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Sample records for amorphous base alloy

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

    DOEpatents

    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.

  2. Salt Fog Testing Iron-Based Amorphous Alloys

    SciTech Connect

    Rebak, Raul B.; Aprigliano, Louis F.; Day, S. Daniel; Farmer, Joseph C.

    2007-07-01

    Iron-based amorphous alloys are hard and highly corrosion resistant, which make them desirable for salt water and other applications. These alloys can be produced as powder and can be deposited as coatings on any surface that needs to be protected from the environment. It was of interest to examine the behavior of these amorphous alloys in the standard salt-fog testing ASTM B 117. Three different amorphous coating compositions were deposited on 316L SS coupons and exposed for many cycles of the salt fog test. Other common engineering alloys such as 1018 carbon steel, 316L SS and Hastelloy C-22 were also tested together with the amorphous coatings. Results show that amorphous coatings are resistant to rusting in salt fog. Partial devitrification may be responsible for isolated rust spots in one of the coatings. (authors)

  3. Amorphous phase formation in mechanically alloyed iron-based systems

    NASA Astrophysics Data System (ADS)

    Sharma, Satyajeet

    Bulk metallic glasses have interesting combination of physical, chemical, mechanical, and magnetic properties which make them attractive for a variety of applications. Consequently there has been a lot of interest in understanding the structure and properties of these materials. More varied applications can be sought if one understands the reasons for glass formation and the methods to control them. The glass-forming ability (GFA) of alloys can be substantially increased by a proper selection of alloying elements and the chemical composition of the alloy. High GFA will enable in obtaining large section thickness of amorphous alloys. Ability to produce glassy alloys in larger section thicknesses enables exploitation of these advanced materials for a variety of different applications. The technique of mechanical alloying (MA) is a powerful non-equilibrium processing technique and is known to produce glassy (or amorphous) alloys in several alloy systems. Metallic amorphous alloys have been produced by MA starting from either blended elemental metal powders or pre-alloyed powders. Subsequently, these amorphous alloy powders could be consolidated to full density in the temperature range between the glass transition and crystallization temperatures, where the amorphous phase has a very low viscosity. This Dissertation focuses on identifying the various Fe-based multicomponent alloy systems that can be amorphized using the MA technique, studying the GFA of alloys with emphasis on improving it, and also on analyzing the effect of extended milling time on the constitution of the amorphous alloy powder produced at earlier times. The Dissertation contains seven chapters, where the lead chapter deals with the background, history and introduction to bulk metallic glasses. The following four chapters are the published/to be published work, where the criterion for predicting glass formation, effect of Niobium addition on glass-forming ability (GFA), lattice contraction on

  4. Enhanced Corrosion Resistance of Iron-Based Amorphous Alloys

    SciTech Connect

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

    2007-02-18

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

  5. Bulk amorphous steels based on Fe alloys

    DOEpatents

    Lu, ZhaoPing; Liu, Chain T.

    2006-05-30

    A bulk amorphous alloy has the approximate composition: Fe.sub.(100-a-b-c-d-e)Y.sub.aMn.sub.bT.sub.cM.sub.dX.sub.e wherein: T includes at least one of the group consisting of: Ni, Cu, Cr and Co; M includes at least one of the group consisting of W, Mo, Nb, Ta, Al and Ti; X includes at least one of the group consisting of Co, Ni and Cr; a is an atomic percentage, and a<5; b is an atomic percentage, and b.ltoreq.25; c is an atomic percentage, and c.ltoreq.25; d is an atomic percentage, and d.ltoreq.25; and e is an atomic percentage, and 5.ltoreq.e.ltoreq.30.

  6. Application of Laser Design of Amorphous Feco-Based Alloys for the Formation of Amorphous-Crystalline Composites

    NASA Astrophysics Data System (ADS)

    Permyakova, I. E.; Glezer, A. M.; Ivanov, A. A.; Shelyakov, A. V.

    2016-01-01

    Morphological and fractographic features of change of FeCo-based amorphous alloy surfaces after laser treatment are studied in detail. Regimes of laser treatment that allow various degrees of crystallization of the examined alloys to be obtained, including thin (<1 •m) crystal layers on amorphous alloy surfaces, amorphous-crystalline composites, and completely crystalline alloys are adjusted. The Vickers hardness is estimated in zones of selective laser irradiation. The structure of the examined alloys attendant to the change of their mechanical properties is analyzed.

  7. Crystallization kinetics of Fe based amorphous alloy

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

  8. Imprinting bulk amorphous alloy at room temperature

    PubMed Central

    Kim, Song-Yi; Park, Eun-Soo; Ott, Ryan T.; Lograsso, Thomas A.; Huh, Moo-Young; Kim, Do-Hyang; Eckert, Jürgen; Lee, Min-Ha

    2015-01-01

    We present investigations on the plastic deformation behavior of a brittle bulk amorphous alloy by simple uniaxial compressive loading at room temperature. A patterning is possible by cold-plastic forming of the typically brittle Hf-based bulk amorphous alloy through controlling homogenous flow without the need for thermal energy or shaping at elevated temperatures. The experimental evidence suggests that there is an inconsistency between macroscopic plasticity and deformability of an amorphous alloy. Moreover, imprinting of specific geometrical features on Cu foil and Zr-based metallic glass is represented by using the patterned bulk amorphous alloy as a die. These results demonstrate the ability of amorphous alloys or metallic glasses to precisely replicate patterning features onto both conventional metals and the other amorphous alloys. Our work presents an avenue for avoiding the embrittlement of amorphous alloys associated with thermoplastic forming and yields new insight the forming application of bulk amorphous alloys at room temperature without using heat treatment. PMID:26563908

  9. Imprinting bulk amorphous alloy at room temperature

    SciTech Connect

    Kim, Song-Yi; Park, Eun-Soo; Ott, Ryan T.; Lograsso, Thomas A.; Huh, Moo-Young; Kim, Do-Hyang; Eckert, Jürgen; Lee, Min-Ha

    2015-11-13

    We present investigations on the plastic deformation behavior of a brittle bulk amorphous alloy by simple uniaxial compressive loading at room temperature. A patterning is possible by cold-plastic forming of the typically brittle Hf-based bulk amorphous alloy through controlling homogenous flow without the need for thermal energy or shaping at elevated temperatures. The experimental evidence suggests that there is an inconsistency between macroscopic plasticity and deformability of an amorphous alloy. Moreover, imprinting of specific geometrical features on Cu foil and Zr-based metallic glass is represented by using the patterned bulk amorphous alloy as a die. These results demonstrate the ability of amorphous alloys or metallic glasses to precisely replicate patterning features onto both conventional metals and the other amorphous alloys. In conclusion, our work presents an avenue for avoiding the embrittlement of amorphous alloys associated with thermoplastic forming and yields new insight the forming application of bulk amorphous alloys at room temperature without using heat treatment.

  10. Amorphous metal alloy

    DOEpatents

    Wang, R.; Merz, M.D.

    1980-04-09

    Amorphous metal alloys of the iron-chromium and nickel-chromium type have excellent corrosion resistance and high temperature stability and are suitable for use as a protective coating on less corrosion resistant substrates. The alloys are stabilized in the amorphous state by one or more elements of titanium, zirconium, hafnium, niobium, tantalum, molybdenum, and tungsten. The alloy is preferably prepared by sputter deposition.

  11. Deployable aerospace PV array based on amorphous silicon alloys

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

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

  12. Deployable aerospace PV array based on amorphous silicon alloys

    NASA Astrophysics Data System (ADS)

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

    1989-04-01

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

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

    SciTech Connect

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

    2007-08-10

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

  14. Nanocrystal dispersed amorphous alloys

    NASA Technical Reports Server (NTRS)

    Perepezko, John H. (Inventor); Allen, Donald R. (Inventor); Foley, James C. (Inventor)

    2001-01-01

    Compositions and methods for obtaining nanocrystal dispersed amorphous alloys are described. A composition includes an amorphous matrix forming element (e.g., Al or Fe); at least one transition metal element; and at least one crystallizing agent that is insoluble in the resulting amorphous matrix. During devitrification, the crystallizing agent causes the formation of a high density nanocrystal dispersion. The compositions and methods provide advantages in that materials with superior properties are provided.

  15. Microstructure Evaluation of Fe-BASED Amorphous Alloys Investigated by Doppler Broadening Positron Annihilation Technique

    NASA Astrophysics Data System (ADS)

    Lu, Wei; Huang, Ping; Wang, Yuxin; Yan, Biao

    2013-07-01

    Microstructure of Fe-based amorphous and nanocrystalline soft magnetic alloy has been investigated by X-ray diffraction (XRD), transmission electronic microscopy (TEM) and Doppler broadening positron annihilation technique (PAT). Doppler broadening measurement reveals that amorphous alloys (Finemet, Type I) which can form a nanocrystalline phase have more defects (free volume) than alloys (Metglas, Type II) which cannot form this microstructure. XRD and TEM characterization indicates that the nanocrystallization of amorphous Finemet alloy occurs at 460°C, where nanocrystallites of α-Fe with an average grain size of a few nanometers are formed in an amorphous matrix. With increasing annealing temperature up to 500°C, the average grain size increases up to around 12 nm. During the annealing of Finemet alloy, it has been demonstrated that positron annihilates in quenched-in defect, crystalline nanophase and amorphous-nanocrystalline interfaces. The change of line shape parameter S with annealing temperature in Finemet alloy is mainly due to the structural relaxation, the pre-nucleation of Cu nucleus and the nanocrystallization of α-Fe(Si) phase during annealing. This study throws new insights into positron behavior in the nanocrystallization of metallic glasses, especially in the presence of single or multiple nanophases embedded in the amorphous matrix.

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

    NASA Astrophysics Data System (ADS)

    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.

  17. Helium-3 behavior in some nickel-based amorphous alloys

    SciTech Connect

    Unlu, K.; Vincent, D.H. )

    1992-04-01

    In this paper, helium trapping and release are studied for the nickel-rich amorphous alloys Ni{sub 75.1}Cr{sub 14.0}P{sub 10.1}C{sub 0.08}, Ni{sub 63.5}Zr{sub 36.5}, and Ni{sub 87.7}P{sub 12.3}. Helium-3 is introduced into the samples by implantation at 150-kev energy. The depth distribution of the implanted helium is observed by neutron depth profiling employing he reaction {sup 3}He(n,p){sup 3}H. Two implantation doses are used: 1 {times} 10{sup 16} and 5 {times} 10{sup 16} {sup 3}He/cm{sup 2}. Both implantation doses were chosen to be low enough to avoid blistering or flaking of the surface of the samples. The helium release behavior of the samples is studied by taking depth profiles after each annealing stage. At the same time, electron diffraction is used on parallel samples to observe the microstructure of the samples as a function of annealing. The annealing sequence for each material is broken off when electron diffraction indicated the existence of relatively large crystals in a sample. Only a small fraction of the implanted helium is released in most cases, and a clear correlation between helium release and recrystallization can be found in only one case.

  18. Densification behavior, nanocrystallization, and mechanical properties of spark plasma sintered Fe-based bulk amorphous alloys

    NASA Astrophysics Data System (ADS)

    Singh, Ashish Kumar

    Fe-based amorphous alloys are gaining increasing attention due to their exceptional wear and corrosion resistance for potential structural applications. Two major challenges that are hindering the commercialization of these amorphous alloys are difficulty in processing of bulk shapes (diameter > 10 mm) and lack of ductility. Spark plasma sintering (SPS) is evolving as a promising technique for processing bulk shapes of amorphous and nanocrystalline materials. The objective of this work is to investigate densification behavior, nanocrystallization, and mechanical properties of SPS sintered Fe-based amorphous alloys of composition Fe48Cr15Mo14Y2C15B6. SPS processing was performed in three distinct temperature ranges of amorphous alloys: (a) below glass transition temperature (Tg), (b) between Tg and crystallization temperature (Tx), and (c) above Tx. Punch displacement data obtained during SPS sintering was correlated with the SPS processing parameters such as temperature, pressure, and sintering time. Powder rearrangement, plastic deformation below T g, and viscous flow of the material between Tg and Tx were observed as the main densification stages during SPS sintering. Micro-scale temperature distributions at the point of contact and macro-scale temperature distribution throughout the sample during SPS of amorphous alloys were modeled. The bulk amorphous alloys are expected to undergo structural relaxation and nanocrystallization during SPS sintering. X-ray diffraction (XRD), small angle neutron scattering (SANS), and transmission electron microscopy (TEM) was performed to investigate the evolution of nanocrystallites in SPS sintered Fe-based bulk amorphous alloys. The SANS analysis showed significant scattering for the samples sintered in the supercooled region indicating local structural and compositional changes with the profuse nucleation of nano-clusters (~4 nm). Compression tests and microhardness were performed on the samples sintered at different

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

    SciTech Connect

    Kaufman, L; Perepezko, J; Hildal, K

    2007-02-08

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

  20. Imprinting bulk amorphous alloy at room temperature

    DOE PAGES

    Kim, Song-Yi; Park, Eun-Soo; Ott, Ryan T.; ...

    2015-11-13

    We present investigations on the plastic deformation behavior of a brittle bulk amorphous alloy by simple uniaxial compressive loading at room temperature. A patterning is possible by cold-plastic forming of the typically brittle Hf-based bulk amorphous alloy through controlling homogenous flow without the need for thermal energy or shaping at elevated temperatures. The experimental evidence suggests that there is an inconsistency between macroscopic plasticity and deformability of an amorphous alloy. Moreover, imprinting of specific geometrical features on Cu foil and Zr-based metallic glass is represented by using the patterned bulk amorphous alloy as a die. These results demonstrate the abilitymore » of amorphous alloys or metallic glasses to precisely replicate patterning features onto both conventional metals and the other amorphous alloys. In conclusion, our work presents an avenue for avoiding the embrittlement of amorphous alloys associated with thermoplastic forming and yields new insight the forming application of bulk amorphous alloys at room temperature without using heat treatment.« less

  1. Industrial Environmental Testing of Coupons and Prototype Cylinders Coated With Iron-Based Amorphous Alloys

    SciTech Connect

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

    2007-03-06

    Iron-based amorphous alloys are desirable for many industrial applications due to their dual capacity to resist corrosion and wear. These alloys may also contain a significant amount of boron which makes them candidates for criticality control, for example, in high-level nuclear waste disposition applications. The Fe-based amorphous alloys can be produced in powder form and then deposited using a HVOF thermal spray process on any surface that needs to be protected. For the current testing coupons of 316L stainless steels were coated with the amorphous alloy SAM2X5 and then tested for corrosion resistance in the salt-fog chamber and in other industrial environments. Prototype cylinders were also prepared and environmentally tested. One cylinder was 30-inch diameter, 88-inch long, and 3/8-inch thick. The coating thickness was 0.015 to 0.019-inch thick. The cylinder was in good condition after the test. Along the body of the cylinder only two pinpoint spot sized signs of rust were seen. Test results will be compared with the behavior of witness materials under the same tested conditions.

  2. Effect of residual strain in Fe-based amorphous alloys on field induced magnetic anisotropy and domain structure

    NASA Astrophysics Data System (ADS)

    Azuma, Daichi; Hasegawa, Ryusuke; Saito, Shin; Takahashi, Migaku

    2013-05-01

    Field induced magnetic anisotropy in two Fe-based amorphous alloys with different saturation induction levels (1.56 T and 1.64 T) was investigated by varying magnetic field strength and annealing temperature and domain images were taken on these samples. Residual strain was evaluated by measuring coercivities of the materials after stress-relief annealing. These results are discussed, clarifying the difference between the two Fe-based amorphous alloys.

  3. Characterization Techniques for Amorphous Alloys

    NASA Astrophysics Data System (ADS)

    Carow-Watamura, U.; Louzguine, D. V.; Takeuchi, A.

    This document is part of Part 2 http://dx.doi.org/10.1007/9getType="URL"/> 'Systems from B-Be-Fe to Co-W-Zr' of Subvolume B 'Physical Properties of Ternary Amorphous Alloys' of Volume 37 'Phase Diagrams and Physical Properties of Nonequilibrium Alloys' of Landolt-Börnstein - Group III 'Condensed Matter'. It contains the Chapter '2 Characterization Techniques for Amorphous Alloys' with the content:

  4. Amorphous metal alloy and composite

    DOEpatents

    Wang, Rong; Merz, Martin D.

    1985-01-01

    Amorphous metal alloys of the iron-chromium and nickel-chromium type have excellent corrosion resistance and high temperature stability and are suitable for use as a protective coating on less corrosion resistant substrates. The alloys are stabilized in the amorphous state by one or more elements of titanium, zirconium, hafnium, niobium, tantalum, molybdenum, and tungsten. The alloy is preferably prepared by sputter deposition.

  5. Effect of chromium and phosphorus on the physical properties of iron and titanium-based amorphous metallic alloy films

    NASA Technical Reports Server (NTRS)

    Distefano, S.; Rameshan, R.; Fitzgerald, D. J.

    1991-01-01

    Amorphous iron and titanium-based alloys containing various amounts of chromium, phosphorus, and boron exhibit high corrosion resistance. Some physical properties of Fe and Ti-based metallic alloy films deposited on a glass substrate by a dc-magnetron sputtering technique are reported. The films were characterized using differential scanning calorimetry, stress analysis, SEM, XRD, SIMS, electron microprobe, and potentiodynamic polarization techniques.

  6. Laser Processing of Fe-Based Bulk Amorphous Alloy Coatings on Titanium

    NASA Astrophysics Data System (ADS)

    Sahasrabudhe, Himanshu; Dittrick, Stanley A.; Bandyopadhyay, Amit

    2013-11-01

    Laser Engineered Net Shaping (LENS™), a solid freeform fabrication technique, was employed for the processing of Fe-based bulk amorphous alloy (Fe BAA) powder on titanium. One and two layers of the Fe BAA were deposited with the same processing parameters. SEM and XRD analyses of the Fe BAA coatings revealed the retention of the feedstock powder's amorphous nature. The mixing of the feedstock powder in the titanium substrate was very small. A crystalline-amorphous composite microstructure evolved from the laser processing in all types of coatings. The coatings were further laser remelted. The amorphous character was found to increase and the crystallites were found to grow during remelting. The Fe BAA coatings showed higher hardness and smaller wear volume compared to the Ti substrate. A further increase in these properties was observed after laser remelting treatment. During the wear testing in NaCl solution, Ti substrate showed intergranular corrosion, whereas the Fe BAA coatings showed signs of low and localized fretting corrosion in a saline environment. Our results demonstrate that using LENS™, amorphous coatings can be deposited on metallic substrates.

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

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

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

  8. Optical properties of surface layers of Co-based amorphous metallic alloys

    NASA Astrophysics Data System (ADS)

    Poperenko, L. V.; Kravets, V. G.; Lysenko, S. I.; Vinnichenko, K. L.

    2005-04-01

    The modification of roughness and structure of the surface layers of a cobalt-based amorphous metal alloy after thermal treatment at elevated and cryogenic temperatures and under the influence of an external magnetic field is studied by light scattering and atomic force microscopy. The parameters of the surface roughness were calculated from the measured indicatrices of light scattering. It is shown that heating of the metal ribbons to T=350-475 °C partially relieves stresses arising in the course of the ribbon preparation and increases the surface roughness compared to freshly prepared samples.

  9. In-Situ Fracture Observation and Fracture Toughness Analysis of Zr-Based Amorphous Alloys Containing Ductile Dendrites

    NASA Astrophysics Data System (ADS)

    Jeon, Changwoo; Kim, Choongnyun Paul; Lee, Sunghak

    2012-10-01

    Effects of dendrite size on fracture properties of Zr-based amorphous alloys containing ductile β dendrites were explained by directly observing microfracture processes using an in-situ loading stage installed inside a scanning electron microscope (SEM) chamber. Three amorphous alloy plates having different thicknesses were fabricated by varying cooling rates after vacuum arc melting. The effective size of β dendrites was varied from 14.7 to 30.1 μm in the alloy plates, while their volume fraction was almost constant. According to microfracture observation of the alloy containing fine β dendrites, shear bands initiated at the amorphous matrix were connected with the notch tip as they were deepened through dendrites, which led to abrupt crack propagation. In the alloy containing coarser β dendrites, shear bands were initiated at the amorphous matrix to form a crack near the notch tip region and were expanded over large matrix areas. The crack propagation was frequently blocked by β dendrites, and many shear bands are formed near or in front of the propagating crack, thereby resulting in stable crack growth, which could be confirmed by the fracture resistance curve ( R-curve) behavior. This increase in fracture resistance with increasing crack length could be explained by mechanisms of blocking of crack growth, multiple shear band formation, and crack blunting.

  10. Fe-based bulk amorphous alloys with iron contents as high as 82 at%

    NASA Astrophysics Data System (ADS)

    Li, Jin-Feng; Liu, Xue; Zhao, Shao-Fan; Ding, Hong-Yu; Yao, Ke-Fu

    2015-07-01

    Fe-based bulk amorphous alloys (BAAs) with high Fe contents are advantageous due to their high saturation magnetization and low cost. However, preparing Fe-based BAAs with Fe contents higher than 80 at% is difficult due to their poor glass forming abilities (GFA). In this study, an Fe81P8.5C5.5B2Si3 BAA with a diameter of 1 mm and a saturation magnetization of 1.56 T was successfully prepared using the fluxing and copper mold casting methods. In addition, by introducing a small amount of elemental Mo to the alloy, an Fe82Mo1P6.5C5.5B2Si3 BAA rod with a diameter of 1 mm, a high saturation magnetization of 1.59 T, a high yield stress of 3265 MPa, and a clear plasticity of 1.3% was prepared in the same way. The cost effectiveness and good magnetic properties of these newly-developed Fe-based BAAs with Fe contents as high as 82 at% would be advantageous and promising for industrial applications.

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

    SciTech Connect

    Kalay, Yunus Eren

    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

  12. Investigation on the crystallization mechanism difference between FINEMET and NANOMET type Fe-based soft magnetic amorphous alloys

    NASA Astrophysics Data System (ADS)

    Wang, Yaocen; Zhang, Yan; Takeuchi, Akira; Makino, Akihiro; Kawazoe, Yoshiyuki

    2016-10-01

    In this article, the atomic behaviors of Nb and P in Fe-based amorphous alloys during nano-crystallization process were studied by the combination of ab initio molecular dynamics simulations and experimental measurements. The inclusion of Nb is found to be tightly bonded with B, resulting in the formation of diffusion barrier that could prevent the over-growth of α-(Fe, Si) grains and the promotion of larger amount of α-(Fe, Si) participation. The P inclusion could delay the diffusion of the metalloids that have to be expelled from the α-(Fe, Si) crystallization region so that the grain growth could be reduced with fast but practically achievable heating rates. The combined addition of P and Nb in high Fe content amorphous alloys failed in exhibiting the potential of good magnetic softness with slow heating (10 K/min) annealing at various temperatures. The sample with optimum crystallization process with confined grain size was annealed at 653 K, with the grain size of 31 nm and a coercivity of ˜120 A/m, much too large to meet the application requirements and to be compared with the currently well-studied alloy systems. This attempt suggests that the inclusion of early transition metal elements might not be effective enough to suppress grain growth in crystallizing high Fe content amorphous alloys.

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

    SciTech Connect

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  15. Spall Fracture Morphologies and Mechanisms of Zr-based Bulk Amorphous Alloys

    NASA Astrophysics Data System (ADS)

    Gupta, Y. M.; Escobedo, J. P.

    2011-06-01

    Plate impact experiments were conducted to examine the dynamic tensile response of Zr-based bulk amorphous alloys (BAAs). Tensile loading was preceded by elastic compressive loading (3.6 to 6.0 GPa). Microscopy results revealed that the BAA samples exhibit brittle behavior (glass like) macroscopically and ductile behavior (metal like) microscopically; corrugations and bumps are observed at the nanoscale. The observed fracture morphologies are related to three key features of our spall experiments and the free volume content of the BAAs. With increasing compressive stress, the available free volume decreases causing a suppression of shear stresses during tension, resulting in brittle cleavage at higher stresses. The high tensile loading rate likely causes cracking by multiple shear band propagation and interception, rendering a serrated surface morphology. Finally, the corrugations are likely created due to a succession of arrest and propagation of mode I cracks. A subsequent dilatation, an effect of the tensile mean stress, caused the corrugations to evolve to bump-type features (10-100 nm). Work supported by DOE/NNSA.

  16. Test environments and mechanical properties of Zr-base bulk amorphous alloys

    SciTech Connect

    Liu, C.T.; Heatherly, L.; Easton, D.S.

    1998-07-01

    The mechanical properties of two Zr-base bulk amorphous alloys (BAA), Zr-10Al-30Cu-5Ni (BAA-10) and Zr-10Al-5Ti-17.9Cu-14.6Ni (BAA-11), were studied by both tensile and compressive tests at room temperature in various test environments. The BAA ingots up to 7 mm in diameter were successfully produced by both arc melting and drop casting and induction melting and injection casting. The BAA specimens deformed mainly elastically, followed by catastrophic failure along shear bands. Examination of the fracture region revealed ductile fracture features resulting from a substantial increase in temperature, which was attributable to the conversion of the stored elastic strain energy to heat. Surprisingly, liquid droplets located at major shear-band cracks adjacent to the fracture section were observed, indicating the occurrence of local melting during fracture. The angle orientation of shear bands, shear-band cracks, and fracture surfaces relative to the stress axis is quite different for BAA specimens tested in tension and compression. This suggests that both shear stress and normal stress may play a role in developing shear bands during plastic deformation. The tensile properties of BAAs were found to be insensitive to the test environment at room temperature. However, the reaction of BAAs with distilled water and heavy water was detected by laser desorption mass spectrometry (LDMS). These results suggest that moisture-induced hydrogen embrittlement in BAAs may be masked by catastrophic fracture following shear bands.

  17. Effects of Changes in Chemistry on Flex Bending Fatigue Behavior of Al-Based Amorphous Alloy Ribbons

    NASA Astrophysics Data System (ADS)

    Huang, Chun-Kuo; Lewandowski, John J.

    2012-08-01

    The effects of changes in composition on the flow behavior and flex bending fatigue behavior of a series of Al-Gd-Ni- X ( X = Fe or Co) amorphous alloy ribbons have been determined at 1 Hz at room temperature. It has been shown that the addition of Fe, Co, and Fe/Co combination into these materials increases the strength, T g, and T x1 in addition to the activation energy for crystallization. The lowest strength ( i.e., 880 MPa) base alloy Al87Gd6Ni7 exhibited the best low-cycle fatigue (LCF) and worst high-cycle fatigue (HCF) behavior, whereas the higher strength alloys (~1100 MPa) Al85Gd6Ni7Fe2 and Al85Gd6Ni7Fe1Co1 exhibited worse LCF and better HCF behavior. The ratio of the stress amplitude at the fatigue limit at 1 × 106 cycles to uniaxial failure strength ranged from 0.25 to 0.37 (240 to 397 MPa), much higher than conventional aluminum alloys. These results are also compared with those obtained on other amorphous alloy ribbons.

  18. Thick amorphous hums of Ni base alloys using high energy (MeV) ion beam mixing

    NASA Astrophysics Data System (ADS)

    Bhattacharya, R. S.; Pronko, P. P.; Rai, A. K.; McCormick, A. W.; Raffoul, C.

    1985-03-01

    This work investigates the potential for applying ion beam mixing techniques to the fabrication of amorphous metallic alloy coatings of MoNi and TiNi on metal substrates to improve their corrosion resistant properties. Alternating layers of 100 Å Mo and 70 Å Ni with total thicknesses of 1450 Å and 2900 Å were prepared by e-beam evaporation on Ni substrates. Similarly, 80 A Ti and 50 Å Ni alternate layers with total thicknesses of 900 Å and 1560 Å were deposited on Ni. A batch of alternating films of total thickness 5200 Å of TiNi with individual thicknesses of 160 Å Ti and 100 Å Ni were also prepared on Ni substrates. The thicknesses of individual films were adjusted in this way to obtain an overall composition of Ni 50Mo 50 and Ni 50Ti 50 after mixing. The films were irradiated with 1 and 2 MeV Au + and 1.5 MeV Ni + ions depending on the total thickness. The ion beam mixing and nucrostructure of these films have been studied as a function of dose using RBS and TEM. Amorphous layers have been tested for their corrosion behavior by potentiodynamic polarization techniques. Measurements carried out in nitric acid solution reveal that both NiMo and NiTi amorphous layers are more resistant to corrosive attack than the polycrystalline multiphased alloys. NiTi exhibited much superior corrosion resistant properties than NiMo.

  19. Effects of graphene/silver nanohybrid additives on electrochemical properties of magnesium-based amorphous alloy

    NASA Astrophysics Data System (ADS)

    Lin-jun, Huang; Yan-xin, Wang; Zhen, Huang; Jian-guo, Tang; Yao, Wang; Ji-xian, Liu; Ji-qing, Jiao; Jing-quan, Liu; Belfiore, Laurence A.

    2014-12-01

    Amorphous Mg-Ni-La alloys for hydrogen storage are prepared by rapid solidification. Ag nanoparticles have been deposited onto graphene sheets to form graphene/Ag (G/A) nanocomposite through solvothermal method using ethylene glycol as solvent and reducing agent. The effects of surface modification of amorphous Mg-Ni-La alloy by introduction of different contents of G/A are systematically investigated by XRD, FT-IR, SEM, TEM and conventional electrochemical tests. The results show that the discharge capacity, cycle life, discharge potential characteristics and electrochemical kinetics of the electrodes are all improved. The surface modification enhances the electrocatalytic activity of the alloy and reduces the contact resistance of the electrodes. The Mg65Ni27La8 with 20 wt.% G/A electrode has the largest discharge capacity of 814.8 mAh g-1, which is 1.33 times that of the electrode without G/A, and the best electrochemical kinetics. Further increasing of G/A content will lead to the increase of contact resistance of the electrode, resulting in the degradation of electrode performance.

  20. Dynamic tensile response of Zr-based bulk amorphous alloys: Fracture morphologies and mechanisms

    NASA Astrophysics Data System (ADS)

    Escobedo, J. P.; Gupta, Y. M.

    2010-06-01

    Plate impact experiments were conducted to examine the dynamic tensile response of Zr-based bulk amorphous alloys (BAAs) having a nominal composition of Zr56.7Cu15.3Ni12.5Nb5.0Al10.0Y0.5. The experimental configuration used in our work permitted soft recovery of the samples to allow a careful examination of the fractured samples along with real-time measurements of the sample free-surface velocity (FSV) histories. Tensile loading was preceded by elastic compressive loading to peak stresses in the 3.6 to 6.0 GPa range. Tensile damage in the recovered samples was examined using optical and electron microscopy. The microscopy results showed that the BAA samples exhibit a brittle behavior (as a glass) at the macroscopic level and a ductile behavior (as a metal) at the microscopic level; in addition, corrugations and bumps are observed at the nanoscale. The observed fracture morphologies are related to three key features present in our spall experiments: preceding compressive stress (3.6-6.0 GPa), high tensile loading rate (˜106/s), high mean tensile stress (˜2.3 GPa); and are intrinsically related to the amorphous glassy structure of the BAAs (free volume content). We propose that the compressive stress depletes the free volume content. With increasing compressive stress, the available free volume decreases causing a suppression of shear stresses during tension. Thus, the mean tensile component becomes more dominant at higher stresses. Consequently, the observed surface morphology results from brittle cleavage, causing an increased damage localization in the recovered samples spalled at higher stresses. These observations support the inferences made from measurements of FSV histories. The high tensile loading rate is proposed to be responsible for cracking by multiple shear band propagation and interception, rendering the observed serrated surface morphology. Finally, we proposed that the corrugations are created due to a succession of arrest and propagation of mode

  1. Characterization of oxide layers on amorphous Mg-based alloys by Auger electron spectroscopy with sputter depth profiling.

    PubMed

    Baunack, S; Subba Rao, R V; Wolff, U

    2003-04-01

    Amorphous ribbons of Mg-Y-TM-[Ag] (TM: Cu, Ni), prepared by melt spinning, were subjected to electrochemical investigations. Oxide layers formed anodically under potentiostatic control in different electrolytes were investigated by AES and sputter depth profiling. Problems and specific features of characterization of the composition of oxide layers and amorphous ternary or quaternary Mg-based alloys have been investigated. In the alloys the Mg(KL(23)L(23)) peak exhibits a different shape compared to that in the pure element. Analysis of the peak of elastically scattered electrons proved the absence of plasmon loss features, characteristic of pure Mg, in the alloy. A different loss feature emerges in Mg(KL(23)L(23)) and Cu(L(23)VV). The system Mg-Y-TM-[Ag] suffers preferential sputtering. Depletion of Mg and enrichment of TM and Y are found. This is attributed mainly to the preferential sputtering of Mg. Thickness and composition of the formed oxide layer depend on the electrochemical treatment. After removing the oxide by sputtering the concentration of the underlying alloy was found to be affected by the treatment.

  2. Interpretation of Fracture Toughness and R-Curve Behavior by Direct Observation of Microfracture Process in Ti-Based Dendrite-Containing Amorphous Alloys

    NASA Astrophysics Data System (ADS)

    Jeon, Changwoo; Kim, Choongnyun Paul; Kim, Hyoung Seop; Lee, Sunghak

    2015-04-01

    Fracture properties of Ti-based amorphous alloys containing ductile β dendrites were explained by directly observing microfracture processes. Three Ti-based amorphous alloys were fabricated by adding Ti, Zr, V, Ni, Al, and Be into a Ti-6Al-4V alloy by a vacuum arc melting method. The effective sizes of dendrites varied from 63 to 104 μm, while their volume fractions were almost constant within the range from 74 to 76 pct. The observation of the microfracture of the alloy containing coarse dendrites revealed that a microcrack initiated at the amorphous matrix of the notch tip and propagated along the amorphous matrix. In the alloy containing fine dendrites, the crack propagation was frequently blocked by dendrites, and many deformation bands were formed near or in front of the propagating crack, thereby resulting in a zig-zag fracture path. Crack initiation toughness was almost the same at 35 to 36 MPa√m within error ranges in the three alloys because it was heavily affected by the stress applied to the specimen at the time of crack initiation at the crack tip as well as strength levels of the alloys. According to the R-curve behavior, however, the best overall fracture properties in the alloy containing fine dendrites were explained by mechanisms of blocking of the crack growth and crack blunting and deformation band formation at dendrites.

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

    NASA Astrophysics Data System (ADS)

    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.

  4. Study of the effects of metalloid elements (P, C, B) on Fe-based amorphous alloys by ab initio molecular dynamics simulations

    SciTech Connect

    Zhang, Wenbiao; Li, Qiang E-mail: dhm@xju.edu.cn; Duan, Haiming E-mail: dhm@xju.edu.cn

    2015-03-14

    In order to understand the effects of the metalloid elements M (M: P, C, B) on the atomic structure, glass formation ability (GFA) and magnetic properties of Fe-based amorphous alloys, Fe{sub 80}P{sub 13}C{sub 7}, Fe{sub 80}P{sub 14}B{sub 6} and Fe{sub 80}B{sub 14}C{sub 6} amorphous alloys are chosen to study through first-principle simulations in the present work. The atomic structure characteristic of the three amorphous alloys is investigated through the pair distribution functions (PDFs) and Voronoi Polyhedra (VPs) analyses. The PDFs and VPs analyses suggest that the GFA of the three alloys dropped in the order of Fe{sub 80}P{sub 13}C{sub 7}, Fe{sub 80}P{sub 14}B{sub 6}, and Fe{sub 80}B{sub 14}C{sub 6}, which is well consistent with the experimental results. The density of state (DOS) of the three amorphous alloys is calculated to investigate their magnetic properties. Based on the DOS analysis, the average magnetic moment of Fe atom in Fe{sub 80}P{sub 13}C{sub 7} and Fe{sub 80}P{sub 14}B{sub 6} amorphous alloys can be estimated to be 1.71 μ{sub B} and 1.70 μ{sub B}, respectively, which are in acceptable agreement with the experimental results. However, the calculated average magnetic moment of Fe atom in Fe{sub 80}B{sub 14}C{sub 6} amorphous alloy is about 1.62 μ{sub B}, which is far less than the experimental result.

  5. Plasma deposition of amorphous metal alloys

    DOEpatents

    Hays, Auda K.

    1986-01-01

    Amorphous metal alloy coatings are plasma-deposited by dissociation of vapors of organometallic compounds and metalloid hydrides in the presence of a reducing gas, using a glow discharge. Tetracarbonylnickel, phosphine, and hydrogen constitute a typical reaction mixture of the invention, yielding a NiPC alloy.

  6. Plasma deposition of amorphous metal alloys

    DOEpatents

    Hays, A.K.

    1979-07-18

    Amorphous metal alloy coatings are plasma-deposited by dissociation of vapors of organometallic compounds and metalloid hydrides in the presence of a reducing gas, using a glow discharge. Tetracarbonylnickel, phosphine, and hydrogen constitute a typical reaction mixture of the invention, yielding a NiPC alloy.

  7. Effect of chromium and phosphorus on the physical properties of iron and titanium-based amorphous metallic alloy films. [FEPC; TIPC; TIBC; CR

    SciTech Connect

    DiStefano, S.; Ramesham, R.; Fitzgerald, D.J. )

    1991-07-01

    Amorphous iron and titanium-based alloys containing various amounts of chromium, phosphorus, and boron exhibit high corrosion resistance. We report some physical properties of Fe and Ti-based metallic alloy films deposited on a glass substrate by a dc-magnetron sputtering technique. The films were characterized using differential scanning calorimetry (DSC), stress analysis, scanning electron microscopy (SEM), x-ray diffraction (XRD), secondary ion mass spectrometry (SIMS), electron microprobe, and potentiodynamic polarization technique.

  8. Annealing behavior of high permeability amorphous alloys

    SciTech Connect

    Rabenberg, L.

    1980-06-01

    Effects of low temperature annealing on the magnetic properties of the amorphous alloy Co/sub 71/ /sub 4/Fe/sub 4/ /sub 6/Si/sub 9/ /sub 6/B/sub 14/ /sub 4/ were investigated. Annealing this alloy below 400/sup 0/C results in magnetic hardening; annealing above 400/sup 0/C but below the crystallization temperature results in magnetic softening. Above the crystallization temperature the alloy hardens drastically and irreversibly. Conventional and high resolution transmission electron microscopy were used to show that the magnetic property changes at low temperatures occur while the alloy is truly amorphous. By imaging the magnetic microstructures, Lorentz electron microscopy has been able to detect the presence of microscopic inhomogeneities in this alloy. The low temperature annealing behavior of this alloy has been explained in terms of atomic pair ordering in the presence of the internal molecular field. Lorentz electron microscopy has been used to confirm this explanation.

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

    SciTech Connect

    Babilas, Rafał

    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.

  10. Development of radiation detectors based on hydrogenated amorphous silicon and its alloys

    SciTech Connect

    Hong, Wan-Shick

    1995-04-01

    Hydrogenated amorphous silicon and related materials have been applied to radiation detectors, utilizing their good radiation resistance and the feasibility of making deposits over a large area at low cost. Effects of deposition parameters on various material properties of a-Si:H have been studied to produce a material satisfying the requirements for specific detection application. Thick(-~50 μm), device quality a-Si:H p-i-n diodes for direct detection of minimum ionizing particles have been prepared with low internal stress by a combination of low temperature growth, He-dilution of silane, and post annealing. The structure of the new film contained voids and tiny crystalline inclusions and was different from the one observed in conventional a-Si:H. Deposition on patterned substrates was attempted as an alternative to controlling deposition parameters to minimize substrate bending and delamination of thick a-Si:H films. Growth on an inversed-pyramid pattern reduced the substrate bending by a factor of 3 ≈ 4 for the same thickness film. Thin (0.1 ≈ 0.2 μm) films of a-Si:H and a-SiC:H have been applied to microstrip gas chambers to control gain instabilities due to charges on the substrate. Light sensitivity of the a-Si:H sheet resistance was minimized and the surface resistivity was successfully` controlled in the range of 1012 ≈ 1017 Ω/(four gradient) by carbon alloying and boron doping. Performance of the detectors with boron-doped a-Si:C:H layers was comparable to that of electronic-conducting glass. Hydrogen dilution of silane has been explored to improve electrical transport properties of a-Si:H material for high speed photo-detectors and TFT applications.

  11. Computer-assisted infrared spectra interpretation for amorphous silicon alloys

    NASA Astrophysics Data System (ADS)

    Kavak, Hamide; Esen, Ramazan

    2005-12-01

    A computer program for the structural interpretation of the infrared (IR) spectra is developed and tested. The interpretation of the IR spectra is made by using an hybrid system which includes library search and rule-based interpretation methods together. The computer programs were written in Pascal Codes. The prototype IR library of silicon alloys includes amorphous silicon (a-Si), amorphous silicon dioxide (a-SiOx), amorphous silicon nitride (a-Si3N4) and amorphous silicon carbide (a-SiC) references. The known spectra of these compounds were fed into the system as an unknown samples. The performance of the developed program was evaluated on a test set of 157 spectra and the percentages of successful identification ranged between 78% and 99% for different alloys.

  12. The thermal stability of amorphous nickel-niobium alloys

    SciTech Connect

    Farrens, S.N.

    1989-01-01

    Amorphous metallic alloys have been found to have features that make them exciting candidate materials for the electron device industry. Some of these features include resistance to electromigration and interdiffusion with other component materials. These features are primarily the result of the absence of grain boundaries in the amorphous alloy. However, if these materials are to be used in devices exposed to elevated temperatures it is important to understand the thermal stability of the amorphous alloy. The thermal stability of amorphous nickel niobium alloys was investigated in this work. The assessment of thermal performance was based on crystallization temperature, diffusion properties, and interface stability of the amorphous alloys with metallic overlayers and silicon substrates. Thermal treatments spanned the temperature range from 400{degree}C to 850{degree}C for times of 5 minutes to 96 hours. The primary experimental methods included x-ray diffraction, Rutherford backscattering spectroscopy, and electron microscopy. The alloys studied had compositions of 60, 65, 70 and 75 atomic percent nickel and are listed in order of their thermal stability. The 60 at% alloys have the highest one hour crystallization temperatures of 700{degree}C. All alloys are very stable until crystallization occurs. This is evidenced by the sluggish diffusion rates (10{sup {minus}19} cm{sup 2}/sec) measured at the overlayer/glass interface. Similarly, substrate interactions are not observed until crystallization has began. Once the grain boundaries develop with the initiation of crystallization interdiffusion of Ni and Si proceeds and eventual silicide formation is observed. Combining the results of the silicide reaction kinetics and the x-ray diffraction data allowed the estimation of the time-temperature-transformation curve.

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

    NASA Astrophysics Data System (ADS)

    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.

  14. Newtonian Flow in Bulk Amorphous Alloys

    SciTech Connect

    Wadsworth, J.; Nieh, T.G.

    2000-09-27

    Bulk amorphous alloys have many unique properties, e.g., superior strength and hardness, excellent corrosion resistance, reduced sliding friction and improved wear resistance, and easy formability in a viscous state. These properties, and particularly easy formability, are expected to lead to applications in the fields of near-net-shape fabrication of structural components. Whereas large tensile ductility has generally been observed in the supercooled liquid region in metallic glasses, the exact deformation mechanism, and in particular whether such alloys deform by Newtonian viscous flow, remains a controversial issue. In this paper, existing data are analyzed and an interpretation for the apparent controversy is offered. In addition, new results obtained from an amorphous alloy (composition: Zr-10Al-5TI-17.9Cu-14.6Ni, in at. %) are presented. Structural evolution during plastic deformation is particularly characterized. It is suggested that the appearance of non-Newtonian behavior is a result of the concurrent crystallization of the amorphous structure during deformation.

  15. Initial stage densification during spark plasma sintering of Fe-based amorphous alloy powder: Analysis of viscous flow

    NASA Astrophysics Data System (ADS)

    Paul, Tanaji; Harimkar, Sandip P.

    2016-10-01

    Understanding the mechanism of densification of amorphous alloy powders is important for determining the parameters during sintering of these materials. In this paper, we report on the analysis of densification of Fe48Cr15Mo14Y2C15B6 amorphous alloy powder during spark plasma sintering. Sintering up to 1000 °C resulted in two clearly distinguishable stages of densification: stage I from 320 °C to 740 °C and stage II from 830 °C to 1000 °C. The maximum densification rate during stage I was attained at 585 °C up to which the sample remained fully amorphous. During the entire stage II, the sample was fully crystalline, and the maximum densification rate attained at 935 °C was much lower than that observed during stage I. Viscous flow during stage I was analyzed, yielding an estimate of the activation energy to be 94.0 ± 0.2 kJ mol-1 in the temperature range from 525 °C to 580 °C.

  16. Multiple cell photoresponsive amorphous alloys and devices

    SciTech Connect

    Ovshinsky, S.R.; Adler, D.

    1990-01-02

    This patent describes an improved photoresponsive tandem multiple solar cell device. The device comprising: at least a first and second superimposed cell of various materials. The first cell being formed of a silicon alloy material. The second cell including an amorphous silicon alloy semiconductor cell body having an active photoresponsive region in which radiation can impinge to produce charge carriers, the amorphous cell body including at least one density of states reducing element. The element being fluorine. The amorphous cell body further including a band gap adjusting element therein at least in the photoresponsive region to enhance the radiation absorption thereof, the adjusting element being germanium: the second cell being a multi-layer body having deposited semiconductor layers of opposite (p and n) conductivity type; and the first cell being formed with the second cell in substantially direct Junction contact therebetween. The first and second cells designed to generate substantially matched currents from each cell from a light source directed through the first cell and into the second cell.

  17. Research of creep deformation in amorphous and nanocrystalline alloys at variable temperature field

    NASA Astrophysics Data System (ADS)

    Fedorov, V. A.; Berezner, A. D.; Pluzhnikova, T. N.

    2017-01-01

    Investigations of Co-based amorphous alloys and Fe-based nanocrystalline alloy failure strain at creep tests within a temperature range being from 300 to 1023 K have been performed. A creep curve analytical form for all investigated alloys has been established.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  19. XRD technique: a way to discriminate structural changes in iron-based amorphous materials [An Alternative Method of Synthesizing Iron-based Amorphous Alloys

    SciTech Connect

    Saw, Cheng K.; Day, Dan; Farmer, Joe C.; Bauer, William

    2008-02-06

    Prevention of corrosion is a vital goal for the Department of Defense when billions of dollars are spent every year. Corrosion resistant materials have applications in all sort of military vehicles, and more importantly in naval vessels and submarines which come in contact with the seawater. It is known that corrosion resistance property can be improved by the used of structurally designed materials in the amorphous state where the atoms are arranged in a non-periodic fashion and specific atoms, tailored to the required properties can be interjected into the matrix for specific application. The XRD techniques reported here is to demonstrate the optimal conditions for characterization of these materials. The samples, which normally contain different compositions of Fe, Cr, B, Mo, Y, Mn, Si and W, are in the form of powders, ribbons and coatings. These results will be compared for the different forms of the sample which appears to correlate to the cooling rate during sample processing. In most cases, the materials are amorphous or amorphous with very small amount of crystallinity. In the ribbon samples for different compositions we observed that the materials are essentially amorphous. In most cases, starting from an amorphous powder sample, the coatings are also observed to be amorphous with a small amount of iron oxide on the surface, probably due to exposure to air.

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

    NASA Astrophysics Data System (ADS)

    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.

  1. Amorphous Alloy Surpasses Steel and Titanium

    NASA Technical Reports Server (NTRS)

    2004-01-01

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

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

    SciTech Connect

    Ghafari, M. E-mail: skamali@utsi.edu; Gleiter, H.; Sakurai, Y.; Itou, M.; Peng, G.; Fang, Y. N.; Feng, T.; Hahn, H.; Kamali, S. E-mail: skamali@utsi.edu

    2015-09-28

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

  3. Time of isothermal holding in the course of in-air heat treatment of soft magnetic Fe-based amorphous alloys and their magnetic properties

    NASA Astrophysics Data System (ADS)

    Skulkina, N. A.; Ivanov, O. A.; Pavlova, I. O.; Minina, O. A.

    2011-12-01

    On the example of soft magnetic Fe81B13Si4C2 and Fe77Ni1Si9B13 amorphous alloys, the relation between the level of magnetic properties and duration of isothermal holding in the course of heat treatment in air has been studied. The optimum temperature-dependent time τ of isothermal holding has been shown to be related to the volume fraction of domains ( V orth) with orthogonal magnetization in the initial (quenched) ribbon by equation V orth = ττ1/3. A temperature dependence of the proportionality coefficient α, which determines the degree of diffusion-process activity, has been determined. The results obtained allow us to substantially simplify the choice of optimum conditions of atmospheric heat treatment of soft magnetic Fe-based amorphous ribbons.

