WorldWideScience

Sample records for amorphous metallic alloys

  1. CVD of refractory amorphous metal alloys

    International Nuclear Information System (INIS)

    In this work, a novel process is described for the fabrication of multi-metallic amorphous metal alloy coatings using a chemical vapor deposition (CVD) technique. Of special interest in this work are amorphous metal alloys containing Mo and/or Cr which have high crystallization temperatures and readily available low decomposition temperature metal-bearing precursors. The conditions for amorphous alloy formation via CVD are described as well as the chemical properties of these materials. High temperature, aqueous corrosion tests have shown these materials (especially those containing Cr) are among the most corrosion resistant metal alloys known

  2. Plasma deposition of amorphous metal alloys

    International Nuclear Information System (INIS)

    Rapid solidification, sputtering and electroless chemical deposition have been used to produce amorphous metal alloys which possess excellent corrosion and abrasion resistance. This paper discusses a new technique for obtaining amorphous metal alloy coatings. Plasma decomposition of Ni(CO)4 and PH3 in argon and hydrogen carrier gases [Ni(CO4/PH3--8/1] yielded films that were black and silver, respectively, in appearance. Both films were amorphous as determined by transmission electron microscopy. Films deposited using a hydrogen carrier gas were three orders of magnitude more conductive than those deposited using an argon carrier gas. Analysis of both films using electron microprobe analysis and inductively-coupled plasma spectroscopy showed an enrichment of P in the films over the P content in the plasma gas mixtures. Reducing the P content of the plasma gas mixture [Ni(CO)4/PH3--17/11 yielded crystalline films with no P enrichment. The grain size in these films was --60Δ as determined by x-ray line-broadening

  3. Features of exoelectron emission in amorphous metallic alloys

    CERN Document Server

    Veksler, A S; Morozov, I L; Semenov, A L

    2001-01-01

    The peculiarities of the photothermostimulated exoelectron emission in amorphous metallic alloys of the Fe sub 6 sub 4 Co sub 2 sub 1 B sub 1 sub 5 composition are studied. It is established that the temperature dependences of the exoelectron emission spectrum adequately reflect the two-stage character of the amorphous alloy transition into the crystalline state. The exoelectron emission spectrum is sensitive to the variations in the modes of the studied sample thermal treatment. The thermal treatment of the amorphous metallic alloy leads to growth in the intensity of the exoelectrons yield. The highest growth in the intensify of the exoelectron emission was observed in the alloys at the initial stage of their crystallization

  4. Structural models for amorphous transition metal binary alloys

    International Nuclear Information System (INIS)

    A dense random packing of 445 hard spheres with two different diameters in a concentration ratio of 3 : 1 was hand-built to simulate the structure of amorphous transition metal-metalloid alloys. By introducing appropriate pair potentials of the Lennard-Jones type, the structure is dynamically relaxed by minimizing the total energy. The radial distribution functions (RDF) for amorphous Fe0.75P0.25, Ni0.75P0.25, Co0.75P0.25 are obtained and compared with the experimental data. The calculated RDF's are resolved into their partial components. The results indicate that such dynamically constructed models are capable of accounting for some subtle features in the RDF of amorphous transition metal-metalloid alloys

  5. Advances in chemical synthesis and application of metal-metalloid amorphous alloy nanoparticulate catalysts

    Institute of Scientific and Technical Information of China (English)

    WU Zhijie; LI Wei; ZHANG Minghui; TAO Keyi

    2007-01-01

    This paper reviews the advances in the chemical synthesis and application of metal-metalloid amorphous alloy nanoparticles consisting of transition metal (M) and metalloid elements (B,P).After a brief introduction on the history of amorphous alloy catalysts,the paper focuses on the properties and characterization of amorphous alloy catalysts,and recent developments in the solution-phase synthesis of amorphous alloy nanoparticles.This paper further outlines the applications of amorphous alloys,with special emphasis on the problems and strategies for the application of amorphous alloy nanoparticles in catalytic reactions.

  6. Ion beam mixing in binary amorphous metallic alloys

    International Nuclear Information System (INIS)

    Ion beam mixing (IM) was measured in homogeneous amorphous metallic alloys of Cu-Er and Ni-Ti as a function of temperature using tracer impurities, i.e., the so-called ''marker geometry''. In Cu-Er, a strong temperature dependence in IM was observed between 80 and 3730K, indicating that radiation-enhanced diffusion mechanisms are operative in this metallic glass. Phase separation of the Cu-Er alloy was also observed under irradiation as Er segregated to the vacuum and SiO2 interfaces of the specimen. At low-temperatures, the amount of mixing in amorphous Ni-Ti is similar to that in pure Ni or Ti, but it is much greater in Cu-Er than in either Cu or Er

  7. High Energy Storage Mg-based amorphous alloys for nickel-metal hydride battery

    International Nuclear Information System (INIS)

    Full text: Mg-based hydrogen storage alloys possess very high hydrogen absorption capacity (For example, Mg2NiH4 contains 3.6 wt.% of hydrogen). Magnesium is also abundant in nature, light in weight and low in cost. As a result, magnesium alloys have become the subject of increasing research world-wide. For a long period, it was thought that Mg-based alloy-hydrogen systems needed to be operated at high temperature (over 250 deg C) and under high hydrogen pressure. However, in recent years, some research work was successfully done to improve the hydrogen absorption kinetics of Mg2Ni by mechanical grinding and alloying. Some nano and amorphous structured Mg2Ni alloys could absorb hydrogen even at room temperature. Our research results show that it is possible to use Mg2Ni-type alloys as promising materials for increasing the negative electrode capacity of Ni-MH batteries because the theoretical discharge capacity of Mg2Ni alloy is approximately 1000 mAh/g, much higher than that of the main commercial LaNi5 alloy (which has a capacity of only about 370 mAh/g). Mg-based alloy electrodes were manufactured by a powder metallurgical technique or a induction melting method followed by ball milling with Ni and/or other metal powders. The discharge capacities of the Mg-based alloy electrodes were significantly improved by ball milling. An amorphous structure is a key factor in order to achieve high discharge capacities. The figure below shows the ball milled amorphous Mg-based alloy electrodes have very high discharge capacities by comparison with crystalline Mg2Ni alloys or commercial AB5 alloy

  8. Fe based amorphous and compounds metallic alloys for magnetic and structural use

    International Nuclear Information System (INIS)

    Massive amorphous metals (thicker than 1mm) are new types of material that could have a wide range of future applications due to a unique combination of their physical properties, mechanics and magnetics. Among these are the elevated tension of fracture and hardness, and excellent soft magnetic properties. Since 1960, when an amorphous metallic alloy was first discovered, progress has continued on the application possibilities for these materials. One of their main limitations, maximum obtainable thickness, has continued to increase, since at first thicknesses of a few microns were obtained. Now amorphous alloys more than 70 mm thick are obtained using different metallic elements. Since 1995 massive amorphous metals can be produced using Fe as the base element. At first they were made in order to achieve good soft magnetic properties (thicknesses of ∼5 mm) and later a renewed interest in their use as structural material led to the development of materials with thicknesses of 16 mm and paramagnetics at room temperature. Increasing the toughness of these materials is also a challenge and investigators have proposed several solutions, among them is the development of composite materials where dendrites from a solid solution act as crack stoppers of fissures that are spread by an amorphous matrix. This work presents the results of studies with two types of synthesized materials using the rapid cooling technique from injection copper mold casting at air temperature: 1) a massive amorphous metallic alloy with composition (Fe0.375Co0.375B0.2Si0.05)96Nb4 (at.%) and 2) a composite of solid solution dendrites α-(FeCo) scattered in an amorphous matrix with a composition similar to alloy 1. Using the samples obtained structural studies were made (optic and electronic microscopy SEM, XRD, EDAX, DTA), magnetic studies (coercive field and saturation magnetization) and mechanical studies (Vickers microhardness). The fully amorphous alloy could be obtained with a maximum

  9. Ion beam mixing in binary amorphous metallic alloys. [Cu-Er; Ni-Ti

    Energy Technology Data Exchange (ETDEWEB)

    Hahn, H.; Averback, R.S.; Diaz de la Rubia, T.; Okamoto, P.R.

    1985-12-01

    Ion beam mixing (IM) was measured in homogeneous amorphous metallic alloys of Cu-Er and Ni-Ti as a function of temperature using tracer impurities, i.e., the so-called ''marker geometry''. In Cu-Er, a strong temperature dependence in IM was observed between 80 and 373K, indicating that radiation-enhanced diffusion mechanisms are operative in this metallic glass. Phase separation of the Cu-Er alloy was also observed under irradiation as Er segregated to the vacuum and SiO2 interfaces of the specimen. At low-temperatures, the amount of mixing in amorphous Ni-Ti is similar to that in pure Ni or Ti, but it is much greater in Cu-Er than in either Cu or Er.

  10. Corrosion resistant amorphous alloys

    International Nuclear Information System (INIS)

    A review of publication data on corrosion resistance of amorphous alloys and the methods of amorphization of surface layers of massive materials (laser treatment, iron implantation, detonation-gas spraying, cathode and ion sputtering, electrodeposition) was made. A study was made on corrosion properties of Fe66Cr11B10Si4 alloy in cast state and after laser irradiation, rendering the surface amorphous as well as the samples of Arenco iron and steel 20 with ion-plasma coatings of Fe-Cr-Ni-Ti alloy. It was established that amorphous coatings posses much higher corrosion resistance as compared to crystalline alloys on the same base

  11. Structural order and magnetism of rare-earth metallic amorphous alloys

    International Nuclear Information System (INIS)

    Local symmetry (as evaluated from the electric field gradient tensor) and radial distribution functions (obtained by EXAFS measurement) are determined in a series of amorphous rare-earth base alloys. Local order is found to increase with the extent of heteroatomic interactions. Various magnetic phases (including ferromagnetic, spin-glass, reentrant spin-glass) occur for europium alloys with simple metals (Mg, Zn, Cd, Al, Au, ...). This variety reflects the sensitivity of exchange interactions to the presence of non-s conduction electrons. Asperomagnetic structures are established for the Dy alloys. The crystalline electric field interactions at the Dy3+ ions are interpreted with the help of local symmetry data. Quadratic axial and non-axial crystal field terms are sufficient and necessary in order to account for the hyperfine and bulk experimental results

  12. Low temperature irradiation effects on iron boron based amorphous metallic alloys

    International Nuclear Information System (INIS)

    Three Fe-B amorphous alloys (Fe80B20, Fe27Mo2B20 and Fe75B25) and the crystallized Fe3B alloy have been irradiated at the temperature of liquid hydrogen. Electron irradiation and irradiation by 10B fission fragments induce point defects in amorphous alloys. These defects are characterized by an intrinsic resistivity and a formation volume. The threshold energy for the displacement of iron atoms has also been calculated. Irradiation by 235U fission fragments induces some important structural modifications in the amorphous alloys

  13. A study of the diffusion mechanisms in amorphous metallic alloys: diffusion and diffusion under high pressure in an amorphous NiZr alloy

    International Nuclear Information System (INIS)

    The aim of this work is a better understanding of the diffusion mechanism in amorphous metallic alloys. Then interdiffusion and hafnium diffusion in amorphous NiZr alloy have been studied. Samples used are made by sputtering co-deposition under vacuum and are well relaxed before the diffusion measurements. The time evolution of resistivity during annealing due to the decay of a composition modulated film has been measured and from this change in resistivity interdiffusion coefficients have been determined. Dependence of Hf diffusion on temperature and pressure has been studied using (SIMS). In this two cases, the diffusion process obeys an Arrhenius law and gives an activation energy of 1.33 eV for interdiffusion, and 0.76 eV for Hf diffusion. An effect of pressure on Hf diffusion has been found leading to an activation volume of 8.5 angstrom3. Thanks to these results, two approaches of the diffusion mechanisms in these systems have been proposed. The first comes from a comparison with the diffusion mechanisms in crystalline metals, that is to say by point defects. The second is an hypothesis of collective motions in these non crystalline alloys. (author)

  14. Iron-based amorphous alloys and methods of synthesizing iron-based amorphous alloys

    Science.gov (United States)

    Saw, Cheng Kiong; Bauer, William A.; Choi, Jor-Shan; Day, Dan; Farmer, Joseph C.

    2016-05-03

    A method according to one embodiment includes combining an amorphous iron-based alloy and at least one metal selected from a group consisting of molybdenum, chromium, tungsten, boron, gadolinium, nickel phosphorous, yttrium, and alloys thereof to form a mixture, wherein the at least one metal is present in the mixture from about 5 atomic percent (at %) to about 55 at %; and ball milling the mixture at least until an amorphous alloy of the iron-based alloy and the at least one metal is formed. Several amorphous iron-based metal alloys are also presented, including corrosion-resistant amorphous iron-based metal alloys and radiation-shielding amorphous iron-based metal alloys.

  15. Plasma resonance of binary amorphous and crystalline Al-transition metal alloys: Experiments and ab initio calculations

    International Nuclear Information System (INIS)

    Highlights: • A comprehensive study of the plasma resonance of amorphous Al-transition metal alloys is given. • A characteristic fingerprint for the plasma energy versus concentration is presented. • The experimental results are supported by DFT calculations. • Amorphous alloys are found to be model systems for studying the influence of interband transitions on the plasma resonance. - Abstract: We report on measurements of the volume plasmon loss energy EP by electron energy loss spectroscopy of binary amorphous Al–(Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Y, Pd, Ce) alloys. In these systems the measured EP can be described by an effective valence of the transition metal independent of the particular transition metal. By exploiting ab initio calculations for the crystalline counterparts in the case of Al–(Ti, V, Fe, Ni) we show that this behavior can be understood in terms of the full dielectric function taking into account intra- and interband transitions mainly due to the presence of d-states close to the Fermi energy. This is validated by the comparison with published experimental data on binary Al systems with the non-transition metals Be, Mg, Ca, and Zn. Due to the absence of composition-dependent structural phase changes, amorphous alloys are found to be model-like systems for studying the influence of interband transitions on the plasma resonance

  16. Plasma resonance of binary amorphous and crystalline Al-transition metal alloys: Experiments and ab initio calculations

    Energy Technology Data Exchange (ETDEWEB)

    Stiehler, M., E-mail: martin.stiehler@mailbox.org [Technische Universität Chemnitz, Institute of Physics, 09107 Chemnitz (Germany); Kaltenborn, S. [Physics Department and Research Center OPTIMAS, University of Kaiserslautern, 67663 Kaiserslautern (Germany); Gillani, S.S.A.; Pudwell, P. [Technische Universität Chemnitz, Institute of Physics, 09107 Chemnitz (Germany); Schneider, H.C., E-mail: hcsch@physik.uni-kl.de [Physics Department and Research Center OPTIMAS, University of Kaiserslautern, 67663 Kaiserslautern (Germany); Häussler, P. [Technische Universität Chemnitz, Institute of Physics, 09107 Chemnitz (Germany)

    2015-07-15

    Highlights: • A comprehensive study of the plasma resonance of amorphous Al-transition metal alloys is given. • A characteristic fingerprint for the plasma energy versus concentration is presented. • The experimental results are supported by DFT calculations. • Amorphous alloys are found to be model systems for studying the influence of interband transitions on the plasma resonance. - Abstract: We report on measurements of the volume plasmon loss energy E{sub P} by electron energy loss spectroscopy of binary amorphous Al–(Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Y, Pd, Ce) alloys. In these systems the measured E{sub P} can be described by an effective valence of the transition metal independent of the particular transition metal. By exploiting ab initio calculations for the crystalline counterparts in the case of Al–(Ti, V, Fe, Ni) we show that this behavior can be understood in terms of the full dielectric function taking into account intra- and interband transitions mainly due to the presence of d-states close to the Fermi energy. This is validated by the comparison with published experimental data on binary Al systems with the non-transition metals Be, Mg, Ca, and Zn. Due to the absence of composition-dependent structural phase changes, amorphous alloys are found to be model-like systems for studying the influence of interband transitions on the plasma resonance.

  17. A thermodynamic approach towards glass-forming ability of amorphous metallic alloys

    Indian Academy of Sciences (India)

    Sonal R Prajapati; Supriya Kasyap; Arun Pratap

    2015-12-01

    A quantitative measure of the stability of a glass as compared to its corresponding crystalline state can be obtained by calculating the thermodynamic parameters, such as the Gibbs free energy difference (), entropy difference () and the enthalpy difference () between the super-cooled liquid and the corresponding crystalline phase. is known as the driving force of crystallization. The driving force of crystallization () provides very important information about the glass-forming ability (GFA) of metallic glasses (MGs). Lesser the driving force of crystallization more is the GFA. The varies linearly with the critical size (). According to Battezzati and Garonne the parameter ( = (1−(/))/(1−( / ))) in the expression for should be a constant (i.e., 0.8), but its uniqueness is not observed for all MGs. The thermal stability of various alloy compositions is studied by their undercooled liquid region ( = − ). Large implies greater stability against crystallization of the amorphous structure. Other GFA parameters are also calculated and correlated with critical size ().

  18. Atomic short-range order in Fe-C amorphous metal alloys

    International Nuclear Information System (INIS)

    Within frameworks of computer experiment by the method of molecular dynamics the processes of structural organization of Fe-C system amorphous alloys are investigated. It is shown that the influence of carbon concentration on the relationship between main constituents of local composition order: atomic configurations with a central position of carbon atoms and iron atoms positioned in apices of the configurations of octahedral and trigonal-prismatic coordination is opposite to that observed in crystalline alloys of the system

  19. Bulk amorphous Mg-based alloys

    DEFF Research Database (Denmark)

    Pryds, Nini

    The present paper describes the preparation and properties of bulk amorphous quarternary Mg-based alloys and the influence of additional elements on the ability of the alloy to form bulk amorphous. The main goal is to find a Mg-based alloy system which shows both high strength to weight ratio and a...... low glass transition temperature. The alloys were prepared by using a relatively simple technique, i.e. rapid cooling of the melt in a copper wedge mould. The essential structural changes that are achieved by going from the amorphous to the crystalline state through the supercooled liquid state are...... discussed in this paper. On the basis of these measurements phase diagrams of the different systems were constructed. Finally, it is demonstrated that when pressing the bulk amorphous alloy onto a metallic dies at temperatures within the supercooled liquid region, the alloy faithfully replicates the surface...

  20. Application of the artificial neural networks for prediction of magnetic saturation of metallic amorphous alloys

    Directory of Open Access Journals (Sweden)

    J. Konieczny

    2008-04-01

    Full Text Available Purpose: The aim of the work is to employ the artificial neural networks for prediction of magnetic saturation ofthe amorphous alloys with the iron and cobalt matrix.Design/methodology/approach: It has been assumed that the artificial neural networks can be used toassign the relationship between the chemical compositions of amorphous alloys, temperature of heat treatment andmagnetic saturation. In order to determine the relationship it has been necessary to work out a suitable calculationmodel. It has been proved that employment of genetic algorithm to selection of input neurons can be very usefultool to improve artificial neural network calculation results. The attempt to use the artificial neural networks forpredicting the effect of the chemical composition and temperature of heat treatment on the magnetic saturation BSsucceeded, as the level of the obtained results was acceptable.Findings: Artificial neural networks, can be applied for predicting the effect of the chemical composition andtemperature of heat treatment on the magnetic saturation.Research limitations/implications: Worked out model should be used for prediction of magnetic saturationonly in particular groups of amorphous alloys, mostly because of the discontinuous character of input data.Practical implications: The results of research make it possible to calculate with a certain admissible error the magneticsaturation Bs value basing on combinations of concentrations of the particular elements and heat treatment temperature.Originality/value: In this paper it has been presented an original trial of prediction of the required magneticproperties of the iron and cobalt amorphous alloys.

  1. Iron - based bulk amorphous alloys

    Directory of Open Access Journals (Sweden)

    R. Babilas

    2010-07-01

    Full Text Available Purpose: The paper presents a structure characterization, thermal and soft magnetic properties analysis of Fe-based bulk amorphous materials in as-cast state and after crystallization process. In addition, the paper gives some brief review about achieving, formation and structure of bulk metallic glasses as a special group of amorphous materials.Design/methodology/approach: The studies were performed on Fe72B20Si4Nb4 metallic glass in form of ribbons and rods. The amorphous structure of tested samples was examined by X-ray diffraction (XRD, transmission electron microscopy (TEM and scanning electron microscopy (SEM methods. The thermal properties of the glassy samples were measured using differential thermal analysis (DTA and differential scanning calorimetry (DSC. The magnetic properties contained initial and maximum magnetic permeability, coercive force and magnetic after-effects measurements were determined by the Maxwell-Wien bridge and VSM methods.Findings: The X-ray diffraction and transmission electron microscopy investigations revealed that the studied as-cast bulk metallic glasses in form of ribbons and rods were amorphous. Two stage crystallization process was observed for studied bulk amorphous alloy. The differences of crystallization temperature between ribbons and rods with chosen thickness are probably caused by different amorphous structures as a result of the different cooling rates in casting process. The SEM images showed that studied fractures could be classified as mixed fractures with indicated two zones contained “river” and “smooth” areas. The changing of chosen soft magnetic properties (μr, Bs, Hc obtained for samples with different thickness is a result of the non-homogenous amorphous structure of tested metallic glasses. The annealing process in temperature range from 373 to 773 K causes structural relaxation of tested amorphous materials, which leads to changes in their physical properties. The qualitative

  2. Anisotropic phase separation through the metal-insulator transition in amorphous Mo-Ge and Fe-Ge alloys

    International Nuclear Information System (INIS)

    Since an amorphous solid is often defined as that which lacks long-range order, the atomic structure is typically characterized in terms of the high-degree of short-range order. Most descriptions of vapor-deposited amorphous alloys focus on characterizing this order, while assuming that the material is chemically homogeneous beyond a few near neighbors. By coupling traditional small-angle x-ray scattering which probes spatial variations of the electron density with anomalous dispersion which creates a species-specific contrast, one can discern cracks and voids from chemical inhomogeneity. In particular, one finds that the chemical inhomogeneities which have been previously reported in amorphous FexGe1-x and MoxGe1-x are quite anisotropic, depending significantly on the direction of film growth. With the addition of small amounts of metal atoms (x2 or MoGe3. Finally, by manipulating the deposited power flux and rates of growth, FexGe1-x films which have the same Fe composition x can be grown to different states of phase separation. These results may help explain the difficulty workers have had in isolating the metal/insulator transition for these and other vapor-deposited amorphous alloys

  3. Anisotropic phase separation through the metal-insulator transition in amorphous Mo-Ge and Fe-Ge alloys

    Energy Technology Data Exchange (ETDEWEB)

    Regan, M.J.

    1993-12-01

    Since an amorphous solid is often defined as that which lacks long-range order, the atomic structure is typically characterized in terms of the high-degree of short-range order. Most descriptions of vapor-deposited amorphous alloys focus on characterizing this order, while assuming that the material is chemically homogeneous beyond a few near neighbors. By coupling traditional small-angle x-ray scattering which probes spatial variations of the electron density with anomalous dispersion which creates a species-specific contrast, one can discern cracks and voids from chemical inhomogeneity. In particular, one finds that the chemical inhomogeneities which have been previously reported in amorphous Fe{sub x}Ge{sub 1-x} and Mo{sub x}Ge{sub 1-x} are quite anisotropic, depending significantly on the direction of film growth. With the addition of small amounts of metal atoms (x<0.2), no films appear isotropic nor homogeneous through the metal/insulator transition. The results indicate that fluctuations in the growth direction play a pivotal role in preventing simple growth models of a columnar structure or one that evolves systematically as it grows. The anomalous scattering measurements identify the metal atoms (Fe or Mo) as the source of the anisotropy, with the Ge atoms distributed homogeneously. The author has developed a method for using these measurements to determine the compositions of the phase-separating species. The results indicate phase separation into an amorphous Ge and an intermetallic phase of stoichiometry close to FeGe{sub 2} or MoGe{sub 3}. Finally, by manipulating the deposited power flux and rates of growth, Fe{sub x}Ge{sub 1-x} films which have the same Fe composition x can be grown to different states of phase separation. These results may help explain the difficulty workers have had in isolating the metal/insulator transition for these and other vapor-deposited amorphous alloys.

  4. In vitro metal ion release and biocompatibility of amorphous Mg67Zn28Ca5 alloy with/without gelatin coating

    International Nuclear Information System (INIS)

    Amorphous zinc-rich Mg–Zn–Ca alloys have exhibited good tissue compatibility and low hydrogen evolution in vivo. However, suboptimal cell–surface interaction on magnesium alloy surface observed in vitro could lead to reduced integration with host tissue for regenerative purpose. This study aims to improve cell–surface interaction of amorphous Mg67Zn28Ca5 alloy by coating a gelatin layer by electrospinning. Coated/uncoated alloys were immersed and extracted for 3 days under different CO2. The immersion results showed that pH and metal ion release in the alloy extracts were affected by gelatin coating and CO2, suggesting their roles in alloy biocorrosion and a mechanism has been proposed for the alloy–CO2 system with/without coating. Cytotoxicity results are evident that gelatin-coated alloy with 2-day crosslinking not only exhibited no indirect cytotoxicity, but also supported attachment of L929 and MG63 cell lines around/on the alloy with high viability. Therefore, amorphous Mg67Zn28Ca5 alloy coated with gelatin by electrospinning technique provides a useful method to improve alloy biocompatibility. - Highlights: • Electrospinning is a new method to coat amorphous Mg67Zn28Ca5 alloy with gelatin. • Gelatin-coated alloy has differential effect on pH and ion release at various CO2. • L929 cell proliferation correlates with Mg2+ level in alloy extracts. • Biomimetic gelatin coating significantly improves cell–surface interaction

  5. A study of the diffusion mechanism in glasses: a theoretical and experimental study of tracers diffusion in amorphous metallic alloys

    International Nuclear Information System (INIS)

    The principal aims of this work are a better understanding of the experimental situation in amorphous metallic alloys and a tentative explanation of the role of collective mechanisms in matter transport. Self- and solute-diffusion of Hf, Au and Cu tracers in amorphous Ni Zr alloy have been studied. We study by SIMS analysis the broadening of the concentration profile with temperature and pressure, in thin amorphous layers which were prepared by sputtering and properly relaxed. The diffusion coefficient variation with temperature shows an Arrhenius behaviour for all of our tracers. The activation energy amount to 1.55 eV for Cu, 1.65 eV for Au and 1.78 eV for Hf and corresponds to nearly one half of the corresponding energy in crystalline zirconium. The diffusion coefficients variation with hydrostatic pressure yields an activation volume equal to one half of an average atomic volume of our matrix for medium and large sized tracers Au, Hf and a smaller activation volume for Cu. The second part of our work consists of numerical simulations of atomic displacements in a generic glass by two complementary methods. In a Lennard-Jones alloy with size effect, we observe by molecular dynamics (MD) some correlated displacements which consist of substitution cycles or chains. The associated energy of these collective events represents nearly 15 pc of that found in crystalline Lennard- Jones. The systematic exploration of energy surface in space configuration made with activation-relaxation technique ART yields energy distributions of stable and saddles positions and opens the way to an evaluation of diffusion coefficients. The events found by ART are qualitatively close to MD ones, but the averaged activation energy associated with these events represents only 10 pc of the crystalline one. This clearly points towards the limit of Lennard-Jones potential, which is not enough representative of actual glasses. This is the reason why an interaction model closer to amorphous

  6. Atomic structure and crystallization processes of amorphous (Co,Ni)–P metallic alloy

    Energy Technology Data Exchange (ETDEWEB)

    Modin, Evgeny B., E-mail: modin.eb@dvfu.ru [Far Eastern Federal University, Shukhanova 8, Vladivostok 690950 (Russian Federation); Pustovalov, Evgeny V.; Fedorets, Aleksander N.; Dubinets, Aleksander V.; Grudin, Boris N.; Plotnikov, Vladimir S. [Far Eastern Federal University, Shukhanova 8, Vladivostok 690950 (Russian Federation); Grabchikov, Sergey S. [Scientific and Practical Centre of Material Science, Belarus National Academy of Sciences, P. Brovki 19, Minsk 220072 (Belarus)

    2015-08-25

    Highlights: • The CoP–CoNiP amorphous alloys were studied by the Cs-corrected high resolution transmission electron microscopy. • In situ heating experiments showed that crystallization starts at 200–250 °C on the network frame and cell boundaries. • Crystal growth occurs at the free surface, then the remaining material in the volume is crystallized. • Adding nickel to the CoP alloy leads to higher thermal stability. • At the beginning of crystallization there are high diffusion coefficients, 1.2–2.4 ∗ 10{sup −18} m{sup 2}/s at 250 °C. - Abstract: This work concerns the in situ investigation of the atomic structure of (Co,Ni)–P alloys during relaxation and crystallization by high resolution transmission electron microscopy. The CoP–CoNiP alloys, in the initial state, have a hierarchical network-like disordered structure. Crystallization starts at 200–250 °C on the network frame and cell boundaries. In the early stages, crystal growth occurs at the free surface, then the remaining material in the volume is crystallized. The diffusion coefficient at the start of crystallization is 1.2–2.4 × 10{sup −18} m{sup 2}/s at 250 °C and we assume that the high diffusion speed is due to surface diffusion.

  7. Atomic structure and crystallization processes of amorphous (Co,Ni)–P metallic alloy

    International Nuclear Information System (INIS)

    Highlights: • The CoP–CoNiP amorphous alloys were studied by the Cs-corrected high resolution transmission electron microscopy. • In situ heating experiments showed that crystallization starts at 200–250 °C on the network frame and cell boundaries. • Crystal growth occurs at the free surface, then the remaining material in the volume is crystallized. • Adding nickel to the CoP alloy leads to higher thermal stability. • At the beginning of crystallization there are high diffusion coefficients, 1.2–2.4 ∗ 10−18 m2/s at 250 °C. - Abstract: This work concerns the in situ investigation of the atomic structure of (Co,Ni)–P alloys during relaxation and crystallization by high resolution transmission electron microscopy. The CoP–CoNiP alloys, in the initial state, have a hierarchical network-like disordered structure. Crystallization starts at 200–250 °C on the network frame and cell boundaries. In the early stages, crystal growth occurs at the free surface, then the remaining material in the volume is crystallized. The diffusion coefficient at the start of crystallization is 1.2–2.4 × 10−18 m2/s at 250 °C and we assume that the high diffusion speed is due to surface diffusion

  8. Amorphous yttrium-iron alloys

    International Nuclear Information System (INIS)

    The magnetic properties of amorphous yttrium-iron alloys Ysub(1-x)Fesub(x) have been studied over a wide concentration range 0.32 2Fe17 alloys, lead in the amorphous state to spin-glass behaviour and asperomagnetic order. The dominant positive interactions produce short-range ferromagnetic correlations which persist up to room temperature. However magnetic saturation cannot be achieved for any of the alloys in applied fields of up to 180 kOe, indicating that strong negative interactions are also present. Exchange interactions become increasingly positive with increasing x, and the magnetic properties of iron-rich alloys approach those of a normal ferromagnet. (author)

  9. In vitro metal ion release and biocompatibility of amorphous Mg{sub 67}Zn{sub 28}Ca{sub 5} alloy with/without gelatin coating

    Energy Technology Data Exchange (ETDEWEB)

    Chan, W.Y., E-mail: chan.wing.yue@sgh.com.sg [School of Mechanical and Aerospace Engineering, Nanyang Technological University (Singapore); Department of Plastic, Reconstructive and Aesthetic Surgery, Singapore General Hospital (Singapore); Chian, K.S.; Tan, M.J. [School of Mechanical and Aerospace Engineering, Nanyang Technological University (Singapore)

    2013-12-01

    Amorphous zinc-rich Mg–Zn–Ca alloys have exhibited good tissue compatibility and low hydrogen evolution in vivo. However, suboptimal cell–surface interaction on magnesium alloy surface observed in vitro could lead to reduced integration with host tissue for regenerative purpose. This study aims to improve cell–surface interaction of amorphous Mg{sub 67}Zn{sub 28}Ca{sub 5} alloy by coating a gelatin layer by electrospinning. Coated/uncoated alloys were immersed and extracted for 3 days under different CO{sub 2}. The immersion results showed that pH and metal ion release in the alloy extracts were affected by gelatin coating and CO{sub 2}, suggesting their roles in alloy biocorrosion and a mechanism has been proposed for the alloy–CO{sub 2} system with/without coating. Cytotoxicity results are evident that gelatin-coated alloy with 2-day crosslinking not only exhibited no indirect cytotoxicity, but also supported attachment of L929 and MG63 cell lines around/on the alloy with high viability. Therefore, amorphous Mg{sub 67}Zn{sub 28}Ca{sub 5} alloy coated with gelatin by electrospinning technique provides a useful method to improve alloy biocompatibility. - Highlights: • Electrospinning is a new method to coat amorphous Mg{sub 67}Zn{sub 28}Ca{sub 5} alloy with gelatin. • Gelatin-coated alloy has differential effect on pH and ion release at various CO{sub 2}. • L929 cell proliferation correlates with Mg{sup 2+} level in alloy extracts. • Biomimetic gelatin coating significantly improves cell–surface interaction.

  10. Influence of the microstructure on the corrosion behavior of magnetron sputter-quenched amorphous metallic alloys

    Science.gov (United States)

    Thakoor, A. P.; Khanna, S. K.; Williams, R. M.; Landel, R. F.

    1983-01-01

    The microstructure and corrosion behavior of magnetron sputter deposited amorphous metallic films of (Mo6ORu40)82B18 under varying sputtering atmospheres have been investigated. The microstructural details and topology of the films have been studied by scanning electron microscopy and correlated with the deposition conditions. By reducing the pressure of pure argon gas, the characteristic features of rough surface and columnar growth full of vertical voids can be converted into a mirror-smooth finish with very dense deposits. Films deposited in the presence of O2 or N2 exhibit columnar structure with vertical voids. Film deposited in pure argon at low pressure show remarkably high corrosion resistance due to the formation of a uniform passive surface layer. The influence of the microstructure and surface texture on the corrosion behavior is discussed.

  11. Amorphous metal based nanoelectromechanical switch

    KAUST Repository

    Mayet, Abdulilah M.

    2013-04-01

    Nanoelectromechanical (NEM) switch is an interesting ultra-low power option which can operate in the harsh environment and can be a complementary element in complex digital circuitry. Although significant advancement is happening in this field, report on ultra-low voltage (pull-in) switch which offers high switching speed and area efficiency is yet to be made. One key challenge to achieve such characteristics is to fabricate nano-scale switches with amorphous metal so the shape and dimensional integrity are maintained to achieve the desired performance. Therefore, we report a tungsten alloy based amorphous metal with fabrication process development of laterally actuated dual gated NEM switches with 100 nm width and 200 nm air-gap to result in <5 volts of actuation voltage (Vpull-in). © 2013 IEEE.

  12. A study of the diffusion mechanisms in amorphous metallic alloys: diffusion and diffusion under high pressure in an amorphous NiZr alloy; Contribution a l`etude des mecanismes de transport dans les materiaux metalliques amorphes: diffusion et diffusion sous pression dans NiZr amorphe

    Energy Technology Data Exchange (ETDEWEB)

    Grandjean, A.

    1996-03-01

    The aim of this work is a better understanding of the diffusion mechanism in amorphous metallic alloys. Then interdiffusion and hafnium diffusion in amorphous NiZr alloy have been studied. Samples used are made by sputtering co-deposition under vacuum and are well relaxed before the diffusion measurements. The time evolution of resistivity during annealing due to the decay of a composition modulated film has been measured and from this change in resistivity interdiffusion coefficients have been determined. Dependence of Hf diffusion on temperature and pressure has been studied using (SIMS). In this two cases, the diffusion process obeys an Arrhenius law and gives an activation energy of 1.33 eV for interdiffusion, and 0.76 eV for Hf diffusion. An effect of pressure on Hf diffusion has been found leading to an activation volume of 8.5 angstrom{sup 3}. Thanks to these results, two approaches of the diffusion mechanisms in these systems have been proposed. The first comes from a comparison with the diffusion mechanisms in crystalline metals, that is to say by point defects. The second is an hypothesis of collective motions in these non crystalline alloys. (author).

  13. Unexpected magnetic behavior in amorphous Co90Sc10 alloy

    International Nuclear Information System (INIS)

    An amorphous alloy Co90Sc10 has been prepared by rapid quenching from the melt. The results of magnetization measurements show that this alloy has the highest Curie temperature reported for any amorphous transition metal based alloys. Furthermore, for a Co based amorphous alloy, the magnetic moment is remarkably high. Moreover, the alloy exhibits soft magnetic properties. Based on the findings, amorphous Co90Sc10 appears to be an attractive candidate for applications as a soft magnetic material. The temperature dependence of the reduced magnetization can be described by the Bloch power law. The results show that the B coefficient of the amorphous Co90Sc10 alloy, which is a measure of the rigidity of spin waves, exhibits the lowest value observed until now for any amorphous alloy and is comparable to crystalline alloys. It is found that the Sc atoms in the Co90Sc10 alloy lead to an increase of the itinerant spin moment of Co atoms, and, in contrast to this behaviour, to a decrease of the local 3d-electrons of Co

  14. Amorphous Alloy Surpasses Steel and Titanium

    Science.gov (United States)

    2004-01-01

    In the same way that the inventions of steel in the 1800s and plastic in the 1900s sparked revolutions for industry, a new class of amorphous alloys is poised to redefine materials science as we know it in the 21st century. Welcome to the 3rd Revolution, otherwise known as the era of Liquidmetal(R) alloys, where metals behave similar to plastics but possess more than twice the strength of high performance titanium. Liquidmetal alloys were conceived in 1992, as a result of a project funded by the California Institute of Technology (CalTech), NASA, and the U.S. Department of Energy, to study the fundamentals of metallic alloys in an undercooled liquid state, for the development of new aerospace materials. Furthermore, NASA's Marshall Space Flight Center contributed to the development of the alloys by subjecting the materials to testing in its Electrostatic Levitator, a special instrument that is capable of suspending an object in midair so that researchers can heat and cool it in a containerless environment free from contaminants that could otherwise spoil the experiment.

  15. Preparation of hydrogenated amorphous silicon tin alloys

    OpenAIRE

    Vergnat, M.; Marchal, G.; Piecuch, M.

    1987-01-01

    This paper describes a new method to obtain hydrogenated amorphous semiconductor alloys. The method is reactive co-evaporation. Silicon tin hydrogenated alloys are prepared under atomic hydrogen atmosphere. We discuss the influence of various parameters of preparation (hydrogen pressure, tungsten tube temperature, substrate temperature, annealing...) on electrical properties of samples.

  16. Crystallization of amorphous Zr-Be alloys

    Science.gov (United States)

    Golovkova, E. A.; Surkov, A. V.; Syrykh, G. F.

    2015-02-01

    The thermal stability and structure of binary amorphous Zr100 - x Be x alloys have been studied using differential scanning calorimetry and neutron diffraction over a wide concentration range (30 ≤ x ≤ 65). The amorphous alloys have been prepared by rapid quenching from melt. The studied amorphous system involves the composition range around the eutectic composition with boundary phases α-Zr and ZrBe2. It has been found that the crystallization of alloys with low beryllium contents ("hypoeutectic" alloys with x ≤ 40) proceeds in two stages. Neutron diffraction has demonstrated that, at the first stage, α-Zr crystallizes and the remaining amorphous phase is enriched to the eutectic composition; at the second stage, the alloy crystallizes in the α-Zr and ZrBe2 phases. At higher beryllium contents ("hypereutectic" alloys), one phase transition of the amorphous phase to a mixture of the α-Zr and ZrBe2 phases has been observed. The concentration dependences of the crystallization temperature and activation energy have been revealed.

  17. Amorphous Alloy Membranes for High Temperature Hydrogen Separation

    Energy Technology Data Exchange (ETDEWEB)

    Coulter, K

    2013-09-30

    At the beginning of this project, thin film amorphous alloy membranes were considered a nascent but promising new technology for industrial-scale hydrogen gas separations from coal- derived syngas. This project used a combination of theoretical modeling, advanced physical vapor deposition fabricating, and laboratory and gasifier testing to develop amorphous alloy membranes that had the potential to meet Department of Energy (DOE) targets in the testing strategies outlined in the NETL Membrane Test Protocol. The project is complete with Southwest Research Institute® (SwRI®), Georgia Institute of Technology (GT), and Western Research Institute (WRI) having all operated independently and concurrently. GT studied the hydrogen transport properties of several amorphous alloys and found that ZrCu and ZrCuTi were the most promising candidates. GT also evaluated the hydrogen transport properties of V, Nb and Ta membranes coated with different transition-metal carbides (TMCs) (TM = Ti, Hf, Zr) catalytic layers by employing first-principles calculations together with statistical mechanics methods and determined that TiC was the most promising material to provide catalytic hydrogen dissociation. SwRI developed magnetron coating techniques to deposit a range of amorphous alloys onto both porous discs and tubular substrates. Unfortunately none of the amorphous alloys could be deposited without pinhole defects that undermined the selectivity of the membranes. WRI tested the thermal properties of the ZrCu and ZrNi alloys and found that under reducing environments the upper temperature limit of operation without recrystallization is ~250 °C. There were four publications generated from this project with two additional manuscripts in progress and six presentations were made at national and international technical conferences. The combination of the pinhole defects and the lack of high temperature stability make the theoretically identified most promising candidate amorphous alloys

  18. Simulation study for atomic size and alloying effects during forming processes of amorphous alloys

    Institute of Scientific and Technical Information of China (English)

    ZHENG Caixing; LIU Rangsu; PENG Ping; ZHOU Qunyi

    2004-01-01

    A molecular dynamics (MD) simulation study has been performed for the solidification processes of two binary liquid alloys Ag6Cu4 and CuNi by adopting the quantum Sutton-Chen many-body potentials. By analyzing bond-types, it is demonstrated that at the cooling rate of 2×1012K/s, the CuNi forms fcc crystal structures, while the Ag6Cu4 forms amorphous structures. The original reason is that the atomic radius ratio (1.13) of the CuAg is bigger than that (1.025) of the CuNi. This shows that the atomic size difference is indeed the main factor for forming amorphous alloys. Moreover, for Ag60Cu40,corresponding to the deep eutectic point in the phase diagram, it forms amorphous structure easily. This confirms that as to the forming tendency and stability of amorphous alloys, the alloying effect plays a key role. In addition, having analyzed the transformation of microstructures by using the bond-type index and cluster-type index methods, not only the key role of the icosahedral configuration to the formation and stability of amorphous alloys can be explained, but also the solidification processes of liquid metals and the characteristics of amorphous structures can be further understood.

  19. Welding of cobalt-based amorphous alloys with Nd: YAG laser

    International Nuclear Information System (INIS)

    The paper describes the results concerning the investigation of the welding of cobalt-based amorphous alloys with Nd:YAG laser. Five alloys with different chemical structure and dimensions in shape of amorphous metal foils were welded. The quality of the welded joints were tested by using a microstructure analysis with an optical microscope and SEM, when the metal graphic structure, the chemical structure and the microhardness of the welded joints were tested as well. (Author)

  20. Amorphous metallic films in silicon metallization systems

    Science.gov (United States)

    So, F.; Kolawa, E.; Nicolet, M. A.

    1985-01-01

    Diffusion barrier research was focussed on lowering the chemical reactivity of amorphous thin films on silicon. An additional area of concern is the reaction with metal overlays such as aluminum, silver, and gold. Gold was included to allow for technology transfer to gallium arsenide PV cells. Amorphous tungsten nitride films have shown much promise. Stability to annealing temperatures of 700, 800, and 550 C were achieved for overlays of silver, gold, and aluminum, respectively. The lower results for aluminum were not surprising because there is an eutectic that can form at a lower temperature. It seems that titanium and zirconium will remove the nitrogen from a tungsten nitride amorphous film and render it unstable. Other variables of research interest were substrate bias and base pressure during sputtering.

  1. Barkhausen effect during hydrogen interaction with amorphous alloy 2NSR

    International Nuclear Information System (INIS)

    The Barkhausen effect electromotive force measurements by the two-side saturation of the 2NSR (Fe78B12Si19Ni1) alloy amorphous band through hydrogen is carried out. The multiple increase in the Barkhausen effect electromotive force by hydrogen saturation is determined. It is assumed that in the metallic alloy over-saturated by hydrogen there originates a special structural state providing for decrease in the potential barrier by transition of the 180 deg boundary of the magnetic domain from the equilibrium state to another one. The value of the Barkhausen effect link with the hydrogen content in the material is indicated

  2. TEM study of amorphous alloys produced by ion implantation

    International Nuclear Information System (INIS)

    Ion implantation is a technique for introducing foreign elements into surface layers of solids. Ions, as a suitably accelerated beam, penetrate the surface, slow down by collisions with target atoms to produce a doped layer. This non-equilibrium technique can provide a wide range of alloys without the restrictions imposed by equilibrium phase diagrams. This paper reports on the production of some amorphous transition metal-metalloid alloys by implantation. Thinned foils of Ni, Fe and stainless steel were implanted at room temperature with Dy+ and P+ ions at doses between 1013 - 1017 ions/cm2 at energies of 20 and 40 keV respectively. Transmission electron microscopy and selected area diffraction analysis were used to investigate the implanted specimens. Radial diffracted intensity measurements confirmed the presence of an amorphous implanted layer. The peak positions of the maxima are in good agreement with data for similar alloys produced by conventional techniques. Only certain ion/target combinations produce these amorphous layers. Implantations at doses lower than those needed for amorphization often result in formation of new crystalline phases such as an h.c.p. phase in nickel and a b.c.c. phase in stainless steel. (Auth.)

  3. Atomic structure of Re-Si amorphous alloys

    International Nuclear Information System (INIS)

    The atomic structure of Re100-xSix (x=0, 4, 11, 20, 31, 47, 54, 70, 82, 88, 100) amorphous alloys (AA) was studied by X-ray diffraction. In as-quenched alloys two amorphous phase were observed: the AI-phase-10-90 at.% Si and AII-phase-45-100 at.% Si, especially that in the composition range 45-90 at.% Si is the coexistence of two phase AI and AII. A comparison of the short range order parameters of the AA and those of the corresponding crystalline compounds has been done. The short-range order of AI-phase and coordination polyhedrons of Re5Si3, ReSi2 compounds is similar. Contrary to the Gaskell's model for metal-metalloid AA (trigonal prismatic structural unit) it seems to be tetragonal antiprism. The structure of AII-phase is the same as a-Si. (orig.)

  4. Superconducting State Parameters of Bulk Amorphous Alloys

    Directory of Open Access Journals (Sweden)

    Aditya M. Vora

    2012-12-01

    Full Text Available Well recognized empty core (EMC pseudopotential of Ashcroft is used to investigate the superconducting state parameters viz; electron-phonon coupling strength λ, Coulomb pseudopotential μ*, transition temperature TC, isotope effect exponent α and effective interaction strength NOV of some (Ni33Zr671 – xVx (x = 0, 0.05, 0.1, 0.15 bulk amorphous alloys. We have incorporated five different types of local field correction functions, proposed by Hartree (H, Taylor (T, Ichimaru-Utsumi (IU, Farid et al. (F and Sarkar et al. (S to show the effect of exchange and correlation on the aforesaid properties. Very strong influence of the various exchange and correlation functions is concluded from the present study. The TC obtained from Sarkar et al. (S local field correction function are found an excellent agreement with available theoretical data. Quadratic TC equation has been proposed, which provide successfully the TC values of bulk amorphous alloys under consideration. Also, the present results are found in qualitative agreement with other such earlier reported data, which confirms the superconducting phase in the s bulk amorphous alloys.

  5. Synthesis and characterization of a bulk amorphous alloy

    International Nuclear Information System (INIS)

    The production and characterization of bulk metallic glasses have been an area of intense focus in materials research for many years because of their superior mechanical properties over their crystalline counterparts. A bulk metallic glass Zr/sub 55/Cu/sub 30/Al/sub 10/Ni/sub 5/ has been synthesized by copper mold casting and characterized by differential scanning calorimetry and x-ray diffraction. Crystallization behavior of the alloy is discussed. Composite of amorphous glass was produced by adding SiC and hardness and tensile strength have been measured. (author)

  6. Formation and crystallization of bulk Pd82Si18 amorphous alloys

    Institute of Scientific and Technical Information of China (English)

    蒲建; 王敬丰; 肖建中; 崔昆

    2003-01-01

    Bulk amorphous Pd82Si18 alloy with the largest diameter of 8 mm was prepared by water quenching the molten alloy with flux medium in a quartz tube. The calculation result indicates that the bulk Pd82Si18 amorphous alloys have a low critical cooling rate (Rc) of 4.589 K/s or less. The experimental results show that purifying melt may improve glass forming ability(GFA) of undercooled melt, while liquid phase separation (LPS) of undercooled melt will decrease its GFA. There are some differences in crystallization experiments between bulk metallic glass and amorphous ribbons of Pd82Si18 alloys. These include the numbers of exothermic peak, glass transition temperature Tg, crystallization temperature Tx, region of undercooling liquid (ΔT=Tx-Tg) respectively. The links of cooling rates of melt and crystallization of Pd82Si18 amorphous alloys are explored.

  7. Unexpected magnetic behavior in amorphous Co{sub 90}Sc{sub 10} alloy

    Energy Technology Data Exchange (ETDEWEB)

    Ghafari, M., E-mail: mohammad.ghafari@kit.edu, E-mail: skamali@utsi.edu; Gleiter, H. [Herbert Gleiter Institute of Nanoscience, Nanjing University of Science and Technology, Nanjing 210094 (China); Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), 76344 Eggenstein-Leopoldshafen (Germany); Sakurai, Y.; Itou, M. [Japan Synchrotron Radiation Research Institute (JASRI), SPring-8, 1-1-1 Kouto, Sayo, Sayo, Hyogo (Japan); Peng, G.; Fang, Y. N.; Feng, T. [Herbert Gleiter Institute of Nanoscience, Nanjing University of Science and Technology, Nanjing 210094 (China); Hahn, H. [Herbert Gleiter Institute of Nanoscience, Nanjing University of Science and Technology, Nanjing 210094 (China); Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), 76344 Eggenstein-Leopoldshafen (Germany); KIT-TUD Joint Research Laboratory Nanomaterials, Institute of Materials Science, Technische Universität Darmstadt (TUD), Jovanka-Bontschits-Str. 2, 64287 Darmstadt (Germany); Kamali, S., E-mail: mohammad.ghafari@kit.edu, E-mail: skamali@utsi.edu [Department of Mechanical, Aerospace and Biomedical Engineering, University of Tennessee Space Institute, Tullahoma, Tennessee 37388 (United States)

    2015-09-28

    An amorphous alloy Co{sub 90}Sc{sub 10} has been prepared by rapid quenching from the melt. The results of magnetization measurements show that this alloy has the highest Curie temperature reported for any amorphous transition metal based alloys. Furthermore, for a Co based amorphous alloy, the magnetic moment is remarkably high. Moreover, the alloy exhibits soft magnetic properties. Based on the findings, amorphous Co{sub 90}Sc{sub 10} appears to be an attractive candidate for applications as a soft magnetic material. The temperature dependence of the reduced magnetization can be described by the Bloch power law. The results show that the B coefficient of the amorphous Co{sub 90}Sc{sub 10} alloy, which is a measure of the rigidity of spin waves, exhibits the lowest value observed until now for any amorphous alloy and is comparable to crystalline alloys. It is found that the Sc atoms in the Co{sub 90}Sc{sub 10} alloy lead to an increase of the itinerant spin moment of Co atoms, and, in contrast to this behaviour, to a decrease of the local 3d-electrons of Co.

  8. Excessively High Vapor Pressure of Al-based Amorphous Alloys

    Directory of Open Access Journals (Sweden)

    Jae Im Jeong

    2015-10-01

    Full Text Available Aluminum-based amorphous alloys exhibited an abnormally high vapor pressure at their approximate glass transition temperatures. The vapor pressure was confirmed by the formation of Al nanocrystallites from condensation, which was attributed to weight loss of the amorphous alloys. The amount of weight loss varied with the amorphous alloy compositions and was inversely proportional to their glass-forming ability. The vapor pressure of the amorphous alloys around 573 K was close to the vapor pressure of crystalline Al near its melting temperature, 873 K. Our results strongly suggest the possibility of fabricating nanocrystallites or thin films by evaporation at low temperatures.

  9. Properties and Applications of Nanocrystalline Alloys from Amorphous Precursors

    CERN Document Server

    Idzikowski, Bogdan; Miglierini, Marcel

    2005-01-01

    Metallic (magnetic and non-magnetic) nanocrystalline materials have been known for over ten years but only recent developments in the research into those complex alloys and their metastable amorphous precursors have created a need to summarize the most important accomplishments in the field. This book is a collection of articles on various aspects of metallic nanocrystalline materials, and an attempt to address this above need. The main focus of the papers is put on the new issues that emerge in the studies of nanocrystalline materials, and, in particular, on (i) new compositions of the alloys, (ii) properties of conventional nanocrystalline materials, (iii) modeling and simulations, (iv) preparation methods, (v) experimental techniques of measurements, and (vi) different modern applications. Interesting phenomena of the physics of nanocrystalline materials are a consequence of the effects induced by the nanocrystalline structure. They include interface physics, the influence of the grain boundaries, the aver...

  10. Composition Range of Amorphous Mg-Ni-Y Alloys

    Institute of Scientific and Technical Information of China (English)

    陈红梅; 钟夏平; 欧阳义芳

    2003-01-01

    Based on the thermodynamic point of view, a method for predication of the composition range of amorphous ternary alloys was proposed. The composition range of amorphous ternary alloys is determined by the comparison of the excess free energy of the amorphous alloy and the free energy of competing crystalline states. The free energy is extrapolated from the data of three binary alloys by using Toop′s model. The method was applied to predict the composition range of amorphous Mg-Ni-Y alloys. The theoretical results are in good agreement with the available experimental results. It indicates that the present method can be used to predict the composition range for amorphous ternary alloys.

  11. Structural analysis of amorphous and hydrogen absorption alloys by neutron diffraction

    International Nuclear Information System (INIS)

    Structural studies of amorphous alloys and hydrogen absorption amorphous alloys by taking advantage of neutron and X-ray diffractions and using the reverse Monte Carlo (RMC) modeling for getting information of the three dimensional atom configuration are reviewed. Voronoi analysis of the RMC models is powerful to elucidate the structural origin of the stability of amorphous state, since Ni-Zr amorphous alloys are unstable in comparison with Cu-Zr ones. The polyhedra around Ni atoms are dominated by trigonal prism-like polyhedra. In contrast, icosahedron-like polyhedra are preferred for Cu. The Ni-Zr amorphous alloys have been reported to stabilize by adding Al. The Voronoi analysis informs us that trigonal prism-like polyhedra decreased in number by adding Al to the Ni-Zr system. On the contrary, the number of icosahedron-like polyhedra was found to increase. The results apparently indicate that the icosahedron-like polyhedra play an important role to stabilize the amorphous state. Moreover, neutron diffraction is a powerful tool to clarify the location of hydrogen atoms in the hydrogen absorption materials. For TbFe2D3.8 and TbNi2D2.4 amorphous alloys, the RMC model structure based on the diffraction data teach us that about 98% of hydrogen atoms occupy tetrahedral sites formed by metal atoms and stabilize the amorphous state. (author)

  12. Laser spot welding of cobalt-based amorphous metal foils

    International Nuclear Information System (INIS)

    The results concerning weldability of amorphous alloy (VAC 6025F) in shape of foils and the quality of laser-spot welded joints are presented in this paper. The aim of the research was the production of a high quality welding joint, by preserving the amorphous structure. The quality of the joint was tested by shear strength analysis and microhardness measuring. The metallographic studies were made by using optical microscope and SEM. The results show that (1) overlapped Co based amorphous metals foils can be welded with high-quality by a pulsed Nd: YAG-Laser, but only within a very narrow laser parameter window; (2) the laser welded spots show comparably high strength as the basic material; (3) the structure of the welded spot remains amorphous, so that the same characteristics as the base material can be achieved. (author)

  13. Amorphous Fe-based metal foam

    International Nuclear Information System (INIS)

    A foam synthesis method that takes advantage of the viscous high-temperature liquid state of Fe-based bulk glass-forming alloys to produce amorphous steel foam is introduced. Zirconium hydride is utilized as a foaming agent taking advantage of the low hydrogen solubility of these glass-forming alloys. Amorphous foams with porosities up to 65% were produced having homogenous cellular morphologies that exhibit cell-size uniformity. Even though intracellular solid regions as thin as a few micrometers are detected, on a global scale the cellular structure is determined to be incapable of alleviating the foam from the brittle nature of the monolithic glass

  14. NMR study in amorphous CoZr thin film alloys

    International Nuclear Information System (INIS)

    59Co NMR study has been carried out in a series of magnetic thin film amorphous Co1-xZrx alloys in the concentration range 0.1< x<0.4. The analysis shows that every Zr nearest neighbour lowers the NMR frequency on Co in the amorphous CoZr alloys by about 30 MHz and that the alloy structure in Co-rich compositions resembles the polytetrahedrally closed packed crystalline phases. (orig.)

  15. Amorphous TM1−xBx alloy particles prepared by chemical reduction (invited)

    DEFF Research Database (Denmark)

    Linderoth, Søren; Mørup, Steen

    1991-01-01

    Amorphous transition-metal boron (TM-B) alloy particles can be prepared by chemical reduction of TM ions by borohydride in aqueous solutions. ln the last few years systematic studies of the parameters which control the composition, and, in turn, many of the properties of the alloy particles, have...... been performed and are reviewed in the present paper. The most important preparation parameters which influence the composition are the concentration of the borohydride solution and the pH of the TM salt solution. By controlling these parameters it is possible to prepare amorphous alloy samples...

  16. LOCAL ATOMIC STRUCTURE OF AMORPHOUS METALS

    OpenAIRE

    Egami, T.; Maed, K.; Srolovitz, D.; Vitek, V.

    1980-01-01

    The local parameters are introduced to describe the local atomic structure of amorphous metals. They define the structural defects which facilitate the explanation of various properties, including the volume change by annealing.

  17. Laser surface treatment of amorphous metals

    Science.gov (United States)

    Katakam, Shravana K.

    Amorphous materials are used as soft magnetic materials and also as surface coatings to improve the surface properties. Furthermore, the nanocrystalline materials derived from their amorphous precursors show superior soft magnetic properties than amorphous counter parts for transformer core applications. In the present work, laser based processing of amorphous materials will be presented. Conventionally, the nanocrystalline materials are synthesized by furnace heat treatment of amorphous precursors. Fe-based amorphous/nanocrystalline materials due to their low cost and superior magnetic properties are the most widely used soft magnetic materials. However, achieving nanocrystalline microstructure in Fe-Si-B ternary system becomes very difficult owing its rapid growth rate at higher temperatures and sluggish diffusion at low temperature annealing. Hence, nanocrystallization in this system is achieved by using alloying additions (Cu and Nb) in the ternary Fe-Si-B system. Thus, increasing the cost and also resulting in reduction of saturation magnetization. laser processing technique is used to achieve extremely fine nanocrystalline microstructure in Fe-Si-B amorphous precursor. Microstructure-magnetic Property-laser processing co-relationship has been established for Fe-Si-B ternary system using analytical techniques. Laser processing improved the magnetic properties with significant increase in saturation magnetization and near zero coercivity values. Amorphous materials exhibit excellent corrosion resistance by virtue of their atomic structure. Fe-based amorphous materials are economical and due to their ease of processing are of potential interest to synthesize as coatings materials for wear and corrosion resistance applications. Fe-Cr-Mo-Y-C-B amorphous system was used to develop thick coatings on 4130 Steel substrate and the corrosion resistance of the amorphous coatings was improved. It is also shown that the mode of corrosion depends on the laser processing

  18. TEM of nanostructured metals and alloys

    Energy Technology Data Exchange (ETDEWEB)

    Karnthaler, H.P.; Waitz, T.; Rentenberger, C.; Mingler, B

    2004-12-15

    Nanostructuring has been used to improve the mechanical properties of bulk metals and alloys. Transmission electron microscopy (TEM) including atomic resolution is therefore appropriate to study these nanostructures; four examples are given as follows. (1) The early stages of precipitation at RT were investigated in an Al-Mg-Si alloy. By high resolution TEM it is shown that the precipitates lie on (0 0 1) planes having an ordered structure. (2) In Co alloys the fronts of martensitic phase transformations were analysed showing that the transformation strains are very small thus causing no surface relief. (3) Re-ordering and recrystallization were studied by in situ TEM of an Ni{sub 3}Al alloy being nanocrystalline after severe plastic deformation. (4) In NiTi severe plastic deformation is leading to the formation of amorphous shear bands. From the TEM analysis it is concluded that the amorphization is caused by plastic shear instability starting in the shear bands.

  19. TEM of nanostructured metals and alloys

    International Nuclear Information System (INIS)

    Nanostructuring has been used to improve the mechanical properties of bulk metals and alloys. Transmission electron microscopy (TEM) including atomic resolution is therefore appropriate to study these nanostructures; four examples are given as follows. (1) The early stages of precipitation at RT were investigated in an Al-Mg-Si alloy. By high resolution TEM it is shown that the precipitates lie on (0 0 1) planes having an ordered structure. (2) In Co alloys the fronts of martensitic phase transformations were analysed showing that the transformation strains are very small thus causing no surface relief. (3) Re-ordering and recrystallization were studied by in situ TEM of an Ni3Al alloy being nanocrystalline after severe plastic deformation. (4) In NiTi severe plastic deformation is leading to the formation of amorphous shear bands. From the TEM analysis it is concluded that the amorphization is caused by plastic shear instability starting in the shear bands

  20. Formation and Corrosion Resistance of Amorphous Ti Base Alloys

    OpenAIRE

    Naka, M.; Okada, T.; T. Matsui

    1996-01-01

    Corrosion resistant amorphous Ti-B and Ti-Si alloys were prepared on various substrates by RF sputtering. The alloying of B content of 8 at% or more stabilizes the amorphous structure. The corrosion properties of Ti alloys were evaluated by measuring the polarization curves in 1N HCl. Although the addition of B to crystalline bulky Ti shifts the corrosion potentials of Ti to the less nobles of -0.5 V(SCE) or less, that of B to amorphous sputtered Ti moves the corrosion potentials to the noble...

  1. Leading research on super metal. 3. Amorphous and nanostructured metallic materials; Super metal no sendo kenkyu. 3. Kogata buzai

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-03-01

    Very fine structure control technique for amorphous and nanostructured metallic materials was reviewed to exceed the marginal performance of small metallic member materials. In Japan, high strength alloys and anticorrosion alloys are currently developed as an amorphous structure control technique, and ultra fine powder production and nano-compaction molding are studied for nanostructured materials. Fabrication of amorphous alloy wire materials and metal glass in USA are also introduced. Fabrication of metallic nanocrystals deposited within gas phase in Germany are attracting attention. The strength and abrasion resistance are remarkably enhanced by making nanostructured crystals and dispersing them. It may be most suitable to utilize amorphous and nanostructured metallic materials for earth-friendly materials having anticorrosion, and catalyst and biomaterial affinities, and also for magnetic materials. It is important for controlling micro-structures to clarify the formation mechanism of structures. For their processing techniques, the diversity and possibility are suggested, as to the condensation and solidification of gaseous and liquid phase metals, the molding and processing of very fine solid phase alloys, and the manufacturing members by heat treatment. 324 refs., 109 figs., 21 tabs.

  2. On amorphization and nanocomposite formation in Al–Ni–Ti system by mechanical alloying

    Indian Academy of Sciences (India)

    K Das; G K Dey; B S Murty; S K Pabi

    2005-11-01

    Amorphous structure generated by mechanical alloying (MA) is often used as a precursor for generating nanocomposites through controlled devitrification. The amorphous forming composition range of ternary Al–Ni–Ti system was calculated using the extended Miedema's semi-empirical model. Eleven compositions of this system showing a wide range of negative enthalpy of mixing (− mix) and amorphization (− amor) of the constituent elements were selected for synthesis by MA. The Al88Ni6Ti6 alloy with relatively small negative mix (−0.4 kJ/mol) and amor (−14.8 kJ/mol) became completely amorphous after 120 h of milling, which is possibly the first report of complete amorphization of an Al-based rare earth element free Al–TM–TM system (TM = transition metal) by MA. The alloys of other compositions selected had much more negative mix and amor; but they yielded either nanocomposites of partial amorphous and crystalline structure or no amorphous phase at all in the as-milled condition, evidencing a high degree of stability of the intermetallic phases under the MA environment. Hence, the negative mix and amor are not so reliable for predicting the amorphization in the present system by MA.

  3. Devitrification of rapidly quenched Al–Cu–Ti amorphous alloys

    Indian Academy of Sciences (India)

    D K Misra; R S Tiwari; O N Srivastava

    2003-08-01

    X-ray diffraction, transmission electron microscopy and differential scanning calorimetry were carried out to study the transformation from amorphous to icosahedral/crystalline phases in the rapidly quenched Al50Cu45Ti5 and Al45Cu45Ti10 alloys. In the present investigation, we have studied the formation and stability of amorphous phase in Al50Cu45Ti5 and Al45Cu45Ti10 rapidly quenched alloys. The DSC curve shows a broad complex type of exothermic overlapping peaks (288–550°C) for Al50Cu45Ti5 and a well defined peak around 373°C for Al45Cu45Ti10 alloy. In the case of Al50Cu45Ti5 alloy amorphous to icosahedral phase transformation has been observed after annealing at 280°C for 73 h. Large dendritic growth of icosahedral phase along with -Al phase has been found. Annealing of Al50Cu45Ti5 alloy at 400°C for 8 h results in formation of Al3Ti type phase. Al45Cu45Ti10 amorphous alloy is more stable in comparison to Al50Cu45Ti5 alloy and after annealing at 400°C for 8 h it also transforms to Al3Ti type phase. However, this alloy does not show amorphous to icosahedral phase transformation.

