04-01

    In thin film technology, future semiconductor and display products with high performance, high density, large area, and ultra high definition with three-dimensional functionalities require high performance thin film transistors (TFTs) with high stability. Zinc oxynitride, a composite of zinc oxide and zinc nitride, has been conceded as a strong substitute to conventional semiconductor film such as silicon and indium gallium zinc oxide due to high mobility value. However, zinc oxynitride has been suffered from poor reproducibility due to relatively low binding energy of nitrogen with zinc, resulting in the instability of composition and its device performance. Here we performed post argon plasma process on zinc oxynitride film, forming nano-crystalline structure in stable amorphous matrix which hampers the reaction of oxygen with zinc. Therefore, material properties and device performance of zinc oxynitride are greatly enhanced, exhibiting robust compositional stability even exposure to air, uniform phase, high electron mobility, negligible fast transient charging and low noise characteristics. Furthermore, We expect high mobility and high stability zinc oxynitride customized by plasma process to be applicable to a broad range of semiconductor and display devices.

  9. Scaffolding, ladders, chains, and rare ferrimagnetism in intermetallic borides: synthesis, crystal chemistry and magnetism.

    Science.gov (United States)

    Goerens, Christian; Brgoch, Jakoah; Miller, Gordon J; Fokwa, Boniface P T

    2011-07-04

    Single-phase polycrystalline samples and single crystals of the complex boride phases Ti(8)Fe(3)Ru(18)B(8) and Ti(7)Fe(4)Ru(18)B(8) have been synthesized by arc melting the elements. The phases were characterized by powder and single-crystal X-ray diffraction as well as energy-dispersive X-ray analysis. They are new substitutional variants of the Zn(11)Rh(18)B(8) structure type, space group P4/mbm (no. 127). The particularity of their crystal structure lies in the simultaneous presence of dumbbells which form ladders of magnetically active iron atoms along the [001] direction and two additional mixed iron/titanium chains occupying Wyckoff sites 4h and 2b. The ladder substructure is ca. 3.0 Å from the two chains at the 4h, which creates the sequence chain-ladder-chain, establishing a new structural and magnetic motif, the scaffold. The other chain (at 2b) is separated by at least 6.5 Å from this scaffold. According to magnetization measurements, Ti(8)Fe(3)Ru(18)B(8) and Ti(7)Fe(4)Ru(18)B(8) order ferrimagnetically below 210 and 220 K, respectively, with the latter having much higher magnetic moments than the former. However, the magnetic moment observed for Ti(8)Fe(3)Ru(18)B(8) is unexpectedly smaller than the recently reported Ti(9)Fe(2)Ru(18)B(8) ferromagnet. The variation of the magnetic moments observed in these new phases can be adequately understood by assuming a ferrimagnetic ordering involving the three different iron sites. Furthermore, the recorded hysteresis loops indicate a semihard magnetic behavior for the two phases. The highest H(c) value (28.6 kA/m), measured for Ti(7)Fe(4)Ru(18)B(8), lies just at the border of those of hard magnetic materials.

  10. Application of Stabilized Lithium Metal Powder (SLMP®) in graphite anode - A high efficient prelithiation method for lithium-ion batteries

    Science.gov (United States)

    Wang, Zhihui; Fu, Yanbao; Zhang, Zhengcheng; Yuan, Shengwen; Amine, Khalil; Battaglia, Vincent; Liu, Gao

    2014-08-01

    Stabilized Lithium Metal Powder (SLMP®) was applied in graphite anode and the effects of this prelithiation method to cell performance were investigated. Performance of prelithiated cells was compared with that of regular graphite based cells. The first cycle capacity loss of SLMP prelithiated cell was largely reduced and the corresponding first cycle Coulombic efficiency was significantly improved. The graphite/NMC cell with SLMP prelithiation but without any standard cell formation process showed better cycle performance than that of none SLMP containing cell with standard formation process. Prelithiation of graphite electrode with SLMP promote stable solid electrolyte interface (SEI) formation on the surface of graphite anode. Application of SLMP in lithium-ion battery thus provides an effective method to enhance capacity, and promises a low cost SEI formation process. This also implies the potential use of other promising anode materials, such as Si and Sn that have large first cycle capacity loss, in commercial lithium-ion batteries.

  11. Characteristics and Modification of Non-metallic Inclusions in Titanium-Stabilized AISI 409 Ferritic Stainless Steel

    Science.gov (United States)

    Kruger, Dirk; Garbers-Craig, Andrie

    2017-06-01

    This study describes an investigation into the improvement of castability, final surface quality and formability of titanium-stabilized AISI 409 ferritic stainless steel on an industrial scale. Non-metallic inclusions found in this industrially produced stainless steel were first characterized using SEM-EDS analyses through the INCA-Steel software platform. Inclusions were found to consist of a MgO·Al2O3 spinel core, which acted as heterogeneous nucleation site for titanium solubility products. Plant-scale experiments were conducted to either prevent the formation of spinel, or to modify it by calcium treatment. Modification to spherical dual-phase spinel-liquid matrix inclusions was achieved with calcium addition, which eliminated submerged entry nozzle clogging for this grade. Complete modification to homogeneous liquid calcium aluminates was achieved at high levels of dissolved aluminum. A mechanism was suggested to explain the extent of modification achieved.

  12. Characteristics and Modification of Non-metallic Inclusions in Titanium-Stabilized AISI 409 Ferritic Stainless Steel

    Science.gov (United States)

    Kruger, Dirk; Garbers-Craig, Andrie

    2017-02-01

    This study describes an investigation into the improvement of castability, final surface quality and formability of titanium-stabilized AISI 409 ferritic stainless steel on an industrial scale. Non-metallic inclusions found in this industrially produced stainless steel were first characterized using SEM-EDS analyses through the INCA-Steel software platform. Inclusions were found to consist of a MgO·Al2O3 spinel core, which acted as heterogeneous nucleation site for titanium solubility products. Plant-scale experiments were conducted to either prevent the formation of spinel, or to modify it by calcium treatment. Modification to spherical dual-phase spinel-liquid matrix inclusions was achieved with calcium addition, which eliminated submerged entry nozzle clogging for this grade. Complete modification to homogeneous liquid calcium aluminates was achieved at high levels of dissolved aluminum. A mechanism was suggested to explain the extent of modification achieved.

  13. Determination of Stability Constants of Triazole Ligand Carrying Naphthol Group with Heavy Metal Ions in Aqueous Solutions

    Directory of Open Access Journals (Sweden)

    Nurhan Gümrükçüoğlu

    2013-12-01

    Full Text Available Interaction of 4-(2-hydroxy-1-naphthylmethylamino-3-methyl-5-(4-tolyl-4H-1,2,4-triazole with heavy metal cations such as Cu2+, Co2+, Cd2+, Ni2+ and Pb2+ was investigated by using UV-visible spectrophotometric technique. The complex stability constants (Log β were determined in aqueous as well as in methanol: water (1:1 system at 25 ± 0.1°C by Buschmann’s method and Valeur’s methods, respectively. The ligand showed good sensitivity for Co2+ with a linear range of 210-6M to 310-5M.

  14. Zr–Cu thin film metallic glasses: An assessment of the thermal stability and phases’ transformation mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Apreutesei, M. [MATEIS Laboratory-INSA de Lyon, Bât. B. Pascal, 7 Avenue Jean Capelle, 69621 Villeurbanne Cedex (France); Steyer, P., E-mail: philippe.steyer@insa-lyon.fr [MATEIS Laboratory-INSA de Lyon, Bât. B. Pascal, 7 Avenue Jean Capelle, 69621 Villeurbanne Cedex (France); Billard, A. [LERMPS-UTBM, Site de Montbéliard, 90010 Belfort Cédex (France); Joly-Pottuz, L.; Esnouf, C. [MATEIS Laboratory-INSA de Lyon, Bât. B. Pascal, 7 Avenue Jean Capelle, 69621 Villeurbanne Cedex (France)

    2015-01-15

    Highlights: • Binary Zr–Cu TFMGs with high glass-forming ability were fabricated. • Crystallization kinetics of Zr–Cu glassy films was studied. • Crystallization is governed by multi-stage step diffusion-controlled growth. • Films exhibit smooth and dense surface morphology and vein-like features. - Abstract: The PVD co-sputtering technology is an efficient way to deposit Zr–Cu thin film metallic glass in a wide composition range. The structural stability and crystallization behavior of metallic glass films are investigated by in situ X-ray diffraction (XRD) via heating up to 873 K. The glassy films within the 33.3–89.1 at.% Cu range maintained their amorphous structure at temperatures higher than 550 K. Within this chemical composition range, films exhibit a smooth and dense surface morphology with 100 nm-sized grains and vein-like features. Glassy films revealed a high thermal stability as reflected by differential scanning calorimetry experiments and in situ high temperature XRD analysis. It was found that the structure evolved with the temperature and copper contents from a highly textured {1 1 1} crystallized fcc-Zr to intermetallic CuZr{sub 2}, Cu{sub 10}Zr{sub 7}, Cu{sub 51}Zr{sub 14} phases to finally {1 1 1} crystallized fcc-Cu. Mechanisms involved in the structural changes of the glassy films together with the multi-stage crystallization process are discussed in the light of the copper contents.

  15. Chemical and thermal stability of refrigerant-lubricant mixtures with metals. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Huttenlocher, D.F.

    1992-10-09

    This report presents the results of a sealed tube stability study on twenty-one refrigerant-lubricant mixtures selected from the following groupings: HFCs R-32, R-125, R-134, R-134a, R-143a, and R-152a with one or more lubricants selected from among three pentaerythritol esters and three polyalkylene glycols. All lubricants were carefully predried to 25 ppm or less moisture content. HCFCs R-22, R-123, R-124, and R-142b, as well as CFC R-11, with one or more lubricants selected from among two mineral oils and one alkylbenzene fluid. Bach test mixture was aged at three temperature levels.

  16. Chemical and thermal stability of refrigerant-lubricant mixtures with metals

    Energy Technology Data Exchange (ETDEWEB)

    Huttenlocher, D.F.

    1992-10-09

    This report presents the results of a sealed tube stability study on twenty-one refrigerant-lubricant mixtures selected from the following groupings: HFCs R-32, R-125, R-134, R-134a, R-143a, and R-152a with one or more lubricants selected from among three pentaerythritol esters and three polyalkylene glycols. All lubricants were carefully predried to 25 ppm or less moisture content. HCFCs R-22, R-123, R-124, and R-142b, as well as CFC R-11, with one or more lubricants selected from among two mineral oils and one alkylbenzene fluid. Bach test mixture was aged at three temperature levels.

  17. Fabrication of aluminum nitride and its stability in liquid alkali metals

    Energy Technology Data Exchange (ETDEWEB)

    Natesan, K.; Rink, D.L. [Argonne National Lab., Chicago, IL (United States)

    1995-04-01

    The objective of this task are to (a) evaluate several fabrication procedures for development of aluminum nitride (AlN) coatings on the candidate first-wall structural material V-5wt.%Cr-5wt.%Ti, (b) evaluate the stability of coatings in contact with the structural alloy and liquid Li at temperatures of 200 to 400{degrees}C, (c) measure the electrical resistivity of the coated films after exposure to liquid Li, (d) evaluate the effects of coating defects on electrical resistivity, and (e) establish in-situ repair procedures to maintain adequate electrical insulating properties for the coatings.

  18. Chemical and thermal stability of refrigerant-lubricant mixtures with metals

    Energy Technology Data Exchange (ETDEWEB)

    Huttenlocher, D.F.

    1992-10-09

    This report presents the results of a sealed tube stability study on twenty-one refrigerant-lubricant mixtures selected from the following groupings: HFCs R-32, R-125, R-134, R-134a, R-143a, and R-152a with one or more lubricants selected from among three pentaerythritol esters and three polyalkylene glycols. All lubricants were carefully predried to 25 ppm or less moisture content. HCFCs R-22, R-123, R-124, and R-142b, as well as CFC R-11, with one or more lubricants selected from among two mineral oils and one alkylbenzene fluid. Bach test mixture was aged at three temperature levels.

  19. Chemical and thermal stability of refrigerant-lubricant mixtures with metals. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Huttenlocher, D.F.

    1992-10-09

    This report presents the results of a sealed tube stability study on twenty-one refrigerant-lubricant mixtures selected from the following groupings: HFCs R-32, R-125, R-134, R-134a, R-143a, and R-152a with one or more lubricants selected from among three pentaerythritol esters and three polyalkylene glycols. All lubricants were carefully predried to 25 ppm or less moisture content. HCFCs R-22, R-123, R-124, and R-142b, as well as CFC R-11, with one or more lubricants selected from among two mineral oils and one alkylbenzene fluid. Bach test mixture was aged at three temperature levels.

  20. Solubility of Iron in Metallic Hydrogen and Stability of Dense Cores in Giant Planets

    CERN Document Server

    Wahl, Sean; Militzer, Burkhard

    2013-01-01

    The formation of the giant planets in our solar system, and likely a majority of giant exoplanets, is commonly explained by the accretion of nebular hydrogen and helium onto a large core of terrestrial-like composition. The fate of this core has important consequences for the evolution of the interior structure of the planet. It has recently been shown that H2O, MgO and SiO2 dissolve in liquid metallic hydrogen at high temperature and pressure. In this study, we perform ab initio calculations to study the solubility of an innermost metallic core. We find dissolution of iron to be strongly favored above 2000 K over the entire pressure range (0.4-4 TPa) considered. We compare with and summarize the results for solubilities on other probable core constituents. The calculations imply that giant planet cores are in thermodynamic disequilibrium with surrounding layers, promoting erosion and redistribution of heavy elements. Differences in solubility behavior between iron and rock may influence evolution of interior...

  1. Selection of a mineral binder with potentialities for the stabilization/solidification of aluminum metal

    Science.gov (United States)

    Cau Dit Coumes, C.; Lambertin, D.; Lahalle, H.; Antonucci, P.; Cannes, C.; Delpech, S.

    2014-10-01

    In a strongly alkaline medium, such as that encountered in conventional cementitious materials based on Portland cement, aluminum metal is corroded, with continued production of hydrogen. In order to develop a mineral matrix having enhanced compatibility with aluminum, a literature review was first undertaken to identify binders capable of reducing the pore solution pH compared with Portland cement. An experimental study was then carried out to measure the hydrogen production resulting from corrosion of aluminum metal rods encapsulated in the different selected cement pastes. The best results were achieved with magnesium phosphate cement, which released very little hydrogen over the duration of the study. This production could be reduced still further by adding a corrosion inhibitor (lithium nitrate) to the mixing solution. Open circuit potential measurement and Electrochemical Impedance Spectroscopy of aluminum electrode encapsulated in two pastes based on Portland cement and magnesium phosphate cement showed different redox behaviors. In the Portland cement paste, the electrochemical data confirmed the corrosion of aluminum whereas this latter tended to a passive state in the magnesium phosphate binder.

  2. Surface effects and phase stability in metal oxides nanoparticles under visible irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Ricci, Pier Carlo, E-mail: carlo.ricci@dsf.unica.it; Carbonaro, C. M., E-mail: carlo.ricci@dsf.unica.it; Corpino, R., E-mail: carlo.ricci@dsf.unica.it; Chiriu, D., E-mail: carlo.ricci@dsf.unica.it; Stagi, L., E-mail: carlo.ricci@dsf.unica.it [Dipartimento di Fisica, Universitá degli Studi di Cagliari, S.P. Monserrato-Sestu Km 0,700, 09042 Monserrato (Canada) (Italy)

    2014-10-21

    The light induced phase transformation between stable phases of metal oxides nanoparticles is analyzed. The surrounding atmosphere as well as the defect density at the surface play a fundamental role. It has been found that in oxygen poor chamber atmosphere the phase transformation is favored, while the phase transition cannot be achieved if the defects at the surface are properly passivated. The phase transition is activated by intragap irradiation, able to activate the F- center at the surface connected to oxygen vacancies, and promoting the activation of the surface and the nucleation of neighboring crystallites. The phase transition was studied in Titanium oxide (TiO{sub 2}) and in Iron oxide (Fe{sub 2}O{sub 3}): Maghemite is subjected to a phase transformation to α−Fe{sub 2}O{sub 3} (hematite), Anatase nanoparticles converts to Rutile. The general mechanism of the phase transition and, more in general, the possibility to optically control the surface activity of metal oxides is discussed.

  3. Comparative Use of Soil Organic and Inorganic Amendments in Heavy Metals Stabilization

    Directory of Open Access Journals (Sweden)

    Agustina Branzini

    2012-01-01

    Full Text Available Remediation strategies are capable to mitigate negative effects of heavy metals (HMs on soils. The distribution of cooper (Cu, zinc (Zn, and chromium (Cr was evaluated in a contaminated soil after adding biosolid compost (BC and phosphate fertilizer (PF. A greenhouse assay and sequential extraction procedure were performed to determine the fractionation of HM in contaminated and remediated soil. In BC treatment, among 4 to 6% of Cu was associated with soil humic substances. Without amendments and with fertilizer application, Zn solubility increased by 15.4 and 8.4%, respectively, with experiment time. Although Cr was significantly adsorbed to the inorganic fraction, with compost application there was a transfer to organic fraction. A single amendment application is not suitable for immobilizing all metals of concern, because there are diverse union’s behaviors between HM and soil matrix. As the organic matter and phosphate fertilizer were effective in reducing mobility of Cu, the organic matter was more effective in the immobilization of Cr, and inorganic amendment induced the Zn precipitation, results from this pilot study suggest a combined use of these two amendments for soil remediation strategies. However, liming may be further needed to prevent soil acidification on longer time scales. Also, we propose the use of chemical and biological remediation strategies for potential improvement of effectiveness.

  4. Effect of metal chloride solutions on coloration and biaxial flexural strength of yttria-stabilized zirconia

    Science.gov (United States)

    Oh, Gye-Jeong; Lee, Kwangmin; Lee, Doh-Jae; Lim, Hyun-Pil; Yun, Kwi-Dug; Ban, Jae-Sam; Lee, Kyung-Ku; Fisher, John G.; Park, Sang-Won

    2012-10-01

    The effect of three kinds of transition metal dopants on the color and biaxial flexural strength of zirconia ceramics for dental applications was evaluated. Presintered zirconia discs were colored through immersion in aqueous chromium, molybdenum and vanadium chloride solutions and then sintered at 1450 °C. The color of the doped specimens was measured using a digital spectrophotometer. For biaxial flexural strength measurements, specimens infiltrated with 0.3 wt% of each aqueous chloride solution were used. Uncolored discs were used as a control. Zirconia specimens infiltrated with chromium, molybdenum and vanadium chloride solutions were dark brown, light yellow and dark yellow, respectively. CIE L*, a*, and b* values of all the chromium-doped specimens and the specimens infiltrated with 0.1 wt% molybdenum chloride solution were in the range of values for natural teeth. The biaxial flexural strengths of the three kinds of metal chloride groups were similar to the uncolored group. These results suggest that chromium and molybdenum dopants can be used as colorants to fabricate tooth colored zirconia ceramic restorations.

  5. Stabilization of fluoroindate glasses by magnesium fluoride and other heavy metal fluorides

    Directory of Open Access Journals (Sweden)

    B. J. Costa

    1998-06-01

    Full Text Available Their extended transparency in the IR makes them attractive for use as optical fibers for CO laser power delivery and optical amplification. This paper firstly describes the spectacular stabilizing effect of MgF2 on the binary system InF3-BaF2. The investigation of the InF3-BaF2-MgF2 system led to samples up to 5mm in thickness. Further optimization of this system was achieved by incorporation of limited amounts of other fluorides and resulted in increased resistence to devitrification. The second approach of this work was concerned to the investigation of the pseudo-ternary system InF3-GdF3-GaF3 at constant concentrations of ZnF2-SrF2-BaF2-NaF. Several compositions were studied in this system. The samples presented a better thermal stability when compared to other families of fluoride glasses. Therefore, these glasses seem to be very promising for the fabrication of special optical fibers. Thermal data are reported.

  6. A novel two-dimensional MgB6 crystal: metal-layer stabilized boron kagome lattice.

    Science.gov (United States)

    Xie, Sheng-Yi; Li, Xian-Bin; Tian, Wei Quan; Chen, Nian-Ke; Wang, Yeliang; Zhang, Shengbai; Sun, Hong-Bo

    2015-01-14

    Based on first-principles calculations, we designed for the first time a boron-kagome-based two-dimensional MgB6 crystal, in which two boron kagome layers sandwich a triangular magnesium layer. The two-dimensional lattice is metallic with several bands across the Fermi level, and among them a Dirac point appears at the K point of the first Brillouin zone. This metal-stabilized boron kagome system displays electron-phonon coupling, with a superconductivity critical transition temperature of 4.7 K, and thus it is another possible superconducting Mg-B compound besides MgB2. Furthermore, the proposed 2D MgB6 can also be used for hydrogen storage after decoration with Ca. Up to five H2 molecules can be attracted by one Ca with an average binding energy of 0.225 eV. The unique properties of 2D MgB6 will spur broad interest in nanoscience and technology.

  7. Flexible high power-per-weight perovskite solar cells with chromium oxide-metal contacts for improved stability in air

    Science.gov (United States)

    Kaltenbrunner, Martin; Adam, Getachew; Głowacki, Eric Daniel; Drack, Michael; Schwödiauer, Reinhard; Leonat, Lucia; Apaydin, Dogukan Hazar; Groiss, Heiko; Scharber, Markus Clark; White, Matthew Schuette; Sariciftci, Niyazi Serdar; Bauer, Siegfried

    2015-10-01

    Photovoltaic technology requires light-absorbing materials that are highly efficient, lightweight, low cost and stable during operation. Organolead halide perovskites constitute a highly promising class of materials, but suffer limited stability under ambient conditions without heavy and costly encapsulation. Here, we report ultrathin (3 μm), highly flexible perovskite solar cells with stabilized 12% efficiency and a power-per-weight as high as 23 W g-1. To facilitate air-stable operation, we introduce a chromium oxide-chromium interlayer that effectively protects the metal top contacts from reactions with the perovskite. The use of a transparent polymer electrode treated with dimethylsulphoxide as the bottom layer allows the deposition--from solution at low temperature--of pinhole-free perovskite films at high yield on arbitrary substrates, including thin plastic foils. These ultra-lightweight solar cells are successfully used to power aviation models. Potential future applications include unmanned aerial vehicles--from airplanes to quadcopters and weather balloons--for environmental and industrial monitoring, rescue and emergency response, and tactical security applications.

