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Sample records for fe-based amorphous coatings

  1. Fe-Based Amorphous Coatings on AISI 4130 Structural Steel for Corrosion Resistance

    NASA Astrophysics Data System (ADS)

    Katakam, Shravana; Santhanakrishnan, S.; Dahotre, Narendra B.

    2012-06-01

    The current study focuses on synthesizing a novel functional coating for corrosion resistance applications, via laser surface alloying. The iron-based (Fe48Cr15Mo14Y2C15B) amorphous precursor powder is used for laser surface alloying on AISI 4130 steel substrate, with a continuous wave ytterbium Nd-YAG fiber laser. The corrosion resistance of the coatings is evaluated for different processing conditions. The microstructural evolution and the response of the microstructure to the corrosive environment is studied using x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Microstructural studies indicate the presence of face-centered cubic Fe-based dendrites intermixed within an amorphous matrix along with fine crystalline precipitates. The corrosion resistance of the coatings decrease with an increase in laser energy density, which is attributed to the precipitation and growth of chromium carbide. The enhanced corrosion resistance of the coatings processed with low energy density is attributed to the self-healing mechanism of this amorphous system.

  2. In Situ Laser Synthesis of Fe-Based Amorphous Matrix Composite Coating on Structural Steel

    NASA Astrophysics Data System (ADS)

    Katakam, Shravana; Hwang, Jun Y.; Paital, Sameer; Banerjee, Rajarshi; Vora, Hitesh; Dahotre, Narendra B.

    2012-12-01

    Iron-based amorphous materials, owing to their very high hardness, elastic modulus, wear resistance, and corrosion resistance, can be potential materials for surface modification and engineering of many structural alloys. The current study focuses on a novel functional coating, synthesized via laser cladding of an iron-based (Fe48Cr15Mo14Y2C15B) amorphous precursor powder, on AISI 4130 steel substrate, using a continuous-wave diode-pumped ytterbium laser. The coatings were characterized by different techniques like X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). SEM and TEM studies indicated the presence of Fe-based nanocrystalline dendrites intermixed within an amorphous matrix. A three-dimensional thermal modeling approach based on COMSOL Multiphysics (COMSOL Inc., Burlington, MA) was used to approximately predict the temperature evolution and cooling rates achieved during laser processing. The mechanisms for the formation of crystalline phases and the morphological changes in the microstructure were studied based on the thermal model developed. Although the thermal model predicted substantially high cooling rates as compared to the critical cooling rate required for retaining an amorphous phase, the formation of crystalline phases is attributed to formation of yttrium oxide, reducing the glass-forming ability, and formation of different oxide phases that act as heterogeneous nucleation sites resulting in the composite microstructure.

  3. Fabrication and Characterization of Thermal-Sprayed Fe-Based Amorphous/Nanocrystalline Composite Coatings: An Overview

    NASA Astrophysics Data System (ADS)

    Guo, Wenmin; Wu, Yuping; Zhang, Jianfeng; Hong, Sheng; Li, Gaiye; Ying, Guobing; Guo, Ji; Qin, Yujiao

    2014-10-01

    This review focuses on the recent development of iron (Fe)-based amorphous/nanocrystalline composite coatings, which have attracted much attention due to their attractive combination of high hardness/strength, elevated abrasive wear resistance, and enhanced corrosion resistance. Accompanying the advancements in various thermal spray technologies, industrial application fields of Fe-based amorphous/nanocrystalline composite coatings are becoming more diverse. In the main part, the typical empirical rules for the design of amorphous alloys with high glass-forming ability are generalized and discussed at first. Then various thermal spray technologies for the fabrication of Fe-based amorphous/nanocrystalline composite coatings, such as high velocity oxygen/air spray (HVOF/HVAF), air plasma spray (APS), low-pressure plasma spray (LPPS), high-energy plasma spray (HPS), and high velocity arc spray (HVAS) processes, are introduced. The microstructures, hardness, wear resistance, and corrosion resistance of Fe-based amorphous/nanocrystalline composite coatings formed using these thermal spray technologies are reviewed and compared. Finally, the existing challenges and future prospects are proposed.

  4. 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.

  5. 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.

  6. Tribocorrosion Behavior of Fe-Based Amorphous Composite Coating Reinforced by Al2O3 in 3.5% NaCl Solution

    NASA Astrophysics Data System (ADS)

    Yasir, Muhammad; Zhang, Cheng; Wang, Wei; Zhang, Zhi-Wei; Liu, Lin

    2016-09-01

    Although corrosion and friction/wear behavior of Fe-based amorphous coatings and their composites has been extensively studied during the past decade, there is very limited work related to tribocorrosion behavior. In this paper, the tribocorrosion behavior of a Fe-based amorphous composite coating reinforced with 20 wt.% Al2O3 particles was investigated in a 3.5% NaCl solution on a ball-on-disk tester and was compared to the monolithic amorphous coating and 316L stainless steel (SS). The results showed that the amorphous composite coating exhibited the highest tribocorrosion resistance among the three materials tested, as evidenced by the lowest coefficient of friction (~0.3) and tribocorrosion wear rate (~1.2 × 10-5 mm3/N·m). In addition, potentiodynamic polarization measurements before and during tribocorrosion testing demonstrated that corrosion resistance of the amorphous composite coating was not influenced so much by mechanical loading compared to the amorphous coating and the 316L SS. Observations on the worn surface revealed a corrosion-wear- and oxidational-wear-dominated tribocorrosion mechanism for the composite coatings. The excellent tribocorrosion resistance of the composite coating results from the effect of chemically stable Al2O3 phase which resists oxidation and delamination during sliding, along with poor wettability with corrosive NaCl droplets.

  7. Preliminary Study of Fabricating Bulk Fe-Based Amorphous Alloy by Cold Gas Dynamic Spraying

    NASA Astrophysics Data System (ADS)

    Guan, Leding; Yan, Biao; Long, Ling; Yang, Sha

    Cold gas dynamic spraying (CGDS) technique makes use of high-speed gas current to spray diversified metal, alloy and composite materials under room temperature or with a little heated. It is one kind of novel surface engineering technologies, aimed at eliminating such negative influences as oxidation, gasification, melt, crystallization and gas decomposition and so on existing in hot spraying technologies. Due to its peculiar characteristics such as low spraying temperature, non-oxidation, low stress among coating layers, compactification, and high utilization rate of raw materials, as well as effective applications in the domain of fabricating coatings, the CGDS technique has attracted great attention. As it has the advantages aforementioned, especially avoiding the changes of material properties resulted from high spraying temperature, CGDS provides a kind of revolutionary means for fabricating such heat-sensitive materials as amorphous alloys. The paper reviews the current situation and application development of the CGDS technique, and presents our preliminary exploration of fabricating bulk Fe-based amorphous alloy via CGDS together with mechanical milling process.

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

    PubMed

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

    2014-04-23

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

  9. 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.

  10. Characterization of Vc-Vb Particles Reinforced Fe-Based Composite Coatings Produced by Laser Cladding

    NASA Astrophysics Data System (ADS)

    Qu, K. L.; Wang, X. H.; Wang, Z. K.

    2016-03-01

    In situ synthesized VC-VB particles reinforced Fe-based composite coatings were produced by laser beam melting mixture of ferrovanadium (Fe-V) alloy, boron carbide (B4C), CaF2 and Fe-based self-melting powders. The results showed that VB particles with black regular and irregular blocky shape and VC with black flower-like shape were uniformly distributed in the coatings. The type, amount, and size of the reinforcements were influenced by the content of FeV40 and B4C powders. Compared to the substrate, the hardness and wear resistance of the composite coatings were greatly improved.

  11. 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.

  12. Microstructure and elevated temperature wear behavior of induction melted Fe-based composite coating

    NASA Astrophysics Data System (ADS)

    Hu, Ge; Meng, Huimin; Liu, Junyou

    2014-10-01

    Fe-based composite coating prepared onto the component of guide wheel using ultrasonic frequency inductive cladding (UFIC) technique has been investigated in terms of microstructure, phase constitutions, microhardness and elevated temperature wear behavior by scanning electron microscopy (SEM), energy-dispersive spectrometer (EDS), X-ray diffraction (XRD), Vickers microhardness tester and ball-on-disc wear tester. The results indicated that the primary phase in the coating contained austenite γ-Fe, eutectic γ-Fe/(Cr,Fe)2B, boride (Cr,Fe)2B and precipitation enriched in Mo. The average microhardness of the coating was 760 ± 10 HV0.2, which was three times higher than that of the substrate. With increasing temperature, the friction coefficients of the coating and high-chromium cast iron decreased gradually while the wear rates increased during dry sliding wear condition. The relative wear resistance of the coating was 1.63 times higher than that of the high-chromium cast iron at 500 °C, which was ascribed to the hard borides with high thermal stability uniformly embedded in the coating and the formation of dense transfer layer formed onto the worn surface. The high temperature wear mechanism of the coating was dominated by mild abrasive wear. The study revealed that Fe-based composite coating had excellent high temperature wear resistance under dry sliding wear condition.

  13. Formation of Aluminide Coatings on Fe-Based Alloys by Chemical Vapor Deposition

    SciTech Connect

    Zhang, Ying; Pint, Bruce A; Cooley, Kevin M; Haynes, James A

    2008-01-01

    Aluminide and Al-containing coatings were synthesized on commercial ferritic (P91) and austenitic (304L) alloys via a laboratory chemical vapor deposition (CVD) procedure for rigorous control over coating composition, purity and microstructure. The effect of the CVD aluminizing parameters such as temperature, Al activity, and post-aluminizing anneal on coating growth was investigated. Two procedures involving different Al activities were employed with and without including Cr-Al pellets in the CVD reactor to produce coatings with suitable thickness and composition for coating performance evaluation. The phase constitution of the as-synthesized coatings was assessed with the aid of a combination of X-ray diffraction, electron probe microanalysis, and existing phase diagrams. The mechanisms of formation of these CVD coatings on the Fe-based alloys are discussed, and compared with nickel aluminide coatings on Ni-base superalloys. In addition, Cr-Al pellets were replaced with Fe-Al metals in some aluminizing process runs and similar coatings were achieved.

  14. Advanced thermal barrier system bond coatings for use on Ni, Co-, and Fe-base alloy substrates

    NASA Technical Reports Server (NTRS)

    Stecura, S.

    1985-01-01

    New and improved Ni-, Co-, and Fe-base bond coatings have been identified for the ZrO2-Y2O3 thermal barrier coatings to be used on NI-, Co-, and Fe-base alloy substrates. These bond coatings were evaluated in a cyclic furnace between 1120 and 1175 C. It was found that MCrAlYb (where M = Ni, Co, or Fe) bond coating thermal barrier systems. The longest life was obtained with the FeCrAlYb thermal barrier system followed by NiCrAlYb and CoCrAlYb thermal barrier systems in that order.

  15. Fractal properties of worn surface of Fe-based alloy coatings during rolling contact process

    NASA Astrophysics Data System (ADS)

    Chen, Shu-ying; Wang, Hai-dou; Ma, Guo-zheng; Kang, Jia-jie; Xu, Bin-shi

    2016-02-01

    The rolling contact fatigue (RCF) failure procedure of Fe-based alloy coating, fabricated by high efficient plasma spray (PS) technology, was investigated by a double-roller test machine with oil lubrication under pure rolling contact condition. The fractal dimension (FD) was utilized to quantitatively characterize the profile of the worn surface at different experiment stage and the failure mechanism of the coating was discussed. The results indicated that the nonlinear morphologies of the worn surface of Fe-Cr alloy coating possessed excellent fractal properties. The failure procedure could be divided into four stages according to the value and change rule of FD, i.e. (1) running-in stage, (2) stable abrade stage, (3) accelerated damage stage, (4) unstable removal stage.

  16. 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.

  17. 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.

  18. Wear Resistant Amorphous and Nanocomposite Coatings

    SciTech Connect

    Racek, O

    2008-03-26

    Glass forming materials (critical cooling rate <10{sup 4}K.s{sup -1}) are promising for their high corrosion and wear resistance. During rapid cooling, the materials form an amorphous structure that transforms to nanocrystalline during a process of devitrification. High hardness (HV 1690) can be achieved through a controlled crystallization. Thermal spray process has been used to apply coatings, which preserves the amorphous/nanocomposite structure due to a high cooling rate of the feedstock particles during the impact on a substrate. Wear properties have been studied with respect to process conditions and feedstock material properties. Application specific properties such as sliding wear resistance have been correlated with laboratory tests based on instrumented indentation and scratch tests.

  19. Accumulated destructive effect of nanosecond repetitive voltage pulses on the insulated coatings of Fe-based nanocrystalline ribbon

    SciTech Connect

    Zhang, Yu; Liu, Jinliang

    2013-03-11

    Fe-based nanocrystalline ribbon is widely employed in pulsed power devices and accelerators. A temperature accumulation model is put forward to explain the accumulated destructive effect of discharge plasma bombardment on the TiO{sub 2} coatings of nanocrystalline ribbon under 50 Hz/100 ns voltage pulses. Experimental results revealed that the plasma channel expansion caused by air breakdown in the coating crack heated the coating repetitively, and the coating temperature was increased and accumulated around the crack. The fact that repetitive voltage pulses were more destructive than a single pulse with the same amplitude was caused by the intensified coating ablation under the temperature accumulation effect.

  20. 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.

    2016-09-01

    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.

  1. 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.

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

    SciTech Connect

    Farmer, J; Choi, J

    2007-07-18

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

  3. 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.

  4. Influence of the Spray Gun Type on Microstructure and Properties of HVAF Sprayed Fe-Based Corrosion Resistant Coatings

    NASA Astrophysics Data System (ADS)

    Milanti, A.; Koivuluoto, H.; Vuoristo, P.

    2015-10-01

    The aim of this study is to evaluate the microstructural details and corrosion properties of novel Fe-based coatings prepared using two different generations of HVAF spray guns. These two generations of HVAF guns are Activated Combustion HVAF (AC-HVAF, 2nd generation) M2 gun and Supersonic Air Fuel HVAF (SAF, 3rd generation) M3 gun. Structural details were analysed using x-ray diffractometry and field-emission scanning electron microscope. Higher denseness with homogeneous microstructure was achieved for Fe-based coating deposited by the M3 process. Such coatings exhibit higher particle deformation and lower oxide content compared to coatings manufactured with M2 gun. Corrosion properties were studied by open-cell potential measurements and electrochemical impedance spectroscopy. The lower porosity and higher interlamellar cohesion of coating manufactured with M3 gun prevent the electrolyte from penetrating through the coating and arriving to the substrate, enhancing the overall corrosion resistance. This can be explained by the improved microstructures and coating performance.

  5. 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.

  6. HVOF Spraying of Fe-Based MMC Coatings with In Situ Formation of Hard Particles by Hot Isostatic Pressing

    NASA Astrophysics Data System (ADS)

    Röttger, A.; Weber, S. L.; Theisen, W.; Rajasekaran, B.; Vaßen, R.

    2012-03-01

    Thick (2-3 mm) Fe-base coatings with admixed ferrotitanium (Fe30Ti70) were applied to austenitic steel by a high-velocity oxy-fuel process (HVOF). Hot-isostatic pressing (HIP) was carried out to the decrease porosity and to increase the material strength, wear resistance, and adhesive bond strength of the deposited coating to the substrate material. SEM and XRD investigations confirmed the formation of hard titanium carbide (TiC) particles during HIP treatment as a result of strong carbon diffusion out of the metal matrix and into the Fe30Ti70 particles. The mechanical and wear properties of the densified coatings were investigated by means of shear tests, hardness measurements, and abrasive wear tests. A comparison of the coatings in the as-sprayed and the HIPed state showed a large increase in the wear resistance due to in situ TiC formation.

  7. Suspension plasma sprayed composite coating using amorphous powder feedstock

    NASA Astrophysics Data System (ADS)

    Chen, Dianying; Jordan, Eric H.; Gell, Maurice

    2009-03-01

    Al 2O 3-ZrO 2 composite coatings were deposited by the suspension plasma spray process using molecularly mixed amorphous powders. X-ray diffraction (XRD) analysis shows that the as-sprayed coating is composed of α-Al 2O 3 and tetragonal ZrO 2 phases with grain sizes of 26 nm and 18 nm, respectively. The as-sprayed coating has 93% density with a hardness of 9.9 GPa. Heat treatment of the as-sprayed coating reveals that the Al 2O 3 and ZrO 2 phases are homogeneously distributed in the composite coating.

  8. 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.

  9. A Study on Cavitation Erosion and Corrosion Behavior of Al-, Zn-, Cu-, and Fe-Based Coatings Prepared by Arc Spraying

    NASA Astrophysics Data System (ADS)

    Kim, Jin-Hong; Lee, Myeong-Hoon

    2010-12-01

    Investigation to find a suitable coating material for a rudder application has been carried out in this study. Ten different coatings were prepared by arc spraying with Al-, Zn-, Cu-, and Fe-based wire feedstock. Both the cavitation erosion and marine corrosion behavior of the arc-sprayed coatings were evaluated, and compared with the conventional anti-corrosion paint. In terms of marine corrosion resistance, aluminum coating was the best among the tested coating systems while stainless steel coating showed the highest resistance against cavitation erosion. In addition, the effects of both the Si composition in Al-based coatings and the Ni composition in Cu- and Fe- based coatings were discussed in this study.

  10. Microstructure and Mechanical Properties of Cr-SiC Particles-Reinforced Fe-Based Alloy Coating

    NASA Astrophysics Data System (ADS)

    Wang, Fu-cheng; Du, Xiao-dong; Zhan, Ma-ji; Lang, Jing-wei; Zhou, Dan; Liu, Guang-fu; Shen, Jian

    2015-12-01

    In this study, SiC particles were first coated with Cr to form a layer that can protect the SiC particles from dissolution in the molten pool. Then, the Cr-SiC powder was injected into the tail of molten pool during plasma-transferred arc welding process (PTAW), where the temperature was relatively low, to prepare Cr-SiC particles reinforced Fe-based alloy coating. The microstructure and phase composition of the powder and surface coatings were analyzed, and the element distribution and hardness at the interfacial region were also evaluated. The protective layer consists of Cr3Si, Cr7C3, and Cr23C6, which play an important role in the microstructure and mechanical properties. The protective layer is dissolved in the molten pool forming a flocculent region and a transition region between the SiC particles and the matrix. The tribological performance of the coating was also assessed using a ring-block sliding wear tester with GGr15 grinding ring under 490 and 980 N load. Cr-SiC particles-reinforced coating has a lower wear rate than the unreinforced coating.

  11. Preparation and uses of amorphous boron carbide coated substrates

    DOEpatents

    Riley, R.E.; Newkirk, L.R.; Valencia, F.A.; Wallace, T.C.

    1979-12-05

    Cloth is coated at a temperature below about 1000/sup 0/C with amorphous boron-carbon deposits in a process which provides a substantially uniform coating on all the filaments making up each yarn fiber bundle of the cloth. The coated cloths can be used in the as-deposited condition for example as wear surfaces where high hardness values are needed; or multiple layers of coated cloths can be hot-pressed to form billets useful for example in fusion reactor wall armor. Also provided is a method of controlling the atom ratio of B:C of boron-carbon deposits onto any of a variety of substrates, including cloths.

  12. Preparation and uses of amorphous boron carbide coated substrates

    DOEpatents

    Riley, Robert E.; Newkirk, Lawrence R.; Valencia, Flavio A.

    1981-09-01

    Cloth is coated at a temperature below about 1000.degree. C. with amorphous boron-carbon deposits in a process which provides a substantially uniform coating on all the filaments making up each yarn fiber bundle of the cloth. The coated cloths can be used in the as-deposited condition for example as wear surfaces where high hardness values are needed; or multiple layers of coated cloths can be hot-pressed to form billets useful for example in fusion reactor wall armor. Also provided is a method of controlling the atom ratio of B:C of boron-carbon deposits onto any of a variety of substrates, including cloths.

  13. 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.

  14. Particle In-Flight and Coating Properties of Fe-Based Feedstock Materials Sprayed with Modern Thermal Spray Systems

    NASA Astrophysics Data System (ADS)

    Bobzin, Kirsten; Kopp, Nils; Warda, Thomas; Petkovic, Ivica; Schaefer, Marcel; Landes, Klaus Dieter; Forster, Guenter; Zimmermann, Stephan; Marques, Jose-Luis; Kirner, Stefan; Kauffeldt, Marina; Schein, Jochen

    2013-03-01

    New developments in the field of thermal spraying systems (increased particle velocities, enhanced process stability) are leading to improved coatings. Innovations in the field of feedstock materials are supporting this trend. The combination of both has led to a renaissance of Fe-based feedstocks. Using modern APS or HVOF systems, it is now possible to compete with classical materials for wear and corrosion applications like Ni-basis or metal-matrix composites. This study intends to give an analysis of the in-flight particle and spray jet properties achievable with two different modern thermal spraying systems using Fe-based powders. The velocity fields are measured with the Laser Doppler Anemometry. Resulting coatings are analyzed and a correlation with the particle in-flight properties is given. The experiments are accompanied by computational fluid dynamics simulations of spray jet and particle velocities, leading to a comprehensive analysis of the achievable particle properties with state-of-the-art HVOF and APS systems.

  15. 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.

  16. Microstructure and Sliding Wear Behavior of Fe-Based Coatings Manufactured with HVOF and HVAF Thermal Spray Processes

    NASA Astrophysics Data System (ADS)

    Milanti, A.; Matikainen, V.; Bolelli, G.; Koivuluoto, H.; Lusvarghi, L.; Vuoristo, P.

    2016-06-01

    The microstructure and micromechanical behavior of thermally sprayed Fe-based coatings manufactured with high-velocity oxygen fuel (HVOF) and high-velocity air fuel (HVAF) processes were investigated. Fe-Cr-Ni-Si-B-C and Fe-Cr-Ni-Mo-Si-B-C powders were used as the feedstock materials. The coatings showed a highly dense microstructure with near-zero oxidation. The microstructure of the feedstock powders was better retained when sprayed with HVAF process. Differential scanning calorimetry revealed two small exothermic peaks at about 600 °C for the HVOF-sprayed coatings, without any increase in weight in thermogravimetric analysis. It suggested the re-precipitation of carbides that were dissolved during spraying due to the higher particle temperature reported by spray diagnostics system during the HVOF process (≈1800 °C) compared to the HVAF one (≈1400 °C). Micro- and nano-indentations helped to show the difference in inter-lamellar cohesive strength and, in turn, in the particle deposition mechanism. Coatings sprayed with Fe-Cr-Ni-Mo-Si-B-C composition possessed higher sliding wear resistance than that of Fe-Cr-Ni-Si-B-C due to higher nano-hardness. More specifically, HVOF-sprayed Fe-Cr-Ni-Mo-Si-B-C coating showed the largest intra-lamellar hardness, the largest elasticity, and high quality of particle interfaces which resulted in lower sliding wear rate.

  17. Substrate/layer interface of amorphous-carbon hard coatings

    NASA Astrophysics Data System (ADS)

    Böhme, O.; Cebollada, A.; Yang, S.; Teer, D. G.; Albella, J. M.; Román, E.

    2000-08-01

    A combined study of the crystalline structure, the chemical interaction, and diffusion processes of the substrate/layer interface of amorphous-carbon hard coatings is presented. The structure of the coatings and their gradient layer interface to a chromium buffer layer has been investigated on two substrates [Si(100) and tool steel] using x-ray diffraction (XRD). Chemical interaction and diffusion processes at the interfaces and within the layers were analyzed by Auger electron spectroscopy and x-ray photoemission spectroscopy depth profiles. The chromium buffer layer revealed similar textured structure on both substrates. The subsequent gradient layer was determined (within XRD limits) to be amorphous and composed of an amorphous-carbon and chromium-carbide composite. The chromium carbide maintains the same stoichiometry (Cr3C2), regardless of the gradually changing chromium content. No large-scale interdiffusion was measured, either between or within the layers.

  18. Performance of Al-Rich Oxidation Resistant Coatings For Fe-Base Alloys

    SciTech Connect

    Pint, Bruce A

    2010-01-01

    Aluminum-rich coatings made by chemical vapor deposition and pack cementation on ferritic (e.g. Fe-9Cr-1Mo) and austenitic (Type 304L) substrates are being evaluated at 650-800 C. For oxidation testing, a humid air environment was used to quantify coating performance, as uncoated substrates experience rapid oxidation at these temperatures. A main goal of this work is to demonstrate the potential benefits and problems with alumina-forming coatings. The higher exposure temperatures were selected to accelerate the degradation of the coating by interdiffusion with the substrate. A general conclusion of this testing was that coatings with less Al and a ferritic Fe(Al) structure could be more durable than higher Al content aluminide coatings which have a large thermal expansion mismatch with these substrates. A lifetime model has been developed using diffusion and oxidation observations to predict coating performance as a function of temperature and initial coating composition. To test and improve the model, additional experiments are now being conducted to determine the effect of substrate composition (e.g. Cr content using Fe-12Cr and Fe-9Cr-2W substrates) and exposure temperature on the critical Al content for coating failure. Because of the unexpectedly low level of Al measured at coating failure ({approx}3.5at.% at 700 C), exposures of specimens with thick ({approx}200 {mu}m) high Al content coatings were stopped after 10kh at 800 C and 20kh at 700 C because extremely long times to failure were predicted. Post-exposure Al concentration profiles for these specimens were measured using electron microprobe.

  19. Performance of Al-rich Oxidation Resistant Coatings for Fe-Base Alloys

    SciTech Connect

    Pint, Bruce A; Zhang, Ying

    2011-01-01

    Aluminum-rich coatings made by chemical vapor deposition and pack cementation on ferritic (e.g. Fe-9Cr-1Mo) and austenitic (Type 304L) substrates are being evaluated at 650-800 C. For oxidation testing, a humid air environment was used to quantify coating performance, as uncoated substrates experience rapid oxidation at these temperatures. A main goal of this work is to demonstrate the potential benefits and problems with alumina-forming coatings. The higher exposure temperatures were selected to accelerate the degradation of the coating by interdiffusion with the substrate. A general conclusion of this testing was that coatings with less Al and a ferritic Fe(Al) structure could be more durable than higher Al content aluminide coatings which have a large thermal expansion mismatch with these substrates. A lifetime model has been developed using diffusion and oxidation observations to predict coating performance as a function of temperature and initial coating composition. To test and improve the model, additional experiments are now being conducted to determine the effect of substrate composition (e.g. Cr content using Fe-12Cr and Fe-9Cr-2W substrates) and exposure temperature on the critical Al content for coating failure. Because of the unexpectedly low level of Al measured at coating failure ({approx}3.5 at.% at 700 C), exposures of specimens with thick ({approx}200 {micro}m) high Al content coatings were stopped after 10kh at 800 C and 20kh at 700 C because extremely long times to failure were predicted. Post-exposure Al concentration profiles for these specimens were measured using electron microprobe.

  20. Plasma deposited stability enhancement coating for amorphous ketoprofen.

    PubMed

    Bosselmann, Stephanie; Owens, Donald E; Kennedy, Rachel L; Herpin, Matthew J; Williams, Robert O

    2011-05-01

    A hydrophobic fluorocarbon coating deposited onto amorphous ketoprofen via pulsed plasma-enhanced chemical vapor deposition (PPECVD) significantly prolonged the onset of recrystallization compared to uncoated drug. Rapid freezing (RF) employed to produce amorphous ketoprofen was followed by PPECVD of perfluorohexane. The effect of coating thickness on the recrystallization and dissolution behavior of ketoprofen was investigated. Samples were stored in open containers at 40°C and 75% relative humidity, and the onset of recrystallization was monitored by DSC. An increase in coating thickness provided enhanced stability against recrystallization for up to 6 months at accelerated storage conditions (longest time of observation) when compared to three days for uncoated ketoprofen. Results from XPS analysis demonstrated that an increase in coating thickness was associated with improved surface coverage thus enabling superior protection. Dissolution testing showed that at least 80% of ketoprofen was released in buffer pH 6.8 from all coated samples. Overall, an increase in coating thickness resulted in a more complete drug release due to decreased adhesion of the coating to the substrate.

  1. Hardness and microplasticity of nanocrystalline and amorphous calcium phosphate coatings

    NASA Astrophysics Data System (ADS)

    Ievlev, V. M.; Kostyuchenko, A. V.; Darinskii, B. M.; Barinov, S. M.

    2014-02-01

    The hardness of thin (1.0-4.0 μm) hydroxyapatite coatings with different structures (nanocrystalline, amorphous-crystalline, and amorphous) grown by rf magnetron sputtering on Ti and Si plates has been studied using the nanoindentation method. All the grown structures are characterized by the strain which has reversible and irreversible components. The hardness of nanocrystalline coatings (about 10 GPa) corresponds to the average hardness of hydroxyapatite single crystals. The structure of nanocrystalline coatings in the indentation zone and outside it has been investigated and changes in the structure under the indenter have been revealed using high-resolution transmission electron microscopy. From a comparison of the hardnesses of coatings with different structures and based on an analysis of the intragranular structure, it has been assumed that the plastic deformation occurs according to a dislocation-free mechanism. The plastic deformation is interpreted in terms of the cluster representation of the hydroxyapatite structure and amorphous calcium phosphates of the same elemental composition and cluster-boundary sliding during the deformation.

  2. Pack cementation diffusion coatings for Fe-base and refractory alloys. Final report

    SciTech Connect

    Rapp, R.A.

    1998-03-10

    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 and refractory metal alloys. A new comprehensive theory to treat the multi-component thermodynamic equilibria in the gas phase for several coexisting solid phases was developed and used. Many different processes to deposit various types of coatings on several types of steels were developed: Cr-Si codeposition for low- or medium-carbon steels, Cr-Al codeposition on low-carbon steels to yield either a Kanthal-type composition (Fe-25Cr-4Al in wt.%) or else a (Fe, Cr){sub 3}Al surface composition. An Fe{sub 3}Al substrate was aluminized to achieve an FeAl surface composition, and boron was also added to ductilize the coating. The developmental Cr-lean ORNL alloys with exceptional creep resistance were Cr-Al coated to achieve excellent oxidation resistance. Alloy wires of Ni-base were aluminized to provide an average composition of Ni{sub 3}Al for use as welding rods. Several different refractory metal alloys based on Cr-Cr{sub 2}Nb have been silicided, also with germanium additions, to provide excellent oxidation resistance. A couple of developmental Cr-Zr alloys were similarly coated and tested.

  3. 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.

  4. 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.

  5. Plastic Deformation in an Amorphous Ni-P Coating

    SciTech Connect

    Shen, Yongfeng; Liu, Wenning; Sun, Xin; Xue, W. Y.; Wang, Y. D.; Zuo, Liang; Liaw, Peter K.

    2012-05-01

    An experimental and numerical investigation of the hardness and associated plastic deformation in as-deposited and as-annealed nickel-phosphorus (Ni-P) coatings was conducted. In addition to the indentation-deformation behavior, the deformation morphology underneath the indenter was examined. The yield strength extracted from the indentation data is as high as 5.6 GPa, indicating pressure-sensitive plasticity. Results show that the as-deposited Ni-P coating was deformed appreciably through the shear-band mechanism with semi-circular and radial shear-band morphologies. From the incremental loading-unloading cyclic experiments, the phenomena on hardening and recovery, which have scarcely been recognized in amorphous materials at room temperature, were observed in the amorphous coating using instrumented nanoindentation. A numerical simulation of the interfacial indentation test between the Ni-P coating and the substrate reveals the pile-up and shear bands of the Ni-P coating that were observed during the indentation tests.

  6. Codeposited chromium and silicon diffusion coatings for Fe-base alloys via pack cementation

    SciTech Connect

    Harper, M.A.; Rapp, R.A. )

    1994-10-01

    The simultaneous deposition of Cr and Si into plain carbon, low-alloy, and austenitic steels using a halide-activated pack-cementation process is described. Equilibrium partial pressures of gaseous species have been calculated using the STEPSOL computer program to aid in designing specific processes for codepositing the desired ratios of Cr and Si into a given alloy. The calculations indicate that NaCl-activated packs are chromizing, while NaF-activated packs deposit more Si with less Cr. THe use of a [open quotes]dual activator[close quotes] (e.g., NaF+NaCl) allows for the deposition of both Cr and Si in the desired amounts. Single-phase ferritic coatings (150-250 microns thick) with a surface concentration of 20-35 wt.% Cr and 2-4% Si have been grown on AISI 1018, Fe-2.25Cr-1.0Mo-0.15C, and Fe-0.5Cr-0.5Mo-0.2C steels using packs containing a 90 wt.% Cr-10Si binary source alloy, a NaF+NaCl activator, and a silica filler. Two-phase coatings (approximately 75 microns thick) containing 20-25 wt.% Cr and 2.0-2.4% Si have been obtained on 304 stainless steel using packs containing a 90 wt.% Cr-10Si binary source alloy, a NaF activator, and an alumina filler. The same pack chemistry allowed the diffusion of Cr and Si into the austenitic Incoloy 800 alloy without a phase change. A coated Fe-2.25Cr-1.0Mo-0.15C coupon with a surface concentration of Fe-34 wt.% Cr-3Si was cyclically oxidized in air at 700[degrees]C for over four months and 47 cycles. The weight gain was very low (<0.2 mg/cm[sup 2]) with no scale spalling detected. Coated coupons of AISI 1018 steel, and Fe-0.5Cr-0.5Mo-0.2C steel have shown excellent oxidation-sulfidation resistance in reducing, sulfur-containing atmospheres at temperatures from 400 to 700[degrees]C and in erosion and erosion-oxidation testing in air at 650 and 850[degrees]C.

  7. In situ detection method for obtaining permeability of Fe-based amorphous alloys: ac resistance measurement for Fe{sub 84}Nb{sub 7}B{sub 9}

    SciTech Connect

    Ichitsubo, Tetsu; Matsubara, Eiichiro; Tanaka, Satoshi; Nishiyama, Nobuyuki; Amiya, Kenji

    2005-01-17

    In this letter, we propose an in situ detection method for obtaining permeability of soft magnetic Fe-based amorphous alloys. The temperature dependence of ac resistance was measured at different frequencies during heat treatment of Fe{sub 84}Nb{sub 7}B{sub 9} amorphous alloys. A significant increase in the ac ({approx}1000 kHz) resistance appears at around 920 K during the heating process, which arises from the skin effect caused by a marked increase in sample permeability. This skin effect diminishes when the sample is heated to approximately 1100 K, which corresponds to the decrease in its permeability. Consequently, we note that the ac resistance measurement is useful for quick in situ assessment to achieve the soft magnetic property of an Fe-based amorphous alloy.

  8. Amorphous metal formulations and structured coatings for corrosion and wear resistance

    DOEpatents

    Farmer, Joseph C.

    2011-12-13

    A system for coating a surface comprising providing a source of amorphous metal that contains more than 11 elements and applying the amorphous metal that contains more than 11 elements to the surface by a spray. Also a coating comprising a composite material made of amorphous metal that contains more than 11 elements. An apparatus for producing a corrosion-resistant amorphous-metal coating on a structure comprises a deposition chamber, a deposition source in the deposition chamber that produces a deposition spray, the deposition source containing a composite material made of amorphous metal that contains more than 11 elements, and a system that directs the deposition spray onto the structure.

  9. Amorphous metal formulations and structured coatings for corrosion and wear resistance

    DOEpatents

    Farmer, Joseph C.

    2014-07-15

    A system for coating a surface comprising providing a source of amorphous metal that contains more than 11 elements and applying the amorphous metal that contains more than 11 elements to the surface by a spray. Also a coating comprising a composite material made of amorphous metal that contains more than 11 elements. An apparatus for producing a corrosion-resistant amorphous-metal coating on a structure comprises a deposition chamber, a deposition source in the deposition chamber that produces a deposition spray, the deposition source containing a composite material made of amorphous metal that contains more than 11 elements, and a system that directs the deposition spray onto the structure.

  10. Bacterial adhesion on amorphous and crystalline metal oxide coatings.

    PubMed

    Almaguer-Flores, Argelia; Silva-Bermudez, Phaedra; Galicia, Rey; Rodil, Sandra E

    2015-12-01

    Several studies have demonstrated the influence of surface properties (surface energy, composition and topography) of biocompatible materials on the adhesion of cells/bacteria on solid substrates; however, few have provided information about the effect of the atomic arrangement or crystallinity. Using magnetron sputtering deposition, we produced amorphous and crystalline TiO2 and ZrO2 coatings with controlled micro and nanoscale morphology. The effect of the structure on the physical-chemical surface properties was carefully analyzed. Then, we studied how these parameters affect the adhesion of Escherichia coli and Staphylococcus aureus. Our findings demonstrated that the nano-topography and the surface energy were significantly influenced by the coating structure. Bacterial adhesion at micro-rough (2.6 μm) surfaces was independent of the surface composition and structure, contrary to the observation in sub-micron (0.5 μm) rough surfaces, where the crystalline oxides (TiO2>ZrO2) surfaces exhibited higher numbers of attached bacteria. Particularly, crystalline TiO2, which presented a predominant acidic nature, was more attractive for the adhesion of the negatively charged bacteria. The information provided by this study, where surface modifications are introduced by means of the deposition of amorphous or crystalline oxide coatings, offers a route for the rational design of implant surfaces to control or inhibit bacterial adhesion.

  11. Iron-Based Amorphous Coatings Produced by HVOF Thermal Spray Processing-Coating Structure and Properties

    SciTech Connect

    Beardsley, M B

    2008-03-26

    The feasibility to coat large SNF/HLW containers with a structurally amorphous material (SAM) was demonstrated on sub-scale models fabricated from Type 316L stainless steel. The sub-scale model were coated with SAM 1651 material using kerosene high velocity oxygen fuel (HVOF) torch to thicknesses ranging from 1 mm to 2 mm. The process parameters such as standoff distance, oxygen flow, and kerosene flow, were optimized in order to improve the corrosion properties of the coatings. Testing in an electrochemical cell and long-term exposure to a salt spray environment were used to guide the selection of process parameters.

  12. Magnetoimpedance of a glass-coated amorphous microwire

    NASA Astrophysics Data System (ADS)

    Sinha, S.; Das, B.; Mandal, K.

    2009-04-01

    A maximum magnetoimpedance (˜66%) was observed at 5.2 MHz in a positive magnetostrictive glass-coated amorphous Co83.2Mn7.6Si5.8B3.3 microwire. Giant magnetoimpedance in this microwire was increased to 129% on short-duration heat treatment by passing four current pulses of amplitude of 100 mA and each of 12 s duration. Magnetoimpedance of the as-quenched and heat treated microwires was investigated as a function of a dc magnetic field Hdc within ±120 Oe and frequency f up to 12.85 MHz. The magnetization measurements of the samples indicated that the increase in giant magnetoimpedance on short-duration annealing is due to the increase in outer shell volume of the domain structure.

  13. Direct coating adherent diamond films on Fe-based alloy substrate: the roles of Al, Cr in enhancing interfacial adhesion and promoting diamond growth.

    PubMed

    Li, X J; He, L L; Li, Y S; Yang, Q; Hirose, A

    2013-08-14

    Direct CVD deposition of dense, continuous, and adherent diamond films on conventional Fe-based alloys has long been considered impossible. The current study demonstrates that such a deposition can be realized on Al, Cr-modified Fe-based alloy substrate (FeAl or FeCrAl). To clarify the fundamental mechanism of Al, Cr in promoting diamond growth and enhancing interfacial adhesion, fine structure and chemical analysis around the diamond film-substrate interface have been comprehensively characterized by transmission electron microscopy. An intermediate graphite layer forms on those Al-free substrates such as pure Fe and FeCr, which significantly deteriorates the interfacial adhesion of diamond. In contrast, such a graphite layer is absent on the FeAl and FeCrAl substrates, whereas a very thin Al-rich amorphous oxide sublayer is always identified between the diamond film and substrate interface. These comparative results indicate that the Al-rich interfacial oxide layer acts as an effective barrier to prevent the formation of graphite phase and consequently enhance diamond growth and adhesion. The adhesion of diamond film formed on FeCrAl is especially superior to that formed on FeAl substrate. This can be further attributed to a synergetic effect including the reduced fraction of Al and the decreased substrate thermal-expansion coefficient on FeCrAl in comparison with FeAl, and a mechanical interlocking effect due to the formation of interfacial chromium carbides. Accordingly, a mechanism model is proposed to account for the different interfacial adhesion of diamond grown on the various Fe-based substrates.

  14. Fabrication and Characterization of Amorphous Alumina-Yttria-Stabilized Zirconia Coatings by Air Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Song, Xuemei; Suhonen, Tomi; Varis, Tommi; Huang, Liping; Zheng, Xuebin; Zeng, Yi

    2014-12-01

    Almost fully amorphous coatings of near-eutectic alumina-yttria-stabilized zirconia (Al2O3-YSZ) were prepared by air plasma spraying using Al2O3 and 8 mol.% YSZ crystalline-mixed powders. The coatings consist of mostly an amorphous phase with a small amount of nanocrystals. Various characterization techniques were used to understand coating formation and the origins of the different phases within the coatings. The formation of the mostly amorphous structure is attributed to the high glass-forming ability of Al2O3-YSZ and the appropriate plasma spraying conditions. A small number of nanocrystals are produced during crystallization of the incoming molten droplets or by recrystallization of the solidified splats by accumulated heat. Scanning electron microscopy shows that the coatings have a dense, layered structure with low porosity, and bright-field transmission electron microscopy images indicate sharp interface rather than grit-blasted wavy surface between splats and substrates in the coatings. The as-sprayed amorphous coatings crystallized at around 920 °C and micro-hardness of the as-sprayed amorphous coatings was 8.12 GPa.

  15. [Microcosmic mechanisms of amorphous indomethacin crystallization and the influence of nano-coating on crystallization].

    PubMed

    Hui, Ou-Yang; Yi, Tao; Zheng, Qin; Liu, Feng

    2011-06-01

    Amorphous drugs have higher solubility, better oral bioavailability and are easier to be absorbed than their crystalline counterparts. However, the amorphous drugs, with weak stability, are so easy to crystallize that they will lose the original advantages. Polarization microscope, scanning electron microscope, differential scanning calorimetry, X-ray diffractomer and Raman spectroscopy were used to study the microcosmic crystallization mechanisms of amorphous indometacin and the performance of the drug crystals. The results showed that the growth rate of amorphous indometacin crystals at the free surface was markedly faster than that through the bulk, and that the crystal growth rate decreased observably after spraying an ultrathin melting gold (10 nm) at the free surface of the drug. These results indicated that the high growth rates of amorphous drugs crystals at the free surface were the key to their stability and that an ultrathin coating could be applied to enhance the stability of amorphous drugs.

  16. Anodic Behavior of SAM2X5 Material Applied as Amorphous Coatings

    SciTech Connect

    Hailey, P D; Farmer, J C; Day, S D; Rebak, R B

    2007-08-10

    Iron-based amorphous alloys are desirable industrial materials since they are highly resistant to corrosion and possess enhanced hardness for wear resistance. The amorphous materials can be produced from the melt as powder and later spray deposited as coatings on large engineering structures. As a laboratory experiment, SAM2X5 powder was coated on electrochemical specimens of 304SS for testing. Results show that the coated specimens did not perform satisfactorily during the laboratory testing. This is because of partial devitrification during the deposition of the powder on the small specimen substrates.

  17. Enhanced Physical Stability of Amorphous Drug Formulations via Dry Polymer Coating.

    PubMed

    Capece, Maxx; Davé, Rajesh

    2015-06-01

    Although amorphous solid drug formulations may be advantageous for enhancing the bioavailability of poorly soluble active pharmaceutical ingredients, they exhibit poor physical stability and undergo recrystallization. To address this limitation, this study investigates stability issues associated with amorphous solids through analysis of the crystallization behavior for acetaminophen (APAP), known as a fast crystallizer, using a modified form of the Avrami equation that kinetically models both surface and bulk crystallization. It is found that surface-enhanced crystallization, occurring faster at the free surface than in the bulk, is the major impediment to the stability of amorphous APAP. It is hypothesized that a novel use of a dry-polymer-coating process referred to as mechanical-dry-polymer-coating may be used to inhibit surface crystallization and enhance stability. The proposed process, which is examined, simultaneously mills and coats amorphous solids with polymer, while avoiding solvents or solutions, which may otherwise cause stability or crystallization issues during coating. It is shown that solid dispersions of APAP (64% loading) with a small particle size (28 μm) could be prepared and coated with the polymer, carnauba wax, in a vibratory ball mill. The resulting amorphous solid was found to have excellent stability as a result of inhibition of surface crystallization. PMID:25902736

  18. Enhanced Physical Stability of Amorphous Drug Formulations via Dry Polymer Coating.

    PubMed

    Capece, Maxx; Davé, Rajesh

    2015-06-01

    Although amorphous solid drug formulations may be advantageous for enhancing the bioavailability of poorly soluble active pharmaceutical ingredients, they exhibit poor physical stability and undergo recrystallization. To address this limitation, this study investigates stability issues associated with amorphous solids through analysis of the crystallization behavior for acetaminophen (APAP), known as a fast crystallizer, using a modified form of the Avrami equation that kinetically models both surface and bulk crystallization. It is found that surface-enhanced crystallization, occurring faster at the free surface than in the bulk, is the major impediment to the stability of amorphous APAP. It is hypothesized that a novel use of a dry-polymer-coating process referred to as mechanical-dry-polymer-coating may be used to inhibit surface crystallization and enhance stability. The proposed process, which is examined, simultaneously mills and coats amorphous solids with polymer, while avoiding solvents or solutions, which may otherwise cause stability or crystallization issues during coating. It is shown that solid dispersions of APAP (64% loading) with a small particle size (28 μm) could be prepared and coated with the polymer, carnauba wax, in a vibratory ball mill. The resulting amorphous solid was found to have excellent stability as a result of inhibition of surface crystallization.

  19. Assessment of Abrasive Wear of Nanostructured WC-Co and Fe-Based Coatings Applied by HP-HVOF, Flame, and Wire Arc Spray

    NASA Astrophysics Data System (ADS)

    Lima, C. R. C.; Libardi, R.; Camargo, F.; Fals, H. C.; Ferraresi, V. A.

    2014-10-01

    Thermal spray processes have been widely used to minimize losses caused by wear mechanisms. Sprayed deposits using conventional wire and powder materials have been long solving tribological problems in engineering equipment. More recently, the option for new different technologies and consumables like nanostructured powder materials and nanocomposite cored wires have expanded the possibilities for technical solutions. Cored wire technology allows the use of compositions that cannot be drawn into wire form like carbides in metallic matrix and high-temperature materials, thus, intensifying the use of spraying processes with low operating cost to demanding wear and corrosion applications. The objective of this work was to study the mechanical characteristics and wear performance of coatings obtained by Flame, Wire Arc, and HVOF spraying using selected nanostructured WC10Co4Cr, WC12Co, and Fe-based 140 MXC powder and wire materials. Abrasive wear performance of the coatings was determinate following the ASTM G-65 standard. Based on the results, a higher abrasive wear resistance was found for the HVOF-sprayed WC10Co4Cr nanostructured coating.

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

    NASA Astrophysics Data System (ADS)

    Lu, Lei; Fan, Xi'an; Zhang, Jianyi; Hu, Xiaoming; Li, Guangqiang; Zhang, Zhan

    2014-10-01

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

  1. Physical properties and microstructural performance of Sn modified laser amorphous-nanocrystals reinforced coating

    NASA Astrophysics Data System (ADS)

    Li, Jia-Ning; Gong, Shui-Li

    2013-01-01

    An amorphous-nanocrystals reinforced composite coating was fabricated on TA15 titanium alloy substrate by laser alloying of Al-Sn-B4C-SiC-TiN-Y2O3 mixed powders, which greatly improved the wear resistance of substrate. Experimental results indicated that Al-Sn nanocrystalline phases were produced through in situ metallurgical reactions, which blocked the motion of dislocation. The productions of the eutectics, such as Ti-Si greatly promoted the formation of amorphous phases in such coating. Compared with the substrate, higher wear resistance of laser alloying coating was mainly ascribed to the hard phase, amorphous-nanocrystalline phases and fine grain strengthening. This research provided essential theoretical and experimental basis to promote the application of laser alloying technique in modern aviation industry.

  2. Comparative Study on the Corrosion Resistance of Fe-Based Amorphous Metal, Borated Stainless Steel and Ni-Cr-Mo-Gd Alloy

    SciTech Connect

    Lian, Tiangan; Day, Daniel; Hailey, Phillip; Choi, Jor-Shan; Farmer, Joseph

    2007-07-01

    Iron-based amorphous alloy 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} was compared to borated stainless steel and Ni-Cr-Mo-Gd alloy on their corrosion resistance in various high-concentration chloride solutions. The melt-spun ribbon of this iron-based amorphous alloy have demonstrated a better corrosion resistance than the bulk borated stainless steel and the bulk Ni-Cr-Mo-Gd alloy, in high-concentration chloride brines at temperatures 90 deg. C or higher. (authors)

  3. Coating of calcia-doped ceria with amorphous silica shell by seeded polymerization technique

    SciTech Connect

    El-Toni, Ahmed Mohamed . E-mail: el-toni@mail.tagen.tohoku.ac.jp; Yin, Shu; Yabe, Shinryo; Sato, Tsugio

    2005-07-12

    Calcia-doped ceria is of potential interest as an ultraviolet (UV) radiation blocking material in personal care products. However, its high catalytic ability for oxidation of organic materials makes it difficult to use as a sunscreen material. Therefore, calcia-doped ceria was coated with amorphous silica by means of seeded polymerization technique in order to depress its oxidation catalytic ability. The catalytic ability as well as UV-shielding ability was investigated for coated particles.

  4. 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

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

    SciTech Connect

    Blink, J; Choi, J; Farmer, J

    2007-07-09

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

  6. Synthesis and Microstructural Evolution of Amorphous/Nanocrystalline Steel Coatings by Different Thermal-Spray Processes

    NASA Astrophysics Data System (ADS)

    Varadaraajan, V.; Guduru, Ramesh K.; Mohanty, P. S.

    2013-04-01

    Amorphous/nanocrystalline coatings are useful in high strength and wear-resistant applications. In the present study, the microstructural evolution of a nanocrystalline high performance steel coatings developed by different spray processes along with a novel "hybrid thermal spray" technique was studied. The hybrid-spray process combines arc and high-velocity oxy-fuel (HVOF) techniques, in which the molten metal at the arcing tip is atomized and rapidly propelled toward the substrate by HVOF jet. This so-called hybrid concept offers the benefits of productivity of electric arc spray combined with improved coating densities of HVOF. The microstructural characterization of the hybrid-spray coatings was performed by x-ray diffraction, electron microscopy, and differential scanning calorimetry, and then compared with coatings of the similar material developed by plasma-, HVOF-, and arc-spray processes individually. The HVOF- and plasma-spray coatings showed amorphous structures with very fine nanocrystals embedded, whereas hybrid- and arc-spray techniques yielded completely crystalline coatings with grain size in the range of several nanometers. The final microstructures in different spray processes could be attributed to the precursor materials employed, process temperatures, and cooling rates during the deposition process.

  7. Amorphous alumina oxidation protective coatings for Zircaloy based on a compositional gradient layer system

    NASA Astrophysics Data System (ADS)

    Park, Sang Tae

    Waterside corrosion of the Zircaloy cladding encasing the uranium oxide pellets is one of the primary factors limiting high "burn up" of nuclear fuel in pressurized water reactors (PWRs). High "burn up" can significantly impact plant safety and economics. Amorphous aluminum oxide coatings with aluminum-based compositional gradient layers (CGLs) were fabricated to develop ceramic coating corrosion protection systems for Zircaloy. Aluminum films were deposited on Zircaloy substrates by electron-beam evaporation, and two-step heat treatments were performed at near the melting temperature of aluminum. Amorphous alumina coatings by rf magnetron sputtering were overcoated on the CGL structures. Morphological and compositional studies were completed using field emission scanning electron microscopy (FE SEM), energy dispersive x-ray analysis (EDX), and auger electron spectroscopy (AES). The AES depth profiles of the annealed coatings showed that gradient compositions of Al, Zr, and O were obtained. Glancing angle x-ray diffraction (GAXRD) analysis showed that a variety of intermetallic and oxide phases (such as Al3Zr, Al2Zr3, Al2O3, ZrO2 and Zr3O) were formed in the coatings during processing. The intermetallic layers improved the adhesion property of the alumina overcoating to Zircaloy substrate, and functioned as oxidation resistant layers. In spite of the successful construction of the compositional gradient layer system with a good adhesion and thermal stability, and the report about the stability of pure alumina and amorphous ceramics in hydrothermal conditions, the amorphous alumina coatings in our study were not stable under nuclear reactor conditions of subcritical water at 350°C and 20.1 MPa (3000 psi). We investigated the behavior of amorphous alumina thin films deposited on Zircaloy substrates in the near-supercritical water. When the coatings were exposed to the subcritical conditions, hydrothermally grown well-faceted crystallite formation was observed

  8. Tribological properties, corrosion resistance and biocompatibility of magnetron sputtered titanium-amorphous carbon coatings

    NASA Astrophysics Data System (ADS)

    Dhandapani, Vishnu Shankar; Subbiah, Ramesh; Thangavel, Elangovan; Arumugam, Madhankumar; Park, Kwideok; Gasem, Zuhair M.; Veeraragavan, Veeravazhuthi; Kim, Dae-Eun

    2016-05-01

    Amorphous carbon incorporated with titanium (a-C:Ti) was coated on 316L stainless steel (SS) by magnetron sputtering technique to attain superior tribological properties, corrosion resistance and biocompatibility. The morphology, topography and functional groups of the nanostructured a-C:Ti coatings in various concentrations were analyzed using atomic force microscopy (AFM), Raman, X-Ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Raman and XPS analyses confirmed the increase in sp2 bonds with increasing titanium content in the a-C matrix. TEM analysis confirmed the composite nature of the coating and the presence of nanostructured TiC for Ti content of 2.33 at.%. This coating showed superior tribological properties compared to the other a-C:Ti coatings. Furthermore, electrochemical corrosion studies were performed against stimulated body fluid medium in which all the a-C:Ti coatings showed improved corrosion resistance than the pure a-C coating. Preosteoblasts proliferation and viability on the specimens were tested and the results showed that a-C:Ti coatings with relatively high Ti (3.77 at.%) content had better biocompatibility. Based on the results of this work, highly durable coatings with good biocompatibility could be achieved by incorporation of optimum amount of Ti in a-C coatings deposited on SS by magnetron sputtering technique.

  9. Amorphous boron coatings produced with vacuum arc deposition technology

    NASA Astrophysics Data System (ADS)

    Klepper, C. C.; Hazelton, R. C.; Yadlowsky, E. J.; Carlson, E. P.; Keitz, M. D.; Williams, J. M.; Zuhr, R. A.; Poker, D. B.

    2002-05-01

    In principle, boron (B) as a material has many excellent surface properties, including corrosion resistance, very high hardness, refractory properties, and a strong tendency to bond with most substrates. The potential technological benefits of the material have not been realized, because it is difficult to deposit it as coatings. B is difficult to evaporate, does not sputter well, and cannot be thermally sprayed. In this article, first successful deposition results from a robust system, based on the vacuum (cathodic) arc technology, are reported. Adherent coatings have been produced on 1100 Al, CP-Ti, Ti-6Al-4V, 316 SS, hard chrome plate, and 52 100 steel. Composition and thickness analyses have been performed by Rutherford backscattering spectroscopy. Hardness (H) and modules (E) have been evaluated by nanoindentation. The coatings are very pure and have properties characteristic of B suboxides. A microhardness of up to 27 GPa has been measured on a 400-nm-thick film deposited on 52 100 steel, with a corresponding modulus of 180 GPa. This gives a very high value for the H/E ratio, a figure-of-merit for impact resistance of the film. A number of applications are contemplated, including corrosion/abrasion protection for die-casting dies and improved wear resistance for biomedical implants.

  10. 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.

  11. 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

  12. Tailoring the optical and hydrophobic property of zinc oxide nanorod by coating with amorphous graphene

    NASA Astrophysics Data System (ADS)

    Pahari, D.; Das, N. S.; Das, B.; Chattopadhyay, K. K.; Banerjee, D.

    2016-09-01

    Zinc oxide (ZnO) nanorods were synthesized at room temperature on potassium permanganate activated silicon and glass substrate by simple chemical method using zinc acetate as precursor. To modify the surface energy of the as prepared ZnO thin films the samples were coated with amorphous graphene (a-G) synthesized by un-zipping of chemically synthesized amorphous carbon nanotubes (a-CNTs). All the pure and coated samples were characterized by x-ray diffraction, field emission scanning electron microscope, Raman spectroscopy, and Fourier transformed infrared spectroscopy. The roughness analysis of the as prepared samples was done by atomic force microscopic analysis. The detail optical properties of all the samples were studied with the help of a UV-Visible spectrophotometer. The surface energy of the as prepared pure and coated samples was calculated by measuring the contact angle of two different liquids. It is seen that the water repellence of ZnO nanorods got increased after they are being coated with a-Gs. Also even after UV irradiation the contact angle remain same unlike the case for the uncoated sample where the contact angle gets decreased significantly after UV irradiation. Existing Cassie-Wenzel model has been employed along with the Owen's approach to determine the different components of surface energy.

  13. Bio-silica coated with amorphous manganese oxide as an efficient catalyst for rapid degradation of organic pollutant.

    PubMed

    Dang, T D; Banerjee, A N; Cheney, M A; Qian, S; Joo, S W; Min, B K

    2013-06-01

    A novel rapid green one-step method is developed for the preparation of bio-silica coated with amorphous MnO2 nanoparticles by treating bio-silica with an acidic permanganate solution. The method developed has the advantage of selectively coating the surface of either one or both sides of the porous silica structure with a thin catalytic active amorphous MnO2 layer in a controlled way. The uncoated and MnO2 coated bio-silica are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The catalytic activity of amorphous MnO2-coated bio-silica is examined by degrading organic dye at ambient condition. The as-synthesized samples show highly efficient and rapid degradation of Rhodamine B. The simplicity and cost-effectiveness of the materials and method can be very useful for highly efficient degradation of organic pollutants for environmental remediation. PMID:23434705

  14. Wetting and spreading of long-chain ZDOL polymer nanodroplet on graphene-coated amorphous carbon

    NASA Astrophysics Data System (ADS)

    Sorkin, V.; Zhang, Y. W.

    2014-12-01

    Wetting transparency/translucency/opacity of graphene recently has attracted great interest. The underlying mechanisms and physics for simple liquid droplets containing small molecules on graphene coated crystalline substrates have been studied extensively. However, the behavior of more complicated polymeric droplets on graphene coated amorphous substrates has not been explored. In this work, we perform molecular dynamics simulations to examine the wetting of long-chain ZDOL polymeric droplet on graphene coated amorphous hydrogenated diamond-like carbon or DLCH. We find that at room temperature, the droplet adopts a nearly spherical cap shape with no protruding foot on bare DLCH, and a complex multi-layered structure is formed at the droplet-substrate interface. With addition of graphene layers, externally, the height of the droplet decreases and the protruding foot at the droplet edge appears and grows in size; while internally, the complex multi-layered structure near the droplet-substrate interface remains, but the density distribution for the formed layers becomes increasingly non-uniform. A steady state of the droplet is attained when the number of graphene layers reaches three. These changes can be explained by the interactions between the droplet and substrate across the number of graphene layers. Therefore, it is concluded that the graphene monolayer and bilayer are translucent, while trilayer and above are opaque from the wetting point of view.

  15. Dextran-coated superparamagnetic amorphous Fe–Co nanoalloy for magnetic resonance imaging applications

    SciTech Connect

    An, Lu; Yu, Yanrong; Li, Xuejian; Liu, Wei; Yang, Hong; Wu, Dongmei; Yang, Shiping

    2014-01-01

    Graphical abstract: A dextran-coated Fe–Co nanoalloy was developed serving as a sensitive contrast agent for magnetic resonance imaging applications. - Highlights: • Amorphous Fe–Co nanoalloy was prepared via wet chemical reduction approach. • The Fe–Co nanoalloy is water-soluble, stable, and biocompatible. • The Fe–Co nanoalloy is superparamagnetic. • The Fe–Co nanoalloy exhibits T{sub 2}-weighted MR enhancement both in vitro and in vivo. - Abstract: For magnetic resonance imaging applications, a facile approach for water-soluble dextran coated amorphous Fe–Co nanoalloy was developed. The as-synthesized nanoalloy had a diameter of 9 nm with a narrow size distribution and showed superparamagnetic property with a saturated magnetization (Ms) of 25 emu/g. In vitro cytotoxicity test revealed that it was biocompatible at a concentration below 120 μg/mL. It can be uptaken by HeLa cells effectively and resulted in the obvious T{sub 2} effect after internalization. Biodistribution studies in conjunction with inductively coupled plasma-atomic emission spectroscopy (ICP-AES) confirmed that Fe–Co nanoalloy was preferentially accumulated in lung and spleen after intravenous injection for 4 h. In vivo MRI, dextran-coated Fe–Co nanoalloy can serve as a sensitive contrast agent for MR imaging, especially in the spleen, so we believe that it maybe hold great promise for diagnosis of splenic disease by appropriately functionalizing their surface.