  4. Determination of properties of high temperature superconductors and amorphous metallic alloys using positron annihilation techniques. Final report for the period 15 January 1992 - 15 July 1995

    International Nuclear Information System (INIS)

    The positron lifetime results obtained on amorphous thermally treated Ni25Zr55Al20 alloy indicate that positrons annihilate at places with different properties. The observed shifts of positron lifetime distribution were analyzed in the terms of a relaxation of free-volume, i.e. chemical (CSRO) and topological (TSRO) short range ordering. The upper limit of the activation energy of CSRO and TSRO relaxation was determined to be 2.2eV and 2.6eV, respectively. Positron lifetime τ and Doppler broadening of the annihilation line measurements on very pure C60 sample as a function of temperature between 120 and 300 K have been reported. A rapid change of τ was observed between 240 and 250 K. This results indicate that the lattice from C60 molecules is undergoing a phase transition and the phases coexist over an ∼ 10K range. The annihilation of positrons in amorphous tetramethylpoly-carbonate has been investigated in the temperature range from 30 to 300 K. The observed dependences of the mean lifetime of oPs and its relative intensity 1 on temperature were interpreted within the framework of the microstructural free-volume concept. The man radius of free space (hole) was deduced to be around 3,1.10-10m. Refs, figs, tabs

  5. Amorphous metal matrix composite ribbons

    International Nuclear Information System (INIS)

    Composite ribbons with amorphous matrix and ceramic (SiC, WC, MoB) particles were produced by modified planar melt flow casting methods. Weldability, abrasive wear and wood sanding examinations were carried out in order to find optimal material and technology for elevated wear resistance and sanding durability. The correlation between structure and composite properties is discussed. (author)

  6. Tribological properties of amorphous alloys and the role of surfaces in abrasive wear of materials

    Science.gov (United States)

    Miyoshi, K.; Buckley, D. H.

    1982-01-01

    The research approach undertaken by the authors relative to the subject, and examples of results from the authors are reviewed. The studies include programs in adhesion, friction, and various wear mechanisms (adhesive and abrasive wear). The materials which have been studied include such ceramic and metallic materials as silicon carbide, ferrites, diamond, and amorphous alloys.

  7. Strain Rate Induced Amorphization in Metallic Nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Qi, Y.; Cagin, T.; Goddard, W.A. III [Materials and Process Simulation Center, California Institute of Technology, Pasadena, California 91125 (United States); Ikeda, H.; Samwer, K.; Johnson, W.L. [Keck Laboratory of Engineering Materials, California Institute of Technology, Pasadena, California 91125 (United States)

    1999-04-01

    Using molecular dynamics simulations with a many-body force field, we studied the deformation of single crystal Ni and NiCu random alloy nanowires subjected to uniform strain rates but kept at 300thinspthinspK. For all strain rates, the Ni nanowire is elastic up to 7.5{percent} strain with a yield stress of 5.5thinspthinspGPa, far above that of bulk Ni. At high strain rates, we find that for both systems the crystalline phase transforms continuously to an amorphous phase, exhibiting a dramatic change in atomic short-range order and a near vanishing of the tetragonal shear elastic constant perpendicular to the tensile direction. This amorphization which occurs directly from the homogeneous, elastically deformed system with no chemical or structural inhomogeneities exhibits a new mode of amorphization. {copyright} {ital 1999} {ital The American Physical Society}

  8. Formation Range, Mechanical Properties and Thermal Stability of Superconducting Zr-Si Amorphous Alloys

    OpenAIRE

    Inoue, Akihisa; Takahashi, Yoshimi; MASUMOTO, Tsuyoshi

    1980-01-01

    New type of refractory metal-metalloid amorphous alloys containing less than 20 at% Si have been found in binary Zr-Si system by a modified melt-spinning technique for high melting point alloys. Specimens are in the form of continuous ribbons of 1-2 mm width and 0.02-0.03 mm thickness. The silicon content in the amorphous range is limited to the range 12 to 24 at%. The Vickers hardness increases from 395 to 495 DPN with increasing silicon content and the tensile strength is of the order of 14...

  9. Enhanced Corrosion Resistance of Iron-Based Amorphous Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Rebak, R B; Day, S D; Lian, T; Aprigliano, L F; Hailey, P D; Farmer, J C

    2007-02-18

    Iron-based amorphous alloys possess enhanced hardness and are highly resistant to corrosion, which make them desirable for wear applications in corrosive environments. It was of interest to examine the behavior of amorphous alloys during anodic polarization in concentrated salt solutions and in the salt-fog testing. Results from the testing of one amorphous material (SAM2X5) both in ribbon form and as an applied coating are reported here. Cyclic polarization tests were performed on SAM2X5 ribbon as well as on other nuclear engineering materials. SAM2X5 showed the highest resistance to localized corrosion in 5 M CaCl{sub 2} solution at 105 C. Salt fog tests of 316L SS and Alloy 22 coupons coated with amorphous SAM2X5 powder showed resistance to rusting. Partial devitrification may be responsible for isolated pinpoint rust spots in some coatings.

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

    International Nuclear Information System (INIS)

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

  11. Short range ordering and microstructure property relationship in amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Shariq, A.

    2006-07-01

    A novel algorithm, ''Next Neighbourhood Evaluation (NNE)'', is enunciated during the course of this work, to elucidate the next neighbourhood atomic vicinity from the data, analysed using tomographic atom probe (TAP) that allows specifying atom positions and chemical identities of the next neighbouring atoms for multicomponent amorphous materials in real space. The NNE of the Pd{sub 55}Cu{sub 23}P{sub 22} bulk amorphous alloy reveals that the Pd atoms have the highest probability to be the next neighbours to each other. Moreover, P-P correlation corroborates earlier investigations with scattering techniques that P is not a direct next neighbour to another P atom. Analogous investigations on the Fe{sub 40}Ni{sub 40}B{sub 20} metallic glass ribbons, in the as quenched state and for a state heat treated at 350 C for 1 hour insinuate a pronounced elemental inhomogeneity for the annealed state, though, it also depicts glimpse of a slight inhomogeneity for B distribution even for the as quenched sample. Moreover, a comprehensive microstructural investigation has been carried out on the Zr{sub 53}Co{sub 23.5}Al{sub 23.5} glassy system. TEM and TAP investigations evince that the as cast bulk samples constitutes a composite structure of an amorphous phase and crystalline phase(s). The crystallization is essentially triggered at the mould walls due to heterogeneous nucleation. The three dimensional atomic reconstruction maps of the volume analysed by TAP reveal a complex stereological interconnected network of two phases. The phase that is rich in Zr and Al concentration is depleted in Co concentration while the phase that is rich in Co concentration is depleted both in Zr and Al. Zr{sub 53}Co{sub 23.5}Al{sub 23.5} glassy splat samples exhibit a single exothermic crystallization peak contrary to the as cast bulk sample with a different T{sub g} temperature. A single homogeneous amorphous phase revealed by TEM investigations depicts that the faster cooling

  12. Structural transformations of Fe81B13Si4C2 amorphous alloy induced by heating

    Czech Academy of Sciences Publication Activity Database

    Minić, Dragica M.; Minić, Dušan M.; Žák, Tomáš; Roupcová, Pavla; David, Bohumil

    2011-01-01

    Roč. 323, č. 5 (2011), s. 400-404. ISSN 0304-8853 R&D Projects: GA MŠk 1M0512 Institutional research plan: CEZ:AV0Z20410507 Keywords : Amorphous material * Metallic glass * Metal and alloy * Phase transition * Thermal analysis * Mössbauer spectrum * X-ray diffraction Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.780, year: 2011

  13. Domain structure and Barkhausen effect in Fe78B12Si9Ni1 amorphous alloy

    International Nuclear Information System (INIS)

    Domain structure is investigated by using new approaches, which are based on registration of micro-volume material magnetization. One demonstrated absence of correlation of dimensions of domain structure elements of Fe78B12Si9Ni1 magnetically soft alloy in initial state upon hydrogen saturation or annealing with the Barkhausen effect characteristics in the mentioned alloy. It is pointed out that conventional view of the Barkhausen effect the nature of which is linked with domain dimensions and mobility of their boundaries, are not true in disordered structures represented by magnetically soft amorphous metal alloys

  14. Molecular dynamics simulation of amorphous segregation inAg-Rh alloys

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jingxiang; BIAN Xiufang

    2003-01-01

    Molecular dynamics simulation was carried out to investigate the liquid and amorphous microstructures of binary Agx-Rh(100-x) (x = 25, 50, 75 in atom fraction) alloys. Segregation feature of homogeneous interatomic binding of Ag-Rh liquid was found and probed, which can be retained into amorphous solids upon rapid cooling. Homogeneous binding may occur when the difference in the elemental atomic sizes is less than 10%. The icosahedra in liquid before the formation of amorphous state exist in a stable state and the network formed by 1551-clusters in molten alloys would inhibit the crystallization and diffusion of atoms. A higher degree of 155 1-clusters will be favorable to form metallic glasses.

  15. Magnetocaloric response of amorphous and nanocrystalline Cr-containing Vitroperm-type alloys

    Science.gov (United States)

    Moreno-Ramírez, L. M.; Blázquez, J. S.; Franco, V.; Conde, A.; Marsilius, M.; Budinsky, V.; Herzer, G.

    2016-07-01

    The broad compositional range in which transition metal (TM) based amorphous alloys can be obtained, yields an easily tunable magnetocaloric effect (MCE) in a wide temperature range. In some TM-based alloys, anomalous behaviors are reported, as a non-monotonous trend with magnetic moment (e.g. FeZrB alloys). Moreover, in certain Cr-containing Vitroperm alloys anomalously high values of the magnetic entropy change were published. In this work, a systematic study on MCE response of Cr-containing amorphous alloys of composition Fe74-xCrxCu1Nb3Si15.5B6.5 (with x=2, 8, 10, 12, 13, 14 and 20) has been performed in a broad Curie temperature range from 100 K to 550 K. Curie temperature and magnetic entropy change peak of the amorphous alloys decrease with the increase of Cr content at rates of -25.6 K/at% Cr and -54 mJ kg-1 K-1/at% Cr, respectively, following a linear trend with the magnetic moment in both cases. The presence of nanocrystalline phases has been considered as a possible cause in order to explain the anomalies. The samples were nanocrystallized in different stages, however, the magnetocaloric response decreases as crystallization progresses due to the large separation of the Curie temperatures of the two phases.

  16. Model calculations of thermodynamic functions of crystallization of Co-B amorphous alloys

    International Nuclear Information System (INIS)

    A model of perfectly associated solution is used for the approximation of the properties of metal melts. The calculation programs are prepared for modelling thermodynamic properties of solutions on the basis of the model of perfectly associated solution, which programs can enable optimizational calculation relying on the results of several series of experiments. Co-B liquid alloys are modelled using all available in the literature experimental data. Estimated values ΔcrH = 10 kJ/mol; ΔcrS = -2 J/(K mol); ΔcrG = -9 kJ/mol are obtained for the crystallization of amorphous Co0.815B0.185 alloy. The calculated value of amorphous alloy crystallization enthalpy is compared with the literature data. 17 refs., 1 tab

  17. Microstructure and properties of hydrophobic films derived from Fe-W amorphous alloy

    Institute of Scientific and Technical Information of China (English)

    Song Wang; Yun-han Ling; Jun Zhang; Jian-jun Wang; Gui-ying Xu

    2014-01-01

    Amorphous metals are totally different from crystalline metals in regard to atom arrangement. Amorphous metals do not have grain boundaries and weak spots that crystalline materials contain, making them more resistant to wear and corrosion. In this study, amorphous Fe-W alloy films were first prepared by an electroplating method and were then made hydrophobic by modification with a water repellent (heptadecafluoro-1,1,2,2-tetradecyl) trimethoxysilane. Hierarchical micro-nano structures can be obtained by slightly oxidizing the as-deposited alloy, accompanied by phase transformation from amorphous to crystalline during heat treatment. The mi-cro-nano structures can trap air to form an extremely thin cushion of air between the water and the film, which is critical to producing hydrophobicity in the film. Results show that the average values of capacitance, roughness factor, and impedance for specific surface areas of a 600°C heat-treated sample are greater than those of a sample treated at 500°C. Importantly, the coating can be fabricated on various metal substrates to act as a corrosion retardant.

  18. Aluminium based composites strengthened with metallic amorphous phase or ceramic (Al2O3) particles

    International Nuclear Information System (INIS)

    Highlights: • Al-based composites with amorphous Al strengthening phase were obtained. • A better adhesion of metallic amorphous particles than of ceramic phase. • Avoiding crystallization of amorphous phase during a composite pressing process. • Properties similar for 10% metallic amorphous and ceramic strengthening phases. • Better amorphization in case of melt spinning than gas atomization of the Al alloy. - Abstract: Two methods were used to obtain amorphous aluminium alloy powder: gas atomization and melt spinning. The sprayed powder contained only a small amount of the amorphous phase and therefore bulk composites were prepared by hot pressing of aluminium powder with the 10% addition of ball milled melt spun ribbons of the Al84Ni6V5Zr5 alloy (numbers indicate at.%). The properties were compared with those of a composite containing a 10% addition of Al2O3 ceramic particles. Additionally, a composite based on 2618A Al alloy was prepared with the addition of the Al84Ni6V5Zr5 powder from the ribbons used as the strengthening phase. X-ray studies confirmed the presence of the amorphous phase with a small amount of aluminium solid solution in the melt spun ribbons. Differential Scanning Calorimetry (DSC) studies showed the start of the crystallization process of the amorphous ribbons at 437 °C. The composite samples were obtained in the process of uniaxial hot pressing in a vacuum at 380 °C, below the crystallization temperature of the amorphous phase. A uniform distribution of both metallic and ceramic strengthening phases was observed in the composites. The hardness of all the prepared composites was comparable and amounted to approximately 50 HV for those with the Al matrix and 120 HV for the ones with the 2618A alloy matrix. The composites showed a higher yield stress than the hot pressed aluminium or 2618A alloy. Scanning Electron Microscopy (SEM) studies after compression tests revealed that the propagation of cracks in the composites

  19. Integral bypass diodes in an amorphous silicon alloy photovoltaic module

    Science.gov (United States)

    Hanak, J. J.; Flaisher, H.

    1991-01-01

    Thin-film, tandem-junction, amorphous silicon (a-Si) photovoltaic modules were constructed in which a part of the a-Si alloy cell material is used to form bypass protection diodes. This integral design circumvents the need for incorporating external, conventional diodes, thus simplifying the manufacturing process and reducing module weight.

  20. Neutron scattering studies of amorphous Invar alloys

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez-Baca, J.A.

    1989-01-01

    This paper reviews recent inelastic neutron scattering experiments performed to study the spin dynamics of two amorphous Invar systems: Fe/sub 100-x/B/sub x/ and Fe/sub 90-x/Ni/sub x/Zr/sub 10/. As in crystalline Invar Fe/sub 65/Ni/sub 35/ and Fe/sub 3/Pt, the excitation of conventional long-wavelength spin waves in these amorphous systems cannot account for the relatively rapid change of their magnetization with temperature. These results are discussed in terms of additional low-lying excitations which apparently have a density of states similar to the spin waves.

  1. Amorphous coatings deposited on aluminum alloy by plasma electrolytic oxidation

    Institute of Scientific and Technical Information of China (English)

    GUAN Yong-jun; XIA Yuan

    2005-01-01

    Amorphous [Al-Si-O] coatings were deposited on aluminum alloy by plasma electrolytic oxidation (PEO). The process parameters, composition, micrograph, and mechanical property of PEO amorphous coatings were investigated. It is found that the growth rate of PEO coatings reaches 4.44 μm/min if the current density is 0.9 mA/mm2. XRD results show that the PEO coatings are amorphous in the current density range of 0.3 - 0.9mA/mm2. EDS results show that the coatings are composed of O, Si and Al elements. SEM results show that the coatings are porous. Nano indentation results show that the hardness of the coatings is about 3 - 4 times of that of the substrate, while the elastic modulus is about the same with the substrate. Furthermore, a formation mechanism of amorphous PEO coatings was proposed.

  2. Synthesis and Performance of Fe-based Amorphous Alloys for Nuclear Waste Applications

    International Nuclear Information System (INIS)

    Recent developments in multi-component Fe-based amorphous alloys have shown that these novel materials exhibit outstanding corrosion resistance compared to typical crystalline alloys such as high-performance stainless steels and Ni-based C-22 alloy. During the past decade, amorphous alloy synthesis has advanced to allow for the casting of bulk metallic glasses. In several Fe-based alloy systems it is possible to produce glasses with cooling rates as low as 100 K/s. At such low cooling rates, there is an opportunity to produce amorphous solids through industrial processes such as thermal spray-formed coatings. Moreover, since cooling rates in typical thermal spray processing exceed 1000 K/s, novel alloy compositions can be synthesized to maximize corrosion resistance (i.e. adding Cr and Mo) and to improve radiation compatibility (adding B) and still maintain glass forming ability. The applicability of Fe-based amorphous coatings in typical environments where corrosion resistance and thermal stability are critical issues has been examined in terms of amorphous phase stability and glass-forming ability through a coordinated computational analysis and experimental validation. For example, a wedge casting technique has been applied to examine bulk glass forming alloys by combining multiple thermal probes with a measurement based kinetics analysis and a computational thermodynamics evaluation to elucidate the phase selection competition and critical cooling rate conditions. Based upon direct measurements and kinetics modeling it is evident that a critical cooling rate range should be considered to account for nucleation behavior and that the relative heat flow characteristics as well as nucleation kinetics are important in judging ease of glass formation. Similarly, a novel computational thermodynamics approach has been developed to explore the compositional sensitivity of glass-forming ability and thermal stability. Also, the synthesis and characterization of alloys

  3. Optimization of operational parameters and bath control for electrodeposion of Ni-Mo-B amorphous alloys

    OpenAIRE

    Marinho Fabiano A.; Santana François S. M.; Vasconcelos André L. S.; Santana Renato A. C.; Prasad Shiva

    2002-01-01

    Optimization of operational parameters of an electrodeposition process for deposition of boron-containing amorphous metallic layer of nickel-molybdenum alloy onto a cathode from an electrolytic bath having nickel sulfate, sodium molybdate, boron phosphate, sodium citrate, sodium-1-dodecylsulfate and ammonia for pH adjustments to 9.5 has been studied. Detailed studies of the efects on bath temperature, mechanical agitation, cathode current density and anode format have led to optimum operation...

  4. Deployable aerospace PV array based on amorphous silicon alloys

    Science.gov (United States)

    Hanak, Joseph J.; Walter, Lee; Dobias, David; Flaisher, Harvey

    1989-01-01

    The development of the first commercial, ultralight, flexible, deployable, PV array for aerospace applications is discussed. It is based on thin-film, amorphous silicon alloy, multijunction, solar cells deposited on a thin metal or polymer by a proprietary, roll-to-roll process. The array generates over 200 W at AM0 and is made of 20 giant cells, each 54 cm x 29 cm (1566 sq cm in area). Each cell is protected with bypass diodes. Fully encapsulated array blanket and the deployment mechanism weigh about 800 and 500 g, respectively. These data yield power per area ratio of over 60 W/sq m specific power of over 250 W/kg (4 kg/kW) for the blanket and 154 W/kg (6.5 kg/kW) for the power system. When stowed, the array is rolled up to a diameter of 7 cm and a length of 1.11 m. It is deployed quickly to its full area of 2.92 m x 1.11 m, for instant power. Potential applications include power for lightweight space vehicles, high altitude balloons, remotely piloted and tethered vehicles. These developments signal the dawning of a new age of lightweight, deployable, low-cost space arrays in the range from tens to tens of thousands of watts for near-term applications and the feasibility of multi-100 kW to MW arrays for future needs.

  5. Glow discharge amorphous silicon tin alloys

    Energy Technology Data Exchange (ETDEWEB)

    Mahan, A H; Sanchez, A; Williamson, D L; von Roedern, B; Madan, A

    1984-06-01

    We present basic density of states, photoresponse, and transport measurements made on low bandgap a-SiSn:H alloys produced by RF glow discharge deposition of SiH/sub 4/, H/sub 2/ and Sn(CH/sub 3/)/sub 4/. Although we demonstrate major changes in the local bonding structure and the density of states, the normalized photoresponse still remains poor. We provide evidence that two types of defect levels are produced with Sn alloying, and that the resultant density of states increase explains not only the n- to p-type conductivity transition reported earlier, but also the photoresponse behavior. We also report that a-SiSn:H can be doped with P. From our device analysis we suggest that in order to improve the alloy performance significantly, the density of states should be decreased to levels comparable to or lower than those presently obtained in a-Si:H.

  6. Developments in the Ni-Nb-Zr amorphous alloy membranes

    Science.gov (United States)

    Sarker, S.; Chandra, D.; Hirscher, M.; Dolan, M.; Isheim, D.; Wermer, J.; Viano, D.; Baricco, M.; Udovic, T. J.; Grant, D.; Palumbo, O.; Paolone, A.; Cantelli, R.

    2016-03-01

    Most of the global H2 production is derived from hydrocarbon-based fuels, and efficient H2/CO2 separation is necessary to deliver a high-purity H2 product. Hydrogen-selective alloy membranes are emerging as a viable alternative to traditional pressure swing adsorption processes as a means for H2/CO2 separation. These membranes can be formed from a wide range of alloys, and those based on Pd are the closest to commercial deployment. The high cost of Pd (USD ~31,000 kg-1) is driving the development of less-expensive alternatives, including inexpensive amorphous (Ni60Nb40)100- x Zr x alloys. Amorphous alloy membranes can be fabricated directly from the molten state into continuous ribbons via melt spinning and depending on the composition can exhibit relatively high hydrogen permeability between 473 and 673 K. Here we review recent developments in these low-cost membrane materials, especially with respect to permeation behavior, electrical transport properties, and understanding of local atomic order. To further understand the nature of these solids, atom probe tomography has been performed, revealing amorphous Nb-rich and Zr-rich clusters embedded in majority Ni matrix whose compositions deviated from the nominal overall composition of the membrane.

  7. Correlation of atomic packing with the boson peak in amorphous alloys

    International Nuclear Information System (INIS)

    Boson peaks (BP) have been observed from phonon specific heats in 10 studied amorphous alloys. Two Einstein-type vibration modes were proposed in this work and all data can be fitted well. By measuring and analyzing local atomic structures of studied amorphous alloys and 56 reported amorphous alloys, it is found that (a) the BP originates from local harmonic vibration modes associated with the lengths of short-range order (SRO) and medium-range order (MRO) in amorphous alloys, and (b) the atomic packing in amorphous alloys follows a universal scaling law, i.e., the ratios of SRO and MRO lengths to solvent atomic diameter are 3 and 7, respectively, which exact match with length ratios of BP vibration frequencies to Debye frequency for the studied amorphous alloys. This finding provides a new perspective for atomic packing in amorphous materials, and has significant implications for quantitative description of the local atomic orders and understanding the structure-property relationship.

  8. Cyclic and Linear Polarization of Yttrium-Containing Iron-Based Amorphous Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Day, S D; Lian, T; Farmer, J C; Rebak, R B

    2007-08-10

    Iron-based amorphous alloys are produced by rapid solidification from the melt. These alloys may possess unique mechanical and corrosion resistant properties. The chemical composition of the alloy may influence the cooling rate that is necessary for the alloys to be completely vitreous. At the same time, the corrosion resistance of the amorphous alloys may also depend on their chemical composition. This paper examines the anodic behavior of iron-based amorphous alloys containing three different concentrations (1, 3 and 5 atomic %) of yttrium (Y) in several electrolyte solutions. Results from polarization resistance potentiodynamic polarization show that when the alloy contains 5% atomic Y, the corrosion resistance decreases.

  9. Ultralight amorphous silicon alloy photovoltaic modules for space applications

    Science.gov (United States)

    Hanak, J. J.; Chen, Englade; Fulton, C.; Myatt, A.; Woodyard, J. R.

    1987-01-01

    Ultralight and ultrathin, flexible, rollup monolithic PV modules have been developed consisting of multijunction, amorphous silicon alloys for either terrestrial or aerospace applications. The rate of progress in increasing conversion efficiency of stable multijunction and multigap PV cells indicates that arrays of these modules can be available for NASA's high power systems in the 1990's. Because of the extremely light module weight and the highly automated process of manufacture, the monolithic a-Si alloy arrays are expected to be strongly competitive with other systems for use in NASA's space station or in other large aerospace applications.

  10. Properties of amorphous FeCoB alloy particles (abstract)

    DEFF Research Database (Denmark)

    Charles, S. W.; Wells, S.; Meagher, A.;

    1988-01-01

    Amorphous and crystalline alloy particles (0.05–0.5 nm) of FexCoyBz in which the ratio x:y ranges from 0 to 1 have been prepared by the borohydride reduction of iron and cobalt salts in aqueous solution. The structure of the particles has been studied using Mössbauer spectroscopy and x....... 1). It has been shown that the fraction of boron in the alloys (10–35 at. %) is dependent upon the rate of addition of salts to borohydride and the concentration of cobalt present; this in turn influences the crystallinity and magnetic properties . Journal of Applied Physics is copyrighted...

  11. Blistering and flaking of amorphous alloys bombarded with He ions

    International Nuclear Information System (INIS)

    The blistering and flaking behavior of many kinds of amorphous alloys under helium ion bombardment at room temperature was investigated. Helium ions with energies of 40 keV and 60 keV was implanted within the fluence range (1.0-4.0) x 1018 ions/cm2. The surface topography of samples after irradiation was observed by using a scanning electron microscope. The diameter of blister and the thickness of exfoliated blister lids were measured. The results showed that many kinds of surface topography characteristics appeared for different fluences, energies and amorphous alloys, such as flaking, blistering, exfoliation, blister rupture, second generation blistering and porous structure. The dependence of surface damage modes and the critical fluence for the onset of blistering and flaking on the sort of materials and ion energy was discussed

  12. DOMAIN WALL PINNING IN INHOMOGENEOUSLY DEFORMED AMORPHOUS ALLOYS

    OpenAIRE

    Gibbs, M.; Evetts, J.; Horton, M.

    1980-01-01

    Inhomogeneous deformation in amorphous alloys is characterized by local regions of intense shear. Experiments on VITROVAC 0040 (Fe40Ni40B20) supplied by Vacuumschmelze (Hanau, Germany) show a direct correlation between the number density of the shear bands and the coercive field after inhomogeneous deformation by cold rolling. The deformation process is also shown to induce an off axis magnetic anisotropy whose mean value is large compared to other residual and induced anisotropies in these m...

  13. Crystallization of amorphous Hf100-xCux alloys

    International Nuclear Information System (INIS)

    The crystallization of Hf100-xCux (x=33, 44, 50, 59) amorphous alloys was studied by the TDPAC technique. The different stages in the transformation towards equilibrium were investigated through the evolution of the quadrupole perturbation after thermal annealings. The crystallization kinetics of Hf67Cu33 and Hf56Cu44 was analyzed using the Johnson-Mehl-Avrami equation. General trends in the crystallization behavior are discussed. (orig.)

  14. Atomic simulation on evolution of nano-crystallizaion in amorphous metals

    Institute of Scientific and Technical Information of China (English)

    WANG Yu; WANG Xiu-xi; WANG Hai-long

    2006-01-01

    The deformation-induced nano-crystallization behavior of amorphous pure Ni was investigated by using a molecular dynamics simulation. The microevolution mechanism of the nano-crystallization,the crystallization process in the multicomponent amorphous Ni-Pd alloys and the temperature effect on the nano-crystallization behavior in amorphous metals were studied. The results show that the small nano-crystalline grain will nucleate and grow during the compression deformation. The deformation induces the growth of the ordered clusters in the amorphous metals and the nano-crystalline grain grows under the shearing combination and shearing deposition. The nano-crystalline grain will nucleate in a lower strain under a higher temperature. The combining severe plastic deformation with thermal annealing treatments presents a new opportunity for developing bulk nano-crystalline materials with controlled microstructures.

  15. Formation of nano-porous GeOx by de-alloying of an Al–Ge–Mn amorphous alloy

    International Nuclear Information System (INIS)

    The present study shows that nanometer-scale amorphous phase separation occurs by spinodal decomposition of the undercooled liquid in a melt-spun Al60Ge30Mn10 alloy, although there is no atomic pair with positive enthalpy of mixing. By adopting a proper de-alloying process, an interconnected nano-porous germanium oxide with an amorphous structure is successfully synthesized. The present study shows that nano-porous amorphous germanium oxide can be easily obtained by de-alloying of Al-based amorphous alloys with nm-scale composition fluctuation

  16. Structure and magnetic properties of Fe-based amorphous alloys

    Directory of Open Access Journals (Sweden)

    K. Błoch

    2013-12-01

    Full Text Available Purpose: This paper presents studies relating to the structure, magnetic properties and thermal stability of the following bulk amorphous alloys: Fe61Co10Ti3-xY6+xB20 (where x = 0 or 1 Design/methodology/approach: The investigated samples were prepared in the form of rods by using the suction-casting method. The material structures were investigated using X-ray diffractometry and Mössbauer spectroscopy. The thermal stability was determined on the basis of Differential Scanning Calorimetry (DSC plots The magnetic properties were studied using a completely automated set up for measuring susceptibility and its disaccommodation. Findings: It was found that both alloys were amorphous in the as-cast state. The DSC curve obtained for Fe61Co10Ti2Y7B20 alloy exhibited one exothermic peak, while for the Fe61Co10Ti3Y6B20 sample, two peaks were distinguishable, corresponding to the crystallization of the sample. The bifurcation of the maximum on the DSC curve for the Fe61Co10Ti3Y6B20 sample may also testify to the presence of the primary crystallizing phase (FeCo23B6 [1,2]. Data obtained from the analysis of the magnetic susceptibility disaccommodation curves clearly show that in the Fe61Co10Ti3Y6B20 alloy there is less free volumes than in the second of the investigated alloys, this results in a lesser range of relaxation time. Moreover, Fe61Co10Ti3Y6B20 alloy exhibits the better time and thermal stability of magnetic properties In both of the studied alloys, at low frequencies, the total losses were comparable with those observed in classical silicon-iron alloys. Practical implications: A Ferrometer was used for the determination of core losses. Originality/value: The paper presents some researches of the Fe-based bulk amorphous alloys obtained by the suction-casting method.

  17. Properties and atomic structure of amorphous early transition metals

    International Nuclear Information System (INIS)

    Recently, we studied the properties of amorphous Zr-TL alloys (TL = Ni, Cu) in order to obtain parameters associated with the electronic structure and interatomic bonding of amorphous Zr. Here, we provide new data for the magnetic, superconducting and mechanical properties of amorphous Hf-TL and Ti-TL alloys. We combine our results with published data in order to obtain parameters appropriate to hypothetical amorphous Hf and Ti. These parameters are very different from those of the stable crystalline phases (hcp) of Hf and Ti and indicate, as for Zr, an fcc-like short range order for amorphous Hf and Ti. This results in an enhanced electronic density of states at the Fermi level, but in weakened interatomic bonding.

  18. Effect of hydrogen on the properties of amorphous alloys 'finemet' type: PEN-X effect

    Energy Technology Data Exchange (ETDEWEB)

    Spivak, L.V.; Skryabina, N.Ye. [Perm State Univ. (Russian Federation)

    1999-09-01

    Elastic properties of the amorphous metallic alloys based on iron and cobalt were found to decrease after hydrogenation, and to recover upon subsequent storage at 295 K. The possible causes for this unusual behaviour are discussed on the basis of measurements of electrical resistance and magnetic susceptibility, as well as X-ray diffraction data.

  19. Performance of single wire earth return transformers with amorphous alloy core in a rural electric energy distribution system

    Directory of Open Access Journals (Sweden)

    Benedito Antonio Luciano

    2012-10-01

    Full Text Available In this paper are presented some considerations about the performance of single wire earth return amorphous alloy core transformers in comparison with conventional silicon steel sheets cores transformers used in rural electric energy distribution network. It has been recognized that amorphous metal core transformers improve electrical power distribution efficiency by reducing transformer core losses. This reduction is due to some electromagnetic properties of the amorphous alloys such as: high magnetic permeability, high resistivity, and low coercivity. Experimental results obtained with some single-phase, 60 Hz, 5 kVA amorphous core transformers installed in a rural area electric distribution system in Northern Brazil have been confirming their superior performance in comparison to identical nominal rated transformers built with conventional silicon steel cores, particularly with regard to the excitation power and to the no-load losses.

  20. Surface-Activated Amorphous Alloy Fuel Electrodes for Methanol Fuel Cell

    OpenAIRE

    Kawashima, Asahi; Hashimoto, Koji

    1983-01-01

    Amorphous alloy electrodes for electrochemical oxidation of methanol and its derivatives were obtained by the surface activation treatment consisting of electrodeposition of zinc on as-quenched amorphous alloy substrates, heating at 200-300℃ for 30 min, and subsequently leaching of zinc in an alkaline solution. The surface activation treatment provided a new method for the preparation of a large surface area on the amorphous alloys. The best result for oxidation of methanol, sodium formate an...

  1. A comparative study of the structure and crystallization of bulk metallic amorphous rod Pr60Ni30Al10 and melt-spun metallic amorphous ribbon Al87Ni10Pr3

    Institute of Scientific and Technical Information of China (English)

    Meng Qing-Ge; Li Jian-Guo; Zhou Jian-Kun

    2006-01-01

    Pr-based bulk metallic amorphous (BM1 rods (Pr60Ni30Al10) and Al-based amorphous ribbons (Al87Ni10Pr3)have been prepared by using copper mould casting and single roller melt-spun techniques, respectively. Thermal parameters deduced from differential scanning calorimeter (DS3 indicate that the glass-forming ability (GF1 of Pr60Nia0Al10 BMA rod is far higher than that of Al87Ni10Pr3 ribbon. A comparative study about the differences in structure between the two kinds of glass-forming alloys, superheated viscosity and crystallization are also made. Compared with the amorphous alloy Al87Ni10Pr3, the BMA alloy Pr60Ni30Al10 shows high thermal stability and large viscosity, small diffusivity at the same superheated temperatures. The results of x-Ray diffraction (XRD) and transmission electron microscope (TEM) show the pronounced difference in structure between the two amorphous alloys.Together with crystallization results, the main structure compositions of the amorphous samples are confirmed. It seems that the higher the GFA, the more topological type clusters in the Pr-Ni-Al amorphous alloys, the GFAs of the present glass-forming alloys are closely related to their structures.

  2. The corrosion resistance and neutron-absorbing properties of coatings based on amorphous alloys

    Science.gov (United States)

    Sevryukov, O. N.; Polyansky, A. A.

    2016-04-01

    The object of the present study was the corrosion-resistant amorphizing alloys with an increased content of boron for cladding the surface of metals, rapidly quenched alloys without boron for protective coatings on a high-boron cladding layer, as well as steel samples with a protective coating with a high content of boron and without boron. The aim of the work is to investigate the corrosion resistance of a coating in water at the temperature of 40 °C in conditions of an open access of oxygen for 1000 h, as well as the features of the microstructure of clad samples before and after the corrosion tests. New data on the corrosion resistance of Cr18Ni10Ti steel samples with a protective layer from a rapidly quenched alloy Ni-19Cr-10Si (in wt.%) on a high-boron coating have been obtained.

  3. Control and optimization of baths for electrodeposition of Co-Mo-B amorphous alloys

    Directory of Open Access Journals (Sweden)

    S. Prasad

    2000-12-01

    Full Text Available Optimization and control of an electrodeposition process for depositing boron-containing amorphous metallic layer of cobalt-molybdenum alloy onto a cathode from an electrolytic bath having cobalt sulfate, sodium molybdate, boron phosphate, sodium citrate, 1-dodecylsulfate-Na, ammonium sulfate and ammonia or sulfuric acid for pH adjustments has been studied. Detailed studies on bath composition, pH, temperature, mechanical agitation and cathode current density have led to optimum conditions for obtaining satisfactory alloy deposits. These alloys were found to have interesting properties such as high hardness, corrosion resistance, wear resistance and also sufficient ductility. A voltammetric method for automatic monitoring and control of the process has been proposed.

  4. Bonding tungsten, W–Cu-alloy and copper with amorphous Fe–W alloy transition

    International Nuclear Information System (INIS)

    W/Cu graded materials are the leading candidate materials used as the plasma facing components in a fusion reactor. However, tungsten and copper can hardly be jointed together due to their great differences in physical properties such as coefficient of thermal expansion and melting point, and the lack of solid solubility between them. To overcome those difficulties, a new amorphous Fe–W alloy transitional coating and vacuum hot pressing (VHP) method were proposed and introduced in this paper. The morphology, composition and structure of the amorphous Fe–W alloy coating and the sintering interface of the specimens were analyzed by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). The thermal shock resistance of the bonded composite was also tested. The results demonstrated that amorphous structure underwent change from amorphous to nano grains during joining process, and the joined W/Cu composite can endued plasma thermal shock resistance with energy density more than 5.33 MW/m2. It provides a new feasible technical to join refractory tungsten to immiscible copper with amorphous Fe–W alloy coating

  5. Crystallization kinetics of Fe based amorphous alloy

    Science.gov (United States)

    Shanker Rao, T.; Lilly Shanker Rao, T.

    2015-02-01

    Differential Scanning Calorimetry(DSC) experimental data under non-isothermal conditions for Fe based Metglas 2605SA1 (wt% Fe=85-95, Si=5-10, B=1-5) metallic glass ribbons are reported and discussed. The DSC Scans performed at different heating rates showed two step crystallization processes and are interpreted in terms of different models like Kissinger, Ozawa, Boswell, Augis & Bennett and Gao & Wang. From the heating rate dependence of the onset temperature (To) and the crystallization peak temperature (Tp), the kinetic triplet, activation energy of crystallization (E), Avrami exponent (n) and the frequency factor (A) are determined. The determined E for peak I is 354.5 ± 2.5 kJ/mol and for the peak II is 348.2 ± 2.2 kJ/mol, respectively. The frequency factor for peak I is 1.1 × 1023sec-1 and for peak II is 6.1 × 1020sec-1.

  6. Amorphous magnetism in Mnx Sn1-x alloys

    International Nuclear Information System (INIS)

    Systematic low temperature in situ 119Sn Moessbauer effect (ME) studies in vapor quenched amorphous Mnx Sn1-x (0.09≤ x ≤0,95) alloys between 150 and 4.2 K, are presented. Its is shown that the magnetic behavior of the system is correctly displayed by the transferred magnetic hyperfine (hf) interactions, at the 119Sn site. A complete magnetic phase diagram is proposed, and the effect of an external magnetic field (up to about 3T) on the spin correlations in the spin-glass state is also discussed. (author)

  7. PREFACE: 13th International Conference on Liquid and Amorphous Metals

    Science.gov (United States)

    Popel, Pjotr; Gelchinskii, Boris; Sidorov, Valeriy; Son, Leonid; Sabirzjanov, Alexandre

    2007-06-01

    The state of the art in the field of liquid and amorphous metals and alloys is regularly updated through two series of complementary international conferences, the LAM (Liquid and Amorphous Metals) and the RQ (Rapidly Quenched Materials). The first series of the conferences started as LM-1 in 1966 at Brookhaven for the basic understanding of liquid metals. The subsequent LM conferences were held in Tokyo (1972) and Bristol (1976). The conference was renewed in Grenoble (1980) as a LAM conference including amorphous metals and continued in Los Angeles (1983), Garmisch-Partenkirchen (1986), Kyoto (1989), Vienna (1992), Chicago (1995), Dortmund (1998), Yokohama (2001) and Metz (2004). The conferences are mainly devoted to liquid and amorphous metals and alloys. However, communications on some non-metallic systems such as semi conductors, quasicrystals etc, were accepted as well. The conference tradition strongly encourages the participation of junior researchers and graduate students. The 13th conference of the LAM series was organized in Ekaterinburg, Russia, by the Institute of Metallurgy of the Ural Branch of the Russian Academy of Sciences (IMet UB RAS) and Ural State Pedagogical University (USPU) and held on 8-13 July 2007 under the chairmanship of Professors Pjotr Popel (USPU) and Boris Gelchinskii (IMet UB RAS). There were 242 active and about 60 guest participants from 20 countries who attended the conference. There were no parallel sessions and all oral reports were separated into three groups: invited talks (40 min), full-scale (25 min) and brief (15 min) oral reports. The program included 10 sessions, ranging from purely theoretical subjects to technological application of molten and amorphous alloys. The following sessions took place: A) Electronic structure and transport, magnetic properties; B) Phase transitions; C) Structure; D) Atomic dynamics and transport; E) Thermodynamics; F) Modelling, simulation; G) Surface and interface; H) Mechanical properties

  8. Extraction of valuable metals from amorphous solid wastes

    OpenAIRE

    E. David

    2007-01-01

    Purpose: This paper undertakes to assess what opportunities exist for the economical recovery of valuable metals from amorphous solid wastes that may be considered as“synthetic ores”. Also, this work is an attempt to optimize a leaching process that is the most determinant step of hydrometallurgical process used to extract metals from ores.Design/methodology/approach: The samples of amorphous material formed from spent industrial catalysts based on Cu, Ni / γ-Al2O3 were physically and ...

  9. Amorphous mixed-metal hydroxide nanostructures for advanced water oxidation catalysts

    Science.gov (United States)

    Gao, Y. Q.; Liu, X. Y.; Yang, G. W.

    2016-02-01

    The design of highly efficient, durable, and earth-abundant catalysts for the oxygen evolution reaction (OER) is crucial in order to promote energy conversion and storage processes. Here, we synthesize amorphous mixed-metal (Ni-Fe) hydroxide nanostructures with a homogeneous distribution of Ni/Fe as well as a tunable Ni/Fe ratio by a simple, facile, green and low-cost electrochemical technique, and we demonstrate that the synthesized amorphous nanomaterials possess ultrahigh activity and super long-term cycle stability in the OER process. The amorphous Ni0.71Fe0.29(OH)x nanostructure affords a current density of 10 mA cm-2 at an overpotential of a mere 0.296 V and a small Tafel slope of 58 mV dec-1, while no deactivation is detected in the CV testing even up to 30 000 cycles, which suggests the promising application of these amorphous nanomaterials in electrochemical oxidation. Meanwhile, the distinct catalytic activities among these amorphous Ni-Fe hydroxide nanostructures prompts us to take notice of the composition of the alloy hydroxides/oxides when studying their catalytic properties, which opens an avenue for the rational design and controllable preparation of such amorphous nanomaterials as advanced OER electrocatalysts.The design of highly efficient, durable, and earth-abundant catalysts for the oxygen evolution reaction (OER) is crucial in order to promote energy conversion and storage processes. Here, we synthesize amorphous mixed-metal (Ni-Fe) hydroxide nanostructures with a homogeneous distribution of Ni/Fe as well as a tunable Ni/Fe ratio by a simple, facile, green and low-cost electrochemical technique, and we demonstrate that the synthesized amorphous nanomaterials possess ultrahigh activity and super long-term cycle stability in the OER process. The amorphous Ni0.71Fe0.29(OH)x nanostructure affords a current density of 10 mA cm-2 at an overpotential of a mere 0.296 V and a small Tafel slope of 58 mV dec-1, while no deactivation is detected in the CV

  10. Local order dynamics: its application to the study of atomic mobility, of point defects in crystalline alloys, and of structural relaxation in amorphous alloys

    International Nuclear Information System (INIS)

    This research thesis addressed the study of the atomic mobility mechanism and of the atom movement dynamics in the case of crystalline alloys and of amorphous alloys. The first part is based on a previous study performed on an α-Cu70-Zn30 crystalline alloy, and addresses the case of an α-Au70-Ni30 alloy. The specificity of this case relies in the fact that the considered solid solution is metastable and susceptible to de-mixing in the considered temperature range. This case of off-equilibrium crystalline alloy is at the crossroad between steady crystalline alloys and metallic glasses which are studied in the second part. The third part addresses the irradiation of metallic amorphous alloys by fast particles (neutrons or electrons). The author tried to characterise atomic defects induced by irradiation and to compare them with pre-existing ones. He studied how these defects may change atomic mobility, and, more generally, to which extent the impact of energetic particles could modify local order status

  11. Synthesis and characterization of Mg-based amorphous alloys and their use for decolorization of Azo dyes

    International Nuclear Information System (INIS)

    Mg-based alloys are light weight and have wide range of applications in the automotive industry. These alloys are widely used because of their very attractive physical and mechanical properties and corrosion resistance. The properties and applications can be further improved by changing the nature of materials from crystalline to amorphous. In this study, melt spun ribbons (MSRs) of Mg70Zn25Ca5 Mg68Zn27Ca5 alloys were prepared by melt spinning technique by using 3-4N pure metals. Characterization of the samples was done by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and energy dispersive x-ray analyzer (EDAX). Microstructural investigations were conducted by using scanning electron microscopy (SEM), atomic force microscopy (AFM) as well as optical and stereo scan microscopy techniques. DSC results showed multistage crystallization. Activation energy was found to be 225 kJ/mol by Kissinger method indicating good thermal stability against crystallization. XRD, DSC, SEM and EDS (energy dispersive spectroscopy) results are agreed very well. In order to study decolorization, the MSRs of Mg70Zn25Ca5 Mg68Zn27Ca5 alloys were treated repeatedly with various azo dyes at room temperature. In order to compare the results, MSRs of amorphous Zr- and Ni-based metallic glasses were also treated. Reaction of MSRs with azo dyes results in their decolorization in a few hours. Decolorization of azo dyes takes place by introducing amorphous MSRs which results in breaking the -N=N- bonds that exist in dye contents. It is concluded that Mg-based alloys are useful for paint and dye industries and will be beneficial to control water pollution. Comparison of results showed that Mg-based alloys are more efficient than Zr- and Ni-based amorphous alloys for decolorization of azo dyes

  12. Synthesis and characterization of Mg-based amorphous alloys and their use for decolorization of Azo dyes

    International Nuclear Information System (INIS)

    Mg-based alloys are light weight and have wide range of applications in the automotive industry. These alloys are widely used because of their very attractive physical and mechanical properties and corrosion resistance. The properties and applications can be further improved by changing the nature of materials from crystalline to amorphous. In this study, melt spun ribbons (MSRs) of Mg/sub 70/Zn/sub 25/Ca/sub 5/ Mg/sub 68/Zn/sub 27/Ca/sub 5/ alloys were prepared by melt spinning technique by using 3-4N pure metals. Characterization of the samples was done by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and energy dispersive x-ray analyzer (EDAX). Microstructural investigations were conducted by using scanning electron microscopy (SEM), atomic force microscopy (AFM) as well as optical and stereo scan microscopy techniques. DSC results showed multistage crystallization. Activation energy was found to be 225 kJ/mol by Kissinger method indicating good thermal stability against crystallization. XRD, DSC, SEM and EDS (energy dispersive spectroscopy) results are agreed very well. In order to study decolorization, the MSRs of Mg/sub 70/Zn/sub 25/Ca/sub 5/ Mg/sub 68/Zn/sub 27/Ca/sub 5/ alloys were treated repeatedly with various azo dyes at room temperature. In order to compare the results, MSRs of amorphous Zr- and Ni-based metallic glasses were also treated. Reaction of MSRs with azo dyes results in their decolorization in a few hours. Decolorization of azo dyes takes place by introducing amorphous MSRs which results in breaking the -N=N- bonds that exist in dye contents. It is concluded that Mg-based alloys are useful for paint and dye industries and will be beneficial to control water pollution. Comparison of results showed that Mg-based alloys are more efficient than Zr- and Ni-based amorphous alloys for decolorization of azo dyes. (author)

  13. Amorphous Metals for Opto-Mechanical Fixtures and Mechanisms Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The new JPL Metallurgy Facility is a small-scale foundry-type laboratory with capabilities for fabricating new metal alloys and metal-matrix-composites, casting...

  14. Formation and thermal stability of amorphous Ni-Mo-P alloys

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yi; MA Jun; FANG Yong-kui; DUAN Ji-guo

    2004-01-01

    The experimental researches on the chemical deposition of Ni-Mo-P amorphous alloys were carried out by adding Na2 MoO4 into acidic solutions. The optimum technology conditions were obtained by orthogonal design experiments. The structures and the relationship between compositions and their thermal stability were studied by energy spectrum (EC), scanning electron micrograph and X-ray diffraction spectrum. Compared with Ni-P amorphous alloys, the Ni-Mo-P amorphous alloys have high crystallization temperature and thermal stability, and the hardness reaches its peak when the annealing temperature is 500 ℃. With the increase of the heat treatment temperature, the surface morphology of the alloys changes.

  15. Kinetics of crystallization of a Fe-based multicomponent amorphous alloy

    Indian Academy of Sciences (India)

    Arun Pratap; T Lilly Shanker Rao; Kinnary Patel; Mukesh Chawda

    2009-10-01

    The Fe-based multicomponent amorphous alloys (also referred to as metallic glasses) are known to exhibit soft magnetic properties and, it makes them important for many technological applications. However, metallic glasses are in a thermodynamically metastable state and in case of high temperature operating conditions, the thermally activated crystallization would be detrimental to their magnetic properties. The study of crystallization kinetics of metallic glasses gives useful insight about its thermal stability. In the present work, crystallization study of Fe67Co18B14Si1 (2605CO) metallic glass has been carried out using differential scanning calorimetry (DSC) technique. Mössbauer study has also been undertaken to know the phases formed during the crystallization process. The alloy shows two-stage crystallization. The activation energy has been derived using the Kissinger method. It is found to be equal to 220 kJ/mol and 349 kJ/mol for the first and second crystallization peaks, respectively. The Mössbauer study indicates the formation of -(Fe, Co) and (Fe, Co)3B phases in the alloy.

  16. Processing and characterization of amorphous magnesium based alloy for application in biomedical implants

    Directory of Open Access Journals (Sweden)

    Telma Blanco Matias

    2014-07-01

    Full Text Available Magnesium-based bulk metallic glasses are attractive due to their single-phase, chemically homogeneous alloy system and the absence of second-phase, which could impair the mechanical properties and corrosion resistance. However, one of the unsolved problems for the manufacturability and the applications of bulk metallic glasses is that their glass-forming ability is very sensitive to the preparation techniques and impurity of components since oxygen in the environment would markedly deteriorate the glass-forming ability. Therefore, the aim of this study was to establish proper processing conditions to obtain a magnesium-based amorphous ternary alloy and its characterization. The final composition was prepared using two binary master alloys by melting in an induction furnace. Carbon steel crucible was used in argon atmosphere with and without addition of SF6 gas in order to minimize the oxygen contamination. The microstructure, amorphous nature, thermal properties and chemical analysis of samples were investigated by scanning electron microscopy (SEM, X-ray diffraction (XRD, differential scanning calorimetry (DSC and inductively coupled plasma emission spectrometry, respectively. The oxygen content of the as-cast samples was chemically analyzed by using carrier gas hot extraction (O/N Analyzer TC-436/LECO and was kept bellow 25 ppm (without SF6 and 10 ppm (with SF6. Bulk samples were produced by rapid cooling in a cooper mold until 1.5 mm thickness, with amorphous structures being observed up to 2.5 mm.

  17. Metal Dusting of Heat-Resistant Alloys

    OpenAIRE

    Al-Meshari, Abdulaziz I.

    2008-01-01

    Metal dusting leads to disintegration of such alloys as iron and nickel-based into a ?dust? of particulate metal, metal carbide, carbon, and/or oxide. It occurs in strongly carburising environments at 400-900?C. Literature survey has shown that alloys behave differently in metal dusting conditions based on their composition and the environment. Metal dusting mechanisms for iron and nickel-based alloys have been proposed but, nevertheless, have not been agreed upon and numerous modifications t...

  18. Discontinuous structural phase transition of liquid metal and alloys (2)

    International Nuclear Information System (INIS)

    The diameter (df) of diffusion fluid cluster before and after phase transition has been calculated in terms of the paper ''Discontinuous structural phase transition of liquid metal and alloy (1)'' Physics Letters. A 326 (2004) 429-435, to verify quantitatively the discontinuity of structural phase transition; the phenomena of thermal contraction and thermal expansion during the phase transition, together with the evolution model of discontinuous structural phase transition are also discussed in this Letter to explore further the nature of structural transition; In addition, based on the viscosity experimental result mentioned in paper [Y. Waseda, The Structure of Non-Crystalline Materials--Liquids and Amorphous Solids, McGraw-Hill, New York, 1980], we present an approach to draw an embryo of the liquid-liquid (L-L) phase diagram for binary alloys above liquidus in the paper, expecting to guide metallurgy process so as to improve the properties of alloys. The idea that controls amorphous structure and its properties by means of the L-L phase diagram for alloys and by the rapid cooling technique to form the amorphous alloy has been brought forward in the end

  19. Impact Ignition and Combustion Behavior of Amorphous Metal-Based Reactive Composites

    Science.gov (United States)

    Mason, Benjamin; Groven, Lori; Son, Steven

    2013-06-01

    Recently published molecular dynamic simulations have shown that metal-based reactive powder composites consisting of at least one amorphous component could lead to improved reaction performance due to amorphous materials having a zero heat of fusion, in addition to having high energy densities and potential uses such as structural energetic materials and enhanced blast materials. In order to investigate the feasibility of these systems, thermochemical equilibrium calculations were performed on various amorphous metal/metalloid based reactive systems with an emphasis on commercially available or easily manufactured amorphous metals, such as Zr and Ti based amorphous alloys in combination with carbon, boron, and aluminum. Based on the calculations and material availability material combinations were chosen. Initial materials were either mixed via a Resodyn mixer or mechanically activated using high energy ball milling where the microstructure of the milled material was characterized using x-ray diffraction, optical microscopy and scanning electron microscopy. The mechanical impact response and combustion behavior of select reactive systems was characterized using the Asay shear impact experiment where impact ignition thresholds, ignition delays, combustion velocities, and temperatures were quantified, and reported. Funding from the Defense Threat Reduction Agency (DTRA), Grant Number HDTRA1-10-1-0119. Counter-WMD basic research program, Dr. Suhithi M. Peiris, program director is gratefully acknowledged.

  20. Low-Temperature Annealing Induced Amorphization in Nanocrystalline NiW Alloy Films

    Directory of Open Access Journals (Sweden)

    Z. Q. Chen

    2013-01-01

    Full Text Available Annealing induced amorphization in sputtered glass-forming thin films was generally observed in the supercooled liquid region. Based on X-ray diffraction and transmission electron microscope (TEM analysis, however, here, we demonstrate that nearly full amorphization could occur in nanocrystalline (NC sputtered NiW alloy films annealed at relatively low temperature. Whilst the supersaturation of W content caused by the formation of Ni4W phase played a crucial role in the amorphization process of NiW alloy films annealed at 473 K for 30 min, nearly full amorphization occurred upon further annealing of the film for 60 min. The redistribution of free volume from amorphous regions into crystalline regions was proposed as the possible mechanism underlying the nearly full amorphization observed in NiW alloys.

  1. Bonding theory for metals and alloys

    CERN Document Server

    Wang, Frederick E

    2005-01-01

    Bonding Theory for Metals and Alloys exhorts the potential existence of covalent bonding in metals and alloys. Through the recognition of the covalent bond in coexistence with the 'free' electron band, the book describes and demonstrates how the many experimental observations on metals and alloys can all be reconciled. Subsequently, it shows how the individual view of metals and alloys by physicists, chemists and metallurgists can be unified. The physical phenomena of metals and alloys covered in this book are: Miscibility Gap between two liquid metals; Phase Equilibrium Diagrams; Phenomenon of Melting. Superconductivity; Nitinol; A Metal-Alloy with Memory; Mechanical Properties; Liquid Metal Embrittlement; Superplasticity; Corrosion; The author introduces a new theory based on 'Covalon' conduction, which forms the basis for a new approach to the theory of superconductivity. This new approach not only explains the many observations made on the phenomenon of superconductivity but also makes predictions that ha...

  2. Soft magnetic amorphous Fe-Zr-Si(Cu) boron-free alloys

    International Nuclear Information System (INIS)

    Research highlights: → Amorphous Fe-Zr-Si(Cu) boron-free alloys were prepared by melt quenching. → Soft magnetic properties were investigated by the specialized rf-Moessbauer technique. → Dependence of coercivity and magnetization on alloy compositions was determined. - Abstract: Amorphous Fe80ZrxSi20-x-yCuy boron-free alloys, in which boron was completely replaced by silicon as a glass forming element, have been prepared in the form of ribbons by using the melt quenching technique. X-ray diffraction and Moessbauer spectroscopy measurements revealed that the as-quenched ribbons with the compositions with x = 6-10 at.% and y = 0, 1 at.% are fully or predominantly amorphous. Differential scanning calorimetry (DSC) measurements allowed the estimation of crystallization temperatures of the amorphous alloys. Soft magnetic properties have been studied by the specialized rf-Moessbauer technique. Since the rf-collapse effect observed is very sensitive to the local anisotropy fields it was possible to evaluate the soft magnetic properties of the amorphous alloys studied. The rf-Moessbauer studies were accompanied by conventional measurements of hysteresis loops from which the magnetization and coercive fields were estimated. It was found that amorphous Fe-Zr-Si(Cu) alloys are magnetically very soft, comparable with those of the conventional amorphous B-containing Fe-based alloys.

  3. Radiation Resistance Studies of Amorphous Silicon Alloy Photovoltaic Materials

    Science.gov (United States)

    Woodyard, James R.

    1994-01-01

    The radiation resistance of commercial solar cells fabricated from hydrogenated amorphous silicon alloys was investigated. A number of different device structures were irradiated with 1.0 MeV protons. The cells were insensitive to proton fluences below 1E12 sq cm. The parameters of the irradiated cells were restored with annealing at 200 C. The annealing time was dependent on proton fluence. Annealing devices for one hour restores cell parameters for fluences below lE14 sq cm require longer annealing times. A parametric fitting model was used to characterize current mechanisms observed in dark I-V measurements. The current mechanisms were explored with irradiation fluence, and voltage and light soaking times. The thermal generation current density and quality factor increased with proton fluence. Device simulation shows the degradation in cell characteristics may be explained by the reduction of the electric field in the intrinsic layer.

  4. The preparation of well-dispersed Ni-B amorphous alloy nanoparticles at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Wen Ming [Department of Chemistry, Tongji University, Shanghai 200092 (China)], E-mail: m_wen@mail.tongji.edu.cn; Li Lujiang; Liu Qiuyan; Qi Haiquan [Department of Chemistry, Tongji University, Shanghai 200092 (China); Zhang Tao [Department of Materials Science and Engineering, Beijing University of Aeronaut and Astronaut, Beijing 100083 (China)

    2008-05-08

    The air-stable well-dispersed Ni-B amorphous alloy nanoparticles in the similar size of 5 nm with narrow deviation were prepared by a chemical solution alloying process at room temperature in a positive microemulsion system. The proposed interface reaction mechanism, element analysis and thermal stability as well as the magnetic behavior of Ni-B amorphous alloy nanoparticles were characterized by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), infrared spectroscopy (IR), differential scanning calorimetry (DSC) and vibrating sample magnetometer (VSM). All the results showed that as synthesized Ni-B amorphous alloy nanoparticles are air-stable in room temperature and coated by macromolecular compound oleic acid. The magnetic property of the as synthesized Ni-B amorphous alloy was discussed based on the obtained results.

  5. Density of states in Mo-Ru amorphous alloys

    International Nuclear Information System (INIS)

    The density of states is calculated for several compositions of amorphous Mo1-x Rux. In order to simulate amorphous clusters, the structures (atomic positions) utilized in the calculations were built from a small dense randomly packed unit of hard spheres with periodic boundary conditions. The density of states is calculated from a tight-binding Hamiltonian with hopping integrals parametrized in terms of the ddσ, ddΠ and ddδ molecular integrals. The results for pure Mo and pure Ru, compared in the canonical band aproximation, agree well with the literature. For binary alloys, the comparison of the calculated density of states with the rigid band aproximation results indicates that a more complex approach than the rigid band model must be used, even when the two atoms have similar bands, with band centers at nearly the same energy. The results also indicate that there is no relation between the peak in the superconducting critical temperature as a function of the number of valence eletrons per atom (e/a) in the region near Mo(e/a=6) and the peak of the density of states at the Fermi level in the same region, as has been sugested by some authors. (Author)

  6. Oxygen Behavior in Bulk Amorphous Zr-base Alloy

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Bulk Zr55Al10Ni5Cu30 metallic glass plates with a dimension of 85 mm×35mm×4 mm and a complicated plate werefabricated by injecting casting method using spongy zirconium and industrial purity aluminum, nickel and copper asraw materials. It was shown that the holding time of liquid metals at elevated temperatures had a great influence onthe oxygen content of the plates due to the contamination resulting from the atmosphere. Increasing holding timeresulted in the increase of oxygen content in the injected alloy. The glass transition temperatures of the bulk metallicglass plates are higher than that reported in the literature and crystallization temperature is lower for the one withhigher oxygen content at the same heating rate. The extension of the undercooled liquid region △Tx reaching about87 K is 3 K higher than that previously reported and 26 K higher than that with oxygen content of 0.076 wt pct forthe one with oxygen content as high as 0.065 wt pct. Therefore the oxygen content of the alloy has a significantinfluence on the glass forming ability and thermal stability of bulk metal glass. It is suggested that direct correlationbetween high glass forming ability and large △Tx is only valid for a well-defined Iow oxygen concentration or has tobe reconsidered by incorporating oxygen as an additional alloying element.

  7. Amorphous metal distribution transformers: The energy-efficient alternative

    Energy Technology Data Exchange (ETDEWEB)

    Garrity, T.F. [GE Power Systems, Schenectady, NY (United States)

    1994-12-31

    Amorphous metal distribution transformers have been commercially available for the past 13 years. During that time, they have realized the promise of exceptionally high core efficiency as compared to silicon steel transformer cores. Utility planners today must consider all options available to meet the requirements of load growth. While additional generation capacity will be added, many demand-side initiatives are being undertaken as complementary programs to generation expansion. The efficiency improvement provided by amorphous metal distribution transformers deserves to be among the demand-side options. The key to understanding the positive impact of amorphous metal transformer efficiency is to consider the aggregate contribution those transformers can make towards demand reduction. It is estimated that distribution transformer core losses comprise at least 1% of the utility`s peak demand. Because core losses are continuous, any significant reduction in their magnitude is of great significance to the planner. This paper describes the system-wide economic contributions amorphous metal distribution transformers can make to a utility and suggests evaluation techniques that can be used. As a conservation tool, the amorphous metal transformer contributes to reduced power plant emissions. Calibration of those emissions reductions is also discussed in the paper.

  8. Effects of superimposed hydrostatic pressure on flow and fracture of a Zr-Ti-Ni-Cu-Be bulk amorphous alloy

    International Nuclear Information System (INIS)

    Recent successes in producing bulk amorphous alloys have renewed interest in this class of materials. Although amorphous metallic alloys have been shown to exhibit strengths in excess of 2.0 GPa, most of the earlier studies on such materials were conducted on tape or ribbon specimens due to the high cooling rates required to achieve the amorphous structure. The primary purpose of this investigation was to determine the effects of superimposed hydrostatic pressure on the flow and fracture behavior of a Zr-Ti-Ni-Cu-Be bulk metallic glass utilizing procedures successfully utilized on a range of structural materials, as reviewed recently. In general, few studies of this type have been conducted on metallic glasses, although thin ribbons (i.e., 300 microm thick) of a Pd-Cu-Si amorphous material tested with superimposed pressure have been reported previously. In particular, the effects of superimposed hydrostatic pressure over levels ranging from 50 MPa to 575 MPa on the flow/fracture behavior of cylindrical tensile specimens were compared to the flow and fracture behavior of identical materials tested in uniaxial tension and compression. It is shown that changes in stress triaxiality, defined as σm/bar σ, over the range of -0.33 to 0.33 produced a negligible effect on the fracture stress and fracture strain, while the orientation of the macroscopic fracture plane with respect to the loading axis was significantly affected by changes in σm/bar σ

  9. Pressure effects on Al89La6Ni5 amorphous alloy crystallization

    DEFF Research Database (Denmark)

    Zhuang, Yanxin; Jiang, Jianzhong; Zhou, T. J.;

    2000-01-01

    The pressure effect on the crystallization of the Al89La6Ni5 amorphous alloy has been investigated by in situ high-pressure and high-temperature x-ray powder diffraction using synchrotron radiation. The amorphous alloy crystallizes in two steps in the pressure range studied (0-4 GPa). The first......(s). The applied pressure strongly affects the crystallization processes of the amorphous alloy. Both temperatures first decrease with pressure in the pressure range of 0-1 GPa and then increase with pressure up to 4 GPa. The results are discussed with reference to competing processes between the thermodynamic...