  4. Glass formation and magnetic properties in the Co and Fe-based amorphous alloy with small Mo or Nb additions

    NASA Astrophysics Data System (ADS)

    Jo, Hye-In; Choi-Yim, Haein

    2012-02-01

    The ferromagnetic metallic glass alloys in the Co-Fe-B-Si-M (M = Mo or Nb) system were investigated. Ingots of [(Co1- x Fe x )0.75B0.2Si0.05]96Mo4 ( x = 0, 0.2, 0.5, 0.8, 1.0) and [(Co1- x Fe x )0.75 B0.2Si0.05]96Nb4 ( x = 0, 0.2, 0.5, 0.8, 1.0) alloys were cast into about 30 µm-thick ribbons by using a melt spinning method. As-spun ribbons were identified as being fully amorphous by using X-ray diffraction (XRD). The thermal stability parameters, such as the supercooled liquid region (Δ T x = T g - T x ) and the exothermic heat (Δ H Exo ), were measured by using differential scanning calorimetry (DSC). For Co-Fe-B-Si-Mo alloys, Δ T x and Δ H Exo were in the range of 41.4-81.7 K and 23.40-104.21 J/g, and for Co-Fe-B-Si-Nb alloys, Δ T x and Δ H Exo were in the range of 60.4-88.0 K and 18.45-62.05 J/g, respectively. These glassy ribbons also exhibited semi-hard magnetic properties, i.e., a coercive force ( H c ) of 67.26-100.68 Oe and a saturation magnetization ( M s ) of 341.288-746.176 emu·cm3.

  5. Unusual Thermal Stability of High-Entropy Alloy Amorphous Structure

    DTIC Science & Technology

    2012-06-20

    1    REPORT Unusual Thermal Stability of High - Entropy Alloy Amorphous Structure Basic research for AOARD 114009 Award No. FA2386-11-1...stability of high - entropy alloy amorphous structure 5a. CONTRACT NUMBER FA23861114009 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Jien-Wei...at least 3 h. If substrate effect could be eliminated, the crystallization temperature would be higher. 15. SUBJECT TERMS high entropy alloys 16

  6. GMI field sensitivity near a zero external field in Co-based amorphous alloy ribbons: experiments and model

    NASA Astrophysics Data System (ADS)

    Zhao, Chenbo; Zhang, Xinlei; Liu, Qingfang; Wang, Jianbo

    2016-02-01

    The giant magnetoimpedance (GMI) effect in Co66Fe4Ni1Si15B14 amorphous ribbons was investigated, and the obvious blunt peaks of GMI curves were observed in a weak external magnetic field (0~3 Oe). The shape of the blunt peaks could be changed by different treatments, such as changing the aspect ratio of the ribbons, premagnetization before magnetoimpedance measurement, and rapid heat-treatment, and the GMI sensitivity is improved. Based on the experimental results, a model in view of magnetostrictive energy is proposed to analyze the bluntness of the peak of the GMI curve and the process of transverse permeability varying with the external field near zero-field in the Co-based amorphous ribbons, and all the experimental results have good agreement with our model.

  7. Comparison of high temperature, high frequency core loss and dynamic B-H loops of two 50 Ni-Fe crystalline alloys and an iron-based amorphous alloy

    NASA Technical Reports Server (NTRS)

    Wieserman, W. R.; Schwarze, G. E.; Niedra, J. M.

    1991-01-01

    The availability of experimental data that characterizes the performance of soft magnetic materials for the combined conditions of high temperature and high frequency is almost nonexistent. An experimental investigation was conducted over the temperature range of 23 to 300 C and frequency range of 1 to 50 kHz to determine the effects of temperature and frequency on the core loss and dynamic B-H loops of three different soft magnetic materials; and oriented grain 50Ni-50Fe alloy, a nonoriented grain 50Ni-Fe alloy, and an iron based amorphous material (Metglas 2605SC). A comparison of these materials shows that the nonoriented grain 50Ni-50Fe alloy tends to have either the lowest or next lowest core loss for all temperatures and frequencies investigated.

  8. High-Velocity Oxygen Fuel Thermal Spray of Fe-Based Amorphous Alloy: a Numerical and Experimental Study

    NASA Astrophysics Data System (ADS)

    Ajdelsztajn, L.; Dannenberg, J.; Lopez, J.; Yang, N.; Farmer, J.; Lavernia, E. J.

    2009-09-01

    The fabrication of dense coatings with appropriate properties using a high velocity oxygen fuel (HVOF) spray process requires an in-depth understanding of the complete gas flow field and particle behavior during the process. A computational fluid dynamics (CFD) model is implemented to investigate the gas flow behavior that occurs during the HVOF process and a simplified one-dimensional decoupled model of the in-flight thermal behavior of the amorphous Fe-based powder particles was developed and applied for three different spray conditions. The numerical results were used to rationalize the different coating microstructures described in the experimental results. Low porosity and amorphous coatings were produced using two different particle size distributions (16 to 25 μm and 25 to 53 μm). The amorphous characteristics of the powder were retained in the coating due to melting and rapid solidification in the case of very fine powder or ligaments (<16 μm) and to the fact that the crystallization temperature was not reached in the case of the large particles (16 to 53 μm).

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

    SciTech Connect

    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.

  10. Increasing Ti-6Al-4V brazed joint strength equal to the base metal by Ti and Zr amorphous filler alloys

    SciTech Connect

    Ganjeh, E.; Sarkhosh, H.; Bajgholi, M.E.; Khorsand, H.; Ghaffari, M.

    2012-09-15

    Microstructural features developed along with mechanical properties in furnace brazing of Ti-6Al-4V alloy using STEMET 1228 (Ti-26.8Zr-13Ni-13.9Cu, wt.%) and STEMET 1406 (Zr-9.7Ti-12.4Ni-11.2Cu, wt.%) amorphous filler alloys. Brazing temperatures employed were 900-950 Degree-Sign C for the titanium-based filler and 900-990 Degree-Sign C for the zirconium-based filler alloys, respectively. The brazing time durations were 600, 1200 and 1800 s. The brazed joints were evaluated by ultrasonic test, and their microstructures and phase constitutions analyzed by metallography, scanning electron microscopy and X-ray diffraction analysis. Since microstructural evolution across the furnace brazed joints primarily depends on their alloying elements such as Cu, Ni and Zr along the joint. Accordingly, existence of Zr{sub 2}Cu, Ti{sub 2}Cu and (Ti,Zr){sub 2}Ni intermetallic compounds was identified in the brazed joints. The chemical composition of segregation region in the center of brazed joints was identical to virgin filler alloy content which greatly deteriorated the shear strength of the joints. Adequate brazing time (1800 s) and/or temperature (950 Degree-Sign C for Ti-based and 990 Degree-Sign C for Zr-based) resulted in an acicular Widmanstaetten microstructure throughout the entire joint section due to eutectoid reaction. This microstructure increased the shear strength of the brazed joints up to the Ti-6Al-4V tensile strength level. Consequently, Ti-6Al-4V can be furnace brazed by Ti and Zr base foils produced excellent joint strengths. - Highlights: Black-Right-Pointing-Pointer Temperature or time was the main factors of controlling braze joint strength. Black-Right-Pointing-Pointer Developing a Widmanstaetten microstructure generates equal strength to base metal. Black-Right-Pointing-Pointer Brittle intermetallic compounds like (Ti,Zr){sub 2}Ni/Cu deteriorate shear strength. Black-Right-Pointing-Pointer Ti and Zr base filler alloys were the best choice for brazing Ti

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

    NASA Astrophysics Data System (ADS)

    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.

  12. Amorphous and Metastable Microcrystalline Rapidly Solidified Alloys: Status and Potential.

    DTIC Science & Technology

    1980-05-01

    Curie temperatures of amorphous FeNi alloys . 75 Figure 14 Magnetically induced anisotropy as a function 77 of composition. Figure 15 The maximum...also needed in developing certain phase diagrams, understanding the role of alloying elements , predicting glassy behavior from thermo- dynamic...especially useful in determining the surroundings for elements that are a minor component of the alloy and/or have low relative scattering power. In

  13. Parametrized dielectric functions of amorphous GeSn alloys

    SciTech Connect

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

    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.

  14. Amorphous Alloy Membranes for High Temperature Hydrogen Separation

    SciTech Connect

    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

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

    SciTech Connect

    Cheng Ming; Zhang Shihong; Wang Ruixue

    2010-06-15

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

  16. Electronic specific heats for amorphous and crystallized alloys.

    PubMed

    Hou, Long; Mo, Jinyong; Liu, Qingling; Liu, Haishun; Yang, Weiming; Shen, Baolong

    2016-01-01

    The low temperature specific heats of (Fe0.5Co0.5)72B20Si4Nb4 amorphous and crystallized alloys are measured and analyzed from 1.4 to 110 K. Specific heats can be well fitted by electronic and phonon contribution terms. It is found that the electronic contribution term in specific heat for amorphous alloy is larger than that for crystallized one, and this phenomenon has been interpreted in detail. The research shows that the electronic density of states at the Fermi level and the localized loose "rattler" atoms in oversized cage structure may make contributions to the enhancement of electronic specific heat coefficient γ, and result in a larger electronic contribution term. This study is significant for further understanding the structure-property relationship for amorphous alloys at low temperature.

  17. New class of Si-based superlattices - Alternating layers of crystalline Si and porous amorphous Si(1-x)Ge(x) alloys

    NASA Technical Reports Server (NTRS)

    Fathauer, R. W.; George, T.; Jones, E. W.; Pike, W. T.; Ksendzov, A.; Vasquez, R. P.

    1992-01-01

    Superlattices consisting of alternating layers of crystalline Si and porous amorphous Si(1-x)Ge(x) have been fabricated. This is accomplished by first growing a Si/Si(0.7)Ge(0.3) superlattice by molecular beam epitaxy, followed by Ar-ion milling to form mesa structures, and finally by immersion in HF:HNO3:H2O. This solution creates a porous structure similar to that created by anodic etching, and a high selectivity is observed for the conversion of the alloy layers relative to the Si layers. The degree of selectivity is found to depend on alloy-layer thickness and strain. Superlattices have been fabricated from 1-micron wide mesas with Si(0.7)Ge(0.3) layers fully converted to 5-nm thick porous amorphous material.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Technical Reports Server (NTRS)

    Hanak, J. J.; Flaisher, H.

    1991-01-01

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

  20. Neutron scattering studies of amorphous Invar alloys

    SciTech Connect

    Fernandez-Baca, J.A.

    1989-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  2. Synthesis of amorphous alloys and amorphous-crystalline composites in the Cu-Nb-Hf system by ion beam mixing

    SciTech Connect

    Luo, S. Y.; Cui, Y. Y.; Wang, T. L.; Ding, N.; Li, J. H.; Liu, B. X.

    2011-06-15

    Seven sets of Cu-Nb-Hf multilayered films were designed and prepared with the overall compositions of Cu{sub 21}Nb{sub 65}Hf{sub 14}, Cu{sub 33}Nb{sub 49}Hf{sub 18}, Cu{sub 34}Nb{sub 34}Hf{sub 32}, Cu{sub 34}Nb{sub 10}Hf{sub 56}, Cu{sub 50}Nb{sub 23}Hf{sub 27}, Cu{sub 58}Nb{sub 10}Hf{sub 32}, and Cu{sub 70}Nb{sub 8}Hf{sub 22}, and an ion beam mixing experiment was then conducted using 200 keV xenon ions. It is found that the Cu-Nb-Hf system is a metallic glass forming one, and the single amorphous alloys could be synthesized in the Cu-Nb-based alloys with less than 18 at.% of Hf as a third addition. Also, when the Hf concentration is greater than 18 at.%, i.e., at the compositions of Cu{sub 34}Nb{sub 34}Hf{sub 32}, Cu{sub 34}Nb{sub 10}Hf{sub 56}, Cu{sub 50}Nb{sub 23}Hf{sub 27}, Cu{sub 58}Nb{sub 10}Hf{sub 32}, and Cu{sub 70}Nb{sub 8}Hf{sub 22}, ion beam mixing resulted in the formation of amorphous-crystalline composites, which might have better mechanical properties than single-phase glassy alloys. In addition, a detailed discussion was presented for the formation mechanism of the amorphous alloys and amorphous-crystalline composites.

  3. Tungsten solution kinetics and amorphization of nickel in mechanically alloyed Ni-W alloys

    NASA Technical Reports Server (NTRS)

    Aning, A. O.; Wang, Z.; Courtney, T. H.

    1993-01-01

    The kinetics of solution of W, and the subsequent amorphization of Ni, in mechanically alloyed Ni-W alloys has been investigated. As W is a highly abrasive material in the energy intensive devices used for mechanical alloying, we studied the above reactions in different mills. One used hardened steel balls as the grinding media, and the other Al2O3. Abrasion is common to both mills, but Fe wear debris from the hardened steel enters into solution in the Ni rich phases whereas Al2O3 debris is present as small dispersoids. The kinetics of W solution and those of subsequent amorphization do not appear strongly affected by the Fe in solution or the Al2O3 dispersoid. Tungsten dissolves in crystalline Ni in amounts in excess of the equilibrium solubility during alloying. Amorphization of the Ni phase occurs if the W content in this phase exceeds ca. 28 at. pct.

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

    SciTech Connect

    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.

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

    SciTech Connect

    Yang, W. M.; Liu, H. S. E-mail: blshen@seu.edu.cn E-mail: jiangjz@zju.edu.cn; Zhao, Y. C.; Liu, X. J.; Chen, G. X.; Man, Q. K.; Chang, C. T.; Li, R. W. E-mail: blshen@seu.edu.cn E-mail: jiangjz@zju.edu.cn; Dun, C. C.; Shen, B. L. E-mail: blshen@seu.edu.cn E-mail: jiangjz@zju.edu.cn; Inoue, A.; and others

    2014-09-28

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

  6. Ultralight amorphous silicon alloy photovoltaic modules for space applications

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  7. Formation of amorphous metal alloys by chemical vapor deposition

    DOEpatents

    Mullendore, Arthur W.

    1990-01-01

    Amorphous alloys are deposited by a process of thermal dissociation of mixtures or organometallic compounds and metalloid hydrides, e.g., transition metal carbonyl such as nickel carbonyl, and diborane. Various sizes and shapes of deposits can be achieved, including near-net-shape free standing articles, multilayer deposits, and the like. Manipulation or absence of a magnetic field affects the nature and the structure of the deposit.

  8. Formation of amorphous metal alloys by chemical vapor deposition

    DOEpatents

    Mullendore, A.W.

    1988-03-18

    Amorphous alloys are deposited by a process of thermal dissociation of mixtures of organometallic compounds and metalloid hydrides,e.g., transition metal carbonyl, such as nickel carbonyl and diborane. Various sizes and shapes of deposits can be achieved, including near-net-shape free standing articles, multilayer deposits, and the like. Manipulation or absence of a magnetic field affects the nature and the structure of the deposit. 1 fig.

  9. Electrodeposition of amorphous ternary nickel-chromium-phosphorus alloy

    DOEpatents

    Guilinger, Terry R.

    1990-01-01

    Amorphous ternary nickel-chromium-phosphorus alloys are electrodeposited from a bath comprising a nickel salt, a chromium salt, a phosphorus source such as sodium hypophosphite, a complexing agent for the nickel ions, supporting salts to increase conductivity, and a buffering agent. The process is carried out at about room temperature and requires a current density between about 20 to 40 A/dm.sup.2.

  10. Nucleation of shear bands in amorphous alloys

    PubMed Central

    Perepezko, John H.; Imhoff, Seth D.; Chen, Ming-Wei; Wang, Jun-Qiang; Gonzalez, Sergio

    2014-01-01

    The initiation and propagation of shear bands is an important mode of localized inhomogeneous deformation that occurs in a wide range of materials. In metallic glasses, shear band development is considered to center on a structural heterogeneity, a shear transformation zone that evolves into a rapidly propagating shear band under a shear stress above a threshold. Deformation by shear bands is a nucleation-controlled process, but the initiation process is unclear. Here we use nanoindentation to probe shear band nucleation during loading by measuring the first pop-in event in the load–depth curve which is demonstrated to be associated with shear band formation. We analyze a large number of independent measurements on four different bulk metallic glasses (BMGs) alloys and reveal the operation of a bimodal distribution of the first pop-in loads that are associated with different shear band nucleation sites that operate at different stress levels below the glass transition temperature, Tg. The nucleation kinetics, the nucleation barriers, and the density for each site type have been determined. The discovery of multiple shear band nucleation sites challenges the current view of nucleation at a single type of site and offers opportunities for controlling the ductility of BMG alloys. PMID:24594599

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

    PubMed

    Hebert, Rainer J; Perepezko, John H; Rösner, Harald; Wilde, Gerhard

    2016-01-01

    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.

  12. Theory of bond-length variations in relaxed, strained, and amorphous silicon-germanium alloys

    NASA Astrophysics Data System (ADS)

    Tzoumanekas, C.; Kelires, P. C.

    2002-11-01

    We present a theoretical study of bond-length and angle variations in relaxed, epitaxially strained, and amorphous Si1-xGex alloys. Our approach is based on Monte Carlo simulations, within the semigrand-canonical ensemble utilizing Ising-like identity flips, and in conjuction with energies calculated using the empirical potential of Tersoff [Phys. Rev. B 39, 5566 (1989)]. The method offers great statistical precision enabling us to extract clear variations through the whole composition range and for all types of bonds. Our simulations show that in relaxed crystalline alloys, where the lattice constant takes its natural value, bond lengths depend on composition x and that these variations are type specific, in agreement with recent experimental studies. Similar type-specific variations are found for the angles and the second-nearest-neighbor distances. This analysis also reveals that the negative deviation of the lattice constant from Vegard's law is mainly due to radial, and not angular, relaxations. In the epitaxially strained alloys, bond lengths decrease with x due to the two-dimensional confinement in the growth layers, in good agreement with predictions based on the macroscopic theory of elasticity. The dimer bond lengths at the (100)-(2×1)-reconstructed alloy surface remain nearly constant, and they are elongated with respect to the bulk values. In the amorphous alloys, we unravel a remarkable behavior of bond lengths at the dilute low-x alloy limit, characterized by strong relaxations and elongation. Furthermore, the bond lengths decrease with increasing Ge content. We offer an explanation of this effect based on the analysis of the enthalpy of formation of the amorphous alloy.

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

    SciTech Connect

    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.

  14. Hartree Fock and DFT Study of Models for Amorphous Chalcogenide Alloys

    NASA Astrophysics Data System (ADS)

    Edwards, Arthur; Shedd, Walter; Pugh, Robert

    2001-03-01

    Recently, it has been shown that certain chalcogenide alloys can be switched electrically between polycrystalline and amorphous phases for up to 10^14 cycles and that there is an accompanying large change in conductivity. The most prevalent alloy is a pseudo-binary (GeTe)_2(Sb_2Te_3). While there is some X-Ray data and one band structure calculation on the crystalline phase, there is to date neither theory nor spectroscopy on the amorphous phase. We present a series of Hartree-Fock and DFT molecular orbital studies on models for the amorphous state of the constituent materials and of the alloy. The amorphous models are built on the assumption that normal valence is preserved and that the solid should, in principle, be constructed from repeating the chosen bonding unit. For the pseudo-binary we assume single bonds between Ge and Sb. The surfaces of the clusters are terminated with hydrogen atoms to preserve the normal valence. We have calculated equilibrium geometries using a variety of bases and thes

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

    NASA Astrophysics Data System (ADS)

    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. Deformation-driven catalysis of nanocrystallization in amorphous Al alloys

    PubMed Central

    Perepezko, John H; Rösner, Harald; Wilde, Gerhard

    2016-01-01

    Summary 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. PMID:27826517

  17. Effect of bending stresses on the high-frequency magnetic properties and their time stability in a cobalt-based amorphous alloy with an extremely low magnetostriction

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    An unusual effect of the stresses of bending (toroidal sample diameter D) on the hysteretic magnetic properties ( H c , μ5) of an amorphous Co69Fe3.7Cr3.8Si12B11 alloy with an extremely low magnetostriction (|λ s | ≤ 10-7) is revealed. These properties are measured in a dynamic regime at a magnetic-field frequency f = 0.1-20 kHz. The coercive force of the alloy H c weakly depends on D at low frequencies ( f < 1 kHz), and permeability μ5 ( H = 5 mOe), in contrast, is independent of D at high frequencies and is dependent on D at low frequencies. The samples subjected to high-temperature (390°C) annealing followed by water quenching exhibit "anomalous" dependences: permeability μ5 increases with decreasing toroidal sample radius, i.e., with increasing bending stresses. The detected dependences are related to the fact that magnetization reversal via the displacement of rigid domain walls is predominant at low frequencies and during static measurements and magnetization reversal via the displacement of flexible domain walls is predominant at high frequencies.

  18. The effect of heat treatment on amorphous Fe74Zr19Ta7 and Fe90Y10 alloys

    NASA Astrophysics Data System (ADS)

    Prater, J. T.; Merz, M. D.

    1981-03-01

    Magnetic measurements are reported for two iron-based amorphous alloys: Fe90Y10 and Fe74Zr19Ta7. Each is prepared by sputter deposition. X-tay diffraction is used to established the amorphous structure and X-ray fluorescence analysis to confirm the composition. Fe74Zr19Ta7 has a Curie temperature of 195 K and a crystallization temperature of 733 K (460 °C). Annealing studies on Fe74Zr19Ta7 indicate that this alloy does not show the dramatic increases in Curie temperature that are commonly observed in amorphous alloys that contain metalloid elements. Rather, this alloy exhibits small irreversible decreases in the Curie temperature following heat treatments up to 733 K (460 °C), the crystallization temperature. The amorphous Fe90Y10 alloy shows only short range order and has a large anisotropy field that prevents the saturation of the magnetic moment in a 10 kOe field at 78 K. The anisotropy decreases upon crystallization to a bcc iron structure, but ferromagnetism is observed only after annealing the alloy at elevated temperatures.

  19. Crystallization and nanoindentation behavior of a bulk Zr-Al-Ti-Cu-Ni amorphous alloy

    SciTech Connect

    Wang, J. G.; Choi, B. W.; Nieh, T. G.; Liu, C. T.

    2000-03-01

    The crystallization and nanoindentation behavior of a Zr-10Al-5Ti-17.9Cu-14.6Ni (at.%) bulk amorphous alloy (BAA) were studied. Resulting from the kinetic nature of phase transformation in multicomponent alloys, the crystallization path is complex. Despite the complexity of different crystallization paths, the main final crystallized product in the Zr-based BAA is Zr{sub 2}Cu. Young's modulus and hardness of the BAA were found to increase with an increase in annealing temperature. The observed mechanical properties were correlated with the microstructure of the material. Also, in the present paper, both the observed crystallization and nanoindentation behavior are compared with existing data. Zr-based BAAs exhibit a ratio of hardness to Young's modulus (H/E ratio) of about 1/10, suggesting the interatomic bonding in the alloys is close to being covalent. (c) 2000 Materials Research Society.

  20. Amorphous phase formation in Fe-6.0wt%Si alloy by mechanical alloying

    SciTech Connect

    Filho, A.F.; Bolfarini, C.; Xu, Y.; Kiminami, C.S.

    1999-12-31

    Mechanical alloying, MA, is a high-energy ball milling technique, in which elemental blends are milled to achieve alloying at atomic level. This communication describes the results of an investigation on the phase transformation of a mixture of Fe and Si powders with 6wt%Si during MA processing. Besides the verification of the effect of milling time on the structure and on the compositional homogeneity, this study was undertaken in order to confirm, by using TEM technique, the possibility of amorphous phase formation for Si content lower than 17.7wt%.

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

    NASA Astrophysics Data System (ADS)

    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.

  2. Electrical transport properties of amorphous Ni32Pd53P15 alloy

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  3. Microstructure and magnetic viscosity of bulk amorphous Nd60Fe20Al5Co10B5 alloy

    NASA Astrophysics Data System (ADS)

    Tan, X. H.; Xu, H.; Man, H.; Tang, Y. J.; Yang, L. P.; Bai, Q.

    2011-04-01

    The microstructure and magnetic viscosity of bulk amorphous Nd60Fe20Al5Co10B5,prepared by suction casting the molten alloy into a copper mold under an argon atmosphere, have been investigated. The results show that clusters with size 3-5 nm are found to be embedded in the amorphous matrix of as-cast bulk amorphous Nd60Fe20Al5Co10B5 alloy. The Nd60Fe20Al5Co10B5 alloy shows hard magnetic behavior at room temperature, with an intrinsic coercivity of 360 kA/m and a remanence of 69.39 mT. The magnetic viscosity of bulk amorphous Nd60Fe20Al5Co10B5 has been investigated on the major hysteresis loop, and simple logarithmic time dependence is observed. A value for the fluctuation field of 8.24 kA/m is obtained. Analysis based on a Henkel plot is used to confirm the existence of magnetic interaction among clusters. The coercivity mechanism responsible for the hard magnetic behavior of bulk amorphous Nd60Fe20Al5Co10B5 alloy is also discussed.

  4. Radiation Resistance Studies of Amorphous Silicon Alloy Photovoltaic Materials

    NASA Technical Reports Server (NTRS)

    Woodyard, James R.

    1994-01-01

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

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

    NASA Astrophysics Data System (ADS)

    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.

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

    SciTech Connect

    Kekalo, I. B.; Mogil’nikov, P. S.

    2015-06-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

  8. Amorphous nickel boride membrane on a platinum–nickel alloy surface for enhanced oxygen reduction reaction

    PubMed Central

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

    2016-01-01

    The low activity of the oxygen reduction reaction in polymer electrolyte membrane fuel cells is a major barrier for electrocatalysis, and hence needs to be optimized. Tuning the surface electronic structure of platinum-based bimetallic alloys, a promising oxygen reduction reaction catalyst, plays a key role in controlling its interaction with reactants, and thus affects the efficiency. Here we report that a dealloying process can be utilized to experimentally fabricate the interface between dealloyed platinum–nickel alloy and amorphous nickel boride membrane. The coating membrane works as an electron acceptor to tune the surface electronic structure of the platinum–nickel catalyst, and this composite catalyst composed of crystalline platinum–nickel covered by amorphous nickel boride achieves a 27-times enhancement in mass activity relative to commercial platinum/carbon at 0.9 V for the oxygen reduction reaction performance. Moreover, this interactional effect between a crystalline surface and amorphous membrane can be readily generalized to facilitate the 3-times higher catalytic activity of commercial platinum/carbon. PMID:27503412

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

    SciTech Connect

    Ipus, J. J.; Blazquez, J. S.; Franco, V.; Conde, A.

    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.

  10. JPRS Report, Science & Technology, Japan, Structure, Properties of Al Amorphous Alloys

    DTIC Science & Technology

    2007-11-02

    JPRS-JST-90-054 4 DECEMBER 1990 FOREIGN BROADCAST INFORMATION SERVICE JPRS Report-- Science & Technology Japan STRUCTURE , PROPERTIES OF AL...JPRS-JST-90-054 4 DECEMBER 1990 SCIENCE & TECHNOLOGY JAPAN STRUCTURE . PROPERTIES OF AL AMORPHOUS ALLOYS 906C7531 Tokyo AL KEI AMORUFASU GOKIN NO KOZO...TO TOKUSEI in Japanese 6 Feb 90 pp 1-40 [Papers presented at the Symposium for Structure and Properties of Al Amorphous Alloys, held 6 Feb 90 in

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

    NASA Astrophysics Data System (ADS)

    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.

  12. Microstructure and surface chemistry of amorphous alloys important to their friction and wear behavior

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1983-01-01

    An investigation was conducted to examine the microstructure and surface chemistry of amorphous alloys, and their effects on tribological behavior. The results indicate that the surface oxide layers present on amorphous alloys are effective in providing low friction and a protective film against wear in air. Clustering and crystallization in amorphous alloys can be enhanced as a result of plastic flow during the sliding process at a low sliding velocity, at room temperature. Clusters or crystallines with sizes to 150 nm and a diffused honeycomb-shaped structure are produced on the wear surface. Temperature effects lead to drastic changes in surface chemistry and friction behavior of the alloys at temperatures to 750 C. Contaminants can come from the bulk of the alloys to the surface upon heating and impart to the surface oxides at 350 C and boron nitride above 500 C. The oxides increase friction while the boron nitride reduces friction drastically in vacuum.

  13. Amorphous Ti-Zr; Base Metglas brazing filler metals

    SciTech Connect

    Rabinkin, A.; Liebermann, H.; Pounds, S.; Taylor, T. )

    1991-01-01

    This paper is the first report on processing, properties and potential application of amorphous titanium/zirconium-base alloys produced in the form of a good quality continuous and ductile ribbon having up to 12.5 mm width. To date, the majority of titanium brazing is accomplished using cooper and aluminum-base brazing filler metals. The brazements produced with these filler metals have rather low ({approximately}300{degrees} C) service temperature, thus impeding progress in aircraft and other technologies and industries. The attempt to develop a generation of high temperature brazing filler metals was made in the late sixties-early seventies studies in detail were a large number of Ti-, Zr-Ti-Zr, Ti-V and Zr-V-Ti based alloys. The majority of these alloys has copper and nickel as melting temperature depressants. The presence of nickel and copper converts them into eutectic alloys having (Ti(Zr)) (Cu(Ni)), intermetallic phases as major structural constituents. This, in turn, results in high alloy brittleness and poor, if any, processability by means of conventional, i.e. melting-ingot casting-deformation technology. In spite of good wettability and high joint strength achieved in dozens of promising alloys, only Ti-15Cu-15Ni is now widely used as a brazing filler metal for high service temperature. Up until now this material could not be produced as a homogeneous foil and is instead applied as a clad strip consisting of three separate metallic layers.

  14. Laser induced crystallization of hydrogenated amorphous silicon-carbon alloys

    NASA Astrophysics Data System (ADS)

    Summonte, C.; Rizzoli, R.; Servidori, M.; Milita, S.; Nicoletti, S.; Bianconi, M.; Desalvo, A.; Iencinella, D.

    2004-10-01

    Laser induced crystallization of hydrogenated amorphous silicon carbon alloy (a-Si1-xCx:H) films has been investigated by means of synchrotron x-ray diffraction. The a-Si1-xCx:H films were deposited on (100) silicon wafers by very high frequency plasma enhanced chemical vapor deposition at 100MHz in hydrogen diluted silane-methane gas mixtures. The substrate was kept at 250°C or 350°C and the stoichiometry was changed from x =0.20 to 0.63. The structural characterization of the as-grown films has been carried out by Rutherford backscattering (hydrogen concentration) and infrared spectroscopy (film ordering). The films were irradiated by a KrF excimer laser (248nm ) with varying energy density and number of pulses. After irradiation, the formation of SiC crystallites has been revealed by synchrotron x-ray diffraction. Besides SiC nanocrystals, the formation of crystalline Si and graphite is observed for under- (x <0.50) and over-stoichiometric (x>0.50) samples, respectively. The essential role played by hydrogen concentration and hydrogen bonding configuration in determining the melting threshold and the consequent SiC grain formation is highlighted.

  15. Effect of compositional variation on the shock wave response of bulk amorphous alloys

    NASA Astrophysics Data System (ADS)

    Jaglinski, T.; Turneaure, Stefan J.; Gupta, Y. M.

    2012-09-01

    The objective of this work was to determine how variations in composition influence the shock wave response of bulk amorphous alloys (BAAs). Toward this end, (Hf,Zr)-based bulk amorphous alloy specimens (nominal composition of (Hf0.5Zr0.5)56.7Cu15.3Ni12.5Nb5.0Al10.0Y0.5) were subjected to peak stresses of 4-16 GPa in plate impact experiments and their response was compared to a previously studied Zr-based BAA (nominal composition of Zr56.7Cu15.3Ni12.5Nb5.0Al10.0Y0.5). The (Hf,Zr)-based BAA displayed a Hugoniot elastic limit (HEL) of ˜7.4 GPa corresponding to an elastic strain of 4.3%. (Hf,Zr)-based BAAs shock compressed above the HEL exhibited distinct two wave structures, small elastic precursor relaxation, non-steady plastic waves, and strength loss. All of these features are qualitatively similar to previous observations in various Zr-based BAAs. One dimensional wave propagation simulations incorporating a strain-softening strength model, developed previously for a Zr-based BAA, showed excellent agreement between measured and simulated particle velocity histories for the (Hf,Zr)-based BAA. The only significant differences in the shock wave responses of the (Hf,Zr)-based alloy and the Zr-based alloy are elastic shock velocity and plastic shock velocity differences which are due to the different ambient densities and different elastic moduli for the two alloy compositions. These findings demonstrate that, apart from differences related to ambient density and elastic stiffness, the substitution of Hf for 50% of the Zr did not significantly alter the shock compression response of the (Hf,Zr)-based BAA as compared to the previously examined Zr-based BAA. Based on the results of this study and other relevant data in the literature, it is expected that monolithic BAAs displaying brittle quasi-static compression behavior will likely display shock compression response that is comparable to Zr-based and (Hf,Zr)-based BAAs.

  16. Corrosion-resistant amorphous metallic films of Mo49Cr33B18 alloy

    NASA Technical Reports Server (NTRS)

    Ramesham, R.; Distefano, S.; Fitzgerald, D.; Thakoor, A. P.; Khanna, S. K.

    1987-01-01

    Corrosion-resistant amorphous metallic alloy films of Mo49Cr33B18 with a crystallization temperature of 590 C were deposited onto glass and quartz substrates by magnetron sputter-quench technique. The amorphous nature of the films was confirmed by their diffuse X-ray diffraction patterns. The deposited films are densely packed (zone T) and exhibit low stress and good adhesion to the substrate. Corrosion current of as-deposited coating of MoCrB amorphous metallic alloy is approximately three orders of magnitude less than the corrosion current of 304 stainless steel in 1N H2SO4 solution.

  17. SUPERCONDUCTING VANADIUM BASE ALLOY

    DOEpatents

    Cleary, H.J.

    1958-10-21

    A new vanadium-base alloy which possesses remarkable superconducting properties is presented. The alloy consists of approximately one atomic percent of palladium, the balance being vanadium. The alloy is stated to be useful in a cryotron in digital computer circuits.

  18. A discussion on decay of discharge capacity for amorphous Mg-Ni-Nd hydrogen storage alloy

    NASA Astrophysics Data System (ADS)

    Liang, G. Y.; Wu, D. C.; Li, Lu; Huang, L. J.

    Amorphous Mg-Ni-Nd alloys were prepared by melt-spun technique and their discharge capacity was measured. Microstructure of amorphous ribbons after different charge-discharge cycles was observed using high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and selected area electron diffraction (SAED). The structure evolution of amorphous (Mg 60Ni 25) 90Nd 10 alloy during the charge-discharge cycles was investigated in detail. Experimental results showed that the structure evolution of amorphous ribbon was responsible for the decay of discharge capacity. During the charge-discharge cycles of amorphous (Mg 60Ni 25) 90Nd 10 alloy, NdMg 2Ni 9 phase appeared after four cycles and Mg 2Ni phase appeared after six cycles. After 20 cycles the stable phases Mg 2Ni, α-Mg and Nd 2H 5 were present and the former NdMg 2Ni 9 phase disappeared. With crystallization of amorphous ribbon, the discharge capacity of amorphous (Mg 60Ni 25) 90Nd 10 alloy dropped off. After 10 cycles the curve of discharge capacity tended to be smooth.

  19. Itinerant magnetism and spin glass states of iron rich amorphous alloys

    NASA Astrophysics Data System (ADS)

    Krey, U.; Krompiewski, S.; Krauss, U.

    1990-04-01

    We generalize our self-consistent treatment of the itinerant magnetism of disordered or amorphous transition metal alloys, given in a series of recent papers, in such a way that now also itinerant spin glasses can be treated; i.e. not only the local magnitude, as before, also the local polarization direction can now differ from site, due to a subtle interplay between the isotropic intra-atomic Coulomb interaction and the anisotropic hopping terms in the Hamiltonian. Using a realistic approach with all relevant orbitals, this theory is then applied to a detailed numerical study of the magnetism of iron-rich amorphous Fe-Zr alloys, including hydrogenated samples, and of fictitious amorphous Fe at various densities. As a result we find that in the non-hydrogenated Fe-Zr alloys and in amorphous Fe the transverse components, although summing up to zero, can locally be almost comparable to the longitudinal polarization per atom.

  20. Amorphous Silicon Based Neutron Detector

    SciTech Connect

    Xu, Liwei

    2004-12-12

    Various large-scale neutron sources already build or to be constructed, are important for materials research and life science research. For all these neutron sources, neutron detectors are very important aspect. However, there is a lack of a high-performance and low-cost neutron beam monitor that provides time and temporal resolution. The objective of this SBIR Phase I research, collaboratively performed by Midwest Optoelectronics, LLC (MWOE), the University of Toledo (UT) and Oak Ridge National Laboratory (ORNL), is to demonstrate the feasibility for amorphous silicon based neutron beam monitors that are pixilated, reliable, durable, fully packaged, and fabricated with high yield using low-cost method. During the Phase I effort, work as been focused in the following areas: 1) Deposition of high quality, low-defect-density, low-stress a-Si films using very high frequency plasma enhanced chemical vapor deposition (VHF PECVD) at high deposition rate and with low device shunting; 2) Fabrication of Si/SiO2/metal/p/i/n/metal/n/i/p/metal/SiO2/ device for the detection of alpha particles which are daughter particles of neutrons through appropriate nuclear reactions; and 3) Testing of various devices fabricated for alpha and neutron detection; As the main results: · High quality, low-defect-density, low-stress a-Si films have been successfully deposited using VHF PECVD on various low-cost substrates; · Various single-junction and double junction detector devices have been fabricated; · The detector devices fabricated have been systematically tested and analyzed. · Some of the fabricated devices are found to successfully detect alpha particles. Further research is required to bring this Phase I work beyond the feasibility demonstration toward the final prototype devices. The success of this project will lead to a high-performance, low-cost, X-Y pixilated neutron beam monitor that could be used in all of the neutron facilities worldwide. In addition, the technologies

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

    NASA Astrophysics Data System (ADS)

    Izu, Masat; Ovshinsky, Stanford R.

    1983-09-01

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

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

    NASA Astrophysics Data System (ADS)

    Wu, C.; Ding, D.; Xia, L.; Chan, K. C.

    2016-03-01

    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.

  3. Calorimetry study of the synthesis of amorphous Ni-Ti alloys by mechanical alloying. [Ni33 Ti67

    SciTech Connect

    Schwarz, R.B.; Petrich, R.R.

    1988-01-01

    We synthesized amorphous Ni/sub 33/Ti/sub 67/ alloy powder by ball milling (a) a mixture of elemental nickel and titanium powders and (b) powders of the crystalline intermetallic NiTi/sub 2/. We characterized the reaction products as a function of ball-milling time by differential scanning calorimetry and x-ray diffraction. The measurements suggest that in process (a) the amorphous alloy forms by a solid-state interdiffusion reaction at the clean Ni/Ti interfaces generated by the mechanical attrition. In process (b), the crystalline alloy powder stores energy in the form of chemical disorder and lattice and point defects. The crystal-to-amorphous transformation occurs when the stored energy reaches a critical value. The achievement of the critical stored energy competes with the dynamic recovery of the lattice. 23 refs., 7 figs.

  4. Amorphous silicon based radiation detectors

    SciTech Connect

    Perez-Mendez, V.; Cho, G.; Drewery, J.; Jing, T.; Kaplan, S.N.; Qureshi, S.; Wildermuth, D. ); Fujieda, I.; Street, R.A. )

    1991-07-01

    We describe the characteristics of thin(1 {mu}m) and thick (>30{mu}m) hydrogenated amorphous silicon p-i-n diodes which are optimized for detecting and recording the spatial distribution of charged particles, x-rays and {gamma} rays. For x-ray, {gamma} ray, and charged particle detection we can use thin p-i-n photosensitive diode arrays coupled to evaporated layers of suitable scintillators. For direct detection of charged particles with high resistance to radiation damage, we use the thick p-i-n diode arrays. 13 refs., 7 figs.

  5. EXAFS Measurements and Reverse Monte Carlo Modeling of Atomic Structure in Amorphous Ni80P20 Alloys

    SciTech Connect

    Luo,W.; Ma, E.

    2008-01-01

    This paper presents a full account of the EXAFS measurements and reverse Monte Carlo (RMC) modeling of the atomic arrangements and short-to-medium range structure in an amorphous Ni-P alloy, expanding on the description included in our recent publication. The atomic packing is analyzed from the standpoint of solute atoms. The short-to-medium range structure is discussed based on single-solute-centered quasi-equivalent clusters that form due to strong chemical short-range ordering, and the topological order is described in terms of both intra-cluster and inter-cluster dense packing for efficient filling of space. This analysis is also conducted for amorphous Ni80P20 prepared via different processing routes, to observe if the polyamorphism suggested in literature for amorphous Ni-P can be confirmed from the local structure perspective. The structural differences between the proposed polymorphs are apparently subtle and a full resolution of this issue is found to be beyond the capabilities of our EXAFS/RMC modeling approach. The amorphous structural features uncovered are also compared briefly with those observed before in amorphous alloy systems with positive heat of mixing.

  6. Synthesis of Amorphous Alloy Nanoparticles by Thermal Plasma Jet in a Quenching Tube

    NASA Astrophysics Data System (ADS)

    Choi, Sooseok; Park, Dong-Wha

    2015-09-01

    Recently, amorphous alloy nanoparticles have received a great attention in various applications such as catalysts, compact and highly efficient transformers, electrode material for Li-ion batteries, etc. Several methods such as microwave heating, laser ablation, and sonification have been studied to synthesize amorphous metal nanoparticles. In the present work, a high velocity thermal plasma jet generated by an arc plasma torch was used to produce iron alloy nanoparticles from an amorphous raw material which was a spherical shaped powder with the mean size of 25 μm. In order to synthesize amorphous alloy nanoparticles, a quenching tube where cooling gas was injected in different axial positions. Alloy nanoparticles were produced in a relatively high input power of higher than 10 kW in a fixed powder feeding at 300 mg/min. The crystallinity of synthesized nanoparticles was decreased with increasing the quenching gas flow rate. The amorphous alloy nanoparticles were found when the quenching gas injection position was 200 mm away from the exit of the plasma torch with the highest quenching gas flow rate of 20 L/min. In the numerical analysis, the highest quenching rate was also expected at the same condition.

  7. The Effect of Spatial Heterogeneities on Nucleation Kinetics in Amorphous Aluminum Alloys

    NASA Astrophysics Data System (ADS)

    Shen, Ye

    The mechanical property of the Al based metallic glass could be enhanced significantly by introducing the high number density of Al-fcc nanocrystals (1021 ˜1023 m-3) to the amorphous matrix through annealing treatments, which motivates the study of the nucleation kinetics for the microstructure control. With the presence of a high number density (1025 m-3) of aluminum-like medium range order (MRO), the Al-Y-Fe metallic glass is considered to be spatially heterogeneous. Combining the classical nucleation theory with the structural configuration, a MRO seeded nucleation model has been proposed and yields theoretical steady state nucleation rates consistent with the experimental results. In addition, this model satisfies all the thermodynamic and kinetic constraints to be reasonable. Compared with the Al-Y-Fe system, the primary crystallization onset temperature decreases significantly and the transient delay time (tau) is shorter in the Al-Y-Fe-Pb(In) systems because the insoluble Pb and In nanoparticles in the amorphous matrix served as extrinsic spatial heterogeneity to provide the nucleation sites for Al-fcc precipitation and the high-resolution transmission electron microscopy (HRTEM) images of the Pb-Al interface revealed a good wetting behavior between the Al and Pb nanoparticles. The study of the transient delay time (tau) could provide insight on the transport behavior during the nucleation and a more convenient approach to evaluate the delay time has been developed by measuring the Al-Y-Fe amorphous alloy glass transition temperature (Tg) shift with the increasing annealing time (tannealing) in FlashDSC. The break point in the Tg vs. log(tannealing) plot has been identified to correspond to the delay time by the TEM characterization. FlashDSC tests with different heating rates and different compositions (Al-Y-Fe-Pb and Zn-Mg-Ca-Yb amorphous alloys) further confirmed the break point and delay time relationship. The amorphous matrix composition and the

  8. Ferrofluids based on Co-Fe-Si-B amorphous nanoparticles

    NASA Astrophysics Data System (ADS)

    Wang, Tianqi; Bian, Xiufang; Yang, Chuncheng; Zhao, Shuchun; Yu, Mengchun

    2017-03-01

    Magnetic Co-Fe-Si-B amorphous nanoparticles were successfully synthesized by chemical reduction method. ICP, XRD, DSC, and TEM were used to investigate the composition, structure and morphology of Co-Fe-Si-B samples. The results show that the Co-Fe-Si-B samples are amorphous, which consist of nearly spherical nanoparticles with an average particle size about 23 nm. VSM results manifest that the saturation magnetization (Ms) of Co-Fe-Si-B samples ranges from 46.37 to 62.89 emu/g. Two kinds of ferrofluids (FFs) were prepared by dispersing Co-Fe-Si-B amorphous nanoparticles and CoFe2O4 nanoparticles in kerosene and silicone oil, respectively. The magnetic properties, stability and viscosity of the FFs were investigated. The FFs with Co-Fe-Si-B samples have a higher Ms and lower coercivity (Hc) than FFs with CoFe2O4 sample. Under magnetic field, the silicone oil-based FFs exhibit high stability. The viscosity of FFs under different applied magnetic fields was measured by a rotational viscometer, indicating that FFs with Co-Fe-Si-B particles present relative strong response to an external magnetic field. The metal-boride amorphous alloy nanoparticles have potential applications in the preparation of magnetic fluids with good stability and good magnetoviscous properties.

  9. Peculiarities in the plasma resonance of binary amorphous Al TM alloys

    NASA Astrophysics Data System (ADS)

    Stiehler, M.; Giegengack, U.; Barzola-Quiquia, J.; Rauchhaupt, J.; Schulze, S.; Häussler, P.

    2007-05-01

    Simple amorphous phases have shown to be ideal model systems for exploring the mechanisms of structure formation in a Hume-Rothery manner. In these systems the electron density is the key quantity. We briefly review measurements for simple amorphous alloys (s- and p-electrons at the Fermi energy only), especially for amorphous semiconductors. The results coincide excellently with theory, using the usual valencies of the elements. In contrary, adding elements with d-electrons as in binary amorphous Al TM alloys (TM: Ca, Ti, V, Cr, Mn, Fe, Co, Ni) causes a breakdown of this simple approach. All the 3d-TM seem to exhibit an identical effective valency. In both cases, the electron densities obtained are compared to those, necessary for explaining structural data.

  10. Length mismatch in random semiconductor alloys. III. Crystalline and amorphous SiGe

    NASA Astrophysics Data System (ADS)

    Mousseau, Normand; Thorpe, M. F.

    1992-12-01

    In the third paper of this series on the length mismatch problem, we study binary semiconductor alloys in both their crystalline and amorphous forms. We have concentratred on SiGe alloys. Applying the theory developed in paper I, we obtain the mean length for both nearest and next-nearest neighbors as well as the nearest-neighbor length distribution for the crystalline alloy. We show that the theoretical results fall within the limits set by experiment. We check our analytical results against computer simulations. We examine the effect of amorphization on the internal strain, using the Wooten, Winer, and Weaire model, and find that the disorders due to the length mismatch and due to amorphization decouple.

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

    SciTech Connect

    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

  12. NICKEL-BASE ALLOY

    DOEpatents

    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.

  13. Specific features of sample preparation from amorphous aluminum alloys for transmission electron microscopy

    SciTech Connect

    Volkov, P. A.; Todorova, E. V.; Bakhteeva, N. D.; Ivanova, A. G.; Vasil'ev, A. L.

    2011-05-15

    An aluminum amorphous alloy doped with transition (Fe and Ni) and rare earth (La) metals has been used as an object of systematic study of the structural transformations that are characteristic of different methods of sample preparation for transmission electron microscopy (the mechanical tearing of ribbons, electrochemical thinning, and Ar{sup +}-ion etching under different conditions). The results of X-ray diffraction analysis and a calorimetric study of the structure in comparison with electron microscopy data made it possible to determine the optimal method of sample preparation, which ensures minimum distortions in the structure of metastable amorphous alloys with a low crystallization temperature.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  15. Nanostructure formation by dynamic densification and recrystallization of amorphous Ti-Si alloy

    NASA Astrophysics Data System (ADS)

    Counihan, P. J.; Crawford, A.; Thadhani, N. N.

