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Sample records for based amorphous alloys

  1. Bulk amorphous Mg-based alloys

    DEFF Research Database (Denmark)

    Pryds, Nini

    2004-01-01

    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...

  2. 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.

  3. 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.

  4. Corrosion resistance of Fe-based amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Botta, W.J., E-mail: wjbotta@ufscar.br [LEPMI, UMR5279 CNRS, Grenoble INP, Université de Savoie, Université Joseph Fourier, 1130, Rue de la piscine, BP 75, 38402 Saint Martin d’Hères (France); Departamento de Engenharia de Materiais, Universidade Federal de São Carlos, Rod. Washington Luiz, Km 235, 13565-905 São Carlos, SP (Brazil); Berger, J.E.; Kiminami, C.S. [Departamento de Engenharia de Materiais, Universidade Federal de São Carlos, Rod. Washington Luiz, Km 235, 13565-905 São Carlos, SP (Brazil); Roche, V.; Nogueira, R.P. [LEPMI, UMR5279 CNRS, Grenoble INP, Université de Savoie, Université Joseph Fourier, 1130, Rue de la piscine, BP 75, 38402 Saint Martin d’Hères (France); Bolfarini, C. [Departamento de Engenharia de Materiais, Universidade Federal de São Carlos, Rod. Washington Luiz, Km 235, 13565-905 São Carlos, SP (Brazil)

    2014-02-15

    Highlights: ► We report corrosion properties of Fe-based amorphous alloys in different media. ► The Cr-containing alloys had corrosion resistance close to that of Pt in all media. ► The wide range of electrochemical stability is relevant in many industrial domains. -- Abstract: Fe-based amorphous alloys can be designed to present an attractive combination of properties with high corrosion resistance and high mechanical strength. Such properties are clearly adequate for their technological use as coatings, for example, in steel pipes. In this work, we studied the corrosion properties of amorphous ribbons of the following Fe-based compositions: Fe{sub 66}B{sub 30}Nb{sub 4}, [(Fe{sub 0.6}Co{sub 0.4}){sub 0.75}B{sub 0.2}Si{sub 0.05}]{sub 96}Nb{sub 4}, [(Fe{sub 0.7}Co{sub 0.3}){sub 0.75}B{sub 0.2}Si{sub 0.05}]{sub 96}Nb{sub 4}, Fe{sub 56}Cr{sub 23}Ni{sub 5.7}B{sub 16}, Fe{sub 53}Cr{sub 22}Ni{sub 5.6}B{sub 19} and Fe{sub 50}Cr{sub 22}Ni{sub 5.4}B{sub 23}. The ribbons were obtained by rapid solidification using the melt-spinning process, and were characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and optical (OM) and scanning electron microscopy (SEM). The corrosion properties were evaluated by corrosion potential survey and potentiodynamic polarization. The Cr containing alloys, that is the FeCrNiB type of alloys, showed the best corrosion resistance properties with the formation of a stable passive film that ensured a very large passivation plateau.

  5. Preparation of Ti-based amorphous brazing alloy

    Institute of Scientific and Technical Information of China (English)

    ZOU Jia-sheng; JIANG Zhi-guo; XU Zhi-rong; CHEN Guang

    2006-01-01

    A new kind of amorphous active brazing alloy foil with the composition of Ti40Zr25Ni15Cu20 was successfully synthesized using melt spinning in roll forging machine in argon atmosphere. The amorphous structure and composition were examined by X-ray diffraction, differential thermal analysis and energy dispersive X-ray detector. The results show that the Ti40Zr25Ni15Cu20 amorphous alloy foil has excellent wettability on Si3N4 ceramic and demonstrate a strong glass forming ability. The reduced glass transition temperature (Trg) and the temperature interval of supercooled liquid region before crystallization are 0.76 and 78 K, respectively.

  6. Research on fabricating Fe base amorphous alloy by bar plasma spraying

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Since amorphous alloys have wider application, they can not be fabricated using the conventional cooling velocity. The bar material plasma spraying is adopted to fabricate Fe base amorphous alloy in this investigation. The crystallization degree, microstructure, micro-hardness, composition, crystallization temperature of the amorphous alloy and the flying rules of the atomized particles in the process of the plasma spray are tested. The results show that the alloy prepared has the high amorphous degree and homogeneous microstructure, micro-hardness and the crystallization temperature can reach 1187HV and 531℃ respectively. The atomization is very well during the process of plasma spraying; and there is high thermal gradient, the cooling velocity reaches 6.07×107K/s.

  7. Structural transformations in wear resistance of iron- and cobalt-based amorphous alloys during abrasive wear

    Science.gov (United States)

    Korshunov, L. G.; Shabashov, V. A.; Chernenko, N. L.

    2010-04-01

    The wear resistance and structural changes in a number of amorphous alloys based on iron and cobalt and in high-carbon tool steels are studied during wear by a fixed abrasive (crondum, Carborundum) at room temperature and -196°C. The abrasive wear resistance of the amorphous alloys is shown to be 1.6-3.1 lower than that of the high-carbon tool steels having a similar hardness. The relatively low level of the abrasive wear resistance of the amorphous alloys is assumed to be caused by strain softening of their surface during wear. A nanocrystalline structure is found to form in local microvolumes in a thin deformed surface layer of the alloys.

  8. Correlation Between Superheated Liquid Fragility And Onset Temperature Of Crystallization For Al-Based Amorphous Alloys

    Directory of Open Access Journals (Sweden)

    Guo J.

    2015-06-01

    Full Text Available Amorphous alloys or metallic glasses have attracted significant interest in the materials science and engineering communities due to their unique physical, mechanical, and chemical properties. The viscous flow of amorphous alloys exhibiting high strain rate sensitivity and homogeneous deformation is considered to be an important characteristic in thermoplastic forming processes performed within the supercooled liquid region because it allows superplastic-like deformation behavior. Here, the correlation between the superheated liquid fragility, and the onset temperature of crystallization for Al-based alloys, is investigated. The activation energy for viscous flow of the liquid is also investigated. There is a negative correlation between the parameter of superheated liquid fragility and the onset temperature of crystallization in the same Al-based alloy system. The activation energy decreases as the onset temperature of crystallization increases. This indicates that the stability of a superheated liquid can affect the thermal stability of the amorphous alloy. It also means that a liquid with a large superheated liquid fragility, when rapidly solidified, forms an amorphous alloy with a low thermal stability.

  9. Crystallization in Fe- and Co-Based Amorphous Alloys Studied by In-Situ X-Ray Diffraction

    Science.gov (United States)

    Zhang, L. J.; Yu, P. F.; Cheng, H.; Zhang, M. D.; Liu, D. J.; Zhou, Z.; Jin, Q.; Liaw, P. K.; Li, G.; Liu, R. P.

    2016-12-01

    The amorphous alloys, Fe80Si20, Fe78Si9B13, and Fe4Co67Mo1.5Si16.5B11, were prepared by the spinning method in pure argon. The crystallization behaviors of the three amorphous alloys were researched by in-situ X-ray diffraction (XRD), and the crystallization activation energy was calculated, based on the results of differential scanning calorimetry. The crystallization mechanism of the Fe- and Co-based alloys was analyzed, based on the experimental data. The transformation kinetics was described in terms of Johnson-Mehl-Avrami kinetics, except that the Avrami exponent of the Fe78Si9B13 amorphous alloy annealed at 753 K (480 °C) was 4.12; the obtained values for the overall Avrami exponents of the other three amorphous alloys were below 1, as usually found for the Fe-Si amorphous alloys.

  10. Ballistic Impact Properties of Zr-Based Amorphous Alloy Composites Reinforced with Woven Continuous Fibers

    Science.gov (United States)

    Kim, Gyeong Su; Son, Chang-Young; Lee, Sang-Bok; Lee, Sang-Kwan; Song, Young Buem; Lee, Sunghak

    2012-03-01

    This study aims at investigating ballistic impact properties of Zr-based amorphous alloy (LM1 alloy) matrix composites reinforced with woven stainless steel or glass continuous fibers. The fiber-reinforced composites with excellent fiber/matrix interfaces were fabricated without pores and misinfiltration by liquid pressing process, and contained 35 to 41 vol pct of woven continuous fibers homogeneously distributed in the amorphous matrix. The woven-STS-continuous-fiber-reinforced composite consisted of the LM1 alloy layer of 1.0 mm in thickness in the upper region and the fiber-reinforced composite layer in the lower region. The hard LM1 alloy layer absorbed the ballistic impact energy by forming many cracks, and the fiber-reinforced composite layer interrupted the crack propagation and blocked the impact and traveling of the projectile, thereby resulting in the improvement of ballistic performance by about 20 pct over the LM1 alloy. According to the ballistic impact test data of the woven-glass-continuous-fiber-reinforced composite, glass fibers were preferentially fragmented to form a number of cracks, and the amorphous matrix accelerated the fragmentation of glass fibers and the initiation of cracks. Because of the absorption process of ballistic impact energy by forming very large amounts of cracks, fragments, and debris, the glass-fiber-reinforced composite showed better ballistic performance than the LM1 alloy.

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

    Energy Technology Data Exchange (ETDEWEB)

    He Jinghua; Wang Wei; Wang Aimin [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Guan Jianguo, E-mail: guanjg@whut.edu.cn [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China)

    2012-09-15

    Fe{sub 74}Ni{sub 3}Si{sub 13}Cr{sub 6}W{sub 4} 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 Degree-Sign C or more are composed of lots of ultra-fine {alpha}-Fe(Si) grains embedded in an amorphous matrix. When T increases from 350 to 750 Degree-Sign 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 Degree-Sign C. Thus the powder samples annealed at 650 Degree-Sign 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: Black-Right-Pointing-Pointer The annealing temperature effect of Fe-based amorphous alloy was studied. Black-Right-Pointing-Pointer Fe-based amorphous and nanocrystalline alloy has a good absorbing property in C-band. Black-Right-Pointing-Pointer There exists a correspondence between microwave properties and microstructure.

  12. Electrocatalytic properties of Ni-Zr based amorphous and nanocrystalline alloys

    Energy Technology Data Exchange (ETDEWEB)

    Baricco, M.; Minichilli, F. [Torino Univ. (Italy). Dipt. di Chimica; Angelini, E.; Spriano, S.; Rosalbino, F.; Spinelli, P.; Antonione, C. [Dipt. di Scienza dei Materiali e Ingegneria Chimica, Politecnico di Torino (Italy)

    1997-12-31

    The electrocatalytic activity of Ni-Zr based crystalline and amorphous alloys has been tested for the hydrogen evolution reaction. Ni{sub 36}Zr{sub 64} and Ni{sub 27}Zr{sub 48}Al{sub 25} amorphous alloys have been produced in ribbon form by rapid solidification. The amorphous-to-crystalline transformation has been followed by DSC, XRD and TEM. The various samples have been subjected to electrochemical tests by means of cathodic polarization curves in 1 M KOH at 25 C and the obtained exchange current density has been taken as a measure of catalytic efficiency. Surface activation treatments have been performed by chemical etching in HF or by leaching in KOH and a morphological and compositional analysis of the surfaces has been performed by SEM/EDS. The electrochemical behaviour of pure elements (Ni and Zr) has also been considered for comparison. All the samples need a chemical pre-treatment in order to become active. A higher electrocatalytic activity has been observed for amorphous with respect to crystalline alloys with the same composition. For a nanocrystalline microstructure, obtained by partial crystallization of amorphous Zr{sub 64}Ni{sub 36}, an electrocatalytic efficiency comparable to that of the amorphous phase has been observed. Treatments with concentrated HF solutions enhance the electrocatalytic activity and this effect has been related to the formation of nanocrystalline Ni at the surfaces. The leaching of Zr{sub 48}Ni{sub 27}Al{sub 25} produces also small Ni particles owing to the dissolution of Al. (orig.) 15 refs.

  13. High-strength Zr-based bulk amorphous alloys containing nanocrystalline and nanoquasicrystalline particles

    Directory of Open Access Journals (Sweden)

    A Inoue, C Fan, J Saida and T Zhang

    2000-01-01

    Full Text Available It was recently found that the addition of special elements leading to the deviation from the three empirical rules for the achievement of high glass-forming ability causes new mixed structures consisting of the amorphous phase containing nanoscale compound or quasicrystal particles in Zr–Al–Ni–Cu–M (M=Ag, Pd, Au, Pt or Nb bulk alloys prepared by the copper mold casting and squeeze casting methods. In addition, the mechanical strength and ductility of the nonequilibrium phase bulk alloys are significantly improved by the formation of the nanostructures as compared with the corresponding amorphous single phase alloys. The composition ranges, formation factors, preparation processes, unique microstructures and improved mechanical properties of the nanocrystalline and nanoquasicrystalline Zr-based bulk alloys are reviewed on the basis of our recent results reported over the last two years. The success of synthesizing the novel nonequilibrium, high-strength bulk alloys with good mechanical properties is significant for the future progress of basic science and engineering.

  14. 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.

  15. 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.

  16. 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

  17. 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)

  18. 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.

  19. Structural transformations of amorphous iron-based alloys upon abrasive and thermal treatments

    Science.gov (United States)

    Korshunov, L. G.; Shabashov, V. A.; Litvinov, A. V.; Chernenko, N. L.

    2010-05-01

    Wear resistance and structural changes have been investigated in amorphous alloys Fe64Co30Si3B3 and Fe73.5Nb3Cu1Si13.5B9 upon wear using a fixed abrasive. The structural studies have been performed by the methods of metallography, electron microscopy, and Mössbauer spectroscopy. It has been shown that the abrasive resistance of amorphous alloys is 1.6-3.1 times lower than that of high-carbon tool steels, which have a close level of hardness. The low abrasive wear resistance of amorphous alloys is caused by the deformation softening of the alloy surface in the process of wear. The major volume of the deformed surface layer of the alloys preserves the amorphous state. Its structural changes upon wear are characterized by the formation of inhomogeneities (fragments with a size of 10-50 nm) and by a decrease in the width of the strongest “halo” in the selected-area electron-diffractions patterns. In the amorphous matrix of the Fe64Co30Si3B3 alloy, a strong magnetic texture is formed and a redistribution of atoms occurs, which leads to an increase in the local shortrange order corresponding to FeB, Fe2B, Fe3B and α-Fe phases. In microvolumes of a thin (several μm) surface layer, the formation of a nanocrystalline structure (on the order of several volume %) was revealed. A tempering of the Fe73.5Cu1Nb3S13.5B9 alloy at temperatures below 500°C does not affect the hardness and wear resistance of the alloy. At 500°C, there occurs an increase in microhardness and wear resistance of the Fe73.5Cu1Nb3S13.5B9 alloy as a result of the formation in it of a nanocrystalline structure with the retention of a certain amount of the amorphous phase. The complete crystallization of the alloy at 540°C increases the brittleness of the alloy, which leads to a sharp reduction in its wear resistance.

  20. 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.

  1. Ferromagnetic Fe-based Amorphous Alloy with High Glass-forming Ability

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A ferromagnetic amorphous Fe73Al4Ge2Nb1P10C6B4 alloy with highglass-forming ability was synthesized by melt spinning. The supercooled liquid region before crystallization reaches about 65.7 K. The crystallized structure consists of α-Fe, Fe3B, FeB, Fe3P and Fe3C phases. The Febased amorphous alloy exhibits good magnetic properties with a high saturation magnetization and a low saturated magnetostriction. The crystallization leads to an obvious decrease in the soft magnetic properties.

  2. Investigation on Crystallization Kinetics of Zr-AI-Based Bulk Amorphous Alloys

    Institute of Scientific and Technical Information of China (English)

    王国明; 李维火; 方守狮; 华勤; 肖学山

    2005-01-01

    Zr65Al10Ni10Cu15, Zr52.5Al10Ni10Cu15Be12.5 and Zr52.5Al10Ni14.6 Cu17.9Ti5bulk amorphous alloys were prepared by copper mould casting. The crystallization kinetics was measured by differential scanning calorimeter(DSC) with different heating rates, and the activation energy was calculated using Kissinger equation. The relationship between thermal stability and rate constant of crystallization reaction is discussed on the view of crystallization kinetics, and the effect of small atom Beryllium on thermal stability of bulk amorphous alloys is also studied.

  3. Micromagnetic model for magnetisation processes in RE-TM based-amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Stoleriu, Laurentiu E-mail: lstoler@uaic.ro; Cimpoesu, Dorin; Stancu, Alexandru; Lupu, Nicoleta; Chiriac, Horia

    2004-05-01

    A micromagnetic model and its results for Nd{sub 90-x}Fe{sub x}Al{sub 10} (x=40-50) amorphous alloys are presented. The high coercive field of this type of alloys can be explained using the real values of the materials constants (distances between atoms, magnetic moments and exchange constants). The morphology of the sample plays an important role--the formation of Fe clusters and the cooperative switching behaviour further increase the coercive field value.

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

    Science.gov (United States)

    Iqbal, M.; Wang, W. H.

    2014-06-01

    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.

  5. Glass-forming ability analysis of selected Fe-based bulk amorphous alloys

    Directory of Open Access Journals (Sweden)

    R. Nowosielski

    2010-09-01

    Full Text Available Purpose: The paper mainly aims to present the structure and thermal stability of selected Fe-based bulk metallic glasses: Fe72B20Si4Nb4 and Fe43Co14Ni14B20Si5Nb4.Design/methodology/approach: The investigated samples were cast in form of the rods by the pressure die casting method. The structure analysis of the studied materials in as-cast state was carried out using XRD and TEM methods. The thermal stability associated with glass transition temperature (Tg, onset (Tx and peak (Tp crystallization temperature was examined by differential scanning calorimetry (DSC. Several parameters have been used to determine the glass-forming ability of studied alloys. The parameters of GFA included reduced glass transition temperature (Trg, supercooled liquid region (ΔTx, the stability (S and (Kgl parameter.Findings: The XRD and TEM investigations revealed that the studied as-cast metallic glasses were fully amorphous. Changes of the onset and peak crystallization temperature and the glass transition temperature as a function of glassy samples thickness were stated. The good glass-forming ability (GFA enabled casting of the Fe72B20Si4Nb4 and Fe43Co14Ni14B20Si5Nb4 glassy rods.Practical implications: The obtained examination results confirm the utility of applied investigation methods in the thermal stability analysis of examined bulk amorphous alloys. It is evident that parameters Trg, ΔTx, Kgl, S could be used to determine glass-forming ability of studied bulk metallic glasses.Originality/value: The success of fabrication of studied Fe-based bulk metallic glasses in form of rods with diameter up to 3 mm is important for the future progress in research of this group of materials.

  6. A resistivity study of crystallization of some FeNiB-based amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Riontino, G.; Baricco, M.; Marino, F.

    1986-07-01

    The amorphous-to-crystalline transformations has been studied extensively since the discovery of glassy alloys. Many physical and chemical properties vary drastically in the course of thermal treatments leading to crystallization, and this seems to be a limit to the applications of these materials. Nevertheless, the intermediate metastable crystallization products, in some cases, or the final crystalline phases show, in several cases, interesting properties. Among the very large number of amorphous systems up to now investigated, Metglas 2826 and 2826A (from Allied Chemical) have received particular attention, because of their magnetic and anticorrosive properties. In the present paper the authors discuss some results on amorphous alloys having compositions similar to the commercial ones and, in particular, they discuss the influence of phosphorus and chromium content on the electrical resistivity variations during thermal treatments up to crystallization.

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

    Institute of Scientific and Technical Information of China (English)

    MuXuhong; ZongBaoning; 等

    2002-01-01

    Amorphous nickel based alloy catalysts(denoted as the SRNA series catalysts)were prepared via rapid quenching method followed by alkali leaching and other activation procedures.The physicochemical characterizations show that nickel,the active component in these catalysts,exists in the amorphous state,and the catalyst particles possess many nanosized voids leading to large surface area(the highest is 145m2/g).The evaluation results in some model reactions show that the SRNA series catalysts have 2 to 4 times higher activity and selectivity than conventional Raney Ni catalyst for the hydrogenation of compounds with unsatur-ated functional groups.At present,the SRNA series catalysts have been successfully used in hydrogenation of glucose,hydrogenation of pharmaceutical intermediates and purification of caprolactam.In order to use these catalysts efficiently,a magnetically stabilized bed(MSB) technology has been developed by combining the ferromagnetic property of the catalyst with the good mass transfer characteristics of MSB.The demonstration unit of MSB hydrogenation technology has been set up and has kept running for 2800 hours.The results show that,after running 2800 hours,the catalyst still retained good activity; meanwhile,the hydrogenation effi-ciency had been improved 10 times in comparison with the traditional CSTR process.

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

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Amorphous nickel based alloy catalysts (denoted as the SRNA series catalysts) were prepared viarapid quenching method followed by alkali leaching and other activation procedures. The physicochemicalcharacterizations show that nickel, the active component in these catalysts, exists in the amorphous state, andthe catalyst particles possess many nanosized voids leading to large surface area (the highest is 145m2/g). Theevaluation results in some model reactions show that the SRNA series catalysts have 2 to 4 times higheractivity and selectivity than conventional Raney Ni catalyst for the hydrogenation of compounds with unsatur-ated functional groups. At present, the SRNA series catalysts have been successfully used in hydrogenation ofglucose, hydrogenation of pharmaceutical intermediates and purification of caprolactam. In order to use thesecatalysts efficiently, a magnetically stabilized bed (MSB) technology has been developed by combining theferromagnetic property of the catalyst with the good mass transfer characteristics of MSB. The demonstrationunit of MSB hydrogenation technology has been set up and has kept running for 2800 hours. The results showthat, after running 2800 hours, the catalyst still retained good activity; meanwhile, the hydrogenation effi-ciency had been improved 10 times in comparison with the traditional CSTR process.

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

    Institute of Scientific and Technical Information of China (English)

    Mu Xuhong; Zong Baoning; Meng Xiangkun; Min Enze

    2002-01-01

    Amorphous nickel based alloy catalysts (denoted as the SRNAseries catalysts) were prepared viarapid quenching method followed by alkali leaching and other activation procedures. The physicochemicalcharacterizations show that nickel, the active component in these catalysts, exists in the amorphous state, andthe catalyst particles possess many nanosized voids leading to large surface area (the highest is 145m2/g). Theevaluation results in some model reactions show that the SRNA series catalysts have 2 to 4 times higheractivity and selectivity than conventional Raney Ni catalyst for the hydrogenation of compounds with unsatur-ated functional groups. At present, the SRNA series catalysts have been successfully used in hydrogenation ofglucose, hydrogenation of pharmaceutical intermediates and purification of caprolactam. In order to use thesecatalysts efficiently, a magnetically stabilized bed (MSB) technology has been developed by combining theferromagnetic property of the catalyst with the good mass transfer characteristics of MSB. The demonstrationunit of MSB hydrogenation technology has been set up and has kept running for 2800 hours. The results showthat, after running 2800 hours, the catalyst still retained good activity; meanwhile, the hydrogenation effi-ciency had been improved 10 times in comparison with the traditional CSTR process.

  10. 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

  11. Microstructure of Cu-based Amorphous Composite Coatings on AZ91D Magnesium Alloy by Laser Cladding

    Institute of Scientific and Technical Information of China (English)

    Kaijin Huang; Changsheng Xie; T.M.Yue

    2009-01-01

    To improve the sliding wear resistance of AZ91D magnesium alloy, Cu-based amorphous composite coatings made of Cu47Ti34Zr11Ni8 and Cu47Ti34Zr11Ni8+20 wt pct SiC powders were fabricated on AZ91D magnesium alloy by laser cladding, respectively. SEM (scanning electron microscopy), EDS (energy dispersive X-ray spectroscopy), XRD (X-ray diffraction) and TEM (transmission electron microscopy) techniques were employed to study the phases of the coatings. The results show that the coatings mainly consist of amorphous phase and different intermetallic compounds. The reason of formation of amorphous phase and the function of SiC particles were explained in details.

  12. Surface modification of Zr-based bulk amorphous alloys by using ion irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Iqbal, M., E-mail: miqbalchishti@yahoo.com [Physics Division, Pakistan Institute of Nuclear Science and Technology (PINSTECH), P.O. Nilore, Islamabad, 45650 (Pakistan); Qayyum, A.; Akhter, J.I. [Physics Division, Pakistan Institute of Nuclear Science and Technology (PINSTECH), P.O. Nilore, Islamabad, 45650 (Pakistan)

    2011-02-10

    Research highlights: > Ion irradiations of two multicomponent bulk amorphous alloys have been done. Ion irradiation produced crystalline phases in the amorphous matrix due to which mechanical properties enhanced. Considerable increase in hardness and elastic modulus was observed. The results are verified, authentic and confirmed. - Abstract: Surfaces of the [Zr{sub 0.65}Cu{sub 0.18}Ni{sub 0.09}Al{sub 0.08}]{sub 98}M{sub 2} (M = Er and Gd) bulk amorphous alloys were modified by irradiation with energetic singly charged argon (Ar{sup +}) ions. Samples of both the alloys were irradiated with 2.17 x 10{sup 17} argon ions of 10 keV energy. As cast and ion irradiated samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Mechanical properties like Vicker's hardness, nanohardness, elastic modulus and elastic recovery were measured. Considerable increase in elastic modulus and hardness was observed because of ion irradiation in these alloys. The ion irradiated samples of the [Zr{sub 0.65}Cu{sub 0.18}Ni{sub 0.09}Al{sub 0.08}]{sub 98}Er{sub 2} alloy showed better properties as compared to [Zr{sub 0.65}Cu{sub 0.18}Ni{sub 0.09}Al{sub 0.08}]{sub 98}Gd{sub 2} alloy. CuZr{sub 2} phase was detected in ion irradiated alloys by XRD and confirmed by EDS. The range of Ar{sup +} ions was found to be approximately 9.3 {+-} 5.4 nm in both alloys.

  13. Structural transformations and wear resistance of abrasive-affected amorphous Fe- and Co-based alloys

    Science.gov (United States)

    Korshunov, L. G.; Chernenko, N. L.

    2008-12-01

    The abrasive wear resistance of the Fe64Co30Si3B3, Fe82.6Nb5Cu3Si8B1.4, Co86.5Cr4Si7B2.5, and Fe81Si4B13C2 amorphous alloys (ribbon 30 μm thick) has been investigated upon sliding over fixed abrasives (corundum and silicon carbide). The character of fracture of the surface and structural transformations initiated in these materials by the abrasive action have been studied by the metallographic, X-ray diffraction, and electron-microscopic methods. It has been shown that the abrasive wear resistance of the amorphous alloys is smaller by a factor of 1.6-2.9 than that of the Kh12M and U8 tool steels possessing approximately the same level of hardness. A pronounced softening of the surface layer of the amorphous alloys in the process of wear, which is characterized by a decrease in their microhardness reaching 12.5%, has been found. It has been shown that in the surface layer of these amorphous alloys upon wear there arises a small amount (on the order of several volume percent) of the nanocrystalline structure, which does not exert a marked effect on the microhardness and wear resistance of the alloys. In the alloys under study, the main factor that is responsible for their comparatively low abrasive wear resistance is their local softening in the process of wear caused by specific features of deformation processes occurring heterogeneously under the action of high shear contact stresses.

  14. 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.

  15. Electrodeposition of amorphous gold alloy films

    Energy Technology Data Exchange (ETDEWEB)

    Kato, Masaru; Senda, Kazutaka [Central Research Laboratory, Kanto Chemical Co., Inc., Saitama 340-0003 (Japan); Advanced Research Institute for Science and Engineering, Waseda University, Tokyo 169-8555 (Japan); Musha, Yuta [Department of Applied Chemistry, School of Science and Engineering, Waseda University, Tokyo 169-8555 (Japan); Sasano, Junji [Kagami Memorial Laboratory for Materials Science and Technology, Waseda University, Tokyo 169-0051 (Japan); Okinaka, Yutaka [Advanced Research Institute for Science and Engineering, Waseda University, Tokyo 169-8555 (Japan); Osaka, Tetsuya [Department of Applied Chemistry, School of Science and Engineering, Waseda University, Tokyo 169-8555 (Japan); Kagami Memorial Laboratory for Materials Science and Technology, Waseda University, Tokyo 169-0051 (Japan); Advanced Research Institute for Science and Engineering, Waseda University, Tokyo 169-8555 (Japan)], E-mail: osakatet@waseda.jp

    2007-11-20

    The process for electroplating amorphous gold-nickel-tungsten alloy that we developed previously based on the addition of a gold salt to a known amorphous Ni-W electroplating solution was investigated further using the X-ray diffraction (XRD) method for the purpose of quickly surveying the effects of various experimental variables on the microstructure of the alloy. In this system the gold concentration in the plating bath was found to be critical; i.e., when it is either very low or very high, the deposit becomes crystalline to XRD. The deposit composition varies linearly with the mole ratio of Au to Ni in solution, and the alloy deposit is amorphous to XRD when the atomic ratio of Au/Ni in the deposit is between 0.5 and 1.5. At suitable concentrations of the metal ions, the deposit contains essentially no tungsten. By extending the work on the Au-Ni-W system, an amorphous Au-Co alloy plating process was also developed.

  16. 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.

  17. Comparison of Crevice Corrosion of Fe-Based Amorphous Metal and Crystalline Ni-Cr-Mo Alloy

    Energy Technology Data Exchange (ETDEWEB)

    Shan, X; Ha, H; Payer, J H

    2008-07-24

    The crevice corrosion behaviors of an Fe-based bulk metallic glass alloy (SAM1651) and a Ni-Cr-Mo crystalline alloy (C-22) were studied in 4M NaCl at 100 C with cyclic potentiodynamic polarization and constant potential tests. The corrosion damage morphologies, corrosion products and the compositions of corroded surfaces of these two alloys were studied with optical 3D reconstruction, Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and Auger Electron Spectroscopy (AES). It was found that the Fe-based bulk metallic glass (amorphous alloy) SAM1651 had a more positive breakdown potential and repassivation potential than crystalline alloy C-22 in cyclic potentiodynamic polarization tests and required a more positive oxidizing potential to initiate crevice corrosion in constant potential test. Once crevice corrosion initiated, the corrosion propagation of C-22 was more localized near the crevice border compared to SAM1651, and SAM1651 repassivated more readily than C-22. The EDS results indicated that the corrosion products of both alloys contained high amount of O and were enriched in Mo and Cr. The AES results indicated that a Cr-rich oxide passive film was formed on the surfaces of both alloys, and both alloys were corroded congruently.

  18. 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.

  19. 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.

  20. Effect of Pd on GFA and Thermal Stability of Zr-based Bulk Amorphous Alloy

    Institute of Scientific and Technical Information of China (English)

    Fengxiang QIN; Haifeng ZHANG; Aimin WANG; Bingzhe DING; Zhuangqi HU

    2004-01-01

    The effect of Pd addition on the glass-forming ability and thermal stability of the Zr5sAl10Cus0Nis-xPdx (x=0, 1, 3,5 at. Pct) alloys upon copper-mold casting has been investigated. The structure, thermal stability and microstructure were studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM), respectively. It was identified that a new bulk amorphous alloy with the larger supercooled liquid region Atx of 100 K is obtained with substituting Ni by 1 at. Pct Pd. Furthermore, the origins that thermal stability and GFA change with increasing of Pd have also beer discussed.

  1. Fabrication of MEMS-based Micro-fluxgate Sensor with Runway-shaped Co-based Amorphous Alloy Core

    Energy Technology Data Exchange (ETDEWEB)

    Wu Shaobin; Ouyang Jun; Zuo Chao; Yu Lei; Yang Xiaofei; Chen Shi, E-mail: s_chen@sina.com [Department of Electronic Science and Technology, Huazhong University of Science and Technology, Wuhan (China)

    2011-01-01

    High-precision magnetic micro-sensor is an interdisciplinary subject of magnetic field measurement techniques and micro-electromechanical systems (MEMS) technology. A micro-fluxgate magnetic sensor based MEMS technology was designed and fabricated in this paper. This device is a micro-magnetic sensor with a symmetric construction, closed magnetic circuits and differential form. A 25{mu}m thick Fluxgate core of runway model, made by Co-based amorphous alloy, was etched by laser and pasted on the substrate accurately. Excitation coil and sensing coil of 3D solenoid structure were prepared by RF magnetron sputtering and UV-lithography. The minimum line width of the coil is 50 {mu}m. The experimental result shows that micro-fluxgate devices with the size of 5.7mmx7.1mmx60{mu}m had a stable structure.

  2. Dynamic tensile deformation behavior of Zr-based amorphous alloy matrix composites reinforced with tungsten or tantalum fibers

    Science.gov (United States)

    Lee, Hyungsoo; Kim, Gyeong Su; Jeon, Changwoo; Sohn, Seok Su; Lee, Sang-Bok; Lee, Sang-Kwan; Kim, Hyoung Seop; Lee, Sunghak

    2016-07-01

    Zr-based amorphous alloy matrix composites reinforced with tungsten (W) or tantalum (Ta) continuous fibers were fabricated by liquid pressing process. Their dynamic tensile properties were investigated in relation with microstructures and deformation mechanisms by using a split Hopkinson tension bar. The dynamic tensile test results indicated that the maximum strength of the W-fiber-reinforced composite (757 MPa) was much lower than the quasi-statically measured strength, whereas the Ta-fiber-reinforced composite showed very high maximum strength (2129 MPa). In the W-fiber-reinforced composite, the fracture abruptly occurred in perpendicular to the tensile direction because W fibers did not play a role in blocking cracks propagated from the amorphous matrix, thereby resulting in abrupt fracture within elastic range and consequent low tensile strength. The very high dynamic tensile strength of the Ta-fiber-reinforced composite could be explained by the presence of ductile Ta fibers in terms of mechanisms such as (1) interrupted propagation of cracks initiated in the amorphous matrix, (2) formation of lots of cracks in the amorphous matrix, and (3) sharing of loads and severe deformation (necking) of Ta fibers in cracked regions.

  3. Creep of FINEMET alloy at amorphous to nanocrystalline transition

    NARCIS (Netherlands)

    Csach, K.; Miškuf, J.; Juríková, A.; Ocelík, V.

    2009-01-01

    The application of FINEMET-type materials with specific magnetic properties prepared by the crystallization of amorphous alloys is often limited by their brittleness. The structure of these materials consists of nanosized Fe-based grains surrounded with amorphous phase. Then the final macroscopic me

  4. Influence of the Quenching Rate on the Structure and Magnetic Properties of the Fe-Based Amorphous Alloy

    Directory of Open Access Journals (Sweden)

    Nabiałek M.

    2016-03-01

    Full Text Available This paper presents the results of investigations into the structure, microstructure and magnetic properties of Fe61Co10Y8W1B20 amorphous alloy. The alloy samples were in two physical forms: (1 plates of approximate thickness 0.5 mm (so-called bulk amorphous alloys and (2 a ribbon of approximate thickness 35 μm (so-called classic amorphous alloy. The investigations comprised: X-ray diffractometry, Mössbauer spectrometry, transmission electron microscopy, and selected magnetic measurements; all of the investigations were carried out on samples in the as-quenched state. Analysis of the obtained SEM and TEM images, X-ray diffraction patterns, Mössbauer spectrometry results and measurements of the magnetisation in a high magnetic field facilitated collectively the detailed description of the structure of the investigated alloy, which was found to depend on the quenching speed.

  5. Characterization of atomic-level structure in Fe-based amorphous and nanocrystalline alloy by experimental and modeling methods

    Energy Technology Data Exchange (ETDEWEB)

    Babilas, Rafał, E-mail: rafal.babilas@polsl.pl

    2015-09-15

    The atomic structure of Fe{sub 70}Nb{sub 10}B{sub 20} alloy in “as-cast” state and after annealing was investigated using high-energy X-ray diffraction (XRD), Mössbauer spectroscopy (MS) and high resolution transmission electron microscopy (HRTEM). The HRTEM observations allowed to indicate some medium-range order (MRO) regions about 2 nm in size and formation of some kinds of short-range order (SRO) structures represented by atomic clusters with diameter ca. 0.5 nm. The Reverse Monte Carlo (RMC) method basing on the results of XRD measurements was used in modeling the atomic structure of Fe-based alloy. The structural model was described by peak values of partial pair correlation functions and coordination numbers determined by Mössbauer spectroscopy investigations. The three-dimensional configuration box of atoms was obtained from the RMC simulation and the representative Fe-centered clusters were taken from the calculated structure. According to the Gonser et al. approach, the measured spectra of alloy studied were decomposed into 5 subspectra representing average Fe–Fe coordination numbers. Basing on the results of disaccommodation of magnetic permeability, which is sensitive to the short order of the random packing of atoms, it was stated that an occurrence of free volume is not detected after nanocrystallization process. - Highlights: • Atomic cluster model of amorphous structure was proposed for studied glassy alloy. • Short range order (ca. 0.5 nm) regions interpreted as clusters were identified by HREM. • Clusters correspond to coordination numbers (N = 4,6,8,9) calculated by using Gonser approach. • Medium-range order (ca. 2 nm) could be referred to few atomic clusters. • SRO regions are able to grow up as nuclei of crystalline bcc Fe and iron borides. • Crystalline particles have spherical morphology with an average diameter of 20 nm.

  6. Production, Properties and Applications of Bulk Amorphous Alloys

    Institute of Scientific and Technical Information of China (English)

    Tao Zhang; Akihisa Inoue

    2000-01-01

    A review is given of recent work concerned with the production method, the characteristic properties(1) Bulk amorphous system; (2) Mechanical and magnetic properties of bulkamorphous alloys; (3)application of bulk amorphous alloys.

  7. Fe基合金薄带的ALDGMI效应%LDGMI effect on amorphous Fe-based alloy ribbons

    Institute of Scientific and Technical Information of China (English)

    张建强; 卢振华

    2012-01-01

    采用单辊快淬法制备的Fe648Co7.2Nb4Si4.8B19.2非晶合金薄带(Fe基合金薄带),在潮湿的大气环境中进行直流焦耳热退火,利用阻抗仪检测了Fe基合金薄带的纵向驱动巨磁阻抗(LDGMI)效应,研究了驱动频率f与LDGMI效应之间的关系,发现存在临界频率fc =80MHz,且当f<fc时LDGMI曲线呈对称性;当f>fc时出现非对称纵向驱动巨磁阻抗效应(ALDGMI).分析认为,出现ALDGMI效应的原因可能是由于薄带表面氧化层与中心非晶软磁层之间的磁交换耦合作用所致.%Amorphous Fe64.8Co7.2Nb4Si4,8Big.2 alloy ribbons(Fe-based alloy ribbons) are prepared by single roller melt-spinning technique. The longitudinal driven gaint magneto-impedance (LDGMI) effect of the Fe-based alloy ribbons which annealed by Joule-heating in the atmosphere of humid air have been investigated by impedance-analyzer. The relationship between ac driven frequencies / and LDGMI effect is discussed and it is proved that has a critical frequency (fc = 80 MHz), the symmetric GMI behavior appears in frequency region(f- fc). The analysis shows that the AGMI effect may be responsible for the magnetic exchange coupling between surface oxide layer and inner amorphous layer.

  8. Amorphous Alloy and Magnetic Stabilization Bed

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    @@ Sponsored by NSFC,a research team led by Prof.Enze Min (CAS Member) from Research Institute of Petroleum Processing,through 20 years' effort,settled the puzzled grave issue that amorphous alloy material has small specific surface area and low thermal stability.

  9. 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.)

  10. Microstructure and tribological properties of Zr-based amorphous-nanocrystalline coatings deposited on the surface of titanium alloys by Electrospark Deposition

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Xiang; Tan, Yefa, E-mail: tanyefa7651@163.com; Zhou, Chunhua; Xu, Ting; Zhang, Zhongwei

    2015-11-30

    Highlights: • Zr-based amorphous-nanocrystalline coatings were well prepared on TC11 titanium alloys. • High glass forming ability of alloy system and high cooling rate of Electrospark Deposition process are beneficial for the generation of amorphous phase. • A model has been applied to investigate the generation of nanocrystalline phases in amorphous coating. • Excellent wear properties obtained due to nanocrystalline phases distributed in amorphous organization. - Abstract: In order to improve the wear resistance of titanium alloys, the Zr-based amorphous-nanocrystalline coatings were prepared by Electrospark Deposition (ESD) on the surface of TC11. The microstructure of the coatings was analyzed and the tribological behavior and mechanism of the coatings were investigated. The results show that the coating is mainly composed of amorphous phase Zr{sub 55}Cu{sub 30}Al{sub 10}Ni{sub 5} and distributed a large number of nano particles with the diameter between 2 nm and 4 nm such as CuZr{sub 3}, Ni{sub 2}Zr{sub 3}, NiZr{sub 2}, etc. The new alloy system made up of molten electrode material of Zr-based alloy and TC11 substrate has a large glass forming ability, which transforms to amorphous phase in the rapid heating and cooling ESD process. The long-range diffusions of atoms such as Zr and Cu in amorphous microstructure play an important role in nano nucleation growth. The coating is dense, uniform, bonding with TC11 substrate metallurgically. The thickness of the coating is from 55 μm to 60 μm and the average microhardness is 801.3 HV{sub 0.025}. The coating has good friction-reducing and anti-wear properties. The friction coefficient of the coating changes between 0.13 and 0.21 with small fluctuation, decreasing about 60% compared to that of TC11 substrate. And the wear resistance of the coating is increased by 57% than that of TC11 substrate. The main wear mechanism of the coating is micro-cutting wear accompanied with oxidation wear.

  11. Effect of Co content on structure and magnetic behaviors of high induction Fe-based amorphous alloys

    Science.gov (United States)

    Roy, Rajat K.; Panda, Ashis K.; Mitra, Amitava

    2016-11-01

    The replacement of Fe with Co is investigated in the (Fe1-xCox)79Si8.5B8.5Nb3Cu1 (x=0, 0.05, 0.2, 0.35, 0.5) amorphous alloys. The alloys are synthesized in the forms of ribbons by single roller melt spinning technique, and the structural and magnetic properties of annealed ribbons are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM), B-H curve tracer, respectively. All as-cast alloys are structurally amorphous, however, their magnetic properties are varying with Co addition. The Co addition within 5-20 at% results in moderate thermal stability, saturation induction, Curie temperature and lowest coercivity, while 35 at% Co causes highest saturation induction, coercivity, Curie temperature and lowest thermal stability. On devitrification, the magnetic properties change with the generation of α-FeCo nanocrystallites and (FeCo)23B6, Fe2B phases during primary and secondary crystallization stages, respectively. A small amount Co is advantageous for maintaining finer nanocrystallites in amorphous matrix even after annealing at 600 °C, leading to high saturation magnetization (>1.5 T) and low coercivity (~35 A/m). The improved magnetic properties at elevated temperatures indicate these alloys have a potential for high frequency transformer core applications.

  12. Deconvolution of ferromagnetic resonance in devitrification process of Co-based amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Montiel, H. [Centro de Ciencias Aplicadas y Desarrollo Tecnologico, Universidad Nacional Autonoma de Mexico UP. O. Box 70-360, Coyoacan, C.P. 04510 (Mexico)]. E-mail: herlinda_m@yahoo.com; Alvarez, G. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico UP. O. Box 70-360, Coyoacan, C.P. 04510 (Mexico); Departamento de ciencia de los Materiales U.P. Adolfo L. Mateos Edif. 9, Av. Instituto Politecnico Nacional S/N, 07738 DF (Mexico); Betancourt, I. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico UP. O. Box 70-360, Coyoacan, C.P. 04510 (Mexico); Zamorano, R. [Escuela de Fisica y Matematicas, IPN U.P. Adolfo L. Mateos Edif. 9, Av. Instituto Politecnico Nacional S/N, 07738 DF (Mexico); Valenzuela, R. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico UP. O. Box 70-360, Coyoacan, C.P. 04510 (Mexico)

    2006-10-01

    Ferromagnetic resonance (FMR) measurements were carried out on soft magnetic amorphous ribbons of composition Co{sub 66}Fe{sub 4}B{sub 12}Si{sub 13}Nb{sub 4}Cu prepared by melt spinning. In the as-cast sample, a simple FMR spectrum was apparent. For treatment times of 5-20 min a complex resonant absorption at lower fields was detected; deconvolution calculations were carried out on the FMR spectra and it was possible to separate two contributions. These results can be interpreted as the combination of two different magnetic phases, corresponding to the amorphous matrix and nanocrystallites. The parameters of resonant absorptions can be associated with the evolution of nanocrystallization during the annealing.

  13. A Comparison of the Corrosion Resistance of Iron-Based Amorphous Metals and Austenitic Alloys in Synthetic Brines at Elevated Temperature

    Energy Technology Data Exchange (ETDEWEB)

    Farmer, J C

    2008-11-25

    Several hard, corrosion-resistant and neutron-absorbing iron-based amorphous alloys have now been developed that can be applied as thermal spray coatings. These new alloys include relatively high concentrations of Cr, Mo, and W for enhanced corrosion resistance, and substantial B to enable both glass formation and neutron absorption. The corrosion resistances of these novel alloys have been compared to that of several austenitic alloys in a broad range of synthetic brines, with and without nitrate inhibitor, at elevated temperature. Linear polarization and electrochemical impedance spectroscopy have been used for in situ measurement of corrosion rates for prolonged periods of time, while scanning electron microscopy (SEM) and energy dispersive analysis of X-rays (EDAX) have been used for ex situ characterization of samples at the end of tests. The application of these new coatings for the protection of spent nuclear fuel storage systems, equipment in nuclear service, steel-reinforced concrete will be discussed.

  14. Brazing of Ti2AlNb Based Alloy with Amorphous Ti-Cu-Zr-Ni Filler

    Institute of Scientific and Technical Information of China (English)

    WANG Gang; HUANG Yongjiang; WANG Guochao; SHEN Jun; CHEN Zhihao

    2015-01-01

    Amorphous Ti-Cu-Zr-Nifi ller foils with low melting point of 1 133 K were synthesized using a melt-spinning method in argon atmosphere. A Ti2AlNb based alloy was brazed at 1 153-1 223 K for 600-3 000 s. The effects of brazing temperature (Tb) and time (tb) on the shear strength of the joints were investigated. The results showed that the joint strength was signifi cantly affected by the reaction layer thickness. The optimum brazing parameters can be determined as follows:Tb=1 173 K, and tb=600 s. The maximum tensile strength of the joint obtained can reach 260 MPa. Furthermore, the activation energyQand the growth velocityA0 of the reaction layer in the brazed joints were calculated to be 161.742 kJ/mol and 0.213 m2/s, respectively. The growth of the reaction layer (y) could be expressed by the expression:y2 =0.213exp(−19 454/Tb)tb.

  15. Study of oxidation behaviour of Zr-based bulk amorphous alloy Zr65Cu17.5Ni10Al7.5 by thermogravimetric analyser

    Indian Academy of Sciences (India)

    A Dhawan; K Raetzke; F Faupel; S K Sharma

    2001-06-01

    The oxidation behaviour of Zr-based bulk amorphous alloy Zr65Cu17.5Ni10Al7.5 has been studied in air environment at various temperatures in the temperature range 591–684 K using a thermogravimetric analyser (TGA). The oxidation kinetics of the alloy in the amorphous phase obeys the parabolic rate law for oxidation in the temperature range 591–664 K. The values of the activation energy and pre-factor as calculated from the Arrhenius temperature dependence of the rate constants have been found to be 1.80 eV and 2.12 × 109 g cm–2.sec–1/2, respectively.

  16. Upper critical fields and superconducting transition temperatures of some zirconium-base amorphous transition-metal alloys

    Science.gov (United States)

    Karkut, M. G.; Hake, R. R.

    1983-08-01

    Superconducting upper critical fields Hc2(T), transition temperatures Tc and normal-state electrical resistivities ρn have been measured in the amorphous transition-metal alloy series Zr1-xCox, Zr1-xNix, (Zr1-xTix)0.78Ni0.22, and (Zr1-xNbx)0.78Ni0.22. Structural integrity of these melt-spun alloys is indicated by x-ray, density, bend-ductility, normal-state electrical resistivity, superconducting transition width, and mixed-state flux-pinning measurements. The specimens display Tc=2.1-3.8 K, ρn=159-190 μΩ cm, and |(dHc2dT)Tc|=28-36 kG/K. These imply electron mean free paths l~2-6 Å, zero-temperature Ginzburg-Landau coherence distances ξG0~50-70 Å, penetration depths λG0~(7-10)×103 Å, and extremely high dirtiness parameters ξ0l~300-1300. All alloys display Hc2(T) curves with negative curvature and (with two exceptions) fair agreement with the standard dirty-limit theory of Werthamer, Helfand, Hohenberg, and Maki (WHHM) for physically reasonable values of spin-orbit-coupling induced, electron-spin-flip scattering time τso. This is in contrast to the anomalously elevated Hc2(T) behavior which is nearly linear in T that is observed by some, and the unphysically low-τso fits to WHHM theory obtained by others, for various amorphous alloys. Current ideas that such anomalies may be due to alloy inhomogeneity are supported by present results on two specimens for which relatively low-τso fits of Hc2(T) to WHHM theory are coupled with superconductive evidence for inhomogeneity: relatively broad transitions at Tc and Hc2 current-density-dependent transitions at Hc2 and (in one specimen) a J-dependent, high-H (>Hc2), resistive "beak effect." In the Zr1-xCox and Zr1-xNix series, Tc decreases linearly with x (and with unfilled-shell average electron-to-atom ratio in the range 5.05previous results for these systems and contrary to the Tc vs behavior of both amorphous and crystalline transition-metal alloys formed between near neighbors in the Periodic Table. Upper

  17. 非晶态Ni基合金电极电子结构的XPS研究%Study on Electron Structure for Ni Base Amorphous Alloy Electrodes

    Institute of Scientific and Technical Information of China (English)

    莫少波; 杨业智; 王龙彪; 吴俊; 黄清安

    2000-01-01

    用XPS测定了含P、Ce、La的Ni基合金的费米能级及各元素的芯级电子结合能,讨论了合金的电子结构以及它与析氢反应的电催化活性即析氢超电势之间的联系。结果表明:合金中各元素的原子间存在着电荷传输,它对析氢反应活性起重要作用。%A study of the electron structure of nickel base amorphous alloys have been made to explains the difference of the catalytic activity for the hydrogen evolution reaction(HER) between Ni-P amorphous alloys and Ni-Ce-P or Ni-La-P amorphous alloys.These alloy layers all were prepared on copper foil by an electrodeposition with the same condition,based on a series of experiments on the hydrogen evolution overpotential and X-ray photoelectron spectra(XPS),the hydrogen evolution overpotential ηH2,the orbital binding energy and Fermi energy level energy of individual element in amorphous alloys Ni-P,Ni-Ce-P and Ni-La-P were all recorded. From these measured results,some interesting conclusions have been shown as follows:①.The change tendency of the hydrogen evolution overpotential is consistent with that of the binding energy of Ni2p3/2 and P2p in above mentioned three alloys.As the binding energies deflct to low,the values of the hydrogen evolution overpotential ηH2 will decreased.Charge transfer from low electronegativity element to high electronegativity element occurs among atoms,the excess electrons are located near those high electronegativity element atoms.In the case,these excess electrons promote proton discharge and provide preferable sites for hydrogen evolution reaction.As the result,the value of the hydrogen evolution overpotential will decrease,and exhibited similarly charge tendency with the binding energy.②The Fermi energy level is also shown to be correlated with the hydrogen evolution overpotential.It is similar to①that the value hydrogen evolution overpotential decrease when the Fermi energy level energies increase.Since Fermi energy

  18. Microstructure and tribological properties of Zr-based amorphous-nanocrystalline coatings deposited on the surface of titanium alloys by Electrospark Deposition

    Science.gov (United States)

    Hong, Xiang; Tan, Yefa; Zhou, Chunhua; Xu, Ting; Zhang, Zhongwei

    2015-11-01

    In order to improve the wear resistance of titanium alloys, the Zr-based amorphous-nanocrystalline coatings were prepared by Electrospark Deposition (ESD) on the surface of TC11. The microstructure of the coatings was analyzed and the tribological behavior and mechanism of the coatings were investigated. The results show that the coating is mainly composed of amorphous phase Zr55Cu30Al10Ni5 and distributed a large number of nano particles with the diameter between 2 nm and 4 nm such as CuZr3, Ni2Zr3, NiZr2, etc. The new alloy system made up of molten electrode material of Zr-based alloy and TC11 substrate has a large glass forming ability, which transforms to amorphous phase in the rapid heating and cooling ESD process. The long-range diffusions of atoms such as Zr and Cu in amorphous microstructure play an important role in nano nucleation growth. The coating is dense, uniform, bonding with TC11 substrate metallurgically. The thickness of the coating is from 55 μm to 60 μm and the average microhardness is 801.3 HV0.025. The coating has good friction-reducing and anti-wear properties. The friction coefficient of the coating changes between 0.13 and 0.21 with small fluctuation, decreasing about 60% compared to that of TC11 substrate. And the wear resistance of the coating is increased by 57% than that of TC11 substrate. The main wear mechanism of the coating is micro-cutting wear accompanied with oxidation wear.

  19. 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.

  20. Parametrized dielectric functions of amorphous GeSn alloys

    Science.gov (United States)

    D'Costa, Vijay Richard; Wang, Wei; Schmidt, Daniel; Yeo, Yee-Chia

    2015-09-01

    We obtained the complex dielectric function of amorphous Ge1-xSnx (0 ≤ x ≤ 0.07) alloys using spectroscopic ellipsometry from 0.4 to 4.5 eV. Amorphous GeSn films were formed by room-temperature implantation of phosphorus into crystalline GeSn alloys grown by molecular beam epitaxy. The optical response of amorphous GeSn alloys is similar to amorphous Ge and can be parametrized using a Kramers-Kronig consistent Cody-Lorentz dispersion model. The parametric model was extended to account for the dielectric functions of amorphous Ge0.75Sn0.25 and Ge0.50Sn0.50 alloys from literature. The compositional dependence of band gap energy Eg and parameters associated with the Lorentzian oscillator have been determined. The behavior of these parameters with varying x can be understood in terms of the alloying effect of Sn on Ge.

  1. Effects of Microalloying on Glass Forming Ability and Thermodynamic Fragility of Cu-Pr-Based Amorphous Alloys

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The effects of microalloying of Ti and B on the glass formation of Cu60Pr30Ni10Al10-2xTixBx(x=0, 0.05%(atom fraction)) amorphous alloys was investigated using differential scanning calorimetry (DSC) and X-ray diffraction (XRD). XRD analysis showed that microalloying with 0.05% Ti and 0.05% B improved the glass forming ability (GFA). The smaller difference in the Gibbs free energy between the liquid and crystalline states at the glass transition temperature (ΔGl-x (Tg)) and the smaller thermodynamic fragility index (ΔSf/Tm, where ΔSf is the entropy of fusion, and Tm is the melting temperature) after microalloying correlated with the higher GFA.

  2. Thermal treatment of the amorphous base alloy Fe 2605SA1, analysis of its defects and microhardness; Tratamiento termico de la aleacion amorfa base Fe 2605SA1, analisis de sus defectos y microdureza

    Energy Technology Data Exchange (ETDEWEB)

    Contreras V, J.A.; Cabral P, A.; Garcia Santibanez S, F.; Ramirez, J.; Lopez M, J.; Villaverde L, A.; Montoya E, A.; Merino, F.J. [Facultad de Ciencias, Universidad Autonoma del Estado de Mexico. El Cerillo Piedras Blancas, 50000 Toluca, Estado de Mexico (Mexico)

    2007-07-01

    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)

  3. Medium-Range Order Structure and Fragility of Superheated Melts of Amorphous CuHf Alloys

    Institute of Scientific and Technical Information of China (English)

    BIAN Xiu-Fang; SUN Bao-An; HU Li-Na

    2006-01-01

    @@ The structural factors of amorphous CuHf alloys at different temperatures are determined by using a high temperature x-ray diffractometer. It is found that not only the short-range order structure but also the medium-range order structure exists in amorphous CuHf alloys. The dynamic viscosities of CuHf alloy melts are measured by a torsional oscillation viscometer. The fragility of superheated melts of CuHf alloys is calculated based on the viscosity data. The experimental results show that the glass-forming ability of the CuHf alloys is closely related to the fragility of their superheated melt. The relationship between the medium-range order structures and the fragility of superheated melts has also been established in amorphous CuHf alloys. In contrast to the fragility of supercooled liquids, the fragility of superheated liquids promises a better approach to reflecting the dynamics of glass forming liquids.

  4. Design of multi materials combining crystalline and amorphous metallic alloys

    Energy Technology Data Exchange (ETDEWEB)

    Volland, A.; Ragani, J.; Liu, Y.; Gravier, S.; Suery, M. [Grenoble University/CNRS, SIMAP Laboratory, Grenoble INP/UJF, 38402 Saint-Martin d' Heres (France); Blandin, J.J., E-mail: jean-jacques.blandin@simap.grenoble-inp.fr [Grenoble University/CNRS, SIMAP Laboratory, Grenoble INP/UJF, 38402 Saint-Martin d' Heres (France)

    2012-09-25

    Highlights: Black-Right-Pointing-Pointer Elaboration of multi materials associating metallic glasses and conventional crystalline alloys by co-deformation performed at temperatures close to the glass transition temperature of the metallic glasses. Black-Right-Pointing-Pointer Elaboration of filamentary metal matrix composites with a core in metallic glass by co extrusion. Black-Right-Pointing-Pointer Sandwich structures produced by co-pressing. Black-Right-Pointing-Pointer Detection of atomic diffusion from the glass to the crystalline alloys during the processes. Black-Right-Pointing-Pointer Good interfaces between the metallic glasses and the crystalline alloys, as confirmed by mechanical characterisation. - Abstract: Multi materials, associating zirconium based bulk metallic glasses and crystalline metallic alloys like magnesium alloys or copper are elaborated by co-deformation processing performed in the supercooled liquid regions (SLR) of the bulk metallic glasses. Two processes are investigated: co-extrusion and co-pressing. In the first case, filamentary composites with various designs can be produced whereas in the second case sandwich structures are obtained. The experimental window (temperature, time) in which processing can be carried out is directly related to the crystallisation resistance of the glass which requires getting information about the crystallisation conditions in the selected metallic glasses. Thermoforming windows are identified for the studied BMGs by thermal analysis and compression tests in their SLR. The mechanical properties of the produced multi materials are investigated thanks to specifically developed mechanical devices and the interfaces between the amorphous and the crystalline alloys are characterised.

  5. High-Efficiency Amorphous Silicon Alloy Based Solar Cells and Modules; Final Technical Progress Report, 30 May 2002--31 May 2005

    Energy Technology Data Exchange (ETDEWEB)

    Guha, S.; Yang, J.

    2005-10-01

    The principal objective of this R&D program is to expand, enhance, and accelerate knowledge and capabilities for development of high-efficiency hydrogenated amorphous silicon (a-Si:H) and amorphous silicon-germanium alloy (a-SiGe:H) related thin-film multijunction solar cells and modules with low manufacturing cost and high reliability. Our strategy has been to use the spectrum-splitting triple-junction structure, a-Si:H/a-SiGe:H/a-SiGe:H, to improve solar cell and module efficiency, stability, and throughput of production. The methodology used to achieve the objectives included: (1) explore the highest stable efficiency using the triple-junction structure deposited using RF glow discharge at a low rate, (2) fabricate the devices at a high deposition rate for high throughput and low cost, and (3) develop an optimized recipe using the R&D batch large-area reactor to help the design and optimization of the roll-to-roll production machines. For short-term goals, we have worked on the improvement of a-Si:H and a-SiGe:H alloy solar cells. a-Si:H and a-SiGe:H are the foundation of current a-Si:H based thin-film photovoltaic technology. Any improvement in cell efficiency, throughput, and cost reduction will immediately improve operation efficiency of our manufacturing plant, allowing us to further expand our production capacity.

  6. 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.

  7. 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.

  8. Powder Processing of Amorphous Tungsten-bearing Alloys and Composites

    Science.gov (United States)

    2015-03-01

    8725 John J. Kingman Road, MS-6201 Fort Belvoir, VA 22060-6201 T E C H N IC A L R E P O R T DTRA-TR-14-73 Powder Processing of Amorphous Tungsten ...Technology, Boise State University, Army Research Laboratory Project Title: Powder Processing of Amorphous Tungsten -bearing Alloys and Composites...strength, we made them better suited to study the mechanical alloying of tungsten -transition metal couples in which interdiffusion during mechanical

  9. Effect of heat treatment in air and a chemically active environment on the magnetic properties of cobalt-based soft magnetic amorphous alloys

    Science.gov (United States)

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

    2016-10-01

    The influence of heat treatment in air on the level of magnetic properties has been studied on the example of a ribbon of an amorphous cobalt-based (Co-Fe-Ni-Cr-Si-B) soft-magnetic alloy with a nearzero saturation magnetostriction. The investigation of the interaction of the ribbon surface with water and water vapor and its influence on the magnetization distribution showed the possibility of applying surface treatment to determine the sign of saturation magnetostriction. The sign of saturation magnetostriction in the initial (quenched) state confirmed the presence of a negative magnetostriction in the ribbon. Based on the results obtained, the dependence of the sign of saturation magnetostriction on the structural state that is obtained upon heat treatment has been revealed.