  10. Iron-Based Amorphous Metals:The High Performance Corrosion Resistant Materials(HPCRM) Program

    Energy Technology Data Exchange (ETDEWEB)

    Farmer, J

    2007-07-09

    An overview of the High-Performance Corrosion-Resistant Materials (HPCRM) Program, which was co-sponsored by the Defense Advanced Research Projects Agency (DARPA) Defense Sciences Office (DSO) and the United States Department of Energy (DOE) Office of Civilian and Radioactive Waste Management (OCRWM), is discussed. Programmatic investigations have included a broad range of topics: alloy design and composition; materials synthesis; thermal stability; corrosion resistance; environmental cracking; mechanical properties; damage tolerance; radiation effects; and important potential applications. Amorphous alloys identified as SAM2X5 (Fe{sub 49.7}Cr{sub 17.7}Mn{sub 1.9}Mo{sub 7.4}W{sub 1.6}B{sub 15.2}C{sub 3.8}Si{sub 2.4}) and SAM1651 (Fe{sub 48}Mo{sub 14}Cr{sub 15}Y{sub 2}C{sub 15}B{sub 6}) have been produced as melt-spun ribbons, drop-cast ingots and thermal-spray coatings. Chromium (Cr), molybdenum (Mo) and tungsten (W) additions provided corrosion resistance, while boron (B) enabled glass formation. Earlier electrochemical studies of melt-spun ribbons and ingots of these amorphous alloys demonstrated outstanding passive film stability. More recently thermal-spray coatings of these amorphous alloys have been made and subjected to long-term salt-fog and immersion tests. Good corrosion resistance has been observed during salt-fog testing. Corrosion rates were measured in situ with linear polarization, while simultaneously monitoring the open-circuit corrosion potentials. Reasonably good performance was observed. The sensitivity of these measurements to electrolyte composition and temperature was determined. The high boron content of this particular amorphous metal makes this amorphous alloy an effective neutron absorber, and suitable for criticality control applications. In general, the corrosion resistance of such iron-based amorphous metals is maintained at operating temperatures up to the glass transition temperature. These materials are much harder than conventional

  11. Iron-Based Amorphous-Metals: High-Performance Corrosion-Resistant Material (HPCRM) Development

    Energy Technology Data Exchange (ETDEWEB)

    Farmer, J C; Choi, J S; Saw, C; Haslam, J; Day, D; Hailey, P; Lian, T; Rebak, R; Perepezko, J; Payer, J; Branagan, D; Beardsley, B; D' Amato, A; Aprigliano, L

    2008-01-09

    An overview of the High-Performance Corrosion-Resistant Materials (HPCRM) Program, which was co-sponsored by the Defense Advanced Research Projects Agency (DARPA) Defense Sciences Office (DSO) and the United States Department of Energy (DOE) Office of Civilian and Radioactive Waste Management (OCRWM), is discussed. Programmatic investigations have included a broad range of topics: alloy design and composition; materials synthesis; thermal stability; corrosion resistance; environmental cracking; mechanical properties; damage tolerance; radiation effects; and important potential applications. Amorphous alloys identified as SAM2X5 (Fe{sub 49.7}Cr{sub 17.7}Mn{sub 1.9}Mo{sub 7.4}W{sub 1.6}B{sub 15.2}C{sub 3.8}Si{sub 2.4}) and SAM1651 (Fe{sub 48}Mo{sub 14}Cr{sub 15}Y{sub 2}C{sub 15}B{sub 6}) have been produced as melt-spun ribbons, drop-cast ingots and thermal-spray coatings. Chromium (Cr), molybdenum (Mo) and tungsten (W) additions provided corrosion resistance, while boron (B) enabled glass formation. Earlier electrochemical studies of melt-spun ribbons and ingots of these amorphous alloys demonstrated outstanding passive film stability. More recently thermal-spray coatings of these amorphous alloys have been made and subjected to long-term salt-fog and immersion tests. Good corrosion resistance has been observed during salt-fog testing. Corrosion rates were measured in situ with linear polarization, while simultaneously monitoring the open-circuit corrosion potentials. Reasonably good performance was observed. The sensitivity of these measurements to electrolyte composition and temperature was determined. The high boron content of this particular amorphous metal makes this amorphous alloy an effective neutron absorber, and suitable for criticality control applications. In general, the corrosion resistance of such iron-based amorphous metals is maintained at operating temperatures up to the glass transition temperature. These materials are much harder than conventional

  12. Iron-Based Amorphous Metals:The High Performance Corrosion Resistant Materials(HPCRM) Program

    International Nuclear Information System (INIS)

    An overview of the High-Performance Corrosion-Resistant Materials (HPCRM) Program, which was co-sponsored by the Defense Advanced Research Projects Agency (DARPA) Defense Sciences Office (DSO) and the United States Department of Energy (DOE) Office of Civilian and Radioactive Waste Management (OCRWM), is discussed. Programmatic investigations have included a broad range of topics: alloy design and composition; materials synthesis; thermal stability; corrosion resistance; environmental cracking; mechanical properties; damage tolerance; radiation effects; and important potential applications. Amorphous alloys identified as SAM2X5 (Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4) and SAM1651 (Fe48Mo14Cr15Y2C15B6) have been produced as melt-spun ribbons, drop-cast ingots and thermal-spray coatings. Chromium (Cr), molybdenum (Mo) and tungsten (W) additions provided corrosion resistance, while boron (B) enabled glass formation. Earlier electrochemical studies of melt-spun ribbons and ingots of these amorphous alloys demonstrated outstanding passive film stability. More recently thermal-spray coatings of these amorphous alloys have been made and subjected to long-term salt-fog and immersion tests. Good corrosion resistance has been observed during salt-fog testing. Corrosion rates were measured in situ with linear polarization, while simultaneously monitoring the open-circuit corrosion potentials. Reasonably good performance was observed. The sensitivity of these measurements to electrolyte composition and temperature was determined. The high boron content of this particular amorphous metal makes this amorphous alloy an effective neutron absorber, and suitable for criticality control applications. In general, the corrosion resistance of such iron-based amorphous metals is maintained at operating temperatures up to the glass transition temperature. These materials are much harder than conventional stainless steel and nickel-based materials, and are proving to have excellent wear

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

    Science.gov (United States)

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

    2009-06-01

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

  14. Crystallization kinetics and magnetic properties of FeSiCr amorphous alloy powder cores

    Science.gov (United States)

    Xu, Hu-ping; Wang, Ru-wu; Wei, Ding; Zeng, Chun

    2015-07-01

    The crystallization kinetics of FeSiCr amorphous alloy, characterized by the crystallization activation energy, Avrami exponent and frequency factor, was studied by non-isothermal differential scanning calorimetric (DSC) measurements. The crystallization activation energy and frequency factor of amorphous alloy calculated from Augis-Bennett model were 476 kJ/mol and 5.5×1018 s-1, respectively. The Avrami exponent n was calculated to be 2.2 from the Johnson-Mehl-Avrami (JMA) equation. Toroid-shaped Fe-base amorphous powder cores were prepared from the commercial FeSiCr amorphous alloy powder and subsequent cold pressing using binder and insulation. The characteristics of FeSiCr amorphous alloy powder and the effects of compaction pressure and insulation content on the magnetic properties, i.e., effective permeability μe, quality factor Q and DC-bias properties of FeSiCr amorphous alloy powder cores, were investigated. The FeSiCr amorphous alloy powder cores exhibit a high value of quality factor and a stable permeability in the frequency range up to 1 MHz, showing superior DC-bias properties with a "percent permeability" of more than 82% at H=100 Oe.

  15. STUDY ON MAXIMUM HYDROGEN CAPACITY FOR Zr-Ni AMORPHOUS ALLOY

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    To design the amorphous hydrogen storage alloy efficiently, the maximum hydrogen capacities for Zr-Ni amorphous alloy were calculated. Based on the Rhomb Unit Structure Model(RUSM) for amorphous alloy and the experimental result that hydrogen atoms exist in 3Zr1Ni and 4Zr tetrahedron interstices in Zr-Ni amorphous alloy, the numbers of 3Zr-1Ni and 4Zr tetrahedron interstices in a RUSM were calculated which correspond to the hydrogen capacity. The two extremum Zr distribution states were calculated, such as highly heterogeneous Zr distribution and homogeneous Zr distribution. The calculated curves of hydrogen capacity with different Zr contents at two states indicate that the hydrogen capacity increases with increasing Zr content and reaches its maximum when Zr is 75%. The theoretical maximum hydrogen capacity for Zr-Ni amorphous alloy is 2.0(H/M). Meanwhile, the hydrogen capacity of heterogeneous Zr distribution alloy is higher than that of homogenous one at the same Zr content. The experimental results prove the calculated results reasonable, and accordingly, the experimental results that the distribution of Zr atom in amorphous alloy occur heterogeneous after a few hydrogen absorption-desorption cycles can be explained.

  16. Sample-Size Effects on the Compression Behavior of a Ni-BASED Amorphous Alloy

    Science.gov (United States)

    Liang, Weizhong; Zhao, Guogang; Wu, Linzhi; Yu, Hongjun; Li, Ming; Zhang, Lin

    Ni42Cu5Ti20Zr21.5Al8Si3.5 bulk metallic glasses rods with diameters of 1 mm and 3 mm, were prepared by arc melting of composing elements in a Ti-gettered argon atmosphere. The compressive deformation and fracture behavior of the amorphous alloy samples with different size were investigated by testing machine and scanning electron microscope. The compressive stress-strain curves of 1 mm and 3 mm samples exhibited 4.5% and 0% plastic strain, while the compressive fracture strength for 1 mm and 3 mm rod is 4691 MPa and 2631 MPa, respectively. The compressive fracture surface of different size sample consisted of shear zone and non-shear one. Typical vein patterns with some melting drops can be seen on the shear region of 1 mm rod, while fish-bone shape patterns can be observed on 3 mm specimen surface. Some interesting different spacing periodic ripples existed on the non-shear zone of 1 and 3 mm rods. On the side surface of 1 mm sample, high density of shear bands was observed. The skip of shear bands can be seen on 1 mm sample surface. The mechanisms of the effect of sample size on fracture strength and plasticity of the Ni-based amorphous alloy are discussed.

  17. Crystallization of Fe83B17 amorphous alloy by electric pulses produced by a capacitor discharge

    International Nuclear Information System (INIS)

    Heating of conductive materials by electric current is used in many technological processes. Application of electric pulses to metallic glasses induces their fast crystallization, which is an interesting and complex phenomenon. In this work, crystallization of the Fe83B17 amorphous alloy induced by pulses of electric current produced has been studied using X-ray diffraction and transmission electron microscopy. Ribbons of the alloy were directly subjected to single pulses of electric current 250 μs long formed by a capacitor discharge. As the value of ∫I2dt was increased from 0.33 to 2.00 A2 s, different crystallization stages could be observed. The crystallization began through the formation of the nuclei of α-Fe. At high values of ∫I2dt, α-Fe and tetragonal and orthorhombic Fe3B and Fe23B6 were detected in the crystallized ribbons with crystallites of about 50 nm. Thermal annealing of the ribbons at 600 C for 2 min resulted in the formation of α-Fe and tetragonal Fe3B. It was concluded that pulses of electric current produced by a capacitor discharge induced transformation of the Fe83B17 amorphous phase into metastable crystalline products. (orig.)

  18. Energy reversible switching from amorphous metal based nanoelectromechanical switch

    KAUST Repository

    Mayet, Abdulilah M.

    2013-08-01

    We report observation of energy reversible switching from amorphous metal based nanoelectromechanical (NEM) switch. For ultra-low power electronics, NEM switches can be used as a complementary switching element in many nanoelectronic system applications. Its inherent zero power consumption because of mechanical detachment is an attractive feature. However, its operating voltage needs to be in the realm of 1 volt or lower. Appropriate design and lower Young\\'s modulus can contribute achieving lower operating voltage. Therefore, we have developed amorphous metal with low Young\\'s modulus and in this paper reporting the energy reversible switching from a laterally actuated double electrode NEM switch. © 2013 IEEE.

  19. Spectroscopic and mechanical studies on the Fe-based amorphous alloy 2605SA1

    Energy Technology Data Exchange (ETDEWEB)

    Cabral P, A.; Garcia S, I. [ININ, Departamento de Quimica, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico); Contreras V, J. A.; Garcia S, F. [Universidad Autonoma del Estado de Mexico, Facultad de Ciencias, El Cerrillo Piedras Blancas, Toluca, Estado de Mexico (Mexico); Nava, N., E-mail: agustin.cabral@inin.gob.m [Instituto Mexicano del Petroleo, Eje Central Lazaro Cardenas No. 152, Col. San Bartolo Atepehuacan, 07730 Mexico D. F. (Mexico)

    2010-07-01

    The Vickers micro-hardness of this alloy was unusually dependent on the heat treatment from 300 to 634 K, inferring important micro-structural changes and the presence of amorphous grains before its phase transition. Once the alloy is crystallized, the micro-hardness is characteristic of a brittle alloy, the main problem of these alloys. Within the amorphous state, other properties like free-volume, magnetic states and Fe-Fe distances were followed by Positron annihilation lifetime spectroscopy and Moessbauer spectroscopy, respectively, to analyze those micro-structural changes, thermally induced, which are of paramount interest to understand their brittleness problem. (Author)

  20. Filler metal development for hastelloy alloy XR

    International Nuclear Information System (INIS)

    A method of alloy designing has been proposed and validated to develop the filler metal for Hastelloy alloy XR(nuclear reactor grade of Hastelloy alloy X), which is the candidate material for high temperature structure of High-Temperature Engineering Test Reactor (HTTR). In the filler metal development for Hastelloy alloy XR, materials of two heats were melted and fabricated with special emphasis placed on manufacturing process. One is the trial products (alloy termed 'C') designed by using multiple regression analysis in the range of the chemical composition specified as Hastelloy alloy X. The other is filler metal (alloy termed 'D') with optimum boron content in the same chemical composition as Hastelloy alloy XR. The results of the tests on several key items may be summarized as follows: (1) Weldments with alloy'C' showed higher strength and ductility at elevated temperatures than those of alloy'D'. (2) Weldments with alloy'D' had more excellent strength characteristics at elevated temperatures than those of the other conventional filler metals. (3) As for weldability, the crater cracks were slightly observed in the FISCO cracking test, but those were out of the problem in the degree of cracking from the viewpoint of practical application. The results of qualification tests on weldability showed good performance for all welding conditions of the present experiments. On the other hand, the mechanism of hot cracking initiation and the controlling factors in hot cracking susceptibility with relation to boron content have been clarified for Hastelloy alloy XR base metal. (author)

  1. High pressure magnetic behaviour of amorphous Ysub(x)Nisub(1-x) alloys

    International Nuclear Information System (INIS)

    High pressure magnetization and Curie temperature measurements have been performed on several amorphous Ysub(x)Nisub(1-x) alloys. The results seem to indicate that ferromagnetism disappears in a rather inhomogeneous way

  2. Effect of High Temperature Aging on the Corrosion Resistance of Iron Based Amorphous Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Day, S D; Haslam, J J; Farmer, J C; Rebak, R B

    2007-08-10

    Iron-based amorphous alloys can be more resistant to corrosion than polycrystalline materials of similar compositions. However, when the amorphous alloys are exposed to high temperatures they may recrystallize (or devitrify) thus losing their resistance to corrosion. Four different types of amorphous alloys melt spun ribbon specimens were exposed to several temperatures for short periods of time. The resulting corrosion resistance was evaluated in seawater at 90 C and compared with the as-prepared ribbons. Results show that the amorphous alloys can be exposed to 600 C for 1-hr. without losing the corrosion resistance; however, when the ribbons were exposed at 800 C for 1-hr. their localized corrosion resistance decreased significantly.

  3. Calorimetric studies of non-isothermal crystallization in amorphous CuTi100– alloys

    Indian Academy of Sciences (India)

    N Mehta; K Singh; N S Saxena

    2011-12-01

    The present paper reports the composition dependence of pre-exponential factor and activation energy of non-isothermal crystallization in amorphous alloys of CuTi100– system using differential scanning calorimeter (DSC) technique. The applicability of Meyer–Neldel relation between the pre-exponential factor and activation energy of non-isothermal crystallization for amorphous alloys of Cu–Ti system was verified.

  4. Initial crystal structure of alloys being amorphisized, amorphous ribbon quality and good yield

    International Nuclear Information System (INIS)

    A study is made into crystal structure of Fe75Ni2B14Si9 and Fe81C1.7B14Si3.3 alloys. It is shown that on casting magnetically soft amorphous alloys the crystals of excessive phase Fe2B are practically always precipitate from the matrix and cause the violations of casting technology for amorphous ribbon production. Accelerated cooling of ingots and melt modification are considered to be useful to prevent coarse crystal formation

  5. Amorphous Formation in an Undercooled Binary Ni-Si Alloy under Slow Cooling Rate

    Institute of Scientific and Technical Information of China (English)

    Yiping Lu; Gencang Yang; Xiong Li; Yaohe Zhou

    2009-01-01

    High undercooling up to 392 K was achieved in eutectic Ni70.2Si29.8 alloy melt by using glass fluxing combined with cyclic superheating.A small quantity of amorphous phase was obtained in bulk eutectic Ni70.2Si29.8 alloy when undercooling exceeds 240 K under slow cooling conditions (about 1 K/s).The amorphous phase was confirmed by high-resolution transmission electron microscopy and differential scanning calorimetry.

  6. Corrosion resistance of amorphous and crystalline Pd40Ni40P20 alloys in aqueous solutions

    DEFF Research Database (Denmark)

    Wu, Y.F.; Chiang, Wen-Chi; Chu, J.; Nieh, T.G.; Kawamura, Y.; Wu, J.K.

    2006-01-01

    The corrosion behaviors of amorphous and crystalline Pd40Ni40P20 alloys in various aqueous solutions are reported in this paper. The corrosion resistance of crystalline (annealed) Pd40Ni40P20 is better than that of amorphous Pd40Ni40P20 in various corrosive solutions, due to crystalline Pd40Ni40P...

  7. A novel approach to quantify nitrogen distribution in nanocrystalline-amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Amini, R. [Department of Materials Science and Engineering, School of Engineering, Shiraz University, Zand Blvd., 7134851154, Shiraz (Iran, Islamic Republic of); Department of Materials Science and Engineering, Shiraz University of Technology, Modarres Blvd., 3619995161, Shiraz (Iran, Islamic Republic of); Salahinejad, E., E-mail: erfan.salahinejad@gmail.com [Department of Materials Science and Engineering, School of Engineering, Shiraz University, Zand Blvd., 7134851154, Shiraz (Iran, Islamic Republic of); Hadianfard, M.J.; Bajestani, E. Askari [Department of Materials Science and Engineering, School of Engineering, Shiraz University, Zand Blvd., 7134851154, Shiraz (Iran, Islamic Republic of); Sharifzadeh, M. [School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798 (Singapore)

    2011-02-03

    Research highlights: > A novel method is introduced to determine nitrogen distribution in nanocrystalline-amorphous alloys, based on X-ray diffraction, thermogravimetry, and differential scanning calorimetery. > The technique determines the contribution of crystal interstitial sites, crystalline defects, and amorphous phase to nitrogen incorporation. > In Fe-18Cr-8Mn-2.5N alloy synthesized by mechanical alloying, about 4, 21 and 75 percent of nitrogen is distributed among the crystal interstitial sites, defects, and amorphous phase, respectively. - Abstract: A method is introduced to estimate nitrogen partitioning in the structure of nanocrystalline-amorphous alloys, based on X-ray diffraction, thermogravimetry, and differential scanning calorimetery. The technique quantitatively determines the contribution of crystal interstitial sites, crystalline defects, and amorphous phase to nitrogen incorporation. Typically, the method shows that in Fe-18Cr-8Mn-2.5N alloy synthesized by mechanical alloying, about 4, 21 and 75 percent of nitrogen is distributed among the crystal interstitial sites, defects, and amorphous phase, respectively.

  8. Electonic properties of hydrogenated amorphous silicon-germanium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Bullot, J.; Galin, M.; Gauthier, M. (Universite de Paris-Sud, Orsay (France)); Bourdon, B. (CIT-Alcatel Transmission, Marcoussis (France))

    1983-06-01

    The electronic properties of some binary hydrogenated amorphous silicon-germanium alloys a-Sisub(x)Gesub(1-x):H in the silicon rich region (x > 0.6) are investigated. Experimental evidence is presented of photo-induced effects similar to those described in Si:H (Staebler-Wronski effect). The electronic properties are then studied from the dual point of view of the germanium content dependence and of the photo and thermal histories of the films. The dark conductivity changes between the annealed state and the light-soaked state are interpreted in terms of the variation of the temperature coefficient of the Fermi level. The photoconductivity efficiency is shown to remain close to that of a-Si:H for 1 > x >= 0.9 and to strongly decrease when the germanium content is further increased: the photoresponse of the Sisub(0.62)Gesub(0.38) alloy is 10/sup 4/ times smaller than that of a-Si:H. This deterioration of the photoconductive properties is explained in terms of the increase of the density of gap states following Ge substitution. This conclusion is based on the study of the width of the exponential absorption edge and on the results of photoconductivity time response studies. The latter data are interpreted by means of the model of Rose of trapping and recombination kinetics and it is found that for x approximately 0.6 the density of states at 0.4-0.5 eV below the mobility edge is 7 x 10/sup 17/ eV/sup -1/ cm/sup -3/ as compared to 2.4 x 10/sup 16/ eV/sup -1/ cm/sup -3/ for x = 0.97.

  9. An introduction to surface alloying of metals

    CERN Document Server

    Hosmani, Santosh S; Goyal, Rajendra Kumar

    2014-01-01

    An Introduction to Surface Alloying of Metals aims to serve as a primer to the basic aspects of surface alloying of metals. The book serves to elucidate fundamentals of surface modification and their engineering applications. The book starts with basics of surface alloying and goes on to cover key surface alloying methods, such as carburizing, nitriding, chromizing, duplex treatment, and the characterization of surface layers. The book will prove useful to students at both the undergraduate and graduate levels, as also to researchers and practitioners looking for a quick introduction to surface alloying.

  10. Amorphous Metal Composites for use in Long-Life, Low-Temperature Gearboxes Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed concept is to explore the use of Amorphous Metals (AMs) and Amorphous Metal Composites (AMCs) (fabricated entirely at JPL) for use as gears and bearing...

  11. Crystallization kinetics and magnetic properties of FeSiCr amorphous alloy powder cores

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Hu-ping [School of Logistics Engineering, Wuhan University of Technology, Wuhan 430063 (China); Wang, Ru-wu, E-mail: ruwuwang@hotmail.com [National Engineering Research Center For Silicon Steel, Wuhan 430080 (China); College of Materials Science and Metallurgical Engineering, Wuhan University of Science and Technology, Wuhan 430081 (China); Wei, Ding [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074 (China); Zeng, Chun [National Engineering Research Center For Silicon Steel, Wuhan 430080 (China)

    2015-07-01

    The crystallization kinetics of FeSiCr amorphous alloy, characterized by the crystallization activation energy, Avrami exponent and frequency factor, was studied by non-isothermal differential scanning calorimetric (DSC) measurements. The crystallization activation energy and frequency factor of amorphous alloy calculated from Augis–Bennett model were 476 kJ/mol and 5.5×10{sup 18} s{sup −1}, respectively. The Avrami exponent n was calculated to be 2.2 from the Johnson–Mehl–Avrami (JMA) equation. Toroid-shaped Fe-base amorphous powder cores were prepared from the commercial FeSiCr amorphous alloy powder and subsequent cold pressing using binder and insulation. The characteristics of FeSiCr amorphous alloy powder and the effects of compaction pressure and insulation content on the magnetic properties, i.e., effective permeability μ{sub e}, quality factor Q and DC-bias properties of FeSiCr amorphous alloy powder cores, were investigated. The FeSiCr amorphous alloy powder cores exhibit a high value of quality factor and a stable permeability in the frequency range up to 1 MHz, showing superior DC-bias properties with a “percent permeability” of more than 82% at H=100 Oe. - Highlights: • The crystallization kinetics of FeSiCr amorphous alloy was investigated. • The FeSiCr powder cores exhibit a high value of Q and a stable permeability. • The FeSiCr powder cores exhibit superior DC-bias properties.

  12. Nonferrous metals - Nickel, lead, and tin alloys, precious metals, primary metals; Reactive metals

    International Nuclear Information System (INIS)

    This book contains specifications for nickel and nickel alloys, including pipe and tube, plate, sheet and strip, rod, bar and wires; other nonferrous metals and alloys, including cadmium, copper, gold, hafnium, iridium, lead, lithium, palladium, platinum, rhodium, ruthenium, silver, tin and zinc; and reactive and refractory metals and alloys: molybdendum, niobium, tantalum, titanium, and zirconium

  13. Hydrogen effect on properties of amorphous alloy 78Fe-3.5Nb-1Cu-4B-13.5Si

    International Nuclear Information System (INIS)

    It is reported about the detection of a practically complete loss of elastic properties after hydrogenation, and about subsequent reconstruction of the latter during exposure of hydrogenated amorphous metal alloy at 275 K. Possible reasons for such an unusual phenomenon are discussed

  14. Anisotropic phase separation in amorphous Fe--Ge alloys

    International Nuclear Information System (INIS)

    Magnetron sputtered amorphous FexGe100-x films have been examined with anomalous small-angle x-ray scattering (ASAXS) in an attempt to characterize composition fluctuations which have been previously reported in this system. Films grown under various deposition conditions have been studied, with the scattering vector both in and oblique to the plane of the films, to search for anisotropy. By manipulating the deposited power flux and rates of growth, films which have the same composition can be grown to different states of phase separation. The total correlation functions have been calculated from the oblique scattering experiments. The anisotropy can be successfully modeled as a close-packing of oriented prolate ellipsoidal particles, with the elongated axis along the direction of film growth. A method for using these measurements to determine the compositions of the phase-separating species has been developed and utilized. The results indicate phase separation into a-Ge and a-FeGe2 for the a-FexGe100-x (x<33) alloy

  15. Hydrogen distribution in amorphous silicon and silicon based alloys

    International Nuclear Information System (INIS)

    The results of hydrogen evolution experiments on amorphous silicon alloys prepared by high frequency PECVD of gas mixtures containing SiH4, NH3, PH2, B2H6 are compared. Using a very low heating rate of 5 degree/min it is possible to resolve fine structure on the exodiffusion spectra. Three evolution processes are observed: (a) low temperature effusion due to included gas (b) mid temperature effusion due to 'clustered' hydrogen bonds (c) high temperature effusion due to 'isolated' hydrogen bonds In addition it is possible to oberve very fine structure 'puffing' due to the release of molecular hydrogen at mid to high temperature. Silicon and silicon nitride films have been annealed at low temperatures before the exodiffusion experiments and changes in the evolution spectra are observed, dependent on the annealing process. A scanning electron microscope study of the effect of high temperature heat treatment has also been undertaken. These results are correlated with infra-red absorption measurements and the influence of doping concentration and substrate character discussed. Under certain preparation conditions the films blister on heating and finally burst forming circular craters, and these effects are shown to be dependent on substrate material and intrinsic stress of the as-grown films

  16. Effect of La addition on glass-forming ability and stability of mechanically alloyed Zr-Ni amorphous alloys

    International Nuclear Information System (INIS)

    Research highlights: → The minor large atom La addition can improve the glass forming ability of Zr-Ni-La and enhance the stability of the amorphous phase against the mechanically induced crystallization. → The stability of the Zr-Ni-La amorphous phase decreases with increasing La content. → The effect of La addition in contrast with the small atomic size C addition plays a significant role in promoting the stability of the amorphous phase. → We try to systematically discuss the reasons of La addition effect on GFA and stability of the amorphous phase from three factor of negative heat of mixing, distance between neighboring atoms and atomic size mismatch, respectively. - Abstract: In this study, the role of La in the microstructural evolution of Zr66.7-xNi33.3Lax (x = 1, 3, 5 at.%) alloys during mechanical alloying has been investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The results show that the single amorphous phase of Zr-Ni-La can be obtained through mechanical alloying. The minor La addition can improve the glass forming ability of Zr-Ni-La, enhance the mechanical stability of the amorphous phase against the mechanically induced crystallization and lead to an altered crystallization mode of Zr-Ni alloy. Moreover, the stability of the Zr-Ni-La amorphous phase decreases with further increasing La content. The best effect is obtained for the Zr65.7Ni33.3La1 alloy. Additionally, the effect of La addition in contrast with the small atomic size C addition plays a more significant role in promoting the stability of the amorphous phase. In addition, the reasons of La addition effect on GFA and stability have also been discussed from three factors of negative heat of mixing, distance between neighboring atoms and atomic size mismatch, respectively.

  17. Unveiling the complex electronic structure of amorphous metal oxides

    OpenAIRE

    Arhammar, C.; Pietzsch, A; Bock, N.; Holmstrom, E.; Araujo, C. M.; Grasjo, J.; Zhao, S.; Green, S; Peery, T.; Hennies, F.; Amerioun, S.; Fohlisch, A.; Schlappa, J.; Schmitt, T; Strocov, V. N.

    2011-01-01

    Amorphous materials represent a large and important emerging area of material’s science. Amorphous oxides are key technological oxides in applications such as a gate dielectric in Complementary metal-oxide semiconductor devices and in Silicon-Oxide-Nitride-Oxide-Silicon and TANOS (TaN-Al2O3-Si3N4-SiO2-Silicon) flash memories. These technologies are required for the high packing density of today’s integrated circuits. Therefore the investigation of defect states in these structures is crucial....

  18. Formation mechanism of amorphous Ni-Fe-P alloys by electrodeposition

    Institute of Scientific and Technical Information of China (English)

    GAO Cheng-hui

    2005-01-01

    The formation mechanism of the amorphous Ni-Fe-P coating was studied by analysis of the forming thermodynamics, dynamics, and crystallography of the amorphous alloy. The results show that, in the initial stage of deposition a thin "crystal epitaxial growth" layer first forms, and then transforms to amorphous gradually. The cross section in Ni-Fe-P coatings by electrolytic etching exhibits a banded structure of alternate dark and light bands. It is proposed that the banded structure is caused by a change in the P content with thickness,which is due to alternated depletion and enrichment of [OH-] in the diffusion layer resulting from the generation and evolution of hydrogen gas. The amorphous Ni-Fe-P coating will be formed in proper composition, high nucleation rate and strongly hindered growth of the crystal nucleus. Amorphous Ni-Fe-P alloys form as islands, and grow up by layer.

  19. Production Of Tandem Amorphous Silicon Alloy Solar Cells In A Continuous Roll-To-Roll Process

    Science.gov (United States)

    Izu, Masat; Ovshinsky, Stanford R.

    1983-09-01

    A roll-to-roll plasma deposition machine for depositing multi-layered amorphous alloys has been developed. The plasma deposition machine (approximately 35 ft. long) has multiple deposition areas and processes 16-inch wide stainless steel substrate continuously. Amorphous photovoltaic thin films (less than 1pm) having a six layered structure (PINPIN) are deposited on a roll of 16-inch wide 1000 ft. long stainless steel substrate, continu-ously, in a single pass. Mass production of low-cost tandem amorphous solar cells utilizing roll-to-roll processes is now possible. A commercial plant utilizing this plasma deposition machine for manufacturing tandem amorphous silicon alloy solar cells is now in operation. At Energy Conversion Devices, Inc. (ECD), one of the major tasks of the photovoltaic group has been the scale-up of the plasma deposition process for the production of amorphous silicon alloy solar cells. Our object has been to develop the most cost effective way of producing amorphous silicon alloy solar cells having the highest efficiency. The amorphous silicon alloy solar cell which we produce has the following layer structure: 1. Thin steel substrate. 2. Multi-layered photovoltaic amorphous silicon alloy layers (approximately 1pm thick; tandem cells have six layers). 3. ITO. 4. Grid pattern. 5. Encapsulant. The deposition of the amorphous layer is technologically the key process. It was clear to us from the beginning of this scale-up program that amorphous silicon alloy solar cells produced in wide width, continuous roll-to-roll production process would be ultimate lowest cost solar cells according to the following reasons. First of all, the material cost of our solar cells is low because: (1) the total thickness of active material is less than 1pm, and the material usage is very small; (2) silicon, fluorine, hydrogen, and other materials used in the device are abundant and low cost; (3) thin, low-cost substrate is used; and (4) product yield is high. In

  20. Friction and wear behavior of electrodeposited amorphous Fe-Co-W alloy deposits

    Institute of Scientific and Technical Information of China (English)

    何凤姣; 雷惊天; 陆欣; 黄宇宁

    2004-01-01

    The microstructures, friction and wear behavior under dry sliding condition of electrodeposited amorphous Fe-Co-W alloy deposits heat treated at different temperatures were studied. A comparative study of hard chrome deposit under the same testing condition was also made. The experimental results show that the hardness and wear resistance of amorphous Fe-Co-W alloy deposits are improved with the increasing of heat treatment temperature, and reach the maximum value at 800 ℃, then decrease above 800 ℃. Under 40 N load, the wear resistance properties of the alloy deposits heat treated at 800 ℃ are superior to those of hard chrome deposit. The main wear mechanisms of amorphous Fe-Co-W alloy deposits heat treated below 600 ℃ are peeling, plastic and flowing deformation; when the deposits are heat treated above 700 ℃, they are plastic and flowing deformation. While the main wear mechanisms of hard chrome are abrasive wear, fatigue and peeling.

  1. Metal induced crystallization of silicon germanium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gjukic, M.

    2007-05-15

    In the framework of this thesis the applicability of the aluminium-induced layer exchange on binary silicon germanium alloys was studied. It is here for the first time shown that polycrstalline silicon-germanium layers can be fabricated over the whole composition range by the aluminium-induced layer exchange. The experimental results prove thet the resulting material exhibits a polycrystalline character with typocal grain sizes of 10-100 {mu}m. Raman measurements confirm that the structural properties of the resulting layers are because of the large crystallites more comparable with monocrystalline than with nano- or microcrystalline silicon-germanium. The alloy ratio of the polycrystalline layer correspondes to the chemical composition of the amorphous starting layer. The polycrystalline silicon-germanium layers possess in the range of the interband transitions a reflection spectrum, as it is otherwise only known from monocrystalline reference layers. The improvement of the absorption in the photovoltaically relevant spectral range aimed by the application of silicon-germanium could be also proved by absorption measurments. Strongly correlated with the structural properties of the polycrystalline layers and the electronic band structure resulting from this are beside the optical properties also the electrical properties of the material, especially the charge-carrier mobility and the doping concentration. For binary silicon-germanium layers the hole concentration of about 2 x 10{sup 18} cm{sup -3} for pure silicon increrases to about 5 x 10{sup 20} cm{sub -3} for pure germanium. Temperature-resolved measurements were applied in order to detect doping levels respectively semiconductor-metal transitions. In the last part of the thesis the hydrogen passivation of polycrystalline thin silicon-germanium layers, which were fabricated by means of aluminium-induced layer exchange, is treated.

  2. Internal gettering by metal alloy clusters

    Science.gov (United States)

    Buonassisi, Anthony; Heuer, Matthias; Istratov, Andrei A.; Pickett, Matthew D.; Marcus, Mathew A.; Weber, Eicke R.

    2010-07-27

    The present invention relates to the internal gettering of impurities in semiconductors by metal alloy clusters. In particular, intermetallic clusters are formed within silicon, such clusters containing two or more transition metal species. Such clusters have melting temperatures below that of the host material and are shown to be particularly effective in gettering impurities within the silicon and collecting them into isolated, less harmful locations. Novel compositions for some of the metal alloy clusters are also described.

  3. Crystallization of the Al-Ni-Sm amorphous alloys; Cristalizacao de ligas amorfas no sistema Al-Ni-Sm

    Energy Technology Data Exchange (ETDEWEB)

    Danez, G.P., E-mail: gabidanez@hotmail.co [Universidade Federal de Sao Carlos (PPG-CEMUFSCar), SP (Brazil). Programa de Pos-Graduacao em Ciencia e Engenharia de Materiais; Aliaga, L.C.R.; Kiminami, C.S.; Bolfarini, C.; Botta, W.J. [Universidade Federal de Sao Carlos (DEMa/UFSCar), SP (Brazil). Dept. de Engenharia de Materiais

    2010-07-01

    Aluminum based amorphous alloys have received special attention due to unique properties such as high mechanical strength, corrosion, ductility and toughness as well as wear resistance. On the other hand, these properties can be improved by controlled crystallization of Al matrix with grain size ranged between 5 to 50 nanometers. The goal of this work was to study the thermal crystallization behavior of Al-Ni-Sm alloys. Compositions with the same topological instability ({lambda} = 0.1) were selected. Alloys were prepared in arc-melting furnace and ribbons were processed by melt-spinning technique. Samples ribbons were submitted to heating in order to induce crystallization, and its structure analyzed by x-ray diffraction. The difference in crystallization behavior is discussed in function of the topological instability due to the variation of the proportion of the transition metal to the rare-earth. (author)

  4. Development of Metallic Sensory Alloys

    Science.gov (United States)

    Wallace Terryl A.; Newman, John A.; Horne, Michael R.; Messick, Peter L.

    2010-01-01

    Existing nondestructive evaluation (NDE) technologies are inherently limited by the physical response of the structural material being inspected and are therefore not generally effective at the identification of small discontinuities, making the detection of incipient damage extremely difficult. One innovative solution to this problem is to enhance or complement the NDE signature of structural materials to dramatically improve the ability of existing NDE tools to detect damage. To address this need, a multifunctional metallic material has been developed that can be used in structural applications. The material is processed to contain second phase sensory particles that significantly improve the NDE response, enhancing the ability of conventional NDE techniques to detect incipient damage both during and after flight. Ferromagnetic shape-memory alloys (FSMAs) are an ideal material for these sensory particles as they undergo a uniform and repeatable change in both magnetic properties and crystallographic structure (martensitic transformation) when subjected to strain and/or temperature changes which can be detected using conventional NDE techniques. In this study, the use of a ferromagnetic shape memory alloy (FSMA) as the sensory particles was investigated.

  5. Tendency of metallic crystals to amorphization in the process of severe (Megaplastic) deformation

    Science.gov (United States)

    Glezer, A. M.; Sundeev, R. V.; Shalimova, A. V.

    2012-11-01

    The main features of the transition of crystalline Ni50Ti30Hf20, Ti50Ni25Cu25, Zr50Ni18Ti17Cu15, and Fe78B8.5Si9P4.5 alloys with various tendencies to amorphization into an amorphous state upon melt quenching and in the course of severe deformation in Bridgman anvils have been considered. The crystalline state of these alloys has been produced using various methods of annealing. In the iron-based alloy, single-phase and two-phase crystalline states have been studied. The nickel- and titanium-based alloys after annealing were in a single-phase crystalline state; the zirconium-based alloy, in a two-phase state. It is shown that at the same degree of deformation the rates of amorphization of crystalline alloys differ substantially; namely, the single-phase crystalline titanium- and iron-based alloys amorphize easily, whereas the Zr-based alloy amorphizes only poorly, just like the two-phase iron-based alloy. It can be assumed that the tendency to deformation-induced amorphization of crystalline alloys and the corresponding crystalline phases is mainly determined by three factors: mechanical, thermodynamic, and concentration-related.

  6. An amorphous alloy stress sensor for wireless battery-free applications

    Science.gov (United States)

    Bowles, Adrian; Gore, Jon; Tomka, George

    2005-05-01

    Battery-free sensor systems would benefit from the availability of a stress or strain sensor that exhibits a large enough property change to allow simplification and power reductions in sensor interface and data transmission circuitry. A new sensor has been developed specifically for this purpose, which uses the large stress induced impedance changes exhibited by ribbons of amorphous magnetic alloy. In comparison to semiconductor strain gauges, which show a change in resistance of 15% when strained to their maximum recommended stress level, the amorphous alloy sensor demonstrates a change in inductance of 315%, when strained to its maximum working level. Although, amorphous magnetic alloys are inherently sensitive to external magnetic fields, a simple, biasing technique renders the stress-sensing device insensitive to modest field strengths. The amorphous magnetic alloys are produced in large volumes and realize an extremely low cost sensor. A low cost and low power analogue electrical circuit has been designed that, in combination with the amorphous alloy sensor, functions as a battery-free sensor 'tag'. The sensor tag can transmit stress data to a transceiver system via an inductive link, negating the need for battery power or a hardwire connection. The system"s range is directly related to the transceiver and tag antenna dimensions; however a system with 20cm diameter antennas has been demonstrated operating over a range of up to 60cm. This range is achieved through the extremely low power demands of the sensor tag (tyre pressure monitoring applications.

  7. Detonation gun and plasma spraying of amorphous metal coatings with improved corrosion resistance: Simulation and experiment

    International Nuclear Information System (INIS)

    Coating formation in detonation gun or plasma spraying involves direct contact of molten particles with cool metal of the substrate, which results in extra high cooling rates in the melt and enables synthesis of coatings with amorphous or metastable crystalline structure. Mathematical modeling of detonation gun and plasma spraying was carried out to determine the physical and engineering parameters for producing hard corrosion resistant coatings. For an iron-base (Fe-Cr-P-C) and a nickel-base (Ni-Cr-Si-B-C) eutectic alloy, spraying process parameters were determined theoretically. Purely amorphous or amorphous-crystalline coatings can be produced by detonation gun and plasma spraying with the use of values of individual layer thickness, pulse separation, powder feed rate, etc. thus obtained. The structure of these coatings whose hardness may be as high as 1,100 HV was described in more detail in a previous paper. Amorphous coatings are shown to outperform 304 stainless steel in resistance to corrosion in hydrochloric acid by no less than an order of magnitude

  8. Extraction of valuable metals from amorphous solid wastes

    Directory of Open Access Journals (Sweden)

    E. David

    2007-11-01

    Full Text Available Purpose: This paper undertakes to assess what opportunities exist for the economical recovery of valuable metals from amorphous solid wastes that may be considered as“synthetic ores”. Also, this work is an attempt to optimize a leaching process that is the most determinant step of hydrometallurgical process used to extract metals from ores.Design/methodology/approach: The samples of amorphous material formed from spent industrial catalysts based on Cu, Ni / γ-Al2O3 were physically and chemically characterized by atomic absortion spectrometry (AAS and chemical analysis for to determine the metals content. Then leaching studies were carried out under room temperature, atmospheric pressure and without gas injection in both sulphuric acid with hydrogen peroxide addition and ammoniacal media for to decide which of them would be the best treatment for this kind of waste materials. Also, the dissolution behaviour of Cu, Ni and Al metals was studied in order to assure the best metal recovery conditions in subsequent processes such as solvent extraction , precipitation or cementation techniques.Findings: The results revealed that addition of hydrogen peroxide to sulphuric acid up to 0.2 M H2O2 concentration enhanced leaching of metals remarkably and thereafter remained relatively constant. The highest extraction of metals was found to be 90% Cu, 85% Ni and 80% Al for the following experimental conditions: H2SO4 2M, H2O2 0.2 M, A 5:1 liquid to solid ratio (L/S.The use of ammoniacal media for leaching allowed the extraction of Cu, Ni and Al but rates of recovery were only about 45 % for Cu, 43 % for Ni and 44 % for Al, much lower than those obtained for sulphuric acid leaching.Research limitations/implications: The investigated process is suitable for all amorphous solid wastes with significant content in metals such as copper, nickel, aluminium.Practical implications: Promising directions for adaptation of appropriate and economic separation

  9. Filler metal development for Hastelloy alloy XR

    International Nuclear Information System (INIS)

    In order to develop the filler metal for Hastelloy alloy XR structure with thick wall, the weldability and high temperature strength properties of Hastelloy alloy XR weldment were investigated using the filler metals, which were alloy-designed on the basis of multiple regression analysis. The former was examined through the chemical analysis in the deposited metal, bend test, FISCO cracking test, optical microscopy and hardness measurement. The latter was investigated by means of tensile and creep test. It was found from these results that the crack susceptibility in the weldment was apparent to be lowered without degrading the high temperature strength properties. Therefore, it is concluded that these filler metals possess excellent performance as the filler metal for Hastelloy alloy XR structure with thick wall. (author)

  10. Hard rhenium–boron–cobalt amorphous alloys with a wide supercooled liquid region

    International Nuclear Information System (INIS)

    Novel Re–B–Co amorphous alloys with compositions of Re65−xB35Cox (at%, x=25, 30, 35, 40, 45, and 50) were fabricated by single-roller melt spinning. These alloys were found to exhibit a clear glass transition phenomenon. The width of supercooled liquid region (ΔTx) is in the range of 52–71 K. Such a large ΔTx allows us to produce amorphous alloy bulks by thermoplastic forming. The Vickers hardness is up to 19.10 GPa for the Re40B35Co25 alloy, which is close to that reported for some hard covalent crystals. Thus, the present alloys with a combination of large ΔTx and high hardness are expected to be used as a new type of structural materials. Furthermore, the relationships of hardness with glass transition temperature and Young's modulus were also discussed

  11. Microstructure and magnetocaloric effects in partially amorphous Gd55Co15Al30-xSix alloys

    International Nuclear Information System (INIS)

    Highlights: → The primary crystalline phase of the metallic glasses is identified to be Gd2Al. → Phase separation is observed in the system with negative heat of mixing. → Relationship between the microstructure and MCE of Gd-based BMG composite. - Abstract: In order to clarify the phase components and further improve the glass-forming ability of Gd55Co15Al30 alloy, substitution of Al with Si was adopted. Although the X-ray powder diffraction experiment indicated an amorphous structure of the Gd55Co15Al30-xSix (x = 1, 2, 3) alloys, precipitation of crystalline Gd2Al phase was evident from the energy-dispersive spectroscopy, selected-area diffraction, and magnetization measurements. The magnetocaloric effect of Si substituted alloys is lower than that of Gd52.5Co16.5Al31 alloy with a similar composition and full amorphous structure, which is ascribed to the presence of antiferromagnetic Gd2Al phase whose magnetic entropy change is lower.

  12. Effect of Viscosity on the Microformability of Bulk Amorphous Alloy in Supercooled Liquid Region

    International Nuclear Information System (INIS)

    Previously published results have shown that viscosity greatly influences on the deformation behavior of the bulk amorphous alloy in supercooled liquid region during microforming process. And viscosity is proved to be a component of the evaluation index which indicating microformability. Based on the fluid flow theory and assumptions, bulk amorphous alloy can be regarded as the viscous materials with a certain viscosity. It is helpful to understand how the viscosity plays an important role in viscous materials with various viscosities by numerical simulation on the process. Analysis is carried out by linear state equation in FEM with other three materials, water, lubricant oil and polymer melt, whose viscosities are different obviously. The depths of the materials flow into the U-shaped groove during the microimprinting process are compared in this paper. The result shows that the deformation is quite different when surface tension effect is not considered in the case. With the lowest viscosity, water can reach the bottom of micro groove in a very short time. Lubricant oil and polymer melt slower than it. Moreover bulk amorphous alloys in supercooled liquid state just flow into the groove slightly. Among the alloys of different systems including Pd-, Mg- and Zr-based alloy, Pd-based alloy ranks largest in the depth. Mg-based alloy is the second. And Zr-based alloy is the third. Further more the rank order of the viscosities of the alloys is Pd-, Mg- and Zr-based. It agrees well with the results of calculation. Therefore viscosity plays an important role in the microforming of the bulk amorphous alloy in the supercooled liquid state.

  13. Low temperature irradiation of FeB amorphous alloys

    International Nuclear Information System (INIS)

    These experiments show that low temperature electron irradiation induce localized defects in the short range order of the amorphous structure. These defects are assumed to be of Frenkel pair type. At low temperature, 2.5 MeV electron irradiation induces an higher concentration of defects in the amorphous than in its crystallized counterpart

  14. Synthesis of amorphous Ti-Al alloys by mechanical alloying of elemental powders

    Institute of Scientific and Technical Information of China (English)

    张俊红; 黄伯云; 贺跃辉; 周科朝; 刘咏

    2002-01-01

    Blended elemental powders with the nominal compositions (mole fraction, %) of Ti54Al46, Ti52Al48 and Ti50Al50 were mechanically alloyed in a planetary ball milling system for up to 100h.The structure evolution in these powders was characterized by scanning electron microscope, X-ray diffraction and differential thermal a nalysis techniques. It was found that elemental powders were progressively trans formed into nanocrystalline Ti(Al) supersaturated solid solution, then into amor phous phase. With increasing Al content, the formation of a fully Ti(Al) supersa turated solid solution and amorphous phase were accelerated, which are attributed to the fine grain size. And the grain size condition for formation of amorpho us phase in this system is ≤16 nm.

  15. Ni-WC composite coatings by carburizing electrodeposited amorphous and nanocrystalline Ni-W alloys

    International Nuclear Information System (INIS)

    In situ formation of tungsten carbide in the matrix of FCC nickel has been achieved by carburizing of the electrodeposited Ni-W alloy coatings. The size of the carbide particles ranges between 100 and 500 nm. The carbide phase is also present in the form of very small precipitates inside the nickel grains. The size of such precipitates is between 10 and 40 nm. The carburizing environment was created by introducing a flowing mixture of vaporized 95.5% alcohol (0.25 ml/min, liquid) and argon (0.5 L/min, gas) into the carburizing furnace. Supersaturated nature of electrodeposited amorphous and nanocrystalline alloys, in addition to high diffusivity, have been attributed for the formation of carbide phase in the deposits at a temperature range of 700-850 deg. C. The carbide-metal interface is clean and the composite coatings are compact. Hardness values up to about 1100 KHN are achieved. Hardness increases with tungsten content and carburizing temperature.

  16. Investigations of the atomic structure of amorphous ytterbium-alloys by Moessbauer spectroscopy

    International Nuclear Information System (INIS)

    Atomic-scale structures of the amorphous alloys Yb80X20 (X = Cu, Ag, Au, Pd, Bi) have been investigated with a 174Yb-Moessbauer source. The distribution of the quadrupole splitting parameters obtained from the analysis of the Moessbauer spectra was compared with the theoretical function for a charge distribution corresponding to dense random packing (DRP) of ions. The atomic structure deduced from the distribution of splitting parameters was consistent with the DRP-model in the amorphous alloys Yb80Cu20, Yb80Ag20, Yb80Au20, Yb80Pd20. In contrast the Moessbauer spectrum of the amorphous alloy Yb80Bi20 showed clear evidence of short range order. This is presumably due to the tendency of bismuth to form covalent bondings. (orig./GSCH)

  17. Preparation and Properties of Mg-Cu-Y-Al bulk Amorphous Alloys

    DEFF Research Database (Denmark)

    Pryds, Nini; Eldrup, Morten Mostgaard; Ohnuma, M.; Pedersen, Allan Schrøder; Hattel, J.; Linderoth, Søren

    2000-01-01

    Bulk amorphous (Mg(1-gamma)Al(gamma))(60)CU(30)Y(10) alloys were prepared using a relatively simple technique of rapid cooling of the melt in a copper wedge mould. The temperature vs, time was recorded during the cooling and solidification process of the melt and compared with a spacial and......-ray diffraction (XRD) and differential scanning calorimetry (DSC) for different alloy compositions and annealing temperatures. On annealing into the supercooled liquid state (441 K), specimens with no Al content remain basically amorphous while nanoparticles are formed and remain stable also at higher...... temperatures in specimens containing a few percent Al. The alloy with no Al crystallises apparently without the formation of nanoparticles. The critical cooling rate for the formation of an amorphous Mg(60)CU(30)Y(10) specimen was determined experimentally by a combination of DSC data and temperature vs, time...

  18. Crystallization kinetics of amorphous Zr65Cu25Al10 alloy

    Institute of Scientific and Technical Information of China (English)

    王焕荣; 石志强; 王艳; 滕新营; 叶以富; 闵光辉; 张均艳

    2002-01-01

    Crystallization behavior of amorphous Zr65Cu25Al10 alloy under isothermal annealing condition was investigated by DSC and XRD. It is found that two exothermic peaks appear in the DSC curve of amorphous Zr65Cu25Al10 alloy, indicating that the crystallization proceeds through double-stage mode. The crystallization process of amorphous Zr65Cu25Al10 alloy under isothermal annealing condition is mainly controlled by nucleation and one-dimensional growth with the crystallized volume fraction smaller than 70%. With the crystallized volume fraction ranging from 70% to 90%, crystallization process is mainly dominated by the growth of three-dimensional pre-existing quench-in nuclei. And when the crystallized volume fraction reaches above 90%, transient nucleation becomes the master of the crystallization process.

  19. Phase separation and crystallization process of amorphous Fe78B12Si9Ni1 alloy

    International Nuclear Information System (INIS)

    The influence of the melt heat treatment on the structure and crystallization process of the rapidly quenched amorphous Fe78B12Si9Ni1 alloys have been investigated by means of x-ray diffraction, DSC and TEM. Amorphous phase separation has been observed in the alloys quenched after the preliminary high temperature heat treatment of the liquid alloy (heating above 1400°C). Comparative analysis of the pair distribution functions demonstrates that this phase separation accompanied by a changes in the local atomic arrangement. It has been found that crystallization process at heating is strongly dependent on the initial amorphous phase structure - homogeneous or phase separated. In the last case crystallization goes through the formation of a new metastable hexagonal phase [a=12.2849(9) Ǻ, c=7.6657(8) Ǻ]. At the same time the activation energy for crystallization (Ea) reduces from 555 to 475 kJ mole−1

  20. Relaxation process of Fe(CuNb)SiB amorphous alloys investigated by dynamical calorimetry

    International Nuclear Information System (INIS)

    Differential scanning calorimetry and dynamic differential scanning calorimetry were used to analyze the relaxation process of Fe(CuNb)SiB amorphous alloys. The Curie temperature (TC) evolution of the amorphous phase during relaxation as a function of heating rate, time and pre-annealing temperature were measured. Two distinct relaxation processes are observed, consequent with topological and chemical short range order changes. copyright 1997 American Institute of Physics

  1. Relaxation process of Fe(CuNb)SiB amorphous alloys investigated by dynamical calorimetry

    OpenAIRE

    Zhu, J.; Clavaguera-Mora, M. T.; Clavaguera, N.

    1997-01-01

    Differential scanning calorimetry and dynamic differential scanning calorimetry were used to analyze the relaxation process of Fe(CuNb)SiB amorphous alloys. The Curie temperature(TC) evolution of the amorphous phase during relaxation as a function of heating rate, time and pre-annealing temperature were measured. Two distinct relaxation processes are observed, consequent with topological and chemical short range order changes.

  2. Layered Structures in Deformed Metals and Alloys

    DEFF Research Database (Denmark)

    Hansen, Niels; Zhang, Xiaodan; Huang, Xiaoxu

    2014-01-01

    Layered structures characterize metals and alloys deformed to high strain. The morphology is typical lamellar or fibrous and the interlamellar spacing can span several length scales down to the nanometer dimension. The layered structures can be observed in bulk or in surface regions, which is shown......-structure relationships. Finally, the results will be discussed based on universal principles for the evolution of microstructure and properties during plastic deformation of metals and alloys from low to high strain....

  3. Magnetic circular X-ray dichroism in amorphous Fe-RE alloys

    International Nuclear Information System (INIS)

    Magnetic circular X-ray dichroism and X-ray absorption near-edge structures were measured at the rare-earth (RE) L3,2 edges in amorphous Fe-RE alloys (RE=Pr, Sm, Gd, Tb and Dy). The Gd 5d spin and orbital moments in the amorphous 80 at% Fe-Gd alloy are evaluated to be about 0.39μB and -0.02μB per atom at room temperature using the sum rules. ((orig.))

  4. Compression behavior and equation of state of Ni77P23 amorphous alloy

    Institute of Scientific and Technical Information of China (English)

    LI Gong; GAO YunPeng; SUN YiNan; MA MingZhen; LIU Jing; LIU RiPing

    2007-01-01

    The compression behavior of Ni77P23 amorphous alloy is investigated at room temperature in a diamond-anvil cell instrument using in-situ high pressure energy dispersive X-ray diffraction with a synchrotron radiation source. The equation of state is determined by fitting the experimental data according to Birch-Murnaghan equation: -△V/V0=0.08606P-3.2×10-4P2+5.7×10-6P3. It is found that the structure of Ni77P23 amorphous alloy is stable under pressures up to 30.5 Gpa.

  5. Compression Behaviour of Ni77P23 Amorphous Alloy up to 30.5 GPa

    Institute of Scientific and Technical Information of China (English)

    LI Gong; ZHANG Xin-Yu; SUN Yi-Nan; QIAN Yu-Qing; LIU Jing; LIU Ri-Ping

    2005-01-01

    @@ The compression behaviour of Ni77P23 amorphous alloy is investigated at room temperature in a diamond-anvil cell instrument using in-situ high pressure energy dispersive x-ray diffraction with a synchrotron radiation source.The equation of state is determined by fitting the experimental data according to the Birch-Murnaghan equation.It is found that the structure of Ni77P23 amorphous alloy is stable under pressures up to 30.5GPa. Within the pressure range from zero to the experimental one, the pressure-induced structural relaxation is reversible.

  6. Effect of Cerium on Chemical Short-Range Order of Al-Fe-Ce Amorphous Alloy

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The chemical short-range order of Al-Fe-Ce amorphous alloy was studied by means of X-ray diffraction(XRD) and differential scanning calorimetry(DSC). It is found that the prepeak position in X-ray diffraction intensity curve shifts to higher angles as the content of Fe increases, but it shifts to smaller angles as the content of Ce increases. The crystallization character of the amorphous alloy changes with the variation of the content of Fe and Ce. Ce can improve the interaction between atoms and the capacity of compound formation, so it is favorable to Al-based glass formability.

  7. Magnetic, magnetocaloric properties and phenomenological model in amorphous Fe60Ru20B20 alloy

    Science.gov (United States)

    Boutahar, A.; Lassri, H.; Hlil, E. K.

    2015-11-01

    Magnetic, magnetocaloric properties and phenomenological model of amorphous Fe60Ru20B20 alloy are investigated in detail. The amorphous alloy has been synthesized using melt spinning method. The magnetic transition nature undergoes a second-order magnetic phase transition from ferromagnetic to paramagnetic states with a Curie temperature of 254 K. Basis on the thermodynamic Maxwell's relation, magnetic entropy change (-ΔSM) is calculated. Further, we also report a theoretical investigation of the magnetocaloric effect using a phenomenological model. The best model parameters and their variation with temperature and the magnetic field were determined. The theoretical predictions are found to agree closely with experimental measurements.

  8. Casting technique for light metal alloy

    International Nuclear Information System (INIS)

    Light metal alloys such as aluminum, magnesium, zinc and etc. can be produced in the various forms by casting technique. The casting technique for aluminum is classified as mold casting either using a sand mold or permanent mold; or both. Aluminum alloys casting are the most versatile of all common foundry alloys and generally have the highest castability ratings. Aluminum is adaptable to many of the commonly used casting methods and can be readily cast in metal molds. This work is attempted to investigate the availability and reliability of casting technique in obtaining of finish product. (Author)

  9. Mössbauer investigations of amorphous Fe(80-x B20Nbx (x=0,4,6,10 alloys

    Directory of Open Access Journals (Sweden)

    R. Babilas

    2012-02-01

    Full Text Available Purpose: The paper presents a structural and magnetic characterization of selected Fe-based metallic glasses in as-cast state.Design/methodology/approach: The studies were performed on Fe(80-xB20Nbx metallic glasses in form of ribbons with Nb addition of 0, 4, 6, 10 at.%. The amorphous structure of tested samples was examined by X-ray diffraction (XRD and Mössbauer spectroscopy methods. The Mössbauer spectroscopy was also applied to comparison of structure in studied amorphous samples with different chemical composition. The thermal properties associated with solidus temperature of master alloys were measured using the differential thermal analysis (DTA. The soft magnetic properties examination of tested materials contained relative magnetic permeability.Findings: The XRD and Mössbauer spectroscopy investigations revealed that the studied alloys in as-cast state were amorphous. The solidus temperature assumed as the onset temperature of the melting peak on the DTA curve reached a value of 1405, 1394, 1392 and 1389 K for Fe80B20, Fe76B20Nb4, Fe74B20Nb6 and Fe70B20Nb10 alloy, adequately. The Mössbauer spectra presented broadened six line patterns characteristic to the structural disorder of amorphous ferromagnetic materials. The changing of the average hyperfine magnetic field with niobium addition is connected with structural changing. A high concentration of Nb atoms with high atomic radius can acting as diffusion barrier what lead to formation of regions rich in iron or boron atoms. The niobium addition in Fe(80-xB20Nbx alloy improves soft magnetic properties in as-cast state. Practical implications: The Mössbauer spectroscopy is very useful method in studying the structural environment of Fe atoms on a nearest-neighbor length scale allowing the analysis of iron-containing phases.Originality/value: The obtained examination results confirm the utility of investigation methods in analysis of microstructure of ferromagnetic glassy alloys.

  10. Study of local crystallization induced in FeSiNbZrB amorphous alloy by swift heavy ion (SHI) irradiation at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Jianrong, E-mail: sunjr@impcas.ac.cn [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Wang, Zhiguang; Wang, Yuyu; Chang, Hailong; Song, Peng; Shen, Tielong; Zhu, Yabin; Pang, Lilong [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Li, Fashen [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China)

    2013-07-15

    Amorphous FeSiNbZrB alloy (metallic glass) ribbons were prepared by melt spinning and swift heavy ion (SHI) irradiation experiments were performed on the materials research terminal of the 320 kV ECR platform at the Institute of Modern Physics (IMP), Lanzhou. XRD, TEM and Mössbauer spectroscopy was used to reveal the irradiation-induced local crystallization, plastic deformation, damages and the magnetic moments rearrangements. The dimensions of our ribbons perpendicular to ion beam direction increased slightly , but the ribbon dimension along the ion beam shrunk; Irradiation of Xe-ions could cause local crystallization of amorphous FeSiNbZrB alloy ribbons and form finer α-Fe(Si) phases precipitations with diameter of 1–2 nm; SHI irradiation could make the distribution of the magnetic moments of amorphous ribbons change their orientation from the in-plane orientation to the perpendicular one.

  11. The effect of minor addition of insoluble elements on transformation kinetics in amorphous Al alloys

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Y.; Perepezko, J.H., E-mail: perepezk@engr.wisc.edu

    2015-09-15

    Highlights: • By doping Pb or In in AlYFe alloys, the primary crystallization of Al is promoted. • The catalytic effect is based on the good wetting behavior between Al and Pb. • Pb promotes crystallization by providing heterogeneous nucleation sites. • Through doping 0.5–2 at.% of In, T{sub x} decreases by 35–47 °C. • The coherent interface shows a good contacting behavior between Al and In. - Abstract: Nanocrystalline metallic materials based on partial devitrification of amorphous aluminum alloys show an attractive combination of high strength and low density. A key feature concerning the improved mechanical properties is the high number density of Al nanocrystals (10{sup 22}–10{sup 23} m{sup −3}) that precipitate within the amorphous precursor structure upon low temperature annealing. For Al{sub 87}Y{sub 7}Fe{sub 5}Pb, the melt-spun ribbons consisted of an amorphous matrix with a dispersion of Pb nanoparticles (10 nm diameter). HRTEM images of the Pb–Al interface revealed a good wetting behavior between the Al and the Pb nanoparticles. Isothermal annealing for Al{sub 87}Y{sub 7}Fe{sub 5}Pb showed no transient stage even though the crystallization onset, T{sub x}, was at a much lower temperature (247 °C) compared with Al{sub 88}Y{sub 7}Fe{sub 5} (267 °C). For Al{sub (88−x)}Y{sub 7}Fe{sub 5}In{sub x} (x = 0.5, 1.0, 1.5, 2.0), the DSC results indicated that T{sub x} continuously decreased from 232 °C to 220 °C as the indium level increases from 0.5 at.% to 2.0 at.%. Under STEM, the image showed a coherent interface between Al and In particles. In the analysis of the transformation kinetics, the addition of minor elements can effectively promote additional nucleation of Al nanocrystals by providing heterogeneous nucleation sites. These developments offer new opportunities for the control of nanoscale microstructures.

  12. Direct observation of microfracture process in metallic-continuous-fiber-reinforced amorphous matrix composites fabricated by liquid pressing process

    International Nuclear Information System (INIS)

    Zr-based amorphous matrix composites reinforced with metallic continuous fibers were fabricated by liquid pressing process, and their fracture property improvement was explained by directly observing microfracture processes. About 60 vol.% of metallic fibers were homogeneously distributed inside the amorphous matrix. Apparent fracture toughness of the tungsten-fiber-reinforced composites was lower than that of monolithic amorphous alloy, while that of the tantalum-fiber-reinforced composite was higher. According to the microfracture observation, shear bands or cracks were initiated at the amorphous matrix, and the propagation of the initiated shear bands or cracks was effectively blocked by fibers, thereby resulting in stable crack growth which could be confirmed by the fracture resistance curve (R-curve) behavior. This increase in fracture resistance with increasing crack length improved fracture properties of the fiber-reinforced composites, and could be explained by the formation of multiple shear bands or multiple cracks at the amorphous matrix, blocking of crack or shear band propagation, and multiple necking at metallic fibers.

  13. Magnetic and mechanical properties in FeXSiB (X = Cu, Zr, Co) amorphous alloys

    OpenAIRE

    P. Kwapuliński; Rasek, J.; Z. Stokłosa; G. Badura; B. Kostrubiec; Haneczok, G.

    2008-01-01

    Purpose: The idea of the paper is to study the influence of different alloying additions (Cu, Zr, Nb) on structuralrelaxation, crystallization, and improvement of soft magnetic properties in amorphous alloys of the type FeXSiBobtained by melt spinning technique.Design/methodology/approach: Magnetic and electric characteristics of the as quenched and successivelyannealed samples were determined at room temperature. Experiments were carried out by applying magneticpermeability measurements (Max...

  14. Bulk Formation of Metallic Glasses and Amorphous Silicon from the Melt

    Science.gov (United States)

    Spaepen, F.

    1985-01-01

    By using metallic glass compositions with a high relative glass transition temperature, such as Pd40Ni40P20, homogeneous nucleation also becomes negligible. Large (5g) masses of this alloys were obtained using a molten B2O3 flux. Presently, bulk glass formation in iron based glasses is being investigated. It is expected that if an undercooling of about 250K can be achieved in a Ge or Si melt, formation of the amorphous semiconductor phase (rather than the crystal) may be kinetically favored. The volumetric behavior of undercooled liquid Ga droplet dispersion is investigated by dilatometry. A theoretical model (both analytical and numerical) was developed for transient nucleation in glass forming melts. The model, originally designed for isothermal conditions, was extended to continuous quenching. It is being applied to glass formation in various metallic and oxide systems. A further refinement will be the inclusion of diffusion controlled interfacial rearrangements governing the growth of the crystal embryos.