  8. Mononuclear Clusterfullerene Single‐Molecule Magnet Containing Strained Fused‐Pentagons Stabilized by a Nearly Linear Metal Cyanide Cluster

    Science.gov (United States)

    Liu, Fupin; Wang, Song; Gao, Cong‐Li; Deng, Qingming; Zhu, Xianjun; Kostanyan, Aram; Westerström, Rasmus; Jin, Fei

    2017-01-01

    Abstract Fused‐pentagons results in an increase of local steric strain according to the isolated pentagon rule (IPR), and for all reported non‐IPR clusterfullerenes multiple (two or three) metals are required to stabilize the strained fused‐pentagons, making it difficult to access the single‐atom properties. Herein, we report the syntheses and isolations of novel non‐IPR mononuclear clusterfullerenes MNC@C76 (M=Tb, Y), in which one pair of strained fused‐pentagon is stabilized by a mononuclear cluster. The molecular structures of MNC@C76 (M=Tb, Y) were determined unambiguously by single‐crystal X‐ray diffraction, featuring a non‐IPR C 2v(19138)‐C76 cage entrapping a nearly linear MNC cluster, which is remarkably different from the triangular MNC cluster within the reported analogous clusterfullerenes based on IPR‐obeying C82 cages. The TbNC@C76 molecule is found to be a field‐induced single‐molecule magnet (SMM). PMID:28079303

  9. Encapsulation of curcumin in cyclodextrin-metal organic frameworks: Dissociation of loaded CD-MOFs enhances stability of curcumin.

    Science.gov (United States)

    Moussa, Zeinab; Hmadeh, Mohamad; Abiad, Mohamad G; Dib, Omar H; Patra, Digambara

    2016-12-01

    Curcumin has been successfully encapsulated in cyclodextrin-metal organic frameworks (CD-MOFs) without altering their crystallinity. The interaction between curcumin and CD-MOFs is strong through hydrogen bond type interaction between the OH group of cyclodextrin of CD-MOFs and the phenolic hydroxyl group of the curcumin. Interestingly, dissolving the curcumin loaded CD-MOFs crystals in water results in formation of a unique complex between curcumin, γCD and potassium cations. In fact, the initial interaction between curcumin and CD-MOF is crucial for the formation of the latter. This new complex formed in alkaline media at pH 11.5 has maximum absorbance at 520nm and emittance at 600nm. Most importantly, the stability of curcumin in this complex was enhanced by at least 3 orders of magnitude compared to free curcumin and curcumin:γ-CD at pH 11.5. These results suggest a promising benign system of CD-MOFs, which can be used to store and stabilize curcumin for food applications.

  10. New insights into non-precious metal catalyst layer designs for proton exchange membrane fuel cells: Improving performance and stability

    Science.gov (United States)

    Banham, Dustin; Kishimoto, Takeaki; Sato, Tetsutaro; Kobayashi, Yoshikazu; Narizuka, Kumi; Ozaki, Jun-ichi; Zhou, Yingjie; Marquez, Emil; Bai, Kyoung; Ye, Siyu

    2017-03-01

    The activity of non-precious metal catalysts (NPMCs) has now reached a stage at which they can be considered as possible alternatives to Pt for some proton exchange membrane fuel cell (PEMFC) applications. However, despite significant efforts over the past 50 years on catalyst development, only limited studies have been performed on NPMC-based cathode catalyst layer (CCL) designs. In this work, an extensive ionomer study is performed to investigate the impact of ionomer equivalent weight on performance, which has uncovered two crucial findings. Firstly, it is demonstrated that beyond a critical CCL conductance, no further improvement in performance is observed. The procedure used to determine this critical conductance can be used by other researchers in this field to aid in their design of high performing NPMC-based CCLs. Secondly, it is shown that the stability of NPMC-based CCLs can be improved through the use of low equivalent weight ionomers. This represents a completely unexplored pathway for further stability improvements, and also provides new insights into the possible degradation mechanisms occurring in NPMC-based CCLs. These findings have broad implications on all future NPMC-based CCL designs.

  11. Deterioration of yttria-stabilized zirconia by boron carbide alone or mixed with metallic or oxidized Fe, Cr, Zr mixtures

    Energy Technology Data Exchange (ETDEWEB)

    De Bremaecker, A., E-mail: adbremae@sckcen.be [Belgian Nuclear Research Center (SCK-CEN), NMS, Mol (Belgium); Ayrault, L., E-mail: laurent.ayrault@cea.fr [Institut de Radio-Protection et Sûreté Nucléaire/DPAM/SEMIC, Bât 702, CEN de Cadarache BP3, F-13115 Saint-Paul-lez-Durance (France); Clément, B. [Institut de Radio-Protection et Sûreté Nucléaire/DPAM/SEMIC, Bât 702, CEN de Cadarache BP3, F-13115 Saint-Paul-lez-Durance (France)

    2014-08-01

    In the frame of severe accident conditions (PHEBUS FPT3 test), different experiments were carried out on the interactions of 20% yttria-stabilized zirconia (YSZ) and 20% ceria-stab zirconia with boron carbide or its oxidation products (B{sub 2}O{sub 3}): either tests under steam between 1230° and 1700 °C with B{sub 4}C alone or B{sub 4}C mixed with metals, either tests under Ar with boron oxide present in a mixture of iron and chromium oxides. In all cases an interaction was observed with formation of intergranular yttrium borate. At 1700 °C boron oxide is able to “pump out” the Y stabiliser from the YSZ grains but also some trace elements (Ca and Al) and to form a eutectic containing YBO{sub 3} and yttrium calcium oxy-borate (YCOB). At the same time a substantial swelling (“bloating”) of the zirconia happens, qualitatively similar to the foaming of irradiated fuel in contact with a Zr-melt. In all samples the lowering of the Y (or Ce)-content in the YSZ grains is so sharp that in the interaction layers zirconia is no longer stabilized. This is important when YSZ is envisaged as simulant of UO{sub 2} or as inert matrix for Am-transmutation.

  12. Potentiometric titration for determining the composition and stability of metal(II) alginates and pectinates in aqueous solutions

    Science.gov (United States)

    Kaisheva, N. Sh.; Kaishev, A. Sh.

    2015-07-01

    The compositions and stabilities of Cu2+, Mn2+, Pb2+, Ca2+, Zn2+, Cd2+, Co2+, and Ni2+ alginates and pectinates are determined in aqueous solutions via titrimetry and potentiometry with calculations performed using Bjerrum's method, the curve intersection technique, and the equilibrium shift method. It is found that the interaction between Cu2+ and polyuronides is a stepwise process and, depending on the ligand concentration and the method of determination, Cu2+ alginate can be characterized by its ML, ML2, and ML3 compositions (where M is the metal ion and L is the structural unit of polyuronide) and stability constants logβ = 2.65, 5.00-5.70, and 7.18-7.80, respectively. The compositions of Cu2+ pectinates are ML and ML2 with logβ = 3.00 and 7.64-7.94, respectively. It is concluded that Pb2+, Ca2+, Mn2+, Zn2+, Cd2+, Co2+, and Ni2+ ions form only alginates and pectinates of ML2 composition with logβ values of 3.45 (Pb2+ alginate), 2.20 (Ca2+ alginate), 1.06 (Mn2+ alginate), 3.51 (Pb2+ pectinate), 2.35 (Ca2+ pectinate), and 1.24 (Mn2+ pectinate). The pectinates are shown to be more stable than the alginates, the most stable compounds being those formed by polyuronides and Cu2+. The least stable are those with Mn2+.

  13. Stabilization of volatile Ti(BH4)3 by nano-confinement in a metal-organic framework.

    Science.gov (United States)

    Callini, E; Szilágyi, P Á; Paskevicius, M; Stadie, N P; Réhault, J; Buckley, C E; Borgschulte, A; Züttel, A

    2016-01-01

    Liquid complex hydrides are a new class of hydrogen storage materials with several advantages over solid hydrides, e.g. they are flexible in shape, they are a flowing fluid and their convective properties facilitate heat transport. The physical and chemical properties of a gaseous hydride change when the molecules are adsorbed on a material with a large specific surface area, due to the interaction of the adsorbate with the surface of the host material and the reduced number of collisions between the hydride molecules. In this paper we report the synthesis and stabilization of gaseous Ti(BH4)3. The compound was successfully stabilized through adsorption in nanocavities. Ti(BH4)3, upon synthesis in its pure form, spontaneously and rapidly decomposes into diborane and titanium hydride at room temperature in an inert gas, e.g. argon. Ti(BH4)3 adsorbed in the cavities of a metal organic framework is stable for several months at ambient temperature and remains stable up to 350 K under vacuum. The adsorbed Ti(BH4)3 reaches approximately twice the density of the gas phase. The specific surface area (BET, N2 adsorption) of the MOF decreased from 1200 m(2) g(-1) to 770 m(2) g(-1) upon Ti(BH4)3 adsorption.

  14. Pickering emulsions stabilized by a metal-organic framework (MOF) and graphene oxide (GO) for producing MOF/GO composites.

    Science.gov (United States)

    Zhang, Fanyu; Liu, Lifei; Tan, Xiuniang; Sang, Xinxin; Zhang, Jianling; Liu, Chengcheng; Zhang, Bingxing; Han, Buxing; Yang, Guanying

    2017-10-02

    Herein we demonstrate the formation of a novel kind of Pickering emulsion that is stabilized by a Zr-based metal-organic framework (Zr-MOF) and graphene oxide (GO). It was found that the Zr-BDC-NO2 and GO solids assembling at the oil/water interface can effectively stabilize the oil droplets that are dispersed in the water phase. Such a Pickering emulsion offers a facile route for fabricating Zr-MOF/GO composite materials. After removing water and oil by freeze drying from Pickering emulsions, the Zr-MOF/GO composites were obtained and their morphologies, structures and interaction properties were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Fourier transform infrared spectrometry, respectively. The influences of the concentration of GO and Zr-MOF on the emulsion microstructures and the properties of the MOF/GO composites were studied. Based on experimental results, the mechanisms for the emulsion formation by Zr-MOF and GO and the as-synthesized superstructures of the Zr-MOF/GO composite were proposed. It is expected that this facile and tunable route can be applied to the synthesis of different kinds of MOF-based or GO-based composite materials.

  15. Deterioration of yttria-stabilized zirconia by boron carbide alone or mixed with metallic or oxidized Fe, Cr, Zr mixtures

    Science.gov (United States)

    De Bremaecker, A.; Ayrault, L.; Clément, B.

    2014-08-01

    In the frame of severe accident conditions (PHEBUS FPT3 test), different experiments were carried out on the interactions of 20% yttria-stabilized zirconia (YSZ) and 20% ceria-stab zirconia with boron carbide or its oxidation products (B2O3): either tests under steam between 1230° and 1700 °C with B4C alone or B4C mixed with metals, either tests under Ar with boron oxide present in a mixture of iron and chromium oxides. In all cases an interaction was observed with formation of intergranular yttrium borate. At 1700 °C boron oxide is able to “pump out” the Y stabiliser from the YSZ grains but also some trace elements (Ca and Al) and to form a eutectic containing YBO3 and yttrium calcium oxy-borate (YCOB). At the same time a substantial swelling (“bloating”) of the zirconia happens, qualitatively similar to the foaming of irradiated fuel in contact with a Zr-melt. In all samples the lowering of the Y (or Ce)-content in the YSZ grains is so sharp that in the interaction layers zirconia is no longer stabilized. This is important when YSZ is envisaged as simulant of UO2 or as inert matrix for Am-transmutation.

  16. Comparative Analysis of Cobalt Oxide Nanoisland Stability and Edge Structures on Three Related Noble Metal Surfaces: Au (111), Pt (111) and Ag (111)

    DEFF Research Database (Denmark)

    Fester, Jakob; Bajdich, Michal; Walton, Alexander

    2017-01-01

    Metal oxide nanostructures and thin films grown on metallic substrates have attracted strong attention as model catalysts and as interesting inverse catalyst systems in their own right. In this study, we investigate the role of metal support in the growth and stabilization of cobalt oxide...... nanostructures on the three related (111) surfaces of Au, Pt and Ag, as investigated by means of high-resolution scanning tunneling microscopy and DFT calculations. All three substrates promote the growth of crystalline CoOx (x = 1−2) islands under oxidative conditions, but we find several noteworthy differences...... for water dissociation....

  17. First-principles study of structural stabilities, elastic and electronic properties of transition metal monocarbides (TMCs) and mononitrides (TMNs)

    Energy Technology Data Exchange (ETDEWEB)

    Rached, H.; Rached, D.; Benalia, S. [Laboratoire des Matériaux Magnétiques, Faculté des Sciences, Université Djillali Liabès de Sidi Bel-Abbès, Sidi Bel-Abbès 22000 (Algeria); Reshak, A.H., E-mail: maalidph@yahoo.co.uk [Institute of Complex Systems, FFPW, CENAKVA, University of South Bohemia in CB, Nove Hrady 37333 (Czech Republic); Center of Excellence Geopolymer and Green Technology, School of Material Engineering, University Malaysia Perlis, 01007 Kangar, Perlis (Malaysia); Rabah, M. [Laboratoire des Matériaux Magnétiques, Faculté des Sciences, Université Djillali Liabès de Sidi Bel-Abbès, Sidi Bel-Abbès 22000 (Algeria); Khenata, R. [Laboratoire de Physique Quantique et de Modélisation Mathématique de la Matière (LPQ3M), université de Mascara, Mascara 29000 (Algeria); Bin Omran, S. [Department of Physics and Astronomy, Faculty of Science, King Saud University, Riyadh 11451 (Saudi Arabia)

    2013-12-16

    The structural stabilities, elastic and electronic properties of 5d transition metal mononitrides (TMNs) XN with (X = Ir, Os, Re, W and Ta) and 5d transition metal monocarbides (TMCs) XC with (X = Ir, Os, Re and Ta) were investigated using the full-potential linear muffin-tin orbital (FP-LMTO) method, in the framework of the density functional theory (DFT) within the local density approximation (LDA) for the exchange correlation functional. The ground state quantities such as the lattice parameter, bulks modulus and its pressure derivatives for the six considered crystal structures, Rock-salt (B1), CsCl (B2), zinc-blend (B3), Wurtzite (B4), NiAs (B8{sub 1}) and the tungsten carbides (B{sub h}) are calculated. The elastic constants of TMNs and TMCs compounds in its different stable phases are determined by using the total energy variation with strain technique. The elastic modulus for polycrystalline materials, shear modulus (G), Young's modulus (E), and Poisson's ratio (ν) are calculated. The Debye temperature (θ{sub D}) and sound velocities (v{sub m}) were also derived from the obtained elastic modulus. The analysis of the hardness of the herein studied compounds classifies OsN – (B4 et B8{sub 1}), ReN – (B8{sub 1}), WN – (B8{sub 1}) and OsC – (B8{sub 1}) as superhard materials. Our results for the band structure and densities of states (DOS), show that TMNs and TMCs compounds in theirs energetically and mechanically stable phase has metallic characteristic with strong covalent nature Metal–Nonmetal elements. - Highlights: • Structural stabilities, elastic, electronic properties of 5d TMNs XN are investigated. • 5d TMCs XC with (X = Ir, Os, Re and Ta) were investigated. • The ground state properties for the six considered crystal structure are calculated. • The elastic constants of TMNs and TMCs in its different stable phases are determined. • The elastic modulus for polycrystalline materials, G, E, and ν are calculated.

  18. Emulsifier type, metal chelation and pH affect oxidative stability of n-3-enriched emulsions

    DEFF Research Database (Denmark)

    Haahr, Anne-Mette; Jacobsen, Charlotte

    2008-01-01

    -enriched oil-in-water emulsion. The selected food emulsifiers were Tween 80, Citrem, sodium caseinate and lecithin. Lipid oxidation was evaluated by determination of peroxide values and secondary volatile oxidation products. Moreover, the zeta potential and the droplet sizes were determined. Twen resulted...... in the least oxidatively stable emulsions, followed by Citrem. When iron was present, caseinate-stabilized emulsions oxidized slower than lecithin emulsions at pH 3, whereas the opposite was the case at pH 7. Oxidation generally progressed faster at pH 3 than at pH 7, irrespective of the addition of iron. EDTA...... generally reduced oxidation, as evaluated by volatiles formation in all emulsions, irrespective of pH and emulsifier type, except in the lecithin and cascinate emulsions where a pro-oxidative effect was observed for some volatiles. The different effects of the emulsifier types could be related...

  19. Stability and structure of metal clusters - Be(13) and Be(55)

    Science.gov (United States)

    Pettersson, Lars G. M.; Bauschlicher, Charles W., Jr.

    1986-01-01

    Face-centered cubic (fcc) and hexagonally close-packed (hcp) structures are compared for Be(13) and Be(55) clusters. Both Be(13) and Be(55) prefer the fcc structure over the bulk hcp structure, but the energy difference per atom decreases for Be(55) relative to Be(13). The binding energy per atom, 1.3 eV for Be(55) and 0.8-0.9 eV for Be(13), reflects the greater total number of bonds in the larger cluster rather than a difference in bonding. The energies per bond are much more similar, in the range of 0.30-0.34 eV for both clusters. The size of the p-basis set used influences both stability and ionization potentials strongly.

  20. Experimental Demonstration of the Stabilizing Effect of Dielectric Coatings on Magnetically Accelerated Imploding Metallic Liners.

    Science.gov (United States)

    Awe, T J; Peterson, K J; Yu, E P; McBride, R D; Sinars, D B; Gomez, M R; Jennings, C A; Martin, M R; Rosenthal, S E; Schroen, D G; Sefkow, A B; Slutz, S A; Tomlinson, K; Vesey, R A

    2016-02-12

    Enhanced implosion stability has been experimentally demonstrated for magnetically accelerated liners that are coated with 70  μm of dielectric. The dielectric tamps liner-mass redistribution from electrothermal instabilities and also buffers coupling of the drive magnetic field to the magneto-Rayleigh-Taylor instability. A dielectric-coated and axially premagnetized beryllium liner was radiographed at a convergence ratio [CR=Rin,0/Rin(z,t)] of 20, which is the highest CR ever directly observed for a strengthless magnetically driven liner. The inner-wall radius Rin(z,t) displayed unprecedented uniformity, varying from 95 to 130  μm over the 4.0 mm axial height captured by the radiograph.

  1. Phase stability and elasticity of C15 transition-metal intermetallic compounds

    Energy Technology Data Exchange (ETDEWEB)

    Chu, F.; Mitchell, T.E.; Chen, S.P. [Los Alamos National Lab., NM (United States); Sob, M.; Siegl, R.; Pope, D.P. [Pennsylvania Univ., Philadelphia, PA (United States). Dept. of Materials Science and Engineering

    1995-03-01

    First-principle quantum mechanical calculations based on the local-density-functional theory have been performed to study the electronic, physical and metallurgical properties of C15 intermetallics MV{sub 2} (M = Zr, Hf, or Ta). The elastic constants of C15 HfV{sub 2} + Nb were measured by the resonant ultrasound spectroscopy technique. The phase stability of C15 HfV{sub 2} + Nb was studied by specific heat measurements and by transmission electron microscopy in a low temperature specimen holder. The total energies and their lattice volume dependence were used to obtain the equilibrium lattice constants and bulk modulus. The band structures at the X-point near the Fermi level were employed to understand the anomalous temperature dependence of shear modulus of the C15 intermetallics. It was found that the double degeneracy with a linear dispersion relation of electronic levels at the X-point near the Fermi surface is mainly responsible for the C15 anomalous elasticity. The density of states at the Fermi level, N(E{sub F}), and the Fermi surface geometry were obtained to understand the low temperature phase instability of C15 HfV{sub 2} and ZrV{sub 2} and the stability of C15 TaV{sub 2}. It was proposed that the large N(E{sub F}) and Fermi surface nesting are the physical reasons for the structural instability of the C15 HfV{sub 2} and ZrV{sub 2} at low temperatures. The relation between anomalous elasticity and structural instability of C15 HfV{sub 2} and ZrV{sub 2} is also discussed.

  2. Magnetism, band gap and stability of half-metallic property for the quaternary Heusler alloys CoFeTiZ (Z = Si, Ge, Sn)

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Y.J. [Department of Physics, University of Science and Technology Beijing, 100083 Beijing (China); Liu, Z.H., E-mail: zhliu@ustb.edu.cn [Department of Physics, University of Science and Technology Beijing, 100083 Beijing (China); Li, G.T.; Ma, X.Q. [Department of Physics, University of Science and Technology Beijing, 100083 Beijing (China); Liu, G.D. [School of Material Science and Engineering, Hebei University of Technology, 300130 Tianjin (China)

    2014-12-15

    Highlights: • CoFeTiZ (Z = Si, Ge) have been predicted to be ferrimagnetism half-metallic alloys. • Effect of the sp element on the band gap and the half-metallicity have been analyzed. • The half-metallicity of these alloys shows good stability. - Abstract: The electronic structures and magnetic properties of quaternary Heusler alloys CoFeTiZ (Z = Si, Ge, Sn) have been studied using first-principles calculations. It has been found that CoFeTiSi and CoFeTiGe are half-metallic ferrimagnets, while CoFeTiSn is a quasi half-metallic ferrimagnet. The total moment in unit cell for CoFeTiZ (Z = Si, Ge, Sn) alloys follows the Slater–Pauling behavior with the total number of valence electrons minus 24. The origin of the magnetism, band gap, and the effect of atom Z on the band gap and the half-metallicity of the alloys have been discussed in detail. The half-metallic property for CoFeTiSi and CoFeTiGe can be retained when their lattice constants are changed in a large range. CoFeTiSn alloy can transform from a quasi half-metallic to a half-metallic alloy by employing a proper compression stress.