  10. 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.

  11. Parametrized dielectric functions of amorphous GeSn alloys

    Energy Technology Data Exchange (ETDEWEB)

    D' Costa, Vijay Richard, E-mail: elevrd@nus.edu.sg; Wang, Wei; Yeo, Yee-Chia, E-mail: eleyeoyc@nus.edu.sg [Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117583 (Singapore); Schmidt, Daniel [Singapore Synchrotron Light Source, National University of Singapore, Singapore 117603 (Singapore)

    2015-09-28

    We obtained the complex dielectric function of amorphous Ge{sub 1−x}Sn{sub x} (0 ≤ x ≤ 0.07) alloys using spectroscopic ellipsometry from 0.4 to 4.5 eV. Amorphous GeSn films were formed by room-temperature implantation of phosphorus into crystalline GeSn alloys grown by molecular beam epitaxy. The optical response of amorphous GeSn alloys is similar to amorphous Ge and can be parametrized using a Kramers-Kronig consistent Cody-Lorentz dispersion model. The parametric model was extended to account for the dielectric functions of amorphous Ge{sub 0.75}Sn{sub 0.25} and Ge{sub 0.50}Sn{sub 0.50} alloys from literature. The compositional dependence of band gap energy E{sub g} and parameters associated with the Lorentzian oscillator have been determined. The behavior of these parameters with varying x can be understood in terms of the alloying effect of Sn on Ge.

  12. Properties of electrodeposited amorphous Fe-Ni-W alloy deposits

    Institute of Scientific and Technical Information of China (English)

    HE Feng-jiao; WANG Miao; LU Xin

    2006-01-01

    A new technique of electroplating amorphous Fe-Ni-W alloy deposits was proposed. The structure and morphology of Fe-Ni-W alloy deposit were detected by XRD and SEM. The friction and wear behavior of Fe-Ni-W alloy deposit were studied and compared with that of chromium deposit. The corrosion properties against 5% sodium chloride, 5% sulfuric acid and 5% sodium hydroxide were also discussed. The experimental results indicate that Fe-Ni-W alloy deposits have superior properties against wear than hard chromium deposits under dry sliding condition. Under oil sliding condition, except their better wear resistance, the deposits can protect their counterparts against wear. The deposits plated on brass and AISI 1045 steel show good behavior against corrosion of 5% sodium chloride, 5% sulfuric acid and 5% sodium hydroxide. The bath of electroplating amorphous Fe-Ni-W alloy deposits is environmentally friendly and would find widely use in industry.

  13. 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

  14. Electroplating process of amorphous Fe-Ni-Cr alloy

    Institute of Scientific and Technical Information of China (English)

    何湘柱; 夏畅斌; 王红军; 龚竹清; 蒋汉瀛

    2001-01-01

    A novel process of electroplating amorphous Fe-Cr-Ni alloy in chloride aqueous solution with Fe( Ⅱ ), Ni ( lⅡ ) and Cr( Ⅲ ) was reported. Couple plasma atomic emission spectrometry (ICP-AES), X-ray diffractometry(XRD),scanning electronic microscopy(SEM), microhardness test and rapid heating-cooling method were adopted to detect the properties of the amorphous Fe-Ni-Cr deposit, such as composition, crystalline structure, micrograph, hardness, and adherence between deposit and substrate. The effects of the operating parameters on the electrodeposit of the amorphous FeNi-Cr alloy were discussed in detail. The results show that a 8.7 μm thick mirror-like amorphous Fe-Ni-Cr alloy deposit,with Vicker's hardness of 530 and composition of 45%~55% Fe, 33%~37% Ni, 9%~23% Cr was obtained by electroplating for 20 min at room temperature( 10 30 C ), cathode current 10~16 A/dm2, pH = 1.0~3.0. The XRD pat terns show that there only appears a broad hump around 2θ of 41 °~47 °for the amorphous Fe-Ni-Cr alloy deposit, while the SEM micrographs show that the deposit contains only a few fine cracks but no pinholes.

  15. XAFS Study on Solid State Amorphization of Alloys by Mechanical Alloying

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Structural evolution of alloys by ball-milling during solid stateamorphization were studied by means of XAFS technique. The first one is amorphization process of Fe and B powder mixtures by mechanical alloying (MA), and the second one is amorphization process of ordered B2 CoZr intermetallic compound by mechanical milling (MM). The mixing process of Fe and B and disintegration process of ordered B2 CoZr intermetallic compound crystal were observed clearly in atomic level by XAFS method. The micro-mechanism of amorphization process of alloy by ball-milling was discussed.

  16. Hydrogen Storage Characteristics of Nanocrystalline and Amorphous Nd-Mg-Ni-Based NdMg12-Type Alloys Synthesized via Mechanical Milling

    Science.gov (United States)

    Zhang, Yanghuan; Shang, Hongwei; Hou, Zhonghui; Yuan, Zeming; Yang, Tai; Qi, Yan

    2016-09-01

    In this study, Mg was partially substituted by Ni with the intent of improving the hydrogen storage kinetics performance of NdMg12-type alloy. Mechanical milling technology was adopted to fabricate the nanocrystalline and amorphous NdMg11Ni + x wt pct Ni (x = 100, 200) alloys. The effects of Ni content and milling duration on the microstructures and hydrogen storage kinetics of as-milled alloys have been systematically investigated. The structures were characterized by XRD and HRTEM. The electrochemical hydrogen storage properties were tested by an automatic galvanostatic system. Moreover, the gaseous hydrogen storage properties were investigated by Sievert apparatus and a differential scanning calorimeter connected with a H2 detector. Hydrogen desorption activation energy of alloy hydrides was estimated by using Arrhenius and Kissinger methods. The results reveal that the increase of Ni content dramatically ameliorates the gaseous and electrochemical hydrogen storage kinetics performance of the as-milled alloys. Furthermore, high rate discharge ability (HRD) reach the maximum value with the variation of milling time. The maximum HRDs of the NdMg11Ni + x wt pct Ni (x = 100, 200) alloys are 80.24 and 85.17 pct. The improved gaseous hydrogen storage kinetics of alloys via increasing Ni content and milling time can be attributed to a decrease in the hydrogen desorption activation energy.

  17. Hydrogen Storage Characteristics of Nanocrystalline and Amorphous Nd-Mg-Ni-Based NdMg12-Type Alloys Synthesized via Mechanical Milling

    Science.gov (United States)

    Zhang, Yanghuan; Shang, Hongwei; Hou, Zhonghui; Yuan, Zeming; Yang, Tai; Qi, Yan

    2016-12-01

    In this study, Mg was partially substituted by Ni with the intent of improving the hydrogen storage kinetics performance of NdMg12-type alloy. Mechanical milling technology was adopted to fabricate the nanocrystalline and amorphous NdMg11Ni + x wt pct Ni ( x = 100, 200) alloys. The effects of Ni content and milling duration on the microstructures and hydrogen storage kinetics of as-milled alloys have been systematically investigated. The structures were characterized by XRD and HRTEM. The electrochemical hydrogen storage properties were tested by an automatic galvanostatic system. Moreover, the gaseous hydrogen storage properties were investigated by Sievert apparatus and a differential scanning calorimeter connected with a H2 detector. Hydrogen desorption activation energy of alloy hydrides was estimated by using Arrhenius and Kissinger methods. The results reveal that the increase of Ni content dramatically ameliorates the gaseous and electrochemical hydrogen storage kinetics performance of the as-milled alloys. Furthermore, high rate discharge ability (HRD) reach the maximum value with the variation of milling time. The maximum HRDs of the NdMg11Ni + x wt pct Ni ( x = 100, 200) alloys are 80.24 and 85.17 pct. The improved gaseous hydrogen storage kinetics of alloys via increasing Ni content and milling time can be attributed to a decrease in the hydrogen desorption activation energy.

  18. EFFECT OF PRE-ALLOYING CONDITION ON THE BULK AMORPHOUS ALLOY ND(60)FE(30)AL(10).

    Energy Technology Data Exchange (ETDEWEB)

    OCONNOR,A.S.; LEWIS,L.H.; MCCALLUM,R.W.; DENNIS,K.W.; KRAMER,M.J.; KIM ANH,D.T.; DAN,N.H.; PHUC,N.X.

    2000-09-10

    Bulk metallic glasses are materials that require only modest cooling rates to obtain amorphous solids directly from the melt. Nd{sub 60}Fe{sub 30}Al{sub 10} has been reported to be a ferromagnetic bulk metallic glass that exhibits high coercivity, a combination unlike conventional Nd-based amorphous magnetic alloys. To clarify the relationship between short-range order and high coercivity in glassy Nd{sub 60}Fe{sub 30}Al{sub 10}, experiments were performed to verify the existence of a homogeneous liquid state prior to rapid solidification. Alloys were prepared by various pre-alloying routes and then melt-spun. Arc-melted alloys were prepared for melt spinning using three different protocols involving: (1) alloying all three elements at once, (2) forming a Nd-Fe alloy which was subsequently alloyed with Al, and (3) forming a Fe-Al alloy for subsequent alloying with Nd. XRD, DTA, and magnetic measurement data from the resultant ribbons indicate significant differences in both the glassy fraction and the crystalline phase present in the as-spun material. These observed differences are attributed to the presence of highly stable nanoscopic aluminide-and/or silicide-phases, or motes, present in the melt prior to solidification. These motes would affect the short-range order and coercivity of the resultant glassy state and are anticipated to provide heterogeneous nucleation sites for crystallization.

  19. Corrosion behavior of Mg-Zn-Ca amorphous alloys with Nd addition in simulated body fluids

    Directory of Open Access Journals (Sweden)

    Qin Chunling

    2014-11-01

    Full Text Available The effects of Nd addition on corrosion behavior of Mg66Zn30Ca4 amorphous alloys in simulated body fluids (SBF were studied in this paper. Electrochemical properties of the samples before and after corrosion were determined. Surface morphologies of samples after immersion in SBF at 37 篊 for different times were observed under scanning electron microscope (SEM. Results show that the corrosion resistance of Mg-based alloys in SBF is improved with the addition of Nd element. The electrochemical properties indicate that microalloying Nd element to the alloys leads to an ennoblement in the open circuit potentials of the alloys and a decrease in the anodic current density in SBF, especially for the Mg66-xZn30Ca4Ndx alloys with Nd content of 1.0at.%-1.5at.%. It was observed that the surface morphologies of the alloys immersed in SBF change with the Nd addition. A flake-like structure parallel to the alloy substrate formed on the surface of 1.0at.% Nd-containing alloy immersed in SBF for 7 days improves the corrosion resistance of the amorphous alloys by blocking the corrosion liquid from attacking the alloys.

  20. SOME PECULIARITIES OF DUCTILE SHEAR FAILURE OF AMORPHOUS ALLOY RIBBONS

    NARCIS (Netherlands)

    BENGUS, VZ; TABACHNIKOVA, ED; SHUMILIN, SE; GOLOVIN, YI; MAKAROV, MV; SHIBKOV, AA; MISKUF, J; CSACH, K; Ocelik, Vaclav

    1993-01-01

    The kinetics of a shear crack propagation under ductile shear failure of amorphous alloys ribbons is studied experimentally. Some phenomena that accompany this failure are also studied: repeated alternation of the shear crack orientation, plastic corrugation of a ribbon, extreme local heating at the

  1. 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.

  2. 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.

  3. 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.

  4. Shear-band propagation in fully amorphous and partially crystallized Mg-based alloys studied by nanoindentation and transmission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Castellero, A. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom) and Laboratory of Metal Physics and Technology, Department of Materials, ETH Zuerich, Wolfgang-Pauli-Strasse 10, CH-8093 Zurich (Switzerland)]. E-mail: alberto.castellero@unito.it; Lloyd, S.J. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Madge, S.V. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), PO Balapur, Hyderabad 500 005 (India); Kovacs, Zs. [Department of General Physics, Eoetvoes Lorand University, Pazmany P. setany 1/a, 1117 Budapest (Hungary); Loeffler, J.F. [Laboratory of Metal Physics and Technology, Department of Materials, ETH Zuerich, Wolfgang-Pauli-Strasse 10, CH-8093 Zurich (Switzerland); Baricco, M. [Dipartimento di Chimica I.F.M. and N.I.S., Universita degli Studi di Torino, Via P. Giuria 9, I-10125 Turin (Italy); Greer, A.L. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom)

    2007-05-31

    Fully amorphous and partially crystallized Mg{sub 66}Ni{sub 20}Nd{sub 14} and partially crystallized Mg{sub 60}Cu{sub 30}Y{sub 10} alloys were indented and, subsequently, thinned along the cross-section of the indent by means of a focused ion beam (FIB) for transmission electron microscopy (TEM) observation. Depending on the crystallized fraction and the crystal size, the volume deformed under the indenter tip shows different features that can be associated with the different ability of the shear bands to propagate in the two partially devitrified metallic glasses.

  5. Surface magnetic anisotropy in amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Tejedor, M.; Rubio, H.; Elbaile, L.; Iglesias, R. (Univ. de Oviedo (Spain). Dept. de Fisica)

    1993-11-01

    The total in-plane magnetic anisotropy and the in-plane surface magnetic anisotropy constants have been measured in nearly-zero magnetostrictive amorphous ribbons in as-quenched state. The magnetostatic energy of a two-dimensional square-lattice of parallelepipeds or ellipsoids, whose dimensions are determined by the parameters characterizing the roughness, is evaluated. From the results obtained, they can conclude that the in-plane surface anisotropy can be magnetostatic in origin but it has little influence on the total in-plane magnetic anisotropy of the ribbon.

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

    Energy Technology Data Exchange (ETDEWEB)

    Moreno-Ramírez, L.M.; Blázquez, J.S.; Franco, V.; Conde, A. [Dpto. Física de la Materia Condensada, ICMSE-CSIC, Universidad de Sevilla, P.O. Box 1065, 41080 Sevilla (Spain); Marsilius, M.; Budinsky, V.; Herzer, G. [Vacuumschmelze GmbH & Co KG, Grüner Weg 37, D-63450 Hanau (Germany)

    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 Fe{sub 74-x}Cr{sub x}Cu{sub 1}Nb{sub 3}Si{sub 15.5}B{sub 6.5} (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{sup −1} K{sup −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. - Highlights: • Study of magnetocaloric effect of amorphous and nanocrystalline Cr-Vitroperm alloys. • Cr content decreases the magnetocaloric response and the Curie temperature. • Nanocrystallization reduces MCE and modifies T{sub C} in a non-monotonous way. • The large difference between T{sub C} of phases decreases MCE of composite.

  7. 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.

  8. Amorphization in Gd-Co alloys and multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Alonso, J.A. [Departamento de Fisica Teorica, Universidad de Valladolid, Valladolid (Spain); Hojvat de Tendler, R. [Instituto de Estudios Nucleares, Centro Atomico Ezeiza, CNEA, Buenos Aires (Argentina); Barbiric, D.A. [Departamento de Quimica Inorganica, Analitica y Quimica Fisica, Universidad de Buenos Aires, Buenos Aires (Argentina); Riveiro, J.M. [Departamento de Fisica Aplicada, Universidad de Castilla-La Mancha, Ciudad Real (Spain)

    2002-10-07

    A semiempirical model is used to analyse the results of published experiments reporting on the solid-state amorphization reactions in bilayers and multilayers formed by Gd and Co. The role of the interfacial effects in raising the free energy of the initial arrangement in a multilayered configuration, and in promoting the amorphization reaction, is studied in detail. The model explains the observation of amorphous alloys over a broad composition range in the bilayer experiments. The preferred composition obtained in the multilayer experiments is discussed critically and the model prediction of a preferred composition Gd{sub 0.46}Co{sub 0.54} is in good agreement with the compositions observed in recent experiments. (author)

  9. 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)

  10. Capacity Fading Mechanism for Mg-Based Amorphous Electrode Alloys%镁基非晶电极合金的容量衰减机制探讨

    Institute of Scientific and Technical Information of China (English)

    黄林军; 王彦欣; 唐建国; 吴东昌; 王瑶; 刘继宪

    2013-01-01

    采用熔体快淬法制备了(Mg70.6 Ni29.4)100-xNdx(x=2,5,10,15)电极合金带,用恒流充放电的方法在三电极电池测试仪上测定其电化学循环性能.用X射线衍射仪、场发射扫描电镜和高分辨电镜对合金在充放电循环过程中的组织结构变化进行了动态检测.结果表明:(Mg70.6 Ni29.4)90Nd10非晶电极合金拥有最高的放电容量(580.5 mAh·g-1),经过20个循环以后,合金表面存在严重的氧化(含氧量为26.7%)和开裂粉化现象;在充放电循环过程中,合金内部逐渐形核长大,形核的初生相NdMg2 Ni9最终转化为Mg2 Ni,α-Mg和Nd2H5相;非晶态Mg-Ni-Nd电极合金在充放电循环过程中放电容量的衰减来自于内外两个方面的综合效应:合金表面碱液的氧化腐蚀和开裂粉化以及非晶合金的晶化导致其贮氢机制失效,反应动力学性能下降,从而引起放电容量的衰减.%Amorphous and nanocrystalline ( Mg70.6Ni29.4 ) 100-xNdx (x = 2, 5, 10, 15) alloys were prepared by rapid solidification. The electrochemical cycling performance was measured by three-electrode cell tester. The phase structures of the ribbons before and after charge/discharge cycling were characterized by high-resolution transmission electron microscopy ( HRTEM) , X-ray diffraction (XRD) and field emission scanning electron microscope(SEM) , respectively. It was found that the amorphous ( Mg70.6Ni29.4)90Nd10 alloy had the highest discharge capacity ( 580. 5 mAh ·g -1 ) , after 20 cycles, there was a serious oxidation ( oxygen content of 26. 7% ) and cracking of the chalking phenomenon in the alloy surface and the NdMg2Ni9 phase formed at beginning gradually decomposed into Mg2Ni, α-Mg and Nd2H5 phases as hydrogenation/dehydrogenation proceeds. The discharge capacity decayed for amorphous Mg-Ni-Nd electrode alloys in the charge-discharge cycle process came from both internal and external aspects: the oxidation of the alloy surface lye corrosion and cracking of the

  11. Formation of nanophases by crystallization of amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Baricco, M. [Turin Univ. (Italy). Dipt. di Chimica Inorganica; Tiberto, P. [Istituto Elettrotecnico Nazionale, Turin (Italy); Battezzati, L. [Turin Univ. (Italy). Dipt. di Chimica Inorganica

    1995-12-31

    A comparison is made of crystallization mechanisms in Fe-based amorphous alloys (Fe{sub 73.5}Cu{sub 1}Nb{sub 3}Si{sub 13.5}B{sub 9}, Fe{sub 90}Zr{sub 7}B{sub 3}), which lead to a nanocrystalline bcc phase with peculiar soft magnetic properties through primary crystallization. In all samples, the nucleation takes place uniformely throughout the material. The presence of atoms with low diffusivity (Zr, Nb) reduces the grain growth rate so that a small size of crystals is maintained. On the contrary, even extremely fast heating and short heat treatment do not produce nanocrystals in Fe{sub 40}Ni{sub 40}B{sub 20} although the crystallization mechanism is modified. However milling the ribbon leads to nanostructured crystalline phases. The formation of nanophases by crystallization is discussed considering the temperature dependence of nucleation frequency and growth rate. The effects of various thermodynamic and kinetic parameters are analyzed and the most favourable conditions for nanocrystallization are outlined. (orig.)

  12. Bulk amorphous metallic alloys: Synthesis by fluxing techniques and properties

    Energy Technology Data Exchange (ETDEWEB)

    He, Yi; Shen, Tongde; Schwarz, R.B.

    1997-05-01

    Bulk amorphous alloys having dimensions of at least 1 cm diameter have been prepared in the Pd-Ni-P, Pd-Cu-P, Pd-Cu-Ni-P, and Pd-Ni-Fe-P systems using a fluxing and water quenching technique. The compositions for bulk glass formation have been determined in these systems. For these bulk metallic glasses, the difference between the crystallization temperature T{sub x}, and the glass transition temperature T{sub g}, {Delta}T = T{sub x} - T{sub g}, ranges from 60 to 1 10 K. These large values of {Delta}T open the possibility for the fabrication of amorphous near net-shape components using techniques such as injection molding. The thermal, elastic, and magnetic properties of these alloys have been studied, and we have found that bulk amorphous Pd{sub 40}Ni{sub 22.5}Fe{sub 17.5}P{sub 20} has spin glass behavior for temperatures below 30 K. 65 refs., 14 figs., 3 tabs.

  13. 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.)

  14. Preparation and characterization of electroplated amorphous gold-nickel alloy film for electrical contact applications

    Energy Technology Data Exchange (ETDEWEB)

    Togasaki, Norihiro [Department of Applied Chemistry, Waseda University, Okubo, Shinjuku, Tokyo 169-8555 (Japan); Okinaka, Yutaka [Advanced Research Institute for Science and Engineering, Waseda University, Okubo, Shinjuku, Tokyo 169-8555 (Japan); Homma, Takayuki [Department of Applied Chemistry, Waseda University, Okubo, Shinjuku, Tokyo 169-8555 (Japan); Advanced Research Institute for Science and Engineering, Waseda University, Okubo, Shinjuku, Tokyo 169-8555 (Japan); Osaka, Tetsuya [Department of Applied Chemistry, Waseda University, Okubo, Shinjuku, Tokyo 169-8555, Japan and Advanced Research Institute for Science and Engineering, Waseda University, Okubo, Shinjuku, Tokyo 169-8555 (Japan)]. E-mail: osakatet@waseda.jp

    2005-11-10

    A process for electroplating amorphous gold-nickel alloy with the atomic ratio of unity was developed. The plating bath was prepared by adding potassium cyanoaurate(I) into a known plating bath which produces amorphous nickel-tungsten alloy. At a sufficiently high gold concentration, the alloy deposit did not contain any tungsten. The amorphous nature of the Au-Ni alloy produced in the new bath was confirmed by using TEM and THEED. Hardness, resistivity, and contact resistance of this new alloy were determined, and the results are discussed for applications as an electrical contact material.

  15. Structural and thermal properties of Cu-Hf-Ti bulk amorphous alloys

    Science.gov (United States)

    Rontó, V.; Nagy, E.; Svéda, M.; Roósz, A.; Tranta, F.

    2009-01-01

    Cu-Hf-Ti amorphous alloys are high strength and wear resistant materials. Master alloys of Cu57.5Hf27.5Ti15 and Cu57.5Hf25Ti17.5 ternary alloys have been prepared by arc melting, and wedge and rod shaped samples have been cast by centrifugal casting. Liquidus and solidus temperatures of the alloys were determined by DTA. The fully amorphous size was determined by X-ray diffraction. Thermodynamic properties of the amorphous alloys were studied by DSC measurements and Kissinger analyses were performed.

  16. 非晶态铁基合金退火样品的偏移回线%DISPLACED HYSTERESIS LOOPS IN ANNEALED Fe-BASED AMORPHOUS ALLOYS

    Institute of Scientific and Technical Information of China (English)

    李印峰; 李笃行; 等

    2001-01-01

    报道了非晶态铁基合金(Fe65.9Cr11.6Si7.5 B15和Fe60Co5.9Cr11.6Si7.5B15)退火样品的回线 偏 移现象. 研究了偏移回线与测量磁场Hm,温度T和时间t的关系. 基于退火产生的 硬磁颗粒与剩余非晶软磁母体之间的静磁相互作用机制,利用等效的单向各向异性模型可以很好地分析和解释实验结果.%We report the displaced hysteresis loops in the annealed amorphous alloys Fe 65.9Cr11.6Si7.5B15 and Fe60Co5.9Cr11.6Si 7.5B15. The effects of measuring field Hm, temperature T and time t on the displacement HD have been studied. On the basis of t he magnetostatic interaction between the hard particle resulting from the anneal i ng and the residual amorphous soft matrix, the experiments could be well explain ed by the unidirectional anisotropy model.

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

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The blistering and flaking behavior of many kinds of amorphous al loys under helium ion bombardment at room temperature was investigated. Helium ions with energies of 40keV and 60keV were implanted within the fluence range (1.0~4.0)×1018ions/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, secondgeneration blistering and porous structure. The dependdence of surface damage modesand the critical fluence for the onset of blistering and flaking on the sort of materials and ion energy was discussed.

  18. Deformation-driven catalysis of nanocrystallization in amorphous Al alloys

    Directory of Open Access Journals (Sweden)

    Rainer J. Hebert

    2016-10-01

    Full Text Available Nanocrystals develop in amorphous alloys usually during annealing treatments with growth- or nucleation-controlled mechanisms. An alternative processing route is intense deformation and nanocrystals have been shown to develop in shear bands during the deformation process. Some controversy surrounded the idea of adiabatic heating in shear bands during their genesis, but specific experiments have revealed that the formation of nanocrystals in shear bands has to be related to localized deformation rather than thermal effects. A much less debated issue has been the spatial distribution of deformation in the amorphous alloys during intense deformation. The current work examines the hypothesis that intense deformation affects the regions outside shear bands and even promotes nanocrystal formation in those regions upon annealing. Melt-spun amorphous Al88Y7Fe5 alloy was intensely cold rolled. Microcalorimeter measurements at 60 °C indicated a slight but observable growth of nanocrystals in shear bands over the annealing time of 10 days. When the cold-rolled samples were annealed at 210 °C for one hour, transmission electron images did not show any nanocrystals for as-spun ribbons, but nanocrystals developed outside shear bands for the cold rolled samples. X-ray analysis indicated an increase in intensity of the Al peaks following the 210 °C annealing while the as-spun sample remained “X-ray amorphous”. These experimental observations strongly suggest that cold rolling affects regions (i.e., spatial heterogeneities outside shear bands and stimulates the formation of nanocrystals during annealing treatments at temperatures well below the crystallization temperature of undeformed ribbons.

  19. Co-Fe based amorphous alloy corrosion resistance: Effects of composition and heat treatment; Effetto della composizione e dei trattamenti termici sulla resistenza alla corrosione di leghe amorfe a base di ferro e cobalto

    Energy Technology Data Exchange (ETDEWEB)

    Angelini, E.; Antonione, C.; Baricco, M.; Rosalbino, F.; Zucchi, F.

    1990-12-31

    This paper examines the influence of composition and heat treatment on the corrosion resistance, in a 1.5 pH solution of Na/sub 2/SO/sub 4/ 0.05M + H/sub 2/SO/sub 4/ 0.05M, of series of iron based amorphous alloys with increasing cobalt content, i.e., Fe/sub 80-x/Co/sub x/B/sub 10/Si/sub 10/ with values of x = 0,30,80. The heat treatments were carried out in an argon atmosphere at increasing durations (30, 60, 120 and 240 min) and temperatures (350, 400, 450, and 500 degrees C). Independently of the type of heat treatment, it was observed that the corrosion resistance increases with increasing cobalt concentration. In comparing samples having the same composition, corrosion resistance deteriorated with increasing heat treatment duration times and temperatures.

  20. 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...

  1. New Approaches to the Computer Simulation of Amorphous Alloys: A Review

    Directory of Open Access Journals (Sweden)

    Fernando Alvarez-Ramirez

    2011-04-01

    Full Text Available In this work we review our new methods to computer generate amorphous atomic topologies of several binary alloys: SiH, SiN, CN; binary systems based on group IV elements like SiC; the GeSe2 chalcogenide; aluminum-based systems: AlN and AlSi, and the CuZr amorphous alloy. We use an ab initio approach based on density functionals and computationally thermally-randomized periodically-continued cells with at least 108 atoms. The computational thermal process to generate the amorphous alloys is the undermelt-quench approach, or one of its variants, that consists in linearly heating the samples to just below their melting (or liquidus temperatures, and then linearly cooling them afterwards. These processes are carried out from initial crystalline conditions using short and long time steps. We find that a step four-times the default time step is adequate for most of the simulations. Radial distribution functions (partial and total are calculated and compared whenever possible with experimental results, and the agreement is very good. For some materials we report studies of the effect of the topological disorder on their electronic and vibrational densities of states and on their optical properties.

  2. Influence Intensive Plastic Deformation on Phase Formation Process in Amorphous Alloys

    Directory of Open Access Journals (Sweden)

    V.I. Lysov

    2016-06-01

    Full Text Available The influence of intensive plastic deformation on structure and properties of amorphous alloys were investigated experimentally. Using highly sensitive dilatometer techniques shown that intensive plastic deformation of amorphous alloys leads to increased of thermal stability interval that can be explained by a shift of the phase equilibria in heterogeneous system: amorphous matrix - frozen crystallization centers. Thus there is a dissolution frozen crystallization centers present in the original sample that confirmed by electron researches.

  3. 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

  4. Calculating formation range of binary amorphous alloys fabricated by electroless plating

    Science.gov (United States)

    Zhang, Bangwei; Liao, Shuzhi; Shu, Xiaolin; Xie, Haowen

    2016-06-01

    A lot of amorphous alloy deposits in the binary (Ni, Co, Cu)-(P, B) alloy systems fabricated by electroless plating (EP) have been reported up to date. But no one reported their theoretical modeling of the amorphous formation and calculated their concentration range of amorphous formation (RAF). Using Miedema model and subregular model scheme, the RAFs for the six EP (Ni, Co, Cu)-(P, B) alloys and three Ni-Cu, Ni-Co and Co-Cu alloys have been calculated systematically for the first time. The calculated results are in agreement with experimental observations. Experiments and calculations for the RAFs in the latter three alloy systems reveal that not any RAF formed except crystalline states. The huge difference between the six metal-metalloid alloys and three metal-metal alloys in RAF has been discussed in detail in the paper.

  5. 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.

  6. Crystallization behaviour of Al-Sm amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Battezzati, L. (Dipartimento di Chimica Inorganica, Chimica Fisica e Chimica dei Materiali, Universita di Torino, Via P. Giuria 9, 10125 Torino (Italy)); Baricco, M. (Dipartimento di Chimica Inorganica, Chimica Fisica e Chimica dei Materiali, Universita di Torino, Via P. Giuria 9, 10125 Torino (Italy)); Schumacher, P. (Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom)); Shih, W.C.; Greer, A.L.

    1994-05-01

    Various Al[sub 100-x]Sm[sub x] alloys (10[<=]qslantx[<=]qslant14) have been rapidly solidified by single-roller melt spinning with careful control of the atmosphere in the quenching device. The structural state and subsequent devitrification behaviour of the melt-spun ribbons are found to be particularly sensitive to the quenching conditions. Except for the thinnest ribbons, there are inhomogeneities both through the ribbon thickness and along the length. Both fully and partially amorphous ribbons have been obtained. The crystallization processes of the amorphous phases have been followed by X-ray diffraction, transmission electron microscopy and differential scanning calorimetry (DSC). Al[sub 92]Sm[sub 8] shows primary crystallization of Al, followed by the formation of metastable phases; Al[sub 90]Sm[sub 10] transforms polymorphically to a metastable intermetallic; Al[sub 88]Sm[sub 12] and Al[sub 86]Sm[sub 14] display eutectic crystallization into Al and a metastable mixture of compounds. For Al[sub 90]Sm[sub 10], the DSC traces involve several overlapping peaks. This may be the result of transformations occurring in distinct parts of the ribbon with different mechanisms. A kinetic analysis of the crystallization processes has been performed by means of isothermal and non-isothermal DSC experiments. A discussion of the kinetic parameters derived from Kissinger and Avrami analyses is provided. ((orig.))

  7. Fabrication of Ti-based composites based on bulk amorphous alloys by spark plasma sintering and crystallization of amorphous phase%放电等离子烧结-非晶晶化法合成钛基块状非晶复合材料

    Institute of Scientific and Technical Information of China (English)

    李元元; 杨超; 李小强; 陈友

    2011-01-01

    In order to circumvent low plasticity of bulk amorphous alloys (BAAs), a material forming method by coupling spark plasma sintering with crystallization of amorphous phase, fabricating composites based on BAAs (CBBAAs) with excellent mechanical property was reviewed systematically. By appropriate annealing of sintered BAAs prepared from spark plasma sintering in the supercooled liquid region of a mechanically alloyed amorphous powder, crystallized ductile β-Ti phase with controllable grain size, phase morphology and distribution can precipitate from the amorphous phase, and therefore, CBBAAs with a matrix of amorphous phase or crystallized β-Ti phase were obtained. The effect of different additions or substitute elements on the particle size, thermal property and microstructure of TiNbCuNiAl amorphous powder, and the influence of different sintering parameters on the microstructure and mechanical property of fabricated CBBAAs were investigated. The theoretical bases of fabricating crystallized phase-containing CBBAAs, and nucleation and growth mechanism of crystalline phase during the crystallization process were elucidated. The facture mechanism of fabricated CBBAAs under stress was explained based on a proposed "Developed hard-soft model". The results provide a promising method for fabricating large-sized crystallized phase-containing bulk composites with excellent mechanical property by powder metallurgy.%鉴于块状非晶合金(BAAs)的低塑性特征,回顾了利用放电等离子烧结-非晶晶化法制备高性能块状材料的成形技术,即先机械合金化制备钛基多组元非晶合金粉末,然后利用放电等离子烧结在粉末的过冷液相区固结非晶粉末,再利用非晶晶化法使烧结的非晶块体在随后的烧结和热处理过程中晶化析出-Ti延性相,控制延性相的形貌、尺度和分布,合成以非晶相或β-Ti晶化相为基体的钛基块状非晶复合材料(CBBAAs),研究不同添加或替换组元对TiNb

  8. Preparation of Plate Fe60Co8Zr10Mo5W2B15 Bulk Amorphous Alloy and Its Fracture Toughness

    Institute of Scientific and Technical Information of China (English)

    XIAO Huaxing; CHEN Guang

    2005-01-01

    With processes of arc melting, inductive melting and copper mold suction casting, a plate Fe-based bulk amorphous alloy Fe60Co8Zr10Mo5W2B15 with a thickness of 1mm was prepared. The surfaces and fractures of the cast bulk amorphous alloy were agleam and with typical metallic luster. The glass transition temperature(Tg), supercooled liquid region(△Tx)and reduced glass transition temperature(T rg)of the prepared Fe-based amorphous alloy are 884 K,63 K, and 0.611 respectively. The fracture toughness of the cast bulk amorphous alloy is at the level of 1.6 MPa·m1/2.

  9. Fabrication of nanoporous silver by de-alloying Cu-Zr-Ag amorphous alloys

    Science.gov (United States)

    Wang, Hui; Xiao, Shang-gang; Zhang, Tao

    2016-07-01

    Nanoporous silver (NPS) with a ligament size ranging from 15 to 40 nm was fabricated by de-alloying (Cu50Zr50)100- x Ag x ( x = 10at%, 20at%, 30at%, and 40at%) amorphous ribbons in a mixed aqueous solution of hydrofluoric (HF) acid and nitric acid under free corrosion conditions. Nanoporous silver ligaments and pore sizes were able to be fine-tuned through tailoring the chemical composition, corrosion conditions, and de-alloying time. The ligament size increases with an increase in Ag content and de-alloying time, but decreases with an increase in HF concentration. This phenomenon may be attributed to the dissolution of Zr/Cu and the diffusion, aggregation, nucleation, and recrystallization of Ag, leading to an oriented attachment of adjacent nanocrystals as revealed by TEM analysis.

  10. Fabrication of nanoporous silver by de-alloying CuZrAg amorphous alloys

    Institute of Scientific and Technical Information of China (English)

    Hui Wang; Shang-gang Xiao; Tao Zhang

    2016-01-01

    Nanoporous silver (NPS) with a ligament size ranging from 15 to 40 nm was fabricated by de-alloying (Cu50Zr50)100-xAgx (x = 10at%, 20at%, 30at%, and 40at%) amorphous ribbons in a mixed aqueous solution of hydrofluoric (HF) acid and nitric acid under free cor-rosion conditions. Nanoporous silver ligaments and pore sizes were able to be fine-tuned through tailoring the chemical composition, corro-sion conditions, and de-alloying time. The ligament size increases with an increase in Ag content and de-alloying time, but decreases with an increase in HF concentration. This phenomenon may be attributed to the dissolution of Zr/Cu and the diffusion, aggregation, nucleation, and recrystallization of Ag, leading to an oriented attachment of adjacent nanocrystals as revealed by TEM analysis.

  11. Anisotropic Magnetoresistance Effect in Amorphous and Nanocrystalline Fe(Cu,Nb)-Si-B Alloys

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The magnetoresistance effect and magnetic properties in amorphous and nanocrystalline Fe(Cu, Nb)-Si-B ribbons have been investigated. It was observed that the anisotropic magnetoresistance (AMR) of nanocrystalline alloy is much smaller than that of amorphous alloy, indicating that the anisotropy of nanocrystalline alloy becomes smaller after crystallizing, and the smallest AMR is coincident with the excellent soft magnetic characteristics. It is believed that the smaller magnetic crystalline anisotropy is the origin of the excellent soft magnetic characteristics of nanocrystalline alloy.

  12. Curie Temperature of the Intergranular Amorphous Phase in Nanocrystalline Fe89Zr7B4 Alloy

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    The FeZrB amorphous alloys for simulating the intergranular amorphous phase in the nanocrystalline Fe89Zr7B4 soft magnetic materials were obtained by mechanical alloying of a mixture of elemental Fe, Zr and B powdersfor 25 h. It is shown that the Curie temperature of the simulated intergranular phase alloy is much lower than thatof the intergranular phase with the same chemical composition in the nanocrystalline Fe89Zr7B4 alloy. The possiblemechanism is mainly due to the strong ferromagnetic exchange force among the nanocrystalline α-Fe grains.

  13. 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...... process, corresponding to simultaneous precipitation of fcc-Al crystals and the metastable bcc-(AlNi)(11)La-3-like phase, is governed by a eutectic reaction. The second process corresponds to the transformation of a residual amorphous alloy into fcc-Al, Al11La3, Al3Ni, and as yet unidentified phase......(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...

  14. The use of amorphous boron powder enhances mechanical alloying in soft magnetic FeNbB alloy: A magnetic study

    Energy Technology Data Exchange (ETDEWEB)

    Ipus, J. J.; Blazquez, J. S.; Franco, V.; Conde, A. [Dpto. Fisica de la Materia Condensada, ICMSE-CSIC, Universidad de Sevilla, P.O. Box 1065, 41080 Sevilla (Spain)

    2013-05-07

    Saturation magnetization and magnetic anisotropy have been studied during mechanical alloying of Fe{sub 75}Nb{sub 10}B{sub 15} alloys prepared using crystalline and commercial amorphous boron. The evolution of saturation magnetization indicates a more efficient dissolution of boron into the matrix using amorphous boron, particularly for short milling times. The magnetization of the crystalline phase increases as boron is incorporated into this phase. Two milling time regimes can be used to describe the evolution of magnetic anisotropy: a first regime governed by microstrains and a second one mainly governed by crystal size and amorphous fraction.

  15. A Novel Carbon Nanotube-Supported NiP Amorphous Alloy Catalyst and Its Hydrogenation Activity

    Institute of Scientific and Technical Information of China (English)

    Yan Ju; Fengyi Li

    2006-01-01

    A carbon nanotube-supported NiP amorphous catalyst (NiP/CNT) was prepared by induced reduction. Benzene hydrogenation was used as a probe reaction for the study of catalytic activity. The effects of the support on the activity and thermal stability of the supported catalyst were discussed based on various characterizations, including XRD, TEM, ICP, XPS, H2-TPD, and DTA. In comparison with the NiP amorphous alloy, the benzene conversion on NiP/CNT catalyst was lower, but the specific activity of NiP/CNT was higher, which is attributed to the dispersion produced by the support, an electron-donating effect, and the hydrogen-storage ability of CNT. The NiP/CNT thermal stability was improved because of the dispersion and electronic effects and the good heat-conduction ability of the CNT support.

  16. 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.

  17. 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.

  18. Magnetoelectric effect in layered structures of amorphous ferromagnetic alloy and gallium arsenide

    Science.gov (United States)

    Bichurin, M. I.; Petrov, V. M.; Leontiev, V. S.; Ivanov, S. N.; Sokolov, O. V.

    2017-02-01

    A paper devotes to theoretical and experimental studying the magnetoelectric interaction in layered structures of amorphous ferromagnetic alloy and single- crystal gallium arsenide. The authors investigated the magnetoelectric effect in the (100) plane of gallium arsenide in the electromechanical resonance range of 200-240 kHz and obtained maximal ME voltage coefficient of 120 V/A at bias field equaled 3.6 kA/m for the direction parallel to the [011] axis. Also the magnetoelectric effect in the (110) and (111) planes is discussed. The results can be used for design of new electronic devices based on the magnetostrictive-semiconductor materials.

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

    Institute of Scientific and Technical Information of China (English)

    庄艳歆[1; 赵德乾[2; 张勇[3; 汪卫华[4; 潘明祥[5

    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.

  20. Development of Amorphous Filler Alloys for the Joining of Nuclear Materials

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jai Young; Kim, Dong Myong; Kang, Yoon Sun; Jung, Jae Han; Yu, Ji Sang; Kim, Hae Yeol; Lee, Ho [Korea Advanced Institute of Science and Technology, Taejon (Korea, Republic of)

    1997-08-01

    In the case of advanced CANDU fuel being useful in future, the fabrication processes for soundness insurance of a improved nuclear fuel bundle must be developed at the same time because it have three times combustibility as existing fuel. In particular, as the improved nuclear fuel bundle in which a coated layer thickness is thinner than existing that, firmity of a joint part is very important. Therefore, we need to develop a joint technique using new solder which can settle a potential problem in current joining method. As the Zr-Be alloy system is composed with the elements having high neutron permeability, they are suitable for joint of nuclear fuel pack. The various compositions Zr-Be binary metallic glass alloys were applicable to the joining the nuclear fuel bundles. The thickness of joint layer using the Zr{sub 1}-{sub x}Be{sub x} amorphous ribbon as a solder is thinner than that using physical vapor deposited Be. Among the Zr{sub 1}-{sub x}Be{sub x} amorphous binary alloys, Zr{sub 0}.7Be-0.3 binary alloy is the most appropriate for joint of nuclear fuel bundle because its joint layer is smooth and thin due to low degree of Be diffusion. In the case of the Zr{sub (}0.7-y)Ti{sub y}Be{sub 0}.3 and Zr{sub (}0.7-y)Nb{sub y}Be{sub 0}3 ternary amorphous alloys, the crystallization temperature(T{sub x}) and activation energy(E{sub x}) increase as the contents of Nb and Ti increase respectively. In the aspect of thermal stability, the ternary amorphous alloys are superior than Zr-Be binary amorphous alloys and Zr-Ti-Be amorphous alloy is superior than Zr-Nb-Be amorphous alloy. 12 refs., 5 tabs., 25 figs. (author)

  1. Transformers with amorphous alloy nucleus in distribution system; Transformadores com nucleo de liga amorfa em sistemas de distribuicao

    Energy Technology Data Exchange (ETDEWEB)

    Luciano, Benedito Antonio; Freire, Raimundo Carlos Silverio [Universidade Federal de Campina Grande (UFCG), PB (Brazil); Bezerra, Reno Barroso [Industria de Transformadores Itaipu, Campinas, SP (Brazil); Inacio, Renato Cucatu [Companhia de Energia Eletrica do Estado do Tocantins (CELTINS), TO (Brazil)

    2010-01-15

    This paper compares the performance of amorphous alloy nucleus with oriented grain silicon steel alloy, related to losses, energy efficiency and energy quality. Besides, are highlighted the process obtention of the amorphous alloys and the electric, magnetic and mechanicals, magneto thermal treatment, effect of oxidation properties, and etc. (author)

  2. The crystallization of Al-Sm amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Rizzi, P. [Turin Univ. (Italy). Dipt. di Chimica Inorganica; Baricco, M. [Turin Univ. (Italy). Dipt. di Chimica Inorganica; Battezzati, L. [Turin Univ. (Italy). Dipt. di Chimica Inorganica; Schumacher, P. [Cambridge Univ. (United Kingdom). Dept. of Metallurgy and Materials Science; Greer, A.L. [Cambridge Univ. (United Kingdom). Dept. of Metallurgy and Materials Science

    1995-12-31

    Amorphous alloys with composition Al{sub 100-x}Sm{sub x} (8 {<=} x {<=} 14) have been prepared by melt spinning in controlled atmosphere. The quenching conditions significantly influence the microstructure of as-quenched samples and their crystallization mechanisms. The crystallization was followed by means of DSC, XRD, TEM and SEM. Different mechanisms are observed as a function of composition. For low Sm content (Al{sub 92}Sm{sub 8}), a primary crystallization occurs at about 180 C, with the formation of Al nanocrystals with a grain size of about 15 nm. A polymorphic crystallization is found in Al{sub 90}Sm{sub 10}, with the formation of a metastable intermetallic phase at about 220 C. For higher Sm content (Al{sub 88}Sm{sub 12} and Al{sub 86}Sm{sub 14}), a eutectic crystallization at about 230 C gives a mixture of stable (Al and Al{sub 11}Sm{sub 3}) and metastable phases. (orig.)

  3. Structural studies of the phase separation of amorphous FexGe100-x alloys

    Science.gov (United States)

    Lorentz, Robert D.; Bienenstock, Arthur; Morrison, Timothy I.

    1994-02-01

    Small-angle x-ray scattering and x-ray-absorption near-edge spectroscopy (XANES) experiments have been performed on amorphous FexGe100-x alloys over the composition range 0Janot for the related FexSn100-x system. This phase separation explains the Mossbauer observation of ``magnetic'' and ``nonmagnetic'' Fe atoms in these alloys.

  4. Investigation of Corrosion Resistance Using Positron Annihilation for an Amorphous Alloy

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    An amorphous alloy with Ni-(17~19) at. pct P prepared by electrodeposition process was studied using positron annihilation technique (PAT) associated with X-ray diffraction and the measurement of corrosion rate. It is suggested that defect or the interface between precipitates and matrix is one of the important factors which decrease corrosion resistance of the alloy after crystallization.

  5. CuZrAl amorphous alloys prepared by casting and milling

    Science.gov (United States)

    Tomolya, K.; Janovszky, D.; Sveda, M.; Hegman, N.; Solyom, J.; Roosz, A.

    2009-01-01

    Several preparation methods are available for the production of amorphous alloys. During the experiment described in this paper (Cu58Zr42)100-xAlx (x = 0-14,8; in at%) amorphous alloys were prepared by casting and ball-milling. The ingots were produced by arc melting. Wedge-shaped samples were prepared from the ingots by centrifugal casting into copper mould. The microstructures of these samples were defined by SEM. The amorphous samples were analysed by DSC and the activation energy of the crystallization processes was calculated from the measured temperatures. The master alloys of identical composition were milled by ball-mill for different periods of time. The powders were analysed by XRD in order to define the amorphous fractions.

  6. 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...

  7. 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.

  8. Achieving tailorable magneto-caloric effect in the Gd-Co binary amorphous alloys

    Directory of Open Access Journals (Sweden)

    C. Wu

    2016-03-01

    Full Text Available Tailorable magnetic properties and magneto-caloric effect were achieved in the Gd-Co binary amorphous alloys. It was found that the Curie temperature (Tc of the GdxCo100-x (x=50, 53, 56, 58, 60 metallic glasses can be tuned by changing the concentration of Gd as Tc =708.8-8.83x, and the mechanism involved was investigated. On the other hand, a linear correlation between the peak value of magnetic entropy change (-Δ Smpeak and Tc-2/3 is found in the amorphous alloys with a linear correlation coefficients of above 0.992. Therefore, the -ΔSmpeak of the Gd-Co binary amorphous alloys under different magnetic fields can be easily tailored by adjusting the composition of the alloy.

  9. Study on Interface Structure and Bond Properties between Cemented Carbide and Tool Steel Blazing with amorphous alloy

    Institute of Scientific and Technical Information of China (English)

    Bao Ming-dong; Xu Jin-fu; Xu Xue-bo; Zou Gui-sheng; Huang Geng-hua

    2004-01-01

    Cemented Carbide YG11C and Tool Steel Crl2MoV was blazed with Ni-base amorphous alloys, QG-1011,MBF-20 and MBF-75, using dynamics thermodynamics analogue testing machine Gleeble 1500D. The effects of brazing temperature, holding time and holding pressure on micro-structure and bond strength were investigated. Results showed that YG11C and Cr12MoV were all wetted well by these three Ni-base alloys, and the bond strength was as high as 220MPa,320MPa, 320MPa respectively. When the blazing temperature was at the point over the melting point 60-70℃ of Ni-base alloy, the holding time was about 2-10min, the suitable pressure was benefit for improving the brazing quality.Microanalysis showed Co in cemented carbide diffused into liquid brazing alloy and formed the Fe-Co solid .solution.

  10. Effect Of Low-Temperature Annealing On The Properties Of Ni-P Amorphous Alloys Deposited Via Electroless Plating

    Directory of Open Access Journals (Sweden)

    Zhao Guanlin

    2015-06-01

    Full Text Available Amorphous Ni-P alloys were prepared via electroless plating and annealing at 200°C at different times to obtain different microstructures. The effects of low-temperature annealing on the properties of amorphous Ni-P alloys were studied. The local atomic structure of the annealed amorphous Ni-P alloys was analyzed by calculating the atomic pair distribution function from their X-ray diffraction patterns. The results indicate that the properties of the annealed amorphous Ni-P alloys are closely related to the order atomic cluster size. However, these annealed Ni-P alloys maintained their amorphous structure at different annealing times. The variation in microhardness is in agreement with the change in cluster size. By contrast, the corrosion resistance of the annealed alloys in 3.5 wt% NaCl solution increases with the decrease in order cluster size.

  11. 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.

  12. Prediction of Failure Due to Thermal Aging, Corrosion and Environmental Fracture in Amorphous and Titanium Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Farmer, J C

    2003-04-15

    DARPA is exploring a number of advanced materials for military applications, including amorphous metals and titanium-based alloys. Equipment made from these materials can undergo degradation due to thermal aging, uniform corrosion, pitting, crevice corrosion, denting, stress corrosion cracking, corrosion fatigue, hydrogen induced cracking and microbial influenced corrosion. Amorphous alloys have exceptional resistance to corrosion, due in part to the absence of grain boundaries, but can undergo crystallization and other phase instabilities during heating and welding. Titanium alloys are extremely corrosion resistant due to the formation of a tenacious passive film of titanium oxide, but is prone to hydrogen absorption in crevices, and hydrogen induced cracking after hydrogen absorption. Accurate predictions of equipment reliability, necessary for strategic planning, requires integrated models that account for all relevant modes of attack, and that can make probabilistic predictions. Once developed, model parameters must be determined experimentally, and the validity of models must be established through careful laboratory and field tests. Such validation testing requires state-of-the-art surface analytical techniques, as well as electrochemical and fracture mechanics tests. The interaction between those processes that perturb the local environment on a surface and those that alter metallurgical condition must be integrated in predictive models. The material and environment come together to drive various modes of corrosive attack (Figure 1). Models must be supported through comprehensive materials testing capabilities. Such capabilities are available at LLNL and include: the Long Term Corrosion Test Facility (LTCTF) where large numbers of standard samples can be exposed to realistic test media at several temperature levels; a reverse DC machine that can be used to monitor the propagation of stress corrosion cracking (SCC) in situ; and banks of potentiostats with

  13. Preparation of Fe-Based Bulk Amorphous Materials and Its Application to Sensors

    Institute of Scientific and Technical Information of China (English)

    Sun Xiaohua; Wu Jinbin; Zhao Zengqi; Zhao Jun; Sun Guangjie; Liu Changsheng

    2004-01-01

    The study of recent years found that big bulk amorphous alloys were formed for some multi-element compositions at rapid cooling speed such as Zr-, La-, Fe-, Mg-based alloys with wide undercooled liquid phase field and high trend of forming glass.( ATx = crystallization temperature Tx - glass transformation temperature Tg) Bulk amorphous copper mold upper suction casting with minus pressure while some new technical processes and adding new elements such as Co, Nb, Ca, etc.were used to improve magnetic properties and other performances of the materials.The results show that Fe-based bulk amorphous alloys have low coercive force and high permeability, which are successfully applied to magnetoelectric sensors with temperature ranges between -45 ℃ and 150 ℃ by special design of magnetic circuits.

  14. NICKEL-BASE ALLOY

    Science.gov (United States)

    Inouye, H.; Manly, W.D.; Roche, T.K.

    1960-01-19

    A nickel-base alloy was developed which is particularly useful for the containment of molten fluoride salts in reactors. The alloy is resistant to both salt corrosion and oxidation and may be used at temperatures as high as 1800 deg F. Basically, the alloy consists of 15 to 22 wt.% molybdenum, a small amount of carbon, and 6 to 8 wt.% chromium, the balance being nickel. Up to 4 wt.% of tungsten, tantalum, vanadium, or niobium may be added to strengthen the alloy.

  15. Mechanical properties of amorphous alloys ribbons prepared by rapid quenching of the melt after different thermal treatments before quenching

    NARCIS (Netherlands)

    Tabachnikova, ED; Bengus, VZ; Egorov, D V; Tsepelev, VS; Ocelik, Vaclav

    1997-01-01

    The mechanical properties of amorphous alloy are greatly influenced by the thermal treatment of its melt before rapid quenching. The strength and the fracture toughness of some amorphous alloys obtained after melt beating above the melt critical temperature T-CR are essentially higher than those obt

  16. Study of The Pd-B/γ-Al2O3 Amorphous Alloy Catalyst

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The Pd-B/γ-Al2O3 amorphous alloy catalyst and Pd/γ-Al2O3 crystalline metal catalyst were prepared by KBH4 reduction and routine impregnation, respectively. Pd-B/γ-A12O3 and Pd/γ-A12O3 catalysts were characterized by XRD and SEM. It was found that the catalytic activity of the Pd-B/γ-A12O3 amorphous alloy catalyst was higher than that of the Pd/γ-A12O3crystalline metal catalyst in the anthraquinone hydrogenation.

  17. Raman Amplifier Based on Amorphous Silicon Nanoparticles

    Directory of Open Access Journals (Sweden)

    M. A. Ferrara

    2012-01-01

    Full Text Available The observation of stimulated Raman scattering in amorphous silicon nanoparticles embedded in Si-rich nitride/silicon superlattice structures (SRN/Si-SLs is reported. Using a 1427 nm continuous-wavelength pump laser, an amplification of Stokes signal up to 0.9 dB/cm at 1540.6 nm and a significant reduction in threshold power of about 40% with respect to silicon are experimentally demonstrated. Our results indicate that amorphous silicon nanoparticles are a great promise for Si-based Raman lasers.

  18. Influence of composition and heat treatments on corrosion resistance of Fe-Co-BSi amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Angelini, E.; Antonione, C.; Baricco, M.; Rosalbino, F.; Zucchi, F. (Ist. Elettrotecnico Nazionale Galileo Ferraris, Turin (Italy) Turin Univ. (Italy) Politecnico di Torino (Italy))

    This paper studies the influence of composition and heat treatments on the corrosion resistance, in a solution of Na/sub 2/SO/sub 4/ 0.05M + H/sub 2/SO/sub 4/ 0.05M, at 1.5 pH, of a series of iron base amorphous alloys with increasing cobalt content, i.e., Fe/sub 80-x/Co/sub x/B/sub 10/Si/sub 10/ with x=0, 30, and 80. The treatments were carried out in an argon atmosphere over increasing time durations: 30, 60, 120, and 240 minutes, and increasing temperatures: 350, 400, 450 and 500 degrees C respectively. It was possible to observe that, independent of heat treatment, the corrosion resistance increased with increasing cobalt concentration. In comparing samples having the same chemical composition, it was noted that their electrochemical behaviour worsened with increasing temperature and time.

  19. Ideal solution behaviour of glassy Cu–Ti, Zr, Hf alloys and properties of amorphous copper

    Energy Technology Data Exchange (ETDEWEB)

    Ristić, R. [Department of Physics, University of Osijek, Trg Ljudevita Gaja 6, HR-3100 Osijek (Croatia); Cooper, J.R. [Department of Physics, Cavendish Laboratory, J.J. Thomson Avenue, CB3 0HE Cambridge (United Kingdom); Zadro, K.; Pajić, D. [Department of Physics, Faculty of Science, Bijenička cesta 32, HR-10002 Zagreb (Croatia); Ivkov, J. [Institute of Physics, Bijenička cesta 46, HR-10002 Zagreb (Croatia); Babić, E. [Department of Physics, Faculty of Science, Bijenička cesta 32, HR-10002 Zagreb (Croatia)

    2015-02-05

    Highlights: • Ideal solution behaviour (ISB) is established in all Cu–Ti, Zr, Hf glassy alloys. • ISB enables reliable estimates for various properties of amorphous Cu. • ISB also impacts glass forming ability in these and probably other similar alloys. - Abstract: A comprehensive study of selected properties of amorphous (a) Cu–TE alloys (TE = Ti, Zr and Hf) has been performed. Data for average atomic volumes of a-Cu–Hf, Ti alloys combined with literature data show that ideal solution behaviour (Vegard’s law) extends over the whole glass forming range (GFR) in all a-Cu–TE alloys. This enables one to obtain an insight into some properties and probable atomic arrangements for both, a-TEs (Ristić et al., 2010) and a-Cu by extrapolation of the data for alloys. Indeed the atomic volumes and other properties studied for all a-Cu–TE alloys extrapolate to the same values for a-Cu. Depending on the property, these values are either close to those of crystalline (c) Cu, or are close to those for liquid (L) Cu. In particular, the electronic transport properties of a-Cu seem close to those of L-Cu, whereas the static properties, such as the density of states, and Young’s modulus, converge to those of c-Cu. The possible impact of these results on our understanding of a-Cu–TE alloys, including glass forming ability, is discussed.

  20. Structural transformations and tribological properties of amorphous alloys upon wear at room and cryogenic temperatures

    Science.gov (United States)

    Korshunov, L. G.; Chernenko, N. L.; Goikhenberg, Yu. N.

    2009-09-01

    The abrasive wear resistance of the Fe64Co30Si3B3, Co86.5Cr4Si7B2.5, Fe73.5Nb3Cu1Si13.5B9, and Fe82.6Nb5Cu3Si8B1.4 commercial amorphous alloys (ribbon 0.03 mm thick and 12 mm wide) has been investigated under the conditions of abrasive and adhesive wear upon sliding friction. The character of fracture of the surface and structural transformations that occur in these materials upon wear have been studied by the metallographic and electron-microscopic methods. It has been shown that at room and cryogenic (-196°C) temperatures of tests the abrasive wear resistance of the amorphous alloys is two-three times lower than that of tool steels Kh12M and U8. A comparatively small abrasive wear resistance of the amorphous alloys is explained by local softening of these materials in the process of wear. Under the conditions of adhesive wear of like friction pairs at room temperature in air and argon, the amorphous alloys are characterized by the rate of wear that is smaller approximately by an order of magnitude than in steels 12Kh13 and 12Kh18N9. It has been established that upon wear the deformed surface layer of the alloys under study retains a predominantly amorphous state but in local sections of this layer nanocrystalline structures that consist of crystals of bcc and fcc phases and borides are formed. The possible effects of this partial crystallization on the microhardness, friction coefficient, and wear resistance of these alloys have been considered.

  1. Band gap tuning of amorphous Al oxides by Zr alloying

    DEFF Research Database (Denmark)

    Canulescu, Stela; Jones, N. C.; Borca, C. N.;

    2016-01-01

    minimum changes non-linearly as well.Fitting of the energy band gap values resulted in a bowing parameter of 2 eV. The band gap bowing of themixed oxides is assigned to the presence of the Zr d-electron states localized below the conduction bandminimum of anodized Al2O3.......The optical band gap and electronic structure of amorphous Al-Zr mixed oxides, with Zr content ranging from4.8 to 21.9% were determined using vacuum ultraviolet (VUV) and X-ray absorption spectroscopy (XAS). Thelight scattering by the nano-porous structure of alumina at low wavelengths...... was estimated based on the Miescattering theory. The dependence of the optical band gap of the Al-Zr mixed oxides on Zr content deviatesfrom linearity and decreases from 7.3 eV for pure anodized Al2O3 to 6.45 eV for Al-Zr mixed oxide with Zrcontent of 21.9%. With increasing Zr content, the conduction band...