  15. SYNTHESIS AND PERFORMANCE OF FE-BASED AMORPHOUS ALLOYS FOR NUCLEAR WASTE REPOSITORY APPLICATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Kaufman, L; Perepezko, J; Hildal, K

    2007-02-08

    In several Fe-based alloy systems it is possible to produce glasses with cooling rates as low as 100 K/s that exhibit outstanding corrosion resistance compared to typical crystalline alloys such as high-performance stainless steels and Ni-based C-22 alloy. Moreover, novel alloy compositions can be synthesized to maximize corrosion resistance (i.e. adding Cr and Mo) and to improve radiation compatibility (adding B) and still maintain glass forming ability. The applicability of Fe-based amorphous coatings in typical environments where corrosion resistance and thermal stability are critical issues has been examined in terms of amorphous phase stability and glass-forming ability through a coordinated computational analysis and experimental validation. Similarly, a novel computational thermodynamics approach has been developed to explore the compositional sensitivity of glass-forming ability and thermal stability. Also, the synthesis and characterization of alloys with increased cross-section for thermal neutron capture will be outlined to demonstrate that through careful design of alloy composition it is possible to tailor the material properties of the thermally spray-formed amorphous coating to accommodate the challenges anticipated in typical nuclear waste storage applications over tens of thousands of years in a variety of corrosive environments.

  16. Evidence of eutectic crystallization and transient nucleation in Al89La6Ni5 amorphous alloy

    DEFF Research Database (Denmark)

    Zhuang, Yanxin; Jiang, Jianzhong; Lin, Z. G.; Mezouar, M.; Crichton, W.; Inoue, A.

    2001-01-01

    The phase evolution with the temperature and time in the process of crystallization of Al89La6Ni5 amorphous alloy has been investigated by in situ high-temperature and high-pressure x-ray powder diffraction using synchrotron radiation. Two crystalline phases, fcc-Al and a metastable bcc-(AlNi)(11...

  17. Electro-oxidation of ethylene glycol on nanoporous Ti-Cu amorphous alloy

    Energy Technology Data Exchange (ETDEWEB)

    Chen Cuijie [School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Zhu Shengli, E-mail: slzhu@tju.edu.cn [School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Tianjin Key Laboratory of Composite and Functional Materials, Tianjin 300072 (China); Yang Xianjin [School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Tianjin Key Laboratory of Composite and Functional Materials, Tianjin 300072 (China); Pi Lele; Cui Zhenduo [School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China)

    2011-11-30

    Highlights: > Nanoporous Ti-Cu amorphous alloy exhibits apparent EG electrocatalytic ability EG electro-oxidation occurs more easily in alkaline medium than in acid medium. > In acid medium, heat treatment plays an enhancing role towards EG oxidation. > In alkaline medium, heat treatment has opposite effect below and above 0.1 V. - Abstract: This work describes ethylene glycol (EG) electro-oxidation over nanoporous structure catalyst prepared by dealloying Ti-Cu amorphous alloy. Scanning electron microscopy (SEM) was used to characterize nanoporous catalysts. Electrocatalytic performances in acid and alkaline mediums were measured by cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). The results showed that nanoporous Ti-Cu amorphous alloy exhibited apparent electrocatalytic ability in terms of higher oxidation current in CV and CA curves comparing to raw Ti-Cu amorphous alloy. Electro-oxidation of EG took place more easily in alkaline medium than that in acid medium. In acid medium, heat treatment improved the electrocatalytic activity of nanoporous catalyst. In alkaline medium, heat treatment played an enhancing role below 0.1 V and a depressing role above 0.1 V. Possible electro-oxidation mechanism of EG was also discussed.

  18. Crystallization behavior of amorphous Zr70Cu20Ni10 alloy annealed at 380℃

    Institute of Scientific and Technical Information of China (English)

    王焕荣; 叶以富; 闵光辉; 张均艳; 滕新营; 石志强

    2002-01-01

    Crystallization behavior of amorphous Zr70Cu20Ni10 alloy isothermally annealed at 380℃ was first investigated by employing the differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). It has been found that an exothermic peak appears in the DSC trace when the annealing time is about 17~18min, indicating a certain phase transformation occurs in the matrix of amorphous Zr70Cu20Ni10 alloy. Meanwhile, isothermal annealing experiments for amorphous Zr70Cu20Ni10 alloy ranging from 360℃ to 400℃ with a temperature interval of 10℃ were also carried out, from which no exothermic reaction can be observed except for the case of 380℃. This behavior indicates that the phase transformation during isothermal annealing of amorphous Zr70Cu20Ni10 alloy is strongly temperature- and time-dependent. Further investigations are required to reveal the nature of such phenomenon.

  19. The magnetic properties and the Barkhausen noise of the hydrogenated Fe-V-B amorphous alloy

    International Nuclear Information System (INIS)

    As a consequence of hydrogenation-dehydrogenation process, in the present paper the study of structural changes which could be followed by measuring structure sensitive magnetic properties as the stress induced anisotropy, coercive force, demagnetizing factor and the Barkhausen noise parameters of the as-cast and hydrogenated Fe80V5B15 amorphous alloys is performed. (author)

  20. Thermally induced crystallization of amorphous Fe40Ni40P14B6 alloy

    Czech Academy of Sciences Publication Activity Database

    Vasić, M.; Blagojević, V. A.; Begović, N. N.; Žák, Tomáš; Pavlović, V. B.; Minić, Dragica M.

    2015-01-01

    Roč. 614, AUG (2015), s. 129-136. ISSN 0040-6031 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0068 Institutional support: RVO:68081723 Keywords : Amorphous alloy * Crystallization * Kinetics * Deconvolution * Impingement * Surface morphology Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.184, year: 2014

  1. Diffusion of 59Fe in amorphous Co79Nb14B7 alloy

    International Nuclear Information System (INIS)

    Amorphous alloys have attracted considerable scientific and technological interest because of their unusual properties. Unfortunately, amorphous alloys are not thermodynamically stable and undergo structural transitions, such as relaxation, phase separation, and crystallization, which remarkably change their properties. Diffusion plays a dominant role in these processes. The crucial problem in carrying out direct diffusion measurements is that diffusion lengths are limited to very short distances, typically about 10 nm, to avoid any undesirable structural transition. Therefore only those experimental methods having a very good depth resolution can be used. Such a method is ion sputtering for serial sectioning, which is mostly used in combination with the radiotracer technique or secondary ion mass spectrometry. In the present paper, the iron impurity diffusion in the same amorphous alloy Co79Nb14B7 is studied. The temperature dependence of 59Fe impurity diffusion coefficients in the relaxed amorphous alloy have been compared with that of 58 Co self-diffusion coefficients determined in. Two procedures of the sample prepared were tested to check the influence of the experimental techniques on the resulting diffusion coefficients

  2. Crystalline and amorphous rare-earth metallic compounds

    International Nuclear Information System (INIS)

    During the last years the study of magnetic behaviour of rare-earth (or yttrium) compounds with cobalt and iron has growth of interest. This interest of justified by a large area of experimental and theoretical problems coming into being in the study of some rare-earth materials as well as in their technical applications. In the last three years a great number of new rare earth materials were studied and also new models explaining the magnetic behaviour of these systems have been used. In this paper we refer especially to some typical systems in order to analyse the magnetic behaviour of iron and cobalt and also the part played by the magnetic interactions in the values of the cobalt or iron moments. The model used will be generally the molecular field model. In the second chapter we present comparatively the structure of crystalline and amorphous compounds for further correlation with the magnetic properties. In chapter III we analyse the magnetic interactions in some crystalline and amorphous rare-earth alloys. Finally, we exemplify the ways in which we ensure better requried characteristics by the technical utilizations of these materials. These have in view the modifications of the magnetic interactions and are closely related with the analysis made in chapter III

  3. Formation and structure of V-Zr amorphous alloy thin films

    KAUST Repository

    King, Daniel J M

    2015-01-01

    Although the equilibrium phase diagram predicts that alloys in the central part of the V-Zr system should consist of V2Zr Laves phase with partial segregation of one element, it is known that under non-equilibrium conditions these materials can form amorphous structures. Here we examine the structures and stabilities of thin film V-Zr alloys deposited at room temperature by magnetron sputtering. The films were characterized by X-ray diffraction, transmission electron microscopy and computational methods. Atomic-scale modelling was used to investigate the enthalpies of formation of the various competing structures. The calculations confirmed that an amorphous solid solution would be significantly more stable than a random body-centred solid solution of the elements, in agreement with the experimental results. In addition, the modelling effort provided insight into the probable atomic configurations of the amorphous structures allowing predictions of the average distance to the first and second nearest neighbours in the system.

  4. Formation and structure of V–Zr amorphous alloy thin films

    International Nuclear Information System (INIS)

    Although the equilibrium phase diagram predicts that alloys in the central part of the V–Zr system should consist of V2Zr Laves phase with partial segregation of one element, it is known that under non-equilibrium conditions these materials can form amorphous structures. Here we examine the structures and stabilities of thin film V–Zr alloys deposited at room temperature by magnetron sputtering. The films were characterized by X-ray diffraction, transmission electron microscopy and computational methods. Atomic-scale modelling was used to investigate the enthalpies of formation of the various competing structures. The calculations confirmed that an amorphous solid solution would be significantly more stable than a random body-centred solid solution of the elements, in agreement with the experimental results. In addition, the modelling effort provided insight into the probable atomic configurations of the amorphous structures allowing predictions of the average distance to the first and second nearest neighbours in the system

  5. Volume and surface magnetic anisotropy of Co75Fe5Si4B16 amorphous alloy

    International Nuclear Information System (INIS)

    Magnetic parameters and processes of mentioned in the title amorphous alloy and its surface layer remagnetization in initial freshly-quenched state after thermomagnetic treatment (TMT) and under the effect of extermnal extension stresses are investigated. The ascertained differences in the values of coercive force and constants of magnetic anisotropy on the surface and in the volume of the alloy testify to the level character of magnetic anisotropy (MA), which is determined by the differences in magnetoelastic energy of local quenching stresses in material microvolumes. Owing to high deficiency of the surface layers, their MA, in cotrast to the alloy volume, is not monoaxial even as a result of optimal model of TMT

  6. Investigation of amorphous and crystalline Ni alloys response to machining with micro-second and pico-second lasers

    International Nuclear Information System (INIS)

    The machining response of amorphous and polycrystalline Ni-based alloys (Ni78B14Si8) when subjected to micro-second and pico-second laser processing is investigated in this research. The shape and topography of craters created with single pulses as a function of laser energy together with holes drilled in both materials were studied. Focused ion beam (FIB) imaging was used to analyse the single craters and the through holes in the amorphous and polycrystalline samples. The material microstructure analysis revealed that processing both materials with micro-second and pico-second lasers does not lead to crystallisation and the short-range atomic ordering of metallic glasses can be retained. When processing the amorphous sample the material laser interactions resulted in a significant ejection of molten material from the bulk that was then followed by its partial re-deposition around the craters. Additionally, there were no signs of crack formation that indicate a higher surface integrity after laser machining. A conclusion is made that laser processing both with short- and long-pulses is a promising technique for micromachining metallic glasses because it does not lead to material crystallisation.

  7. 21 CFR 872.3060 - Noble metal alloy.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Noble metal alloy. 872.3060 Section 872.3060 Food... DEVICES DENTAL DEVICES Prosthetic Devices § 872.3060 Noble metal alloy. (a) Identification. A noble metal alloy is a device composed primarily of noble metals, such as gold, palladium, platinum, or silver,...

  8. 21 CFR 872.3710 - Base metal alloy.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Base metal alloy. 872.3710 Section 872.3710 Food... DEVICES DENTAL DEVICES Prosthetic Devices § 872.3710 Base metal alloy. (a) Identification. A base metal alloy is a device composed primarily of base metals, such as nickel, chromium, or cobalt, that...

  9. Annealing temperature effect on microstructure, magnetic and microwave properties of Fe-based amorphous alloy powders

    International Nuclear Information System (INIS)

    Fe74Ni3Si13Cr6W4 amorphous alloy powders were annealed at different temperature (T) for 1.5 h to fabricate the corresponding amorphous and nanocrystalline powders. The influences of T on the crystalline structure, morphology, magnetic and microwave electromagnetic properties of the resultant samples were investigated via X-ray diffraction, scanning electron microscopy, vibrating sample magnetometer and vector network analyzer. The results show that the powder samples obtained at T of 650 °C or more are composed of lots of ultra-fine α-Fe(Si) grains embedded in an amorphous matrix. When T increases from 350 to 750 °C, the saturated magnetization and coercivity of the as-annealed powder samples both increase monotonously whereas the relative real permittivity shows a minimal value and the relative real permeability shows a maximal value at T of 650 °C. Thus the powder samples annealed at 650 °C show optimal reflection loss under −10 dB in the whole C-band. These results here suggest that the annealing heat treatment of Fe-based amorphous alloy is an effective approach to fabricate high performance microwave absorber with reasonable permittivity and large permeability simultaneously via adjusting T. - Highlights: ► The annealing temperature effect of Fe-based amorphous alloy was studied. ► Fe-based amorphous and nanocrystalline alloy has a good absorbing property in C-band. ► There exists a correspondence between microwave properties and microstructure.

  10. 57Fe NMR study of amorphous and rapidly quenched crystalline Fe-B alloys

    Science.gov (United States)

    Pokatilov, V. S.

    2009-01-01

    Amorphous and crystalline Fe-B alloys (5-25 at % B) were studied using pulsed 57Fe nuclear magneticr esonance at 4.2 K. The alloy samples were prepared from a mixture of the 57Fe and 10B isotopes by rapid quenching from the melt. In the microcrystalline Fe-(5-12 at %) B alloys, the resonance frequencies were measured for local states of 57Fe nuclei in the tetragonal and orthorhombic Fe3B phases and also in α-Fe. The resonance frequencies characteristic of 57Fe nuclei in α-Fe crystallites with substitutional impurity boron atoms in the nearest neighborhood were also revealed. In the resonance frequency distribution P( f) in the amorphous Fe-(18-25) at % B alloys, there are frequencies corresponding to local Fe atom states with short-range order of the tetragonal and orthorhombic Fe3B phases. As the boron content decreases below 18 at %, the P( f) distributions are shifted to higher frequencies corresponding to 57Fe NMR for atoms exhibiting a short-range order of the α-Fe type. The local magnetic structure of the amorphous Fe-B alloys is also considered.

  11. Wear mechanism of electrodeposited amorphous Ni-Fe-P alloys

    Institute of Scientific and Technical Information of China (English)

    高诚辉; 赵源

    2004-01-01

    The wear mechanism of amorphous Ni-Fe-P coating was discussed. The wear resistance of the amor phous Ni-Fe-P coatings was tested on a Timken wear apparatus, and the wear track of the amorphous Ni-Fe-P coat ings as-deposited and heated at various temperatures was observed by SEM. The results show that the wear resistthe coating will change with the heating temperature increasing from pitting+plowing at 200 ℃ to pitting at 400 ℃,and to plowing at 600 ℃. The pits on the worn surface of the amorphous Ni-Fe-P coating result from the tribo-fatigue fracture. The cracks of spalling initiate at pits and propagate at certain angle with the sliding direction on sur face, and then extend into sub-surface along the poor P layers or the interface between layers. Finally under repeated action of the stress in the rubbing process the cracks meet and the debris forms. The generation of the pits and spal-ling is related with the internal stress, brittleness and layer structure of the amorphous Ni-Fe-P coating.

  12. Amorphous structure in a laser clad Ni-Cr-Al coating on Al-Si alloy

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A mixing microstructure containing Ni-based amorphous structures was observed by TEM in the laser cladzones. As the uniformity of chemical composition and temperature is poor in the laser cladding, the amorphous structurewith some Ni3Al crystals coexists in the cladding. The microhardness of the mixing amorphous structure is HV 600 ~800, which is lower than that of crystal phases in the coating. Differential thermal analysis (DTA) shows that Ni-basedamorphous structure exhibits a higher initial crystallizing temperature (about 588 ℃ ), which is slightly higher than that ofthe eutectic temperature of Al-Si alloy. The wear test results indicate that there are some amorphous structures in the laserclad coating, which reduces the peeling of the granular phases from matrix, and improves the wear resistance

  13. In Situ Nanocrystallization-Induced Hardening of Amorphous Alloy Matrix Composites Consolidated by Spark Plasma Sintering

    Science.gov (United States)

    Singh, Ashish; Paul, Tanaji; Katakam, Shravana; Dahotre, Narendra B.; Harimkar, Sandip P.

    2016-07-01

    In situ nanocrystallization of amorphous alloys has recently emerged as a suitable technique for forming nanocomposites with improved mechanical properties. In this paper, we report on the spark plasma sintering (SPS) of Fe-based amorphous alloys with in situ-formed nanocrystals of (Fe,Cr)23(C,B)6. The SPS was performed with a range of sintering temperatures (570-800°C) in and above the supercooled liquid region of the alloy. Significant enhancement in relative density was observed with increasing sintering temperature due to particle deformation and improved interparticle contacts. The formation of nanocrystalline particles and enhanced densification resulted in an increase in the hardness of the nanocomposites from about 1150-1375 VHN.

  14. Mg amorphous alloys for biodegradable implants; Ligas amorfas de magnesio utilizadas em implantes consumiveis

    Energy Technology Data Exchange (ETDEWEB)

    Danez, G.P., E-mail: gabidanez@hotmail.co [Universidade Federal de Sao Carlos (PPG-CEMUFSCar), SP (Brazil). Programa de Pos-Graduacao em Ciencia e Engenharia de Materiais; Koga, G.Y.; Tonucci, S.; Bolfarini, C.; Kiminami, C.S.; Botta Filho, W.J. [Universidade Federal de Sao Carlos (DEMa/UFSCar), SP (Brazil). Dept. de Engenharia de Materiais

    2010-07-01

    The use of implants made from amorphous alloys magnesium-based with additions of zinc and calcium are promising. Properties such as biocompatibility, low density, high mechanical strength, low modulus (as compared to alloys such as stainless steel and titanium), corrosion resistance and wear resistance make it attractive for use in implants. Moreover, the by-products of corrosion and wear are not toxic and may contribute to fixation. Aiming to understand the tendency of this amorphous ternary (Mg-Zn-Ca) and expand the information about this system, this work involved the use of the topological criterion of instability ({lambda}) and the criterion of electronegativity ({Delta}e) to the choice of compositions. The alloys were processed into wedge-shaped and analyzed structurally and in X-ray diffraction and scanning electron microscopy. (author)

  15. Molecular dynamics study of structural and dynamical properties of amorphous Si-Ge alloys

    International Nuclear Information System (INIS)

    Structural and dynamical properties of amorphous silicon-germanium (a-Si1-xGex) alloys have been examined by molecular dynamics simulations using the Tersoff interatomic potential. Amorphous networks were generated by rapid quenching from liquid Si1-xGex alloys. Good agreement was obtained between the simulated and experimentally measured radial distribution functions and phonon densities of states, suggesting that the Tersoff potential is useful for analyzing the atomic configurations and vibrational properties of a-Si1-xGex alloys. Local atomistic structures, such as topological and chemical short-range order states, were also examined in detail, and we compared them with experimental and theoretical results reported previously. On the basis of the results obtained here, we proposed that the bond length and bond angle around Ge atoms have more distortion than those around Si atoms in a-Si1-xGex networks

  16. Iron-Based Amorphous-Metals: High-Performance Corrosion-Resistant Materials (HPCRM) Development Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Farmer, J C; Choi, J; Saw, C; Haslem, J; Day, D; Hailey, P; Lian, T; Rebak, R; Perepezko, J; Payer, J; Branagan, D; Beardsley, B; D' Amato, A; Aprigliano, L

    2009-03-16

    An overview of the High-Performance Corrosion-Resistant Materials (HPCRM) Program, which was co-sponsored by the Defense Advanced Research Projects Agency (DARPA) Defense Sciences Office (DSO) and the United States Department of Energy (DOE) Office of Civilian and Radioactive Waste Management (OCRWM), is discussed. Programmatic investigations have included a broad range of topics: alloy design and composition; materials synthesis; thermal stability; corrosion resistance; environmental cracking; mechanical properties; damage tolerance; radiation effects; and important potential applications. Amorphous alloys identified as SAM2X5 (Fe{sub 49.7}Cr{sub 17.7}Mn{sub 1.9}Mo{sub 7.4}W{sub 1.6}B{sub 15.2}C{sub 3.8}Si{sub 2.4}) and SAM1651 (Fe{sub 48}Mo{sub 14}Cr{sub 15}Y{sub 2}C{sub 15}B{sub 6}) have been produced as melt-spun ribbons, drop-cast ingots and thermal-spray coatings. Chromium (Cr), molybdenum (Mo) and tungsten (W) additions provided corrosion resistance, while boron (B) enabled glass formation. Earlier electrochemical studies of melt-spun ribbons and ingots of these amorphous alloys demonstrated outstanding passive film stability. More recently thermal-spray coatings of these amorphous alloys have been made and subjected to long-term salt-fog and immersion tests. Good corrosion resistance has been observed during salt-fog testing. Corrosion rates were measured in situ with linear polarization, while simultaneously monitoring the open-circuit corrosion potentials. Reasonably good performance was observed. The sensitivity of these measurements to electrolyte composition and temperature was determined. The high boron content of this particular amorphous metal make this amorphous alloy an effective neutron absorber, and suitable for criticality control applications. In general, the corrosion resistance of these iron-based amorphous metals is maintained at operating temperatures up to the glass transition temperature. These materials are much harder than conventional

  17. Iron-Based Amorphous-Metals: High-Performance Corrosion-Resistant Materials (HPCRM) Development Final Report

    International Nuclear Information System (INIS)

    An overview of the High-Performance Corrosion-Resistant Materials (HPCRM) Program, which was co-sponsored by the Defense Advanced Research Projects Agency (DARPA) Defense Sciences Office (DSO) and the United States Department of Energy (DOE) Office of Civilian and Radioactive Waste Management (OCRWM), is discussed. Programmatic investigations have included a broad range of topics: alloy design and composition; materials synthesis; thermal stability; corrosion resistance; environmental cracking; mechanical properties; damage tolerance; radiation effects; and important potential applications. Amorphous alloys identified as SAM2X5 (Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4) and SAM1651 (Fe48Mo14Cr15Y2C15B6) have been produced as melt-spun ribbons, drop-cast ingots and thermal-spray coatings. Chromium (Cr), molybdenum (Mo) and tungsten (W) additions provided corrosion resistance, while boron (B) enabled glass formation. Earlier electrochemical studies of melt-spun ribbons and ingots of these amorphous alloys demonstrated outstanding passive film stability. More recently thermal-spray coatings of these amorphous alloys have been made and subjected to long-term salt-fog and immersion tests. Good corrosion resistance has been observed during salt-fog testing. Corrosion rates were measured in situ with linear polarization, while simultaneously monitoring the open-circuit corrosion potentials. Reasonably good performance was observed. The sensitivity of these measurements to electrolyte composition and temperature was determined. The high boron content of this particular amorphous metal make this amorphous alloy an effective neutron absorber, and suitable for criticality control applications. In general, the corrosion resistance of these iron-based amorphous metals is maintained at operating temperatures up to the glass transition temperature. These materials are much harder than conventional stainless steel and nickel-based materials, and are proving to have excellent wear

  18. Structure and thermal stability of biodegradable Mg–Zn–Ca based amorphous alloys synthesized by mechanical alloying

    International Nuclear Information System (INIS)

    Room temperature solid state diffusion reaction induced by mechanical alloying (MA) of elemental blends of Mg, Zn and Ca of nominal composition 60 at.% Mg–35 at.% Zn–5 at.% Ca has been studied. Formation of fully amorphous structure has been identified after 5 h of MA performed in a SPEX 8000M shaker mill, with milling continued up to 8 h to confirm the formation of homogeneous amorphous phase. Thermal stability of the amorphous phase has been studied using differential scanning calorimetry (DSC) and isothermal heat treatment at different temperatures. The amorphous powder consolidated using cold isostatic pressing (CIP) showed an envelope density ∼80% of absolute density, which increased to an envelope density ∼84% of absolute density after sintering at an optimized temperature of ∼523 K for 9 h. Electrochemical bio-corrosion testing of the CIP compacted amorphous pellet as well as the sintered pellet performed in Dulbecco's Modified Eagle Medium, showed improved corrosion resistance in comparison to the as-cast pure Mg. Cytotoxicity testing of the CIP compacted amorphous pellet, performed using the MTT assay with MC3T3 osteoblastic cells, showed low cytotoxicity in comparison to the as-cast pure Mg.

  19. Laser surface alloying of aluminium-transition metal alloys

    Directory of Open Access Journals (Sweden)

    Almeida, A.

    1998-04-01

    Full Text Available Laser surface alloying has been used as a tool to produce hard and corrosion resistant Al-transition metal (TM alloys. Cr and Mo are particularly interesting alloying elements to produce stable highstrength alloys because they present low diffusion coefficients and solid solubility in Al. To produce Al-TM surface alloys a two-step laser process was developed: firstly, the material is alloyed using low scanning speed and secondly, the microstructure is modified by a refinement step. This process was used in the production of Al-Cr, Al-Mo and Al-Nb surface alloys by alloying Cr, Mo or Nb powder into an Al and 7175 Al alloy substrate using a CO2 laser. This paper presents a review of the work that has been developed at Instituto Superior Tecnico on laser alloying of Al-TM alloys, over the last years.

    En el presente trabajo se estudia la aleación superficial mediante láser de aluminio con metales de transición. El cromo y el molibdeno son particularmente interesantes porque producen aleaciones de alta resistencia y por el bajo coeficiente de difusión y solución sólida en aluminio. Para producir estas aleaciones se ha seguido un procedimiento desarrollado en dos partes. En primer lugar, el material se alea usando una baja velocidad de procesado y en segundo lugar la estructura se modifica mediante un refinamiento posterior. Este procedimiento se ha empleado en la producción de aleaciones Al-Cr, Al-Mo y Al-Nb mediante aleación con láser de CO2 de polvos de Cr, Mo o Nb en aluminio y la aleación 7175. Este trabajo es una revisión del desarrollado en el Instituto Superior Técnico de Lisboa en los últimos años.

  20. Nanoporous nickel-copper-phosphorus amorphous alloy film for methanol electro-oxidation in alkaline medium

    International Nuclear Information System (INIS)

    Highlights: • Novel Ni-Cu-P amorphous alloy with nanoporous structure was fabricated by LSV etching. • Lower onset oxidation potential of methanol at NP-NiCuP than both S-NiCuP and NP-NiCu. • Superior activity and stability for methanol oxidation at the NP-NiCuP electrode. • Long lifetime of the NP-NiCuP electrode. - Abstract: Nanoporous Ni-Cu-P amorphous alloy (NP-NiCuP) and nanoporous Ni-Cu crystalline alloy (NP-NiCu) are prepared by the linear sweep voltammetry (LSV) etching of copper from the electroless Ni-Cu-P and Ni-Cu alloy coatings, respectively. The results of X-ray diffraction (XRD) analysis show that the nanoporous Ni-Cu-P alloy is amorphous structure. The scanning electron microscopy (SEM) analysis demonstrates the NP-NiCuP shows a 3-D bi-continuous porous structure with the pore size of 150–200 nm and the ligament size of around 100 nm. Electrochemical performances are measured by cyclic voltammetry (CV) and chronoamperometry (CA). The results prove that the NP-NiCuP electrode exhibits higher the proton diffusion coefficient (D0) of Ni(OH)2 and surface coverage (Γ*) of the redox species than those on smooth electroless Ni-Cu-P amorphous alloy (S-NiCuP) and NP-NiCu electrodes in alkaline solution obviously. Moreover, electro-oxidation of methanol suggests that the NP-NiCuP electrode holds higher anodic current density and lower onset potential than the S-NiCuP and NP-NiCu electrodes. Finally, the NP-NiCuP electrode has stable redox behavior and superior catalytic stability for methanol oxidation

  1. Application of Be-free Zr-based amorphous sputter coatings as a brazing filler metal in CANDU fuel bundle manufacture

    International Nuclear Information System (INIS)

    Amorphous sputter coatings of Be-free multi-component Zr-based alloys were applied as a novel brazing filler metal for Zircaloy-4 brazing. By applying the homogeneous and amorphous-structured layers coated by sputtering the crystalline targets, the highly reliable joints were obtained with the formation of predominantly grown α-Zr grains owing to a complete isothermal solidification, exhibiting high tensile and fatigue strengths as well as excellent corrosion resistance, which were comparable to those of Zircaloy-4 base metal. The present investigation showed that Be-free and Zr-based multi-component amorphous sputter coatings can offer great potential for brazing Zr alloys and manufacturing fuel rods in CANDU fuel bundle system. (author)

  2. Microstructures of the silicon carbide nanowires obtained by annealing the mechanically-alloyed amorphous powders

    International Nuclear Information System (INIS)

    Silicon, graphite and boron nitride powders were mechanically alloyed for 40 h in argon. The as-milled powders were annealed at 1700 °C in nitrogen for 30 min. The annealed powders are covered by a thick layer of gray–green SiC nanowires, which are 300 nm to 1000 nm in diameter and several hundred microns in length. Trace iron in the raw powders acts as a catalyst, promoting the V–L–S process. It follows that the actual substances contributing to the growth of the SiC nanowires may be silicon, graphite and the metal impurities in the raw powders. The results from HRTEM and XRD reveal that the products contain both straight α/β-SiC nanowires and nodular α/β-SiC nanochains. It is interestingly found that 6H–SiC coexists with 3C–SiC in one nodular nanowire. This novel structure may introduce periodic potential field along the longitudinal direction of the nanowires, and may find applications in the highly integrated optoelectronic devices. - Graphical abstract: Display Omitted - Highlights: • SiC nanowires were prepared by annealing the mechanically alloyed amorphous powders. • SiC nanowires are 300 nm to 1000 nm in diameter and several hundred microns in length. • The products contain both straight α/β-SiC nanowires and nodular α/β-SiC nanochains. • Trace Fe in the raw powders acts as a catalyst, promoting the V–L–S process. • 6H–SiC coexists with 3C–SiC in one nodular SiC nanowire

  3. Microstructures of the silicon carbide nanowires obtained by annealing the mechanically-alloyed amorphous powders

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Pengfei, E-mail: zhangpengfei1984@163.com; Li, Xinli

    2015-07-15

    Silicon, graphite and boron nitride powders were mechanically alloyed for 40 h in argon. The as-milled powders were annealed at 1700 °C in nitrogen for 30 min. The annealed powders are covered by a thick layer of gray–green SiC nanowires, which are 300 nm to 1000 nm in diameter and several hundred microns in length. Trace iron in the raw powders acts as a catalyst, promoting the V–L–S process. It follows that the actual substances contributing to the growth of the SiC nanowires may be silicon, graphite and the metal impurities in the raw powders. The results from HRTEM and XRD reveal that the products contain both straight α/β-SiC nanowires and nodular α/β-SiC nanochains. It is interestingly found that 6H–SiC coexists with 3C–SiC in one nodular nanowire. This novel structure may introduce periodic potential field along the longitudinal direction of the nanowires, and may find applications in the highly integrated optoelectronic devices. - Graphical abstract: Display Omitted - Highlights: • SiC nanowires were prepared by annealing the mechanically alloyed amorphous powders. • SiC nanowires are 300 nm to 1000 nm in diameter and several hundred microns in length. • The products contain both straight α/β-SiC nanowires and nodular α/β-SiC nanochains. • Trace Fe in the raw powders acts as a catalyst, promoting the V–L–S process. • 6H–SiC coexists with 3C–SiC in one nodular SiC nanowire.

  4. Self-similar transformation of surface relief of amorphous alloy stressed foil

    International Nuclear Information System (INIS)

    Paper contains a series (time sequence) of topographic patterns of the stressed surface of Fe70Cr15B15 amorphous alloy foil. It is shown that in contrast to the standard (polycrystalline) metal foil the surface relief of the mentioned material is characterized initially by the fractal properties due to the nonequilibrium conditions of its formation. Upon reaching of tensile stress equal to 500 MPa at the surface the relief fractal dimension initially increases from 1.21 ± 0.02 up to 1.22 ± 0.02 and then drops up to 1.12 ± 0.03 and, finally, increases step-by-step up to 1.22 ± 0.02. Approximately in an hour and a half a system of regular bands of shift with about 300 nm amplitude substitutes for an intricate relief with the peculiar depth equal to several tens of nanometers. Self-similar transformations of relief are explained by competition of the following processes: cracking, straightening of a stretched surface, self-diffusion

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

    International Nuclear Information System (INIS)

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

  6. Soft magnetic and microstructural investigation in Fe-based amorphous alloy

    International Nuclear Information System (INIS)

    Highlights: • Samples were obtained using the injection-casting method. • The samples were manufactured in the shape of plates of the thickness 0.5 mm. • The amorphous and nanocrystalline structure was confirmed using XRD, SEM, TEM, CT. • Magnetic properties were analysed in terms of contents of the spin waves stiffness parameter b. - Abstract: In this paper, the results of investigations concerning Fe61Co10Y8W1B20 alloy are presented. The alloy samples were produced, using an injection-casting method, in the form of plates of approximate thickness 0.5 mm. Analysis of the results facilitates the description of structural transformations which occurred within the amorphous material as a result of isothermal annealing, the latter having been carried out under specified conditions. This thermal treatment led to the creation within the amorphous matrix of evenly distributed nanometric sized crystalline grains. The structure and microstructure of the samples in the as-quenched and nanocrystalline states were analysed by means of: X-ray diffractometry (XRD), scanning and transmission electron microscopy (SEM and TEM) and computer tomography (CT). The influence of the structural changes on the magnetic properties was studied using a vibrating sample magnetometer (VSM). Detailed analysis of the microstructure was performed on the ferromagnetic alloy samples with amorphous and nanocrystalline structure; this, in connection with the magnetic studies, facilitated full description of the influence of changes in the microstructure, and imperfections created during the production process, on the magnetic properties

  7. Formation and crystallization kinetics of Nd-Fe-B-based bulk amorphous alloy

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Qiong; Ge, Hongliang; Zhang, Pengyue; Li, Dongyun; Wang, Zisheng [China Jiliang University, Magnetism Key Laboratory of Zhejiang Province, Hangzhou (China)

    2014-06-15

    In order to improve the glass-forming ability (GFA) of Nd-Fe-B ternary alloys to obtain fully amorphous bulk Nd-Fe-B-based alloy, the effects of Mo and Y doping on GFA of the alloys were investigated. It was found that the substitution of Mo for Fe and Y for Nd enhanced the GFA of the Nd-Y-Fe-Mo-B alloys. It was also revealed that the GFA of the samples was optimized by 4 at.% Mo doping and increased with theYcontent. The fully amorphous structures were all formed in the Nd{sub 6-x}Y{sub x}Fe{sub 68}Mo{sub 4}B{sub 22} (x =1-5) alloy rods with 1.5 mm-diameter. After subsequent crystallization, the devitrified Nd{sub 3}Y{sub 3}Fe{sub 68}Mo{sub 4}B{sub 22} alloy rod exhibited a uniform distribution of grains with a coercivity of 364.1 kA/m. The crystallization behavior of Nd{sub 3}Y{sub 3}Fe{sub 68}Mo{sub 4}B{sub 22} BMG was investigated in isothermal situation. The Avrami exponent n determined by JAM plot is lower than 2.5, implying that the crystallization is mainly governed by a growth of particles with decreasing nucleation rate. (orig.)

  8. Microstructural studies of suck cast (Zr-SS)-3 and 5 AI alloys for nuclear metallic waste form

    International Nuclear Information System (INIS)

    Management of radioactive metallic waste using 'alloy melting route' is currently being investigated. For disposal of Zr and SS base nuclear metallic wastes, Zr-stainless steel (SS) hybrid alloys are being considered as baseline alloys for developing metallic-waste-form (MWF) alloys. In this context Zr-16 wt. %55 has been selected for MWF alloy in our previous study. In present study, to include amorphous phase in this alloy, 3 and 5 wt. % Al has been added in order to improve desirable properties and useful features of MWF and the two alloys have been prepared by suck casting techniques. Microstructure of these alloys have been investigated by optical and electron microscopy which shows occurrence of two different phases, e.g. dark grey and white phases, in (Zr-16 SS)-3 Al and three different phases, e.g. grey, dark grey and white phases in (Zr-16 SS)-5 AI. Electron diffraction and X-ray diffraction (XRD) analyses of these two alloy specimens revealed the occurrence of Zr (Fe, Cr, AI) (dark grey) and Zr2 (Fe, Cr, AI) (white) phases in (Zr-16 SS)-3 Al whereas, Zr (Fe, Cr, AI) (dark grey), Zr2 (Fe, Cr, AI) (grey) and Zr3(Fe, Cr, AI) (white) phases were found in (Zr-16 SS)-5 AI. In addition, presence of amorphous phase was indicated by XRD analysis that could be confirmed by transmission electron microscopy of these two alloys. (author)

  9. Pressure-induced Transformations of Dense Carbonyl Sulfide to Singly Bonded Amorphous Metallic Solid.

    Science.gov (United States)

    Kim, Minseob; Dias, Ranga; Ohishi, Yasuo; Matsuoka, Takehiro; Chen, Jing-Yin; Yoo, Choong-Shik

    2016-01-01

    The application of pressure, internal or external, transforms molecular solids into non-molecular extended network solids with diverse crystal structures and electronic properties. These transformations can be understood in terms of pressure-induced electron delocalization; however, the governing mechanisms are complex because of strong lattice strains, phase metastability and path dependent phase behaviors. Here, we present the pressure-induced transformations of linear OCS (R3m, Phase I) to bent OCS (Cm, Phase II) at 9 GPa; an amorphous, one-dimensional (1D) polymer at 20 GPa (Phase III); and an extended 3D network above ~35 GPa (Phase IV) that metallizes at ~105 GPa. These results underscore the significance of long-range dipole interactions in dense OCS, leading to an extended molecular alloy that can be considered a chemical intermediate of its two end members, CO2 and CS2. PMID:27527241

  10. Developments in the Ni-Nb-Zr amorphous alloy membranes. A review

    Energy Technology Data Exchange (ETDEWEB)

    Sarker, S.; Chandra, D. [University of Nevada, Materials Science and Engineering, Reno, NV (United States); Hirscher, M. [Max-Planck-Institut fuer Intelligente Systeme, Stuttgart (Germany); Dolan, M.; Viano, D. [CSIRO, QCAT, Energy, Pullenvale, QLD (Australia); Isheim, D. [Northwestern University, Materials Science and Engineering, Evanston, IL (United States); Wermer, J. [Los Alamos National Laboratory, Los Alamos, NM (United States); Baricco, M. [University of Turin, Department of Chemistry and NIS, Turin (Italy); Udovic, T.J. [National Institute of Standards and Technology, Gaithersburg, MD (United States); Grant, D. [University of Nottingham, Nottingham (United Kingdom); Palumbo, O.; Paolone, A. [CNR-ISC, U.O.S. La Sapienza, Rome (Italy); Cantelli, R. [University of Rome, La Sapienza, Roma (Italy)

    2016-03-15

    Most of the global H{sub 2} production is derived from hydrocarbon-based fuels, and efficient H{sub 2}/CO{sub 2} separation is necessary to deliver a high-purity H{sub 2} product. Hydrogen-selective alloy membranes are emerging as a viable alternative to traditional pressure swing adsorption processes as a means for H{sub 2}/CO{sub 2} separation. These membranes can be formed from a wide range of alloys, and those based on Pd are the closest to commercial deployment. The high cost of Pd (USD ∝31,000 kg{sup -1}) is driving the development of less-expensive alternatives, including inexpensive amorphous (Ni{sub 60}Nb{sub 40}){sub 100-x} Zr{sub x} alloys. Amorphous alloy membranes can be fabricated directly from the molten state into continuous ribbons via melt spinning and depending on the composition can exhibit relatively high hydrogen permeability between 473 and 673 K. Here we review recent developments in these low-cost membrane materials, especially with respect to permeation behavior, electrical transport properties, and understanding of local atomic order. To further understand the nature of these solids, atom probe tomography has been performed, revealing amorphous Nb-rich and Zr-rich clusters embedded in majority Ni matrix whose compositions deviated from the nominal overall composition of the membrane. (orig.)

  11. Preparation and Properties of Mg-Cu-Y-Al bulk Amorphous Alloys

    DEFF Research Database (Denmark)

    Pryds, Nini; Eldrup, Morten Mostgaard; Ohnuma, M.;

    2000-01-01

    temporal numerical simulation of that process. It is concluded that good thermal contact is maintained between the amorphous part of the solidified sample and the mould, while a rather poor contact develops between the crystalline part of the sample and the mould, probably due to the appearance of a narrow...... temperatures in specimens containing a few percent Al. The alloy with no Al crystallises apparently without the formation of nanoparticles. The critical cooling rate for the formation of an amorphous Mg(60)CU(30)Y(10) specimen was determined experimentally by a combination of DSC data and temperature vs, time...

  12. Corrosion-Resistant Amorphous Alloy Ribbons for Electromagnetic Filtration of Iron Rusts from Water

    OpenAIRE

    Kawashima, Asahi; Asami, Katsuhiko; Sato, Takeaki; Hashimoto, Koji

    1985-01-01

    An attempt was made to use corrosion-resistant amorphous Fe-9Cr-13P-7C alloy ribbons as an electromagnetic filter material for trapping various iron rusts suspended in water at 40℃. The ferrimagnetic Fe_3O_4 rust was trapped with the 100% efficiency and paramagnetic rusts such as α-Fe_2O_3, α-FeOOH and amorphous ferric oxyhydroxide were trapped with certain efficiencies at the magnetic field strength of 0.5-10 kOe. The regeneration of the filter by back-washing was easy. The trapping capacity...

  13. Comparison of surface and bulk crystallization of the amorphous Fe70Co10B20 alloy

    International Nuclear Information System (INIS)

    The effects of surface and bulk crystallization of the amorphous Fe70Co10B22 alloy are investigated by the aid of optical microscopy, scanning electron microscopy, and Moessbauer spectroscopy after annealings detecting γ-radiation and conversion electrons. The chemical composition of the amorphous matrix and of crystalline particles are determined by energy and wave dispersive analyses of X-rays. Measurements show that eutectic particles of crystallizing phases are observed in the bulk. Besides the non-uniformly distributed eutectic crystallites, an appreciable amount of α-Fe-Co phase is present at the surface of the sample

  14. Spontaneously Passivating Amorphous Fe-Cr-Mo-Metalloid Alloys in 6 N HCl at Room Temperature and 80℃

    OpenAIRE

    Kobayashi, Ken-ichi; Hashimoto, Koji; MASUMOTO, Tsuyoshi

    1980-01-01

    Amorphous iron-base alloys capable of passivating spontaneously in 6 N HCl at 80℃ were prepared by rapid quenching of molten alloys. The corrosion resistance and passivating ability of the alloys increased with increasing chromium and molybdenum contents. The critical concentrations of chromium and molybdenum in the alloys necessary for spontaneous passivation in 6 N HCl at room temperature and 80℃ were established. These concentrations were greatly affected by coexisting metalloids. The pass...

  15. Crystallization of Fe{sub 83}B{sub 17} amorphous alloy by electric pulses produced by a capacitor discharge

    Energy Technology Data Exchange (ETDEWEB)

    Georgarakis, Konstantinos [WPI-AIMR Tohoku University, Sendai (Japan); Institut Polytechnique de Grenoble (INPG), Science et Ingenierie des Materiaux et Procedes (SIMAP-CNRS), Saint-Martin-d' Heres (France); Dudina, Dina V. [Siberian Branch of Russian Academy of Sciences, Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk (Russian Federation); Novosibirsk State University, Novosibirsk (Russian Federation); Mali, Vyacheslav I.; Anisimov, Alexander G. [Siberian Branch of Russian Academy of Sciences, Lavrentyev Institute of Hydrodynamics, Novosibirsk (Russian Federation); Bulina, Natalia V. [Siberian Branch of Russian Academy of Sciences, Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk (Russian Federation); Moreira Jorge, Alberto Jr. [Institut Polytechnique de Grenoble (INPG), Science et Ingenierie des Materiaux et Procedes (SIMAP-CNRS), Saint-Martin-d' Heres (France); Federal University of Sao Carlos, Department of Materials Science and Engineering, Sao Carlos, SP (Brazil); Yavari, Alain R. [Institut Polytechnique de Grenoble (INPG), Science et Ingenierie des Materiaux et Procedes (SIMAP-CNRS), Saint-Martin-d' Heres (France)

    2015-09-15

    Heating of conductive materials by electric current is used in many technological processes. Application of electric pulses to metallic glasses induces their fast crystallization, which is an interesting and complex phenomenon. In this work, crystallization of the Fe{sub 83}B{sub 17} amorphous alloy induced by pulses of electric current produced has been studied using X-ray diffraction and transmission electron microscopy. Ribbons of the alloy were directly subjected to single pulses of electric current 250 μs long formed by a capacitor discharge. As the value of ∫I{sup 2}dt was increased from 0.33 to 2.00 A{sup 2} s, different crystallization stages could be observed. The crystallization began through the formation of the nuclei of α-Fe. At high values of ∫I{sup 2}dt, α-Fe and tetragonal and orthorhombic Fe{sub 3}B and Fe{sub 23}B{sub 6} were detected in the crystallized ribbons with crystallites of about 50 nm. Thermal annealing of the ribbons at 600 C for 2 min resulted in the formation of α-Fe and tetragonal Fe{sub 3}B. It was concluded that pulses of electric current produced by a capacitor discharge induced transformation of the Fe{sub 83}B{sub 17} amorphous phase into metastable crystalline products. (orig.)

  16. Invar behavior of NANOPERM-type amorphous Fe–(Pt)–Zr–Nb–Cu–B alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gondro, J.; Świerczek, J., E-mail: swiercz@wip.pcz.pl; Rzącki, J.; Ciurzyńska, W.; Olszewski, J.; Zbroszczyk, J.; Błoch, K.; Osyra, M.; Łukiewska, A.

    2013-09-15

    Transmission Mössbauer spectra of amorphous Fe{sub 86}Zr{sub 7}Nb{sub 1}Cu{sub 1}B{sub 5}, Fe{sub 81}Zr{sub 7}Nb{sub 1}Cu{sub 1}B{sub 10} and Fe{sub 81}Pt{sub 5}Zr{sub 7}Nb{sub 1}Cu{sub 1}B{sub 5} alloys in the as-quenched state and subjected to the accumulative annealing for 15 min in the temperature range from 573 K up to 750 K are presented. After these heat treatments the alloys remain in the amorphous state. The accumulative annealing for 15 min at 573 K and then 600 K of the Fe{sub 86}Zr{sub 7}Nb{sub 1}Cu{sub 1}B{sub 5} and Fe{sub 81}Zr{sub 7}Nb{sub 1}Cu{sub 1}B{sub 10} alloys causes the narrowing of the transmission Mössbauer spectra as compared to the as-quenched state and the decrease of the average hyperfine field induction which is connected with the invar effect. For similar behavior in Fe{sub 81}Pt{sub 5}Zr{sub 7}Nb{sub 1}Cu{sub 1}B{sub 5} alloy the accumulative annealing up to 700 K is needed. With further increase of the annealing temperature up to 750 K the broadening of the Mössbauer spectra and the increase of the average hyperfine field induction occur. The lowest value of the average hyperfine field induction of amorphous samples is accompanied by the lowest value of the Curie temperature. The investigated amorphous alloys do not reach the magnetic saturation up to the magnetizing field of 2 T and the coefficient in Holstein–Primakoff term is about one order in magnitude larger than in other classical FeCo-based amorphous alloys due to the non-collinear magnetic structure. The Mössbauer spectra and hysteresis loops of the amorphous Fe{sub 86}Zr{sub 7}Nb{sub 1}Cu{sub 1}B{sub 5} alloy in the as-quenched state and after the accumulative annealing at 573+620 K for 15 min are sensitive to the tensile stresses subjected to the sample. Such behavior is ascribed to the invar anomalies. - Highlights: • Complex magnetic transformations found in the amorphous Fe{sub 86}Zr{sub 7}Nb{sub 1}Cu{sub 1}B{sub 5}, Fe{sub 81}Zr{sub 7}Nb{sub 1}Cu{sub 1}B

  17. Some aspects of hydrogen interaction with amorphous metallic materials

    International Nuclear Information System (INIS)

    For the first time is considered change of some properties of amorphous metallic materials (AMM) directly in the process of hydrogenation. A supposition is made that many found effects are consequence of accumulation and relief of internal stresses during hydrogenation, exposure or following annealing of AMM. Fe81B14Si15, Fe52Co20Si15B13, Fe5Co70Si15B10, Fe5Co58Ni10Si11B16, Co67Fe4Cr7Si8B1484KChSP, Ni60Nb35Ti5, Ni60Nb40 and Pd17,5Cu6Si16.5 AMM were investigated. 24 refs.; 4 figs

  18. Polarization and resistivity measurements of post-crystallization changes in amorphous Fe-B-Si alloys

    International Nuclear Information System (INIS)

    The effects of grain growth and compositional changes on the electrochemical behavior and the resistivity of amorphous iron-boron-silicon (Fe77.5B15Si7.5) alloys after crystallization were studied. Deterioration of the protective passive film was observed, along with increased annealing. Potentiodynamic polarization provided excellent information about microstructural and chemical changes. It was concluded that electrochemical measurements could be used in conjunction with resistivity measurements in direct studies of grain growth and chemical changes occurring in different phases of the devitrified alloy

  19. Mossbauer studies of amorphous Fe73.5Cu1Nb3Si13.5B9 alloy

    DEFF Research Database (Denmark)

    Jiang, Jianzhong

    1996-01-01

    This paper reports a Mossbauer study of amorphous Fe73.5Cu1Nb3Si13.5B9 alloy between 10 and 673 K. The Curie temperature Tc is found to be 620-+ 1 K. The temperature dependence of the reduced average hyperfine field can be explained on the basis of Handrich's model of amorphous ferromagnetism, in...

  20. A non-resonant RF cavity loaded with amorphous alloy for proton cancer therapy

    CERN Document Server

    Makita, Y; Nayayama, T; Tsuchidate, H; Tsukishima, C; Yoshida, K

    1999-01-01

    A non-resonant RF cavity loaded with amorphous alloy cores has been designed and tested. The cavity has a re-entrant structure loaded with 8 amorphous alloy toroidal core and its characteristic impedance is designed as 450 Omega . The RF power is fed by 1 kW solid state amplifier using a step-up transformer with 1:9 impedance ratio. In the high power test, an accelerating gap voltage of more than 900 V was measured with input power of 1 kW in the frequency range of 1 to 10 MHz. The voltage standing wave ratio (VSWR) was less than 2.0. The results prove that the cavity may be used successfully within a compact proton synchrotron for a cancer therapy facility. (3 refs).

  1. Tensile and compression properties of Zr-based bulk amorphous alloy at different temperatures

    Institute of Scientific and Technical Information of China (English)

    WANG; Xu; LOU; Decheng; GAO; Zhanjun; LIU; Lei; LIANG; Hong

    2005-01-01

    Mechanical properties of the Zr41Ti14Cu12.5Ni10Be22.5 bulk amorphous alloy at different temperatures were investigated. The compression test was carried out on a Gleebe-3200 machine at 345 and 375℃, respectively, in the supercooled liquid region. It is shown that decreasing the compressive rate and increasing temperature have a similar influence trend on the compressive behavior of the bulk amorphous alloy. Room and low temperature tensile strengths were tested on the Instron materials testing system. At low temperature, the tensile strength decreased with decreasing of the testing temperature.Hardness measurement indicated that below the glass transition temperature, the hardness decreased with increasing of the annealing temperature and duration time. It,however, increased when the annealing treatment was performed above the glass transition temperature.

  2. Magnetic Properties Of Amorphous And Nanocrystalline FeNiZrCuB Alloys

    International Nuclear Information System (INIS)

    The coercive fields Hc, saturation magnetizations Js and magnetostrictions λs of the amorphous Fe86-xNixZr7Cu1B6 alloys different contents of Ni(0-86 at.%) were investigated at room temperature. Thermomagnetic analyses by means of initial AC permeability and resistivity at the amorphous and nanocrystalline states of the investigated alloys were performed up to 5500 C. It was found that additions of Ni up to x = 33 at.% cause an increase of Hc, Js, λs. Additions of Ni (x = 0 - 43) cause drastic increase of the Curie temperature from 71 deg C for x 0at.% to 373 deg C for x = 43at.% of Ni. Higher concentration of Ni causes a decrease of Hc, Js, λs and Tc. (Authors)

  3. Structure of amorphous Ag/Ge/S alloys: experimentally constrained density functional study

    Science.gov (United States)

    Akola, J.; Beuneu, B.; Jones, R. O.; Jóvári, P.; Kaban, I.; Kolář, J.; Voleská, I.; Wágner, T.

    2015-12-01

    Density functional/molecular dynamics simulations have been performed to determine structural and other properties of amorphous Ag/Ge/S and Ge/S alloys. In the former, the calculations have been combined with experimental data (x-ray and neutron diffraction, extended x-ray absorption fine structure). Ag/Ge/As alloys have high ionic conductivity and are among the most promising candidates for future memristor technology. We find excellent agreement between the experimental results and large-scale (500 atoms) simulations in Ag/Ge/S, and we compare and contrast the structures of Ge/S and Ag/Ge/S. The calculated electronic structures, vibrational densities of states, ionic mobilities, and cavity distributions of the amorphous materials are discussed and compared with data on crystalline phases where available. The high mobility of Ag in solid state electrolyte applications is related to the presence of cavities and can occur via jumps to a neighbouring vacant site.

  4. Evidence of eutectic crystallization and transient nucleation in Al89La6Ni5 amorphous alloy

    International Nuclear Information System (INIS)

    The phase evolution with the temperature and time in the process of crystallization of Al89La6Ni5 amorphous alloy has been investigated by in situ high-temperature and high-pressure x-ray powder diffraction using synchrotron radiation. Two crystalline phases, fcc-Al and a metastable bcc-(AlNi)11La3-like phase, were identified after the first crystallization reaction, revealing a eutectic reaction instead of a primary reaction suggested in the literature. Time-dependent nucleation in the amorphous alloy is detected and the experimental data can be fitted by both the Zeldovich's and Kashchiev's transient nucleation models with transient nucleation times of 220 and 120 min, respectively. Copyright 2001 American Institute of Physics

  5. Hydrogen diffusion in Zr35Ni55V10 amorphous alloy

    Institute of Scientific and Technical Information of China (English)

    CHENG Xiao-ying; WAHG Fang

    2007-01-01

    Hydrogen diffusion in Zr35Ni55V10 amorphous alloy was measured by chronopotentiometry. The results show that at lower molar ratio of hydrogen (x<0.06, x=n(H)/n(M)), the diffusivity of hydrogen increases rapidly with increasing the molar ratio of hydrogen. However, when x(H)>0.1, the diffusivity of hydrogen decreases slightly with increasing the molar ratio of hydrogen, which is similar to the change in crystalline alloy. It is proposed that hydrogen atoms mainly occupy the sites corresponding to tetrahedra with 4 Zr atoms at lower molar ratio of hydrogen. When the molar ratio of hydrogen is higher, the additional hydrogen atoms are in sites with higher energy and these sites in amorphous state are similar to these in crystalline states.

  6. The magnetic entropy change on amorphous FeMnZr alloys

    International Nuclear Information System (INIS)

    The magnetization behaviors have been measured for amorphous Fe90-xMnxZr10 (x=0,4,6) alloys. The Curie temperature is decreased from 243 to 218K with increasing Mn concentration (x=0-6). The magnetization measurements were conducted at temperatures above the Curie temperature in the paramagnetic region. In all samples, the magnetic properties showed superparamagnetic behavior above Tc where the mean magnetic moment of the superparamagnetic spin clusters decreased with increasing temperature. A large magnetic entropy change ΔSM, which is calculated from H vs. M curves associated with the ferromagnetic-paramagnetic transitions in amorphous state, has been observed. The maximum of ΔSM was found to appear in the vicinity of the Curie temperature of the amorphous phase. The value is 2.96, 2.51 and 2.29J/kgK at x=0,4 and 6, respectively

  7. Magnetic Compton scattering study of the ferromagnetic amorphous alloys Fe1-xBx

    International Nuclear Information System (INIS)

    The boron contribution to the total spin moment in the amorphous alloys Fe1-xBx (x=0.2,0.24) has been determined using magnetic Compton scattering. The magnitude of the induced boron moment was found to be ∼-0.04μB per formula unit which is a factor of ∼2 less than that suggested by supercell linearized muffin-tin orbital electronic structure calculations

  8. Crystallization kinetics of an amorphous Co77Si11.5B11.5 alloy

    OpenAIRE

    R. Nowosielski; A. Zajdel; S. Lesz; B. Kostrubiec; Z. Stokłosa

    2006-01-01

    Purpose: This paper describes crystallization kinetics and changes magnetic properties involved by process of crystallization Co-Si-B amorphous alloy.Design/methodology/approach: The following experimental techniques were used: X-ray diffraction (XRD), electrical resistivity in situ measurements (four-point probe) static and dynamic measurements of magnetic properties (magnetic balance, fluxmeter, Maxwell-Wien bridge).Findings: In this work has been performed influence of thermal annealing on...

  9. Crystallization of the Fesub(84-x)Vsub(x)B16 amorphous alloys

    International Nuclear Information System (INIS)

    Resistometric and Moessbauer measurements of the isothermal crystallization of nearly eutectic Fe-V-B amorphous alloys containing up to 8 at.% V were performed. The concentration dependence of the hyperfine fields of the crystallization products was found. The α-Fe-V and tetragonal mixed boride were detected and their contents in the course of crystallization estimated. The crystallization kinetics corresponds to the growth of α-phase nuclei proved by CEMS at the contact surface. (Auth.)

  10. Silicon nanocrystals on amorphous silicon carbide alloy thin films: Control of film properties and nanocrystals growth

    International Nuclear Information System (INIS)

    The present study demonstrates the growth of silicon nanocrystals on amorphous silicon carbide alloy thin films. Amorphous silicon carbide films [a-Si1−xCx:H (with x 1−xCx:H layer. The effect of short-time annealing at 700 °C on the composition and properties of the layer was studied by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. It was observed that the silicon-to-carbon ratio in the layer remains unchanged after short-time annealing, but the reorganization of the film due to a large dehydrogenation leads to a higher density of SiC bonds. Moreover, the film remains amorphous after the performed short-time annealing. In a second part, it was shown that a high density (1 × 1012 cm−2) of silicon nanocrystals can be grown by low pressure chemical vapor deposition on a-Si0.8C0.2 surfaces at 700 °C, from silane diluted in hydrogen. The influence of growth time and silane partial pressure on nanocrystals size and density was studied. It was also found that amorphous silicon carbide surfaces enhance silicon nanocrystal nucleation with respect to SiO2, due to the differences in surface chemical properties. - Highlights: ► Silicon nanocrystals (Si-NC) growth on amorphous silicon carbide alloy thin films ► Plasma deposited amorphous silicon carbide films with well-controlled properties ► Study on the thermal effect of 700 °C short-time annealing on the layer properties ► Low pressure chemical vapor deposition (LPCVD) of Si-NC ► High density (1 × 1012 cm−2) of Si-NC was achieved on a-Si0.8C0.2 surfaces by LPCVD.

  11. Cast bulk Zr57Ti5Al10Cu20Ni8 amorphous alloy with tendency of phase separation

    International Nuclear Information System (INIS)

    Zr-Ti-Al-Cu-Ni alloys show excellent glass forming ability (GFA). Amorphous cylindrical samples of diameter from 8 to 20 mm were produced by casting the Zr57Cu20Al10Ni8Ti5 alloy melt into a copper mould. The Zr57Cu20Al10Ni8Ti5 amorphous alloy shows some particular crystallization characteristics: measurements by differential scanning calorimetry (DSC) reveal three exothermic peaks in the DSC traces at continuous heating. The third peak of the highest peak temperature shifts towards lower temperature with the decrease of the cooling rates at which the amorphous alloys were formed, while the first two peaks remain unchanged. Isothermal annealing near the glass transition temperature causes the third peak shifting towards a definitive temperature and then it becomes quite stable during further annealing. The shift of the third peak is attributed to the tendency of phase separation of the alloy. (orig.)

  12. Amorphous Alloy Membranes Prepared by Melt-Spin methods for Long-Term use in Hydrogen Separation Applications

    Energy Technology Data Exchange (ETDEWEB)

    Chandra, Dhanesh; Kim, Sang-Mun; Adibhatla, Anasuya; Dolan, Michael; Paglieri, Steve; Flanagan, Ted; Chien, Wen-Ming; Talekar, Anjali; Wermer, Joseph

    2013-02-28

    Amorphous Ni-based alloy membranes show great promise as inexpensive, hydrogenselective membrane materials. In this study, we developed membranes based on nonprecious Ni-Nb-Zr alloys by adjusting the alloying content and using additives. Several studies on crystallization of the amorphous ribbons, in-situ x-ray diffraction, SEM and TEM, hydrogen permeation, hydrogen solubility, hydrogen deuterium exchange, and electrochemical studies were conducted. An important part of the study was to completely eliminate Palladium coatings of the NiNbZr alloys by hydrogen heattreatment. The amorphous alloy (Ni0.6Nb0.4)80Zr20 membrane appears to be the best with high hydrogen permeability and good thermal stability.

  13. Structural relaxation in Fe(Co)SiAlGaPCB amorphous alloys

    International Nuclear Information System (INIS)

    Highlights: • Structural relaxation of a Fe(Co)SiAlGaPCB amorphous alloys was studied by DSC. • Two relaxation times were use to fit the experimental values of different magnitudes. • HRTEM images suggest some medium range structural order in the amorphous. -- Abstract: The structural relaxation of multicomponent Fe(Co)SiAlGaPCB amorphous alloys was investigated calorimetrically for annealed samples over a wide temperature range below the glass transition temperature. Upon heating, the annealed samples exhibit an endothermic reaction (enthalpy relaxation) starting around the annealing temperature and continuing over a temperature range of about 50–140 K, that it is followed by a broad exothermic reaction. Changes in the heat flow curves with annealing temperature and time were analyzed. Experimental values of the overall enthalpy change, ΔH, the peak temperature of the difference in heat flow between the annealed and the as-quenched samples, Tp, and Curie temperature, TC, were fitted by exponential functions including two relaxation times. Values of the two relaxation times are the same for different annealing temperatures regardless the considered property. Saturation values of these magnitudes show a linear dependence with the inverse of the annealing temperature. Tiny domains (2–3 nm in diameter) in the matrix observed by spherical aberration corrected high-resolution transmission electron microscopy could be attributed to some medium-range order in the atomic structure of these quenched alloys

  14. Glass Forming Ability and Magnetic Property of Fe74Al4Sn2(PSiB)20 Amorphous Alloy

    Institute of Scientific and Technical Information of China (English)

    CHEN Fei-fei; ZHOU Shao-xiong

    2004-01-01

    Amorphous ribbons of Fe74Al4Sn2(PSiB)20 alloy have been synthesized by melt spinning and axial design method. The thermal properties of the amorphous ribbons have been measured by differential scanning calorimeter (DSC). The DSC results show that the Fe74Al4Sn2P12Si4B4 amorphous alloy has relatively wider supercooled liquid region with a temperature interval of 40.38 K (ΔTx=Tx-Tg). The alloys with a higher phosphorous content in the metalloid element composition triangle of Fe74Al4Sn2(PSiB)20 have high glass forming ability. The amorphous alloys also show good magnetic properties in which Fe74Al4Sn2P6.67Si6.67B6.67 alloy has a large maximum permeability (μm), Fe78Al4Sn2P3Si3B10 alloy exhibits a high square ratio (Br/B10) and Fe74Al4Sn2P4Si12B4 shows a low core loss (P0.5/1.3T). High glass forming ability and good magnetic properties make Fe74Al4Sn2(PSiB)20 amorphous alloys valuable in future research.

  15. Overlay metallic-cermet alloy coating systems

    Science.gov (United States)

    Gedwill, M. A.; Levine, S. R.; Glasgow, T. K. (Inventor)

    1984-01-01

    A substrate, such as a turbine blade, vane, or the like, which is subjected to high temperature use is coated with a base coating of an oxide dispersed, metallic alloy (cermet). A top coating of an oxidation, hot corrosion, erosion resistant alloy of nickel, cobalt, or iron is then deposited on the base coating. A heat treatment is used to improve the bonding. The base coating serves as an inhibitor to interdiffusion between the protective top coating and the substrate. Otherwise, the protective top coating would rapidly interact detrimentally with the substrate and degrade by spalling of the protective oxides formed on the outer surface at elevated temperatures.

  16. Photochemical route for accessing amorphous metal oxide materials for water oxidation catalysis.

    Science.gov (United States)

    Smith, Rodney D L; Prévot, Mathieu S; Fagan, Randal D; Zhang, Zhipan; Sedach, Pavel A; Siu, Man Kit Jack; Trudel, Simon; Berlinguette, Curtis P

    2013-04-01

    Large-scale electrolysis of water for hydrogen generation requires better catalysts to lower the kinetic barriers associated with the oxygen evolution reaction (OER). Although most OER catalysts are based on crystalline mixed-metal oxides, high activities can also be achieved with amorphous phases. Methods for producing amorphous materials, however, are not typically amenable to mixed-metal compositions. We demonstrate that a low-temperature process, photochemical metal-organic deposition, can produce amorphous (mixed) metal oxide films for OER catalysis. The films contain a homogeneous distribution of metals with compositions that can be accurately controlled. The catalytic properties of amorphous iron oxide prepared with this technique are superior to those of hematite, whereas the catalytic properties of a-Fe(100-y-z)Co(y)Ni(z)O(x) are comparable to those of noble metal oxide catalysts currently used in commercial electrolyzers. PMID:23539180

  17. CORROSION OF AMORPHOUS AND NANOCRYSTALLINE Fe-BASED ALLOYS IN NaCl AND H2SO4 SOLUTIONS

    Science.gov (United States)

    Li, Xiang; Lu, Wei; Wang, Yuxin; Yan, Biao; Pan, Deng

    2013-07-01

    Corrosion resistance of nanocrystalline Fe73.5Si13.5B9Nb3Cu1 alloy was investigated and compared to its amorphous counterpart. Low-temperature crystallization occurred during the annealing of amorphous tapes was used to obtain a nanocrystalline structure. The influence of annealing condition on the structure and corrosion resistance of the alloy in NaCl and H2SO4 solutions was investigated. Based on the testing results, it was found that nanocrystalline tapes have higher corrosion resistance than amorphous counterpart and H2SO4 can promote the occurrence of corrosion compared with NaCl.

