Science.gov

Sample records for cu ag ni

  1. Corrosion behavior of Au and Ag modified Cu-Ni-Mn alloys.

    PubMed

    Wright, S R; Cocks, F H; Gettleman, L

    1980-04-01

    The linear electrochemical polarization method was used to provide quantitative in vitro measurements of corrosion rates as a function of exposure time for Cu-Ni-Mn, Cu-Ni-Mn-Au, Cu-Ni-Mn-Ag, and Cu-Ni-Mn-Au-Ag alloys in artificial saliva. Both Au and Ag additives to dental-cast Cu-Ni-Mn alloys lowered the corrosion rate significantly.

  2. Global optimization of bimetallic cluster structures. I. Size-mismatched Ag-Cu, Ag-Ni, and Au-Cu systems.

    PubMed

    Rapallo, Arnaldo; Rossi, Giulia; Ferrando, Riccardo; Fortunelli, Alessandro; Curley, Benjamin C; Lloyd, Lesley D; Tarbuck, Gary M; Johnston, Roy L

    2005-05-15

    A genetic algorithm approach is applied to the optimization of the potential energy of a wide range of binary metallic nanoclusters, Ag-Cu, Ag-Ni, Au-Cu, Ag-Pd, Ag-Au, and Pd-Pt, modeled by a semiempirical potential. The aim of this work is to single out the driving forces that make different structural motifs the most favorable at different sizes and chemical compositions. Paper I is devoted to the analysis of size-mismatched systems, namely, Ag-Cu, Ag-Ni, and Au-Cu clusters. In Ag-Cu and Ag-Ni clusters, the large size mismatch and the tendency of Ag to segregate at the surface of Cu and Ni lead to the location of core-shell polyicosahedral minimum structures. Particularly stable polyicosahedral clusters are located at size N = 34 (at the composition with 27 Ag atoms) and N = 38 (at the composition with 32 and 30 Ag atoms). In Ag-Ni clusters, Ag32Ni13 is also shown to be a good energetic configuration. For Au-Cu clusters, these core-shell polyicosahedra are less common, because size mismatch is not reinforced by a strong tendency to segregation of Au at the surface of Cu, and Au atoms are not well accommodated upon the strained polyicosahedral surface.

  3. Deformation-induced nanoscale mixing reactions in Cu/Ni and Ag/Pd multilayers

    SciTech Connect

    Wang, Z.; Perepezko, J. H.

    2013-11-04

    During the repeated cold rolling of Cu/Ni and Ag/Pd multilayers, a solid solution forms at the interfaces as nanoscale layer structure with a composition that replicates the overall multilayer composition. The interfacial mixing behavior was investigated by means of X-ray diffraction and scanning transmission electron microscopy. During deformation induced reaction, the intermixing behavior of the Cu/Ni and Ag/Pd multilayers is in contrast to thermally activated diffusion behavior. This distinct behavior can provide new kinetic pathways and offer opportunities for microstructure control that cannot be achieved by thermal processing.

  4. Oxygen reduction on Ni, Ag, and Cu meniscus electrodes in molten carbonate

    SciTech Connect

    Ogura, Hiroyuki; Shirogami, Tamotsu

    1994-12-31

    The oxygen reduction pathways in molten carbonates have been investigated by analyzing the charge transfer resistances of the i-V curves on the meniscus electrodes of Ni, Cu, and Ag screens at 550 C. The electrochemical reduction pathways of oxygen at the meniscus electrode were found to be different depending on the electrode materials. For the Ni meniscus electrode system, the reactive material of charge transfer is the lithium doped nickel oxide, for the Ag system that is the silver oxide ion, and for the Cu system that is peroxide ion, respectively.

  5. Study of Metal-NH[subscript 3] Interfaces (Metal= Cu, Ni, Ag) Using Potentiostatic Curves

    ERIC Educational Resources Information Center

    Nunes, Nelson; Martins, Angela; Leitao, Ruben Elvas

    2007-01-01

    Experiment is conducted to determine the kinetic parameters of metal-solution interfaces. During the experiment the kinetic parameters for the interfaces Cu-NH[subscript 3], Ag-NH[subscript 3] and Ni-NH[subscript 3] is easily determined.

  6. Interfacial microstructure between Sn-3Ag-xBi alloy and Cu substrate with or without electrolytic Ni plating

    NASA Astrophysics Data System (ADS)

    Hwang, Chi-Won; Lee, Jung-Goo; Suganuma, Katsuaki; Mori, Hirotaro

    2003-02-01

    The microstructure of the interfacial phase of Sn-3Ag-xBi alloy on a Cu substrate with or without electrolytic Ni plating was evaluated. Bismuth additions into Sn-Ag alloys do not affect interfacial phase formations. Without plating, η-Cu6Sn5/ɛ-Cu3Sn interfacial phases developed as reaction products in the as-soldered condition. The η-phase Cu6Sn5 with a hexagonal close-packed structure grows about 1-µm scallops. The ɛ-phase Cu3Sn with an orthorhombic structure forms with small 100-nm grains between η-Cu6Sn5 and Cu. For Ni plating, a Ni3Sn4 layer of monoclinic structure formed as the primary reaction product, and a thin η-Ni3Sn2 layer of hexagonal close-packed structure forms between the Ni3Sn4 and Ni layer. In the Ni layer, Ni-Sn compound particles of nanosize distribute by Sn diffusion into Ni. On the total thickness of interfacial reaction layers, Sn-3Ag-6Bi joints are thicker by about 0.9 µm for the joint without Ni plating and 0.18 µm for the joint with Ni plating than Sn-3Ag joints, respectively. The thickening of interfacial reaction layers can affect the mechanical properties of strength and fatigue resistance.

  7. The Influence of Cu on Metastable NiSn4 in Sn-3.5Ag- xCu/ENIG Joints

    NASA Astrophysics Data System (ADS)

    Belyakov, S. A.; Gourlay, C. M.

    2016-01-01

    We have investigated the effect of small amounts of Cu on suppression of metastable βSn-NiSn4 eutectic growth in solder joints between Sn-3.5Ag- xCu solders and Ni-based substrates. For Sn-3.5Ag/electroless nickel immersion gold (ENIG) and Sn-3.5Ag/Ni solder joints we showed that the eutectic mixture contains βSn, Ag3Sn, and metastable NiSn4. It was found that addition of only 0.005 wt.% Cu to Sn-3.5Ag- xCu/ENIG or Sn-3.5Ag- xCu/Ni joints promoted formation of a stable βSn-Ni3Sn4 eutectic and that both Ni3Sn4 and NiSn4 occur in the eutectic at this Cu level. We also showed that for complete prevention of formation of metastable NiSn4 during eutectic solidification of the solder joint, addition of at least 0.3 wt.% Cu was required.

  8. Phase equilibria of the Sn-Ag-Cu-Ni quaternary system at the sn-rich corner

    NASA Astrophysics Data System (ADS)

    Chen, Sinn-Wen; Chang, Cheng-An

    2004-10-01

    Knowledge of phase equilibria of the Sn-Ag-Cu-Ni quaternary system at the Sn-rich corner is important for the understanding of the interfacial reactions at the Sn-Ag-Cu/Ni contacts, which are frequently encountered in recent microelectronic products. Various Sn-Ag-Cu-Ni alloys were prepared and equilibrated at 250°C. The alloys were then quenched and analyzed. The phases were determined by metallography, compositional analysis, and x-ray diffraction (XRD) analysis. No quaternary phases were found. The isoplethal sections at 60at.%Sn, 70at.%Sn, 80at.%Sn, and 90at.%Sn at 250°C are determined. The phase equilibrium relationship was proposed based on the quaternary experimental results and the 250°C isothermal sections of the four constituent ternary systems, Sn-Ag-Cu, Sn-Ag-Ni, Sn-Cu-Ni, and Cu-Ag-Ni. Because there are no ternary phases in all these three systems, all the compounds are in fact binary compounds with various solubilities of the other two elements.

  9. Electromigration effect upon the Sn-0.7 wt% Cu/Ni and Sn-3.5 wt% Ag/Ni interfacial reactions

    NASA Astrophysics Data System (ADS)

    Chen, Chih-ming; Chen, Sinn-wen

    2001-08-01

    This study investigates the effect of electromigration upon the interfacial reactions between the promising lead-free solders, Sn-Cu and Sn-Ag, with Ni substrate. Sandwich-type reaction couples, Sn-0.7 wt% Cu/Ni/Sn-0.7 wt% Cu and Sn-3.5 wt% Ag/Ni/Sn-3.5 wt% Ag, were reacted at 160, 180, and 200 °C for various lengths of time with and without the passage of electric currents. Without passage of electric currents through the couples, only one intermetallic compound Ni3Sn4 with ˜7 at. % Cu solubility was found at both interfaces of the Sn-0.7 wt% Cu/Ni couples. With the passage of an electric current of 500 A/cm2 density, the Cu6Sn5 phase was formed at the solder/Ni interface besides the Ni3Sn4 phase. Similar to those without the passage of electric currents, only the Ni3Sn4 phase was found at the Ni/solder interface. Directions of movement of electrons, Sn, and Cu atoms are the same at the solder/Ni interface, and the growth rates of the intermetallic layers were enhanced. At the Ni/solder interface, the electrons flow in the opposite direction of the Sn and Cu movement, and the growth rates of the intermetallic layers were retarded. Only the Ni3Sn4 phase was formed from the Sn-3.5 wt% Ag/Ni interfacial reaction with and without the passage of electric currents. Similar to the Sn-0.7 wt% Cu/Ni system, the movement of electrons enhances or retards the growth rates of the intermetallic layers at the solder/Ni and Ni/solder interfaces, respectively. Calculation results show the apparent effective charge za* decreases in magnitude with raising temperatures, which indicates the electromigration effect becomes insignificant at higher temperatures.

  10. Influence of Cu Nanoparticles on Microstructure and Mechanical Properties of Sn0.7Ag0.5Cu-BiNi/Cu Solder Joint

    NASA Astrophysics Data System (ADS)

    Ban, G. F.; Sun, F. L.; Fan, J. J.; Liu, Y.; Cong, S. N.

    2017-02-01

    The influence of Cu nanoparticles addition on microstructure and mechanical properties of Sn0.7Ag0.5Cu-BiNi/Cu solder joint after reflow and isothermal aging has been investigated in this study. Experimental results indicate that the addition of Cu nanoparticles suppresses the growth of intermetallic compound (IMC) layer at the interface after reflow and aging. Moreover, the bulk solder appears with refined microstructure after adding Cu nanoparticles. In addition, solder joints containing Cu nanoparticles display higher microhardness due to the dispersive distribution of Cu nanoparticles as well as the refined IMC particles. The addition of 0.1% Cu nanoparticles can improve the microhardness by 16% compared with the noncomposite. However, the existing porosity in the solder exerts a negative effect on microhardness and shear strength. The mechanism of porosity formation has been discussed in detail. Porosity increases markedly with increasing Cu nanoparticles proportion.

  11. Containerless electromagnetic levitation melting of Cu-Fe and Ag-Ni alloys

    NASA Technical Reports Server (NTRS)

    Abbaschian, G. J.; Ethridge, E. C.

    1983-01-01

    The feasibility of producing silver or copper alloys containing finely dispersed nickel or iron particles, respectively, by utilizing containerless electromagnetic levitation casting techniques was investigated. A levitation coil was designed to successfully levitate and melt a variety of alloys including Nb-Ge, Cu-Fe, Fe-C, and Ag-Ni. Samples of 70 Cu-30 Fe and 80 Ag-20 Ni (atomic %), prepared by mechanical pressing of the constituent powders, were levitated and heated either to the solid plus liquid range of the alloys or to the fully liquid region. The samples were then solidified by passing helium gas into the bell jar or they were dropped into a quenching oil. The structure of the samples which were heated to the solid plus liquid range consists of uniform distribution of Fe or Ni particle in their respective matrices. A considerable amount of entrapped gas bubbles were contained. Upon heating for longer periods or to higher temperatures, the bubbles coalesced and burst, causing the samples to become fragmented and usually fall out of the coil.

  12. The effect of intermetallic compound morphology on Cu diffusion in Sn-Ag and Sn-Pb solder bump on the Ni/Cu Under-bump metallization

    NASA Astrophysics Data System (ADS)

    Jang, Guh-Yaw; Duh, Jenq-Gong

    2005-01-01

    The eutectic Sn-Ag solder alloy is one of the candidates for the Pb-free solder, and Sn-Pb solder alloys are still widely used in today’s electronic packages. In this tudy, the interfacial reaction in the eutectic Sn-Ag and Sn-Pb solder joints was investigated with an assembly of a solder/Ni/Cu/Ti/Si3N4/Si multilayer structures. In the Sn-3.5Ag solder joints reflowed at 260°C, only the (Ni1-x,Cux)3Sn4 intermetallic compound (IMC) formed at the solder/Ni interface. For the Sn-37Pb solder reflowed at 225°C for one to ten cycles, only the (Ni1-x,Cux)3Sn4 IMC formed between the solder and the Ni/Cu under-bump metallization (UBM). Nevertheless, the (Cu1-y,Niy)6Sn5 IMC was observed in joints reflowed at 245°C after five cycles and at 265°C after three cycles. With the aid of microstructure evolution, quantitative analysis, and elemental distribution between the solder and Ni/Cu UBM, it was revealed that Cu content in the solder near the solder/IMC interface played an important role in the formation of the (Cu1-y,Niy)6Sn5 IMC. In addition, the diffusion behavior of Cu in eutectic Sn-Ag and Sn-Pb solders with the Ni/Cu UBM were probed and discussed. The atomic flux of Cu diffused through Ni was evaluated by detailed quantitative analysis in an electron probe microanalyzer (EPMA). During reflow, the atomic flux of Cu was on the order of 1016-1017 atoms/cm2sec in both the eutectic Sn-Ag and Sn-Pb systems.

  13. Reaction Mechanism and Mechanical Properties of the Flip-Chip Sn-3.0Ag-0.5Cu Solder Bump with Cu/Ni- xCu/Ti Underbump Metallization After Various Reflows

    NASA Astrophysics Data System (ADS)

    Peng, Chung-Nan; Duh, Jenq-Gong

    2009-12-01

    Ni underbump metallization (UBM) has been widely used as the diffusion barrier between solder and Cu pads. To retard the fast dissolution rate of Ni UBM, Cu was added into Ni thin films. The Ni-Cu UBM can provide extra Cu to the solders to maintain the Cu6Sn5 intermetallic compound (IMC) at the interface, which can thus significantly decrease the Ni dissolution rate. In this study, the Cu content of the sputtered Cu/Ni- xCu/Ti UBM was varied from 0 wt.% to 20 wt.%. Sn-3Ag-0.5Cu solder was reflowed with Cu/Ni-Cu/Ti UBM one, three, and five times. Reflow and cooling conditions altered the morphology of the IMCs formed at the interface. The amount of (Cu,Ni)6Sn5 increased with increasing Cu content in the Ni-Cu film. The Cu concentration of the intermetallic compound was strongly dependent on the composition of the Ni-Cu films. The results of this study suggest that Cu-rich Ni- xCu UBM can be used to suppress interfacial spalling and improve shear strength and pull strength of solder joints.

  14. Hydrazine reduction of metal ions to porous submicro-structures of Ag, Pd, Cu, Ni, and Bi

    SciTech Connect

    Wang Yue; Shi Yongfang; Chen Yubiao; Wu Liming

    2012-07-15

    Porous submicro-structures of Ag, Pd, Cu, Ni, and Bi with high surface area have been prepared by the reduction of hydrazine in glycerol-ethanol solution at room temperature or 120-180 Degree-Sign C. Phase purity, morphology, and specific surface area have been characterized. The reactions probably undergo three different mechanisms: simple reduction for Ag and Pd, coordination-then-reduction for Cu and Ni, and hydrolysis-then-reduction for Bi. The reductant hydrazine also plays an important role to the formation of the porous submicro-structure. The reaction temperature influences the size of the constituent particles and the overall architecture of the submicro-structure so as to influence the surface area value. The as-prepared porous metals have shown the second largest surface area ever reported, which are smaller than those made by the reduction of NaBH{sub 4}, but larger than those made by hard or soft template methods. - Graphical abstract: Porous submicro-structures of Ag, Pd, Cu, Ni, and Bi with high surface area have been prepared by the reduction of hydrazine in the glycerol-ethanol solution at room temperature or 120-180 Degree-Sign C. The reactions undergo different mechanisms: simple reduction for Ag and Pd, coordination-then-reduction for Cu and Ni, and hydrolysis-then-reduction for Bi. Highlights: Black-Right-Pointing-Pointer Syntheses of porous Ag, Pd, Cu, Ni, and Bi with high surface area. Black-Right-Pointing-Pointer Ag and Pd undergo simple reduction. Black-Right-Pointing-Pointer Cu and Ni undergo coordination-then-reduction. Black-Right-Pointing-Pointer Bi undergoes hydrolysis-then-reduction. Black-Right-Pointing-Pointer The as-prepared metals have shown the second largest surface area ever reported.

  15. Investigation of interfacial reaction between Sn-Ag eutectic solder and Au/Ni/Cu/Ti thin film metallization

    NASA Astrophysics Data System (ADS)

    Park, J. Y.; Yang, C. W.; Ha, J. S.; Kim, C.-U.; Kwon, E. J.; Jung, S. B.; Kang, C. S.

    2001-09-01

    This paper reports the formation of intermetallic compounds in Au/Ni/Cu/Ti under-bump-metallization (UBM) structure reacted with Ag-Sn eutectic solder. In this study, UBM is prepared by evaporating Au(500 Å)/Ni(1000 Å)/Cu(7500 Å) /Ti (700 Å) thin films on top of Si substrates. It is then reacted with Ag-Sn eutectic solder at 260 C for various times to induce different stages of the interfacial reaction. Microstructural examination of the interface, using both chemical and crystallographic analysis, indicates that two types of intermetallic compounds are formed during the interfacial reaction. The first phase, formed at the intial stage of the reaction, is predominantly Ni3Sn4. At longer times the Ni3Sn4 phase transforms into (Cu, Ni)6Sn6, probably induced by interdiffusion of Cu and Ni. At this stage, the underlying Cu layer also reacts with Sn and forms the same phase, (Cu,Ni)6Sn5. As a result, the fully reacted interface is found to consist of two intermetallic layers with the same phase but different morphologies.

  16. HRLEED study of the roughening transitions in Cu(110), Ni(110) and Ag(110) surfaces

    SciTech Connect

    Wang, K.; Montano, P.A. |

    1996-12-01

    The authors present the results of High Resolution Low Energy Electron Diffraction (HRLEED) measurements of the thermal roughening transition on Cu(110), Ag(110) and Ni(110) surfaces. They performed careful spot profile intensity measurements as a function of temperature. They observed a proliferation of steps along the (110) and (001) directions. In addition a strong deviation from a Debye model was observed in the scattered intensity of the Bragg reflections. This deviation from the harmonic approximation occurs well below the roughening transition temperature. The behavior of the three metal surfaces is qualitatively similar except for the transition temperatures. Ni shows the highest transition temperature (1,300 K), Cu is intermediate (1,000 K) and Ag has the lowest temperature (730 K). Analyzing the behavior of the (00) reflection intensity, and the evolution of the line shape as a function of the temperature, they found clear evidence of a roughening transition at the (110) surface. A lineshape analysis of the (00) reflection shows the transition from a Lorentzian lineshape to a power law. They also proved, based on the experimental data and a recent theoretical model, that there is a tremendous increase in step density and a decrease in the average terrace size as the temperature increases. They used STM to corroborate the HRLEED results at room temperature. They found excellent agreement.

  17. Preparation of Ag-Ni-Cu Composite Material by Ultrasonic Arc Spray Forming and Accumulative Roll Bonding and the Evolution of Its Microstructure

    NASA Astrophysics Data System (ADS)

    Zhang, Ke; Qin, Guo-Yi; Xu, Si-Yong; Guo, Jin-Xin; Ma, Guang

    2015-02-01

    We prepared a layered composite material by subjecting a deposition billet of AgNiCu15-5 formed by ultrasonic arc spray forming (UASF) to extrusion at 773 K (500 °C), rolling at 673 K (400 °C), and accumulative roll bonding (ARB). The evolution of the microstructure of the formed AgNiCu15-5 strips was analyzed through X-ray diffraction analysis, scanning electron microscopy, and energy-dispersive spectrometry. The deposition billet had a rapid solidification microstructure consisting of β-Ni particles dispersed in α-Ag matrix. ARB significantly refined the microstructure of the AgNiCu15-5 samples. There was no further decrease in the grain size after the 9th ARB cycle. Thus, UASF combined with extrusion and ARB is suitable for producing high-performance AgNiCu15-5-based electrical contact materials efficiently and economically.

  18. The Maximum Fluidity Length of Solidifying Sn-Cu-Ag-Ni Solder Alloys

    NASA Astrophysics Data System (ADS)

    Gourlay, C. M.; Read, J.; Nogita, K.; Dahle, A. K.

    2008-01-01

    During wave soldering, it is important that a solder is able to flow easily to fill joints and to drain away to leave tidy fillets. The maximum fluidity length ( L f) is a simple measure of the flow behavior of solidifying alloys, defined as the distance a cooling and solidifying alloy can flow in a constant cross-section before the developing microstructure arrests flow. This paper explores the influence of alloy composition on L f in Sn-rich Sn-Cu-Ag-Ni alloys with compositions relevant to wave soldering. Significant differences in L f are measured among candidate lead-free solder alloys, which are discussed with respect to the phase diagrams and the mode of solidification.

  19. Copper-based alloys, crystallographic and crystallochemical parameters of alloys in binary systems Cu-Me (Me=Co, Rh, Ir, Cu, Ag, Au, Ni, Pd, Pt)

    NASA Astrophysics Data System (ADS)

    Porobova, Svetlana; Markova, Tat'jana; Klopotov, Vladimir; Klopotov, Anatoliy; Loskutov, Oleg; Vlasov, Viktor

    2016-01-01

    The article presents the results of the analysis of phase equilibrium of ordered phases in binary systems based on copper Cu- Me (where Me - Co, Rh, Ir, Ag, Au, Ni, Pd, Pt) to find correlations of crystallochemical and crystallographic factors. It is established that the packing index in disordered solid solutions in binary systems based on copper is close to the value of 0.74 against the background of an insignificant deviation of atomic volumes from the Zen's law.

  20. Copper-based alloys, crystallographic and crystallochemical parameters of alloys in binary systems Cu-Me (Me=Co, Rh, Ir, Cu, Ag, Au, Ni, Pd, Pt)

    SciTech Connect

    Porobova, Svetlana Loskutov, Oleg; Markova, Tat’jana; Klopotov, Vladimir; Klopotov, Anatoliy; Vlasov, Viktor

    2016-01-15

    The article presents the results of the analysis of phase equilibrium of ordered phases in binary systems based on copper Cu- Me (where Me - Co, Rh, Ir, Ag, Au, Ni, Pd, Pt) to find correlations of crystallochemical and crystallographic factors. It is established that the packing index in disordered solid solutions in binary systems based on copper is close to the value of 0.74 against the background of an insignificant deviation of atomic volumes from the Zen’s law.

  1. Infrared Brazing of Ti50Ni50 Shape Memory Alloy and Inconel 600 Alloy with Two Ag-Cu-Ti Active Braze Alloys

    NASA Astrophysics Data System (ADS)

    Shiue, Ren-Kae; Wu, Shyi-Kaan; Yang, Sheng-Hao

    2017-02-01

    Infrared brazing of Ti50Ni50 SMA and Inconel 600 alloy using Cusil-ABA and Ticusil filler metals has been investigated. The joints were dominated by Ag-Cu eutectic with proeutectic Cu in the Cusil-ABA brazed joint and with proeutectic Ag in the Ticusil one. A continuous curved belt composed of a Ni3Ti layer and a (Cu x Ni1- x )2Ti layer formed in the brazed Ti50Ni50/Ticusil/Inconel 600 joint. On the Ti50Ni50 SMA side, an intermetallic layer of (Cu x Ni1- x )2Ti formed in all joints, with x values around 0.81 and 0.47. Layers of (Cu x Ni1- x )2Ti, Ni3Ti, and mixed Ni3Ti and Ni2Cr intermetallics were observed next to the Inconel 600 substrate in the brazed Ti50Ni50/Cusil-ABA/Inconel 600 joint. The maximum shear strengths of the joints using the Cusil-ABA filler metal and the Ticusil filler metal were 324 and 300 MPa, respectively. In the Cusil-ABA brazed joint, cracks with cleavage-dominated fracture propagated along the (Cu x Ni1- x )2Ti interfacial layer next to the Ti50Ni50 SMA substrate. In the Ticusil brazed joint, ductile dimple fracture occurred in the Ag-rich matrix near the Inconel 600 alloy substrate. The absence of a detrimental Ti-Fe-(Cu) layer on the Inconel 600 substrate side can effectively improve the shear strength of the joint.

  2. Ni/Cu/Ag plated contacts: A study of resistivity and contact adhesion for crystalline-Si solar cells

    NASA Astrophysics Data System (ADS)

    ur Rehman, Atteq; Lee, Sang Hee; Bhopal, Muhammad Fahad; Lee, Soo Hong

    2016-07-01

    Ni/Cu/Ag plated contacts were examined as an alternate to Ag screen printed contacts for silicon (Si) solar cell metallization. To realize a reliable contact for industrial applications, the contact resistance and its adhesion to Si substrates were evaluated. Si surface roughness by picosecond (ps) laser ablation of silicon-nitride (SiNx) antireflection coating (ARC) was done in order to prepare the patterns. The sintering process after Ni/Cu/Ag full metallization in the form of the post-annealing process was applied to investigate the contact resistivity and adhesion. A very low contact resistivity of approximately 0.5 mΩcm2 has been achieved with measurements made by the transfer length method (TLM). Thin finger lines of about 26 μm wide and a line resistance of 0.51 Ω/cm have been realized by plating technology. Improved contact adhesion by combining the ps-laser-ablation and post-annealing process has been achieved. We have shown the peel-off strengths >1 N/mm with a higher average adhesion of 1.9 N/mm. Our pull-tab adhesion tests demonstrate excellent strength well above the wafer breakage force. [Figure not available: see fulltext.

  3. Creep Properties of Sn-1.0Ag-0.5Cu Lead-Free Solder with Ni Addition

    NASA Astrophysics Data System (ADS)

    Che, F. X.; Zhu, W. H.; Poh, Edith S. W.; Zhang, X. R.; Zhang, Xiaowu; Chai, T. C.; Gao, S.

    2011-03-01

    In this work, tensile creep tests for Sn-1.0Ag-0.5Cu-0.02Ni solder have been conducted at various temperatures and stress levels to determine its creep properties. The effects of stress level and temperature on creep strain rate were investigated. Creep constitutive models (such as the simple power-law model, hyperbolic sine model, double power-law model, and exponential model) have been reviewed, and the material constants of each model have been determined based on experimental results. The stress exponent and creep activation energy have been studied and compared with other researchers' results. These four creep constitutive models established in this paper were then implemented into a user-defined subroutine in the ANSYS™ finite-element analysis software to investigate the creep behavior of Sn-1.0Ag-0.5Cu-0.02Ni solder joints of thin fine-pitch ball grid array (TFBGA) packages for the purpose of model comparison and application. Similar simulation results of creep strain and creep strain energy density were achieved when using the different creep constitutive models, indicating that the creep models are consistent and accurate.

  4. 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.

  5. Effect of Isothermal Aging on the Long-Term Reliability of Fine-Pitch Sn-Ag-Cu and Sn-Ag Solder Interconnects With and Without Board-Side Ni Surface Finish

    NASA Astrophysics Data System (ADS)

    Lee, Tae-Kyu; Duh, Jeng-Gong

    2014-11-01

    The combined effects on long-term reliability of isothermal aging and chemically balanced or unbalanced surface finish have been investigated for fine-pitch ball grid array packages with Sn-3.0Ag-0.5Cu (SAC305) (wt.%) and Sn-3.5Ag (SnAg) (wt.%) solder ball interconnects. Two different printed circuit board surface finishes were selected to compare the effects of chemically balanced and unbalanced structure interconnects with and without board-side Ni surface finish. NiAu/solder/Cu and NiAu/solder/NiAu interconnects were isothermally aged and thermally cycled to evaluate long-term thermal fatigue reliability. Weibull plots of the combined effects of each aging condition and each surface finish revealed lifetime for NiAu/SAC305/Cu was reduced by approximately 40% by aging at 150°C; less degradation was observed for NiAu/SAC305/NiAu. Further reduction of characteristic life-cycle number was observed for NiAu/SnAg/NiAu joints. Microstructure was studied, focusing on its evolution near the board and package-side interfaces. Different mechanisms of aging were apparent under the different joint configurations. Their effects on the fatigue life of solder joints are discussed.