  2. Novel Fe-based amorphous magnetic powder cores with ultra-low core losses

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Amorphous magnetic alloy powders were prepared from bulk metallic glasses Fe74Cr2Mo2Sn2P10Si4B4C2 with supercooled liq-uid region of 32 K by water atomization.Amorphous magnetic powder core precursor was produced from a mixture of the amorphous alloy powder with addition of insulation and bonding materials by mold compacting at room temperature.After annealing the core precursor,the amorphous magnetic core exhibits superior magnetic properties as compared with molypermalloy powder core.The initial permeability up to 1 MHz was about 80,the flux density at 300 Oe was 1.06 T and the core loss at 100 kHz for Bm=0.1 T was only 329 kW/m3.The ultra-low core loss is attributed to the combination of relatively high resistivity and the amorphous structure of the Fe-based amorphous powder.Besides the outstanding magnetic properties,the Fe-based amorphous magnetic powder core had a much lower cost which renders the powder cores a potential candidate for a variety of industrial applications.

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

    DEFF Research Database (Denmark)

    Zhuang, Yanxin; Jiang, Jianzhong; Lin, Z. G.;

    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...

  4. A New Physical Metallurgy Phenomenon-the Shock Wave Nanocrystallization of Amorphous Alloys

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Some results of amorphous alloy nanocrystallization by shock wave are presented. Compared with the well knownannealing crystallization, these results seem novel and are very difficult to be explained by the diffusion theory, such asnucleation and growth mechanism in the solid state phase transitions. The shock wave crystallization of amorphousalloy is a new metallurgical phenomenon with possibilities for improving the crystallization theory in physics.

  5. Annealing crystallization and catalytic activity of ultrafine NiB amorphous alloy

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Annealing crystallization of ultrafine NiB amorphous alloy prepared by the chemical reduction method was studied by DTA,XRD and XAFS techniques. The XRD and XAFS results have revealed that the crystallization process of ultrafine NiB amorphous alloy proceeds in two steps. First,ultrafine NiB amorphous alloy is crystallized to form metastable nanocrystalline Ni3B at an annealing temperature of 325℃. Second,the nanocrystalline Ni3B is further decom-posed into crystalline Ni at 380℃ or higher tempera ture,the local structure around Ni atoms in resultant product is similar to that in Ni foil. It was found that the catalytic ac-tivity of nanocrystalline Ni3B for benzene hydrogenation is much higher than that of ultrafine NiB amorphous alloy or crystalline Ni. The result indicates that the active sites of nanocrystalline Ni3B for benzene hydrogenation are com-posed of both Ni and B with proper geometry configuration.

  6. Superconductivity in the amorphous phase of topological insulator Bi x Sb100-x alloys

    Science.gov (United States)

    Barzola-Quiquia, J.; Lauinger, C.; Zoraghi, M.; Stiller, M.; Sharma, S.; Häussler, P.

    2017-01-01

    In this work we investigated the electrical properties of rapidly quenched amorphous Bi x Sb{}100-x alloys in the temperature range of 1.2 K to 345 K. The resistance reveals that for a broad range of different compositions, including that for the topological insulator (TI), a superconducting state in the amorphous phase is present. After crystallization and annealing at an intermediate temperature, we found that in pure Bi and Bi x Sb{}100-x alloys with composition corresponding to the TI, the superconductivity persists, but the transition shifts to a lower temperature. The highest superconducting transition temperature {T}{{C}0} was found for pure Bi and those TI’s, with a shift to low temperatures when the Sb content is increased. After annealing at a maximum temperature of T = 345 K, the samples are non-superconducting within the experimental range and the behavior changes from semiconducting-like for pure Bi, to metallic-like for pure Sb. Transition temperature {T}{{C}0} of the amorphous Bi x Sb{}100-x alloys have been calculated in the BCS-Eliashberg-McMillan framework, modified for binary alloys. The results can explain the experimental results and show that amorphous Bi x Sb{}100-x exhibits a strong to intermediate electron-phonon coupling.

  7. Chemical vapor deposition of amorphous ruthenium-phosphorus alloy films

    Energy Technology Data Exchange (ETDEWEB)

    Shin Jinhong [Texas Materials Institute, University of Texas at Austin, Austin, TX 78750 (United States); Waheed, Abdul [Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 78712 (United States); Winkenwerder, Wyatt A. [Department of Chemical Engineering, University of Texas at Austin, Austin, TX 78712 (United States); Kim, Hyun-Woo [Department of Chemical Engineering, University of Texas at Austin, Austin, TX 78712 (United States); Agapiou, Kyriacos [Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 78712 (United States); Jones, Richard A. [Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 78712 (United States); Hwang, Gyeong S. [Department of Chemical Engineering, University of Texas at Austin, Austin, TX 78712 (United States); Ekerdt, John G. [Department of Chemical Engineering, University of Texas at Austin, Austin, TX 78712 (United States)]. E-mail: ekerdt@che.utexas.edu

    2007-05-07

    Chemical vapor deposition growth of amorphous ruthenium-phosphorus films on SiO{sub 2} containing {approx} 15% phosphorus is reported. cis-Ruthenium(II)dihydridotetrakis-(trimethylphosphine), cis-RuH{sub 2}(PMe{sub 3}){sub 4} (Me = CH{sub 3}) was used at growth temperatures ranging from 525 to 575 K. Both Ru and P are zero-valent. The films are metastable, becoming increasingly more polycrystalline upon annealing to 775 and 975 K. Surface studies illustrate that demethylation is quite efficient near 560 K. Precursor adsorption at 135 K or 210 K and heating reveal the precursor undergoes a complex decomposition process in which the hydride and trimethylphosphine ligands are lost at temperatures as low at 280 K. Phosphorus and its manner of incorporation appear responsible for the amorphous-like character. Molecular dynamics simulations are presented to suggest the local structure in the films and the causes for phosphorus stabilizing the amorphous phase.

  8. 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.

  9. Amorphization Induced High Magneto-Caloric Effect of Gd55A120Ni25 Ternary Alloy

    Institute of Scientific and Technical Information of China (English)

    DING Ding; XIA Lei; YU Zhong-Hua; DONG Yuan-Da

    2008-01-01

    We report the amorphization induced high magneto-caloric effect (MCE) of recently developed Gd55Al15Ni30 bulk metallic glass (BMG). The magnetic properties of the Gd55Al15Ni30 BMG are investigated in comparison with that of its crystalline counterpart. It is found that amorphization can increase the saturation magnetization and decrease the hysteresis of Gd55Al15Ni30 alloys, which indicate the possible enhancement of MCE. The magnetic entropy changes and the refrigerant capacity of the BMG as well as the crystalline samples is calculated directly from isothermal magnetic measurements. The results show the amorphization induced high MCE of the alloy and the excellent refrigerant efficiency of Gd55A115Ni30 bulk metallic glass.

  10. 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.

  11. 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)

  12. TUNGSTEN BASE ALLOYS

    Science.gov (United States)

    Schell, D.H.; Sheinberg, H.

    1959-12-15

    A high-density quaternary tungsten-base alloy having high mechanical strength and good machinability composed of about 2 wt.% Ni, 3 wt.% Cu, 5 wt.% Pb, and 90wt.% W is described. This alloy can be formed by the powder metallurgy technique of hot pressing in a graphite die without causing a reaction between charge and the die and without formation of a carbide case on the final compact, thereby enabling re-use of the graphite die. The alloy is formable at hot- pressing temperatures of from about 1200 to about 1350 deg C. In addition, there is little component shrinkage, thereby eliminating the necessity of subsequent extensive surface machining.

  13. Magneto-caloric effect of a Gd50Co50 amorphous alloy near the freezing point of water

    Directory of Open Access Journals (Sweden)

    L. Xia

    2015-09-01

    Full Text Available In the present work, we report the magneto-caloric effect (MCE of a binary Gd50Co50 amorphous alloy near the freezing temperature of water. The Curie temperature of Gd50Co50 amorphous ribbons is about 267.5 K, which is very close to room temperature. The peak value of the magnetic entropy change (-ΔSmpeak and the resulting adiabatic temperature rise (ΔTad. of the Gd50Co50 amorphous ribbons is much higher than that of any other amorphous alloys previously reported with a Tc near room temperature. On the other hand, although the -ΔSmpeak of Gd50Co50 amorphous ribbons is not as high as those of crystalline alloys near room temperature, its refrigeration capacity (RC is still much larger than the RC values of these crystalline alloys. The binary Gd50Co50 amorphous alloy provides a basic alloy for developing high performance multi-component amorphous alloys near room temperature.

  14. 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.

  15. Properties of amorphous FeCoB alloy particles (abstract)

    DEFF Research Database (Denmark)

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

    1988-01-01

    -ray diffraction. Magnetic measurements of the saturation magnetization, coercivity, and remanence of the particles have been measured. The transition from the amorphous-to-crystalline state has been studied using differential scanning calorimetry (DSC) and thermomagnetometry up to a temperature of 450 °C (see Fig...

  16. Amorphization of Ni61 Nb39 Alloy by Laser Surface Treatment

    Institute of Scientific and Technical Information of China (English)

    Zhong-xiang LU; Ran LI; Yan LI; Tao ZHANG

    2016-01-01

    The surface of Ni61 Nb39 crystalline ingot was treated by laser surface melting with different processing parame-ters.A fully amorphous layer with a thickness of approximately 10 μm could be produced on the top surface under optimal parameters.An amorphous-crystalline composite layer with the depth from 10 to 50 μm,consisting of amor-phous matrix and intermetallic phases of Ni3 Nb and Ni6 Nb7 ,could be formed.The micro-hardness (about 831 HV) of the treated surface was remarkably improved by nearly 100% compared with the value of the crystalline substrate caused by the formation of the fully amorphous structure.A finite volume simulation was adopted to evaluate the temperature distribution in the laser-affected zone of Ni6 1 Nb3 9 alloys and to reveal the mechanism of glass formation in the laser-affected zone.

  17. 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.

  18. Amorphous metallic alloys for oxygen reduction reaction in a polymer electrolyte membrane fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez-Huerta, R.; Guerra-Martinez, I.; Lopez, J.S. [Inst. Politecnico Nacional, ESIQIE, Mexico City (Mexico). Lab. de Electroquimica; Pierna, A.R. [Basque Country Univ., San Sebastian (Spain). Dept. of Chemical Engineering and Environment; Solorza-Feria, O. [Inst. Politenico Nacional, Centro de Investigacion y de Estudios Avanzados, Mexico City (Mexico). Dept. de Quimica

    2010-07-15

    Direct methanol fuel cells (DMFC) and polymer electrolyte membrane fuel cells (PEMFC) represent an important, environmentally clean energy source. This has motivated extensive research on the synthesis, characterization and evaluation of novel and stable oxygen reduction electrocatalysts for the direct four-electron transfer process to water formation. Studies have shown that amorphous alloyed compounds can be used as electrode materials in electrochemical energy conversion devices. Their use in PEMFCs can optimize the electrocatalyst loading in the membrane electrode assembly (MEA). In this study, amorphous metallic PtSn, PtRu and PtRuSn alloys were synthesized by mechanical milling and used as cathodes for the oxygen reduction reaction (ORR) in sulphuric acid and in a single PEM fuel cell. Two different powder morphologies were observed before and after the chemical activation in a hydrofluoric acid (HF) solution at 25 degrees C. The kinetics of the ORR on the amorphous catalysts were investigated. The study showed that the amorphous metallic PtSn electrocatalyst was the most active of the 3 electrodes for the cathodic reaction. Fuel cell experiments were conducted at various temperatures at 30 psi for hydrogen (H{sub 2}) and at 34 psi for oxygen (O{sub 2}). MEAs made of Nafion 115 and amorphous metallic PtSn dispersed on carbon powder in a PEMFC had a power density of 156 mW per cm{sup 2} at 0.43V and 80 degrees C. 12 refs., 1 tab., 5 figs.

  19. Amorphous metal nanocrystallization changes due to mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Bonastre, Jordi; Escoda, Lluisa; Sunol, Joan Josep [GRMT, EPS, Campus Montilivi s/n, Girona University, 17071 Girona (Spain); Hernando, Blanca; Sanchez-Llamazares, Jose Luis [Dept. Fisica, Univ. Oviedo, Calvo Sotelo s/n, 33007 Oviedo (Spain)

    2010-11-15

    A detailed knowledge of the temperature dependence of the transformed fraction is an essential issue in the development of nanomaterials and the control of their microstructure. In technical applications, the thermal stability of nanocrystalline alloys is a problem of fundamental interest in order to determine the useful working temperature ranges. The transformation diagrams give information relative to the stability and applicability of these materials. In this work the temperature-heating rate transformation diagram of a Co-rich alloy obtained by mechanical alloying or rapid solidification was built using an isoconversional approach in order to obtain a good prediction even for low transformed fractions (0.1). (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Effects of TM on stability of structure corresponding to prepeak of amorphous Al90TM5Ce5 Alloys

    Institute of Scientific and Technical Information of China (English)

    赵芳; 吴佑实

    2002-01-01

    X-ray diffraction and DSC were used to investigate the crystallization process of amorphous Al90Fe5Ce5 and Al90Ni5Ce5 alloys, and the stability of the structure corresponding to the prepeak. Both these amorphous alloys are crystallized by two stages. The stability of the structure corresponding to the prepeak has a large difference. The structure corresponding to the prepeak for amorphous Al90Fe5Ce5 alloy is more stable than the amorphous matrix. However, it is not stable for amorphous Al90Ni5Ce5 alloys during the first crystallization stage. The prepeak position of amorphous Al90Ni5Ce5 alloys is very close to that of amorphous Al90Fe5Ce5 alloys. It is estimated that the prepeak is also due to diffraction peak broadening caused by very fine quasi-crystalline structure and the structural unit is an icosahedral quasi-crystalline structure with Ni as the central atom. The large difference of the stability of the structure corresponding to the prepeak is likely caused by different stability of the quasi-crystalline structure.

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

    DEFF Research Database (Denmark)

    Wu, Y.F.; Chiang, Wen-Chi; Chu, J.;

    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 Pd40Ni40P20...... and mainly consists of inert Pd5P2, NI3P, Ni2Pd2P and noble Pd phases. These inert and noble properties result in a higher corrosion resistance in crystalline Pd40Ni40P20....

  2. Recent developments in amorphous silicon-based solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Beneking, C.; Rech, B.; Foelsch, J.; Wagner, H. [Forschungszentrum Juelich GmbH (Germany). Inst. fuer Schicht- und Ionentechnik

    1996-03-01

    Two examples of recent advances in the field of thin-film, amorphous hydrogenated silicon (a-Si:H) pin solar cells are described: the improved understanding and control of the p/i interface, and the improvement of wide-bandgap a-Si:H material deposited at low substrate temperature as absorber layer for cells with high stabilized open-circuit voltage. Stacked a-Si:H/a-Si:H cells incorporating these concepts exhibit less than 10% (relative) efficiency degradation and show stabilized efficiencies as high as 9 to 10% (modules 8 to 9%). The use of low-gap a-Si:H and its alloys like a-SiGe:H as bottom cell absorber materials in multi-bandgap stacked cells offers additional possibilities. The combination of a-Si:H based top cells with thin-film crystalline silicon-based bottom cells appears as a promising new trend. It offers the perspective to pass significantly beyond the present landmark of 10% module efficiency reached by the technology utilizing exclusively amorphous silicon-based absorber layers, while keeping its advantages of potentially low-cost production. (orig.) 47 refs.

  3. Magnetocaloric effect in amorphous and partially crystallized Fe40Ni38Mo4B18 alloys

    Directory of Open Access Journals (Sweden)

    T. Thanveer

    2016-05-01

    Full Text Available A study of magnetocaloric effect in amorphous and partially crystallized Fe40Ni38Mo4B18 alloys is reported. Amorphous Fe40Ni38Mo4B18, near its magnetic ordering temperature (600K showed a magnetic entropy change ΔSM of 1.1 J/KgK and a relative cooling power of 36J/Kg in a field change of 10 kOe. Amorphous samples were partially crystallized by annealing at 700 K at different time intervals. Partially crystallized samples showed two distinct magnetic ordering temperature, one corresponding to the precipitated FeNi nanocrystals and the other one corresponding to the boron rich amorphous matrix. Magnetic ordering temperature of the residual amorphous matrix got shifted to the lower temperatures on increasing the annealing duration. Partially crystallised samples showed a magnetic entropy change of about 0.27J/kgK near the magnetic ordering temperature of the amorphous matrix (540K in a field change of 10 kOe. The decrease in ΔSM on partial crystallisation is attributed to the biphasic magnetic nature of the sample.

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

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jianfeng, E-mail: jfwang316@zzu.edu.cn [School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001 (China); Zhu, Shijie; Wang, Liguo; Guan, Shaokang [School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001 (China); Li, Ran; Zhang, Tao [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China)

    2015-10-01

    Novel Re–B–Co amorphous alloys with compositions of Re{sub 65−x}B{sub 35}Co{sub x} (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 (ΔT{sub x}) is in the range of 52–71 K. Such a large ΔT{sub x} allows us to produce amorphous alloy bulks by thermoplastic forming. The Vickers hardness is up to 19.10 GPa for the Re{sub 40}B{sub 35}Co{sub 25} alloy, which is close to that reported for some hard covalent crystals. Thus, the present alloys with a combination of large ΔT{sub x} 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.

  5. FORCED VOLUME MAGNETOSTRICTION IN AMORPHOUS Co-Si-B ALLOYS

    OpenAIRE

    Baczewski, L.

    1985-01-01

    The room temperature forced volume magnetostriction constant σω/σH was calculated from the field dependence of saturation magnetostriction for the magnetic field parallel and perpendicular to the length of ribbons. Compositional dependences of forced volume magnetostriction - both as a function of Co and Si content - were determined. On the basis of the thermodynamical relations the pressure dependence of Curie temperature for the studied alloys from σω/σH measurements was derived.

  6. 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.

  7. Chemical preparation and investigation of Fe-P-B ultrafine amorphous alloy particles

    Institute of Scientific and Technical Information of China (English)

    胡征; 吴勇; 范以宁; 颜其洁; 陈懿

    1997-01-01

    A series of Fe-P-B ultrafine amorphous alloy particles has been prepared by the chemical reduction method The composition and size of the particles have been effectively adjusted.Mossbauer spectroscopy in addition to sonic other techniques has been used to investigate the reaction process,the factors that influence the preparation,the crystallization of the particles,and the interactions between the components within them.The results indicate that the co-deposition of iron,phosphorus and boron atoms in the solution at room temperature forms Fe-P-B amorphous alloy particles,and a preferential bonding of Fe-P bond to Fe-B one exists in the particles.

  8. Nanocrystallization of Al80Ni6Y8Co4Cu2 amorphous alloy

    Institute of Scientific and Technical Information of China (English)

    边赞; 孙玉峰; 何国; 陈国良

    2001-01-01

    Nanoscale α(Al) phase with a size of 15  nm was precipitated from Al80Ni6Y8Co4Cu2 amorphous ribbons after annealing. The microhardness increases with increasing the crystallization volume fraction of nanoscale α(Al) phase. The combination effect of alloy strengthening and dispersion strengthening is main reason for the increase of microhardness. The formation of intermetallic compound (Al3Ni) with a small volume fraction leads to the decrease of microhardness resulting from the depletion of the solute elements in the residual amorphous matrix and the weakening of alloy strengthening. With increasing the volume fraction of intermetallic compound, microhardness increases again due to dispersion strengthening of nanoscale intermetallic compound.

  9. 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...

  10. Amorphous Fe-B alloys in B-Fe-Ag multilayers studied by magnetization and Mössbauer measurements

    DEFF Research Database (Denmark)

    Kiss, L. F.; Balogh, J.; Bujdoso, L.;

    2011-01-01

    –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...

  11. Preparation of Uniform Ni-B Amorphous Alloy Catalyst on CNTs and its Performance for Acetylene Selective Hydrogenation

    Institute of Scientific and Technical Information of China (English)

    Chang Yuan HU; Feng Yi LI; Rong Bin ZHANG; Li HUA

    2006-01-01

    Uniform Ni-B amorphous alloys about 14 nm have been prepared on CNTs-A support,named Ni-B/CNTs-A. In comparison with the Ni-B/CNTs amorphous catalyst, Ni-B/CNTs-A showed higher nickel loading, determined by ICP and better catalytic activity and ethylene selectivity in the acetylene hydrogenation reaction.

  12. Icosahedral medium-range orders and backbone formation in an amorphous alloy

    Science.gov (United States)

    Lee, Mirim; Kim, Hong-Kyu; Lee, Jae-Chul

    2010-12-01

    Analyses of metallic amorphous solids constructed using molecular dynamics (MD) simulations have demonstrated that individual short-range orders (SROs) are linked with neighboring SROs and form various medium-range orders (MROs). These MROs have been observed to have different structural stability depending on their linking patterns. On the basis of the assessment of the structural stability of various MROs, we propose new types of structural organization, namely, icosahedral medium-range orders (I-MROs) and their extended-range order that forms the backbone of amorphous solids. We also discuss why the atomic-scale structure of an amorphous alloy can be more appropriately described in terms of I-MROs, rather than by the degree of short-range ordering as characterized by the fractions of SROs.

  13. Hydrogen-induced phase separation of an amorphous cerium-copper alloy

    Energy Technology Data Exchange (ETDEWEB)

    Felsch, W.; Volkmer, H.; Schneider, S.; Kohlmann, J.; Regenbrecht, A.; Samwer, K. (Goettingen Univ. (Germany, F.R.). 1. Physikalisches Inst.)

    1989-01-01

    X-ray diffraction and differential scanning calorimetry show that the amorphous alloy Ce{sub 26}Cu{sub 74} decomposes gradually into a two-phase amorphous structure by the absorption of hydrogen. There is evidence that these phases are close, in their metallic composition, to the intermetallic compounds CeCu{sub 2} and CeCu{sub 6}. Hydrogen is absorbed almost entirely by the amorphous phase related to CeCu{sub 2}. The electrical resistivity increases steeply by a factor of 3 near H/M=0.4. While the magnetic susceptibility shows a small reduction only on the spin-glass temperature due to hydrogen absorption, the low-temperature specific heat is substantially modified, indicating a considerably diminished exchange coupling between the Ce-4f and conduction electrons. (orig.).

  14. Thermal relaxation of magnetic clusters in amorphous Hf_{57}Fe_{43} alloy

    OpenAIRE

    Pajic, Damir; Zadro, Kreso; Ristic, Ramir; Zivkovic, Ivica; Skoko, Zeljko; Babic, Emil

    2006-01-01

    The magnetization processes in binary magnetic/nonmagnetic amorphous alloy Hf_{57}Fe_{43} are investigated by the detailed measurements of magnetic hysteresis loops, temperature dependence of magnetization, relaxation of magnetization and magnetic ac susceptibility, including a nonlinear term. Blocking of magnetic moments at lower temperatures is accompanied with the slow relaxation of magnetization and magnetic hysteresis loops. All of the observed properties are explained with the superpara...

  15. A Novel Ultrafine Ru-B Amorphous Alloy Catalyst for Glucose Hydrogenation to Sorbitol

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    An ultrafine Ru-B amorphous alloy catalyst was prepared by chemical reduction with KBH4 in aqueous solution, which exhibited perfect selectivity to sorbitol (~100%) and very high activity during the liquid phase glucose hydrogenation, much higher than the corresponding crystallized Ru-B, the pure Ru powder, and Raney Ni catalysts. The correlation of the catalytic activity to both the structural and surface electronic characteristics was discussed briefly.

  16. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Borrego, J.M., E-mail: jmborrego@us.es [Dpto. Física de la Materia Condensada, Instituto de Ciencia de Materiales, C.S.I.C., Universidad de Sevilla, P.O. Box 1065, 41080 Sevilla (Spain); Blázquez, J.S. [Dpto. Física de la Materia Condensada, Instituto de Ciencia de Materiales, C.S.I.C., Universidad de Sevilla, P.O. Box 1065, 41080 Sevilla (Spain); Lozano-Pérez, S.; Kim, J.S. [Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom); Conde, C.F.; Conde, A. [Dpto. Física de la Materia Condensada, Instituto de Ciencia de Materiales, C.S.I.C., Universidad de Sevilla, P.O. Box 1065, 41080 Sevilla (Spain)

    2014-01-25

    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, T{sub p}, and Curie temperature, T{sub C}, 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.

  18. 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.

  19. Chemical short-range order domain in bulk amorphous alloy and the prediction of glass forming ability

    Institute of Scientific and Technical Information of China (English)

    HUI; Xidong(惠希东); YAO; Kefu(姚可夫); KOU; Hongchao(寇宏超); CHEN; Guoliang(陈国良)

    2003-01-01

    Short-range order domains of face central cubic Zr2Ni (F-Zr2Ni) and tetragonal Zr2Ni (T-Zr2Ni) type structure with a size about 1-3 nanometers were observed in bulk amorphous Zr52.5Cu17.9Ni14.6Al10Ti5 alloy by using HREM and nano-beam electron diffraction technique. A new thermodynamic model was formulated based on the concept of chemical short-range order (SCRO). The molar fractions of CSRO and thermodynamic properties in Ni-Zr, Cu-Zr, Al-Zr, Al-Ni, Zr-Ni-Al and Zr-Ni-Cu were calculated. According to the principle of maximum the optimum glass forming ability (GFA) compositions were predicted in binary and ternary alloys. These results were proved to be valid by the experimental data of crystallizing activation energy, ΔTx and XRD patterns. The TTT curves of Zr-Ni-Cu alloys calculated based on CSRO model shows that the lowest critical cooling rate GFA is in the order of 100 K/s, which is close to the practical cooling rate for the preparation of Zr-based BMG alloys.

  20. Crystallization Process of Heat-treated Amorphous Ni-P Alloy Coating

    Directory of Open Access Journals (Sweden)

    JIN Shi-wei

    2016-09-01

    Full Text Available Amorphous Ni-P alloy coatings were prepared on 45 carbon steel blocks using electrodeposition method. The thermal effect and quality change of Ni-P alloy coating under heating rate of 20℃/min were analyzed by differential scanning calorimetry (DSC and thermogravimetry (TG. Coatings were heat-treated at 300℃ and 400℃ for 0, 15, 30, 45, 60, 75min respectively, coating surface was characterized by scanning electron microscope (SEM, energy dispersive spectrometer (EDS, X-ray diffraction (XRD, microhardness tester. The result shows that the exothermic peak of Ni-P alloy coating appears at 284.8℃, coating quality and elemental composition are stable during the heat treatment. Crystallization process experiences a transformation of amorphous, metastable state NiP and Ni5P2, stable state Ni3P. The microhardness of coating can be improved remarkably after heat treatment, namely, the maximum value of heat-treated coating is 1036.56HV, which is nearly 2 times as hard as as-deposited coating. The corrosion resistance of heat-treated Ni-P alloy coating in NaCl solution is inferior to as-deposited coating, but they are both much better than 45 carbon steel substrate.

  1. Study of Critical Behavior in Amorphous Fe85Sn5Zr10 Alloy Ribbon

    Science.gov (United States)

    Han, L. A.; Hua, X. H.; Zhu, H. Z.; Yang, J.; Yang, H. P.; Yan, Z. X.; Zhang, T.

    2016-10-01

    We have investigated the critical behavior in amorphous Fe85Sn5Zr10 alloy ribbon prepared using a single-roller melt-spinning method. This alloy shows a second-order magnetic transition from paramagnetic to ferromagnetic (FM) state at the Curie temperature T C (˜306 K). To obtain more information on the features of the magnetic transition, a detailed critical exponent study was carried out using isothermal magnetization M (H, T) data in the vicinity of the T C. Modified Arrott plot, Kouvel-Fisher plot, Widom's scaling relation and critical isotherm analysis techniques were used to investigate the critical behavior of this alloy system around its phase transition point. The values of critical exponents determined using the above methods are self-consistent. The estimated critical exponents are fairly close to the theoretical prediction of the three-dimensional (3D) Heisenberg model, implying that short-range FM interactions dominate the critical behavior in amorphous Fe85Sn5Zr10 alloy ribbon.

  2. Study of Critical Behavior in Amorphous Fe85Sn5Zr10 Alloy Ribbon

    Science.gov (United States)

    Han, L. A.; Hua, X. H.; Zhu, H. Z.; Yang, J.; Yang, H. P.; Yan, Z. X.; Zhang, T.

    2017-02-01

    We have investigated the critical behavior in amorphous Fe85Sn5Zr10 alloy ribbon prepared using a single-roller melt-spinning method. This alloy shows a second-order magnetic transition from paramagnetic to ferromagnetic (FM) state at the Curie temperature T C (˜306 K). To obtain more information on the features of the magnetic transition, a detailed critical exponent study was carried out using isothermal magnetization M ( H, T) data in the vicinity of the T C. Modified Arrott plot, Kouvel-Fisher plot, Widom's scaling relation and critical isotherm analysis techniques were used to investigate the critical behavior of this alloy system around its phase transition point. The values of critical exponents determined using the above methods are self-consistent. The estimated critical exponents are fairly close to the theoretical prediction of the three-dimensional (3D) Heisenberg model, implying that short-range FM interactions dominate the critical behavior in amorphous Fe85Sn5Zr10 alloy ribbon.

  3. New Cu-Free Ti-Based Composites with Residual Amorphous Matrix

    Directory of Open Access Journals (Sweden)

    Mircea Nicoara

    2016-04-01

    Full Text Available Titanium-based bulk metallic glasses (BMGs are considered to have potential for biomedical applications because they combine favorable mechanical properties and good biocompatibility. Copper represents the most common alloying element, which provides high amorphization capacity, but reports emphasizing cytotoxic effects of this element have risen concerns about possible effects on human health. A new copper-free alloy with atomic composition Ti42Zr10Pd14Ag26Sn8, in which Cu is completely replaced by Ag, was formulated based on Morinaga’s d-electron alloy design theory. Following this theory, the actual amount of alloying elements, which defines the values of covalent bond strength Bo and d-orbital energy Md, situates the newly designed alloy inside the BMG domain. By mean of centrifugal casting, cylindrical rods with diameters between 2 and 5 mm were fabricated from this new alloy. Differential scanning calorimetry (DSC and X-rays diffraction (XRD, as well as microstructural analyses using optical and scanning electron microscopy (OM/SEM revealed an interesting structure characterized by liquid phase-separated formation of crystalline Ag, as well as metastable intermetallic phases embedded in residual amorphous phases.

  4. 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.

  5. 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.

  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. Crystallisation of partially amorphized Ni-Mo alloy

    Energy Technology Data Exchange (ETDEWEB)

    Martinez-Sanchez, R.; Diaz de la Torre, S.; Espinosa-Magana, F. [Centro de Investigacion en Materiales Avanzados (CIMAV), Chihuahua (Mexico); Bejar Gomez, L. [Centro de Investigacion en Materiales Avanzados (CIMAV), Chihuahua (Mexico); Univ. Michoacana de San Nicolas de Hidalgo, Morelia (Mexico); Cabanas-Moreno, J.G. [Inst. Politecnico Nacional, ESFM, UPALM-Zacatenco, Mexico D.F. (Mexico)

    2001-07-01

    The Ni-Mo system processed through mechanical alloying (MA) technique has been widely investigated. Complete or partial amorphisation in this binary system mainly depends on the concentration of the elements. A new microstructural phase, called ''Y'' has been reported upon crystallisation of the powder. Although the ''Y'' phase formation has been attributed to the presence of C, O or N contaminants, its identification and characteristics remains unclear. In this work, an oxicarbide (Ni{sub 6}Mo{sub 6}(C,O){sub 1.06}) has been identified in samples in the as-heated condition and has been found as the crystallised phase in major amount in the final product. The XRD pattern of this oxicarbide is very similar to that reported before for a new phase called ''Y''. The simulated XRD pattern of oxicarbide (Ni{sub 6}Mo{sub 6}(C,O){sub 1.06}) is in good agreement with that experimentally found in this work. The activation energy required to induce crystallisation ({proportional_to}336 kJ/mol) matches well to the values reported in literature. (orig.)

  8. PREPARATION AND ACTIVATION OF RAPIDLY SOLIDIFIED Ni-Zr-Al AMORPHOUS ALLOY FOR CATALYTIC PURPOSE%快速凝固Ni-Zr-Al非晶态催化合金的制备与活化处理

    Institute of Scientific and Technical Information of China (English)

    张国胜; 张海峰; 沈宁福

    1999-01-01

    @@ As new catalytic materials, amorphous alloys have attracted much attention since 1980s. Rapid solidification is one of the main techniques to prepare amorphous alloys.However, as-cast rapidly solidified alloys usually can not be directly used as the catalyst for their poor surface area, oxide film on their surface, etc. Therefore, activation pretreatment must be carried out. Recently, leaching aluminum has been attempted to activate rapidly solidified amorphous catalytic alloys containing aluminum. In order to carry out such an activation pretreatment, the Al-rich amorphous precursor alloys must be obtained first, in which the content of active component must be sufficiently high so that the catalytic activity of the activated catalyst can be attained. On the other hand, the chemical composition of the precursor must approach eutectic point or contribute to the range of low liquidus temperature so that the glass transition can be easily achieved according to the solidification theory[1]. So far Al-based alloys which meet the dual confinement have not been found yet. For Ni-Al and Cu-Al systems,only the microcrystalline alloys can be obtained through rapid solidification[2,3].In the present study, glass formation was achieved by introducing promotion elements in Ni-Al system precursor alloys.

  9. Ion-implantation-induced amorphization of InxGa1-xP alloys as functions of stoichiometry and temperature

    Science.gov (United States)

    Hussain, Z. S.; Wendler, E.; Wesch, W.; Schnohr, C. S.; Ridgway, M. C.

    2016-05-01

    Rutherford Backscattering Spectrometry/Channeling and Extended X-ray Absorption Fine Structure measurements have been combined to investigate the amorphization of InxGa1-xP alloys at 15 and 300 K for selected stoichiometries representative of the entire stoichiometric range. The amorphization kinetics differs considerably for the two temperatures: at 15 K, the amorphization kinetics of InxGa1-xP is intermediate between the two binary extremes while at 300 K, InxGa1-xP is more easily amorphized than both InP and GaP. Direct impact and stimulated amorphization both contribute to the amorphization process at 15 K. Dynamic annealing via thermally induced Frenkel pair recombination reduces the influence of direct impact amorphization at 300 K such that the stimulated amorphization is dominant. At this temperature, stimulated amorphization in ternary InxGa1-xP alloys is supported by the structural disorder inherent from the bimodal bond length distribution.

  10. Atomic Diffusion in Amorphous Alloy Melts%非晶合金熔体的原子扩散

    Institute of Scientific and Technical Information of China (English)

    胡金亮; 朱纯傲; 耿永亮; 张博

    2014-01-01

    Diffusion in amorphous alloy melts is an important kinetic parameter to describe the properties in melts.Dif-ferent from the normal alloy melts,the diffusion behavior of amorphous alloy melts tend to have their own unique proper-ties,such as representing a typical slow diffusivity and a complex temperature dependent.But the researches on atomic diffusion are still at a preliminary stage whether in domestic or international study due to technical and theoretical difficul-ties.This paper mainly introduced some measurement techniques of the diffusion coefficient,including our self-designed sliding cell method,which combined the merits of the traditional long capillary method and the shear cell method,and ruled out the undesired atomic diffuse occuring in heating process.It’s concerned as an effective way to measure the diffu-sion coefficient.In addition,based on the diffusion results and models of the amorphous alloy melts,the diffusion research in amorphous alloy melts were summarized and discussed.As some good models to describe the diffusion behavior of the simple liquids,Arrhenius relationship,VFT function,Tn relationship,Darken equation and S-E relationship show a lot of limitations in amorphous alloy melts.At the same time,although MCT theory can predict the dynamics of glass forming liquids,which were confirmed by experiments and simulations,it also have some issues that are difficult to overcome.%非晶合金熔体的扩散是描述非晶合金熔体动力学行为的重要参数,不同于一般的金属熔体,非晶合金熔体的扩散行为具有自己独特的性质,如表现出典型的慢扩散和复杂的温度依赖关系等。由于技术、理论上的原因,目前无论是国内还是国际上,对非晶合金熔体扩散的研究尚处于不成熟的阶段。主要介绍了扩散系数的几种比较可行的测量方法,其中包括最近本课题组在传统长管法和切单元法基础上开发的滑动剪切技术,该技术能

  11. Effect of Laser Power on the Quality of Drilled Micro Hole Using Cu50Zr50 Amorphous Alloys Foils

    Directory of Open Access Journals (Sweden)

    Chuan-Jie Wang

    2014-11-01

    Full Text Available The rapid growth of the micro-electro-mechanical systems (MEMS is being driven by the rapid development of the micro manufacturing processes. Laser beam machining is one of the micro manufacturing processes which can shape almost all ranges of engineering materials. In this study, the effect of laser power on the quality of drilled micro holes using Cu50Zr50 amorphous alloys foils is experimentally investigated. It indicates that both entrance and exit circularities diameters increase with laser power. The circularities of the holes at the entry and the exit are in the range of 0.893 to 0.997. The taper of drilled holes increases quickly to a stable value with the increase of laser power from 60 to 110 W, then decreases quickly when the laser power becomes larger than 170 W. The micro holes with a diameter of 400 to 1200 μm are manufactured successfully by laser drilling processes. The formation mechanism of the quality of the laser drilled hole is analyzed based on the laser beam and the properties of amorphous alloys foils.

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

    Directory of Open Access Journals (Sweden)

    R. Nowosielski

    2006-04-01

    Full Text Available 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 crystallization kinetics and magnetic properties amorphous Co77Si11.5B11.5 alloy.Practical implications: The attractive properties of Co-Si-B alloy are of special interest for basic research on the materials as well as for their potential applications, like magnetic sensors. The Co soft magnetic material is used in noise filters, saturable reactors, miniature inductance elements for abating spike noise, mains transformers, choke coils, zero-phase current transformers, and magnetic heads etc., i.e., devices which are expected to exhibit high levels of permeability at high frequencies.Originality/value: It has been shown that thermal annealing at temperature close to the crystallization temperature leads to a significant increase of the initial magnetic permeability.

  13. Annealed Crystallization and Catalytic activity of Ultrafine NiB Amorphous Alloy

    Institute of Scientific and Technical Information of China (English)

    WEIShiqing; HUTiandou; 等

    2001-01-01

    A Ultrafine amorphous NiB alloy was prepared via chemical reduction method;Its structures during the crystallizatioin precess was characterized by such techniques as Differential thermal analysis (DTA),X-ray absorption fine structure (XAFS) and X-ray diffraction(XRD),and correlated to the catalytic properties for benzene hydrogenation.It was found that the crystallization of amorphous NiB alloy was carried out in two steps,as indicated by two exothermic peaks centered at 598 and 652K respectively.During the first step.two metastable crystalline phases,i.e.,Ni3B and a noaocrstalline Ni phase(Ni-rich NiB alloy),were formed.Further annealing at higher temperature of 652 K may result in the decomposition of crystalline Ni3B and aggregation of nanocrystalline Ni,the benzene hydrogenation is optimized around the annealing temperature of 623K.It most probably results from the maximum amount of active site on nanocrystalline Ni formed by thermal treatment at appropriate annealing temperature.

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

    Energy Technology Data Exchange (ETDEWEB)

    Quintana, I., E-mail: iquintana@tekniker.es [CIC marGUNE, Pol. Ibaitarte 5, 20870, Elgoibar, Guipuzcoa (Spain); Dobrev, T. [Manufacturing Engineering Centre, Cardiff University, Cardiff, CF24 3AA (United Kingdom); Aranzabe, A. [Manufacturing Processes Department, Fundacion Tekniker, Av. Otaola 20, 2060, Eibar, Guipuzcoa (Spain); Lalev, G.; Dimov, S. [Manufacturing Engineering Centre, Cardiff University, Cardiff, CF24 3AA (United Kingdom)

    2009-04-15

    The machining response of amorphous and polycrystalline Ni-based alloys (Ni{sub 78}B{sub 14}Si{sub 8}) 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.

  15. Reactive wetting of amorphous silica by molten Al-Mg alloys and their interfacial structures

    Science.gov (United States)

    Shi, Laixin; Shen, Ping; Zhang, Dan; Jiang, Qichuan

    2016-07-01

    The reactive wetting of amorphous silica substrates by molten Al-Mg alloys over a wide composition range was studied using a dispensed sessile drop method in a flowing Ar atmosphere. The effects of the nominal Mg concentration and temperature on the wetting and interfacial microstructures were discussed. The initial contact angle for pure Al on the SiO2 surface was 115° while that for pure Mg was 35° at 1073 K. For the Al-Mg alloy drop, it decreased with increasing nominal Mg concentration. The reaction zone was characterized by layered structures, whose formation was primarily controlled by the variation in the alloy concentration due to the evaporation of Mg and the interfacial reaction from the viewpoint of thermodynamics as well as by the penetration or diffusion of Mg, Al and Si from the viewpoint of kinetics. In addition, the effects of the reaction and the evaporation of Mg on the movement of the triple line were examined. The spreading of the Al-Mg alloy on the SiO2 surface was mainly attributed to the formation of Mg2Si at the interface and the recession of the triple line to the diminishing Mg concentration in the alloy.

  16. 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.

  17. Nanoscale order and crystallization in nitrogen-alloyed amorphous GeTe

    Energy Technology Data Exchange (ETDEWEB)

    Darmawikarta, Kristof; Abelson, John R., E-mail: abelson@illinois.edu [Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, 1304 W. Green St., Urbana, Illinois 61801 (United States); Coordinated Science Laboratory, University of Illinois at Urbana-Champaign, 1308 W. Main St., Urbana, Illinois 61801 (United States); Raoux, Simone [IBM T. J. Watson Research Center, 1101 Kitchawan Road, Route 134, Yorktown Heights, New York 10598 (United States); Bishop, Stephen G. [Coordinated Science Laboratory, University of Illinois at Urbana-Champaign, 1308 W. Main St., Urbana, Illinois 61801 (United States); Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, 1406 W. Green St., Urbana, Illinois 61801 (United States)

    2014-11-10

    The nanoscale order in amorphous GeTe thin films is measured using fluctuation transmission electron microscopy (FTEM). The order increases upon annealing at 145 °C, which indicates a coarsening of subcritical nuclei. This correlates with a reduction in the nucleation delay time in laser crystallization. A shift in the FTEM peak positions may indicate a transformation in local bonding. In samples alloyed with 12 at. % nitrogen, the order does not change upon annealing, the peak does not shift, and the nucleation time is longer. The FTEM data indicate that nitrogen suppresses the structural evolution necessary for the nucleation process and increases the thermal stability of the material.

  18. 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.

  19. Stability of amorphous silicon alloy triple-junction solar cells and modules

    Energy Technology Data Exchange (ETDEWEB)

    Sato, K.; Aiga, M.; Otsubo, M.

    1987-06-25

    Results on reliability test for amorphous silicon alloy triple-junction solar cells and modules are described. It has been found that, for a-SiGe:H pin cells, reduction of the stress in the film is of first importance for stability. Application of low-temperature-deposited microcrystalline p-layer for each sub cell and of thinner i-layers for the middle and the bottom cells improves stability of triple-junction cells, by enhancing the electric field in the i-layers.

  20. 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

  1. Fe-Zr-Nd-Y-B permanent magnet derived from crystallization of bulk amorphous alloy

    Science.gov (United States)

    Tan, Xiaohua; Xu, Hui; Bai, Qin; Dong, Yuanda

    2007-12-01

    The microstructure and magnetic properties of Nd2Fe14B/(Fe3B,α-Fe) nanocomposite magnet derived form crystallization of bulk amorphous Fe68Zr2Y4B21Nd5 alloy, which was prepared by copper mold casting, have been investigated. The obtaining maximum values of Ms, Mr, Hci, and (BH)max annealed at 963K for Fe68Zr2Nd5Y4B21 alloy are 86Am2/kg, 49Am2/kg, 380kA/m, and 43kJ/m3, respectively. δM plot, high resolution transmission electron microscopy observation, and three-dimensional atom probe technique clarified that the hard magnetic behavior is due to the exchange coupling between soft and hard magnetic nanophases.

  2. 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 located in a TiO2 unit in the oxide layer, but rather in a mixed Ti-Al oxide layer. The optical band gap energy of the anodic oxide layers was determined by vacuum ultraviolet spectroscopy in the energy range from 4.1 to 9.2 eV (300–135 nm). The results indicate that amorphous anodic Al2O3 has a direct...

  3. Effect of high pressure on microstructure of crystallizing amorphous Nd9Fe85B6 alloy

    Institute of Scientific and Technical Information of China (English)

    WU Wei; LI Hui; XIE Yanwu; ZHANG Xiangyi

    2008-01-01

    The effect of high pressure on the microstructure of annealed amorphous NdgFegsB6 alloy was studied. It was found that applica- tion of high pressure made the microstructure of the crystallized alloy much more homogeneous. The average grain size of the Nd2Fe14B phase decreased with the increase of pressure, whereas, the size of the α-Fe first increased when a pressure of 1 Gpa was applied and then decreased with further increase of pressure. Pressure-induced (410) texture of the Nd2Fe14B phase was also observed. The present study sug-gested an effective route for controlling the microstructure in a nanoscale solid.

  4. 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

  5. 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

  6. Experimental and molecular dynamics simulation study of structure of liquid and amorphous Ni62Nb38 alloy

    Science.gov (United States)

    Zhang, Y.; Ashcraft, R.; Mendelev, M. I.; Wang, C. Z.; Kelton, K. F.

    2016-11-01

    The state-of-the-art experimental and atomistic simulation techniques were utilized to study the structure of the liquid and amorphous Ni62Nb38 alloy. First, the ab initio molecular dynamics (AIMD) simulation was performed at rather high temperature where the time limitations of the AIMD do not prevent to reach the equilibrium liquid structure. A semi-empirical potential of the Finnis-Sinclair (FS) type was developed to almost exactly reproduce the AIMD partial pair correlation functions (PPCFs) in a classical molecular dynamics simulation. This simulation also showed that the FS potential well reproduces the bond angle distributions. The FS potential was then employed to elongate the AIMD PPCFs and determine the total structure factor (TSF) which was found to be in excellent agreement with X-ray TSF obtained within the present study demonstrating the reliability of the AIMD for the simulation of the structure of the liquid Ni-Nb alloys as well as the reliability of the developed FS potential. The glass structure obtained with the developed potential was also found to be in excellent agreement with the X-ray data. The analysis of the structure revealed that a network of the icosahedra clusters centered on Ni atoms is forming during cooling the liquid alloy down to Tg and the Nb Z14, Z15, and Z16 clusters are attached to this network. This network is the main feature of the Ni62Nb38 alloy and further investigations of the properties of this alloy should be based on study of the behavior of this network.

  7. The features of CNT growth on catalyst-content amorphous alloy layer by CVD-method

    Science.gov (United States)

    Dubkov, S.; Bulyarskii, S.; Pavlov, A.; Trifonov, A.; Kitsyuk, E.; Mierczynski, P.; Maniecki, T.; Ciesielski, R.; Gavrilov, S.; Gromov, D.

    2016-12-01

    This work is devoted to the CVD-synthesis of arrays of carbon nanotubes (CNTs) on Co-Zr-N-(O), Ni-Nb-N-(O), Co- Ta-N-(O) catalytic alloy films from gas mixture of C2H2+NH3+Ar at a substrate temperature of about 550°C.Heating of the amorphous alloy causes its crystallization and squeezing of the catalytic metal onto the surface. As a result, small catalyst particles are formed on the surface. The CNT growth takes place after wards on these particles. It should be noted that the growth of CNT arrays on these alloys is insensitive to the thickness of alloy film, which makes this approach technically attractive. In particular, the possibility of local CNT growth at the ends of the Co-Ta-N-(O) film and three-level CNT growth at the end of more complex structure SiO2/Ni-Nb-N-O/SiO2/Ni-Nb-N-O/SiO2/Ni-Nb-N-O/SiO2 is demonstrated.

  8. 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.

  9. Structural, microstructural and magnetic properties of amorphous/nanocrystalline Ni{sub 63}Fe{sub 13}Mo{sub 4}Nb{sub 20} powders prepared by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Karimi, L., E-mail: leilakarimi@iauahvaz.ac.ir [Materials Science and Engineering Department, Islamic Azad University of Ahvaz, Ahvaz (Iran, Islamic Republic of); Shokrollahi, H. [Materials Science and Engineering Department, Shiraz University of Technology, 71555-313, Shiraz (Iran, Islamic Republic of)

    2011-06-09

    Highlights: > The amorphous/nanocrystalline Ni{sub 63}Fe{sub 13}Mo{sub 4}Nb{sub 20} magnetic powders were prepared by mechanical alloying. > The saturation magnetization decreases and the coercivity increases as a result of the electronic interactions and the grain size reduction. > The use of amorphous alloy is due to the lower magnetic losses and higher electrical resistivity compared with other magnetic material - Abstract: This paper focuses on the magnetic, structural and microstructural studies of amorphous/nanocrystalline Ni{sub 63}Fe{sub 13}Mo{sub 4}Nb{sub 20} powders prepared by mechanical alloying. The ball-milling of Ni, Fe, Mo and Nb powders leads to alloying the element powders, the nanocrystalline and an amorphization matrix with Mo element up to 120 h followed by the strain and thermal-induced nucleation of a single nanocrystalline Ni-based phase from the amorphous matrix at 190 h. The results showed that the saturation magnetization decreases as a result of the electronic interactions between magnetic and non-magnetic elements and finally increases by the partial crystallization of the amorphous matrix. The coercive force increases as the milling time increases and finally decreases due to sub-grains formation.

  10. Preparation of Mg55Ni35Si10 Amorphous Powders by Mechanical Alloying and Consolidation by Vacuum Hot Pressing

    Institute of Scientific and Technical Information of China (English)

    YANG Deng-Ke; WEN Cui-E; HAN Fu-Sheng; WANG Qing-Zhou; LI Hai-Jin

    2006-01-01

    @@ Amorphous Mg55Ni35Si10 powders are fabricated by using a mechanical alloying technique. The amorphous powders are found to exhibit a relatively high crystallization temperature of 380℃. The as-milled amorphous Mg55Ni35Si10 powders are consolidated successfully into bulk body by vacuum hot pressing technique. Limited nanocrystallization is noticed. The Vickers microhardness range of the Mg55Ni35Si10 bulk sample is 7834 to 8048 Mpa. Its bending strength and compressive strength are 529 Mpa and 1466 Mpa, respectively.

  11. Stoichiometry dependence of resistance drift phenomena in amorphous GeSnTe phase-change alloys

    Science.gov (United States)

    Luckas, J.; Piarristeguy, A.; Bruns, G.; Jost, P.; Grothe, S.; Schmidt, R. M.; Longeaud, C.; Wuttig, M.

    2013-01-01

    In phase-change materials, the amorphous state resistivity increases with time following a power law ρ ∝ (t/t0)αRD. This drift in resistivity seriously hampers the potential of multilevel-storage to achieve an increased capacity in phase-change memories. This paper presents the stoichiometric dependence of drift phenomena in amorphous GeSnTe systems (a-GeSnTe) and other known phase-change alloys with the objective to identify low drift materials. The substitution of Ge by Sn results in a systematic decrease of the drift parameter from a-GeTe (αRD = 0.129) to a-Ge2Sn2Te4 (αRD = 0.053). Furthermore, with increasing Sn content a decrease in crystallization temperature, trap state density, optical band gap, and activation energy for electronic conduction is observed. In a-GeSnTe, a-GeSbTe, and a-AgInSbTe alloys as well, the drift parameter αRD correlates to the activation energy for electronic conduction. This study indicates that low drift materials are characterized by low activation energies of electronic conduction. The correlation found between drift and activation energy of electronic conduction manifests a useful criterion for material optimization.

  12. First-principles study of amorphous Ga4Sb6Te3 phase-change alloys

    Science.gov (United States)

    Bouzid, Assil; Gabardi, Silvia; Massobrio, Carlo; Boero, Mauro; Bernasconi, Marco

    2015-05-01

    First-principles molecular dynamics simulations within the density functional theory framework were performed to generate amorphous models of the Ga4Sb6Te3 phase change alloy by quenching from the melt. We find that Ga-Sb and Ga-Te are the most abundant bonds with only a minor amount of Sb-Te bonds participating to the alloy network. Ga and four-coordinated Sb atoms present a tetrahedral-like geometry, whereas three-coordinated Sb atoms are in a pyramidal configuration. The tetrahedral-like geometries are similar to those of the crystalline phase of the two binary compounds GaTe and GaSb. A sizable fraction of Sb-Sb bonds is also present, indicating a partial nanoscale segregation of Sb. Despite the fact that the composition Ga4Sb6Te3 lies on the pseudobinary Ga Sb -Sb2Te3 tie line, the amorphous network can be seen as a mixture of the two binary compounds GaTe and GaSb with intertwined elemental Sb.

  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. Effect of Ion Bombardment on the Growth and Properties of Hydrogenated Amorphous Silicon-Germanium Alloys

    Science.gov (United States)

    Perrin, Jérôme; Takeda, Yoshihiko; Hirano, Naoto; Matsuura, Hideharu; Matsuda, Akihisa

    1989-01-01

    We report a systematic investigation of the effect of ion bombardment during the growth of amorphous silicon-germanium alloy films from silane and germane rf-glow discharge. Independent control of the plasma and the ion flux and energy is obtained by using a triode configuration. The ion contribution to the total deposition rate can reach 20% on negatively biased substrates. Although the Si and Ge composition of the film does not depend on the ion flux and energy, the optical, structural and electronic properties are drastically modified at low deposition temperatures when the maximum ion energy increases up to 50 eV, and remain constant above 50 eV. For a Ge atomic concentration of 37% and a temperature of 135°C, the optical gap decreases from 1.67 to 1.45 eV. This is correlated with a modification of hydrogen bonding configurations. Silicon dihydride sites disappear and preferential attachment of hydrogen to silicon is reduced in favour of germanium. Moreover the photoconductivity increases which shows that ion bombardment is a key parameter to optimize the quality of low band gap amorphous silicon-germanium alloys.

  15. Nanocrystals and amorphous matrix phase studies of Finemet-like alloys containing Ge

    Energy Technology Data Exchange (ETDEWEB)

    Moya, J.A., E-mail: jmoya.fi.uba@gmail.co [IESIING, Facultad de Ingenieria e Informatica, UCASAL, A4402FYP Salta (Argentina); Lab. Solidos Amorfos, Facultad de Ingenieria, INTECIN, UBA-CONICET (Argentina); CONICET (Argentina)

    2010-07-15

    Two simple models were developed in order to determine the chemical composition of both nanocrystals and intergranular amorphous phases in nanocrystallized Fe{sub 73.5}Si{sub 13.5}B{sub 9}Nb{sub 3}Cu{sub 1} containing Ge using data from X-ray diffraction and Moessbauer spectroscopy techniques. Saturation magnetization of the amorphous intergranular matrix (M{sub s}{sup am}) was calculated considering the contribution of the alpha-Fe(Si,Ge) nanocrystals and saturation magnetization of the alloys. The behavior of M{sub s}{sup am} with the iron content of the matrix was obtained and discussed. The exchange stiffness constant for the nanograins and for the amorphous phases was determined. The increment in the coercive field (H{sub c}) with increasing Ge content was evaluated using two theoretical models for the random magnetocrystalline anisotropy constant (). Results show that the magnetic hardening observed could not be attributed to an increase in but mainly to an important increment of the magnetostriction constant of the alpha-Fe(Si,Ge) nanocrystals (lambda{sub s}{sup cr}). Values for lambda{sub s}{sup cr} are proposed.

  16. Nano-crystallization and magnetic mechanisms of Fe{sub 85}Si{sub 2}B{sub 8}P{sub 4}Cu{sub 1} amorphous alloy by ab initio molecular dynamics simulation

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yaocen; Takeuchi, Akira; Makino, Akihiro [Institute for Material Research, Tohoku University, Sendai 980-8577 (Japan); Liang, Yunye [New Industry Creation Hatchery Center, Tohoku University, Sendai 980-8579 (Japan); Kawazoe, Yoshiyuki [New Industry Creation Hatchery Center, Tohoku University, Sendai 980-8579 (Japan); Kutateladze Institute of Thermophysics, Siberian Branch of Russian Academy of Sciences, 630090 Novosibirsk (Russian Federation)

    2014-05-07

    Iron-based amorphous and nano-crystalline alloys have attracted a growing interest due to their potential in the application of magnetic coil production. However, fundamental understanding of the nano-crystallization mechanisms and magnetic features in the amorphous structure are still lack of knowledge. In the present work, we performed ab initio molecular dynamics simulation to clarify the ionic and electronic structure in atomic scale, and to derive the origin of the good magnetic property of Fe{sub 85}Si{sub 2}B{sub 8}P{sub 4}Cu{sub 1} amorphous alloy. The simulation gave a direct evidence of the Cu-P bonding preference in the amorphous alloy, which may promote nucleation in nano-crystallization process. On the other hand, the electron transfer and the band/orbital features in the amorphous alloy suggests that alloying elements with large electronegativity and the potential to expand Fe disordered matrix are preferred for enhancing the magnetization.

  17. Effect of the milling time on thermal stability of mechanically alloyed Mg{sub 5}0 Ni{sub 5}0 amorphous alloy; Efecto del tiempo de molienda sobre la estabilidad termica del amorfo Mg{sub 5}0 Ni:50 producido mediante aleado mecanico

    Energy Technology Data Exchange (ETDEWEB)

    Guzman, D.; Ordonez, S.; Serafini, D.; Rojas, P.; Aguilar, C.; Santander, M.; Navea, L.

    2009-07-01

    In order to study the relationship between the milling time used in the production of Mg{sub 5}0Ni{sub 5}0 amorphous alloy and its thermal stability, seven amorphous alloys were produced by milling for 20, 25, 30, 35, 40, 50 and 60 h each sample. The obtained powders were morphological and structurally characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. The thermal stability of amorphous alloys was study by differential scanning calorimetry (DSC). Based on the obtained results, it can be concluded that the increase in the added energy when milling for longer time causes the homogenization of the microstructure with an increase in amorphous phase, which dissolves a large amount of nickel in its structure. Therefore, the simultaneous crystallization of the Mg{sub 2}Ni and MgNi{sub 2} intermetallic compounds at 345 degree centigrade can be explained. (Author) 19 refs.

  18. Local structure of amorphous GaN{sub 1-x}As{sub x} semiconductor alloys across the composition range

    Energy Technology Data Exchange (ETDEWEB)

    Levander, A. X.; Dubon, O. D.; Wu, J. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Department of Materials Science and Engineering, University of California, Berkeley, California 94720 (United States); Yu, K. M.; Liliental-Weber, Z.; Walukiewicz, W. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Novikov, S. V.; Foxon, C. T. [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom)

    2013-06-28

    Typically only dilute (up to {approx}10%) highly mismatched alloys can be grown due to the large differences in atomic size and electronegativity of the host and the alloying elements. We have overcome the miscibility gap of the GaN{sub 1-x}As{sub x} system using low temperature molecular beam epitaxy. In the intermediate composition range (0.10 < x < 0.75), the resulting alloys are amorphous. To gain a better understanding of the amorphous structure, the local environment of the As and Ga atoms was investigated using extended x-ray absorption fine structure (EXAFS). The EXAFS analysis shows a high concentration of dangling bonds compared to the crystalline binary endpoint compounds of the alloy system. The disorder parameter was larger for amorphous films compared to crystalline references, but comparable with other amorphous semiconductors. By examining the Ga local environment, the dangling bond density and disorder associated with As-related and N-related bonds could be decoupled. The N-related bonds had a lower dangling bond density and lower disorder.

  19. 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.

  20. 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 ().

  1. Kinetic Characteristic of Hydrogenation Zr-Ti-Cu-Ni-Be Bulk Amorphous Alloys

    Institute of Scientific and Technical Information of China (English)

    Delin PENG; Jun SHEN; Jianfei SUN; Yuyong CHEN

    2004-01-01

    The relationship between the hydrogen content and the microhardness and the charging period, the effect of hydrogen on the activation energy, the kinetics of glass transition and crystallization of Zr-Ti-Cu-Ni-Be bulk amorphous alloy were studied by differential scanning calorimetry (DSC) and the Kissinger equation. It shows that both of the hydrogen content and the microhardness are related to the charging period, and that the glass transition and crystallization behavior are associated with the heating rate, and possess the kinetic effect. Hydrogen increases the glass transition temperature and the crystallization temperature, decreasing the enthalpies in the different stages of crystallization.Hydrogen increases the activation energies of the glass transition and the crystallization and changes the kinetic effect. The dependent extent between the glass transition, the crystallization and heating rate decreases after hydrogen charging.