  16. Wear and Corrosion Behaviors of FeCrBSiNbW Amorphous/Nanocrystalline Coating Prepared by Arc Spraying Process

    NASA Astrophysics Data System (ADS)

    Cheng, J. B.; Wang, Z. H.; Xu, B. S.

    2012-09-01

    FeCrBSiNbW coatings were synthesized using robotically manipulating twin wires arc spraying system. The microstructure and mechanical properties of the coating were characterized. The coating has a laminated structure, and its porosity is 2.8%. The microstructure of the coating consists of amorphous and α-(Fe,Cr) nanocrystalline. The nanocrystalline grains with a scale of 20-75 nm are homogenously dispersed in amorphous matrix. The results show that FeCrBSiNbW coating has excellent wear and corrosion resistance. The wear resistance of the coating is about 4.6 times higher than that of 3Cr13 coating under the same testing condition. In 3.5% NaCl aqueous solution, the amorphous/nanocrystalline coating presents lower I corr values in polarization curves and higher fitted R t values in EIS plots than that of the 0Cr18Ni9 coating (chemical composition by EDAX analysis: C1.07-O12.38-Si0.49-Cr15.18-Mn0.89-Ni7.09-Fe62.24 at.%).

  17. Fabrication of barium/strontium carbonate coated amorphous carbon nanotubes as an improved field emitter

    NASA Astrophysics Data System (ADS)

    Maity, S.; Jha, A.; Das, N. S.; Chattopadhyay, K. K.

    2013-02-01

    Amorphous carbon nanotubes (aCNTs) were synthesized by a chemical reaction between ferrocene and ammonium chloride at a temperature ˜250 ∘C in an air furnace. As-synthesized aCNTs were coated with the barium/strontium carbonate through a simple chemical process. The coating of barium/strontium carbonate was confirmed by a high resolution transmission electron microscopy, X-ray diffraction, and Fourier transformed infrared spectroscopy. Morphology of the as-prepared samples was studied by field emission scanning electron microscopy. Thermal gravimetric analysis showed that barium/strontium carbonate coated aCNTs are more stable than the pristine aCNTs. As-prepared barium/strontium carbonate coated aCNTs showed significantly improved field emission properties with a turn-on field as low as 2.5 V/μm. The variation of field emission characteristics of the barium/strontium carbonate coated aCNTs with interelectrode distances was also studied.

  18. Effect of heat treatment on pulsed laser deposited amorphous calcium phosphate coatings.

    PubMed

    García, F; Arias, J L; Mayor, B; Pou, J; Rehman, I; Knowles, J; Best, S; León, B; Pérez-Amor, M; Bonfield, W

    1998-01-01

    Amorphous calcium phosphate coatings were produced by pulsed laser deposition from targets of nonstoichiometric hydroxyapatite (Ca/P = 1.70) at a low substrate temperature of 300 degrees C. They were heated in air at different temperatures: 300, 450, 525 and 650 degrees C. Chemical and structural analyses of these coatings were performed using X-ray diffraction (XRD), FTIR, and SEM, XRD analysis of the as-deposited and heated coatings revealed that their crystallinity improved as heat treatment temperature increased. The main phase was apatitic, with some beta-tricalcium phosphate in the coatings heated at 525 and 600 degrees C. In the apatitic phase there was some carbonate substitution for phosphate and hydroxyl ions at 450 degrees C and almost solely for phosphate at 525 and 600 degrees C as identified by FTIR. This was accompanied by a higher hydroxyl content at 525 and 600 degrees C. At 450 degrees C a texture on the coating surface was observable by SEM that was attributable to a calcium hydroxide and calcite formation by XRD. These phases almost disappeared at 600 degrees C, probably due to a transformation into calcium oxide.

  19. 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.

  20. Magnetoelastic Anisotropy of FeSiB Glass-Coated Amorphous Microwires

    NASA Astrophysics Data System (ADS)

    Liu, Kai-Huang; Lu, Zhi-Chao; Liu, Tian-Cheng; Li, De-Ren

    2013-01-01

    The magnetoelastic anisotropy of Fe77.5Si7.5B15 glass-coated amorphous microwires is investigated by the law of approach to saturation magnetization in comparison with the ferromagnetic resonance technique. The anisotropy field of the inner core determined by the former method is 7.6 × 104 A/m, which is larger than the value 2.5 × 104 A/m measured by the ferromagnetic resonance method. This difference is ascribed to the skin effect and the uneven distribution of the internal stresses. However, the anisotropy field of the outer shell has a negative value indicating that it has an easy basal plane.

  1. Microstructure and physical properties of laser Zn modified amorphous-nanocrystalline coating on a titanium alloy

    NASA Astrophysics Data System (ADS)

    Li, Jia-Ning; Gong, Shui-Li; Shi, Yi-Ning; Suo, Hong-Bo; Wang, Xi-Chang; Deng, Yun-Hua; Shan, Fei-Hu; Li, Jian-Quan

    2014-02-01

    A Zn modified amorphous-nanocrystalline coating was fabricated on a Ti-6Al-4V alloy by laser cladding of the Co-Ti-B4C-Zn-Y2O3 mixed powders. Such coating was researched by means of a scanning electron microscope (SEM) and a high resolution transmission electron microscope (HRTEM), etc. Experimental results indicated that the Co5Zn21 and TiB2 nanocrystalline phases were produced through in situ metallurgical reactions, which blocked the motion of dislocation, and TiB2 grew along (010), (111) and (024). The Co5Zn21 nanocrystals were produced attached to the ceramics, which mainly consisted of the Co nanoparticles embedded in a heterogeneous zinc, and had varied crystalline orientations.

  2. Synthesis and Characterization of Zr-BASED Amorphous and Crystalline Composite Coating on Ti Substrate by Laser Cladding

    NASA Astrophysics Data System (ADS)

    Tang, D. M.; Zhang, D. C.; Peng, W.; Luo, Z. C.; Wu, X. Q.; Wang, Y. M.; Lin, J. G.

    2014-02-01

    A thin strip of a Zr-based alloy with a composition of Zr60Cu25Fe5Al10 (in atom percent) was used as a raw material, and the composite coatings containing Zr-based amorphous phase and crystallites on Ti substrate were fabricated by a one-step laser cladding method without protection. The microstructure, phase constitution, microhardness and wear properties of the coatings were investigated. The results indicate that the microstructure of the coatings is strongly dependent on the laser scanning speed under the conditions of the laser power of 1300 W and laser beam diameter of 6 mm, and the composite coating mainly containing amorphous phase with a small amount of the crystallites can be obtained at the laser scanning speed of 10 mm/s. The composite coating exhibits much higher microhardness than the pure Ti substrate, and thus it behaves superior wear resistance in comparison with the substrate.

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

    NASA Astrophysics Data System (ADS)

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

    1999-09-01

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

  4. 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.

  5. Electron Cloud in Steel Beam Pipe vs Titanium Nitride Coated and Amorphous Carbon Coated Beam Pipes in Fermilab's Main Injector

    SciTech Connect

    Backfish, Michael

    2013-04-01

    This paper documents the use of four retarding field analyzers (RFAs) to measure electron cloud signals created in Fermilab’s Main Injector during 120 GeV operations. The first data set was taken from September 11, 2009 to July 4, 2010. This data set is used to compare two different types of beam pipe that were installed in the accelerator. Two RFAs were installed in a normal steel beam pipe like the rest of the Main Injector while another two were installed in a one meter section of beam pipe that was coated on the inside with titanium nitride (TiN). A second data run started on August 23, 2010 and ended on January 10, 2011 when Main Injector beam intensities were reduced thus eliminating the electron cloud. This second run uses the same RFA setup but the TiN coated beam pipe was replaced by a one meter section coated with amorphous carbon (aC). This section of beam pipe was provided by CERN in an effort to better understand how an aC coating will perform over time in an accelerator. The research consists of three basic parts: (a) continuously monitoring the conditioning of the three different types of beam pipe over both time and absorbed electrons (b) measurement of the characteristics of the surrounding magnetic fields in the Main Injector in order to better relate actual data observed in the Main Injector with that of simulations (c) measurement of the energy spectrum of the electron cloud signals using retarding field analyzers in all three types of beam pipe.

  6. Synthesis and characterization of hydrogenated amorphous carbon-based tribological coatings

    NASA Astrophysics Data System (ADS)

    Zhao, Bo

    The development of low friction surfaces is needed to improve performance and energy efficiency for macroscopic and microscopic mechanical systems. Minimizing unwanted friction and wear can lead to dramatic economic and environmental benefits. Such research is an important approach to addressing the world's increasing energy concerns. Hydrogenated amorphous carbon (CHx) thin films are ideal for some tribological applications because of their low wear rates and low coefficients of friction. The primary goal of this research is to develop and characterize modified CHx coatings so that they can be used in a variety of applications in humid environments and under higher contact loads. Doping CHx films with a small amount of sulfur (CHx+S) enables them to achieve ultralow coefficients of friction in ambient humidity. Temperature-programmed desorption and quartz crystal microbalance were used to determine that sulfur reduces water adsorption onto the film surface. Sulfur-doped films showed a decrease in the activation energy for desorption of water, or weaker film-water bonding. This decrease causes a shorter residence time of water on the surface and less equilibrium water adsorption. At a given relative humidity, sulfur-doped films adsorbed less water than undoped films. Even at 90% relative humidity, sulfur-doped films adsorbed less than 1 monolayer of water. Sulfur acts to passivate dangling bonds at the film surface susceptible to oxidation and reduces the number of surface dipoles available to attract water. This enhanced hydrophobicity increases the contact angle of adsorbed water islands, which lowers the likelihood of coalescence into a water meniscus on the film surface. The decreased quantity and discontinuity of adsorbed water molecules are responsible for CHx+S being able to achieve lower friction in humid environments. Adding titanium diboride (TiB2) to the CHx coatings yielded films with improved mechanical properties. TiB2 and CH x were synthesized in

  7. Timescales and mechanisms of formation of amorphous silica coatings on fresh basalts at Kīlauea Volcano, Hawai'i

    NASA Astrophysics Data System (ADS)

    Chemtob, Steven M.; Rossman, George R.

    2014-10-01

    Young basalts from Kīlauea Volcano, Hawai'i, frequently feature opaque surface coatings, 1-80 μm thick, composed of amorphous silica and Fe-Ti oxides. These coatings are the product of interaction of the basaltic surface with volcanically-derived acidic fluids. Previous workers have identified these coatings in a variety of contexts on Hawai'i, but the timescales of coating development, coating growth rates, and factors controlling lateral coating heterogeneity were largely unconstrained. We sampled and analyzed young lava flows (of varying ages, from hours to ~ 40 years) along Kīlauea's southwest and east rift zones to characterize variation in silica coating properties across the landscape. Coating thickness varies as a function of flow age, flow surface type, and proximity to acid sources like local fissure vents and regional plumes emitted from Kīlauea Caldera and Pu'u Ō'ō. Silica coatings that form in immediate proximity to acid sources are more chemically pure than those forming in higher pH environments, which contain significant Al and Fe. Incipient siliceous alteration was observed on basalt surfaces as young as 8 days old, but periods of a year or more are required to develop contiguous coatings with obvious opaque coloration. Inferred coating growth rates vary with environmental conditions but were typically 1-5 μm/year. Coatings form preferentially on flow surfaces with glassy outer layers, such as spatter ramparts, volcanic bombs, and dense pahoehoe breakouts, due to glass strain weakening during cooling. Microtextural evidence suggests that the silica coatings form both by in situ dissolution-reprecipitation and by deposition of silica mobilized in solution. Thin films of water, acidified by contact with volcanic vapors, dissolved near-surface basalt, then precipitated amorphous silica in place, mobilizing more soluble cations. Additional silica was transported to and deposited on the surface by silica-bearing altering fluids derived from the

  8. Microstructure and Dry Sliding Wear Behavior of Fe-Based (Cr, Fe)7C3 Composite Coating Fabricated by PTA Welding Process

    NASA Astrophysics Data System (ADS)

    Yuan, Y. L.; Li, Z. G.

    2013-11-01

    Using Cr3C2 and Fe-CrNiBSi powder blends as raw materials, an α-Fe matrix composite coating reinforced by in situ (Cr, Fe)7C3 rods, with a thickness of about 3.6 mm, was fabricated on the surface of AISI A36 low carbon steel by means of plasma-transferred arc welding. The results of microstructural analysis show that in the coating, a large number of carbides, (Cr, Fe)7C3, in rod shape grow, and radiate around some half-dissolved Cr3C2 particles. The results of dry sliding wear tests at loads 100, 200, and 300 N show that the wear resistances of (Cr, Fe)7C3-reinforced coating, respectively, are about 6.9, 14.9, and 17 times higher than that of nonreinforced pure Fe-CrNiBSi alloy coating; the average value and fluctuation range of friction coefficient (FC) of (Cr, Fe)7C3-reinforced coating are less than those of pure Fe-CrNiBSi alloy coating; the main wear mechanisms of pure Fe-CrNiBSi alloy coating are ploughing, deformation, and adhesive wear, whereas those of (Cr, Fe)7C3-reinforced coating are microcutting, abrasive, and oxidation wear; the cracks on surfaces of (Cr, Fe)7C3 rods increased with the increasing loads; and the matrix α-Fe can prevent them from extending further in the composite coating.

  9. Nanoelectromechanical digital logic circuits using curved cantilever switches with amorphous-carbon-coated contacts

    NASA Astrophysics Data System (ADS)

    Ayala, Christopher L.; Grogg, Daniel; Bazigos, Antonios; Bleiker, Simon J.; Fernandez-Bolaños, Montserrat; Niklaus, Frank; Hagleitner, Christoph

    2015-11-01

    Nanoelectromechanical (NEM) switches have the potential to complement or replace traditional CMOS transistors in the area of ultra-low-power digital electronics. This paper reports the demonstration of prototype circuits including the first 3-stage ring oscillator built using cell-level digital logic elements based on curved NEM switches. The ring oscillator core occupies an area of 30 μm × 10 μm using 6 NEM switches. Each NEM switch device has a footprint of 5 μm × 3 μm, an air gap of 60 μm and is coated with amorphous carbon (a-C) for reliable operation. The ring oscillator operates at a frequency of 6.7 MHz, and confirms the simulated inverter propagation delay of 25 ns. The successful fabrication and measurement of this demonstrator are key milestones on the way towards an optimized, scaled technology with sub-nanosecond switching times, lower operating voltages and VLSI implementation.

  10. Tribocharging phenomena in hard disk amorphous carbon coatings with and without perfluoropolyether lubricants

    SciTech Connect

    van den Oetelaar, Ronald J.A.; Xu, Lei; Ogletree, D. Frank; Salmeron, Miquel; Tang, Hung; Gui, Jing

    2000-08-01

    Scanning polarization force microscopy was used to study changes in surface potential (tribocharging) caused by the contact between a tungsten carbide tip and the amorphous carbon coating of a hard disk,both when bare and when covered with Zdol-TX lubricant. The surface potential change produced by tip contact decays with time at a rate that is strongly dependent on lubricant coverage, and on the presence of oxygen and water vapor in the environment. Two different charging mechanisms are proposed. One involves chemical modification of the surface by removal of oxygen bound to the surface. This gives rise to a potential change that decays with time. Another mechanism involves trapping of charge in states within the energy gap of the insulating carbon film. The potential change due to this trapped charge does not decay over periods much greater than 1 hour.

  11. Criticality-Control Applications in the Nuclear Industry for Thermal Spray Amorphous Metal and Ceramic Coatings

    SciTech Connect

    Farmer, J; Choi, J

    2007-07-18

    Amorphous metal and ceramic thermal spray coatings have been developed that can be used to enhance the corrosion resistance of containers for the transportation, aging and disposal of spent nuclear fuel and high-level radioactive wastes. Iron-based amorphous metal formulations with chromium, molybdenum and tungsten have shown the corrosion resistance believed to be necessary for such applications. Rare earth additions enable very low critical cooling rates to be achieved. The boron content of these materials, and their stability at high neutron doses, enable them to serve as high efficiency neutron absorbers for criticality control. The high boron content of 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} (SAM2X5) makes it an effective neutron absorber, and suitable for criticality control applications. Average measured values of the neutron absorption cross section in transmission ({Sigma}{sub t}) for Type 316L stainless steel, Alloy C-22, borated stainless steel, a Ni-Cr-Mo-Gd alloy, and SAM2X5 have been determined to be approximately 1.1, 1.3, 2.3, 3.8 and 7.1 cm{sup -1}, respectively.

  12. Multi-layer laser solid forming of Zr65Al7.5Ni10Cu17.5 amorphous coating: Microstructure and corrosion resistance

    NASA Astrophysics Data System (ADS)

    Gan, Yu; Wang, Wenxian; Guan, Zhuosen; Cui, Zeqin

    2015-06-01

    Multi-layer Zr65Al7.5Ni10Cu17.5 amorphous coatings were produced by laser solid forming on A283 substrate. The coatings with few pores and free of cracks had good metallurgical bonding with the substrate. The microstructural characterization, phase composition, chemical component distribution and corrosion behavior of the coatings were investigated. The results revealed that the amorphization degree increased from the substrate to the coating surface mainly due to the dilution and stir influence from the melted substrate. In the five layers coating, the volume fraction of amorphous phase in the 5th layer, 3rd layer and 1st layer was about 77%, 64% and 49% respectively. With regard to corrosion property, potentiodynamic polarization plots, Nyquist plots and the equivalent circuits were employed in 3.5 wt% sodium chloride solution. Attributing to the presence of amorphous phase and passivation, the LSF coatings exhibit excellent corrosion resistance.

  13. Metallic amorphous electrodeposited molybdenum coating from aqueous electrolyte: Structural, electrical and morphological properties under current density

    NASA Astrophysics Data System (ADS)

    Nemla, Fatima; Cherrad, Djellal

    2016-07-01

    Molybdenum coatings are extensively utilized as back contact for CIGS-based solar cells. However, their electrodeposition from aqueous electrolyte still sophisticates, since long time, owing to the high reactivity with oxygen. In this study, we present a successful 30 min electrodeposition experiment of somewhat thick (∼0.98-2.9 μm) and of moderate surface roughness RMS (∼47-58 nm), metallic bright Mo coating from aqueous electrolyte containing molybdate ions. XRD analysis and Hall Effect measurements have been used to confirm the presence of Mo. The crystal structure of deposits was slightly amorphous in nature to body centred cubic structure (bcc) Mo (110), (211) and (220) face. Lattice parameters exhibit some weak fluctuated tensile stress when compared to the reference lattice parameter. Additionally, our calculated lattice parameters are in good agreement with some previous works from literature. Discussions on the grain growth prove that they are constrained by grain boundary energy not the thickness effect. Further discussions were made on the electrical resistivity and surface morphology. Resonance scattering of Fermi electrons are expected to contribute towards the variation in the film resistivity through the carrier mobility limitation. However, studied samples might be qualified as candidates for solar cell application.

  14. Dynamic response of laser ablative shock waves from coated and uncoated amorphous Boron nanoparticles

    NASA Astrophysics Data System (ADS)

    Paturi, Prem Kiran; Chelikani, Leela; Pinnoju, Venkateshwarlu; Verma, Pankaj; Singh, Raja V.; Acrhem Collaboration; Hemrl Collaboration

    2015-06-01

    Nanoparticles (NP) improve the performance of solid rocket motors with increased burning rate and lower ignition threshold owing to their larger surface area. We present spatio-temporal evolution of laser ablative shock waves (LASWs) from compacted amorphous Boron (B) and Lithium Fluoride coated Boron (LiF-B) of 70-110nm sizes that were compacted to form pellets. Thickness of the LiF coating is 5.5 +/- 1 nm in LiF-B. Laser pulses from second harmonic of Nd:YAG laser (532 nm, 7 ns) are used to generate LASWs expanding in ambient air. The precise time of energy release from the pellets under extreme ablative pressures is studied using shadowgraphy with a temporal resolution of 1.5 ns. Different nature of the shock front (SF) following Sedov-Taylor theory, before and after detachment, indicated two specific time dependent stages of energy release. From the position of SF, velocity behind the SF, similar to that of exhaust velocity is measured. Specific impulse of 241 +/- 5 and 201 +/- 4 sec for LiF-B and B, respectively, at a delay of 0.8 μs from shock inducing laser pulse makes them potential candidates for laser based micro thruster applications. The work is supported by Defence Research and Developement Organization, India through Grants-in-Aid Program.

  15. Nanometer-thick amorphous-SnO2 layer as an oxygen barrier coated on a transparent AZO electrode

    NASA Astrophysics Data System (ADS)

    Lee, Hee Sang; Woo, Seong Ihl

    2016-07-01

    It is necessary for transparent conducting electrodes used in dye-sensitized or perovskite solar cells to have high thermal stability which is required when TiO2 is coated on the electrode. AZO films with their low-cost and good TCO properties are unfortunately unstable above 300 °C in air because of adsorbed oxygen. In this paper, the thermal stability of AZO films is enhanced by depositing an oxygen barrier on AZO films to block the oxygen. As the barrier material, SnO2 is used due to its high heat stability, electrical conductivity, and transmittance. Moreover, when the SnO2 is grown as amorphous phase, the protective effect become greater than the crystalline phase. The thermal stability of the amorphous-SnO2/AZO films varies depending on the thickness of the amorphous SnO2 layer. Because of the outstanding oxygen blocking properties of amorphous SnO2, its optimal thickness is very thin and it results in only a slight decrease in transmittance. The sheet resistance of the amorphous-SnO2/AZO film is 5.4 Ω sq-1 after heat treatment at 500 °C for 30 min in air and the average transmittance in the visible region is 83.4%. The results show that the amorphous-SnO2/AZO films have thermal stability with excellent electrical and optical properties. [Figure not available: see fulltext.

  16. Novel nanometer-level uniform amorphous carbon coating for boron powders by direct pyrolysis of coronene without solvent.

    PubMed

    Ye, ShuJun; Song, MingHui; Kumakura, Hiroaki

    2015-01-30

    A 3 nm coronene coating and a 4 nm amorphous carbon coating with a uniform shell-core encapsulation structure for nanosized boron (B) powders are formed by a simple process in which coronene is directly mixed with boron particles without a solvent and heated at 520 °C for 1 h or at 630 °C for 3 h in a vacuum-sealed silica tube. Coronene has a melting point lower than its decomposition temperature, which enables liquid coronene to cover B particles by liquid diffusion and penetration without the need for a solvent. The diffusion and penetration of coronene can extend to the boundaries of particles and to inside the agglomerated nanoparticles to form a complete shell-core encapsulated structure. As the temperature is increased, thermal decomposition of coronene on the B particles results in the formation of a uniform amorphous carbon coating layer. This novel and simple nanometer-level uniform amorphous carbon coating method can possibly be applied to many other powders; thus, it has potential applications in many fields at low cost.

  17. Amorphous GeOx-Coated Reduced Graphene Oxide Balls with Sandwich Structure for Long-Life Lithium-Ion Batteries.

    PubMed

    Choi, Seung Ho; Jung, Kyeong Youl; Kang, Yun Chan

    2015-07-01

    Amorphous GeOx-coated reduced graphene oxide (rGO) balls with sandwich structure are prepared via a spray-pyrolysis process using polystyrene (PS) nanobeads as sacrificial templates. This sandwich structure is formed by uniformly coating the exterior and interior of few-layer rGO with amorphous GeOx layers. X-ray photoelectron spectroscopy analysis reveals a Ge:O stoichiometry ratio of 1:1.7. The amorphous GeOx-coated rGO balls with sandwich structure have low charge-transfer resistance and fast Li(+)-ion diffusion rate. For example, at a current density of 2 A g(-1), the GeOx-coated rGO balls with sandwich and filled structures and the commercial GeO2 powders exhibit initial charge capacities of 795, 651, and 634 mA h g(-1), respectively; the corresponding 700th-cycle charge capacities are 758, 579, and 361 mA h g(-1). In addition, at a current density of 5 A g(-1), the rGO balls with sandwich structure have a 1600th-cycle reversible charge capacity of 629 mA h g(-1) and a corresponding capacity retention of 90.7%, as measured from the maximum reversible capacity at the 100th cycle.

  18. 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.

  19. Effects of amorphous silica coating on cerium oxide nanoparticles induced pulmonary responses

    PubMed Central

    Ma, Jane; Mercer, Robert R.; Barger, Mark; Schwegler-Berry, Diane; Cohen, Joel M.; Demokritou, Philip; Castranova, Vincent

    2015-01-01

    Recently cerium compounds have been used in a variety of consumer products, including diesel fuel additives, to increase fuel combustion efficiency and decrease diesel soot emissions. However, cerium oxide (CeO2) nanoparticles have been detected in the exhaust, which raises a health concern. Previous studies have shown that exposure of rats to nanoscale CeO2 by intratracheal instillation (IT) induces sustained pulmonary inflammation and fibrosis. In the present study, male Sprague–Dawley rats were exposed to CeO2 or CeO2 coated with a nano layer of amorphous SiO2 (aSiO2/CeO2) by a single IT and sacrificed at various times post-exposure to assess potential protective effects of the aSiO2 coating. The first acellular bronchoalveolar lavage (BAL) fluid and BAL cells were collected and analyzed from all exposed animals. At the low dose (0.15 mg/kg), CeO2 but not aSiO2/CeO2 exposure induced inflammation. However, at the higher doses, both particles induced a dose-related inflammation, cytotoxicity, inflammatory cytokines, matrix metalloproteinase (MMP)-9, and tissue inhibitor of MMP at 1 day post-exposure. Morphological analysis of lung showed an increased inflammation, surfactant and collagen fibers after CeO2 (high dose at 3.5 mg/kg) treatment at 28 days post-exposure. aSiO2 coating significantly reduced CeO2-induced inflammatory responses in the airspace and appeared to attenuate phospholipidosis and fibrosis. Energy dispersive X-ray spectroscopy analysis showed Ce and phosphorous (P) in all particle-exposed lungs, whereas Si was only detected in aSiO2/CeO2-exposed lungs up to 3 days after exposure, suggesting that aSiO2 dissolved off the CeO2 core, and some of the CeO2 was transformed to CePO4 with time. These results demonstrate that aSiO2 coating reduce CeO2-induced inflammation, phospholipidosis and fibrosis. PMID:26210349

  20. Optical coatings of variable refractive index and high laser-resistance from physical-vapor-deposited perfluorinated amorphous polymer

    DOEpatents

    Chow, Robert; Loomis, Gary E.; Thomas, Ian M.

    1999-01-01

    Variable index optical single-layers, optical multilayer, and laser-resistant coatings were made from a perfluorinated amorphous polymer material by physical vapor deposition. This was accomplished by physically vapor depositing a polymer material, such as bulk Teflon AF2400, for example, to form thin layers that have a very low refractive index (.about.1.10-1.31) and are highly transparent from the ultra-violet through the near infrared regime, and maintain the low refractive index of the bulk material. The refractive index can be varied by simply varying one process parameter, either the deposition rate or the substrate temperature. The thus forming coatings may be utilized in anti-reflectors and graded anti-reflection coatings, as well as in optical layers for laser-resistant coatings at optical wavelengths of less than about 2000 nm.

  1. Optical coatings of variable refractive index and high laser-resistance from physical-vapor-deposited perfluorinated amorphous polymer

    DOEpatents

    Chow, R.; Loomis, G.E.; Thomas, I.M.

    1999-03-16

    Variable index optical single-layers, optical multilayer, and laser-resistant coatings were made from a perfluorinated amorphous polymer material by physical vapor deposition. This was accomplished by physically vapor depositing a polymer material, such as bulk Teflon AF2400, for example, to form thin layers that have a very low refractive index (ca. 1.10--1.31) and are highly transparent from the ultra-violet through the near infrared regime, and maintain the low refractive index of the bulk material. The refractive index can be varied by simply varying one process parameter, either the deposition rate or the substrate temperature. The thus forming coatings may be utilized in anti-reflectors and graded anti-reflection coatings, as well as in optical layers for laser-resistant coatings at optical wavelengths of less than about 2000 nm. 2 figs.

  2. Amorphous calcium phosphate nanospheres/polylactide composite coated tantalum scaffold: facile preparation, fast biomineralization and subchondral bone defect repair application.

    PubMed

    Zhou, Rong; Xu, Wei; Chen, Feng; Qi, Chao; Lu, Bing-Qiang; Zhang, Hao; Wu, Jin; Qian, Qi-Rong; Zhu, Ying-Jie

    2014-11-01

    Calcium phosphate (CaP) materials are widely used in various biomedical areas such as drug/gene delivery and bone repair/tissue engineering. In this study, amorphous CaP nanospheres synthesized by a simple co-precipitation method are used to prepare the CaP-polylactide (CaP-PLA) composite. Then, the as-prepared CaP-PLA composite is used to coat tantalum (Ta) plates and porous scaffolds. Compared with bare Ta plate, CaP-PLA coated Ta plates show a high performance of surface biomineralization in simulated body fluid (SBF). In addition, the hydrophilicity of the CaP-PLA coated Ta plates is significantly improved. CaP-PLA coated Ta plates with bovine serum albumin (BSA) are prepared and used for the investigation of BSA release in vitro. The experimental results indicate a sustained BSA release property and simultaneous biomineralization of the as-prepared BSA-containing CaP-PLA coated Ta plates. Furthermore, CaP-PLA coated Ta scaffolds are favorable for the human osteoblast-like MG63 cells adhesion and spreading. The vascular endothelial growth factor (VEGF) and transforming growth factor (TGF)-containing CaP-PLA coated porous Ta scaffolds are used for the study of rabbit subchondral bone defect repair, covering with autogeneic periosteums. The as-prepared CaP-PLA composite coated Ta scaffolds are useful to guide the bone regeneration in vivo.

  3. Amorphous calcium phosphate nanospheres/polylactide composite coated tantalum scaffold: facile preparation, fast biomineralization and subchondral bone defect repair application.

    PubMed

    Zhou, Rong; Xu, Wei; Chen, Feng; Qi, Chao; Lu, Bing-Qiang; Zhang, Hao; Wu, Jin; Qian, Qi-Rong; Zhu, Ying-Jie

    2014-11-01

    Calcium phosphate (CaP) materials are widely used in various biomedical areas such as drug/gene delivery and bone repair/tissue engineering. In this study, amorphous CaP nanospheres synthesized by a simple co-precipitation method are used to prepare the CaP-polylactide (CaP-PLA) composite. Then, the as-prepared CaP-PLA composite is used to coat tantalum (Ta) plates and porous scaffolds. Compared with bare Ta plate, CaP-PLA coated Ta plates show a high performance of surface biomineralization in simulated body fluid (SBF). In addition, the hydrophilicity of the CaP-PLA coated Ta plates is significantly improved. CaP-PLA coated Ta plates with bovine serum albumin (BSA) are prepared and used for the investigation of BSA release in vitro. The experimental results indicate a sustained BSA release property and simultaneous biomineralization of the as-prepared BSA-containing CaP-PLA coated Ta plates. Furthermore, CaP-PLA coated Ta scaffolds are favorable for the human osteoblast-like MG63 cells adhesion and spreading. The vascular endothelial growth factor (VEGF) and transforming growth factor (TGF)-containing CaP-PLA coated porous Ta scaffolds are used for the study of rabbit subchondral bone defect repair, covering with autogeneic periosteums. The as-prepared CaP-PLA composite coated Ta scaffolds are useful to guide the bone regeneration in vivo. PMID:25293870

  4. Preparation of ZrC nano-particles reinforced amorphous carbon composite coating by atmospheric pressure chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Sun, W.; Xiong, X.; Huang, B. Y.; Li, G. D.; Zhang, H. B.; Xiao, P.; Chen, Z. K.; Zheng, X. L.

    2009-05-01

    To eliminate cracks caused by thermal expansion mismatch between ZrC coating and carbon-carbon composites, a kind of ZrC/C composite coating was designed as an interlayer. The atmospheric pressure chemical vapor deposition was used as a method to achieve co-deposition of ZrC and C from ZrCl 4-C 3H 6-H 2-Ar source. Zirconium tetrachloride (ZrCl 4) powder carrier was especially made to control accurately the flow rate. The microstructure of ZrC/C composite coating was studied using analytical techniques. ZrC/C coating shows same morphology as pyrolytic carbon. Transmission electron microscopy (TEM) shows ZrC grains with size of 10-50 nm embed in turbostratic carbon. The formation mechanism is that the growth of ZrC crystals was inhibited by surrounding pyrolytic carbon and kept as nano-particles. Fracture morphologies imply good combination between coating and substrate. The ZrC crystals have stoichiometric proportion near 1, with good crystalline but no clear preferred orientation while pyrolytic carbon is amorphous. The heating-up oxidation of ZrC/C coating shows 11.58 wt.% loss. It can be calculated that the coating consists of 74.04 wt.% ZrC and 25.96 wt.% pyrolytic carbon. The average density of the composite coating is 5.892 g/cm 3 by Archimedes' principle.

  5. Field emission property improvement of ZnO nanowires coated with amorphous carbon and carbon nitride films

    NASA Astrophysics Data System (ADS)

    Liao, L.; Li, J. C.; Wang, D. F.; Liu, C.; Liu, C. S.; Fu, Q.; Fan, L. X.

    2005-06-01

    In this paper, we report an approach to prepare a new type of field emitter made up of ZnO nanowires coated with an amorphous carbon (a-C) or carbon nitride film (a-CNx). The coated ZnO nanowires form coaxial nanocables. The best field emission properties, which showed a very low turn-on electric field of 1.5 V µm-1 and an emission current density of 1 mA cm-2 (enough to produce a luminance of 300 cd m-2 from a VGA FED with a typical high-voltage phosphor screen efficacy of 9 lm W-1) under the field of only 2.5 V µm-1, have been obtained from the a-CNx coated ZnO nanowire field emitter among three kinds of emitters: a-C coated ZnO nanowires, a-CNx coated ZnO nanowires and uncoated ZnO nanowires. Microstructures and crystal configuration were investigated by scanning electron microscopy, x-ray diffraction and transmission electron microscopy. Band edge transition without any significant photoluminescence peak relating to intrinsic defects has been observed by photoluminescence measurement. The superior properties of the field emission are attributed to the low work function of the coated carbon nitride film and good electron transport property of the ZnO nanowires with an extremely sharp tip.

  6. Chemical Bonding In Amorphous Si Coated-carbon Nanotube As Anodes For Li ion Batteries: A XANES Study

    SciTech Connect

    Zhou, Jigang; Hu, Yongfeng; Li, Xiaolin; Wang, Chong M.; Zuin, Lucia

    2014-03-11

    The chemical bonding nature and its evolution upon electrochemical cycling in amorphous Si coated-carbon nanotube (Si-CNT) anode has been investigated using comprehensive X-ray absorption spectroscopy (XANES) at Si L- and K-edges along with C and O K-edges. The Si nanolayer on CNT is found to be anchored to CNT via Si-O-C bonding. This bond weakens upon electrochemical cycling accompanied with generation of Li2CO3 on the surface of Si-CNT. Those findings are crucial in designing further improved Si-C composite anode for lithium ion battery.

  7. Physico-chemical studies of cuprous oxide (Cu2O) nanoparticles coated on amorphous carbon nanotubes (α-CNTs)

    NASA Astrophysics Data System (ADS)

    Johan, Mohd Rafie; Meriam Suhaimy, Syazwan Hanani; Yusof, Yusliza

    2014-01-01

    Amorphous carbon nanotubes (α-CNTs) were synthesized by a chemical reaction between ferrocene and ammonium chloride at a temperature (∼250 °C) in an air furnace. As- synthesized α-CNTs were purified with deionized water and hydrochloric acid. A purified α-CNTs were hybridized with cuprous oxide nanoparticles (Cu2O) through a simple chemical process. Morphology of the samples was analyzed with field emission scanning electron microscope (FESEM) and transmission electron microscopy (TEM). Fourier transform infrared (FTIR) spectra showed the attachment of acidic functional groups onto the surface of α-CNTs and the formation of hybridized α-CNTs-Cu2O. Raman spectra reveal the amorphous nature of the carbon. X-ray diffraction (XRD) pattern confirmed the amorphous phase of the carbon and the formation of Cu2O crystalline phase. The coating of Cu2O was confirmed by FESEM, TEM, and XRD. Optical absorption of the samples has also been investigated and the quantum confinement effect was illustrated in the absorption spectra.

  8. Application of Neutron-Absorbing Structural-Amorphous Metal (SAM) Coatings for Spent Nuclear Fuel (SNF) Container to Enhance Criticality Safety Control

    SciTech Connect

    Choi, J

    2007-01-12

    This report describes the analysis and modeling approaches used in the evaluation for criticality-control applications of the neutron-absorbing structural-amorphous metal (SAM) coatings. The applications of boron-containing high-performance corrosion-resistant material (HPCRM)--amorphous metal as the neutron-absorbing coatings to the metallic support structure can enhance criticality safety controls for spent nuclear fuel in baskets inside storage containers, transportation casks, and disposal containers. The use of these advanced iron-based, corrosion-resistant materials to prevent nuclear criticality in transportation, aging, and disposal containers would be extremely beneficial to the nuclear waste management programs.

  9. Effect of tetrahedral amorphous carbon coating on the resistivity and wear of single-walled carbon nanotube network

    NASA Astrophysics Data System (ADS)

    Iyer, Ajai; Kaskela, Antti; Novikov, Serguei; Etula, Jarkko; Liu, Xuwen; Kauppinen, Esko I.; Koskinen, Jari

    2016-05-01

    Single walled carbon nanotube networks (SWCNTNs) were coated by tetrahedral amorphous carbon (ta-C) to improve the mechanical wear properties of the composite film. The ta-C deposition was performed by using pulsed filtered cathodic vacuum arc method resulting in the generation of C+ ions in the energy range of 40-60 eV which coalesce to form a ta-C film. The primary disadvantage of this process is a significant increase in the electrical resistance of the SWCNTN post coating. The increase in the SWCNTN resistance is attributed primarily to the intrinsic stress of the ta-C coating which affects the inter-bundle junction resistance between the SWCNTN bundles. E-beam evaporated carbon was deposited on the SWCNTNs prior to the ta-C deposition in order to protect the SWCNTN from the intrinsic stress of the ta-C film. The causes of changes in electrical resistance and the effect of evaporated carbon thickness on the changes in electrical resistance and mechanical wear properties have been studied.

  10. The peculiar behavior of the glass transition temperature of amorphous drug-polymer films coated on inert sugar spheres.

    PubMed

    Dereymaker, Aswin; Van Den Mooter, Guy

    2015-05-01

    Fluid bed coating has been proposed in the past as an alternative technology for manufacturing of drug-polymer amorphous solid dispersions, or so-called glass solutions. It has the advantage of being a one-step process, and thus omitting separate drying steps, addition of excipients, or manipulation of the dosage form. In search of an adequate sample preparation method for modulated differential scanning calorimetry analysis of beads coated with glass solutions, glass transition broadening and decrease of the glass transition temperature (Tg ) were observed with increasing particle size of crushed coated beads and crushed isolated films of indomethacin (INDO) and polyvinylpyrrolidone (PVP). Substituting INDO with naproxen gave comparable results. When ketoconazole was probed or the solvent in INDO-PVP films was switched to dichloromethane (DCM) or a methanol-DCM mixture, two distinct Tg regions were observed. Small particle sizes had a glass transition in the high Tg region, and large particle sizes had a glass transition in the low Tg region. This particle size-dependent glass transition was ascribed to different residual solvent amounts in the bulk and at the surface of the particles. A correlation was observed between the deviation of the Tg from that calculated from the Gordon-Taylor equation and the amount of residual solvent at the Tg of particles with different sizes.

  11. STEM-EELS analysis reveals stable high-density He in nanopores of amorphous silicon coatings deposited by magnetron sputtering.

    PubMed

    Schierholz, Roland; Lacroix, Bertrand; Godinho, Vanda; Caballero-Hernández, Jaime; Duchamp, Martial; Fernández, Asunción

    2015-02-20

    A broad interest has been showed recently on the study of nanostructuring of thin films and surfaces obtained by low-energy He plasma treatments and He incorporation via magnetron sputtering. In this paper spatially resolved electron energy-loss spectroscopy in a scanning transmission electron microscope is used to locate and characterize the He state in nanoporous amorphous silicon coatings deposited by magnetron sputtering. A dedicated MATLAB program was developed to quantify the helium density inside individual pores based on the energy position shift or peak intensity of the He K-edge. A good agreement was observed between the high density (∼35-60 at nm(-3)) and pressure (0.3-1.0 GPa) values obtained in nanoscale analysis and the values derived from macroscopic measurements (the composition obtained by proton backscattering spectroscopy coupled to the macroscopic porosity estimated from ellipsometry). This work provides new insights into these novel porous coatings, providing evidence of high-density He located inside the pores and validating the methodology applied here to characterize the formation of pores filled with the helium process gas during deposition. A similar stabilization of condensed He bubbles has been previously demonstrated by high-energy He ion implantation in metals and is newly demonstrated here using a widely employed methodology, magnetron sputtering, for achieving coatings with a high density of homogeneously distributed pores and He storage capacities as high as 21 at%.

  12. STEM-EELS analysis reveals stable high-density He in nanopores of amorphous silicon coatings deposited by magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Schierholz, Roland; Lacroix, Bertrand; Godinho, Vanda; Caballero-Hernández, Jaime; Duchamp, Martial; Fernández, Asunción

    2015-02-01

    A broad interest has been showed recently on the study of nanostructuring of thin films and surfaces obtained by low-energy He plasma treatments and He incorporation via magnetron sputtering. In this paper spatially resolved electron energy-loss spectroscopy in a scanning transmission electron microscope is used to locate and characterize the He state in nanoporous amorphous silicon coatings deposited by magnetron sputtering. A dedicated MATLAB program was developed to quantify the helium density inside individual pores based on the energy position shift or peak intensity of the He K-edge. A good agreement was observed between the high density (˜35-60 at nm-3) and pressure (0.3-1.0 GPa) values obtained in nanoscale analysis and the values derived from macroscopic measurements (the composition obtained by proton backscattering spectroscopy coupled to the macroscopic porosity estimated from ellipsometry). This work provides new insights into these novel porous coatings, providing evidence of high-density He located inside the pores and validating the methodology applied here to characterize the formation of pores filled with the helium process gas during deposition. A similar stabilization of condensed He bubbles has been previously demonstrated by high-energy He ion implantation in metals and is newly demonstrated here using a widely employed methodology, magnetron sputtering, for achieving coatings with a high density of homogeneously distributed pores and He storage capacities as high as 21 at%.

  13. 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.

  14. The Effect of Oxygen Contamination on the Amorphous Structure of Thermally Sprayed Coatings of Cu47Ti33Zr11Ni8Si1

    SciTech Connect

    Matthew Frank Besser

    2002-05-27

    this research has shown that it is possible to deposit coatings of gas atomized Cu{sub 47}Ti{sub 33}Zr{sub 11}Ni{sub 8}Si{sub 1} powders containing various levels of oxygen contamination using plasma arc spray methods. The structure of the coating was found to depend primarily on the spray environment, with an argon atmosphere producing the most amorphous samples for a given starting powder. The oxygen content of the coatings reflected the relative levels of the oxygen contamination in the starting powders. The analysis of the starting powders displayed oxygen contents ranging from 0.125-0.79 wt.%. It was shown that higher oxygen levels lead to more crystalline structure in the starting powders as determined by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). This trend was found to be true for both the starting powders and for the plasma sprayed coatings. Chemical composition for all starting powders was very close to the nominal alloy composition. Chemical changes in the coatings involved the loss of Cu in coatings where high levels of oxidation were found. Cavitation erosion testing of selected coatings showed a weak trend that coatings prepared by vacuum plasma spray (VPS) had lower damage rates, but there was no clear data to indicate which coating parameters were superior. The range of data produced from testing duplicate coating was too wide to provide a good statistical measure of cavitation erosion resistance. of interest was the fact that when coatings began to show damage from cracking, all samples of a group showed similar damage and usually the damage pattern was somewhat unique to that group of samples. Failure of the coatings was due to features inherent to plasma arc spray (PAS) coating (i.e., pores, splat boundaries, oxide inclusions) rather than the mechanical characteristics of the amorphous alloy.

  15. Magnesium-Aluminum-Zirconium Oxide Amorphous Ternary Composite: A Dense and Stable Optical Coating

    NASA Technical Reports Server (NTRS)

    Sahoo, N. K.; Shapiro, A. P.

    1998-01-01

    In the present work, the process parameter dependent optical and structural properties of MgO-Al(2)O(3)-ZrO(2) ternary mixed-composite material have been investigated. Optical properties were derived from spectrophotometric measurements. The surface morphology, grain size distributions, crystallographic phases and process dependent material composition of films have been investigated through the use of Atomic Force Microscopy (AFM), X-ray diffraction analysis and Energy Dispersive X- ray (EDX) analysis. EDX analysis made evident the correlation between the optical constants and the process dependent compositions in the films. It is possible to achieve environmentally stable amorphous films with high packing density under certain optimized process conditions.

  16. Amorphous MoSx thin-film-coated carbon fiber paper as a 3D electrode for long cycle life symmetric supercapacitors

    NASA Astrophysics Data System (ADS)

    Balasingam, Suresh Kannan; Thirumurugan, Arun; Lee, Jae Sung; Jun, Yongseok

    2016-06-01

    Amorphous MoSx thin-film-coated carbon fiber paper as a binder-free 3D electrode was synthesized by a facile hydrothermal method. The maximum specific capacitance of a single electrode was 83.9 mF cm-2, while it was 41.9 mF cm-2 for the symmetric device. Up to 600% capacitance retention was observed for 4750 cycles.Amorphous MoSx thin-film-coated carbon fiber paper as a binder-free 3D electrode was synthesized by a facile hydrothermal method. The maximum specific capacitance of a single electrode was 83.9 mF cm-2, while it was 41.9 mF cm-2 for the symmetric device. Up to 600% capacitance retention was observed for 4750 cycles. Electronic supplementary information (ESI) available. See DOI: 10.1039/C6NR01200K

  17. Molecular dynamics simulations of the tribological behaviour of a water-lubricated amorphous carbon-fluorine PECVD coating

    NASA Astrophysics Data System (ADS)

    Rullich, Markus; Weiss, Volker C.; Frauenheim, Thomas

    2013-07-01

    Hybrid bearings comprising ceramic balls and steel rings exhibit increased wear-resistance and a reduced coefficient of friction (COF) compared with standard steel bearings. Using plasma-enhanced chemical vapour deposition (PECVD) coatings to modify the surface properties, the performance of these bearings can be further improved. Fluorine-containing amorphous hydrogenated carbon (a-C : F : H) films are well suited to this purpose. To study the influence of such coatings on the friction characteristics of key parts of hybrid bearings, a model of an a-C : F : H film was constructed and employed in molecular dynamics simulations of two slabs sliding past each other, lubricated by water. With one slab being pulled by a virtual spring, the perpendicular force (load) was kept constant using a barostat. For comparison, a system of two silicon dioxide (cristobalite) slabs and a mixed system consisting of a cristobalite slab and an a-C : F : H slab were investigated. Our results indicate a linear dependence of the friction force on the perpendicular force. With an increasing amount of water between the slabs, the COFs decrease. A decrease in temperature leads to an increased COF, while a decrease in the relative velocity of the slabs does not influence the COF between two a-C : F : H slabs, but reduces the COF for the other two systems. Our results for the COF and its dependence on temperature and relative sliding velocity generally agree well both with experiments and with simulations for similar systems reported in the literature.

  18. Amorphous MoSx thin-film-coated carbon fiber paper as a 3D electrode for long cycle life symmetric supercapacitors.

    PubMed

    Balasingam, Suresh Kannan; Thirumurugan, Arun; Lee, Jae Sung; Jun, Yongseok

    2016-06-01

    Amorphous MoSx thin-film-coated carbon fiber paper as a binder-free 3D electrode was synthesized by a facile hydrothermal method. The maximum specific capacitance of a single electrode was 83.9 mF cm(-2), while it was 41.9 mF cm(-2) for the symmetric device. Up to 600% capacitance retention was observed for 4750 cycles.

  19. Characterization and simulation on antireflective coating of amorphous silicon oxide thin films with gradient refractive index

    NASA Astrophysics Data System (ADS)

    Huang, Lu; Jin, Qi; Qu, Xingling; Jin, Jing; Jiang, Chaochao; Yang, Weiguang; Wang, Linjun; Shi, Weimin

    2016-08-01

    The optical reflective properties of silicon oxide (SixOy) thin films with gradient refractive index are studied both theoretically and experimentally. The thin films are widely used in photovoltaic as antireflective coatings (ARCs). An effective finite difference time domain (FDTD) model is built to find the optimized reflection spectra corresponding to structure of SixOy ARCs with gradient refractive index. Based on the simulation analysis, it shows the variation of reflection spectra with gradient refractive index distribution. The gradient refractive index of SixOy ARCs can be obtained in adjustment of SiH4 to N2O ratio by plasma-enhanced chemical vapor deposition (PECVD) system. The optimized reflection spectra measured by UV-visible spectroscopy confirms to agree well with that simulated by FDTD method.

  20. Synthesis and electrochemical performances of amorphous carbon-coated Sn-Sb particles as anode material for lithium-ion batteries

    SciTech Connect

    Wang Zhong; Tian Wenhuai; Liu Xiaohe; Yang Rong; Li Xingguo

    2007-12-15

    The amorphous carbon coating on the Sn-Sb particles was prepared from aqueous glucose solutions using a hydrothermal method. Because the outer layer carbon of composite materials is loose cotton-like and porous-like, it can accommodate the expansion and contraction of active materials to maintain the stability of the structure, and hinder effectively the aggregation of nano-sized alloy particles. The as-prepared composite materials show much improved electrochemical performances as anode materials for lithium-ion batteries compared with Sn-Sb alloy and carbon alone. This amorphous carbon-coated Sn-Sb particle is extremely promising anode materials for lithium secondary batteries and has a high potentiality in the future use. - Graphical abstract: The amorphous carbon coating on the Sn-Sb particles was prepared from aqueous glucose solutions using a hydrothermal method. Because the outer layer carbon of composite materials is loose cotton-like and porous-like, it can accommodate the expansion and contraction of active materials to maintain the stability of the structure, and hinder effectively the aggregation of nano-sized alloy particles.

  1. FY05 HPCRM Annual Report: High-Performance Corrosion-Resistant Iron-Based Amorphous Metal Coatings Evaluation of Corrosion Reistance FY05 HPCRM Annual Report # Rev. 1DOE-DARPA Co-Sponsored Advanced Materials Program

    SciTech Connect

    Farmer, J C; Haslam, J J; Day, S D

    2007-09-19

    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

  2. Structural characterization of ion-vapor deposited hydrogenated amorphous carbon coatings by solid state {sup 13}C nuclear magnetic resonance

    SciTech Connect

    Xu, Jiao; Kato, Takahisa; Watanabe, Sadayuki; Hayashi, Hideo; Kawaguchi, Masahiro

    2014-01-07

    In the present study, unique structural heterogeneity was observed in ion-vapor deposited a-C:H coatings by performing {sup 13}C MAS and {sup 1}H-{sup 13}C CPMAS experiments on solid state nuclear magnetic resonance devices. Two distinct types of sp{sup 2} C clusters were discovered: one of them denoted as sp{sup 2} C′ in content of 3–12 at. % was non-protonated specifically localized in hydrogen-absent regions, while the other dominant one denoted as sp{sup 2} C″ was hydrogenated or at least proximate to proton spins. On basis of the notably analogous variation of sp{sup 2} C′ content and Raman parameters as function of substrate bias voltage in the whole range of 0.5 kV–3.5 kV, a model of nano-clustering configuration was proposed that the sp{sup 2} C′ clusters were embedded between sp{sup 2} C″ clusters and amorphous sp{sup 3} C matrix as trapped interfaces or boundaries where the sp{sup 2} carbon bonds were highly distorted. Continuous increase of bias voltage would promote the nano-clustering and re-ordering of dominant sp{sup 2} C″ clusters, thus results in a marked decrease of interspace and a change of the content of sp{sup 2} C′ clusters. Further investigation on the {sup 13}C magnetization recovery showed typical stretched-exponential approximation due to the prominent presence of paramagnetic centers, and the stretched power α varied within 0.6–0.9 from distinct types of sp{sup 2} C clusters. Differently, the magnetization recovery of {sup 1}H showed better bi-exponential approximation with long and short T{sub 1}(H) fluctuated within 40–60 ms and 0.1–0.3 ms approximately in content of 80% ± 5% and 20% ± 5%, respectively, varying with various bias voltages. Meanwhile, the interrupted {sup 13}C saturation recovery with an interval of short T{sub 1}(H) showed that most of quick-relaxing protons were localized in sp{sup 2} C″ clusters. Such a short T{sub 1}(H) was only possibly resulted from a relaxation mechanism

  3. Amorphous diamond films

    DOEpatents

    Falabella, S.

    1998-06-09

    Amorphous diamond films having a significant reduction in intrinsic stress are prepared by biasing a substrate to be coated and depositing carbon ions thereon under controlled temperature conditions. 1 fig.

  4. 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

  5. Influences of carbon content and coating carbon thickness on properties of amorphous CoSnO3@C composites as anode materials for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Fan, Fuqiang; Fang, Guoqing; Zhang, Ruixue; Xu, Yanhui; Zheng, Junwei; Li, Decheng

    2014-08-01

    A series of core-shell carbon coated amorphous CoSnO3 (CoSnO3@C) with different carbon content are synthesized. Effects of carbon content and coating carbon thickness on the physical and electrochemical performances of the samples were studied in detail. The samples were analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), galvanostatic charge-discharge and AC impedance spectroscopy, respectively. The results indicate that controlling the concentration of aqueous glucose solution influences the generation of in-situ carbon layer thickness. The optimal concentration of aqueous glucose solution, carbon content and carbon layer thickness are suggested as 0.25 M, 35.1% and 20 nm, respectively. CoSnO3@C composite prepared under the optimal conditions exhibits excellent cycling performance, whose reversible capacity could reach 491 mA h g-1 after 100 cycles.

  6. Amorphous Fe2O3 nanoshells coated on carbonized bacterial cellulose nanofibers as a flexible anode for high-performance lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Huang, Yang; Lin, Zixia; Zheng, Mingbo; Wang, Tianhe; Yang, Jiazhi; Yuan, Fanshu; Lu, Xiaoyu; Liu, Lin; Sun, Dongping

    2016-03-01

    A three-dimensional (3D) carbonaceous aerogel derived from biomass bacterial cellulose (BC) is introduced as a flexible framework for iron oxides in Li-ion batteries (LIBs). The 3D carbonized BC (CBC) with highly interconnected nanofibrous structure exhibits good electrical conductivity and mechanical stability. The amorphous Fe2O3 is tightly coated on the nanofibers of CBC through a simple in situ thermal decomposition method. The obtained amorphous Fe2O3 anode (denoted as A-Fe2O3@CBC) exhibits stable cycling performance and high rate capability when assembled into a half-cell, which is supposed to benefit from the well-dispersed Fe2O3 nanoshells and the hierarchical pores in A-Fe2O3@CBC composite. The rational design of the nanostructure could improve the transportation of electrons/ions and effectively alleviate volume changes of Fe2O3 during the electrochemical cycling. Meanwhile, the amorphous nature of the Fe2O3 in anode provides an enhanced capacitive-like lithium storage and flexible structure of the active materials, resulting in much higher specific capacity and longer cycle life when compared with its crystalline counterpart. This work provides a promising approach to design and construct the flexible metal oxide anode materials based on 3D carbonaceous aerogel for high-performance LIBs.

  7. Recrystallization and formation of spheroidal gold particles in amorphous-like AlN-TiB2-TiSi2 coatings after annealing and subsequent implantation

    NASA Astrophysics Data System (ADS)

    Pogrebnjak, A. D.; Dem'yanenko, A. A.; Beresnev, V. M.; Sobol', O. V.; Ivasishin, O. M.; Oyoshi, K.; Takeda, Y.; Amekura, H.; Kupchishin, A. I.

    2016-07-01

    The recrystallization of the structure of an X-ray amorphous AlN-TiB2-TiSi2 coating containing short-range order regions with characteristic sizes of 0.8-1.0 nm has been performed using a negative gold ion (Au-) beam and high-temperature annealing. Direct measurements using methods of high-resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray spectral (EDXS) microanalysis have demonstrated that thermal annealing at a temperature of 1300°C in air results in the formation of nanoscale (10-15 nm) phases AlN, AlB2, Al3O3, and TiO2, whereas the ion implantation of negative ions Au- leads to a fragmentation (decrease in the size) of nanograins to 2-5 nm with the formation of spheroidal gold nanocrystallites a few nanometers in size, as well as to the formation of an amorphous oxide film in the depth (near-surface layer) of the coating due to ballistic ion mixing and collision cascades.

  8. Influence of varying metal-to-glass ratio on GMI effect in CoFeBSiCr amorphous glass-coated microwires

    NASA Astrophysics Data System (ADS)

    Qin, F. X.; Peng, H. X.; Phan, M. H.

    2010-01-01

    The influence of a varying metal-to-glass ratio on the GMI effect in amorphous glass-coated Co 70.3Fe 3.7B 10Si 13Cr 3 microwires has been investigated. In the range of frequencies investigated (1-10 MHz), the magnitude of the GMI effect increases as the metal-to-glass ratio (h) increases from 4.11 to 9.29. The GMI curves for the h=4.11 microwire exhibit a single-peak feature for f≤1 MHz and a double-peak feature for f>1 MHz, whereas a consistent double-peak feature is observed for microwires with h=8.07,8.72, and 9.29. The largest GMI effect is achieved for microwires with h=9.29. The anisotropy field (H), determined from GMI curves, increases with h=4.11 to h=8.07 and decreases when h>8.07. The calculated radial stress decreases as h increases from 4.11 to 9.29. These results provide further insights into the correlation between the GMI effect and microwire dimensions towards the GMI optimization of amorphous glass-coated magnetic microwires for sensor applications.

  9. High pressure die casting of Fe-based metallic glass

    NASA Astrophysics Data System (ADS)

    Ramasamy, Parthiban; Szabo, Attila; Borzel, Stefan; Eckert, Jürgen; Stoica, Mihai; Bárdos, András

    2016-10-01

    Soft ferromagnetic Fe-based bulk metallic glass key-shaped specimens with a maximum and minimum width of 25.4 and 5 mm, respectively, were successfully produced using a high pressure die casting (HPDC) method, The influence of die material, alloy temperature and flow rate on the microstructure, thermal stability and soft ferromagnetic properties has been studied. The results suggest that a steel die in which the molten metal flows at low rate and high temperature can be used to produce completely glassy samples. This can be attributed to the laminar filling of the mold and to a lower heat transfer coefficient, which avoids the skin effect in the steel mold. In addition, magnetic measurements reveal that the amorphous structure of the material is maintained throughout the key-shaped samples. Although it is difficult to control the flow and cooling rate of the molten metal in the corners of the key due to different cross sections, this can be overcome by proper tool geometry. The present results confirm that HPDC is a suitable method for the casting of Fe-based bulk glassy alloys even with complex geometries for a broad range of applications.

  10. High pressure die casting of Fe-based metallic glass

    PubMed Central

    Ramasamy, Parthiban; Szabo, Attila; Borzel, Stefan; Eckert, Jürgen; Stoica, Mihai; Bárdos, András

    2016-01-01

    Soft ferromagnetic Fe-based bulk metallic glass key-shaped specimens with a maximum and minimum width of 25.4 and 5 mm, respectively, were successfully produced using a high pressure die casting (HPDC) method, The influence of die material, alloy temperature and flow rate on the microstructure, thermal stability and soft ferromagnetic properties has been studied. The results suggest that a steel die in which the molten metal flows at low rate and high temperature can be used to produce completely glassy samples. This can be attributed to the laminar filling of the mold and to a lower heat transfer coefficient, which avoids the skin effect in the steel mold. In addition, magnetic measurements reveal that the amorphous structure of the material is maintained throughout the key-shaped samples. Although it is difficult to control the flow and cooling rate of the molten metal in the corners of the key due to different cross sections, this can be overcome by proper tool geometry. The present results confirm that HPDC is a suitable method for the casting of Fe-based bulk glassy alloys even with complex geometries for a broad range of applications. PMID:27725780

  11. 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.