  6. Reactions of Sn-3.5Ag-Based Solders Containing Zn and Al Additions on Cu and Ni(P) Substrates

    NASA Astrophysics Data System (ADS)

    Kotadia, H. R.; Mokhtari, O.; Bottrill, M.; Clode, M. P.; Green, M. A.; Mannan, S. H.

    2010-12-01

    In this study we consider the effect of separately adding 0.5 wt.% to 1.5 wt.% Zn or 0.5 wt.% to 2 wt.% Al to the eutectic Sn-3.5Ag lead-free solder alloy to limit intermetallic compound (IMC) growth between a limited volume of solder and the contact metallization. The resultant solder joint microstructure after reflow and high-temperature storage at 150°C for up to 1000 h was investigated. Experimental results confirmed that the addition of 1.0 wt.% to 1.5 wt.% Zn leads to the formation of Cu-Zn on the Cu substrate, followed by massive spalling of the Cu-Zn IMC from the Cu substrate. Growth of the Cu6Sn5 IMC layer is significantly suppressed. The addition of 0.5 wt.% Zn does not result in the formation of a Cu-Zn layer. On Ni substrates, the Zn segregates to the Ni3Sn4 IMC layer and suppresses its growth. The addition of Al to Sn-3.5Ag solder results in the formation of Al-Cu IMC particles in the solder matrix when reflowed on the Cu substrate, while on Ni substrates Al-Ni IMCs spall into the solder matrix. The formation of a continuous barrier layer in the presence of Al and Zn, as reported when using solder baths, is not observed because of the limited solder volumes used, which are more typical of reflow soldering.

  7. Designed synthesis of MOx (M = Zn, Fe, Sn, Ni, Mn, Co, Ce, Mg, Ag), Pt, and Au nanoparticles supported on hierarchical CuO hollow structures.

    PubMed

    Zhang, Zailei; Jung, Ji Chul; Yan, Ning

    2016-12-01

    Despite intensive research into support substrates for the dispersal of nanoparticles and their applications, there has been a lack of general methods to produce metal oxide hollow substrates supporting a wide range of metal and metal oxides. Herein, a synthetic protocol for the preparation of CuO hollow structure-supported MOx (M = Zn, Fe, Ni, Sn, Mn, Co, Ce, Mg, and Ag) and noble metals (Pt and Au) with the desired properties and shell structure, such as CuO/Fe2O3, CuO/ZnO, CuO/SnO2, CuO/MgO, CuO/NiO, CuO/Mn2O3, CuO/CoO, CuO/CeO2, CuO/Ag2O, CuO/Pt, CuO/Au hollow cubes, CuO/ZnO double-shell hollow cubes, CuO/SnO2 double-shell hollow octahedra, CuO/SnO2/Fe2O3 and CuO/Mn2O3/NiO double-shell hollow cubes, was developed based on controlled calcination and etching. These hybrid hollow structures were employed not only as support substrates but also as active constituents for catalytic reactions. As an example, we demonstrated that CuO/ZnO hollow cubes are remarkably efficient in converting solid chitin biomass to liquid chemicals in methanol. In addition, CuO/ZnO double-shell hollow cubes were highly effective in the oxidation of benzyl alcohol in the presence of H2O2, whereas CuO/Pt and CuO/Au hollow cubes promoted the oxidation of benzyl alcohol in pure O2. The strategy developed in this work extends the controllable fabrication of high-quality CuO hollow structure-supported nanoparticles using various compositions and shell structures, paving the way to the exploration and systematic comparison of these materials in a wider range of applications.

  8. Novel method for fabrication of integrated resistors on bilayer Ag/YBa2Cu3O7 films using Ni implantation

    NASA Astrophysics Data System (ADS)

    LaGraff, J. R.; Chan, H.; Murduck, J. M.; Hong, S. H.; Ma, Q. Y.

    1997-10-01

    A novel ion implantation method is described for fabricating low inductance integrated resistors on Ag/YBa2Cu3O7 (YBCO) bilayer thin films. Parallel high and low value resistors were simultaneously formed by patterning bilayer films into 10-μm-wide lines, then masking and implanting with Ni to selectively inhibit superconductivity in YBCO. Low value resistors (<1 Ω/sq) were formed at 77 K as the supercurrent bypassed the Ni-doped nonsuperconducting YBCO and was shunted through the overlying low resistivity Ag metal. High value resistors (20-140 Ω/sq) were formed by removing Ag from above the implanted YBCO forcing the current through the implanted YBCO region. The sheet resistance of both types of resistors was found to increase systematically with increasing Ni implant energy.

  9. Deformation Behavior and Microstructure Evolution of the Cu-2Ni-0.5Si-0.15Ag Alloy During Hot Compression

    NASA Astrophysics Data System (ADS)

    Zhang, Yi; Volinsky, Alex A.; Xu, Qian-Qian; Chai, Zhe; Tian, Baohong; Liu, Ping; Tran, Hai T.

    2015-12-01

    Hot deformation behavior of the Cu-2Ni-0.5Si-0.15Ag alloy was investigated by hot compression tests using the Gleeble-1500D thermo-simulator in the 873 K to 1073 K (600 °C to 800 °C) temperatures range with the 0.01 to 5 s-1 strain rate. The flow stress strongly depends on the deformation parameters, including temperature and strain rate. The flow stress decreases with the deformation temperature and increases with the strain rate. The constitutive relationship between the peak stress, the strain rate, and the deformation temperature can be described by the Zener-Hollomon Z parameter in the hyperbolic sine function with the hot deformation activation energy of 316 kJ/mol. The dynamic recrystallization (DRX) is one of the important softening mechanisms of the Cu-2Ni-0.5Si-0.15Ag alloy during hot deformation. The DRX behavior of the Cu-2Ni-0.5Si-0.15Ag alloy is strongly affected by the Z parameter. Lower Z parameter leads to more adequate DRX proceeding.

  10. A Ni-free ZrCuFeAlAg bulk metallic glass with potential for biomedical applications.

    PubMed

    Liu, Yan; Wang, Yi-Mei; Pang, Hui-Fang; Zhao, Qiu; Liu, Lin

    2013-06-01

    The mechanical properties and biocompatibility of an Ni-free Zr-based bulk metallic glass (BMG) Zr60.14Cu22.31Fe4.85Al9.7Ag3 were investigated in detail to evaluate its potential as a biomaterial. The BMG was found to have a low Young's modulus of 82±1.9GPa, a high strength of 1720±28MPa and a high fracture toughness of 94±19MPam(1/2), as well as good fatigue strength over 400MPa. The corrosion behavior of the alloy was investigated in simulated body fluid (SBF) by electrochemical measurements, which indicates that the Zr-based BMG has a better corrosion resistance than pure Zr and Ti6Al4V. X-ray photoelectron spectroscopy analysis revealed that the passive film formed on the BMG surface is enriched in Al- and Zr-oxides, which could account for the good corrosion resistance of the BMG. On the other hand, metal ion release of the BMG in SBF was determined by inductively coupled plasma mass spectrometry after the BMG was immersed in SBF at 37°C for 30days, showing a ppb (ngml(-1)) level of metal ion release. The in vitro test via cell culture indicates that the BMG exhibits a cytotoxicity of Grade 0-1, which is as good as Ti6Al4V alloy. Cell adhesion morphological analysis shows that the cells were flattened and well spread out on the surfaces of the BMG, showing that the BMG had good biocompatibility. The combination of good mechanical properties and biocompatibility demonstrates that the Ni-free Zr-based BMG studied in this work is a good candidate for a new type of load-bearing biomedical material.

  11. Characterization of the effects of binary metal mixtures on short-term uptake of Ag, Cu, and Ni by rainbow trout (Oncorhynchus mykiss).

    PubMed

    Brix, Kevin V; Tellis, Margaret S; Crémazy, Anne; Wood, Chris M

    2016-11-01

    Single metal Biotic Ligand Models (BLMs) have been developed for a number of metals and model organisms. While these BLMs improve our ability to regulate metals in the aquatic environment, in reality, organisms are often simultaneously exposed to metal mixtures. Recently, several attempts have been made to develop mixture BLMs (mBLMs). Some of these models assume competitive interactions between all metals, while others assume only metals with a similar mode of action (e.g., Na(+) or Ca(2+) antagonists) will competitively interact. To begin testing these assumptions in the mBLM framework, standard 3-h gill metal binding assays with Ag, Cu, and Ni (primary metals), were performed in vivo on freshwater rainbow trout. Fish were exposed across a range of concentrations encompassing the 96-h LC50 for that metal to characterize uptake kinetics for each of these three primary metals (radiolabelled) in the presence and absence of a secondary metal (Ag, Cd, Cu, Ni, Pb, or Zn; not radiolabelled). We observed a complex series of interactions in binary mixtures that frequently contradicted theoretical expectations. Metals with similar modes of action did competitively interact in some instances, but not others, and when they did compete the competition was not necessarily reciprocal (e.g., Cu inhibited Ag uptake but Ag did not inhibit Cu uptake). We also observed examples of interactions between metals with dissimilar modes of action and several examples of metals stimulating the uptake of other metals. The underlying mechanisms for these unexpected interactions are unclear, but suggest that many of the current assumptions in mBLMs regarding the number and types of metal uptake sites and corresponding metal interactions are not correct. Careful characterization of metal mixture interactions is clearly needed before a reliable mBLM can be developed.

  12. Effect of reaction time and P content on mechanical strength of the interface formed between eutectic Sn-Ag solder and Au/electroless Ni(P)/Cu bond pad

    NASA Astrophysics Data System (ADS)

    Alam, M. O.; Chan, Y. C.; Tu, K. N.

    2003-09-01

    In this work, shear strengths of the solder joints for Sn-Ag eutectic alloy with the Au/electroless Ni(P)/Cu bond pad were measured for three different electroless Ni(P) layers. Sn-Ag eutectic solder alloy was kept in molten condition (240 °C) on the Au/electroless Ni(P)/Cu bond pad for different time periods ranging from 0.5 min to 180 min to render the ultimate interfacial reaction and the consecutive shear strength. After the shear test, fracture surfaces were investigated by scanning electron microscopy equipped with energy dispersed x ray. Cross-sectional studies of the interfaces were also conducted to correlate with the fracture surfaces. It was found that formation of crystalline phosphorous-rich Ni layer at the solder interface of Au/electroless Ni(P)/Cu bond pad with Sn-Ag eutectic alloy deteriorates the mechanical strength of the joints significantly. It was also noticed that such weak P-rich Ni layer appears quickly for high-P content electroless Ni(P) layer. However, when this P-rich Ni layer disappears from a prolonged reaction, the shear strength increases again.

  13. First-principles investigation for M(CO)n/Ag(110) (M=Fe, Co, Ni, Cu, Zn, and Ag; n=1, 2) systems: Geometries, STM images, and vibrational frequencies

    NASA Astrophysics Data System (ADS)

    Yuan, Lan-Feng; Yang, Jinlong; Li, Qunxiang; Zhu, Qing-Shi

    2002-01-01

    Fe, Cu atoms and CO molecules were manipulated with a scanning tunneling microscope (STM) on a Ag(110) surface, and one or two CO can transfer from the surface and bond with a metal atom through the STM tip [H. J. Lee and W. Ho, Science 286, 1719 (1999); Phys. Rev. B 61, R16347 (2000)]. We perform a density-functional cluster model investigation for the systems. The experimental geometries are validated and understood using the frontier orbital theory. The STM topographic images are reproduced. The vibrational frequencies of the adsorbate systems are obtained by diagonalizing the second-derivative matrices and are in excellent agreement with the experimental measurements. The geometries and C-O stretch frequencies are predicted for systems with the adsorbate metal atom being Co, Ni, Zn, and Ag. These systems can be divided to two classes, and each class exhibits a different set of properties.

  14. Frequency-Dependent Low Cycle Fatigue of Sn1Ag0.1Cu(In/Ni) Solder Joints Subjected to High-Frequency Loading

    NASA Astrophysics Data System (ADS)

    Wong, E. H.; Seah, S. K. W.; Shim, V. P. W.

    2014-02-01

    The low-cycle-fatigue characteristics of solder joints, formed by reflowing Sn98.8/Ag1.0/Cu0.1/In0.05/Ni0.02 solder over electroless nickel immersion gold-plated copper pads, were investigated by dynamic cyclic bending of printed circuit boards (PCBs). The PCB strain amplitudes were varied from 1.2 × 10-3 to 2.4 × 10-3 and the flexural frequencies ranged from 30 Hz to 150 Hz, to simulate drop impact-induced PCB resonant frequencies. A trend of drastically decreasing fatigue life with cyclic frequency was observed, in contrast with previous reports indicating the reverse; this is attributed to the different failure mechanisms activated. A systematic procedure involving optimization followed by transformation was used to condense the strain-frequency-life data into a master curve expressed in strain-life space.

  15. Microstructural Development and Mechanical Properties for Reactive Air Brazing of ZTA to Ni Alloys using Ag-CuO Braze Alloys

    SciTech Connect

    Prevost, Erica; DeMarco, A.Joseph; MacMichael, Beth; Joshi, Vineet V.; Meier, Alan; Hoffman, John W.; Walker, William J.

    2014-12-01

    Reactive air brazing (RAB) is a potential joining technique to join metal alloys to ceramics for a variety of applications. In the current study, nickel (Ni) alloys were heat treated to form an oxide layer prior to RAB joining to zirconia toughened alumina (ZTA). The Ni alloys evaluated were Nicrofer 6025 HT, Inconel 600, Inconel 693, Haynes 214 and Inconel 601. The ZTA studied had compositions of 0 to 15 wt% zirconia and 0 to 14 wt% glass. Four point-bend tests were performed to evaluate the joint strength of ZTA/ZTA and ZTA/nickel alloys brazed with Ag-2wt% CuO braze alloys. It was determined that the joint strength is not a function of the ZTA composition, but that the strength is a strong function of the chemistry and microstructure of the oxide layer formed on the nickel alloy. It was determined that an increase in the aluminum content of the Ni alloy resulted in an increase of the thickness of alumina in the oxide layer and was directly proportional to the bond strength with the exception of Inconel 601 which exhibited relatively high joint strengths even though it had a relatively low aluminum content.

  16. Bonding analyses, formation energies, and vibrational properties of M-R2dtc complexes (M=Ag(I), Ni(II), Cu(II), or Zn(II)).

    PubMed

    Georgieva, I; Trendafilova, N

    2007-12-20

    Detailed theoretical studies based on density functional theory (DFT)/B3LYP calculations of dimethyl- and diethyldithiocarbamate complexes of Ni(II), Cu(II), Zn(II), and Ag(I) are performed to characterize the metal-ligand bonding type as well as the metal-ligand bonding strength depending on the metal and the dialkyl substituent. The metal-ligand interactions in the studied complexes are investigated by means of charge decomposition analysis, energy partitioning analysis (EPA), and natural bond orbital analysis. According to the EPA calculations, the electrostatic attraction is the dominant contribution to the M-S2(R2dtc) (dtc=dithiocarbamate) bonding. The electrostatic and the orbital energies follow the order of the total binding energy, and hence both contributions are responsible for the binding energy order of M(R2dtc)2 complexes. The stability of the M(R2dtc)2 complexes is estimated by means of calculated formation reaction energies in the gas phase and solution, and it decreases in the order Ni(R2dtc)2>Cu(R2dtc)2>Zn(R2dtc)2. Larger formation reaction energies are found for M(Et2dtc)2 than for M(Me2dtc)2 complexes. The calculations predict stabilization of M(II)(R2dtc)2 complexes going from the gas phase to a polar solvent and destabilization of the bidentate AgR2dtc complex in a polar solvent. Gas-phase frequency calculations of all possible bonding types, symmetrical, asymmetrical, and uni- and bidentate, predict one band due to the nu(CS) IR absorption, and therefore the number of the bands in the 1060-920 cm(-1) region could not be used to discern the metal-ligand bonding type. Periodic DFT frequency calculations for Cu(Et2dtc)2 reveal that the splitting observed in the solid-state spectra of the complexes arises from the nonplanar MS4 fragment and intermolecular contacts but not from asymmetrical bonding. The calculations suggest that the important vibrational characteristic that can be used to discern uni- and bidentate bonding is the Raman activity of

  17. Application of activated M/ZnO (M = Mn, Co, Ni, Cu, Ag) in photocatalytic degradation of diazo textile coloring dye.

    PubMed

    Milenova, K; Avramova, I; Eliyas, A; Blaskov, V; Stambolova, I; Kassabova, Nikoleta

    2014-11-01

    Activated ZnO powder has been prepared by procedures involving first its dissolution in nitric acid, then simultaneous treatment by adding NH4OH and CO2 bubbling leading to precipitation as Zn(OH)CO3 (ZH) and further thermal decomposition of ZH at 400 °C. The gas evolution leads to formation of pores and increase in the specific surface area. Chemically activated M/ZnO powders doped with Mn, Co, Ni, Cu, and Ag have been obtained by the impregnation method. The samples have been characterized by ultraviolet-visible (UV-Vis) spectroscopy, diffuse reflectance (DR) UV-Vis, X-ray diffraction (XRD), single point Brunauer-Emmet-Teller (BET), scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS) methods. The experiments have shown that metal-doped activated ZnO powders possess higher photocatalytic activities in oxidative discoloration of model contaminant textile coloring dye Reactive Black 5 in slurry reactor compared to that of the pure ZnO. The XRD and XPS data have shown the presence of defects, nonstoichiometricity implying the formation of solid solutions. Copper-doped (1.5 wt%) activated ZnO (Cu(2+) replaces Zn(2+)) is outstanding in its photocatalytic performance in discoloration of the dye due to the higher specific surface area and improved charge carrier separation.

  18. Effect of Ag, Ni and Bi Additions on Solderability of Lead-Free Solders

    NASA Astrophysics Data System (ADS)

    Nobari, Amir Hossein; Maalekian, Mehran; Seelig, Karl; Pekguleryuz, Mihriban

    2017-01-01

    In this study, the effects of Ag, Ni and Bi additions on the melting, solidification, fluidity and wetting behavior of Sn-0.7Cu base solder alloy are studied. The addition of a small amount of Ni reduces the undercooling and improves the feeding distance (fluidity length); however, Ni does not improve the wetting and the spreading performance. The effect of Ni on the fluidity length of Ag-containing Sn-0.7Cu (SAC alloy) is marginal. Bi and Ag both improve wetting performance and also lower the melting temperature; however, they do not improve the fluidity; instead, they reduce the maximum length of fluidity.

  19. Magnetic properties of Ni and Cu-Ni nanoparticles

    NASA Astrophysics Data System (ADS)

    Ganga, B. G.; Santhosh, P. N.; Thomas, P. John

    2012-06-01

    Ni and Cu-Ni nanoparticles were prepared by solution phase method and crystal phase was identified by XRD. SEM and EDX were used to analyze morphology and elemental composition of nanoparticles. Magnetic measurements indicate that Ni nanoparticles are superparamagnetic at room temperature and blocking temperature is around 103 K. Ferromagnetism is observed in the case of Cu-Ni nanoparticles with decrease in magnetization compared to Ni nanoparticles.

  20. Intermetallic compounds of the heaviest elements and their homologs: The electronic structure and bonding of MM', where M =Ge, Sn, Pb, and element 114, and M'=Ni, Pd, Pt, Cu, Ag, Au, Sn, Pb, and element 114

    NASA Astrophysics Data System (ADS)

    Pershina, V.; Anton, J.; Fricke, B.

    2007-10-01

    Fully relativistic (four-component) density-functional theory calculations were performed for intermetallic dimers MM', where M =Ge, Sn, Pb, and element 114, and M'=group 10 elements (Ni, Pd, and Pt) and group 11 elements (Cu, Ag, and Au). PbM and 114M, where M are group 14 elements, were also considered. The results have shown that trends in spectroscopic properties—atomization energies De, vibrational frequencies ωe, and bond lengths Re, as a function of M', are similar for compounds of Ge, Sn, Pb, and element 114, except for De of PbNi and 114Ni. They were shown to be determined by trends in the energies and space distribution of the valence ns(M ') atomic orbitals (AOs). According to the results, element 114 should form the weakest bonding with Ni and Ag, while the strongest with Pt due to the largest involvement of the 5d(Pt) AOs. In turn, trends in the spectroscopic properties of MM' as a function of M were shown to be determined by the behavior of the np1/2(M ) AOs. Overall, De of the element 114 dimers are about 1eV smaller and Re are about 0.2a.u. larger than those of the corresponding Pb compounds. Such a decrease in bonding of the element 114 dimers is caused by the large SO splitting of the 7p orbitals and a decreasing contribution of the relativistically stabilized 7p1/2(114) AO. On the basis of the calculated De for the dimers, adsorption enthalpies of element 114 on the corresponding metal surfaces were estimated: They were shown to be about 100-150kJ/mol smaller than those of Pb.

  1. Optical properties and electronic structures of d- and f-electron metals and alloys, Ag-In, Ni-Cu, AuGa sub 2 , PtGa sub 2 ,. beta. prime -NiAl,. beta. prime -CoAl, CeSn sub 3 , and LaSn sub 3

    SciTech Connect

    Kim, Kwang Joo.

    1990-10-17

    Optical properties and electronic structures of disordered Ag{sub 1- x}In{sub x}(x = 0.0, 0.04, 0.08, 0.12) and Ni{sub 1-x}Cu{sub x} (x = 0.0, 0.1, 0.3, 0.4) alloys and ordered AuGa{sub 2}, PtGa{sub 2}, {beta}{prime}-NiAl, {beta}{prime}-CoAl, CeSn{sub 3}, and LaSn{sub 3} have been studied. The complex dielectric functions have been determined for Ag{sub 1-x}In{sub x}, Ni{sub 1-x}Cu{sub x}, AuGa{sub 2}, and PtGa{sub 2} in the 1.2--5.5 eV region and for CeSn{sub 3} and LaSn{sub 3} in the 1.5--4.5 eV region using spectroscopic ellipsometry. Self-consistent relativistic band calculations using the linearized-augmented-plane-wave method have been performed for AuGa{sub 2}, PtGa{sub 2}, {beta}{prime}-NiAl, {beta}{prime}-CoAl, CeSn{sub 3}, and LaSn{sub 3} to interpret the experimental optical spectra.

  2. Effects of temperature, silicate melt composition, and oxygen fugacity on the partitioning of V, Mn, Co, Ni, Cu, Zn, As, Mo, Ag, Sn, Sb, W, Au, Pb, and Bi between sulfide phases and silicate melt

    NASA Astrophysics Data System (ADS)

    Li, Yuan; Audétat, Andreas

    2015-08-01

    In order to assess the role of sulfide in controlling the ore metal budgets and fractionation during magmatic genesis and differentiation, the partition coefficients (D) of V, Mn, Co, Ni, Cu, Zn, As, Mo, Ag, Sn, Sb, W, Au, Pb, and Bi between sulfide liquid (SL), monosulfide solid solution (MSS), and basaltic to rhyolitic melts (SM) were determined at 900-1200 °C, 0.5-1.5 GPa, and oxygen fugacity (fO2) ranging from ∼FMQ-2 to FMQ+3, in a piston-cylinder apparatus. The DSL/SM values range from 0.4 to 2 for V, 0.5 to 3 for Mn, 80 to 580 for Co, 2300 to 18,000 for Ni, 800 to 4600 for Cu, 1 to 11 for Zn, 20 to 180 for As, 4 to 230 for Mo, 450 to 1600 for Ag, 5 to 24 for Sn, 10 to 80 for Sb, 0.03 to 0.16 for W, 2000 to 29,000 for Au, 24 to 170 for Pb, and 830 to 11,000 for Bi; whereas the DMSS/SM values range from 0.04 to 10 for V, 0.5 to 10 for Mn, 70 to 2500 for Co, 650 to 18,000 for Ni, 280 to 42,000 for Cu, 0.1 to 80 for Zn, 0.2 to 30 for As, 1 to 820 for Mo, 20 to 500 for Ag, 0.2 to 220 for Sn, 0.1 to 40 for Sb, 0.01 to 24 for W, 10 to 2000 for Au, 0.03 to 6 for Pb, and 1 to 350 for Bi. Both DMSS/SM and DSL/SM values generally increase with decreasing temperature or decreasing FeOtot content in silicate melt, except for Mo, DMSS/SM and DSL/SM of which show a clear decrease with decreasing temperature. At given temperature and FeOtot content, high oxygen fugacity appears to lead to a significant decrease in DMSS/SM of Au, Bi, Mo, and potentially As. The partitioning data obtained experimentally in this study and previous studies were fitted to an empirical equation that expresses the DMSS/SM and/or DSL/SM of a given element as a function of temperature, oxygen fugacity, and FeOtot content of the silicate melt: log (DSL/SMorDMSS/SM = d + a · 10, 000 / T + b · (ΔFMQ) + c · log (FeOmelt) in which T is temperature in K, FeOmelt denotes wt% FeOtot in silicate melt, and ΔFMQ denotes log fO2 relative to the fayalite-magnetite-quartz (FMQ) oxygen buffer. The

  3. Advances of Ag, Cu, and Ag-Cu alloy nanoparticles synthesized via chemical reduction route

    NASA Astrophysics Data System (ADS)

    Tan, Kim Seah; Cheong, Kuan Yew

    2013-04-01

    Silver (Ag) and copper (Cu) nanoparticles have shown great potential in variety applications due to their excellent electrical and thermal properties resulting high demand in the market. Decreasing in size to nanometer scale has shown distinct improvement in these inherent properties due to larger surface-to-volume ratio. Ag and Cu nanoparticles are also shown higher surface reactivity, and therefore being used to improve interfacial and catalytic process. Their melting points have also dramatically decreased compared with bulk and thus can be processed at relatively low temperature. Besides, regularly alloying Ag into Cu to create Ag-Cu alloy nanoparticles could be used to improve fast oxidizing property of Cu nanoparticles. There are varieties methods have been reported on the synthesis of Ag, Cu, and Ag-Cu alloy nanoparticles. This review aims to cover chemical reduction means for synthesis of those nanoparticles. Advances of this technique utilizing different reagents namely metal salt precursors, reducing agents, and stabilizers, as well as their effects on respective nanoparticles have been systematically reviewed. Other parameters such as pH and temperature that have been considered as an important factor influencing the quality of those nanoparticles have also been reviewed thoroughly.

  4. Interface Characterization of Cu-Cu and Cu-Ag-Cu Low Temperature Solid State Bonds.

    DTIC Science & Technology

    1987-12-01

    produce low -. 0 onnos s boniecnstrated, the thrust o: tnis texann a ecne: onaractorlstics as a function c.: 4 time, temperature and pressure . The...conducted under y hyrostatic pressure to avoid deformation of the tensile specimen. At 2Cksi the tensile yield strength of the silver has been exceeded by...A19i 915 INTERFACE CHARACTERIZATION OF CU-CU AND CU-AG-CU LOW 1/1 TEMPERATURE SOLID STATE BONDS(U) NAVAL POSTGRADUATE SCHOO0L MONTEREY CA R Z DALBEY

  5. 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.

  6. 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.

  7. Unravelling the composition of the surface layers formed on Cu, Cu-Ni, Cu-Zn and Cu-Ni-Zn in clean and polluted environments

    NASA Astrophysics Data System (ADS)

    Awad, Nasser K.; Ashour, E. A.; Allam, Nageh K.

    2015-08-01

    The performance of copper and copper-based alloys in working environments is controlled by the composition of the layers formed on their surfaces. Herein, we report the detailed structural and compositional analyses of the layers formed on the surface of Cu, Cu-Ni, Cu-Zn and Cu-Ni-Zn upon their use in both NaCl and Na2S-polluted NaCl solutions. In clean NaCl environments, X-ray photoelectron spectroscopy (XPS) analysis revealed that Cu2O is the major compound formed over the surfaces of pure Cu and Cu-Ni, whereas mixed oxides/hydroxides were detected over the surfaces of Cu-Zn (Cu2O and ZnO) and Cu-Ni-Zn alloy (CuO, ZnO, Cu(OH)2 and Ni(OH)2). However, in Na2S- polluted NaCl environments, sulphide compounds (such as Cu2S) were detected on the surfaces of Cu-Ni and Cu-Zn. X-ray diffraction (XRD) analysis confirmed the XPS findings, where Cu2O was confirmed in case of Cu and CuO in case of Cu-Ni-Zn in pure NaCl solutions. However, in sulphide-polluted media, compounds such as Cu4(S2)2(CuS)2 were identified in case of Cu-Ni, and CuS in case of Cu-Zn. Further, the morphology of the surface of Cu-Ni-Zn tested in Na2S-polluted NaCl solution looks compact and has a wide band gap (4.47 eV) as revealed from the UV-vis absorption measurements. Therefore, the formation of mixed oxides/hydroxides and/or sulphides on the surface of Cu-Ni-Zn alloy is ultimately responsible for the enhancement of its dissolution resistance.

