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Sample records for al cr cu

  1. Cyclic Oxidation Behavior of CuCrAl Cold-Sprayed Coatings for Reusable Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Raj, Sai; Karthikeyan, J.

    2009-01-01

    The next generation of reusable launch vehicles is likely to use GRCop-84 [Cu-8(at.%)Cr-4%Nb] copper alloy combustion liners. The application of protective coatings on GRCop-84 liners can minimize or eliminate many of the environmental problems experienced by uncoated liners and significantly extend their operational lives and lower operational cost. A newly developed Cu- 23 (wt.%) Cr-5% Al (CuCrAl) coating, shown to resist hydrogen attack and oxidation in an as-cast form, is currently being considered as a protective coating for GRCop-84. The coating was deposited on GRCop-84 substrates by the cold spray deposition technique, where the CuCrAl was procured as gas-atomized powders. Cyclic oxidation tests were conducted between 773 and 1,073 K to characterize the coated substrates.

  2. Comparison of the Isothermal Oxidation Behavior of As-Cast Cu-17%Cr and Cu-17%Cr-5%Al. Part 1; Oxidation Kinetics

    NASA Technical Reports Server (NTRS)

    Raj. Sai V.

    2008-01-01

    The isothermal oxidation kinetics of as-cast Cu-17%Cr and Cu-17%Cr-5%Al in air were studied between 773 and 1173 K under atmospheric pressure. These observations reveal that Cu- 17%Cr-5%Al oxidizes at significantly slower rates than Cu-17%Cr. The rate constants for the alloys were determined from generalized analyses of the data without an a priori assumption of the nature of the oxidation kinetics. Detailed analyses of the isothermal thermogravimetric weight change data revealed that Cu-17%Cr exhibited parabolic oxidation kinetics with an activation energy of 165.9 9.5 kJ mol-1. In contrast, the oxidation kinetics for the Cu-17%Cr- 5%Al alloy exhibited a parabolic oxidation kinetics during the initial stages followed by a quartic relationship in the later stages of oxidation. Alternatively, the oxidation behavior of Cu-17%CR- 5%Al could be better represented by a logarithmic relationship. The parabolic rate constants and activation energy data for the two alloys are compared with literature data to gain insights on the nature of the oxidation mechanisms dominant in these alloys.

  3. Comparison of the Isothermal Oxidation Behavior of As-Cast Cu-17 Percent Cr and Cu-17 Percent Cr-5 Percent Al. Part 1; Oxidation Kinetics

    NASA Technical Reports Server (NTRS)

    Raj, S. V.

    2008-01-01

    The isothermal oxidation kinetics of as-cast Cu-17%Cr and Cu-17%Cr-5%Al in air were studied between 773 and 1173 K under atmospheric pressure. These observations reveal that Cu-17%Cr-5%Al oxidizes at significantly slower rates than Cu-17%Cr. The rate constants for the alloys were determined from generalized analyses of the data without an a priori assumption of the nature of the oxidation kinetics. Detailed analyses of the isothermal thermogravimetric weight change data revealed that Cu-17%Cr exhibited parabolic oxidation kinetics with an activation energy of 165.9+/-9.5 kJ/mol. In contrast, the oxidation kinetics for the Cu-17%Cr-5%Al alloy exhibited a parabolic oxidation kinetics during the initial stages followed by a quartic relationship in the later stages of oxidation. Alternatively, the oxidation behavior of Cu-17%CR-5%Al could be better represented by a logarithmic relationship. The parabolic rate constants and activation energy data for the two alloys are compared with literature data to gain insights on the nature of the oxidation mechanisms dominant in these alloys.

  4. Comparison of the Isothermal Oxidation Behavior of As-Cast Cu-17%Cr and Cu-17%Cr-5%Al. Part 1; Oxidation Kinetics

    NASA Technical Reports Server (NTRS)

    Raj. Sai V.

    2008-01-01

    The isothermal oxidation kinetics of as-cast Cu-17%Cr and Cu-17%Cr-5%Al in air were studied between 773 and 1173 K under atmospheric pressure. These observations reveal that Cu- 17%Cr-5%Al oxidizes at significantly slower rates than Cu-17%Cr. The rate constants for the alloys were determined from generalized analyses of the data without an a priori assumption of the nature of the oxidation kinetics. Detailed analyses of the isothermal thermogravimetric weight change data revealed that Cu-17%Cr exhibited parabolic oxidation kinetics with an activation energy of 165.9 +/- 9.5 kJ/mol. In contrast, the oxidation kinetics for the Cu-17%Cr- 5%Al alloy exhibited a parabolic oxidation kinetics during the initial stages followed by a quartic relationship in the later stages of oxidation. Alternatively, the oxidation behavior of Cu-17%CR- 5%Al could be better represented by a logarithmic relationship. The parabolic rate constants and activation energy data for the two alloys are compared with literature data to gain insights on the nature of the oxidation mechanisms dominant in these alloys.

  5. New type of Schottky diode-based Cu-Al-Mn-Cr shape memory material films

    NASA Astrophysics Data System (ADS)

    Aksu Canbay, C.; Dere, A.; Mensah-Darkwa, Kwadwo; Al-Ghamdi, Ahmed; Karagoz Genç, Z.; Gupta, R. K.; Yakuphanoglu, F.

    2016-07-01

    Cr-doped CuAlMn shape memory alloys were produced by arc melting method. The effects of Cr content on microstructure and transformation parameters of were investigated. The alloys were characterized by X-ray analysis, optical microscope observations and differential scanning calorimetry measurements. The grain size of the alloys was decreased by the addition of Cr into CuAlMn alloy system. The martensite transformation temperature was shifted both the lower temperature and higher temperature with the addition of chromium. This change was explained on the basis of the change in the thermodynamics such as enthalpy, entropy and activation energy values. The obtained results indicate that the phase transformation temperatures of the CuAlMn alloy system can be controlled by addition of Cr. We fabricated a Schottky barrier diode and observed that ideality factor and barrier height increase with increasing temperature. The diodes exhibited a thermal sensor behavior. This indicates that Schottky diode-based Cu-Al-Mn-Cr shape memory material films can be used as a sensor in high-temperature measurement applications.

  6. Characterization of a CuAlBe Alloy with Different Cr Contents

    NASA Astrophysics Data System (ADS)

    da M. Candido, Gemierson Valois; de A. Melo, Tadeu Antônio; De Albuquerque, Victor Hugo C.; Gomes, Rodinei Medeiros; de Lima, Severino Jackson G.; Tavares, João Manuel R. S.

    2012-11-01

    In this article, the use of chromium (Cr) as a grain refiner for a CuAlBe shape memory alloy is discussed. Alloys with 0.1, 0.2, 0.3, and 0.5 wt.% Cr were characterized by optical microscopy, scanning electron microscope, and x-ray diffraction. Also, the influence of the different percentages of Cr on the grain size and on the mechanical properties was analyzed through macro- and microscopic evaluations and by tensile and hardness tests, respectively. Finally, the phase transformation temperatures of the alloys were determined by thermal analysis using differential scanning calorimetry. The results showed that the higher the Cr content, the greater the grain refinement effect and lower the hardness. In addition, at room temperature the alloys with 0.1 and 0.2 wt.% Cr were austenitic, while the rest were martensitic. The tensile tests showed that the alloy with 0.2 wt.% Cr provided the best strain-stress performance. The conclusion was that the use of 0.2 wt.% Cr as a grain refiner improved the mechanical properties of the CuAlBe alloy; however, the same was not observed for the other Cr contents.

  7. Characterization of Cold Sprayed CuCrAl Coated GRCop-84 Substrates for Reusable Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Raj, S . V.; Barrett, C. A.; Lerch, B. A.; Karthikeyan, J.; Ghosn, L. J.; Haynes, J.

    2005-01-01

    An advanced Cu-8(at.%)Cr-4%Nb alloy developed at NASA's Glenn Research Center, and designated as GRCop-84, is currently being considered for use as combustor liners and nozzles in NASA's future generations of reusable launch vehicles (RLVs). Despite the fact that this alloy has superior mechanical and oxidation properties compared to many commercially available copper alloys, it is felt that its high temperature and environmental resistance capabilities can be further enhanced with the development and use of suitable coatings. Several coatings and processes are currently being evaluated for their suitability and future down selection. A newly developed CuCrAl has shown excellent oxidation resistance compared to current generation Cu-Cr coating alloys. Cold spray technology for depositing the CuCrAl coating on a GRCop-84 substrate is currently being developed under NASA's Next Generation Launch Technology (NGLT) Propulsion Research and Technology (PR&T) project. The microstructures, mechanical and thermophysical properties of overlay coated GRCop-84 substrates are discussed.

  8. Comparison of the Isothermal Oxidation Behavior of As-Cast Cu-17 Percent Cr and Cu-17 Percent Cr-5 Percent Al Part II: Scale Microstructures

    NASA Technical Reports Server (NTRS)

    Raj, Sai V.

    2008-01-01

    The isothermal oxidation kinetics of as-cast Cu-17%Cr and Cu-17%Cr-5%Al in air were studied between 773 and 1173 K under atmospheric pressure. Details of the oxidation kinetics of these alloys were discussed in Part I. This paper analyzes the microstructures of the scale and its composition in an attempt to elucidate the oxidation mechanisms in these alloys. The scales formed on Cu-17%Cr specimens oxidized between 773 and 973 K consisted of external CuO and subsurface Cu2O layers. The total thickness of these scales varied from about 10 m at 773 K to about 450 m at 973 K. In contrast, thin scales formed on Cu-17%Cr-5%Al alloys oxidized between 773 and 1173 K. The exact nature of these scales could not be determined by x-ray diffraction but energy dispersive spectroscopy analyses were used to construct a scale composition map. Phenomenological oxidation mechanisms are proposed for the two alloys.

  9. Comparison of the Isothermal Oxidation Behavior of As-Cast Cu-17 Percent Cr and Cu-17 Percent Cr-5 Percent Al. Part 2; Scale Microstructures

    NASA Technical Reports Server (NTRS)

    Raj, S. V.

    2008-01-01

    The isothermal oxidation kinetics of as-cast Cu-17%Cr and Cu-17%Cr-5%Al in air were studied between 773 and 1173 K under atmospheric pressure. Details of the oxidation kinetics of these alloys were discussed in Part I. This paper analyzes the microstructures of the scale and its composition in an attempt to elucidate the oxidation mechanisms in these alloys. The scales formed on Cu-17%Cr specimens oxidized between 773 and 973 K consisted of external CuO and subsurface Cu2O layers. The total thickness of these scales varied from about 10 m at 773 K to about 450 m at 973 K. In contrast, thin scales formed on Cu-17%Cr-5%Al alloys oxidized between 773 and 1173 K. The exact nature of these scales could not be determined by x-ray diffraction but energy dispersive spectroscopy analyses were used to construct a scale composition map. Phenomenological oxidation mechanisms are proposed for the two alloys.

  10. Effect of Cr on Microstructure and Properties of a Series of AlTiCr x FeCoNiCu High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Li, Anmin; Ma, Ding; Zheng, Qifeng

    2014-04-01

    A series of AlTiCr x FeCoNiCu ( x: molar ratio, x = 0.5, 1.0, 1.5, 2.0, 2.5) high-entropy alloys (HEAs) were prepared by vacuum arc furnace. These alloys consist of α-phase, β-phase, and γ-phase. These phases are solid solutions. The structure of α-phase and γ-phase is face-centered cubic structure and that of β-phase is body-centered cubic (BCC) structure. There are four typical cast organizations in these alloys such as petal organization (α-phase), chrysanthemum organization (α-phase + β-phase), dendrite (β-phase), and inter-dendrite (γ-phase). The solidification mode of these alloys is affected by Chromium. If γ-phase is not considered, AlTiCr0.5FeCoNiCu and AlTiCrFeCoNiCu belong to hypoeutectic alloys; AlTiCr1.5FeCoNiCu, AlTiCr2.0FeCoNiCu, and AlTiCr2.5FeCoNiCu belong to hypereutectic alloys. The cast organizations of these alloys consist of pro-eutectic phase and eutectic structure (α + β). Compact eutectic structure and a certain amount of fine β-phase with uniform distribution are useful to improve the microhardness of the HEAs. More γ-phase and the microstructure with similar volume ratio values of α-phase and β-phase improve the compressive strength and toughness of these alloys. The compressive fracture of the series of AlTiCr x FeCoNiCu HEAs shows brittle characteristics, suggesting that these HEAs are brittle materials.

  11. Electrochemical deposition and microstructural characterization of AlCrFeMnNi and AlCrCuFeMnNi high entropy alloy thin films

    NASA Astrophysics Data System (ADS)

    Soare, V.; Burada, M.; Constantin, I.; Mitrică, D.; Bădiliţă, V.; Caragea, A.; Târcolea, M.

    2015-12-01

    Al-Cr-Fe-Mn-Ni and Al-Cr-Cu-Fe-Mn-Ni high entropy alloy thin films were prepared by potentiostatic electrodeposition and the microstructure of the deposits was investigated. The thin films were co-deposited in an electrolyte based on a DMF (N,N-dimethylformamide)-CH3CN (acetonitrile) organic compound. The energy dispersive spectrometry investigation (EDS) indicated that all the five respectively six elements were successfully co-deposited. The scanning electron microscopy (SEM) analysis revealed that the film consists of compact and uniform particles with particle sizes of 500 nm to 4 μm. The X-ray diffractometry (XRD) patterns indicated that the as-deposited thin films were amorphous. Body-centered-cubic (BCC) structures were identified by XRD after the films were annealed at various temperatures under inert Ar atmosphere. The alloys adhesion on the substrate was determined by the scratch-testing method, with higher values obtained for the Al-Cr-Cu-Fe-Mn-Ni alloy.

  12. Characterization of Cold Sprayed CuCrAl-Coated and Uncoated GRCop-84 Substrates for Space Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Raj, S. V.; Karthikeyan, J.; Lerch, B. A.; Barrett, C.; Garlich, R.

    2007-01-01

    A newly developed Cu-23(wt.%)Cr-5%Al (CuCrAl) alloy is currently being considered as a protective coating for GRCop-84 (Cu-8(at.%)Cr-4%Nb). The coating was deposited on GRCop-84 substrates by the cold spray deposition technique. Cyclic oxidation tests conducted in air on both coated and uncoated substrates between 773 and 1073 K revealed that the coating remained intact and protected the substrate up to 1073 K. No significant weight loss of the coated specimens were observed at 773 and 873 K even after a cumulative cyclic time of 500 h. In contrast, the uncoated substrate lost as much as 80% of its original weight under similar test conditions. Low cycle fatigue tests revealed that the fatigue lives of thinly coated GRCop-84 specimens were similar to the uncoated specimens within the limits of experimental scatter. It is concluded that the cold sprayed CuCrAl coating is suitable for protecting GRCop-84 substrates.

  13. Cyclic Oxidation Behavior of Cold Sprayed CuCrAl-Coated and Uncoated GRCop-84 Substrates for Space Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Raj, S. V.; Barrett, C.; Karthikeyan, J.; Garlick, R.

    2006-01-01

    A newly developed Cu-23 (wt %) Cr-5%Al (CuCrAl) alloy shown to resist hydridation and oxidation in an as-cast form is currently being considered as a protective coating for GRCop-84, which is an advanced copper alloy containing 8 (at.%) Cr and 4 (at.%) Nb. The coating was deposited on GRCop-84 substrates by the cold spray deposition technique. Cyclic oxidation tests conducted in air on both coated and uncoated substrates between 773 and 1073 K revealed that the coating remained intact and protected the substrate up to 1073 K. No significant weight loss of the coated specimens were observed at 773 and 873 K even after a cumulative cyclic time of 500 h. About a 10 percent weight loss observed at 973 and 1073 K was attributed to the excessive oxidation of the uncoated sides. In contrast, the uncoated substrate lost as much as 80 percent of its original weight under similar test conditions. It is concluded that the cold sprayed CuCrAl coating is suitable for protecting GRCop-84 substrates.

  14. Experimental Verification of the Theoretical Prediction of the Phase Structure of a Ni-Al-Ti-Cr-Cu Alloy

    NASA Technical Reports Server (NTRS)

    Wilson, A.; Bozzolo, G.; Noebe, R. D.; Howe, J. M.

    2002-01-01

    The Bozzolo-Ferrante-Smith (BFS) method for alloys was applied to the study of NiAl-based materials to assess the effect of alloying additions on structure. Ternary, quaternary and even pentalloys based on NiAl with additions of Ti, Cr and Cu were studied and experimental verification of the theoretical predictions including the phase structure of a Ni-Al-Ti-Cr-Cu alloy is presented. Two approaches were used, Monte Carlo simulations to determine low energy structures, and analytical calculations of the energy of high symmetry configurations which give physical insight into preferred structures. The energetics for site occupancy in ternary and quaternary systems were calculated leading to an indirect determination of solubility limits at 0 K. Precipitate formation with information concerning structure and lattice parameter were also 'observed' computationally and the general characteristics of a Ni-Al-Ti-Cr-Cu alloy were correctly predicted. The results indicate that the BFS method for alloys can be a useful tool for alloy design and can be used to complement experimental alloy design programs.

  15. Impact of CrSiTi and NiSi on the Thermodynamics, Microstructure, and Properties of AlCoCuFe-Based High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Rong; Wang, Zhao-Qin; Lin, Tie-Song; He, Peng; Sekulic, Dusan P.

    2016-05-01

    Aiming to solve the problem of spontaneous combustion on titanium via electrospark deposition (ESD), two AlCoCuFe-based high-entropy alloys (HEAs), AlCoCuFe- x ( x = CrSiTi, NiSi), were produced by vacuum arc melting as electrodes in ESD process. The thermodynamic analysis of AlCoCuFe-based HEAs were carried out using the concept of mixing enthalpy matrix and a powerful thermodynamic calculation toolbox (HEA-Thermo-Calcu). The microstructure and mechanical properties of the two alloys were investigated. The AlCoCuFeCrSiTi alloy contains a body-centered cubic (BCC) phase and a face-centered cubic (FCC) phase. The AlCoCuFeNiSi alloy is composed of two BCC phases and an FCC phase. Addition of CrSiTi and NiSi to AlCoCuFe-based alloys makes the enthalpy of mixing to be sizably more negative than for the other AlCoCuFe-based HEAs. Notwithstanding the fact that the thermodynamic parameters do not agree with Yang's proposition, the two alloys form simple solid solutions. The electronegativity difference (Δ χ) favors a formation of the solid solution when Δχ ≤ 14.2. The hardness of AlCoCuFe- x ( x = CrSiTi, NiSi) alloys reaches 935 HV and 688 HV, respectively. The yield strength, fracture strength, and ultimate strain of AlCoCuFeNiSi are larger, i.e., 29, 30, and 45%, respectively, than those of the AlCoCuFeCrSiTi alloy.

  16. Impact of CrSiTi and NiSi on the Thermodynamics, Microstructure, and Properties of AlCoCuFe-Based High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Rong; Wang, Zhao-Qin; Lin, Tie-Song; He, Peng; Sekulic, Dusan P.

    2016-03-01

    Aiming to solve the problem of spontaneous combustion on titanium via electrospark deposition (ESD), two AlCoCuFe-based high-entropy alloys (HEAs), AlCoCuFe-x (x = CrSiTi, NiSi), were produced by vacuum arc melting as electrodes in ESD process. The thermodynamic analysis of AlCoCuFe-based HEAs were carried out using the concept of mixing enthalpy matrix and a powerful thermodynamic calculation toolbox (HEA-Thermo-Calcu). The microstructure and mechanical properties of the two alloys were investigated. The AlCoCuFeCrSiTi alloy contains a body-centered cubic (BCC) phase and a face-centered cubic (FCC) phase. The AlCoCuFeNiSi alloy is composed of two BCC phases and an FCC phase. Addition of CrSiTi and NiSi to AlCoCuFe-based alloys makes the enthalpy of mixing to be sizably more negative than for the other AlCoCuFe-based HEAs. Notwithstanding the fact that the thermodynamic parameters do not agree with Yang's proposition, the two alloys form simple solid solutions. The electronegativity difference (Δχ) favors a formation of the solid solution when Δχ ≤ 14.2. The hardness of AlCoCuFe-x (x = CrSiTi, NiSi) alloys reaches 935 HV and 688 HV, respectively. The yield strength, fracture strength, and ultimate strain of AlCoCuFeNiSi are larger, i.e., 29, 30, and 45%, respectively, than those of the AlCoCuFeCrSiTi alloy.

  17. Influence cobalt on microstructural and hardness property of Al-Zn-Mg-Cu-Fe-Cr-Ni P/ M alloys

    NASA Astrophysics Data System (ADS)

    Naeem, Haider T.; Mohammad, Kahtan S.; Hussin, Kamarudin; Rahmat, Azim; Bashirom, Nurhuda

    2015-05-01

    In this study, influence cobalt additives on the microstructural and hardness properties of an Al-Zn-Mg-Cu-Fe-Cr-Ni PM alloy undergone the retrogression and re-aging treatment were carried out. Green compacts pressed at 370 MPa were then sintered at temperature 650°C in argon atmosphere for two hours. The sintered compacts subjected to a homogenizing treated at 470°C for 1.5 hours then aged at 120°C for 24 hours and retrogressed at 180°C for 30 minutes, and then re-aged at 120°C for 24 hours. Microstructural results of the Al-Zn-Mg-Cu-Fe-Cr-Ni-Co alloys introduced an intermetallics compound in the matrix of alloy, identified as the Al5Co2, Al70Co20Ni10 and Al4Ni3 phases besides to the MgZn2 and Mg2Zn11 phases which produced of the precipitation hardening during heat treatment. These compounds with precipitates provided strengthening of dispersion that led to improved Vickers's hardness and dinsifications properties of the alloy. The highest Vickers hardness of aluminum alloy containing cobalt was gotten after applying the retrogression and re-aging treatment.

  18. Effect of Cr, Ti, V, and Zr Micro-additions on Microstructure and Mechanical Properties of the Al-Si-Cu-Mg Cast Alloy

    NASA Astrophysics Data System (ADS)

    Shaha, S. K.; Czerwinski, F.; Kasprzak, W.; Friedman, J.; Chen, D. L.

    2016-05-01

    Uniaxial static and cyclic tests were used to assess the role of Cr, Ti, V, and Zr additions on properties of the Al-7Si-1Cu-0.5Mg (wt pct) alloy in as-cast and T6 heat-treated conditions. The microstructure of the as-cast alloy consisted of α-Al, eutectic Si, and Cu-, Mg-, and Fe-rich phases Al2.1Cu, Al8.5Si2.4Cu, Al5.2CuMg4Si5.1, and Al14Si7.1FeMg3.3. In addition, the micro-sized Cr/Zr/Ti/V-rich phases Al10.7SiTi3.6, Al6.7Si1.2TiZr1.8, Al21.4Si3.4Ti4.7VZr1.8, Al18.5Si7.3Cr2.6V, Al7.9Si8.5Cr6.8V4.1Ti, Al6.3Si23.2FeCr9.2V1.6Ti1.3, Al92.2Si16.7Fe7.6Cr8.3V1.8, and Al8.2Si30.1Fe1.6Cr18.8V3.3Ti2.9Zr were present. During solution treatment, Cu-rich phases were completely dissolved, while the eutectic silicon, Fe-, and Cr/Zr/Ti/V-rich intermetallics experienced only partial dissolution. Micro-additions of Cr, Zr, Ti, and V positively affected the alloy strength. The modified alloy in the T6 temper during uniaxial tensile tests exhibited yield strength of 289 MPa and ultimate tensile strength of 342 MPa, being significantly higher than that for the Al-Si-Cu-Mg base. Besides, the cyclic yield stress of the modified alloy in the T6 state increased by 23 pct over that of the base alloy. The fatigue life of the modified alloy was substantially longer than that of the base alloy tested using the same parameters. The role of Cr, Ti, V, and Zr containing phases in controlling the alloy fracture during static and cyclic loading is discussed.

  19. Effects of Severe Cold Rolling on Exfoliation Corrosion Behavior of Al-Zn-Mg-Cu-Cr Alloy

    NASA Astrophysics Data System (ADS)

    Lin, Lianghua; Liu, Zhiyi; Li, Yao; Han, Xiangnan; Chen, Xu

    2012-06-01

    The exfoliation corrosion (EXCO) behavior of Al-Zn-Mg-Cu-Cr alloy after severe cold rolling was investigated by optical microscope, transmission electron microscope, and electrochemical technique. The results show that the EXCO resistance decreased with increasing cold rolling reduction because of the grain boundaries which were decorated with the continuously distributed particles . After the solution treatment, the samples with different reductions retained the fibrous grains, and the elongated grains accelerated the growth of the corrosion cracks according to crack propagation analysis. Furthermore, the increase of deformation enhanced the degree of recrystallization, while the number of corrosion cells increased greatly when in the electrolyte, which tended to reduce the resistance to EXCO.

  20. Development of a CuNiCrAl Bond Coat for Thermal Barrier Coatings in Rocket Combustion Chambers

    NASA Astrophysics Data System (ADS)

    Fiedler, Torben; Rösler, Joachim; Bäker, Martin

    2015-12-01

    The lifetime of rocket combustion chambers can be increased by applying thermal barrier coatings. The standard coating systems usually used in gas turbines or aero engines will fail at the bond coat/substrate interface due to the chemical difference as well as the different thermal expansion between the copper liner and the applied NiCrAlY bond coat. A new bond coat alloy for rocket engine applications was designed previously with a chemical composition and coefficient of thermal expansion more similar to the copper substrate. Since a comparable material has not been applied by thermal spraying before, coating tests have to be carried out. In this work, the new Ni-30%Cu-6%Al-5%Cr bond coat alloy is applied via high velocity oxygen fuel spraying. In a first step, the influence of different coating parameters on, e.g., porosity, amount of unmolten particles, and coating roughness is investigated and a suitable parameter set for further studies is chosen. In a second step, copper substrates are coated with the chosen parameters to test the feasibility of the process. The high-temperature behavior and adhesion is tested with laser cycling experiments. The new coatings showed good adhesion even at temperatures beyond the maximum test temperatures of the NiCrAlY bond coat in previous studies.

  1. Tribological Properties of AlCrCuFeNi2 High-Entropy Alloy in Different Conditions

    NASA Astrophysics Data System (ADS)

    Liu, Yong; Ma, Shengguo; Gao, Michael C.; Zhang, Chuan; Zhang, Teng; Yang, Huijun; Wang, Zhihua; Qiao, Junwei

    2016-07-01

    In order to understand the environmental effect on the mechanical behavior of high-entropy alloys, the tribological properties of AlCrCuFeNi2 are studied systematically in dry, simulated rainwater, and deionized water conditions against the Si3N4 ceramic ball at a series of different normal loads. The present study shows that both the friction and wear rate in simulated rainwater are the lowest. The simulated rainwater plays a significant role in the tribological behavior with the effect of forming passive film, lubricating, cooling, cleaning, and corrosion. The wear mechanism in simulated rainwater is mainly adhesive wear accompanied by abrasive wear as well as corrosive wear. In contrast, those in dry condition and deionized water are abrasive wear, adhesive wear, and surface plastic deformation. Oxidation contributes to the wear behavior in dry condition but is prevented in liquid condition. In addition, the phase diagram of Al x CrCuFeNi2 is predicted using CALPHAD modeling, which is in good agreement with the literature report and the present study.

  2. Tribological Properties of AlCrCuFeNi2 High-Entropy Alloy in Different Conditions

    NASA Astrophysics Data System (ADS)

    Liu, Yong; Ma, Shengguo; Gao, Michael C.; Zhang, Chuan; Zhang, Teng; Yang, Huijun; Wang, Zhihua; Qiao, Junwei

    2016-02-01

    In order to understand the environmental effect on the mechanical behavior of high-entropy alloys, the tribological properties of AlCrCuFeNi2 are studied systematically in dry, simulated rainwater, and deionized water conditions against the Si3N4 ceramic ball at a series of different normal loads. The present study shows that both the friction and wear rate in simulated rainwater are the lowest. The simulated rainwater plays a significant role in the tribological behavior with the effect of forming passive film, lubricating, cooling, cleaning, and corrosion. The wear mechanism in simulated rainwater is mainly adhesive wear accompanied by abrasive wear as well as corrosive wear. In contrast, those in dry condition and deionized water are abrasive wear, adhesive wear, and surface plastic deformation. Oxidation contributes to the wear behavior in dry condition but is prevented in liquid condition. In addition, the phase diagram of Al x CrCuFeNi2 is predicted using CALPHAD modeling, which is in good agreement with the literature report and the present study.

  3. The influence of cooling rate and Fe/Cr content on the evolution of Fe-rich compounds in a secondary Al-Si-Cu diecasting alloy

    NASA Astrophysics Data System (ADS)

    Fabrizi, A.; Timelli, G.

    2016-03-01

    This study investigates the morphological evolution of primary α-Al(Fe,Mn,Cr)Si phase in a secondary Al-Si-Cu alloy with respect to the initial Fe and Cr contents as well as to the cooling rate. The solidification experiments have been designed in order to cover a wide range of cooling rates, and the Fe and Cr contents have been varied over two levels. Metallographic and image analysis techniques have been used to quantitatively examine the microstructural changes occurring at different experimental conditions. The morphological evolution of the α-Fe phase has been also analysed by observing deep etched samples. By changing the cooling rate, α-Al15(Fe,Mn,Cr)3Si2 dodecahedron crystals, as well as Chinese- script, branched structures and dendrites form, while primary coarse β-Al5(Fe,Mn)Si needles appear in the alloy with the highest Fe content at low cooling rates.

  4. Luminescence, magnetic and vibrational properties of novel heterometallic niccolites [(CH3)2NH2][CrIIIMII(HCOO)6] (MII=Zn, Ni, Cu) and [(CH3)2NH2][AlIIIZnII(HCOO)6]:Cr3+

    NASA Astrophysics Data System (ADS)

    Mączka, Mirosław; Pietraszko, Adam; Pikul, Adam; Hermanowicz, Krzysztof

    2016-01-01

    We report synthesis of three novel heterometallic MOFs, [(CH3)2NH2][CrIIIMII(HCOO)6] with M=Zn (DMCrZn), Ni (DMCrNi) and Cu (DMCrCu), crystallizing in the niccolite type structure. We also successfully synthesized [(CH3)2NH2][AlCu(HCOO)6] (DMAlCu) and [(CH3)2NH2][AlZn(HCOO)6] doped with 5.8 mol% of Cr3+ (DMAlZn: Cr). X-ray diffraction shows that DMCrZn, DMCrNi and DMAlZn: Cr3+ crystallize in the trigonal structure (space group P 3 bar1c) while DMCrCu and DMAlCu crystallize in the monoclinic structure (space group C2/c). Magnetic investigation of the chromium-based niccolites reveals no magnetic order in DMCrZn and ferromagnetic order in DMCrNi and DMCrCu below 23 and 11 K, respectively. Optical studies show that DMCrZn and DMAlZn: Cr samples exhibit efficient emission typical for chromium ions located at sites of strong crystal field with the Dq/B values 2.62 and 2.67, respectively. We also discuss role of geometrical parameters in stability of the perovskite and niccolite structures.

  5. Effect of Cr Addition on Wetting Behavior Between Cu and High-Temperature Zn-25Sn-0.15Al-0.1Ga- xCr Pb-Free Solder

    NASA Astrophysics Data System (ADS)

    Liu, Chin-Wei; Lin, Kwang-Lung

    2014-12-01

    In this study the effect of Cr content (0.02 wt.% to 0.2 wt.%) on the wetting interaction between high-temperature Zn-25Sn-0.15Al-0.1Ga- xCr Pb-free solders and Cu has been investigated using the wetting balance method. Differential scanning calorimetry (DSC) investigation showed that Cr addition reduces the liquidus temperature slightly while raising the solidus temperature. Flux-assisted wetting experiments were carried out at an immersion rate of 15 mm/s at 435°C. The results show that the shortest wetting time of around 0.7 s was achieved when 0.1 wt.% Cr was added, but the wetting force tends to decrease with the Cr content. Cr addition enhances the formation of interfacial Cu5Zn8 intermetallic compound (IMC) during air cooling, but the opposite effect was observed for water cooling. The results suggest that Cr addition depresses the formation of the Cu5Zn8 layer in liquid/solid reaction, but enhances the formation of the Cu5Zn8 layer in solid/solid reaction.

  6. Laser surface forming of AlCoCrCuFeNi particle reinforced AZ91D matrix composites

    NASA Astrophysics Data System (ADS)

    Meng, Guanghui; Yue, T. M.; Lin, Xin; Yang, Haiou; Xie, Hui; Ding, Xu

    2015-07-01

    Traditionally, the laser melt injection (LMI) technique can only be used for forming ceramic particles reinforced metal matrix composites (MMCs) for enhancing surface properties of lightweight engineering materials. In this research, the LMI method was employed to form metal particles reinforced MMCs on AZ91D instead. This was viable because of the unique properties of the AlCoCrCuFeNi high-entropy alloy (HEA) metal particles used. The large difference in melting point between the HEA and the substrate material (AZ91D), and the limited reaction and the lack of fusion between the HEA and Mg have made it possible that a metal particles reinforced AZ91D composite material was produced. The reason of limited reaction was considered mainly due to the relatively high mixing enthalpy between the HEA constituent elements and Mg. Although there was some melting occurred at the particles surface with some solute segregation found in the vicinity close to the surface, intermetallic compounds were not observed. With regard to the wear resistance of the MMCs, it was found that when the volume fraction of the reinforcement phase, i.e. the HEA particles, reached about 0.4, the wear volume loss of the coating was only one-seventh of that of the substrate material.

  7. Cu-Cr Literature Review

    SciTech Connect

    Need, Ryan F.

    2012-08-09

    Cu-Cr alloys are part of a class of face-centered cubic (FCC)-body-centered cubic (BCC) composites that includes similar alloys, such as Cu-Nb and Cu-Ta. When heavily deformed, these FCC-BCC materials create 'in situ' composites with a characteristic structure-nanoscale BCC filaments in a ductile FCC matrix. The strength of these composites is vastly greater than predicted by the rule of mixtures, and has been shown to be inversely proportional to the filament spacing. Lower raw materials costs suggest that Cu-Cr alloys may offer more economical solution to high-strength, high-conductivity wire than either their Nb or Ta counterparts. However, Cr is also more brittle and soluble in Cu than Nb or Ta. These qualities necessitate thermal treatments to remove solute atoms from the Cu matrix, improve conductivity, and maintain the ductility of the Cr filaments. Through the use of different thermomechanical processing routes or the addition of select dopants, alloys with strength in excess of 1 GPa at 70% IACS have been achieved. To date, previous research on Cu-Cr alloys has focused on a relatively small number of alloy compositions and processing methods while the effects of dopants and ageing treatments have only been studied independently. Consequently, there remains considerable opportunity for the development and optimization of these alloys as a leading high-strength, high-conductivity material.

  8. Effect of Zr on microstructures and mechanical properties of an Al-Mg-Si-Cu-Cr alloy prepared by low frequency electromagnetic casting

    SciTech Connect

    Meng, Yi Cui, Jianzhong; Zhao, Zhihao; He, Lizi

    2014-06-01

    The Al-1.6Mg-1.2Si-1.1Cu-0.15Cr (all in wt. %) alloys with and without Zr addition prepared by low frequency electromagnetic casting process were investigated by using the optical microscope, scanning electron microscope and transmission electron microscope equipped with energy dispersive analytical X-ray. The effects of Al{sub 3}Zr phases on the microstructures and mechanical properties during solidification, homogenization, hot extrusion and solid solution were studied. The results show that Al{sub 3}Zr phases reduce the grain size by ∼ 29% and promote the formation of an equiaxed grain structure during solidification. Numerous spherical Al{sub 3}Zr dispersoids with 35–60 nm in diameters precipitate during homogenization, and these fine dispersoids change little during subsequent hot extrusion and solid solution. Adding 0.15 wt. % Zr results in no recrystallization after hot extrusion and partial recrystallization after solid solution, while the recrystallized grain size is 400–550 μm in extrusion direction in the Zr-free alloy. In addition, adding 0.15 wt. % Zr can obviously promote Q′ phase precipitation, while the β″ phases are predominant in the alloy without Zr. Adding 0.15 wt. % Zr, the ultimate tensile strength of the T6 treated alloy increases by 45 MPa, while the elongation remains about 16.7%. - Highlights: • Minor Zr can refine as-cast grains of the LFEC Al-Mg-Si-Cu-Cr alloy. • L1{sub 2} Al{sub 3}Zr phases with 35–60 nm in diameter precipitate during homogenization. • L1{sub 2} and DO{sub 22} Al{sub 3}Zr phases result in partial recrystallization after solid solution. • Minor Zr can promote the precipitation of Q′ phases. • Mechanical properties of Al-Mg-Si-Cu-Cr-Zr alloy are higher than those of AA7005.

  9. Observations of a Cast Cu-Cr-Zr Alloy

    NASA Technical Reports Server (NTRS)

    Ellis, David L.

    2006-01-01

    Prior work has demonstrated that Cu-Cr-Nb alloys have considerable advantages over the copper alloys currently used in regeneratively cooled rocket engine liners. Observations indicated that Zr and Nb have similar chemical properties and form very similar compounds. Glazov and Zakharov et al. reported the presence of Cr2Zr in Cu-Cr-Zr alloys with up to 3.5 wt% Cr and Zr though Zeng et al. calculated that Cr2Zr could not exist in a ternary Cu-Cr-Zr alloy. A cast Cu-6.15 wt% Cr-5.25 wt% Zr alloy was examined to determine if the microstructure developed would be similar to GRCop-84 (Cu-6.65 wt% Cr-5.85 wt% Nb). It was observed that the Cu-Cr-Zr system did not form any Cr2Zr even after a thermal exposure at 875 C for 176.5 h. Instead the alloy consisted of three phases: Cu, Cu5Zr, and Cr.

  10. Photocatalytic reduction of Cr(VI) on the new hetero-system CuAl2O4/TiO2.

    PubMed

    Gherbi, R; Nasrallah, N; Amrane, A; Maachi, R; Trari, M

    2011-02-28

    Visible light driven HCrO(4)(-) reduction was successfully achieved over the new hetero-system CuAl(2)O(4)/TiO(2). The spinel, elaborated by nitrate route, was characterized photo electrochemically. The optical gap was found to be 1.70 eV and the transition is directly allowed. The conduction band (-1.05 V(SCE)) is located below that of TiO(2), more negative than the HCrO(4)(-)/Cr(3+) level (+0.58 V(SCE)) yielding a thermodynamically feasible chromate reduction upon visible illumination. CuAl(2)O(4) is stable against photo corrosion by holes consumption reaction involving salicylic acid which favors the charges separation. There is a direct correlation between the dark adsorption and the photo activity. A reduction of more than 95% of chromate was achieved after 3 h irradiation at pH 2 with an optimal mass ratio (CuAl(2)O(4)/TiO(2)) equal to 1/3. The reduction follows a first order kinetic with a half life of ∼1 h and a quantum yield of 0.11% under polychromatic light. Prolonged illumination was accompanied by a deceleration of the Cr(VI) reduction thanks to the competitive water discharge. The hydrogen evolution, an issue of energetic concern, took place with a rate of 3.75 cm(3) (g catalyst)(-1) h(-1). PMID:21177028

  11. The Mechanical and Corrosion Behaviors of As-cast and Re-melted AlCrCuFeMnNi Multi-Component High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

    Soare, Vasile; Mitrica, Dumitru; Constantin, Ionut; Popescu, Gabriela; Csaki, Ioana; Tarcolea, Mihai; Carcea, Ioan

    2015-04-01

    A multi-component AlCrCuFeMnNi high-entropy alloy, prepared by vacuum induction melting, was investigated for structural, mechanical, and corrosion characteristics, before and after the re-melting process. Optical microscopy analysis revealed a dendritic solidification behavior. The interdendritic area contains two main phases and occasionally small hard phases. The re-melting process produced a finer dendritic structure, with rounded dendrites and reduced interdendritic hard phases. The SEM-EDAX analysis showed that the dendrite region contains a Widmanstatten type of structure and are composed of Cr-Fe rich phases, whereas the interdendrite region contains Cu and Mn rich phases. XRD analysis revealed two disordered BCC type A2 structures with high Cr and Fe content and an FCC A12 type of structure for the Cu and Mn rich interdendritic phase. The lattice constants, determined by X-ray diffraction, are 2.87 and 2.91 Å for the A2 phases and 3.67 Å for A1 phase. The Vickers micro hardness increased with the homogeneity of the alloy, having a maximum value of 4370 MPa for the re-melted sample. Corrosion tests carried out in 3.5 wt pct sodium chloride aerated solution indicated that the corrosion resistance improved with the re-melting process, being 1.5 to 2 times better than that of 304 stainless steel.

  12. Structural transformation in nano-structured CuAl{sub x}Cr{sub x}Fe{sub 2-2x}O{sub 4} system

    SciTech Connect

    Mehta, D. K.; Chhantbar, M. C.; Joshi, H. H.

    2015-06-24

    Polycrystalline spinel ferrite system CuAl{sub x}Cr{sub x}Fe{sub 2-2x}O{sub 4} (x=0.2, 0.6) was synthesized by solid-state reaction route. Nanoparticles of the samples have been prepared by using high energy ball milling technique with different milling durations and characterized by X-ray Diffraction and Tunneling Electron Microscope. It is observed that the structural transformation occurred from Cubic to tetragonal and particle size varied between 29 nm -14 nm with increase of milling time.

  13. Catalytic properties of mixed oxides in the Nd-Mg-Cu-Cr-Al-O system in oxidation of carbon monoxide

    SciTech Connect

    Varlamov, V.I.; Komarov, V.S.

    1986-04-10

    Much attention is being devoted to effective catalysts for treatment of exhaust gases having improved activity and thermal and chemical stability. The authors study the influence of individual components of the Nd-Mg-Cu-Cr-Ar-O system on its catalytic properties in oxidation of carbon monoxide. The samples were prepared from analytical-grade neodymium oxalate and 1 M aqueous solutions of nitrates of the corrosponding metals. The compositions and certain physicochemical properties of the synthesized samples are presented with the results of x-ray diffraction and IR-spectroscopic investigations. The results show that formation of crystalline phases in the system is observed at 700 deg, and at 900 deg all samples had well-defined crystalline structure. The sample not containing iron oxide has high thermal stability.

  14. Observations Of A Cast Cu-Cr-Zr Alloy

    NASA Technical Reports Server (NTRS)

    Ellis, David L.

    2006-01-01

    The calculated phase diagram and observations of Zeng et al were confirmed. 1) Additional X-ray diffraction peaks for aged sample indicates possibility that additional metastable phases may form; 2) Cu5Zr was observed rather than the Cu9Zr2 proposed for the binary Cu-Zr phase diagram. Despite similarities between Zr and Nb, Cu-Cr-Zr does not appear to be a good candidate alloy system for rocket engine applications.

  15. Elevated-Temperature Corrosion of CoCrCuFeNiAl0.5Bx High-Entropy Alloys in Simulated Syngas Containing H2S

    SciTech Connect

    Dogan, Omer N; Nielsen, Benjamin C; Hawk, Jeffrey A

    2013-08-01

    High-entropy alloys are formed by synthesizing five or more principal elements in equimolar or near equimolar concentrations. Microstructure of the CoCrCuFeNiAl{sub 0.5}B{sub x} (x = 0, 0.2, 0.6, 1) high-entropy alloys under investigation is composed of a mixture of disordered bcc and fcc phases and borides. These alloys were tested gravimetrically for their corrosion resistance in simulated syngas containing 0, 0.01, 0.1, and 1 % H{sub 2}S at 500 °C. The exposed coupons were characterized using XRD and SEM. No significant corrosion was detected at 500 °C in syngas containing 0 and 0.01 % H{sub 2}S while significant corrosion was observed in syngas containing 0.1 and 1 % H{sub 2}S. Cu{sub 1.96}S was the primary sulfide in the external corrosion scale on the low-boron high-entropy alloys, whereas FeCo{sub 4}Ni{sub 4}S{sub 8} on the high-boron high-entropy alloys. Multi-phase Cu-rich regions in the low-B high-entropy alloys were vulnerable to corrosive attack.

  16. Microstructure and Tensile Behavior of Al8Co17Cr17Cu8Fe17Ni33 (at.%) High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

    Daoud, H. M.; Manzoni, A.; Völkl, R.; Wanderka, N.; Glatzel, U.

    2013-12-01

    Microstructure evolution and tensile behavior of the high-entropy alloy Al8Co17Cr17Cu8Fe17Ni33 (at.%) are investigated at room temperature and at 500°C in the as-cast state and under different heat-treatment conditions. Detailed microstructural characterizations are carried out using optical microscopy, scanning electron microscopy, and transmission electron microscopy. The equilibrium phase evolution as a function of temperature was calculated using the Thermo-Calc software (Thermo-Calc Software, Stockholm, Sweden) integrated with TTNi-7 database. The observed majority phase is a face-centered cubic solid solution for all tested specimens. Tensile ductility at room temperature and at elevated temperature is enhanced by heat treatment at 1150°C. An embrittlement phenomenon has been observed after a heat treatment at 700°C resulting in significant degradation in tensile properties.

  17. Synthesis and catalytic properties of mixed oxides in the Sr-Nd-Cu-Cr-Al-O system in oxidation of carbon monoxide

    SciTech Connect

    Komarov, V.S.; Varlamov, V.I.

    1986-05-10

    Much attention is being devoted to production of effective mixed oxide catalysts for treatment of exhaust gases. It was of interest in this connection to study the influence of the individual components of the Sr-Nd-Cu-Cr-Al-O system on the phase composition and catalytic properties of samples obtained from it. The test samples were prepared from analytical-grade neodymium oxalate and 1 M aqueous solutions of metal nitrates of the same purity grade. Weighed portions of the neodymium salt and of triammonium citrate were added n the required proportions to an a equimolar mixture of these solutions. The reaction mixture was evaporated on a water bath with periodic stirring until a resinous product was obtained; this was decomposed at its ignition temperature with the aid of an incandescent lamp. The resultant mass was powdered and heated in air at 700 and 900 for 6 h.

  18. Effects of temperature on serrated flows of Al0.5CoCrCuFeNi high-entropy alloy

    DOE PAGESBeta

    Chen, Shuying; Xie, Xie; Chen, Bilin; Qiao, Junwei; Zhang, Yong; Ren, Yang; Dahmen, Karin A.; Liaw, Peter K.

    2015-08-14

    Compression behavior of the Al0.5CoCrCuFeNi high-entropy alloy (HEA) was studied at different temperatures from 673K to 873K at a low strain rate of 5 x 10-5/s to investigate the temperature effect on the mechanical properties and serration behavior. The face-centered cubic (FCC) structure is confirmed at the lower temperature of 673 K and 773 K, and a structure of mixed FCC and body-centered cubic (BCC) is identified at a higher temperature of 873 K after compression tests using high-energy synchrotron X-ray diffraction. As a result, by comparing the stress-strain curves at different temperatures, two opposite directions of serrations types weremore » found, named upward serrations appearing at 673 K and 773 K and downward serrations at 873 K, which may be due to dynamic strain aging.« less

  19. Effects of temperature on serrated flows of Al0.5CoCrCuFeNi high-entropy alloy

    SciTech Connect

    Chen, Shuying; Xie, Xie; Chen, Bilin; Qiao, Junwei; Zhang, Yong; Ren, Yang; Dahmen, Karin A.; Liaw, Peter K.

    2015-08-14

    Compression behavior of the Al0.5CoCrCuFeNi high-entropy alloy (HEA) was studied at different temperatures from 673K to 873K at a low strain rate of 5 x 10-5/s to investigate the temperature effect on the mechanical properties and serration behavior. The face-centered cubic (FCC) structure is confirmed at the lower temperature of 673 K and 773 K, and a structure of mixed FCC and body-centered cubic (BCC) is identified at a higher temperature of 873 K after compression tests using high-energy synchrotron X-ray diffraction. As a result, by comparing the stress-strain curves at different temperatures, two opposite directions of serrations types were found, named upward serrations appearing at 673 K and 773 K and downward serrations at 873 K, which may be due to dynamic strain aging.

  20. Electrochemical and corrosion properties of YNi{sub 2.5}M{sub 0.5} (M = Ni, Al, Fe, Cr, Cu, Co, Mn) hybride-forming alloys

    SciTech Connect

    Korobov, I.I.; Vasina, S.Ya.; Petrii, O.A.

    1995-06-01

    Hydrogen sorption by electrode materials based on YNi{sub 2.5}M{sub 0.5} (M = Ni, Al, Fe, Cr, Co, Cu, Mn) intermetallic compounds (IMC) with Cu and PTFE binders is studied in 1 M NaOH solution. The obtained reversible electrochemical capacities correspond to YNi{sub 2.5}M{sub 0.5}H{sub 1.3-1.7} hybrides which are stable at room temperature and atmospheric pressure. The application of Cu binder allows one to more completely use the material sorption capacity and promotes both extraction and sorption of hydrogen by IMC.

  1. Spectroscopic studies of Lix FeP O4 and Lix M0.03 Fe0.97 P O4 (M=Cr,Cu,Al,Ti)

    NASA Astrophysics Data System (ADS)

    Gouveia, D. X.; Lemos, V.; de Paiva, J. A. C.; Souza Filho, A. G.; Mendes Filho, J.; Lala, S. M.; Montoro, L. A.; Rosolen, J. M.

    2005-07-01

    Mössbauer and Raman measurements for LixFePO4 and LixM0.03Fe0.97PO4 (M=Cr,Cu,Al,Ti) were performed. The results for the Li0.11FePO4 oxide require an unknown additional contribution, besides the high-spin Fe2+ doublet and the high-spin Fe3+ doublet, for the Mössbauer profile to be properly accounted for. The corresponding Raman scattering suggests a two-phase material and an additional disordered structure present in the mixture. The Mössbauer-transformed patterns indicate the unknown doublet to be due to a disordered phase also. In addition, the observation of a high amount of Fe2+ sites for the low-lithium-content LixM0.03Fe0.97PO4 oxides is analyzed on the basis of the electronic charge configuration of the Li-lacking octahedral units to suffer small changes upon lithium extraction.

  2. Fabrication of CuAl{sub 1−x}M{sub x}O{sub 2} (M = Fe, Cr)/Ni film delafossite compounds using spin coating and their microstructure and dielectric constant

    SciTech Connect

    Diantoro, Markus Yuwita, Pelangi Eka Olenka, Desyana Nasikhudin

    2014-09-25

    The discovery of delafossite compound has encouraged more rapid technological developments particularly in transparent electronic devices. Copper oxide-based transparent thin films delafossite semiconductor recently give much attention in the field of optoelectronic technology, after the discovery of p-type CuAlO{sub 2}. The potential applications of a p-type semiconductor transparent conductive oxides (TCO) have been applied in broad field of optoelectronics. To explore a broad physical properties interms of magnetic conducting subtitution is understudied. In this work we report the fabrication of delafossite film on Ni substrate and their characterization of CuAl{sub 1−x}M{sub x}O{sub 2} delafossite compounds doped with Cr{sup 3+} and Fe{sup 3+} from the raw material of Cu(NO{sub 3}){sub 2}@@‡3H{sub 2}O, Al(NO{sub 3}){sub 3}@@‡9H{sub 2}O, Fe(NO{sub 3}){sub 3}@@‡9H{sub 2}O and Cr(NO{sub 3}){sub 3}@@‡9H{sub 2}O. The films were prepared using spin coating through a sol-gel technique at various concentrations of x = 0, 0.03, 0.04, and 0.05 for chromium and x = 0, 0.02, 0.04, 0.06, and 0.08 for iron doped. Crystal and microstructure were characterized by means of Cu-Kα Bragg-Brentano X-RD followed by High Score Plus and SEM-EDAX. The dielectric constants of the films were characterized using LCR meter. It was found that the CuAl{sub 1−x}M{sub x}O{sub 2}/Ni delafossite films were successfully fabricated. The CuAl{sub 1−x}Fe{sub x}O{sub 2} compound crystallized with lattice parameters of a = b ranged from 2.8603 Å to 2.8675 Å and c ranged from 16.9576 to 17.0763 Å. The increase of the dopant give rise to the increase of the lattice parameters. Since iron has bigger ionic radius (69 pm) than original site of Al{sup 3+} with radius of 53 pm the crystal volume lattice also increase. Further analyses of increasing volume of the crystal, as expected, affected to the decreasing of its dielectric constant. The similar trends also shown by Cr{sup 3+} doped of

  3. Influence of W, Mo and Ti trace elements on the phase separation in Al8Co17Cr17Cu8Fe17Ni33 based high entropy alloy.

    PubMed

    Manzoni, Anna M; Daoud, Haneen M; Voelkl, Rainer; Glatzel, Uwe; Wanderka, Nelia

    2015-12-01

    Compositionally complex alloys, also called high entropy alloys, have been investigated for over a decade in view of different applications, but so far only a small number of alloys can be considered as presenting good enough properties for industrial application. The most common family of elements is Al-Co-Cr-Cu-Fe-Ni. The equiatomic alloy having 5 phases and being too brittle, the composition has been modified in order to improve the mechanical properties. Different compositions have been tested and as a first result ductile Al8Co17Cr17Cu8Fe17Ni33 has been chosen for deeper investigation. It shows a dendritic segregation into Co-Cr-Fe rich cores and Al-Cu-Ni rich interdendritic sites. The as-cast state is characterized mainly by two phases, namely Al-Cu-Ni rich precipitates of L12 structure inside a solid solution matrix. After homogenization both alloys consists of a single solid solution phase. Results are compared to calculations by ThermoCalc. In order to further improve the properties of the alloy the Cr content has been decreased and replaced by trace elements W, Mo and Ti, which, according to ThermoCalc, increase the melting point and the phase transition temperature which leads to the formation of the L12 phase. As-cast and heat treated samples of the base and the modified alloy have been investigated by transmission electron microscopy and three dimensional atom probe. Results of the investigations will be discussed in terms of microstructure, hardness and coherence with Thermo Calc predictions. PMID:26159736

  4. Annealing effect on the structural and magnetic properties of the CuAl{sub 0.6}Cr{sub 0.2}Fe{sub 1.2}O{sub 4} nano-ferrites

    SciTech Connect

    Amer, M.A.; Meaz, T.M.; Mostafa, A.G.; El-Ghazally, H.F.

    2015-07-15

    Graphical abstract: Mössbauer spectra of the as-prepared (AP) and annealed CuAl{sub 0.6}Cr{sub 0.2}Fe{sub 1.2}O{sub 4} samples. - Highlights: • As-prepared Cu–Al–Cr nano-ferrite samples were annealed at different temperatures T{sub A}. • Sample structure was transformed from cubic to tetragonal by JTE at 1000 °C. • Spontaneous and saturation magnetizations showed similar behavior against T{sub A}. • The deduced parameters showed dependence on T{sub A} and proved their affect by JTE. • Spontaneous magnetization proved dependence on crystallite size. - Abstract: Amounts of the as-synthesized CuAl{sub 0.6}Cr{sub 0.2}Fe{sub 1.2}O{sub 4} nanoparticles by the chemical co-precipitation method were annealed for 4 h at one of the temperatures T{sub A} = 300, 500, 600, 800 and 1000 °C for each. The techniques used for characterizing the samples were X-ray diffractions, infrared (IR) and Mössbauer spectroscopy and vibrating sample magnetometer. This study proved single-phase cubic structure of the samples annealed at T{sub A} ≤ 800 °C and tetragonal structure of the sample annealed at 1000 °C. The cubic-to-tetragonal structure transformation was attributed to the tetragonal distortion by Jahn–Teller effect (JTE) of Cu{sup 2+} ions. This study revealed that all deduced parameters were affected by JTE, whereas the crystallite size, lattice parameters, strain, threshold frequency, force constants, Debye temperature and stiffness constant were dependent on T{sub A}. IR absorption band positions and intensities were dependent on T{sub A} and proved the existence of Fe{sup 2+}, Fe{sup 4+} and Cr{sup 4+} ions in the crystal sublattices. The spontaneous and saturation magnetization and hyperfine magnetic field of the tetrahedral and octahedral sites were deduced and discussed as functions of T{sub A}.

  5. Precipitation in 9Ni-12Cr-2Cu maraging steels

    SciTech Connect

    Stiller, K.; Haettestrand, M.; Danoix, F.

    1998-11-02

    Two maraging steels with the compositions 9Ni-12Cr-2Cu-4Mo (wt%) and 9Ni-12Cr-2Cu and with small additions of Al and Ti were investigated using atom probe field ion microscopy. Tomographic atom probe investigations were performed to clarify the spatial distribution of elements in and close to the precipitates. Materials heat treated at 475 C for 5, 25 min, 1, 2, 4 and 400 h were analyzed. Precipitates in the Mo-rich material were observed already after 5 min of aging, while in the material without MO, precipitation started later. In both materials precipitation begins with the formation of Cu-rich particles which work as nucleation sites for a Ni-rich phase of type Ni{sub 3}(Ti,Al). A Mo-rich phase was detected in the Mo-rich steel after 2 h of aging. The distribution of alloying elements in the precipitates, their role in the precipitation process, and the mechanism of hardening in the two materials are discussed.

  6. On reversion phenomena in Cu-Zr-Cr alloys

    NASA Technical Reports Server (NTRS)

    Suzuki, H.; Kitano, H.; Kanno, M.

    1985-01-01

    Reversion phenomena in aged Cu-0.12% Zr-0.28% Cr alloy were investigated by means of resistivity measurement and transmission electron microscopy and compared with those of Cu-0.30% Zr and Cu-0.26% Cr alloys. Specimens in the form of a 0.5 mm sheet were solution-treated at 950 F for 1 hr water-quenched, aged, and finally reversed. The reversion phenomena were confirmed to exist in Cu-Zr and Cu-Zr-Cr alloys as well as Cu-Cr alloys, at aging temperatures of 300 to 500 F. The critical aging temperature for the reversion was not observed in all the alloys. Split aging increased the amount of reversion, particularly in Cu-Zr and Cu-Zr-Cr alloys, compared with that by conventional aging. The amount of reversion in Cu-Zr-Cr alloy was greatly affected by the resolution of Cr precipitate formed by preaging. Structural changes in Cu-Zr-Cr alloy due to the reversion were hardly observed by transmission electron microscopy.

  7. IR spectroscopic and thermal desorption studies of the interaction of the SO2 + O2 mixture with the 9% Ni-Cu-Cr/2% Ce/(θ + α)-Al2O3 catalyst

    NASA Astrophysics Data System (ADS)

    Dosumov, K.; Popova, N. M.; Umbetkaliev, A. K.; Brodskii, A. R.; Tungatarova, S. A.; Zheksenbaeva, Z. T.

    2012-10-01

    Data on the formation of surface structures during the adsorption of sulfur dioxide on alumina-supported metal and oxide catalysts in the presence of oxygen were reviewed. The results of our IR spectroscopic and thermal desorption studies of the interaction of the SO2+O2 mixture with the 9% Ni-Cu-Cr/2% Ce/(θ + α)-Al2O3 catalyst are presented. At 673 K chemisorption of SO2 takes place (absorption band 1165 cm-1, T {des/m} = 673 K), and SO2 is oxidized to form sulfate structures (absorption bands 1235, 1140, 1100, 985, and 615 cm-1, T {des/m} = 973 K), which decompose into SO2 and O2 at 973 K and decay when reduced in H2.

  8. The Influence of the Ion-Plasma Synthesis Regimes on the Features of Structural-Phase State of Multi-Component Nanocomposite Al-Cr-Si-Ti-Cu-N Coatings

    NASA Astrophysics Data System (ADS)

    Korotaev, A. D.; Ditenberg, I. A.; Berezovskaya, V. R.; Denisov, K. I.; Pinzhin, Yu. P.; Borisov, D. P.

    2015-02-01

    Within the concept of formation of multi-component, nanocomposite coatings, which assumes a simultaneous nucleation of islands of mutually insoluble or slightly-soluble phases under conditions of self-assembling microstructure during their synthesis, Al-Cr-Si-Ti-Cu-N coatings are designed and formed. Using the methods of X-ray diffraction analysis, scanning and transmission electron microscopy, a comprehensive investigation is performed of the influence of the operating modes of an ion-plasma synthesis of the resulting coatings on the features of their microstructure, microhardness, and elemental and phase composition. The procedures for optimization of the regimes of formation of multi-component, nanocomposite coatings of the above system are discussed.

  9. Evaluation of Ti-Cr-Cu alloys for dental applications

    NASA Astrophysics Data System (ADS)

    Koike, Marie; Okabe, Toru; Itoh, Masayuki; Okuno, Osamu; Kimura, Kohei; Takeda, Osamu; Okabe, Toru H.

    2005-12-01

    This study examined the characteristics of as-cast Ti-Cr(7 19%)-Cu(3 7%) (all percentages in this article are mass%) alloys to evaluate their suitability for dental applications; studies on the alloy structures and mechanical properties, grindability, and corrosion behavior were included in the investigation. The alloys were centrifugally cast and bench-cooled in investment molds. The x-ray diffractometry of the as-cast alloys bench-cooled in the molds indicated the following phases: α+β+ω in the 7% Cr and 7% Cr+3% Cu; β+ω in the 13%Cr; and β in the 13%Cr+3% Cu through the 19%Cr+3% Cu alloys. The strengths of the binary β Ti-Cr and ternary β Ti-Cr-Cu alloys with 13 and 19% Cr were approximately two times higher than those of CP Ti. The alloy ductility was dependent on the chemical composition and thus, the microstructure. The 7% Cr alloys were extremely brittle and hard due to the ω phase, but the ductility was restored in the 13 and 19% Cr alloys. The hardness (HV) of the cast 13 and 19% Cr alloys was approximately 300 350 compared with a value of 200 for CP Ti. The grindability of the cast alloys was examined using a rotating SiC wheel at speeds (circumferential) of 500 and 1250 m/min. At the higher speed, the grindability of the 13 and 19% Cr alloys increased with the Cu content. The grindability of the 13% Cr alloy with 7% Cu was similar to that of CP Ti. Evaluation of the corrosion behavior in an artificial saliva revealed that the alloys are like many other titanium alloys within the normal intraoral oxidation potential. The wear resistance testing of these alloys also showed favorable results.

  10. Mechanical Properties of Cu-Cr-Nb Alloys

    NASA Technical Reports Server (NTRS)

    Ellis, David L.

    1997-01-01

    The chemical compositions of the alloys are listed. The alloying levels were near the values for stochiometric Cr2Nb. A slight excess of Cr was chosen for increased hydrogen embrittlement resistance. The microstructures of all Cu-Cr-Nb alloys were very similar. Two typical transmission electron microscope (TEM) micrographs are presented. The images show the presence of large mount of Cr2Nb precipitates in a nearly pure Cu matrix. The interactions between dislocations and precipitates are currently under investigations, but as the images demonstrates, the extremely fine (less then 15 nm) Cr2Nb are the primary strengtheners for the alloy.

  11. K-italic-shell ionization cross sections for Al, Ti, V, Cr, Fe, Ni, Cu, and Ag by protons and oxygen ions in the energy range 0. 3--6. 4 MeV

    SciTech Connect

    Geretschlaeger, M.; Benka, O.

    1986-08-01

    Absolute K-italic-shell ionization cross sections have been measured for thin targets of Al, Ti, and Cu for protons in the energy range 0.3--2.0 MeV and for thin targets of Ti, V, Cr, Fe, Ni, Cu, and Ag for oxygen ions in the energy range 1.36--6.4 Mev. The experimental results are compared to the perturbed-stationary-state (PSS) approximation with energy-loss (E), Coulomb (C), and relativistic (R) corrections, i.e., the ECPSSR approximation (Brandt and Lapicki), to the semiclassical approximation (Laegsgaard, Andersen, and Lund), and to a theory for direct Coulomb ionization of the 1s-italicsigma molecular orbital (Montenegro and Sigaud (MS)). The proton results agree within 3% with empirical reference cross sections. Also, the ECPSSR provides best overall agreement for protons. For oxygen ions, ECPSSR and MS predict experimental results satisfactorily for scaled velocities xi> or =0.4. For lower scaled velocities, the experimental cross sections become considerably higher than theoretical predictions for Coulomb ionization. This deviation increases with increasing Z-italic/sub 1//Z/sub 2/; it cannot be explained by electron transfer to the projectile or by ionization due to target recoil atoms.

  12. Interfacial Phenomena in Al/Al, Al/Cu, and Cu/Cu Joints Soldered Using an Al-Zn Alloy with Ag or Cu Additions

    NASA Astrophysics Data System (ADS)

    Pstruś, Janusz; Gancarz, Tomasz

    2014-05-01

    The studies of soldered joints were carried out in systems: Al/solder/Al, Al/solder/Cu, Cu/solder/Cu, where the solder was (Al-Zn)EUT, (Al-Zn)EUT with 0.5, 1.0, and 1.5 at.% of Ag and (Al-Zn)EUT with 0.5, 1.0, and 1.5 at.% of Cu addition. Brazing was performed at 500 °C for 3 min. The EDS analysis indicated that the composition of the layers starting from the Cu pad was CuZn, Cu5Zn8, and CuZn4, respectively. Wetting tests were performed at 500 °C for 3, 8, 15, and 30 min, respectively. Thickness of the layers and their kinetics of growth were measured based on the SEM micrographs. The formation of interlayers was not observed from the side of Al pads. On the contrary, dissolution of the Al substrate and migration of Al-rich particles into the bulk of the solder were observed.

  13. Structural and magnetic properties of Cu Ni Cr spinel oxides

    NASA Astrophysics Data System (ADS)

    Tovar, M.; Torabi, R.; Welker, C.; Fleischer, F.

    2006-11-01

    The compounds CuCr 2O 4 and NiCr 2O 4 crystallize at room temperature in a tetragonal distorted spinel structure, s.g. I4 1/amd, with axes ratio c/ a<1 and >1, respectively. The distortion is caused by the Jahn-Teller ions Cu 2+ and Ni 2+ which flatten or elongate their surrounding oxygen tetrahedron. CuCr 2O 4 and NiCr 2O 4 form a complete solid solution series Cu 1-xNi xCr 2O 4 where for 0.825< x<0.875 members with orthorhombic symmetry were found. Using neutron powder diffraction and thermal analysis methods several members of the solid solution series were investigated. On cooling, all samples showed a temperature-dependent crystallographic phase transition from cubic to tetragonal symmetry between 865 K (CuCr 2O 4) and 310 K (NiCr 2O 4). The phase Cu 0.15Ni 0.85Cr 2O 4 undergoes a second crystallographic transition to orthorhombic symmetry, space group Fddd, at T=300 K. The neutron diffraction experiments as well as SQUID measurements reveal magnetic ordering of the ions between 150 and 50 K which partially occurs as a two-step mechanism.

  14. Polyoxometalate-supported transition metal complexes and their charge complementarity: synthesis and characterization of [M(OH)6Mo6O18[Cu(Phen)(H2O)2]2][M(OH)6Mo6O18[Cu(Phen)(H2O)Cl]2].5H2O (M = Al(+, Cr3+).

    PubMed

    Shivaiah, Vaddypally; Das, Samar K

    2005-11-28

    Two Anderson-type heteropolyanion-supported copper phenanthroline complexes, [Al(OH)6Mo6O18[Cu(phen)(H2O)2]2]1+ (1c) and [Al(OH)6Mo6O18[Cu(phen)(H2O)Cl]2]1- (1a) complement their charges in one of the title compounds [Al(OH)6Mo6O18[Cu(phen)(H2O)2]2][Al(OH)6Mo6O18[Cu(phen)(H2O)Cl]2].5H2O [1c][1a].5 H2O 1. Similar charge complementarity exists in the chromium analogue, [Cr(OH)6Mo6O18[Cu(phen)(H2O)2]2][Cr(OH)6Mo6O18[Cu(phen)(H2O)Cl]2].5 H2O [2c][2a].5 H2O 2. The chloride coordination to copper centers of 1a and 2a makes the charge difference. In both compounds, the geometries around copper centers are distorted square pyramidal and those around aluminum/chromium centers are distorted octahedral. Three lattice waters, from the formation of intermolecular O-H.....O hydrogen bonds, have been shown to self-assemble into an "acyclic water trimer" in the crystals of both 1 and 2. The title compounds have been synthesized in a simple one pot aqueous wet-synthesis consisting of aluminum/chromium chloride, sodium molybdate, copper nitrate, phenanthroline, and hydrochloric acid, and characterized by elemental analyses, EDAX, IR, diffuse reflectance, EPR, TGA, and single-crystal X-ray diffraction. Both compounds crystallize in the triclinic space group P. Crystal data for 1: a = 10.7618(6), b = 15.0238(8), c = 15.6648(8) angstroms, alpha = 65.4570(10), beta = 83.4420(10), gamma = 71.3230(10), V = 2182.1(2) angstroms3. Crystal data for 2: a = 10.8867(5), b = 15.2504(7), c = 15.7022(7) angstroms, alpha = 64.9850(10), beta = 83.0430(10), gamma = 71.1570(10), V = 2235.47(18) angstroms3. In the electronic reflectance spectra, compounds 1 and 2 exhibit a broad d-d band at approximately 700 nm, which is a considerable shift with respect to the value of 650-660 nm for a square-pyramidal [Cu(phen)2L] complex, indicating the coordination of [M(OH)6Mo6O18]3- POM anions (as a ligand) to the monophenanthroline copper complexes to form POM-supported copper complexes 1c, 1a, 2c, and 2a. The

  15. Mesoporous delafossite CuCrO2 and spinel CuCr2O4: synthesis and catalysis

    NASA Astrophysics Data System (ADS)

    Zhang, Peng; Shi, Yifeng; Chi, Miaofang; Park, Jung-Nam; Stucky, Galen D.; McFarland, Eric W.; Gao, Lian

    2013-08-01

    Delafossite CuCrO2 and spinel CuCr2O4 with mesoporous structures have been successfully synthesized using nanocasting methods based on a KIT-6 template. The functional activity of the mesoporous materials was evaluated in applications as heterogeneous catalysts. The activity for photocatalytic hydrogen production of the delafossite structures with different morphologies was characterized and the oxidation state changes associated with photocorrosion of Cu+ investigated using electron energy loss spectroscopy (EELS). Mg2+ doping was found to facilitate the casting of ordered structures for CuCrO2 and improves the photocorrosion resistance of delafossite structures. The mesoporous spinel CuCr2O4 nanostructures were found to be active for low temperature CO oxidation.

  16. Uptake of Al, As, Cr, Cd, Cu, Fe, Mn, Ni, Pb, Sr, and Zn in native wheatgrasses, wildryes, and bluegrass on three metal-contaminated soils from Montana

    Technology Transfer Automated Retrieval System (TEKTRAN)

    One of the biggest challenges to successfully phytoremediate contaminated mineland soils is the identification of native plants that possess a broad adaptation to ecological sites and either exclude or uptake heavy metals of interest. This study evaluated forage concentrations of aluminum (Al), ars...

  17. Ferromagnetic Fe2CrAl Nanowires

    NASA Astrophysics Data System (ADS)

    Dulal, Rajendra; Dahal, Bishnu; Pegg, Ian L.; Philip, John

    Heusler alloy Fe2CrAl (FCA) nanowires were grown on silicon substrates. Nanowires have diameters in the range 50 to 200 nm and lengths up to 100 µm. They exhibit cubic L21 and A2 type structure with a space group, Pm m. Magnetic characterization reveals that they display ferromagnetic behavior and has a Curie temperature above 400 K. Magnetic behavior of FCA nanowires is different from the reported bulk behavior. Bulk FCA with L21 structure has a Curie temperature around 274 K. National Science Foundation under ECCS-0845501 and NSF-MRI, DMR-0922997.

  18. Creep and Toughness of Cryomilled NiAl Containing Cr

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Aikin, Beverly; Salem, Jon

    2000-01-01

    NiAl-AlN + Cr composites were produced by blending cryomilled NiAl powder with approx. 10 vol % Cr flakes. In comparison to the as-consolidated matrices, hot isostatically pressed Cr-modified materials did not demonstrate any significant improvement in toughness. Hot extruded NiAl-AlN+10.5Cr, however, possessed a toughness twice that determine for the base NiAl-AlN alloy. Measurement of the 1200 to 1400 K plastic flow properties revealed that the strength of the composites was completely controlled by the properties of the NiAl-AlN matrices. This behavior could be successfully modeled by the Rule-of-Mixtures, where load is shed from the weak Cr to the strong matrix.

  19. Structure, Magnetism, and Transport of CuCr2Se4 Thin Films

    SciTech Connect

    Bettinger, J.S.; Chopdekar, R.V.; Liberati, M.; Neulinger, J.R.; Chshiev, M.; Takamura, Y.; Alldredge, L.M.B.; Arenholz, E.; Idzerda,Y.U.; Stacy, A.M.; Butler, W.H.; Suzuki, Y.

    2007-04-01

    We report the successful growth of highly spin-polarized chalcogenide thin films of CuCr{sub 2}Se{sub 4}, which are promising candidates for spin-based electronic applications. We also present electronic structure calculations for CuCr{sub 2}Se{sub 4} that, together with magnetic and transport data, imply that the stoichiometric compound is a metallic ferromagnet with a relatively low density of hole-like carriers at the Fermi energy. These calculations also predict that a deficiency of Se will deplete the minority density of states at the Fermi energy perhaps leading to a half-metal. We have successfully grown thin films of CuCr{sub 2}Se{sub 4} by pulsed laser deposition on isostructural MgAl{sub 2}O{sub 4} substrates followed by an anneal in a Se-rich environment. X-ray diffraction confirms the structure of CuCr{sub 2}Se{sub 4} on MgAl{sub 2}O{sub 4} substrates as well as a secondary phase of Cr{sub 2}Se{sub 3}. X-ray absorption spectroscopy indicates that the chemical structure at the surface of the films is similar to that of bulk CuCr{sub 2}Se{sub 4} single crystals. Magnetization measurements indicate that these films saturate with a magnetic moment close to 5 {micro}{sub B} per formula unit and a T{sub c} above 400 K. X-ray magnetic circular dichroism shows that the magnetism persists to the surface of the film. Resistivity and Hall effect measurements are consistent with a p-type ferromagnetic metallic behavior and with the electronic structure calculations.