  18. Skeletal Amorphous Nickel Based Alloy Catalysts and Magnetically Stabilized Bed Hydrogenation Technology

    Institute of Scientific and Technical Information of China (English)

    Min Enze

    2004-01-01

    Looking toward 21 century, smaller, cleaner and more energy-efficient technology will be an important trend in the development of chemical industry. In light of the new process requirements,a number of technology breakthroughs have occurred. One of these discoveries, the magnetically stabilized bed (MSB), has been proven a powerful process for intensification. Since its initial research in the late 1980's at Research Institute of Petroleum Processing (RIPP), the MSB technology and related catalytic material have matured rapidly through an intensive research and engineering program, primarily focused on its scaling-up.In this paper, we report the discovery of a novel skeletal amorphous nickel-based alloy and its use in magnetically stabilized bed (MSB). Amorphous alloys are new kinds of catalytic materials with short-range order but long-range disorder structure. In comparison with Raney Ni, the skeletal amorphous nickel-based alloy has an increasingly higher activity in the hydrogenation of reactive groups and compounds including nitro, nitrile, olefin, acetylene, aromatics, etc. Up to now, the amorphous nickel based alloy catalysts, SRNA series catalyst, one with high Ni ratio have been commercially manufactured more than four year. The new SRNA catalyst has been successfully implemented for hydrogenation applications in slurry reactor at Balin Petrochemical, SINOPEC.SRNA catalyst with further improvement in catalytic activity and stability raise its relative stability to 2~4 times of that of conventional catalyst. In the course of the long-cycle operation of SRNA-4 the excellent catalyst activity and stability can bring about such advantage as low reaction temperature, good selectivity and low catalyst resumption.Magnetically stabilized bed (MSB), a fluidized bed of magnetizable particles by applying a spatially uniform and time-invariant magnetic field oriented axially relative to the fluidizing fluid flow, had many advantages such as the low pressure drop and

  19. Effect of Rare Earth Metals on Structure and Properties of Electroless Co-B Alloy Coating

    Institute of Scientific and Technical Information of China (English)

    宣天鹏; 张雷; 黄秋华

    2002-01-01

    The effect of rare earth metals cerium, lanthanum and yttrium on chemical composition, structure and properties of electroless Co-B alloy coating was studied. By plasma transmitting spectrograph, electron energy spectrometer, X-ray diffractometter, micro-hardometer and vibratory sample magnetometer the chemical constitution, structure and properties of the alloy coatings were analyzed and inspected. The results show that with a tiny quantity of rare earth metal added into Co-B alloy coating, the content of boron is decreased in the alloy coatings, and the kinds of rare earth metal have enormous effect on the structure and properties of electroless Co-B alloy coating. At the same time electroless Co-B alloy with amorphous structure is transformed to electroless Co-B-RE alloy with microcrystalline or crystalline structure. In this way microhardness of the coatings is increased remarkably. Cerium and lanthanum would also increase the saturated magnetic intensity and decrease coercitive force of the coating. So soft magnetization of the coatings would be improved.

  20. Preparation and characterisation of electrodeposited amorphous Sn-Co-Fe ternary alloys

    International Nuclear Information System (INIS)

    Electrochemical deposition was investigated as a process to obtain alloys of Sn-Co-Fe, which to date have not been reported in the literature. A constant current technique was used to electrochemically deposit tin-cobalt-iron alloys from a gluconate electrolyte. The gluconate system was chosen as an electrolyte, which could potentially provide an environmentally safe process. The effect of plating parameters such as current density, deposition time, temperature and pH are discussed. Results are reported for current density and plating time using an electrolyte temperature of 20-60 deg. C and pH of 7.0 in relation to phase composition, crystal structure and magnetic anisotropy of the deposited alloys. Investigations were conducted using 57Fe conversion electron Moessbauer spectroscopy (CEMS), 119Sn CEMS, transmission Moessbauer Spectroscopy and XRD. The 57Fe and 119Sn CEMS spectra and XRD showed that the dominant phase in the deposits was amorphous Sn-Co-Fe. The relative area of the 2nd and 5th lines of the sextets representing the magnetic iron containing phases was found to decrease continuously with increasing current density while at the same time no significant changes in the magnetic anisotropy was found with plating time. Magnetically split 119Sn spectra reflecting a transferred hyperfine field were also observed. A range of good quality amorphous Sn-Co-Fe ternary alloys was obtained over a range of operating conditions from an environmentally acceptable gluconate electrolyte

  1. Low-emissivity coating of amorphous diamond-like carbon/Ag-alloy multilayer on glass

    International Nuclear Information System (INIS)

    Transparent low-emissivity (low-e) coatings comprising dielectrics of amorphous diamond-like carbon (DLC) and Ag-alloy films are investigated. All films have been prepared by dc magnetron sputtering. An index of refraction of the DLC film deposited in a gas mixture of Ar/H2 (4%) shows n = 1.80 + 0.047i at 500 nm wavelength. A multilayer stack of DLC (70 nm thick)/Ag87.5Cu12.5-alloy (10 nm)/DLC (140 nm)/Ag87.5Cu12.5-alloy (10 nm)/DLC (70 nm) has revealed clear interference spectra with spectra selectivity. This coating performs low emittance less than 0.1 for black body radiation at 297 K, exhibiting a transparent heat mirror property embedded in DLC films

  2. Glass forming ability of iron based amorphous alloys depending on Mo, Cr and Co content

    International Nuclear Information System (INIS)

    The Fe41Co7Cr15Mo14C15B6Y2 multicomponent Fe-based alloy is known to be one of the best glass formers in iron-based systems and shows a critical casting thickness of 16 mm. The elements constituting the alloy have different influences on the glass forming ability. Therefore, the content of Mo, Cr and Co was systematically changed in the master alloy Fe77-x(Co,Cr,Mo)xC15B6Y2 to investigate how these three elements support the glassy microstructure. It was found that a certain content of Mo, Cr, and Co leads to a microstructure of amorphous matrix and α-Fe precipitates without any carbides.

  3. Critical behavior of electrical resistivity in amorphous Fe–Zr alloys

    Indian Academy of Sciences (India)

    A Perumal

    2001-04-01

    Electrical resistivity (ρ) of the amorphous (a-)Fe100-Zr ( = 8.5, 9.5 and 10) alloys has been measured in the temperature range 77 to 300 K, which embraces the second-order magnetic phase transition at the Curie temperature point . Analysis of the resistivity data particularly in the critical region reveals that these systems have a much wider range of critical region compared to other crystalline ferromagnetic materials. The value of and specific heat critical exponent, has the same values as those determined from our earlier magnetic measurements. The value of for all the present investigated alloys are in close agreement with the values predicted for three-dimensional (3D) Heisenberg ferromagnet systems, which gives contradiction to the earlier results on similar alloys. It is observed from the analysis that the presence of quenched disorder does not have any influence on critical behavior.

  4. Properties and local structure of plasma-deposited amorphous silicon-carbon alloys

    International Nuclear Information System (INIS)

    Hydrogenated amorphous silicon-carbon alloy films were plasma-deposited from methane and silane, varying gas ratio, R.F. power and substrate temperature. Carbon addition increases the optical gap, but also raises the dangling bond density while decreasing conductivity. Low C alloys can be gas-phase doped both p and n type. In the IR spectra the various Si-C stretching modes observed between 650 and 780 cm/sup -1/ are explained by back bonding variations. A tentative method of assigning this shift to back bonding of C to the Si is given. A distribution of modes is observed for all alloys, with each mode appearing even at 2% C. The distribution is sensitive to substrate temperature, but is stable after vacuum annealing to 4000C

  5. Electrical transport properties of amorphous Ni32Pd53P15 alloy

    Science.gov (United States)

    Prakruti, Chaudhari; Joshi, R. H.; Bhatt, N. K.; Thakore, B. Y.

    2015-08-01

    A ternary alloy containing nickel, palladium and phosphorous in amorphous form has been studied. The electrical transport properties viz. electrical resistivity, thermoelectrical power (TEP), thermal conductivity are computed using our recently proposed potential. In the present work, five screening functions have been employed to incorporate the exchange and correlation effects. The theoretical structure factors due to hard core fluid theory have been used in the calculations. The liquid alloy is studied as a function of its composition at temperature 294 K. The partial structure factors of the compound-forming Ni32Pd53P15 ternary alloy has been calculated by considering Hoshino's m-component hard-sphere mixture, which is based on Percus-Yevic equation of Hiroike.

  6. Amorphous Structures in Laser Cladding of ZL111 Aluminum Alloy:Semi-quantitative Study by Differential Thermal Analysis (DTA)

    Institute of Scientific and Technical Information of China (English)

    LI Xianqin; CHENG Zhaogu; XIA Jin'an; XU Guoliang; LIANG Gongying

    2000-01-01

    This paper deals with amorphous structures in the laser cladding. ZL111 alloy is the substrate and Ni-Cr-Al alloy is sprayed on the substrate as the coating material. The coating is clad by a 5 kW transverse flow CO2 laser. The observation of SEM and TEM reveal that in the laser cladding there are amorphous structures of two different morphologies: one is space curved flake-like, and exists in the white web-like structures; the other is fir leaf-like, and exists in the grain-like structures. Differential thermal analysis (DTA) is used to semi-quantitatively determine the content of the amorphous structures. A relation is obtained between the content of amorphous structures and the dimensionless laser cladding parameter C. We also show the changes of the amorphous structures after annealing.

  7. Soft magnetic and microstructural investigation in Fe-based amorphous alloy

    Energy Technology Data Exchange (ETDEWEB)

    Nabiałek, Marcin, E-mail: nmarcell@wp.pl

    2015-09-05

    Highlights: • Samples were obtained using the injection-casting method. • The samples were manufactured in the shape of plates of the thickness 0.5 mm. • The amorphous and nanocrystalline structure was confirmed using XRD, SEM, TEM, CT. • Magnetic properties were analysed in terms of contents of the spin waves stiffness parameter b. - Abstract: In this paper, the results of investigations concerning Fe{sub 61}Co{sub 10}Y{sub 8}W{sub 1}B{sub 20} alloy are presented. The alloy samples were produced, using an injection-casting method, in the form of plates of approximate thickness 0.5 mm. Analysis of the results facilitates the description of structural transformations which occurred within the amorphous material as a result of isothermal annealing, the latter having been carried out under specified conditions. This thermal treatment led to the creation within the amorphous matrix of evenly distributed nanometric sized crystalline grains. The structure and microstructure of the samples in the as-quenched and nanocrystalline states were analysed by means of: X-ray diffractometry (XRD), scanning and transmission electron microscopy (SEM and TEM) and computer tomography (CT). The influence of the structural changes on the magnetic properties was studied using a vibrating sample magnetometer (VSM). Detailed analysis of the microstructure was performed on the ferromagnetic alloy samples with amorphous and nanocrystalline structure; this, in connection with the magnetic studies, facilitated full description of the influence of changes in the microstructure, and imperfections created during the production process, on the magnetic properties.

  8. Survey of BGFA Criteria for the Cu-Based Bulk Amorphous Alloys

    Directory of Open Access Journals (Sweden)

    D. Janovszky

    2011-01-01

    Full Text Available To verify the effect of composition on the bulk glass forming ability (BGFA of Cu-based alloys, properties have been collected from the literature (~100 papers, more than 200 alloys. Surveying the BGFA criteria published so far, it has been found that the atomic mismatch condition of Egami-Waseda is fulfilled for all the Cu-based BGFAs, the value being above 0,3. The Zhang Bangwei criterion could be applied for the binary Cu-based alloys. The Miracle and Senkov criteria do not necessarily apply for Cu based bulk amorphous alloys. The critical thickness versus =/(+ plot of Lu and Liu extrapolates to =0.36, somewhat higher than the 0.33 value found in other BGFA alloys. The Park and Kim parameter correlates rather poorly with the critical thickness for Cu based alloys. The Cheney and Vecchino parameter is a good indicator to find the best glass former if it is possible to calculate the exact liquids projection. In 2009 Xiu-lin and Pan defined a new parameter which correlates a bit better with the critical thickness. Based on this survey it is still very difficult to find one parameter in order to characterize the real GFA without an unrealized mechanism of crystallization.

  9. Crystallization Kinetics of Pr8Fe86-xZrxB6 Amorphous Alloys

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Crystallization kinetics of Pr8Fe86-xZrxB6 (x=0, 1, 2) amorphous alloys was studied by DTA and XRD methods. The experimental results showed that the crystalline phases of Pr8Fe86B6 alloy are composed of α-Fe phase, Pr2Fe23B3 and Pr2Fe14B, when crystallization temperature is below 900 ℃. The activation energy of α-Fe phase remains relatively constant about 306.09 kJ/mol, as the crystalline fraction of α-Fe phase is below 8 %. At the beginning of crystallization, the activation energy of Pr2Fe23B3 and Pr2Fe14B phases are 510.85 kJ/mol and 725.97 kJ/mol, respectively, and then the activation energy of three phases declines with increasing the crystalline fraction. The crystallization behavior of α-Fe and Pr2Fe14B essentially results in the formation of a α-Fe/Pr2Fe14B composite microstructure with a coarse grain size in annealed Pr8Fe86B6 alloy, which is attributed to a difficult nucleation and an easy growth for both the α-Fe and Pr2Fe14B in the alloy. Zr can be used to change the crystallization behavior of the α-Fe phase in Pr-Fe-B amorphous alloy, which is helpful to the formation of the α-Fe/Pr2Fe14B nanocomposite microstructure with a fine grain size for the α-Fe phase in the alloy.

  10. SHORT-RANGE ORDER IN AMORPHOUS Co-Sn ALLOYS THROUGH NMR AND MÖSSBAUER SPECTROSCOPIES

    OpenAIRE

    Nabli, H; Piecuch, M.; Durand, J.; Marchal, G.

    1985-01-01

    The hyperfine field distribution on 59Co obtained by NMR in ferromagnetic amorphous Co-Sn alloys is related to the distribution of Sn environment around the Co resonant nuclei. The mean values of the quadrupole splitting and of the isomershift for tin in paramagnetic Co-Sn alloys, as obtained by 119Sn Mössbauer spectroscopy, suggest that the tin atoms in these alloys are located at the center of trigonal prisms of cobalt atoms.

  11. Fundamentals of amorphous solids structure and properties

    CERN Document Server

    Stachurski, Zbigniew H

    2014-01-01

    Long awaited, this textbook fills the gap for convincing concepts to describe amorphous solids. Adopting a unique approach, the author develops a framework that lays the foundations for a theory of amorphousness. He unravels the scientific mysteries surrounding the topic, replacing rather vague notions of amorphous materials as disordered crystalline solids with the well-founded concept of ideal amorphous solids. A classification of amorphous materials into inorganic glasses, organic glasses, glassy metallic alloys, and thin films sets the scene for the development of the model of ideal amorph

  12. Alloy metal nanoparticles for multicolor cancer diagnostics

    Science.gov (United States)

    Baptista, Pedro V.; Doria, Gonçalo; Conde, João

    2011-03-01

    Cancer is a multigenic complex disease where multiple gene loci contribute to the phenotype. The ability to simultaneously monitor differential expression originating from each locus results in a more accurate indicator of degree of cancerous activity than either locus alone. Metal nanoparticles have been thoroughly used as labels for in vitro identification and quantification of target sequences. We have synthesized nanoparticles with assorted noble metal compositions in an alloy format and functionalized them with thiol-modified ssDNA (nanoprobes). These nanoprobes were then used for the simultaneous specific identification of several mRNA targets involved in cancer development - one pot multicolor detection of cancer expression. The different metal composition in the alloy yield different "colors" that can be used as tags for identification of a given target. Following a non-cross-linking hybridization procedure previously developed in our group for gold nanoprobes, these multicolor nanoprobes were used for the molecular recognition of several different targets including differently spliced variants of relevant genes (e.g. gene products involved in chronic myeloid leukemia BCR, ABL, BCR-ABL fusion product). Based on the spectral signature of mixtures, before and after induced aggregation of metal nanoparticles, the correct identification could be made. Further application to differentially quantify expression of each locus in relation to another will be presented. The differences in nanoparticle stability and labeling efficiency for each metal combination composing the colloids, as well as detection capability for each nanoprobe will be discussed. Additional studies will be conducted towards allele specific expression studies.

  13. Altering strength and plastic deformation behavior via alloying and laminated structure in nanocrystalline metals

    Energy Technology Data Exchange (ETDEWEB)

    Gu, C. [State Key Laboratory for Mechanical Behavior of Material, Xi' an Jiaotong University, Xi' an 710049 (China); Wang, F., E-mail: wangfei@mail.xjtu.edu.cn [State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi' an Jiaotong University, Xi' an 710049 (China); Huang, P., E-mail: huangping@mail.xjtu.edu.cn [State Key Laboratory for Mechanical Behavior of Material, Xi' an Jiaotong University, Xi' an 710049 (China); Lu, T.J. [State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi' an Jiaotong University, Xi' an 710049 (China); MOE Key Laboratory for Multifunctional Materials and Structures, Xi' an Jiaotong University, Xi' an 710049 (China); Xu, K.W. [State Key Laboratory for Mechanical Behavior of Material, Xi' an Jiaotong University, Xi' an 710049 (China)

    2015-07-29

    Nanoindentation and electron microscope techniques have been performed on sputtering deposited monolayered nanocrystalline CuNb and multilayered CuNb/Cu thin films. Microstructural features, hardness and surface morphologies of residual indentation have been evaluated to identify the effects of alloying and laminated structure on strength and plastic deformation behavior of nanocrystalline metals. By altering the content of Nb in CuNb alloy and adding crystalline Cu layers into CuNb alloy, the volume fraction of amorphous phase in CuNb alloy and interface structures changed dramatically, resulting in various trends that are related to hardness, indentation induced pileup and shear banding deformation. Based on the experimental results, the dominant deformation mechanisms of the CuNb and CuNb/Cu thin films with various Nb contents were proposed and extended to be discussed.

  14. Altering strength and plastic deformation behavior via alloying and laminated structure in nanocrystalline metals

    International Nuclear Information System (INIS)

    Nanoindentation and electron microscope techniques have been performed on sputtering deposited monolayered nanocrystalline CuNb and multilayered CuNb/Cu thin films. Microstructural features, hardness and surface morphologies of residual indentation have been evaluated to identify the effects of alloying and laminated structure on strength and plastic deformation behavior of nanocrystalline metals. By altering the content of Nb in CuNb alloy and adding crystalline Cu layers into CuNb alloy, the volume fraction of amorphous phase in CuNb alloy and interface structures changed dramatically, resulting in various trends that are related to hardness, indentation induced pileup and shear banding deformation. Based on the experimental results, the dominant deformation mechanisms of the CuNb and CuNb/Cu thin films with various Nb contents were proposed and extended to be discussed

  15. Structures of bulk amorphous Zr41Ti14Ni10Cu12.5Be22.5 alloy in amorphous, crystalline, supercooled liquid and liquid states

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The amorphous and crystal structures of Zr41Ti14Ni10Cu12.5Be22.5 alloy have been analyzed with X-ray diffractometer. The structures of bulk amorphous Zr41Ti14Ni10Cu12.5B22.5 alloy in solid, supercooled liquid and liquid states are almost of the same structure. The RDFs (Radius Distribution Function), the first coordination number, the first coordination radius, the correlation radius and atom number of the cluster were calculated for bulk amorphous Zr41Ti14Ni10Cu12.5B22.5 alloy in different states. The first coordination sphere radii and the first coordination numbers are 0.312nm, 11.2 in solid state, 0.301nm, 10.932 in supercooled liquid region and 0.305nm, 11.296 in liquid state. The crystal structure of Zr41Ti14Ni10Cu12.5B22.5 alloy is consisted of several intermetallic compounds which are CuZr2, Be2Zr, etc. The reason of formation glass for this alloy is that there is a larger resistance for atoms to rearrange and form intermetallic compounds in a long range order.

  16. Amorphous nickel boride membrane on a platinum-nickel alloy surface for enhanced oxygen reduction reaction

    Science.gov (United States)

    He, Daping; Zhang, Libo; He, Dongsheng; Zhou, Gang; Lin, Yue; Deng, Zhaoxiang; Hong, Xun; Wu, Yuen; Chen, Chen; Li, Yadong

    2016-08-01

    The low activity of the oxygen reduction reaction in polymer electrolyte membrane fuel cells is a major barrier for electrocatalysis, and hence needs to be optimized. Tuning the surface electronic structure of platinum-based bimetallic alloys, a promising oxygen reduction reaction catalyst, plays a key role in controlling its interaction with reactants, and thus affects the efficiency. Here we report that a dealloying process can be utilized to experimentally fabricate the interface between dealloyed platinum-nickel alloy and amorphous nickel boride membrane. The coating membrane works as an electron acceptor to tune the surface electronic structure of the platinum-nickel catalyst, and this composite catalyst composed of crystalline platinum-nickel covered by amorphous nickel boride achieves a 27-times enhancement in mass activity relative to commercial platinum/carbon at 0.9 V for the oxygen reduction reaction performance. Moreover, this interactional effect between a crystalline surface and amorphous membrane can be readily generalized to facilitate the 3-times higher catalytic activity of commercial platinum/carbon.

  17. Radioisotope spectrometric method to determine diffusion coefficients in metals and alloys

    International Nuclear Information System (INIS)

    A brief description of the spectrometric installation to study diffusion in metals using #betta#-decay radio-isotopes is presented. Diffusion coefficients of nickel in 70% Co-5% Fe-15% Si-10% B amorphous alloy are determined according to #betta#-radiation absorption in diffusion zone. Plate samples of 10x10 mm size and about 300 μm in thickness are used. Diffusion annealing is conducted during 100 hrs. The calculation of the diffusion coefficients has been carried out by the formula I/I0= esup(μsup(2)Dtau)erfc μ √ Dtau, where I0, I is an initial and a final radiation intensity; μ- an absorption coefficient of 63Ni #betta#-ray in the given material (at calculation μ=1.3x106 m-1 was taken); tau- duration of diffusion annealing; D- diffusion coefficient at the designed temperature. The value of the diffusion coefficient of nickel in 70% Co-5% Fe-15% S-10% B amorphous alloy at the temperature of 200 deg C is turned out to be equal to 4x10-21 m2/s. It should be noted that the self-diffusion coefficient of cobalt in Co-Fe alloy, found by extrapolation from high-temperature region, is equal to 10-35 m2/s, i.e. in 14 orders lower than that of the same basis in amorphous alloy

  18. Laser processing of metals and alloys

    International Nuclear Information System (INIS)

    Laser, due to its high degree of coherence can produce powder density in the range of 103-1011 W/mm2. This high power density of the laser beam enables it to be utilized for many industrial applications, e.g. welding, cutting, drilling, surface treatment, etc. Laser processing of materials has many advantages, e.g. good quality product at high processing speed, least heat affected zone, minimum distortion, etc. In addition, the same laser system can be utilized for different applications, a very cost effective factor for any industry. Therefore laser has been adopted for processing of different materials for a wide range of applications and is now replacing conventional materials processing techniques on commercial merits with several economic and metallurgical advantages. Applications of laser to process materials of different thicknesses varying from 0.1 mm to 100 mm have demonstrat ed its capability as an important manufacturing tool for engineering industries. While lasers have most widely been utilized in welding, cutting and drilling they have also found applications in surface treatment of metals and alloys, e.g. transfor mation hardening and annealing. More recently, there has been significant amount of research being undertaken in laser glazing, laser surface alloying and laser cladding for obtaining improved surface properties. This report reviews the stat us of laser processing of metals and alloys emphasising its metallurgical aspects a nd deals with the different laser processes like welding, cutting, drilling and surface treatment highlighting the types and choice of laser and its interaction with metals and alloys and the applications of these processes. (author). 93 refs., 32 figs., 7 tables

  19. Effect of surfactants on the corrosion of amorphous 76Ni-24P alloy in neutral solutions

    Energy Technology Data Exchange (ETDEWEB)

    Gomaa, N.G. (Alexandria Univ. (Egypt). Physics Dept.); Khamis Ibrahim, E. (Alexandria Univ. (Egypt). Chemistry Dept.); Ahmed, A. (Alexandria Univ. (Egypt). Chemistry Dept.); Abaza, S. (Alexandria Univ. (Egypt). Physics Dept.)

    1994-04-01

    76Ni-24P amorphous alloys have been electrodeposited from solutions containing sodium lauryl sulphate (SLS) and triton-X 100 (TX-100) to improve the surface quality of the specimens. Corrosion behaviour of electrodeposited amorphous alloys in sulphate and chloride solutions at 25 C has been studied by potential-time decay, linear polarization resistance and potentiodynamic techniques. Anodic polarization curves show that the specimens exhibit mild passivity at potentials between approximately -200 mV and 200 mV (SCE) and dissolve transpassively above 200 mV (SCE). The sulphate solution was found to increase the dissolution of the samples treated by the surfactants during the substrate brass plating. The nonanionic surfactant increases the corrosion current by 10 times compared to the anionic one which enhances the current by 400 times; the interpretation was based on the enhanced dissolution of the microcrystals of the specimens in the sulphate solution and to the steric hindrance of the surfactants. In addition, the alloys are more resistant to chlorides due to the formation of a phosphate/hypophosphite film which protects the surface from dissolution. (orig.)

  20. Effect of surfactants on the corrosion of amorphous 76Ni-24P alloy in neutral solutions

    Energy Technology Data Exchange (ETDEWEB)

    Gomaa, N.G. (Alexandria Univ., Physics Dept. (Egypt)); Khamis, E. (Alexandria Univ., Chemistry Dept. (Egypt)); Ahmed, A. (Alexandria Univ., Chemistry Dept. (Egypt)); Abaza, S. (Alexandria Univ., Physics Dept. (Egypt))

    1993-12-01

    76Ni-24P amorphous alloys have been electrodeposited from solutions containing sodium lauryl sulphate (SLS) and triton-X 100 (TX-100) to improve the surface quality of the specimens. Corrosion behaviour of electrodeposited amorphous alloys in sulphate and chloride solutions at 25 C has been studied by potential-time decay, linear polarization resistance and potentiodynamic techniques. Anodic polarization curves show that the specimens exhibit mild passivity at potentials between approximately -200 mV and 200 mV (SCE) and dissolve transpassively above 200 mV (SCE). The sulphate solution was found to increase the dissolution of the samples treated by the surfactants during the substrate brass plating. The nonanionic surfactant increases the corrosion current by 10 times compard to the anionic one which enhances the current by 400 times; the interpretation was based on the enhanced dissolution of the microcrystals of the specimens in the sulphate solution and to the steric hindrance of the surfactants. In addition, the alloys are more resistant to chlorides due to the formation of a phosphate/hypophosphite film which protects the surface from dissolution. (orig.)

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

    International Nuclear Information System (INIS)

    The reversibility of residual bending stresses is revealed in ribbon samples of cobalt- and iron-based amorphous alloys Co69Fe3.7Cr3.8Si12.5B11 and Fe57Co31Si2.9B9.1: the ribbons that are free of applied stresses and bent under the action of residual stresses become completely or incompletely straight upon annealing at the initial temperatures. The influence of annealing on the relaxation of bending stresses is studied. Preliminary annealing is found to sharply decrease the relaxation rate of bending stresses, and the initial stage of fast relaxation of these stresses is absent. Complete straightening of preliminarily annealed ribbons is shown to occur at significantly higher temperatures than that of the initial ribbons. Incomplete straightening of the ribbons is explained by the fact that bending stresses relaxation at high annealing temperatures proceeds due to both reversible anelastic deformation and viscous flow, which is a fully irreversible process. Incomplete reversibility is also caused by irreversible processes, such as the release of excess free volume and clustering (detected by small-angle X-ray scattering). The revealed differences in the relaxation processes that occur in the cobalt- and iron-based amorphous alloys are discussed in terms of different atomic diffusion mobilities in these alloys

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

    Energy Technology Data Exchange (ETDEWEB)

    Kekalo, I. B.; Mogil’nikov, P. S., E-mail: pavel-mog@mail.ru [National University of Science and Technology MISiS (Russian Federation)

    2015-06-15

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

  3. Topological and chemical short-range order in amorphous Ni-Ti alloys

    International Nuclear Information System (INIS)

    Neutron and x-ray scattering measurements were made on amorphous Ni35Ti65 and Ni40Ti60 alloys prepared by the melt-spinning process. The x-ray interference functions (structure factors) S/sup x/(K) are dominated by the topological short-range order (TSRO) S/sub NN/(K), but exhibited a small prepeak. The neutron structure factors S/sup n/(K) are dominated by the CSRO S/sub CC/(K)/(c1c2), describing the concentration fluctuations in the alloys. Assuming that the size effect term S/sub NC/(K) which describes the correlation between number density and concentration can be approximated by the Percus-Yevick hard sphere model, the TSRO S/sub NN/(K) and CSRO S/sub CC/(K)/(c1c2) were evaluated. From their Fourier transforms it became possible to evaluate the chemical short-range order parameter α which is of the order of -0.1 to -0.15 indicating a preference for unlike nearest neighbors in the amorphous Ni-Ti alloys

  4. Density and glass forming ability in amorphous atomic alloys: The role of the particle softness

    Science.gov (United States)

    Douglass, Ian; Hudson, Toby; Harrowell, Peter

    2016-04-01

    A key property of glass forming alloys, the anomalously small volume difference with respect to the crystal, is shown to arise as a direct consequence of the soft repulsive potentials between metals. This feature of the inter-atomic potential is demonstrated to be responsible for a significant component of the glass forming ability of alloys due to the decrease in the enthalpy of fusion and the associated depression of the freezing point.

  5. Atomic simulation of mechanical behavior of Mg in a super-lattice of nanocrystalline Mg and amorphous Mg-Al alloy

    Energy Technology Data Exchange (ETDEWEB)

    Song, H. Y., E-mail: gsfshy@sohu.com [School of Aeronautics, Northwestern Polytechnical University, Xi' an 710072 (China); College of Material Science and Engineering, Xi' an Shiyou University, Xi' an 710065 (China); An, M. R.; Li, Y. L., E-mail: liyulong@nwpu.edu.cn; Deng, Q. [School of Aeronautics, Northwestern Polytechnical University, Xi' an 710072 (China)

    2014-12-07

    The mechanical properties of a super-lattice architecture composed of nanocrystalline Mg and Mg-Al amorphous alloy are investigated using molecular dynamics simulation. The results indicate that deformation mechanism of nanocrystalline Mg is obviously affected by the amorphous boundary spacing and temperature. The strength of the material increases with the decrease of amorphous boundary spacing, presenting a Hall-Petch effect at both 10 K and 300 K. A stress platform and following stiffness softening, as well as a linear strengthening in the plastic stage, are observed when the amorphous boundary spacing below 8.792 nm at 10 K. The implying reason may be that the amorphous boundary acts as the dislocations emission and absorption source. However, the second stress peak is not observed for the models at 300 K. Instead, the flow stress in plastic stage is a nearly constant value. The simulation demonstrates the emergence of the new grain, accompanied by the deformation twins and stacking faults associated with the plastic behaviors at 300 K. The general conclusions derived from this work may provide a guideline for the design of high-performance hexagonal close-packed metals.

  6. Mechanical behaviour of nanocomposites derived from zirconium based bulk amorphous alloys

    International Nuclear Information System (INIS)

    The effects on mechanical properties of partial crystallization of a zirconium based bulk amorphous alloy (Vit1) are investigated. Nanocomposites are produced by appropriate heat treatments at temperatures higher than the glass transition temperature. Mechanical properties at room temperature are investigated by compression tests and hardness measurements including nanoindentation. The variation of the fracture stress with the degree of crystallinity is related to the nature, the size and the dispersion of the crystals in the amorphous phase. The variations of microstructure are estimated thanks to differential scanning calorimetry, X-ray diffraction and transmission electron microscopy. A significant connexion between crystals induces a decrease of the fracture stress whereas hardness continuously increases with crystallinity. From nanoindentation tests, Young's modulus and apparent yield stresses were roughly estimated and it is concluded that crystallization tends to increase the yield stress. Nevertheless, AFM observations of the imprints after indentation suggest that the mechanism of deformation can vary significantly with crystallization

  7. First-principle simulation on the crystallization tendency and enhanced magnetization of Fe76B19P5 amorphous alloy

    International Nuclear Information System (INIS)

    Iron-based amorphous alloys have attracted a growing interest due to their potential in the application of magnetic coil production. However, the magnetization of this kind of material is usually low due to the lack of long range ordering and high alloying element content. In this paper, an Fe76B19P5 amorphous alloy was simulated with ab initio molecular dynamics based on a previous simulation work on an Fe76Si9B10P5 amorphous alloy exhibiting that electron absorbers such as B and P can help enhance the magnetization of nearby Fe atoms. The present simulation results show that replacing Si with B can destabilize the amorphous structure, making it easier to crystallize, but no separate α-Fe participation can be observed in experiments during annealing due to its high B/P content. The results also show an increase in saturation magnetization by 8% can be expected due to the intensified electron transfer from Fe to B/P, and the glass forming ability decreases correspondingly. The idea of enhancing electron transfer can be applied to the development of other Fe-based amorphous alloys for the purpose of larger saturation magnetization. (paper)

  8. AMORPHOUS COATING FORMING IN THE CONDITIONS OF GAS THERMAL SPRAYING

    Directory of Open Access Journals (Sweden)

    V. V. Artemchuk

    2010-06-01

    Full Text Available In the article the issues of forming amorphous coatings in the conditions of gas thermal spraying of coating are considered. On the basis of theoretical analysis the technological factors, determining possibility of obtaining the amorphous coatings at detonation spraying, are formulated. Two groups of factors, influencing on formation of amorphous structure in detonation sprayed coatings from metallic alloys, are marked.

  9. Crystallization of amorphous silicon thin films deposited by PECVD on nickel-metalized porous silicon

    OpenAIRE

    Ben Slama, Sonia; Hajji, Messaoud; Ezzaouia, Hatem

    2012-01-01

    Porous silicon layers were elaborated by electrochemical etching of heavily doped p-type silicon substrates. Metallization of porous silicon was carried out by immersion of substrates in diluted aqueous solution of nickel. Amorphous silicon thin films were deposited by plasma-enhanced chemical vapor deposition on metalized porous layers. Deposited amorphous thin films were crystallized under vacuum at 750°C. Obtained results from structural, optical, and electrical characterizations show that...

  10. Ordering in binary transition metal alloys

    Energy Technology Data Exchange (ETDEWEB)

    Rusakov, G. [Institute for Metal Physics UB RAS, 18 Kovalevskoj St., 620990 Ekaterinburg (Russian Federation); Ural State Technical University - UPI, 19 Mira St., 620002 Ekaterinburg (Russian Federation); Son, L., E-mail: ldson@yandex.ru [Ural State Pedagogical University, 26 Cosmonavtov Ave, 620017 Ekaterinburg (Russian Federation); Efimova, E. [Institute for Metal Physics UB RAS, 18 Kovalevskoj St., 620990 Ekaterinburg (Russian Federation); Ural State Technical University - UPI, 19 Mira St., 620002 Ekaterinburg (Russian Federation); Dubinin, N. [Institute for Metallurgy UB RAS, 101 Amundsen St., 620016 Ekaterinburg (Russian Federation); Ural State Technical University - UPI, 19 Mira St., 620002 Ekaterinburg (Russian Federation)

    2012-03-20

    We present the phenomenological thermodynamic modeling of binary alloys which demonstrate solubility of the components at high temperatures, and form intermediate phase near equiatomic composition at lower ones (the so-called sigma-phase). Besides, the regular solution miscibility gap takes place also. The nonequilibrium thermodynamic potential is written out as a sum of the free energy of regular solution and polynomial term of scalar order parameter {phi}, which describes the {sigma}-phase ordering. There are four parameters in the model: the energy of regular solution mixing, the energy of {sigma}-phase formation at zero temperature, and the widths of temperature and concentration intervals of {sigma}-phase existence in the alloy with frozen-in random distribution of components. Up to now, both phase transitions which take place in a number of transition metals binary alloys (the {sigma}-phase formation and miscibility in the regular solution) have been treated separately. In present work, the standard technique of phase diagram calculation allows us to analyze all possible phase diagrams which may arise in the alloy.

  11. Investigation of the structure and properties of Fe-Co-B-Si-Nb bulk amorphous alloy obtained by pressure die casting method

    Directory of Open Access Journals (Sweden)

    W. Pilarczyk

    2012-12-01

    Full Text Available Purpose: The main aim of this paper is investigation of the microstructure and thermal properties of selected Fe-Co-B-Si-Nb bulk amorphous alloy.Design/methodology/approach: The studies were performed on Fe-Co-B-Si-Nb alloy in form of rods with diameter of ø=1.5 and ø=2 mm. Master alloy ingot with compositions of Fe37.44Co34.56B19.2Si4.8Nb4 was prepared by induction melting of pure Fe, Co, B, Si and Nb elements in argon atmosphere. The structure analysis of the studied materials in as-cast state was carried out using X-ray diffraction (XRD. The thermal properties: glass transition temperature (Tg, onset crystallization temperature (Tx and peak crystallization temperature (Tp of the as-cast alloys were examined by differential scanning calorimetry (DSC method. The microscopic observation of the fracture morphology of studied amorphous materials in rods form with different diameter was carried out by means of scanning electron microscope (SEM, within different magnification.Findings: The Fe-based bulk metallic glasses in form of rod were successfully produced by die pressure casting method. The investigation revealed that the studied rods are amorphous. These materials exhibit good glassforming ability. These tested rods with diameter of 1.5 and 2 mm exhibit similar characteristic temperatures (Tg, Tx, Tp. The exothermic peaks describing crystallization process of studied bulk metallic glasses are observed Morphology of cross section rods is changing having contact with copper mould during casting from smooth fracture inside rod to fine narrow dense veins pattern near to rod surface. These rods have smooth surface and metallic luster. The presented fractures are characteristic for metallic glasses.Practical implications: The success of production of studied Fe-based bulk metallic glasses is important for future practical application of those materials as elements of magnetic circuits, sensors and precise current transformers

  12. Optical response of noble metal alloy nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Bansal, Amit, E-mail: amit.bansal133@yahoo.com; Verma, S.S.

    2015-01-23

    The optical response, stability, and cost-effectiveness of individual noble metals can be improved by combining them to form alloy nanostructures. The present work reveals the influence of shape, size, and metal type on the optical response of alloy nanoparticles using discrete dipole approximation (DDA) simulations. It is found that sharp corner nanostructures show enhanced plasmonic properties in comparison to rounded counterpart. For all the three shapes, viz., nanocubes, rectangular, and nanobar particles, the increase in length resulted in redshifts of the longitudinal plasmon resonance alongwith enhancement in the scattering yield as well as relative efficiency parameters except for nanocubes of edge length 120 nm. The effect of size on full width at half maxima (FWHM) has also been studied and found to be maximal for nanocubes in comparison to other nanostructures. - Highlights: • The optical response of alloy nanostructures has been studied by discrete dipole approximation. • Sharp corner nanostructures show enhanced plasmonic properties. • Nanobars may be preferred over other nanostructures for absorption-based plasmonic applications. • Nanocubes of edge length greater than 100 nm may be useful for plasmonic solar cells. • Rectangular and nanobar particles may be preferred over nanocubes in plasmon sensing.

  13. Optical response of noble metal alloy nanostructures

    International Nuclear Information System (INIS)

    The optical response, stability, and cost-effectiveness of individual noble metals can be improved by combining them to form alloy nanostructures. The present work reveals the influence of shape, size, and metal type on the optical response of alloy nanoparticles using discrete dipole approximation (DDA) simulations. It is found that sharp corner nanostructures show enhanced plasmonic properties in comparison to rounded counterpart. For all the three shapes, viz., nanocubes, rectangular, and nanobar particles, the increase in length resulted in redshifts of the longitudinal plasmon resonance alongwith enhancement in the scattering yield as well as relative efficiency parameters except for nanocubes of edge length 120 nm. The effect of size on full width at half maxima (FWHM) has also been studied and found to be maximal for nanocubes in comparison to other nanostructures. - Highlights: • The optical response of alloy nanostructures has been studied by discrete dipole approximation. • Sharp corner nanostructures show enhanced plasmonic properties. • Nanobars may be preferred over other nanostructures for absorption-based plasmonic applications. • Nanocubes of edge length greater than 100 nm may be useful for plasmonic solar cells. • Rectangular and nanobar particles may be preferred over nanocubes in plasmon sensing

  14. Amorphous Hydrogenated Carbon-Nitrogen Alloy Thin Films for Solar Cell Application

    Institute of Scientific and Technical Information of China (English)

    ZHOU Zhi-Bin; DING Zheng-Ming; PANG Qian-Jun; CUI Rong-Qiang

    2001-01-01

    Amorphous hydrogenated carbon-nitrogen alloy (a-CNx :H) thin films have been deposited on silicon substratesby improved dc magnetron sputtering from a graphite target in nitrogen and hydrogen gas discharging. Thefilms are investigated by using Raman spectroscopy, x-ray photoelectron spectroscopy, spectral ellipsometer and electron spin resonance techniques. The optimized process condition for solar cell application is discussed. Thephotovoltaic property of a-CNx:H/silicon heterojunctions can be improved by the adjustment of the pressureratio of hydrogen to nitrogen and unbalanced magnetic field intensity. Open-circuit voltage and short-circuitcurrent reach 300mV and 5.52 Ma/cm2, respectively.

  15. Hydrogen effect on properties of iron and cobalt base amorphous alloys

    International Nuclear Information System (INIS)

    Stress relaxation studies were carried out for amorphous alloys 71KNSR (AS-1), 82k3KhSR (AS-2) and Fe78Nb3.5Cu1Si13.5 (AS-3) in their annealing and hydrogenation. Reversible change of elastic properties on hydrogenation is revealed. The restoration of elastic properties is observed in the process of holding at the temperature of 295 K. It is shown that elastic properties vary synchronously with electric conductivity and magnetic susceptibility. On the basis of electric and magnetic variables measurements as well as X-ray diffraction studies possible reasons for phenomena observed are discussed

  16. STUDY ON THE SHOCK WAVE CRYSTALLIZATION OF AMORPHOUS ALLOYS BY DSC

    Institute of Scientific and Technical Information of China (English)

    H.Y. Zhao; H. Wang; Q.J. Liu; J.D. Kan; Z.Q. Liu

    2002-01-01

    Shock wave and annealing crystallization of amorphous alloys FeSiB, FeMoSiB andFeCuNbSiB were studied by isothermal and non-isothermal DSC technique. It wasfound that the shock wave crystallization is very perfect, the fraction crystallized isvery close to 100%, though the period of crystallization is very short, only about10-4-10-6 s. Their produced phases differ from the parent phase in structure andcomposition. The high velocity of the transformation is very difficult to explain by thediffusion theory of solid state phase transition.

  17. Correlation between Structures of Bulk Amorphous Zr-Ti-Ni-Cu-Be Alloy in Different States

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The structures of the bulk amorphous Zr41Ti14Cu12.5Ni10.0Be22.5 alloy have been analyzed in solid, supercooled liquid and liquid with X-ray diffraction. The first coordination sphere radii and the first coordination numbers are 0.312 nm, 11.2 in solid state, 0.301 nm, 10.932 in supercooled liquid region and 0.305 nm, 11.296 in liquid state. The structures are the same in different states. But it shows some tendency to crystallizing that the first coordination sphere radius and the first coordination number drop in supercooled liquid region.

  18. Kinetics of glass transition and crystallization in multicomponent bulk amorphous alloys

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Differential scanning calorimeter (DSC) is used to investigate apparent activation energy of glass transition and crystallization of Zr-based bulk amorphous alloys by Kissinger equation under non-isothermal condition. It is shown that the glass transition behavior as well as crystallization reaction depends on the heating rate and has a characteristic of kinetic effects. After being isothermally annealed near glass transition temperature, the apparent activation energy of glass transition increases and the apparent activation energy of crystallization reaction decreases. However, the kinetic effects are independent of the pre-annealing.

  19. Magnetically stabilized bed reactor for selective hydrogenation of olefins in reformate with amorphous nickel alloy catalyst

    Institute of Scientific and Technical Information of China (English)

    Xuhong; Mu; Enze; Min

    2007-01-01

    A magnetically stabilized bed (MSB) reactor for selective hydrogenation of olefins in reformate was developed by combining the advantages of MSB and amorphous nickel alloy catalyst. The effects of operating conditions, such as temperature, pressure, liquid space velocity, hydrogen-to-oil ratio, and magnetic field intensity on the reaction were studied. A mathematical model of MSB reactor for hydrogenation of olefins in reformate was established. A reforming flow scheme with a post-hydrogenation MSB reactor was proposed. Finally, MSB hydrogenation was compared with clay treatment and conventional post-hydrogenation.

  20. Magnetic exchange coupling in amorphous Fe80-xDy xB20 alloys

    International Nuclear Information System (INIS)

    Amorphous Fe80-xDy xB20 alloys have been prepared by melt spinning and their magnetic properties have been studied. The mean field theory has been used to explain the temperature dependence of the magnetization. The exchange interactions between Co-Co and Dy-Co atom pairs have been evaluated. High-field magnetization studies on samples with stoichiometry close to that of a compensated ferrimagnet show a magnetic behavior that is characteristic of a non-collinear magnetic structure of the Dy and Fe sublattices. The region of the canted moments can be described by a phase diagram in the H-T plane

  1. Silicon nanocrystals on amorphous silicon carbide alloy thin films: Control of film properties and nanocrystals growth

    Energy Technology Data Exchange (ETDEWEB)

    Barbe, Jeremy, E-mail: jeremy.barbe@hotmail.com [CEA, Liten, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France); Universite de Toulouse, UPS, INPT, LAPLACE (Laboratoire Plasma et Conversion d' Energie), 118 route de Narbonne, 31062 Toulouse (France); Xie, Ling; Leifer, Klaus [Department of Engineering Sciences, Uppsala University, Box 534, S-751 21 Uppsala (Sweden); Faucherand, Pascal; Morin, Christine; Rapisarda, Dario; De Vito, Eric [CEA, Liten, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France); Makasheva, Kremena; Despax, Bernard [Universite de Toulouse, UPS, INPT, LAPLACE (Laboratoire Plasma et Conversion d' Energie), 118 route de Narbonne, 31062 Toulouse (France); CNRS, LAPLACE, F-31062 Toulouse (France); Perraud, Simon [CEA, Liten, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France)

    2012-11-01

    The present study demonstrates the growth of silicon nanocrystals on amorphous silicon carbide alloy thin films. Amorphous silicon carbide films [a-Si{sub 1-x}C{sub x}:H (with x < 0.3)] were obtained by plasma enhanced chemical vapor deposition from a mixture of silane and methane diluted in hydrogen. The effect of varying the precursor gas-flow ratio on the film properties was investigated. In particular, a wide optical band gap (2.3 eV) was reached by using a high methane-to-silane flow ratio during the deposition of the a-Si{sub 1-x}C{sub x}:H layer. The effect of short-time annealing at 700 Degree-Sign C on the composition and properties of the layer was studied by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. It was observed that the silicon-to-carbon ratio in the layer remains unchanged after short-time annealing, but the reorganization of the film due to a large dehydrogenation leads to a higher density of SiC bonds. Moreover, the film remains amorphous after the performed short-time annealing. In a second part, it was shown that a high density (1 Multiplication-Sign 10{sup 12} cm{sup -2}) of silicon nanocrystals can be grown by low pressure chemical vapor deposition on a-Si{sub 0.8}C{sub 0.2} surfaces at 700 Degree-Sign C, from silane diluted in hydrogen. The influence of growth time and silane partial pressure on nanocrystals size and density was studied. It was also found that amorphous silicon carbide surfaces enhance silicon nanocrystal nucleation with respect to SiO{sub 2}, due to the differences in surface chemical properties. - Highlights: Black-Right-Pointing-Pointer Silicon nanocrystals (Si-NC) growth on amorphous silicon carbide alloy thin films Black-Right-Pointing-Pointer Plasma deposited amorphous silicon carbide films with well-controlled properties Black-Right-Pointing-Pointer Study on the thermal effect of 700 Degree-Sign C short-time annealing on the layer properties Black-Right-Pointing-Pointer Low pressure

  2. EFFECT OF THE TEMPERATURE ON THE FRICTION AND WEAR PROPERTIES OF BULK AMORPHOUS ALLOY

    OpenAIRE

    DAWIT ZENEBE SEGU; PYUNG HWANG; SEOCK-SAM KIM

    2014-01-01

    The present paper report the results of an experimental investigation of the temperature effect on the sliding friction and wear properties of the bulk metallic glass (BMG). To improve the friction and wear properties of the BMG, the disk specimens were developed in the alloy system of Fe67.6C7.1Si3.3B5.5P8.7Cr2.3Mo2.6Al2Co1.0 using hot metal and industrial ferro-alloys. The friction and wear test was performed using flat-on-flat contact configuration of unidirectional tribometer and Si3N4 ce...

  3. Cyclic Fatigue Fracture of Zr55Al10Ni5Cu30 Bulk Amorphous Alloy with Quenched-in Crystallites

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The effects of quenched-in crystallites on the fracture of bulk amorphous alloys under cyclic loading condition wereinvestigated in this paper. For the fully amorphous alloy and specimen with fine crystallites the fatigue crack initiationoccurred on the surface. For the specimen with larger crystallites the crack originated from a big broken crystallitenear the surface. The average striation spacing on amorphous area is much larger than that on the crystallite.Crack initiation occurred at the crystallites is due to that the brittle crystallites broke easily under cyclic deformationcondition. The fine crystallites seemed to be protruded from the amorphous matrix and some bulges appeared onthe surface of specimen with fine crystallites under cyclic loading.

  4. Development of modified alloy 52 filler metal for weldability

    International Nuclear Information System (INIS)

    Alloy 690 was developed to improve resistance to Primary Water Stress Corrosion Cracking (PWSCC) compared with conventional Alloy 600. Alloy 690 weld metal (Alloy 52 filler metal) is also used in PWR nuclear power plants for welding of dissimilar-metal joints, such as safe-end welds of reactor vessels. Alloy 52, however, tends to be inferior to Alloy 600 weld metal (Alloy 82 filler metal) in terms of weldability due to its large amount of oxide scale generation on the weld bead surfaces. In this study, the effects of alloying elements on hot-cracking susceptibility and oxide scale generation were investigated in Alloy 52 filler metals. By means of cracking tests and cladding tests, investigation results were obtained as follows; 1) Increase of Nb and S contents increase hot-cracking susceptibility, although Ta dose not influence hot-cracking susceptibility. 2) Al and Ti contents influences amount of oxide scale generation. Modified Alloy 52 filler metal, which was developed based on the investigation results, showed improvements in suppression of oxide scale generation and hot cracking susceptibility. (author)

  5. Bioaccessibility of metals in alloys: Evaluation of three surrogate biofluids

    International Nuclear Information System (INIS)

    Bioaccessibility in vitro tests measure the solubility of materials in surrogate biofluids. However, the lack of uniform methods and the effects of variable test parameters on material solubility limit interpretation. One aim of this study was to measure and compare bioaccessibility of selected economically important alloys and metals in surrogate physiologically based biofluids representing oral, inhalation and dermal exposures. A second aim was to experimentally test different biofluid formulations and residence times in vitro. A third aim was evaluation of dissolution behavior of alloys with in vitro lung and dermal biofluid surrogates. This study evaluated the bioaccessibility of sixteen elements in six alloys and 3 elemental/metal powders. We found that the alloys/metals, the chemical properties of the surrogate fluid, and residence time all had major impacts on metal solubility. The large variability of bioaccessibility indicates the relevancy of assessing alloys as toxicologically distinct relative to individual metals. -- Highlights: • All alloy grades, independent of biofluid, revealed time-dependent release. • Different alloy materials are useful for testing of bioaccessibility parameters. • Minor changes in biofluid formulations have effects on bioaccessibility. • Dissolution studies illustrated effects of alloy and media on metal dissolution. • Metal solubility is compared in a series of alloys in various surrogate biofluids. -- We illustrate in vitro bioaccessibility tests of alloys for health characterization purposes; bio-surrogate formulations, and residence times have a major impact on bioaccessibility

  6. Cu clustering stage before the crystallization in Fe-Si-B-Nb-Cu amorphous alloys

    DEFF Research Database (Denmark)

    Ohnuma, M.; Hono, K.; Onodera, H.;

    1999-01-01

    The Cu clustering stage before the crystallization of Fe-Si-B-Nb-Cu amorphous alloys have been studied by three dimensional atom probe (3DAP) small-angle neutron scattering (SANS) and high sensitive differential calorimetry (DSC). Cu clustering occurs prior to the onset of the primary...... crystallization reaction. The number of the clusters estimated by 3DAP is large enough to provide heterogeneous nucleation sites to all bcc/D0(3) Fe-Si crystals which appear at higher temperatures. This fact indicates that the distribution of nanocrystalline Fe-Si is strongly affected by that of the Cu......-enriched clusters. The average diameter and interparticle distance of the Cu-enriched clusters have also been estimated by SANS. An exothermic reaction is observed above the Curie Temperature in the DSC curves of the Fe-Si-B-Nb-Cu alloys. The onset temperature of the exothermic reaction is shifted to lower...

  7. Crystallization of amorphous silicon thin films deposited by PECVD on nickel-metalized porous silicon.

    Science.gov (United States)

    Ben Slama, Sonia; Hajji, Messaoud; Ezzaouia, Hatem

    2012-01-01

    Porous silicon layers were elaborated by electrochemical etching of heavily doped p-type silicon substrates. Metallization of porous silicon was carried out by immersion of substrates in diluted aqueous solution of nickel. Amorphous silicon thin films were deposited by plasma-enhanced chemical vapor deposition on metalized porous layers. Deposited amorphous thin films were crystallized under vacuum at 750°C. Obtained results from structural, optical, and electrical characterizations show that thermal annealing of amorphous silicon deposited on Ni-metalized porous silicon leads to an enhancement in the crystalline quality and physical properties of the silicon thin films. The improvement in the quality of the film is due to the crystallization of the amorphous film during annealing. This simple and easy method can be used to produce silicon thin films with high quality suitable for thin film solar cell applications. PMID:22901341

  8. Study of the fabrication and thermally induced transformation of amorphous Mg50Ni50 obtained by mechanical alloying

    International Nuclear Information System (INIS)

    This work studied the amorphization process by mechanical alloying of a Mg50Ni50 alloy and its later thermal transformation into stable equilibrium phases. The amorphous alloy was produced using a SPEX 8000D mill, under controlled Ar atmosphere, with a ratio in ball mass: material of 20:1, from powders of Ni and cuttings of Mg. The evolution of the phases during the amorphization process was qualitatively determined by X-ray diffraction. The results showed that a noticeable microstructural refinement of the Mg and Ni occurs at the start of the milling, and that this accumulation of defects amorphitizes part of the system, producing an amorphous precursor, which mechanically crystallizes the Mg2Ni. As the milling time increases and more energy is added to the system, the structure of the Mg2Ni collapses giving way to the appearance of the amorphous Mg50Ni50 phase. With reference to the thermal transformation of the amorphous solid to the stable equilibrium phases, the joint results obtained by differential scanning calorimetry and X-ray diffraction, indicate that this occurs in two stages: at temperatures close to 350oC the amorphous Mg50Ni50 transforms into a mixture of phases, composed of Mg2Ni and a residual amorphous, which at temperatures close to 450oC undergoes the transformation into MgNi2. A temperature-heating rate-transformation (T-HR-T) diagram was built for the passage of the amorphous Mg50Ni50 into Mg2Ni and MgNi2 using the calorimetric data (au)

  9. Effect of the nanocrystallization of amorphous soft magnetic Fe-P-Nb alloys on corrosion resistance in a damp SO2-polluted atmosphere

    Science.gov (United States)

    Vavilova, V. V.; Zabolotnyi, V. T.; Korneev, V. P.; Anosova, M. O.; Baldokhin, Yu. V.

    2014-09-01

    The effect of the nanocrystallization of amorphous soft magnetic Fe-P-Nb alloys on their electrochemical behavior in a damp SO2-polluted industrial atmosphere is studied. It is shown that their electro-chemical characteristics shit toward positive values when the phosphorus content in the Fe-P-Nb alloys increases and when they undergo nanocrystallization from an amorphous state.

  10. Crystallization process in rapidly solidified Al-Nd-Ni amorphous alloy prepared by melt spinning

    Institute of Scientific and Technical Information of China (English)

    肖于德; 黎文献; 马正青

    2004-01-01

    Rapidly solidified ribbons of Al90 Nd7 Ni3 metallic glasses were prepared by using melt spinning. Crystal lization process of the totally amorphous ribbons was investigated by differential scanning calorimetry and X-ray diffraction analysis, under continuous heating regime. The results show that, under continuous heating regime, the metallic glass devitrifies via two main stages: primary crystallization, resulting in two-phase mixture of α(Al) plus residual amorphous phase, and secondary crystallization, corresponding to some inter-metallic phases appearing,successively including Al11 Nd3, Al3 Ni, and some unknown phases, in the Al amorphous/crystal matrix. Four peaks appear on the continuous heating DSC curves. Their peak temperatures are respectively 470.8, 570.8, 585.6, and731.6 K at infinitesimal heating rate, and their activation energies of the respective phase transformation are 183.0,294.7, 232.5 and 269.1 kJ/mol. The values of Avrami exponent of the four reactions decrease with increasing relative transformation degree. At the earlier stage of phase transformation, the values of n are larger than 4, and at the later stage the values of n become close to some value from 0.5 to 2.0.

  11. Study of α-phase precipitation on crystallization of Fe88B12 amorphous alloy by NMR method

    International Nuclear Information System (INIS)

    NMR method is used to study processes, occurring at heating of Fe88B12 amorphous alloy to determine the possibility of preparation of supersaturated boron solid solution in α-iron. Samples in the form of 15-25 mcm thickness tape were prepared by means of spinning. Crystallization of amorphous matrix begins over 593 K and passes two stages. α-Fe precipitates during the first stage. Crystallization second stage starts over 723 K and results in essential structural variations. At this stage the residual amorphous matrix is crystallized with formation of metastable tetragonal boride Fe3B. Thus, one may conclude, that boron eurichment of amorphous matrix at heating results in change of orthorhombic Fe3B type short-range order for tetragonal F3B. At 730 K residual amorphous phase approaches stoichiometric boride-Fe3B-composition

  12. Room-temperature amorphous alloy field-effect transistor exhibiting particle and wave electronic transport

    International Nuclear Information System (INIS)

    The realization of room-temperature macroscopic field effect transistors (FETs) will lead to new epoch-making possibilities for electronic applications. The Id-Vg characteristics of the millimeter-sized aluminum-oxide amorphous alloy (Ni0.36Nb0.24Zr0.40)90H10 FETs were measured at a gate-drain bias voltage of 0–60 μV in nonmagnetic conditions and under a magnetic fields at room temperature. Application of dc voltages to the gate electrode resulted in the transistor exhibiting one-electron Coulomb oscillation with a period of 0.28 mV, Fabry-Perot interference with a period of 2.35 μV under nonmagnetic conditions, and a Fano effect with a period of 0.26 mV for Vg and 0.2 T under a magnetic field. The realization of a low-energy controllable device made from millimeter-sized Ni-Nb-Zr-H amorphous alloy throws new light on cluster electronics

  13. Room-temperature amorphous alloy field-effect transistor exhibiting particle and wave electronic transport

    Energy Technology Data Exchange (ETDEWEB)

    Fukuhara, M., E-mail: fukuhara@niche.tohoku.ac.jp [New Industry Creation Hatchery Center, Tohoku University, Sendai 980-8579 (Japan); Kawarada, H. [Research and Development Center, Waseda University, Tokyo 162-0041 (Japan)

    2015-02-28

    The realization of room-temperature macroscopic field effect transistors (FETs) will lead to new epoch-making possibilities for electronic applications. The I{sub d}-V{sub g} characteristics of the millimeter-sized aluminum-oxide amorphous alloy (Ni{sub 0.36}Nb{sub 0.24}Zr{sub 0.40}){sub 90}H{sub 10} FETs were measured at a gate-drain bias voltage of 0–60 μV in nonmagnetic conditions and under a magnetic fields at room temperature. Application of dc voltages to the gate electrode resulted in the transistor exhibiting one-electron Coulomb oscillation with a period of 0.28 mV, Fabry-Perot interference with a period of 2.35 μV under nonmagnetic conditions, and a Fano effect with a period of 0.26 mV for Vg and 0.2 T under a magnetic field. The realization of a low-energy controllable device made from millimeter-sized Ni-Nb-Zr-H amorphous alloy throws new light on cluster electronics.

  14. Dynamic magnetic characteristics of Fe78Si13B9 amorphous alloy subjected to operating temperature

    Science.gov (United States)

    He, Aina; Wang, Anding; Yue, Shiqiang; Zhao, Chengliang; Chang, Chuntao; Men, He; Wang, Xinmin; Li, Run-Wei

    2016-06-01

    The operating temperature dependence of dynamic magnetic characteristics of the annealed Fe78Si13B9 amorphous alloy core was systematically investigated. The core loss, magnetic induction intensity and complex permeability of the amorphous core were analyzed by means of AC B-H loop tracer and impedance analyzer. It is found that the operating temperature below 403 K has little impact on core loss when the induction (B) is less than 1.25 T. As B becomes higher, core loss measured at high temperature becomes higher. For the cores measured at power frequency, the B at 80 A/m and the coercivity (Hc) at 1 T decline slightly as the temperature goes up. Furthermore, the real part of permeability (μ‧) increases with the rise of temperature. The imaginary part of permeability (μ″) maxima shifts to lower frequency side with increasing temperature, indicating the magnetic relaxation behavior in the sample. In addition, with the rise in the operating temperature of the annealed amorphous core, the relaxation time tends to increase.

  15. Amorphous structure and properties in laser-clad Ni-Cr-Al coating on Al-Si alloy

    Science.gov (United States)

    Liang, Gongying; Wong, T. T.; Su, J. Y.; Woo, C. H.

    1999-09-01

    A Ni-Cr-Al coating was clad by a 5 kW CO2 laser with different laser power on Al-Si alloy. Using transmission electron microscopy, a mixing microstructure containing Ni- based amorphous structures was observed in the laser clad zones. As the uniformity of chemical composition and temperature is poor in the laser cladding, the amorphous structure with some Ni3Al crystals coexisted in the cladding. According to the morphologies of Ni-based amorphous structures, the amorphous structure existed not only in the net-like boundaries surrounding the granular structure but also in the granular structure. The microhardness of the mixture amorphous structure is between HV 600 - 800, which is lower than that of crystal phases in the coating. A differential thermal analysis showed that Ni- based amorphous structure exhibits a higher initial crystallizing temperature (about 588 degree(s)C), which is slightly higher than that of the eutectic temperature of Al- Si alloy. The wear experimental results showed that some amorphous structure exist in the laser cladding can reduce the peeling of the granular phases from matrix, and improve the its wear resistance.

  16. The effect of nitrogen on the glass-forming ability and micro-hardness of Fe-Cr-Mn-N amorphous alloys prepared by mechanical alloying

    International Nuclear Information System (INIS)

    In this research, the effect of nitrogen on the thermal behavior and micro-hardness of Fe-Cr-Mn-N amorphous alloys synthesized by mechanical alloying under a nitrogen atmosphere has been considered. The characterization of the as-milled powders by X-ray diffraction, scanning and transmission electron microscopy showed that a fully amorphous structure has been developed by the mechanical alloying process. Differential scanning calorimetry results revealed that the glass transition temperatures and onset crystallization temperatures are in the ranges of 764-766 K and 855-861 K, respectively, for the alloys containing 3.45-3.95 wt.% nitrogen, giving considerable supercooled liquid regions of 91-95 K. The amorphous alloys exhibited an increase in the glass-forming ability by increasing the nitrogen amount. Furthermore, the as-milled amorphous powders showed high micro-hardness values of nearly 1015-1070 HV with an elastic-plastic deformation feature during the indentations. A decrease in the micro-hardness values was found by increasing the nitrogen content.

  17. Glass formation ability, structure and magnetocaloric effect of a heavy rare-earth bulk metallic glassy Gd55Co20Fe5Al20 alloy

    International Nuclear Information System (INIS)

    The glass formation ability, the structure and the magnetocaloric effect of the bulk metallic glassy Gd55Co20Fe5Al20 alloy were investigated. Bulk metallic glassy (BMGs) alloys were prepared by a copper-mold casting method. The glass forming ability and their structure were studied by using X-ray diffraction (XRD) and differential scanning calorimeter (DSC). The XRD analysis revealed that the as-cast cylinder of Gd55Co20Fe5Al20 alloy showed fully amorphous structure in 2 mm diameter. The DSC revealed that the bulk cylinder of the Gd55Co20Fe5Al20 alloy showed a distinct glass transition temperature and a relatively wide supercooled liquid region before crystallization. SQUID investigated the magnetic properties and the entropy changes. The Curie temperature of Gd55Co20Fe5Al20 BMGs alloy was about 130 K, but the maximum magnetic entropy changes(-ΔSM) showed at about 125 K, a little lower than the Curie temperature 130 K. The reason could probably be due to the presence of a little amount of nanocrystalline particles between amorphous phases. The BMG alloy has the characteristic of second-order transition (SOT) on Arrott plots. The results showed that the amorphous sample had a relatively improved magnetocaloric effect, indicating that the amorphous alloy could be considered as a candidate for magnetic refrigeration applications in the temperature interval range of 100-200 K

  18. Atomic scale modelling of hexagonal structured metallic fission product alloys

    OpenAIRE

    Middleburgh, S. C.; King, D M; Lumpkin, G. R.