  8. Incoherent Ag islands growth on Ni(100)

    NASA Astrophysics Data System (ADS)

    Marie, J. B.; Braems, I.; Bellec, A.; Chacon, C.; Creuze, J.; Girard, Y.; Gueddani, S.; Lagoute, J.; Repain, V.; Rousset, S.

    2017-02-01

    Growth of two-dimensional superstructure and island morphologies of silver atoms evaporated on a nickel (100) surface are studied by scanning tunneling microscopy. Near-equilibrium islands form at moderate annealing temperature (lower than 500 K) and present two kinds of morphologies. While they share a common monolayer c(2×8) superstructure, two distinct populations of islands coexist: rounded islands grown on the surface and spindle-shaped islands grown inside the Ni surface. The latter present a clear saturation of their density with increasing coverage. These shapes are mostly dominated by boundary energies as confirmed by a simple two-dimensional Wulff model whose parameters are derived using molecular statics simulations. Further annealing to 700 K leads to long Ag strips decorating the Ni step edges.

  9. Enhancing the ag precipitation by surface mechanical attrition treatment on Cu-Ag alloys

    NASA Astrophysics Data System (ADS)

    Liu, Jiabin; Zhang, Lehao; Liu, Jingjing; Huang, Liuyi; Gu, Hao; Fang, Youtong; Meng, Liang; Zhang, Jian

    2016-09-01

    The influence of surface mechanical attrition treatment (SMAT) on Ag precipitation in Cu-Ag alloys was investigated. Cu-6 wt% Ag was melt, cold rolled and solution treated to be Cu-Ag solid solution, which was either aged at 250 and 350 °C for 24 h directly or SMAT-ed before aging. Ag precipitates were hard be found in the directly aged Cu-Ag sample while they were observed clearly in the SMAT-ed counterpart at 250 °C. The Ag precipitates formed in the surface layer by SMAT are much coarser than those in the un-SMAT-ed sample. It is obvious that the precipitating behavior of Ag was promoted significantly by SMAT approach. A large number of defects were generated by SMAT and they were acting as fast atomic diffusion channels that facilitated the atomic diffusion of Ag.

  10. Investigation of electrochemical migration on Sn-0.7Cu-0.3Ag-0.03P-0.005Ni solder alloy in HNO{sub 3} solution

    SciTech Connect

    Sarveswaran, C.; Othman, N. K.; Ali, M. Yusuf Tura; Ani, F. Che; Samsudin, Z.

    2015-09-25

    Current issue in lead-free solder in term of its reliability is still under investigation. This high impact research attempts to investigate the electrochemical migration (ECM) on Sn-0.7Cu-0.3Ag-0.03P-0.005Ni solder alloy by Water Drop Test (WDT) in different concentration of HNO{sub 3} solution. The concentration of HNO{sub 3} solution used in this research was 0.05, 0.10, 0.50 and 1M. Optical Microscope (OM), Field Emission Scanning Electron Microscope (FESEM) and Energy Dispersive X-Ray Analysis (EDX) were carried out in order to analysis the ECM behavior based on the growth of dendrite formation after WDT. In general, the results demonstrated that dendrite growth is faster in higher concentration compared with low concentration of HNO{sub 3}. The concentration of HNO{sub 3} solution used has a strong correlation with Mean-Time-To-Failure (MTTF). As the concentration of HNO{sub 3} increases, the MTTF value decreases. Based on the MTTF results the solder alloy in 1M HNO{sub 3} solution is most susceptible to ECM. SnO{sub 2} forms as a corrosion by-product in the samples proved by EDX analysis. The solder alloy poses a high reliability risk in microelectronic devices during operation in 1M HNO{sub 3} solution.

  11. Synthesis of Cu-Ag@Ag particles using hyperbranched polyester as template

    NASA Astrophysics Data System (ADS)

    Han, Wen-Song

    2015-07-01

    In this manuscript, the third-generation hyperbranched polyester was synthesized with 2, 2-dimethylol propionic acid as AB2 monomer and pentaerythrite as core molecule by using step by step polymerization process at first. Then, the Cu-Ag particles were prepared by co-reduction of silver nitrate and copper nitrate with ascorbic acid in the aqueous solution using hyperbranched polyester as template. Finally, the Cu-Ag@Ag particles were prepared by coating silver on the surface of Cu-Ag particles by reduction of silver nitrate. The synthesized hyperbranched polyester and Cu-Ag@Ag particles were characterized by Fourier transform infrared (FT-IR) spectroscopy, UV-vis spectra, x-ray diffraction, Laser light scattering, thermogravimetric analysis (TGA) and SEM. UV-vis spectra results showed that the Cu-Ag@Ag particles had a strong absorption band at around 420 nm. Laser light scattering and SEM studies confirmed that the most frequent particle sizes of Cu-Ag@Ag particles were 1.2 um. TGA results indicated that the Cu-Ag@Ag particles had good thermal stability. [Figure not available: see fulltext.

  12. Double dumbbell shaped AgNi alloy by pulsed electrodeposition

    SciTech Connect

    Dhanapal, K.; Vasumathi, M.; Santhi, Kalavathy; Narayanan, V. Stephen, A.

    2014-01-28

    Silver-Nickel is the well-known thermally immiscible system that makes them quite complex for the formation of alloy. This kind of alloy can be attained from electrodeposition method. In the present work, AgNi alloy was synthesized by pulsed electrodeposition in a single bath two electrode system with the use of anodic alumina membrane. The prepared AgNi alloy and pure Ag were characterized with X-ray Diffraction (XRD) for structural confirmation, Scanning Electron Microscopy (SEM) for morphological, and magnetic properties by Vibrating Sample Magnetometer, respectively. The X-ray Diffraction study shows the formation of cubic structure for pure Ag. SEM analysis reveals the double dumbbell morphology for AgNi alloy and spherically agglomeration for pure silver. Hysteresis behaviour from VSM measurement indicates that the AgNi alloy have good ferro-magnetic properties.

  13. Effects of Ag on the Kirkendall void formation of Sn-xAg/Cu solder joints

    NASA Astrophysics Data System (ADS)

    Kim, Sunghwan; Yu, Jin

    2010-10-01

    Binary Sn-Ag solders with varying amounts of Ag (0.5, 2.0, and 3.5 wt %) were reacted with Cu under bump metallurgy (UBM) which was electroplated with bis-sodium sulfopropyl-disulfide additive, and the characteristics of Kirkendall void formation at the solder joints were investigated. The results indicate that the propensity to form Kirkendall voids at the solder joint decreased with the Ag content. Subsequent Auger electron spectroscopy analyses showed that Ag dissolved in the Cu UBM reduced the segregation of S to the Cu3Sn/Cu interface, which suppressed the nucleation of Kirkendall voids at the interface.

  14. Domain structure and magnetization process of a giant magnetoimpedance geometry FeNi/Cu/FeNi(Cu)FeNi/Cu/FeNi sensitive element

    NASA Astrophysics Data System (ADS)

    Kurlyandskaya, G. V.; Elbaile, L.; Alves, F.; Ahamada, B.; Barrué, R.; Svalov, A. V.; Vas'kovskiy, V. O.

    2004-09-01

    The magnetization process and the magnetic domains of the FeNi (100 nm)/Cu (2.5 nm)/FeNi (100 nm)/Cu (480 nm)/FeNi (100 nm)/Cu (2.5 nm)/FeNi (100 nm) structure were studied. This geometry consists of two FeNi/Cu/FeNi trilayers with a thick in the direction perpendicular to the plane of the sensitive element and narrow in the direction of the flowing current Cu electrode in the centre. Ferromagnet/conductor/ferromagnet is the typical geometry of magnetoimpedance thin-film-based sensitive elements used to detect small magnetic fields. Multilayered structures were prepared by rf-sputtering in a magnetic field of 100 Oe applied perpendicular to the Cu electrode in order to induce transverse magnetic anisotropy. The magnetic measurements and magnetic domain structure observations were made in magnetic fields applied one at a time parallel or perpendicular to the Cu electrode. Different magnetization processes with non-homogeneous rotations in the first case and dominant multiple nucleation and merging of domains in the second one were observed.

  15. Morphology and mechanical properties of nanocrystalline Cu/Ag alloy

    NASA Astrophysics Data System (ADS)

    Li, Ao; Szlufarska, Izabela

    2017-04-01

    Hybrid Monte Carlo (MC)/molecular dynamics (MD) simulations are conducted to study the microstructures of nanocrystalline (nc) Cu/Ag alloys with various Ag concentrations. When the Ag concentration is below 50 Ag atoms/nm!, an increase in Ag concentration leads to a gradual growth of monolayer grain boundary (GB) complexions into nanolayer complexions. Above the concentration of 50 Ag atoms/nm!, wetting layers with a bulk crystalline phase are observed. The effects of Ag on mechanical properties and deformation mechanisms of nc Cu/Ag alloys are investigated in MD simulations of uniaxial tension. GB sliding resistance is found to first increase and then decrease with an increase in Ag concentration. Surprisingly, we also find that the dislocation density decreases monotonically with an increase in Ag concentration, which suggests that the grain interiors are softened by the introduction of Ag dopants at GBs. In addition, there is a critical Ag concentration that maximizes flow stress of nc Cu/Ag alloys. The flow stress, GB sliding resistance, and the intragranular dislocation densities become less sensitive to Ag dopants when the grain diameter increases from 5nm to 40nm.

  16. Enhanced Noble Gas Adsorption in Ag@MOF-74Ni

    SciTech Connect

    Liu, Jian; Strachan, Denis M.; Thallapally, Praveen K.

    2014-01-14

    Various amounts of Ag nanoparticles were successfully deposited in porous MOF-74Ni (or Ni/DOBDC) with an auto-reduction method. An optimized silver-loaded MOF-74Ni was shown to have an improved Xe adsorption capacity (15% more) at STP compared to the MOF without silver nanoparticles. The silver-loaded sample also has a higher Xe/Kr selectivity. These results are explained by the stronger interactions between polarizable Xe molecules and the well-dispersed Ag nanoparticles.

  17. Thermo-Mechanical Response of Monolithic and NiTi Shape Memory Alloy Fiber Reinforced Sn-3.8Ag-0.7Cu Solder

    DTIC Science & Technology

    2005-09-01

    still exist from this high thermal mismatch deformation , resulting in large solder-joint stresses and strains and causing fatigue failure. The...life, but have not shown the needed improvements in thermo-mechanical fatigue life under strain - controlled conditions, which is a primary deformation ...A NiTi fiber will deform until it consists only of the correspondence variant (crystallographic orientation) that produces maximum strain . However

  18. Structural evolution of NiAg heterogeneous alloys upon annealing

    NASA Astrophysics Data System (ADS)

    Proux, O.; Mimault, J.; Revenant-Brizard, C.; Regnard, J. R.; Mevel, B.

    1999-01-01

    NiAg heterogeneous alloys were studied by x-ray diffraction and x-ray absorption spectroscopy at the Ni K-edge using a total electron yield detection. In the as-deposited 0953-8984/11/1/013/img8 alloys of 0.10 and 0.15 Ni atomic fraction, most of the Ni atoms are in substitutional sites in the Ag matrix. At higher Ni concentration, the Ni atoms outside the Ag-rich phase become numerous enough to group together in small clusters. An important disorder in the neighbourhood of Ni atoms is demonstrated. At low annealing temperature (up to 0953-8984/11/1/013/img9C), in 0953-8984/11/1/013/img10 and 0953-8984/11/1/013/img11, some Ni atoms are still present in substitutional sites in the Ag matrix and the small Ni particles are under strain. A very short-range order exists in this state. After a 0953-8984/11/1/013/img9C annealing, the Ni particles grow, and the Ag-rich phase remains in a steady structural state. After a higher annealing (0953-8984/11/1/013/img13C), the local Ni atomic environment becomes well ordered and typical of the pure Ni FCC phase. The Ag-rich crystallites are impoverished in Ni atoms and grow with elimination of defects. Ni grains are generally smaller than 1 nm for as-deposited alloys and reach several nanometres after a 0953-8984/11/1/013/img13C annealing for 10 min.

  19. Enthalpies of Formation of (Cu,Ni)3Sn, (Cu,Ni)6Sn5-HT and (Ni,Cu)3Sn2-HT.

    PubMed

    Schmetterer, C; Rodriguez-Hortala, M; Flandorfer, H

    Standard enthalpies of formation of ternary phases in the Cu-Ni-Sn system were determined along sections at 25, 41 and 45.5 at.% Sn applying tin solution drop calorimetry. Generally, the interaction of Ni with Sn is much stronger than that of Cu with Sn. Along all sections the enthalpy of formation changes almost linearly with the mutual substitution of Cu and Ni within the respective homogeneity ranges. Thus no additional ternary interaction promoting the formation of further Cu-Ni-Sn phases can be assumed. The results are discussed and compared with literature values relevant to this system.

  20. Microstructure and properties of Cu-Ti-Ni alloys

    NASA Astrophysics Data System (ADS)

    Liu, Jia; Wang, Xian-hui; Guo, Ting-ting; Zou, Jun-tao; Yang, Xiao-hong

    2015-11-01

    The effects of Ni addition and aging treatments on the microstructure and properties of a Cu-3Ti alloy were investigated. The microstructure and precipitation phases were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy; the hardness, electrical conductivity, and elastic modulus of the resulting alloys were also tested. The results show that Ni addition increases the electrical conductivity and elastic modulus, but decreases the hardness of the aged Cu-3Ti alloy. Within the range of the experimentally investigated parameters, the optimal two-stage aging treatment for the Cu-3Ti-1Ni and Cu-3Ti-5Ni alloy was 300°C for 2 h and 450°C for 7 h. The hardness, electrical conductivity, and elastic modulus of the Cu-3Ti-1Ni alloy were HV 205, 18.2% IACS, and 146 GPa, respectively, whereas the hardness, electrical conductivity, and elastic modulus of the Cu-3Ti-5Ni alloy were HV 187, 31.32% IACS, and 147 GPa, respectively. Microstructural analyses revealed that β'-Ni3Ti and β'-Cu4Ti precipitate from the Cu matrix during aging of the Cu-3Ti-5Ni alloy and that some residual NiTi phase remains. The increased electrical conductivity is ascribed to the formation of NiTi, β'-Ni3Ti, and β'-Cu4Ti phases.

  1. Dislocation interactions with characteristic interfaces in AgCu eutectic

    NASA Astrophysics Data System (ADS)

    Eftink, Benjamin P.

    In the AgCu eutectic alloy, the observation of deformation twinning in Cu proposed to be induced by direct transmission of deformation twinning partial dislocations in Ag highlights the question of how interfaces in bi-phase materials respond to deformation. AgCu eutectic alloy was produced by both directional solidification and cast water-quenching. Control over processing variables enabled the synthesis of Ag/Cu eutectic with three predominant interface types: ones with a cube-on-cube orientation relationship with {111} Ag||{111}Cu interface habit planes, twin orientation relationship with {111}Ag||{111}Cu interface habit planes, and twin orientation relationship with near {313}Ag||{ 112}Cu interface habit planes. How dislocations interacted with each of the interfaces was determined using in situ and ex situ TEM straining experiments. It was determined that how strain transfers across Ag/Cu interfaces is consistent with criteria of strain transfer across grain boundaries in single phase materials. Specifically, the magnitude of the Burgers vector of the residual dislocation, |bres |, left in the interface should be small. This criterion was determining enough to drive Cu to twin under conditions where otherwise it would not. When transmission of a dislocation would result in a high |bres|, which is common for most slip systems encountering an incoherent twin interface, the interfaces were observed to block the dislocations. It was found that the increased effectiveness of the incoherent twin interfaces to block dislocations compared to the cube-on-cube interfaces resulted in an increased in the yield strength of the material. Interfaces with the cube-on-cube orientation relationship and mutual {111} interface plane between Ag and Cu results in transfer of twinning defects from Ag into Cu. This was found at length scales in the tens of nano-meters to the micron range. Twinning in both phases was observed after both split-Hopkinson pressure bar ex situ straining

  2. Melting curve of metals Cu, Ag and Au under pressure

    NASA Astrophysics Data System (ADS)

    Tam, Pham Dinh; Hoc, Nguyen Quang; Tinh, Bui Duc; Tan, Pham Duy

    2016-01-01

    In this paper, the dependence of the melting temperature of metals Cu, Ag and Au under pressure in the interval from 0 kbar to 40 kbar is studied by the statistical moment method (SMM). This dependence has the form of near linearity and the calculated slopes of melting curve are 3.9 for Cu, 5.7 for Ag and 6 for Au. These results are in good agreement with the experimental data.

  3. Nanoporous Ag prepared from the melt-spun Cu-Ag alloys

    NASA Astrophysics Data System (ADS)

    Li, Guijing; Song, Xiaoping; Sun, Zhanbo; Yang, Shengchun; Ding, Bingjun; Yang, Sen; Yang, Zhimao; Wang, Fei

    2011-07-01

    Nanoporous Ag ribbons with different morphology and porosity were achieved by the electrochemical corrosion of the melt-spun Cu-Ag alloys. The Cu-rich phase in the alloys was removed, resulting in the formation of the nanopores distributed across the whole ribbon. It is found that the structures, morphology and porosity of the nanoporous Ag ribbons were dependent on the microstructures of the parent alloys. The most of ligaments presented a rod-like shape due to the formation of pseudoeutectic microstructure in the melt-spun Cu 55Ag 45 and Cu 70Ag 30 alloys. For nanoporous Ag prepared from Cu 85Ag 15 alloys, the ligaments were camber-like because of the appearance of the divorced microstructures. Especially, a novel bamboo-grove-like structure could be observed at the cross-section of the nanoporous Ag ribbons. The experiment reveals that nanoporous Ag ribbons exhibited excellent enhancement of surface-enhanced Raman scattering (SERS) effect, but a slight difference existed due to the discrepancy of their morphology.

  4. Structure of the ophiolite-hosted Outokumpu Cu-Co-Zn-Ni-Ag-Au sulfide ore district revealed by combined 3D modelling and 2D high-resolution seismic reflection data

    NASA Astrophysics Data System (ADS)

    Saalmann, Kerstin; Laine, Eevaliisa

    2015-04-01

    The Outokumpu district within the North Karelia Schist Belt in eastern Finland hosts Cu-Co-Zn-Ni-Ag-Au sulfide deposits which are associated with Palaeoproterozoic ophiolitic metaperidotites that were tectonically interleaved with allochthonous metaturbidites. Extensive metasomatism of the peridotites produced a rim of quartz-carbonate-calc-silicate rocks, grouped as the Outokumpu assemblage (OKA). A tectonic history comprising various phases of folding and shearing followed by several faulting events dismembered the metaperidotites so that ore bodies cannot be easily followed along strike. Future exploration has to expand the search into deeper areas and consequently requires better knowledge of the subsurface geology. In order to unravel the complex structure 3D geologic models of different scales have been built using a variety of information: geological maps, aeromagnetic and gravity maps, digital terrain models, mine cross sections, drill core logs combined with observations from underground mine galleries, structural measurements, and data from seismic survey lines. The latter have been used to detect upper crustal-scale structures and have been reprocessed for our purpose. The models reveal that the ore body has formed during remobilisation of a proto-ore and is closely related to thrust zones that truncate the OKA. Later faults dismembered the ore explaining the variable depth of the different ore bodies along the Outokumpu ore zone. On a larger scale, at least four km-scale thrust sheets separated by major listric shear zones (curved dislocations in the seismic lines) can be recognized, each internally further imbricated by subordinate shear zones containing a number of lens-shape bodies of probably OKA rocks. Thrust stacking was followed by at least 3 stages of faulting that divided the ore belt into fault-bounded blocks with heterogeneous displacements: (i) NW-dipping faults with unresolved kinematics, (ii) reverse faulting along c.50°-60° SE

  5. EBSD Investigation of Cu-Sn IMC Microstructural Evolution in Cu/Sn-Ag/Cu Microbumps During Isothermal Annealing

    NASA Astrophysics Data System (ADS)

    Wang, S. J.; Hsu, L. H.; Wang, N. K.; Ho, C. E.

    2014-01-01

    The microstructural evolution of Cu/Sn-Ag (~5 μm)/Cu Cu-bump-on-line (CuBOL) joints during isothermal annealing at 180°C was examined using a field-emission scanning electron microscope equipped with an electron backscatter diffraction (EBSD) system. Cu6Sn5 and Cu3Sn were the two key intermetallic compound (IMC) species that appeared in the CuBOL joints. After annealing for 24 h (= t), the solder had completely converted to Cu-Sn IMCs, forming an "IMC" joint with Cu/Cu3Sn/Cu6Sn5/Cu3Sn/Cu structure. EBSD analyses indicated that the preferred orientation of the hexagonal Cu6Sn5 (η) was , while the preferred orientation was (100) for the monoclinic Cu6Sn5 structure (η'). Upon increasing t to 72 h, Cu6Sn5 entirely transformed into Cu3Sn, and the IMC joint became Cu/Cu3Sn/Cu accordingly. Interestingly, the grain size and crystallographic orientation of Cu3Sn displayed location dependence. Detailed EBSD analyses in combination with transmission electron microscopy on Cu3Sn were performed in the present study. This research offers better understanding of crystallographic details, including crystal structure, grain size, and orientation, for Cu6Sn5 and Cu3Sn in CuBOL joints after various annealing times.

  6. Infrared Brazing Ti50Ni50 and Invar Using Ag-Based Filler Foils

    NASA Astrophysics Data System (ADS)

    Shiue, R. K.; Chang, Y. H.; Wu, S. K.

    2013-10-01

    Infrared brazing Ti50Ni50 and Invar using BAg-8 and Cusil-ABA foils was investigated. The Ag-Cu eutectic matrix dominates both brazed joints. The maximum shear strengths of the brazed joints using BAg-8 and Cusil-ABA fillers are 158 and 249 MPa. Failure of interfacial Fe2Ti/Ni3Ti reaction layers is responsible for the BAg-8 joint. In contrast, the Cusil-ABA brazed joint is fractured along the interfacial Fe2Ti intermetallic compound. Both fractographs are characterized with cleavage dominated fracture.

  7. Microstructure and Interfacial Reactions During Vacuum Brazing of Stainless Steel to Titanium Using Ag-28 pct Cu Alloy

    NASA Astrophysics Data System (ADS)

    Laik, A.; Shirzadi, A. A.; Sharma, G.; Tewari, R.; Jayakumar, T.; Dey, G. K.

    2015-02-01

    Microstructural evolution and interfacial reactions during vacuum brazing of grade-2 Ti and 304L-type stainless steel (SS) using eutectic alloy Ag-28 wt pct Cu were investigated. A thin Ni-depleted zone of -Fe(Cr, Ni) solid solution formed on the SS-side of the braze zone (BZ). Cu from the braze alloy, in combination with the dissolved Fe and Ti from the base materials, formed a layer of ternary compound , adjacent to Ti in the BZ. In addition, four binary intermetallic compounds, CuTi, CuTi, CuTi and CuTi formed as parallel contiguous layers in the BZ. The unreacted Ag solidified as islands within the layers of CuTi and CuTi. Formation of an amorphous phase at certain locations in the BZ could be revealed. The -Ti(Cu) layer, formed due to diffusion of Cu into Ti-based material, transformed to an -Ti + CuTi eutectoid with lamellar morphology. Tensile test showed that the brazed joints had strength of 112 MPa and failed at the BZ. The possible sequence of events that led to the final microstructure and the mode of failure of these joints were delineated.

  8. Ultra-Fast Synthesis for Ag2Se and CuAgSe Thermoelectric Materials

    NASA Astrophysics Data System (ADS)

    DUAN, H. Z.; LI, Y. L.; ZHAO, K. P.; QIU, P. F.; SHI, X.; CHEN, L. D.

    2016-10-01

    Ag2Se and CuAgSe have been recently reported as promising thermoelectric materials at room temperature. The traditional melting-annealing-sintering processes are used to grow Ag2Se and CuAgSe materials with the disadvantages of high costs of energy and time. In this work, phase-pure polycrystalline Ag2Se and CuAgSe compounds were synthesized from raw elemental powders directly by manual mixing followed by spark plasma sintering (MM-SPS) in a few minutes. The influence of SPS heating rate on the phase composition, microstructure, and thermoelectric properties, including Seebeck coefficient, electrical conductivity, and thermal conductivity, were investigated. The zTs of 0.8 at 390 K and 0.6 at 450 K are obtained for Ag2Se and CuAgSe, respectively, which is comparable with the values in the materials prepared by the traditional method. Furthermore, this ultrafast sample synthesis can significantly save material synthesis time and thus has the obvious advantage for large-scale production.

  9. Nanoindentation on SnAgCu lead-free solder joints and analysis

    NASA Astrophysics Data System (ADS)

    Xu, Luhua; Pang, John H. L.

    2006-12-01

    The lead-free SnAgCu (SAC) solder joint on copper pad with organic solderability preservative (Cu-OSP) and electroless nickel and immersion gold (ENIG) subjected to thermal testing leads to intermetallic growth. It causes corresponding reliability concerns at the interface. Nanoindentation characterization on SnAgCu solder alloy, intermetallic compounds (IMCs), and the substrates subjected to thermal aging is reported. The modulus and hardness of thin IMC layers were measured by nanoindentation continuous stiffness measurement (CSM) from planar IMC surface. When SAC/Ni(Au) solder joints were subject to thermal aging, the Young’s modulus of the NiCuSn IMC at the SAC/ENIG specimen changed from 207 GPa to 146 GPa with different aging times up to 500 h. The hardness decreased from 10.0 GPa to 7.3 GPa. For the SAC/Cu-OSP reaction couple, the Young’s modulus of Cu6Sn5 stayed constant at 97.0 GPa and hardness about 5.7 GPa. Electron-probe microanalysis (EPMA) was used to thermal aging. The creep effect on the measured result was analyzed when measuring SnAgCu solder; it was found that the indentation penetration, and thus the hardness, is loading rate dependent. With the proposed constant P/P experiment, a constant indentation strain rate h/h and hardness could be achieved. The log-log plot of indentation strain rate versus hardness for the data from the constant P/P experiments yields a slope of 7.52. With the optimized test method and CSM Technique, the Modulus of SAC387 solder alloy and all the layers in a solder joint were investigated.

  10. Structure and electronic behavior of 26-atom Cu-Ag and Cu-Au nanoalloys

    NASA Astrophysics Data System (ADS)

    Guzmán-Ramírez, Gregorio; Robles, Juvencio; Aguilera-Granja, Faustino

    2016-09-01

    We hereby present a density functional theory (DFT) study of the structural, energetic, and electronic properties of the binary clusters Cu n X26- n (with X = Ag and Au). Our electronic calculations were performed with the DFT package GAUSSIAN 09, and we chose the BPW91 exchange correlation functional in combination with an effective core potential LANL2DZ basis set as our level of theory. We find that in the case of these clusters and in a completely different way - as compared to the bulk chemical order observed in both alloys CuAg (segregation) and CuAu (ordering) -, for small n both Ag and Au clusters exhibit a similar chemical order, finding the Cu atoms in the center of the cluster with the tendency to form core shell structures. On the other hand, for large n values the Ag and Au atoms tend to occupy surface positions forming separated surface islands that keep the two metal atoms separated as long as the concentration allows it. Concerning the structural properties, a clear increase in the interatomic distance of the Ag-Ag and Au-Au surface pairs is observed, particularly in the equiatomic region. In conclusion, both nanoalloys CuAg and CuAu behave quite similarly in contrast to their respective bulk cases.

  11. Pb-free Sn-Ag-Cu ternary eutectic solder

    DOEpatents

    Anderson, I.E.; Yost, F.G.; Smith, J.F.; Miller, C.M.; Terpstra, R.L.

    1996-06-18

    A Pb-free solder includes a ternary eutectic composition consisting essentially of about 93.6 weight % Sn-about 4.7 weight % Ag-about 1.7 weight % Cu having a eutectic melting temperature of about 217 C and variants of the ternary composition wherein the relative concentrations of Sn, Ag, and Cu deviate from the ternary eutectic composition to provide a controlled melting temperature range (liquid-solid ``mushy`` zone) relative to the eutectic melting temperature (e.g. up to 15 C above the eutectic melting temperature). 5 figs.

  12. Pb-free Sn-Ag-Cu ternary eutectic solder

    DOEpatents

    Anderson, Iver E.; Yost, Frederick G.; Smith, John F.; Miller, Chad M.; Terpstra, Robert L.

    1996-06-18

    A Pb-free solder includes a ternary eutectic composition consisting essentially of about 93.6 weight % Sn-about 4.7 weight % Ag-about 1.7 weight % Cu having a eutectic melting temperature of about 217.degree. C. and variants of the ternary composition wherein the relative concentrations of Sn, Ag, and Cu deviate from the ternary eutectic composition to provide a controlled melting temperature range (liquid-solid "mushy" zone) relative to the eutectic melting temperature (e.g. up to 15.degree. C. above the eutectic melting temperature).