  3. Regional heavy metal pollution in crops by integrating physiological function variability with spatio-temporal stability using multi-temporal thermal remote sensing

    Science.gov (United States)

    Liu, Meiling; Liu, Xiangnan; Zhang, Biyao; Ding, Chao

    2016-09-01

    Heavy metal stress in crops is characterized by stability in space and time, which differs from other stressors that are typically more transient (e.g., drought, pests/diseases, and mismanagement). The objective of this study is to assess regional heavy metal stress in rice by integrating physiological function variability with spatio-temporal stability based on multi-temporal thermal infrared (TIR) remote sensing images. The field in which the experiment was conducted is located in Zhuzhou City, Hunan Province, China. HJ-1B images and in-situ measured data were collected from rice growing in heavy metal contaminated soils. A stress index (SI) was devised as an indicator for the degree of heavy metal stress of the rice in different growth stages, and a time-spectrum feature space (TSFS) model was used to determine rice heavy metal stress levels. The results indicate that (i) SI is a good indicator of rice damage caused by heavy metal stress. Minimum values of SI occur in rice subject to high pollution, followed by larger SI with medium pollution and maximum SI for low pollution, for the same growth stage. (ii) SI shows some variation for different growth stages of rice, and the minimum SI occurs at the flowering stage. (iii) The TSFS model is successful at identifying rice heavy metal stress, and stress levels in rice stabilized regardless of the model being applied in the two different years. This study suggests that regional heavy metal stress in crops can be accurately detected using TIR technology, if a sensitive indicator of crop physiological function impairment is used and an effective model is selected. A combination of spectrum and spatio-temporal information appears to be a very promising method for monitoring crops with various stressors.

  4. Reduction and Oxidation of Copper Oxide Thin Films and Thermal Stability Issues in Copper-Based Metallization.

    Science.gov (United States)

    Li, Jian

    This thesis investigates the oxidation and reduction of Cu-oxides and thermal induced reactions of Cu with metals. The combination of ^{16}O( alpha,alpha)^{16}O oxygen resonance and transmission electron microscopy (TEM) provides an effective method of studying the oxidation and reduction of copper oxide thin films. A discontinuous morphology of grain growth of Cu_2O in found in the CuO matrix during reduction. The migration of the Cu_2O-CuO phase boundary is induced by oxygen diffusion along the moving boundary. Grain growth is the dominant process in the transformation from CuO to Cu_2O; nucleation is the dominant process in the reverse transformation, i.e. from Cu_2O to CuO. The reduction and oxidation of copper oxides are asymmetrical; the latter is significantly faster. The metastable phase Cu _4O_3 was formed by ion milling CuO. Carbon and refractory metals such as Ti or Zr can enhance the reduction rate of CuO. Three topics relating to thermal stability issues in Cu-based metallization were investigated: (1) texturing in electroless copper films on epitaxial copper seed layers; (2) predicting first phase formation in Cu/metal bilayer structures; and (3) encapsulation of Cu fine line structures with TiN. (100)- and (111)-textured copper layers were deposited by electroless plating on copper seed layers grown epitaxially on Si (100) and Si (111) substrates, respectively. (111) -textured copper films are more oxidation-resistant. Rutherford backscattering spectrometry (RBS) and in situ transmission electron microscopy (TEM) were used to determine phase formation in Cu-M (M = Ti, Zr, Mg, Sb, Pd and Pt) bilayer systems. An effective heat of formation rule was employed to predict first phase formation in these systems. A TiN-encapsulated copper structure was made by annealing a Cu-10at%Ti alloy film evaporated on a SiO _2/Si(100) substrate at 550^ circC in an NH_3 ambient. Fast heating rates (70^circC/min.) to 550^circC can effectively suppress the formation of Cu

  5. Comparison of the fixation effects of heavy metals by cement rotary kiln co-processing and cement based solidification/stabilization.

    Science.gov (United States)

    Zhang, Junli; Liu, Jianguo; Li, Cheng; Jin, Yiying; Nie, Yongfeng; Li, Jinhui

    2009-06-15

    Cement rotary kiln co-processing of hazardous wastes and cement based solidification/stabilization could both immobilize heavy metals. The different retention mechanisms of the two technologies lead to different fixation effects of heavy metals. The same amount of heavy metal compounds were treated by the two types of fixation technologies. Long-term leaching test (160 days), the maximum availability leaching test (NEN 7341) and a modified three-step sequential extraction procedure, proposed by the Commission of the European Communities Bureau of Reference (BCR) were employed to compare the fixation effects of the two fixation technologies. The leaching concentrations in NEN 7341 and long-term leaching tests were compared with identification standard for hazardous wastes (GB5085.3-1996) and drinking water standard (GB5749-2005). The results indicate that the leaching concentrations of the long-term leaching test and NEN 7341 test were lower than the regulatory limits and the leached ratios were small. Both cement based solidification/stabilization and cement rotary kiln co-processing could effectively fix heavy metals. Calcination in a cement rotary kiln and the following hydration that follows during cement application could fix As, Cd, Pb and Zn more effectively and decrease the release to the environment. Cement solidification/stabilization technology has better effect in immobilizing Cr and Ni. Cr wastes are more fitful to be treated by cement solidification/stabilization.

  6. Investigation of heavy metal (Cu, Pb, Cd, and Cr) stabilization in river sediment by nano-zero-valent iron/activated carbon composite.

    Science.gov (United States)

    Chen, Wei-fang; Zhang, Jinghui; Zhang, Xiaomao; Wang, Weiya; Li, Yuxiang

    2016-01-01

    Nano-zero-valent iron/activated carbon (nZVI/AC) composite was evaluated for its effectiveness in the stabilization of Cu, Pb, Cd, and Cr in dredged river sediment. Synthetic precipitation leaching procedure (SPLP) and toxicity characteristic leaching procedure (TCLP) were adopted to compare the effects of nZVI/AC dosage, particle size, time duration, and temperature on heavy metal leachability. The results show that leachability dropped considerably with the addition of nZVI/AC and powdered particles in the size of 0.075-0.18 mm was more effective in stabilization than granular ones. Stabilization effect was stable in long-term and robust against changes in temperature. Tessier sequential extraction revealed that heavy metals were associated with solid particle, inorganic or organic matters in sediment. The addition of nZVI/AC was able to convert relatively weakly bound heavy metals into more strongly bound species and thus reduce the bioavailability and toxicity. Also, the standard potential of heavy metals may decide the mechanism of stabilization process.

  7. A porous metal-organic framework based on Zn6O2 clusters: chemical stability, gas adsorption properties and solvatochromic behavior.

    Science.gov (United States)

    Cui, Jiehu; Li, Yizhi; Guo, Zijian; Zheng, Hegen

    2013-01-21

    A highly connected 3D metal-organic framework with tfz-d topology based on Zn(6)O(2) clusters and flexible carboxylate ligands has been synthesized. The obtained Zn-MOF shows solvatochromic behavior for fluorescence sensing of small molecules, gas adsorption properties and exceptional chemical stability and might have applications for separation and detection purposes.

  8. Thermal stability and spontaneous breakdown of free-standing metal nanowires

    Science.gov (United States)

    Michailov, Michail; Ranguelov, Bogdan; Giazitzidis, Paraskevas; Argyrakis, Panos

    2017-01-01

    We present a model for vacancy-mediated spontaneous breakdown of free-standing monatomic nanowire based on exclusively random, thermally activated motion of atoms. The model suggests a new two-step vacancy-mediated mechanism for nanowire rupture compared to the more complex three-step hole-mediated mechanism driving the disintegration of nanowire on crystalline surface. It also demonstrates that a free-standing nanowire breaks down much more rapidly than a nanowire on a substrate, because it cannot experience the stabilizing effect of the nanowire/substrate interactions. The rupture mechanism includes single atomic vacancy generation, preceded by appearance of weakly bonded active atoms. The analysis of the simulation data indicates that the active atoms act as a precursor of vacancy formation. These two successive events in the temporal evolution of the nanowire morphology bring the free-standing nanowire into irreversible unstable state, leading to its total disintegration. The present study also manifests an unexpected substantial increase of the nanowire lifetime with diminishing the strength of the atomic interactions between the nanowire atoms. The simulation data reveal three energy regions where a large oscillatory variation of nanowire lifetime is realized. The first region of strong atomic interactions is characterized by tight nanowire rigidity and short lifetime. The next, second region in the consecutive step-down of the attractive interatomic force is characterized by generation of wave-shaped morphology of the atomic chain, enhanced flexibility and dramatic increase of nanowire lifetime. In the last, third region, further weakening of the interactions returns the nanowire again to unstable, short-lifetime state. The observed phenomenon is considered as a "stick-like" to "polymer-like" transition in the nanowire atomic structure as a result of interaction energy variation. The enhanced flexibility reduces the nanowire free energy since it favors and

  9. Concentrated dual-salt electrolytes for improving the cycling stability of lithium metal anodes

    Science.gov (United States)

    Pin, Liu; Qiang, Ma; Zheng, Fang; Jie, Ma; Yong-Sheng, Hu; Zhi-Bin, Zhou; Hong, Li; Xue-Jie, Huang; Li-Quan, Chen

    2016-07-01

    Lithium (Li) metal is an ideal anode material for rechargeable Li batteries, due to its high theoretical specific capacity (3860 mAh/g), low density (0.534 g/cm3), and low negative electrochemical potential (-3.040 V vs. standard hydrogen electrode). In this work, the concentrated electrolytes with dual salts, composed of Li[N(SO2F)2] (LiFSI) and Li[N(SO2CF3)2] (LiTFSI) were studied. In this dual-salt system, the capacity retention can even be maintained at 95.7% after 100 cycles in Li|LiFePO4 cells. A Li|Li cell can be cycled at 0.5 mA/cm2 for more than 600 h, and a Li|Cu cell can be cycled at 0.5 mA/cm2 for more than 200 cycles with a high average Coulombi efficiency of 99%. These results show that the concentrated dual-salt electrolytes exhibit superior electrochemical performance and would be a promising candidate for application in rechargeable Li batteries. Project supported by the National Nature Science Foundation of China (Grant Nos. 51222210, 51472268, 51421002, and 11234013) and the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA09010300).

  10. Concentrated dual-salt electrolytes for improving the cycling stability of lithium metal anodes

    Institute of Scientific and Technical Information of China (English)

    刘品; 马强; 方铮; 马洁; 胡勇胜; 周志彬; 李泓; 黄学杰; 陈立泉

    2016-01-01

    Lithium (Li) metal is an ideal anode material for rechargeable Li batteries, due to its high theoretical specific ca-pacity (3860 mAh/g), low density (0.534 g/cm3), and low negative electrochemical potential (−3.040 V vs. standard hydrogen electrode). In this work, the concentrated electrolytes with dual salts, composed of Li[N(SO2F)2] (LiFSI) and Li[N(SO2CF3)2] (LiTFSI) were studied. In this dual-salt system, the capacity retention can even be maintained at 95.7%after 100 cycles in Li|LiFePO4 cells. A Li|Li cell can be cycled at 0.5 mA/cm2 for more than 600 h, and a Li|Cu cell can be cycled at 0.5 mA/cm2 for more than 200 cycles with a high average Coulombi efficiency of 99%. These results show that the concentrated dual-salt electrolytes exhibit superior electrochemical performance and would be a promising candidate for application in rechargeable Li batteries.

  11. Chemical and thermal stability of refrigerant-lubricant mixture with metal

    Energy Technology Data Exchange (ETDEWEB)

    Huttenlocher, D.F. (Spauschus Associates, Inc., Atlanta, GA (United States))

    1992-03-31

    This report presents completed sealed tube stability test results for the R-123/mineral oil mixture and preliminary results for seven of the eighteen contracted refrigerant-lubricant mixtures. The R-123 mixture was tested at 105, 150, and 175{degrees}C. The results obtained indicate that prolonged exposure to temperatures of about 150{degree}C and higher will lead to rapid chemical deterioration of the R-123/mineral oil system. Chlorotrifluoroethane (R-133a) and trifluoroethane (R-143a) have been identified as decomposition products of R-123. Testing at 150 and 175{degrees}C have been completed for the HCFC refrigerants R-22, R-124, and R-142b with either mineral oil or alkylbenzene lubricants. These mixtures were very stable at the indicated temperatures. Testing at a higher temperature level will be necessary to define their upper temperature limits. Similarily, partial test results are available for HFC refrigerants R-32, R-125, R-134a (two esters), and R-143a with pentaerythritol ester lubricants at the 150 and 175{degrees}C temperature levels. Again, all five mixtures were found to be extremely stable at the test temperatures and additional testing will be needed to establish their upper temperature limits.

  12. Theoretical investigation of polymer chain stability in the metal coordinated azorubine and cyclam complex

    Energy Technology Data Exchange (ETDEWEB)

    Vlassa, Mihaela, E-mail: mihaela_cecilia@yahoo.com [' ' Babes-Bolyai' ' University, Raluca Ripan Institute of Research in Chemistry, 30 Fantanele Str., 400294 Cluj-Napoca (Romania); Bende, Attila, E-mail: bende@itim-cj.ro [Molecular and Biomolecular Physics Department, National Institute for Research and Development of Isotopic and Molecular Technologies, Str. Donat 67-103, Cluj Napoca RO-400293 (Romania)

    2015-08-18

    Highlights: • Ni(II)- and Zn(II)-coordinated cyclam–azorubine complexes are described using DFT. • Ni(II) coordinated system shows a reasonably small singlet–triplet energy gap. • Intersystem crossing gives high barrier between singlet and triplet geometries. • For the Zn(II) case only the singlet state is energetically favorable. • The stability of a longer polymer (oligomer) chain was described using DFTB. - Abstract: Theoretical investigations have been performed for unit systems with Ni(II) and Zn(II) coordination between azorubine and 1,4,8,11-tetraazacyclotetradecane (cyclam) complexes using the conventional DFT and the DFT-based tight binding (DFTB) methods. Two different geometries (short and long) and spin states (singlet and triplet) of the model system built by two mesylate groups and the cyclam ring together with Ni(II) and Zn(II) ions were energetically characterized. For the Ni(II) coordination complex the triplet geometry is preferred, but one could not exclude also the presence of the singlet spin configuration due to the huge energy barrier defined by the intersystem crossing. The intersystem crossing geometry of the singlet–triplet transition was studied in details and the corresponding spin–orbit couplings were discussed. For the Zn(II) coordination complex only the singlet state was found. Polymer chain build up from four unit systems presents irregular forms with strong coordination bonds between units.

  13. Shear instabilities in metallic nanoparticles: hydrogen-stabilized structure of Pt37 on carbon.

    Science.gov (United States)

    Wang, Lin-Lin; Johnson, D D

    2007-03-28

    Using density functional theory calculations, we have studied the morphology of a Pt37 nanoparticle supported on carbon with and without hydrogen (H) passivation that arises with postprocessing of nanoparticles before characterization. Upon heating in an anneal cycle, we find that without H (e.g., in a helium atmosphere or evacuation at high temperature), the morphology change of a truncated cuboctahedral Pt37 is driven by the shearing of (100) to (111) facets to lower the surface energy, a remnant shear instability that drives surface reconstruction in semi-infinite Pt(100). With H passivation from a postprocessing anneal, we show that the sheared structure automatically reverts to the observed truncated cuboctahedral structure and the average first nearest-neighbor Pt-Pt bond length increases by 3%, agreeing well with experiment. We explain the stabilization of the truncated cuboctahedral structure due to H passivation via adsorption energetics of hydrogen on Pt(100) and (111) facets, specifically, the preference for H adsorption at bridge sites on (100) facets, which should be considered in a realistic model for H adsorption on Pt nanoparticles. We find that dramatic morphological change of a nanoparticle can occur even with small changes to first-shell Pt-Pt coordination number. The implications of our findings when comparing to experimental data are discussed.

  14. Epoxidized Soybean Oil: Evaluation of Oxidative Stabilization and Metal Quenching/Heat Transfer Performance

    Science.gov (United States)

    Simencio Otero, Rosa L.; Canale, Lauralice C. F.; Said Schicchi, Diego; Agaliotis, Eliana; Totten, George E.; Sánchez Sarmiento, Gustavo

    2013-07-01

    Vegetable and animal oils as a class of fluids have been used for hundreds of years, if not longer, as quenchants for hardening steel. However, when petroleum oils became available in the late 1800s and early 1900s, the use of these fluids as quenchants, in addition to their use in other industrial oil applications, quickly diminished. This was primarily, but not exclusively, due to their generally very poor thermal-oxidative instability and the difficulty for formulating fluid analogs with varying viscosity properties. Interest in the use of renewable fluids, such as vegetable oils, has increased dramatically in recent years as alternatives to the use of relatively non-biodegradable and toxic petroleum oils. However, the relatively poor thermal-oxidative stability has continued to be a significant reason for their general non-acceptance in the marketplace. Soybean oil (SO) is one of the most highly produced vegetable oils in Brazil. Currently, there are commercially produced epoxidized versions of SO which are available. The objective of this paper is to discuss the potential use of epoxidized SO and its heat transfer properties as a viable alternative to petroleum oils for hardening steel.

  15. Hydrogen-doping stabilized metallic VO{sub 2} (R) thin films and their application to suppress Fabry-Perot resonances in the terahertz regime

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Yong; Pan, Xuan; Bernussi, Ayrton A.; Fan, Zhaoyang, E-mail: Zhaoyang.Fan@ttu.edu [Department of Electrical and Computer Engineering and Nano Tech Center, Lubbock, Texas 79409 (United States); Karaoglan-Bebek, Gulten [Department of Physics and Nano Tech Center, Lubbock, Texas 79409 (United States); Holtz, Mark [Department of Physics and MSEC, Texas State University, San Marcos, Texas 78666 (United States)

    2014-06-16

    We demonstrate that catalyst-assisted hydrogen spillover doping of VO{sub 2} thin films significantly alters the metal-insulator transition characteristics and stabilizes the metallic rutile phase at room temperature. With hydrogen inserted into the VO{sub 2} lattice, high resolution X-ray diffraction reveals expansion of the V-V chain separation when compared to the VO{sub 2}(R) phase. The donated free electrons, possibly from O-H bond formation, stabilize the VO{sub 2}(R) to low temperatures. By controlling the amount of dopants to obtain mixed insulating and metallic phases, VO{sub 2} resistivity can be continuously tuned until a critical condition is achieved that suppresses Fabry-Perot resonances. Our results demonstrate that hydrogen spillover is an effective technique to tune the electrical and optical properties of VO{sub 2} thin films.

  16. Optical stability of 3d transition metal ions doped-cadmium borate glasses towards γ-rays interaction

    Science.gov (United States)

    Marzouk, M.; ElBatal, H.; Eisa, W.

    2016-07-01

    This work reports the preparation of glasses of binary cadmium borate with the basic composition (mol% 45 CdO 55 B2O3) and samples of the same composition containing 0.2 wt% dopants of 3d transition metal (TM) oxides (TiO2 → CuO). The glasses have been investigated by combined optical and Fourier Transform infrared spectroscopic measurements before and after being subjected to gamma irradiation with a dose of 8 Mrad (8 × 104 Gy). Optical absorption of the undoped glass before irradiation reveals strong charge transfer UV absorption which is related to the presence of unavoidable contaminated trace iron impurities (mainly Fe3+) within the raw materials used for the preparation of the base cadmium borate glass. The optical spectra of the 3d TM ions exhibit characteristic bands which are related the stable oxidation state of the 3d TM ions within the host glass. Gamma irradiation produces some limited variations in the optical spectra due to the stability of the host glass containing high percent 45 mol% of heavy metal oxide (CdO) which causes some shielding effects towards irradiation. From the absorption edge data, the values of the optical band gap Eopt and Urbach energy (∆E) have been calculated. The values of the optical energy gap are found to be dependent on the glass composition. Infrared absorption spectral measurements reveal characteristic absorption bands due to both triangular and tetrahedral borate groups with the BO3 units vibrations more intense than BO4 units due to the known limit value for the change of BO3 to BO4 groups. The introduction of 3d TM ions with the doping level (0.2 wt%) causes no changes in the number or position of the IR bands because of the presence of TM ions in modifying sites in the glass network. It is observed that gamma irradiation causes some limited changes in the FT-IR spectral bands due to the stability of the host heavy cadmium borate glass.

  17. Evaluation of Colloidal Stability and Ecotoxicity of Metal-based Nanoparticles in the Aquatic and Terrestrial Systems

    Science.gov (United States)

    Pokhrel, Lok Raj

    Intrinsic to the many nano-enabled products are atomic-size multifunctional engineered nanomaterials, which upon release contaminate the environments, raising considerable health and safety concerns. This Ph.D. dissertation is designed to investigate (i) whether metals or oxide nanoparticles are more toxic than ions, and if MetPLATE(TM) bioassay is applicable as a rapid nanotoxicity screening tool; (ii) how variable water chemistry (dissolved organic carbon (DOC), pH, and hardness) and organic compounds (cysteine, humic acid, and trolox) modulate colloidal stability, ion release, and aquatic toxicity of silver nanoparticles (AgNP); and (iii) the developmental responses of crop plants exposed to Ag- or ZnO- (zinc oxide) nanoparticles. Results suggest that the MetPLATE can be considered a high-throughput screening tool for rapid nanotoxicity evaluation. Detectable changes in the colloidal diameter, surface charge, and plasmonic resonance revealed modulating effects of variable water chemistry and organic ligands on the particle stability, dissolution, and toxicity of AgNPs against Escherichia coli or Daphnia magna. Silver dissolution increased as a function of DOC concentrations but decreased with increasing hardness, pH, cysteine, or trolox levels. Notably, the dissociated Ag+ was inadequate to explain AgNP toxicity, and that the combined effect of AgNPs and dissolved Ag+ under each ligand treatment was lower than of AgNO 3. Significant attenuation by trolox signifies an oxidative stress-mediated AgNP toxicity; its inability to attenuate AgNO3 toxicity, however, negates oxidative stress as Ag+ toxicity mechanism, and that cysteine could effectively quench free Ag+ to alleviate AgNO 3 toxicity in D. magna. Surprisingly, DOC-AgNPs complex that apparently formed at higher DOC levels might have led daphnids filter-feed on aggregates, potentially elevating internal dose, and thus higher mortality. Maize root anatomy showed differential alterations upon exposure to Ag

  18. Dynamic chiral-at-metal stability of tetrakis(d/l-hfc)Ln(III) complexes capped with an alkali metal cation in solution.