  20. Thermomechanical Processing and Roll Bonding of Tri-Layered Cu-Ni-Zn/Cu-Cr/Cu-Ni-Zn Composite

    NASA Astrophysics Data System (ADS)

    Kim, Hobyung; Kang, Gyeong Tae; Hong, Sun Ig

    2016-05-01

    Tri-layered Cu-Ni-Zn/Cu-Cr/Cu-Ni-Zn composite was processed by roll bonding and the effect of thermomechanical processing on the mechanical performance and electrical conductivity was studied. Roll-bonded composite exhibited the brief work hardening and subsequent rapid work softening because of the high stored deformation energy, leading to failure at the plastic strain of 8 to 10 pct. The mechanical instability of as-roll-bonded composites was abated by heat treatment (HT) at 723 K (450 °C) and the extended work hardening with enhanced ductility compared to that of the as-roll-bonded composites was observed after HT. The strength and electrical conductivity of clad composite is dependent on the precipitation strengthening of Cu-Cr and recovery softening of Cu-Ni-Zn during post-roll-bonding HT. The increase of roll-bonding temperature enhances the precipitation kinetics and it takes shorter time to reach maximum hardness in Cu-Cr layer during post-roll-bonding HT. The toughness of as-roll-bonded Cu-Ni-Zn/Cu-Cr/Cu-Ni-Zn clad composite at 773 K (500 °C) [42 MJ/mm3] is greater than those at 723 K (450 °C) [24 MJ/mm3] and 823 K (550 °C) [38 MJ/mm3]. The maximum toughness [100 MJ/mm3] with the electrical conductivity of 68 pct IACS was obtained in the Cu-Ni-Zn/Cu-Cr/Cu-Ni-Zn clad composite roll-bonded at 773 K (500 °C) and subsequently heat-treated at 723 K (450 °C).

  1. Magnetic resonance in a gallium-doped Cu-Cr-S structure

    NASA Astrophysics Data System (ADS)

    Vorotynov, A. M.; Pankrats, A. I.; Abramova, G. M.; Velikanov, D. A.; Bovina, A. F.; Sokolov, V. V.; Filatova, I. Yu.

    2016-04-01

    A layered Cu-Cr-S structure doped with Ga ions and consisting of single-crystal CuCrS2 layers, embedded with thin plates of spinel phases CuCr2S4 and CuGa x Cr2- x S4, has been studied using the magnetic resonance and magnetic susceptibility methods. The Curie temperature and the saturation magnetization of the spinel phases of the samples have been determined. The spinel phase layer thickness has been estimated.

  2. Thermoelectric Properties of CuAgSe doped with Co, Cr

    NASA Astrophysics Data System (ADS)

    Czajka, Peter; Yao, Mengliang; Opeil, Cyril

    Thermoelectric materials represent one way that reliable cooling below the boiling point of nitrogen can be realized. Current materials do not exhibit sufficiently high efficiencies at cryogenic temperatures, but significant progress is being made. One material that has generated significant interest recently is CuAgSe. It has been demonstrated (Ishiwata et al., Nature Mater. 2013) that doping CuAgSe with 10% Ni at the Cu sites increases the material's thermoelectric figure of merit (ZT) at 100 K from 0.02 to 0.10. This is intriguing not just because of the dramatic effect that the Ni doping produces, but also because CuAgSe is a semimetal and semimetals are not usually able to exhibit the kind of asymmetric carrier activation necessary for strong thermoelectric performance. In order to further investigate the unusual nature of thermoelectricity in CuAgSe and its strong dependence on chemical composition, we have synthesized and measured the thermoelectric properties of a series of CuAgSe samples doped with Co and Cr. Temperature-dependent magnetic and thermoelectric transport properties of CuAgSe as a function of Co and Cr doping will be discussed. This work is supported by the Department of Defense, AFOSR, MURI Program Contract # FA9550-10-1-0533 and the Trustees of Boston College.

  3. Preparation of Al-Cr-Fe Coatings by Heat Treatment of Electrodeposited Cr/Al Composite Coatings

    NASA Astrophysics Data System (ADS)

    Zhang, Min; Chen, Chang'an; Zhang, Guikai; Rao, Yongchu; Ling, Guoping

    Al-Cr-Fe coatings have been widely used in the surface engineering field of materials, due to their excellent corrosion resistance to water vapor and fused salt deposits. In this study, a new two-step approach was developed to prepare Al-Cr-Fe coatings on surfaces of SUS430 stainless steels. First, the Cr/Al composite coatings were prepared by electrodepositing Cr from aqueous solution then electrodepositing Al from AlCl3-1-ethyl-3-methyl-imidazolium chloride (AlCl3-EMIC) ionic liquid on SUS430 stainless steel substrate. In the second, heat treatment of the Cr/Al composite coatings was carried out to acquire Al-Cr-Fe coatings. Effects of the thickness of Cr/Al composite coatings, the time and temperature of heat treatment on composition and phase structure of alloy layers were studied by using scanning electron microscope (SEM), backscattered electron (BSE), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The structure transformation process and formation mechanism of Al-Cr-Fe coatings were discussed.

  4. Mechanical and Thermal Properties of Two Cu-Cr-Nb Alloys and NARloy-Z

    NASA Technical Reports Server (NTRS)

    Ellis, David L.; Michal, Gary M.

    1996-01-01

    A series of creep tests were conducted on Cu-8 Cr-4 Nb (Cu-8 at.% Cr-4 at.% Nb), Cu-4 Cr-2 Nb (Cu-4 at.% Cr-2 at% Nb), and NARloy-Z (Cu-3 wt.% Ag-0.5 wt.% Zr) samples to determine their creep properties. In addition, a limited number of low cycle fatigue and thermal conductivity tests were conducted. The Cu-Cr-Nb alloys showed a clear advantage in creep life and sustainable load over the currently used NARloy-Z. Increases in life at a given stress were between 100% and 250% greater for the Cu-Cr-Nb alloys depending on the stress and temperature. For a given life, the Cu-Cr-Nb alloys could support a stress between 60% and 160% greater than NARloy-Z. Low cycle fatigue lives of the Cu-8 Cr-4 Nb alloy were equivalent to NARloy-Z at room temperature. At elevated temperatures (538 C and 650 C), the fatigue lives were 50% to 200% longer than NARloy-Z samples tested at 538 C. The thermal conductivities of the Cu-Cr-Nb alloys remained high, but were lower than NARloy-Z and pure Cu. The Cu-Cr-Nb thermal conductivities were between 72% and 96% that of pure Cu with the Cu-4 Cr-2 Nb alloy having a significant advantage in thermal conductivity over Cu-8 Cr4 Nb. In comparison, stainless steels with equivalent strengths would have thermal conductivities less than 25% the thermal conductivity of pure Cu. The combined results indicate that the Cu-Cr-Nb alloys offer an attractive alternative to current high temperature Cu-based alloys such as NARloy-Z.

  5. Room Temperature Radiolytic Synthesized Cu@CuAlO2-Al2O3 Nanoparticles

    PubMed Central

    Abedini, Alam; Saion, Elias; Larki, Farhad; Zakaria, Azmi; Noroozi, Monir; Soltani, Nayereh

    2012-01-01

    Colloidal Cu@CuAlO2-Al2O3 bimetallic nanoparticles were prepared by a gamma irradiation method in an aqueous system in the presence of polyvinyl pyrrolidone (PVP) and isopropanol respectively as a colloidal stabilizer and scavenger of hydrogen and hydroxyl radicals. The gamma irradiation was carried out in a 60Co gamma source chamber with different doses up to 120 kGy. The formation of Cu@CuAlO2-Al2O3 nanoparticles was observed initially by the change in color of the colloidal samples from colorless to brown. Fourier transform infrared spectroscopy (FTIR) confirmed the presence of bonds between polymer chains and the metal surface at all radiation doses. Results of transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDX), and X-ray diffraction (XRD) showed that Cu@CuAlO2-Al2O3 nanoparticles are in a core-shell structure. By controlling the absorbed dose and precursor concentration, nanoclusters with different particle sizes were obtained. The average particle diameter increased with increased precursor concentration and decreased with increased dose. This is due to the competition between nucleation, growth, and aggregation processes in the formation of nanoclusters during irradiation. PMID:23109893

  6. Electronic structure, magnetism and stability of Co2CrX (X =Al, Ga, In) ab initio study

    NASA Astrophysics Data System (ADS)

    Dahmane, F.; Mesri, D.; Tadjer, A.; Khenata, R.; Benalia, S.; Djoudi, L.; Doumi, B.; Boumia, L.; Aourag, H.

    2016-01-01

    The structural, electronic as well as the magnetic properties of the Co2CrX (X =Al, Ga and In) full-Heusler alloy have been studied using first-principles calculations performed in the framework of density functional theory (DFT) within the generalized gradient approximation (GGA). It was taken into account both possible L21 structures (i.e. Hg2CuTi- and Cu2MnAl-type). Basically, for all compounds, the Cu2MnAl-type structure is energetically more stable than Hg2CuTi-type structure at the equilibrium volume. The electronic structure calculations for Co2CrAl reveal that half-metallic (HM) character in Cu2MnAl-type structure, Co2CrGa show nearly HM behavior and Co2CrIn has a metallic character. The predicted total magnetic moment is 3μB for Co2CrX (X =Al, Ga) which is in good convergence with the Slater-Pauling (SP) rule.

  7. High temperature coarsening of Cr2Nb precipitates in Cu-8 Cr-4 Nb alloy

    NASA Technical Reports Server (NTRS)

    Anderson, Kenneth Reed

    1996-01-01

    A new high-temperature-strength, high-conductivity Cu-Cr-Nb alloy with a CrNb ratio of 2:1 was developed to achieve improved performance and durability. The Cu-8 Cr4 Nb alloy studied has demonstrated remarkable thermal and microstructural stability after long exposures at temperatures up to 0.98 T(sub m). This stability was mainly attributed to the slow coarsening kinetics of the Cr2Nb precipitates present in the alloy. At all temperatures, the microstructure consists of a bimodal and sometimes trimodal distribution of strengthening Cr2Nb precipitates, depending on precipitation condition, i.e. from liquid or solid solution, and cooling rates. These precipitates remain in the same size range, i.e. large precipitates of approximately I pm, and small precipitates less dm 300 nm, and effectively pin the grain boundaries thus retaining a fine grain size of 2.7 micro-m after 100 h at 1323 K. (A relatively small number of Cr-rich and Nb-rich particles were also present.) This grain boundary pinning and sluggish coarsening of Cr2Nb particles explain the retention of good mechanical properties after prolonged holding at very high temperatures, e.g., 75% of the original hardness after aging for 100 h at 1273 K. Application of LSW-based coarsening models indicated that the coarsening kinetics of the large precipitates are most likely governed by grain boundary diffsion and, to a lesser extent, volume diffusion mechanisms.

  8. Ductile Chromium in Heavily Cold-Drawn Cu75Cr25 Alloy

    NASA Astrophysics Data System (ADS)

    Chang, Yanli; Zhou, Zhiming; Guo, Ziqin; Wang, Yaping

    2016-01-01

    Microstructure evolution, gas content, and properties of the heavily cold-drawn Cu75Cr25 alloy were studied. Results showed that the oxygen and nitrogen contents of Cu75Cr25 alloy prepared by vacuum induction melting in calcia crucibles were low, about 320 and 20 ppm, respectively. The Cu75Cr25 material with low gas content can be cold drawn to lines with diameter less than 0.1 mm, in which Cr phase displays thin and curving morphology. The coherent interface, forming between Cu(111) and Cr(110) during the heavily cold-drawing process, constrained Cr phase and greatly improved its deformability as well as increased the strength of the Cu-Cr alloy. The breaking strength and electrical conductivity of the Cu75Cr25 alloy were about 577 MPa and 60 pct IACS, respectively.

  9. Thermal fatigue damage of Cu-Cr-Zr alloys

    NASA Astrophysics Data System (ADS)

    Chatterjee, Arya; Mitra, R.; Chakraborty, A. K.; Rotti, C.; Ray, K. K.

    2013-11-01

    The primary aim of this investigation is to examine thermal fatigue damage (TFD) in Cu-Cr-Zr alloys used in High Heat Flux components of Tokamak and its subsystems. Thermal fatigue experiments have been carried out between 290 °C and 30 °C, which is analogous to the condition of service application on two Cu-Cr-Zr alloys having different aging treatments. The extents of TFD have been examined by standard measurements of electrical conductivity, lattice strain, residual stress and dynamic elastic modulus, supplemented by characterizations of microstructure and determination of hardness and tensile properties. The results lead to infer that the relative amounts of damage are different in the two alloys which are further dependent on their aging conditions; the reasons for the observed difference have been explained. The operative mechanisms of TFD are revealed to be as formation and subsequent coalescence of microvoids, and/or initiation and growth of microcracks.

  10. Hot Corrosion Performance of AlO-CrO/NiCoCrAlYTa and AlO/NiCoCrAlYTa Coatings Deposited by Atmospheric Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Tao, Chong; Wang, Lei; Cheng, Nailiang; Hu, Hengfa; Liu, Yang; Song, Xiu

    2016-04-01

    AlO-CrO/NiCoCrAlYTa and AlO/NiCoCrAlYTa coatings were deposited on 316L stainless steel substrate using atmospheric plasma spraying, respectively, in order to improve the oxidation and corrosion resistance. The hot corrosion performance of the coatings at 700 and 900 °C were studied, and the detailed microstructures and phase composition of the coatings were analyzed using x-ray diffraction, scanning electron microscope with energy dispersive spectrometer, and transmission electron microscope. The results show that both coatings are structurally featured by slatted layers, consisting of amorphous phase, Cr2O3, Ni3Al, and Al2O3. The hot corrosion resistance of AlO-CrO/NiCoCrAlYTa coating is better than that of AlO/NiCoCrAlYTa coating. This improvement is attributed to lower porosity and more compact Cr2O3 in AlO-CrO/NiCoCrAlYTa coating which performs better than Al2O3 in blocking further inward progress of corrosion and oxidization.

  11. Adsorption and desorption of Zn, Cu, and Cr by sediments from the Raisi River (Michigan)

    SciTech Connect

    Young, T.C.; DePinto, J.V.; Kipp, T.W.

    1987-01-01

    Metal adsorption by Raisin River sediments in vitro depended linearly on soluble metal concentration to adsorption densities of 6,000-9,000 microg/g with 48 hr partition coefficients of approximately 50, 30, and 25 L/g for Cu, Cr, and Zn, respectively. Partition coefficients computed from field data spanned a comparatively wider range of values in a manner consistent with the often reported adsorbent concentration effect, but other factors likely contributed, too. Desorption of Zn was complete and rapid (24-48 hr) in contrast to Cr, which was incomplete and much slower; Cu desorption was intermediate to Zn and Cr. A reversible-resistant equilibrium model (DiToro et al. 1986) could not describe the observations as Cu and Cr had not reached metastable desorption equilibria after 24 days. Metal desorption, however, could be described kinetically by distributing sorbed cations between either of two classes; rapidly desorbing and slowly desorbing cations. Sequential and simultaneous desorption models gave similar predictions. Aqueous chemical considerations suggested precipitated as well as adsorbed species could give rise to the observations, but available data did not permit adequate tests of this hypothesis. The extent to which kinetic constraints rather than irreversible reactions account for the desorption-resistant binding signifies a potentially greater metal mobility or bioavailability than would otherwise be assumed.

  12. Preparation and Performance of Cu-Cr Contact Materials for Vacuum Switches with Low Contact Pressure

    NASA Astrophysics Data System (ADS)

    Chang, Yanli; Zheng, Wei; Zhou, Zhiming; Zhai, Yuxiang; Wang, Yaping

    2016-07-01

    Insufficient anti-welding properties limit the application of Cu-Cr contact material in vacuum switches with low contact pressure. The CuCr-W-C alloys that are prepared are for decreasing welding tendencies and keeping the voltage withstand by addition of W and C elements. It is found that the average welding force of CuCr-W-C alloys is reduced more than 50% compared with that of the Cu50 Cr50 alloy. Especially for CuCrW3.0C0.3 and CuCrW1.0C0.5, the welding forces reduce to only 10% of Cu50Cr50. Arc erosion areas of CuCr-W-C alloys are enlarged by five times more than that of the Cu50Cr50 alloy in the same arcing conditions. The results of type tests were qualified. The results suggested that the CuCrW2.0C1.0 alloy could be used in vacuum switches with low contact pressure to replace the W-Cu type contacts.

  13. Enhanced Magnetization of CuCr2O4 Thin Films by Substrate-Induced Strain

    SciTech Connect

    Iwata, Jodi M.; Chopdekar, Rajesh V.; Wong, Franklin; Nelson-Cheeseman, Brittany B.; Arenholz, Elke; Suzuki, Yuri

    2008-09-17

    We report the synthesis of epitaxial spinel CuCr{sub 2}O{sub 4} thin films that display enhanced magnetization in excess of 200% of the bulk values when grown on single-crystal (110) MgAl{sub 2}O{sub 4} substrates. Bulk CuCr{sub 2}O{sub 4} is a ferrimagnetic insulator with a net magnetic moment of 0.5 {micro}{sub B} due to its distorted tetragonal unit cell (c/a= 1.29) and frustrated triangular moment configuration. We show that through epitaxial growth and substrate-induced strain, it is possible to tune the magnetic functionality of our films by reducing the tetragonal distortion of the unit cell which effectively decreases the frustration of the magnetic moments allowing for an overall greater net moment.

  14. Relaxor-like dielectric response of spin liquid CuCrO{sub 2}

    SciTech Connect

    Mazumder, N. Roy, R.; Ghorai, U. K.; Saha, S.; Chattopadhyay, K. K.

    2014-04-24

    Broadband dielectric analysis (10{sup −2}-10{sup 7} Hz) of layered triangular lattice CuCrO{sub 2} is performed (123 K - 473 K) and analyzed in connection with recently observed spin frustration in this multiferroic [M. Poienar et al. Phys. Rev. B 81, 104411, (2010); M. Frontzek et al. Phys. Rev. B 84, 094448, (2011)]. Most unexpectedly, this well known delafossite has found to have nontrivial charge degrees of freedom, being characterized by a relaxor-like dielectric relaxation around 375 K with FWHM of ∼100K. The result strongly suggests the existence of intermolecular Coulomb interaction between charge disproportionation induced electric dipoles.

  15. Ti-Cr-Al-O Thin Film Resistors

    SciTech Connect

    Jankowski, A F; Hayes, J P

    2002-03-21

    Thin films of Ti-Cr-Al-O are produced for use as an electrical resistor material. The films are rf sputter deposited from ceramic targets using a reactive working gas mixture of Ar and O{sub 2}. Vertical resistivity values from 10{sup 4} to 10{sup 10} Ohm-cm are measured for Ti-Cr-Al-O films. The film resistivity can be design selected through control of the target composition and the deposition parameters. The Ti-Cr-Al-O thin film resistor is found to be thermally stable unlike other metal-oxide films.

  16. Oxidation of Fe-Cr-Al and Fe-Cr-Al-Y Single Crystals

    NASA Astrophysics Data System (ADS)

    Grabke, H. J.; Siegers, M.; Tolpygo, V. K.

    1995-03-01

    Single crystal samples of the alloy Fe-20%Cr-5%Al with and without Y-doping were used to study the "reactive element" (RE) effect, which causes improved oxidation behaviour and formation of a protective Al2O3 layer on this alloy. The oxidation was followed by AES at 10-7 mbar O2 up to about 1000 °C. Most observations were peculiar for this low pO2 environment, but yttrium clearly favors the formation of Al-oxide and stabilizes it also under these conditions, probably by favoring its nucleation. The oxides formed are surface compounds of about monolayer thickness, not clearly related to bulk oxides. Furthermore, the morphologies of oxide scales were investigated by SEM, after oxidation at 1000°C for 100 h at 133 mbar O2. On Fe-Cr-Al the scale is strongly convoluted and tends to spalling, whereas the presence of Y leads to flat scales which are well adherent. This difference is explained by a change in growth mechanism. The tendency for separation of oxide and metal was highest for the samples with low energy metal surface, i.e. (100) and (110), the scale was better adherent on the (111) oriented surface and on the polycrystalline specimen, since in the latter cases the overall energy for scale/metal separation is higher. All observations, from the low and from the high pO2 experiments, are discussed in relation to the approximately ten mechanisms proposed in the literature for explanation of the RE effects.

  17. Effect of mechanical activation on thermal and electrical conductivity of sintered Cu, Cr, and Cu/Cr composite powders

    NASA Astrophysics Data System (ADS)

    Rogachev, A. S.; Kuskov, K. V.; Moskovskikh, D. O.; Usenko, A. A.; Orlov, A. O.; Shkodich, N. F.; Alymov, M. I.; Mukasyan, A. S.

    2016-06-01

    The results of measurement of electric resistivity and thermal conductivity of materials obtained by spark plasma sintering from powders of Cu, Cr, and their mixtures in the range of 300-600 K are presented. It is shown that the grinding of powders in planetary mills results in a reasonably substantial change in the electric and thermal properties of materials: to increasing electric resistivity and decreasing thermal conductivity and temperature coefficients of electric resistivity. The possible causes of these effects are considered.

  18. Stabilization of As, Cr, Cu, Pb and Zn in soil using amendments--a review.

    PubMed

    Kumpiene, Jurate; Lagerkvist, Anders; Maurice, Christian

    2008-01-01

    The spread of contaminants in soil can be hindered by the soil stabilization technique. Contaminant immobilizing amendments decrease trace element leaching and their bioavailability by inducing various sorption processes: adsorption to mineral surfaces, formation of stable complexes with organic ligands, surface precipitation and ion exchange. Precipitation as salts and co-precipitation can also contribute to reducing contaminant mobility. The technique can be used in in situ and ex situ applications to reclaim and re-vegetate industrially devastated areas and mine-spoils, improve soil quality and reduce contaminant mobility by stabilizing agents and a beneficial use of industrial by-products. This study is an overview of data published during the last five years on the immobilization of one metalloid, As, and four heavy metals, Cr, Cu, Pb and Zn, in soils. The most extensively studied amendments for As immobilization are Fe containing materials. The immobilization of As occurs through adsorption on Fe oxides by replacing the surface hydroxyl groups with the As ions, as well as by the formation of amorphous Fe(III) arsenates and/or insoluble secondary oxidation minerals. Cr stabilization mainly deals with Cr reduction from its toxic and mobile hexavalent form Cr(VI) to stable in natural environments Cr(III). The reduction is accelerated in soil by the presence of organic matter and divalent iron. Clays, carbonates, phosphates and Fe oxides were the common amendments tested for Cu immobilization. The suggested mechanisms of Cu retention were precipitation of Cu carbonates and oxy-hydroxides, ion exchange and formation of ternary cation-anion complexes on the surface of Fe and Al oxy-hydroxides. Most of the studies on Pb stabilization were performed using various phosphorus-containing amendments, which reduce the Pb mobility by ionic exchange and precipitation of pyromorphite-type minerals. Zn can be successfully immobilized in soil by phosphorus amendments and clays

  19. Mechanical Characterization of CrN/CrAlN Multilayer Coatings Deposited by Magnetron Sputtering System

    NASA Astrophysics Data System (ADS)

    Kaouther, Khlifi; Hafedh, Dhiflaoui; Lassaad, Zoghlami; Ahmed, Ben Cheikh Larbi

    2015-10-01

    Chromium-based coatings are deposited on a 100Cr6 (AISI 52100) substrate by a physical vapor deposition magnetron sputtering system. The coatings have different structures, such as a CrN monolayer and CrAlN multilayer. The structural and morphological compositions of the coatings were evaluated using glow discharge optical emission spectroscopy, atomic force microscopy, and cross-sectional scanning electron microscopy. Nano-indentation tests were performed to investigate the mechanical properties. Domes and craters are shown to be uniformly distributed over the entire surfaces of the two coatings. Additionally, the CrN/CrAlN multilayer coating exhibits a rough surface, attractive mechanical properties, a high compressive stress, and a high plastic and elastic deformation resistance. The improvement of the mechanical properties of the CrN/CrAlN coating is mainly attributed to a reduction in the crystallite size. We found that this reduction was related to three factors: (1) the compositional change resulting from the substitution of aluminum for chromium, which can produce a decrease in the interatomic distance; (2) the structure of CrN/CrAlN, which was characterized by grain size refinement; and (3) the high number of interfaces, which explains the widely accepted concept of dislocation blocking by the layer interfaces.

  20. Mechanism of Corrosion in Al-Si-Cu

    NASA Astrophysics Data System (ADS)

    Hayasaka, Nobuo; Koga, Yuri; Shimomura, Koji; Yoshida, Yukimasa; Okano, Haruo

    1991-07-01

    An Al-Cu local cell was formed between the Cu precipitation and adjacent Al in an Al-Si-Cu alloy when Cu was added in excess to the alloy. Once an Al-Cu local cell was formed, corrosion took place simply by dipping the alloy in deionized water without any contamination. Furthermore, it was found that corrosion was enhanced at the Al-Si-Cu lines in contact with the p+-n junction of Si. The reason for this is that holes are injected into Al-Si-Cu from p+-Si due to electromotive force produced by light irradiation and an external circuit connecting the alloy and n-Si formed by the adsorption of moisture on the surface. Furthermore, it was found that the irradiation of light with a wavelength between 320 to 380 nm was most effective in enhancing the corrosion reaction.

  1. TI--CR--AL--O thin film resistors

    DOEpatents

    Jankowski, Alan F.; Schmid, Anthony P.

    2000-01-01

    Thin films of Ti--Cr--Al--O are used as a resistor material. The films are rf sputter deposited from ceramic targets using a reactive working gas mixture of Ar and O.sub.2. Resistivity values from 10.sup.4 to 10.sup.10 Ohm-cm have been measured for Ti--Cr--Al--O film <1 .mu.m thick. The film resistivity can be discretely selected through control of the target composition and the deposition parameters. The application of Ti--Cr--Al--O as a thin film resistor has been found to be thermodynamically stable, unlike other metal-oxide films. The Ti--Cr--Al--O film can be used as a vertical or lateral resistor, for example, as a layer beneath a field emission cathode in a flat panel display; or used to control surface emissivity, for example, as a coating on an insulating material such as vertical wall supports in flat panel displays.

  2. Fretting Wear of Ti-48Al-2Cr-2Nb

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Lerch, Bradley A.; Draper, Susan L.

    2001-01-01

    An investigation was conducted to examine the wear behavior of gamma titanium aluminide (Ti-48Al-2Cr-2Nb in atomic percent) in contact with a typical nickel-base superalloy under repeated microscopic vibratory motion in air at temperatures from 296-823 K. The surface damage observed on the interacting surfaces of both Ti-48Al-2Cr-2Nb and superalloy consisted of fracture pits, oxides, metallic debris, scratches, craters, plastic deformation, and cracks. The Ti-48Al-2Cr-2Nb transferred to the superalloy at all fretting conditions and caused scuffing or galling. The increasing rate of oxidation at elevated temperatures led to a drop in Ti-48Al-2Cr-2Nb wear at 473 K. Mild oxidative wear was observed at 473 K. However, fretting wear increased as the temperature was increased from 473-823 K. At 723 and 823 K, oxide disruption generated cracks, loose wear debris, and pits on the Ti-48Al-2Cr-2Nb wear surface. Ti-48Al-2Cr-2Nb wear generally decreased with increasing fretting frequency. Both increasing slip amplitude and increasing load tended to produce more metallic wear debris, causing severe abrasive wear in the contacting metals. Keywords

  3. Elastocaloric effect in CuAlZn and CuAlMn shape memory alloys under compression.

    PubMed

    Qian, Suxin; Geng, Yunlong; Wang, Yi; Pillsbury, Thomas E; Hada, Yoshiharu; Yamaguchi, Yuki; Fujimoto, Kenjiro; Hwang, Yunho; Radermacher, Reinhard; Cui, Jun; Yuki, Yoji; Toyotake, Koutaro; Takeuchi, Ichiro

    2016-08-13

    This paper reports the elastocaloric effect of two Cu-based shape memory alloys: Cu68Al16Zn16 (CuAlZn) and Cu73Al15Mn12 (CuAlMn), under compression at ambient temperature. The compression tests were conducted at two different rates to approach isothermal and adiabatic conditions. Upon unloading at a strain rate of 0.1 s(-1) (adiabatic condition) from 4% strain, the highest adiabatic temperature changes (ΔTad) of 4.0 K for CuAlZn and 3.9 K for CuAlMn were obtained. The maximum stress and hysteresis at each strain were compared. The stress at the maximum recoverable strain of 4.0% for CuAlMn was 120 MPa, which is 70% smaller than that of CuAlZn. A smaller hysteresis for the CuAlMn alloy was also obtained, about 70% less compared with the CuAlZn alloy. The latent heat, determined by differential scanning calorimetry, was 4.3 J g(-1) for the CuAlZn alloy and 5.0 J g(-1) for the CuAlMn alloy. Potential coefficients of performance (COPmat) for these two alloys were calculated based on their physical properties of measured latent heat and hysteresis, and a COPmat of approximately 13.3 for CuAlMn was obtained.This article is part of the themed issue 'Taking the temperature of phase transitions in cool materials'. PMID:27402936

  4. Phase correlations in the CuAlSe2-CuAlTe2 system

    NASA Astrophysics Data System (ADS)

    Korzun, B. V.; Fadzeyeva, A. A.; Bente, K.; Schmitz, W.; Kommichau, G.

    2005-07-01

    Alloys in the CuAlSe2-CuAlTe2 system were synthesized in BN-crucibles in silica tubes under vacuum to obtain the corresponding phase equilibria. X-ray powder diffraction and thermal analytic data of the T-x phase diagram revealed a complete solid solutions series in the subsolidus region. Within the CuAlSe2xTe2(1-x) system the refined lattice parameters a and c approximately obey the Vegard rule and also the cell volume and the heat of fusion confirm linear correlations with the composition of the mixed crystals. The anion position parameter calculated after S. C. Abrahams & J. L. Bernstein (uAB) and J. E Jaffe & A. Zunger (uJZ) is greater than 0.25 and reveals a linear dependence on composition. The liquidus part of the CuAlSe2xTe2(1-x) system with x < 0.35 exhibits vertical section behaviour with a ternary peritectic followed up by a ternary monotectic whereas the region with x > 0.35 shows quasibinary equilibria.

  5. Low voltage tunneling magnetoresistance in CuCrO{sub 2}-based semiconductor heterojunctions at room temperature

    SciTech Connect

    Li, X. R.; Han, M. J.; Shan, C.; Hu, Z. G. Zhu, Z. Q.; Chu, J. H.; Wu, J. D.

    2014-12-14

    CuCrO{sub 2}-based heterojunction diodes with rectifying characteristics have been fabricated by combining p-type Mg-doped CuCrO{sub 2} and n-type Al-doped ZnO. It was found that the current for the heterojunction in low bias voltage region is dominated by the trap-assisted tunneling mechanism. Positive magnetoresistance (MR) effect for the heterojunction can be observed at room temperature due to the tunneling-induced antiparallel spin polarization near the heterostructure interface. The MR effect becomes enhanced with the magnetic field, and shows the maximum at a bias voltage around 0.5 V. The phenomena indicate that the CuCrO{sub 2}-based heterojunction is a promising candidate for low-power semiconductor spintronic devices.

  6. LiCaAl/sub 6/:Cr/sup 3+/

    SciTech Connect

    Payne, S.A.; Chase, L.L.; Newkirk, H.W.; Smith, L.K.; Krupke, W.F. )

    1988-11-01

    The authors report the discovery of a new laser, LiCaAIF/sub 6/:Cr/sup 3/ (Cr/sup 3+/ :LiCAF). The intrinsic (extrapolated maximum) slope efficiency was found to be 67 percent. For comparison, they also measured the intrinsic slope efficiencies of BeAl/sub 2/O/sub 4/:Cr/sup 3+/ (alexandrite), Na/sub 3/Ga/sub 2/Li/sub 3/F/sub 12/:Cr/sup 3+/, and ScBO/sub 3/:Cr/sup 3+/, and obtained values of 65,28, and 26 percent, respectively. The tuning range of LiCaAIF/sub 6/:Cr/sup 3+/ was determined to be at least 720-840 nm. The conventional spectroscopic properties, such as the absorption, emission, and emission lifetimes as a function of temperature, are reported as well.

  7. CuCrZr alloy microstructure and mechanical properties after hot isostatic pressing bonding cycles

    NASA Astrophysics Data System (ADS)

    Frayssines, P.-E.; Gentzbittel, J.-M.; Guilloud, A.; Bucci, P.; Soreau, T.; Francois, N.; Primaux, F.; Heikkinen, S.; Zacchia, F.; Eaton, R.; Barabash, V.; Mitteau, R.

    2014-04-01

    ITER first wall (FW) panels are a layered structure made of the three following materials: 316L(N) austenitic stainless steel, CuCrZr alloy and beryllium. Two hot isostatic pressing (HIP) cycles are included in the reference fabrication route to bond these materials together for the normal heat flux design supplied by the European Union (EU). This reference fabrication route ensures sufficiently good mechanical properties for the materials and joints, which fulfil the ITER mechanical specifications, but often results in a coarse grain size for the CuCrZr alloy, which is not favourable, especially, for the thermal creep properties of the FW panels. To limit the abnormal grain growth of CuCrZr and make the ITER FW fabrication route more reliable, a study began in 2010 in the EU in the frame of an ITER task agreement. Two material fabrication approaches have been investigated. The first one was dedicated to the fabrication of solid CuCrZr alloy in close collaboration with an industrial copper alloys manufacturer. The second approach investigated was the manufacturing of CuCrZr alloy using the powder metallurgy (PM) route and HIP consolidation. This paper presents the main mechanical and microstructural results associated with the two CuCrZr approaches mentioned above. The mechanical properties of solid CuCrZr, PM CuCrZr and joints (solid CuCrZr/solid CuCrZr and solid CuCrZr/316L(N) and PM CuCrZr/316L(N)) are also presented.

  8. Intermetallic Phase Formation in Explosively Welded Al/Cu Bimetals

    NASA Astrophysics Data System (ADS)

    Amani, H.; Soltanieh, M.

    2016-05-01

    Diffusion couples of aluminum and copper were fabricated by explosive welding process. The interface evolution caused by annealing at different temperatures and time durations was investigated by means of optical microscopy, scanning electron microscopy equipped with energy dispersive spectroscopy, and x-ray diffraction. Annealing in the temperature range of 573 K to 773 K (300 °C to 500 °C) up to 408 hours showed that four types of intermetallic layers have been formed at the interface, namely Al2Cu, AlCu, Al3Cu4, and Al4Cu9. Moreover, it was observed that iron trace in aluminum caused the formation of Fe-bearing intermetallics in Al, which is near the interface of the Al-Cu intermetallic layers. Finally, the activation energies for the growth of Al2Cu, AlCu + Al3Cu4, Al4Cu9, and the total intermetallic layer were calculated to be about 83.3, 112.8, 121.6, and 109.4 kJ/mol, respectively. Considering common welding methods (i.e., explosive welding, cold rolling, and friction welding), although there is a great difference in welding mechanism, it is found that the total activation energy is approximately the same.

  9. Intermetallic Phase Formation in Explosively Welded Al/Cu Bimetals

    NASA Astrophysics Data System (ADS)

    Amani, H.; Soltanieh, M.

    2016-08-01

    Diffusion couples of aluminum and copper were fabricated by explosive welding process. The interface evolution caused by annealing at different temperatures and time durations was investigated by means of optical microscopy, scanning electron microscopy equipped with energy dispersive spectroscopy, and x-ray diffraction. Annealing in the temperature range of 573 K to 773 K (300 °C to 500 °C) up to 408 hours showed that four types of intermetallic layers have been formed at the interface, namely Al2Cu, AlCu, Al3Cu4, and Al4Cu9. Moreover, it was observed that iron trace in aluminum caused the formation of Fe-bearing intermetallics in Al, which is near the interface of the Al-Cu intermetallic layers. Finally, the activation energies for the growth of Al2Cu, AlCu + Al3Cu4, Al4Cu9, and the total intermetallic layer were calculated to be about 83.3, 112.8, 121.6, and 109.4 kJ/mol, respectively. Considering common welding methods ( i.e., explosive welding, cold rolling, and friction welding), although there is a great difference in welding mechanism, it is found that the total activation energy is approximately the same.

  10. Magnetic properties of CuCr2Se4 and CuCr1.5Ti0.5Se4

    NASA Astrophysics Data System (ADS)

    Behera, P. Suchismita; Bhobe, P. A.; Nigam, A. K.

    2016-05-01

    CuCr2Se4 is a potentially attractive versatile material, from the point of view of spintronics application. It shows characteristics of a ferromagnetic conductor at room temperature and with suitable doping it is proposed to show half-metallicity. With an aim to understand the effect of doping at Cr-site by a non-magnetic ion, we carried out investigation of magnetic and crystal structure properties of polycrystalline CuCr2Se4 and CuCr1.5Ti0.5Se4 spinel. These materials were prepared by solid state synthesis and characterized using room temperature powder XRD and measurement of magnetic properties. The XRD patterns were analyzed using Rietveld technique and lattice constants were estimated. Formation of a small amount of Cr3Se4 phase was identified from the XRD profiles. However, the magnetic properties do not seem to be affected much by it. Compared to parent compound, CuCr2Se4, the ferromagnetic Curie temperature TC in CuCr1.5Ti0.5Se4 was found to decrease to 208 K. But its magnetic moment (μB/f.u.) determined from the saturation magnetization value measured at 5 K, differed only slightly from that of CuCr2Se4. Our preliminary results are presented here.

  11. Residual Stresses in Thermal Barrier Coatings for a Cu-8Cr-4Nb Substrate System

    NASA Technical Reports Server (NTRS)

    Ghosn, Louis J.; Raj, Sai V.

    2002-01-01

    Analytical calculations were conducted to determine the thermal stresses developed in a coated copper-based alloy, Cu-8%(at.%)Cr-4%Nb (designated as GRCop-84), after plasma spraying and during heat-up in a simulated rocket engine environment. Finite element analyses were conducted for two coating systems consisting of a metallic top coat, a pure copper bond coat and the GRCop-84. The through thickness temperature variations were determined as a function of coating thickness for two metallic coatings, a Ni-17%(wt%)Cr-6%Al-0.5%Y alloy and a Ni-50%(at.%)Al alloy. The residual stresses after low-pressure plasma spraying of the NiCrAlY and NiAl coatings on GRCop-84 substrate were also evaluated. These analyses took into consideration a 50.8 mm copper bond coat and the effects of an interface coating roughness. The through the thickness thermal stresses developed in coated liners were also calculated after 15 minutes of exposure in a rocket environment with and without an interfacial roughness.

  12. Substitution Effect on the Magnetic State of Delafossite CuCrO2 Having a Spin-3/2 Antiferromagnetic Triangular Sublattice

    NASA Astrophysics Data System (ADS)

    Okuda, T.; Oozono, S.; Hokazono, T.; Uto, K.; Fujii, Y.; Beppu, Y.; Seki, S.; Onose, Y.; Tokura, Y.; Kajimoto, R.; Matsuda, M.

    2012-12-01

    We have investigated substitution effects on transport, magnetic, and thermal properties of delafossite CuCrO2 having a spin-3/2 antiferromagnetic triangular sublattice by measurements of resistivity, magnetization, specific heat, and neutron scattering. In the proceeding, we show unique effects of hole-doping by a substitution of nonmagnetic Mg2+ ions for magnetic Cr3+ ions (S = 3/2), randomness introduced between CrO2 layers by a substitution of Ag+ ions for Cu+ ions, and spin-defect introduced into CrO2 layers by a substitution of nonmagnetic Al3+ ions for Cr3+ ions upon the magnetic state in CuCrO2.

  13. Influence of FeCrAl Content on Microstructure and Bonding Strength of Plasma-Sprayed FeCrAl/Al2O3 Coatings

    NASA Astrophysics Data System (ADS)

    Zhou, Liang; Luo, Fa; Zhou, Wancheng; Zhu, Dongmei

    2016-02-01

    Low-power plasma-sprayed FeCrAl/Al2O3 composite coatings with 1.5 mm thickness have been fabricated for radar absorption applications. The effects of FeCrAl content on the coating properties were studied. The FeCrAl presents in the form of a few thin lamellae and numerous particles, demonstrating relatively even distribution in all the coatings. Results show that the micro-hardness and porosity decrease with the increase in FeCrAl content. With FeCrAl content increasing from 28 to 47 wt.%, the bonding strength of the coatings with 1.5 mm thickness increases from 10.5 to 27 MPa, and the failure modes are composed of cohesive and adhesive failure, which are ascribed to the coating microstructure and the residual stress, respectively.

  14. Facile synthesis of dendritic Cu by electroless reaction of Cu-Al alloys in multiphase solution

    NASA Astrophysics Data System (ADS)

    Wang, Ying; Liang, Shuhua; Yang, Qing; Wang, Xianhui

    2016-11-01

    Two-dimensional nano- or micro-scale fractal dendritic coppers (FDCs) were synthesized by electroless immersing of Cu-Al alloys in hydrochloric acid solution containing copper chloride without any assistance of template or surfactant. The FDC size increases with the increase of Al content in Cu-Al alloys immersed in CuCl2 + HCl solution. Compared to Cu40Al60 and Cu45Al55 alloys, the FDC shows hierarchical distribution and homogeneous structures using Cu17Al83 alloy as the starting alloy. The growth direction of the FDC is <110>, and all angles between the trunks and branches are 60°. Nanoscale Cu2O was found at the edge of FDC. Interestingly, nanoporous copper (NPC) can also be obtained through Cu17Al83 alloy. Studies showed that the formation of FDC depended on two key factors: the potential difference between CuAl2 intermetallic and α-Al phase of dual-phase Cu-Al alloys; a replacement reaction that usually occurs in multiphase solution. The electrochemical experiment further proved that the multi-branch dendritic structure is very beneficial to the proton transfer in the process of catalyzing methanol.

  15. The General Isothermal Oxidation Behavior of Cu-8Cr-4Nb

    NASA Technical Reports Server (NTRS)

    Thomas-Ogbuji, L. U.; Gray, Hugh R. (Technical Monitor)

    2002-01-01

    Oxidation kinetics of Cu-8Cr-4Nb was investigated by TGA (thermogravimetric) exposures between 500 and 900-C (at 25-50 C intervals) and the oxide scale morphologies examined by microscopy and micro-analysis. Because Cu-8Cr-4Nb is comprised of fine Cr2Nb precipitates in a Cu matrix, the results were interpreted by comparison with the behavior of copper (OFHC) and 'NARloy-Z' (a rival candidate material for thrust cell liner applications in advanced rocket engines) under the same conditions. While NARloy-Z and Cu exhibited identical oxidation behavior, Cu-8Cr-4Nb differed markedly in several respects: below approx. 700 C its oxidation rates were significantly lower than those of Cu; At higher temperatures its oxidation rates fell into two categories: an initial rate exceeding that of Cu, and a terminal rate comparable to that of Cu. Differences in oxide morphologies paralleled the kinetic differences at higher temperature: While NARloy-Z and Cu produced a uniform oxide scale of Cu2O inner layer and CuO outer layer, the inner (Cu2O) layer on Cu-8Cr-4Nb was stratified, with a highly porous/spongy inner stratum (responsible for the fast initial kinetics) and a dense/blocky outer stratum (corresponding to the slow terminal kinetics). Single and spinel oxides of Nb and Cr were found at the interface between the oxide scale and Cu-8Cr-4Nb substrate and it appears that these oxides were responsible for its suppressed oxidation rates at the intermediate temperatures. No difference was found between Cu-8Cr-4Nb oxidation in air and in oxygen at 1.0 atm.

  16. Intermetallic compound formation at Cu-Al wire bond interface

    SciTech Connect

    Bae, In-Tae; Young Jung, Dae; Chen, William T.; Du Yong

    2012-12-15

    Intermetallic compound (IMC) formation and evolution at Cu-Al wire bond interface were studied using focused ion beam /scanning electron microscopy, transmission electron microscopy (TEM)/energy dispersive x-ray spectroscopy (EDS), nano beam electron diffraction (NBED) and structure factor (SF) calculation. It was found that discrete IMC patches were formed at the Cu/Al interface in as-packaged state and they grew toward Al pad after high temperature storage (HTS) environment at 150 Degree-Sign C. TEM/EDS and NBED results combined with SF calculation revealed the evidence of metastable {theta} Prime -CuAl{sub 2} IMC phase (tetragonal, space group: I4m2, a = 0.404 nm, c= 0.580 nm) formed at Cu/Al interfaces in both of the as-packaged and the post-HTS samples. Two feasible mechanisms for the formation of the metastable {theta} Prime -CuAl{sub 2} phase are discussed based on (1) non-equilibrium cooling of wire bond that is attributed to highly short bonding process time and (2) the epitaxial relationships between Cu and {theta} Prime -CuAl{sub 2}, which can minimize lattice mismatch for {theta} Prime -CuAl{sub 2} to grow on Cu.

  17. Characteristics of p-type transparent conductive CuCrO2 thin films

    NASA Astrophysics Data System (ADS)

    Yu, Ruei-Sung; Wu, Chung-Ming

    2013-10-01

    Cu-Cr-O films were prepared using reactive magnetron sputtering deposition followed by annealing at temperatures ranging from 550 to 625 °C in 25 °C increments. Correlations between the optoelectronic and microstructural properties of the p-type CuCrO2 films are discussed. The as-deposited film was amorphous; after annealing at 550 and 575 °C, films adopted mixed CuO and CuCr2O4 phases. Annealing at 600 °C led to the formation of a dominant phase of delafossite CuCrO2. The 625 °C-annealed film was single-phase CuCrO2 which had a bar- and polygonal-like mixed surface appearance, with a root mean square roughness of 17.7 nm. CuCrO2 is an intrinsic p-type semiconductor which exhibits electrical conductivity and transparency over the visible wavelength range. Two higher-energy subband transitions at 3.69 and 4.82 eV were observed in the band structure of CuCrO2. Point defects were the main reason source of hole carrier scattering in the material. The single-phase CuCrO2 film had the lowest resistivity of the films, 4.31 Ω cm, and had a direct band gap of 3.14 eV and light transmittance of 62% at 600 nm.

  18. Precipitation in dilute Cu-Cr alloys; The effects of phosphorus impurities and aging procedure

    SciTech Connect

    Luo, C.P.; Dahmen, U.; Witcomb, M.J.; Westmacott, K.H. )

    1992-02-15

    This paper reports that precipitation in dilute Cu-Cr alloys has been studied extensively in part because this alloy can be used as a model system for the investigation of the crystallography and interfaces in FCC-BCC phase transformations. Hall et al. first reported needle- or lath-shaped Cr-rich precipitates with a {l brace}335{r brace}{sub f} habit plane and a variable orientation relationship ranging from Nishiyama-Wasserman (N-W) to Kurdjumov-Sachs (K-S). Hall and Aaronson later confirmed their early findings. Weatherly et al. however, found a constant K-S orientation relationship for this alloy system and a preferred growth direction of {l angle}651{r angle}{sub f} for the needle-shaped precipitates. The variation of the orientation relationship and its potential effect on the precipitate morphology and interface structure have become key points in studying the precipitate crystallography of this alloy system. Dahmen et al. attributed the variation of the orientation relationship to the different quenching and aging conditions applied to the alloy; a direct quench from the solutionizing to the aging temperature employed by Hall et al. would result in a heterogeneous nucleation and hence a variation in the precipitation behavior, while the water quench and aging procedure utilized by Weatherly et al, would facilitate homogeneous nucleation and produce a constant crysallography.

  19. Vacuum Plasma Spray of Cu-8Cr-4Nb for Advanced Liquid-Fuel Combustion Chambers

    NASA Technical Reports Server (NTRS)

    Zimmerman, F.; Elam, S.; Ellis, D.; Miller, H.; McKechnie, T.; Hickman, R.

    2001-01-01

    Vacuum plasma spray (VPS) formed Cu-8Cr-4Nb alloy, with low oxygen, exhibits higher strength at room and elevated temperature than material formed by extrusion. The VPS formed material exhibits slightly lower ductility than the extruded material. VPS forming of Cu-8Cr-4Nb can be used to produce near net structures with mechanical properties comparable to current extruded material.

  20. Cu Cr O nanocomposites: Synthesis and characterization as catalysts for solid state propellants

    NASA Astrophysics Data System (ADS)

    Li, Wei; Cheng, Hua

    2007-08-01

    In this article we present the synthesis of Cu-Cr-O nanocomposites via a citric acid (CA) complexing approach and the evaluation of the as-synthesized Cu-Cr-O nanocomposites as additives for the catalytic combustion of AP (ammonium perchlorate)-based solid state propellants. Techniques of thermo-gravimetric/differential thermal analyzer (TG-DTA), X-ray diffraction (XRD), transmission electron microscopy (TEM) as well as scanning electron microscopy (SEM) have been employed to characterize the thermal decomposition procedure, crystal phase, micro-structural morphologies and grain size of the as-synthesized materials, respectively. The results show that well-crystallized Cu-Cr-O nanocomposites can be produced by using a temperature as low as 600 °C. Phase structure of the as-obtained Cu-Cr-O nanocomposites depends on the Cu/Cr molar ratio in the starting reactants. Addition of the as-synthesized Cu-Cr-O nanocomposites as catalysts enhances the burning rate as well as lowers the pressure exponent of the AP-based solid state propellants considerably. Noticeably, solid state propellants containing Cu-Cr-O nanocomposites with a Cu/Cr molar ratio of 0.7 exhibits the most stable combustion at all pressures.

  1. Fate of Cu, Cr, and As during combustion of impregnated wood with and without peat additive

    SciTech Connect

    Karin Lundholm; Dan Bostroem; Anders Nordin; Andrei Shchukarev

    2007-09-15

    The EU Directive on incineration of waste regulates the harmful emissions of particles and twelve toxic elements, including copper, chromium, and arsenic. Using a 15 kW pellets-fueled grate burner, experiments were performed to determine the fate of copper, chromium, and arsenic during combustion of chromate copper arsenate (CCA) preservative wood. The fate and speciation of copper, chromium, and arsenic were determined from analysis of the flue gas particles and the bottom ash using SEM-EDS, XRD, XPS, and ICP-AES. Chemical equilibrium model calculations were performed to interpret the experimental findings. The results revealed that about 5% copper, 15% chromium, and 60% arsenic were volatilized during combustion of pure CCA-wood, which is lower than predicted volatilization from the individual arsenic, chromium, and copper oxides. This is explained by the formation of more stable refractory complex oxide phases for which the stability trends and patterns are presented. When co-combusted with peat, an additional stabilization of these phases was obtained and thus a small but noteworthy decrease in volatilization of all three elements was observed. The major identified phases for all fuels were CuCrO{sub 2}(s), (Fe,Mg,Cu)(Cr,Fe,Al)O{sub 4}(s), Cr{sub 2}O{sub 3}(s), and Ca{sub 3}(AsO{sub 4}){sub 2}(s). Arsenic was also identified in the fine particles as KH{sub 2}AsO{sub 4}(s) and As{sub 2}O{sub 3}). A strong indication of hexavalent chromium in the form of K{sub 2}CrO{sub 4} or as a solid solution between K{sub 3}Na(CrO{sub 4}){sub 2} and K{sub 3}Na(SO{sub 4}){sub 2} was found in the fine particles. Good qualitative agreement was observed between experimental data and chemical equilibrium model calculations. 38 refs., 6 figs., 2 tabs.

  2. Protection of Advanced Copper Alloys With Lean Cu-Cr Coatings

    NASA Technical Reports Server (NTRS)

    Greenbauer-Seng, L. (Technical Monitor); Thomas-Ogbuji, L.

    2003-01-01

    Advanced copper alloys are used as liners of rocket thrusters and nozzle ramps to ensure dissipation of the high thermal load generated during launch, and Cr-lean coatings are preferred for the protection of these liners from the aggressive ambient environment. It is shown that adequate protection can be achieved with thin Cu-Cr coatings containing as little as 17 percent Cr.

  3. Spin glass state and enhanced spiral phase in doped delafossite oxide CuCr O2

    NASA Astrophysics Data System (ADS)

    Yan, Z. R.; Qin, M. H.; Dong, S.; Zeng, M.; Lu, X. B.; Gao, X. S.; Liu, J.-M.

    2016-07-01

    In this paper, we study the doping effects on the magnetic states of CuCr O2 based on the classical frustrated spin model [13aa Lin et al., Phys. Rev. B 89, 220405(R) (2014), 10.1103/PhysRevB.89.220405]. Several experimental observations can be well reproduced by the Monte Carlo simulations of the modified spin models. Our paper suggests that the disorder induced by V/Al doping cooperating with the frustration in the system may contribute to the emergence of the spin glass state. Furthermore, the hole doping by M g2 + substituting C r3 + enhances the quantum fluctuations and bond disorder which modulate the biquadratic exchanges and in turn results in the promotion of the spiral phase, consistent with the experimental report.

  4. Nucleation and Growth of Cu-Al Intermetallics in Al-Modified Sn-Cu and Sn-Ag-Cu Lead-Free Solder Alloys

    NASA Astrophysics Data System (ADS)

    Reeve, Kathlene N.; Anderson, Iver E.; Handwerker, Carol A.

    2015-03-01

    Lead-free solder alloys Sn-Cu (SC) and Sn-Ag-Cu (SAC) are widely used by the microelectronics industry, but enhanced control of the microstructure is needed to improve solder performance. For such control, nucleation and stability of Cu-Al intermetallic compound (IMC) solidification catalysts were investigated by variation of the Cu (0.7-3.0 wt.%) and Al (0.0-0.4 wt.%) content of SC + Al and SAC + Al alloys, and of SAC + Al ball-grid array (BGA) solder joints. All of the Al-modified alloys produced Cu-Al IMC particles with different morphologies and phases (occasionally non-equilibrium phases). A trend of increasing Cu-Al IMC volume fraction with increasing Al content was established. Because of solidification of non-equilibrium phases in wire alloy structures, differential scanning calorimetry (DSC) experiments revealed delayed, non-equilibrium melting at high temperatures related to quenched-in Cu-Al phases; a final liquidus of 960-1200°C was recorded. During cooling from 1200°C, the DSC samples had the solidification behavior expected from thermodynamic equilibrium calculations. Solidification of the ternary alloys commenced with formation of ternary β and Cu-Al δ phases at 450-550°C; this was followed by β-Sn, and, finally, Cu6Sn5 and Cu-Al γ1. Because of the presence of the retained, high-temperature phases in the alloys, particle size and volume fraction of the room temperature Cu-Al IMC phases were observed to increase when the alloy casting temperature was reduced from 1200°C to 800°C, even though both temperatures are above the calculated liquidus temperature of the alloys. Preliminary electron backscatter diffraction results seemed to show Sn grain refinement in the SAC + Al BGA alloy.

  5. Hydrogen permeation characteristics of some Fe-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Van Deventer, E. H.; Maroni, V. A.

    1983-01-01

    Hydrogen permeation data are reported for two Fe-Cr-Al alloys, Type-405 SS (Cr 14-A1 0.2) and a member of the Fecralloy family of alloys (Cr 16-A1 5). The hydrogen permeability of each alloy (in a partially oxidized condition) was measured over a period of several weeks at randomly selected temperatures (between 150 and 850°C) and upstream H 2 pressures (between 2 and 1.5 × 10 4 Pa). The permeabilities showed considerable scatter with both time and temperature and were 10 2 to 10 3 times lower than those of pure iron, even in strongly reducing environments. The exponent, n, for the relationship between upstream H 2 pressure, P, and permeability, φ, ( φ ~ Pn) was closer to 0.7 than to the expected 0.5, indicating a process limited by surface effects (e.g., surface oxide films) as opposed to bulk material effects. Comparison of these results with prior permeation measurements on other Fe-Cr-Al alloys, on Fe-Cr alloys, and on pure iron shows that the presence of a few weight percent aluminum offers the best prospects for achieving low tritium permeabilities with martensitic and ferritic steels used in fusion-reactor first wall and blanket applications.

  6. Mercury embrittlement of Cu-Al alloys under cyclic loading

    NASA Technical Reports Server (NTRS)

    Regan, T. M.; Stoloff, N. S.

    1977-01-01

    The effect of mercury on the room temperature, high cycle fatigue properties of three alloys: Cu-5.5 pct Al, Cu-7.3 pct Al, and Cu-6.3 pct Al-2.5 pct Fe has been determined. Severe embrittlement under cyclic loading in mercury is associated with rapid crack propagation in the presence of the liquid metal. A pronounced grain size effect is noted under mercury, while fatigue properties in air are insensitive to grain size. The fatigue results are discussed in relation to theories of adsorption-induced liquid metal embrittlement.

  7. Electronic Structure of Halogen Doped CuCr2Se4

    SciTech Connect

    Arenholz, Elke; Liberati, M.; Neulinger, J. R.; Chopdekar, R.V.; Bettinger, J.S.; Arenholz, E.; Butler, W.; Stacy, A.M.; Idzerda, Y.I.; Suzuki, Y.

    2008-09-13

    We have employed element and chemically sensitive X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) in order to address a long standing controversy regarding the electronic and magnetic state of CuCr{sub 2}Se{sub 4} via halogen doping of the Se anion site in CuCr{sub 2}Se{sub 4-x}Y{sub x} (Y=Cl and Br). Long range magnetic order is observed above room temperature for all samples. The Cr L{sub 2,3} XAS spectra show a prevalent 3+ valence for the Cr ions independent of doping concentration and doping agent. The Cu L{sub 2,3} XAS spectra show a combination of 1+ and 2+ valence states for all samples. XMCD spectra indicate the presence of a magnetic moment associated with the Cu ions that is aligned antiparallel to the Cr moment.

  8. A new Cu-8 Cr-4 Nb alloy for high temperature applications

    NASA Technical Reports Server (NTRS)

    Ellis, D. L.; Michal, G. M.; Dreshfield, R. L.

    1995-01-01

    Various applications exist where a high conductivity alloy with good strength and creep resistance are required. NASA LeRC has developed a Cu-8 at. percent Cr-4 at. percent Nb (Cu-8 Cr-4 Nb) alloy for these applications. The alloy is designed for use up to 700 C and shows exceptional strength, low cycle fatigue (LCF) resistance, and creep resistance. Cu-8 Cr-4 Nb also has a thermal conductivity of at least 72 percent that of pure Cu. Furthermore, the microstructure and mechanical properties of the alloy are very stable. In addition to the original application in combustion chambers, Cu-8 Cr-4 Nb shows promise for welding electrodes, brazing fixtures, and other applications requiring high conductivity and strength at elevated temperatures.

  9. Some TEM observations of Al2O3 scales formed on NiCrAl alloys

    NASA Technical Reports Server (NTRS)

    Smialek, J.; Gibala, R.

    1979-01-01

    The microstructural development of Al2O3 scales on NiCrAl alloys has been examined by transmission electron microscopy. Voids have been observed within grains in scales formed on a pure NiCrAl alloy. Both voids and oxide grains grew measurably with oxidation time at 1100 C. The size and amount of porosity decreased towards the oxide-metal growth interface. It was postulated that the voids resulted from an excess number of oxygen vacancies near the oxide-metal interface. Short-circuit diffusion paths were discussed in reference to current growth stress models for oxide scales. Transient oxidations of pure, Y-doped, and Zr-doped NiCrAl was also examined. Oriented alpha-(Al,Cr)2O3 and Ni(Al,Cr)2O4 scales often coexisted in layered structures on all three alloys. Close-packed oxygen planes and directions in the corundum and spinel layers were parallel. The close relationships between oxide layers provided a gradual transition from initial transient scales to steady state Al2O3 growth.

  10. Some TEM observations of Al2O3 scales formed on NiCrAl alloys

    NASA Technical Reports Server (NTRS)

    Smialek, J.; Gibala, R.

    1979-01-01

    The microstructural development of Al2O3 scales on NiCrAl alloys has been examined by transmission electron microscopy. Voids were observed within grains in scales formed on a pure NiCrAl alloy. Both voids and oxide grains grew measurably with oxidation time at 1100 C. The size and amount of porosity decreased towards the oxide-metal growth interface. The voids resulted from an excess number of oxygen vacancies near the oxidemetal interface. Short-circuit diffusion paths were discussed in reference to current growth stress models for oxide scales. Transient oxidation of pure, Y-doped, and Zr-doped NiCrAl was also examined. Oriented alpha-(Al, Cr)2O3 and Ni(Al, Cr)2O4 scales often coexisted in layered structures on all three alloys. Close-packed oxygen planes and directions in the corundum and spinel layers were parallel. The close relationship between oxide layers provided a gradual transition from initial transient scales to steady state Al2O3 growth.

  11. Composition dependence of superconductivity in YBa2(Cu(3-x)Al(x))Oy

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    1991-01-01

    Eleven different compositions in the system YBa2(Cu(3-x)Al(x))O(y) (x = 0 to 0.3) have been synthesized and characterized by electrical resistivity measurements, powder x-ray diffraction, and scanning electron microscopy. The superconducting transition temperature T sub c (onset) was almost unaffected by the presence of alumina due to its limited solubility in YBa2Cu3O(7-x). However, T sub c(R = 0) gradually decreased, and the resistive tails became longer with increasing Al2O3 concentration. This was probably due to formation of BaAl2O4 and other impurity phases from chemical decomposition of the superconducting phase by reaction with Al2O3.

  12. Composition dependence of superconductivity in YBa2(Cu(3-x)Al(x))O(y)

    NASA Technical Reports Server (NTRS)

    Bansal, N. P.

    1993-01-01

    Eleven different compositions in the system YBa2(Cu(3-x)Al(x))O(y) (x = 0 to 0.3) have been synthesized and characterized by electrical resistivity measurements, powder X-ray diffraction, and scanning electron microscopy. The superconducting transition temperature T sub c (onset) was almost unaffected by the presence of alumina due to its limited solubility in YBa2Cu3O(7-x). However, T sub c(R = 0) gradually decreased, and the resistive tails became longer with increasing Al2O3 concentration. This was probably due to formation of BaAl2O4 and other impurity phases from chemical decomposition of the superconducting phase by reaction with Al2O3.

  13. Positron lifetime studies of decomposition in 2024 (Al-Cu-Mg) and 7010 (Al-Zn-Cu-Mg) alloys

    SciTech Connect

    Dlubek, G. |; Lademann, P.; Krause, H.; Krause, S.; Unger, R.

    1998-09-04

    In the current paper, the decomposition behavior of the engineering alloys 2024 (Al-Cu-Mg) and 7010 (Al-Zn-Cu-Mg) is studied using positron lifetime measurements. Positrons probe open volume defects such as vacancies and dislocations. However, they may also be used to investigate coherent zones and incoherent precipitates. In order to understand the rather complicated precipitation sequences and the response of positrons to different type of precipitates occurring in 2024 and 7010 alloys, binary and ternary laboratory alloys were also investigated under the same experimental conditions as the engineering alloys. The interpretations of the results are based on experiences of the group from extensive positron studies of laboratory alloys such as Al-Zn, Al-Zn-Mg, Al-Cu, and further Al alloys (see also the review (4)). Their collected results are shown as lifetimes and curve-shape parameters S of the electron-positron momentum distribution curves characteristic for different precipitates in Al alloys.

  14. Wetting and Interfacial Chemistry of SnZnCu Alloys with Cu and Al Substrates

    NASA Astrophysics Data System (ADS)

    Fima, Przemysław; Pstruś, Janusz; Gancarz, Tomasz

    2014-05-01

    Wetting of Cu and Al pads by Sn-Zn eutectic-based alloys with 0.5, 1, and 1.5 wt.% of Cu was studied at 250 °C, in the presence of ALU33® flux, with wetting times of 15, 30, 60, and 180 s, respectively. With increasing wetting time the wetting angle decreases only slightly and the angles on Cu pads are higher than those on Al pads. Selected, solidified solder-pad couples were cross-sectioned and subjected to SEM-EDS study of the interfacial microstructure. The results revealed that the microstructure of the SnZnCu/Cu interface is much different from SnZnCu/Al interface. In the first case continuous interlayers are observed while in the latter case there is no interlayer but the alloy dissolves the substrate along grain boundaries.

  15. Interfacial Reaction during Friction Stir Welding of Al and Cu

    NASA Astrophysics Data System (ADS)

    Genevois, C.; Girard, M.; Huneau, B.; Sauvage, X.; Racineux, G.

    2011-08-01

    Commercially pure copper was joined to a 1050 aluminum alloy by friction stir welding. A specific configuration where the tool pin was fully located in the aluminum plate was chosen. In such a situation, there is no mechanical mixing between the two materials, but frictional heating gives rise to a significant thermally activated interdiffusion at the copper/aluminum interface. This gives rise to the formation of defect-free joints where the bonding is achieved by a very thin intermetallic layer at the Cu/Al interface. Nanoscaled grains within this bonding layer were characterized using transmission electron microscopy (TEM). Two phases were identified, namely, Al2Cu and Al4Cu9 phases. The nucleation and growth of these two phases are discussed and compared to the standard reactive interdiffusion reactions between Cu and Al.

  16. Adherent Al2O3 scales formed on undoped NiCrAl alloys

    NASA Technical Reports Server (NTRS)

    Smialek, James L.

    1987-01-01

    Changes in the spalling behavior of Al2O3 scales formed on an undoped NiCrAl alloy are described. Two samples of Ni-15Cr-13Al (wt pct), one a control and the other sanded, were subjected to 25 oxidation cycles. It is observed that adherent scales formed on the sanded sample; however, the control sample had speckled, spalled scales. The data reveal that the adherent scales are caused by repeated removal of surface layers after each oxidation cycle. It is determined that interfacial segregation of sulfur influences spallation and sulfur removal increases bonding. The effect of moisture on scale adhesions is investigated.

  17. Temporal evolution of ion energy distribution functions and ion charge states of Cr and Cr-Al pulsed arc plasmas

    SciTech Connect

    Tanaka, Koichi; Anders, André

    2015-11-15

    To study the temporal evolution of ion energy distribution functions, charge-state-resolved ion energy distribution functions of pulsed arc plasmas from Cr and Cr-Al cathodes were recorded with high time resolution by using direct data acquisition from a combined energy and mass analyzer. The authors find increases in intensities of singly charged ions, which is evidence that charge exchange reactions took place in both Cr and Cr-Al systems. In Cr-Al plasmas, the distributions of high-charge-state ions exhibit high energy tails 50 μs after discharge ignition, but no such tails were observed at 500 μs. The energy ratios of ions of different charge states at the beginning of the pulse, when less neutral atoms were in the space in front of the cathode, suggest that ions are accelerated by an electric field. The situation is not so clear after 50 μs due to particle collisions. The initial mean ion charge state of Cr was about the same in Cr and in Cr-Al plasmas, but it decreased more rapidly in Cr-Al plasmas compared to the decay in Cr plasma. The faster decay of the mean ion charge state and ion energy caused by the addition of Al into a pure Cr cathode suggests that the mean ion charge state is determined not only by ionization processes at the cathode spot but also by inelastic collision between different elements.

  18. Microstructures and Thermal Properties of Cold-Sprayed Cu-Cr Composite Coatings

    NASA Astrophysics Data System (ADS)

    Kikuchi, S.; Yoshino, S.; Yamada, M.; Fukumoto, M.; Okamoto, K.

    2013-08-01

    Copper-based composites for thermal conductive components were prepared via the cold spray process, and the deposition efficiency and adhesion morphology of feedstock powders on Cu substrate were evaluated. Cu-based composites were fabricated using Cu-Cr mixed powders with their mixture ratio of 20, 35, 50, and 65 mass% Cr onto oxygen-free copper substrate with N2 carrier gas. Cu-Cr composite coatings were investigated for their Cr content ratio, microstructures, and thermal conductivity. The Cr content ratio in the coating was approximately 50-60% of feedstock mixture ratio due to the low formability of the hard particles. Transmission electron microscopy characterizations revealed that an oxygen-rich layer exists at the Cr particle/Cu substrate interface, which contributes to the deposition of the Cr particles. After the heat treatment at 1093 K, the coatings showed denser cross-sectional structures than those before the heat treatment, and the thermal conductivity was improved as a result of the recrystallization of Cu matrix.

  19. Phase Separation kinetics in an Fe-Cr-Al alloy

    SciTech Connect

    Capdevila, C.; Miller, Michael K; Chao, J.

    2012-01-01

    The {alpha}-{alpha}{prime} phase separation kinetics in a commercial Fe-20 wt.% Cr-6 wt.% Al oxide dispersion-strengthened PM 2000{trademark} steel have been characterized with the complementary techniques atom probe tomography and thermoelectric power measurements during isothermal aging at 673, 708, and 748 K for times up to 3600 h. A progressive decrease in the Al content of the Cr-rich {alpha}{prime} phase was observed at 708 and 748 K with increasing time, but no partitioning was observed at 673 K. The variation in the volume fraction of the {alpha}{prime} phase well inside the coarsening regime, along with the Avrami exponent 1.2 and activation energy 264 kJ mol{sup -1}, obtained after fitting the experimental results to an Austin-Rickett type equation, indicates that phase separation in PM 2000{trademark} is a transient coarsening process with overlapping nucleation, growth, and coarsening stages.

  20. Two-Phase (TiAl+TiCrAl) Coating Alloys for Titanium Aluminides

    NASA Technical Reports Server (NTRS)

    Brady, Michael P. (Inventor); Smialek, James L. (Inventor); Brindley, William J. (Inventor)

    1998-01-01

    A coating for protecting titanium aluminide alloys, including the TiAl gamma + Ti3Al (alpha(sub 2)) class, from oxidative attack and interstitial embrittlement at temperatures up to at least 1000 C. is disclosed. This protective coating consists essentially of titanium, aluminum. and chromium in the following approximate atomic ratio: Ti(41.5-34.5)Al(49-53)Cr(9.5-12.5)

  1. Structure and wear behavior of AlCrSiN-based coatings

    NASA Astrophysics Data System (ADS)

    Chen, Yun; Du, Hao; Chen, Ming; Yang, Jun; Xiong, Ji; Zhao, Haibo

    2016-05-01

    AlCrN, AlCrSiCN, AlCrSiN/MoN, and AlCrSiN/NbN coatings have been deposited on high-polished WC-Co cemented carbide substrate and tools by mid-frequency magnetron sputtering in Ar/N2 mixtures. Al0.6Cr0.4, Al0.6Cr0.3Si0.1, and C/Mo/Nb targets were used during the deposition. The microstructure and mechanical properties of as-deposited coatings were investigated. Investigations of the wear behaviors of coated tools were also performed. The results showed that cubic structure was formed in the coatings. Broader CrAlN (1 1 1) and (2 0 0) peaks without SiNx peak were formed in the AlCrSiN/MexN coatings, which showed a nanocomposited structure. Meanwhile, according to SEM micrographs, AlCrN exhibited a columnar structure, while, AlCrSiCN, AlCrSiN/MoN, and AlCrSiN/NbN coatings showed nanocrystalline morphology. The nano-multilayered coatings performed higher hardness, H/E, and H3/E2 ratios compared with AlCrN coating. Through the Rockwell adhesion test, all the coatings exhibited adhesion strength quality HF1. After turning Inconel 718 under dry condition, the nano-multilyered coatings showed better wear resistance than AlCrN coating. Due to the molybdenum and niobium in the coating, AlCrSiN/MoN and AlCrSiN/NbN coatings showed the best wear resistance.

  2. Electrical Transport Properties of Liquid Al-Cu Alloys

    NASA Astrophysics Data System (ADS)

    Thakore, B. Y.; Khambholja, S. G.; Suthar, P. H.; Jani, A. R.

    2010-06-01

    Electrical transport properties viz. electrical resistivity, thermoelectric power and thermal conductivity of liquid Al-Cu alloys as a function of Cu concentration have been studied in the present paper. Ashcroft empty core model potential has been used to incorporate the ion-electron interaction. To incorporate the exchange and correlation effects, five different forms of local field correction functions viz. Hartree, Taylor, Ichimaru et al., Farid et al. and Sarkar et al. have been used. The transport properties of binary system have been studied using Faber-Ziman formulation combined with Ashcroft-Langreth (AL) partial structure factor. The computed values of electrical resistivity are compared with experimental data and for low Cu concentration, good agreement has been observed. Further, thermoelectric power and thermal conductivity have also been predicted.

  3. Comparison of AlCrN and AlCrTiSiN coatings deposited on the surface of plasma nitrocarburized high carbon steels

    NASA Astrophysics Data System (ADS)

    Chen, Wanglin; Zheng, Jie; Lin, Yue; Kwon, Sikchol; Zhang, Shihong

    2015-03-01

    The AlCrN and AlCrTiSiN coatings were produced on the surface of plasma nitrocarburized T10 steels by multi-arc ion plating. The comparison of the microstructures and mechanical properties of the duplex coatings were investigated by means of X-ray diffraction, optical microscope, scanning electron microscope and transmission electron microscope, in association with mechanical property measurement. The results show that the AlCrN coatings with columnar grown are mainly composed of nanocrytalline fcc-(Cr,Al)N phases with {111} preferred orientation, whereas the superlattice and nanocomposite AlCrTiSiN coatings with planar growth mainly consist of nanocrystalline fcc-(Cr,Al)N phases with {100} perfected orientation, hcp-AlN and Si3N4 amorphous phases. The AlCrTiSiN duplex coating with the compound layer reveals higher hardness, adhesion strength, load capacity and lower friction coefficient when compared with the other duplex coatings, which is due to its superlattice and nanocomposite structure. Additionally, these improved properties are related to the appearance of the γ‧-phase which plays the nucleation sites for the coating nitrides and provides a strong supporting effect for the AlCrN and AlCrTiSiN coatings. The main wear mechanism of the duplex coatings without compound layer is spalling and chipping wear as well as tribooxidation wear, whereas the main wear mechanism of the duplex coatings with compound layer is tribooxidation wear.

  4. Enhancing the Reactivity of Al/CuO Nanolaminates by Cu Incorporation at the Interfaces.

    PubMed

    Marín, Lorena; Nanayakkara, Charith E; Veyan, Jean-Francois; Warot-Fonrose, Bénédicte; Joulie, Sébastien; Estève, Alain; Tenailleau, Christophe; Chabal, Yves J; Rossi, Carole

    2015-06-10

    In situ deposition of a thin (∼5 nm) layer of copper between Al and CuO layers is shown to increase the overall nanolaminate material reactivity. A combination of transmission electron microscopy imaging, in situ infrared spectroscopy, low energy ion scattering measurements, and first-principles calculations reveals that copper spontaneously diffuses into aluminum layers (substantially less in CuO layers). The formation of an interfacial Al:Cu alloy with melting temperature lower than pure Al metal is responsible for the enhanced reactivity, opening a route to controlling the stochiometry of the aluminum layer and increasing the reactivity of the nanoenergetic multilayer systems in general. PMID:25988997

  5. Electrical conductivity and mechanical properties of Cu-0.7wt% Cr and Cu-1.0wt% Cr alloys processed by severe plastic deformation

    NASA Astrophysics Data System (ADS)

    Kommel, L.; Pokatilov, A.