    1998-07-01

    Dynamic densification was used to consolidate mechanically amorphized Ti-Si alloy powders, using a 3-capsule, plate-impact, gas-gun loading system at velocities of 300 and 500 m/s. The recovered amorphous compacts were subsequently annealed above the crystallization temperature. A single-phase nano-structured (50-90 nm) Ti5Si3 compound was produced, as revealed by TEM and XRD analysis. In this paper, the influence of dynamic densification on the crystallization behavior of amorphous Ti-Si, and the formation of nano-crystals will be discussed.

  16. Synthesis and Thermal Stability of Amorphous Be-B-X Alloy Coatings

    SciTech Connect

    Jankowski, A F; Wall, M A; Nieh, T G

    2004-10-14

    Amorphous Be-B-X alloys are vapor deposited as coatings. The microstructure and hardness of the Be-B-X coatings are examined using transmission electron microscopy and nanoindentation, respectively. Whereas a Be-B-2.5 at.% Cu amorphous coating is found to crystallize to a cubic Be-33 at.% B phase at 673 K, a coating of Be-B-1.8 at.% Fe-0.4 at.% Cr-0.3 at.% Co does not crystallize until at a higher temperature of 748 K. The hardness of the amorphous Be-B-X coating increases with B content but is less than its crystalline counterparts.

  17. Corrosion resistance and cytocompatibility of biodegradable surgical magnesium alloy coated with hydrogenated amorphous silicon.

    PubMed

    Xin, Yunchang; Jiang, Jiang; Huo, Kaifu; Tang, Guoyi; Tian, Xiubo; Chu, Paul K

    2009-06-01

    The fast degradation rates in the physiological environment constitute the main limitation for the applications of surgical magnesium alloys as biodegradable hard-tissue implants. In this work, a stable and dense hydrogenated amorphous silicon coating (a-Si:H) with desirable bioactivity is deposited on AZ91 magnesium alloy using magnetron sputtering deposition. Raman spectroscopy and Fourier transform infrared spectroscopy reveal that the coating is mainly composed of hydrogenated amorphous silicon. The hardness of the coated alloy is enhanced significantly and the coating is quite hydrophilic as well. Potentiodynamic polarization results show that the corrosion resistance of the coated alloy is enhanced dramatically. In addition, the deterioration process of the coating in simulated body fluids is systematically investigated by open circuit potential evolution and electrochemical impedance spectroscopy. The cytocompatibility of the coated Mg is evaluated for the first time using hFOB1.19 cells and favorable biocompatibility is observed.

  18. Investigating the Effects of Low Temperature Annealing of Amorphous Corrosion Resistant Alloys.

    DTIC Science & Technology

    1980-11-01

    24 vii BACKGROUND The advent of amorphousalloys containing film -forming elements such as chromium has led to intensive research into corrosion...hypothesis is supported by evidence that passive films formed on Fe-Ni-Cr-P-C alloys are similar in structure to those observed on crystalline stainless...steels. 5 ’ It has also been shown that phosphorus enhances corrosion resistance, presumably by enriching the passive film in hydrated chromium

  19. Phase transformation during mechano-synthesis of nanocrystalline/amorphous Fe–32Mn–6Si alloys

    SciTech Connect

    Amini, Rasool; Shamsipoor, Ali; Ghaffari, Mohammad; Alizadeh, Morteza; Okyay, Ali Kemal

    2013-10-15

    Mechano-synthesis of Fe–32Mn–6Si alloy by mechanical alloying of the elemental powder mixtures was evaluated by running the ball milling process under an inert argon gas atmosphere. In order to characterize the as-milled powders, powder sampling was performed at predetermined intervals from 0.5 to 192 h. X-ray florescence analyzer, X-ray diffraction, scanning electron microscope, and high resolution transmission electron microscope were utilized to investigate the chemical composition, structural evolution, morphological changes, and microstructure of the as-milled powders, respectively. According to the results, the nanocrystalline Fe–Mn–Si alloys were completely synthesized after 48 h of milling. Moreover, the formation of a considerable amount of amorphous phase during the milling process was indicated by quantitative X-ray diffraction analysis as well as high resolution transmission electron microscopy image and its selected area diffraction pattern. It was found that the α-to-γ and subsequently the amorphous-to-crystalline (especially martensite) phase transformation occurred by milling development. - Graphical abstract: Mechano-synthesis of nanocrystalline/amorphous Fe–32Mn–6Si shape memory alloys in the powder form: amorphous phase formation, α-to-γ phase transformation, mechano-crystallization of the amorphous, and martensite phase formation during the process. Highlights: • During MA, the α-to-γ phase transformation and amorphization occurred. • Mechano-crystallization of the amorphous phase occurred at sufficient milling time. • The formation of high amount of ε-martensite was evidenced at high milling times. • The platelet, spherical, and then irregular particle shapes was extended by MA. • By MA, the particles size was increased, then reduced, and afterward re-increased.

  20. Light scattering by the surface of amorphous alloy ribbons modified by annealing and cryogenic treatment

    NASA Astrophysics Data System (ADS)

    Poperenko, L. V.; Lysenko, S. I.; Vinnichenko, K. L.

    2004-03-01

    The modification of the microrelief and structure of the surface layers of ribbons of an amorphous metal alloy based on iron and cobalt after thermal treatment at elevated and cryogenic temperatures and under the action of an external magnetic field is studied by the method of light scattering. The parameters of the surface roughness were calculated from the experimentally found indicatrices of light scattering. It is shown that heating of the metal ribbons to T=650-750 K partially relieves stresses arising in the course of the ribbon preparation and reduces the surface roughness as compared to that of freshly prepared samples. Cryogenic treatment at T=78 K increases the surface roughness, and application of a magnetic field to a ribbon causes anisotropy in the surface layer due to the magnetostrictive effect.

  1. Electron transport behaviour and soft magnetic properties of bulk amorphous Fe72Si4B20Nb4 alloy

    NASA Astrophysics Data System (ADS)

    Panda, A. K.; Ghosh Chowdhury, S.; Mitra, A.; Nishiyama, N.; Inoue, A.

    2006-08-01

    The crystallization behaviour, electrical resistivity, magnetic and mechanical properties of as-quenched bulk amorphous Fe72Si4B20Nb4 alloy was investigated. The alloy, prepared in the form of rods by a copper mould casting technique, revealed an amorphous structure as observed from x-ray diffractometry. Differential scanning calorimetry and thermal variation of electrical resistivity measurements showed distinct glass transition temperature, Tg occurring 50-60 K below the crystallization onset (TX). Such a wide supercooled range was also attributed to the highly reduced glass transition temperature, Trg which was in the range of 0.56-0.58 found to be prevalent in good glass forming alloys. The alloy also showed a non-linear decrease in stability time at different temperatures between Tg and TX. The bulk amorphous alloy exhibited a drastic decrease in electrical resistivity around the glass transition temperature which was attributed to high electron propagation due to enhanced stress relaxation as result of a decrease in viscosity. The material exhibited superior soft magnetic properties with a coercivity value of 212 mOe, which is fairly low with respect to reported bulk amorphous alloys. The amorphous alloy also showed saturation induction of 12 kG and a moderate Curie temperature of 595 K. The as-quenched bulk amorphous alloy exhibited a high mechanical hardness of 1250 HV (Vickers). The superior soft magnetic properties coupled with high mechanical hardness opens up the scope for bulk amorphous Fe-Si-B systems with Nb incorporation.

  2. Structural transformations in amorphous ↔ crystalline phase change of Ga-Sb alloys

    SciTech Connect

    Edwards, T. G.; Sen, S.; Hung, I.; Gan, Z.; Kalkan, B.; Raoux, S.

    2013-12-21

    Ga-Sb alloys with compositions ranging between ∼12 and 50 at. % Ga are promising materials for phase change random access memory applications. The short-range structures of two such alloys with compositions Ga{sub 14}Sb{sub 86} and Ga{sub 46}Sb{sub 54} are investigated, in their amorphous and crystalline states, using {sup 71}Ga and {sup 121}Sb nuclear magnetic resonance spectroscopy and synchrotron x-ray diffraction. The Ga and Sb atoms are fourfold coordinated in the as-deposited amorphous Ga{sub 46}Sb{sub 54} with nearly 40% of the constituent atoms being involved in Ga-Ga and Sb-Sb homopolar bonding. This necessitates extensive bond switching and elimination of homopolar bonds during crystallization. On the other hand, Ga and Sb atoms are all threefold coordinated in the as-deposited amorphous Ga{sub 14}Sb{sub 86}. Crystallization of this material involves phase separation of GaSb domains in Sb matrix and a concomitant increase in the Ga coordination number from 3 to 4. Results from crystallization kinetics experiments suggest that the melt-quenching results in the elimination of structural “defects” such as the homopolar bonds and threefold coordinated Ga atoms in the amorphous phases of these alloys, thereby rendering them structurally more similar to the corresponding crystalline states compared to the as-deposited amorphous phases.

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

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1982-01-01

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

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

    NASA Astrophysics Data System (ADS)

    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.

  5. New Fe-Ni based metal-metalloid glassy alloys prepared by mechanical alloying and rapid solidification

    SciTech Connect

    Sunol, J.J.; Clavaguera-Mora, M.T.; Clavaguera, N.; Pradell, T.

    1997-12-31

    Mechanical alloying and rapid solidification are two important routes to obtain glassy alloys. New Fe-Ni based metal-metalloid (P-Si) alloys prepared by these two different processing routes were studied by differential scanning calorimetry and transmission Moessbauer spectroscopy. Mechanical alloyed samples were prepared with elemental precursors, and different nominal compositions. Rapidly solidified alloys were obtained by melt-spinning. The structural analyses show that, independent of the composition, the materials obtained by mechanical alloying are not completely disordered whereas fully amorphous alloys were obtained by rapid solidification. Consequently, the thermal stability of mechanically alloyed samples is lower than that of the analogous material prepared by rapid solidification. The P/Si ratio controls the magnetic interaction of the glassy ribbons obtained by rapid solidification. The experimental results are discussed in terms of the degree of amorphization and crystallization versus processing route and P/Si ratio content.

  6. Surface amorphization of NiTi alloy induced by Ultrasonic Nanocrystal Surface Modification for improved mechanical properties.

    PubMed

    Ye, Chang; Zhou, Xianfeng; Telang, Abhishek; Gao, Hongyu; Ren, Zhencheng; Qin, Haifeng; Suslov, Sergey; Gill, Amrinder S; Mannava, S R; Qian, Dong; Doll, Gary L; Martini, Ashlie; Sahai, Nita; Vasudevan, Vijay K

    2016-01-01

    We report herein the effects of Ultrasonic Nano-crystal Surface Modification (UNSM), a severe surface plastic deformation process, on the microstructure, mechanical (hardness, wear), wettability and biocompatibility properties of NiTi shape memory alloy. Complete surface amorphization of NiTi was achieved by this process, which was confirmed by X-ray diffraction and high-resolution transmission electron microscopy. The wear resistance of the samples after UNSM processing was significantly improved compared with the non-processed samples due to increased surface hardness of the alloy by this process. In addition, cell culture study demonstrated that the biocompatibility of the samples after UNSM processing has not been compromised compared to the non-processed sample. The combination of high wear resistance and good biocompatibility makes UNSM an appealing process for treating alloy-based biomedical devices.

  7. TUNGSTEN BASE ALLOYS

    DOEpatents

    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.

  8. Microstructure and surface chemistry of amorphous alloys important to their friction and wear behavior

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1986-01-01

    An investigation was conducted to examine the microstructure and surface chemistry of amorphous alloys, and their effects on tribological behavior. The results indicate that the surface oxide layers present on amorphous alloys are effective in providing low friction and a protective film against wear in air. Clustering and crystallization in amorphous alloys can be enhanced as a result of plastic flow during the sliding process at a low sliding velocity, at room temperature. Clusters or crystallines with sizes to 150 nm and a diffused honeycomb-shaped structure are produced on sizes to 150 nm and a diffused honeycomb-shaped structure are produced on the wear surface. Temperature effects lead to drastic changes in surface chemistry and friction behavior of the alloys at temperatures to 750 C. Contaminants can come from the bulk of the alloys to the surface upon heating and impart to the surface oxides at 350 C and boron nitride above 500 C. The oxides increase friction while the boron nitride reduces friction drastically in vacuum.

  9. Interdiffusion in amorphous AlxZr1-x alloys

    NASA Astrophysics Data System (ADS)

    Noah, Martin A.; Wang, Zumin; Mittemeijer, Eric J.

    2017-01-01

    Interdiffusion in amorphous Alx Zr1 -x compositionally modulated multilayers was investigated by Auger electron spectroscopy sputter-depth profiling. Microstructural characterisation was performed by X-ray diffraction and cross-sectional transmission electron microscopy. The temperature-dependent chemical diffusion coefficient could be deduced at a series of temperatures in the range of 356 °C to 415 °C and was found to be weakly dependent on composition. The activation enthalpy for the chemical diffusion coefficients is slightly smaller at the composition of the Al-rich am- Al0.62 Zr0.38 sublayer (1.6 eV) than at the composition of the Zr-rich am- Al0.27 Zr0.73 sublayer (1.8 eV), which is not related to the concentration dependence of the excess free volume but to the smaller atomic size and mass of Al as compared to Zr. The smaller activation enthalpy for interdiffusion in partially crystallised specimens than in entirely amorphous Alx Zr1 -x multilayers is ascribed to the relatively large excess free volume in the grain boundaries of the nanocrystalline sublayers, as compared to the amorphous phase, at large Al concentrations. On the basis of an evaluation of the role of diffusion-induced stress in amorphous systems, it is shown that stresses induced by interdiffusion relax relatively fast by viscous flow and do not affect the determined diffusion coefficients.

  10. Ion-beam amorphization of semiconductors: A physical model based on the amorphous pocket population

    SciTech Connect

    Mok, K.R.C.; Jaraiz, M.; Martin-Bragado, I.; Rubio, J.E.; Castrillo, P.; Pinacho, R.; Barbolla, J.; Srinivasan, M.P.

    2005-08-15

    We introduce a model for damage accumulation up to amorphization, based on the ion-implant damage structures commonly known as amorphous pockets. The model is able to reproduce the silicon amorphous-crystalline transition temperature for C, Si, and Ge ion implants. Its use as an analysis tool reveals an unexpected bimodal distribution of the defect population around a characteristic size, which is larger for heavier ions. The defect population is split in both size and composition, with small, pure interstitial and vacancy clusters below the characteristic size, and amorphous pockets with a balanced mixture of interstitials and vacancies beyond that size.

  11. Electrode properties and the dehydrogenation process of amorphous Mg-Ni-La alloys

    NASA Astrophysics Data System (ADS)

    Huang, Lin-Jun; Wang, Yan-Xin; Wu, Dong-Chang; Tang, Jian-Guo; Wang, Yao; Liu, Ji-Xian; Huang, Zhen; Jiao, Ji-Qing; Liu, Jing-Quan

    2014-03-01

    Amorphous Mg-Ni-La hydrogen-storage alloys were prepared by melt-spinning. The phase structures of the ribbons before and after charge/discharge cycling were characterized by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) analysis, respectively. The effects of different contents of La are discussed on the basis of discharge-capacity, the morphology, limiting current density and electrochemical impedance spectra of the Mg-Ni-La electrodes. The Mg65Ni27La8 alloy exhibits the best reaction kinetics performance, the lowest contact resistance and a maximum discharge capacity of 582 mAh g-1 at room temperature. The non-isothermal dehydrogenation process of Mg65Ni27La8 alloy was analyzed in detail by differential scanning calorimetry (DSC) and thermogravimetry (TG). The experimental results showed a maximum 4.0 wt.% of released hydrogen at a heating rate of 5 °C min-1. The non-isothermal dehydrogenation process of the alloy can be divided in two steps, corresponding to the dehydrogenation of amorphous phase (1.45 wt.% H) and Mg2NiH4 (2.55 wt.% H), respectively. It indicated that the amorphous structure was a key factor to achieve high discharge capacity and good cycling stability.

  12. Crystallization Kinetics Study on Magnetron-Sputtered Amorphous TiAl Alloy Thin Films

    NASA Astrophysics Data System (ADS)

    Shui, Lu-Yu; Yan, Biao

    2014-04-01

    Crystallization kinetics of magnetron-sputtered amorphous TiAl alloy thin films is investigated by differential scanning calorimetry through isothermal analysis and non-isothermal analysis. In non-isothermal analysis, the Kissinger method and the Ozawa method are used to calculate the apparent activation energy and local activation energy, respectively, in the crystallization processes of amorphous TiAl thin films. Furthermore, the crystallization mechanism is discussed from the investigation of the Avrami exponent by isothermal analysis. In addition, x-ray diffraction is utilized to reveal the grain orientation and evolution during the crystallization of TiAl thin films.

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

    SciTech Connect

    Chattoraj, I.; Bhattamishra, A.K. . CRP Div.); Mitra, A. . MTP Div.)

    1993-09-01

    The effects of grain growth and compositional changes on the electrochemical behavior and the resistivity of amorphous iron-boron-silicon (Fe[sub 77.5]B[sub 15]Si[sub 7.5]) alloys after crystallization were studied. Deterioration of the protective passive film was observed, along with increased annealing. Potentiodynamic polarization provided excellent information about microstructural and chemical changes. It was concluded that electrochemical measurements could be used in conjunction with resistivity measurements in direct studies of grain growth and chemical changes occurring in different phases of the devitrified alloy.

  14. Preferential magnetic orientation in amorphous alloys determined by NFS and Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Procházka, Vít; Vrba, Vlastimil; Šretrová, Pavla; Smrčka, David; Miglierini, Marcel

    2016-10-01

    Amorphous and nanocrystalline alloys frequently exhibit anisotropic behavior, which is a consequence of magnetic moments preferential orientation. This study reports the results obtained from a set of nuclear forward scattering experiments and transmission Mössbauer spectroscopy experiments that we have run in order to determine the degree of crystallization and the preferential orientation of magnetic moments in the material. The nuclear forward scattering of synchrotron radiation and the transmission Mössbauer spectroscopy were performed on the nanocrystalline alloy of the composition Fe79Mo8Cu1B12. The experimental data were evaluated and magnetic texture was determined. Relevance of the results was confronted with transmission Mössbauer experiments.

  15. Control of nanocrystalline orientation using the application of a stress field in an amorphous alloy

    NASA Astrophysics Data System (ADS)

    Ogura, A.; Tarumi, R.; Shimojo, M.; Takashima, K.; Higo, Y.

    2001-08-01

    Precipitation of nanocrystals in a Ni-P amorphous alloy film during application of a stress field has been investigated. Microsized cantilever-beam-type specimens were prepared from the film by focused-ion-beam machining and bending stress was applied to the specimen using a mechanical testing machine for microsized specimens. Transmission electron microscopy observation in the plane strain deformed region has revealed that the deformation induces the precipitation of nanocrystalline Ni particles, and a (111) plane of all crystalline particles is aligned parallel to the side surface of the specimen. This suggests that control of the nanocrystalline orientation in amorphous alloys would be possible using the application of a stress field.

  16. Effects of tensile stress on the magnetic Barkhausen effect in 2605 Co amorphous alloy

    SciTech Connect

    Mitra, A.; Jiles, D.C.

    1995-11-01

    A study of the magnetic Barkhausen effect emissions in 2605 Co amorphous alloys has been made. These emissions, which appear as magnetization pulses in the material, can be detected by a pick-up coil and analyzed in a variety of ways. In this study the Barkhausen effect signals were found to be dependent on both magnetic field and applied tensile stress. This dependence was in accordance with a theoretical model of the Barkhausen effect developed previously. The analysis and modeling of the resulting behavior was found to be particularly simple because amorphous alloys have no crystalline anisotropy, and therefore the effects of stress on the Barkhausen emission were not masked by competing effects.

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

    NASA Astrophysics Data System (ADS)

    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.

  18. Nanostructure Formation by Dynamic Densification and Recrystallization of Amorphous Ti-Si Alloy

    NASA Astrophysics Data System (ADS)

    Counihan, P. J.; Thadhani, N. N.

    1997-07-01

    Dynamic densification was used to consolidate mechanically amorphized Ti-Si alloy powders. A 3-capsule, plate-impact, gas-gun loading system was used to densify the powders at impact velocities of 300 and 500 m/s. The recovered compacts were observed to retain the amorphous structure as evidenced by x-ray diffraction (XRD) and transmission microscopy (TEM) analysis. The densified material was subsequently annealed at various temperatures (above the crystallization temperature) to produce a nanocrystalline Ti_5Si3 microstructure. TEM and XRD analysis revealed retention of a nano-grain microstructure (< 100 nm) in the crystallized compacts. In this presentation the influence of dynamic densification on the crystallization of the amorphous compound and retention of the nano-scale grain size in the crystallized compacts will be discussed.

  19. SIMS Characterization of Amorphous Silicon Germanium Alloys Grown by Hot-Wire Deposition

    SciTech Connect

    Reedy, R. C.; Mason, A. R.; Nelson, B. P.; Xu, Y.

    1998-10-16

    In this paper, we present methods for the quantitative secondary ion mass spectrometry (SIMS) characterization of amorphous SiGe:H alloy materials. A set of samples was grown with germanium content ranging from 5% to 77% and was subsequently analyzed by electron probe X-ray microanalysis (EPMA) and nuclear reaction analysis (NRA). Calibration of the SIMS quantification was performed with respect to EPMA data for germanium and NRA data for hydrogen.

  20. Proton and deuteron nuclear magnetic resonance studies of amorphous hydrogenated silicon, carbon, and carbon alloys

    NASA Astrophysics Data System (ADS)

    Kernan, Mary Jane Wurth

    Despite the profound influence of semiconductors and the changes they have produced, many fundamental questions remain unanswered. We have used proton and deuteron nuclear magnetic resonance (NMR) to explore the role of hydrogens in amorphous silicon and amorphous carbon and carbon alloy films. In the carbon films, dipolar filtering techniques reveal a two-component shifted lineshape in the proton NMR spectra and deuteron magnetic resonance (DMR) data demonstrate a feedstock gas dependence in the film deposition process. In these measurements, DMR is used to examine the effect of hydrogen on the photovoltaic properties of amorphous silicon thin films. We have measured the effects of photoillumination on amorphous silicon, particularly with respect to the process of metastable defect formation (the Staebler-Wronski effect). The creation and passivation of dangling silicon bonds is observed and quantified. We report large-scale light-induced atomic rearrangements which produce shifts and broadenings of the DMR lineshapes. The deuterium NMR lineshape component most affected by atomic rearrangements is a broad central feature which is shown to be molecular in origin. This spectral feature includes hydrogens trapped and immobile on surfaces created by strains and dislocations in the material. Narrowing of the lineshape at elevated temperatures indicates motion with a small activation energy. The substantial population represented by this feature is shown to account for at least 15% of the total hydrogens in high-quality amorphous silicon samples.

  1. Study of Critical Behavior in Amorphous Fe85Sn5Zr10 Alloy Ribbon

    NASA Astrophysics Data System (ADS)

    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.

  2. Magnetic properties of Nd-Fe-Co(Cu)-Al-B amorphous alloys prepared by nonequilibrium techniques

    NASA Astrophysics Data System (ADS)

    Kumar, G.; Eckert, J.; Roth, S.; Löser, W.; Ram, S.; Schultz, L.

    2002-03-01

    The amorphous alloys Nd40Fe40Co5Al8B7, Nd57Fe20Co5Al10B8, and Nd57Fe20Cu5Al10B8 were prepared by copper mold casting, melt spinning, and mechanical alloying. Despite their similar x-ray diffraction patterns, samples display different magnetic and thermal behavior correlated with the method of preparation. The fully amorphous melt-spun ribbons exhibit relatively soft magnetic properties with coercivities ≈40 kA/m at room temperature and a Curie temperature (TC)≈474 K. Apparently only the mold-cast cylinders of 3 mm diameter show hard magnetic behavior with a coercivity in the range of 258-270 kA/m (depending on composition) and have approximately the same TC as that of the melt-spun ribbons. An additional magnetic transition at 585 K due to the presence of Nd2Fe14B phase in the case of Nd40Fe40Co5Al8B7 cast rod has been observed. Heat treatment above crystallization temperature in as-cast Nd57Fe20Co5Al10B8 and Nd57Fe20Cu5Al10B8 samples destroys the hard magnetic properties. In contrast, mechanically alloyed amorphous samples are soft magnetic with maximum coercivity up to 11 kA/m but show an entirely different TC≈680-740 K, which is rather characteristic of an Fe solid solution. The magnetic properties are discussed in terms of different local atomic environment and cluster sizes in amorphous samples prepared by different methods.

  3. Characterization of amorphous Co-P alloy coatings electrodeposited with pulse current using gluconate bath

    NASA Astrophysics Data System (ADS)

    Bera, Parthasarathi; Seenivasan, H.; Rajam, K. S.; William Grips, V. K.

    2012-10-01

    Co-P alloy coatings were electrodeposited with pulse current using gluconate bath and characterized by XRD, FESEM, AFM, DSC and XPS. Co-P alloy coatings are amorphous in nature as demonstrated by XRD. FESEM exhibits the “cauliflower type” morphology that is distinctive of nanocrystalline metals and alloys. Co-P alloys are found to follow instantaneous growth mechanism as revealed by AFM studies. Two exothermic peaks at 320 and 340 °C in DSC profiles of Co-P deposit correspond to the crystallization of the deposit. Detailed XPS studies of these alloy coatings have shown that as-deposited coatings consist of Co metal as well as oxidized Co species. P has mostly been present as bulk alloy on the surface as Pδ- form. Increase in the amounts of Co metal and Pδ- are observed upon intermittent sputtering. No appreciable increase in microhardness is observed with increase in the phosphorous content, but it increases with heat treatment significantly.

  4. Invar and Elinvar type amorphous Fe-Cr-B alloys with high corrosion resistance

    NASA Technical Reports Server (NTRS)

    Kikuci, M.; Fukamichi, K.; Masumoto, T.

    1987-01-01

    Amorphous (Fe(1-x)Cr(x))85B15 alloys (x = 0 to 0.15) were prepared from the melts by rapid quenching using a single roller techinque, and their Invar and Elinvar characteristics and corrosion resistance were investigated. With an increase in chromium content the Curie temperature and the saturation magnetic moment per iron atom decreased monotonically, while the crystallization temperature incresed gradually. The thermal expansion coefficient alpha around room temperature became slightly larger with increasing chromium content. Nevertheless, these amorphous alloys exhibited excellent Invar characteristics below the Curie temperature. The value of Young's modulus increased remarkably in a relatively low magnetic field and then saturated at a field of about 80 kA/m, showing a large delta E effect. Its value as well as a longitudinal linear magnetostriction became smaller with an increase in chromium content. The temperature coefficient of Young's modulus changed from postive to negative, and the temperature range showing the Elinvar characteristics became narrower with chromium content. The temperature coefficient of delay time determined from the values of alpha and e was very small. The corrosion resistance of these alloys was extremely improved by chromium addition.

  5. Laser micro-processing of amorphous and partially crystalline Cu45Zr48Al7 alloy

    NASA Astrophysics Data System (ADS)

    Aqida, S. N.; Brabazon, D.; Naher, S.; Kovacs, Z.; Browne, D. J.

    2010-11-01

    This paper presents a microstructural study of laser micro-processed high-purity Cu45Zr48Al7 alloys prepared by arc melting and Cu-mould casting. Microprocessing of the Cu45Zr48Al7 alloy was performed using a Rofin DC-015 diffusion-cooled CO2 slab laser system with 10.6-μm wavelength. The laser was defocused to a spot size of 0.2 mm on the sample surface. The laser parameters were set to give 300- and 350-W peak power, 30% duty cycle and a 3000-Hz laser pulse repetition frequency (PRF). About 100-micrometer-wide channels were scribed on the surfaces of disk-shaped amorphous and partially crystalline samples at traverse speeds of 500 and 5000 mm/min. These channels were analysed using scanning electron microscopy (SEM) and 2D stylus profilometry. The metallographic study and profile of these processed regions are discussed in terms of the applied laser processing parameters. The SEM micrographs showed that striation marks developed at the edge and inside these regions as a result of the laser processing. The results from this work showed that microscale features can be produced on the surface of amorphous Cu-Zr-Al alloys by CO2 laser processing.

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

    NASA Astrophysics Data System (ADS)

    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.

  7. On the amorphization behavior and hydrogenation performance of high-energy ball-milled Mg{sub 2}Ni alloys

    SciTech Connect

    Kou, Hongchao; Hou, Xiaojiang; Zhang, Tiebang Hu, Rui; Li, Jinshan; Xue, Xiangyi

    2013-06-15

    Amorphous Mg{sub 2}Ni alloy was prepared by high energy ball-milling starting with polycrystalline Mg{sub 2}Ni which was prepared with the help of a metallurgy method by using a SPEX 8000D mill. The microstructural and phase structure characterization of the prepared materials was performed via scanning electron microscopy, transition electron microscope and X-ray diffraction. The thermal stabilities were investigated by differential scanning calorimetry. The apparent activation energies were determined by means of the Kissinger method. The first and second crystallization reactions take place at ∼ 255 °C and ∼ 410 °C, and the corresponding activation energy of crystallization is E{sub a1} = 276.9 and E{sub a2} = 382.4 kJ/mol, respectively. At 3 MPa hydrogen pressure and 250 °C, the hydrogen absorption capacities of crystalline, partially and fully amorphous Mg{sub 2}Ni alloy are 2.0 wt.%, 3.2 wt.% and 3.5 wt.% within 30 min, respectively. - Graphical Abstract: We mainly focus on the amorphization behavior of crystalline Mg{sub 2}Ni alloy in the high energy ball-milling process and the crystallization behavior of the amorphous Mg{sub 2}Ni alloy in a follow-up heating process. The relationship of milling, microstructure and hydrogenation properties is established and explained by models. - Highlights: • Amorphous Mg{sub 2}Ni has been obtained by high energy ball milling the as-cast alloy. • The amorphization behavior of polycrystalline Mg{sub 2}Ni is presented. • The crystallization behavior of the amorphous Mg{sub 2}Ni alloy is illustrated. • Establish the relationship of milling, microstructure and hydrogenation properties.

  8. Saturation and forced volume magnetostriction of Fe-rich FeZr amorphous alloys

    NASA Astrophysics Data System (ADS)

    Tange, H.; Tanaka, Y.; Goto, M.; Fukamichi, K.

    1989-10-01

    AC susceptibility, saturation and forced volume magnetostriction were studied on iron-rich zirconium amorphous alloys a-Fe 100- xZr x (8 at% ≤ x ≤ 12 at%). The experimental results are discussed in relation to the re-entrant spin glass state. It is found that the transverse magnetostriction accompanies a remarkable magnetic aftereffect in the spin glass phase, and that the forced volume magnetostriction shows an apparent peak at the ferromagnet to spin glass transition where the ac susceptibility has a cusp.

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

    SciTech Connect

    Darmawikarta, Kristof; Abelson, John R.; Raoux, Simone; Bishop, Stephen G.

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  11. Thermally Induced Structural Transformations of Fe40Ni40P14B6 Amorphous Alloy

    NASA Astrophysics Data System (ADS)

    Vasić, Milica M.; Roupcová, Pavla; Pizúrová, Naděžda; Stevanović, Sanja; Blagojević, Vladimir A.; Žák, Tomáš; Minić, Dragica M.

    2016-01-01

    Thermal stability and thermally induced structural transformations of Fe40Ni40P14B6 amorphous alloy were examined under non-isothermal and isothermal conditions. Formation of metastable α-(Fe,Ni), and stable γ-(Fe,Ni) and (Fe,Ni)3(P,B) crystalline phases as the main crystallization products was observed, while the presence of small amounts of other crystalline phases like Fe23B6 and Fe2NiB was indicated by electron diffraction in HRTEM. Thermomagnetic curve indicated that Fe content in different crystalline phases is very different, resulting in markedly different Curie temperatures after crystallization. Transmission electron microscopy and atomic force microscopy study suggested multiple-layered platelet-shaped morphology, both on the surface and in the bulk of the crystallized alloy sample. The thermal treatment heating rate and maximum temperature affected surface roughness and grain size inhomogeneity.

  12. Ultrafast crystalline-to-amorphous phase transition in Ge{sub 2}Sb{sub 2}Te{sub 5} chalcogenide alloy thin film using single-shot imaging spectroscopy

    SciTech Connect

    Takeda, Jun Oba, Wataru; Minami, Yasuo; Katayama, Ikufumi; Saiki, Toshiharu

    2014-06-30

    We have observed an irreversible ultrafast crystalline-to-amorphous phase transition in Ge{sub 2}Sb{sub 2}Te{sub 5} chalcogenide alloy thin film using broadband single-shot imaging spectroscopy. The absorbance change that accompanied the ultrafast amorphization was measured via single-shot detection even for laser fluences above the critical value, where a permanent amorphized mark was formed. The observed rise time to reach the amorphization was found to be ∼130–200 fs, which was in good agreement with the half period of the A{sub 1} phonon frequency in the octahedral GeTe{sub 6} structure. This result strongly suggests that the ultrafast amorphization can be attributed to the rearrangement of Ge atoms from an octahedral structure to a tetrahedral structure. Finally, based on the dependence of the absorbance change on the laser fluence, the stability of the photoinduced amorphous phase is discussed.

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

    SciTech Connect

    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

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

    SciTech Connect

    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

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

    NASA Astrophysics Data System (ADS)

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

    2009-06-01

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

  16. Mechanical properties of amorphous LixSi alloys: a reactive force field study

    NASA Astrophysics Data System (ADS)

    Fan, Feifei; Huang, Shan; Yang, Hui; Raju, Muralikrishna; Datta, Dibakar; Shenoy, Vivek B.; van Duin, Adri C. T.; Zhang, Sulin; Zhu, Ting

    2013-10-01

    Silicon is a high-capacity anode material for lithium-ion batteries. Electrochemical cycling of Si electrodes usually produces amorphous LixSi (a-LixSi) alloys at room temperature. Despite intensive investigation of the electrochemical behaviors of a-LixSi alloys, their mechanical properties and underlying atomistic mechanisms remain largely unexplored. Here we perform molecular dynamics simulations to characterize the mechanical properties of a-LixSi with a newly developed reactive force field (ReaxFF). We compute the yield and fracture strengths of a-LixSi alloys under a variety of chemomechanical loading conditions, including the constrained thin-film lithiation, biaxial compression, uniaxial tension and compression. Effects of loading sequence and stress state are investigated to correlate the mechanical responses with the dominant atomic bonding, featuring a transition from the covalent to the metallic glass characteristics with increasing Li concentration. The results provide mechanistic insights for interpreting experiments, understanding properties and designing new experiments on a-LixSi alloys, which are essential to the development of durable Si electrodes for high-performance lithium-ion batteries.

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

    NASA Astrophysics Data System (ADS)

    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.

  18. In situ observation of defect annihilation in Kr ion-irradiated bulk Fe/amorphous-Fe 2 Zr nanocomposite alloy

    DOE PAGES

    Yu, K. Y.; Fan, Z.; Chen, Y.; ...

    2014-08-26

    Enhanced irradiation tolerance in crystalline multilayers has received significant attention lately. However, little is known on the irradiation response of crystal/amorphous nanolayers. We report on in situ Kr ion irradiation studies of a bulk Fe96Zr4 nanocomposite alloy. Irradiation resulted in amorphization of Fe2Zr and formed crystal/amorphous nanolayers. α-Fe layers exhibited drastically lower defect density and size than those in large α-Fe grains. In situ video revealed that mobile dislocation loops in α-Fe layers were confined by the crystal/amorphous interfaces and kept migrating to annihilate other defects. This study provides new insights on the design of irradiation-tolerant crystal/amorphous nanocomposites.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    SciTech Connect

    Fukuhara, M.; Kawarada, H.

    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.

  1. Bimetallic non-alloyed NPs for improving the broadband optical absorption of thin amorphous silicon substrates

    PubMed Central

    2014-01-01

    We propose the use of bimetallic non-alloyed nanoparticles (BNNPs) to improve the broadband optical absorption of thin amorphous silicon substrates. Isolated bimetallic NPs with uniform size distribution on glass and silicon are obtained by depositing a 10-nm Au film and annealing it at 600°C; this is followed by an 8-nm Ag film annealed at 400°C. We experimentally demonstrate that the deposition of gold (Au)-silver (Ag) bimetallic non-alloyed NPs (BNNPs) on a thin amorphous silicon (a-Si) film increases the film's average absorption and forward scattering over a broad spectrum, thus significantly reducing its total reflection performance. Experimental results show that Au-Ag BNNPs fabricated on a glass substrate exhibit resonant peaks at 437 and 540 nm and a 14-fold increase in average forward scattering over the wavelength range of 300 to 1,100 nm in comparison with bare glass. When deposited on a 100-nm-thin a-Si film, Au-Ag BNNPs increase the average absorption and forward scattering by 19.6% and 95.9% compared to those values for Au NPs on thin a-Si and plain a-Si without MNPs, respectively, over the 300- to 1,100-nm range. PMID:24725390

  2. Structure and Phase Separation in Ultrathin Ag/Cu Amorphous Alloy System

    NASA Astrophysics Data System (ADS)

    Chen, Hao

    2005-03-01

    The structure of disordered metallic alloys is an important but unsolved problem. Previous studies on Ag-Cu system showed that relatively homogeneous solid solutions formed at liquid nitrogen temperature decompose into separate phases or evolve into crystalline structure at a higher temperature. In this research project, we prepared ultra-thin Ag-Cu films on amorphous carbon support by HV magnetron sputtering with both targets. With high energy Ag and Cu atoms bombarding on the carbon substrate, they are forced to form amorphous alloy or nano-crystalline thin film at room temperature. We have investigated the structure of ultra-thin Ag-Cu films by examining their pair distribution function (PDF) using electron diffraction and observed phase separation process directly in STEM images. In the STEM Z-contrast images, since the contrast is directly related to the atomic number (Z) of the components, we can see clearly the phase separation process. Experimental results show that the sample morphology evolutions are different in samples with different thickness, and the phase separation depends on various Ag/Cu atomic ratios. In Ag50Cu50 sample, early stage phase separation is associated with increasing Cu crystallite size, indicates that Cu diffuse out of Ag-Cu solid solution phase.

  3. 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

    SciTech Connect

    Wang, Yaocen; Takeuchi, Akira; Makino, Akihiro; Liang, Yunye; Kawazoe, Yoshiyuki

    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.

  4. Anomalous small angle x-ray scattering studies of amorphous metal-germanium alloys

    SciTech Connect

    Rice, M.

    1993-12-01

    This dissertation addresses the issue of composition modulation in sputtered amorphous metal-germanium thin films with the aim of understanding the intermediate range structure of these films as a function of composition. The investigative tool used in this work is anomalous small-angle X-ray scattering (ASAXS). The primary focus of this investigation is the amorphous iron-germanium (a-Fe{sub x}Ge{sub 100-x}) system with particular emphasis on the semiconductor-rich regime. Brief excursions are made into the amorphous tungsten-germanium (a-W{sub x}Ge{sub 100-x}) and the amorphous molybdenum-germanium (a-Mo{sub x}Ge{sub 100-x}) systems. All three systems exhibit an amorphous structure over a broad composition range extending from pure amorphous germanium to approximately 70 atomic percent metal when prepared as sputtered films. Across this composition range the structures change from the open, covalently bonded, tetrahedral network of pure a-Ge to densely packed metals. The structural changes are accompanied by a semiconductor-metal transition in all three systems as well as a ferromagnetic transition in the a-Fe{sub x}Ge{sub 100-x} system and a superconducting transition in the a-Mo{sub x}Ge{sub 100-x} system. A long standing question, particularly in the a-Fe{sub x}Ge{sub 100-x} and the a-Mo{sub x}Ge{sub 100-x} systems, has been whether the structural changes (and therefore the accompanying electrical and magnetic transitions) are accomplished by homogeneous alloy formation or phase separation. The application of ASAXS to this problem proves unambiguously that fine scale composition modulations, as distinct from the simple density fluctuations that arise from cracks and voids, are present in the a-Fe{sub x}Ge{sub 100-x}, a-W{sub x}Ge{sub 100-x}, and a-Mo{sub x}Ge{sub 100-x} systems in the semiconductor-metal transition region. Furthermore, ASAXS shows that germanium is distributed uniformly throughout each sample in the x<25 regime of all three systems.

  5. Regularities of the effect of the value of initial bending stresses on their relaxation under the annealing of amorphous magnetically soft alloys of various classes

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

    It has been shown that, in some amorphous alloys, the value of initial bending stresses σm can influence the development of the relaxation of these stresses during the annealing of the alloys. These alloys include Co69Fe3.7Cr3.8Si12.5B11, with a nearly zero saturation magnetostriction (λs < 10-7) and the Fe78Ni1Si8B13 alloy with λs = 25 × 10-6. In the iron-based Fe81Si4B13C2 and Fe57Co31Si2.9B9.1 alloys, no effect of the initial bending stresses on their relaxation has been observed. No this effect has also been observed in the metalloid-free alloys Co80Mo10Zr10 and Co80Mo8Ni2Zr10 with a nearly zero saturation magnetostriction λs. When this effect manifests itself, the activation energy U of the given process becomes a function of two factors; i.e., this energy depends on both the composition of the alloy (that is, interatomic forces) and the value of the initial bending stresses. In this case, the activation energy U cannot be considered to be characteristic of the material.

  6. Continuous-annealing method for producing a flexible, curved, soft magnetic amorphous alloy ribbon

    NASA Astrophysics Data System (ADS)

    Francoeur, Bruno; Couture, Pierre

    2012-04-01

    A method has been developed for continuous annealing of an amorphous alloy ribbon moving forward at several meters per second, giving a curved shape to the ribbon that remains flexible afterward and can be easily wound into a toroidal core with excellent soft magnetic properties. A heat pulse was applied by a compact system on a Metglas 2605HB1 ribbon moving forward at 5 m/s to initiate a thermal treatment at 460 °C, near crystallization onset. The treatment duration was less than 0.1 s, and the heating and cooling rates were above 10 000 °C/s, which helped preserve most of the alloy as-cast ductility state. Such high temperature rates were achieved by forcing a static contact between the moving ribbon and a temperature-controlled roller. A tensile stress and a series of bending configurations were applied on the moving ribbon during the treatment to induce the development of magnetic anisotropy and to obtain the desired natural curvature radius. The core losses at 60 Hz of a toroidal test core wound with the resulting ribbon are lower than the specific values reported by the alloy manufacturer. This method can be implemented at the casting plant for supplying a low-cost, ready-to-use ribbon, easy to handle and cut, for mass production of toroidal cores for distribution transformer kernels (core and coil only), pulse power cores, etc.

  7. Gallium-enhanced phase contrast in atom probe tomography of nanocrystalline and amorphous Al-Mn alloys.

    PubMed

    Ruan, Shiyun; Torres, Karen L; Thompson, Gregory B; Schuh, Christopher A

    2011-07-01

    Over a narrow range of composition, electrodeposited Al-Mn alloys transition from a nanocrystalline structure to an amorphous one, passing through an intermediate dual-phase nanocrystal/amorphous structure. Although the structural change is significant, the chemical difference between the phases is subtle. In this study, the solute distribution in these alloys is revealed by developing a method to enhance phase contrast in atom probe tomography (APT). Standard APT data analysis techniques show that Mn distributes uniformly in single phase (nanocrystalline or amorphous) specimens, and despite some slight deviations from randomness, standard methods reveal no convincing evidence of Mn segregation in dual-phase samples either. However, implanted Ga ions deposited during sample preparation by focused ion-beam milling are found to act as chemical markers that preferentially occupy the amorphous phase. This additional information permits more robust identification of the phases and measurement of their compositions. As a result, a weak partitioning tendency of Mn into the amorphous phase (about 2 at%) is discerned in these alloys.

  8. Influence of boron on the magnetic and transport properties of FeZr amorphous and nanocrystalline alloys

    SciTech Connect

    Barandiaran, J.M.; Gorria, P. . Dept. de Electricidad y Electronica); Sal, J.C.G.; Brquin, L.F. ); Kaul, S.N. . School of Physics)

    1994-11-01

    The magnetic properties and electrical resistivity of amorphous and nanocrystalline FeZr and FeZrB(Cu) alloys are compared in a wide range of temperatures (4 to 1,000 K). The addition of boron increases the Curie temperature of the alloys and induces a broad minimum in the resistivity vs temperatures. A first step of crystallization occurs around 700 K in all the alloys, giving rise to [alpha]-Fe crystallites of very small size. Small amounts of boron greatly influence the exchange interactions, enhancing the ferromagnetic character of these compounds.

  9. Tissue Response to Base-Metal Dental Alloys.

    DTIC Science & Technology

    RESPONSE(BIOLOGY), *CASTING ALLOYS, *BASE METAL, * DENTAL PROSTHESES, TISSUES(BIOLOGY), COMPATIBILITY, NICKEL ALLOYS, BERYLLIUM, DENTISTRY, CANCER, HISTOLOGY, DENTAL IMPLANTOLOGY , COBALT ALLOYS, CHROMIUM ALLOYS.

  10. Method of casting articles of a bulk-solidifying amorphous alloy

    DOEpatents

    Lin, X.; Johnson, W.L.; Peker, A.

    1998-08-25

    A casting charge of a bulk-solidifying amorphous alloy is cast into a mold from a temperature greater than its crystallized melting temperature, and permitted to solidify to form an article. The oxygen content of the casting charge is limited to an operable level, as excessively high oxygen contents produce premature crystallization during the casting operation. During melting, the casting charge is preferably heated to a temperature above a threshold temperature to eliminate heterogeneous crystallization nucleation sites within the casting charge. The casting charge may be cast from above the threshold temperature, or it may be cooled to the casting temperature of more than the crystallized melting point but not more than the threshold temperature, optionally held at this temperature for a period of time, and thereafter cast. 8 figs.

  11. Identification of infrared absorption peaks of amorphous silicon-carbon alloy by thermal annealing

    NASA Astrophysics Data System (ADS)

    Lin, Wei-Liang; Tsai, Hsiung-Kuang; Lee, Si-Chen; Sah, Wen-Jyh; Tzeng, Wen-Jer

    1987-12-01

    Amorphous silicon-carbon hydrogen alloy was prepared by radio frequency glow discharge decomposition of a silane-methane mixture. The infrared absorption spectra were measured at various stages of thermal annealing. By observing the change of relative intensities between these peaks the hydrogen bonding responsible for the absorption peaks could be assigned more accurately, for example, the stretching mode of monohydride Si-H is determined by its local environment, which supports H. Wagner's and W. Beyer's results [Solid State Commun. 48, 585 (1983)] but is inconsistent with the commonly believed view. It is also found that a significant fraction of carbon atoms are introduced into the film in -CH3 configuration which forms a local void and enhances the formation of polysilane chain and dangling bond defects. Only after high-temperature annealing are the hydrogen atoms driven out, and Si and C start to form a better silicon carbide network.

  12. Coercivity of domain wall motion in thin films of amorphous rare earth-transition metal alloys

    NASA Technical Reports Server (NTRS)

    Mansuripur, M.; Giles, R. C.; Patterson, G.

    1991-01-01

    Computer simulations of a two dimensional lattice of magnetic dipoles are performed on the Connection Machine. The lattice is a discrete model for thin films of amorphous rare-earth transition metal alloys, which have application as the storage media in erasable optical data storage systems. In these simulations, the dipoles follow the dynamic Landau-Lifshitz-Gilbert equation under the influence of an effective field arising from local anisotropy, near-neighbor exchange, classical dipole-dipole interactions, and an externally applied field. Various sources of coercivity, such as defects and/or inhomogeneities in the lattice, are introduced and the subsequent motion of domain walls in response to external fields is investigated.

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

    SciTech Connect

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

    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

  14. Ferromagnetic resonance studies of amorphous and nanocrystalline FeCuNbSiB alloys

    SciTech Connect

    Schmool, D.S.; Gorria, P.; Barandiaran, J.M.

    1997-04-01

    Alloys with composition Fe{sub 73.5}Cu{sub 1}Nb{sub 3}Si{sub 22.5{minus}x}B{sub x}, where x=6 and 9, have been studied from the as-cast state, through various stages of crystallization, in annealing range of 300{endash}650{degree}C, by the technique of ferromagnetic resonance (FMR). The annealing was performed isothermally at preset temperatures to produce nanocrystalline structures in an amorphous matrix. Both the nanocrystalline structures and the surrounding amorphous matrix are ferromagnetic, and will therefore contribute to the FMR spectra. The spectral features, resonance field, intensity, and linewidth have been used to characterize the structurally related changes in the sample during the crystallization process. The major changes in the spectra are observed to occur in the region of the crystallization peak in the differential thermal analysis curves for these samples. The FMR spectra exhibit a complex in-plane angular variation, which is understood in terms of preferential orientation of the magnetization vector in the direction of the ribbon, and shape effects. The square cut samples give rise to multipeaked spectra when the external magnetic field is applied in an {open_quotes}off-square{close_quotes} direction. This is the first report of the appearance of a second resonance feature of this type. This is explained as arising from the magnetic confinement of the nanocrystallites in the amorphous matrix, producing spin waves localized at the interface of the two phases. {copyright} {ital 1997 American Institute of Physics.}

  15. Self-propagating crystallization waves in the TiCu amorphous alloy

    NASA Astrophysics Data System (ADS)

    Rogachev, A. S.; Vadchenko, S. G.; Shchukin, A. S.; Kovalev, I. D.; Aronin, A. S.