  12. Neutron-Absorbing Coatings for Safe Storage of Fissile Materials with Enhanced Shielding & Criticality Safety

    SciTech Connect

    Choi, J; Farmer, J; Lee, C; Fischer, L; Boussoufi, M; Liu, B; Egbert, H

    2007-07-03

    Neutron-absorbing Fe-based amorphous-metal coatings have been developed that are more corrosion resistant than other criticality-control materials, including Al-B{sub 4}C composites, borated stainless steels, and Ni-Cr-Mo-Gd alloys. The presence of relatively high concentration of boron in these coatings not only enhances its neutron-absorption capability, but also enables these coatings to exist in the amorphous state. Exceptional corrosion resistance has been achieved with these Fe-based amorphous-metal alloys through additions of chromium, molybdenum, and tungsten. The addition of rare earth elements such as yttrium has lowered the critical cooling rate of these materials, thereby rendering them more easily processed. Containers used for the storage of nuclear materials, and protected from corrosion through the application of amorphous metal coatings, would have greatly enhanced service lives, and would therefore provide greater long-term safety. Amorphous alloy powders have been successfully produced in multi-ton quantities with gas atomization, and applied to several half-scale spent fuel storage containers and criticality control structures with the high-velocity oxy-fuel (HVOF) thermal spray process. Salt fog testing and neutron radiography of these prototypes indicates that such an approach is viable for the production of large-scale industrial-scale facilities and containers. The use of these durable neutron-absorbing materials to coat stainless steel containers and storage racks, as well as vaults, hot-cell facilities and glove boxes could substantially reduce the risk of criticality in the event of an accident. These materials are particularly attractive for shielding applications since they are fire proof. Additionally, layers of other cold and thermal sprayed materials that include carbon and/or carbides can be used in conjunction with the high-boron amorphous metal coatings for the purpose of moderation. For example, various carbides, including boron

  13. Application of Neutron-Absorbing Structural-Amorphous Metal (SAM) Coatings for Spent Nuclear Fuel (SNF) Container to Enhance Criticality Safety Controls

    SciTech Connect

    Choi, Jor-Shan; Lee, Chuck; Farmer, Joseph; Day, Dan; Wall, Mark; Saw, Cheng; Boussoufi, Moe; Liu, Ben; Egbert, Harold; Branagan, Dan; D'Amato, Andy

    2007-07-01

    Spent nuclear fuel contains fissionable materials ({sup 235}U, {sup 239}Pu, {sup 241}Pu, etc.). To prevent nuclear criticality in spent fuel storage, transportation, and during disposal, neutron-absorbing materials (or neutron poisons, such as borated stainless steel, Boral{sup TM}, Metamic{sup TM}, Ni-Gd, and others) would have to be applied. The success in demonstrating that the High-Performance Corrosion- Resistant Material (HPCRM){sup [1]} can be thermally applied as coating onto base metal to provide for corrosion resistance for many naval applications raises the interest in applying the HPCRM to USDOE/OCRWM spent fuel management program. The fact that the HPCRM relies on the high content of boron to make the material amorphous - an essential property for corrosion resistance - and that the boron has to be homogeneously distributed in the HPCRM qualify the material to be a neutron poison. (authors)

  14. Fabrication of amorphous diamond films

    DOEpatents

    Falabella, S.

    1995-12-12

    Amorphous diamond films having a significant reduction in intrinsic stress are prepared by biasing a substrate to be coated and depositing carbon ions thereon under controlled temperature conditions. 1 fig.

  15. An in-situ gas chromatography investigation into the suppression of oxygen gas evolution by coated amorphous cobalt-phosphate nanoparticles on oxide electrode

    PubMed Central

    Gim, Jihyeon; Song, Jinju; Kim, Sungjin; Jo, Jeonggeun; Kim, Seokhun; Yoon, Jaegu; Kim, Donghan; Hong, Suk-Gi; Park, Jin-Hwan; Mathew, Vinod; Han, Junhee; Song, Sun-Ju; Kim, Jaekook

    2016-01-01

    The real time detection of quantitative oxygen release from the cathode is performed by in-situ Gas Chromatography as a tool to not only determine the amount of oxygen release from a lithium-ion cell but also to address the safety concerns. This in-situ gas chromatography technique monitoring the gas evolution during electrochemical reaction presents opportunities to clearly understand the effect of surface modification and predict on the cathode stability. The oxide cathode, 0.5Li2MnO3∙0.5LiNi0.4Co0.2Mn0.4O2, surface modified by amorphous cobalt-phosphate nanoparticles (a-CoPO4) is prepared by a simple co-precipitation reaction followed by a mild heat treatment. The presence of a 40 nm thick a-CoPO4 coating layer wrapping the oxide powders is confirmed by electron microscopy. The electrochemical measurements reveal that the a-CoPO4 coated overlithiated layered oxide cathode shows better performances than the pristine counterpart. The enhanced performance of the surface modified oxide is attributed to the uniformly coated Co-P-O layer facilitating the suppression of O2 evolution and offering potential lithium host sites. Further, the formation of a stable SEI layer protecting electrolyte decomposition also contributes to enhanced stabilities with lesser voltage decay. The in-situ gas chromatography technique to study electrode safety offers opportunities to investigate the safety issues of a variety of nanostructured electrodes. PMID:27001370

  16. Internal stresses in wear and corrosion resistant amorphous metallic coatings of (W/0.6/Re/0.4/)76B24 and (Mo/0.6/Ru/0.4/)82B18

    NASA Technical Reports Server (NTRS)

    Thakoor, A. P.; Lamb, J. L.; Williams, R. M.; Khanna, S. K.

    1985-01-01

    Hard protective coatings in the W-Re-B and Mo-Ru-B alloy systems have been deposited by magnetron sputtering onto soda-lime glass and heat-treated AISI 52100 steel substrates. X-ray diffraction has confirmed the amorphous nature of the as-deposited coatings, and their crystallization temperatures were determined by differential thermal analysis to be 1000 and 790 C for W-Re-B and Mo-Ru-B coatings, respectively. Both coatings exhibit high microhardness; Mo-Ru-B, in addition, has excellent corrosion resistance by comparison with pure Mo at high anodic potentials. Attention is given to the influence of internal stresses on the protective properties of the coatings deposited under different conditions.

  17. Internal stresses in wear and corrosion resistant amorphous metallic coatings of (W/0. 6/Re/0. 4/)76B24 and (Mo/0. 6/Ru/0. 4/)82B18

    SciTech Connect

    Thakoor, A.P.; Lamb, J.L.; Williams, R.M.; Khanna, S.K.

    1985-06-01

    Hard protective coatings in the W-Re-B and Mo-Ru-B alloy systems have been deposited by magnetron sputtering onto soda-lime glass and heat-treated AISI 52100 steel substrates. X-ray diffraction has confirmed the amorphous nature of the as-deposited coatings, and their crystallization temperatures were determined by differential thermal analysis to be 1000 and 790 C for W-Re-B and Mo-Ru-B coatings, respectively. Both coatings exhibit high microhardness; Mo-Ru-B, in addition, has excellent corrosion resistance by comparison with pure Mo at high anodic potentials. Attention is given to the influence of internal stresses on the protective properties of the coatings deposited under different conditions. 20 references.

  18. Hard coating of ultrananocrystalline diamond/nonhydrogenated amorphous carbon composite films on cemented tungsten carbide by coaxial arc plasma deposition

    NASA Astrophysics Data System (ADS)

    Naragino, Hiroshi; Egiza, Mohamed; Tominaga, Aki; Murasawa, Koki; Gonda, Hidenobu; Sakurai, Masatoshi; Yoshitake, Tsuyoshi

    2016-08-01

    Ultrananocrystalline diamond (UNCD)/nonhydrogenated amorphous carbon (a-C) composite (UNCD/a-C) films were deposited on cemented carbide containing Co by coaxial arc plasma deposition. With decreasing substrate temperature, the hardness was enhanced accompanied by an enhancement in the sp3/(sp2 + sp3). Energy-dispersive X-ray and secondary ion mass spectrometry spectroscopic measurements exhibited that the diffusion of Co atoms from the substrates into the films hardly occurs. The film deposited at room temperature exhibited the maximum hardness of 51.3 GPa and Young's modulus of 520.2 GPa, which evidently indicates that graphitization induced by Co in the WC substrates, and thermal deformation from sp3 to sp2 bonding are suppressed. The hard UNCD/a-C films can be deposited at a thickness of approximately 3 μm, which is an order larger than that of comparably hard a-C films. The internal compressive stress of the 51.3-GPa film is 4.5 GPa, which is evidently smaller than that of comparably hard a-C films. This is a reason for the thick deposition. The presence of a large number of grain boundaries in the film, which is a structural specific to UNCD/a-C films, might play a role in releasing the internal stress of the films.

  19. Coatings.

    ERIC Educational Resources Information Center

    Anderson, Dennis G.

    1989-01-01

    This review covers analytical techniques applicable to the examination of coatings, raw materials, and substrates upon which coatings are placed. Techniques include chemical and electrochemical methods, chromatography, spectroscopy, thermal analysis, microscopy, and miscellaneous techniques. (MVL)

  20. Physicochemical Characterization and In Vivo Evaluation of Amorphous and Partially Crystalline Calcium Phosphate Coatings Fabricated on Ti-6Al-4V Implants by the Plasma Spray Method.

    PubMed

    Bonfante, Estevam A; Witek, Lukasz; Tovar, Nick; Suzuki, Marcelo; Marin, Charles; Granato, Rodrigo; Coelho, Paulo G

    2012-01-01

    Objective. To characterize the topographic and chemical properties of 2 bioceramic coated plateau root form implant surfaces and evaluate their histomorphometric differences at 6 and 12 weeks in vivo. Methods. Plasma sprayed hydroxyapatite (PSHA) and amorphous calcium phosphate (ACP) surfaces were characterized by scanning electron microscopy (SEM), interferometry (IFM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). Implants were placed in the radius epiphysis, and the right limb of dogs provided implants that remained for 6 weeks, and the left limb provided implants that remained 12 weeks in vivo. Thin sections were prepared for bone-to-implant contact (BIC) and bone-area-fraction occupancy (BAFO) measurements (evaluated by Friedman analysis P < 0.05). Results. Significantly, higher S(a) (P < 0.03) and S(q) (P < 0.02) were observed for ACP relative to PSHA. Chemical analysis revealed significantly higher HA, calcium phosphate, and calcium pyrophosphate for the PSHA surface. BIC and BAFO measurements showed no differences between surfaces. Lamellar bone formation in close contact with implant surfaces and within the healing chambers was observed for both groups. Conclusion. Given topographical and chemical differences between PSHA and ACP surfaces, bone morphology and histomorphometric evaluated parameters showed that both surfaces were osseoconductive in plateau root form implants. PMID:22969806

  1. Physicochemical Characterization and In Vivo Evaluation of Amorphous and Partially Crystalline Calcium Phosphate Coatings Fabricated on Ti-6Al-4V Implants by the Plasma Spray Method

    PubMed Central

    Bonfante, Estevam A.; Witek, Lukasz; Tovar, Nick; Suzuki, Marcelo; Marin, Charles; Granato, Rodrigo; Coelho, Paulo G.

    2012-01-01

    Objective. To characterize the topographic and chemical properties of 2 bioceramic coated plateau root form implant surfaces and evaluate their histomorphometric differences at 6 and 12 weeks in vivo. Methods. Plasma sprayed hydroxyapatite (PSHA) and amorphous calcium phosphate (ACP) surfaces were characterized by scanning electron microscopy (SEM), interferometry (IFM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). Implants were placed in the radius epiphysis, and the right limb of dogs provided implants that remained for 6 weeks, and the left limb provided implants that remained 12 weeks in vivo. Thin sections were prepared for bone-to-implant contact (BIC) and bone-area-fraction occupancy (BAFO) measurements (evaluated by Friedman analysis P < 0.05). Results. Significantly, higher Sa (P < 0.03) and Sq (P < 0.02) were observed for ACP relative to PSHA. Chemical analysis revealed significantly higher HA, calcium phosphate, and calcium pyrophosphate for the PSHA surface. BIC and BAFO measurements showed no differences between surfaces. Lamellar bone formation in close contact with implant surfaces and within the healing chambers was observed for both groups. Conclusion. Given topographical and chemical differences between PSHA and ACP surfaces, bone morphology and histomorphometric evaluated parameters showed that both surfaces were osseoconductive in plateau root form implants. PMID:22969806

  2. Comparison of electrorheological performance between urea-coated and graphene oxide-wrapped core-shell structured amorphous TiO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Dong, Xufeng; Huo, Shuang; Qi, Min

    2016-01-01

    Polar molecules and graphene oxide (GO) have been used as the shell materials to prepare core-shell structured particles with enhanced electrorheological (ER) properties. Nevertheless, few studies compared the ER performance and stability of the suspensions with the two kinds of shell. In this study, urea and GO are used as the shell materials to prepare TiO2/urea and TiO2/GO core-shell particles-based ER fluids, respectively. Particle characterization results indicate the two kinds of core-shell structured particles present little change in size, morphology and crystal structure compared with the bare amorphous TiO2. Some polar groups are distributed on the surface of the two kinds of core-shell structured particles, which is responsible for their improved ER performance with respect to the bare TiO2 particles. The TiO2/GO particles-based ER fluid presents higher yield stress, lower leakage current density, better sedimentation stability but lower ER efficiency than the TiO2/urea particles-based sample. The larger surface area, stronger connection with the bare TiO2 particles, and larger number of polar groups of the GO-coating is the possible reason for the different properties of TiO2/GO particles-based ER fluid compared with the TiO2/urea particles-based sample.

  3. Application of Neutron-Absorbing Structural-Amorphous Metal (SAM) Coatings for Spent Nuclear Fuel (SNF) Container to Enhance Criticality Safety Controls

    SciTech Connect

    Choi, J; Lee, C; Day, D; Wall, M; Saw, C; MoberlyChan, W; Farmer, J; Boussoufl, M; Liu, B; Egbert, H; Branagan, D; D'Amato, A

    2006-11-13

    Spent nuclear fuel contains fissionable materials ({sup 235}U, {sup 239}Pu, {sup 241}Pu, etc.). Neutron multiplication and the potential for criticality are enhanced by the presence of a moderator during cask loading in water, water incursion in accidents conditions during spent fuel storage or transport. To prevent nuclear criticality in spent fuel storage, transportation, and during disposal, neutron-absorbing materials (or neutron poisons, such as borated stainless steel, Boral{trademark}, Metamic{trademark}, Ni-Gd, and others) would have to be applied. The success in demonstrating that the High-Performance Corrosion-Resistant material (HPCRM) can be thermally applied as coating onto base metal to provide for corrosion resistance for many naval applications raises the interest in applying the HPCRM to USDOE/OCRWM spent fuel management program. The fact that the HPCRM relies on the high content of boron to make the material amorphous--an essential property for corrosion resistance--and that the boron has to be homogeneously distributed in the HPCRM qualify the material to be a neutron poison.

  4. Efficiently-cooled plasmonic amorphous silicon solar cells integrated with a nano-coated heat-pipe plate

    NASA Astrophysics Data System (ADS)

    Zhang, Yinan; Du, Yanping; Shum, Clifford; Cai, Boyuan; Le, Nam Cao Hoai; Chen, Xi; Duck, Benjamin; Fell, Christopher; Zhu, Yonggang; Gu, Min

    2016-04-01

    Solar photovoltaics (PV) are emerging as a major alternative energy source. The cost of PV electricity depends on the efficiency of conversion of light to electricity. Despite of steady growth in the efficiency for several decades, little has been achieved to reduce the impact of real-world operating temperatures on this efficiency. Here we demonstrate a highly efficient cooling solution to the recently emerging high performance plasmonic solar cell technology by integrating an advanced nano-coated heat-pipe plate. This thermal cooling technology, efficient for both summer and winter time, demonstrates the heat transportation capability up to ten times higher than those of the metal plate and the conventional wickless heat-pipe plates. The reduction in temperature rise of the plasmonic solar cells operating under one sun condition can be as high as 46%, leading to an approximate 56% recovery in efficiency, which dramatically increases the energy yield of the plasmonic solar cells. This newly-developed, thermally-managed plasmonic solar cell device significantly extends the application scope of PV for highly efficient solar energy conversion.

  5. Efficiently-cooled plasmonic amorphous silicon solar cells integrated with a nano-coated heat-pipe plate

    PubMed Central

    Zhang, Yinan; Du, Yanping; Shum, Clifford; Cai, Boyuan; Le, Nam Cao Hoai; Chen, Xi; Duck, Benjamin; Fell, Christopher; Zhu, Yonggang; Gu, Min

    2016-01-01

    Solar photovoltaics (PV) are emerging as a major alternative energy source. The cost of PV electricity depends on the efficiency of conversion of light to electricity. Despite of steady growth in the efficiency for several decades, little has been achieved to reduce the impact of real-world operating temperatures on this efficiency. Here we demonstrate a highly efficient cooling solution to the recently emerging high performance plasmonic solar cell technology by integrating an advanced nano-coated heat-pipe plate. This thermal cooling technology, efficient for both summer and winter time, demonstrates the heat transportation capability up to ten times higher than those of the metal plate and the conventional wickless heat-pipe plates. The reduction in temperature rise of the plasmonic solar cells operating under one sun condition can be as high as 46%, leading to an approximate 56% recovery in efficiency, which dramatically increases the energy yield of the plasmonic solar cells. This newly-developed, thermally-managed plasmonic solar cell device significantly extends the application scope of PV for highly efficient solar energy conversion. PMID:27113558

  6. Efficiently-cooled plasmonic amorphous silicon solar cells integrated with a nano-coated heat-pipe plate.

    PubMed

    Zhang, Yinan; Du, Yanping; Shum, Clifford; Cai, Boyuan; Le, Nam Cao Hoai; Chen, Xi; Duck, Benjamin; Fell, Christopher; Zhu, Yonggang; Gu, Min

    2016-04-26

    Solar photovoltaics (PV) are emerging as a major alternative energy source. The cost of PV electricity depends on the efficiency of conversion of light to electricity. Despite of steady growth in the efficiency for several decades, little has been achieved to reduce the impact of real-world operating temperatures on this efficiency. Here we demonstrate a highly efficient cooling solution to the recently emerging high performance plasmonic solar cell technology by integrating an advanced nano-coated heat-pipe plate. This thermal cooling technology, efficient for both summer and winter time, demonstrates the heat transportation capability up to ten times higher than those of the metal plate and the conventional wickless heat-pipe plates. The reduction in temperature rise of the plasmonic solar cells operating under one sun condition can be as high as 46%, leading to an approximate 56% recovery in efficiency, which dramatically increases the energy yield of the plasmonic solar cells. This newly-developed, thermally-managed plasmonic solar cell device significantly extends the application scope of PV for highly efficient solar energy conversion.

  7. Efficiently-cooled plasmonic amorphous silicon solar cells integrated with a nano-coated heat-pipe plate.

    PubMed

    Zhang, Yinan; Du, Yanping; Shum, Clifford; Cai, Boyuan; Le, Nam Cao Hoai; Chen, Xi; Duck, Benjamin; Fell, Christopher; Zhu, Yonggang; Gu, Min

    2016-01-01

    Solar photovoltaics (PV) are emerging as a major alternative energy source. The cost of PV electricity depends on the efficiency of conversion of light to electricity. Despite of steady growth in the efficiency for several decades, little has been achieved to reduce the impact of real-world operating temperatures on this efficiency. Here we demonstrate a highly efficient cooling solution to the recently emerging high performance plasmonic solar cell technology by integrating an advanced nano-coated heat-pipe plate. This thermal cooling technology, efficient for both summer and winter time, demonstrates the heat transportation capability up to ten times higher than those of the metal plate and the conventional wickless heat-pipe plates. The reduction in temperature rise of the plasmonic solar cells operating under one sun condition can be as high as 46%, leading to an approximate 56% recovery in efficiency, which dramatically increases the energy yield of the plasmonic solar cells. This newly-developed, thermally-managed plasmonic solar cell device significantly extends the application scope of PV for highly efficient solar energy conversion. PMID:27113558

  8. Corrosion resistant amorphous metals and methods of forming corrosion resistant amorphous metals

    DOEpatents

    Farmer, Joseph C.; Wong, Frank M. G.; Haslam, Jeffery J.; Yang, Nancy; Lavernia, Enrique J.; Blue, Craig A.; Graeve, Olivia A.; Bayles, Robert; Perepezko, John H.; Kaufman, Larry; Schoenung, Julie; Ajdelsztajn, Leo

    2009-11-17

    A system for coating a surface comprises providing a source of amorphous metal, providing ceramic particles, and applying the amorphous metal and the ceramic particles to the surface by a spray. The coating comprises a composite material made of amorphous metal that contains one or more of the following elements in the specified range of composition: yttrium (.gtoreq.1 atomic %), chromium (14 to 18 atomic %), molybdenum (.gtoreq.7 atomic %), tungsten (.gtoreq.1 atomic %), boron (.ltoreq.5 atomic %), or carbon (.gtoreq.4 atomic %).

  9. Corrosion resistant amorphous metals and methods of forming corrosion resistant amorphous metals

    DOEpatents

    Farmer, Joseph C.; Wong, Frank M.G.; Haslam, Jeffery J.; Yang, Nancy; Lavernia, Enrique J.; Blue, Craig A.; Graeve, Olivia A.; Bayles, Robert; Perepezko, John H.; Kaufman, Larry; Schoenung, Julie; Ajdelsztajn, Leo

    2014-07-15

    A system for coating a surface comprises providing a source of amorphous metal, providing ceramic particles, and applying the amorphous metal and the ceramic particles to the surface by a spray. The coating comprises a composite material made of amorphous metal that contains one or more of the following elements in the specified range of composition: yttrium (.gtoreq.1 atomic %), chromium (14 to 18 atomic %), molybdenum (.gtoreq.7 atomic %), tungsten (.gtoreq.1 atomic %), boron (.ltoreq.5 atomic %), or carbon (.gtoreq.4 atomic %).

  10. Amorphous Computing

    NASA Astrophysics Data System (ADS)

    Sussman, Gerald

    2002-03-01

    Digital computers have always been constructed to behave as precise arrangements of reliable parts, and our techniques for organizing computations depend upon this precision and reliability. Two emerging technologies, however, are begnning to undercut these assumptions about constructing and programming computers. These technologies -- microfabrication and bioengineering -- will make it possible to assemble systems composed of myriad information- processing units at almost no cost, provided: 1) that not all the units need to work correctly; and 2) that there is no need to manufacture precise geometrical arrangements or interconnection patterns among them. Microelectronic mechanical components are becoming so inexpensive to manufacture that we can anticipate combining logic circuits, microsensors, actuators, and communications devices integrated on the same chip to produce particles that could be mixed with bulk materials, such as paints, gels, and concrete. Imagine coating bridges or buildings with smart paint that can sense and report on traffic and wind loads and monitor structural integrity of the bridge. A smart paint coating on a wall could sense vibrations, monitor the premises for intruders, or cancel noise. Even more striking, there has been such astounding progress in understanding the biochemical mechanisms in individual cells, that it appears we'll be able to harness these mechanisms to construct digital- logic circuits. Imagine a discipline of cellular engineering that could tailor-make biological cells that function as sensors and actuators, as programmable delivery vehicles for pharmaceuticals, as chemical factories for the assembly of nanoscale structures. Fabricating such systems seem to be within our reach, even if it is not yet within our grasp Fabrication, however, is only part of the story. We can envision producing vast quantities of individual computing elements, whether microfabricated particles, engineered cells, or macromolecular computing

  11. Tribological properties of amorphous hydrogenated (a-C:H) and hydrogen-free tetrahedral (ta-C) diamond-like carbon coatings under jatropha biodegradable lubricating oil at different temperatures

    NASA Astrophysics Data System (ADS)

    Mobarak, H. M.; Masjuki, H. H.; Mohamad, E. Niza; Kalam, M. A.; Rashedul, H. K.; Rashed, M. M.; Habibullah, M.

    2014-10-01

    The application of diamond-like carbon (DLC) coatings on automotive components is emerging as a favorable strategy to address the recent challenges in the industry. DLC coatings can effectively lower the coefficient of friction (CoF) and wear rate of engine components, thereby improving their fuel efficiency and durability. The lubrication of ferrous materials can be enhanced by a large amount of unsaturated and polar components of oils. Therefore, the interaction between nonferrous coatings (e.g., DLC) and vegetable oil should be investigated. A ball-on-plate tribotester was used to run the experiments. Stainless steel plates coated with amorphous hydrogenated (a-C:H) DLC and hydrogen-free tetrahedral (ta-C) DLC that slide against 440C stainless steel ball were used to create a ball-on-plate tribotester. The wear track was investigated through scanning electron microscopy. Energy dispersive and X-ray photoelectron spectroscopies were used to analyze the tribofilm inside the wear track. Raman analysis was performed to investigate the structural changes in the coatings. At high temperatures, the CoF in both coatings decreased. The wear rate, however, increased in the a-C:H but decreased in the ta-C DLC-coated plates. The CoF and the wear rate (coated layer and counter surface) were primarily influenced by the graphitization of the coating. Tribochemical films, such as polyphosphate glass, were formed in ta-C and acted as protective layers. Therefore, the wear rate of the ta-C DLC was lower than that of the-C:H DLC.

  12. 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.

  13. New bulk amorphous magnetic materials

    NASA Astrophysics Data System (ADS)

    Chiriac, H.; Lupu, N.

    2001-06-01

    The relationship between structure and magnetic properties of the melt-spun ribbons with thicknesses up to 200 μm and rods having up to 3 mm diameter prepared by mould casting and suction casting techniques, of nominal compositions Fe 56Co 7Ni 7Zr 6M 1.5Nb 2.5B 20 (M=Zr, Ti, Ta or Mo) and Nd 50Fe 40Si 10- xAl x was investigated. Saturation magnetisations up to 1.1 T, coercive fields of about 5 A/m, magnetic permeabilities of 25 000-30 000 in the as-cast state were measured for the Fe-based amorphous alloys. The large values over 200 kA/m of the intrinsic coercive field at room temperature and over 600 kA/m at 200 K measured in low magnetic fields for the Nd-Fe-based “X-ray amorphous” alloys, and its dependence on temperature and cooling rate are ascribed to the existence of very small ferromagnetic clusters embedded in an Nd-rich matrix. The thermal treatments applied to the amorphous samples below the crystallisation temperature cause an improvement in the magnetic properties as a consequence of structural relaxation.

  14. The activation mechanism of Fe-based olefin metathesis catalysts

    NASA Astrophysics Data System (ADS)

    Poater, Albert; Pump, Eva; Vummaleti, Sai Vikrama Chaitanya; Cavallo, Luigi

    2014-08-01

    Density functional theory calculations have been used to describe the first turnover for olefin metathesis reaction of a homogenous Fe-based catalyst bearing a N-heterocyclic carbene ligand with methoxyethene as a substrate. Equal to conventional Ru-based catalysts, the activation of its Fe congener occurs through a dissociative mechanism, however with a more exothermic reaction energy profile. Predicted upper energy barriers were calculated to be on average ∼2 kcal/mol more beneficial for Fe catalyzed metathesis. Overall, this present computational study emphasises on advantages of Fe-based metathesis and gives a potential recipe for the design of an efficient Fe-based olefin metathesis catalysts.

  15. 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)

  16. Amorphic complexity

    NASA Astrophysics Data System (ADS)

    Fuhrmann, G.; Gröger, M.; Jäger, T.

    2016-02-01

    We introduce amorphic complexity as a new topological invariant that measures the complexity of dynamical systems in the regime of zero entropy. Its main purpose is to detect the very onset of disorder in the asymptotic behaviour. For instance, it gives positive value to Denjoy examples on the circle and Sturmian subshifts, while being zero for all isometries and Morse-Smale systems. After discussing basic properties and examples, we show that amorphic complexity and the underlying asymptotic separation numbers can be used to distinguish almost automorphic minimal systems from equicontinuous ones. For symbolic systems, amorphic complexity equals the box dimension of the associated Besicovitch space. In this context, we concentrate on regular Toeplitz flows and give a detailed description of the relation to the scaling behaviour of the densities of the p-skeletons. Finally, we take a look at strange non-chaotic attractors appearing in so-called pinched skew product systems. Continuous-time systems, more general group actions and the application to cut and project quasicrystals will be treated in subsequent work.

  17. Amorphous-diamond electron emitter

    DOEpatents

    Falabella, Steven

    2001-01-01

    An electron emitter comprising a textured silicon wafer overcoated with a thin (200 .ANG.) layer of nitrogen-doped, amorphous-diamond (a:D-N), which lowers the field below 20 volts/micrometer have been demonstrated using this emitter compared to uncoated or diamond coated emitters wherein the emission is at fields of nearly 60 volts/micrometer. The silicon/nitrogen-doped, amorphous-diamond (Si/a:D-N) emitter may be produced by overcoating a textured silicon wafer with amorphous-diamond (a:D) in a nitrogen atmosphere using a filtered cathodic-arc system. The enhanced performance of the Si/a:D-N emitter lowers the voltages required to the point where field-emission displays are practical. Thus, this emitter can be used, for example, in flat-panel emission displays (FEDs), and cold-cathode vacuum electronics.

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

    DOE PAGES

    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. 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

  19. 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.

  20. Thermal conductivity and interface thermal conductance of amorphous and crystalline Zr47Cu31Al13Ni9 alloys with a Y2O3 coating

    NASA Astrophysics Data System (ADS)

    Shukla, Nitin C.; Liao, Hao-Hsiang; Abiade, Jeremiah T.; Liu, Fengxiao; Liaw, Peter K.; Huxtable, Scott T.

    2009-02-01

    We examine the thermal conductivity k and interface thermal conductance G for amorphous and crystalline Zr47Cu31Al13Ni9 alloys in contact with polycrystalline Y2O3. Using time-domain thermoreflectance, we find k =4.5 W m-1 K-1 for the amorphous metallic alloy of Zr47Cu31Al13Ni9 and k =5.0 W m-1 K-1 for the crystalline Zr47Cu31Al13Ni9. We also measure G =23 MW m-2 K-1 for the metallic glass/Y2O3 interface and G =26 MW m-2 K-1 for the interface between the crystalline Zr47Cu31Al13Ni9 and Y2O3. The thermal conductivity of the crystalline Y2O3 layer is found to be k =5.0 W m-1 K-1, and the conductances of Al/Y2O3 and Y2O3/Si interfaces are 68 and 45 MW m-2 K-1, respectively.

  1. RAPID COMMUNICATION: Studies of the magnetostriction of as-prepared and annealed glass-coated Co-rich amorphous microwires by SAMR method

    NASA Astrophysics Data System (ADS)

    Zhukova, V.; Blanco, J. M.; Zhukov, A.; Gonzalez, J.

    2001-11-01

    The saturation magnetostriction constant, λs, of as-prepared and current annealed glass-covered Co57Fe6.1Ni10B15.9Si11, Co67.5Fe4Ni1.5B14Si12Mo1, Co69.1Fe5.2Ni1B14.8Si9.9 and Co69.5Fe3.9Ni1B12.8Si10.8Mo2 amorphous microwires has been measured by the small angle magnetization rotation method. As-prepared samples exhibit negative λs ranging between -0.9×10-6 and -0.3×10-6. Current annealing results in a significant change of λs, that is, a general tendency to increase towards zero.

  2. Structural evolution, thermomechanical recrystallization and electrochemical corrosion properties of Ni-Cu-Mg amorphous coating on mild steel fabricated by dual-anode electrolytic processing

    NASA Astrophysics Data System (ADS)

    Abdulwahab, M.; Fayomi, O. S. I.; Popoola, A. P. I.

    2016-07-01

    The electrolytic Ni-Cu based alloy coating with admixed interfacial blend of Mg have been successfully prepared on mild steel substrate by dual anode electroplating processes over a range of applied current density and dwell time. The electrocodeposition of Ni-Cu-Mg coating was investigated in the presence of other bath additives. The influence of deposition current on surface morphology, adhesion behavior, preferred crystal orientation, surface topography and electrochemical activity of Ni-Cu-Mg alloy coating on mild steel were systematically examined. The thermal stability of the developed composite materials was examined via isothermal treatment. Scanning electron microscope equipped with EDS, X-ray diffraction, Atomic force microscope, micro-hardness tester and 3 μmetrohm Potentiostat/galvanostat were used to compare untreated and isothermally treated electrocodeposited composite. The induced activity of the Ni-Cu-Mg alloy changed the surface modification and results to crystal precipitation within the structural interface by the formation of Cu, Ni2Mg3 phase. The obtained results showed that the introduction of Mg particles in the plating bath generally modified the surface and brings an increase in the hardness and corrosion resistance of Ni-Cu-Mg layers fabricated. Equally, isothermally treated composites demonstrated an improved properties indicating 45% increase in the micro-hardness and 79.6% corrosion resistance which further showed that the developed composite is thermally stable.

  3. New analysis of the small-angle-magnetization-rotation method for magnetostriction measurements on amorphous ribbons

    NASA Astrophysics Data System (ADS)

    Severino, A. M.; Missell, F. P.

    1987-09-01

    The small-angle-magnetization-rotation (SAMR) method for measuring the saturation magnetostrictin λ s has been reanalyzed, taking into account the underlying domain structure of the amorphous ribbon. Although the condition for determining λ s reamins unchenged, the modifications introduced allow one to understand many additional features of the experimental data. With the appropriate modifications, the SAMR method can be used to study stress relaxation in amorphous alloys. Examples are given Fe-based and Co-based alloys.

  4. Development of magnetic Fe-based metallic glasses without metalloids

    SciTech Connect

    Mastrogiacomo, Giovanni; Kradolfer, Juerg; Loeffler, Joerg F.

    2006-01-15

    The glass-forming ability of Fe-based metallic glasses has a direct relationship with their metalloid content. A good glass-former usually needs a metalloid content of approximately 20 at. %. However, a high metalloid content causes deterioration not only in magnetic properties but also in elasticity and plasticity. Based on destabilization of the solid state we have developed a series of metalloid-free Fe-based metallic glasses of composition (Fe{sub 0.582}Co{sub 0.418}){sub 100-x-y}Cr{sub x}Zr{sub y} (10{<=}x{<=}28 and 8{<=}y{<=}11). Via this destabilization the liquid state is stabilized, which results in a decreasing liquidus temperature. The mechanical and magnetic properties of the metalloid-free Fe-based metallic glass with the highest Fe and Co fractions were analyzed. The alloy of composition (Fe{sub 0.582}Co{sub 0.418}){sub 80}Cr{sub 10}Zr{sub 10} exhibits bending elasticity and plasticity. Magnetization measurements reveal a saturation magnetization of up to 1.1 T and an inverted hysteresis. The origin of this inverted hysteresis presumably lies in the inclination to decompose in a ferromagnetic iron-rich {alpha}{sub 1} phase and an antiferromagnetic chromium-rich {alpha}{sub 2} phase.

  5. Improved cycling performance of 5 V spinel LiMn1.5Ni0.5O4 by amorphous FePO4 coating

    NASA Astrophysics Data System (ADS)

    Liu, Dilong; Bai, Ying; Zhao, Sen; Zhang, Weifeng

    2012-12-01

    Cycling stability of 5 V spinel LiMn1.5Ni0.5O4 (LMNO) is improved by surface modification with FePO4 through a chemical deposition method. The pristine, 0.5 wt.%, 1 wt.% and 3 wt.% FePO4-coated LMNO are characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy and field emission scanning electron microscopy. It is found that the coating process is in favor of the disorder-order phase transition. The investigation on their cycling performance demonstrates that 1 wt.% FePO4-modified LMNO cathode exhibits the best cycling performance, with the capacity retention ratio of 99.3% after 50 cycles, much better than that of the pristine LMNO (only 79%). Electrochemical impedance spectroscopy is applied to explain the galvanostatic results. The enhanced cycling performance of the surface-modified samples can be attributed to the decreasing contact area between the electrode and electrolyte and the suppression of undesirable thick SEI (solid electrolyte interfacial) layer.

  6. Amorphous metal composites

    DOEpatents

    Byrne, Martin A.; Lupinski, John H.

    1984-01-01

    An improved amorphous metal composite and process of making the composite. The amorphous metal composite comprises amorphous metal (e.g. iron) and a low molecular weight thermosetting polymer binder. The process comprises placing an amorphous metal in particulate form and a thermosetting polymer binder powder into a container, mixing these materials, and applying heat and pressure to convert the mixture into an amorphous metal composite.

  7. PREFACE: Focus on superconductivity in Fe-based systems Focus on superconductivity in Fe-based systems

    NASA Astrophysics Data System (ADS)

    Prozorov, Ruslan; Chubukov, Andrey; Meingast, Christoph; Putti, Marina

    2012-08-01

    The past four years of incredibly intense research into Fe-based superconductors have brought about many unexpected surprises. Our understanding of their behavior and physical properties is constantly evolving. Unlike any other superconductors, those containing iron span diverse groups of materials: pnictides, chalcogenides, intermetallics and oxides. Some major properties of the materials are quite similar, yet each group has its own distinct features. Significant effort has been put into identifying new superconducting compositions, modifying the existing ones with new dopants and treatments, and producing single crystals, thin films, wires and polycrystalline bulk material. A wide array of experimental techniques was applied to study Fe-based superconductors and the result is a tremendous amount of data collected over a period of less than four years. Theoretical debates are still lively, and there is an ongoing search for possible universalities and commonalities with other unconventional superconductors, like high-Tc cuprates or heavy fermion materials. The three-dimensional electronic structures of Fe-based superconductors, as well as their extreme sensitivity to disorder, present serious challenges for both theoretical analysis and the interpretation of experiments. However, some key properties emerge from multiple studies. Unconventional, multiband superconductivity originating from an electronic mechanism has found both experimental and theoretical support. There has been great progress in the understanding of various anisotropies of superconducting gap structures, including the possibility of gap nodes even if the gap symmetry is s-wave. Similar to high-Tc cuprates, the superconducting phase has a dome-like shape on T-doping or T-pressure phase diagrams. The anisotropy of the superconducting gap evolves with doping and is likely to become stronger at the dome's edge. In many Fe-based superconductors there is a range where superconductivity coexists and

  8. 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.

  9. Initial results and long-term clinical follow-up of an amorphous hydrogenated silicon-carbide-coated stent in daily practice.

    PubMed

    Hanekamp, Clara EE; Bonnier, Hans JRM; Michels, Rolf H; Peels, Kathinka H; Heijmen, Eric PCM; Hagen Ev, Eduard van; Koolen, Jacques J

    1998-01-01

    The hemocompatibility and biocompatibility of a stent are determined by the physical and electrochemical properties of the stent surface. The aim of this study was to determine the feasibility, safety and efficacy of implantation of a stent coated with silicon carbide. Baseline characteristics were collected prospectively. The occurrence of cardiac adverse events and the angina score were assessed at clinical follow-up. A total of 193 Tensum stents were implanted in 174 patients. In hospital, one patient experienced stent thrombosis and in 6% of the patients a creatinine kinase elevation to 240 U/l or more occurred. Long-term follow-up was performed in 172 patients, with a mean follow-up of 454 +/- 181 days. Ninety-seven per cent were still alive, 15% had undergone target-vessel revascularization, and 2% had angiographic restenosis and were treated with medication only. Seventy-one per cent of the patients were free of anginal complaints, and 20% had anginal complaints in Canadian Cardiac Society class I or II. The Tensum coronary stent showed to be a safe and efficacious device in this study, with a high primary success rate and favorable long-term clinical followup.

  10. Magnetism in Na-filled Fe-based skutterudites.

    PubMed

    Xing, Guangzong; Fan, Xiaofeng; Zheng, Weitao; Ma, Yanming; Shi, Hongliang; Singh, David J

    2015-06-01

    The interplay of superconductivity and magnetism is a subject of ongoing interest, stimulated most recently by the discovery of Fe-based superconductivity and the recognition that spin-fluctuations near a magnetic quantum critical point may provide an explanation for the superconductivity and the order parameter. Here we investigate magnetism in the Na filled Fe-based skutterudites using first principles calculations. NaFe4Sb12 is a known ferromagnet near a quantum critical point. We find a ferromagnetic metallic state for this compound driven by a Stoner type instability, consistent with prior work. In accord with prior work, the magnetization is overestimated, as expected for a material near an itinerant ferromagnetic quantum critical point. NaFe4P12 also shows a ferromagnetic instability at the density functional level, but this instability is much weaker than that of NaFe4Sb12, possibly placing it on the paramagnetic side of the quantum critical point. NaFe4As12 shows intermediate behavior. We also present results for skutterudite FeSb3, which is a metastable phase that has been reported in thin film form.

  11. Magnetism in Na-filled Fe-based skutterudites

    SciTech Connect

    Xing, Guangzong; Fan, Xiaofeng; Zheng, Weitao; Ma, Yanming; Shi, Hongliang; Singh, David J.

    2015-06-01

    The interplay of superconductivity and magnetism is a subject of ongoing interest, stimulated most recently by the discovery of Fe-based superconductivity and the recognition that spin-fluctuations near a magnetic quantum critical point may provide an explanation for the superconductivity and the order parameter. We investigate magnetism in the Na filled Fe-based skutterudites using first principles calculations. NaFe4Sb12 is a known ferromagnet near a quantum critical point. We find a ferromagnetic metallic state for this compound driven by a Stoner type instability, consistent with prior work. In accord with prior work, the magnetization is overestimated, as expected for a material near an itinerant ferromagnetic quantum critical point. NaFe4P12 also shows a ferromagnetic instability at the density functional level, but this instability is much weaker than that of NaFe4Sb12, possibly placing it on the paramagnetic side of the quantum critical point. NaFe4As12 shows intermediate behavior. We also present results for skutterudite FeSb3, which is a metastable phase that has been reported in thin film form.

  12. Magnetism in Na-filled Fe-based skutterudites

    DOE PAGES

    Xing, Guangzong; Fan, Xiaofeng; Zheng, Weitao; Ma, Yanming; Shi, Hongliang; Singh, David J.

    2015-06-01

    The interplay of superconductivity and magnetism is a subject of ongoing interest, stimulated most recently by the discovery of Fe-based superconductivity and the recognition that spin-fluctuations near a magnetic quantum critical point may provide an explanation for the superconductivity and the order parameter. We investigate magnetism in the Na filled Fe-based skutterudites using first principles calculations. NaFe4Sb12 is a known ferromagnet near a quantum critical point. We find a ferromagnetic metallic state for this compound driven by a Stoner type instability, consistent with prior work. In accord with prior work, the magnetization is overestimated, as expected for a material nearmore » an itinerant ferromagnetic quantum critical point. NaFe4P12 also shows a ferromagnetic instability at the density functional level, but this instability is much weaker than that of NaFe4Sb12, possibly placing it on the paramagnetic side of the quantum critical point. NaFe4As12 shows intermediate behavior. We also present results for skutterudite FeSb3, which is a metastable phase that has been reported in thin film form.« less

  13. Magnetism in Na-filled Fe-based skutterudites

    PubMed Central

    Xing, Guangzong; Fan, Xiaofeng; Zheng, Weitao; Ma, Yanming; Shi, Hongliang; Singh, David J.

    2015-01-01

    The interplay of superconductivity and magnetism is a subject of ongoing interest, stimulated most recently by the discovery of Fe-based superconductivity and the recognition that spin-fluctuations near a magnetic quantum critical point may provide an explanation for the superconductivity and the order parameter. Here we investigate magnetism in the Na filled Fe-based skutterudites using first principles calculations. NaFe4Sb12 is a known ferromagnet near a quantum critical point. We find a ferromagnetic metallic state for this compound driven by a Stoner type instability, consistent with prior work. In accord with prior work, the magnetization is overestimated, as expected for a material near an itinerant ferromagnetic quantum critical point. NaFe4P12 also shows a ferromagnetic instability at the density functional level, but this instability is much weaker than that of NaFe4Sb12, possibly placing it on the paramagnetic side of the quantum critical point. NaFe4As12 shows intermediate behavior. We also present results for skutterudite FeSb3, which is a metastable phase that has been reported in thin film form. PMID:26027504

  14. Improve the catalytic activity of {alpha}-Fe{sub 2}O{sub 3} particles in decomposition of ammonium perchlorate by coating amorphous carbon on their surface

    SciTech Connect

    Zhang Yifu; Liu Xinghai; Nie Jiaorong; Yu Lei; Zhong Yalan; Huang Chi

    2011-02-15

    Sphere- and pod-like {alpha}-Fe{sub 2}O{sub 3} particles have been selectively synthesized using NH{sub 3}.H{sub 2}O and NaOH solution to adjust the pH value of the designed synthetic system, respectively. The sphere-like {alpha}-Fe{sub 2}O{sub 3} particles with diameter about 25 nm on average were encapsulated into carbon shells to fabricate a novel core-shell composite ({alpha}-Fe{sub 2}O{sub 3}-C) through the coating experiments. The catalytic performance of the products on the thermal decomposition of ammonium perchlorate (AP) was investigated by thermal gravimetric analyzer (TG) and differential thermal analysis (DTA). The thermal decomposition temperatures of AP in the presence of pod-like {alpha}-Fe{sub 2}O{sub 3}, sphere-like {alpha}-Fe{sub 2}O{sub 3} and {alpha}-Fe{sub 2}O{sub 3}-C are reduced by 72, 81 and 109 {sup o}C, respectively, which show that {alpha}-Fe{sub 2}O{sub 3}-C core-shell composites have higher catalytic activity than that of {alpha}-Fe{sub 2}O{sub 3}. -- Graphical abstract: The catalytic performance of pod-like {alpha}-Fe{sub 2}O{sub 3}, sphere-like {alpha}-Fe{sub 2}O{sub 3} and {alpha}-Fe{sub 2}O{sub 3}-C on the thermal decomposition of ammonium perchlorate (AP). Display Omitted Research highlights: {yields} Sphere- and pod-like {alpha}-Fe{sub 2}O{sub 3} particles have been selectively synthesized using NH{sub 3}.H{sub 2}O and NaOH solution to adjust the pH value. {yields} A novel core-shell composite ({alpha}-Fe{sub 2}O{sub 3}-C core-shell structured composite) has been successfully synthesized using sphere-like {alpha}-Fe{sub 2}O{sub 3} particles as the cores and glucose as the source of carbon. {yields} The thermal decomposition temperatures of AP in the presence of pod-like {alpha}-Fe{sub 2}O{sub 3}, sphere-like {alpha}-Fe{sub 2}O{sub 3} and {alpha}-Fe{sub 2}O{sub 3}-C are reduced by 72, 81 and 109 {sup o}C, respectively, which shows that these materials have high catalytic activity.

  15. Germanium detector passivated with hydrogenated amorphous germanium

    DOEpatents

    Hansen, William L.; Haller, Eugene E.

    1986-01-01

    Passivation of predominantly crystalline semiconductor devices (12) is provided for by a surface coating (21) of sputtered hydrogenated amorphous semiconductor material. Passivation of a radiation detector germanium diode, for example, is realized by sputtering a coating (21) of amorphous germanium onto the etched and quenched diode surface (11) in a low pressure atmosphere of hydrogen and argon. Unlike prior germanium diode semiconductor devices (12), which must be maintained in vacuum at cryogenic temperatures to avoid deterioration, a diode processed in the described manner may be stored in air at room temperature or otherwise exposed to a variety of environmental conditions. The coating (21) compensates for pre-existing undesirable surface states as well as protecting the semiconductor device (12) against future impregnation with impurities.

  16. 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.

  17. Long-Term Corrosion Testing of Thermal Spray Coatings of Amorphous Metals: Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4 and Fe48Mo14Cr15Y2C15B6

    SciTech Connect

    Farmer, J; Day, D; Lian, T; Saw, C; Hailey, P; Payer, J; Aprigliano, L; Beardsley, B; Branagan, D

    2007-07-09

    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 SAM2X5 also made it an effective neutron absorber, and suitable for criticality control applications.

  18. 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

  19. Efficient degradation of rhodamine B using Fe-based metallic glass catalyst by Fenton-like process.

    PubMed

    Wang, Xianfei; Pan, Ye; Zhu, Zirun; Wu, Jili

    2014-12-01

    An efficient heterogeneous catalyst, Fe-based metallic glass (Fe–Si–B amorphous ribbon), was successfully prepared for Fenton-like degradation of rhodamine B (RhB) by a melt-spinning method. The catalyst was characterized using XRD and SEM. The effects of various reaction parameters such as H2O2 dosage, temperature, initial pH value, Fe–Si–B dosage and initial RhB concentration on the degradation of RhB were studied. Almost complete degradation of RhB (20 mg L−1) was achieved within only 10 min by 0.5 g L−1 Fe–Si–B catalyst and 1.6 mM H2O2 at pH 3.0 at 295 K. Kinetic analyses showed that the degradation process could be described by a pseudo-first-order kinetic model. The catalytic stability was also investigated and it was found that the Fe–Si–B catalyst exhibited good structural stability and no loss of performance even after three cycles. It was concluded that the Fe–Si–B amorphous ribbon was a potential heterogeneous Fenton-like catalyst for industrial wastewater treatment.

  20. Effect of heavy-ion and electron irradiation on properties of Fe-based superconductors

    NASA Astrophysics Data System (ADS)

    Konczykowski, Marcin

    2013-03-01

    The introduction of defects by particle irradiation is used to reveal the role of disorder in matter, which is unavoidable in all crystalline solids. In superconductors defects introduce flux pinning, controlling critical current, Jc; as well as pair-breaking scattering, limiting the critical temperature, Tc. To elucidate defect related properties of Fe-based superconductors (FBS) we precede in two types of irradiation: heavy ion (6GeV Pb) to create disorder in the form of amorphous tracks and low temperature electron irradiation (2.5MeV at 20K) to create point like defects. Substantial increase of irreversible magnetization and an upward shift of the irreversibility line are observed after heavy ion irradiation of all FBS investigated to date. In BaK 122 , signatures of a Bose-glass vortex state; angular dependence and variable-range hopping flux creep are revealed. Remarkably, heavy ion irradiation does not depress Tc, however, point-like disorder introduced by electron irradiation does substantially. In isovalently substituted Ba(FeAs1 - xPx) 2 and Ba(Fe1 - x Rux As) 2 crystals, Tc decreases linearly with dose. Suppression to 40 % of initial value of Tc was achieved in Ba(FeAs1 - xPx) 2 . An increase of normal state resistivity is observed and correlated to depression of Tc. Change of superconducting gap structure with disorder was determined from penetration depth measurements, λ (T) dependence, at various stages of irradiation. Linear in T variation of pristine samples, indicative of the presence of nodes in gap, turned at low irradiation dose to exponential T variation, indicative of a fully gaped state. T2 variation of λ is observed at higher doses. This behaviour is incompatible with symmetry-imposed nodes of d-wave pairing but consistent with S + / - , S + / + mechanisms. This is the first observation of the impurity-induced node lifting expected in anisotropic s-wave superconductors

  1. Corrosion Resistance of Amorphous Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4 coating - a new criticality-controlled material

    SciTech Connect

    Farmer, J C; Choi, J S; Saw, C K; Rebak, R; Day, S D; Lian, T; Hailey, P; Payer, J H; Branagan, D J; Aprigliano, L F

    2007-03-28

    An iron-based amorphous metal with good corrosion resistance and a high absorption cross-section for thermal neutrons has been developed and is reported here. This amorphous alloy has the approximate formula 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 is known as SAM2X5. Chromium (Cr), molybdenum (Mo) and tungsten (W) were added to provide corrosion resistance, while boron (B) was added to promote glass formation and the absorption of thermal neutrons. Since this amorphous metal has a higher boron content than conventional borated stainless steels, it provides the nuclear engineer with design advantages for criticality control structures with enhanced safety. While melt-spun ribbons with limited practical applications were initially produced, large quantities (several tons) of gas atomized powder have now been produced on an industrial scale, and applied as thermal-spray coatings on prototypical half-scale spent nuclear fuel containers and neutron-absorbing baskets. These prototypes and other SAM2X5 samples have undergone a variety of corrosion testing, including both salt-fog and long-term immersion testing. Modes and rates of corrosion have been determined in various relevant environments, and are reported here. While these coatings have less corrosion resistance than melt-spun ribbons and optimized coatings produced in the laboratory, substantial corrosion resistance has been achieved.

  2. Low temperature London penetration depth and superfluid density in Fe-based superconductors

    SciTech Connect

    Kim, Hyunsoo

    2013-01-01

    The superconducting gap symmetry of the Fe-based superconductors was studied by measurements and analysis of London penetration depth and super uid density. Tunnel diode resonator technique for these measurements was implemented in a dilution refrigerator allowing for the temperatures down to 50 mK. For the analysis of the super uid density, we used both experimental studies of Al-coated samples and original thermodynamic approach based on Rutgers relation. In three systems studied, we found that the superconducting gap at the optimal doping is best described in multi-gap full gap scenario. By performing experiments on samples with arti cially introduced disorder with heavy ion irradiation, we show that evolution of the superconducting transition temperature and of the super uid density are consistent with full-gap sign changing s superconducting state. The superconducting gap develops strong modulation both in the under-doped and the over-doped regimes. In the terminal hole-doped KFe{sub 2}As{sub 2}, both temperature dependence of the super uid density and its evolution with increase of the scattering rate are consistent with symmetry imposed vertical line nodes in the superconducting gap. By comparative studies of hole-doped (Ba,K)Fe{sub 2}As{sub 2} and electron-doped Ca10-3-8, we show that the superconducting gap modulation in the under-doped regime is intrinsic and is not induced by the coexisting static magnetic order.

  3. A short-range ordering in soft magnetic Fe-based metallic glasses studied by Mössbauer spectroscopy and Reverse Monte Carlo method

    NASA Astrophysics Data System (ADS)

    Babilas, Rafał; Mariola, Kądziołka-Gaweł; Burian, Andrzej; Temleitner, László

    2016-05-01

    Selected soft magnetic amorphous alloys Fe80B20, Fe70Nb10B20 and Fe62Nb8B30 were produced by the melt-spinning and characterized by X-ray diffraction (XRD), transmission Mössbauer spectroscopy (MS), Reverse Monte Carlo modeling (RMC) and relative magnetic permeability measurements. The Mössbauer spectroscopy allowed to study the local environments of the Fe-centered atoms in the amorphous structure of binary and ternary glassy alloys. The MS provided also information about the changes in the amorphous structure due to the modification of chemical composition by various boron and niobium content. The RMC simulation based on the structure factors determined by synchrotron XRD measurements was also used in modeling of the atomic arrangements and short-range order in Fe-based model alloys. Addition of boron and niobium in the ternary model alloys affected the disorder in as-cast state and also influenced on the number of nearest neighbor Fe-Fe atoms, consequently. The distributions of Fe- and B-centered coordination numbers showed that N=10, 9 and 8 are dominated around Fe atoms and N=9, 8 and 7 had the largest population around B atoms in the examined amorphous alloys. Moreover, the relationship between the content of the alloying elements, the local atomic ordering and the magnetic permeability (magnetic after-effects) was mentioned.

  4. 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.

  5. The Phagocytosis and Toxicity of Amorphous Silica

    PubMed Central

    Costantini, Lindsey M.; Gilberti, Renée M.; Knecht, David A.

    2011-01-01

    Background Inhalation of crystalline silica is known to cause an inflammatory reaction and chronic exposure leads to lung fibrosis and can progress into the disease, silicosis. Cultured macrophages bind crystalline silica particles, phagocytose them, and rapidly undergo apoptotic and necrotic death. The mechanism by which particles are bound and internalized and the reason particles are toxic is unclear. Amorphous silica has been considered to be a less toxic form, but this view is controversial. We compared the uptake and toxicity of amorphous silica to crystalline silica. Methodology/Principal Findings Amorphous silica particles are phagocytosed by macrophage cells and a single internalized particle is capable of killing a cell. Fluorescent dextran is released from endo-lysosomes within two hours after silica treatment and Caspase-3 activation occurs within 4 hours. Interestingly, toxicity is specific to macrophage cell lines. Other cell types are resistant to silica particle toxicity even though they internalize the particles. The large and uniform size of the spherical, amorphous silica particles allowed us to monitor them during the uptake process. In mCherry-actin transfected macrophages, actin rings began to form 1-3 minutes after silica binding and the actin coat disassembled rapidly following particle internalization. Pre-loading cells with fluorescent dextran allowed us to visualize the fusion of phagosomes with endosomes during internalization. These markers provided two new ways to visualize and quantify particle internalization. At 37°C the rate of amorphous silica internalization was very rapid regardless of particle coating. However, at room temperature, opsonized silica is internalized much faster than non-opsonized silica. Conclusions/Significance Our results indicate that amorphous and crystalline silica are both phagocytosed and both toxic to mouse alveolar macrophage (MH-S) cells. The pathway leading to apoptosis appears to be similar in both

  6. Topological Superconductivity on the Surface of Fe-Based Superconductors.

    PubMed

    Xu, Gang; Lian, Biao; Tang, Peizhe; Qi, Xiao-Liang; Zhang, Shou-Cheng

    2016-07-22

    As one of the simplest systems for realizing Majorana fermions, the topological superconductor plays an important role in both condensed matter physics and quantum computations. Based on ab initio calculations and the analysis of an effective 8-band model with superconducting pairing, we demonstrate that the three-dimensional extended s-wave Fe-based superconductors such as Fe_{1+y}Se_{0.5}Te_{0.5} have a metallic topologically nontrivial band structure, and exhibit a normal-topological-normal superconductivity phase transition on the (001) surface by tuning the bulk carrier doping level. In the topological superconductivity (TSC) phase, a Majorana zero mode is trapped at the end of a magnetic vortex line. We further show that the surface TSC phase only exists up to a certain bulk pairing gap, and there is a normal-topological phase transition driven by the temperature, which has not been discussed before. These results pave an effective way to realize the TSC and Majorana fermions in a large class of superconductors. PMID:27494494

  7. Topological Superconductivity on the Surface of Fe-Based Superconductors.

    PubMed

    Xu, Gang; Lian, Biao; Tang, Peizhe; Qi, Xiao-Liang; Zhang, Shou-Cheng

    2016-07-22

    As one of the simplest systems for realizing Majorana fermions, the topological superconductor plays an important role in both condensed matter physics and quantum computations. Based on ab initio calculations and the analysis of an effective 8-band model with superconducting pairing, we demonstrate that the three-dimensional extended s-wave Fe-based superconductors such as Fe_{1+y}Se_{0.5}Te_{0.5} have a metallic topologically nontrivial band structure, and exhibit a normal-topological-normal superconductivity phase transition on the (001) surface by tuning the bulk carrier doping level. In the topological superconductivity (TSC) phase, a Majorana zero mode is trapped at the end of a magnetic vortex line. We further show that the surface TSC phase only exists up to a certain bulk pairing gap, and there is a normal-topological phase transition driven by the temperature, which has not been discussed before. These results pave an effective way to realize the TSC and Majorana fermions in a large class of superconductors.

  8. Topological Superconductivity on the Surface of Fe-Based Superconductors

    NASA Astrophysics Data System (ADS)

    Xu, Gang; Lian, Biao; Tang, Peizhe; Qi, Xiao-Liang; Zhang, Shou-Cheng

    2016-07-01

    As one of the simplest systems for realizing Majorana fermions, the topological superconductor plays an important role in both condensed matter physics and quantum computations. Based on ab initio calculations and the analysis of an effective 8-band model with superconducting pairing, we demonstrate that the three-dimensional extended s -wave Fe-based superconductors such as Fe1 +ySe0.5 Te0.5 have a metallic topologically nontrivial band structure, and exhibit a normal-topological-normal superconductivity phase transition on the (001) surface by tuning the bulk carrier doping level. In the topological superconductivity (TSC) phase, a Majorana zero mode is trapped at the end of a magnetic vortex line. We further show that the surface TSC phase only exists up to a certain bulk pairing gap, and there is a normal-topological phase transition driven by the temperature, which has not been discussed before. These results pave an effective way to realize the TSC and Majorana fermions in a large class of superconductors.

  9. 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.

  10. Quantification of corrosion resistance of a new-class of criticality control materials: thermal-spray coatings of high-boron iron-based amorphous metals - Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4

    SciTech Connect

    Farmer, J C; Choi, J S; Shaw, C K; Rebak, R; Day, S D; Lian, T; Hailey, P; Payer, J H; Branagan, D J; Aprigliano, L F

    2007-03-28

    An iron-based amorphous metal, 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} (SAM2X5), with very good corrosion resistance was developed. This material was produced as a melt-spun ribbon, as well as gas atomized powder and a thermal-spray coating. Chromium (Cr), molybdenum (Mo) and tungsten (W) provided corrosion resistance, and boron (B) enabled glass formation. The high boron content of this particular amorphous metal made it an effective neutron absorber, and suitable for criticality control applications. Earlier studies have shown that ingots and melt-spun ribbons of these materials have good passive film stability in these environments. Thermal spray coatings of these materials have now been produced, and have undergone a variety of corrosion testing, including both atmospheric and long-term immersion testing. The modes and rates of corrosion have been determined in the various environments, and are reported here.