    Science.gov (United States)

    Lin, Yiji; Zou, Fang; Wan, Shigang; Ouyang, Jie; Lin, Lirong; Zhang, Hui

    2012-06-14

    Chiral tetrakis(β-diketonate) Ln(III) complexes Δ-[NaLa(d-hfc)(4)(CH(3)CN)] (1) and Λ-[NaLa(l-hfc)(4) (CH(3)CN)] (2) (d/l-hfc(-) = 3-heptafluo-robutylryl-(+)/(-)-camphorate) are a pair of enantiomers and crystallize in the same Sohncke space group (P2(1)2(1)2(1)) with dodecahedral (DD) geometry. Typically positive and negative exciton splitting patterns around 320 nm were observed in the solid-state circular dichroism (CD) spectra of complexes 1 and 2, which indicate that their shell configurational chiralities are Δ and Λ, respectively. The apparent bisignate couplets in the solid-state CD spectra of [CsLn(d-hfc)(4)(H(2)O)] [Ln = La (3), Yb (5)] and [CsLn(l-hfc)(4)(H(2)O)] [Ln = La (4), Yb (6)] show that they are a pair of enantiomers and their absolute configurations are denoted Δ and Λ, respectively. The crystallographic data of 5 reveals that its coordination polyhedron is the square antiprism (SAP) geometry and it undergoes a phase transition from triclinic (α phase, P1) to monoclinic (β phase, C2) upon cooling. The difference between the two phases is brought about by the temperature dependent behaviour of the coordination water molecules, but this did not affect the configurational chirality of the Δ-SAP-[Yb(d-hfc)(4)](-) moiety. Furthermore, time-dependent CD, UV-vis and (19)F NMR were applied to study the solution behavior of these complexes. It was found that the chiral-at-metal stability of the three pairs of complexes is different and affected by both the Ln(3+) and M(+) ion size. The results show that the Cs(+) cation can retain the metal center chirality and stablize the structures of [Ln(d/l-hfc)(4)](-) or the dissociated tris(d/l-hfc)Ln(III) species in solution for a longer time than that of the Na(+) cation, and it is important that the Cs(+) ion successfully lock the configurational chirality around the Yb(3+) center of the complex species in solution. This is reasoned by the short Cs(+)···FC, Cs(+)···O-Yb and Cs(+)···Yb(3

  19. Ab Initio Quantum Mechanical Study of the Structure and Stability of the Alkaline Earth Metal Oxides and Peroxides

    Science.gov (United States)

    Königstein, Markus; Catlow, C. Richard A.

    1998-10-01

    We report a detailed computationally study of the stability of the alkaline earth metal peroxidesMO2(M=Ba, Sr, Ca, Mg, Be) with respect to decomposition into the corresponding oxidesMOand molecular oxygen using Hartree-Fock and density functional theory (DFT) techniques. A comparison between calculated and experimental binding energies indicates that the DFT method is most suitable for a correct description of the peroxide bond. The DFT reaction energies for the peroxide decompositionMO2→MO+{1}/{2}O2show that only BaO2and SrO2are thermodynamically stable compounds, while CaO2(in the calcium carbide structure), MgO2, and BeO2(in the pyrite structure) are energetically unstable with reaction energies of -24.7, -26.8, and -128.7kJ/mol, respectively, and are therefore unlikely to exist as pure compounds. The published calcium carbide structure for CaO2is probably incorrect, at least for pure calcium peroxide, since apart from the thermodynamical instability the compound is more stable in the pyrite structure by 25.5 kJ/mol. Our analysis suggests that the water and/or hydrogen peroxide content of experimentally prepared MgO2samples is necessary for the stabilization of the structure, while BeO2is clearly unstable under ambient conditions. We studied also the effect of the zero point energies and the entropies on the decomposition free energies and, for this purpose, performed atomistic lattice simulations based on interatomic potentials, which we derived from ourab initiodata; the results indicate a negligible effect of the zero point energies, while the entropy terms favor the decomposition reaction by ca. 20 kJ/mol at 298.15 K.

  20. Ab initio quantum mechanical study of the structure and stability of the alkaline earth metal oxides and peroxides

    Energy Technology Data Exchange (ETDEWEB)

    Koenigstein, M.; Catlow, C.R.A. [Royal Institution of Great Britain, London (United Kingdom). Davy Faraday Research Lab.

    1998-10-01

    The authors report a detailed computational study of the stability of the alkaline earth metal peroxides MO{sub 2} (M = Ba, Sr, Ca, Mg, Be) with respect to decomposition into the corresponding oxides Mo and molecular oxygen using Hartree-Fock and density functional theory (DFT) techniques. A comparison between calculated and experimental binding energies indicates that the DFT method is most suitable for a correct description of the peroxide bond. The DFT reaction energies for the peroxide decomposition MO{sub 2} {yields} MO + {1/2}O{sub 2} show that only BaO{sub 2} and SrO{sub 2} are thermodynamically stable compounds, while CaO{sub 2} (in the calcium carbide structure), MgO{sub 2}, and BeO{sub 2} (in the pyrite structure) are energetically unstable with reaction energies of {minus}24.7, {minus}26.8, and {minus}128.7 kJ/mol, respectively, and are therefore unlikely to exist as pure compounds. The published calcium carbide structure for CaO{sub 2} is probably incorrect, at least for pure calcium peroxide, since apart from the thermodynamical instability the compound is more stable in the pyrite structure by 25.5 kJ/mol. The analysis suggests that the water and/or hydrogen peroxide content of experimentally prepared MgO{sub 2} samples is necessary for the stabilization of the structure, while BeO{sub 2} is clearly unstable under ambient conditions. The authors studied also the effect of the zero point energies and the entropies on the decomposition free energies and, for this purpose, performed atomistic lattice simulations based on interatomic potentials, which they derived from their ab initio data; the results indicate a negligible effect of the zero point energies, while the entropy terms favor the decomposition reaction by ca. 20 kJ/mol at 298.15 K.

  1. Lysosomal membrane stability and metallothionein content in Mytilus galloprovincialis (L.), as biomarkers Combination with trace metal concentrations

    Energy Technology Data Exchange (ETDEWEB)

    Domouhtsidou, G.P.; Dailianis, S.; Kaloyianni, M.; Dimitriadis, V.K

    2004-03-01

    The simultaneous study of two biomarkers, the lysosomal membrane stability (LMS) of the digestive gland and the metallothionein (MT) content of the digestive gland, the gills and the mantle/gonad complex of the mussel Mytilus galloprovincialis was examined in an enclosed estuarine system in June and October 2001. Mussels were collected along the Gulf of Thermaikos (northern Greece) from stations displaying a pollution gradient, while Olympiada in the Gulf of Strymonikos was used as a reference station. In addition, the heavy metal (Cd, Pb, Cu and Zn) content, using atomic absorption spectrophotometry (AAS), were evaluated in the digestive gland, the gills and the mantle/gonad complex of mussels collected from the same sites and seasons. LMS values were significantly greater, and the MT content of the studied tissues were significantly less in mussels collected from the reference station compared to mussels from more polluted stations located in the Gulf of Thermaikos. Significant correlation was observed between the MT content of the gills and the mantle/gonad complex with the LMS values.

  2. Thermodynamic modelling of phase equilibrium in system Ti-B-Si-C, synthesis and phases composition of borides and carbides layers on titanic alloyVT-1 at electron beam treatment in vacuum

    Science.gov (United States)

    Smirnyagina, N. N.; Khaltanova, V. M.; Lapina, A. E.; Dasheev, D. E.

    2017-01-01

    Composite layers on the basis of carbides and borides the titan and silicon on titanic alloy VT-1 are generated at diffused saturation in vacuum. Formation in a composite of MAX phase Ti3SiC2 is shown. Thermodynamic research of phase equilibrium in systems Ti-Si-C and Ti-B-C in the conditions of high vacuum is executed. The thermodynamics, formation mechanisms of superfirm layers borides and carbides of the titan and silicon are investigated.

  3. Stabilizing and increasing the magnetic moment of half-metals: The role of Li in half-Heusler LiMn Z (Z =N,P,Si)

    Science.gov (United States)

    Damewood, L.; Busemeyer, B.; Shaughnessy, M.; Fong, C. Y.; Yang, L. H.; Felser, C.

    2015-02-01

    Due to their similarities to metastable zinc-blende half-metals, we systematically examined the half-Heusler compounds β -LiMnZ (Z =N,P and Si) for their electronic, magnetic, and stability properties at optimized lattice constants and strained lattice constants that exhibit half-metallic properties. We also report the other phases of the half-Heusler structure (α and γ phases), but they are unlikely to be grown. The magnetic moments of these stable Li-based compounds are expected to reach as high as 4 μB per unit cell when Z =Si and 5 μB per unit cell when Z =N and P; however, the antiferromagnetic spin configuration is energetically favored when Z is a pnictogen. β -LiMnSi at a lattice constant 14% larger than its equilibrium lattice constant is a promising half-metal due to its large magnetic moment, large gap, and vibrational stability. The modified Slater-Pauling rule for these compounds is determined. Finally, we investigated a plausible method for developing half-metallic Li xMn Z at equilibrium by tuning x , but this type of alloying introduces local structural changes that preclude half-metallicity.

  4. ENVIRONMENTAL MANAGEMENT SCIENCE PROGRAM PROJECT NUMBER 87016 CO-PRECIPITATION OF TRACE METALS IN GROUNDWATER AND VADOSE ZONE CALCITE: IN SITU CONTAINMENT AND STABILIZATION OF STRONTIUM-90 AND OTHER DIVALENT METALS AND RADIONUCLIDES AT ARID WESTERN DOE SITES

    Energy Technology Data Exchange (ETDEWEB)

    Ferris, F. Grant; Fujita, Yoshiko; Smith, Robert W.

    2004-06-15

    Radionuclide and metal contaminants are present in the vadose zone and groundwater throughout the U.S. Department of Energy (DOE) weapons complex. In situ containment and stabilization of these contaminants in vadose zones or groundwater is a cost-effective treatment strategy. Our facilitated approach relies upon the hydrolysis of introduced urea to cause the acceleration of calcium carbonate precipitation (and trace metal coprecipitation) by increasing groundwater pH and alkalinity (Fujita et al., 2000; Warren et al., 2001). Subsurface urea hydrolysis is catalyzed by the urease enzyme, which may be either introduced with the urea or produced in situ by ubiquitous subsurface urea hydrolyzing microorganisms. Because the precipitation processes are irreversible and many western aquifers are saturated with respect to calcite, the co-precipitated metals and radionuclides will be effectively removed from groundwater. The rate at which trace metals are incorporated into calcite is a function of calcite precipitation kinetics, adsorption interactions between the calcite surface and the trace metal in solution (Zachara et al., 1991), solid solution properties of the trace metal in calcite (Tesoriero and Pankow, 1996), and also the surfaces upon which the calcite is precipitating. A fundamental understanding of the coupling of calcite precipitation and trace metal partitioning, and how this occurs in aquifers and vadose environments is lacking. This report summarizes work undertaken during the second year of this project.

  5. Effects of Mo addition on thermal stability and magnetic properties of a ferromagnetic Fe75P10C10B5 metallic glass

    Science.gov (United States)

    Zhang, Wei; Jia, Xingjie; Li, Yanhui; Fang, Canfeng

    2014-05-01

    The effects of Mo content on the thermal stability, glass-forming ability (GFA), magnetic and mechanical properties of Fe75-xMoxP10C10B5 (x = 0-10) metallic glasses were investigated. The stabilization of supercooled liquid and GFA were significantly enhanced by addition of Mo. Although the saturation magnetization (Is) of the alloys reduced with increasing Mo content, the coercive force (Hc) decreased. The metallic glasses with x = 2.5-7.5 exhibit low glass transition temperature of 733-749 K, large supercooled liquid region of 61-96 K, and high GFA with critical fully glassy sample diameters of 1.5-3.0 mm. They also possess rather high Is of 0.81-1.11 T, low Hc of 2.07-4.87 A/m, high Vicker's hardness of 860-992, high compressive yield strength of over 3000 MPa with a distinct plastic strain.

  6. A computational study on structure, stability and bonding in Noble Gas bound metal Nitrates, Sulfates and Carbonates (Metal = Cu, Ag, Au)

    Indian Academy of Sciences (India)

    MANAS GHARA; SUDIP PAN; JYOTIRMOY DEB; ANAND KUMAR; UTPAL SARKAR; PRATIM KUMAR CHATTARAJ

    2016-10-01

    A density functional theory based study is performed to investigate the noble gas (Ng = Ar-Rn) binding ability of nitrates, sulfates and carbonates of noble metal (M). Their ability to bind Ng atoms is assessed through bond dissociation energy and thermochemical parameters like dissociation enthalpy and dissociation free energy change corresponding to the dissociation of Ng bound compound producing Ngand the respective salt. The zero-point energy corrected dissociation energy values per Ng atom for the dissociation process producing Ng atom(s) and the corresponding salts range within 6.0–13.1 kcal/mol in NgCuNO₃, 3.1–9.8 kcal/mol in NgAgNO₃, 6.0–13.2 kcal/mol in NgCuSO₄, 3.2–10.1 kcal/mol in NgAgSO₄, 5.1–11.7 kcal/mol in Ng₂Cu₂SO₄, 2.5–8.6 kcal/mol in Ng₂Ag₂SO₂, 8.1–19.9 kcal/mol in Ng₂Au2SO₂, 5.7–12.4 kcal/mol in NgCuCO₃, 2.3–8.0 kcal/mol in Ng₂Ag₂CO₃ and 7.3–18.2 kcal/mol in Ng₂Au₂CO₃, with a gradual increase in moving from Ar to Rn. For a given type of system, the stability of Ng bound analogues follows the order as Au > Cu > Ag. All dissociation processes are endothermic in nature whereas they become endergonic as well in most of the cases of Kr-Rn bound analogues at 298 K. Natural population analysis along with the computation of Wiberg bond indices, and electron density analyses provide insights into the nature of the Ng-M bonds. The Ng-M bonds can be represented as partial covalent bonds as supported by the different electron density descriptors.

  7. 99Tc and Re incorporated into metal oxide polyoxometalates: oxidation state stability elucidated by electrochemistry and theory.

    Science.gov (United States)

    McGregor, Donna; Burton-Pye, Benjamin P; Mbomekalle, Israel M; Aparicio, Pablo A; Romo, Susanna; López, Xavier; Poblet, Josep M; Francesconi, Lynn C

    2012-08-20

    The radioactive element technetium-99 ((99)Tc, half-life = 2.1 × 10(5) years, β(-) of 253 keV), is a major byproduct of (235)U fission in the nuclear fuel cycle. (99)Tc is also found in radioactive waste tanks and in the environment at National Lab sites and fuel reprocessing centers. Separation and storage of the long-lived (99)Tc in an appropriate and stable waste-form is an important issue that needs to be addressed. Considering metal oxide solid-state materials as potential storage matrixes for Tc, we are examining the redox speciation of Tc on the molecular level using polyoxometalates (POMs) as models. In this study we investigate the electrochemistry of Tc complexes of the monovacant Wells-Dawson isomers, α(1)-P(2)W(17)O(61)(10-) (α1) and α(2)-P(2)W(17)O(61)(10-) (α2) to identify features of metal oxide materials that can stabilize the immobile Tc(IV) oxidation state accessed from the synthesized Tc(V)O species and to interrogate other possible oxidation states available to Tc within these materials. The experimental results are consistent with density functional theory (DFT) calculations. Electrochemistry of K(7-n)H(n)[Tc(V)O(α(1)-P(2)W(17)O(61))] (Tc(V)O-α1), K(7-n)H(n)[Tc(V)O(α(2)-P(2)W(17)O(61))] (Tc(V)O-α2) and their rhenium analogues as a function of pH show that the Tc-containing derivatives are always more readily reduced than their Re analogues. Both Tc and Re are reduced more readily in the lacunary α1 site as compared to the α2 site. The DFT calculations elucidate that the highest oxidation state attainable for Re is VII while, under the same electrochemistry conditions, the highest oxidation state for Tc is VI. The M(V)→ M(IV) reduction processes for Tc(V)O-α1 are not pH dependent or only slightly pH dependent suggesting that protonation does not accompany reduction of this species unlike the M(V)O-α2 (M = (99)Tc, Re) and Re(V)O-α1 where M(V/IV) reduction process must occur hand in hand with protonation of the terminal M═O to

  8. Linearized model for the hydrodynamic stability investigation of molten fuel jets into the coolant of a Liquid Metal Fast Breeder Reactor (LMFBR)

    Science.gov (United States)

    Hartel, K.

    1986-02-01

    The hydrodynamic stability of liquid jets in a liquid continuum, both characterized by low viscosity was analyzed. A linearized mathematical model was developed. This model enables the length necessary for fragmentation of a vertical, symmetric jet of molten fuel by hydraulic forces in the coolant of a liquid metal fast breeder reactor to be evaluated. On the basis of this model the FRAG code for numerical calculation of the hydrodynamic fragmentation mechanism was developed.

  9. Stretchable, Transparent Electrodes as Wearable Heaters Using Nanotrough Networks of Metallic Glasses with Superior Mechanical Properties and Thermal Stability.

    Science.gov (United States)

    An, Byeong Wan; Gwak, Eun-Ji; Kim, Kukjoo; Kim, Young-Cheon; Jang, Jiuk; Kim, Ju-Young; Park, Jang-Ung

    2016-01-13

    Mechanical robustness, electrical and chemical reliabilities of devices against large deformations such as bending and stretching have become the key metrics for rapidly emerging wearable electronics. Metallic glasses (MGs) have high elastic limit, electrical conductivity, and corrosion resistance, which can be promising for applications in wearable electronics. However, their applications in wearable electronics or transparent electrodes have not been extensively explored so far. Here, we demonstrate stretchable and transparent electrodes using CuZr MGs in the form of nanotrough networks. MG nanotroughs are prepared by electrospinning and cosputtering process, and they can be transferred to various desired substrates, including stretchable elastomeric substrates. The resulting MG nanotrough network is first utilized as a stretchable transparent electrode, presenting outstanding optoelectronic (sheet resistance of 3.8 Ω/sq at transmittance of 90%) and mechanical robustness (resistance change less than 30% up to a tensile strain of 70%) as well as excellent chemical stability against hot and humid environments (negligible degradation in performance for 240 h in 85% relative humidity and 85 °C). A stretchable and transparent heater based on the MG nanotrough network is also demonstrated with a wide operating temperature range (up to 180 °C) and excellent stretchability (up to 70% in the strain). The excellent mechanical robustness of these stretchable transparent electrode and heater is ascribed to the structural configuration (i.e., a nanotrough network) and inherent high elastic limit of MGs, as supported by experimental results and numerical analysis. We demonstrate their real-time operations on human skin as a wearable, transparent thermotherapy patch controlled wirelessly using a smartphone as well as a transparent defroster for an automobile side-view mirror, suggesting a promising strategy toward next-generation wearable electronics or automobile

  10. Efficiency modeling of solidification/stabilization of multi-metal contaminated industrial soil using cement and additives

    Energy Technology Data Exchange (ETDEWEB)

    Voglar, Grega E. [RDA - Regional Development Agency Celje, Kidriceva ulica 25, 3000 Celje (Slovenia); Lestan, Domen, E-mail: domen.lestan@bf.uni-lj.si [Agronomy Department, Centre for Soil and Environmental Science, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana (Slovenia)

    2011-08-30

    Highlights: {yields} We assess the feasibility of using soil S/S for industrial land reclamation. {yields} Retarders, accelerators, plasticizers were used in S/S cementitious formulation. {yields} We proposed novel S/S efficiency model for multi-metal contaminated soils. - Abstract: In a laboratory study, formulations of 15% (w/w) of ordinary Portland cement (OPC), calcium aluminate cement (CAC) and pozzolanic cement (PC) and additives: plasticizers cementol delta ekstra (PCDE) and cementol antikorodin (PCA), polypropylene fibers (PPF), polyoxyethylene-sorbitan monooleate (Tween 80) and aqueous acrylic polymer dispersion (Akrimal) were used for solidification/stabilization (S/S) of soils from an industrial brownfield contaminated with up to 157, 32,175, 44,074, 7614, 253 and 7085 mg kg{sup -1} of Cd, Pb, Zn, Cu, Ni and As, respectively. Soils formed solid monoliths with all cementitious formulations tested, with a maximum mechanical strength of 12 N mm{sup -2} achieved after S/S with CAC + PCA. To assess the S/S efficiency of the used formulations for multi-element contaminated soils, we propose an empirical model in which data on equilibrium leaching of toxic elements into deionized water and TCLP (toxicity characteristic leaching procedure) solution and the mass transfer of elements from soil monoliths were weighed against the relative potential hazard of the particular toxic element. Based on the model calculation, the most efficient S/S formulation was CAC + Akrimal, which reduced soil leachability of Cd, Pb, Zn, Cu, Ni and As into deionized water below the limit of quantification and into TCLP solution by up to 55, 185, 8750, 214, 4.7 and 1.2-times, respectively; and the mass transfer of elements from soil monoliths by up to 740, 746, 104,000, 4.7, 343 and 181-times, respectively.