  13. Liquidus Projections of Sn-Co-Ni and Sn-Rich Sn-Ag-Co-Ni Systems

    NASA Astrophysics Data System (ADS)

    Chen, Sinn-wen; Chen, Tung-Kai; Hsu, Chia-ming; Chang, Jui-shen; Pan, Kevin

    2014-07-01

    Alloys based on Sn and Sn-Ag are commonly used as Pb-free solders, and Ni is frequently used in barrier layers. Co has been studied as a possible alloying element in both solders and barrier layers. Thus, the Sn-Co-Ni and Sn-Ag-Co-Ni alloy systems are important for electronic soldering. Forty-nine Sn-Co-Ni alloys and 24 Sn-rich Sn-Ag-Co-Ni alloys were prepared. The primary solidification phases of these as-cast alloys were determined, and based on these results and the available phase diagrams of the constituent systems, the liquidus projections of Sn-Co-Ni ternary and Sn-Ag-Co-Ni quaternary systems at 90 at.% and 95 at.% Sn were determined. In the Sn-Co-Ni system, no ternary compound was found; (Ni,Co)3Sn2 and (Ni,Co) are continuous solid solutions, and there are eight kinds of primary solidification phases: Sn, CoSn3, CoSn2, CoSn, (Ni,Co)3Sn2, (Ni,Co), Ni3Sn, and Ni3Sn4. In the 90 at.% and 95 at.% Sn isoplethal sections of the Sn-Ag-Co-Ni liquidus projection, the primary solidification phases are CoSn2, CoSn, Ni3Sn4, and Ag3Sn.

  14. Dynamic viscosities of pure tin and Sn-Ag, Sn-Cu, and Sn-Ag-Cu eutectic melts

    NASA Astrophysics Data System (ADS)

    Rozhitsina, E. V.; Gruner, S.; Kaban, I.; Hoyer, W.; Sidorov, V. E.; Popel', P. S.

    2011-02-01

    The dynamic viscosities of the melts of pure tin and eutectic Sn-Ag, Sn-Cu, and Sn-Ag-Cu alloys are studied in heating followed by cooling, and the maximum heating temperature was 1200°C. An irreversible decrease in the viscosity is found in the temperature range 800-1000°C in the polytherms of all melts. This finding is related to the loss of a local order in a melt and can be used to develop temperature regimes for the production of lead-free solders.

  15. Communication: Kinetics of chemical ordering in Ag-Au and Ag-Ni nanoalloys

    NASA Astrophysics Data System (ADS)

    Calvo, F.; Fortunelli, A.; Negreiros, F.; Wales, D. J.

    2013-09-01

    The energy landscape and kinetics of medium-sized Ag-Au and Ag-Ni nanoalloy particles are explored via a discrete path sampling approach, focusing on rearrangements connecting regions differing in chemical order. The highly miscible Ag27Au28 supports a large number of nearly degenerate icosahedral homotops. The transformation from reverse core-shell to core-shell involves large displacements away from the icosahedron through elementary steps corresponding to surface diffusion and vacancy formation. The immiscible Ag42Ni13 naturally forms an asymmetric core-shell structure, and about 10 eV is required to extrude the nickel core to the surface. The corresponding transformation occurs via a long and smooth sequence of surface displacements. For both systems the rearrangement kinetics exhibit Arrhenius behavior. These results are discussed in the light of experimental observations.

  16. Ion-exchange synthesis of Ag/Ag2S/Ag3CuS2 ternary hollow microspheres with efficient visible-light photocatalytic activity.

    PubMed

    Xing, Chaosheng; Zhang, Yuan; Wu, Zhudong; Jiang, Deli; Chen, Min

    2014-02-21

    Ternary Ag/Ag2S/Ag3CuS2 hollow microspheres were synthesized via an in situ ion-exchange method using Cu7S4 hollow submicrospheres as the template. The as-obtained Ag/Ag2S/Ag3CuS2 composite exhibited a well-defined uniform hollow microsphere morphology with an average diameter of about 1.3 μm. The photocatalytic property of the as-prepared Ag/Ag2S/Ag3CuS2 hollow microsphere composite was investigated by the decomposition of methyl orange (MO) under visible light irradiation (λ > 420 nm). It was shown that the photocatalytic activity of the Ag/Ag2S/Ag3CuS2 hollow microsphere was higher than those of Ag/Ag2S, Cu2O, Cu7S4 and P25 for the photodegradation of MO under visible light irradiation. Radical scavenger experiments demonstrated that superoxide radicals and holes were the main reactive species for MO degradation.

  17. Controlled growth of Cu-Ni nanowires and nanospheres for enhanced microwave absorption properties

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoxia; Dong, Lifeng; Zhang, Baoqin; Yu, Mingxun; Liu, Jingquan

    2016-03-01

    Copper is a good dielectric loss material but has low stability, whereas nickel is a good magnetic loss material and is corrosion resistant but with low conductivity, therefore Cu-Ni hybrid nanostructures have synergistic advantages as microwave absorption (MA) materials. Different Cu/Ni molar ratios of bimetallic nanowires (Cu13@Ni7, Cu5@Ni5 and Cu7@Ni13) and nanospheres (Cu13@Ni7, Cu5@Ni5 and Cu1@Ni3) have been successfully synthesized via facile reduction of hydrazine under similar reaction conditions, and the morphology can be easily tuned by varying the feed ratio or the complexing agent. Apart from the concentrations of Cu2+ and Ni2+, the reduction parameters are similar for all samples to confirm the effects of the Cu/Ni molar ratio and morphology on MA properties. Ni is incorporated into the Cu-Ni nanomaterials as a shell over the Cu core at low temperature, as proved by XRD, SEM, TEM and XPS. Through the complex relative permittivity and permeability, reflection loss was evaluated, which revealed that the MA capacity greatly depended on the Cu/Ni molar ratio and morphology. For Cu@Ni nanowires, as the molar ratio of Ni shell increased the MA properties decreased accordingly. However, for Cu@Ni nanospheres, the opposite trend was found, that is, as the molar ratio of the Ni shell increased the MA properties increased.

  18. Tensile properties and thermal shock reliability of Sn-Ag-Cu solder joint with indium addition.

    PubMed

    Yu, A-Mi; Jang, Jae-Won; Lee, Jong-Hyun; Kim, Jun-Ki; Kim, Mok-Soon

    2012-04-01

    The thermal shock reliability and tensile properties of a newly developed quaternary Sn-1.2Ag-0.5Cu-0.4In (wt%) solder alloy were investigated and compared to those of ternary Sn-Ag-Cu based Pb-free solder alloys. It was revealed that the Sn-1.2Ag-0.5Cu-0.4In solder alloy shows better thermal shock reliability compared to the Sn-1.0Ag-0.5Cu and Sn-3.0Ag-0.5Cu solder alloys. The quaternary alloy has higher strength than Sn-1.0Ag-0.5Cu alloy, and higher elongation than Sn-3.0Ag-0.5Cu alloy. It was also revealed that the addition of indium promotes the formation of Ag3(Sn, In) phase in the solder joint during reflow process.

  19. Morphology Effect of Ni-Ag/CARBON Nanomaterials on Their Electrocatalytic Activity for Glucose Oxidation

    NASA Astrophysics Data System (ADS)

    Ouyang, Ruizhuo; Li, Weiwei; Yang, Yang; Zhang, Wangyao; Feng, Kai; Zong, Tianyu; An, Yarui; Zhou, Shuang; Miao, Yuqing

    2016-06-01

    We presented here three carbon-nanomaterials-based modified glassy carbon electrodes (GCE) with Ni-Ag nanohybrid nanoparticles (NPs) deposited upon, including single-wall carbon nanotubes (SWCNTs), multi-wall carbon nanotubes (MWCNTs) and the mesoporous carbons (MPCs), and compared their morphology effects on both Ni-Ag deposition quality and electrocatalytic performances toward Glu oxidation. After being deposited with Ni-Ag NPs, a homogenous surface with very small Ni-Ag NPs was obtained for Ni-Ag/SWCNTs/GCE, while heterogeneous, coarse surfaces with obvious embedment with large Ni-Ag particles were observed for both Ni-Ag/MWCNTs/GCE and Ni-Ag/MPC/GCE. All three modified electrodes were well characterized in terms of surface morphology, electron transfer rate, hydrophilicity, interference resistance, stability, electrocatalytic behaviors as well as practicability in real samples, based on which Ni-Ag/SWCNTs/GCE was always proved to be more advantageous over other two composite electrodes. Such advantage of Ni-Ag/SWCNTs/GCE was attributed to its desirable surface morphology good for Ni-Ag deposition and exposure of as many active sites as possible to Glu oxidation, leading to the extraordinary electrocatalytic performance.

  20. Ag@Ni core-shell nanowire network for robust transparent electrodes against oxidation and sulfurization.

    PubMed

    Eom, Hyeonjin; Lee, Jaemin; Pichitpajongkit, Aekachan; Amjadi, Morteza; Jeong, Jun-Ho; Lee, Eungsug; Lee, Jung-Yong; Park, Inkyu

    2014-10-29

    Silver nanowire (Ag NW) based transparent electrodes are inherently unstable to moist and chemically reactive environment. A remarkable stability improvement of the Ag NW network film against oxidizing and sulfurizing environment by local electrodeposition of Ni along Ag NWs is reported. The optical transmittance and electrical resistance of the Ni deposited Ag NW network film can be easily controlled by adjusting the morphology and thickness of the Ni shell layer. The electrical conductivity of the Ag NW network film is increased by the Ni coating via welding between Ag NWs as well as additional conductive area for the electron transport by electrodeposited Ni layer. Moreover, the chemical resistance of Ag NWs against oxidation and sulfurization can be dramatically enhanced by the Ni shell layer electrodeposited along the Ag NWs, which provides the physical barrier against chemical reaction and diffusion as well as the cathodic protection from galvanic corrosion.

  1. Physical Characterization of Cu-Ni-P Thin Films aiming at Cu/Cu-Ni-P Thermocouples

    NASA Astrophysics Data System (ADS)

    Tomachevski, F.; Sparvoli, M.; dos Santos Filho, S. G.

    2015-03-01

    Cu-Ni-P thin films have a high-thermoelectric power, which allows the fabrication of very sensitive heat-flux sensors based on planar technology. In this work, (100) silicon surfaces were pre-activated in a diluted hydrofluoric acid solution containing PdCl2. Following, Cu-Ni-P thin films were chemically deposited using an alkaline chemical bath containing 15 g/l NiSO4.6H2O; 0.2 g/l CuSO4.5H2O; 15 g/l Na2HPO2.H2O and 60 g/l Na3C6H5O7.2H2O at temperature of 80 °C where NH4OH was added until pH was 8.0. It was noteworthy that the stoichiometric percentages of Ni and Cu vary substantially for immersion times in the range of 1 to 3 min and they become almost stable at 50% and 35%, respectively, when the immersion time is higher than 3 min. In addition, the percentage of P remains almost constant around 1718 % for all the immersion times studied. On the other hand, the sheet resistance also varies substantially for immersion times in the range of 1 to 3 min. Based on the surface morphology, smaller grains with size in the range of 0.02 to 0.1 μm are initially grown on the silicon surface and exposed regions of silicon without deposits are also observed for immersion times in the range of 1 to 3min. Therefore, the discontinuities and non uniformities of the films are promoting, respectively, the observed behaviours of sheet resistance and stoichiometry.

  2. Stripe-to-bubble transition of magnetic domains at the spin reorientation of (Fe/Ni)/Cu/Ni/Cu(001)

    SciTech Connect

    Wu, J.; Choi, J.; Won, C.; Wu, Y. Z.; Scholl, A.; Doran, A.; Hwang, Chanyong; Qiu, Z.

    2010-06-09

    Magnetic domain evolution at the spin reorientation transition (SRT) of (Fe/Ni)/Cu/Ni/Cu(001) is investigated using photoemission electron microscopy. While the (Fe/Ni) layer exhibits the SRT, the interlayer coupling of the perpendicularly magnetized Ni layer to the (Fe/Ni) layer serves as a virtual perpendicular magnetic field exerted on the (Fe/Ni) layer. We find that the perpendicular virtual magnetic field breaks the up-down symmetry of the (Fe/Ni) stripe domains to induce a net magnetization in the normal direction of the film. Moreover, as the virtual magnetic field increases to exceed a critical field, the stripe domain phase evolves into a bubble domain phase. Although the critical field depends on the Fe film thickness, we show that the area fraction of the minority domain exhibits a universal value that determines the stripe-to-bubble phase transition.

  3. Facile Preparation of Ag/NiO Composite Nanosheets and Their Antibacterial Activity

    NASA Astrophysics Data System (ADS)

    Shi, Cui-E.; Pan, Lu; Wang, Cheng-Run; He, Yi; Wu, Yong-Feng; Xue, Sai-Sai

    2016-01-01

    Sheet-like precursors of NiO and Ag/NiO with different Ag contents were synthesized by a facile and easily controlled hydrothermal method. The NiO and Ag/NiO composite nanosheets were prepared by calcination of the corresponding precursors at 400°C for 3 h. The as-synthesized samples were characterized by thermogravimetric analysis, x-ray diffraction, transmission electron microscopy, and scanning electron microscopy. The antibacterial activity of NiO and Ag/NiO composites to several gram-positive and gram-negative bacteria was examined. Results showed that NiO nanosheets hardly exhibited antibacterial activity; however, Ag/NiO composites displayed higher activity even with low Ag content.

  4. Recrystallization of Cu-poor CuInS{sub 2} assisted by metallic Cu or Ag

    SciTech Connect

    Rodriguez-Alvarez, Humberto; Mainz, Roland; Marsen, Bjoern; Schock, Hans-Werner

    2010-04-15

    We monitor the recrystallization of Cu-poor CuInS{sub 2} thin films assisted by pure Cu or pure Ag by means of real-time synchrotron-based polychromatic X-ray diffraction. In both cases a new microstructure is formed accompanied by an increase in grain size. In the case of Cu, the onset temperature of the thin-film recrystallization is higher than 370 deg. C. In the case of Ag, the thin-film recrystallization comes to an end at 270 deg. C. The Ag-assisted recrystallization occurs in the presence of the body-centered cubic beta-Ag{sub 2}S phase. We find that domain growth and diffusion of silver into the film occur simultaneously. - Graphical abstract Keywords: Recrystallization; Thin-film solar cells; Energy-dispersive x-ray diffraction: In-situ monitoring by means of energy-dispersive X-ray diffraction of the thin-film recrystallization of Cu-poor CuInS{sub 2} assisted by metallic Ag.

  5. Cu-Ag sulfides as indicators of pre-porphyritic epithermal Au-Ag deposits in Northeastern Russia

    NASA Astrophysics Data System (ADS)

    Savva, N. E.; Sidorov, A. A.; Volkov, A. V.

    2016-08-01

    Au-Ag mineralization of the Olcha and Teploe epithermal deposits underwent thermal metamorphism due to porphyritic intrusions. The presence of Bi-bearing galena and matildite in the ores (Teploe), Cu-Te-bearing naumannite (Olcha), the occurrence of middle- and high-temperature facies of metasomatic rocks (epidote and actinolite), and temperature formation conditions are related, firstly, to the influence of granitoids on the ore process, which supplied not only Cu and Mo, but also Bi, Te, and, secondly, to the heating of host rocks containing pre-porphyritic epithermal Au-Ag mineralization. The abundance of Cu-Ag sulfides and Cu-acanthite resulted from the enrichment of later mineral phases in Cu and Ag under the substance redistribution with the formation of Ag-acanthite ores. The data considered in the paper are of practical importance for regional forecasting of metallogenic constructions, exploration, and evaluation of the epithermal Au-Ag deposits.

  6. Quaternary PtMnCuX/C (X = Fe, Co, Ni, and Sn) and PtMnMoX/C (X = Fe, Co, Ni, Cu and Sn) alloys catalysts: Synthesis, characterization and activity towards ethanol electrooxidation

    NASA Astrophysics Data System (ADS)

    Ammam, Malika; Easton, E. Bradley

    2012-10-01

    In this account, two series of quaternary PtMnCuX/C (X = Fe, Co, Ni, and Sn) and PtMnMoX/C (X = Fe, Co, Ni, Cu and Sn) alloys catalysts have been synthesized and characterized by ICP, XRD, XPS, TEM and cyclic voltammetry. XRD spectra of each series illustrated that PtMnCuX/C (X = Fe, Co and Ni) and PtMnMoX/C (X = Fe, Co, Ni and Cu) alloys have been formed without significant free Mn, Cu, Mo or X co-catalysts. For PtMnCuSn/C and PtMnMoSn/C, in addition to alloy formation, significant free Sn-oxides are present in each catalyst. Cyclic voltammetry and chronoamperometry revealed that all quaternary showed superior electrocatalytic activity towards ethanol oxidation compared to the ternary precursor. Also, shift of the onset potential of ethanol oxidation towards less positive values were also recorded with the quaternary alloys, demonstrating a facilitated oxidation with the quaternary alloys compared to ternary alloy precursor. The magnitude of the gain in potential depend on the alloy composition and PtMnMoSn/C was found to be the best of all synthetized quaternary alloys with an onset potential of ethanol oxidation of only 0.059 V vs. Ag/AgCl.

  7. Microstructure of Cu-Ag Uniform Nanoparticulate Films on Polyurethane 3D Catheters: Surface Properties.

    PubMed

    Rtimi, Sami; Sanjines, Rosendo; Pulgarin, Cesar; Kiwi, John

    2016-01-13

    The preparation, characterization, and antibacterial testing of Cu-Ag sputtered polyurethane (PU) catheters are addressed in this study. PU catheters with different atomic ratios Cu:Ag have been sputtered and led to different optical properties as followed by diffuse reflectance spectroscopy (DRS) and the surface redox properties were also different for different Cu-Ag ratios as observed by X-ray photoelectron spectroscopy (XPS). The surface atomic percentage concentration of the oxidized/reduced C-species originating from bacterial cultures before and after bacterial inactivation were determined on the Cu-Ag PU catheters. The crystallographic properties were determined by X-ray diffraction (XRD). The XRD-diffractogram showed the presence of Cu2O (111), Cu (200), CuO (020), and Ag (111) indicating that Cu nanoparticles present a more crystalline character compared to Ag nanoparticles. Increasing the percentage of Ag in the Cu-Ag films, bigger Ag-particle agglomerates were detected by scanning transmission electron microscopy (STEM) microanalysis confirming the results obtained by AFM. The bacterial inactivation kinetics of the sputtered Cu-Ag films on PU catheters was investigated in detail. Quasi-instantaneous bacterial inactivation kinetics was induced by the sputtered films on PU catheters after optimization of the Cu-Ag film thickness.

  8. Atomic diffusion in liquid Ni, NiP, PdNiP, and PdNiCuP alloys

    SciTech Connect

    Chathoth, S. Mavila; Meyer, A.; Koza, M.M.; Juranyi, F.

    2004-11-22

    We investigated the self-diffusion of Ni in liquid Ni, Ni{sub 80}P{sub 20}, Pd{sub 40}Ni{sub 40}P{sub 20}, and Pd{sub 43}Ni{sub 10}Cu{sub 27}P{sub 20} at temperatures up to 1795 K with incoherent, quasielastic neutron scattering. Values of measured self-diffusion coefficients vary over the accessible temperature ranges as a function of composition only within 10%. Although mixing has a drastic effect on the liquidus temperature and the undercooling capabilities, a relation between these properties and the atomic diffusion in the liquid is not observed. Apparently, diffusive motion is governed by the packing fraction of the atoms, that is very similar in these dense liquids.

  9. Vibrations on Cu surfaces covered with Ni monolayer

    NASA Astrophysics Data System (ADS)

    Sklyadneva, I. Yu.; Rusina, G. G.; Chulkov, E. V.

    1999-08-01

    Vibrational modes on the Cu(100) and Cu(111) surfaces covered with a Ni monolayer have been calculated using the embedded-atom method. A detailed discussion of the dispersion relations and polarizations of adsorbate modes and surface phonons is presented. The dispersion of the Rayleigh phonon is in good agreement with the experimental EELS data. The changes in interatomic force constants are discussed.

  10. Magnetic interlayer coupling between Co films across Cu/Ni30Cu70/Cu(100) double quantum wells

    SciTech Connect

    Zhang, Z.D.; Choi, H.J.; Kawakami, R.K.; Escorcia-Aparicio, E.J.; Bowen, M.O.; Rotenberg, E.; Smith, N.V.; Qiu, Z.Q.

    1999-05-18

    Magnetic interlayer coupling between two Co layers across Cu/Ni 30 Cu 70 /Cu(100) was investigated by the surface magneto-optic Kerr effect. The Ni 30 Cu 70 layer at the center of the Cu layer was shown to shift the peak positions, rather than to change the strength, of the magnetic interlayer coupling. The density of states near the Fermi level was investigated by photoemission spectroscopy. We show that the peak-position shift in the magnetic interlayer coupling is associated with the quantum-well behavior in a symmetric double-quantum-well system. The phase accumulation model was applied to explain the results quantitatively.

  11. Microwave absorption of electroplated NiFeCu/Cu multilayers deposited directly on Si (100) substrates

    NASA Astrophysics Data System (ADS)

    Silva, B. G.; Gonzalez-Chavez, D. E.; Filho, J. Gomes; Sommer, R. L.

    2016-12-01

    We study the magnetic properties and broadband microwave absorption of electroplated NiFeCu/Cu multilayered thin films deposited directly on Si (100) substrates. We produced samples with 20 nm thick NiFeCu layers and Cu layer thickness tCu in the range 0-2.8 nm. Structural properties were studied by grazing incidence X-ray diffraction (GIXRD), while the composition and morphological aspects were studied by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). GIXRD confirmed the cubic face centered FCC phase of NiFeCu with all diffraction peaks drifting toward lower angles with tCu. SEM images show the appearance of Cu islands instead of continuous Cu layers. A minimum coercive field of 1.4 Oe is obtained for tCu = 1.0 nm, while the ferromagnetic resonance linewidth exhibited 200 Oe constant values for tCu between 0.7 and 2.1 nm. The effective magnetization increases with tCu, possibly associated to the increase on Fe content as observed by EDX. The effective dynamic anisotropy behavior with tCu seems to be associated to the island structure observed in the films.

  12. Anodic vacuum arc developed nanocrystalline Cu-Ni and Fe-Ni thin film thermocouples

    SciTech Connect

    Mukherjee, S. K.; Sinha, M. K.; Pathak, B.; Rout, S. K.; Barhai, P. K.

    2009-12-01

    This paper deals with the development of nanocrystalline Cu-Ni and Fe-Ni thin film thermocouples (TFTCs) by using ion-assisted anodic vacuum arc deposition technique. The crystallographic structure and surface morphology of individual layer films have been studied by x-ray diffraction and scanning electron microscopy, respectively. The resistivity, temperature coefficient of resistance, and thermoelectric power of as deposited and annealed films have been measured. The observed departure of these transport parameters from their respective bulk values can be understood in terms of intrinsic scattering due to enhanced crystallite boundaries. From the measured values of thermoelectric power and the corresponding temperature coefficient of resistance of annealed Cu, Ni, and Fe films, the calculated values of log derivative of the mean free path of conduction electrons at the Fermi surface with respect to energy (U) are found to be -0.51, 3.22, and -8.39, respectively. The thermoelectric response of annealed Cu-Ni and Fe-Ni TFTCs has been studied up to a maximum temperature difference of 300 deg. C. Reproducibility of TFTCs has been examined in terms of the standard deviation in thermoelectric response of 16 test samples for each pair. Cu-Ni and Fe-Ni TFTCs agree well with their wire thermocouple equivalents. The thermoelectric power values of Cu-Ni and Fe-Ni TFTCs at 300 deg. C are found to be 0.0178 and 0.0279 mV/ deg. C, respectively.

  13. Anodic vacuum arc developed nanocrystalline Cu-Ni and Fe-Ni thin film thermocouples

    NASA Astrophysics Data System (ADS)

    Mukherjee, S. K.; Sinha, M. K.; Pathak, B.; Rout, S. K.; Barhai, P. K.

    2009-12-01

    This paper deals with the development of nanocrystalline Cu-Ni and Fe-Ni thin film thermocouples (TFTCs) by using ion-assisted anodic vacuum arc deposition technique. The crystallographic structure and surface morphology of individual layer films have been studied by x-ray diffraction and scanning electron microscopy, respectively. The resistivity, temperature coefficient of resistance, and thermoelectric power of as deposited and annealed films have been measured. The observed departure of these transport parameters from their respective bulk values can be understood in terms of intrinsic scattering due to enhanced crystallite boundaries. From the measured values of thermoelectric power and the corresponding temperature coefficient of resistance of annealed Cu, Ni, and Fe films, the calculated values of log derivative of the mean free path of conduction electrons at the Fermi surface with respect to energy (U) are found to be -0.51, 3.22, and -8.39, respectively. The thermoelectric response of annealed Cu-Ni and Fe-Ni TFTCs has been studied up to a maximum temperature difference of 300°C. Reproducibility of TFTCs has been examined in terms of the standard deviation in thermoelectric response of 16 test samples for each pair. Cu-Ni and Fe-Ni TFTCs agree well with their wire thermocouple equivalents. The thermoelectric power values of Cu-Ni and Fe-Ni TFTCs at 300°C are found to be 0.0178 and 0.0279mV/°C, respectively.

  14. Surfactant-mediated layer-by-layer homoepitaxial growth of Cu/In/Cu(100) and Ag/Sb/Ag(111) systems: A theoretical study

    NASA Astrophysics Data System (ADS)

    Jiang, Ming; Zhao, Yu-Jun; Cao, Pei-Lin

    1998-04-01

    Two typical surfactant-mediated homoepitaxial metal systems, Cu/In/Cu(100) and Ag/Sb/Ag(111), are studied by using first-principles calculations and a kinetic Monte Carlo method. Our results confirm the validity of the model that Zhang and Lagally suggested for Cu/In/Cu(100) system. A repulsion model is proposed for the Ag/Sb/Ag(111) system where surface-substitutional Sb atoms repel diffusing Ag adatoms. The layer-by-layer growth for Ag/Sb/Ag(111) system is achieved with a repulsion model in kinetic Monte Carlo simulation. By comparing the two different growth models, the importance of the additional barrier ΔE and effectiveness of two ways of reducing ΔE are confirmed in determining film morphology.

  15. Theoretical studies of diatomic and triatomic systems containing the group IB atoms Cu, Ag, and Au

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.; Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.

    1986-01-01

    Selected portions of the ground state potential energy surfaces of the Cu3, Ag3, AgCu2, and AuCu2 trimers are studied at the single-reference singles plus doubles configuration interaction and couple pair functional levels correlating 33 electrons. The calculations use the effective core potentials of Hay and Wadt (1985) to replace the deep core levels. The Cu3 and Ag3 molecules are found to have 2B2 obtuse-angled ground states, with low-lying 2A1 acute-angled excited states. The AgCu2 and AuCu2 molecules have 2A1 acute-angled ground states. The Cu3 molecule has a smaller 3d population than Ag3, and Cu3 has a smaller s electron density in the open-shell orbital than does Ag3, in agreement with recent ESR experiments.

  16. Microfluidic synthesis of Ag@Cu2O core-shell nanoparticles with enhanced photocatalytic activity.

    PubMed

    Tao, Sha; Yang, Mei; Chen, Huihui; Ren, Mingyue; Chen, Guangwen

    2017-01-15

    A microfluidic-based method for the continuous synthesis of Ag@Cu2O core-shell nanoparticles (NPs) has been developed. It only took 32s to obtain Ag@Cu2O core-shell NPs, indicating a high efficiency of this microfluidic-based method. Triangular Ag nanoprisms were employed as the cores for the overgrowth of Cu2O through the reduction of Cu(OH)4(2-) with ascorbic acid. The as-synthesized samples were characterized by XRD, TEM, SEM, HAADF-STEM, EDX, HRTEM, UV-vis spectra and N2 adsorption-desorption. The characterization results revealed that the as-synthesized Ag@Cu2O core-shell NPs exhibited a well-defined core-shell nanostructure with a polycrystalline shell, which was composed of numbers of Cu2O domains epitaxially growing on the triangular Ag nanoprism. It was concluded that the synthesis parameters such as the molar ratio of trisodium citrate to AgNO3, H2O2 to AgNO3, NaOH to CuSO4, ascorbic acid to CuSO4 and AgNO3 to CuSO4 had significant effect on the synthesis of Ag@Cu2O core-shell NPs. Moreover, Ag@Cu2O core-shell NPs exhibited superior catalytic activity in comparison with pristine Cu2O NPs towards the visible light-driven degradation of methyl orange. This enhanced photocatalytic activity of Ag@Cu2O core-shell NPs was attributed to the larger BET surface area and improved charge separation efficiency. The trapping experiment indicated that holes and superoxide anion radicals were the major reactive species in the photodegradation of methyl orange over Ag@Cu2O core-shell NPs. In addition, Ag@Cu2O core-shell NPs showed no obvious deactivation in the cyclic test.