  2. Synthesis and Electro-Magneto-Mechanical Properties of Graphene Aerogels Functionalized with Co-Fe-P Amorphous Alloys

    Directory of Open Access Journals (Sweden)

    Guang-Ping Zheng

    2016-07-01

    Full Text Available Graphene aerogels (GAs are functionalized with Fe-Co-P alloy using an electro-deposition method. The Fe-Co-P alloy coated on the graphene nanosheets is found to possess an amorphous structure and a nanoporous architecture of GAs. The electro-mechanical properties of GAs are significantly affected by the Fe-Co-P nanoparticles embedded inside GAs. The electro-mechanical responses of GA/Fe-Co-P nanoporous hybrid structures are sensitive to an applied magnetic field, demonstrating that they are promising for electro-magneto-mechanical applications. The light-weight, high-strength and nanoporous GAs functionalized with Fe-Co-P amorphous alloys are desirable sensors, actuators, and nano-electro-mechanical systems that could be controlled or manipulated by mechanical, electric and magnetic fields.

  3. Microstructural characterization and amorphous phase formation in Co{sub 40}Fe{sub 22}Ta{sub 8}B{sub 30} powders produced by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Taghvaei, Amir Hossein, E-mail: amirtaghvaei@gmail.com [Department of Materials Science and Engineering, School of Engineering, Shiraz University, Shiraz (Iran, Islamic Republic of); Stoica, Mihai [IFW Dresden, Institute for Complex Materials, Helmholtzstr. 20, D-01069 Dresden (Germany); Vaughan, Gavin [ESRF, F-38042 Grenoble (France); Ghaffari, Mohammad [School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798 (Singapore); Maleksaeedi, Saeed [Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, Singapore 638075 (Singapore); Janghorban, Kamal [Department of Materials Science and Engineering, School of Engineering, Shiraz University, Shiraz (Iran, Islamic Republic of)

    2012-01-25

    Highlights: Black-Right-Pointing-Pointer Mechanical alloying developed the amorphous phase in Co{sub 40}Fe{sub 22}Ta{sub 8}B{sub 30} alloy. Black-Right-Pointing-Pointer The powders had 96 wt% amorphous phase after 200 h milling. Black-Right-Pointing-Pointer The 200 h milled powders showed the huge relaxation hump in the DSC plot. Black-Right-Pointing-Pointer The mean volume lattice strain was calculated based on the Miracle's model. - Abstract: In this work, microstructural evolution and amorphous phase formation in Co{sub 40}Fe{sub 22}Ta{sub 8}B{sub 30} alloy produced by mechanical alloying (MA) of the elemental powder mixture under argon gas atmosphere was investigated. Milling time had a profound effect on the phase transformation, microstructure, morphological evolution and thermal behavior of the powders. These effects were studied by the X-ray powder diffraction (XRD) in reflection mode using Cu K{alpha} and in transmission configuration using synchrotron radiation, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The results showed that at the early stage of the milling, microstructure consisted of nanocrystalline bcc-(Fe, Co) phases and unreacted tantalum. Further milling, produced an amorphous phase, which became a dominant phase with a fraction of 96 wt% after 200 h milling. The DSC profile of 200 h milled powders demonstrated a huge and broad exothermic hump due to the structural relaxation, followed by a single exothermic peak, indicating the crystallization of the amorphous phase. Further XRD studies in transmission mode by synchrotron radiation revealed that the crystalline products were (Co, Fe){sub 20.82}Ta{sub 2.18}B{sub 6}, (Co, Fe){sub 21} Ta{sub 2} B{sub 6}, and (Co, Fe){sub 3}B{sub 2}. The amorphization mechanisms were discussed in terms of severe grain refinement, atomic size effect, the concept of local topological instability and the heat of mixing of the reactants.

  4. Influence of bath composition on the electrodeposition of cobalt-molybdenum amorphous alloy thin films

    Institute of Scientific and Technical Information of China (English)

    Qiaoying Zhou; Hongliang Ge; Guoying Wei; Qiong Wu

    2008-01-01

    Cobalt-molybdenum (Co-Mo) amorphous alloy thin films were deposited on copper substrates by the electrochemical method at pH 4.0. Among the experimental electrodeposition parameters, only the concentration ratio of molybdate to cobalt ions ([ MoO2-4 ]/[CO2+]) was varied to analyze its influence on the mechanism of induced cobalt-molybdenum codeposition. Voltammetry was one of the main techniques, which was used to examine the voltammetric response, revealing that cobalt-molybdenum codeposi-tion depended on the nature of the species in solution. To correlate the type of the film to the electrochemical response, various co-bait-molybdenum alloy thin films obtained from different [ MoO2-4]/[Co2+] solutions were tested. Crack-free homogeneous films could be easily obtained from the low molybdate concentrations ([ MoO2-4]/[Co2+]≈0.05) applying low deposition potentials.Moreover, the content of molybdenum up to 30wt% could be obtained from high molybdate concentration; in this case, the films showed cracks. The formation of these cracked films could be predicted from the observed distortions in the curves of electric cur-rent-time (j-t) deposition transients. The films with amorphous stmeture were obtained. The hysteresis loops suggested that the easily film were obtained when the deposition potential was -1025 mV, and [ MoO2-4]/[Co2+] was 0.05 in solution, which exhibited a nicer soft-magnetic response.

  5. 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

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

    Science.gov (United States)

    Chiang, Han-Hsin; Lu, Jian-Ming; Kuo, Chin-Lung

    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 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) cm(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 LixSi, indicating a more profound dependence on the

  7. 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...

  8. Bulk amorphous Al{sub 75}V{sub 12.5}Fe{sub 12.5−x}Cu{sub x} alloys fabricated by consolidation of mechanically alloyed amorphous powders

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Bo; Wang, Xinfu; Li, Xianyu; Wang, Dan; Qin, Yong; Han, Fusheng, E-mail: fshan@issp.ac.cn

    2014-02-15

    Highlights: • Al{sub 75}V{sub 12.5}Fe{sub 12.5−x}Cu{sub x} (x = 0, 6.25, and 12.5 at%) amorphous powders were synthesized by MA. • Bulk Al{sub 75}V{sub 12.5}Fe{sub 12.5} amorphous alloy is obtained by means of hydraulic pressing. • The Vickers microhardness of bulk sample is in the range of 821-927 HV. -- Abstract: Hydraulic press was used to produce bulk amorphous Al{sub 75}V{sub 12.5}Fe{sub 12.5−x}Cu{sub x} (x = 0, 6.25, and 12.5) (at.%) alloy by consolidation of mechanically alloyed amorphous powder. The as-milled powders and bulk alloy were examined by X-ray diffraction, transmission electron microscopy and differential scanning calorimetry. The glass-forming ability was evaluated in accordance with the milling time. The results show that the glass-forming ability of the mechanical-alloyed Al{sub 75}V{sub 12.5}Fe{sub 12.5−x}Cu{sub x} powders decreases with the increase of x. The onset crystallization temperatures (T{sub x}{sup onset}) of the three powders are 749 K, 771 K and 712 K, respectively. The results also indicate that the quality of consolidation is very good and the product’s Vickers microhardness is relatively high (821–927 HV)

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

    Science.gov (United States)

    Latif, Saadia; Mehmood, Mazhar; Ahmad, Jamil; Aslam, Muhammad; Ahmed, Maqsood; Zhang, Zhi-dong

    2010-03-01

    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 °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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Latif, Saadia [National Centre for Nanotechnology, Department of Chemical and Materials Engineering, Pakistan Institute of Engineering and Applied Sciences (PIEAS), Nilore, Islamabad 45650 (Pakistan); Mehmood, Mazhar, E-mail: mazhar@pieas.edu.pk [National Centre for Nanotechnology, Department of Chemical and Materials Engineering, Pakistan Institute of Engineering and Applied Sciences (PIEAS), Nilore, Islamabad 45650 (Pakistan); Ahmad, Jamil; Aslam, Muhammad [National Centre for Nanotechnology, Department of Chemical and Materials Engineering, Pakistan Institute of Engineering and Applied Sciences (PIEAS), Nilore, Islamabad 45650 (Pakistan); Ahmed, Maqsood [Physics Division, PINSTECH, P.O. Nilore, Islamabad (Pakistan); Zhang Zhidong [Institute of Metals Research, Chinese Academy of Science, Shenyang (China)

    2010-03-01

    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.

  11. Study on hemocompatibility and corrosion behavior of ion implanted TiNi shape memory alloy and Co-based alloys.

    Science.gov (United States)

    Liang, Chenghao; Huang, Naibao

    2007-10-01

    Biomedical TiNi shape memory alloy and Co-based alloys were ion implanted, and corrosion resistance and hemocompatibility of these had been investigated with electrochemical method, dynamic clotting time, and hemolysis rate tests. The results indicated that the electrochemical stability and anodic polarization behavior of the materials were improved significantly after ion implantation. When TiNi, Co-based alloys were implanted Mo + C and Ti + C, respectively, the corrosion potentials were enhanced more than 200 mV, passive current densities decreased, and passive ranges were broadened. Dynamic clotting time of the ion implanted substances was prolonged and hemolysis rate decreased. All the results pointed out that corrosion resistance and hemocompatibility of the alloys were improved by ion implantation, and effects of dual implantation was better than that of C single implantation. X-ray diffraction analysis of the alloys after dual implantation revealed that TiC, Mo(2)C, Mo(9)Ti(4), and Mo appeared on the surface of TiNi alloy, and CoC(x), Co(3)Ti, TiC, and TiO on the surface of Co-based alloys. These phases dispersing on the alloy surface formed amorphous film, prevented dissolving of alloy elements and improved the corrosion resistance and hemocompatibility of the alloys.

  12. Vacuum Brazing TC4 Titanium Alloy to 304 Stainless Steel with Cu-Ti-Ni-Zr-V Amorphous Alloy Foil

    Science.gov (United States)

    Dong, Honggang; Yang, Zhonglin; Wang, Zengrui; Deng, Dewei; Dong, Chuang

    2014-10-01

    Dissimilar metal vacuum brazing between TC4 titanium alloy and 304 stainless steel was conducted with newly designed Cu-Ti-Ni-Zr-V amorphous alloy foils as filler metals. Solid joints were obtained due to excellent compatibility between the filler metal and stainless steel substrate. Partial dissolution of stainless steel substrate occurred during brazing. The shear strength of the joint brazed with Cu43.75Ti37.5Ni6.25Zr6.25V6.25 foil was 105 MPa and that with Cu37.5Ti25Ni12.5Zr12.5V12.5 was 116 MPa. All the joints fractured through the gray layer in the brazed seam, revealing brittle fracture features. Cr4Ti, Cu0.8FeTi, Fe8TiZr3 and Al2NiTi3C compounds were found in the fractured joint brazed with Cu43.75Ti37.5Ni6.25Zr6.25V6.25 foil, and Fe2Ti, TiCu, Fe8TiZr3 and NiTi0.8Zr0.3 compounds were detected in the joint brazed with Cu37.5Ti25Ni12.5Zr12.5V12.5 foil. The existence of Cr-Ti, Fe-Ti, Cu-Fe-Ti, and Fe-Ti-V intermetallic compounds in the brazed seam caused fracture of the resultant joints.

  13. Hydriding and dehydriding characteristics of nanocrystalline and amorphous Mg20-xLaxNi10(x=0-6) alloys prepared by melt-spinning

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yanghuan; ZHAO Dongliang; REN Huiping; GUO Shihai; WANG Qingchun; WANG Xinlin

    2009-01-01

    In order to improve the hydrogenation and dehydrogenation performances of the Mg2Ni-type alloys, Mg was partially substituted by La in the alloy, and melt spinning technology was used for the preparation of the Mg20-xLaxNi10 (x=0, 2, 4, 6) hydrogen storage alloys. The structures of the alloys were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). It was found that no amorphous phase formed in the as-spun La-free alloy, but the as-spun alloys containing La held a major amorphous phase. When La content x≤2, the major phase in the as-cast alloys was Mg2Ni phase, but with further increase of La content, the major phase of the as-cast alloys changed into LaNi5+LaMg3 phase. Thermal stability of the as-spun alloys was studied by differential scanning calorimetry (DSC), showing that spinning rate was a negligible factor on the crystallization temperature of the amor-phous phase. The hydrogen absorption and desorption kinetics of the as-cast and as-spun alloys were measured using an automatically con-trolled Sieverts apparatus, confirming that the hydrogen absorption and desorption capacities and kinetics of the as-cast alloys clearly in-creased with rising La content. For La content x=2, the as-spun alloy displayed optimal hydrogen desorption kinetics at 200 ℃.

  14. Amorphous Li-Al-Based Compounds: A Novel Approach for Designing High Performance Electrode Materials for Li-Ion Batteries

    Directory of Open Access Journals (Sweden)

    Franziska Thoss

    2013-11-01

    Full Text Available A new amorphous compound with the initial atomic composition Al43Li43Y6Ni8 applied as electrode material for Li-ion batteries is investigated. Unlike other amorphous compounds so-far investigated as anode materials, it already contains Li as a base element in the uncycled state. The amorphous compound powder is prepared by high energy ball milling of a master alloy. It shows a strongly enhanced specific capacity in contrast to amorphous alloys without Li in the initial state. Therewith, by enabling a reversible (delithiation of metallic electrodes without the phase transition caused volume changes it offers the possibility of much increased specific capacities than conventional graphite anodes. According to the charge rate (C-rate, the specific capacity is reversible over 20 cycles at minimum in contrast to conventional crystalline intermetallic phases failing by volume changes. The delithiation process occurs quasi-continuously over a voltage range of nearly 4 V, while the lithiation is mainly observed between 0.1 V and 1.5 V. That way, the electrode is applicable for different potential needs. The electrode stays amorphous during cycling, thus avoiding volume changes. The cycling performance is further enhanced by a significant amount of Fe introduced as wear debris from the milling tools, which acts as a promoting element.

  15. Magnetic properties of Fe80-xCoxZr7Si13 (x = 0 - 30) amorphous alloys

    Science.gov (United States)

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

    2011-11-01

    Amorphous Fe80-xCoxZr7Si13 (x = 0 - 30) alloys, in which boron was completely replaced by silicon as a glass forming element, have been prepared by melt quenching. Partial substitution of iron by cobalt causes the increase of the hyperfine fields from about 19 to 27 T for x = 0 and 30, respectively, as revealed by conventional Mössbauer spectroscopy. The specialized rf-Mössbauer technique permitted us to estimate the soft magnetic properties of the alloys. The rf-collapse effect, which is very sensitive to the local anisotropy field, is observed for all amorphous FeCoZrSi alloys revealing that they are magnetically very soft. The rf-sidebands intensities, which are related to the magnetostriction, increase with the increase of Co content in the alloys. In Fe60Co20Zr7Si13 and Fe50Co30Zr7Si13 samples the rf field exposure induced partial crystallization that was attributed to mechanical deformations related to high frequency magnetostrictive vibrations forced by the rf field. The magnetostrictive origin of this effect was supported by the measurements of magnetostriction constants of the studied alloys. Measurements of the hysteresis loops revealed that coercivity increases for higher Co content.

  16. Parametric Study of Amorphous High-Entropy Alloys formation from two New Perspectives: Atomic Radius Modification and Crystalline Structure of Alloying Elements

    Science.gov (United States)

    Hu, Q.; Guo, S.; Wang, J.M.; Yan, Y.H.; Chen, S.S.; Lu, D.P.; Liu, K.M.; Zou, J.Z.; Zeng, X.R.

    2017-01-01

    Chemical and topological parameters have been widely used for predicting the phase selection in high-entropy alloys (HEAs). Nevertheless, previous studies could be faulted due to the small number of available data points, the negligence of kinetic effects, and the insensitivity to small compositional changes. Here in this work, 92 TiZrHfM, TiZrHfMM, TiZrHfMMM (M = Fe, Cr, V, Nb, Al, Ag, Cu, Ni) HEAs were prepared by melt spinning, to build a reliable and sufficiently large material database to inspect the robustness of previously established parameters. Modification of atomic radii by considering the change of local electronic environment in alloys, was critically found out to be superior in distinguishing the formation of amorphous and crystalline alloys, when compared to using atomic radii of pure elements in topological parameters. Moreover, crystal structures of alloying element were found to play an important role in the amorphous phase formation, which was then attributed to how alloying hexagonal-close-packed elements and face-centered-cubic or body-centered-cubic elements can affect the mixing enthalpy. Findings from this work not only provide parametric studies for HEAs with new and important perspectives, but also reveal possibly a hidden connection among some important concepts in various fields. PMID:28051186

  17. Parametric Study of Amorphous High-Entropy Alloys formation from two New Perspectives: Atomic Radius Modification and Crystalline Structure of Alloying Elements.

    Science.gov (United States)

    Hu, Q; Guo, S; Wang, J M; Yan, Y H; Chen, S S; Lu, D P; Liu, K M; Zou, J Z; Zeng, X R

    2017-01-04

    Chemical and topological parameters have been widely used for predicting the phase selection in high-entropy alloys (HEAs). Nevertheless, previous studies could be faulted due to the small number of available data points, the negligence of kinetic effects, and the insensitivity to small compositional changes. Here in this work, 92 TiZrHfM, TiZrHfMM, TiZrHfMMM (M = Fe, Cr, V, Nb, Al, Ag, Cu, Ni) HEAs were prepared by melt spinning, to build a reliable and sufficiently large material database to inspect the robustness of previously established parameters. Modification of atomic radii by considering the change of local electronic environment in alloys, was critically found out to be superior in distinguishing the formation of amorphous and crystalline alloys, when compared to using atomic radii of pure elements in topological parameters. Moreover, crystal structures of alloying element were found to play an important role in the amorphous phase formation, which was then attributed to how alloying hexagonal-close-packed elements and face-centered-cubic or body-centered-cubic elements can affect the mixing enthalpy. Findings from this work not only provide parametric studies for HEAs with new and important perspectives, but also reveal possibly a hidden connection among some important concepts in various fields.

  18. Effect of crystallization on corrosion behavior of Fe40Ni38B18Mo4 amorphous alloy in 3.5% sodium chloride solution

    DEFF Research Database (Denmark)

    Wu, Y.F.; Chiang, Wen-Chi; Wu, J.K.

    2008-01-01

    After the crystallization of F40Ni38B18Mo4 amorphous alloy by vacuum annealing, the corrosion resistance of its crystalline state shows inferior to its amorphous state due to the local cell action between Ni phase and (Fe, Ni, Mo)(23)B-6 phase in matrix....

  19. Reversible amorphous-crystalline phase changes in a wide range of Se1-xTex alloys studied using ultrafast differential scanning calorimetry

    NARCIS (Netherlands)

    Vermeulen, Paul. A.; Momand, Jamo; Kooi, Bart J.

    2014-01-01

    The reversible amorphous-crystalline phase change in a chalcogenide material, specifically the Se1-xTex alloy, has been investigated for the first time using ultrafast differential scanning calorimetry. Heating rates and cooling rates up to 5000 K/s were used. Repeated reversible amorphous-crystalli

  20. 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.

  1. Thin-film amorphous silicon alloy research partnership, Phase I. Annual technical progress report, February 2, 1995--February 1, 1996

    Energy Technology Data Exchange (ETDEWEB)

    Guha, S. [United Solar Systems Corp., Troy, MI (United States)

    1996-04-01

    The principal objective of this R&D program is to expand, enhance and accelerate knowledge and capabilities for the development of high-performance, two-terminal multifunction amorphous silicon (a-Si) alloy modules. The near-term goal of the program is to achieve 12% stable module efficiency by 1998 using the multifunction approach. This report describes research on back reflectors of Ag/TiO{sub 2}/ZnO.

  2. 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.

  3. Electrical and Magneto-Resistivity Measurements on Amorphous Copper-Titanium Alloys at Low Temperatures

    Science.gov (United States)

    Fan, Renyong

    1992-01-01

    The anomalous transport properties of highly disordered metallic glasses, which require corrections to the classical Boltzmann theory, are due to quantum interference effects of the scattered electron waves. These corrections provide new contributions to the resistivity: "weak localization" and "electron-electron interaction". To study these quantum interference effects, we have made the highest-precision measurements, so far, of the resistances of the amorphous rm Cu_{50}Ti_{50 } and rm Cu_{60}Ti _{40} ribbons at much lower temperatures than before (15mK 0.15K. In contrast, at the lowest temperatures, the magnetoresistances were dominated by weak localization with Zeeman splitting and Maki-Thompson superconducting fluctuations. For higher magnetic fields and lowest temperatures (B/T > 1 T/K), we find discrepancies between our data and the theoretical calculations. We found that most of the parameters of the theoretical fits to the data were similar for both rm Cu_{50}Ti_{50} and rm Cu_{60}Ti_ {40} alloys. The two important exceptions were the inelastic and spin-orbit lifetimes: their zero -field values were about an order of magnitude smaller than those from the magnetoresistances. Also the inelastic lifetimes tend to saturate for T<0.1K in non-zero magnetic fields. Finally, we were also able to estimate the expected superconducting transition temperatures of both rm Cu_{50}Ti_{50} and rm Cu_{60}Ti _{40} alloys: less than 15mK and 5mK, respectively. Our novel technique can, in principle, be used to make high precision resistance measurements down to 15mK on any ribbon or film-like high resistivity metal.

  4. Reduction of Vibration Noise for Amorphous Metal Alloy Core Distribution Transformer

    Institute of Scientific and Technical Information of China (English)

    Liu Daosheng刘道生; Du Boxue杜伯学; Zhang Jiangong张建功; Xu Qiuyuan徐秋元; Qi Zhihai祁治海; Guo Ying郭英

    2015-01-01

    To understand the vibration noise behaviors of amorphous metal alloy core distribution transformer (AMACDT), a 10 kVA prototype was tested under no-load and short-circuit conditions, respectively. The vibration characteristics were described when rated voltage was applied to the secondary side, and the primary side was con-nected with different load resistances. The largest amplitude positions on the upper bracket and tank surfaces were recorded by vibration sensors arranged on the surface. A data-acquisition platform was set up for signal measure-ment. The vibration amplitude related to frequency was discussed, and experimental results indicated that the posi-tion with the largest amplitude accrued in the middle of the upper bracket and tank surface, at phases a and c, re-spectively. The experimental results suggest that magnetostrictive and electrodynamic forces play a major role in exciting the vibration noise. At the same time, some rib-reinforcements were welded on the upper bracket and tank surfaces to lessen the vibration energy, which reduced the noise.

  5. Amorphous oxide alloys as interfacial layers with broadly tunable electronic structures for organic photovoltaic cells.

    Science.gov (United States)

    Zhou, Nanjia; Kim, Myung-Gil; Loser, Stephen; Smith, Jeremy; Yoshida, Hiroyuki; Guo, Xugang; Song, Charles; Jin, Hosub; Chen, Zhihua; Yoon, Seok Min; Freeman, Arthur J; Chang, Robert P H; Facchetti, Antonio; Marks, Tobin J

    2015-06-30

    In diverse classes of organic optoelectronic devices, controlling charge injection, extraction, and blocking across organic semiconductor-inorganic electrode interfaces is crucial for enhancing quantum efficiency and output voltage. To this end, the strategy of inserting engineered interfacial layers (IFLs) between electrical contacts and organic semiconductors has significantly advanced organic light-emitting diode and organic thin film transistor performance. For organic photovoltaic (OPV) devices, an electronically flexible IFL design strategy to incrementally tune energy level matching between the inorganic electrode system and the organic photoactive components without varying the surface chemistry would permit OPV cells to adapt to ever-changing generations of photoactive materials. Here we report the implementation of chemically/environmentally robust, low-temperature solution-processed amorphous transparent semiconducting oxide alloys, In-Ga-O and Ga-Zn-Sn-O, as IFLs for inverted OPVs. Continuous variation of the IFL compositions tunes the conduction band minima over a broad range, affording optimized OPV power conversion efficiencies for multiple classes of organic active layer materials and establishing clear correlations between IFL/photoactive layer energetics and device performance.

  6. Electrical properties and degradation behavior of hydrogenated amorphous Si alloys for solar cells

    Science.gov (United States)

    Krühler, W.; Kusian, W.; Karg, F.; Pfleiderer, H.

    1986-12-01

    The electrical properties and the degradation behavior of hydrogenated amorphous silicon alloys (a-Si1- x A x : H, with A=C, Ge, B, P) in designs of pin, pip, nin, and MOS structures are investigated by measuring the dark and light I(V) characteristics and the spectral response as well as the space-charge-limited current (SCLC), the time of flight (TOF) of carriers and the field effect (FE). These investigations give an overview of our recent work combined with new results emphasizing the physics of the a-Si:H pin solar cells. We discuss the stabilizing influence on the degradation behavior achieved by profiling the i layers of the pin solar cells with P and B. Two kinds of pin solar cells, namely glass/SnO2/p(C)in/metal and glass/metal/pin/ITO, are investigated and an explanation of their different spectral response behavior is given. SCLC measurements lead to the conclusion that trapping is also involved in the degradation mechanism, as is recombination. TOF experiments on a-Si1- x Ge x : H pin diodes indicate that the incorporation of Ge widens the tail-state distribution below the conduction band. FE measurements showed densities of gap states of about 5×l016cm-3eV-1.

  7. Improved physical stability of amorphous state through acid base interactions.

    Science.gov (United States)

    Telang, Chitra; Mujumdar, Siddharthya; Mathew, Michael

    2009-06-01

    To investigate role of specific interactions in aiding formation and stabilization of amorphous state in ternary and binary dispersions of a weakly acidic drug. Indomethacin (IMC), meglumine (MU), and polyvinyl pyrollidone (PVP) were the model drug, base, and polymer, respectively. Dispersions were prepared using solvent evaporation. Physical mixtures were cryogenically coground. XRPD, PLM, DSC, TGA, and FTIR were used for characterization. MU has a high crystallization tendency and is characterized by a low T(g) (17 degrees C). IMC crystallization was inhibited in ternary dispersion with MU compared to IMC/PVP alone. An amorphous state formed readily even in coground mixtures. Spectroscopic data are indicative of an IMC-MU amorphous salt and supports solid-state proton transfer. IMC-MU salt displays a low T(g) approximately 50 degrees C, but is more physically stable than IMC, which in molecular mixtures with MU, resisted crystallization even when present in stoichiometric excess of base. This is likely due to a disrupted local structure of amorphous IMC due to specific interactions. IMC showed improved physical stability on incorporating MU in polymer, in spite of low T(g) of the base indicating that chemical interactions play a dominant role in physical stabilization. Salt formation could be induced thermally and mechanically.

  8. 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.

  9. Mg based alloys obtained by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Ordonez, S. [Univ. de Santiago de Chile (Chile). Fac. de Ingenieria; Garcia, G.; Serafini, D.; San Martin, A.

    1999-07-01

    In the present work, we studied the production of magnesium alloys, of stoichiometry 2Mg + Ni, by mechanical alloying (MA) and the behavior of the alloys under hydrogen in a Sievert`s type apparatus. The elemental powders were milled under argon atmosphere in a Spex 8000 high energy ball mill. The milled materials were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Only minimum amounts of the Mg{sub 2}Ni intermetallic compound was obtained after 22 h of milling time. Most of the material was sticked to the inner surface of the container as well as to the milling balls. Powders milled only for 12 hours transforms to the intermetallic at around 433 K. Effects of the MA on the hydrogen absorption kinetics were also studied. (orig.) 10 refs.

  10. Vibrational, optical and structural studies of an amorphous Se{sub 0.90}S{sub 0.10} alloy produced by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Machado, K D; Sanchez, D F; Maciel, G A [Departamento de Fisica, Centro Politecnico, Universidade Federal do Parana, 81531-990, Curitiba, PR (Brazil); Brunatto, S F [Departamento de Engenharia Mecanica, Centro Politecnico, Universidade Federal do Parana, 81531-990, Curitiba, PR (Brazil); Mangrich, A S [Departamento de Quimica, Centro Politecnico, Universidade Federal do Parana, 81531-990, Curitiba, PR (Brazil); Stolf, S F [Centro de Engenharia e Ciencias Exatas, UNIOESTE, 85903-000, Toledo, PR (Brazil)], E-mail: kleber@fisica.ufpr.br

    2009-05-13

    The local atomic order of an amorphous Se{sub 0.90}S{sub 0.10} alloy produced by mechanical alloying was studied by x-ray diffraction and extended x-ray absorption fine structure (EXAFS) data obtained at three temperatures, T = 300, 200 and 30 K. From the cumulant analysis of the EXAFS data, structural properties such as average interatomic distances, average coordination numbers, Debye-Waller factors and anharmonicity, given by the third cumulant, were obtained. The results found indicate that there is alloying at an atomic level, and Se-S pairs are more disordered and distorted than Se-Se ones due to the milling process.

  11. 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.

  12. 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.

  13. 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

  14. Machine learning based interatomic potential for amorphous carbon

    Science.gov (United States)

    Deringer, Volker L.; Csányi, Gábor

    2017-03-01

    We introduce a Gaussian approximation potential (GAP) for atomistic simulations of liquid and amorphous elemental carbon. Based on a machine learning representation of the density-functional theory (DFT) potential-energy surface, such interatomic potentials enable materials simulations with close-to DFT accuracy but at much lower computational cost. We first determine the maximum accuracy that any finite-range potential can achieve in carbon structures; then, using a hierarchical set of two-, three-, and many-body structural descriptors, we construct a GAP model that can indeed reach the target accuracy. The potential yields accurate energetic and structural properties over a wide range of densities; it also correctly captures the structure of the liquid phases, at variance with a state-of-the-art empirical potential. Exemplary applications of the GAP model to surfaces of "diamondlike" tetrahedral amorphous carbon (ta -C) are presented, including an estimate of the amorphous material's surface energy and simulations of high-temperature surface reconstructions ("graphitization"). The presented interatomic potential appears to be promising for realistic and accurate simulations of nanoscale amorphous carbon structures.

  15. Nanocrystalline Al-based alloys - lightweight materials with attractive mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Latuch, J; Cieslak, G; Dimitrov, H; Krasnowski, M; Kulik, T, E-mail: takulik@rekt.pw.edu.p [Warsaw University of Technology, Faculty of Materials Science and Engineering, Woloska 141, 02-507 Warsaw (Poland)

    2009-01-01

    In this study, several ways of bulk nanocrystalline Al-based alloys' production by high-pressure compaction of powders were explored. The effect of chemical composition and compaction parameters on the structure, quality and mechanical properties of the bulk samples was studied. Bulk nanocrystalline Al-Mm-Ni-(Fe,Co) alloys were prepared by ball-milling of amorphous ribbons followed by consolidation. The maximum microhardness (540 HV0.1) was achieved for the samples compacted at 275 deg. C under 7.7 GPa (which resulted in an amorphous bulk) and nanocrystallised at 235 deg. C for 20 min. Another group of the produced materials were bulk nanocrystalline Al-Si-(Ni,Fe)-Mm alloys obtained by ball-milling of nanocrystalline ribbons and consolidation. The hardness of these samples achieved the value five times higher (350HV) than that of commercial 4xxx series Al alloys. Nanocrystalline Al-based alloys were also prepared by mechanical alloying followed by hot-pressing. In this group of materials, there were Al-Fe alloys containing 50-85 at.% of Al and ternary or quaternary Al-Fe-(Ti, Si, Ni, Mg, B) alloys. Microhardness of these alloys was in the range of 613 - 1235 HV0.2, depending on the composition.

  16. Effect of melt spinning on gaseous hydrogen storage characteristics of nanocrystalline and amorphous Nd-added Mg2Ni-type alloys

    Institute of Scientific and Technical Information of China (English)

    张羊换; 袁泽明; 杨泰; 祁焱; 郭世海; 赵栋梁

    2016-01-01

    Nanocrystalline and amorphous Mg-Nd-Ni-Cu quaternary alloys with a composition of (Mg24Ni10Cu2)100-xNdx (x=0, 5, 10, 15, 20) were prepared by melt spinning technology and their structures as well as gaseous hydrogen storage characteristics were investigated. The XRD, TEM and SEM linked with EDS detections reveal that the as-spun Nd-free alloy holds an entire nanocrystalline structure but a nanocrystalline and amorphous structure for the as-spun Nd-added alloy, implying that the addition of Nd facilitates the glass forming in the Mg2Ni-type alloy. Furthermore, the degree of amorphization of the as-spun Nd-added alloy and thermal stability of the amorphous structure clearly increase with the spinning rate rising. The melt spinning ameliorates the hydriding and dehydriding kinetics of the alloys dramatically. Specially, the rising of the spinning rate from 0 (the as-cast was defined as the spinning rate of 0 m/s) to 40 m/s brings on the hydrogen absorption saturation ratio(a)5R(a ratio of the hydrogen absorption quantity in 5 min to the saturated hydrogen absorption capacity) increasing from 36.9% to 91.5% and the hydrogen desorption ratio(d)10R(a ratio of the hydrogen desorption quantity in 10 min to the saturated hydrogen absorption capacity) rising from 16.4% to 47.7% for the (x=10) alloy, respectively.

  17. Corrosion behavior of Mg-Zn-Ca amorphous alloys with Nd addition in simulated body fluids

    Institute of Scientific and Technical Information of China (English)

    Qin Chunling; Xiao Tongna; Li Yongyan; Wang Zhifeng; Liu Li; Xiong Hanqing; Zhao Weimin

    2014-01-01

    The effects of Nd addition on corrosion behavior of Mg66Zn30Ca4 amorphous al oys in simulated body fluids (SBF) were studied in this paper. Electrochemical properties of the samples before and after corrosion were determined. Surface morphologies of samples after immersion in SBF at 37 ºC for different times were observed under scanning electron microscope (SEM). Results show that the corrosion resistance of Mg-based al oys in SBF is improved with the addition of Nd element. The electrochemical properties indicate that microal oying Nd element to the al oys leads to an ennoblement in the open circuit potentials of the al oys and a decrease in the anodic current density in SBF, especial y for the Mg66-xZn30Ca4Ndx al oys with Nd content of 1.0at.%-1.5at.%. It was observed that the surface morphologies of the al oys immersed in SBF change with the Nd addition. A flake-like structure paral el to the al oy substrate formed on the surface of 1.0at.% Nd-containing al oy immersed in SBF for 7 days improves the corrosion resistance of the amorphous al oys by blocking the corrosion liquid from attacking the al oys.

  18. Development of CANDU advanced fuel fabrication technology - A development of amorphous alloys for the solder of nuclear reactor materials

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jai Young; Lee, Ki Young; Kim, Yoon Kee; Jung, Jae Han; Yu, Ji Sang; Kim, Hae Yeol; Han, Young Su [Korea Advanced Institute of Science and Technology, Taejon (Korea, Republic of)

    1996-07-01

    In the case of advanced CANDU fuel being useful in future, the fabrication processes for soundness insurance of a improved nuclear fuel bundle must be developed at the same time because it have three times combustibility as existing fuel. In particular, as the improved nuclear fuel bundle in which a coated layer thickness is thinner than existing that, firmity of a joint part is very important. Therefore, we need to develop a joint technique using new solder which can settle a potential problem in current joining method. As the Zr-Be alloy system and the Ti-Be system are composed with the elements having high neutron permeability, they are suitable for joint of nuclear fuel pack. The various compositions Zr-Be and Ti-Be binary metallic glass alloys were applicable to the joining the nuclear fuel bundles. The thickness of joint layer using the Zr{sub 1-x} Be{sub x} amorphous ribbon as a solder is thinner than that using physical vapor deposited Be. Among the Zr{sub 1-x} Be{sub x} amorphous binary alloys, Zr{sub 0.7} Be{sub 0.3} binary alloy is the most appropriated for joint of nuclear fuel bundle because its joint layer is smooth and thin due to low degree of Be diffusion. The microstructures of brazed layer using Ti{sub 1-y} Be{sub y} alloy, however, a solid-solution layer composed with Zr and Ti is formed toward the Zr cladding sheath and many of Zr is detected in the joint lever. 20 refs., 8 tabs., 23 figs. (author)

  19. 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.

  20. Properties of laser alloyed surface layers on magnesium base alloys

    Energy Technology Data Exchange (ETDEWEB)

    Galun, R.; Weisheit, A.; Mordike, B.L. (Technische Univ. Clausthal, Clausthal-Zellerfeld (Germany). Inst. fuer Werkstoffkunde und Werkstofftechnik)

    1998-01-01

    The investigations have shown that laser surface alloying is a promising process to improve the wear and corrosion properties of magnesium base alloys without affecting the initial bulk properties like the low density. With an alloying element combination of aluminium and nickel the wear rate in the scratch test was reduced by 90% compared to untreated pure magnesium. Additionally the corrosion resistance was improved by laser alloying with this element combination. Because of distortion or crack formation in the case of large area treatments, the laser alloying should be limited to the treatment of smaller areas. In the near future this process could be an interesting alternative to surface coating or to a partially reinforcement with ceramic fibres or particles. (orig.)

  1. Enhanced thermoelectric performance of amorphous Nb based oxynitrides

    Energy Technology Data Exchange (ETDEWEB)

    Music, Denis, E-mail: music@mch.rwth-aachen.de; Geyer, Richard W.; Hans, Marcus

    2015-12-15

    Using density functional theory, amorphous Nb{sub 0.27}Ru{sub 0.06}O{sub 0.56}N{sub 0.10} was designed to facilitate a combination of an enhanced Seebeck coefficient and low electrical resistivity. Based on a positive Cauchy pressure, ductile behavior is expected. To verify these predictions, the transport and mechanical properties of amorphous thin films were evaluated. Metallic electrical resistivity and the Seebeck coefficient of −94 µV K{sup −1} are obtained, which is consistent with our predictions. As there is no crack formation, these samples can be perceived as ductile. We demonstrate that the power factor can be increased by an order of magnitude, while keeping the thermal fatigue low.

  2. Recent progress in high B{sub s} Fe-based nanocrystalline soft magnetic alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ohta, M; Yoshizawa, Y, E-mail: motoki_ohta@hitachi-metals.co.jp [Hitachi Metals Ltd., 2-15-17 Egawa, Shimamoto Osaka, 961-0013 (Japan)

    2011-02-16

    High saturation magnetic flux density (high-B{sub s}) alloy has been developed in an Fe-based nanocrystalline alloy system. A nanocrystalline phase with an average grain size of about 20 nm is obtained by annealing Cu-substituted and/or Cu-and-Si-complex-substituted Fe-B amorphous alloys. The alloy exhibits low coercivity of less than 7 A m{sup -1} and a high B{sub s} of more than 1.8 T. The iron loss at 50 Hz and 1.6 T for a toroidal core made of Fe{sub 80.5}Cu{sub 1.5}Si{sub 4}B{sub 14} nanocrystalline alloy is 0.46 W kg{sup -1}, which is about 2/3 of that of grain-oriented Si steel. Moreover, the iron loss at 10 kHz and 0.2 T for a wound core made of this alloy is 7.5 W kg{sup -1}, which is about 25% of that of non-grain-oriented Si steel and about 60% of that of an Fe-based amorphous alloy. In addition, the cut cores made of the alloy show good superimposed dc-current characteristics and appear promising in applications such as power choke coils (at the high-frequency region).

  3. 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.

  4. Formation of amorphous Ti alloy layers by excimer laser mixing of Ti on AISI 304 stainless-steel surfaces

    Science.gov (United States)

    Jervis, T. R.; Nastasi, M.; Zocco, T. G.; Martin, J. A.

    1988-07-01

    We used excimer laser radiation at 308 nm to mix thin layers of Ti into AISI 304 stainless steel. Different numbers of shots at a fluence about twice the threshold for melting varied the amount of mixing. When mixing is sufficiently complete, an amorphous surface layer is formed with Ti substituting for Fe on a one-to-one basis in the alloy. The laser mixing process, unlike Ti ion implantation, does not result in high incorporation of C in the processed layer, although some C from surface and interface contamination is incorporated into the surface layer.

  5. 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.

  6. Crystallization and thermal fatigue of ZrTiCuNiBe bulk amorphous alloys heated by laser pulses

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The crystallization and thermal fatigue behavior of Zr41Ti14Cu12.5Ni10Be22.5 bulk amorphous alloys heated by laser pulses was investigated. The results showed that crystallization occurred even below the crystallization temperature Tx in a low cycle time. Cracks appearred before or after crystallization of the heated area in the sample. The crystallization degree increased with the heating temperature and cycles. An increase in the fatigue cracks number was also observed. The plastic deformation in the heated area of the sample surface occurred, and became more pronounced with cycles and heating temperature.

  7. Evaluation of mechanical properties of partially amorphous and nanocrystalline Al{sub 50}Ti{sub 40}Si{sub 10} composites prepared by mechanical alloying and hot isostatic pressing

    Energy Technology Data Exchange (ETDEWEB)

    Roy, D., E-mail: droy2k6@gmail.com [Mechanical and Manufacturing Engineering Department, University of Manitoba, Winnipeg, Canada R3T 2N2 (Canada); Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695-7907 (United States); Metallurgical and Materials Engineering Department, Indian Institute of Technology, Kharagpur 721302 (India); Metallurgical and Materials Engineering Department, NIFFT, Ranchi 834003 (India); Polish Academy of Sciences, Institute of High Pressure Physics (UNIPRESS), Sokolowska 29/37, Warszawa 01-142 (Poland); Mitra, R. [Metallurgical and Materials Engineering Department, Indian Institute of Technology, Kharagpur 721302 (India); Ojo, O.A. [Mechanical and Manufacturing Engineering Department, University of Manitoba, Winnipeg, Canada R3T 2N2 (Canada); Singh, S.S. [Metallurgical and Materials Engineering Department, Indian Institute of Technology, Kharagpur 721302 (India); Kolesnikov, D.; Lojkowski, W. [Polish Academy of Sciences, Institute of High Pressure Physics (UNIPRESS), Sokolowska 29/37, Warszawa 01-142 (Poland); Scattergood, R.O.; Koch, C.C. [Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695-7907 (United States); Manna, I. [Central Glass and Ceramic Research Institute, Jadavpur, Kolkata 700032 (India)

    2012-10-15

    Graphical abstract: - Abstract: Mechanically alloyed in situ nano Al{sub 3}Ti dispersed Al{sub 50}Ti{sub 40}Si{sub 10} amorphous matrix alloy powder was consolidated by hot isostatic pressing in the temperature range of 300-600 Degree-Sign C with a pressure of 1.2 GPa and holed at this temperature for 10 min. Microstructural and phase evolution studies of the mechanically alloyed powder and sintered compacts were conducted by X-ray diffraction and transmission electron microscopy. Alloy sintered at 500 Degree-Sign C recorded an excellent combination of high hardness (8.61 GPa), compressive strength (1212 MPa) and Young's modulus (149 GPa). Furthermore, these results have been compared with that of earlier studies based on conventional sintering (CCS), and high pressure sintering (HPS).

  8. Analysis and evaluation for practical application of photovoltaic power generation system. Analysis and evaluation for thin substrate polycrystalline solar cells (alloy-base amorphous materials, PIN layers, strains in the interface, and effects of impurities); Taiyoko hatsuden system jitsuyoka no tame no kaiseki hyoka. Usumaku taiyo denchi jitsuyoka no tame no kaiseki hyoka (gokinkei amorphous zairyo pin kakuso kaimen ni okeru yugami fujunbutsu nado no eikyo)

    Energy Technology Data Exchange (ETDEWEB)

    Matsuda, A.; Oeda, H.; Yamasaki, S.; Hata, N.; Kondo, M.; Toshima, Y.; Sakata, I.; Ganguly, G.; Suzuki, A.; Kamei, T.; Okushi, H.; Nonaka, H.; Oda, N.; Katagiri, H.; Ichimura, N.; Kokubu, K.; Nakamura, K.; Sekikawa, T.; Yamanaka, M. [Electrotechnical Laboratory, Tsukuba (Japan)

    1994-12-01

    Described herein are the results of the FY1994 research program for analysis and evaluation for thin film solar cells. The study on quantitative analysis of hydrogen atoms in a plasma determines quantity of hydrogen atoms in the plasma of monosilane diluted with hydrogen. It is found, contrary to expectation, that quantity of hydrogen atoms in the plasma decreases as it is more diluted with hydrogen. The study on light-induced degradation of the thin chlorine-base amorphous silicon films confirms that the plasma CVD method with 20% of dichlorosilane gas added to monosilane gas produces the thin amorphous silicon film 3 times faster than the conventional method. The thin film has essentially the same defect density as the one prepared by the conventional method, showing good photoelectric characteristics. The thin film of chlorinated amorphous silicon has a 1 digit lower defect density than the conventional one of amorphous silicon, as revealed by the accelerated degradation test with irradiated laser light and the constant current method to determine saturated defect density. 3 figs.

  9. Magnetoimpedance of cobalt-based amorphous ribbons/polymer composites

    Science.gov (United States)

    Semirov, A. V.; Derevyanko, M. S.; Bukreev, D. A.; Moiseev, A. A.; Kudryavtsev, V. O.; Safronov, A. P.

    2016-10-01

    The combined influence of the temperature, the elastic tensile stress and the external magnetic field on the total impedance and impedance components were studied for rapidly quenched amorphous Co75Fe5Si4B16 ribbons. Both as-cast amorphous ribbons and Co75Fe5Si4B16/polymer amorphous ribbon based composites were considered. Following polymer coverings were studied: modified rubber solution in o-xylene, solution of butyl methacrylate and methacrylic acid copolymer in isopropanol and solution of polymethylphenylsiloxane resin in toluene. All selected composites showed very good adhesion of the coverings and allowed to provide temperature measurements from 163 K up to 383 K under the applied deforming tensile force up to 30 N. The dependence of the modulus of the impedance and its components on the external magnetic field was influenced by the elastic tensile stresses and was affected by the temperature of the samples. It was shown that maximal sensitivity of the impedance and its components to the external magnetic field was observed at minimal temperature and maximal deforming force depended on the frequency of an alternating current.

  10. Experimental and molecular dynamics simulation study of structure of liquid and amorphous Ni 62 Nb 38 alloy

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Y.; Ashcraft, R.; Mendelev, M. I.; Wang, C. Z.; Kelton, K. F.

    2016-11-28

    The state-of-the-art experimental and atomistic simulation techniques were utilized to study the structure of the liquid and amorphous Ni62Nb38 alloy. First, the ab initio molecular dynamics (AIMD) simulation was performed at rather high temperature where the time limitations of the AIMD do not prevent to reach the equilibrium liquid structure. A semi-empirical potential of the Finnis-Sinclair (FS) type was developed to almost exactly reproduce the AIMD partial pair correlation functions (PPCFs) in a classical molecular dynamics simulation. This simulation also showed that the FS potential well reproduces the bond angle distributions. The FS potential was then employed to elongate the AIMD PPCFs and determine the total structure factor (TSF) which was found to be in excellent agreement with X-ray TSF obtained within the present study demonstrating the reliability of the AIMD for the simulation of the structure of the liquid Ni–Nb alloys as well as the reliability of the developed FS potential. The glass structure obtained with the developed potential was also found to be in excellent agreement with the X-ray data. The analysis of the structure revealed that a network of the icosahedra clusters centered on Ni atoms is forming during cooling the liquid alloy down to Tg and the Nb Z14, Z15, and Z16 clusters are attached to this network. This network is the main feature of the Ni62Nb38 alloy and further investigations of the properties of this alloy should be based on study of the behavior of this network.

  11. Cobalt-Base Alloy Gun Barrel Study

    Science.gov (United States)

    2014-07-01

    are presented in Section 5. 2. Materials and methods The composition of the cobalt -base alloy (CBA) is presented in Table 1. The production of this... Cobalt -Base Alloy Gun Barrel Study by William S. de Rosset and Jonathan S. Montgomery ARL-RP-0491 July 2014 A reprint...21005-5069 ARL-RP-0491 July 2014 Cobalt -Base Alloy Gun Barrel Study William S. de Rosset and Jonathan S. Montgomery Weapons and Materials

  12. Temperature dependence of amorphous and interface phases in the Fe{sub 80}Nb{sub 7}Cu{sub 1}B{sub 12} nanocrystalline alloy

    Energy Technology Data Exchange (ETDEWEB)

    Miglierini, M. [Slovak University of Technology, Department of Nuclear Physics and Technology (Slovakia); Greneche, J.-M. [Universite du Maine, Faculte des Sciences, F-72085 Le, Laboratoire de Physique de l' Etat Condense, UPRESA CNRS 6087 (France)

    1999-11-15

    Temperature measurements (77-625 K) of Fe{sub 80}Nb{sub 7}Cu{sub 1}B{sub 12} nanocrystalline alloy prepared from amorphous precursor annealed for 1 h at 470 deg. C and 620 deg. C are presented. Structural and magnetic behaviours of the crystalline phase, the amorphous residual matrix, and the interface zone between crystalline grains and the amorphous phase are studied by distributions of hyperfine magnetic fields. Magnetic regions are developing in the retained amorphous phase with rising temperature of annealing. They can be suppressed, however, at high enough measuring temperatures turning the amorphous matrix into paramagnetic state. As a consequence, the respective spectral components do not interfere so much and the role of interface zone can be studied.

  13. 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.)

  14. The Effect of Substitution of Fe By Co on Rapidly Quenched (FeCoMoCuB Amorphous Alloys

    Directory of Open Access Journals (Sweden)

    Clara F. Conde

    2005-01-01

    Full Text Available (Fe1-xCox79Mo8Cu1B15 amorphous alloys ware prepared in the form of ribbons by rapid quenching for x=0. 0.25 and 0.5. The effect of variation of Co/Fe ratio is analyzed with respect to the formation of amorphous state and to transformation of the structure into nancrystalline phases formed after subsequent thermal treatment. Selected properties and atomic structure in as-quenched state are studied by TEM, AFM, XRD any by measurement of magnetoresistance characteristics. The influence of heat treatment on transport and magnetic properties is shown on temperature dependencies of electrical resistivity and magnetization. It was founf that while the increase of Co content leads to the increase of Curie temperature of as-quenched structure, transition to nanocrystalline state is not affected in a significant manner. The as-quenched state for alloy without Co was found to contain thin crystal-containing layer which, however, was observed, contary to general behavior, at the side of the ribbon exposed to higher quenching rates.

  15. 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.

  16. 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.)

  17. Effects of Mo additions on the glass-forming ability and magnetic properties of bulk amorphous Fe-C-Si-B-P-Mo alloys

    Institute of Scientific and Technical Information of China (English)

    YI; Seonghoon

    2010-01-01

    Glass formation, mechanical and magnetic properties of the Fe76-xC7.0Si3.3B5.0P8.7Mox (x=0, 1 at.%, 3 at.% and 5 at.%) alloys prepared using an industrial Fe-P master alloy have been studied. With the substitution of Mo for Fe, glass-forming ability (GFA) was significantly enhanced and fully amorphous rods with a diameter of up to 5 mm were produced in the alloy with 3% Mo. The Mo-containing amorphous alloys also exhibited high fracture strength of 3635–3881 MPa and excellent magnetic properties including a high saturation magnetization of 1.10–1.41 T, a high Curie temperature and a low coercive force. The unique combination of high GFA, high fracture strength and excellent magnetic properties make the newly developed bulk metallic glasses viable for practical engineering applications.

  18. Hot-press sintering of MA Fe-based nanocrystalline/amorphous soft magnetic powder

    Institute of Scientific and Technical Information of China (English)

    卢斌; 易丹青; 严彪; 殷俊林; 刘会群; 吴标理; 陈小丽

    2004-01-01

    Microstructures and magnetic properties of Fe84 Nb7 B9, Fe80 Ti8 B12 and Fe32 Ni36 (Nb/Ⅴ) 7 Si8 B17 powders and their bulk alloys prepared by mechanical alloying(MA) method and hot-press sintering were studied. The results show that: 1) After MA for 20 h, nanocrystalline bcc single phase supersaturated solid solution forms in Fe84-Nb7 B9 and Fe8o Ti8 B12 alloys, amorphous structure forms in Fe32 Ni36 Nb7 Si8 B17 alloy, duplex microstructure composed of nanocrystalline γ-(FeNi) supersaturated solid solution and trace content of Fe2B phase forms in Fe32 Ni36-V7 Si8 B17 alloy. 2) The decomposition process of supersaturated solid solution phases in Fe84 Nb7 B9 and Fe80 Ti8 B12alloys happens at 710 -780 ℃, crystallization reaction in Fe32 Ni36 Nb7 Si8 B17 alloy happens at 530 ℃ (the temperature of peak value) and residual amorphous crystallized further happens at 760 ℃ (the temperature of peak value), phase decomposition process of supersaturated solid solution at 780 ℃ (the temperature of peak value) and crystallization reaction at 431 ℃ (the temperature of peak value) happens in Fe32 Ni36 V7Si8B17 alloy. 3) under 900 ℃, 30 MPa,0.5 h hot-press sintering conditions, bulk alloys with high relative density(94.7%- 95.8%) can be obtained. Except that the grain size of Fe84 Nb7B9 bulk alloy is large, superfine grains (grain size 50 - 200 nm) are obtained in other alloys. Except that single phase microstructure is obtained in Fe80 Ti8B12 bulk alloy, multi-phase microstructures are obtained in other alloys. 4) The magnetic properties of Fe80 Ti8 B12 bulk alloy(Bs = 1.74 T, Hc = 4.35 kA/m) are significantly superior to those of other bulk alloys, which is related to the different phases of nanocrystalline or amorphous powder formed during hot-press sintering process and grain size.

  19. M-Si-B合金非晶形成能力的CALPHAD模式评估%Evaluation of the amorphous-forming ability of M-Si-B ternary alloys using CALPHAD approach

    Institute of Scientific and Technical Information of China (English)

    长谷部光弘

    2005-01-01

    A thermodynamic study has been carried out on M-Si-B (M=Fe, Ni) ternary systems. A regular solution approximation based on the sublattice model was adopted to describe the Gibbs energy for the individual phases in the binary and ternary systems. Thermodynamic parameters for each phase were evaluated by using the experimental data. These parameters enabled us to obtain reproducible calculations of the isothermal and vertical section diagrams.The amorphous-forming ability of M-Si-B ternary alloys has been evaluated by introducing thermodynamic quantities obtained from the phase diagram calculations into Davies-Uhlmann kinetic formulations. For the computation, the timetemperature- transformation (TTT) diagram, which gives the time necessary for the formation of the detectable amount of crystal during transformation, was obtained at a finite temperature The critical cooling rate for amorphization could be defined as the minimum cooling speed that does not intersect the TTT curve and, hence, these critical cooling rates enable us to evaluate the glass-forming ability of M-Si-B ternary alloys. The driving force for the crystallization of the crystalline phase was derived, on the basis of the thermodynamic functions of each phase formulated by the present study. The calculated results showed good agreement with the experimental data on the compositional range of amorphization in these alloy systems.

  20. Magnetic Sensors Based on Amorphous Ferromagnetic Materials: A Review.

    Science.gov (United States)

    Morón, Carlos; Cabrera, Carolina; Morón, Alberto; García, Alfonso; González, Mercedes

    2015-11-11

    Currently there are many types of sensors that are used in lots of applications. Among these, magnetic sensors are a good alternative for the detection and measurement of different phenomena because they are a "simple" and readily available technology. For the construction of such devices there are many magnetic materials available, although amorphous ferromagnetic materials are the most suitable. The existence in the market of these materials allows the production of different kinds of sensors, without requiring expensive manufacture investments for the magnetic cores. Furthermore, these are not fragile materials that require special care, favouring the construction of solid and reliable devices. Another important feature is that these sensors can be developed without electric contact between the measuring device and the sensor, making them especially fit for use in harsh environments. In this review we will look at the main types of developed magnetic sensors. This work presents the state of the art of magnetic sensors based on amorphous ferromagnetic materials used in modern technology: security devices, weapon detection, magnetic maps, car industry, credit cards, etc.

  1. Magnetic Sensors Based on Amorphous Ferromagnetic Materials: A Review

    Directory of Open Access Journals (Sweden)

    Carlos Morón

    2015-11-01

    Full Text Available Currently there are many types of sensors that are used in lots of applications. Among these, magnetic sensors are a good alternative for the detection and measurement of different phenomena because they are a “simple” and readily available technology. For the construction of such devices there are many magnetic materials available, although amorphous ferromagnetic materials are the most suitable. The existence in the market of these materials allows the production of different kinds of sensors, without requiring expensive manufacture investments for the magnetic cores. Furthermore, these are not fragile materials that require special care, favouring the construction of solid and reliable devices. Another important feature is that these sensors can be developed without electric contact between the measuring device and the sensor, making them especially fit for use in harsh environments. In this review we will look at the main types of developed magnetic sensors. This work presents the state of the art of magnetic sensors based on amorphous ferromagnetic materials used in modern technology: security devices, weapon detection, magnetic maps, car industry, credit cards, etc.

  2. Preparation and Characterization of Amorphous Layer on Aluminum Alloy Formed by Plasma Electrolytic Deposition (PED)

    Institute of Scientific and Technical Information of China (English)

    GUAN Yong-jun; XIA Yuan

    2004-01-01

    In this investigation, protective layers were formed on aluminum substrate by Plasma Electrolytic Deposition (PED) using sodium silicate solution. The relation between the thickness of the layer and process time were studied. XRD,SEM, EDS were used to study the layer's structure, composition and micrograph. The results show that the deposited layers are amorphous and contain mainly oxygen, silicon, and aluminum. The possible formation mechanism of amorphous [Al-Si-O] layer was proposed: During discharge periods, Al2O3 phase of the passive film and SiO32-near the substrate surface are sintered into xSiO2(1-x)Al2O3 and then transformed into amorphous [Al-Si-O] phase.

  3. Intrinsic complexity of the melt-quenched amorphous Ge2Sb2Te5 memory alloy

    Science.gov (United States)

    Krbal, M.; Kolobov, A. V.; Fons, P.; Tominaga, J.; Elliott, S. R.; Hegedus, J.; Uruga, T.

    2011-02-01

    Through the use of first-principles Ge K-edge XANES simulations we demonstrate that the structure of melt-quenched amorphous Ge-Sb-Te is intrinsically complex and is a mixture of Ge(3):Te(3) and Ge(4):Te(2) configurations in comparable concentrations, in contrast to the as-deposited amorphous phase that is dominated by the Ge(4):Te(2) configurations. The reasons for Ge-Te polyvalency are discussed and it is argued that both configurations are compatible with the Mott 8-N rule and the definition of an ideal amorphous solid. The near-perfect Te-Te distance match between the two major configurations accounts for the high cyclability of phase-change materials. Stable compositions in the Ge-Sb-Te system are suggested.

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

    Science.gov (United States)

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

    2014-04-23

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

  5. Ductile Bulk Aluminum-Based Alloy with Good Glass-Forming Ability and High Strength

    Institute of Scientific and Technical Information of China (English)

    ZHUO Long-Chao; PANG Shu-Jie; WANG Hui; ZHANG Tao

    2009-01-01

    Based on a new approach for designing glassy alloy compositions,bulk Al-based alloys with good glass-forming ability (GFA) are synthesized.The cast Al86Si0.5Ni4.06Co2.94 Y6Sc0.5 rod with a diameter of 1 mm shows almost fully amorphous structure besides about 5% fcc-Al nucleated in the center of the rod.The bulk alloy with high Al concentration exhibits an ultrahigh yield strength of 1.18 Gpa and maximum strength of 1.27 Gpa as well as an obvious plastic strain of about 2.4% during compressive deformation.This light Al-based alloy with good GFA and mechanical properties is promising as a new high specific strength material with good deformability.

  6. Shape memory alloy based motor

    Indian Academy of Sciences (India)

    S V Sharma; M M Nayak; N S Dinesh

    2008-10-01

    Design and characterization of a new shape memory alloy wire based Poly Phase Motor has been reported in this paper. The motor can be used either in stepping mode or in servo mode of operation. Each phase of the motor consists of an SMA wire with a spring in series. The principle of operation of the poly phase motor is presented. The motor resembles a stepper motor in its functioning though the actuation principles are different and hence has been characterized similar to a stepper motor. The motor can be actuated in either direction with different phase sequencing methods, which are presented in this work. The motor is modelled and simulated and the results of simulations and experiments are presented. The experimental model of the motor is of dimension 150 mm square, 20 mm thick and uses SMA wire of 0·4 mm diameter and 125 mm of length in each phase.