  11. Advanced Thermal-Barrier Bond Coatings for Alloys

    NASA Technical Reports Server (NTRS)

    Secura, Stephen

    1987-01-01

    New and improved bond coatings developed for use in thermal-barrier systems on Ni, Co-, and Fe-base alloy substrates. Use of these new bond coatings, containing ytterbium instead of yttrium, significantly increased lives of resultant thermal-barrier systems. Uses include many load-bearing applications in high-temperature, hostile environments.

  12. Transmissive metallic contact for amorphous silicon solar cells

    DOEpatents

    Madan, A.

    1984-11-29

    A transmissive metallic contact for amorphous silicon semiconductors includes a thin layer of metal, such as aluminum or other low work function metal, coated on the amorphous silicon with an antireflective layer coated on the metal. A transparent substrate, such as glass, is positioned on the light reflective layer. The metallic layer is preferably thin enough to transmit at least 50% of light incident thereon, yet thick enough to conduct electricity. The antireflection layer is preferably a transparent material that has a refractive index in the range of 1.8 to 2.2 and is approximately 550A to 600A thick.

  13. Hydrogen in amorphous silicon

    SciTech Connect

    Peercy, P. S.

    1980-01-01

    The structural aspects of amorphous silicon and the role of hydrogen in this structure are reviewed with emphasis on ion implantation studies. In amorphous silicon produced by Si ion implantation of crystalline silicon, the material reconstructs into a metastable amorphous structure which has optical and electrical properties qualitatively similar to the corresponding properties in high-purity evaporated amorphous silicon. Hydrogen studies further indicate that these structures will accomodate less than or equal to 5 at.% hydrogen and this hydrogen is bonded predominantly in a monohydride (SiH/sub 1/) site. Larger hydrogen concentrations than this can be achieved under certain conditions, but the excess hydrogen may be attributed to defects and voids in the material. Similarly, glow discharge or sputter deposited amorphous silicon has more desirable electrical and optical properties when the material is prepared with low hydrogen concentration and monohydride bonding. Results of structural studies and hydrogen incorporation in amorphous silicon were discussed relative to the different models proposed for amorphous silicon.

  14. Trehalose amorphization and recrystallization.

    PubMed

    Sussich, Fabiana; Cesàro, Attilio

    2008-10-13

    The stability of the amorphous trehalose prepared by using several procedures is presented and discussed. Amorphization is shown to occur by melting (T(m)=215 degrees C) or milling (room temperature) the crystalline anhydrous form TRE-beta. Fast dehydration of the di-hydrate crystalline polymorph, TRE-h, also produces an amorphous phase. Other dehydration procedures of TRE-h, such as microwave treatment, supercritical extraction or gentle heating at low scan rates, give variable fractions of the polymorph TRE-alpha, that undergo amorphization upon melting (at lower temperature, T(m)=130 degrees C). Additional procedures for amorphization, such as freeze-drying, spray-drying or evaporation of trehalose solutions, are discussed. All these procedures are classified depending on the capability of the undercooled liquid phase to undergo cold crystallization upon heating the glassy state at temperatures above the glass transition temperature (T(g)=120 degrees C). The recrystallizable amorphous phase is invariably obtained by the melt of the polymorph TRE-alpha, while other procedures always give an amorphous phase that is unable to crystallize above T(g). The existence of two different categories is analyzed in terms of the transformation paths and the hypothesis that the systems may exhibit different molecular mobilities.

  15. Development of Fe-based bulk metallic glasses as potential biomaterials.

    PubMed

    Li, Shidan; Wei, Qin; Li, Qiang; Jiang, Bingliang; Chen, You; Sun, Yanfei

    2015-01-01

    A new series of Fe80-x-yCrxMoyP13C7 (x = 10, y = 10; x = 20, y = 5; x = 2 0, y = 10, all in at.%) bulk metallic glasses (BMGs) with the maximum diameter of 6mm have been developed for biomedical implant application by the combination method of fluxing treatment and J-quenching technique. The corrosion performance of the present Fe-based BMGs is investigated in both Hank's solution (pH = 7.4) and artificial saliva solution (pH = 6.3) at 37 °C by electrochemical measurements. The result indicates that the corrosion resistance of the present Fe-based BMGs in the above two simulated body solutions is much better than that of biomedical 316 L stainless steel (316 L SS), and approaching that of Ti6Al4V biomedical alloy (TC4). The concentrations of Fe, Ni and Cr ions released into the Hank's solution and artificial saliva solution from the present Fe-based BMGs after potentiodynamic polarization are significant lower than that released from 316 L SS. The biocompatibility of the present Fe-based BMGs is evaluated through the in vitro test of NIH3T3 cells culture in the present Fe-based BMG extraction media for 1, 3 and 5 days. The result indicates that the present Fe-based BMGs exhibit no cytotoxicity to NIH3T3 cells. And the test result of the cell adhesion and growth on the surface of the samples indicates that the present Fe-based BMGs exhibit the better cell viability compared with 316 L SS and TC4 biomedical alloys. The present Fe-based BMGs, especially Fe55Cr20Mo5P13C7 BMG, exhibit good glass formation ability, the high corrosion resistance and excellent biocompatibility, suggesting their promising potential as biomaterials. PMID:25953563

  16. Structural and soft magnetic properties of a new nanocrystalline Fe-based and B-free alloy

    NASA Astrophysics Data System (ADS)

    Long, Jianguo; Laughlin, D. E.; McHenry, M. E.

    2008-04-01

    A new nanocrystalline Fe-based soft magnetic alloy is discussed here. Ingots of nanocrystalline alloys (FeCu)80ZrxSi20-x (x =5, 6, and 8) were prepared by arc melting. The ingots were remelted and cast into 25-30μm thick ribbons by a single roller melt spinning method. X-ray diffraction (XRD) revealed the as-spun ribbons to be amorphous. The structural evolution of these samples was studied by XRD and transmission electron microscopy (TEM) after annealing at 450, 480, and 550°C. XRD shows the primary nanocrystallization product to be the α-Fe(Si ) phase. The grain size was observed by TEM to be ˜10nm after annealing at 480°C for 1h and 14nm after 550°C for 1h. ac soft magnetic properties were measured using a Walker AMH 401 ac permeameter. The core loss at an exciting frequency f =100kHz and maximum induction Bm=1kG was determined to be less than 19W/kg.

  17. Characterization of Amorphous and Co-Amorphous Simvastatin Formulations Prepared by Spray Drying.

    PubMed

    Craye, Goedele; Löbmann, Korbinian; Grohganz, Holger; Rades, Thomas; Laitinen, Riikka

    2015-01-01

    In this study, spray drying from aqueous solutions, using the surface-active agent sodium lauryl sulfate (SLS) as a solubilizer, was explored as a production method for co-amorphous simvastatin-lysine (SVS-LYS) at 1:1 molar mixtures, which previously have been observed to form a co-amorphous mixture upon ball milling. In addition, a spray-dried formulation of SVS without LYS was prepared. Energy-dispersive X-ray spectroscopy (EDS) revealed that SLS coated the SVS and SVS-LYS particles upon spray drying. X-ray powder diffraction (XRPD) and differential scanning calorimetry (DSC) showed that in the spray-dried formulations the remaining crystallinity originated from SLS only. The best dissolution properties and a "spring and parachute" effect were found for SVS spray-dried from a 5% SLS solution without LYS. Despite the presence of at least partially crystalline SLS in the mixtures, all the studied formulations were able to significantly extend the stability of amorphous SVS compared to previous co-amorphous formulations of SVS. The best stability (at least 12 months in dry conditions) was observed when SLS was spray-dried with SVS (and LYS). In conclusion, spray drying of SVS and LYS from aqueous surfactant solutions was able to produce formulations with improved physical stability for amorphous SVS. PMID:26633346

  18. Fabrication of FeSiBPNb amorphous powder cores with high DC-bias and excellent soft magnetic properties

    NASA Astrophysics Data System (ADS)

    Guo, Junjiang; Dong, Yaqiang; Man, Qikui; Li, Qiang; Chang, Chuntao; Wang, Xin-Min; Li, Run-Wei

    2016-03-01

    Fe-based amorphous magnetic alloy powders with a composition of (Fe0.76Si0.09B0.1P0.05)99Nb1 were first prepared by water atomization, and then amorphous magnetic powder cores were produced from a mixture of the amorphous alloy powders with diameters of below 75 μm and different volume of insulation and bonding materials by mold compacting with a compact pressure of 2200 MPa at room temperature. The amorphous magnetic cores exhibit superior DC-bias properties and excellent soft magnetic properties after appropriate heating treatment. The DC-bias properties of the present amorphous magnetic cores just decrease 15% as the external field increases to 100 Oe. Meanwhile, it also exhibits a high permeability of 56 at 1 MHz and a low core loss of 451 W/kg at Bm=0.1 T and f=100 kHz. The present Fe-based amorphous magnetic powder cores with superior DC-bias properties are a potential candidate for a variety of industrial applications.

  19. 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.

  20. Structural Amorphous Steels

    NASA Astrophysics Data System (ADS)

    Lu, Z. P.; Liu, C. T.; Thompson, J. R.; Porter, W. D.

    2004-06-01

    Recent advancement in bulk metallic glasses, whose properties are usually superior to their crystalline counterparts, has stimulated great interest in fabricating bulk amorphous steels. While a great deal of effort has been devoted to this field, the fabrication of structural amorphous steels with large cross sections has remained an alchemist’s dream because of the limited glass-forming ability (GFA) of these materials. Here we report the discovery of structural amorphous steels that can be cast into glasses with large cross-section sizes using conventional drop-casting methods. These new steels showed interesting physical, magnetic, and mechanical properties, along with high thermal stability. The underlying mechanisms for the superior GFA of these materials are discussed.

  1. Amorphous semiconductor solar cell

    DOEpatents

    Dalal, Vikram L.

    1981-01-01

    A solar cell comprising a back electrical contact, amorphous silicon semiconductor base and junction layers and a top electrical contact includes in its manufacture the step of heat treating the physical junction between the base layer and junction layer to diffuse the dopant species at the physical junction into the base layer.

  2. Amorphous silicon photovoltaic devices

    DOEpatents

    Carlson, David E.; Lin, Guang H.; Ganguly, Gautam

    2004-08-31

    This invention is a photovoltaic device comprising an intrinsic or i-layer of amorphous silicon and where the photovoltaic device is more efficient at converting light energy to electric energy at high operating temperatures than at low operating temperatures. The photovoltaic devices of this invention are suitable for use in high temperature operating environments.

  3. Application of STEM characterization for investigating radiation effects in BCC Fe-based alloys

    DOE PAGES

    Parish, Chad M.; Field, Kevin G.; Certain, Alicia G.; Wharry, Janelle P.

    2015-04-20

    This paper provides a general overview of advanced scanning transmission electron microscopy (STEM) techniques used for characterization of irradiated BCC Fe-based alloys. Advanced STEM methods provide the high-resolution imaging and chemical analysis necessary to understand the irradiation response of BCC Fe-based alloys. The use of STEM with energy dispersive x-ray spectroscopy (EDX) for measurement of radiation-induced segregation (RIS) is described, with an illustrated example of RIS in proton- and self-ion irradiated T91. Aberration-corrected STEM-EDX for nanocluster/nanoparticle imaging and chemical analysis is also discussed, and examples are provided from ion-irradiated oxide dispersion strengthened (ODS) alloys. In conclusion, STEM techniques for void,more » cavity, and dislocation loop imaging are described, with examples from various BCC Fe-based alloys.« less

  4. Application of STEM characterization for investigating radiation effects in BCC Fe-based alloys

    SciTech Connect

    Parish, Chad M.; Field, Kevin G.; Certain, Alicia G.; Wharry, Janelle P.

    2015-04-20

    This paper provides a general overview of advanced scanning transmission electron microscopy (STEM) techniques used for characterization of irradiated BCC Fe-based alloys. Advanced STEM methods provide the high-resolution imaging and chemical analysis necessary to understand the irradiation response of BCC Fe-based alloys. The use of STEM with energy dispersive x-ray spectroscopy (EDX) for measurement of radiation-induced segregation (RIS) is described, with an illustrated example of RIS in proton- and self-ion irradiated T91. Aberration-corrected STEM-EDX for nanocluster/nanoparticle imaging and chemical analysis is also discussed, and examples are provided from ion-irradiated oxide dispersion strengthened (ODS) alloys. In conclusion, STEM techniques for void, cavity, and dislocation loop imaging are described, with examples from various BCC Fe-based alloys.

  5. Tensile Properties and Deformation Characteristics of a Ni-Fe-Base Superalloy for Steam Boiler Applications

    NASA Astrophysics Data System (ADS)

    Zhong, Zhihong; Gu, Yuefeng; Yuan, Yong; Shi, Zhan

    2014-01-01

    Ni-Fe-base superalloys due to their good manufacturability and low cost are the proper candidates for boiler materials in advanced power plants. The major concerns with Ni-Fe-base superalloys are the insufficient mechanical properties at elevated temperatures. In this paper, tensile properties, deformation, and fracture characteristics of a Ni-Fe-base superalloy primarily strengthened by γ' precipitates have been investigated from room temperature to 1073 K (800 °C). The results showed a gradual decrease in the strength up to about 973 K (700 °C) followed by a rapid drop above this temperature and a ductility minimum at around 973 K (700 °C). The fracture surfaces were studied using scanning electron microscopy and the deformation mechanisms were determined by the observation of deformed microstructures using transmission electron microscopy. An attempt has been made to correlate the tensile properties and fracture characteristics at different temperatures with the observed deformation mechanisms.

  6. Health hazards due to the inhalation of amorphous silica.

    PubMed

    Merget, R; Bauer, T; Küpper, H U; Philippou, S; Bauer, H D; Breitstadt, R; Bruening, T

    2002-01-01

    Occupational exposure to crystalline silica dust is associated with an increased risk for pulmonary diseases such as silicosis, tuberculosis, chronic bronchitis, chronic obstructive pulmonary disease (COPD) and lung cancer. This review summarizes the current knowledge about the health effects of amorphous (non-crystalline) forms of silica. The major problem in the assessment of health effects of amorphous silica is its contamination with crystalline silica. This applies particularly to well-documented pneumoconiosis among diatomaceous earth workers. Intentionally manufactured synthetic amorphous silicas are without contamination of crystalline silica. These synthetic forms may be classified as (1) wet process silica, (2) pyrogenic ("thermal" or "fumed") silica, and (3) chemically or physically modified silica. According to the different physicochemical properties, the major classes of synthetic amorphous silica are used in a variety of products, e.g. as fillers in the rubber industry, in tyre compounds, as free-flow and anti-caking agents in powder materials, and as liquid carriers, particularly in the manufacture of animal feed and agrochemicals; other uses are found in toothpaste additives, paints, silicon rubber, insulation material, liquid systems in coatings, adhesives, printing inks, plastisol car undercoats, and cosmetics. Animal inhalation studies with intentionally manufactured synthetic amorphous silica showed at least partially reversible inflammation, granuloma formation and emphysema, but no progressive fibrosis of the lungs. Epidemiological studies do not support the hypothesis that amorphous silicas have any relevant potential to induce fibrosis in workers with high occupational exposure to these substances, although one study disclosed four cases with silicosis among subjects exposed to apparently non-contaminated amorphous silica. Since the data have been limited, a risk of chronic bronchitis, COPD or emphysema cannot be excluded. There is no study

  7. Corrosion resistant coating

    NASA Technical Reports Server (NTRS)

    Khanna, S. K.; Thakoor, A. P.; Williams, R. M. (Inventor)

    1985-01-01

    A method of coating a substrate with an amorphous metal is described. A solid piece of the metal is bombarded with ions of an inert gas in the presence of a magnetic field to provide a vapor of the metal which is deposited on the substrate at a sufficiently low gas pressure so that there is formed on the substrate a thin, uniformly thick, essentially pinhole-free film of the metal.

  8. Short-range order in Fe-based metallic glasses: Wide-angle X-ray scattering studies

    SciTech Connect

    Babilas, Rafał; Hawełek, Łukasz; Burian, Andrzej

    2014-11-15

    The local atomic structure of the Fe{sub 80}B{sub 20}, Fe{sub 70}Nb{sub 10}B{sub 20} and Fe{sub 62}Nb{sub 8}B{sub 30} glasses prepared in the form of ribbons has been studied by wide-angle X-ray scattering. Structural information about the amorphous ribbons has been derived from analysis of the radial distribution functions using the least-squares curve-fitting method. The obtained structural parameters indicate that Fe–Fe, Fe–B, Fe–Nb and Nb–B contributions are involved in the near-neighbor coordination spheres. The possible similarities of the local atomic arrangement in the investigated glasses and the crystalline Fe{sub 3}B, Fe{sub 23}B{sub 6} and bcc Fe structures are also discussed. - Graphical abstract: Pair distribution functions (a) and best-fit model and experimental radial distribution functions for Fe{sub 80}B{sub 20} (b), Fe{sub 70}Nb{sub 10}B{sub 20} (c) and Fe{sub 62}Nb{sub 8}B{sub 30} (d) metallic glasses. - Highlights: • The short-range ordering in the Fe-based metallic glasses is presented. • The results of RDF function have been analyzed using the least-squares method. • The Fe–Fe, Fe–B, Fe–Nb or Nb–B contributions are involved in coordination spheres. • The structural unit is distorted triangular prism containing B, Fe or Nb atoms. • Similarities of atomic arrangement in glassy and crystalline structures are discussed.

  9. Amorphous silicon radiation detectors

    DOEpatents

    Street, R.A.; Perez-Mendez, V.; Kaplan, S.N.

    1992-11-17

    Hydrogenated amorphous silicon radiation detector devices having enhanced signal are disclosed. Specifically provided are transversely oriented electrode layers and layered detector configurations of amorphous silicon, the structure of which allow high electric fields upon application of a bias thereby beneficially resulting in a reduction in noise from contact injection and an increase in signal including avalanche multiplication and gain of the signal produced by incoming high energy radiation. These enhanced radiation sensitive devices can be used as measuring and detection means for visible light, low energy photons and high energy ionizing particles such as electrons, x-rays, alpha particles, beta particles and gamma radiation. Particular utility of the device is disclosed for precision powder crystallography and biological identification. 13 figs.

  10. Amorphous silicon radiation detectors

    DOEpatents

    Street, Robert A.; Perez-Mendez, Victor; Kaplan, Selig N.

    1992-01-01

    Hydrogenated amorphous silicon radiation detector devices having enhanced signal are disclosed. Specifically provided are transversely oriented electrode layers and layered detector configurations of amorphous silicon, the structure of which allow high electric fields upon application of a bias thereby beneficially resulting in a reduction in noise from contact injection and an increase in signal including avalanche multiplication and gain of the signal produced by incoming high energy radiation. These enhanced radiation sensitive devices can be used as measuring and detection means for visible light, low energy photons and high energy ionizing particles such as electrons, x-rays, alpha particles, beta particles and gamma radiation. Particular utility of the device is disclosed for precision powder crystallography and biological identification.

  11. Surface modification and performance of inexpensive Fe-based bipolar plates for proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Bai, Ching-Yuan; Wen, Tse-Min; Huang, Mao-Suan; Hou, Kung-Hsu; Ger, Ming-Der; Lee, Shuo-Jen

    A reforming pack chromization with rolling pretreatment process is utilized to develop inexpensive and high-performance Fe-based metal bipolar plates (SS 420, SS 430, and SS 316 stainless steels) for PEMFC systems. Rolling process is previously performed to reduce the chromizing temperature and generate a coating possessing excellent conductivity and corrosion resistance on the steels during chromization. The power efficiencies of rolled-chromized and simple chromized bipolar plates are compared with graphite bipolar plates employed in PEMFCs. The results show that the rolled-chromized bipolar plates have a corrosion current (I corr) of 7.87 × 10 -8 A cm -2 and an interfacial contact resistance of 9.7 mΩ cm 2. Moreover, the power density of the single cell assembled with rolled-chromized bipolar plates is 0.46 W cm -2, which is very close to that of graphite (0.50 W cm -2), in the tested conditions of this study.

  12. Amorphous to amorphous transition in particle rafts

    NASA Astrophysics Data System (ADS)

    Varshney, Atul; Sane, A.; Ghosh, Shankar; Bhattacharya, S.

    2012-09-01

    Space-filling assemblies of athermal hydrophobic particles floating at an air-water interface, called particle rafts, are shown to undergo an unusual phase transition between two amorphous states, i.e., a low density “less-rigid” state and a high density “more-rigid” state, as a function of particulate number density (Φ). The former is shown to be a capillary bridged solid and the latter is shown to be a frictionally coupled one. Simultaneous studies involving direct imaging as well as measuring its mechanical response to longitudinal and shear stresses show that the transition is marked by a subtle structural anomaly and a weakening of the shear response. The structural anomaly is identified from the variation of the mean coordination number, mean area of the Voronoi cells, and spatial profile of the displacement field with Φ. The weakened shear response is related to local plastic instabilities caused by the depinning of the contact line of the underlying fluid on the rough surfaces of the particles.

  13. Amorphous to amorphous transition in particle rafts.

    PubMed

    Varshney, Atul; Sane, A; Ghosh, Shankar; Bhattacharya, S

    2012-09-01

    Space-filling assemblies of athermal hydrophobic particles floating at an air-water interface, called particle rafts, are shown to undergo an unusual phase transition between two amorphous states, i.e., a low density "less-rigid" state and a high density "more-rigid" state, as a function of particulate number density (Φ). The former is shown to be a capillary bridged solid and the latter is shown to be a frictionally coupled one. Simultaneous studies involving direct imaging as well as measuring its mechanical response to longitudinal and shear stresses show that the transition is marked by a subtle structural anomaly and a weakening of the shear response. The structural anomaly is identified from the variation of the mean coordination number, mean area of the Voronoi cells, and spatial profile of the displacement field with Φ. The weakened shear response is related to local plastic instabilities caused by the depinning of the contact line of the underlying fluid on the rough surfaces of the particles.

  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. Amorphous Diamond MEMS and Sensors

    SciTech Connect

    SULLIVAN, JOHN P.; FRIEDMANN, THOMAS A.; ASHBY, CAROL I.; DE BOER, MAARTEN P.; SCHUBERT, W. KENT; SHUL, RANDY J.; HOHLFELDER, ROBERT J.; LAVAN, D.A.

    2002-06-01

    This report describes a new microsystems technology for the creation of microsensors and microelectromechanical systems (MEMS) using stress-free amorphous diamond (aD) films. Stress-free aD is a new material that has mechanical properties close to that of crystalline diamond, and the material is particularly promising for the development of high sensitivity microsensors and rugged and reliable MEMS. Some of the unique properties of aD include the ability to easily tailor film stress from compressive to slightly tensile, hardness and stiffness 80-90% that of crystalline diamond, very high wear resistance, a hydrophobic surface, extreme chemical inertness, chemical compatibility with silicon, controllable electrical conductivity from insulating to conducting, and biocompatibility. A variety of MEMS structures were fabricated from this material and evaluated. These structures included electrostatically-actuated comb drives, micro-tensile test structures, singly- and doubly-clamped beams, and friction and wear test structures. It was found that surface micromachined MEMS could be fabricated in this material easily and that the hydrophobic surface of the film enabled the release of structures without the need for special drying procedures or the use of applied hydrophobic coatings. Measurements using these structures revealed that aD has a Young's modulus of {approx}650 GPa, a tensile fracture strength of 8 GPa, and a fracture toughness of 8 MPa{center_dot}m {sup 1/2}. These results suggest that this material may be suitable in applications where stiction or wear is an issue. Flexural plate wave (FPW) microsensors were also fabricated from aD. These devices use membranes of aD as thin as {approx}100 nm. The performance of the aD FPW sensors was evaluated for the detection of volatile organic compounds using ethyl cellulose as the sensor coating. For comparable membrane thicknesses, the aD sensors showed better performance than silicon nitride based sensors. Greater than

  16. Study of the recrystallization in coated pellets - effect of coating on API crystallinity.

    PubMed

    Nikowitz, Krisztina; Pintye-Hódi, Klára; Regdon, Géza

    2013-02-14

    Coated diltiazem hydrochloride-containing pellets were prepared using the solution layering technique. Unusual thermal behavior was detected with differential scanning calorimetry (DSC) and its source was determined using thermogravimetry (TG), X-ray powder diffraction (XRPD) and hot-stage microscopy. The coated pellets contained diltiazem hydrochloride both in crystalline and amorphous form. Crystallization occurs on heat treatment causing an exothermic peak on the DSC curves that only appears in pellets containing both diltiazem hydrochloride and the coating. Results indicate that the amorphous fraction is situated in the coating layer. The migration of drugs into the coating layer can cause changes in its degree of crystallinity. Polymeric coating materials should therefore be investigated as possible crystallization inhibitors. PMID:23291037

  17. Study of the recrystallization in coated pellets - effect of coating on API crystallinity.

    PubMed

    Nikowitz, Krisztina; Pintye-Hódi, Klára; Regdon, Géza

    2013-02-14

    Coated diltiazem hydrochloride-containing pellets were prepared using the solution layering technique. Unusual thermal behavior was detected with differential scanning calorimetry (DSC) and its source was determined using thermogravimetry (TG), X-ray powder diffraction (XRPD) and hot-stage microscopy. The coated pellets contained diltiazem hydrochloride both in crystalline and amorphous form. Crystallization occurs on heat treatment causing an exothermic peak on the DSC curves that only appears in pellets containing both diltiazem hydrochloride and the coating. Results indicate that the amorphous fraction is situated in the coating layer. The migration of drugs into the coating layer can cause changes in its degree of crystallinity. Polymeric coating materials should therefore be investigated as possible crystallization inhibitors.

  18. Surface transport properties of Fe-based superconductors: The influence of degradation and inhomogeneity

    SciTech Connect

    Plecenik, T.; Gregor, M.; Sobota, R.; Truchly, M.; Satrapinskyy, L.; Kus, P.; Plecenik, A.; Kurth, F.; Holzapfel, B.; Iida, K.

    2013-07-29

    Surface properties of Co-doped BaFe{sub 2}As{sub 2} epitaxial superconducting thin films were inspected by X-ray photoelectron spectroscopy, scanning spreading resistance microscopy (SSRM), and point contact spectroscopy (PCS). It has been shown that surface of Fe-based superconductors degrades rapidly if being exposed to air, what results in suppression of gap-like structure on PCS spectra. Moreover, SSRM measurements revealed inhomogeneous surface conductivity, what is consistent with strong dependence of PCS spectra on contact position. Presented results suggest that fresh surface and small probing area should be assured for surface sensitive measurements like PCS to obtain intrinsic properties of Fe-based superconductors.

  19. Evolution of the Superconducting State of Fe-Based Compounds with Doping

    SciTech Connect

    Maier, Thomas A

    2011-01-01

    We introduce an effective low-energy pairing model for Fe-based superconductors with s- and d-wave interaction components and a small number of input parameters and use it to study the doping evolution of the symmetry and the structure of the superconducting gap. We argue that the model describes the entire variety of pairing states found so far in the Fe-based superconductors and allows one to understand the mechanism of the attraction in s{sup {+-}} and d{sub x{sup 2}-y{sup 2}} channels, the competition between s- and d-wave solutions, and the origin of superconductivity in heavily doped systems, when only electron or only hole pockets are present.

  20. Comparison of Tunneling in Fe-based Superconductors with Multi-band MgB2

    NASA Astrophysics Data System (ADS)

    Zasadzinski, John; Iavarone, Maria

    MgB2 is an s-wave, phonon coupled, multiband superconductor that exhibits novel tunneling spectra including a subtle dip feature due to quasiparticle transfer between bands. Since this feature mimics the above-gap spectral dip feature observed in Fe-based superconductors, typically attributed to a strong coupling boson, it is worthwhile to consider whether quasiparticle transfer is relevant. We first show that the dip in MgB2 appears in the π-band, DOS (Δ = 2.4 meV) and is due to quasiparticle transfer to the σ-band with Δ = 7.2 meV. Reviewing the spectral dip in Fe-based superconductors, including new data on FeSe crystals, there are inconsistencies with quasiparticle transfer as the origin. The conclusion is that the spectral dip is more likely due to a boson, the resonance spin excitation, as found in cuprate superconductors.

  1. Relationship between amorphous silica and precious metal in quartz veins

    NASA Astrophysics Data System (ADS)

    Harrichhausen, N.; Rowe, C. D.; Board, W. S.; Greig, C. J.

    2015-12-01

    Super-saturation of silica is common in fault fluids, due to pressure changes associated with fracture, fault slip, or temperature gradients in hydrothermal systems. These mechanisms lead to precipitation of amorphous silica, which will recrystallize to quartz under typical geologic conditions. These conditions may also promote the saturation of precious metals, such as gold, and the precipitation of nanoparticles. Previous experiments show that charged nanoparticles of gold can attach to the surface of amorphous silica nanoparticles. Thus, gold and silica may be transported as a colloid influencing mineralization textures during amorphous silica recrystallization to quartz. This may enrich quartz vein hosted gold deposits, but the instability of hydrous silica during subsequent deformation means that the microstructural record of precipitation of gold is lost. We investigate a recent, shallow auriferous hydrothermal system at Dixie Valley, Nevada to reveal the nano- to micro-scale relationships between gold and silica in fresh veins. Fault slip surfaces at Dixie Valley exhibit layers of amorphous silica with partial recrystallization to quartz. Transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) show amorphous silica can contain a few wt. % gold while areas recrystallized to quartz are barren. At the Jurassic Brucejack deposit in British Columbia, Canada we observe the cryptocrystalline quartz textures that may indicate recrystallization from amorphous silica within quartz-carbonate veins containing high grade gold. Comb quartz within syntaxial veins, vugs, and coating breccia clasts indicate structural dilation. Vein geometry is investigated to determine relative importance of fault slip in creating dilational sites. By comparing quartz-carbonate veins from the Dixie Valley to Brucejack, we can determine whether amorphous silica formed in different environments show similar potential to affect precious metal mineralization.

  2. Amorphous silicon ionizing particle detectors

    DOEpatents

    Street, Robert A.; Mendez, Victor P.; Kaplan, Selig N.

    1988-01-01

    Amorphous silicon ionizing particle detectors having a hydrogenated amorphous silicon (a--Si:H) thin film deposited via plasma assisted chemical vapor deposition techniques are utilized to detect the presence, position and counting of high energy ionizing particles, such as electrons, x-rays, alpha particles, beta particles and gamma radiation.

  3. Amorphous silicon ionizing particle detectors

    DOEpatents

    Street, R.A.; Mendez, V.P.; Kaplan, S.N.

    1988-11-15

    Amorphous silicon ionizing particle detectors having a hydrogenated amorphous silicon (a--Si:H) thin film deposited via plasma assisted chemical vapor deposition techniques are utilized to detect the presence, position and counting of high energy ionizing particles, such as electrons, x-rays, alpha particles, beta particles and gamma radiation. 15 figs.

  4. Compensated amorphous silicon solar cell

    DOEpatents

    Devaud, Genevieve

    1983-01-01

    An amorphous silicon solar cell including an electrically conductive substrate, a layer of glow discharge deposited hydrogenated amorphous silicon over said substrate and having regions of differing conductivity with at least one region of intrinsic hydrogenated amorphous silicon. The layer of hydrogenated amorphous silicon has opposed first and second major surfaces where the first major surface contacts the electrically conductive substrate and an electrode for electrically contacting the second major surface. The intrinsic hydrogenated amorphous silicon region is deposited in a glow discharge with an atmosphere which includes not less than about 0.02 atom percent mono-atomic boron. An improved N.I.P. solar cell is disclosed using a BF.sub.3 doped intrinsic layer.

  5. CORROSION STUDY OF AMORPHOUS METAL RIBBONS

    SciTech Connect

    Lian, T; Day, S D; Farmer, J C

    2006-07-31

    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 potential advantages of amorphous metals have been recognized for some time [Latanison 1985]. Iron-based corrosion-resistant, amorphous-metal coatings under development may prove important for maritime applications [Farmer et al. 2005]. Such materials could also be used to coat the entire outer surface of containers for the transportation and long-term storage of spent nuclear fuel, or to protect welds and heat affected zones, thereby preventing exposure to environments that might cause stress corrosion cracking [Farmer et al. 1991, 2000a, 2000b]. In the future, it may be possible to substitute such high-performance iron-based materials for more-expensive nickel-based alloys, thereby enabling cost savings in a wide variety of industrial applications. It should be noted that thermal-spray ceramic coatings have also been investigated for such applications [Haslam et al. 2005]. This report focuses on the corrosion resistance of iron-based melt-spun amorphous metal ribbons. Melt-Spun ribbon is made by rapid solidification--a stream of molten metal is dropped onto a spinning copper wheel, a process that enables the manufacture of amorphous metals which are unable to be manufactured by conventional cold or hot rolling techniques. The study of melt-spun ribbon allows quick evaluation of amorphous metals corrosion resistance. The melt-spun ribbons included in this study are DAR40, SAM7, and SAM8, SAM1X series, and SAM2X series. The SAM1X series ribbons have

  6. The studies of high-frequency magnetic properties and absorption characteristics for amorphous-filler composites

    NASA Astrophysics Data System (ADS)

    Li, Z. W.; Yang, Z. H.

    2015-10-01

    Pure amorphous flake fillers and amorphous flakes coated by ferrite nanoparticles with core-shell-like structure were fabricated using mechanical ball-milling. The later with core-shell-like structure can greatly decrease permittivity and improve the absorption properties, as compared to the former. The absorption of all amorphous-filler composites has its origin in a quarter-wavelength resonator. Based on the resonator model, absorption frequency fA and the corresponding return loss RL are calculated, which are well consistent with observed values. It is also found that the resonance frequency is proportional to effective resistivity, based on William-Shockley-Kittel's eddy model.

  7. 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.

  8. Thermal Cycling Assessment of Steel-Based Thermal Barrier Coatings for Al Protection

    NASA Astrophysics Data System (ADS)

    Poirier, Dominique; Lamarre, Jean-Michel; Legoux, Jean-Gabriel

    2015-01-01

    There is a strong interest from the transportation industry to achieve vehicle weight reduction through the replacement of steel components by aluminum parts. For some applications, aluminum requires protective coatings due to its limited wear and lower temperature resistance compared to steel. The objective of this study was to assess the potential of amorphous-type plasma-sprayed steel coatings and conventional arc-sprayed steel coatings as thermal barrier coatings, mainly through the evaluation of their spalling resistance under thermal cycling. The microstructures of the different coatings were first compared via SEM. The amorphicity of the coatings produced via plasma spraying of specialized alloyed steel and the crystalline phases of the conventional arc-sprayed steel coatings were confirmed through x-ray diffraction. The thermal diffusivity of all coatings produced was measured to be about a third of that of bulk stainless steel. Conventional arc-sprayed steel coatings typically offered better spalling resistance under thermal cycling than steel-based amorphous coatings due probably to their higher initial bond strength. However, the presence of vertical cracks in the steel-based amorphous coatings was found to have a beneficial effect on their thermal cycling resistance. The amorphous plasma-sprayed steel coatings presented indications of recrystallization after their exposure to high temperature.

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  10. Amorphous materials molded IR lens progress report

    NASA Astrophysics Data System (ADS)

    Hilton, A. R., Sr.; McCord, James; Timm, Ronald; Le Blanc, R. A.

    2008-04-01

    Amorphous Materials began in 2000 a joint program with Lockheed Martin in Orlando to develop molding technology required to produce infrared lenses from chalcogenide glasses. Preliminary results were reported at this SPIE meeting by Amy Graham1 in 2003. The program ended in 2004. Since that time, AMI has concentrated on improving results from two low softening glasses, Amtir 4&5. Both glasses have been fully characterized and antireflection coatings have been developed for each. Lenses have been molded from both glasses, from Amtir 6 and from C1 Core glass. A Zygo unit is used to evaluate the results of each molded lens as a guide to improving the molding process. Expansion into a larger building has provided room for five production molding units. Molded lens sizes have ranged from 8 mm to 136 mm in diameter. Recent results will be presented

  11. 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

  12. Processing of amorphous PEEK and amorphous PEEK based composites

    SciTech Connect

    Kenny, J.; D'amore, A.; Nicolais, L.; Iannone, M.; Scatteia, B.; Aeritalia, S.p.A., Naples )

    1989-08-01

    An analysis of the crystallization behavior of amorphous PEEK, its carbon fiber composite, and its relationships with dynamic-mechanical properties of the system measured during and after processing is presented. The effect of the processing conditions, time and temperature, on the quality and on the amount of the crystallinity developed during cold crystallization has been investigated in order to evaluate the processability window of amorphous PEEK and amorphous PEEK based composite above the glass transition temperature and below the melting point. Also, the anomalous behavior of the amorphous matrix, crystallized at low temperatures, has been studied. Multiple melting peaks and changes of the glass transition during crystallization are explained in terms of crystalline morphology and molecular mobility. 20 refs.

  13. Apatite Formation from Amorphous Calcium Phosphate and Mixed Amorphous Calcium Phosphate/Amorphous Calcium Carbonate.

    PubMed

    Ibsen, Casper J S; Chernyshov, Dmitry; Birkedal, Henrik

    2016-08-22

    Crystallization from amorphous phases is an emerging pathway for making advanced materials. Biology has made use of amorphous precursor phases for eons and used them to produce structures with remarkable properties. Herein, we show how the design of the amorphous phase greatly influences the nanocrystals formed therefrom. We investigate the transformation of mixed amorphous calcium phosphate/amorphous calcium carbonate phases into bone-like nanocrystalline apatite using in situ synchrotron X-ray diffraction and IR spectroscopy. The speciation of phosphate was controlled by pH to favor HPO4 (2-) . In a carbonate free system, the reaction produces anisotropic apatite crystallites with large aspect ratios. The first formed crystallites are highly calcium deficient and hydrogen phosphate rich, consistent with thin octacalcium phosphate (OCP)-like needles. During growth, the crystallites become increasingly stoichiometric, which indicates that the crystallites grow through addition of near-stoichiometric apatite to the OCP-like initial crystals through a process that involves either crystallite fusion/aggregation or Ostwald ripening. The mixed amorphous phases were found to be more stable against phase transformations, hence, the crystallization was inhibited. The resulting crystallites were smaller and less anisotropic. This is rationalized by the idea that a local phosphate-depletion zone formed around the growing crystal until it was surrounded by amorphous calcium carbonate, which stopped the crystallization. PMID:27460160

  14. Structure, magnetic order and excitations in the 245 family of Fe-based superconductors.

    PubMed

    Bao, Wei

    2015-01-21

    Elastic neutron scattering simultaneously probes both the crystal structure and magnetic order in a material. Inelastic neutron scattering measures phonons and magnetic excitations. Here, we review the average composition, crystal structure and magnetic order in the 245 family of Fe-based superconductors and in related insulating compounds from neutron diffraction works. A three-dimensional phase-diagram summarizes various structural, magnetic and electronic properties as a function of the sample composition. A high pressure phase diagram for the superconductor is also provided. Magnetic excitations and the theoretic Heisenberg Hamiltonian are provided for the superconductor. Issues for future works are discussed. PMID:25427222

  15. Alloying Element Nitride Development in Ferritic Fe-Based Materials Upon Nitriding: A Review

    NASA Astrophysics Data System (ADS)

    Steiner, T.; Mittemeijer, E. J.

    2016-06-01

    With the aim of achieving a better understanding of the nitriding process of iron-based components (steels), as applied in engineering practice, the theoretical background and experimental observations currently available on the crystallographic, morphological, and compositional properties of the nitride precipitates in nitrided model binary and ternary, ferritic Fe-based alloys are summarily presented. Thermodynamic and kinetic considerations are employed in order to highlight their importance for the nitriding reaction and the resulting properties of the nitrided zone, thereby providing a more fundamental understanding of the nitriding process.

  16. X-ray Diffraction Techniques for Structural Determination of Amorphous Materials

    SciTech Connect

    Saw, C K; Lian, T; Day, S D; Farmer, J C

    2006-10-16

    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. An important application of the corrosion resistant material is in the radioactive waste disposable field where the vessels or containers are expected to hold the radioactive toxic materials for thousands of years to surpass the half life of the radiation. It has been known that corrosion resistance can be improved by the used of structurally designed materials in the amorphous state where the atoms are arranged in a non-periodic conditions, even though, some local chemical short range ordering may occur in the amorphous arrangement. On the other hand, the final material can also be elementally tailored to specific application. This work documents in details the characterization effort for the amorphous materials using x-ray diffraction technique as part of the High Performance Corrosion-Resistant Material--Structural Amorphous Metal (HPCRM-SAM) program here at LLNL. The samples are in the form of powders, ribbons and coatings deposited onto parts. Some brief theoretical background is given in order to interpret the results, instrumentation will also be described. The results suggest that the formation of amorphous phase in the metal alloys powders greatly depends on the processing conditions. In most of the powders, especially lot No.06, the result indicates that the materials are amorphous with a very small amount of iron boron alloy. In the ribbon samples, all the samples and of different compositions as well are observed to be 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, probably due to exposure to air during the thermal spraying process.

  17. Method of controllong the deposition of hydrogenated amorphous silicon and apparatus therefor

    DOEpatents

    Hanak, Joseph J.

    1985-06-25

    An improved method and apparatus for the controlled deposition of a layer of hydrogenated amorphous silicon on a substrate. Means is provided for the illumination of the coated surface of the substrate and measurement of the resulting photovoltage at the outermost layer of the coating. Means is further provided for admixing amounts of p type and n type dopants to the reactant gas in response to the measured photovoltage to achieve a desired level and type of doping of the deposited layer.

  18. Josephson current in Fe-based superconducting junctions: Theory and experiment

    NASA Astrophysics Data System (ADS)

    Burmistrova, A. V.; Devyatov, I. A.; Golubov, Alexander A.; Yada, Keiji; Tanaka, Yukio; Tortello, M.; Gonnelli, R. S.; Stepanov, V. A.; Ding, Xiaxin; Wen, Hai-Hu; Greene, L. H.

    2015-06-01

    We present a theory of the dc Josephson effect in contacts between Fe-based and spin-singlet s -wave superconductors. The method is based on the calculation of temperature Green's function in the junction within the tight-binding model. We calculate the phase dependencies of the Josephson current for different orientations of the junction relative to the crystallographic axes of Fe-based superconductor. Further, we consider the dependence of the Josephson current on the thickness of an insulating layer and on temperature. Experimental data for PbIn/Ba 1 -xKx (FeAs) 2 point-contact Josephson junctions are consistent with theoretical predictions for s± symmetry of an order parameter in this material. The proposed method can be further applied to calculations of the dc Josephson current in contacts with other new unconventional multiorbital superconductors, such as Sr2RuO4 and the superconducting topological insulator CuxBi2Se3 .

  19. The magnetic moment enigma in Fe-based high temperature superconductors.

    PubMed

    Mannella, Norman

    2014-11-26

    The determination of the most appropriate starting point for the theoretical description of Fe-based materials hosting high-temperature superconductivity remains among the most important unsolved problem in this relatively new field. Most of the work to date has focused on the pnictides, with LaFeAsO, BaFe(2)As(2) and LiFeAs being representative parent compounds of three families known as 1111, 122 and 111, respectively. This topical review examines recent progress in this area, with particular emphasis on the implication of experimental data which have provided evidence for the presence of electron itinerancy and the detection of local spin moments. In light of the results presented, the necessity of a theoretical framework contemplating the presence and the interplay between itinerant electrons and large spin moments is discussed. It is argued that the physics at the heart of the macroscopic properties of pnictides Fe-based high-temperature superconductors appears to be far more complex and interesting than initially predicted. PMID:25352180

  20. A highly efficient degradation mechanism of methyl orange using Fe-based metallic glass powders

    PubMed Central

    Xie, Shenghui; Huang, Ping; Kruzic, Jamie J.; Zeng, Xierong; Qian, Haixia

    2016-01-01

    A new Fe-based metallic glass with composition Fe76B12Si9Y3 (at. %) is found to have extraordinary degradation efficiency towards methyl orange (MO, C14H14N3SO3) in strong acidic and near neutral environments compared to crystalline zero-valent iron (ZVI) powders and other Fe-based metallic glasses. The influence of temperature (294–328 K) on the degradation reaction rate was measured using ball-milled metallic glass powders revealing a low thermal activation energy barrier of 22.6 kJ/mol. The excellent properties are mainly attributed to the heterogeneous structure consisting of local Fe-rich and Fe-poor atomic clusters, rather than the large specific surface and strong residual stress in the powders. The metallic glass powders can sustain almost unchanged degradation efficiency after 13 cycles at room temperature, while a drop in degradation efficiency with further cycles is attributed to visible surface oxidation. Triple quadrupole mass spectrometry analysis conducted during the reaction was used to elucidate the underlying degradation mechanism. The present findings may provide a new, highly efficient and low cost commercial method for azo dye wastewater treatment. PMID:26902824

  1. A highly efficient degradation mechanism of methyl orange using Fe-based metallic glass powders

    NASA Astrophysics Data System (ADS)

    Xie, Shenghui; Huang, Ping; Kruzic, Jamie J.; Zeng, Xierong; Qian, Haixia

    2016-02-01

    A new Fe-based metallic glass with composition Fe76B12Si9Y3 (at. %) is found to have extraordinary degradation efficiency towards methyl orange (MO, C14H14N3SO3) in strong acidic and near neutral environments compared to crystalline zero-valent iron (ZVI) powders and other Fe-based metallic glasses. The influence of temperature (294–328 K) on the degradation reaction rate was measured using ball-milled metallic glass powders revealing a low thermal activation energy barrier of 22.6 kJ/mol. The excellent properties are mainly attributed to the heterogeneous structure consisting of local Fe-rich and Fe-poor atomic clusters, rather than the large specific surface and strong residual stress in the powders. The metallic glass powders can sustain almost unchanged degradation efficiency after 13 cycles at room temperature, while a drop in degradation efficiency with further cycles is attributed to visible surface oxidation. Triple quadrupole mass spectrometry analysis conducted during the reaction was used to elucidate the underlying degradation mechanism. The present findings may provide a new, highly efficient and low cost commercial method for azo dye wastewater treatment.

  2. Corrosion Performance of Fe-Based Alloys in Simulated Oxy-Fuel Environment

    NASA Astrophysics Data System (ADS)

    Zeng, Zuotao; Natesan, Ken; Cai, Zhonghou; Rink, David L.

    2016-09-01

    The long-term corrosion of Fe-based alloys in simulated oxy-fuel environment at 1023 K (750 °C) was studied. Detailed results are presented on weight change, scale thickness, internal penetration, microstructural characteristics of the corrosion products, and the cracking of scales for the alloys after exposure at 1023 K (750 °C) for up to 3600 hours. An incubation period during which the corrosion rate was low was observed for the alloys. After the incubation period, the corrosion accelerated, and the corrosion process followed linear kinetics. Effects of alloy, CaO-containing ash, and gas composition on the corrosion rate were also studied. In addition, synchrotron nanobeam X-ray analysis was employed to determine the phase and chemical composition of the oxide layers on the alloy surface. Results from these studies are being used to address the long-term corrosion performance of Fe-based alloys in various coal-ash combustion environments and to develop methods to mitigate high-temperature ash corrosion.

  3. Design and performance of a pulse transformer based on Fe-based nanocrystalline core

    NASA Astrophysics Data System (ADS)

    Yi, Liu; Xibo, Feng; Lin, Fuchang

    2011-08-01

    A dry-type pulse transformer based on Fe-based nanocrystalline core with a load of 0.88 nF, output voltage of more than 65 kV, and winding ratio of 46 is designed and constructed. The dynamic characteristics of Fe-based nanocrystalline core under the impulse with the pulse width of several microseconds were studied. The pulse width and incremental flux density have an important effect on the pulse permeability, so the pulse permeability is measured under a certain pulse width and incremental flux density. The minimal volume of the toroidal pulse transformer core is determined by the coupling coefficient, the capacitors of the resonant charging circuit, incremental flux density, and pulse permeability. The factors of the charging time, ratio, and energy transmission efficiency in the resonant charging circuit based on magnetic core-type pulse transformer are analyzed. Experimental results of the pulse transformer are in good agreement with the theoretical calculation. When the primary capacitor is 3.17 μF and charge voltage is 1.8 kV, a voltage across the secondary capacitor of 0.88 nF with peak value of 68.5 kV, rise time (10%-90%) of 1.80 μs is obtained.

  4. Design and performance of a pulse transformer based on Fe-based nanocrystalline core.

    PubMed

    Yi, Liu; Xibo, Feng; Lin, Fuchang

    2011-08-01

    A dry-type pulse transformer based on Fe-based nanocrystalline core with a load of 0.88 nF, output voltage of more than 65 kV, and winding ratio of 46 is designed and constructed. The dynamic characteristics of Fe-based nanocrystalline core under the impulse with the pulse width of several microseconds were studied. The pulse width and incremental flux density have an important effect on the pulse permeability, so the pulse permeability is measured under a certain pulse width and incremental flux density. The minimal volume of the toroidal pulse transformer core is determined by the coupling coefficient, the capacitors of the resonant charging circuit, incremental flux density, and pulse permeability. The factors of the charging time, ratio, and energy transmission efficiency in the resonant charging circuit based on magnetic core-type pulse transformer are analyzed. Experimental results of the pulse transformer are in good agreement with the theoretical calculation. When the primary capacitor is 3.17 μF and charge voltage is 1.8 kV, a voltage across the secondary capacitor of 0.88 nF with peak value of 68.5 kV, rise time (10%-90%) of 1.80 μs is obtained. PMID:21895262

  5. 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.

  6. Catalytic conversion of syngas to mixed alcohols over Zn-Mn promoted Cu-Fe based catalyst

    SciTech Connect

    Lu, Yongwu; Yu, Fei; Hu, Jin; Liu, Jian

    2012-04-12

    Zn-Mn promoted Cu-Fe based catalyst was synthesized by the co-precipitation method. Mixed alcohols synthesis from syngas was studied in a half-inch tubular reactor system after the catalyst was reduced. Zn-Mn promoted Cu-Fe based catalyst was characterized by SEM-EDS, TEM, XRD, and XPS. The liquid phase products (alcohol phase and hydrocarbon phase) were analyzed by GC-MS and the gas phase products were analyzed by GC. The results showed that Zn-Mn promoted Cu-Fe based catalyst had high catalytic activity and high alcohol selectivity. The maximal CO conversion rate was 72%, and the yield of alcohol and hydrocarbons were also very high. Cu (111) was the active site for mixed alcohols synthesis, Fe2C (101) was the active site for olefin and paraffin synthesis. The reaction mechanism of mixed alcohols synthesis from syngas over Zn-Mn promoted Cu-Fe based catalyst was proposed. Here, Zn-Mn promoted Cu-Fe based catalyst can be regarded as a potential candidate for catalytic conversion of biomass-derived syngas to mixed alcohols.

  7. Catalytic conversion of syngas to mixed alcohols over Zn-Mn promoted Cu-Fe based catalyst

    DOE PAGES

    Lu, Yongwu; Yu, Fei; Hu, Jin; Liu, Jian

    2012-04-12

    Zn-Mn promoted Cu-Fe based catalyst was synthesized by the co-precipitation method. Mixed alcohols synthesis from syngas was studied in a half-inch tubular reactor system after the catalyst was reduced. Zn-Mn promoted Cu-Fe based catalyst was characterized by SEM-EDS, TEM, XRD, and XPS. The liquid phase products (alcohol phase and hydrocarbon phase) were analyzed by GC-MS and the gas phase products were analyzed by GC. The results showed that Zn-Mn promoted Cu-Fe based catalyst had high catalytic activity and high alcohol selectivity. The maximal CO conversion rate was 72%, and the yield of alcohol and hydrocarbons were also very high. Cumore » (111) was the active site for mixed alcohols synthesis, Fe2C (101) was the active site for olefin and paraffin synthesis. The reaction mechanism of mixed alcohols synthesis from syngas over Zn-Mn promoted Cu-Fe based catalyst was proposed. Here, Zn-Mn promoted Cu-Fe based catalyst can be regarded as a potential candidate for catalytic conversion of biomass-derived syngas to mixed alcohols.« less

  8. Aluminide coatings

    SciTech Connect

    Henager, Jr; Charles, H; Shin, Yongsoon; Samuels, William D

    2009-08-18

    Disclosed herein are aluminide coatings. In one embodiment coatings are used as a barrier coating to protect a metal substrate, such as a steel or a superalloy, from various chemical environments, including oxidizing, reducing and/or sulfidizing conditions. In addition, the disclosed coatings can be used, for example, to prevent the substantial diffusion of various elements, such as chromium, at elevated service temperatures. Related methods for preparing protective coatings on metal substrates are also described.

  9. COATED ALLOYS

    DOEpatents

    Harman, C.G.; O'Bannon, L.S.

    1958-07-15

    A coating is described for iron group metals and alloys, that is particularly suitable for use with nickel containing alloys. The coating is glassy in nature and consists of a mixture containing an alkali metal oxide, strontium oxide, and silicon oxide. When the glass coated nickel base metal is"fired'' at less than the melting point of the coating, it appears the nlckel diffuses into the vitreous coating, thus providing a closely adherent and protective cladding.

  10. Nanostructures having crystalline and amorphous phases

    DOEpatents

    Mao, Samuel S; Chen, Xiaobo

    2015-04-28

    The present invention includes a nanostructure, a method of making thereof, and a method of photocatalysis. In one embodiment, the nanostructure includes a crystalline phase and an amorphous phase in contact with the crystalline phase. Each of the crystalline and amorphous phases has at least one dimension on a nanometer scale. In another embodiment, the nanostructure includes a nanoparticle comprising a crystalline phase and an amorphous phase. The amorphous phase is in a selected amount. In another embodiment, the nanostructure includes crystalline titanium dioxide and amorphous titanium dioxide in contact with the crystalline titanium dioxide. Each of the crystalline and amorphous titanium dioxide has at least one dimension on a nanometer scale.

  11. Functionalized Amorphous Aluminosilicates

    NASA Astrophysics Data System (ADS)

    Mesgar, Milad

    Alkali treated aluminosilicate (geopolymer) was functionalized by surfactant to increase the hydrophobicity for making Pickering emulsion for the first part of this work. In the first part of this study, alkali treated metakaolin was functionalized with cetyltrimethylammonium bromide ((C16H33)N(CH 3)3Br, CTAB). The electrostatic interaction between this quaternary ammonium and the surface of the aluminosilicate which has negative charge has taken place. The particles then were used to prepare Pickering emulsion. The resulting stable dispersions, obtained very fast at very simple conditions with low ratio of aluminosilicate to liquid phase. In the second part, the interaction between geopolymer and glycerol was studied to see the covalent grafting of the geopolymer for making geopolymer composite. The composite material would be the basis material to be used as support catalyst, thin coating reagent and flame retardant material and so on, Variety of techniques, Thermogravimetric (TGA), Particle-induced X-ray emission (PIXE), FTIR, Solid state NMR, Powder X-ray diffraction (PXRD), BET surface area, Elemental analysis (CHN), TEM, SEM and Optical microscopy were used to characterize the functionalized geopolymer.

  12. Evaluation of a novel sugar coating method for moisture protective tablets.

    PubMed

    Ando, Masaki; Ito, Rina; Ozeki, Yuichi; Nakayama, Yukiharu; Nabeshima, Toshitaka

    2007-05-24

    A novel method of manufacturing one-step dry-coated (OSDRC) tablets, which we recently invented, was used to produce sugar-coated tablets protected from moisture without the need for a conventional complicated sugar coating process. Amorphous sucrose was selected for the outer layer of the OSDRC tablets as sugar-coated layer. The isothermal crystallization behavior and characteristics such as water vapor permeability, tensile strength, and disintegration time of compressed amorphous sucrose were investigated. Water vapor adsorption measurements showed the crystallization behavior of amorphous tablets to be similar to that of amorphous powder, although it was affected by compression pressure. We found that the crystallized amorphous sucrose after compression at 200 MPa was moisture protective, and the water vapor permeability coefficient was decreased to 1/2000 or less compared with a tablet prepared with a lactose-microcrystalline cellulose (MCC) mixture, hydroxypropylmethylcellulose (HPMC), and sucrose crystal. The water vapor permeability and physicochemical characteristics were influenced by the amorphous content or additive content. It was confirmed that a new sugar-coated tablet using amorphous sucrose and OSDRC technology was moisture protective, therefore, it was concluded that the novel sugar coating method was very useful to obtain a moisture protective tablet.

  13. Evaluation of a novel sugar coating method for moisture protective tablets.

    PubMed

    Ando, Masaki; Ito, Rina; Ozeki, Yuichi; Nakayama, Yukiharu; Nabeshima, Toshitaka

    2007-05-24

    A novel method of manufacturing one-step dry-coated (OSDRC) tablets, which we recently invented, was used to produce sugar-coated tablets protected from moisture without the need for a conventional complicated sugar coating process. Amorphous sucrose was selected for the outer layer of the OSDRC tablets as sugar-coated layer. The isothermal crystallization behavior and characteristics such as water vapor permeability, tensile strength, and disintegration time of compressed amorphous sucrose were investigated. Water vapor adsorption measurements showed the crystallization behavior of amorphous tablets to be similar to that of amorphous powder, although it was affected by compression pressure. We found that the crystallized amorphous sucrose after compression at 200 MPa was moisture protective, and the water vapor permeability coefficient was decreased to 1/2000 or less compared with a tablet prepared with a lactose-microcrystalline cellulose (MCC) mixture, hydroxypropylmethylcellulose (HPMC), and sucrose crystal. The water vapor permeability and physicochemical characteristics were influenced by the amorphous content or additive content. It was confirmed that a new sugar-coated tablet using amorphous sucrose and OSDRC technology was moisture protective, therefore, it was concluded that the novel sugar coating method was very useful to obtain a moisture protective tablet. PMID:17258875

  14. In-Plane Anisotropy of Transport Coefficients in Fe-Based Superconductors due to Orbital Polarization

    NASA Astrophysics Data System (ADS)

    Kontani, Hiroshi; Onari, Seiichiro

    2015-03-01

    The origin of the structure transition and the nematic electronic states has been attracting great attention in Fe-based superconductors. Its main candidate is the orbital polarization nyz >nxz , which is microscopically reproduced by including the vertex correction on the basis of the five-orbital Hubbard model. To clarify the origin, we study the in-plane anisotropy of transport coefficients in the multiorbital Hubbard model. By introducing the orbital polarization (nyz >nxz), spin fluctuations increase at q = (π , 0) whereas they decrease at q = (0 , π) , consistently with recent neutron scattering measurements. This result leads to the strong anisotropic inelastic scattering. For this reason, the obtained thermoelectric power along y-axis (Sy) increases drastically whereas Sx decreases. The obtained sizable anisotropy Sy >>Sx is consistent with the experiment in detwinned EuFe2(As,P)2. The present study strongly supports the orbital polarization scenario.

  15. Effects of Lifshitz transition on charge transport in magnetic phases of Fe-based superconductors.

    PubMed

    Wang, Y; Gastiasoro, Maria N; Andersen, Brian M; Tomić, M; Jeschke, Harald O; Valentí, Roser; Paul, Indranil; Hirschfeld, P J

    2015-03-01

    The unusual temperature dependence of the resistivity and its in-plane anisotropy observed in the Fe-based superconducting materials, particularly Ba(Fe_{1-x}Co_{x})_{2}As_{2}, has been a long-standing puzzle. Here, we consider the effect of impurity scattering on the temperature dependence of the average resistivity within a simple two-band model of a dirty spin density wave metal. The sharp drop in resistivity below the Néel temperature T_{N} in the parent compound can only be understood in terms of a Lifshitz transition following Fermi surface reconstruction upon magnetic ordering. We show that the observed resistivity anisotropy in this phase, arising from nematic defect structures, is affected by the Lifshitz transition as well. PMID:25793844

  16. Spin-orbit interactions and the nematicity observed in the fe-based superconductors.

    PubMed

    Johnson, P D; Yang, H-B; Rameau, J D; Gu, G D; Pan, Z-H; Valla, T; Weinert, M; Fedorov, A V

    2015-04-24

    High-resolution angle-resolved photoelectron spectroscopy is used to examine the electronic band structure of FeTe_{0.5}Se_{0.5} near the Brillouin zone center. A consistent separation of the α_{1} and α_{2} bands is observed with little k_{z} dependence of the α_{1} band. First-principles calculations for bulk and thin films demonstrate that the antiferromagnetic coupling between the Fe atoms and hybridization-induced spin-orbit effects lifts the degeneracy of the Fe d_{xz} and d_{yz} orbitals at the zone center leading to orbital ordering. These experimental and computational results provide a natural microscopic basis for the nematicity observed in the Fe-based superconductors. PMID:25955070

  17. Deterministic character of all-optical magnetization switching in GdFe-based ferrimagnetic alloys

    NASA Astrophysics Data System (ADS)

    Le Guyader, L.; El Moussaoui, S.; Buzzi, M.; Savoini, M.; Tsukamoto, A.; Itoh, A.; Kirilyuk, A.; Rasing, Th.; Nolting, F.; Kimel, A. V.