  17. Modified Ni-Cu catalysts for ethanol steam reforming

    SciTech Connect

    Dan, M.; Mihet, M.; Almasan, V.; Borodi, G.; Katona, G.; Muresan, L.; Lazar, M. D.

    2013-11-13

    Three Ni-Cu catalysts, having different Cu content, supported on γ-alumina were synthesized by wet co-impregnation method, characterized and tested in the ethanol steam reforming (ESR) reaction. The catalysts were characterized for determination of: total surface area and porosity (N{sub 2} adsorption - desorption using BET and Dollimer Heal methods), Ni surface area (hydrogen chemisorption), crystallinity and Ni crystallites size (X-Ray Diffraction), type of catalytic active centers (Hydrogen Temperature Programmed Reduction). Total surface area and Ni crystallites size are not significantly influenced by the addition of Cu, while Ni surface area is drastically diminished by increasing of Cu concentration. Steam reforming experiments were performed at atmospheric pressure, temperature range 150-350°C, and ethanol - water molar ration of 1 at 30, using Ar as carrier gas. Ethanol conversion and hydrogen production increase by the addition of Cu. At 350°C there is a direct connection between hydrogen production and Cu concentration. Catalysts deactivation in 24h time on stream was studied by Transmission Electron Microscopy (TEM) and temperature-programmed reduction (TPR) on used catalysts. Coke deposition was observed at all studied temperatures; at 150°C amorphous carbon was evidenced, while at 350°C crystalline, filamentous carbon is formed.

  18. Magnetron sputtered Cu3N/NiTiCu shape memory thin film heterostructures for MEMS applications

    NASA Astrophysics Data System (ADS)

    Kaur, Navjot; Choudhary, Nitin; Goyal, Rajendra N.; Viladkar, S.; Matai, I.; Gopinath, P.; Chockalingam, S.; Kaur, Davinder

    2013-03-01

    In the present study, for the first time, Cu3N/NiTiCu/Si heterostructures were successfully grown using magnetron sputtering technique. Nanocrystalline copper nitride (Cu3N with thickness 200 nm) thin films and copper nanodots were subsequently deposited on the surface of 2-μm-thick NiTiCu shape memory thin films in order to improve the surface corrosion and nickel release properties of NiTiCu thin films. Interestingly, the phase transformation from martensite phase to austenite phase has been observed in Cu3N/NiTiCu heterostructures with corresponding change in texture and surface morphology of top Cu3N films. Field emission scanning electron microscopy and atomic force microscope images of the heterostructures reveals the formation of 20-nm-sized copper nanodots on NiTiCu surface at higher deposition temperature (450 °C) of Cu3N. Cu3N passivated NiTiCu films possess low corrosion current density with higher corrosion potential and, therefore, better corrosion resistance as compared to pure NiTiCu films. The concentration of Ni released from the Cu3N/NiTiCu samples was observed to be much less than that of pure NiTiCu film. It can be reduced to the factor of about one-ninth after the surface passivation resulting in smooth, homogeneous and highly corrosion resistant surface. The antibacterial and cytotoxicity of pure and Cu3N coated NiTiCu thin films were investigated through green fluorescent protein expressing E. coli bacteria and human embryonic kidney cells. The results show the strong antibacterial property and non cytotoxicity of Cu3N/NiTiCu heterostructure. This work is of immense technological importance due to variety of BioMEMS applications.

  19. Cu multiply twinned particle precipitation in low-temperature fired Ni-Zn-Cu ferrite

    NASA Astrophysics Data System (ADS)

    Fujimoto, Masayuki; Hoshi, Ken-Ichi; Nakazawa, Mutsuo; Sekiguchi, Shoichi

    1993-12-01

    Cu metal precipitates and truncated Cu metal multiply twinned particles (MTPs) were observed in low-temperature fired ferrite with a small excess of Ni-Zn-Cu chemical composition. The Cu metal precipitates suggest the existence of Cu solid solution and accelerated grain growth during the sintering accompanied with the formation of defect structures, such as oxygen vacancies in the ferrite spinel structure. The defect structure compensation during the cooling process after sintering results in Cu metal precipitation at the multiple grain junction.

  20. Cu Multiply Twinned Particle Precipitation in Low-Temperature Fired Ni-Zn-Cu Ferrite

    NASA Astrophysics Data System (ADS)

    Fujimoto, Masayuki; Hoshi, Ken-ichi; Nakazawa, Mutsuo; Sekiguchi, Shoichi

    1993-12-01

    Cu metal precipitates and truncated Cu metal multiply twinned particles (MTPs) were observed in low-temperature fired ferrite with a small excess of Ni-Zn-Cu chemical composition. The Cu metal precipitates suggest the existence of Cu solid solution and accelerated grain growth during the sintering accompanied with the formation of defect structures, such as oxygen vacancies in the ferrite spinel structure. The defect structure compensation during the cooling process after sintering results in Cu metal precipitation at the multiple grain junction.

  1. In Situ Electromigration in Cu-Sn and Ni-Sn Critical Solder Length for Three-Dimensional Integrated Circuits

    NASA Astrophysics Data System (ADS)

    Huang, Y. T.; Chen, C. H.; Lee, B. H.; Chen, H. C.; Wang, C. M.; Wu, Albert T.

    2016-12-01

    An in situ electromigration study has been conducted on U-groove Cu/Sn-3.5Ag/Cu and Ni/Sn-3.5Ag/Ni sandwich structures; the results were used to simulate microsolder joints passing current density of 1 × 104 A/cm2 at 150°C. The solder gap was only 15 μm, shorter than the critical length of Sn-3.5Ag solder. Backstress was proved to exist at critical solder lengths and to influence the electromigration mechanism. Theoretical calculations of the diffusivity of Cu and Ni in Sn solder indicated that the degree to which the dominant diffusion species (Cu or Ni atoms) diffused through the solder line is retarded by the backstress effect. The morphologies of intermetallic compounds (IMCs) were observed, and the grain boundaries in Sn solder were measured using electron backscatter diffraction to determine the kinetics of intermetallic growth. The results reveal that the unique electromigration characteristics of microbump joints, including the diffusivity, morphology, and backstress, can be determined. The retardation of atomic migration improves the reliability against electromigration.

  2. Preparation and Sintering Properties of Ag27Cu2Sn Nanopaste as Die Attach Material

    NASA Astrophysics Data System (ADS)

    Liu, Xiaojian; Liu, Wei; Wang, Chunqing; Zheng, Zhen; Kong, Lingchao

    2016-10-01

    Ag27Cu2Sn nanopaste has been prepared by mixing Ag, Cu, and Sn nanoparticles with an organic solvent system. Sintering and mechanical properties of this nanopaste were characterized and investigated. Effects of sintering temperature and time on the sintered microstructure of the nanopaste and shear strength of Cu/Ag27Cu2Sn/Cu structure were analyzed. The results showed that the organic shells coated on the outside of metal nanoparticles could effectively prevent metal nanoparticles from being oxidized below 480°C. When the paste was sintered at 480°C without pressure, few voids or large particles formed within the sintered layer and distributions of Ag, Cu, and Sn were quite uniform. This sintering temperature was much lower than the eutectic temperature (779°C) of Ag-Cu bulk material. Moreover, mutual solid solubilities of Ag and Cu were increased remarkably, which may be caused by high surface activity of Ag and Cu nanoparticles and the important role of the Sn addition. Shear strength of samples with Cu/Ag27Cu2Sn/Cu structure could reach 21 MPa, which could compare with that of Ag nanopaste or conductive adhesives.

  3. Au-Ag-Cu nano-alloys: tailoring of permittivity

    NASA Astrophysics Data System (ADS)

    Hashimoto, Yoshikazu; Seniutinas, Gediminas; Balčytis, Armandas; Juodkazis, Saulius; Nishijima, Yoshiaki

    2016-04-01

    Precious metal alloys enables new possibilities to tailor materials for specific optical functions. Here we present a systematic study of the effects of a nanoscale alloying on the permittivity of Au-Ag-Cu metals at 38 different atomic mixing ratios. The permittivity was measured and analyzed numerically by applying the Drude model. X-ray diffraction (XRD) revealed the face centered cubic lattice of the alloys. Both, optical spectra and XRD results point towards an equivalent composition-dependent electron scattering behavior. Correlation between the fundamental structural parameters of alloys and the resulting optical properties is elucidated. Plasmonic properties of the Au-Ag-Cu alloy nanoparticles were investigated by numerical simulations. Guidelines for designing plasmonic response of nano- structures and their patterns are presented from the material science perspective.

  4. Au-Ag-Cu nano-alloys: tailoring of permittivity

    PubMed Central

    Hashimoto, Yoshikazu; Seniutinas, Gediminas; Balčytis, Armandas; Juodkazis, Saulius; Nishijima, Yoshiaki

    2016-01-01

    Precious metal alloys enables new possibilities to tailor materials for specific optical functions. Here we present a systematic study of the effects of a nanoscale alloying on the permittivity of Au-Ag-Cu metals at 38 different atomic mixing ratios. The permittivity was measured and analyzed numerically by applying the Drude model. X-ray diffraction (XRD) revealed the face centered cubic lattice of the alloys. Both, optical spectra and XRD results point towards an equivalent composition-dependent electron scattering behavior. Correlation between the fundamental structural parameters of alloys and the resulting optical properties is elucidated. Plasmonic properties of the Au-Ag-Cu alloy nanoparticles were investigated by numerical simulations. Guidelines for designing plasmonic response of nano- structures and their patterns are presented from the material science perspective. PMID:27118459

  5. Fabrication and SERS properties of Ag/Cu2S composite micro-nanostructures over Cu foil.

    PubMed

    Song, Wei; Wang, Jinjie; Mao, Zhu; Xu, Weiqing; Zhao, Bing

    2011-09-01

    A new kind of Ag/Cu2S composite micro/nanostructures has been prepared via a convenient galvanic reduction method. SEM images of these micro/nanostructures showed that Ag nanoparticles with the size of around 50-100 nm were well deposited on the surface of Cu2S micro/nanostructures. The SEM images also indicated that the Ag nanoparticles were preferentially grown on the big polygonal Cu2S microstructures, which could be explained by a localization of the electrons on the surface of the polygonal Cu2S microstructures after the electron transfer step. Owing to the introduction of Ag nanoparticles on the surface of Cu2S micro/nanostructures, the resulting Ag/Cu2S composite micro-nanostructures could be used as a versatile substrate for surface enhanced Raman scattering.

  6. 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.

  7. Effects of PCB Pad Metal Finishes on the Cu-Pillar/Sn-Ag Micro Bump Joint Reliability of Chip-on-Board (COB) Assembly

    NASA Astrophysics Data System (ADS)

    Kim, Youngsoon; Lee, Seyong; Shin, Ji-won; Paik, Kyung-Wook

    2016-06-01

    While solder bumps have been used as the bump structure to form the interconnection during the last few decades, the continuing scaling down of devices has led to a change in the bump structure to Cu-pillar/Sn-Ag micro-bumps. Cu-pillar/Sn-Ag micro-bump interconnections differ from conventional solder bump interconnections in terms of their assembly processing and reliability. A thermo-compression bonding method with pre-applied b-stage non-conductive films has been adopted to form solder joints between Cu pillar/Sn-Ag micro bumps and printed circuit board vehicles, using various pad metal finishes. As a result, various interfacial inter-metallic compounds (IMCs) reactions and stress concentrations occur at the Cu pillar/Sn-Ag micro bumps joints. Therefore, it is necessary to investigate the influence of pad metal finishes on the structural reliability of fine pitch Cu pillar/Sn-Ag micro bumps flip chip packaging. In this study, four different pad surface finishes (Thin Ni ENEPIG, OSP, ENEPIG, ENIG) were evaluated in terms of their interconnection reliability by thermal cycle (T/C) test up to 2000 cycles at temperatures ranging from -55°C to 125°C and high-temperature storage test up to 1000 h at 150°C. The contact resistances of the Cu pillar/Sn-Ag micro bump showed significant differences after the T/C reliability test in the following order: thin Ni ENEPIG > OSP > ENEPIG where the thin Ni ENEPIG pad metal finish provided the best Cu pillar/Sn-Ag micro bump interconnection in terms of bump joint reliability. Various IMCs formed between the bump joint areas can account for the main failure mechanism.

  8. The Influence of Size Effect on Sensitivity of Cu/CuNi Thin- film Thermocouple

    NASA Astrophysics Data System (ADS)

    Yang, Lihong; Zhao, Yuanshen; Feng, Cenming; Zhou, Hua

    In this paper, the influence of size effect on the sensitivity of Cu/CuNi thin-film thermocouple was studied through experiments and theoretical analysis. Cu/CuNi thin-film thermocouples with different thicknesses of 0.5 μm, 1.0 μm, 1.5 μm and 2.0 μm were fabricated on the substrate with SiO2 lining by means of reactive magnetron sputtering. After static calibration, the sensitivities of the thermocouples were obtained respectively of 46.49 μV/°C, 45.23 μ/°C, 44.56 μV/°C and 43.94 μV/°C. According to the experimental results, it can be seen that the sensitivity of Cu/CuNi thin-film thermocouple is higher than that of the bulk Cu/CuNi thermocouple, and the sensitivity S will increase with the reciprocal of the thickness 1/δ as long as the thickness of the film is greater than the critical value.

  9. Microstructure development in Al-Cu-Ag-Mg quaternary alloy

    NASA Astrophysics Data System (ADS)

    Zhou, Bin; Froyen, L.

    2012-01-01

    The solidification behaviour of multi-component and multi-phase systems has been largely investigated in binary and ternary alloys. In the present study, a quaternary model system is proposed based on the well known Al-Cu-Ag and Al-Cu-Mg ternary eutectic alloys. The quaternary eutectic composition and temperature were determined by EDS (Energy Dispersive Spectrometry) and DSC (Differential Scanning Calorimetry) analysis, respectively. The microstructure was then characterised by SEM (Scanning Electron Microscope). In the DSC experiments, two types of quaternary eutectics were determined according to their phase composition. For each type of eutectic, various microstructures were observed, which result in different eutectic compositions. Only one of the determined eutectic compositions was further studied by the controlled growth technique in a vertical Bridgeman type furnace. In the initial part of the directionally solidified sample, competing growth between two-phase dendrites and three-phase eutectics was obtained, which was later transformed to competing growth between three-phase and four-phase eutectics. Moreover, silver enrichment was measured at the solidification front, which is possibly caused by Ag sedimentation due to gravity and Ag rejection from dendritic and three-phase eutectic growth, and its accumulation at the solidification front.

  10. Tailoring the magnetoimpedance effect of NiFe/Ag multilayer

    NASA Astrophysics Data System (ADS)

    Corrêa, M. A.; Bohn, F.; Chesman, C.; da Silva, R. B.; Viegas, A. D. C.; Sommer, R. L.

    2010-07-01

    The magnetoimpedance (MI) effect was investigated in NiFe/Ag multilayered (ML) and ML/SiO2/Ag/SiO2/ML structured multilayered (SD) ferromagnetic films grown by magnetron sputtering. The MI measurements were performed with an impedance analyzer over a wide frequency range, from 10 MHz to 1.8 GHz. Sample geometries are mainly responsible for the different MI behaviours and by considering the entire frequency range, distinct mechanisms responsible for MI changes were associated. For the ML sample, a maximum value of 80%, associated with the appearance of ferromagnetic resonance (FMR), was reached at around 1 GHz. For the SD sample, the striking feature is the existence of two distinct frequency ranges with high MI% values of 80% at around 100 MHz, related to the skin and magnetoinductive effects, and of 120% at around 1 GHz, associated with the strong skin and FMR effect.

  11. Inner shell excitation of Cu, Ag and Au

    NASA Astrophysics Data System (ADS)

    Stauffer, Allan; McEachran, Robert

    2016-09-01

    The ground states of Cu, Ag and Au have the configuration nd10(n +1)s with n = 3, 4 and 5. The lowest excited manifold for Cu and Au has the configuration nd9(n +1)s2 which is well separated from the next excited manifold nd10(n +1)p. However, for Ag, the lowest 4d95s2 level with J = 5/2 lies between the two levels of the 4d105p manifold. In we compared our Relativistic Distorted Wave calculations for the excitation of the 4d105p manifold with experimental measurements which would have included a contribution from the 4d95s2 J = 5/2 level. While we do not expect the cross section for this forbidden transition to be large compared to the optical allowed transitions of the P levels, we decided to investigate excitation of these inner shell levels, in part because they are the lowest excited levels in Cu and Au, We will discuss the theoretical expressions for these excitations as well as give numerical results of our cross section calculations.

  12. High thermally stable Ni /Ag(Al) alloy contacts on p-GaN

    NASA Astrophysics Data System (ADS)

    Chou, C. H.; Lin, C. L.; Chuang, Y. C.; Bor, H. Y.; Liu, C. Y.

    2007-01-01

    Ag agglomeration was found to occur at Ni /Ag to p-GaN contacts after annealing at 500°C. This Ag agglomeration led to the poor thermal stability showed by the Ni /Ag contacts in relation to the reflectivity and electrical properties. However, after alloying with 10at.% Al by e-gun deposition, the Ni /Ag(Al) p-GaN contacts were found to effectively retard Ag agglomeration thereby greatly enhancing the thermal stability. Based on the x-ray photoelectron spectroscopy analysis, the authors believe that the key for the retardation of Ag agglomeration was the formation of ternary Al-Ni-O layer at p-GaN interface.

  13. Spin pumping and inverse Rashba-Edelstein effect in NiFe/Ag/Bi and NiFe/Ag/Sb

    SciTech Connect

    Zhang, Wei Jungfleisch, Matthias B.; Jiang, Wanjun; Pearson, John E.; Hoffmann, Axel

    2015-05-07

    The Rashba effect is an interaction between the spin and the momentum of electrons induced by the spin-orbit coupling in surface or interface states. We measured the inverse Rashba-Edelstein effect via spin pumping in Ag/Bi and Ag/Sb interfaces. The spin current is injected from the ferromagnetic resonance of a NiFe layer towards the Rashba interfaces, where it is further converted into a charge current. Using spin pumping theory, we quantify the conversion parameter of spin to charge current to be 0.11 ± 0.02 nm for Ag/Bi and a factor of ten smaller for Ag/Sb. The relative strength of the effect is in agreement with spectroscopic measurements and first principles calculations. We also vary the interlayer materials to study the voltage output in relation to the change of the effective spin mixing conductance. The spin pumping experiment offers a straight-forward approach of using spin current as an efficient probe for detecting interface Rashba splitting.

  14. Cu2O Photocathode for Low Bias Photoelectrochemical Water Splitting Enabled by NiFe-Layered Double Hydroxide Co-Catalyst

    NASA Astrophysics Data System (ADS)

    Qi, Huan; Wolfe, Jonathan; Fichou, Denis; Chen, Zhong

    2016-08-01

    Layered double hydroxides (LDHs) are bimetallic hydroxides that currently attract considerable attention as co-catalysts in photoelectrochemical (PEC) systems in view of water splitting under solar light. A wide spectrum of LDHs can be easily prepared on demand by tuning their chemical composition and structural morphology. We describe here the electrochemical growth of NiFe-LDH overlayers on Cu2O electrodes and study their PEC behavior. By using the modified Cu2O/NiFe-LDH electrodes we observe a remarkable seven-fold increase of the photocurrent intensity under an applied voltage as low as ‑0.2 V vs Ag/AgCl. The origin of such a pronounced effect is the improved electron transfer towards the electrolyte brought by the NiFe-LDH overlayer due to an appropriate energy level alignment. Long-term photostability tests reveal that Cu2O/NiFe-LDH photocathodes show no photocurrent loss after 40 hours of operation under light at ‑0.2 V vs Ag/AgCl low bias condition. These improved performances make Cu2O/NiFe-LDH a suitable photocathode material for low voltage H2 production. Indeed, after 8 hours of H2 production under ‑0.2 V vs Ag/AgCl the PEC cell delivers a 78% faradaic efficiency. This unprecedented use of Cu2O/NiFe-LDH as an efficient photocathode opens new perspectives in view of low biasd or self-biased PEC water splitting under sunlight illumination.

  15. Cu2O Photocathode for Low Bias Photoelectrochemical Water Splitting Enabled by NiFe-Layered Double Hydroxide Co-Catalyst

    PubMed Central

    Qi, Huan; Wolfe, Jonathan; Fichou, Denis; Chen, Zhong

    2016-01-01

    Layered double hydroxides (LDHs) are bimetallic hydroxides that currently attract considerable attention as co-catalysts in photoelectrochemical (PEC) systems in view of water splitting under solar light. A wide spectrum of LDHs can be easily prepared on demand by tuning their chemical composition and structural morphology. We describe here the electrochemical growth of NiFe-LDH overlayers on Cu2O electrodes and study their PEC behavior. By using the modified Cu2O/NiFe-LDH electrodes we observe a remarkable seven-fold increase of the photocurrent intensity under an applied voltage as low as −0.2 V vs Ag/AgCl. The origin of such a pronounced effect is the improved electron transfer towards the electrolyte brought by the NiFe-LDH overlayer due to an appropriate energy level alignment. Long-term photostability tests reveal that Cu2O/NiFe-LDH photocathodes show no photocurrent loss after 40 hours of operation under light at −0.2 V vs Ag/AgCl low bias condition. These improved performances make Cu2O/NiFe-LDH a suitable photocathode material for low voltage H2 production. Indeed, after 8 hours of H2 production under −0.2 V vs Ag/AgCl the PEC cell delivers a 78% faradaic efficiency. This unprecedented use of Cu2O/NiFe-LDH as an efficient photocathode opens new perspectives in view of low biasd or self-biased PEC water splitting under sunlight illumination. PMID:27487918

  16. Effect of Cross-Interaction between Ni and Cu on Growth Kinetics of Intermetallic Compounds in Ni/Sn/Cu Diffusion Couples during Aging

    NASA Astrophysics Data System (ADS)

    Hong, K. K.; Ryu, J. B.; Park, C. Y.; Huh, J. Y.

    2008-01-01

    The solid-state, cross-interaction between the Ni layer on the component side and the Cu pad on the printed circuit board (PCB) side in ball grid array (BGA) solder joints was investigated by employing Ni(15 μm)/Sn(65 μm)/Cu ternary diffusion couples. The ternary diffusion couples were prepared by sequentially electroplating Sn and Ni on a Cu foil and were aged isothermally at 150, 180, and 200°C. The growth of the intermetallic compound (IMC) layer on the Ni side was coupled with that on the Cu side by the mass flux across the Sn layer that was caused by the difference in the Ni content between the (Cu1- x Ni x )6Sn5 layer on the Ni side and the (Cu1- y Ni y )6Sn5 layer on the Cu side. As the consequence of the coupling, the growth rate of the (Cu1- x Ni x )6 Sn5 layer on the Ni side was rapidly accelerated by decreasing Sn layer thickness and increasing aging temperature. Owing to the cross-interaction with the top Ni layer, the growth rate of the (Cu1- y Ni y )6Sn5 layer on the Cu side was accelerated at 150°C and 180°C but was retarded at 200°C, while the growth rate of the Cu3Sn layer was always retarded. The growth kinetic model proposed in an attempt to interpret the experimental results was able to reproduce qualitatively all of the important experimental observations pertaining to the growth of the IMC layers in the Ni/Sn/Cu diffusion couple.

  17. Effect of Reflow Time on Wetting Behavior, Microstructure Evolution, and Joint Strength of Sn-2.5Ag-0.5Cu Solder on Bare and Nickel-Coated Copper Substrates

    NASA Astrophysics Data System (ADS)

    Sona, Mrunali; Prabhu, K. Narayan

    2016-07-01

    The effect of reflow time on wetting behavior of Sn-2.5Ag-0.5Cu lead-free solder on bare and nickel-coated copper substrates has been investigated. The solder alloy was reflowed at 270°C for various reflow times of 10 s, 100 s, 300 s, and 500 s. On bare copper substrate, the intermetallic compound (IMC) thickness increased with increase in reflow time, whereas on Ni-coated Cu substrate, the IMC thickness increased up to 300 s followed by a drop for solder alloy reflowed for 500 s. The spreading behavior of the solder alloy was categorized into capillary, gravity (diffusion), and viscous zones. Gravity zone was obtained from 3.8 ± 0.43 s to 38.97 ± 3.38 s and from 5.99 ± 0.5 s to 77.82 ± 8.84 s for the Sn-2.5Ag-0.5Cu/Cu and Sn-2.5Ag-0.5Cu/Ni/Cu system, respectively. Sn-2.5Ag-0.5Cu solder alloy was also reflowed for the period corresponding to the end of the gravity zone (40 s and 80 s on bare and Ni-coated Cu, respectively). The joint strength was maximum at reflow time of 40 s and 80 s for the Sn-2.5Ag-0.5Cu/Cu and Sn-2.5Ag-0.5Cu/Ni/Cu system, respectively. The dynamic contact angle at the end of the gravity (diffusion) zone ( θ gz) was found to be a better parameter compared with the stabilized contact angle ( θ f) to assess the effect of the wettability of the liquid solder on the microstructure and joint strength. The present investigation reveals the significance of the gravity zone in assessment of optimum reflow time for lead-free solder alloys.

  18. Spin Reorientation Transition in Magnetically Coupled Fe/Cu/Ni/Cu(001)

    NASA Astrophysics Data System (ADS)

    Choi, H. J.; Ling, W. L.; Wolfe, J. H.; Toyama, F.; Paik, S.; Bovensiepen, U.; Qiu, Z. Q.; Scholl, A.; Nolting, F.; Anders, S.

    2001-03-01

    We investigated Spin Reorientation Transition (SRT) of Fe film in Fe/Cu/Ni/Cu(001) where the Fe layer is magnetically coupled to the perpendicular magnetization of Ni with the interlayer coupling strength being controlled by the Cu thickness. With in situ surface magneto-optic Kerr effect measurement, we show that the Fe-Ni interlayer coupling results in an alternating alignment of the Fe magnetization with Cu thickness for Fe film thinner than the SRT thickness dR, but has no effect for Fe film thicker than dR. The SRT thickness dR, defined as the onset of in-plane magnetization, was found to be independent of the Fe-Ni interlayer coupling. Within the SRT pseudo-gap region, however, the magnetic remanence exhibits oscillatory behavior with Cu thickness with a periodicity exactly half of that in the oscillatory interlayer coupling. This result shows that the strip domains are severely modified by the strength of the Fe-Ni interlayer coupling. To provide more detailed information, element specific domain imaging was taken in this system using photoemission electron microscope at the Advanced Light Source of Lawrence Berkeley National Laboratory.

  19. A novel multifunctional NiTi/Ag hierarchical composite

    NASA Astrophysics Data System (ADS)

    Hao, Shijie; Cui, Lishan; Jiang, Jiang; Guo, Fangmin; Xiao, Xianghui; Jiang, Daqiang; Yu, Cun; Chen, Zonghai; Zhou, Hua; Wang, Yandong; Liu, Yuzi; Brown, Dennis E.; Ren, Yang

    2014-06-01

    Creating multifunctional materials is an eternal goal of mankind. As the properties of monolithic materials are necessary limited, one route to extending them is to create a composite by combining contrasting materials. The potential of this approach is neatly illustrated by the formation of nature materials where contrasting components are combined in sophisticated hierarchical designs. In this study, inspired by the hierarchical structure of the tendon, we fabricated a novel composite by subtly combining two contrasting components: NiTi shape-memory alloy and Ag. The composite exhibits simultaneously exceptional mechanical properties of high strength, good superelasticity and high mechanical damping, and remarkable functional properties of high electric conductivity, high visibility under fluoroscopy and excellent thermal-driven ability. All of these result from the effective-synergy between the NiTi and Ag components, and place the composite in a unique position in the properties chart of all known structural-functional materials providing new opportunities for innovative electrical, mechanical and biomedical applications. Furthermore, this work may open new avenues for designing and fabricating advanced multifunctional materials by subtly combining contrasting multi-components.

  20. Ni doping on Cu surfaces: Reduced copper resistivity

    SciTech Connect

    Zheng, P. Y.; Deng, R. P.; Gall, D.

    2014-09-29

    The resistivity of 9.3-nm-thick epitaxial and polycrystalline Cu is reduced by 11%–13% when coated with 0.75 nm Ni. Sequential in situ and ex situ transport measurements show that this is due to electron surface scattering which exhibits a specularity p = 0.7 for the Cu-vacuum interface that transitions to completely diffuse (p = 0) when exposed to air. In contrast, Ni-coated surfaces exhibit partial specularity with p = 0.3 in vacuum and p = 0.15 in air, as Cu{sub 2}O formation is suppressed, leading to a smaller surface potential perturbation and a lower density of localized surface states, yielding less diffuse electron scattering.