    2014-08-01

    As-cast Cu-0.7wt% Cr and Cu-1.0wt% Cr alloys were subjected to equal-channel angular pressing (ECAP), hard cyclic viscoplastic (HCV) deformation and post deformation heat treatment for receiving an ultrafine grained material with a combination of high strength, good wear resistance and high electric conductivity. Samples from Cu-0.7wt% Cr alloy were processed up to six passes and Cu-1wt% Cr alloy samples were processed up to four passes of ECAP via Bc route. HCV deformation of samples was conducted by frequency of 0.5 Hz for 20 cycles at tension-compression strain amplitudes of +/-0.05%, +/-0.1%, +/-0.5%, +/-1% and +/-1.5%, respectively. During HCV deformation, as-cast Cu-0./wt% Cr alloy show fully viscoelastic behavior at strain/stress amplitude of +/-0.05% while ECAP processed material show the same behavior at strain amplitude of +/-0.1%. The Young modulus was increased from ~120 GPa up to ~150 GPa. The results illustrated that specific volume wear decrease with increasing of hardness but the measured coefficient of friction (COF ~ 0.6) was approximately the same for all samples at the end of wear testing. The hardness after ECAP for 6 passes by Bc route was 192HV0.1 and electric conduction 74.16% IACS, respectively. By this the as-cast Cu-0./wt% Cr alloy (heat treated at 1000 °C for 2h) has microhardness ~70HV0.1 and electrical conductivity of ~40% IACS. During aging at the temperatures in the interval of 250-550 °C for 1h the hardness and electrical conductivity were stabilized to mean values of 120+/-5HV0.1 and to 93.4+/-0.3% IACS, respectively. The hardness and electric conductivity took decrease by temperature increase over ~550 °C, respectively. The results of present experimental investigation show that UFG Cu- 0.7wt% Cr alloy with compare to Cu-1.0% Cr alloy is a highly electrical conductive and high temperature wear resistant material for using in electrical industry.

  6. Adhesion enhancement of ion beam mixed Cu/Al/polyimide

    NASA Astrophysics Data System (ADS)

    Chang, G. S.; Jung, S. M.; Lee, Y. S.; Choi, I. S.; Whang, C. N.; Woo, J. J.; Lee, Y. P.

    1997-01-01

    Cu (400 Å)/polyimide was mixed with 80 keV Ar+ and N2+ from 1.0×1015 to 2.0×1016 ions/cm2. The same processes were repeated for the Cu (400 Å)/Al (50 Å)/polyimide system which has Al as a buffer layer. The quantitative adhesion strength was measured by a standard scratch test. X-ray photoelectron spectroscopy was employed to investigate the change in the chemical bonds of the ion beam mixed polyimide substrate and the intermediate effects for the adhesion enhancement in Cu/Al/polyimide. Two distinct tendencies are observed in the adhesion strength: Cu/Al/polyimide is more adhesive than Cu/polyimide after ion beam mixing, and N2+ ions are more effective in the adhesion enhancement than Ar+. The formation of an interlayer compound of CuAl2O4 accounts for the former, while the latter is understood by the fact that N2+ ions produce more pyridinelike moiety, amide group and tertiary amine moiety which are known as adhesion promoters.

  7. Experimental evidence of Cr magnetic moments at low temperature in Cr2A(A=Al, Ge)C.

    PubMed

    Jaouen, M; Bugnet, M; Jaouen, N; Ohresser, P; Mauchamp, V; Cabioc'h, T; Rogalev, A

    2014-04-30

    From x-ray magnetic circular dichroism experiments performed at low temperature on Cr2AlC and Cr2GeC thin films, it is evidenced that Cr atoms carry a net magnetic moment in these ternary phases. It is shown that the Cr magnetization of the Al-based compound nearly vanished at 100 K in agreement with what has been recently observed on bulk. X-ray linear dichroism measurements performed at various angles of incidence and temperatures clearly demonstrate the existence of a charge ordering along the c axis of the structure of Cr2AlC. All these experimental observations support, in part, theoretical calculations claiming that Cr dd correlations have to be considered to correctly describe the structure and properties of these Cr-based ternary phases. PMID:24721758

  8. Synthesis of porous Cu from Al-Cu-Co decagonal quasicrystalline alloys

    NASA Astrophysics Data System (ADS)

    Kalai Vani, V.; Kwon, O. J.; Hong, S. M.; Fleury, E.

    2011-07-01

    The formation of a porous Cu structure from cast Al-Cu-Co decagonal quasicrystalline alloys has been studied using a selective corrosion technique. Two alkaline solutions were selected based on the electrochemical properties of the constituent elements. Selective corrosion of Al and Co was achieved by chemical immersion of the cast Al-Cu-Co alloy in both 5 M NaOH and 0.5 M Na2CO3 solutions; values for BET surface-to-weight ratio of up to 30 m2/g could be reached. Microstructural analyses indicated that the architecture of the resulting porous structures was composed of a needle-type phase, remaining from the decagonal phase, in addition to Cu and Cu-Co phases.

  9. Effects of competing magnetic interactions on the electronic transport properties of CuCrSe{sub 2}

    SciTech Connect

    Tewari, Girish C.; Karppinen, Maarit; Rastogi, Ashok K.

    2013-02-15

    We have synthesized single-phase samples of the CuCrSe{sub 2} phase that exhibits hexagonal-rhombohedral layered crystal structure with space group R3m. Here we present a detailed study of electronic transport and magnetic properties of CuCrSe{sub 2}. We moreover investigate the heat capacity of CuCrSe{sub 2} in comparison to that of CuCrS{sub 2}. The electrical resistivity of CuCrSe{sub 2} shows metallic-like behavior down to 2 K, while the thermoelectric power is large around 100 {mu}V K{sup -1} at 300 K. A weak anomaly in resistivity and a rounded maximum in magnetic susceptibility are observed around 55 K. No sharp transition at 55 K is observed in the heat capacity of CuCrSe{sub 2}, rather a visible maximum is seen. At low temperatures from 2 to 14 K, the magnetic heat capacity follows T{sup 2}-dependence. We tentatively believe this behavior of CuCrSe{sub 2} to be due to competing magnetic interactions between intralayer Cr atoms. The ferromagnetic Cr-Se-Cr indirect exchange among intralayer Cr atoms is enhanced in the selenide compound (that is more metallic than the sulfide compound), and competes with the antiferromagnetic Cr-Cr direct interactions. The interlayer antiferromagnetic exchange through Cu atoms leads to magnetic ordering at low temperature at T{sub N}=55 K. - Graphical abstract: Comparison of magnetic properties of CuCrSe{sub 2} and CuCrS{sub 2} indicates a sharp cusp-like anomaly in magnetic susceptibility at the antiferromagnetic transition of CuCrS{sub 2} while the maximum of CuCrSe{sub 2} is well rounded. Magnetization is reversible after field-cooling (FC) and zero-field-cooling (ZFC) for both compounds. Highlights: Black-Right-Pointing-Pointer Layered CuCrSe{sub 2} can be synthesized in both fully and partially cation-ordered forms. Black-Right-Pointing-Pointer Contrary to previously believed insulating nature the cation-ordered phase is metallic. Black-Right-Pointing-Pointer Magnetic property of CuCrSe{sub 2} is somewhat different from

  10. Al/sub 2/O/sub 3/ adherence on CoCrAl alloys

    SciTech Connect

    Kingsley, L.M.

    1980-04-01

    Adherence of protective oxides on NiCrAl and CoCrAl superalloys has been promoted by a dispersion of a highly oxygen reactive element or its oxide being produced within the protection system. Two aspects of this subject are investigated here: the use of Al/sub 2/O/sub 3/ as both the dispersion and protective oxide; and the production of an HfO/sub 2/ dispersion while simultaneously aluminizing the alloy. It was found that an Al/sub 2/O/sub 3/ dispersion will act to promote the adherence of an external scale of Al/sub 2/O/sub 3/ to a degree comparable to previously tested dispersions and an HfO/sub 2/ dispersion comparable to that produced by a Rhines pack treatment is produced during aluminization.

  11. Corrosion Behavior of Al-Al3Ni and Al-Al2Cu Functionally Graded Materials Fabricated by a Centrifugal Method

    NASA Astrophysics Data System (ADS)

    Noda, Kazuhiko; Miyahara, Keita; Watanabe, Yoshimi

    2008-02-01

    Intermetallic compounds, such as Al3Ni and Al2Cu, are effective for enhancing the mechanical properties of an alloy. Al-Al3Ni and Al-Al2Cu functionally graded materials (FGMs) might be attractive materials for advanced materials. Al-Al3Ni and Al-Al2Cu FGMs were fabricated by a centrifugal method; the centrifugal method is an extremely effective method for fabricating FGMs. Al-Al3Ni and Al-Al2Cu FGMs that had a graded distribution of intermetallic compounds could be produced by this in-situ centrifugal method. Particle size, particle shape and the distribution of intermetallic compounds were controlled by varying the content of the alloy element (Ni, Cu) in the master alloy, the cooling rate in casting and the gravity number. The casting mechanism is explained in terms of the microstructures of the Al-Al3Ni and Al-Al2Cu FGMs fabricated by this method. The corrosion behavior of the FGMs was investigated by electrochemical analysis. Polarization curves of the FGMs in a borate solution were measured by a potentiodynamic method. The presence of Al2Cu exerted a larger effect on the corrosion behavior of the FGMs than Al3Ni. Analysis of the polarization curve parameters was effective for evaluating the corrosion resistance of the FGMs.

  12. Characterization of transparent superconductivity Fe-doped CuCrO2 delafossite oxide

    NASA Astrophysics Data System (ADS)

    Taddee, Chutirat; Kamwanna, Teerasak; Amornkitbamrung, Vittaya

    2016-09-01

    Delafossite CuCr1-xFexO2 (0.0 ≤ x ≤ 0.15) semiconductors were synthesized using a self-combustion urea nitrate process. The effects of Fe concentration on its microstructural, optical, magnetic, and electrical properties were investigated. X-ray diffraction (XRD) analysis results revealed the delafossite structure in all the samples. The lattice spacing of CuCr1-xFexO2 slightly increased with increasing substitution of Fe at the Cr sites. The optical properties measured at room temperature using UV-visible spectroscopy showed a weak absorbability in the visible light and near IR regions. The corresponding direct optical band gap was about 3.61 eV, exhibiting transparency in the visible region. The magnetic hysteresis loop measurements showed that the Fe-doped CuCrO2 samples exhibited ferromagnetic behavior at room temperature. This indicated that the substitution of Fe3+ for Cr3+ produced a mixed effect on the magnetic properties of CuCrO2 delafossite oxide. The temperature dependent resistivity measurements clearly revealed the presence of superconductivity in the CuCr1-xFexO2 with a superconducting transition up to 118 K.

  13. Importance of doping and frustration in itinerant Fe-doped Cr2Al

    DOE PAGESBeta

    Susner, M. A.; Parker, D. S.; Sefat, A. S.

    2015-05-12

    We performed an experimental and theoretical study comparing the effects of Fe-doping of Cr2Al, an antiferromagnet with a N el temperature of 670 K, with known results on Fe-doping of antiferromagnetic bcc Cr. (Cr1-xFex)2Al materials are found to exhibit a rapid suppression of antiferromagnetic order with the presence of Fe, decreasing TN to 170 K for x=0.10. Antiferromagnetic behavior disappears entirely at x≈0.125 after which point increasing paramagnetic behavior is exhibited. Moreover, this is unlike the effects of Fe doping of bcc antiferromagnetic Cr, in which TN gradually decreases followed by the appearance of a ferromagnetic state. Theoretical calculations explainmore » that the Cr2Al-Fe suppression of magnetic order originates from two effects: the first is band narrowing caused by doping of additional electrons from Fe substitution that weakens itinerant magnetism; the second is magnetic frustration of the Cr itinerant moments in Fe-substituted Cr2Al. In pure-phase Cr2Al, the Cr moments have an antiparallel alignment; however, these are destroyed through Fe substitution and the preference of Fe for parallel alignment with Cr. This is unlike bulk Fe-doped Cr alloys in which the Fe anti-aligns with the Cr atoms, and speaks to the importance of the Al atoms in the magnetic structure of Cr2Al and Fe-doped Cr2Al.« less

  14. Temperature dependence diode parameters studies of Al/CuPc/n-Si/Al structure

    NASA Astrophysics Data System (ADS)

    Kumar, Ratnesh; Kaur, Ramneek; Sharma, Mamta; Kaur, Maninder; Tripathi, S. K.

    2015-08-01

    This paper presents the fabrication of Al/CuPc/n-Si/Al metal-organic-semiconductor diode. The copper phthalocyanine as organic layer is deposited on Si substrate by thermal evaporation technique. The temperature dependent current-voltage measurements are performed on Al/CuPc/n-Si structure. The important diode parameters i.e. the barrier height and ideality factor have been calculated. The temperature dependence of barrier height and ideality factor has been studied.

  15. Formation Mechanism of CuAlO2 Prepared by Rapid Thermal Annealing of Al2O3/Cu2O/Sapphire Sandwich Structure

    NASA Astrophysics Data System (ADS)

    Shih, C. H.; Tseng, B. H.

    Single-phase CuAlO2 films were successfully prepared by thin-film reaction of an Al2O3/Cu2O/sapphire sandwich structure. We found that the processing parameters, such as heating rate, holding temperature and annealing ambient, were all crucial to form CuAlO2 without second phases. Thermal annealing in pure oxygen ambient with a lower temperature ramp rate might result in the formation of CuAl2O4 in addition to CuAlO2, since part of Cu2O was oxidized to form CuO and caused the change in reaction path, i.e. CuO + Al2O3 → CuAl2O4. Typical annealing conditions successful to prepare single-phase CuAlO2 would be to heat the sample with a temperature rampt rate higher than 7.3 °C/sec and hold the temperature at 1100 °C in air ambient. The formation mechanism of CuAlO2 has also been studied by interrupting the reaction after a short period of annealing. TEM observations showed that the top Al2O3 layer with amorphous structure reacted immediately with Cu2O to form CuAlO2 in the early stage and then the remaining Cu2O reacted with the sapphire substrate.

  16. Interstitial precipitation in Fe-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Spear, W. S.; Polonis, D. H.

    1994-06-01

    Two separate stages of precipitation have been identified during the aging of ternary Fel8Cr3Al and Fel8Cr5Al alloys at temperatures in the vicinity of 475 °C. The first stage involves the formation of interstitial precipitates resulting from C and N impurities; the second and slower stage is the formation of the Cr-rich α' phase. Transmission electron microscopy (TEM) results show that carbonitride precipitation occurs preferentially at dislocations, stacking faults, and grain boundaries, and also uniformly through the matrix. Aging for times in excess of 400 hours at 475 °C promotes coarsening of the heterogeneous precipitates and dissolution of the uniformly distributed matrix particles. A resistometric analysis shows that the kinetics of the initial stages of precipitation can be described by a (time)2/3 relation. This kinetic behavior is explained in terms of stress-assisted diffusion in the highly stressed matrix resulting from coherency strains accompanying carbonitride precipitation. Experimental values of the activation energy for the first stage reaction correlate closely with those reported for the interstitial diffusion of C and N in alpha iron.

  17. Creep Testing of High-Temperature Cu-8 Cr-4 Nb Alloy Completed

    NASA Technical Reports Server (NTRS)

    1995-01-01

    A Cu-8 at.% Cr-4 at.% Nb (Cu-8 Cr-4 Nb) alloy is under development for high-temperature, high heatflux applications, such as actively cooled, hypersonic vehicle heat exchangers and rocket engine combustion chambers. Cu-8 Cr-4 Nb offers a superior combination of strength and conductivity. It has also shown exceptional low-cycle fatigue properties. Following preliminary testing to determine the best processing route, a more detailed testing program was initiated to determine the creep lives and creep rates of Cu-8 Cr-4 Nb alloy specimens produced by extrusion. Testing was conducted at the NASA Lewis Research Center with constant-load vacuum creep units. Considering expected operating temperatures and mission lives, we developed a test matrix to accurately determine the creep properties of Cu-8 Cr-4 Nb between 500 and 800 C. Six bars of Cu-8 Cr-4 Nb were extruded. From these bars, 54 creep samples were machined and tested. The figure on the left shows the steady-state, or second-stage, creep rates for the samples. Comparison data for NARloy-Z (Cu-3 wt % Ag-0.5 wt % Zr), the alloy currently used in combustion chamber liners, were not unavailable. Therefore the steady-state creep rates for Cu at similar temperatures are presented. As expected, in comparison to pure Cu, the creep rates for Cu-8 Cr-4 Nb are much lower. The lives of the samples are presented in the figure on the right. As shown, Cu-8 Cr-4 Nb at 800 C is comparable to NARloy-Z at 648 C. At equivalent temperatures, Cu-8 Cr-4 Nb enjoys a 20 to 50 percent advantage in stress for a given life and 1 to 3 orders of magnitude greater life at a given stress. The improved properties allow for design tradeoffs and improvements in new and existing heat exchangers such as the next generation of combustion chamber liners. Average creep rates for Cu-8 Cr-4 Nb and pure Cu are shown. Average creep lives for Cu-8 Cr- 4 Nb and NARloy-Z are also shown. Currently, two companies are interested in the commercial usage of the Cu

  18. Interdiffusion in. beta. phase Cu--Al alloys

    SciTech Connect

    Romig, A.D. Jr.

    1983-06-01

    The diffusion behavior of ..beta.. phase Cu--Al has been studied at 800, 850, and 950 /sup 0/C using the experimental approach and analysis scheme of Kirkendall and Darken. Diffusion couples were made using the window frame technique and concentration profiles were determined by electron probe microanalysis. The chemical diffusion coefficient, D was found to be D = 0.65 exp(-42200/RT) cm/sup 2//s. The diffusivity was observed to be independent of composition over the range 11--13 wt. % Al. The self-diffusion coefficients D/sub Cu/ and D/sub Al/ were determined to be D/sub Al/ = 0.13 exp(-38900/RT) cm/sup 2//s and D/sub Cu/ = 2.2 exp(-43400/RT) cm/sup 2//s. All activation energies are in calories/mole.

  19. Diffusion bonding of beryllium to CuCrZr for ITER applications.

    SciTech Connect

    Cadden, Charles H.; Puskar, Joseph David; Goods, Steven Howard

    2008-08-01

    Low temperature diffusion bonding of beryllium to CuCrZr was investigated for fusion reactor applications. Hot isostatic pressing was accomplished using various metallic interlayers. Diffusion profiles suggest that titanium is effective at preventing Be-Cu intermetallics. Shear strength measurements suggest that acceptable results were obtained at temperatures as low as 540C.

  20. Fate of Cu, Cr, and As during combustion of impregnated wood with and without peat additive.

    PubMed

    Lundholm, Karin; Boström, Dan; Nordin, Anders; Shchukarev, Andrei

    2007-09-15

    The E.U. Directive on incineration of waste regulates the harmful emissions of particles and twelve toxic elements, including copper, chromium, and arsenic. More information is critically needed on the speciation and behavior of these trace elements during combustion, including the effects of different process variables, as well as of different fuels and fuel mixtures. Using a 15 kW pellets-fueled grate burner, experiments were performed to determine the fate of copper, chromium, and arsenic during combustion of chromate copper arsenate (CCA) preservative wood. The effects of co-combustion of CCA-wood with peat were also studied since peat fuels previously have proved to generally reduce ash related problems. The fate and speciation of copper, chromium, and arsenic were determined from analysis of the flue gas particles and the bottom ash using SEM-EDS, XRD, XPS, and ICP-AES. In addition, chemical equilibrium model calculations were performed to interpret the experimental findings. The results revealed that about 5% copper, 15% chromium, and 60% arsenic were volatilized during combustion of pure CCA-wood, which is lower than predicted volatilization from the individual arsenic, chromium, and copper oxides. This is explained by the formation of more stable refractory complex oxide phases for which the stability trends and patterns are presented. When co-combusted with peat, an additional stabilization of these phases was obtained and thus a small but noteworthy decrease in volatilization of all three elements was observed. The major identified phases for all fuels were CuCrO2(s), (Fe, Mg, Cu)(Cr, Fe, Al)04(s), Cr2O3(s), and Ca3(AsO4)2(s). Arsenic was also identified in the fine particles as KH2AsO4(s) and As2O3(s). A strong indication of hexavalent chromium in the form of K2CrO4 or as a solid solution between K3Na(CrO4)2 and K3Na(SO4)2 was found in the fine particles. Good qualitative agreement was observed between experimental data and chemical equilibrium model

  1. Normal and excess nitrogen uptake by iron-based Fe-Cr-Al alloys: the role of the Cr/Al atomic ratio

    NASA Astrophysics Data System (ADS)

    Jung, K. S.; Schacherl, R. E.; Bischoff, E.; Mittemeijer, E. J.

    2011-06-01

    Upon nitriding ferritic iron-based Fe-Cr-Al alloys, containing a total of 1.50 at. % (Cr + Al) alloying elements with varying Cr/Al atomic ratio (0.21-2.00), excess nitrogen uptake occurred, i.e. more nitrogen was incorporated in the specimens than compatible with only inner nitride formation and equilibrium nitrogen solubility of the unstrained ferrite matrix. The amount of excess nitrogen increased with decreasing Cr/Al atomic ratio. The microstructure of the nitrided zone was investigated by X-ray diffraction, electron probe microanalysis, transmission electron microscopy and electron energy loss spectroscopy. Metastable, fine platelet-type, mixed Cr1- x Al x N nitride precipitates developed in the nitrided zone for all of the investigated specimens. The degree of coherency of the nitride precipitates with the surrounding ferrite matrix is discussed in view of the anisotropy of the misfit. Analysis of nitrogen-absorption isotherms, recorded after subsequent pre- and de-nitriding treatments, allowed quantitative differentiation of different types of nitrogen taken up. The amounts of the different types of excess nitrogen as function of the Cr/Al atomic ratio are discussed in terms of the nitride/matrix misfit and the different chemical affinities of Cr and Al for N. The strikingly different nitriding behaviors of Fe-Cr-Al and Fe-Cr-Ti alloys could be explained on this basis.

  2. Comparative Study of CuO Species on CuO/Al2O3, CuO/CeO2-Al2O3 and CuO/La2O-Al2O3 Catalysts for CO Oxidation

    NASA Astrophysics Data System (ADS)

    Jin, Ling-yun; He, Mai; Lu, Ji-qing; Luo, Meng-fei; Fang, Ping; Xie, Yun-long

    2007-10-01

    CuO/Al2O3, CuO/CeO2-Al2O3, and CuO/La2O3-Al2O3 (denoted as Cu/Al, Cu/CeAl, and Cu/LaAl) catalysts were prepared by an impregnation method. CuO species and CuO/Al2O3 thermal solid-solid interaction were characterized by in situ XRD, Raman spectroscopy and H2-TPR techniques. For the Cu/Al catalyst, a CuAl2O4 phase exists between the CuO and Al2O3 layer and the CuO phase exists on the surface in both highly dispersed and bulk forms. For the Cu/CeAl catalyst, there is highly dispersed and bulk CuO on the surface, but most of the CuO has transferred into the internal layer of CeO2 as bulk CuO and CuAl2O4. For the Cu/LaAl catalyst, only bulk CuO is present on the surface of the catalyst and no CuAl2O4 is formed. The catalytic activity order for CO oxidation is Cu/CeAl>Cu/Al>Cu/LaAl. The highly dispersed CuO on the catalyst surface may be the active phase for CO oxidation. The results show that the addition of CeO2 not only promotes both the transference of CuO and the formation of CuAl2O4 but also favors the CO oxidation due to the association of highly dispersed CuO with CeO2, while La2O3 hinders the transference of CuO and the formation of CuAl2O4.

  3. Carbon Nanostructures Grown on Fe-Cr-Al Alloy

    NASA Astrophysics Data System (ADS)

    Čaplovičová, Mária; Čaplovič, Ľubomír; Búc, Dalibor; Vinduška, Peter; Janík, Ján

    2010-11-01

    The morphology and nanostructure of carbon nanotubes (CNTs), synthesized directly on Fe-Cr-Al-based alloy substrate using an alcohol catalytic chemical vapour deposition method (ACCVD), were examined by transmission electron microscopy (TEM). The grown CNTs were entangled with chain-like, bamboo-like, and necklace-like morphologies. The CNT morphology was affected by the elemental composition of catalysts and local instability of deposition process. Straight and bended CNTs with bamboo-like nanostructure grew mainly on γ-Fe and Fe3C particles. The synthesis of necklace-like nanostructures was influenced by silicon oxide, and growth of chain-like nanostructures was supported by a catalysts consisting of Fe, Si, oxygen and trace of Cr. Most of nanotubes grew according to base growth mechanism.

  4. Supercoducting property of Zr-Cu-Al-Ni-Nb alloys

    NASA Astrophysics Data System (ADS)

    Okai, D.; Motoyama, G.; Kimura, H.; Inoue, A.

    The superconducting property of Zr55Cu(30-X)Al10Ni5NbX alloys prepared by arc melting and liquid quenching methods was investigated by magnetic susceptibility measurements. The crystalline alloys with X = 0∼25 at.% prepared by arc melting method exhibited superconductivity with maximum Tc,on of 10.1 K. The alloys (X = 10∼23 at.%) with crystalline particles embedded in an amorphous structure, which were fabricated by melt spinning method, showed superconductivity with Tc,on of less than 4.0 K. The superconducting property of the Zr-Cu-Al-Ni-Nb alloys was attributed to superconducting phases of Zr2Cu, Zr2Ni, Zr65Al10Nb25 and Zr-Nb contained in the Zr-Cu-Al-Ni-Nb alloys. The melt-spun Zr55Cu(30-X)Al10Ni5NbX (X = 10∼20 at.%) alloys exhibited glass transition at 718∼743 K and were found to be superconducting metallic glasses.

  5. Zener Relaxation Peak in an Fe-Cr-Al Alloy

    NASA Astrophysics Data System (ADS)

    Zhou, Zheng-Cun; Cheng, He-Fa; Gong, Chen-Li; Wei, Jian-Ning; Han, Fu-Sheng

    2002-11-01

    We have studied the temperature spectra of internal friction and relative dynamic modulus of the Fe-(25 wt%)Cr-(5 wt%)Al alloy with different grain sizes. It is found that a peak appears in the internal friction versus temperature plot at about 550°C. The peak is of a stable relaxation and is reversible, which occurs not only during heating but also during cooling. Its activation energy is 2.5 (+/- 0.15) eV in terms of the Arrhenius relation. In addition, the peak is not obvious in specimens with a smaller grain size. It is suggested that the peak originates from Zener relaxation.

  6. Microstructure and Mechanical Properties of Vacuum Plasma Sprayed Cu-8Cr-4Nb

    NASA Technical Reports Server (NTRS)

    Holmes, Richard; Ellis, David; McKechnie, Timothy; Hickman, Robert

    1997-01-01

    This paper compares the tensile properties of Cu-8Cr-4Nb material produced by VPS to material previously produced by extrusion. The microstructure of the VPS material is also presented. The combustion chamber liner of rocket motors represents an extreme materials application. The liner hot wall is exposed to a 2760 C (5000 F) flame while the cold side is exposed to cryogenic hydrogen liquid. Materials for use in the combustion chamber liner require a combination of high temperature strength, creep resistance, and low cycle fatigue resistance along with high thermal conductivity. The hot side is also subject to localized cycles between reducing and oxidizing environments that degrade the liner by a process called blanching. A new Cu-8 at.% Cr-4 at% Nb (Cu-8Cr-4Nb) alloy has been developed at NASA Lewis Research Center as a replacement for the currently used alloy, NARloy-z (Cu-3 wt.% Ag-0.5 wt.% Zr). The alloy is strengthened by a fine dispersion of Cr2Nb particles. The alloy has better mechanical properties than NARloy-Z while retaining most of the thermal conductivity of pure copper. The alloy has been successfully consolidated by extrusion and hot isostatic pressing (HIPing). However, vacuum plasma spraying (VPS) offers several advantages over prior consolidation methods. VPS can produce a near net shape piece with the profile of the liner. In addition, oxidation resistant and thermal barrier coatings can be incorporated as an integral part of the liner hot wall during the VPS deposition. The low oxygen VPS Cu-8Cr-4Nb exhibits a higher strength than Cu-8Cr-4Nb produced by extrusion at elevated temperatures and a comparable strength at room temperature. Moduli and ductility were not significantly different. However, the ability to produce parts to near-net shape and maintain the good elevated temperature tensile properties of the extruded Cu-8Cr-4Nb makes VPS an attractive processing method for fabricating rocket engine combustion liners.

  7. Controlling Bulk Cu6Sn5 Nucleation in Sn0.7Cu/Cu Joints with Al Micro-alloying

    NASA Astrophysics Data System (ADS)

    Xian, J. W.; Belyakov, S. A.; Gourlay, C. M.

    2016-01-01

    We show that dilute Al additions can control the size of primary Cu6Sn5 rods in Sn-0.7Cu/Cu ball grid array joints. In Sn-0.7Cu-0.05Al/Cu joints, the number of primary Cu6Sn5 per mm2 is ˜7 times higher and the mean three-dimensional length of rods is ˜4 times smaller than in Al-free Sn-0.7Cu/Cu joints, while the area fraction of primary Cu6Sn5 is similar. It is shown that epitaxial nucleation of primary Cu6Sn5 occurs on δ-Cu33Al17 or γ 1-Cu9Al4 particles, which are stable in the Sn-0.7Cu-0.05Al melt during holding at 250°C. The observed facet relationships agree well with previously determined orientation relationships between δ-Cu33Al17 and Cu6Sn5 in hypereutectic Sn-Cu-Al alloys and result in a good lattice match with <˜2.5% lattice mismatch on two different interfacial planes.

  8. Growth and characterization of TiAlN/CrAlN superlattices prepared by reactive direct current magnetron sputtering

    SciTech Connect

    Barshilia, Harish C.; Deepthi, B.; Rajam, K. S.; Bhatti, Kanwal Preet; Chaudhary, Sujeet

    2009-01-15

    TiAlN and CrAlN coatings were prepared using a reactive direct current magnetron sputtering system from TiAl and CrAl targets. Structural characterization of the coatings using x-ray diffraction (XRD) revealed the B1 NaCl structure of TiAlN and CrAlN coatings with a prominent reflection along the (111) plane. The XPS data confirmed the bonding structures of TiAlN and CrAlN single layer coatings. Subsequently, nanolayered multilayer coatings of TiAlN/CrAlN were deposited on silicon and mild steel (MS) substrates at different modulation wavelengths ({lambda}) with a total thickness of approximately 1.0 {mu}m. The modulation wavelengths were calculated from the x-ray reflectivity data using modified Bragg's law. TiAlN/CrAlN multilayer coatings were textured along (111) for {lambda}<200 A and the XRD patterns showed the formation of superlattice structure for coatings deposited at {lambda}=102 A. The x-ray reflectivity data showed reflections of fifth and seventh orders for multilayer coatings deposited at {lambda}=102 and 138 A, respectively, indicating the formation of sharp interfaces between TiAlN and CrAlN layers. The cross-sectional scanning electron microscopy image of TiAlN/CrAlN multilayer coatings indicated a noncolumnar and dense microstructure. A maximum hardness of 39 GPa was observed for TiAlN/CrAlN multilayer coatings deposited at {lambda}=93 A, which was higher than the rule-of-mixture value (30 GPa) for TiAlN and CrAlN. Study of thermal stability of the coatings in air using micro-Raman spectroscopy indicated that the TiAlN/CrAlN multilayer coatings were stable up to 900 deg. C in air. TiAlN/CrAlN multilayer coatings also exhibited improved corrosion resistance when compared to the MS substrate.

  9. Development and High Temperature Property Evaluation of Ni-Co-Cr-Al Composite Electroforms

    NASA Astrophysics Data System (ADS)

    Srivastava, Meenu; Siju; Balaraju, J. N.; Ravisankar, B.

    2015-05-01

    Ni-Co-Cr-Al composite electroforms were developed with cobalt content of 10 and 40 wt.%. Cr and Al nano-particles were suspended in sulphamate electrolyte and co-deposited in the Ni-Co matrices. The surface morphology was investigated using field emission scanning electron microscope and the composition analyzed by energy-dispersive x-ray analysis. The oxidation resistance of the electroforms was studied from 600 to 1000 °C. The weight gain of Ni-10 wt.%Co-Cr-Al was less (better oxidation resistance) compared to Ni-Cr-Al and Ni-40 wt.%Co-Cr-Al. The x-ray diffraction studies revealed that the oxidation product formed on the surface of Ni-Cr-Al and Ni-10 wt.%Co-Cr-Al consisted of NiO and Al2O3, while Ni-40 wt.%Co-Cr-Al comprised oxides such as NiCo2O4, CrO3, CoO, NiO, and Al2O3. The hot corrosion behavior was investigated in 75%Na2SO4 + 25%NaCl environment at 800 °C. It was found that the hot corrosion resistance of the composite coating improved with increase in cobalt content. The probable composition suitable for high-temperature applications was found to be Ni-10 wt.%Co-Cr-Al.

  10. Oxidation of diesel soot on binary oxide CuCr(Co)-based monoliths.

    PubMed

    Soloviev, Sergiy O; Kapran, Andriy Y; Kurylets, Yaroslava P

    2015-02-01

    Binary oxide systems (CuCr2O4, CuCo2O4), deposited onto cordierite monoliths of honeycomb structure with a second support (finely dispersed Al2O3), were prepared as filters for catalytic combustion of diesel soot using internal combustion engine's gas exhausts (O2, NOx, H2O, CO2) and O3 as oxidizing agents. It is shown that the second support increases soot capacity of aforementioned filters, and causes dispersion of the particles of spinel phases as active components enhancing thereby catalyst activity and selectivity of soot combustion to CO2. Oxidants used can be arranged with reference to decreasing their activity in a following series: O3≫NO2>H2O>NO>O2>CO2. Ozone proved to be the most efficient oxidizing agent: the diesel soot combustion by O3 occurs intensively (in the presence of copper chromite based catalyst) even at closing to ambient temperatures. Results obtained give a basis for the conclusion that using a catalytic coating on soot filters in the form of aforementioned binary oxide systems and ozone as the initiator of the oxidation processes is a promising approach in solving the problem of comprehensive purification of automotive exhaust gases at relatively low temperatures, known as the "cold start" problem. PMID:25662252

  11. Host Atom Diffusion in Ternary Fe-Cr-Al Alloys

    NASA Astrophysics Data System (ADS)

    Rohrberg, Diana; Spitzer, Karl-Heinz; Dörrer, Lars; Kulińska, Anna J.; Borchardt, Günter; Fraczkiewicz, Anna; Markus, Torsten; Jacobs, Michael H. G.; Schmid-Fetzer, Rainer

    2014-01-01

    In the Fe-rich corner of the Fe-Cr-Al ternary phase diagram, both interdiffusion experiments [1048 K to 1573 K (775 °C to 1300 °C)] and 58Fe tracer diffusion experiments [873 K to 1123 K (600 °C to 850 °C)] were performed along the Fe50Cr50-Fe50Al50 section. For the evaluation of the interdiffusion data, a theoretical model was used which directly yields the individual self-diffusion coefficients of the three constituents and the shift of the original interface of the diffusion couple through inverse modeling. The driving chemical potential gradients were derived using a phenomenological Gibbs energy function which was based on thoroughly assessed thermodynamic data. From the comparison of the individual self-diffusivities of Fe as obtained from interdiffusion profiles and independent 58Fe tracer diffusivities, the influence of the B2-A2 order-disorder transition becomes obvious, resulting in a slightly higher activation enthalpy for the bcc-B2 phase and a significantly lower activation entropy for this phase.

  12. Hot corrosion of Co-Cr, Co-Cr-Al, and Ni-Cr alloys in the temperature range of 700-750 deg C

    NASA Technical Reports Server (NTRS)

    Chiang, K. T.; Meier, G. H.

    1980-01-01

    The effect of SO3 pressure in the gas phase on the Na2SO4 induced hot corrosion of Co-Cr, Ni-Cr, and Co-Cr-Al alloys was studied in the temperature range 700 to 750 C. The degradation of the Co-Cr and Ni-Cr alloys was found to be associated with the formation of liquid mixed sulfates (CoSO4-Na2SO4 or NiSO4-Na2SO4) which provided a selective dissolution of the Co or Ni and a subsequent sulfidation oxidation mode of attack which prevented the maintenance of a protective Cr2O3 film. A clear mechanism was not developed for the degradation of Co-Cr-Al alloys. A pitting corrosion morphology was induced by a number of different mechanisms.

  13. Effect of hydrogen exposure on a Cu-8 Cr-4 Nb alloy

    NASA Technical Reports Server (NTRS)

    Ellis, David L.; Misra, Ajay K.; Dreshfield, Robert L.

    1993-01-01

    The advanced regeneratively cooled rocket thrust chamber may require new materials to achieve long life and improved performance. Current materials such as NARloy-Z (Cu-3 wt. percent Ag-0.5 wt. percent Zr), while highly conductive, do not have sufficient high temperature strength and creep resistance to meet the projected needs of advanced rocket motors. A Cu-8 at. percent Cr-4 at. percent Nb (Cu-8 Cr-4 Nb) alloy has been identified as a promising material for this application. However, hydrogen embrittlement is a concern given the presence of high pressure, high temperature hydrogen in regeneratively cooled rocket motors. Thermodynamic analysis of the reaction between Cr-rich Cr2Nb and H2 showed that there is a possibility of reaction at temperatures up to 323 K in a 35 MPa H2 environment. Above 323 K the pressure necessary to achieve reaction rapidly increased beyond the range experienced in rocket motors. Tensile specimens exposed in 34.5 MPa H2 at room temperatures and during cycling to 705 C did not show any degradation of properties. No evidence of reaction was observed for Cr2Nb precipitate observed on the fracture surfaces. Based on these results the Cu-8 Cr-4 Nb alloy was judged to be sufficiently stable for use in rocket motors.

  14. A model of the interfacial processes inhibiting the environmental degradation of Al-Cu alloys

    NASA Astrophysics Data System (ADS)

    Kearns, Jeffery Robert

    A better understanding of the composition and structure of chemically treated Al alloy surfaces is necessary to devise new, more environmentally benign, coating systems for aircraft. In this work, the surface of AA2024-T3, as well as analogs for constituent intermetallic compounds (IMC), were examined at various stages of the Al alloy pretreatment and chromate conversion coating (CCC) process. A complement of techniques were used: imaging and dyanmic Secondary Ion Mass Spectroscopy (SIMS), Variable-Angle X-ray Photoelectron Spectroscopy (VA/XPS), Synchrotron Infrared Microspectroscopy (SIRS), X-ray Absorption Spectroscopy (XAS), and Electrochemical Impedance Spectroscopy (EIS). The water and hydrocarbons in commercial CCC destabilized Cr(VI) during exposure to soft x-rays. However, it was possible to prevent photochemical reduction with the ultra-clean vacuum pumping practice recently developed at Stony Brook. The type of pretreatment used prior to chromate conversion coating influenced the extent of IMC removal, Cu (re)distribution, and surface activity. Cu(I) was observed on all the chemically treated surfaces. Samples pretreated in Sanchem 1000 while galvanically coupled to a Pt mesh had a more desirable distribution of Cu for subsequent processing. Chromate reduction was not a significant factor in CCC aging over a 24-hr period, but surface dehydration and structural change were correlated and causative. Imaging SIMS revealed heterogeneities in the CCC that varied laterally with IMC in the alloy substrate. These regions were depleted in compounds containing Cr, F, and CN. Cu was found at localized sites in the CCC contact surface. Cyano groups were bound as Cr(IlI)-CNFe(H). The chromate available for CCC repair was located on matrix regions through the entire bulk of the CCC. The presence of residual contaminants (e.g. cleaning agents, metal working fluid, ink) affected the distribution of activator compounds (e.g. ferricyanide) in a CCC. The cyanide complex

  15. Al-augite and Cr-diopside ultramafic xenoliths in basaltic rocks from western United States

    USGS Publications Warehouse

    Wilshire, H.G.; Shervais, J.W.

    1975-01-01

    Ultramafic xenoliths in basalts from the western United States are divided into Al-augite and Cr-diopside groups. The Al-augite group is characterized by Al, Ti-rich augites, comparatively Fe-rich olivine and orthopyroxene, and Al-rich spinel, the Cr-diopside group by Cr-rich clinopyroxene and spinel and by Mg-rich olivine and pyroxenes. Both groups have a wide range of subtypes, but the Al-augite group is dominated by augite-rich varieties, and the Cr-diopside group by olivine-rich lherzolites. ?? 1975.

  16. Process development for Ni-Cr-ThO2 and Ni-Cr-Al-ThO2 sheet

    NASA Technical Reports Server (NTRS)

    Cook, R. C.; Norris, L. F.

    1973-01-01

    A process was developed for the production of thin gauge Ni-Cr-ThO2 sheet. The process was based on the elevated temperature deposition of chromium onto a wrought Ni-2%ThO2 sheet and subsequent high temperature diffusion heat treatments to minimize chromium concentration gradients within the sheet. The mechanical properties of the alloy were found to be critically dependent on those of the Ni-2%ThO2 sheet. A similar process for the production of a Ni-Cr-Al-ThO2 alloy having improved oxidation resistance was investigated but the non-reproducible deposition of aluminum from duplex Cr/Al packs precluded successful scale-up. The mechanical properties of the Ni-Cr-Al-ThO2 alloys were generally equivalent to the best Ni-Cr-ThO2 alloy produced in the programme.

  17. Ti3CrCu4: A possible 2-D ferromagnetic spin fluctuating system

    NASA Astrophysics Data System (ADS)

    Dhar, S. K.; Provino, A.; Manfrinetti, P.; Kulkarni, R.; Goyal, Neeraj; Paudyal, D.

    2016-05-01

    Ti3CrCu4 is a new ternary compound which crystallizes in the tetragonal Ti3Pd5 structure type. The Cr atoms form square nets in the a-b plane (a = 3.124 Å) which are separated by an unusually large distance c = 11.228 Å along the tetragonal axis, thus forming a -2-D Cr-sublattice. The paramagnetic susceptibility is characterized by a low effective moment, μeff = 1.1 μB, a low paramagnetic Curie temperature θP (below 7 K) and a temperature independent χ0 = 6.7 x 10-4 emu/mol. The magnetization at 1.8 K increases rapidly with field nearly saturating to 0.2 μB/f.u. The zero field heat capacity C/T shows an upturn below 7 K (˜190 mJ/mol K2 at ˜0.1K) which is suppressed in applied magnetic fields and interpreted as suggesting the presence of spin fluctuations. The resistivity at low temperatures shows non-Fermi liquid behavior. Overall, the experimental data thus reveal an unusual magnetic state in Ti3CrCu4, which likely has its origin in the layered nature of the Cr sub-lattice and ferromagnetic spin fluctuations. Density functional theoretical calculations reveal a sharp Cr density of states peak just above the Fermi level, indicating the propensity of Ti3CrCu4 to become magnetic.

  18. Recrystallization Behavior of CoCrCuFeNi High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

    Park, Nokeun; Watanabe, Ikuto; Terada, Daisuke; Yokoyama, Yoshihiko; Liaw, Peter K.; Tsuji, Nobuhiro

    2015-04-01

    We investigated the recrystallization behavior of a cold-rolled CoCrCuFeNi high-entropy alloy (HEA). Two different face-centered cubic phases having different chemical compositions and lattice constants in the as-cast specimen have different chemical compositions: One phase was the Cu-lean matrix and the other was the Cu-rich second phase. The second phase remained even after a heat treatment at 1373 K (1100 °C) and Cu enriched more in the Cu-rich second phase. The calculated mixing enthalpies of both Cu-lean and Cu-rich phases in the as-cast and heat-treated specimens explained that Cu partitioning during the heat treatment decreased the mixing enthalpy in both phases. In the specimens 90 pct cold rolled and annealed at 923 K, 973 K, and 1073 K (650 °C, 700 °C, and 800 °C), recrystallization proceeded with increasing the annealing temperature, and ultrafine recrystallized grains with grain sizes around 1 μm could be obtained. The microhardness tended to decrease with increasing the fraction recrystallized, but it was found that the microhardness values of partially recrystallized specimens were much higher than those expected by a simple rule of mixture between the initial and cold-rolled specimens. The reason for the higher hardness was discussed based on the ultrafine grain size, sluggish diffusion expected in HEAs, and two-phase structure in the CoCrCuFeNi alloy.

  19. A sulfur segregation study of PWA 1480, NiCrAl, and NiAl alloys

    NASA Technical Reports Server (NTRS)

    Jayne, D. T.; Smialek, J. L.

    1993-01-01

    Some nickel based superalloys show reduced oxidation resistance from the lack of an adherent oxide layer during high temperature cyclic oxidation. The segregation of sulfur to the oxide-metal interface is believed to effect oxide adhesion, since low sulfur alloys exhibit enhanced adhesion. X ray Photoelectron Spectroscopy (XPS) was combined with an in situ sample heater to measure sulfur segregation in NiCrAl, PWA 1480, and NiAl alloys. The polished samples with a 1.5 to 2.5 nm (native) oxide were heated from 650 to 1100 C with hold times up to 6 hr. The sulfur concentration was plotted as a function of temperature versus time at temperature. One NiCrAl sulfur study was performed on the same casting used by Browning to establish a base line between previous Auger Electron Spectroscopy (AES) results and the XPS results of this study. Sulfur surface segregation was similar for PWA 1480 and NiCrAl and reached a maximum of 30 at% at 800 to 850 C. Above 900 C the sulfur surface concentration decreased to about 3 at% at 1100 C. These results are contrasted to the minimal segregation observed for low sulfur hydrogen annealed materials which exhibit improved scale adhesion.

  20. Composition and Structure Control of Cu-Al-O Films Prepared by Reactive Sputtering and Annealing

    NASA Astrophysics Data System (ADS)

    Tsuboi, Nozomu; Itoh, Yuji; Ogata, Junya; Kobayashi, Satoshi; Shimizu, Hidehiko; Kato, Keizo; Kaneko, Futao

    2007-01-01

    Cu-Al-O films were prepared on quartz glass substrates at 500-700 °C by sputtering the Cu and Al targets alternately on atomic-layer scale under an Ar-diluted O2 (5-20%) gas atmosphere, and then annealed at 1050 °C under a nitrogen atmosphere. The [Cu]/[Al] ratio was controlled by changing the Cu and Al deposition periods. The composition of as-deposited films corresponded to the slightly oxygen-rich region of the CuO-CuAl2O4-Al2O3 system. Films as-deposited at 500 °C had an amorphous structure, while films as-deposited at 700 °C had CuAl2O4 and CuO phases. After thermal annealing in a nitrogen atmosphere, the composition of the films approached that of the Cu2O-CuAlO2-Al2O3 system line, causing a noticeable appearance of the CuAlO2 phase along with the disappearance of the CuAl2O4 and CuO phases. Cu- and Al-rich annealed films had in addition a Cu2O phase and an amorphous Al2O3 phase, respectively. All annealed films exhibited p-type conductivity. The annealed films with [Cu]/[Al]≈ 1 had an absorption edge corresponding to the energy gap of CuAlO2. These results indicate that the change in the Cu ion from divalent to monovalent through nitrogen annealing results in the preparation of transparent conductive films dominated by CuAlO2.

  1. Nanoscale Cellular Structures at Phase Boundaries of Ni-Cr-Al-Ti and Ni-Cr-Mo-Al-Ti Superalloys

    NASA Astrophysics Data System (ADS)

    Wang, Cong; Dunand, David C.

    2015-06-01

    The microstructural evolution of Ni-20 pct Cr wires was studied during pack cementation where Al and Ti, with and without prior cementation with Mo, are deposited to the surface of the Ni-Cr wires and subsequently homogenized in their volumes. Mo deposition promotes the formation of Kirkendall pores and subsequent co-deposition of Al and Ti creates a triple-layered diffusional coating on the wire surface. Subsequent homogenization drives the alloying element to distribute evenly in the wires which upon further heat treatment exhibit the γ + γ' superalloy structure. Unexpectedly, formation of cellular structures is observed at some of the boundaries between primary γ' grains and γ matrix grains. Based on additional features ( i.e., ordered but not perfectly periodic structure, confinement at γ + γ' phase boundaries as a cellular film with ~100 nm width, as well as lack of topologically close-packed phases), and considering that similar, but much larger, microstructures were reported in commercial superalloys, it is concluded that the present cellular structure solidified as a thin film, composed of eutectic γ + γ' and from which the γ' phase was subsequently etched, which was created by incipient melting of a region near the phase boundary with high solute segregation.

  2. Half-metallic antiferromagnetism in double perovskite BiPbCrCuO{sub 6}

    SciTech Connect

    Weng, Ke-Chuan; Wang, Y. K.

    2015-05-07

    The electronic structure and magnetic properties of BiPbCrCuO{sub 6} double perovskite are investigated based on first-principles density functional calculations with generalized gradient approximation (GGA) and GGA incorporated with Coulomb correlation interaction U (GGA + U). The results suggest the half-metallic (HM) and antiferromagnetic (AFM) properties of BiPbCrCuO{sub 6} double perovskite. The HM-AFM property of the double perovskite is caused by the double-exchange mechanism between neighboring Cr{sup 5+}(t{sub 2g}{sup 1}↓) and Cu{sup 2+}(t{sub 2g}{sup 3}↑t{sub 2g}{sup 3}↓e{sub g}{sup 2}↑e{sub g}↓) via the intermediate O{sup 2−}(2s{sup 2}2p{sup 6}) ion.

  3. Transparent ferrimagnetic semiconducting CuCr2O4 thin films by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Tripathi, T. S.; Yadav, C. S.; Karppinen, M.

    2016-04-01

    We report the magnetic and optical properties of CuCr2O4 thin films fabricated by atomic layer deposition (ALD) from Cu(thd)2, Cr(acac)3, and ozone; we deposit 200 nm thick films and anneal them at 700 °C in oxygen atmosphere to crystallize the spinel phase. A ferrimagnetic transition at 140 K and a direct bandgap of 1.36 eV are determined for the films from magnetic and UV-vis spectrophotometric measurements. Electrical transport measurements confirm the p-type semiconducting behavior of the films. As the ALD technique allows the deposition of conformal pin-hole-free coatings on complex 3D surfaces, our CuCr2O4 films are interesting material candidates for various frontier applications.

  4. Explosive bonding of 316L to C18150 CuCrZr alloy for ITER applications.

    SciTech Connect

    Puskar, Joseph David; Butler, Don J.; Goods, Steven Howard; Brasher, Dave G.

    2010-10-01

    Recent developments in the ITER experimental fusion reactor require that a 316L stainless steel substructure be bonded to a precipitation strengthened CuCrZr heat sink alloy, C18150. This bond defines the cooling water pressure boundary. Given the importance of this interface, a variety of experiments with fusion welding and solid-state joining techniques have been performed. Analysis of the joints includes mechanical measurements of bond strength and microstructural analysis using optical and electron microscopy techniques. A particular emphasis was placed on the mechanical properties of the CuCrZr, since it undergoes additional thermal processing and cannot be solutionized and aged hardened per standard heat treatments. It was determined that the explosion bonding, of all the techniques examined, maximized the residual mechanical strength of the CuCrZr. The bonding parameters were optimized to minimize the amount of mixing and porosity at the interface. The details of these results and the optimization will be discussed.

  5. Numerical exploration into the potential of tungsten reinforced CuCrZr matrix composites

    NASA Astrophysics Data System (ADS)

    Hohe, Jörg; Fliegener, Sascha; Findeisen, Claudio; Reiser, Jens; Widak, Verena; Rieth, Michael

    2016-03-01

    The present study provides a numerical investigation into the potential of tungsten reinforced CuCrZr materials in order to overcome their limited performance at higher temperatures. Metal matrix composites including (i) particle reinforced microstructures, (ii) short fiber reinforced microstructures with both randomly orientated and (iii) aligned fibers as well as (iv) laminates consisting of stacked tungsten and CuCrZr layers are considered. The numerical analysis is performed by means of an energy based homogenization procedure in conjunction with a finite element analysis of representative volume elements for the respective microstructures. The results of the screening analysis reveal a distinct improvement of the mechanical properties of CuCrZr materials by the tungsten reinforcements even for moderate tungsten volume fractions. In a comparison of the different microstructures, the ordered microstructures, i.e. laminates and the aligned short fiber reinforced composites in most cases outperform their disordered counterparts.

  6. Ab initio molecular dynamics simulations of short-range order in Zr50Cu45Al5 and Cu50Zr45Al5 metallic glasses.

    PubMed

    Huang, Yuxiang; Huang, Li; Wang, C Z; Kramer, M J; Ho, K M

    2016-03-01

    Comparative analysis between Zr-rich Zr50Cu45Al5 and Cu-rich Cu50Zr45Al5 metallic glasses (MGs) is extensively performed to locate the key structural motifs accounting for their difference of glass forming ability. Here we adopt ab initio molecular dynamics simulations to investigate the local atomic structures of Zr50Cu45Al5 and Cu50Zr45Al5 MGs. A high content of icosahedral-related (full and distorted) orders was found in both samples, while in the Zr-rich MG full icosahedrons [Formula: see text] is dominant, and in the Cu-rich one the distorted icosahedral orders, especially [Formula: see text] and [Formula: see text], are prominent. And the [Formula: see text] polyhedra in Cu50Zr45Al5 MG mainly originate from Al-centered clusters, while the [Formula: see text] in Zr50Cu45Al5 derives from both Cu-centered clusters and Al-centered clusters. These difference may be ascribed to the atomic size difference and chemical property between Cu and Zr atoms. The relatively large size of Zr and large negative heat of mixing between Zr and Al atoms, enhancing the packing density and stability of metallic glass system, may be responsible for the higher glass forming ability of Zr50Cu45Al5. PMID:26828778

  7. Ab initio molecular dynamics simulations of short-range order in Zr50Cu45Al5 and Cu50Zr45Al5 metallic glasses

    NASA Astrophysics Data System (ADS)

    Huang, Yuxiang; Huang, Li; Wang, C. Z.; Kramer, M. J.; Ho, K. M.

    2016-03-01

    Comparative analysis between Zr-rich Zr50Cu45Al5 and Cu-rich Cu50Zr45Al5 metallic glasses (MGs) is extensively performed to locate the key structural motifs accounting for their difference of glass forming ability. Here we adopt ab initio molecular dynamics simulations to investigate the local atomic structures of Zr50Cu45Al5 and Cu50Zr45Al5 MGs. A high content of icosahedral-related (full and distorted) orders was found in both samples, while in the Zr-rich MG full icosahedrons < 0,0,12,0> is dominant, and in the Cu-rich one the distorted icosahedral orders, especially < 0,2,8,2> and < 0,2,8,1> , are prominent. And the < 0,2,8,2> polyhedra in Cu50Zr45Al5 MG mainly originate from Al-centered clusters, while the < 0,0,12,0> in Zr50Cu45Al5 derives from both Cu-centered clusters and Al-centered clusters. These difference may be ascribed to the atomic size difference and chemical property between Cu and Zr atoms. The relatively large size of Zr and large negative heat of mixing between Zr and Al atoms, enhancing the packing density and stability of metallic glass system, may be responsible for the higher glass forming ability of Zr50Cu45Al5.

  8. Ab initio molecular dynamics simulations of short-range order in Zr50Cu45Al5 and Cu50Zr45Al5 metallic glasses

    DOE PAGESBeta

    Huang, Yuxiang; Huang, Li; Wang, C. Z.; Kramer, M. J.; Ho, K. M.

    2016-02-01

    Comparative analysis between Zr-rich Zr50Cu45Al5 and Cu-rich Cu50Zr45Al5 metallic glasses (MGs) is extensively performed to locate the key structural motifs accounting for their difference of glass forming ability. Here we adopt ab initio molecular dynamics simulations to investigate the local atomic structures of Zr50Cu45Al5 and Cu50Zr45Al5 MGs. A high content of icosahedral-related (full and distorted) orders was found in both samples, while in the Zr-rich MG full icosahedrons < 0,0,12,0 > is dominant, and in the Cu-rich one the distorted icosahedral orders, especially < 0,2,8,2 > and < 0,2,8,1 >, are prominent. And the < 0,2,8,2 > polyhedra in Cu50Zr45Al5more » MG mainly originate from Al-centered clusters, while the < 0,0,12,0 > in Zr50Cu45Al5 derives from both Cu-centered clusters and Al-centered clusters. These difference may be ascribed to the atomic size difference and chemical property between Cu and Zr atoms. Lastly, the relatively large size of Zr and large negative heat of mixing between Zr and Al atoms, enhancing the packing density and stability of metallic glass system, may be responsible for the higher glass forming ability of Zr50Cu45Al5.« less

  9. Ab initio molecular dynamics simulations of short-range order in Zr50Cu45Al5 and Cu50Zr45Al5 metallic glasses

    DOE PAGESBeta

    Huang, Yuxiang; Huang, Li; Wang, C. Z.; Kramer, M. J.; Ho, K. M.

    2016-02-01

    In this study, comparative analysis between Zr-rich Zr50Cu45Al5 and Cu-rich Cu50Zr45Al5 metallic glasses (MGs) is extensively performed to locate the key structural motifs accounting for their difference of glass forming ability. Here we adopt ab initio molecular dynamics simulations to investigate the local atomic structures of Zr50Cu45Al5 and Cu50Zr45Al5 MGs. A high content of icosahedral-related (full and distorted) orders was found in both samples, while in the Zr-rich MG full icosahedrons <0,0,12,0> is dominant, and in the Cu-rich one the distorted icosahedral orders, especially <0,2,8,2> and <0,2,8,1>, are prominent. And the <0,2,8,2> polyhedra in Cu50Zr45Al5 MG mainly originate from Al-centeredmore » clusters, while the <0,0,12,0> in Zr50Cu45Al5 derives from both Cu-centered clusters and Al-centered clusters. These difference may be ascribed to the atomic size difference and chemical property between Cu and Zr atoms. The relatively large size of Zr and large negative heat of mixing between Zr and Al atoms, enhancing the packing density and stability of metallic glass system, may be responsible for the higher glass forming ability of Zr50Cu45Al5.« less

  10. Reduced Cu concentration in CuAl-LPE-grown thin Si layers

    SciTech Connect

    Wang, T.H.; Ciszek, T.F.; Asher, S.; Reedy, R.

    1995-08-01

    Cu-Al has been found to be a good solvent system to grow macroscopically smooth Si layers with thicknesses in tens of microns on cast MG-Si substrates by liquid phase epitaxy (LPE) at temperatures near 900{degrees}C. This solvent system utilizes Al to ensure good wetting between the solution and substrate by removing silicon native oxides, and employs Cu to control Al doping into the layers. Isotropic growth is achieved because of a high concentration of solute silicon in the solution and the resulting microscopically rough interface. The incorporation of Cu in the Si layers, however, was a concern since Cu is a major solution component and is generally regarded as a bad impurity for silicon devices due to its fast diffusivity and deep energy levels in the band gap. A study by Davis shows that Cu will nonetheless not degrade solar cell performance until above a level of 10{sup 17} cm{sup -3}. This threshold is expected to be even higher for thin layer silicon solar cells owing to the less stringent requirement on minority carrier diffusion length. But to ensure long term stability of solar cells, lower Cu concentrations in the thin layers are still preferred.

  11. NiAl(110)/Cr(110) interface: A density functional theory study

    NASA Astrophysics Data System (ADS)

    Liu, W.; Li, J. C.; Zheng, W. T.; Jiang, Q.

    2006-05-01

    The optimal geometries, thermodynamic properties, and electronic structures of NiAl(110)/Cr(110) interface are studied using a first-principle density functional plane-wave ultrasoft pseudopotential method. Surface energies of different NiAl surfaces are compared with those obtained based on the classical broken-bond rule. Simulation results indicate that the structure of Ni and Al placed in the hollow sites of Cr atoms at the interface is more thermodynamically stable, and the NiCr bonding is dominated by 3d electrons of Ni and Cr. It is found that NiAl(110)/Cr(110) alloying could lower brittleness of NiAl compounds. With simulated values of adhesion work and interface energy for NiAl(110)/Cr(110) system, its mechanical and thermodynamic properties are also discussed.

  12. Cu(II) Catalytic Reduction of Cr(VI) by Tartaric Acid Under the Irradiation of Simulated Solar Light

    PubMed Central

    Li, Ying; Qin, Chao; Zhang, Jing; Lan, Yeqing; Zhou, Lixiang

    2014-01-01

    Abstract Cu(II) catalytic reduction of Cr(VI) by tartaric acid under the irradiation of simulated solar light was investigated through batch experiments at pHs from 3 to 6 and at temperatures from 15°C to 35°C. Results demonstrated that introduction of Cu(II) could markedly improve reduction of Cr(VI) in comparison with tartaric acid alone. Optimal removal of Cr(VI) was achieved at pH 4. Reduction of Cr(VI) increased with increasing temperatures and initial concentrations of Cu(II) and tartaric acid. The catalytic role of Cu(II) in the reduction of Cr(VI) was ascribed to the formation of Cu(II)-tartaric acid complex, which generated active reductive intermediates, including Cu(I) and tartaric acid radicals through a pathway of metal–ligand–electron transfer with light. Cu(II) photocatalytic reduction of Cr(VI) by tartaric acid followed pseudo zero-order kinetics with regard to Cr(VI), and the activation energy was calculated to be 21.48 kJ/mol. To date, such a role of Cu(II) has not been reported. The results from the present study are helpful in fully understanding the photochemical reductive behavior of Cr(VI) in the presence of both tartaric acid and Cu(II) in soil and aquatic environments. PMID:25125941

  13. Effects of Thermal and Mechanical Processing on Microstructures and Desired Properties of Particle-Strengthened Cu-Cr-Nb Alloys

    NASA Technical Reports Server (NTRS)

    Anderson, Kenneth Reed

    2000-01-01

    Ternary Cu-Cr-Nb alloys, particularly Cu-8 Cr-4 Nb (in at.%), have demonstrated good thermal stability as well as high strength and conductivity at elevated temperatures. The initial powder material has a bimodal size distribution of Cr2Nb precipitates. Primary Cr2Nb precipitates are approx. 1 micron, and secondary Cr2Nb particles are 30-200 nm. The particle coarsening was analyzed and found to follow LSW-type behavior, This study provides a detailed examination of the stability and strengthening effects of Cr2Nb particles. This investigation also revealed that the primary particles provide direct grain boundary pinning and indirect grain boundary strengthening but virtually no Orowan strengthening. The secondary particles found within grains do provide Orowan strengthening. For extruded material, grain bound-ary strengthening (Hall-Petch effect) accounts for two-thirds of the strength with Orowan effects contributing the remainder. The proven advantages of Cu-Cr-Nb were the motivation to improve these attributes via microstructural refinement. Mechanical milling (MM) of Cu- 4 Cr-2 Nb and Cu-8 Cr-2 Nb produced an increase in hot pressed Vickers hardness of 122% and 96%, respectively. The increase in hardness was more due to Cu grain-size refinement than to Cr,,Nb refinement. This study also demonstrated enhanced stability of MM Cu-4 Cr-2 Nb. Hot pressed 4 h milled Cu-4 Cr-2 Nb experienced only a 22% drop in hardness when annealed at 1273 K for 50 h versus a 30% drop for extruded Cu-8 Cr-4 Nb. The goal of improving the strength and stability of Cu-4 Cr-2 Nb to better than such properties for as- extruded Cu-8 Cr-4 Nb has been met. In addition, a figure-of-merit (FOM) coupling hardness and thermal conductivity was maximized for the case of 4 h milled Cu-4 Cr-2 Nb material. Overall, Cu-Cr-Nb alloys not only possess high strength, conductivity and thermal stability but also can be further developed to improve strength and stability.

  14. On the strong impact of doping in the triangular antiferromagnet CuCrO 2

    NASA Astrophysics Data System (ADS)

    Maignan, A.; Martin, C.; Frésard, R.; Eyert, V.; Guilmeau, E.; Hébert, S.; Poienar, M.; Pelloquin, D.

    2009-06-01

    Electronic band structure calculations using the augmented spherical wave method have been performed for CuCrO 2. For this antiferromagnetic ( TN=24 K) semiconductor crystallizing in the delafossite structure, it is found that the valence band maximum is mainly due to the t 2g orbitals of Cr 3+ and that spin polarization is predicted with 3 μ per Cr 3+. The structural characterizations of CuCr 1- xMg xO 2 reveal a very limited range of Mg 2+ substitution for Cr 3+ in this series. As soon as x=0.02, a maximum of 1% Cr ions are substituted by Mg site is measured in the sample. This result is also consistent with the detection of Mg spinel impurities from X-ray diffraction for x=0.01. This explains the saturation of the Mg 2+ effect upon the electrical resistivity and thermoelectric power observed for x>0.01. Such a very weak solubility limit could also be responsible for the discrepancies found in the literature. Furthermore, the measurements made under magnetic field (magnetic susceptibility, electrical resistivity and Seebeck coefficient) support that the Cr 4+ "holes", created by the Mg 2+substitution, in the matrix of high spin Cr 3+ ( S=3/2) are responsible for the transport properties of these compounds.

  15. Flux Pinning by Cr Nanoparticles in Cu_{0.5} Tl_{0.5} Ba2 Ca2 Cu3 O_{10-δ } Superconductor

    NASA Astrophysics Data System (ADS)

    Waqee-ur-Rehman, M.; Mumtaz, M.; Qasim, Irfan; Nadeem, K.

    2016-04-01

    Increase in flux pinning strength of Cu_{0.5} Tl_{0.5} Ba2 Ca2 Cu3 O_{10-δ } (CuTl-1223) superconductor has been observed after addition of Cr nanoparticles. We have thoroughly investigated the infield response of Cr nanoparticles-added CuTl-1223 superconductor in an external applied magnetic field in the range of 0-7 T. Solid-state reaction technique has been employed to synthesize (Cr)x -CuTl-1223; x = 0-1.00 wt% nanoparticle-superconductor composites. The flux pinning mechanism has been analyzed on the basis of thermally activated flux flow model in the presence of a small current (10 μ A). The increase in activation energy and decrease in transition width of CuTl-1223 superconducting phase show the enhancement in its flux pinning strength upon the addition of Cr nanoparticles.

  16. Flux Pinning by Cr Nanoparticles in Cu_{0.5}Tl_{0.5}Ba2Ca2Cu3O_{10-δ } Superconductor

    NASA Astrophysics Data System (ADS)

    Waqee-ur-Rehman, M.; Mumtaz, M.; Qasim, Irfan; Nadeem, K.

    2016-09-01

    Increase in flux pinning strength of Cu_{0.5}Tl_{0.5}Ba2Ca2Cu3O_{10-δ }(CuTl-1223) superconductor has been observed after addition of Cr nanoparticles. We have thoroughly investigated the infield response of Cr nanoparticles-added CuTl-1223 superconductor in an external applied magnetic field in the range of 0-7 T. Solid-state reaction technique has been employed to synthesize (Cr)x-CuTl-1223; x = 0-1.00 wt% nanoparticle-superconductor composites. The flux pinning mechanism has been analyzed on the basis of thermally activated flux flow model in the presence of a small current (10 μ A). The increase in activation energy and decrease in transition width of CuTl-1223 superconducting phase show the enhancement in its flux pinning strength upon the addition of Cr nanoparticles.

  17. Chemical separation and mass spectrometry of Cr, Fe, Ni, Zn, and Cu in terrestrial and extraterrestrial materials using thermal ionization mass spectrometry.

    PubMed

    Yamakawa, Akane; Yamashita, Katsuyuki; Makishima, Akio; Nakamura, Eizo

    2009-12-01

    A sequential chemical separation technique for Cr, Fe, Ni, Zn, and Cu in terrestrial and extraterrestrial silicate rocks was developed for precise and accurate determination of elemental concentration by the isotope dilution method (ID). The technique uses a combination of cation-anion exchange chromatography and Eichrom nickel specific resin. The method was tested using a variety of matrixes including bulk meteorite (Allende), terrestrial peridotite (JP-1), and basalt (JB-1b). Concentrations of each element was determined by thermal ionization mass spectrometry (TIMS) using W filaments and a Si-B-Al type activator for Cr, Fe, Ni, and Zn and a Re filament and silicic acid-H3PO4 activator for Cu. The method can be used to precisely determine the concentrations of these elements in very small silicate samples, including meteorites, geochemical reference samples, and mineral standards for microprobe analysis. Furthermore, the Cr mass spectrometry procedure developed in this study can be extended to determine the isotopic ratios of 53Cr/52Cr and 54Cr/52Cr with precision of approximately 0.05epsilon and approximately 0.10epsilon (1epsilon = 0.01%), respectively, enabling cosmochemical applications such as high precision Mn-Cr chronology and investigation of nucleosynthetic isotopic anomalies in meteorites. PMID:19886654

  18. Gain measurements and average power capabilities of Cr(3+):LiSrAlF6

    NASA Astrophysics Data System (ADS)

    Hanson, F.; Bendall, C.; Poirier, P.

    1993-09-01

    Gain for flash-lamp-pumped Cr:LiSrAlF6 and Cr:Li(Sr(1-x),Ca(x))AlF6 from 790 to 1000 nm is reported. For Cr:LiSrAlF6 thermal fracture occurred at heat loadings of 4.5 W/cm and about 6 W/sq cm in the rod and slab geometry, respectively. Excited-state upconversion losses were evident in the slabs at high pump energy.

  19. Measurement and analysis of radioactivity induced in CuCrZr by D?T neutrons

    NASA Astrophysics Data System (ADS)

    Eichin, R.; Adelhelm, C.; Blokhin, A. I.; Forrest, R. A.; Freiesleben, H.; Kovalchuk, V. D.; Markovskij, D. V.; Seidel, K.; Unholzer, S.

    2004-08-01

    CuCrZr is used in high heat flux components of ITER and other fusion reactor designs. A CuCrZr alloy of the European Fusion Technology Programme was irradiated with D-T neutrons, and the γ-activities of all nuclides which are relevant up to the recycling limit of the material were measured. The results were analysed with the European Activation System (versions EASY-2001 and EASY-2003). The calculated total activation property of the material was validated within 10%. The long-term radioactivity was estimated to be well below the hands-on limit with an uncertainty of 19%.

  20. [CrIII8MII6]12+ Coordination Cubes (MII=Cu, Co)**

    PubMed Central

    Sanz, Sergio; O'Connor, Helen M; Pineda, Eufemio Moreno; Pedersen, Kasper S; Nichol, Gary S; Mønsted, Ole; Weihe, Høgni; Piligkos, Stergios; McInnes, Eric J L; Lusby, Paul J; Brechin, Euan K

    2015-01-01

    [CrIII8MII6]12+ (MII=Cu, Co) coordination cubes were constructed from a simple [CrIIIL3] metalloligand and a “naked” MII salt. The flexibility in the design proffers the potential to tune the physical properties, as all the constituent parts of the cage can be changed without structural alteration. Computational techniques (known in theoretical nuclear physics as statistical spectroscopy) in tandem with EPR spectroscopy are used to interpret the magnetic behavior. PMID:25891167

  1. Effects of the Formation of Al x Cu y Gradient Interfaces on Mechanical Property of Steel/Al Laminated Sheets by Introducing Cu Binding-Sheets

    NASA Astrophysics Data System (ADS)

    Wei, Aili; Liu, Xinghai; Shi, Quanxin; Liang, Wei

    2015-07-01

    Steel/Cu/Al laminated sheets were fabricated by two-pass hot rolling to improve the mechanical properties of steel/Al sheets. The bonding properties and deformability of the steel/Cu/Al sheets were studied. Steel/Al and steel/Cu/Al samples were rolled at 350°C for 15 min with the first-pass reduction of 40%, and then heated at 600°C for 5 min with different reductions. It was found that the steel/Cu/Al samples rolled by the second-pass reduction of 85% could endure the maximum 90° bend cycle times of 45, exhibiting excellent fatigue resistance as well as deformability. The steel/Al samples could only reach the maximum 90° bend cycle times of 20. Furthermore, the scanning electron microscope, energy-dispersive spectrometer, and electron backscattered diffraction results showed that the preferred growth orientations of Cu, Al4Cu9, and Al2Cu on the steel/Cu/Al laminated sheets are {-1, 1, 2} <1, -1, 1>, {1, 0, 0} <0, 1, 0> and {-1, 1, 2} <1, -1, 1> {1, 1, 0} <0, 0, 1>. The orientation relationships between Cu and Al2Cu are {1, 1, 0}(fcc)//{1, 1, 0}(bct) and {1, 1, 1}(fcc)//{1, 1, 1}(bct). The improved bonding property and excellent fatigue resistance as well as deformability were mainly ascribed to the tight combination and consistent deformability across steel, Al, and the transition layers (Cu, Al4Cu9, and Al2Cu).

  2. Effect of Cr and Cu addition on corrosion behavior of Ni-Ti alloys.

    PubMed

    Iijima, M; Endo, K; Ohno, H; Mizoguchi, I

    1998-03-01

    The corrosion behavior of three Ni-Ti alloys with compositions as commercial super-elastic orthodontic wires was investigated using polished plate specimens. Corrosion resistance was estimated by potentiodynamic polarization measurement in 0.9% NaCl and 1% lactic acid solutions and analysis of released metals by atomic absorption spectrophotometry. The influence of Cr and Cu addition on the structure of the surface oxide film was examined by X-ray photoelectron spectroscopy (XPS). Addition of 0.19 at% Cr had little effect on the structure of the oxide films and the corrosion resistance of the Ni-Ti alloys. For Ni-Ti-5Cu-0.3Cr alloy, the metallic Cu was enriched at the alloy/oxide film interface, resulting in increased susceptibility to pitting corrosion above +1000 mV. However, the passive current density and the amount of released Ni were not significantly increased by the addition of Cu. The study showed that small amounts of Cr and Cu added to change the super-elastic characteristics do not change the corrosion resistance of the Ni-Ti alloy freely immersed in simulated physiological environments. PMID:9663060

  3. Intermetallic Formation at Interface of Al/Cu Clad Fabricated by Hydrostatic Extrusion and Its Properties.

    PubMed

    Lee, Jongbeom; Jeong, Haguk

    2015-11-01

    Al/Cu clad composed of Al core and Cu sheath has been produced by hydrostatic extrusion at 523 K, at an extrusion rate of 27. The prepared specimen was post-annealed at temperatures of 673 K and 773 K for various time durations, and the effect of annealing conditions have been analyzed. The hardness at the interface between Al and Cu matrix of the Al/Cu bimetal clad increases because of annealing. Results indicate that the hardness is more sensitive to annealing temperature than the annealing time. Three kinds of intermetallic compounds (IMC), namely, CuAl, Cu3Al2, and CuAl2, are formed at the Al-Cu interface, upon annealing at 673 K. On the other hand, four kinds of IMCs, namely, Cu4Al3, CuAl, Cu3Al2, CuAl2, are formed at the annealing temperature of 773 K. The growth of each IMC follows the parabolic law as a function of annealing times at certain annealing temperature. The growth rate of each IMC is limited to its interdiffusion rate constant. The IMC Cu4Al3 appears upon annealing at 773 K, and not during annealing at 673 K, because of the higher value of activation energy associated with its formation, when compared to other IMCs. PMID:26726557

  4. Relationships involving process, microstructure, and properties of weldments of Al-Cu and Al-Cu-Li alloys

    SciTech Connect

    Martukanitz, R.P.; Howell, P.R.