    2016-04-01

    Using photoemission electron microscopy with x-ray magnetic circular dichroism as a contrast mechanism, new insights into the all-optical magnetization switching (AOS) phenomenon in GdFe-based rare-earth transition-metal ferrimagnetic alloys are provided. From a sequence of static images taken after single linearly polarized laser pulse excitation, the repeatability of AOS can be quantified with a correlation coefficient. It is found that low coercivity enables thermally activated domain-wall motion, limiting in turn the repeatability of the switching. Time-resolved measurements of the magnetization dynamics reveal that while AOS occurs below and above the magnetization compensation temperature TM, it is not observed in GdFe samples where TM is absent. Finally, AOS is experimentally demonstrated against an applied magnetic field of up to 180 mT.

  18. Spin-Orbit Interactions and the Nematicity Observed in the Fe-Based Superconductors

    NASA Astrophysics Data System (ADS)

    Johnson, P. D.; Yang, H.-B.; Rameau, J. D.; Gu, G. D.; Pan, Z.-H.; Valla, T.; Weinert, M.; Fedorov, A. V.

    2015-04-01

    High-resolution angle-resolved photoelectron spectroscopy is used to examine the electronic band structure of FeTe0.5Se0.5 near the Brillouin zone center. A consistent separation of the α1 and α2 bands is observed with little kz dependence of the α1 band. First-principles calculations for bulk and thin films demonstrate that the antiferromagnetic coupling between the Fe atoms and hybridization-induced spin-orbit effects lifts the degeneracy of the Fe dx z and dy z orbitals at the zone center leading to orbital ordering. These experimental and computational results provide a natural microscopic basis for the nematicity observed in the Fe-based superconductors.

  19. Superconductivity in Fe-Based Compound EuAFe4As4 (A = Rb and Cs)

    NASA Astrophysics Data System (ADS)

    Kawashima, Kenji; Kinjo, Tatsuya; Nishio, Taichiro; Ishida, Shigeyuki; Fujihisa, Hiroshi; Gotoh, Yoshito; Kihou, Kunihiro; Eisaki, Hiroshi; Yoshida, Yoshiyuki; Iyo, Akira

    2016-06-01

    We report the discovery of a novel Fe-based superconductor EuAFe4As4 (A = Rb, Cs) and describe its superconducting properties. EuAFe4As4 has a tetragonal unit cell with a P4/mmm (No. 123) space group, indicating that this material is an 1144-type compound. The magnetic susceptibility and electrical resistivity indicate superconducting transitions at approximately 36 and 35 K for EuRbFe4As4 and EuCsFe4As4, respectively. Moreover, an anomalous magnetic transition appears at approximately 15 K, suggesting the coexistence of superconductivity and a magnetic ordered state formed by the Eu2+ ions. The determined upper critical magnetic fields and coherence lengths are approximately 920 kOe and 1.8 nm for EuRbFe4As4 and 875 kOe and 1.9 nm for EuCsFe4As4, respectively.

  20. Orbital-Parity Selective Superconducting Pairing Structures of Fe-based Superconductors under Glide Symmetry

    NASA Astrophysics Data System (ADS)

    Lin, Chiahui; Chou, Chung-Pin; Yin, Wei-Guo; Ku, Wei

    2014-03-01

    We show that the superconductivity in Fe-based superconductors consists of zero and finite momentum (π , π , 0) Cooper pairs with the same and different parities of the Fe 3 d orbitals respectively. The former develops the distinct gap structures for each orbital parity, and the latter is characteristic of spin singlet, spacial oddness and time reversal symmetry breaking. This originates from the unit cell containing two Fe atoms and two anions of staggered positioning with respect to the Fe square lattice. The in-plane translation is turned into glide translation, which dictates orbital-parity selective quasiparticles. Such novel pairing structures explain the unusual gap angular modulation on the hole pockets in recent ARPES and STS experiments. Work supported by DOE DE-AC02-98CH10886 and Chinese Academy of Engineering Physics and Ministry of Science and Technology.

  1. Annealing studies of amorphous alloys

    SciTech Connect

    Wiley, J.D.; Perepezko, J.H.; Nordman, J.E.

    1983-04-01

    Amorphous films of the alloys Ni-Nb, Ni-Mo, Mo-Si, and W-Si were sputter deposited on single-crystal semiconductor substrates. One-hour crystallization temperatures of the films were determined to within +-25/sup 0/C by annealing and x-ray diffraction measurements. Interdiffusion between Au or Cu overlayers and the amorphous films were studied by annealing combined with Auger Electron Spectroscopy (AES) profiling, and by Rutherford Backscatter (RBS) analysis. Supplementary measurements used to study structural relaxation and crystallization included resistivity as a function of temperature; DTA and DSC; and electron microscopy.

  2. Using gap symmetry and structure to reveal the pairing mechanism in Fe-based superconductors

    NASA Astrophysics Data System (ADS)

    Hirschfeld, Peter J.

    2016-01-01

    I review theoretical ideas and implications of experiments for the gap structure and symmetry of the Fe-based superconductors. Unlike any other class of unconventional superconductors, one has in these systems the possibility to tune the interactions by small changes in pressure, doping or disorder. Thus, measurements of order parameter evolution with these parameters should enable a deeper understanding of the underlying interactions. I briefly review the "standard paradigm" for s-wave pairing in these systems, and then focus on developments in the past several years which have challenged this picture. I further discuss the reasons for the apparent close competition between pairing in s- and d-wave channels, particularly in those systems where one type of Fermi surface pocket - hole or electron - is missing. Observation of a transition between s- and d-wave symmetry, possibly via a time reversal symmetry breaking "s + id" state, would provide an important confirmation of these ideas. Several proposals for detecting these novel phases are discussed, including the appearance of order parameter collective modes in Raman and optical conductivities. Transitions between two different types of s-wave states, involving various combinations of signs on Fermi surface pockets, can also proceed through a T-breaking "s + is" state. I discuss recent work that suggests pairing may take place away from the Fermi level over a surprisingly large energy range, as well as the effect of glide plane symmetry of the Fe-based systems on the superconductivity, including various exotic, time and translational invariance breaking pair states that have been proposed. Finally, I address disorder issues, and the various ways systematic introduction of disorder can (and cannot) be used to extract information on gap symmetry and structure.

  3. Unregulated emissions from diesel engine with particulate filter using Fe-based fuel borne catalyst.

    PubMed

    Zhao, Hong; Ge, Yunshan; Zhang, Tiezhu; Zhang, Jipeng; Tan, Jianwei; Zhang, Hongxin

    2014-10-01

    The alteration and formation of toxic compounds and potential changes in the toxicity of emissions when using after-treatment technologies have gained wide attention. Volatile organic compound (VOC), carbonyl compound and particle-phase polycyclic aromatic hydrocarbon (PAH) emissions were tested at European Steady State Cycle (ESC) to study unregulated emissions from a diesel engine with a fuel-borne catalyst and diesel particulate filter (FBC-DPF). An Fe-based fuel-borne catalyst was used for this study. According to the results, brake specific emissions of total VOCs without and with DPF were 4.7 and 4.9mg/kWh, respectively, showing a 4.3% increase. Benzene and n-undecane emissions increased and toluene emission decreased, while other individual VOC emissions basically had no change. When retrofitted with the FBC-DPF, total carbonyl compound emission decreased 15.7%, from 25.8 to 21.8mg/kWh. The two highest carbonyls, formaldehyde and acetaldehyde, were reduced from 20.0 and 3.7 to 16.5 and 3.3mg/kWh respectively. The specific reactivity (SR) with DPF was reduced from 6.68 to 6.64mg/kWh. Total particle-phase PAH emissions decreased 66.4% with DPF compared to that without DPF. However, the Benzo[a]pyrene equivalent (BaPeq) with DPF had increased from 0.016 to 0.030mg/kWh. Fluoranthene and Pyrene had the greatest decrease, 91.1% and 88.4% respectively. The increase of two- and three-ring PAHs with DPF indicates that the fuel-borne catalyst caused some gas-phase PAHs to adsorb on particles. The results of this study expand the knowledge of the effects of using a particulate filter and a Fe-based fuel-borne catalyst on diesel engine unregulated emissions.

  4. Unregulated emissions from diesel engine with particulate filter using Fe-based fuel borne catalyst.

    PubMed

    Zhao, Hong; Ge, Yunshan; Zhang, Tiezhu; Zhang, Jipeng; Tan, Jianwei; Zhang, Hongxin

    2014-10-01

    The alteration and formation of toxic compounds and potential changes in the toxicity of emissions when using after-treatment technologies have gained wide attention. Volatile organic compound (VOC), carbonyl compound and particle-phase polycyclic aromatic hydrocarbon (PAH) emissions were tested at European Steady State Cycle (ESC) to study unregulated emissions from a diesel engine with a fuel-borne catalyst and diesel particulate filter (FBC-DPF). An Fe-based fuel-borne catalyst was used for this study. According to the results, brake specific emissions of total VOCs without and with DPF were 4.7 and 4.9mg/kWh, respectively, showing a 4.3% increase. Benzene and n-undecane emissions increased and toluene emission decreased, while other individual VOC emissions basically had no change. When retrofitted with the FBC-DPF, total carbonyl compound emission decreased 15.7%, from 25.8 to 21.8mg/kWh. The two highest carbonyls, formaldehyde and acetaldehyde, were reduced from 20.0 and 3.7 to 16.5 and 3.3mg/kWh respectively. The specific reactivity (SR) with DPF was reduced from 6.68 to 6.64mg/kWh. Total particle-phase PAH emissions decreased 66.4% with DPF compared to that without DPF. However, the Benzo[a]pyrene equivalent (BaPeq) with DPF had increased from 0.016 to 0.030mg/kWh. Fluoranthene and Pyrene had the greatest decrease, 91.1% and 88.4% respectively. The increase of two- and three-ring PAHs with DPF indicates that the fuel-borne catalyst caused some gas-phase PAHs to adsorb on particles. The results of this study expand the knowledge of the effects of using a particulate filter and a Fe-based fuel-borne catalyst on diesel engine unregulated emissions. PMID:25288546

  5. Porous alumina based ordered nanocomposite coating for wear resistance

    NASA Astrophysics Data System (ADS)

    Yadav, Arti; Muthukumar, M.; Bobji, M. S.

    2016-08-01

    Uniformly dispersed nanocomposite coating of aligned metallic nanowires in a matrix of amorphous alumina is fabricated by pulsed electrodeposition of copper into the pores of porous anodic alumina. Uniform deposition is obtained by controlling the geometry of the dendritic structure at the bottom of pores through stepwise voltage reduction followed by mild etching. The tribological behaviour of this nanocomposite coating is evaluated using a ball on flat reciprocating tribometer under the dry contact conditions. The nanocomposite coating has higher wear resistance compared to corresponding porous alumina coating. Wear resistant nanocomposite coating has wide applications especially in protecting the internal surfaces of aluminium internal combustion engines.

  6. ARPES measurements of the superconducting gap of Fe-based superconductors and their implications to the pairing mechanism.

    PubMed

    Richard, P; Qian, T; Ding, H

    2015-07-29

    Its direct momentum sensitivity confers to angle-resolved photoemission spectroscopy (ARPES) a unique perspective in investigating the superconducting gap of multi-band systems. In this review we discuss ARPES studies on the superconducting gap of high-temperature Fe-based superconductors. We show that while Fermi-surface-driven pairing mechanisms fail to provide a universal scheme for the Fe-based superconductors, theoretical approaches based on short-range interactions lead to a more robust and universal description of superconductivity in these materials. Our findings are also discussed in the broader context of unconventional superconductivity. PMID:26153847

  7. 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

  8. Imprinting bulk amorphous alloy at room temperature.

    PubMed

    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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    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.

  10. 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.

  11. Advanced thermal barrier system bond coatings for use on nickel-, cobalt- and iron-base alloy substrates

    NASA Technical Reports Server (NTRS)

    Stecura, S.

    1986-01-01

    New and improved Ni-, Co-, and Fe-base bond coatings have been identified for the ZrO2-Y2O3 thermal barrier coatings to be used on Ni-, Co-, and Fe-base alloy substrates. These bond coatings were evaluated in a cyclic furnace between 1120 and 1175 C. It was found that MCrAlYb (where M = Ni, Co, or Fe) bond coating thermal barrier systems have significantly longer lives than MCrAlY bond coating thermal barrier systems. The longest life was obtained with the FeCrAlYb thermal barrier system followed by NiCrAlYb and CoCrAlYb thermal barrier systems in that order.

  12. Amorphous rare earth magnet powders

    SciTech Connect

    Sellers, C.H.; Branagan, D.J.; Hyde, T.A.; Lewis, L.H.; Panchanathan, V.

    1996-08-01

    Gas atomization (GA) processing does not generally have a high enough cooling rate to produce the initial amorphous microstructure needed to obtain optimal magnetic properties in RE{sub 2}Fe{sub 14}B alloys. Phase separation and an underquenched microstructure result from detrimental {alpha}-Fe precipitation, and the resulting magnetic domain structure is very coarse. Additionally, there is a dramatic dependence of the magnetic properties on the cooling rate (and therefore the particle size) and the powders can be sensitive to environmental degradation. Alloy compositions designed just for GA (as opposed to melt spinning) are necessary to produce an amorphous structure that can be crystallized to result in a fine structure with magnetic properties which are independent of particle size. The addition of titanium and carbon to the melt has been found to change the solidification process sufficiently to result in an ``overquenched`` state in which most of the powder size fractions have an amorphous component. Crystallization with a brief heat treatment produces a structure which has improved magnetic properties, in part due to the ability to use compositions with higher Fe contents without {alpha}-Fe precipitation. Results from magnetometry, magnetic force microscopy, and x-ray analyses will be used to contrast the microstructure, domain structure, and magnetic properties of this new generation of amorphous powders with their multiphase predecessors.

  13. Amorphous titanium-oxide supercapacitors

    PubMed Central

    Fukuhara, Mikio; Kuroda, Tomoyuki; Hasegawa, Fumihiko

    2016-01-01

    The electric capacitance of an amorphous TiO2-x surface increases proportionally to the negative sixth power of the convex diameter d. This occurs because of the van der Waals attraction on the amorphous surface of up to 7 mF/cm2, accompanied by extreme enhanced electron trapping resulting from both the quantum-size effect and an offset effect from positive charges at oxygen-vacancy sites. Here we show that a supercapacitor, constructed with a distributed constant-equipment circuit of large resistance and small capacitance on the amorphous TiO2-x surface, illuminated a red LED for 37 ms after it was charged with 1 mA at 10 V. The fabricated device showed no dielectric breakdown up to 1,100 V. Based on this approach, further advances in the development of amorphous titanium-dioxide supercapacitors might be attained by integrating oxide ribbons with a micro-electro mechanical system. PMID:27767103

  14. Tandem junction amorphous silicon solar cells

    DOEpatents

    Hanak, Joseph J.

    1981-01-01

    An amorphous silicon solar cell has an active body with two or a series of layers of hydrogenated amorphous silicon arranged in a tandem stacked configuration with one optical path and electrically interconnected by a tunnel junction. The layers of hydrogenated amorphous silicon arranged in tandem configuration can have the same bandgap or differing bandgaps.

  15. Compilation of diamond-like carbon properties for barriers and hard coatings

    SciTech Connect

    Outka, D.A.; Hsu, Wen L.; Boehme, D.R.; Yang, N.Y.C.; Ottesen, D.K.; Johnsen, H.A.; Clift, W.M.; Headley, T.J.

    1994-02-01

    Diamond-like carbon (DLC) is an amorphous form of carbon which resembles diamond in its hardness, lubricity, and interest for hardness, lubricity, and resistance to chemical attack. Such properties make DLC of use in barrier and hard coating technology. This report examines a variety of properties of DLC coatings which are relevant to its use as a protective coating. This includes examining substrates on which DLC coatings can be deposited; the resistance of DLC coatings to various chemical agents; adhesion of DLC coatings; and characterization of DLC coatings by electron microscopy, FTIR, sputter depth profiling, stress measurements, and nanoindentation.

  16. Controlled release of chlorhexidine from amorphous microporous silica.

    PubMed

    Verraedt, E; Pendela, M; Adams, E; Hoogmartens, J; Martens, J A

    2010-02-25

    A new system for the controlled release of the antiseptic chlorhexidine is presented. Amorphous microporous silica (AMS) excipient material was synthesized via an acid catalyzed sol-gel method and shaped as powder or coating. Chlorhexidine diacetate was introduced into the pores of the AMS silica via the incipient wetness impregnation method. This silica reservoir maintained a slow release of chlorhexidine over more than 7days. Chlorhexidine release was controlled by configurational diffusion in the AMS pores having free diameters of less than 1nm. The release of chlorhexidine was fine tuned by adapting particle size and pore diameter. Controlled release of chlorhexidine from an AMS coating on silicon wafer was demonstrated. PMID:19804804

  17. Polymer Encapsulation of an Amorphous Pharmaceutical by initiated Chemical Vapor Deposition for Enhanced Stability.

    PubMed

    Christian, Paul; Ehmann, Heike M A; Coclite, Anna Maria; Werzer, Oliver

    2016-08-24

    The usage of amorphous solids in practical applications, such as in medication, is commonly limited by the poor long-term stability of this state, because unwanted crystalline transitions occur. In this study, three different polymeric coatings are investigated for their ability to stabilize amorphous films of the model drug clotrimazole and to protect against thermally induced transitions. For this, drop cast films of clotrimazole are encapsulated by initiated chemical vapor deposition (iCVD), using perfluorodecyl acrylate (PFDA), hydroxyethyl methacrylate (HEMA), and methacrylic acid (MAA). The iCVD technique operates under solvent-free conditions at low temperatures, thus leaving the solid state of the encapsulated layer unaffected. Optical microscopy and X-ray diffraction data reveal that at ambient conditions of about 22 °C, any of these iCVD layers extends the lifetime of the amorphous state significantly. At higher temperatures (50 or 70 °C), the p-PFDA coating is unable to provide protection, while the p-HEMA and p-MAA strongly reduce the crystallization rate. Furthermore, p-HEMA and p-MAA selectively facilitate a preferential alignment of clotrimazole and, interestingly, even suppress crystallization upon a temporary, rapid temperature increase (3 °C/min, up to 150 °C). The results of this study demonstrate how a polymeric coating, synthesized directly on top of an amorphous phase, can act as a stabilizing agent against crystalline transitions, which makes this approach interesting for a variety of applications. PMID:27467099

  18. Polymer Encapsulation of an Amorphous Pharmaceutical by initiated Chemical Vapor Deposition for Enhanced Stability

    PubMed Central

    2016-01-01

    The usage of amorphous solids in practical applications, such as in medication, is commonly limited by the poor long-term stability of this state, because unwanted crystalline transitions occur. In this study, three different polymeric coatings are investigated for their ability to stabilize amorphous films of the model drug clotrimazole and to protect against thermally induced transitions. For this, drop cast films of clotrimazole are encapsulated by initiated chemical vapor deposition (iCVD), using perfluorodecyl acrylate (PFDA), hydroxyethyl methacrylate (HEMA), and methacrylic acid (MAA). The iCVD technique operates under solvent-free conditions at low temperatures, thus leaving the solid state of the encapsulated layer unaffected. Optical microscopy and X-ray diffraction data reveal that at ambient conditions of about 22 °C, any of these iCVD layers extends the lifetime of the amorphous state significantly. At higher temperatures (50 or 70 °C), the p-PFDA coating is unable to provide protection, while the p-HEMA and p-MAA strongly reduce the crystallization rate. Furthermore, p-HEMA and p-MAA selectively facilitate a preferential alignment of clotrimazole and, interestingly, even suppress crystallization upon a temporary, rapid temperature increase (3 °C/min, up to 150 °C). The results of this study demonstrate how a polymeric coating, synthesized directly on top of an amorphous phase, can act as a stabilizing agent against crystalline transitions, which makes this approach interesting for a variety of applications. PMID:27467099

  19. Amorphous calcium phosphates for tooth mineralization.

    PubMed

    Tung, Ming S; Eichmiller, Frederick C

    2004-09-01

    The destruction of tooth structure through caries and erosive processes is due to two types of acidic challenges that affect the tooth in different ways. Acidic attack by cariogenic bacteria initially produces subsurface lesions that weaken the enamel and, if left unchecked, can progress through the enamel and dentin and eventually into the pulpal cavity. Erosive attack by acidic foods and beverages removes mineral from the surface of enamel and initially causes dulling and loss of tooth luster; if left unchecked, it can progress to a more severe loss of enamel thickness and contour. This article focuses on the potential means of improving the cosmetic appearance of teeth by depositing mineral into surface defects. Several approaches use the unique properties of amorphous calcium phosphate (ACP) compounds, which have the highest rates of formation and dissolution among all the calcium phosphates. ACP has been shown to rapidly hydrolyze to form apatite, similar to carbonated apatite, the tooth mineral. Products containing ACP or ingredients that form ACP can include toothpastes, mouth rinses, artificial saliva, chewing gums, topically applied coatings, and other vehicles for topical use. When applied, they readily precipitate ACPs on and into tooth-surface defects. These products hopefully will provide users with new tools to restore and enhance the smoothness and luster of their teeth.

  20. Ferromagnetic resonance in submicron amorphous wires

    NASA Astrophysics Data System (ADS)

    Kraus, Luděk; Frait, Zdeněk; Ababei, Gabriel; Chayka, Oleksandr; Chiriac, Horia

    2012-03-01

    Ferromagnetic resonance in glass-coated amorphous wires with the diameter of metallic core varying from 25 μm to 133 nm is investigated. The microwave frequencies of 49.1 and 69.7 GHz are used and static magnetic field is applied either parallel or perpendicular to the long wire axis. In agreement with theoretical predictions the resonance curves of submicron wires substantially differ from the curves of the bulk wires. Depending on the symmetry and intensity of microwave electric and magnetic fields in the sample vicinity the circumferential and/or dipolar resonance modes can be excited. In bulk wires the resonance fields of the two modes coincide. In submicron wires, however, their resonance fields differ, indicating the metallic character of the circumferential mode and the insulator character of the dipolar mode. In wires with diameters 717 and 869 nm radial standing spin wave resonances are observed in parallel field configuration. The experimental results for the parallel field configuration can be well explained by the rigorous theoretical model. From the fit of experimental data the exchange stiffness constant A = 8.2 10-12 J/m and perpendicular surface anisotropy constant Ks = 6 × 10-4 J/m2 are obtained. The resonance curves measured in the transversal field configuration can be well explained in the frame of the skin effect and quasistatic approximations for the bulk and submicron wires, respectively. In submicron wires, however, an additional resonance of unknown origin is observed at higher magnetic fields.

  1. High-Performance Corrosion-Resistant Iron-Based Amorphous Metals - The Effects of Composition, Structure and Environment: Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4

    SciTech Connect

    Farmer, J; Haslam, J; Day, S; Lian, T; Saw, C; Hailey, P; Choi, J; Yang, N; Bayles, R; Aprigliano, L; Payer, J; Perepezko, J; Hildal, K; Lavernia, E; Ajdelsztajn, L; Branagan, D J; Beardsely, M B

    2006-10-20

    Several Fe-based amorphous metal formulations have been identified that appear to have corrosion resistance comparable to (or better than) that of Ni-based Alloy C-22 (UNS No. N06022), based on measurements of breakdown potential and corrosion rate in seawater. Both chromium (Cr) and molybdenum (Mo) provide corrosion resistance, boron (B) enables glass formation, and rare earths such as yttrium (Y) lower critical cooling rate (CCR). 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 no yttrium, and is characterized by relatively high critical cooling rates of approximately 600 Kelvin per second. Data for the SAM2X5 formulation is reported here. In contrast to yttrium-containing iron-based amorphous metals, SAM2X5 can be readily gas atomized to produce spherical powders 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 or inhibitor. SAM2X5 also experiences 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 SAM2X5 can be applied as coatings with the same corrosion resistance as a fully-dense completely amorphous melt-spun ribbon, provided that its amorphous nature is preserved during thermal spraying. The hardness of Type 316L Stainless Steel is approximately 150 VHN, that of Alloy C-22 is approximately 250 VHN, and that of HVOF SAM2X5 ranges from 1100-1300 VHN [MRS12-13]. Such hardness makes these materials particularly attractive for applications where corrosion-erosion and wear are also issues. Since SAM2X5 has high boron content, it can absorb neutrons efficiently, and may therefore find

  2. Coatings for rubber bonding and paint adhesion

    NASA Astrophysics Data System (ADS)

    Boulos, M. S.; Petschel, M.

    1997-08-01

    Conversion coatings form an important base for the adhesion of paint to metal substrates and for the bonding of rubber to metal parts. Four types of conversion coatings were assessed as base treatments for the bonding of rubber to steel and for the corrosion protection of metal substrates under paint: amorphous iron phosphate, heavy zinc phosphate, and three types of modified zinc phosphates that utilized one or more metal cations in addition to zinc. When applied, these conversion coatings formed a thin film over the metal substrate that was characterized by scanning electron microscopy, x-ray diffraction, and chemical methods. The performance of the coatings was assessed using physical methods such as dry adhesion, conical mandrel, impact, and stress adhesion for the rubber-bonded parts, and by corrosion resistance methods such as humidity, salt spray, and cyclic corrosion. Coating characterization and performance were correlated.

  3. Metal Coatings

    NASA Technical Reports Server (NTRS)

    1994-01-01

    During the Apollo Program, General Magnaplate Corporation developed process techniques for bonding dry lubricant coatings to space metals. The coatings were not susceptible to outgassing and offered enhanced surface hardness and superior resistance to corrosion and wear. This development was necessary because conventional lubrication processes were inadequate for lightweight materials used in Apollo components. General Magnaplate built on the original technology and became a leader in development of high performance metallurgical surface enhancement coatings - "synergistic" coatings, - which are used in applications from pizza making to laser manufacture. Each of the coatings is designed to protect a specific metal or group of metals to solve problems encountered under operating conditions.

  4. Single walled carbon nanotube network—Tetrahedral amorphous carbon composite film

    SciTech Connect

    Iyer, Ajai Liu, Xuwen; Koskinen, Jari; Kaskela, Antti; Kauppinen, Esko I.; Johansson, Leena-Sisko

    2015-06-14

    Single walled carbon nanotube network (SWCNTN) was coated by tetrahedral amorphous carbon (ta-C) using a pulsed Filtered Cathodic Vacuum Arc system to form a SWCNTN—ta-C composite film. The effects of SWCNTN areal coverage density and ta-C coating thickness on the composite film properties were investigated. X-Ray photoelectron spectroscopy measurements prove the presence of high quality sp{sup 3} bonded ta-C coating on the SWCNTN. Raman spectroscopy suggests that the single wall carbon nanotubes (SWCNTs) forming the network survived encapsulation in the ta-C coating. Nano-mechanical testing suggests that the ta-C coated SWCNTN has superior wear performance compared to uncoated SWCNTN.

  5. Change in soft magnetic properties of Fe-based metallic glasses during hydrogen absorption and desorption

    SciTech Connect

    Novak, L.; Lovas, A.; Kiss, L.F.

    2005-08-15

    The stress level can be altered in soft magnetic amorphous alloys by hydrogen absorption. The resulting changes in the soft magnetic parameters are reversible or irreversible, depending on the chemical composition. Some of these effects are demonstrated in Fe-B, Fe-W-B, and Fe-V-B glassy ribbons, in which various magnetic parameters are measured mainly during hydrogen desorption. The rate of hydrogen desorption is also monitored by measuring the pressure change in a hermetically closed bomb. The observed phenomena are interpreted on the basis of induced stresses and chemical interactions between the solute metal and hydrogen.

  6. A parallel framework for the FE-based simulation of knee joint motion.

    PubMed

    Wawro, Martin; Fathi-Torbaghan, Madjid

    2004-08-01

    We present an object-oriented framework for the finite-element (FE)-based simulation of the human knee joint motion. The FE model of the knee joint is acquired from the patients in vivo by using magnetic resonance imaging. The MRI images are converted into a three-dimensional model and finally an all-hexahedral mesh for the FE analysis is generated. The simulation environment uses nonlinear finite-element analysis (FEA) and is capable of handling contact of the model to handle the complex rolling/sliding motion of the knee joint. The software strictly follows object-oriented concepts of software engineering in order to guarantee maximum extensibility and maintainability. The final goal of this work-in-progress is the creation of a computer-based biomechanical model of the knee joint which can be used in a variety of applications, ranging from prosthesis design and treatment planning (e.g., optimal reconstruction of ruptured ligaments) over surgical simulation to impact computations in crashworthiness simulations.

  7. Understanding and eliminating the fast creep problem in Fe-based superconductors

    NASA Astrophysics Data System (ADS)

    Civale, Leonardo; Eley, Serena; Maiorov, Boris; Miura, Masashi

    One surprising characteristic of Fe-based superconductors is that they exhibit flux creep rates (S) as large as, or larger than, those found in oxide high temperature superconductors (HTS). This very fast vortex dynamics appears to be inconsistent with the estimate of the influence of the thermal fluctuations as quantified by the Ginzburg number (Gi), which measures the ratio of the thermal energy to the condensation energy in an elemental superconducting volume. In particular, compounds of the AFe2As2 family (``122'') have Gi ~10-5 to 10-4, so S could be expected to lie between that of low Tc materials (where typically Gi ~ 10-8) and HTS such as YBa2Cu3O7 (Gi ~ 10-2) , as indeed occurs in other superconductors with intermediate fluctuations, such as MgB2 (Gi ~10-6 to 10-4) . We have found the solution to this puzzle: the fast creep rates in 122 compounds are due to non-optimized pinning landscapes. Initial evidence comes from our previous studies showing that the introduction of additional disorder by irradiation decreases creep significantly in 122 single crystals, although still remaining well above the ideal limit. We now have new evidence from 122 thin films demonstrating that S can be reduced to the lower limit set by Gi by appropriate engineering of the pinning landscape.

  8. Group precipitation and age hardening of nanostructured Fe-based alloys with ultra-high strengths

    DOE PAGES

    Jiao, Z. B.; Luan, J. H.; Miller, M. K.; Yu, C. Y.; Liu, C. T.

    2016-02-19

    The precipitation of nanoparticles plays a key role in determining the properties of many structural materials, and the understanding of their formation and stabilization mechanisms has been a long standing interest in the material field. However, the critical issues involving the group precipitation of various nanoparticles and their cooperative hardening mechanism remain elusive in the newly discovered Fe-based alloys with nanostructures. Here we quantitatively elucidate the nucleation mechanism, evolution kinetics and hardening effects of the group-precipitated nanoparticles in the Fe-Cu-Ni-Al-based alloys by atom probe tomography together with both first-principles and thermodynamic calculations. Our results provide the compelling evidence for twomore » interesting but complex group precipitation pathways of nanoparticles, i.e., the Cu-rich and NiAl-based precipitations. Lastly, the co-existence of the two precipitation pathways plays a key role in age hardening kinetics and ultimately enhances the hardening response, as compared to the single particle type of strengthening, therefore providing an effective new approach for strengthening materials for structural applications.« less

  9. Group precipitation and age hardening of nanostructured Fe-based alloys with ultra-high strengths.

    PubMed

    Jiao, Z B; Luan, J H; Miller, M K; Yu, C Y; Liu, C T

    2016-02-19

    The precipitation of nanoparticles plays a key role in determining the properties of many structural materials, and the understanding of their formation and stabilization mechanisms has been a long standing interest in the material field. However, the critical issues involving the group precipitation of various nanoparticles and their cooperative hardening mechanism remain elusive in the newly discovered Fe-based alloys with nanostructures. Here we quantitatively elucidate the nucleation mechanism, evolution kinetics and hardening effects of the group-precipitated nanoparticles in the Fe-Cu-Ni-Al-based alloys by atom probe tomography together with both first-principles and thermodynamic calculations. Our results provide the compelling evidence for two interesting but complex group precipitation pathways of nanoparticles, i.e., the Cu-rich and NiAl-based precipitations. The co-existence of the two precipitation pathways plays a key role in age hardening kinetics and ultimately enhances the hardening response, as compared to the single particle type of strengthening, therefore providing an effective new approach for strengthening materials for structural applications.

  10. Group precipitation and age hardening of nanostructured Fe-based alloys with ultra-high strengths

    NASA Astrophysics Data System (ADS)

    Jiao, Z. B.; Luan, J. H.; Miller, M. K.; Yu, C. Y.; Liu, C. T.

    2016-02-01

    The precipitation of nanoparticles plays a key role in determining the properties of many structural materials, and the understanding of their formation and stabilization mechanisms has been a long standing interest in the material field. However, the critical issues involving the group precipitation of various nanoparticles and their cooperative hardening mechanism remain elusive in the newly discovered Fe-based alloys with nanostructures. Here we quantitatively elucidate the nucleation mechanism, evolution kinetics and hardening effects of the group-precipitated nanoparticles in the Fe-Cu-Ni-Al-based alloys by atom probe tomography together with both first-principles and thermodynamic calculations. Our results provide the compelling evidence for two interesting but complex group precipitation pathways of nanoparticles, i.e., the Cu-rich and NiAl-based precipitations. The co-existence of the two precipitation pathways plays a key role in age hardening kinetics and ultimately enhances the hardening response, as compared to the single particle type of strengthening, therefore providing an effective new approach for strengthening materials for structural applications.

  11. Unfolding of electronic structure through induced representations of space groups: Application to Fe-based superconductors

    NASA Astrophysics Data System (ADS)

    Tomić, Milan; Jeschke, Harald O.; Valentí, Roser

    2014-11-01

    We revisit the problem that relevant parts of band structures for a given cell choice can reflect exact or approximate higher symmetries of subsystems in the cell and can therefore be significantly simplified by an unfolding procedure that recovers the higher symmetry. We show that band-structure unfolding can be understood as projection onto induced irreducible representations of a group obtained by extending the original group of translations with a number of additional symmetry operations. The resulting framework allows us to define a generalized unfolding procedure that includes the point group operations and can be applied to any quantity in the reciprocal space. The unfolding of the Brillouin zone follows naturally from the properties of the induced irreducible representations. In this context, we also introduce a procedure to derive tight-binding models of reduced dimensionality by making use of point group symmetries. Further, we show that careful consideration of unfolding has important consequences on the interpretation of angle-resolved photoemission experiments. Finally, we apply the unfolding procedure to various representative examples of Fe-based superconductor compounds and show that the one-iron picture arises as an irreducible representation of the glide-reflection group, and we comment on the consequences for the interpretation of one-iron versus two-iron Brillouin zone representations.

  12. PHASE SEPARATION IN PM 2000 FE-BASE ODS ALLOY: EXPERIMENTAL STUDY AT THE ATOMIC LEVEL

    SciTech Connect

    Capdevila, C.; Miller, Michael K; Russell, Kaye F; Chao, J.; Gonzalez-Carrasco, J. L.

    2008-01-01

    The coarsening of the three-dimensional microstructure resulting from phase separation during ageing at 748 K of a Fe-based PM 2000{trademark} oxide dispersion strengthened (ODS) steel has been investigated by atom probe tomography and hardness measurements. Phase separation resulted in the formation of isolated particles of the chromium-enriched {alpha}{prime} phase. The aluminum and titanium were found to preferential partition to the iron-rich {alpha} phase. The partitioning of aluminum is consistent with theoretical calculations. The change in the scale of the chromium-enriched {alpha}{prime} phase was found to fit a power law with a time exponent of 0.32 in accordance with that predicted by the classical Lifshitz, Slyozov and Wagner (LSW) theory. The solute concentrations of the coexisting {alpha} and {alpha}{prime} phases were estimated from concentration frequency distributions with the Langer-Bar-on-Miller (LBM) method and proximity histograms. The hardness was linearly related to the chromium content of the {alpha}{prime} phase.

  13. Interplay of structure, magnetism and superconductivity in the 112 Fe based superconducting family

    NASA Astrophysics Data System (ADS)

    Ni, Ni

    Both cuprates and Fe-based superconductors, the two known high Tc superconducting families, show rich emergent phenomena near the superconductivity (SC). To understand the mechanism of unconventional SC, it is crucial to unravel the nature of these emergent orders. The 112 Fe pnictide superconductor (FPS), Ca1-xRExFeAs2 (CaRE112), shows SC up to 42 K, the highest bulk Tc among all nonoxide FPS [2]. Being an exceptional FPS where the global C4 rotational symmetry is broken even at room temperature, it is important to extract the similarities and differences between 112 and other FPS so that critical ingredients in inducing SC in FPS can be filtered. In this talk, I will review current progress in the study of 112. The comparison between Co doped CaLa112 and Co doped 10-3-8 will be made and the importance of interlayer coupling will be discussed. The work on 112 is supported by NSF while the work on 10-3-8 is supported by DOE.

  14. Group precipitation and age hardening of nanostructured Fe-based alloys with ultra-high strengths

    PubMed Central

    Jiao, Z. B.; Luan, J. H.; Miller, M. K.; Yu, C. Y.; Liu, C. T.

    2016-01-01

    The precipitation of nanoparticles plays a key role in determining the properties of many structural materials, and the understanding of their formation and stabilization mechanisms has been a long standing interest in the material field. However, the critical issues involving the group precipitation of various nanoparticles and their cooperative hardening mechanism remain elusive in the newly discovered Fe-based alloys with nanostructures. Here we quantitatively elucidate the nucleation mechanism, evolution kinetics and hardening effects of the group-precipitated nanoparticles in the Fe-Cu-Ni-Al-based alloys by atom probe tomography together with both first-principles and thermodynamic calculations. Our results provide the compelling evidence for two interesting but complex group precipitation pathways of nanoparticles, i.e., the Cu-rich and NiAl-based precipitations. The co-existence of the two precipitation pathways plays a key role in age hardening kinetics and ultimately enhances the hardening response, as compared to the single particle type of strengthening, therefore providing an effective new approach for strengthening materials for structural applications. PMID:26892834

  15. Excimer laser crystallization of amorphous silicon on metallic substrate

    NASA Astrophysics Data System (ADS)

    Delachat, F.; Antoni, F.; Slaoui, A.; Cayron, C.; Ducros, C.; Lerat, J.-F.; Emeraud, T.; Negru, R.; Huet, K.; Reydet, P.-L.

    2013-06-01

    An attempt has been made to achieve the crystallization of silicon thin film on metallic foils by long pulse duration excimer laser processing. Amorphous silicon thin films (100 nm) were deposited by radiofrequency magnetron sputtering on a commercial metallic alloy (N42-FeNi made of 41 % of Ni) coated by a tantalum nitride (TaN) layer. The TaN coating acts as a barrier layer, preventing the diffusion of metallic impurities in the silicon thin film during the laser annealing. An energy density threshold of 0.3 J cm-2, necessary for surface melting and crystallization of the amorphous silicon, was predicted by a numerical simulation of laser-induced phase transitions and witnessed by Raman analysis. Beyond this fluence, the melt depth increases with the intensification of energy density. A complete crystallization of the layer is achieved for an energy density of 0.9 J cm-2. Scanning electron microscopy unveils the nanostructuring of the silicon after laser irradiation, while cross-sectional transmission electron microscopy reveals the crystallites' columnar growth.

  16. Uranium incorporation into amorphous silica.

    PubMed

    Massey, Michael S; Lezama-Pacheco, Juan S; Nelson, Joey M; Fendorf, Scott; Maher, Kate

    2014-01-01

    High concentrations of uranium are commonly observed in naturally occurring amorphous silica (including opal) deposits, suggesting that incorporation of U into amorphous silica may represent a natural attenuation mechanism and promising strategy for U remediation. However, the stability of uranium in opaline silicates, determined in part by the binding mechanism for U, is an important factor in its long-term fate. U may bind directly to the opaline silicate matrix, or to materials such as iron (hydr)oxides that are subsequently occluded within the opal. Here, we examine the coordination environment of U within opaline silica to elucidate incorporation mechanisms. Precipitates (with and without ferrihydrite inclusions) were synthesized from U-bearing sodium metasilicate solutions, buffered at pH ∼ 5.6. Natural and synthetic solids were analyzed with X-ray absorption spectroscopy and a suite of other techniques. In synthetic amorphous silica, U was coordinated by silicate in a double corner-sharing coordination geometry (Si at ∼ 3.8-3.9 Å) and a small amount of uranyl and silicate in a bidentate, mononuclear (edge-sharing) coordination (Si at ∼ 3.1-3.2 Å, U at ∼ 3.8-3.9 Å). In iron-bearing synthetic solids, U was adsorbed to iron (hydr)oxide, but the coordination environment also contained silicate in both edge-sharing and corner-sharing coordination. Uranium local coordination in synthetic solids is similar to that of natural U-bearing opals that retain U for millions of years. The stability and extent of U incorporation into opaline and amorphous silica represents a long-term repository for U that may provide an alternative strategy for remediation of U contamination. PMID:24984107

  17. Stability study of amorphous valdecoxib.

    PubMed

    Ambike, Anshuman A; Mahadik, K R; Paradkar, Anant

    2004-09-10

    Formulation of poorly water-soluble drugs in the most stable dosage form for oral delivery perhaps presents the greatest challenge to pharmaceutical industry. Physical transformation of drug substance into its more soluble but metastable amorphous form is one of the approaches for improving dissolution rate of such drugs. The present study utilizes technique of spray drying for preparation of solid dispersions (SDs) and includes stability study of the same. Valdecoxib (VLD), a prototype of poorly water-soluble drugs, has been the drug of choice. The hydrophilic carriers selected were polyvinylpyrrolidone K30 (PVP) and hydroxypropylcellulose (HPC). SDs and pure VLD in the form of spray dried powder (SDVLD) in comparison with pure drug and corresponding physical mixtures (PMs) were initially characterized and then subjected to stability testing at ambient temperature and relative humidity up to 3 months. During initial characterization, increase in saturation solubility and dissolution rate was observed in all samples. DSC and XRPD studies of SDVLD and SDs suggested generation of amorphous form of drug. IR spectroscopy revealed presence of hydrogen bonding in SDs. During stability testing, there was gradual decrease in saturation solubility and dissolution rate of SDs, over the period of 3 months. While, saturation solubility of SDVLD dropped drastically within 15 days and was almost comparable with pure VLD. SD PVP retained the amorphous form of drug throughout stability period, whereas SD HPC and SDVLD presented incidence of crystallinity after 1 month and 15 days, respectively. This was justified by enthalpy relaxation studies in which, amorphous VLD showed considerable relaxation of enthalpy at Tg, while it was totally suppressed in SD PVP and partly in SD HPC. The study thus definitely reveals tremendous potential of solid dispersions of valdecoxib with PVP, from stability point of view.

  18. Nanocrystallization in spark plasma sintered Fe48Cr15Mo14Y2C15B6 bulk amorphous alloy

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

    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)23C6 crystallites. The SANS data also indicate the evolution of bimodal crystallite distribution at higher sintering temperatures (above Tx1). 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.

  19. The corrosion behavior of electroless Ni-P coating in Cl-/H2S environment

    NASA Astrophysics Data System (ADS)

    Xiu-qing, Xu; Jian, Miao; Zhen-quan, Bai; Yao-rong, Feng; Qiu-rong, Ma; Wen-zhen, Zhao

    2012-09-01

    At present, the Cl-/H2S corrosion of refinery heat exchanger at low temperature has a great impact on safety production. Aimed at this problem, an amorphous state Ni-P coating was prepared by electroless plating method in this paper. The electrochemical behavior and corrosion resistance of Ni-P coating in Cl-/H2S environment were investigated by means of electrochemical equipment and autoclave, respectively. The scanning electron microscopy (SEM) and transmission electron microscope (TEM) analysis suggest that the Ni-P coating is amorphous state and little microporous appears on its surface. The electrochemical measurement and autoclave test results show that the corrosion resistance of Ni-P coating is superior to that of 316L stainless due to its amorphous state structure and low porosity. The corrosion rate of Ni-P coating in this Cl-/H2S environment is only 0.0011 mm/a.

  20. Visual Observations of the Amorphous-Amorphous Transition in H2O Under Pressure.

    PubMed

    Mishima, O; Takemura, K; Aoki, K

    1991-10-18

    The vapor-deposited low-density amorphous phase of H(2)O was directly compressed at 77 kelvin with a diamond-anvil cell, and the boundary between the low-density amorphous phase and the high-density amorphous phase was observed while the sample was warmed under compression. The transition from the low-density amorphous phase to the high-density amorphous phase was distinct and reversible in an apparently narrow pressure range at approximately 130 to approximately 150 kelvin, which provided experimental evidence for polymorphism in amorphous H(2)O. PMID:17742228

  1. Computational and Experimental Design of Fe-Based Superalloys for Elevated-Temperature Applications

    SciTech Connect

    Liaw, Peter K.; Fine, Morris E.; Ghosh, Gautam; Asta, Mark D.; Liu, Chain T.; Sun, Zhiqian; Huang, Shenyan; Teng, Zhenke; Wang, Gongyao

    2012-04-13

    Analogous to nickel-based superalloys, Fe-based superalloys, which are strengthened by coherent B2- type precipitates are proposed for elevated-temperature applications. During the period of this project, a series of ferritic superalloys have been designed and fabricated by methods of vacuum-arc melting and vacuum-induction melting. Nano-scale precipitates were characterized by atom-probe tomography, ultrasmall- angle X-ray scattering, and transmission-electron microscopy. A duplex distribution of precipitates was found. It seems that ferritic superalloys are susceptible to brittle fracture. Systematic endeavors have been devoted to understanding and resolving the problem. Factors, such as hot rolling, precipitate volume fractions, alloy compositions, precipitate sizes and inter-particle spacings, and hyperfine cooling precipitates, have been investigated. In order to understand the underlying relationship between the microstructure and creep behavior of ferric alloys at elevated temperatures, in-situ neutron studies have been carried out. Based on the current result, it seems that the major role of β' with a 16%-volume fraction in strengthening ferritic alloys is not load sharing but interactions with dislocations. The oxidation behavior of one ferritic alloy, FBB8 (Fe-6.5Al-10Ni-10Cr-3.4Mo-0.25Zr-0.005B, weight percent), was studied in dry air. It is found that it possesses superior oxidation resistance at 1,023 and 1,123 K, compared with other creep-resistant ferritic steels [T91 (modified 9Cr-1Mo, weight percent) and P92 (9Cr-1.8W-0.5Mo, weight percent)]. At the same time, the calculation of the interfacial energies between the -iron and B2-type intermetallics (CoAl, FeAl, and NiAl) has been conducted.

  2. Conformal coating of highly structured surfaces

    DOEpatents

    Ginley, David S.; Perkins, John; Berry, Joseph; Gennett, Thomas

    2012-12-11

    Method of applying a conformal coating to a highly structured substrate and devices made by the disclosed methods are disclosed. An example method includes the deposition of a substantially contiguous layer of a material upon a highly structured surface within a deposition process chamber. The highly structured surface may be associated with a substrate or another layer deposited on a substrate. The method includes depositing a material having an amorphous structure on the highly structured surface at a deposition pressure of equal to or less than about 3 mTorr. The method may also include removing a portion of the amorphous material deposited on selected surfaces and depositing additional amorphous material on the highly structured surface.

  3. 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.

  4. Tin-Doped Inorganic Amorphous Films for Use as Transparent Monolithic Phosphors.

    PubMed

    Masai, Hirokazu; Miyata, Hiroki; Yamada, Yasuhiro; Okumura, Shun; Yanagida, Takayuki; Kanemitsu, Yoshihiko

    2015-01-01

    Although inorganic crystalline phosphors can exhibit high quantum efficiency, their use in phosphor films has been limited by a reliance on organic binders that have poor durability when exposed to high-power and/or high excitation energy light sources. To address this problem, Sn(2+)-doped transparent phosphate films measuring several micrometers in thickness have been successfully prepared through heat treatment and a subsequent single dip-coating process. The resulting monolithic inorganic amorphous film exhibited an internal quantum efficiency of over 60% and can potentially utilize transmitted light. Analysis of the film's emissivity revealed that its color can be tuned by changing the amount of Mn and Sn added to influence the energy transfer from Sn(2+) to Mn(2+). It is therefore concluded that amorphous films containing such emission centers can provide a novel and viable alternative to conventional amorphous films containing crystalline phosphors in light-emitting devices.

  5. Tin-Doped Inorganic Amorphous Films for Use as Transparent Monolithic Phosphors

    NASA Astrophysics Data System (ADS)

    Masai, Hirokazu; Miyata, Hiroki; Yamada, Yasuhiro; Okumura, Shun; Yanagida, Takayuki; Kanemitsu, Yoshihiko

    2015-06-01

    Although inorganic crystalline phosphors can exhibit high quantum efficiency, their use in phosphor films has been limited by a reliance on organic binders that have poor durability when exposed to high-power and/or high excitation energy light sources. To address this problem, Sn2+ -doped transparent phosphate films measuring several micrometers in thickness have been successfully prepared through heat treatment and a subsequent single dip-coating process. The resulting monolithic inorganic amorphous film exhibited an internal quantum efficiency of over 60% and can potentially utilize transmitted light. Analysis of the film’s emissivity revealed that its color can be tuned by changing the amount of Mn and Sn added to influence the energy transfer from Sn2+ to Mn2+. It is therefore concluded that amorphous films containing such emission centers can provide a novel and viable alternative to conventional amorphous films containing crystalline phosphors in light-emitting devices.

  6. Tin-Doped Inorganic Amorphous Films for Use as Transparent Monolithic Phosphors

    PubMed Central

    Masai, Hirokazu; Miyata, Hiroki; Yamada, Yasuhiro; Okumura, Shun; Yanagida, Takayuki; Kanemitsu, Yoshihiko

    2015-01-01

    Although inorganic crystalline phosphors can exhibit high quantum efficiency, their use in phosphor films has been limited by a reliance on organic binders that have poor durability when exposed to high-power and/or high excitation energy light sources. To address this problem, Sn2+ -doped transparent phosphate films measuring several micrometers in thickness have been successfully prepared through heat treatment and a subsequent single dip-coating process. The resulting monolithic inorganic amorphous film exhibited an internal quantum efficiency of over 60% and can potentially utilize transmitted light. Analysis of the film’s emissivity revealed that its color can be tuned by changing the amount of Mn and Sn added to influence the energy transfer from Sn2+ to Mn2+. It is therefore concluded that amorphous films containing such emission centers can provide a novel and viable alternative to conventional amorphous films containing crystalline phosphors in light-emitting devices. PMID:26061744

  7. Compilation of diamond-like carbon properties for barriers and hard coatings

    SciTech Connect

    Outka, D.A.; Hsu, Wen L.; Phillips, K.; Boehme, D.R.; Yang, N.Y.C.; Ottesen, D.K.; Johnsen, H.A.; Clift, W.M.; Headley, T.J.

    1994-05-01

    Diamond-like carbon (DLC) is an amorphous form of carbon which resembles diamond in its hardness, lubricity, and resistance to chemical attack. Such properties make DLC of interest for use in barrier and hard coating technology. This report examines a variety of properties of DLC coatings. This includes examining substrates on which DLC coatings can be deposited; the resistance of DLC coatings to various chemical agents; adhension of DLC coatings; and characterization of DLC coatings by electron microscopy, FTIR, sputter depth profiling, stress measurements and nanoindentation.

  8. Amorphous silicon solar cell allowing infrared transmission

    DOEpatents

    Carlson, David E.

    1979-01-01

    An amorphous silicon solar cell with a layer of high index of refraction material or a series of layers having high and low indices of refraction material deposited upon a transparent substrate to reflect light of energies greater than the bandgap energy of the amorphous silicon back into the solar cell and transmit solar radiation having an energy less than the bandgap energy of the amorphous silicon.

  9. Micro- and nano-testing of calcium phosphate coatings produced by pulsed laser deposition.

    PubMed

    Arias, J L; Mayor, M B; Pou, J; Leng, Y; León, B; Pérez-Amor, M

    2003-09-01

    Micro- and nano-testing methods have been explored to study the thin calcium phosphate coatings with high adhesive strength. The pulsed laser deposition (PLD) technique was utilised to produce calcium phosphate coatings on metal substrates, because this type of coatings exhibit much higher adhesive strength with substrates than conventional plasma-sprayed coatings. Due to the limitations of the conventional techniques to evaluate the mechanical properties of these thin coatings (1 microm thick), micro-scratch testing has been applied to evaluate the coating-to-substrate adhesion, and nano-indentation to determine the coating hardness and elastic modulus. The test results showed that the PLD produced amorphous and crystalline HA coatings are more ductile than titanium substrates, and the PLD coatings are not delaminated from the substrates by scratch. Also, the results showed that the crystalline HA coating is superior in internal cohesion to the amorphous one, even though the lower elastic modulus of amorphous coating could be more mechanically compatible with natural bone. PMID:12809768

  10. Preparation of amorphous sulfide sieves

    DOEpatents

    Siadati, Mohammad H.; Alonso, Gabriel; Chianelli, Russell R.

    2006-11-07

    The present invention involves methods and compositions for synthesizing catalysts/porous materials. In some embodiments, the resulting materials are amorphous sulfide sieves that can be mass-produced for a variety of uses. In some embodiments, methods of the invention concern any suitable precursor (such as thiomolybdate salt) that is exposed to a high pressure pre-compaction, if need be. For instance, in some cases the final bulk shape (but highly porous) may be same as the original bulk shape. The compacted/uncompacted precursor is then subjected to an open-flow hot isostatic pressing, which causes the precursor to decompose and convert to a highly porous material/catalyst.

  11. Biodegradable Fe-based alloys for use in osteosynthesis: outcome of an in vivo study after 52 weeks.

    PubMed

    Kraus, Tanja; Moszner, Frank; Fischerauer, Stefan; Fiedler, Michael; Martinelli, Elisabeth; Eichler, Johannes; Witte, Frank; Willbold, Elmar; Schinhammer, Michael; Meischel, Martin; Uggowitzer, Peter J; Löffler, Jörg F; Weinberg, Annelie

    2014-07-01

    This study investigates the degradation performance of three Fe-based materials in a growing rat skeleton over a period of 1 year. Pins of pure Fe and two Fe-based alloys (Fe-10 Mn-1Pd and Fe-21 Mn-0.7C-1Pd, in wt.%) were implanted transcortically into the femur of 38 Sprague-Dawley rats and inspected after 4, 12, 24 and 52 weeks. The assessment was performed by ex vivo microfocus computed tomography, weight-loss determination, surface analysis of the explanted pins and histological examination. The materials investigated showed signs of degradation; however, the degradation proceeded rather slowly and no significant differences between the materials were detected. We discuss these unexpected findings on the basis of fundamental considerations regarding iron corrosion. Dense layers of degradation products were formed on the implants' surfaces, and act as barriers against oxygen transport. For the degradation of iron, however, the presence of oxygen is an indispensable prerequisite. Its availability is generally a critical factor in bony tissue and rather limited there, i.e. in the vicinity of our implants. Because of the relatively slow degradation of both pure Fe and the Fe-based alloys, their suitability for bulk temporary implants such as those in osteosynthesis applications appears questionable.

  12. Manufacturing and Properties of High-Velocity Oxygen Fuel (HVOF)-Sprayed FeVCrC Coatings

    NASA Astrophysics Data System (ADS)

    Sassatelli, Paolo; Bolelli, Giovanni; Lusvarghi, Luca; Manfredini, Tiziano; Rigon, Rinaldo

    2016-09-01

    This paper studies the microstructure, sliding wear behavior and corrosion resistance of high-velocity oxygen fuel (HVOF)-sprayed FeVCrC-based coatings. Various process parameters were tested to evaluate their effects on the coating properties, which were also compared to those of HVOF-sprayed NiCrBSi and Stellite-6 coatings. The Fe alloy coatings are composed of flattened splats, originating from molten droplets and consisting of a super-saturated solid solution, together with rounded particles, coming from partially unmolten material and containing V- and Fe-based carbide precipitates. All process parameters, apart from "extreme" settings with excess comburent in the flame, produce dense coatings, indicating that the feedstock powder is quite easily processable by HVOF. These coatings, with a microhardness of 650-750 HV0.3, exhibit wear rates of ≈2 × 10-6 mm3/(Nm) in ball-on-disk tests against sintered Al2O3 spheres. They perform far better than the reference coatings, and better than other Fe- and Ni-based alloy coatings tested in previous research. On the other hand, the corrosion resistance of the coating material (tested by electrochemical polarization in 0.1 M HCl solution) is quite low. Even in the absence of interconnected porosity, this results in extensive, selective damage to the Fe-based matrix. This coating material is therefore unadvisable for severely corrosive environments.

  13. Manufacturing and Properties of High-Velocity Oxygen Fuel (HVOF)-Sprayed FeVCrC Coatings

    NASA Astrophysics Data System (ADS)

    Sassatelli, Paolo; Bolelli, Giovanni; Lusvarghi, Luca; Manfredini, Tiziano; Rigon, Rinaldo

    2016-10-01

    This paper studies the microstructure, sliding wear behavior and corrosion resistance of high-velocity oxygen fuel (HVOF)-sprayed FeVCrC-based coatings. Various process parameters were tested to evaluate their effects on the coating properties, which were also compared to those of HVOF-sprayed NiCrBSi and Stellite-6 coatings. The Fe alloy coatings are composed of flattened splats, originating from molten droplets and consisting of a super-saturated solid solution, together with rounded particles, coming from partially unmolten material and containing V- and Fe-based carbide precipitates. All process parameters, apart from "extreme" settings with excess comburent in the flame, produce dense coatings, indicating that the feedstock powder is quite easily processable by HVOF. These coatings, with a microhardness of 650-750 HV0.3, exhibit wear rates of ≈2 × 10-6 mm3/(Nm) in ball-on-disk tests against sintered Al2O3 spheres. They perform far better than the reference coatings, and better than other Fe- and Ni-based alloy coatings tested in previous research. On the other hand, the corrosion resistance of the coating material (tested by electrochemical polarization in 0.1 M HCl solution) is quite low. Even in the absence of interconnected porosity, this results in extensive, selective damage to the Fe-based matrix. This coating material is therefore unadvisable for severely corrosive environments.

  14. Development of RF sputtered chromium oxide coating for wear application

    NASA Technical Reports Server (NTRS)

    Bhushan, B.

    1979-01-01

    The radio frequency sputtering technique was used to deposite a hard refractory, chromium oxide coating on an Inconel X-750 foil 0.1 mm thick. Optimized sputtering parameters for a smooth and adherent coating were found to be as follows: target-to-substrate spacing, 41.3 mm; argon pressure, 5-10 mTorr; total power to the sputtering module, 400 W (voltage at the target, 1600 V), and a water-cooled substrate. The coating on the annealed foil was more adherent than that on the heat-treated foil. Substrate biasing during the sputter deposition of Cr2O3 adversely affected adherence by removing naturally occurring interfacial oxide layers. The deposited coatings were amorphous and oxygen deficient. Since amorphous materials are extremely hard, the structure was considered to be desirable.

  15. Photoemissive coating

    NASA Technical Reports Server (NTRS)

    Gange, R. A.

    1972-01-01

    Polystyrene coating is applied to holographic storage tube substrate via glow discharge polymerization in an inert environment. After deposition of styrene coating, antimony and then cesium are added to produce photoemissive layer. Technique is utilized in preparing perfectly organized polymeric films useful as single-crystal membranes.

  16. Influence Of Carboxymethyl Cellulose For The Transport Of Titanium Dioxide Nanoparticles In Clean Silica And Mineral-Coated Sands

    EPA Science Inventory

    The transport properties of titanium dioxide (anatase polymorph) nanoparticles encapsulated by carboxymethyl cellulose (CMC) were evaluated as a function of changes in the solute chemical properties in clean quartz, amorphous aluminum and iron hydroxide-coated sands. While prist...

  17. Li + ion diffusion in nanoscale alumina coatings

    NASA Astrophysics Data System (ADS)

    Johannes, Michelle; Bernstein, Noam

    Nanoscale coatings of alumina are used to stabilize surfaces for a variety of technologies. Diffusion of ions through these coatings is of primary importance: in some cases, diffusion is unwanted (e.g. corrosion) and in others (e.g. electrode materials), it is necessary. In this work DFT and AIMD calculations are used to investigate Li+ ion diffusion through a nano-layer of alumina, examining the phase (alpha, gamma, and amorphous), ion concentration, and electron count dependence. We look at the role of the surface itself in promoting diffusion. One of our main findings is that as the number of ions or charge increases, the diffusivity rises. We show how our data can explain electrochemical data from coated LiCoO2 cathodes and may point toward better and more efficient coatings for stabilizing electrodes.

  18. Is Mg-stabilized amorphous calcium carbonate a homogeneous mixture of amorphous magnesium carbonate and amorphous calcium carbonate?