  1. Plasmon-assisted site-selective growth of Ag nanotriangles and Ag-Cu2O hybrids.

    PubMed

    Xie, Ying; Ma, Liang; Cheng, Zi-Qiang; Yang, Da-Jie; Zhou, Li; Hao, Zhong-Hua; Wang, Qu-Quan

    2017-03-21

    We report a plasmon-assisted growth of metal and semiconductor onto the tips of Ag nanotriangles (AgNTs) under light irradiation. The site-selective growth of Ag onto AgNTs are firstly demonstrated on the copper grids and amine-coated glass slides. As the irradiation time increases, microscopic images indicate that AgNTs gradually touch with each other and finally "weld" tip-to-tip together into the branched chains. Meanwhile, the redshift of plasmon band is observed in the extinction spectra, which agrees well the growth at the tips of AgNTs and the decrease of the gaps between the adjacent nanotriangles. We also synthesize AgNT-Cu2O nanocomposites by using a photochemical method and find that the Cu2O nanoparticles preferably grow on the tips of AgNTs. The site-selective growth of Ag and Cu2O is interpreted by the local field concentration at the tips of AgNTs induced by surface plasmon resonance under light excitation.

  2. Plasmon-assisted site-selective growth of Ag nanotriangles and Ag-Cu2O hybrids

    NASA Astrophysics Data System (ADS)

    Xie, Ying; Ma, Liang; Cheng, Zi-Qiang; Yang, Da-Jie; Zhou, Li; Hao, Zhong-Hua; Wang, Qu-Quan

    2017-03-01

    We report a plasmon-assisted growth of metal and semiconductor onto the tips of Ag nanotriangles (AgNTs) under light irradiation. The site-selective growth of Ag onto AgNTs are firstly demonstrated on the copper grids and amine-coated glass slides. As the irradiation time increases, microscopic images indicate that AgNTs gradually touch with each other and finally “weld” tip-to-tip together into the branched chains. Meanwhile, the redshift of plasmon band is observed in the extinction spectra, which agrees well the growth at the tips of AgNTs and the decrease of the gaps between the adjacent nanotriangles. We also synthesize AgNT-Cu2O nanocomposites by using a photochemical method and find that the Cu2O nanoparticles preferably grow on the tips of AgNTs. The site-selective growth of Ag and Cu2O is interpreted by the local field concentration at the tips of AgNTs induced by surface plasmon resonance under light excitation.

  3. Plasmon-assisted site-selective growth of Ag nanotriangles and Ag-Cu2O hybrids

    PubMed Central

    Xie, Ying; Ma, Liang; Cheng, Zi-Qiang; Yang, Da-Jie; Zhou, Li; Hao, Zhong-Hua; Wang, Qu-Quan

    2017-01-01

    We report a plasmon-assisted growth of metal and semiconductor onto the tips of Ag nanotriangles (AgNTs) under light irradiation. The site-selective growth of Ag onto AgNTs are firstly demonstrated on the copper grids and amine-coated glass slides. As the irradiation time increases, microscopic images indicate that AgNTs gradually touch with each other and finally “weld” tip-to-tip together into the branched chains. Meanwhile, the redshift of plasmon band is observed in the extinction spectra, which agrees well the growth at the tips of AgNTs and the decrease of the gaps between the adjacent nanotriangles. We also synthesize AgNT-Cu2O nanocomposites by using a photochemical method and find that the Cu2O nanoparticles preferably grow on the tips of AgNTs. The site-selective growth of Ag and Cu2O is interpreted by the local field concentration at the tips of AgNTs induced by surface plasmon resonance under light excitation. PMID:28322264

  4. Synthesis of 3D Printable Cu-Ag Core-Shell Materials: Kinetics of CuO Film Removal

    NASA Astrophysics Data System (ADS)

    Hong, Seongik; Kim, Namsoo

    2015-03-01

    In this research, Cu-Ag core-shell particles were synthesized as a functional and 3D printable material. Using the solid-liquid method, Cu-Ag core-shell particles were simply synthesized, and different particle sizes of 100 nm and 2 μm were used to confirm the size effect in the synthesis and reaction control of the Cu-Ag core-shell particles. In addition, highly viscous Cu-Ag core-shell particle paste was also prepared, and its electrical conductivity was measured. As a result, the reaction rate in the case of the 2 μm Cu particles was controlled by film diffusion, whereas for the 100 nm Cu particles, the reaction rate was controlled by CuO film produced before reacting with Ag ions in solution, and limited by chemical reaction control. Through the solid-liquid method, dendrite-shaped Cu-Ag core-shell particles were formed. Also, the electrical conductivity increased with increasing sintering temperature and core-shell particle concentration.

  5. Aging Characteristics of Sn-Ag Eutectic Solder Alloy with the Addition of Cu, In, and Mn

    NASA Astrophysics Data System (ADS)

    Ghosh, M.; Kar, Abhijit; Das, S. K.; Ray, A. K.

    2009-10-01

    In the present investigation, three types of solder alloy, i.e., Sn-Ag-Cu, Sn-Ag-In, and Sn-Ag-Cu-Mn, have been prepared and joined with Cu substrate. In the reflowed condition, the joint interface is decorated with Cu6Sn5 intermetallic in all cases. During aging at 100 °C for 50 to 200 hours, Cu3Sn formation took place in the diffusion zone of the Sn-Ag-Cu and Sn-Ag-In vs Cu assembly, which was not observed for the Sn-Ag-Cu-Mn vs Cu joint. Aging also leads to enhancement in the width of reaction layers; however, the growth is sluggish (~134 KJ/mol) for the Sn-Ag-Cu-Mn vs Cu transition joint. In the reflowed condition, the highest shear strength is obtained for the Sn-Ag-Cu-Mn vs Cu joint. Increment in aging time results in decrement in shear strength of the assemblies; yet small reduction is observed for the Sn-Ag-Cu-Mn vs Cu joint. The presence of Mn in the solder alloy is responsible for the difference in microstructure of the Sn-Ag-Cu-Mn solder alloy vs Cu assembly in the reflowed condition, which in turn influences the microstructure of the same after aging with respect to others.

  6. Tuning the magnetic properties of multisegmented Ni/Cu electrodeposited nanowires with controllable Ni lengths.

    PubMed

    Susano, M; Proenca, M P; Moraes, S; Sousa, C T; Araújo, J P

    2016-08-19

    The fabrication of segmented Ni/Cu nanowires (NWs), with tunable structural and magnetic properties, is reported. A potentiostatic electrodeposition method with a single electrolytic bath has been used to fabricate multisegmented Ni/Cu NWs inside a highly hexagonally ordered anodic nanoporous alumina membrane, with diameters of 50 nm and Ni segment lengths (L Ni) tuned from 10 nm up to 140 nm. The x-ray diffraction results evidenced a strong dependence of the Ni NWs crystallographic face-centered-cubic (fcc) texture along the [220] direction on the aspect ratio of the NWs. The magnetic behavior of the multisegmented Ni/Cu NW arrays, as a function of the magnetic field and temperature, is also studied and correlated with their structural and morphological properties. Micromagnetic simulations, together with the experimental results, showed a dominant antiferromagnetic coupling between Ni segments along the wire length for small low aspect-ratio magnetic segments. When increasing the Ni segments' length, the magnetic interactions between these along the wire became stronger, favouring a ferromagnetic coupling. The Curie temperature of the NWs was also found to strongly depend on the Ni magnetic segment length. Particularly the Curie temperature was found to be reduced 75 K for the 20 nm Ni segments, following the finite-size scaling relation with ξ 0 = 8.1 Å and γ = 0.48. These results emphasize the advantages of using a template assisted method to electrodeposit multilayer NWs, as it allows an easy tailor of the respective morphological, chemical, structural and magnetic properties.

  7. Study on synthesis of ultrafine Cu-Ag core-shell powders with high electrical conductivity

    NASA Astrophysics Data System (ADS)

    Peng, Yu-hsien; Yang, Chih-hao; Chen, Kuan-ting; Popuri, Srinivasa R.; Lee, Ching-Hwa; Tang, Bo-Shin

    2012-12-01

    Cu-Ag composite powders with high electrical conductivity were synthesized by electroless plating of silver sulfate, copper powders with eco-friendly sodium citrate as reducing agent, dispersant and chelating agent in an aqueous system. The influences of sodium citrate/Ag ratio on Ag coatings of Cu powders were investigated. Ag was formed a dense coating on the surface of Cu powders at a molar ratio of sodium citrate/Ag = 0.07/1. SEM showed an uniformity of Ag coatings on Cu powders. SEM-EDX also revealed that Cu cores were covered by Ag shells on the whole. The surface composition analysis by XPS indicated that without Cu or Ag atoms in the surface were oxidized. The resistivity measurements of Cu-Ag paste shows that they have closer resistivity as the pure silver paste's after 250 °C for 30 min heat-treatment (2.55 × 10-4 Ω cm) and 350 °C for 30 min heat-treatment (1.425 × 10-4 Ω cm).

  8. Morphology and electrochemical behavior of Ag-Cu nanoparticle-doped amalgams.

    PubMed

    Chung, Kwok-Hung; Hsiao, Li-Yin; Lin, Yu-Sheng; Duh, Jenq-Gong

    2008-05-01

    The aim of this study was to introduce Ag-Cu phase nanopowder as an additive to improve the corrosion behavior of dental amalgams. A novel Ag-Cu nanopowder was synthesized by the precipitation method. An amalgam alloy powder (World-Cap) was added and mixed with 5 wt.% and 10 wt.% of Ag-Cu nanopowders, respectively, to form experimental amalgam alloy powders. The original alloy powder was used as a control. Alloy powders were examined using X-ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy and electron probe microanalysis. Amalgam disk specimens of metallurgically prepared were tested in 0.9% NaCl solution using electrochemical methods. The changes in the corrosion potential and anodic polarization characteristics were determined. Corrosion potential data were analyzed statistically (n=3, analysis of variance, Tukey's test, p<0.05). The diameters of lamellar structure Ag-Cu nanoparticles were measured to be approximately 30 nm. The composition of the Ag-Cu nanoparticles determined by TEM-energy-dispersive spectroscopy was 56.28 at.% Ag-43.72 at.% Cu. A light-shaded phase was found mixing with dark Cu-Sn reaction particles in the reaction zones of Ag-Cu nanoparticle-doped amalgams. The Ag-Cu nanoparticle-doped amalgams exhibited zero current potentials more positive than the control (p<0.05) and no current peak was observed at -325mV that related to Ag-Hg phase and Cu6Sn5 phase in anodic polarization curves. The results indicated that the corrosion resistance of high-copper single-composition amalgam could be improved by Ag-Cu nanoparticle-doping.

  9. Increasing foliar Zn:Ni or Cu:Ni concentration ratios increase severity of nickel deficiency symptoms

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The influence of essential micronutrients on the endogenous bioavailability of Ni is unknown. This study examines the linkage between Ni deficiency and endogenous foliar concentration of Ni, Zn, and Cu. It was hypothesized that expression of morphological symptoms of Ni deficiency by pecan [Carya i...

  10. Comparison of the early stages of condensation of Cu and Ag on Mo/100/ with Cu and Ag on W/100/

    NASA Technical Reports Server (NTRS)

    Soria, F.; Poppa, H.

    1980-01-01

    The adsorption and condensation of Cu and Ag, up to several monolayers in thickness, onto Mo(100) has been observed at pressures below 2 times 10 to the -10th torr in a study that used combined LEED, Auger, TDS (Thermal Desorption Spectroscopy), and work function measurements in a single experimental setup. The results show that Cu behaves similarly on Mo(100) and W(100) substrates, while some differences are found for Ag adsorption.

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

    NASA Astrophysics Data System (ADS)

    Chen, Hao

    2005-03-01

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

  12. 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.

  13. An electrochemical and multispectroscopic study of corrosion of Ag-Pd-Cu-Au alloys.

    PubMed

    Niemi, L; Minni, E; Ivaska, A

    1986-06-01

    Corrosion of a multi-phase Ag-Pd-Cu-Au-based commercial dental casting alloy and a Cu-Pd-rich and Ag-rich single-phase alloy was studied by open-circuit potential measurements, atomic absorption spectrometry, and electron spectroscopy. The alloys were immersed in an artificial saliva solution for 24 hr while the open-circuit potentials of the alloys were measured. The potentials were found to stabilize at certain levels after a steep rise during the first hours of the experiment. Cu was found to dissolve considerably from the Cu-Pd-rich alloy, with simultaneous enrichment of Pd in the surface layer of the alloy. Ag dissolved slightly from the Ag-rich alloy, but both Cu and Ag were found to dissolve from the multi-phase alloy. Neither Pd nor Au dissolved from any of the alloys studied.

  14. Size effect model on kinetics of interfacial reaction between Sn-xAg-yCu solders and Cu substrate

    PubMed Central

    Huang, M. L.; Yang, F.

    2014-01-01

    The downsizing of solder balls results in larger interfacial intermetallic compound (IMC) grains and less Cu substrate consumption in lead-free soldering on Cu substrates. This size effect on the interfacial reaction is experimentally demonstrated and theoretically analyzed using Sn-3.0Ag-0.5Cu and Sn-3.5Ag solder balls. The interfacial reaction between the Sn-xAg-yCu solders and Cu substrates is a dynamic response to a combination of effects of interfacial IMC growth, Cu substrate consumption and composition variation in the interface zone. A concentration gradient controlled (CGC) kinetics model is proposed to explain the combined effects. The concentration gradient of Cu at the interface, which is a function of solder volume, initial Cu concentration and reaction time, is the root cause of the size effect. We found that a larger Cu concentration gradient results in smaller Cu6Sn5 grains and more consumption of Cu substrate. According to our model, the growth kinetics of interfacial Cu6Sn5 obeys a t1/3 law when the molten solder has approached the solution saturation, and will be slower otherwise due to the interfering dissolution mechanism. The size effect introduced in this model is supported by a good agreement between theoretical and experimental results. Finally, the scope of application of this model is discussed. PMID:25408359

  15. Fabrication of Cu-Ag core-shell bimetallic superfine powders by eco-friendly reagents and structures characterization

    SciTech Connect

    Zhao Jun; Zhang Dongming; Zhao Jie

    2011-09-15

    Superfine bimetallic Cu-Ag core-shell powders were synthesized by reduction of copper sulfate pentahydrate and silver nitrate with eco-friendly ascorbic acid as a reducing agent and cyclodextrins as a protective agent in an aqueous system. The influence of Ag/Cu ratio on coatings was investigated. Ag was homogeneously distributed on the surface of Cu particles at a mole ratio of Ag/Cu=1. FE-SEM showed an uniformity of Ag coatings on Cu particles. Antioxidation of Cu particles was improved by increasing Ag/Cu ratio. TEM-EDX and UV-vis spectra also revealed that Cu cores were covered by Ag nanoshells on the whole. The surface composition analysis by XPS indicated that only small parts of Cu atoms in the surface were oxidized. It was noted that the hindrance of cyclodextrins chemisorbed on particles plays an important role in forming high quality and good dispersity Cu-Ag (Cu-Ag) core-shell powders. - Graphical abstract: Mechanism of fabricating Cu-Ag particles with good dispersibility using {beta}-CDs as a protective agent was studied because of its special structure. Highlights: > Green supramolecular {beta}-CD used as a protective agent and ascorbic acid(Vc) as a reducing agent to fabricate Cu-Ag powders. > Particles are monodisperse and the diameter is close to nanoscale(100-150 nm). > Resistance of Cu particles to oxidation was higher. > Formation mechanism explained.

  16. Electromigration of composite Sn-Ag-Cu solder bumps

    NASA Astrophysics Data System (ADS)

    Sharma, Ashutosh; Xu, Di Erick; Chow, Jasper; Mayer, Michael; Sohn, Heung-Rak; Jung, Jae Pil

    2015-11-01

    This study investigates the electromigration (EM) behavior of lead free Sn-Ag-Cu (SAC) solder alloys that were reinforced with different types of nanoparticles [Copper-coated carbon nanotubes (Cu/CNT), La2O3, Graphene, SiC, and ZrO2]. The composite solders were bumped on a Cu substrate at 220°C, and the resistance of the bumped solders was measured using a four wire setup. Current aging was carried out for 4 hours at a temperature of 160°C, and an increase in resistance was noted during this time. Of all the composite solders that were studied, La2O3 and SiC reinforced SAC solders exhibited the smallest resistances after current aging. However, the rate of change in the resistance at room temperature was lower for the SiC-reinforced SAC solder. The SAC and Graphene reinforced SAC solder bumps completely failed within 15 - 20 min of these tests. The SiC nanoparticles were reported to possibly entrap the SAC atoms better than other nanoparticles with a lower rate of EM. [Figure not available: see fulltext.

  17. [Mechanical properties of wiredrawn Ag-Pd-Cu alloys].

    PubMed

    Hasegawa, T; Miyagawa, Y; Nakamura, K

    1989-01-01

    Nine experimental Ag-Pd-Cu ternary alloys, containing 20-30 wt% Pd and 10-20 wt% Cu, were cast into rods 4.5 mm in diameter using an original vacuum/argon-pressure oxide-free casting technique. Test samples 2.0 mm in diameter were made from the rods by wire-drawing. After softening and hardening heat treatments, mechanical properties (modulus of elasticity, elastic limit, proof stress, tensile strength, elongation, and Vickers hardness) of the samples were measured to analyze the effects of composition and fifteen sets of correlations between the mechanical properties on the condition that few internal casting defects existed. After softening heat treatment, values of hardness and strength increased with increasing Cu and Pd contents, while they increased approximately with increasing Pd content after hardening heat treatment. After softening and hardening heat treatments, tensile strength ranged from 44.4 to 60.7 and from 68.1 to 89.1 kgf/mm2, respectively. Values of elongation were more than 10% even after hardening heat treatment. Fourteen out of fifteen correlation coefficients (r) were statistically significant (p less than 0.01). One of the regression lines derived was as follows. Tensile strength (kgf/mm2) = 9.1 +/- 0.305 Hv (r = 0.990) Moreover, the mechanical properties observed in this investigation were compared with those of ordinarily cast samples with the same compositions.

  18. Controlled synthesis of Ni/CuOx/Ni nanowires by electrochemical deposition with self-compliance bipolar resistive switching

    PubMed Central

    Park, Kyuhyun; Lee, Jang-Sik

    2016-01-01

    We demonstrate synthesis of Ni/CuOx/Ni nanowires (NWs) by electrochemical deposition on anodized aluminum oxide (AAO) membranes. AAO with pore diameter of ~70 nm and pore length of ~50 μm was used as the template for synthesis of NWs. After deposition of Au as the seed layer, NWs with a structure of Ni/CuOx/Ni were grown with a length of ~12 μm. The lengths of 1st Ni, CuOx, and 2nd Ni were ~4.5 μm, ~3 μm, and ~4.5 μm, respectively. The Ni/CuOx/Ni device exhibits bipolar resistive switching behavior with self-compliance characteristics. Due to the spatial restriction of the current path in NW the Ni/CuOx/Ni NW devices are thought to exhibit self-compliance behaviour. Ni/CuOx/Ni NWs showed bipolar resistive changes possibly due to conducting filaments that are induced by oxygen vacancies. The reliability of the devices was confirmed by data retention measurement. The NW-based resistive switching memory has applications in highly scalable memory devices and neuromorphic devices. PMID:26975330

  19. Enhanced low temperature thermoelectric performance of Ag-doped BiCuSeO

    NASA Astrophysics Data System (ADS)

    Tan, S. G.; Lei, Hechang; Shao, D. F.; Lv, H. Y.; Lu, W. J.; Huang, Y. N.; Liu, Y.; Yuan, B.; Zu, L.; Kan, X. C.; Song, W. H.; Sun, Y. P.

    2014-08-01

    We investigated the physical properties of the silver doped layered oxyselenides BiCu1-xAgxSeO (x = 0-0.4), which crystallize in an unusual intergrowth structure with [Cu2Se2]2- and [Bi2O2]2+ layers. The total thermal conductivity is decreased because the heavier Ag doping in BiCuSeO lattice decreased the lattice thermal conductivity. The undoped BiCuSeO exhibits a semiconducting behavior, and the Ag-doped BiCuSeO performs much improved electrical conductivity. Although Ag-doping causes a decreasing Seebeck coefficient, the significant increase of the electrical conductivity compensates the moderate decrease of the Seebeck coefficient, which leads to the strongly improved power factor values. Finally, the figure of merit is improved and reaches a maximum ˜0.07 at 300 K for the sample BiCu0.7Ag0.3SeO.

  20. Ni spin switching induced by magnetic frustration in FeMn/Ni/Cu(001)

    SciTech Connect

    Wu, J.; Choi, J.; Scholl, A.; Doran, A.; Arenholz, E.; Hwang, Chanyong; Qiu, Z. Q.

    2009-03-08

    Epitaxially grown FeMn/Ni/Cu(001) films are investigated by Photoemission Electron Microscopy and Magneto-Optic Kerr Effect. We find that as the FeMn overlayer changes from paramagnetic to antiferromagnetic state, it could switch the ferromagnetic Ni spin direction from out-of-plane to in-plane direction of the film. This phenomenon reveals a new mechanism of creating magnetic anisotropy and is attributed to the out-of-plane spin frustration at the FeMn-Ni interface.

  1. Oxygen reduction reaction on Cu-doped Ag cluster for fuel-cell cathode.

    PubMed

    Ma, Wenqiang; Chen, Fuyi; Zhang, Nan; Wu, Xiaoqiang

    2014-10-01

    The development of fuel cells as clean-energy technologies is largely limited by the prohibitive cost of the noble-metal catalysts needed for catalyzing the oxygen reduction reaction (ORR) in fuel cells. A fundamental understanding of catalyst design principle that links material structures to the catalytic activity can accelerate the search for highly active and abundant bimetallic catalysts to replace platinum. Here, we present a first-principles study of ORR on Ag12Cu cluster in alkaline environment. The adsorptions of O2, OOH, and OH on Cu-doped Ag13 are stronger than on Ag13. The d-band centers of adsorption sites show the Cu-doping makes d-electrons transferred to higher energy state, and improves O2 dissociation. ORR processes on Ag12Cu and Ag13 indicate Cu-doping can strongly promote ORR, and ORR process can be better preformed on Ag12Cu than on Ag13. For four-electron transfer, the effective reversible potential is 0.401 V/RHE on Ag12Cu in alkaline medium.

  2. Cellular Energy Allocation to Assess the Impact of Nanomaterials on Soil Invertebrates (Enchytraeids): The Effect of Cu and Ag.

    PubMed

    Gomes, Susana I L; Scott-Fordsmand, Janeck J; Amorim, Mónica J B

    2015-06-16

    The effects of several copper (Cu) and silver (Ag) nanomaterials were assessed using the cellular energy allocation (CEA), a methodology used to evaluate the energetic status and which relates with organisms' overall condition and response to toxic stress. Enchytraeus crypticus (Oligochatea), was exposed to the reproduction effect concentrations EC20/50 of several Cu and Ag materials (CuNO3, Cu-Field, Cu-Nwires and Cu-NPs; AgNO3, Ag NM300K, Ag-NPs Non-coated and Ag-NPs PVP-coated) for 7 days (0-3-7d). The parameters measured were the total energy reserves available (protein, carbohydrate and lipid budgets) and the energy consumption (Ec) integrated to obtain the CEA. Results showed that these parameters allowed a clear discrimination between Cu and Ag, but less clearly within each of the various materials. For Cu there was an increase in Ec and protein budget, while for Ag a decrease was observed. The results corroborate known mechanisms, e.g., with Cu causing an increase in metabolic rate whereas Ag induces mitochondrial damage. The various Cu forms seem to activate different mechanisms with size and shape (e.g., Cu-NPs versus Cu-Nwires), causing clearly different effects. For Ag, results are in line with a slower oxidation rate of Ag-NMs in comparison with Ag-salt and hence delayed effects.

  3. Interdiffusion analysis of the soldering reactions in Sn-3.5Ag/Cu couples

    NASA Astrophysics Data System (ADS)

    Bae, K. S.; Kim, S. J.

    2001-11-01

    Extensive microstructural and kinetic studies on the formation and growth of the intermetallics of Sn-rich solder/Cu couples have been reported. However, experimental data on the interdiffusion mechanisms during soldering reactions are limited and in conflict. The interdiffusion processes for soldering of Sn-3.5Ag alloy/Cu couples were investigated by using the Cr-evaporated surface as a reference line. At the beginning of soldering, Cu was observed to outdiffuse to the molten Sn-3.5Ag alloy until saturation, and the Sn-Ag solder dissolved with Cu collapsed below the reference line. As a result, the scallop-shaped Cu6Sn5 intermetallic compound was formed at the newly-formed Sn-Ag-Cu solder/Cu interface below the original Cu surface. When the soldered joint was reflowed at the lower temperature to suppress the Cu dissolution, the Cu6Sn5/Cu interface moved into the Cu substrate. Therefore, Sn is the dominant diffusing species for the intermetallic formation during the soldering process, although the extensive Cu dissolution occurs at the early stage of soldering.

  4. Giant Magnetoresistance and Coercivity of electrodeposited multilayered FeCoNi/Cu and CrFeCoNi/Cu

    NASA Astrophysics Data System (ADS)

    Shakya, P.; Cox, B.; Davis, D.

    2012-02-01

    The effect of Cr addition on electrodeposited multilayered nanowires CrFeCoNi/Cu was investigated from a magnetic property perspective: current perpendicular to the plane-Giant Magnetoresistance (CPP-GMR) and Coercivity (BH loops). The magnetic behavior of multilayered nanowires of CrFeNiCo/Cu was also affected by the alloy deposition potential, alloy pulsing time (layer thickness) and number of bilayers. Furthermore, the addition of Cr influenced both the nanowires GMR and Coercivity. Cr addition to the ferromagnetic FeCoNi layer induced a reduction in the room temperature GMR from 10.64% to 5.62%; however, the magnetic saturation field decreased from 0.45 to 0.27 T. The increase in the number of bilayers, from 1000 to 2500, resulted in a higher GMR value, 14.56% with 0.35 T magnetic saturation field. Addition of Cr to the ferromagnetic layer decreased the coercivity from 0.015 to 0.0054 T. Low saturation field CPP-GMR nanowires showing low coercivity at room temperature opens a new door for magnetic sensing devices. To the best of our knowledge, this is the first study on electrodeposited CrFeCoNi/Cu multilayered nanowires.

  5. Origin of the Distinct Diffusion Behaviors of Cu and Ag in Covalent and Ionic Semiconductors.

    PubMed

    Deng, Hui-Xiong; Luo, Jun-Wei; Li, Shu-Shen; Wei, Su-Huai

    2016-10-14

    It is well known that Cu diffuses faster than Ag in covalent semiconductors such as Si, which has prevented the replacement of Ag by Cu as a contact material in Si solar cells for reducing the cost. Surprisingly, in more ionic materials such as CdTe, Ag diffuses faster than Cu despite that it is larger than Cu, which has prevented the replacement of Cu by Ag in CdTe solar cells to improve the performance. But, so far, the mechanisms behind these distinct diffusion behaviors of Cu and Ag in covalent and ionic semiconductors have not been addressed. Here we reveal the underlying mechanisms by combining the first-principles calculations and group theory analysis. We find that the symmetry controlled s-d coupling plays a critical role in determining the diffusion behaviors. The s-d coupling is absent in pure covalent semiconductors but increases with the ionicity of the zinc blende semiconductors, and is larger for Cu than for Ag, owing to its higher d orbital energy. In conjunction with Coulomb interaction and strain energy, the s-d coupling is able to explain all the diffusion behaviors from Cu to Ag and from covalent to ionic hosts. This in-depth understanding enables us to engineer the diffusion of impurities in various semiconductors.

  6. Origin of the Distinct Diffusion Behaviors of Cu and Ag in Covalent and Ionic Semiconductors

    NASA Astrophysics Data System (ADS)

    Deng, Hui-Xiong; Luo, Jun-Wei; Li, Shu-Shen; Wei, Su-Huai

    2016-10-01

    It is well known that Cu diffuses faster than Ag in covalent semiconductors such as Si, which has prevented the replacement of Ag by Cu as a contact material in Si solar cells for reducing the cost. Surprisingly, in more ionic materials such as CdTe, Ag diffuses faster than Cu despite that it is larger than Cu, which has prevented the replacement of Cu by Ag in CdTe solar cells to improve the performance. But, so far, the mechanisms behind these distinct diffusion behaviors of Cu and Ag in covalent and ionic semiconductors have not been addressed. Here we reveal the underlying mechanisms by combining the first-principles calculations and group theory analysis. We find that the symmetry controlled s -d coupling plays a critical role in determining the diffusion behaviors. The s -d coupling is absent in pure covalent semiconductors but increases with the ionicity of the zinc blende semiconductors, and is larger for Cu than for Ag, owing to its higher d orbital energy. In conjunction with Coulomb interaction and strain energy, the s -d coupling is able to explain all the diffusion behaviors from Cu to Ag and from covalent to ionic hosts. This in-depth understanding enables us to engineer the diffusion of impurities in various semiconductors.