    1996-12-31

    The evolution of microstructure within the heat affected zone for Al-Cu and Al-Cu-Li alloys is qualitatively described in terms of diffusion controlled modifications that result in the minimization of chemical free energy. Coarsening of strengthening precipitate is anticipated at relatively low peak temperatures; whereas, dissolution is expected to dominate the microstructural modifications within the heat affected zone for these alloys. Transmission electron microscopy of alloy 2195-T8 was performed to validate the analysis. Dissolution of {theta}{prime} (Al{sub 2}Cu) was seen to occur within the heat affected zone at temperatures below 220 C. The primary strengthening phase, T{sub 1} (Al{sub 2}CuLi), exhibited partial dissolution at peak temperatures of 320 C. Peak temperatures up to 500 C resulted in partial dissolution of T{sub 1} during heating and growth upon cooling. Positions near the fusion zone interface resulted in complete dissolution of strengthening precipitate and re-precipitation of copper-rich zones upon cooling. The effect of microstructural modifications within the heat affected zone on mechanical properties is discussed in terms of strengthening mechanisms.

  5. Ferromagnetism studies of Cu-doped and (Cu, Al) co-doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    Wu, S. Z.; Yang, H. L.; Xu, X. G.; Miao, J.; Jiang, Y.

    2011-01-01

    We have studied the room temperature ferromagnetism (FM) in Cu-doped and (Cu, Al) co-doped ZnO thin films which were grown on quartz substrates by chemical method based on a sol-gel process combining with spin-coating technology. X-ray diffraction (XRD) patterns demonstrate that both the Cu-doped and (Cu, Al) co-doped ZnO films have the hexagonal wurtzite structure with c-axis orientation. Alternating Gradient Magnetometer (AGM) measurements confirm that all the doped ZnO samples are ferromagnetic at room temperature. When the doped Cu content is 1 %, the Cu-doped ZnO film has the strongest FM. The FM significantly decreases in the (Cu, Al) co-doped ZnO films. The doping of Al ions suppresses the FM induced by the doped Cu ions.

  6. Third element effect in the surface zone of Fe-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Airiskallio, E.; Nurmi, E.; Heinonen, M. H.; Väyrynen, I. J.; Kokko, K.; Ropo, M.; Punkkinen, M. P. J.; Pitkänen, H.; Alatalo, M.; Kollár, J.; Johansson, B.; Vitos, L.

    2010-01-01

    The third element effect to improve the high temperature corrosion resistance of the low-Al Fe-Cr-Al alloys is suggested to involve a mechanism that boosts the recovering of the Al concentration to the required level in the Al-depleted zone beneath the oxide layer. We propose that the key factor in this mechanism is the coexistent Cr depletion that helps to maintain a sufficient Al content in the depleted zone. Several previous experiments related to our study support that conditions for such a mechanism to be functional prevail in real oxidation processes of Fe-Cr-Al alloys.

  7. Revisiting the properties of delafossite CuCrO{sub 2}: A single crystal study

    SciTech Connect

    Poienar, Maria; Hardy, Vincent; Kundys, Bohdan; Singh, Kiran; Maignan, Antoine; Damay, Francoise; Martin, Christine

    2012-01-15

    Platelet-like single-crystals of delafossite CuCrO{sub 2} have been successfully grown and characterised by X-ray diffraction and pole figures, scanning electron and atomic force microscopy. Transport measurements reveal that the resistivity is highly anisotropic, with a ratio of about 35 at 300 K between the in- and out-of-plane directions, reflecting the layered crystal structure. The magnetization and specific heat data show that CuCrO{sub 2} undergoes a unique antiferromagnetic transition at T{sub N}=24.0 K, in contrast to a recent report on CuCrO{sub 2} single-crystals showing the existence of two magnetic transitions, T{sub N1}=24.2 K and T{sub N2}=23.6 K, depending on the orientation of the applied magnetic field along and perpendicular to c, respectively. - Graphical abstract: 3R-CuCrO{sub 2} platelet-like single crystals have been successfully grown by the flux method. As revealed by {chi}(T) and C(T) measurements, their properties are characterised by a unique antiferromagnetic transition at T{sub N}=24 K. Interestingly, despite a very small magnetic anisotropy, a large one is evidenced by the resistivity ratio, {rho}{sub c}/{rho}{sub ab}{approx}35, at 300 K. This suggests an easier charge hopping in the [CrO{sub 2}] planes rather than along (Cr-O-Cu) pathways, i.e. along c axis. Highlights: Black-Right-Pointing-Pointer R-CuCrO{sub 2} plate-like single crystals have been synthesised by the flux method. Black-Right-Pointing-Pointer Growth takes place layer-by-layer and some growth defects have been observed. Black-Right-Pointing-Pointer CuCrO{sub 2} single crystals exhibit a unique antiferromagnetic transition at T{sub N}=24 K. Black-Right-Pointing-Pointer Transport measurements reveal that the resistivity is highly anisotropic.

  8. Vacuum Plasma Spray of CuCrNb Alloy for Advanced Liquid - Fuel Combustion Chambers

    NASA Technical Reports Server (NTRS)

    Zimmerman, Frank

    2000-01-01

    The copper-8 atomic percent chromium-4 atomic percent niobium (CuCrNb) alloy was developed by Glenn Research Center (formally Lewis Research Center) as an improved alloy for combustion chamber liners. In comparison to NARloy-Z, the baseline (as in Space Shuttle Main Engine) alloy for such liners, CuCrNb demonstrates mechanical and thermophysical properties equivalent to NARloy-Z, but at temperatures 100 C to 150 C (180 F to 270 F) higher. Anticipated materials related benefits include decreasing the thrust cell liner weight 5% to 20%, increasing the service life at least two fold over current combustion chamber design, and increasing the safety margins available to designers. By adding an oxidation and thermal barrier coating to the liner, the combustion chamber can operate at even higher temperatures. For all these benefits, however, this alloy cannot be formed using conventional casting and forging methods because of the levels of chromium and niobium, which exceed their solubility limit in copper. Until recently, the only forming process that maintains the required microstructure of CrNb intermetallics is powder metallurgy formation of a billet from powder stock, followed by extrusion. This severely limits its usefulness in structural applications, particularly the complex shapes required for combustion chamber liners. Vacuum plasma spray (VPS) has been demonstrated as a method to form structural articles including small combustion chambers from the CuCrNb alloy. In addition, an oxidation and thermal barrier layer can be formed integrally on the hot wall of the liner that improve performance and extend service life. This paper discusses the metallurgy and thermomechanical properties of VPS formed CuCrNb versus the baseline powder metallurgy process, and the manufacturing of small combustion chamber liners at Marshall Space Flight Center using the VPS process. The benefits to advanced propulsion initiatives of using VPS to fabricate combustion chamber liners

  9. Optical properties of heusler alloys Co2FeSi, Co2FeAl, Co2CrAl, and Co2CrGa

    NASA Astrophysics Data System (ADS)

    Shreder, E. I.; Svyazhin, A. D.; Belozerova, K. A.

    2013-11-01

    The results of an investigation of optical properties and the calculations of the electronic structure of Co2FeSi, Co2FeAl, Co2CrAl, and Co2CrGa Heusler alloys are presented. The main focus of our attention is the study of the spectral dependence of the real part (ɛ1) and imaginary part (ɛ2) of the dielectric constant in the range of wavelengths λ = 0.3-13 μm using the ellipsometric method. An anomalous behavior of the optical conductivity σ(ω) has been found in the infrared range in the Co2CrAl and Co2CrGa alloys, which differs substantially from that in the Co2FeSi and Co2FeAl alloys. The results obtained are discussed based on the calculations of the electronic structure.

  10. Production and processing of Cu-Cr-Nb alloys

    NASA Technical Reports Server (NTRS)

    Ellis, David L.; Michal, Gary M.; Orth, Norman W.

    1990-01-01

    A new Cu-based alloy possessing high strength, high conductivity, and good stability at elevated temperatures was recently produced. This paper details the melting of the master alloys, production of rapidly solidified ribbon, and processing of the ribbon to sheet by hot pressing and hot rolling.

  11. Ternary Borides Cr2AlB2, Cr3AlB4, and Cr4AlB6: The First Members of the Series (CrB2)nCrAl with n = 1, 2, 3 and a Unifying Concept for Ternary Borides as MAB-Phases.

    PubMed

    Ade, Martin; Hillebrecht, Harald

    2015-07-01

    Single crystals of the ternary borides Cr2AlB2, Cr3AlB4, Cr4AlB6, MoAlB, WAlB, Mn2AlB2, and Fe2AlB2 were grown from the elements with an excess of Al. Structures were refined by X-ray methods on the basis of single crystal data. All compounds crystallize in orthorhombic space groups. In each case boron atoms show the typical trigonal prisms BM6. The BM6-units are linked by common rectangular faces forming B-B-bonds. Thus, zigzag chains of boron atoms are obtained for MoAlB, WAlB, and M2AlB2 (M = Cr, Mn, Fe); chains of hexagons for Cr3AlB4; and double chains of hexagons for Cr4AlB6. The same subunits are known for the binary borides CrB, Cr3B4, Cr2B3, and β-WB, too. The boride partial structures are separated by single layers of Al-atoms in the case of the chromium compounds and double layers for WAlB, i.e., W2Al2B2. All crystal structures can be described using a unified building set principle with quadratic 4(4)-nets of metal atoms. The different compositions and crystal structures are obtained by different numbers of metal layers in the corresponding parts according to the formula (MB)2Aly(MB2)x. This principle is an extension of a scheme which was developed for the boridecarbides of niobium. Furthermore, there is a close similarity to the group of ternary carbides MAl(MC)n, so-called MAX-phases. Therefore, they might be named as "MAB-phases". The pronounced two-dimensionality and the mixture of strong covalent and metallic interactions make MAB-phases to promising candidates for interesting material properties. All compositions were confirmed by EDX measurements. Additionally, microhardness measurements were performed. PMID:26069993

  12. ADSORPTION AND DESORPTION OF ZN, CU, AND CR BY SEDIMENTS FROM THE RAISIN RIVER (MICHIGAN)

    EPA Science Inventory

    Metal adsorption by Raisin River sediments in vitro depended linearly on soluble metal concentration to adsorption densities of 6,000-9,000 ug/g with 48 hr partition coefficients of approximately 50, 30, and 25 L/g for Cu, Cr, and Zn, respectively. artition coefficients computed ...

  13. Electrokinetic Treatment of Cr-, Cu-, and Zn-Contaminated Sediment: Cathode Modification

    PubMed Central

    Rajić, Ljiljana; Dalmacija, Božo; Perović, Svetlana Ugarčina; Krčmar, Dejan; Rončević, Srđan; Tomašević, Dragana

    2013-01-01

    Abstract Enhanced electrokinetic (EK) removal of Cr, Cu, and Zn from sediment by using original and modified integrated ion exchange (IIX™) cathodes was investigated. IIX cathode design and EK device process modifications were made to improve performance: separation of IIX cathode components (IIXS), combination of modified IIX cathode with pulsed electric field (IIXSP), and separation of IIX cathode components with addition of an anion exchange resin compartment (IIXA). After using the IIXSP, overall Cr, Cu, and Zn removal efficacies were significantly improved compared with the other treatments investigated. No improvements in overall Cr, Cu, and Zn removal efficacies were achieved by utilization of IIXA. Nevertheless, significant removal efficacies occurred at the anode region since distribution of the alkaline front was prevented. However, metal accumulation in the cathode region occurred. This was a consequence of metal cation complexation with Cl− released from the anion exchange resin that changed the direction of metal migration. Enhancing EK remediation of Cr-, Cu-, and Zn-contaminated sediment can be achieved by using a modified IIX cathode. PMID:24381480

  14. Electrokinetic Treatment of Cr-, Cu-, and Zn-Contaminated Sediment: Cathode Modification.

    PubMed

    Rajić, Ljiljana; Dalmacija, Božo; Perović, Svetlana Ugarčina; Krčmar, Dejan; Rončević, Srđan; Tomašević, Dragana

    2013-12-01

    Enhanced electrokinetic (EK) removal of Cr, Cu, and Zn from sediment by using original and modified integrated ion exchange (IIX™) cathodes was investigated. IIX cathode design and EK device process modifications were made to improve performance: separation of IIX cathode components (IIXS), combination of modified IIX cathode with pulsed electric field (IIXSP), and separation of IIX cathode components with addition of an anion exchange resin compartment (IIXA). After using the IIXSP, overall Cr, Cu, and Zn removal efficacies were significantly improved compared with the other treatments investigated. No improvements in overall Cr, Cu, and Zn removal efficacies were achieved by utilization of IIXA. Nevertheless, significant removal efficacies occurred at the anode region since distribution of the alkaline front was prevented. However, metal accumulation in the cathode region occurred. This was a consequence of metal cation complexation with Cl(-) released from the anion exchange resin that changed the direction of metal migration. Enhancing EK remediation of Cr-, Cu-, and Zn-contaminated sediment can be achieved by using a modified IIX cathode. PMID:24381480

  15. Solid state phase equilibria and intermetallic compounds of the Al-Cr-Ho system

    SciTech Connect

    Pang, Mingjun; Zhan, Yongzhong; Du, Yong

    2013-02-15

    The solid state phase equilibria of the Al-Cr-Ho ternary system at 500 Degree-Sign C were experimentally investigated. The phase relations at 500 Degree-Sign C are governed by 14 three-phase regions, 29 two-phase regions and 15 single-phase regions. The existences of 10 binary compounds and 2 ternary phases have been confirmed. Al{sub 11}Cr{sub 2}, Al{sub 11}Cr{sub 4} and Al{sub 17}Ho{sub 2} were not found at 500 Degree-Sign C. Crystal structures of Al{sub 9}Cr{sub 4} and Al{sub 8}Cr{sub 4}Ho were determined by the Rietveld X-ray powder data refinement. Al{sub 9}Cr{sub 4} was found to exhibit cubic structure with space group I4-bar 3m (no. 217) and lattice parameters a=0.9107(5) nm. Al{sub 8}Cr{sub 4}Ho crystallizes in ThMn{sub 12} structure type with space group I4/mmm (no. 139) and lattice parameters a=0.8909(4) nm, c=0.5120(5) nm. It is concluded that the obtained Al{sub 4}Cr phase in this work should be {mu}-Al{sub 4}Cr by comparing with XRD pattern of the hexagonal {mu}-Al{sub 4}Mn compound. - Graphical abstract: The solid state phase equilibria of the Al-Cr-Ho ternary system at 500 Degree-Sign C. Highlights: Black-Right-Pointing-Pointer Al-Cr-Ho system has been investigated. Black-Right-Pointing-Pointer Al{sub 9}Cr{sub 4} has cubic structure with space group I4-bar 3m. Black-Right-Pointing-Pointer Al{sub 8}Cr{sub 4}Ho crystallizes in ThMn{sub 12} type with space group I4/mmm. Black-Right-Pointing-Pointer Al{sub 4}Cr phase is {mu}-type at 500 Degree-Sign C.

  16. Hydrogen isotope trapping in Al-Cu binary alloys

    DOE PAGESBeta

    Chao, Paul; Karnesky, Richard A.

    2016-01-01

    In this study, the trapping mechanisms for hydrogen isotopes in Al–X Cu (0.0 at. % < X < 3.5 at. %) alloys were investigated using thermal desorption spectroscopy (TDS), electrical conductivity, and differential scanning calorimetry. Constant heating rate TDS was used to determine microstructural trap energies and occupancies. In addition to the trapping states in pure Al reported in the literature (interstitial lattice sites, dislocations, and vacancies), a trap site due to Al–Cu intermetallic precipitates is observed. The binding energy of this precipitate trap is (18 ± 3) kJ•mol–1 (0.19 ± 0.03 eV). Typical occupancy of this trap is high;more » for Al–2.6 at. % Cu (a Cu composition comparable to that in AA2219) charged at 200 °C with 130 MPa D2 for 68 days, there is ca. there is 3.15×10–7 mol D bound to the precipitate trap per mol of Al, accounting for a third of the D in the charged sample.« less

  17. Hydrogen isotope trapping in Al-Cu binary alloys

    SciTech Connect

    Chao, Paul; Karnesky, Richard A.

    2016-01-01

    In this study, the trapping mechanisms for hydrogen isotopes in Al–X Cu (0.0 at. % < X < 3.5 at. %) alloys were investigated using thermal desorption spectroscopy (TDS), electrical conductivity, and differential scanning calorimetry. Constant heating rate TDS was used to determine microstructural trap energies and occupancies. In addition to the trapping states in pure Al reported in the literature (interstitial lattice sites, dislocations, and vacancies), a trap site due to Al–Cu intermetallic precipitates is observed. The binding energy of this precipitate trap is (18 ± 3) kJ•mol–1 (0.19 ± 0.03 eV). Typical occupancy of this trap is high; for Al–2.6 at. % Cu (a Cu composition comparable to that in AA2219) charged at 200 °C with 130 MPa D2 for 68 days, there is ca. there is 3.15×10–7 mol D bound to the precipitate trap per mol of Al, accounting for a third of the D in the charged sample.

  18. Corrosion and protection of heterogeneous cast Al-Si (356) and Al-Si-Cu-Fe (380) alloys by chromate adn cerium inhibitors

    NASA Astrophysics Data System (ADS)

    Jain, Syadwad

    In this study, the localized corrosion and conversion coating on cast alloys 356 (Al-7.0Si-0.3Mg) and 380 (Al-8.5Si-3.5Cu-1.6Fe) were characterized. The intermetallic phases presence in the permanent mold cast alloy 356 are primary-Si, Al5FeSi, Al8Si6Mg3Fe and Mg2Si. The die cast alloy 380 is rich in Cu and Fe elements. These alloying elements result in formation of the intermetallic phases Al 5FeSi, Al2Cu and Al(FeCuCr) along with primary-Si. The Cu- and Fe-rich IMPS are cathodic with respect to the matrix phase and strongly govern the corrosion behavior of the two cast alloys in an aggressive environment due to formation of local electrochemical cell in their vicinity. Results have shown that corrosion behavior of permanent mould cast alloy 356 is significantly better than the die cast aluminum alloy 380, primarily due to high content of Cu- and Fe-rich phases such as Al2Cu and Al 5FeSi in the latter. The IMPS also alter the protection mechanism of the cast alloys in the presence of inhibitors in an environment. The presence of chromate in the solution results in reduced cathodic activity on all the phases. Chromate provides some anodic inhibition by increasing pitting potentials and altering corrosion potentials for the phases. Results have shown that performance of CCC was much better on 356 than on 380, primarily due to inhomogeneous and incomplete coating deposition on Cu- and Fe- phases present in alloy 380. XPS and Raman were used to characterize coating deposition on intermetallics. Results show evidence of cyanide complex formation on the intermetallic phases. The presence of this complex is speculated to locally suppress CCC formation. Formation and breakdown of cerium conversion coatings on 356 and 380 was also analyzed. Results showed that deposition of cerium hydroxide started with heavy precipitation on intermetallic particles with the coatings growing outwards onto the matrix. Electrochemical analysis of synthesized intermetallics compounds in the

  19. Microstructural stability of Fe-Cr-Al alloys at 450-550 °C

    NASA Astrophysics Data System (ADS)

    Ejenstam, Jesper; Thuvander, Mattias; Olsson, Pär; Rave, Fernando; Szakalos, Peter

    2015-02-01

    Iron-Chromium-Aluminium (Fe-Cr-Al) alloys have been widely investigated as candidate materials for various nuclear applications. Albeit the excellent corrosion resistance, conventional Fe-Cr-Al alloys suffer from α-α‧ phase separation and embrittlement when subjected to temperatures up to 500 °C, due to their high Cr-content. Low-Cr Fe-Cr-Al alloys are anticipated to be embrittlement resistant and provide adequate oxidation properties, yet long-term aging experiments and simulations are lacking in literature. In this study, Fe-10Cr-(4-8)Al alloys and a Fe-21Cr-5Al were thermally aged in the temperature interval of 450-550 °C for times up to 10,000 h, and the microstructures were evaluated mainly using atom probe tomography. In addition, a Kinetic Monte Carlo (KMC) model of the Fe-Cr-Al system was developed. No phase separation was observed in the Fe-10Cr-(4-8)Al alloys, and the developed KMC model yielded results in good agreement with the experimental data.

  20. Dendrite coherency of Al-Si-Cu alloys

    NASA Astrophysics Data System (ADS)

    Veldman, Natalia L. M.; Dahle, Arne K.; Stjohn, David H.; Arnberg, Lars

    2001-01-01

    The dendrite coherency point of Al-Si-Cu alloys was determined by thermal analysis and rheological measurement methods by performing parallel measurements at two cooling rates for aluminum alloys across a wide range of silicon and copper contents. Contrary to previous findings, the two methods yield significantly different values for the fraction solid at the dendrite coherency point. This disparity is greatest for alloys of low solute concentration. The results from this study also contradict previously reported trends in the effect of cooling rate on the dendritic coherency point. Consideration of the results shows that thermal analysis is not a valid technique for the measurement of coherency. Analysis of the results from rheological testing indicates that silicon concentration has a dominant effect on grain size and dendritic morphology, independent of cooling rate and copper content, and thus is the factor that determines the fraction solid at dendrite coherency for Al-Si-Cu alloys.

  1. The Zeno Line for Al, Cu, and U.

    PubMed

    Apfelbaum, E M; Vorob'ev, V S

    2016-06-01

    We show that the property of linearity for a line of unit compressibility factor (Zeno line) can be confirmed for metals (Al, Cu, and U) in liquid phase. The embedded atom potentials (EAM) have been used to describe the interaction between the particles. The numerical simulations within Monte Carlo (MC) technique with the EAM potential have resulted in the straight Zeno-line for considered metals and have allowed us to define the Zeno line parameters. The similarity relations between the critical and the Zeno line parameters, which were observed previously for nonmetallic substances, have appeared to be valid for Al and Cu as well. For uranium there is a contradiction between the calculated and experimental data, indicating the limitation for these similarities. PMID:27158747

  2. Investigation of new type Cu-Hf-Al bulk glassy alloys

    NASA Astrophysics Data System (ADS)

    Nagy, E.; Rontó, V.; Sólyom, J.; Roósz, A.

    2009-01-01

    In the last years new type Cu-Hf-Al ternary alloys were developed with high glass forming ability and ductility. The addition of Al to Cu-Hf alloys results in improvements in glass formation, thermal stability and mechanical properties of these alloys. We have investigated new Cu-based bulk amorphous alloys in Cu-Hf-Al ternary system. The alloys with Cu49Hf42Al9, Cu46Hf45Al9, Cu50Hf42.5Al7.5 and Cu50Hf45Al5 compositions were prepared by arc melting. The samples were made by centrifugal casting and were investigated by X-ray diffraction method. Thermodynamic properties were examined by differential scanning calorimetry and the structure of the crystallising phases by scanning electron microscopy. The determination of liquidus temperatures of alloys were measured by differential thermal analysis.

  3. Microstructure/Oxidation/Microhardness Correlations in Gamma-Based and Tau-Based Al-Ti-Cr Alloys

    NASA Technical Reports Server (NTRS)

    Brady, Michael P.; Smialek, J. L.; Humphrey, D. L.

    1994-01-01

    The relationships between alloy microstructure and air oxidation kinetics and alloy microstructure and microhardness in the Al-Ti-Cr system for exposures at 800 C and 1000 C were investigated. The relevant phases were identified as tau (Ll2), gamma (LIO), r-Al2Ti, TiCrAl (laves), and Cr2AI. Protective alumina formation was associated with tau, Al-rich TiCrAl, and gamma/TiCrAl mixtures. Brittleness was associated with the TiCrAl phase and tau decomposition to A12Ti + Cr2AI. It was concluded that two-phase gamma + TiCrAl alloys offer the greatest potential for oxidation resistance and room temperature ductility in the Al-Ti-Cr system.

  4. Indium Helps Strengthen Al/Cu/Li Alloy

    NASA Technical Reports Server (NTRS)

    Blackburn, Linda B.; Starke, Edgar A., Jr.

    1992-01-01

    Experiments on Al/Cu/Li alloys focus specifically on strengthening effects of minor additions of In and Cd. Indium-bearing alloy combines low density with ability to achieve high strength through heat treatment alone. Tensile tests on peak-aged specimens indicated that alloy achieved yield strength approximately 15 percent higher than baseline alloy. Alloy highly suitable for processing to produce parts of nearly net shape, with particular applications in aircraft and aerospace vehicles.

  5. Viscous and acoustic properties of AlCu melts

    NASA Astrophysics Data System (ADS)

    Khusnutdinoff, R. M.; Mokshin, A. V.; Menshikova, S. G.; Beltyukov, A. L.; Ladyanov, V. I.

    2016-05-01

    The atomic dynamics of the binary Al100- x Cu x system is simulated at a temperature T = 973 K, a pressure p = 1.0 bar, and various copper concentrations x. These conditions (temperature, pressure) make it possible to cover the equilibrium liquid Al100- x Cu x phase at copper concentrations 0 ≤ x ≤ 40% and the supercooled melt in the concentration range 40% ≤ x ≤ 100%. The calculated spectral densities of the time correlation functions of the longitudinal {tilde C_L}( k, ω) and transverse {tilde C_T}( k, ω) currents in the Al100- x Cu x melt at a temperature T = 973 K reveal propagating collective excitations of longitudinal and transverse polarizations in a wide wavenumber range. It is shown that the maximum sound velocity in the v L ( x) concentration dependence takes place for the equilibrium melt at an atomic copper concentration x = 10 ± 5%, whereas the supercooled Al100- x Cu x melt saturated with copper atoms ( x ≥ 40%) is characterized by the minimum sound velocity. In the case of the supercooled melt, the concentration dependence of the kinematic viscosity ν( x) is found to be interpolated by a linear dependence, and a deviation from the linear dependence is observed in the case of equilibrium melt at x < 40%. An insignificant shoulder in the ν( x) dependence is observed at low copper concentrations ( x < 20%), and it is supported by the experimental data. This shoulder is caused by the specific features in the concentration dependence of the density ρ( x).

  6. Synthesis and characterization of Sr(Al,Cr) 12O 19 solid solution

    NASA Astrophysics Data System (ADS)

    Sandiumenge, Felip; Galí, Salvador

    1989-09-01

    Magnetoplumbite-type crystalline powders with SrAl 12- xCr xO 19 composition were synthesized in the range 0 ≤ x ≤ 4.4 by two different solid state reactions in air. The limited substitution of Al by trivalent Cr is accompanied by the appearance of a sesquioxide Al 2- yCr yO 3 solid solution and a new cubic phase with composition 3Al 2O 3 · SrCrO 4. These results are compared with those obtained in the synthesis of Sr(Fe,Cr) 12O 19 and Sr(Al,Fe) 12O 19 solid solutions. Finally, the cation distribution of Al and Cr in the system Sr(Al,Cr) 12O 19(Al,Cr) 2O 3 was obtained from X-ray diffraction profile analysis. The cationic distribution suggests that the solid solution range depends more on the crystal chemistry of the substitution than on the starting compounds used in the synthesis.

  7. Comparative studies on the thermal stability and corrosion resistance of CrN, CrSiN, and CrSiN/AlN coatings

    SciTech Connect

    Kim, Gwang Seok; Kim, Sung Min; Lee, Sang Yul; Lee, Bo Young

    2009-07-15

    In this work, three kinds of Cr-based nitride coatings such as monolithic CrN, CrSiN coatings, and multilayered CrSiN/AlN coating with bilayer period of 3.0 nm were deposited on both Si (100) wafer and AISI H13 steel substrates by unbalanced magnetron sputtering. Thermal stability of these coatings was evaluated by annealing the coatings at temperatures between 600 and 1000 degree sign C for 30 min in air. In addition, the corrosion behaviors of these coatings were investigated by potentiodynamic polarization tests in a deaerated 3.5 wt. % NaCl solution at 40 degree sign C. Results from annealing test show the monolithic CrN and CrSiN coatings were completely oxidized after annealed at 800 and 900 degree sign C, and their cross sectional images and atomic force microscopy showed a loose and very porous morphology due to the oxidation. Also, the hardness values of the monolithic CrN and CrSiN coatings were decreased significantly from 22 and 27 GPa to 8 and 14 GPa, respectively. However, the multilayered CrSiN/AlN coating still exhibited a dense microstructure without visible change after annealed at 1000 degree sign C, and moreover, the relatively high hardness of 25 GPa was maintained. The superior thermal stability of the CrSiN/AlN multilayer coating could be attributed to the formation of the dense and stable oxidation barrier consisted of the Al{sub 2}O{sub 3}, Cr{sub 2}O{sub 3}, and amorphous SiO{sub 2} phases near the surface region, which retard the diffusion of oxygen into the coating. In the potentiodynamic polarization test results, it was found that the significantly improved corrosion resistance of the multilayered CrSiN/AlN coating was observed in comparison with those from the monolithic CrN and CrSiN coatings, and its corrosion current density (i{sub corr}) and protective efficiency were measured to be approximately 4.21 {mu}A/cm{sup 2} and 95%, respectively.

  8. High temperature oxidation resistant coatings for the directionally solidified Ni-Nb-Cr-Al eutectic superalloy

    NASA Technical Reports Server (NTRS)

    Strangman, T. E.; Ulion, N. E.; Felten, E. J.

    1977-01-01

    Protective coatings required for the Ni-Nb-Cr-Al directionally solidified eutectic superalloy were developed and evaluated on the basis of oxidation resistance, diffusional stability, thermal fatigue, and creep resistance. NiCrAlY+Pt and NiCrAlY physical vapor-deposition coating systems exhibited the best combination of properties. Burner-rig testing indicated that the useful life of a 127-micron-thick NiCrAlY+Pt coating exceeds 1000 h at 1366 K. Eutectic-alloy creep lives at 1311 K and a stress of 151.7 MN/sq m were greater for NiCrAlY+Pt-coated specimens than for uncoated specimens by a factor of two.

  9. The effect of coarse second phase particles on fatigue crack propagation of an Al-Zn-Mg-Cu alloy

    SciTech Connect

    Guerbuez, R.; Alpay, S.P. . Dept. of Metallurgical Engineering)

    1994-06-01

    The objective of this study is to determine the role of the most commonly observed coarse second phase particles; Al[sub 7]Cu[sub 2]Fe, Mg[sub 2]Si and CuAl[sub 2]Mg on the Stage 2 fatigue crack propagation of a 7050 aluminum alloy. The differences in the composition of this alloy when compared to the conventional 7075 alloy are: (1) increased Cu content for additional strengthening during aging and for increasing the temperature range of GP zone stability; (2) replacement of Cr by Zr to reduce quench sensitivity; (3) reduced Fe and Si contents to improve fracture toughness which, however, decreases fatigue crack growth threshold, [Delta]K[sub th], slightly; and (4) increased Zn content for strengthening.

  10. Evaluation of Ti-48Al-2Cr-2Nb Under Fretting Conditions

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Lerch, Bradley A.; Draper, Susan L.; Raj, Sai V.

    2001-01-01

    The fretting behavior of Ti-48Al-2Cr-2Nb (y-TiAl) in contact with the nickel-base superalloy 718 was examined in air at temperatures from 296 to 823 K (23 to 550 C). The interfacial adhesive bonds between Ti-48Al-2Cr-2Nb and superalloy 718 were generally stronger than the cohesive bonds within Ti-48Al-2Cr-2Nb. The failed Ti-48Al-2Cr-2Nb debris subsequently transferred to the superalloy 718. In reference experiments conducted with Ti-6Al-4V against superalloy 718 under identical fretting conditions, the degree of transfer was greater for Ti-6A1-4V than for Ti-48Al-2Cr-2Nb. Wear of Ti-48Al-2Cr-2Nb generally decreased with increasing fretting frequency. The increasing rate of oxidation at elevated temperatures led to a drop in wear at 473 K. However, fretting wear increased as the temperature was increased from 473 to 823 K. At 723 and 823 K, oxide film disruption generated cracks, loose wear debris, and pits on the Ti-48Al-2Cr-2Nb wear surface. Both increasing slip amplitude and increasing load tended to produce more metallic wear debris, causing severe abrasive wear in the contacting metals.

  11. Cu-Al spinel oxide as an efficient catalyst for methanol steam reforming.

    PubMed

    Xi, Hongjuan; Hou, Xiaoning; Liu, Yajie; Qing, Shaojun; Gao, Zhixian

    2014-10-27

    Cu-Al spinel oxide, which contains a small portion of the CuO phase, has been successfully used in methanol steam reforming (MSR) without prereduction. The omission of prereduction not only avoids the copper sintering prior to the catalytic reaction, but also slows down the copper-sintering rate in MSR. During this process, the CuO phase can initiate MSR at a lower temperature, and CuAl2O4 releases active copper gradually. The catalyst CA2.5-900, calcined at 900 °C with n(Al)/n(Cu) = 2.5, has a higher CuAl2O4 content, higher BET surface area, and smaller CuAl2O4 crystal size. Its activity first increases and then decreases during MSR. Furthermore, both fresh and regenerated CA2.5-900 showed better catalytic performance than the commercial Cu-Zn-Al catalyst. PMID:25213737

  12. FeAl underlayers for CoCrPt thin film longitudinal media

    SciTech Connect

    Lee, L.; Laughlin, D.E.; Lambeth, D.N.

    1997-04-01

    B2 ordered FeAl films with a small, uniform grain size have been produced by rf diode sputter deposition on glass substrates. CoCrPt films grown on FeAl underlayers were found to have the (10{bar 1}0) lamellar texture. The in-plane coercivities (H{sub c}) of the CoCrPt/FeAl films are comparable to those of the CoCrPt/Cr films and they can be further improved by inserting a thin Cr intermediate layer between the CoCrPt and the FeAl layers. By employing a MgO seed layer or a (002) textured Cr seed layer, (001) textured FeAl can be obtained. However, the (001) FeAl underlayer only induces a weak (11{bar 2}0) textured CoCrPt. Thus no improvement in H{sub c} over those produced on unseeded FeAl underlayers was observed. {copyright} {ital 1997 American Institute of Physics.}

  13. Structural disorder and magnetism in the spin-gapless semiconductor CoFeCrAl

    NASA Astrophysics Data System (ADS)

    Choudhary, Renu; Kharel, Parashu; Valloppilly, Shah R.; Jin, Yunlong; O'Connell, Andrew; Huh, Yung; Gilbert, Simeon; Kashyap, Arti; Sellmyer, D. J.; Skomski, Ralph

    2016-05-01

    Disordered CoFeCrAl and CoFeCrSi0.5Al0.5 alloys have been investigated experimentally and by first-principle calculations. The melt-spun and annealed samples all exhibit Heusler-type superlattice peaks, but the peak intensities indicate a substantial degree of B2-type chemical disorder. Si substitution reduces the degree of this disorder. Our theoretical analysis also considers several types of antisite disorder (Fe-Co, Fe-Cr, Co-Cr) in Y-ordered CoFeCrAl and partial substitution of Si for Al. The substitution transforms the spin-gapless semiconductor CoFeCrAl into a half-metallic ferrimagnet and increases the half-metallic band gap by 0.12 eV. Compared CoFeCrAl, the moment of CoFeCrSi0.5Al0.5 is predicted to increase from 2.01 μB to 2.50 μB per formula unit, in good agreement with experiment.

  14. Long range order and vacancy properties in Al-rich Fe{sub 3}Al and Fe{sub 3}Al(Cr) alloys

    SciTech Connect

    Kim, S.M.; Morris, D.G.

    1998-05-01

    Neutron powder diffraction measurements have been carried out in situ from room temperature to about 100 C in Fe28Al (28 at.% Al), Fe32.5Al (32.5 at.% Al) and Fe28Al15Cr (28 at.% Al, 5 at.% Cr) alloys. X-ray diffraction and TEM studies provided supporting information. The data were analyzed to obtain information about the temperature dependence of the DO{sub 3} and B2 long range order parameters, the location of the Cr atoms and their effect on the ordering energies, and on the vacancy formation and migration properties in Fe28Al and Fe32.5Al alloys. The location of the ternary alloying addition in DO{sub 3} and B2 ordered Al-rich Fe{sub 3}Al is shown to be consistent with considerations of interatomic bond energies.

  15. Microstructure evolution during annealing of TiAl/NiCoCrAl multilayer composite prepared by EB-PVD

    SciTech Connect

    Zhang, Rubing; Zhang, Deming; Chen, Guiqing; Wang, Yuesheng

    2014-07-01

    TiAl/NiCoCrAl laminate composite sheet with a thickness of 0.4–0.6 mm as well as a dimension of 150 mm × 100 mm was fabricated successfully by using electron beam physical vapor deposition (EB-PVD) method. The annealing treatment was processed at 1123 and 1323 K for 3 h in a high vacuum atmosphere, respectively. The phase composition and microstructure of TiAl/NiCoCrAl microlaminated sheet have been analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Based on the sheet characterization and results of the microstructure evolution during annealing treatment process, the diffusion mechanism of interfacial reaction in TiAl/NiCoCrAl microlaminate was investigated and discussed.

  16. Investigation of the nanostructure and wear properties of physical vapor deposited CrCuN nanocomposite coatings

    SciTech Connect

    Baker, M.A.; Kench, P.J.; Tsotsos, C.; Gibson, P.N.; Leyland, A.; Matthews, A.

    2005-05-01

    This article presents results on CrCuN nanocomposite coatings grown by physical vapor deposition. The immiscibility of Cr (containing a supersaturation of nitrogen) and Cu offers the potential of depositing a predominantly metallic (and therefore tough) nanocomposite, composed of small Cr(N) metallic and/or {beta}-Cr{sub 2}N ceramic grains interdispersed in a (minority) Cu matrix. A range of CrCuN compositions have been deposited using a hot-filament enhanced unbalanced magnetron sputtering system. The stoichiometry and nanostructure have been studied by x-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy, and x-ray diffraction. Hardness, wear resistance, and impact resistance have been determined by nanoindentation, reciprocating-sliding, and ball-on-plate high-cycle impact. Evolution of the nanostructure as a function of composition and correlations of the nanostructure and mechanical properties of the CrCuN coatings are discussed. A nanostructure comprised of 1-3 nm {alpha}-Cr(N) and {beta}-Cr{sub 2}N grains separated by intergranular regions of Cu gives rise to a coating with significantly enhanced resistance to impact wear.

  17. Irradiation-enhanced α' precipitation in model FeCrAl alloys

    DOE PAGESBeta

    Edmondson, Philip D.; Briggs, Samuel A.; Yamamoto, Yukinori; Howard, Richard H.; Sridharan, Kumar; Terrani, Kurt A.; Field, Kevin G.

    2016-02-17

    Model FeCrAl alloys with varying compositions (Fe(10–18)Cr(10–6)Al at.%) have been neutron irradiated at ~ 320 to damage levels of ~ 7 displacements per atom (dpa) to investigate the compositional influence on the formation of irradiation-induced Cr-rich α' precipitates using atom probe tomography. In all alloys, significant number densities of these precipitates were observed. Cluster compositions were investigated and it was found that the average cluster Cr content ranged between 51.1 and 62.5 at.% dependent on initial compositions. This is significantly lower than the Cr-content of α' in binary FeCr alloys. As a result, significant partitioning of the Al from themore » α' precipitates was also observed.« less

  18. Adsorption and desorption of Zn, Cu, and Cr by sediments from the Raisin River (Michigan)

    SciTech Connect

    Young, T.C.; DePinto, J.V.; Kipp, T.W.

    1987-01-01

    Metal absorption by Raisin River sediments in vitro depended linearly on soluble metal concentration to adsorption densities of 6000-9000 ..mu..g/g with 48 hr partition coefficients of approximately 50, 30, and 25 L/g for Cu, Cr, and Zn, respectively. Partition coefficient computed from field data spanned a comparatively wider range of values in a manner consistent with the often reported adsorbent concentration effect, but other factors likely contributed, too. Desorption of Zn was complete and rapid in contrast to Cr, which was incomplete and much slower; Cu desorption was intermediate to Zn and Cr. A reversible-resistant equilibrium model could not describe the observations as Cu and Cr had not reached metastable desorption equilibria after 24 days. Metal desorption, however, could be described kinetically by distributing sorbed cations between either of two classes; rapidly desorbing and slowly desorbing cations. Sequential and simultaneous desorption models gave similar predictions. Aqueous chemical considerations suggested precipitated as well as adsorbed species could give rise to the observations, but available data did not permit adequate tests of this hypothesis. The extent to which kinetic constraints rather than irreversible reactions account for the desorption-resistant binding signifies a potentially greater metal mobility of bioavailability than would otherwise be assumed. 27 references, 5 figures, 4 tables.

  19. 1100 to 1500 K Slow Plastic Compressive Behavior of NiAl-xCr Single Crystals

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Darolia, Ram

    2003-01-01

    The compressive properties of near <001> and <111> oriented NiAl-2Cr single crystals and near <011> oriented NiAl-6Cr samples have been measured between 1100 and 1500 K. The 2Cr addition produced significant solid solution strengthening in NiAl, and the <111> and <001> single crystals possessed similar strengths. The 6Cr crystals were not stronger than the 2Cr versions. At 1100 and 1200 K plastic flow in all three Cr-modified materials was highly dependent on stress with exponents > 10. The <011> oriented 6Cr alloy exhibited a stress exponent of about 8 at 1400 and 1500 K; whereas both <001> and <111> NiAl-2Cr crystals possessed stress exponents near 3 which is indicative of a viscous dislocation glide creep mechanism. While the Cottrell-Jaswon solute drag model predicted creep rates within a factor of 3 at 1500 K for <001>-oriented NiAl-2Cr; this mechanism greatly over predicted creep rates for other orientations and at 1400 K for <001> crystals.

  20. Diffusional transport during the cyclic oxidation of gamma + beta, Ni-Cr-Al(Y, Zr) alloys

    NASA Technical Reports Server (NTRS)

    Nesbitt, J. A.; Heckel, R. W.

    1988-01-01

    The cyclic oxidation behavior of several cast gamma + beta, Ni-Cr-Al(Y, Zr) alloys and one low-pressure plasma spraying gamma + beta, Ni-Co-Cr-Al(Y) alloy was studied. Cyclic oxidation was found to result in a decreasing Al concentration at the oxide-metal interface due to a high rate of Al consumption coupled with oxide scale cracking and spalling. Diffusion paths plotted on the ternary phase diagram showed higher Ni concentrations with increasing cyclic oxidation exposures. The alloy with the highest rate of Al consumption and the highest Al content underwent breakaway oxidation following 500 1-hr cycles at 1200 C.

  1. Tribological Properties of the Fe-Al-Cr Alloyed Layer by Double Glow Plasma Surface Metallurgy

    NASA Astrophysics Data System (ADS)

    Luo, Xixi; Yao, Zhengjun; Zhang, Pingze; Zhou, Keyin; Wang, Zhangzhong

    2016-07-01

    A Fe-Al-Cr alloyed layer was deposited onto the surface of Q235 low-carbon steel via double glow plasma surface metallurgy (DGPSM) to improve the steel's wear resistance. After the DGPSM treatment, the Fe-Al-Cr alloyed layer grown on the Q235 low-carbon steel was homogeneous and compact and had a thickness of 25 µm. The layer was found to be metallurgically adhered to the substrate. The frictional coefficient and specific wear rate of the sample with a Fe-Al-Cr alloyed layer (treated sample) were both lower than those of the bare substrate (untreated sample) at the measured temperatures (25, 250 and 450 °C). The results indicated that the substrate and the alloyed layer suffered oxidative wear and abrasive wear, respectively, and that the treated samples exhibited much better tribological properties than did the substrate. The formation of Fe2AlCr, Fe3Al(Cr), FeAl(Cr), Fe(Cr) sosoloid and Cr23C6 phases in the alloyed layer dramatically enhanced the wear resistance of the treated sample. In addition, the alloyed layer's oxidation film exhibited a self-healing capacity with lubrication action that also contributed to the improvement of the wear resistance at high temperature. In particular, at 450 °C, the specific wear rate of treated sample was 2.524 × 10-4 mm3/N m, which was only 45.2% of the untreated sample.

  2. Low-moment ferrimagnetic phase of the Heusler compound Cr2CoAl

    NASA Astrophysics Data System (ADS)

    Jamer, Michelle E.; Marshall, Luke G.; Sterbinsky, George E.; Lewis, Laura H.; Heiman, Don

    2015-11-01

    Synthesizing half-metallic fully compensated ferrimagnets that form in the inverse Heusler phase could lead to superior spintronic devices. These materials would have high spin polarization at room temperature with very little fringing magnetic fields. Previous theoretical studies indicated that Cr2CoAl should form in a stable inverse Heusler lattice due to its low activation energy. Here, stoichiometric Cr2CoAl samples were arc-melted and annealed at varying temperatures, followed by studies of their structural and magnetic properties. High-resolution synchrotron X-ray diffraction revealed a chemically ordered Heusler phase in addition to CoAl and Cr phases. Soft X-ray magnetic circular dichroism revealed that the Cr and Co magnetic moments are antiferromagnetically oriented leading to the observed low magnetic moment in Cr2CoAl.

  3. Comparison in mechanical and tribological properties of CrTiAlMoN and CrTiAlN nano-multilayer coatings deposited by magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Zhang, Guojun; Jiang, Bailing

    2016-02-01

    CrTiAlN and CrTiAlMoN nano-multilayer coatings were deposited by closed field unbalanced magnetron sputtering. TiMoN and CrTiMoN nano-multilayer coatings with same Mo2N layer thickness were also prepared for comparison. The structure of these coatings is investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The mechanical and tribological properties were characterized and compared by nano-indentation and ball-on-disc test. It was found that these coatings were structured by fcc metal nitride phases (including CrN, TiN, AlN and Mo2N) and the preferred orientation changed from (1 1 1) to (2 0 0) with the increase of Mo content. The TEM results showed that the coatings exhibited typical columnar structure and nano-multilayer structure with modulation periods ranged from 3.2 nm to 7.6 nm. Among these coatings, CrTiAlMoN coatings presented the highest hardness, lowest coefficient of friction (COF) and wear rate. The hardness of these nano-multilayer coatings were determined by layer interfaces: TiN/Mo2N and AlN/Mo2N layer interface showed benefit on hardness enhancement while CrN/Mo2N layer interface led to a great hardness decrement. In comparison with the other as-deposited coatings, the low COF of CrTiAlMoN coatings was not only affected by Mo addition but also related to its oxidation behaviors.

  4. Preparation and thermoelectric properties of ternary superionic conductor CuCrS{sub 2}

    SciTech Connect

    Chen Yuexing; Zhang Boping; Ge Zhenhua; Shang Pengpeng

    2012-02-15

    Transition metal chalcogenide CuCrS{sub 2} powder was synthesized by mechanical alloying (MA) and then consolidated by spark plasma sintering (SPS) technique at 673-1073 K. The phase structure, microstructure and thermoelectric properties of samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and Seebeck coefficient/electrical conductivity measuring system, respectively. All the bulks indicated a single phase CuCrS{sub 2}, while the high relative density over 90% were attained for the samples sintered at 873-1073 K. The electrical conductivity of bulk samples displayed a typical characteristic of semiconductor. With increasing measuring temperature, the conductive behaviour of bulk samples sintered over 973 K showed a semiconductor transformation from n-type to p-type due to the changes of main carrier type. The sample obtained by applying SPS at 873 K got the highest power factor 83.2 {mu}W m{sup -1} K{sup -2}, and the largest ZT value 0.11 at 673 K. - Graphical abstract: The samples sintered above 873 K, both of the Seebeck coefficient and electrical conductivity exhibit an increase tendency with increasing temperature, which is due to the mechanism of mix-conduction for CuCrS{sub 2}. Highlights: Black-Right-Pointing-Pointer Single phase CuCrS{sub 2} powder was synthesized by ball-milling at 425 rpm for 40 h. Black-Right-Pointing-Pointer Dense CuCrS{sub 2} bulks were fabricated using SPS techniques at sintering temperature 873-1073 K. Black-Right-Pointing-Pointer Seebeck coefficient of CuCrS{sub 2} samples sintered over 973 K change the signs. Black-Right-Pointing-Pointer Highest power factor reached 83.2 {mu}W m{sup -1} K{sup -2} at 673 K for the sample sintered at 873 K. Black-Right-Pointing-Pointer ZT value was 0.11 at 673 K for the sample sintered at 873 K.

  5. Solidification behavior and structure of Al-Cu alloy welds

    SciTech Connect

    Brooks, J.A.; Li, M.; Yang, N.C.Y.

    1997-09-01

    The microsegregation behavior of electron beam (EB) and gas tungsten arc (GTA) welds of Al-Cu alloys covering a range from 0.19 to 7.74 wt% Cu were characterized for dendrite core concentrations and fraction eutectic solidification. Although a single weld speed of 12.7 mm/sec was used, some differences were observed in the segregation behavior of the two weld types. The microsegregation behavior was also modeled using a finite differences technique considering dendrite tip and eutectic undercooling and solid state diffusion. Fairly good agreement was observed between measured and calculated segregation behavior although differences between the two weld types could not be completely accounted for. The concept of dendrite tip undercooling was used to explain the formation of a single through thickness centerline grain in the higher alloy content GTA welds.

  6. Development of ODS FeCrAl alloys for accident-tolerant fuel cladding

    SciTech Connect

    Dryepondt, Sebastien N.; Hoelzer, David T.; Pint, Bruce A.; Unocic, Kinga A.

    2015-09-18

    FeCrAl alloys are prime candidates for accident-tolerant fuel cladding due to their excellent oxidation resistance up to 1400 C and good mechanical properties at intermediate temperature. Former commercial oxide dispersion strengthened (ODS) FeCrAl alloys such as PM2000 exhibit significantly better tensile strength than wrought FeCrAl alloys, which would alloy for the fabrication of a very thin (~250 m) ODS FeCrAl cladding and limit the neutronic penalty from the replacement of Zr-based alloys by Fe-based alloys. Several Fe-12-Cr-5Al ODS alloys where therefore fabricated by ball milling FeCrAl powders with Y2O3 and additional oxides such as TiO2 or ZrO2. The new Fe-12Cr-5Al ODS alloys showed excellent tensile strength up to 800 C but limited ductility. Good oxidation resistance in steam at 1200 and 1400 C was observed except for one ODS FeCrAl alloy containing Ti. Rolling trials were conducted at 300, 600 C and 800 C to simulate the fabrication of thin tube cladding and a plate thickness of ~0.6mm was reached before the formation of multiple edge cracks. Hardness measurements at different stages of the rolling process, before and after annealing for 1h at 1000 C, showed that a thinner plate thickness could likely be achieved by using a multi-step approach combining warm rolling and high temperature annealing. Finally, new Fe-10-12Cr-5.5-6Al-Z gas atomized powders have been purchased to fabricate the second generation of low-Cr ODS FeCrAl alloys. The main goals are to assess the effect of O, C, N and Zr contents on the ODS FeCrAl microstructure and mechanical properties, and to optimize the fabrication process to improve the ductility of the 2nd gen ODS FeCrAl while maintaining good mechanical strength and oxidation resistance.

  7. NMR study of the ternary carbides M2 AlC (M=Ti,V,Cr)

    NASA Astrophysics Data System (ADS)

    Lue, C. S.; Lin, J. Y.; Xie, B. X.

    2006-01-01

    We have performed a systematic study of the layered ternary carbides Ti2AlC , V2AlC , and Cr2AlC using Al27 NMR spectroscopy. The quadrupole splittings, Knight shifts, as well as spin-lattice relaxation times on each material have been identified. The sign of the isotropic Knight shift varies from positive for Ti2AlC and V2AlC to negative for Cr2AlC , attributed to the enhancement of hybridization with increasing valence electron count in the transition metal. Universally long relaxation times are found for these alloys. Results provide a measure of Al-s Fermi-level density of states Ns(EF) for Ti2AlC and V2AlC . In addition, the evidence that Ns(EF) correlates with the transition metal d -electron count has been explored in the present NMR investigation.

  8. The influence of Cu /Al ratio on properties of chemical-vapor-deposition-grown p-type Cu-Al-O transparent semiconducting films

    NASA Astrophysics Data System (ADS)

    Cai, Jianling; Gong, Hao

    2005-08-01

    Transparent p-type copper aluminum oxide (Cu-Al-O) semiconducting thin films, with Cu /Al atomic ratios ranging from 1.0 to 4.3, were deposited by plasma-enhanced metal-organic chemical-vapor deposition. The films were grown on z-cut single-crystal quartz substrates, at a substrate temperature of 450°C. Crystalline CuAlO2 was found dominant in the films, including small amounts of CuAl2O4, Al2O3, and amorphous Cu2O. The effect of varying Cu /Al ratio on the structural, electrical, and optical properties of the films were studied by x-ray diffraction, energy dispersive x-ray spectroscopy, x-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, and Seebeck technique, and discussed. We were able to optimize the Cu /Al ratio for the p-type conductivity and transmittance in copper aluminum oxide thin films, and the best conductive film, with a room-temperature conductivity of 0.289Scm-1 and a transparency of 80%, was found to have a Cu /Al ratio of 1.4±0.3. In addition, the mechanism of the p-type conduction of copper aluminum oxide was discussed.

  9. CO sub 2 induced inhibition of the localized corrosion of aluminum, Al-0. 5% Cu, and Al-2% Cu in dilute HF solution

    SciTech Connect

    Scully, J.R. . Dept. of Materials Science); Peebles, D.E. )

    1991-01-01

    This study presents work on corrosion of aluminum, Al-.5% Cu, and Al-2% Cu. Electrochemical tests were performed in dilute HF solutions both with and without CO{sub 2} sparging. It is suggested that CO{sub 2} or its reaction products interact with the passive film so that exposure of Cu in the oxide-solution interface is minimized. CO{sub 2} is investigated as a corrosion inhibitor. 4 refs. (JDL)

  10. The influence of Cr and Al pack cementation on low carbon steel to improve oxidation resistance

    NASA Astrophysics Data System (ADS)

    Prasetya, Didik; Sugiarti, Eni; Destyorini, Fredina; Thosin, Kemas Ahmad Zaini

    2012-06-01

    Pack chromizing and aluminizing has been widely used for many years to improve hot temperature oxidation and corrosion resistance of metals. The coating process involves packing the steel in a powder mixture which contain aluminum and chromium source, and inert filler (usually alumina), and halide activator NH4Cl. Al and Cr were deposited onto carbon steel by pack cementation process using elemental Al and Cr powder as Al and Cr source, whereas NiCo alloys codeposited by electrodeposition. The position of Al and Cr could be under or over Ni-Co alloys deposited. Pack cementation was heated on dry inert gas at temperature 800 °C about 5 hours and 20 minute for Cr and Al respectively. Al and Cr was successfully deposited. Laying down effect of Al and Cr onto carbon steel whether up and down toward NiCo alloys coating have affected to oxidation resistance. The pack aluminizing as top layer given best resitance to restrain excessive oxide scale, in contrast pack chromizing reveal bad oxidation resistance, moreover occured spallation on layer.

  11. Enhanced magnetism of Cu{sub n} clusters capped with N and endohedrally doped with Cr

    SciTech Connect

    Datta, Soumendu; Banerjee, Radhashyam; Mookerjee, Abhijit

    2015-01-14

    The focus of our work is on the production of highly magnetic materials out of Cu clusters. We have studied the relative effects of N-capping as well as N mono-doping on the structural stability and electronic properties of the small Cu clusters using first principles density functional theory based electronic structure calculations. We find that the N-capped clusters are more promising in producing giant magnetic moments, such as 14 μ{sub B} for the Cu{sub 6}N{sub 6} cluster and 29 μ{sub B} for the icosahedral Cu{sub 13}N{sub 12} cluster. This is accompanied by a substantial enhancement in their stability. We suggest that these giant magnetic moments of the capped Cu{sub n} clusters have relevance to the observed room temperature ferromagnetism of Cu doped GaN. For cage-like hollow Cu-clusters, an endohedral Cr-doping together with the N-capping appears as the most promising means to produce stable giant magnetic moments in the copper clusters.

  12. Kinetics of borided 31CrMoV9 and 34CrAlNi7 steels

    SciTech Connect

    Efe, Goezde Celebi; Ipek, Mediha; Ozbek, Ibrahim; Bindal, Cuma

    2008-01-15

    In this study, kinetics of borides formed on the surface of 31CrMoV9 and 34CrAlNi7 steels borided in solid medium consisting of Ekabor II at 850-900-950 deg. C for 2, 4, 6 and 8 h were investigated. Scanning electron microscopy and optical microscopy examinations showed that borides formed on the surface of borided steels have columnar morphology. The borides formed in the coating layer confirmed by X-ray diffraction analysis are FeB, Fe{sub 2}B, CrB, and Cr{sub 2}B. The hardnesses of boride layers are much higher than that of matrix. It was found that depending on process temperature and time the fracture toughness of boride layers ranged from 3.93 to 4.48 MPa m{sup 1/2} for 31CrMoV9 and from 3.87 to 4.40 MPa m{sup 1/2} for 34CrAlNi7 steel. Activation energy, growth rate and growth acceleration of boride layer calculated according to these kinetic studies revealed that lower activation energy results in the fast growth rate and high growth acceleration.

  13. Solid state reduction of chromium (VI) pollution for Al2O3-Cr metal ceramics application

    NASA Astrophysics Data System (ADS)

    Zhu, Hekai; Fang, Minghao; Huang, Zhaohui; Liu, Yangai; Tang, Hao; Min, Xin; Wu, Xiaowen

    2016-04-01

    Reduction of chromium (VI) from Na2CrO4 through aluminothermic reaction and fabrication of metal-ceramic materials from the reduction products have been investigated in this study. Na2CrO4 could be successfully reduced into micrometer-sized Cr particles in a flowing Ar atmosphere in presence of Al powder. The conversion ratio of Na2CrO4 to metallic Cr attained 96.16% efficiency. Al2O3-Cr metal-ceramic with different Cr content (5 wt%, 10 wt%, 15 wt%, 20 wt%) were further prepared from the reduction product Al2O3-Cr composite powder, and aluminum oxide nanopowder via pressure-less sintering. The phase composition, microstructure and mechanical properties of metal-ceramic composites were characterized to ensure the potential of the Al2O3-Cr composite powder to form ceramic materials. The highest relative density and bending strength can reach 93.4% and 205 MP, respectively. The results indicated that aluminothermic reduction of chromium (VI) for metal-ceramics application is a potential approach to remove chromium (VI) pollutant from the environment.

  14. Pack cementation Cr-Al coating of steels and Ge-doped silicide coating of Cr-Nb alloy

    SciTech Connect

    He, Y.R.; Zheng, M.H.; Rapp, R.A.

    1995-08-01

    Carbon steels or low-alloy steels used in utility boilers, heat exchangers, petrochemical plants and coal gasification systems are subjected to high temperature corrosion attack such as oxidation, sulfidation and hot corrosion. The pack cementation coating process has proven to be an economical and effective method to enhance the corrosion resistance by modifying the surface composition of steels. With the aid of a computer program, STEPSOL, pack cementation conditions to produce a ferrite Cr-Al diffusion coating on carbon-containing steels by using elemental Cr and Al powders have been calculated and experimentally verified. The cyclic oxidation kinetics for the Cr-Al coated steels are presented. Chromium silicide can maintain high oxidation resistance up to 1100{degrees}C by forming a SiO{sub 2} protective scale. Previous studies at Ohio State University have shown that the cyclic oxidation resistance of MOSi{sub 2} and TiSi{sub 2} can be further improved by Ge addition introduced during coating growth. The halide-activated pack cementation process was modified to produce a Ge-doped silicide diffusion coating in a single processing step for the ORNL-developed Cr-Nb advanced intermetallic alloy. The oxidation behavior of the silicide-coated Cr-Nb alloy was excellent: weight gain of about 1 mg/cm{sup 2} upon oxidation at 1100{degrees}C in air for 100 hours.

  15. Interaction of CO and NO with the spinel CuCr2O4 (100) surface: A DFT study

    NASA Astrophysics Data System (ADS)

    Xu, Xiang-Lan; Chen, Wen-Kai; Chen, Zhan-Hong; Li, Jun-Qian; Li, Yi

    The characteristics of CO and NO molecules at Cu2+ and Cr3+ ion sites on the CuCr2O4 (100) surface have been studied by first principles calculations based on spin-polarized density functional theory (DFT). The calculated results show that adsorption energies for X-down(C, N) adsorption vary in the order: Cu2+-CO>Cr3+-NO≈Cr3+-CO>Cu2+-NO. CO molecules are preferentially adsorbed at Cu sites, whereas NO molecules adsorb favorably at Cu2+ and Cr3+ ion sites. The C-O and N-O stretching frequencies are red-shifted upon adsorption. Combining the analysis of frontier molecular orbitals and Mulliken charge, for CO and NO X-down adsorption systems, the 5sigma orbitals donate electrons and the 2pi* orbitals obtain back-donated electrons. Although for NO with O-down adsorption systems, the NO-2pi* orbitals obtain back-donated electrons from substrates without 5sigma-donation. Coadsorption calculations show the CO/NO mixture adsorb selectively at the Cu2+ion site but simultaneously at the Cr3+ ion site, respectively.

  16. Al-21Ti-23Cr high-temperature protective coating on TiAl intermetallic compounds by RF magnetron sputtering

    SciTech Connect

    Park, J.Y.; Lee, H.N.; Wee, D.M.; Park, S.W.; Oh, M.H.

    1997-12-31

    Ti-48Al specimens were coated with Al-21Ti-23Cr film at 200 W, 0.8 Pa and 573 K by RF magnetron sputtering. The oxidation behavior of the coated specimens was investigated through isothermal and cyclic oxidation tests, and the tensile deformation properties of the coated specimens were also investigated before and after oxidation. The isothermal and cyclic oxidation curves showed that the Al-21Ti-23Cr film was very effective in decreasing the oxidation rate of Ti-48Al. This excellent oxidation resistance is attributable to the formation of a protective Al{sub 2}O{sub 3} layer on the surface of the Al-21Ti-23Cr film. It was found from the results of the tensile test that the protective Al{sub 2}O{sub 3} layer on the surface of the Al-21Ti-23Cr film enabled the Ti-48Al to maintain its tensile properties in an oxidizing environment.

  17. Photocatalytic property and structural stability of CuAl-based layered double hydroxides

    SciTech Connect

    Lv, Ming; Liu, Haiqiang

    2015-07-15

    Three types of CuMAl layered double hydroxides (LDHs, M=Mg, Zn, Ni) were successfully synthesized by coprecipitation. Powder X-ray diffraction (XRD), inductively coupled plasma atomic emission spectrometry (ICP-AES) and UV–Vis diffuse reflectance spectrum (UV–vis) were used to confirm the formation of as-synthesized solids with good crystal structure. The photocatalytic activity of those LDH materials for CO{sub 2} reduction under visible light was investigated. The experimental results show that CuNiAl-LDHs with narrowest band gap and largest surface areas behave highest efficiency for methanol generation under visible light compared with CuMgAl-LDHs and CuZnAl-LDHs. The CuNiAL-LDH showed high yield for methanol production i.e. 0.210 mmol/g h, which was high efficient. In addition, the influence of the different M{sup 2+} on the structures and stability of the CuMAl-LDHs was also investigated by analyzing the geometric parameters, electronic arrangement, charge populations, hydrogen-bonding, and binding energies by density functional theory (DFT) analysis. The theoretical calculation results show that the chemical stability of LDH materials followed the order of CuMgAl-LDHs>CuZnAl-LDHs>CuNiAl-LDHs, which is just opposite with the photocatalytic activity and band gaps of three materials. - Graphical abstract: The host–guest calculation models and XRD patterns of CuMAl-LDHs: CuMgAl-LDHs (a), CuZnAl-LDHs (b) and CuNiAl-LDHs (c). - Highlights: • Three types of CuMAl layered double hydroxides (LDHs, M=Mg, Zn, Ni) has been synthesized. • CuMgNi shows narrower band gap and more excellent textural properties than other LDHs. • The band gap: CuMgAl based on result from UV–vis analysis. • CuMgAl shows the highest stability and lowest photocatalytic activity, while CuNiAl just opposite.

  18. Structure and optoelectronic properties of spray deposited Mg doped p-CuCrO2 semiconductor oxide thin films

    NASA Astrophysics Data System (ADS)

    Rastogi, A. C.; Lim, S. H.; Desu, S. B.

    2008-07-01

    Transparent p-type Mg doped CuCrO2 wide-band-gap oxide semiconductor thin films were deposited over quartz substrates by chemical spray technique using metallo-organic precursors. Crystalline single phase CuCrO2 delafossite structure was dominant in ≥700 °C argon ambient annealed films but the as-deposited films contained spinel CuCr2O4 mixed phases. X-ray photoelectron Cr 2p spectra show spin-orbit splitting energy ˜9.8 eV consistent with Cr3+ valance state and Cr 2p3/2 resolved peaks show mixed valence state on Cr4+/Cr6+ confirming CuCr0.93Mg0.07O2 compound phase in spray deposited films. The effect of substrate temperature and film thickness on optical, electrical conductivity, and thermoelectric coefficient was investigated. Highly transparent ≥80% CuCr0.93Mg0.07O2 films with direct and indirect optical band gaps of 3.08 and 2.58 eV for 155 nm and 3.14 and 2.79 for 305 nm thin films, respectively, were obtained. Photoluminescence emission bands at 532 and 484 nm interpreted to arise from 3d94s1 and 3d10 Cu+ intraband transitions confirm mixing of Cu 3d, 4s, and 4p with O 2p orbitals necessary for realizing p-type CuCrO2 films. Electrical conductivity of CuCr0.93Mg0.07O2 films ranged 0.6-1 S cm-1 exhibiting activation energies ˜0.11 eV in 300-420 °K and ˜0.23 eV in ≥420 °K regions ascribed to activated conduction and grain boundary trap assisted conduction, respectively. Transparent p-(CuCr1-xMgxO2)/n-(ZnO) heterojunction diodes showing rectifying current-voltage characteristics were fabricated.

  19. Thermodynamic analysis of chemical compatibility of several compounds with Fe-Cr-Al alloys

    NASA Technical Reports Server (NTRS)

    Misra, Ajay K.

    1993-01-01

    Chemical compatibility between Fe-19.8Cr-4.8Al (weight percent), which is the base composition for the commercial superalloy MA956, and several carbides, borides, nitrides, oxides, and silicides was analyzed from thermodynamic considerations. The effect of addition of minor alloying elements, such as Ti, Y, and Y2O3, to the Fe-Cr-Al alloy on chemical compatibility between the alloy and various compounds was also analyzed. Several chemically compatible compounds that can be potential reinforcement materials and/or interface coating materials for Fe-Cr-Al based composites were identified.

  20. Spectroscopic properties of {Cr}^{3+} in the spinel solid solution {ZnAl}_{2-x}{Cr}x{O}_4

    NASA Astrophysics Data System (ADS)

    Verger, Louisiane; Dargaud, Olivier; Rousse, Gwenaelle; Rozsályi, Emese; Juhin, Amélie; Cabaret, Delphine; Cotte, Marine; Glatzel, Pieter; Cormier, Laurent

    2016-01-01

    The evolution of the structural environment of {Cr}{^{3+}} along the solid solution {ZnAl}_{2-x}{Cr}x{O}_4 has been investigated using a multi-analytical approach. X-ray diffraction confirms that the system follows Vegard's law. Diffuse reflectance spectra show a decrease of the crystal field parameter with the Cr content, usually related to the increase of the Cr-O bond length in a point charge model. This interpretation is discussed and compared to the data obtained by first-principle calculations based on density functional theory. X-ray absorption near edge structure spectra at the Cr K-edge show a pronounced evolution in the pre-edge with the Cr content, characterised by the appearance of a third feature. Calculations enable to assign the origin of this feature to Cr neighbours. The colour change from pink to brownish pink and eventually green along the solid solution has also been quantified by calculating the L*, a*, b* and x, y coefficients in the system defined by the International Commission on Illumination.

  1. Creep of Uncoated and Cu-Cr Coated NARloy-Z

    NASA Technical Reports Server (NTRS)

    Walter, R. J.; Chiang, K. T.

    1998-01-01

    Stress rupture creep tests were performed on uncoated and Cu-30vol%Cr coated NARloy-Z copper alloy specimens exposed to air at 482 C to 704 C. The results showed that creep failure in air of unprotected NARloy-Z was precipitated by brittle intergranular surface cracking produced by strain assisted grain boundary oxidation (SAGBO) which in turn caused early onset of tertiary creep. For the protected specimens, the Cu-Cr coating remained adherent throughout the tests and was effective in slowing down the rate of oxygen absorption, particularly at the higher temperatures, by formation of a continuous chromium oxide scale. As the result of reducing oxygen ingress, the coating prevented SAGBO initiated early creep failure, extended creep deformation and increased the creep rupture life of NARloy-Z over the entire 482 C to 704 C test temperature range.

  2. Magnetic properties of delafossite oxide: CuCr1-xTixO2

    NASA Astrophysics Data System (ADS)

    Majee, M. K.; Bhobe, P. A.; Nigam, A. K.

    2016-05-01

    In order to increase the possibility for technological applications of CuCrO2, there have been attempts to introduce ferromagnetic (FM) order by doping at B-site. With this aim, we present here study of polycrystalline CuCr1-xTixO2 with x=0.0, 0.05, 0.1. The samples have been prepared using solid state synthesis method and characterized for its crystal structure and magnetic properties. All the samples crystallize in the 2H delafossite structure with R-3m space group. Ti substitution causes the expansion of unit cell with increase in both the lattice constants. Antiferromagnetic ordering temperature is seen to decrease with increasing Ti. Ferromagnetic-like signature is obtained in one of the compositions at low applied magnetic field of 100 Oe.

  3. The electrical conductivity of CuCrZr alloy after SPD processing

    NASA Astrophysics Data System (ADS)

    Lipińska, M.; Bazarnik, P.; Lewandowska, M.

    2014-08-01

    CuCrZr alloys exhibit very good relation between mechanical properties and electrical conductivity. However, for its use in some advanced applications improvement of mechanical strength while preserving high electrical conducting is required. Therefore, in this work a CuCrZr alloy was subjected to a series of thermo-mechanical treatments, including solution annealing and water quenching, SPD processing (using hydrostatic extrusion and ECAP) as well as aging in order to improve mechanical strength. The influence of these processing procedures on microstructure features and mechanical properties was determined by TEM observation and microhardness measurements, respectively. Electrical conductivity of the samples was measured by four-points method. The results have shown that it is possible to improve mechanical strength while preserving good electrical conductivity by a proper combination of SPD processing and heat treatment.

  4. Quasi-one-dimensional antiferromagnetism and multiferroicity in CuCrO4

    NASA Astrophysics Data System (ADS)

    Law, J. M.; Reuvekamp, P.; Glaum, R.; Lee, C.; Kang, J.; Whangbo, M.-H.; Kremer, R. K.

    2011-07-01

    The bulk magnetic properties of the new quasi-one-dimensional Heisenberg antiferromagnet, CuCrO4, were characterized by magnetic susceptibility, heat capacity, optical spectroscopy, electron paramagnetic resonance and dielectric capacitance measurements, and density functional evaluations of the intrachain and interchain spin-exchange interactions. We found type-II multiferroicity below the Néel temperature of 8.2(5) K, arising from competing antiferromagnetic nearest-neighbor (Jnn) and next-nearest-neighbor (Jnnn) intrachain spin-exchange interactions. Experimental and theoretical results indicate that the ratio Jnn/Jnnn is close to 2, putting CuCrO4 in the vicinity of the Majumdar-Ghosh point.

  5. Quasi-one-dimensional antiferromagnetism and multiferroicity in CuCrO4

    NASA Astrophysics Data System (ADS)

    Kremer, Reinhard K.; Law, J. M.; Reuvekamp, P.; Glaum, R.; Lee, C.; Kang, J.; Whangbo, M.-H.

    2012-02-01

    The bulk magnetic properties of the new quasi-one-dimensional Heisenberg antiferromagnet, CuCrO4, were characterized by magnetic susceptibility, heat capacity, optical spectroscopy, EPR and dielectric capacitance measurements and density functional evaluations of the intra- and interchain spin exchange interactions. We found type-II multiferroicity below the N'eel temperature of 8.2(5) K, arising from competing antiferromagnetic nearest-neighbor (Jnn) and next-nearest-neighbor (Jnnn) intra-chain spin exchange interactions. Experimental and theoretical results indicate that the ratio Jnn/Jnnn is close to 2, putting CuCrO4 in the vicinity of the Majumdar-Ghosh point. First low-temperature neutron powder diffraction data are consistent with a canted magnetic structure below ˜8 K.

  6. Oxidation behavior of arc evaporated Al-Cr-Si-N thin films

    SciTech Connect

    Tritremmel, Christian; Daniel, Rostislav; Mitterer, Christian; Mayrhofer, Paul H.; Lechthaler, Markus; Polcik, Peter

    2012-11-15

    The impact of Al and Si on the oxidation behavior of Al-Cr-(Si)-N thin films synthesized by arc evaporation of powder metallurgically prepared Al{sub x}Cr{sub 1-x} targets with x = Al/(Al + Cr) of 0.5, 0.6, and 0.7 and (Al{sub 0.5}Cr{sub 0.5}){sub 1-z}Si{sub z} targets with Si contents of z = 0.05, 0.1, and 0.2 in N{sub 2} atmosphere was studied in detail by means of differential scanning calorimetry, thermogravimetric analysis (TGA), x-ray diffraction, and Raman spectroscopy. Dynamical measurements in synthetic air (up to 1440 Degree-Sign C) revealed the highest onset temperature of pronounced oxidation for nitride coatings prepared from the Al{sub 0.4}Cr{sub 0.4}Si{sub 0.2} target. Isothermal TGA at 1100, 1200, 1250, and 1300 Degree-Sign C highlight the pronounced improvement of the oxidation resistance of Al{sub x}Cr{sub 1-x}N coatings by the addition of Si. The results show that Si promotes the formation of a dense coating morphology as well as a dense oxide scale when exposed to air.

  7. Corrosion behavior of Cu and the Cu-Zn-Al shape memory alloy in simulated uterine fluid.

    PubMed

    Chen, Bangyi; Liang, Chenghao; Fu, Daojun; Ren, Deming

    2005-09-01

    Chemical immersion tests, electrochemical methods and atomic absorption spectrometry were employed to investigate the corrosion behavior of Cu and the Cu-Zn-Al shape memory alloy (SMA) in simulated uterine fluid. The effect of pH on corrosion rate and corrosion potential was also investigated. The results indicated that in the static state in simulated uterine fluid, dealuminumification of the Cu-Zn-Al alloy occurred with Cl- combining with aluminum ions to form hydroxyl aluminum chloride. The hydroxyl aluminum chloride hydrolyzed readily and facilitated further dealuminumification corrosion. The corrosion process of Cu and Cu-Zn-Al SMA in simulated uterine fluid was controlled by cathodic reduction of oxygen. Because the tendency for surface ionization is greater for aluminum than for zinc, a compact protective aluminum layer was formed, which inhibited the cathodic reduction of oxygen. Hence, the corrosion rate of Cu-Zn-Al SMA was smaller than that of Cu in simulated uterine fluid. With increasing pH, the corrosion rate of Cu and Cu-Zn-Al SMA in simulated uterine fluid decreased and the open-circuit potential moved in a positive direction. PMID:16102560

  8. Oxidation behavior of cubic phases formed by alloying Al3Ti with Cr and Mn

    NASA Technical Reports Server (NTRS)

    Parfitt, L. J.; Nic, J. P.; Mikkola, D. E.; Smialek, J. L.