  7. Nanocrystallization in Co67Cr7Fe4Si8B14 Amorphous Alloy Ribbons

    Directory of Open Access Journals (Sweden)

    Zahra Jamili-Shirvan

    2013-12-01

    Full Text Available The nanocrystallization of Co67Fe4Cr7Si8B14 amorphous ribbons which prepared by planar flow melt spinning process (PFMS was investigated. Crystallization of the ribbons was studied by differential thermal analysis (DTA, X-ray diffraction (XRD and transmission electron microscopy (TEM. The DTA result of amorphous ribbon at heating rate of 10˚C/min showedoccurrence of phase transitions in two stages. The ribbons were isothermally annealed for 30 minutes in argon atmosphere at different temperatures between 300 and 650ºC with 25ºC steps. The magnetic properties of annealed samples were measured using a vibrating sample magnetometer (VSM. The VSM results revealed that optimum soft magnetic properties occurred at 400ºC. XRD patterns showed that the samples isothermally annealed up to 450ºC were amorphous, while TEM results at 400ºC indicated 7-8 nm mean size nanocrytallites in amorphous matrix and size of the nanocrystallites increased by increasing temperature. Also by X-ray diffraction pattern, precipitation of different phases at higher temperatures confirmed.

  8. 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

    measurements to be 60-150 K/s, in agreement with estimates from the literature. The Vickers hardness (Hv) of the amorphous material for y = 2% is higher (similar to 360 kg/mm(2)) than for y = 0 (similar to 290 kg/mm(2)). On crystallisation the hardness of the latter material increases to the 400 kg/mm(2) level...

  9. 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.

  10. A tunable amorphous p-type ternary oxide system: The highly mismatched alloy of copper tin oxide

    Energy Technology Data Exchange (ETDEWEB)

    Isherwood, Patrick J. M., E-mail: P.J.M.Isherwood@lboro.ac.uk; Walls, John M. [CREST, School of Electronic, Electrical and Systems Engineering, Loughborough University, Loughborough, Leicestershire LE11 3TU (United Kingdom); Butler, Keith T.; Walsh, Aron [Centre for Sustainable Technologies and Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom)

    2015-09-14

    The approach of combining two mismatched materials to form an amorphous alloy was used to synthesise ternary oxides of CuO and SnO{sub 2}. These materials were analysed across a range of compositions, and the electronic structure was modelled using density functional theory. In contrast to the gradual reduction in optical band gap, the films show a sharp reduction in both transparency and electrical resistivity with copper contents greater than 50%. Simulations indicate that this change is caused by a transition from a dominant Sn 5s to Cu 3d contribution to the upper valence band. A corresponding decrease in energetic disorder results in increased charge percolation pathways: a “compositional mobility edge.” Contributions from Cu(II) sub band-gap states are responsible for the reduction in optical transparency.

  11. L-S mass transfer in G-L-S countercurrent magnetically stabilized bed with amorphous alloy SRNA-4 catalyst

    Institute of Scientific and Technical Information of China (English)

    Wei; Li; Baoning; Zong; Xiaofang; Li; Xiangkun; Meng; Jinli; Zhang

    2007-01-01

    Liquid-solid (L-S) mass transfer coefficients (Ks) were characterized in a gas-liquid-solid (G-L-S) three-phase countercurrent magnetically stabilized bed (MSB) using amorphous alloy SRNA-4 as the solid phase. Effects of superficial liquid velocity, superficial gas velocity, magnetic field strength, liquid viscosity and surface tension were investigated. Experimental results indicated that the external magnetic field increased Ks in three-phase MSB, as compared to those in conventional G-L-S fluidized beds; that Ks increased with magnetic field strength, superficial gas and liquid velocities and decreased with liquid viscosity and surface tension; and that Ks showed uniform axial and radial distributions except for small increases close to the wall. Dimensionless correlations were established to estimate Ks of the G-L-S countercurrent MSB using SRNA-4catalyst, with an average error of 3.6%.

  12. Hydrogenation of furfuryl alcohol to tetrahydrofurfuryl alcohol on NiB/SiO2 amorphous alloy catalyst

    Institute of Scientific and Technical Information of China (English)

    SONG Yun; LI Wei; ZHANG Minghui; TAO Keyi

    2007-01-01

    NiB/SiO2 amorphous alloy catalyst was prepared by power electroless plating method and characterized by induction coupled plasma (ICP),Brunauer-Emmett-Teller method (BET),transmission electron microscope (TEM)and X-ray diffraction (XRD) techniques.The catalytic performance of NiB/SiO2 was investigated for the hydrogenation of furfuryl alcohol (FA) to tetrahydrofurfuryl alcohol (THFA).The effects of operational conditions,such as reaction temperature,pressure,and stirring rate were carefully studied.The proper conditions were determined as the following:pressure 2.0 MPa,temperature 120℃ and stirring rate 550 r/min.A typical result with FA conversion of 99%and THFA selectivity of 100% was obtained under such conditions,which was close to that over Raney Ni.

  13. PREPARATION AND MAGNETIC-PROPERTIES OF AMORPHOUS FE1-XBX (15-LESS-THAN-OR-EQUAL-TO X LESS-THAN-40 ATMOSPHERIC PERCENT) ALLOY PARTICLES

    DEFF Research Database (Denmark)

    Linderoth, Søren; Mørup, S.

    1992-01-01

    Amorphous Fe1-xBx alloy particles have been prepared in aqueous solutions by reduction of Fe2+ ions to the metallic state by the use of NaBH4. It is demonstrated, that by changing the pH of the aqueous metal ion solution the amount of boron incorporated in the alloy particles can be varied between...... 15 and 28 at.%. Fe-57 Mossbauer spectra have been obtained at 10, 80 and 295 K. The hyperfine parameters for amorphous particles have been found to be similar to those found for ribbons and films prepared by the liquid-quench and sputtering techniques, respectively, though with a tendency...... for the magnetic hyperfine fields for the chemically prepared and sputter prepared alloys to deviate slightly from those for melt-spun samples. The magnetic hyperfine fields decrease linearly as a function of T3/2....

  14. Effect of temperature and magnetic fields on the structural state of the Fe-Zr-B amorphous alloy below crystallization temperature

    Directory of Open Access Journals (Sweden)

    Fedotova N.L.

    2011-05-01

    Full Text Available Amorphous materials give the possibility to observe the phase and structural transformations in sufficiently narrow temperature intervals with the retention of their unchanged chemical composition. The present report is concerned with the results of the study of structure evolution and its dependence on magnetic field upon heating in the Fe-Zr-B amorphous alloy by the method of the photometric analysis of structural images (PHASI. The PHASI method makes it possible to establish the effect of external temperature and magnetic fields on the brightness spectra of the reflection from the surface of the object under study and the distribution of the zones, in which these changes are localized. The established temperature dependence of the energy characteristics of the reflection brightness spectrum in arbitrary units indicates the complex structural transformations caused by heating of the alloy under study. Also it is shown that the magnetic field produces residual structural changes in the alloy in comparison with its initial state

  15. Glass forming ability of Zr-and Fe-based alloys at quenching from melts

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The master alloy ingots(MAI)with the nominal composition Zr52.5 Ti5Cu17.9 Ni14.6Al10 and Fe61Co7Zr10Mo5W2B15(at%)were prepared by arc-melting in Ti-gettered Ar atmosphere.The Zr-based buttons of 6 mm and 9 mm in diameter were fully amorphous,but those of 13 mm in diameter experienced crystallization.The glass forming ability(GFA)of Fe-based alloys was relatively lower,and the buttons obtained were fully crystallized.The microhardness of the Zr-based buttons was about 500(Hv),and the Fe-based rod obtained by injection technique exhibited a high Vickers hardness of 1329.In addition,an amorphous-crystalline transition layers were observed in both the buttons and the rods.

  16. 铁基非晶合金整体磁芯轴向拉压型测力传感器的研究与设计%Research and Desing on a Axial Tensile and Compression Force Sensor With a Fe-base Amorphous Alloy Magnetic Core

    Institute of Scientific and Technical Information of China (English)

    石延平; 范书华; 侯金柱

    2013-01-01

    By wrapping Fe-based amorphous alloy strip into a cylindrical stress-sensitive magnetic a force sensor was made based on magneto-elastic effect,it can measure the tension,but also to measure the compression.The principle and structure of the sensor were presented,and its output characteristic equation was derived.By making a tensile and compression measuring experiment,the best excitation magnetic field strength,static characteristics and temperature characteristics of the sensor were analyzed.The experimental result shows when the sensor measure tensile and compression force,its the maximum linearity error is respectively 0.41% F.S and1.12% F.S,repetitive error 0.86% F.S and 0.85% F.S,and the average sensitivity is respectively 0.71 mV/kN and 1.16 mV/kN.%将铁基非晶态合金薄带缠绕成圆柱型应力敏感磁芯,基于压磁效应,使同一传感器实现既能测量拉力,又能测量压力.介绍了传感器的结构和原理,推导出传感器的输出特性方程.通过拉伸和压缩试验,分析了传感器的最佳激磁磁场强度、静态特性以及温度特性.试验数据显示,传感器测量拉伸和压缩载荷时,最大非线性误差分别为0.41%F.S和1.12%F.S,重复性误差分别为0.86%F.S和0.85%F.S,平均灵敏度为0.71 mV/kN和1.16 mV/kN.

  17. 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.

  18. The fluidity and molding ability of glass-forming Zr-based alloy melt

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The fluidity and filling ability of glass-forming Zr-based alloy melt in copper mould were investigated both theoretically and experimentally. The major factors which affected the flowing behavior of the metallic melt in the mold were determined,which provides the foundation for overcoming the contradiction between the filling and formation of amorphous alloy during the rapid cooling process of the metallic melts. The casting factors to prepare a metallic ring were discussed and selected. As a result,a Zr-based bulk metallic glass ring was prepared successfully.

  19. Effects of Ti and Co on the Electrochemical Characteristics of MgNi-Based Alloy Electrodes

    Institute of Scientific and Technical Information of China (English)

    FENG,Yan; JIAO,Li-Fang; YUAN,Hua-Tang; ZHAO,Ming

    2007-01-01

    Mg-based hydrogen storage alloys MgNi, Mg0.9Ti0.1Ni and Mg0.9Ti0.1Ni0.9Co0.1 were successfully prepared by means of mechanical alloying (MA). The structure and the electrochemical characteristics of these Mg-based materials were also studied. The results of X-ray diffraction (XRD) and scanning electron microscopy (SEM) show that the main phases of the alloys exhibit amorphous structures, and trace of Ni co-exists. The charge-discharge cycle tests indicate these alloys have good electrochemical active characteristics. And the cycle stability of Ti and Co doped alloy was better than that of MgNi alloy. After 50 cycle charge-discharge, the discharge capacity of the Mg0.9Ti0.1Ni0.9Co0.1 alloy was much better than that of MgNi and Mg0.9Ti0.1Ni alloys. The discharge capacity of Mg0.9Ti0.1Ni0.9Co0.1 was 102.8% higher than that of MgNi alloy, and 45.49% higher than that of the Mg0.9Ti0.1Ni alloy. During the process of charge-discharge cycle test, the main reason for the electrode capacity fading is the corrosion of Mg to Mg(OH)2 on the surface of alloys. The Tafel polarization test indicates Ti and Co improve the anticorrosion in an alkaline solution. The EIS results suggest that proper amount of Ti and Co doping improve the electrochemical catalytical activity on the Mg-based alloy surface significantly.

  20. F-Alloy: An Alloy Based Model Transformation Language

    OpenAIRE

    Gammaitoni, Loïc; Kelsen, Pierre

    2015-01-01

    Model transformations are one of the core artifacts of a model-driven engineering approach. The relational logic language Alloy has been used in the past to verify properties of model transformations. In this paper we introduce the concept of functional Alloy modules. In essence a functional Alloy module can be viewed as an Alloy module representing a model transformation. We describe a sublanguage of Alloy called F-Alloy that allows the specification of functional Alloy modules. Module...

  1. 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

  2. Co-catalytic effect of Rh and Ru for the ethanol electro-oxidation in amorphous microparticulated alloys

    Energy Technology Data Exchange (ETDEWEB)

    Blanco, Tamara C.; Pierna, Angel R.; Barroso, Javier [Dpto. de Ingenieria Quimica y del Medio Ambiente, Universidad del Pais Vasco, San Sebastian (Spain)

    2011-11-15

    The ethanol electro-oxidation on platinum catalyst in acid media leads to the formation of acetaldehyde and acetic acid as main products. Another problem is the poisoning of the electro-catalyst surface with CO formed during the fuel oxidation reaction. To increase the performance of Direct Ethanol Fuel Cells (DEFCs) it is necessary to develop new electrode materials or modification of the existing Pt catalysts. This work presents the electrochemical response to ethanol and CO oxidation of different compositional amorphous alloys obtained by ball milling technique, used as electrodes. Alloys with Ni{sub 59}Nb{sub 40}Pt{sub 0.6}Rh{sub 0.4} and Ni{sub 59}Nb{sub 40}Pt{sub 0.6}Rh{sub 0.2}Ru{sub 0.2} composi-tions were studied. The current density towards ethanol oxidation decreases with the presence of ruthenium; however, this electrode shows the best tolerance to CO, with lower surface coverage (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. The influence of d- and f-states on structure formation - amorphous alloys containing rare earths as model systems

    Energy Technology Data Exchange (ETDEWEB)

    Stiehler, Martin; Pleul, Michael; Haeussler, Peter [Chemnitz University of Technology, 09126 Chemnitz (Germany)

    2011-07-01

    Amorphous phases as precursors of the crystalline state are interesting for investigating fundamental structure forming processes and the related evolution of electronic transport. During the last years we were able to show that many different classes of alloys organize themselves under the influence of a resonance-like interaction between the global subsystems of the electrons and the static structure. Especially for binary Al-TM alloys TM: the transition metals of the 4th period (Sc,Ti,V,Cr,Mn,Fe,Co,Ni,Cu) we reported recently on an electronic influence on phase stability driven by hybridization effects between the Al-p- and the TM-d-states, showing an interesting systematics depending on the number of unoccupied TM-d-states reflected in different properties. Currently we are about to extend those investigations to systems with transition metals of the 5th and 6th period. Embedded in this class of elements are the so-called Rare Earth metals (Sc, Y, La, and the Lanthanoids). These elements exhibit very similar chemical properties although some of them (the Lanthanoids) contain f-electrons. This provides the possibility of studying the influence of localized magnetic moments (f-states) on structure formation. In this contribution we report on results concerning the static structure, the electrical resistivity and the Hall effect of the binary systems Al-Y and Al-Ce.

  4. The influence of d- and f-states on structure formation - amorphous alloys containing Rare Earths as model systems

    Energy Technology Data Exchange (ETDEWEB)

    Stiehler, Martin; Pleul, Michael; Haeussler, Peter [Chemnitz University of Technology, 09126 Chemnitz (Germany)

    2010-07-01

    Amorphous phases as precursors of the crystalline state are interesting for investigating fundamental structure forming processes and the related evolution of electronic transport. During the last years we were able to show that many different classes of alloys organize themselves under the influence of a resonance interaction between the global subsystems of the electrons and the static structure. Especially for binary Al-TM alloys (TM: the transition metals of the 4th period Sc,Ti,V,Cr,Mn,Fe,Co,Ni,Cu) we reported recently on an electronic influence on phase stability driven by hybridization effects between the Al-p- and the TM-d-states, showing an interesting systematics depending on the number of unoccupied TM-d-states reflected in different properties. Currently we are about to extend the investigations to systems with transition metals of the 5th and 6th period. Embedded in this class of elements are the so-called Rare Earth metals (Sc, Y, La, and the Lanthanoids). These elements exhibit very similar chemical properties although some of them (the Lanthanoids) contain f-electrons. This provides the possibility of studying the influence of magnetic influences, provided by the localized f-states, on structure formation. In this contribution we report on preliminary results concerning the static structure, the electrical resistivity and the Hall effect of the binary systems Al-Y and Al-Ce.

  5. Effect of the residual stresses on surface coercive force in amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Tejedor, M.; Garcia, J.A.; Carrizo, J.; Elbaile, L. E-mail: elbaile@pinon.ccu.uniovi.es; Santos, J.D

    2000-06-02

    The dependence of the coercivity H{sub c} on the applied stress {sigma} in the surfaces of various amorphous ribbons with positive magnetostriction is studied. The results obtained show that the behaviour of H{sub c}({sigma}) in the surfaces is the same as in the bulk and the minimum of H{sub c}({sigma}) does not depend on the residual stresses. The residual stresses affect the value of the coercive field but not its stress dependence.

  6. Evidence for weak localization effects on the critical magnetic field for the amorphous alloys V/sub 1-//sub x/Si/sub x/

    Energy Technology Data Exchange (ETDEWEB)

    Ousset, J.C.; Rakoto, H.; Broto, J.M.; Dupuis, V.; Durand, J.; Marchal, G.; Pavuna, D.

    1987-04-01

    In this paper we present measurements of the temperature dependence of the upper critical field H/sub c//sub 2/ and of the magnetoresistance for V/sub 1-//sub x/Si/sub x/ superconducting amorphous alloys. Negative deviations from the classical variation of H/sub c//sub 2/ in a dirty superconductor are observed related to a positive magnetoresistance due to weak localization in amorphous systems with finite spin-orbit coupling. These deviations can be qualitatively explained through the model recently developed by Coffey et al.

  7. Control of gigahertz permeability and permittivity dispersion by means of nanocrystallization in FeCo based nanocrystalline alloy

    Science.gov (United States)

    Han, Mangui; Lu, Haipeng; Deng, Longjiang

    2010-11-01

    An amorphous (FeCo) based alloy has been prepared by a rapid quench method. Subsequent annealing on the amorphous samples gives rise to the coexistence of two magnetic phases: amorphous matrix and nanocrystalline grains (α'-FeCo) with an average size of 9.8 nm. Permeability dispersion behaviors have been studied by Kittel theory [C. Kittel, J. Phys. Radium 12, 332 (1951)]. The results show that these two magnetic phases contribute to the permeability dispersion. The Cole-Cole dispersion law [K. S. Cole and R. H. Cole, J. Chem. Phys. 9, 341 (1941)] has been employed to explain the permittivity dispersion within microwave region based on the assumption that multiple dielectric relaxation processes existing. Our results indicate the possibility of tuning the high frequency permeability and permittivity values of (FeCo) based alloy by controlling the magnetic microstructure, which suggests an alternative method to develop smart electromagnetic materials.

  8. 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.

  9. Amorphous silicon carbide passivating layers for crystalline-silicon-based heterojunction solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Boccard, Mathieu; Holman, Zachary C. [School of Electrical, Computer, and Energy Engineering, Arizona State University, Tempe, Arizona 85287-5706 (United States)

    2015-08-14

    Amorphous silicon enables the fabrication of very high-efficiency crystalline-silicon-based solar cells due to its combination of excellent passivation of the crystalline silicon surface and permeability to electrical charges. Yet, amongst other limitations, the passivation it provides degrades upon high-temperature processes, limiting possible post-deposition fabrication possibilities (e.g., forcing the use of low-temperature silver pastes). We investigate the potential use of intrinsic amorphous silicon carbide passivating layers to sidestep this issue. The passivation obtained using device-relevant stacks of intrinsic amorphous silicon carbide with various carbon contents and doped amorphous silicon are evaluated, and their stability upon annealing assessed, amorphous silicon carbide being shown to surpass amorphous silicon for temperatures above 300 °C. We demonstrate open-circuit voltage values over 700 mV for complete cells, and an improved temperature stability for the open-circuit voltage. Transport of electrons and holes across the hetero-interface is studied with complete cells having amorphous silicon carbide either on the hole-extracting side or on the electron-extracting side, and a better transport of holes than of electrons is shown. Also, due to slightly improved transparency, complete solar cells using an amorphous silicon carbide passivation layer on the hole-collecting side are demonstrated to show slightly better performances even prior to annealing than obtained with a standard amorphous silicon layer.

  10. Investigation of Amorphous/Nanocrystalline Iron-Based Thermal Barrier Coatings

    Science.gov (United States)

    Bobzin, K.; Öte, M.; Königstein, T.

    2017-02-01

    Because of their favorable thermophysical properties, good machinability and low material costs, iron-based coatings which exhibit a highly amorphous/nanocrystalline microstructure are currently in the focus of research. Considering the crystallization temperature of the material, iron-based coatings might be the next generation of thermal barrier coatings (TBCs) for low-temperature systems, reducing thermal losses. The objective of this research project is the development of highly amorphous, iron-based coatings. For this purpose, amorphous feedstock materials with different chromium contents have been developed and characterized regarding their microstructures, phase compositions, crystallization temperatures and amorphous content. The results show that the amorphous content is reduced with increasing particle size and chromium content. The coatings were deposited by air plasma spraying (APS) and high-velocity oxygen fuel spraying (HVOF). It is shown that all coatings exhibit amorphous structures. HVOF coatings show a smaller amount of amorphous content compared to the feedstock materials, indicating crystallization occurring in not fully melted particles or insufficient rapid cooling. The APS process can increase the amount of amorphous content compared to the feedstock material, as shown for x Cr = 15%. All coatings proof good thermal shock behavior. Lowest thermal diffusivity values were determined for APS coatings, which confirms the potential of iron-based TBCs.

  11. Evolution of structure and infrared radiation properties for ferrite-based amorphous coating

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Lei [State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081 (China); Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan 430081 (China); Fan, Xi’an, E-mail: groupfxa@163.com [State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081 (China); Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan 430081 (China); Zhang, Jianyi [State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081 (China); Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan 430081 (China); Hu, Xiaoming [Suzhou Sagreon New Materials Co., Ltd, Zhangjiagang 215625 (China); Li, Guangqiang; Zhang, Zhan [State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081 (China); Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan 430081 (China)

    2014-10-15

    Highlights: • The ferrite-based amorphous infrared radiation coating was prepared by plasma spraying. • The coating could keep amorphous structure when the temperature was below 700 °C. • The amorphous structure can improve the emissivity of ferrite-based coatings. • The amorphous coating exhibited a higher emissivity than that by brushing process. • The coating has an excellent thermal shock resistance and can work at 1000 °C. - Abstract: The ferrite-based amorphous coatings with high infrared radiation properties have been successfully prepared on the surface of carbon steel substrate by plasma spraying process. The phase, morphology, microstructure, thermal behavior and infrared emissivity were determined by X-ray diffraction, scanning electron microscopy, differential scanning calorimetry and infrared spectroscopy. The prepared coating could keep amorphous structure when the ambient temperature was below 700 °C and it would crystallize gradually with further increasing the temperature. The amorphous structure is confirmed to be constructive for improving the emissivity of ferrite-based coatings, especially in the 3–8 μm band. The emissivity of the amorphous coating obtained by plasma spraying was over 0.8 in 3–8 μm band at 800 °C, which was higher than that of the coating with same composition prepared by conventional brushing method. The excellent thermal shock resistance of the coatings makes them to be good candidates for sensible energy-saving materials, which could work for long term at 1000 °C.

  12. Investigation of Amorphous/Nanocrystalline Iron-Based Thermal Barrier Coatings

    Science.gov (United States)

    Bobzin, K.; Öte, M.; Königstein, T.

    2017-01-01

    Because of their favorable thermophysical properties, good machinability and low material costs, iron-based coatings which exhibit a highly amorphous/nanocrystalline microstructure are currently in the focus of research. Considering the crystallization temperature of the material, iron-based coatings might be the next generation of thermal barrier coatings (TBCs) for low-temperature systems, reducing thermal losses. The objective of this research project is the development of highly amorphous, iron-based coatings. For this purpose, amorphous feedstock materials with different chromium contents have been developed and characterized regarding their microstructures, phase compositions, crystallization temperatures and amorphous content. The results show that the amorphous content is reduced with increasing particle size and chromium content. The coatings were deposited by air plasma spraying (APS) and high-velocity oxygen fuel spraying (HVOF). It is shown that all coatings exhibit amorphous structures. HVOF coatings show a smaller amount of amorphous content compared to the feedstock materials, indicating crystallization occurring in not fully melted particles or insufficient rapid cooling. The APS process can increase the amount of amorphous content compared to the feedstock material, as shown for x Cr = 15%. All coatings proof good thermal shock behavior. Lowest thermal diffusivity values were determined for APS coatings, which confirms the potential of iron-based TBCs.

  13. Experimental and Computer Modelling Studies of Metastability of Amorphous Silicon Based Solar Cells

    NARCIS (Netherlands)

    Munyeme, Geoffrey

    2003-01-01

    We present a combination of experimental and computer modelling studies of the light induced degradation in the performance of amorphous silicon based single junction solar cells. Of particular interest in this study is the degradation kinetics of different types of amorphous silicon single junction

  14. Magnetocaloric effect and refrigeration cooling power in amorphous Gd7Ru3 alloys

    Science.gov (United States)

    Kumar, Pramod; Kumar, Rachana

    2015-07-01

    In this paper, we report the magnetic, heat capacity and magneto-caloric effect (MCE) of amorphous Gd7Ru3 compound. Both, temperature dependent magnetization and heat capacity data reveals that two transitions at 58 K and 34 K. MCE has been calculated in terms of isothermal entropy change (ΔSM) and adiabatic temperature change (ΔTad) using the heat capacity data in different fields. The maximum values of ΔSM and ΔTad are 21 Jmol-1K-1 and 5 K respectively, for field change of 50 kOe whereas relative cooling power (RCP) is ˜735 J/kg for the same field change.

  15. Domain Wall Mobility in Co-Based Amorphous Wire

    Directory of Open Access Journals (Sweden)

    Maria Kladivova

    2007-01-01

    Full Text Available Dynamics of the domain wall between opposite circularly magnetized domains in amorphous cylindrical sample with circular easy direction is theoretically studied. The wall is driven by DC current. Various mechanisms which influence the wall velocity were taken into account: current magnitude, deformation of the mowing wall, Hall effect, axially magnetized domain in the middle of the wire. Theoretical results obtained are in a good agreement with experiments on Cobased amorphous ferromagnetic wires.

  16. Highly improved hydrogen storage capacity and kinetics of the nanocrystalline and amorphous PrMg12-type alloys by mechanical milling

    Science.gov (United States)

    Zhang, Y. H.; Shang, H. W.; Li, Y. Q.; Yuan, Z. M.; Yang, T.; Zhao, D. L.

    2017-01-01

    Nanocrystalline and amorphous PrMg11Ni + x wt.% Ni (x = 100, 200) alloys were synthesized by mechanical milling. Effects of Ni content and milling duration on the structures, hydrogen storage capacity and kinetics of the as-milled alloys were investigated systematically. The structures were characterized by XRD and HRTEM. The hydrogen desorption activation energy was calculated by using Kissinger method. The results show that increasing Ni content dramatically improves the electrochemical discharge capacity of the as-milled alloys. Furthermore, the variation of milling time has a significant impact on the kinetics of the alloys. As the milling time increased, the high-rate discharge ability (HRD), gaseous hydrogen absorption capacity and hydrogenation rate increased at first but decreased finally, while the dehydrogenation rate always increased.

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

    Science.gov (United States)

    1981-10-01

    alloys investigated. Rksums-Nous avons trouve que certains verres metalliques etaient fragilises par un recuit a basse temperature, comme certains aciers ...article, nous pr sentons les effets de I’addition de Sb, Sc and Te, qui sont des elements fragilisant des aciers , sur des verres metalliques dont les...les aciers . On augmente l’effect d’un element fragilisant en remplaqant du Ni par du Fe. Nous n’avons pas vu de changement notable du DSC ou des

  18. Low-Energy Amorphization of Ti1Sb2Te5 Phase Change Alloy Induced by TiTe2 Nano-Lamellae

    Science.gov (United States)

    Ding, Keyuan; Rao, Feng; Lv, Shilong; Cheng, Yan; Wu, Liangcai; Song, Zhitang

    2016-07-01

    Increasing SET operation speed and reducing RESET operation energy have always been the innovation direction of phase change memory (PCM) technology. Here, we demonstrate that ∼87% and ∼42% reductions of RESET operation energy can be achieved on PCM cell based on stoichiometric Ti1Sb2Te5 alloy, compared with Ge2Sb2Te5 and non-stoichiometric Ti0.4Sb2Te3 based PCM cells at the same size, respectively. The Ti1Sb2Te5 based PCM cell also shows one order of magnitude faster SET operation speed compared to that of the Ge2Sb2Te5 based one. The enhancements may be caused by substantially increased concentration of TiTe2 nano-lamellae in crystalline Ti1Sb2Te5 phase. The highly electrical conduction and lowly thermal dissipation of the TiTe2 nano-lamellae play a major role in enhancing the thermal efficiency of the amorphization, prompting the low-energy RESET operation. Our work may inspire the interests to more thorough understanding and tailoring of the nature of the (TiTe2)n(Sb2Te3)m pseudobinary system which will be advantageous to realize high-speed and low-energy PCM applications.

  19. Effect of rare-earth elements on nanophase evolution, crystallization behaviour and mechanical properties in Al–Ni–R (R = La/Mischmetal) amorphous alloys

    Indian Academy of Sciences (India)

    K L Sahoo; Amitava Mitra; Sukomal Ghosh

    2005-10-01

    The crystallization behaviour and evolution of nanoparticles in amorphous Al–Ni–Mischmetal (Mm) and Al–Ni–La alloys during heat treatment have been studied. Rapidly solidified ribbons were obtained by induction melting and ejecting the melt onto a rotating Cu wheel in an Ar atmosphere. The crystallization behaviour of the melt-spun ribbons was investigated using differential scanning calorimetry and X-ray diffractometry (XRD). XRD studies confirmed that all the ribbons were fully amorphous. Al–Ni–Mm systems showed a three-stage crystallization process whereas Al–Ni–La system, in general, showed a two-stage crystallization process on annealing. Crystallization kinetics was analysed by Kissinger and Johnson–Mehl–Avrami approaches. In Al–Ni–La alloys, the crystallization pathways depend on the La concentration. Microhardness of all the ribbons was examined at different temperatures and correlated with the corresponding evolution of phases.

  20. The temperature dependence of the magnetoelastic characteristics of cores for force sensors utilizing Fe70Ni8Si10B12 amorphous alloy

    Indian Academy of Sciences (India)

    Roman Szewczyk; Adam Bieńkowski; Jacek Salach

    2008-09-01

    This paper presents the results of investigation on the influence of temperature on magnetoelastic characteristics of the two ring-shaped cores, made of Fe70Ni8Si10B12 amorphous alloy. The cores were annealed for 1 h at 350 and 400° C, respectively. The compressive force was applied perpendicular to the direction of the magnetizing field in the sample. Special cylindrical backing enables application of the uniform compressive stress to the wound ring sample. A resistive furnace heated the experimental set-up. Results presented in the paper indicate a significant influence of the temperature on the magnetoelastic characteristics of Fe70Ni8Si10B12 amorphous alloy. Information about the magnetoelastic characteristics of this material may be useful in the magnetoelastic sensor development. Also this will create new possibilities in the development of physical model of magnetoelastic effect.

  1. Microstructure and property characterization of a modified zinc-base alloy and comparison with bearing alloys

    Science.gov (United States)

    Prasad, B. K.; Patwardhan, A. K.; Yegneswaran, A. H.

    1998-02-01

    The microstructure and physical, mechanical, and tribological properties of a modified zinc-base alloy have been characterized. In order to assess its utility as a bearing alloy, its properties have also been compared with those of a similarly processed conventional zinc-base alloy and a leaded-tin bronze (conforming to ZA27 and SAE 660 specifications, respectively) used for bearing applications. The modified zinc-base alloy shows promise in terms of better elevated-temperature strength and wear response at higher sliding speeds relative to the conventional zinc-base alloy. Interestingly, the wear behavior (especially the seizure pressure) of the modified alloy was also comparable to that of the bronze specimens at the maximum sliding speed, and was superior at the minimum sliding speed. The modified alloy also attained lower density and better hardness. Alloy behavior has been linked to the nature and type of the alloy microconstituents.

  2. Molecular field analysis for melt-spun amorphous Fe sub 1 sub 0 sub 0 sub - sub x Gd sub x alloys (18<=60)

    CERN Document Server

    Yano, K

    2000-01-01

    The magnetic properties for the melt-spun amorphous Fe sub 1 sub 0 sub 0 sub - sub x Gd sub x alloys were analyzed using the molecular field theory (MFT). A concentration dependence of three exchange interaction constants was derived over a wide concentration range (18=T sub c sub o sub m sub p. Curvature of the Arrott plot in Gd-rich region was qualitatively simulated.

  3. Structural features and the microscopic dynamics of the three-component Zr47Cu46Al7 system: Equilibrium melt, supercooled melt, and amorphous alloy

    Science.gov (United States)

    Khusnutdinoff, R. M.; Mokshin, A. V.; Klumov, B. A.; Ryltsev, R. E.; Chtchelkatchev, N. M.

    2016-08-01

    The structural and dynamic properties of the three-component Zr47Cu46Al7 system are subjected to a molecular dynamics simulation in the temperature range T = 250-3000 K at a pressure p = 1.0 bar. The temperature dependences of the Wendt-Abraham parameter and the translation order parameter are used to determine the glass transition temperature in the Zr47Cu46Al7 system, which is found to be T c ≈ 750 K. It is found that the bulk amorphous Zr47Cu46Al7 alloy contains localized regions with an ordered atomic structures. Cluster analysis of configuration simulation data reveals the existence of quasi-icosahedral clusters in amorphous metallic Zr-Cu-Al alloys. The spectral densities of time radial distribution functions of the longitudinal ( C˜ L( k, ω)) and transverse ( C˜ T ( k, ω)) fluxes are calculated in a wide wavenumber range in order to study the mechanisms of formation of atomic collective excitations in the Zr47Cu46Al7 system. It was found that a linear combination of three Gaussian functions is sufficient to reproduce the ( C˜ L ( k, ω)) spectra, whereas at least four Gaussian contributions are necessary to exactly describe the ( C˜ T ( k, ω)) spectra of the supercooled melt and the amorphous metallic alloy. It is shown that the collective atomic excitations in the equilibrium melt at T = 3000 K and in the amorphous metallic alloy at T = 250 K are characterized by two dispersion acoustic-like branches related with longitudinal and transverse polarizations.

  4. Crystallization and Corrosion Resistance in Different Aqueous Solutions of Zr50.7Ni28Cu9Al12.3 Amorphous Alloy and Its Crystallization Counterparts

    Science.gov (United States)

    Ge, Wenjuan; Li, Boyu; Axinte, Eugen; Zhang, Zitang; Shang, Caiyun; Wang, Yan

    2017-02-01

    The Zr50.7Ni28Cu9Al12.3 amorphous alloy and its crystallization counterparts have been prepared using a melt spinning technique and proper annealing treatment. The as-annealed products at 768 K are amorphous composites consisting of a main amorphous phase and a few ZrO2 nanocrystals. The corrosion behaviors have been investigated in 0.5-M NaCl, 1-M HCl, and 0.5-M H2SO4 solutions. The results show that amorphous composites present the enhanced corrosion resistance in Cl- containing solutions due to the formation of compact passive films, which are promoted by an appropriate quantity of ZrO2 nanocrystals. Nevertheless, the relaxed samples possess good corrosion resistance in H2SO4 solution, which is attributed to the existence of Zr(Al, Ni)-rich protective film induced by the depletion of Cu. In addition, corrosion resistance of the tested alloys is relatively superior in H2SO4 solution, especially for pitting corrosion resistance, and inferior in HCl solution.

  5. Magnetocaloric effect and refrigeration cooling power in amorphous Gd7Ru3 alloys

    Directory of Open Access Journals (Sweden)

    Pramod Kumar

    2015-07-01

    Full Text Available In this paper, we report the magnetic, heat capacity and magneto-caloric effect (MCE of amorphous Gd7Ru3 compound. Both, temperature dependent magnetization and heat capacity data reveals that two transitions at 58 K and 34 K. MCE has been calculated in terms of isothermal entropy change (ΔSM and adiabatic temperature change (ΔTad using the heat capacity data in different fields. The maximum values of ΔSM and ΔTad are 21 Jmol−1K−1 and 5 K respectively, for field change of 50 kOe whereas relative cooling power (RCP is ∼735 J/kg for the same field change.

  6. Kinetics of formation of Al nanocrystals from amorphous Al-Sm alloys

    Energy Technology Data Exchange (ETDEWEB)

    Rizzi, P. [Torino Univ. (Italy). Dipt. di Chimica Inorganica, Chimica Fisica e Chimica dei Materiali; Baricco, M. [Torino Univ. (Italy). Dipt. di Chimica Inorganica, Chimica Fisica e Chimica dei Materiali; Battezzati, L. [Torino Univ. (Italy). Dipt. di Chimica Inorganica, Chimica Fisica e Chimica dei Materiali; Schumacher, P. [Cambridge Univ. (United Kingdom). Dept. of Metallurgy and Materials Science; Greer, A.L. [Cambridge Univ. (United Kingdom). Dept. of Metallurgy and Materials Science

    1997-06-01

    This paper presents results on the formation of nanocrystals in Al{sub 92}Sm{sub 8} amorphous ribbons produced by melt-spinning. Their crystallization behaviour was examined by means of DSC, XRD and TEM. DSC scans at 40 K/min show that a primary crystallization of {alpha}-Al nanocrystals occurs at about 453 K. Isothermal analysis are performed at the temperature of 444 K for various annealing times in order to obtain information on the transformed fraction, the nucleation frequency and the growth rate. From TEM observations the mean crystal size and the density of crystals are determined. It is found that the nucleation rate is considerable during the first minutes of annealing and then decreases steadily. Growth is also fast at the beginning of annealing and then is very sluggish. (orig.)

  7. Synthesis and photocatlytic performance of nano-sized TiO{sub 2} materials prepared by dealloying Ti–Cu–Pd amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Jing [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); Xu, Wence; Cui, Zhenduo [School of Materials Science and Engineering, Tianjin University, 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)

    2015-05-15

    Highlights: • TiO{sub 2} nanospindles were synthesized by dealloying Ti–Cu–Pd amorphous alloy. • Pd significantly enhanced the exposure of high-energy (0 0 1) facet of TiO{sub 2}. • TiO{sub 2} with high-energy (0 0 1) facet showed good photocatalytic activity. - Abstract: TiO{sub 2} nanospindles with exposed (0 0 1) facet were synthesized through a simple dealloying reaction. The rutile photocatalysts were characterized by X-ray diffraction, scanning electron microscope and transmission electron microscope, inductively coupled plasma optical emission spectrometry and ultraviolet–visible spectrophotometer. A Rhodamine B dye (RhB) was used to detect the photocatalytic activity of TiO{sub 2} under full light irradiation. The presence of Pd in the original amorphous alloy reduced the surface free energy of TiO{sub 2}, stabilized the (0 0 1) facet. The Pd8-TiO{sub 2} sample exhibited the largest crystal size along the direction which is perpendicular to the (0 0 1) facet. The photocatalytic degradation rate of RhB was improved due to the Pd addition in the original amorphous alloy. This indicated that the exposure of (0 0 1) facets could enhance the activity of TiO{sub 2} photocatalyst. In addition, the presence of isolated Pd atoms on the surface of TiO{sub 2} would be another probable reason for the improvement of photocatalytic activity.

  8. Correlation between isothermal expansion and functional properties change of the Fe81B13Si4C2 amorphous alloy

    Directory of Open Access Journals (Sweden)

    Kalezić-Glišović A.

    2009-01-01

    Full Text Available The structural changes effect on functional properties of ribbon shaped samples of the Fe81B13Si4C2 amorphous alloy during annealing process was investigated in this paper. Differential scanning calorimetry method has shown that this alloy crystallizes in one stage, in temperature range from room temperature up to 700°C. Structural relaxation process was investigated by sensitive dilatation method in nonisothermal and isothermal conditions. It has been shown that structural relaxation process occurs in two stages by measuring thermal expansion at constant temperatures of t1=420°C, t2 = 440°C and t3 = 460°C. The first stage is characterized by linear logarithmic dependence of thermal expansion upon time at constant temperature. The second stage of structural relaxation process is characterized by linear dependence of isothermal expansion upon the square root of process time. These results imply that the first stage of structural relaxation process is a rapid kinetic process, while the second stage of structural relaxation process is a slow diffusion process. The rate constants k11 = 2,27⋅10- 3 s-1, k12 = 2,79⋅10-3 s-1, k13 = 3,6⋅10-3 s-1, k21 = 0,67⋅10-4 s-1, k22 = 3,72⋅10-4 s-1, k23 = 21,53⋅10-4 s-1 and activation energies E1 = 48,64 kJ/mol and E2 = 366, 23 kJ/mol were determined for both stages of structural relaxation process. The distinct correlation between structural relaxation process and magnetic susceptibility relative change was determined by thermomagnetic measurements. It has been shown that magnetic susceptibility can be increased by up to 80%, by convenient annealings after structural relaxation process, at magnetic field intensity of 8 kA/m.

  9. Influence of the rare earth concentration on the crystallization process of Fe-Dy-B amorphous alloys. Study of Fe74Dy6B20 and Fe70Dy10B20 alloys

    Science.gov (United States)

    Ravach, G.; Machizaud, F.; Teillet, J.; LeBreton, J. M.; Fnidiki, A.

    2000-04-01

    The crystallization behaviour of Fe74 Dy6 B20 and Fe70 Dy10 B20 amorphous alloys was carefully investigated by differential scanning calorimetry, Mössbauer spectrometry and x-ray diffraction up to 800 °C. Calorimetric studies were performed in limited temperature ranges that were progressively extended. For Fe74 Dy6 B20 , after partial crystallization into the tetragonal Fe3 B compound, the remaining amorphous part segregates into two amorphous `phases', respectively enriched and impoverished in dysprosium. Tetragonal Fe3 B further transforms into orthorhombic Fe3 B. Metastable Dy3 Fe62 B14 compound then forms from the Dy-impoverished amorphous fraction, and subsequent crystallization of the Dy1 + icons/Journals/Common/varepsilon" ALT="varepsilon" ALIGN="MIDDLE"/> Fe4 B4 phase occurs in the Dy-enriched fraction. Finally, Dy3 Fe62 B14 decomposes into bcc iron, Dy1 + icons/Journals/Common/varepsilon" ALT="varepsilon" ALIGN="MIDDLE"/> Fe4 B4 and iron borides. The nature of the first crystallization product suggests the existence of local environments of t-Fe3 B type for this Dy concentration. The crystallization process of Fe70 Dy10 B20 strongly differs from that of Fe74 Dy6 B20 . Segregation phenomena occur in the amorphous state prior to any crystallization. If the nature of the first crystallization product is assumed to be correlated with short-range order in the amorphous state, our results suggest that the local environments differ from those of Fe74 Dy6 B20 , as they probably involve dysprosium atoms. This behaviour would agree with a previous Mössbauer study performed on the as-quenched amorphous alloys, providing evidence for a structural modification of the iron environments in the rare earth concentration range 8-9 at.%.

  10. Manufacture of iron-based, amorphous coatings with high fracture toughness

    Science.gov (United States)

    Bobzin, K.; Öte, M.; Königstein, T.

    2017-03-01

    Amorphous iron-based material have excellent corrosion behaviour, show good tribological performances and exhibit interesting thermophysical properties. The deposition as a coating system by thermal spraying technology is an innovative approach to manufacture these materials. In this study, the mechanical properties of three iron-based amorphous coatings with different chromium content xCr = 0, 5 and 15 at.% are presented deposited by means of High Velocity Oxygen Fuel Spraying. For the determination of the amorphous content the linear relationship between crystallization energy and amount of amorphous structures is used. Comparing the crystallization energies of amorphous ribbons manufactured by melt spinning to those of feedstock materials and free standing coatings, assumptions regarding the amorphous contents are drawn. The results show that the amorphous content in the feedstock material is influenced by the amount of chromium content. Furthermore, the amorphous content of all coatings do not exceed those of the feedstock materials. Powder xCr = 15 at.% and the corresponding coating exhibit smallest amount of amorphous structure, presumably due to a not fully melted state of the impacting particles. The values of fracture toughness of the coatings are determined by means of indentation and subsequent measurement of the crack lengths. Furthermore, values of indentation modulus and hardness are measured and compared to each other. While length of indentation cracks decreases with increasing chromium content, an increase in indention modulus and hardness is observed. In comparison to ceramic reference YSZ and the steel reference 1.4404, all amorphous coatings show promising properties such as low indentation crack lengths and high hardness.

  11. Mathematical modelling of frequency-dependent hysteresis and energy loss of FeBSiC amorphous alloy

    Science.gov (United States)

    Koprivica, Branko; Milovanovic, Alenka; Mitrovic, Nebojsa

    2017-01-01

    The aim of this paper is to present a novel mathematical model of frequency-dependent magnetic hysteresis. The major hysteresis loop in this model is represented by the ascending and descending curve over an arctangent function. The parameters of the hysteresis model have been calculated from a measured hysteresis loop of the FeBSiC amorphous alloy sample. A number of measurements have been performed with this sample at different frequencies of the sinusoidal excitation magnetic field. A variation of the coercive magnetic field with the frequency has been observed and used in the modelling of frequency-dependent hysteresis with the proposed model. A comparison between measured and modelled hysteresis loops has been presented. Additionally, the areas of the obtained hysteresis loops, representing the energy loss per unit volume, have been calculated and the dependence of the energy loss on the frequency is shown. Furthermore, two models of the frequency dependence of the coercivity and two models of the energy loss separation have been used for fitting the experimental and simulation results. The relations between these models and their parameters have been observed and analysed. Also, the relations between parameters of the hysteresis model and the parameters of the energy loss separation models have been analysed and discussed.

  12. Development of plastic elongation in nanocrystalline and amorphous Ni–W dual phase alloys by brushing technique

    Energy Technology Data Exchange (ETDEWEB)

    Nakayama, S., E-mail: 00sm.uk0806@gmail.com; Adachi, H., E-mail: adachi@eng.u-hyogo.ac.jp; Yamasaki, T., E-mail: yamasaki@eng.u-hyogo.ac.jp

    2015-09-15

    Highlights: • A novel agitation technique called the brushing technique is proposed. • A homogeneous material can be obtained with the brushing technique. • The brushed material exhibits large plastic elongation with work hardening. - Abstract: A novel agitation technique, referred to as the “brushing technique” is proposed to treat the surface of a Ni–W alloy film during electrodeposition. This technique was developed to directly remove hydrogen bubbles on the film surface and to apply Ni ions to the interfacial layer with the substrate. The intrinsic mechanical properties of the Ni–W electrodeposits are then evaluated with respect to application. High resolution transmission electron microscopy observations revealed that both treated and untreated films have nanocrystallites of approximately 5 nm in diameter and an amorphous phase. There was a compositional difference of about. 1.4 at% W between the face side and the reverse side of the film that was not subjected to the brushing technique, whereas this difference was absent in the film subjected to the brushing technique. In addition, the brushing technique reduced the surface roughness of the film and decreased the number of defects. As a result, a large plastic strain of about. 2.9% was observed with work hardening under tensile testing.

  13. Impact of Ion Irradiation upon Structure and Magnetic Properties of NANOPERM-Type Amorphous and Nanocrystalline Alloys

    Directory of Open Access Journals (Sweden)

    Marcel Miglierini

    2015-01-01

    Full Text Available Structural modifications and their impact upon magnetic properties are studied in amorphous and nanocrystalline NANOPERM-type 57Fe75Mo8Cu1B16 alloy. They are introduced by irradiation with 130 keV N+ ions to the total fluencies of up to 2.5 × 1017 ions/cm2 under different cooling conditions. Increased temperature during the irradiation triggers formation of nanocrystallites of bcc-Fe in those subsurface regions that are affected by bombarding ions. No crystallization occurs when good thermal contact between the irradiated sample and a sample holder is assured. Instead, structural rearrangement which favours development of magnetically active regions was determined by the local probe methods of Mössbauer spectrometry. Dipole magnetic interactions dominate in subsurface regions on that side of the ribbons which was exposed to ion irradiation. Nevertheless, structural modifications demonstrate themselves also via macroscopic magnetic parameters such as temperature dependence of magnetization, Curie temperature, and hysteresis loops. Impact of only the temperature itself to the observed effects is assessed by the help of samples that were subjected just to heat treatment, that is, without ion irradiation.

  14. Mechanical spectroscopy studies of partially amorphous Nd{sub 60}Fe{sub 30}Al{sub 10} alloys

    Energy Technology Data Exchange (ETDEWEB)

    Tarnowski, German C. [Facultad de Ingenieria, Universidad Nacional de Misiones, 3360 Obera (Argentina); Salva, Horacio [Centro Atomico Bariloche, Instituto Balseiro, C.N.E.A.-U.N.Cuyo, 8400 S. C. de Bariloche (Argentina); Consejo Nacional de Investigaciones Cientificas y Tecnicas, 1033 Buenos Aires (Argentina); Ghilarducci, Ada A. [Centro Atomico Bariloche, Instituto Balseiro, C.N.E.A.-U.N.Cuyo, 8400 S. C. de Bariloche (Argentina); Urreta, Silvia E. [Facultad de Matematica, Astronomia y Fisica, Universidad Nacional de Cordoba, Ciudad Universitaria, 5000 Cordoba (Argentina)]. E-mail: urreta@famaf.unc.edu.ar; Billoni, Orlando V. [Facultad de Matematica, Astronomia y Fisica, Universidad Nacional de Cordoba, Ciudad Universitaria, 5000 Cordoba (Argentina); Fabietti, Luis M. [Facultad de Matematica, Astronomia y Fisica, Universidad Nacional de Cordoba, Ciudad Universitaria, 5000 Cordoba (Argentina)

    2004-12-31

    The hard magnetic properties of melt spun Nd{sub 60}Fe{sub 30}Al{sub 10} alloys are attributed to a major matrix nominally amorphous for X-ray diffraction, composed by two metastable nanosized ({approx}5 nm) phases with different intrinsic magnetic properties. This composite system is investigated for the first time by mechanical spectroscopy techniques in the temperature range between 50 K and 450 K (1 kHz) where large annealing effects and two damping phenomena are detected. The as-cast microstructure irreversibly changes during annealing above 330 K, leading to a large modulus recovery accompanied by a reduction in the internal friction level. A relatively large relaxation effect is observed about 290 K, evidenced by a narrow internal friction peak with the corresponding step in the elastic modulus; this peak remains stable under thermal cycling between 200 K and 300 K but is affected by aging at 330 K and practically vanishes after heating to 450 K. Another internal friction peak is observed at about 250 K which has associated an anomalous modulus effect; in this temperature range, the internal friction and the elastic modulus exhibit heating/cooling hysteresis, which strongly depends on the extreme temperatures of the thermal cycle, a behavior frequently associated to first-order phase transformations.

  15. Applicability of Johnson-Mehl-Avrami model to crystallization kinetics of Zr60Al15Ni25 bulk amorphous alloy

    Institute of Scientific and Technical Information of China (English)

    YAN Zhi-jie; DANG Shu-e; WANG Xiang-hui; LIAN Pei-xia

    2008-01-01

    The applicability of Johnson-Mehl-Avrami(JMA) model to the crystallization kinetics of Zr60Al15Ni25 bulk amorphous alloy is investigated by differential scanning calorimetry(DSC) under isochronal and isothermal conditions. A criterion xm, at which a defined function z(x) exhibits the maximum value, is introduced to check the validity of JMA model to the kinetics analysis. The value of xm has a constant of 0.632 for JMA model. It is found that the values of xm at different isothermal annealing temperatures (743, 748, 753 and 758 K) are almost near 0.632, which indicates that the isothermal crystallization kinetics can be modeled by JMA equation. However, the values of xm at different heating rates (10, 20, 30 and 40 K/min) are about 0.52, implying that JMA model is not valid to the isochronal crystallization kinetics. The reason why the JMA model is not valid to the isochronal crystallization kinetics is discussed.

  16. Thermal activation analysis of the structural and phase transformations in the Zr-Cu-Nb amorphous alloy

    Directory of Open Access Journals (Sweden)

    Fedotova N.L.

    2011-05-01

    Full Text Available In the present work, the procedure of the estimation of the thermal activation parameters from the data of dilatometric measurements and the results of its application to the Zr-Cu-Nb amorphous alloy discussed. The determination of the thermal activation parameters of the processes occurring in materials under known temperature-force conditions can be useful for the identification of the structural mechanisms of phase transformations and the evolution of defect structure. We used the data of dilatometric measurements for evaluating the effective activation energy. This method exhibits some advantages over the conventional one due to the design features of dilatometers. First, it ensures the precise measurement of strains; second, the assigned temperature regime is very precisely maintained both at the stage of heating and upon isothermal holding; third, it ensures a high-speed continuous record of the experimental data. The developed method of evaluating the effective activation energy from the results of dilatometric experiments provides statistically reliable results. The data of the photometric analysis of structure images are in accordance with the results of dilatometric experiments

  17. Multiscale investigation of inhomogeneous plastic deformation of NiTi shape memory alloy based on local canning compression

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Shuyong, E-mail: jiangshy@sina.com [Industrial Training Centre, Harbin Engineering University, Harbin 150001 (China); Hu, Li [College of Materials Science and Chemical Engineering, Harbin Engineering University, Harbin 150001 (China); Zhao, Yanan; Zhang, Yanqiu [Industrial Training Centre, Harbin Engineering University, Harbin 150001 (China); Liang, Yulong [College of Materials Science and Chemical Engineering, Harbin Engineering University, Harbin 150001 (China)

    2013-05-01

    As a severe plastic deformation (SPD) technique, local canning compression provides a novel approach to produce bulk amorphous and nanocrystalline nickel–titanium shape memory alloy (NiTi SMA). From the macroscale, mesoscale and microscale viewpoint, physical mechanism of inhomogeneous plastic deformation of NiTi alloy under local canning compression is investigated by means of optical microscopy, transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). Inhomogeneous plastic deformation of NiTi alloy leads to coexistence of amorphous phase, nanocrystalline phase, B2 austenite and B19′ martensite. The interaction between the dislocations and the grain boundaries lays the profound foundation for guaranteeing the continuity and the compatibility between the grains in a polycrystalline NiTi sample subjected to inhomogeneous plastic deformation. Deformation twinning and dislocation slip are the two important deformation modes in plastic deformation of NiTi alloy under local canning compression. Based on the statistically stored dislocation and the geometrically necessary dislocation, the mechanism of the critical dislocation density plays a predominant role in the occurrence of the amorphous phase in the deformed NiTi sample. When the deformation temperature is higher than a critical temperature, the amorphous phase is not able to occur in the NiTi sample subjected to SPD.

  18. Structural and magnetic properties of Fe{sub 76}P{sub 5}(Si{sub 0.3}B{sub 0.5}C{sub 0.2}){sub 19} amorphous alloy

    Energy Technology Data Exchange (ETDEWEB)

    Lavorato, G.C. [INTECIN (FIUBA-CONICET), Paseo Colon 850, Capital Federal (Argentina); Dipartimento di Chimica IFM and NIS, Universita di Torino, Torino (Italy); Fiore, G. [Dipartimento di Chimica IFM and NIS, Universita di Torino, Torino (Italy); Tiberto, P. [INRIM, Electromagnetism Division, Torino (Italy); Baricco, M. [Dipartimento di Chimica IFM and NIS, Universita di Torino, Torino (Italy); Sirkin, H. [INTECIN (FIUBA-CONICET), Paseo Colon 850, Capital Federal (Argentina); Moya, J.A., E-mail: jmoya.fi.uba@gmail.com [GIM - IESIING, Universidad Catolica de Salta, INTECIN (UBA-CONICET) (Argentina)

    2012-09-25

    Highlights: Black-Right-Pointing-Pointer Fe{sub 76}P{sub 5}(Si{sub 0.3}B{sub 0.5}C{sub 0.2}){sub 19} amorphous alloy in ribbons and 1 mm and 2 mm rod samples. Black-Right-Pointing-Pointer Good glass forming ability with {Delta}T = 50 K and {gamma} = 0.37 and off-eutectic composition. Black-Right-Pointing-Pointer Good soft magnetic properties with magnetization saturation of 1.44 T. Black-Right-Pointing-Pointer 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 Fe{sub 76}P{sub 5}(Si{sub 0.3}B{sub 0.5}C{sub 0.2}){sub 19} amorphous alloy prepared by two quenching techniques has been studied. Amorphous ribbons of about 40 {mu}m 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

  19. Modelling of primary bcc-Fe crystal growth in a Fe{sub 85}B{sub 15} amorphous alloy

    Energy Technology Data Exchange (ETDEWEB)

    Palumbo, M. [Dip. Chimica I.F.M. and NIS, Universita di Torino, via Giuria 9, 10125 Turin (Italy); Baricco, M. [Dip. Chimica I.F.M. and NIS, Universita di Torino, via Giuria 9, 10125 Turin (Italy)]. E-mail: marcello.baricco@unito.it

    2005-05-15

    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 Fe{sub 85}B{sub 15} samples have been prepared and examined by differential scanning calorimetry. Calculated and experimental results, both on continuous heating and isothermal conditions, have been compared.

  20. 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.

  1. Production and processing of ultra-fine grained, nano structured and amorphous alloys by mechanical alloying; Obtencion y procesado de aleaciones de grano ultrafino, nanometrico y amorgas mediante aleado mecanico

    Energy Technology Data Exchange (ETDEWEB)

    Cintas, J.; Cuevas, F. G.; Montes, J. M.; Rodriguez, J. A.; Urban, P.; Gallardo, J. M.

    2007-07-01

    Several consolidation procedures have been developed during the last fifteen years to process mechanically alloyed (MA) powders at the Metallurgy and Materials Engineering Group (University of Seville). MA powders were processed by conventional cold pressing and vacuum sintering. In addition, several densification promoters were used. The resulting parts, with second phases precipitated during the consolidation, showed good tensile strength, both at room and high temperature. Nowadays, nano structured and amorphous MA alloys are being processed by electrical resistance sintering (ERS), which prevents microstructure evolution during consolidation. (Author) 49 refs.

  2. Preparation of Zr50Al15−Ni10Cu25Y amorphous powders by mechanical alloying and thermodynamic calculation

    Indian Academy of Sciences (India)

    Woyun Long; Anxian Lu; Jing Li

    2013-12-01

    Amorphous Zr50Al15−Ni10Cu25Y powders were fabricated by mechanical alloying at a low rotation speed from commercial pure element powders. The beneficial effect of Al partially substituted by Y in Zr50Al15Ni10Cu25 on glass-forming ability was investigated. The as-milled powders were characterized by X-ray diffraction and transmission electron microscopy. The results show that partial substitution of Al by Y can improve the glass-forming ability of Zr50Al15Ni10Cu25 alloy. Thermodynamic calculation of equivalent free energy shows that Zr50Al13.8Ni10Cu25Y1.2 alloy has the highest glass-forming ability, which is in good agreement with the report of orthogonal experiments.

  3. Crystalline to amorphous transition in solids upon high-pressure torsion

    Energy Technology Data Exchange (ETDEWEB)

    Sundeev, R.V., E-mail: apricisvir@gmail.com [I.P. Bardin Central Research Institute for Ferrous Metallurgy, 2-ya Baumanskaya 9/23, Moscow 105005 (Russian Federation); Moscow State University of Instrument Engineering and Computer Science, Stromynka 20, Moscow 107996 (Russian Federation); Glezer, A.M. [I.P. Bardin Central Research Institute for Ferrous Metallurgy, 2-ya Baumanskaya 9/23, Moscow 105005 (Russian Federation); Moscow State University of Instrument Engineering and Computer Science, Stromynka 20, Moscow 107996 (Russian Federation); National University of Science and Technology “MISIS”, Leninsky avenue 4, Moscow 119049 (Russian Federation); Shalimova, A.V. [I.P. Bardin Central Research Institute for Ferrous Metallurgy, 2-ya Baumanskaya 9/23, Moscow 105005 (Russian Federation)

    2014-10-25

    Highlights: • Ti–Ni, Zr and Fe-based alloys were deformed using HTP processing. • Ability to deformation-induced amorphization (DIA) of these alloys was studied. • Amorphization is determined by mechanical, thermodynamic and concentration factors. • The smaller stability of phases the higher their ability to deformation amorphization. • There is the difference between of DIA and to thermal amorphization in the nature. - Abstract: The amorphization behavior of the crystalline multicomponent Ni{sub 50}Ti{sub 30}Hf{sub 20}, Ti{sub 50}Ni{sub 25}Cu{sub 25,} Zr{sub 50}Ni{sub 18}Ti{sub 17}Cu{sub 15}, and Fe{sub 78}B{sub 8.5}Si{sub 9}P{sub 4.5} alloys upon severe plastic deformation (SPD) has been studied. It is shown that the crystalline to amorphous transition is determined by the ability of the crystals to accumulation of deformation defects under mechanical action, by the thermodynamic stability of the crystalline phases contained in the alloy, and by the possibility of the diffusion processes necessary for the change in the chemical composition of the crystalline and amorphous phases upon deformation. It is found that the susceptibility to amorphization upon SPD does not coincide with the tendency of the alloys to amorphization upon melt quenching.