  7. Thermodynamic Modeling of Ag-Ni System Combining Experiments and Molecular Dynamic Simulation

    NASA Astrophysics Data System (ADS)

    Rajkumar, V. B.; Chen, Sinn-wen

    2017-04-01

    Ag-Ni is a simple and important system with immiscible liquids and (Ag,Ni) phases. Previously, this system has been thermodynamically modeled utilizing certain thermochemical and phase equilibria information based on conjecture. An attempt is made in this study to determine the missing information which are difficult to measure experimentally. The boundaries of the liquid miscibility gap at high temperatures are determined using a pyrometer. The temperature of the liquid ⇌ (Ag) + (Ni) eutectic reaction is measured using differential thermal analysis. Tie-lines of the Ag-Ni system at 1023 K and 1473 K are measured using a conventional metallurgical method. The enthalpy of mixing of the liquid at 1773 K and the (Ag,Ni) at 973 K is calculated by molecular dynamics simulation using a large-scale atomic/molecular massively parallel simulator. These results along with literature information are used to model the Gibbs energy of the liquid and (Ag,Ni) by a calculation of phase diagrams approach, and the Ag-Ni phase diagram is then calculated.

  8. Nanoporous microtubes obtained from a Cu-Ni metallic wire

    NASA Astrophysics Data System (ADS)

    Marano, Emanuele Francesco; Lussana, Danilo; Castellero, Alberto; Baricco, Marcello

    2016-03-01

    Nanoporous microtubes of a nickel-copper alloy were obtained from a Cu-44Ni-1Mn (wt%) commercial wire (200 μm diameter). A new synthesis method was established through three steps: 1) partial oxidation of the wire at 1173 K in air, 2) removal of the inner unoxidized core by chemical etching, 3) reduction in 10 bar hydrogen atmosphere. During oxidation, the segregation of Cu and Ni occurred because of their different diffusion coefficients in the corresponding oxides. As a consequence, pores were formed by Kirkendall effect and due to selective chemical etching of the different oxides. Additional porosity formed because of volume contraction during reduction with hydrogen. After reduction, the microtube shows a composition gradient from the inner wall (almost pure nickel) to the outer wall (almost pure copper). The process allowed to obtain microtubes with tuneable wall thickness and inner pores around 180 ± 80 nm. The morphological features developed suggest improved capillarity properties for applications in MEMS.

  9. Intermixing in Cu/Ni multilayers induced by cold rolling

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Perepezko, J. H.; Larson, D.; Reinhard, D.

    2015-04-01

    Repeated cold rolling was performed on multilayers of Cu60/Ni40 and Cu40/Ni60 foil arrays to study the details of driven atomic scale interfacial mixing. With increasing deformation, there is a significant layer refinement down to the nm level that leads to the formation of a solid solution phase from the elemental end members. Intriguingly, the composition of the solid solution is revealed by an oscillation in the composition profile across the multilayers, which is different from the smoothly varying profile due to thermally activated diffusion. During the reaction, Cu mixed into Ni preferentially compared to Ni mixing into Cu, which is also in contrast to the thermal diffusion behavior. This is confirmed by observations from X-ray diffraction, electron energy loss spectrum and atom probe tomography. The diffusion coefficient induced by cold rolling is estimated as 1.7 × 10-17 m2/s, which cannot be attributed to any thermal effect. The effective temperature due to the deformation induced mixing is estimated as 1093 K and an intrinsic diffusivity db, which quantifies the tendency towards equilibrium in the absence of thermal diffusion, is estimated as 6.38 × 10-18 m2/s. The fraction of the solid solution phase formed is illustrated by examining the layer thickness distribution and is described by using an error function representation. The evolution of mixing in the solid solution phase is described by a simplified sinusoid model, in which the amplitude decays with increased deformation level. The promoted diffusion coefficient could be related to the effective temperature concept, but the establishment of an oscillation in the composition profile is a characteristic behavior that develops due to deformation.

  10. Intermixing in Cu/Ni multilayers induced by cold rolling

    SciTech Connect

    Wang, Z.; Perepezko, J. H.; Larson, D.; Reinhard, D.

    2015-04-28

    Repeated cold rolling was performed on multilayers of Cu60/Ni40 and Cu40/Ni60 foil arrays to study the details of driven atomic scale interfacial mixing. With increasing deformation, there is a significant layer refinement down to the nm level that leads to the formation of a solid solution phase from the elemental end members. Intriguingly, the composition of the solid solution is revealed by an oscillation in the composition profile across the multilayers, which is different from the smoothly varying profile due to thermally activated diffusion. During the reaction, Cu mixed into Ni preferentially compared to Ni mixing into Cu, which is also in contrast to the thermal diffusion behavior. This is confirmed by observations from X-ray diffraction, electron energy loss spectrum and atom probe tomography. The diffusion coefficient induced by cold rolling is estimated as 1.7 × 10{sup −17} m{sup 2}/s, which cannot be attributed to any thermal effect. The effective temperature due to the deformation induced mixing is estimated as 1093 K and an intrinsic diffusivity d{sub b}, which quantifies the tendency towards equilibrium in the absence of thermal diffusion, is estimated as 6.38 × 10{sup −18} m{sup 2}/s. The fraction of the solid solution phase formed is illustrated by examining the layer thickness distribution and is described by using an error function representation. The evolution of mixing in the solid solution phase is described by a simplified sinusoid model, in which the amplitude decays with increased deformation level. The promoted diffusion coefficient could be related to the effective temperature concept, but the establishment of an oscillation in the composition profile is a characteristic behavior that develops due to deformation.

  11. Sn-Ag-Cu Nanosolders: Solder Joints Integrity and Strength

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

    Although considerable research has been dedicated to the synthesis and characterization of lead-free nanoparticle solder alloys, only very little has been reported on the reliability of the respective joints. In fact, the merit of nanoparticle solders with depressed melting temperatures close to the Sn-Pb eutectic temperature has always been challenged when compared with conventional solder joints, especially in terms of inferior solderability due to the oxide shell commonly present on the nanoparticles, as well as due to compatibility problems with common fluxing agents. Correspondingly, in the current study, Sn-Ag-Cu (SAC) nanoparticle alloys were combined with a proper fluxing vehicle to produce prototype nanosolder pastes. The reliability of the solder joints was successively investigated by means of electron microscopy and mechanical tests. As a result, the optimized condition for employing nanoparticles as a competent nanopaste and a novel procedure for surface treatment of the SAC nanoparticles to diminish the oxide shell prior to soldering are being proposed.

  12. Effects of the crystallographic orientation of Sn on the electromigration of Cu/Sn-Ag-Cu/Cu ball joints

    SciTech Connect

    Lee, Kiju; Kim, Keun-Soo; Tsukada, Yutaka; Suganuma, Katsuaki; Yamanaka, Kimihiro; Kuritani, Soichi; Ueshima, Minoru

    2011-11-17

    Electromigration behavior and fast circuit failure with respect to crystallographic orientation of Sn grains were examined. The test vehicle was Cu/Sn-3.0 wt% Ag-0.5 wt% Cu/Cu ball joints, and the applied current density was 15 kA/cm2 at 160 °C. The experimental results indicate that most of the solder bumps show different microstructural changes with respect to the crystallographic orientation of Sn grains. Fast failure of the bump occurred due to the dissolution of the Cu circuit on the cathode side caused by the fast interstitial diffusion of Cu atoms along the c-axis of the Sn grains when the c-axis was parallel to the electron flow. Slight microstructural changes were observed when the c-axis was perpendicular to the electron flow. In addition, Cu6Sn5 intermetallic compound (IMC) was formed along the direction of the c-axis of the Sn grains instead of the direction of electron flow in all solder ball joints.

  13. Carbon tolerance of Ni-Cu and Ni-Cu/YSZ sub-μm sized SOFC thin film model systems

    NASA Astrophysics Data System (ADS)

    Götsch, Thomas; Schachinger, Thomas; Stöger-Pollach, Michael; Kaindl, Reinhard; Penner, Simon

    2017-04-01

    Thin films of YSZ, unsupported Ni-Cu 1:1 alloy phases and YSZ-supported Ni-Cu 1:1 alloy solutions have been reproducibly prepared by magnetron sputter deposition on Si wafers and NaCl(001) single crystal facets at two selected substrate temperatures of 298 K and 873 K. Subsequently, the layer properties of the resulting sub-μm thick thin films as well as the tendency towards carbon deposition following treatment in pure methane at 1073 K has been tested comparatively. Well-crystallized structures of cubic YSZ, cubic NiCu and cubic NiCu/YSZ have been obtained following deposition at 873 K on both substrates. Carbon is deposited on all samples following the trend Ni-Cu (1:1) = Ni-Cu (1:1)/YSZ > pure YSZ, indicating that at least the 1:1 composition of layered Ni-Cu alloy phases is not able to suppress the carbon deposition completely, rendering it unfavorable for usage as anode component in sub-μm sized fuel cells. It is shown that surfaces with a high Cu/Ni ratio nevertheless prohibit any carbon deposition.

  14. Photoelectron angular distributions of ultrathin Ni/Cu(001) films

    SciTech Connect

    Mankey, G.J.; Subramanian, K.; Stockbauer, R.L.; Kurtz, R.L.

    1996-12-31

    The authors present measurements of the evolution with film thickness of the 3d electronic states at the Fermi energy of ultrathin Ni films. The morphology and thickness of the films is determined from x-ray photoelectron spectroscopy, x-ray photoelectron diffraction and x-ray magnetic linear dichroism using synchrotron radiation. Photoelectron angular distributions were measured using an ellipsoidal mirror analyzer. Even at submonolayer Ni coverages, the 3d electronic states exhibit bulk-like properties. This is attributed to the short screening length of electrons in metals, the localization of the 3d electrons, the similarity of the Ni and Cu ion cores, and finally the interaction with the underlying fcc periodic potential.

  15. Corrosion resistance evaluation of Pd-free Ag-Au-Pt-Cu dental alloys.

    PubMed

    Fujita, Takeshi; Shiraishi, Takanobu; Takuma, Yasuko; Hisatsune, Kunihiro

    2011-01-01

    The corrosion resistance of nine experimental Pd-free Ag-Au-Pt-Cu dental alloys in a 0.9% NaCl solution was investigated using cyclic voltammetry (CV), optical microscopy, and scanning electron microscopy (SEM). CV measurements revealed that the breakdown potential (E(bd)) and zero current potential (E(zc)) increased with increasing Au/(Au+Ag) atomic ratio. Thus, the Au/(Au+Ag) atomic ratio, but not the Cu content, influenced the corrosion resistance of Ag-Au-Pt-Cu alloys. After the forward scan of CV, both optical and scanning electron microscope images showed that in all the experimental alloys, the matrix phase was corroded but not the second phase. From corrosion resistance viewpoint, the Ag-Au-Pt-Cu alloys seemed to be suitable for clinical application.

  16. Characterization of Cu3P phase in Sn3.0Ag0.5Cu0.5P/Cu solder joints

    NASA Astrophysics Data System (ADS)

    Chen, Jian-xun; Zhao, Xing-ke; Zou, Xu-chen; Huang, Ji-hua; Hu, Hai-chun; Luo, Hai-lian

    2014-01-01

    This article reports the effects of phosphorus addition on the melting behavior, microstructure, and mechanical properties of Sn3.0Ag0.5Cu solder. The melting behavior of the solder alloys was determined by differential scanning calorimetry. The interfacial microstructure and phase composition of solder/Cu joints were studied by scanning electron microscopy and energy dispersive spectrometry. Thermodynamics of Cu-P phase formation at the interface between Sn3.0Ag0.5Cu0.5P solder and the Cu substrate was characterized. The results indicate that P addition into Sn3.0Ag0.5Cu solder can change the microstructure and cause the appearance of rod-like Cu3P phase which is distributed randomly in the solder bulk. The Sn3.0Ag0.5Cu0.5P joint shows a mixture of ductile and brittle fracture after shear testing. Meanwhile, the solidus temperature of Sn3.0Ag0.5Cu solder is slightly enhanced with P addition.

  17. Cu-Ni core-shell nanoparticles: structure, stability, electronic, and magnetic properties: a spin-polarized density functional study

    NASA Astrophysics Data System (ADS)

    Wang, Qiang; Wang, Xinyan; Liu, Jianlan; Yang, Yanhui

    2017-02-01

    Bimetallic core-shell nanoparticles (CSNPs) have attracted great interest not only because of their superior stability, selectivity, and catalytic activity but also due to their tunable properties achieved by changing the morphology, sequence, and sizes of both core and shell. In this study, the structure, stability, charge transfer, electronic, and magnetic properties of 13-atom and 55-atom Cu and Cu-Ni CSNPs were investigated using the density functional theory (DFT) calculations. The results show that Ni@Cu CSNPs with a Cu surface shell are more energetically favorable than Cu@Ni CSNPs with a Ni surface shell. Interestingly, three-shell Ni@Cu12@Ni42 is more stable than two-shell Cu13@Ni42, while two-shell Ni13@Cu42 is more stable than three-shell Cu@Ni12@Cu42. Analysis of Bader charge illustrates that the charge transfer increases from Cu core to Ni shell in Cu@Ni NPs, while it decreases from Ni core to Cu shell in Ni@Cu NPs. Furthermore, the charge transfer results that d-band states have larger shift toward the Fermi level for the Ni@Cu CSNPs with Cu surface shell, while the Cu@Ni CSNPs with Ni surface shell have similar d-band state curves and d-band centers with the monometallic Ni NPs. In addition, the Cu-Ni CSNPs possess higher magnetic moment when the Ni atoms aggregated at core region of CSNPs, while having lower magnetic moment when the Ni atoms segregate on surface region. The change of the Cu atom location in CSNPs has a weak effect on the total magnetic moment. Our findings provide useful insights for the design of bimetallic core-shell catalysts.

  18. Cu/Ag-based bifunctional nanoparticles obtained by one-pot laser-assisted galvanic replacement

    NASA Astrophysics Data System (ADS)

    Giorgetti, Emilia; Marsili, Paolo; Canton, Patrizia; Muniz-Miranda, Maurizio; Caporali, Stefano; Giammanco, Francesco

    2013-01-01

    We have prepared, for the first time, stable and uncapped Ag/Cu-based bifunctional nanoparticles (NPs) (BFNPs) in water, by combining ps laser ablation in liquid environment and galvanic replacement. The particles were obtained in a single step by 1,064 nm irradiation of a Cu target in water solutions of AgNO3 or AgNO2. Under proper salt concentration and irradiation conditions, the laser beam activates formation of deep orange colloids, which are positively charged and stable for weeks. High resolution transmission electron microscopy (HRTEM) analysis showed a predominance of composite crystalline nanostructures with size in the 1-15 nm range and consisting of fcc Ag and fcc Cu (or its oxides). While CuO tenorite crystalline phase was detected by HRTEM, X-ray photoelectron spectroscopy analysis permitted to observe also the Cu(I) oxidation state of Cu, being the Cu(I)/Cu(II) ratio different in the samples obtained in AgNO3 or AgNO2 baths. Functionalization with organic ligands and subsequent Raman tests demonstrated the SERS activity of the BFNPs and the existence of different complexing surface sites.

  19. Surface modification of oleylamine-capped Ag-Cu nanoparticles to fabricate low-temperature-sinterable Ag-Cu nanoink

    NASA Astrophysics Data System (ADS)

    Kim, Na Rae; Jong Lee, Yung; Lee, Changsoo; Koo, Jahyun; Lee, Hyuck Mo

    2016-08-01

    By treating oleylamine (OA)-capped Ag-Cu nanoparticles with tetramethylammonium hydroxide (TMAH), we obtained metal nanoparticles that are suspended in polar solvents and sinterable at low temperatures. The simple process with ultra sonication enables synthesis of monodispersed and high purity nanoparticles in an organic base, where the resulting nanoparticles are dispersible in polar solvents such as ethanol and isopropyl alcohol. To investigate the surface characteristics, we conducted Fourier-transform infrared and zeta-potential analyses. After thermal sintering at 200 °C, which is approximately 150 °C lower than the thermal decomposition temperature of OA, an electrically conductive thin film was obtained. Electrical resistivity measurements of the TMAH-treated ink demonstrate that surface modified nanoparticles have a low resistivity of 13.7 × 10-6 Ω cm. These results confirm the prospects of using low-temperature sinterable nanoparticles as the electrode layer for flexible printed electronics without damaging other stacked polymer layers.

  20. Synthesis and formation mechanism of Ag-Ni alloy nanoparticles at room temperature

    NASA Astrophysics Data System (ADS)

    Yan, Shi; Sun, Dongbai; Tan, Yuanyuan; Xing, Xueqing; Yu, Hongying; Wu, Zhonghua

    2016-11-01

    Ag-Ni nanoparticles were prepared with a chemical reduction method in the presence of polyvinylpyrrolidone (PVP) used as a stabilizing agent. During the synthesis of Ag-Ni nanoparticles, silver nitrate was used as the Ag+ source while nickel sulfate hexahydrate was used as Ni2+ source. Mixed solutions of Ag+ source and Ni2+ source were used as the precursors and sodium borohydride was used as the reducing agent. Five ratios of Ag+/Ni2+ (9:1, 3:1, 1:1, 1:3, and 1:9) suspensions were prepared in the corresponding precursors. Ag-Ni alloy nanoparticles were obtained with this method at room temperature. Scanning electronic microscope (SEM), energy dispersive spectrum (EDS), high resolution transmission electron microscope (HRTEM) were used to characterize the morphology, composition and crystal structure of the nanoparticles. The crystal structure was also investigated with X-ray diffraction (XRD). In all five Ag/Ni ratios, two kinds of particle structures were observed that are single crystal structure and five-fold twinned structure respectively. Free energy of nanoparticles with different crystal structures were calculated at each Ag/Ni ratio. Calculated results revealed that, with identical volume, free energy of single crystal particle is lower than multi-twinned particle and the difference becomes smaller with the increase of particle size; increase of Ni content will lead the increase of free energy for both structures. Formation of different crystal structures are decided by the structure of the original nuclei at the very early stage of the reduction process.

  1. Adsorption of Cu, Ag, and other metals on Fe-oxides as a control on elemental composition of stratiform and red bed copper deposits

    SciTech Connect

    Rose, A.W.; Bianchi, G.C.

    1985-01-01

    In low-temperature red bed and stratiform Cu deposits like Zambia-Zaire, Kupferschiefer, and Redstone, Cu is accompanied by various combinations of Ag, Co, Pb and Zn, and appears to be emplaced during diagenesis. Red bed sediments near deposits in Pennsylvania and beneath the Redstone deposit are strongly depleted in Cu but show little change in Pb, Zn, Ni and Co. Formation of cuprous chloride complexes under slightly reducing conditions allow solubility of Cu, but these solutions also transport Pb, Zn, Ni and Co. The effect of adsorption by Fe-oxides in the red beds as a control on metal ratios has been tested by experiments on 0.5 ppm Cu, Ag, Pb, Zn, Ni and Co with 0.8 g/1 goethite at 25/sup 0/C in 1 M NaCl. Under oxidized conditions (air),the pH values above which more than 50% of the metals are adsorbed are: Cu 5.0, Pb 5.5, Zn 6.5, Co 7.5, Ni 7.8, and Ag > 9. For more reduced conditions near the Fe/sup 2 +/-goethite boundary, the 50% adsorption values for Pb, Zn, Co, Ni and Ag are decreased by 0.5 to 1 pH unit, perhaps because of competition with Fe/sup 2 +/, but Cu (as CuCl/sub 2//sup -/ and CuCl/sub 3//sup 2 -/) shows adsorption of only about 20% at pH 5, 25% at pH 6, 35% at pH 7, and 100% at pH 8. At 50/sup 0/C, adsorption at pH 5 and 6 is about 10% and 20%, respectively, for Cu. By changes in Eh, pH, temperature, and molality of Cl and other species such as SO/sub 4/, CO/sub 3/, Ca, and Mg, it appears that various combinations of metals can be mobilized or left immobile. The time of mobilization and nature of Fe-oxide may also be critical.

  2. Integrated logic gate for fluorescence turn-on detection of histidine and cysteine based on Ag/Au bimetallic nanoclusters-Cu²⁺ ensemble.

    PubMed

    Sun, Jian; Yang, Fan; Zhao, Dan; Chen, Chuanxia; Yang, Xiurong

    2015-04-01

    By means of employing 11-mercaptoundecanoic acid (11-MUA) as a reducing agent and protecting ligand, we present straightforward one-pot preparation of fluorescent Ag/Au bimetallic nanoclusters (namely AgAuNCs@11-MUA) from AgNO3 and HAuCl4 in alkaline aqueous solution at room temperature. It is found that the fluorescence of AgAuNCs@11-MUA has been selectively quenched by Cu(2+) ions, and the nonfluorescence off-state of the as-prepared AgAuNCs@11-MUA-Cu(2+) ensemble can be effectively switched on upon the addition of histidine and cysteine. By incorporating Ni(2+) ions and N-ethylmaleimide, this phenomenon is further exploited as an integrated logic gate and a specific fluorescence turn-on assay for selectively and sensitively sensing histidine and cysteine has been designed and established based on the original noncovalent AgAuNCs@11-MUA-Cu(2+) ensemble. Under the optimal conditions, histidine and cysteine can be detected in the concentration ranges of 0.25-9 and 0.25-7 μM; besides, the detection limits are found to be 87 and 111 nM (S/N = 3), respectively. Furthermore, we demonstrate that the proposed AgAuNCs@11-MUA-based fluorescent assay can be successfully utilized for biological fluids sample analysis.

  3. Sulfur isotope and trace element systematics of zoned pyrite crystals from the El Indio Au-Cu-Ag deposit, Chile

    NASA Astrophysics Data System (ADS)

    Tanner, Dominique; Henley, Richard W.; Mavrogenes, John A.; Holden, Peter

    2016-04-01

    We present a comparative study between early, massive pyrite preceding (Cu-Ag) sulfosalt mineralization in high-temperature feeder zones (`early pyrite') and late pyrite that formed during silicic alteration associated with Au deposition (`late pyrite') at the El Indio high-sulfidation Au-Ag-Cu deposit, Chile. We use coupled in situ sulfur isotope and trace element analyses to chronologically assess geochemical variations across growth zones in these pyrite crystals. Early pyrite that formed in high-temperature feeder zones shows intricate oscillatory zonation of Cu, with individual laminae containing up to 1.15 wt% Cu and trace Co, As, Bi, Ni, Zn, Se, Ag, Sb, Te, Au, Pb and Bi. Late pyrite formed after (Cu-Ag) sulfosalt mineralization. It contains up to 1.14 wt% As with trace Cu, Zn, Pb, V, Mn, Co, Ni, Ge, Se, Ag, Sb, Te, Pb and Bi, as well as colloform Cu-rich growth bands containing vugs toward the outer edges of some crystals. Plotting the trace element data in chronological order (i.e., from core to rim) revealed that Co and Ni were the only elements to consistently co-vary across growth zones. Other trace elements were coupled in specific growth zones, but did not consistently co-vary across any individual crystal. The δ34S of early pyrite crystals in high-temperature feeder zones range from -3.19 to 1.88 ‰ (±0.5 ‰), consistent with sublimation directly from a high-temperature magmatic vapor phase. Late pyrite crystals are distinctly more enriched in δ34S than early pyrite (δ34S = 0.05-4.77 ‰, ±0.5 ‰), as a consequence of deposition from a liquid phase at lower temperatures. It is unclear whether the late pyrite was deposited from a small volume of liquid condensate, or a larger volume of hydrothermal fluid. Both types of pyrite exhibit intracrystalline δ34S variation, with a range of up to 3.31 ‰ recorded in an early pyrite crystal and up to 4.48 ‰ in a late pyrite crystal. Variations in δ34Spyrite at El Indio did not correspond with

  4. Investigation of Pd-Modified Ag-CuO Air Braze Filler Metals

    SciTech Connect

    Darsell, Jens T.; Hardy, John S.; Kim, Jin Yong; Weil, K. Scott

    2006-01-10

    Palladium was added as a ternary component to a series of silver - copper oxide alloys in an effort to increase the use temperature of these materials for potential ceramic air brazing applications. Large portions of the silver component of the Ag-CuO system were substituted by palladium forming the following alloys: (100-y)[(100-z)Pd - (z)Ag] - (y)CuOx where y = 0 - 34 mol% CuOx, z = 50 - 100 mol% silver, and x = 0, 0.5, and 1, denoting copper metal, Cu2O, or CuO. From differential scanning calorimetry, it was determined that the addition of palladium causes an increase in the solidus and liquidus temperatures of the resulting Pd-Ag-CuO brazes. In general, the liquidus was found to increase by approximately 220°C for the (100-y)(25Pd - 75Ag) - (z)CuOx filler metal compositions relative to comparable Ag-CuOx alloys. Likewise, the solidus was found to increase for these alloys, respectively by 185°C and 60°C, respectively for CuOx contents of y = 0 - 1mol% and 4 - 10 mol%. For the (100-y)(50Pd - 50Ag) - (y)CuOx alloys, the solidus increased between 280 - 390°C over a copper oxide compositional range of x = 0 to 8 mol%. It was determined from sessile drop experiments that palladium causes an increase in the wetting angle for all of the samples tested. Alloy compositions of (100-y)(25Pd - 75Ag) - (y)CuOx displayed increased wetting angles of 5-20° relative to comparable binary compositions. (100-y)(50Pd - 50Ag) - (y)CuOx alloys exhibited an increase in contact angle of 10-60° and compositions containing less than 10 mol% CuOx were not able to wet the substrate. Scanning electron microscopy indicates that the microstructure of the braze consists of Ag-Pd solid solution with CuOx precipitates. In general, a reaction layer consisting of CuAlO2 forms adjacent to the alumina substrate. However, the formation of this layer is apparently hindered by the addition of large amounts of palladium, causing poor wetting behavior, as denoted by substantial porosity found along

  5. Phase-dependent corrosion of titanium-to-stainless steel joints brazed by Ag-Cu eutectic alloy filler and Ag interlayer

    NASA Astrophysics Data System (ADS)

    Lee, M. K.; Park, J. J.; Lee, J. G.; Rhee, C. K.

    2013-08-01

    The electrochemical corrosion properties of Ti-STS dissimilar joints brazed by a 72Ag-28Cu alloy filler and an Ag interlayer were studied in a 3.5% NaCl solution using potentiodynamic polarization and ac impedance spectroscopy. For a joint with a layered structure of Ti(base)/TiAg/Ag solid solution/Ag-Cu eutectic/STS(base), galvanic corrosion mostly occurred in the TiAg phase with a severe material loss, indicating that the TiAg layer acted as an anode in the galvanic couple in the layered joint. The Ag-rich solid solution layer was also corroded to a certain extent, but the corrosion in this layer was dominated by the selective pitting corrosion of the eutectic Cu-rich phase. With an increase in the brazing temperature, the Cu-rich phases disappeared owing to the enhanced isothermal solidification effect, leading to an improvement of the corrosion resistance.

  6. Effect of Ag Addition on the Electrochemical Performance of Cu10Al in Artificial Saliva

    PubMed Central

    Salgado-Salgado, R. J.; Sotelo-Mazon, O.; Rodriguez-Diaz, R. A.; Salinas-Solano, G.

    2016-01-01

    In this work we proposed to evaluate the corrosion resistance of four different alloys by electrochemical techniques, a binary alloy Cu10Al, and three ternary alloys Cu10Al-xAg (x = 5, 10, and 15 wt.%) to be used like biomaterials in dental application. Biomaterials proposed were tested in artificial saliva at 37°C for 48 h. In addition, pure metals Cu, Al, Ag, and Ti as reference materials were evaluated. In general the short time tests indicated that the Ag addition increases the corrosion resistance and reduces the extent of localized attack of the binary alloy. Moreover, tests for 48 hours showed that the Ag addition increases the stability of the passive layer, thereby reducing the corrosion rate of the binary alloy. SEM analysis showed that Cu10Al alloy was preferably corroded by grain boundaries, and the Ag addition modified the form of attack of the binary alloy. Cu-rich phases reacted with SCN− anions forming a film of CuSCN, and the Ag-rich phase is prone to react with SCN− anions forming AgSCN. Thus, binary and ternary alloys are susceptible to tarnish in the presence of thiocyanate ions. PMID:27660601

  7. Thermal Stability of Cu/NiSi-Contacted p+n Shallow Junction

    NASA Astrophysics Data System (ADS)

    Wang, Chao-Chun; Lin, Hsin-Hung; Chen, Mao-Chieh

    2004-09-01

    The thermal stability of Cu/NiSi-contacted p+n shallow junction diodes was investigated with respect to their electrical characteristics and metallurgical reactions. The TaN/Cu/NiSi/p+n junction diode remained intact after 30 min thermal annealing at temperatures of up to 350°C. Upon annealing at 375°C, a marked increase in reverse bias leakage current occurred, and secondary ion mass spectrometry (SIMS) analysis indicated that Cu started to penetrate into the NiSi-contacted shallow junction region. After a higher temperature annealing at 425°C, a Cu3Si phase was formed. The failure of the TaN/Cu/NiSi/p+n junction diodes is attributed to the penetration of Cu through the NiSi layer into the junction region, leading to junction degradation by introducing deep-level trap states and the eventual formation of Cu3Si.