    2015-01-01

    Noble metal particles in the Mo-Pd-Rh-Ru-Tc system have been simulated on the atomic scale using density functional theory techniques for the first time. The composition and behaviour of the epsilon phases are consistent with high-entropy alloys (or multi-principal component alloys)—making the epsilon phase the only hexagonally close packed high-entropy alloy currently described. Configurational entropy effects were considered to predict the stability of the alloys with increasing temperature...

  19. The influence of structural changes on electrical and magnetic characteristics of amorphous powder of the nixmoy alloy

    Directory of Open Access Journals (Sweden)

    Ribić-Zelenović Lenka

    2006-01-01

    Full Text Available Nickel and molybdenum alloy powder was electrodeposited on a titanium cathode from a NiSO4⋅7H2O and (NH46 Mo7O24⋅4H2O ammonium solution. The desired chemical composition, structure, size and shape of particles in the powder samples were achieved by an appropriate choice of electrolysis parameters (current density, composition and temperature of the solution, cathode material and electrolysis duration. Metal coatings form in the current density range 15 mA cm-2alloy decreases with the increase of the current density of deposition. Smaller sized particles form at higher current density. X-ray analysis, differential scanning calorimetric and measurements of the temperature dependence of electric resistance and magnetic permeability of the powder samples were all used to establish a predominantly amorphous structure of the powder samples formed at the current density of j≥70mA cm-2. The crystalline particle content in the powder samples increases with the decrease of the current density of deposition. Powder heating causes structural changes. The process of thermal stabilization of nickel and molybdenum amorphous powders takes place in the temperature interval from 463K to 573K and causes a decrease in electrical resistance and increase in magnetic permeability. The crystallization temperature depends on the value of current density of powder electrodeposition. Powder formed at j=180 mA cm-2 begins to crystallize at 573K, while the powder deposited at j=50 mA cm-2 begins to crystallize at 673K. Crystallization of the powder causes a decrease in electric resistivity and magnetic

  20. Effect of annealing on atomic ordering of amorphous ZrTaTiNbSi alloy

    Science.gov (United States)

    Yang, Tsung-Han; Huang, Rong-Tang; Wu, Cheng-An; Chen, Fu-Rong; Gan, Jon-Yiew; Yeh, Jien-Wei; Narayan, Jagdish

    2009-12-01

    In this letter, we have reported on initial stages of atomic ordering in ZrTaTiNbSi amorphous films during annealing. The atomic ordering and structure evolution were studied in Zr17Ta16Ti19Nb22Si26 amorphous films as a function of annealing temperature in the temperature range from 473 to 1173 K. Up to annealing temperature of 1173 K, the films retained amorphous structure, but the degree of disorder is increased with the increase in temperature. The formation of Si-M covalent bonds, which contributed to the local atomic arrangement, occurred in the initial stages of ordering. The bonding reactions between Si and other metal species explain the anomalous structural changes which were observed in x-ray diffraction and transmission electron microscopy. We discuss the stages of phase transformation for amorphous films as a function of annealing temperature. From these results, we propose that annealing leads to formation of random Si-M4 tetrahedron, and two observed rings, a first and second in the electron diffraction patterns compared to M-M and Si-M bond length, respectively.

  1. [Alloys for metal-ceramics 3].

    Science.gov (United States)

    Quintero Englembright, M A; Barceló Santana, F; Palma Calero, M

    1991-01-01

    A wide variety of restoration materials for prosthetic odontology is now available to the dental surgeon, either of the covalent type (acrylic resins), metallic (alloys), ionic (porcelains), or a combination of them, as in the so-called composites, such as the composite resins, or as ceramics-metals mixtures. An example of the latter is a product called Miracle-Mix, a glass ionomere cement reinforced with an amalgam alloy. In those cases where the blend is done by a synterization process, the material is called Cermet. The above-listed alternatives clearly evidence day-to-day advances in odontology, with researchers and manufacturers engaged the world over in improving existing products or developing new ones to enrich the dentist's armamentarium. As a side effect of this constant renewal, those dentists who have failed to update their knowledge fall behind in their practice as they persist in using products they have known for years, and may be deceived by advertisements of too-often unreliable products. It is, therefore, important to be aware of available products and their latest improvements. PMID:1946199

  2. In vivo apatite formation induced on titanium metal and its alloys by chemical treatment

    Energy Technology Data Exchange (ETDEWEB)

    Kokubo, T.; Kim, H.M. [Kyoto Univ. (Japan). Dept. of Material Chemistry; Nishiguchi, S.; Nakamura, T. [Kyoto Univ. (Japan). Dept. of Orthopaedic Surgery

    2001-07-01

    NaOH and heat treatments form an amorphous sodium titanate layer with a graded structure on the surfaces of titanium metal and its alloys. These treatments give no adverse effect on mechanical properties of the metals. Thus treated metals form an apatite layer on their surfaces in the living body by taking the calcium and phosphate ions from the surrounding fluid. This apatite layer is tightly integrated to the metal substrates through a graded structure, and bonds to the living bone in a short period, because of its structure and composition analogous to those of the bone mineral. This kind of bioactive metals are believed to be useful as bone substitutes even under load bearing conditions such as hip joints and dental implants. (orig.)

  3. X-ray diffraction study of the structure Ti{sub 1-x}Ni{sub x} amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Barmin, Yu. [State Technical Univ., Voronezh (Russian Federation). Dept. of Solid State Physics; Doonichev, I.; Kosilov, A. [Dept. of Physics of Metals, State Technical Univ., Voronezh (Russian Federation)

    2000-07-01

    The Ti-Ni amorphous alloys were prepared by high rate sputter-deposition. The Ti{sub 1-x}Ni{sub x} (x = 0,61; 0,65; 0,74) alloys structure was investigated by the X-ray diffraction method. The topological short-range order parameters (the radius of the first coordination sphere and coordination number) was established. The experimental data were compared with the results of computer simulation. (orig.)

  4. Effect of amorphous evolution on structure and absorption properties of FeSiCr alloy powders

    International Nuclear Information System (INIS)

    The master alloys of Fe87.5−xSi13.5Crx (x=0, 4, 8, 12 at%) were prepared in vacuum induction melting furnace. Corresponding powder samples were obtained by 60 h ball milling of the crushed master alloys, and studied by morphological, microstructural, electromagnetic and microwave absorption tests in the frequency range from 0.5 to 18 GHz. The powders were characterized by a particle size less than 1 μm and a grain size less than 100 nm. In the cases of x≥8, Fe3Si phase with D03-type structure was observed, and the powders became amorphous completely. A crystallization temperature of 685 K was found for x=8. Coercivity force and saturation magnetization of the powders decreased with the increasing of Cr content. As an electromagnetic wave absorbing material, the minimum reflectivity was −15.5 dB at 8.5 GHz and the absorption band was broad for x=8 powders. - Highlights: ► When Cr is 8 at%, after 60 h milling, D03 superlattice appeared. And exothermic peak appears at 685 K. ► With increasing Cr content, Ms decreases from 145 to 99 emu/g; μ″ is larger than the others at low frequency. ► The minimum reflectivity is −15.5 dB at 8.5 GHz for Cr content is 8 at% when thickness is 2 mm. ► The amorphous Fe78.5Si13.5Cr8 alloy can be applied as electromagnetic wave absorber

  5. A new Ti-Zr-Hf-Cu-Ni-Si-Sn bulk amorphous alloy with high glass-forming ability

    International Nuclear Information System (INIS)

    The effect of Sn substitution for Cu on the glass-forming ability was investigated in Ti41.5Zr2.5Hf5Cu42.5-xNi7.5Si1Sn x (x = 0, 1, 3, 5, 7) alloys by using differential scanning calorimetry (DSC) and X-ray diffractometry. The alloy containing 5% Sn shows the highest glass-forming ability (GFA) among the Ti-Zr-Hf-Cu-Ni-Si-Sn system. Fully amorphous rod sample with diameters up to 6 mm could be successfully fabricated by the copper mold casting Ti41.5Zr2.5Hf5Cu37.5Ni7.5Si1Sn5 alloy. The activation energies for glass transition and crystallization for Ti41.5Zr2.5Hf5Cu37.5Ni7.5Si1Sn5 amorphous alloy are both larger than those values for the Sn-free alloy. The enhancement in GFA and thermal stability after the partial replacement of Cu by Sn may be contributed to the strong atomic bonding nature between Ti and Sn and the increasing of atomic packing density. The amorphous Ti41.5Zr2.5Hf5Cu37.5Ni7.5Si1Sn5 alloy also possesses superior mechanical properties

  6. Superconducting Metallic Glass Transition-Edge-Sensors

    Science.gov (United States)

    Hays, Charles C. (Inventor)

    2013-01-01

    A superconducting metallic glass transition-edge sensor (MGTES) and a method for fabricating the MGTES are provided. A single-layer superconducting amorphous metal alloy is deposited on a substrate. The single-layer superconducting amorphous metal alloy is an absorber for the MGTES and is electrically connected to a circuit configured for readout and biasing to sense electromagnetic radiation.

  7. Effect of cobalt on the corrosion behaviour of amorphous Fe-Co-Cr-B-Si alloys in dilute mineral acids

    International Nuclear Information System (INIS)

    The aim of this paper was to investigate the effect of increasing cobalt content on the corrosion resistance of the Fe-Co-Cr-B-Si alloys in dilute mineral acids. The corrosion rates in 0.5N HCl, 1N HCl and 1N H2SO4 significantly decrease with an increase in cobalt content. The alloys with a larger amount of cobalt can passivate spontaneously. The high corrosion resistance of the Fe-Co-Cr-B-Si alloys is also due to the formation of chromium -enriched passive film. Generally, the corrosion resistance of chromium -bearing alloy is improved by alloying with various metalloids but it is lowered by addition of boron and silicon. The corrosion behaviour of the amorphous Fe75-xCoxCr1B7Si17 alloys obtained by the melt-spinning technique was studied using gravimetric method. The best results were obtained with Fe65Co10Cr1B7Si17 alloy. The studied amorphous alloy ribbons exhibit not only excellent physical properties which are useful for many electric and magnetic applications: magnetic sensors, power transformers, high frequency transformers, etc., but also a very good corrosion resistance which extend their application domain. (Author).

  8. Magnetic Properties of Nanometer-sized Crystalline and Amorphous Particles

    DEFF Research Database (Denmark)

    Mørup, Steen; Bødker, Franz; Hansen, Mikkel Fougt; Jiang, Jianzhong

    Amorphous transition metal-metalloid alloy particles can be prepared by chemical preparation techniques. We discuss the preparation of transition metal-boron and iron-carbon particles and their magnetic properties. Nanometer-sized particles of both crystalline and amorphous magnetic materials are...

  9. Cu-based bulk amorphous alloy with larger glass-forming ability and supercooled liquid region

    Energy Technology Data Exchange (ETDEWEB)

    Fu, H.M. [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); School of Engineering, University of Queensland, St. Lucia, Qld 4072 (Australia)], E-mail: waterdrophmfu@hotmail.com; Zhang, H.F. [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Wang, H. [Faculty of Engineering and Surveying, University of Southern Queensland, Toowoomba, Qld 4350 (Australia); Hu, Z.Q. [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China)

    2008-06-30

    The glassy rod with a maximum sample thickness of 11 mm and larger supercooled liquid region of 108 K was successfully fabricated when substituting Cu with minor amount of Ag in the Cu-Zr-Al-Gd alloy system. The value of {gamma} reaches a maximum of 0.418 for the Cu{sub 45.5}Zr{sub 45}Al{sub 7}Gd{sub 2}Ag{sub 0.5} bulk metallic glass (BMG) alloy. The high glass-forming ability (GFA) and larger supercooled liquid region are discussed from atomic size, negative mixing heat among constituent elements and thermodynamics.

  10. Formation of ultra-thin amorphous conversion films on zinc alloy coatings

    International Nuclear Information System (INIS)

    Within the two parts of this contribution a detailed investigation of the nucleation and growth of ultra-thin amorphous conversion coatings on hot dip galvanised steel is reported. The first part deals with the composition and reactivity of the native ultra-thin oxyhydroxide films that are formed on the zinc alloy surface during the hot dip galvanising process due to the enrichment of aluminium at the outer surface of the alloy coating. Complimentary surface analytical techniques such as FT-IR-spectroscopy at grazing incidence and X-ray photo electron spectroscopy, high resolution AFM on selected grains to study the surface topography and cyclovoltammetry as well as quasi stationary current potential curves and Kelvin probe measurements to study surface ion and electron transfer reactions were applied. Changes in the chemical composition, the electronic properties and the morphology of the ultra-thin surface could thereby be analysed. The surface of the ZnAl alloy is composed of an about 3-4 nm thick mixed Zn and Al-oxyhydroxide layer with Zn-oxyhydroxide slightly enriched at the outermost surface. This mixed oxyhydroxide causes to a significant inhibition of electron transfer reactions. During alkaline cleaning the surface is nanoscopically roughened and the mixed oxyhydroxide is converted into an electro-conducting hydroxyl rich pure Zn-oxyhydroxide layer with a thickness of about 4 nm. In the second part of this paper the effect of the inorganic surface layer on the film formation is correlated with these findings

  11. Ballistic impact properties of mixed multi-layered amorphous surface alloyed materials fabricated by high-energy electron-beam irradiation

    International Nuclear Information System (INIS)

    The objective of this study is to investigate ballistic impact properties of multi-layered amorphous surface alloyed materials fabricated by high-energy electron-beam irradiation. The mixture of Zr-based amorphous alloy powders and LiF+MgF2 flux powders was deposited on a Ti alloy substrate, and then electron beam was irradiated on this powder mixture to fabricate an one-layered surface alloyed material. On top of this layer, the powder mixture was deposited again and then irradiated with electron beam whose beam current was decreased to fabricate the multi-layered surface alloyed material. In the mixed multi-layered surface alloyed materials fabricated with LM1 alloy powders and LM2 or LM10 alloy powders, the surface region consisted of amorphous phases, together with a small amount of crystalline particles, whereas the center region was complicatedly composed of amorphous phases, crystallized phases, and dendritic β phases. Since the surface region mostly composed of amorphous matrix was quite hard, the alloyed materials sufficiently blocked the travel of a projectile. When cracks formed at the surface region propagated into the center region, the formation of many cracks or debris was accelerated, which could beneficially work for absorbing the ballistic impact energy, thereby leading to the higher ballistic impact properties than the surface alloyed materials fabricated with LM1 or LM2 alloy powders

  12. A physical model of the effect of irreversible changes in structure and properties of amorphous alloys caused by low-temperature treatment

    International Nuclear Information System (INIS)

    A low temperature ΔT-effect physical model for amorphous metallic alloys (AMA) is developed. Using Ni-P, Fe-Co-Si-B, Co-Ni-Fe-Si-B, Fe-Si-B, Fe-Ni-Si-B, Fe-Cu-Nb-Si-B alloys the studies are carried out which results support basic concepts of the theory, namely: a motive force for atom drift, resulting in irreversible changes of a short-range order, is at the heart of longitudinal oscillations of AMA ribbon initiate the process of changing the initial short-range order. Variations of topological and short-range orders are responsible for a decrease in yield strength and Young modulus, a Curie point shift, an increase of saturation magnetization at an insignificant drop of coercive force or a significant drop of coercive force at a slight increase of saturation magnetization

  13. Effect of replacing RE and TM on magnetic properties and thermal stability of some Al–Ni-based amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Uporov, S.A., E-mail: segga@bk.ru [Institute of Metallurgy UB RAS, Ekaterinburg (Russian Federation); Uporova, N.S. [Ural State Pedagogical University, Ekaterinburg (Russian Federation); Bykov, V.A.; Kulikova, T.V.; Pryanichnikov, S.V. [Institute of Metallurgy UB RAS, Ekaterinburg (Russian Federation)

    2014-02-15

    Highlights: ► X-ray diffraction analysis of the quenched Al–Ni-based alloys revealed a clear prepeak. ► The amorphous alloys demonstrate the superparamagnetic behavior. ► The variation of the RE and TM caused the radical changes of thermal properties. -- Abstract: Amorphous ribbons Al{sub 86}Ni{sub 8}Ho{sub 6}, Al{sub 86}Ni{sub 8}Gd{sub 6} and Al{sub 86}Ni{sub 6}Co{sub 2}Gd{sub 4}Y{sub 2} were prepared by quenching from 1580–1600 K using spinning technique at a wheel speed of 32 m/s. X-ray diffraction (XRD) analysis of the quenched alloys revealed a clear prepeak located below the main amorphous peak. The specimens crystallize in three stages but glass transition temperature was not found. The crystalinity was calculated by both XRD and differential scanning calorimetry (DSC) methods for all samples. Magnetic properties of ribbons were investigated in wide ranges of temperature (T = 4–900 K) and magnetic field (up to 30 kOe) by Faraday method and vibration sample magnetometry (VSM). The amorphous alloys investigated have no magnetic ordering at low temperatures down to T = 4 K but demonstrate the superparamagnetic behavior. The magnetic properties are discussed in the frames of conception of existence the superparamagnetic clusters with ferrimagnetic ordering.

  14. Effect of replacing RE and TM on magnetic properties and thermal stability of some Al–Ni-based amorphous alloys

    International Nuclear Information System (INIS)

    Highlights: ► X-ray diffraction analysis of the quenched Al–Ni-based alloys revealed a clear prepeak. ► The amorphous alloys demonstrate the superparamagnetic behavior. ► The variation of the RE and TM caused the radical changes of thermal properties. -- Abstract: Amorphous ribbons Al86Ni8Ho6, Al86Ni8Gd6 and Al86Ni6Co2Gd4Y2 were prepared by quenching from 1580–1600 K using spinning technique at a wheel speed of 32 m/s. X-ray diffraction (XRD) analysis of the quenched alloys revealed a clear prepeak located below the main amorphous peak. The specimens crystallize in three stages but glass transition temperature was not found. The crystalinity was calculated by both XRD and differential scanning calorimetry (DSC) methods for all samples. Magnetic properties of ribbons were investigated in wide ranges of temperature (T = 4–900 K) and magnetic field (up to 30 kOe) by Faraday method and vibration sample magnetometry (VSM). The amorphous alloys investigated have no magnetic ordering at low temperatures down to T = 4 K but demonstrate the superparamagnetic behavior. The magnetic properties are discussed in the frames of conception of existence the superparamagnetic clusters with ferrimagnetic ordering

  15. Nanocrystal Growth in Thermally Treated Fe75Ni2Si8B13C2 Amorphous Alloy

    Czech Academy of Sciences Publication Activity Database

    Minić, Dragica M.; Blagojević, V.; Minić, Dušan M.; David, Bohumil; Pizúrová, Naděžda; Žák, Tomáš

    43A, č. 9 (2012), s. 3062-3069. ISSN 1073-5623 R&D Projects: GA MŠk 1M0512 Institutional support: RVO:68081723 Keywords : Nanocrystal growth * Fe75Ni2Si8B13C2 * Amorphous alloy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.627, year: 2012

  16. Thermal treatment of the amorphous base alloy Fe 2605SA1, analysis of its defects and microhardness

    International Nuclear Information System (INIS)

    By means of the use of the positron lifetime technique those characteristics of the present crystalline defects in an amorphous base alloy Fe (SA1) are determined, when this is subjected to thermal treatments from 293 K until 808 K. Also, some results about the microhardness and electric resistivity are presented. (Author)

  17. Defects in the structure of Fe60Co10W2Me2Y8B18 amorphous metallic glasses, where Me=(Mo,Nb

    Directory of Open Access Journals (Sweden)

    S. Garus

    2013-12-01

    Full Text Available Purpose: The paper presents results of the effect of structural defects on the process of magnetization in high magnetic fields in metallic glasses based on amorphous Fe60Co10W2Me2Y8B18 (where Me=Mo, Nb Design/methodology/approach: Bulk amorphous material samples were obtained with the method of rapid radial cooling in the copper liquid-cooled mould in a protective atmosphere of inert gas. The samples in the state after solidification were then examined using a vibrating magnetometer in the magnetic fields up to 2T. Static magnetic hysteresis loops and primary magnetization curve were recorded. Findings: Changing a small amount of the element from the group of transition metals have a significant effect on the magnetic properties of the produced alloy. Depending on the substituent also the type of defects identified in the examined materials changes. Research limitations/implications: It is advisable to conduct studies on samples with compositions close to studied in this work for better prediction of magnetic properties of materials. Practical implications: Bulk amorphous metallic glass are used in the electrical industry as cores in modern high-efficiency high-power transformers. Originality/value: W Paper presents studies on the influence of structure defects on the process of primary magnetization for amorphous Fe60Co10W2Mo2Y8B18 and Fe60Co10W2Nb2Y8B18 alloys. Alloys of given composition has not yet been tested for the influence of defects on the magnetization process.

  18. Short-range order in ab initio computer generated amorphous and liquid Cu–Zr alloys: A new approach

    International Nuclear Information System (INIS)

    Using ab initio molecular dynamics and a new approach based on the undermelt-quench method we generated amorphous and liquid samples of CuxZr100−x (x=64, 50, 36) alloys. We characterized the topology of our resulting structures by means of the pair distribution function and the bond-angle distribution; a coordination number distribution was also calculated. Our results for both amorphous and liquids agree well with experiment. Dependence of short-range order with the concentration is reported. We found that icosahedron-like geometry plays a major role whenever the alloys are Cu-rich or Zr-rich disregarding if the samples are amorphous or liquid. The validation of these results, in turn would let us calculate other properties so far disregarded in the literature

  19. Short-range order in ab initio computer generated amorphous and liquid Cu–Zr alloys: A new approach

    Energy Technology Data Exchange (ETDEWEB)

    Galván-Colín, Jonathan, E-mail: jgcolin@ciencias.unam.mx [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Apartado Postal 70-360, México, D.F. 04510, México (Mexico); Valladares, Ariel A., E-mail: valladar@unam.mx [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Apartado Postal 70-360, México, D.F. 04510, México (Mexico); Valladares, Renela M.; Valladares, Alexander [Facultad de Ciencias, Universidad Nacional Autónoma de México, Apartado Postal 70-542, México, D.F. 04510, México (Mexico)

    2015-10-15

    Using ab initio molecular dynamics and a new approach based on the undermelt-quench method we generated amorphous and liquid samples of Cu{sub x}Zr{sub 100−x} (x=64, 50, 36) alloys. We characterized the topology of our resulting structures by means of the pair distribution function and the bond-angle distribution; a coordination number distribution was also calculated. Our results for both amorphous and liquids agree well with experiment. Dependence of short-range order with the concentration is reported. We found that icosahedron-like geometry plays a major role whenever the alloys are Cu-rich or Zr-rich disregarding if the samples are amorphous or liquid. The validation of these results, in turn would let us calculate other properties so far disregarded in the literature.

  20. Effect of bonding time on joint properties of vacuum brazed WC - Co hard metal/carbon steel using stacked Cu and Ni alloy as insert metal

    Energy Technology Data Exchange (ETDEWEB)

    Lee, W.B.; Jung, S.B. [Sungkyunkwan Univ., Dept. of Advanced Materials Engineering, Suwon, Kyounggi-do (Korea); Kwon, B.D. [Seoul Technical High School, Dept. of Metallurgy, Seoul (Korea)

    2004-11-15

    Hard metal WC - Co and carbon steel were successfully joined using double layered Cu alloy and amorphous Ni alloy as inert metal and an oil cooling method after brazing. Defects such as cracks and voids were not formed near the bonded zone. This result means that double layered insert metals and oil cooling minimised the residual stress near the bonded zone after brazing. The shear strength of the joints decreased with increasing bond time. The reasons why the shear strength decreased as bond time increased could be many, including shape of the interface, formation and growth of brittle intermetallic compounds, and coarsening of WC particles near the bond zone. The maximum shear strength of the joints was 310 MPa under conditions 0.6 ks bond time and 8 wt-%Co content in the WC hard alloy. (Author)

  1. Applications Ni59Nb40Pt(1-x) Xx (X= Sn,Sby and Ru) amorphous alloy as anodes for direct methanol (DMFC) fuel cells

    International Nuclear Information System (INIS)

    The search of new anode materials of amorphous nature for methanol fuel cells is one of the aims of this work.The main problem that fuel cells present is related to the catalytic material and its distribution in a suitable matrix.Amorphous alloys are particularly attractive materials as catalyst supports because of their high conductivity, high corrosion resistance in sulphuric acid, as well as the possibility of a good distribution of the electrocatalytic particles, mainly platinum and platinum-tin, on a conducting matrix.The electrooxidation of methanol, in percloric acid medium, has been used as probe to evaluate the performance of metallic amorphous electrodes, with compositions Ni59Nb40Pt1, Ni59Nb40Pt0.6Sn0.4, Ni59Nb40Pt0.6Sb0.4 and Ni59Nb40Pt0.6Ru0.4.The electrocatalytic activity of the alloyed ribbons of compositions (x = 0.6, 1% at. in platinum) is improved considerably, so much for the change in their composition, as for the roughness degree that the catalytic surfaces present. The increase of the tolerance to adsorbed species, and better resistance to the poisoning of their catalytic centers, can be observed by means of voltammetric experiments at different activation times with HF 48%. The electrooxidation of methanol in the amorphous alloy of composition Ni59Nb40Pt1, is influenced by the nature of the used electrolyte, presenting smaller values of current density in solutions 1M H2SO4 than in 1M of HClO4.This behavior is not observed in the alloy Ni59Nb40Pt0.6Sn0.4, Ni59Nb40Pt0.6Sb0.4 and Ni59Nb40Pt0.6Ru0.4which does not present a poisoning of the catalytic centers depending on the used electrolyte.Adding tin to the alloys showed the existence of a synergetic effect in the methanol electrooxidation process, attaining to a descent of 20 mV vs Ag/AgCl in the onset potential, and about 200 mV in the maximun peak potential

  2. Cyclic deformation of metals and alloys

    International Nuclear Information System (INIS)

    Phenomena associated with rapid hardening or softening caused by cyclic straining in the early stages of fatigue life of metals and alloys are reviewed. The factors which control these phenomena are described and also the dislocation structures which are associated with them. In so far as the mechanisms of cyclic deformation are understood these too are described and a number of parallels between cyclic and unidirectional deformation are pointed out. A similar approach is then taken for materials which contain second phases for strength. Note that these studies apply to cycling at ambient temperatures or below. High-temperature cyclic deformation is beyond the scope of this review. An engineering method of predicting cyclic stress-strain response from tensile testing data is examined in the light of the fundamental knowledge described, and is shown to be severely limited. A method of improving such prediction by introducing additional microstructural information which is readily available is suggested. 117 references

  3. Influence of Si on glass forming ability and properties of the bulk amorphous alloy Mg60Cu30Y10

    International Nuclear Information System (INIS)

    Research highlights: → The partial substitution of Cu by the right amount of Si increases the glass forming ability of the bulk amorphous alloy Mg60Cu30Y10. → The serrations size of Mg60Cu30-xY10Six is dependent on the content of Si. → The creep displacement of Mg60Cu30-xY10Six alloys decrease with increasing Si content. → The elastic modulus and nano-hardness of Mg60Cu30-xY10Six are dependent on the Si content. - Abstract: We studied the influence of partially replacing Cu by Si in the bulk amorphous alloy Mg30Cu30Y10. Glass forming ability (GFA), examined using X-ray diffraction and a differential scanning calorimeter, was increased at 1% Si, but decreased for larger Si concentrations. Nano-indentation measured nano-hardness, elastic modulus and load-displacement curves. The elastic modulus and nano-hardness increased with increasing Si content to a maximum at 2.5%. The load-displacement curves during nano-indentation revealed displacement serrations. These increased with decreasing loading rates, decreased with increasing Si content. The load-displacement curves also indicated that these bulk amorphous alloys exhibited primary creep at room temperature just like other high strength alloys. The creep displacement decreased with increasing Si content.

  4. General laws of the effect of hydrogen on the crystallization of amorphous alloys based on the quasi-binary TiNi-TiCu system

    Science.gov (United States)

    Spivak, L. V.; Shelyakov, A. V.; Shchepina, N. E.

    2014-02-01

    The crystallization processes that occur during heating of hydrogen-containing melt-quenched alloys based on the quasi-binary TiNi-TiCu system alloyed with aluminum, iron, hafnium, and zirconium are studied by high-resolution differential scanning calorimetry. The general laws of the transition of the hydrogen-containing alloys from an amorphous into a crystalline state are determined.

  5. Amorphous and nanocrystalline phase formation in highly-driven Al-based binary alloys

    Energy Technology Data Exchange (ETDEWEB)

    Kalay, Yunus Eren [Iowa State Univ., Ames, IA (United States)

    2009-01-01

    Remarkable advances have been made since rapid solidification was first introduced to the field of materials science and technology. New types of materials such as amorphous alloys and nanostructure materials have been developed as a result of rapid solidification techniques. While these advances are, in many respects, ground breaking, much remains to be discerned concerning the fundamental relationships that exist between a liquid and a rapidly solidified solid. The scope of the current dissertation involves an extensive set of experimental, analytical, and computational studies designed to increase the overall understanding of morphological selection, phase competition, and structural hierarchy that occurs under far-from equilibrium conditions. High pressure gas atomization and Cu-block melt-spinning are the two different rapid solidification techniques applied in this study. The research is mainly focused on Al-Si and Al-Sm alloy systems. Silicon and samarium produce different, yet favorable, systems for exploration when alloyed with aluminum under far-from equilibrium conditions. One of the main differences comes from the positions of their respective T0 curves, which makes Al-Si a good candidate for solubility extension while the plunging T0 line in Al-Sm promotes glass formation. The rapidly solidified gas-atomized Al-Si powders within a composition range of 15 to 50 wt% Si are examined using scanning and transmission electron microscopy. The non-equilibrium partitioning and morphological selection observed by examining powders at different size classes are described via a microstructure map. The interface velocities and the amount of undercooling present in the powders are estimated from measured eutectic spacings based on Jackson-Hunt (JH) and Trivedi-Magnin-Kurz (TMK) models, which permit a direct comparison of theoretical predictions. For an average particle size of 10 {micro}m with a Peclet number of ~0.2, JH and TMK deviate from

  6. Electronic structure and sign reversal of the Hall coefficient in amorphous CuZr alloys

    Energy Technology Data Exchange (ETDEWEB)

    Manh, D.N.; Pavuna, D.; Cyrot-Lackmann, F.; Mayou, D.; Pasturel, A.

    1986-04-15

    We present calculated densities of states (DOS) for Cu/sub x/Zr/sub 1-x/ amorphous alloys across the compositional range. We find that for x<80 at. % Cu there is no ordering and the Fermi level E/sub F/ is dominated by the Zr 4d subband, while above 80 at. % Cu the local order increases and the DOS at E/sub F/ abruptly decreases and is dominated by the s states. These changes in DOS and the fact that the energy derivative of the self-energy changes its sign (implying a change of sign of the Fermi velocity) gives further insight into the experimentally observed sign reversal of the Hall coefficient which occurs for 80< or =x< or =85 at. % Cu.

  7. Electronic structure and sign reversal of the Hall coefficient in amorphous CuZr alloys

    International Nuclear Information System (INIS)

    We present calculated densities of states (DOS) for Cu/sub x/Zr/sub 1-x/ amorphous alloys across the compositional range. We find that for x<80 at. % Cu there is no ordering and the Fermi level E/sub F/ is dominated by the Zr 4d subband, while above 80 at. % Cu the local order increases and the DOS at E/sub F/ abruptly decreases and is dominated by the s states. These changes in DOS and the fact that the energy derivative of the self-energy changes its sign (implying a change of sign of the Fermi velocity) gives further insight into the experimentally observed sign reversal of the Hall coefficient which occurs for 80< or =x< or =85 at. % Cu

  8. Computer experiments on radiation strength and radiation enhanced segregation of Al–Si amorphous alloys

    International Nuclear Information System (INIS)

    Computer experiments of irradiated Al–Si alloys were performed to clarify the mechanism of radiation enhanced segregation. The atomic configurations of pure Al, Al–5 at%Si and Al–10 at%Si with amorphous structure after the irradiation of high energy beam were calculated by the molecular dynamics method. We estimated the threshold energies to create voids in pure Al, Al–5 at%Si and Al–10 at%Si as 0.23, 0.25 and 0.25 keV/nm, respectively. This fact means that addition of Si to Al enhances strength against void formation by beam irradiation. We also confirmed that addition of Si to Al gave strong effect on radiation enhanced segregation. The degree of enhancement depended on the degree of dispersion of Si atoms in Al matrix because the Si atoms enhances clustering of the Al atoms surrounding them. (author)

  9. SEM investigation of surface blistering for argon ion bombarded amorphous alloys

    International Nuclear Information System (INIS)

    Surface blistering of the amorphous alloys Co70.2Fe3.9Nb3.9Si14B8 and Co66Fe4.5V2.25Ni2.25Si10B15 due to argon ion bombardment at energies of 150, 195 and 300 keV has been observed with a scanning electron microscope (SEM). The critical dose for onset of blistering and the blister diameter are determined and found to increase with increasing projectile energy. Above about 195 keV, blisters and rupture of blisters are the predominant surface damage phenomena. However, at 150 keV, there is no evidence of cracked blisters. The effects are interpreted in terms of argon agglomeration, building-up of the critical argon pressure, and argon releasing from near-surface regions

  10. Intensity dependence of the minority-carrier difusion length in amorphous silicon based alloys

    Science.gov (United States)

    Hack, M.; Shur, M.

    1984-04-01

    Many of the recent measurements of the minority-carrier diffusion length (Lp) in amorphous silicon based alloys have been based on a utilization of the surface photovoltage (SPV). In this case an equation relating photon flux and Lp under ideal conditions has to be modified because of the back diffusion of carriers and the effects of high field regions. To account for the high field region, the 'aparent' diffusion length has been determined for varying intensities of bias light. In the present investigation, a theoretical analysis shows that the zero field diffusion length is indeed intensity dependent and that this dependence can be directly related to the slope of the density of states near the valence band edge. The intensity dependence of the minority carrier diffusion length and the energy slope of the density of states near the valence band edge are obtained on the basis of experimental results.

  11. Structure of amorphous silicon alloy films: Annual subcontract report, January 15, 1988--January 14, 1989

    Energy Technology Data Exchange (ETDEWEB)

    Norberg, R.E.; Fedders, P.A.

    1989-06-01

    The principal objective of this research program has been to improve the understanding at the microscopic level of amorphous silicon-germanium-alloy films deposited under various conditions to assist researchers to produce higher quality films. The method has been a joint theoretical and experimental approach to the correlation of NMR, ESR, and other characterizations, especially relating to rearrangements of hydrogen. Deuteron magnetic resonance reveals the presence of (and changes in) tightly bonded hydrogen (deuterium), weakly bonded hydrogen, molecular hydrogen, and rotating silyl groups. Microvoids are investigated via observation of para D/sub 2/ for which /Delta/M/sub J/ transitions are frozen out. Solid echoes reveal HD and ortho D/sub 2/ trapped as singles in the semiconductor matrix. Theoretical calculations show dangling bonds to be more likely than floating bonds. 23 refs., 11 figs.

  12. Amorphous and nanocrystalline phase formation in highly-driven Al-based binary alloys

    International Nuclear Information System (INIS)

    Remarkable advances have been made since rapid solidification was first introduced to the field of materials science and technology. New types of materials such as amorphous alloys and nanostructure materials have been developed as a result of rapid solidification techniques. While these advances are, in many respects, ground breaking, much remains to be discerned concerning the fundamental relationships that exist between a liquid and a rapidly solidified solid. The scope of the current dissertation involves an extensive set of experimental, analytical, and computational studies designed to increase the overall understanding of morphological selection, phase competition, and structural hierarchy that occurs under far-from equilibrium conditions. High pressure gas atomization and Cu-block melt-spinning are the two different rapid solidification techniques applied in this study. The research is mainly focused on Al-Si and Al-Sm alloy systems. Silicon and samarium produce different, yet favorable, systems for exploration when alloyed with aluminum under far-from equilibrium conditions. One of the main differences comes from the positions of their respective T0 curves, which makes Al-Si a good candidate for solubility extension while the plunging T0 line in Al-Sm promotes glass formation. The rapidly solidified gas-atomized Al-Si powders within a composition range of 15 to 50 wt% Si are examined using scanning and transmission electron microscopy. The non-equilibrium partitioning and morphological selection observed by examining powders at different size classes are described via a microstructure map. The interface velocities and the amount of undercooling present in the powders are estimated from measured eutectic spacings based on Jackson-Hunt (JH) and Trivedi-Magnin-Kurz (TMK) models, which permit a direct comparison of theoretical predictions. For an average particle size of 10 (micro)m with a Peclet number of ∼0.2, JH and TMK deviate from each other. This

  13. Low-field magnetic properties of amorphous and nanocystalline FeCrCuNbSiB alloys

    International Nuclear Information System (INIS)

    The AC susceptibility dependence on magnetic field, time and temperature of amorphous as well as nanocrystalline Fe73.5-xCrxCu1Nb3Si13.5B9 (x=0-4) alloys was studied. Micromagnetic model is used for calculating the activation energy spectra (AES) of the magnetic after-effect (MAE). It was observed that addition of Cr to the amorphous FeCrCuNbSiB alloys highly decreases the amplitude of the MAE so that no MAE is observed for Cr content higher than 2 at%. After annealing at 550 deg. C, the initial susceptibility increases as a result of magnetic softening during nanocrystallization and the MAE vanishes. The nanocrystalline state was characterized by the high magnetic as well as structural stability. Moreover, addition of 1 at% Cr makes the initial susceptibility of the nanocrytalline sample higher than in the FINEMET alloy

  14. Effect of crystalline metallic particles on the compressive behavior of a cellular amorphous metal

    International Nuclear Information System (INIS)

    Highlights: → Open-porosity foam with struts consisting of Zr-based BMG containing W particles. → Acoustic emissions used to evaluate damage evolution during compression. → Metallic-glass-matrix composite higher damage accumulation single-phase BMG foam. -- Molten Vit106 (Zr57Nb5Cu15.4Ni12.6Al10) was infiltrated into a BaF2 preform containing W particles, and quenched. Salt dissolution resulted in an open-porosity foam with struts consisting of amorphous Vit106 containing crystalline W particles. This composite foam exhibits high compressive strains (∼75%), a low plateau stress (∼30 MPa) and higher damage accumulation than prior single-phase Vit106 foams. Likely explanations are the lower porosity in the composite foam (43% vs. 76%), damage from galvanic corrosion during salt removal, and tungsten embrittlement during processing.

  15. Magneto x-ray study of a gadolinium-iron amorphous alloy

    International Nuclear Information System (INIS)

    This work reports the measurement of the magnetic x-ray absorption of an amorphous Gd-Fe ferrimagnetic thin film. The Gd to Fe concentration in the sample was 1:4. The magnetic x-ray effect is the x-ray analog of magneto-optic absorption effects. Magneto x-ray effects arise when a solid has different indices of refraction for right and left circularly polarized x-rays. The difference in absorption of left and right circularly polarized x-rays is called the magneto x-ray absorption. This absorption is proportional to the net spin of the final state density of states. At the L3 edge, the main x-ray transition is from initial Gd(2p) core states to final Gd(5d) unoccupied states. Since the 5d states have a net spin polarization in ferromagnetic Gd, this experiment hoped to directly observe how that polarization changes for Gd in the alloy. The magneto x-ray absorption at the Gd L3 edge will be proportional to the sign and amount of the net spin polarization of the 5d electrons. The magnetic x-ray absorption coefficient was found to be at least 0.0005 smaller than the linear absorption coefficient at the Gd white line energy. This was measured for the amorphous alloy at room temperature. Lock-in techniques were used to obtain the small limit to the absorption. A simple model for the size of the magnetic x-ray absorption coefficient in Gd suggests that the Gd(5d) net spin polarization is less than 0.01 Bohr magnetons per atom

  16. Modelling of primary bcc-Fe crystal growth in a Fe85B15 amorphous alloy

    International Nuclear Information System (INIS)

    A kinetic modelling of primary crystallization in metallic glasses, based on the CALPHAD approach and the moving boundary model, has been applied to the Fe-B system. The DICTRA software has been used to perform numerical calculations. Kinetic and thermodynamic parameters (atomic mobilities and thermodynamic factors) are required and they have been obtained from the literature. Various simulations have been performed in order to evaluate the influence of different parameters choice. The soft impingement effect has been discussed. Furthermore, amorphous Fe85B15 samples have been prepared and examined by differential scanning calorimetry. Calculated and experimental results, both on continuous heating and isothermal conditions, have been compared

  17. Search for novel amorphous alloys with high crystallization temperature by combinatorial arc plasma deposition

    International Nuclear Information System (INIS)

    This paper describes a combinatorial search for novel amorphous alloys with high crystallization temperatures (Tx) using combinatorial arc plasma deposition (CAPD). The CAPD technique can deposit 1089 (33 x 33) thin film samples with different compositions on a substrate at one time. These 1089 samples on the substrate are individually referred to as CAPD samples and collectively referred to as a thin film library. Thin film libraries of Ir-Zr-Fe, Ir-Zr-Al, Mo-Zr-Al, Mo-Zr-Si, Ru-Zr-Fe and Ru-Zr-Si were deposited by CAPD. The compositions and phases of the CAPD samples were measured by energy dispersive X-ray fluorescence spectrometry and X-ray diffractometry, respectively. The results revealed that each library included amorphous CAPD samples. Since it is impossible to measure the Tx, fracture strength, fracture strain and Young's modulus of the CAPD samples by conventional measurement methods, larger samples having the same compositions as the amorphous CAPD samples were fabricated by a sputtering system. Since all CAPD samples of Ir-Zr-Fe and Ir-Zr-Al were too brittle, their corresponding sputter-deposited samples were not prepared. Sputter-deposited Mo-Zr-Al, Mo-Zr-Si, Ru-Zr-Fe and Ru-Zr-Si samples with ∼50 at.% Mo- or Ru-content were fabricated, and Tx and mechanical properties of these sputter-deposited samples were evaluated. All the sputter-deposited samples of Mo-Zr-Al and Mo-Zr-Si showed high Tx exceeding 973 K and as well as brittle characteristics. Ru50Zr35Fe10 samples showed high Tx exceeding 1273 K and a low fracture strength of 0.26 GPa. Samples of Ru51Zr5Si44 showed a high Tx of 923 K and a high fracture strength of 1.25 GPa

  18. First-principles study of the structural and dynamic properties of the liquid and amorphous Li–Si alloys

    International Nuclear Information System (INIS)

    We have performed density functional theory calculations and ab initio molecular dynamics to investigate the structures and dynamic properties of the liquid and amorphous LixSi alloys over a range of composition from x = 1.0 − 4.8. Our results show that Si atoms can form a variety of covalently bonded polyanions with diverse local bonding structures in the liquid alloys. Like in c-LiSi, Si atoms can form a continuous bond network in liquid Li1.0Si at 1050 K, while it gradually disintegrates into many smaller Si polyanions as the Li content increases in the alloys. The average sizes of Si polyanions in these liquid alloys were found to be relatively larger than those in their crystalline counterparts, which can even persist in the highly lithiated Li4.81Si alloy at 1500 K. Our results also show that amorphous LixSi alloys have similar local bonding structures but a largely increased short-range order as compared to their liquid counterparts. The differences between the average coordination number of each atomic pair in amorphous solids and that in the liquids are less than 1.1. Furthermore, our calculations reveal that Li and Si atoms can exhibit very distinct dynamic behaviors in the liquids and their diffusivities appear to be largely dependent on the chemical composition of the alloys. The diffusivity of Li was found to increase with the Li content in the alloys primarily because of the reduced interactions between Li and Si atoms, while the Si diffusivity also increases due to the gradual disintegration of the strongly interconnected Si bond network. The diffusivity of Li in amorphous LixSi was predicted to lie in the range between 10−7 and 10−9 cm2/s at 300 K, which is more than 20-fold larger than that of Si over the composition range considered. Our calculations further show that the diffusivities of both Li and Si can increase by two orders of magnitude as x increases from 1.0 to 3.57 in amorphous LixSi, indicating a more profound dependence on the

  19. First-principles study of the structural and dynamic properties of the liquid and amorphous Li–Si alloys

    Energy Technology Data Exchange (ETDEWEB)

    Chiang, Han-Hsin; Kuo, Chin-Lung, E-mail: chinlung@ntu.edu.tw [Department of Materials Science and Engineering, National Taiwan University, Taipei 10617, Taiwan (China); Lu, Jian-Ming [National Center for High-Performance Computing, Tainan 74147, Taiwan (China)

    2016-01-21

    We have performed density functional theory calculations and ab initio molecular dynamics to investigate the structures and dynamic properties of the liquid and amorphous Li{sub x}Si alloys over a range of composition from x = 1.0 − 4.8. Our results show that Si atoms can form a variety of covalently bonded polyanions with diverse local bonding structures in the liquid alloys. Like in c-LiSi, Si atoms can form a continuous bond network in liquid Li{sub 1.0}Si at 1050 K, while it gradually disintegrates into many smaller Si polyanions as the Li content increases in the alloys. The average sizes of Si polyanions in these liquid alloys were found to be relatively larger than those in their crystalline counterparts, which can even persist in the highly lithiated Li{sub 4.81}Si alloy at 1500 K. Our results also show that amorphous Li{sub x}Si alloys have similar local bonding structures but a largely increased short-range order as compared to their liquid counterparts. The differences between the average coordination number of each atomic pair in amorphous solids and that in the liquids are less than 1.1. Furthermore, our calculations reveal that Li and Si atoms can exhibit very distinct dynamic behaviors in the liquids and their diffusivities appear to be largely dependent on the chemical composition of the alloys. The diffusivity of Li was found to increase with the Li content in the alloys primarily because of the reduced interactions between Li and Si atoms, while the Si diffusivity also increases due to the gradual disintegration of the strongly interconnected Si bond network. The diffusivity of Li in amorphous Li{sub x}Si was predicted to lie in the range between 10{sup −7} and 10{sup −9} cm{sup 2}/s at 300 K, which is more than 20-fold larger than that of Si over the composition range considered. Our calculations further show that the diffusivities of both Li and Si can increase by two orders of magnitude as x increases from 1.0 to 3.57 in amorphous Li

  20. Highly ordered amorphous silicon-carbon alloys obtained by RF PECVD

    CERN Document Server

    Pereyra, I; Carreno, M N P; Prado, R J; Fantini, M C A

    2000-01-01

    We have shown that close to stoichiometry RF PECVD amorphous silicon carbon alloys deposited under silane starving plasma conditions exhibit a tendency towards c-Si C chemical order. Motivated by this trend, we further explore the effect of increasing RF power and H sub 2 dilution of the gaseous mixtures, aiming to obtain the amorphous counterpart of c-Si C by the RF-PECVD technique. Doping experiments were also performed on ordered material using phosphorus and nitrogen as donor impurities and boron and aluminum as acceptor ones. For nitrogen a doping efficiency close to device quality a-Si:H was obtained, the lower activation energy being 0,12 eV with room temperature dark conductivity of 2.10 sup - sup 3 (OMEGA.cm). Nitrogen doping efficiency was higher than phosphorous for all studied samples. For p-type doping, results indicate that, even though the attained conductivity values are not device levels, aluminum doping conducted to a promising shift in the Fermi level. Also, aluminum resulted a more efficie...

  1. Design and fabrication of a mechanical alloying system for preparing intermetallic, nanocrystalline, amorphous and quasicrystalline compounds

    International Nuclear Information System (INIS)

    In this work a grinding system was designed and fabricated which allowed to improve the operation conditions in time, frequency, temperature and selection of the grinding media and that allow the contamination decrease of the compounds. By means of this method of mechanical alloying new metallic compounds can be produced, starting from elemental powders, with fine and controlled microstructures. These compounds prepared by this method are going to be used as materials for the hydrogen storage. (Author)

  2. Highly mismatched crystalline and amorphous GaN(1-x)As(x) alloys in the whole composition range

    Energy Technology Data Exchange (ETDEWEB)

    Yu, K. M.; Novikov, S. V.; Broesler, R.; Demchenko, I. N.; Denlinger, J. D.; Liliental-Weber, Z.; Luckert, F.; Martin, R. W.; Walukiewicz, W.; Foxon, C. T.

    2009-08-29

    Alloying is a commonly accepted method to tailor properties of semiconductor materials for specific applications. Only a limited number of semiconductor alloys can be easily synthesized in the full composition range. Such alloys are, in general, formed of component elements that are well matched in terms of ionicity, atom size, and electronegativity. In contrast there is a broad class of potential semiconductor alloys formed of component materials with distinctly different properties. In most instances these mismatched alloys are immiscible under standard growth conditions. Here we report on the properties of GaN1-xAsx, a highly mismatched, immiscible alloy system that was successfully synthesized in the whole composition range using a nonequilibrium low temperature molecular beam epitaxy technique. The alloys are amorphous in the composition range of 0.17amorphous films have smooth morphology, homogeneous composition, and sharp, well defined optical absorption edges. The band gap energy varies in a broad energy range from ~;;3.4 eV in GaN to ~;;0.8 eV at x~;;0.85. The reduction in the band gap can be attributed primarily to the downward movement of the conduction band for alloys with x>0.2, and to the upward movement of the valence band for alloys with x<0.2. The unique features of the band structure offer an opportunity of using GaN1-xAsx alloys for various types of solar power conversion devices.

  3. Tunable magnetocaloric effect in transition metal alloys

    Science.gov (United States)

    Belyea, Dustin D.; Lucas, M. S.; Michel, E.; Horwath, J.; Miller, Casey W.

    2015-10-01

    The unpredictability of geopolitical tensions and resulting supply chain and pricing instabilities make it imperative to explore rare earth free magnetic materials. As such, we have investigated fully transition metal based “high entropy alloys” in the context of the magnetocaloric effect. We find the NiFeCoCrPdx family exhibits a second order magnetic phase transition whose critical temperature is tunable from 100 K to well above room temperature. The system notably displays changes in the functionality of the magnetic entropy change depending on x, which leads to nearly 40% enhancement of the refrigerant capacity. A detailed statistical analysis of the universal scaling behavior provides direct evidence that heat treatment and Pd additions reduce the distribution of exchange energies in the system, leading to a more magnetically homogeneous alloy. The general implications of this work are that the parent NiFeCoCr compound can be tuned dramatically with FCC metal additives. Together with their relatively lower cost, their superior mechanical properties that aid manufacturability and their relative chemical inertness that aids product longevity, NiFeCoCr-based materials could ultimately lead to commercially viable magnetic refrigerants.

  4. Preparation of uniform nanoparticles of ultra-high purity metal oxides, mixed metal oxides, metals, and metal alloys

    Science.gov (United States)

    Woodfield, Brian F.; Liu, Shengfeng; Boerio-Goates, Juliana; Liu, Qingyuan; Smith, Stacey Janel

    2012-07-03

    In preferred embodiments, metal nanoparticles, mixed-metal (alloy) nanoparticles, metal oxide nanoparticles and mixed-metal oxide nanoparticles are provided. According to embodiments, the nanoparticles may possess narrow size distributions and high purities. In certain preferred embodiments, methods of preparing metal nanoparticles, mixed-metal nanoparticles, metal oxide nanoparticles and mixed-metal nanoparticles are provided. These methods may provide tight control of particle size, size distribution, and oxidation state. Other preferred embodiments relate to a precursor material that may be used to form nanoparticles. In addition, products prepared from such nanoparticles are disclosed.

  5. Short-range ferromagnetism and transport properties of amorphous (Gd,Y)xSi1-x alloys

    International Nuclear Information System (INIS)

    A theoretical description and electrical conductivity measurements for amorphous (Gd,Y)xSi1-x alloys with 0.1 < x < 0.2 is presented. In the model, the strong topological disorder in the system, causing the appearance of regions with higher electron density (electron drops) around nanoscale structural defects enriched with rare-earth ions (clusters) is took into account. The local density of electron states in the drops and in the matrix is calculated and the criterion for local instability towards ferromagnetism is established. In the framework of the local phase transition approach, it is found that short-range ferromagnetic order is more favorable inside the drops than in the matrix and exists in a wide temperature range. Recent measurements of the temperature and magnetic-field dependence of the electrical conductivity in these systems are analyzed and it is shown that the spin polarization of the electron states in the drops enhances the tendency towards the metal-insulator transition

  6. Microstructures of nickel-base alloy dissimilar metal welds

    OpenAIRE

    Mouginot, Roman; Hänninen, Hannu

    2013-01-01

    Dissimilar metal welds (DMWs) between low-alloy steels (LAS), stainless steels (SS) and nickel-base alloys are very important in the design of conventional and nuclear power plants (NPPs). They help to reach better performances for high temperature environment but they can promote premature failure of components. Failure is often related to cracking in the heat affected zone of base materials. In this study, a literature review was conducted concerning the behavior of Inconel Ni-base alloy...

  7. Bacterial adhesion on amorphous and crystalline metal oxide coatings

    Energy Technology Data Exchange (ETDEWEB)

    Almaguer-Flores, Argelia [Facultad de Odontología, División de Estudios de Posgrado e Investigación, Universidad Nacional Autónoma de México, Circuito exterior s/n, Ciudad Universitaria, 04510 México D.F. (Mexico); Silva-Bermudez, Phaedra, E-mail: suriel21@yahoo.com [Unidad de Ingeniería de Tejidos, Terapia Celular y Medicina Regenerativa, Instituto Nacional de Rehabilitación, Calzada México-Xochimilco No. 289, Col. Arenal de Guadalupe, 14389 México D.F. (Mexico); Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, 04510 México D.F. (Mexico); Galicia, Rey; Rodil, Sandra E. [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, 04510 México D.F. (Mexico)

    2015-12-01

    Several studies have demonstrated the influence of surface properties (surface energy, composition and topography) of biocompatible materials on the adhesion of cells/bacteria on solid substrates; however, few have provided information about the effect of the atomic arrangement or crystallinity. Using magnetron sputtering deposition, we produced amorphous and crystalline TiO{sub 2} and ZrO{sub 2} coatings with controlled micro and nanoscale morphology. The effect of the structure on the physical–chemical surface properties was carefully analyzed. Then, we studied how these parameters affect the adhesion of Escherichia coli and Staphylococcus aureus. Our findings demonstrated that the nano-topography and the surface energy were significantly influenced by the coating structure. Bacterial adhesion at micro-rough (2.6 μm) surfaces was independent of the surface composition and structure, contrary to the observation in sub-micron (0.5 μm) rough surfaces, where the crystalline oxides (TiO{sub 2} > ZrO{sub 2}) surfaces exhibited higher numbers of attached bacteria. Particularly, crystalline TiO{sub 2}, which presented a predominant acidic nature, was more attractive for the adhesion of the negatively charged bacteria. The information provided by this study, where surface modifications are introduced by means of the deposition of amorphous or crystalline oxide coatings, offers a route for the rational design of implant surfaces to control or inhibit bacterial adhesion. - Highlights: • Amorphous (a) and crystalline (c) TiO{sub 2} and ZrO{sub 2} coatings were deposited. • The atomic ordering influences the coatings surface charge and nano-topography. • The atomic ordering modifies the bacterial adhesion for the same surface chemistry. • S. aureus adhesion was lower on a-TiO{sub 2} and a-ZrO{sub 2} than on their c-oxide counterpart. • E. coli adhesion on a-TiO{sub 2} was lower than on the c-TiO{sub 2}.

  8. PIXE from thin films and amorphous alloys induced by medium energy heavy ions

    International Nuclear Information System (INIS)

    Highlights: •Low energy heavy-ion PIXE were used for surface characterization. •It was performed in time sequence and at grazing incidence-exit geometry. •Stability of thin films against implantation and interface mixing was analyzed. •Sputtering of multicomponent alloys subjected to irradiation was monitored. -- Abstract: Characteristic X-rays emitted under impact of fast light ions with surfaces (PIXE) provide information not only on atomic excitation and further recombination processes but also on elemental composition and dynamics of restructuration of the surface. In this work radiation emitted during interaction of medium energy (∼200 keV) heavy ions (Ar, N) with Si (1 1 0) surface and with Fe/Si and Fe/Cu/Si thin (1–50 nm) films in grazing incidence-exit angle geometry were measured in time sequence in order to show that dynamics of selective modification of surface structure and composition can be monitored in-situ with PIXE. It is shown that surfaces of amorphous alloys are not stable against heavy ions (HI) irradiation due to preferential sputtering and implantation and that the dynamics of such modification can also be monitored with PIXE. The method is used for example to find detection limit for implanted Ar ions

  9. Amorphous Fe-B alloys in B-Fe-Ag multilayers studied by magnetization and Moessbauer measurements

    Energy Technology Data Exchange (ETDEWEB)

    Kiss, L.F., E-mail: kissl@szfki.hu [Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest (Hungary); Balogh, J.; Bujdoso, L.; Kaptas, D.; Kemeny, T. [Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest (Hungary); Kovacs, A. [Center for Electron Nanoscopy, Technical University of Denmark, Kgs. Lyngby 2800 (Denmark); Vincze, I. [Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest (Hungary)

    2011-06-15

    Research highlights: > The magnetic properties of B-Fe-Ag multi-trilayers were investigated. > They are influenced by the Ag thickness when it is below 5 nm. > The formation of amorphous Fe-B alloys of different B content is observed. > It is due to the role of the Ag layer as barrier to the mixing of Fe and B. > The ultra-thin Fe-rich alloy between Ag and B layers shows ferromagnetic properties. - Abstract: Bulk and local magnetic properties were studied in [1 nm B + 1 nm {sup 57}Fe + x nm Ag]{sub 5}, x = 1, 2, 4, 5 and 10, multilayer samples. Although Ag does not mix with either of the other two elements the magnetic properties of the multilayers are strongly influenced by the Ag thickness below x = 5, whereas no such effect is observed above this value. The Moessbauer measurements indicate a complete amorphization of the thin Fe layers in each sample, as a result of intermixing with the B layers. The variation of the magnetic properties is explained by the variation of the average B concentration of the amorphous Fe-B layers, which depends on the thickness of the Ag barrier layers. The magnetization measurements indicate ferromagnetic behaviour of the ultra-thin amorphous layers with the presence of less than 10% superparamagnetic moments for x = 5 and 10. The average B concentration of the amorphous Fe-B alloy, as estimated from the Fe hyperfine fields, is around 40 at%. It is significantly lower than the 60 at% nominal B concentration, suggesting the presence of an unalloyed B layer, as well. This picture is supported by transmission electron microscopy investigations which reveal two amorphous layers of different B concentration in between the crystalline Ag layers.

  10. Structural and magnetic properties of Fe76P5(Si0.3B0.5C0.2)19 amorphous alloy

    International Nuclear Information System (INIS)

    Highlights: ► Fe76P5(Si0.3B0.5C0.2)19 amorphous alloy in ribbons and 1 mm and 2 mm rod samples. ► Good glass forming ability with ΔT = 50 K and γ = 0.37 and off-eutectic composition. ► Good soft magnetic properties with magnetization saturation of 1.44 T. ► Geometrical factors are the primary causes of magnetic losses in frequencies above 10 Hz. - Abstract: Recently, bulk amorphous alloys were produced in the Fe–B–Si–P–C system with high glass forming ability, excellent magnetic properties and the advantage of containing no expensive glass-forming elements, such as Ga, Y, Cr or Nb, having, therefore, a good perspective of commercial applications. In the present work, the Fe76P5(Si0.3B0.5C0.2)19 amorphous alloy prepared by two quenching techniques has been studied. Amorphous ribbons of about 40 μm thick were obtained by planar-flow casting together with cylinders having 1 and 2 mm diameter produced by copper mold injection casting. All the samples appear fully amorphous after X-ray diffraction analysis. A comprehensive set of thermal data (glass, crystallization, melting and liquidus temperatures) were obtained as well as a description of the melting and solidification processes. Mechanical microhardness tests showed that the samples have a hardness of 9.7 ± 0.3 GPa. Good soft-magnetic properties were obtained, including a high magnetization of 1.44 T and a low coercivity (4.5 A/m for ribbons and 7.5 A/m in the case of 1 mm rod samples, both in as-cast state). Thermomagnetic studies showed a Curie temperature around 665 K and the precipitation of new magnetic phases upon temperatures of 1000 K. Furthermore, the frequency dependence of magnetic losses at a fixed peak induction was studied. The results suggest the occurrence of a fine magnetic domain structure in bulk samples. The good soft magnetic properties of the bulk metallic glass obtained by copper mold casting for this particular Fe-based composition suggests possible applications in

  11. Anticorrosion surface alloying of ferrous metal by carbide formers

    International Nuclear Information System (INIS)

    It is shown theoretically and experimentally that in cases of surface chromizing and titanizing of ferrous metal, proper carbon of the latter plays an important positive role, providing the formation of exclusively dense surface carbide layers with high and durable corrosion and mechanic stability. In the future surface alloying must become a more effective method of anticorrosion alloying

  12. Radiation effects on metals, alloys and cement

    International Nuclear Information System (INIS)

    High - energy particle irradiation of materials brings as a consequence changes in their atomic structures that alter the electrical, magnetic and mechanical properties which are the most important characteristics for practical applications of metals and alloys. A review is made on experimental results of in-pile (IEA-RI reactor) and CV-28 cyclotron irradiated materials. Resistivity measurements on CuPd and FeNi alloys showed different behaviour during fast neutron irradiation. While CuPd had almost coincidental relaxation curves, FeNi presented a distinguishable short and long-range ordering with the critical order-disorder temperature at 5150C. Vacancy supersaturation curves of FeNiSi (49-49-2 at %), FeNiCr (49-95-49, 95-0,1 at. %), FeNiMo (50-50 at.% + 50 ppm) and pure FeNi (50-50 at.%), determined by means of the Magnetic After Effect are presented as an effective pre-selection method of nuclear materials before the destructive stage of void formation and swelling. A displacement of damage peak from 480 to 500 and 5700C was detected on pure AISI 321 stainless steel and with 0,05 wt.% and 0,10 wt.% of Nb additions by means of resistivity and micro-hardness. Ultrasound techniques applied to fast neutron irradiated portland cement paste (fluence 7,2 x 1018 n/cm2) showed a 24% decrease in its dynamic elasticity modulus. Helium diffusion on Au, Ag and Al foils irradiated in cyclotron was studied, suggesting a vacancy mechanism for single He atom diffusion. Embrittlement by Alpha particle implantation in cyclotron to simulate in-pile (n,α) reaction-was measured by high temperature creep on AISI 316 stainles steel. (author)

  13. Theory of the transition temperature of superconducting amorphous transition metals

    International Nuclear Information System (INIS)

    In the present paper first the transition temperature Tsub(c) is shown to be a local quantity, which depends on the (average) short range order, and second it is demonstrated how to calculate local electronic properties in the framework of a short range order model and the transition temperature of amorphous systems based on accepted structure models of the amorphous state. In chapter I the theoretical basis of this work is presented in brief. The model used to study the role of short range order (in periodically ordered as well as in disordered system) is described in chapter II. The results of this model for the periodically ordered case are compared in chapter III with band structure calculations. In chapter IV it is shown how to establish short range order models for disordered systems and what kind of information can be obtained with respect to the electronic properties. Finally in chapter V it is discussed to what extend the interpretation of the transition temperature Tsub(c) as being determined by short range order effects can be supported by the electronic properties, which are calculated in the chapters III and IV. (orig.)

  14. Influence of pulsing current on the glass transition and crystallizing kinetics of a Zr base bulk amorphous alloy

    Institute of Scientific and Technical Information of China (English)

    WU Wenfei; YAO Kefu; ZHAO Zhankui

    2004-01-01

    Based on the thermal analysis, the influence of pulsing current on the glass transition and crystallizing kinetics of Zr41.3Ti14.2Cu12.8Ni10.3Be21.4 bulk amorphous alloy has been studied. The obtained results show that after the Zr41.3Ti14.2Cu12.8Ni10.3Be21.4 bulk amorphous alloy was pretreated by high-density pulsing current at low temperature, its glass transition temperature Tg, the initial crystallizing temperature Tx and the corresponding exothermic peak of crystallization Tpi were reduced. But the temperature range of supercooled liquid ΔT=Tx-Tg is almost the same. The calculated results with Kissinger equation show that the activation energy of glass transition of the alloy pretreated is reduced significantly, while the activation energy of crystallization is basically unchanged. The influence of pulsing current on the glass transition and crystallization of the Zr41.3Ti14.2Cu12.8Ni10.3Be21.4 bulk amorphous alloy is believed to be related with the structure relaxation of the glass caused by the current.

  15. Functional oxide structures on a surface of metals and alloys

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    @@ The investigations of the plasma electrolytic processes in our laboratory are aimed to the development of conditions of formation of oxide layers with determined composition, structure and functional properties on the surface of valve metals (Al, Ti) and their alloys.

  16. Crystallization kinetics of Fe-B based amorphous alloys studied in-situ using X-rays diffraction and differential scanning calorimetry

    Directory of Open Access Journals (Sweden)

    Santos D.R. dos

    2001-01-01

    Full Text Available The crystallization processes for the amorphous metallic alloys Fe74B17Si2Ni4Mo3 and Fe86B6Zr7Cu1 (at. % were investigated using X-rays diffraction measurements performed in-situ during Joule-heating, with simultaneous monitoring of the electrical resistance. We determined the main structural transitions and crystalline phases formed during heating, and correlated these results to the observed resistance variations. As the annealing current is increased, the resistance shows an initial decrease due to stress relaxation, followed by a drop to a minimum value due to massive nucleation and growth of alpha-Fe nanocrystals. Further annealing causes the formation of small fractions of Fe-B, B2Zr or ZrO2, while the resistance increases due to temperature enhancement. In situ XRD measurements allowed the identification of metastable phases, as the gamma-Fe phase which occurs at high temperatures. The exothermal peaks observed in the differential scanning calorimetry (DSC for each alloy corroborate the results. We also have performed DSC measurements with several heating rates, which allowed the determination of the Avrami exponent and crystallization activation energy for each alloy. The obtained activation energies (362 and 301 kJ/mol for Fe-B-Zr-Cu; 323 kJ/mol for Fe-B-Si-Ni-Mo are comparable to reported values for amorphous iron alloys, while the Avrami exponent values (n = 1.0 or n = 1.2 are consistent with diffusion controlled crystallization processes with nucleation rates close to zero.