  4. 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...

  5. Irradiation creep of vanadium-base alloys

    Energy Technology Data Exchange (ETDEWEB)

    Tsai, H.; Billone, M.C.; Strain, R.V.; Smith, D.L. [Argonne National Lab., IL (United States); Matsui, H. [Tohoku Univ. (Japan)

    1998-03-01

    A study of irradiation creep in vanadium-base alloys is underway with experiments in the Advanced Test Reactor (ATR) and the High Flux Isotope Reactor (HFIR) in the United States. Test specimens are thin-wall sealed tubes with internal pressure loading. The results from the initial ATR irradiation at low temperature (200--300 C) to a neutron damage level of 4.7 dpa show creep rates ranging from {approx}0 to 1.2 {times} 10{sup {minus}5}/dpa/MPa for a 500-kg heat of V-4Cr-4Ti alloy. These rates were generally lower than reported from a previous experiment in BR-10. Because both the attained neutron damage levels and the creep strains were low in the present study, however, these creep rates should be regarded as only preliminary. Substantially more testing is required before a data base on irradiation creep of vanadium alloys can be developed and used with confidence.

  6. Microstructure and Wear Properties of Fe-based Amorphous Coatings Deposited by High-velocity Oxygen Fuel Spraying

    Institute of Scientific and Technical Information of China (English)

    Gang WANG; Ping XIAO; Zhong-jia HUANG; Ru-jie HE

    2016-01-01

    Fe-based powder with a composition of Fe42·87 Cr15·98 Mo16·33 C15·94 B8·88 (at·%)was used to fabricate coatings by high-velocity oxygen fuel spraying.The effects of the spraying parameters on the microstructure and the wear properties of the Fe-based alloy coatings were systematically studied.The results showed that the obtained Fe-based coatings with a thickness of about 400μm consisted of a large-volume amorphous phase and some nanocrystals.With increasing the fuel and oxygen flow rates,the porosity of the obtained coatings decreased.The coating deposited un-der optimized parameters exhibited the lowest porosity of 2·8%.The excellent wear resistance of this coating was at-tributed to the properties of the amorphous matrix and the presence of nanocrystals homogeneously distributed with-in the matrix.The wear mechanism of the coatings was discussed on the basis of observations of the worn surfaces.

  7. Glass-Forming Ability of an Iron-Based Alloy Enhanced by Co Addition and Evaluated by a New Criterion

    Institute of Scientific and Technical Information of China (English)

    CHEN Qing-Jun; SHEN Jun; FAN Hong-Bo; SUN Jian-Fei; HUANG Yong-Jiang; MCCARTNEY D. G.

    2005-01-01

    @@ A new Fe-based alloy that can be cast into a fully amorphous rod with a diameter of at least 16mm by the conventional copper-mould casting technique is obtained by partially replacing Fe with Co in a previously reported Fe-based bulk metallic glass. The preliminary thermodynamic analysis indicates that the Co-containing alloy has a significantly lower Gibbs free energy difference between the undercooled melt and the corresponding crystalline solid, compared to the Co-free alloy, reflecting the dramatic role of the Co addition in stabilizing the supercooled melt and facilitating glass formation in iron-based alloys. Here, a new criterion, derived from the classical nucleation and growth theory, is introduced to evaluate the glass-forming ability of Fe-based bulk metallic glasses.

  8. Magnetoresistance and magnetic properties in amorphous Fe-based wires

    Science.gov (United States)

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

    2001-06-01

    The longitudinal and transverse magnetoresistances in amorphous Fe 77.5Si 7.5B 15 wires are studied at different values of the DC-bias currents in order to clarify the mechanism of the magnetization according to a 'core-shell' domain model. The role of closure domain structures in the magnetization process of the wires is analysed. Moreover, the effects of the Joule heating on the internal stresses, introduced during the rapid quenching in the sample preparation, are examined.

  9. Magnetic Sensors Based on Amorphous Ferromagnetic Materials: A Review

    OpenAIRE

    Carlos Morón; Carolina Cabrera; Alberto Morón; Alfonso García; Mercedes González

    2015-01-01

    Currently there are many types of sensors that are used in lots of applications. Among these, magnetic sensors are a good alternative for the detection and measurement of different phenomena because they are a “simple” and readily available technology. For the construction of such devices there are many magnetic materials available, although amorphous ferromagnetic materials are the most suitable. The existence in the market of these materials allows the production of different kinds of senso...

  10. Influences of hydrogen-induced amorphization and annealing treatment on gaseous hydrogen storage properties of La{sub 1−x}Pr{sub x}MgNi{sub 3.6}Co{sub 0.4} (x = 0–0.4) alloys

    Energy Technology Data Exchange (ETDEWEB)

    Zhai, Tingting [Department of Functional Material Research, Central Iron and Steel Research Institute, Beijing 100081 (China); College of Science, Northeastern University, Shenyang 110819 (China); Yang, Tai; Yuan, Zeming; Xu, Sheng; Bu, Wengang [Department of Functional Material Research, Central Iron and Steel Research Institute, Beijing 100081 (China); Qi, Yang [College of Science, Northeastern University, Shenyang 110819 (China); Zhang, Yanghuan, E-mail: zhangyh59@sina.com [Department of Functional Material Research, Central Iron and Steel Research Institute, Beijing 100081 (China); Key Laboratory of Integrated Exploitation of Baiyun Obo Multi-Metal Resources, Inner Mongolia University of Science and Technology, Baotou 014010 (China)

    2015-08-05

    Highlights: • The La–Mg–Ni-based AB{sub 2}-type alloys were prepared by casting. • La was substituted by a small amount of Pr in the experimental alloys. • The hydrogen absorption/desorption cycling properties of the alloys were studied. • The influences of hydrogen-induced amorphization were investigated in details. • The annealing treatment was applied to recover hydrogen storage capacity. - Abstract: La{sub 1−x}Pr{sub x}MgNi{sub 3.6}Co{sub 0.4} (x = 0–0.4) alloys are prepared by vacuum induction melting. The phase composition and microstructure of the as-cast alloys is characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The gaseous hydrogen absorption capacity of the alloys was measured by an automatically controlled Sieverts apparatus. The results indicate that the as-cast alloys consist of two phases of LaMgNi{sub 4} and LaNi{sub 5}. The maximum gaseous hydrogen storage capacity of the La{sub 1−x}Pr{sub x}MgNi{sub 3.6}Co{sub 0.4} (x = 0–0.4) alloys is 1.768, 1.745, 1.721, 1.681 and 1.653 wt%, respectively, under 3 MPa H{sub 2} at 373 K. But the hydrogen storage capacity after 20 cycles decays off to 0.746, 0.843, 0.947, 1.003 and 1.10 wt%, respectively. In order to reveal the mechanism of rapid degradation of the capacity, the structures of the alloys before and after hydrogen absorption/desorption cycle were analyzed. SEM observation displays that the micro-cracks can be clearly seen on the surface of the alloy particles after 20 cycles. XRD detection finds that the repeated hydrogen absorption/desorption cycles give rise to a obvious broadening of the diffraction peaks of the alloys, exhibiting a typical amorphous structure, which is termed as hydrogen-induced amorphization. The La{sub 1−x}Pr{sub x}MgNi{sub 3.6}Co{sub 0.4} (x = 0–0.4) alloys after 20 cycles were annealed at 623 K for 8 h, finding that the hydrogen storage capacity of the alloys recovers to 1.348, 1.365, 1.50, 1.485 and 1.30 wt

  11. An Alternate to Cobalt-Base Hardfacing Alloys

    Science.gov (United States)

    Hickl, Anthony J.

    1980-03-01

    The price of cobalt has risen dramatically in the last few years, and supply has often been uncertain. The most popular hardfacing alloys contain substantial amounts of cobalt, and have thus been especially affected by these factors. The present study has developed a new hardfacing alloy, HAYNES Alloy No. 716, with lower cobalt content, to replace the most popular alloy, HAYNES STELLITE Alloy No. 6 which is cobalt based. The alloy design which led to the development of the new alloy is discussed, and properties are compared with Alloy No. 6. Hardness at room temperature and elevated temperatures, weldability, and corrosion and abrasion resistance of the new alloy compare favorably with Alloy No. 6.

  12. Corrosion behaviour of amorphous Ti48Cu52, Ti50Cu50 and Ti60Ni40 alloys investigated by potentiodynamic polarization method

    Indian Academy of Sciences (India)

    A Dhawan; S Roychowdhury; P K De; S K Sharma

    2003-10-01

    Potentiodynamic polarization studies were carried out on virgin specimens of amorphous alloys Ti48Cu52, Ti50Cu50 and Ti60Ni40 in 0.5 M HNO3, 0.5 M H2SO4 and 0.5 M NaOH aqueous media at room temperature. The value of the corrosion current density (corr) was maximum for Ti48Cu52 alloy in all the three aqueous media as compared to the remaining two alloys. The value of corr for the alloy Ti48Cu52 was maximum (corr = 2.6 × 10-5 A/cm2) in 0.5 M H2SO4 and minimum (corr = 3.5 × 10-6 A/cm2) in 0.5 M NaOH aqueous solutions. In contrast, the alloy Ti60Ni40 exhibited the least corrosion current density in 0.5 M HNO3 (corr = 4.0 × 10-7 A/cm2) and in 0.5 M NaOH (corr = 5.5 × 10-7 A/cm2) aqueous media as compared to those for Ti–Cu alloys, while its value in 0.5 M H2SO4 was comparable to that for Ti50Cu50. It is suggested that the alloy Ti60Ni40 is more corrosion resistant than the alloys Ti48Cu52 and Ti50Cu50 in all the three aqueous media.

  13. Fabrication and microstructure of Fe-based amorphous composite coatings by laser cladding

    Institute of Scientific and Technical Information of China (English)

    Zhu Qingjun; Zou Zengda; Qu Shiyao; Wang Xinhong

    2008-01-01

    Fe-based amorphous composite coatings were fabricated on AISI 1045 steel by laser cladding. The results of the X-ray diffraction and transmission electron microscopy analyses show the coating is composed of an amorphous phase in majority and a nanocrystalline phase in minority. Phase composition of the coating changes along the depth of the coating. The reasonable scanning speed for fabricating an amorphous composite coating is 3 500mm/min when the laser power is 4 800W and the laser beam diameter is 2mm. If the scanning speed is lower than 3 500mm/min, the intensity of the two main diffraction peaks in X-ray diffraction patterns of the coatings decreases with the scanning speeds increasing. At the same time, a broad halo peak emerges and enlarges. High laser power and fast scanning speed are the essential conditions of amorphization. The coating exhibits high microhardness.

  14. Effect of amorphous Mg{sub 50}Ni{sub 50} on hydriding and dehydriding behavior of Mg{sub 2}Ni alloy

    Energy Technology Data Exchange (ETDEWEB)

    Guzman, D., E-mail: danny.guzman@uda.cl [Departamento de Ingenieria en Metalurgia, Facultad de Ingenieria, Universidad de Atacama y Centro Regional de Investigacion y Desarrollo Sustentable de Atacama (CRIDESAT), Av. Copayapu 485, Copiapo (Chile); Ordonez, S. [Departamento de Ingenieria Metalurgica, Facultad de Ingenieria, Universidad de Santiago de Chile, Av. Lib. Bernardo O' Higgins 3363, Santiago (Chile); Fernandez, J.F.; Sanchez, C. [Departamento de Fisica de Materiales, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco 28049, Madrid (Spain); Serafini, D. [Departamento de Fisica, Facultad de Ciencias, Universidad de Santiago de Chile and Center for Interdisciplinary Research in Materials, CIMAT, Av. Lib. Bernardo O' Higgins 3363, Santiago (Chile); Rojas, P.A. [Escuela de Ingenieria Mecanica, Facultad de Ingenieria, Av. Los Carrera 01567, Quilpue, Pontificia Universidad Catolica de Valparaiso, PUCV (Chile); Aguilar, C. [Departamento de Ingenieria Metalurgica y Materiales, Universidad Tecnica Federico Santa Maria, Av. Espana 1680, Valparaiso (Chile); Tapia, P. [Departamento de Ingenieria en Metalurgia, Facultad de Ingenieria, Universidad de Atacama, Av. Copayapu 485, Copiapo (Chile)

    2011-04-15

    Composite Mg{sub 2}Ni (25 wt.%) amorphous Mg{sub 50}Ni{sub 50} was prepared by mechanical milling starting with nanocrystalline Mg{sub 2}Ni and amorphous Mg{sub 50}Ni{sub 50} 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 Mg{sub 50}Ni{sub 50} improved the hydriding and dehydriding kinetics of Mg{sub 2}Ni alloy upon cycling. A tentative rationalization of experimental observations is proposed. - Research Highlights: {yields} First study of the hydriding behavior of composite Mg{sub 2}Ni (25 wt.%) amorphous Mg{sub 50}Ni{sub 50}. {yields} Microstructural characterization of composite material using XRD and SEM was obtained. {yields} An improved effect of Mg{sub 50}Ni{sub 50} on the Mg{sub 2}Ni hydriding behavior was verified. {yields} The apparent activation energy for the hydrogen desorption of composite was obtained.

  15. Soft magnetic properties of amorphous Fe52Co34Hf7B6Cu1 alloy treated by pulsed magnetic field and annealing

    Institute of Scientific and Technical Information of China (English)

    Gu Yue; Chao Yue-Sheng; Zhang Yan-Hui

    2012-01-01

    The crystallization,microstructure,and soft magnetic properties of Fe52Co34Hf7B6Cu1 alloy are studied.Amorphous Fe52Co34Hf7B6Cu1 alloys are first treated by a pulsed magnetic field with a medium frequency,and then annealed at 100 ℃-400 ℃ for 30 min in a vacuum.The rise in temperature during the treatment by a pulsed magnetic field is measured by a non-contact infrared thermometer.The soft magnetic properties of specimens are measured by a vibrating sample magnetometer (VSM).The microstructure changes of specimens are observed by a M(o)ssbauer spectroscopy and transmission electron microscope (TEM).The results show the medium-frequency pulsating magnetic field will promote nanocrystallization of the amorphous alloy with a lower temperature rise.The nanocrystalline phase is α-Fe(Co)with bcc crystal structure,and the grain size is about 10 nm.After vacuum annealing at 100 ℃ for 30 min,scattering nanocrystalline phases become more uniform,the coercive force and the saturation magnetization of the specimens are 41.98 A/m and 185.15 emu/g.

  16. Synthesis, characterization and understanding of the mechanisms of electroplating of nanocrystalline–amorphous nickel–tungsten alloys using in situ electrochemical impedance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ahmadi, Majid; Guinel, Maxime J-F., E-mail: maxime.guinel@upr.edu

    2013-10-15

    Highlights: •Nanocrystalline–amorphous Ni–W alloys were electro co-deposited. •A better understanding of the co-deposition mechanisms was achieved. •The in situ EIS results were modeled and simulated to an equivalent circuit. •The deposited films were characterized using SEM, XRD and HRTEM. -- Abstract: In this study, a series of Nickel (Ni)–Tungsten (W) alloys were electrodeposited onto copper (Cu) substrates using electroplating baths and tri-sodium citrate (Na{sub 3}C{sub 6}H{sub 5}O{sub 7}) as the complex agent. The electro co-deposition of Ni–W alloys was carried out by varying several important experimental parameters: the tungstate ion [WO{sub 4}]{sup 2-} concentration, the bath temperature and the speed of stirring. Potentio-dynamic polarization and in-situ electrochemical impedance spectroscopy (EIS) techniques were used as electroplating methods to study the processes. The phases present in the films were identified using powder X-ray diffraction (XRD) and electron diffraction (ED). The films were examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and their elemental compositions determined using X-ray energy dispersive spectrometry (XEDS). The electrodeposited films were found to be a mixture of amorphous and nanocrystalline Ni–W. This study has allowed us to reach a better understanding of the complex mechanisms and effective parameters of co-deposition of Ni and W using citrate ions complex baths.

  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. Magnetic Properties of Fe- and FeNi-based Amorphous Composite Ribbons

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    M8-T curves and hysteresis loops were investigated for amorphous Fe78Si9B13, (FeNi)78(CrSiB)22, their lap-wound-cores, and their composite ribbons made by two-chamber-crucible technique. The properties of the lap-wound cores of the two kinds of ribbons are similar. For the composite ribbons, the intrinsic properties are the average of the two alloys. Their technological properties, i.e., hysteresis loops, however, are no longer the average of the two alloys. Instead, they show some dramatic changes compared to the lap-wound-cores. Especially, the shape of the hysteresis loop of the composite ribbon cores is largely different from that of lap-wound-cores. The reason for the difference is supposed to be internal stress induced from cooling after annealing.

  19. Magnetoimpedance effect in current annealed Co-based amorphous wires

    Science.gov (United States)

    Ghanaatshoar, M.; Tehranchi, M. M.; Mohseni, S. M.; Parhizkari, M.; Roozmeh, S. E.; Jazayeri Gharehbagh, A.

    2006-09-01

    Current-annealing of Co68.15Fe4.35Si12.5B15 amorphous wires has been studied at various vacuum orders. Structure-sensitive properties such as the electrical resistance during Joule heating treatment have been monitored to investigate the structural changes. Different driving currents have been flowed through the samples at different vacuums between 6×10-2 and 6×10-5 mbar. Regarding the giant magnetoimpedance (GMI) effect, annealing at different vacuums but with the same current can lead to various responses.

  20. Amorphous nanophotonics

    CERN Document Server

    Scharf, Toralf

    2013-01-01

    This book represents the first comprehensive overview over amorphous nano-optical and nano-photonic systems. Nanophotonics is a burgeoning branch of optics that enables many applications by steering the mould of light on length scales smaller than the wavelength with devoted nanostructures. Amorphous nanophotonics exploits self-organization mechanisms based on bottom-up approaches to fabricate nanooptical systems. The resulting structures presented in the book are characterized by a deterministic unit cell with tailored geometries; but their spatial arrangement is not controlled. Instead of periodic, the structures appear either amorphous or random. The aim of this book is to discuss all aspects related to observable effects in amorphous nanophotonic material and aspects related to their design, fabrication, characterization and integration into applications. The book has an interdisciplinary nature with contributions from scientists in physics, chemistry and materials sciences and sheds light on the topic fr...

  1. Hot Corrosion of Cobalt-Base Alloys

    Science.gov (United States)

    1975-06-01

    scale is similar to that which has already been proposed for cobalt . The oxide ions would react with the Al203 to form aluminate ions in the Na2S04...resistance of cobalt -base and nickel-base alloys. The contract was accomplished under the technical direction of Dr. H. C. Graham of the Aerospace Research...Oxidized Specimens RESULTS AND DISCUSSION 1. INTRODUCfiON 2. SODIUM SULFATE INDUCED HOT CORROSION OF COBALT a. Introduction b. Experimental c

  2. Embrittlement and conditions of the optimization of magnetic properties in the amorphous alloy Co69Fe3.7Cr3.8Si12.5B11 in the absence of a viscous-brittle transition

    Science.gov (United States)

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

    2016-07-01

    The influence of the holding time upon annealing on the temperature of the viscous-brittle transition (temperature of embrittlement) T f in a cobalt-based amorphous alloy of the composition Co69Fe3.7Cr3.8Si12.5B11 with a very low saturation magnetostriction λs (<10-7) has been studied. It has been established that the dependence of the embrittlement temperature T f on the of time of holding t a can be described by an Arrhenius equation and that the embrittlement at the annealing temperatures above and below 300°C is described by different kinetic parameters. In the alloy under study, irrespective of the holding time, embrittlement occurs in a very narrow range of annealing temperatures, which does not exceed 5 K. Based on the experimental data on the evolution of the hysteresis magnetic properties upon the isochronous annealings and upon the isothermal holding, the regime of heat treatment that ensures a very high (about 50000) magnitude of the permeability µ5 ( H = 5 mOe, f = 1 kHz) without the transition of the alloy into a brittle state has been determined.

  3. Critical behavior of amorphous Fe80 - xMxB14Si6 alloys with M=Mo, V, Mn, and 2 <= x <= 14

    Science.gov (United States)

    Jen, S. U.; Lee, C. C.; Huang, P. L.; Lin, S. T.

    1990-05-01

    Amorphous Fe80-xMxB14Si6 alloys with M=Mo, V, Mn, and 2≤x≤14 have been made by the rapid quenching method. The critical exponents β, γ, δ, and Tc were determined by two independent methods: the method of Kouvel-Fisher and the scaling plot. With the addition of M, β, and γ deviate more from the values predicted by the three-dimensional Heisenberg model, and are closer to the values proposed by Sobotta and Wagner. δ remains less changed. The magnetic inhomogeneity of these alloys is evidenced by the specific heat, the forced magnetoresistance, and the Mössbauer measurements. By increasing x, the peak of specific heat becomes smeared and less divergent, and forced magnetoresistance changes from negative to positive around Tc.

  4. Hydrogen storage kinetics of nanocrystalline and amorphous NdMg{sub 12}-type alloy-Ni composites synthesized by mechanical milling

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yanghuan; Cui, Songsong; Cai, Ying [Inner Mongolia University of Science and Technology, Baotou (China). Lab. of Integrated Exploitation of Baiyun Obo Multi-Metal Resources; Song, Xiping [Univ. of Science and Technology, Beijing (China). State Key Lab. for Advanced Metals and Materials; Zhang, Peilong; Zhu, Yongguo [Whole Win (Beijing) Materials Sci. and Tech. Co., Ltd., Beijing (China)

    2016-07-15

    Nanocrystalline and amorphous NdMg{sub 11}Ni + x wt.% Ni (x = 100, 200) composites were synthesized by mechanical milling, and their gaseous and electrochemical hydrogen storage kinetic performances were systematically investigated. Hydrogen absorption and desorption properties were investigated by means of a Sievert apparatus and a differential scanning calorimeter connected with an H{sub 2} detector. Electrochemical hydrogen storage kinetics of the as-milled alloys were tested by an automatic galvanostatic system. Results show that increasing Ni content significantly improves gaseous and electrochemical hydrogen storage kinetics. The improved gaseous hydrogen storage kinetics of the alloys are ascribed to the decrease in hydrogen desorption activation energy caused by increasing Ni content and milling time.

  5. Effects of alloying side B on Ti-based AB2 hydrogen storage alloys

    Institute of Scientific and Technical Information of China (English)

    王家淳; 于荣海; 刘庆

    2004-01-01

    Ti-based AB2-type hydrogen storage alloys are a group of promising materials, which will probably replace the prevalent rare earth-based AB5-type alloys and be adopted as the main cathode materials of nickelmetal hydride (Ni-MH) batteries in the near future. Alloying in side B is a major way to improve the performance of Ti-based AB2-type alloys. Based on recent studies, the effects of alloying elements in side B upon the performance of Ti-based AB2 -type hydrogen storage alloys are systematically reviewed here. These performances are divided into two categories, namely PCI characteristics, including hydrogen storage capacity (HSC), plateau pressure (PP), pressure hysteresis (PH) and pressure plateau sloping (PPS) , and electrochemical properties, including discharge capacity (DC), activation property (AP), cycling stability (CS) and high-rate dischargeability (HRD). Furthermore, the existing problems in these investigations and some suggestions for future research are proposed.

  6. Fabric cutting application of FeAl-based alloys

    Energy Technology Data Exchange (ETDEWEB)

    Sikka, V.K.; Blue, C.A. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.; Sklad, S.P. [Univ. of Virginia, Charlottesville, VA (United States); Deevi, S.C. [Philip Morris U.S.A., Richmond, VA (United States); Shih, H.R. [Jackson State Univ., MS (United States)

    1998-11-01

    Four intermetallic-based alloys were evaluated for cutting blade applications. These alloys included Fe{sub 3}Al-based (FAS-II and FA-129), FeAl-based (PM-60), and Ni{sub 3}Al-based (IC-50). These alloys were of interest because of their much higher work-hardening rates than the conventionally used carbon and stainless steels. The FeAl-based PM-60 alloy was of further interest because of its hardening possibility through retention of vacancies. The vacancy retention treatment is much simpler than the heat treatments used for hardening of steel blades. Blades of four intermetallic alloys and commercially used M2 tool steel blades were evaluated under identical conditions to cut two-ply heavy paper. Comparative results under identical conditions revealed that the FeAl-based alloy PM-60 outperformed the other intermetallic alloys and was equal to or somewhat better than the commercially used M2 tool steel.

  7. Effects of Ti and Zr Substituted on the Electrochemical Characteristics of MgNi-Based Alloy Electrodes

    Institute of Scientific and Technical Information of China (English)

    FENG Yan; JIAO Li-Fang; YUAN Hua-Tang; ZHAO Ming

    2007-01-01

    Mg-based hydrogen storage alloys MgNi, Mg0.9Ti0.1Ni, and Mg0.9Ti0.06Zr0.04Ni were successfully prepared by means of mechanical alloying (MA). The structure and the electrochemical characteristics of these Mg-based materials were studied. The X-ray diffraction (XRD) result shows that the main phases of the alloys exhibit amorphous structure. The scanning electron microscopy (SEM) photograph shows that the particle size of Ti and Zr substituted alloys was about 2-4 μm in diameter. The cycle lives of the alloys were prolonged by adding Ti and Zr. After 50charge-discharge cycles, the discharge capacity of Mg0.9Ti0.06Zr0.04Ni was 91.74% higher than that of MgNi alloy and 37.96% higher than that of Mg0.9Ti0.1Ni alloy. The main reason for the electrode capacity decay is the formation of Mg(OH)2 (product of Mg corrosion) at the surface of alloy. The potentiodynamic polarization result indicates that Ti and Zr doping improves the anticorrosion in an alkaline solution. The electrochemical impedance spectroscopy (EIS) results suggest that proper amount of Ti and Zr doping improves the electrochemical catalytic activity significantly.

  8. Amorphous IZO-based transparent thin film transistors

    Energy Technology Data Exchange (ETDEWEB)

    Paine, David C. [Division of Engineering, Brown University, Providence, RI 02912 (United States)], E-mail: David_Paine@Brown.edu; Yaglioglu, Burag; Beiley, Zach; Lee, Sunghwan [Division of Engineering, Brown University, Providence, RI 02912 (United States)

    2008-07-01

    Active electronics implemented on cheap flexible polymer substrates offer the promise of novel display technologies, wearable electronics, large area memory, and a multitude of other, as-yet-unthought-of applications that require low cost and high volume manufacturing. Thin film transistors (TFT's) fabricated on temperature-sensitive plastic substrates at low temperatures are the key to this technology. TFT's that use metal (In, Zn, Sn, Ga) oxide channels offer both high mobility (relative to amorphous Si) and the advantage of optical transparency in the visible regime. We report on the fabrication and performance of amorphous oxide transparent thin film transistors that use dc-magnetron sputter techniques to deposit IZO (In{sub 2}O{sub 3} - 10 wt.% ZnO) at low oxygen potential (0 vol.% O{sub 2}) for the source, drain, and gate-contact metallization and, at higher oxygen partial pressures (10 vol.% O{sub 2}), for the semi-conducting channel. The devices in this study were processed at room temperature except for a single 280 {sup o}C PECVD deposition step to deposit a 230 nm-thick SiO{sub x} gate dielectric. The devices are optically transparent and operate in depletion mode with a threshold voltage of - 5 V, mobility of 15 cm{sup 2}/V s, an on-off ratio of > 10{sup 6} and, a sub-threshold slope of 1.2 V/decade. In addition, we report persistent photo-conductivity in the channel region of these devices when exposed to UV illumination.

  9. Structural and electronic properties of binary amorphous aluminum alloys with transition metals and rare earth metals; Strukturelle und elektronische Eigenschaften binaerer amorpher Aluminiumlegierungen mit Uebergangsmetallen und Metallen der Seltenen Erden

    Energy Technology Data Exchange (ETDEWEB)

    Stiehler, Martin

    2012-02-03

    The influence of the d-states of the transition metals on the structure formation in amorphous alloys has so far only been inadequately understood. The present work aims to elaborate additional contributions to the understanding of binary amorphous aluminum alloys with transition metals. Special emphasis was placed on alloys with a subgroup of the transition metals, the rare earth metals. Within the scope of the present work, layers of Al-Ce in the region of 15at% Ce-80at% Ce were produced by sequential flash evaporation at 4.2K in the high vacuum, and characterized electronically by electrical resistance and Hall effect measurements as well as structurally by transmission electron diffraction. In addition, studies of plasma resonance were carried out by means of electron energy loss spectroscopy. In the range of 25at% Ce-60at% Ce, homogeneous amorphous samples were obtained. Especially the structural investigations were made difficult by oxidation of the material. The influence of the Ce-4f electrons manifests itself mainly in the low-temperature and magnetoresistance, both of which are dominated by the Kondo effect. The Hall effect in Al-Ce is dominated by anomalous components over the entire temperature range (2K-320K), which are attributed to skew-scattering effects, also due to Ce-4f electrons. Down to 2K there was no macroscopic magnetic order. In the region 2K-20K, the existence of clusters of ordered magnetic moments is concluded. For T> 20K, paramagnetic behavior occurs. With regard to the structural and electronic properties, a-Al-Ce can be classified as a group with a-Al- (Sc, Y, La). In the sense of plasma resonance, a-Al-Ce is excellently arranged in a system known from other Al transition metal alloys. Furthermore, by increasing the results of binary amorphous Al transition metal alloys from the literature, it has been found that the structure formation in these systems is closely linked to a known but still unexplained structure-forming effect that

  10. In situ X-Ray Absorption Spectro-Electrochemical Study of Amorphous Tin-Based Composite Oxide Material

    Energy Technology Data Exchange (ETDEWEB)

    Mansour, A. N.; Mukerjee, S.; Yang, X. Q.; McBreen, J.

    1998-11-01

    We have measured the XAFS spectra of a sample of tin-based composite oxide (TCO) material with a nominal composition of Sn{sub 1.0}B{sub 0.56}P{sub 0.40}Al{sub 0.42}O{sub 3.47} during the discharge and charge cycles in an ''in situ'' configuration. Our results confirm the amorphous nature of TCO and show that Sn in TCO is coordinated with 3 oxygen atoms at a distance of 2.12 {angstrom}. Upon discharging, initially, Li interacts with the electrochemically active Sn-O center forming metallic Sn in the form of clusters containing just a few atoms. Upon further discharge, Li alloys with Sn forming initially highly dispersed forms of Li{sub 2}Sn{sub 5} and/or LiSn and then Li{sub 7}Sn{sub 3}, Li{sub 5}Sn{sub 2}, Li{sub 13}Sn{sub 5}, or Li{sub 7}Sn{sub 2}. The true nature of the formed alloys could be significantly different from that of the corresponding crystalline phases. Upon charging, metallic Sn is produced with a Sn-Sn distance intermediate to those of gray and white Sn.

  11. Effect of heat treatment on structure and magnetic properties of Fe65.5Cr4Mo4Ga4P12C5B5.5 bulk amorphous alloy

    Directory of Open Access Journals (Sweden)

    Bratislav Cukic

    2017-01-01

    Full Text Available This study deals with the Fe65.5Cr4Mo4Ga4P12C5B5.5 ferromagnetic bulk amorphous alloy. XRD analysis showed an amorphous structure of the as-cast sample. The same method revealed that, after annealing at 973 K for τ=10 min, the sample displayed a crystalline structure with crystalline phases formed. The crystallization process of the alloy was examined by DTA analysis. It was shown that crystallization took place in the temperature range between 810 K and 860 K with the exo-maximum peak temperature at 846 K with a heating rate of 20 Kmin-1. The method also showed that, at temperatures ranging from 753 K to 810 K, the alloy exhibited the properties of supercooled liquids. A correlation between heat-induced structural changes and magnetic properties of the alloy was determined by thermomagnetic measurements. Maximum magnetization M=3.7 Am2kg-1 of the alloy was reached after its annealing at 733 K for τ=10 min. Upon annealing, the alloy exhibited a relaxed amorphous structure. Annealing the alloy above the crystallization temperature led to a decrease in bulk magnetization. After annealing at 973 K for τ=10 min, the bulk magnetization of the alloy was M'=0.45 Am2kg-1. Accordingly, after crystallization and formation of new compounds, the magnetization of the alloy was decreased by a factor of about 7.7. The strength of the magnetic field applied during the measurements was H=10 kAm-1. The samples were tested for changes in the microstructure and hardness of both the amorphous phase and the resulting crystalline phase.

  12. Discontinuous precipitation in copper base alloys

    Indian Academy of Sciences (India)

    K T Kashyap

    2009-08-01

    Discontinuous precipitation (DP) is associated with grain boundary migration in the wake of which alternate plates of the precipitate and the depleted matrix form. Some copper base alloys show DP while others do not. In this paper the misfit strain parameter, , has been calculated and predicted that if 100 > ± 0.1, DP is observed. This criterion points to diffusional coherency strain theory to be the operative mechanism for DP.

  13. Development of amorphous silicon-germanium-alloys for stacked solar cells; Entwicklung von amorphen Silizium-Germanium-Legierungen fuer den Einsatz in Stapelsolarzellen

    Energy Technology Data Exchange (ETDEWEB)

    Lundszien, D.

    2001-01-01

    To obtain high efficiency silicon based thin film solar cells, the concept of stacked solar cells is routinely used. The use of component cells with different optical bandgaps provides a better utilization of the solar spectrum. In a stacked cell structure, a high quality narrow bandgap material is needed for the active layer of the bottom cell. Amorphous silicon-germanium-alloys (a-SiGe:H) have been successfully employed because of their tunable optical bandgap E{sub G} between 1.8 eV (a-Si:H) and 1.1 eV (a-Ge:H). Considerable effort has been put into the development of a-SiGe:H. Still, with increasing Ge content, the material shows a characteristic deterioration of its electronic properties, like an exponential increase of the defect density, thus counteracting the gain in absorption obtained for higher Ge contents. It is the defect density which has the dominant influence on carrier transport and cell efficiency by affecting the mobility lifetime product and the electric field in the devices. The performance of a-SiGe:H pin solar cells with a wide range of Ge contents i.e. a wide range of optical band gaps (E{sub G}=1.3 to 1.6 eV) are compared. It is demonstrated how the deterioration of the material properties can be overcome by careful adjustment of the device design and the use of highly reflective ZnO/Ag back contacts. (orig.)

  14. Effect of External Electric Field on Phase Selection and Stability of Amorphous( Nd0.1Fe0.9 )3 B Alloy

    Institute of Scientific and Technical Information of China (English)

    李山东; 唐建成; 袁钻如; 顾本喜; 都有为

    2004-01-01

    The effect of an external electric field on the crystallization behavior of amorphous(Nd0.1Fe0.9)3B alloy was investigated. The crystallization product of Nd2Fe23B3 phase was obtained for this amorphous alloy annealed at 923 K for 300 s in the presence of an external electric field of 300 kV·m-1(50 Hz); while the crystallization products are Nd1.1Fe4B4, α-Fe, and Fe3B phases under the same annealing condition except for free-electric field. On the other hand, the samples were annealed at 1023 K, which is higher than the decomposition temperature of metastable Nd2Fe23B3 phase, for 600 s. In the case of the presence of an external electric field, the metastable Nd2Fe23B3 phase, as a main phase, is still stayed in the sample. This fact suggests that the external electric field enhances the stabilization of the metastable Nd2Fe23B3 phase. The effect of the external electric field on the phase selection and stabilization was explained in terms of the specific conductance difference between the crystallization products.

  15. New Developments of Ti-Based Alloys for Biomedical Applications

    Directory of Open Access Journals (Sweden)

    Yuhua Li

    2014-03-01

    Full Text Available Ti-based alloys are finding ever-increasing applications in biomaterials due to their excellent mechanical, physical and biological performance. Nowdays, low modulus β-type Ti-based alloys are still being developed. Meanwhile, porous Ti-based alloys are being developed as an alternative orthopedic implant material, as they can provide good biological fixation through bone tissue ingrowth into the porous network. This paper focuses on recent developments of biomedical Ti-based alloys. It can be divided into four main sections. The first section focuses on the fundamental requirements titanium biomaterial should fulfill and its market and application prospects. This section is followed by discussing basic phases, alloying elements and mechanical properties of low modulus β-type Ti-based alloys. Thermal treatment, grain size, texture and properties in Ti-based alloys and their limitations are dicussed in the third section. Finally, the fourth section reviews the influence of microstructural configurations on mechanical properties of porous Ti-based alloys and all known methods for fabricating porous Ti-based alloys. This section also reviews prospects and challenges of porous Ti-based alloys, emphasizing their current status, future opportunities and obstacles for expanded applications. Overall, efforts have been made to reveal the latest scenario of bulk and porous Ti-based materials for biomedical applications.

  16. 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

  17. Cerium-based conversion coatings on magnesium alloys

    Science.gov (United States)

    Castano Londono, Carlos Eduardo

    This research is primarily focused on gaining a better understanding of the deposition and corrosion behavior of cerium-based conversion coatings (CeCCs) on AZ31B and AZ91D Mg alloys. Deposition of homogenous and protective CeCCs was highly dependent on the surface preparation steps. The best results were obtained when Mg samples underwent grinding, acid cleaning, and alkaline cleaning processes. This reduced the number of active cathodic sites and promoted the formation of a protective Al-rich Mg oxide/hydroxide layer. Electrochemical properties of the CeCCs were also strongly correlated with morphological, microstructural, and chemical characteristics. Protective CeCCs were deposited on both AZ31 and AZ91 Mg alloys using a range of deposition times (5 to 180 s) and temperatures (10 to 80 °C). However, shorter deposition times (5 s) and lower deposition temperatures (~10 °C) showed higher impedance and longer bath stability than other deposition conditions. The increase in impedance was related with fewer cracks and smaller nodule sizes. Additional investigations of post-treated CeCCs exposed to NaCl environments showed an increased in the total impedance. The increase in corrosion protection of the CeCCs was associated with an overall increase in coating thickness from 400 to 800 nm. A microstructural evolution from ~3 nm nodular nanocrystals of CeO2/CePO4*H2O embedded in an amorphous matrix to >50 nm CePO4*H2O nanocrystals was responsible for the electrochemically active corrosion protection. Exposure of CeCCs to sunlight in humid environments promoted the reduction of Ce(IV) into Ce(III) species compared to unexposed coatings. This reduction process was related with photocatalytic water oxidation reaction.

  18. Modeling Physical Stability of Amorphous Solids Based on Temperature and Moisture Stresses.

    Science.gov (United States)

    Zhu, Donghua Alan; Zografi, George; Gao, Ping; Gong, Yuchuan; Zhang, Geoff G Z

    2016-09-01

    Isothermal microcalorimetry was utilized to monitor the crystallization process of amorphous ritonavir (RTV) and its hydroxypropylmethylcellulose acetate succinate-based amorphous solid dispersion under various stressed conditions. An empirical model was developed: ln(τ)=ln(A)+EaRT-b⋅wc, where τ is the crystallization induction period, A is a pre-exponential factor, Ea is the apparent activation energy, b is the moisture sensitivity parameter, and wc is water content. To minimize the propagation of errors associated with the estimates, a nonlinear approach was used to calculate mean estimates and confidence intervals. The physical stability of neat amorphous RTV and RTV in hydroxypropylmethylcellulose acetate succinate solid dispersions was found to be mainly governed by the nucleation kinetic process. The impact of polymers and moisture on the crystallization process can be quantitatively described by Ea and b in this Arrhenius-type model. The good agreement between the measured values under some less stressful test conditions and those predicted, reflected by the slope and R(2) of the correlation plot of these 2 sets of data on a natural logarithm scale, indicates its predictability of long-term physical stability of amorphous RTV in solid dispersions. To further improve the model, more understanding of the impact of temperature and moisture on the amorphous physical stability and fundamentals regarding nucleation and crystallization is needed.

  19. Microstructural characterization of rapidly solidified Cu{sub 50}Zr{sub 40}Ni{sub 5}Ti{sub 5} amorphous alloy

    Energy Technology Data Exchange (ETDEWEB)

    Kursun, Celal, E-mail: celalkursun@ksu.edu.tr [Department of Physics, Faculty of Art and Sciences, Kahramanmaras Sutcu Imam University, Kahramanmaras 46100 (Turkey); Gögebakan, Musa [Department of Physics, Faculty of Art and Sciences, Kahramanmaras Sutcu Imam University, Kahramanmaras 46100 (Turkey); Gencer, Yucel [Department of Materials Science and Engineering, Gebze Institute of Technology, Gebze, 41400 Kocaeli (Turkey)

    2015-09-15

    The amorphous Cu{sub 50}Zr{sub 40}Ni{sub 5}Ti{sub 5} alloy was produced by melt-spinning at wheel speeds of 35, 38 and 41 m s{sup −1}. The resulting melt-spun ribbons were characterised using X-ray diffraction (XRD), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDX), differential scanning calorimetry (DSC) and Vickers microhardness (HV) tester. The XRD and SEM results revealed that the rapidly solidified ribbons have a fully amorphous structure. After partial or fully crystallisation of Cu{sub 50}Zr{sub 40}Ni{sub 5}Ti{sub 5} ribbons upon annealing, the microstructure had uneven and irregularly shaped features with the existence of Cu{sub 10}Zr{sub 7}, Cu{sub 8}Zr{sub 3}, CuZr and FCC-Cu phases while as quenched ribbons had featureless microstructure. The SEM-EDX analysis confirmed compositional homogeneity of the Cu{sub 50}Zr{sub 40}Ni{sub 5}Ti{sub 5} alloy ribbon. According to DSC results, the amorphous ribbons exhibited distinct glass transition temperature (T{sub g}) and wide supercooled liquid region (ΔT{sub x} = T{sub x} − T{sub g}) before crystallization. Accordingly, T{sub g} and ΔT{sub x} are around 409–414 °C and 37–54 °C, respectively. The microhardness of the as-quenched ribbons was about 522 HV while it decreased with increasing annealing temperature and had a value of 463 HV for 725 °C.

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

    Science.gov (United States)

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

    2015-03-01

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

  1. Indentation toughness of Mo5Si3-based alloys

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The indentation toughness of Mo5Si3 -based phases was studied with regard to different alloying elements, amount of alloying addition as well as the presence of secondary phases. Cr, Ti, Nb, Ni and Co were added as alloying elements. The results show that the indentation fracture toughness of Mo5Si3 increases with the alloying additions, from 2.4 Mpa *m1/2 for mon olithic to just over 3 Mpa*m1/2 for highly alloyed Mo5Si3. Small volume fractions of brittle secondary phases may have a positive impact on the inde ntation toughness; while larger fractions seems to lower the toughness.

  2. Influence of Y, Gd and Sm on the glass forming ability and thermal crystallization of aluminum based alloy; Efeito das terras raras Y, Gd e Sm na tendencia a formacao de amorfo e na cristalizacao termica em ligas a base de aluminio

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-07-01

    Al-based amorphous alloys represent an important family of metals and a great scientific activity has been devoted to determine the main features of both glass forming ability (GFA) and crystallization behavior in order to have a comprehensive framework aimed at potential technological applications. Nowadays, it is well known that the best Al-based amorphous alloys are formed in ternary systems such as Al- RE-TM, where RE is a rare earth and TM a transition metal. This paper presents results of research in Al{sub 85}Ni{sub 10}RE{sub 5} alloys (RE = Y, Gd and Sm). Amorphous ribbons were processed by melt-spinning under the same conditions and subsequently characterized by x-ray diffraction (XRD) and differential scanning calorimetry (DSC). Results show appreciable micro structural differences as function of the rare earth, thus crystal is obtained for Y, nano-glassy for Gd and, fully amorphous structure for Sm. (author)

  3. Electrochemical hydrogen storage performances of the nanocrystalline and amorphous (Mg24Ni10Cu2)100-xNdx (x=0-20) alloys applied to Ni-MH battery

    Institute of Scientific and Technical Information of China (English)

    张羊换; 王海涛; 杨泰; 翟亭亭; 张国芳; 赵栋梁

    2013-01-01

    Melt spinning technology was used to prepare the Mg2Ni-type (Mg24Ni10Cu2)100-xNdx (x=0, 5, 10, 15, 20) alloys in order to obtain a nanocrystalline and amorphous structure. The effects of Nd content and spinning rate on the structures and electrochemical hydrogen storage performances of the alloys were investigated. The structure characterizations of X-ray diffraction (XRD), transmis-sion electron microscopy (TEM) and scanning electron microscopy (SEM) linked with energy dispersive spectroscopy (EDS) re-vealed that the as-spun Nd-free alloy displayed an entire nanocrystalline structure, whereas the as-spun Nd-added alloys held a nanocrystalline and amorphous structure and the degree of amorphization visibly increased with the rising of Nd content and spinning rate, suggesting that the addition of Nd facilitated the glass forming of the Mg2Ni-type alloy. The electrochemical measurements in-dicated that the addition of Nd and melt spinning improved the electrochemical hydrogen storage performances of the alloys signifi-cantly. The discharge capacities of the as-cast and spun alloys exhibited maximum values when Nd content was x=10, which were 86.4, 200.5, 266.3, 402.5 and 452.8 mAh/g corresponding to the spinning rate of 0 (As-cast was defined as the spinning rate of 0 m/s), 10, 20, 30 and 40 m/s, respectively. The cycle stability (S20, the capacity maintain rate at 20th cycle) of the as-cast alloy always rose with the increasing of Nd content, and those of the as-spun alloys exhibited the maximum values for Nd content x=10, which were 77.9%, 83.4%89.2%and 89.7%, corresponding to the spinning rate of 10, 20, 30 and 40 m/s, respectively.

  4. Corrosion and wear protective composition modulated alloy coatings based on ternary Ni-P-X alloys

    DEFF Research Database (Denmark)

    Leisner, P.; Benzon, M. E.; Christoffersen, Lasse

    1996-01-01

    Scattered reporting in the litterature describes a number of ternary Ni-P-X alloyes (where X can be Co, Cr, Cu, Mo, Pd, Re or W) with promising corrosin and wear protective performance. Based on a systematic study of Ni-P-X alloys it is the intention to produce coatings with improved corrosion...

  5. Preparation and Characterization of Amorphous Layer on Aluminum Alloy Formed by Plasma Electrolytic Deposition (PED)

    Institute of Scientific and Technical Information of China (English)

    GUANYong-jun; XIAYuan

    2004-01-01

    In this investigation, protective layers were formed on aluminum substrate by Plasma Electrolytic Deposition (PED) using sodium silicate solution. The relation between the thickness of the layer and process time were studied. XRD, SEM, EDS were used to study the layer's structure, composition and micrograph. The results show that the deposited layers are amorphous and contain mainly oxygen, silicon, and aluminum. The possible formation mechanism of amorphous[Al-Si-O] layer was proposed: During discharge periods, Al2O3 phase of the passive film and SiO32- near the substrate surface are sintered into xSiO2(1-x)Al2O3 and then transformed into amorphous [Al-Si-O] phase.

  6. Crystallisation process in Mg{sub 60}Cu{sub 30}Gd{sub 10-x}Nd{sub x}(x = 0, 8.5) amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Rizzi, P; Satta, M; Baricco, M [Dip. Chimica IFM and NIS/CNISM/INSTM, Universita di Torino, V. Giuria 7, 10125 Torino (Italy); Enzo, S [Dipartimento di Chimica, Universita di Sassari, Via Vienna 2, 07100 Sassari (Italy); Georgarakis, K; Yavari, A R, E-mail: paola.rizzi@unito.i [Institut National Polytechnique de Grenoble, 1130 rue de la Piscine, BP 75, 38402 Grenoble (France)

    2009-01-01

    Mg{sub 60}Cu{sub 30}Gd{sub 10} and Mg{sub 60}Cu{sub 30}Gd{sub 1.5}Nd{sub 8.5} ribbons were obtained by melt spinning. For both compositions, a fully amorphous phase was found and a clear Tg was observed. In-situ XRD measurements were carried out during heating of ribbons at the ID11 synchrotron beamline of ESRF, Grenoble (France). In order to identify the crystallisation products, an annealed Mg{sub 60}Cu{sub 30}Gd{sub 10} master alloy was analysed by SEM/EDS and XRD. The existence of new ternary compounds (MgCu{sub 4}Gd and Mg{sub 2}CuGd) in the Mg-Cu-Gd system is suggested.

  7. Cast iron-base alloy for cylinder/regenerator housing

    Science.gov (United States)

    Witter, Stewart L.; Simmons, Harold E.; Woulds, Michael J.

    1985-01-01

    NASACC-1 is a castable iron-base alloy designed to replace the costly and strategic cobalt-base X-40 alloy used in the automotive Stirling engine cylinder/generator housing. Over 40 alloy compositions were evaluated using investment cast test bars for stress-rupture testing. Also, hydrogen compatibility and oxygen corrosion resistance tests were used to determine the optimal alloy. NASACC-1 alloy was characterized using elevated and room temperature tensile, creep-rupture, low cycle fatigue, heat capacity, specific heat, and thermal expansion testing. Furthermore, phase analysis was performed on samples with several heat treated conditions. The properties are very encouraging. NASACC-1 alloy shows stress-rupture and low cycle fatigue properties equivalent to X-40. The oxidation resistance surpassed the program goal while maintaining acceptable resistance to hydrogen exposure. The welding, brazing, and casting characteristics are excellent. Finally, the cost of NASACC-1 is significantly lower than that of X-40.

  8. 非晶态Cr-C合金镀层制备及其耐腐蚀性%Preparation and Corrosion Resistance of Amorphous Cr-C Alloy Coating

    Institute of Scientific and Technical Information of China (English)

    杨毕学; 揭晓华; 李国亮

    2012-01-01

    以酒石酸为添加剂,采用电沉积法制备了非晶态Cr-C合金镀层。用X射线衍射、扫描电子显微镜及能谱仪对镀层结构、形貌及成分进行表征,并对镀层进行电化学耐腐蚀性测试。结果表明,当酒石酸加入量为40g/L时,镀层的x射线衍射图出现非晶态的特征峰,镀层表面平整、致密,无裂纹和针孔,与普通晶态Cr镀层相比,非晶态Cr-C合金镀层具有更优良的耐腐蚀性能。%Amorphous Cr-C alloy coating was prepared by electrodepositing in tartaric acid additive bath. The microstructure, composition and surface morphology of the coating were detected by ?(ray diffraction, SEM and EDS, also the microhardness, electrochemical corrosion resistance of the coating were tested. The results showed that a broad diffraction peak appeared on the Xray diffraction pattern, the coating had a smooth and dense surface without pinhole and crack when the dosage of tartaric acid was 40 g/L. Compared with conventional crystalline Cr coating, amorphous Cr-C alloy coating had better corrosion resistance.

  9. Hydrogen solubility in rare earth based hydrogen storage alloys

    Energy Technology Data Exchange (ETDEWEB)

    Uchida, Hirohisa [Tokai Univ., Kanagawa (Japan). School of Engineering; Kuji, Toshiro [Mitsui Mining and Smelting Co. Ltd., Saitama (Japan)

    1999-09-01

    This paper reviews significant results of recent studies on the hydrogen storage properties of rare earth based AB{sub 5} (A: rare earth element, B: transition element) alloys The hydrogen solubility and the hydride formation, typically appeared in pressure-composition isotherms (PCT), are strongly dependent upon alloy composition, structure, morphology and even alloy particle size. Typical experimental results are shown to describe how these factors affect the hydrogen solubility and storage properties.

  10. Non-alloyed Ni3Al based alloys – preparation and evaluation of mechanical properties

    Directory of Open Access Journals (Sweden)

    J. Malcharcziková

    2013-07-01

    Full Text Available The paper reports on the fabrication and mechanical properties of Ni3Al based alloy, which represents the most frequently used basic composition of nickel based intermetallic alloys for high temperature applications. The structure of the alloy was controlled through directional solidification. The samples had a multi-phase microstructure. The directionally solidified specimens were subjected to tensile tests with concurrent measurement of acoustic emission (AE. The specimens exhibited considerable room temperature ductility before fracture. During tensile testing an intensive AE was observed.

  11. HIGH CYCLE FATIGUE PROPERTIES OF NICKEL-BASE ALLOY 718

    Institute of Scientific and Technical Information of China (English)

    K.Kobayashi; K.Yamaguchi; M.Hayakawa; M.Kimura

    2004-01-01

    The fatigue properties of nickel-base Alloy 718 with fine- and grain-coarse grains were investigated. In the fine-grain alloy, the fatigue strength normalized by the tensile strengtn was 0.51 at 107 cycles. In contrast, the fatigue strength of the coarse-grain alloy was 0.32 at the same cycles, although the fatigue strengths in the range from 103to 105 cycles are the same for both alloys. The fracture appearances fatigued at around 106 cycles showed internal fractures originating from the flat facets of austenite grains for both alloys. The difference in fatigue strength at 107 cycles between the fine- and coarse-grain alloys could be explained in terms of the sizes of the facets from which the fractures originated.

  12. Black GE based on crystalline/amorphous core/shell nanoneedle arrays

    Science.gov (United States)

    Javey, Ali; Chueh, Yu-Lun; Fan, Zhiyong

    2014-03-04

    Direct growth of black Ge on low-temperature substrates, including plastics and rubber is reported. The material is based on highly dense, crystalline/amorphous core/shell Ge nanoneedle arrays with ultrasharp tips (.about.4 nm) enabled by the Ni catalyzed vapor-solid-solid growth process. Ge nanoneedle arrays exhibit remarkable optical properties. Specifically, minimal optical reflectance (black Ge can have important practical implications for efficient photovoltaic and photodetector applications on nonconventional substrates.

  13. Wear Behavior of Mechanically Alloyed Ti-Based Bulk Metallic Glass Composites Containing Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Yung-Sheng Lin

    2016-11-01

    Full Text Available The present paper reports the preparation and wear behavior of mechanically alloyed Ti-based bulk metallic glass composites containing carbon nanotube (CNT particles. The differential scanning calorimeter results show that the thermal stability of the amorphous matrix is affected by the presence of CNT particles. Changes in glass transition temperature (Tg and crystallization temperature (Tx suggest that deviations in the chemical composition of the amorphous matrix occurred because of a partial dissolution of the CNT species into the amorphous phase. Although the hardness of CNT/Ti50Cu28Ni15Sn7 bulk metallic glass composites is increased with the addition of CNT particles, the wear resistance of such composites is not directly proportional to their hardness, and does not follow the standard wear law. A worn surface under a high applied load shows that the 12 vol. % CNT/Ti50Cu28Ni15Sn7 bulk metallic glass composite suffers severe wear compared with monolithic Ti50Cu28Ni15Sn7 bulk metallic glass.

  14. Effect of rare earth additions on magnetic properties of Fe{sub 82}Nb{sub 2}B{sub 14}RE{sub 2} (RE = Y, Gd, Tb and Dy) amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Chrobak, A., E-mail: artur.chrobak@us.edu.pl [Institute of Physics, Silesian University, 4 Uniwersytecka, 40-007 Katowice (Poland); Nosenko, V. [G.V. Kurdyumov Institute for Physics of Metals, NAS of Ukraine, Vernadsky ave. 36, 03142 Kyiv (Ukraine); Haneczok, G. [University of Silesia, Institute of Materials Science, 12 Bankowa, 40-007 Katowice (Poland); Boichyshyn, L.; Kotur, B. [Ivan Franko National University of Lviv, Kyryla and Mefodia St. 6, 79005 Lviv (Ukraine); Bajorek, A. [Institute of Physics, Silesian University, 4 Uniwersytecka, 40-007 Katowice (Poland); Zivotsky, O.; Hendrych, A. [Technical University of Ostrava, Institute of Physics, 17. listopadu 15, 708 33 Ostrava-Poruba (Czech Republic)

    2011-10-17

    Highlights: {yields} We studied magnetic properties of Fe{sub 82}Nb{sub 2}B{sub 14}RE{sub 2} (RE=Y,Gd,Tb,Dy) amorphous alloys. {yields} In a comparison with Fe{sub 82}Nb{sub 2}B{sub 14}Y{sub 2} alloy the rare earth editions cause an increase of the Curie temperature and a decrease of magnetic moment per magnetic atom. {yields} Doping of Tb and Dy lead to a strong decrease of magnetic permeability and a formation of low dimensional finger-print magnetic domains. - Abstract: In the present paper the influence of RE alloying additions (Y, Gd, Tb and Dy) on magnetic properties (Curie temperatures, low temperature magnetization, zero field cooling-field cooling curves, domain structure, room temperature magnetostriction and magnetic permeability) of amorphous alloys of type Fe{sub 82}Nb{sub 2}B{sub 14}RE{sub 2} are carefully examined. It was shown that substituting of yttrium atoms by magnetic elements, i.e. Gd, Tb and Dy leads to (i) an increase of the Curie temperature of amorphous phase from 416 K (for Fe{sub 82}Nb{sub 2}B{sub 14}Y{sub 2}) to 450 K (for Fe{sub 82}Nb{sub 2}B{sub 14}Gd{sub 2}) and (ii) a decrease of magnetization in saturation (magnetic field 7 T) which can be explained by antiferromagnetic Fe-RE coupling resulting in a decrease of magnetic moment calculated per magnetic atom from 2.00 {mu}{sub B} for the Fe{sub 82}Nb{sub 2}B{sub 14}Y{sub 2} alloy (Fe in amorphous phase) to 1.51 {mu}{sub B} for the Fe{sub 82}Nb{sub 2}B{sub 14}Tb{sub 2} alloy. It was concluded that Tb and Dy alloying additions introduce a local magnetic anisotropy responsible for significant decrease of initial magnetic permeability (about 5 times in relation to Fe{sub 82}Nb{sub 2}B{sub 14}Y{sub 2} or Fe{sub 82}Nb{sub 2}B{sub 14}Gd{sub 2} alloy), increase of magnetic irreversibility effect measured at 2 K (about 10 times in relation to the same alloys) and appearing of the finger-print magnetic domain regions (not observed for the Fe{sub 82}Nb{sub 2}B{sub 14}Y{sub 2} and Fe{sub 82}Nb

  15. Microstructural and Microhardness Variation of Amorphous Fe78Si9B13 Alloy during Bend Stress Relaxation

    Institute of Scientific and Technical Information of China (English)

    Xifeng LI; Kaifeng ZHANG; Changli WANG; Wenbo HAN; Guofeng WANG

    2007-01-01

    The amorphous Fe78Si9B13 ribbons were bend stress relaxed at various temperature well below the crystallization temperature (Tx) for different time. The effect of pre-annealing on the subsequent bend stress relaxation was examined. The variation of the microstructure and microhardness during bend stress relaxation process was studied using X-ray diffraction (XRD), atomic force microscopy (AFM) and Vickers microhardness test,respectively. Curvature radius of the amorphous Fe78Si9B13 ribbons decreased with increase bend stress relaxation temperature and time. The microhardness of the stress relaxed specimens increased with time at 300℃ due to the forming of nanocrystals during bend stress relaxation. The pre-annealing reduced the decrease rate of the curvature radius of stress relaxed specimens.

  16. Optimisation of soft magnetic properties in Fe-Cu-X-Si{sub 13}B{sub 9} (X=Cr, Mo, Zr) amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Kwapulinski, P.; Rasek, J.; Stoklosa, Z.; Haneczok, G. E-mail: haneczok@us.edu.pl

    2001-09-01

    In the present paper a group of Fe-Cu-X-Si{sub 13}B{sub 9} (X=Cr, Mo, Zr) amorphous alloys has been examined by applying different experimental techniques--magnetic permeability, magnetic after-effect, coercive force and electrical resistivity measurements. It has been shown that their soft magnetic properties can be optimised by 1-h thermal annealing at the temperature close to the crystallisation temperature. This leads to an increase of permeability and a decrease of coercive force, thermal instability (magnetic after-effect intensity) and electrical resistivity of the material. The optimisation effect is discussed in terms of different processes--(i) a formation of a nanocrystalline phase with the grain size much smaller than the ferromagnetic exchange length, (ii) an annealing out of microvoids formed during the fabrication process and also (iii) a decrease of the effective magnetostriction constant. The temperature of optimisation annealing treatment is always higher than the Curie temperatures of the materials and varies approximately linearly with the atomic radius of the alloying additions.