    PubMed

    Yang, Sheng-Yu; Chang, Hsun-Hui; Lin, Cang-Jie; Huang, Shing-Jong; Chan, Jerry C C

    2016-10-01

    We find two types of carbonate ions in Mg stabilized amorphous calcium carbonate (Mg-ACC), whose short-range orders are identical to those of ACC and amorphous magnesium carbonate (AMC). Mg-ACC comprises a homogeneous mixture of the nano-clusters of ACC and AMC. Their relative amount varies systematically at different pH. PMID:27524162

  19. Silica nanoparticles on front glass for efficiency enhancement in superstrate-type amorphous silicon solar cells

    NASA Astrophysics Data System (ADS)

    Das, Sonali; Banerjee, Chandan; Kundu, Avra; Dey, Prasenjit; Saha, Hiranmay; Datta, Swapan K.

    2013-10-01

    Antireflective coating on front glass of superstrate-type single junction amorphous silicon solar cells (SCs) has been applied using highly monodispersed and stable silica nanoparticles (NPs). The silica NPs having 300 nm diameter were synthesized by Stober technique where the size of the NPs was controlled by varying the alcohol medium. The synthesized silica NPs were analysed by dynamic light scattering technique and Fourier transform infrared spectroscopy. The NPs were spin coated on glass side of fluorinated tin oxide (SnO2: F) coated glass superstrate and optimization of the concentration of the colloidal solution, spin speed and number of coated layers was done to achieve minimum reflection characteristics. An estimation of the distribution of the NPs for different optimization parameters has been done using field-emission scanning electron microscopy. Subsequently, the transparent conducting oxide coated glass with the layer having the minimum reflectance is used for fabrication of amorphous silicon SC. Electrical analysis of the fabricated cell indicates an improvement of 6.5% in short-circuit current density from a reference of 12.40 mA cm-2 while the open circuit voltage and the fill factor remains unaltered. A realistic optical model has also been proposed to gain an insight into the system.

  20. Production of Organic Grain Coatings by Surface-Mediated Reactions and the Consequences of This Process for Meteoritic Constituents

    NASA Technical Reports Server (NTRS)

    Nuth, Joseph A., III; Johnson, Natasha M.

    2011-01-01

    When hydrogen, nitrogen and CO are exposed to amorphous iron silicate surfaces at temperatures between 500 - 900K, a carbonaceous coating forms via Fischer-Tropsch type reactions. Under normal circumstances such a catalytic coating would impede or stop further reaction. However, we find that this coating is a better catalyst than the amorphous iron silicates that initiate these reactions. The formation of a self-perpetuating catalytic coating on grain surfaces could explain the rich deposits of macromolecular carbon found in primitive meteorites and would imply that protostellar nebulae should be rich in organic material. Many more experiments are needed to understand this chemical system and its application to protostellar nebulae.

  1. Regulatory Aspects of Coatings

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This chapter gives a history of the development and uses of edible coating regulations, detailed chapters on coating caracteristics, determination of coating properties, methods for making coatings, and discription of coating film formers (polysaccharieds, lipids, resins, proteins). The chapter also...

  2. Fluorination of amorphous thin-film materials with xenon fluoride

    DOEpatents

    Weil, Raoul B.

    1988-01-01

    A method is disclosed for producing fluorine-containing amorphous semiconductor material, preferably comprising amorphous silicon. The method includes depositing amorphous thin-film material onto a substrate while introducing xenon fluoride during the film deposition process.

  3. Fluorination of amorphous thin-film materials with xenon fluoride

    DOEpatents

    Weil, R.B.

    1987-05-01

    A method is disclosed for producing fluorine-containing amorphous semiconductor material, preferably comprising amorphous silicon. The method includes depositing amorphous thin-film material onto a substrate while introducing xenon fluoride during the film deposition process.

  4. Method of making amorphous metal composites

    DOEpatents

    Byrne, Martin A.; Lupinski, John H.

    1982-01-01

    The process comprises placing an amorphous metal in particulate form and a low molecular weight (e.g., 1000-5000) thermosetting polymer binder powder into a container, mixing these materials, and applying heat and pressure to convert the mixture into an amorphous metal composite.

  5. Electron tunnelling into amorphous germanium and silicon.

    NASA Technical Reports Server (NTRS)

    Smith, C. W.; Clark, A. H.

    1972-01-01

    Measurements of tunnel conductance versus bias, capacitance versus bias, and internal photoemission were made in the systems aluminum-oxide-amorphous germanium and aluminium-oxide-amorphous silicon. A function was extracted which expresses the deviation of these systems from the aluminium-oxide-aluminium system.

  6. Electron beam recrystallization of amorphous semiconductor materials

    NASA Technical Reports Server (NTRS)

    Evans, J. C., Jr.

    1968-01-01

    Nucleation and growth of crystalline films of silicon, germanium, and cadmium sulfide on substrates of plastic and glass were investigated. Amorphous films of germanium, silicon, and cadmium sulfide on amorphous substrates of glass and plastic were converted to the crystalline condition by electron bombardment.

  7. Imprinting bulk amorphous alloy at room temperature

    DOE PAGES

    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 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

  8. New generation of plasma-sprayed mullite coatings on silicon carbide

    NASA Technical Reports Server (NTRS)

    Lee, Kang N.; Miller, Robert A.; Jacobson, Nathan S.

    1995-01-01

    Mullite is promising as a protective coating for silicon-based ceramics in aggressive high-temperature environments. Conventionally plasma-sprayed mullite on SiC tends to crack and debond on thermal cycling. It is shown that this behavior is due to the presence of amorphous mullite in the conventionally sprayed mullite. Heating the SiC substrate during the plasma spraying eliminated the amorphous phase and produced coatings with dramatically improved properties. The new coating exhibits excellent adherence and crack resistance under thermal cycling between room temperature and 1000 to 1400 C. Preliminary tests showed good resistance to Na2CO3-induced hot corrosion.

  9. Compensated amorphous-silicon solar cell

    DOEpatents

    Devaud, G.

    1982-06-21

    An amorphous silicon solar cell including an electrically conductive substrate, a layer of glow discharge deposited hydrogenated amorphous silicon having regions of differing conductivity with at least one region of intrinsic hydrogenated amorphous silicon. The layer of hydrogenated amorphous silicon has opposed first and second major surfaces where the first major surface contacts the elecrically conductive substrate and an electrode for electrically contacting the second major surface. The intrinsic hydrogenated amorphous silicon region is deposited in a glow discharge with an atmosphere which includes not less than about 0.02 atom percent mono-atomic boron. An improved N.I.P. solar cell is disclosed using a BF/sub 3/ doped intrinsic layer.

  10. Structure, thermodynamics, and crystallization of amorphous hafnia

    SciTech Connect

    Luo, Xuhui; Demkov, Alexander A.

    2015-09-28

    We investigate theoretically amorphous hafnia using the first principles melt and quench method. We identify two types of amorphous structures of hafnia. Type I and type II are related to tetragonal and monoclinic hafnia, respectively. We find type II structure to show stronger disorder than type I. Using the phonon density of states, we calculate the specific heat capacity for type II amorphous hafnia. Using the nudged elastic band method, we show that the averaged transition barrier between the type II amorphous hafnia and monoclinic phase is approximately 0.09 eV/HfO{sub 2}. The crystallization temperature is estimated to be 421 K. The calculations suggest an explanation for the low thermal stability of amorphous hafnia.

  11. Solid-state diffusion in amorphous zirconolite

    SciTech Connect

    Yang, C.; Dove, M. T.; Trachenko, K.; Zarkadoula, E.; Todorov, I. T.; Geisler, T.; Brazhkin, V. V.

    2014-11-14

    We discuss how structural disorder and amorphization affect solid-state diffusion, and consider zirconolite as a currently important case study. By performing extensive molecular dynamics simulations, we disentangle the effects of amorphization and density, and show that a profound increase of solid-state diffusion takes place as a result of amorphization. Importantly, this can take place at the same density as in the crystal, representing an interesting general insight regarding solid-state diffusion. We find that decreasing the density in the amorphous system increases pre-factors of diffusion constants, but does not change the activation energy in the density range considered. We also find that atomic species in zirconolite are affected differently by amorphization and density change. Our microscopic insights are relevant for understanding how solid-state diffusion changes due to disorder and for building predictive models of operation of materials to be used to encapsulate nuclear waste.

  12. Solid-state diffusion in amorphous zirconolite

    NASA Astrophysics Data System (ADS)

    Yang, C.; Zarkadoula, E.; Dove, M. T.; Todorov, I. T.; Geisler, T.; Brazhkin, V. V.; Trachenko, K.

    2014-11-01

    We discuss how structural disorder and amorphization affect solid-state diffusion, and consider zirconolite as a currently important case study. By performing extensive molecular dynamics simulations, we disentangle the effects of amorphization and density, and show that a profound increase of solid-state diffusion takes place as a result of amorphization. Importantly, this can take place at the same density as in the crystal, representing an interesting general insight regarding solid-state diffusion. We find that decreasing the density in the amorphous system increases pre-factors of diffusion constants, but does not change the activation energy in the density range considered. We also find that atomic species in zirconolite are affected differently by amorphization and density change. Our microscopic insights are relevant for understanding how solid-state diffusion changes due to disorder and for building predictive models of operation of materials to be used to encapsulate nuclear waste.

  13. Neutron irradiation induced amorphization of silicon carbide

    SciTech Connect

    Snead, L.L.; Hay, J.C.

    1998-09-01

    This paper provides the first known observation of silicon carbide fully amorphized under neutron irradiation. Both high purity single crystal hcp and high purity, highly faulted (cubic) chemically vapor deposited (CVD) SiC were irradiated at approximately 60 C to a total fast neutron fluence of 2.6 {times} 10{sup 25} n/m{sup 2}. Amorphization was seen in both materials, as evidenced by TEM, electron diffraction, and x-ray diffraction techniques. Physical properties for the amorphized single crystal material are reported including large changes in density ({minus}10.8%), elastic modulus as measured using a nanoindentation technique ({minus}45%), hardness as measured by nanoindentation ({minus}45%), and standard Vickers hardness ({minus}24%). Similar property changes are observed for the critical temperature for amorphization at this neutron dose and flux, above which amorphization is not possible, is estimated to be greater than 130 C.

  14. Spray coating of superhydrophobic and angle-independent coloured films.

    PubMed

    Ge, Dengteng; Yang, Lili; Wu, Gaoxiang; Yang, Shu

    2014-03-01

    Angle-independent coloured films with superhydrophobicity were fabricated from quasi-amorphous arrays of monodispersed fluorinated silica nanoparticles via one-step spray coating. The film exhibited a high contact angle (>150°) and a low roll-off angle (~2°) and the colour could be tuned to blue, green and moccasin by varying the size of the nanoparticles.

  15. Locomotion of Amorphous Surface Robots

    NASA Technical Reports Server (NTRS)

    Bradley, Arthur T. (Inventor)

    2016-01-01

    An amorphous robot includes a compartmented bladder containing fluid, a valve assembly, and an outer layer encapsulating the bladder and valve assembly. The valve assembly draws fluid from a compartment(s) and discharges the drawn fluid into a designated compartment to displace the designated compartment with respect to the surface. Another embodiment includes elements each having a variable property, an outer layer that encapsulates the elements, and a control unit. The control unit energizes a designated element to change its variable property, thereby moving the designated element. The elements may be electromagnetic spheres with a variable polarity or shape memory polymers with changing shape and/or size. Yet another embodiment includes an elongated flexible tube filled with ferrofluid, a moveable electromagnet, an actuator, and a control unit. The control unit energizes the electromagnet and moves the electromagnet via the actuator to magnetize the ferrofluid and lengthen the flexible tube.

  16. Biologically formed amorphous calcium carbonate.

    PubMed

    Weiner, Steve; Levi-Kalisman, Yael; Raz, Sefi; Addadi, Lia

    2003-01-01

    Many organisms from a wide variety of taxa produce amorphous calcium carbonate (ACC), despite the fact that it is inherently unstable and relatively soluble in its pure state. These properties also make it difficult to detect and characterize ACC. Raman spectroscopy is a particularly useful method for investigating ACC because the sample can be examined wet, and extended X-ray absorption fine structure (EXAFS) analysis can provide detailed information on the short-range order. Other methods for characterizing ACC include infrared spectroscopy, thermogravimetric analysis and differential thermal analysis (TGA and DTA), transmission electron microscopy (TEM), and electron and X-ray diffraction. Because of the difficulties involved, we suspect that ACC is far more widely distributed than is presently known, and a comparison of EXAFS spectra shows that different biogenic ACC phases have different short-range order structures. We also suspect that ACC fulfils many different functions, including as a transient precursor phase during the formation of crystalline calcium carbonate.

  17. Locomotion of Amorphous Surface Robots

    NASA Technical Reports Server (NTRS)

    Bradley, Arthur T. (Inventor)

    2014-01-01

    An amorphous robot includes a compartmented bladder containing fluid, a valve assembly, and an outer layer encapsulating the bladder and valve assembly. The valve assembly draws fluid from a compartment(s) and discharges the drawn fluid into a designated compartment to displace the designated compartment with respect to the surface. Another embodiment includes elements each having a variable property, an outer layer that encapsulates the elements, and a control unit. The control unit energizes a designated element to change its variable property, thereby moving the designated element. The elements may be electromagnetic spheres with a variable polarity or shape memory polymers with changing shape and/or size. Yet another embodiment includes an elongated flexible tube filled with ferrofluid, a moveable electromagnet, an actuator, and a control unit. The control unit energizes the electromagnet and moves the electromagnet via the actuator to magnetize the ferrofluid and lengthen the flexible tube.

  18. Nanostructural haemocompatible coatings for the internal side of artificial blood vessels

    NASA Astrophysics Data System (ADS)

    Trembecka-Wojciga, K.; Major, R.; Lackner, J. M.; Butruk-Raszeja, B.; Sanak, M.; Major, B.

    2016-03-01

    The main goal of the work was to elaborate low thrombogenicity of surface inside tube-like elements for cardiovascular system support by combination of low-temperature glow discharge and hydrogel coatings to inhibit blood-clotting cascade activation. A large share of amorphous phase silicon was observed in the microstructure analysis. The crystalline elements were uniformly distributed in the amorphous structure. Combination of low thickness, the proper microstructure and density of the coatings provided a highly flexible nature of the whole system. The blood-material interaction was analyzed in vitro in dynamic conditions by using a designed and fabricated novel blood flow simulator. Coatings deposited by the glow discharge expressed good hemocopatibile properties. The use of hydrogel coatings did not reduce coagulation parameter. Hydrogel coatings did not improve the hemocompatibility of the surface modified with carbon based coatings. Modification of surface with hydrogel resulted in further increased risk of hemolysis.

  19. Protective Coating

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Inorganic Coatings, Inc.'s K-Zinc 531 protective coating is water-based non-toxic, non-flammable and has no organic emissions. High ratio silicate formula bonds to steel, and in 30 minutes, creates a very hard ceramic finish with superior adhesion and abrasion resistance. Improved technology allows application over a minimal commercial sandblast, fast drying in high humidity conditions and compatibility with both solvent and water-based topcoats. Coating is easy to apply and provides long term protection with a single application. Zinc rich coating with water-based potassium silicate binder offers cost advantages in materials, labor hours per application, and fewer applications over a given time span.

  20. Impacts of amorphous and crystalline cobalt ferrite layers on the giant magneto-impedance response of a soft ferromagnetic amorphous ribbon

    SciTech Connect

    Mukherjee, D.; Devkota, J.; Ruiz, A.; Hordagoda, M.; Hyde, R.; Witanachchi, S.; Mukherjee, P.; Srikanth, H.; Phan, M. H.

    2014-09-28

    A systematic study of the effect of depositing CoFe₂O₄ (CFO) films of various thicknesses (d = 0–600 nm) on the giant magneto-impedance (GMI) response of a soft ferromagnetic amorphous ribbon Co₆₅Fe₄Ni₂Si₁₅B₁₄ has been performed. The CFO films were grown on the amorphous ribbons by the pulsed laser deposition technique. X-ray diffraction and transmission electron microscopy revealed a structural variation of the CFO film from amorphous to polycrystalline as the thickness of the CFO film exceeded a critical value of 300 nm. Atomic force microscopy evidenced the increase in surface roughness of the CFO film as the thickness of the CFO film was increased. These changes in the crystallinity and morphology of the CFO film were found to have a distinct impact on the GMI response of the ribbon. Relative to the bare ribbon, coating of amorphous CFO films significantly enhanced the GMI response of the ribbon, while polycrystalline CFO films decreased it considerably. The maximum GMI response was achieved near the onset of the structural transition of the CFO film. These findings are of practical importance in developing high-sensitivity magnetic sensors.

  1. A High-Performance Corrosion-Resistant Iron-Based Amorphous Metal - The Effects of Composition, Structure and Environment on Corrosion Resistance

    SciTech Connect

    Farmer, J.; Haslam, J.; Day, D.; Lian, T.; Saw, C.; Hailey, P.; Choi, J.S.; Rebak, R.; Yang, N.; Bayles, R.; Aprigliano, L.; Payer, J.; Perepezko, J.; Hildal, K.; Lavernia, E.; Ajdelsztajn, L.; Branagan, D.; Beardsley, B.

    2007-07-01

    The passive film stability of several Fe-based amorphous metal formulations have been found to be comparable to that of high-performance Ni-based alloys, and superior to that of stainless steels, based on electrochemical measurements of the passive film breakdown potential and general corrosion rates. 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 also makes it an effective neutron absorber, and suitable for criticality control applications, as discussed in companion publications. Corrosion data for 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}) is discussed here. (authors)

  2. Research on stable, high-efficiency amorphous silicon multijunction modules

    SciTech Connect

    Guha, S. )

    1992-09-01

    This report describes research on semiconductor and non-semiconductor materials to enhance the performance of multi-band-gap, multijunction panel with an area greater than 900 cm[sup 2] by 1992. Double-junction and triple-junction cells are mode on a Ag/ZnO back reflector deposited on stainless steel substrates. An a-SiGe alloy is used for the i-layer in the bottom and the middle cells; the top cell uses an amorphous silicon alloy. After the evaporation of an antireflection coating, silver grids and bus bars are put on the top surface and the panel is encapsulated in an ethylene vinyl acetate (EVA)/Tefzel structure to make a 1-ft[sup 2] monolithic module.

  3. Synthesis and characterization of Fe-based metal and oxide based nanoparticles: discoveries and research highlights of potential applications in biology and medicine.

    PubMed

    Long, Nguyen Viet; Thi, Cao Minh; Yong, Yang; Cao, Yanqin; Wu, Haibo; Nogami, Masayuki

    2014-01-01

    In this review, we have presented the controlled synthesis of Fe-based metal and oxide nanoparticles with large size by chemical methods. The issues of the size, shape and morphology of Fe nanoparticles are discussed in the certain ranges of practical applications in biology and medicine. The homogeneous nanosystems of Fe-based metal and oxide nanoparticles with various sizes and shapes from the nano-to-micro ranges can be used in order to meet the demands of the treatments of dangerous tumors and cancers through magnetic hyperthermia and magnetic resonance imaging (MRI). In this context, the polyhedral Fe-based metal and oxide nanoparticles having large size in the ranges from 1000 nm to 5000 nm can be potentially used in magnetic hyperthermia and MRI in the innovative drug delivery, diagnosis, treatment, and therapy of tumor and cancer diseases because of their very high bio-adaptability. We have suggested that high stability and durability of Fe-based metal and oxide nanoparticles are very crucial to recent magnetic hyperthermia and MRI technology. The roles of various Fe-based nanostructures are focused in biomedical applications of tumors and cancers diagnostics, targeted drug delivery, and magnetic hyperthermia. Finally, Fe-based, α-, β- and γ-Fe2O3, and Fe3O4-based nanoparticles are shortly discussed in various potential applications in catalysis, biology, and medicine.

  4. Comparison of subset-based local and FE-based global digital image correlation: Theoretical error analysis and validation

    NASA Astrophysics Data System (ADS)

    Pan, B.; Wang, B.; Lubineau, G.

    2016-07-01

    Subset-based local and finite-element-based (FE-based) global digital image correlation (DIC) approaches are the two primary image matching algorithms widely used for full-field displacement mapping. Very recently, the performances of these different DIC approaches have been experimentally investigated using numerical and real-world experimental tests. The results have shown that in typical cases, where the subset (element) size is no less than a few pixels and the local deformation within a subset (element) can be well approximated by the adopted shape functions, the subset-based local DIC outperforms FE-based global DIC approaches because the former provides slightly smaller root-mean-square errors and offers much higher computation efficiency. Here we investigate the theoretical origin and lay a solid theoretical basis for the previous comparison. We assume that systematic errors due to imperfect intensity interpolation and undermatched shape functions are negligibly small, and perform a theoretical analysis of the random errors or standard deviation (SD) errors in the displacements measured by two local DIC approaches (i.e., a subset-based local DIC and an element-based local DIC) and two FE-based global DIC approaches (i.e., Q4-DIC and Q8-DIC). The equations that govern the random errors in the displacements measured by these local and global DIC approaches are theoretically derived. The correctness of the theoretically predicted SD errors is validated through numerical translation tests under various noise levels. We demonstrate that the SD errors induced by the Q4-element-based local DIC, the global Q4-DIC and the global Q8-DIC are 4, 1.8-2.2 and 1.2-1.6 times greater, respectively, than that associated with the subset-based local DIC, which is consistent with our conclusions from previous work.

  5. Quantification of surface amorphous content using dispersive surface energy: the concept of effective amorphous surface area.

    PubMed

    Brum, Jeffrey; Burnett, Daniel

    2011-09-01

    We investigate the use of dispersive surface energy in quantifying surface amorphous content, and the concept of effective amorphous surface area is introduced. An equation is introduced employing the linear combination of surface area normalized square root dispersive surface energy terms. This equation is effective in generating calibration curves when crystalline and amorphous references are used. Inverse gas chromatography is used to generate dispersive surface energy values. Two systems are investigated, and in both cases surface energy data collected for physical mixture samples comprised of amorphous and crystalline references fits the predicted response with good accuracy. Surface amorphous content of processed lactose samples is quantified using the calibration curve, and interpreted within the context of effective amorphous surface area. Data for bulk amorphous content is also utilized to generate a thorough picture of how disorder is distributed throughout the particle. An approach to quantifying surface amorphous content using dispersive surface energy is presented. Quantification is achieved by equating results to an effective amorphous surface area based on reference crystalline, and amorphous materials. PMID:21725707

  6. Left-handed properties dependence versus the interwire distance in Fe-based microwires metastructures

    NASA Astrophysics Data System (ADS)

    Ababei, Gabriel; Olariu, Cristina Stefania; Lupu, Nicoleta; Chiriac, Horia

    2016-05-01

    Experimental and theoretical investigations on the left-handed properties dependence versus the interwire distance of three new proposed Fe77.5Si7.5B15 glass coated microwires-based metastructures are presented. The left-handed characteristics of the metastructures were determined in the frequency range 8.2 ÷ 12 GHz and external d.c. magnetic fields ranging from 0 to 32 kA/m. The experimental results show that the electromagnetic losses of the metastructures increase with the decreasing of the interwire distance due to the increasing of the long-range dynamic dipole-dipole interaction within inter-wires in the presence of the microwave field. The numerical calculations using Nicolson-Weiss-Ross algorithm are in agreement with the experimental results. The variation of the interwire distance proves to be a useful tool to obtain metastructures with controlled left-handed characteristics.

  7. Observation of a rapid amorphization reaction

    SciTech Connect

    Hufnagel, T.C. ); Brennan, S. ); Payne, A.P.; Clemens, B.M. )

    1992-08-01

    We have observed a rapid amorphization reaction at ambient temperature in the Gd/Co system by employing grazing incidence x-ray scattering. We find that a 135 A crystalline Gd film is amporhized in less than 30 min by deposition of Co. We postulate that the rapidity of the reaction is due to surface diffusion of Co atoms after deposition to fast diffusion sites such as grain boundaries in the Gd film. Once the interfacial region has been amorphized these fast diffusion paths are sealed off from the surface, rapid diffusion of Co into the Gd crystalline layer is prevented, and the amorphization reaction stops.

  8. Pressure induced crystallization in amorphous silicon

    NASA Astrophysics Data System (ADS)

    Pandey, K. K.; Garg, Nandini; Shanavas, K. V.; Sharma, Surinder M.; Sikka, S. K.

    2011-06-01

    We have investigated the high pressure behavior of amorphous silicon (a-Si) using x-ray diffraction and Raman scattering techniques. Our experiments show that a-Si undergoes a polyamorphous transition from the low density amorphous to the high density amorphous phase, followed by pressure induced crystallization to the primitive hexagonal (ph) phase. On the release path, the sequence of observed phase transitions depends on whether the pressure is reduced slowly or rapidly. Using the results of our first principles calculations, pressure induced preferential crystallization to the ph phase is explained in terms of a thermodynamic model based on phenomenological random nucleation and the growth process.

  9. Selective laser sintering of amorphous metal powder

    NASA Astrophysics Data System (ADS)

    Fischer, P.; Blatter, A.; Romano, V.; Weber, H. P.

    2005-02-01

    For the first time, selective sintering of amorphous PtCuNiP powder with a pulsed Nd:YAG laser has been studied. Upon pulsed interaction, the grains melt only superficially to build necks between the grains. Depending on the laser parameters, the sintered material can be crystallized or retained amorphous. By contrast with crystalline powder, laser sintering of amorphous powder is achieved at substantially lower pulse energies due to its low melting point. The obtained results are compared with previous results from selective laser sintering of titanium powder.

  10. Method of producing hydrogenated amorphous silicon film

    DOEpatents

    Wiesmann, Harold J.

    1980-01-01

    This invention relates to hydrogenated amorphous silicon produced by thermally decomposing silane (SiH.sub.4) or other gases comprising H and Si, from a tungsten or carbon foil heated to a temperature of about 1400.degree.-1600.degree. C., in a vacuum of about 10.sup.-6 to 19.sup.-4 torr, to form a gaseous mixture of atomic hydrogen and atomic silicon, and depositing said gaseos mixture onto a substrate independent of and outside said source of thermal decomposition, to form hydrogenated amorphous silicon. The presence of an ammonia atmosphere in the vacuum chamber enhances the photoconductivity of the hydrogenated amorphous silicon film.

  11. The effect of high energy concentration source irradiation on structure and properties of Fe-based bulk metallic glass

    NASA Astrophysics Data System (ADS)

    Pilarczyk, Wirginia

    2016-06-01

    Metallic glasses exhibit metastable structure and maintain this relatively stable amorphous state within certain temperature range. High intensity laser beam was used for the surface irradiation of Fe-Co-B-Si-Nb bulk metallic glasses. The variable parameter was laser beam pulse energy. For the analysis of structure and properties of bulk metallic glasses and their surface after laser remelting the X-ray analysis, microscopic observation and test of mechanical properties were carried out. Examination of the nanostructure of amorphous materials obtained by high pressure copper mold casting method and the irradiated with the use of TITAN 80-300 HRTEM was carried out. Nanohardness and reduced Young's modulus of particular amorphous and amorphous-crystalline material zone of the laser beam were examined with the use of Hysitron TI950 Triboindenter nanoindenter and with the use of Berkovich's indenter. The XRD and microscopic analysis showed that the test material is amorphous in its structure before irradiation. Microstructure observation with electron transmission microscopy gave information about alloy crystallization in the irradiated process. Identification of given crystal phases allows to determine the kind of crystal phases created in the first place and also further changes of phase composition of alloy. The main value of the nanohardness of the surface prepared by laser beam has the order of magnitude similar to bulk metallic glasses formed by casting process irrespective of the laser beam energy used. Research results analysis showed that the area between parent material and fusion zone is characterized by extraordinarily interesting structure which is and will be the subject of further analysis in the scope of bulk metallic glasses amorphous structure and high energy concentration source. The main goal of this work is the results' presentation of structure and chosen properties of the selected bulk metallic glasses after casting process and after irradiation

  12. Protective coatings for high-temperature polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Harding, David R.; Sutter, James K.; Papadopoulos, Demetrios S.

    1993-01-01

    Plasma-enhanced chemical vapor deposition was used to deposit silicon nitride on graphite-fiber-reinforced polyimide composites to protect against oxidation at elevated temperatures. The adhesion and integrity of the coating were evaluated by isothermal aging (371 C for 500 hr) and thermal cycling. The amorphous silicon nitride (a-SiN:H) coating could withstand stresses ranging from approximately 0.18 GPa (tensile) to -1.6 GPa (compressive) and provided a 30 to 80 percent reduction in oxidation-induced weight loss. The major factor influencing the effectiveness of a-SiN:H as a barrier coating against oxidation is the surface finish of the polymer composite.

  13. Crystallization of amorphous solid films

    NASA Astrophysics Data System (ADS)

    Safarik, Douglas Joseph

    2003-06-01

    Below ˜130 K, H2O can exist for prolonged periods in a thermodynamically unstable, non-crystalline solid form known as amorphous solid water (ASW). When warmed to above 135 K, ASW crystallizes to the thermodynamically favored state, cubic ice I, on a laboratory time scale. Despite the relevance of ASW crystallization to a variety of scientific problems ranging from astrophysical phenomena to cryopreservation, the kinetics of this transformation are largely uncharacterized, and its mechanism is not fully understood. In the present work, the crystallization kinetics of vapor-deposited, nonporous ASW films less than one micron thick are investigated experimentally near 140 K. The amorphous to crystalline transition is characterized using a probe molecule, chlorodifluoromethane (CHF2Cl), whose adsorbed states and hence desorption kinetics are sensitive to the crystallinity of solid water surfaces. The transformation kinetics of very thick ASW films are found to be both independent of specimen size and consistent with simultaneous homogeneous nucleation and isotropic growth of crystalline ice grains. As the ASW film thickness is reduced from 385 nm to 55 nm, however, the rate of surface crystallization decelerates, in apparent conflict with a homogeneous nucleation and growth mechanism. In an attempt to explain this behavior, a geometrical model of phase transition kinetics at the surface of solids, with special consideration of finite specimen size in one dimension, is constructed. For materials in which nucleation occurs spatially randomly, phase change is predicted to decelerate when film thickness is reduced below the mean crystal grain size. This phenomenon originates from a reduction in the number of crystallites available to transform the surface as the sample becomes thinner. Good quantitative agreement between this simple model and the experimental data is attained using a minimum of kinetic parameters, suggesting it captures the essential physics of ASW

  14. The microstructure and mechanical reliability of alumina scales and coatings

    SciTech Connect

    Alexander, K.B.; Pruessner, K.; Tortorelli, P.F.

    1997-09-01

    Alumina scales on iron-aluminides (Fe{sub 3}Al-based) and NiCrAl- based alloys were characterized in order to develop the knowledge to control the oxidation performance of alloys by controlling the microstructure and microchemistry of their scales. Plasma-deposited amorphous alumina coatings on iron-aluminides were used to study phase transformations, transport processes in the scales, and S segregation to the scale/metal interface. It was found that during heat treatment in absence of oxidation, amorphous coatings first transform to {gamma}-Al{sub 2}O{sub 3} and eventually {alpha}-Al{sub 2}O{sub 3} nucleates at the scale/metal interface. Sulfur from the Zr- free alloy segregates to the scale/metal interface during heat treatment. Thermally grown scales on Zr-doped iron-aluminides were compared to those formed after oxidation of a specimen with an alumina coating. Microstructural and gravimetric results showed that the primarily amorphous alumina coating promoted the nucleation and growth of metastable alumina phases, which resulted in more rapid oxidation. The thermally grown oxide was found on top of the coating. The NiCrAl-based alloys formed columnar alumina scales underneath a layer of mixed oxides. Segregation of alloying elements like Y, Hf, and At was found at both oxide grain boundaries and scale/metal interfaces.

  15. 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.

  16. Magnetocaloric effect in heavy rare-earth elements doped Fe-based bulk metallic glasses with tunable Curie temperature

    SciTech Connect

    Li, Jiawei; Huo, Juntao; Chang, Chuntao E-mail: dujun@nimte.ac.cn; Du, Juan E-mail: dujun@nimte.ac.cn; Man, Qikui; Wang, Xinmin; Li, Run-Wei; Law, Jiayan

    2014-08-14

    The effects of heavy rare earth (RE) additions on the Curie temperature (T{sub C}) and magnetocaloric effect of the Fe-RE-B-Nb (RE = Gd, Dy and Ho) bulk metallic glasses were studied. The type of dopping RE element and its concentration can easily tune T{sub C} in a large temperature range of 120 K without significantly decreasing the magnetic entropy change (ΔS{sub M}) and refrigerant capacity (RC) of the alloys. The observed values of ΔS{sub M} and RC of these alloys compare favorably with those of recently reported Fe-based metallic glasses with enhanced RC compared to Gd{sub 5}Ge{sub 1.9}Si{sub 2}Fe{sub 0.1}. The tunable T{sub C} and large glass-forming ability of these RE doped Fe-based bulk metallic glasses can be used in a wide temperature range with the final required shapes.

  17. Nanostructured Coatings

    NASA Astrophysics Data System (ADS)

    Rivière, J.-P.

    In many branches of technology where surfaces are playing a growing role, the use of coatings is often the only way to provide surfaces with specific functional properties. For example, the austenitic stainless steels or titanium alloys exhibit poor resistance to wear and low hardness values, which limits the field of applications. The idea then is to develop new solutions which would improve the mechanical performance and durability of objects used in contact and subjected to mechanical forces in hostile gaseous or liquid environments. Hard coatings are generally much sought after to enhance the resistance to wear and corrosion. They are of particular importance because they constitute a class of protective coatings which is already widely used on an industrial scale to improve the hardness and lifetime of cutting tools.

  18. Protective Coatings

    NASA Technical Reports Server (NTRS)

    1980-01-01

    General Magnaplate Corporation's pharmaceutical machine is used in the industry for high speed pressing of pills and capsules. Machine is automatic system for molding glycerine suppositories. These machines are typical of many types of drug production and packaging equipment whose metal parts are treated with space spinoff coatings that promote general machine efficiency and contribute to compliance with stringent federal sanitation codes for pharmaceutical manufacture. Collectively known as "synergistic" coatings, these dry lubricants are bonded to a variety of metals to form an extremely hard slippery surface with long lasting self lubrication. The coatings offer multiple advantages; they cannot chip, peel or be rubbed off. They protect machine parts from corrosion and wear longer, lowering maintenance cost and reduce undesired heat caused by power-robbing friction.

  19. Amorphization of silicon carbide by carbon displacement

    NASA Astrophysics Data System (ADS)

    Devanathan, R.; Gao, F.; Weber, W. J.

    2004-05-01

    We have used molecular dynamics simulations to examine the possibility of amorphizing silicon carbide (SiC) by exclusively displacing C atoms. At a defect generation corresponding to 0.2 displacements per atom, the enthalpy surpasses the level of melt-quenched SiC, the density decreases by about 15%, and the radial distribution function shows a lack of long-range order. Prior to amorphization, the surviving defects are mainly C Frenkel pairs (67%), but Si Frenkel pairs (18%) and antisite defects (15%) are also present. The results indicate that SiC can be amorphized by C sublattice displacements. Chemical short-range disorder, arising mainly from Frenkel pair production, plays a significant role in the amorphization.

  20. Amorphous Semiconductor Thin Films, an Introduction

    SciTech Connect

    Martin, Peter M.

    2003-12-01

    The field of amorphous semiconductors is so large that I cannot do it justice, but I hope this short column gives you some insight into the properties and materials available, and the issues involved.

  1. Fracture in Bulk Amorphous Alloys

    SciTech Connect

    Horton, J.A.; Wright, J.L.

    1998-11-30

    The fracture behavior of a Zr-based bulk amorphous alloy, Zr-10 AI-5 Ti-17.9 Cu-14.6 Ni, was examined by transmission electron microscopy (TEM) and x-ray diffraction for any evidence of crystallization preceding crack propagation. No evidence for crystallization was found in shear bands in compression specimens or at the fracture surface in tensile specimens. In- situ TEM deformation experiments were performed to more closely examine actual crack tip regions. During the in-situ deformation experiment controlled crack growth occurred to the point where the specimen was approximately 20 {micro}m thick at which point uncontrolled crack growth occurred. No evidence of any crystallization was found at the crack tips or the crack flanks. Subsequent scanning microscope examination showed that the uncontrolled crack growth region exhibited ridges and veins that appeared to have resulted from melting. Performing the deformations, both bulk and in-situ TEM, at liquid nitrogen temperatures (LN{sub 2}) resulted in an increase in the amount of controlled crack growth. The surface roughness of the bulk regions fractured at LN{sub 2} temperatures corresponded with the roughness of the crack propagation observed during the in-situ TEM experiment, suggesting that the smooth-appearing room temperature fracture sur-faces may also be a result of localized melting.

  2. Ductile crystalline–amorphous nanolaminates

    PubMed Central

    Wang, Yinmin; Li, Ju; Hamza, Alex V.; Barbee, Troy W.

    2007-01-01

    It is known that the room-temperature plastic deformation of bulk metallic glasses is compromised by strain softening and shear localization, resulting in near-zero tensile ductility. The incorporation of metallic glasses into engineering materials, therefore, is often accompanied by complete brittleness or an apparent loss of useful tensile ductility. Here we report the observation of an exceptional tensile ductility in crystalline copper/copper–zirconium glass nanolaminates. These nanocrystalline–amorphous nanolaminates exhibit a high flow stress of 1.09 ± 0.02 GPa, a nearly elastic-perfectly plastic behavior without necking, and a tensile elongation to failure of 13.8 ± 1.7%, which is six to eight times higher than that typically observed in conventional crystalline–crystalline nanolaminates (<2%) and most other nanocrystalline materials. Transmission electron microscopy and atomistic simulations demonstrate that shear banding instability no longer afflicts the 5- to 10-nm-thick nanolaminate glassy layers during tensile deformation, which also act as high-capacity sinks for dislocations, enabling absorption of free volume and free energy transported by the dislocations; the amorphous–crystal interfaces exhibit unique inelastic shear (slip) transfer characteristics, fundamentally different from those of grain boundaries. Nanoscale metallic glass layers therefore may offer great benefits in engineering the plasticity of crystalline materials and opening new avenues for improving their strength and ductility. PMID:17592136

  3. 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.

  4. Amorphous Phases on the Surface of Mars

    NASA Technical Reports Server (NTRS)

    Rampe, E. B.; Morris, R. V.; Ruff, S. W.; Horgan, B.; Dehouck, E.; Achilles, C. N.; Ming, D. W.; Bish, D. L.; Chipera, S. J.

    2014-01-01

    Both primary (volcanic/impact glasses) and secondary (opal/silica, allophane, hisingerite, npOx, S-bearing) amorphous phases appear to be major components of martian surface materials based on orbital and in-situ measurements. A key observation is that whereas regional/global scale amorphous components include altered glass and npOx, local scale amorphous phases include hydrated silica/opal. This suggests widespread alteration at low water-to-rock ratios, perhaps due to snow/ice melt with variable pH, and localized alteration at high water-to-rock ratios. Orbital and in-situ measurements of the regional/global amorphous component on Mars suggests that it is made up of at least three phases: npOx, amorphous silicate (likely altered glass), and an amorphous S-bearing phase. Fundamental questions regarding the composition and the formation of the regional/global amorphous component(s) still remain: Do the phases form locally or have they been homogenized through aeolian activity and derived from the global dust? Is the parent glass volcanic, impact, or both? Are the phases separate or intimately mixed (e.g., as in palagonite)? When did the amorphous phases form? To address the question of source (local and/or global), we need to look for variations in the different phases within the amorphous component through continued modeling of the chemical composition of the amorphous phases in samples from Gale using CheMin and APXS data. If we find variations (e.g., a lack of or enrichment in amorphous silicate in some samples), this may imply a local source for some phases. Furthermore, the chemical composition of the weathering products may give insight into the formation mechanisms of the parent glass (e.g., impact glasses contain higher Al and lower Si [30], so we might expect allophane as a weathering product of impact glass). To address the question of whether these phases are separate or intimately mixed, we need to do laboratory studies of naturally altered samples made

  5. Gold Coating

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Epner Technology Inc. responded to a need from Goddard Space Flight Center for the ultimate in electroplated reflectivity needed for the Mars Global Surveyor Mars Orbiter Laser Altimeter (MOLA). Made of beryllium, the MOLA mirror was coated by Epner Technology Laser Gold process, specially improved for the project. Improved Laser Gold- coated reflectors have found use in an epitaxial reactor built for a large semiconductor manufacturer as well as the waveguide in Braun-Thermoscan tympanic thermometer and lasing cavities in various surgical instruments.

  6. A Magnetic Sensor with Amorphous Wire

    PubMed Central

    He, Dongfeng; Shiwa, Mitsuharu

    2014-01-01

    Using a FeCoSiB amorphous wire and a coil wrapped around it, we have developed a sensitive magnetic sensor. When a 5 mm long amorphous wire with the diameter of 0.1 mm was used, the magnetic field noise spectrum of the sensor was about 30 pT/√Hz above 30 Hz. To show the sensitivity and the spatial resolution, the magnetic field of a thousand Japanese yen was scanned with the magnetic sensor. PMID:24940865

  7. Amorphous Carbon-Boron Nitride Nanotube Hybrids

    NASA Technical Reports Server (NTRS)

    Kim, Jae Woo (Inventor); Siochi, Emilie J. (Inventor); Wise, Kristopher E. (Inventor); Lin, Yi (Inventor); Connell, John (Inventor)

    2016-01-01

    A method for joining or repairing boron nitride nanotubes (BNNTs). In joining BNNTs, the nanotube structure is modified with amorphous carbon deposited by controlled electron beam irradiation to form well bonded hybrid a-C/BNNT structures. In repairing BNNTs, the damaged site of the nanotube structure is modified with amorphous carbon deposited by controlled electron beam irradiation to form well bonded hybrid a-C/BNNT structures at the damage site.

  8. Tetrahedral Amorphous Carbon (ta-C) Ultra Thin Films for Slider Overcoat Application

    NASA Astrophysics Data System (ADS)

    Shi, X.; Hu, Y. H.; Hu, L.

    Tetrahedral Amorphous Carbon (ta-C) thin film by using Filtered Cathodic Vacuum Arc (FCVA) technique has proven to be wear-resistive and corrosion resistant for a wide range of electrical, optical, and mechanical applications. Many investigations have shown that the ta-C film prepared by the FCVA technique can provide a superior ultra thin overcoat for the sliders and media compared to ECR-CVD and IBD coating technology. The ta-C film excels in terms of the film density, hardness, surface roughness and corrosion resistance. Nanofilm Technology International (NTI) has successfully developed and commercialized the FCVA coating system (FS series) for the slider overcoat application, which provides a good quality film with a high hardness (~50 GPa), low stress (2~3 GPa), low macro-particle density (~1/cm2 for particles > 0.3 μm), good uniformity (< 4%$ in 8 inch coating area) and high production repeatability (< 5%).

  9. 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

  10. 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

  11. 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

  12. Amorphization of ZrO2 + CeO2 Powders Through Mechanical Milling for the Use of Kinetic Spray

    NASA Astrophysics Data System (ADS)

    Li, Songlin; Wang, Lei; Xiong, Yuming; Bae, Gyuyeol; Lee, Changhee

    2013-12-01

    The coating formation in a kinetic spray process mainly depends on the impact of inflight particles at a high velocity. The plastic deformation at the impact interface would disrupt the native oxide scale on the particle and the substrate to generate the intimate contact of the atomic structures. Accordingly, it poses a challenge in producing ceramic coating during kinetic spray because of the lack of plasticity of ceramic powders at room temperature. In this study, we proposed to prepare ZrO2 ceramic coatings using partially amorphized powder with nanometer size in the kinetic spray process. To prepare the powder for the use of the kinetic spray, the amorphization and grain refinement of ZrO2 powder in mechanical ball milling were studied. The results showed that the amorphization and grain refinement were improved because of the formation of solid solution when the CeO2 agent was added. Subsequently, a nearly spherical powder was achieved via spray drying using the milled powders. The plasticity of the milled powders was tested in the kinetic spray process using Nitrogen as process gas. A dense ZrO2-CeO2 coating with a thickness of 50 μm was formed, whereas spraying milled ZrO2 powder can only lead to an inhomogeneous dispersion of the destructible particles on the surface of the substrate.

  13. Thermal transport in amorphous materials: a review

    NASA Astrophysics Data System (ADS)

    Wingert, Matthew C.; Zheng, Jianlin; Kwon, Soonshin; Chen, Renkun

    2016-11-01

    Thermal transport plays a crucial role in performance and reliability of semiconductor electronic devices, where heat is mainly carried by phonons. Phonon transport in crystalline semiconductor materials, such as Si, Ge, GaAs, GaN, etc, has been extensively studied over the past two decades. In fact, study of phonon physics in crystalline semiconductor materials in both bulk and nanostructure forms has been the cornerstone of the emerging field of ‘nanoscale heat transfer’. On the contrary, thermal properties of amorphous materials have been relatively less explored. Recently, however, a growing number of studies have re-examined the thermal properties of amorphous semiconductors, such as amorphous Si. These studies, which included both computational and experimental work, have revealed that phonon transport in amorphous materials is perhaps more complicated than previously thought. For instance, depending on the type of amorphous materials, thermal transport occurs via three types of vibrations: propagons, diffusons, and locons, corresponding to the propagating, diffusion, and localized modes, respectively. The relative contribution of each of these modes dictates the thermal conductivity of the material, including its magnitude and its dependence on sample size and temperature. In this article, we will review the fundamental principles and recent development regarding thermal transport in amorphous semiconductors.

  14. Amorphous boron nitride at high pressure

    NASA Astrophysics Data System (ADS)

    Durandurdu, Murat

    2016-06-01

    The pressure-induced phase transformation in hexagonal boron nitrite and amorphous boron nitrite is studied using ab initio molecular dynamics simulations. The hexagonal-to-wurtzite phase transformation is successfully reproduced in the simulation with a transformation mechanism similar to one suggested in experiment. Amorphous boron nitrite, on the other hand, gradually transforms to a high-density amorphous phase with the application of pressure. This phase transformation is irreversible because a densified amorphous state having both sp3 and sp2 bonds is recovered upon pressure release. The high-density amorphous state mainly consists of sp3 bonds and its local structure is quite similar to recently proposed intermediate boron nitrite phases, in particular tetragonal structure (P42/mnm), rather than the known the wurtzite or cubic boron nitrite due to the existence of four membered rings and edge sharing connectivity. On the basis of this finding we propose that amorphous boron nitrite might be best candidate as a starting structure to synthesize the intermediate phase(s) at high pressure and temperature (probably below 800 °C) conditions.

  15. Controlled motion of domain walls in submicron amorphous wires

    NASA Astrophysics Data System (ADS)

    Ťibu, Mihai; Lostun, Mihaela; Allwood, Dan A.; Rotǎrescu, Cristian; Atiťoaie, Alexandru; Lupu, Nicoleta; Óvári, Tibor-Adrian; Chiriac, Horia

    2016-05-01

    Results on the control of the domain wall displacement in cylindrical Fe77.5Si7.5B15 amorphous glass-coated submicron wires prepared by rapid quenching from the melt are reported. The control methods have relied on conical notches with various depths, up to a few tens of nm, made in the glass coating and in the metallic nucleus using a focused ion beam (FIB) system, and on the use of small nucleation coils at one of the sample ends in order to apply magnetic field pulses aimed to enhance the nucleation of reverse domains. The notch-based method is used for the first time in the case of cylindrical ultrathin wires. The results show that the most efficient technique of controlling the domain wall motion in this type of samples is the simultaneous use of notches and nucleation coils. Their effect depends on wire diameter, notch depth, its position on the wire length, and characteristics of the applied pulse.

  16. Laminated Amorphous Silicon Neutron Detector (pre-print)

    SciTech Connect

    Harry McHugh, Howard Branz, Paul Stradins, and Yueqin Xu

    2009-01-29

    An internal R&D project was conducted at the Special Technologies Laboratory (STL) of National Security Technologies, LLC (NSTec), to determine the feasibility of developing a multi-layer boron-10 based thermal neutron detector using the amorphous silicon (AS) technology currently employed in the manufacture of liquid crystal displays. The boron-10 neutron reaction produces an alpha that can be readily detected. A single layer detector, limited to an approximately 2-micron-thick layer of boron, has a theoretical sensitivity of about 3%; hence a thin multi-layer device with high sensitivity can theoretically be manufactured from single layer detectors. Working with National Renewable Energy Laboratory (NREL), an AS PiN diode alpha detector was developed and tested. The PiN diode was deposited on a boron-10 coated substrate. Testing confirmed that the neutron sensitivity was nearly equal to the theoretical value of 3%. However, adhesion problems with the boron-10 coating prevented successful development of a prototype detector. Future efforts will include boron deposition work and development of integrated AS signal processing circuitry.

  17. Anti-wear properties of Cr C and Ni Co alloy coatings as substitutes for conventional nanocrystalline Cr coatings

    NASA Astrophysics Data System (ADS)

    Zeng, Zhixiang; Zhang, Junyan

    2008-09-01

    Nanocrystalline Ni-Co, amorphous Cr-C alloy and nanocrystalline Cr-C coatings were electrodeposited from 'environmentally acceptable' electrolytes as potential substitutes for conventional nanocrystalline Cr coatings electrodeposited from noxious hexavalent chromium. The structure, morphology and hardness of coatings are investigated using a transmission electron microscope, a scanning electronic microscope and a Vickers hardness tester, respectively. Anti-wear properties are tested on a pin-on-plate vibrant wear tester. The correlation between the wear resistance, hardness, brittleness and the lubricated state is investigated. The results show that the wear behaviour of specimens significantly depends on their lubricated state, hardness and brittleness. Under the lubricated sliding condition, abrasive wear is the primary wear mechanism for all specimens. With respect to the abrasive wear mechanism, both the elastic and plastic deformations play important roles during the lubricated sliding process. Thus, the amorphous and nanocrystalline Cr-C alloy coatings, with both high brittleness and high hardness, exhibit a lower wear rate than the conventional Cr and Ni-Co coatings. On the other hand, under the dry sliding condition, the annealed Ni-Co coating, with an excellent compromise between high hardness and toughness, exhibits an abrasive wear mechanism and a relatively low wear rate; in contrast, the brittle Cr-matrix coatings exhibit a severe fatigue/delamination wear mechanism and high wear rate.

  18. Time-Domain Thermoreflectance Measurements of Thermal Transport in Amorphous SiC Thin Films

    NASA Astrophysics Data System (ADS)

    Daly, Brian; Hondongwa, Donald; King, Sean

    2010-03-01

    We present ultrafast optical pump-probe measurements of thermal transport in a series of amorphous SiC samples. The samples were grown on Si wafers by plasma enhanced chemical vapor deposition utilizing various combinations of methylsilanes and H2 and He diluent gases. The sample films were well characterized and found to have densities (1.3 -- 2.3 g cm-3) and dielectric constants (4.0 -- 7.2) that spanned a wide range of values. Prior to their measurement, the samples were coated with 40-70 nm of polycrystalline Al. The pump-probe measurements were performed at room temperature using a modelocked Ti:sapphire laser that produced sub-picosecond pulses of a few nJ. The pulses heat the Al coating, causing a transient reflectivity change. As the Al film cools into the SiC film, the reflectivity change can be measured, giving a measure of the thermal effusivity of the SiC film. We then extract values for the thermal conductivity of the SiC films and find that it varies from less than half of the thermal conductivity of amorphous SiO2 for the lower density materials to somewhat larger than amorphous SiO2 for the highest density films.

  19. Suspension High Velocity Oxy-Fuel (SHVOF)-Sprayed Alumina Coatings: Microstructure, Nanoindentation and Wear

    NASA Astrophysics Data System (ADS)

    Murray, J. W.; Ang, A. S. M.; Pala, Z.; Shaw, E. C.; Hussain, T.

    2016-10-01

    Suspension high velocity oxy-fuel spraying can be used to produce thermally sprayed coatings from powdered feedstocks too small to be processed by mechanical feeders, allowing formation of nanostructured coatings with improved density and mechanical properties. Here, alumina coatings were produced from submicron-sized feedstock in aqueous suspension, using two flame combustion parameters yielding contrasting microstructures. Both coatings were tested in dry sliding wear conditions with an alumina counterbody. The coating processed with high combustion power of 101 kW contained 74 wt.% amorphous phase and 26 wt.% crystalline phase (95 wt.% gamma and 3 wt.% alpha alumina), while the 72-kW coating contained lower 58 wt.% amorphous phase and 42 wt.% crystalline phases (73 wt.% was alpha and 26 wt.% gamma). The 101-kW coating had a dry sliding specific wear rate between 4 and 4.5 × 10-5 mm3/Nm, 2 orders of magnitude higher than the 72-kW coating wear rate of 2-4.2 × 10-7 mm3/Nm. A severe wear regime dominated by brittle fracture and grain pullout of the coating was responsible for the wear of the 101-kW coating, explained by mean fracture toughness three times lower than the 72-kW coating, owing to the almost complete absence of alpha alumina.

  20. Bioactive Glass-Ceramic Coatings Synthesized by the Liquid Precursor Plasma Spraying Process

    NASA Astrophysics Data System (ADS)

    Xiao, Yanfeng; Song, Lei; Liu, Xiaoguang; Huang, Yi; Huang, Tao; Chen, Jiyong; Wu, Yao; Wu, Fang

    2011-03-01

    In this study, the liquid precursor plasma spraying process was used to manufacture P2O5-Na2O-CaO-SiO2 bioactive glass-ceramic coatings (BGCCs), where sol and suspension were used as feedstocks for plasma spraying. The effect of precursor and spray parameters on the formation and crystallinity of BGCCs was systematically studied. The results indicated that coatings with higher crystallinity were obtained using the sol precursor, while nanostructured coatings predominantly consisting of amorphous phase were synthesized using the suspension precursor. For coatings manufactured from suspension, the fraction of the amorphous phase increased with the increase in plasma power and the decrease in liquid precursor feed rate. The coatings synthesized from the suspension plasma spray process also showed a good in vitro bioactivity, as suggested by the fast apatite formation when soaking into SBF.

  1. Heat-Induced Agglomeration of Amorphous Silicon Nanoparticles Toward the Formation of Silicon Thin Film.

    PubMed

    Jang, Bo Yun; Kim, Ja Young; Seo, Gyeongju; Shin, Chae-Ho; Ko, Chang Hyun

    2016-01-01

    The thermal behavior of silicon nanoparticles (Si NPs) was investigated for the preparation of silicon thin film using a solution process. TEM analysis of Si NPs, synthesized by inductively coupled plasma, revealed that the micro-structure of the Si NPs was amorphous and that the Si NPs had melted and merged at a comparatively low temperature (~750 °C) considering bulk melting temperature of silicon (1414 °C). A silicon ink solution was prepared by dispersing amorphous Si NPs in propylene glycol (PG). It was then coated onto a silicon wafer and a quartz plate to form a thin film. These films were annealed in a vacuum or in an N₂ environment to increase their film density. N2 annealing at 800 °C and 1000 °C induced the crystallization of the amorphous thin film. An elemental analysis by the SIMS depth profile showed that N₂annealing at 1000 °C for 180 min drastically reduced the concentrations of carbon and oxygen inside the silicon thin film. These results indicate that silicon ink prepared using amorphous Si NPs in PG can serve as a proper means of preparing silicon thin film via solution process. PMID:27398566

  2. Core-shell amorphous silicon-carbon nanoparticles for high performance anodes in lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Sourice, Julien; Bordes, Arnaud; Boulineau, Adrien; Alper, John P.; Franger, Sylvain; Quinsac, Axelle; Habert, Aurélie; Leconte, Yann; De Vito, Eric; Porcher, Willy; Reynaud, Cécile; Herlin-Boime, Nathalie; Haon, Cédric

    2016-10-01

    Core-shell silicon-carbon nanoparticles are attractive candidates as active material to increase the capacity of Li-ion batteries while mitigating the detrimental effects of volume expansion upon lithiation. However crystalline silicon suffers from amorphization upon the first charge/discharge cycle and improved stability is expected in starting with amorphous silicon. Here we report the synthesis, in a single-step process, of amorphous silicon nanoparticles coated with a carbon shell (a-Si@C), via a two-stage laser pyrolysis where decomposition of silane and ethylene are conducted in two successive reaction zones. Control of experimental conditions mitigates silicon core crystallization as well as formation of silicon carbide. Auger electron spectroscopy and scanning transmission electron microscopy show a carbon shell about 1 nm in thickness, which prevents detrimental oxidation of the a-Si cores. Cyclic voltammetry demonstrates that the core-shell composite reaches its maximal lithiation during the first sweep, thanks to its amorphous core. After 500 charge/discharge cycles, it retains a capacity of 1250 mAh.g-1 at a C/5 rate and 800 mAh.g-1 at 2C, with an outstanding coulombic efficiency of 99.95%. Moreover, post-mortem observations show an electrode volume expansion of less than 20% and preservation of the nanostructuration.

  3. Application of HAADF STEM image analysis to structure determination in rotationally disordered and amorphous multilayered films

    NASA Astrophysics Data System (ADS)

    Mitchson, Gavin; Ditto, Jeffrey; Woods, Keenan N.; Westover, Richard; Page, Catherine J.; Johnson, David C.

    2016-08-01

    We report results from high angle annular dark field scanning transmission electron microscopy (HAADF STEM) image analysis of complex semi-crystalline and amorphous materials, and apply the insights gained from local structure information towards global structure determination. Variations in HAADF STEM intensities for a rotationally disordered heterostructure and an amorphous oxide film are statistically analyzed to extract information regarding the inhomogeneity of the films perpendicular to the substrate. By assuming chemical homogeneity in the film axis parallel to the substrate, the signal intensity variation parallel to the substrate is used to estimate the signal noise level, allowing evaluation of the significance of intensity differences in the substrate normal direction. The positions of HAADF STEM intensity peaks in the perpendicular direction, averaged from multiple images, provide a valuable initial model for a Rietveld refinement of the global c-axis structure of the heterostructure. For an amorphous multi-coat solution-cast oxide sample, the analysis reveals statistically significant variations in the HAADF STEM intensity profile perpendicular to the substrate. These variations indicate an inhomogeneous density profile, presumably related to the spin-casting of individual layers and have implications for understanding the chemical interactions that occur between layers when preparing multilayer amorphous oxide films from solution.

  4. FY06 Annual Report: Amorphous Semiconductors for Gamma Radiation Detection (ASGRAD)

    SciTech Connect

    Johnson, Bradley R.; Riley, Brian J.; Crum, Jarrod V.; Sundaram, S. K.; Henager, Charles H.; Zhang, Yanwen; Shutthanandan, V.

    2007-01-01

    We describe progress in the development of new materials for portable, room-temperature, gamma-radiation detection at Pacific Northwest National Laboratory at the Hanford Site in Washington State. High Z, high resistivity, amorphous semiconductors are being designed for use as solid-state detectors at near ambient temperatures; principles of operation are analogous to single-crystal semiconducting detectors. Amorphous semiconductors have both advantages and disadvantages compared to single crystals, and this project is developing methods to mitigate technical problems and design optimized material for gamma detection. Several issues involved in the fabrication of amorphous semiconductors are described, including reaction thermodynamics and kinetics, the development of pyrolytic coating, and the synthesis of ingots. The characterization of amorphous semiconductors is described, including sectioning and polishing protocols, optical microscopy, X-ray diffraction, scanning electron microscopy, optical spectroscopy, particle-induced X-ram emission, Rutherford backscattering, and electrical testing. Then collaboration with the University of Illinois at Urbana-Champaign is discussed in the areas of Hall-effect measurements and current voltage data. Finally, we discuss the strategy for continuing the program.

  5. Synthesis of Core-shell Structured Amorphous Si Nanoparticles by Induction Thermal Plasmas

    NASA Astrophysics Data System (ADS)

    Okamoto, Daisuke; Kageyama, Takuya; Tanaka, Manabu; Sone, Hirotaka; Watanabe, Takayuki

    2015-09-01

    Core-shell structured amorphous Si nanoparticles were synthesized by induction thermal plasma. Crystalline Si powder with 3 μm of average diameter was injected into the induction thermal plasma at 4 MHz. The Si raw materials immediately evaporate in the high temperature plasma region and nanoparticles were produced through the quenching process. Counterflow quenching gas was injected from downstream of the torch with its direction against the plasma flow. The effect of the operating parameter such as flow rate of quenching gas and input power was investigated. Collected particles were characterized by X-ray diffraction, transmission electron microscopy, electron energy-loss spectroscopy, and Raman spectroscopy. Obtained results indicate that amorphization degree of the synthesized nanoparticles is more than 90% when additional quenching gas of 20 L/min is injected. The quenching rate of the prepared nanoparticles in the growth region have an important role on determining the amorphization degree. Moreover, EELS and Raman analyses showed the synthesized nanoparticles were coated by the SiO2 shell with thickness of 2-4 nm. These findings indicated that amorphous Si/SiO2 core-shell structured nanoparticles were successfully synthesized by induction thermal plasma in single step.