  17. Applications in the Nuclear Industry for Thermal Spray Amorphous Metal and Ceramic Coatings

    International Nuclear Information System (INIS)

    Amorphous metal and ceramic thermal spray coatings have been developed that can be used to enhance the corrosion resistance of containers for the transportation, aging and disposal of spent nuclear fuel and high-level radioactive wastes. Iron-based amorphous metal formulations with chromium, molybdenum and tungsten have shown the corrosion resistance believed to be necessary for such applications. Rare earth additions enable very low critical cooling rates to be achieved. The boron content of these materials, and their stability at high neutron doses, enable them to serve as high efficiency neutron absorbers for criticality control. Ceramic coatings may provide even greater corrosion resistance for container applications, though the boron-containing amorphous metals are still favored for criticality control applications. These amorphous metal and ceramic materials have been produced as gas atomized powders and applied as near full density, non-porous coatings with the high-velocity oxy-fuel process. This paper summarizes the performance of these coatings as corrosion-resistant barriers, and as neutron absorbers. Relevant corrosion models are also discussed, as well as a cost model to quantify the economic benefits possible with these new materials

  18. Applications in the Nuclear Industry for Corrosion-Resistant Amorphous-Metal Thermal-Spray Coatings

    Energy Technology Data Exchange (ETDEWEB)

    Farmer, J; Choi, J

    2007-07-18

    Amorphous metal and ceramic thermal spray coatings have been developed that can be used to enhance the corrosion resistance of containers for the transportation, aging and disposal of spent nuclear fuel and high-level radioactive wastes. Fe-based amorphous metal formulations with chromium, molybdenum and tungsten have shown the corrosion resistance believed to be necessary for such applications. Rare earth additions enable very low critical cooling rates to be achieved. The boron content of these materials, and their stability at high neutron doses, enable them to serve as high efficiency neutron absorbers for criticality control. Ceramic coatings may provide even greater corrosion resistance for container applications, though the boron-containing amorphous metals are still favored for criticality control applications. These amorphous metal and ceramic materials have been produced as gas atomized powders and applied as near full density, non-porous coatings with the high-velocity oxy-fuel process. This paper summarizes the performance of these coatings as corrosion-resistant barriers, and as neutron absorbers. Relevant corrosion models are also discussed, as well as a cost model to quantify the economic benefits possible with these new materials.

  19. Differential enthalpy of cation exchange of alkaline metals on amorphous zirconium phosphate

    International Nuclear Information System (INIS)

    Work presents the results of calorimetric research of sorption process of alkaline metals cations on hydrogen form of amorphous zirconium phosphates. It is defined that the general regularities of passing of ion exchange reaction are the same for the samples of zirconium phosphate with different content of phosphor.

  20. Deformation induced alloying in crystalline – metallic glass nano-composites

    International Nuclear Information System (INIS)

    We study the mechanisms of deformation driven chemical mixing in a metallic nanocomposite model system. More specific, we investigate shear banding at the atomic scale in an amorphous CuZr/ crystalline Cu nanolaminate, deformed by microindentation. Three CuZr/Cu multilayer systems (100 nm Cu/100 nm CuZr, 50 nm Cu/100 nm CuZr, and 10 nm Cu/100 nm CuZr) are fabricated to study the effect of layer thickness on shear band formation and deformation induced alloying. The chemical and structural evolution at different strain levels are traced by atom probe tomography and transmission electron microscopy combined with nano-beam diffraction mapping. The initially pure crystalline Cu and amorphous CuZr layers chemically mix by cross-phase shear banding after reaching a critical layer thickness. The Cu inside the shear bands develops a high dislocation density and can locally undergo transition to an amorphous state when sheared and mixed. We conclude that the severe deformation in the shear bands in the amorphous layer squeeze Zr atoms into the Cu dislocation cores in the Cu layers (thickness <5 nm), resulting in local chemical mixing

  1. Developing Gradient Metal Alloys through Radial Deposition Additive Manufacturing

    OpenAIRE

    Douglas C. Hofmann; Scott Roberts; Richard Otis; Joanna Kolodziejska; R. Peter Dillon; Jong-ook Suh; Shapiro, Andrew A; Zi-Kui Liu; John-Paul Borgonia

    2014-01-01

    Interest in additive manufacturing (AM) has dramatically expanded in the last several years, owing to the paradigm shift that the process provides over conventional manufacturing. Although the vast majority of recent work in AM has focused on three-dimensional printing in polymers, AM techniques for fabricating metal alloys have been available for more than a decade. Here, laser deposition (LD) is used to fabricate multifunctional metal alloys that have a strategically graded composition to a...

  2. The corrosion behaviour of nanograined metals and alloys

    OpenAIRE

    P. Herrasti; Ponce de León, C.; Walsh, F. C.

    2012-01-01

    There has been considerable interest in the properties of nanocrystalline materials over the last decade. Such materials include metals and alloys with a crystal size within the order of 1 to 100 nm. The interest arises due to the substantial differences in electrical, optical and magnetic properties and also due to their high adsorption capability and chemical reactivity compared to their larger grained counterparts. In this paper, the corrosion of nanocrystalline metals and alloys is invest...

  3. Mechanically driven nanocrystallization of amorphous Fe73.5Cu1Nb3Si13.5B9 alloy induced by high-energy ball milling

    International Nuclear Information System (INIS)

    The mechanically driven nanocrystallization of amorphous Finemet alloy caused by high-energy ball milling was investigated by XRD, DSC and TEM techniques. A structural relaxation occurred in the amorphous Finemet alloy after milling for 0.5-2 h. Further milling for more than 3.5 h, uniformly and randomly distributed nanocrystalline α-Fe with grain size from ∝2 nm to ∝5 nm formed. The kinetics of the mechanical nanocrystallization of amorphous Finemet alloy was described by JMA model with the Avrami exponent n=1.55, which indicates a zero-nucleation rate and grain growth in all shapes from very small dimensions. In addition, the mechanical crystallization of amorphous Finemet alloys is mainly due to the severe deformation and local temperature rise during ball milling. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Microstructure evolution and mechanical properties of Nb-alloyed Cu-based bulk metallic glasses and composites

    International Nuclear Information System (INIS)

    Highlights: • The microstructures of as-cast BMGs undergo a composite-amorphous evolution. • The 15.1% of plasticity and the 2205 MPa of fracture strength are achieved. • The dispersed crystals in glassy matrix enhance the plasticity of BMG. - Abstract: This paper reports the microstructure evolution of Cu50.2 Zr40.8Ti9−xNbx (x = 0.5, 1.0, and 2.0 at.%) bulk metallic glass and bulk metallic glass composites accompanied with the addition of Nb and the corresponding mechanical properties. The X-ray diffraction and characterization of microstructures demonstrate that the microstructures of as-cast alloys undergo a composite-amorphous evolution. DSC analysis indicates that the glass-forming ability of as-cast alloys increases with addition of Nb. The microstructure evolution can be contributed to the combination of the stabilization of Nb on precipitated crystalline phases and cooling time. 1.0 at.% Nb-alloyed sample has the best plasticity (15.1%) and the highest fracture strength (2205 MPa) among three as-cast alloys. This work suggests that the uniformly dispersed tiny crystalline phases in glassy matrix can enhance the plasticity of bulk metallic glasses

  5. Weak crystallization theory of metallic alloys

    Science.gov (United States)

    Martin, Ivar; Gopalakrishnan, Sarang; Demler, Eugene A.

    2016-06-01

    Crystallization is one of the most familiar, but hardest to analyze, phase transitions. The principal reason is that crystallization typically occurs via a strongly first-order phase transition, and thus rigorous treatment would require comparing energies of an infinite number of possible crystalline states with the energy of liquid. A great simplification occurs when crystallization transition happens to be weakly first order. In this case, weak crystallization theory, based on unbiased Ginzburg-Landau expansion, can be applied. Even beyond its strict range of validity, it has been a useful qualitative tool for understanding crystallization. In its standard form, however, weak crystallization theory cannot explain the existence of a majority of observed crystalline and quasicrystalline states. Here we extend the weak crystallization theory to the case of metallic alloys. We identify a singular effect of itinerant electrons on the form of weak crystallization free energy. It is geometric in nature, generating strong dependence of free energy on the angles between ordering wave vectors of ionic density. That leads to stabilization of fcc, rhombohedral, and icosahedral quasicrystalline (iQC) phases, which are absent in the generic theory with only local interactions. As an application, we find the condition for stability of iQC that is consistent with the Hume-Rothery rules known empirically for the majority of stable iQC; namely, the length of the primary Bragg-peak wave vector is approximately equal to the diameter of the Fermi sphere.

  6. Effect of alloying elements on the hydrogen embrittlement of medium-alloy deposited metal

    International Nuclear Information System (INIS)

    The effect was investigated of the main alloying elements in the metal of electrodes for welding steels upon the tendency to hydrogen embrittlement of medium-alloy built-up metal which was evaluated by the work of inception of cracks and by the work of crack propagation. Specimens from blanks were tested for static bending and rupture. It was established that when developing welding electrodes in was expedient to choose the alloying range of the built-up metal with due regard for the effect of alloying elements upon the hydrogen embrittlement. For a low content of diffusion hydrogen in the built-up metal, the work of inception of a crack diminishes with the increase in carbon, silicon, nickel and molybdenum contents. The work of crack propagation increases with the content of nickel ans varies according to a curve with a maxium as the contents of carbon, silicon, manganese and chromium rise

  7. Comparative anomalous small-angle X-ray scattering study of hotwire and plasma grown amorphous silicon-germanium alloys

    OpenAIRE

    Goerigk, G.; Williamson, D. L.

    2001-01-01

    The nanostructure of hydrogenated amorphous silicon-germanium alloys, a-Si1-xGex:H, prepared by the hotwire deposition technique (x=0.06-0.79) and by the plasma enhanced chemical vapor deposition technique (x=0 and 0.50) was analyzed by anomalous small-angle x-ray scattering experiments. For all alloys with x >0 the Ge component was found to be inhomogeneously distributed with correlation lengths of about 1 nm. A systematic increase of the separated scattering was found due to the increasing ...

  8. Transition metal oxide window layer in thin film amorphous silicon solar cells

    International Nuclear Information System (INIS)

    Pin-type hydrogenated amorphous silicon solar cells have been fabricated by replacing state of the art silicon based window layer with more transparent transition metal oxide (TMO) materials. Three kinds of TMOs: vanadium oxide, tungsten oxide, and molybdenum oxide (MoOx) were comparatively investigated to reveal the design principles of metal oxide window layers. It was found that MoOx exhibited the best performance due to its higher work function property compared to other materials. In addition, the band alignment between MoOx and amorphous Si controls the series resistance, which was verified through compositional variation of MoOx thin films. The design principles of TMO window layer in amorphous Si solar cells are summarized as follows: A wide optical bandgap larger than 3.0 eV, a high work function larger than 5.2 eV, and a band alignment condition rendering efficient hole collection from amorphous Si absorber layer. - Highlights: • High work function metal oxides can potentially replace the conventional p-a-SiC. • V2Ox, WOx, and MoOx are comparatively investigated in this study. • MoOx is the most relevant material due to its highest work function. • Slightly oxygen deficient MoOx exhibited performance enhancement at x = 2.9

  9. The glass-forming ability of model metal-metalloid alloys

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Kai; Liu, Yanhui; Schroers, Jan [Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520 (United States); Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06520 (United States); Shattuck, Mark D. [Department of Physics and Benjamin Levich Institute, The City College of the City University of New York, New York, New York 10031 (United States); Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520 (United States); O’Hern, Corey S. [Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520 (United States); Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06520 (United States); Department of Physics, Yale University, New Haven, Connecticut 06520 (United States); Department of Applied Physics, Yale University, New Haven, Connecticut 06520 (United States)

    2015-03-14

    Bulk metallic glasses (BMGs) are amorphous alloys with desirable mechanical properties and processing capabilities. To date, the design of new BMGs has largely employed empirical rules and trial-and-error experimental approaches. Ab initio computational methods are currently prohibitively slow to be practically used in searching the vast space of possible atomic combinations for bulk glass formers. Here, we perform molecular dynamics simulations of a coarse-grained, anisotropic potential, which mimics interatomic covalent bonding, to measure the critical cooling rates for metal-metalloid alloys as a function of the atomic size ratio σ{sub S}/σ{sub L} and number fraction x{sub S} of the metalloid species. We show that the regime in the space of σ{sub S}/σ{sub L} and x{sub S} where well-mixed, optimal glass formers occur for patchy and LJ particle mixtures, coincides with that for experimentally observed metal-metalloid glass formers. Thus, our simple computational model provides the capability to perform combinatorial searches to identify novel glass-forming alloys.

  10. The glass-forming ability of model metal-metalloid alloys

    International Nuclear Information System (INIS)

    Bulk metallic glasses (BMGs) are amorphous alloys with desirable mechanical properties and processing capabilities. To date, the design of new BMGs has largely employed empirical rules and trial-and-error experimental approaches. Ab initio computational methods are currently prohibitively slow to be practically used in searching the vast space of possible atomic combinations for bulk glass formers. Here, we perform molecular dynamics simulations of a coarse-grained, anisotropic potential, which mimics interatomic covalent bonding, to measure the critical cooling rates for metal-metalloid alloys as a function of the atomic size ratio σS/σL and number fraction xS of the metalloid species. We show that the regime in the space of σS/σL and xS where well-mixed, optimal glass formers occur for patchy and LJ particle mixtures, coincides with that for experimentally observed metal-metalloid glass formers. Thus, our simple computational model provides the capability to perform combinatorial searches to identify novel glass-forming alloys

  11. Preparation and Cycling Performance of Iron or Iron Oxide Containing Amorphous Al-Li Alloys as Electrodes

    Directory of Open Access Journals (Sweden)

    Franziska Thoss

    2014-12-01

    Full Text Available Crystalline phase transitions cause volume changes, which entails a fast destroying of the electrode. Non-crystalline states may avoid this circumstance. Herein we present structural and electrochemical investigations of pre-lithiated, amorphous Al39Li43Fe13Si5-powders, to be used as electrode material for Li-ion batteries. Powders of master alloys with the compositions Al39Li43Fe13Si5 and Al39Li43Fe13Si5 + 5 mass-% FeO were prepared via ball milling and achieved amorphous/nanocrystalline states after 56 and 21.6 h, respectively. In contrast to their Li-free amorphous pendant Al78Fe13Si9, both powders showed specific capacities of about 400 and 700 Ah/kgAl, respectively, after the third cycle.

  12. Structural relaxation and crystallization in the Fe-Cr-Si-B and Fe-Cu-Cr-Si-B amorphous alloys

    International Nuclear Information System (INIS)

    Structural relaxation, crystallization and optimisation processes in soft magnetic amorphous alloys based on iron are examined by applying different experimental techniques: X-ray diffraction analysis, high-resolution electron microscopy, measurements of magnetic and electric properties (permeability, after-effect resistivity). The presented results are discussed in terms of annealing out of microvoids, formation of nanocrystalline phase and changes of effective magnetostriction constant. (author)

  13. Influence of Kinetic and Thermodynamic Factors on the Glass-Forming Ability of Zirconium-Based Bulk Amorphous Alloys

    OpenAIRE

    Mukherjee, S.; Schroers, J.; Johnson, W. L.; Rhim, W. K.

    2005-01-01

    The time-temperature-transformation curves for three zirconium-based bulk amorphous alloys are measured to identify the primary factors influencing their glass-forming ability. The melt viscosity is found to have the most pronounced influence on the glass-forming ability compared to other thermodynamic factors. Surprisingly, it is found that the better glass former has a lower crystal-melt interfacial tension. This contradictory finding is explained by the icosahedral short-range order of the...

  14. Amorphous ribbons consolidation of Cu{sub 46}Zr{sub 42}Al{sub 7}Y{sub 5} alloy by hot extrusion; Consolidacao de fitas amorfas da liga The Cu{sub 46}Zr{sub 42}Al{sub 7}Y{sub 5} alloy with amorphous structure shows a temperature rangepor extrusao a quente

    Energy Technology Data Exchange (ETDEWEB)

    Melle, A.K.; Bolfarini, C.; Botta Filho, W.J.; Kiminami, C.S. [Universidade Federal de Sao Carlos (DEMa/UFSCar), SP (Brazil). Dept. de Engenharia de Materiais; Peres, M.M., E-mail: anakarla13_8@hotmail.co [Universidade Federal de Itajuba (UNIFEI), Itabira, MG (Brazil)

    2010-07-01

    The Cu{sub 46}Zr{sub 42}Al{sub 7}Y{sub 5} alloy with amorphous structure shows a temperature range between the glass transition temperature (Tg) and the crystallization temperature (Tx) of Tx-Tg={Delta}T{sub x}= 100K. At this temperature range, the metal behavior is of a supercooled liquid with viscosity {approx_equal} 10{sup 6} N.s/m{sup 2}. The aim of this work is to contribute on the development of a processing route to produce bulk metallic glass. Amorphous ribbons was produced by rapid quenching using 'melt spinning' process, the ribbons were fragmented in small pieces, compacted at room temperature and consolidated by hot extrusion under extrusion temperatures on the {Delta}T{sub x}, ram speed of 1mm/min and extrusion ratio of 3:1. The extruded samples were characterized by X-ray diffractometry (XRD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The results showed that extrusion temperature was fundamental to promote a full or partial consolidation of the amorphous ribbons, but causing the formation of some voids and inducing some regions to crystallization that showing the high sensibility to fit the extrusion temperature.(author)

  15. Electrophoretically applied dielectrics for amorphous metal foils used in pulsed power saturable reactors

    International Nuclear Information System (INIS)

    Amorphous metal foil-wound inductors have been tested as ferromagnetic saturable inductive elements for pulse-power (multi-terawatt) switching nodules. Saturation switching may provide large 100 ns current bursts necessary to accelerate ion beams for the fusion fuel pellet implosion required, for example, in PBFA (particle beam fusion accelerator) operation. In simulated capacitor testing premature dielectric breakdown of thin polyethylene terephthalate film insulation in the inductor windings occurs at considerably below 2500 V. This appears to be due to inadvertent dielectric damage from micro-spikes on the amorphous foil surface. Electron micrographs and dielectric breakdown data illustrate that electrophoretically-applied dielectric coatings, deposited from organic aqueous colloid dispersions, can be used to provide insulating coatings on the foil which provide a 240% improvement (6000 V) in the breakdown strength of wound amorphous foil inductors. The theory and operation of a dedicated electrophoretic continuous coating system is described

  16. Nanocrystallization behaviour of a ternary amorphous alloy during isothermal annealing: a Monte Carlo simulation

    Institute of Scientific and Technical Information of China (English)

    Jin Shi-Feng; Wang Wei-Min; Zhou Jian-Kun; Guo Hong-Xuan; J.F. Webb; Bian Xiu-Fang

    2005-01-01

    The nanocrystallization behaviour of Zr70Cu20Ni10 metallic glass during isothermal annealing is studied by employing a Monte Carlo simulation incorporating with a modified Ising model and a Q-state Potts model. Based on the simulated microstructure and differential scanning calorimetry curves, we find that the low crystal-amorphous interface energy of Ni plays an important role in the nanocrystallization of primary Zr2Ni. It is found that when T < TImax (where TImax is the temperature with maximum nucleation rate), the increase of temperature results in a larger growth rate and a much finer microstructure for the primary Zr2Ni, which accords with the microstructure evolution in "flash annealing". Finally, the Zr2Ni/Zr2Cu interface energy σG contributes to the pinning effect of the primary nano-sized Zr2Ni grains in the later formed normal Zr2Cu grains.

  17. Ab initio molecular dynamics simulation of the atom packing and density of Al-Ni amorphous alloys

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Al-Ni alloys have better glass forming ability (GFA) than other Al-based alloys. However, the relationship among the atomic arrangement, glass transition, packing density and composition hasn’t been systematically studied. In this paper the ab initio molecular dynamics simulation (AIMD) was performed on the atom packing and density of AlxNi100-x (x=80, 83, 85, 86, 87 and 90) alloys. The pair correlation function and Voronoi tessellation indicated that there are obvious topological and chemical short-range orders in these alloys. The topological structure consists of Al-centered icosahedra like and Ni-centered tri-capped trigonal prism (TTP) like polyhedra. There is strong chemical short-range ordering between Al and Ni atoms indicated by the bond-length of Al-Ni pair shorter than the sum of the radii of Al and Ni atoms, which increases with the increasing of Ni content. It is shown that the densities of amorphous alloys don’t agree with the linear law with a peak at x=85. Based on the features of the structure and density, it is concluded that Al-Ni alloys at x=84–86 have high GFA, which can be extended to multi-component Al-based alloys.

  18. Local Chemical Reactivity of a Metal Alloy Surface

    DEFF Research Database (Denmark)

    Hammer, Bjørk; Scheffler, Matthias

    1995-01-01

    The chemical reactivity of a metal alloy surface is studied by density functional theory investigating the interaction of H2 with NiAl(110). The energy barrier for H2 dissociation is largely different over the Al and Ni sites without, however, reflecting the barriers over the single component metal...

  19. Protective properties and structure of amorphous alumosilicophosphate coatings for niobium alloys

    International Nuclear Information System (INIS)

    Results of thermal tests of niobium alloy samples with a protective coating in gas media with different content of oxygen are presented. Microhardness of the metal under the coating and of the coating as such prior to and after thermal testing was studied. Near the contact areas of the metal and coating were studied using electron microscopy, X-ray diffraction microprobe and X-ray phase analyses. Information on the structure, elementary and phase compositions of the near the contact areas was obtained. The processes occurring during formation and subsequent long-term annealing of the coating, which give rise to structural changes in the coating providing its adhesion to substrate and high protective efficiency, were interpreted

  20. Mechanisms of diffusional phase transformations in metals and alloys

    CERN Document Server

    Aaronson, Hubert I; Lee, Jong K

    2010-01-01

    Developed by the late metallurgy professor and master experimentalist Hubert I. Aaronson, this collection of lecture notes details the fundamental principles of phase transformations in metals and alloys upon which steel and other metals industries are based. Mechanisms of Diffusional Phase Transformations in Metals and Alloys is devoted to solid-solid phase transformations in which elementary atomic processes are diffusional jumps, and these processes occur in a series of so-called nucleation and growth through interface migration. Instead of relying strictly on a pedagogical approach, it doc

  1. Thermodynamic analysis of metals and alloys interaction with nitrogen oxides

    International Nuclear Information System (INIS)

    Interaction thermodynamic analysis of Fe, Cr, Ni, Mo, Mn, Ti (taking into account thermodynamic activity in steels and alloys) and atmospheres, containing different quantities of NsOk (N2O4, NO2, NO) is conducted. Thermodynamic characteristic analysis of nitrogen oxide interaction with metals allows one to give a number of recommendations, concerning metal protection against corrosion in gaseous atmospheres, containing NsO=k: utilization of pure metals or doped steels and alloys as structural materials, working in contact with NsOk, does not substantially change the picture of the material thermodynamic resistance: any of the materials under consideration is thermodynamically reactive at PNs-Ok >> 10-1 MPa. However, steels and alloys, containing Cr, Si may produce heat-resistant oxidonitride surface films. Corrosion resistance of a metal product, containing with NsOk, can be increased both by preliminary nitration and oxidation of its surface

  2. Elastic and plastic characteristics of a model Cu–Zr amorphous alloy

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, Akiho; Kamimura, Yasushi [Institute of Industrial Science, The University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Edagawa, Keiichi, E-mail: edagawa@iis.u-tokyo.ac.jp [Institute of Industrial Science, The University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Takeuchi, Shin [Tokyo University of Science, Kagurazaka, Sinjuku-ku, Tokyo 162-8601 (Japan)

    2014-09-22

    Athermal quasistatic simulation of shear deformation has been conducted for a realistic model Cu–Zr amorphous alloy to investigate characteristic features of elasticity and plasticity of the material. Significant reduction of the shear modulus by nonaffine atomic displacements and appreciable nonlinearity of elasticity have been observed. The fourth-order elastic constant in shear deformation and the ideal shear strength have been evaluated. Plastic deformation has been observed to start with isolated local shear transformations (LSTs) followed by collective LSTs leading to the formation of a shear band. Participation-ratio analysis (PRA) has demonstrated how the nonaffine displacement field converges as the system approaches the critical point of losing structural stability. PRA has also evaluated quantitatively the numbers of atoms participating in LSTs – the average number is about 30. Spatially anisotropic development of nascent shear band on a plane has been shown, attributable to anisotropic internal stress field induced by an LST. The evaluated stresses for the shear-band nucleation and for its propagation have indicated that the yielding in real materials is controlled by the shear-band propagation, as previously pointed out.

  3. Brazing ZrO2 ceramic to Ti–6Al–4V alloy using NiCrSiB amorphous filler foil: Interfacial microstructure and joint properties

    International Nuclear Information System (INIS)

    Reliable brazing of ZrO2 ceramic and Ti–6Al–4V alloy was achieved using NiCrSiB amorphous filler foil. The interfacial microstructure of ZrO2/Ti–6Al–4V joints was characterized by scanning electron microscope, energy dispersive spectrometer and micro-focused X-ray diffractometer. The effects of brazing temperature on the interfacial microstructure and joining properties of brazed joints were investigated in detail. Active Ti of Ti–6Al–4V alloy dissolved into molten filler metal and reacted with ZrO2 ceramic to form a continuous TiO reaction layer, which played an important role in brazing. Various reaction phases including Ti2Ni, Ti5Si3 and β-Ti were formed in brazed joints. With an increasing of brazing temperature, the TiO layer thickened gradually while the Ti2Ni amount reduced. Shear test indicated that brazed joints tend to fracture at the interface between ZrO2 ceramic and brazing seam or Ti2Ni intermetallic layer. The maximum average shear strength reached 284.6 MPa when brazed at 1025 °C for 10 min. - Graphical Abstract: Interfacial microstructure of ZrO2/TC4 joint brazed using NiCrSiB amorphous filler foil was: ZrO2/TiO/Ti2Ni + β-Ti + Ti5Si3/β-Ti/Widmanstätten structure/TC4. - Highlights: • Brazing of ZrO2 ceramic and Ti-6Al-4V alloy was achieved. • Interfacial microstructure was TiO/Ti2Ni + β + Ti5Si3/β/Widmanstätten structure. • The formation of TiO produced the darkening effect of ZrO2 ceramic. • The highest joining strength of 284.6MPa was obtained

  4. PHB, crystalline and amorphous magnesium alloys: Promising candidates for bioresorbable osteosynthesis implants?

    International Nuclear Information System (INIS)

    In this study various biodegradable materials were tested for their suitability for use in osteosynthesis implants, in particular as elastically stable intramedullary nails for fracture treatment in paediatric orthopaedics. The materials investigated comprise polyhydroxybutyrate (PHB), which belongs to the polyester family and is produced by microorganisms, with additions of ZrO2 and a bone graft substitute; two crystalline magnesium alloys with significantly different degradation rates ZX50 (MgZnCa, fast) and WZ21 (MgYZnCa, slow); and MgZnCa bulk metallic glasses (BMG). Push-out tests were conducted after various implantation times in rat femur meta-diaphysis to evaluate the shear forces between the implant material and the bone. The most promising materials are WZ21 and BMG, which exhibit high shear forces and push-out energies. The degradation rate of ZX50 is too fast and thus the alloy does not maintain its mechanical stability long enough during the fracture-healing period. PHB exhibits insufficient mechanical properties: it degrades very slowly and the respective low shear forces and push-out energy levels are unsatisfactory. - Highlights: ► In-vivo (rat model) investigation of biodegradable materials suitable for ESIN. ► Materials: polymer PHB, crystalline Mg ZX50 and Mg WZ21, MgZnCa bulk metallic glasses. ► Evaluated interface shear strength, push-out energies, stiffness, histology. ► Mg WZ21 suitable, other materials only after alterations.

  5. Homogeneous Plastic Flow of Fully Amorphous and Partially Crystallized Zr41.2Ti13.8Cu12.5Ni10Be22.5 Bulk Metallic Glass

    Institute of Scientific and Technical Information of China (English)

    Q.WANG; J.J. Blandin; M. Suery; B. Van de Moortéle; J.M. Pelletier

    2003-01-01

    The homogeneous plastic flow of fully amorphous and partially crystallized Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk metallic glass (Vit1) has been investigated by compression tests at high temperatures in supercooled liquid region. Experimental results show that at sufficiently low strain rates, the supercooled liquid of the fully amorphous alloy reveals Newtonian flow with a linear relationship between the flow stress and strain rate. As the strain rate is increased, a transition from linear Newtonian to nonlinear flow is detected, which can be explained by the transition state theory.Over the entire strain rate interval investigated, however, only nonlinear flow is present in the partially crystallized alloy, and the flow stress for each strain rate is much higher. It is found that the strain rate-stress relationship for the partially crystallized alloy at the given temperature of 646 K also obeys the sinh law derived from the transition state theory, similar to that of the initial homogeneous amorphous alloy. Thus, it is proposed that the flow behavior of the nanocrystalline/amorphous composite at 646 K is mainly controlled by the viscous flow of the remaining supercooled liquid.

  6. FY05 HPCRM Annual Report: High-Performance Corrosion-Resistant Iron-Based Amorphous Metal Coatings

    Energy Technology Data Exchange (ETDEWEB)

    Farmer, J; Choi, J; Haslam, J; Day, S; Yang, N; Headley, T; Lucadamo, G; Yio, J; Chames, J; Gardea, A; Clift, M; Blue, G; Peters, W; Rivard, J; Harper, D; Swank, D; Bayles, R; Lemieux, E; Brown, R; Wolejsza, T; Aprigliano, L; Branagan, D; Marshall, M; Meacham, B; Aprigliano, L; Branagan, D; Marshall, M; Meacham, B; Lavernia, E; Schoenung, J; Ajdelsztajn, L; Dannenberg, J; Graeve, O; Lewandowski, J; Perepezko, J; Hildal, K; Kaufman, L; Boudreau, J

    2007-09-20

    New corrosion-resistant, iron-based amorphous metals have been identified from published data or developed through combinatorial synthesis, and tested to determine their relative corrosion resistance. Many of these materials can be applied as coatings with advanced thermal spray technology. Two compositions have corrosion resistance superior to wrought nickel-based Alloy C-22 (UNS No. N06022) in some very aggressive environments, including concentrated calcium-chloride brines at elevated temperature. Two Fe-based amorphous metal formulations have been found that appear to have corrosion resistance comparable to, or better than that of Ni-based Alloy C-22, based on breakdown potential and corrosion rate. Both Cr and Mo provide corrosion resistance, B enables glass formation, and Y lowers critical cooling rate (CCR). SAM1651 has yttrium added, and has a nominal critical cooling rate of only 80 Kelvin per second, while SAM2X7 (similar to SAM2X5) has no yttrium, and a relatively high critical cooling rate of 610 Kelvin per second. Both amorphous metal formulations have strengths and weaknesses. SAM1651 (yttrium added) has a low critical cooling rate (CCR), which enables it to be rendered as a completely amorphous thermal spray coating. Unfortunately, it is relatively difficult to atomize, with powders being irregular in shape. This causes the powder to be difficult to pneumatically convey during thermal spray deposition. Gas atomized SAM1651 powder has required cryogenic milling to eliminate irregularities that make flow difficult. SAM2X5 (no yttrium) has a high critical cooling rate, which has caused problems associated with devitrification. SAM2X5 can be gas atomized to produce spherical powders of SAM2X5, which enable more facile thermal spray deposition. The reference material, nickel-based Alloy C-22, is an outstanding corrosion-resistant engineering material. Even so, crevice corrosion has been observed with C-22 in hot sodium chloride environments without buffer

  7. Graded coatings for metallic implant alloys

    Energy Technology Data Exchange (ETDEWEB)

    Saiz, Eduardo; Tomsia, Antoni P.; Fujino, Shigeru; Gomez-Vega, Jose M.

    2002-08-01

    Graded glass and glass-hydroxyapatite coatings on Ti-based and Co-Cr alloys have been prepared using a simple enameling technique. The composition of the glasses has been tailored to match the thermal expansion of the alloys. By controlling the firing time, and temperature, it has been possible to control the reactivity between the glass and the alloy and to fabricate coatings (25 to 150 mu m thick) with excellent adhesion to the substrate, resistant to corrosion and able to precipitate hydroxyapatite during in vitro tests in simulated body fluid.

  8. Properties of cemented carbides alloyed by metal melt treatment

    International Nuclear Information System (INIS)

    The paper presents the results of investigations into the influence of alloying elements introduced by metal melt treatment (MMT-process) on properties of WC-Co and WC-Ni cemented carbides. Transition metals of the IV - VIll groups (Ti, Zr, Ta, Cr, Re, Ni) and silicon were used as alloying elements. It is shown that the MMT-process allows cemented carbides to be produced whose physico-mechanical properties (bending strength, fracture toughness, total deformation, total work of deformation and fatigue fracture toughness) are superior to those of cemented carbides produced following a traditional powder metallurgy (PM) process. The main mechanism and peculiarities of the influence of alloying elements added by the MMT-process on properties of cemented carbides have been first established. The effect of alloying elements on structure and substructure of phases has been analyzed. (author)

  9. Method of separating radioactive metals from iron alloy

    International Nuclear Information System (INIS)

    Purpose: To reduce volume of enriched Co-Fe alloy to a large extent by effectively separating radioactive cobalt in the solid waste at the nuclear power plant. Method: Non-radioactive cobalt is added to iron alloy including radioactive cobalt. Under such a condition, more than 10 times amount of Sn, Pb and Sn-Pb alloy are used to dissolve the above metals in the molten metal bath. Then, Fe-Si phase is separated by adding silicon, and Fe-Co-Si phase is separated by adding silicon again. Thus, it is possible to carry the depletion process of less-contaminated iron alloy scrap in the nuclear power plant and further to reuse cobalt-removed Fe components as ferro-silicon. etc. (Takahashi, M.)

  10. Cleavage crystallography of liquid metal embrittled aluminum alloys

    Science.gov (United States)

    Reynolds, A. P.; Stoner, G. E.

    1991-01-01

    The crystallography of liquid metal-induced transgranular cleavage in six aluminum alloys having a variety of microstructures has been determined via Laue X-ray back reflection. The cleavage crystallography was independent of alloy microstructure, and the cleavage plane was 100-plane oriented in all cases. It was further determined that the cleavage crystallography was not influenced by alloy texture. Examination of the fracture surface indicated that there was not a unique direction of crack propagation. In addition, the existence of 100-plane cleavage on alloy 2024 fracture surfaces was inferred by comparison of secondary cleavage crack intersection geometry on the 2024 surfaces with the geometry of secondary cleavage crack intersections on the test alloys.

  11. 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. PMID:26726416

  12. Microstructure and mechanical behavior of metallic glass fiber-reinforced Al alloy matrix composites

    Science.gov (United States)

    Wang, Z.; Georgarakis, K.; Nakayama, K. S.; Li, Y.; Tsarkov, A. A.; Xie, G.; Dudina, D.; Louzguine-Luzgin, D. V.; Yavari, A. R.

    2016-04-01

    Metallic glass-reinforced metal matrix composites are an emerging class of composite materials. The metallic nature and the high mechanical strength of the reinforcing phase offers unique possibilities for improving the engineering performance of composites. Understanding the structure at the amorphous/crystalline interfaces and the deformation behavior of these composites is of vital importance for their further development and potential application. In the present work, Zr-based metallic glass fibers have been introduced in Al7075 alloy (Al-Zn-Mg-Cu) matrices using spark plasma sintering (SPS) producing composites with low porosity. The addition of metallic glass reinforcements in the Al-based matrix significantly improves the mechanical behavior of the composites in compression. High-resolution TEM observations at the interface reveal the formation of a thin interdiffusion layer able to provide good bonding between the reinforcing phase and the Al-based matrix. The deformation behavior of the composites was studied, indicating that local plastic deformation occurred in the matrix near the glassy reinforcements followed by the initiation and propagation of cracks mainly through the matrix. The reinforcing phase is seen to inhibit the plastic deformation and retard the crack propagation. The findings offer new insights into the mechanical behavior of metal matrix composites reinforced with metallic glasses.

  13. Microstructure and mechanical behavior of metallic glass fiber-reinforced Al alloy matrix composites

    Science.gov (United States)

    Wang, Z.; Georgarakis, K.; Nakayama, K. S.; Li, Y.; Tsarkov, A. A.; Xie, G.; Dudina, D.; Louzguine-Luzgin, D. V.; Yavari, A. R.

    2016-01-01

    Metallic glass-reinforced metal matrix composites are an emerging class of composite materials. The metallic nature and the high mechanical strength of the reinforcing phase offers unique possibilities for improving the engineering performance of composites. Understanding the structure at the amorphous/crystalline interfaces and the deformation behavior of these composites is of vital importance for their further development and potential application. In the present work, Zr-based metallic glass fibers have been introduced in Al7075 alloy (Al-Zn-Mg-Cu) matrices using spark plasma sintering (SPS) producing composites with low porosity. The addition of metallic glass reinforcements in the Al-based matrix significantly improves the mechanical behavior of the composites in compression. High-resolution TEM observations at the interface reveal the formation of a thin interdiffusion layer able to provide good bonding between the reinforcing phase and the Al-based matrix. The deformation behavior of the composites was studied, indicating that local plastic deformation occurred in the matrix near the glassy reinforcements followed by the initiation and propagation of cracks mainly through the matrix. The reinforcing phase is seen to inhibit the plastic deformation and retard the crack propagation. The findings offer new insights into the mechanical behavior of metal matrix composites reinforced with metallic glasses. PMID:27067824

  14. Enhanced Hydrogen Storage Kinetics of Nanocrystalline and Amorphous Mg2Ni-type Alloy by Melt Spinning

    Directory of Open Access Journals (Sweden)

    Hui-Ping Ren

    2011-01-01

    Full Text Available Mg2Ni-type Mg2Ni1−xCox (x = 0, 0.1, 0.2, 0.3, 0.4 alloys were fabricated by melt spinning technique. The structures of the as-spun alloys were characterized by X-ray diffraction (XRD and transmission electron microscopy (TEM. The hydrogen absorption and desorption kinetics of the alloys were measured by an automatically controlled Sieverts apparatus. The electrochemical hydrogen storage kinetics of the as-spun alloys was tested by an automatic galvanostatic system. The results show that the as-spun (x = 0.1 alloy exhibits a typical nanocrystalline structure, while the as-spun (x = 0.4 alloy displays a nanocrystalline and amorphous structure, confirming that the substitution of Co for Ni notably intensifies the glass forming ability of the Mg2Ni-type alloy. The melt spinning treatment notably improves the hydriding and dehydriding kinetics as well as the high rate discharge ability (HRD of the alloys. With an increase in the spinning rate from 0 (as-cast is defined as spinning rate of 0 m/s to 30 m/s, the hydrogen absorption saturation ratio ( of the (x = 0.4 alloy increases from 77.1 to 93.5%, the hydrogen desorption ratio ( from 54.5 to 70.2%, the hydrogen diffusion coefficient (D from 0.75 × 10−11 to 3.88 × 10−11 cm2/s and the limiting current density IL from 150.9 to 887.4 mA/g.

  15. Metal Injection Molding (MIM) of Magnesium and Its Alloys

    OpenAIRE

    Martin Wolff; Johannes G. Schaper; Marc René Suckert; Michael Dahms; Frank Feyerabend; Thomas Ebel; Regine Willumeit-Römer; Thomas Klassen

    2016-01-01

    Current research has highlighted that magnesium and its alloys as biodegradable material are highly suitable for biomedical applications. The new material fully degrades into nontoxic elements and offers material properties matching those of human bone tissue. As biomedical implants are rather small and complex in shape, the metal injection molding (MIM) technique seems to be well suited for the near net shape mass production of such parts. Furthermore, MIM of Mg-alloys is of high interest in...

  16. EMBEDDED MOLECULAR CLUSTER APPROACH TO THE ELECTRONIC STRUCTURE OF AMORPHOUS AND LIQUID METALS

    OpenAIRE

    Delley, B.; Ellis, D.; Freeman, A

    1980-01-01

    In this approach to the electronic structure of amorphous and liquid metals, we represent the system by molecular clusters which are embedded in an external potential chosen as a suitable representation of the rest of the system. We have determined the electronic structure of a number of Cu, Zr and Cu-Zr clusters using the self-consistent discrete variational-LCAO approach within local density functional theory. Effects due to deviations from perfect crystalline symmetry are analyzed. Total d...

  17. Electrical resistivity of liquid noble metal alloys

    International Nuclear Information System (INIS)

    Calculations of the dependence of the electrical resistivity in liquid Ag-Au, Cu-Ag, Cu-Au binary alloys on composition are reported. The structure of the binary alloy is described as a hard sphere system. A one-parameter local pseudopotential, which incorporates s-d hybridization effects phenomenologically, is employed in the resistivity calculation. A reasonable agreement with experimental trends is observed in cases where experimental information is available. (author)

  18. Preface: Proceedings of the 13th Conference on Liquid and Amorphous Metals (LAM13) (Ekaterinburg, Russia, 8 14 July 2007)

    Science.gov (United States)

    Popel, Pjotr; Gelchinskii, Boris; Sidorov, Valeriy

    2008-03-01

    The most recent developments in the field of liquid and amorphous metals and alloys are regularly updated through two complementary international conferences: the liquid and amorphous metals conference (LAM) and the rapidly quenched materials (RQ) conference. The first series of conferences started as LM1 in 1966 at Brookhaven for the basic understanding of liquid metals. The subsequent LM conferences were held in Tokyo (1972) and Bristol (1976). The conference was renewed in Grenoble (1980) as a LAM conference including amorphous metals and continued in Los Angeles (1983), Garmisch-Partenkirchen (1986), Kyoto (1989), Vienna (1992), Chicago (1995), Dortmund (1998), Yokohama (2001) and Metz (2004). The conferences are mainly devoted to liquid and amorphous metals and alloys. However, communications on some non-metallic systems such as semiconductors, quasicrystals etc, are also accepted. The conference tradition strongly encourages participation from junior researchers and graduate students. The 13th conference of the LAM series was organized in Ekaterinburg, Russia, by the Institute of Metallurgy of the Ural Branch of the Russian Academy of Sciences (IMet UB RAS) and the Ural State Pedagogical University (USPU), and held from 8-14 July 2007 under the chairmanship of Professors Pjotr Popel (USPU) and Boris Gelchinskii (IMet UB RAS). Two hundred and forty two active participants and about 60 guest participants from 20 countries attended the conference. There were no parallel sessions and all oral reports were separated into three groups: invited talks (40 min), full-scale oral reports (25 min), and brief oral reports (15 min). The program included ten sessions, ranging from purely theoretical subjects to the technological application of molten and amorphous alloys. The following sessions took place: A: Electronic structure and transport, magnetic properties; B: Phase transitions; C: Structure; D: Atomic dynamics and transport; E: Thermodynamics; F: Modelling

  19. Water oxidation catalysis: electrocatalytic response to metal stoichiometry in amorphous metal oxide films containing iron, cobalt, and nickel.

    Science.gov (United States)

    Smith, Rodney D L; Prévot, Mathieu S; Fagan, Randal D; Trudel, Simon; Berlinguette, Curtis P

    2013-08-01

    Photochemical metal-organic deposition (PMOD) was used to prepare amorphous metal oxide films containing specific concentrations of iron, cobalt, and nickel to study how metal composition affects heterogeneous electrocatalytic water oxidation. Characterization of the films by energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy confirmed excellent stoichiometric control of each of the 21 complex metal oxide films investigated. In studying the electrochemical oxidation of water catalyzed by the respective films, it was found that small concentrations of iron produced a significant improvement in Tafel slopes and that cobalt or nickel were critical in lowering the voltage at which catalysis commences. The best catalytic parameters of the series were obtained for the film of composition a-Fe20Ni80. An extrapolation of the electrochemical and XPS data indicates the optimal behavior of this binary film to be a manifestation of iron stabilizing nickel in a higher oxidation level. This work represents the first mechanistic study of amorphous phases of binary and ternary metal oxides for use as water oxidation catalysts, and provides the foundation for the broad exploration of other mixed-metal oxide combinations. PMID:23883103

  20. In vitro cytotoxicity of metallic ions released from dental alloys.

    Science.gov (United States)

    Milheiro, Ana; Nozaki, Kosuke; Kleverlaan, Cornelis J; Muris, Joris; Miura, Hiroyuki; Feilzer, Albert J

    2016-05-01

    The cytotoxicity of a dental alloy depends on, but is not limited to, the extent of its corrosion behavior. Individual ions may have effects on cell viability that are different from metals interacting within the alloy structure. We aimed to investigate the cytotoxicity of individual metal ions in concentrations similar to those reported to be released from Pd-based dental alloys on mouse fibroblast cells. Metal salts were used to prepare seven solutions (concentration range 100 ppm-1 ppb) of the transition metals, such as Ni(II), Pd(II), Cu(II), and Ag(I), and the metals, such as Ga(III), In(III), and Sn(II). Cytotoxicity on mouse fibroblasts L929 was evaluated using the MTT assay. Ni, Cu, and Ag are cytotoxic at 10 ppm, Pd and Ga at 100 ppm. Sn and In were not able to induce cytotoxicity at the tested concentrations. Transition metals were able to induce cytotoxic effects in concentrations similar to those reported to be released from Pd-based dental alloys. Ni, Cu, and Ag were the most cytotoxic followed by Pd and Ga; Sn and In were not cytotoxic. Cytotoxic reactions might be considered in the etiopathogenesis of clinically observed local adverse reactions. PMID:25549610

  1. Mechanical alloying and amorphization in Cu-Nb-Ag in situ composite wires studied by transmission electron microscopy and atom probe tomography

    International Nuclear Information System (INIS)

    We have studied deformation-driven alloying in a Cu-5 at.% Ag-3 at.% Nb in situ composite by transmission electron microscopy and atom probe tomography. In addition to alloying at interfaces, amorphization of nanosized Cu areas was observed after heavy wire drawing (true strain: η = 10.5) at some of the Cu-Nb interfaces. We discuss the alloying in terms of trans-phase dislocation-shuffling and shear banding mechanisms where lattice dislocations penetrate the interfaces between abutting phases. We interpret local amorphization in terms of the thermodynamic destabilization of a Cu-Nb crystalline phase between 35 and 80 at.% Cu due to enforced mixing. Deformation-driven mechanical alloying and amorphization are hence closely associated phenomena.

  2. Fundamentals of radiation materials science metals and alloys

    CERN Document Server

    Was, Gary S

    2017-01-01

    The revised second edition of this established text offers readers a significantly expanded introduction to the effects of radiation on metals and alloys. It describes the various processes that occur when energetic particles strike a solid, inducing changes to the physical and mechanical properties of the material. Specifically it covers particle interaction with the metals and alloys used in nuclear reactor cores and hence subject to intense radiation fields. It describes the basics of particle-atom interaction for a range of particle types, the amount and spatial extent of the resulting radiation damage, the physical effects of irradiation and the changes in mechanical behavior of irradiated metals and alloys. Updated throughout, some major enhancements for the new edition include improved treatment of low- and intermediate-energy elastic collisions and stopping power, expanded sections on molecular dynamics and kinetic Monte Carlo methodologies describing collision cascade evolution, new treatment of t...

  3. Bonding effects in dilute transition-metal alloys

    International Nuclear Information System (INIS)

    The Moessbauer isomer-shift data of transition-metal nuclei as impurities in metals were considered in previous papers where it was shown that, once volume effects were suitably accounted for, the data fell on a ''universal'' curve. In this paper, the deviations from universality are examined in more detail in an attempt to better understand the alloying behavior. It is found that atom A as an impurity in metal B does not sustain a shift of the same magnitude as atom B does when it is an impurity in metal A. The results are discussed in terms of d-band hybridization and of the asymmetry in the solubility behavior in transition-metal-alloy phase diagrams

  4. Bonding effects in dilute transition-metal alloys

    Energy Technology Data Exchange (ETDEWEB)

    Watson, R.E.; Swartzendruber, L.J.; Bennett, L.H.

    1981-12-01

    The Moessbauer isomer-shift data of transition-metal nuclei as impurities in metals were considered in previous papers where it was shown that, once volume effects were suitably accounted for, the data fell on a ''universal'' curve. In this paper, the deviations from universality are examined in more detail in an attempt to better understand the alloying behavior. It is found that atom A as an impurity in metal B does not sustain a shift of the same magnitude as atom B does when it is an impurity in metal A. The results are discussed in terms of d-band hybridization and of the asymmetry in the solubility behavior in transition-metal-alloy phase diagrams.

  5. Metallic ion release from biocompatible cobalt-based alloy

    Directory of Open Access Journals (Sweden)

    Dimić Ivana D.

    2014-01-01

    Full Text Available Metallic biomaterials, which are mainly used for the damaged hard tissue replacements, are materials with high strength, excellent toughness and good wear resistance. The disadvantages of metals as implant materials are their susceptibility to corrosion, the elastic modulus mismatch between metals and human hard tissues, relatively high density and metallic ion release which can cause serious health problems. The aim of this study was to examine metallic ion release from Co-Cr-Mo alloy in artificial saliva. In that purpose, alloy samples were immersed into artificial saliva with different pH values (4.0, 5.5 and 7.5. After a certain immersion period (1, 3 and 6 weeks the concentrations of released ions were determined using Inductively Coupled Plasma - Mass Spectrophotometer (ICP-MS. The research findings were used in order to define the dependence between the concentration of released metallic ions, artificial saliva pH values and immersion time. The determined released metallic ions concentrations were compared with literature data in order to describe and better understand the phenomenon of metallic ion release from the biocompatible cobalt-based alloy. [Projekat Ministarstva nauke Republike Srbije, br. III 46010 i br. ON 174004

  6. Influence of annealing on microstructure and magnetic properties of cobalt-based amorphous/nanocrystalline powders synthesized by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Taghvaei, Amir Hossein, E-mail: Amirtaghvaei@gmail.com [Department of Materials Science and Engineering, Shiraz University of Technology, Shiraz (Iran, Islamic Republic of); Bednarčik, Jozef [Photon Science DESY, Notkestraße 85, 22603 Hamburg (Germany); Eckert, Jürgen [IFW Dresden, Institute for Complex Materials, Helmholtzstr. 20, 01069 Dresden (Germany); TU Dresden, Institute of Materials Science, 01062 Dresden (Germany)

    2015-05-25

    Highlights: • Structural relaxation in mechanically alloyed Co{sub 40}Fe{sub 22}Ta{sub 8}B{sub 30} powders was studied. • Isochronal annealing notably changes the short-range order of the amorphous phase. • The medium-range correlations experienced volume shrinkage upon annealing. • Annealing decreased the coercivity and saturation magnetization of the powders. - Abstract: The effects of isochronal annealing on microstructure and magnetic properties of Co{sub 40}Fe{sub 22}Ta{sub 8}B{sub 30} powders with a large content of amorphous phase produced by mechanical alloying have been investigated. The differential scanning calorimetry (DSC) results indicate that the synthesized powders exhibit a huge exothermic reaction before the crystallization temperature corresponding to structural relaxation of amorphous phase. Furthermore, the structural evolution of the powders upon isochronal heating has been investigated by in-situ X-ray diffraction (XRD) using high energy synchrotron radiation. The occurrence of an irreversible structural relaxation is confirmed by significant changes in position of the first and second diffuse maxima of the total structure factor S(Q) upon isochronal heating–cooling cycles. Moreover, analysis of the reduced pair distribution functions (PDFs) yields a volume shrinkage of about 1.5% after annealing due to annihilation of the excess free volume generated upon milling. The isochronal annealing significantly affects the magnetic properties of the powders through decreasing the saturation magnetization and coercivity. The correlation between structural relaxation and magnetic properties of the powders is discussed.

  7. Magnetic properties and loss separation in Fe76−xAgxNb2Si13B9 amorphous alloys

    International Nuclear Information System (INIS)

    Highlights: • Soft magnetic properties can be optimized by applying a suitable heat treatment. • Low field magnetic permeability of the optimized samples increases about 10 times. • Total magnetic loss of the optimized samples decreases at least 10 times. • Plasticity is much higher than that reported for similar nanocrystalline alloys. • Observed effects are attributed to formation of the relaxed amorphous phase. - Abstract: Some selected properties (magnetic, plastic, elastic) in amorphous Fe76−xAgxNb2Si13B9 (x = 0.5, 0.75, 1.0) alloys, obtained by melt spinning technique, are presented and discussed in detail. It was shown that a suitable heat treatment of the as quenched samples (i.e. the optimization annealing) leads to a significant improvement of soft magnetic properties (permeability increases at least 10 times). The observed effect is attributed to formation of the so-called relaxed amorphous phase free of iron nanograins. Special attention is paid for loss separation into different components: hysteresis loss, eddy-current loss and residual loss. The latter effect can be attributed to diffusion of free volume and practically disappear after the optimization annealing

  8. Structural evolution and the kinetics of Cu clustering in the amorphous phase of Fe-Cu-Nb-Si-B alloy

    Science.gov (United States)

    Gupta, P.; Gupta, A.; Shukla, A.; Ganguli, Tapas; Sinha, A. K.; Principi, G.; Maddalena, A.

    2011-08-01

    An attempt has been made to investigate the evolution of the structure of the amorphous phase of Fe73.9 Cu0.9 Nb3.1 Si13.2 B8.9 (finemet) alloy by a combination of wide-angle x-ray scattering, small angle x-ray scattering (SAXS), Mössbauer spectroscopy and X-ray absorption near edge spectroscopy on the supposition that they would provide complementary information. Before the onset of nanocrystallization, the amorphous phase undergoes a structural relaxation resulting in small increase in the hyperfine field and a decrease in the width of the first diffraction maxima. There is an increase in the topological ordering in the system, though chemical inhomogeneity sets-in due to the clustering of Cu atoms in the pure amorphous state of this alloy. Annealing at 400 °C (well below the crystallization temperature) for different time durations results in occurrence of Cu clusters having fcc structure. Kinetics of Cu clustering is studied using SAXS. The incubation time for the clustering at 400 °C is ˜120 min. With further annealing, the average cluster size gradually increases from the initial value of ˜0.4 nm, reaching a value of ˜0.6 nm after annealing for 720 min. Cluster size exhibits a t1/2 dependence, suggesting a diffusion controlled growth.

  9. Carbonate-coordinated metal complexes precede the formation of liquid amorphous mineral emulsions of divalent metal carbonates†

    Science.gov (United States)

    Wolf, Stephan E.; Müller, Lars; Barrea, Raul; Kampf, Christopher J.; Leiterer, Jork; Panne, Ulrich; Hoffmann, Thorsten

    2011-01-01

    During the mineralisation of metal carbonates MCO3 (M = Ca, Sr, Ba, Mn, Cd, Pb) liquid-like amorphous intermediates emerge. These intermediates that form via a liquid/liquid phase separation behave like a classical emulsion and are stabilized electrostatically. The occurrence of these intermediates is attributed to the formation of highly hydrated networks whose stability is mainly based on weak interactions and the variability of the metal-containing pre-critical clusters. Their existence and compositional freedom are evidenced by electrospray ionization mass spectrometry (ESI-MS). Liquid intermediates in non-classical crystallisation pathways seem to be more common than assumed. PMID:21218241

  10. Development of radiation detectors based on hydrogenated amorphous silicon and its alloys

    International Nuclear Information System (INIS)

    Hydrogenated amorphous silicon and related materials have been applied to radiation detectors, utilizing their good radiation resistance and the feasibility of making deposits over a large area at low cost. Effects of deposition parameters on various material properties of a-Si:H have been studied to produce a material satisfying the requirements for specific detection application. Thick(-∼50 μm), device quality a-Si:H p-i-n diodes for direct detection of minimum ionizing particles have been prepared with low internal stress by a combination of low temperature growth, He-dilution of silane, and post annealing. The structure of the new film contained voids and tiny crystalline inclusions and was different from the one observed in conventional a-Si:H. Deposition on patterned substrates was attempted as an alternative to controlling deposition parameters to minimize substrate bending and delamination of thick a-Si:H films. Growth on an inversed-pyramid pattern reduced the substrate bending by a factor of 3∼4 for the same thickness film. Thin (0.1 ∼ 0.2 μm) films of a-Si:H and a-SiC:H have been applied to microstrip gas chambers to control gain instabilities due to charges on the substrate. Light sensitivity of the a-Si:H sheet resistance was minimized and the surface resistivity was successfully' controlled in the range of 1012 ∼ 1017 Ω/□ by carbon alloying and boron doping. Performance of the detectors with boron-doped a-Si:C:H layers was comparable to that of electronic-conducting glass. Hydrogen dilution of silane has been explored to improve electrical transport properties of a-Si:H material for high speed photo-detectors and TFT applications

  11. PHB, crystalline and amorphous magnesium alloys: Promising candidates for bioresorbable osteosynthesis implants?

    Energy Technology Data Exchange (ETDEWEB)

    Celarek, Anna [Institute for Building Construction and Technology E-206-4, Vienna University of Technology, Karlsplatz 13, 1040 Vienna (Austria); Kraus, Tanja [Department of Paediatric Orthopaedics, Medical University of Graz, Auenbruggerplatz 34, 8036 Graz (Austria); Tschegg, Elmar K., E-mail: elmar.tschegg@tuwien.ac.at [Institute for Building Construction and Technology E-206-4, Vienna University of Technology, Karlsplatz 13, 1040 Vienna (Austria); Fischerauer, Stefan F. [Department of Paediatric and Adolescent Surgery, Medical University of Graz, Auenbruggerplatz 34, 8036 Graz (Austria); Stanzl-Tschegg, Stefanie [Department of Material Sciences and Process Engineering, Institute of Physics and Materials Science, University of Natural Resources and Life Sciences, Peter Jordan Str. 82, 1190 Vienna (Austria); Uggowitzer, Peter J. [Department of Materials, Laboratory for Metal Physics and Technology, ETH Zurich, 8093 Zurich (Switzerland); Weinberg, Annelie M. [Department of Paediatric and Adolescent Surgery, Medical University of Graz, Auenbruggerplatz 34, 8036 Graz (Austria)

    2012-08-01

    In this study various biodegradable materials were tested for their suitability for use in osteosynthesis implants, in particular as elastically stable intramedullary nails for fracture treatment in paediatric orthopaedics. The materials investigated comprise polyhydroxybutyrate (PHB), which belongs to the polyester family and is produced by microorganisms, with additions of ZrO{sub 2} and a bone graft substitute; two crystalline magnesium alloys with significantly different degradation rates ZX50 (MgZnCa, fast) and WZ21 (MgYZnCa, slow); and MgZnCa bulk metallic glasses (BMG). Push-out tests were conducted after various implantation times in rat femur meta-diaphysis to evaluate the shear forces between the implant material and the bone. The most promising materials are WZ21 and BMG, which exhibit high shear forces and push-out energies. The degradation rate of ZX50 is too fast and thus the alloy does not maintain its mechanical stability long enough during the fracture-healing period. PHB exhibits insufficient mechanical properties: it degrades very slowly and the respective low shear forces and push-out energy levels are unsatisfactory. - Highlights: Black-Right-Pointing-Pointer In-vivo (rat model) investigation of biodegradable materials suitable for ESIN. Black-Right-Pointing-Pointer Materials: polymer PHB, crystalline Mg ZX50 and Mg WZ21, MgZnCa bulk metallic glasses. Black-Right-Pointing-Pointer Evaluated interface shear strength, push-out energies, stiffness, histology. Black-Right-Pointing-Pointer Mg WZ21 suitable, other materials only after alterations.

  12. Effect of amorphous Mg50Ni50 on hydriding and dehydriding behavior of Mg2Ni alloy

    International Nuclear Information System (INIS)

    Composite Mg2Ni (25 wt.%) amorphous Mg50Ni50 was prepared by mechanical milling starting with nanocrystalline Mg2Ni and amorphous Mg50Ni50 powders, by using a SPEX 8000 D mill. The morphological and microstructural characterization of the powders was performed via scanning electron microscopy and X-ray diffraction. The hydriding characterization of the composite was performed via a solid gas reaction method in a Sievert's-type apparatus at 363 K under an initial hydrogen pressure of 2 MPa. The dehydriding behavior was studied by differential thermogravimetry. On the basis of the results, it is possible to conclude that amorphous Mg50Ni50 improved the hydriding and dehydriding kinetics of Mg2Ni alloy upon cycling. A tentative rationalization of experimental observations is proposed. - Research Highlights: → First study of the hydriding behavior of composite Mg2Ni (25 wt.%) amorphous Mg50Ni50. → Microstructural characterization of composite material using XRD and SEM was obtained. → An improved effect of Mg50Ni50 on the Mg2Ni hydriding behavior was verified. → The apparent activation energy for the hydrogen desorption of composite was obtained.

  13. Electromagnetic Characterization Of Metallic Sensory Alloy

    Science.gov (United States)

    Wincheski, Russell A.; Simpson, John; Wallace, Terryl A.; Newman, John A.; Leser, Paul; Lahue, Rob

    2012-01-01

    Ferromagnetic shape-memory alloy (FSMA) particles undergo changes in both electromagnetic properties and crystallographic structure when strained. When embedded in a structural material, these attributes can provide sensory output of the strain state of the structure. In this work, a detailed characterization of the electromagnetic properties of a FSMA under development for sensory applications is performed. In addition, a new eddy current probe is used to interrogate the electromagnetic properties of individual FSMA particles embedded in the sensory alloy during controlled fatigue tests on the multifunctional material.

  14. Thermal stability and glass-forming ability of amorphous Nd-Al-TM (TM=Fe, Co, Ni or Cu) alloys

    International Nuclear Information System (INIS)

    Bulk amorphous alloys were prepared for Nd70Al10TM20 and Nd60Al10TM30 (TM=Fe or Co) alloys by copper mold casting. The maximum sample thickness for glass formation reaches 15 mm for the Nd-Al-Fe alloys and 5 mm for the Nd-Al-Co alloys. A significant difference in the phase transition upon heating is recognized between the Fe- and Co-containing alloys. No glass transition before crystallization is observed for the Nd-Al-Fe alloys, but the Nd-Al-Co alloys exhibit the glass transition. The ΔTx(=Tx-Tg) and Tg/Tm are 40-55 K and 0.65-0.67, respectively, for the latter alloys. The absence of supercooled liquid for the former alloys is different from those for all bulk amorphous alloys reported up to date. The Tx/Tm and ΔTm(=Tm-Tx) are 0.85-0.89 and 88-137 K, respectively, for the Nd-Al-Fe alloys and, hence, the large glass-forming ability is presumably due to the high Tx/Tm and small ΔTm values. (orig.)

  15. Formation of amorphous Fe 50Si 50 alloy by diffusion reaction

    Science.gov (United States)

    Yan, Zhihua; Wang, Wenkui; Li, Jingfeng; Wang, Yuming

    1989-02-01

    The solid state reaction in the multilayer film with alternative polycrystalline Fe and amorphous Si layers has been studied with X-ray diffraction. Amorphous Fe 50Si 50 phase was formed after annealing isothermally at 300°C, which is explained in view of the consideration that an amorphous phase can be more favorable to form than a supersaturated solution in thermodynamics as well as than an equilibrium compound FeSi in kenetics.

  16. Influence of Microstructure on Microhardness of Fe81Si4B13C2 Amorphous Alloy after Thermal Treatment

    Czech Academy of Sciences Publication Activity Database

    Minić, Dragica, M.; Blagojević, V.; Minić, Dušan M.; Gavrilović, A.; Rafailović, L.; Žák, Tomáš

    42A, č. 13 (2011), s. 4106-4112. ISSN 1073-5623 R&D Projects: GA MŠk(CZ) 1M0512 Institutional research plan: CEZ:AV0Z2041904 Keywords : bulk metallic -glass * mechanical properties * Fe81B13SI4C2 alloy * B alloys * alpha-Fe * crystallization * phase * nanocrystallization * behavior Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.545, year: 2011

  17. Origin of high thermal stability of amorphous Ge1Cu2Te3 alloy: A significant Cu-bonding reconfiguration modulated by Te lone-pair electrons for crystallization

    International Nuclear Information System (INIS)

    Ge1Cu2Te3 is an important candidate for high-temperature phase change memory due to the fine amorphous stability. Yet, the basic bonding chemistry for its high-temperature application is still not completely clear. In this work, a new bonding mechanism for its amorphous and crystalline phases is proposed and demonstrated by first-principles calculations. Compared to the tetrahedral environment distributed evenly in crystalline form, Cu atoms in the amorphous state tend to be accumulated as trigonal clusters. For the crystalline phase, a bonding configuration of nonequivalent sp3 hybridization with Te lone-pair electrons is proposed without Cu d electron participation. In the amorphous phase, however, a significant bonding reconfiguration of Cu d electrons occurs due to the isolation of the Te lone-pair electrons. Therefore, the notable contrast in the Cu atomic and electronic structures between the crystalline and amorphous phases results in an obvious phase transition barrier for high-temperature storage. The mechanism presented in this study serves as a reference for other transition-metal alloyed phase-change materials

  18. Processing of Refractory Metal Alloys for JOYO Irradiations

    Energy Technology Data Exchange (ETDEWEB)

    RF Luther; ME Petrichek

    2006-02-21

    This is a summary of the refractory metal processing experienced by candidate Prometheus materiats as they were fabricated into specimens destined for testing within the JOYO test reactor, ex-reactor testing at Oak Ridge National Laboratory (ORNL), or testing within the NRPCT. The processing is described for each alloy from the point of inception to the point where processing was terminated due to the cancellation of Naval Reactor's involvement in the Prometheus Project. The alloys included three tantalum-base alloys (T-111, Ta-10W, and ASTAR-811C), a niobium-base alloy, (FS-85), and two molybdenum-rhenium alloys, one containing 44.5 w/o rhenium, and the other 47.5 w/o rhenium. Each of these alloys was either a primary candidate or back-up candidate for cladding and structural applications within the space reactor. Their production was intended to serve as a forerunner for large scale production ingots that were to be procured from commercial refractory metal vendors such as Wah Chang.