  11. Predicting the Potentials, Solubilities and Stabilities of Metal-Acetylacetonates for Non-Aqueous Redox Flow Batteries Using Density Functional Theory Calculations.

    Energy Technology Data Exchange (ETDEWEB)

    Kucharyson, J. F.; Cheng, L.; Tung, S. O.; Curtiss, L. A.; Thompson, L. T.

    2017-07-14

    New active materials are needed to improve the performance and reduce the cost of non-aqueous redox flow batteries (RFBs) for grid-scale energy storage applications. Efforts to develop better performing materials, which have largely been empirical, would benefit from a better understanding of relationships between structural, electronic and RFB-relevant functional properties. This paper focuses on metal-acetylacetonates, a class of metal coordination complexes that has shown promise for use in RFBs, and describes correlations between their experimentally measured standard potentials, solubilities, and stabilities (cycle lifes), and selected chemical, structural and electronic properties determined from Density Functional Theory (DFT) calculations. The training set consisted of 16 complexes including 5 different metals and 11 different substituents on the acetylacetonate ligand. Standard potentials for those compounds were calculated and are in good agreement with experimentally measured results. A predictive equation based on the solvation energies and dipole moments, two easily computed properties, reasonably modeled the experimentally determined solubilities. Importantly, we were able to identify a descriptor for the stability of acetylacetonates. The experimentally determined stability, quantified as the cycle life to a given degree of degradation, correlated with the percentage of the highest occupied (HOMO) or lowest unoccupied molecular orbital (LUMO) on the metal of the complex. This percentage is influenced by the degree of ligand innocence (irreducibility), and complexes with the most innocent ligands yielded the most stable redox reactions. To this end, VO(acetylacetonate)(2) and Fe(acetylacetonate)(3), with nearly 80% of the HOMO and LUMO on the metal, possessed the most stable oxidation and reduction half-reactions, respectively. The structure-function relationships and correlations presented in this paper could be used to predict new, highly soluble

  12. Thermodynamic Stability of Transition-Metal-Substituted LiMn2-x Mx O4 (M=Cr, Fe, Co, and Ni) Spinels.

    Science.gov (United States)

    Lai, Chenying; Chen, Jiewei; Knight, James C; Manthiram, Arumugam; Navrotsky, Alexandra

    2016-07-01

    The formation enthalpies from binary oxides of LiMn2 O4 , LiMn2-x Crx O4 (x=0.25, 0.5, 0.75 and 1), LiMn2-x Fex O4 (x=0.25 and 0.5), LiMn2-x Cox O4 (x=0.25, 0.5, and 0.75) and LiMn1.75 Ni0.25 O4 at 25 °C were measured by high temperature oxide melt solution calorimetry and were found to be strongly exothermic. Increasing the Cr, Co, and Ni content leads to more thermodynamically stable spinels, but increasing the Fe content does not significantly affect the stability. The formation enthalpies from oxides of the fully substituted spinels, LiMnMO4 (M=Cr, Fe and Co), become more exothermic (implying increasing stability) with decreasing ionic radius of the metal and lattice parameters of the spinel. The trend in enthalpy versus metal content is roughly linear, suggesting a close-to-zero heat of mixing in LiMn2 O4 -LiMnMO4 solid solutions. These data confirm that transition-metal doping is beneficial for stabilizing these potential cathode materials for lithium-ion batteries.

  13. Stabilization and reuse of heavy metal contaminated soils by means of quicklime sulfate salt treatment. Final report, September 1992--February 1995

    Energy Technology Data Exchange (ETDEWEB)

    Dermatas, D.

    1995-08-01

    Capillary and hydraulic flows of water in porous media contaminated by heavy metal species often result in severe aquifer contamination. In the present study a chemical admixture stabilization approach is proposed, where heavy metal stabilization/immobilization is achieved by means of quicklime-based treatment. Both in-situ treatment by injection and on-site stabilization by excavation, mixing, and compaction will be investigated. In addition, the potential to reuse the resulting stabilized material as readily available construction material will also be investigated. The heavy metals under study include: arsenic, chromium, lead, and mercury. The proposed technical approach consists of three separate phases. During phase A, both artificial and naturally occurring contaminated soil mixes were treated, and then tested for stress-strain properties, leachability, micromorphology, mineralogical composition, permeability, setting time, and durability. In such a way, the effectiveness of the proposed remediation technology was verified, the treatment approach was optimized, and the underlying mechanisms responsible for stabilization were established. During phase B, the proposed technology will be tested for two DOE-site subscale systems, involving naturally occurring contaminated soil, using the same testing methodology as the one outlined for phase A. Provided that the proposed technology is proven effective for the subscale systems, a field application will be demonstrated. Again process quality monitoring will be performed by testing undisturbed samples collected from the treated sites, in the same fashion as for the previous phases. Following completion of the proposed study, a set of comprehensive guidelines for field applications will be developed. 42 refs., 196 figs., 26 tabs.

  14. Influence of Schiff base and lanthanide metals on the synthesis, stability, and reactivity of monoamido lanthanide complexes bearing two Schiff bases.

    Science.gov (United States)

    Han, Fubin; Teng, Qiaoqiao; Zhang, Yong; Wang, Yaorong; Shen, Qi

    2011-03-21

    The monoamido lanthanide complexes stabilized by Schiff base ligand L(2)LnN(TMS)(2) (L = 3,5-Bu(t)(2)-2-(O)-C(6)H(2)CH═N-8-C(9)H(6)N, Ln = Yb (1), Y (2), Eu (3), Nd (4), and La (5)) were synthesized in good yields by the reactions of Ln[N(TMS)(2)](3) with 1.8 equiv of HL in hexane at room temperature. It was found that the stability of 1-5 depends greatly on the size of the lanthanide metals with the increasing trend of Yb ≈ Y metals of Y and Yb, L''(2)LnN(TMS)(2) (Ln = Yb (13) and Y (14)), and the more stable tris-Schiff base complexes with the large metals of La and Nd, yielded L''(3)Ln as the only product. Complexes 1-14 were fully characterized including X-ray crystal structural analysis. Complexes 1-5, 10, and 14 can serve as the efficient catalysts for addition of amines to carbodiimides, and the catalytic activity is greatly affected by the lanthanide metals with the active sequence of Yb < Y < Eu ≈ Nd ≈ La.

  15. Enhanced Electroresponse of Alkaline Earth Metal-Doped Silica/Titania Spheres by Synergetic Effect of Dispersion Stability and Dielectric Property.

    Science.gov (United States)

    Yoon, Chang-Min; Lee, Seungae; Cheong, Oug Jae; Jang, Jyongsik

    2015-09-01

    A series of alkaline earth metal-doped hollow SiO2/TiO2 spheres (EM-HST) are prepared as electrorheological (ER) materials via sonication-mediated etching method with various alkaline earth metal hydroxides as the etchant. The EM-HST spheres are assessed to determine how their hollow interior and metal-doping affects the ER activity. Both the dispersion stability and the dielectric properties of these materials are greatly enhanced by the proposed one-step etching method, which results in significant enhancement of ER activity. These improvements are attributed to increased particle mobility and interfacial polarization originating from the hollow nature of the EM-HST spheres and the effects of EM metal-doping. In particular, Ca-HST-based ER fluid exhibits ER performance which is 7.1-fold and 3.1-fold higher than those of nonhollow core/shell silica/titania (CS/ST) and undoped hollow silica/titania (HST)-based ER fluids, respectively. This study develops a versatile and simple approach to enhancing ER activity through synergetic effects arising from the combination of dispersion stability and the unique dielectric properties of hollow EM-HST spheres. In addition, the multigram scale production described in this experiment can be an excellent advantage for practical and commercial ER application.

  16. Leaching behavior and effectiveness of curing days (7& 28) of solidified/stabilized fly ash based geopolymer (multi-metal bearing sludge): experimental and modeling study.

    Science.gov (United States)

    Chaudhary, Rubina; Khaleb, Divya; Badur, Smita

    2012-04-01

    This paper presents the study of the immobilization of heavy metals like Pb, Fe, Mn, Cu and Zn by fly ash based geopolymers. The purpose of this study was to investigate the effectiveness of fly ash based geopolymeric solidification/stabilization technology. For S/S of waste, geopolymer as a binding agent was mixed with waste at different ratios. For initial waste characterization, contaminants concentration and some physical waste characterization such as dry density, bulk density, specific gravity, porosity, moisture holding capacity, and moisture content were determined. Waste and geopolymer mixture were cured for 7 and 28 days to study the effect of curing days on the solidified/ stabilized product. Diffusion leaching test was performed on the geopolymers containing industrial sludge to determine the leaching mechanism of binders to entrap the waste constituents within their matrix. Movement of the elements was identified with the help of leachability index. S/S through geopolymer was found to be effective in immobilizing toxic metals present in the sludge. Zn was 100% and other metals like Pb, Fe, Mn and Cu were in the range 80-99% immobilized. The order of fixation of metals was Zn >Cu > Fe > Mn > Pb.

  17. Irving-Williams Order in the Framework of Connectivity Index 3χv Enables Simultaneous Prediction of Stability Constants of Bivalent Transition Metal Complexes

    Directory of Open Access Journals (Sweden)

    Ante Miličević

    2011-01-01

    Full Text Available Logarithms of stability constants, log K1 and log β2, of the first transition series metal mono- and bis-complexes with any of four aliphatic amino acids (glycine, alanine, valine and leucine decrease monotonously with third order valence connectivity index, 3χv, from Cu2+ to Mn2+. While stability of the complexes with the same metal is linearly dependent on 3χv, stability constants of Mn2+, Fe2+, Co2+, and Ni2+complexes with the same ligand show a quadratic dependence on 3χv. As Cu2+ complexes deviate significantly from quadratic functions, models for the simultaneous estimation of the stability constants, yielding r = 0.999 (S.E. = 0.05 and r = 0.998 (S.E. = 0.11, for log K1 and log β2, respectively, were developed only for Mn2+, Fe2+, Co2+, and Ni2+ complexes with amino acids.

  18. Influence of Metal Transfer Stability and Shielding Gas Composition on CO and CO2 Emissions during Short-circuiting MIG/MAG Welding

    Directory of Open Access Journals (Sweden)

    Valter Alves de Meneses

    Full Text Available Abstract: Several studies have demonstrated the influence of parameters and shielding gas on metal transfer stability or on the generation of fumes in MIG/MAG welding, but little or nothing has been discussed regarding the emission of toxic and asphyxiating gases, particularly as it pertains to parameterization of the process. The purpose of this study was to analyze and evaluate the effect of manufacturing aspects of welding processes (short-circuit metal transfer stability and shielding gas composition on the gas emission levels during MIG/MAG welding (occupational health and environmental aspects. Using mixtures of Argon with CO2 and O2 and maintaining the same average current and the same weld bead volume, short-circuit welding was performed with carbon steel welding wire in open (welder’s breathing zone and confined environments. The welding voltage was adjusted to gradually vary the transfer stability. It was found that the richer the composition of the shielding gas is in CO2, the more CO and CO2 are generated by the arc. However, unlike fume emission, voltage and transfer stability had no effect on the generation of these gases. It was also found that despite the large quantity of CO and CO2 emitted by the arc, especially when using pure CO2 shielding gas, there was no high level residual concentration of CO and CO2 in or near the worker’s breathing zone, even in confined work cells.

  19. Full potential calculations and atom in molecule analysis of the bonding properties of perovskites Borides XRh3B (X=Dy, Ho, Er)

    OpenAIRE

    Ouahrani T.; Merad Boudia I.; Lasri B.

    2013-01-01

    ab initio calculations were performed for the cubic perovskites Borides XRh3B, (X=Dy, Ho, Er). In this work, we have used the augmented plane-wave plus local orbital method to compute the equilibrium structural parameters and electronic structure of densities of states, as well as for the first time, prediction of the thermo-elastic properties of these crystals are presented. The chemical bonding of these compounds has been investigated by using of topological analyses grounded in the theory ...

  20. Rice Husk Ash to Stabilize Heavy Metals Contained in Municipal Solid Waste Incineration Fly Ash: First Results by Applying New Pre-treatment Technology

    Directory of Open Access Journals (Sweden)

    Laura Benassi

    2015-10-01

    Full Text Available A new technology was recently developed for municipal solid waste incineration (MSWI fly ash stabilization, based on the employment of all waste and byproduct materials. In particular, the proposed method is based on the use of amorphous silica contained in rice husk ash (RHA, an agricultural byproduct material (COSMOS-RICE project. The obtained final inert can be applied in several applications to produce “green composites”. In this work, for the first time, a process for pre-treatment of rice husk, before its use in the stabilization of heavy metals, based on the employment of Instant Pressure Drop technology (DIC was tested. The aim of this work is to verify the influence of the pre-treatment on the efficiency on heavy metals stabilization in the COSMOS-RICE technology. DIC technique is based on a thermomechanical effect induced by an abrupt transition from high steam pressure to a vacuum, to produce changes in the material. Two different DIC pre-treatments were selected and thermal annealing at different temperatures were performed on rice husk. The resulting RHAs were employed to obtain COSMOS-RICE samples, and the stabilization procedure was tested on the MSWI fly ash. In the frame of this work, some thermal treatments were also realized in O2-limiting conditions, to test the effect of charcoal obtained from RHA on the stabilization procedure. The results of this work show that the application of DIC technology into existing treatment cycles of some waste materials should be investigated in more details to offer the possibility to stabilize and reuse waste.

  1. Friction-reducing and antiwear behavior of metal halide-stabilized linear phosphazene derivatives as lubricants for a steel-on-steel contact

    Institute of Scientific and Technical Information of China (English)

    ZHU; Jiamei; LIU; Weimin; LIANG; Yongmin

    2005-01-01

    A series of novel metal halide-stabilized linear phosphazene derivatives were synthesized. The friction-reducing and antiwear abilities of the resulting products as the lubricants for a steel-on-steel contact were comparatively investigated on an Optimol SRV oscillating friction and wear tester. The morphology of the worn steel surface was observed on a scanning electron microscope, while the chemical states of some typical elements on the worn steel surface were examined by means of X-ray photoelectron spectroscopy. It was found that both the side branch structures and central metals influenced the friction-reducing and antiwear behaviors of the synthetic derivatives as the lubricants, which was related to the different adsorption activities of the organic compounds composed of different organic ingredients and metallic ions on a nascent metal surface. All the synthetic lubricants except for the iron (III) derivative showed increased antiwear abilities with increasing metallic ionic radius. A protective layer originated from the tribochemical reaction together with the adsorbed boundary lubricating layer containing organic fluorine compounds, nitrogen oxide, and Fe3(PO4)2 plays an important role in improving the friction and wear behavior of the steel-on-steel system.

  2. The Effect of Thermal Cycling Treatments on the Thermal Stability and Mechanical Properties of a Ti-Based Bulk Metallic Glass Composite

    Directory of Open Access Journals (Sweden)

    Fan Bu

    2016-11-01

    Full Text Available The effect of thermal cycling treatments on the thermal stability and mechanical properties of a Ti48Zr20Nb12Cu5Be15 bulk metallic glass composite (BMGC has been investigated. Results show that moderate thermal cycles in a temperature range of −196 °C (cryogenic temperature, CT to 25 °C (room temperature, RT or annealing time at CT has not induced obvious changes of thermal stability and then it decreases slightly over critical thermal parameters. In addition, the dendritic second phases with a bcc structure are homogeneously embedded in the amorphous matrix; no visible changes are detected, which shows structural stability. Excellent mechanical properties as high as 1599 MPa yield strength and 34% plastic strain are obtained, and the yield strength and elastic modulus also increase gradually. The effect on the stability is analyzed quantitatively by crystallization kinetics and plastic-flow models, and indicates that the reduction of structural relaxation enthalpy, which is related to the degradation of spatial heterogeneity, reduces thermal stability but does not imperatively deteriorate the plasticity.

  3. Effect of Mg, Ca, and Zn on stability of LiBH{sub 4} through computational thermodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sung Hoon; Manga, Venkateswara Rao; Liu, Zi-Kui [Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802 (United States)

    2010-07-15

    The effect of divalent metal-dopants, Mg, Ca, and Zn, on the stability of LiBH{sub 4} is studied by using the first-principles calculations and CALPHAD (CALculation of PHAse Diagram) modeling. The ground states of Mg{sub 1/2}BH{sub 4}, Ca{sub 1/2}BH{sub 4}, and Zn{sub 1/2}BH{sub 4} are shown to be I anti 4m2, F2dd, and I anti 4m2, respectively, through first-principles calculations. Positive enthalpy of mixing between Li and the alloying element is predicted, indicating unfavorable solubility of alloying elements in LiBH{sub 4} and thus offering possibility to decrease the stability of LiBH{sub 4}. The ionic sublattice model of (Li{sup +}, M{sup 2+}, Va){sub 1}(BH{sub 4}{sup -}){sub 1} is adopted for the metal substituted LiBH{sub 4} phase. It is observed that the addition of Mg or Zn has limited effect as the decomposition temperature is between those of LiBH{sub 4} and M{sub 1/2}BH{sub 4} for Mg and Zn substitutions. LiBH{sub 4} is destabilized with magnesium borides or LiZn{sub 4} formation but its decomposition temperature is higher than that of M{sub 1/2}BH{sub 4}. On the other hand, the addition of Ca significantly reduces the H{sub 2} releasing temperature due to the formation of highly stable CaB{sub 6}. (author)

  4. Small pH and salt variations radically alter the thermal stability of metal-binding domains in the copper transporter, Wilson disease protein.

    Science.gov (United States)

    Nilsson, Lina; Ådén, Jörgen; Niemiec, Moritz S; Nam, Kwangho; Wittung-Stafshede, Pernilla

    2013-10-24

    Although strictly regulated, pH and solute concentrations in cells may exhibit temporal and spatial fluctuations. Here we study the effect of such changes on the stability, structure, and dynamics in vitro and in silico of a two-domain construct (WD56) of the fifth and sixth metal-binding domains of the copper transport protein, ATP7B (Wilson disease protein). We find that the thermal stability of WD56 is increased by 40 °C when increasing the pH from 5.0 to 7.5. In contrast, addition of salt at pH 7.2 decreases WD56 stability by up to 30 °C. In agreement with domain-domain coupling, fractional copper loading increases the stability of both domains. HSQC chemical shift changes demonstrate that, upon lowering the pH from 7.2 to 6, both His in WD6 as well as the second Cys of the copper site in each domain become protonated. MD simulations reveal increased domain-domain fluctuations at pH 6 and in the presence of high salt concentration, as compared to at pH 7 and low salt concentration. Thus, the surface charge distribution at high pH contributes favorably to overall WD56 stability. By introducing more positive charges by lowering the pH, or by diminishing charge-charge interactions by salt, fluctuations among the domains are increased and thereby overall stability is reduced. Copper transfer activity also depends on pH: delivery of copper from chaperone Atox1 to WD56 is more efficient at pH 7.2 than at pH 6 by a factor of 30. It appears that WD56 is an example where the free energy landscapes for folding and function are linked via structural stability.

  5. Small hazardous waste generators in developing countries: use of stabilization/solidification process as an economic tool for metal wastewater treatment and appropriate sludge disposal.

    Science.gov (United States)

    Silva, Marcos A R; Mater, Luciana; Souza-Sierra, Maria M; Corrêa, Albertina X R; Sperb, Rafael; Radetski, Claudemir M

    2007-08-25

    The aim of this study was to propose a profitable destination for an industrial sludge that can cover the wastewater treatment costs of small waste generators. Optimized stabilization/solidification technology was used to treat hazardous waste from an electroplating industry that is currently released untreated to the environment. The stabilized/solidified (S/S) waste product was used as a raw material to build concrete blocks, to be sold as pavement blocks or used in roadbeds and/or parking lots. The quality of the blocks containing a mixture of cement, lime, clay and waste was evaluated by means of leaching and solubility tests according to the current Brazilian waste regulations. Results showed very low metal leachability and solubility of the block constituents, indicating a low environmental impact. Concerning economic benefits from the S/S process and reuse of the resultant product, the cost of untreated heavy metal-containing sludge disposal to landfill is usually on the order of US$ 150-200 per tonne of waste, while 1tonne of concrete roadbed blocks (with 25% of S/S waste constitution) has a value of around US$ 100. The results of this work showed that the cement, clay and lime-based process of stabilization/solidification of hazardous waste sludge is sufficiently effective and economically viable to stimulate the treatment of wastewater from small industrial waste generators.

  6. Stability Constants of Mixed Ligand Complexes of Transition Metal(II Ions with Salicylidene-4-methoxyaniline as Primary Ligand and 5-Bromosalicylidene-4-nitroaniline as Secondary Ligand

    Directory of Open Access Journals (Sweden)

    N. G. Nadkarni

    2011-01-01

    Full Text Available Binary and ternary complexes of the type M-Y and M-X-Y [M = Mn(II, Ni(II, Cu(II and Zn(II; X = salicylidene-4-methoxyaniline and Y=5-bromosalicylidene-4-nitroaniline] have been examined pH-metrically at 27±0.5 °C and at constant ionic strength, μ= 0.1 M (KCl in 75 : 25(v/v 1,4-dioxne-water medium. The stability constants for binary (M-Y and ternary (M-X-Y systems were calculated. The relative stability (Δ log KT values of the ternary complexes with corresponding binary complexes for all the metal(II ions in the present study found to be negative indicating that ternary 1:1:1 (M-X-Y complexes are less stable than binary 1:1 (M-Y complexes. In the ternary system studied, the order of stability constants of mixed ligand complexes with respect to the metal ions was found to be Cu(II > NI(II > Mn(II > Zn(II; which is same as in the corresponding binary (M-Y systems.