  17. Influence of milling time on the structural, microstructural and magnetic properties of mechanically alloyed Ni{sub 58}Fe{sub 12}Zr{sub 10}Hf{sub 10}B{sub 10} nanostructured/amorphous powders

    Energy Technology Data Exchange (ETDEWEB)

    Besmel, R., E-mail: r.besmel@iauahvaz.ac.ir [Materials Science and Engineering Department, Islamic Azad University Ahvaz Branch, Ahvaz (Iran, Islamic Republic of); Ghaffari, M. [School of Electrical and Electronic Engineering, Sensor and Actuator Laboratory II, BLK S2.1, B6-02, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Shokrollahi, H., E-mail: shokrollahi@sutech.ac.ir [Electroceramics Group, Materials Science and Engineering Department, Shiraz University of Technology, 71555-313, Shiraz (Iran, Islamic Republic of); Chitsazan, B.; Karimi, L. [Materials Science and Engineering Department, Islamic Azad University Ahvaz Branch, Ahvaz (Iran, Islamic Republic of)

    2011-11-15

    This paper investigates structural, microstructural and magnetic properties of amorphous/nanocrystalline Ni{sub 58}Fe{sub 12}Zr{sub 10}Hf{sub 10}B{sub 10} powders prepared by high energy milling. Ball milling of Ni, Fe, Zr, Hf and B leads to alloying of the element powders at 120 h. The results show that at 190 h the amorphous content is at the highest level and the grain size is about 2 nm. The magnetic measurements reveal that the coercivity and the saturation magnetization reach about 20 Oe and 30 emu/g at 190 h and become approximately 5 Oe and 40 emu/g after a suitable heat treatment, respectively. - Highlights: > We investigated the influence of milling time on the structural and magnetic properties of mechanically alloyed Ni{sub 58}Fe{sub 12}Zr{sub 10}Hf{sub 10}B{sub 10} nanostructured/amorphous powders. > Results showed that at 190 h the amorphous content is at the highest level and the grain size is about 2 nm. > By obtaining the amorphous structure and applying a suitable heat treatment the magnetic properties were improved.

  18. 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.

  19. 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)

  20. Magnetocaloric effect and critical behavior of amorphous (Gd{sub 4}Co{sub 3}){sub 1−x}Si{sub x} alloys

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Z.G., E-mail: mszgzheng@scut.edu.cn [School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Zhong, X.C.; Liu, Z.W. [School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Zeng, D.C., E-mail: medczeng@scut.edu.cn [School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Franco, V. [Department of Condensed Matter Physics, ICMSE-CSIC, Sevilla University, P.O. Box 1065, 41080 Sevilla (Spain); Zhang, J.L. [Department of Physics and Materials Science, City University of Hong Kong, Hong Kong (China)

    2013-10-15

    The amorphous alloys (Gd{sub 4}Co{sub 3}){sub 1−x}Si{sub x} (x=0, 0.05, and 0.10) were prepared by melt spinning. The Curie temperature can be tuned from 213 to 198 K with increasing Si content, while the maximum value of magnetic entropy change for a magnetic field change of 0–5 T can reach 7.3, 7.2 and 6.4 J kg{sup −1} K{sup −1} for x=0, 0.05 and 0.10 respectively. Large values of the refrigerant capacity are obtained in these alloys. The saturation magnetization at 5 K equals 26.5μ{sub B}, 24.2μ{sub B} and 22.4μ{sub B} per (Gd{sub 4}Co{sub 3}){sub 1−x}Si{sub x} formula with x=0, 0.05 and 0.10, respectively. All samples undergo a second order ferri–paramagnetic phase transition. The critical behavior around the transition temperature is investigated by means of the modified Arrott plots technique, the Kouvel–Fisher method and the Widom scaling relation. The results indicate that for x=0 and 0.05, the critical exponents are close to those of the 3D Ising model, while the critical exponents for x=0.1 are between those of the 3D Ising model and mean-field model. - Highlights: • The Curie temperature of amorphous (Gd{sub 4}Co{sub 3}){sub 1−x}Si{sub x} alloy is between 213 K and 198 K. • The magnetic entropy change gets a maximum of 7.3 J kg{sup −1} K{sup −1} under 0–5 T. • The maximum refrigerant capacity value of 547 J kg{sup −1} is obtained at 5 T. • The calculated critical exponents are close to those of the 3D Ising model.

  1. An alternative system for mycotoxin detection based on amorphous silicon sensors

    Science.gov (United States)

    Caputo, D.; de Cesare, G.; De Rossi, P.; Fanelli, C.; Nascetti, A.; Ricelli, A.; Scipinotti, R.

    2007-05-01

    In this work we investigate, for the first time, the performances of a system based on hydrogenated amorphous silicon photosensors for the detection of Ochratoxin A. The sensor is a n-type/intrinsic/p-type amorphous silicon stacked structure deposited on a glass substrate. The mycotoxin is deposited on a thin layer chromatographic plate and aligned with the sensor. An ultraviolet radiation excites the ochratoxin A, whose fluorescence produces a photocurrent in the sensor. The photocurrent value is proportional to the deposited mycotoxin quantity. An excellent linearity of the detector response over more than two orders of magnitude of ochratoxin A amount is observed. The minimum detected mycotoxin quantity is equal to 0.1ng, suggesting that the presented detection system could be a good candidate to perform rapid and analytical ochratoxin A analysis in different kind of samples.

  2. Temperature affecting the magnetic properties of the Co{sub 79−x}Fe{sub 3}Cr{sub 3}Si{sub 15}B{sub x} amorphous alloy

    Energy Technology Data Exchange (ETDEWEB)

    Tsepelev, Vladimir, E-mail: v.s.tsepelev@urfu.ru [Boris Yeltzin Ural Federal University, Mira 19, Ekaterinburg 620002 (Russian Federation); Starodubtsev, Yuri [Boris Yeltzin Ural Federal University, Mira 19, Ekaterinburg 620002 (Russian Federation); Research and Production Enterprise «Gammamet», Kirov 28, Ekaterinburg 620028 (Russian Federation); Zelenin, Viktor; Belozerov, Vladimir [Research and Production Enterprise «Gammamet», Kirov 28, Ekaterinburg 620028 (Russian Federation); Konashkov, Viktor [Boris Yeltzin Ural Federal University, Mira 19, Ekaterinburg 620002 (Russian Federation)

    2015-09-15

    The paper studies the effect the temperature has on the magnetic properties of the Co{sub 79−x}Fe{sub 3}Cr{sub 3}Si{sub 15}B{sub x} amorphous alloy with different boron content. Magnetic saturation induction B{sub s} and Curie temperature T{sub C} decrease as the boron content increases. Within the range of relatively high temperatures, magnetic saturation induction B{sub s} = μ{sub 0}M{sub s} is related to the temperature by B{sub s}(T) ∼ (T{sub C} − T){sup 0.38}. In the Co{sub 79−x}Fe{sub 3}Cr{sub 3}Si{sub 15}B{sub x} amorphous alloys with the Curie temperature of lower than 180 °C the initial permeability of 200,000 and the coercive force of 0.1 A/m were obtained. The high initial permeability of the amorphous alloy is attributed to the absence of the crystalline, magnetoelastic and induced magnetic anisotropy in this alloy. Low Curie temperature near which the permeability appreciably increases (Hopkinson effect) is another approach to the ideal magnetic softness.

  3. On the Tendency of the Co-, Ni-, and Fe-Based Melts to the Bulk Amorphization

    Science.gov (United States)

    Sterkhova, Irina V.; Lad'yanov, Vladimir I.; Kamaeva, Larisa V.; Umnova, Nadezhda V.; Umnov, Pavel P.

    2016-11-01

    In this article, the influence of the liquid phase state on the glass-forming ability and solidification processes of the Co65.5Fe6.5Si18B10, Ni64.4Fe4Cr4.9Mn2B16.2C0.5Si8, and Fe50Cr15Mo14C15B6 alloys was studied. It was shown that in conditions of quenching from the melt at ~103 K/s, the largest fraction of the amorphous phase is achieved by cooling from a narrow temperature range near 1573 K (1300 °C) for Co65.5Fe6.5Si18B10, 1503 K (1230 °C) for Ni64.4Fe4Cr4.9Mn2B16.2C0.5Si8, and 1653 K (1380 °C) for Fe50Cr15Mo14C15B6. It was found that at these temperatures, there are anomalies in the viscosity and undercooling polytherms caused by changes in short-range ordering in these melts. Overheating the Co65.5Fe6.5Si18B10, Ni64.4Fe4Cr4.9Mn2B16.2C0.5Si8, and Fe50Cr15Mo14C15B6 melts above these temperatures is accompanied by changing the nature of their crystallization. It was shown that the analysis of the temperature dependences of undercooling and kinematic viscosity can be used to determine the optimum temperatures of the melts quenching to achieve their best bulk amorphization.

  4. INFLUENCE OF ALLOY COMPOSITION ON WORK HARDENING BEHAVIOR OF ZIRCONIUM-BASED ALLOYS

    Directory of Open Access Journals (Sweden)

    HYUN-GIL KIM

    2013-08-01

    Full Text Available Three types of zirconium base alloy were evaluated to study how their work hardening behavior is affected by alloy composition. Repeated-tensile tests (5% elongation at each test were performed at room temperature at a strain rate of 1.7 × 10−3 s−1 for the alloys, which were initially controlled for their microstructure and texture. After considering the yield strength and work hardening exponent (n variations, it was found that the work hardening behavior of the zirconium base alloys was affected more by the Nb content than the Sn content. The facture mode during the repeated tensile test was followed by the slip deformation of the zirconium structure from the texture and microstructural analysis.

  5. Corrosion resistance improvement of titanium base alloys

    Energy Technology Data Exchange (ETDEWEB)

    Popa, Mihai V.; Vasilescu, Ecaterina; Drob, Paula; Vasilescu, Cora; Drob, Silviu I., E-mail: ec_vasilescu@yahoo.co [Institute of Physical Chemistry ' Ilie Murgulescu' , Bucharest (Romania); Mareci, Daniel [Technical University ' Gh. Asachi' , Iasi (Romania); Rosca, Julia C. Mirza [Las Palmas de Gran Canaria University, Tafira (Spain). Mechanical Engineering Dept.

    2010-07-01

    The corrosion resistance of the new Ti-6Al-4V-1Zr alloy in comparison with ternary Ti-6Al-4V alloy in Ringer-Brown solution and artificial Carter-Brugirard saliva of different pH values was studied. In Ringer-Brown solution, the new alloy presented an improvement of all electrochemical parameters due to the alloying with Zr; also, impedance spectra revealed better protective properties of its passive layer. In Carter-Brugirard artificial saliva, an increase of the passive film thickness was proved. Fluoride ions had a slight negative influence on the corrosion and ion release rates, without to affect the very good stability of the new Ti-6Al-4V-1Zr alloy. (author)

  6. Corrosion resistance improvement of titanium base alloys

    Directory of Open Access Journals (Sweden)

    Mihai V. Popa

    2010-01-01

    Full Text Available The corrosion resistance of the new Ti-6Al-4V-1Zr alloy in comparison with ternary Ti-6Al-4V alloy in Ringer-Brown solution and artificial Carter-Brugirard saliva of different pH values was studied. In Ringer-Brown solution, the new alloy presented an improvement of all electrochemical parameters due to the alloying with Zr; also, impedance spectra revealed better protective properties of its passive layer. In Carter-Brugirard artificial saliva, an increase of the passive film thickness was proved. Fluoride ions had a slight negative influence on the corrosion and ion release rates, without to affect the very good stability of the new Ti-6Al-4V-1Zr alloy.

  7. Fabric cutting application of FeAl-based alloys

    Energy Technology Data Exchange (ETDEWEB)

    Sikka, V.K.; Blue, C.A. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.; Sklad, S.P. [University of Virginia, Charlottesville, VA 22905 (United States); Deevi, S.C. [Research, Development, and Engineering Center, Philip Morris USA, Richmond, VA 23234 (United States); Shih, H.-R. [Jackson State University, 1400 J.R. Lynch Street, Jackson, MS 39217 (United States)

    1998-12-31

    Four intermetallic-based alloys were evaluated for cutting blade applications. These alloys included Fe{sub 3}Al-based (FAS-II and FA-129), FeAl-based (PM-60) and Ni{sub 3}Al-based (IC-50). These alloys were of interest because of their much higher work-hardening rates than the conventionally used carbon and stainless steels. The FeAl-based PM-60 alloy was of further interest because of its hardening possibility through retention of vacancies. The vacancy retention treatment is much simpler than the heat treatments used for hardening of steel blades. Blades of four intermetallic alloys and commercially used M2 tool steel blades were evaluated under identical conditions to cut two-ply heavy paper. Comparative results under identical conditions revealed that the FeAl-based alloy PM-60 outperformed the other intermetallic alloys and was equal to or somewhat better than the commercially used M2 tool steel. (orig.) 18 refs.

  8. Irradiation-induced disordering and amorphization of Al3Ti-based intermetallic compounds

    Science.gov (United States)

    Park, Jeong-Yong; Kim, Il-Hyun; Motta, Arthur T.; Ulmer, Christopher J.; Kirk, Marquis A.; Ryan, Edward A.; Baldo, Peter M.

    2015-12-01

    An in situ ion-irradiation study, simultaneously examined using transmission electron microscopy, was performed to investigate irradiation-induced disordering and amorphization of Al3Ti-based intermetallic compounds. Thin foil samples of two crystalline structures: D022-structured Al3Ti and L12-structured (Al,Cr)3Ti were irradiated using 1.0 MeV Kr ions at a temperature range from 40 K to 573 K to doses up to 4.06 × 1015 ions/cm2. The results showed that both the compounds underwent an order-disorder transformation under irradiation, where both Al3Ti and (Al,Cr)3Ti ordered structures were fully transformed to the disordered face-centered cubic (FCC) structure except at the highest irradiation temperature of 573 K. A slightly higher irradiation dose was required for order-disorder transformation in case of Al3Ti as compared to (Al,Cr)3Ti at a given temperature. However, their amorphization resistances were different: while the disordered FCC (Al,Cr)3Ti amorphized at the irradiation dose of 6.25 × 1014 ions/cm2 (0.92 dpa) at 40 K and 100 K, the Al3Ti compound with the same disordered FCC structure maintained crystallinity up to 4.06 × 1015 ions/cm2 (5.62 dpa) at 40 K. The critical temperature for amorphization of (Al,Cr)3Ti under Kr ion irradiation is likely between 100 K and room temperature and the critical temperature for disordering between room temperature and 573 K.

  9. Influence of the chemical composition of rapidly quenched amorphous alloys (Ni, Fe, Cr)-B-Si on its crystallization process

    Science.gov (United States)

    Elmanov, G.; Dzhumaev, P.; Ivanitskaya, E.; Skrytnyi, V.; Ruslanov, A.

    2016-04-01

    This paper presents results of research of the structure and phase transformations during the multistage crystallization of the metallic glasses with the compositions Ni71,5Cr6,8Fe2,7B11,9Si7,1 and Ni63,4Cr7,4Fe4,3Mn0,8B15,6Si8,5 labeled as AWS BNi-2 according to American Welding Society. Differential scanning calorimetry (DSC), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray microanalysis (EDX) were used as experimental research methods. The influence of the alloys chemical composition (boron, manganese and iron) on the temperatures and the exothermic heat effects of phase transformations, as well as on the phase composition of alloys at three stages of crystallization was analyzed. We present a thermodynamic explanation of the observed heat effects. It has been shown that manganese has the main influence on the phase transformations temperatures and heat effects in these two alloys. It is also assumed that at the final crystallization stage simultaneously with the formation of phases Ni3B and β1-Ni3Si should occur the nucleation of borides of CrB type with high Cr and low Si content.

  10. Ab initio modeling of decomposition in iron based alloys

    Science.gov (United States)

    Gorbatov, O. I.; Gornostyrev, Yu. N.; Korzhavyi, P. A.; Ruban, A. V.

    2016-12-01

    This paper reviews recent progress in the field of ab initio based simulations of structure and properties of Fe-based alloys. We focus on thermodynamics of these alloys, their decomposition kinetics, and microstructure formation taking into account disorder of magnetic moments with temperature. We review modern theoretical tools which allow a consistent description of the electronic structure and energetics of random alloys with local magnetic moments that become totally or partially disordered when temperature increases. This approach gives a basis for an accurate finite-temperature description of alloys by calculating all the relevant contributions to the Gibbs energy from first-principles, including a configurational part as well as terms due to electronic, vibrational, and magnetic excitations. Applications of these theoretical approaches to the calculations of thermodynamics parameters at elevated temperatures (solution energies and effective interatomic interactions) are discussed including atomistic modeling of decomposition/clustering in Fe-based alloys. It provides a solid basis for understanding experimental data and for developing new steels for modern applications. The precipitation in Fe-Cu based alloys, the decomposition in Fe-Cr, and the short-range order formation in iron alloys with s-p elements are considered as examples.

  11. Field-emission transmission electron microscopy study of the reaction sequence between Sn–Ag–Cu alloy and an amorphous Pd(P) thin film in microelectronic packaging

    Energy Technology Data Exchange (ETDEWEB)

    Ho, C.E., E-mail: ceho1975@hotmail.com; Wang, C.C.; Rahman, M.A.; Lin, Y.C.

    2013-02-01

    The reaction sequence between liquid Sn–3Ag–0.5Cu solder and solid Au/Pd(P)/electrolytic-Ni films was carefully examined using a field-emission transmission electron microscope at different exposure times (15 s, 30 s, and 120 s). After 15 s of exposure, the uppermost layer of Au was removed from the interface and a portion of the Pd(P) film remained. At this stage of the reaction, the predominant products were PdSn{sub 3} and Pd{sub 3}P. After 30 s of exposure, Pd(P) was completely exhausted, and three additional intermetallic species, including Pd–Sn–P, Pd{sub 6}P, and Pd{sub 15}P{sub 2}, nucleated. After 120 s of exposure, the aforementioned species were destroyed, and Cu and Ni were involved in the reaction. The predominant product became (Cu,Ni){sub 6}Sn{sub 5}, and the nucleation of a nanocrystalline Ni{sub 2}SnP layer in the middle of (Cu,Ni){sub 6}Sn{sub 5} resulted. These results suggest that Pd and P play a vital role in the early stage of soldering reaction, even though the Pd(P) film is only a few submicrons thick and its P content is quite low (2–5%). - Highlights: ► Reaction sequence between an amorphous Pd(P) film and Sn–Ag–Cu alloy. ► Solder reaction assisted the crystallization of amorphous Pd(P) into Pd–P phase(s). ► Direct proof of the Pd(P)-induced Ni{sub 2}SnP nucleation. ► Pd and P both played a central role in the early stage of soldering reaction.

  12. Cr{sub 2}Nb-based alloy development

    Energy Technology Data Exchange (ETDEWEB)

    Liu, C.T.; Tortorelli, P.F.; Horton, J.A. [Oak Ridge National Lab., TN (United States)] [and others

    1996-08-01

    Alloys of Cr-Cr{sub 2}Nb with exceptionally high strength at 1200{degrees}C have been developed. However, these compositions suffer from limited ductility and toughness at room temperature. Despite improvements from processing modifications, as-fabricated defects still limit room temperature mechanical behavior. In contrast, an alloy system with only a small mismatch of the coefficients of thermal expansion of the two phases, Cr-Cr{sub 2}Zr, showed good fabricability. However, these alloys are weaker than Cr-Cr{sub 2}Nb compositions at high temperatures and have poor oxidation resistance. Silicide coatings can provide high-temperature oxidation and sulfidation protection of these alloys. Improvements in room temperature mechanical properties of Laves-phase-strengthened alloys will rely on further development based on increasing the ductility of the matrix phase by impurity control and compositional modifications.

  13. Synthesis of aluminum-based scandium-yttrium master alloys

    Science.gov (United States)

    Bazhin, V. Yu.; Kosov, Ya. I.; Lobacheva, O. L.; Dzhevaga, N. V.

    2015-07-01

    The preparation technology for an Al-2% Sc-0.5% Y master alloy using aluminum-manganese alloys has been developed and tested. The microstructure of the prepared master alloy is studied and the compositions of intermetallics is determined. The efficient technological parameters of the synthesis are determined. It is shown that varying the compositions of starting reagents and alloying additions and optimizing the process conditions (temperature, mixing, etc.) allow us to forecast the manufacturing and operating characteristics of aluminum-based master alloys. Joint additions of scandium and yttrium oxides to a charge favor a substantial decrease in the grain size of the formed intermetallics; this effect appears to the utmost in the case of microallying with yttrium up to 0.5 wt %.

  14. Simulation of the effects of voids on the deformation behavior of bulk amorphous alloys%含孔洞大块非晶合金变形行为的数值研究

    Institute of Scientific and Technical Information of China (English)

    徐剑晴; 王宇

    2011-01-01

    建立能够描述静水压力影响和塑性体积膨胀的率相关的大块非晶合金本构模型.通过编写ABAQUS材料用户子程序VUMAT,对含不同形态孔洞的Zr基大块非晶合金的变形行为进行有限元分析,并对其细观变化规律进行研究.%A rate-dependent constitutive model for the deformation behavior of amorphous alloys with the effects of hydrostatic-pressure sensitivity and plastically-dilatancy was developed. The constitutive model was implemented in a finite element analysis to study the effects of the voids on the deformation behavior of bulk amorphous alloys by writing a user subroutine in ABAQUS/VUMAT. The mesoscope evolvement law of the deformation was also studied.

  15. Full breast digital mammography with an amorphous silicon-based flat panel detector: Physical characteristics of a clinical prototype

    OpenAIRE

    2000-01-01

    The physical characteristics of a clinical prototype amorphous silicon-based flat panel imager for full-breast digital mammography have been investigated. The imager employs a thin thallium doped CsI scintillator on an amorphous silicon matrix of detector elements with a pixel pitch of 100 μm. Objective criteria such as modulation transfer function (MTF), noise power spectrum, detective quantum efficiency (DQE), and noise equivalent quanta were employed for this evaluation. The presampling MT...

  16. Hyperfine interaction and some thermomagnetic properties of amorphous and partially crystallized Fe70−xMxMo5Cr4Nb6B15 (M = Co or Ni, x = 0 or 10 alloys

    Directory of Open Access Journals (Sweden)

    Rzącki Jakub

    2015-03-01

    Full Text Available As revealed by Mössbauer spectroscopy, replacement of 10 at.% of iron in the amorphous Fe70Mo5Cr4Nb6B15 alloy by cobalt or nickel has no effect on the magnetic structure in the vicinity of room temperature, although the Curie point moves from 190 K towards ambient one. In the early stages of crystallization, the paramagnetic crystalline Cr12Fe36Mo10 phase appears before α-Fe or α-FeCo are formed, as is confirmed by X-ray diffractometry and transmission electron microscopy. Creation of the crystalline Cr12Fe36Mo10 phase is accompanied by the amorphous ferromagnetic phase formation at the expense of amorphous paramagnetic one.

  17. In situ X-ray diffraction study of structural evaluation in Fe73Cu1.5Nd3Si13.5B9 amorphous alloy at high temperature

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The thermodynamics structural relaxation of Fe73Cu1.5Nd3Si13.5B9 amorphous alloy from room temperature to 400℃ has been investigated by measuring the structure factor with in situ X-ray diffraction. The structural information of the atomic con-figuration such as radial distribution function (RDF) and neighbor atomic distance was gained by Fourier transformation. The research result shows that the amor-phous structure remains stable in the temperature range of 30 to 400℃ but exhibits distinct changes in local atomic configuration with the increase of temperature. The quantitative determination of the neighbor atomic distance suggests that the de-gree of short-range order changes by the temperature altering the second nearest neighbor local atomic configuration of the amorphous when structural relaxation occurs.

  18. On the mechanical properties of TiNb based alloys

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Y. [SIMAP-CNRS, Institut Polytechnique de Grenoble, BP 75, St. Martin d’Hères 38402 (France); Georgarakis, K. [WPI Advanced Institute for Materials Research, Tohoku University, Sendai (Japan); SIMAP-CNRS, Institut Polytechnique de Grenoble, BP 75, St. Martin d’Hères 38402 (France); Yokoyama, Y. [WPI Advanced Institute for Materials Research, Tohoku University, Sendai (Japan); Yavari, A.R., E-mail: euronano@minatec.inpg.fr [SIMAP-CNRS, Institut Polytechnique de Grenoble, BP 75, St. Martin d’Hères 38402 (France)

    2013-09-15

    Highlights: •Systematic study of compressive behaviors of TiNb based alloys in different states. •Comparison between X-ray diffraction results in reflection and transmission mode. •High melting temperature TiNb based alloys were fabricated by copper mold casting. •Textures of studied alloys are analyzed through synchrotron radiation data. -- Abstract: A series of TiNb(Sn) alloys were synthesized by copper mold suction casting and subjected to different heat treatments (furnace cooling or water quenching). The microstructure, thermal and mechanical properties of the as-cast and heat treated samples were investigated. For the Ti–8.34 at.% Nb alloy, the as-cast and water quenched samples possess martensitic α′′ phase at room temperature and compression tests of these samples show occurrence of shape memory effect. For β phase Ti–25.57 at.% Nb alloys, stress-induced martensitic transformation was found during compression in the as-cast and water quenched samples. For the ternary Ti–25.05 at.%Nb–2.04 at.%Sn alloy, conventional linear elastic behavior was observed. It is shown that the addition of Sn increases the stability of the β phase. The Young’s moduli of these alloys were also measured by ultrasonic measurements. Water-quenched Ti–25.57 at.%Nb alloy was found to exhibit the lowest Young’s modulus value. Sn addition has small impact on the Young’s moduli of the TiNb alloys.

  19. Development of Mg-based Hydrogen Storage Alloy

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Mg-based hydrogen storage alloys are considered as a promising candidate for hydrogen system because of its lightweight, high storage capacity, low price and rich mineral resources. In detail,we reviewed the preparation and properties of Mg-Ni-based hydrogen storage alloys. All kinds of attempts have been done to improve the hydriding and dehydriding behaviors. It is found that the partial substitution of foreign elements can decrease the hydrogen absorption temperature,especially the substitution of a more electronegative element, such as Al and Mn. Mechanical alloying (MA) and mechanical grinding (MG) are the most effective methods to improve the hydriding/dehydriding kinetics and electrochemical capacity, and decrease the desorption temperature, but the corrosion resistance is so poor that the 80% of maximum capacity is lost within ten cycles. Microencapsulation is a useful measurement for improving the corrosion resistance and electrocatalytic activity. In order to improve the properties of the alloys for practical application, the alloys should have a large number of defects, which give activated sites, subsequently,MA, MG and electroless plating should be used to improve the hydriding/dehydriding kinetics and protect the surface of alloys, respectively. The new composite Mg-based alloys give a new way for the hydrogen storage material to practical application. Furthermore we put forward several problems which will be discussed in future.

  20. 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

  1. Effect of Cu, Nb and Ta addition on the structural and magnetic properties of amorphous Fe-Si-B alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, A. E-mail: agupta@iucindore.ernet.inkane_sn@yahoo.com; Kane, S.N.; Bhagat, N.; Kulik, T

    2003-01-01

    The effect of successive additions of Cu, Nb and Ta in amorphous Fe{sub 77.5}Si{sub 13.5}B{sub 9} has been studied using X-ray diffraction and Moessbauer spectroscopy. Addition of Nb/Ta results in an increased near-neighbor distance as well as a decrease in topological order in the system. On the other hand, Cu addition results in a significant increase in the topological order. Addition of Cu does not significantly change the average hyperfine field, whereas, addition of Nb/Ta decreases the hyperfine field. Nb and Ta addition results in appearance of an additional hump in B{sub hf} around 13 T due to Fe atoms with Nb/Ta near neighbors. Thermal annealing of the specimens at 390 deg. C results in changes in the short-range order, which are mainly chemical in nature.

  2. Effects of micro-alloying with Sc and Mn on microstructure and mechanical properties of Al-Mg based alloys

    Institute of Scientific and Technical Information of China (English)

    CHEN Xian-ming; LUO Cheng-ping; PAN Qing-lin; YIN Zhi-ming

    2005-01-01

    An extensive investigation was made on the effects of micro-alloying with small amounts of Sc and Mn on the microstructure and mechanical properties of the Al-Mg based alloys. It is found that the micro-alloying can significantly enhance the tensile strength of the alloys, and eliminate the dendritic cast structure in it. Many fine,spherical and dispersive Al3Sc particles are found in the annealed Al-Mg-Mn-Sc alloys, which can strongly pin up dislocations and subgrain boundaries, thus strongly retarding the recrystallization of the alloys. The strengthening of the micro-alloyed Al-Mg alloys is attributed to the precipitation strengthening by the Al3Sc particles and to the substructure strengthening.

  3. Crystallisation and magnetic behaviour of amorphous and nanocrystalline Fe{sub 81-x-y}Ni{sub x}Co{sub y}Zr{sub 7}B{sub 12} alloys

    Energy Technology Data Exchange (ETDEWEB)

    Kopcewicz, M. [Institute of Electronic Materials Technology, Wolczynska Street 133, 01-919 Warszawa (Poland); Latuch, J.; Kulik, T. [Faculty of Materials Science and Engineering, Warsaw University of Technology, Woloska Street 141, 02-507 Warszawa (Poland)

    2007-09-15

    The amorphous precursors Fe{sub 81-x} {sub -y}Ni {sub x}Co {sub y}Zr {sub 7}B {sub 12} (x = 50, 40, 30, 20; y = 0, 10, 20), prepared by the melt quenching technique, have been characterised in terms of their ability to form nanocrystalline grains on annealing. The crystallisation process was studied in detail using Moessbauer spectroscopy, X-ray diffraction (XRD) and differential scanning calorimetry measurements. The crystalline phases formed were identified and their transformation versus annealing temperature was followed. Bulk and surface crystallisation of amorphous precursors was compared using conversion electron Moessbauer spectroscopy. The size of nanograins was estimated from the XRD results using the Scherrer formula. The magnetic properties of amorphous and nanocrystalline Fe {sub 81-x} {sub -y}Ni {sub x}Co {sub y}Zr {sub 7}B {sub 12} alloys were studied using an unconventional 'rf-Moessbauer' technique. The rf-Moessbauer technique provides information on the soft magnetic behaviour of alloys. The rf sidebands observed are directly related to magnetostriction and their presence provides a good test for the formation of the nanocrystalline alloy. The rf-Moessbauer results revealed that the anisotropy field increased significantly with the introduction of Co. The rf-Moessbauer measurements were accompanied by conventional measurements of hysteresis loops that fully supported the rf-Moessbauer results. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Review of amorphous silicon based particle detectors: the quest for single particle detection

    Science.gov (United States)

    Wyrsch, N.; Ballif, C.

    2016-10-01

    Hydrogenated amorphous silicon (a-Si:H) is attractive for radiation detectors because of its radiation resistance and processability over large areas with mature Si microfabrication techniques. While the use of a-Si:H for medical imaging has been very successful, the development of detectors for particle tracking and minimum-ionizing-particle detection has lagged, with almost no practical implementation. This paper reviews the development of various types of a-Si:H-based detectors and discusses their respective achievements and limitations. It also presents more recent developments of detectors that could potentially achieve single particle detection and be integrated in a monolithic fashion into a variety of applications.

  5. Surface segregations in platinum-based alloy nanoparticles

    Science.gov (United States)

    Yamakawa, Shunsuke; Asahi, Ryoji; Koyama, Toshiyuki

    2014-04-01

    A phase-field model that describes the radial distributions of the ordered-disordered phase and surface segregation in a single-alloy nanoparticle is introduced to clarify the overall behavior of surface segregation of various Pt-based alloy nanoparticles. One of the obstacles to apply a platinum-transition metal alloy as a cathode electro-catalyst of a polymer electrolyte fuel cell is the need to ensure the retention of the designed surface composition in an alloy nanoparticle against the alloy combinations, a particle size, and heat treatment. From the results of calculations for CrPt, FePt, CoPt, NiPt, CuPt, PdPt, IrPt, and AuPt binary nanoparticles with diameters below 10 nm at 973.15 K, the compositional variation within a single particle was found to depend on the balance between the atomic interaction within particles and the surface free energy. In addition, the obtained specific steady-state composition of the surface varied significantly with alloy combination and particle diameter. Based on the general tendencies of a binary system to exhibit segregation, attempts to control the amount of platinum segregation on the surface using a ternary-alloy system were examined.

  6. Microstructures and oxidation behavior of some Molybdenum based alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ray, Pratik Kumar [Iowa State Univ., Ames, IA (United States)

    2011-01-01

    The advent of Ni based superalloys revolutionized the high temperature alloy industry. These materials are capable of operating in extremely harsh environments, comprising of temperatures around 1050 C, under oxidative conditions. Demands for increased fuel efficiency, however, has highlighted the need for materials that can be used under oxidative conditions at temperatures in excess of 1200 C. The Ni based superalloys are restricted to lower temperatures due to the presence of a number of low melting phases that melt in the 1250 - 1450 C, resulting in softening of the alloys above 1000 C. Therefore, recent research directions have been skewed towards exploring and developing newer alloy systems. This thesis comprises a part of such an effort. Techniques for rapid thermodynamic assessments were developed and applied to two different systems - Mo-Si alloys with transition metal substitutions (and this forms the first part of the thesis) and Ni-Al alloys with added components for providing high temperature strength and ductility. A hierarchical approach towards alloy design indicated the Mo-Ni-Al system as a prospective candidate for high temperature applications. Investigations on microstructures and oxidation behavior, under both isothermal and cyclic conditions, of these alloys constitute the second part of this thesis. It was seen that refractory metal systems show a marked microstructure dependence of oxidation.

  7. Corrosion evaluation of gold-based dental alloys.

    Science.gov (United States)

    Corso, P P; German, R M; Simmons, H D

    1985-05-01

    Three commercial gold-based dental alloys and three constant-nobility ternary alloys (Au-Ag-Cu) were evaluated for corrosion using a quantitative test battery. Integration of the current density, in a de-aerated solution of 1% NaCl along the approximate potential range found in the mouth (-300 mV to +300 mV vs. SCE), yields a quantitative rank ordering of the test alloys. The results are combined with prior findings on other commercial alloys to demonstrate the interaction of nobility and microstructure. Nobility determines the overall corrosion resistance for gold-based alloys. However, because of mutual insolubility, alloying with copper induces silver segregation, resulting in a higher corrosion rate at a given nobility. Thus, microstructure has an influence on corrosion, but heat treatments are largely ineffective in altering the basic corrosion characteristics. The test techniques, in combination with tarnish evaluations, provide a quantitative battery for alloy evaluation. The results indicate the combinations of nobility, microstructure, and environment most likely to avoid corrosion difficulties.

  8. Glass forming range of the Ti-Fe-Si amorphous alloys: An effective materials-design approach coupling CALPHAD and topological instability criterion

    Science.gov (United States)

    Zhao, Guo-Hua; Mao, Huahai; Louzguine-Luzgin, Dmitri V.

    2016-11-01

    A method of composition design for metallic glasses was proposed by using the Calculation of Phase Diagrams (CALPHAD) with the assistance of the topological instability criterion. This methodology was demonstrated in the quick and effective searching of glass-forming regions for Ti-Fe-Si and Ti-Zr-Fe-Si alloys containing no biologically toxic elements, e.g., Ni and Cu. In addition, the Ti-Fe-Si system may promote the glass formation owing to the existence of a deep eutectic at the Ti-rich corner. A self-consistent thermodynamic database was constructed based on the CALPHAD approach. The liquidus projection, isothermal sections, and the enthalpy of mixing were calculated by using the database. On the basis of these calculations coupling with the topological instability "lambda λ criterion," the potential glass-forming alloy compositions in a narrow region were suggested for experimental validation. Thereafter, the isothermal sections of the Ti-Zr-Fe-Si quaternary system were calculated at certain contents of Zr. The designed alloys were prepared by arc-melting and followed by melt-spinning to the ribbon shape. The experimental verifications matched reasonably well with the theoretical calculations. This work offers new insights for predicting glass-forming alloys based on thermodynamic arguments; it shall be of benefit for the exploration of new metallic glasses.

  9. Fabrication and characterization of monolithically integrated microchannel plates based on amorphous silicon.

    Science.gov (United States)

    Franco, Andrea; Geissbühler, Jonas; Wyrsch, Nicolas; Ballif, Christophe

    2014-04-04

    Microchannel plates are vacuum-based electron multipliers for particle--in particular, photon--detection, with applications ranging from image intensifiers to single-photon detectors. Their key strengths are large signal amplification, large active area, micrometric spatial resolution and picosecond temporal resolution. Here, we present the first microchannel plate made of hydrogenated amorphous silicon (a-Si:H) instead of lead glass. The breakthrough lies in the possibility of realizing amorphous silicon-based microchannel plates (AMCPs) on any kind of substrate. This achievement is based on mastering the deposition of an ultra-thick (80-120 μm) stress-controlled a-Si:H layer from the gas phase at temperatures of about 200 °C and micromachining the channels by dry etching. We fabricated AMCPs that are vertically integrated on metallic anodes of test structures, proving the feasibility of monolithic integration of, for instance, AMCPs on application-specific integrated circuits for signal processing. We show an electron multiplication factor exceeding 30 for an aspect ratio, namely channel length over aperture, of 12.5:1. This result was achieved for input photoelectron currents up to 100 pA, in the continuous illumination regime, which provides a first evidence of the a-Si:H effectiveness in replenishing the electrons dispensed in the multiplication process.

  10. Bulk amorphous alloys: Preparation and properties of (Mg0.98Al0.02)x(Cu0.75Y0.25)100-x

    DEFF Research Database (Denmark)

    Eldrup, Morten Mostgaard; Pedersen, Allan Schrøder; Ohnuma, M.;

    2000-01-01

    provides a range of cooling rates within a single ingot during the solidification that link the slowly and rapidly cooled microstructure for each alloy composition. Hence, the maximum thickness of the amorphous part of the cast material will be a measure of the glass forming ability (GFA) of the particular...... alloy. X-ray diffraction (XRD) and Differential Scanning Calorimetry (DSC) have been used to investigate the structure and the various structural transitions in the alloys. One observation is that the GFA decreases with increasing content of (Mg0.98Al0.02)(x). For x > similar to 75 at.% no amorphous...... phase is formed. Based on these measurements a phase diagram was constructed....

  11. Thin-film amorphous silicon alloy research partnership. Phase 2, Annual technical progress report, 2 February 1996--1 February 1997

    Energy Technology Data Exchange (ETDEWEB)

    Guha, S [United Solar Systems Corp., Troy, MI (United States)

    1997-06-01

    This is Phase II of a 3-phase, 3-year program. It is intended to expand, enhance, and accelerate knowledge and capabilities for developing high-performance, two-terminal multijunction amorphous Si alloy modules. We discuss investigations on back reflectors to improve cell performance and investigate uniformity in performance over a 1-sq.-ft. area. We present results on component cell performance, both in the initial and in the light-degraded states, deposited over a 1-sq.-ft. area. The uniformity in deposited is investigated by studying the performance of subcells deposited over the entire area. We also present results on the performance of triple- junction cells and modules. The modules use grid-lines and encapsulants compatible with our production technology. We discuss the novel laser-processing technique that has bee developed at United Solar to improve energy-conversion efficiency and reduce manufacturing costs. We discuss in detail the optimization of the processing steps, and the performance of a laser-processed, triple- junction device of 12.6 cm{sup 2} area is presented. We also present experimental results on investigations of module reliability.

  12. Influence of structural changes on electrical and magnetic properties of the Co84Fe5,3Si8,5B2,2 amorphous alloy

    Directory of Open Access Journals (Sweden)

    Đukić S.R.

    2005-01-01

    Full Text Available The crystallization process of the Co84Fe5.3Si8.5B2.2 amorphous alloy examined by differential scanning calorimetry (DSC exhibits three exothermal steps at Tcr1=649K, Tcr2=800K, and Tcr3=838K. The rate constants of the first relaxation process (determined at 598K and 623K are k1=5*10-4 s and k2=8*10-4 s and the corresponding activation energy Ea1=26.23 kJ/mol. The data for the relaxation process before the second crystallization step (determined at 683K and 713K are k3=14.5*10-4 s and k4=17.5*10-4 s and the corresponding activation energy Ea2=60.0 kJ/mol. The process of structural relaxation in non-isothermal and isothermal conditions was studied by analysis of the results of measurements of the thermo electromotive force (TEMF. From the change of the temperature coefficient of TEMF that follows each annealing process, the relative electronic state density changes at the Fermi level were determined: ΔN21/N2=5,45%, ΔN22/N2=5,76%, ΔN23/N2=7,57% and ΔN24/N2=9,85%.

  13. Crystallization kinetics and phase transformation in amorphous Fe74Co10B16 and Fe67Co18B14Si1 alloys

    Directory of Open Access Journals (Sweden)

    B. Bhanu Prasad

    2015-06-01

    Full Text Available Crystallization kinetics and phase transformation studies have been carried out on amorphous Fe74Co10B16 (S1 and Fe67Co18B14Si1 (S2 alloys using Mossbauer Spectroscopy (MS, Electrical Resistivity (ER, Differential Scanning Calorimetry(DSC, X-ray Diffraction(XRD and Transmission Electron Microscopy(TEM to determine the thermal stability. Results show that the transformation to an equilibrium crystalline state occurs through a two step process. Crystallization process is associated with precipitation of two or more phases which are magnetic in nature. From DSC curves, the activation energy of sample S2 has been calculated using Kissinger, Matusita-Sakka and Augis-Bennet methods and the average value is found to be 211 kJ/mol. The detected phases upon crystallization in the samples are α–(Fe-Co and (Fe-Co2B. Exact compositions of these phases in the completely crystallized sample are found to be α–(Fe0.7Co0.3 and (Fe0.3Co0.72B.

  14. Far-Infrared and Raman Spectroscopy Investigation of Phonon Modes in Amorphous and Crystalline Epitaxial GeTe-Sb2Te3 Alloys

    Science.gov (United States)

    Bragaglia, V.; Holldack, K.; Boschker, J. E.; Arciprete, F.; Zallo, E.; Flissikowski, T.; Calarco, R.

    2016-06-01

    A combination of far-infrared and Raman spectroscopy is employed to investigate vibrational modes and the carrier behavior in amorphous and crystalline ordered GeTe-Sb2Te3 alloys (GST) epitaxially grown on Si(111). The infrared active GST mode is not observed in the Raman spectra and vice versa, indication of the fact that inversion symmetry is preserved in the metastable cubic phase in accordance with the Fm3 space group. For the trigonal phase, instead, a partial symmetry break due to Ge/Sb mixed anion layers is observed. By studying the crystallization process upon annealing with both the techniques, we identify temperature regions corresponding to the occurrence of different phases as well as the transition from one phase to the next. Activation energies of 0.43 eV and 0.08 eV for the electron conduction are obtained for both cubic and trigonal phases, respectively. In addition a metal-insulator transition is clearly identified to occur at the onset of the transition between the disordered and the ordered cubic phase.

  15. Chemical Synthesis and Magnetic Properties of Nanocrystalline (La0.67-XGdX)Sr0.33MnO3 Using Amorphous Molecular Alloy as Precursors

    Institute of Scientific and Technical Information of China (English)

    WANG Gui; LU Bing; ZHANG Shiliang; ZHAO Lun; FEI Guangtao; ZHANG Lide; MA Yonglin; LI Baowei

    2007-01-01

    A new route to synthesize nanosized crystalline of (La0.67-XGdX)Sr0.33MnO3(X=0.05,0.10,0.15,0.20) perovskite-type complex oxides at calcination temperature of 600-1000℃ using the amorphous molecular alloy as precursors was reported.The precursor could be completely decomposed into complex oxide at temperature below 500℃ according to the TGA and DTA results.XRD demonstrates that the decomposed species is composed of perovskite-type structure at calcination temperature of 600℃ for 2 h.The particle size that depends on the calcination temperature of the precursor is in a range of 30-120 nm as determined by transmission electron microscopy (TEM).This method is effective and can be easily quantitatively controlled to synthesize nanosized perovskite-type complex oxides.The magnetic properties of (La0.67-XGdX)Sr0.33MnO3 nanocrystalline were preliminary studied.

  16. Mechanical spectroscopy study on the Cu{sub 54}Zr{sub 40}Al{sub 6} amorphous matrix alloy at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Marques, P.W.B., E-mail: paulowilmar@df.ufscar.br [Departamento de Física, Universidade Federal de São Carlos, CP-676, São Carlos, SP (Brazil); Chaves, J.M.; Silva, P.S.; Florêncio, O. [Departamento de Física, Universidade Federal de São Carlos, CP-676, São Carlos, SP (Brazil); Moreno-Gobbi, A. [Instituto de Física, Facultad de Ciencias (UDELAR), Iguá 4225, CEP 11400 Montevideo (Uruguay); Aliaga, L.C.R.; Botta, W.J. [Departamento de Engenharia de Materiais, Universidade Federal de São Carlos, CP-676, São Carlos, SP (Brazil)

    2015-02-05

    Highlights: • Cu{sub 54}Zr{sub 40}Al{sub 6} alloy was characterized by mechanical spectroscopy at low temperature. • Flexural and ultrasonic methods showed peaks associated to rearrangement of clusters. • The peaks less stable were associated with annihilation of Zr or Cu clusters. • MHz range can be favors the formation of Cu an Al-centered icosahedral structures. • TEM images show an increase in the size and number of crystal in amorphous matrix. - Abstract: A mechanical spectroscopy study of Cu{sub 54}Zr{sub 40}Al{sub 6} bulk metallic glasses composites was carried out in the kHz and MHz frequency ranges, by means of flexural and ultrasonic methods, respectively, in the temperature interval 150–300 K. In internal friction and attenuation curves at low temperature were observed peaks which were associated with distortions in the configuration of atomic clusters, which absorbed different quantities of energy due to short and medium order rearrangements. Changes within the clusters or atomic jumps between clusters occurring in the specimen induced the onset of polyamorphic peaks, since electronic interactions and bonding changed abruptly.

  17. A Computationally Based Approach to Homogenizing Advanced Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Jablonski, P D; Cowen, C J

    2011-02-27

    We have developed a computationally based approach to optimizing the homogenization heat treatment of complex alloys. The Scheil module within the Thermo-Calc software is used to predict the as-cast segregation present within alloys, and DICTRA (Diffusion Controlled TRAnsformations) is used to model the homogenization kinetics as a function of time, temperature and microstructural scale. We will discuss this approach as it is applied to both Ni based superalloys as well as the more complex (computationally) case of alloys that solidify with more than one matrix phase as a result of segregation. Such is the case typically observed in martensitic steels. With these alloys it is doubly important to homogenize them correctly, especially at the laboratory scale, since they are austenitic at high temperature and thus constituent elements will diffuse slowly. The computationally designed heat treatment and the subsequent verification real castings are presented.

  18. Electrochemical properties of TiV-based hydrogen storage alloys

    Institute of Scientific and Technical Information of China (English)

    朱云峰; 李锐; 高明霞; 刘永锋; 潘洪革; 王启东

    2003-01-01

    The electrochemical properties of the super-stoichiometric TiV-based hydrogen storage electrode alloys(Ti0.8Zr0.2)(V0.533Mn0.107Cr0.16Ni0.2)x(x=2, 3, 4, 5, 6) were studied. It is found by XRD analysis that all the al-loys mainly consist of a C14 Laves phase with hexagonal structure and a V-based solid solution phase with BCCstructure. The lattice parameters and the unit cell volumes of the two phases decrease with increasing x. The cyclelife, the linear polarization, the anode polarization and the electrochemical impedance spectra of the alloy electrodeswere investigated systematically. The overall electrochemical properties of the alloy electrode are found improvedgreatly as the result of super-stoichiometry and get to the best when x= 5.

  19. Hall current sensor IC with integrated Co-based alloy thin film magnetic concentrator

    Science.gov (United States)

    Palumbo, V.; Marchesi, M.; Chiesi, V.; Paci, D.; Iuliano, P.; Toia, F.; Casoli, F.; Ranzieri, P.; Albertini, F.; Morelli, M.

    2013-01-01

    This work deals with a cobalt-based alloy thin film magnetic concentrator (MC) which is fully integrated on a Hall sensor integrated circuit (IC) developed in the 0.35 µm Bipolar CMOS DMOS (BCD) technology on 8" silicon wafer. An amorphous magnetic film with a thickness of 1µm, coercitive field Hc<10A/m and saturation magnetization (µ0MS) of 0.45T has been obtained with a sputtering process. The Hall sensor IC has shown sensitivity to magnetic field at room temperature of 240V/AT without concentrator and 2550V/AT with concentrator, gaining a factor of 10.5. A current sensor demonstrator has been realized showing linear response in the range -50 to 50A.

  20. Hall current sensor IC with integrated Co-based alloy thin film magnetic concentrator

    Directory of Open Access Journals (Sweden)

    Albertini F.

    2013-01-01

    Full Text Available This work deals with a cobalt-based alloy thin film magnetic concentrator (MC which is fully integrated on a Hall sensor integrated circuit (IC developed in the 0.35 µm Bipolar CMOS DMOS (BCD technology on 8” silicon wafer. An amorphous magnetic film with a thickness of 1µm, coercitive field Hc<10A/m and saturation magnetization (µ0MS of 0.45T has been obtained with a sputtering process. The Hall sensor IC has shown sensitivity to magnetic field at room temperature of 240V/AT without concentrator and 2550V/AT with concentrator, gaining a factor of 10.5. A current sensor demonstrator has been realized showing linear response in the range -50 to 50A.

  1. Microstructural Characterization and Wear Properties of Fe-Based Amorphous-Crystalline Coating Deposited by Twin Wire Arc Spraying

    Directory of Open Access Journals (Sweden)

    Ana Arizmendi-Morquecho

    2014-01-01

    Full Text Available Twin wire arc spraying (TWAS was used to produce an amorphous crystalline Fe-based coating on AISI 1018 steel substrate using a commercial powder (140MXC in order to improve microhardness and wear properties. The microstructures of coating were characterized by X-ray diffraction (XRD, scanning electron microscopy (SEM, and transmission electron microscopy (TEM as well as the powder precursor. Analysis in the coating showed the formation of an amorphous matrix with boron and tungsten carbides randomly dispersed. At high amplifications were identified boron carbides at interface boron carbide/amorphous matrix by TEM. This kind of carbides growth can be attributed to partial crystallization by heterogeneous nucleation. These interfaces have not been reported in the literature by thermal spraying process. The measurements of average microhardness on amorphous matrix and boron carbides were 9.1 and 23.85 GPa, respectively. By contrast, the microhardness values of unmelted boron carbide in the amorphous phase were higher than in the substrate, approaching 2.14 GPa. The relative wear resistance of coating was 5.6 times that of substrate. These results indicate that the twin wire arc spraying is a promising technique to prepare amorphous crystalline coatings.

  2. Investigation of surface finishing of carbon based coated tools for dry deep drawing of aluminium alloys

    Science.gov (United States)

    Steiner, J.; Andreas, K.; Merklein, M.

    2016-11-01

    Global trends like growing environmental awareness and demand for resource efficiency motivate an abandonment of lubricants in metal forming. However, dry forming evokes increased friction and wear. Especially, dry deep drawing of aluminum alloys leads to intensive interaction between tool and workpiece due to its high adhesion tendency. One approach to improve the tribological behavior is the application of carbon based coatings. These coatings are characterized by high wear resistance. In order to investigate the potential of carbon based coatings for dry deep drawing, friction and wear behavior of different coating compositions are evaluated in strip drawing tests. This setup is used to model the tribological conditions in the flange area of deep drawing operations. The tribological behavior of tetrahedral amorphous (ta-C) and hydrogenated amorphous carbon coatings with and without tungsten modification (a-C:H:W, a-C:H) is investigated. The influence of tool topography is analyzed by applying different surface finishing. The results show reduced friction with decreased roughness for coated tools. Besides tool topography the coating type determines the tribological conditions. Smooth tools with ta-C and a-C:H coatings reveal low friction and prevent adhesive wear. In contrast, smooth a-C:H:W coated tools only lead to slight improvement compared to rough, uncoated specimen.

  3. GMI effect in CuO coated Co-based amorphous ribbons

    Energy Technology Data Exchange (ETDEWEB)

    Taysioglu, Asli Ayten [Department of Physics, Sciences and Arts Faculty, Uludag University, 16059 Gorukle, Bursa (Turkey); Peksoz, Ahmet, E-mail: peksoz@uludag.edu.t [Department of Physics, Sciences and Arts Faculty, Uludag University, 16059 Gorukle, Bursa (Turkey); Kaya, Yunus [Department of Chemistry, Sciences and Arts Faculty, Uludag University, 16059 Gorukle, Bursa (Turkey); Derebasi, Naim [Department of Physics, Sciences and Arts Faculty, Uludag University, 16059 Gorukle, Bursa (Turkey); Irez, Gazi [Department of Chemistry, Sciences and Arts Faculty, Uludag University, 16059 Gorukle, Bursa (Turkey); Kaynak, Gokay [Department of Physics, Sciences and Arts Faculty, Uludag University, 16059 Gorukle, Bursa (Turkey)

    2009-11-13

    A Copper oxide (CuO) film has been grown on a surface of Co-based amorphous ribbon using chemical successive ionic layer adsorption and reaction technique, at room temperature and atmosphere pressure. The influence of coating and width of ribbon on giant magneto impedance have been investigated over a frequency range from 0.1 to 3 MHz and under a static magnetic field between -8 and +8 kA/m. The results showed that Co-based amorphous ribbons, which are coated CuO film, have a significant effect on the magnitude and operation frequency for the giant magneto impedance effect as compared to the samples without coating. The highest giant magneto impedance effect was found to be 14.90 on 5 mm width coated ribbon, which is 60% higher than the sample without coating. A surface observation of these samples has been carried out by an atomic force microscope. The AFM images reveal the difference between surfaces of coated and as-cast sample.

  4. Processes of structural relaxation in the amorphous alloy Co69Fe3.7Cr3.8Si12.5B11 with a near-zero magnetostriction and their effect on the magnetic properties and the characteristics of magnetic noise caused by Barkhausen jumps

    Science.gov (United States)

    Kekalo, I. B.; Lubyanyi, D. Z.; Mogil'nikov, P. S.; Chichibaba, I. A.

    2015-07-01

    The evolution of hysteretic magnetic properties and the characteristics of magnetic noise caused by Barkhausen jumps have been studied in different ranges of annealing temperature where different processes of structural relaxation develop. It has been shown that the amorphous cobalt-based alloy under study is characterized by a high (in comparison with the iron-based alloys) spatial homogeneity of magnetic noise. The stabilization of domain walls was caused by directional ordering (at annealing temperatures T a T C) fixed by the method of small-angle X-ray scattering not only affect the level of hysteretic magnetic properties, but also determine the magnetic-noise characteristics of the alloy. A comparison of the dynamics of magnetic-noise behavior with changes in the saturation magnetostriction λs made it possible to conclude that the magnetic-noise characteristics depend not only on the directional, but also on the isotropic short-range ordering. The ranges of annealing temperature that ensure acceptable values of hysteretic magnetic properties and, simultaneously, a low level of magnetic noise have been established. This situation takes place at a certain optimum concentration of clusters arising in the alloy studied.

  5. In situ Moessbauer and magnetization studies of Fe-Si nanocrystallization in Fe{sub 73.5}Si{sub 13.5}B{sub 9}Cu{sub 1}Nb{sub 1} X{sub 2}, with X = Nb, Zr, Mo, amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Pena Rodriguez, V.A. [Universidad Nacional Mayor de San Marcos, Facultad de Ciencias Fisicas (Peru); Baggio-Saitovitch, E.M.; Takeuchi, A.Y.; Garcia, F. [Centro Brasileiro de Pesquisas Fisicas (Brazil); Passamani, E.C. [Universidade Federal de Espirito Santo, Vitoria, Departamento de Fisica (Brazil); Borrego, J.M.; Conde, A. [Universidad de Sevilla, Departamento de Fisica de la Materia Condensada (Spain)

    1999-11-15

    The Fe-Si nanosized particles were obtained by controlled partial crystallization of Fe{sub 73.5}Si{sub 13.5}B{sub 9}Cu{sub 1}Nb{sub 1}X{sub 2} (X = Nb, Zr, Mo) amorphous alloys. In situ Moessbauer spectroscopy and magnetization measurements have been used to follow the temperature-dependent magnetization of the amorphous as well as of the nanosized Fe-Si particles. Our results, for the residual amorphous and of nanoparticles phases, show that the temperature dependence of the hyperfine field and magnetization of both residual amorphous and nanocrystalline Fe(Si) phases are different from that of the as-quenched bulk amorphous or crystalline Fe{sub 3}Si alloys. Likewise, from the temperature dependence studies it was possible to determine that the onset temperature of the nanocrystallization process increases in the sequence Mo < Nb < Zr, for the same annealing conditions.

  6. Effect of Annealing on Rare Earth Based Hydrogen Storage Alloys

    Institute of Scientific and Technical Information of China (English)

    Li Jinhua

    2004-01-01

    Rare earth-based hydrogen storage alloy used as negative electrode materials for nickel-metal hydride (Ni-MH) batteries are used commercially.The effect of annealing treatment with different annealing temperature and time on the MLNi3.68 Co0.78 Mn0.35 Al0.27 and MMNi3.55 Co0.75 Mn0.40 Al0.30 alloys were investigated.The crystal microstructure,pressure-composition-isotherms (p-C-T) and electrochemical properties of alloys were examined by X-ray diffraction (XRD), automatic PCI monitoring system and electrical performance testing instruments.The optimum annealing treatment conditions of two kinds of alloys were determined.

  7. New Zr-based glass-forming alloys containing Gd and Sm

    Directory of Open Access Journals (Sweden)

    Luis César Rodríguez Aliaga

    2012-10-01

    Full Text Available The effect of minor additions of Gd and Sm on the glass-forming ability (GFA of Cu-Zr-Al alloys is investigated here. The rationale for these additions is the fact that the atomic size distribution can increase GFA by changing the topology of the alloy as a function of cluster stability, which is tied to the electronegativity and ionic and covalent nature of alloys. Ingots with nominal compositions of Cu40Zr49Al10.5Gd0.5, Cu40Zr49Al10.5Sm0.5 and Cu39Zr50Al9Gd2 were prepared by arc-melting and rapidly quenched ribbons were produced by the melt-spinning technique. Bulk samples with a thickness of up to 10 mm were also produced by casting, using a wedge-shaped copper mold. The samples were characterized by differential scanning calorimetry, X-ray diffractometry and scanning electron microscopy. The three compositions showed a fully amorphous structure in the ribbons and a predominantly homogeneous amorphous structure with a thickness of up to 10 mm, although some gadolinium oxide crystals as well as samarium compounds were found to be scattered in the amorphous matrix in 5-mm-thick samples. The amorphous phases in the alloys showed high thermal stability with a supercooled liquid region (ΔTx of about 70 K.

  8. Preparation and characterization of a ferrimagnetic amorphous alloy of GdCo entering the design of magnetic tunnel junctions: ionizing radiations hardness of magnetic tunnel junctions; preparation et caracterisation d'un alliage amorphe ferrimagnetique de GdCo entrant dans la conception de jonctions tunnel magnetiques. Resistance des jonctions tunnel magnetiques aux rayonnements ionisants

    Energy Technology Data Exchange (ETDEWEB)

    Conraux, Y

    2005-10-15

    The magnetic random access memories (MRAM) are on the way to supplant the other forms of random access memories using the states of electric charge, and this thanks to their many technical advantages: not-volatility, speed, low consumption power, robustness. Also, the MRAM are alleged insensitive with the ionizing radiations, which was not checked in experiments until now. The current architecture of the MRAM is based on the use of magnetic tunnel junctions (MTJ). These MRAM can present an important disadvantage, because they are likely of present errors of addressing, in particular when integration (density of memory cells) is increasingly thorough. The work undertaken during this thesis relates to these two points: - to check the functional reliability of the MRAM containing JTM exposed to high energy ionizing radiations; - to study a ferrimagnetic amorphous alloy, GdCo, likely to enter the composition of JTM and allowing to free from the possible errors of addressing by a process of thermal inhibition of the memory cells. This work of thesis showed that the MRAM containing JTM preserve their functional properties fully when they are subjected to intense ionizing radiations, and that GdCo is a very interesting material from the point of view of the solid state physics and magnetism, that its physical properties are very promising as for its applications, and that its integration in a JTM still claims technological developments. (author)

  9. Laser cladding of Ni-based alloy on stainless steel

    Institute of Scientific and Technical Information of China (English)

    XUE Chun-fang; TIAN Xin-li; TAN Yong-sheng; WU Zhi-yuan

    2004-01-01

    The coatings on a stainless steel substrate were conducted by laser cladding of Ni-based alloy, using a 5 kW continuous wave CO2 flow transverse laser. SEM, EDX and X-ray diffraction were used to analyze the microstructure and constituent phases of the obtained coatings by laser cladding with direct injection of the powder into the melt pool. Solidification planar, cellular and dendrite structures were observed in Ni-based alloy coating. There exists an optimum metallurgical bond between Ni-based laser cladding layer and the base material. The high hardness of the Ni-based alloy coating is attributed to the presence of M7C3-type carbides (essentially chromium-riched carbide) dispersed in the γ(Ni,Fe) phase matrix.