    2016-11-01

    Self-propagating crystallization waves are detected and experimentally demonstrated in the Ti50Cu50 amorphous alloy obtained by the melt spinning (ultrafast quenching) method. High-speed thermographic recording has shown that crystallization waves can appear spontaneously at the heating of an amorphous strip to 300-350°C or at the local initiation by a hot tungsten coil of a small segment of the strip preliminarily heated to 230-250°C. In the former case, the crystallization wave propagates at a velocity of 7 cm/s; in the latter case, the crystallization wave propagates in a self-oscillation mode at an average velocity of 1.2 cm/s. The temperature gradient across the wavefront is about 150°C. The samples crystallized in the self-oscillation mode have a characteristic banded structure with a smaller grain in depression regions. The crystallization product in all samples is the TiCu tetragonal intermetallic phase.

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

    SciTech Connect

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

    2009-08-29

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

  17. Corrosion Characterization of Iron-Based High-Performance Amorphous-Metal Thermal-Spray Coatings

    SciTech Connect

    Farmer, J C; Haslam, J J; Day, S D; Branagan, D J; Blue, C A; Rivard, J K; Aprigliano, L F; Yang, N; Perepezko, J H; Beardsley, M B

    2005-03-21

    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 N06022) in some very aggressive environments, including concentrated calcium-chloride brines at elevated temperature. One of these compositions, SAM1651, is discussed in detail to illustrate the promise of this general class of materials.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  1. Amorphization of Al[sub 6]Mn phase in an Al-14 a/o Mn alloy during low energy helium ion bombardment

    SciTech Connect

    Nair, K.G.M.; Krishan, K. . Materials Science Division); Vijayalakshmi, M. . Metallurgy Division)

    1993-10-01

    Amorphization of ordered intermetallic compounds has been observed during ion, electron and neutron irradiations. Investigations have been carried out in a number of systems. It has been generally observed that intermetallic compounds with a narrow range of homogeneity (line compounds) amorphize on irradiation. The present paper reports the observation of irradiation-induced amorphization in the Al[sub 6]Mn phase in an Al-14 a/o Mn alloy. The dose and energy dependence of the amorphization process are discussed. The present studies suggest that the defects produced during irradiation rather than the implanted atoms (helium) play a major role in the crystalline to amorphous transition.

  2. Microstructure development and hydrogen gas interaction of oxidized Zr65Pd35 and Zr60Pd35Ce5 amorphous alloys

    NASA Astrophysics Data System (ADS)

    Ozawa, Masakuni; Kato, Shiro; Kobayashi, Katsutoshi; Yogo, Toshinobu; Yamamura, Shin-ichi

    2016-01-01

    The microstructure of composites derived from amorphous Zr65Pd35 and Zr65Pd35Ce5 alloys was studied. X-ray diffractograms, Raman spectroscopy profiles and scanning electron micrographs indicated that the mixtures containing ZrO2, metallic Pd, and PdO were formed for both amorphous alloys after heat treatment in air. The amorphous Zr60Pd35Ce5 alloy at temperatures of 280-400 °C changed to the composites in which very small Pd precipitates with a diameter less than 100 nm were embedded in a ZrO2 matrix. The hydrogen-temperature-programmed reduction was applied to study the reactivity of hydrogen gas with the oxidized Zr60Pd35Ce5 material. A rapid hydrogen absorption and release behavior was observed on the composite derived from the amorphous alloy.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed Central

    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

  7. Saturation and forced volume magnetostrictions of Fe-rich FeZr and FeNiZr amorphous alloys

    NASA Astrophysics Data System (ADS)

    Tange, H.; Kamimori, T.; Goto, M.; Fukamichi, K.

    1990-12-01

    The saturation and forced volume magnetostrictions, ac susceptibility have been investigated for Fe 90Zr 10 and Fe 90-xNi xZr 10 amorphous alloys. The linear magnetostriction in the re-entrant spin glass state exhibits a hysteresis due to a remarkable magnetic after effect. The temperature dependence of the forced volume magnetostriction shows a peak at the spin freezing temperature.

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

    SciTech Connect

    Guha, S.

    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.

  9. Large Magnetocaloric Effect Around Room Temperature in Amorphous Fe-Gd-Zr Alloy Ribbon with Short-Range Interactions

    NASA Astrophysics Data System (ADS)

    Thanh, Tran Dang; Yen, Nguyen Hai; Duc, Nguyen Huu; Phan, The-Long; Dan, Nguyen Huy; Yu, Seong-Cho

    2016-05-01

    In this work, we present a detailed study on the magnetocaloric effect and the critical behaviors of an amorphous Fe88Gd2Zr10 alloy ribbon prepared by using a rapid quenching method. We point out that the value of maximum magnetic entropy change (|∆ S max|) of amorphous Fe88Gd2Zr10 alloy ribbon appeared at near room temperature and versus Δ H obeys a power law, |∆ S max| = a·Δ H n. In addition, all Δ S m( T, Δ H) data measured at different Δ H values are collapsed onto a universal master curve. Interestingly, M 2 versus H/ M curves prove amorphous Fe88Gd2Zr10 ribbon exhibitied a second-order magnetic phase transition. The critical exponents ( β, γ, and δ) obtained from the modified Arrott plots and the Kouvel-Fisher methods, and critical isotherm analysis are very close to those expected for the 3D-Heisenberg model, proving ferromagnetic short-range interactions exist in amorphous Fe88Gd2Zr10 ribbon.

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

    PubMed

    Chan, W Y; Chian, K S; Tan, M J

    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 Mg67Zn28Ca5 alloy by coating a gelatin layer by electrospinning. Coated/uncoated alloys were immersed and extracted for 3 days under different CO2. The immersion results showed that pH and metal ion release in the alloy extracts were affected by gelatin coating and CO2, suggesting their roles in alloy biocorrosion and a mechanism has been proposed for the alloy-CO2 system with/without coating. Cytotoxicity results are evident that gelatin-coated alloy with 2-day crosslinking not only exhibited no indirect cytotoxicity, but also supported attachment of L929 and MG63 cell lines around/on the alloy with high viability. Therefore, amorphous Mg67Zn28Ca5 alloy coated with gelatin by electrospinning technique provides a useful method to improve alloy biocompatibility.

  11. Non-isothermal kinetic parameters and models of crystallization for amorphous Fe-Co-Nb-Cu-B alloys

    NASA Astrophysics Data System (ADS)

    Wang, Xin; Deng, Longjiang; Xie, Jianliang; Liang, Difei

    2013-02-01

    The non-isothermal differential scanning calorimetry (DSC) measurements are often used to study kinetics of amorphous alloys. However non-isothermal kinetic parameters and models of amorphous alloy crystallization process were unclear. In our research, amorphous (FexCo1-x)NbCuB (x=0.33, 0.5 and 0.75) alloys were produced in the form of ribbon by a single roller melt-spinning method. DSC curves at heating rate 5, 10, 15, 20 and 25 K/min were obtained. Kissinger, Ozawa and model-free methods obtain identical activation energies at each exothermic peak of all compositions. We conclude that first exothermic reaction is determined by the migration activation energy of Fe or Co atom; second reaction determined by the energy between parent and product boride phases; and the third reaction determined by the energy between parent α-FeCo phase and product bcc-Fe/fcc-Co phases. We hypothesized a non-isothermal kinetic modelf(α)=α(1, which fit our experiment results well. In this model, m depends on nucleus shape and growth dimension, and n are determined by lattice positions participated in new phase formation.

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

    SciTech Connect

    Zhang, Pengfei Li, Xinli

    2015-07-15

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

  13. High strength forgeable tantalum base alloy

    NASA Technical Reports Server (NTRS)

    Buckman, R. W., Jr.

    1975-01-01

    Increasing tungsten content of tantalum base alloy to 12-15% level will improve high temperature creep properties of existing tantalum base alloys while retaining their excellent fabrication and welding characteristics.

  14. Electron cyclotron resonance deposition of amorphous silicon alloy films and devices

    SciTech Connect

    Shing, Y.H. )

    1992-10-01

    This report describes work to develop a state-of-the-art electron cyclotron resonance (ECR) plasma-enhanced chemical vapor deposition (PECVD) system. The objective was to understand the deposition processes of amorphous silicon (a-Si:H) and related alloys, with a best-effort improvement of optoelectronic material properties and best-effort stabilization of solar cell performance. ECR growth parameters were systematically and extensively investigated; materials characterization included constant photocurrent measurement (CPM), junction capacitance, drive-level capacitance profiling (DLCP), optical transmission, light and dark photoconductivity, and small-angle X-ray scattering (SAXS). Conventional ECR-deposited a-Si:H was compared to a new form, a-Si:(Xe, H), in which xenon gas was added to the ECR plasma. a-Si:(Xe,H) possessed low, stable dark conductivities and high photosensitivites. Light-soaking revealed photodegradation rates about 35% lower than those of comparable radio frequency (rf)-deposited material. ECR-deposited p-type a SiC:H and intrinsic a-Si:H films underwent evaluation as components of p-i-n solar cells with standard rf films for the remaining layers.

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

    PubMed Central

    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.

    2015-01-01

    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. PMID:26080437

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

    SciTech Connect

    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.

    2015-06-15

    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. Lastly, 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.

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

    PubMed

    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.

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

    DOE PAGES

    Zhou, Nanjia; Kim, Myung -Gil; Loser, Stephen; ...

    2015-06-15

    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 photoactivemore » 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. Lastly, 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.« less

  19. Structure and magnetic properties of amorphous Fe-(Zr,Nb)-B melt spun alloys

    NASA Astrophysics Data System (ADS)

    Zamora, J.; Betancourt, I.

    2017-04-01

    In this work, we report the structure and magnetic behavior of an amorphous Fe81Zr5Nb4B10 melt-spun alloy. The radial distribution function (RDF) afforded the resolution of the nearest-neighbor configuration on the basis of the atom-pair distance information, for which the positions of each peak indicated the atom-to-atom separation involved for short-range ordering. The first peaks of RDF were attributed to the distances of B-B, Fe-Fe and Zr-Nb atomic pairs, indicating a glassy structure equivalent to a distorted bcc-Fe cluster. From magnetic measurements, a magnetic moment of 0.65 Bohr magneton per Fe atom was established, together with a Curie temperature of 334 K and an initial ac permeability of 550 for frequencies as high as 250 kHz. In addition, the magnetocaloric effect, quantified from isothermal magnetization measurements through the magnetic entropy variation, reached a maximum of 2.0 J/kg K for a magnetic field change of 2.0 T.

  20. On-demand release of corrosion-inhibiting ions from amorphous Al-Co-Ce alloys.

    PubMed

    Jakab, M A; Scully, J R

    2005-09-01

    Controlled release technologies are often used to supply chemicals or drugs at given rates. Release often occurs on contact with solution. However, some applications, such as corrosion protection, require containment of the active species in a reservoir and their slow release when needed. Conductive polymers have been used as reservoirs for corrosion inhibitors whose triggered release occurs by galvanic reduction or ion exchange. This work shows one of the first examples of pH-controlled release of corrosion-inhibiting ions from an amorphous metallic coating where the pH change that triggers release is a consequence of the onset of corrosion. This corrosion-inhibition strategy provides further corrosion protection beyond the traditional roles of barrier and sacrificial cathodic protection using a metal coating. For instance, zinc galvanizing provides sacrificial cathodic protection and acts as a barrier, but does not supply inhibitor ions. In the coating described here, protection of an underlying structural alloy exposed at coating defects is demonstrated by inhibitor ion release in addition to barrier function and sacrificial cathodic protection.

  1. Prediction of Formation of Amorphous Alloys During Annealing of Ti-binary Alloys and Validation of the Same

    DTIC Science & Technology

    2009-11-22

    several titanium binary alloys and also in some other alloys such as niobium binary systems. The following observations have been made: (a) the formation...Annealing of Titanium Binary Alloys and Validation of the Same 5a. CONTRACT NUMBER FA48690810005 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S...thermodynamics of the phenomenon of this inverse melting in Ti-binary alloys and validate the same. 15. SUBJECT TERMS Thermodynamics, Titanium Alloy

  2. Hyperfine and X-ray investigations of amorphous Fe2Er and Fe2Ce alloys and the effect of hydrogenation on short-range order

    NASA Astrophysics Data System (ADS)

    Ghafari, M.; Keune, W.; Matsuura, M.; Schletz, K. P.

    1990-07-01

    The effect of hydrogenation on the short-range order of amorphous Fe2Er and Fe2Ce alloys has been investigated by Mössbauer, X-ray and magnetization measurements. The hydrogenation leads to drastic changes in the short-range order. The results of Mössbauer measurements show two different distributions of magnetic hyperfine fields for amorphous Fe2CeH4 alloys (a-Fe2CeH4). For a-Fe2ErH3 alloys we found drastic changes in magnetic structure, which is different from the well-known magnetic structures.

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

    SciTech Connect

    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

  4. Effect of the nanocrystallization of a soft magnetic amorphous Fe-P-Mo alloy on its corrosion resistance in a damp industrial SO2-contaminated atmosphere

    NASA Astrophysics Data System (ADS)

    Vavilova, V. V.; Korneev, V. P.; Anosova, M. O.

    2016-09-01

    The study of the electrochemical behavior of a soft magnetic amorphous Fe-P-Mo alloy in a 0.1M Na2SO4 solution, which simulates a damp SO2-contaminated atmosphere, shows that the corrosion resistance of the nanocrystalline Fe80.2P17.1Mo2.7 alloy is comparable to that of a FINEMET alloy. No molybdenum is required for manufacturing the Fe80.2P17.1Mo2.7 alloy, because it can be prepared using natural alloy ferrophosphorus containing molybdenum.

  5. Machine learning based interatomic potential for amorphous carbon

    NASA Astrophysics Data System (ADS)

    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.

  6. Corrosion-resistant amorphous metallic films of Mo/sub 49/Cr/sub 33/B/sub 18/ alloy

    SciTech Connect

    Ramesham, R.; DiStefano, S.; Fitzgerald, D.; Thakoor, A.P.; Khanna, S.K.

    1987-09-01

    Amorphous metallic films of Mo/sub 49/Cr/sub 33/B/sub 18/ have been deposited onto glass and quartz substrates by the magnetron sputter quenching technique. The amorphous nature of the as-deposited films was confirmed by their diffuse x-ray diffraction patterns. The crystallization temperature of the as-deposited films was 590/sup 0/C, according to the differential scanning calorimetry studies. Surface texture and cross-sectional features of the coatings were examined by scanning electron microscopy. Electron microprobe analysis was used to determine the chemical composition of the films. Chemical compositional uniformity of the as-deposited amorphous metallic films was verified by secondary ion mass spectrometry. As-deposited films exhibited microhardness of the order of 600-850 HV. Kinetics of corrosion of the alloy films in H/sub 2/SO/sub 4/ (1N) solution has been studied by potentiodynamic and galvanostatic techniques. As-deposited amorphous films exhibited corrosion current density three orders of magnitude less than the corrosion current density of 304 stainless steel in H/sub 2/SO/sub 4/ (1N) solution. A reaction mechanism at the corrosion potential is proposed.

  7. Polyimide based amorphous silicon solar modules

    NASA Technical Reports Server (NTRS)

    Jeffrey, Frank R.; Grimmer, Derrick P.; Martens, Steven A.; Abudagga, Khaled; Thomas, Michael L.; Noak, Max

    1993-01-01

    Requirements for space power are increasingly emphasizing lower costs and higher specific powers. This results from new fiscal constraints, higher power requirements for larger applications, and the evolution toward longer distance missions such as a Lunar or Mars base. The polyimide based a-Si modules described are being developed to meet these needs. The modules consist of tandem a-Si solar cell material deposited directly on a roll of polyimide. A laser scribing/printing process subdivides the deposition into discrete cell strips which are series connected to produce the required voltage without cutting the polymer backing. The result is a large, monolithic, blanket type module approximately 30 cm wide and variable in length depending on demand. Current production modules have a specific power slightly over 500 W/Kg with room for significant improvement. Costs for the full blanket modules range from $30/Watt to $150/Watt depending on quantity and engineering requirements. Work to date focused on the modules themselves and adjusting them for the AMO spectrum. Work is needed yet to insure that the modules are suitable for the space environment.

  8. Enhanced thermoelectric performance of amorphous Nb based oxynitrides

    NASA Astrophysics Data System (ADS)

    Music, Denis; Geyer, Richard W.; Hans, Marcus

    2015-12-01

    Using density functional theory, amorphous Nb0.27Ru0.06O0.56N0.10 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-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.

  9. Physiologically Based Absorption Modeling for Amorphous Solid Dispersion Formulations.

    PubMed

    Mitra, Amitava; Zhu, Wei; Kesisoglou, Filippos

    2016-09-06

    Amorphous solid dispersion (ASD) formulations are routinely used to enable the delivery of poorly soluble compounds. This type of formulations can enhance bioavailability due to higher kinetic solubility of the drug substance and increased dissolution rate of the formulation, by the virtue of the fact that the drug molecule exists in the formulation in a high energy amorphous state. In this article we report the application of physiologically based absorption models to mechanistically understand the clinical pharmacokinetics of solid dispersion formulations. Three case studies are shown here to cover a wide range of ASD bioperformance in human and modeling to retrospectively understand their in vivo behavior. Case study 1 is an example of fairly linear PK observed with dose escalation and the use of amorphous solubility to predict bioperformance. Case study 2 demonstrates the development of a model that was able to accurately predict the decrease in fraction absorbed (%Fa) with dose escalation thus demonstrating that such model can be used to predict the clinical bioperformance in the scenario where saturation of absorption is observed. Finally, case study 3 shows the development of an absorption model with the intent to describe the observed incomplete and low absorption in clinic with dose escalation. These case studies highlight the utility of physiologically based absorption modeling in gaining a thorough understanding of ASD performance and the critical factors impacting performance to drive design of a robust drug product that would deliver the optimal benefit to the patients.

  10. Recent progress in high Bs Fe-based nanocrystalline soft magnetic alloys

    NASA Astrophysics Data System (ADS)

    Ohta, M.; Yoshizawa, Y.

    2011-02-01

    High saturation magnetic flux density (high-Bs) 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-1 and a high Bs of more than 1.8 T. The iron loss at 50 Hz and 1.6 T for a toroidal core made of Fe80.5Cu1.5Si4B14 nanocrystalline alloy is 0.46 W kg-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-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).

  11. The chemically-specific structure of an amorphous molybdenum germanium alloy by anomalous x-ray scattering

    NASA Astrophysics Data System (ADS)

    Ishii, Hope Ami

    2002-09-01

    Since its inception in the late 1970s, anomalous x-ray scattering (AXS) has been employed for chemically-specific structure determination in a wide variety of non-crystalline materials. These studies have successfully produced differential distribution functions (DDFs) which provide information about the compositionally-averaged environment of a specific atomic species in the sample. Despite the wide success in obtaining DDFs, there are very few examples of successful extraction of the fully-chemically-specific partial pair distribution functions (PPDFs), the most detailed description of an amorphous sample possible by x-ray scattering. Extracting the PPDFs is notoriously difficult since the matrix equation involved is ill-conditioned and thus extremely sensitive to errors present in the experimental quantities that enter the equation. Instead of addressing this sensitivity by modifying the data through mathematical regularization methods, sources of error have been removed experimentally: A focussing analyzer crystal was combined with a position-sensitive linear detector to experimentally eliminate unwanted inelastic scattering intensity over most of the reciprocal space range probed. This instrumentation has been used in data collection for the extraction of PPDFs from amorphous (a)-MoGe3, the phase separation endpoint in the sputter-deposited Mo-Ge amorphous alloys. This alloy is of particular interest because it acts as the conducting phase in a percolative metal-insulator transition but has a composition with no crystalline analogue. Since the first Ge-rich compound in the Mo-Ge equilibrium system is MoGe 2, previous workers have speculated that perhaps a unique MoGe 3 compound exists in the amorphous system. Rather than indicating a distinct MoGe3 compound with definitive local structure, however, the coordination results are more consistent with a densely-packed alloy having a wide range of solid solubility. Significant improvement in the quality and

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

    NASA Astrophysics Data System (ADS)

    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.

  13. AB Initi Molecular Dynamics Simulation of the Amorphous Structure of Ca-Mg-Cu and Ca-Mg-Zn Alloys (Postprint)

    DTIC Science & Technology

    2012-09-26

    order (SRO) and medium range order ( MRO ) of alloying elements in the amorphous structure. It is therefore interesting to analyze the amorphous...allowed calculation of local structural features (SRO and MRO ) such as total and partial CN, type and distribution of characteristic coordination...Statement A. Approved for public release; distribution unlimited. MRO , in metallic glasses can produce structures that have only a small energetic

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

    SciTech Connect

    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.

  15. Growth and characterization of CVD ruthenium and amorphous ruthenium-phosphorus alloy films for liner application in copper interconnect

    NASA Astrophysics Data System (ADS)

    Shin, Jinhong

    Copper interconnect requires liner materials that function as a diffusion barrier, a seed layer for electroplating, and an adhesion promoting layer. Ruthenium has been considered as a promising liner material, however it has been reported that Ru itself is not an effective Cu diffusion barrier due to its microstructure, which is polycrystalline with columnar grains. The screening study of Ru precursors revealed that all Ru films were polycrystalline with columnar structure, and, due to its strong 3D growth mode, a conformal and ultrathin Ru film was difficult to form, especially on high aspect ratio features. The microstructure of Ru films can be modified by incorporating P. Amorphous Ru(P) films are formed by chemical vapor deposition at 575 K using a single source precursor, cis-RuH2(P(CH3) 3)4, or dual sources, Ru3(CO)12 and P(CH3)3 or P(C6H5)3. The films contain Ru and P, which are in zero-valent states, and C as an impurity. Phosphorus dominantly affects the film microstructure, and incorporating >13% P resulted in amorphous Ru(P) films. Metastable Ru(P) remains amorphous after annealing at 675 K for 3 hr, and starts recrystallization at ˜775 K. The density of states analysis of the amorphous Ru(P) alloy illustrates metallic character of the films, and hybridization between Ru 4d and P 3p orbitals, which contributes to stabilizing the amorphous structure. Co-dosing P(CH) 3 with Ru3(CO)12 improves film step coverage, and the most conformal Ru(P) film is obtained with cis-RuH 2(P(CH3)3)4; a fully continuous 5 nm Ru(P) film is formed within 1 mum deep, 8:1 aspect ratio trenches. First principles density functional theory calculations illustrate degraded Cu/Ru adhesion by the presence of P at the interface, however, due to the strong Ru-Cu bonds, amorphous Ru(P) forms a stronger interface with Cu than Ta and TaN do. Cu diffusion studies at 575 K suggests improved barrier property of amorphous Ru(P) films over polycrystalline PVD Ru.

  16. Microstructural and nuclear magnetic resonance studies of solid-state amorphization in Al-Ti-Si composites prepared by mechanical alloying

    SciTech Connect

    Manna, I.; Nandi, P.; Bandyopadhyay, B.; Ghoshray, K.; Ghoshray, A

    2004-08-16

    Three Al{sub 30}Ti{sub 70-x} Si{sub x} (x=10, 20, 30), along with an Al-rich (Al{sub 50}Ti{sub 40}Si{sub 10}) and an Al-lean (Al{sub 10}Ti{sub 60}Si{sub 30}) elemental powder blends were subjected to mechanical alloying by high-energy planetary ball milling to yield a composite microstructure with varying proportions of amorphous and nanocrystalline intermetallic phases. Microstructural characterization at different stages of milling was carried out by X-ray diffraction, high-resolution transmission electron microscopy and energy dispersive X-ray spectroscopy. Furthermore, {sup 27}Al nuclear magnetic resonance (NMR) studies were undertaken to probe the mechanism of solid-state amorphization. Ball milling leads to alloying, nanocrystallization and partial solid-state amorphization followed/accompanied by strain-induced nucleation of nanocrystalline intermetallic phases from an amorphous solid solution. Both these amorphous and nano-intermetallic phases are associated with characteristic NMR peaks at lower frequencies (than that of pure Al). Thus, mechanical alloying of Al-Ti-Si appears a suitable technique for developing nanocrystalline intermetallic phase/compound dispersed amorphous matrix composites.

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

    NASA Astrophysics Data System (ADS)

    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 < T < 6K) and in small magnetic fields (0T < B < 0.2T). To measure the resistance and temperature accurately, we developed a novel method: measuring the resistance perpendicular to the ribbons with potassium as the non-superconducting glue between the CuTi ribbons and two Cu electrodes in order to make excellent electrical and thermal contact. With this method, we were able to measure the resistances with a relative precision of Deltarho/rho = 10^{-7}-10 ^{-8} and temperatures reliably down to 15mK with an error of less than 1mK. The zero field resistances and magnetoresistances were analyzed using weak localization theories that include the Zeeman splitting and electron-electron interaction theories. Possible background contributions from the K layers, the Cu electrodes, and their boundaries are quantified in the analysis. In zero field, these background contributions were negligible for T<3K. At zero magnetic field and T<0.15K, we found that electron -electron interaction dominates the resistance, while weak localization makes a nontrivial contribution to the resistance for T>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

  18. Cobalt-Base Alloy Gun Barrel Study

    DTIC Science & Technology

    2014-07-01

    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...DATE (DD-MM-YYYY) July 2014 2. REPORT TYPE Reprint 3. DATES COVERED (From - To) October–November 2013 4. TITLE AND SUBTITLE Cobalt -Base Alloy

  19. Estimation of Density of Localized States in Amorphous Se80Te20 and Se80Te10M10 (M = Cd, In, Sb) Alloys Using AC Conductivity Measurements

    NASA Astrophysics Data System (ADS)

    Chandel, N.; Mehta, N.; Kumar, A.

    2015-08-01

    The ac conductivity of amorphous Se80Te20 (a-Se80Te20) and amorphous Se80Te10M10 (a-Se80Te10M10) alloys has been measured as a function of temperature and frequency in a low-temperature regime. An analysis of the experimental data confirms that ac conductivity is reasonably well interpreted by the Austin-Mott model. The density of localized states was determined in the low-temperature region from 201 K to 280 K. Possible explanations of "metal-induced effects" on the conduction mechanism of a-Se80Te20 alloy are discussed.

  20. The effect of microstructure on properties and behaviors of annealed Fe/sub 78/B/sub 13/Si/sub 9/ amorphous alloy ribbon

    SciTech Connect

    Liebermann, H.H.; Martis, R.J.; Wong, C.P. ); Marti, J. )

    1989-01-01

    Changes in various properties with annealing of amorphous alloys have been studied by many researchers. The present work examines the annealing treatment dependence of mechanical relaxation, thermal, and magnetic properties and behaviors in light of microstructure as determined by TEM. The experimental results show that both the onset of embrittlement and the change in DC coercive field with annealing are consistent with microstructural development. An interrelationship among the various experimental measurements and observations is advanced as a unifying construct of the annealing treatment dependence of various properties in Fe/sub 78/B/sub 13/Si/sub 9/ amorphous alloy.

  1. In situ observation of defect annihilation in Kr ion-irradiated bulk Fe/amorphous-Fe 2 Zr nanocomposite alloy

    SciTech Connect

    Yu, K. Y.; Fan, Z.; Chen, Y.; Song, M.; Liu, Y.; Wang, H.; Kirk, M. A.; Li, M.; Zhang, X.

    2014-08-26

    Enhanced irradiation tolerance in crystalline multilayers has received significant attention lately. However, little is known on the irradiation response of crystal/amorphous nanolayers. We report on in situ Kr ion irradiation studies of a bulk Fe96Zr4 nanocomposite alloy. Irradiation resulted in amorphization of Fe2Zr and formed crystal/amorphous nanolayers. α-Fe layers exhibited drastically lower defect density and size than those in large α-Fe grains. In situ video revealed that mobile dislocation loops in α-Fe layers were confined by the crystal/amorphous interfaces and kept migrating to annihilate other defects. This study provides new insights on the design of irradiation-tolerant crystal/amorphous nanocomposites.

  2. Formation of amorphous alloys on 4H-SiC with NbNi film using pulsed-laser annealing

    NASA Astrophysics Data System (ADS)

    De Silva, Milantha; Ishikawa, Seiji; Miyazaki, Takamichi; Kikkawa, Takamaro; Kuroki, Shin-Ichiro

    2016-07-01

    Amorphous alloys containing Ni-Si-Nb-C were formed on 4H-SiC creating a low resistance Ohmic contact electrode. In a conventional nickel silicide (NiSi) electrode on SiC, a carbon agglomeration at the silicide/SiC interface occurs, and contact resistance between NiSi and SiC substrate becomes larger. For carbon agglomeration suppression, nanosecond non-equilibrium laser annealing was introduced, and to form metal carbides, carbon-interstitial type metals Nb and Mo were introduced. Ni, Nb, Mo, Nb/Ni, Mo/Ni multilayer contacts, and NbNi mixed contact were formed on the C-face side of n-type 4H-SiC wafers. The electrical contact properties were investigated after a 45 ns pulse laser annealing in N2 ambient. As a result, with NbNi film, an amorphous alloy with Ni-Si-Nb-C was formed, and a low specific contact resistance of 5.3 × 10-4 Ω cm2 was realized.

  3. Magnetic and Distribution of Magnetic Moments in Amorphous Fe89.7 P10.3 Alloy Nanowire Arrays

    NASA Astrophysics Data System (ADS)

    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 3 μm have been fabricated in an anodic aluminium oxide template by electrodeposition. Magnetic properties of the samples are investigated by mean of vibrating sample magnetometer, transmission Mössbauer spectroscopy and conversion electron Mössbauer spectroscopy at room temperature. It is found that the nanowire arrays have obvious perpendicular magnetic anisotropy and are ferromagnetic at room temperature, with its Mössbauer spectra consisting of six broad lines. The average angles between the Fe magnetic moment and the wire axis are about 14° inside and 28° at the end of the amorphous Fe89.7P10.3 alloy nanowire arrays, respectively. The magnetic behaviour is decided by the shape anisotropy and the dipolar interaction between wires. In addition, the magnetic moments distribution is theoretically demonstrated by using the symmetric fanning mechanism of the spheres chain model.

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

    SciTech Connect

    Regan, Michael 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 FexGe1-x and MoxGe1-x are quite anisotropic, depending significantly on the direction of film growth. With the addition of small amounts of metal atoms (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 FeGe2or MoGe3. Finally, by manipulating the deposited power flux and rates of growth, FexGe1-x films which have the same Fe composition x can be grown to different states of phase separation. These results may help explain the difficulty workers have had in isolating the metal/insulator transition for these and other vapor-deposited amorphous alloys.

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

    NASA Astrophysics Data System (ADS)

    Jiao, Zengbao; Li, Hongxiang; Wu, Yuan; Gao, Jingen; Wang, Shanlin; Yi, Seonghoon; Lu, Zhaoping

    2010-03-01

    Glass formation, mechanical and magnetic properties of the Fe76- x C7.0Si3.3B5.0P8.7Mo x ( 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.

  6. Itenerant spin glass states and asperomagnetism of amorphous Fe and iron-rich Fe/Zr alloys

    NASA Astrophysics Data System (ADS)

    Krey, U.; Krauss, U.; Krompiewski, S.

    1992-01-01

    A realistic tight-binding approach for the self-consistent calculation of the itinerant spin configurations of disordered metallic systems has been developed and is used to study numerically the problem of the magnetic states at T = 0 K of iron-rich amorphous alloys of the type Fe 1- xZr xH y, and of fictitious amorphous Fe of different densities. In our approach, the local spin polarization is not restricted to the z-direction, i.e. the polarization magnitude as well as its direction can vary from site to site. The calculations show that the spin configurations depend strongly on the preparation, and that changes of the relative spin orientations can lead to drastic changes of the itinerant atomic moments. Metastable spin configurations with essentially isotropic distribution can be prepared by relaxing the system in gradually vanishing external fields with isotropically distributed randomness and zero spatial average, whereas with a non-vanishing average the so-called asperomagnetic configurations are obtained, i.e. ferromagnetic states with randomly frozen transverse components. For iron-rich Fe 1- xZr x alloys with x = 0.07, according to our calculation, the isotropic spin glass configuration would have slightly lower energy than the asperomagnetic state, by amounts corresponding to ≈ 0.003 eV per electron, while for the hydrogenated system Fe 1- xZr xH y with y ≈ 2 x, the asperomagnetic state would be favoured by ≈ 0.004 eV. For two computer models of (fictitious) amorphous Fe with densities of 7.39 and 9.19 g cm -3, the spin-glass and the asperomagnetic states have roughly the same energy, although for the low-density sample the magnitudes of the moments are quite different in both states.

  7. Ab Initio Molecular Dynamics Simulation of the Amorphous Structure of Ca-Mg-Cu and Ca-Mg-Zn Alloys (Preprint)

    DTIC Science & Technology

    2012-08-01

    believed to depend on the type of short range order (SRO) and medium range order ( MRO ) of alloying elements in the amorphous structure. It is...which allowed calculation of local structural features (SRO and MRO ) such as total and partial CN, type and distribution of characteristic...indicate the presence of MRO in these alloys [32,33], as well as the fluctuation in the atomic scattering cross-sections: The solutes, Cu, Zn and Mg

  8. The study on surface chemical modification of Fe71.5Cu1Nb3Si13.5B9V2 amorphous alloy ribbons and its piezomagnetic effect

    NASA Astrophysics Data System (ADS)

    Chen, Jie; Zhu, Zhenghou

    2016-12-01

    In this paper, a type of smooth even endogeny conversion coat composed of Cu0.86Fe2.14O4 and (Cu0.18Fe0.82)Cu0.82Fe1.18O4 phases was successfully obtained by a conversion reaction on the surfaces of Fe71.5Cu1Nb3Si13.5B9V2 amorphous alloy ribbons. In this way, its ribbon thickness was decreased about 6-8 μm equivalently. The phase composition and microstructure of the conversion coat were investigated by XRD and SEM. In addition, the adhesion test of epoxy resin and amorphous alloy ribbon was verified by dipping experiments. It is found that the interface bonding strength between the conversion coat and ribbons is strong comparatively. On one hand, the proper interface between conversion coat and epoxy resin make it easy for ribbons to be encapsulated; on the other hand, the ribbons perform better significant piezomagnetic effect than the untreated ones due to a thinner thickness. This work may be a good basic for the applications of Fe71.5Cu1Nb3Si13.5B9V2 amorphous alloy ribbons in piezomagnetic sensor and other devices based on the piezomagnetism effect.

  9. Magnesium-based hydrogen storage materials modified by mechanical alloying

    SciTech Connect

    Cui, N.; He, P.; Luo, J.L.

    1999-10-26

    The effects of mechanical alloying on microstructure and electrochemical performance of a Mg-Ni-Y-Al hydrogen storage alloy in 6 M KOH solution were studied. The ball-milled powders were examined by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected-area electron diffraction (SED) and energy dispersion spectrometry (EDS). TEM and EDS results clearly reveal that the smaller nickel clusters or particles were well dispersed on the surface of larger magnesium alloy particles by mechanical grinding for 72 h. With an increase in milling time to 240 h, the nickel clusters or particles disappeared and a new monophase alloy with amorphous structure was formed. The electrochemical capacity of the modified material significantly increased with increasing milling time within 72 h and then dropped to nearly nil when the milling time reached 240 h. The capacity decay, however, was always improved with increasing grinding time. Further analysis and discussion were made based on d.c. polarization and a.c. impedance spectroscopy measurement results.

  10. Development of Lightweight Titanium Base Alloys

    DTIC Science & Technology

    1989-04-15

    program on Development of Lightweight Titanium Base Alloys was to develop new titanium alloys with 10% lower density, 50% higher elastic modulus, and...program. permitted the cvaluation of a low-dc-isity. dislicrsion-strengthcnicd 02 + y titanium aluminide , which has excellent high temperature strength...713e alloy has significantly higher strength than the titanium aluminides . The limited data for ’i-34AI-4Be show it to be very strong above 7(X)°C

  11. In Situ Synthesis and Characterization of Zr-Based Amorphous Composite by Laser Direct Deposition

    NASA Astrophysics Data System (ADS)

    Ye, Xiaoyang; Bae, Heehun; Shin, Yung C.; Stanciu, Lia A.

    2015-09-01

    Zr-based bulk metallic glasses have attracted extensive interest for structural applications due to their excellent glass-forming ability, superior mechanical properties, and unique thermal and corrosion properties. In this study, Zr65Al10Ni10Cu15 amorphous composites with a large fraction of amorphous phase were in situ synthesized by laser direct deposition. X-ray diffraction confirmed the existence of both amorphous and crystalline phases. Laser parameters were optimized in order to increase the fraction of amorphous phase. The microstructure analysis by scanning electron microscopy revealed the deposited structure was composed of periodically repeated amorphous and crystalline phases. Overlapping regions with nanoparticles aggregated were crystallized by laser reheating and remelting processes during subsequent laser scans. Vickers microhardness of the amorphous region showed around 35 pct higher than that of crystalline region. Average hardness obtained by a Rockwell macrohardness tester was very close to the microhardness of the amorphous region. The compression test showed that the fracture strain of Zr65Al10Ni10Cu15 amorphous composites was enhanced from less than 2 pct to as high as 5.7 pct, compared with fully amorphous metallic glass. Differential scanning calorimetry test results further revealed the amorphous structure and glass transition temperature T g was observed to be around 660 K (387 °C). In 3 mol/L NaCl solution, laser direct deposited amorphous composites exhibited distinctly improved corrosion resistance, compared with fully crystallized samples.

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

    PubMed Central

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

    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 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. PMID:26569244

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

    PubMed

    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.

  14. Partial amorphization of a Cu-Zr-Ti alloy by high pressure torsion

    SciTech Connect

    Revesz, Adam; Hobor, Sandor; Labar, Janos L.; Zhilyaev, Alex P.; Kovacs, Zsolt

    2006-11-15

    High pressure torsion was applied to produce disk-shape specimen of Cu{sub 60}Zr{sub 20}Ti{sub 20} composition. Radial dependence of the microstructure was monitored by x-ray diffraction, scanning, and transmission electron microscopies. The disk consists of a top surface layer, homogeneous on a micrometer scale with an average thickness of 10-20 {mu}m, and an inhomogeneous bulk region of 200 {mu}m thickness. Calorimetric studies revealed that the disk contains detectable amount of amorphous phase. Characteristics of this amorphous content were compared to a fully amorphous melt-quenched Cu{sub 60}Zr{sub 20}Ti{sub 20} ribbon.

  15. Magnetic entropy change in amorphous and partially crystallized Fe-Mo-Cu-B alloy

    NASA Astrophysics Data System (ADS)

    Świerczek, Jan; Kupczyk, Anna

    2015-07-01

    Microstructure of the amorphous Fe76Mo10Cu1B13 ribbons in the as-quenched state and after the annealing at 723 K for 0.5 h is studied by transmission electron microscopy and Mössbauer spectroscopy. In the as-cast state α-Fe medium range ordered (MRO) regions are revealed and become the nuclei of crystalline grains. Nanograins 6 nm in the average diameter are observed in the sample subjected to the heat treatment. Mössbauer spectrum at 300 K of the annealed sample is decomposed into three subspectra ascribed to the amorphous paramagnetic and ferromagnetic phases and interface. At room temperature nanograins do not contribute to the spectra in the form of a single sextet due to magnetic relaxations. At 77 K the single sextet can be evidently introduced and its hyperfine parameters indicate the existence of the α-Fe(Mo) crystalline phase. The Curie point (TC) of the amorphous phase in the annealed samples shifts from 277 K in the as-cast state to 320 K after the annealing. The maximum of the magnetic entropy change (- ΔSM) in the as-quenched state occurs at temperature around TC of the amorphous phase and distinctly decreases after the annealing and shifts towards higher temperature but lower than TC of the amorphous remainder. - ΔSM in the superparamagnetic temperature range, i.e. above the Curie temperature of the amorphous phase obeys the phenomenological relation: - ΔSM = a(T)Bm / T + b B.m 2 / (T - Θ) 2 . The excellent | ΔSM | × Bm-2 = f(Bm-1) linear dependences for both, as-quenched and annealed samples are observed.

  16. X-Ray Diffraction in Situ Study of Phase Formation and Amorphous-To Transformation in FeCuNbSiB Alloys

    NASA Astrophysics Data System (ADS)

    Tuong, Le Thi Cat; Phuc, Phan Vinh; Nghi, Nguyen Hoang

    2001-04-01

    This paper presents some reeenl results of a X-ray in situ study of phase formation process and amorphous-to-nanocrystalline transformation in FeCuNbSiB alloy. Measurements were carried out on the diffractometer Siemens-D5000 with high temperature attachment. Our experiments were performed in both isothermal and nonisothermal regimes in argon atmosphere with time periods from a minute to 3 hours and different temperatures ranging from room temperature to 900°C. The X-ray diffraction data were used to determine the amount of crystalline fraction rs temperature and vs time. Both the first amorphous halo and the (110) diffraction peak of the bcc Fe-based solid solution were fitted, after background substruction. by means of the pseudo-voigt function. The grain sizes for even annealing temperature were determined by the X-ray profile analysis and using Bruker Win-Crysize program package. The kinetics of the nanocrystallization process was investigated and the activation energy was estimated. All the obtained results were compared with those of conventional studies.

  17. Pressure tunes electrical resistivity by four orders of magnitude in amorphous Ge2Sb2Te5 phase-change memory alloy.

    PubMed

    Xu, M; Cheng, Y Q; Wang, L; Sheng, H W; Meng, Y; Yang, W G; Han, X D; Ma, E

    2012-05-01

    Ge-Sb-Te-based phase-change memory is one of the most promising candidates to succeed the current flash memories. The application of phase-change materials for data storage and memory devices takes advantage of the fast phase transition (on the order of nanoseconds) and the large property contrasts (e.g., several orders of magnitude difference in electrical resistivity) between the amorphous and the crystalline states. Despite the importance of Ge-Sb-Te alloys and the intense research they have received, the possible phases in the temperature-pressure diagram, as well as the corresponding structure-property correlations, remain to be systematically explored. In this study, by subjecting the amorphous Ge(2)Sb(2)Te(5) (a-GST) to hydrostatic-like pressure (P), the thermodynamic variable alternative to temperature, we are able to tune its electrical resistivity by several orders of magnitude, similar to the resistivity contrast corresponding to the usually investigated amorphous-to-crystalline (a-GST to rock-salt GST) transition used in current phase-change memories. In particular, the electrical resistivity drops precipitously in the P = 0 to 8 GPa regime. A prominent structural signature representing the underlying evolution in atomic arrangements and bonding in this pressure regime, as revealed by the ab initio molecular dynamics simulations, is the reduction of low-electron-density regions, which contributes to the narrowing of band gap and delocalization of trapped electrons. At P > 8 GPa, we have observed major changes of the average local structures (bond angle and coordination numbers), gradually transforming the a-GST into a high-density, metallic-like state. This high-pressure glass is characterized by local motifs that bear similarities to the body-centered-cubic GST (bcc-GST) it eventually crystallizes into at 28 GPa, and hence represents a bcc-type polyamorph of a-GST.

  18. Pressure tunes electrical resistivity by four orders of magnitude in amorphous Ge[subscript 2]Sb[subscript 2]Te[subscript 5] phase-change memory alloy

    SciTech Connect

    Xu, M.; Cheng, Y.Q.; Wang, L.; Sheng, H.W.; Meng, Y.; Yang, W.G.; Hang, X.D.; Ma, E.

    2012-05-22

    Ge-Sb-Te-based phase-change memory is one of the most promising candidates to succeed the current flash memories. The application of phase-change materials for data storage and memory devices takes advantage of the fast phase transition (on the order of nanoseconds) and the large property contrasts (e.g., several orders of magnitude difference in electrical resistivity) between the amorphous and the crystalline states. Despite the importance of Ge-Sb-Te alloys and the intense research they have received, the possible phases in the temperature-pressure diagram, as well as the corresponding structure-property correlations, remain to be systematically explored. In this study, by subjecting the amorphous Ge{sub 2}Sb{sub 2}Te{sub 5} (a-GST) to hydrostatic-like pressure (P), the thermodynamic variable alternative to temperature, we are able to tune its electrical resistivity by several orders of magnitude, similar to the resistivity contrast corresponding to the usually investigated amorphous-to-crystalline (a-GST to rock-salt GST) transition used in current phase-change memories. In particular, the electrical resistivity drops precipitously in the P = 0 to 8 GPa regime. A prominent structural signature representing the underlying evolution in atomic arrangements and bonding in this pressure regime, as revealed by the ab initio molecular dynamics simulations, is the reduction of low-electron-density regions, which contributes to the narrowing of band gap and delocalization of trapped electrons. At P > 8 GPa, we have observed major changes of the average local structures (bond angle and coordination numbers), gradually transforming the a-GST into a high-density, metallic-like state. This high-pressure glass is characterized by local motifs that bear similarities to the body-centered-cubic GST (bcc-GST) it eventually crystallizes into at 28 GPa, and hence represents a bcc-type polyamorph of a-GST.

  19. Deuterium dynamics in the icosahedral and amorphous phases of the Ti40Zr40Ni20 hydrogen-absorbing alloy studied by 2H NMR

    NASA Astrophysics Data System (ADS)

    Gradišek, A.; Kocjan, A.; McGuiness, P. J.; Apih, T.; Kim, Hae Jin; Dolinšek, J.

    2008-11-01

    The Ti40Zr40Ni20 hydrogen-absorbing alloy was prepared in the icosahedral and amorphous phases by controlling the rotation speed of the melt-spinning method of sample preparation, and the deuterium dynamics was investigated by 2H NMR dynamic lineshape and spin-lattice relaxation. The results were analysed by the lineshape and relaxation models that assume deuterium thermally activated hopping within a manifold of different chemical environments. The observed 8% larger activation energy for the deuterium hopping over the interstitial sites and the 10% larger static spectrum width of the amorphous phase, as compared to the icosahedral phase, can be accounted for by the larger deuterium content of the investigated amorphous sample. From the deuterium dynamics point of view, the icosahedral phase is not special with respect to the amorphous modification of the same material.

  20. Morphology and magnetic behavior of cobalt rich amorphous/nanocrystalline (Co-Ni)70Ti10B20 alloyed powders

    NASA Astrophysics Data System (ADS)

    Raanaei, Hossein; Mohammad-Hosseini, Vahid

    2016-09-01

    The effect of milling time on microstructural and magnetic behavior of mechanically alloyed Co49Ni21Ti10B20 is investigated by using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, differential scanning calorimetry and vibrating sample magnetometer. It is shown, with increasing milling time, the crystallite size decreases and finally reaches to a low value after 190 h of milling time. The increase in microstrain is also observed during the milling process. The results indicate the coexistence between amorphous and nanocrystalline phases after 190 h of milling time. Moreover, the lowest magnetic coercivity of about 39 Oe at the final milling stage is observed. The results of annealed sample reveal structural ordering of constituent elements.

  1. Structure of Al87Y8Ni5 Amorphous Alloy Analyzed by Anomalous X-ray Scattering

    NASA Astrophysics Data System (ADS)

    Arima, Hiroshi; Kawamata, Toru; Yokoyama, Yoshihiko; Sugiyama, Kazumasa

    The structure of Al87Y8Ni5 amorphous alloy was investigated by the anomalous X-ray scattering (AXS) coupled with a model calculation using reverse Monte Carlo (RMC) simulation, and a three-dimensional structural model was obtained. The model showed the existence of a pre-peak on the small-Q side of the first main peak for the structure factor, and the geometrical origin of this peak is discussed. Partial structure factors indicated that pre-peaks for environmental structure factors around Ni and Y were caused by pair correlations associated with Ni atoms. Further, Voronoi analysis of the nearest-neighbor region suggested that the structure around Ni atoms was dominated by a tetragonal dodecahedron. The origin of the pre-peak would be attributed to the unique local atomic arrangement of prism-like polyhedra around Ni atoms.

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

    SciTech Connect

    Isherwood, Patrick J. M. Walls, John M.; Butler, Keith T.; Walsh, Aron

    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.

  3. Influence of laser irradiation on change properties of bulk amorphous Zr-Pd metallic alloys

    NASA Astrophysics Data System (ADS)

    Fedorov, V. A.; Yakovlev, A. V.; Pluzhnikova, T. N.; Shlikova, A. A.; Berezner, A. D.