    1991-01-01

    Gravimetric, SEM, and XRD data are presented which document the significant improvement obtainable in the oxidation resistance of Al3Ti-containing alloys through additions of Cr. The L1(2) Al(67)Cr(8)Ti25 alloy exhibited excellent cyclic oxidation resistance at 1473 K, with the primary oxide formed being the ideally protective alpha-Al2O3. The Al(67)Mn(8)Ti(25) alloy also tested for comparison exhibited poor cyclic oxidation resistance, with substantial occurrence of TiO2 in the protective scales. Catastrophic oxidation was also encountered in the quaternary alloy Al(67)Mn(8)Ti(22)V(3).

  9. /Al-4Cu Composite Material Produced by Squeeze Casting Method

    NASA Astrophysics Data System (ADS)

    Ficici, Ferit

    2014-05-01

    The wear behavior of a weight fraction of particles with up to 30 wt.% in situ AlB2 flakes reinforced in Al-4Cu matrix alloy composites and fabricated by a squeeze casting method was investigated in a pin-on-disk abrasion test instrument against different SiC abrasives at room conditions. Wear tests were performed under the load of 10 N against SiC abrasive papers of 80, 100, and 120 mesh grits. The effects of sliding speed, AlB2 flake content, and abrasive grit sizes on the abrasive wear properties of the matrix alloy and composites have been evaluated. The main wear mechanisms were identified using an optical microscope. The results showed that in situ AlB2 flake reinforcement improved the abrasion resistance against all the abrasives used, and the abrasive wear resistance decreased with an increase in the sliding speed and the abrasive grit size. The wear resistances of the composites were considerably bigger than those of the matrix alloy and increased with increases in in situ AlB2 flake contents.

  10. Al-Si-Cu/TiN multilayer interconnection and Al-Ge reflow sputtering technologies for quarter-micron devices

    NASA Astrophysics Data System (ADS)

    Kikkawa, Takamaro; Kikuta, Kuniko

    1993-05-01

    Issues of interconnection technologies for quarter-micron devices are the reliability of metal lines with quarter-micron feature sizes and the formation of contact-hole-plugs with high aspect ratios. This paper describes a TiN/Al-Si-Cu/TiN/Al-Si-Cu/TiN/Ti multilayer conductor structure as a quarter-micron interconnection technology and aluminum-germanium (Al-Ge) reflow sputtering as a contact-hole filling technology. The TiN/Al-Si-Cu/TiN/Al-Si-Cu/TiN/Ti multilayer conductor structure could suppress stress-induced voiding and improve the electromigration mean-time to failure. These improvements are attributed to the fact that the grain boundaries for the Al-Si-Cu film and the interfaces between the Al-Si-Cu and the TiN films are strengthened by the rigid intermetallic compound, TiAl3. The Al-Ge alloy reflow sputtering is a candidate for contact- and via-hole filling technologies in terms of reducing fabrication costs. The Al-Ge reflow sputtering achieved low temperature contact hole filling at 300 degree(s)C. Contact holes with a diameter of 0.25 micrometers and aspect ratio of 4 could be filled. This is attributed to the low eutectic temperature for Al-Ge (424 degree(s)C) and the effect of thin polysilicon underlayer on the enhancement of Al-Ge reflow.

  11. Dependency of simultaneous Cr(VI), Cu(II) and Cd(II) reduction on the cathodes of microbial electrolysis cells self-driven by microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Zhang, Yong; Yu, Lihua; Wu, Dan; Huang, Liping; Zhou, Peng; Quan, Xie; Chen, Guohua

    2015-01-01

    Microbial fuel cells (MFCs) using either Cr(VI) (MFCsCr) or Cu(II) (MFCsCu) as a final electron acceptor, are stacked to self-drive microbial electrolysis cells (MECs) using Cd(II) (MECsCd) as an electron acceptor for simultaneous reduction of Cr(VI) in MFCsCr, Cu(II) in MFCsCu and Cd(II) in MECsCd with no external energy consumption. Titanium sheet (TS) and carbon rod (CR) as the cathodes of MECsCd are assessed for efficient system performance. MFCsCr and MFCsCu in series is superior to the parallel configuration, and higher Cd(II) reduction along with simultaneous Cr(VI) and Cu(II) reduction supports TS function as a good cathode material. Conversely, CR can not entirely proceed Cd(II) reduction in MECsCd despite of more Cr(VI) and Cu(II) reduction in the same serial configuration than either system alone. While a decrease in cathode volume in both MFCsCr and MFCsCu with serial connection benefits to reduction of Cr(VI) in MFCsCr and Cu(II) in MFCsCu, Cd(II) reduction in MECsCd is substantially enhanced under a decrease in cathode volume in individual MFCsCr and serially connected with volume-unchanged MFCsCu. This study demonstrates simultaneous Cr(VI), Cu(II) and Cd(II) recovery from MFCsCr-MFCsCu-MECsCd self-driven system is feasible, and TS as the cathodes of MECsCd is critical for efficient system performance.

  12. Luminescence Spectra of ZnAl 2 O 4 {:}Cr 3+ Spinel Nanopowders

    NASA Astrophysics Data System (ADS)

    Luc, H. H.; Nguyen, T. K.; Nguyen, V. M.; Suchocki, A.; Kamiñska, A.; Le, V. K.; Nguyen, V. H.; Luong, T. T.

    2002-12-01

    The synthetic ZnAl 2 O 4 spinels doped with Cr 3+ ions are prepared from ZnSO,dwi{4}>, Al 2 (SO 4 ) 3 , and Cr 2 (SO 4 ) 3 . The spinel single phase is detected from X-ray diffraction. Luminescence properties of Cr 3+ in ZnAl 2 O 4 were studied by low temperature luminescence and decay measurements. Four luminescence lines at 14570, 14520, 14460, and 14330 cm -1 were found to originate from structure distortion and the line at 14175 cm -1 - from chromium pairs. The broad emission band at about 13540 cm -1 is considered to arise from a new Cr 3+ center in ZnCr 2 O 4 .

  13. Viscosities of aluminum-rich Al-Cu liquid alloys

    NASA Astrophysics Data System (ADS)

    Ganesan, S.; Speiser, R.; Poirier, D. R.

    1987-06-01

    Viscosity data for Al-Cu liquid alloys in the ranges of 0≤ C L≤33.1 wt pct Cu and 1173≤ T ≤973 K are reviewed. It was found that Andrade's equation can be used to represent the variation of viscosity with temperature for a given composition, but that each of the two parameters in Andrade's equation shows no systematic variation with composition of the liquid-alloys. Consequently, arithmetic averages of the parameters were used and assumed to apply to all compositions in the range 0≤ C L ≤33.1 wt pct Cu. Such a procedure implies that the viscosity happens to vary with composition solely because the specific volume varies with composition. In order to establish the predictability of extrapolating such simple behavior, a more complex model was considered. The latter model was recently presented by Kucharski and relates viscosity to the structure and thermodynamics of liquid alloys. Viscosities obtained by interpolating Andrade's equation and Kucharski's model compare closely; furthermore, values obtained by extrapolations to lower temperatures also compare favorably. Finally the simpler model was used to calculate the viscosity of the interdendritic liquid during solidification.

  14. Cr Isotopes in Allende Ca-Al-rich Inclusions

    NASA Technical Reports Server (NTRS)

    Bogdanovski, O.; Papanastassiou, D. A.; Wasserburg, G. J.

    2002-01-01

    We have determined Cr isotope compositions in minerals from Allende CAI in order to address the initial 53Mn (half-life 3.7 Ma) abundance in the solar system. Additional information is contained in the original extended abstract.

  15. Thermal, solution and reductive decomposition of Cu-Al layered double hydroxides into oxide products

    SciTech Connect

    Britto, Sylvia; Vishnu Kamath, P.

    2009-05-15

    Cu-Al layered double hydroxides (LDHs) with [Cu]/[Al] ratio 2 adopt a structure with monoclinic symmetry while that with the ratio 0.25 adopt a structure with orthorhombic symmetry. The poor thermodynamic stability of the Cu-Al LDHs is due in part to the low enthalpies of formation of Cu(OH){sub 2} and CuCO{sub 3} and in part to the higher solubility of the LDH. Consequently, the Cu-Al LDH can be decomposed thermally (150 deg. C), hydrothermally (150 deg. C) and reductively (ascorbic acid, ambient temperature) to yield a variety of oxide products. Thermal decomposition at low (400 deg. C) temperature yields an X-ray amorphous residue, which reconstructs back to the LDH on soaking in water or standing in the ambient. Solution decomposition under hydrothermal conditions yields tenorite at 150 deg. C itself. Reductive decomposition yields a composite of Cu{sub 2}O and Al(OH){sub 3}, which on alkali-leaching of the latter, leads to the formation of fine particles of Cu{sub 2}O (<1 {mu}m). - Graphical abstract: SEM image of (a) the Cu{sub 2}O-Al(OH){sub 3} composite obtained on reductive decomposition of CuAl{sub 4}-LDH and (b) Cu{sub 2}O obtained on leaching of Al(OH){sub 3} from (a).

  16. Investigation on the microstructure and mechanical properties of CuCrZr after manufacturing thermal cycle for plasma facing component

    NASA Astrophysics Data System (ADS)

    Park, Jeong-Yong; Jung, Yang-Il; Choi, Byung-Kwon; Lee, Jung-Suk; Jeong, Yong Hwan; Hong, Bong Guen

    2011-10-01

    The effects of manufacturing thermal cycle on the various mechanical properties of CuCrZr were investigated. Vickers hardness was changed with an aging temperature in an identical manner with the strength change in a wide range of heat treatment. The change of Charpy impact energy with an aging temperature exhibited an opposite trend to the changes of the strength and hardness. At least in terms of the impact energy of CuCrZr, aging at a higher temperate would be preferable if the strength of CuCrZr could be maintained higher than the limitation value after the completion of the fabrication of ITER first wall. The fatigue life of CuCrZr was influenced to a certain extent by the cooling rate and the aging temperature. Especially in the higher strain amplitude, the contribution of the elastic and plastic components to the fatigue response was dependent on the yield strength which is determined by the aging temperature.

  17. Monolithic Cu-Cr-Nb Alloys for High Temperature, High Heat Flux Applications

    NASA Technical Reports Server (NTRS)

    Ellis, David L.; Locci, Ivan E.; Michal, Gary M.; Humphrey, Derek M.

    1999-01-01

    Work during the prior four years of this grant has resulted in significant advances in the development of Cu-8 Cr4 Nb and related Cu-Cr-Nb alloys. The alloys are nearing commercial use in the Reusable Launch Vehicle (RLV) where they are candidate materials for the thrust cell liners of the aerospike engines being developed by Rocketdyne. During the fifth and final year of the grant, it is proposed to complete development of the design level database of mechanical and thermophysical properties and transfer it to NASA Glenn Research Center and Rocketdyne. The database development work will be divided into three main areas: Thermophysical Database Augmentation, Mechanical Testing and Metallography and Fractography. In addition to the database development, work will continue that is focussed on the production of alternatives to the powder metallurgy alloys currently used. Exploration of alternative alloys will be aimed at both the development of lower cost materials and higher performance materials. A key element of this effort will be the use of Thermo-Calc software to survey the solubility behavior of a wide range of alloying elements in a copper matrix. The ultimate goals would be to define suitable alloy compositions and processing routes to produce thin sheets of the material at either a lower cost, or, with improved mechanical and thermal properties compared to the current Cu-Cr-Nb powder metallurgy alloys.

  18. Antiferromagnetic half metallicity in codoped chalcopyrite semiconductors Cu(Al 1 - 2 xAxBx)Se2 (A and B are 3d transition-metal atoms)

    NASA Astrophysics Data System (ADS)

    Shahjahan, M.; Oguchi, T.

    2016-06-01

    Electronic structures and magnetic properties of group I-III-VI2 chalcopyrite-type compounds Cu(Al 1 - 2 xAxBx)Se2 are calculated using the Korringa-Kohn-Rostoker Green's function method, where A (Ti, V, Cr, Mn) and B (Fe, Co, Ni) are 3d transition metal atoms, and x is atomic concentration. We found that codoping of Cr-Co and V-Ni pairs at Al site of host CuAlSe2 exhibit antiferromagnetic (AF) half metallicity with low Curie temperature (TC). The AF half metallic property is supported by nullified net magnetic moment and compensated density of states in the minority spin direction. On the other hand, codoping of Cr-Ni, Mn-Co, V-Co, and Ti-Co pairs at Al site of host CuAlSe2 manifest ferrimagnetic half metallicity with a small net magnetization and keeping antiparallel local spin moments. In Mn-Co case TC is close to room temperature. Besides, Cr-Fe, V-Fe, and Ti-Ni codoping cases lead to an instable magnetic ordering and therefore obtain a disordered local moment (spin-glass like) state.

  19. Formation Mechanisms of Alloying Element Nitrides in Recrystallized and Deformed Ferritic Fe-Cr-Al Alloy

    NASA Astrophysics Data System (ADS)

    Akhlaghi, Maryam; Meka, Sai Ramudu; Jägle, Eric A.; Kurz, Silke J. B.; Bischoff, Ewald; Mittemeijer, Eric J.

    2016-07-01

    The effect of the initial microstructure (recrystallized or cold-rolled) on the nitride precipitation process upon gaseous nitriding of ternary Fe-4.3 at. pct Cr-8.1 at. pct Al alloy was investigated at 723 K (450 °C) employing X-ray diffraction (XRD) analyses, transmission electron microscopy (TEM), atom probe tomography (APT), and electron probe microanalysis (EPMA). In recrystallized Fe-Cr-Al specimens, one type of nitride develops: ternary, cubic, NaCl-type mixed Cr1-x Al x N. In cold-rolled Fe-Cr-Al specimens, precipitation of two types of nitrides occurs: ternary, cubic, NaCl-type mixed Cr1-x Al x N and binary, cubic, NaCl-type AlN. By theoretical analysis, it was shown that for the recrystallized specimens an energy barrier for the nucleation of mixed Cr1-x Al x N exists, whereas in the cold-rolled specimens no such energy barriers for the development of mixed Cr1-x Al x N and of binary, cubic AlN occur. The additional development of the cubic AlN in the cold-rolled microstructure could be ascribed to the preferred heterogeneous nucleation of cubic AlN on dislocations. The nitrogen concentration-depth profile of the cold-rolled specimen shows a stepped nature upon prolonged nitriding as a consequence of instantaneous nucleation of nitride upon arrival of nitrogen and nitride growth rate-limited by nitrogen transport through the thickening nitrided zone.

  20. Formation Mechanisms of Alloying Element Nitrides in Recrystallized and Deformed Ferritic Fe-Cr-Al Alloy

    NASA Astrophysics Data System (ADS)

    Akhlaghi, Maryam; Meka, Sai Ramudu; Jägle, Eric A.; Kurz, Silke J. B.; Bischoff, Ewald; Mittemeijer, Eric J.

    2016-09-01

    The effect of the initial microstructure (recrystallized or cold-rolled) on the nitride precipitation process upon gaseous nitriding of ternary Fe-4.3 at. pct Cr-8.1 at. pct Al alloy was investigated at 723 K (450 °C) employing X-ray diffraction (XRD) analyses, transmission electron microscopy (TEM), atom probe tomography (APT), and electron probe microanalysis (EPMA). In recrystallized Fe-Cr-Al specimens, one type of nitride develops: ternary, cubic, NaCl-type mixed Cr1- x Al x N. In cold-rolled Fe-Cr-Al specimens, precipitation of two types of nitrides occurs: ternary, cubic, NaCl-type mixed Cr1- x Al x N and binary, cubic, NaCl-type AlN. By theoretical analysis, it was shown that for the recrystallized specimens an energy barrier for the nucleation of mixed Cr1- x Al x N exists, whereas in the cold-rolled specimens no such energy barriers for the development of mixed Cr1- x Al x N and of binary, cubic AlN occur. The additional development of the cubic AlN in the cold-rolled microstructure could be ascribed to the preferred heterogeneous nucleation of cubic AlN on dislocations. The nitrogen concentration-depth profile of the cold-rolled specimen shows a stepped nature upon prolonged nitriding as a consequence of instantaneous nucleation of nitride upon arrival of nitrogen and nitride growth rate-limited by nitrogen transport through the thickening nitrided zone.

  1. Cu-Al-Ni-SMA-Based High-Damping Composites

    NASA Astrophysics Data System (ADS)

    López, Gabriel A.; Barrado, Mariano; San Juan, Jose; Nó, María Luisa

    2009-08-01

    Recently, absorption of vibration energy by mechanical damping has attracted much attention in several fields such as vibration reduction in aircraft and automotive industries, nanoscale vibration isolations in high-precision electronics, building protection in civil engineering, etc. Typically, the most used high-damping materials are based on polymers due to their viscoelastic behavior. However, polymeric materials usually show a low elastic modulus and are not stable at relatively low temperatures (≈323 K). Therefore, alternative materials for damping applications are needed. In particular, shape memory alloys (SMAs), which intrinsically present high-damping capacity thanks to the dissipative hysteretic movement of interfaces under external stresses, are very good candidates for high-damping applications. A completely new approach was applied to produce high-damping composites with relatively high stiffness. Cu-Al-Ni shape memory alloy powders were embedded with metallic matrices of pure In, a In-10wt.%Sn alloy and In-Sn eutectic alloy. The production methodology is described. The composite microstructures and damping properties were characterized. A good particle distribution of the Cu-Al-Ni particles in the matrices was observed. The composites exhibit very high damping capacities in relatively wide temperature ranges. The methodology introduced provides versatility to control the temperature of maximum damping by adjusting the shape memory alloy composition.

  2. Al-Cu-Li and Al-Mg-Li alloys: Phase composition, texture, and anisotropy of mechanical properties (Review)

    NASA Astrophysics Data System (ADS)

    Betsofen, S. Ya.; Antipov, V. V.; Knyazev, M. I.

    2016-04-01

    The results of studying the phase transformations, the texture formation, and the anisotropy of the mechanical properties in Al-Cu-Li and Al-Mg-Li alloys are generalized. A technique and equations are developed to calculate the amounts of the S1 (Al2MgLi), T1 (Al2CuLi), and δ' (Al3Li) phases. The fraction of the δ' phase in Al-Cu-Li alloys is shown to be significantly higher than in Al-Mg-Li alloys. Therefore, the role of the T1 phase in the hardening of Al-Cu-Li alloys is thought to be overestimated, especially in alloys with more than 1.5% Li. A new model is proposed to describe the hardening of Al-Cu-Li alloys upon aging, and the results obtained with this model agree well with the experimental data. A texture, which is analogous to that in aluminum alloys, is shown to form in sheets semiproducts made of Al-Cu-Li and Al-Mg-Li alloys. The more pronounced anisotropy of the properties of lithium-containing aluminum alloys is caused by a significant fraction of the ordered coherent δ' phase, the deformation mechanism in which differs radically from that in the solid solution.

  3. Flat panel display using Ti-Cr-Al-O thin film

    DOEpatents

    Jankowski, Alan F.; Schmid, Anthony P.

    2002-01-01

    Thin films of Ti--Cr--Al--O are used as a resistor material. The films are rf sputter deposited from ceramic targets using a reactive working gas mixture of Ar and O.sub.2. Resistivity values from 10.sup.4 to 10.sup.10 Ohm-cm have been measured for Ti--Cr--Al--O film <1 .mu.m thick. The film resistivity can be discretely selected through control of the target composition and the deposition parameters. The application of Ti--Cr--Al--O as a thin film resistor has been found to be thermodynamically stable, unlike other metal-oxide films. The Ti--Cr--Al--O film can be used as a vertical or lateral resistor, for example, as a layer beneath a field emission cathode in a flat panel display; or used to control surface emissivity, for example, as a coating on an insulating material such as vertical wall supports in flat panel displays.

  4. Process for producing Ti-Cr-Al-O thin film resistors

    DOEpatents

    Jankowski, Alan F.; Schmid, Anthony P.

    2001-01-01

    Thin films of Ti-Cr-Al-O are used as a resistor material. The films are rf sputter deposited from ceramic targets using a reactive working gas mixture of Ar and O.sub.2. Resistivity values from 10.sup.4 to 10.sup.10 Ohm-cm have been measured for Ti-Cr-Al-O film <1 .mu.m thick. The film resistivity can be discretely selected through control of the target composition and the deposition parameters. The application of Ti-Cr-Al-O as a thin film resistor has been found to be thermodynamically stable, unlike other metal-oxide films. The Ti-Cr-Al-O film can be used as a vertical or lateral resistor, for example, as a layer beneath a field emission cathode in a flat panel display; or used to control surface emissivity, for example, as a coating on an insulating material such as vertical wall supports in flat panel displays.

  5. NiAl-based Polyphase in situ Composites in the NiAl-Ta-X (X = Cr, Mo, or V) Systems

    NASA Technical Reports Server (NTRS)

    Johnson, D. R.; Oliver, B. F.; Noebe, R. D.; Whittenberger, J. D.

    1995-01-01

    Polyphase in situ composites were generated by directional solidification of ternary eutectics. This work was performed to discover if a balance of properties could be produced by combining the NiAl-Laves phase and the NiAl-refractory metal phase eutectics. The systems investigated were the Ni-Al-Ta-X (X = Cr, Mo, or V) alloys. Ternary eutectics were found in each of these systems and the eutectic composition, temperature, and morphology were determined. The ternary eutectic systems examined were the NiAl-NiAlTa-(Mo, Ta), NiAl-(Cr, Al) NiTa-Cr, and the NiAl-NiAlTa-V systems. Each eutectic consists of NiAl, a C14 Laves phase, and a refractory metal phase. Directional solidification was performed by containerless processing techniques in a levitation zone refiner to minimize alloy contamination. Room temperature fracture toughness of these materials was determined by a four-point bend test. Preliminary creep behavior was determined by compression tests at elevated temperatures, 1100-l400 K. Of the ternary eutectics, the one in the NiAl-Ta-Cr system was found to be the most promising. The fracture toughness of the NiAl-(Cr, Al)NiTa-Cr eutectic was intermediate between the values of the NiAl-NiAlTa eutectic and the NiAl-Cr eutectic. The creep strength of this ternary eutectic was similar to or greater than that of the NiAl-Cr eutectic.

  6. Preliminary assessment of metal-porcelain bonding strength of CoCrW alloy after 3wt.% Cu addition.

    PubMed

    Lu, Yanjin; Zhao, Chaoqian; Ren, Ling; Guo, Sai; Gan, Yiliang; Yang, Chunguang; Wu, Songquan; Lin, Junjie; Huang, Tingting; Yang, Ke; Lin, Jinxin

    2016-06-01

    In this work, a novel Cu-bearing CoCrW alloy fabricated by selective laser melting for dental application has been studied. For its successful application, the bonding strength of metal-porcelain is essential to be systematically investigated. Therefore, the aim of this study was to evaluate the metal-porcelain bonding strength of CoCrWCu alloy by three-point bending test, meanwhile the Ni-free CoCrW alloy was used as control. The oxygen content was investigated by an elemental analyzer; X-ray photoelectron spectroscopy (XPS) was used to analyze the surface chemical composition of CoCrW based alloy after preoxidation treatment; the fracture mode was investigated by X-ray energy spectrum analysis (EDS) and scanning electron microscope (SEM). Result from the oxygen content analysis showed that the content of oxygen dramatically increased after the Cu addition. And the XPS suggested that Co-oxidation, Cr2O3, CrO2, WO3, Cu2O and CuO existed on the preoxidated surface of the CoCrWCu alloy; the three-point bending test showed that the bonding strength of the CoCrWCu alloy was 43.32 MPa, which was lower than that of the CoCrW group of 47.65 MPa. However, the average metal-porcelain bonding strength is significantly higher than the minimum value in the ISO 9693 standard. Results from the SEM images and EDS indicated that the fracture mode of CoCrWCu-porcelain was mixed between cohesive and adhesive. Based on the results obtained in this study, it can be indicated that the Cu-bearing CoCrW alloy fabricated by the selective laser melting is a promising candidate for use in dental application. PMID:27040193

  7. The promoter effect and a rate expression of the catalytic incineration of (CH3)2S2 over an improved CuO-MoO3/gamma-Al2O3 catalyst.

    PubMed

    Wang, Ching-Huei; Lin, Shiow-Shyung; Liou, Shen-Ben; Weng, Hung-Shan

    2002-10-01

    The CuO-MoO3/gamma-Al2O3 catalyst, confirmed previously as having good activity in the catalytic incineration of (CH3)2S2, was employed as the principal catalyst in this study. With the aim of improving catalyst activity and resistance to deactivation by sulfur compounds, a promoter was added either before adding the precursors of Cu and Mo or together with Cu and Mo onto the gamma-Al2O3. Promoters included transition metals and elements from groups IA-VIIA in the chemical periodic table. Experimental results reveal Cr2O3 as the most effective promoter, with an optimal composition of 5 wt.% Cu, 6 wt.% Mo and 4 wt.% Cr (designated as Cu(5)-Mo(6)-Cr(4)/gamma-Al2O3). Knowing that higher acidity can improve activity, we further investigated the effect of acid treatment on the performance of the Cu(5)-Mo(6)-Cr(4)/gamma-Al2O3 catalyst. Experimental results indicate the H2SO4-treated catalyst (Cu(5)-Mo(6)-Cr(4)/sulfated-gamma-Al2O3) has a better activity and durability. A study for finding an appropriate rate expression for the catalytic incineration of (CH3)2S2 by Cu(5)-Mo(6)-Cr(4)/sulfated-gamma-Al2O3 was carried out in a differential reactor. The results show that the Mars-Van Krevelen model is applicable to this destructive oxidation reaction. Results additionally reveal that competitive adsorption of CH4 reduces conversion of (CH3)2S2. PMID:12365836

  8. Hydrogen permeation in FeCrAl alloys for LWR cladding application

    NASA Astrophysics Data System (ADS)

    Hu, Xunxiang; Terrani, Kurt A.; Wirth, Brian D.; Snead, Lance L.

    2015-06-01

    FeCrAl, an advanced oxidation-resistant iron-based alloy class, is a highly prevalent candidate as an accident-tolerant fuel cladding material. Compared with traditional zirconium alloy fuel cladding, increased tritium permeation through FeCrAl fuel cladding to the primary coolant is expected, raising potential safety concerns. In this study, the hydrogen permeability of several FeCrAl alloys was obtained using a static permeation test station, which was calibrated and validated using 304 stainless steel. The high hydrogen permeability of FeCrAl alloys leads to concerns with respect to potentially significant tritium release when used for fuel cladding in LWRs. The total tritium inventory inside the primary coolant of a light water reactor was quantified by applying a 1-dimensional steady state tritium diffusion model to demonstrate the dependence of tritium inventory on fuel cladding type. Furthermore, potential mitigation strategies for tritium release from FeCrAl fuel cladding were discussed and indicate the potential for application of an alumina layer on the inner clad surface to serve as a tritium barrier. More effort is required to develop a robust, economical mitigation strategy for tritium permeation in reactors using FeCrAl clad fuel assemblies.

  9. Hydrogen permeation in FeCrAl alloys for LWR cladding application

    DOE PAGESBeta

    Hu, Xunxiang; Terrani, Kurt A.; Wirth, Brian D.; Snead, Lance L.

    2015-03-19

    FeCrAl is an advanced oxidation-resistant iron-based alloy class, is a highly prevalent candidate as an accident-tolerant fuel cladding material. Compared with traditional zirconium alloy fuel cladding, increased tritium permeation through FeCrAl fuel cladding to the primary coolant is expected, raising potential safety concerns. In our study, the hydrogen permeability of several FeCrAl alloys was obtained using a static permeation test station, which was calibrated and validated using 304 stainless steel. The high hydrogen permeability of FeCrAl alloys leads to concerns with respect to potentially significant tritium release when used for fuel cladding in LWRs. Also, the total tritium inventory insidemore » the primary coolant of a light water reactor was quantified by applying a 1-dimensional steady state tritium diffusion model to demonstrate the dependence of tritium inventory on fuel cladding type. Furthermore, potential mitigation strategies for tritium release from FeCrAl fuel cladding were discussed and indicate the potential for application of an alumina layer on the inner clad surface to serve as a tritium barrier. More effort is required to develop a robust, economical mitigation strategy for tritium permeation in reactors using FeCrAl clad fuel assemblies.« less

  10. Hydrogen permeation in FeCrAl alloys for LWR cladding application

    SciTech Connect

    Hu, Xunxiang; Terrani, Kurt A.; Wirth, Brian D.; Snead, Lance L.

    2015-03-19

    FeCrAl is an advanced oxidation-resistant iron-based alloy class, is a highly prevalent candidate as an accident-tolerant fuel cladding material. Compared with traditional zirconium alloy fuel cladding, increased tritium permeation through FeCrAl fuel cladding to the primary coolant is expected, raising potential safety concerns. In our study, the hydrogen permeability of several FeCrAl alloys was obtained using a static permeation test station, which was calibrated and validated using 304 stainless steel. The high hydrogen permeability of FeCrAl alloys leads to concerns with respect to potentially significant tritium release when used for fuel cladding in LWRs. Also, the total tritium inventory inside the primary coolant of a light water reactor was quantified by applying a 1-dimensional steady state tritium diffusion model to demonstrate the dependence of tritium inventory on fuel cladding type. Furthermore, potential mitigation strategies for tritium release from FeCrAl fuel cladding were discussed and indicate the potential for application of an alumina layer on the inner clad surface to serve as a tritium barrier. More effort is required to develop a robust, economical mitigation strategy for tritium permeation in reactors using FeCrAl clad fuel assemblies.

  11. Effects of water absorption of dielectric underlayers on Al-Si-Cu film properties and electromigration performance in Al-Si-Cu/Ti/TiN/Ti interconnects

    NASA Astrophysics Data System (ADS)

    Yoshida, Tomoyuki; Hashimoto, Shoji; Ohwaki, Takeshi; Mitsushima, Yasuichi; Taga, Yasunori

    1998-01-01

    The effects of underlying dielectric (phosphosilicate glass and borophosphosilicate glass) films to a humid air ambient on Al-Si-Cu film properties and electromigration (EM) performance in Al-Si-Cu/Ti/TiN/Ti layered films have been investigated as a function of the boron content and exposure time of the dielectric films. The Al(111) orientation in the layered films was found to improve drastically with increasing boron content and exposure time. The full width at half maximum value of an Al(111) x-ray rocking curve reached less than 1°. It was also found that the Al-Si-Cu surface becomes smoother and grain sizes increase as the Al(111) orientation improves. The improved Al(111) orientation was attributed to the improved Ti(002) orientation of the bottom Ti films. Further, it was demonstrate that interconnects fabricated from the improved layered film have excellent EM performance.

  12. Characteristics of Cu stabilized Nb3Al strands with low Cu ratio

    SciTech Connect

    Kikuchi, A.; Yamada, R.; Barzi, E.; Kobayashi, M.; Lamm, M.; Nakagawa, K.; Sasaki, K.; Takeuchi, T.; Turrioni, D.; Zlobin, A.V.; /NIMC, Tsukuba /Fermilab /Hitachi, Tsuchiura Works /KEK, Tsukuba

    2008-12-01

    Characteristics of recently developed F4-Nb{sub 3}Al strand with low Cu ratio are described. The overall J{sub c} of the Nb{sub 3}Al strand could be easily increased by decreasing of the Cu ratio. Although the quench of a pulse-like voltage generation is usually observed in superconducting unstable conductor, the F4 strand with a low Cu ratio of 0.61 exhibited an ordinary critical transition of gradual voltage generation. The F4 strand does not have magnetic instabilities at 4.2 K because of the tantalum interfilament matrix. The overall J{sub c} of the F4 strand achieved was 80-85% of the RRP strand. In the large mechanical stress above 100 MPa, the overall J{sub c} of the F4 strand might be comparable to that of high J{sub c} RRP-Nb{sub 3}Sn strands. The Rutherford cable with a high packing factor of 86.5% has been fabricated using F4 strands. The small racetrack magnet, SR07, was also fabricated by a 14 m F4 cable. The quench current, I{sub q}, of SR07 were obtained 22.4 kA at 4.5 K and 25.2 kA at 2.2 K. The tantalum matrix Nb{sub 3}Al strands are promising for the application of super-cooled high-field magnets as well as 4.2 K operation magnets.

  13. Thermomechanical properties of Cr:Tm:Ho:Y sub 3 Al sub 5 O sub 12

    SciTech Connect

    Marion, J.E.

    1990-05-15

    The thermomechanical properties of Cr:Ho:Tm:Y{sub 3}Al{sub 5}O{sub 12} have been measured and compared to similar measurements on Nd:Y{sub 3}Al{sub 5}O{sub 12}. We find that, in general, the properties are similar, with the single exception being thermal diffusivity. Nd:YAG has substantially higher thermal diffusivity than Cr:Tm:Ho:YAG. Consequently, the intrinsic thermal stress resistance figure of merit which governs a materials resistance to fracture in the presence of a steady thermal gradient is lower in Cr:Tm:Ho:YAG than in Nd:YAG. 6 refs., 1 tab.

  14. Modeling degradation and failure of Ni-Cr-Al overlay coatings

    NASA Technical Reports Server (NTRS)

    Nesbitt, J. A.; Heckel, R. W.

    1984-01-01

    Degradation of a Ni-16Cr-25Al-0.06Zr overlay coating on a Ni-22Cr substrate was examined after oxidation accompanied by thermal cycling. Concentration/distance profiles were measured in the coating and substrate after various one-hour cycles at 1150 C. A numerical model was developed to simulate coating degradation by simultaneous oxidation and coating/substrate interdiffusion. The validity of the model was confirmed by comparison of predicted and measured concentration/distance profiles. The ability of the model to identify critical system parameters was demonstrated for the case of the initial Al and Cr content of the coating and substrate.

  15. Structural relaxation around substitutional Cr3+ in MgAl2O4

    NASA Astrophysics Data System (ADS)

    Juhin, Amélie; Calas, Georges; Cabaret, Delphine; Galoisy, Laurence; Hazemann, Jean-Louis

    2007-08-01

    The structural environment of a substitutional Cr3+ ion in a MgAl2O4 spinel has been investigated by Cr K -edge extended x-ray absorption fine structure and x-ray absorption near edge structure (XANES) spectroscopies. First-principles computations of the structural relaxation and of the XANES spectrum have been performed, with a good agreement with the experiment. The Cr-O distance is close to that in MgCr2O4 , indicating a full relaxation of the first neighbors, and the second shell of Al atoms relaxes partially. These observations demonstrate that Vegard’s law is not obeyed in the MgAl2O4-MgCr2O4 solid solution. Despite some angular site distortion, the local D3d symmetry of the B site of the spinel structure is retained during the substitution of Cr for Al. Here, we show that the relaxation is accommodated by strain-induced bond buckling, with angular tilts of the Mg-centered tetrahedra around the Cr-centered octahedron. By contrast, there is no significant alteration of the angles between the edge-sharing octahedra, which build chains aligned along the three fourfold axes of the cubic structure.

  16. Influence of Al/CuO reactive multilayer films additives on exploding foil initiator

    NASA Astrophysics Data System (ADS)

    Zhou, Xiang; Shen, Ruiqi; Ye, Yinghua; Zhu, Peng; Hu, Yan; Wu, Lizhi

    2011-11-01

    An investigation on the influence of Al/CuO reactive multilayer films (RMFs) additives on exploding foil initiator was performed in this paper. Cu film and Cu/Al/CuO RMFs were produced by using standard microsystem technology and RF magnetron sputtering technology, respectively. Scanning electron microscopy characterization revealed the distinct layer structure of the as-deposited Al/CuO RMFs. Differential scanning calorimetry was employed to ascertain the amount of heat released in the thermite reaction between Al films and CuO films, which was found to be 2024 J/g. Electrical explosion tests showed that 600 V was the most matching voltage for our set of apparatus. The explosion process of two types of films was observed by high speed camera and revealed that compared with Cu film, an extra distinct combustion phenomenon was detected with large numbers of product particles fiercely ejected to a distance of about six millimeters for Cu/Al/CuO RMFs. By using the atomic emission spectroscopy double line technique, the reaction temperature was determined to be about 6000-7000 K and 8000-9000 K for Cu film and Cu/Al/CuO RMFs, respectively. The piezoelectricity of polyvinylidene fluoride film was employed to measure the average velocity of the slapper accelerated by the explosion of the films. The average velocities of the slappers were calculated to be 381 m/s and 326 m/s for Cu film and Cu/Al/CuO RMFs, respectively, and some probable reasons were discussed with a few suggestions put forward for further work.

  17. Assessing the elastic properties and ductility of Fe-Cr-Al alloys from ab initio calculations

    NASA Astrophysics Data System (ADS)

    Nurmi, E.; Wang, G.; Kokko, K.; Vitos, L.

    2016-01-01

    Fe-Al is one of the best corrosion resistant alloys at high temperatures. The flip side of Al addition to Fe is the deterioration of the mechanical properties. This problem can be solved by adding a suitable amount of third alloying component. In the present work, we use ab initio calculations based on density functional theory to study the elastic properties of Fe?Cr?Al? alloys for Al and Cr contents up to 20 at.%. We assess the ductility as a function of chemistry by making use of the semi-empirical correlations between the elastic parameters and mechanical properties. In particular, we derive the bulk modulus to shear modulus ratio and the Cauchy pressure and monitor their trends in terms of chemical composition. The present findings are contrasted with the previously established oxidation resistance of Fe-Cr-Al alloys.

  18. Photoelectric phenomena in the Cu (Al, In)/p-CuIn{sub 3}Se{sub 5} Schottky barriers

    SciTech Connect

    Bodnar', I. V. Rud, V. Yu. Rud', Yu. V.

    2007-01-15

    Structures are formed on the p-CuIn{sub 3}Se{sub 5} crystals and photoelectric phenomena in the Cu/p-CuIn{sub 3}Se{sub 5}, Al/p-CuIn{sub 3}Se{sub 5}, and In/p-CuIn{sub 3}Se{sub 5} Schottky barriers are studied. The spectra of quantum efficiency for photoconversion in new structures were obtained for the first time. The characteristics of the interband transitions are discussed, and the CuIn{sub 3}Se{sub 5} band gap is determined. It is concluded that CuIn{sub 3}Se{sub 5} crystals can be used in the fabrication of high-efficiency broadband photoconverters of optical radiation.

  19. First-principles study of Al-Cu energetics and consequences on athermal formation of Cu-rich compounds

    NASA Astrophysics Data System (ADS)

    Besson, R.; Kwon, J.; Thuinet, L.; Avettand-Fènoël, M.-N.; Legris, A.

    2014-12-01

    In spite of its practical interest, the Al-Cu system remains largely unexplored, especially on its Cu-rich side. In order to improve the knowledge of this system, we perform a thorough ab initio study of fcc-based Al-Cu energetics, using the recently proposed M2BCE reciprocal-space cluster expansion approach. We demonstrate the existence of two clearly distinct composition domains, revealing complex ground-state properties. Below 50% Cu, the GP 2 -A l3Cu compound appears as highly favored, in agreement with the well-documented transformation sequence in Al-based alloys. Conversely, the domain between 50% and 80% Cu displays a much shallower landscape, characterized by the existence of a wealth of compounds undergoing fcc →bcc structural instabilities. While such "Bain paths" have been identified for a long time in iron-based alloys, our work gives evidence for their existence in the Al-Cu system. As a striking application, these instabilities provide plausible athermal mechanisms for the formation of Cu-rich phases, in particular for the unexpected emergence of γ1-A l4C u9 , a Hume-Rothery compound observed in various nonequilibrium conditions.

  20. Spin-induced symmetry breaking in orbitally ordered NiCr2O4 and CuCr2O4

    NASA Astrophysics Data System (ADS)

    Suchomel, Matthew R.; Shoemaker, Daniel P.; Ribaud, Lynn; Kemei, Moureen C.; Seshadri, Ram

    2012-08-01

    At room temperature, the normal oxide spinels NiCr2O4 and CuCr2O4 are tetragonally distorted and crystallize in the I41/amd space group due to cooperative Jahn-Teller ordering driven by the orbital degeneracy of tetrahedral Ni2+ (t24) and Cu2+ (t25). Upon cooling, these compounds undergo magnetic ordering transitions; interactions are somewhat frustrated for NiCr2O4 but not for CuCr2O4. We employ variable-temperature high-resolution synchrotron x-ray powder diffraction to establish that at the magnetic ordering temperatures there are further structural changes, which result in both compounds distorting to an orthorhombic structure consistent with the Fddd space group. NiCr2O4 exhibits additional distortion, likely within the same space group, at a yet-lower transition temperature of T=30 K. The tetragonal to orthorhombic structural transition in these compounds appears to primarily involve changes in NiO4 and CuO4 tetrahedra.

  1. Decrease and increase profile of Cu, Cr and Pb during stable phase of removal by duckweed (Lemna minor L.).

    PubMed

    Uçüncü, Esra; Tunca, Evren; Fikirdeşici, Seyda; Altindağ, Ahmet

    2013-01-01

    The present work details the decrease-increase profiles of Cu, Cr, and Pb by the aquatic plant Lemna minor. A mixture of these metals were utilized at different concentrations. Removal profiles of each metal was determined with water samples taken every 24 h for a 144 h period after the 48 h mark and was examined with correlation analysis. Removal profiles of Cr and Pb by L. minor from the mixture were observed to be highly similar with each other (r = 0.943). High proportion of Cr and Pb were removed compared to Cu and removal equations were defined with the aid of regression analysis. PMID:23488003

  2. X-Ray Videomicroscopy Studies of Eutectic Al-Si Solidification in Al-Si-Cu

    NASA Astrophysics Data System (ADS)

    Mathiesen, R. H.; Arnberg, L.; Li, Y.; Meier, V.; Schaffer, P. L.; Snigireva, I.; Snigirev, A.; Dahle, A. K.

    2011-01-01

    Al-Si eutectic growth has been studied in-situ for the first time using X-ray video microscopy during directional solidification (DS) in unmodified and Sr-modified Al-Si-Cu alloys. In the unmodified alloys, Si is found to grow predominantly with needle-like tip morphologies, leading a highly irregular progressing eutectic interface with subsequent nucleation and growth of Al from the Si surfaces. In the Sr-modified alloys, the eutectic reaction is strongly suppressed, occurring with low nucleation frequency at undercoolings in the range 10 K to 18 K. In order to transport Cu rejected at the eutectic front back into the melt, the modified eutectic colonies attain meso-scale interface perturbations that eventually evolve into equiaxed composite-structure cells. The eutectic front also attains short-range microscale interface perturbations consistent with the characteristics of a fibrous Si growth. Evidence was found in support of Si nucleation occurring on potent particles suspended in the melt. Yet, both with Sr-modified and unmodified alloys, Si precipitation alone was not sufficient to facilitate the eutectic reaction, which apparently required additional undercooling for Al to form at the Si-particle interfaces.

  3. Fracture toughness of an Al-Li-Cu-In alloy

    SciTech Connect

    Wagner, J.A.; Gangloff, R.P. Virginia, University, Charlottesville )

    1992-06-01

    The crack initiation and growth fracture toughness of select AL-Li-Cu alloy variants are characterized and elucidated. Conventionally processed plates form large DC cast ingots are investigated to eliminate the variation in microstructure associated with laboratory scale and SPF-processed material. Fracture resistance is characterized using the J-integral method to establish crack initiation and growth behavior at 25 and -185 C. It is shown that state-of-the-art 2090-T81 has superior toughness compared to 2090 + In-T6 at both test temperatures, with the low toughness of 2090 + In-T6 associated with intersubgranular fracture attributed to a high density of subboundary precipitates. 21 refs.

  4. Fracture toughness of an Al-Li-Cu-In alloy

    NASA Technical Reports Server (NTRS)

    Wagner, John A.; Gangloff, Richard P.

    1992-01-01

    The crack initiation and growth fracture toughness of select AL-Li-Cu alloy variants are characterized and elucidated. Conventionally processed plates form large DC cast ingots are investigated to eliminate the variation in microstructure associated with laboratory scale and SPF-processed material. Fracture resistance is characterized using the J-integral method to establish crack initiation and growth behavior at 25 and -185 C. It is shown that state-of-the-art 2090-T81 has superior toughness compared to 2090 + In-T6 at both test temperatures, with the low toughness of 2090 + In-T6 associated with intersubgranular fracture attributed to a high density of subboundary precipitates.

  5. Concentric nano rings observed on Al-Cu-Fe microspheres

    NASA Astrophysics Data System (ADS)

    Li, Chunfei; Wang, Limin; Hampikian, Helen; Bair, Matthew; Baker, Andrew; Hua, Mingjian; Wang, Qiongshu; Li, Dingqiang

    2016-05-01

    It is well known that when particle size is reduced, surface effect becomes important. As a result, micro/nanoparticles tend to have well defined geometric shapes to reduce total surface energy, as opposed to the irregular shapes observed in most bulk materials. The surface of such micro/nanostructures are smooth. Any deviation from a smooth surface implies an increased surface energy which is not energetically favorable. Here, we report an observation of spherical particles in an alloy of Al65Cu20Fe15 nominal composition prepared by arc melting. Such spherical particles stand out from those reported so far due to the decoration of concentric nanorings on the surface. Three models for the formation of these concentric ring patterns are suggested. The most prominent ones assume that the rings are frozen features of liquid motion which could open the door to investigate the kinetics of liquid motion on the micro/nanometer scale.

  6. Photoluminescence Studies in CuAlS2 Crystals

    NASA Astrophysics Data System (ADS)

    Shirakata, Sho; Aksenov, Igor; Sato, Katsuaki; Isomura, Shigehiro

    1992-08-01

    Photoluminescence (PL) measurements have been carried out at low temperature (77 and 10 K) on CuAlS2 crystals grown by the chemical vapor transport method. Seven sharp PL lines have been observed near the band edge. Based on the photoreflectance measurements, the PL line at 3.550 eV has been assigned to a free exciton emission. The lines at 3.540, 3.532, 3.500 and 3.475 eV are tentatively assigned to the bound excitons, and they are discussed in terms of the crystal composition and the annealing conditions. This study also refers to the PL lines and peaks at about 2.9 eV.

  7. Manufacturing and High Heat Flux Testing of Brazed Flat-Type W/CuCrZr Plasma Facing Components

    NASA Astrophysics Data System (ADS)

    Lian, Youyun; Liu, Xiang; Feng, Fan; Chen, Lei; Cheng, Zhengkui; Wang, Jin; Chen, Jiming

    2016-02-01

    Water-cooled flat-type W/CuCrZr plasma facing components with an interlayer of oxygen-free copper (OFC) have been developed by using vacuum brazing route. The OFC layer for the accommodation of thermal stresses was cast onto the surface of W at a temperature range of 1150 °C-1200 °C in a vacuum furnace. The W/OFC cast tiles were vacuum brazed to a CuCrZr heat sink at 940 °C using the silver-free filler material CuMnSiCr. The microstructure, bonding strength, and high heat flux properties of the brazed W/CuCrZr joint samples were investigated. The W/Cu joint exhibits an average tensile strength of 134 MPa, which is about the same strength as pure annealed copper. High heat flux tests were performed in the electron beam facility EMS-60. Experimental results indicated that the brazed W/CuCrZr mock-up experienced screening tests of up to 15 MW/m2 and cyclic tests of 9 MW/m2 for 1000 cycles without visible damage. supported by National Natural Science Foundation of China (No. 11205049) and the National Magnetic Confinement Fusion Science Program of China (No. 2011GB110004)

  8. Simulation of the aluminothermic smelting of Mo-Ti-Al and Mo-Ti-V-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Udoeva, L. Yu.; Chumarev, V. M.; Larionov, A. V.; Rylov, A. N.; Trubachev, M. V.

    2013-08-01

    Thermodynamic simulation is performed to estimate the parameters and indicators of the aluminothermic melting of Mo-Ti-Al and Mo-Ti-V-Cr-Al master alloys intended for the alloying of titanium. The simulation is carried out with the HSC 6.1 Chemistry software package and is based on approximate calculations of the thermodynamic properties of Mo, Cr, and V aluminides, which are unavailable in handbooks. A comparison of the calculated and experimental data on the compositions of the forming alloys demonstrates that the developed models are adequate to technological processes and can be applied to optimize the parameters and to predict the compositions of smelting products.

  9. Mechanical properties of Al-Cu alloy-SiC composites

    SciTech Connect

    Anggara, B. S.; Handoko, E.; Soegijono, B.

    2014-09-25

    The synthesis of aluminum (Al) alloys, Al-Cu, from mixture 96.2 % Al and 3.8 % Cu has been prepared by melting process at a temperature of 1200°C. The adding 12.5 wt% up to 20 wt% of SiC on Al-Cu alloys samples has been investigated. The structure analyses were examined by X-Ray Diffractometer (XRD) and scanning electron microscope (SEM). Moreover, the morphology of Al-Cu alloys has been seen as structure in micrometer range. The hardness was measured by hardness Vickers method. According to the results, it can be assumed that the 15 wt% of SiC content is prefer content to get better quality of back to back hardness Vickers of Al-Cu alloys.

  10. Effect of the ITER FW Manufacturing Process on the Microstructure and Properties of a CuCrZr Alloy

    NASA Astrophysics Data System (ADS)

    Liu, Danhua; Wang, Pinghuai; Song, Yi; Li, Qian; Chen, Jiming

    2015-10-01

    The first wall (FW) is one of the core components in ITER. As the heat sink material, the CuCrZr alloy shall be properly jointed with beryllium and stainless steel. At present, the grains of CuCrZr are prone to coarsen seriously in the thermal cycle process of FW manufacturing, which has become a critical issue for ITER parties. To investigate the mirostructure and mechanical properties of the optimized CuCrZr alloy in the first wall fabricating thermal cycle, simulative experiments have been done in this study. The alloy ingot was forged and hot rolled into plates, and then solid solution annealed, cold rolled and aged for strengthening. Several heat treatments were done to the CuCrZr samples, and the changes of microstructure, micro-hardness and tensile strength were investigated. The results indicated that the original elongated grains had changed into equiaxed ones, and the vickers hardness had declined to about 60 after experiencing the process of CuCrZr/316L(N) bi-metallic plate manufacturing, either by hot isostatic pressing at a higher temperature or by explosion welding followed by solution annealing. Joining Be/CuCrZr by hot isostatic pressing acts as an aging process for CuCrZr, so after the simulated heat treatment, the hardness of the alloy increased to about 110 HV and the tensile yield strength at 250°C rose to about 170 MPa. Meanwhile, the average grain size was controlled below 200 μm. supported by the International Nuclear Thermonuclear Experimental Reactor (ITER) Specific Program of China (No. 2014GB126000)

  11. Feasibility of constructed wetland planted with Leersia hexandra Swartz for removing Cr, Cu and Ni from electroplating wastewater.

    PubMed

    You, Shao-Hong; Zhang, Xue-Hong; Liu, Jie; Zhu, Yi-Nian; Gu, Chen

    2014-01-01

    As a low-cost treatment technology for effluent, the constructed wetlands can be applied to remove the heavy metals from wastewater. Leersia hexandra Swartz is a metal-accumulating hygrophyte with great potential to remove heavy metal from water. In this study, two pilot-scale constructed wetlands planted with L. hexandra (CWL) were set up in greenhouse to treat electroplating wastewater containing Cr, Cu and Ni. The treatment performance of CWL under different hydraulic loading rates (HLR) and initial metal concentrations were also evaluated. The results showed that CWL significantly reduced the concentrations of Cr, Cu and Ni in wastewater by 84.4%, 97.1% and 94.3%, respectively. High HLR decreased the removal efficiencies of Cr, Cu and Ni; however, the heavy metal concentrations in effluent met Emission Standard of Pollutants for Electroplating in China (ESPE) at HLR less than 0.3 m3/m2 d. For the influent of 5 mg/L Cr, 10 mg/L Cu and 8 mg/L Ni, effluent concentrations were below maximum allowable concentrations in ESPE, indicating that the removal of Cr, Cu and Ni by CWL was feasible at considerably high influent metal concentrations. Mass balance showed that the primary sink for the retention of contaminants within the constructed wetland system was the sediment, which accounted for 59.5%, 83.5%, and 73.9% of the Cr, Cu and Ni, respectively. The data from the pilot wetlands support the view that CWL could be used to successfully remove Cr, Cu and Ni from electroplating wastewater. PMID:24600856

  12. Band structure, Fermi surface, elastic, thermodynamic, and optical properties of AlZr 3 , AlCu 3 , and AlCu 2 Zr: First-principles study

    NASA Astrophysics Data System (ADS)

    Parvin, R.; Parvin, F.; Ali, M. S.; Islam, A. K. M. A.

    2016-08-01

    The electronic properties (Fermi surface, band structure, and density of states (DOS)) of Al-based alloys AlM 3 (M = Zr and Cu) and AlCu2Zr are investigated using the first-principles pseudopotential plane wave method within the generalized gradient approximation (GGA). The structural parameters and elastic constants are evaluated and compared with other available data. Also, the pressure dependences of mechanical properties of the compounds are studied. The temperature dependence of adiabatic bulk modulus, Debye temperature, specific heat, thermal expansion coefficient, entropy, and internal energy are all obtained for the first time through quasi-harmonic Debye model with phononic effects for T = 0 K–100 K. The parameters of optical properties (dielectric functions, refractive index, extinction coefficient, absorption spectrum, conductivity, energy-loss spectrum, and reflectivity) of the compounds are calculated and discussed for the first time. The reflectivities of the materials are quite high in the IR–visible–UV region up to ∼ 15 eV, showing that they promise to be good coating materials to avoid solar heating. Some of the properties are also compared with those of the Al-based Ni3Al compound.

  13. Thermal stability and thermo-mechanical properties of magnetron sputtered Cr-Al-Y-N coatings

    SciTech Connect

    Rovere, Florian; Mayrhofer, Paul H.

    2008-01-15

    Cr{sub 1-x}Al{sub x}N coatings are promising candidates for advanced machining and high temperature applications due to their good mechanical and thermal properties. Recently the authors have shown that reactive magnetron sputtering using Cr-Al targets with Al/Cr ratios of 1.5 and Y contents of 0, 2, 4, and 8 at % results in the formation of stoichiometric (Cr{sub 1-x}Al{sub x}){sub 1-y}Y{sub y}N films with Al/Cr ratios of {approx}1.2 and YN mole fractions of 0%, 2%, 4%, and 8%, respectively. Here, the impact of Y on thermal stability, structural evolution, and thermo-mechanical properties is investigated in detail. Based on in situ stress measurements, thermal analyzing, x-ray diffraction, and transmission electron microscopy studies the authors conclude that Y effectively retards diffusional processes such as recovery, precipitation of hcp-AlN and fcc-YN, grain growth, and decomposition induced N{sub 2} release. Hence, the onset temperature of the latter shifts from {approx}1010 to 1125 deg. C and the hardness after annealing at T{sub a}=1100 deg. C increases from {approx}32 to 39 GPa with increasing YN mole fraction from 0% to 8%, respectively.

  14. Preliminary Study on Fatigue Strengths of Fretted Ti-48Al-2Cr-2Nb

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Lerch, Bradley A.; Draper, Susan L.

    2002-01-01

    The fatigue behavior (stress-life curve) of gamma titanium aluminide (Ti-48Al-2Cr-2Nb, atomic percent) was examined by conducting two tests: first, a fretting wear test with a fatigue specimen in contact with a typical nickel-based superalloy contact pad in air at temperatures of 296 and 823 K and second, a high-cycle fatigue test of the prefretted Ti-48Al-2Cr-2Nb fatigue specimen at 923 K. Reference high-cycle fatigue tests were also conducted with unfretted Ti-48Al-2Cr-2Nb specimens at 923 K. All Ti-48Al-2Cr-2Nb fatigue specimens were machined from cast slabs. The results indicate that the stress-life results for the fretted Ti-48Al-2Cr-2Nb specimens exhibited a behavior similar to those of the unfretted Ti-48Al-2Cr-2Nb specimens. The values of maximum stress and life for the fretted specimens were almost the same as those for the unfretted specimens. The resultant stress-life curve for the unfretted fatigue specimens was very flat. The flat appearance in the stress-life curve of the unfretted specimens is attributed to the presence of a high density of casting pores. The fatigue strengths of both the fretted and unfretted specimens can be significantly affected by the presence of this porosity, which can decrease the fatigue life of Ti-48Al-2Cr-2Nb. The presence of the porosity made discerning the effect of fretting damage on fatigue strength and life of the specimens difficult.

  15. Cr4 + :Gd3Sc2Ga3O12 passive Q-switch for the Cr3 + :LiCaAlF6 laser

    NASA Astrophysics Data System (ADS)

    Kuo, Yen-Kuang; Yang, Yang; Birnbaum, Milton

    1994-05-01

    A Cr4+:Gd3Sc2Ga3O12 (Cr4+:GSGG) broad-band saturable absorber has been demonstrated to be an excellent passive Q-switch for the flashlamp-pumped tunable Cr3+:LiCaAlF6 (Cr:LiCAF) laser at room temperature. A single Q-switched laser output pulse of 11 mJ in energy and 37 ns in duration at 778 nm was obtained in a nonoptimized laser.

  16. Undercooling and solidification behavior of melts of the quasicrystal-forming alloys Al-Cu-Fe and Al-Cu-Co

    SciTech Connect

    Holland-Moritz, D.; Schroers, J.; Herlach, D.M.; Grushko, B.; Urban, K.

    1998-03-02

    Al-Cu-Fe, Al-Fe and Al-Cu-Co melts of different compositions were undercooled by containerless processing in an electromagnetic levitation facility. The phase selection during solidification from the undercooled melt was determined by direct measurements of the temperature changes during recalescence. Complimentarily, the phase selection and microstructure development was studied by scanning- and transmission electron microscopy (SEM, TEM) and X-ray diffraction (XRD) on the as-solidified samples with the undercooling and the alloy composition as experimental parameters. For comparison, rapidly quenched samples of the same alloys were produced by splat-cooling and investigated by TEM and XRD. The undercooling results were analyzed within the framework of classical nucleation theory. The activation threshold for the nucleation was found to be small for the icosahedral quasicrystalline phase in Al-Cu-Fe, medium for the decagonal D-phase in Al-Cu-Co and crystalline phases with polytetrahedral symmetry elements (Al{sub 13}Fe{sub 4} and Al{sub 5}Fe{sub 2}), but large for the cubic phase of Al{sub 50}(CuCo){sub 50} with non-polytetrahedral crystalline symmetry. These results are explained assuming of an icosahedral short-range order that prevails in the undercooled melt and gives rise to an interfacial energy decreasing with increasing degree of polytetrahedral order in the solid nucleus.

  17. Overview spectra and axial distribution of spectral line intensities in a high-current vacuum arc with CuCr electrodes

    SciTech Connect

    Lisnyak, M.; Pipa, A. V.; Gorchakov, S. E-mail: weltmann@inp-greifswald.de; Iseni, S.; Franke, St.; Khapour, A.; Methling, R.; Weltmann, K.-D. E-mail: weltmann@inp-greifswald.de

    2015-09-28

    Spectroscopic investigations of free-burning vacuum arcs in diffuse mode with CuCr electrodes are presented. The experimental conditions of the investigated arc correspond to the typical system for vacuum circuit breakers. Spectra of six species Cu I, Cu II, Cu III, Cr I, Cr II, and Cr III have been analyzed in the wavelength range 350–810 nm. The axial intensity distributions were found to be strongly dependent on the ionization stage of radiating species. Emission distributions of Cr II and Cu II can be distinguished as well as the distributions of Cr III and Cu III. Information on the axial distribution was used to identify the spectra and for identification of overlapping spectral lines. The overview spectra and some spectral windows recorded with high resolution are presented. Analysis of axial distributions of emitted light, which originates from different ionization states, is presented and discussed.

  18. Oxidation Resistant Ti-Al-Fe Diffusion Barrier for FeCrAlY Coatings on Titanium Aluminides

    NASA Technical Reports Server (NTRS)

    Brady, Michael P. (Inventor); Smialke, James L. (Inventor); Brindley, William J. (Inventor)

    1996-01-01

    A diffusion barrier to help protect titanium aluminide alloys, including the coated alloys of the TiAl gamma + Ti3Al (alpha2) class, from oxidative attack and interstitial embrittlement at temperatures up to at least 1000 C is disclosed. The coating may comprise FeCrAlX alloys. The diffusion barrier comprises titanium, aluminum, and iron in the following approximate atomic percent: Ti-(50-55)Al-(9-20)Fe. This alloy is also suitable as an oxidative or structural coating for such substrates.

  19. Photocatalytic property and structural stability of CuAl-based layered double hydroxides

    NASA Astrophysics Data System (ADS)

    Lv, Ming; Liu, Haiqiang

    2015-07-01

    Three types of CuMAl layered double hydroxides (LDHs, M=Mg, Zn, Ni) were successfully synthesized by coprecipitation. Powder X-ray diffraction (XRD), inductively coupled plasma atomic emission spectrometry (ICP-AES) and UV-Vis diffuse reflectance spectrum (UV-vis) were used to confirm the formation of as-synthesized solids with good crystal structure. The photocatalytic activity of those LDH materials for CO2 reduction under visible light was investigated. The experimental results show that CuNiAl-LDHs with narrowest band gap and largest surface areas behave highest efficiency for methanol generation under visible light compared with CuMgAl-LDHs and CuZnAl-LDHs. The CuNiAL-LDH showed high yield for methanol production i.e. 0.210 mmol/g h, which was high efficient. In addition, the influence of the different M2+ on the structures and stability of the CuMAl-LDHs was also investigated by analyzing the geometric parameters, electronic arrangement, charge populations, hydrogen-bonding, and binding energies by density functional theory (DFT) analysis. The theoretical calculation results show that the chemical stability of LDH materials followed the order of CuMgAl-LDHs>CuZnAl-LDHs>CuNiAl-LDHs, which is just opposite with the photocatalytic activity and band gaps of three materials.

  20. Interconnection between microstructure and microhardness of directionally solidified binary Al-6wt.%Cu and multicomponent Al-6wt.%Cu-8wt.%Si alloys.

    PubMed

    Vasconcelos, Angela J; Kikuchi, Rafael H; Barros, André S; Costa, Thiago A; Dias, Marcelino; Moreira, Antonio L; Silva, Adrina P; Rocha, Otávio L

    2016-05-31

    An experimental study has been carried out to evaluate the microstructural and microhardness evolution on the directionally solidified binary Al-Cu and multicomponent Al-Cu-Si alloys and the influence of Si alloying. For this purpose specimens of Al-6wt.%Cu and Al-6wt.%Cu-8wt.%Si alloys were prepared and directionally solidified under transient conditions of heat extraction. A water-cooled horizontal directional solidification device was applied. A comprehensive characterization is performed including experimental dendrite tip growth rates (VL) and cooling rates (TR) by measuring Vickers microhardness (HV), optical microscopy and scanning electron microscopy with microanalysis performed by energy dispersive spectrometry (SEM-EDS). The results show, for both studied alloys, the increasing of TR and VL reduced the primary dendrite arm spacing (l1) increasing the microhardness. Furthermore, the incorporation of Si in Al-6wt.%Cu alloy to form the Al-6wt.%Cu-8wt.%Si alloy influenced significantly the microstructure and consequently the microhardness but did not affect the primary dendritic growth law. An analysis on the formation of the columnar to equiaxed transition (CET) is also performed and the results show that the occurrence of CET is not sharp, i.e., the CET in both cases occurs in a zone rather than in a parallel plane to the chill wall, where both columnar and equiaxed grains are be able to exist. PMID:27254454

  1. Refinement and growth enhancement of Al2Cu phase during magnetic field assisting directional solidification of hypereutectic Al-Cu alloy

    NASA Astrophysics Data System (ADS)

    Wang, Jiang; Yue, Sheng; Fautrelle, Yves; Lee, Peter D.; Li, Xi; Zhong, Yunbo; Ren, Zhongming

    2016-04-01

    Understanding how the magnetic fields affect the formation of reinforced phase during solidification is crucial to tailor the structure and therefor the performance of metal matrix in situ composites. In this study, a hypereutectic Al-40 wt.%Cu alloy has been directionally solidified under various axial magnetic fields and the morphology of Al2Cu phase was quantified in 3D by means of high resolution synchrotron X-ray tomography. With rising magnetic fields, both increase of Al2Cu phase’s total volume and decrease of each column’s transverse section area were found. These results respectively indicate the growth enhancement and refinement of the primary Al2Cu phase in the magnetic field assisting directional solidification. The thermoelectric magnetic forces (TEMF) causing torque and dislocation multiplication in the faceted primary phases were thought dedicate to respectively the refinement and growth enhancement. To verify this, a real structure based 3D simulation of TEMF in Al2Cu column was carried out, and the dislocations in the Al2Cu phase obtained without and with a 10T high magnetic field were analysed by the transmission electron microscope.

  2. Refinement and growth enhancement of Al2Cu phase during magnetic field assisting directional solidification of hypereutectic Al-Cu alloy.

    PubMed

    Wang, Jiang; Yue, Sheng; Fautrelle, Yves; Lee, Peter D; Li, Xi; Zhong, Yunbo; Ren, Zhongming

    2016-01-01

    Understanding how the magnetic fields affect the formation of reinforced phase during solidification is crucial to tailor the structure and therefor the performance of metal matrix in situ composites. In this study, a hypereutectic Al-40 wt.%Cu alloy has been directionally solidified under various axial magnetic fields and the morphology of Al2Cu phase was quantified in 3D by means of high resolution synchrotron X-ray tomography. With rising magnetic fields, both increase of Al2Cu phase's total volume and decrease of each column's transverse section area were found. These results respectively indicate the growth enhancement and refinement of the primary Al2Cu phase in the magnetic field assisting directional solidification. The thermoelectric magnetic forces (TEMF) causing torque and dislocation multiplication in the faceted primary phases were thought dedicate to respectively the refinement and growth enhancement. To verify this, a real structure based 3D simulation of TEMF in Al2Cu column was carried out, and the dislocations in the Al2Cu phase obtained without and with a 10T high magnetic field were analysed by the transmission electron microscope. PMID:27091383

  3. Refinement and growth enhancement of Al2Cu phase during magnetic field assisting directional solidification of hypereutectic Al-Cu alloy

    PubMed Central

    Wang, Jiang; Yue, Sheng; Fautrelle, Yves; Lee, Peter D.; Li, Xi; Zhong, Yunbo; Ren, Zhongming

    2016-01-01

    Understanding how the magnetic fields affect the formation of reinforced phase during solidification is crucial to tailor the structure and therefor the performance of metal matrix in situ composites. In this study, a hypereutectic Al-40 wt.%Cu alloy has been directionally solidified under various axial magnetic fields and the morphology of Al2Cu phase was quantified in 3D by means of high resolution synchrotron X-ray tomography. With rising magnetic fields, both increase of Al2Cu phase’s total volume and decrease of each column’s transverse section area were found. These results respectively indicate the growth enhancement and refinement of the primary Al2Cu phase in the magnetic field assisting directional solidification. The thermoelectric magnetic forces (TEMF) causing torque and dislocation multiplication in the faceted primary phases were thought dedicate to respectively the refinement and growth enhancement. To verify this, a real structure based 3D simulation of TEMF in Al2Cu column was carried out, and the dislocations in the Al2Cu phase obtained without and with a 10T high magnetic field were analysed by the transmission electron microscope. PMID:27091383

  4. Ultrasonic spray-pyrolyzed CuCrO2 thin films

    NASA Astrophysics Data System (ADS)

    Sánchez-Alarcón, R. I.; Oropeza-Rosario, G.; Gutierrez-Villalobos, A.; Muro-López, M. A.; Martínez-Martínez, R.; Zaleta-Alejandre, E.; Falcony, C.; Alarcón-Flores, G.; Fragoso, R.; Hernández-Silva, O.; Perez-Cappe, E.; Mosqueda Laffita, Yodalgis; Aguilar-Frutis, M.

    2016-05-01

    In this paper the optical, structural and electrical properties of CuCrO2 thin films deposited by ultrasonic spray pyrolysis at temperatures from 400 to 600 °C in steps of 50 °C are presented. Copper and chromium acetylacetonates were chosen as sources of Cu and Cr, respectively, and N,N-dimethylformamide was used as the solvent. X-ray results confirmed that the films as deposited showed the CuCrO2 phase without any post-deposition thermal annealing. The surface morphology was observed to be mirror like, and as the films were deposited at different temperatures, they gradually revealed the presence of small crystallites. The best film’s optical percentage transmission (in the visible region), about 58%, was obtained in films deposited at 450 °C, and the highest band gap energy (3.17 eV) was measured in films deposited at 400 °C. The electrical properties of the films were obtained by the Hall effect. A hole concentration in the range 1019-1021 cm-3, conductivity as high as 35 S cm-1, and mobility lower than 1 cm2 V-1 s-1 were obtained in the films. p-type conductivity was confirmed using the hot point probe arrangement, and the Seebeck coefficient was estimated. The hole conductivity is thought to be due to excess oxygen in the films. Finally, the minimum energy required to transfer carriers from acceptor level to the valence band in the films was estimated by impedance spectroscopy.

  5. μSR study on CuCr1-xMgxO2

    NASA Astrophysics Data System (ADS)

    Ikedo, Yutaka; Sugiyama, Jun; Nozaki, Hiroshi; Mukai, Kazuhiko; Russo, Peter L.; Andreica, Daniel; Amato, Alex; Ono, Yasuhiro; Kajitani, Tsuyoshi

    2009-04-01

    In order to clarify the magnetic nature of a delafossite-type oxide, CuCr1-xMgxO2 ( x=0 and 0.03), we have performed zero field (ZF-) and weak transversal field (wTF-) μ+SR measurements in the temperature range between 1.8 and 50 K using polycrystalline samples. The wTF- μ+SR measurements suggested that both samples undergo a magnetic transition at Tm=26 K, clarifying that Tm is not altered by the Cr substitution with Mg. The ZF- μ+SR measurements indicated the existence of a clear muon-spin precession ( ∼50 MHz at T→0 K) signal for the x=0 sample below Tm, indicating a long-range antiferromagnetic order state, whereas the absence of long-range order for the x=0.03 sample even at 1.8 K.

  6. Radiation tolerance of neutron-irradiated model Fe-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Field, Kevin G.; Hu, Xunxiang; Littrell, Kenneth C.; Yamamoto, Yukinori; Snead, Lance L.

    2015-10-01

    The Fe-Cr-Al alloy system has the potential to form an important class of enhanced accident-tolerant cladding materials in the nuclear power industry owing to the alloy system's higher oxidation resistance in high-temperature steam environments compared with traditional zirconium-based alloys. However, radiation tolerance of Fe-Cr-Al alloys has not been fully established. In this study, a series of Fe-Cr-Al alloys with 10-18 wt % Cr and 2.9-4.9 wt % Al were neutron irradiated at 382 °C to 1.8 dpa to investigate the irradiation-induced microstructural and mechanical property evolution as a function of alloy composition. Dislocation loops with Burgers vector of a/2<111> and a<100> were detected and quantified. Results indicate precipitation of Cr-rich α‧ is primarily dependent on the bulk chromium composition. Mechanical testing of sub-size-irradiated tensile specimens indicates the hardening response seen after irradiation is dependent on the bulk chromium composition. A structure-property relationship was developed; it indicated that the change in yield strength after irradiation is caused by the formation of these radiation-induced defects and is dominated by the large number density of Cr-rich α‧ precipitates at sufficiently high chromium contents after irradiation.

  7. Radiation tolerance of neutron-irradiated model Fe-Cr-Al alloys

    DOE PAGESBeta

    Field, Kevin G.; Hu, Xunxiang; Littrell, Kenneth C.; Yamamoto, Yukinori; Snead, Lance Lewis

    2015-07-14

    The Fe Cr Al alloy system has the potential to form an important class of enhanced accident-tolerant cladding materials in the nuclear power industry owing to the alloy system's higher oxidation resistance in high-temperature steam environments compared with traditional zirconium-based alloys. However, radiation tolerance of Fe Cr Al alloys has not been fully established. In this study, a series of Fe Cr Al alloys with 10 18 wt % Cr and 2.9 4.9 wt % Al were neutron irradiated at 382 C to 1.8 dpa to investigate the irradiation-induced microstructural and mechanical property evolution as a function of alloy composition.more » Dislocation loops with Burgers vector of a/2 111 and a 100 were detected and quantified. Results indicate precipitation of Cr-rich is primarily dependent on the bulk chromium composition. Mechanical testing of sub-size-irradiated tensile specimens indicates the hardening response seen after irradiation is dependent on the bulk chromium composition. Furthermore, a structure property relationship was developed; it indicated that the change in yield strength after irradiation is caused by the formation of these radiation-induced defects and is dominated by the large number density of Cr-rich α' precipitates at sufficiently high chromium contents after irradiation.« less

  8. Radiation tolerance of neutron-irradiated model Fe-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Field, Kevin G.; Hu, Xunxiang; Littrell, Kenneth C.; Yamamoto, Yukinori; Snead, Lance L.

    2015-10-01

    The Fe-Cr-Al alloy system has the potential to form an important class of enhanced accident-tolerant cladding materials in the nuclear power industry owing to the alloy system's higher oxidation resistance in high-temperature steam environments compared with traditional zirconium-based alloys. However, radiation tolerance of Fe-Cr-Al alloys has not been fully established. In this study, a series of Fe-Cr-Al alloys with 10-18 wt % Cr and 2.9-4.9 wt % Al were neutron irradiated at 382 °C to 1.8 dpa to investigate the irradiation-induced microstructural and mechanical property evolution as a function of alloy composition. Dislocation loops with Burgers vector of a/2<111> and a<100> were detected and quantified. Results indicate precipitation of Cr-rich α‧ is primarily dependent on the bulk chromium composition. Mechanical testing of sub-size-irradiated tensile specimens indicates the hardening response seen after irradiation is dependent on the bulk chromium composition. A structure-property relationship was developed; it indicated that the change in yield strength after irradiation is caused by the formation of these radiation-induced defects and is dominated by the large number density of Cr-rich α‧ precipitates at sufficiently high chromium contents after irradiation.