  19. Processing of Refractory Metal Alloys for JOYO Irradiations

    International Nuclear Information System (INIS)

    This is a summary of the refractory metal processing experienced by candidate Prometheus materiats as they were fabricated into specimens destined for testing within the JOYO test reactor, ex-reactor testing at Oak Ridge National Laboratory (ORNL), or testing within the NRPCT. The processing is described for each alloy from the point of inception to the point where processing was terminated due to the cancellation of Naval Reactor's involvement in the Prometheus Project. The alloys included three tantalum-base alloys (T-111, Ta-10W, and ASTAR-811C), a niobium-base alloy, (FS-85), and two molybdenum-rhenium alloys, one containing 44.5 w/o rhenium, and the other 47.5 w/o rhenium. Each of these alloys was either a primary candidate or back-up candidate for cladding and structural applications within the space reactor. Their production was intended to serve as a forerunner for large scale production ingots that were to be procured from commercial refractory metal vendors such as Wah Chang

  20. Thermal stability of Zr55Al10Ni5Cu30 bulk amorphous alloy during continuous heating and isothermal annealing

    Institute of Scientific and Technical Information of China (English)

    高玉来; 沈军; 孙剑飞; 王刚; 邢大伟; 周彼德

    2003-01-01

    The crystallization behavior of Zr55Al10Ni5Cu30 (mole fraction, %) bulk amorphous alloy during continuous heating and isothermal annealing was investigated. The results show that there exists a first order exponential decay relation between the characteristic temperatures and the heating rates during continuous heating process. The activation energy for glass transition Eg and that for crystallization Ep and Ex during continuous heating were evaluated by Kissinger plots. In addition, there is a second order exponential decay relation between the annealing temperature and the corresponding crystallization time during isothermal annealing. The isothermal activation energy obtained by Arrhenius equation increases as crystallization proceeds, indicating the sufficient stability of the residual amorphous structure after initial crystallization.

  1. 49 CFR 173.187 - Pyrophoric solids, metals or alloys, n.o.s.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Pyrophoric solids, metals or alloys, n.o.s. 173... Class 1 and Class 7 § 173.187 Pyrophoric solids, metals or alloys, n.o.s. Packagings for pyrophoric solids, metals, or alloys, n.o.s. must conform to the requirements of part 178 of this subchapter at...

  2. Chemical bond approach to metals and alloys

    International Nuclear Information System (INIS)

    The BCS theory of superconductivity was extended to the transition elements and their alloys by a chemical bond approach based on the electronic configurations of the Engel-- Brewer theory of alloys. The net attractive potential between electrons in Cooper pairs, V/sub BCS/, for the late transition series elements and alloys is shown to arise mainly from a generalized electron--electron interaction related to bonding of electrons on the d level alone, the phonon-induced attraction being nearly zero. A mechanism is proposed in which a scattering of superconducting d electrons into nonsuperconducting s and p states is responsible for a predictable reduction in V/sub BCS/. The electron-per-atom ratio and a new chemical parameter, the average atomic radius for coordination twelve, were applied successfully to the prediction of the maximum energy product of multiphase commercial permanent magnets. The correlations developed for the maximum energy product with these two parameters can be applied to optimize the compositions of existing permanent magnets or suggest hypothetical alloy mixtures of possibly better magnetic properties. Heats of reaction of the

  3. Complex metallic alloys as new materials for additive manufacturing

    International Nuclear Information System (INIS)

    Additive manufacturing processes allow freeform fabrication of the physical representation of a three-dimensional computer-aided design (CAD) data model. This area has been expanding rapidly over the last 20 years. It includes several techniques such as selective laser sintering and stereolithography. The range of materials used today is quite restricted while there is a real demand for manufacturing lighter functional parts or parts with improved functional properties. In this article, we summarize recent work performed in this field, introducing new composite materials containing complex metallic alloys. These are mainly Al-based quasicrystalline alloys whose properties differ from those of conventional alloys. The use of these materials allows us to produce light-weight parts consisting of either metal–matrix composites or of polymer–matrix composites with improved properties. Functional parts using these alloys are now commercialized. (review)

  4. An overview of uncooled infrared sensors technology based on amorphous silicon and silicon germanium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ambrosio, Roberto; Mireles, Jose Jr. [Technology and Engineering Institute, Ciudad Juarez University UACJ, Av. Del Charro 450N, 32310 Chihuahua (Mexico); Moreno, Mario; Torres, Alfonso; Kosarev, Andrey [National Institute for Astrophysics Optics and Electronics INAOE, Luis E. Erro 1, PO Box 51 and 216, 7200 Puebla (Mexico); Heredia, Aurelio [Universidad Popular Autonoma del Estado de Puebla, 21 sur 1103 Col. Santiago, 72160 Puebla (Mexico)

    2010-04-15

    At the present time there are commercially available large un-cooled micro-bolometer arrays (as large as 1024 x 768 pixels) for a variety of thermal imaging applications. Different thermo-sensing materials have been employed as thermo sensing elements as Vanadium Oxide (VO{sub x}), metals, and amorphous and polycrystalline semiconductors. Those materials present good characteristics but also have some disadvantages. As a consequence none of the commercially available arrays contain optimum pixels with an optimum thermo-sensing material. This paper reviews the development of the un-cooled bolometer technology and the research achievements on this area, with special attention on the key factors that would lead to improve the pixels performance characteristics. The work considers the R and D of microbolometer arrays and the integration with MEMS and IC technologies. A comparative study with the state of the art and data reported in literature is presented. Finally, further directions of uncooled bolometer based in thin films materials are also discussed in this paper. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Atmospheric corrosion of metals in tropics and subtropic. 2. Corrosion resistance of different metals and alloys

    International Nuclear Information System (INIS)

    Data from 169 sources concerning corrosion of different metals, alloys and means of protection, obtained for a 30-year period (up to 1987) in different continent including Europe (Bulgaria, Spain, Italy, France, USSR); America (USA, Panama, Cuba, Venezuela, Brasil, Argentine); Africa (Nigeria, SAR); Australia, New Zeland, Papua-Newguinea, Philippines, are systemized. Actual results of full-scal atmospheric testings of iron, zinc, copper, cadmium, aluminium, tin, lead, carbon, low-alloys. Stainless steels, cast irons, halvanic coatings, copper, aluminium, nickel, titanium, magnesium alloys are presented. Data on the fracture rate can be used for creating the data base in banks on atmospheric resistance of metal materials

  6. Pressure tunes electrical resistivity by four orders of magnitude in amorphous Ge2Sb2Te5 phase-change memory alloy

    International Nuclear Information System (INIS)

    Ge-Sb-Te-based phase-change memory is one of the most promising candidates to succeed the current flash memories. The application of phase-change materials for data storage and memory devices takes advantage of the fast phase transition (on the order of nanoseconds) and the large property contrasts (e.g., several orders of magnitude difference in electrical resistivity) between the amorphous and the crystalline states. Despite the importance of Ge-Sb-Te alloys and the intense research they have received, the possible phases in the temperature-pressure diagram, as well as the corresponding structure-property correlations, remain to be systematically explored. In this study, by subjecting the amorphous Ge2Sb2Te5 (a-GST) to hydrostatic-like pressure (P), the thermodynamic variable alternative to temperature, we are able to tune its electrical resistivity by several orders of magnitude, similar to the resistivity contrast corresponding to the usually investigated amorphous-to-crystalline (a-GST to rock-salt GST) transition used in current phase-change memories. In particular, the electrical resistivity drops precipitously in the P = 0 to 8 GPa regime. A prominent structural signature representing the underlying evolution in atomic arrangements and bonding in this pressure regime, as revealed by the ab initio molecular dynamics simulations, is the reduction of low-electron-density regions, which contributes to the narrowing of band gap and delocalization of trapped electrons. At P > 8 GPa, we have observed major changes of the average local structures (bond angle and coordination numbers), gradually transforming the a-GST into a high-density, metallic-like state. This high-pressure glass is characterized by local motifs that bear similarities to the body-centered-cubic GST (bcc-GST) it eventually crystallizes into at 28 GPa, and hence represents a bcc-type polyamorph of a-GST.

  7. Internal friction and rigidity modulus change associated with structural relaxation and crystallization in amorphous Zr67Fe33 alloy

    International Nuclear Information System (INIS)

    The internal friction and the rigidity modulus of an amorphous Zr67Fe33 alloy have been measured in an inverted torsion pendulum apparatus with a frequency range of 0.3-2 Hz. The rigidity modulus increases irreversibly with the annealing which suggests a two-step structural relaxation. It is clarified that the internal friction due to the structural relaxation and the crystallization depends on the heating rate and the vibrational frequency. It is suggested that the internal friction has a ''transient component'' which is proportional to the amount of structural change during one period of the vibration. (orig.)

  8. Effect of small additions of Cu and Cr on crystallization of Fe80B9Si11 amorphous alloy

    International Nuclear Information System (INIS)

    By means of differential thermal and X-ray structure analyses, as well as, by measurement of microstrength one studied the effect of small additions of chromium and copper on the peculiarities of crystallization of Fe80B9Si11 amorphous alloy (Fe79Cr1B9Si11 and Fe79Cu1B9Si11). Chromium was determined to stabilize Fe3B nonequilibrium phase the formation of which resulted in eutectic type of crystallization at early stages while copper was determined to enable formation of α-Fe and Fe2B equilibrium phases and primary crystallization with precipitation of α-Fe primary crystals

  9. Uniaxial tension effect on geometrical parameters of surface relief of amorphous alloy Fe77Ni1Si9B13

    International Nuclear Information System (INIS)

    The uniaxial tension effect on the topography of the Fe77Ni1Si9B13 amorphous alloy surface is studied within the wide range of loads (0-3 GPA) by the method of scanning tunnel microscopy. The change in the defects distributions by vertical and lateral dimensions, in particular, the increase in the number of the large-scale defects and also increase in the surface fractal dimensionality, by the load growth is determined. The supposition on the diffusion mechanism of the relief formation and also on the role of the observed effects in originating the seats of destruction on the surface is expressed

  10. Enhancement of the Thermal Stability and Mechanical Hardness of Zr-Al-Co Amorphous Alloys by Ag Addition

    Science.gov (United States)

    Wang, Yongyong; Dong, Xiao; Song, Xiaohui; Wang, Jinfeng; Li, Gong; Liu, Riping

    2016-05-01

    The thermal and mechanical properties of Zr57Al15Co28- X Ag X ( X = 0 and 8) amorphous alloys were investigated using differential scanning calorimetry, in situ high-pressure angle dispersive X-ray diffraction measurements with synchrotron radiation, and nanoindentation. Results show that Ag doping improves effective activation energy, nanohardness, elastic modulus, and bulk modulus. Ag addition enhances topological and chemical short-range orderings, which can improve local packing efficiency and restrain long-range atom diffusion. This approach has implications for the design of the microstructure- and property-controllable functional materials for various applications.

  11. Temperature dependence of the iron hyperfine field distribution in amorphous Fe-rich Fe-Zr alloys

    International Nuclear Information System (INIS)

    The temperature dependence of the iron hyperfine field distribution is reported in melt-quenched amorphous Fe-Zr alloys. The most remarkable feature is the compositinal change in the shape of the average hyperfine field versus temperature curves. The unusual increase in the average hyperfine field below about 85 K is a characteristic feature of the RSG systems; however, no anomaly is observed in the width of the hyperfine field distribution as a function of temperature. The results cannot be properly explained in the framework of the existing spin glass models. (orig.)

  12. Functional oxide structures on a surface of metals and alloys

    Institute of Scientific and Technical Information of China (English)

    Rudnev; V.; S.; Yarovaya; T.; P.; Boguta; D.; L.; Lukiyanchuk; I.; V.; Tyrina; L.; M.; Morozova; V.; P.; Nedozorov; P.; M.; Vasilyeva; M.; S.; Kondrikov; N.; B.

    2005-01-01

    The investigations of the plasma electrolytic processes in our laboratory are aimed to the development of conditions of formation of oxide layers with determined composition, structure and functional properties on the surface of valve metals (Al, Ti) and their alloys.……

  13. Chapter 6. High temperature deformation of metals and alloys

    International Nuclear Information System (INIS)

    The mechanisms which characterize the high temperature deformation of metals and alloys are described: non-conservative motions of dislocations by emission and absorption of vacancies, decrease of grain boundary strength and intergranular sliding, dynamic recrystallization. These mechanisms explain the rearrangement of the removal of defects created during the deformation and enable an understanding of the high temperature plastic deformation

  14. Surface segregation energies in transition-metal alloys

    DEFF Research Database (Denmark)

    Ruban, Andrei; Skriver, Hans Lomholt; Nørskov, Jens Kehlet

    1999-01-01

    to the electrostatic potential and energy. We use the database to establish the major factors which govern surface segregation in transition metal alloys. We find that the calculated trends are well described by Friedel's rectangular state density model and that the few but significant deviations...

  15. Structure of the glass-forming metallic liquids by ab-initio and classical molecular dynamics, a case study: Quenching the Cu60Ti20Zr20 alloy

    International Nuclear Information System (INIS)

    We consider the question of the amorphization of metallic alloys by melt quenching, as predicted by molecular dynamics simulations with semi-empirical potentials. The parametrization of the potentials is discussed on the example of the ternary Cu-Ti-Zr transition metals alloy, using the ab-initio simulation as a reference. The pair structure in the amorphous state is computed from a potential of the Stillinger-Weber form. The transferability of the parameters during the quench is investigated using two parametrizations: from solid state data, as usual and from a new parametrization on the liquid structure. When the adjustment is made on the pair structure of the liquid, a satisfactory transferability is found between the pure components and their alloys. The liquid structure predicted in this way agrees well with experiment, in contrast with the one obtained using the adjustment on the solid. The final structure, after quenches down to the amorphous state, determined with the new set of parameters is shown to be very close to the ab-initio one, the latter being in excellent agreement with recent X-rays diffraction experiments. The corresponding critical temperature of the glass transition is estimated from the behavior of the heat capacity. Discussion on the consistency between the structures predicted using semi-empirical potentials and ab-initio simulation, and comparison of different experimental data underlines the question of the dependence of the final structure on the thermodynamic path followed to reach the amorphous state

  16. Magnetic properties of iron-based amorphous and nanocrystalline Fe-Zr-X-B (X: Cu, Al) alloy films

    International Nuclear Information System (INIS)

    Thermal stability and magnetic properties of thin films, of a few Fe-based amorphous and nanocrystalline alloys, have been studied. The alloys belong to the class Fe-M-B, whose representatives are Fe87Zr4CuB8, Fe87Zr7B6, and Fe87Zr7AlB5 and are of particular interest because of their wide variety of magnetic properties. The films were prepared by flash evaporation onto liquid nitrogen cooled substrates. Measurements of the Kerr effect, the Hall effect, and ferromagnetic resonance in the films were carried out as functions of the annealing temperature. It was found that the changes in the coercive field Hc, resonance linewidth ΔHpp, effective magnetization Meff, Hall parameters, and resistance were correlated with the structural changes in the studied films. (author)

  17. A Combinatorial Approach to the Investigation of Metal Systems that Form Both Bulk Metallic Glasses and High Entropy Alloys

    Science.gov (United States)

    Welk, Brian A.; Gibson, Mark A.; Fraser, Hamish L.

    2016-03-01

    In this work, compositionally graded specimens were deposited using the laser engineered net-shaping (LENS™) additive manufacturing technique to study the glass-forming ability of two bulk metallic glass (BMG) and high entropy alloy (HEA) composite systems. The first graded specimen varied from Zr57Ti5Al10Cu20Ni8 (BMG) to CoCrFeNiCu0.5 (HEA) and the second graded specimen varied from TiZrCuNb (BMG) to (TiZrCuNb)65Ni35 (HEA). After deposition, laser surface melting experiments were performed parallel to the gradient to remelt and rapidly solidify the specimen. Scanning electron microscopy and energy dispersive x-ray spectroscopy were used to determine the morphology and composition variations in the as-deposited and laser surface melted phases. Selected area diffraction of the melt pool regions confirmed an almost fully amorphous region in the first gradient and an amorphous matrix/crystalline dendrite composite structure in the second gradient.

  18. Metal redox processes for the controlled synthesis of metal alloy nanoparticles.

    Science.gov (United States)

    Kirkeminde, Alec; Spurlin, Stan; Draxler-Sixta, Laura; Cooper, Jamie; Ren, Shenqiang

    2015-03-27

    Nanocrystalline metals have received widespread interest and found various applications owing to their magnetic and catalytic properties and in energy-related fields. A flexible approach for the growth of nanoalloys with controlled properties and well-defined structures on the atomic scale is thus greatly desired. A new synthetic method that avoids incompatible reduction potentials and rates would be critical to grow metal nanostructures with high purities and the desired stoichiometries. A metal-redox strategy that employs spontaneous oxidation/reduction reactions to grow nanocrystalline alloys using molecular-scale zerovalent metal precursors is now described. The selection of suitable zerovalent metal species allows for thermodynamic control of the compositional stoichiometry during the temperature-dependent formation of the metal alloy nanoparticles. A practical and scalable strategy for nanoalloy growth that can potentially produce key metal components of superior metallurgical quality for catalytic and magnetic systems has thus been developed. PMID:25651105

  19. The effect of femtosecond laser micromachining on the surface characteristics and subsurface microstructure of amorphous FeCuNbSiB alloy

    Energy Technology Data Exchange (ETDEWEB)

    Jia Wei [Ultrafast Laser Laboratory, School of Precision Instruments and Optoelectrons Engineering, Tianjin University, Tianjin 300072 (China)]. E-mail: jiaw@tju.edu.cn; Peng Zhinong [Ultrafast Laser Laboratory, School of Precision Instruments and Optoelectrons Engineering, Tianjin University, Tianjin 300072 (China); Wang Zhijun [Ultrafast Laser Laboratory, School of Precision Instruments and Optoelectrons Engineering, Tianjin University, Tianjin 300072 (China); Ni Xiaochang [Ultrafast Laser Laboratory, School of Precision Instruments and Optoelectrons Engineering, Tianjin University, Tianjin 300072 (China); Wang Chingyue [Ultrafast Laser Laboratory, School of Precision Instruments and Optoelectrons Engineering, Tianjin University, Tianjin 300072 (China)

    2006-11-30

    Detailed studies on the effects of femtosecond laser ablation on surface characteristics and subsurface microstructure of amorphous FeCuNbSiB alloy are reported. Three types of ripple structures were observed on the material surface in the gentle ablated (damaged) zone. As observed with X-ray diffraction (XRD), amorphous form is kept in the damaged zone, and there is few crystallization form in ablation zone.

  20. Hydrogen absorption induced metal deposition on palladium and palladium-alloy particles

    Science.gov (United States)

    Wang, Jia X.; Adzic, Radoslav R.

    2009-03-24

    The present invention relates to methods for producing metal-coated palladium or palladium-alloy particles. The method includes contacting hydrogen-absorbed palladium or palladium-alloy particles with one or more metal salts to produce a sub-monoatomic or monoatomic metal- or metal-alloy coating on the surface of the hydrogen-absorbed palladium or palladium-alloy particles. The invention also relates to methods for producing catalysts and methods for producing electrical energy using the metal-coated palladium or palladium-alloy particles of the present invention.

  1. Study on electrical properties of metal/GaSb junctions using metal-GaSb alloys

    Energy Technology Data Exchange (ETDEWEB)

    Nishi, Koichi, E-mail: nishi@mosfet.t.u-tokyo.ac.jp; Yokoyama, Masafumi; Kim, Sanghyeon; Takenaka, Mitsuru; Takagi, Shinichi [The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Yokoyama, Haruki [NTT Photonics Laboratories, NTT Corporation, Atsugi 243-0198 (Japan)

    2014-01-21

    We study the metal-GaSb alloy formation, the structural properties and the electrical characteristics of the metal-alloy/GaSb diodes by employing metal materials such as Ni, Pd, Co, Ti, Al, and Ta, in order to clarify metals suitable for GaSb p-channel metal-oxide-semiconductor field-effect transistors (pMOSFETs) as metal-GaSb alloy source/drain (S/D). It is found that Ni, Pd, Co, and Ti can form alloy with GaSb by rapid thermal annealing at 250, 250, 350, and 450 °C, respectively. The Ni-GaSb and Pd-GaSb alloy formation temperature of 250 °C is lower than the conventional dopant activation annealing for ion implantation, which enable us to lower the process temperature. The alloy layers show lower sheet resistance (R{sub Sheet}) than that of p{sup +}-GaSb layer formed by ion implantation and activation annealing. We also study the electrical characteristics of the metal-alloy/GaSb junctions. The alloy/n-GaSb contact has large Schottky barrier height (ϕ{sub B}) for electrons, ∼0.6 eV, and low ϕ{sub B} for holes, ∼0.2 eV, which enable us to realize high on/off ratio in pMOSFETs. We have found that the Ni-GaSb/GaSb Schottky junction shows the best electrical characteristics with ideal factor (n) of 1.1 and on-current/off-current ratio (I{sub on}/I{sub off}) of ∼10{sup 4} among the metal-GaSb alloy/GaSb junctions evaluated in the present study. These electrical properties are also superior to those of a p{sup +}-n diode fabricated by Be ion implantation with activation annealing at 350 °C. As a result, the Ni-GaSb alloy can be regarded as one of the best materials to realize metal S/D in GaSb pMOSFETs.

  2. Study on electrical properties of metal/GaSb junctions using metal-GaSb alloys

    International Nuclear Information System (INIS)

    We study the metal-GaSb alloy formation, the structural properties and the electrical characteristics of the metal-alloy/GaSb diodes by employing metal materials such as Ni, Pd, Co, Ti, Al, and Ta, in order to clarify metals suitable for GaSb p-channel metal-oxide-semiconductor field-effect transistors (pMOSFETs) as metal-GaSb alloy source/drain (S/D). It is found that Ni, Pd, Co, and Ti can form alloy with GaSb by rapid thermal annealing at 250, 250, 350, and 450 °C, respectively. The Ni-GaSb and Pd-GaSb alloy formation temperature of 250 °C is lower than the conventional dopant activation annealing for ion implantation, which enable us to lower the process temperature. The alloy layers show lower sheet resistance (RSheet) than that of p+-GaSb layer formed by ion implantation and activation annealing. We also study the electrical characteristics of the metal-alloy/GaSb junctions. The alloy/n-GaSb contact has large Schottky barrier height (ϕB) for electrons, ∼0.6 eV, and low ϕB for holes, ∼0.2 eV, which enable us to realize high on/off ratio in pMOSFETs. We have found that the Ni-GaSb/GaSb Schottky junction shows the best electrical characteristics with ideal factor (n) of 1.1 and on-current/off-current ratio (Ion/Ioff) of ∼104 among the metal-GaSb alloy/GaSb junctions evaluated in the present study. These electrical properties are also superior to those of a p+-n diode fabricated by Be ion implantation with activation annealing at 350 °C. As a result, the Ni-GaSb alloy can be regarded as one of the best materials to realize metal S/D in GaSb pMOSFETs

  3. Superior metallic alloys through rapid solidification processing (RSP) by design

    Energy Technology Data Exchange (ETDEWEB)

    Flinn, J.E. [Idaho National Engineering Laboratory, Idaho Falls, ID (United States)

    1995-05-01

    Rapid solidification processing using powder atomization methods and the control of minor elements such as oxygen, nitrogen, and carbon can provide metallic alloys with superior properties and performance compared to conventionally processing alloys. Previous studies on nickel- and iron-base superalloys have provided the baseline information to properly couple RSP with alloy composition, and, therefore, enable alloys to be designed for performance improvements. The RSP approach produces powders, which need to be consolidated into suitable monolithic forms. This normally involves canning, consolidation, and decanning of the powders. Canning/decanning is expensive and raises the fabrication cost significantly above that of conventional, ingot metallurgy production methods. The cost differential can be offset by the superior performance of the RSP metallic alloys. However, without the performance database, it is difficult to convince potential users to adopt the RSP approach. Spray casting of the atomized molten droplets into suitable preforms for subsequent fabrication can be cost competitive with conventional processing. If the fine and stable microstructural features observed for the RSP approach are preserved during spray casing, a cost competitive product can be obtained that has superior properties and performance that cannot be obtained by conventional methods.

  4. COST 507: Thermophysical properties of light metal alloys. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Jaroma-Weiland, G.; Brandt, R.; Neuer, G.

    1994-02-15

    The thermophysical properties of Al-, Mg- and Ti-based light metal alloys have been studied by reviewing the literature published so far, evaluating the empirical results and by empirical investigations. The properties to the covered in the literature research are: thermal conductivity, thermal diffusivity, specific heat capacity, thermal expansion and electrical resistivity. The data have been stored in the factual data base THERSYST together with the results of experimental measurements supplied from participants of the COST 507-action (Group D). Altogether 1325 data-sets referring to 146 alloys have been stored. They have been uniformly represented and critically analyzed by means of the THERSYST program moduli. These numerical data cover a number of systems with variing chemical composition and thermal treatment. Partly large discrepancies especially of the thermal conductivity have been found for similar alloys. The problem of experimental uncertainities has been studied in detail by investigation of AA-8090 alloy (Al-2.5Li-1.1Cu). The thermophysical properties of monolithic alloy KS1275 (AlSi12CuNi) and metal matrix composite (KS1275 reinforced with Al2O3 short fibre) have been determined experimentally. (orig.)

  5. New applications and novel processing of refractory metal alloys

    International Nuclear Information System (INIS)

    Refractory metals have often been limited in their application because of their propensity to oxidize and to undergo a loos of yield strength at elevated temperatures. However, recent developments in both processing and alloy composition have opened the possibility that these materials might be used in structural applications that were not considered possible in the past. At the same time, the use of refractory metals in the electronics industry is growing, particularly with the use of tantalum as a diffusion barrier for copper metallization. Finally, the application of grain boundary engineering to the problem of intergranular fracture in these materials may allow processes to be developed that will produce alloys with a greater resistance to fracture. (author)

  6. Amorphous metal-aluminophosphate catalysts for aldol condensation of n-heptanal and benzaldehyde to jasminaldehyde

    Institute of Scientific and Technical Information of China (English)

    A. Hamza; N. Nagaraju

    2015-01-01

    Amorphous aluminophosphate (AlP) and metal‐aluminophosphates (MAlPs, where M=2.5 mol%Cu, Zn, Cr, Fe, Ce, or Zr) were prepared by coprecipitation method. Their surface properties and catalytic activity for the synthesis of jasminaldehyde through the aldol condensation of n‐heptanal and benzaldehyde were investigated. The nitrogen adsorption‐desorption isotherms showed that the microporosity exhibited by the aluminophosphate was changed to a mesoporous and macroporous structure which depended on the metal incorporated, with a concomitant change in the surface area. Temperature‐programmed desorption of NH3 and CO2 revealed that the materials possessed both acidic and basic sites. The acidic strength of the material was either increased or decreased depending on the nature of the metal. The basicity was increased compared to AlP. All the materials were X‐ray amorphous and powder X‐ray diffraction studies indicated the absence of metal oxide phases. The Fourier transform infrared analysis confirmed the presence of phosphate groups and also the absence of any M‐O moieties in the materials. The selected organic reaction occurred only in the presence of the AlP and MAlPs. The selectivity for the jasminaldehyde product was up to 75%with a yield of 65%. The best conversion of n‐heptanal with a high selectivity to jasminaldehyde was obtained with FeAlP as the catalyst, and this material was characterized to have less weak acid sites and more basic sites.

  7. Mechanical properties of metal-ceramic systems from nickel-chromium and cobalt-chromium alloys

    OpenAIRE

    Mirković Nemanja

    2007-01-01

    Background/Aim. Metal-ceramic bond strength and alloys' elastic modulus clearly determine the potential of alloy application, because the ceramic integrity during mastication depends on these two characteristics. The aim of this study was to evaluate metal-ceramic bond strength and elastic modulus of cobalt-chromium alloys in making porcelainfused- to-metal restorations, regarding the application of the most frequent nickel-chromium alloy. Methods. The research was performed as an experimenta...

  8. Electron field emission from 2-induced insulating to metallic behaviour of amorphous carbon (-C) films

    Indian Academy of Sciences (India)

    Pitamber Mahanandia; P N Viswakarma; Prasad Vishnu Bhotla; S V Subramanyam; Karuna Kar Nanda

    2010-06-01

    The influence of concentration and size of 2 cluster on the transport properties and electron field emissions of amorphous carbon films have been investigated. The observed insulating to metallic behaviour from reduced activation energy derived from transport measurement and threshold field for electron emission of -C films can be explained in terms of improvements in the connectivity between 2 clusters. The connectivity is resulted by the cluster concentration and size. The concentration and size of 2 content cluster is regulated by the coalescence of carbon globules into clusters, which evolves with deposition conditions.

  9. Thermal treatment of the Fe78Si9B13 alloy in it amorphous phase studied by means of Moessbauer spectroscopy

    International Nuclear Information System (INIS)

    The magnetic and microhardness changes, dependents of the temperature that occur in the Fe78Si9B13 alloy in it amorphous state were studied by means of the Moessbauer spectroscopy and Vickers microhardness. According to the Moessbauer parameters and in particular that of the hyperfine magnetic field, this it changes according to the changes of the microhardness; i.e. if the microhardness increases, the hyperfine magnetic field increases. The registered increment of hardness in the amorphous state of this alloy should be considered as anomalous, according to the prediction of the Hall-Petch equation, the one that relates negative slopes with grain sizes every time but small. (Author)

  10. Electron-irradiation-induced crystallization at metallic amorphous/silicon oxide interfaces caused by electronic excitation

    Science.gov (United States)

    Nagase, Takeshi; Yamashita, Ryo; Lee, Jung-Goo

    2016-04-01

    Irradiation-induced crystallization of an amorphous phase was stimulated at a Pd-Si amorphous/silicon oxide (a(Pd-Si)/SiOx) interface at 298 K by electron irradiation at acceleration voltages ranging between 25 kV and 200 kV. Under irradiation, a Pd-Si amorphous phase was initially formed at the crystalline face-centered cubic palladium/silicon oxide (Pd/SiOx) interface, followed by the formation of a Pd2Si intermetallic compound through irradiation-induced crystallization. The irradiation-induced crystallization can be considered to be stimulated not by defect introduction through the electron knock-on effects and electron-beam heating, but by the electronic excitation mechanism. The observed irradiation-induced structural change at the a(Pd-Si)/SiOx and Pd/SiOx interfaces indicates multiple structural modifications at the metal/silicon oxide interfaces through electronic excitation induced by the electron-beam processes.

  11. Biocompatibility evaluation of nickel-titanium shape memory metal alloy

    OpenAIRE

    Ryhänen, J. (Jorma)

    1999-01-01

    Abstract The shape memory effect, superelasticity, and good damping properties, uncommon in other implant alloys, make the nickel-titanium shape memory metal alloy (Nitinol or NiTi) a fascinating material for surgical applications. It provides a possibility to make self-locking, self-expanding and self-compressing implants. The purpose of this work was to determine if NiTi is a safe material for surgical implant applications. The primary cytotoxicity and the corrosion rate of NiTi were...

  12. Coating with overlay metallic-cermet alloy systems

    Science.gov (United States)

    Gedwill, M. A.; Levine, S. R.; Glasgow, T. K. (Inventor)

    1984-01-01

    A base layer of an oxide dispersed, metallic alloy (cermet) is arc plasma sprayed onto a substrate, such as a turbine blade, vane, or the like, which is subjected to high temperature use. A top layer of an oxidation, hot corrosion, erosion resistant alloy of nickel, cobalt, or iron is then arc plasma sprayed onto the base layer. A heat treatment is used to improve the bonding. The base layer serves as an inhibitor to interdiffusion between the protective top layer and the substrate. Otherwise, the 10 protective top layer would rapidly interact detrimentally with the substrate and degrade by spalling of the protective oxides formed on the outer surface at elevated temperatures.

  13. Magnetic and Distribution of Magnetic Moments in Amorphous Fe89.7 P10.3 Alloy Nanowire Arrays

    International Nuclear Information System (INIS)

    Binary amorphous Fe89.7P10.3 alloy nanowire arrays in diameter of about 40nm and length of about 3 μm have been fabricated in an anodic aluminium oxide template by electrodeposition. Magnetic properties of the samples are investigated by mean of vibrating sample magnetometer, transmission Mössbauer spectroscopy and conversion electron Mössbauer spectroscopy at room temperature. It is found that the nanowire arrays have obvious perpendicular magnetic anisotropy and are ferromagnetic at room temperature, with its Mössbauer spectra consisting of six broad lines. The average angles between the Fe magnetic moment and the wire axis are about 14° inside and 28° at the end of the amorphous Fe89.7P10.3 alloy nanowire arrays, respectively. The magnetic behaviour is decided by the shape anisotropy and the dipolar interaction between wires. In addition, the magnetic moments distribution is theoretically demonstrated by using the symmetric fanning mechanism of the spheres chain model

  14. Magnetic and Distribution of Magnetic Moments in Amorphous Fe89.7P10.3Alloy Nanowire Arrays

    Institute of Scientific and Technical Information of China (English)

    SHI Hui-Gang; XUE De-Sheng

    2008-01-01

    Binary amorphous Fe89.7P10.3 alloy nanowire arrays in diameter of about 40nm and length of about 3μm have been fabricated in an anodic aluminium oxide template by electrodeposition.Magnetic properties of the samples are investigated by mean of vibrating sample magnetometer,transmission M(o)ssbauer spectroscopy and conversion electron M(o)ssbauer spectroscopy at room temperature.It is found that the nanowire arrays have obvious perpendicular magnetic anisotropy,and are ferromagnetic at room temperature,with its M(o)ssbauer spectra consisting of six broad lines.The average anglas between the Fe magnetic moment and the wire axis are about 14°inside and 28°at the end of the amorphous Fe89.7P10.3 alloy nanowire arrays,respectively.The magnetic behaviour is decided by the shape anisotropy and the dipolar interaction between wires.In addition,the magnetic moments distribution is theoretically demonstrated by using the symmetric fanning mechanism of the spheres chain model.

  15. Atomically resolved surface structures of vapor deposited amorphous silicon-carbon alloys: An atomic force microscopy and spectroscopic study

    International Nuclear Information System (INIS)

    Silicon carbide alloys are widely used in high-tech applications due to their interesting combination of chemical, mechanical and electronic properties. Growing thin films of this material in a simple and controlled way is a hot topic in modern material's science. In particular, the possibility to tailor the film properties just by tuning the deposition temperature would be an important progress. In the present work amorphous silicon-carbon alloys thin films have been deposited by electron beam sublimation of a poly-crystalline silicon carbide target in vacuum environment. The deposition temperature was varied from Room Temperature to about 1300 K. The resulting films were analyzed by means of Ultra High Vacuum-Atomic Force Microscopy (UHV-AFM) down to even atomic resolution. The observed features agree with literature data, e.g. interatomic bond lengths, as achieved by others methods, and the structural arrangements of silicon and carbon atoms as concluded from IR and Raman spectroscopy measurements carried out on the same samples. The results not only allow a correlation between film properties and deposition temperature but also support the notion of the UHV-AFM images of the amorphous surfaces being atomically resolved.

  16. Ni-based amorphous alloy-coating for bipolar plate of PEM fuel cell by electrochemical plating

    International Nuclear Information System (INIS)

    In this study, the Ni-Cr-P amorphous alloy-coated bipolar plates were produced by electro-plating on the Cu base plates with a flow field. The power generation tests of a single fuel cell with those Ni-Cr-P bipolar plates were conducted at 353 K. It was found that the single fuel cell with those Ni-Cr-P bipolar plates showed excellent I-V performance as well as that with the carbon graphite bipolar plates. It was also found that the single cell with those Ni-Cr-P bipolar plates showed better I-V performance than that with the Ni-P amorphous alloy-coated bipolar plates. Furthermore, the long-time operation test was conducted for 440 h with those Ni-Cr-P bipolar plates at the constant current density of 200 mA·cm−2. As a result, it was found that the cell voltage gradually decreased at the beginning of the measurement before 300 h and then the voltage was kept constant after 300 h.

  17. The Chemically-Specific Structure of an Amorphous Molybdenum Germanium Alloy by Anomalous X-ray Scattering

    International Nuclear Information System (INIS)

    Since its inception in the late 1970s, anomalous x-ray scattering (AXS) has been employed for chemically-specific structure determination in a wide variety of noncrystalline materials. These studies have successfully produced differential distribution functions (DDFs) which provide information about the compositionally-averaged environment of a specific atomic species in the sample. Despite the wide success in obtaining DDFs, there are very few examples of successful extraction of the fully chemically-specific partial pair distribution functions (PPDFs), the most detailed description of an amorphous sample possible by x-ray scattering. Extracting the PPDFs is notoriously difficult since the matrix equation involved is ill-conditioned and thus extremely sensitive to errors present in the experimental quantities that enter the equation. Instead of addressing this sensitivity by modifying the data through mathematical methods, sources of error have been removed experimentally: A focusing analyzer crystal was combined with a position-sensitive linear detector to experimentally eliminate unwanted inelastic scattering intensity over most of the reciprocal space range probed. This instrumentation has been used in data collection for the extraction of PPDFs from amorphous (a)-MoGe3. This composition arises as a phase separation endpoint in the Ge-rich region of the vapor-deposited Mo-Ge amorphous alloy system but is not present at equilibrium. Since the first Ge-rich compound in the Mo-Ge equilibrium system is MoGe2, previous workers have speculated that perhaps a unique MoGe3 compound exists in the amorphous system. Rather than indicating a distinct MoGe3 compound with definitive local structure, however, the coordination results are more consistent with a densely-packed alloy having a wide range of solid solubility. Significant improvement in the quality and reliability of experimental PPDFs from a-MoGe3 by AXS has been achieved solely through the experimental

  18. Effect of irradiation temperature on crystallization of {alpha}-Fe induced by He irradiations in Fe{sub 80}B{sub 20} amorphous alloy

    Energy Technology Data Exchange (ETDEWEB)

    San-noo, Toshimasa; Toriyama, Tamotsu; Wakabayashi, Hidehiko; Iijima, Hiroshi [Musashi Inst. of Tech., Tokyo (Japan); Hayashi, Nobuyuki; Sakamoto, Isao

    1997-03-01

    Since amorphous alloys are generally highly resistant to irradiation and their critical radiation dose is an order of magnitude higher for Fe-B amorphous alloy than Mo-methods, these alloys are expected to become applicable as for fusion reactor materials. The authors investigated {alpha}-Fe crystallization in an amorphous alloy, Fe{sub 80}B{sub 20} using internal conversion electron Moessbauer spectroscopy. The amount of {alpha}-Fe component was found to increase by raising the He-irradiation dose. The target part was modified to enable He ion radiation at a lower temperature (below 400 K) by cooling with Peltier element. Fe{sub 80}B{sub 20} amorphous alloy was cooled to keep the temperature at 300 K and exposed to 40 keV He ion at 1-3 x 10{sup 8} ions/cm{sup 2}. The amount of {alpha}-Fe crystal in each sample was determined. The crystal formation was not observed for He ion radiation below 2 x 10{sup 18} ions/cm{sup 2}, but that at 3 x 10{sup 8} ions/ cm{sup 2} produced a new phase ({delta} +0.40 mm/sec, {Delta} = 0.89 mm/sec). The decrease in the radiation temperature from 430 to 300 K resulted to extremely repress the production of {alpha}-Fe crystal, suggesting that the crystallization induced by He-radiation cascade is highly depending on the radiation temperature. (M.N.)

  19. Second amorphous-to-crystalline phase transformation in Cu60Ti20Zr20 bulk metallic glass

    DEFF Research Database (Denmark)

    Cao, Q.P.; Li, J.F.; Zhang, P.N.;

    2007-01-01

    The second amorphous-to-crystalline phase transformation in Cu60Ti20Zr20 bulk metallic glass was investigated by differential scanning calorimetry and x-ray diffractometry. The difference of the Gibbs free energies between the amorphous phase and the crystalline products during the transformation...... the order of 400 kJ mol(-1). The average Avrami exponent n is about 2.0, indicating that the crystallization is diffusion controlled....

  20. Multiscale model of metal alloy oxidation at grain boundaries.

    Science.gov (United States)

    Sushko, Maria L; Alexandrov, Vitaly; Schreiber, Daniel K; Rosso, Kevin M; Bruemmer, Stephen M

    2015-06-01

    High temperature intergranular oxidation and corrosion of metal alloys is one of the primary causes of materials degradation in nuclear systems. In order to gain insights into grain boundary oxidation processes, a mesoscale metal alloy oxidation model is established by combining quantum Density Functional Theory (DFT) and mesoscopic Poisson-Nernst-Planck/classical DFT with predictions focused on Ni alloyed with either Cr or Al. Analysis of species and fluxes at steady-state conditions indicates that the oxidation process involves vacancy-mediated transport of Ni and the minor alloying element to the oxidation front and the formation of stable metal oxides. The simulations further demonstrate that the mechanism of oxidation for Ni-5Cr and Ni-4Al is qualitatively different. Intergranular oxidation of Ni-5Cr involves the selective oxidation of the minor element and not matrix Ni, due to slower diffusion of Ni relative to Cr in the alloy and due to the significantly smaller energy gain upon the formation of nickel oxide compared to that of Cr2O3. This essentially one-component oxidation process results in continuous oxide formation and a monotonic Cr vacancy distribution ahead of the oxidation front, peaking at alloy/oxide interface. In contrast, Ni and Al are both oxidized in Ni-4Al forming a mixed spinel NiAl2O4. Different diffusivities of Ni and Al give rise to a complex elemental distribution in the vicinity of the oxidation front. Slower diffusing Ni accumulates in the oxide and metal within 3 nm of the interface, while Al penetrates deeper into the oxide phase. Ni and Al are both depleted from the region 3-10 nm ahead of the oxidation front creating voids. The oxide microstructure is also different. Cr2O3 has a plate-like structure with 1.2-1.7 nm wide pores running along the grain boundary, while NiAl2O4 has 1.5 nm wide pores in the direction parallel to the grain boundary and 0.6 nm pores in the perpendicular direction providing an additional pathway for oxygen

  1. Multiscale model of metal alloy oxidation at grain boundaries

    International Nuclear Information System (INIS)

    High temperature intergranular oxidation and corrosion of metal alloys is one of the primary causes of materials degradation in nuclear systems. In order to gain insights into grain boundary oxidation processes, a mesoscale metal alloy oxidation model is established by combining quantum Density Functional Theory (DFT) and mesoscopic Poisson-Nernst-Planck/classical DFT with predictions focused on Ni alloyed with either Cr or Al. Analysis of species and fluxes at steady-state conditions indicates that the oxidation process involves vacancy-mediated transport of Ni and the minor alloying element to the oxidation front and the formation of stable metal oxides. The simulations further demonstrate that the mechanism of oxidation for Ni-5Cr and Ni-4Al is qualitatively different. Intergranular oxidation of Ni-5Cr involves the selective oxidation of the minor element and not matrix Ni, due to slower diffusion of Ni relative to Cr in the alloy and due to the significantly smaller energy gain upon the formation of nickel oxide compared to that of Cr2O3. This essentially one-component oxidation process results in continuous oxide formation and a monotonic Cr vacancy distribution ahead of the oxidation front, peaking at alloy/oxide interface. In contrast, Ni and Al are both oxidized in Ni-4Al forming a mixed spinel NiAl2O4. Different diffusivities of Ni and Al give rise to a complex elemental distribution in the vicinity of the oxidation front. Slower diffusing Ni accumulates in the oxide and metal within 3 nm of the interface, while Al penetrates deeper into the oxide phase. Ni and Al are both depleted from the region 3–10 nm ahead of the oxidation front creating voids. The oxide microstructure is also different. Cr2O3 has a plate-like structure with 1.2–1.7 nm wide pores running along the grain boundary, while NiAl2O4 has 1.5 nm wide pores in the direction parallel to the grain boundary and 0.6 nm pores in the perpendicular direction providing an additional pathway for

  2. Synchrotron radiation photoemission study of metal overlayers on hydrogenated amorphous silicon at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Pi, J.

    1990-09-21

    In this dissertation, metals deposited on a hydrogenated amorphous silicon (a-Si:H) film at room temperature are studied. The purpose of this work is mainly understanding the electronic properties of the interface, using high-resolution synchrotron radiation photoemission techniques as a probe. Atomic hydrogen plays an important role in passivating dangling bonds of a-Si:H films, thus reducing the gap-state distribution. In addition, singly bonded hydrogen also reduces states at the top of the valence band which are now replaced by deeper Si-H bonding states. The interface is formed by evaporating metal on an a-Si:H film in successive accumulations at room temperature. Au, Ag, and Cr were chosen as the deposited metals. Undoped films were used as substrates. Since some unique features can be found in a-Si:H, such as surface enrichment of hydrogen diffused from the bulk and instability of the free surface, we do not expect the metals/a-Si:H interface to behave exactly as its crystalline counterpart. Metal deposits, at low coverages, are found to gather preferentially around regions deficient in hydrogen. As the thickness is increased, some Si atoms in those regions are likely to leave their sites to intermix with metal overlayers like Au and Cr. 129 refs., 30 figs.

  3. Wetting and reaction characteristics of crystalline and amorphous SiO2 derived rice-husk ash and SiO2/SiC substrates with Al-Si-Mg alloys

    Science.gov (United States)

    Bahrami, A.; Pech-Canul, M. I.; Gutiérrez, C. A.; Soltani, N.

    2015-12-01

    A study of the wetting behavior of three substrate types (SiC, SiO2-derived RHA and SiC/SiO2-derived RHA) by two Al-Si-Mg alloys using the sessile drop method has been conducted, using amorphous and crystalline SiO2 in the experiment. Mostly, there is a transition from non-wetting to wetting contact angles, being the lowest θ values achieved with the alloy of high Mg content in contact with amorphous SiO2. The observed wetting behavior is attributed to the deposited Mg on the substrates. A strong diffusion of Si from the SiC/Amorphous RHA substrate into the metal drop explains the free Si segregated at the drop/substrate interface and drop surface. Although incorporation of both SiO2-derived RHA structures into the SiC powder compact substrates increases the contact angles in comparison with the SiC substrate alone, the still observed acute contact angles in RHA/SiC substrates make them promising for fabrication of composites with high volume fraction of reinforcement by the pressureless infiltration technique. The observed wetting characteristics, with decrease in surface tension and contact angles is explained by surface related phenomena. Based on contact angle changes, drop dimensions and surface tension values, as well as on the interfacial elemental mapping, and XRD analysis of substrates, some wetting and reaction pathways are proposed and discussed.

  4. The effect of mechanical milling on the soft magnetic properties of amorphous FINEMET alloy

    Energy Technology Data Exchange (ETDEWEB)

    Gheiratmand, T., E-mail: t.gheiratmand@yahoo.com [Department of Materials Science and Engineering, Sharif University of Technology, Azadi Ave., P.O. Box 11155-9466, Tehran (Iran, Islamic Republic of); Hosseini, H.R. Madaah; Davami, P. [Department of Materials Science and Engineering, Sharif University of Technology, Azadi Ave., P.O. Box 11155-9466, Tehran (Iran, Islamic Republic of); Gjoka, M. [Institute of Nanoscience and Nanotechnology, National Center for Scientific Research, DEMOKRITOS, Agia Paraskevi, 15310 Athens (Greece); Song, M. [State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083 (China)

    2015-05-01

    The effect of milling time on the magnetic properties of FINEMET amorphous ribbons has been investigated using X-ray diffraction, Mössbauer spectroscopy, thermo-magnetic measurements, transmission electron microscopy and SQUID magnetometery. Ribbons were melt-spun at a wheel speed of 38 ms{sup -1} and then mechanically milled for different periods up to 45 min. The results showed that the partially crystallization of the amorphous powder occurs during milling. TEM observations confirmed the formation of small volume fraction of the crystalline phase with ~9 nm crystallite size in the amorphous matrix for the ribbon milled for 45 min. Thermo-magnetic measurements indicated the enhancement of the Curie temperature of amorphous phase during milling which is due to the annihilation of free volumes and microstructural ordering. The Hopkinson effect led to the monotonic increase of magnetization with respect to the temperature before reaching the Curie temperature of the milled samples. Moreover; the magnetization increased with the formation of the Fe(Si) phase while the coercivity decreased. Mössbauer spectroscopy and thermo-magnetic measurements revealed the existence of 13% Fe in crystalline phase. The composition of crystalline phase was determined as Fe–16.5Si. Hyperfine field values increased with milling time, suggesting the ordering of the structure and enhancement of the number of Fe–Fe atomic pairs in the crystalline phase comparing to the primary amorphous ribbon. - Highlights: • Effect of crystallization of amorphous FINEMET during milling has been investigated. • Milling of amorphous ribbons for 45 min caused the formation of nano crystals. • Annihilation of free volumes increased the Curie temperature of amorphous phase. • Hyperfine field values increased with milling time suggesting ordering of the structure. • Hopkinson effect led to the monotonic increase in magnetization before T{sub c}.

  5. Effect of alloying on elastic properties of ZrN based transition metal nitride alloys

    KAUST Repository

    Kanoun, Mohammed

    2014-09-01

    We report the effect of composition and metal sublattice substitutional element on the structural, elastic and electronic properties of ternary transition metal nitrides Zr1-xMxN with M=Al, Ti, Hf, V, Nb, W and Mo. The analysis of the elastic constants, bulk modulus, shear modulus, Young\\'s modulus, and Poisson\\'s ratio provides insights regarding the mechanical behavior of Zr1-xMxN. We predict that ternary alloys are more ductile compared to their parent binary compounds. The revealed trend in the mechanical behavior might help for experimentalists on the ability of tuning the mechanical properties during the alloying process by varying the concentration of the transition metal. © 2014 Elsevier B.V.

  6. Phase separation of metallic hydrogen-helium alloys

    Science.gov (United States)

    Straus, D. M.; Ashcroft, N. W.; Beck, H.

    1977-01-01

    Calculations are presented for the thermodynamic functions and phase-separation boundaries of solid metallic hydrogen-helium alloys at temperatures between zero and 19,000 K and at pressures between 15 and 90 Mbar. Expressions for the band-structure energy of a randomly disordered alloy (including third order in the electron-ion interaction) are derived and evaluated. Short- and long-range orders are included by the quasi-chemical method, and lattice dynamics in the virtual-crystal harmonic approximation. It is concluded that at temperatures below 4000 K, there is essentially complete phase separation of hydrogen-helium alloys and that a miscibility gap remains at the highest temperatures and pressures considered. The relevance of these results to models of the deep interior of Jupiter is briefly discussed.

  7. Stress and annealing induced changes in the Curie temperature of amorphous and nanocrystalline FeZr and FeNb based alloys

    International Nuclear Information System (INIS)

    The stress and annealing dependence of the Curie temperature in FeZrBCu alloys is presented. A change of about 50 /GPa has been observed. The change in amorphous matrix composition upon crystallization produces an expected increase in TC (about 200 C) which is similar to the experimentally observed increase. This behaviour is opposite to that observed in Fe-Nb based alloys. (orig.)

  8. Investigation of amorphous RuMoC alloy films as a seedless diffusion barrier for Cu/p-SiOC:H ultralow-k dielectric integration

    Energy Technology Data Exchange (ETDEWEB)

    Jiao, Guohua [Shenzhen Institutes of Advanced Technology Chinese Academy of Sciences, Shenzhen (China); The Chinese University of Hong Kong, Shatin, Hong Kong (China); Liu, Bo [Sichuan University, Key Laboratory of Radiation Physics and Technology of Ministry of Education, Institute of Nuclear Science and Technology, Chengdu (China); Li, Qiran [CNRS-Universite Paris Sud UMR 8622, Institut d' Electronique Fondamentale, Orsay (France)

    2015-08-15

    Ultrathin RuMoC amorphous films prepared by magnetron co-sputtering with Ru and MoC targets in a sandwiched scheme Si/p-SiOC:H/RuMoC/Cu were investigated as barrier in copper metallization. The evolution of final microstructure of RuMoC alloy films show sensitive correlation with the content of doped Mo and C elements and can be easily controlled by adjusting the sputtering power of the MoC target. There was no signal of interdiffusion between the Cu and SiOC:H layer in the sample of Cu/RuMoC/p-SiOC:H/Si, even annealing up to 500 C. Very weak signal of oxygen have been confirmed in the RuMoC barrier layer both as-deposited and after being annealed, and a good performance on preventing oxygen diffusion has been proved. Leakage current and resistivity evaluations also reveal the excellent thermal reliability of this Si/p-SiOC:H/RuMoC/Cu film stack at the temperatures up to 500 C, indicating its potential application in the advanced barrierless Cu metallization. (orig.)

  9. Effect of milling time on the structure, micro-hardness, and thermal behavior of amorphous/nanocrystalline TiNiCu shape memory alloys developed by mechanical alloying

    International Nuclear Information System (INIS)

    Highlights: • Potential to produce B1′ (thermal- and stress-induced) and B2 was established. • Martensitic transformation occurred without the formation of intermediate R-phase. • Formation of unwanted intermetallics during heating was hindered by milling. • During milling, microhardness was increased, then reduced, and afterward re-increased. • By milling evolution, thermal crystallization steps changed from 3 to 2. - Abstract: In the present paper, the effect of milling process on the chemical composition, structure, microhardness, and thermal behavior of Ti–41Ni–9Cu compounds developed by mechanical alloying was evaluated. The structural characteristic of the alloyed powders was evaluated by X-ray diffraction (XRD). The chemical composition homogeneity and the powder morphology and size were studied by scanning electron microscopy coupled with electron dispersive X-ray spectroscopy. Moreover, the Vickers micro-indentation hardness of the powders milled for different milling times was determined. Finally, the thermal behavior of the as-milled powders was studied by differential scanning calorimetery. According to the results, at the initial stages of milling (typically 0–12 h), the structure consisted of a Ni solid solution and amorphous phase, and by the milling evolution, nanocrystalline martensite (B19′) and austenite (B2) phases were initially formed from the initial materials and then from the amorphous phase. It was found that by the milling development, the composition uniformity is increased, the inter-layer thickness is reduced, and the powders microhardness is initially increased, then reduced, and afterward re-increased. It was also realized that the thermal behavior of the alloyed powders and the structure of heat treated samples is considerably affected by the milling time

  10. Three-dimensional shear transformation zone dynamics model for amorphous metals

    International Nuclear Information System (INIS)

    A fully three-dimensional (3D) mesoscale modeling framework for the mechanical behavior of amorphous metals is proposed. The model considers the coarse-grained action of shear transformation zones (STZs) as the fundamental deformation event. The simulations are controlled through the kinetic Monte Carlo algorithm and the mechanical response of the system is captured through finite-element analysis, where STZs are mapped onto a 3D finite-element mesh and are allowed to shear in any direction in three dimensions. Implementation of the technique in uniaxial creep tests over a wide range of conditions validates the model's ability to capture the expected behaviors of an amorphous metal, including high temperature flow conforming to the expected constitutive law and low temperature localization in the form of a nascent shear band. The simulation results are combined to construct a deformation map that is comparable to experimental deformation maps. The flexibility of the modeling framework is illustrated by performing a contact test (simulated nanoindentation) in which the model deforms through STZ activity in the region experiencing the highest shear stress

  11. An amorphous titanium dioxide metal insulator metal selector device for resistive random access memory crossbar arrays with tunable voltage margin

    Science.gov (United States)

    Cortese, Simone; Khiat, Ali; Carta, Daniela; Light, Mark E.; Prodromakis, Themistoklis

    2016-01-01

    Resistive random access memory (ReRAM) crossbar arrays have become one of the most promising candidates for next-generation non volatile memories. To become a mature technology, the sneak path current issue must be solved without compromising all the advantages that crossbars offer in terms of electrical performances and fabrication complexity. Here, we present a highly integrable access device based on nickel and sub-stoichiometric amorphous titanium dioxide (TiO2-x), in a metal insulator metal crossbar structure. The high voltage margin of 3 V, amongst the highest reported for monolayer selector devices, and the good current density of 104 A/cm2 make it suitable to sustain ReRAM read and write operations, effectively tackling sneak currents in crossbars without compromising fabrication complexity in a 1 Selector 1 Resistor (1S1R) architecture. Furthermore, the voltage margin is found to be tunable by an annealing step without affecting the device's characteristics.

  12. Deformation of Zr41 Ti14 CU12.5 Ni10 Be22.5 bulk amorphous alloy under isobaric pressure in super-cooled liquid region

    Institute of Scientific and Technical Information of China (English)

    ZHANG Ke-qin; LU Qi-zhu

    2005-01-01

    The curve of crystallization transition during continuous heating for the Zr41Ti14Cu12.5Ni10Be22.5 bulk amorphous alloy was measured by means of dilatation(Fully automatic transformation recording/measuring instrument) and X-ray diffraction(XRD) method. The deformation behavior of the alloy at various heating rates in the supercooled liquid region was studied. The results show that the glass transition temperature of the alloy increases slightly and the supercooled liquid region(SLR) increases significantly with increasing heating rate. The deformation amount under isobaric pressure of 1 N for the alloy in the SLR increases with increasing heating rate. As the heating rate of the alloy increases from 5 to 100 ℃/min, the amount of deformation of the alloy increases from 8.3% to 45%.

  13. Environmental and alloying effects on corrosion of metals and alloys

    Science.gov (United States)

    Liang, Dong

    2009-12-01

    In the first part of this project, corrosion studies were carried out on 304L stainless steel samples welded with Cr-free consumables, which were developed to minimize the concentration of chromate species in the weld fume. The corrosion properties of Ni-Cu and Ni-Cu-Pd Gas Tungsten Arc (GTA) welds and Shielded Metal Arc (SMA) welds are comparable to those of welds fabricated with SS308L consumable, which is the standard consumable for welding 304L. Although the breakdown potentials of the new welds from both welding processes are lower than that of the SS308L weld, the repassivation potential of these new welds is much higher. Generally, the repassivation potential is a more conservative measure of susceptibility to localized corrosion. Our studies showed that the Ni-Cu and Ni-Cu-Pd welds are more resistant to crevice corrosion than SS308L welds, which is related to the high repassivation potential. Also, addition of Pd improved the corrosion resistance of the new welds, which is consistent with previous studies from button samples and bead-on-plate samples. Other corrosion studies such as creviced and uncreviced long time immersion, atmospheric exposure, and slow strain rate testing suggest that Ni-Cu-Pd welds can be a qualified substitute for SS308 weld. In the second part of this project, efforts are put on the connection between lab and field exposure tests because sometimes the correspondence between lab atmospheric corrosion tests (ASTM B117) and field exposures is poor as a result of differences in the critical conditions controlling chemical and electrochemical reactions on surfaces. Recent studies in atmospheric chemistry revealed the formation of extremely reactive species from interactions between UV light, chloride aerosols above oceans and oxidizing agents such as ozone or peroxide. Atmospheric corrosion of metals can be affected by these species which might be transported long distances in the atmosphere to locations far from oceans. However, these

  14. Solidification crack susceptibility of aluminum alloy weld metals

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The susceptibilities of the three aluminum alloys to solidification crack were studied with trans-varestraint tests and tensile tests at elevated temperature. Their metallurgical characteristics, morphologies of the fractured surface and dynamic cracking behaviors at elevated temperature were analyzed with a series of micro-analysis methods. The results show that dynamic cracking models can be classified into three types. The first model has the healing effect which is called type A. The second is the one with deformation and breaking down of metal bridge, called type B. The last one is with the separation of liquid film along grain boundary, called type C.Moreover, the strain rate has different effects on crack susceptibility of aluminum alloys with different cracking models. ZL101 and 5083 alloys belong to type A and type C cracking model respectively, in which strain rate has greater effect on eutectic healing and plastic deformation of metal bridge. 6082 alloy is type B cracking model in which the strain rate has little effect on the deformation ability of the liquid film.

  15. Carbonate-coordinated metal complexes precede the formation of liquid amorphous mineral emulsions of divalent metal carbonates

    Science.gov (United States)

    Wolf, Stephan E.; Müller, Lars; Barrea, Raul; Kampf, Christopher J.; Leiterer, Jork; Panne, Ulrich; Hoffmann, Thorsten; Emmerling, Franziska; Tremel, Wolfgang

    2011-03-01

    During the mineralisation of metal carbonates MCO3 (M = Ca, Sr, Ba, Mn, Cd, Pb) liquid-like amorphous intermediates emerge. These intermediates that form via a liquid/liquid phase separation behave like a classical emulsion and are stabilized electrostatically. The occurrence of these intermediates is attributed to the formation of highly hydrated networks whose stability is mainly based on weak interactions and the variability of the metal-containing pre-critical clusters. Their existence and compositional freedom are evidenced by electrospray ionization mass spectrometry (ESI-MS). Liquid intermediates in non-classical crystallisation pathways seem to be more common than assumed.During the mineralisation of metal carbonates MCO3 (M = Ca, Sr, Ba, Mn, Cd, Pb) liquid-like amorphous intermediates emerge. These intermediates that form via a liquid/liquid phase separation behave like a classical emulsion and are stabilized electrostatically. The occurrence of these intermediates is attributed to the formation of highly hydrated networks whose stability is mainly based on weak interactions and the variability of the metal-containing pre-critical clusters. Their existence and compositional freedom are evidenced by electrospray ionization mass spectrometry (ESI-MS). Liquid intermediates in non-classical crystallisation pathways seem to be more common than assumed. Electronic supplementary information (ESI) available: (S1 and S5) TEM at higher magnifications and of crystallizations conducted at pH = 6.0, 9.0 and 11.3; (S2) sketch of a spreading liquid particle on a TEM grid; (S3) wide-angle scattering of BaCO3 and CdCO3; (S4 and S6-S9) ESI-MS spectra of a solution of carbon dioxide and of bicarbonates of Sr, Ba, Pb, Mn and Cd. See DOI: 10.1039/c0nr00761g

  16. Carrier Transport at Metal/Amorphous Hafnium-Indium-Zinc Oxide Interfaces.

    Science.gov (United States)

    Kim, Seoungjun; Gil, Youngun; Choi, Youngran; Kim, Kyoung-Kook; Yun, Hyung Joong; Son, Byoungchul; Choi, Chel-Jong; Kim, Hyunsoo

    2015-10-14

    In this paper, the carrier transport mechanism at the metal/amorphous hafnium-indium-zinc oxide (a-HIZO) interface was investigated. The contact properties were found to be predominantly affected by the degree of interfacial reaction between the metals and a-HIZO; that is, a higher tendency to form metal oxide phases leads to excellent Ohmic contact via tunneling, which is associated with the generated donor-like oxygen vacancies. In this case, the Schottky-Mott theory is not applicable. Meanwhile, metals that do not form interfacial metal oxide, such as Pd, follow the Schottky-Mott theory, which results in rectifying Schottky behavior. The Schottky characteristics of the Pd contact to a-HIZO can be explained in terms of the barrier inhomogeneity model, which yields a mean barrier height of 1.40 eV and a standard deviation of 0.14 eV. The work function of a-HIZO could therefore be estimated as 3.7 eV, which is in good agreement with the ultraviolet photoelectron spectroscopy (3.68 eV). Our findings will be useful for establishing a strategy to form Ohmic or Schottky contacts to a-HIZO films, which will be essential for fabricating reliable high-performance electronic devices. PMID:26411354

  17. Analysis of metals and alloys for improved material compatibility

    International Nuclear Information System (INIS)

    Various metals and alloys are used in boilers and heat exchangers. Chemical and physical reactions occurring in the boiler may lead to destruction of materials of construction or to the formation of scales and sludge. Many of the problems associated with boilers can be minimised by suitable material selection. Analytical techniques play a vital role in this task. The use of conventional wet chemical methods are well established and yield accurate results for the assay of major constituents. The use of atomic absorption spectrophotometry has led to the development of elegant procedures for a convenient and rapid estimation of minor constituents without any need for separation of matrix elements. The various procedures developed at Analytical Chemistry Division for trace analysis metals and alloys are described in this paper with special reference to the analysis of steel and other nuclear materials. (author)

  18. Gas porosity in metals and alloys irradiated by helium ions

    International Nuclear Information System (INIS)

    Experimental studies of the development of gas porosity in metals and alloys during irradiation with helium ions up to high doses and during post-irradiation annealings, are reviewed. The main theoretical problems of the mechanisms of bubble formation and growth, the regularities and peculiarities of bubble development in a thin near-the surface layer during the introduction of helium with the energy of tens of kiloelectron volt, are considered

  19. Band gap structure modification of amorphous anodic Al oxide film by Ti-alloying

    DEFF Research Database (Denmark)

    Canulescu, Stela; Rechendorff, K.; Borca, C. N.;

    2014-01-01

    The band structure of pure and Ti-alloyed anodic aluminum oxide has been examined as a function of Ti concentration varying from 2 to 20 at. %. The band gap energy of Ti-alloyed anodic Al oxide decreases with increasing Ti concentration. X-ray absorption spectroscopy reveals that Ti atoms are not...

  20. Plating on some difficult-to-plate metals and alloys

    International Nuclear Information System (INIS)

    Electrodeposition of coatings on metals such as beryllium, beryllium-copper, Kovar, lead, magnesium, thorium, titanium, tungsten, uranium, zirconium, and their alloys can be problematic. This is due in most cases to a natural oxide surface film that readily reforms after being removed. The procedures we recommend for plating on these metals rely on replacing the oxide film with a displacement coating, or etching to allow mechanical keying between the substrate and plated deposit. The effectiveness of the procedures is demonstrated by interface bond strengths found in ring-shear and conical-head tensile tests