    2017-01-01

    We study the morphological features of laser irradiation zones formed on the surface of the bulk metallic glasses. We use the nanoindentation method for estimation alloys properties caused by impulse heating during irradiation.

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

    NASA Astrophysics Data System (ADS)

    Douglass, Ian; Hudson, Toby; Harrowell, Peter

    2016-04-01

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

  5. Effect of an amorphous titania nanotubes coating on the fatigue and corrosion behaviors of the biomedical Ti-6Al-4V and Ti-6Al-7Nb alloys.

    PubMed

    Campanelli, Leonardo Contri; Bortolan, Carolina Catanio; da Silva, Paulo Sergio Carvalho Pereira; Bolfarini, Claudemiro; Oliveira, Nilson Tadeu Camarinho

    2017-01-01

    An array of self-organized TiO2 nanotubes with an amorphous structure was produced on the biomedical Ti-6Al-4V and Ti-6Al-7Nb alloys, and the resulting fatigue and corrosion behaviors were studied. The electrochemical response of the nanotubular oxide surfaces was investigated in Ringer physiological solution through potentiodynamic polarization and electrochemical impedance spectroscopy measurements. The absence of transpassivation in the chloride-containing solution, in addition to the micron-scale values of the passivation current density, indicated the excellent corrosion behavior of the coating and the satisfactory protection against the creation of potential stress concentrators in the surface. Axial fatigue tests were performed in physiological solution on polished and coated conditions, with characterization of the treated surfaces by scanning electron microscopy before and after the tests. The surface modification was not deleterious to the fatigue response of both alloys mainly due to the nano-scale dimension of the nanotubes layer. An estimation based on fracture mechanics revealed that a circumferential crack in the range of 5μm depth would be necessary to affect the fatigue performance, which is far from the thickness of the studied coating, although no cracks were actually observed in the oxide surfaces after the tests.

  6. Domain observations of Fe and Co based amorphous wires

    SciTech Connect

    Takajo, M.; Yamasaki, J. . Dept. of Electrical Engineering); Humphrey, F.B. )

    1993-11-01

    Domain observations were made on Fe and Co based amorphous magnetic wires that exhibit a large Barkhausen discontinuity during flux reversal. Domain patterns observed on the wire surface were compared with those found on a polished section through the center of the wire. It was confirmed that the Fe based wire consists of a shell and core region as previously proposed, however, there is a third region between them. This fairly thick transition region made up of domains at an angle of about 45[degree] to the wire axis clearly lacking the closure domains of the previous model. The Co based wire does not have a clear core and shell domain structure. The center of the wire had a classic domain structure expected of uniaxial anisotropy with the easy axis normal to the wire axis. When a model for the residual stress quenched-in during cooling of large Fe bars is applied to the wire, the expected anisotropy is consistent with the domain patterns in the Fe based wire, however, shape anisotropy still plays a dominant role in defining the wire core in the Co based wire.

  7. Amorphous Calcium Carbonate Based-Microparticles for Peptide Pulmonary Delivery.

    PubMed

    Tewes, Frederic; Gobbo, Oliviero L; Ehrhardt, Carsten; Healy, Anne Marie

    2016-01-20

    Amorphous calcium carbonate (ACC) is known to interact with proteins, for example, in biogenic ACC, to form stable amorphous phases. The control of amorphous/crystalline and inorganic/organic ratios in inhalable calcium carbonate microparticles may enable particle properties to be adapted to suit the requirements of dry powders for pulmonary delivery by oral inhalation. For example, an amorphous phase can immobilize and stabilize polypeptides in their native structure and amorphous and crystalline phases have different mechanical properties. Therefore, inhalable composite microparticles made of inorganic (i.e., calcium carbonate and calcium formate) and organic (i.e., hyaluronan (HA)) amorphous and crystalline phases were investigated for peptide and protein pulmonary aerosol delivery. The crystalline/amorphous ratio and polymorphic form of the inorganic component was altered by changing the microparticle drying rate and by changing the ammonium carbonate and HA initial concentration. The bioactivity of the model peptide, salmon calcitonin (sCT), coprocessed with alpha-1-antitrypsin (AAT), a model protein with peptidase inhibitor activity, was maintained during processing and the microparticles had excellent aerodynamic properties, making them suitable for pulmonary aerosol delivery. The bioavailability of sCT after aerosol delivery as sCT and AAT-loaded composite microparticles to rats was 4-times higher than that of sCT solution.

  8. Anomalous small-angle X-ray scattering of nanoporous two-phase atomistic models for amorphous silicon–germanium alloys

    SciTech Connect

    Chehaidar, A.

    2015-09-15

    The present work deals with a detailed analysis of the anomalous small-angle X-ray scattering in amorphous silicon–germanium alloy using the simulation technique. We envisage the nanoporous two-phase alloy model consisting in a mixture of Ge-rich and Ge-poor domains and voids at the nanoscale. By substituting Ge atoms for Si atoms in nanoporous amorphous silicon network, compositionally heterogeneous alloys are generated with various composition-contrasts between the two phases. After relaxing the as-generated structure, we compute its radial distribution function, and then we deduce by the Fourier transform technique its anomalous X-ray scattering pattern. Using a smoothing procedure, the computed X-ray scattering patterns are corrected for the termination errors due to the finite size of the model, allowing so a rigorous quantitative analysis of the anomalous small-angle scattering. Our simulation shows that, as expected, the anomalous small-angle X-ray scattering technique is a tool of choice for characterizing compositional heterogeneities coexisting with structural inhomogeneities in an amorphous alloy. Furthermore, the sizes of the compositional nanoheterogeneities, as measured by anomalous small-angle X-ray scattering technique, are X-ray energy independent. A quantitative analysis of the separated reduced anomalous small-angle X-ray scattering, as defined in this work, provided a good estimate of their size.

  9. Hot Corrosion of Cobalt-Base Alloys

    DTIC Science & Technology

    1975-06-01

    Cast Alloys : NASA VIA, B-1900, 713C and 738X", Report NASA TN D-7682, Lewis Research Center, Cleveland, Ohio, August 1974. 36. Giggins, C.S. and...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...Interpretation of Results 3. SODIUM SULFATE INDUCED HOT CORROSION OF Co-25Al AND Co-35Cr ALLOYS a. Introduction b. Experimental Co-25Al c. Experimental

  10. Magnetic and Mossbauer study of amorphous and nanocrystalline Fe[sub 86]Zr[sub 7]Cu[sub 1]B[sub 6] alloys

    SciTech Connect

    Gorria, P.; Orue, I.; Plazaola, F.; Fernandez-Gubieda, M.L.; Barandiaran, J.M. . Dept. de Electricidad y Electronica)

    1993-11-01

    Amorphous alloys of composition Fe[sub 86]Zr[sub 7]Cu[sub 1]B[sub 6] have been prepared and annealed in the temperature range from 570 to 950 K, obtaining several degrees of nanocrystallization. Magnetic and Moessbauer measurements show the different phases that appear in the samples after the heating, and their percentage, depending on the annealing temperature. The Curie temperature of the amorphous phase is shown to remain almost unchanged during the crystallization. Moessbauer spectroscopy however, reveals subtle changes in the structure.

  11. Wetting and reaction characteristics of crystalline and amorphous SiO2 derived rice-husk ash and SiO2/SiC substrates with Al-Si-Mg alloys

    NASA Astrophysics Data System (ADS)

    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.

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

    SciTech Connect

    Boccard, Mathieu; Holman, Zachary C.

    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.

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

    SciTech Connect

    Boccard, Mathieu; Holman, Zachary C.

    2015-08-14

    With this study, 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.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  16. Magnetization distribution in a soft magnetic amorphous alloy ribbon in as-quenched state and efficiency of heat treatment

    NASA Astrophysics Data System (ADS)

    Skulkina, N. A.; Ivanov, O. A.; Shubina, L. N.; Blinova, O. V.

    2016-11-01

    The effect of heat treatment in air on the formation of magnetic properties has been studied based on the example of soft magnetic Fe77Ni1Si9B13 and Fe81B13Si4C2 amorphous ribbons characterized by positive magneto-striction. The magnetization distribution in the ribbons in the as-quenched state was shown to affect the efficiency of annealing. Under certain conditions, heat treatment, which results in the formation of mainly amorphous state of ribbon surface, is more efficient for samples characterized by high volume of orthogonally magnetized domains. This can be related to high in-plane tensile stresses, which are induced by hydrogen and oxygen atoms introduced into the ribbon surface upon its interaction with atmospheric water vapor.

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

    DTIC Science & Technology

    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. Amorphous and crystalline silicon based heterojunction solar cells

    NASA Astrophysics Data System (ADS)

    Schüttauf, J. A.

    2011-10-01

    In this thesis, research on amorphous and crystalline silicon heterojunction (SHJ) solar cells is described. Probably the most important feature of SHJ solar cells is a thin intrinsic amorphous silicion (a-Si:H) layer that is deposited before depositing the doped emitter and back surface field. The passivation properties of such intrinsic layers made by three different chemical vapor deposition (CVD) techniques have been investigated. For layers deposited at 130°C, all techniques show a strong reduction in surface recombination velocity (SRV) after annealing. Modelling indicates that dangling bond saturation by atomic hydrogen is the predominant mechanism. We obtain outstanding carrier lifetimes of 10.3 ms, corresponding to SRVs of 0.56 cm/s. For a-Si:H films made at 250°C, an as-deposited minority carrier lifetime of 2.0 ms is observed. In contrast to a-Si:H films fabricated at 130°C, however, no change in passivation quality upon thermal annealing is observed. These films were fabricated for the first time using a continuous in-line HWCVD mode. Wafer cleaning before a-Si:H deposition is a crucial step for c-Si surface passivation. We tested the influence of an atomic hydrogen treatment before a-Si:H deposition on the c-Si surface. The treatments were performed in a new virgin chamber to exclude Si deposition from the chamber walls. Subsequently, we deposited a-Si:H layers onto the c-Si wafers and measured the lifetime for different H treatment times. We found that increasing hydrogen treatment times led to lower effective lifetimes. Modelling of the measured minority carrier lifetime data shows that the decreased passivation quality is caused by an increased defect density at the amorphous-crystalline interface. Furtheremore, the passivation of different a-Si:H containing layers have been tested. For intrinsic films and intrinsic/n-type stacks, an improvement in passivation up to 255°C and 270°C is observed. This improvement is attributed to dangling bond

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed Central

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

    2016-01-01

    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. PMID:27469931

  1. Critical behavior and its correlation with magnetocaloric effect in amorphous Fe80-xVxB12Si8 (x=8, 10 and 13.7) alloys

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    The critical exponents in Fe80-xVxB12Si8 (x=8, 10 and 13.7) amorphous alloys were investigated near ferromagnetic to paramagnetic phase transition temperature. All amorphous alloys exhibit a second order ferromagnetic to paramagnetic phase transition (SOMT). The critical exponents (β, γ and δ) were estimated using the modified Arrott plot technique (MAP), the Widom scaling relation (WSR), and the critical isotherm analysis (CIA). In addition, an independent analysis of the critical behavior is presented in terms of the magnetocaloric effect (MCE). It shows in accordance with conclusion from magnetization data analysis. The estimated critical exponent values are found to be consistent and comparable to those predicted by the mean field model. This result points out to the ferromagnetic exchange interaction of long-range type.

  2. Abrasion Resistance of Al-Ni-Mm-Fe Amorphous and Nanocrystalline Composite Coating on the Surface of AZ91 Magnesium Alloy

    NASA Astrophysics Data System (ADS)

    Zhang, Z. B.; Liang, X. B.; Chen, Y. X.; Xu, B. S.

    An Al-Ni-Mm-Fe amorphous and nanocrystalline composite coating was prepared onto the surface of AZ91 magnesium alloy by high velocity arc spraying process. And the microstructure of the coating was analyzed by scanning electron microscope (TEM) and X-ray diffraction (XRD). The analysis results indicated that the coating consists of amorphous, nanocrystalline and crystalline phases. It has a dense structure with a low porosity of about 2.0%. Its average micro Vickers hardness value is about 330 HV0.1, which is five times than that of AZ91 magnesium alloy (62 HV0.1) and four times than that of pure Al coating (71 HV0.1). The abrasion tests showed that the Al-Ni-Mm-Fe coating exhibits a good abrasion resistance.

  3. Hybrid photovoltaics based on semiconductor nanocrystals and amorphous silicon.

    PubMed

    Sun, Baoquan; Findikoglu, Alp T; Sykora, Milan; Werder, Donald J; Klimov, Victor I

    2009-03-01

    Semiconductor nanocrystals (NCs) are promising materials for applications in photovoltaic (PV) structures that could benefit from size-controlled tunability of absorption spectra, the ease of realization of various tandem architectures, and, perhaps, increased conversion efficiency in the ultraviolet region through carrier multiplication. The first practical step toward utilization of the unique properties of NCs in PV technologies could be through their integration into traditional silicon-based solar cells. Here, we demonstrate an example of such hybrid PV structures that combine colloidal NCs with amorphous silicon. In these structures, NCs and silicon are electronically coupled, and the regime of this coupling can be tuned by altering the alignment of NC energy states with regard to silicon band edges. For example, using wide-gap CdSe NCs we demonstrate a photoresponse which is exclusively due to the NCs. On the other hand, in devices comprising narrow-gap PbS NCs, both the NCs and silicon contribute to photocurrent, which results in PV response extending from the visible to the near-infrared region. The hybrid silicon/PbS NC solar cells show external quantum efficiencies of approximately 7% at infrared energies and 50% in the visible and a power conversion efficiency of up to 0.9%. This work demonstrates the feasibility of hybrid PV devices that combine advantages of mature silicon fabrication technologies with the unique electronic properties of semiconductor NCs.

  4. Study on glass-forming ability and hydrogen storage properties of amorphous Mg{sub 60}Ni{sub 30}La{sub 10−x}Co{sub x} (x = 0, 4) alloys

    SciTech Connect

    Lv, Peng; Wang, Zhong-min Zhang, Huai-gang; Balogun, Muhammad-Sadeeq; Ji, Zi-jun; Deng, Jian-qiu; Zhou, Huai-ying

    2013-12-15

    Mg{sub 60}Ni{sub 30}La{sub 10−x}Co{sub x} (x = 0, 4) amorphous alloys were prepared by rapid solidification, using a melt-spinning technique. X-ray diffraction and differential scanning calorimetry analysis were employed to measure their microstructure, thermal stability and glass-forming ability, and hydrogen storage properties were studied by means of PCTPro2000. Based on differential scanning calorimetry results, their glass-forming ability and thermal stability were investigated by Kissinger method, Lasocka curves and atomic cluster model, respectively. The results indicate that glass-forming ability, thermal properties and hydrogen storage properties in the Mg-rich corner of Mg–Ni–La–Co system alloys were enhanced by Co substitution for La. It can be found that the smaller activation energy (ΔΕ) and frequency factor (υ{sub 0}), the bigger value of B (glass transition point in Lasocka curves), and higher glass-forming ability of Mg–Ni–La–Co alloys would be followed. In addition, atomic structure parameter (λ), deduced from atomic cluster model is valuable in the design of Mg–Ni–La–Co system alloys with good glass-forming ability. With an increase of Co content from 0 to 4, the hydrogen desorption capacity within 4000 s rises from 2.25 to 2.85 wt.% at 573 K. - Highlights: • Amorphous Mg{sub 60}Ni{sub 30}La{sub 10−x}Co{sub x} (x = 0 and 4) alloys were produced by melt spinning. • The GFA and hydrogen storage properties were enhanced by Co substitution for La. • With an increase of Co content, the hydrogen desorption capacity rises at 573 K.

  5. Transient oxidation of multiphase Ni-Cr base alloys

    SciTech Connect

    Baran, G.; Meraner, M.; Farrell, P.

    1988-06-01

    Four commercially available Ni-Cr-based alloys used with porcelain enamels were studied. Major alloying elements were Al, Be, Si, B, Nb, and Mo. All alloys were multiphase. During heat treatments simulating enameling conditions, phase changes occurred in most alloys and were detected using hardness testing, differential thermal analysis (DTA), and microscopy. Oxidation of these alloys at 1000/degrees/C for 10 min produced an oxide layer consisting principally of chromium oxide, but the oxide morphology varied with each alloy depending on the alloy microstructure. Controlling alloy microstructure while keeping the overall composition unchanged may be a means of preventing wrinkled poorly adherent scales from forming.

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

    NASA Astrophysics Data System (ADS)

    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.

  7. Small-angle x-ray scattering study of phase separation in amorphous alloys during heating with use of synchrotron radiation

    SciTech Connect

    Yavari, A.R.; Osamura, K.; Okuda, H.; Amemia, Y.

    1988-05-01

    Some recent reports suggest that amorphous Pd/sub 46/Ni/sub 36/P/sub 18/ and Cu/sub 50/Zr/sub 50/ alloys phase separate during heating at temperatures 50--200 K below their crystallization temperatures. We have therefore obtained improved small-angle x-ray scattering (SAXS) measurements during heating of these alloys using a new experimental setup. The experimental improvements included in-the-beam heating using the very-high-intensity x-ray radiation available at the Synchrotron Radiation Laboratory, K.E.K., the use of Joule self-heating of the samples, which is made possible by the high resistivity of the amorphous phase and the use of regularly shaped, constant thickness amorphous tapes obtained by planar flow casting. No evidence of phase separation during heating prior to crystallization was obtained in glassy Pd/sub 46/Ni/sub 36/P/sub 18/ and Cu/sub 50/Zr/sub 50/ alloys.

  8. Oxide composite prepared from intermetallic and amorphous Zr67Fe30M3- (M=Au, Pt) alloys and their catalytic activity for CO oxidation

    NASA Astrophysics Data System (ADS)

    Huang, Yung-Han; Wang, Sea-Fue; Kameoka, Satoshi; Miyamoto, Kanji; Tsai, An-Pang

    2017-01-01

    In this study, Zr67Fe30M3 (M=Au, Pt) intermetallic compounds and amorphous alloys were prepared and used as precursors for the synthesis of oxides. Oxidation treatment of the intermetallic compounds at 500 °C followed by X-ray diffraction (XRD) analysis indicated that zirconium and iron were oxidized to ZrO2 and Fe2O3, respectively. In the case of Zr67Fe30M3 amorphous alloys, cubic Zr6Fe3O was observed on the surface of the ribbons after heat treatment at 500 °C in vacuum. Addition of 3% of gold or platinum to the alloy resulted in an increase in the lattice constants of the Zr6Fe3O phase. Grounding the treated ribbons into powders followed by an oxidation treatment at 500 °C in air produced Fe2O3 and ZrO2 supports, where Au and Pt are dissolved in the oxides as confirmed by X-ray photoelectron spectroscopy (XPS). No matter precursors are intermetallics or amorphous phases, the resultant oxides are the same. Although Pt and Au dissolved in the oxides, catalytic activities for CO oxidation were significant improved.

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

    SciTech Connect

    Jiang, Jing; Zhu, Shengli; Xu, Wence; Cui, Zhenduo; Yang, Xianjin

    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.

  10. Phase separation and crystallization process of amorphous Fe{sub 78}B{sub 12}Si{sub 9}Ni{sub 1} alloy

    SciTech Connect

    Mukhgalin, V. V.; Lad’yanov, V. I.

    2015-08-17

    The influence of the melt heat treatment on the structure and crystallization process of the rapidly quenched amorphous Fe{sub 78}B{sub 12}Si{sub 9}Ni{sub 1} alloys have been investigated by means of x-ray diffraction, DSC and TEM. Amorphous phase separation has been observed in the alloys quenched after the preliminary high temperature heat treatment of the liquid alloy (heating above 1400°C). Comparative analysis of the pair distribution functions demonstrates that this phase separation accompanied by a changes in the local atomic arrangement. It has been found that crystallization process at heating is strongly dependent on the initial amorphous phase structure - homogeneous or phase separated. In the last case crystallization goes through the formation of a new metastable hexagonal phase [a=12.2849(9) Ǻ, c=7.6657(8) Ǻ]. At the same time the activation energy for crystallization (Ea) reduces from 555 to 475 kJ mole{sup −1}.

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

    DOE PAGES

    Boccard, Mathieu; Holman, Zachary C.

    2015-08-14

    With this study, 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, amorphousmore » 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.« less

  12. Crystallization behavior of iron-based amorphous nanoparticles prepared sonochemically.

    PubMed

    Enomoto, Naoya; Hirata, Shingo; Inada, Miki; Hayashi, Katsuro

    2017-03-01

    In general, a rapid quenching is required to obtain an amorphous metal. It is known that an intensive ultrasonication generates a very high temperature within cavitation bubbles in a very short moment, which enables a rapid quenching process in a liquid phase synthesis. In this study, the sonochemically-derived "amorphous iron" from Fe(CO)5 was carefully examined by XRD, TEM, TG-DTA. The product was found to be an amorphous containing a certain amount (∼15%) of volatile component that can be removed by heating in a nitrogen flow. After annealed in the inert atmosphere at 600°C, cooled down to room temperature, and then exposed in air (oxygen), the sample showed a strong exotherm accompanied by a weight gain. This is due to oxidation of fine metallic iron. Experimental operations of such a reactive material were examined.

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

    NASA Astrophysics Data System (ADS)

    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.

  14. Triphenylamine-based amorphous polymers for bulk-heterojunction photovoltaic cells

    NASA Astrophysics Data System (ADS)

    Yasuda, Takeshi

    2014-03-01

    In this paper, the recent research progress on triphenylamine (TPA)-based donor-acceptor (D-A) amorphous polymers including our developed polymers is reviewed. TPA has three-dimensional branched structures and can provide D-A polymers containing D and A units in the main chain or side chain. The use of TPA-based amorphous polymers in the fabrication of organic photovoltaics (OPVs) offers great advantages over the use of a polycrystalline film in terms of high reproducibility of the OPV performance. The amorphous polymer design using TPA, therefore, indicates a promising direction for the development of new donor materials in OPVs.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    SciTech Connect

    Song, H. Y.; An, M. R.; Li, Y. L. Deng, Q.

    2014-12-07

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

  17. Ti-based glassy alloys in Ti-Cu-Zr-Sn system

    NASA Astrophysics Data System (ADS)

    Wang, ZengRui; Dong, DanDan; Qiang, JianBing; Wang, Qing; Wang, YingMin; Dong, Chuang

    2013-07-01

    Bulk amorphous formation in Ti-Cu-based multicomponent alloys, free of Ni, Pd and Be elements, were studied using the cluster-plus-glue-atom model. The basic cluster formula was revealed as [Ti9Cu6]Cu3 to explain the best binary glass forming composition Ti50Cu50=Ti9Cu9, where the CN14 rhombi-dodecahedron Ti9Cu6 was the principal cluster in the devitrification phase CuTi. This basic cluster formula was further alloyed with Zr and Sn and a critical glass forming ability was reached at (Ti7.2Zr1.8)(Cu8.72Sn0.28) and (Ti7.2Zr1.8)(Cu8.45Sn0.55) up to 5 mm in diameter by suction casting, which was the largest in Ti-Cu-based and Ni-, Pd- and Be-free alloys.

  18. Welding and brazing of nickel and nickel-base alloys

    NASA Technical Reports Server (NTRS)

    Mortland, J. E.; Evans, R. M.; Monroe, R. E.

    1972-01-01

    The joining of four types of nickel-base materials is described: (1) high-nickel, nonheat-treatable alloys, (2) solid-solution-hardening nickel-base alloys, (3) precipitation-hardening nickel-base alloys, and (4) dispersion-hardening nickel-base alloys. The high-nickel and solid-solution-hardening alloys are widely used in chemical containers and piping. These materials have excellent resistance to corrosion and oxidation, and retain useful strength at elevated temperatures. The precipitation-hardening alloys have good properties at elevated temperature. They are important in many aerospace applications. Dispersion-hardening nickel also is used for elevated-temperature service.

  19. 21 CFR 872.3710 - Base metal alloy.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 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...

  20. 21 CFR 872.3710 - Base metal alloy.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 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...

  1. 21 CFR 872.3710 - Base metal alloy.

    Code of Federal Regulations, 2010 CFR

    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...

  2. 21 CFR 872.3710 - Base metal alloy.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 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...

  3. 21 CFR 872.3710 - Base metal alloy.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 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...

  4. Irradiation creep of vanadium-base alloys

    SciTech Connect

    Tsai, H.; Billone, M.C.; Strain, R.V.; Smith, D.L.; Matsui, H.

    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.

  5. Oxygen diffusion in vanadium-based alloys

    SciTech Connect

    de Avillez, R.R.

    1981-01-01

    The experimental study of transport and equilibrium properties of oxygen in vanadium-based alloys was made by EMF measurements on solid electrolytic cells over the temperature range of 873 to 1423/sup 0/K. The oxygen diffusion in vanadium was not significantly modified by small additions of Ti, Cr, Ni, Nb and Ta. The increase in the activation energy for oxygen diffusion in the V-based alloys containing Cr, Ni, Nb and Ta probably reflects the effect of these substitutional solutes on the activity coefficient of oxygen. The oxygen activity was increased by the addition of 1 at % of Cr, Ni and Nb, and decreased by the addition of Ti and Ta. However, the effects in the alloys containing Nb and Ta are very small.

  6. Rapid solidification of Nb-base alloys

    NASA Technical Reports Server (NTRS)

    Gokhale, A. B.; Javed, K. R.; Abbaschian, G. J.; Lewis, R. E.

    1988-01-01

    New Nb-base alloys are of interest for aerospace structural applications at high temperatures, viz, 800 to 1650 C. Fundamental information regarding the effects of rapid solidification in achieving greatly refined microstructures, extended solid solubility, suppression of embrittling equilibrium phases, and formation of new phases is desired in a number of Nb-X alloys. The microstructures and selected properties of Nb-Si and other Nb-base alloys are presented for materials both rapidly quenched from the equilibrium liquidus and rapidly solidified following deep supercooling. Electromagnetic levitation was used to achieve melting and supercooling in a containerless inert gas environment. A variety of solidification conditions were employed including splatting or drop casting of supercooled samples. The morphology and composition of phases formed are discussed in terms of both solidification history and bulk composition.

  7. Nanocrystallization in spark plasma sintered Fe{sub 48}Cr{sub 15}Mo{sub 14}Y{sub 2}C{sub 15}B{sub 6} bulk amorphous alloy

    SciTech Connect

    Singh, Ashish; Harimkar, Sandip P.; Katakam, Shravana; Dahotre, Narendra B.; Ilavsky, Jan

    2013-08-07

    Spark plasma sintering (SPS) is evolving as an attractive process for the processing of multi-component Fe-based bulk amorphous alloys and their in-situ nanocomposites with controlled primary nanocrystallization. Extended Q-range small angle neutron scattering (EQ-SANS) analysis, complemented by x-ray diffraction and transmission electron microscopy, was performed to characterize nanocrystallization behavior of SPS sintered Fe-based bulk amorphous alloys. The SANS experiments show significant scattering for the samples sintered in the supercooled region indicating local structural/compositional changes associated with the profuse nucleation of nanoclusters (∼4 nm). For the samples spark plasma sintered near and above crystallization temperature (>653 °C), the SANS data show the formation of interference maximum indicating the formation and growth of (Fe,Cr){sub 23}C{sub 6} crystallites. The SANS data also indicate the evolution of bimodal crystallite distribution at higher sintering temperatures (above T{sub x1}). The growth of primary nanocrystallites results in impingement of concentration gradient fields (soft impingement effect), leading to non-random nucleation of crystallites near the primary crystallization.

  8. Ion irradiation induced nanocrystal formation in amorphous Zr 55Cu 30Al 10Ni 5 alloy

    NASA Astrophysics Data System (ADS)

    Carter, Jesse; Fu, E. G.; Martin, Michael; Xie, Guoqiang; Zhang, X.; Wang, Y. Q.; Wijesundera, D.; Wang, X. M.; Chu, Wei-Kan; McDeavitt, Sean M.; Shao, Lin

    2009-09-01

    Ion irradiation can be used to induce partial crystallization in metallic glasses to improve their surface properties. We investigated the microstructural changes in ribbon Zr 55Cu 30Al 10Ni 5 metallic glass after 1 MeV Cu-ion irradiation at room temperature, to a fluence of 1.0 × 10 16 cm -2. In contrast to a recent report by others that there was no irradiation induced crystallization in the same alloy [S. Nagata, S. Higashi, B. Tsuchiya, K. Toh, T. Shikama, K. Takahiro, K. Ozaki, K. Kawatusra, S. Yamamoto, A. Inouye, Nucl. Instr. and Meth. B 257 (2007) 420], we have observed nanocrystals in the as-irradiated samples. Two groups of nanocrystals, one with diameters of 5-10 nm and another with diameters of 50-100 nm are observed by using high resolution transmission electron microscopy. Experimentally measured planar spacings ( d-values) agree with the expectations for Cu 10Zr 7, NiZr 2 and CuZr 2 phases. We further discussed the possibility to form a substitutional intermetallic (Ni xCu 1-x)Zr 2 phase.

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

    NASA Astrophysics Data System (ADS)

    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.

  10. First-principles study of crystalline and amorphous AlMgB14-based materials

    NASA Astrophysics Data System (ADS)

    Ivashchenko, V. I.; Turchi, P. E. A.; Veprek, S.; Shevchenko, V. I.; Leszczynski, Jerzy; Gorb, Leonid; Hill, Frances

    2016-05-01

    We report first-principles investigations of crystalline and amorphous boron and M1xM2yXzB14-z (M1, M2 = Al, Mg, Li, Na, Y; X = Ti, C, Si) phases (so-called "BAM" materials). Phase stability is analyzed in terms of formation energy and dynamical stability. The atomic configurations as well as the electronic and phonon density states of these phases are compared. Amorphous boron consists of distorted icosahedra, icosahedron fragments, and dioctahedra, connected by an amorphous network. The presence of metal atoms in amorphous BAM materials precludes the formation of icosahedra. For all the amorphous structures considered here, the Fermi level is located in the mobility gap independent of the number of valence electrons. The intra-icosahedral vibrations are localized in the range of 800 cm-1, whereas the inter-icosahedral vibrations appear at higher wavenumbers. The amorphization leads to an enhancement of the vibrations in the range of 1100-1250 cm-1. The mechanical properties of BAM materials are investigated at equilibrium and under shear and tensile strain. The anisotropy of the ideal shear and tensile strengths is explained in terms of a layered structure of the B12 units. The strength of amorphous BAM materials is lower than that of the crystalline counterparts because of the partial fragmentation of the boron icosahedra in amorphous structures. The strength enhancement found experimentally for amorphous boron-based films is very likely related to an increase in film density, and the presence of oxygen impurities. For crystalline BAM materials, the icosahedra are preserved during elongation upon tension as well as upon shear in the (010)[100] slip system.

  11. Changes in cluster magnetism and suppression of local superconductivity in amorphous FeCrB alloy irradiated by Ar+ ions

    NASA Astrophysics Data System (ADS)

    Okunev, V. D.; Samoilenko, Z. A.; Szymczak, H.; Szewczyk, A.; Szymczak, R.; Lewandowski, S. J.; Aleshkevych, P.; Malinowski, A.; Gierłowski, P.; Więckowski, J.; Wolny-Marszałek, M.; Jeżabek, M.; Varyukhin, V. N.; Antoshina, I. A.

    2016-02-01

    We show that сluster magnetism in ferromagnetic amorphous Fe67Cr18B15 alloy is related to the presence of large, D=150-250 Å, α-(Fe Cr) clusters responsible for basic changes in cluster magnetism, small, D=30-100 Å, α-(Fe, Cr) and Fe3B clusters and subcluster atomic α-(Fe, Cr, B) groupings, D=10-20 Å, in disordered intercluster medium. For initial sample and irradiated one (Φ=1.5×1018 ions/cm2) superconductivity exists in the cluster shells of metallic α-(Fe, Cr) phase where ferromagnetism of iron is counterbalanced by antiferromagnetism of chromium. At Φ=3×1018 ions/cm2, the internal stresses intensify and the process of iron and chromium phase separation, favorable for mesoscopic superconductivity, changes for inverse one promoting more homogeneous distribution of iron and chromium in the clusters as well as gigantic (twice as much) increase in density of the samples. As a result, in the cluster shells ferromagnetism is restored leading to the increase in magnetization of the sample and suppression of local superconductivity. For initial samples, the temperature dependence of resistivity ρ(T) T2 is determined by the electron scattering on quantum defects. In strongly inhomogeneous samples, after irradiation by fluence Φ=1.5×1018 ions/cm2, the transition to a dependence ρ(T) T1/2 is caused by the effects of weak localization. In more homogeneous samples, at Φ=3×1018 ions/cm2, a return to the dependence ρ(T) T2 is observed.

  12. Amorphous Silk Nanofiber Solutions for Fabricating Silk-Based Functional Materials.

    PubMed

    Dong, Xiaodan; Zhao, Qun; Xiao, Liying; Lu, Qiang; Kaplan, David L

    2016-09-12

    As a functional material, silk has been widely used in tissue engineering, drug release, and tissue regeneration. Increasing subtle control of silk hierarchical structures and thus specific functional performance is required for these applications but remains a challenge. Here, we report a novel silk nanofiber solution achieved through tuning solvent systems used to generate the material. Unlike the β-sheet rich silk nanofibers reported previously, these new silk nanofibers are mainly composed of amorphous structures and maintain a solution state in aqueous environments. The amorphous silk nanofibers are stable enough for storage and also metastable, making them easy to use in the further fabrication of materials through various processes. Silk scaffolds, hydrogels, and films were prepared from these silk nanofiber solutions. These silk materials from amorphous nanofiber solutions show different properties and tunable performance features. Therefore, these amorphous silk nanofibers are suitable units or building blocks for designing silk-based materials.

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

    SciTech Connect

    Guzman, D.; Ordonez, S.; Fernandez, J.F.; Sanchez, C.; Serafini, D.; Rojas, P.A.; Aguilar, C.; Tapia, P.

    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.

  14. Predicted Optimum Composition for the Glass-Forming Ability of Bulk Amorphous Alloys: Application to Cu-Zr-Al.

    PubMed

    An, Qi; Samwer, Konrad; Goddard, William A; Johnson, William L; Jaramillo-Botero, Andres; Garret, Glenn; Demetriou, Marios D

    2012-11-01

    Metallic glasses have been established to have unique properties such as ductility, toughness, and soft magnetism with promising engineering applications. However, the glass-forming ability (GFA) has not been sufficient to synthesize the bulk metallic glasses (BMGs) required for many engineering applications. Attempts to develop the understanding of the GFA required to predict the optimum alloys have not yet been proven successful. We develop here a computational model based on molecular dynamics simulations that explains the dramatic change of GFA with alloying small amounts of Al into Cu-Zr. We find that the high GFA to form BMGs depends on a combination of three factors, (a) a low thermodynamic driving force for crystallization, (b) a high melt viscosity, and (c) large ratios of icosahedral structures in the liquid phase. These computational methods to predict these factors that suppress formation of crystal nuclei and slow the dynamic motions in the liquids are practical for in silico prediction of new alloys with optimal GFA.

  15. Local structure of the crystalline and amorphous states of Ga2Te3 phase-change alloy without resonant bonding: A combined x-ray absorption and ab initio study

    NASA Astrophysics Data System (ADS)

    Kolobov, A. V.; Fons, P.; Krbal, M.; Mitrofanov, K.; Tominaga, J.; Uruga, T.

    2017-02-01

    Phase-change memories are usually associated with GeTe-Sb2Te3 quasibinary alloys, where the large optical contrast between the crystalline and amorphous phases is attributed to the formation of resonant bonds in the crystalline phase, which has a rocksalt-like structure. The recent findings that tetrahedrally bonded Ga2Te3 possesses a similarly large property contrast and very low thermal conductivity in the crystalline phase and undergoes low-energy switching [H. Zhu et al., Appl. Phys. Lett. 97, 083504 (2010), 10.1063/1.3483762; K. Kurosaki et al., Appl. Phys. Lett. 93, 012101 (2008), 10.1063/1.2940591] challenge the existing paradigm. In this work we report on the local structure of the crystalline and amorphous phases of Ga2Te3 obtained from x-ray absorption measurements and ab initio simulations. Based on the obtained results, a model of phase change in Ga2Te3 is proposed. We argue that efficient switching in Ga2Te3 is due to the presence of primary and secondary bonding in the crystalline phase originating from the high concentration of Ga vacancies, whereas the structural stability of both phases is ensured by polyvalency of Te atoms due to the presence of lone-pair electrons and the formation of like-atom bonds in the amorphous phase.

  16. Laser surface treatment of amorphous metals

    NASA Astrophysics Data System (ADS)

    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

  17. Progress in ODS Alloys: A Synopsis of a 2010 Workshop on Fe- Based ODS Alloys

    SciTech Connect

    Kad, Bimal; Dryepondt, Sebastien N; Jones, Andy R.; Vito, Cedro III; Tatlock, Gordon J; Pint, Bruce A; Tortorelli, Peter F; Rawls, Patricia A.

    2012-01-01

    In Fall 2010, a workshop on the role and future of Fe-based Oxide Dispersion Strengthened (ODS) alloys gathered together ODS alloy suppliers, potential industrial end-users, and technical experts in relevant areas. Presentations and discussions focused on the current state of development of these alloys, their availability from commercial suppliers, past major evaluations of ODS alloy components in fossil and nuclear energy applications, and the technical and economic issues attendant to commercial use of ODS alloys. Significant progress has been achieved in joining ODS alloys, with creep resistant joints successfully made by inertia welding, friction stir welding and plasma-assisted pulse diffusion bonding, and in improving models for the prediction of lifetime components. New powder and alloy fabrication methods to lower cost or improve endproduct properties were also described. The final open discussion centered on challenges and pathways for further development and large-scale use of ODS alloys.

  18. A Hydrogen-Deuterium Exchange Study on Nickel-based Binary-Ternary Amorphous and Crystalline Membranes

    NASA Astrophysics Data System (ADS)

    Adibhatla, Anasuya

    Hydrogen is a major role player in current global sustainable energy scenario. Research around the world is carried out to harness hydrogen from all possible sources. One of these sources is water gas shift reaction after the coal gasification process. Sustainable infrastructure can be viable in countries like USA and Australia, making this process viable. Various methods are used to harness this hydrogen from the water gas. One of these methods is the use of inorganic membranes based on Pd, Ag, Ni, Zr and other transition metals. Pd addition to the membranes makes the membranes more expensive for commercial use. Various bulk properties like hydrogen permeation and absorption are studied on Pd and Pd-based alloys. Alternate alloys based on Ni, V, Ta etc are being studied to substitute the use of Pd making this technology more cost efficient. A current balance in research in this area is fund to exist by coating the non-precious metal membranes with Pd to improve the surface interaction with hydrogen. The nature of membranes used for hydrogen separation is important aspect for the overall performance. Crystalline materials provide better bulk properties, however, are not durable under high temperature and hydrogen pressure. In this research, non-Pd coated Ni-based amorphous membranes were made by melt spin technique, which have been studied for their surface properties. Gas phase H2-D2 exchange reaction has been carried out on the membrane surface. This provides a measure of catalytic activity of the above mentioned membranes. More studies included the crystallographic phase change determination, bulk hydrogen solubility measurements, surface conduction measurements and surface morphological studies. During this research, it has been observed that crystalline materials provide more surface activity for hydrogen than their amorphous counterparts. Ni64Zr36 alloy has been shown to exhibit similar kinetic rates as metallic Ni. Also, microkinetic analysis was performed

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

    NASA Astrophysics Data System (ADS)

    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. THERMOSTATICS AND KINETICS OF TRANSFORMATIONS IN PU-BASED ALLOYS

    SciTech Connect

    Turchi, P; Kaufman, L; Liu, Z

    2006-06-30

    CALPHAD assessment of the thermodynamic properties of a series of Pu-based alloys is briefly presented together with some results on the kinetics of phase formation and transformations in Pu-Ga alloys.

  1. Optimization of Iron Cobalt-based Nanocomposite Alloys for High Induction and Increased Resistivity

    NASA Astrophysics Data System (ADS)

    Shen, Shen

    FeCo-based nanocrystalline soft magnetic materials are promising to provide high saturation induction, high Curie temperature and excellent soft magnetic properties for electric vehicle and high frequency power conversion applications. The increasing operation frequency of various inductive applications requires nanocomposite alloys with higher resistivity to suppress power losses. In this thesis, the method of measuring as-cast and annealed resistivity of melt-spun ribbon alloys by obtaining alloy densities was established. Archimedes method with deionized water as a medium was used to determine the density of crystalline alloys. A gas pycnometer using dry Helium gas as the medium exhibited improved accuracy in measuring the density of amorphous ribbon alloys compared to the conventional Archimedes method using a liquid medium. This method was applied to previously developed HITPERM (FeCoZrBCu) and HTX002 (FeCoBSiCu) type of alloys as well as carbon-containing (FeCoBCCu) alloys to guide composition adjustments pursuing for improved magnetic properties. In the HITPERM type of alloys, the composition dependence of as-cast resistivity was studied and simulated by Mott's two-current model with a rigid-band assumption which provided guidance for further adjusting alloy composition looking for higher resistivity. An alloy designed with the Fe:Co ratio for maximum as-cast resistivity and Hf as glass former exhibits low power loss values being approximately 1/4 of those measured on the alloy with the original HITPERM composition for a range of frequencies. The Al and Si additions were found effective to achieve a high resistivity of 151.9 muO·cm in the as-cast alloys but also lead to embrittlement of melt-spun ribbons. Composition adjustments on the HTX002 type of alloys which are castable in air and available for larger-scale production were also explored. Increasing the ferromagnetic late transition metal content by reducing glass formers was found effective to achieve

  2. Vanadium-base alloys for fusion reactor applications

    SciTech Connect

    Smith, D.L.; Loomis, B.A.; Diercks, D.R.

    1984-10-01

    Vanadium-base alloys offer potentially significant advantages over other candidate alloys as a structural material for fusion reactor first wall/blanket applications. Although the data base is more limited than that for the other leading candidate structural materials, viz., austenitic and ferritic steels, vanadium-base alloys exhibit several properties that make them particularly attractive for the fusion reactor environment. This paper presents a review of the structural material requirements, a summary of the materials data base for selected vanadium-base alloys, and a comparison of projected performance characteristics compared to other candidate alloys. Also, critical research and development (R and D) needs are defined.

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

    NASA Astrophysics Data System (ADS)

    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. On the magnetic anisotropy in Fe78Si9B13 ingots and amorphous ribbons: Orientation aligning of Fe-based phases/clusters

    NASA Astrophysics Data System (ADS)

    Wang, X.; Ma, H. J.; Sheng, Z. H.; Jin, S. F.; Xu, W.; Ferry, M.; Chen, L.; Duan, J. Q.; Wang, W. M.

    2017-01-01

    Magnetic anisotropy in Fe-based amorphous ribbon plays an important role in various applications and is still not fully understood. To gain an in-depth understanding of this phenomenon, the structure and magnetic properties of Fe78Si9B13 master alloy ingots and melt-spun amorphous ribbons were measured by various techniques. For the ingot samples, both the <100>α-Fe and <001>Fe2B axes are aligned parallel with the radial direction (RD) of the original cylindrical ingot, i.e. the maximum temperature gradient direction, and their other orthogonal axes have several preferred directions in the plane vertical to RD. The hard magnetic axis of the ingot samples is parallel to RD, which is due to the large magnetocrystalline anisotropy energy difference between <001> and {001} of the Fe2B phase. For the amorphous ribbons, there is an in-plane magnetic anisotropy: the easy or hard axis of magnetization is aligned on the plane of the ribbon, and parallel to or at an angle of about 60° to its width direction, respectively. According to the structural heredity between the melts and glasses/crystals during solidification, we deduce that the magnetic anisotropy in the ribbon plane is ascribed to the orientation alignment of Fe-Si and Fe-B clusters, i.e. a hidden order beyond short-range order, in Fe78Si9B13 amorphous ribbons.

  5. Fabric cutting application of FeAl-based alloys

    SciTech Connect

    Sikka, V.K.; Blue, C.A.; Sklad, S.P.; Deevi, S.C.; Shih, H.R.

    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.

  6. Synthesis and thermal behavior of tin-based alloy (Sn-Ag-Cu) nanoparticles.

    PubMed

    Roshanghias, Ali; Yakymovych, Andriy; Bernardi, Johannes; Ipser, Herbert

    2015-03-19

    The prominent melting point depression of nanoparticles has been the subject of a considerable amount of research. For their promising applications in electronics, tin-based nano-alloys such as near-eutectic Sn-Ag-Cu (SAC) alloys have been synthesized via various techniques. However, due to issues such as particle aggregation and oxidation or introduced impurities, the application of these nano-size particles has been confined or aborted. For instance, thermal investigations by DTA/DSC in a large number of studies revealed exothermic peaks in the range of 240-500 °C, i.e. above the melting point of SAC nanoparticles, with different and quite controversial explanations for this unclear phenomenon. This represents a considerable drawback for the application of nanoparticles. Correspondingly, in the current study, the thermal stability of SAC nanoparticles has been investigated via electron microscopy, XRD, FTIR, and DSC/TG analysis. It was found that the nanoparticles consist mainly of a metallic β-Sn core and an amorphous tin hydroxide shell structure. The SnO crystalline phase formation from this amorphous shell has been associated with the exothermic peaks on the first heating cycle of the nanoparticles, followed by a disproportionation reaction into metallic Sn and SnO₂.The results also revealed that the surfactant and reducing agent cannot only affect the size and size distribution of the nanoparticles, they might also alter the ratio between the amorphous shell and the crystalline core in the structure of particles.

  7. Deformation analysis of amorphous metals based on atomic elastic stiffness coefficients

    NASA Astrophysics Data System (ADS)

    Yashiro, K.; Nishimura, M.; Tomita, Y.

    2006-06-01

    The elastic limit of a crystal can be evaluated by the positiveness of elastic stiffness coefficients, Bijkl. We had demonstrated that the nucleation of lattice defects such as dislocation and cleavage cracking can be predicted by the atomic Bijkl at each atom point. Amorphous metals and bulk metallic glasses draw intense interest whether the criteria are applicable or not since they are regarded as the ultimate of lattice defects. In the present study, an amorphous Ni-Al binary alloy is made by a usual melt-quench simulation and subjected to tension by means of molecular dynamics simulation. During simulations, the positiveness of atomic Bijkl is discussed for all atoms. Contrary to an Ni-Al crystal, many atoms show negative value even in the initial equilibrium of the amorphous before loading. These unstable atoms turn out to be the non-clustered atom or the outer-shell of the local cluster such as 12(0, 0, 12, 0) icosahedron. On the other hand, the centre atoms of the local clusters show high stability resulting in the positive Bijkl of the whole system. It is also demonstrated that the change in the atomic Bijkl can reveal the collapse and re-configuration of local clusters during the deformation.

  8. Characterization of two ceramic-base-metal alloys.

    PubMed

    Huget, E F; Vlica, J M; Wall, R M

    1978-12-01

    Compositions, microstructures, properties, and heat treatment characteristics of two ceramic-base-metal alloys were studied. The materials displayed significant compositional and structural differences. Both alloys were strengthened by precipitation hardening. Strength and rigidity of the nickel-chromium alloys suggest their potential usefulness in fixed prosthodontic procedures.

  9. Itinerant magnetic properties of amorphous metallic systems II: Magnetic moment distribution in the Fe-B alloys and the magnetism of amorphous Fe

    NASA Astrophysics Data System (ADS)

    Krompiewski, S.; Krey, U.; Krauss, U.; Ostermeier, H.

    1988-05-01

    For realistic structural models of amorphous Fe 1- xB x with 0.2⩽x⩽0.6 and for the fictitious case of x = 0 (amorphous iron, a-Fe), we calculate the distribution function p( ml) of the local magnetic moments ml by means of a self-consistent itinerant electron approach. Generally, p( ml) is rather broad and agrees with experimental hyperfine field distributions. For x→0 and x > 0.5, even negative moments appear, although overlinem remains positive. Additionally we find that for a-Fe a rather drastic transition from paramagnetic behaviour at densities ρ<ρ c(≈8.3 g/cm 3) to ferromagnetism at ρ > ρ c would happen, if the magnetization could be forced to remain homogeneous. However, if the ml are allowed to relax to their local values, no such transition happens. Finally, we study the question whether the spread of the local moments is important for the density of states and find that this is the case except for 0.2⩽x⩽0.35.