  10. Amorphous silicon based p-i-i-n photodetectors for point-of-care testing

    Energy Technology Data Exchange (ETDEWEB)

    Furin, Dominik; Proll, Guenther; Gauglitz, Guenther [Universitaet Tuebingen, Institut fuer Physikalische und Theoretische Chemie, Auf der Morgenstelle 8, 72076 Tuebingen (Germany); Thielmann, Johannes; Harendt, Christine [Institut fuer Mikroelektronik Stuttgart, Allmandring 30a, 70569 Stuttgart (Germany); Pfaefflin, Albrecht; Schleicher, Erwin [Universitaetsklinikum und Medizinische Fakultaet, Universitaetsklinikum Tuebingen, Geissweg 3, 72076 Tuebingen (Germany); Schubert, Markus B. [Institut fuer Physikalische Elektronik, Universitaet Stuttgart, Pfaffenwaldring 47, 70569 Stuttgart (Germany); Saemann, Marc

    2010-04-15

    Modern medical diagnostics demands point-of-care testing (POCT) systems for quick tests in clinical or out-patient environments. This investigation combines the Reflectometric Interference Spectroscopy (RIfS) with thin film technology for a highly sensitive, direct optical and label-free detection of proteins, e.g. inflammation or cardiovascular markers. Amorphous silicon (a-Si) based thin film photodetectors replace the so far needed spectrometer and permit downsizing of the POCT system. Photodetectors with p-i-i-n structure adjust their spectral sensitivity according to the applied read-out voltage. The use of amorphous silicon carbide in the p-type and the first intrinsic layer enhances the sensitivity through very low dark currents of the photodetectors and enables the adjustment of their absorption characteristics. Integrating the thin film photodetectors on the rear side of the RIfS substrate eliminates optical losses and distortions, as compared to the standard RIfS setup. An integrated Application Specific Integrated Circuit (ASIC) chip performs a current-frequency conversion to accurately detect the photocurrent of up to eight parallel photodetector channels. In addition to the optimization of the photo-detectors, this contribution presents first successful direct optical and label-free RIfS measurements of C-reactive protein (CRP) and D-dimer in buffer solution in physiological relevant concentrations. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Laser multi-layer cladding of Mg-based alloys

    Institute of Scientific and Technical Information of China (English)

    陈长军; 王东生; 王茂才

    2003-01-01

    By laser multi-layer cladding using a pulsed Nd-YAG irradiation the thickness of the cladding zone Mg-based alloys(ZM2 and ZM5) can reach about 1. 0 mm. The microstructure of the substrate and the cladding zone wasstudied using optical microscope, scanning electron microscopy(SEM), X-ray diffractometry(XRD) and micro hard-ness analysis. It is observed that constituent of ZM5 alloy is δ+Mg17 Al12, that of ZM2 alloy is α+MgZn+Mg9Ce.That of cladding layer ZM2 alloy(L-ZM2) is Mg+ Mg2 Zn11 +MgCe; while that of the cladding layer ZM5 alloy(L-ZM5) is Mg+Mg32 (Al, Zn)49. The hardness of the cladding area can be increased to values above HV127. Veryfine uniform microstructure and the produced new phases of nanometer/sub-micrometer order were obtained. Now,many repaired Mg-based alloy components have been passed by flying test in outside field.

  12. HIGHWAY INFRASTRUCTURE FOCUS AREA NEXT-GENERATION INFRASTRUCTURE MATERIALS VOLUME I - TECHNICAL PROPOSAL & MANAGEMENTENHANCEMENT OF TRANSPORTATION INFRASTRUCTURE WITH IRON-BASED AMORPHOUS-METAL AND CERAMIC COATINGS

    Energy Technology Data Exchange (ETDEWEB)

    Farmer, J C

    2007-12-04

    The infrastructure for transportation in the United States allows for a high level of mobility and freight activity for the current population of 300 million residents, and several million business establishments. According to a Department of Transportation study, more than 230 million motor vehicles, ships, airplanes, and railroads cars were used on 6.4 million kilometers (4 million miles) of highways, railroads, airports, and waterways in 1998. Pipelines and storage tanks were considered to be part of this deteriorating infrastructure. The annual direct cost of corrosion in the infrastructure category was estimated to be approximately $22.6 billion in 1998. There were 583,000 bridges in the United States in 1998. Of this total, 200,000 bridges were steel, 235,000 were conventional reinforced concrete, 108,000 bridges were constructed using pre-stressed concrete, and the balance was made using other materials of construction. Approximately 15 percent of the bridges accounted for at this point in time were structurally deficient, primarily due to corrosion of steel and steel reinforcement. Iron-based amorphous metals, including SAM2X5 (Fe{sub 49.7}Cr{sub 17.7}Mn{sub 1.9}Mo{sub 7.4}W{sub 1.6}B{sub 15.2}C{sub 3.8}Si{sub 2.4}) and SAM1651 (Fe{sub 48}Mo{sub 14}Cr{sub 15}Y{sub 2}C{sub 15}B{sub 6}) have been developed, and have very good corrosion resistance. These materials have been prepared as a melt-spun ribbons, as well as gas atomized powders and thermal-spray coatings. During electrochemical testing in several environments, including seawater at 90 C, the passive film stabilities of these materials were found to be comparable to that of more expensive high-performance alloys, based on electrochemical measurements of the passive film breakdown potential and general corrosion rates. These materials also performed very well in standard salt fog tests. Chromium (Cr), molybdenum (Mo) and tungsten (W) provided corrosion resistance, and boron (B) enabled glass formation

  13. Development of an amorphous selenium-based photodetector driven by a diamond cold cathode.

    Science.gov (United States)

    Masuzawa, Tomoaki; Saito, Ichitaro; Yamada, Takatoshi; Onishi, Masanori; Yamaguchi, Hisato; Suzuki, Yu; Oonuki, Kousuke; Kato, Nanako; Ogawa, Shuichi; Takakuwa, Yuji; Koh, Angel T T; Chua, Daniel H C; Mori, Yusuke; Shimosawa, Tatsuo; Okano, Ken

    2013-10-11

    Amorphous-selenium (a-Se) based photodetectors are promising candidates for imaging devices, due to their high spatial resolution and response speed, as well as extremely high sensitivity enhanced by an internal carrier multiplication. In addition, a-Se is reported to show sensitivity against wide variety of wavelengths, including visible, UV and X-ray, where a-Se based flat-panel X-ray detector was proposed. In order to develop an ultra high-sensitivity photodetector with a wide detectable wavelength range, a photodetector was fabricated using a-Se photoconductor and a nitrogen-doped diamond cold cathode. In the study, a prototype photodetector has been developed, and its response to visible and ultraviolet light are characterized.

  14. Characterization of the microstructure in Mg based alloy

    KAUST Repository

    Kutbee, Arwa T

    2013-06-01

    The cast products Mg–Sn based alloys are promising candidates for automobile industries, since they provide a cheap yet thermally stable alternative to existing alloys. One drawback of the Mg–Sn based alloys is their insufficient hardness. The hardenability can be improved by engineering the microstructure through additions of Zn to the base alloy and selective aging conditions. Therefore, detailed knowledge about the microstructural characteristics and the role of Zn to promote precipitation hardening is essential for age hardenable Mg-based alloys. In this work, microstructural investigation of the Mg–1.4Sn–1.3Zn–0.1Mn (at.%) precipitation system was performed using TEM. The chemical composition of the precipitates was analyzed using EDS. APT was employed to obtain precise chemical information on the distribution of Zn in the microstructure. It was found from microstructural studies that different precipitates with varying sizes and phases were present; lath-shaped precipitates of the Mg2Sn phase have an incoherent interface with the matrix, unlike the lath-shaped MgZn2 precipitates. Furthermore, nano-sized precipitates dispersed in the microstructure with short-lath morphology can either be enriched with Sn or Zn. On the other hand, APT analysis revealed the strong repulsion between Sn and Zn atoms in a portion of the analysis volume. However, larger reconstruction volume required to identify the role of Zn is still limited to the optimization of specimen preparation.

  15. Durable pd-based alloy and hydrogen generation membrane thereof

    Science.gov (United States)

    Benn, Raymond C.; Opalka, Susanne M.; Vanderspurt, Thomas Henry

    2010-02-02

    A durable Pd-based alloy is used for a H.sub.2-selective membrane in a hydrogen generator, as in the fuel processor of a fuel cell plant. The Pd-based alloy includes Cu as a binary element, and further includes "X", where "X" comprises at least one metal from group "M" that is BCC and acts to stabilize the .beta. BCC phase for stability during operating temperatures. The metal from group "M" is selected from the group consisting of Fe, Cr, Nb, Ta, V, Mo, and W, with Nb and Ta being most preferred. "X" may further comprise at least one metal from a group "N" that is non-BCC, preferably FCC, that enhances other properties of the membrane, such as ductility. The metal from group "N" is selected from the group consisting of Ag, Au, Re, Ru, Rh, Y, Ce, Ni, Ir, Pt, Co, La and In. The at. % of Pd in the binary Pd--Cu alloy ranges from about 35 at. % to about 55 at. %, and the at. % of "X" in the higher order alloy, based on said binary alloy, is in the range of about 1 at. % to about 15 at. %. The metals are selected according to a novel process.

  16. Several Issues in the Development of Ti-Nb-Based Shape Memory Alloys

    Science.gov (United States)

    Kim, Hee Young; Miyazaki, Shuichi

    2016-12-01

    Ni-free Ti-based shape memory alloys, particularly Ti-Nb-based alloys, have attracted increasing attraction since the early 2000s due to their wide application potentials in biomedical fields. Recently, there has been significant progress in understanding the martensitic transformation behavior of Ti-Nb-based alloys and many novel superelastic alloys have been developed. The superelastic properties of Ti-Nb-based alloys have been remarkably improved through the optimization of alloying elements and microstructure control. In this paper, in order to explore and establish the alloy design strategy, several important issues in the development of Ti-Nb-based shape memory alloys are reviewed. Particularly, the effects of alloying elements on the martensitic transformation temperature and the transformation strain are analyzed. The effects of omega phase and texture on the superelastic properties are also discussed.

  17. Solid solution or amorphous phase formation in TiZr-based ternary to quinternary multi-principal-element films

    Directory of Open Access Journals (Sweden)

    Mariana Braic

    2014-08-01

    The deposited films exhibited only solid solution (fcc, bcc or hcp or amorphous phases, no intermetallic components being detected. It was found that the hcp structure was stabilized by the presence of Hf or Y, bcc by Nb or Al and fcc by Cu. For the investigated films, the atomic size difference, mixing enthalpy, mixing entropy, Gibbs free energy of mixing and the electronegativity difference for solid solution and amorphous phases were calculated based on Miedema׳s approach of the regular solution model. It was shown that the atomic size difference and the ratio between the Gibbs free energies of mixing of the solid solution and amorphous phases were the most significant parameters controlling the film crystallinity.

  18. The effect of selected alloying element additions on properties of Mg-based alloy as bioimplants: A literature review

    Science.gov (United States)

    Zhang, Li-Nan; Hou, Zeng-Tao; Ye, Xin; Xu, Zhao-Bin; Bai, Xue-Ling; Shang, Peng

    2013-09-01

    This review investigates the current application limitations of Mg and Mg alloys. The key issues hindering the application of biodegradable Mg alloys as implants are their fast degradation rate and biological consideration. We have discussed the effect of some selected alloying element additions on the properties of the Mg-based alloy, especially the nutrient elements in human (Zn, Mn, Ca, Sr). Different grain sizes, phase constituents and distributions consequently influence the mechanical properties of the Mg alloys. Solution strengthening and precipitation strengthening are enhanced by the addition of alloying elements, generally improving the mechanical properties. Besides, the hot working process can also improve the mechanical properties. Combination of different processing steps is suggested to be adopted in the fabrication of Mg-based alloys. Corrosion properties of these Mg-based alloys have been measured in vitro and in vivo. The degradation mechanism is also discussed in terms of corrosion types, rates, byproducts and response of the surrounding tissues. Moreover, the clinical response and requirements of degradable implants are presented, especially for the nutrient elements (Ca, Mn, Zn, Sr). This review provides information related to different Mg alloying elements and presents the promising candidates for an ideal implant.

  19. Recrystallization characteristics of oxide dispersion strengthened nickel-base alloys

    Science.gov (United States)

    Hotzler, R. K.; Glasgow, T. K.

    1980-01-01

    Electron microscopy was employed to study the process of recrystallization in two oxide dispersion strengthened (ODS) mechanically alloyed nickel-base alloys, MA 754 and MA 6000E. MA 754 contained both fine, uniformly dispersed particles and coarser oxides aligned along the working direction. Hot rolled MA 754 had a grain size of 0.5 microns and high dislocation densities. After partial primary recrystallization, the fine grains transformed to large elongated grains via secondary (or abnormal) grain growth. Extruded and rolled MA 6000E contained equiaxed grains of 0.2 micron diameter. Primary recrystallization occurring during working eliminated virtually all dislocations. Conversion from fine to coarse grains was triggered by gamma prime dissolution; this was also a process of secondary or abnormal grain growth. Comparisons were made to conventional and oxide dispersion strengthened nickel-base alloys.

  20. Weldability and Microstructure of Nickel-Silicon Based Alloys

    Institute of Scientific and Technical Information of China (English)

    LIU Qing-cai; LIU Yi; YANG Jian; J.W.Newkirk; ZHANG Shan-hong

    2006-01-01

    The NiSix based alloy typically has poor weldability due to its lower ductility. A limited amount of work has been performed on the weldability of NiSix based alloys. Therefore, the effect of heat treatment and welding parameters on weldability of the alloys, and the relationship between the weldability and microstructure were studied. The results show that the as-cast Ni-Si-Nb-B alloy (Ni 76.5%, Si 20%, Nb 3%, and B 0.5%) could be successfully welded after preheating at 600 ℃. The welding procedure should be performed on the alloys before any heat treatment and a preheating at 600 ℃ should be used. The fusion zone is harder than the matrix due to a large amount of γ phase and a finer microstructure. The cracks are predominantly intergranular in heat affected zone and associated with the needle-like γ phase. The heat treatment before welding increases the tendency of cracking in the fusion zone.

  1. Cr{sub 2}Nb-based alloy development

    Energy Technology Data Exchange (ETDEWEB)

    Liu, C.T.; Tortorelli, P.F.; Horton, J.A.; Easton, D.S.; Heatherly, L.

    1996-06-01

    The objective of this work is to develop a new generation of structural materials based on intermetallic alloys for use at high temperatures in advanced fossil energy conversion systems. Target applications of such ultrahigh strength alloys include hot components (for example, air heat exchangers) in advanced energy conversion systems and heat engines. However, these materials may also find use as wear-resistant parts in coal handling systems (for example, nozzles), drill bits for oil/gas wells, and valve guides in diesel engines. One potential class of such alloys is that based on Cr-Cr{sub 2}Nb alloys. The intermetallic phase, Cr{sub 2}Nb, with a complex cubic structure (C-15) has been selected for initial development because of its high melting point (1770{degrees}C), relatively low material density (7.7 g/cm{sup 2}), and excellent high-temperature strength (at 1000 to 1250{degrees}C). This intermetallic phase, like many other Laves phases, has a wide range of compositional homogeneity suggesting the possibility of improving its mechanical and metallurgical properties by alloying additions.

  2. Melting and casting of FeAl-based cast alloy

    Energy Technology Data Exchange (ETDEWEB)

    Sikka, V.K. [Oak Ridge National Lab., TN (United States); Wilkening, D. [Columbia Falls Aluminum Co., Columbia Falls, MT (United States); Liebetrau, J.; Mackey, B. [AFFCO, L.L.C., Anaconda, MT (United States)

    1998-11-01

    The FeAl-based intermetallic alloys are of great interest because of their low density, low raw material cost, and excellent resistance to high-temperature oxidation, sulfidation, carburization, and molten salts. The applications based on these unique properties of FeAl require methods to melt and cast these alloys into complex-shaped castings and centrifugal cast tubes. This paper addresses the melting-related issues and the effect of chemistry on the microstructure and hardness of castings. It is concluded that the use of the Exo-Melt{trademark} process for melting and the proper selection of the aluminum melt stock can result in porosity-free castings. The FeAl alloys can be melted and cast from the virgin and revert stock. A large variation in carbon content of the alloys is possible before the precipitation of graphite flakes occurs. Titanium is a very potent addition to refine the grain size of castings. A range of complex sand castings and two different sizes of centrifugal cast tubes of the alloy have already been cast.

  3. Melting and casting of FeAl-based cast alloy

    Energy Technology Data Exchange (ETDEWEB)

    Sikka, V.K. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.; Wilkening, D. [Columbia Falls Aluminum Co., 2000 Aluminum Dr., Columbia Falls, MT 59912 (United States); Liebetrau, J.; Mackey, B. [AFFCO, L.L.C., P.O. Box 1071, Anaconda, MT 59711 (United States)

    1998-12-31

    The FeAl-based intermetallic alloys are of great interest because of their low density, low raw material cost, and excellent resistance to high-temperature oxidation, sulfidation, carburization, and molten salts. The applications based on these unique properties of FeAl require methods to melt and cast these alloys into complex-shaped castings and centrifugal cast tubes. This paper addresses the melting-related issues and the effect of chemistry on the microstructure and hardness of castings. It is concluded that the use of the Exo-Melt{sup TM} process for melting and the proper selection of the aluminum melt stock can result in porosity-free castings. The FeAl alloys can be melted and cast from the virgin and revert stock. A large variation in carbon content of the alloys is possible before the precipitation of graphite flakes occurs. Titanium is a very potent addition to refine the grain size of castings. A range of complex sand castings and two different sizes of centrifugal cast tubes of the alloy have already been cast. (orig.) 18 refs.

  4. Zr基大块非晶的研究%Study of Zr52.5Cu17.9Ni14.6Al10Ti5 Bulk Amorphous Alloys

    Institute of Scientific and Technical Information of China (English)

    边赞; 何国; 陈国良

    2000-01-01

    利用射流成型法制备出Zr52.5Cu17.9Ni14.6Al10Ti5大块非晶.该合金系统具有很强的玻玻璃转化温度Tg=650.63K,晶化温度Tx=721.90K,过冷区△Tx=Tx=Tg=71.27K.Vicker硬度为558kg/mm2,压缩断裂强度1730GPa,弹性模量82GPa.观察其断口有大量纹络状河流花样,并有融化的液滴存在.该合金系统大的玻璃形成能力应归功于合金组元的多样性、组元间大的原子半径比率、组元间大的混合负热及在冷却过程中过冷区粘度的急剧上升等因素.%Zr52.5Cu17.9Ni14.6Al10Ti5 bulk amorphous alloy was prepared by a water-cooled copper mold. The alloy system has an excellent glass formation ability (GFA ) and a wide supercooled liquid region. The glass transition temperature (Tg), the crystallization temperature (Tx), the fracture stress, the plastic, Vickers hardness and elastic modulus for the bulk amorphous alloys with a diameter of 3 mm are 377.63℃,448.9℃, 1 730 MPa, 0.5%, 558 and 82 GPa, respectively. The bulk amorphous alloys have good mechanical properties. The excellent glass formation ability of Zr52.5Cu17.9Ni14.6Al10Ti5 alloys is presumably due to a combination of significantly different atomic size ratios above about 12%, multicomponent alloy system consisting of more than three elements and optimum negative heats of mixing among the constituent elements.

  5. Spectroscopic Ellipsometry Studies of n-i-p Hydrogenated Amorphous Silicon Based Photovoltaic Devices

    Directory of Open Access Journals (Sweden)

    Laxmi Karki Gautam

    2016-02-01

    Full Text Available Optimization of thin film photovoltaics (PV relies on characterizing the optoelectronic and structural properties of each layer and correlating these properties with device performance. Growth evolution diagrams have been used to guide production of materials with good optoelectronic properties in the full hydrogenated amorphous silicon (a-Si:H PV device configuration. The nucleation and evolution of crystallites forming from the amorphous phase were studied using in situ near-infrared to ultraviolet spectroscopic ellipsometry during growth of films prepared as a function of hydrogen to reactive gas flow ratio R = [H2]/[SiH4]. In conjunction with higher photon energy measurements, the presence and relative absorption strength of silicon-hydrogen infrared modes were measured by infrared extended ellipsometry measurements to gain insight into chemical bonding. Structural and optical models have been developed for the back reflector (BR structure consisting of sputtered undoped zinc oxide (ZnO on top of silver (Ag coated glass substrates. Characterization of the free-carrier absorption properties in Ag and the ZnO + Ag interface as well as phonon modes in ZnO were also studied by spectroscopic ellipsometry. Measurements ranging from 0.04 to 5 eV were used to extract layer thicknesses, composition, and optical response in the form of complex dielectric function spectra (ε = ε1 + iε2 for Ag, ZnO, the ZnO + Ag interface, and undoped a-Si:H layer in a substrate n-i-p a-Si:H based PV device structure.

  6. Mechanical alloying of Cu/Al plates and preparation of bulk amorphous/nanocrystalline composite by thermoplastic deformation%搅拌摩擦法制备Cu-Al非晶/纳米晶复合材料

    Institute of Scientific and Technical Information of China (English)

    徐红霞; 段辉平; 宋洪海

    2013-01-01

    利用搅拌摩擦技术,使叠放在一起的Cu、Al板材发生强烈的热塑性变形.对搅拌区产物的显微结构分析表明:Cu、Al板材被搅拌破碎并充分混合在一起,Cu、Al元素发生扩散并实现合金化;在搅拌区中有许多尺寸> 1μm的非晶相和非晶/纳米晶复合相,非晶相的基体中含有平均尺寸约为5nm的纳米晶.热塑性变形技术不仅可用于块体金属材料的机械合金化,也可用于制备块体非晶/纳米晶复合材料.%Strong thermoplastic deformation of overlapped Cu and Al plates had been realized by stir friction processing. Transmission electron microscopy investigation on the microstructure of the stirred zone demonstrate that the Cu and Al plates are torn into shreds and well-mixed in the stirred zone. The inter-diffusion between Cu and Al shreds happens, resulting in the mechanical alloying of Cu/Al plates. There are many amorphous phases with size of more than 1 micron and amorphous/nanocrystalline composite phases in the deformation zone. The average size of the nanocrystallines surrounded by amorphous phases, is about 5 nanometers. Experimental results strongly suggest that the thermoplastic deformation technique can not only be used to do mechanical alloying for bulk metallic materials but also to fabricate bulk amorphous/crystalline materials.

  7. Preparation and Magnetocaloric Effect in Amorphous Fe91-xLaxZr9 Alloys%非晶态Fe91-xLaxZr9合金的制备与磁热效应

    Institute of Scientific and Technical Information of China (English)

    李海军; 特古斯; 刘雨江; 张伟; 陈晓君; 利胜

    2013-01-01

    采用电弧熔炼和真空电磁感应甩带方法制备了Fe91-xLaxZr9(x=1,3,5,10)系列非晶合金,研究了该非晶合金的磁性和磁热效应.X-射线衍射结果显示,样品的形成主要为非晶态合金.非晶态Fe8lLal0Zr9合金的磁熵变随温度变化的曲线表明,外场为1.5T时样品最大等温磁熵变为0.8J/(kg·K),半峰宽对应的温度变化范围为245~285K.%In this article, we investigated the preparation of amorphous Fe91-xLaxZr9 (x= 1,3, 5,10 ) alloys and their magnetic and magnetocaloric properties. The samples of the amorphous alloys were prepared by using arc melting and melt spinning methods. X-ray diffraction shows that the samples form in amorphous state. The isothermal magnetic entropy change of Fe81La10Zr9 alloy was determined from magnetization data basis on Maxwell relation. The result shows that the maximal magnetic entropy change is 0. 8 J/(kg · K). The half-peak wide temperature span is from 245 K to 285 K.

  8. Magnetic and electrical properties of amorphous Fe-Cr-P-C-Si

    Science.gov (United States)

    Sayouri, S.; Berraho, R.; Moustaide, A.; Benbachir, K.; Kaal, A.; Tlemçani, M.; Berrada, A.

    2003-03-01

    Magnetic and electrical properties of melt-spun amorphous Fe 100- y- zCr y(PCSi) z alloys, 4⩽ y⩽11, 19⩽ z⩽22, have been investigated. The magnetic moment, μCr, of Cr has been estimated and the magnetic coupling constants, JFe-Fe, JFe-Cr and JCr-Cr, between Fe-Fe, Fe-Cr, and Cr-Cr atoms respectively, have been evaluated using the molecular field theory of two-sublattice model. Temperature dependence of electrical resistivity of these amorphous alloys was also studied. The electrical resistivity was measured between 170 and 330 K. The alloys studied exhibit a resistivity minimum at a relatively high temperature. The temperature of resistivity minimum, Tmin, increases with increasing Cr content. The effect of Cr addition in these compounds is compared with that of Co and Ni addition on the electrical resistivity on Fe-based alloys.

  9. Thermodynamic and structural properties of Bi-based liquid alloys

    Science.gov (United States)

    Yadav, S. K.; Jha, L. N.; Adhikari, D.

    2015-10-01

    Thermodynamic and microscopic structural properties of two Bi-based liquid alloys, such as In-Bi at 900 K and Tl-Bi at 750 K have been studied employing the regular associated solution model. We have estimated the mole fractions of the complexes and the free monomers assuming the existence of complexes In2 Bi in In-Bi melt and TlBi in Tl-Bi melt. The thermodynamic properties have been studied by computing the Gibbs free energy of mixing, enthalpy of mixing, entropy of mixing and activities of the monomers. The compositional contributions of the heat associated with the formation of complexes and the heat of mixing of the monomers to the net enthalpy change has also been studied. The structural properties of the liquid alloys have been studied by computing concentration fluctuation in the long-wavelength limit, chemical short-range order parameter and the ratio of mutual to intrinsic diffusion coefficients. For both of the alloy systems, the theoretical as well as the experimental values of SCC (0) are found to be lower than the corresponding ideal values over the whole composition range, indicating the hetero-coordinating nature of Bi-In and Bi-Tl alloy melts. All the interaction energy parameters are found to be negative and temperature dependent, and both the alloy systems are found to be weakly interacting.

  10. [Dimensional changes of silver and gallium-based alloy].

    Science.gov (United States)

    Ballester, R Y; Markarian, R A; Loguercio, A D

    2001-01-01

    Gallium-based dental alloys were created with the aim of solving the problem of toxicity of mercury. The material shows mechanical properties similar to those of dental amalgam, but researches point out two unfavorable characteristics: great corrosion and excessive post-setting expansion, and the latter is capable of cracking dental structures. The aim of this study was to evaluate, during 7 days, the in vitro dimensional alteration of a gallium dental alloy (Galloy, SDI, Australia), in comparison with a dental amalgam containing zinc (F400, SDI, Australia), as a function of the contact with saline solution (0.9% NaCl) during the setting period. The storage experimental conditions were: storage in dry environment, immersion in saline solution and contamination during condensation. Additionally, the effects of contamination during the trituration of dental amalgam and the effects of protecting the surface of the gallium alloy with a fluid resin were studied. Specimens were stored at 37 degrees C +/- 1 degree C, and measuring was carried out, sequentially, every 24 h during 7 days. When the gallium alloy was either contaminated or immersed, an expansion significantly greater than that observed in the other experimental conditions was noticed after 7 days. The application of a fluid resin to protect the surface of the cylinders was able to avoid the increase in expansion caused by superficial moisture. The amalgam alloy did not show significant dimensional alterations, except when it was contaminated during trituration.

  11. The physics and applications of amorphous semiconductors

    CERN Document Server

    Madan, Arun

    1988-01-01

    This comprehensive, detailed treatise on the physics and applications of the new emerging technology of amorphous semiconductors focuses on specific device research problems such as the optimization of device performance. The first part of the book presents hydrogenated amorphous silicon type alloys, whose applications include inexpensive solar cells, thin film transistors, image scanners, electrophotography, optical recording and gas sensors. The second part of the book discusses amorphous chalcogenides, whose applications include electrophotography, switching, and memory elements. This boo

  12. Improved Mg-based alloys for hydrogen storage

    Energy Technology Data Exchange (ETDEWEB)

    Sapru, K.; Ming, L.; Stetson, N.T.; Evans, J. [Energy Conversion Devices, Inc., Troy, MI (United States)

    1998-08-01

    The overall objective of this on-going work is to develop low temperature alloys capable of reversibly storing at least 3 wt.% hydrogen, allowing greater than for 2 wt.% at the system level which is required by most applications. Surface modification of Mg can be used to improve its H-sorption kinetics. The authors show here that the same Mg-transition metal-based multi-component alloy when prepared by melt-spinning results in a more homogeneous materials with a higher plateau pressure as compared to preparing the material by mechanical grinding. They have also shown that mechanically alloyed Mg{sub 50}Al{sub 45}Zn{sub 5} results in a sample having a higher plateau pressure.

  13. Diffusion Bonding between TiAl Based Alloys and Steels

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The joint of 40Cr steel and TiAl based alloy has been studied by means of a high frequency induction diffusion welder. The experimental results show that, the higher the temperature and pressure, the higher the strength of the joints. The optimum parameters are: T=1123~1323 K,t=10~30 min, P=5~20 MPa.

  14. Kinetic and microstructural studies on the devitrification of Fe{sub 60-x}Co{sub 18}Mn{sub x}Nb{sub 6}B{sub 16} amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Benaini, H.; Blazquez, J.S.; Conde, C.F. [Departamento de Fisica de la Materia Condensada, ICMSE-CSIC, Universidad de Sevilla, P.O. Box 1065, 41080 Sevilla (Spain); Conde, A. [Departamento de Fisica de la Materia Condensada, ICMSE-CSIC, Universidad de Sevilla, P.O. Box 1065, 41080 Sevilla (Spain)], E-mail: conde@us.es

    2008-04-24

    Kinetic and microstructural studies have been performed on Fe{sub 60-x}Co{sub 18}Mn{sub x}Nb{sub 6}B{sub 16} (x = 0, 2, 4) alloys by using different techniques. Isothermal and non-isothermal kinetics agree describing the nanocrystallization as a strongly impinged growth process. Developed microstructure is similar for all the studied alloys. Nanocrystals are irregularly shaped, {approx}20 nm in size, and formed by agglomerates of smaller and more regular units of {approx}5 nm diameter. From the present data it is not possible to exclude the presence of Mn atoms inside the crystals. However, a preferential partition of this element into the residual amorphous matrix is clearly derived from Moessbauer results.

  15. Novel alginate based coatings on Mg alloys

    Energy Technology Data Exchange (ETDEWEB)

    Sangeetha, K.; Roy, Abhijit [Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15261 (United States); Singh, Satish [Department of Chemical Engineering, University of Pittsburgh, Pittsburgh, PA 15261 (United States); Lee, Boeun [Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15261 (United States); Kumta, Prashant N., E-mail: pkumta@pitt.edu [Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15261 (United States); Department of Chemical Engineering, University of Pittsburgh, Pittsburgh, PA 15261 (United States); Center for Craniofacial Regeneration, University of Pittsburgh, Pittsburgh, PA 15261 (United States); Center for Complex Engineered Multifunctional Materials, University of Pittsburgh, Pittsburgh, PA 15261 (United States); Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, PA 15261 (United States)

    2011-12-15

    Coatings on yttrium doped magnesium (Mg4Y) alloy substrates were prepared using alginate hydrogels by dip coating method to improve the surface bioactive properties of the substrate. Furthermore, composite coatings containing nano-sized calcium phosphate corresponding to hydroxyapatite (HA) phase entrapped within alginate hydrogel were also synthesized on the Mg4Y substrates. Surface characteristics of these coated substrates have been investigated using FTIR-ATR, SEM and EDS. The results show that the coatings with alginate alone are not stable in vitro; however, incorporation of NanoCaPs slightly improves the stability of these coatings. In addition, these composite coatings showed cell attachments with fibronectin incorporation. These results indicate that alginate hydrogels have the potential to be used as bioactive coating materials for different biofunctional applications.

  16. Acoustic Emission Analysis of Damage during Compressive Deformation of Amorphous Zr-Based Foams with Aligned, Elongated Pores

    Science.gov (United States)

    Cox, Marie E.; Dunand, David C.

    2013-07-01

    Acoustic emission methods are used to investigate the evolution of internal microfractural damage during uniaxial compression of amorphous Zr-based foams with aligned, elongated pores. The foams are fabricated by means of densifying a blend of crystalline W powders and amorphous Zr-based powders with two oxygen contents (0.078 and 0.144 wt pct) by warm equal channel angular extrusion, followed by dissolution of the elongated W phase from the fully densified amorphous matrix. For the high-oxygen foams, prior powder boundaries in the amorphous struts promote damage that accumulates during compression, resulting in energy-absorbing properties comparable with the low-oxygen foams without stress-concentrating powder boundaries. The influence of pore orientation on the evolution of microfracture damage and the ability of the foams to accumulate damage without catastrophic failure is also investigated: pores oriented from 24 to 68 deg to the loading direction promote wall bending, resulting in foams with more diffuse damage and better energy-absorbing properties.

  17. Zirconium-based alloys, nuclear fuel rods and nuclear reactors including such alloys, and related methods

    Science.gov (United States)

    Mariani, Robert Dominick

    2014-09-09

    Zirconium-based metal alloy compositions comprise zirconium, a first additive in which the permeability of hydrogen decreases with increasing temperatures at least over a temperature range extending from 350.degree. C. to 750.degree. C., and a second additive having a solubility in zirconium over the temperature range extending from 350.degree. C. to 750.degree. C. At least one of a solubility of the first additive in the second additive over the temperature range extending from 350.degree. C. to 750.degree. C. and a solubility of the second additive in the first additive over the temperature range extending from 350.degree. C. to 750.degree. C. is higher than the solubility of the second additive in zirconium over the temperature range extending from 350.degree. C. to 750.degree. C. Nuclear fuel rods include a cladding material comprising such metal alloy compositions, and nuclear reactors include such fuel rods. Methods are used to fabricate such zirconium-based metal alloy compositions.

  18. Alloy

    Science.gov (United States)

    Cabeza, Sandra; Garcés, Gerardo; Pérez, Pablo; Adeva, Paloma

    2014-07-01

    The Mg98.5Gd1Zn0.5 alloy produced by a powder metallurgy route was studied and compared with the same alloy produced by extrusion of ingots. Atomized powders were cold compacted and extruded at 623 K and 673 K (350 °C and 400 °C). The microstructure of extruded materials was characterized by α-Mg grains, and Mg3Gd and 14H-LPSO particles located at grain boundaries. Grain size decreased from 6.8 μm in the extruded ingot, down to 1.6 μm for powders extruded at 623 K (350 °C). Grain refinement resulted in an increase in mechanical properties at room and high temperatures. Moreover, at high temperatures the PM alloy showed superplasticity at high strain rates, with elongations to failure up to 700 pct.

  19. Downstream processing of polymer-based amorphous solid dispersions to generate tablet formulations.

    Science.gov (United States)

    Démuth, B; Nagy, Z K; Balogh, A; Vigh, T; Marosi, G; Verreck, G; Van Assche, I; Brewster, M E

    2015-01-01

    Application of amorphous solid dispersions (ASDs) is considered one of the most promising approaches to increase the dissolution rate and extent of bioavailability of poorly water soluble drugs. Such intervention is often required for new drug candidates in that enablement, bioavailability is not sufficient to generate a useful product. Importantly, tableting of ASDs is often complicated by a number of pharmaceutical and technological challenges including poor flowability and compressibility of the powders, compression-induced phase changes or phase separation and slow disintegration due to the formation of a gelling polymer network (GPN). The design principles of an ASD-based system include its ability to generate supersaturated systems of the drug of interest during dissolution. These metastable solutions can be prone to precipitation and crystallization reducing the biopharmaceutical performance of the dosage form. The main aim of the research in this area is to maintain the supersaturated state and optimally enhance bioavailability, meaning that crystallization should be delayed or inhibited during dissolution, as well as in solid phase (e.g., during manufacturing and storage). Based on the expanding use of ASD technology as well as their downstream processing, there is an acute need to summarize the results achieved to this point to better understand progress and future risks. The aim of this review is to focus on the conversion of ASDs into tablets highlighting results from various viewpoints.

  20. Replacement of Cobalt base alloys hardfacing by NOREM alloy; EDF experience and development, some metallurgical considerations. Valves application (CLAMA, RAMA)

    Energy Technology Data Exchange (ETDEWEB)

    Carnus, M. [EDF DPN UTO Direction Expertise Technique, Noisy le Grand (France); Confort, X. [VELAN SAS, Lyon (France)

    2011-07-01

    Cobalt base alloys, such as Stellite 6 and 21, are used extensively in applications where superior resistance to wear and corrosion are required. However the use of Cobalt alloys hardfacing materials, especially on valves, is a major contributor to the level of radioactive contamination of nuclear facilities. NOREM alloys, an iron base and cobalt free materials, have been developed through an Electric Power Research Institute (EPRI) long running program during the eighties as an alternative of Stellite. This alloy has relatively good weldability properties, it was developed initially for repairing Stellite hardfacing (deposit over existing hardfacing alloys). This alloy has good corrosion resistance properties associated with elevated hardness (HRC 36-42). Technological properties (such as galling resistance, wear resistance) have been evaluated through different testing programs led by EPRI, AECL(Atomic Energy of Canada Limited), Valves manufacturers, EDF and others during the nineties. More recently EDF (for replacement of globe valves) has carried out testing program focused on weld deposit chemistry and mechanical properties. NOREM is a candidate for replacement of stellite hardfacing on valves. However this alloy is not so versatile as stellite alloys regarding technological properties (such as wear resistance) at elevated temperature and under high contact pressure. As a consequence some limits have to be considered for application on valves operating at elevated temperature and under high contact pressure (> 20 Mpa). Examples of application on valves, from VELAN manufacturer, for EDF PWR equipment are given. The industrial feedback from installed equipment (CLAMA, RAMA) since 2006 on EDF PWR has been good

  1. Melt Protection of Mg-Al Based Alloys

    Directory of Open Access Journals (Sweden)

    María J. Balart

    2016-05-01

    Full Text Available This paper reports the current status of Mg melt protection in view to identify near-future challenges, but also opportunities, for Mg melt protection of Mg-Al based alloys. The goal is to design and manufacture sustainable Mg alloys for resource efficiency, recycling and minimising waste. Among alternative cover gas technologies for Mg melt protection other than SF6: commercially available technologies containing―HFC-134a, fluorinated ketone and dilute SO2―and developed technologies containing solid CO2, BF3 and SO2F2, can potentially produce toxic and/or corrosive by-products. On the other hand, additions of alkaline earth metal oxides to Mg and its alloys have developed a strong comparative advantage in the field of Mg melt protection. The near-future challenges and opportunities for Mg-Al based alloys include optimising and using CO2 gas as feedstock for both melt protection and grain refinement and TiO2 additions for melt protection.

  2. Vanadium based amorphous mixed oxides used as negative electrodes of lithium batteries; Oxydes mixtes amorphes a base de vanadium comme electrodes negatives de batteries au lithium

    Energy Technology Data Exchange (ETDEWEB)

    Guyomard, D.; Leroux, F.; Sigala, C.; Le Gal La Salle, A.; Piffard, Y. [Institut des Materiaux de Nantes, 44 (France). Laboratoire de Chimie des Solides

    1996-12-31

    This paper presents recent results concerning the chemical and electrochemical synthesis, the electrochemical properties and the characterization of two new families of amorphous oxides of formula Li{sub x}MVO{sub 4} (1

  3. Thin-film amorphous silicon alloy research partnership. Final technical progress report, 2 February 1995--28 February 1998

    Energy Technology Data Exchange (ETDEWEB)

    Guha, S [United Solar Systems Corp., Troy, MI (United States)

    1998-05-01

    This report describes the status and accomplishments of work performed by United Solar Systems Corp. under this subcontract. Investigations were carried out on Ag/ZnO, Ag/TiO{sub 2}/ZnO and Ag/MgF{sub 2}/ZnO back reflectors to assess their suitability for use in cell structures. Arrays of high-efficiency component cells were made over 1-ft{sup 2} areas. Single-junction top cells were made with an average stabilized power density of 5.4 mW/cm{sup 2} measured under global AM1.5 illumination. Single-junction middle cells were optimized to give average stabilized power density of 3.6 mW/cm{sup 2} under global AM1.5 illumination with a cut-on filter with {lambda} > 530 nm. Arrays of high-efficiency triple-junction cells of 0.25-cm{sup 2} active area were fabricated over 1-ft{sup 2} area with average stabilized efficiency of 12% as measured under AM1.5 illumination. A triple-junction module of a 416-cm{sup 2} aperture area was fabricated with an initial efficiency of 11.7% and stabilized efficiency of 10.24%. A 922-cm{sup 2} aperture-area module exhibited an initial efficiency of 11.5%. The novel laser-drilling approach was used successfully to fabricate modules of 1-ft{sup 2} area with shadow loss of approximately 1%. Using this laser-drilling approach, an initial total-area efficiency of 11.5% was achieved in a triple-cell structure of 12.6 cm{sup 2} area. An initial total-area efficiency of 10.6% was achieved in a module of 300-cm{sup 2} area. Reliability studies based on NREL`s Interim Qualification Testing were carried out to confirm the suitability of the module encapsulation materials and processes. 29 figs., 17 tabs.

  4. Analysis of thermoelectric properties of high-temperature complex alloys of nickel-base, iron-base and cobalt-base groups

    Science.gov (United States)

    Holanda, R.

    1984-01-01

    The thermoelectric properties alloys of the nickel-base, iron-base, and cobalt-base groups containing from 1% to 25% 106 chromium were compared and correlated with the following material characteristics: atomic percent of the principle alloy constituent; ratio of concentration of two constituents; alloy physical property (electrical resistivity); alloy phase structure (percent precipitate or percent hardener content); alloy electronic structure (electron concentration). For solid-solution-type alloys the most consistent correlation was obtained with electron concentration, for precipitation-hardenable alloys of the nickel-base superalloy group, the thermoelectric potential correlated with hardener content in the alloy structure. For solid-solution-type alloys, no problems were found with thermoelectric stability to 1000; for precipitation-hardenable alloys, thermoelectric stability was dependent on phase stability. The effects of the compositional range of alloy constituents on temperature measurement uncertainty are discussed.

  5. Temperature of phase transformations in heat-resistant nickel-base alloys

    Science.gov (United States)

    Ivanov, A. D.; Ukhlinov, A. G.

    1997-11-01

    The study of phase transformations in heating and cooling of alloys is needed for choosing optimum regimes of their melting, plastic deformation, and heat treatment. In the present paper differential thermal analysis is used to determine the temperature of phase transformations in complexly alloyed nickel-base alloys. Industrial nickel alloys with intermetallic reinforcement manufactured by means of vacuum arc remelting (VAR) and hot deformation (HD) were studied. Alloy KhN56MBYuD was studied after different metallurgical processes, namely, electroslag remelting (ESR), centrifugal casting (CC), powder spraying (PS), and hot isostatic pressing (HIP). All the alloys were studied in the initial state and after heat treatment.

  6. Effect of Impurities and Cerium on Stress Concentration Sensitivity of Al-Li Based Alloys

    Institute of Scientific and Technical Information of China (English)

    孟亮; 田丽

    2002-01-01

    A notch sensitivity factor was derived in order to evaluate the stress concentration sensitivity of Al-Li based alloys. The factor values for the Al-Li alloy sheets containing various contents of impurities and cerium addition were evaluated by determining the mechanical properties. It is found that the impurities Fe, Si, Na and K significantly enhance the stress concentration sensitivity of the alloys 2090 and 8090, whereas cerium addition reduces the stress concentration sensitivity to a certain degree for the high strength alloys. However, an excess amount of cerium addition in the high ductility alloy 1420 can significantly increase the stress concentration sensitivity. As compared with conventional aluminum alloys, the Al-Li based alloys generally show high stress concentration sensitivity. Therefore, a special attention must be paid to this problem in the practical application of Al-Li based alloys.

  7. Feasibility of Amorphous Selenium Based Photon Counting Detectors for Digital Breast Tomosynthesis

    Energy Technology Data Exchange (ETDEWEB)

    Chen, J.; O' Connor, P.; Lehnert, J., De Geronimo, G., Dolazza, E., Tousignant, O., Laperriere, L., Greenspan, J., Zhao, W.

    2009-02-27

    Amorphous selenium (a-Se) has been incorporated successfully in direct conversion flat panel x-ray detectors, and has demonstrated superior image quality in screening mammography and digital breast tomosynthesis (DBT) under energy integration mode. The present work explores the potential of a-Se for photon counting detectors in DBT. We investigated major factors contributing to the variation in the charge collected by a pixel upon absorption of each x-ray photon. These factors included x-ray photon interaction, detector geometry, charge transport, and the pulse shaping and noise properties of the photon counting readout circuit. Experimental measurements were performed on a linear array test structure constructed by evaporating an a-Se layer onto an array of 100 {mu}m pitch strip electrodes, which are connected to a 32 channel low noise photon counting integrated circuit. The measured pulse height spectrum (PHS) under polychromatic xray exposure was interpreted quantitatively using the factors identified. Based on the understanding of a-Se photon counting performance, design parameters were proposed for a 2D detector with high quantum efficiency and count rate that could meet the requirements of photon counting detector for DBT.

  8. Nitriding behavior of Ni and Ni-based binary alloys

    Energy Technology Data Exchange (ETDEWEB)

    Fonovic, Matej

    2015-01-15

    Gaseous nitriding is a prominent thermochemical surface treatment process which can improve various properties of metallic materials such as mechanical, tribological and/or corrosion properties. This process is predominantly performed by applying NH{sub 3}+H{sub 2} containing gas atmospheres serving as the nitrogen donating medium at temperatures between 673 K and 873 K (400 C and 600 C). NH{sub 3} decomposes at the surface of the metallic specimen and nitrogen diffuses into the surface adjacent region of the specimen whereas hydrogen remains in the gas atmosphere. One of the most important parameters characterizing a gaseous nitriding process is the so-called nitriding potential (r{sub N}) which determines the chemical potential of nitrogen provided by the gas phase. The nitriding potential is defined as r{sub N} = p{sub NH{sub 3}}/p{sub H{sub 2}{sup 3/2}} where p{sub NH{sub 3}} and p{sub H{sub 2}} are the partial pressures of the NH{sub 3} and H{sub 2} in the nitriding atmosphere. In contrast with nitriding of α-Fe where the nitriding potential is usually in the range between 0.01 and 1 atm{sup -1/2}, nitriding of Ni and Ni-based alloys requires employing nitriding potentials higher than 100 atm{sup -1/2} and even up to ∞ (nitriding in pure NH{sub 3} atmosphere). This behavior is compatible with decreased thermodynamic stability of the 3d-metal nitrides with increasing atomic number. Depending on the nitriding conditions (temperature, nitriding potential and treatment time), different phases are formed at the surface of the Ni-based alloys. By applying very high nitriding potential, formation of hexagonal Ni{sub 3}N at the surface of the specimen (known as external nitriding) leads to the development of a compound layer, which may improve tribological properties. Underneath the Ni{sub 3}N compound layer, two possibilities exist: (i) alloying element precipitation within the nitrided zone (known as internal nitriding) and/or (ii) development of metastable and

  9. Investigation of the Precipitation Behavior in Aluminum Based Alloys

    KAUST Repository

    Khushaim, Muna S.

    2015-11-30

    The transportation industries are constantly striving to achieve minimum weight to cut fuel consumption and improve overall performance. Different innovative design strategies have been placed and directed toward weight saving combined with good mechanical behavior. Among different materials, aluminum-based alloys play a key role in modern engineering and are widely used in construction components because of their light weight and superior mechanical properties. Introduction of different nano-structure features can improve the service and the physical properties of such alloys. For intelligent microstructure design in the complex Al-based alloy, it is important to gain a deep physical understanding of the correlation between the microstructure and macroscopic properties, and thus atom probe tomography with its exceptional capabilities of spatially resolution and quantitative chemical analyses is presented as a sophisticated analytical tool to elucidate the underlying process of precipitation phenomena in aluminum alloys. A complete study examining the influence of common industrial heat treatment on the precipitation kinetics and phase transformations of complex aluminum alloy is performed. The qualitative evaluation results of the precipitation kinetics and phase transformation as functions of the heat treatment conditions are translated to engineer a complex aluminum alloy. The study demonstrates the ability to construct a robust microstructure with an excellent hardness behavior by applying a low-energy-consumption, cost-effective method. The proposed strategy to engineer complex aluminum alloys is based on both mechanical strategy and intelligent microstructural design. An intelligent microstructural design requires an investigation of the different strengthen phases, such as T1 (Al2CuLi), θ′(Al2Cu), β′(Al3Zr) and δ′(Al3Li). Therefore, the early stage of phase decomposition is examined in different binary Al-Li and Al-Cu alloys together with different

  10. M"ossbauer study of the effect of Nb in Fe-based nanocrystalline alloy

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Microstructure of nanocrystalline alloys of Fe73.5Cu1Nb3Si13.5B9and (Fe3Si)0.95Nb0.05 was investigated by M"ossbauerspectroscopy. A Nb-rich interfaciallayer with weak magnetism formed in the residual amorphous phase of these materials.It has an important effect on the exchange coupling and magnetic properties.

  11. Tracer Diffusion Mechanism in Amorphous Solids

    Directory of Open Access Journals (Sweden)

    P. K. Hung

    2011-01-01

    Full Text Available Tracer diffusion in amorphous solid is studied by mean of nB-bubble statistic. The nB-bubble is defined as a group of atoms around a spherical void and large bubble that represents a structural defect which could be eliminated under thermal annealing. It was found that amorphous alloys such as CoxB100−x (x=90, 81.5 and 70 and Fe80P20 suffer from a large number of vacancy bubbles which function like diffusion vehicle. The concentration of vacancy bubble weakly depends on temperature, but essentially on the relaxation degree of considered sample. The diffusion coefficient estimated for proposed mechanism via vacancy bubbles is in a reasonable agreement with experiment for actual amorphous alloys. The relaxation effect for tracer diffusion in amorphous alloys is interpreted by the elimination of vacancy bubbles under thermal annealing.

  12. Performance improvement in amorphous silicon based uncooled microbolometers through pixel design and materials development

    Science.gov (United States)

    Ajmera, Sameer; Brady, John; Hanson, Charles; Schimert, Tom; Syllaios, A. J.; Taylor, Michael

    2011-06-01

    Uncooled amorphous silicon microbolometers have been established as a field-worthy technology for a broad range of applications where performance and form factor are paramount, such as soldier-borne systems. Recent developments in both bolometer materials and pixel design at L-3 in the 17μm pixel node have further advanced the state-of-the-art. Increasing the a-Si material temperature coefficient of resistance (TCR) has the impact of improving NETD sensitivity without increasing thermal time constant (TTC), leading to an improvement in the NETD×TTC product. By tuning the amorphous silicon thin-film microstructure using hydrogen dilution during deposition, films with high TCR have been developed. The electrical properties of these films have been shown to be stable even after thermal cycling to temperatures greater than 300oC enabling wafer-level vacuum packaging currently performed at L-3 to reduce the size and weight of the vacuum packaged unit. Through appropriate selection of conditions during deposition, amorphous silicon of ~3.4% TCR has been integrated into the L-3 microbolometer manufacturing flow. By combining pixel design enhancements with improvements to amorphous silicon thin-film technology, L-3's amorphous silicon microbolometer technology will continue to provide the performance required to meet the needs to tomorrow's war-fighter.

  13. The thermomechanical stability of Fe-based amorphous ribbons exhibiting magnetocaloric effect

    Science.gov (United States)

    Shishkin, D. A.; Volegov, A. S.; Baranov, N. V.

    2016-12-01

    The Fe-Nb-B and Fe71.5Cr2Si13.5B9Nb3Cu1 alloys have been prepared by rapid quenching from the melt, and the magnetic properties of alloys in the vicinity of the magnetic ordering have been studied before and after thermomechanical processing. It has been shown that change in the Fe:Nb:B ratio allows tuning the magnetic ordering temperature and the position of maximum of the isothermal magnetic entropy change | { - Δ Sm } | from 256 to 333 K. The thermomechanical treatment of alloys at 623 K under applied tensile stresses observed does not affect remarkably the magnetocaloric properties of alloys. The combination of high thermomechanical stability, good electrical, anti-corrosive and thermomagnetic properties makes these alloys promising for use in magnetic refrigeration devices.

  14. CuZn Alloy- Based Electrocatalyst for CO2 Reduction

    KAUST Repository

    Alazmi, Amira

    2014-06-01

    ABSTRACT CuZn Alloy- Based Electrocatalyst for CO2 Reduction Amira Alazmi Carbon dioxide (CO2) is one of the major greenhouse gases and its emission is a significant threat to global economy and sustainability. Efficient CO2 conversion leads to utilization of CO2 as a carbon feedstock, but activating the most stable carbon-based molecule, CO2, is a challenging task. Electrochemical conversion of CO2 is considered to be the beneficial approach to generate carbon-containing fuels directly from CO2, especially when the electronic energy is derived from renewable energies, such as solar, wind, geo-thermal and tidal. To achieve this goal, the development of an efficient electrocatalyst for CO2 reduction is essential. In this thesis, studies on CuZn alloys with heat treatments at different temperatures have been evaluated as electrocatalysts for CO2 reduction. It was found that the catalytic activity of these electrodes was strongly dependent on the thermal oxidation temperature before their use for electrochemical measurements. The polycrystalline CuZn electrode without thermal treatment shows the Faradaic efficiency for CO formation of only 30% at applied potential ~−1.0 V vs. RHE with current density of ~−2.55 mA cm−2. In contrast, the reduction of oxide-based CuZn alloy electrode exhibits 65% Faradaic efficiency for CO at lower applied potential about −1.0 V vs. RHE with current density of −2.55 mA cm−2. Furthermore, stable activity was achieved over several hours of the reduction reaction at the modified electrodes. Based on electrokinetic studies, this improvement could be attributed to further stabilization of the CO2•− on the oxide-based Cu-Zn alloy surface.

  15. Synthesis and characterization of nanostructured palladium-based alloy electrocatalysts

    Science.gov (United States)

    Sarkar, Arindam

    Low temperature fuel cells like proton exchange membrane fuel cells (PEMFC) are expected to play a crucial role in the future hydrogen economy, especially for transportation applications. These electrochemical devices offer significantly higher efficiency compared to conventional heat engines. However, use of exotic and expensive platinum as the electrocatalyst poses serious problems for commercial viability. In this regard, there is an urgent need to develop low-platinum or non-platinum electrocatalysts with electrocatalytic activity for the oxygen reduction reaction (ORR) superior or comparable to that of platinum. This dissertation first investigates non-platinum, palladium-based alloy electrocatalysts for ORR. Particularly, Pd-M (M = Mo and W) alloys are synthesized by a novel thermal decomposition of organo-metallic precursors. The carbon-supported Pd-M (M = Mo, W) electrocatalyts are then heat treated up to 900°C in H2 atmosphere and investigated for their phase behavior. Cyclic voltammetry (CV) and rotating disk electrode (RDE) measurements reveal that the alloying of Pd with Mo or W significantly enhances the catalytic activity for ORR as well as the stability (durability) of the electrocatalysts. Additionally, both the alloy systems exhibit high tolerance to methanol, which is particularly advantageous for direct methanol fuel cells (DMFC). The dissertation then focuses on one-pot synthesis of carbon-supported multi-metallic Pt-Pd-Co nanoalloys by a rapid microwave-assisted solvothermal (MW-ST) method. The multi-metallic alloy compositions synthesized by the MW-ST method show much higher catalytic activity for ORR compared to their counterparts synthesized by the conventional borohydride reduction method. Additionally, a series of Pt encapsulated Pd-Co nanoparticle electrocatalysts are synthesized by the MW-ST method and characterized to understand their phase behavior, surface composition, and electrocatalytic activity for ORR. Finally, the dissertation

  16. Cr{sub 2}Nb-based alloy development

    Energy Technology Data Exchange (ETDEWEB)

    Liu, C.T.; Tortorelli, P.F.; Horton, J.A. [Oak Ridge National Lab., TN (United States)] [and others

    1995-06-01

    The objective of this task is to develop a new generation of structural materials based on intermetallic alloys for use as critical hot components in advanced fossil energy conversion systems. The intermetallic phase, Cr{sub 2}Nb, with a complex cubic structure (C-15) has been selected for this development because of its high melting point (1770{degrees}C), relatively low material density (7.7 g/cm{sup 2}), excellent high-temperature strength (at 1000 to 1250{degrees}C), and potential resistance to oxidation and corrosion. This intermetallic phase, like many other Laves phases, has a wide range of compositional homogeneity suggesting the possibility of improving its mechanical and metallurgical properties by alloying additions. The major engineering concern with Cr{sub 2}Nb and other A{sub 2}B Laves phases is their poor fracture toughness and fracture resistance at ambient temperatures. The single-phase Cr{sub 2}Nb is very hard ({approximately}800 DPH) and brittle at room temperature. Because of this brittleness, the development effort has concentrated on two-phase structures containing the hard intermetallic phase Cr{sub 2}Nb and the softer Cr-rich solid solution phase. Potential applications of Cr-Cr{sub 2}Nb alloys include hot components (for example, air heat exchangers and turbine blades) in advanced energy conversion systems and heat engines, wear-resistant parts in coal handling systems (e.g., nozzles), drill bits for oil/gas wells, and valve guides in diesel engines. Current studies are focuses on enhancement of fracture resistance in tension at ambient temperatures and oxidation resistance above 1000{degrees}C. This report summarizes recent progress on controlling microstructure and improving the mechanical and metallurgical properties and the high-temperature corrosion behavior of Cr-Cr{sub 2}Nb alloys through alloying conditions, material processing, and heat treatment.

  17. Synthesis of metastable aluminum-based intermetallics by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Schwarz, R.B.; Srinivasan, S.; Desch, P.B.

    1991-01-01

    We have used mechanical alloying (MA) to prepare fine-grained powders of Al 25 at. % X (X = Ti, Zr, Hf) having the metastable cubic L1{sub 2} structure. Hexane (C{sub 6}H{sub 14}) is added to the milling media to avoid the agglomeration of the aluminum powder. Carbon from the decomposition of the hexane incorporates into the powder to form a fine dispersion of carbides. These carbides are beneficial because they limit grain growth during consolidation and add strength to the alloy. We have consolidated the mechanically alloyed powders using conventional hot-pressing and non-conventional dynamic pressing. We used hot pressing to consolidate mechanically alloyed L1{sub 2}-Al{sub 3}Ti powder in the presence of excess of Al. The compact has the DO{sub 22} structure. Its room-temperature compressive strength is 1.2 GPa (exceeding that of cast Al{sub 3}Ti by a factor of 10). At 400{degrees}C, the compressive strength decreases to 1 GPa. The ductility, which is negligible at room temperature, increases to 6% at 400{degrees}C. We used dynamic pressing to consolidate L1{sub 2}-Al{sub 5}CuZr{sub 2} powder. The compact, having the L1{sub 2} structure, has fine grains (44 nm) and a fine dispersion of ZrC precipitates (7 nm). Its hardness is in the range of 1030 kg mm{sup {minus}2}. Current efforts are to investigate ternary alloys based on fine-grained trialuminides which include a ductile second phase. 26 refs., 8 figs.

  18. Preparation and research on poisoning resistant Zr-Co based hydrogen storage alloys

    Institute of Scientific and Technical Information of China (English)

    LI Hualing; WANG Shumao; JIANG Lijun; ZHANG Lidong; LIU Xiaopeng; LI Zhinian

    2008-01-01

    At present,all hydrogen storage alloys are poisoned by hydrogen mixed with CO,CO2,etc,which decreases the hydrogen storage property sharply.Zr-Co based hydrogen storage alloys with good poisoning resistance were prepared by alloying,fluorinating,and electroless plating.The experiment results show that the poisoning resistance of the Zr-Co based alloy was improved remarkably after the treatments.The poisoning resistance mechanism of the Zr-Co based hydrogen storage alloys was analyzed.

  19. Microscopic study of the structure of the Steel Ni-based Alloy: Hastelloy G35 Alloy

    Science.gov (United States)

    Sabir, F.; Ben Lenda, O.; Saissi, S.; Marbouh, K.; Tyouke, B.; Zerrouk, L.; Ibnlfassi, A.; Ouzaouit, K.; Elmadani, S.

    2017-