  7. ESTABLISHING SUSTAINABLE US HEV/PHEV MANUFACTURING BASE: STABILIZED LITHIUM METAL POWDER, ENABLING MATERIAL AND REVOLUTIONARY TECHNOLOGY FOR HIGH ENERGY LI-ION BATTERIES

    Energy Technology Data Exchange (ETDEWEB)

    Yakovleva, Marina

    2012-12-31

    FMC Lithium Division has successfully completed the project “Establishing Sustainable US PHEV/EV Manufacturing Base: Stabilized Lithium Metal Powder, Enabling Material and Revolutionary Technology for High Energy Li-ion Batteries”. The project included design, acquisition and process development for the production scale units to 1) produce stabilized lithium dispersions in oil medium, 2) to produce dry stabilized lithium metal powders, 3) to evaluate, design and acquire pilot-scale unit for alternative production technology to further decrease the cost, and 4) to demonstrate concepts for integrating SLMP technology into the Li- ion batteries to increase energy density. It is very difficult to satisfy safety, cost and performance requirements for the PHEV and EV applications. As the initial step in SLMP Technology introduction, industry can use commercially available LiMn2O4 or LiFePO4, for example, that are the only proven safer and cheaper lithium providing cathodes available on the market. Unfortunately, these cathodes alone are inferior to the energy density of the conventional LiCoO2 cathode and, even when paired with the advanced anode materials, such as silicon composite material, the resulting cell will still not meet the energy density requirements. We have demonstrated, however, if SLMP Technology is used to compensate for the irreversible capacity in the anode, the efficiency of the cathode utilization will be improved and the cost of the cell, based on the materials, will decrease.

  8. Compressibility of AlB sub 2 -type transition metal diborides

    CERN Document Server

    Pereira, A S; Jornada, J A; Leger, J M; Haines, J

    2002-01-01

    The pressure behaviour of a series of transition metal borides has been studied both experimentally and by means of ab initio calculations. X-ray diffraction patterns measured up to approx 50 GPa for VB sub 2 and ZrB sub 2 show no obvious phase transition. Bulk moduli of 322 and 317 GPa, respectively, were obtained using a Murnaghan equation of state. Hartree-Fock LCCO (linear combination of crystal orbitals) calculations performed for TiB sub 2 have allowed its compression behaviour to be studied. The bulk modulus obtained (292 GPa) and the proposed important contribution of the interlayer interaction to the elastic behaviour under high pressure are consistent with the experimental results for the other borides.

  9. Thermal Treatment of Iron Oxide Stabilized APC Residues from Waste Incineration and the Effect on Heavy Metal Binding

    DEFF Research Database (Denmark)

    Sørensen, Mette Abildgaard; Stackpoole, M.; Bender-Koch, C.

    2000-01-01

    Iron oxide stabilized APC residues from MSWI were heat treated at 600°C and 900°C. The thermal treatments resulted in a change in product stability by forcing a transformation in the mineralogical structures of the products. The treatments, moreover, simulated somewhat the natural aging processes...

  10. Stability, sub-gap current, 1/f-noise, and elemental depth profiling of annealed Al:Mn-AlOX-Al normal metal-insulator-superconducting tunnel junctions

    Science.gov (United States)

    Julin, J. K.; Chaudhuri, S.; Laitinen, M.; Sajavaara, T.; Maasilta, I. J.

    2016-12-01

    In this paper we report a study of the effect of vacuum annealing at 400°C on the properties of normal metal-insulator-superconductor (NIS) tunnel junctions, with manganese doped aluminium (Al:Mn) as the normal metal, aluminum as the superconductor and amorphous aluminum oxide as the tunneling barrier (Al:Mn-AlOx-Al). The annealing treatment improves the stability of the junctions, increases their tunneling resistance and does not have a negative impact on the low-temperature current-voltage characteristics. The measured 1/f resistance noise of the junctions also changes after annealing, in the best case decreasing by over an order of magnitude. All these observations show that annealing is a viable route to improve NIS junction devices after the sample has been fabricated.

  11. Effects of alkaline earth metal ion complexation on amino acid zwitterion stability: Results from infrared action spectroscopy

    NARCIS (Netherlands)

    Bush, M. F.; Oomens, J.; Saykally, R. J.; Williams, E. R.

    2008-01-01

    The structures of isolated alkaline earth metal cationized amino acids are investigated using infrared multiple photon dissociation (IRMPD) spectroscopy and theory. These results indicate that arginine, glutamine, proline, serine, and valine all adopt zwitterionic structures when complexed with diva

  12. Platinum and Other Transition Metal Nanoclusters (Pd, Rh) Stabilized by PAMAM Dendrimer as Excellent Heterogeneous Catalysts: Application to the Methylcyclopentane (MCP) Hydrogenative Isomerization.

    Science.gov (United States)

    Deraedt, Christophe; Melaet, Gérôme; Ralston, Walter T; Ye, Rong; Somorjai, Gabor A

    2017-03-08

    Pt, Rh, and Pd nanoclusters stabilized by PAMAM dendrimer are used for the first time in a gas flow reactor at high temperature (150-250 °C). Pt nanoclusters show a very high activity for the hydrogenation of the methylcyclopentane (MCP) at 200-225 °C with turnover freqency (TOF) up to 334 h(-1) and selectivity up to 99.6% for the ring opening isomerization at very high conversion (94%). Rh nanoclusters show different selectivity for the reaction, that is, ring opening isomerization at 175 °C and cracking at higher temperature whereas Pd nanoclusters perform ring enlargement plus dehydrogenation, while maintaining a high activity. The difference in these results as compared to unsupported/uncapped nanoparticles, demonstrates the crucial role of dendrimer. The tunability of the selectivity of the reaction as well as the very high activity of the metal nanoclusters stabilized by dendrimer under heterogeneous conditions open a new application for dendrimer catalysts.

  13. Structural Phase Transformation (F. C. C. - B. C. C.) in F. C. C. Metals and Their Stability on the Path of Transformation

    Science.gov (United States)

    Öztekýn, Yasemin; Çolakoðlu, Kemal

    1997-08-01

    Because of its importance in Solid-State Physics, Metalurgy, Solid Mechanics and geophysics, theoretical strength calculations are performed to locate the stress-free b.c.c phase on three f.c.c metals (Ca, Pb, Ir). Internal energies correspponding to the unstresed b.c.c. and f.c.c. phase, and the required stress and energy changes for f.c.c.-b.c.c. transformation for these crystals are computed. To determine the range of stability (G stability), the Born criterion is used by calculating the values of deformation connecting the stress-free b.c.c. and stress-free f.c.c. phases of Ca, Pb and Ir. The studied crystals are subjected to unconstrained (100) uniaxial tension in all computations, and E.G.E.P. (Extended generalized exponantial potential) model is used to carry out these calculations.

  14. Study of the stability of electrode metal melting and transfer in the process of consumable electrode welding powered by supplies with differing dynamic characteristics

    Science.gov (United States)

    Saraev, Y. N.; Chinakhov, D. A.; Il'yashchenko, D. P.; Kiselev, A. S.; Gardiner, A. S.; Raev, I. V.

    2016-11-01

    In the paper we present the results of the study of the power supply characteristics effect upon the stability of electrode metal melting and transfer into the weld pool in the process of consumable electrode welding. It was shown that application of inverter type welding power supplies of the new generation results in changing the characteristics of the heat and mass transfer which has a decisive impact upon the heat content of the weld pool, reduction of residual stresses in the heat-affected zone (HAZ). The authors also substantiate the tendency to the reduction of the structural constituents in the area of the permanent joint.

  15. Genome Structure of the Heavy Metal Hyperaccumulator Noccaea caerulescens and Its Stability on Metalliferous and Nonmetalliferous Soils1[OPEN

    Science.gov (United States)

    Mandáková, Terezie; Singh, Vasantika; Krämer, Ute; Lysak, Martin A.

    2015-01-01

    Noccaea caerulescens (formerly known as Thlaspi caerulescens), an extremophile heavy metal hyperaccumulator model plant in the Brassicaceae family, is a morphologically and phenotypically diverse species exhibiting metal tolerance and leaf accumulation of zinc, cadmium, and nickel. Here, we provide a detailed genome structure of the approximately 267-Mb N. caerulescens genome, which has descended from seven chromosomes of the ancestral proto-Calepineae Karyotype (n = 7) through an unusually high number of pericentric inversions. Genome analysis in two other related species, Noccaea jankae and Raparia bulbosa, showed that all three species, and thus probably the entire Coluteocarpeae tribe, have descended from the proto-Calepineae Karyotype. All three analyzed species share the chromosome structure of six out of seven chromosomes and an unusually high metal accumulation in leaves, which remains moderate in N. jankae and R. bulbosa and is extreme in N. caerulescens. Among these species, N. caerulescens has the most derived karyotype, with species-specific inversions on chromosome NC6, which grouped onto its bottom arm functionally related genes of zinc and iron metal homeostasis comprising the major candidate genes NICOTIANAMINE SYNTHASE2 and ZINC-INDUCED FACILITATOR-LIKE1. Concurrently, copper and organellar metal homeostasis genes, which are functionally unrelated to the extreme traits characteristic of N. caerulescens, were grouped onto the top arm of NC6. Compared with Arabidopsis thaliana, more distal chromosomal positions in N. caerulescens were enriched among more highly expressed metal homeostasis genes but not among other groups of genes. Thus, chromosome rearrangements could have facilitated the evolution of enhanced metal homeostasis gene expression, a known hallmark of metal hyperaccumulation. PMID:26195571

  16. Impact of carboxymethyl cellulose coating on iron sulphide nanoparticles stability, transport, and mobilization potential of trace metals present in soils and sediment.

    Science.gov (United States)

    Van Koetsem, Frederik; Van Havere, Lynn; Du Laing, Gijs

    2016-03-01

    The stability and transport behaviour of carboxymethyl cellulose (CMC) stabilized iron sulphide (FeS) engineered nanoparticles (ENPs) as well as their concurrent scavenging and mobilization of trace metal contaminants from field-contaminated soils and sediment was studied through a series of batch and column experiments. The synthesized CMC-FeS ENPs were shown to have a hydrodynamic diameter of 154.5 ± 5.8 nm and remained stable in suspension for a prolonged period of time (several weeks) when kept under anaerobic conditions. In the absence of CMC, much larger FeS particles were formed, which quickly aggregated and precipitated within minutes. Batch experiments indicated that the CMC-FeS ENPs have a high affinity for metal contaminants (e.g., Cd, Cr, Cu, Hg, Ni, Pb, and Zn), as high amounts of these trace metals could be retrieved in the aqueous phase after treatment of the soils with the nanoparticles (i.e., up to 29 times more compared to the water-leachable metal contents). Furthermore, batch retention of the nanoparticles by the solid soil phase was low (trace metals, although no clear trend could be observed and metal leaching appeared to depend on the specific element under consideration, the type of extraction liquid, as well as on soil properties. Column breakthrough tests demonstrated that the CMC-FeS ENPs were highly mobile in the tested soil, even without the use of an external pressure (i.e., just via gravitational percolation). Maximal breakthrough of the nanoparticles was observed after approximately 10 or 16 pore volumes (PVs) for 83.3 or 500 mg L(-1) CMC-FeS ENPs, respectively, and only about 7% of the nanoparticles were retained by the soil after 22.7 PVs. Simultaneous elution of trace elements showed that up to 19, 8.7, or 11% of the respective Cd, Pb, or Zn content originally present in the soil was extracted after 22.7 PVs, with initial peaking occurring during the first 5 PVs. Moreover, filtration of the percolates over 0.10 μm (which

  17. First-principles investigations of metal (V, Nb, Ta)-doped monolayer MoS2: Structural stability, electronic properties and adsorption of gas molecules

    Science.gov (United States)

    Zhu, Jia; Zhang, Hui; Tong, Yawen; Zhao, Ling; Zhang, Yongfan; Qiu, Yuzhi; Lin, Xianning

    2017-10-01

    Two-dimensional (2D) layered materials are at the forefront of research because of their unique structures and promising catalytic abilities. Here, the structural stability, electronic properties and gas adsorption of metal (V, Nb, Ta)-doped monolayer MoS2 have been investigated by density functional theory calculations. Our results show that the metal (V, Nb, Ta)-doped monolayer MoS2 is a stable catalyst under room temperature, due to the strong interaction between the doped metals (V, Nb, Ta) and S vacancy of monolayer MoS2. Compared with the gas adsorption (CO, NO2, H2O, NH3) on pristine monolayer MoS2, doped metal (V, Nb, Ta) can significantly improve the adsorption properties, chemical activity and the sensitivity of that of adsorbed gas molecules. This effect occurs due to the strong overlap between the metal nd orbitals and gas molecule orbitals, result in activation of the adsorbed gas molecules. Analysis of Bader charge shows that, more charge transfer (-0.66 e to -0.72 e) occur from metal (V, Nb, Ta)-doped monolayer MoS2 to the oxidizing gas molecules (NO2) acting as acceptors. While for the adsorption of CO molecules, the relative less electrons (about -0.24 e - -0.35 e) transfer occuring from substrate to the adsorbed gases. Whereas the direction of charge transfers is reversed for the adsorption of the reducing gas (H2O and NH3) behaving as donors, in which small electrons (0.04 e -0.09 e) transfer from adsorbed gas to metal (V, Nb, Ta)-doped monolayer MoS2. Our results suggested that metal (V, Nb, Ta)-doped monolayer MoS2 might be a good candidate for low-cost, highly active, and stable catalysts and gas sensors, providing an avenue to facilitate the design of high active MoS2-based two dimensional catalysts and gas sensors.

  18. Ab-initio study on the stability, electronic and mechanical properties of transition metal nitrides under external pressure

    Science.gov (United States)

    Tan, Xin; Li, Xuan; Wang, Yangyang; Liu, Xuejie; Yu, Changyong; Ren, Yuan

    2017-04-01

    Structures of transition metal nitrides (TMNs) were optimized using the plane-wave pseudopotential method based on density functional theory. Energy as a function of volume curves were calculated to predict the phase transition pressures. Density of states (DOS), charge density difference, and charge transfers were calculated. The elastic constant (C11) and modulus (G) as a function of pressure were computed. Results showed that TMNs in the WC structure was most stable at normal pressure. All TMNs exhibited metallic, covalent and ionic property. Metallic character increased and covalent property reduced with increasing atomic number of TM atom. The elastic constant (C11) and modulus (G) increased linearly with increasing pressure due to stronger hybridization, bonding and covalent property. Thus, mechanical property enhanced under external pressure.

  19. Cyclotron Production of High-Specific Activity 55Co and In Vivo Evaluation of the Stability of 55Co Metal-Chelate-Peptide Complexes.

    Science.gov (United States)

    Mastren, Tara; Marquez, Bernadette V; Sultan, Deborah E; Bollinger, Elizabeth; Eisenbeis, Paul; Voller, Tom; Lapi, Suzanne E

    2015-01-01

    This work describes the production of high-specific activity 55Co and the evaluation of the stability of 55Co-metal-chelate-peptide complexes in vivo. 55Co was produced via the 58Ni(p,α)55Co reaction and purified using anion exchange chromatography with an average recovery of 92% and an average specific activity of 1.96 GBq/μmol. 55Co-DO3A and 55Co-NO2A peptide complexes were radiolabeled at 3.7 MBq/μg and injected into HCT-116 tumor xenografted mice. Positron emission tomography (PET) and biodistribution studies were performed at 24 and 48 hours postinjection and compared to those of 55CoCl2. Both 55Co-metal-chelate complexes demonstrated good in vivo stability by reducing the radiotracers' uptake in the liver by sixfold at 24 hours with ~ 1% ID/g and at 48 hours with ~ 0.5% ID/g and reducing uptake in the heart by fourfold at 24 hours with ~ 0.7% ID/g and sevenfold at 48 hours with ~ 0.35% ID/g. These results support the use of 55Co as a promising new radiotracer for PET imaging of cancer and other diseases.

  20. Evaluation of Stability of Complexes of Inner Transition Metal Ions with 2-Oxo-1-pyrrolidine Acetamide and Role of Systematic Errors

    Directory of Open Access Journals (Sweden)

    Sangita Sharma

    2011-01-01

    Full Text Available BEST FIT models were used to study the complexation of inner transition metal ions like Y(III, La(III, Ce(III, Pr(III, Nd(III, Sm(III, Gd(III, Dy(III and Th(IV with 2-oxo-1-pyrrolidine acetamide at 30 °C in 10%, 20, 30, 40, 50% and 60% v/v dioxane-water mixture at 0.2 M ionic strength. Irving Rossotti titration method was used to get titration data. Calculations were carried out with PKAS and BEST Fortran IV computer programs. The expected species like L, LH+, ML, ML2 and ML(OH3, were obtained with SPEPLOT. Stability of complexes has increased with increasing the dioxane content. The observed change in stability can be explained on the basis of electrostatic effects, non electrostatic effects, solvating power of solvent mixture, interaction between ions and interaction of ions with solvents. Effect of systematic errors like effect of dissolved carbon dioxide, concentration of alkali, concentration of acid, concentration of ligand and concentration of metal have also been explained here.

  1. Two-phase zirconium boride thin film obtained by ultra-short pulsed laser ablation of a ZrB{sub 12} target

    Energy Technology Data Exchange (ETDEWEB)

    De Bonis, A., E-mail: angela.debonis@unibas.it [Dipartimento di Scienze, Università della Basilicata, Viale dell’Ateneo Lucano, 10 -85100 Potenza (Italy); Istituto di Metodologie Inorganiche e dei Plasmi, Consiglio Nazionale delle Ricerche, U.O.S. di Potenza, C.da Santa Loja, 85010 Tito Scalo, Potenza (Italy); Santagata, A. [Istituto di Metodologie Inorganiche e dei Plasmi, Consiglio Nazionale delle Ricerche, U.O.S. di Potenza, C.da Santa Loja, 85010 Tito Scalo, Potenza (Italy); Rau, J.V. [Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, Via del Fosso del Cavaliere 100, 00133 Rome (Italy); Latini, A. [Università di Roma “La Sapienza”, Dipartimento di Chimica, Piazzale Aldo Moro, 5 -00185 Rome (Italy); Mori, T. [National Institute for Materials Science (NIMS) WPI Materials Nanoarchitectonics Center (MANA), Namiki 1-1, Tsukuba 305-0044 (Japan); Medici, L. [Istituto di Metodologie per le Analisi Ambientali, Consiglio Nazionale delle Ricerche, U.O.S. di Potenza, C.da Santa Loja, 85010 Tito Scalo, Potenza (Italy); Teghil, R. [Dipartimento di Scienze, Università della Basilicata, Viale dell’Ateneo Lucano, 10 -85100 Potenza (Italy)

    2013-10-15

    Two-phase zirconium boride thin films have been obtained by ultra-short pulsed laser ablation (PLA) of a zirconium dodecaboride (ZrB{sub 12}) target performed in vacuum. The ablation source was a frequency doubled (λ = 527 nm) Nd:glass laser with a pulse duration of 250 fs. Laser induced plasma has been studied by ICCD imaging and time and space resolved optical emission spectroscopy (OES), whereas the deposited films have been characterized by atomic force microscopy, scanning electron microscopy, X-Ray diffraction and micro-Raman spectroscopy. The film morphology and composition have been interpreted on the basis of the laser ablation mechanism.

  2. IR spectroscopy of cationized aliphatic amino acids: Stability of charge-solvated structure increases with metal cation size

    NARCIS (Netherlands)

    Drayss, M. K.; Armentrout, P. B.; Oomens, J.; Schaefer, M.

    2010-01-01

    Gas-phase structures of alkali metal cationized (Li+, Na+,K+, Rb+, and Cs+) proline (Pro) and N-methyl alanine have been investigated using infrared multiple photon dissociation (IRMPD) spectroscopy utilizing light generated by a free electron laser and computational modeling. Measured IRMPD spectra

  3. IR spectroscopy of cationized aliphatic amino acids: Stability of charge-solvated structure increases with metal cation size

    NARCIS (Netherlands)

    Drayß, M.K.; Armentrout, P.B.; Oomens, J.; Schäfer, M.

    2010-01-01

    Gas-phase structures of alkali metal cationized (Li+, Na+, K+, Rb+, and Cs+) proline (Pro) and N-methyl alanine have been investigated using infrared multiple photon dissociation (IRMPD) spectroscopy utilizing light generated by a free electron laser and computational modeling. Measured IRMPD spectr

  4. Nature of low dimensional structural modulations and relative phase stability in RexMo(W)1-xS2 transition metal dichalcogenide alloys

    KAUST Repository

    Sahu, R.

    2017-03-08

    We report on the various types of Peierls like two dimensional structural modulations and relative phase stability of 2H and 1T poly-types in the RexMo1-xS2 and RexW1-xS2 alloy system. Theoretical calculation predicts a polytype phase transition cross over at ∼50 at. % of Mo and W in ReS2 in both monolayer and bulk form, respectively. Experimentally, two different types of structural modulations at 50% and a modulation corresponding to trimerization at 75% alloy composition are observed for RexMo1-xS2 and only one type of modulation is observed at the 50% RexW1-xS2 alloy system. The 50% alloy system is found to be a suitable monolithic candidate for metal semiconductor transition with minute external perturbation. ReS2 is known to be in the 2D Peierls distorted 1Td structure and forms a chain like superstructure. Incorporation of Mo and W atoms into the ReS2 lattice modifies the metal-metal hybridization between the cations and influences the structural modulation and electronic properties of the system. The results offer yet another effective way to tune the electronic structure and poly-type phases of this class of materials other than intercalation, strain, and vertical stacking arrangement.

  5. A simple sol–gel approach to synthesize nanocrystalline 8 mol% yttria stabilized zirconia from metal-chelate precursors: Microstructural evolution and conductivity studies

    Energy Technology Data Exchange (ETDEWEB)

    Bagchi, Biswajoy; Basu, Rajendra Nath, E-mail: ragenbasu54@gmail.com

    2015-10-25

    A facile non alkoxide based sol–gel technique has been used to synthesize homogeneously distributed nanocrystalline 8 mol% yttria stabilized zirconia (YSZ) powder. The two steps of such powder preparation are gelation and thermal decomposition of metal-chelate complex in aqueous solution. Such nano powder was characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), Field emission scanning electron microscope (FESEM), Fourier transform infra-red spectroscopy (FTIR) and BET surface area analyser. Upon calcinations at 600 °C, well crystallized nano-sized (10–15 nm) YSZ powder is obtained having spherical morphology and reasonably high surface area. The required ionic conductivity (0.107 S/cm) is achieved with 1200 °C sintered samples when measured at 1000 °C in air. - Graphical abstract: A facile non-alkoxide sol–gel route based on metal-EDTA chelate precursor is provided to synthesize dense nanocrystalline YSZ for use as SOFC electrolyte. - Highlights: • Facile one-step non-alkoxide based sol–gel approach. • Nanocrystalline YSZ synthesis from metal-chelate complex. • High ionic conductivity at low sintering temperature.