  9. Radiation tolerance of neutron-irradiated model Fe-Cr-Al alloys

    SciTech Connect

    Field, Kevin G.; Hu, Xunxiang; Littrell, Kenneth C.; Yamamoto, Yukinori; Snead, Lance Lewis

    2015-07-14

    The Fe Cr Al alloy system has the potential to form an important class of enhanced accident-tolerant cladding materials in the nuclear power industry owing to the alloy system's higher oxidation resistance in high-temperature steam environments compared with traditional zirconium-based alloys. However, radiation tolerance of Fe Cr Al alloys has not been fully established. In this study, a series of Fe Cr Al alloys with 10 18 wt % Cr and 2.9 4.9 wt % Al were neutron irradiated at 382 C to 1.8 dpa to investigate the irradiation-induced microstructural and mechanical property evolution as a function of alloy composition. Dislocation loops with Burgers vector of a/2 111 and a 100 were detected and quantified. Results indicate precipitation of Cr-rich is primarily dependent on the bulk chromium composition. Mechanical testing of sub-size-irradiated tensile specimens indicates the hardening response seen after irradiation is dependent on the bulk chromium composition. Furthermore, a structure property relationship was developed; it indicated that the change in yield strength after irradiation is caused by the formation of these radiation-induced defects and is dominated by the large number density of Cr-rich α' precipitates at sufficiently high chromium contents after irradiation.

  10. Structural and magnetic properties CuAl1-xCrxS2 alloys

    NASA Astrophysics Data System (ADS)

    Ortega López, C.; Casiano Jiménez, G.; Espitia, M. J.

    2016-02-01

    In this paper computational calculations were performed based on the density functional theory DFT, to investigate the structural, electronic and magnetic properties of CuAl1-xCrxS2 (x=0.0, 0.50 and 1.00) alloys. Pseudopotential method was used, as is implemented in the Quantum-Espresso code. We found that the alloys crystallize in a tetragonal structure belonging to space group 122 (I-42d) with lattice constants a=5.290Å, c=10.378Å for x=0.5 and a=5.283Å, c=10.366Å for x=1.00. These values are in good agreement with experimental results. Additionally, we found that the alloys possess an antiferromagnetic behaviour with magnetic moments 4,20μβ/cell and 4,05μβ/cell, respectively. From the analysis of the density of states, it is clear that the alloys have a half-metallic behaviour due to the Cr-d and Cu-d states crossing the Fermi level. This compounds can be used in spintronic.

  11. Nanostructured Cu-Cr alloy with high strength and electrical conductivity

    SciTech Connect

    Islamgaliev, R. K. Nesterov, K. M.; Bourgon, J.; Champion, Y.; Valiev, R. Z.

    2014-05-21

    The influence of nanostructuring by high pressure torsion (HPT) on strength and electrical conductivity in the Cu-Cr alloy has been investigated. Microstructure of HPT samples was studied by transmission electron microscopy with special attention on precipitation of small chromium particles after various treatments. Effect of dynamic precipitation leading to enhancement of strength and electrical conductivity was observed. It is shown that nanostructuring leads to combination of high ultimate tensile strength of 790–840 MPa, enhanced electrical conductivity of 81%–85% IACS and thermal stability up to 500 °C. The contributions of grain refinement and precipitation to enhanced properties of nanostructured alloy are discussed.

  12. Spin correlated dielectric memory and rejuvenation in multiferroic CuCrS{sub 2}

    SciTech Connect

    Karmakar, A.; Dey, K.; Majumdar, S.; Giri, S.; Chatterjee, S.

    2014-02-03

    We report a rare consequence of memory effect in dielectric response (ϵ) and magnetic field induced rejuvenation in a relaxor-type multiferroic chalcogenide, CuCrS{sub 2}. Despite reasonably high conductivity, we are able to detect significant spontaneous polarization using an improvised technique verifying ferroelectric (FE) order. Concomitant appearance of both FE and antiferromagnetic orders authenticates multiferroicity. A smeared out FE transition and strong frequency dependence of the broadened peak in ϵ obeying Dynamical scaling law signify relaxor properties. We discuss the role of geometrical frustration in the antiferromagnetically coupled layered triangular lattice and metal ligand hybridization for these unusual properties.

  13. A detailed study of the magnetic phase transition in CuCrO2.

    PubMed

    Ehlers, G; Podlesnyak, A A; Frontzek, M; Freitas, R S; Ghivelder, L; Gardner, J S; Shiryaev, S V; Barilo, S

    2013-12-11

    The phase transition in CuCrO2 to an ordered magnetic state is studied with bulk measurements and elastic and inelastic neutron scattering techniques. The reported onset of spontaneous electric polarization at T = 23.5 K coincides with the appearance, on cooling, of elastic magnetic scattering. At higher temperatures long range magnetic correlations gradually develop but they are dynamic. The ground state is characterized by three-dimensional long range magnetic ordering but along the c direction the correlation length remains limited to ∼200 Å. PMID:24214902

  14. Thermal contact resistance for a CU/G-10CR interface in a cylindrical geometry

    SciTech Connect

    Phelan, P.E.; Niemann, R.C.; Nicol, T.H.

    1996-07-01

    A major component of a high-T[sub c] superconductor current lead designed to provide current to low-T[sub c] superconductor magnets is the heat intercept connection, which is a cylindrical structure consisting of an inner Cu disk, a thin-walled G-10CR composite tube, and an outer Cu ring, assembled by a thermal interference fit. It was determined in a previous study that the thermal contact resistance (R[sub c]) between the composite tube and the two Cu pieces contributed a substantial portion of the total thermal resistance between the inner and outer Cu pieces. This report emphasizes the analysis of the data for the third and final design of the heat intercept connection. In particular, it is found that R[sub c] decreases dramatically with increasing heat flux, a result consistent with earlier studies of composite cylinders. However, for the present data, the thermal contact conductance [=1/R{sub c}]varies with the calculated contact pressure with a power-law exponent of approximately 10, as compared to a theoretical value near 1. In addition, the presence of He or N[sub 2] gas substantially reduces R [sub c] even though the contacting surfaces are coated with a thermal grease.

  15. Oxidation Behavior of GRCop-84 (Cu-8Cr-4Nb) at Intermediate and High Temperatures

    NASA Technical Reports Server (NTRS)

    Thomas-Ogbuji, Linus U.; Humphrey, Donald L.; Greenbauer-Seng, Leslie (Technical Monitor)

    2000-01-01

    The oxidation behavior of GRCop-84 (Cu-8 at %Cr-4 at %Nb) has been investigated in air and in oxygen, for durations of 0.5 to 50 hours and temperatures ranging from 500 to 900 C. For comparison, data was also obtained for the oxidation of Cu and NARloy-Z (Cu-3 wt% Ag-0.5 wt% Zr) under the same conditions. Arrhenius plots of those data showed that all three materials had similar oxidation rates at high temperatures (> 750 C). However, at intermediate temperatures (500 to 750 C) GRCop exhibited significantly higher oxidation resistance than Cu and NARloy-Z. The oxidation kinetics of GRCop-84 exhibited a sharp and discontinuous jump between the two regimes. Also, in the high temperature regime GRCop-84 oxidation rate was found to change from a high initial value to a significantly smaller terminal value at each temperature, with progress of oxidation; the two different oxidation rates were found to correlate with a porous intial oxide and a dense final oxide, respectively.

  16. The release of As, Cr and Cu from contaminated soil stabilized with APC residues under landfill conditions.

    PubMed

    Travar, I; Kihl, A; Kumpiene, J

    2015-03-15

    The aim of this study was to investigate the stability of As, Cr and Cu in contaminated soil treated with air pollution control residues under landfill conditions. The influence of landfill gas and temperature on the release of trace elements from stabilized soil was simulated using a diffusion test. The air pollution control residues immobilized As through the precipitation of Ca-As minerals (calcium arsenate (Ca5H2(AsO4)3 × 5H2O), weilite (CaAsO4) and johnbaumite (Ca5(AsO4)3(OH)), incorporation of As into ettringite (Ca6Al2(SO4)3(OH)12 × 26H2O) and adsorption by calcite (CaCO3). The air pollution control residues generally showed a high resistance to pH reduction, indicating high buffer capacity and stability of immobilized As in a landfill over time. Generation of heat in a landfill might increase the release of trace elements. The release of As from stabilized soil was diffusion-controlled at 60 °C, while surface wash-off, dissolution, and depletion prevailed at 20 °C. The air pollution control residues from the incineration of municipal solid waste immobilized Cr, indicating its stability in a landfill. The treatment of soil with air pollution control residues was not effective in immobilization of Cu. Contaminated soils treated with air pollution control residues will probably have a low impact on overall leachate quality from a landfill. PMID:25528268

  17. Friction Stir Welding of Al-Cu Bilayer Sheet by Tapered Threaded Pin: Microstructure, Material Flow, and Fracture Behavior

    NASA Astrophysics Data System (ADS)

    Beygi, R.; Kazeminezhad, M.; Kokabi, A. H.; Loureiro, A.

    2015-06-01

    The fracture behavior and intermetallic formation are investigated after friction stir welding of Al-Cu bilayer sheets performed by tapered threaded pin. To do so, temperature, axial load, and torque measurements during welding, and also SEM and XRD analyses and tensile tests on the welds are carried out. These observations show that during welding from Cu side, higher axial load and temperature lead to formation of different kinds of Al-Cu intermetallics such as Al2Cu, AlCu, and Al4Cu9. Also, existence of Al(Cu)-Al2Cu eutectic structures, demonstrates liquation during welding. The presence of these intermetallics leads to highly brittle fracture and low strength of the joints. In samples welded from Al side, lower axial load and temperature are developed during welding and no intermetallic compound is observed which results in higher strength and ductility of the joints in comparison with those welded from Cu side.

  18. Infiltration of Saffil alumina fiber with AlCu and AlSi alloys

    SciTech Connect

    Garbellini, O.; Morando, C.; Biloni, H.; Palacio, H. . Inst. de Fisica de Materiales)

    1999-06-18

    Currently there is a considerable scientific and technological interest in the composite materials, which a strong ceramic reinforcement is incorporated into a metal matrix (MMC) to tailor its properties for specific applications. Among the various techniques for fabricating MMC, the liquid metal infiltration process by means of a pressurized gas is an attractive fabrication route for near net shaped metal matrix composite and has been successfully used to fabricate Al, Mg and more recently, Ni and Ni aluminide matrix composites, which can be reinforced by SiC or Al[sub 2]O[sub 3] particles, whiskers, or short fibers. This paper describes the experimental technique used and presents an experimental investigation of the effects of the process parameters employed, such as the preform and melt temperatures, the volume fraction of fibers in the preform and the applied pressure upon the infiltration length of a chopped preform during a unidirectional infiltration aided by gas pressure casting. The experiments of the present work were conducted to provide kinetic data with a view to optimizing the selection of the process initial conditions for infiltration which have an effect on the infiltration length of the molten matrix alloy into a preform and it is a first step in investigating the correlation between the infiltration length (fluidity) of AlCuSi matrix alloys and the microstructure of the composites fabricated by pressure casting. For this purpose, this paper focuses on AlCu and AlSi matrix alloys reinforced by short-fibers [delta]-alumina SAFFIL. The experiments reported here were performed with the fibers initially at a temperature significantly below the metal melting point. This is the case of practical interest for the fabrication of many fiber-reinforced metal components.

  19. The Low-Lying States of AlCu and AlAg

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Partridge, Harry

    1994-01-01

    The singlet and triplet states of AlCu and AlAg below about 32 000/cm are studied using the internally contracted multireference configuration-interaction method. A more elaborate study of the X(sup 1)Sum(sup +) ground state of AlCu is undertaken using extended Gaussian basis sets, including the effect of inner-shell correlation and including a perturbational estimate of relativistic effects. Our best estimate of the spectroscopic constants (r(sub 0), DeltaG(sub 1/2), and D(sub 0)) for the X(sup 1)Sum(sup+) state with the experimental values in parentheses are: 4.416(4.420) a(sub 0), 295 (294) /cm, and 2.318 (2.315) eV. The calculations definitively assign the upper state in the observed transition at 14 892/cm to the lowest (sup 1)Prod state. The calculated spectroscopic constants and radiative lifetime for the (sup 1)Prod state are in good agreement with experiment. The calculations support the tentative assignments of Behm et al. for three band systems observed in the visible region between 25 000 and 28 000 / cm. However, the computed spectroscopic constants are in very poor agreement with those deduced from an analysis of the spectra. Analogous theoretical results for AlAg suggest that the (2)(sup 3)Prod, (3)(sup 3)Prod, and (3)(sup 1)Sum(sup +) states account for the bands observed, but not assigned, by Duncan and co-workers.

  20. Synthesis of TiB2/Fe-Cr-Al nanocomposite powder.

    PubMed

    Sachan, Ritesh; Park, Jong-Woo

    2008-10-01

    In this study, a route for synthesizing TiB2/Fe-Cr-Al nanocomposite is proposed via high energy ball milling by using directly coarse powders of TiB2, Fe, Cr and Al. Various compositions of these powder mixtures are milled up to 48 hrs to investigate the effect of composition on the crystalline refinement. The crystalline size is analyzed by an X-ray diffractometer for powder samples containing 30 to 100 wt% TiB2 (the rest of the powder consists of Fe-20 wt%Cr-5 wt%Al composition). The crystalline size after 48 hrs of ball milling decreases with increasing TiB2, and then again increases after reaching a minimum value of 18 nm at 70% TiB2. By transmission electron microscopic analysis, it is confirmed that particles of TiB2 are significantly reduced and finely dispersed in the Fe-Cr-Al matrix. The particle size of TiB2 is found around 20-25 nm, reinforced in the matrix. Considering the results of this study, the proposed mechanical milling route can be recommended as a promising way for fabrication of TiB2/Fe-Cr-Al nanocomposite powder. PMID:19198473

  1. Optical behavior and structural property of CuAlS₂ and AgAlS₂ wide-bandgap chalcopyrites.

    PubMed

    Ho, Ching-Hwa; Pan, Chia-Chi

    2014-08-01

    Single crystals of CuAlS₂ and AgAlS₂ were grown by chemical vapor transport method using ICl₃ as the transport. The as-grown CuAlS₂ crystals reveal transparent and light-green color. Most of them possess a well-defined (112) surface. The AgAlS₂ crystals essentially show transparent and white color in vacuum. As the AgAlS₂ was put into the atmosphere, the crystal surface gradually darkened and became brownish because of the surface reaction with humidity or hydrogen gas. After a long-term chemical reaction process, the AgAlS₂ will transform into a AgAlO₂ oxide with yellow color. From x-ray diffraction measurements, both CuAlS₂ and AgAlS₂ as-grown crystals show single-phase and isostructural to a chalcopyrite structure. The (112) face is more preferable for the formation of the chalcopyrite crystals. The energies of interband transitions of the CuAlS₂ and AgAlS₂ were determined accurately by thermoreflectance measurements in a wide energy range of 2-6 eV. The valence-band electronic structures of CuAlS₂ and AgAlS₂ have been detailed and characterized using polarized-thermoreflectance measurements in the temperature range between 30 and 300 K. The band-edge transitions belonging to the E(∥) and E(⊥) polarizations have been, respectively, identified. The band edge of AgAlS₂ is near 3.2 eV while that of AgAlS₂ is about 3.5 eV. On the basis of the experimental analyses, optical and sensing behaviors of the chalcopyrite crystals have been realized. PMID:25090358

  2. Photocatalytic removal of M(2+) (Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+) and Ag(+)) over new catalyst CuCrO(2).

    PubMed

    Ketir, W; Bouguelia, A; Trari, M

    2008-10-30

    The metal ions M(2+) (Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+) and Ag(+)) are potentially toxic. Their electro deposition has been carried out in aqueous air-equilibrated CuCrO(2) suspension upon visible illumination. The delafossite CuCrO(2) is p-type semiconductor characterized by a low band gap (1.28 eV) and a long-term chemical stability. The corrosion rate is found to be 10(-2) micromol m(-2)month(-1) in aqua regia. The oxide has been elaborated through nitrate route where the specific surface area is increased via the surface/bulk ratio. A correlation exists between the dark M(2+) adsorption, the redox potential of M(2+/0) couple and the conduction band of CuCrO(2) positioned at -1.06 V(SCE). Ag(+) cannot be photoreduced because of its positive potential located far above the valence band. By contrast, Zn(2+) is efficiently deposited due to the large driving force at the interface. The improved photoactivity of copper with a deposition percentage (90%) is attributed to the strong dark adsorption onto the surface catalyst. The results indicate a competitive effect with the water reduction; it has been observed that the M(2+) deposition goes parallel with the hydrogen evolution. Such behavior is attributed to the low H(2) over voltage when ultra fine aggregate of M islands are photodeposited onto CuCrO(2) substrate. PMID:18384943

  3. Control of p-type conduction in Mg doped monophase CuCrO2 thin layers

    NASA Astrophysics Data System (ADS)

    Chikoidze, E.; Boshta, M.; Gomaa, M.; Tchelidze, T.; Daraselia, D.; Japaridze, D.; Shengelaya, A.; Dumont, Y.; Neumann-Spallart, M.

    2016-05-01

    This work aims to clarify the origin of hole conduction in undoped and Mg-doped CuCrO2 oxide in order to have the possibility of controlling it by corresponding growth parameters. A chemical spray pyrolysis procedure for the deposition of p-type semiconductor thin films is described. The as-deposited films were amorphous. The formation of highly crystalline CuCrO2 and Mg-doped CuCrO2 films with a single phase delafossite structure was realized by annealing between 600 °C and 960 °C in a nitrogen atmosphere. The carrier concentration and the point defects of the samples are calculated by using the developed Kroger method of quasi-chemical reactions. p-type conductivity was predicted and observed in the undoped and Mg doped CuCrO2 sample, and with n ~ 1018 cm‑3 carrier concentrations for 4%Mg doping. The electrical resistivity for a 4% Mg doped sample was 1.4 Ω·cm with a Seebeck coefficient of  +130 μV K‑1 at 40 °C. By electroparamagnetic resonance spectroscopy Cr3+ and Cu2+ related defects were studied.

  4. Effect of Heat Treatment on the Microstructure and Properties of Deformation-Processed Cu-7Cr In Situ Composites

    NASA Astrophysics Data System (ADS)

    Liu, Keming; Jiang, Zhengyi; Zhou, Haitao; Lu, Deping; Atrens, Andrej; Yang, Yanling

    2015-11-01

    The effect of heat treatment on the microstructure, electrical conductivity, and tensile strength of deformation-processed Cu-7Cr in situ composites produced by thermo-mechanical processing was investigated. The Cr fibers in the Cu-7Cr in situ composite underwent coarsening, break-up, and spheroidization after exposure to elevated temperatures. The conductivity and tensile strength of the in situ composite first increased with increasing isochronal heat treatment temperature, reached a peak value, and decreased at higher temperatures. The isothermal heat treatment temperature was determined to be 625 °C. The Z ( Z is an optimization parameter to evaluate the service performance of deformation-processed Cu-based in situ composites) value of the deformation-processed Cu-7Cr in situ composite, at η = 7 ( η is a cumulative cold deformation strain) after the heat treatment at 625 °C for 1 h, reached the peak value of 3.46 × 107 MPa2 % International Annealed Copper Standard (IACS). The isochronal heat treatment time was determined to be 1 h. The following combination of conductivity and tensile strength of the deformation-processed Cu-7Cr in situ composite with a cumulative cold deformation strain of eight after isochronal aging treatments for 1 h could be attained respectively as (i) 76.0% IACS and 889 MPa; (ii) 76.8% IACS and 876 MPa; or (iii) 77.5% IACS and 779 MPa.

  5. Preparation and characterization of CuCrO2/TiO2 heterostructure photocatalyst with enhanced photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Xiong, Dehua; Chang, Haimei; Zhang, Qingqing; Tian, Shouqin; Liu, Baoshun; Zhao, Xiujian

    2015-08-01

    A series of novel p-type CuCrO2/n-type TiO2 heterostructure photocatalysts were fabricated for the first time by depositing CuCrO2 nanoparticles on TiO2 nanorod-array film through a facile spin-coating method. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and photocurrent response were employed to characterize the as-synthesized composites. The photocatalytic activity of CuCrO2/TiO2 for degradation of methylene blue (MB) aqueous solution was much higher than pure TiO2, which could be ascribed to the formation of p-n heterojunctions between CuCrO2 nanoparticles and TiO2 nanorods. In particular, the best degradation efficiency of CuCrO2/TiO2 heterojunction was 85.3%, about 1.14 times higher than pure TiO2 (74.6%), which could be attributed to their high separation efficiency of photogenerated electrons and holes. It is expected this strategy of p-n junction for enhancing photocatalytic activity can have considerable impact to promote the development of high efficient photocatalyst and industrial application for degrading pollutant, treating waste water and other environmental protection fields.

  6. Nature, density, and catalytic role of exposed species on dispersed VOx/CrOx/Al2O3 catalysts.

    PubMed

    Yang, Shuwu; Iglesia, Enrique; Bell, Alexis T

    2006-02-16

    The structure and surface composition of binary oxides consisting of CrO(x) and VO(x) dispersed on alumina and their effects on the rate and selectivity of oxidative dehydrogenation (ODH) of propane were examined and compared with those for CrO(x) and VO(x) dispersed on alumina. VO(x) deposition on an equivalent CrO(x) monolayer on alumina and deposition of CrO(x) on an equivalent monolayer of VO(x) deposited on alumina led to CrVO(4) species during thermal treatment with concomitant reduction of Cr(6+) to Cr(3+). Autoreduction of Cr(6+) to Cr(3+) is also detected for CrO(x), even without the presence of VO(x). Infrared spectroscopy of NO adsorbed at 153 K probes the relative abundance of alumina and of V(5+), Cr(3+), and Cr(6+) at surfaces. This technique detects differences in the surface composition of VO(x)/CrO(x)()/Al(2)O(3) and CrO(x)/VO(x)/Al(2)O(3). The first of these samples is enriched in VO(x) relative to CrO(x) compared with the second sample. Consistent with this finding, VO(x)/CrO(x)/Al(2)O(3) and CrO(x)/VO(x)/Al(2)O(3) are distinguishable in their ODH activities and propene selectivities. The highest ODH activity and propene selectivity is observed for VO(x)/CrO(x)/Al(2)O(3), which exhibits a surface enriched in VO(x) and having a low surface concentration of Cr(6+). PMID:16471878

  7. Cu-Cr-Nb-Zr Alloy for Rocket Engines and Other High-Heat- Flux Applications

    NASA Technical Reports Server (NTRS)

    Ellis, David L.

    2013-01-01

    Rocket-engine main combustion chamber liners are used to contain the burning of fuel and oxidizer and provide a stream of high-velocity gas for propulsion. The liners in engines such as the Space Shuttle Main Engine are regeneratively cooled by flowing fuel, e.g., cryogenic hydrogen, through cooling channels in the back side of the liner. The heat gained by the liner from the flame and compression of the gas in the throat section is transferred to the fuel by the liner. As a result, the liner must either have a very high thermal conductivity or a very high operating temperature. In addition to the large heat flux (>10 MW/sq m), the liners experience a very large thermal gradient, typically more than 500 C over 1 mm. The gradient produces thermally induced stresses and strains that cause low cycle fatigue (LCF). Typically, a liner will experience a strain differential in excess of 1% between the cooling channel and the hot wall. Each time the engine is fired, the liner undergoes an LCF cycle. The number of cycles can be as few as one for an expendable booster engine, to as many as several thousand for a reusable launch vehicle or reaction control system. Finally, the liners undergo creep and a form of mechanical degradation called thermal ratcheting that results in the bowing out of the cooling channel into the combustion chamber, and eventual failure of the liner. GRCop-84, a Cu-Cr-Nb alloy, is generally recognized as the best liner material available at the time of this reporting. The alloy consists of 14% Cr2Nb precipitates in a pure copper matrix. Through experimental work, it has been established that the Zr will not participate in the formation of Laves phase precipitates with Cr and Nb, but will instead react with Cu to form the desired Cu-Zr compounds. It is believed that significant improvements in the mechanical properties of GRCop-84 will be realized by adding Zr. The innovation is a Cu-Cr-Nb-Zr alloy covering the composition range of 0.8 to 8.1 weight

  8. Pure CuCr2O4 nanoparticles: Synthesis, characterization and their morphological and size effects on the catalytic thermal decomposition of ammonium perchlorate

    NASA Astrophysics Data System (ADS)

    Hosseini, Seyed Ghorban; Abazari, Reza; Gavi, Azam

    2014-11-01

    In the present paper a pure phase of the copper chromite spinel nanoparticles (CuCr2O4 SNPs) were synthesized via the sol-gel route using citric acid as a complexing agent. Then, the CuCr2O4 SNPs has been characterized by field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). In the next step, with the addition of Cu-Cr-O nanoparticles (NPs), the effects of different parameters such as Cu-Cr-O particle size and the Cu/Cr molar ratios on the thermal behavior of Cu-Cr-O NPs + AP (ammonium perchlorate) mixtures were investigated. As such, the catalytic effect of the Cu-Cr-O NPs for thermal decomposition of AP was evaluated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). TGA/DSC results showed that the samples with different morphologies exhibited different catalytic activity in different stages of thermal decomposition of AP. Also, in the presence of Cu-Cr-O nanocatalysts, all of the exothermic peaks of AP shifted to a lower temperature, indicating the thermal decomposition of AP was enhanced. Moreover, the heat released (ΔH) in the presence of Cu-Cr-O nanocatalysts was increased to 1490 J g-1.

  9. Application of Al-Nb alloy film to metal capping layer on Cu

    NASA Astrophysics Data System (ADS)

    Takeyama, Mayumi B.; Noya, Atsushi

    2016-02-01

    An Al-Nb alloy film with the Al72Nb28 composition is applied as a candidate metal capping layer on Cu interconnects. In the Al72Nb28/Cu/SiO2/Si model system, the preferential oxidation of Al forming a thin surface Al2O3 layer occurs owing to oxidation in air for 1 h at temperatures up to ˜300 °C, resulting in the protection of the layers underneath from further oxidation, although a slight Cu intermixing into Al-Nb occurs. With increasing oxidation temperature up to 500 °C, the surface Al2O3 layer still grows by the preferential oxidation of Al and rejects Cu atoms from the surface oxidized layer. Although Nb atoms are left behind in the surface oxidized layer, they are in a metallic state owing to the high solubility of oxygen before forming an oxide. The extremely low solubility of Nb in Cu also protects Cu without excess intermixing. A good passivation characteristic of the Al72Nb28 alloy film on Cu is demonstrated.

  10. Influence of recrystallization on phase separation kinetics of oxide dispersion strengthened Fe Cr Al alloy

    SciTech Connect

    Capdevila, C.; Miller, Michael K; Pimentel, G.; Chao, J.

    2012-01-01

    The effect of different starting microstructures on the kinetics of Fe-rich ({alpha}) and Cr-rich ({alpha}') phase separation during aging of Fe-Cr-Al oxide dispersion strengthened (ODS) alloys has been analyzed with a combination of atom probe tomography and thermoelectric power measurements. The results revealed that the high recrystallization temperature necessary to produce a coarse grained microstructure in Fe-base ODS alloys affects the randomness of Cr-atom distributions and defect density, which consequently affect the phase separation kinetics at low annealing temperatures.

  11. Radial macrosegregation and dendrite clustering in directionally solidified Al-7Si and Al-19Cu alloys

    NASA Astrophysics Data System (ADS)

    Ghods, M.; Johnson, L.; Lauer, M.; Grugel, R. N.; Tewari, S. N.; Poirier, D. R.

    2016-05-01

    Hypoeutectic Al-7 wt% Si and Al-19 wt% Cu alloys were directionally solidified upward in a Bridgman furnace through a range of constant growth speeds and thermal gradients. Though processing is thermo-solutally stable, flow initiated by gravity-independent advection at, slightly leading, central dendrites moves rejected solute out ahead and across the advancing interface. Here any lagging dendrites are further suppressed which promotes a curved solid-liquid interface and the eventual dendrite "clustering" seen in transverse sections (dendrite "steepling" in longitudinal orientations) as well as extensive radial macrosegregation. Both aluminum alloys showed considerable macrosegregation at the low growth speeds (10 and 30 μm s-1) but not at higher speed (72 μm s-1). Distribution of the fraction eutectic-constituent on transverse sections was determined in order to quantitatively describe radial macrosegregation. The convective mechanisms leading to dendrite-steepling were elucidated with numerical simulations, and their results compared with the experimental observations.

  12. Role of Y in the oxidation resistance of CrAlYN coatings

    NASA Astrophysics Data System (ADS)

    Domínguez-Meister, S.; El Mrabet, S.; Escobar-Galindo, R.; Mariscal, A.; Jiménez de Haro, M. C.; Justo, A.; Brizuela, M.; Rojas, T. C.; Sánchez-López, J. C.

    2015-10-01

    CrAlYN coatings with different aluminum (4-12 at.%) and yttrium (2-5 at.%) contents are deposited by d.c. reactive magnetron sputtering on silicon and M2 steel substrates using metallic targets and Ar/N2 mixtures. The influence of the nanostructure and chemical elemental distribution on the oxidation resistance after heating in air at 1000 °C is studied by means of cross-sectional scanning electron microscopy (X-SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD) and glow discharge optical emission spectroscopy (GD-OES). The sequential exposure to the metallic targets during the synthesis leads to a multilayer structure where concentration of metallic elements (Cr, Al and Y) is changing periodically. A good oxidation resistance is observed when Al- and Y-rich regions are separated by well-defined CrN layers, maintaining crystalline coherence along the columnar structure. This protective behavior is independent of the type of substrate and corresponds to the formation of a thin mixed (Al, Cr)-oxide scale that protects the film underneath. The GD-OES and XRD analysis have demonstrated that Y acts as a reactive element, blocking the Fe and C atoms diffusion from the steel and favoring higher Al/Cr ratio in the passivation layer after heating. The coating with Y content around 4 at.% exhibited the best performance with a thinner oxide scale, a delay in the CrN decomposition and transformation to Cr2N, and a more effective Fe and C blocking.

  13. Tribological properties of Zr61Ti2Cu25Al12 bulk metallic glass under simulated physiological conditions.

    PubMed

    Wang, Yu; Shi, Ling-ling; Duan, De-li; Li, Shu; Xu, Jian

    2014-04-01

    In this work, wear resistance of a Zr61Ti2Cu25Al12 (ZT1) bulk metallic glass (BMG) in dry-sliding and simulated physiological media was investigated using ball-on-flat tribological approach and Si3N4 ball as counterpart. It was indicated that wear resistance of the BMG in air and deionized water is superior to Ti6Al4V alloy but inferior to 316L stainless steel (316L SS) and Co28Cr6Mo (CoCrMo) alloy. However, under simulated physiological media such as phosphate buffered solution (PBS) and Dulbecco's modified Eagle medium with 10vol.% fetal bovine serum (DMEM+FBS), the ZT1 BMG exhibits decreased wear resistance in comparison with the Ti6Al4V, 316L SS and CoCrMo. This is probably associated with its moderate pitting corrosion resistance in the medium containing chloride ions. The presence of protein in the solution has a significant effect to ruin pitting resistance of the BMG, then causing more severe wear damage. Under the dry-wear condition, abrasive wear is a predominant wear mechanism for the ZT1, whereas under deionized water, deterioration induced by abrasive wear can be mitigated. In simulated physiological media, wear deterioration is a typical tribocorrosion controlled by synergistic effects of the abrasive and corrosive wear. For the four investigated metals, wear resistance does not exhibit distinct correlation with hardness, whereas the material with high Young's modulus possesses better wear resistance. PMID:24582252

  14. BeAl6O10: Cr3+: a promising active medium for femtosecond lasers

    NASA Astrophysics Data System (ADS)

    Petrov, V. V.; Pestryakov, Efim V.; Trunov, V. I.; Kirpichnikov, A. V.; Alimpiev, A. I.

    2003-10-01

    The new laser crystals BeAl6O10:Cr3+ were grown, spectral-luminescence and CW laser properties were investigated and compared with those of well-known laser medium-alexandrite (BeAl2O4:Cr3+). CW laser generation on vibronic transition 4T2-4A2 of Cr3+ ions in BeAl6O10 crystals was realized in the range of 800-880 nm under Ar+ laser pumping. The emission cross-section of laser transition was estimated about 6×10-20 cm2. We confirmed these crystals are perspective for generation of femtosecond pulses in the near IR region under LD pumping.

  15. Effect of Microstructure on Creep in Directionally Solidified NiAl-31Cr-3Mo

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Raj, S. V.; Locci, I. E.

    2001-01-01

    The 1200 to 1400 K slow strain rate characteristics of the directionally solidified (DS) eutectic Ni-33Al-31Cr-3 Mo have been determined as a function of growth rate. While differences in the light optical level microstructure were observed in alloys grown at rates ranging from 7.6 to 508 mm/h, compression testing indicated that all had essentially the same strength. The exception was Ni-33 Al-31Cr-3Mo DS at 25.4 mm/h which was slightly stronger than the other growth velocities; no microstructural reason could be found for this improvement. Comparison of the approximately 1300 K properties revealed that four different DS NiAl-34(Cr,Mo) alloys have a similar creep resistance which suggests that there is a common, but yet unknown, strengthening mechanism.

  16. Effect of Microstructure on Creep in Directionally Solidified NiAl-31Cr-3Mo

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.; Raj, S. V.; Locci, I. E.

    2001-01-01

    The 1200 to 1400 K slow strain rate characteristics of the directionally solidified (DS) eutectic Ni-33Al-31Cr-3 Mo have been determined as a function of growth rate. While differences in the light optical level microstructure were observed in alloys grown at rates ranging from 7.6 to 508 mm/h, compression testing indicated that all had essentially the same strength. The exception was Ni-33Al-31Cr-3Mo DS at 25.4 mm/h which was slightly stronger than the other growth velocities; no microstructural reason could be found for this improvement. Comparison of the approx. 1300 K properties revealed that four different DS NiAl-34(Cr,Mo) alloys have a similar creep resistance which suggests that there is a common, but yet unknown, strengthening mechanism.

  17. Direct catalytic oxyamination of benzene to aniline over Cu(II) nanoclusters supported on CuCr2O4 spinel nanoparticles via simultaneous activation of C-H and N-H bonds.

    PubMed

    Acharyya, Shankha S; Ghosh, Shilpi; Bal, Rajaram

    2014-11-11

    We report the facile synthesis of a highly efficient, reusable catalyst comprising Cu(II) nanoclusters supported on CuCr2O4 spinel nanoparticles for the oxyamination of benzene to aniline (H2O2 + NH3) under mild aqueous reaction conditions. The synergy between the Cu(II) nanoclusters and CuCr2O4 spinel nanoparticles plays the most vital role towards its high catalytic activity. PMID:24990186

  18. Electrodialytic removal of Cu, Cr, and As from chromated copper arsenate-treated timber waste

    SciTech Connect

    Ribeiro, A.B.; Mateus, E.P.; Ottosen, L.M.; Bech-Nielsen, G.

    2000-03-01

    Waste of wood treated with chromated copper arsenate (CCA) is expected to increase in volume over the next decades. Alternative disposal options to landfilling are becoming more attractive to study, especially those that promote reuse. The authors have studied the electrodialytic removal of Cu, Cr, and As from CCA-treated timber wastes. The method uses a low-level direct current as the cleaning agent, combining the electrokinetic movement of ions in the matrix with the principle of electrodialysis. The technique was tested in four experiments using a laboratory cell on sawdust of an out-of-service CCA-treated Pinus pinaster Ait. pole. The duration of all the experiments was 30 days, and the current density was kept constant at 0.2 mA/cm{sup 2}. The experiments differ because in one the sawdust was saturated with water (experiment 1) and in the rest it was saturated with oxalic acid, 2.5, 5, and 7.5% (w/w), respectively, in experiments 2--4. The highest removal rates obtained were 93% of Cu, 95% of Cr, and 99% of As in experiment 2. Other experimental conditions might possibly optimize the removal rates.

  19. Hot Deformation Characteristics and Processing Maps of the Cu-Cr-Zr-Ag Alloy

    NASA Astrophysics Data System (ADS)

    Zhang, Yi; Chai, Zhe; Volinsky, Alex A.; Sun, Huili; Tian, Baohong; Liu, Ping; Liu, Yong

    2016-03-01

    The hot deformation behavior of the Cu-Cr-Zr-Ag alloy has been investigated by hot compressive tests in the 650-950 °C temperature and 0.001-10 s-1 strain rate ranges using Gleeble-1500D thermo-mechanical simulator. The microstructure evolution of the alloy during deformation was characterized using optical and transmission electron microscopy. The flow stress decreases with the deformation temperature and increases with the strain rate. The apparent activation energy for hot deformation of the alloy was 343.23 kJ/mol. The constitutive equation of the alloy based on the hyperbolic-sine equation was established to characterize the flow stress as a function of the strain rate and the deformation temperature. The processing maps were established based on the dynamic material model. The optimal processing parameters for hot deformation of the Cu-Cr-Zr-Ag alloy are 900-950 °C and 0.001-0.1 s-1 strain rate. The evolution of DRX microstructure strongly depends on the deformation temperature and the strain rate.

  20. Influence of thermomechanical processing on the microstructure and properties of a Cu-Cr-P Alloy

    NASA Astrophysics Data System (ADS)

    Gao, N.; Tiainen, T.; Huttunen-Saarivirta, E.; Ji, Y.

    2002-08-01

    The microstructure and properties of a Cu-0.55 wt. % Cr-0.07 wt. % P alloy were studied by using optical microscopy, transmission electron microscopy, and the measurements of Vickers hardness and electrical conductivity after it was subjected to conventional aging and two thermomechanical treatments. The hardness increment resulting from the thermomechanical treatments was 50% higher than the increment produced by conventional aging. The thermomechanical procedure, including two aging steps (double aging), produced a 5% International Annealed Copper Standard (IACS) higher increase in conductivity than the procedure including a single aging step. However, the former procedure did not lead to more efficient hardening in the studied alloy than the latter procedure because during the second aging step extensive recovery or even the onset of recrystallization tended to suppress precipitation hardening to some extent. After being subjected to a thermomechanical treatment that included three cold-drawing steps and one aging step, the studied alloy showed a tensile strength of 550 MPa with a conductivity of 74% IACS. Based on the obtained results as well as on the comparison with other Cu-Cr type alloys, some suggestions were given for improving the thermomechanical processing route of the studied alloy.

  1. Microstructure and mechanical properties of (Ti,Al,Zr)N/(Ti,Al,Zr,Cr)N films on cemented carbide substrates

    NASA Astrophysics Data System (ADS)

    Zhao, Shi-lu; Zhang, Jun; Zhang, Zhen; Wang, Shuang-hong; Zhang, Zheng-gui

    2014-01-01

    (Ti,Al,Zr)N/(Ti,Al,Zr,Cr)N bilayer films were deposited on cemented carbide (WC-8%Co) substrates by multi-arc ion plating (MAIP) using two Ti-Al-Zr alloy targets and one pure Cr target. To investigate the composition, morphology, and crystalline structure of the bilayer films, a number of complementary methods of elemental and structural analysis were used, namely, scanning electron microscopy (SEM), energy disperse X-ray spectroscopy (EDS), and X-ray diffraction (XRD). Adhesive strength and mechanical properties of the films were evaluated by scratch testing and Vickers microindentation, respectively. It is shown that the resulting films have a TiN-type face-centered cubic (FCC) structure. The films exhibit fully dense, uniform, and columnar morphology. Furthermore, as the bias voltages vary from -50 to -200 V, the microhardness (max. Hv0.01 4100) and adhesive strength (max. > 200 N) of the bilayer films are superior to those of the (Ti,Al,Zr)N and (Ti,Al,Zr,Cr)N monolayer films.

  2. The Influence of Tungsten on the Chemical Composition of a Temporally Evolving Nanostructure of a Model Ni-Al-Cr Superalloy

    NASA Technical Reports Server (NTRS)

    Sudbrack, Chantal K.; Isheim, Dieter; Noebe, Ronald D.; Jacobson, Nathan S.; Seidman, David N.

    2004-01-01

    The influence of W on the temporal evolution of gamma' precipitation toward equilibrium in a model Ni-Al-Cr alloy is investigated by three-dimensional atom-probe (3DAP) microscopy and transmission electron microscopy (TEM). We report on the alloys Ni-10 Al-8.5 Cr (at.%) and Ni-10 Al-8.5 Cr-2 W (at.%), which were aged isothermally in the gamma + gamma' two-phase field at 1073 K, for times ranging from 0.25 to 264 h. Spheroidal-shaped gamma' precipitates, 5-15 nm diameter, form during quenching from above the solvus temperature in both alloys at a high number density (approx. 10(exp 23/cu m). As gamma' precipitates grow with aging at 1073 K, a transition from spheriodal- to cuboidal-shaped precipitates is observed in both alloys. The elemental partitioning and spatially resolved concentration profiles across the gamma' precipitates are obtained as a function of aging time from three-dimensional atom-by-atom reconstructions. Proximity histogram concentration profiles of the quaternary alloy demonstrate that W concentration gradients exist in gamma' precipitates in the as-quenched and 0.25-h aging states, which disappear after 1 h of aging. The diffusion coefficient of W in gamma' is estimated to be 6.2 x 10(exp -20) sq m/s at 1073 K. The W addition decreases the coarsening rate constant, and leads to stronger partitioning of Al to gamma' and Cr to gamma.

  3. SDAS, Si and Cu Content, and the Size of Intermetallics in Al-Si-Cu-Mg-Fe Alloys

    NASA Astrophysics Data System (ADS)

    Sivarupan, Tharmalingam; Taylor, John Andrew; Cáceres, Carlos Horacio

    2015-05-01

    Plates of Al-(a)Si-(b)Cu-Mg-(c)Fe alloys with varying content of (mass pct) Si ( a = 3, 4.5, 7.5, 9, 10, or 11), Cu ( b = 0, 1, or 4), and Fe ( c = 0.2, 0.5 or 0.8) were cast in sand molds with a heavy chill at one end to ensure quasi-directional solidification over a wide range of Secondary Dendrite Arm Spacing (SDAS). Statistical analysis on the size of the β-Al5FeSi, α-Al8Fe2Si, or Al2Cu intermetallics on Backscattered Electron images showed that a high Si content reduced the size of the β platelets in alloys with up to 0.5 Fe content regardless of the SDAS, whereas at small SDAS the refining effect extended up to 0.8 Fe, and involved α-phase intermetallics which replaced the beta platelets at those concentrations. At low Si contents, a high Cu level appeared to have similar refining effects as increased Si, through the formation of α-phase particles in the post-eutectic stage which agglomerated with the Al2Cu intermetallics. A high content of Si appears to make the overall refining process less critical in terms of SDAS/cooling rate.

  4. Elastic Modulus Measurement of ORNL ATF FeCrAl Alloys

    SciTech Connect

    Thompson, Zachary T.; Terrani, Kurt A.; Yamamoto, Yukinori

    2015-10-01

    Elastic modulus and Poisson’s ratio for a number of wrought FeCrAl alloys, intended for accident tolerant fuel cladding application, are determined via resonant ultrasonic spectroscopy. The results are reported as a function of temperature from room temperature to 850°C. The wrought alloys were in the fully annealed and unirradiated state. The elastic modulus for the wrought FeCrAl alloys is at least twice that of Zr-based alloys over the temperature range of this study. The Poisson’s ratio of the alloys was 0.28 on average and increased very slightly with increasing temperature.

  5. Development and quality assessments of commercial heat production of ATF FeCrAl tubes

    SciTech Connect

    Yamamoto, Yukinori

    2015-09-01

    Development and quality assessment of the 2nd generation ATF FeCrAl tube production with commercial manufacturers were conducted. The manufacturing partners include Sophisticated Alloys, Inc. (SAI), Butler, PA for FeCrAl alloy casting via vacuum induction melting, Oak Ridge National Laboratory (ORNL) for extrusion process to prepare the master bars/tubes to be tube-drawn, and Rhenium Alloys, Inc. (RAI), North Ridgeville, OH, for tube-drawing process. The masters bars have also been provided to Los Alamos National Laboratory (LANL) who works with Century Tubes, Inc., (CTI), San Diego, CA, as parallel tube production effort under the current program.

  6. The effect of yttrium and thorium on the oxidation behavior of Ni-Cr-Al alloys

    NASA Technical Reports Server (NTRS)

    Kumar, A.; Douglass, D. L.; Nasrallah, M.

    1974-01-01

    The investigation reported included a determination of the optimum composition of a Ni-Cr-Al ternary alloy with respect to oxidation resistance and minimum film-spalling tendencies. Yttrium and thorium in small amounts were added to the ternary alloy and an investigation of the oxidation mechanism and the oxide scale adherence was conducted. It was found that the oxidation mechanism of Ni-Cr-Al ternary alloys depends upon the composition of the alloy as well as the time, oxygen pressure, and temperature of oxidation.

  7. Thermal- and electromigration-induced stresses in passivated Al- and AlSiCu-interconnects

    SciTech Connect

    Beckers, D.; Schroeder, H.; Schilling, W.; Eppler, I.

    1997-05-01

    Mechanical stresses in microelectronic devices are of special interest because of degradation effects in microelectronic circuits such as stress induced voiding or electromigration. Al and al-alloys are commonly used as interconnect materials in integrated electronic devices. Stress induced voiding and degradation of metal lines by electromigration are closely related to the stresses in the lines. The authors have studied the strain and stress evolution during thermal cycling, isothermal relaxation and due to electromigration in passivated Al and AlSi(1%)Cu(0.5%) lines by X-Ray diffraction with variation of experimental parameters such as the aspect ratio and the electrical current density. Furthermore the extent of voiding and plastic shear deformation has been determined from the experimental metal strains with the help of finite element calculations. Main results are: (1) During thermal cycling the voiding is less than 2 {center_dot} 10{sup {minus}3}. The extent of plastic shear deformation increases with increasing line width and with decreasing flowstress. (2) During isothermal relaxation void growth occurs but no significant change in the plastic shear deformation. (3) An electric current in the lines causes no measurable additional change of the volume averaged stresses up to line failure.

  8. The effect of copper, chromium, and zirconium on the microstructure and mechanical properties of Al-Zn-Mg-Cu alloys

    NASA Technical Reports Server (NTRS)

    Wagner, John A.; Shenoy, R. N.

    1991-01-01

    The present study evaluates the effect of the systematic variation of copper, chromium, and zirconium contents on the microstructure and mechanical properties of a 7000-type aluminum alloy. Fracture toughness and tensile properties are evaluated for each alloy in both the peak aging, T8, and the overaging, T73, conditions. Results show that dimpled rupture essentially characterize the fracture process in these alloys. In the T8 condition, a significant loss of toughness is observed for alloys containing 2.5 pct Cu due to the increase in the quantity of Al-Cu-Mg-rich S-phase particles. An examination of T8 alloys at constant Cu levels shows that Zr-bearing alloys exhibit higher strength and toughness than the Cr-bearing alloys. In the T73 condition, Cr-bearing alloys are inherently tougher than Zr-bearing alloys. A void nucleation and growth mechanism accounts for the loss of toughness in these alloys with increasing copper content.

  9. Multiple diffraction in an icosahedral Al-Cu-Fe quasicrystal

    NASA Astrophysics Data System (ADS)

    Fan, C. Z.; Weber, Th.; Deloudi, S.; Steurer, W.

    2011-07-01

    In order to reveal its influence on quasicrystal structure analysis, multiple diffraction (MD) effects in an icosahedral Al-Cu-Fe quasicrystal have been investigated in-house on an Oxford Diffraction four-circle diffractometer equipped with an Onyx™ CCD area detector and MoKα radiation. For that purpose, an automated approach for Renninger scans (ψ-scans) has been developed. Two weak reflections were chosen as the main reflections (called P) in the present measurements. As is well known for periodic crystals, it is also observed for this quasicrystal that the intensity of the main reflection may significantly increase if the simultaneous (H) and the coupling (P-H) reflections are both strong, while there is no obvious MD effect if one of them is weak. The occurrence of MD events during ψ-scans has been studied based on an ideal structure model and the kinematical MD theory. The reliability of the approach is revealed by the good agreement between simulation and experiment. It shows that the multiple diffraction effect is quite significant.

  10. Thermal imaging of Al-CuO thermites

    NASA Astrophysics Data System (ADS)

    Densmore, John; Sullivan, Kyle; Kuntz, Joshua; Gash, Alex

    2013-06-01

    We have performed spatial in-situ temperature measurements of aluminum-copper oxide thermite reactions using high-speed color pyrometry. Electrophoretic deposition was used to create thermite microstructures. Tests were performed with micron- and nano-sized particles at different stoichiometries. The color pyrometry was performed using a high-speed color camera. The color filter array on the image sensor collects light within three spectral bands. Assuming a gray-body emission spectrum a multi-wavelength ratio analysis allows a temperature to be calculated. An advantage of using a two-dimensional image sensor is that it allows heterogeneous flames to be measured with high spatial resolution. Light from the initial combustion of the Al-CuO can be differentiated from the light created by the late time oxidization with atmosphere. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  11. Quantification of Microsegregation in Cast Al-Si-Cu Alloys

    NASA Astrophysics Data System (ADS)

    Ganesan, M.; Thuinet, L.; Dye, D.; Lee, P. D.

    2007-08-01

    The random sampling approach offers an elegant yet accurate way of validating microsegregation models. However, both instrumental errors and interference from secondary phases complicate the treatment of randomly sampled microprobe data. This study demonstrates that the normal procedure of sorting the data for each element independently can lead to inaccurate estimation of segregation profiles within multicomponent, multiphase, aluminum alloys. A recently proposed alloy-independent approach is shown to more reliably isolate these interferences, allowing more accurate validation of microsegregation models. Application of this approach to examine solidification segregation of a 319-type alloy demonstrated that, for these slowly cooled castings, neither Sr or TiB2 additions significantly affected coring of Cu within the primary α-Al dendrites. Comparison against predictions of CALPHAD-type Gulliver-Scheil models was less satisfactory. Consideration of back-diffusion and morphology effects through a one-dimensional (1-D) numerical model do not improve the agreement. Possible reasons for the lack of agreement are hypothesized.

  12. Research of Mechanical Property Gradient Distribution of Al-Cu Alloy in Centrifugal Casting

    NASA Astrophysics Data System (ADS)

    Sun, Zhi; Sui, Yanwei; Liu, Aihui; Li, Bangsheng; Guo, Jingjie

    Al-Cu alloy castings are obtained using centrifugal casting. The regularity of mechanical property gradient distribution of Al-Cu alloy castings with the same centrifugal radius at different positions is investigated. The result shows that the tensile strength, yield strength, elongation and microscope hardness exhibit the following gradient distribution characteristic — high on both sides and low on the center. The trend of mechanical property gradient distribution of Al-Cu alloy increases with the increase in the rotation speed. Moreover, the mechanical properties of casting centerline two sides have asymmetry. The reason is that the grain size of casting centerline two sides and Al2Cu phase and Cu content change correspondingly.

  13. Effect of sintering on the relative density of Cr-coated diamond/Cu composites prepared by spark plasma sintering

    NASA Astrophysics Data System (ADS)

    Cui, Wei; Xu, Hui; Chen, Jian-hao; Ren, Shu-bin; He, Xin-bo; Qu, Xuan-hui

    2016-06-01

    Cr-coated diamond/Cu composites were prepared by spark plasma sintering. The effects of sintering pressure, sintering temperature, sintering duration, and Cu powder particle size on the relative density and thermal conductivity of the composites were investigated in this paper. The influence of these parameters on the properties and microstructures of the composites was also discussed. The results show that the relative density of Cr-coated diamond/Cu reaches ~100% when the composite is gradually compressed to 30 MPa during the heating process. The densification temperature increases from 880 to 915°C when the diamond content is increased from 45vol% to 60vol%. The densification temperature does not increase further when the content reaches 65vol%. Cu powder particles in larger size are beneficial for increasing the relative density of the composite.

  14. Deformation and annealing study of NiCrAlY

    NASA Technical Reports Server (NTRS)

    Ebert, L. J.; Trela, D. M.

    1978-01-01

    The elevated temperature properties (tensile and creep) of NiCrALY, a nickel base alloy containing nominally 16% chromium, 4% aluminum, and 2 to 3% yttria (Y2O3) were evaluated and the optimal combination of thermomechanical treatments for maximum creep resistance was determined. Stored strain energy in as-extruded bars (14:1 extrusion ratio) permitted the development of a large grain size in the material when it was annealed at the maximum safe temperature 2450 F (1343 C). With a one-hour anneal at this temperature, the relatively fine grain size of the as-extruded material was changed to one in which the average grain diameter approached 1 mm, and the aspect ratio was about 10. The material was capable of being cold worked (by rolling) in amounts greater than 30% reduction in area. When the cold worked material was given a relaxation treatment, consisting of heating one hour at 1600 F(871 C), and then a high temperature anneal at 2450 F (1343 C) for one hour, both the high temperature strength and the high temperature creep resistance of the material was further enhanced.

  15. Importance of doping and frustration in itinerant Fe-doped Cr2Al

    SciTech Connect

    Susner, M. A.; Parker, D. S.; Sefat, A. S.

    2015-05-12

    We performed an experimental and theoretical study comparing the effects of Fe-doping of Cr2Al, an antiferromagnet with a N el temperature of 670 K, with known results on Fe-doping of antiferromagnetic bcc Cr. (Cr1-xFex)2Al materials are found to exhibit a rapid suppression of antiferromagnetic order with the presence of Fe, decreasing TN to 170 K for x=0.10. Antiferromagnetic behavior disappears entirely at x≈0.125 after which point increasing paramagnetic behavior is exhibited. Moreover, this is unlike the effects of Fe doping of bcc antiferromagnetic Cr, in which TN gradually decreases followed by the appearance of a ferromagnetic state. Theoretical calculations explain that the Cr2Al-Fe suppression of magnetic order originates from two effects: the first is band narrowing caused by doping of additional electrons from Fe substitution that weakens itinerant magnetism; the second is magnetic frustration of the Cr itinerant moments in Fe-substituted Cr2Al. In pure-phase Cr2Al, the Cr moments have an antiparallel alignment; however, these are destroyed through Fe substitution and the preference of Fe for parallel alignment with Cr. This is unlike bulk Fe-doped Cr alloys in which the Fe anti-aligns with the Cr atoms, and speaks to the importance of the Al atoms in the magnetic structure of Cr2Al and Fe-doped Cr2Al.

  16. Optical properties of undoped and Mg doped CuCrO{sub 2} powders synthesized by sol-gel route

    SciTech Connect

    Srinivasan, Radhakrishnan; Bolloju, Satish

    2014-01-28

    In this work, CuCrO{sub 2} was synthesized by sol-gel method using citric acid as a gelling agent. The different parameters like ratio of citric acid to metal ions, calcination temperature, and duration were studied. A green colored powder with particle size around 300 nm was formed at the calcination temperature of 800 °C for four hours duration. The increase in temperature has a profound impact on crystallite size and in turn effected the optical properties. Band gap of the obtained CuCrO{sub 2} has varied from 2.3 to 1.7 eV by increasing the temperature from 800 °C to 900 °C. Doping studies were performed by introducing Mg{sup 2+} ion to substitute Cr{sup 3+} in CuCrO{sub 2}. X-ray powder diffraction and SEM studies on 2% Mg doped samples indicated a clear formation of side phases. According to the X-ray powder patterns, the reflections from side phases were increasing with the increase in doping concentrations of Mg from 2 to 5%. The side phases were found to be MgCr{sub 2}O{sub 4} spinel and CuO. The band gap has decreased for doped samples in comparison to undoped one. In this paper, sol-gel synthesis and characterization by Xray powder diffraction, SEM studies and UV-Vis-Diffuse Reflectance spectra are presented.

  17. RF reactive sputter deposition and characterization of transparent CuAlO2 thin films

    NASA Astrophysics Data System (ADS)

    Lu, Y. M.; He, Y. B.; Yang, B.; Polity, A.; Volbers, N.; Neumann, C.; Hasselkamp, D.; Meyer, B. K.

    2006-09-01

    CuAlO2 thin films have been prepared on quartz glass and sapphire substrates by radio-frequency (RF) reactive sputtering using a CuAlO2 ceramic target. The deposition process was optimized by varying the sputter parameters, such as the substrate temperature and the oxygen flow. In addition a post-growth annealing has been carried out. X-ray diffraction (XRD) revealed that the as-sputtered films are amorphous, and crystallize in the delafossite-type CuAlO2 or in a phase mixture of CuAlO2 and CuAl2O4 after annealing in air at 1100°C. The surface morphology of the films was characterized by scanning electron microscopy (SEM). The as-grown films are nearly stoichiometric in terms of Cu to Al ratio and have good depth homogeneity as examined by Rutherford backscattering spectroscopy (RBS) and secondary ion mass spectroscopy (SIMS), respectively. The optical bandgap of the films was estimated by wavelength-dependent transmission measurements at room temperature, which revealed a direct bandgap of 3.38 and 3.80 eV for the as-sputtered and post-growth annealed CuAlO2 films, respectively.

  18. Structural and Superconducting Properties of (Al2O3) y /CuTl-1223 Composites

    NASA Astrophysics Data System (ADS)

    Jabbar, Abdul; Qasim, Irfan; Waqee-ur-Rehman, M.; Zaman, Munawar; Nadeem, K.; Mumtaz, M.

    2015-01-01

    The effects of nano-Alumina (Al2O3) particles inclusion on the structural and superconducting transport properties of (Cu0.5Tl0.5)Ba2Ca2Cu3O10-δ (CuTl-1223) matrix were explored in detail. Different concentrations (i.e. y = 0-1.5 wt.%) of Al2O3 nanoparticles were added to a CuTl-1223 matrix to obtain the desired (Al2O3) y /CuTl-1223 nano-superconducting composites. No significant change was observed in the crystal structure and stoichiometry of the host CuTl-1223 superconducting phase after the addition of Al2O3 nanoparticles. This indicates the occupancy of these nanoparticles at the inter-granular spaces. The superconductivity was suppressed with increasing Al2O3 nanoparticles contents in the CuTl-1223 matrix. The suppression of superconducting properties is most probably due to a pair-breaking mechanism caused by the reflection/scattering of carriers across the insulating nano-Al2O3 particles present at the grain boundaries. The non-monotonic variation of the superconducting properties may be due to inhomogeneous distribution of Al2O3 nanoparticles at the grain boundaries.

  19. Microstructural dependence of annealing temperature in magnetron-sputtered Al-Si-Cu films

    NASA Astrophysics Data System (ADS)

    Liang, Ming-Kaan; Ling, Yong-Chien

    1993-09-01

    The effect of sputtering temperature, sputtering bias, and annealing temperature upon the sheet resistance, WO3 formation at the Al-Si-Cu/Ti-W interface, and diffraction intensity of the Al2Cu precipitates of magnetron-sputtered Al-Si-Cu films were investigated. Statistical methods and microcharacterization techniques were applied to study these effects. Statistical analysis verifies the effect of annealing temperature on the measured sheet resistance. Annealing temperature alone is the dominant factor upon the WO3 formation at the Al-Si-Cu/Ti-W interface and the Al2Cu (211) plane diffraction intensity. Annealed samples are of higher sheet resistance. Increase in sheet resistance is ascribed to the formation of interfacial WO3. Reduced electromigration is related to the formation of Al2Cu precipitates. Secondary ion mass spectrometry (SIMS) analysis of the as-deposited sample depicts the presence of an excess amount of oxygen atoms at the surface and the Al-Si-Cu/Ti-W and Ti-W/Ti interfaces. Rutherford backscattering spectrometry and SIMS analyses reveal the outdiffusion of W from the Ti-W layer toward the Al-Si-Cu layer, the presence of Si nodules at the Al-Si-Cu/Ti-W interface, and the formation of Ti silicides at the Ti/Si interface. These phenomena are confirmed by transmission electron microscopy, energy dispersive x-ray analysis, and scanning electron microscopy analyses. It is concluded that interfacial oxygen, which reacts with W to form WO3 upon annealing, warrants further reduction to yield films of better sheet resistance.

  20. Evaluation of the microstructure of Al-Cu-Li-Ag-Mg Weldalite (tm) alloys, part 4

    NASA Technical Reports Server (NTRS)

    Pickens, Joseph R.; Kumar, K. S.; Brown, S. A.; Gayle, Frank W.

    1991-01-01

    Weldalite (trademark) 049 is an Al-Cu-Li-Ag-Mg alloy designed to have ultrahigh strength and to serve in aerospace applications. The alloy displays significantly higher strength than competitive alloys in both naturally aged and artificially aged tempers. The strengthening phases in such tempers have been identified to, in part, explain the mechanical properties attained. In general, the alloy is strengthened by delta prime Al3Li and Guinier-Preston (GP) zones in the naturally aged tempers. In artificially aged tempers in slightly underaged conditions, strengthening is provided by several phases including GP zones, theta prime Al2Cu, S prime Al2CuMg, T(sub 1) Al2CuLi, and possibly a new phase. In the peak strength artificially aged tempers, T(sub 1) is the predominant strengthening phase.

  1. Development of ODS FeCrAl for compatibility in fusion and fission energy applications

    DOE PAGESBeta

    Pint, Bruce A.; Dryepondt, Sebastien N.; Unocic, Kinga A.; Hoelzer, David T.

    2014-11-15

    In this paper, oxide dispersion strengthened (ODS) FeCrAl alloys with 12–15% Cr are being evaluated for improved compatibility with Pb-Li for a fusion energy application and with high temperature steam for a more accident-tolerant light water reactor fuel cladding application. A 12% Cr content alloy showed low mass losses in static Pb-Li at 700°C, where a LiAlO2 surface oxide formed and inhibited dissolution into the liquid metal. All the evaluated compositions formed a protective scale in steam at 1200°C, which is not possible with ODS FeCr alloys. However, most of the compositions were not protective at 1400°C, which is amore » general and somewhat surprising problem with ODS FeCrAl alloys that is still being studied. More work is needed to optimize the alloy composition, microstructure and oxide dispersion, but initial promising tensile and creep results have been obtained with mixed oxide additions, i.e. Y2O3 with ZrO2, HfO2 or TiO2.« less

  2. Development of ODS FeCrAl for compatibility in fusion and fission energy applications

    SciTech Connect

    Pint, Bruce A.; Dryepondt, Sebastien N.; Unocic, Kinga A.; Hoelzer, David T.

    2014-11-15

    In this paper, oxide dispersion strengthened (ODS) FeCrAl alloys with 12–15% Cr are being evaluated for improved compatibility with Pb-Li for a fusion energy application and with high temperature steam for a more accident-tolerant light water reactor fuel cladding application. A 12% Cr content alloy showed low mass losses in static Pb-Li at 700°C, where a LiAlO2 surface oxide formed and inhibited dissolution into the liquid metal. All the evaluated compositions formed a protective scale in steam at 1200°C, which is not possible with ODS FeCr alloys. However, most of the compositions were not protective at 1400°C, which is a general and somewhat surprising problem with ODS FeCrAl alloys that is still being studied. More work is needed to optimize the alloy composition, microstructure and oxide dispersion, but initial promising tensile and creep results have been obtained with mixed oxide additions, i.e. Y2O3 with ZrO2, HfO2 or TiO2.

  3. Development of ODS FeCrAl for Compatibility in Fusion and Fission Energy Applications

    NASA Astrophysics Data System (ADS)

    Pint, B. A.; Dryepondt, S.; Unocic, K. A.; Hoelzer, D. T.

    2014-12-01

    Oxide dispersion strengthened (ODS) FeCrAl alloys with 12-15% Cr are being evaluated for improved compatibility with Pb-Li for a fusion energy application and with high temperature steam for a more accident-tolerant light water reactor fuel cladding application. A 12% Cr content alloy showed low mass losses in static Pb-Li at 700°C, where a LiAlO2 surface oxide formed and inhibited dissolution into the liquid metal. All the evaluated compositions formed a protective scale in steam at 1200°C, which is not possible with ODS FeCr alloys. However, most of the compositions were not protective at 1400°C, which is a general and somewhat surprising problem with ODS FeCrAl alloys that is still being studied. More work is needed to optimize the alloy composition, microstructure and oxide dispersion, but initial promising tensile and creep results have been obtained with mixed oxide additions, i.e. Y2O3 with ZrO2, HfO2 or TiO2.

  4. Lattice Changes in Shape Memory CuZnAl Alloys on Aging at Room Temperature

    NASA Astrophysics Data System (ADS)

    Çakmak, Seyfettýn; Artunç, Ekrem; Kayali, Nejdet; Adigüzel, Osman

    2001-09-01

    The aging behavior of CuZnAl martensites (Cu-21.62 wt.% Zn-5.68 wt.% Al and Cu-24.98 wt.% Zn-4.43 wt.% Al) at about 297 K was studied by analyzing diffraction line profiles obtained by X-ray diffractometry. For the alloys, the change of the lattice parameters and the tetragonality associated with the aging time at room temperature were investigated. The habit planes versus the aging time at room temperature were calculated using the De Vos-Aernoundt-Delaey model, based on the crystallographic theory of Wechsler-Lieberman-Read(WLR), and from the DO3→ 18R martensite transformation theory.

  5. Microstructural variations in Cu/Nb and Al/Nb nanometallic multilayers

    SciTech Connect

    Polyakov, M. N.; Hodge, A. M.; Courtois-Manara, E.; Wang, D.; Kuebel, C.; Chakravadhanula, K.

    2013-06-17

    Miscible (Al/Nb) and immiscible (Cu/Nb) nanometallic multilayer systems were characterized by means of transmission electron microscopy techniques, primarily by automated crystallographic orientation mapping, which allows for the resolution of crystal structures and orientations at the nanoscale. By using this technique, distinctive Nb orientations in relation to the crystallographic state of the Al and Cu layer structures can be observed. Specifically, the Al and Cu layers were found to consist of amorphous, semi-amorphous, and crystalline regions, which affect the overall multilayer microstructure.

  6. 30 W Cr:LiSrAlF6 flashlamp-pumped pulsed laser

    NASA Astrophysics Data System (ADS)

    Samad, Ricardo Elgul; Baldochi, Sonia Licia; Calvo Nogueira, Gesse Eduardo; Dias Vieira, Nilson, Jr.

    2007-01-01

    We report the performance of a flashlamp-pumped Cr:LiSrAlF6 (Cr:LiSAF) laser developed and built by us. The pumping cavity incorporates filters that select the flashlamps' emission spectrum to match the absorption bands of the gain medium, allowing control of the amount of nonradiactive decay heat contribution of the optical cycle, minimizing thermal effects on the laser operation. The laser generated 2 J pulses at 15 Hz, resulting in 30 W of average power, the highest power extracted from a Cr:LiSAF rod laser to our knowledge. We were able to conclude that the laser efficiency is affected by resonator configuration changes due to thermal lens effects, and not to thermal quenching of the Cr:LiSAF luminescence.

  7. Properties and performance of the LiCaAlF6:Cr3+ laser material

    NASA Astrophysics Data System (ADS)

    Payne, Stephen A.; Chase, Lloyd L.; Atherton, L. Jeffrey; Caird, John A.; Kway, Wayne L.; Shinn, Michelle D.; Hughes, Robert S.; Smith, Larry K.

    1990-04-01

    The laser properties of the LiCaAlF6:Cr3+ (Cr:LiCAF) material are reviewed. The impact of the absorption and emission spectra on the laser performance is discussed. Laser-pumping and flashlamp-pumping experiments have shown that Cr:LiCAF has potential for high efficiency, although the presence of scattering losses remains a significant problem. The "gradient freeze" growth technique has been found to generate lower-loss material compared to Czochralski growth. The thermal lensing of Cr:LiCAF has been measured to be small and is in rough agreement with the magnitude expected on the basis of the intrinsic thermo-optical properties.

  8. 30 W Cr:LiSrAlF 6 flashlamp-pumped pulsed laser.

    PubMed

    Samad, Ricardo Elgul; Baldochi, Sonia Licia; Calvo Nogueira, Gesse Eduardo; Vieira, Nilson Dias

    2007-01-01

    We report the performance of a flashlamp-pumped Cr:LiSrAlF(6) (Cr:LiSAF) laser developed and built by us. The pumping cavity incorporates filters that select the flashlamps' emission spectrum to match the absorption bands of the gain medium, allowing control of the amount of nonradiactive decay heat contribution of the optical cycle, minimizing thermal effects on the laser operation. The laser generated 2 J pulses at 15 Hz, resulting in 30 W of average power, the highest power extracted from a Cr:LiSAF rod laser to our knowledge. We were able to conclude that the laser efficiency is affected by resonator configuration changes due to thermal lens effects, and not to thermal quenching of the Cr:LiSAF luminescence. PMID:17167580

  9. Hafnium influence on the microstructure of FeCrAl alloys

    NASA Astrophysics Data System (ADS)

    Geanta, V.; Voiculescu, I.; Stanciu, E.-M.

    2016-06-01

    Due to their special properties at high temperatures, FeCrAl alloys micro-alloyed with Zr can be regarded as potential materials for use at nuclear power plants, generation 4R. These materials are resistant to oxidation at high temperatures, to corrosion, erosion and to the penetrating radiations in liquid metal environments. Also, these are able to form continuously, by the self-generation process of an oxide coating with high adhesive strength. The protective oxide layers must be textured and regenerable, with a good mechanical strength, so that crack and peeling can not appear. To improve the mechanical and chemical characteristics of the oxide layer, we introduced limited quantities of Zr, Ti, Y, Hf, Ce in the range of 1-3%wt in the FeCrAl alloy. These elements, with very high affinity to the oxygen, are capable to stabilize the alumina structure and to improve the oxide adherence to the metallic substrate. FeCrAl alloys microalloyed with Hf were prepared using VAR (Vacuum Arc Remelting) unit, under high argon purity atmosphere. Three different experimental alloys have been prepared using the same metallic matrix of Fe-14Cr-5Al, by adding of 0.5%wt Hf, 1.0%wt Hf and respectively 1.5%wt Hf. The microhardness values for the experimental alloys have been in the range 154 ... 157 HV0.2. EDAX analyses have been performed to determine chemical composition on the oxide layer and in the bulk of sample and SEM analyze has been done to determine the microstructural features. The results have shown the capacity of FeCrAl alloy to form oxide layers, with different texture and rich in elements such as Al and Hf.

  10. Progress in the material development of LiCaAlF sub 6 :Cr sup 3+ laser crystals

    SciTech Connect

    Michelle D. Shinn.; Chase, L.L.; Caird, J.A.; Payne, S.A.; Atherton, L.J.; Kway, W.L.

    1990-03-01

    High Cr{sup 3+} doping levels, up to 8 mole percent, and low losses have been obtained with the tunable solid-state laser material LiCaAlF{sub 6}:Cr{sup 3+} (Cr:LiCAF). Measurements and calculations show that high pumping and extraction efficiencies are possible with the improved material. 13 refs., 4 figs., 1 tab.

  11. Microstructural observations in rapidly-solidified and heat-treated Ni3Al-Cr alloys

    NASA Technical Reports Server (NTRS)

    Carro, G.; Flanagan, W. F.

    1992-01-01

    The microstructural development following heat treatments of several rapidly-solidified Ni3Al-Cr and Ni3Al-Cr-B alloys is presented. Depending on composition, the as-solidified samples were either 100 percent gamma-prime phase - in the form of fine antiphase domains (APD) - or a mixture of gamma-prime (APDs) and beta phases. Upon annealing, the as-solidified microstructures transform to either APD-free gamma-prime or mixtures of gamma and gamma-prime phases. For those compositions where the quenched microstructures were 100 percent gamma-prime it was observed that APD coarsening followed conventional grain-growth kinetics, but when gamma phase precipitated on the APD boundaries the rate constant changed abruptly while the time exponent remained unaffected. It was also found that alloys containing critical amounts of chromium and boron are susceptible to precipitation of the boride Cr5B3.

  12. The effect of heat treatments on the microstructure and properties of FeAl+Cr

    SciTech Connect

    Munroe, P.R.; Kong, C.H.

    1997-12-31

    Microstructural studies were performed on an alloy of composition Fe{sub 45}Cr{sub 5}Al{sub 50} heat treated at 950 C and oil-quenched and then given isothermal annealing treatments for times up to 200 hours at either 400 C or 500 C. The observed microstructures were correlated with variations in hardness during isothermal annealing. It was deduced that the thermal vacancies retained following the initial heat treatment are removed relatively rapidly from the lattice, which leads to an initial drop in hardness. However, during prolonged annealing, the coarsening of both FeAl{sub 2} particles and a disordered {alpha}(Fe,Cr) phase leads to further softening. It was also deduced that the chromium atoms, which remain in solution, are effective solute strengtheners. The {alpha}(Fe,Cr) phase, which is coherent with the B2 matrix, appears to coarsen by a ledge growth mechanism.

  13. Photoluminescence of the Cr 3+ ions in α-ZnAl 2S 4:Cr single crystals

    NASA Astrophysics Data System (ADS)

    Broussell, Isabelle; Fortin, Emery; Kulyuk, Leonid; Popov, Sergei

    1996-09-01

    Photoluminescence measurements have been performed on chromium doped α-ZnAl 2S 4 spinel-type crystals in the temperature range 2-540 K. a single configuration coordinate diagram for the Cr 3+ ions in the α-ZnAl 2S 4 host is constructed to interpret the absorption and emission spectra and to allow a determination of the energy gaps between the 2E g - 2T 1g and 2E g - 4T 2g states. A fit of the measured temperature dependence of the luminescence decay, using a simplified four level model gave the lifetimes of the 2Eg, 2T1 g and 4T2 g excited levels and confirmed the gap values obtained from steady state measurements.

  14. The oxidation behavior of Ni-Cr-Al-2ThO2 alloys at 1093 and 1204 C.

    NASA Technical Reports Server (NTRS)

    Seltzer, M. S.; Wilcox, B. A.; Stringer, J.

    1972-01-01

    A pack diffusion process has been developed which permits the introduction of nearly 6 wt % Al into solid solution in the near surface region of TDNiCr (Ni-20 wt % Cr-2 vol % ThO2) and Ni-20Cr. Alumina scales, adherent under cyclic heating and cooling conditions, were produced on TDNiCr-5.86Al upon exposure to an environment of 1330 N/sq m (10 torr) or 101,000 N/sq m (760 torr) air at temperatures of 1093 and 1204 C. While the same oxidation kinetics were observed in isothermal tests for Ni-14.6Cr-5.86Al as were obtained for the TDNiCr-5.86Al, the dispersion-strengthened alloy exhibited superior oxide scale adhesion during cyclic testing. At 1204 C, continuous weight gains were observed under all test conditions for TDNiCr-5.86Al, in contrast to the weight loss with time which occurred several hours after exposure of TDNiCr to an oxidizing environment. TDNiCr with an initial aluminum surface concentration of 4.95 wt % has nearly comparable oxidation resistance to the TDNiCr-5.86Al alloy.