  6. Interdiffusion Behavior in Aluminide Coatings for Power Generation Applications

    SciTech Connect

    Zhang, Y.; Pint, B.A.; Haynes, J.A.; Cooley, K.M.; Wright, I.G.

    2003-04-22

    One of the critical issues for the application of iron aluminide coatings is the loss of Al from the coating into the Fe-base substrate alloys which do not contain aluminum. The interdiffusion behavior between chemical vapor deposited (CVD) aluminide coatings and ferritic and austenitic substrates is being studied for times up to 10,000h in the temperature range of 500-800 C. Coatings were synthesized using a laboratory-scale CVD reactor on representative commercial ferritic (Fe-9Cr-1Mo) and austenitic (type 304L stainless steel) alloys. The aluminide coatings on both alloys typically consisted of a relatively thin (20-25 {micro}m) Al-rich outer layer and a thicker (150- 250 {micro}m) inner layer with less Al. The composition profiles before and after interdiffusion testing were measured by electron probe microanalysis (EPMA). The decrease of the Al content at the coating surface was not significant after extended diffusion times ({le} 5000h) at temperatures {le} 700 C. More interdiffusion occurred at 800 C in coatings on both Fe-9Cr-1Mo and 304L alloys. Particularly, a two-phase microstructure was formed in the outer coating layer on 304L after interdiffusion of 2000h at 800 C. The interdiffusion behavior also was simulated using a computer model COSIM (Coating Oxidation and Substrate Interdiffusion Model), which was originally developed for MCrAlY overlay coatings by NASA. Reasonable agreement was observed between the simulated and experimental composition profiles although more work is needed to confirm assumptions made in the model.

  7. Microstructural studies of thermal spray coatings for biomedical applications

    NASA Astrophysics Data System (ADS)

    Sun, Limin

    2002-01-01

    This project aims to address two major concerns with the use of hydroxyapatite [Ca10(PO4)6(OH)2, i.e., HA] coatings; i.e., (i) the resorption of the coating, and (ii) the resorption of bone. The objective is to optimize coating design through microstructural studies of two coating systems: a HA coating and a HA/polymer composite coating. For the HA coating, the HA powders were atmospherically plasma sprayed (APS) using various process parameters. The phase, structure and microstructure of the coatings were investigated and the mechanical property and dissolution behavior measured. Both crystallinity and hydroxyl contents decreased with increasing spray power and stand-off distance (SOD), and increased from the coating interface to surface. Impurity phase contents increased with increasing spray power. Crystallinity alone cannot reflect coating quality due to the existence of various HA, i.e., unmelted, recrystallized and dehydroxylated, and the gradient structure. Coating microstructure varied from a porous structure to a smooth glassy structure or a typical lamellar structure, and some newly formed nanocrystalline regions were revealed. These effects were associated with the temperature-time experiences of particles, their cooling rates and the heat and hydroxyl accumulation during coating buildup. Different coating properties and performance resulted from the characteristic differences. The coating with highest recrystallization displayed the highest microhardness. Dissolution of all coatings reached a saturation value much lower compared to their pulverized counterparts in a fresh solution despite a higher and similar dissolution in the initial immersion stage. The coating with higher recrystallization exhibited higher saturation value. Microstructural analysis indicated the complete and preferential dissolution of amorphous and impurity phases and some precipitation of apatite observable for coatings with higher recrystallization. For the composite coating, HA

  8. Electrons and phonons in amorphous semiconductors

    NASA Astrophysics Data System (ADS)

    Prasai, Kiran; Biswas, Parthapratim; Drabold, D. A.

    2016-07-01

    The coupling between lattice vibrations and electrons is one of the central concepts of condensed matter physics. The subject has been deeply studied for crystalline materials, but far less so for amorphous and glassy materials, which are among the most important for applications. In this paper, we explore the electron-lattice coupling using current tools of a first-principles computer simulation. We choose three materials to illustrate the phenomena: amorphous silicon (a-Si), amorphous selenium (a-Se) and amorphous gallium nitride (a-GaN). In each case, we show that there is a strong correlation between the localization of electron states and the magnitude of thermally induced fluctuations in energy eigenvalues obtained from the density-functional theory (i.e. Kohn–Sham eigenvalues). We provide a heuristic theory to explain these observations. The case of a-GaN, a topologically disordered partly ionic insulator, is distinctive compared to the covalent amorphous examples. Next, we explore the consequences of changing the charge state of a system as a proxy for tracking photo-induced structural changes in the materials. Where transport is concerned, we lend insight into the Meyer–Neldel compensation rule and discuss a thermally averaged Kubo–Greenwood formula as a means to estimate electrical conductivity and especially its temperature dependence. We close by showing how the optical gap of an amorphous semiconductor can be computationally engineered with the judicious use of Hellmann–Feynman forces (associated with a few defect states) using molecular dynamics simulations. These forces can be used to close or open an optical gap, and identify a structure with a prescribed gap. We use the approach with plane-wave density functional methods to identify a low-energy amorphous phase of silicon including several coordination defects, yet with a gap close to that of good quality a-Si models.

  9. Electrons and phonons in amorphous semiconductors

    NASA Astrophysics Data System (ADS)

    Prasai, Kiran; Biswas, Parthapratim; Drabold, D. A.

    2016-07-01

    The coupling between lattice vibrations and electrons is one of the central concepts of condensed matter physics. The subject has been deeply studied for crystalline materials, but far less so for amorphous and glassy materials, which are among the most important for applications. In this paper, we explore the electron-lattice coupling using current tools of a first-principles computer simulation. We choose three materials to illustrate the phenomena: amorphous silicon (a-Si), amorphous selenium (a-Se) and amorphous gallium nitride (a-GaN). In each case, we show that there is a strong correlation between the localization of electron states and the magnitude of thermally induced fluctuations in energy eigenvalues obtained from the density-functional theory (i.e. Kohn-Sham eigenvalues). We provide a heuristic theory to explain these observations. The case of a-GaN, a topologically disordered partly ionic insulator, is distinctive compared to the covalent amorphous examples. Next, we explore the consequences of changing the charge state of a system as a proxy for tracking photo-induced structural changes in the materials. Where transport is concerned, we lend insight into the Meyer-Neldel compensation rule and discuss a thermally averaged Kubo-Greenwood formula as a means to estimate electrical conductivity and especially its temperature dependence. We close by showing how the optical gap of an amorphous semiconductor can be computationally engineered with the judicious use of Hellmann-Feynman forces (associated with a few defect states) using molecular dynamics simulations. These forces can be used to close or open an optical gap, and identify a structure with a prescribed gap. We use the approach with plane-wave density functional methods to identify a low-energy amorphous phase of silicon including several coordination defects, yet with a gap close to that of good quality a-Si models.

  10. Tailoring Fe-Base Alloys for Intermediate Temperature SOFC Interconnect Application

    SciTech Connect

    J.H. Zhu; M.P. Brady; H.U. Anderson

    2007-12-31

    -Ni-Co alloys as precursor to synthesize a protective spinel layer on commercial ferritic steels has been initiated to facilitate the utilization of the Cr-free spinel as a surface seal to block Cr evaporation. It is suggested that low-cost Fe-Ni-Co alloy coating on commercial ferritic steels might be the best approach to completely eliminate the Cr poisoning problem in SOFC stacks, while maintaining the relatively low overall cost of the interconnect component.

  11. 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.

  12. Characterisation and tribological investigation on thermally processed nanostructured Fe-based and Cu-based cermet materials.

    PubMed

    Basak, A K; Eddine, W Zein; Celis, J P; Matteazzi, P

    2010-02-01

    The feasibility of achieving a nanostructured material after different thermal processing of nanosized powders is presented. The thermal processing was done by either atmospheric plasma spraying, laser sintering, or extrusion followed by hot isostatic pressing. The structural characterisation of such thermally processed nanostructured Fe-based and Cu-based metallic or Al2O3 reinforced cermets, confirmed the retention of a nanostructure after each of these thermal processes. Hardness measurements confirmed an increased hardness as expected in the case that nanostructuring is achieved. The role of grain boundaries and second phase particles on the retention of the nanostructure after thermal processing is discussed. Finally, the possible benefit of nanostructuring on the friction and wear behaviour of materials in sliding tests against corundum in ambient air is reported and discussed. PMID:20352775

  13. Performance of Alumina-Forming Austenitic Steels, Fe-base and Ni-base alloys exposed to metal dusting environments

    SciTech Connect

    Vande Put Ep Rouaix, Aurelie; Unocic, Kinga A; Pint, Bruce A; Brady, Michael P

    2011-01-01

    A series of conventional Fe- and Ni- base, chromia- and alumina- forming alloys, and a newly developed creep-resistant, alumina-forming austenitic steel were developed and its performance relative to conventional Fe- and Ni-based chromia-forming alloys was evaluated in metal dusting environments with a range of water vapor contents. Five 500h experiments have been performed at 650 C with different water vapor contents and total pressures. Without water vapor, the Ni-base alloys showed greater resistance to metal dusting than the Fe-base alloys, including AFA. However, with 10-28% water vapor, more protective behavior was observed with the higher-alloyed materials and only small mass changes were observed. Longer exposure times are in progress to further differentiate performance.

  14. 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.

  15. Synthesis of magnetic Fe-based bulk metallic glasses starting from the Fe-Cr-Co system

    SciTech Connect

    Mastrogiacomo, Giovanni; Kradolfer, Juerg; Loeffler, Joerg F.

    2007-01-01

    The glass-forming ability of Fe-based bulk metallic glasses is strongly correlated with the amount of metalloids they contain. Starting from a ferromagnetic and ductile Fe-based metallic glass of composition (Fe{sub 0.582}Co{sub 0.418}){sub 80}Cr{sub 10}Zr{sub 10}, we were able to produce several bulk metallic glasses by alloying titanium and boron. The resulting alloys of composition [(Fe{sub 0.582}Co{sub 0.418}){sub 0.81}Cr{sub 0.10}Zr{sub 0.07}Ti{sub 0.02}]{sub 100-x}B{sub =} x (x=10-20 at. %) exhibit a critical casting thickness of 0.5 mm, a wide undercooled liquid region {delta}T{sub x}(=T{sub x}-T{sub g}) of 16-84 K, and ferromagnetic properties. dc magnetization measurements show an inverted hysteresis at room temperature, and small-angle neutron scattering on the [(Fe{sub 0.582}Co{sub 0.418}){sub 0.81}Cr{sub 0.10}Zr{sub 0.07}Ti{sub 0.02}]{sub 90}B{sub 10} bulk metallic glass reveals a power-law dependence of the differential scattering cross-section. The latter indicates a pronounced short-range order with a surface fractal dimension of 2.5. A splat-cooled sample of the same composition does not reveal this pronounced short-range order, but still an inverted hysteresis. From the scaling behavior of the magnetization curves, measured at different temperatures between 50 and 300 K for the splat-cooled sample, we find that an antagonistic internal magnetic field is present in this material. The resulting inverted hysteresis is presumably caused by interacting superparamagnetic and blocked regions.

  16. Cytotoxicity of corrosion products of degradable Fe-based stents: relevance of pH and insoluble products.

    PubMed

    Fagali, Natalia S; Grillo, Claudia A; Puntarulo, Susana; Fernández Lorenzo de Mele, Mónica A

    2015-04-01

    Fe-based biodegradable metallic materials (Fe-BMMs) have been proposed for cardiovascular applications and are expected to disappear via corrosion after an appropriate period. However, in vivo studies showed that Fe ions release leads to accumulation of orange and brownish insoluble products at the biomaterial/cell interface. As an additional consequence, sharp changes in pH may affect the biocompatibility of these materials. In the present work, the experimental protocols were designed with the aim of evaluating the relative importance that these factors have on biocompatibility evaluation of BMMs. Mitochondrial activity (MTT assay) and thiobarbituric acid reactive substances (TBARS) assay on mammalian cells, exposed to 1-5 mM of added Fe3+ salt, were assessed and compared with results linked exclusively to pH effects. Soluble Fe concentration in culture medium and intracellular Fe content were also determined. The results showed that: (i) mitochondrial activity was affected by pH changes over the entire range of concentrations of added Fe3+ assayed, (ii) at the highest added Fe3+ concentrations (≥3 mM), precipitation was detected and the cells were able to incorporate the precipitate, that seems to be linked to cell damage, (iii) the extent of precipitation depends on the Fe/protein concentration ratio; and (iv) lipid peroxidation products were detected over the entire range of concentrations of added Fe3+. Hence, a new approach opens in the biocompatibility evaluation of Fe-based BMMs, since the cytotoxicity would not be solely a function of released (and soluble) ions but of the insoluble degradation product amount and the pH falling at the biomaterial/cell interface. The concentration of Fe-containing products at the interface depends on diffusional conditions in a very complex way that should be carefully analyzed in the future.

  17. High-resolution transmission electron microscopy of grain-refining particles in amorphous aluminum alloys

    SciTech Connect

    Schumacher, P.; Greer, A.L.

    1996-10-01

    The nucleation mechanism of Al-Ti-B grain refiners is studied in an Al-based amorphous alloy. The ability to limit growth of {alpha}-Al in the amorphous alloy permits the microscopical observation of nucleation events on boride particles. Earlier studies of this kind are extended by using high-resolution electron microscopy. This shows that the efficient nucleation {alpha}-Al depends on the TiB{sub 2} particles being coated with a thin layer of Al{sub 3}Ti, which can form only when there is some excess titanium in the melt. The aluminide layer, stabilized by adsorption effects, can be as little as a few monolayers thick, and is coherent with the boride. The nature of this layer, and its importance for the nucleation mechanism are discussed. The fading of the grain refinement action is also considered.

  18. Molecular dynamics study of the mechanical loss in amorphous pure and doped silica

    SciTech Connect

    Hamdan, Rashid; Trinastic, Jonathan P.; Cheng, H. P.

    2014-08-07

    Gravitational wave detectors and other precision measurement devices are limited by the thermal noise in the oxide coatings on the mirrors of such devices. We have investigated the mechanical loss in amorphous oxides by calculating the internal friction using classical, atomistic molecular dynamics simulations. We have implemented the trajectory bisection method and the non-local ridge method in the DL-POLY molecular dynamics simulation software to carry out those calculations. These methods have been used to locate the local potential energy minima that a system visits during a molecular dynamics trajectory and the transition state between any two consecutive minima. Using the numerically calculated barrier height distributions, barrier asymmetry distributions, relaxation times, and deformation potentials, we have calculated the internal friction of pure amorphous silica and silica mixed with other oxides. The results for silica compare well with experiment. Finally, we use the numerical calculations to comment on the validity of previously used theoretical assumptions.

  19. Plasma-enhanced chemical vapor deposition of amorphous Si on graphene

    NASA Astrophysics Data System (ADS)

    Lupina, G.; Strobel, C.; Dabrowski, J.; Lippert, G.; Kitzmann, J.; Krause, H. M.; Wenger, Ch.; Lukosius, M.; Wolff, A.; Albert, M.; Bartha, J. W.

    2016-05-01

    Plasma-enhanced chemical vapor deposition of thin a-Si:H layers on transferred large area graphene is investigated. Radio frequency (RF, 13.56 MHz) and very high frequency (VHF, 140 MHz) plasma processes are compared. Both methods provide conformal coating of graphene with Si layers as thin as 20 nm without any additional seed layer. The RF plasma process results in amorphization of the graphene layer. In contrast, the VHF process keeps the high crystalline quality of the graphene layer almost intact. Correlation analysis of Raman 2D and G band positions indicates that Si deposition induces reduction of the initial doping in graphene and an increase of compressive strain. Upon rapid thermal annealing, the amorphous Si layer undergoes dehydrogenation and transformation into a polycrystalline film, whereby a high crystalline quality of graphene is preserved.

  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. Microstructure of Suspension Plasma Spray and Air Plasma Spray Al2O3-ZrO2 Composite Coatings

    NASA Astrophysics Data System (ADS)

    Chen, Dianying; Jordan, Eric H.; Gell, Maurice

    2009-09-01

    Al2O3-ZrO2 coatings were deposited by the suspension plasma spray (SPS) molecularly mixed amorphous powder and the conventional air plasma spray (APS) Al2O3-ZrO2 crystalline powder. The amorphous powder was produced by heat treatment of molecularly mixed chemical solution precursors below their crystallization temperatures. Phase composition and microstructure of the as-synthesized and heat-treated SPS and APS coatings were characterized by XRD and SEM. XRD analysis shows that the as-sprayed SPS coating is composed of α-Al2O3 and tetragonal ZrO2 phases, while the as-sprayed APS coating consists of tetragonal ZrO2, α-Al2O3, and γ-Al2O3 phases. Microstructure characterization revealed that the Al2O3 and ZrO2 phase distribution in SPS coatings is much more homogeneous than that of APS coatings.

  2. Understanding Thermal Conductivity in Amorphous Materials

    NASA Astrophysics Data System (ADS)

    Kommandur, Sampath; Yee, Shannon

    2014-03-01

    Current energy technologies such as thermoelectrics, photovoltaics, and LEDs make extensive use of amorphous materials and are limited by heat transfer. Device improvements necessitate a better understanding of the thermal conductivity in amorphous materials. While there are basic theories that capture the trends in thermal conductivity of a select set of amorphous materials, a general framework is needed to explain the fundamental transport of heat in all amorphous materials. One empirical theory that has been successful at describing the thermal conductivity in some materials is the k-min model, however, assumptions in that model limit its generalizability. Another theory defines the existence of propagons, diffusons, and locons, which constitute vibrational modes that carry heat. Our work first presents a summary of literature on the thermal conductivity in amorphous materials and then compares those theories to a breadth of experimental data. Based upon those results, a generic model is proposed that is widely applicable with the ultimate goal of this work being to describe the temperature dependent thermal conductivity of polymers. -/abstract- Sampath Kommandur and Shannon K. Yee 21.1.1: Thermoelectric Phenomena, Materials, Devices, and Applications (GER

  3. SURVIVAL OF AMORPHOUS WATER ICE ON CENTAURS

    SciTech Connect

    Guilbert-Lepoutre, Aurelie

    2012-10-01

    Centaurs are believed to be Kuiper Belt objects in transition between Jupiter and Neptune before possibly becoming Jupiter family comets. Some indirect observational evidence is consistent with the presence of amorphous water ice in Centaurs. Some of them also display a cometary activity, probably triggered by the crystallization of the amorphous water ice, as suggested by Jewitt and this work. Indeed, we investigate the survival of amorphous water ice against crystallization, using a fully three-dimensional thermal evolution model. Simulations are performed for varying heliocentric distances and obliquities. They suggest that crystallization can be triggered as far as 16 AU, though amorphous ice can survive beyond 10 AU. The phase transition is an efficient source of outgassing up to 10-12 AU, which is broadly consistent with the observations of the active Centaurs. The most extreme case is 167P/CINEOS, which barely crystallizes in our simulations. However, amorphous ice can be preserved inside Centaurs in many heliocentric distance-obliquity combinations, below a {approx}5-10 m crystallized crust. We also find that outgassing due to crystallization cannot be sustained for a time longer than 10{sup 4}-10{sup 4} years, leading to the hypothesis that active Centaurs might have recently suffered from orbital changes. This could be supported by both observations (although limited) and dynamical studies.

  4. Synthesis method for amorphous metallic foam

    NASA Astrophysics Data System (ADS)

    Schroers, Jan; Veazey, Chris; Demetriou, Marios D.; Johnson, William L.

    2004-12-01

    A synthesis method for the production of amorphous metallic foam is introduced. This method utilizes the thermodynamic stability and thermoplastic formability of the supercooled liquid state to produce low-density amorphous metallic foams in dimensions that are not limited to the critical casting thickness. The method consists of three stages: the prefoaming stage, in which a large number of small bubbles are created in the equilibrium liquid under pressure; the quenching stage, in which the liquid prefoam is quenched to its amorphous state; the foam expansion stage, in which the amorphous prefoam is reheated to the supercooled liquid region and is processed under pressures substantially lower than those applied in the prefoaming step. Results from a dynamic model suggest that the foam expansion process is feasible, as the kinetics of bubble expansion in the supercooled liquid region are faster than the kinetics of crystallization. Within the proposed synthesis method, bulk amorphous foam products characterized by bubble volume fractions of as high as 85% are successfully produced.

  5. COATING METHOD

    DOEpatents

    Townsend, R.G.

    1959-08-25

    A method is described for protectively coating beryllium metal by etching the metal in an acid bath, immersing the etched beryllium in a solution of sodium zincate for a brief period of time, immersing the beryllium in concentrated nitric acid, immersing the beryhlium in a second solution of sodium zincate, electroplating a thin layer of copper over the beryllium, and finally electroplating a layer of chromium over the copper layer.

  6. Tribological evaluation and analysis of coating materials

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa

    1992-01-01

    A physical characterization of coating materials by analytical techniques such as XPS, AES, ellipsometry, and nuclear reaction analysis can contribute to the understanding of adhesion and friction of the coatings and can partially predict the tribological properties of the coatings. This two-part paper describes the tribological properties and physical characteristics of (1) diamondlike carbon (DLC) films and (2) silicon nitride (SiN(x)) films. Emphasis is to relate plasma deposition conditions to the film chemistry and composition and to the adhesion and friction of the films. With the DLC films, the higher the plasma deposition power, the less the hydrogen concentration and the greater the film density and the hardness. The friction behavior of DLC films deposited at higher deposition powers (200 to 300 W) is similar to that of bulk diamond. Even in a vacuum, the DLC films effectively lubricate ceramic surfaces (Si3N4) at temperatures to 500 C. With SiN(x) films, the silicon to nitrogen ratios and the amount of amorphous silicon depend on deposition frequency. The presence of rich amorphous silicon in the high-frequency plasma-deposited SiN(x) films increases their adhesion and friction above 500 C in vacuum.

  7. Cluster model of amorphized particles formation by plasma spraying of metallic powder

    NASA Astrophysics Data System (ADS)

    Barakhtin, Boris K.; Nesterova, E. V.

    1999-05-01

    Multifunctional coatings from materials with amorphized microcrystalline or nano-phase structure cause a considerable scientific and practical interest. With their help it is to manufacture heat resistant neutralizers of harmful ejections, to produce ecologically clean sources of electric current, to design electromagnetic protective shields and to fabricate a lot of other technical products. The variety of application and a unique complex of operating characteristics (ductility, strength, magnetic and chemical properties) are governed by the basic peculiarity of material in amorphized state - its thermodynamic instability. In comparison with traditional thermodynamically equilibrium metallic alloys, the kinetics of structure changes in amorphous materials is quite different. Thus, it is suggested, that they have peculiar defects (phasonics) which are not typical of materials in crystalline state, they have no translational symmetry and elementary cells. In the process of coatings forming with non-equilibrium structure states can be realized in them, which are characterized by a fluctuation type of origin, entropy export, appearance of space or temporary symmetry uncertainty of the transition direction 'order $ARLR disorder' in bifurcation points. The aforesaid explains a great scientific (not only practical) interest in the structure study of disordered medium. Functional coatings with amorphized, nano- and microcrystalline structure components formed on copper substrate by plasma spraying of dispersed (to 50 mcm) Ni-Al powder. According to the constitutional diagram it was expected to obtain a mixture from equilibrium intermetallide phases NiAl3 + Ni2Al3. The experimental results and investigations performed by X-ray structure, X-ray spectrum and electron microscopy techniques have shown it is possible to obtain phases of variable composition (Ni)m(Al)n with Ni content from 25 to 75 vol.%, including NiAl. It turned out that in the process of spraying the

  8. Measurement and Modeling of Short and Medium Range Order in Amorphous Ta2O5 Thin Films

    PubMed Central

    Shyam, Badri; Stone, Kevin H.; Bassiri, Riccardo; Fejer, Martin M.; Toney, Michael F.; Mehta, Apurva

    2016-01-01

    Amorphous films and coatings are rapidly growing in importance. Yet, there is a dearth of high-quality structural data on sub-micron films. Not understanding how these materials assemble at atomic scale limits fundamental insights needed to improve their performance. Here, we use grazing-incidence x-ray total scattering measurements to examine the atomic structure of the top 50–100 nm of Ta2O5 films; mirror coatings that show high promise to significantly improve the sensitivity of the next generation of gravitational-wave detectors. Our measurements show noticeable changes well into medium range, not only between crystalline and amorphous, but also between as-deposited, annealed and doped amorphous films. It is a further challenge to quickly translate the structural information into insights into mechanisms of packing and disorder. Here, we illustrate a modeling approach that allows translation of observed structural features to a physically intuitive packing of a primary structural unit based on a kinked Ta-O-Ta backbone. Our modeling illustrates how Ta-O-Ta units link to form longer 1D chains and even 2D ribbons, and how doping and annealing influences formation of 2D order. We also find that all the amorphousTa2O5 films studied in here are not just poorly crystalline but appear to lack true 3D order. PMID:27562542

  9. Measurement and Modeling of Short and Medium Range Order in Amorphous Ta2O5 Thin Films.

    PubMed

    Shyam, Badri; Stone, Kevin H; Bassiri, Riccardo; Fejer, Martin M; Toney, Michael F; Mehta, Apurva

    2016-01-01

    Amorphous films and coatings are rapidly growing in importance. Yet, there is a dearth of high-quality structural data on sub-micron films. Not understanding how these materials assemble at atomic scale limits fundamental insights needed to improve their performance. Here, we use grazing-incidence x-ray total scattering measurements to examine the atomic structure of the top 50-100 nm of Ta2O5 films; mirror coatings that show high promise to significantly improve the sensitivity of the next generation of gravitational-wave detectors. Our measurements show noticeable changes well into medium range, not only between crystalline and amorphous, but also between as-deposited, annealed and doped amorphous films. It is a further challenge to quickly translate the structural information into insights into mechanisms of packing and disorder. Here, we illustrate a modeling approach that allows translation of observed structural features to a physically intuitive packing of a primary structural unit based on a kinked Ta-O-Ta backbone. Our modeling illustrates how Ta-O-Ta units link to form longer 1D chains and even 2D ribbons, and how doping and annealing influences formation of 2D order. We also find that all the amorphousTa2O5 films studied in here are not just poorly crystalline but appear to lack true 3D order. PMID:27562542

  10. Measurement and Modeling of Short and Medium Range Order in Amorphous Ta2O5 Thin Films

    NASA Astrophysics Data System (ADS)

    Shyam, Badri; Stone, Kevin H.; Bassiri, Riccardo; Fejer, Martin M.; Toney, Michael F.; Mehta, Apurva

    2016-08-01

    Amorphous films and coatings are rapidly growing in importance. Yet, there is a dearth of high-quality structural data on sub-micron films. Not understanding how these materials assemble at atomic scale limits fundamental insights needed to improve their performance. Here, we use grazing-incidence x-ray total scattering measurements to examine the atomic structure of the top 50–100 nm of Ta2O5 films; mirror coatings that show high promise to significantly improve the sensitivity of the next generation of gravitational-wave detectors. Our measurements show noticeable changes well into medium range, not only between crystalline and amorphous, but also between as-deposited, annealed and doped amorphous films. It is a further challenge to quickly translate the structural information into insights into mechanisms of packing and disorder. Here, we illustrate a modeling approach that allows translation of observed structural features to a physically intuitive packing of a primary structural unit based on a kinked Ta-O-Ta backbone. Our modeling illustrates how Ta-O-Ta units link to form longer 1D chains and even 2D ribbons, and how doping and annealing influences formation of 2D order. We also find that all the amorphousTa2O5 films studied in here are not just poorly crystalline but appear to lack true 3D order.

  11. Measurement and modeling of short and medium range order in amorphous Ta2O5 thin films

    DOE PAGES

    Shyam, Badri; Stone, Kevin H.; Bassiri, Riccardo; Fejer, Martin M.; Toney, Michael F.; Mehta, Apurva

    2016-08-26

    Here, amorphous films and coatings are rapidly growing in importance. Yet, there is a dearth of high-quality structural data on sub-micron films. Not understanding how these materials assemble at atomic scale limits fundamental insights needed to improve their performance. Here, we use grazing-incidence x-ray total scattering measurements to examine the atomic structure of the top 50–100 nm of Ta2O5 films; mirror coatings that show high promise to significantly improve the sensitivity of the next generation of gravitational-wave detectors. Our measurements show noticeable changes well into medium range, not only between crystalline and amorphous, but also between as-deposited, annealed and dopedmore » amorphous films. It is a further challenge to quickly translate the structural information into insights into mechanisms of packing and disorder. Here, we illustrate a modeling approach that allows translation of observed structural features to a physically intuitive packing of a primary structural unit based on a kinked Ta-O-Ta backbone. Our modeling illustrates how Ta-O-Ta units link to form longer 1D chains and even 2D ribbons, and how doping and annealing influences formation of 2D order. We also find that all the amorphousTa2O5 films studied in here are not just poorly crystalline but appear to lack true 3D order.« less

  12. Measurement and Modeling of Short and Medium Range Order in Amorphous Ta2O5 Thin Films

    NASA Astrophysics Data System (ADS)

    Shyam, Badri; Stone, Kevin H.; Bassiri, Riccardo; Fejer, Martin M.; Toney, Michael F.; Mehta, Apurva

    2016-08-01

    Amorphous films and coatings are rapidly growing in importance. Yet, there is a dearth of high-quality structural data on sub-micron films. Not understanding how these materials assemble at atomic scale limits fundamental insights needed to improve their performance. Here, we use grazing-incidence x-ray total scattering measurements to examine the atomic structure of the top 50-100 nm of Ta2O5 films; mirror coatings that show high promise to significantly improve the sensitivity of the next generation of gravitational-wave detectors. Our measurements show noticeable changes well into medium range, not only between crystalline and amorphous, but also between as-deposited, annealed and doped amorphous films. It is a further challenge to quickly translate the structural information into insights into mechanisms of packing and disorder. Here, we illustrate a modeling approach that allows translation of observed structural features to a physically intuitive packing of a primary structural unit based on a kinked Ta-O-Ta backbone. Our modeling illustrates how Ta-O-Ta units link to form longer 1D chains and even 2D ribbons, and how doping and annealing influences formation of 2D order. We also find that all the amorphousTa2O5 films studied in here are not just poorly crystalline but appear to lack true 3D order.

  13. Novel high damage-tolerant, wear resistant MoSi2-based nanocomposite coatings

    NASA Astrophysics Data System (ADS)

    Xu, Jiang; Li, Zhengyang; Xie, Zong-Han; Munroe, Paul; Lu, Xiao Lin; Lan, Xiu Feng

    2013-04-01

    In this study, novel MoSi2-based nanocomposite coatings were deposited on Ti-6Al-4V substrates by a two-step process involving firstly, deposition of MoSi2-based coatings, using a double cathode glow discharge process and, secondly, plasma nitridation of the as-deposited coatings. The aim of this latter step is to introduce nitrogen into the coating and promote the formation of amorphous silicon nitride. The resulting coatings were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscope (XPS), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). It was found that the nanocomposite coatings were composed of nanocrystallite Mo5Si3 and MoSi2 grains embedded in an amorphous Si3N4 matrix. The mechanical properties and damage resistance of the coatings were evaluated by both Vickers indentation and nanoindentation techniques. Dry sliding wear tests were performed using a ball-on-disc type tribometer, in which the coated samples were tested against a ZrO2 ceramic ball at normal loads of 2.8 and 4.3 N under ambient conditions. Compared with the monolithic MoSi2 nanocrystalline coating, the specific wear rates of the nanocomposite coatings decreased by an order of magnitude. The specific wear rate was further improved by about 20% through the addition of Al, which was attributed to an optimum combination of mechanical properties.

  14. Amorphous metallic films in silicon metallization systems

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

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

  15. Phase transitions in biogenic amorphous calcium carbonate.

    PubMed

    Gong, Yutao U T; Killian, Christopher E; Olson, Ian C; Appathurai, Narayana P; Amasino, Audra L; Martin, Michael C; Holt, Liam J; Wilt, Fred H; Gilbert, P U P A

    2012-04-17

    Crystalline biominerals do not resemble faceted crystals. Current explanations for this property involve formation via amorphous phases. Using X-ray absorption near-edge structure (XANES) spectroscopy and photoelectron emission microscopy (PEEM), here we examine forming spicules in embryos of Strongylocentrotus purpuratus sea urchins, and observe a sequence of three mineral phases: hydrated amorphous calcium carbonate (ACC · H(2)O) → dehydrated amorphous calcium carbonate (ACC) → calcite. Unexpectedly, we find ACC · H(2)O-rich nanoparticles that persist after the surrounding mineral has dehydrated and crystallized. Protein matrix components occluded within the mineral must inhibit ACC · H(2)O dehydration. We devised an in vitro, also using XANES-PEEM, assay to identify spicule proteins that may play a role in stabilizing various mineral phases, and found that the most abundant occluded matrix protein in the sea urchin spicules, SM50, stabilizes ACC · H(2)O in vitro. PMID:22492931

  16. IUE observations of amorphous hot galaxies

    NASA Technical Reports Server (NTRS)

    Lamb, S. A.; Hjellming, M. S.; Gallagher, J. S., III; Hunter, D. A.

    1985-01-01

    Blue amorphous galaxies are star-forming, irregularlike systems which lack the spatially distinct OB stellar groups that are characteristic of most late-type galaxies. In order to better understand the nature of star-formation processes in these unusual galaxies, short-wavelength IUE spectra of the amorphous galaxies NGC 1705 and NGC 1800 have been obtained. It is found that NGC 1705 contains a normal mix of OB stars, which is consistent with the nearly constant recent star-formation rate inferred from new optical data. NGC 1800 is likely to have similar properties, and blue galaxies with amorphous structures thus do not show evidence for anomalies in stellar populations. The UV spectra of these galaxies and a variety of other hot extragalactic stellar systems in fact have similar characteristics, which suggests OB stellar populations are often homogeneous in their properties.

  17. Synthesis and photocurrent of amorphous boron nanowires.

    PubMed

    Ge, Liehui; Lei, Sidong; Hart, Amelia H C; Gao, Guanhui; Jafry, Huma; Vajtai, Robert; Ajayan, Pulickel M

    2014-08-22

    Although theoretically feasible, synthesis of boron nanostructures is challenging due to the highly reactive nature, high melting and boiling points of boron. We have developed a thermal vapor transfer approach to synthesizing amorphous boron nanowire using a solid boron source. The amorphous nature and chemical composition of boron nanowires were characterized by high resolution transmission electron microscopy, selected area electron diffraction, and electron energy loss spectroscopy. Optical properties and photoconduction of boron nanowires have not yet been reported. In our investigation, the amorphous boron nanowire showed much better optical and electrical properties than previously reported photo-response of crystalline boron nanobelts. When excited by a blue LED, the photo/dark current ratio (I/I₀) is 1.5 and time constants in the order of tens of seconds. I/I₀ is 1.17 using a green light. PMID:25061013

  18. Superior radiation tolerant materials: Amorphous silicon oxycarbide

    NASA Astrophysics Data System (ADS)

    Nastasi, Michael; Su, Qing; Price, Lloyd; Colón Santana, Juan A.; Chen, Tianyi; Balerio, Robert; Shao, Lin

    2015-06-01

    We studied the radiation tolerance of amorphous silicon oxycarbide (SiOC) alloys by combining ion irradiation, X-ray diffraction (XRD) and transmission electron microscopy (TEM). The amorphous SiOC alloys thin films were grown via co-sputtering from SiO2 and SiC (amorphous phase) targets either on a surface oxidized Si (100) substrate or on a sodium chloride substrate. By controlling the sputtering rate of each target, SiOC alloys with different compositions (1:2, 1:1, 2:1 ratios) were obtained. These alloys were irradiated by 100 keV He+ ions at both room temperature and 600 °C with damage levels ranging from 1 to 20 displacements per atom (dpa). TEM characterization shows no sign of crystallization, void formation or segregation in all irradiated samples. Our findings suggest that SiOC alloys are a class of promising radiation-tolerant materials.

  19. Enthalpy of crystallization of amorphous yttrium oxide

    SciTech Connect

    Reznitskii, L.A.

    1988-02-01

    Measurements have been made on the enthalpies of crystallization of amorphous Fe/sub 2/O/sub 3/ and Y/sub 3/Fe/sub 5/O/sub 12/ from amorphous Fe/sub 2/O/sub 3/ and Y/sub 2/O/sub 3/ as determined by the DSC method. The heat of crystallization for Y/sub 2/O/sub 3am/ does not make itself felt on the heating thermogram, in contrast to that for Fe/sub 2/O/sub 3/, evidently because it is spread out over a wide temperature range, so it is difficult to measure. One can combine thermochemical equations to calculate the enthalpy of crystallization for amorphous yttrium oxide as ..delta..H = -24.9 kJ/mole.

  20. Cooling of hot electrons in amorphous silicon

    SciTech Connect

    Vanderhaghen, R.; Hulin, D.; Cuzeau, S.; White, J.O.

    1997-07-01

    Measurements of the cooling rate of hot carriers in amorphous silicon are made with a two-pump, one-probe technique. The experiment is simulated with a rate-equation model describing the energy transfer between a population of hot carriers and the lattice. An energy transfer rate proportional to the temperature difference is found to be consistent with the experimental data while an energy transfer independent of the temperature difference is not. This contrasts with the situation in crystalline silicon. The measured cooling rates are sufficient to explain the difficulty in observing avalanche effects in amorphous silicon.

  1. Thermal conductivity of sputtered amorphous Ge films

    SciTech Connect

    Zhan, Tianzhuo; Xu, Yibin; Goto, Masahiro; Tanaka, Yoshihisa; Kato, Ryozo; Sasaki, Michiko; Kagawa, Yutaka

    2014-02-15

    We measured the thermal conductivity of amorphous Ge films prepared by magnetron sputtering. The thermal conductivity was significantly higher than the value predicted by the minimum thermal conductivity model and increased with deposition temperature. We found that variations in sound velocity and Ge film density were not the main factors in the high thermal conductivity. Fast Fourier transform patterns of transmission electron micrographs revealed that short-range order in the Ge films was responsible for their high thermal conductivity. The results provide experimental evidences to understand the underlying nature of the variation of phonon mean free path in amorphous solids.

  2. Production feature of soft magnetic amorphous alloys

    NASA Astrophysics Data System (ADS)

    Tyagunov, A. G.; Baryshev, E. E.; Shmakova, K. Yu

    2016-06-01

    Methods for making nanocrystalline alloys have been discussed. Temperature dependences of the surface tension (σ), electric resistivity (ρ), magnetic susceptibility (χ) and kinematic viscosity (ν) have been obtained. Comparison of the properties of amorphous ribbons obtained by the pilot and serial technologies has been conducted. Science-based technology of multi-component alloy smelting makes it possible to prepare equilibrium smelt, the structure of which has a significant effect on the properties of the amorphous ribbon before spinning and kinetics of its crystallization has been offered.

  3. Ion bombardment and disorder in amorphous silicon

    SciTech Connect

    Sidhu, L.S.; Gaspari, F.; Zukotynski, S.

    1997-07-01

    The effect of ion bombardment during growth on the structural and optical properties of amorphous silicon are presented. Two series of films were deposited under electrically grounded and positively biased substrate conditions. The biased samples displayed lower growth rates and increased hydrogen content relative to grounded counterparts. The film structure was examined using Raman spectroscopy. The transverse optic like phonon band position was used as a parameter to characterize network order. Biased samples displayed an increased order of the amorphous network relative to grounded samples. Furthermore, biased samples exhibited a larger optical gap. These results are correlated and attributed to reduced ion bombardment effects.

  4. Short range order in amorphous polycondensates

    SciTech Connect

    Lamers, C.; Richter, D.; Schweika, W.; Batoulis, J.; Sommer, K.; Cable, J.W.; Shapiro, S.M.

    1992-12-01

    The static coherent structure factors S(Q) of the polymer glass Bisphenol-A-Polycarbonate and its chemical variation Bisphenol-A- Polyctherkctone- both in differently deuterated versions- have been measured by spin polarized neutron scattering. The method of spin polarization analysis provided an experimental separation of coherent and incoherent scattering and a reliable intensity calibration. Results are compared to structure factors calculated for model structures which were obtained by ``amorphous cell`` computer simulations. In general reasonable agreement is found between experiment and simulation; however, certain discrepancies hint at an insufficient structural relaxation in the amorphous cell method. 15 refs, 1 fig, 1 tab.

  5. Amorphous Insulator Films With Controllable Properties

    NASA Technical Reports Server (NTRS)

    Alterovitz, Samuel A.; Warner, Joseph D.; Liu, David C.; Pouch, John J.

    1987-01-01

    In experiments described in report, amorphous hydrogenated carbon films grown at room temperature by low-frequency plasma deposition, using methane or butane gas. Films have unique array of useful properties; (a) adhere to wide variety of materials; (b) contain only carbon and hydrogen; (c) smooth and free of pinholes; (d) resistant to attack by moisture and chemicals; and (e) have high electric-breakdown strength and electrical resistivity. Two of optical properties and hardness of this film controlled by deposition conditions. Amorphous a-C:H and BN films used for hermetic sealing and protection of optical, electronic, magnetic, or delicate mechanical systems, and for semiconductor field dielectrics.

  6. New Amorphous Silicon Alloy Systems

    NASA Astrophysics Data System (ADS)

    Kapur, Mridula N.

    1990-01-01

    The properties of hydrogenated amorphous silicon (a-Si:H) have been modified by alloying with Al, Ga and S respectively. The Al and Ga alloys are in effect quaternary alloys as they were fabricated in a carbon-rich discharge. The alloys were prepared by the plasma assisted chemical vapor deposition (PACVD) method. This method has several advantages, the major one being the relatively low defect densities of the resulting materials. The PACVD system used to grow the alloy films was designed and constructed in the laboratory. It was first tested with known (a-Si:H and a-Si:As:H) materials. Thus, it was established that device quality alloy films could be grown with the home-made PACVD setup. The chemical composition of the alloys was characterized by secondary ion mass spectrometry (SIMS), and electron probe microanalysis (EPMA). The homogeneous nature of hydrogen distribution in the alloys was established by SIMS depth profile analysis. A quantitative analysis of the bulk elemental content was carried out by EPMA. The analysis indicated that the alloying element was incorporated in the films more efficiently at low input gas concentrations than at the higher concentrations. A topological model was proposed to explain the observed behavior. The optical energy gap of the alloys could be varied in the 0.90 to 1.92 eV range. The Al and Ga alloys were low band gap materials, whereas alloying with S had the effect of widening the energy gap. It was observed that although the Si-Al and Si-Ga alloys contained significant amounts of C and H, the magnitude of the energy gap was determined by the metallic component. The various trends in optical properties could be related to the binding characteristics of the respective alloy systems. A quantitative explanation of the results was provided by White's tight binding model. The dark conductivity-temperature dependence of the alloys was examined. A linear dependence was observed for the Al and Ga systems. Electronic conduction in

  7. Biological characteristics of the MG-63 human osteosarcoma cells on composite tantalum carbide/amorphous carbon films.

    PubMed

    Chang, Yin-Yu; Huang, Heng-Li; Chen, Ya-Chi; Hsu, Jui-Ting; Shieh, Tzong-Ming; Tsai, Ming-Tzu

    2014-01-01

    Tantalum (Ta) is a promising metal for biomedical implants or implant coating for orthopedic and dental applications because of its excellent corrosion resistance, fracture toughness, and biocompatibility. This study synthesizes biocompatible tantalum carbide (TaC) and TaC/amorphous carbon (a-C) coatings with different carbon contents by using a twin-gun magnetron sputtering system to improve their biological properties and explore potential surgical implant or device applications. The carbon content in the deposited coatings was regulated by controlling the magnetron power ratio of the pure graphite and Ta cathodes. The deposited TaC and TaC/a-C coatings exhibited better cell viability of human osteosarcoma cell line MG-63 than the uncoated Ti and Ta-coated samples. Inverted optical and confocal imaging was used to demonstrate the cell adhesion, distribution, and proliferation of each sample at different time points during the whole culture period. The results show that the TaC/a-C coating, which contained two metastable phases (TaC and a-C), was more biocompatible with MG-63 cells compared to the pure Ta coating. This suggests that the TaC/a-C coatings exhibit a better biocompatible performance for MG-63 cells, and they may improve implant osseointegration in clinics.

  8. Biological characteristics of the MG-63 human osteosarcoma cells on composite tantalum carbide/amorphous carbon films.

    PubMed

    Chang, Yin-Yu; Huang, Heng-Li; Chen, Ya-Chi; Hsu, Jui-Ting; Shieh, Tzong-Ming; Tsai, Ming-Tzu

    2014-01-01

    Tantalum (Ta) is a promising metal for biomedical implants or implant coating for orthopedic and dental applications because of its excellent corrosion resistance, fracture toughness, and biocompatibility. This study synthesizes biocompatible tantalum carbide (TaC) and TaC/amorphous carbon (a-C) coatings with different carbon contents by using a twin-gun magnetron sputtering system to improve their biological properties and explore potential surgical implant or device applications. The carbon content in the deposited coatings was regulated by controlling the magnetron power ratio of the pure graphite and Ta cathodes. The deposited TaC and TaC/a-C coatings exhibited better cell viability of human osteosarcoma cell line MG-63 than the uncoated Ti and Ta-coated samples. Inverted optical and confocal imaging was used to demonstrate the cell adhesion, distribution, and proliferation of each sample at different time points during the whole culture period. The results show that the TaC/a-C coating, which contained two metastable phases (TaC and a-C), was more biocompatible with MG-63 cells compared to the pure Ta coating. This suggests that the TaC/a-C coatings exhibit a better biocompatible performance for MG-63 cells, and they may improve implant osseointegration in clinics. PMID:24760085

  9. Biological Characteristics of the MG-63 Human Osteosarcoma Cells on Composite Tantalum Carbide/Amorphous Carbon Films

    PubMed Central

    Chang, Yin-Yu; Huang, Heng-Li; Chen, Ya-Chi; Hsu, Jui-Ting; Shieh, Tzong-Ming; Tsai, Ming-Tzu

    2014-01-01

    Tantalum (Ta) is a promising metal for biomedical implants or implant coating for orthopedic and dental applications because of its excellent corrosion resistance, fracture toughness, and biocompatibility. This study synthesizes biocompatible tantalum carbide (TaC) and TaC/amorphous carbon (a-C) coatings with different carbon contents by using a twin-gun magnetron sputtering system to improve their biological properties and explore potential surgical implant or device applications. The carbon content in the deposited coatings was regulated by controlling the magnetron power ratio of the pure graphite and Ta cathodes. The deposited TaC and TaC/a-C coatings exhibited better cell viability of human osteosarcoma cell line MG-63 than the uncoated Ti and Ta-coated samples. Inverted optical and confocal imaging was used to demonstrate the cell adhesion, distribution, and proliferation of each sample at different time points during the whole culture period. The results show that the TaC/a-C coating, which contained two metastable phases (TaC and a-C), was more biocompatible with MG-63 cells compared to the pure Ta coating. This suggests that the TaC/a-C coatings exhibit a better biocompatible performance for MG-63 cells, and they may improve implant osseointegration in clinics. PMID:24760085

  10. Novel Investigation on Nanostructured Multilayer and Functionally Graded Ni-P Electroless Coatings on Stainless Steel

    NASA Astrophysics Data System (ADS)

    Anvari, S. R.; Monirvaghefi, S. M.; Enayati, M. H.

    2015-06-01

    In this study, step-wise multilayer and functionally graded Ni-P coatings were deposited with electroless in which the content of phosphorus and nickel would be changed gradually and step-wise through the thickness of the coatings, respectively. To compare the properties of these coatings with Ni-P single-layer coatings, three types of coatings with different phosphorus contents were deposited. Heat treatment of coatings was performed at 400 °C for 1 h. The microstructure and phase transformation of coatings were characterized by SEM/EDS, TEM, and XRD. The mechanical properties of coatings were studied by nanoindentation test. According to the results of the single-layer coatings, low P coating had the maximum hardness and also the ratio of hardness ( H) to elasticity modulus ( E) for the mentioned coating was maximum. In addition, low and medium P coatings had crystalline and semi-crystalline structure, respectively. The mentioned coatings had <111> texture and after heat treatment their texture didn't change. While high P coating had amorphous structure, after heat treatment it changed to crystalline structure with <100> texture for nickel grains. Furthermore, the results showed that functionally graded and step-wise multilayer coatings were deposited successfully by using the same initial bath and changing the temperature and pH during deposition. Nanoindentation test results showed that the hardness of the mentioned coatings changed from 670 Hv near the substrate to 860 Hv near the top surface of coatings. For functionally graded coating the hardness profile had gradual changes, while step-wise multilayer coating had step-wise hardness profile. After heat treatment trend of hardness profiles was changed, so that near the substrate, hardness was measured 1400 Hv and changed to 1090 Hv at the top coat.

  11. Aluminide Coatings for Power-Generation Applications

    SciTech Connect

    Zhang, Y

    2003-11-17

    Aluminide coatings are of interest for many high temperature applications because of the possibility of improving the oxidation of structural alloys by forming a protective external alumina scale. In order to develop a comprehensive lifetime evaluation approach for aluminide coatings used in fossil energy systems, some of the important issues have been addressed in this report for aluminide coatings on Fe-based alloys (Task I) and on Ni-based alloys (Task II). In Task I, the oxidation behavior of iron aluminide coatings synthesized by chemical vapor deposition (CVD) was studied in air + 10vol.% H{sub 2}O in the temperature range of 700-800 C and the interdiffusion behavior between the coating and substrate was investigated in air at 500-800 C. Commercial ferritic (Fe-9Cr-1Mo) and type 304L (Fe-18Cr-9Ni, nominally) austenitic stainless steels were used as the substrates. For the oxidation study, the as-deposited coating consisted of a thin (<5 {micro}m), Al-rich outer layer above a thicker (30-50 {micro}m), lower Al inner layer. The specimens were cycled to 1000 1-h cycles at 700 C and 500 1-h cycles at 800 C, respectively. The CVD coating specimens showed excellent performance in the water vapor environment at both temperatures, while the uncoated alloys were severely attacked. These results suggest that an aluminide coating can substantially improve resistance to water vapor attack under these conditions. For the interdiffusion study, the ferritic and austenitic steels were coated with relatively thicker aluminide coatings consisting of a 20-25 {micro}m outer layer and a 150-250 {micro}m inner layer. The composition profiles before and after interdiffusion testing (up to 5,000h) were measured by electron probe microanalysis (EPMA). The decrease of the Al content at the coating surface was not significant after extended diffusion times ({le} 5,000h) at temperatures {le} 700 C. More interdiffusion occurred at 800 C in coatings on both Fe- 9Cr-1Mo and 304L alloys; a

  12. Thermal radiative properties: Coatings.

    NASA Technical Reports Server (NTRS)

    Touloukian, Y. S.; Dewitt, D. P.; Hernicz, R. S.

    1972-01-01

    This volume consists, for the most part, of a presentation of numerical data compiled over the years in a most comprehensive manner on coatings for all applications, in particular, thermal control. After a moderately detailed discussion of the theoretical nature of the thermal radiative properties of coatings, together with an overview of predictive procedures and recognized experimental techniques, extensive numerical data on the thermal radiative properties of pigmented, contact, and conversion coatings are presented. These data cover metallic and nonmetallic pigmented coatings, enamels, metallic and nonmetallic contact coatings, antireflection coatings, resin coatings, metallic black coatings, and anodized and oxidized conversion coatings.

  13. Plasmonic and silicon spherical nanoparticle antireflective coatings

    PubMed Central

    Baryshnikova, K. V.; Petrov, M. I.; Babicheva, V. E.; Belov, P. A.

    2016-01-01

    Over the last decade, plasmonic antireflecting nanostructures have been extensively studied to be utilized in various optical and optoelectronic systems such as lenses, solar cells, photodetectors, and others. The growing interest to all-dielectric photonics as an alternative optical technology along with plasmonics motivates us to compare antireflective properties of plasmonic and all-dielectric nanoparticle coatings based on silver and crystalline silicon respectively. Our simulation results for spherical nanoparticles array on top of amorphous silicon show that both silicon and silver coatings demonstrate strong antireflective properties in the visible spectral range. For the first time, we show that zero reflectance from the structure with silicon coatings originates from the destructive interference of electric- and magnetic-dipole responses of nanoparticle array with the wave reflected from the substrate, and we refer to this reflection suppression as substrate-mediated Kerker effect. We theoretically compare the silicon and silver coating effectiveness for the thin-film photovoltaic applications. Silver nanoparticles can be more efficient, enabling up to 30% increase of the overall absorbance in semiconductor layer. Nevertheless, silicon coatings allow up to 64% absorbance increase in the narrow band spectral range because of the substrate-mediated Kerker effect, and band position can be effectively tuned by varying the nanoparticles sizes. PMID:26926602

  14. Plasmonic and silicon spherical nanoparticle antireflective coatings.

    PubMed

    Baryshnikova, K V; Petrov, M I; Babicheva, V E; Belov, P A

    2016-01-01

    Over the last decade, plasmonic antireflecting nanostructures have been extensively studied to be utilized in various optical and optoelectronic systems such as lenses, solar cells, photodetectors, and others. The growing interest to all-dielectric photonics as an alternative optical technology along with plasmonics motivates us to compare antireflective properties of plasmonic and all-dielectric nanoparticle coatings based on silver and crystalline silicon respectively. Our simulation results for spherical nanoparticles array on top of amorphous silicon show that both silicon and silver coatings demonstrate strong antireflective properties in the visible spectral range. For the first time, we show that zero reflectance from the structure with silicon coatings originates from the destructive interference of electric- and magnetic-dipole responses of nanoparticle array with the wave reflected from the substrate, and we refer to this reflection suppression as substrate-mediated Kerker effect. We theoretically compare the silicon and silver coating effectiveness for the thin-film photovoltaic applications. Silver nanoparticles can be more efficient, enabling up to 30% increase of the overall absorbance in semiconductor layer. Nevertheless, silicon coatings allow up to 64% absorbance increase in the narrow band spectral range because of the substrate-mediated Kerker effect, and band position can be effectively tuned by varying the nanoparticles sizes. PMID:26926602

  15. Amorphization and nanocrystallization of silcon under shock compression

    SciTech Connect

    Remington, B. A.; Wehrenberg, C. E.; Zhao, S.; Hahn, E. N.; Kad, B.; Bringa, E. M.; Meyers, M. A.

    2015-11-06

    High-power, short-duration, laser-driven, shock compression and recovery experiments on [001] silicon unveiled remarkable structural changes above a pressure threshold. Two distinct amorphous regions were identified: (a) a bulk amorphous layer close to the surface and (b) amorphous bands initially aligned with {111} slip planes. Further increase of the laser energy leads to the re-crystallization of amorphous silicon into nanocrystals with high concentration of nano-twins. This amorphization is produced by the combined effect of high magnitude hydrostatic and shear stresses under dynamic shock compression. Shock-induced defects play a very important role in the onset of amorphization. Calculations of the free energy changes with pressure and shear, using the Patel-Cohen methodology, are in agreement with the experimental results. Molecular dynamics simulation corroborates the amorphization, showing that it is initiated by the nucleation and propagation of partial dislocations. As a result, the nucleation of amorphization is analyzed qualitatively by classical nucleation theory.

  16. Inverted amorphous silicon solar cell utilizing cermet layers

    DOEpatents

    Hanak, Joseph J.

    1979-01-01

    An amorphous silicon solar cell incorporating a transparent high work function metal cermet incident to solar radiation and a thick film cermet contacting the amorphous silicon opposite to said incident surface.

  17. High efficiency turbine blade coatings.

    SciTech Connect

    Youchison, Dennis L.; Gallis, Michail A.

    2014-06-01

    The development of advanced thermal barrier coatings (TBCs) of yttria stabilized zirconia (YSZ) that exhibit lower thermal conductivity through better control of electron beam - physical vapor deposition (EB-PVD) processing is of prime interest to both the aerospace and power industries. This report summarizes the work performed under a two-year Lab-Directed Research and Development (LDRD) project (38664) to produce lower thermal conductivity, graded-layer thermal barrier coatings for turbine blades in an effort to increase the efficiency of high temperature gas turbines. This project was sponsored by the Nuclear Fuel Cycle Investment Area. Therefore, particular importance was given to the processing of the large blades required for industrial gas turbines proposed for use in the Brayton cycle of nuclear plants powered by high temperature gas-cooled reactors (HTGRs). During this modest (~1 full-time equivalent (FTE)) project, the processing technology was developed to create graded TBCs by coupling ion beam-assisted deposition (IBAD) with substrate pivoting in the alumina-YSZ system. The Electron Beam - 1200 kW (EB-1200) PVD system was used to deposit a variety of TBC coatings with micron layered microstructures and reduced thermal conductivity below 1.5 W/m.K. The use of IBAD produced fully stoichiometric coatings at a reduced substrate temperature of 600 oC and a reduced oxygen background pressure of 0.1 Pa. IBAD was also used to successfully demonstrate the transitioning of amorphous PVD-deposited alumina to the -phase alumina required as an oxygen diffusion barrier and for good adhesion to the substrate Ni2Al3 bondcoat. This process replaces the time consuming thermally grown oxide formation required before the YSZ deposition. In addition to the process technology, Direct Simulation Monte Carlo plume modeling and spectroscopic characterization of the PVD plumes were performed. The project consisted of five tasks. These included the production of layered

  18. High resolution amorphous silicon radiation detectors

    DOEpatents

    Street, Robert A.; Kaplan, Selig N.; Perez-Mendez, Victor

    1992-01-01

    A radiation detector employing amorphous Si:H cells in an array with each detector cell having at least three contiguous layers (n type, intrinsic, p type), positioned between two electrodes to which a bias voltage is applied. An energy conversion layer atop the silicon cells intercepts incident radiation and converts radiation energy to light energy of a wavelength to which the silicon cells are responsive. A read-out device, positioned proximate to each detector element in an array allows each such element to be interrogated independently to determine whether radiation has been detected in that cell. The energy conversion material may be a layer of luminescent material having a columnar structure. In one embodiment a column of luminescent material detects the passage therethrough of radiation to be detected and directs a light beam signal to an adjacent a-Si:H film so that detection may be confined to one or more such cells in the array. One or both electrodes may have a comb structure, and the teeth of each electrode comb may be interdigitated for capacitance reduction. The amorphous Si:H film may be replaced by an amorphous Si:Ge:H film in which up to 40 percent of the amorphous material is Ge. Two dimensional arrays may be used in X-ray imaging, CT scanning, crystallography, high energy physics beam tracking, nuclear medicine cameras and autoradiography.

  19. High resolution amorphous silicon radiation detectors

    DOEpatents

    Street, R.A.; Kaplan, S.N.; Perez-Mendez, V.

    1992-05-26

    A radiation detector employing amorphous Si:H cells in an array with each detector cell having at least three contiguous layers (n-type, intrinsic, p-type), positioned between two electrodes to which a bias voltage is applied. An energy conversion layer atop the silicon cells intercepts incident radiation and converts radiation energy to light energy of a wavelength to which the silicon cells are responsive. A read-out device, positioned proximate to each detector element in an array allows each such element to be interrogated independently to determine whether radiation has been detected in that cell. The energy conversion material may be a layer of luminescent material having a columnar structure. In one embodiment a column of luminescent material detects the passage therethrough of radiation to be detected and directs a light beam signal to an adjacent a-Si:H film so that detection may be confined to one or more such cells in the array. One or both electrodes may have a comb structure, and the teeth of each electrode comb may be interdigitated for capacitance reduction. The amorphous Si:H film may be replaced by an amorphous Si:Ge:H film in which up to 40 percent of the amorphous material is Ge. Two dimensional arrays may be used in X-ray imaging, CT scanning, crystallography, high energy physics beam tracking, nuclear medicine cameras and autoradiography. 18 figs.

  20. Excess specific heat in evaporated amorphous silicon.

    PubMed

    Queen, D R; Liu, X; Karel, J; Metcalf, T H; Hellman, F

    2013-03-29

    The specific heat C of e-beam evaporated amorphous silicon (a-Si) thin films prepared at various growth temperatures T(S) and thicknesses t was measured from 2 to 300 K, along with sound velocity v, shear modulus G, density n(Si), and Raman spectra. Increasing T(S) results in a more ordered amorphous network with increases in n(Si), v, G, and a decrease in bond angle disorder. Below 20 K, an excess C is seen in films with less than full density where it is typical of an amorphous solid, with both a linear term characteristic of two-level systems (TLS) and an additional (non-Debye) T3 contribution. The excess C is found to be independent of the elastic properties but to depend strongly on density. The density dependence suggests that low energy glassy excitations can form in a-Si but only in microvoids or low density regions and are not intrinsic to the amorphous silicon network. A correlation is found between the density of TLS n0 and the excess T3 specific heat c(ex) suggesting that they have a common origin.