  10. FY05 HPCRM Annual Report: High-Performance Corrosion-Resistant Iron-Based Amorphous Metal Coatings

    SciTech Connect

    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

  11. The Corrosion Resistance of Fe-Based Amorphous Metals: Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4 and Other Compositions

    SciTech Connect

    Farmer, J; Haslam, J; Day, S; Lian, T; Saw, C; Hailey, P; Choi, J; Rebak, R; Payer, J; Blue, C; Peters, W; Branagan, D

    2007-07-09

    Several Fe-based amorphous metals were developed with good corrosion resistance. These materials have been produced as melt-spun ribbons, ingots, and thermal-spray coatings. Cyclic polarization has been conducted in several aggressive environments, at ambient temperature, as well as temperatures approaching the boiling points of the test solutions. The hypothesis that the corrosion resistance of iron-based amorphous metals can be enhanced through application of heuristic principles related to the additions of chromium, molybdenum, tungsten has been tested and found to have merit. Chromium (Cr), molybdenum (Mo) and tungsten (W) provide corrosion resistance; boron (B) enables glass formation; and rare earths such as yttrium (Y) lower critical cooling rate (CCR). 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.

  12. Deformation behavior of an amorphous Cu64.5Zr35.5 alloy: A combined computer simulation and experimental study

    NASA Astrophysics Data System (ADS)

    Mendelev, M. I.; Ott, R. T.; Heggen, M.; Feuerebacher, M.; Kramer, M. J.; Sordelet, D. J.

    2008-12-01

    Molecular dynamics (MD) simulations were performed to examine the temperature-dependent elastic properties and high-temperature deformation behavior of a Cu64.5Zr35.5 amorphous alloy. From the simulations we find that the elastic constants of the amorphous solid and supercooled liquid exhibit an approximately linear temperature dependence. The predicted temperature dependence of the Young's modulus for the amorphous solid obtained from the MD simulations is in good agreement with experimental measurements using dynamic mechanical analysis. Furthermore, the high-temperature plastic deformation behavior determined by MD simulations is qualitatively in good agreement with results from plastic deformation experiments performed on 1 mm diameter Cu64.5Zr35.5 metallic glass rods at 698 K. Notably, the MD simulations reveal that the flow softening regime of the stress-strain curve corresponds to an increase in the free volume in the atomic structure. Moreover, the simulations indicate that the atomic mobility significantly increases within the same regime.

  13. Cerium-based conversion coatings on magnesium alloys

    NASA Astrophysics Data System (ADS)

    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.

  14. Mechanism of Dissolution-Induced Nanoparticle Formation from a Copovidone-Based Amorphous Solid Dispersion.

    PubMed

    Harmon, Paul; Galipeau, Kendra; Xu, Wei; Brown, Chad; Wuelfing, W Peter

    2016-05-02

    Amorphous solid dispersions (ASDs) have been increasingly used to maximize human exposures from poorly soluble drug candidates. One well-studied advantage of ASDs is the increased amorphous drug solubility compared to crystalline forms. This provides more rapid dissolution rates. An additional advantage of ASDs is that the dissolution process of the ASD particle may also rapidly transform much of the drug present in the ASD particle to small (<1 μm) amorphous drug nanoparticles which will have fast dissolution rates. This work examines the mechanism by which this nanoparticle formation occurs by studying an ASD consisting of 70-80% copovidone, 20% anacetrapib (a low solubility lipophilic drug), and 0-10% TPGS (d-α-tocopheryl polyethylene glycol 1000 succinate, a surfactant). Nanoparticle formation is found to derive from a rapid amorphous drug domain formation within the ASD particle, driven by copovidone dissolution from the particle. The role of surfactant in the ASD particle is to prevent an otherwise rapid, local drug domain aggregation event, which we term "hydrophobic capture". Surfactant thus allows the amorphous drug domains to escape hydrophobic capture and diffuse to bulk solution, where they are reported as nanoparticles. This view of surfactant and nanoparticle formation is compared to the prevailing view in the literature. The work here clarifies the different roles that surfactant might play in increasing nanoparticle yields and extending the useful drug loading ranges in copovidone-based ASDs.

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

    PubMed

    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.

  16. DISPERSION STRENGTHENED NICKEL-BASE ALLOYS.

    DTIC Science & Technology

    The swaged cone of extruded Nichrome-thoria alloys prepared by the thermal decomposition of thorium nitrate onto alloy powder indicated descreased... swaging of these dispersion-strengthened Nichrome alloys was dependent on the presence of a mild steel jacket on the alloy rod as a result of the canned...extrusion practice. Efforts to cold swage the alloy materials without this jacket were unsuccessful. (Author)

  17. Grain Refinement of Permanent Mold Cast Copper Base Alloys

    SciTech Connect

    M.Sadayappan; J.P.Thomson; M.Elboujdaini; G.Ping Gu; M. Sahoo

    2005-04-01

    Grain refinement is a well established process for many cast and wrought alloys. The mechanical properties of various alloys could be enhanced by reducing the grain size. Refinement is also known to improve casting characteristics such as fluidity and hot tearing. Grain refinement of copper-base alloys is not widely used, especially in sand casting process. However, in permanent mold casting of copper alloys it is now common to use grain refinement to counteract the problem of severe hot tearing which also improves the pressure tightness of plumbing components. The mechanism of grain refinement in copper-base alloys is not well understood. The issues to be studied include the effect of minor alloy additions on the microstructure, their interaction with the grain refiner, effect of cooling rate, and loss of grain refinement (fading). In this investigation, efforts were made to explore and understand grain refinement of copper alloys, especially in permanent mold casting conditions.

  18. Cast Fe-base cylinder/regenerator housing alloy

    NASA Technical Reports Server (NTRS)

    Larson, F.; Kindlimann, L.

    1980-01-01

    The development of an iron-base alloy that can meet the requirements of automotive Stirling engine cylinders and regenerator housings is described. Alloy requirements are as follows: a cast alloy, stress for 5000-hr rupture life of 200 MPa (29 ksi) at 775 C (1427 F), oxidation/corrosion resistance comparable to that of N-155, compatibility with hydrogen, and an alloy cost less than or equal to that of 19-9DL. The preliminary screening and evaluation of ten alloys are described.

  19. Amorphous Si thin film based photocathodes with high photovoltage for efficient hydrogen production.

    PubMed

    Lin, Yongjing; Battaglia, Corsin; Boccard, Mathieu; Hettick, Mark; Yu, Zhibin; Ballif, Christophe; Ager, Joel W; Javey, Ali

    2013-01-01

    An amorphous Si thin film with TiO2 encapsulation layer is demonstrated as a highly promising and stable photocathode for solar hydrogen production. With platinum as prototypical cocatalyst, a photocurrent onset potential of 0.93 V vs RHE and saturation photocurrent of 11.6 mA/cm(2) are measured. Importantly, the a-Si photocathodes exhibit impressive photocurrent of ~6.1 mA/cm(2) at a large positive bias of 0.8 V vs RHE, which is the highest for all reported photocathodes at such positive potential. Ni-Mo alloy is demonstrated as an alternative low-cost catalyst with onset potential and saturation current similar to those obtained with platinum. This low-cost photocathode with high photovoltage and current is a highly promising photocathode for solar hydrogen production.

  20. Improvements in Microstructure and Wear Resistance of Plasma-Sprayed Fe-Based Amorphous Coating by Laser-Remelting

    NASA Astrophysics Data System (ADS)

    Jiang, Chaoping; Chen, Hong; Wang, Gui; Chen, Yongnan; Xing, Yazhe; Zhang, Chunhua; Dargusch, Matthew

    2017-03-01

    Amorphous coating technology is an attractive way of taking advantage of the superior properties of amorphous alloys for structural applications. However, the limited bonds between splats within the plasma-sprayed coatings result in a typically lamellar and porous coating structure. To overcome these limitations, the as-sprayed coating was treated by a laser-remelting process. The microstructure and phase composition of two coatings were analyzed using scanning electron microscopy with energy-dispersive spectroscopy, transmission electron microscopy, and x-ray diffraction. The wear resistance of the plasma-sprayed coating and laser-remelted coating was studied comparatively using a pin-on-disc wear test under dry friction conditions. It was revealed that the laser-remelted coating exhibited better wear resistance because of its defect-free and amorphous-nanocrystalline composited structure.

  1. Microwave properties of /Fe(0.82)B(0.18)/(0.90)La(0.05)R(0.05) amorphous metal alloys

    NASA Astrophysics Data System (ADS)

    Vittoria, C.; Koon, N. C.; Lubitz, P.; Geohegan, J. A.

    1984-03-01

    Microwave properties of amorphous metal alloys of /Fe(0.82)B(0.18)/(0.90)La(0.05)R(0.05), where R = La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, and Er, are reported. The microwave measurements consisted of fixed (9 GHz) and swept (0.01-18 GHz) frequency magnetic resonance experiments. The ferromagnetic resonance linewidth, Delta H, and g factor were measured. Delta H has a minimum for R = Gd and is equal to 100 Oe. Delta H appears to scale with the product of the spin and orbital angular momentum operators of the R ion. The measured g factor obeys the Wangsness relation as R is varied.

  2. Investigation of the stability and 1.0 MeV proton radiation resistance of commercially produced hydrogenated amorphous silicon alloy solar cells

    NASA Technical Reports Server (NTRS)

    Lord, Kenneth R., II; Walters, Michael R.; Woodyard, James R.

    1994-01-01

    The radiation resistance of commercial solar cells fabricated from hydrogenated amorphous silicon alloys is reported. A number of different device structures were irradiated with 1.0 MeV protons. The cells were annealing at 200 C. The annealing time was dependent on proton fluence. Annealing devices for one hour restores cell parameters or fluences below 1(exp 14) cm(exp -2); fluences above 1(exp 14) cm(exp -2) require longer annealing times. A parametric fitting model was used to characterize current mechanisms observed in dark I-V measurements. The current mechanisms were explored with irradiation fluence, and voltage and light soaking times. The thermal generation current density and quality factor increased with proton fluence. Device simulation shows the degradation in cell characteristics may be explained by the reduction of the electric field in the intrinsic layer.

  3. Investigation of the Stability and 1.0 MeV Proton Radiation Resistance of Commercially Produced Hydrogenated Amorphous Silicon Alloy Solar Cells

    NASA Technical Reports Server (NTRS)

    Lord, Kenneth R., II; Walters, Michael R.; Woodyard, James R.

    1994-01-01

    The radiation resistance of commercial solar cells fabricated from hydrogenated amorphous silicon alloys is reported. A number of different device structures were irradiated with 1.0 MeV protons. The cells were insensitive to proton fluences below 1E12 sq cm. The parameters of the irradiated cells were restored with annealing at 200 C. The annealing time was dependent on proton fluence. Annealing devices for one hour restores cell parameters for fluences below 1E14 sq cm fluences above 1E14 sq cm require longer annealing times. A parametric fitting model was used to characterize current mechanisms observed In dark I-V measurements. The current mechanism were explored with irradiation fluence, and voltage and light soaking times. The thermal generation current density and quality factor increased with proton fluence. Device simulation shows the degradation in cell characteristics may be explained by the reduction of the electric field in the intrinsic layer.

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

    NASA Technical Reports Server (NTRS)

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    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-crystalline phase switching was achieved by consecutively melting, melt-quenching, and recrystallizing upon heating. Using a well-conditioned method, the composition of a single sample was allowed to shift slowly from 15 at. %Te to 60 at. %Te, eliminating sample-to-sample variability from the measurements. Using Energy Dispersive X-ray Spectroscopy composition analysis, the onset of melting for different Te-concentrations was confirmed to coincide with the literature solidus line, validating the use of the onset of melting Tm as a composition indicator. The glass transition Tg and crystallization temperature Tc could be determined accurately, allowing the construction of extended phase diagrams. It was found that Tm and Tg increase (but Tg/Tm decrease slightly) with increasing Te-concentration. Contrarily, the Tc decreases substantially, indicating that the amorphous phase becomes progressively unfavorable. This coincides well with the observation that the critical quench rate to prevent crystallization increases about three orders of magnitude with increasing Te concentration. Due to the employment of a large range of heating rates, non-Arrhenius behavior was detected, indicating that the undercooled liquid SeTe is a fragile liquid. The activation energy of crystallization was found to increase 0.5-0.6 eV when the Te concentration increases from 15 to 30 at. % Te, but it ceases to increase when approaching 50 at. % Te.

  6. Reversible amorphous-crystalline phase changes in a wide range of Se(1-x)Te(x) alloys studied using ultrafast differential scanning calorimetry.

    PubMed

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

    2014-07-14

    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-crystalline phase switching was achieved by consecutively melting, melt-quenching, and recrystallizing upon heating. Using a well-conditioned method, the composition of a single sample was allowed to shift slowly from 15 at. %Te to 60 at. %Te, eliminating sample-to-sample variability from the measurements. Using Energy Dispersive X-ray Spectroscopy composition analysis, the onset of melting for different Te-concentrations was confirmed to coincide with the literature solidus line, validating the use of the onset of melting Tm as a composition indicator. The glass transition Tg and crystallization temperature Tc could be determined accurately, allowing the construction of extended phase diagrams. It was found that Tm and Tg increase (but Tg/Tm decrease slightly) with increasing Te-concentration. Contrarily, the Tc decreases substantially, indicating that the amorphous phase becomes progressively unfavorable. This coincides well with the observation that the critical quench rate to prevent crystallization increases about three orders of magnitude with increasing Te concentration. Due to the employment of a large range of heating rates, non-Arrhenius behavior was detected, indicating that the undercooled liquid SeTe is a fragile liquid. The activation energy of crystallization was found to increase 0.5-0.6 eV when the Te concentration increases from 15 to 30 at. % Te, but it ceases to increase when approaching 50 at. % Te.

  7. A MHO-based magnetic hysteresis model for amorphous materials

    NASA Astrophysics Data System (ADS)

    Ma, Lianwei; Shen, Yu; Li, Jinrong; Zhao, Xinlong

    2014-12-01

    A magnetic hysteretic operator (MHO) is proposed in this paper. Based on the constructed MHO, the input space of neural networks is expanded from one-dimension to two-dimension using the expanded space method so that the one-to-multiple mapping of magnetic hysteresis is transformed into one-to-one mapping. Based on the expanded input space, a neural network is employed to identify magnetic hysteresis. The result of an experimental example suggests the proposed approach is effective.

  8. The development of nontoxic Ag-based brazing alloys

    SciTech Connect

    Timmins, P.F. )

    1994-09-01

    An experimental investigation wad conducted to produce nontoxic, Cd-free brazing alloys that possessed similar melting ranges and mechanical properties to those alloys within the Ag-Cu-Zn-Cd system. The investigation consisted of phase equilibria, Zn equivalence, thermal analysis, extrusion, wire drawing and mechanical testing of alloys based in the Ag-Cu-Zn system. Thermal analysis of these new alloys yielded liquidus temperatures in the range 680 to 775 C (1256--1427 F) and solidus temperatures in the range 625 to 675 C (1157--1247 F). These values compared favorably to the Ag-Cu-Zn-Cd alloys, which have liquidus and solidus temperatures in the ranges of 640 to 710 C (1184--1310 F) and 610 to 620 C (1130--1148 F), respectively, for Ag contents in the 20 to 50 wt-% range. Tensile tests revealed the ultimate tensile strengths of the as-cast Ag-Cu-Zn-Sn alloys to be higher than the toxic Cd-containing alloys of higher Ag content and higher than the ternary Ag-Cu-Zn alloys. For example, the alloy at 35Ag-34Cu-30Zn-1Sn exhibited an as-cast tensile strength of 47.6 kg/mm[sup 2] (67.7 ksi) compared to the alloy at 50Ag-15Cu-16Zn-19Cd with an as-cast tensile strength of 45.7 kg/mm[sup 2] (65 ksi).

  9. Helium-3 in nickel-base amorphous metals: Surface features, subsurface microstructure, migration, and release upon annealing

    SciTech Connect

    Uenleu, K.

    1989-01-01

    The amorphous alloys Ni{sub 75.1}Cr{sub 14}P{sub 10.1}C{sub 0.08}, Ni{sub 63.5}Zr{sub 36.5}, and Ni{sub 87.7}P{sub 12.3} have been implanted with 150 keV helium-3 ions with doses 1 {times} 10{sup 16} He{sup 3}/cm{sup 2} and 5 {times} 10{sup 16} He{sup 3}/cm{sup 2}. The samples were isochronally annealed at several consecutive stages up t their crystallization temperatures. The surface features were examined by scanning electron microscope, subsurface microstructural changes were investigated by electron diffraction using a scanning transmission electron microscope, and helium-3 depth profiles were measured by a thermal neutron induced nuclear reaction technique called neutron depth profiling (NDP). It was confirmed that for amorphous metals: (a) the helium-3 release is concentration dependent; (b) the migration and the release of helium-3 is controlled by detrapping mechanism; and (c) the crystallization temperatures obtained in this study are in agreement with the reported values. The penetration depth or the projected depth of helium-3 ions with an initial energy of 150 keV is measured here for the first time after obtaining the depth profiles by using the NDP technique. The most probable range values are: 320 nm for Ni{sub 75.1}Cr{sub 14}P{sub 10.1}C{sub 0.08}, 378 nm for Ni{sub 63.5}Zr{sub 36.5} and 375 nm for Ni{sub 87.7}P{sub 12.3}. No blisters, bubbles or pitting were observed on the samples when they were annealed up to their crystallization temperature. Some of the helium-3 trapped in amorphous metals seems not to be as strongly bound as in single crystal nickel. More helium-3 release was observed for the metal-metal amorphous metal samples than the metal-metalloid amorphous metal. For metal-metal amorphous alloy the helium-3 release behavior can be correlated with the partial or full crystallization. For metal-metalloid amorphous alloys this correlation may depend on the chemical composition.

  10. Graphene as a transparent electrode for amorphous silicon-based solar cells

    SciTech Connect

    Vaianella, F. Rosolen, G.; Maes, B.

    2015-06-28

    The properties of graphene in terms of transparency and conductivity make it an ideal candidate to replace indium tin oxide (ITO) in a transparent conducting electrode. However, graphene is not always as good as ITO for some applications, due to a non-negligible absorption. For amorphous silicon photovoltaics, we have identified a useful case with a graphene-silica front electrode that improves upon ITO. For both electrode technologies, we simulate the weighted absorption in the active layer of planar amorphous silicon-based solar cells with a silver back-reflector. The graphene device shows a significantly increased absorbance compared to ITO-based cells for a large range of silicon thicknesses (34.4% versus 30.9% for a 300 nm thick silicon layer), and this result persists over a wide range of incidence angles.

  11. Large Barkhausen discontinuities in Co-based amorphous wires with negative magnetostriction

    SciTech Connect

    Yamasaki, J.; Humphrey, F.B.; Mohri, K.; Kawamura, H.; Takamure, H.; Maelmhaell, R.

    1988-04-15

    Magnetic properties, such as domain patterns and anisotropy, were measured for negative magnetostrictive Co-Si-B amorphous wires exhibiting large Barkhausen discontinuities and the results are compared to those of Fe-Si-B wires with positive magnetostriction. The Co-based wire was found to have a bamboolike domain structure at the wire surface. It was also shown that the amorphous wires prepared by the in-water quenching technique store tensile stress in the radial direction. The magnetostrictive anisotropy due to residual stress will produce an axial component of magnetization in conjunction with the two-dimensional geometry of wires making both Co- and Fe-based wires exhibit large Barkhausen discontinuities along the axis of the wire.

  12. Thermal and structural stability of cosputtered amorphous Ta(x)Cu(1-x) alloy thin films on GaAs

    NASA Technical Reports Server (NTRS)

    Oh, J. E.; Woolam, J. A.; Aylesworth, K. D.; Sellmyer, D. J.; Pouch, J. J.

    1986-01-01

    The characteristics of thin films of Ta-Cu, prepared over a wide range of compositions by cosputter deposition onto GaAs and fused quartz substrates, are studied by X-ray diffraction and van der Pauw resistivity measurement. Results show films to be amorphous over the range of 55-95 at. pct, and show Ta(93)Cu(7) barriers to be effective in preventing Au in-diffusion, with a 3000-A layer remaining unpenetrated after an annealing at 700 C for 20 min. Diffusion of Ga and/or As into amorphous 93 at. pct Ta is found to be more rapid than that of Au, and interfacial reactions were shown to form compounds including Ta3Au, CuAu, TaAs2, and Ga3Cu7 above 700 C.

  13. Wear Resistant Amorphous and Nanocomposite Steel Coatings

    SciTech Connect

    Branagan, Daniel James; Swank, William David; Haggard, Delon C; Fincke, James Russell; Sordelet, D.

    2001-10-01

    In this article, amorphous and nanocomposite thermally deposited steel coatings have been formed by using both plasma and high-velocity oxy-fuel (HVOF) spraying techniques. This was accomplished by developing a specialized iron-based composition with a low critical cooling rate (?104 K/s) for metallic glass formation, processing the alloy by inert gas atomization to form micron-sized amorphous spherical powders, and then spraying the classified powder to form coatings. A primarily amorphous structure was formed in the as-sprayed coatings, independent of coating thickness. After a heat treatment above the crystallization temperature (568°C), the structure of the coatings self-assembled (i.e., devitrified) into a multiphase nanocomposite microstructure with 75 to 125 nm grains containing a distribution of 20 nm second-phase grain-boundary precipitates. Vickers microhardness testing revealed that the amorphous coatings were very hard (10.2 to 10.7 GPa), with further increases in hardness after devitrification (11.4 to 12.8 GPa). The wear characteristics of the amorphous and nanocomposite coatings were determined using both two-body pin-on-disk and three-body rubber wheel wet-slurry sand tests. The results indicate that the amorphous and nanocomposite steel coatings are candidates for a wide variety of wear-resistant applications.

  14. Synthesis and thermal behavior of tin-based alloy (Sn-Ag-Cu) nanoparticles

    NASA Astrophysics Data System (ADS)

    Roshanghias, Ali; Yakymovych, Andriy; Bernardi, Johannes; Ipser, Herbert

    2015-03-01

    The prominent melting point depression of nanoparticles has been the subject of a considerable amount of research. For their promising applications in electronics, tin-based nano-alloys such as near-eutectic Sn-Ag-Cu (SAC) alloys have been synthesized via various techniques. However, due to issues such as particle aggregation and oxidation or introduced impurities, the application of these nano-size particles has been confined or aborted. For instance, thermal investigations by DTA/DSC in a large number of studies revealed exothermic peaks in the range of 240-500 °C, i.e. above the melting point of SAC nanoparticles, with different and quite controversial explanations for this unclear phenomenon. This represents a considerable drawback for the application of nanoparticles. Correspondingly, in the current study, the thermal stability of SAC nanoparticles has been investigated via electron microscopy, XRD, FTIR, and DSC/TG analysis. It was found that the nanoparticles consist mainly of a metallic β-Sn core and an amorphous tin hydroxide shell structure. The SnO crystalline phase formation from this amorphous shell has been associated with the exothermic peaks on the first heating cycle of the nanoparticles, followed by a disproportionation reaction into metallic Sn and SnO2.The results also revealed that the surfactant and reducing agent cannot only affect the size and size distribution of the nanoparticles, they might also alter the ratio between the amorphous shell and the crystalline core in the structure of particles.The prominent melting point depression of nanoparticles has been the subject of a considerable amount of research. For their promising applications in electronics, tin-based nano-alloys such as near-eutectic Sn-Ag-Cu (SAC) alloys have been synthesized via various techniques. However, due to issues such as particle aggregation and oxidation or introduced impurities, the application of these nano-size particles has been confined or aborted. For

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

    NASA Astrophysics Data System (ADS)

    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.

  16. Narrow band gap amorphous silicon semiconductors

    DOEpatents

    Madan, A.; Mahan, A.H.

    1985-01-10

    Disclosed is a narrow band gap amorphous silicon semiconductor comprising an alloy of amorphous silicon and a band gap narrowing element selected from the group consisting of Sn, Ge, and Pb, with an electron donor dopant selected from the group consisting of P, As, Sb, Bi and N. The process for producing the narrow band gap amorphous silicon semiconductor comprises the steps of forming an alloy comprising amorphous silicon and at least one of the aforesaid band gap narrowing elements in amount sufficient to narrow the band gap of the silicon semiconductor alloy below that of amorphous silicon, and also utilizing sufficient amounts of the aforesaid electron donor dopant to maintain the amorphous silicon alloy as an n-type semiconductor.

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

    NASA Astrophysics Data System (ADS)

    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.

  18. On the cytocompatibility of biodegradable Fe-based alloys.

    PubMed

    Schinhammer, Michael; Gerber, Isabel; Hänzi, Anja C; Uggowitzer, Peter J

    2013-03-01

    Biodegradable iron-based alloys are potential candidates for application as temporary implant material. This study summarizes the design strategy applied in the development of biodegradable Fe-Mn-C-Pd alloys and describes the key factors which make them suitable for medical applications. The study's in vitro cytotoxicity tests using human umbilical vein endothelial cells revealed acceptable cytocompatibility based on the alloys' eluates. An analysis of the eluates revealed that Fe is predominantly bound in insoluble degradation products, whereas a considerable amount of Mn is in solution. The investigation's results are discussed using dose-response curves for the main alloying elements Fe and Mn. They show that it is mainly Mn which limits the cytocompatibility of the alloys. The study also supplies a summary of the alloying elements' influence on metabolic processes. The results and discussion presented are considered important and instructive for future alloy development. The Fe-based alloys developed show an advantageous combination of microstructural, mechanical and biological properties, which makes them interesting as degradable implant material.

  19. Tantalum modified ferritic iron base alloys

    NASA Technical Reports Server (NTRS)

    Oldrieve, R. E.; Blankenship, C. P. (Inventor)

    1977-01-01

    Strong ferritic alloys of the Fe-CR-Al type containing 0.4% to 2% tantalum were developed. These alloys have improved fabricability without sacrificing high temperature strength and oxidation resistance in the 800 C (1475 F) to 1040 C (1900 F) range.

  20. Application of amorphous carbon based materials as antireflective coatings on crystalline silicon solar cells

    NASA Astrophysics Data System (ADS)

    da Silva, D. S.; Côrtes, A. D. S.; Oliveira, M. H.; Motta, E. F.; Viana, G. A.; Mei, P. R.; Marques, F. C.

    2011-08-01

    We report on the investigation of the potential application of different forms of amorphous carbon (a-C and a-C:H) as an antireflective coating for crystalline silicon solar cells. Polymeric-like carbon (PLC) and hydrogenated diamond-like carbon films were deposited by plasma enhanced chemical vapor deposition. Tetrahedral amorphous carbon (ta-C) was deposited by the filtered cathodic vacuum arc technique. Those three different amorphous carbon structures were individually applied as single antireflective coatings on conventional (polished and texturized) p-n junction crystalline silicon solar cells. Due to their optical properties, good results were also obtained for double-layer antireflective coatings based on PLC or ta-C films combined with different materials. The results are compared with a conventional tin dioxide (SnO2) single-layer antireflective coating and zinc sulfide/magnesium fluoride (ZnS/MgF2) double-layer antireflective coatings. An increase of 23.7% in the short-circuit current density, Jsc, was obtained using PLC as an antireflective coating and 31.7% was achieved using a double-layer of PLC with a layer of magnesium fluoride (MgF2). An additional increase of 10.8% was obtained in texturized silicon, representing a total increase (texturization + double-layer) of about 40% in the short-circuit current density. The potential use of these materials are critically addressed considering their refractive index, optical bandgap, absorption coefficient, hardness, chemical inertness, and mechanical stability.

  1. Irradiation-induced disordering and amorphization of Al3Ti-based intermetallic compounds

    NASA Astrophysics Data System (ADS)

    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.

  2. Surface energy driven crystallization of amorphous Ni{sub 69}Cr{sub 14}P{sub 17} alloy

    SciTech Connect

    Schumacher, G.; Wanderka, N.; Wahi, R.P.

    1994-11-01

    Amorphous Ni{sub 69}Cr{sub l4}P{sub l7} specimens thinned for transmission electron microscopy have been studied in situ during thermal treatment. In the thinnest regions of the specimens (thickness d < 50 nm), a metastable hexagonal (Ni,Cr){sub 3}P phase nucleates at the perforation edge with the c-axis perpendicular to the specimen surface. The crystal width of this phase grows linearly with time. Above 530{degrees}C the hexagonal phase transforms into a stable b.c.t. (Ni,Cr){sub 3}P phase. It is concluded that the surface and grain boundary energies dominate nucleation and growth.

  3. Annealing characteristics of amorphous silicon alloy solar cells irradiated with 1.00 MeV protons

    NASA Technical Reports Server (NTRS)

    Abdulaziz, Salman S.; Woodyard, James R.

    1991-01-01

    Amorphous Si:H and amorphous Si sub x, Ge sub (1-x):H solar cells were irradiated with 1.00 MeV proton fluences in the range of 1.00E14 to 1.25E15 cm (exp -2). Annealing of the short circuit current density was studied at 0, 22, 50, 100, and 150 C. Annealing times ranged from an hour to several days. The measurements confirmed that annealing occurs at 0 C and the initial characteristics of the cells are restored by annealing at 200 C. The rate of annealing does not appear to follow a simple nth order reaction rate model. Calculations of the short-circuit current density using quantum efficiency measurements and the standard AM1.5 global spectrum compare favorably with measured values. It is proposed that the degradation in J sub sc with irradiation is due to carrier recombination through the fraction of D (o) states bounded by the quasi-Fermi energies. The time dependence of the rate of annealing of J sub sc does appear to be consistent with the interpretation that there is a thermally activated dispersive transport mechanism which leads to the passivation of the irradiation induced defects.

  4. The corrosion behavior and microstructure of high-velocity oxy-fuel sprayed nickel-base amorphous/nanocrystalline coatings

    NASA Astrophysics Data System (ADS)

    Dent, A. H.; Horlock, A. J.; McCartney, D. G.; Harris, S. J.

    1999-09-01

    The corrosion characteristics of two Ni-Cr-Mo-B alloy powders sprayed by the high-velocity oxy-fuel (HVOF) process have been studied using potentiodynamic and potentiostatic corrosion analysis in 0.5 M H2SO4. The deposits were also microstructurally characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM) (utilizing both secondary electron and backscattered electron modes), and transmission electron microscopy (TEM). Results from the microstructural examination of the two alloys have revealed a predominantly amorphous/nanocrystalline face centered cubic (fcc) matrix containing submicron boride precipitates as well as regions of martensitically transformed laths. Apparent recrystallization of the amorphous matrix has also been observed in the form of cellular crystals with a fcc structure. The oxide stringers observed at splat boundaries were found to be columnar grained α-Cr2O3, though regions of the spinel oxide NiCr2O4 with a globular morphology were also observed. The coatings of the two alloys exhibited comparable resistance to corrosion in 0.5 M H2SO4, as revealed by potentiodynamic tests. They both had rest potentials approximately equal to -300 mV saturated calomel electrode (SCE) and passive region current densities of ˜1 mA/cm2. Microstructural examination of samples tested potentiostatically revealed the prevalence of degradation at splat boundaries, especially those where significant oxidation of the deposit occurred.

  5. Influence of the chemical composition of rapidly quenched amorphous alloys (Ni, Fe, Cr)-B-Si on its crystallization process

    NASA Astrophysics Data System (ADS)

    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.

  6. Ab initio modeling of decomposition in iron based alloys

    NASA Astrophysics Data System (ADS)

    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.

  7. Cr{sub 2}Nb-based alloy development

    SciTech Connect

    Liu, C.T.; Tortorelli, P.F.; Horton, J.A.

    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.

  8. Evaluation of soldered connectors of two base metal ceramic alloys.

    PubMed

    Lima Verde, M A; Stein, R S

    1994-04-01

    Soldered connectors for two base metal ceramic alloys (nickel-chromium and cobalt-chromium) were compared by use of four different techniques: (1) infrared preceramic soldering, (2) gas and oxygen preceramic soldering, (3) porcelain furnace postsoldering under vacuum, and (4) porcelain furnace postsoldering without vacuum. A control group was established with solid cast specimens of each alloy. No statistically significant difference was noted between infrared and torch preceramic soldering techniques for either of the two alloys. However, the joints postsoldered under vacuum were significantly superior to postsoldered connectors without vacuum (p < 0.0001). No significant differences were observed among techniques 1, 2, and 3, although the three groups were substantially superior to technique 4 for both alloys (p = 0.05). The control group for both alloys was appreciably stronger than the soldered groups (p < 0.0001), and the nickel-chromium samples within the control group were significantly stronger than the Co-Cr samples.

  9. Atomic packing and diffusion in Fe{sub 85}Si{sub 2}B{sub 9}P{sub 4} amorphous alloy analyzed by ab initio molecular dynamics simulation

    SciTech Connect

    Wang, Yaocen; Takeuchi, Akira; Makino, Akihiro; Liang, Yunye; Kawazoe, Yoshiyuki

    2015-05-07

    In the work reported in this paper, ab initio molecular dynamics simulation was performed on Fe{sub 85}Si{sub 2}B{sub 9}P{sub 4} amorphous alloy. Preferred atomic environment of the elements was analyzed with Voronoi polyhedrons. It showed that B and P atoms prefer less neighbors compared with Fe and Si, making them structurally incompatible with Fe rich structure and repulsive to the formation of α-Fe. However, due to the low bonding energy of B and P caused by low coordination number, the diffusion rates of them were considerably large, resulting in the requirement of fast annealing for achieving optimum nano-crystallization for its soft magnetic property. The simulation work also indicates that diffusion rate in amorphous alloy is largely determined by bonding energy rather than atomic size.

  10. Films of Soft-Magnetic Fe-Based Nanocrystalline Alloys for High-Density Magnetic Storage Application

    NASA Astrophysics Data System (ADS)

    Shefteľ, E. N.; Bannykh, O. A.

    This paper presents a review of works related to the problem of development of soft-magnetic film Fe-based alloys exhibiting the combination of properties, such as the high saturation inductance, high level of soft-magnetic parameters over a wide range of MHz-frequencies, high wear-resistance and thermal stability, and an ability to be prepared by thin-film technologies. Magnetic cores of high-density recording heads are the principal application of these materials. Physical fundamentals of explanation of ferromagnetic behavior of a material with nano-sized structure, which have been developed for FINEMETs (Fe-Nb-Cu-Si-B) with the mixed amorphous + nanocrystalline structure, are considered. A new class of alloys Fe-Me-X (Me=Metal of III-V groups of the Periodic Table and X=C, N, O, and B) whose properties are higher that those of FINEMETs are discussed. The structure of these alloys consists of two nanocrystalline phases, such as the ferromagnetic α-Fe-based and nonmagnetic MeX phases. This structure provides the dispersion strengthening of the alloys. Metal science approaches to the selection of both chemical compositions and conditions of structure formation for these film alloys have been developed by authors and are discussed in this article.

  11. Rapidly Solidified Oxidation Resistant Niobium Base Alloys

    DTIC Science & Technology

    1992-03-01

    107 Figure 4.25 Graph showing the weight change / area versus time for Nb-Ti alioys, commercial Nb alloys and Rene ’ 41 during the 800’C...properties with better oxidation resistance than Nb alloys ............................. J09 Figure 4.29 Cross sectional optical micrographs of Rene ’ 41 ...186 Figure 5.58 Optical cross sectional micrographs of etched Rene ’ 41 after 760*C cyclic oxidation and hardness testing. A

  12. Atomic structure of amorphous Mg40Cu35Ti25 alloy: An ab initio molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Durandurdu, Murat

    2013-01-01

    Ab initio molecular dynamics simulations are carried out to model amorphous Mg40Cu35Ti25 and its local structural packing are investigated using a variety of analyzing techniques. Cu-atoms commonly form 12 fold coordinated clusters and some of which are perfect or defective types icosahedrons, implying an icosohedral short range order around Cu atoms. Mg and Ti atoms, on the other hand, favor to structure in higher coordinated polyhedrons. The coordination number of Ti atoms is slightly less than Mg atoms. The immiscibility effect between Ti and Mg is reflected by a low fraction of Mg-Ti bonding in the model. The atomic packing of Mg40Cu35Ti25 appears to be noticeably different from that of Mg-Cu-X (X=Y and Gd) metallic glasses even though all these materials exhibit primarily the same type of bonding natures.

  13. Formation of amorphous materials

    DOEpatents

    Johnson, William L.; Schwarz, Ricardo B.

    1986-01-01

    Metastable amorphous or fine crystalline materials are formed by solid state reactions by diffusion of a metallic component into a solid compound or by diffusion of a gas into an intermetallic compound. The invention can be practiced on layers of metals deposited on an amorphous substrate or by intermixing powders with nucleating seed granules. All that is required is that the diffusion of the first component into the second component be much faster than the self-diffusion of the first component. The method is practiced at a temperature below the temperature at which the amorphous phase transforms into one or more crystalline phases and near or below the temperature at which the ratio of the rate of diffusion of the first component to the rate of self-diffusion is at least 10.sup.4. This anomalous diffusion criteria is found in many binary, tertiary and higher ordered systems of alloys and appears to be found in all alloy systems that form amorphous materials by rapid quenching. The method of the invention can totally convert much larger dimensional materials to amorphous materials in practical periods of several hours or less.

  14. Omni-directional selective shielding material based on amorphous glass coated microwires

    NASA Astrophysics Data System (ADS)

    Ababei, G.; Chiriac, H.; David, V.; Dafinescu, V.; Nica, I.

    2012-01-01

    The shielding effectiveness of the omni-directional selective shielding material based on CoFe-glass coated amorphous wires in 0.8 GHz-3 GHz microwave frequency range is investigated. The measurements were done in a controlled medium using a TEM cell and in the free space using horn antennas, respectively. Experimental results indicate that the composite shielding material can be developed with desired shielding effectiveness and selective absorption of the microwave frequency range by controlling the number of the layers and the length of microwires.

  15. Conditions for a carrier multiplication in amorphous-selenium based photodetector

    SciTech Connect

    Masuzawa, Tomoaki; Kuniyoshi, Shingo; Onishi, Masanori; Kato, Richika; Saito, Ichitaro; Okano, Ken; Yamada, Takatoshi; Koh, Angel T. T.; Chua, Daniel H. C.; Shimosawa, Tatsuo

    2013-02-18

    Amorphous selenium is a promising candidate for high sensitivity photodetector due to its unique carrier multiplication phenomenon. More than 10 carriers can be generated per incident photon, which leads to high photo-conversion efficiency of 1000% that allows real-time imaging in dark ambient. However, application of this effect has been limited to specific devices due to the lack in material characterization. In this article, mechanism of carrier multiplication has been clarified using time-of-flight secondary ion mass spectroscopy and Raman spectroscopy. A prototype photodetector achieved photo conversion efficiency of 4000%, which explains the signal enhancement mechanism in a-Se based photodetector.

  16. Exploratory Investigation of Advanced-Temperature Nickel-Base Alloys

    NASA Technical Reports Server (NTRS)

    Freche, John C.; Waters, William J.

    1959-01-01

    An investigation was conducted to provide an advanced-temperature nickel-base alloy with properties suitable for aircraft turbine blades as well as for possible space vehicle applications. An entire series of alloys that do not require vacuum melting techniques and that generally provide good stress-rupture and impact properties was evolved. The basic-alloy composition of 79 percent nickel, 8 percent molybdenum, 6 percent chromium, 6 percent aluminum, and 1 percent zirconium was modified by a series of element additions such as carbon, titanium, and boron, with the nickel content adjusted to account for the additives. Stress-rupture, impact, and swage tests were made with all the alloys. The strongest composition (basic alloy plus 1.5 percent titanium plus 0.125 percent carbon) displayed 384- and 574-hour stress-rupture lives at 1800 F and 15,000 psi in the as-cast and homogenized conditions, respectively. All the alloys investigated demonstrated good impact resistance. Several could not be broken in a low-capacity Izod impact tester and, on this basis, all compared favorably with several high-strength high-temperature alloys. Swaging cracks were encountered with all the alloys. In several cases, however, these cracks were slight and could be detected only by zyglo examination. Some of these compositions may become amenable to hot working on further development. On the basis of the properties indicated, it appears that several of the alloys evolved, particularly the 1.5 percent titanium plus 0.125 percent carbon basic-alloy modification, could be used for advanced- temperature turbine blades, as well as for possible space vehicle applications.

  17. Corrosion evaluation of gold-based dental alloys.

    PubMed

    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.

  18. Microstructures and oxidation behavior of some Molybdenum based alloys

    SciTech Connect

    Ray, Pratik Kumar

    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.

  19. Glass forming range of the Ti-Fe-Si amorphous alloys: An effective materials-design approach coupling CALPHAD and topological instability criterion

    NASA Astrophysics Data System (ADS)

    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.

  20. Super-cooled and amorphous lipid-based colloidal dispersions for the delivery of phytosterols.

    PubMed

    Ribeiro, H S; Gupta, R; Smith, K W; van Malssen, K F; Popp, A K; Velikov, K P

    2016-07-06

    Super-cooled and amorphous lipid-based colloids are highly desirable delivery systems because of their ability to encapsulate compounds in a soluble or in a non-crystalline state. In this study, we demonstrate the preparation and characterization of super-cooled and amorphous lipid-based nanoscale colloidal dispersions containing high concentrations of phytosterols (PSs). PSs are highly hydrophobic natural bioactive compounds that are known to significantly reduce blood cholesterol levels in humans, but are insoluble in water and are poorly soluble in common lipids such as triacylglycerols (TAGs). Using the ultrahigh pressure homogenization of pre-heated dispersions, followed by temperature quenching, colloidal dispersions with varying concentrations of PSs in the lipid phase are prepared. Long and medium chain TAGs in combination with a non-ionic surfactant are used. The particle size, morphology and stability are analysed by dynamic and static light scattering, electron microscopy, and X-ray diffraction. Rapid temperature quenching enables the formation of stable colloidal dispersions of 10 wt% PSs, more than five times the equilibrium solubility at room temperature. Super-cooled emulsions are formed using liquid TAG, whereas amorphous particles are formed in the case of solid TAG. In both cases, the complete suppression of the crystallization of both PSs and lipids is observed due to the nanoscale confinement. The colloidal dispersions are stable for at least four months. The insights of this work will help understand the colloid formation and particle morphology control in the development of delivery systems for hydrophobic bio-actives such as drugs, cosmeceuticals, nutraceuticals, nutritional and agricultural nanoscale formulations.

  1. Cladding burst behavior of Fe-based alloys under LOCA

    DOE PAGES

    Terrani, Kurt A.; Dryepondt, Sebastien N.; Pint, Bruce A.; ...

    2015-12-17

    Burst behavior of austenitic and ferritic Fe-based alloy tubes has been examined under a simulated large break loss of coolant accident. Specifically, type 304 stainless steel (304SS) and oxidation resistant FeCrAl tubes were studied alongside Zircaloy-2 and Zircaloy-4 that are considered reference fuel cladding materials. Following the burst test, characterization of the cladding materials was carried out to gain insights regarding the integral burst behavior. Given the widespread availability of a comprehensive set of thermo-mechanical data at elevated temperatures for 304SS, a modeling framework was implemented to simulate the various processes that affect burst behavior in this Fe-based alloy. Themore » most important conclusion is that cladding ballooning due to creep is negligible for Fe-based alloys. Thus, unlike Zr-based alloys, cladding cross-sectional area remains largely unchanged up to the point of burst. Furthermore, for a given rod internal pressure, the temperature onset of burst in Fe-based alloys appears to be simply a function of the alloy's ultimate tensile strength, particularly at high rod internal pressures.« less

  2. Cladding burst behavior of Fe-based alloys under LOCA

    SciTech Connect

    Terrani, Kurt A.; Dryepondt, Sebastien N.; Pint, Bruce A.; Massey, Caleb P.

    2015-12-17

    Burst behavior of austenitic and ferritic Fe-based alloy tubes has been examined under a simulated large break loss of coolant accident. Specifically, type 304 stainless steel (304SS) and oxidation resistant FeCrAl tubes were studied alongside Zircaloy-2 and Zircaloy-4 that are considered reference fuel cladding materials. Following the burst test, characterization of the cladding materials was carried out to gain insights regarding the integral burst behavior. Given the widespread availability of a comprehensive set of thermo-mechanical data at elevated temperatures for 304SS, a modeling framework was implemented to simulate the various processes that affect burst behavior in this Fe-based alloy. The most important conclusion is that cladding ballooning due to creep is negligible for Fe-based alloys. Thus, unlike Zr-based alloys, cladding cross-sectional area remains largely unchanged up to the point of burst. Furthermore, for a given rod internal pressure, the temperature onset of burst in Fe-based alloys appears to be simply a function of the alloy's ultimate tensile strength, particularly at high rod internal pressures.

  3. METHOD FOR ANNEALING AND ROLLING ZIRCONIUM-BASE ALLOYS

    DOEpatents

    Picklesimer, M.L.

    1959-07-14

    A fabrication procedure is presented for alpha-stabilized zirconium-base alloys, and in particular Zircaloy-2. The alloy is initially worked at a temperature outside the alpha-plus-beta range (810 to 970 deg ), held at a temperature above 970 deg C for 30 minutes and cooled rapidly. The alloy is then cold-worked to reduce the size at least 20% and annealed at a temperature from 700 to 810 deg C. This procedure serves both to prevent the formation of stringers and to provide a randomly oriented crystal structure.

  4. Photosensor application of amorphous InZnO-based thin film transistor

    NASA Astrophysics Data System (ADS)

    Liu, Po-Tsun; Chou, Yi-Teh; Teng, Li-Feng

    2010-03-01

    Thin film transistor (TFT) device structure with transparent conductive oxide semiconductor is proposed for the photosensor application. The adoption of TFT-based photosensor device also is promising to be integrated with pixel-array circuits in a flat panel display and realize the system-on-panel (SoP) concept. The photosensitive TFT device can be applied to sense the ambient light brightness and then give the feedback to the backlight system adjusting the backlight intensity for the power-saving green displays. In this work, we studied the photosensitivity of amorphous indium zinc oxide (a-IZO) TFT to ultraviolet light. The a-IZO-based semiconductors have been paid much attention due to their uniform amorphous phase and high field-effect carrier mobility characteristics. The obvious threshold voltage shift was observed after light illumination, and exhibited slow recovery while returning to initial status after removing the light source. This mechanism for the photoreaction is well explained by the dynamic equilibrium of charge exchange reaction between O2(g) and O2- in the backchannel region of IZO-based films. An electrical trigger using charge pumping method is used to confirm the proposed mechanism and accelerate photoreaction recoverability for the first time. Using knowledge of photoreaction behavior, an operation scheme of photosensing elements consist of a-IZO TFTs is also demonstrated in this paper.

  5. Fabrication and characterization of monolithically integrated microchannel plates based on amorphous silicon.

    PubMed

    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.

  6. Fabrication and characterization of monolithically integrated microchannel plates based on amorphous silicon

    PubMed Central

    Franco, Andrea; Geissbühler, Jonas; Wyrsch, Nicolas; Ballif, Christophe

    2014-01-01

    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. PMID:24698955

  7. Far-Infrared and Raman Spectroscopy Investigation of Phonon Modes in Amorphous and Crystalline Epitaxial GeTe-Sb2Te3 Alloys

    NASA Astrophysics Data System (ADS)

    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.

  8. Electron cyclotron resonance deposition of amorphous silicon alloy films and devices. Final subcontract report, 1 April 1991--31 March 1992

    SciTech Connect

    Shing, Y.H.

    1992-10-01

    This report describes work to develop a state-of-the-art electron cyclotron resonance (ECR) plasma-enhanced chemical vapor deposition (PECVD) system. The objective was to understand the deposition processes of amorphous silicon (a-Si:H) and related alloys, with a best-effort improvement of optoelectronic material properties and best-effort stabilization of solar cell performance. ECR growth parameters were systematically and extensively investigated; materials characterization included constant photocurrent measurement (CPM), junction capacitance, drive-level capacitance profiling (DLCP), optical transmission, light and dark photoconductivity, and small-angle X-ray scattering (SAXS). Conventional ECR-deposited a-Si:H was compared to a new form, a-Si:(Xe, H), in which xenon gas was added to the ECR plasma. a-Si:(Xe,H) possessed low, stable dark conductivities and high photosensitivites. Light-soaking revealed photodegradation rates about 35% lower than those of comparable radio frequency (rf)-deposited material. ECR-deposited p-type a SiC:H and intrinsic a-Si:H films underwent evaluation as components of p-i-n solar cells with standard rf films for the remaining layers.

  9. Thin-film amorphous silicon alloy research partnership. Phase 2, Annual technical progress report, 2 February 1996--1 February 1997

    SciTech Connect

    Guha, S

    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.

  10. Urchin-Like Amorphous Ni2B Alloys: Efficient Antibacterial Materials and Catalysts for Hydrous Hydrazine Decomposition to Produce H2.