  15. Formation of (Cr, Al)UO4 from doped UO2 and its influence on partition of soluble fission products

    NASA Astrophysics Data System (ADS)

    Cooper, M. W. D.; Gregg, D. J.; Zhang, Y.; Thorogood, G. J.; Lumpkin, G. R.; Grimes, R. W.; Middleburgh, S. C.

    2013-11-01

    CrUO4 and (Cr, Al)UO4 have been fabricated by a sol-gel method, studied using diffraction techniques and modelled using empirical pair potentials. Cr2O3 was predicted to preferentially form CrUO4 over entering solution into hyper-stoichiometric UO2+x by atomic scale simulation. Further, it was predicted that the formation of CrUO4 can proceed by removing excess oxygen from the UO2 lattice. Attempts to synthesise AlUO4 failed, instead forming U3O8 and Al2O3. X-ray diffraction confirmed the structure of CrUO4 and identifies the existence of a (Cr, Al)UO4 phase for the first time (with a maximum Al to Cr mole ratio of 1:3). Simulation was subsequently used to predict the partition energies for the removal of fission products or fuel additives from hyper-stoichiometric UO2+x and their incorporation into the secondary phase. The partition energies are consistent only with smaller cations (e.g. Zr4+, Mo4+ and Fe3+) residing in CrUO4, while all divalent cations are predicted to remain in UO2+x. Additions of Al had little effect on partition behaviour. The reduction of UO2+x due to the formation of CrUO4 has important implications for the solution limits of other fission products as many species are less soluble in UO2 than UO2+x.

  16. Thermal stability of TiAlN/CrN multilayer coatings studied by atom probe tomography.

    PubMed

    Choi, Pyuck-Pa; Povstugar, Ivan; Ahn, Jae-Pyeong; Kostka, Aleksander; Raabe, Dierk

    2011-05-01

    This study is about the microstructural evolution of TiAlN/CrN multilayers (with a Ti:Al ratio of 0.75:0.25 and average bilayer period of 9 nm) upon thermal treatment. Pulsed laser atom probe analyses were performed in conjunction with transmission electron microscopy and X-ray diffraction. The layers are found to be thermally stable up to 600 °C. At 700 °C TiAlN layers begin to decompose into Ti- and Al-rich nitride layers in the out-of-plane direction. Further increase in temperature to 1000 °C leads to a strong decomposition of the multilayer structure as well as grain coarsening. Layer dissolution and grain coarsening appear to begin at the surface. Domains of AlN and TiCrN larger than 100 nm are found, together with smaller nano-sized AlN precipitates within the TiCrN matrix. Fe and V impurities are detected in the multilayers as well, which diffuse from the steel substrate into the coating along columnar grain boundaries. PMID:21146308

  17. Solute transport during the cyclic oxidation of Ni-Cr-Al alloys. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Nesbitt, J. A.

    1982-01-01

    Important requirements for protective coatings of Ni-Cr-Al alloys for gas turbine superalloys are resistance to oxidation accompanied by thermal cycling, resistance to thermal fatigue cracking. The resistance to oxidation accompanied by thermal cycling is discussed. The resistance to thermal fatigue cracking is also considered.

  18. Understanding phase stability of Al-Co-Cr-Fe-Ni high entropy alloys

    DOE PAGESBeta

    Zhang, Chuan; Zhang, Fan; Diao, Haoyan; Gao, Michael C.; Tang, Zhi; Poplawsky, Jonathan D.; Liaw, Peter K.

    2016-07-19

    The concept of high entropy alloy (HEA) opens a vast unexplored composition range for alloy design. As a well-studied system, Al-Co-Cr-Fe-Ni has attracted tremendous amount of attention to develop new-generation low-density structural materials for automobile and aerospace applications. In spite of intensive investigations in the past few years, the phase stability within this HEA system is still poorly understood and needs to be clarified, which poses obstacles to the discovery of promising Al-Co-Cr-Fe-Ni HEAs. In the present work, the CALPHAD approach is employed to understand the phase stability and explore the phase transformation within the Al-Co-Cr-Fe-Ni system. As a result,more » the phase-stability mapping coupled with density contours is then constructed within the composition - temperature space, which provides useful guidelines for the design of low-density Al-Co-Cr-Fe-Ni HEAs with desirable properties.« less

  19. The effect of Al and Cr additions on pack cementation zinc coatings

    NASA Astrophysics Data System (ADS)

    Chaliampalias, D.; Papazoglou, M.; Tsipas, S.; Pavlidou, E.; Skolianos, S.; Stergioudis, G.; Vourlias, G.

    2010-03-01

    Zinc is widely used as a protective coating material due to its corrosion resistant properties. The structure and oxidation resistance of Al and Cr mixed zinc coatings, deposited by pack cementation process, is thoroughly examined in this work. The morphology and chemical composition of the as-deposited and oxidized samples was accomplished by electron microscopy while the phase identification was performed by XRD diffraction analysis. The experimental results showed that the addition of aluminum or chromium in the pack mixture forms only Al and Cr rich phases on the surface of the specimens without affecting significantly the phase composition of the rest zinc coatings. In the case of Zn-Al coatings, the overlying layer contains high concentrations of Al together with lower amounts of zinc and iron and in Zn-Cr coatings this layer contains Cr, Fe and Zn atoms and has much smaller thickness. The presence of these additional layers promotes significantly the oxidation resistance of the zinc pack coatings and they preserve most of their initial thickness and chemical content when exposed to an aggressive environment while their oxidation mass gain was measured at low levels during the oxidation tests.

  20. Investigation of heat-resistant layered coating of Al-Cr-Ni

    NASA Astrophysics Data System (ADS)

    Shmorgun, V. G.; Trykov, Y. P.; Bogdanov, A. I.; Taube, A. O.

    2016-02-01

    The paper shows the transformation of the structure and phase composition of the layered coating system Al-Cr-Ni, obtained by the heat treatment of multilayered composite H20N80+AD1, welded by explosion, in the time range 1-300 hours. The cyclic heat resistance of the coating at 1150 ° C is studied.

  1. Gain measurements and average power capabilities of Cr(3+): LiSrAlF6

    NASA Astrophysics Data System (ADS)

    Hanson, F.; Bendall, C.; Poirier, P.

    1993-09-01

    Long wavelength operation of Cr:LiSrAlF6 is reported. The problem of thermal fracture effectively limits flash-lamp-pumped rod geometries to lower repetition rates. Thin face-pumped slabs allow higher average power capability, but peak gain could be limited by upconversion losses.

  2. Ion irradiation testing and characterization of FeCrAl candidate alloys

    SciTech Connect

    Anderoglu, Osman; Aydogan, Eda; Maloy, Stuart Andrew; Wang, Yongqiang

    2014-10-29

    The Fuel Cycle Research and Development program’s Advanced Fuels Campaign has initiated a multifold effort aimed at facilitating development of accident tolerant fuels. This effort involves development of fuel cladding materials that will be resistant to oxidizing environments for extended period of time such as loss of coolant accident. Ferritic FeCrAl alloys are among the promising candidates due to formation of a stable Al₂O₃ oxide scale. In addition to being oxidation resistant, these promising alloys need to be radiation tolerant under LWR conditions (maximum dose of 10-15 dpa at 250 – 350°C). Thus, in addition to a number of commercially available alloys, nuclear grade FeCrAl alloys developed at ORNL were tested using high energy proton irradiations and subsequent characterization of irradiation hardening and damage microstructure. This report summarizes ion irradiation testing and characterization of three nuclear grade FeCrAl cladding materials developed at ORNL and four commercially available Kanthal series FeCrAl alloys in FY14 toward satisfying FCRD campaign goals.

  3. Study of the effects of implantation on the high Fe-Ni-Cr and Ni-Cr-Al alloys

    NASA Technical Reports Server (NTRS)

    Ribarsky, M. W.

    1985-01-01

    A theoretical study of the effects of implantation on the corrosion resistance of Fe-Ni-Cr and Ni-Cr-Al alloys was undertaken. The purpose was to elucidate the process by which corrosion scales form on alloy surfaces. The experiments dealt with Ni implanted with Al, exposed to S at high temperatures, and then analyzed using scanning electron microscopy, scanning Auger spectroscopy and X-ray fluorescence spectroscopy. Pair bonding and tight-binding models were developed to study the compositions of the alloys and as a result, a new surface ordering effect was found which may exist in certain real alloys. With these models, the behavior of alloy constituents in the presence of surface concentrations of O or S was also studied. Improvements of the models to take into account the important effects of long- and short-range ordering were considered. The diffusion kinetics of implant profiles at various temperatures were investigated, and it was found that significant non-equilibrium changes in the profiles can take place which may affect the implants' performance in the presence of surface contaminants.

  4. Creep and oxidation behavior of modified CF8C-plus with W, Cu, Ni, and Cr

    DOE PAGESBeta

    Unocic, Kinga A.; Dryepondt, Sebastien N.; Yamamoto, Yukinori; Maziasz, Philip J.

    2016-02-01

    Here, the microstructures of modified CF8C-Plus (Fe-19Cr-12Ni-0.4W-3.8Mn-0.2Mo-0.6Nb-0.5Si-0.9C) with W and Cu (CF8CPWCu) and CF8CPWCu enhanced with 21Cr + 15Ni or 22Cr + 17.5Ni were characterized in the as-cast condition and after creep testing. When imaged at lower magnifications, the as-cast microstructure was similar among all three alloys as they all contained a Nb-rich interdendritic phase and Mn-based inclusions. Transmission electron microscopy (TEM) analysis showed the presence of nanoscale Cu-rich nanoprecipitates distributed uniformly throughout the matrix of CF8CPWCu, whereas in CF8CPWCu22/17, Cu precipitates were found primarily at the grain boundaries. The presence of these nanoscale Cu-rich particles, in addition to W-richmore » Cr23C6, nanoscale Nb carbides, and Z-phase (Nb2Cr2N2), improved the creep strength of the CF8CPWCu steel. Modification of CF8CPWCu with Cr and Ni contents slightly decreased the creep strength but significantly improved the oxidation behavior at 1073 K (800 °C). In particular, the addition of 22Cr and 17.5Ni strongly enhanced the oxidation resistance of the stainless steel resulting in a 100 degrees or greater temperature improvement, and this composition provided the best balance between improving both mechanical properties and oxidation resistance.« less

  5. Creep and Oxidation Behavior of Modified CF8C-Plus with W, Cu, Ni, and Cr

    NASA Astrophysics Data System (ADS)

    Unocic, Kinga A.; Dryepondt, Sebastien; Yamamoto, Yukinori; Maziasz, Philip J.

    2016-04-01

    The microstructures of modified CF8C-Plus (Fe-19Cr-12Ni-0.4W-3.8Mn-0.2Mo-0.6Nb-0.5Si-0.9C) with W and Cu (CF8CPWCu) and CF8CPWCu enhanced with 21Cr + 15Ni or 22Cr + 17.5Ni were characterized in the as-cast condition and after creep testing. When imaged at lower magnifications, the as-cast microstructure was similar among all three alloys as they all contained a Nb-rich interdendritic phase and Mn-based inclusions. Transmission electron microscopy (TEM) analysis showed the presence of nanoscale Cu-rich nanoprecipitates distributed uniformly throughout the matrix of CF8CPWCu, whereas in CF8CPWCu22/17, Cu precipitates were found primarily at the grain boundaries. The presence of these nanoscale Cu-rich particles, in addition to W-rich Cr23C6, nanoscale Nb carbides, and Z-phase (Nb2Cr2N2), improved the creep strength of the CF8CPWCu steel. Modification of CF8CPWCu with Cr and Ni contents slightly decreased the creep strength but significantly improved the oxidation behavior at 1073 K (800 °C). In particular, the addition of 22Cr and 17.5Ni strongly enhanced the oxidation resistance of the stainless steel resulting in a 100 degrees or greater temperature improvement, and this composition provided the best balance between improving both mechanical properties and oxidation resistance.

  6. The role of copper species on Cu/γ-Al2O3 catalysts for NH3-SCO reaction

    NASA Astrophysics Data System (ADS)

    Liang, Chunxia; Li, Xinyong; Qu, Zhenping; Tade, Moses; Liu, Shaomin

    2012-02-01

    UV-vis spectra, XRD, H2-TPR, TEM and ESR were used to characterize a series of Cu/γ-Al2O3 catalysts, which were prepared by incipient wetness impregnation using copper nitrate, copper acetate or copper sulfate as precursors, to study the role of Cu species on Cu/γ-Al2O3 catalysts for NH3-SCO reaction. It was found that the mixture of CuO phase and CuAl2O4 phase formed on various Cu/γ-Al2O3 catalysts, and the Cu species and dispersion had significant influence on the Cu/γ-Al2O3 activity. Highly dispersed CuO phase on the support would be related with its high activity for the NH3-SCO reaction.

  7. Catalytic ozonation of petroleum refinery wastewater utilizing Mn-Fe-Cu/Al2O 3 catalyst.

    PubMed

    Chen, Chunmao; Yoza, Brandon A; Wang, Yandan; Wang, Ping; Li, Qing X; Guo, Shaohui; Yan, Guangxu

    2015-04-01

    There is of great interest to develop an economic and high-efficient catalytic ozonation system (COS) for the treatment of biologically refractory wastewaters. Applications of COS require options of commercially feasible catalysts. Experiments in the present study were designed to prepare and investigate a novel manganese-iron-copper oxide-supported alumina-assisted COS (Mn-Fe-Cu/Al2O3-COS) for the pretreatment of petroleum refinery wastewater. The highly dispersed composite metal oxides on the catalyst surface greatly promoted the performance of catalytic ozonation. Hydroxyl radical mediated oxidation is a dominant reaction in Mn-Fe-Cu/Al2O3-COS. Mn-Fe-Cu/Al2O3-COS enhanced COD removal by 32.7% compared with a single ozonation system and by 8-16% compared with Mn-Fe/Al2O3-COS, Mn-Cu/Al2O3-COS, and Fe-Cu/Al2O3-COS. The O/C and H/C ratios of oxygen-containing polar compounds significantly increased after catalytic ozonation, and the biodegradability of petroleum refinery wastewater was significantly improved. This study illustrates potential applications of Mn-Fe-Cu/Al2O3-COS for pretreatment of biologically refractory wastewaters. PMID:25649390

  8. After-Corrosion Suppression Using Low-Temperature Al-Si-Cu Etching

    NASA Astrophysics Data System (ADS)

    Aoki, Hidemitsu; Ikawa, Eiji; Kikkawa, Takamaro; Teraoka, Yuden; Nishiyama, Iwao

    1991-07-01

    The authors investigated the low-temperature etching effect on Al-Si-Cu after-corrosion. The after-corrosion extent was evaluated from the corrosion point density generated on the rinsed Al-Si-Cu stripes after dry etching. As the etching temperature was reduced, after-corrosion was suppressed. In order to study the low-temperature etching effect, the authors analyzed the Cl compounds remaining on the Al-Si-Cu film by thermal desorption spectroscopy (TDS). TDS revealed that the Cl concentration remaining on the Al-Si-Cu film etched at -60°C after rinsing in water was smaller than that remaining on the film etched at 30°C. Consequently, suppression of after-corrosion by low temperature etching could be attributed to the smaller number of Al-Cu bonds remaining in the Al-Si-Cu etch surface after removal of the AlClx layer by rinsing with water. This fact is due to the reduction of chemical reaction and diffusion rate by lowering the substrate temperature.

  9. Effect of Silicon on the Thixoformability of Al-Si-Cu Alloys

    NASA Astrophysics Data System (ADS)

    Benati, Davi Munhoz; Zoqui, Eugênio José

    2014-09-01

    The thixoformability of new Al-Si-Cu alloys was evaluated and characterized by their microstructural and rheological behavior. Alloys Al1Si2.6Cu, Al2Si2.6Cu, Al4Si2.6Cu, and Al7Si2.6Cu were produced with the addition of Al5Ti1B grain refiner alloy. The materials were heat treated under two controlled conditions: holding times of 0, 30, 90, and 210 s and solid fraction of 45 and 60%. The evaluation of the microstructure and semisolid behavior was characterized by globule size, shape factor (SF), minimum stress to flow, maximum stress, and apparent viscosity. The heat treatment times promoted the globularization of solid phase particles to achieve better apparent viscosity results for the alloys treated for 210 s. Both 45 and 60% solid fraction showed no significant differences in terms of SF, but the alloys containing lower solid fraction showed better performance for apparent viscosity. Better working ranges for these new Al-Si-Cu alloys were determined reaching average strain of 0.5 MPa and apparent viscosity of 105 Pa s.

  10. IBA analysis and corrosion resistance of TiAlPtN/TiAlN/TiAl multilayer films deposited over a CoCrMo using magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Canto, C. E.; Andrade, E.; de Lucio, O.; Cruz, J.; Solís, C.; Rocha, M. F.; Alemón, B.; Flores, M.; Huegel, J. C.

    2016-03-01

    The corrosion resistance and the elemental profile of multilayer coatings of TiAlPtN/TiAlN/TiAl synthesized by Physical Vapor Deposition (PVD) reactive magnetron sputtering over a CoCrMo alloy substrate in 10 periods of 30 min each were analyzed and compared to those of the substrate alone and to that of a TiAlPtN single layer coating of the same thickness. The objective of the present work was to create multilayers with different amounts of Pt to enhance the corrosion resistance of a biomedical alloy of CoCrMo. Corrosion tests were performed using Simulated Body Fluid (SBF) using potentiodynamic polarization tests at typical body temperature. The elemental composition and thickness of the coatings were evaluated with the combination of two ion beam analysis (IBA) techniques: a Rutherford Backscattering Spectroscopy (RBS) with alpha beam and a Nuclear Reaction Analysis with a deuteron beam.

  11. Properties and features of structure formation CuCr-contact alloys in electron beam cladding

    SciTech Connect

    Durakov, Vasiliy G.; Dampilon, Bair V. E-mail: gnusov@rambler.ru; Gnyusov, Sergey F. E-mail: gnusov@rambler.ru

    2014-11-14

    The microstructure and properties of the contact CuCr alloy produced by electron-beam cladding have been investigated. The effect of the electron beam cladding parameters and preheating temperature of the base metal on the structure and the properties of the coatings has been determined. The bimodal structure of the cladding coating has been established. The short circuit currents tests have been carried out according to the Weil-Dobke synthetic circuit simulating procedure developed for vacuum circuit breakers (VCB) test in real electric circuits. Test results have shown that the electron beam cladding (EBC) contact material has better breaking capacity than that of commercially fabricated sintered contact material. The application of the technology of electron beam cladding for production of contact material would significantly improve specific characteristics and reliability of vacuum switching equipment.

  12. Energy levels and radiative rates for Cr-like Cu VI and Zn VII

    NASA Astrophysics Data System (ADS)

    Aggarwal, K. M.; Bogdanovich, P.; Keenan, F. P.; Kisielius, R.

    2016-09-01

    Energy levels and radiative rates (A-values) for transitions in Cr-like Cu VI and Zn VII are reported. These data are determined in the quasi-relativistic approach (QR), by employing a very large configuration interaction (CI) expansion which is highly important for these ions. No radiative rates are available in the literature to compare with our results, but our calculated energies are in close agreement with those compiled by NIST and other available theoretical data, for a majority of the levels. The A-values (and resultant lifetimes) are listed for all significantly contributing E1, E2 and M1 radiative transitions among the energetically lowest 322 levels of each ion.

  13. Phase-Specific Elastic/Plastic Interface Interactions in Layered Cr-NiAl Structures

    SciTech Connect

    Barabash, Rozaliya; Liu, W.; Tischler, Jonathan Zachary; Bei, Hongbin; Budai, John D

    2012-01-01

    The depth-dependent, as-grown and deformation-induced strain and dislocations partitioned through the interfaces in a two-phase layered NiAl-Cr(Mo) structure are directly measured at the mesoscale using 3-D X-ray microdiffraction. It is demonstrated that in the as-grown, undeformed state, neighboring submicron Cr solid solution and NiAl eutectic lamellae (doped with {approx}3% Mo) form a heterointerface with 180{sup o} rotation around a <1 1 2> pole. It is shown that the mechanical response to the indentation of a layered composite with alternating Cr(Mo)-NiAl lamellae is distinct from the response of single-phase materials. In the center of the indent, after the load is released, the NiAl lamellae are under compressive forward stresses (with the same sign as the indentation-induced compression) while Cr solid solution lamellae are under tensile back stresses (with opposite sign from the indentation load). The depth-dependent alternation of compressive/tensile residual strains in the neighboring Cr solid solution and NiAl lamellae is understood in the framework of the Mughrabi's composite model considering two types of structure elements: harder and softer regions. Under indentation, both kinds of lamellae are assumed to deform compatibly. After the load is released, residual forward stresses are formed in the harder lamellae, and back stresses are formed in the mechanically softer lamellae. Line-broadening analysis of the intensity distribution along the diffraction vector reveals a 15-times increase in dislocation density in the near-surface zone in the center of the indent. Such a large increase is typical for severe deformation.

  14. Microstructures, mechanical properties, and electrical resistivity of rapidly quenched Fe-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Naohara, T.; Inoue, A.; Minemura, T.; Masumoto, T.; Kumada, K.

    1982-03-01

    By the rapid quenching technique, ductile supersaturated ferrite solid solution with high hardness and strength as well as unusual electrical properties has been found in Fe-Cr-Al ternary system. This formation range is limited to less than about 35 at. pct Cr and 23 at. pct Al. The ferrite phase has fine grains of about 10 μm in diameter. Their hardness, yield strength, and tensile fracture strength increase with increase in the amounts of chromium and aluminum, and the highest values reach about 290 DPN, 720 MPa, and 740 MPa. These alloys are so ductile that no cracks are observed even after closely contacted bending test. The good strength and ductility remain almost unchanged on tempering for one hour until heated to about 923 K where a large amount of Cr2Al compound begins to precipitate preferentially along the grain boundaries of the ferrite phase. The room-temperature resistivity increases with increasing chromium and aluminum contents and reaches as high as 1.86 μ Ώ m for Fe50Cr30Al20 alloy. Also, the temperature coefficient of resistivity in the temperature range between room temperature and 773 K decreases with increasing chromium and aluminum contents and becomes zero in the vicinity of 20 to 30 at. pct Cr and 15 at. pct Al. Thus, the present alloys may be attractive as fine gauge high-resistance and/or standard-resistance wires and plates because of the unusual electrical properties combined with high strength and good ductility.

  15. Nucleation Effects in Thermally Managed Graphite Fiber-Reinforced Al-Cu and Al-Si Composites

    NASA Astrophysics Data System (ADS)

    Seong, H. G.; Lopez, H. F.; Gajdardziska-Josifovska, M.; Rohatgi, P. K.

    2007-11-01

    The influence of heat extraction through fiber reinforcements on the resultant solidification morphologies was investigated in cast Al-Cu and Al-Si alloy composites reinforced with graphite fibers (GRFs). For this purpose, the GRFs were externally cooled by exposing their ends to ambient air during pressure infiltration. It was found that in the Al-Cu system, heat extraction through the fiber ends promoted the development of single α-Al envelopes around the GRFs. In particular, radial growth of the α envelopes occurred with a planar solid/liquid solidification front as a result of heat extraction. Apparently, the high thermal conductivity of GRFs causes significant heat extraction to enable the development of a positive temperature gradient at the GRF/melt interface. High-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAD) unveiled the occurrence of (002) α-Al//(0002)GR orientation relationship at α-Al/GRF interfaces. Preferential nucleation of primary Si along the graphite surfaces of the GRF-reinforced Al-Si alloy composite was also promoted by external fiber heat extraction. However, in this case, numerous nucleation events along the fiber interfaces were common, as well as nucleation at active substrates within the constrained melt. Finally, differential thermal analysis (DTA) indicated that the onset temperatures for nucleation shift toward higher values (by 7 °C for the Al-Cu composite and 2 °C for the Al-Si composite) when compared with their corresponding matrix alloys.

  16. Advanced ODS FeCrAl alloys for accident-tolerant fuel cladding

    SciTech Connect

    Dryepondt, Sebastien N; Unocic, Kinga A; Hoelzer, David T; Pint, Bruce A

    2014-09-01

    ODS FeCrAl alloys are being developed with optimum composition and properties for accident tolerant fuel cladding. Two oxide dispersion strengthened (ODS) Fe-15Cr-5Al+Y2O3 alloys were fabricated by ball milling and extrusion of gas atomized metallic powder mixed with Y2O3 powder. To assess the impact of Mo on the alloy mechanical properties, one alloy contained 1%Mo. The hardness and tensile properties of the two alloys were close and higher than the values reported for fine grain PM2000 alloy. This is likely due to the combination of a very fine grain structure and the presence of nano oxide precipitates. The nano oxide dispersion was however not sufficient to prevent grain boundary sliding at 800 C and the creep properties of the alloys were similar or only slightly superior to fine grain PM2000 alloy. Both alloys formed a protective alumina scale at 1200 C in air and steam and the mass gain curves were similar to curves generated with 12Cr-5Al+Y2O3 (+Hf or Zr) ODS alloys fabricated for a different project. To estimate the maximum temperature limit of use for the two alloys in steam, ramp tests at a rate of 5 C/min were carried out in steam. Like other ODS alloys, the two alloys showed a significant increase of the mas gains at T~ 1380 C compared with ~1480 C for wrought alloys of similar composition. The beneficial effect of Yttrium for wrought FeCrAl does not seem effective for most ODS FeCrAl alloys. Characterization of the hardness of annealed specimens revealed that the microstructure of the two alloys was not stable above 1000 C. Concurrent radiation results suggested that Cr levels <15wt% are desirable and the creep and oxidation results from the 12Cr ODS alloys indicate that a lower Cr, high strength ODS alloy with a higher maximum use temperature could be achieved.

  17. High-Temperature Thermometer Using Cr-Doped GdAlO3 Broadband Luminescence

    NASA Technical Reports Server (NTRS)

    Eldridge, Jeffrey; Chambers, Matthew

    2011-01-01

    A new concept has been developed for a high-temperature luminescence-based optical thermometer that both shows the desired temperature sensitivity in the upper temperature range of present state-of-the-art luminescence thermometers (above 1,300 C), while maintaining substantial stronger luminescence signal intensity that will allow these optical thermometers to operate in the presence of the high thermal background radiation typical of industrial applications. This objective is attained by using a Cr-doped GdAlO3 (Cr:GdAlO3) sensor with an orthorhombic perovskite structure, resulting in broadband luminescence that remains strong at high temperature due to the favorable electron energy level spacing of Cr:GdAlO3. The Cr:GdAlO3 temperature (and pressure) sensor can be incorporated into, or applied onto, a component s surface when a non-contact surface temperature measurement is desired, or alternatively, the temperature sensor can be attached to the end of a fiber-optic probe that can then be positioned at the location where the temperature measurement is desired. In the case of the fiber-optic probe, both the pulsed excitation and the luminescence emission travel through the fiber-optic light guide. In either case, a pulsed light source provides excitation of the luminescence, and the broadband luminescence emission is collected. Real-time temperature measurements are obtain ed using a least-squares fitting algorithm that determines the luminescence decay time, which has a known temperature dependence established by calibration. Due to the broad absorption and emission bands for Cr:GdAlO3, there is considerable flexibility in the choice of excitation wavelength and emission wavelength detection bands. The strategic choice of the GdAlO3 host is based on its high crystal field, phase stability, and distorted symmetry at the Cr3+ occupation sites. The use of the broadband emission for temperature sensing at high temperatures is a key feature of the invention and is

  18. Effect of current reversal on the failure mechanism of Al-Cu-Si narrow interconnects

    NASA Astrophysics Data System (ADS)

    Kim, Choong-Un; Kang, S. H.; Morris, J. W.

    1996-02-01

    The work reported here concerns the effect of a brief exposure to a reversed current on the electromigration failure of narrow Al-Cu thin-film conducting lines. While the precise mechanism by which Cu retards electromigration in AlCu alloys is not fully understood, the consistent observation that electromigration failure is preceded by the sweeping of Cu from the failure site can be used to improve electromigration resistance by stabilizing the distribution of Cu. One way of doing this is to expose the Al-Cu line to a reverse current for some period of time. The present work shows that this method is particularly effective in thin lines with “quasi-bamboo” microstructures. It has the effect of building a reservoir of Cu at the upstream ends of the polygranular segments that are the preferred failure sites, and significantly increases both the mean time to failure, and the time to first failure of a distribution of lines. It can be inferred from these results that Al-Cu lines that conduct alternating current should be exceptionally resistant to electromigration failure.

  19. Fretting corrosion of CoCrMo and Ti6Al4V interfaces.

    PubMed

    Swaminathan, Viswanathan; Gilbert, Jeremy L

    2012-08-01

    Mechanically assisted corrosion (fretting corrosion, tribocorrosion etc.,) of metallic biomaterials is a primary concern for numerous implant applications, particularly in the performance of highly-loaded medical devices. While the basic underlying concepts of fretting corrosion or tribocorrosion and fretting crevice corrosion are well known, there remains a need to develop an integrated systematic method for the analysis of fretting corrosion involving metal-on-metal contacts. Such a method can provide detailed and quantitative information on the processes present and explore variations in surfaces, alloys, voltages, loadings, motion and solution conditions. This study reports on development of a fretting corrosion test system and presents elements of an in-depth theoretical fretting corrosion model that incorporates both the mechanical and the electrochemical aspects of fretting corrosion. To demonstrate the capabilities of the new system and validate the proposed model, experiments were performed to understand the effect of applied normal load on fretting corrosion performance of Ti6Al4V/Ti6Al4V, CoCrMo/Ti6Al4V, and CoCrMo/CoCrMo material couples under potentiostatic conditions with a fixed starting surface roughness. The results of this study show that fretting corrosion is affected by material couples, normal load and the motion conditions at the interface. In particular, fretting currents and coefficient of friction (COF) vary with load and are higher for Ti6Al4V/Ti6Al4V couple reaching 3 mA/cm(2) and 0.63 at about 73 MPa nominal contact stress, respectively. Ti6Al4V coupled with CoCrMo displayed lower currents (0.6 mA/cm(2)) and COF (0.3), and the fretting corrosion behavior was comparable to CoCrMo/CoCrMo couple (1.2 mA/cm(2) and 0.3, respectively). Information on the mechanical energy dissipated at the interface, the sticking behavior, and the load dependence of the inter-asperity distance calculated using the model elucidated the influence of

  20. Thermoelectric properties of Ni-doped CuAlO 2

    NASA Astrophysics Data System (ADS)

    Wongcharoen, Ngamnit; Gaewdang, Thitinai

    2009-07-01

    The polycrystalline Ni-doped CuAlO2 were obtained by solid state reaction method. The mixture of high purity grade of CuO, Al2O3 and Ni(NO3)2.6H2O powders was ground and then pressed by using uniaxial pressure. The obtained pellet was sintered in air at 1423 K for 24 h. XRD patterns showed the crystal structure of the as-sintered CuAl1-xNixO2 (0≤x≤0.10) belonging to rhombohedral, space group. No evidence of second phase was observed when Ni doping up to x=0.01. At Ni content x≥0.01 CuAl1-xNixO2 solid solution phase along with the CuO and CuAl2O4 phases were observed. From SEM micrographs, the grain size decreased from 6 to 2 μm when the amount of Ni in CuAl1-xNixO2 samples increased. Hall mobility and hole concentration of the as-sintered samples were obtained from Hall effect measurements at room temperature. The activation energy values deduced from the electrical resistivity measurements as a function of temperature were reported. The variation of Seebeck coefficient and power factor as a function of temperature was also investigated. From the experimental results, the substitution of Ni2+ ion in Cu+ site of CuAl1-xNixO2 material may be drawn.

  1. Bioaccessibility of Cr, Cu, Fe, Mg, Mn, Mo, Se and Zn from nutritional supplements by the unified BARGE method.

    PubMed

    Tokalıoğlu, Serife; Clough, Robert; Foulkes, Mike; Worsfold, Paul

    2014-05-01

    In this study, the Unified Bioaccessibility Research Group of Europe (BARGE) in vitro method was used to assess the bioaccessibility of Cr, Cu, Fe, Mg, Mn, Mo, Se, and Zn in ten nutritional supplement samples and three certified reference materials. The total digest, gastric phase and gastro-intestinal phase concentrations of Cu, Fe, Mg, Mn and Zn were determined by ICP-OES and Cr, Mo and Se by ICP-MS. The bioaccessible fractions of the elements in the gastric phase for the nutritional supplements were in the range 13-89% for Cr, 9-79% for Cu, 55-99% for Fe, 33-95% for Mg, 83-94% for Mn, 42-101% for Mo, 74-125% for Se and 81-104% for Zn. The range for the gastrointestinal phase was 6-65% for Cr, 27-66% for Cu, 3-14% for Fe, 34-91% for Mg, 53-62% for Mn, 40-109% for Mo, 53-146% for Se and 3-35% for Zn. PMID:24360457

  2. Tunable Magnetic Properties in CuCr2- x Fe x O4 Ceramics by Doping of Fe

    NASA Astrophysics Data System (ADS)

    Zhu, C. M.; Wang, L. G.; Bao, D. L. G. C.; Luo, H.; Tian, Z. M.; Yuan, S. L.

    2016-08-01

    CuCr2- x Fe x O4 ceramics have been successfully synthesized using the sol-gel method for the first time. With pure formation, material structure has been characterized by x-ray diffraction. The samples have been identified as having the spinel structure with formulae CuCr2- x Fe x O4. Micrographs obtained by scanning electron microscopy show the dense microstructure of the samples. The stoichiometric ratio of the ceramics has been measured through energy dispersive spectra. Magnetic properties of CuCr2- x Fe x O4 ceramics have been discussed. Temperature dependence of magnetization presents the gradually increasing irreversible temperature as the content of Fe element increases from x = 0 to 1. Coercive field ( H C), remanent magnetization ( M r), and saturation magnetization ( M S) respectively display the monotonous variation phenomena with increasing content of Fe. The increasing M r, M S and the decreasing H C can be attributed to the change of magnetic exchange interaction because of the doped Fe. It also proves that the magnetic properties of CuCr2- x Fe x O4 ceramics can be effectively tuned by the doping content of Fe.

  3. Oxide scales formed on Fe-Cr-Al-based model alloys exposed to oxygen containing molten lead

    NASA Astrophysics Data System (ADS)

    Weisenburger, A.; Jianu, A.; Doyle, S.; Bruns, M.; Fetzer, R.; Heinzel, A.; DelGiacco, M.; An, W.; Müller, G.

    2013-06-01

    Based on the state of the art oxide maps concerning oxidation behavior of Fe-Cr-Al model alloys at 800 and 1000 °C in oxygen atmosphere, ten compositions, belonging to this alloy system, were designed in order to tap the borders of the alumina stability domain, during their exposure to oxygen (10-6 wt.%) containing lead, at 400, 500 and 600 °C. Eight alloys, Fe-6Cr-6Al, Fe-8Cr-6Al, Fe-10Cr-5Al, Fe-14Cr-4Al, Fe-16Cr-4Al, Fe-6Cr-8Al, Fe-10Cr-7Al and Fe-12Cr-5Al, were found to be protected against corrosion in oxygen containing lead, either by a duplex layer (Fe3O4 + (Fe1-x-yCrxAly)3O4) or by (Fe1-x-yCrxAly)3O4, depending on the temperature at which they were exposed. Two alloys namely Fe-12Cr-7Al and Fe-16Cr-6Al were found to form transient aluminas, κ-Al2O3 (at 400 and 500 °C) and θ-Al2O3 (at 600 °C), as protective oxide scale against corrosion in oxygen containing lead. An oxide map illustrating the stability domain of alumina, grown on Fe-Cr-Al alloys when exposed to molten, oxygen containing lead, was drawn. The map includes also additional points, extracted from literature and corresponding to alumina forming alloys, when exposed to HLMs, which fit very well with our findings. Chromium and aluminium contents of 12.5-17 wt.% and 6-7.5 wt.%, respectively, are high enough to obtain thin, stable and protective alumina scales on Fe-Cr-Al-based alloys exposed to oxygen containing lead at 400, 500 and 600 °C. For the temperature range and exposure times used during the current evaluation, the growth rate of the alumina scale was low. No area with detached scale was observed and no trace of α-Al2O3 was detected.

  4. CuO nanoparticles encapsulated inside Al-MCM-41 mesoporous materials via direct synthetic route

    NASA Astrophysics Data System (ADS)

    Huo, Chengli; Ouyang, Jing; Yang, Huaming

    2014-01-01

    Highly ordered aluminum-containing mesoporous silica (Al-MCM-41) was prepared using attapulgite clay mineral as a Si and Al source. Mesoporous complexes embedded with CuO nanoparticles were subsequently prepared using various copper sources and different copper loadings in a direct synthetic route. The resulting CuO/Al-MCM-41 composite possessed p6mm hexagonally symmetry, well-developed mesoporosity, and relatively high BET surface area. In comparison to pure silica, these mesoporous materials embedded with CuO nanoparticles exhibited smaller pore diameter, thicker pore wall, and enhanced thermal stability. Long-range order in the aforementioned samples was observed for copper weight percentages as high as 30%. Furthermore, a significant blue shift of the absorption edge for the samples was observed when compared with that of bulk CuO. H2-TPR measurements showed that the direct-synthesized CuO/Al-MCM-41 exhibited remarkable redox properties compared to the post-synthesized samples, and most of the CuO nanoparticles were encapsulated within the mesoporous structures. The possible interaction between CuO and Al-MCM-41 was also investigated.

  5. CuO nanoparticles encapsulated inside Al-MCM-41 mesoporous materials via direct synthetic route

    PubMed Central

    Huo, Chengli; Ouyang, Jing; Yang, Huaming

    2014-01-01

    Highly ordered aluminum-containing mesoporous silica (Al-MCM-41) was prepared using attapulgite clay mineral as a Si and Al source. Mesoporous complexes embedded with CuO nanoparticles were subsequently prepared using various copper sources and different copper loadings in a direct synthetic route. The resulting CuO/Al-MCM-41 composite possessed p6mm hexagonally symmetry, well-developed mesoporosity, and relatively high BET surface area. In comparison to pure silica, these mesoporous materials embedded with CuO nanoparticles exhibited smaller pore diameter, thicker pore wall, and enhanced thermal stability. Long-range order in the aforementioned samples was observed for copper weight percentages as high as 30%. Furthermore, a significant blue shift of the absorption edge for the samples was observed when compared with that of bulk CuO. H2-TPR measurements showed that the direct-synthesized CuO/Al-MCM-41 exhibited remarkable redox properties compared to the post-synthesized samples, and most of the CuO nanoparticles were encapsulated within the mesoporous structures. The possible interaction between CuO and Al-MCM-41 was also investigated. PMID:24419589

  6. Deformation and fracture of a directionally solidified NiAl-28Cr-6Mo eutectic alloy

    NASA Technical Reports Server (NTRS)

    Chen, X. F.; Johnson, D. R.; Noebe, R. D.; Oliver, B. F.

    1995-01-01

    A directionally solidified alloy based on the NiAl-(Cr, Mo) eutectic was examined by transmission and scanning electron microscopy to characterize the microstructure and room temperature deformation and fracture behavior. The microstructure consisted of a lamellar morphology with a group of zone axes (111) growth direction for both the NiAl and (Cr, Mo) phases. The interphase boundary between the eutectic phases was semicoherent and composed of a well-defined dislocation network. In addition, a fine array of coherent NiAl precipitates was dispersed throughout the (Cr, Mo) phase. The eutectic morphology was stable at 1300 K with only coarsening of the NiAl precipitates occurring after heat treatment for 1.8 ks (500 h). Fracture of the aligned eutectic is characterized primarily by a crack bridging/renucleation mechanism and is controlled by the strength of the semicoherent interface between the two phases. However, contributions to the toughness of the eutectic may arise from plastic deformation of the NiAl phase and the geometry associated with the fracture surface.

  7. Experimental study and thermodynamic modeling of the Al-Co-Cr-Ni system

    NASA Astrophysics Data System (ADS)

    Gheno, Thomas; Liu, Xuan L.; Lindwall, Greta; Liu, Zi-Kui; Gleeson, Brian

    2015-10-01

    A thermodynamic database for the Al-Co-Cr-Ni system is built via the Calphad method by extrapolating re-assessed ternary subsystems. A minimum number of quaternary parameters are included, which are optimized using experimental phase equilibrium data obtained by electron probe micro-analysis and x-ray diffraction analysis of NiCoCrAlY alloys spanning a wide compositional range, after annealing at 900 °C, 1100 °C and 1200 °C, and water quenching. These temperatures are relevant to oxidation and corrosion resistant MCrAlY coatings, where M corresponds to some combination of nickel and cobalt. Comparisons of calculated and measured phase compositions show excellent agreement for the β-γ equilibrium, and good agreement for three-phase β-γ-σ and β-γ-α equilibria. An extensive comparison with existing Ni-base databases (TCNI6, TTNI8, NIST) is presented in terms of phase compositions.

  8. Cu-doped AlN: A possible spinaligner at room-temperature grown by molecular beam epitaxy?

    SciTech Connect

    Ganz, P. R.; Schaadt, D. M.

    2011-12-23

    Cu-doped AlN was prepared by plasma assisted molecular beam epitaxy on C-plane sapphire substrates. The growth conditions were investigated for different Cu to Al flux ratios from 1.0% to 4.0%. The formation of Cu-Al alloys on the surface was observed for all doping level. In contrast to Cu-doped GaN, all samples showed diamagnetic behavior determined by SQUID measurements.

  9. Investigation of thermal, mechanical and magnetic behaviors of the Cu-11%Al alloy with Ag and Mn additions

    SciTech Connect

    Silva, R.A.G.; Paganotti, A.; Gama, S.; Adorno, A.T.; Carvalho, T.M.; Santos, C.M.A.

    2013-01-15

    The investigation of thermal, mechanical and magnetic behaviors of the Cu-11%Al, Cu-11%Al-3%Ag, Cu-11%Al-10%Mn and Cu-11%Al-10%Mn-3%Ag alloys was made using microhardness measurements, differential scanning calorimetry, X-ray diffractometry, scanning electron microscopy, energy dispersion X-ray spectroscopy and magnetic moment change with applied field measurement. The results indicated that the Mn addition changes the phase stability range, the microhardness values and makes undetectable the eutectoid reaction in annealed Cu-11%Al and Cu-11%Al-3%Ag alloys while the presence of Ag does not modify the phase transformation sequence neither microhardness values of the annealed Cu-11%Al and Cu-11%Al-10%Mn alloys, but it increases the magnetic moment of this latter at about 2.7 times and decreases the rates of eutectoid and peritectoid reactions of the former. - Highlights: Black-Right-Pointing-Pointer The microstructure of Cu-Al alloy is modified in the Ag presence. Black-Right-Pointing-Pointer ({alpha} + {gamma}) phase is stabilized down to room temperature when Ag is added to Cu-Al alloy. Black-Right-Pointing-Pointer Ag-rich phase modifies the magnetic characteristics of Cu-Al-Mn alloy.

  10. Spark plasma sintering of a nanocrystalline Al-Cu-Mg-Fe-Ni-Sc alloy

    NASA Astrophysics Data System (ADS)

    Zúñiga, Alejandro; Ajdelsztajn, Leonardo; Lavernia, Enrique J.

    2006-04-01

    The microstructure and aging behavior of a nanocrystalline Al-Cu-Mg-Fe-Ni-Sc alloy was studied. The nanocrystalline powders were produced by milling at liquid nitrogen temperature and then consolidated using spark plasma sintering (SPS). The microstructure after SPS consisted of a bimodal aluminum grain structure (coarse-grained and fine-grained regions), along with Al9FeNi and Al2CuMg particles dispersed throughout. The microstructure observed in the as-consolidated sample is rationalized on the basis of high current densities that are generated during sintering. Solution treatment and aging of the SPS Al-Cu-Mg-Fe-Ni-Sc sample resulted in softening instead of hardening. This observation can be explained by the reduced amount of Cu, Mg, and Si in solid solution available to form S' Al2CuMg due to the precipitation of Al7FeCu2 and Si-rich particles, and by the fact that rodlike S' Al2CuMg particles could only precipitate out in the coarse-grained regions, greatly decreasing their influence on the hardness. This lack of precipitation in the fine-grained region is argued to represent a new physical observation and is rationalized on the basis of physical and thermodynamic effects. The nanocrystalline SPS Al-Cu-Mg-Fe-Ni-Sc sample was also extremely thermally stable, retaining a fine-grained structure even after solution treatment at 530°C for 5 h. The observed thermal stability is rationalized on the basis of solute drag and Zener pinning caused by the impurities introduced during the cryomilling process.

  11. Interatomic force interaction in an i-AlCuFe quasicrystal

    SciTech Connect

    Parshin, P. P.; Zemlyanov, M. G. Brand, R. A.

    2007-11-15

    Partial spectra of thermal vibrations of Al, Cu, and Fe atoms in an icosahedral quasicrystal have been obtained by the isotopic-contrast method in inelastic neutron scattering. Joint analysis of these results and the published data on the atomic and electronic structures of the icosahedral i-AlCuFe quasicrystal has been performed. A physical model of the quasicrystal structure is proposed that is in agreement with the existing experimental data and qualitatively describes the peculiarities of interatomic interaction.

  12. Thermal and structural characterization of Cu-Al-Mn-X (Ti, Ni) shape memory alloys

    NASA Astrophysics Data System (ADS)

    Canbay, C. Aksu; Genc, Z. Karagoz; Sekerci, M.

    2014-05-01

    In this study, the Cu-Al-Mn-X (X = Ni, Ti) shape memory alloys at the range of 10-12 at.% of aluminum and 4-5 at.% manganese were produced by arc melting. We have investigated the effects of the alloying elements on the transformation temperatures, and the structural and the magnetic properties of the quaternary Cu-Al-Mn-X (X = Ni, Ti) shape memory alloys. The evolution of the transformation temperatures was studied by differential scanning calorimetry with different heating and cooling rates. The characteristic transformation temperatures and the thermodynamic parameters were highly sensitive to variations in the aluminum and manganese content, and it was observed that the nickel addition into the Cu-Al-Mn system decreased the transformation temperature although Ti addition caused an increase in the transformation temperatures. The effect of the nickel and the titanium on the thermodynamic parameters such as enthalpy and entropy values was investigated. The structural changes of the samples were studied by X-ray diffraction measurements and by optical microscope observations at room temperature. It is evaluated that the element Ni has been completely soluble in the matrix, and the main phase of the Cu-Al-Mn-Ni sample is martensite, and due to the low solubility of the Ti, the Cu-Al-Mn-Ti sample has precipitates, and a martensite phase at room temperature. The magnetic properties of the Cu-Al-Mn, Cu-Al-Mn-Ni and Cu-Al-Mn-Ti samples were investigated, and the effect of the nickel and the titanium on the magnetic properties was studied.

  13. Influence of Zr alloying on the mechanical properties, thermal stability and oxidation resistance of Cr-Al-N coatings

    NASA Astrophysics Data System (ADS)

    Li, W. Z.; Chen, Q. Z.; Polcar, T.; Serra, R.; Cavaleiro, A.

    2014-10-01

    Cr-Al-N coatings with Zr alloying (Zr contents from 0 to 29.5 at.%) were deposited by d.c. reactive magnetron sputtering. The chemical composition and the morphology of as-deposited coatings were characterized, and the phase structure, mechanical properties and wear resistance of the coatings before and after thermal annealing were analyzed and evaluated. With the increase of Zr content, both Cr and N contents decrease whereas Al shows a growing trend. Low Zr (<26.9 at.%) coatings are stoichiometric and present a fcc NaCl-type B1 structure with columnar morphology, while high Zr (≥26.9 at.%) coatings are in N deficiency and have low crystallinity degree. The alloying of low contents of Zr improves the coating hardness and H/E ratio; however, for low ordered coatings these properties decrease significantly. After thermal annealing, fcc structure is kept in low Zr films whereas the crystalline degree is improved in the high Zr ones and their mechanical properties were slightly improved. Two coatings were selected for further testing, representatives of low (CrAlZr5N) and high (CrAlZr27N) Zr contents. The onset oxidation temperature is ∼900 °C and 600 °C for CrAlZr5N and CrAlZr27N coatings, respectively. Mainly Cr2O3 is formed on low Zr coatings whereas mixed oxides of ZrO2 and Cr2O3 are detected on CrAlZr27N sample after thermal exposure. In all tribological tests, low Zr coating presents lower wear rate than the CrAlZr27N coating. In general, the addition of very high Zr contents (>20 at.%) with N deficiency markedly weakens the mechanical properties and the oxidation resistance of Cr-Al-Zr-N coatings.

  14. Growth process of Cu2Al6B4O17 whiskers

    NASA Astrophysics Data System (ADS)

    Zhu, Chengcai; Nai, Xueying; Zhu, Donghai; Guo, Fengqin; Zhang, Yongxing; Li, Wu

    2013-01-01

    The reactions occurred and growth process in the preparation of copper aluminum borate (Cu2Al6B4O17) whiskers based on flux method (Al2(SO4)3/CuSO4/H3BO3 as raw materials, K2SO4 as flux) were investigated. The thermogravimetric and differential scanning calorimetry analysis (TG-DSC), inductively coupled plasma atomic emission spectrum analysis (ICP-AES) and X-ray diffraction analysis (XRD) results of reactants mixture quenched at various temperatures and phase diagrams of K2SO4-Al2(SO4)3 system and B2O3-Al2O3 system showed that the reaction process proceeds through three steps: the formation and decomposition of two different kinds of potassium aluminum sulfate (K3Al(SO4)3 and KAl(SO4)2); the formation of aluminum borate (Al4B2O9) and decomposition of copper sulfate (CuSO4) and boric acid (H3BO3); growth and formation of copper aluminum borate (Cu2Al6B4O17) whiskers. The scanning electron microscopy (SEM) analysis results indicated that morphology in growth of Cu2Al6B4O17 whiskers develops through three stages: nanoparticles, fan-shaped whiskers and agminate-needlelike whiskers.

  15. Preparation and characterization of α-Al2O3 film by low temperature thermal oxidation of Al8Cr5 coating

    NASA Astrophysics Data System (ADS)

    Zhang, Min; Xu, Bajin; Ling, Guoping

    2015-03-01

    In this paper, α-Al2O3 film was prepared by low temperature thermal oxidation of Al8Cr5 coating. The Al8Cr5 alloy coating was prepared on SUS430 stainless steel through a two-step approach including electrodepositing Cr/Al composite coating and subsequent heat treatment at 740 °C for 16 h. After mechanical polishing removal of voids on the surface, the Al8Cr5 coating was thermal oxidized at 720 °C in argon for 100 h. The samples were characterized by SEM, EDX, XRD, XPS and TEM. XPS detection on the surface of oxidized Al8Cr5 coating showed that the oxide film mainly consisted of Al2O3. TEM characterization of the oxide film showed that it was α-Al2O3 films ca. 110 nm. The formation of α-Al2O3 films at low temperature can be attributed to the formation of Cr2O3 nuclei at the initial stage of oxidation which lowers the nucleation energy barrier of α-Al2O3.

  16. YZ (Y = V, Cr; Z = Al, Ga) under pressure: a DFT study

    NASA Astrophysics Data System (ADS)

    Seema, K.; Kumar, Ranjan

    2014-09-01

    The structural, electronic and magnetic properties of Co-based Heusler compounds Co2YZ (Y = V, Cr; Z = Al, Ga) under pressure are studied using first principles density functional theory. The calculations are performed within generalized gradient approximation. The total magnetic moment decreases slightly on compression. Under application of external pressure, the valence band and conduction band are shifted downward which leads to the modification of electronic structure. There exists an indirect band gap along Г- X for all the alloys studied. Co2CrAl shows half-metallic nature up to 85 GPa. After this pressure transition from true half-metallic behavior to nearly half-metallic behavior is observed and at 90 GPa it shows metallic behavior. Co2CrGa shows nearly half-metallic behavior at ambient pressure, but true half-metallic behavior is observed as pressure is increased to 100 GPa. For Co2VGa, true half-metallic to nearly half-metallic transition is observed at 40 GPa and around 100 GPa, Co2VGa shows metallic behavior. For Co2VAl, true half-metallic behavior is not observed at ambient as well as higher pressures. The half metal-to-metal transition in Co2VAl and Co2CrAl is accompanied by quenching of magnetic moment.

  17. Nanostructured Ternary FeCrAl Oxide Photocathodes for Water Photoelectrolysis.

    PubMed

    Kondofersky, Ilina; Müller, Alexander; Dunn, Halina K; Ivanova, Alesja; Štefanić, Goran; Ehrensperger, Martin; Scheu, Christina; Parkinson, Bruce A; Fattakhova-Rohlfing, Dina; Bein, Thomas

    2016-02-17

    A sol-gel method for the synthesis of semiconducting FeCrAl oxide photocathodes for solar-driven hydrogen production was developed and applied for the production of meso- and macroporous layers with the overall stoichiometry Fe0.84Cr1.0Al0.16O3. Using transmission electron microscopy and energy-dispersive X-ray spectroscopy, phase separation into Fe- and Cr-rich phases was observed for both morphologies. Compared to prior work and to the mesoporous layer, the macroporous FeCrAl oxide photocathode had a significantly enhanced photoelectrolysis performance, even at a very early onset potential of 1.1 V vs RHE. By optimizing the macroporous electrodes, the device reached current densities of up to 0.68 mA cm(-2) at 0.5 V vs RHE under AM 1.5 with an incident photon-to-current efficiency (IPCE) of 28% at 400 nm without the use of catalysts. Based on transient measurements, this performance increase could be attributed to an improved collection efficiency. At a potential of 0.75 V vs RHE, an electron transfer efficiency of 48.5% was determined. PMID:26743183

  18. Phase formation in Au-Al and Cu-Al thin-film systems under ion beam bombardment

    SciTech Connect

    Chang, C.T.; Campisano, S.U.; Cannavo, S.; Rimini, E.

    1984-05-01

    Au-Al and Cu-Al thin film bilayers were bombarded at 80 K with Kr/sup +/ ions of 60--240 keV energy. The Au/sub 2/Al+AuAl/sub 2/ and Al/sub 4/Cu/sub 9/ phases formed during bombardment and they were investigated by backscattering and x-ray diffraction techniques. In all the cases the growth kinetics is linear with the parameter (fluence x interfacial deposited energy density)/sup 1//sup ///sup 2/ suggesting a correlation with a diffusion-like process. Comparison with calculations of diffusion enhanced within the collision cascade gives good agreement with the experimental results.

  19. β-Cyclodextrin assisted solubilization of Cu and Cr complexes of flavonoids in aqueous medium: A DNA-interaction study

    NASA Astrophysics Data System (ADS)

    Jabeen, Erum; Janjua, Naveed Kausar; Hameed, Shahid

    2014-07-01

    Cu and Cr complexes of three flavonoids (morin, quercetin and 6-hydroxyflavone) were synthesized and included in beta-cyclodextrin (βCD) with the objective of improving their pharmacokinetic profiles. Then binding with ds.DNA was studied to monitor their interactive tendencies at physiological conditions. The binding constants and other thermodynamic data from UV-vis spectroscopy and cyclic voltammetry revealed Cr-flavonoid-βCD to interact with ds.DNA at pH-7.4 through electrostatic mode of binding while Cu-flavonoid-βCD can intercalate into DNA. The strong binding propensity of Cu-flavonoid-βCD with ds.DNA encourages their application as anticancerous agent.

  20. Dissolution of Precipitates During Solution Treatment of Al-Mg-Si-Cu Alloys

    NASA Astrophysics Data System (ADS)

    Zhang, Xukai; Guo, Mingxing; Zhang, Jishan; Zhuang, Linzhong

    2016-02-01

    A model combining classical diffusion-controlled dissolution equation for a single spherical particle and Johnson-Mehl-Avrami-like equation is used to deal with dissolution process for different kinds of precipitations (Si, Mg2Si, Q(Al1.9Mg4.1Si3.3Cu)) in Al-Mg-Si-Cu alloys. The results reveal that the dissolution time of precipitates increases with increasing their sizes and solute concentrations in the alloy matrix; for the same size and concentration, their dissolution times follow Si > Q(Al1.9Mg4.1Si3.3Cu) > Mg2Si. Two precipitates (Mg2Si and Al1.9Mg4.1Si3.3Cu) with a size of about 700 nm were obtained in a cold rolled Al-Mg-Si-Cu-Zn alloy, and the complete dissolution time is about 15 seconds, which is basically the same as the calculated time by the developed model. The theoretical prediction of dissolution time can be greatly used to design solution treatment and thermomechanical processing parameters of Al-Mg-Si-Cu alloys.

  1. Comparison of GRCop-84 to Other Cu Alloys with High Thermal Conductivities

    NASA Technical Reports Server (NTRS)

    deGroh, Henry C., III; Ellis, David L.; Loewenthal, William S.

    2007-01-01

    The mechanical properties of six highly conductive copper alloys, GRCop-84, AMZIRC, GlidCop Al-15, Cu-1Cr-0.1Zr, Cu-0.9Cr, and NARloy-Z were compared. Tests were done on as-received hard drawn material, and after a heat treatment designed to simulate a brazing operation at 935 C. In the as-received condition AMZIRC, GlidCop Al-15, Cu- 1Cr-0.1Zr and Cu-0.9Cr had excellent strengths at temperatures below 500 C. However, the brazing heat treatment substantially decreased the mechanical properties of AMZIRC, Cu-1Cr-0.1Zr, Cu-0.9Cr, and NARloy-Z. The properties of GlidCop Al-15 and GRCop-84 were not significantly affected by the heat treatment. Thus there appear to be advantages to GRCop-84 over AMZIRC, Cu-1Cr-0.1Zr, Cu-0.9Cr, and NARloy-Z if use or processing temperatures greater than 500 C are expected. Ductility was lowest in GlidCop Al-15 and Cu-0.9Cr; reduction in area was particularly low in GlidCop Al-15 above 500 C, and as- received Cu-0.9Cr was brittle between 500 and 650 C. Tensile creep tests were done at 500 and 650 C; the creep properties of GRCop-84 were superior to those of brazed AMZIRC, Cu-1Cr- 0.1Zr, Cu-0.9Cr, and NARloy-Z. In the brazed condition, GRCop-84 was superior to the other alloys due to its greater strength and creep resistance (compared to AMZIRC, Cu-1Cr-0.1Zr, Cu-0.9Cr, and NARloy-Z) and ductility (compared to GlidCop Al-15).

  2. Effect of surface roughness on the development of protective Al 2O 3 on Fe-10Al (at.%) alloys containing 0-10 at.% Cr

    NASA Astrophysics Data System (ADS)

    Zhang, Z. G.; Hou, P. Y.; Gesmundo, F.; Niu, Y.

    2006-11-01

    The effect of alloy surface roughness, achieved by different degrees of surface polishing, on the development of protective alumina layer on Fe-10 at.% Al alloys containing 0, 5, and 10 at.% Cr was investigated during oxidation at 1000 °C in 0.1 MPa oxygen. For alloys that are not strong Al 2O 3 formers (Fe-10Al and Fe-5Cr-10Al), the rougher surfaces increased Fe incorporation into the overall surface layer. On the Fe-10Al, more iron oxides were formed in a uniform layer of mixed aluminum- and iron-oxides since the layer was thicker. On the Fe-5Cr-10Al, more iron-rich nodules developed on an otherwise thin Al 2O 3 surface layer. These nodules nucleated preferentially along surface scratch marks but not on alloy grain boundaries. For the strong Al 2O 3-forming Fe-10Cr-10Al alloy, protective alumina surface layers were observed regardless of the surface roughness. These results indicate that the formation of a protective Al 2O 3 layer on Fe-Cr-Al surfaces is not dictated by Al diffusion to the surface. More cold-worked surfaces caused an enhanced Fe diffusion, hence produced more Fe-rich oxides during the early stage of oxidation.

  3. Wetting of TiC by Al-Cu alloys and interfacial characterization.

    PubMed

    Contreras, A

    2007-07-01

    The wetting behavior and the interfacial reactions that occurred between molten Al-Cu alloys (1, 4, 8, 20, 33, and 100 wt% Cu) and solid TiC substrates were studied by the sessile drop technique in the temperature range of 800-1130 degrees C. The effect of wetting behavior on the interfacial reaction layer was studied. All the Al-Cu alloys react with TiC at the interface forming an extensive reaction layer. The interface thickness varied with the samples, and depends on the temperature, chemical composition of the alloy and the time of the test. Wetting increases with increasing concentration of copper in the Al-Cu alloy at 800 and 900 degrees C. In contrast, at higher temperature such as 1000 degrees C wetting decreases with increasing copper content. The spreading kinetics and the work of adhesion were evaluated. The high values of activation energies indicated that spreading is not a simple viscosity controlled phenomenon but is a chemical reaction process. The spreading of the aluminum drop is observed to occur according to the formation of Al4C3, CuAl2O4, CuAl2, TiCux mainly, leading to a decreases in the contact angle. As the contact angle decreases the work of adhesion increases with increasing temperature. Al-Cu/TiC assemblies showed cohesive fracture corresponding to a strong interface. However, using pure Cu the adhesion work is poor, and the percentage of cohesion work is also too low (27-34%). PMID:17359993

  4. Comparative study of hydrogen sulfide adsorption in the MIL-53(Al, Cr, Fe), MIL-47(V), MIL-100(Cr), and MIL-101(Cr) metal-organic frameworks at room temperature.

    PubMed

    Hamon, Lomig; Serre, Christian; Devic, Thomas; Loiseau, Thierry; Millange, Franck; Férey, Gérard; De Weireld, Guy

    2009-07-01

    Hydrogen sulfide gravimetric isotherm adsorption measurements were carried out on MIL-53(Al, Cr, Fe), MIL-47(V), MIL-100(Cr), and MIL-101(Cr) metal-organic frameworks (MOFs). A two-step adsorption mechanism related to a breathing effect was observed for MIL-53 terephthalate-based MOFs. Methane adsorption measurements highlighted the regenerability of MIL-53(Al, Cr) and MIL-47(V) MOFs after H(2)S treatment, whereas MIL-100 and MIL-101 CH(4) adsorption capacities were significantly decreased. PMID:19505146

  5. Effect of delayed aging on mechanical properties of an Al-Cu-Mg alloy

    SciTech Connect

    Ravindranathan, S.P.; Kashyap, K.T.; Kumar, S.R.; Ramachandra, C.; Chatterji, B.

    2000-02-01

    The effect of delayed aging on mechanical properties is characteristically found in Al-Mg-Si alloys. Delayed aging refers to the time elapsed between solutionizing and artificial aging. Delayed aging leads to inferior properties. This effect was investigated in an Al-Cu-Mg alloy (AU2GN) of nominal composition Al-2Cu-1.5Mg-1Fe-1Ni as a function of delay. This alloy also showed a drop in mechanical properties with delay. The results are explained on the basis of Pashley's kinetic model to qualitatively explain the evolution of a coarse precipitate structure with delay. It is found that all the results of delayed aging in the Al-Cu-Mg alloys are similar to those found in Al-Mg-Si alloys.

  6. Cr diffusion in MgAl2O4 synthetic spinels: preliminary results

    NASA Astrophysics Data System (ADS)

    Freda, C.; Celata, B.; Andreozzi, G.; Perinelli, C.; Misiti, V.

    2012-04-01

    Chromian spinel is an accessory phase common in crustal and mantle rocks, including peridotites, gabbros and basalts. Spinel, it has been identified as one of the most effective, sensible, and versatile petrogenetic indicator in mafic and ultramafic rock systems due to the strict interdependence between its physico-chemical properties (chemical composition, cation configuration etc.) and genetic conditions (temperature, pressure, and chemical characteristics of the system). In particular, studies on intra- and inter-crystalline Mg-Fe2+, Cr-Al exchange demonstrated the close relationship between spinel composition and both degree of partial melting and equilibrium temperature of spinel-peridotites. Moreover, studies focused on the chemical zoning of Mg-Fe2+ and/or Cr-Al components in spinel have been used, combined with a diffusion model, to provide quantitative information on peridotites and gabbros pressure-temperature paths and on deformation mechanisms. Although these potentials, most of the experimental studies have been performed on spinels hosting a limited content of divalent iron (sensu stricto, MgAl2O4), whereas the scarce studies on Cr-Al inter-diffusion coefficient have been performed at 3-7 GPa as pressure boundary condition. In order to contribute to the understanding of processes occurring in the lithospheric mantle, we have initiated an experimental research project aiming at determining the Cr-Al inter-diffusion in spinel at 2 GPa pressure and temperature ranging from 1100 to 1250 °C. The experiments were performed in a end-loaded piston cylinder by using a 19 mm assembly and graphite-Pt double capsules. As starting materials we used synthetic Mg-Al spinel (200-300 μm in size) and Cr2O3 powder. Microanalyses of experimental charge were performed on polished carbon-coated mounts by electronic microprobe. Line elemental analyses were made perpendicular to the contact surface between Cr2O3 powder and spinel, at interval of 2 μm. By processing these

  7. Quantification of microsegregation during rapid solidification of Al-Cu powders

    NASA Astrophysics Data System (ADS)

    Prasad, Arvind; Nenein, Hani; Conlon, Kelly

    2006-05-01

    A new technique is introduced to quantify microsegregation during rapid solidification. The quantification involves calculation of the average solute solubility in the primary phase during solidification of an Al-Cu binary alloy. The calculation is based on using volume percent eutectic and weight percent of second phase (in the eutectic), which were obtained experimentally. Neutron diffraction experiments and stereology calculation on scanning electron microscope images were done on impulse atomized Al-Cu alloys of three compositions (nominal), 5 wt pct Cu, 10 wt pct Cu, and 17 wt pct Cu, atomized under N2 and He gas. Neutron diffraction experiments yielded weight percent CuAl2 data and stereology yielded volume percent eutectic data. These two data were first used to determine the weight percent eutectic. Using the weight percent eutectic and weight percent CuAl2 in mass and volume balance equations, the average solute solubility in the primary phase could be calculated. The experimental results of the amount of eutectic, tomography results from previous work, and results from the calculations suggest that the atomized droplets are in metastable state during the nucleation undercooling of the primary phase, and the effect of metastability propagates through to the eutectic formation stage. The metastable effect is more pronounced in alloys with higher solute composition.

  8. New type of Al-based decagonal quasicrystal in Al60Cr20Fe10Si10 alloy

    NASA Astrophysics Data System (ADS)

    He, Zhanbing; Ma, Haikun; Li, Hua; Li, Xingzhong; Ma, Xiuliang

    2016-03-01

    A new kind of decagonal quasicrystal (DQC) with a periodicity of 1.23 nm was observed in the as-cast quaternary Al60Cr20Fe10Si10 alloy. The intensity distribution of some spots in the selected-area electron diffraction pattern along the tenfold zone axis was found to be different from other Al-based DQCs. High-angle annular dark-field scanning transmission electron microscopy was adopted to reveal the structural features at an atomic level. Both the tenfold symmetry and symmetry-broken decagonal (D) clusters of 1.91 nm in diameter were found, but with structural characteristics different from the corresponding D clusters in the other Al-based DQCs. The neighboring D clusters are connected by sharing one edge rather than covering, suggesting the tiling model is better than the covering model for structural description.

  9. New type of Al-based decagonal quasicrystal in Al60Cr20Fe10Si10 alloy

    PubMed Central

    He, Zhanbing; Ma, Haikun; Li, Hua; Li, Xingzhong; Ma, Xiuliang

    2016-01-01

    A new kind of decagonal quasicrystal (DQC) with a periodicity of 1.23 nm was observed in the as-cast quaternary Al60Cr20Fe10Si10 alloy. The intensity distribution of some spots in the selected-area electron diffraction pattern along the tenfold zone axis was found to be different from other Al-based DQCs. High-angle annular dark-field scanning transmission electron microscopy was adopted to reveal the structural features at an atomic level. Both the tenfold symmetry and symmetry-broken decagonal (D) clusters of 1.91 nm in diameter were found, but with structural characteristics different from the corresponding D clusters in the other Al-based DQCs. The neighboring D clusters are connected by sharing one edge rather than covering, suggesting the tiling model is better than the covering model for structural description. PMID:26928759

  10. An analytical electron microscopic investigation of precipitation in an Al-Cu-Zn-Mg-Ag alloy.

    PubMed

    Hasan, F; Lorimer, G W

    1993-03-01

    The distribution, morphology, chemistry, and crystallography of the precipitates formed during aging of an Al-Cu-Zn-Mg-Ag alloy have been studied using analytical transmission electron microscopy. The first precipitates to appear during aging at 150 degrees C were thin hexagonal-shaped plate-like precipitates which formed on the (111)Al planes. These precipitates had a face-centred orthorhombic crystal structure and their composition was essentially CuAl2 although they contained a trace of silver. At peak hardness the microstructure consisted of the plate-like precipitates on (111)Al planes and theta' precipitates on (100)Al planes. Overaging resulted in the precipitation of equilibrium theta, CuAl2, which exhibited a lath morphology and an orientation-relationship with the matrix (210)Al magnitude of (110)gamma; (001)Al misoriented from (001)gamma by approximately 6 degrees. Prolonged overaging at 250 degrees C resulted in the formation of cuboid-shaped Al5(Cu,Zn)6Mg2 precipitates which had a cubic crystal structure and a cube:cube orientation-relationship with the matrix. PMID:8513176

  11. Luminescence of photoactivated pristine and Cr-doped MgAl2O4 spinel

    NASA Astrophysics Data System (ADS)

    Artemyeva, E. S.; Barinov, D. S.; Atitar, F. M.; Murashkina, A. A.; Emeline, A. V.; Serpone, N.

    2015-04-01

    This Letter reports a comparative study of the luminescence from pristine and Cr-doped MgAl2O4 spinel induced by different excitation mechanisms: photoluminescence (PhL), thermoluminescence (ThL) and Photo-Induced Chemisorption Luminescence (the PhICL phenomenon) to understand the mechanism of PhICL emission. Cr-doping alters the major pathway of physical relaxation through a luminescence pathway: quenching of the luminescence associated with intrinsic defects and appearance of the luminescence from Cr3+-states. The similarity between ThL and PhICL spectra suggest the mechanism of the PhICL phenomenon is due to electron transfer from the surface to the emission centers of luminescence; an energy transfer pathway is not precluded.

  12. Properties of Cr:LiSrAlF[sub 6] crystals for laser operation

    SciTech Connect

    Chai, B.H.T. ); Payne, S.A.; Smith, L.K.; Beach, R.J.; Tassano, J.H.; DeLoach, L.D.; Kway, W.L.; Solarz, R.W.; Krupke, W.F. )

    1994-08-20

    We have performed several physical and optical measurements on the Cr:LiSAF (LiSrAlF[sub 6]) laser material that are relevant to its laser performance, including thermal and mechanical properties, water durabilities, and Auger upconversion constants. The expansion coefficient, Young's modulus, fracture toughness, thermal conductivity, and heat capacity are all used to determine an overall thermomechanical figure of merit for the crystal. An investigation of the water durability suggests that the cooling solution should be maintained at pH = 7 to ameliorate problems associated with water dissolution. The Auger constant was found to become much more significant at higher Cr doping, in which excited-state migration leads to a substantial increase in the upconversion rate. We propose a design for a 50-W Cr:LiSAF laser system that is based on a detailed knowledge of all the relevant material parameters.

  13. Optical and physical properties of the LiSrAlF[sub 6]:Cr laser crystal

    SciTech Connect

    Smith, L.K.; Payne, S.A.; Tassano, J.B.; DeLoach, L.D.; Kway, W.L.; Krupke, W.F.

    1993-05-18

    We have measured several of the physical and optical parameters of the LiSrAlF[sub 6]:Cr or Cr:LiSAF laser material that are important to its laser performance, including the thermomechanical properties, water durabilities and Auger upconversion constants. A thermomechanical figure-of-merit has been determined from measurements of the fracture toughness, expansion coefficient, thermal conductivity, Young's modulus, and heat capacity. Tests of water durability suggest that a neutral pH of 7 is optimum to minimize water dissolution. The Auger effect was found to be a significant factor at higher Cr concentration, where excited-state migration leads to an increase in the upconversion rate. 17 refs, 1 fig, 4 tabs.

  14. Optical and physical properties of the LiSrAlF{sub 6}:Cr laser crystal

    SciTech Connect

    Smith, L.K.; Payne, S.A.; Tassano, J.B.; DeLoach, L.D.; Kway, W.L.; Krupke, W.F.

    1993-05-18

    We have measured several of the physical and optical parameters of the LiSrAlF{sub 6}:Cr or Cr:LiSAF laser material that are important to its laser performance, including the thermomechanical properties, water durabilities and Auger upconversion constants. A thermomechanical figure-of-merit has been determined from measurements of the fracture toughness, expansion coefficient, thermal conductivity, Young`s modulus, and heat capacity. Tests of water durability suggest that a neutral pH of 7 is optimum to minimize water dissolution. The Auger effect was found to be a significant factor at higher Cr concentration, where excited-state migration leads to an increase in the upconversion rate. 17 refs, 1 fig, 4 tabs.

  15. Coercivity enhancement in Mn-Al-Cu flakes produced by surfactant-assisted milling

    NASA Astrophysics Data System (ADS)

    Saravanan, P.; Hsu, Jen-Hwa; Vinod, V. T. P.; Černík, Miroslav; Kamat, S. V.

    2015-11-01

    We herein report the achievement of exceptionally high coercivity (Hc) values: 9.92 and 5.86 kOe at 5 and 300 K, respectively, for Mn55Al43Cu2 flakes produced by surfactant-assisted milling process without employing any heat-treatment. The use of surfactants such as oleic acid and oleylamine during milling yielded high-aspect ratio flakes for the Mn-Al-Cu alloy. Structural studies confirmed the presence of τ- and β-phases as the major constituents in the Mn-Al-Cu flakes. The observed Hc enhancement is due to the increase in anisotropy field and structural defects, which is hypothesized to originate from the domain-wall pinning as a consequence of precipitation of fine Cu-particles present at the grain boundaries.

  16. First-principles study of molecular hydrogen adsorption and dissociation on Al(n)Cr (n = 1-13) clusters.

    PubMed

    Guo, Ling

    2013-04-25

    Hydrogen adsorption dissociation on clusters is a widely studied subject that provides the opportunity to gain a basic understanding of the complicated nature of many interesting problems, such as hydrogen embrittlement of metals, catalytic processes, hydrogen storage, etc. In this study, I present density functional calculations of H2 adsorption and dissociation on small-sized Al(n)Cr clusters for n = 1-13. My results show that H2 is easily physically absorbed on the top Cr atom of AlnCr clusters with a side-on orientation rather than an end-on orientation. In addition, I investigate a possible dissociation mechanism and dissociation pathway of H2 on selected Al2Cr and Al7Cr. My findings suggest that the hydrogen dissociation behavior on Al(n)Cr clusters characterized by the activation barrier and reaction energy can be tuned by controllable doping. Thus, Al2Cr and Al7Cr clusters might serve as highly efficient and low-cost catalysts for hydrogen dissociation. PMID:23581518

  17. Study of the effect of different fermenting microorganisms on the Se, Cu, Cr, and Mn contents in fermented goat and cow milks.