  6. Morphological transformation of the silicon(112) surface through metal adsorption. Faceting vs. stabilization; Morphologische Transformation der Silizium(112) Oberflaeche durch Metalladsorption. Facettierung vs. Stabilisierung

    Energy Technology Data Exchange (ETDEWEB)

    Wiethoff, Christian

    2010-06-21

    Semiconductor nanowires lately attracted immense attention in worldwide research. Lots of possible applications were discussed and partially realized. Gold is the most commonly used metal in catalyzed nanowire growth, but exhibits poor electronic properties for building integrated circuits. Recently, aluminium was achieved to work as a catalyst and the nanowires grown this way showed extremely smooth surfaces. This is in contrast to surfaces grown with other metals. In this work the modification of the silicon (112) surface by metal adsorption is studied. Since nanowires with [111] growth direction have [112]-like sidewalls, this way a virtually endless nanowire surface is used to study the interaction of gold, silver and aluminium with the silicon surface. Spot Profile Analysis Low Energy Electron Diffraction (SPA-LEED) is used to analyze the surfaces. This high resolution diffraction method allows for detailed characterization of the surface structures and facets. Gold adsorption leads to eight different surface phases, the most stable one exhibits 111- and 113-facets and is shown to occur on nanowire surfaces if they were grown with gold as a catalyst. Silver adsorption pushes the surface to form 111- and 115-facets. The facet size distribution is quite narrow, so the finite size effect creates intensity minima in the vicinity of the bragg points in diffraction patterns. Aluminium adsorption finally leads to a stabilization of the silicon (112) surface, no facets are formed. This atomic flat surface was seen on nanowire sidewalls, grown with aluminium as catalyst. (orig.)

  7. Structural criteria for the rational design of selective ligands. 2. Effect of alkyl substitution on metal ion complex stability with ligands bearing ethylene-bridged ether donors

    Energy Technology Data Exchange (ETDEWEB)

    Hay, B.P.; Zhang, D.; Rustad, J.R. [Pacific Northwest National Laboratory, Richland, WA (United States)

    1996-04-24

    A novel approach is presented for the application and interpretation of molecular methanics calculations in ligand structural design. The methodology yields strain energies that (i) provide a yardstick for the measurements of ligand binding site organization for metal ion complexation and (ii) allow the comparison of any two ligands independent of either the number and type of donor atoms or the identity of the metal ion. Application of this methodology is demonstrated in a detailed examination of the influence of alkyl substitution on the structural organization of ethylene-bridged, bidentate, ether donor ligands for the alkali and alkaline earth cations. Nine cases are examined, including the unsubstituted ethylene bridge (dimethoxyethane), all possible arrangements of individual alkyl groups (monoalkylation, gem-dialkylation, meso-dialkylation, d,l-dialkylation, trialkylation, and tetraalkylation), and both cis and trans attachments of the cyclohexyl group. The calculated degree of binding site organization for metal ion complexation afforded by these connecting structures is shown to correlate with known changes in complex stability caused by alkyl substitution of crown ether macrocycles.

  8. Triphenylamine-Based Metal-Organic Frameworks as Cathode Materials in Lithium-Ion Batteries with Coexistence of Redox Active Sites, High Working Voltage, and High Rate Stability.

    Science.gov (United States)

    Peng, Zhe; Yi, Xiaohui; Liu, Zixuan; Shang, Jie; Wang, Deyu

    2016-06-15

    Through rational organization of two redox active building block, a triphenylamine-based metal-organic framework (MOF) material, Cu-TCA (H3TCA = tricarboxytriphenyl amine), was synthesized and applied as a cathode active material for the first time in lithium batteries. Cu-TCA exhibited redox activity both in the metal clusters (Cu(+)/Cu(2+)) and organic ligand radicals (N/N(+)) with separated voltage plateaus and a high working potential vs Li/Li(+) up to 4.3 V, comparing with the current commercial LiCoO2 cathode materials. The electrochemical behaviors of this MOF electrode material at different states of charge were carefully studied by cyclic voltammetry, X-ray photoelectron spectroscopy, and photoluminescence techniques. Long cycling stability of this MOF was achieved with an average Coulombic efficiency of 96.5% for 200 cycles at a 2 C rate. Discussing the electrochemical performances on the basis of capacity contributions from the metal clusters (Cu(+)/Cu(2+)) and organic ligands (N/N(+)) proposes an alternative mechanism of capacity loss for the MOF materials used in lithium batteries. This improved understanding will shed light on the designing principle of MOF-based cathode materials for their practical application in battery sciences.

  9. Thermal stability and hcp-fcc allotropic transformation in supported Co metal catalysts probed near operando by ferromagnetic NMR.

    Science.gov (United States)

    Andreev, Andrey S; d'Espinose de Lacaillerie, Jean-Baptiste; Lapina, Olga B; Gerashenko, Alexander

    2015-06-14

    Despite the fact that cobalt based catalysts are used at the industrial scale for Fischer-Tropsch synthesis, it is not yet clear which cobalt metallic phase is actually at work under operando conditions and what is its state of dispersion. As it turns out, the different phases of metallic cobalt, fcc and hcp, give rise to distinct ferromagnetic nuclear magnetic resonance. Furthermore, within one Co metal particle, the occurrence of several ferromagnetic domains of limited sizes can be evidenced by the specific resonance of Co in multi-domain particles. Consequently, by ferromagnetic NMR, one can follow quantitatively the sintering and phase transitions of dispersed Co metal particles in supported catalysts under near operando conditions. The minimal size probed by ferromagnetic Co NMR is not precisely known but is considered to be in the order of 10 nm for supported Co particles at room temperature and increases to about 35 nm at 850 K. Here, in Co metal Fischer-Tropsch synthesis catalysts supported on β-SiC, the resonances of the fcc multi-domain, fcc single-domain and hcp Co were clearly distinguished. A careful rationalization of their frequency and width dependence on temperature allowed a quantitative analysis of the spectra in the temperature range of interest, thus reflecting the state of the catalysts under near operando conditions that is without the uncertainty associated with prior quenching. The allotropic transition temperature was found to start at 600-650 K, which is about 50 K below the bulk transition temperature. The phase transition was fully reversible and a significant part of the hcp phase was found to be stable up to 850 K. This anomalous behavior that was observed without quenching might prove to be crucial to understand and model active species not only in catalysts but also in battery materials.

  10. Hydromagnetic Stability of Metallic Nanofluids (Cu-Water and Ag-Water Using Darcy-Brinkman Model

    Directory of Open Access Journals (Sweden)

    J. Ahuja

    2016-01-01

    Full Text Available Thermal convection of a nanofluid layer in the presence of imposed vertical magnetic field saturated by a porous medium is investigated for both-free, rigid-free, and both-rigid boundaries using Darcy-Brinkman model. The effects of Brownian motion and thermophoretic forces due to the presence of nanoparticles and Lorentz’s force term due to the presence of magnetic field have been considered in the momentum equations along with Maxwell’s equations. Keeping in mind applications of flow through porous medium in geophysics, especially in the study of Earth’s core, and the presence of nanoparticles therein, the hydromagnetic stability of a nanofluid layer in porous medium is considered in the present formulation. An analytical investigation is made by applying normal mode technique and Galerkin type weighted residuals method and the stability of Cu-water and Ag-water nanofluids is compared. Mode of heat transfer is through stationary convection without the occurrence of oscillatory motions. Stability of the system gets improved appreciably by raising the Chandrasekhar number as well as Darcy number whereas increase in porosity hastens the onset of instability. Further, stability of the system gets enhanced as we proceed from both-free boundaries to rigid-free and to both-rigid boundaries.

  11. Thermal stability and magnetic properties of Fe–Co–M–Zr–Nb–Ge–B (M=Mo, Cr bulk metallic glasses

    Directory of Open Access Journals (Sweden)

    Min Xu

    2014-04-01

    Full Text Available Fe62Co8−xMxZr6Nb4Ge1B19 (M=Mo, Cr bulk metallic glasses were synthesized in the diameter range up to 2 mm by copper mold casting, which exhibit high thermal stability and large glass-forming ability. The super-cooled liquid region diminishes by the dissolution of Mo. The addition of 2 at% Cr leads to the broading of the liquid region remarkably, resulting in the improvement of thermal stability. The crystallization takes place through a single exothermic reaction, accompanying the precipitation of more than three kinds of crystallized phases such as α-Fe, Fe2Zr and ZrB2. The Fe-based alloys show soft ferromagnetic properties. The saturation magnetization (σs decreases with increasing Mo or Cr content while the saturated magnetostriction increases with raising Mo or Cr content. There is no evident change in the σs and coercive force (Hc with annealing temperature below the crystallization temperature, which suggests a more relaxed atomic configuration the glasses have. The crystallization causes a substantial enhancement in both σs and Hc. Each soft magnetic property of the glasses containing Cr with higher thermal stability is superior to that of the alloys containing Mo.

  12. Thermal stability and magnetic properties of Fe-Co-M-Zr-Nb-Ge-B (M ¼ Mo, Cr) bulk metallic glasses

    Institute of Scientific and Technical Information of China (English)

    Min Xu; Qunjiao Wang

    2014-01-01

    Fe62Co8-xMxZr6Nb4Ge1B19 (M=Mo, Cr) bulk metallic glasses were synthesized in the diameter range up to 2 mm by copper mold casting, which exhibit high thermal stability and large glass-forming ability. The super-cooled liquid region diminishes by the dissolution of Mo. The addition of 2 at%Cr leads to the broading of the liquid region remarkably, resulting in the improvement of thermal stability. The crystallization takes place through a single exothermic reaction, accompanying the precipitation of more than three kinds of crystallized phases such asα-Fe, Fe2Zr and ZrB2. The Fe-based alloys show soft ferromagnetic properties. The saturation magnetization (ss) decreases with increasing Mo or Cr content while the saturated magnetostriction increases with raising Mo or Cr content. There is no evident change in the ss and coercive force (Hc) with annealing temperature below the crystallization temperature, which suggests a more relaxed atomic configuration the glasses have. The crystallization causes a substantial enhancement in both ss and Hc. Each soft magnetic property of the glasses containing Cr with higher thermal stability is superior to that of the alloys containing Mo.

  13. Molar absorption coefficients and stability constants of metal complexes of 4-(2-pyridylazo)resorcinol (PAR): Revisiting common chelating probe for the study of metalloproteins.

    Science.gov (United States)

    Kocyła, Anna; Pomorski, Adam; Krężel, Artur

    2015-11-01

    4-(2-Pyridylazo)resorcinol (PAR) is one of the most popular chromogenic chelator used in the determination of the concentrations of various metal ions from the d, p and f blocks and their affinities for metal ion-binding biomolecules. The most important characteristics of such a sensor are the molar absorption coefficient and the metal-ligand complex dissociation constant. However, it must be remembered that these values are dependent on the specific experimental conditions (e.g. pH, solvent components, and reactant ratios). If one uses these values to process data obtained in different conditions, the final result can be under- or overestimated. We aimed to establish the spectral properties and the stability of PAR and its complexes accurately with Zn(2+), Cd(2+), Hg(2+), Co(2+), Ni(2+), Cu(2+), Mn(2+) and Pb(2+) at a multiple pH values. The obtained results account for the presence of different species of metal-PAR complexes in the physiological pH range of 5 to 8 and have been frequently neglected in previous studies. The effective molar absorption coefficient at 492 nm for the ZnHx(PAR)2 complex at pH7.4 in buffered water solution is 71,500 M(-1) cm(-1), and the dissociation constant of the complex in these conditions is 7.08×10(-13) M(2). To confirm these values and estimate the range of the dissociation constants of zinc-binding biomolecules that can be measured using PAR, we performed several titrations of zinc finger peptides and zinc chelators. Taken together, our results provide the updated parameters that are applicable to any experiment conducted using inexpensive and commercially available PAR.

  14. Constraints on phase stability, defect energies, and elastic constants of metals described by EAM-type potentials

    Science.gov (United States)

    Sukhomlinov, Sergey V.; Müser, Martin H.

    2016-10-01

    We demonstrate that the embedded-atom method and related potentials predict many dimensionless properties of simple metals to depend predominantly on a single coefficient μ, which typically lies between 0.3 and 0.45. Among other relations presented in this work, we find that {{E}\\text{c}}\\propto {{Z}μ} , {{E}\\text{v}}/{{E}\\text{c}}=μ , and G/B\\propto μ hold within 25% accuracy and also find a linear dependence of the melting temperature on μ. The used variables are cohesive energy E c, coordination number Z, vacancy energy E v, and bulk modulus B, while G is the average of ordinary and tetragonal shear modulus. We provide analytical arguments for these findings, which are obeyed reasonably well by several metals.

  15. Improved stability of a metallic state in benzothienobenzothiophene-based molecular conductors: an effective increase of dimensionality with hydrogen bonds.

    Science.gov (United States)

    Higashino, Toshiki; Ueda, Akira; Yoshida, Junya; Mori, Hatsumi

    2017-02-27

    A dihydroxy-substituted benzothienobenzothiophene, BTBT(OH)2, was synthesized, and its charge-transfer (CT) salt, β-[BTBT(OH)2]2ClO4, was successfully obtained. Thanks to the introduced hydroxy groups, a hydrogen-bonded chain structure connecting the BTBT molecules and counter anions was formed in the CT salt, which effectively increases the dimensionality of the electronic structure and consequently leads to a stable metallic state.

  16. Density functional theory screening of gas-treatment strategies for stabilization of high energy-density lithium metal anodes

    Science.gov (United States)

    Koch, Stephan L.; Morgan, Benjamin J.; Passerini, Stefano; Teobaldi, Gilberto

    2015-11-01

    To explore the potential of molecular gas treatment of freshly cut lithium foils in non-electrolyte-based passivation of high-energy-density Li anodes, density functional theory (DFT) has been used to study the decomposition of molecular gases on metallic lithium surfaces. By combining DFT geometry optimization and Molecular Dynamics, the effects of atmospheric (N2, O2, CO2) and hazardous (F2, SO2) gas decomposition on Li(bcc) (100), (110), and (111) surfaces on relative surface energies, work functions, and emerging electronic and elastic properties are investigated. The simulations suggest that exposure to different molecular gases can be used to induce and control reconstructions of the metal Li surface and substantial changes (up to over 1 eV) in the work function of the passivated system. Contrary to the other considered gases, which form metallic adlayers, SO2 treatment emerges as the most effective in creating an insulating passivation layer for dosages ≤1 mono-layer. The substantial Li → adsorbate charge transfer and adlayer relaxation produce marked elastic stiffening of the interface, with the smallest change shown by nitrogen-treated adlayers.

  17. First-principles and Monte Carlo studies on the magnetic stability of half-metallic zinc-blende CaC and similar compounds

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Shengjie [Department of Physics, Tianjin Normal University, Tianjin 300387 (China); Ding, Hang-Chen [Key Laboratory of Polar Materials and Devices, East China Normal University, Shanghai 200062 (China); Zhou, Baozeng [Department of Applied Physics, Faculty of Science, Tianjin University, Tianjin 300072 (China); Duan, Chun-Gang [Key Laboratory of Polar Materials and Devices, East China Normal University, Shanghai 200062 (China); National Laboratory for Infrared Physics, Chinese Academy of Sciences, Shanghai 200083 (China); Wu, Ping [Department of Applied Physics, Faculty of Science, Tianjin University, Tianjin 300072 (China); Zhao, Hui, E-mail: naihuizhao@gmail.com [Department of Physics, Tianjin Normal University, Tianjin 300387 (China)

    2015-03-15

    Using the first-principles calculation based on density functional theory and Monte Carlo simulation within the Heisenberg Hamiltonian, we have investigated the magnetic stability at finite pressure and temperature of CaC and some other selected hypothetical II{sup A}–IV{sup A} compounds with the zinc-blende crystal structure. The results from simulated external pressure and temperature test indicate that the magnetic stability is dependent on the variation in atomic number of anion or cation element. Additionally, the origin of sp magnetism is mentioned briefly in this work and the dependence of Curie temperature on the volume is also discussed. First-principles computational charge-injection test show that the magnetization of these sp compounds originates in the spin polarization of the p shell of anions. For CaC, the exchange parameter J{sub 1} of the Heisenberg Hamiltonian depends strongly on the lattice constant, while the J{sub 2} and J{sub 3} are weakly dependent on the lattice constant. Moreover, discussion of volume-conserving deformations for CaC further demonstrates the stability of ferromagnetism and half metallicity for the compounds. - Highlights: • CaC and some other compounds with the zinc-blende crystal structure. • The first-principles calculation and Monte Carlo simulation within the Heisenberg Hamiltonian. • The magnetic stability is dependent on the variation in atomic number of anion or cation element. • The magnetic properties depend on the deformation of the lattice. • The normalized magnetic moment and specific heat capacity as a function of temperature.

  18. Strategies to curb structural changes of lithium/transition metal oxide cathode materials & the changes’ effects on thermal & cycling stability

    Science.gov (United States)

    Xiqian, Yu; Enyuan, Hu; Seongmin, Bak; Yong-Ning, Zhou; Xiao-Qing, Yang

    2016-01-01

    Structural transformation behaviors of several typical oxide cathode materials during a heating process are reviewed in detail to provide in-depth understanding of the key factors governing the thermal stability of these materials. We also discuss applying the information about heat induced structural evolution in the study of electrochemically induced structural changes. All these discussions are expected to provide valuable insights for designing oxide cathode materials with significantly improved structural stability for safe, long-life lithium ion batteries, as the safety of lithium-ion batteries is a critical issue; it is widely accepted that the thermal instability of the cathodes is one of the most critical factors in thermal runaway and related safety problems. Project supported by the U.S. Department of Energy, the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies (Grant No. DE-SC0012704).

  19. Effects of (Cr,Fe){sub 2}B borides on hardness in powder-injection-molded product fabricated with Fe-based alloy powders

    Energy Technology Data Exchange (ETDEWEB)

    Do, Jeonghyeon; Jeon, Changwoo; Paul Kim, Choongnyun; Lee, Byeong-Joo [Center for Advanced Aerospace Material, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Lee, Sunghak, E-mail: shlee@postech.ac.kr [Center for Advanced Aerospace Material, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Lee, Eon-Sik [Advanced Metallic Materials Research Department, Research Institute of Industrial Science and Technology, Pohang 790-330 (Korea, Republic of); Shik Yoon, Tae [Bestner Co., 146-8 Sangdaewon-dong, Sungnam 462-121 (Korea, Republic of); Su Shin, Yang [New Growth Technology Strategy Department, POSCO, Seoul 135-777 (Korea, Republic of)

    2012-10-30

    In the present study, a powder injection molding (PIM) product containing (Cr,Fe){sub 2}B borides was fabricated with Fe-based alloy powders, and its microstructure and hardness were investigated in relation with volume fraction of (Cr,Fe){sub 2}B. In the Fe-based alloys designed by the thermodynamic calculation, the volume fractions of (Cr,Fe){sub 2}B increased with increasing (X{sub Cr}+X{sub B}) value, and were well matched with those obtained from the thermodynamic calculation. The hardness of the Fe-based alloys linearly increased with increasing volume fraction of (Cr,Fe){sub 2}B. When Fe-based alloy powders were injection-molded and sintered at 1165 Degree-Sign C, a densified microstructure with almost no pores was obtained. In the sintered microstructure, 56 vol% of (Cr,Fe){sub 2}B borides, together with a few pores (porosity; 0.5%), were relatively homogeneously distributed in the tempered martensite matrix, which resulted in the very high hardness over 600 VHN. Such a high hardness suggested that the present Fe-based alloy powders could be readily adopted for fabricating PIM products or for replacing conventional stainless steel PIM products.

  20. Plutonium inventories for stabilization and stabilized materials

    Energy Technology Data Exchange (ETDEWEB)

    Williams, A.K.

    1996-05-01

    The objective of the breakout session was to identify characteristics of materials containing plutonium, the need to stabilize these materials for storage, and plans to accomplish the stabilization activities. All current stabilization activities are driven by the Defense Nuclear Facilities Safety Board Recommendation 94-1 (May 26, 1994) and by the recently completed Plutonium ES&H Vulnerability Assessment (DOE-EH-0415). The Implementation Plan for accomplishing stabilization of plutonium-bearing residues in response to the Recommendation and the Assessment was published by DOE on February 28, 1995. This Implementation Plan (IP) commits to stabilizing problem materials within 3 years, and stabilizing all other materials within 8 years. The IP identifies approximately 20 metric tons of plutonium requiring stabilization and/or repackaging. A further breakdown shows this material to consist of 8.5 metric tons of plutonium metal and alloys, 5.5 metric tons of plutonium as oxide, and 6 metric tons of plutonium as residues. Stabilization of the metal and oxide categories containing greater than 50 weight percent plutonium is covered by DOE Standard {open_quotes}Criteria for Safe Storage of Plutonium Metals and Oxides{close_quotes} December, 1994 (DOE-STD-3013-94). This standard establishes criteria for safe storage of stabilized plutonium metals and oxides for up to 50 years. Each of the DOE sites and contractors with large plutonium inventories has either started or is preparing to start stabilization activities to meet these criteria.