    PubMed

    Deng, Miao; Fu, Shi Yan; Yang, Fan; Wu, Ping; Tong, Dong Ge

    2016-03-01

    Urchin-like amorphous Ni2B alloys were successfully prepared for the first time from a mixture of Ni(NH3)6(2+) and polyvinyl alcohol (PVA) via a solution plasma process (SPP). The as-synthesized samples were characterized by X-ray powder diffraction (XRD), inductively coupled plasma atomic emission spectrometry (ICP-AES) X-ray photoelectron spectroscopy (XPS), scanning transmission electron microscopy (STEM), selected-area electron diffraction patterns (SAED) and nitrogen adsorption-desorption isotherms. In the performance test, the obtained Ni-B urchins showed great antibacterial activities, comparable with those of amikacin and kanamycin, especially towards Pseudomonas aeruginosa (P. aeruginosa). Meanwhile, the magnetic properties of Ni-B urchins are enhanced in comparison with those of conventional Ni-B. During hydrous hydrazine (N2H4) decomposition, the dehydrogenation performance of Ni-B urchins is superior to those of Raney Ni and conventional Ni-B. The enhanced catalytic performance of Ni-B urchins is attributed to their high surface area of active species nickel and the enhanced intrinsic activity resulting from their unique structure.

  11. Far-Infrared and Raman Spectroscopy Investigation of Phonon Modes in Amorphous and Crystalline Epitaxial GeTe-Sb2Te3 Alloys

    PubMed Central

    Bragaglia, V.; Holldack, K.; Boschker, J. E.; Arciprete, F.; Zallo, E.; Flissikowski, T.; Calarco, R.

    2016-01-01

    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. PMID:27340085

  12. Hydrogen transport in nickel-base alloys

    NASA Astrophysics Data System (ADS)

    Turnbull, A.; Ballinger, R. G.; Hwang, I. S.; Morra, M. M.; Psaila-Dombrowski, M.; Gates, R. M.

    1992-12-01

    The electrochemical permeation technique has been used to characterize hydrogen transport and trapping in pure nickel and in alloys 600, X-750, and 718 at a temperature of 80 °C. The “effective diffusivity ” of hydrogen atoms in alloy 600 is reduced by a factor of about 5 compared to pure nickel. This is attributed to both compositional changes and the presence of [(Ti, Nb)C] carbides. Aging of alloy 600, with subsequent M23C6 carbide precipitation, does not significantly influence the measured “effective diffusivity,” which is explained by the dominant effect of preexisting [(Ti, Nb)C] carbides. The “effective diffusivity” of hydrogen atoms in solution-annealed alloy X-750 is reduced by a factor of about 9 compared to that of pure nickel. This is also attributed to compositional changes and [(Ti,Nb)C] carbides. Aging of alloy X-750, which causes precipitation of γ'[Ni3(Al, Ti)], reduces the “effective diffusivity” by an additional factor of 5 or more. Double aging at 885 °C/24 hours, 704 °C/20 hours following hot working yields the greatest reduction in “effective diffusivity.” Analysis of permeation transients using a diffusion- trapping model indicates a binding energy associated with trapping due to the γ phase of be- tween -31 and -37 kJ/mol. The “effective diffusivity” of hydrogen in alloy 718 is about 40 pct greater than for alloy X-750 for the same double and direct aging treatments. The average “effective diffusivities” of the double-aged and direct-aged alloy 718 are comparable, but the permeation transients for the double-aged treatment are significantly steeper. The double-aged treatment with predominantly δ phase (orthorhombic Ni3Nb) yields a binding energy of about -30 kJ/mol. Analysis of the direct aged-treated 718, which contains predominantly γ″ phase (body-centered tetragonal Ni3Nb) gave a binding energy between -23 and -27 kJ/mol. Seg- regation of hydrogen atoms to the γ matrix interface, combined with a

  13. Damping capacity of TiNi-based shape memory alloys

    NASA Astrophysics Data System (ADS)

    Rong, L. J.; Jiang, H. C.; Liu, S. W.; Zhao, X. Q.

    2007-07-01

    Damping capacity is another primary characteristic of shape memory alloys (SMA) besides shape memory effect and superelasticity. Damping behavior of Ti-riched TiNi SMA, porous TiNi SMA and a novel TiNi/AlSi composite have been investigated using dynamic mechanical analyzer (DMA) in this investigation. All these alloys are in martensitic state at room temperature and thus possess the high potential application value. Ti 50.2Ni 49.8 SMA has better damping capacity in pure martensitic state and phase transformation region due to the motion of martensite twin interface. As a kind of promising material for effective dampers and shock absorbing devices, porous TiNi SMA can exhibit higher damping capacity than the dense one due to the existence of the three-dimensioned connecting pore structure. It is found that the internal friction of porous TiNi SMA mainly originates from microplastic deformation and mobility of martensite interface and increases with the increase of the porosity. A novel TiNi/AlSi composite has been developed successfully by infiltrating AlSi alloy into the open pores of porous TiNi alloy with 60% porosity through compression casting. It shows the same phase transformation characteristics as the porous TiNi alloy. The damping capacity of the composite has been increased and the compressive strength has been also promoted remarkably. Suggestions for developing higher damping alloys based on TiNi shape memory alloy are proposed in this paper.

  14. Investigation of surface finishing of carbon based coated tools for dry deep drawing of aluminium alloys

    NASA Astrophysics Data System (ADS)

    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.

  15. Amorphous thieno[3,2-b]thiophene and benzothiadiazole based copolymers for organic photovoltaics.

    PubMed

    Lee, Wonho; Cha, Hyojung; Kim, Yu Jin; Jeong, Ji-Eun; Hwang, Sungu; Park, Chan Eon; Woo, Han Young

    2014-11-26

    Three types of amorphous thienothiophene (TT)-benzothiadiazole (BT) based copolymers (PFTTBT) were synthesized by incorporating alkyl-substituted fluorene moieties as a third component in the polymer backbone. Their optical, electrochemical, morphological, and photovoltaic properties were examined by a comparison with those of a crystalline TT-BT derivative (PTTBT14). PTTBT14 was reported to have a high hole mobility (0.26 cm(2)/(V s)) due to the pronounced interchain ordering but poor photovoltaic power conversion efficiency (PCE) of 2.4-2.6% was reported due to excessively strong self-interactions with poor miscibility with fullerene structures. By incorporating fluorene units, the UV-vis spectra showed an increased bandgap (∼1.9 eV) with the disappearance of the packing-originated shoulder peak, and the valence band decreased compared to crystalline PTTBT14. The amorphous PFTTBT polymers showed substantially improved photovoltaic properties compared to PTTBT14, even though they showed poor hole mobility (∼10(-6) cm2/(V s)) and fill factor. The optimal devices were achieved by blending with excess PC71BM (polymer:PC71BM=1:4 by weight), showing little improvement in the thermal and additive treatments. Under simulated solar illumination of AM 1.5 G, the best PCE of 6.6% was achieved for a PFehTTBT:PC71BM device with an open-circuit voltage of 0.92 V, a short-circuit current of 15.1 mA/cm2, and a fill factor of 0.48. These results suggest that it is useful to disrupt partially the interchain organizations of excessively crystalline polymers, enabling fine-control of intermolecular ordering and the morphological properties (i.e., miscibility with fullerene derivatives, etc.) to utilize the advantages of both crystalline and amorphous materials for further improving PCE of polymer solar cells.

  16. Fe-based long range ordered alloys

    DOEpatents

    Liu, C.T.

    Malleable long range ordered alloys with high critical ordering temperatures exist in the V(Co,Fe)/sub 3/ and V(Co,Fe,Ni)/sub 3/ system. The composition comprising by weight 22 to 23% V, 35 to 50% Fe, 0 to 22% Co and 19 to 40% Ni with an electron density no greater than 8.00. Excellent high temperature properties occur in alloys having compositions comprising by weight 22 to 23% V, 35 to 45% Fe, 0 to 10% Co, 25 to 35% Ni; 22 to 23% V, 28 to 33% Ni and the remainder Fe; and 22 to 23% V, 19 to 22% Co and the remainder Fe. The alloys are fabricable by casting, deforming and annealing for sufficient time to provide ordered structure.

  17. Fe-based long range ordered alloys

    DOEpatents

    Liu, Chain T; Inouye, Henry; Schaffhauser, Anthony C.

    1980-01-01

    Malleable long range ordered alloys having high critical ordering temperatures exist in the V(Co,Fe).sub.3 and V(Co,Fe,Ni).sub.3 system having the composition comprising by weight 22-23% V, 35-50% Fe, 0-22% Co and 19-40% Ni with an electron density no greater than 8.00. Excellent high temperature properties occur in alloys having compositions comprising by weight 22-23% V, 35-45% Fe, 0-10% Co, 25-35% Ni; 22-23% V, 28-33% Ni and the remainder Fe; and 22-23% V, 19-22% Ni, 19-22% Co and the remainder Fe. The alloys are fabricable by casting, deforming and annealing for sufficient time to provide ordered structure.

  18. Directionally solidified iron-base eutectic alloys

    NASA Technical Reports Server (NTRS)

    Tewari, S. N.

    1976-01-01

    Pseudobinary eutectic alloys with nominal compositions of Fe-25Ta-22Ni-10Cr and Fe-15.5Nb-14.5Ni-6.0Cr were directionally solidified at 0.5 centimeter per hour. Their microstructure consisted of the fcc, iron solid-solution, matrix phase reinforced by about 41-volume-percent, hcp, faceted Fe2Ta fibers and 41-volume-percent, hcp, Fe2Nb lamellae for the tantalum- and niobium-containing alloys, respectively. The microstructural stability under thermal cycling and the temperature dependence of tensile properties were investigated. These alloys showed low elevated-temperature strength and were not considered suitable for application in aircraft-gas-turbine blades although they may have applicability as vane materials.

  19. Fabrication of tungsten wire reinforced nickel-base alloy composites

    NASA Technical Reports Server (NTRS)

    Brentnall, W. D.; Toth, I. J.

    1974-01-01

    Fabrication methods for tungsten fiber reinforced nickel-base superalloy composites were investigated. Three matrix alloys in pre-alloyed powder or rolled sheet form were evaluated in terms of fabricability into composite monotape and multi-ply forms. The utility of monotapes for fabricating more complex shapes was demonstrated. Preliminary 1093C (2000F) stress rupture tests indicated that efficient utilization of fiber strength was achieved in composites fabricated by diffusion bonding processes. The fabrication of thermal fatigue specimens is also described.

  20. Fundamental studies of defect generation in amorphous silicon alloys grown by remote plasma-enhanced chemical-vapor deposition. Final subcontract report, 1 July 1989--31 December 1992

    SciTech Connect

    Lucovsky, G.

    1993-08-01

    This report describes research to reduce the intrinsic bonding defects in amorphous and microcrystalline Si alloys by controlling the bonding chemistry and the microstructure via the deposition process reactions. The specific approach was to use remote plasma-enhanced, chemical-vapor deposition (PECVD) and reactive magnetron sputtering to limit the multiplicity of deposition inaction pathways, and thereby gain increased control over the thin-film chemistry and microstrucre. The research included (1) the deposition of amorphous and microcrystalline Si alloy materials by the PECVD process and by reactive magnetron sputtering, and (2) the evaluation of the material properties of these films for potential applications in PV devices. The focus of the research was on pining a fundamental understanding of the relationships between deposition reaction pathways, the bonding of dopant and alloy atoms, and the electrical provides of importance for PV applications. This involved studying the factors that contribute to defect generation and to defect removal and/or neutralization. In addition to the experimental studies, the research also included theoretical and modeling studies aimed at understanding the relationships between local atomic arrangements of Si and alloy atoms, and the electrical, optical, vibrational, and defect properties.

  1. Crystallization Kinetics of Fe76.5-x C6.0Si3.3B5.5P8.7Cu x (x = 0, 0.5, and 1 at. pct) Bulk Amorphous Alloy

    NASA Astrophysics Data System (ADS)

    Jung, Hyo Yun; Stoica, Mihai; Yi, Seonghoon; Kim, Do Hyang; Eckert, Jürgen

    2014-08-01

    The influence of Cu on crystallization kinetics of Fe76.5-x C6.0Si3.3B5.5P8.7Cu x (x = 0, 0.5, and 1 at. pct) bulk amorphous alloys was investigated by isothermal and isochronal differential scanning calorimetry combined with X-ray diffraction. The thermal analysis revealed that the crystallization of the amorphous matrix proceeds through at least two exothermic events. The Cu-free glassy alloy forms by primary crystallization the metastable Fe23C6 phase, while upon 0.5 at. pct Cu addition the primary crystallized phase is α-Fe. The activation energy for crystallization, calculated using both Kissinger and Ozawa methods, decreases from about 500 kJ/mol to about 330 kJ/mol. Further increase of Cu addition to 1 at. pct promotes the concomitant crystallization of several phases, as α-Fe, FeB, Fe3C, and Fe2P. In order to understand the crystallization behavior of the alloys as a function of Cu content, the Avrami exponent n, evaluated from the Johnson-Mehl-Avrami equation, was in details analyzed. The current study reveals that the minor Cu addition plays a crucial role at the initial stage of the crystallization. Among the studied alloys, the glassy samples with 0.5 at. pct Cu addition have the optimum compositional condition for the single α-Fe formation with a high nucleation rate.

  2. Crystallization Kinetics of Fe76.5- x C6.0Si3.3B5.5P8.7Cu x ( x = 0, 0.5, and 1 at. pct) Bulk Amorphous Alloy

    NASA Astrophysics Data System (ADS)

    Jung, Hyo Yun; Stoica, Mihai; Yi, Seonghoon; Kim, Do Hyang; Eckert, Jürgen

    2015-06-01

    The influence of Cu on crystallization kinetics of Fe76.5- x C6.0Si3.3B5.5P8.7Cu x ( x = 0, 0.5, and 1 at. pct) bulk amorphous alloys was investigated by isothermal and isochronal differential scanning calorimetry combined with X-ray diffraction. The thermal analysis revealed that the crystallization of the amorphous matrix proceeds through at least two exothermic events. The Cu-free glassy alloy forms by primary crystallization the metastable Fe23C6 phase, while upon 0.5 at. pct Cu addition the primary crystallized phase is α-Fe. The activation energy for crystallization, calculated using both Kissinger and Ozawa methods, decreases from about 500 kJ/mol to about 330 kJ/mol. Further increase of Cu addition to 1 at. pct promotes the concomitant crystallization of several phases, as α-Fe, FeB, Fe3C, and Fe2P. In order to understand the crystallization behavior of the alloys as a function of Cu content, the Avrami exponent n, evaluated from the Johnson-Mehl-Avrami equation, was in details analyzed. The current study reveals that the minor Cu addition plays a crucial role at the initial stage of the crystallization. Among the studied alloys, the glassy samples with 0.5 at. pct Cu addition have the optimum compositional condition for the single α-Fe formation with a high nucleation rate.

  3. Amorphous Ni-B alloy nanoparticle film on Ni foam: rapid alternately dipping deposition for efficient overall water splitting

    NASA Astrophysics Data System (ADS)

    Liang, Yanhui; Sun, Xuping; Asiri, Abdullah M.; He, Yuquan

    2016-03-01

    It is highly attractive, but still remains challenging, to develop noble metal-free bifunctional electrocatalysts efficient for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline media. In this letter, we describe the rapid electroless deposition of amorphous Ni-B nanoparticle film on Ni foam (Ni-B/Ni foam) by alternative dipping of Ni foam into Ni precursor and reducing solutions. This Ni-B/Ni foam acts as an efficient and durable 3D catalytic electrode for water splitting, affording 100 mA cm-2 at 360 mV overpotential for the OER and 20 mA cm-2 at 125 mV overpotential for the HER in 1.0 M KOH, and its two-electrode electrolyzer demands a cell voltage of 1.69 V to afford 15 mA cm-2 water-splitting current. Moreover, the catalyst loading can be easily tuned and this alternately dipping deposition technique works universally for other conductive substrates.

  4. Bulk amorphous materials

    SciTech Connect

    Schwarz, R.B.; Archuleta, J.I.; Sickafus, K.E.

    1998-12-01

    This is the final report for a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The objective of this work was to develop the competency for the synthesis of novel bulk amorphous alloys. The authors researched their synthesis methods and alloy properties, including thermal stability, mechanical, and transport properties. The project also addressed the development of vanadium-spinel alloys for structural applications in hostile environments, the measurement of elastic constants and thermal expansion in single-crystal TiAl from 300 to 750 K, the measurement of elastic constants in gallium nitride, and a study of the shock-induced martensitic transformations in NiTi alloys.

  5. Improved Toughness Alloys Based on Titanium Aluminides

    DTIC Science & Technology

    1989-10-26

    2Sn-4Zr2Mo and creep rupture =to inconel 718). 6C AVIAGIE 20 -- ALLOYS Am VERAGE FOR to 400 O’)ALLOYS 20 x" T, 20kl- I Oft3V 1 46 T1. IF 110 kb 3V O0MQ...I~j 00 00 I 0 0 (A 30 ) C L 0 o ( 0(D D ( - r_ 00 . C-0. -n r- r- Cfr -H - CD 1- LO t Ne4) C) 00U’ L S..)~O 0c% 0~~ o~~r 𔃺 C,4 0 - - . o. I I - LAC. 0

  6. 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

    NASA Astrophysics Data System (ADS)

    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) and the processes of clustering (at 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.

  7. Magnetic and Electrical Characteristics of Cobalt-Based Amorphous Materials and Comparison to a Permalloy Type Polycrystalline Material

    NASA Technical Reports Server (NTRS)

    Wieserman, William R.; Schwarze, Gene E.; Niedra, Janis M.

    2005-01-01

    Magnetic component designers are always looking for improved soft magnetic core materials to increase the efficiency, temperature rating and power density of transformers, motors, generators and alternators, and energy density of inductors. In this paper, we report on the experimental investigation of commercially available cobalt-based amorphous alloys which, in their processing, were subjected to two different types of magnetic field anneals: A longitudinal magnetic field anneal or a transverse magnetic field anneal. The longitudinal field annealed material investigated was Metglas 2714A. The electrical and magnetic characteristics of this material were investigated over the frequency range of 1 to 200 kHz and temperature range of 23 to 150 C for both sine and square wave voltage excitation. The specific core loss was lower for the square than the sine wave voltage excitation for the same maximum flux density, frequency and temperature. The transverse magnetic field annealed core materials include Metglas 2714AF and Vacuumschmelze 6025F. These two materials were experimentally characterized over the frequency range of 10 to 200 kHz for sine wave voltage excitation and 23 C only. A comparison of the 2174A to 2714AF found that 2714AF always had lower specific core loss than 2714A for any given magnetic flux density and frequency and the ratio of specific core loss of 2714A to 2714AF was dependent on both magnetic flux density and frequency. A comparison was also made of the 2714A, 2714AF, and 6025F materials to two different tape thicknesses of the polycrystalline Supermalloy material and the results show that 2714AF and 6025F have the lowest specific core loss at 100 kHz over the magnetic flux density range of 0.1 to 0.4 Tesla.

  8. The development of lightweight hydride alloys based on magnesium

    SciTech Connect

    Guthrie, S.E.; Thomas, G.J.; Yang, N.Y.C.; Bauer, W.

    1996-02-01

    The development of a magnesium based hydride material is explored for use as a lightweight hydrogen storage medium. It is found that the vapor transport of magnesium during hydrogen uptake greatly influences the surface and hydride reactions in these alloys. This is exploited by purposely forming near-surface phases of Mg{sub 2}Ni on bulk Mg-Al-Zn alloys which result in improved hydrogen adsorption and desorption behavior. Conditions were found where these near-surface reactions yielded a complex and heterogeneous microstructure that coincided with excellent bulk hydride behavior. A Mg-Al alloy hydride is reported with near atmospheric plateau pressures at temperatures below 200{degrees}C. Additionally, a scheme is described for low temperature in-situ fabrication of Mg{sub 2}Ni single phase alloys utilizing the high vapor pressure of Mg.

  9. Ductile superconducting copper-base alloys.

    PubMed

    Tsuei, C C

    1973-04-06

    A new class of ductile superconductors has been prepared by casting and appropriate heat treatments. These alloys superconduct between 4 degrees and 18 degrees K and contain at least 90 atom percent copper and a superconducting phase such as Nb(3)Sn or niobium. They can be processed into wires by conventional metallurgical techniques.

  10. Visible-light-induced instability in amorphous metal-oxide based TFTs for transparent electronics

    SciTech Connect

    Ha, Tae-Jun

    2014-10-15

    We investigate the origin of visible-light-induced instability in amorphous metal-oxide based thin film transistors (oxide-TFTs) for transparent electronics by exploring the shift in threshold voltage (V{sub th}). A large hysteresis window in amorphous indium-gallium-zinc-oxide (a-IGZO) TFTs possessing large optical band-gap (≈3 eV) was observed in a visible-light illuminated condition whereas no hysteresis window was shown in a dark measuring condition. We also report the instability caused by photo irradiation and prolonged gate bias stress in oxide-TFTs. Larger V{sub th} shift was observed after photo-induced stress combined with a negative gate bias than the sum of that after only illumination stress and only negative gate bias stress. Such results can be explained by trapped charges at the interface of semiconductor/dielectric and/or in the gate dielectric which play a role in a screen effect on the electric field applied by gate voltage, for which we propose that the localized-states-assisted transitions by visible-light absorption can be responsible.

  11. Specific energy yield comparison between crystalline silicon and amorphous silicon based PV modules

    NASA Astrophysics Data System (ADS)

    Ferenczi, Toby; Stern, Omar; Hartung, Marianne; Mueggenburg, Eike; Lynass, Mark; Bernal, Eva; Mayer, Oliver; Zettl, Marcus

    2009-08-01

    As emerging thin-film PV technologies continue to penetrate the market and the number of utility scale installations substantially increase, detailed understanding of the performance of the various PV technologies becomes more important. An accurate database for each technology is essential for precise project planning, energy yield prediction and project financing. However recent publications showed that it is very difficult to get accurate and reliable performance data of theses technologies. This paper evaluates previously reported claims the amorphous silicon based PV modules have a higher annual energy yield compared to crystalline silicon modules relative to their rated performance. In order to acquire a detailed understanding of this effect, outdoor module tests were performed at GE Global Research Center in Munich. In this study we examine closely two of the five reported factors that contribute to enhanced energy yield of amorphous silicon modules. We find evidence to support each of these factors and evaluate their relative significance. We discuss aspects for improvement in how PV modules are sold and identify areas for further study further study.

  12. Amorphous metallic foam

    NASA Astrophysics Data System (ADS)

    Schroers, Jan; Veazey, Chris; Johnson, William L.

    2003-01-01

    The bulk glass forming alloy Pd43Ni10Cu27P20 is processed into a low-density amorphous metallic foam. Pd43Ni10Cu27P20 is mixed with hydrated B2O3, which releases gas at elevated temperature and/or low pressure. Very homogeneous foams are achieved due to the high viscosity of the alloy even at its liquidus temperature. By processing at the liquidus temperature and decreasing the pressure to 10-2 mbar, well-distributed bubbles expand to foam the material. Foam densities as low as 1.4×103 kg/m3 were obtained, corresponding to a bubble volume fraction of 84%. The bubble diameter ranges between 2×10-4 and 1×10-3 m. Thermal analysis by differential scanning calorimetry confirms the amorphous nature of the foam. Furthermore, it reveals that the foam's thermal stability is comparable to the bulk material.

  13. Origin of Magnetic Properties in Amorphous Metals.

    DTIC Science & Technology

    1979-12-01

    Magnetic Properties of Fe-Ni-B Amorphous Alloys," F. E. Luborsky, J. L. Walter, and H. H. Liebermann , IEEE Trans. on Magnetics MAG-15, 909 (1979). Also GE...Report 78CRD132. 2. "Formation and Magnetic Properties of Fe-B-Si Amorphous Alloys," F. E. Luborsky, J. J. Becker, J. L. Walter, and H. H. Liebermann ...Amorphous Alloys," F. E. Luborsky and H. H. Liebermann , J. Appl. Phys., to appear. Also GE Report 79CRD177. 4. "The Effect of Temperature on Magnetic

  14. Corrosion Resistances of Iron-Based Amorphous Metals with Yttrium and Tungsten Additions in Hot Calcium Chloride Brine & Natural Seawater: Fe48Mo14CR15Y2C15B6 and Variants

    SciTech Connect

    Farmer, J; Haslam, J; Day, S; Lian, T; Saw, C; Hailey, P; Choi, J; Yang, N; Blue, C; Peter, W; Payer, J; Perepezko, J; Hildal, K; Branagan, D J; Beardsley, M B; Aprigliano, L

    2006-10-12

    The passive film stability of several Fe-based amorphous metal formulations have been found to be comparable to that of stainless steels and Ni-based Alloy C-22 (UNS No. N06022), based on electrochemical measurements of the passive film breakdown potential and general corrosion rates. Electrochemical studies of the passive film stability of SAM1651 are reported here. Chromium (Cr), molybdenum (Mo) and tungsten (W) provide corrosion resistance; boron (B) enables glass formation; and rare earths such as yttrium (Y) lower critical cooling rate (CCR). Yttrium-containing SAM1651, also known as SAM7 (Fe{sub 48.0}Cr{sub 15.0}Mo{sub 14.0}B{sub 6.0}C{sub 15.0}Y{sub 2.0}), has a critical cooling rate (CCR) of approximately 80 Kelvin per second, while yttrium-free 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}) has a higher critical cooling rate of approximately 600 Kelvin per second. SAM1651's low CCR enables it to be rendered as a completely amorphous material in practical materials processes. While the yttrium enables a low CCR to be achieved, it makes the material relatively difficult to atomize, due to increases in melt viscosity. Consequently, the powders have irregular shape, which makes pneumatic conveyance during thermal spray deposition difficult. 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 or inhibitor. SAM1651 may also experience crevice corrosion under sufficiently harsh conditions. Both Alloy C-22 and Type 316L stainless lose their resistance to corrosion during thermal spraying, due to the formation of deleterious intermetallic phases which depletes the matrix of key alloy elements, whereas SAM1651 can be applied as coatings with the same corrosion resistance as a fully-dense completely amorphous melt-spun ribbon, provided that its amorphous

  15. HIGHWAY INFRASTRUCTURE FOCUS AREA NEXT-GENERATION INFRASTRUCTURE MATERIALS VOLUME I - TECHNICAL PROPOSAL & MANAGEMENTENHANCEMENT OF TRANSPORTATION INFRASTRUCTURE WITH IRON-BASED AMORPHOUS-METAL AND CERAMIC COATINGS

    SciTech Connect

    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

  16. The resistance of selected high strength alloys to embrittlement by a hydrogen environment. [iron and cobalt base alloys

    NASA Technical Reports Server (NTRS)

    Benson, R. B., Jr.

    1974-01-01

    Selected high strength iron base and cobalt base alloys were resistant to degradation of mechanical properties in a one atmosphere hydrogen environment at ambient temperature. These alloys were strengthened initially by cold working which produced strain induced martensite and fcc mechanical twins in an fcc matrix. Heat treatment of the cobalt base alloy after cold working produced carbide precipitates with retention of an hcp epsilon phase which increased the yield strength level. High strength alloys can be produced which have some resistance to degradation of mechanical properties by a hydrogen environment under certain conditions.

  17. Iron and iron-based alloys for temporary cardiovascular applications.

    PubMed

    Francis, A; Yang, Y; Virtanen, S; Boccaccini, A R

    2015-03-01

    In the last decade, biodegradable metals have emerged as a topic of interest for particular biomedical applications which require high strength to bulk ratio, including for cardiovascular stents. The advantages of biodegradable materials are related to the reduction of long term risks associated with the presence of permanent metal implants, e.g. chronic inflammation and in-stent restenosis. From a structural point of view, the analysis of the literature reveals that iron-based alloys used as temporary biodegradable stents have several advantages over Mg-based alloys in terms of ductility and strength. Efforts on the modification and tunability of iron-based alloys design and compositions have been mainly focused on controlling the degradation rate while retaining the mechanical integrity within a reasonable period. The early pre-clinical results of many iron-based alloys seem promising for future implants developments. This review discusses the available literature focusing mainly on: (i) Fe and Fe-based alloys design and fabrication techniques; (ii) in vitro and in vivo performance; (iii) cytotoxicity and cell viability tests.

  18. Development of an Amorphous Selenium-Based Photodetector Driven by a Diamond Cold Cathode

    PubMed Central

    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

    2013-01-01

    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. PMID:24152932

  19. Stress Corrosion Cracking and Oxidation Characteristics of Boride-Strengthend Microcrystalline Iron and Nickel Based Alloys.

    DTIC Science & Technology

    1984-10-22

    through subsequent thermomechanical treatments make this class of alloy attractive for many applications. One such relatively new class of alloys based...crystallizing it in the solid state) using controlled thermal or thermomechanical treatments. Preliminary evaluations of the Fe, Ni, and Co-based micrystalline...and iron in alloys 3 and 4). Each of the four microcrystalline alloys was processed in similar ways. Each alloy was induction melted and chill block

  20. DEVELOPMENT OF PROTECTIVE COATINGS FOR TANTALUM-BASE ALLOYS

    DTIC Science & Technology

    PHASE STUDIES, PHYSICAL PROPERTIES, REFRACTORY MATERIALS, SILICIDES , SILICON COATINGS , SILICON COMPOUNDS, TANTALUM, TENSILE PROPERTIES, TITANIUM COMPOUNDS, TUNGSTEN ALLOYS, VANADIUM ALLOYS, VAPOR PLATING, ZINC COATINGS ....TANTALUM ALLOYS, ALLOYS, ALUMINUM COATINGS , ALUMINUM COMPOUNDS, BORON COMPOUNDS, CERAMIC COATINGS , CHROMIUM COMPOUNDS, COATINGS , FLAME SPRAYING...HAFNIUM ALLOYS, HAFNIUM COMPOUNDS, HARDNESS, HEAT RESISTANT ALLOYS, INTERMETALLIC COMPOUNDS, METAMATHEMATICS, NIOBIUM ALLOYS, OSCILLOGRAPHS, OXIDES

  1. Structure and dielectric properties of amorphous high-κ oxides: HfO2, ZrO2, and their alloys

    NASA Astrophysics Data System (ADS)

    Wang, Yin; Zahid, Ferdows; Wang, Jian; Guo, Hong

    2012-06-01

    High-κ metal oxides are a class of materials playing an increasingly important role in modern device physics and technology. Here we report theoretical investigations of the properties of structural and lattice dielectric constants of bulk amorphous metal oxides by a combined approach of classical molecular dynamics (MD), for structure evolution, and quantum mechanical first-principles density function theory (DFT), for electronic structure analysis. Using classical MD based on the Born-Mayer-Buckingham potential function within a melt and quench scheme, amorphous structures of high-κ metal oxides Hf1-xZrxO2 with different values of the concentration x are generated. The coordination numbers and the radial distribution functions of the structures are in good agreement with the corresponding experimental data. We then calculate the lattice dielectric constants of the materials from quantum mechanical first principles, and the values averaged over an ensemble of samples agree well with the available experimental data and are very close to the dielectric constants of their cubic form.

  2. Durable pd-based alloy and hydrogen generation membrane thereof

    DOEpatents

    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.

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

    SciTech Connect

    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 (<1%) is observed, even for high angles of incidence (.about.75.degree.) and for relatively short nanoneedle lengths (.about.1 .mu.m). Furthermore, the material exhibits high optical absorption efficiency with an effective band gap of .about.1 eV. The reported black Ge can have important practical implications for efficient photovoltaic and photodetector applications on nonconventional substrates.

  4. Microprocessor-based controller for automatic amorphous silicon solar cells characterization

    SciTech Connect

    Cibils, R.M.; Buitrago, R.H.

    1984-07-01

    This work describes an innovation of traditional systems used in C--V and G--V curve measurements. Although this system has been specifically developed to be used in the characterization of hydrogenated amorphous silicon (a-Si:H), it is useful when information about conductance (G) or capacitance (C) frequency dependence is needed. The highlights of the new system are signal heterodination and microprocessor-based digital control over current range and modulation frequency. The outstanding advantages of this system are significant reduction of operation time and more reliable measurements. Additionally, there is no waste of computer time in the control of data-acquisition operations. The system has an excellent signal-to-noise ratio, a nearly infinite line signal rejection, and a broad frequency range of operation (20 to 10/sup 5/ Hz).

  5. Semiconducting properties of amorphous GaZnSnO thin film based on combinatorial electronic structures

    SciTech Connect

    Kim, B. K.; Park, J. S.; Kim, D. H.; Chung, K. B.

    2014-05-05

    Semiconducting properties and electronic structures of amorphous GaZnSnO (GZTO) thin films are investigated with respect to metal cationic composition. An increase of the cationic Sn ratio resulted in an increase of the carrier concentration and a decrease of the mobility of the films. Combinatorial analysis revealed that the electrical characteristics of GZTO films are strongly correlated to changes in electronic structure. The increase in carrier concentration is related to the generation of vacancies by the changes of oxygen coordination around the cationic metal and the shallow band edge state below the conduction band. On the other hand, the decrease of mobility can be explained by the deep band edge state, and the difference between the experimental conduction band and simulated conduction band by the combinatorial electronic structure based on the chemical composition.

  6. Several Issues in the Development of Ti-Nb-Based Shape Memory Alloys

    NASA Astrophysics Data System (ADS)

    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.

  7. Research on stable, high-efficiency, large-area, amorphous-silicon-based submodules

    SciTech Connect

    Delahoy, A.E.; Tonon, T.; Macneil, J. )

    1991-06-01

    The primary objective of this subcontract is to develop the technology for same bandgap, amorphous silicon tandem junction photovoltaic modules having an area of at least 900 cm{sup 2} with the goal of achieving an aperture area efficiency of 9%. A further objective is to demonstrate modules that retain 95% of their under standard light soaking conditions. Our approach to the attainment of these objective is based on the following distinctive technologies: (a) in-house deposition of SiO{sub 2}/SnO{sub 2}:F onto soda lime glass by APCVD to provide a textured, transparent electrode, (b) single chamber r.f. flow discharge deposition of the a-Si:H layers onto vertical substrates contained with high package density in a box carrier'' to which the discharge is confined (c) sputter deposition of highly reflecting, ZnO-based back contacts, and (d) laser scribing of the a-Si:H and electrodes with real-time scribe tracking to minimize area loss. Continued development of single junction amorphous silicon was aggressively pursued as proving ground for various optical enhancement schemes, new p-layers, and i-layers quality. We have rigorously demonstrated that the introduction of a transitional i-layer does not impair stability and that the initial gain in performance is retained. We have demonstrated a small improvement in cell stability through a post-fabrication treatment consisting of multiple, intense light flashes followed by sufficient annealing. Finally, several experiments have indicated that long term stability can be improved by overcoating the SnO{sub 2} with ZnO. 25 refs., 17 figs.

  8. The effect of selected alloying element additions on properties of Mg-based alloy as bioimplants: A literature review

    NASA Astrophysics Data System (ADS)

    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.

  9. Recrystallization characteristics of oxide dispersion strengthened nickel-base alloys

    NASA Technical Reports Server (NTRS)

    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.

  10. Cr{sub 2}Nb-based alloy development

    SciTech Connect

    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.

  11. Melting and casting of FeAl-based cast alloy

    SciTech Connect

    Sikka, V.K.; Wilkening, D.; Liebetrau, J.; Mackey, B.

    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.

  12. Gigahertz range electromagnetic wave absorbers made of amorphous-carbon-based magnetic nanocomposites

    NASA Astrophysics Data System (ADS)

    Liu, Jiu Rong; Itoh, Masahiro; Horikawa, Takashi; Machida, Ken-Ichi; Sugimoto, Satoshi; Maeda, Toru

    2005-09-01

    Nanocomposite magnetic materials α-Fe/C(a), Fe2B/C(a), and Fe1.4Co0.6B/C(a) were prepared by mechanically grinding α-Fe, Fe2B, or Fe1.4Co0.6B with amorphous carbon [C(a)] powders. Complex permittivity, permeability, and electromagnetic wave absorption properties of resin compacts containing 40-vol % composite powders of α-Fe/C(a), Fe2B/C(a), and Fe1.4Co0.6B/C(a) were characterized according to a conventional reflection/transmission technique. The real part (ɛr') and imaginary part (Vr'') of the relative permittivity are low and almost independent of frequency between 0.05 and 40 GHz. The Imaginary part (μr'') of the relative permeability exhibited wide peaks in the 1-9-GHz range for α-Fe/C(a), in the 2-18-GHz range for Fe2B/C(a), and in the 18-40-GHz range for Fe1.4Co0.6B/C(a) owing to their different magnetocrystalline anisotropy field (HA) values. Consequently, the resin compacts of 40-vol % α-Fe/C(a), Fe2B/C(a), and Fe1.4Co0.6B/C(a) powders provided good electromagnetic (em) wave absorption performances (reflection loss<-20 dB) in ranges of 4.3-8.2 GHz (G band), 7.5-16.0 GHz (X band), and 26.5-40 GHz (Q band) over absorber thicknesses of 1.8-3.3, 1.2-2.2, and 0.63-0.82 mm, respectively. Our experimental results demonstrate that the amorphous-carbon-based magnetic nanocomposites are promising for the application to produce thin and light EM wave absorbers.

  13. In vitro corrosion of dental Au-based casting alloys in polyvinylpyrrolidone-iodine solution.

    PubMed

    Takasusuki, Norio; Ida, Yusuke; Hirose, Yukito; Ochi, Morio; Endo, Kazuhiko

    2013-01-01

    The corrosion and tarnish behaviors of two Au-based casting alloys (ISO type 1 and type 4 Au alloys) and their constituent pure metals, Au, Ag, Cu, Pt, and Pd in a polyvinylpyrrolidone-iodine solution were examined. The two Au alloys actively corroded, and the main anodic reaction for both was dissolution of Au as AuI₂(-). The amount of Au released from the ISO type 1 Au alloy was significantly larger than that from the ISO type 4 Au alloy (P<0.05). Visible light spectrophotometry revealed that the type 1 alloy exhibited higher susceptibility to tarnishing than the type 4 alloy. The corrosion forms of the two Au alloys were found to be completely different, i.e., the type 1 alloy exhibited the corrosion attack over the entire exposed surface with a little irregularity whereas the type 4 alloy exhibited typical intergranular corrosion, which was caused by local cells produced by segregation of Pd and Pt.

  14. Magnetic and electrical properties of amorphous Fe-Cr-P-C-Si

    NASA Astrophysics Data System (ADS)

    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.

  15. The Bain path of paramagnetic Fe-Cr based alloys

    NASA Astrophysics Data System (ADS)

    Al-Zoubi, N.; Johansson, B.; Nilson, G.; Vitos, L.

    2011-07-01

    Employing the first-principles exact muffin-tin orbital method in combination with the coherent potential approximation, we calculated the total energy and local magnetic moments of paramagnetic Fe-Cr-M (M = Cr, Mn, Fe, Co, Ni) alloys along the tetragonal distortion (Bain) path connecting the body centered cubic (bcc) and the face centered cubic (fcc) structures. The paramagnetic phase is modeled by the disordered local magnetic moment scheme. For all alloys, the local magnetic moments on Fe atoms decrease from the maximum value corresponding to the bcc phase toward the minimum value realized for the fcc phase. Cobalt atoms have non-vanishing local magnetic moments only for tetragonal lattices with c/a < 1.30, whereas the local magnetic moments of Mn show weak crystal structure dependence. We find that Cr stabilizes the bcc lattice and increases the energy barrier as going from the bcc toward the fcc phase. Both Co and Ni favor the fcc lattice and decrease the energy barrier relative to the bcc phase. On the other hand, the tetragonal distortion around the fcc phase is facilitated by Cr and to a somewhat lesser extent also by Ni, but strongly impeded by Co. Manganese has negligible effect on the structural energy difference as well as on the energy barrier along the Bain path. Our findings on the alloying induced softening or hardening of Fe-Cr based alloys against tetragonal distortions are important for understanding the interstitial driven martensitic transformations in alloy steels.

  16. Advanced nickel base alloys for high strength, corrosion applications

    DOEpatents

    Flinn, J.E.

    1998-11-03

    Improved nickel-base alloys of enhanced strength and corrosion resistance, produced by atomization of an alloy melt under an inert gas atmosphere and of composition 0--20Fe, 10--30Cr, 2--12Mo, 6 max. Nb, 0.05--3 V, 0.08 max. Mn, 0.5 max. Si, less than 0.01 each of Al and Ti, less than 0.05 each of P and S, 0.01--0.08C, less than 0.2N, 0.1 max. 0, bal. Ni. 3 figs.

  17. Advanced nickel base alloys for high strength, corrosion applications

    DOEpatents

    Flinn, John E.

    1998-01-01

    Improved nickel-base alloys of enhanced strength and corrosion resistance, produced by atomization of an alloy melt under an inert gas atmosphere and of composition 0-20Fe, 10-30Cr, 2-12Mo, 6 max. Nb, 0.05-3 V, 0.08 max. Mn, 0.5 max. Si, less than 0.01 each of Al and Ti, less than 0.05 each of P and S, 0.01-0.08C, less than 0.2N, 0.1 max. 0, bal. Ni.

  18. Hot corrosion of S-57, 1 cobalt-base alloy

    NASA Technical Reports Server (NTRS)

    Santoro, G. J.

    1977-01-01

    A cobalt base alloy, S-57, was hot corrosion tested in Mach 0.3 burner rig combustion gases at maximum alloy temperatures of 900 and 1000 C. Various salt concentrations were injected into the burner: 0.5, 2, 5, and 10 ppm synthetic sea salt and 4 ppm sodium sulfate (Na2SO4). S-57 underwent accelerated corrosion only under the most severe test conditions, for example, 4 ppm Na2SO4 at 900 C. The process of the accelerated corrosion was primarily sulfidation.

  19. Improved Mg-based alloys for hydrogen storage

    SciTech Connect

    Sapru, K.; Ming, L.; Stetson, N.T.; Evans, J.

    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.

  20. Nickel base alloy. [for gas turbine engine stator vanes

    NASA Technical Reports Server (NTRS)

    Freche, J. C.; Waters, W. J. (Inventor)

    1977-01-01

    A nickel base superalloy for use at temperatures of 2000 F (1095 C) to 2200 F (1205 C) was developed for use as stator vane material in advanced gas turbine engines. The alloy has a nominal composition in weight percent of 16 tungsten, 7 aluminum, 1 molybdenum, 2 columbium, 0.3 zirconium, 0.2 carbon and the balance nickel.

  1. Acoustic Emission Analysis of Damage during Compressive Deformation of Amorphous Zr-Based Foams with Aligned, Elongated Pores

    NASA Astrophysics Data System (ADS)

    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.

  2. Corrosive electrochemical behavior of amorphous and nanocrystalline Fe-P-Si-Mn-V alloys in a moist SO2-contaminated atmosphere

    NASA Astrophysics Data System (ADS)

    Vavilova, V. V.; Korneev, V. P.; Anosova, M. O.

    2016-01-01

    Nanocrystalline soft magnetic Finemet alloys, which are currently used in power electrical engineering and electrical equipment, are alloyed with expensive and scarce metals (Nb, Cu). We searched for low-cost soft magnetic alloys that are comparable with Finemets in the corrosion resistance.

  3. NOREM wear-resistant, iron-based hard-facing alloys: Final report

    SciTech Connect

    Grobner, P.; Ohriner, E.K.; Wada, T.; Whelan, E.P.

    1989-07-01

    Wear-resistance cobalt-free hardfacing alloys are needed to replace the cobalt-base alloys used to hardface nuclear valves in order to reduce the exposure of maintenance personnel. Some thirty heats of cast iron-base alloys were prepared and characterized. Selected heats were prepared and applied as hardfacing overlays on austenitic steel substrates using both GTA and PTA welding processes. Some of the iron-base alloys exhibited galling wear resistance as high as that of cobalt-base standards both in the cast condition and in the PTA overlays. Hardness, mechanical properties, and galling wear resistance were determined on weld overlays and on cast alloys. Dilution and thermal expansivity were determined for weld overlays. X-ray diffraction and scanning electron microscopy were used to determine the alloys' microstructures. Other commercially available alloys were tested for galling wear resistance and compared to iron-base alloys. 7 refs., 2 figs., 2 tabs.

  4. Zirconium-based alloys, nuclear fuel rods and nuclear reactors including such alloys, and related methods

    DOEpatents

    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.

  5. Electrochemical hydrogen storage alloys and batteries fabricated from Mg containing base alloys

    DOEpatents

    Ovshinsky, Stanford R.; Fetcenko, Michael A.

    1996-01-01

    An electrochemical hydrogen storage material comprising: (Base Alloy).sub.a M.sub.b where, Base Alloy is an alloy of Mg and Ni in a ratio of from about 1:2 to about 2:1, preferably 1:1; M represents at least one modifier element chosen from the group consisting of Co, Mn, Al, Fe, Cu, Mo, W, Cr, V, Ti, Zr, Sn, Th, Si, Zn, Li, Cd, Na, Pb, La, Mm, and Ca; b is greater than 0.5, preferably 2.5, atomic percent and less than 30 atomic percent; and a+b=100 atomic percent. Preferably, the at least one modifier is chosen from the group consisting of Co, Mn, Al, Fe, and Cu and the total mass of the at least one modifier element is less than 25 atomic percent of the final composition. Most preferably, the total mass of said at least one modifier element is less than 20 atomic percent of the final composition.

  6. Downstream processing of polymer-based amorphous solid dispersions to generate tablet formulations.

    PubMed

    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.

  7. XRD Technique: A way to disseminate structural changes in iron-based amorphous materials

    SciTech Connect

    Saw, C K; Lian, T; Day, D; Farmer, J

    2007-05-24

    Prevention of corrosion is a vital goal for the Department of Defense when billions of dollars are spent every year. Corrosion resistant materials have applications in all sort of military vehicles, and more importantly in naval vessels and submarines which come in contact with the seawater. It is known that corrosion resistance property can be improved by the used of structurally designed materials in the amorphous state where the atoms are arranged in a non-periodic fashion and specific atoms, tailored to the required properties can be interjected into the matrix for specific application. The XRD techniques reported here is to demonstrate the optimal conditions for characterization of these materials. The samples, which normally contain different compositions of Fe, Cr, B, Mo, Y, Mn, Si and W, are in the form of powders, ribbons and coatings. These results will be compared for the different forms of the sample which appears to correlate to the cooling rate during sample processing. In most cases, the materials are amorphous or amorphous with very small amount of crystallinity. In the ribbon samples for different compositions we observed that the materials are essentially amorphous. In most cases, starting from an amorphous powder sample, the coatings are also observed to be amorphous with a small amount of iron oxide on the surface, probably due to exposure to air.

  8. Ni3Al-based alloys for die and tool application

    DOEpatents

    Liu, Chain T.; Bloom, Everett E.

    2001-01-01

    A novel Ni.sub.3 Al-based alloy exhibits strengths and hardness in excess of the standard base alloy IC-221M at temperatures of up to about 1000.degree. C. The alloy is useful in tool and die applications requiring such temperatures, and for structural elements in engineering systems exposed to such temperatures.

  9. Fabrication of full-color InGaN-based light-emitting diodes on amorphous substrates by pulsed sputtering.

    PubMed

    Shon, Jeong Woo; Ohta, Jitsuo; Ueno, Kohei; Kobayashi, Atsushi; Fujioka, Hiroshi

    2014-06-23

    InGaN-based light-emitting diodes (LEDs) have been widely accepted as highly efficient light sources capable of replacing incandescent bulbs. However, applications of InGaN LEDs are limited to small devices because their fabrication process involves expensive epitaxial growth of InGaN by metalorganic vapor phase epitaxy on single-crystal wafers. If we can utilize a low-cost epitaxial growth process, such as sputtering on large-area substrates, we can fabricate large-area InGaN light-emitting displays. Here, we report the growth of GaN (0001) and InGaN (0001) films on amorphous SiO2 by pulsed sputtering deposition. We found that using multilayer graphene buffer layers allows the growth of highly c-axis-oriented GaN films even on amorphous substrates. We fabricated red, green, and blue InGaN LEDs and confirmed their successful operation. This successful fabrication of full-color InGaN LEDs on amorphous substrates by sputtering indicates that the technique is quite promising for future large-area light-emitting displays on amorphous substrates.

  10. Thin-film amorphous silicon alloy research partnership. Final technical progress report, 2 February 1995--28 February 1998

    SciTech Connect

    Guha, S

    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.

  11. Analysis of thermoelectric properties of high-temperature complex alloys of nickel-base, iron-base and cobalt-base groups

    NASA Technical Reports Server (NTRS)

    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.