    PubMed

    Quintana, Aida Verónica; Olalla-Herrera, Manuel; Ruiz-López, María Dolores; Moreno-Montoro, Miriam; Navarro-Alarcón, Miguel

    2015-12-01

    The aim of this study was to determine the Se, Cu, Cr, and Mn concentrations of different types of goat- and cow-milk fermented products and evaluate the influence of fermenting bacteria (classical fermenting starters and a probiotic strain) on these concentrations. Atomic absorption spectrometry with hydride generation was used to measure Se and electrothermal atomization to measure Cu, Cr and Mn. Analytical parameters determined in the fermented milks demonstrated that the procedures used were adequate for Se, Cu, Cr, and Mn analyses. Se levels were significantly lower in fermented goat milk products than in fermented cow milk products (p<0.05). Se, Cu, Cr, and Mn levels did not differ as a function of the fermenting bacteria used in commercial fermented goat or cow milks or in the lab-produced goat yoghurt. Given the Se, and Cr intakes for healthy adults, goat and cow yogurts may be important dietary sources. PMID:26041187

  18. Microwave Dielectric Resonance and Negative Permittivity Behavior in Al2O3-CuO-Cu Nanocomposites

    NASA Astrophysics Data System (ADS)

    Calame, Jeffrey; Battat, Jacob

    2006-03-01

    The frequency-dependent microwave (0.1-18 GHz) complex permittivity of nanocomposites based on the Al2O3/CuO/Cu system is investigated. The composites are formed by solution infusion of copper precursors into a porous Al2O3 matrix, followed by thermal decomposition to copper oxides and localized formation of CuAl2O4 spinels, and finally partial reduction by H2 firing. The final material has a complicated microstructure and exhibits strong amplitude, relatively narrowband dielectric resonance in the microwave regime at intermediate concentrations (˜15-18% by volume) of Cu. The resonances are superficially similar in structure to plasmon and Reststrahlen resonances typically seen in conductors at far-infrared to optical frequencies, but occurring at much lower frequencies in the composites. This is in contrast to the usual broadband induced-polarization dielectric relaxations observed in standard composites. Large concentrations of copper cause negative permittivity behavior below 6 GHz. Permittivity data, SEM micrographs, and possible explanations will be presented.

  19. The effect of ion implantation on the oxidation resistance of vacuum plasma sprayed CoNiCrAlY coatings

    NASA Astrophysics Data System (ADS)

    Jiang, Jie; Zhao, Huayu; Zhou, Xiaming; Tao, Shunyan; Ding, Chuanxian

    2012-11-01

    CoNiCrAlY coatings prepared by vacuum plasma spraying (VPS) were implanted with Nb and Al ions at a fluence of 1017 atoms/cm2. The effects of ion implantation on the oxidation resistance of CoNiCrAlY coatings were investigated. The thermally grown oxide (TGO) formed on each specimen was characterized by XRD, SEM and EDS, respectively. The results showed that the oxidation process of CoNiCrAlY coatings could be divided into four stages and the key to obtaining good oxidation resistance was to remain high enough amount of Al and promote the lateral growth of TGO. The implantation of Nb resulted in the formation of continuous and dense Al2O3 scale to improve the oxidation resistance. The Al implanted coating could form Al2O3 scale at the initial stage, however, the scale was soon broken and TGO transformed to non-protective spinel.

  20. X-ray diffraction line profile analysis for defect study in Cu-1 wt.% Cr-0.1 wt.% Zr alloy

    SciTech Connect

    Kapoor, K. . E-mail: kapoork@nfc.ernet.in; Lahiri, D.; Batra, I.S.; Rao, S.V.R.; Sanyal, T.

    2005-02-15

    X-ray line profile analysis (LPA) has been used for microstructural analysis of a Cu-1 wt.% Cr-0.1 wt.% Zr alloy. Using this technique, the stacking fault probability (SFP) and stacking fault energy (SFE) has been determined for the pure Cu and the Cu-1 wt.% Cr-0.1 wt.% Zr alloy. It is observed that there is an increase in the stacking fault probability (and corresponding decrease in stacking fault energy) in case of the alloy. The increased formation of faulted regions in the Cu-1 wt.% Cr-0.1 wt.% Zr alloy is supported by the observation of extended dislocation nodes and fringe contrast due to staking faults under TEM, and higher work hardening rate in the tension test. The high thermal fatigue resistance of this alloy is attributed to decrease in the stacking fault energy by addition of Cr and Zr to Cu.

  1. Chemically sensitive amorphization process in the nanolaminated Cr2AC (A = Al or Ge) system from TEM in situ irradiation

    NASA Astrophysics Data System (ADS)

    Bugnet, Matthieu; Mauchamp, Vincent; Oliviero, Erwan; Jaouen, Michel; Cabioc'h, Thierry

    2013-10-01

    The effect of 320 keV Xe2+ ion-irradiation in Cr2AlC and Cr2GeC is investigated in situ in the transmission electron microscope. Both compounds amorphize at moderate fluences (1013-1014 Xe cm-2) but exhibit different amorphization mechanisms, bearing witness of the major influence of the chemical composition of the nanolaminated Mn+1AXn phases. It is proposed that amorphization takes place via a direct impact amorphization process in Cr2GeC whereas it is governed by a defect accumulation process in Cr2AlC.

  2. An experimental and thermodynamic equilibrium investigation of the Pb, Zn, Cr, Cu, Mn and Ni partitioning during sewage sludge incineration.

    PubMed

    Liu, Jingyong; Fu, Jiewen; Ning, Xun'an; Sun, Shuiyu; Wang, Yujie; Xie, Wuming; Huang, Shaosong; Zhong, Sheng

    2015-09-01

    The effects of different chlorides and operational conditions on the distribution and speciation of six heavy metals (Pb, Zn, Cr, Cu, Mn and Ni) during sludge incineration were investigated using a simulated laboratory tubular-furnace reactor. A thermodynamic equilibrium investigation using the FactSage software was performed to compare the experimental results. The results indicate that the volatility of the target metals was enhanced as the chlorine concentration increased. Inorganic-Cl influenced the volatilization of heavy metals in the order of Pb>Zn>Cr>Cu>Mn>Ni. However, the effects of organic-Cl on the volatility of Mn, Pb and Cu were greater than the effects on Zn, Cr and Ni. With increasing combustion temperature, the presence of organic-Cl (PVC) and inorganic-Cl (NaCl) improved the transfer of Pb and Zn from bottom ash to fly ash or fuse gas. However, the presence of chloride had no obvious influence on Mn, Cu and Ni. Increased retention time could increase the volatilization rate of heavy metals; however, this effect was insignificant. During the incineration process, Pb readily formed PbSiO4 and remained in the bottom ash. Different Pb compounds, primarily the volatile PbCl2, were found in the gas phase after the addition of NaCl; the dominant Pb compounds in the gas phase after the addition of PVC were PbCl2, Pb(ClO4)2 and PbCl2O4. PMID:26354691

  3. The Temporal Evolution of the Nanostructure of a Model Ni-Al-Cr Superalloy

    NASA Technical Reports Server (NTRS)

    Sudbrack, Chantal K.; Yoon, Kevin E.; Noebe, Ronald D.; Seidman, David N.

    2004-01-01

    The early to the later stages of precipitation of ordered gamma'-precipitates (L1(sub 2)) in Ni-5.2 Al-14.2 Cr (at.%) are studied at 873 K. Precipitates with radii as small as 0.45 nm are characterized fully by three-dimensional atom-probe (3DAP) microscopy. Contrary to what is often assumed by theory or in models, the average precipitate composition is shown to evolve with time, such that solute concentrations decrease toward an equilibrium value given by the solvus lines. Power-law time dependencies of the number density, mean radius, and supersaturations of Al and Cr are discussed in light of theoretical predictions for Ostwald ripening.

  4. Synthesis of Waste Form in the Gd-Fe-Al-Ni-Mn-Cr-O System

    SciTech Connect

    Chae, S.C.; Jang, Y.N.; Bae, I.K.; Ryu, K.W.

    2006-07-01

    Poly-phase waste form which was the mixture of Gd{sub 3}Fe{sub 2}Al{sub 3}O{sub 12} and (Ni{sub x}Mn{sub 1-x})(Fe{sub y}Cr{sub 1-y}){sub 2}O{sub 4} was synthesized. Also, we are intended to examine phase relation and physicochemical properties of coexisted phases in the compositions and to confirm accommodation relation of elements and phases. Two types of phase series were observed: Garnet-perovskite-spinel and Garnet-spinel. The compositions of garnets and spinels were nonstoichiometric, and especially, this poly-phase ceramics may be in a good waste form. The excessive Gd in garnets indicated the immobilization of higher content of actinides. The nonstoichiometric compositions of garnet and spinel were attributed to the formation of perovskite in that perovskite contained Gd, Fe and Al from garnet and Cr from spinel. (authors)

  5. Fuel Performance Calculations for FeCrAl Cladding in BWRs

    SciTech Connect

    George, Nathan; Sweet, Ryan; Maldonado, G. Ivan; Wirth, Brian D.; Powers, Jeffrey J.; Worrall, Andrew

    2015-01-01

    This study expands upon previous neutronics analyses of the reactivity impact of alternate cladding concepts in boiling water reactor (BWR) cores and directs focus toward contrasting fuel performance characteristics of FeCrAl cladding against those of traditional Zircaloy. Using neutronics results from a modern version of the 3D nodal simulator NESTLE, linear power histories were generated and supplied to the BISON-CASL code for fuel performance evaluations. BISON-CASL (formerly Peregrine) expands on material libraries implemented in the BISON fuel performance code and the MOOSE framework by providing proprietary material data. By creating material libraries for Zircaloy and FeCrAl cladding, the thermomechanical behavior of the fuel rod (e.g., strains, centerline fuel temperature, and time to gap closure) were investigated and contrasted.

  6. 1300 K Compressive Properties of Directionally Solidified Ni-33Al-33Cr-1Mo

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Raj, S. V.; Locci, Ivan E.

    2000-01-01

    The Ni-33Al-33Cr-1Mo eutectic has been directionally solidified by a modified Bridgeman technique at growth rates ranging from 7.6 to 508 mm/h to produce grain/cellular microstructures, containing alternating plates of NiAl and Cr alloyed with Mo. The grains had sharp boundaries for slower growth rates (< 12.7 mm/h), while faster growth rates (> 25.4 mm/h) lead to cells bounded by intercellular regions. Compressive testing at 1300 K indicated that alloys DS'ed at rates between 25.4 to 254 mm/h possessed the best strengths which exceed that for the as-cast alloy.

  7. Synthesis, characterization and photocatalytic activity of cubic-like CuCr2O4 for dye degradation under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Yuan, Wenhui; Liu, Xiaoxia; Li, Li

    2014-11-01

    CuCr2O4 nanoparticles with cubic-like morphology were prepared via hydrothermal synthesis method without template. The CuCr2O4 samples were characterized by thermogravimetry and differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectra (DRS) and Zeta potentials, respectively. The results indicated that cubic-like CuCr2O4 could be successfully synthesized by calcining the precursor at 600 °C, and the calcination temperature greatly influenced the morphology and optical performance of CuCr2O4. The pH at the point of zero charge (pHpzc) of the CuCr2O4 calcined at 600 °C was about 4.52. The photocatalytic activity of CuCr2O4 was evaluated for degradation of rhodamine B (RhB), methylene blue (MB), and methyl orange (MO) in the presence of H2O2 under visible light irradiation and the effects of the calcination temperature, dosage of photocatalyst, etc., on photocatalytic activity were studied in detail. The photocatalytic results revealed that the CuCr2O4 photocatalyst was of high activity for degradation of RhB (96.8%) and MB (99.5%), but very low activity for degradation of MO (14%). The CuCr2O4 sample calcined at 600 °C possesses the best photocatalytic activity, and the optimal dosage of the CuCr2O4 photocatalyst is 0.4 g/L.

  8. Synthesis and characterization of lamellar and fibre-reinforced NiAl-Mo and NiAl-Cr

    NASA Astrophysics Data System (ADS)

    Haenschke, T.; Gali, A.; Heilmaier, M.; Krüger, M.; Bei, H.; George, E. P.

    2010-07-01

    Directionally solidified (DS) alloys of the eutectic systems NiAl-10Mo and NiAl-34Cr (at.%) are potential candidates for high-temperature structural applications. Here, these alloys were first arc-melted and drop-cast. Thereafter, they were directionally solidified (DS) at growth rates of 20 and 80 mm/h while rotating at a fixed rotation speed of 60 revolutions per minute. Specimens of the DS alloys were tested in three-point-bending and uniaxial compression to obtain mechanical properties, including the ductile to brittle transition temperature (DBTT). For the NiAl-Cr system DBTT was found to be around 300 °C. Microstructural observations revealed that in the section perpendicular to the growth direction a uniform distribution of fibres was observed. The expected decrease of the fibre diameter with increasing growth rate was not observed. Instead, the fibre diameter slightly increased with increasing crystal growth rates. First compression tests were performed to get insights into the creep behaviour of these fibre-reinforced microstructures.

  9. Characterization of CuAlO2 Thin Films Prepared on Sapphire Substrates by Reactive Sputtering and Annealing

    NASA Astrophysics Data System (ADS)

    Tsuboi, Nozomu; Moriya, Tomohiro; Kobayashi, Satoshi; Shimizu, Hidehiko; Kato, Keizo; Kaneko, Futao

    2008-01-01

    As-deposited films were prepared on sapphire substrates at 500-680 °C by alternately sputtering Cu and Al targets in Ar-diluted O2 gas atmosphere. The composition of the as-deposited films corresponded to that of the slightly oxygen-rich region of the CuO-CuAl2O4-Al2O3 system. The films as-deposited at 500 °C had an amorphous structure, while the films as-deposited at 680 °C had CuAl2O4 phase but no CuAlO2 phase. Annealing at 1050 °C in nitrogen flow caused a reduction in the molar fraction of oxygen, i.e., the composition of the annealed films with [Cu]/[Al] ≈1 corresponded to CuAlO2. The annealed films were predominated by the CuAlO2 phase. The preferential orientation of the films toward the c-axis normal to the substrate surface is due to the small lattice mismatch between the rhombohedral [010] of delafossite-type CuAlO2 and the hexagonal [1100] of the sapphire substrate. The annealed films had an absorption edge corresponding to the energy gap of CuAlO2 and exhibited p-type conductivity.

  10. Analysis of the FeCrAl Accident Tolerant Fuel Concept Benefits during BWR Station Blackout Accidents

    SciTech Connect

    Robb, Kevin R

    2015-01-01

    Iron-chromium-aluminum (FeCrAl) alloys are being considered for fuel concepts with enhanced accident tolerance. FeCrAl alloys have very slow oxidation kinetics and good strength at high temperatures. FeCrAl could be used for fuel cladding in light water reactors and/or as channel box material in boiling water reactors (BWRs). To estimate the potential safety gains afforded by the FeCrAl concept, the MELCOR code was used to analyze a range of postulated station blackout severe accident scenarios in a BWR/4 reactor employing FeCrAl. The simulations utilize the most recently known thermophysical properties and oxidation kinetics for FeCrAl. Overall, when compared to the traditional Zircaloy-based cladding and channel box, the FeCrAl concept provides a few extra hours of time for operators to take mitigating actions and/or for evacuations to take place. A coolable core geometry is retained longer, enhancing the ability to stabilize an accident. Finally, due to the slower oxidation kinetics, substantially less hydrogen is generated, and the generation is delayed in time. This decreases the amount of non-condensable gases in containment and the potential for deflagrations to inhibit the accident response.

  11. A new type of Cu-Al-Ta shape memory alloy with high martensitic transformation temperature

    NASA Astrophysics Data System (ADS)

    Wang, C. P.; Su, Y.; Y Yang, S.; Shi, Z.; Liu, X. J.

    2014-02-01

    In this study, a new type of Cu-Al-Ta (Cu86Al12Ta2 wt%) shape memory alloy with high martensitic transformation temperature is explored. The microstructure, reversible martensitic transformation and shape memory properties are investigated by means of optical microscopy, back-scattered electron, electron probe microanalysis, x-ray diffraction, differential scanning calorimetry and tensile tests. It is proposed that Cu86Al12Ta2 alloy consists of a mixture of primarily {\\beta }_{1}^{\\prime} martensite and a little {\\gamma }_{1}^{\\prime} martensite and some different precipitates. The tiny thin-striped Ta2(Al,Cu)3 precipitate is predominant in the as-quenched condition, whereas the particle-shaped Cu(Al, Ta) precipitate is dominant after hot-rolling. Additionally, the dendritic-shaped γ1(Cu9Al4) phase begins to appear after hot-rolling, but it disappears when the sample is re-quenched. All studied samples have reversible martensitic transformation temperatures higher than 450 ° C. The results show that two-step martensitic transformation behavior is observed for Cu86Al12Ta2 alloy in all three different conditions due to the transformations between ({\\beta }_{1}^{\\prime}+{\\gamma }_{1}^{\\prime}) martensites and the austenite parent phase. The results further show that the recovery ratios are almost 100% when the pre-strains are ≤2.5%, then they gradually decrease with further increase of the pre-strains. The shape memory effects clearly increase as a result of increase of the pre-strains, up to a maximum value of 3.2%.

  12. The effect of zirconium on the cyclic oxidation of NiCrAl alloys

    NASA Technical Reports Server (NTRS)

    Barrett, C. A.; Khan, A. S.; Lowell, C. E.

    1981-01-01

    This paper examines results with cyclic oxidation tests of Ni(9-20) Cr(15-30) Al-(x)Zr alloys carried out at 1100 C and 1200 C in static air. The concentration of zirconium varies from 0 to 0.63 atomic percent. Significant aluminum penetration is found in metallographic and electron microscopic examination of oxidized surfaces. Small amounts of zirconium lead to minimal penetration, and with increased zirconium content pronounced oxide penetration is observed.

  13. Effects of ruthenium on phase separation in a model Ni-Al-Cr-Ru superalloy

    NASA Astrophysics Data System (ADS)

    Zhou, Yang; Isheim, Dieter; Hsieh, Gillian; Noebe, Ronald D.; Seidman, David N.

    2013-04-01

    The temporal evolution of a Ni-10.0Al-8.5Cr-2.0Ru (at.%) alloy aged at 1073 K was investigated using transmission electron microscopy (TEM) and atom-probe tomography. The γ‧(L12)-precipitate morphology is spheroidal through 256 h of ageing as a result of adding Ru, which decreases the lattice parameter misfit between the γ‧(L12)- and γ(f.c.c.)-phases. The addition of Ru accelerates the compositional evolution of the γ‧(L12)- and γ(f.c.c.)-phases, which achieve their equilibrium compositions after 0.25 h. Initially, Ru accelerates the partitioning of Ni and Cr to the γ(f.c.c.)-phase, and the partitioning of Al to the γ‧(L12)-phase, but after 0.25 h, Ru, which partitions to the γ(f.c.c.)-phase, decreases the partitioning of Ni and increases the partitioning of Al and Cr. The temporal evolution of the average radius, ⟨R(t)⟩, number density, volume fraction of the γ‧(L12)-precipitates, and the supersaturations of Ni, Al, Cr, and Ru in the γ(f.c.c.)- and γ‧(L12)-phases are compared in detail with predictions of coarsening models and PrecipiCalc simulations. Based on a spline function fitting procedure of the concentration profiles between the γ‧(L12)- and γ(f.c.c.)-phases, it is demonstrated that the temporal evolution of the normalized interfacial width, δ/⟨R(t)⟩ vs. ⟨R(t)⟩, of each element, decreases with increasing ageing time: δ is the interfacial width.

  14. Vibrational structure of luminiscence spectrum of Cr3+ in MgAl2O4

    NASA Astrophysics Data System (ADS)

    Czaja, M.; Mazurak, Z.

    1993-07-01

    The optical absorption and luminescence spectra of MgAl2O4:Cr3+ natural spinel (from Ural) have been measured at 77 K and 293 K. The luminescent emission from 4 T 2 g , 2 E g covers wide region of 600 750 nm. The emission spectrum at 77 K shows a very rich vibrational structure which can be mainly explained through the vibrational modes of the oxygen octahedron.

  15. Tribological Properties of CrN/AlN Films Produced by Reactive Magnetron Sputtering

    NASA Astrophysics Data System (ADS)

    Rojo, A.; Solís, J.; Oseguera, J.; Salas, O.; Reichelt, R.

    2010-04-01

    The microstructure of CrN/AlN films, prepared by reactive magnetron sputtering under various conditions, was analyzed and related to the wear behavior of the films. One set of films was prepared by conventional reactive magnetron sputtering, a second set adding an extra amount of reactive gas to the initial Ar + N2 mixture and a third set adding an extra source of nitrogen near the substrate during sputtering. The samples were analyzed by scanning electron microscopy + energy dispersive microanalysis, high resolution scanning electron microscopy, atomic force microscopy, and x-ray diffraction. The results of the microstructural analysis revealed a clear difference in the morphology growth of the films when extra nitrogen was used compared to the conventionally prepared films. Formation of CrN was significantly faster than that of AlN. The most effective method to produce AlN was to introduce extra nitrogen. Pin-on-disk wear experiments were carried out in ambient air, to investigate the tribological behavior of the CrN/AlN system against a steel ball under dry conditions for various loads and a constant sliding speed. The results revealed that tribological properties of the layers improved unlike those of the untreated H13 steel. The friction behavior is closely related to the structure of the deposited films. The thicker CrN layer contributed to the higher load capacity of the coated steel when compared to the unmodified steel. However, wear life for the coating system was very short, denoted by the fairly poor adhesion of the film system to the steel substrate.

  16. Microstructural Observations in a Cast Al-Si-Cu/TiC Composite

    NASA Astrophysics Data System (ADS)

    Karantzalis, A. E.; Lekatou, A.; Georgatis, E.; Poulas, V.; Mavros, H.

    2010-06-01

    A 3-5 vol.% TiC particulate Al-Si-Cu composite was prepared by diluting Al/20 vol.% TiC composite in an Al-7Si-4Cu alloy matrix. TiC particle distribution consists of isolated and clustered particles which are both located at the primary-α grain boundaries and at the areas of the last solidified liquid. Particle pushing by the solidification front is responsible for the final particle location. The solidified microstructure consists of primary and intermetallic phases formed by a sequence of possible eutectic reactions. No evidence of TiC particle degradation was observed.

  17. Oxidation and Hot Corrosion Behavior of Plasma-Sprayed MCrAlY-Cr2O3 Coatings

    NASA Astrophysics Data System (ADS)

    Zhang, Tiantian; Huang, Chuanbing; Lan, Hao; Du, Lingzhong; Zhang, Weigang

    2016-08-01

    The oxidation and hot corrosion behavior of two atmospheric plasma-sprayed NiCoCrAlY-Cr2O3 and CoNiCrAlY-Cr2O3 coatings, which are primarily designed for wear applications at high temperature, were investigated in this study. The two coatings were exposed to air and molten salt (75%Na2SO4-25%NaCl) environment at 800 °C under cyclic conditions. Oxidation and hot corrosion kinetic curves were obtained by thermogravimetric technique. X-ray diffraction analysis and scanning electron microscopy with energy-dispersive x-ray spectrometry were employed to characterize the coatings' microstructure, surface oxides, and composition. The results showed that both coatings provided the necessary oxidation resistance with oxidation rates of about 1.03 × 10-2 and 1.36 × 10-2 mg/cm2 h, respectively. The excellent oxidation behavior of these two coatings is attributed to formation of protective (Ni,Co)Cr2O4 spinel on the surface, while as-deposited Cr2O3 in the coatings also acted as a barrier to diffusion of oxidative and corrosive substances. The greater presence of Co in the CoNiCrAlY-Cr2O3 coating restrained internal diffusion of sulfur and slowed down the coating's degradation. Thus, the CoNiCrAlY-Cr2O3 coating was found to be more protective than the NiCoCrAlY-Cr2O3 coating under hot corrosion condition.

  18. TEM and SNMS studies of protective alumina scales on NiCrAlY-alloys.

    PubMed

    Clemens, D; Vosberg, V; Hobbs, W; Breuer, U; Quadakkers, W J; Nickel, H

    1996-06-01

    The effect of Si addition on the oxidation behaviour of NiCrAlY alloys in the temperature range 950 bis 1100 degrees C has been investigated. During isothermal oxidation oxide growth rates were practically independent of the Si-content. However during cyclic oxidation Si additions were beneficial. Si additions of 1-2(m)/(0) appeared to shift the onset for spallation to longer times. It was found that Si stabilizes the beta-phase and probably it suppresses the formation of metastable Al(2)O(3) modifications. PMID:15045347

  19. Brazeability of a 3003 Aluminum alloy with Al-Si-Cu-based filler metals

    NASA Astrophysics Data System (ADS)

    Tsao, L. C.; Weng, W. P.; Cheng, M. D.; Tsao, C. W.; Chuang, T. H.

    2002-08-01

    Al-Si-Cu-based filler metals have been used successfully for brazing 6061 aluminum alloy as reported in the authors’ previous studies. For application in heat exchangers during manufacturing, the brazeability of 3003 aluminum alloy with these filler metals is herein further evaluated. Experimental results show that even at such a low temperature as 550 °C, the 3003 alloys can be brazed with the Al-Si-Cu fillers and display bonding strengths that are higher than 77 MPa as well. An optimized 3003 joint is attained in the brazements with the innovative Al-7Si-20Cu-2Sn-1Mg filler metal at 575 °C for 30 min, which reveals a bonding strength capping the 3003 Al matrix.

  20. Effects of Solute Concentrations on Kinetic Pathways in Ni-Al-Cr Alloys

    NASA Technical Reports Server (NTRS)

    Booth-Morrison, Christopher; Weninger, Jessica; Sudbrack, Chantal K.; Mao, Zugang; Seidman, David N.; Noebe, Ronald D.

    2008-01-01

    The kinetic pathways resulting from the formation of coherent gamma'-precipitates from the gamma-matrix are studied for two Ni-Al-Cr alloys with similar gamma'-precipitate volume fractions at 873 K. The details of the phase decompositions of Ni-7.5Al-8.5Cr at.% and Ni-5.2Al-14.2Cr at.% for aging times from 1/6 to 1024 h are investigated by atom-probe tomography, and are found to differ significantly from a mean-field description of coarsening. The morphologies of the gamma'-precipitates of the alloys are similar, though the degrees of gamma'-precipitate coagulation and coalescence differ. Quantification within the framework of classical nucleation theory reveals that differences in the chemical driving forces for phase decomposition result in differences in the nucleation behavior of the two alloys. The temporal evolution of the gamma'-precipitate average radii and the gamma-matrix supersaturations follow the predictions of classical coarsening models. The compositional trajectories of the gamma-matrix phases of the alloys are found to follow approximately the equilibrium tie-lines, while the trajectories of the gamma'-precipitates do not, resulting in significant differences in the partitioning ratios of the solute elements.

  1. Fe-Cr-Al containing oxide semiconductors as potential solar water-splitting materials.

    PubMed

    Sliozberg, Kirill; Stein, Helge S; Khare, Chinmay; Parkinson, Bruce A; Ludwig, Alfred; Schuhmann, Wolfgang

    2015-03-01

    A high-throughput thin film materials library for Fe-Cr-Al-O was obtained by reactive magnetron cosputtering and analyzed with automated EDX and XRD to elucidate compositional and structural properties. An automated optical scanning droplet cell was then used to perform photoelectrochemical measurements of 289 compositions on the library, including electrochemical stability, potentiodynamic photocurrents and photocurrent spectroscopy. The photocurrent onset and open circuit potentials of two semiconductor compositions (n-type semiconducting: Fe51Cr47Al2Ox, p-type semiconducting Fe36.5Cr55.5Al8Ox) are favorable for water splitting. Cathodic photocurrents are observed at 1.0 V vs RHE for the p-type material exhibiting an open circuit potential of 0.85 V vs RHE. The n-type material shows an onset of photocurrents at 0.75 V and an open circuit potential of 0.6 V. The p-type material showed a bandgap of 1.55 eV, while the n-type material showed a bandgap of 1.97 eV. PMID:25650842

  2. Structural and Magnetic Study of Cu x FeCr1- x O2 Oxides Under High External Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Ozkendir, Osman Murat

    2013-06-01

    The structural, electronic, and magnetic behaviors of Cu x FeCr1- x O2 polycrystals are investigated. Investigations are conducted for increasing chromium substitution, according to varying x values in the formula versus copper, for x = 0, 0.2, 0.4, 0.6, 0.8, and 1. The magnetic response of polycrystalline samples under increasing external magnetic field from 0.4 T to 5 T is also studied. The partial crystal structure deformation/transition from delafossite CuFeO2 structure to corundum-type FeCrO3 structure containing CrO2 and Cr2O3 blocks is determined. The change in the crystal structure geometry with increasing Cr substitution is observed. Besides, prominent changes in magnetic ordering are observed from antiferromagnetic ( x = 1, 0.8, and 0.6) to ferromagnetic ordering ( x = 0.4 and 0.2) for high applied external magnetic fields above 2 T.

  3. Grain-size control in Ti-48Al-2Cr-2Nb with yttrium additions

    NASA Astrophysics Data System (ADS)

    Trivedi, P. B.; Patankar, S. N.; (Sam) Froes, F. H.; Baburaj, E. G.; Genç, A.; Ovecoglu, L.

    2002-08-01

    A gas-atomized (GA) prealloyed powder of the Ti-48Al-2Cr-2Nb intermetallic and 1.6 wt pct Y were mechanically alloyed (MA) and hot isostatically pressed (hipped) to produce a fully dense nanocrystalline material. Mechanical alloying of the as-blended powder for 16 hours resulted in the formation of a disordered fcc phase. Hipping of the alloy powder produced a single-phase nanocrystalline TiAl intermetallic, containing a distribution of 20 to 35-nm-sized Al2Y4O9 particles. The formation of oxide particles occurred by the chemical combination of Al and Y with oxygen, which entered as a contaminant during milling. Oxide particles increased the hardness of the intermetallic compound and minimized grain growth even at 0.8 T m , where T m is the melting point of the compound.

  4. High field magnetotransport and point contact Andreev reflection measurements on CuCr{sub 2}Se{sub 4} and CuCr{sub 2}Se{sub 3}Br—Degenerate magnetic semiconductor single crystals

    SciTech Connect

    Borisov, K. Coey, J. M. D.; Stamenov, P.; Alaria, J.

    2014-05-07

    Single crystals of the metallically degenerate fully magnetic semiconductors CuCr{sub 2}Se{sub 4} and CuCr{sub 2}Se{sub 3}Br have been prepared by the Chemical Vapour Transport method, using either Se or Br as transport agents. The high-quality, millimetre-sized, octahedrally faceted, needle- and platelet-shaped crystals are characterised by means of high field magnetotransport (μ{sub 0}H≤ 14 T) and Point Contact Andreev Reflection. The relatively high spin polarisation observed |P|>0.56, together with the relatively low minority carrier effective mass of 0.25 m{sub e}, and long scattering time  10{sup −13} s, could poise these materials for integration in low- and close-to-room temperature minority injection bipolar heterojunction transistor demonstrations.

  5. Analysis of the microstructure of Cr-Ni surface layers deposited on Fe{sub 3}Al by TIG

    SciTech Connect

    Ma Haijun . E-mail: hjma123@mail.sdu.edu.cn; Li Yajiang; Wang Juan

    2006-12-15

    A series of Cr-Ni alloys were overlaid on a Fe{sub 3}Al surface by tungsten inert gas arc welding (TIG) technology. The microstructure of the Cr-Ni surface layers were analysed by means of optical metallography, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results indicated that when the appropriate TIG parameters were used and Cr25-Ni13 and Cr25-Ni20 alloys were used for the overlaid materials, the Cr-Ni surface layers were crack-free. The matrix of the surface layer was austenite (A), pro-eutectoid ferrite (PF), acicular ferrite (AF), carbide-free bainite (CFB) and lath martensite (LM), distributed on the austenitic grain boundaries as well as inside the grains. The phase constituents of the Cr25-Ni13 surface layer were {gamma}-Fe, Fe{sub 3}Al, FeAl, NiAl, an Fe-C compound and an Fe-C-Cr compound. The microhardness of the fusion zone was lower than that of the Fe{sub 3}Al base metal and Cr25-Ni13 surface layer.

  6. Spatially resolved quantitative magnetic order measurement in spinel CuCr{sub 2}S{sub 4} nanocrystals

    SciTech Connect

    Negi, D. S.; Loukya, B.; Datta, R.; Ramasamy, K.; Gupta, A.

    2015-05-04

    We have utilized spatially resolved high resolution electron energy loss spectroscopy to quantify the relative percentage of ferromagnetic order in the core and the surface regions of CuCr{sub 2}S{sub 4} nanoparticles with nanocube and nanocluster morphology. The organic capping layer is found to play a significant role in restoring magnetic order at the surface. The technique is based on recording the fine features of the Cr L{sub 3} absorption edge and matching them with the theoretical spectra. The nanoscale probing technique we have developed is quite versatile and can be extended to understand magnetic ordering in a number of nanodimensional magnetic materials.

  7. Assessment of Post-eutectic Reactions in Multicomponent Al-Si Foundry Alloys Containing Cu, Mg, and Fe

    NASA Astrophysics Data System (ADS)

    Javidani, Mousa; Larouche, Daniel; Grant Chen, X.

    2015-07-01

    Post-eutectic reactions occurring in Al-Si hypoeutectic alloys containing different proportions of Cu, Mg, and Fe were thoroughly investigated in the current study. As-cast microstructures were initially studied by optical and electron microscopy to investigate the microconstituents of each alloy. Differential scanning calorimetry (DSC) was then used to examine the phase transformations occurring during the heating and cooling processes. Thermodynamic calculations were carried out to assess the phase formation under equilibrium and in nonequilibrium conditions. The Q-Al5Cu2Mg8Si6 phase was predicted to precipitate from the liquid phase, either at the same temperature or earlier than the θ-Al2Cu phase depending on the Cu content of the alloy. The AlCuFe-intermetallic, which was hardly observed in the as-cast microstructure, significantly increased after the solution heat treatment in the alloys containing high Cu and Fe contents following a solid-state transformation of the β-Al5FeSi phase. After the solution heat treatment, the AlCuFe-intermetallics were mostly identified with the stoichiometry of the Al7Cu2Fe phase. Thermodynamic calculations and microstructure analysis helped in determining the DSC peak corresponding to the melting temperature of the N-Al7Cu2Fe phase. The effect of Cu content on the formation temperature of π-Al8Mg3FeSi6 is also discussed.

  8. Elementary surface chemistry during CuO/Al nanolaminate-thermite synthesis: copper and oxygen deposition on aluminum (111) surfaces.

    PubMed

    Lanthony, Cloé; Guiltat, Mathilde; Ducéré, Jean Marie; Verdier, Agnes; Hémeryck, Anne; Djafari-Rouhani, Mehdi; Rossi, Carole; Chabal, Yves J; Estève, Alain

    2014-09-10

    The surface chemistry associated with the synthesis of energetic nanolaminates controls the formation of the critical interfacial layers that dominate the performances of nanothermites. For instance, the interaction of Al with CuO films or CuO with Al films needs to be understood to optimize Al/CuO nanolaminates. To that end, the chemical mechanisms occurring during early stages of molecular CuO adsorption onto crystalline Al(111) surfaces are investigated using density functional theory (DFT) calculations, leading to the systematic determination of their reaction enthalpies and associated activation energies. We show that CuO undergoes dissociative chemisorption on Al(111) surfaces, whereby the Cu and O atoms tend to separate from each other. Both Cu and O atoms form islands with different properties. Copper islanding fosters Cu insertion (via surface site exchange mechanism) into the subsurface, while oxygen islands remain stable at the surface. Above a critical local oxygen coverage, aluminum atoms are extracted from the Al surface, leading to oxygen-aluminum intermixing and the formation of aluminum oxide (γ-alumina). For Cu and O co-deposition, copper promotes oxygen-aluminum interaction by oxygen segregation and separates the resulting oxide from the Al substrate by insertion into Al and stabilization below the oxide front, preventing full mixing of Al, Cu, and O species. PMID:25089744

  9. Formation of α-alumina scales in the Fe-Al(Cr) diffusion coating on China low activation martensitic steel

    NASA Astrophysics Data System (ADS)

    Zhan, Qin; Zhao, Weiwei; Yang, Hongguang; Hatano, Yuji; Yuan, Xiaoming; Nozaki, Teo; Zhu, Xinxin

    2015-09-01

    To study the formation mechanism of stable α-Al2O3 scales, the oxidation behavior of Fe-Al(Cr) diffusion coating on China low activation martensitic steel has been investigated under the oxygen partial pressure ranging from 1 to 20,000 Pa at 1253 K. A single, continuous Al2O3 scale with the maximum thickness of about 2000 nm was formed on the Fe-Al(Cr) diffusion layer. The phase transformation of alumina scales on the surface of Fe-Al(Cr) layer was studied at different oxidation times ranging from 3 to 180 min. With the increase in oxygen partial pressure, the phase transformation time of α-Al2O3 is decreased. The metastable γ-Al2O3 and transition α-(Al0.948Cr0.052)2O3 phases were formed in the earlier oxidation process and finally transformed to the stable α-Al2O3 phase, which were detected by grazing incidence angle X-ray diffraction and confirmed by transmission electron microscopy. This implies that Cr shows the third element effect and serves as a template for the nucleation of the stable α-Al2O3.

  10. Synthesis, Structure, and Physical Properties of Ln(Cu,Al,Ga)13-x (Ln = La-Pr, and Eu) and Eu(Cu,Al)13-x

    SciTech Connect

    Phelan, W Adam; Kangas, Michael J; McCandless, Gregory T; Drake, Brenton L; Haldolaarachchige, Neel; Zhao, Liang L; Wang, Jiakui K; Wang, Xiaoping P; Young, David P; Morosan, Emilia; Hoffmann, Christina; Chan, Julia Y

    2012-09-10

    Ln(Cu,Al,Ga)13–x (Ln = La–Pr, and Eu; x ~ 0.2) were synthesized by a combined Al/Ga flux. Single crystal X-ray and neutron diffraction experiments revealed that these compounds crystallize in the NaZn13 structure-type (space group Fm3⁻c) with lattice parameters of a ~ 12 Å, V ~ 1600 Å, and Z ~ 8. Our final neutron models led us to conclude that Cu is occupationally disordered on the 8b Wyckoff site while Cu, Al, and Ga are substitutionally disordered on the 96i Wyckoff site of this well-known structure-type. The magnetic susceptibility data show that Ce(Cu,Al,Ga)13–x and Pr(Cu,Al,Ga)13–x exhibit paramagnetic behavior down to the lowest temperatures measured while Eu(Cu,Al,Ga)13–x displays ferromagnetic behavior below 6 K. Eu(Cu,Al)13–x was prepared via arc-melting and orders ferromagnetically below 8 K. The magnetocaloric properties of Eu(Cu,Al,Ga)13–x and Eu(Cu,Al)13–x were measured and compared. Additionally, an enhanced value of the Sommerfeld coefficient (γ = 356 mJ/mol-K2) was determined for Pr(Cu,Al,Ga)13–x. Herein, we present the synthesis, structural refinement details, and physical properties of Ln(Cu,Al,Ga)13–x (Ln = La–Pr, and Eu) and Eu(Cu,Al)13–x.

  11. Adhesion strength and nucleation thermodynamics of four metals (Al, Cu, Ti, Zr) on AlN substrates

    NASA Astrophysics Data System (ADS)

    Tao, Yuan; Ke, Genshui; Xie, Yan; Chen, Yigang; Shi, Siqi; Guo, Haibo

    2015-12-01

    Devices based on AlN generally require adherent and strong interfaces between AlN and other materials, whereas most metals are known to be nonwetting to AlN and form relatively weak interfaces with AlN. In this study, we selected four representative metals (Al, Cu, Ti, and Zr) to study the adhesion strength of the AlN/metal interfaces. Mathematical models were constructed between the adhesion strength and enthalpy of formation of Al-metal solid solutions, the surface energies of the metals, and the lattice mismatch between the metals and AlN, based on thermodynamic parameters calculated using density functional theory. It appears that the adhesion strength is mainly determined by the lattice mismatch, and is in no linear correlation with either the Al-metal solution's formation enthalpies or the metals' surface energies. We also investigated the nucleation thermodynamics of the four metals on AlN substrates. It was found that Ti forms the strongest interface with AlN, and has the largest driving force for nucleation on AlN substrates among the four metals.

  12. CuAl{sub 2} revisited: Composition, crystal structure, chemical bonding, compressibility and Raman spectroscopy

    SciTech Connect

    Grin, Yuri . E-mail: grin@cpfs.mpg.de; Wagner, Frank R.; Armbruester, Marc; Kohout, Miroslav; Leithe-Jasper, Andreas; Schwarz, Ulrich; Wedig, Ulrich; Georg von Schnering, Hans

    2006-06-15

    The structure of CuAl{sub 2} is usually described as a framework of base condensed tetragonal antiprisms [CuAl{sub 8/4}]. The appropriate symmetry governed periodic nodal surface (PNS) divides the space of the structure into two labyrinths. All atoms are located in one labyrinth, whereas the second labyrinth seems to be 'empty'. The bonding of the CuAl{sub 2} structure was analyzed by the electron localization function (ELF), crystal orbital Hamiltonian population (COHP) analysis and Raman spectroscopy. From the ELF representation it is seen, that the 'empty' labyrinth is in fact the place of important covalent interactions. ELF, COHP in combination with high-pressure X-ray diffraction and Raman spectroscopy show that the CuAl{sub 2} structure is described best as a network built of interpenetrating graphite-like nets of three-bonded aluminum atoms with the copper atoms inside the tetragonal-antiprismatic cavities. - Graphical abstract: Atomic interactions in the crystal structure of the intermetallic compound CuAl{sub 2}: Three-bonded aluminum atoms form interpenetrating graphite-like nets. The copper atoms are located in the channels of aluminum network by means of three-center bonds. The bonding model is in agreement with the result of polarized Raman spectroscopy and high-pressure X-ray powder diffraction.

  13. CONSTITUTIVE BEHAVIOR OF AS-QUENCHED Al-Cu-Mn ALLOY

    NASA Astrophysics Data System (ADS)

    Yang, Xia-Wei; Zhu, Jing-Chuan; Nong, Zhi-Sheng; Ye, Mao; Lai, Zhong-Hong; Liu, Yong

    2013-07-01

    The hot flow stress of as-quenched Al-Cu-Mn alloy was modeled using the constitutive equations. The as-quenched Al-Cu-Mn alloy were treated with isothermal hot compression tests in the temperature range of 350-500°C, the strain rate range of 0.001-1 s-1. The hyperbolic sine equation was found to be appropriate for flow stress modeling and prediction. Based on the hyperbolic sine equation, a constitutive equation is a relation between 0.2 pct yield stress and deformation conditions (strain rate and deformation temperature) was established. The corresponding hot deformation activation energy (Q) for as-quenched Al-Cu-Mn alloy was determined to be 251.314 kJ/mol. Parameters of constitutive equation of as-quenched Al-Cu-Mn alloy were calculated at different small strains (≤ 0.01). The calculated flow stresses from the constitutive equation are in good agreement with the experimental results. Therefore, this constitutive equation can be used as an accurate temperature-stress model to solve the problems of quench distortion of Al-Cu-Mn alloy parts.

  14. Micro-chip initiator realized by integrating Al/CuO multilayer nanothermite on polymeric membrane

    NASA Astrophysics Data System (ADS)

    Taton, G.; Lagrange, D.; Conedera, V.; Renaud, L.; Rossi, C.

    2013-10-01

    We have developed a new nanothermite based polymeric electro-thermal initiator for non-contact ignition of a propellant. A reactive Al/CuO multilayer nanothermite resides on a 100 µm thick SU-8/PET (polyethyleneterephtalate) membrane to insulate the reactive layer from the silicon bulk substrate. When current is supplied to the initiator, the chemical reaction Al+CuO occurs and sparkles are spread to a distance of several millimeters. A micro-manufacturing process for fabricating the initiator is presented and the electrical behaviors of the ignition elements are also investigated. The characteristics of the initiator made on a 100 µm thick SU-8/PET membrane were compared to two bulk electro-thermal initiators: one on a silicon and one on a Pyrex substrate. The PET devices give 100% of Al/CuO ignition success for an electrical current >250 mA. Glass based reactive initiators give 100% of Al/CuO ignition success for an electrical current >500 mA. Reactive initiators directly on silicon cannot initiate even with a 4 A current. At low currents (<1 A), the initiation time is two orders of magnitude longer for Pyrex initiator compared to those obtained for PET initiator technology. We also observed that, the Al/CuO thermite film on PET membrane reacts within 1 ms (sparkles duration) whereas it reacts within 4 ms on Pyrex. The thermite reaction is 40 times greater in intensity using the PET substrate in comparison to Pyrex.

  15. Effect of sample size on intermetallic Al2Cu microstructure and orientation evolution during directional solidification

    NASA Astrophysics Data System (ADS)

    Gao, Ka; Li, Shuangming; Xu, Lei; Fu, Hengzhi

    2014-05-01

    Al-40% Cu hypereutectic alloy samples were successfully directionally solidified at a growth rate of 10 μm/s in different sizes (4 mm, 1.8 mm, and 0.45 mm thickness in transverse section). Using the serial sectioning technique, the three-dimensional (3D) microstructures of the primary intermetallic Al2Cu phase of the alloy can be observed with various growth patterns, L-shape, E-shape, and regular rectangular shape with respect to growth orientations of the (110) and (310) plane. The L-shape and regular rectangular shape of Al2Cu phase are bounded by {110} facets. When the sample size was reduced from 4 mm to 0.45 mm, the solidified microstructures changed from multi-layer dendrites to single-layer dendrite along the growth direction, and then the orientation texture was at the plane (310). The growth mechanism for the regular faceted intermetallic Al2Cu at different sample sizes was interpreted by the oriented attachment mechanism (OA). The experimental results showed that the directionally solidified Al-40% Cu alloy sample in a much smaller size can achieve a well-aligned morphology with a specific growth texture.

  16. Plasma-Sprayed High Entropy Alloys: Microstructure and Properties of AlCoCrFeNi and MnCoCrFeNi

    NASA Astrophysics Data System (ADS)

    Ang, Andrew Siao Ming; Berndt, Christopher C.; Sesso, Mitchell L.; Anupam, Ameey; S, Praveen; Kottada, Ravi Sankar; Murty, B. S.

    2015-02-01

    High entropy alloys (HEAs) represent a new class of materials that present novel phase structures and properties. Apart from bulk material consolidation methods such as casting and sintering, HEAs can also be deposited as a surface coating. In this work, thermal sprayed HEA coatings are investigated that may be used as an alternative bond coat material for a thermal barrier coating system. Nanostructured HEAs that were based on AlCoCrFeNi and MnCoCrFeNi were prepared by ball milling and then plasma sprayed. Splat studies were assessed to optimise the appropriate thermal spray parameters and spray deposits were prepared. After mechanical alloying, aluminum-based and manganese-based HEA powders revealed contrary prominences of BCC and FCC phases in their X-ray diffraction patterns. However, FCC phase was observed as the major phase present in both of the plasma-sprayed AlCoCrFeNi and MnCoCrFeNi coatings. There were also minor oxide peaks detected, which can be attributed to the high temperature processing. The measured porosity levels for AlCoCrFeNi and MnCoCrFeNi coatings were 9.5 ± 2.3 and 7.4 ± 1.3 pct, respectively. Three distinct phase contrasts, dark gray, light gray and white, were observed in the SEM images, with the white regions corresponding to retained multicomponent HEAs. The Vickers hardness (HV0.3kgf) was 4.13 ± 0.43 and 4.42 ± 0.60 GPa for AlCoCrFeNi and MnCoCrFeNi, respectively. Both type of HEAs coatings exhibited anisotropic mechanical behavior due to their lamellar, composite-type microstructure.

  17. High resolution electron microscopy study of a high Cu variant of Weldalite (tm) 049 and a high strength Al-Cu-Ag-Mg-Zr alloy

    NASA Technical Reports Server (NTRS)

    Herring, R. A.; Gayle, Frank W.; Pickens, Joseph R.

    1991-01-01

    Weldalite (trademark) 049 is an Al-Cu-Li-Ag-Mg alloy that is strengthened in artificially aged tempers primarily by very thin plate-like precipitates lying on the set of (111) matrix planes. This precipitate might be expected to be the T(sub 1) phase, Al2CuLi, which has been observed in Al-Cu-Li alloys. However, in several ways this precipitate is similar to the omega phase which also appears as the set of (111) planes plates and is found in Al-Cu-Ag-Mg alloys. The study was undertaken to identify the set of (111) planes precipitate or precipitates in Weldalite (trademark) 049 in the T8 (stretched and artificially aged) temper, and to determine whether T(sub 1), omega, or some other phase is primarily responsible for the high strength (i.e., 700 MPa tensile strength) in this Al-Cu-Li-Ag-Mg alloy.

  18. Effects of Electron Beam Welding on Microstructure, Microhardness, and Electrical Conductivity of Cu-Cr-Zr Alloy Plates

    NASA Astrophysics Data System (ADS)

    Kanigalpula, P. K. C.; Chatterjee, Arya; Pratihar, D. K.; Jha, M. N.; Derose, J.

    2015-12-01

    In this study, the effects of electron beam welding on the microstructure, microhardness, and electrical conductivity of precipitation-hardened Cu-0.804%Cr-0.063%Zr (wt.%) alloy plates were investigated. Experiments were carried out following a central composite design of experiments. Five welding schedules yielding the higher hardness were chosen and then were subjected to standard metallographic and various microscopy techniques to reveal the type, morphology, and distribution of the precipitates and to obtain the sub-structural information from the weld zone. X-ray diffraction studies revealed predominant formation of intermetallic phases in the welded zones of some of the samples, which could have resulted in higher hardness and better electrical conductivity compared to those of other ones. Microhardness values in the fusion zone and heat-affected zone were found to be less than that of the parent material. The mechanism of damage in Cu-Cr-Zr plates due to welding was also explained.

  19. Assessment of the effects of Cr, Cu, Ni and Pb soil contamination by ecotoxicological tests.

    PubMed

    Maisto, Giulia; Manzo, Sonia; De Nicola, Flavia; Carotenuto, Rita; Rocco, Annamaria; Alfani, Anna

    2011-11-01

    This study aimed to assess soil quality by chemical and ecotoxicological investigations and to check the correspondence between soil metal concentrations and ecotoxicity. For these purposes, surface soils collected at four adjacent roadside urban parks and at a former industrial area were characterized for C/N, organic matter content, texture, and pH. Cr, Cu, Ni and Pb, chosen among the most representative soil metal contaminants, were measured as total content and as available and water soluble fractions. In addition, the total concentrations of the investigated metals were used to calculate two chemical indices: the contamination and the potential ecological risk factors. The toxicity of the investigated soils was evaluated by an ecotoxicity test battery carried out on both soil samples (Vibrio fischeri, Heterocypris incongruens and Sinapis alba) and elutriates (Vibrio fischeri, Daphnia magna and Selenastrum capricornutum). The findings, both by the chemical and ecotoxicological approaches, would suggest that the soils with high metal contamination pose ecological risks. On the other hand, moderately metal contaminated soils did not exclude soil ecotoxicity. In fact, toxic effects were also highlighted in soils with low metal content, toxicity being affected by metal availability and soil characteristics. Moreover, the results suggest the importance of using a battery of tests to assess soil ecotoxicity. PMID:21918769

  20. Microstructure and microhardness evolution of melt-spun Al-Si-Cu alloy

    NASA Astrophysics Data System (ADS)

    Ahmed, Emad M.; Ebrahim, M. R.

    2014-04-01

    Al-11 wt.% Si-11 wt.% Cu (11.29 at.% Si-5.1 at.% Cu) melt was rapidly solidified into ribbons and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and microhardness technique. The Rietveld X-ray diffraction analysis was applied successfully to analyze the microstructure and phase precipitations. The high cooling rate obtained in rapid solidification has a significant influence on the microstructure and microhardness of this alloy. On the basis of the Al peaks shift measured in the XRD scans, a solid solubility extension value of 3.95 at.% Si and 3.54 at.% Cu in α-Al were determined. No XRD peaks of the Si phase have been detected. XRD peaks of the intermetallic Al2Cu phase have been observed clearly with estimated content of 12.6 wt.%. During prolonged annealing process at 350°C/25 h, XRD peaks of the Si phase clearly appeared with estimated content of 8.6 wt.% and, moreover, the Al2Cu phase content increased to 16 wt.%. The estimated crystallite size and micro-strain % of α-Al are 30 nm and 0.056, respectively. The melt-spun wheel side ribbon represents ultra-fine microstructure with particles size less than 1μm and exhibits enhancement of hardness to 241 HV. Hardness has further increased to 291 HV during heat treatment (150°C/12 h). Rapid solidification exhibited a great influence on microstructure and microhardness of the Al-Si-Cu alloy.

  1. Low temperature spin dynamics in Cr7Ni-Cu-Cr7Ni coupled molecular rings

    SciTech Connect

    Bordonali, L; Furukawa, Y; Mariani, M; Sabareesh, K P; Garlatti, E; Carretta, S; Lascialfari, A; Timco, G; Winpenny, R E; Borsa, F

    2014-05-07

    Proton Nuclear Magnetic Resonance (NMR) relaxation measurements have been performed down to very low temperature (50 mK) to determine the effect of coupling two Cr7 Ni molecular rings via a Cu2+ ion. No difference in the spin dynamics was found from nuclear spin lattice relaxation down to 1.5 K. At lower temperature, the 1H-NMR line broadens dramatically indicating spin freezing. From the plot of the line width vs. magnetization, it is found that the freezing temperature is higher (260 mK) in the coupled ring with respect to the single Cr7 Ni ring (140 mK).

  2. Cu-based catalyst resulting from a Cu,Zn,Al hydrotalcite-like compound: a microstructural, thermoanalytical, and in situ XAS study.

    PubMed

    Kühl, Stefanie; Tarasov, Andrey; Zander, Stefan; Kasatkin, Igor; Behrens, Malte

    2014-03-24

    A Cu-based methanol synthesis catalyst was obtained from a phase pure Cu,Zn,Al hydrotalcite-like precursor, which was prepared by co-precipitation. This sample was intrinsically more active than a conventionally prepared Cu/ZnO/Al2O3 catalyst. Upon thermal decomposition in air, the [(Cu0.5Zn0.17Al0.33)(OH)2(CO3)0.17]⋅mH2O precursor is transferred into a carbonate-modified, amorphous mixed oxide. The calcined catalyst can be described as well-dispersed "CuO" within ZnAl2 O4 still containing stabilizing carbonate with a strong interaction of Cu(2+) ions with the Zn-Al matrix. The reduction of this material was carefully analyzed by complementary temperature-programmed reduction (TPR) and near-edge X-ray absorption fine structure (NEXAFS) measurements. The results fully describe the reduction mechanism with a kinetic model that can be used to predict the oxidation state of Cu at given reduction conditions. The reaction proceeds in two steps through a kinetically stabilized Cu(I) intermediate. With reduction, a nanostructured catalyst evolves with metallic Cu particles dispersed in a ZnAl2 O4 spinel-like matrix. Due to the strong interaction of Cu and the oxide matrix, the small Cu particles (7 nm) of this catalyst are partially embedded leading to lower absolute activity in comparison with a catalyst comprised of less-embedded particles. Interestingly, the exposed Cu surface area exhibits a superior intrinsic activity, which is related to a positive effect of the interface contact of Cu and its surroundings. PMID:24615857

  3. Phase composition and structure of aluminum Al-Cu-Si-Sn-Pb alloys

    NASA Astrophysics Data System (ADS)

    Belov, N. A.; Stolyarova, O. O.; Murav'eva, T. I.; Zagorskii, D. L.

    2016-06-01

    The structure and phase composition of cast and heat treated Al-Cu-Si-Sn-Pb alloys containing 6 wt % Sn, 2 wt % Pb, 0-4 wt % Cu, 0-10 wt % Si have been studied using calculations and experimental methods. Polythermal and isothermal sections are reported, which indicate the existence of two liquid phases. It was found that the low-melting phase is inhomogeneous and consists of individual leadand tin-based particles.

  4. The formation mechanism of eutectic microstructures in NiAl-Cr composites.

    PubMed

    Tang, Bin; Cogswell, Daniel A; Xu, Guanglong; Milenkovic, Srdjan; Cui, Yuwen

    2016-07-20

    NiAl-based eutectic alloys, consisting of an ordered bcc matrix (B2) and disordered bcc fibers (A2), have been a subject of intensive efforts aimed at tailoring the properties of many of the currently used nickel-based superalloys. A thermodynamic phase field model was developed on a thermodynamic foundation and fully integrated with a thermo-kinetic database of the Ni-Al-Cr ternary system to elucidate the resulting peculiar eutectic microstructure. Invoking a variation of the liquid/solid interfacial thickness with temperature, we simulated the characteristic sunflower-like eutectic microstructures in the NiAl-Cr composites, consistent with experimental observations. The mechanism that governs the formation of the peculiar eutectic morphology was envisioned from the modeled evolutions associated with six sequential steps. Our calculations show that the conditional spinodal decomposition occurring in sequence could further trim and revise the microstructure of the eutectics by generating fine-domain structures, thereby providing an additional method to explore the novel NiAl-based eutectic composites with tunable properties at elevated temperatures. PMID:27385194

  5. Surface tension of liquid Al-Cu and wetting at the Cu/Sapphire solid-liquid interface

    NASA Astrophysics Data System (ADS)

    Schmitz, J.; Brillo, J.; Egry, I.

    2014-02-01

    For the study of the interaction of a liquid alloy with differently oriented single crystalline sapphire surfaces precise surface tension data of the liquid are fundamental. We measured the surface tension of liquid Al-Cu contactlessly on electromagnetically levitated samples using the oscillating drop technique. Data were obtained for samples covering the entire range of composition and in a broad temperature range. The surface tensions can be described as linear functions of temperature with negative slopes. Moreover, they decrease monotonically with an increase of aluminium concentration. The observed behaviour with respect to both temperature and concentration is in agreement with a thermodynamic model calculation using the regular solution approximation. Surface tensions were used to calculate interfacial energies from the contact angles of liquid Cu droplets, deposited on the C(0001), A(11-20), R(1-102) surfaces of an α-Al2O3 substrate. The contact angles were measured by means of the sessile drop method at 1380 K. In the Cu/α-Al2O3 system, no anisotropy is evident neither for the contact angles nor for the interfacial energies of different surfaces. The work of adhesion of this system is isotropic, too.

  6. Simultaneous extraction of Cr(VI) and Cu(II) from humic acid with new synthesized EDTA derivatives.

    PubMed

    Zhang, Tao; Wu, Ying-Xin; Huang, Xiong-Fei; Liu, Jun-Min; Xia, Bing; Zhang, Wei-Hua; Qiu, Rong-Liang

    2012-07-01

    Soil washing is one of the few permanent treatment alternatives for removing metal contaminants. Ethylenediaminetetraacetic acid and its salts (EDTA) is very effective at removing cationic metals and has been utilized globally. However it is ineffective for anionic metal contaminants or metals bound to soil organic matter. The simultaneous removal of cationic and anionic metal contaminants by soil washing is difficult due to differences in their properties. The present study evaluated the potential of a washing process using two synthesized EDTA-derivatives, C(6)HEDTA (2,2'-((2-((carboxymethyl)(2-(hexanoyloxy)ethyl)amino)ethyl)azanediyl)diacetic acid) and C(12)HEDTA (2,2'-((2-((carboxymethyl) (2-(dodecanoyloxy)ethyl)amino)ethyl)azanediyl)diacetic acid), which consist of a hydrophilic polycarboxylic moiety and a hydrophobic moiety with a monoalkyl ester group. A series of equilibrium batch experiments at room temperature were conducted to investigate the efficacy of C(6)HEDTA and C(12)HEDTA as extractants for both oxyanion Cr(VI) and cationic Cu(II). Results showed that either C(6)HEDTA or C(12)HEDTA can extract both Cr(VI) and Cu(II) from humic acid simultaneously. However, C(6)HEDTA was less effective for Cr(VI) probably because it has no surface activities to increase solubility of humic acid, like C(12)HEDTA. Extraction of Cr(VI) was mainly attributed to the decreased surface tension and enhanced solubility of organic matter. Extraction of Cu(II) was attributed to both the Cu(II) chelation and enhanced solubility of humic acid. It was demonstrated that the hydrophilic polycarboxylic moiety of C(12)HEDTA chelates cations while the monoalkyl ester group produces surface active properties that enhance the solubility of humic acid. PMID:22555067

  7. Microscopic origin of the different colors displayed by MgAl2O4:Cr3+ and emerald

    NASA Astrophysics Data System (ADS)

    García-Lastra, J. M.; Barriuso, M. T.; Aramburu, J. A.; Moreno, M.

    2008-08-01

    The difference in color between emerald ( Be3Si6Al2O18:Cr3+ , green) and the Cr3+ -doped spinel MgAl2O4 (red) is striking, considering that in both systems color is due to CrO69- complexes with a close local symmetry ( D3 and the D3d , respectively) and that the measured Cr3+-O2- distance is practically the same ( 1.98±0.01 and 1.97±0.01Å , respectively). By means of density-functional calculations it is shown that this surprising difference can reasonably be explained once the electric field, ER , which all lattice ions lying outside the CrO69- complex exert on localized electrons, is taken into consideration. The origin of the different shape of ER in the two host lattices is analyzed in detail. It is shown that ER raises (decreases) the 2p(O) levels for Be3Si6Al2O18:Cr3+ (MgAl2O4:Cr3+) along the trigonal axis thus favoring a decrease (increase) of 10Dq . The present work demonstrates the key role played by ER (not considered in the traditional ligand field theory) for understanding the differences exhibited by the same complex embedded in host lattices which do not have the same crystal structure. Some remarks on the color of Cr2O3 pure compound are also reported.

  8. HIGH TEMPERATURE BRAZING ALLOY FOR JOINT Fe-Cr-Al MATERIALS AND AUSTENITIC AND FERRITIC STAINLESS STEELS

    DOEpatents

    Cost, R.C.

    1958-07-15

    A new high temperature brazing alloy is described that is particularly suitable for brazing iron-chromiumaluminum alloys. It consists of approximately 20% Cr, 6% Al, 10% Si, and from 1.5 to 5% phosphorus, the balance being iron.

  9. Removal of Cu(II) and Cr(VI) from wastewater by an amphoteric sorbent based on cellulose-rich biomass.

    PubMed

    Zhong, Qian-Qian; Yue, Qin-Yan; Li, Qian; Gao, Bao-Yu; Xu, Xing

    2014-10-13

    A cellulose-rich biomass was modified as a new amphoteric sorbent to eliminate toxic Cu(II) and Cr(VI) from wastewater. The product (WSCA, which stands for modified wheat straw containing both cationic and anionic characters) presents high sorption capacities for the two ions which was evidenced by the comparison with unmodified wheat and other similar samples. Kinetic data and sorption equilibrium isotherms were conducted in batch process. The sorption kinetic analysis revealed that sorption of Cu(II) and Cr(VI) followed the pseudo second-order model well during the whole sorption process. The linear Langmuir isotherm model could perfectly describe the equilibrium data for Cu(II), while the sorption data of Cr(VI) were well fitted by the Freundlich. Results of the static test illustrated the complicated interactions between Cr(VI)/Cu(II) and WSCA including complexation and/or electrostatic attraction mechanisms. PMID:25037417

  10. Optoelectronic properties of delafossite structure CuCr0.93Mg0.07O2 sputter deposited coatings

    NASA Astrophysics Data System (ADS)

    Sun, Hui; Arab Pour Yazdi, Mohammad; Sanchette, Frederic; Billard, Alain

    2016-05-01

    CuCr0.93Mg0.07O2 thin films with improved optoelectronic properties were deposited by reactive magnetron sputtering on fused quartz substrates. The influence of annealing temperature under vacuum on optoelectronic properties of the films was investigated. The amorphous films annealed under vacuum at temperatures higher than 923 K are single-phased delafossite structure, while impurity phases like CuCr2O4 that affect the optoelectronic properties of the films are detected below 873 K. c-axis orientation is observed for CuCr0.93Mg0.07O2 layers and the annealing temperature window in which the films are single-phased delafossite is much larger with Mg doping (923 K  →  1073 K) than that for undoped films (~953 K). The optical and electrical behaviours of the films are enhanced by Mg substitution and their direct band gap energy of about 3.12–3.14 eV is measured. The film possesses the optimum properties after annealing under vacuum at about 1023 K its average transmittance in the visible region can reach 54.23% while the film’s conductivity is about 0.27 S cm‑1.

  11. Magnetic States in Ensemble of Ferromagnetic Nanoparticles in Cu-Mn-Al Alloy.

    PubMed

    Konoplyuk, S M; Kozlova, L E; Kokorin, V V; Perekos, A O; Kolomiets, O V

    2016-12-01

    Two Cu-Mn-Al samples of different compositions were studied: one exhibiting martensitic transformation, another without structural transition. X-ray diffraction and magnetic measurements demonstrate that different magnetic behaviors of alloys originate from different concentrations and sizes of ferromagnetic nanoparticles, which appear after solid solution decomposition.Estimation of magnetic moments of ferromagnetic nanoparticles from magnetization curves was performed using Langevin function and compared to those obtained from X-ray examination. Granular systems are known to show giant magnetoresistance. Therefore, magnetoresistance of Cu-Mn-Al melt-spun ribbons after different aging times was measured. The study has shown that increase in the concentration of Mn atoms and time of aging in Cu-Mn-Al alloy leads to an increase in the amount of precipitated phase appearing as ferromagnetic nanoparticles. PMID:26762264

  12. Local crystallography and stress voiding in Al-Si-Cu versus copper interconnects

    NASA Astrophysics Data System (ADS)

    Keller, R. R.; Kalnas, C. E.; Phelps, J. M.

    1999-07-01

    We compare the local crystallographic orientations associated with stress voids in Al-1Si-0.5Cu (wt %) with those in pure copper interconnects. Orientations were sorted by whether grains were immediately adjacent to voids. Grains adjacent to voids in Al-Si-Cu showed a <111> fiber texture that was slightly stronger than those in intact regions. This is in contrast to copper, which showed weaker local <111> texture around voids. We postulate the difference to be due to the relative effectiveness of the diffusion paths available in the lines. For Al-Si-Cu, the presence of defects associated with precipitates may allow more rapid diffusion than grain boundaries. Voiding in copper, which is free from such defects, depends more on grain boundary structure.

  13. 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.

  14. Effects of the Buffer Layers on the Adhesion and Antimicrobial Properties of the Amorphous ZrAlNiCuSi Films

    NASA Astrophysics Data System (ADS)

    Chiang, Pai-Tsung; Chen, Guo-Ju; Jian, Sheng-Rui; Shih, Yung-Hui

    2011-06-01

    To extend the practical applications of the bulk metallic glasses (BMGs), the preparation of the metallic glass coatings on various substrates becomes an important research issue. Among the interfacial properties of the coatings, the adhesion between films and substrates is the most crucial. In this study, amorphous Zr61Al7.5Ni10Cu17.5Si4 (ZrAlNiCuSi) thin films were deposited on SUS304 stainless steel at various sputtering powers by DC sputtering. According to the scratch tests, the introduction of the Cr and Ti buffer layers effectively improves the adhesion between the amorphous thin films and substrate without changing the surface properties, such as roughness and morphology. The antimicrobial results show that the biological activities of these microbes, except Acinetobacter baumannii, are effectively suppressed during the test period.

  15. Potential and frequency effects on fretting corrosion of Ti6Al4V and CoCrMo surfaces.

    PubMed

    Swaminathan, Viswanathan; Gilbert, Jeremy L

    2013-09-01

    Fretting corrosion has been reported at the metal-metal interfaces of a wide range of medical devices, including total joint replacements, spinal devices, and overlapping cardiovascular stents. Currently, the fretting corrosion phenomenon associated with metal-on-metal contacts is not fully understood. This study investigated the effect of potential and fretting frequency on the fretting corrosion performance of Ti6Al4V/Ti6Al4V, Ti6Al4V/CoCrMo, and CoCrMo/CoCrMo alloy combinations at fixed normal load and displacement conditions using a custom built fretting corrosion test system. The results showed that the fretting current densities increased with increases in potential and were highest for Ti6Al4V/Ti6Al4V couple (1.5 mA/cm(2) at 0 V vs. Ag/AgCl). The coefficient of friction varied with potential and was about two times higher for Ti6Al4V/Ti6Al4V (0.71 V at 0 V vs. Ag/AgCl). In most of the potential range tested, the fretting corrosion behavior of CoCrMo/Ti6Al4V and CoCrMo/CoCrMo was similar and dominated by the CoCrMo surface. Increase in applied fretting frequency linearly increased the fretting current densities in the regions where the passive film is stable. Also, the model-based fretting current densities were in excellent agreement with the experimental results. Overall, Ti6Al4V/Ti6Al4V couple was more susceptible to fretting corrosion compared with other couples. However, the effects of these processes on the biological system were not assessed. PMID:23404905

  16. Thermo-mechanical processing (TMP) of Ti-48Al-2Nb-2Cr based alloys

    SciTech Connect

    Fuchs, G.E.

    1995-02-01

    The effects of heat treatment and deformation processing on the microstructures and properties of {gamma}-TiAl based alloys produced by ingot metallurgy (I/M) and powder metallurgy (P/M) techniques were examined. The alloy selected for this work is the second generation {gamma}-TiAl based alloy -- Ti-48Al-2Nb-2Cr (at %). Homogenization of I/M samples was performed at a variety of temperatures, followed by hot working by isothermal forging. P/M samples were prepared from gas atomized powders, consolidated by both HIP and extrusion and some of the HIPed material was then hot worked by isothermal forging. The effects of processing, heat treatment and hot working on the microstructures and properties will be discussed.

  17. First-principles study on the magnetism and electronic structure in 3d transition metal (X=Sc, V, Cr, Mn, Fe, Ni, Cu) doped CoO

    NASA Astrophysics Data System (ADS)

    Liu, R. X.; Wang, X. C.; Chen, G. F.; Yang, B. H.

    2016-03-01

    We have studied the electronic structure and magnetism of the single transitional metal element X=Sc, V, Cr, Mn, Fe, Ni, Cu-doped CoO systems by first-principles calculations. At X=Sc, Cr, Cu, the binding energy of the doped systems is lower than pure CoO, suggesting that these systems are energetically stable. In the Sc, V, Cr, Mn, Fe, Ni, Cu-doped 2×2×2 CoO supercells, the total magnetic moments are 3.03, 5.64, 6.80, 7.70, 6.93, 2.30 and 1.96 μB, respectively. At X=Cr and Fe, the doped CoO systems are half-metallic with a high spin polarization. The large magnetic moment and high spin polarization in the Cr and Fe-doped CoO are important for the design of the spintronic devices.

  18. Precipitation strengthened high strength, high conductivity Cu-Cr-Nb alloys produced by chill block melt spinning. Final Report Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Ellis, David L.; Michal, Gary M.

    1989-01-01

    A series of Cu-based alloys containing 2 to 10 a/o Cr and 1 to 5 a/o Nb were produced by chill block melt spinning (CBMS). The melt spun ribbons were consolidated and hot rolled to sheet to produce a supersaturated Cu-Cr-Nb solid solution from which the high melting point intermetallic compound Cr2Nb could be precipitated to strengthen the Cu matrix. The results show that the materials possess electrical conductivities in excess of 90 percent that of pure Cu at 200 C and above. The strengths of the Cu-Cr-Nb alloys were much greater than Cu, Cu-0.6 Cr, NARloy-A, and NARloy-Z in the as-melt spun condition. The strengths of the consolidated materials were less than Cu-Cr and Cu-Cr-Zr below 500 C and 600 C respectively, but were significantly better above these temperatures. The strengths of the consolidated materials were greater than NARloy-Z, at all temperatures. The GLIDCOP possessed similar strength levels up to 750 C when the strength of the Cu-Cr-Nb alloys begins to degrade. The long term stability of the Cu-Cr-Nb alloys was measured by the microhardness of aged samples and the growth of precipitates. The microhardness measurements indicate that the alloys overage rapidly, but do not suffer much loss in strength between 10 and 100 hours which confirms the results of the electrical resistivity measurements taken during the aging of the alloys at 500 C. The loss in strength from peak strength levels is significant, but the strength remains exceptionally good. Transmission electron microscopy (TEM) of the as-melt spun samples revealed that Cr2Nb precipitates formed in the liquid Cu during the chill block melt spinning, indicating a very strong driving force for the formation of the precipitates. The TEM of the aged and consolidated materials indicates that the precipitates coarsen considerably, but remain in the submicron range.

  19. Joule-Heating-Induced Damage in Cu-Al Wedge Bonds Under Current Stressing

    NASA Astrophysics Data System (ADS)

    Yang, Tsung-Han; Lin, Yu-Min; Ouyang, Fan-Yi

    2014-01-01

    Copper wires are increasingly used to replace gold wires in wire-bonding technology owing to their better electrical properties and lower cost. However, not many studies have been conducted on electromigration-induced failure of Cu wedge bonds on Al metallization. In this study, we investigated the failure mechanism of Cu-Al wedge bonds under high current stressing from 4 × 104 A/cm2 to 1 × 105 A/cm2 at ambient temperature of 175°C. The resistance evolution of samples during current stressing and the microstructure of the joint interface between the Cu wire and Al-Si bond pad were examined. The results showed that abnormal crack formation accompanying significant intermetallic compound growth was observed at the second joint of the samples, regardless of the direction of electric current for both current densities of 4 × 104 A/cm2 and 8 × 104 A/cm2. We propose that this abnormal crack formation at the second joint is mainly due to the higher temperature induced by the greater Joule heating at the second joint for the same current stressing, because of its smaller bonded area compared with the first joint. The corresponding fluxes induced by the electric current and chemical potential difference between Cu and Al were calculated and compared to explain the failure mechanism. For current density of 1 × 105 A/cm2, the Cu wire melted within 0.5 h owing to serious Joule heating.

  20. Partition coefficients for Al, Ca, Ti, Cr, and Ni in olivine obtained by melting experiment on an LL6 chondrite

    NASA Technical Reports Server (NTRS)

    Miyamoto, M.; Mikouchi, T.; Mckay, G. A.

    1994-01-01

    We report the partition coefficients for Ca, Al, Ti, Cr, and Ni in olivine obtained through a series of melting experiments on an LL6 chondrite under varying conditions of temperature and oxygen fugacity. It is necessary to examine the variation of partition coefficients up to extremely reducing conditions in order to study meteoritic olivines. For Ca, Al, and Cr, the partition coefficients tend to decrease as temperature increases, but do not change even under extremely reducing conditions.