  1. Metal electrode for amorphous silicon solar cells

    DOEpatents

    Williams, Richard

    1983-01-01

    An amorphous silicon solar cell having an N-type region wherein the contact to the N-type region is composed of a material having a work function of about 3.7 electron volts or less. Suitable materials include strontium, barium and magnesium and rare earth metals such as gadolinium and yttrium.

  2. Transient amorphous calcium phosphate in forming enamel.

    PubMed

    Beniash, Elia; Metzler, Rebecca A; Lam, Raymond S K; Gilbert, P U P A

    2009-05-01

    Enamel, the hardest tissue in the body, begins as a three-dimensional network of nanometer size mineral particles, suspended in a protein gel. This mineral network serves as a template for mature enamel formation. To further understand the mechanisms of enamel formation we characterized the forming enamel mineral at an early secretory stage using X-ray absorption near-edge structure (XANES) spectromicroscopy, transmission electron microscopy (TEM), FTIR microspectroscopy and polarized light microscopy. We show that the newly formed enamel mineral is amorphous calcium phosphate (ACP), which eventually transforms into apatitic crystals. Interestingly, the size, shape and spatial organization of these amorphous mineral particles and older crystals are essentially the same, indicating that the mineral morphology and organization in enamel is determined prior to its crystallization. Mineralization via transient amorphous phases has been previously reported in chiton teeth, mollusk shells, echinoderm spicules and spines, and recent reports strongly suggest the presence of transient amorphous mineral in forming vertebrate bones. The present finding of transient ACP in murine tooth enamel suggests that this strategy might be universal. PMID:19217943

  3. NICKEL COATED URANIUM ARTICLE

    DOEpatents

    Gray, A.G.

    1958-10-01

    Nickel coatings on uranium and various methods of obtaining such coatings are described. Specifically disclosed are such nickel or nickel alloy layers as barriers between uranium and aluminum- silicon, chromium, or copper coatings.

  4. Effects of Cr and B Contents on Volume Fraction of (Cr,Fe)2B and Hardness in Fe-Based Alloys Used for Powder Injection Molding

    NASA Astrophysics Data System (ADS)

    Do, Jeonghyeon; Lee, Hyuk-Joong; Jeon, Changwoo; Ha, Dae Jin; Kim, Choongnyun Paul; Lee, Byeong-Joo; Lee, Sunghak; Shin, Yang Su

    2012-07-01

    In the current study, Fe-based alloys were used for powder injection molding (PIM) parts with various qualities and hardness ranges by varying chemical compositions according to thermodynamically calculated phase diagrams. Their microstructure and hardness values were analyzed and compared with those of the PIM specimens made from conventional Fe-based alloy powders or stainless steel powders. The Cr-to-B ratio ( X Cr/ X B) and the sum of Fe, Cr, and B content ( X Fe+ X Cr+ X B) were varied to design nine Fe-based alloy compositions based on the composition of Armacor "M" alloy powders (Liquidmetal Technologies, Lake Forest, CA). According to the microstructural analysis results of the cast and heat-treated Fe-based alloys, large amounts of (Cr,Fe)2B were formed in the tempered martensite matrix. The volume fraction of (Cr,Fe)2B was varied from 42 pct to 91 pct with alloy compositions, and these results were well matched with the thermodynamically calculated volume fractions of (Cr,Fe)2B. The hardness of the fabricated alloys was varied from 300 VHN to 1600 VHN with alloy compositions, and this value increased linearly with the increasing volume fraction of (Cr,Fe)2B. From the correlation data between the volume fraction of (Cr,Fe)2B and hardness, the high-temperature equilibrium phase diagram, which could be used for the design of Fe-based alloys with various fractions and hardness values of (Cr,Fe)2B, was made.

  5. 2012 IUPAP C10 Young Scientist Prize on the Structure and Dynamics of Condensed Matter Lecture: Spin Fluctuations and Pairing in Fe-based Superconductors

    NASA Astrophysics Data System (ADS)

    Christianson, A. D.

    2012-02-01

    The origin of superconductivity in the Fe-based superconductors, like that in other unconventional superconductors, remains shrouded in mystery. How the pairing bosons emerge either due to or in spite of the strong magnetic interactions found in the Fe-based superconductors is one of the most thoroughly investigated questions in the field. A prominent example of the interplay of superconductivity and magnetism is the dramatic shift of spectral weight from the low energy spin excitations to an energy which is related to the superconducting gap resulting in a peak in the spin excitation spectrum localized in both momentum and energy which occurs at the onset of superconductivity. The appearance of the new peak in the spin excitation spectrum below the superconducting transition temperature is referred to as s spin resonance and is most commonly interpreted as indicating a sign change of the superconducting order parameter on different portions of the Fermi surface and thus is consistent with an extended s-wave or s± pairing symmetry in many Fe-based superconductors. We will review the observations and implications of the spin resonance across the Fe-based superconductors. In particular we will examine the relationship between the resonance energy and the superconducting transition temperature as a function of chemical doping and pressure. While the spin resonance provides important information about pairing symmetry, there does not appear to be sufficient spectral to explain the pairing strength. Thus the remainder of the spin excitation spectrum must be examined to determine if spin fluctuations are ultimately responsible for pairing in the Fe-based materials. Consequently, we will discuss in detail the way in which the spin excitations evolve from the nonsuperconducting compounds to their superconducting relatives as a function of chemical doping.

  6. Fabrication process development for high-purity germanium radiation detectors with amorphous semiconductor contacts

    NASA Astrophysics Data System (ADS)

    Looker, Quinn

    High-purity germanium (HPGe) radiation detectors are well established as a valuable tool in nuclear science, astrophysics, and nuclear security applications. HPGe detectors excel in gamma-ray spectroscopy, offering excellent energy resolution with large detector sizes for high radiation detection efficiency. Although a robust fabrication process has been developed, improvement is needed, especially in developing electrical contact and surface passivation technology for position-sensitive detectors. A systematic study is needed to understand how the detector fabrication process impacts detector performance and reliability. In order to provide position sensitivity, the electrical contacts are segmented to form multiple electrodes. This segmentation creates new challenges in the fabrication process and warrants consideration of additional detector effects related to the segmentation. A key area of development is the creation of the electrical contacts in a way that enables reliable operation, provides low electronic noise, and allows fine segmentation of electrodes, giving position sensitivity for radiation interactions in the detector. Amorphous semiconductor contacts have great potential to facilitate new HPGe detector designs by providing a thin, high-resistivity surface coating that is the basis for electrical contacts that block both electrons and holes and can easily be finely segmented. Additionally, amorphous semiconductor coatings form a suitable passivation layer to protect the HPGe crystal surface from contamination. This versatility allows a simple fabrication process for fully passivated, finely segmented detectors. However, the fabrication process for detectors with amorphous semiconductors is not as highly developed as for conventional technologies. The amorphous semiconductor layer properties can vary widely based on how they are created and these can translate into varying performance of HPGe detectors with these contacts. Some key challenges include

  7. Microwires fabricated by glass-coated melt spinning

    SciTech Connect

    Zhao, Y. Y.; Li, H.; Hao, H. Y.; Li, M.; Zhang, Y.; Liaw, P. K.

    2013-07-15

    The glass-coated melt spinning method offers a route for the manufacture of metal filaments with a few micrometers in diameter in a single operation directly from the melt. Cobalt-based amorphous wires, Cu-15.0 atomic percent (at. %) Sn shape-memory wires, and Ni{sub 2}MnGa (atomic percent) ferromagnetic wires were successfully produced by this method. The cobalt-based amorphous wire is flexible, and Cu-15.0 at. % Sn shape-memory wires have the tensile elongation of 14%. However, because of chemical reaction with glass and oxidation, it is hard to make Cu–Al–Ni shape-memory wires and Ni–Nb–Sn amorphous wires. Conditions for preparing these materials were summarized, and the differences of the solidification processes among glass-coated amorphous cobalt-based wires, Cu-15.0 at. % Sn shape-memory wires, and Ni{sub 2}MnGa wires were analyzed and discussed.

  8. Amorphous silica-like carbon dioxide.

    PubMed

    Santoro, Mario; Gorelli, Federico A; Bini, Roberto; Ruocco, Giancarlo; Scandolo, Sandro; Crichton, Wilson A

    2006-06-15

    Among the group IV elements, only carbon forms stable double bonds with oxygen at ambient conditions. At variance with silica and germania, the non-molecular single-bonded crystalline form of carbon dioxide, phase V, only exists at high pressure. The amorphous forms of silica (a-SiO2) and germania (a-GeO2) are well known at ambient conditions; however, the amorphous, non-molecular form of CO2 has so far been described only as a result of first-principles simulations. Here we report the synthesis of an amorphous, silica-like form of carbon dioxide, a-CO2, which we call 'a-carbonia'. The compression of the molecular phase III of CO2 between 40 and 48 GPa at room temperature initiated the transformation to the non-molecular amorphous phase. Infrared spectra measured at temperatures up to 680 K show the progressive formation of C-O single bonds and the simultaneous disappearance of all molecular signatures. Furthermore, state-of-the-art Raman and synchrotron X-ray diffraction measurements on temperature-quenched samples confirm the amorphous character of the material. Comparison with vibrational and diffraction data for a-SiO2 and a-GeO2, as well as with the structure factor calculated for the a-CO2 sample obtained by first-principles molecular dynamics, shows that a-CO2 is structurally homologous to the other group IV dioxide glasses. We therefore conclude that the class of archetypal network-forming disordered systems, including a-SiO2, a-GeO2 and water, must be extended to include a-CO2. PMID:16778885

  9. Corrosion resistant coating

    DOEpatents

    Wrobleski, D.A.; Benicewicz, B.C.; Thompson, K.G.; Bryan, C.J.

    1997-08-19

    A method of protecting a metal substrate from corrosion including coating a metal substrate of, e.g., steel, iron or aluminum, with a conductive polymer layer of, e.g., polyaniline, coating upon said metal substrate, and coating the conductive polymer-coated metal substrate with a layer of a topcoat upon the conductive polymer coating layer, is provided, together with the resultant coated article from said method.

  10. Corrosion resistant coating

    DOEpatents

    Wrobleski, Debra A.; Benicewicz, Brian C.; Thompson, Karen G.; Bryan, Coleman J.

    1997-01-01

    A method of protecting a metal substrate from corrosion including coating a metal substrate of, e.g., steel, iron or aluminum, with a conductive polymer layer of, e.g., polyaniline, coating upon said metal substrate, and coating the conductive polymer-coated metal substrate with a layer of a topcoat upon the conductive polymer coating layer, is provided, together with the resultant coated article from said method.

  11. Laser fabrication nanocrystalline coatings using simultaneous powders/wire feed

    NASA Astrophysics Data System (ADS)

    Li, Jianing; Zhai, Tongguang; Zhang, Yuanbin; Shan, Feihu; Liu, Peng; Ren, Guocheng

    2016-07-01

    Laser melting deposition (LMD) fabrication is used to investigate feasibilty of simultaneously feeding TC17 wire and the Stellite 20-Si3N4-TiC-Sb mixed powders in order to increase the utilization ratio of materials and also quality of LMD composite coatings on the TA1 substrate. SEM images indicated that such LMD coating with metallurgical joint to substrate was formed free of the obvious defects. Lots of the ultrafine nanocrystals (UNs) were produced, which distributed uniformly in some coating matrix location, retarding growth of the ceramics in a certain extent; UNs were intertwined with amorphous, leading the yarn-shape materials to be produced. Compared with substrate, an improvement of wear resistance was achieved for such LMD coating.

  12. Biomimetic whisker-shaped apatite coating of titanium powder.

    PubMed

    Sim, Young Uk; Kim, Jong Hee; Yang, Tae Young; Yoon, Seog Young; Park, Hong Chae

    2010-05-01

    Biomimetic apatite coatings on chemically modified titanium powder have been processed and the resulting coating layers evaluated in terms of morphology, composition and structure, using TF-XRD, XPS, SEM, TEM and FTIR analysis. After 7 days immersion in a simulated body fluid (SBF), nanometer-sized fine precipitates with an amorphous whisker-like phase and a Ca/P atomic ratio of 1.94 were obtained on the external surface of the titanium particles. When the immersion time in SBF was extended to 16 days, the coating layer consisted of the whisker-like nanostructured crystals of carbonated hydroxyapatite with a atomic ratio of 3; in such a case, a double coating layer was developed. The double layer could be divided into two regions and could be clearly distinguished: an inner dense region (approximately 200 nm in thickness) which may include hard agglomerated crystals and an outer less dense region (> 500 nm in thickness) in which crystals are loosely distributed.

  13. Pressure-induced amorphous-to-amorphous configuration change in Ca-Al metallic glasses

    PubMed Central

    Lou, H. B.; Fang, Y. K.; Zeng, Q. S.; Lu, Y. H.; Wang, X. D.; Cao, Q. P.; Yang, K.; Yu, X. H.; Zheng, L.; Zhao, Y. D.; Chu, W. S.; Hu, T. D.; Wu, Z. Y.; Ahuja, R.; Jiang, J. Z.

    2012-01-01

    Pressure-induced amorphous-to-amorphous configuration changes in Ca-Al metallic glasses (MGs) were studied by performing in-situ room-temperature high-pressure x-ray diffraction up to about 40 GPa. Changes in compressibility at about 18 GPa, 15.5 GPa and 7.5 GPa during compression are detected in Ca80Al20, Ca72.7Al27.3, and Ca66.4Al33.6 MGs, respectively, whereas no clear change has been detected in the Ca50Al50 MG. The transfer of s electrons into d orbitals under pressure, reported for the pressure-induced phase transformations in pure polycrystalline Ca, is suggested to explain the observation of an amorphous-to-amorphous configuration change in this Ca-Al MG system. Results presented here show that the pressure induced amorphous-to-amorphous configuration is not limited to f electron-containing MGs. PMID:22530094

  14. The Chemistry of Coatings.

    ERIC Educational Resources Information Center

    Griffith, James R.

    1981-01-01

    The properties of natural and synthetic polymeric "coatings" are reviewed, including examples and uses of such coatings as cellulose nitrate lacquers (for automobile paints), polyethylene, and others. (JN)

  15. Amorphous carbon nanotube/MnO2/graphene oxide ternary composite electrodes for electrochemical capacitors.

    PubMed

    Im, Changbin; Yun, Young Soo; Kim, Bona; Park, Hyun Ho; Jin, Hyoung-Joon

    2013-03-01

    Ternary composites of amorphous carbon nanotube/MnO2/graphene oxide (a-CNT/MnO2/GO) were synthesized by a facile direct redox reaction between potassium permanganate and a-CNT, which was prepared by anodic aluminum oxide template method following co-filtration with GO. Needle-like, 100-nm-thick, MnO2 crystals were homogeneously coated on the a-CNT surface, which was then covered with GO. The electrochemical performance of the resulting MnO2-coated a-CNTs exhibited a specific capacitance of 473 F/g at a scan rate of 5 mV/s, and excellent charge/discharge stability after 500 cycles.

  16. On the superconducting symmetry of Fe-based systems — Impurity effect studies and neutron scattering measurements-

    DOE PAGES

    Sato, Masatoshi; Kobayashi, Yoshiaki; Kawamata, Takayuki; Yasui, Yukio; Suzuki, Kazunori; Itoh, M.; Kajimoto, Ryoichi; Ikeuchi, Kazuhiko; Arai, M.; Bourges, Phillipe

    2013-07-09

    To identify the superconducting symmetry of Fe-based superconductors, we studied effects of nonmagnetic-impurities on Tc, magnetic excitation spectra x" and NMR 1/T1 - T curve, which are sensitive to the relative signs between the order parameters on the disconnected Fermi surfaces in reciprocal space, because the symmetry is closely connected with the pairing mechanism: If the signs are opposite (symmetry S±), the mechanism is considered to be a magnetic one, but when the signs are the same (symmetry S++), a novel mechanism is plausible because the ordinary phonon mechanism cannot realize the Tc value as high as ~55 K foundmore » in Ln1111 (Ln=lanthanide). Results are as follows: (a) The very small rates of Tc-suppression by impurity atoms M of LnFe1-yMyAs0.89-xF0.11+x (M=Ni, Co, Ru) can be explained only by S++. (b) The x"-data for Ba(Fe, Co)2As2 (Tc ~ 23 K) and Ca-Fe-Pt-As crystals seem to be well explained by S++ rather than by S±. (c) The nuclear magnetic resonance data can be consistently understood by S++, too. These results suggest the S++ symmetry and a novel pairing mechanism, which can be considered to be related to the elastic softening of C66 induced by the orbital fluctuation of the system.« less

  17. Anomalous scaling behavior of the Specific Heat jump ΔC vs. Tc in the Fe-based superconductors

    NASA Astrophysics Data System (ADS)

    Bang, Yunkyu; Stewart, G. R.

    2015-03-01

    So called BNC scaling (ΔC ~Tc3)-) - has been observed in a wide range of the Fe-based superconducting compounds such as Ba(Fe1-x,Cox)2As2, Ba(Fe1-x,Nix)2As2,BaFe2(AsP)2,andBa1-xNaxFe2As2. More recently, however, Canfield and coworkers reported that the Ba1-xKxFe2As2 compound severely deviates from this scaling when x>0.7 and argued that this is an indication of the Lifshitz transition in the Ba1-xKxFe2As2 compound at higher hole-doping. In this presentation, we propose a theory that the BNC scaling as well as its strong deviation, as observed in Ba1-xKxFe2As2, are an intrinsic property of the multiband superconductor mediated by a dominant interband pairing potential as realized in the sign-changing S-wave state.

  18. Analysis of the low-frequency magnetoelectric performance in three-phase laminate composites with Fe-based nanocrystalline ribbon

    NASA Astrophysics Data System (ADS)

    Chen, Lei; Li, Ping; Wen, Yumei; Zhu, Yong

    2013-11-01

    The theoretical analysis of magnetoelectric (ME) performance in three-phase Terfenol-D/PZT/FeCuNbSiB (MPF) laminate composite is presented in this paper. The ME couplings at low frequency for ideal and less than ideal interface couplings are studied, respectively, and our analysis predicts that (i) the ME voltage coefficient for ideal interface coupling increases with the increasing layers (n) of Fe-based nanocrystalline ribbon FeCuNbSiB (Fe73.5Cu1Nb3Si13.5B9) while the sizes of PZT (Pb(Zr1-xTix)O3) and Terfenol-D (Tb1-xDyxFe2-y) are kept constant, and then it tends to be a constant when the layers of FeCuNbSiB are >100 (ii) by introducing the interface coupling factor k and considering the degradation of d33m,f with n, the ME voltage coefficient for a less than ideal interface condition is predicted. As the FeCuNbSiB layer increases, it first increases and reaches to a maximum value, and then slowly decreases. Various MPF laminates are fabricated and tested. It is found that the theoretical predictions for the consideration of actual boundary conditions at the interface are in agreement with the experimental observations. This study plays a guiding role for the design of MPF composite in real applications.

  19. 42214 layered Fe-based superconductors: An ab initio study of their structural, magnetic, and electronic properties

    NASA Astrophysics Data System (ADS)

    Bucci, F.; Sanna, A.; Continenza, A.; Katrych, S.; Karpinski, J.; Gross, E. K. U.; Profeta, G.

    2016-01-01

    As a follow-up to the discovery of a new family of Fe-based superconductors, namely, the RE4Fe2As2Te1 -xO4 (42214) (RE = Pr, Sm, and Gd), we present a detailed ab initio study of these compounds highlighting the role of rare-earth (RE) atoms, external pressure, and Te content on their physical properties. Modifications of the structural, magnetic, and electronic properties of the pure (e.g., x =0.0 ) 42214 compounds and their possible correlations with the observed superconducting properties are calculated and discussed. The careful analysis of the results obtained shows that (i) changing the RE atoms allows one to tune the internal pressure acting on the As height with respect to the Fe planes; (ii) similarly to other Fe pnictides, the 42214 pure compounds show an antiferromagnetic-stripe magnetic ground state phase joined by an orthorhombic distortion (not experimentally found yet); (iii) smaller RE atoms increase the magnetic instability of the compounds possibly favoring the onset of the superconducting state; (iv) external pressure induces the vanishing of the magnetic order with a transition to the tetragonal phase and can be a possible experimental route towards higher superconducting critical temperature (Tc) ; and (v) Te vacancies act on the structural parameters, changing the As height and affecting the stability of the magnetic phase.

  20. Investigation of Properties and Wear Behavior of HVOF Sprayed TiC-Strengthened Fe Coatings

    NASA Astrophysics Data System (ADS)

    Bobzin, Kirsten; Schlaefer, Thomas; Richardt, Katharina; Warda, Thomas; Reisel, Guido

    2009-12-01

    High-velocity oxyfuel (HVOF) sprayed carbide based coatings (such as Cr3C2/NiCr) are industrially well established for wear protection applications. Due to their high carbide content of typically 75 wt.% and more, they provide very high hardness and excellent wear resistance. Unfortunately, costs for matrix materials such as nickel underlie strong fluctuations and are normally well above the prices for iron. Therefore an alternative concept to conventional carbides is based on TiC-strengthened low-cost Fe-base materials, which are already used for sintering processes. Depending on the carbon content, the Fe-base material can additionally offer a temperable matrix for enhanced wear behavior. The sprayability of TiC-strengthened Fe-powders with a gaseous and a liquid fuel driven HVOF system was investigated in this study. The resulting coatings were analyzed with respect to microstructure, hardness, and phase composition and compared with galvanic hard chrome, NiCrBSi, and Cr3C2/NiCr (80/20) coatings as well as with sintered Fe/TiC reference materials. Furthermore, the Fe/TiC coatings were heat treated to proof the retained temperability of the Fe matrix after thermal spray process. Tribometer tests (pin-on-disk tests) were conducted to determine wear properties.

  1. Fabricating amorphous silicon solar cells by varying the temperature _of the substrate during deposition of the amorphous silicon layer

    DOEpatents

    Carlson, David E.

    1982-01-01

    An improved process for fabricating amorphous silicon solar cells in which the temperature of the substrate is varied during the deposition of the amorphous silicon layer is described. Solar cells manufactured in accordance with this process are shown to have increased efficiencies and fill factors when compared to solar cells manufactured with a constant substrate temperature during deposition of the amorphous silicon layer.

  2. Making silica rock coatings in the lab: synthetic desert varnish

    NASA Astrophysics Data System (ADS)

    Perry, Randall S.; Kolb, Vera M.; Philip, Ajish I.; Lynne, Bridget Y.; McLoughlin, Nicola; Sephton, Mark; Wacey, David; Green, Owen R.

    2005-09-01

    Desert varnish and silica rock coatings have perplexed investigators since Humboldt and Darwin. They are found in arid regions and deserts on Earth but the mechanism of their formation remains challenging (see Perry et al. this volume). One method of researching this is to investigate natural coatings, but another way is to attempt to produce coatings in vitro. Sugars, amino acids, and silicic acid, as well as other organic and (bio)organic compounds add to the complexity of naturally forming rock coatings. In the lab we reduced the complexity of the natural components and produced hard, silica coatings on basaltic chips obtained from the Mojave Desert. Sodium silicate solution was poured over the rocks and continuously exposed to heat and/or UV light. Upon evaporation the solutions were replenished. Experiments were performed at various pH's. The micro-deposits formed were analyzed using optical, SEM-EDAX, and electron microprobe. The coatings formed are similar in hardness and composition to silica glazes found on basalts in Hawaii as well as natural desert varnish found in US southwest deserts. Thermodynamic mechanisms are presented showing the theoretical mechanisms for overcoming energy barriers that allow amorphous silica to condense into hard coatings. This is the first time synthetic silica glazes that resemble natural coatings in hardness and chemical composition have been successfully reproduced in the laboratory, and helps to support an inorganic mechanism of formation of desert varnish as well as manganese-deficient silica glazes.

  3. Electromagnetic wave absorbing properties of amorphous carbon nanotubes.

    PubMed

    Zhao, Tingkai; Hou, Cuilin; Zhang, Hongyan; Zhu, Ruoxing; She, Shengfei; Wang, Jungao; Li, Tiehu; Liu, Zhifu; Wei, Bingqing

    2014-07-10

    Amorphous carbon nanotubes (ACNTs) with diameters in the range of 7-50 nm were used as absorber materials for electromagnetic waves. The electromagnetic wave absorbing composite films were prepared by a dip-coating method using a uniform mixture of rare earth lanthanum nitrate doped ACNTs and polyvinyl chloride (PVC). The microstructures of ACNTs and ACNT/PVC composites were characterized using transmission electron microscope and X-ray diffraction, and their electromagnetic wave absorbing properties were measured using a vector-network analyzer. The experimental results indicated that the electromagnetic wave absorbing properties of ACNTs are superior to multi-walled CNTs, and greatly improved by doping 6 wt% lanthanum nitrate. The reflection loss (R) value of a lanthanum nitrate doped ACNT/PVC composite was -25.02 dB at 14.44 GHz, and the frequency bandwidth corresponding to the reflector loss at -10 dB was up to 5.8 GHz within the frequency range of 2-18 GHz.

  4. Molecular dynamics modeling of ultrathin amorphous carbon films

    SciTech Connect

    Glosli, J.N.; Belak, J.; Philpott, M.R.

    1995-05-01

    Amorphous carbon films about 20 mn thick are used by the computer industry as protective coatings on magnetic disks. The structure and function of this family of materials at the atomic level is poorly understood. The growth and properties of a:C and a:CH films 1 to 5 nm thick has been simulated using classical molecular dynamics and a bond-order potential with torsional terms. Studies of quenched melts that verify the ability of this potential to reproduce known features of extended structures of carbon in two and three dimensions are briefly described. In molecular dynamics calculations the incident species were neutral atoms C, or C and H with energies up to 100 eV. The stoichiometry, chemical bonding and distribution functions within the films were analyzed using IBM`s Power Visualization System for different incident gas energies. Microscopic features such as multiple ring structures, including planar graphitic structures, were easily identified. Some preliminary studies of the nanotribology of the a:C films are described, including nano-indentation and sliding in contact with a rigid probe.

  5. High efficiency neutron sensitive amorphous silicon pixel detectors

    SciTech Connect

    Mireshghi, A.; Cho, G.; Drewery, J.S.; Hong, W.S.; Jing, T.; Lee, H.; Kaplan, S.N.; Perez-Mendez, V.

    1993-11-01

    A multi-layer a-Si:H based thermal neutron detector was designed, fabricated and simulated by Monte Carlo method. The detector consists of two PECVD deposited a-Si:H pin detectors interfaced with coated layers of Gd, as a thermal neutron converter. Simulation results indicate that a detector consisting of 2 Gd films with thicknesses of 2 and 4 {mu}m, sandwiched properly with two layers of sufficiently thick ({approximately}30{mu}m) amorphous silicon diodes, has the optimum parameters. The detectors have an intrinsic efficiency of about 42% at a threshold setting of 7000 electrons, with an expected average signal size of {approximately}12000 electrons which is well above the noise. This efficiency will be further increased to nearly 63%, if we use Gd with 50% enrichment in {sup 157}Gd. We can fabricate position sensitive detectors with spatial resolution of 300 {mu}m with gamma sensitivity of {approximately}1 {times} 10{sup {minus}5}. These detectors are highly radiation resistant and are good candidates for use in various application, where high efficiency, high resolution, gamma insensitive position sensitive neutron detectors are needed.

  6. Electromagnetic Wave Absorbing Properties of Amorphous Carbon Nanotubes

    PubMed Central

    Zhao, Tingkai; Hou, Cuilin; Zhang, Hongyan; Zhu, Ruoxing; She, Shengfei; Wang, Jungao; Li, Tiehu; Liu, Zhifu; Wei, Bingqing

    2014-01-01

    Amorphous carbon nanotubes (ACNTs) with diameters in the range of 7–50 nm were used as absorber materials for electromagnetic waves. The electromagnetic wave absorbing composite films were prepared by a dip-coating method using a uniform mixture of rare earth lanthanum nitrate doped ACNTs and polyvinyl chloride (PVC). The microstructures of ACNTs and ACNT/PVC composites were characterized using transmission electron microscope and X-ray diffraction, and their electromagnetic wave absorbing properties were measured using a vector-network analyzer. The experimental results indicated that the electromagnetic wave absorbing properties of ACNTs are superior to multi-walled CNTs, and greatly improved by doping 6 wt% lanthanum nitrate. The reflection loss (R) value of a lanthanum nitrate doped ACNT/PVC composite was −25.02 dB at 14.44 GHz, and the frequency bandwidth corresponding to the reflector loss at −10 dB was up to 5.8 GHz within the frequency range of 2–18 GHz. PMID:25007783

  7. Nanohole Structuring for Improved Performance of Hydrogenated Amorphous Silicon Photovoltaics.

    PubMed

    Johlin, Eric; Al-Obeidi, Ahmed; Nogay, Gizem; Stuckelberger, Michael; Buonassisi, Tonio; Grossman, Jeffrey C

    2016-06-22

    While low hole mobilities limit the current collection and efficiency of hydrogenated amorphous silicon (a-Si:H) photovoltaic devices, attempts to improve mobility of the material directly have stagnated. Herein, we explore a method of utilizing nanostructuring of a-Si:H devices to allow for improved hole collection in thick absorber layers. This is achieved by etching an array of 150 nm diameter holes into intrinsic a-Si:H and then coating the structured material with p-type a-Si:H and a conformal zinc oxide transparent conducting layer. The inclusion of these nanoholes yields relative power conversion efficiency (PCE) increases of ∼45%, from 7.2 to 10.4% PCE for small area devices. Comparisons of optical properties, time-of-flight mobility measurements, and internal quantum efficiency spectra indicate this efficiency is indeed likely occurring from an improved collection pathway provided by the nanostructuring of the devices. Finally, we estimate that through modest optimizations of the design and fabrication, PCEs of beyond 13% should be obtainable for similar devices.

  8. Nanohole Structuring for Improved Performance of Hydrogenated Amorphous Silicon Photovoltaics.

    PubMed

    Johlin, Eric; Al-Obeidi, Ahmed; Nogay, Gizem; Stuckelberger, Michael; Buonassisi, Tonio; Grossman, Jeffrey C

    2016-06-22

    While low hole mobilities limit the current collection and efficiency of hydrogenated amorphous silicon (a-Si:H) photovoltaic devices, attempts to improve mobility of the material directly have stagnated. Herein, we explore a method of utilizing nanostructuring of a-Si:H devices to allow for improved hole collection in thick absorber layers. This is achieved by etching an array of 150 nm diameter holes into intrinsic a-Si:H and then coating the structured material with p-type a-Si:H and a conformal zinc oxide transparent conducting layer. The inclusion of these nanoholes yields relative power conversion efficiency (PCE) increases of ∼45%, from 7.2 to 10.4% PCE for small area devices. Comparisons of optical properties, time-of-flight mobility measurements, and internal quantum efficiency spectra indicate this efficiency is indeed likely occurring from an improved collection pathway provided by the nanostructuring of the devices. Finally, we estimate that through modest optimizations of the design and fabrication, PCEs of beyond 13% should be obtainable for similar devices. PMID:27227369

  9. Defect-induced solid state amorphization of molecular crystals

    NASA Astrophysics Data System (ADS)

    Lei, Lei; Carvajal, Teresa; Koslowski, Marisol

    2012-04-01

    We investigate the process of mechanically induced amorphization in small molecule organic crystals under extensive deformation. In this work, we develop a model that describes the amorphization of molecular crystals, in which the plastic response is calculated with a phase field dislocation dynamics theory in four materials: acetaminophen, sucrose, γ-indomethacin, and aspirin. The model is able to predict the fraction of amorphous material generated in single crystals for a given applied stress. Our results show that γ-indomethacin and sucrose demonstrate large volume fractions of amorphous material after sufficient plastic deformation, while smaller amorphous volume fractions are predicted in acetaminophen and aspirin, in agreement with experimental observation.

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

    PubMed

    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

  11. Comparison of microstructure and magnetic properties of 3% Si-steel, amorphous and nanostructure Finemet

    NASA Astrophysics Data System (ADS)

    Yousefi, M.; Rahmani, Kh.; Amiri Kerahroodi, M. S.

    2016-12-01

    This paper presents a comparison of microstructure and magnetic properties of polycrystalline 3%Si-steel, amorphous and nano-crystalline alloy Fe73.5Cu1Nb3Si13.5B9 (known as Finemet). Si-steels are industrially produced by casting, hot and cold rolling, annealing and coating. Samples of thin amorphous ribbons were prepared by the planar flow casting (PFC) method. Nano-crystalline samples are obtained after annealing in vacuum furnace at 560 °C for 1 h. The structure of specimens was investigated by XRD, SEM and FE-SEM. Also, magnetic properties were measured using vibrating sample magnetometer (VSM). The results showed that, hysteresis losses in as-quenched and nano-crystalline ribbons were by 94.75% and 96.06% less than 3%Si-steel, respectively. After the heat treatment of amorphous specimens, hysteresis area was decreased by 25% in comparison with heat treated specimen. This decreasing is occurred due to the formation of Fe3Si nanostructure with size of 10-17 nm and removing segregation after heat treatment.

  12. Synthesis and electrochemical evaluation of an amorphous titanium dioxide derived from a solid state precursor

    NASA Astrophysics Data System (ADS)

    Joyce, Christopher D.; McIntyre, Toni; Simmons, Sade; LaDuca, Holly; Breitzer, Jonathan G.; Lopez, Carmen M.; Jansen, Andrew N.; Vaughey, J. T.

    Titanium oxides are an important class of lithium-ion battery electrodes owing to their good capacity and stability within the cell environment. Although most Ti(IV) oxides are poor electronic conductors, new methods developed to synthesize nanometer scale primary particles have achieved the higher rate capability needed for modern commercial applications. In this report, the anionic water stable titanium oxalate anion [TiO(C 2O 4) 2] 2- was isolated in high yield as the insoluble DABCO (1,4-diazabicyclo[2.2.2]octane) salt. Powder X-ray diffraction studies show that the titanium dioxide material isolated after annealing in air is initially amorphous, converts to N-doped anatase above 400 °C, then to rutile above 600 °C. Electrochemical studies indicate that the amorphous titanium dioxide phase within a carbon matrix has a stable cycling capacity of ∼350 mAh g -1. On crystallizing at 400 °C to a carbon-coated anatase the capacity drops to 210 mAh g -1, and finally upon carbon burn-off to 50 mAh g -1. Mixtures of the amorphous titanium dioxide and Li 4Ti 5O 12 showed a similar electrochemical profile and capacity to Li 4Ti 5O 12 but with the addition of a sloping region to the end of the discharge curve that could be advantageous for determining state-of-charge in systems using Li 4Ti 5O 12.

  13. Influence of different polymers on the crystallization tendency of molecularly dispersed amorphous felodipine.

    PubMed

    Konno, Hajime; Taylor, Lynne S

    2006-12-01

    The ability of various polymers to inhibit the crystallization of amorphous felodipine was studied in amorphous molecular dispersions. Spin-coated films of felodipine with poly(vinylpyrrolidone) (PVP), hydroxypropylmethylcellulose acetate succinate (HPMCAS), and hydroxypropylmethylcellulose (HPMC) were prepared and used for measurement of the nucleation rate and to probe drug-polymer intermolecular interactions. Bulk solid dispersions were prepared by a solvent evaporation method and characterized using thermal analysis. It was found that each polymer was able to significantly decrease the nucleation rate of amorphous felodipine even at low concentrations (3-25% w/w). Each polymer was found to affect the nucleation rate to a similar extent at an equivalent weight fraction. For HPMC and HPMCAS, thermal analysis indicated that the glass transition temperature (T(g)) of the solid dispersions were not significantly different from that of felodipine alone, whereas an increase in T(g) was observed for the PVP containing solid dispersions. Infrared spectroscopic studies indicated that hydrogen bonding interactions were formed between felodipine and each of the polymers. These interactions were stronger between felodipine and PVP than for the other polymers. It was speculated that, at the concentrations employed, the polymers reduce the nucleation rate through increasing the kinetic barrier to nucleation.

  14. 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

  15. 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.

  16. Co-blasting of titanium surfaces with an abrasive and hydroxyapatite to produce bioactive coatings: substrate and coating characterisation.

    PubMed

    Dunne, Conor F; Twomey, Barry; O'Neill, Liam; Stanton, Kenneth T

    2014-01-01

    The aim of this work is to assess the influence of two blast media on the deposition of hydroxyapatite onto a titanium substrate using a novel ambient temperature coating technique named CoBlast. CoBlast was developed to address the problems with high temperature coating techniques. The blasting media used in this study were Al2O3 and a sintered apatite powder. The prepared and coated surfaces were compared to plasma sprayed hydroxyapatite on the same substrates using the same hydroxyapatite feedstock powder. X-ray diffraction analysis revealed the coating crystallinity was the same as the original hydroxyapatite feedstock powder for the CoBlast samples while evidence of amorphous hydroxyapatite phases and β-TCP was observed in the plasma sprayed samples. The blast media type significantly influences the adhesive strength of the coating, surface roughness of both the substrate and coating and the microstructure of the substrate. The coating adhesion increased for the CoBlasted samples from 50 MPa to 60 MPa for sintered apatite powder and alumina, respectively, while plasma spray samples were significantly lower (5 MPa) when tested using a modified pull-test. In conclusion, the choice of blast medium is shown to be a key parameter in the CoBlast process. This study indicates that sintered apatite powder is the most suitable candidate for use as a blast medium in the coating of medical devices.

  17. Atomic-scale disproportionation in amorphous silicon monoxide

    NASA Astrophysics Data System (ADS)

    Hirata, Akihiko; Kohara, Shinji; Asada, Toshihiro; Arao, Masazumi; Yogi, Chihiro; Imai, Hideto; Tan, Yongwen; Fujita, Takeshi; Chen, Mingwei

    2016-05-01

    Solid silicon monoxide is an amorphous material which has been commercialized for many functional applications. However, the amorphous structure of silicon monoxide is a long-standing question because of the uncommon valence state of silicon in the oxide. It has been deduced that amorphous silicon monoxide undergoes an unusual disproportionation by forming silicon- and silicon-dioxide-like regions. Nevertheless, the direct experimental observation is still missing. Here we report the amorphous structure characterized by angstrom-beam electron diffraction, supplemented by synchrotron X-ray scattering and computer simulations. In addition to the theoretically predicted amorphous silicon and silicon-dioxide clusters, suboxide-type tetrahedral coordinates are detected by angstrom-beam electron diffraction at silicon/silicon-dioxide interfaces, which provides compelling experimental evidence on the atomic-scale disproportionation of amorphous silicon monoxide. Eventually we develop a heterostructure model of the disproportionated silicon monoxide which well explains the distinctive structure and properties of the amorphous material.

  18. Amorphous-crystalline transition in thermoelectric NbO2

    NASA Astrophysics Data System (ADS)

    Music, Denis; Chen, Yen-Ting; Bliem, Pascal; Geyer, Richard W.

    2015-06-01

    Density functional theory was employed to design enhanced amorphous NbO2 thermoelectrics. The covalent-ionic nature of Nb-O bonding is identical in amorphous NbO2 and its crystalline counterpart. However, the Anderson localisation occurs in amorphous NbO2, which may affect the transport properties. We calculate a multifold increase in the absolute Seebeck coefficient for the amorphous state. These predictions were critically appraised by measuring the Seebeck coefficient of sputtered amorphous and crystalline NbO2 thin films with the identical short-range order. The first-order phase transition occurs at approximately 550 °C, but amorphous NbO2 possesses enhanced transport properties at all temperatures. Amorphous NbO2, reaching  -173 μV K-1, exhibits up to a 29% larger absolute Seebeck coefficient value, thereby validating the predictions.

  19. Atomic-scale disproportionation in amorphous silicon monoxide.

    PubMed

    Hirata, Akihiko; Kohara, Shinji; Asada, Toshihiro; Arao, Masazumi; Yogi, Chihiro; Imai, Hideto; Tan, Yongwen; Fujita, Takeshi; Chen, Mingwei

    2016-05-13

    Solid silicon monoxide is an amorphous material which has been commercialized for many functional applications. However, the amorphous structure of silicon monoxide is a long-standing question because of the uncommon valence state of silicon in the oxide. It has been deduced that amorphous silicon monoxide undergoes an unusual disproportionation by forming silicon- and silicon-dioxide-like regions. Nevertheless, the direct experimental observation is still missing. Here we report the amorphous structure characterized by angstrom-beam electron diffraction, supplemented by synchrotron X-ray scattering and computer simulations. In addition to the theoretically predicted amorphous silicon and silicon-dioxide clusters, suboxide-type tetrahedral coordinates are detected by angstrom-beam electron diffraction at silicon/silicon-dioxide interfaces, which provides compelling experimental evidence on the atomic-scale disproportionation of amorphous silicon monoxide. Eventually we develop a heterostructure model of the disproportionated silicon monoxide which well explains the distinctive structure and properties of the amorphous material.

  20. Characterization of Poly-Amorphous Indomethacin by Terahertz Spectroscopy

    NASA Astrophysics Data System (ADS)

    Otsuka, Makoto; Nishizawa, Jun-ichi; Fukura, Naomi; Sasaki, Tetsuo

    2012-09-01

    Since the stability of amorphous solids of pharmaceuticals differs depending on the method of preparation, there are several solid-state chemical structures in amorphous solids, which like poly-amorphous solids might have different characteristics the same as in crystalline solids. However, it is not easy to identify the differences in solid-state characteristics between amorphous solids using conventional analytical methods, such as powder X-ray diffraction analysis, since all of the poly-amorphous solids had similar halo X-ray diffraction patterns. However, terahertz spectroscopy can distinguish the amorphous solids of indomethacin with different physicochemical properties, and is expected to provide a rapid and non-destructive qualitative analysis for the solid materials, it would be useful for the qualitative evaluation of amorphous solids in the pharmaceutical industry.

  1. Characterization of Poly-Amorphous Indomethacin by Terahertz Spectroscopy

    NASA Astrophysics Data System (ADS)

    Otsuka, Makoto; Nishizawa, Jun-ichi; Fukura, Naomi; Sasaki, Tetsuo

    2012-05-01

    Since the stability of amorphous solids of pharmaceuticals differs depending on the method of preparation, there are several solid-state chemical structures in amorphous solids, which like poly-amorphous solids might have different characteristics the same as in crystalline solids. However, it is not easy to identify the differences in solid-state characteristics between amorphous solids using conventional analytical methods, such as powder X-ray diffraction analysis, since all of the poly-amorphous solids had similar halo X-ray diffraction patterns. However, terahertz spectroscopy can distinguish the amorphous solids of indomethacin with different physicochemical properties, and is expected to provide a rapid and non-destructive qualitative analysis for the solid materials, it would be useful for the qualitative evaluation of amorphous solids in the pharmaceutical industry.

  2. Atomic-scale disproportionation in amorphous silicon monoxide

    PubMed Central

    Hirata, Akihiko; Kohara, Shinji; Asada, Toshihiro; Arao, Masazumi; Yogi, Chihiro; Imai, Hideto; Tan, Yongwen; Fujita, Takeshi; Chen, Mingwei

    2016-01-01

    Solid silicon monoxide is an amorphous material which has been commercialized for many functional applications. However, the amorphous structure of silicon monoxide is a long-standing question because of the uncommon valence state of silicon in the oxide. It has been deduced that amorphous silicon monoxide undergoes an unusual disproportionation by forming silicon- and silicon-dioxide-like regions. Nevertheless, the direct experimental observation is still missing. Here we report the amorphous structure characterized by angstrom-beam electron diffraction, supplemented by synchrotron X-ray scattering and computer simulations. In addition to the theoretically predicted amorphous silicon and silicon-dioxide clusters, suboxide-type tetrahedral coordinates are detected by angstrom-beam electron diffraction at silicon/silicon-dioxide interfaces, which provides compelling experimental evidence on the atomic-scale disproportionation of amorphous silicon monoxide. Eventually we develop a heterostructure model of the disproportionated silicon monoxide which well explains the distinctive structure and properties of the amorphous material. PMID:27172815

  3. Electrocurtain coating process for coating solar mirrors

    DOEpatents

    Kabagambe, Benjamin; Boyd, Donald W.; Buchanan, Michael J.; Kelly, Patrick; Kutilek, Luke A.; McCamy, James W.; McPheron, Douglas A.; Orosz, Gary R.; Limbacher, Raymond D.

    2013-10-15

    An electrically conductive protective coating or film is provided over the surface of a reflective coating of a solar mirror by flowing or directing a cation containing liquid and an anion containing liquid onto the conductive surface. The cation and the anion containing liquids are spaced from, and preferably out of contact with one another on the surface of the reflective coating as an electric current is moved through the anion containing liquid, the conductive surface between the liquids and the cation containing liquid to coat the conductive surface with the electrically conductive coating.

  4. Surface smoothing effect of an amorphous thin film deposited by atomic layer deposition on a surface with nano-sized roughness

    SciTech Connect

    Lau, W. S. Wan, X.; Xu, Y.; Wong, H.; Zhang, J.; Luo, J. K.

    2014-02-15

    Previously, Lau (one of the authors) pointed out that the deposition of an amorphous thin film by atomic layer deposition (ALD) on a substrate with nano-sized roughness probably has a surface smoothing effect. In this letter, polycrystalline zinc oxide deposited by ALD onto a smooth substrate was used as a substrate with nano-sized roughness. Atomic force microscopy (AFM) and cross-sectional transmission electron microscopy (XTEM) were used to demonstrate that an amorphous aluminum oxide thin film deposited by ALD can reduce the surface roughness of a polycrystalline zinc oxide coated substrate.

  5. 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.

  6. Thermoluminescence characteristics of hydrogenated amorphous zirconia

    NASA Astrophysics Data System (ADS)

    Montalvo, T. R.; Tenorio, L. O.; Nieto, J. A.; Salgado, M. B.; Estrada, A. M. S.; Furetta, C.

    2005-05-01

    This paper reports the experimental results concerning the thermoluminescent (TL) characteristics of hydrogenated amorphous zirconium oxide (a-Zr:H) powder prepared by the sol-gel method. The advantages of this method are the homogeneity and the purity of the gels associated with a relatively low sintering temperature. Hydrogenated amorphous powder was characterized by thermal analysis and X-ray diffraction. The main TL characteristics investigated were the TL response as a function of the absorbed dose, the reproducibility of the TL readings and the fading. The undoped a-Zr:H powder presents a TL glow curve with two peaks centered at 150 and 260 degrees C, respectively, after beta irradiation. The TL response a-Zr:H as a function of the absorbed dose showed a linear behavior over a wide range. The results presented open the possibility to use this material as a good TL dosimeter.

  7. Characterization of Amorphous Zinc Tin Oxide Semiconductors

    SciTech Connect

    Rajachidambaram, Jaana Saranya; Sanghavi, Shail P.; Nachimuthu, Ponnusamy; Shutthanandan, V.; Varga, Tamas; Flynn, Brendan T.; Thevuthasan, Suntharampillai; Herman, Gregory S.

    2012-06-12

    Amorphous zinc tin oxide (ZTO) was investigated to determine the effect of deposition and post annealing conditions on film structure, composition, surface contamination, and thin film transistor (TFT) device performance. X-ray diffraction results indicated that the ZTO films remain amorphous even after annealing to 600 °C. We found that the bulk Zn:Sn ratio of the sputter deposited films were slightly tin rich compared to the composition of the ceramic sputter target, and there was a significant depletion of zinc at the surface. X-ray photoelectron spectroscopy also indicated that residual surface contamination depended strongly on the sample post-annealing conditions where water, carbonate and hydroxyl species were absorbed to the surface. Electrical characterization of ZTO films, using TFT test structures, indicated that mobilities as high as 17 cm2/Vs could be obtained for depletion mode devices.

  8. Reversibility and criticality in amorphous solids

    PubMed Central

    Regev, Ido; Weber, John; Reichhardt, Charles; Dahmen, Karin A.; Lookman, Turab

    2015-01-01

    The physical processes governing the onset of yield, where a material changes its shape permanently under external deformation, are not yet understood for amorphous solids that are intrinsically disordered. Here, using molecular dynamics simulations and mean-field theory, we show that at a critical strain amplitude the sizes of clusters of atoms undergoing cooperative rearrangements of displacements (avalanches) diverges. We compare this non-equilibrium critical behaviour to the prevailing concept of a ‘front depinning' transition that has been used to describe steady-state avalanche behaviour in different materials. We explain why a depinning-like process can result in a transition from periodic to chaotic behaviour and why chaotic motion is not possible in pinned systems. These findings suggest that, at least for highly jammed amorphous systems, the irreversibility transition may be a side effect of depinning that occurs in systems where the disorder is not quenched. PMID:26564783

  9. Reversibility and criticality in amorphous solids

    DOE PAGES

    Regev, Ido; Weber, John; Reichhardt, Charles; Dahmen, Karin A.; Lookman, Turab

    2015-11-13

    The physical processes governing the onset of yield, where a material changes its shape permanently under external deformation, are not yet understood for amorphous solids that are intrinsically disordered. Here, using molecular dynamics simulations and mean-field theory, we show that at a critical strain amplitude the sizes of clusters of atoms undergoing cooperative rearrangements of displacements (avalanches) diverges. We compare this non-equilibrium critical behaviour to the prevailing concept of a ‘front depinning’ transition that has been used to describe steady-state avalanche behaviour in different materials. We explain why a depinning-like process can result in a transition from periodic to chaoticmore » behaviour and why chaotic motion is not possible in pinned systems. As a result, these findings suggest that, at least for highly jammed amorphous systems, the irreversibility transition may be a side effect of depinning that occurs in systems where the disorder is not quenched.« less

  10. Reversibility and criticality in amorphous solids

    SciTech Connect

    Regev, Ido; Weber, John; Reichhardt, Charles; Dahmen, Karin A.; Lookman, Turab

    2015-11-13

    The physical processes governing the onset of yield, where a material changes its shape permanently under external deformation, are not yet understood for amorphous solids that are intrinsically disordered. Here, using molecular dynamics simulations and mean-field theory, we show that at a critical strain amplitude the sizes of clusters of atoms undergoing cooperative rearrangements of displacements (avalanches) diverges. We compare this non-equilibrium critical behaviour to the prevailing concept of a ‘front depinning’ transition that has been used to describe steady-state avalanche behaviour in different materials. We explain why a depinning-like process can result in a transition from periodic to chaotic behaviour and why chaotic motion is not possible in pinned systems. As a result, these findings suggest that, at least for highly jammed amorphous systems, the irreversibility transition may be a side effect of depinning that occurs in systems where the disorder is not quenched.

  11. Reversibility and criticality in amorphous solids.

    PubMed

    Regev, Ido; Weber, John; Reichhardt, Charles; Dahmen, Karin A; Lookman, Turab

    2015-01-01

    The physical processes governing the onset of yield, where a material changes its shape permanently under external deformation, are not yet understood for amorphous solids that are intrinsically disordered. Here, using molecular dynamics simulations and mean-field theory, we show that at a critical strain amplitude the sizes of clusters of atoms undergoing cooperative rearrangements of displacements (avalanches) diverges. We compare this non-equilibrium critical behaviour to the prevailing concept of a 'front depinning' transition that has been used to describe steady-state avalanche behaviour in different materials. We explain why a depinning-like process can result in a transition from periodic to chaotic behaviour and why chaotic motion is not possible in pinned systems. These findings suggest that, at least for highly jammed amorphous systems, the irreversibility transition may be a side effect of depinning that occurs in systems where the disorder is not quenched. PMID:26564783

  12. [Physical mechanisms of solid-protein interactions in the interface between amorphous silicon carbide and fibrinogen].

    PubMed

    Bolz, A; Schaldach, M

    1992-11-01

    State of the art in biomaterial research and implant design is a compromise between functionality and biocompatibility. Consequently the results often have disadvantages with respect to both aspects. In regard to biocompatibility the activation of the clotting system by alloplastic materials is of great significance, because it necessitates anticoagulant therapy. Further improvements of implant technology require an understanding of the interactions between blood and implants. Therefore a microscopic model of thrombogenesis at alloplastic surfaces will shortly be presented, which relates thrombogenicity of a material to the electronic structure of its surface. The requirements for high hemocompatibility, which result from this model--especially in regard to the density of states and the conductivity at the surface--are fulfilled by an amorphous alloy of silicon and carbon (a-SiC:H). The advantage of amorphous materials is that they do not obey stoichiometric rules. Thus they allow a continuous adjustment of the electronic parameters without fundamental changes of their mechanical and chemical properties. The theoretical results where checked by total internal reflection intrinsic fluorescence spectroscopy (TIRIF) as well as thrombelastography experiments (TEG). In comparison to conventional materials like titanium or LTI carbon the TEG-clotting time of a-SiC:H-coatings is prolonged in excess of 200%. As a consequence a-SiC:H is well suited as a hemocompatible coating material for hybrid structuring of cardiovascular implants.

  13. Bulk metallic glass coating of polymer substrates

    NASA Astrophysics Data System (ADS)

    Soinila, Erno; Sharma, Parmanand; Heino, Markku; Pischow, Kaj; Inoue, Akihisa; Hänninen, Hannu

    2009-01-01

    Bulk Metallic Glass (BMG) alloy with the composition of Zr55Cu30Al10Ni5 was deposited by sputtering as thin films on several different engineering polymers and polymer composites. Polycarbonate, polymethyl methacrylate, polyamide 12, polyarylamide (50GF=50 % glass fibers), polyphenylene sulfide (30GF) and polybutylene terephthalate (30GF) were used as substrates. The microstructure of the deposited BMG coatings was studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results of XRD and SEM studies were consistent with amorphous microstructure. Elemental compositions of the coatings were verified by energy dispersive spectroscopy (EDS). Mechanical properties of the coatings were compared to copper mould cast BMG using nano- indentation tests with similar results. According to the cross-cut tape tests good adhesion was achieved between the studied BMG alloy and all other polymer substrates except polycarbonate. Nano-indentation results showed similar mechanical properties for coating and cast BMG. The results of this study look promising as they open new opportunities for BMG- polymer composite applications.

  14. Spin-current-driven thermoelectric coating.

    PubMed

    Kirihara, Akihiro; Uchida, Ken-ichi; Kajiwara, Yosuke; Ishida, Masahiko; Nakamura, Yasunobu; Manako, Takashi; Saitoh, Eiji; Yorozu, Shinichi

    2012-06-17

    Energy harvesting technologies, which generate electricity from environmental energy, have been attracting great interest because of their potential to power ubiquitously deployed sensor networks and mobile electronics. Of these technologies, thermoelectric (TE) conversion is a particularly promising candidate, because it can directly generate electricity from the thermal energy that is available in various places. Here we show a novel TE concept based on the spin Seebeck effect, called 'spin-thermoelectric (STE) coating', which is characterized by a simple film structure, convenient scaling capability, and easy fabrication. The STE coating, with a 60-nm-thick bismuth-substituted yttrium iron garnet (Bi:YIG) film, is applied by means of a highly efficient process on a non-magnetic substrate. Notably, spin-current-driven TE conversion is successfully demonstrated under a temperature gradient perpendicular to such an ultrathin STE-coating layer (amounting to only 0.01% of the total sample thickness). We also show that the STE coating is applicable even on glass surfaces with amorphous structures. Such a versatile implementation of the TE function may pave the way for novel applications making full use of omnipresent heat.

  15. Tribological Behavior of Electroless Ni-P Coatings in Various Corrosive Environments

    NASA Astrophysics Data System (ADS)

    Panja, Bikash; Das, Suman Kalyan; Sahoo, Prasanta

    2016-04-01

    The present paper deals with the study of tribological characteristics, viz. friction and wear, of electroless Ni-P coating in corrosive environments (brine, acidic and alkaline) by varying different coating process parameters as well as varying the tribological testing parameters, viz. applied load and speed. The optimized results of coating process parameters for minimum friction and wear performance of the coating are presented. Moreover, a detailed study of the tribological behavior of the coating is undertaken individually for the three corrosive environments. The results obtained are compared among each other and also with the dry condition test of the coating. It is found that the friction coefficient of Ni-P coating decreases with increase in load for all environments. In case of wear, the wear rate of Ni-P coating gradually increases with increase in load for all mediums but the same decreases after 40N in brine and alkaline mediums. However, for acidic solution, the wear rate shows a continuous increasing trend. It is observed that alkaline and brine environments are favorable from friction and wear point of view of the coating, respectively. Microstructure study of the coatings is also performed and the coating is found to be of cauliflower-like morphology. The coating also exhibits amorphous structure in as-deposited condition, which gradually turns crystalline with heat treatment.

  16. Effect of Annealing Temperature on Hardness and Wear Resistance of Electroless Ni-B-Mo Coatings

    NASA Astrophysics Data System (ADS)

    Serin, Ihsan Gökhan; Göksenli, Ali

    2015-06-01

    Formation of nickel-boron-molybdenum (Ni-B-Mo) coating on steel by electroless plating and evaluation of their morphology, hardness and tribological properties post heat treatment at different temperatures for 1 h is investigated. The 25 μm thick coating is uniform and adhesion between the substrate and coating is good. Ni-B-Mo coating was amorphous-like structure in their as-plated condition and by 400°C heat-treated coating, nickel fully crystallized and nickel borides and molybdenum carbide were formed. All coatings exhibited higher hardness than the substrate steel. Hardness values of all coatings up to 400°C did not change distinctively but decreased partly beyond 400°C. Friction coefficient reached lowest value post heat treatment at 300°C but later increased with increasing tempering temperature. Wear resistance was lowest in as-plated coating; however it reached the highest value at 300°C. Worn surface of the coatings showed the abrasive wear as the dominant wear mechanism. An additional adhesive wear mechanism was detected in coating tempered at 550°C. Moreover, our results confirmed that the molybdenum addition improved the thermal stability of the resulting coating. Therefore, Ni-B-Mo coating has potential for application in precision mould, optical parts mould or bipolar plates, where thermal stability is essential.

  17. Bioactive bredigite coating with improved bonding strength, rapid apatite mineralization and excellent cytocompatibility.

    PubMed

    Yi, Deliang; Wu, Chengtie; Ma, Bing; Ji, Heng; Zheng, Xuebin; Chang, Jiang

    2014-05-01

    Previous studies have shown that bredigite (Ca7MgSi4O16) bioceramics possessed excellent biocompatibility, apatite-mineralization ability and mechanical properties. In this paper, the bredigite coating on Ti-6Al-4 V substrate was prepared by plasma spraying technique. The main compositions of the coating were bredigite crystal phase with small parts of amorphous phases. The bonding strength of the coating to Ti-6Al-4 V substrate reached 49.8 MPa, which was significantly higher than that of hydroxyapatite coating and other silicate-based bioceramic coatings prepared by same method. After immersed in simulated body fluid for 2 days, a distinct apatite layer was deposited on the surface of bredigite coating, indicating that the prepared bredigite coating has excellent apatite-mineralization ability. The prepared bredigite coating supported the attachment and proliferation of rabbit bone marrow stem cells. The proliferation level of bone marrow stem cells was significantly higher than that on the hydroxyapatite coating. Our further study showed that the released SiO4 (4-) and Mg(2+) ions from bredigite coating as well as the formed nano-apatite layer on the coating surface might mainly contribute to the improvement of cell proliferation. The results indicated that the bredigite coating may be applied on orthopedic implants due to its excellent bonding strength, apatite mineralization and cytocompatibility.

  18. Design Requirements for Amorphous Piezoelectric Polymers

    NASA Technical Reports Server (NTRS)

    Ounaies, Z.; Young, J. A.; Harrison, J. S.

    1999-01-01

    An overview of the piezoelectric activity in amorphous piezoelectric polymers is presented. The criteria required to render a polymer piezoelectric are discussed. Although piezoelectricity is a coupling between mechanical and electrical properties, most research has concentrated on the electrical properties of potentially piezoelectric polymers. In this work, we present comparative mechanical data as a function of temperature and offer a summary of polarization and electromechanical properties for each of the polymers considered.

  19. Synthesis of new amorphous metallic spin glasses

    DOEpatents

    Haushalter, R.C.

    1985-02-11

    Disclosed are: amorphous metallic precipitates having the formula (M/sub 1/)/sub a/(M/sub 2/)/sub b/ wherein M/sub 1/ is at least one transition metal, M/sub 2/ is at least one main group metal and the integers ''a'' and ''b'' provide stoichiometric balance; the precipitates having a degree of local order characteristic of chemical compounds from the precipitation process and useful electrical and mechanical properties.

  20. Synthesis of new amorphous metallic spin glasses

    DOEpatents

    Haushalter, Robert C.

    1988-01-01

    Amorphous metallic precipitates having the formula (M.sub.1).sub.a (M.sub.2).sub.b wherein M.sub.1 is at least one transition metal, M.sub.2 is at least one main group metal and the integers "a" and "b" provide stoichiometric balance; the precipitates having a degree of local order characteristic of chemical compounds from the precipitation process and useful electrical and mechanical properties.