  1. Improving Hardness and Toughness of Boride Composites Based on AIMgB14

    Energy Technology Data Exchange (ETDEWEB)

    Peters, Justin Steven [Iowa State Univ., Ames, IA (United States)

    2007-01-01

    The search for new super-hard materials has usually focused on strongly bonded, highly symmetric crystal structures similar to diamond. The two hardest single-phase materials, diamond and cubic boron nitride (cBN), are metastable, and both must be produced at high temperatures and pressures, which makes their production costly. In 2000, a superhard composite based on a low-symmetry, boron-rich compound was reported. Since then, many advances have been made in the study of this AlMgB14-TiB2 composite. The composite has been shown to exhibit hardness greater than either of its constituent phases, relying on its sub-micron microstructure to provide hardening and strengthening mechanisms. With possible hardness around 40 GPa, an AlMgB14 - 60 vol% TiB2 approaches the hardness of cBN, yet is amenable to processing under ambient pressure conditions. There are interesting aspects of both the AlMgB14 and TiB2 phases. AlMgB14 is comprised of a framework of boron, mostly in icosahedral arrangements. It is part of a family of 12 known compounds with the same boron lattice, with the metal atoms replaced by Li, Na, Y or a number of Lanthanides. Another peculiar trait of this family of compounds is that every one contains a certain amount of intrinsic vacancies on one or both of the metal sites. These vacancies are significant, ranging from 3 to 43% of sites depending on the composition. TiB2 is a popular specialty ceramic material due to its high hardness, moderate toughness, good corrosion resistance, and high thermal and electrical conductivity. The major drawback is the difficulty of densification of pure TiB2 ceramics. A combination of sintering aids, pressure, and temperatures of 1800 C are often required to achieve near full density articles. The AlMgB14 - TiB2 composites can achieve 99% density from hot-pressing at 1400 C. This is mostly due to the

  2. Effect of Hafnium and Zirconium to Glass Forming Ability, Thermal Stability, Plasticity Deformation and Crystallization of Ni-Free Pentabasic Ti-Based Bulk Metallic Glasses

    Directory of Open Access Journals (Sweden)

    Oak J.J.

    2017-06-01

    Full Text Available The newly designed Ti-based bulk metallic glass (BMG in which case of fracture behavior was observed 1990MPa to compressive strength with a wide plastic deformation around 7% after process of elastic deformation. This phenomenon can be compared with those of Ti-based alloys and other Ti-based BMGs and indicates high potential to be applied in use. It was evaluated the Ti-based BMG for thermal stability that the reduced glass parameters, ΔTx, Trg and γ, are 79K, 0.50 and 0.38, respectively. In addition, it reveals high activation energies for crystallization in which are estimated to Ex1 = 291.77 ±9.71 kJ/mol, Ex2 = 588.77 ±28.88 kJ/mol and Ex3 = 330.26 ±3.61 kJ/mol on kissinger plotting in this study.

  3. Structural stability, electronic structure and magnetic properties of the new hypothetical half-metallic ferromagnetic full-Heusler alloy CoNiMnSi

    Directory of Open Access Journals (Sweden)

    Elahmar M.H.

    2016-03-01

    Full Text Available We investigated the structural stability as well as the mechanical, electronic and magnetic properties of the Full-Heusler alloy CoNiMnSi using the full-potential linearized augmented plane wave (FP-LAPW method. Two generalized gradient approximations (GGA and GGA + U were used to treat the exchange-correlation energy functional. The ground state properties of CoNiMnSi including the lattice parameter and bulk modulus were calculated. The elastic constants (Cij and their related elastic moduli as well as the thermodynamic properties for CoNiMnSi have been calculated for the first time. The existence of half-metallic ferromagnetism (HM-FM in this material is apparent from its band structure. Our results classify CoNiMnSi as a new HM-FM material with high spin polarization suitable for spintronic applications.

  4. All Metal Organic Deposited High-Tc Superconducting Transition Edge Bolometer on Yttria-Stabilized Zirconia Substrate

    DEFF Research Database (Denmark)

    Mohajeri, Roya; Opata, Yuri Aparecido; Wulff, Anders Christian;

    2016-01-01

    We report on the results of a YBa2Cu3O7−x (YBCO) superconductive transition edge bolometer (TEB) fabricated on a Ce0.9La0.1O2−7 (CLO) buffered single crystalline yttria-stabilized zirconia (YSZ) substrate. Metal organic deposition was used for the fabrication of both the YBCO thin film as well...... as CLO buffer layer, while standard photolithography was applied for TEB preparation. YBCO thin film properties were analysed using scanning electron microscopy (SEM), X-ray diffraction (XRD), AC susceptibility and resistance versus temperature measurements. Optical response of the TEB in terms...... of voltage amplitude and phase was analysed and measured through four-probe technique in a liquid nitrogen cooling system. An increase in voltage amplitude response was observed for the fabricated YBCO/CLO/YSZ bolometer compared to previously reported TEBs with similarly deposited YBCO thin film on a SrTiO3...

  5. Unusual Transformation from a Solvent-Stabilized 1D Coordination Polymer to a Metal-Organic Framework (MOF)-Like Cross-Linked 3D Coordination Polymer.

    Science.gov (United States)

    Lee, Seung-Chul; Choi, Eun-Young; Lee, Sang-Beom; Kim, Sang-Wook; Kwon, O-Pil

    2015-10-26

    An unusual 1D-to-3D transformation of a coordination polymer based on organic linkers containing highly polar push-pull π-conjugated side chains is reported. The coordination polymers are synthesized from zinc nitrate and an organic linker, namely, 2,5-bis{4-[1-(4-nitrophenyl)pyrrolidin-2-yl]butoxy}terephthalic acid, which possesses highly polar (4-nitrophenyl)pyrrolidine groups, with high dipole moments of about 7 D. The coordination polymers exhibit an unusual transformation from a soluble, solvent-stabilized 1D coordination polymer into an insoluble, metal-organic framework (MOF)-like 3D coordination polymer. The coordination polymer exhibits good film-forming ability, and the MOF-like films are insoluble in conventional organic solvents.

  6. High thermal stability of the amorphous oxide in Ti44.5Cu44.5Zr7Be4 metallic glass

    Directory of Open Access Journals (Sweden)

    Sung Hyun Park

    2015-11-01

    Full Text Available The oxidation behavior of Ti44.5Cu44.5Zr7Be4 metallic glass has been investigated. The oxide layer with a fully amorphous structure forms when heated up to the SCL temperature region, indicating that the presence of Be in the oxide layer improves the thermal stability of the amorphous oxide. The amorphous oxide is stable even when heated above the crystallization onset temperature. The thickness of the amorphous oxide layer reaches to ∼160 nm when heated up to 773 K. The oxide layer grows in both inward and outward directions, leaving Cu-enriched crystalline particles at the middle section of the oxide layer.

  7. The Effect of Iron Content on Glass Forming Ability and Thermal Stability of Co–Fe–Ni–Ta–Nb–B–Si Bulk Metallic Glass

    Directory of Open Access Journals (Sweden)

    Aytekin Hitit

    2016-12-01

    Full Text Available In this study, change in glass forming ability (GFA and thermal stability of Co–Fe-based bulk metallic glasses were investigated as a function of iron content. Cylindrical samples of alloys with diameters of up to 4 mm were synthesized by a suction casting method in an arc furnace. Structures and thermal properties of the as-cast samples were determined by X-ray diffraction (XRD and differential scanning calorimetry (DSC, respectively. It was found that the critical casting thickness of the alloys reduced as iron content was increased and cobalt content was decreased. It was determined that GFA parameters, reduced glass transition temperature (Tg/Tl and δ (= Tx/(Tl − Tg, show a very good correlation with critical casting thickness values. It was also observed that changing iron content did not effect thermal properties of the alloys.

  8. Cation and anion dependence of stable geometries and stabilization energies of alkali metal cation complexes with FSA(-), FTA(-), and TFSA(-) anions: relationship with physicochemical properties of molten salts.

    Science.gov (United States)

    Tsuzuki, Seiji; Kubota, Keigo; Matsumoto, Hajime

    2013-12-19

    Stable geometries and stabilization energies (Eform) of the alkali metal complexes with bis(fluorosulfonyl)amide, (fluorosulfonyl)(trifluoromethylslufonyl)amide and bis(trifluoromethylsulfonyl)amide (FSA(-), FTA(-) and TFSA(-)) were studied by ab initio molecular orbital calculations. The FSA(-) complexes prefer the bidentate structures in which two oxygen atoms of two SO2 groups have contact with the metal cation. The FTA(-) and TFSA(-) complexes with Li(+) and Na(+) prefer the bidentate structures, while the FTA(-) and TFSA(-) complexes with Cs(+) prefer tridentate structures in which the metal cation has contact with two oxygen atoms of an SO2 group and one oxygen atom of another SO2 group. The two structures are nearly isoenergetic in the FTA(-) and TFSA(-) complexes with K(+) and Rb(+). The magnitude of Eform depends on the alkali metal cation significantly. The Eform calculated for the most stable TFSA(-) complexes with Li(+), Na(+), K(+), Rb(+) and Cs(+) cations at the MP2/6-311G** level are -137.2, -110.5, -101.1, -89.6, and -84.1 kcal/mol, respectively. The viscosity and ionic conductivity of the alkali TFSA molten salts have strong correlation with the magnitude of the attraction. The viscosity increases and the ionic conductivity decreases with the increase of the attraction. The melting points of the alkali TFSA and alkali BETA molten salts also have correlation with the magnitude of the Eform, which strongly suggests that the magnitude of the attraction play important roles in determining the melting points of these molten salts. The anion dependence of the Eform calculated for the complexes is small (less than 2.9 kcal/mol). This shows that the magnitude of the attraction is not the cause of the low melting points of alkali FTA molten salts compared with those of corresponding alkali TFSA molten salts. The electrostatic interactions are the major source of the attraction in the complexes. The electrostatic energies for the most stable TFSA

  9. Thermal stability of the anionic sigma complexes of 2,4,6-trinitroanisole with the methylates of the alkaline-earth metals

    Energy Technology Data Exchange (ETDEWEB)

    Glaz, A.I.; Soldatova, T.A.; Golopolosova, T.V.; Gitis, S.S.

    1987-09-10

    The study of the stability of the 1,1-dimethoxy-2,4,6-trinitrocyclohexadienates of the alkali metals when they are heated in air showed that their temperature of decomposition and the heat effect of the process are dependent on the nature of the cation. Our study centered on the thermal decomposition of the products resulting from the addition of the methylates of calcium, strontium, and barium to 2,4,6-trinitroanisole. For a quantitative assessment of the process we used the combined methods of differential-thermal analysis and differential thermogravimetry. The anionic sigma-complexes of 2,4,6-trinitroanisole with the methylates of the alkaline-earth metals decompose on heating into the corresponding picrates; at the same time, when one passes from the calcium slat to the strontium and barium salts the decomposition temperature and the heat effect of the process show a drop which is linked to the structure both of the complexes and of the picrates forming therefrom.

  10. High-temperature catalytic reforming of n-hexane over supported and core-shell Pt nanoparticle catalysts: role of oxide-metal interface and thermal stability.

    Science.gov (United States)

    An, Kwangjin; Zhang, Qiao; Alayoglu, Selim; Musselwhite, Nathan; Shin, Jae-Youn; Somorjai, Gabor A

    2014-08-13

    Designing catalysts with high thermal stability and resistance to deactivation while simultaneously maintaining their catalytic activity and selectivity is of key importance in high-temperature reforming reactions. We prepared Pt nanoparticle catalysts supported on either mesoporous SiO2 or TiO2. Sandwich-type Pt core@shell catalysts (SiO2@Pt@SiO2 and SiO2@Pt@TiO2) were also synthesized from Pt nanoparticles deposited on SiO2 spheres, which were encapsulated by either mesoporous SiO2 or TiO2 shells. n-Hexane reforming was carried out over these four catalysts at 240-500 °C with a hexane/H2 ratio of 1:5 to investigate thermal stability and the role of the support. For the production of high-octane gasoline, branched C6 isomers are more highly desired than other cyclic, aromatic, and cracking products. Over Pt/TiO2 catalyst, production of 2-methylpentane and 3-methylpentane via isomerization was increased selectively up to 420 °C by charge transfer at Pt-TiO2 interfaces, as compared to Pt/SiO2. When thermal stability was compared between supported catalysts and sandwich-type core@shell catalysts, the Pt/SiO2 catalyst suffered sintering above 400 °C, whereas the SiO2@Pt@SiO2 catalyst preserved the Pt nanoparticle size and shape up to 500 °C. The SiO2@Pt@TiO2 catalyst led to Pt nanoparticle sintering due to incomplete protection of the TiO2 shells during the reaction at 500 °C. Interestingly, over the Pt/TiO2 catalyst, the average size of Pt nanoparticles was maintained even after 500 °C without sintering. In situ ambient pressure X-ray photoelectron spectroscopy demonstrated that the Pt/TiO2 catalyst did not exhibit TiO2 overgrowth on the Pt surface or deactivation by Pt sintering up to 600 °C. The extraordinarily high stability of the Pt/TiO2 catalyst promoted high reaction rates (2.0 μmol · g(-1) · s(-1)), which was 8 times greater than other catalysts and high isomer selectivity (53.0% of C6 isomers at 440 °C). By the strong metal-support interaction

  11. The biocompatibility of metal-organic framework coatings: an investigation on the stability of SURMOFs with regard to water and selected cell culture media.

    Science.gov (United States)

    Hanke, Maximilian; Arslan, Hasan K; Bauer, Stella; Zybaylo, Olexandra; Christophis, Christof; Gliemann, Hartmut; Rosenhahn, Axel; Wöll, Christof

    2012-05-01

    Highly porous thin films based on a [Cu(bdc)(2)](n) (bdc = benzene-1,4-dicarboxylic acid) metal-organic framework, MOF, grown using liquid-phase epitaxy (LPE) show remarkable stability in pure water as well as in artificial seawater. This opens the possibility to use these highly porous coatings for environmental and life science applications. Here we characterize in detail the stability of these SURMOF 2 thin films under aqueous and cell culture conditions. We find that the material degrades only very slowly in water and artificial seawater (ASW) whereas in typical cell culture media (PBS and DMEM) a rapid dissolution is observed. The release of Cu(2+) ions resulting from the dissolution of the SURMOF 2 in the liquids exhibits no adverse effect on the adhesion of fibroblasts, prototype eukaryotic cells, to the substrate and their subsequent proliferation, thus demonstrating the biocompatibility of SURMOF 2 surface coatings. Thus, the results are an important step toward application of these porous materials as a slow release matrix, for example, for pharmaceuticals and growth factors.

  12. NON-EQUILIBRIUM STATIONARY STATE IN CHEMICAL REACTION OF SiO2/Fe AT INTERFACE OF SLAG/METAL AND ITS STABILITY DURING ARC WELDING

    Institute of Scientific and Technical Information of China (English)

    LI Xiaoquan; DU Zeyu; YANG Xuguang

    2007-01-01

    For characteristics of open and far from thermodynamic equilibrium in welding chemical reaction, a new kind of quantitative method, which is used to analyze direction and extent for chemical reaction of SiO2/Fe during quasi-steady state period, is introduced with the concept of non-equilibrium stationary state. The main idea is based on thermodynamic driving forces, which result in non-zero thermodynamic fluxes and lead to chemical reaction far away from thermodynamic equilibrium. There exists certain dynamic equilibrium relationship between rates of diffusion fluxes in liquid phase of reactants or products and the rate equation of chemical reaction when welding is in quasi-steady state. As result of this, a group of non-linear equations containing concentrations of all substances at interface of slag/liquid-metal may be established. Moreover the stability of this non-equilibrium stationary state is discussed using dissipative structure theory and it is concluded theoretically that this non-equilibrium stationary state for welding chemical reaction is of stability.

  13. An insight into the effects of B-site transition metals on the activity, activation effect and stability of perovskite oxygen electrodes for solid oxide electrolysis cells

    Science.gov (United States)

    Bi, Jiaxin; Yang, Shengbing; Zhong, Shaohua; Wang, Jian-Qiang; Fan, Chou; Chen, Xinbing; Liu, Yihui

    2017-09-01

    Here, effects of B-site transition metals (TMs) in the (La0.6Sr0.4)XO3-δ (X = Mn, Fe, Co) perovskite structure on the activity and stability of the oxygen electrodes during high temperature electrolysis are discussed to provide a deep understanding of the phenomena observed for different oxygen electrodes under anodic polarizations. Performance and stability of the electrodes vary significantly at 800 °C as the TMs changed from Mn to Fe and Co, which is attributed to the different ionic conductivities and surface chemistry of the materials that have a strong dependence on the valence state and electronic structure of TMs. Under an anodic current passage of 200 mA cm-2 at 800 °C, electrode polarization resistance (RE) and overpotential (η) of the (La0.6Sr0.4)MnO3-δ (LSM) electrode decrease significantly by 1.75 Ω cm2 and 101 mV during the 1200 min test, compared with the constant values of RE and η for the (La0.6Sr0.4)FeO3-δ (LSF) and (La0.6Sr0.4)CoO3-δ (LSC) electrodes, an indication of the influence of B-site TMs on the electrode performance and stability. Most serious degradation is observed at the (La0.6Sr0.4)MnO3-δ electrode due to the electrode detachment arising from the accelerated SrO surface segregation and related disintegration of LSM particles near the electrode/electrolyte interface.

  14. Understanding the mechanisms leading to failure in metallic nanowire-based transparent heaters, and solution for stability enhancement.

    Science.gov (United States)

    Lagrange, M; Sannicolo, T; Muñoz-Rojas, D; Lohan, B Guillo; Khan, A; Anikin, M; Jiménez, C; Bruckert, F; Bréchet, Y; Bellet, D

    2017-02-03

    Silver nanowire (AgNW) networks are emerging as one of the most promising alternatives to indium tin oxide (ITO) for transparent electrodes in flexible electronic devices. They can be used in a variety of optoelectronic applications such as solar cells, touch panels and organic light-emitting diodes. Recently they have also proven to be very efficient when used as transparent heaters (THs). In addition to the study of AgNW networks acting as THs in regular use, i.e. at low voltage and moderate temperature, their stability and physical behavior at higher voltages and for longer durations should be studied in view of their integration into real devices. The properties of AgNW networks deposited by spray coating on glass or flexible transparent substrates are thoroughly studied via in situ measurements. The AgNW networks' behavior at different voltages for different durations and under different atmospheric conditions, both in air and under vacuum, has been examined. At low voltage, a reversible electrical response is observed while irreversibility and even failure are observed at higher voltages. In order to gain a deeper insight into the behavior of AgNW networks used as THs, simple but realistic physical models are proposed and are found to be in fair agreement with the experimental data. Finally, as the stability of AgNW networks is a key issue, we demonstrate that coating AgNW networks with a very thin layer of TiO2 using atomic layer deposition (ALD) improves the material's resistance against electrical and thermal instabilities without altering optical transmittance. We show that the critical annealing temperature associated to network breakdown increases from 270 °C for the as-deposited AgNW networks to 420 °C for AgNW networks coated with TiO2. Similarly, the electrical failure which occurs at 7 V for the as-deposited networks increases to 13 V for TiO2-coated networks. TiO2 is also proved to stabilize AgNW networks during long duration operation and at

  15. Understanding the mechanisms leading to failure in metallic nanowire-based transparent heaters, and solution for stability enhancement

    Science.gov (United States)

    Lagrange, M.; Sannicolo, T.; Muñoz-Rojas, D.; Guillo Lohan, B.; Khan, A.; Anikin, M.; Jiménez, C.; Bruckert, F.; Bréchet, Y.; Bellet, D.

    2017-02-01

    Silver nanowire (AgNW) networks are emerging as one of the most promising alternatives to indium tin oxide (ITO) for transparent electrodes in flexible electronic devices. They can be used in a variety of optoelectronic applications such as solar cells, touch panels and organic light-emitting diodes. Recently they have also proven to be very efficient when used as transparent heaters (THs). In addition to the study of AgNW networks acting as THs in regular use, i.e. at low voltage and moderate temperature, their stability and physical behavior at higher voltages and for longer durations should be studied in view of their integration into real devices. The properties of AgNW networks deposited by spray coating on glass or flexible transparent substrates are thoroughly studied via in situ measurements. The AgNW networks’ behavior at different voltages for different durations and under different atmospheric conditions, both in air and under vacuum, has been examined. At low voltage, a reversible electrical response is observed while irreversibility and even failure are observed at higher voltages. In order to gain a deeper insight into the behavior of AgNW networks used as THs, simple but realistic physical models are proposed and are found to be in fair agreement with the experimental data. Finally, as the stability of AgNW networks is a key issue, we demonstrate that coating AgNW networks with a very thin layer of TiO2 using atomic layer deposition (ALD) improves the material’s resistance against electrical and thermal instabilities without altering optical transmittance. We show that the critical annealing temperature associated to network breakdown increases from 270 °C for the as-deposited AgNW networks to 420 °C for AgNW networks coated with TiO2. Similarly, the electrical failure which occurs at 7 V for the as-deposited networks increases to 13 V for TiO2-coated networks. TiO2 is also proved to stabilize AgNW networks during long duration operation and at

  16. Bending stability of GaN grown on a metallic flexible substrate by plasma-assisted molecular beam epitaxy

    Science.gov (United States)

    Rodríguez, A. G.; Chávez-Veloz, S. G.; Compeán-García, V. D.; López-Luna, E.; Vidal, M. A.

    2017-08-01

    GaN thin films were grown on flexible metallic substrates by molecular beam epitaxy. MgO buffer layers were deposited by spin coating on Ni-Mo-Cr (Hastelloy C-276) alloy tapes that were used as substrates. The structural characterization of the GaN/MgO/hastelloy samples was performed by x-ray diffraction and Raman spectroscopy. The obtained nanometric films have the stable hexagonal phase (α-GaN) with an average crystallite size of 18 nm. The long and short range order of GaN decrease when the structure is bent. The most significant variations in the structural properties occur between 100 and 250 bending cycles.

  17. Nanostructured Metal Carbides for Aprotic Li-O2 Batteries: New Insights into Interfacial Reactions and Cathode Stability.