  12. Scaling of slip avalanches in sheared amorphous materials based on large-scale atomistic simulations

    NASA Astrophysics Data System (ADS)

    Zhang, Dansong; Dahmen, Karin A.; Ostoja-Starzewski, Martin

    2017-03-01

    Atomistic simulations of binary amorphous systems with over 4 million atoms are performed. Systems of two interatomic potentials of the Lennard-Jones type, LJ12-6 and LJ9-6, are simulated. The athermal quasistatic shearing protocol is adopted, where the shear strain is applied in a stepwise fashion with each step followed by energy minimization. For each avalanche event, the shear stress drop (Δ σ ), the hydrostatic pressure drop (Δ σh ), and the potential energy drop (Δ E ) are computed. It is found that, with the avalanche size increasing, the three become proportional to each other asymptotically. The probability distributions of avalanche sizes are obtained and values of scaling exponents fitted. In particular, the distributions follow a power law, P (Δ U )˜Δ U-τ , where Δ U is a measure of avalanche sizes defined based on shear stress drops. The exponent τ is 1.25 ±0.1 for the LJ12-6 systems, and 1.15 ±0.1 for the LJ9-6 systems. The value of τ for the LJ12-6 systems is consistent with that from an earlier atomistic simulation study by Robbins et al. [Phys. Rev. Lett. 109, 105703 (2012)], 10.1103/PhysRevLett.109.105703, but the fitted values of other scaling exponents differ, which may be because the shearing protocol used here differs from that in their study.

  13. A physics-based model of threshold voltage for amorphous oxide semiconductor thin-film transistors

    NASA Astrophysics Data System (ADS)

    Chen, Chi-Le; Chen, Wei-Feng; Zhou, Lei; Wu, Wei-Jing; Xu, Miao; Wang, Lei; Peng, Jun-Biao

    2016-03-01

    In the application of the Lambert W function, the surface potential for amorphous oxide semiconductor thin-film transistors (AOS TFTs) under the subthreshold region is approximated by an asymptotic equation only considering the tail states. While the surface potential under the above-threshold region is approximated by another asymptotic equation only considering the free carriers. The intersection point between these two asymptotic equations represents the transition from the weak accumulation to the strong accumulation. Therefore, the gate voltage corresponding to the intersection point is defined as threshold voltage of AOS TFTs. As a result, an analytical expression for the threshold voltage is derived from this novel definition. It is shown that the threshold voltage achieved by the proposed physics-based model is agreeable with that extracted by the conventional linear extrapolation method. Furthermore, we find that the free charge per unit area in the channel starts increasing sharply from the threshold voltage point, where the concentration of the free carriers is a little larger than that of the localized carriers. The proposed model for the threshold voltage of AOS TFTs is not only physically meaningful but also mathematically convenient, so it is expected to be useful for characterizing and modeling AOS TFTs.

  14. Feasibility of Amorphous Selenium Based Photon Counting Detectors for Digital Breast Tomosynthesis

    SciTech Connect

    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.

  15. Amorphous Calcium Phosphate-Based Bioactive Polymeric Composites for Mineralized Tissue Regeneration

    PubMed Central

    Skrtic, D.; Antonucci, J. M.; Eanes, E. D.

    2003-01-01

    Amorphous calcium phosphate (ACP), a postulated precursor in the formation of biological hydroxyapatite, has been evaluated as a filler phase in bioactive polymeric composites that utilize dental monomers to form the matrix phase on polymerization. In addition to excellent biocompatibility, these composites provided sustained release of calcium and phosphate ions into simulated saliva milieus. In an effort to enhance the physicochemical and mechanical properties and extend the utility of remineralizing ACP composites to a greater variety of dental applications, we have focused on: a) hybridizing ACP by introducing silica and/or zirconia, b) assessing the efficacy of potential coupling agents, c) investigating the effects of chemical structure and compositional variation of the resin matrices on the mechanical strength and ion-releasing properties of the composites, and d) improving the intrinsic adhesiveness of composites by using bifunctional monomers with an affinity for tooth structure in resin formulations. Si- and Zr-modified ACPs along with several monomer systems are found useful in formulating composites with improved mechanical and remineralizing properties. Structure-property studies have proven helpful in advancing our understanding of the remineralizing behavior of these bioactive composites. It is expected that this knowledge base will direct future research and lead to clinically valuable products, especially therapeutic materials appropriate for the healing or even regeneration of defective teeth and bone structures. PMID:27413603

  16. Efficient nanorod-based amorphous silicon solar cells with advanced light trapping

    NASA Astrophysics Data System (ADS)

    Kuang, Y.; van Lare, M. C.; Veldhuizen, L. W.; Polman, A.; Rath, J. K.; Schropp, R. E. I.

    2015-11-01

    We present a simple, low-cost, and scalable approach for the fabrication of efficient nanorod-based solar cells. Templates with arrays of self-assembled ZnO nanorods with tunable morphology are synthesized by chemical bath deposition using a low process temperature at 80 °C. The nanorod templates are conformally coated with hydrogenated amorphous silicon light absorber layers of 100 nm and 200 nm thickness. An initial efficiency of up to 9.0% is achieved for the optimized design. External quantum efficiency measurements on the nanorod cells show a substantial photocurrent enhancement both in the red and the blue parts of the solar spectrum. Key insights in the light trapping mechanisms in these arrays are obtained via a combination of three-dimensional finite-difference time-domain simulations, optical absorption, and external quantum efficiency measurements. Front surface patterns enhance the light incoupling in the blue, while rear side patterns lead to enhanced light trapping in the red. The red response in the nanorod cells is limited by absorption in the patterned Ag back contact. With these findings, we develop and experimentally realize a further advanced design with patterned front and back sides while keeping the Ag reflector flat, showing significantly enhanced scattering from the back reflector with reduced parasitic absorption in the Ag and thus higher photocurrent generation. Many of the findings in this work can serve to provide insights for further optimization of nanostructures for thin-film solar cells in a broad range of materials.

  17. Elevated temperature tribology of cobalt and tantalum-based alloys

    SciTech Connect

    Scharf, T. W.; Prasad, S. V.; Kotula, P. G.; Michael, J. R.; Robino, C. V.

    2014-12-31

    This paper describes the friction and wear behavior of a Co–Cr alloy sliding on a Ta–W alloy. Measurements were performed in a pin-on-flat configuration with a hemispherically tipped Co-base alloy pin sliding on a Ta–W alloy flat from ambient to 430°C. Focused ion beam-scanning electron microscopy (FIB-SEM) and cross-sectional transmission electron microscopy (TEM) were used to identify the friction-induced changes to the chemistry and crystal structure in the subsurface regions of wear tracks. During sliding contact, transfer of material varied as a function of the test temperature, either from pin-to-flat, flat-to-pin, or both, resulting in either wear loss and/or volume gain. Friction coefficients (μ) and wear rates also varied as a function of test temperature. The lowest friction coefficient (μ=0.25) and wear rate (1×10–4 mm3/N•m) were observed at 430°C in argon atmosphere. This was attributed to the formation of a Co-base metal oxide layer (glaze), predominantly (Co, Cr)O with Rocksalt crystal structure, on the pin surface. Part of this oxide film transferred to the wear track on Ta–W, providing a self-mated oxide-on-oxide contact. Once the oxide glaze is formed, it is able to provide friction reduction for the entire temperature range of this study, ambient to 430°C. Furthermore, the results of this study indicate that glazing the surfaces of Haynes alloys with continuous layers of cobalt chrome oxide prior to wear could protect the cladded surfaces from damage.

  18. Elevated temperature tribology of cobalt and tantalum-based alloys

    DOE PAGES

    Scharf, T. W.; Prasad, S. V.; Kotula, P. G.; ...

    2014-12-31

    This paper describes the friction and wear behavior of a Co–Cr alloy sliding on a Ta–W alloy. Measurements were performed in a pin-on-flat configuration with a hemispherically tipped Co-base alloy pin sliding on a Ta–W alloy flat from ambient to 430°C. Focused ion beam-scanning electron microscopy (FIB-SEM) and cross-sectional transmission electron microscopy (TEM) were used to identify the friction-induced changes to the chemistry and crystal structure in the subsurface regions of wear tracks. During sliding contact, transfer of material varied as a function of the test temperature, either from pin-to-flat, flat-to-pin, or both, resulting in either wear loss and/or volumemore » gain. Friction coefficients (μ) and wear rates also varied as a function of test temperature. The lowest friction coefficient (μ=0.25) and wear rate (1×10–4 mm3/N•m) were observed at 430°C in argon atmosphere. This was attributed to the formation of a Co-base metal oxide layer (glaze), predominantly (Co, Cr)O with Rocksalt crystal structure, on the pin surface. Part of this oxide film transferred to the wear track on Ta–W, providing a self-mated oxide-on-oxide contact. Once the oxide glaze is formed, it is able to provide friction reduction for the entire temperature range of this study, ambient to 430°C. Furthermore, the results of this study indicate that glazing the surfaces of Haynes alloys with continuous layers of cobalt chrome oxide prior to wear could protect the cladded surfaces from damage.« less

  19. Tungsten wire-nickel base alloy composite development

    NASA Technical Reports Server (NTRS)

    Brentnall, W. D.; Moracz, D. J.

    1976-01-01

    Further development and evaluation of refractory wire reinforced nickel-base alloy composites is described. Emphasis was placed on evaluating thermal fatigue resistance as a function of matrix alloy composition, fabrication variables and reinforcement level and distribution. Tests for up to 1,000 cycles were performed and the best system identified in this current work was 50v/o W/NiCrAlY. Improved resistance to thermal fatigue damage would be anticipated for specimens fabricated via optimized processing schedules. Other properties investigated included 1,093 C (2,000 F) stress rupture strength, impact resistance and static air oxidation. A composite consisting of 30v/o W-Hf-C alloy fibers in a NiCrAlY alloy matrix was shown to have a 100-hour stress rupture strength at 1,093 C (2,000 F) of 365 MN/square meters (53 ksi) or a specific strength advantage of about 3:1 over typical D.S. eutectics.

  20. Microstructure Evolution of Gas Atomized Iron Based ODS Alloys

    SciTech Connect

    Rieken, J.R.; Anderson, I.E.; Kramer, M.J.; Anderegg, J.W.; Shechtman, D.

    2009-12-01

    In a simplified process to produce precursor powders for oxide dispersion-strength- ened (ODS) alloys, gas-atomization reaction synthesis (GARS) was used to induce a surface oxide layer on molten droplets of three differing erritic stainless steel alloys during break-up and rapid solidification. The chemistry of the surface oxide was identified using auger electron spectroscopy (AES) and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). The precursor iron-base powders were consolidated at 850 C and 1,300 C using hot isostatic pressing (HIPing). Consolidation at the lower temperature resulted in a fully dense microstructure, while preventing substantial prior particle-boundary-oxide dissociation. Microstructural analysis of the alloys consolidated at the higher temperature confirmed a significant reduction in prior-particle-boundary-oxide volume fraction, in comparison with the lower-temperature-consolidated sample. This provided evidence that a high-temperature internal oxygen-exchange reaction occurred between the metastable prior particle-boundary-oxide phase (chromium oxide) and the yttrium contained within each prior particle. This internal oxygen-exchange reaction is shown to result in the formation of yttrium-enriched oxide dispersoids throughout the alloy microstructure. The evolving microstructure was characterized using transmission electron microscopy (TEM) and high-energy X-ray diffraction (HE-XRD).

  1. Microstructure Evolution of Gas Atomized Iron Based ODS Alloys

    SciTech Connect

    Rieken, J.R.; Anderson, I.E.; Kramer, M.J.

    2011-08-09

    In a simplified process to produce precursor powders for oxide dispersion-strengthened (ODS) alloys, gas-atomization reaction synthesis (GARS) was used to induce a surface oxide layer on molten droplets of three differing erritic stainless steel alloys during break-up and rapid solidification. The chemistry of the surface oxide was identified using auger electron spectroscopy (AES) and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). The precursor iron-base powders were consolidated at 850 C and 1,300 C using hot isostatic pressing (HIPing). Consolidation at the lower temperature resulted in a fully dense microstructure, while preventing substantial prior particle-boundary-oxide dissociation. Microstructural analysis of the alloys consolidated at the higher temperature confirmed a significant reduction in prior-particle-boundary-oxide volume fraction, in comparison with the lower-temperature-consolidated sample. This provided evidence that a high-temperature internal oxygen-exchange reaction occurred between the metastable prior particle-boundary-oxide phase (chromium oxide) and the yttrium contained within each prior particle. This internal oxygen-exchange reaction is shown to result in the formation of yttrium-enriched oxide dispersoids throughout the alloy microstructure. The evolving microstructure was characterized using transmission electron microscopy (TEM) and high-energy X-ray diffraction (HE-XRD).

  2. Performance improvement in amorphous silicon based uncooled microbolometers through pixel design and materials development

    NASA Astrophysics Data System (ADS)

    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.

  3. The thermomechanical stability of Fe-based amorphous ribbons exhibiting magnetocaloric effect

    NASA Astrophysics Data System (ADS)

    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.

  4. Processing, properties, and applications of Ni{sub 3}Al-based alloys

    SciTech Connect

    Sikka, V.K.; Santella, M.L.; Liu, C.T.

    1997-06-01

    The Ni{sub 3}Al-based alloys represent a quantum jump in advanced alloys for structural applications at elevated temperatures. These alloys offer benefits of oxidation, carburization, and chlorination resistance, and significantly higher strength than many commercially used alloys. The commercial applications of the Ni{sub 3}Al-based alloys have begun to occur because of their comprehensive development This paper is to provide a review of. (1) alloy development, (2) melting, casting, and processing of alloys, (3) property data, (4) welding process and weldment properties, and (5) case histories of current applications. It is concluded that the cast alloy IC-221M is on its way to commercialization. 22 refs., 8 figs., 2 tabs.

  5. Dendritic growth and structure of undercooled nickel base alloys

    NASA Technical Reports Server (NTRS)

    Flemings, M. C.; Shiohara, Y.

    1988-01-01

    The principal objectives of this overall investigation are to: study means for obtaining high undercooling in levitation melted droplets, and study structures produced upon the solidification of these undercooled specimens. Thermal measurements are made of the undercooling, and of the rapid recalescence, to develop an understanding of the solidification mechanism. Comparison of results is made with the modeling studies. Characterization and metallographic work is done to gain an understanding of the relationship between rapid solidification variables and the structures so produced. In ground based work to date, solidification of undercooled Ni-25 wt percent Sn alloy was observed by high-speed cinematography and the results compared with optical temperature measurements. Also in ground based work, high-speed optical temperature measurements were made of the solidification behavior of levitated metal samples within a transparent glass medium. Two undercooled Ni-Sn alloys were examined. Measurements were carried out on samples at undercoolings up to 330 K. Microstructures of samples produced in ground based work were determined by optical metallography and by SEM, and microsegregation by electron microprobe measurements. A series of flight tests were planned to conduct experiments similar to the ground based experiments. The Space Shuttle Columbia carried an alloy undercooled experiment in the STS 61-C mission in January 1986. A sample of Ni-32.5 wt percent Sn eutectic was melted and solidified under microgravity conditions.

  6. Synthesis and characterization of nanostructured palladium-based alloy electrocatalysts

    NASA Astrophysics Data System (ADS)

    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

  7. Cr{sub 2}Nb-based alloy development

    SciTech Connect

    Liu, C.T.; Tortorelli, P.F.; Horton, J.A.

    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.

  8. Microscopic study of the structure of the Steel Ni-based Alloy: Hastelloy G35 Alloy

    NASA Astrophysics Data System (ADS)

    Sabir, F.; Ben Lenda, O.; Saissi, S.; Marbouh, K.; Tyouke, B.; Zerrouk, L.; Ibnlfassi, A.; Ouzaouit, K.; Elmadani, S.

    2017-03-01

    The study of the influence of heat treatment on changes of mechanical and structural properties of Steel Ni-based Alloy is a highly interdisciplinary topic at the interface of the physical chemistry of metallic materials, which also helps in environmental and economic protection.After heat treatment, the structural and micro-structural studies for the different transformation temperature led to identify phases formed and the morphology. This work has been carried out using different techniques: X-ray diffraction, optical microscopy and scanning electron microscopy.

  9. Investigation on the primary creep of a nickel based alloy. [Nimonic 75 type alloy

    SciTech Connect

    Kong, Q.P.; Wang, X. )

    1993-07-01

    It is widely accepted that dislocation climb is involved in the steady state (i.e. secondary) creep at high temperatures, which is characterized by the formation and evolution of substructures. In current theories of steady state creep, dislocation climb is regarded as the rate controlling process. However, the role of dislocation climb in the primary (i.e. transient) creep at high temperatures is not clear. The present paper is to report the observations by transmission electron microscopy (TEM) on high temperature creep of a nickel based alloy. It will be shown that dislocation climb plays an important role not only in the steady state creep, but also in the primary creep.

  10. Polarization-corrosion behavior of commercial gold- and silver-base casting alloys in Fusayama solution.

    PubMed

    Johnson, D L; Rinne, V W; Bleich, L L

    1983-12-01

    Based on polarization measurements, high Au alloys are highly corrosion-resistant and exhibit the lowest corrosion rates; intermediate Au, Ag, and Pd alloys with Cu are passive but exhibit higher corrosion rates. Twenty weight percent (w/o) In-Ag alloys exhibit active corrosion behavior at potentials only 100 mV noble to the corrosion potential.

  11. An investigation of the initiation stage of hot corrosion in Ni-base alloys

    NASA Technical Reports Server (NTRS)

    Huang, T. T.; Meier, G. H.

    1979-01-01

    The commercial nickel base alloy, IN-738, and high purity laboratory alloys were prepared to simulate the effects of the major elements in IN-738. Results indicate that the initiation of hot corrosion attack of IN-738 and other similar alloys is the result of local penetration of molten salt through the protective oxide scale.

  12. Substrate and Passivation Techniques for Flexible Amorphous Silicon-Based X-ray Detectors

    PubMed Central

    Marrs, Michael A.; Raupp, Gregory B.

    2016-01-01

    Flexible active matrix display technology has been adapted to create new flexible photo-sensing electronic devices, including flexible X-ray detectors. Monolithic integration of amorphous silicon (a-Si) PIN photodiodes on a flexible substrate poses significant challenges associated with the intrinsic film stress of amorphous silicon. This paper examines how altering device structuring and diode passivation layers can greatly improve the electrical performance and the mechanical reliability of the device, thereby eliminating one of the major weaknesses of a-Si PIN diodes in comparison to alternative photodetector technology, such as organic bulk heterojunction photodiodes and amorphous selenium. A dark current of 0.5 pA/mm2 and photodiode quantum efficiency of 74% are possible with a pixelated diode structure with a silicon nitride/SU-8 bilayer passivation structure on a 20 µm-thick polyimide substrate. PMID:27472329

  13. Ultrafast all-optical arithmetic logic based on hydrogenated amorphous silicon microring resonators

    NASA Astrophysics Data System (ADS)

    Gostimirovic, Dusan; Ye, Winnie N.

    2016-03-01

    For decades, the semiconductor industry has been steadily shrinking transistor sizes to fit more performance into a single silicon-based integrated chip. This technology has become the driving force for advances in education, transportation, and health, among others. However, transistor sizes are quickly approaching their physical limits (channel lengths are now only a few silicon atoms in length), and Moore's law will likely soon be brought to a stand-still despite many unique attempts to keep it going (FinFETs, high-k dielectrics, etc.). This technology must then be pushed further by exploring (almost) entirely new methodologies. Given the explosive growth of optical-based long-haul telecommunications, we look to apply the use of high-speed optics as a substitute to the digital model; where slow, lossy, and noisy metal interconnections act as a major bottleneck to performance. We combine the (nonlinear) optical Kerr effect with a single add-drop microring resonator to perform the fundamental AND-XOR logical operations of a half adder, by all-optical means. This process is also applied to subtraction, higher-order addition, and the realization of an all-optical arithmetic logic unit (ALU). The rings use hydrogenated amorphous silicon as a material with superior nonlinear properties to crystalline silicon, while still maintaining CMOS-compatibility and the many benefits that come with it (low cost, ease of fabrication, etc.). Our method allows for multi-gigabit-per-second data rates while maintaining simplicity and spatial minimalism in design for high-capacity manufacturing potential.

  14. Structure-Composition-Property Relationships in Polymeric Amorphous Calcium Phosphate-Based Dental Composites†

    PubMed Central

    O’Donnell, Justin N.R.; Schumacher, Gary E.; Antonucci, Joseph M.; Skrtic, Drago

    2009-01-01

    Our studies of amorphous calcium phosphate (ACP)-based materials over the last decade have yielded bioactive polymeric composites capable of protecting teeth from demineralization or even regenerating lost tooth mineral. The anti-cariogenic/re-mineralizing potential of these ACP composites originates from their propensity, when exposed to the oral environment, to release in a sustained manner sufficient levels of mineral-forming calcium and phosphate ions to promote formation of stable apatitic tooth mineral. However, the less than optimal ACP filler/resin matrix cohesion, excessive polymerization shrinkage and water sorption of these experimental materials can adversely affect their physicochemical and mechanical properties, and, ultimately, limit their lifespan. This study demonstrates the effects of chemical structure and composition of the methacrylate monomers used to form the matrix phase of composites on degree of vinyl conversion (DVC) and water sorption of both copolymers and composites and the release of mineral ions from the composites. Modification of ACP surface via introducing cations and/or polymers ab initio during filler synthesis failed to yield mechanically improved composites. However, moderate improvement in composite’s mechanical stability without compromising its remineralization potential was achieved by silanization and/or milling of ACP filler. Using ethoxylated bisphenol A dimethacrylate or urethane dimethacrylate as base monomers and adding moderate amounts of hydrophilic 2-hydroxyethyl methacrylate or its isomer ethyl-α-hydroxymethacrylate appears to be a promising route to maximize the remineralizing ability of the filler while maintaining high DVC. Exploration of the structure/composition/property relationships of ACP fillers and polymer matrices is complex but essential for achieving a better understanding of the fundamental mechanisms that govern dissolution/re-precipitation of bioactive ACP fillers, and, ultimately, the

  15. Method of polishing nickel-base alloys and stainless steels

    DOEpatents

    Steeves, Arthur F.; Buono, Donald P.

    1981-01-01

    A chemical attack polish and polishing procedure for use on metal surfaces such as nickel base alloys and stainless steels. The chemical attack polish comprises Fe(NO.sub.3).sub.3, concentrated CH.sub.3 COOH, concentrated H.sub.2 SO.sub.4 and H.sub.2 O. The polishing procedure includes saturating a polishing cloth with the chemical attack polish and submicron abrasive particles and buffing the metal surface.

  16. Attack polish for nickel-base alloys and stainless steels

    DOEpatents

    Steeves, Arthur F.; Buono, Donald P.

    1983-01-01

    A chemical attack polish and polishing procedure for use on metal surfaces such as nickel base alloys and stainless steels. The chemical attack polish comprises Fe(NO.sub.3).sub.3, concentrated CH.sub.3 COOH, concentrated H.sub.2 SO.sub.4 and H.sub.2 O. The polishing procedure includes saturating a polishing cloth with the chemical attack polish and submicron abrasive particles and buffing the metal surface.

  17. Attack polish for nickel-base alloys and stainless steels

    DOEpatents

    Not Available

    1980-05-28

    A chemical attack polish and polishing procedure for use on metal surfaces such as nickel base alloys and stainless steels is described. The chemical attack polich comprises FeNO/sub 3/, concentrated CH/sub 3/COOH, concentrated H/sub 2/SO/sub 4/ and H/sub 2/O. The polishing procedure includes saturating a polishing cloth with the chemical attack polish and submicron abrasive particles and buffing the metal surface.

  18. Iron-based alloys with corrosion resistance to oxygen-sulfur mixed gases

    DOEpatents

    Natesan, K.

    1992-11-17

    An iron-based alloy with improved performance with exposure to oxygen-sulfur mixed gases with the alloy containing about 9--30 wt. % Cr and a small amount of Nb and/or Zr implanted on the surface of the alloy to diffuse a depth into the surface portion, with the alloy exhibiting corrosion resistance to the corrosive gases without bulk addition of Nb and/or Zr and without heat treatment at temperatures of 1000--1100 C. 7 figs.

  19. Iron-based alloys with corrosion resistance to oxygen-sulfur mixed gases

    DOEpatents

    Natesan, Krishnamurti

    1992-01-01

    An iron-based alloy with improved performance with exposure to oxygen-sulfur mixed gases with the alloy containing about 9-30 wt. % Cr and a small amount of Nb and/or Zr implanted on the surface of the alloy to diffuse a depth into the surface portion, with the alloy exhibiting corrosion resistance to the corrosive gases without bulk addition of Nb and/or Zr and without heat treatment at temperatures of 1000.degree.-1100.degree. C.

  20. Compositions of corrosion-resistant Fe-based amorphous metals suitable for producing thermal spray coatings

    DOEpatents

    Farmer, Joseph C; Wong, Frank M.G.; Haslam, Jeffery J; Ji, Xiaoyan; Day, Sumner D; Blue, Craig A; Rivard, John D.K.; Aprigliano, Louis F; Kohler, Leslie K; Bayles, Robert; Lemieux, Edward J; Yang, Nancy; Perepezko, John H; Kaufman, Larry; Heuer, Arthur; Lavernia, Enrique J

    2013-09-03

    A method of coating a surface comprising providing a source of amorphous metal that contains manganese (1 to 3 atomic %), yttrium (0.1 to 10 atomic %), and silicon (0.3 to 3.1 atomic %) in the range of composition given in parentheses; and that contains the following elements in the specified range of composition given in parentheses: chromium (15 to 20 atomic %), molybdenum (2 to 15 atomic %), tungsten (1 to 3 atomic %), boron (5 to 16 atomic %), carbon (3 to 16 atomic %), and the balance iron; and applying said amorphous metal to the surface by a spray.

  1. Compositions of corrosion-resistant Fe-based amorphous metals suitable for producing thermal spray coatings

    DOEpatents

    Farmer, Joseph C.; Wong, Frank M. G.; Haslam, Jeffery J.; Ji, Xiaoyan; Day, Sumner D.; Blue, Craig A.; Rivard, John D. K.; Aprigliano, Louis F.; Kohler, Leslie K.; Bayles, Robert; Lemieux, Edward J.; Yang, Nancy; Perepezko, John H.; Kaufman, Larry; Heuer, Arthur; Lavernia, Enrique J.

    2013-07-09

    A method of coating a surface comprising providing a source of amorphous metal that contains manganese (1 to 3 atomic %), yttrium (0.1 to 10 atomic %), and silicon (0.3 to 3.1 atomic %) in the range of composition given in parentheses; and that contains the following elements in the specified range of composition given in parentheses: chromium (15 to 20 atomic %), molybdenum (2 to 15 atomic %), tungsten (1 to 3 atomic %), boron (5 to 16 atomic %), carbon (3 to 16 atomic %), and the balance iron; and applying said amorphous metal to the surface by a spray.

  2. Room-temperature fabrication of light-emitting thin films based on amorphous oxide semiconductor

    SciTech Connect

    Kim, Junghwan Miyokawa, Norihiko; Ide, Keisuke; Toda, Yoshitake; Hiramatsu, Hidenori; Hosono, Hideo; Kamiya, Toshio

    2016-01-15

    We propose a light-emitting thin film using an amorphous oxide semiconductor (AOS) because AOS has low defect density even fabricated at room temperature. Eu-doped amorphous In-Ga-Zn-O thin films fabricated at room temperature emitted intense red emission at 614 nm. It is achieved by precise control of oxygen pressure so as to suppress oxygen-deficiency/excess-related defects and free carriers. An electronic structure model is proposed, suggesting that non-radiative process is enhanced mainly by defects near the excited states. AOS would be a promising host for a thin film phosphor applicable to flexible displays as well as to light-emitting transistors.

  3. Resistance of a directionally solidified gamma/gamma prime-delta eutectic alloy to recrystallization. [Ni-base alloy

    NASA Technical Reports Server (NTRS)

    Tewari, S. N.; Scheuermann, C. M.; Andrews, C. W.

    1976-01-01

    A lamellar nickel-base directionally-solidified eutectic gamma/gamma prime-delta alloy has potential as an advanced gas turbine blade material. The microstructural stability of this alloy was investigated. Specimens were plastically deformed by uniform compression or Brinell indentation, then annealed between 750 and 1120 C. Microstructural changes observed after annealing included gamma prime coarsening, pinch-off and spheroidization of delta lamellae, and appearance of an unidentified blocky phase in surface layers. All but the first of these was localized in severely deformed regions, suggesting that microstructural instability may not be a serious problem in the use of this alloy.

  4. Growth and microstructure formation of isothermally-solidified Zircaloy-4 joints brazed by a Zr-Ti-Cu-Ni amorphous alloy ribbon

    NASA Astrophysics Data System (ADS)

    Kim, K. H.; Lim, C. H.; Lee, J. G.; Lee, M. K.; Rhee, C. K.

    2013-10-01

    The microstructure and growth characteristics of Zircaloy-4 joints brazed by a Zr48Ti16Cu17Ni19 (at.%) amorphous filler metal have been investigated with regard to the controlled isothermal solidification and intermetallic formation. Two typical joints were produced depending on the isothermal brazing temperature: (1) a dendritic growth structure including bulky segregation in the central zone (at 850 °C), and (2) a homogeneous dendritic structure throughout the joint without segregation (at 890 °C). The primary α-Zr phase was solidified isothermally, nucleating to grow into a joint with a cellular or dendritic structure. Also, the continuous Zr2Ni and particulate Zr2Cu phases were formed in the segregated center zone and at the intercellular region, respectively, owing to the different solubility and atomic mobility of the solute elements (Ti, Cu, and Ni) in the α-Zr matrix. A disappearance of the central Zr2Ni phase was also rate-controlled by the outward diffusion of the Cu and Ni elements. When the detrimental Zr2Ni intermetallic phase was eliminated by a complete isothermal solidification at 890 °C, the strengths of the joints were high enough to cause yielding and fracture in the base metal, exceeding those of the bulk Zircaloy-4, at room temperature as well as at elevated temperatures (up to 400 °C).

  5. Deformation and fracture of a composite material based on a high-strength maraging steel covered with a melt-quenched Co69Fe4Cr4Si12B11 alloy layer

    NASA Astrophysics Data System (ADS)

    Sevost'yanov, M. A.; Kolmakov, A. G.; Molokanov, V. V.; Zabolotnyi, V. T.; Umnov, P. P.; Umnova, N. V.

    2011-04-01

    Multifractal analysis is used to study the deformation and fracture of a promising composite material consisting of a wire base made of K17N9M14 maraging steel covered with a surface layer made from a Co69Fe4Cr4Si12B11 amorphous alloy. As compared to its components, this material has a substantially better set of the mechanical properties.

  6. Melt Spinning of Crystalline Alloys.

    DTIC Science & Technology

    1980-01-01

    manufactoring iron-based amorphous alloys for magnetic appli- cations (2). Liebermann and Graham (3) and Kavesh (-)’have discussed the effect of melt spinning...and Mn. The main objectige was to determine whether the conclusions of Liebermann and Graham and Kavesh can be applied over a wide range of materials...length, width and thickness, p is density (2.71.103 Kgm-3 ), and W is the measured weight. Liebermann and Graham (3) applied Bernoulli’s equation

  7. Alloying Behavior and Properties of Al-Based Composites Reinforced with Al85Fe15 Metallic Glass Particles Fabricated by Mechanical Alloying and Hot Pressing Consolidation

    NASA Astrophysics Data System (ADS)

    Zhang, Lanxiang; Yang, LiKun; Leng, Jinfeng; Wang, Tongyang; Wang, Yan

    2017-01-01

    In this study, Al85Fe15 metallic glass particles with high onset crystallization temperature (1209 K) were synthesized by a mechanical alloying method. High-quality 6061Al-based composites reinforced with Al85Fe15 metallic glass particles were fabricated by a vacuum hot-pressing sintering technique. The glass particles with flake-like shape are distributed uniformly in the Al matrix. The bulk composites possess high relative density, excellent hardness and strength. The microhardness values of the Al-based bulk composites with the additions of 20 vol.% and 30 vol.% Al85Fe15 particles are 204 MPa and 248 MPa, respectively, which are much higher than that of 6061Al (61 MPa). The compressive yield strength of the 30 vol.% glass-reinforced composite is 478 MPa, which is enhanced by 273% compared with 6061Al. The amorphous characteristic and homogeneous dispersion of glass particles account for the excellent mechanical properties of the Al-based composites. In addition, the corrosion behavior of Al-based composites in a seawater solution has been investigated by electrochemical polarization measurements. Compared to 6061Al, the 30 vol.% glass-reinforced composite shows the lower corrosion/passive current density and larger passive region, indicating the greatly enhanced corrosion resistance.

  8. Efficient nanorod-based amorphous silicon solar cells with advanced light trapping

    SciTech Connect

    Kuang, Y.; Lare, M. C. van; Polman, A.; Veldhuizen, L. W.; Schropp, R. E. I.; Rath, J. K.

    2015-11-14

    We present a simple, low-cost, and scalable approach for the fabrication of efficient nanorod-based solar cells. Templates with arrays of self-assembled ZnO nanorods with tunable morphology are synthesized by chemical bath deposition using a low process temperature at 80 °C. The nanorod templates are conformally coated with hydrogenated amorphous silicon light absorber layers of 100 nm and 200 nm thickness. An initial efficiency of up to 9.0% is achieved for the optimized design. External quantum efficiency measurements on the nanorod cells show a substantial photocurrent enhancement both in the red and the blue parts of the solar spectrum. Key insights in the light trapping mechanisms in these arrays are obtained via a combination of three-dimensional finite-difference time-domain simulations, optical absorption, and external quantum efficiency measurements. Front surface patterns enhance the light incoupling in the blue, while rear side patterns lead to enhanced light trapping in the red. The red response in the nanorod cells is limited by absorption in the patterned Ag back contact. With these findings, we develop and experimentally realize a further advanced design with patterned front and back sides while keeping the Ag reflector flat, showing significantly enhanced scattering from the back reflector with reduced parasitic absorption in the Ag and thus higher photocurrent generation. Many of the findings in this work can serve to provide insights for further optimization of nanostructures for thin-film solar cells in a broad range of materials.

  9. High spatial resolution radiation detectors based on hydrogenated amorphous silicon and scintillator

    SciTech Connect

    Jing, Tao

    1995-05-01

    Hydrogenated amorphous silicon (a-Si:H) as a large-area thin film semiconductor with ease of doping and low-cost fabrication capability has given a new impetus to the field of imaging sensors; its high radiation resistance also makes it a good material for radiation detectors. In addition, large-area microelectronics based on a-Si:H or polysilicon can be made with full integration of peripheral circuits, including readout switches and shift registers on the same substrate. Thin a-Si:H p-i-n photodiodes coupled to suitable scintillators are shown to be suitable for detecting charged particles, electrons, and X-rays. The response speed of CsI/a-Si:H diode combinations to individual particulate radiation is limited by the scintillation light decay since the charge collection time of the diode is very short (< 10ns). The reverse current of the detector is analyzed in term of contact injection, thermal generation, field enhanced emission (Poole-Frenkel effect), and edge leakage. A good collection efficiency for a diode is obtained by optimizing the p layer of the diode thickness and composition. The CsI(Tl) scintillator coupled to an a-Si:H photodiode detector shows a capability for detecting minimum ionizing particles with S/N ~20. In such an arrangement a p-i-n diode is operated in a photovoltaic mode (reverse bias). In addition, a p-i-n diode can also work as a photoconductor under forward bias and produces a gain yield of 3--8 for shaping times of 1 {micro}s. The mechanism of the formation of structured CsI scintillator layers is analyzed. Initial nucleation in the deposited layer is sensitive to the type of substrate medium, with imperfections generally catalyzing nucleation. Therefore, the microgeometry of a patterned substrate has a significant effect on the structure of the CsI growth.

  10. The status of lightweight photovoltaic space array technology based on amorphous silicon solar cells

    NASA Technical Reports Server (NTRS)

    Hanak, Joseph J.; Kaschmitter, Jim

    1991-01-01

    Ultralight, flexible photovoltaic (PV) array of amorphous silicon (a-Si) was identified as a potential low cost power source for small satellites. A survey was conducted of the status of the a-Si PV array technology with respect to present and future performance, availability, cost, and risks. For existing, experimental array blankets made of commercial cell material, utilizing metal foil substrates, the Beginning of Life (BOL) performance at Air Mass Zero (AM0) and 35 C includes total power up to 200 W, power per area of 64 W/sq m and power per weight of 258 W/kg. Doubling of power per weight occurs when polyimide substrates are used. Estimated End of Life (EOL) power output after 10 years in a nominal low earth orbit would be 80 pct. of BOL, the degradation being due to largely light induced effects (-10 to -15 pct.) and in part (-5 pct.) to space radiation. Predictions for the year 1995 for flexible PV arrays, made on the basis of published results for rigid a-Si modules, indicate EOL power output per area and per weight of 105 W/sq m and 400 W/kg, respectively, while predictions for the late 1990s based on existing U.S. national PV program goals indicate EOL values of 157 W/sq m and 600 W/kg. Cost estimates by vendors for 200 W ultralight arrays in volume of over 1000 units range from $100/watt to $125/watt. Identified risks include the lack of flexible, space compatible encapsulant, the lack of space qualification effort, recent partial or full acquisitions of US manufacturers of a-Si cells by foreign firms, and the absence of a national commitment for a long range development program toward developing of this important power source for space.

  11. Effect of Si additions on thermal stability and the phase transition sequence of sputtered amorphous alumina thin films

    SciTech Connect

    Bolvardi, H.; Baben, M. to; Nahif, F.; Music, D. Schnabel, V.; Shaha, K. P.; Mráz, S.; Schneider, J. M.; Bednarcik, J.; Michalikova, J.

    2015-01-14

    Si-alloyed amorphous alumina coatings having a silicon concentration of 0 to 2.7 at. % were deposited by combinatorial reactive pulsed DC magnetron sputtering of Al and Al-Si (90-10 at. %) split segments in Ar/O{sub 2} atmosphere. The effect of Si alloying on thermal stability of the as-deposited amorphous alumina thin films and the phase formation sequence was evaluated by using differential scanning calorimetry and X-ray diffraction. The thermal stability window of the amorphous phase containing 2.7 at. % of Si was increased by more than 100 °C compared to that of the unalloyed phase. A similar retarding effect of Si alloying was also observed for the α-Al{sub 2}O{sub 3} formation temperature, which increased by more than 120 °C. While for the latter retardation, the evidence for the presence of SiO{sub 2} at the grain boundaries was presented previously, this obviously cannot explain the stability enhancement reported here for the amorphous phase. Based on density functional theory molecular dynamics simulations and synchrotron X-ray diffraction experiments for amorphous Al{sub 2}O{sub 3} with and without Si incorporation, we suggest that the experimentally identified enhanced thermal stability of amorphous alumina with addition of Si is due to the formation of shorter and stronger Si–O bonds as compared to Al–O bonds.

  12. Wear resistant zirconium base alloy article for water reactors

    SciTech Connect

    Gillett, J.E.; Shockling, L.A.; Sherwood, D.G.

    1988-03-01

    In a water reactor operating environment, the combination having improved fretting wear resistance is described comprising: an elongated tubular water displacer rod; having a low neutron absorption cross section guide support plates distributed along the length of the water displacer rod; the water displacer rod intersecting the guide support plates through apertures in the guide support plates; the water displacer rod having a plurality of spaced apart annular electrospark deposited coatings, each coating facing the wall of a respective aperture, the electrospark deposited coatings comprising Cr/sub 2/C/sub 3/; wherein the water displacer rod has a tube wall composed of a zirconium base alloy; and wherein the guide support plates are composed of a stainless steel alloy.

  13. Induced Anisotropy in FeCo-Based Nanocrystalline Ferromagnetic Alloys (HITPERM) by Very High Field Annealing

    NASA Technical Reports Server (NTRS)

    Johnson, F.; Garmestani, H.; Chu, S.-Y.; McHenry, M. E.; Laughlin, D. E.

    2004-01-01

    Very high magnetic field annealing is shown to affect the magnetic anisotropy in FeCo-base nanocrystalline soft ferromagnetic alloys. Alloys of composition Fe(44.5)Co(44.5)Zr(7)B(4) were prepared by melt spinning into amorphous ribbons, then wound to form toroidal bobbin cores. One set of cores was crystallized in a zero field at 600 deg. C for 1 h, then, field annealed at 17 tesla (T) at 480 deg. C for 1 h. Another set was crystallized in a 17-T field at 480 deg. C for 1 h. Field orientation was transverse to the magnetic path of the toroidal cores. An induced anisotropy is indicated by a sheared hysteresis loop. Sensitive torque magnetometry measurements with a Si cantilever sensor indicated a strong, uniaxial, longitudinal easy axis in the zero-field-crystallized sample. The source is most likely magnetoelastic anisotropy, caused by the residual stress from nanocrystallization and the nonzero magnetostriction coefficient for this material. The magnetostrictive coefficient lambda(5) is measured to be 36 ppm by a strain gage technique. Field annealing reduces the magnitude of the induced anisotropy. Core loss measurements were made in the zero-field-crystallized, zero-field-crystallized- than-field-annealed, and field-crystallized states. Core loss is reduced 30%-50% (depending on frequency) by field annealing. X-ray diffraction reveals no evidence of crystalline texture or orientation that would cause the induced anisotropy. Diffusional pair ordering is thought to be the cause of the induced anisotropy. However, reannealing the samples in the absence of a magnetic field at 480 deg. C does not completely remove the induced anisotropy.

  14. DEVELOPMENT OF PROTECTIVE COATING FOR TANTALUM BASE ALLOYS.

    DTIC Science & Technology

    TANTALUM ALLOYS, PROTECTIVE TREATMENTS), (*REFRACTORY COATINGS , SILICIDES ), TUNGSTEN ALLOYS, OXIDATION, OXIDES, OXYGEN, DIFFUSION, HIGH TEMPERATURE...HAFNIUM COMPOUNDS, ZIRCONIUM COMPOUNDS, NIOBIUM ALLOYS, VANADIUM ALLOYS, THERMAL EXPANSION, THERMAL STRESSES, MICROSTRUCTURE, YTTRIUM COMPOUNDS...TANTALUM COMPOUNDS, ADDITIVES, ALUMINUM, BORON, CHROMIUM, MANGANESE, MOLYBDENUM, TITANIUM, TUNGSTEN, VANADIUM, NIOBIUM , SODIUM COMPOUNDS, FLUORIDES, SILICON

  15. Tellurium n-type doping of highly mismatched amorphous GaN1-xAsx alloys in plasma-assisted molecular beam epitaxy

    DOE PAGES

    Novikov, S. V.; Ting, M.; Yu, K. M.; ...

    2014-10-01

    In this paper we report our study on n-type Te doping of amorphous GaN1-xAsx layers grown by plasma-assisted molecular beam epitaxy. We have used a low temperature PbTe source as a source of tellurium. Reproducible and uniform tellurium incorporation in amorphous GaN1-xAsx layers has been successfully achieved with a maximum Te concentration of 9×10²⁰ cm⁻³. Tellurium incorporation resulted in n-doping of GaN1-xAsx layers with Hall carrier concentrations up to 3×10¹⁹ cm⁻³ and mobilities of ~1 cm²/V s. The optimal growth temperature window for efficient Te doping of the amorphous GaN1-xAsx layers has been determined.

  16. Femtosecond laser-induced phase transformations in amorphous Cu{sub 77}Ni{sub 6}Sn{sub 10}P{sub 7} alloy

    SciTech Connect

    Zhang, Y.; Zou, G.; Wu, A.; Bai, H.; Liu, L.; Chen, N.; Zhou, Y.

    2015-01-14

    In this study, the femtosecond laser-induced crystallization of CuNiSnP amorphous ribbons was investigated by utilizing an amplified Ti:sapphire laser system. X-ray diffraction and scanning electronic microscope were applied to examine the phase and morphology changes of the amorphous ribbons. Micromachining without crystallization, surface patterning, and selective crystallization were successfully achieved by changing laser parameters. Obvious crystallization occurred under the condition that the laser fluence was smaller than the ablation threshold, indicating that the structural evolution of the material depends strongly on the laser parameters. Back cooling method was used to inhibit heat accumulation; a reversible transformation between the disordered amorphous and crystalline phases can be achieved by using this method.

  17. High-Performance Corrosion-Resistant Materials: Iron-Based Amorphous-Metal Thermal-Spray Coatings: SAM HPCRM Program ? FY04 Annual Report ? Rev. 0 - DARPA DSO & DOE OCRWM Co-Sponsored Advanced Materials Program

    SciTech Connect

    Farmer, J; Haslam, J; Wong, F; Ji, S; Day, S; Branagan, D; Marshall, M; Meacham, B; Buffa, E; Blue, C; Rivard, J; Beardsley, M; Buffa, E; Blue, C; Rivard, J; Beardsley, M; Weaver, D; Aprigliano, L; Kohler, L; Bayles, R; Lemieux, E; Wolejsza, T; Martin, F; Yang, N; Lucadamo, G; Perepezko, J; Hildal, K; Kaufman, L; Heuer, A; Ernst, F; Michal, G; Kahn, H; Lavernia, E

    2007-09-19

    The multi-institutional High Performance Corrosion Resistant Materials (HPCRM) Team is cosponsored by the Defense Advanced Projects Agency (DARPA) Defense Science Office (DSO) and the Department of Energy (DOE) Office of Civilian Radioactive Waste Management (OCRWM), and has developed new corrosion-resistant, iron-based amorphous metals that 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 very aggressive environments, including concentrated calcium-chloride brines at elevated temperature. Corrosion costs the Department of Defense billions of dollars every year, with an immense quantity of material in various structures undergoing corrosion. For example, in addition to fluid and seawater piping, ballast tanks, and propulsions systems, approximately 345 million square feet of structure aboard naval ships and crafts require costly corrosion control measures. The use of advanced corrosion-resistant materials to prevent the continuous degradation of this massive surface area would be extremely beneficial. The Fe-based corrosion-resistant, amorphous-metal coatings under development may prove of importance for applications on ships. Such coatings could be used as an 'integral drip shield' on spent fuel containers, as well as protective coatings that could be applied over welds, thereby preventing exposure to environments that might cause stress corrosion cracking. In the future, such new high-performance iron-based materials could be substituted for more-expensive nickel-based alloys, thereby enabling a reduction in the $58-billion life cycle cost for the long-term storage of the Nation's spent nuclear fuel by tens of percent.

  18. Role of alloying elements in adhesive transfer and friction of copper-base alloys

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1978-01-01

    Sliding friction experiments were conducted in a vacuum with binary-copper alloy riders sliding against a conventional bearing-steel surface with normal residual oxides present. The binary alloys contained 1 atomic percent of various alloying elements. Auger spectroscopy analysis was used to monitor the adhesive transfer of the copper alloys to the bearing-steel surface. A relation was found to exist between adhesive transfer and the reaction potential and free energy of formation of the alloying element in the copper. The more chemically active the element and the more stable its oxide, the greater was the adhesive transfer and wear of the copper alloy. Transfer occurred in all the alloys except copper-gold after relatively few (25) passes across the steel surface.

  19. Alloys based on NiAl for high temperature applications

    NASA Technical Reports Server (NTRS)

    Vedula, K. M.; Pathare, V.; Aslanidis, I.; Titran, R. H.

    1984-01-01

    The NiAl alloys for potential high temperature applications were studied. Alloys were prepared by powder metallurgy techniques. Flow stress values at slow strain rates and high temperatures were measured. Some ternary alloying additions (Hf, Ta and Nb) were identified. The mechanism of strengthening in alloys containing these additions appears to be a form of particle dislocation interaction. The effects of grain size and stoichiometry in binary alloys are also presented.

  20. Pack cementation diffusion coatings for iron-base alloys

    SciTech Connect

    Rapp, R.A.

    1995-02-01

    With the aid of computer-assisted calculations of the equilibrium vapor pressures in halide-activated cementation packs, processing conditions have been identified and experimentally verified for the codeposition of two or more alloying elements in a diffusion coating on a variety of steels. The Cr-Si ferrite layers have proven to be very resistant to high temperature cyclic oxidation and to pitting in aqueous solutions. The process has been patented, and is being transferred for industrial application, e.g. for water walls of utility boilers, etc. In the proposed extension of this project, the use of mixed pure metal powders in the pack will be extended to achieve similar ferrite Fe-Cr-Al coatings with excellent oxidation resistance, with the eventual transfer of the technology to industry. In other recent studies, Ni-base alloy rods were aluminized by the halide-activated pack cementation process to bring their average composition to that for the ORNL-developed Ni{sub 3}Al, for use as a welding rod. A similar effort to develop a welding rod for the ORNL Fe{sub 3}Al alloy did not yield reproducible coating compositions or growth kinetics. The continued effort to produce Duriron-type (Fe-18Si-5Cr) coatings on steels was not successful. Literature for the intrinsic diffusion coefficients suggests that this task cannot be achieved.