  8. Dealloying NiCo and NiCoCu Alloy Thin Films Using Linear Sweep Voltammetry

    NASA Astrophysics Data System (ADS)

    Peecher, Benjamin; Hampton, Jennifer

    When electrodeposited into thin films, metals have well-known electrochemical potentials at which they will be removed from the film. These potential differences can be utilized to re-oxidize only certain metals in an alloy, altering the film's structure and composition. Here we discuss NiCo and NiCoCu thin films' response to linear sweep voltammetry (LSV) as a means of electrochemical dealloying. For each of four different metal ratios, films were dealloyed to various potentials in order to gain insight into the evolution of the film over the course of the LSV. Capacitance, topography, and composition were examined for each sample before and after linear sweep voltammetry was performed. For NiCo films with high percentages of Ni, dealloying resulted in almost no change in composition, but did result in an increased capacitance, with greater increases occurring at higher LSV potentials. Dealloying also resulted in the appearance of large (100-1000 nm) pores on the surface of the film. For NiCoCu films with high percentages of Ni, Cu was almost completely removed from the film at LSV potentials greater than 500 mV. The LSV first removed larger copper-rich dendrites from the film's surface before creating numerous nano-pores, resulting in a net increase in area. This work is supported by an Award to Hope College from the HHMI Undergraduate Science Education Program, the Hope College Department of Physics Frissel Research Fund, and the National Science Foundation under Grants RUI-DMR-1104725 and MRI-CHE-0959282.

  9. Reaction pathways of furfural, furfuryl alcohol and 2-methylfuran on Cu(111) and NiCu bimetallic surfaces

    SciTech Connect

    Xiong, Ke; Wan, Weiming; Chen, Jingguang G.

    2016-02-23

    Hydrodeoxygenation (HDO) is an important reaction for converting biomass-derived furfural to value-added 2-methylfuran, which is a promising fuel additive. In this work, the HDO of furfural to produce 2-methylfuran occurred on the NiCu bimetallic surfaces prepared on either Ni(111) or Cu(111). The reaction pathways of furfural were investigated on Cu(111) and Ni/Cu(111) surfaces using density functional theory (DFT) calculations, temperature programmed desorption (TPD) and high resolution electron energy loss spectroscopy (HREELS) experiments. These studies provided mechanistic insights into the effects of bimetallic formation on enhancing the HDO activity. Specifically, furfural weakly adsorbed on Cu(111), while it strongly adsorbed on Ni/Cu(111) through an η2(C,O) configuration which led to the HDO of furfural on Ni/Cu(111). Lastly, the ability to dissociate H2 on Ni/Cu(111) is also an important factor for enhancing the HDO activity over Cu(111).

  10. Reaction pathways of furfural, furfuryl alcohol and 2-methylfuran on Cu(111) and NiCu bimetallic surfaces

    NASA Astrophysics Data System (ADS)

    Xiong, Ke; Wan, Weiming; Chen, Jingguang G.

    2016-10-01

    Hydrodeoxygenation (HDO) is an important reaction for converting biomass-derived furfural to value-added 2-methylfuran, which is a promising fuel additive. In this work, the HDO of furfural to produce 2-methylfuran occurred on the NiCu bimetallic surfaces prepared on either Ni(111) or Cu(111). The reaction pathways of furfural were investigated on Cu(111) and Ni/Cu(111) surfaces using density functional theory (DFT) calculations, temperature-programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS) experiments. These studies provided mechanistic insights into the effects of bimetallic formation on enhancing the HDO activity. Specifically, furfural weakly adsorbed on Cu(111), while it strongly adsorbed on Ni/Cu(111) through an η2(C,O) configuration, which led to the HDO of furfural on Ni/Cu(111). The ability to dissociate H2 on Ni/Cu(111) is also an important factor for enhancing the HDO activity over Cu(111).

  11. Reaction pathways of furfural, furfuryl alcohol and 2-methylfuran on Cu(111) and NiCu bimetallic surfaces

    DOE PAGES

    Xiong, Ke; Wan, Weiming; Chen, Jingguang G.

    2016-02-23

    Hydrodeoxygenation (HDO) is an important reaction for converting biomass-derived furfural to value-added 2-methylfuran, which is a promising fuel additive. In this work, the HDO of furfural to produce 2-methylfuran occurred on the NiCu bimetallic surfaces prepared on either Ni(111) or Cu(111). The reaction pathways of furfural were investigated on Cu(111) and Ni/Cu(111) surfaces using density functional theory (DFT) calculations, temperature programmed desorption (TPD) and high resolution electron energy loss spectroscopy (HREELS) experiments. These studies provided mechanistic insights into the effects of bimetallic formation on enhancing the HDO activity. Specifically, furfural weakly adsorbed on Cu(111), while it strongly adsorbed on Ni/Cu(111)more » through an η2(C,O) configuration which led to the HDO of furfural on Ni/Cu(111). Lastly, the ability to dissociate H2 on Ni/Cu(111) is also an important factor for enhancing the HDO activity over Cu(111).« less

  12. Cu-Ag core-shell nanoparticles with enhanced oxidation stability for printed electronics

    NASA Astrophysics Data System (ADS)

    Lee, Changsoo; Kim, Na Rae; Koo, Jahyun; Jong Lee, Yung; Lee, Hyuck Mo

    2015-11-01

    In this work, we synthesized uniform Cu-Ag core-shell nanoparticles using a facile two-step process that consists of thermal decomposition and galvanic displacement methods. The core-shell structure of these nanoparticles was confirmed through characterization using transmission electron microscopy, energy-dispersive spectroscopy, and x-ray diffraction. Furthermore, we investigated the oxidation stability of the Cu-Ag core-shell nanoparticles in detail. Both qualitative and quantitative x-ray photoelectron spectroscopy analyses confirm that the Cu-Ag core-shell nanoparticles have considerably higher oxidation stability than Cu nanoparticles. Finally, we formulated a conductive ink using the synthesized nanoparticles and coated it onto glass substrates. Following the sintering process, we compared the resistivity of the Cu-Ag core-shell nanoparticles with that of the Cu nanoparticles. The results of this study clearly show that the Cu-Ag core-shell nanoparticles can potentially be used as an alternative to Ag nanoparticles because of their superior oxidation stability and electrical properties.

  13. Cu-Ag core-shell nanoparticles with enhanced oxidation stability for printed electronics.

    PubMed

    Lee, Changsoo; Kim, Na Rae; Koo, Jahyun; Lee, Yung Jong; Lee, Hyuck Mo

    2015-11-13

    In this work, we synthesized uniform Cu-Ag core-shell nanoparticles using a facile two-step process that consists of thermal decomposition and galvanic displacement methods. The core-shell structure of these nanoparticles was confirmed through characterization using transmission electron microscopy, energy-dispersive spectroscopy, and x-ray diffraction. Furthermore, we investigated the oxidation stability of the Cu-Ag core-shell nanoparticles in detail. Both qualitative and quantitative x-ray photoelectron spectroscopy analyses confirm that the Cu-Ag core-shell nanoparticles have considerably higher oxidation stability than Cu nanoparticles. Finally, we formulated a conductive ink using the synthesized nanoparticles and coated it onto glass substrates. Following the sintering process, we compared the resistivity of the Cu-Ag core-shell nanoparticles with that of the Cu nanoparticles. The results of this study clearly show that the Cu-Ag core-shell nanoparticles can potentially be used as an alternative to Ag nanoparticles because of their superior oxidation stability and electrical properties.

  14. Abnormal magnetization behaviors in Sm-Ni-Fe-Cu alloys

    NASA Astrophysics Data System (ADS)

    Yang, W. Y.; Zhang, Y. F.; Zhao, H.; Chen, G. F.; Zhang, Y.; Du, H. L.; Liu, S. Q.; Wang, C. S.; Han, J. Z.; Yang, Y. C.; Yang, J. B.

    2016-06-01

    The magnetization behaviors in Sm-Ni-Fe-Cu alloys at low temperatures have been investigated. It was found that the hysteresis loops show wasp-waisted character at low temperatures, which has been proved to be related to the existence of multi-phases, the Fe/Ni soft magnetic phases and the CaCu5-type hard magnetic phase. A smooth-jump behavior of the magnetization is observed at T>5 K, whereas a step-like magnetization process appears at T<5 K. The CaCu5-type phase is responsible for such abnormal magnetization behavior. The magnetic moment reversal model with thermal activation is used to explain the relation of the critical magnetic field (Hcm) to the temperature (T>5 K). The reversal of the moment direction has to cross over an energy barrier of about 6.6×10-15 erg. The step-like jumps of the magnetization below 5 K is proposed to be resulted from a sharp increase of the sample temperature under the heat released by the irreversible domain wall motion.

  15. Prediction of Phase Formation in Nanoscale Sn-Ag-Cu Solder Alloy

    NASA Astrophysics Data System (ADS)

    Wu, Min; Lv, Bailin

    2016-01-01

    In a dynamic nonequilibrium process, the effective heat of formation allows the heat of formation to be calculated as a function of concentrations of the reacting atoms. In this work, we used the effective heat of formation rule to predict the formation and size of compound phases in a nanoscale Sn-Ag-Cu lead-free solder. We calculated the formation enthalpy and effective formation enthalpy of compounds in the Sn-Ag, Sn-Cu, and Ag-Cu systems by using the Miedema model and effective heat of formation. Our results show that, considering the surface effect of the nanoparticle, the effective heat of formation rule successfully predicts the phase formation and sizes of Ag3Sn and Cu6Sn5 compounds, which agrees well with experimental data.

  16. Possible charge disproportionation in 3R-AgNiO2 studied by neutron powder diffraction

    NASA Astrophysics Data System (ADS)

    Chung, J.-H.; Lim, J.-H.; Shin, Y. J.; Kang, J.-S.; Jaiswal-Nagar, D.; Kim, K. H.

    2008-12-01

    Using neutron-scattering techniques, we have investigated the nuclear and the magnetic structures of the triangular antiferromagnet 3R-AgNiO2 . The symmetry analysis based on the group theory suggests that the 3×3 charge order proposed for 2H-AgNiO2 [E. Wawrzyńska , Phys. Rev. Lett. 99, 157204 (2007)] will have a monoclinic symmetry if present in the trigonal lattice of 3R-AgNiO2 . The Rietveld refinement shows that symmetry reduction in the NiO2 layer is consistent with the prediction of the group theory. The pair density function consistently shows that the nearest-neighbor Ni-O bonds split into two groups separated by approximately 0.1Å . The antiferromagnetic Bragg peaks observed below TN=25K can be described by the propagation vector k=(0,1,0) of the monoclinic unit cell. The similarities of the local structure and the antiferromagnetic order strongly suggest that the novel charge order observed in 2H-AgNiO2 also exists in 3R-AgNiO2 .

  17. Local structure of disordered Au-Cu and Au-Ag alloys

    NASA Astrophysics Data System (ADS)

    Frenkel, A. I.; Machavariani, V. Sh.; Rubshtein, A.; Rosenberg, Yu.; Voronel, A.; Stern, E. A.

    2000-10-01

    X-ray-absorption fine structure (XAFS) and x-ray-diffraction (XRD) measurements of disordered alloys AuxCu1-x and Au0.5Ag0.5 prepared by melt spinning were performed. In the Au0.5Ag0.5 alloy, no significant local deviations of the atoms from the average fcc lattice were detected while in AuxCu1-x alloys, significant deviations of atoms from the average fcc lattice were found. Mean-square vibrations of the Cu-Cu distances revealed by the XAFS in AuxCu1-x alloys indicate the weakening of contact between Cu atoms in the dilute limit. Our computer simulation for AuxCu1-x clusters of 105 atoms reproduces the main features of both the XAFS and XRD data.

  18. Electromagnetic properties of Fe53Ni47 and Fe53Ni47/Cu granular composite materials in the microwave range

    NASA Astrophysics Data System (ADS)

    Massango, Herieta; Tsutaoka, Takanori; Kasagi, Teruhiro

    2016-09-01

    The electromagnetic proprieties of Fe53Ni47 granular composite materials and Fe53Ni47/Cu hybrid granular composites have been studied by measuring the relative complex permeability and permittivity spectra as well as the ac electrical conductivity. In the Fe53Ni47 composite, the variation of the ac conductivity at 1 kHz with the particle volume content shows an insulator-metal transition at the percolation threshold at 61 vol% particle content. A negative permeability spectrum due to the magnetic resonance in Fe53Ni47 particles was observed in the 85 vol% composite. Meanwhile, the negative permittivity spectrum caused by the plasmoinc state of the percolated Fe53Ni47 particle clusters appears at 90 vol%. The Fe53Ni47/Cu hybrid composite containing 85 vol% of Fe53Ni47/Cu hybrid particle as filers shows the percolative metallic properties; the ac conductivity increases with increasing the Cu particle volume fraction in the Fe53Ni47/Cu particle system. The negative permittivity spectrum appears above the Cu particle volume fraction of 0.16; the double negative characteristic was observed at that of 0.20 and 0.24 hybrid composites in the frequency range from 300 MHz to 1.8 GHz in the absence of the external magnetic field.

  19. A highly sensitive non-enzymatic glucose sensor based on bimetallic Cu-Ag superstructures.

    PubMed

    Li, Hua; Guo, Chun-Yan; Xu, Cai-Ling

    2015-01-15

    Bimetallic Cu-Ag superstructures were successfully fabricated for the first time by using the natural leaves as reducing agent through a facile one-step hydrothermal process. Morphology, structure and composition of the Cu-Ag superstructures were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS) and inductively coupled plasma-optical emission spectroscopy (ICP-OES), respectively. The results reveal that the Cu-Ag superstructure is bimetallic nanocomposite constructed by nanoparticles with low Ag content and shows a rough surface and porous flexural algae-like microstructure. By using a three-dimensional nickel foam as the scaffold, a novel non-enzymatic glucose sensor based on Cu-Ag nanocomposites has been fabricated and applied to non-enzymatic glucose detection. The as-prepared Cu-Ag nanocomposites based glucose sensor displays distinctly enhanced electrocatalytic activity compared to those obtained with pure Cu nanomaterials prepared with a similar procedure, revealing a synergistic effect of the matrix Cu and the doped Ag. Cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy indicate that the Cu-Ag superstructures based glucose sensor displays a fascinating sensitivity up to 7745.7 μA mM(-1) cm(-2), outstanding detection limit of 0.08 μM and fast amperometric response (<2 s) for glucose detection. Furthermore, the sensor also exhibits significant selectivity, excellent stability and reproducibility, as well as attractive feasibility for real sample analysis. Because of its excellent electrochemical performance, low cost and easy preparation, this novel electrode material is a promising candidate in the development of non-enzymatic glucose sensor.

  20. CrCuAgN PVD nanocomposite coatings: Effects of annealing on coating morphology and nanostructure

    NASA Astrophysics Data System (ADS)

    Liu, Xingguang; Iamvasant, Chanon; Liu, Chang; Matthews, Allan; Leyland, Adrian

    2017-01-01

    CrCuAgN PVD nanocomposite coatings were produced using pulsed DC unbalanced magnetron sputtering. This investigation focuses on the effects of post-coat annealing on the surface morphology, phase composition and nanostructure of such coatings. In coatings with nitrogen contents up to 16 at.%, chromium exists as metallic Cr with N in supersaturated solid solution, even after 300 °C and 500 °C post-coat annealing. Annealing at 300 °C did not obviously change the phase composition of both nitrogen-free and nitrogen-containing coatings; however, 500 °C annealing resulted in significant transformation of the nitrogen-containing coatings. The formation of Ag aggregates relates to the (Cu + Ag)/Cr atomic ratio (threshold around 0.2), whereas the formation of Cu aggregates relates to the (Cu + Ag + N)/Cr atomic ratio (threshold around 0.5). The primary annealing-induced changes were reduced solubility of Cu, Ag and N in Cr, and the composition altering from a mixed ultra-fine nanocrystalline and partly amorphous phase constitution to a coarser, but still largely nanocrystalline structure. It was also found that, with sufficient Cu content (>12 at.%), annealing at a moderately high temperature (e.g. 500 °C) leads to transportation of both Cu and Ag (even at relatively low concentrations of Ag, ≤3 at.%) from inside the coating to the coating surface, which resulted in significant reductions in friction coefficient, by over 50% compared to that of the substrate (from 0.31 to 0.14 with a hemispherical diamond indenter, and from 0.83 to 0.40 with an alumina ball counterface, respectively). Results indicate that the addition of both Cu and Ag (in appropriate concentrations) to nitrogen-containing chromium is a viable strategy for the development of 'self-replenishing' silver-containing thin film architectures for temperature-dependent solid lubrication requirements or antimicrobial coating applications.

  1. Cathodoluminescence and Thermoluminescence of Undoped LTB and LTB:A (A = Cu, Ag, Mn)

    DTIC Science & Technology

    2013-03-01

    CATHODOLUMINESCENCE AND THERMOLUMINESCENCE OF UNDOPED LTB AND LTB:A (A = Cu, Ag, Mn) THESIS Zachary L. Hadfield, USA AFIT-ENP-13-M-13...CATHODOLUMINESCENCE AND THERMOLUMINESCENCE OF UNDOPED LTB AND LTB:A (A = Cu, Ag, Mn) THESIS Presented to the Faculty Department of Engineering...crystals and one each doped with silver, copper, and manganese. Thermoluminescence measurements were conducted using a Harshaw Model 3500 Manual TLD

  2. Graphene as a diffusion barrier for isomorphous systems: Cu-Ni system

    NASA Astrophysics Data System (ADS)

    Roy, Apurba; Punith Kumar, M. K.; Srivastava, Chandan

    2016-02-01

    Electrochemical exfoliation technique using the pyrophosphate anion derived from tetra sodium pyrophosphate was employed to produce graphene. As-synthesized graphene was then drop dried over a cold rolled Cu sheet. Ni coating was then electrodeposited over bare Cu and graphene-Cu substrates. Both substrates were then isothermally annealed at 800 °C for 3 h. WDS analysis showed substantial atomic diffusion in annealed Ni-Cu sample. Cu-graphene-Ni sample, on the other hand, showed negligible diffusion illustrating the diffusion barrier property of the graphene coating.

  3. Cu-Ni-Fe anodes having improved microstructure

    DOEpatents

    Bergsma, S. Craig; Brown, Craig W.

    2004-04-20

    A method of producing aluminum in a low temperature electrolytic cell containing alumina dissolved in an electrolyte. The method comprises the steps of providing a molten electrolyte having alumina dissolved therein in an electrolytic cell containing the electrolyte. A non-consumable anode and cathode is disposed in the electrolyte, the anode comprised of Cu--Ni--Fe alloys having single metallurgical phase. Electric current is passed from the anode, through the electrolyte to the cathode thereby depositing aluminum on the cathode, and molten aluminum is collected from the cathode.

  4. Microstructural investigation of the oxidation behavior of Cu in Ag-coated Cu films using a focused ion beam transmission electron microscopy technique

    NASA Astrophysics Data System (ADS)

    Kim, Ji Hwan; Lee, Jong-Hyun

    2016-06-01

    With the aim of elucidating a detailed mechanism for the oxidation behavior in submicron Cu particles coated with a thin Ag layer, the dewetting of Ag and the oxidation behavior of Cu in Ag-coated Cu films upon heating were investigated with a focused ion beam transmission electron microscopy technique. A slight dewetting of the Ag layer began at approximately 200 °C and aggregates of Cu2O particles were formed on the Ag layer, indicating that the initial Cu2O phase was formed on the thin Ag layer. Voids were formed in the Cu layer because of Cu atoms diffusing through the thin Ag layer to be oxidized in the upper Cu2O aggregates. After being heated to 250 °C, the Ag layer became more irregular, and in some regions, it disappeared because of intensive dewetting. The number and average size of the voids also increased. At 300 °C, a hollow structure with a Cu2O shell was formed. Pillar-like structures of unoxidized Cu and large voids were found under the Cu2O layer.

  5. 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.

  6. Barrierless Cu-Ni-Mo Interconnect Films with High Thermal Stability Against Silicide Formation

    NASA Astrophysics Data System (ADS)

    Li, X. N.; Liu, L. J.; Zhang, X. Y.; Chu, J. P.; Wang, Q.; Dong, C.

    2012-12-01

    Cu-Ni-Mo alloys were investigated to increase thermal stability against silicide formation. The alloy compositions were chosen such that an insoluble element (Mo) solute was dissolved into Cu via a third element Ni which is soluble in both Cu and Ni. Thin-film Cu-Ni-Mo alloys were prepared by magnetron sputtering. The films with Mo/Ni ratio of 1/12 exhibited low electrical resistivities in combination with high thermal stabilities against silicide formation, in support of a tentative "cluster-plus-glue-atom" model for stable solid solutions. In particular, a (Mo1/13Ni12/13)0.3Cu99.7 sample reached a minimum resistivity of 2.6 μΩ cm after 400°C/1 h annealing and remained highly conductive with resistivities below 3 μΩ cm even after 400°C/40 h annealing. These alloys are promising candidates for future interconnect materials.

  7. Effect of Synthesis Techniques on Crystallization and Optical Properties of Ag-Cu Bimetallic Nanoparticles

    NASA Astrophysics Data System (ADS)

    Xiong, Ziye; Qin, Fen; Huang, Po-Shun; Nettleship, Ian; Lee, Jung-Kun

    2016-04-01

    Silver (Ag)-copper (Cu) bimetallic nanoparticles (NPs) were synthesized by the reduction of silver nitrate and copper (II) acetate monohydrate using ethylene glycol in a microwave (MW) heating system with controlled reaction times ranging from 5 min to 30 min. The molar ratio Ag/Cu was varied from 1:1 to 1:3. The effect of reaction conditions on the bimetallic NPs structures and compositions were characterized by x-ray photoelectron spectroscopy, x-ray diffraction and transmission electron microscopy. The average particle size was approximately 150 nm. The surface plasmon resonance (SPR) of Ag-Cu bimetallic NPs was investigated by monitoring the SPR band peak behavior via UV/Vis spectrophotometry. The resonance peak positions and peak widths varied due to the different structures of the bimetallic NPs created under the synthesis conditions. In the MW heating method, the reduction of Cu was increased and Cu was inhomogeneously deposited over the Ag cores. As the composition of Cu becoming higher in the Ag-Cu bimetallic NPs, the absorption between 400 nm to 600 nm was greatly enhanced.

  8. Tunable synthesis of hierarchical NiCo2O4 nanosheets-decorated Cu/CuOx nanowires architectures for asymmetric electrochemical capacitors

    NASA Astrophysics Data System (ADS)

    Kuang, Min; Zhang, Yu Xin; Li, Tong Tao; Li, Kai Feng; Zhang, Sheng Mao; Li, Gang; Zhang, Wei

    2015-06-01

    We demonstrate a facile and tunable preparative strategy of porous NiCo2O4 nanosheets-decorated Cu-based nanowires hybrids as high-performance supercapacitor electrodes. A fast faradic reaction has been realized by inducing elementary copper core in the composite, which assists in high electric conductivity of the cell and creates intimate channels for fast charge collection and electron transfer. As a result, this hybrid composite electrode displays high specific capacitance (578 F g-1 at current density of 1.0 A g-1) and rate capability (80.1% capacitance retention from 1 A g-1 to 10 A g-1). Additionally, asymmetric device is constructed from NiCo2O4/Cu-based NWs and activated graphene (AG) with an operation potential from 0 to 1.4 V. The asymmetric device exhibits an energy density of 12.6 Wh kg-1 at a power density of 344 W kg-1 and excellent long-term cycling stability (only 1.8% loss of its initial capacitance after 10,000 cycles). These attractive findings suggest that such unique NiCo2O4/Cu-based NWs hybrid architecture is promising for electrochemical applications as efficient electrode material.

  9. Low temperature growth of graphene on Cu-Ni alloy nanofibers for stable, flexible electrodes

    NASA Astrophysics Data System (ADS)

    Liu, Zheng-Dong; Yin, Zong-You; Du, Ze-Hui; Yang, Yang; Zhu, Min-Min; Xie, Ling-Hai; Huang, Wei

    2014-04-01

    Here, we report a facile approach to grow graphene on Cu-Ni alloy NFs at a temperature as low as 450-500 °C, in which solid polystyrene (PS) carbon source and two-temperature-zone furnace were used to prepare graphene. The graphene coated Cu-Ni (designated as G-coated Cu-Ni) NFs were fully characterized by Raman spectra, XPS, FESEM and TEM. The G-coated Cu-Ni NFs exhibited excellent anti-oxidation, anti-corrosion and flexibility properties. The anti-corrosion of G-coated Cu-Ni NFs was examined through cyclic voltammetry measurements by using sea water as the electrolyte solution. Finally, using crossed arrays of G-coated Cu-Ni NF composite electrode thin films (sheet resistance is ~10 Ω sq-1) as the flexible electrode, an alternating current (AC) electroluminescent (EL) device with a configuration of G-coated Cu-Ni/active layer (ZnS : Cu phosphor)/dielectric layer (BaTiO3)/front electrode (CNT) has been fabricated. Under an AC voltage of 200 V and frequency of 1300 Hz, the ACEL device emitted blue light at 496 nm with a brightness of 103 cd m-2.Here, we report a facile approach to grow graphene on Cu-Ni alloy NFs at a temperature as low as 450-500 °C, in which solid polystyrene (PS) carbon source and two-temperature-zone furnace were used to prepare graphene. The graphene coated Cu-Ni (designated as G-coated Cu-Ni) NFs were fully characterized by Raman spectra, XPS, FESEM and TEM. The G-coated Cu-Ni NFs exhibited excellent anti-oxidation, anti-corrosion and flexibility properties. The anti-corrosion of G-coated Cu-Ni NFs was examined through cyclic voltammetry measurements by using sea water as the electrolyte solution. Finally, using crossed arrays of G-coated Cu-Ni NF composite electrode thin films (sheet resistance is ~10 Ω sq-1) as the flexible electrode, an alternating current (AC) electroluminescent (EL) device with a configuration of G-coated Cu-Ni/active layer (ZnS : Cu phosphor)/dielectric layer (BaTiO3)/front electrode (CNT) has been fabricated. Under

  10. Structure and magnetic properties of Ni/Cu/Fe/MgO(001) films.

    PubMed

    Lauhoff, G; Vaz, C A F; Bland, J A C

    2009-04-15

    The structural and magnetic properties of thin Ni films grown on Cu/Fe/MgO(001) and Cu/MgO(001) buffer layers are investigated and compared to those grown on Cu/Si(001). The use of an Fe seed layer a few monolayers thick leads to the epitaxial growth of high surface quality Cu(001) buffer layers on MgO(001), while Cu growth on the bare MgO(001) substrate results in polycrystalline films. Magneto-optic Kerr effect magnetometry shows that Ni films grown on Cu/Fe/MgO(001) exhibit dominant perpendicular magnetic anisotropy up to ∼90 Å, which is similar to that of Ni films grown on Cu/Si(001). The polycrystalline Ni films also exhibit perpendicular magnetic remanence, but with a dominant in-plane magnetization component.

  11. Visual determination of Cu2+ through copper-catalysed in situ formation of Ag nanoparticles.

    PubMed

    Yuan, Xun; Chen, Yi

    2012-10-07

    A new strategy was explored for the visual determination of Cu(2+) using copper-catalysed in situ formation of Ag nanoparticles. In this method, only common reagents were used and the pre-synthesis and modification of nanoparticles are avoided. Ag(+) can form a milk-white suspension (AgBr) with Br(-) in an aqueous solution composed of AgNO(3), cetyltrimethylammonium bromide, ascorbic acid, bovine serum albumin, and NaNO(3). The reaction will be stopped by addition of Cu(2+), accompanied by a colour change from milk-white to orange or brilliant yellow. Cu(+) (the reduction product of Cu(2+)) consumes the dissolved O(2) and prevents the O(2) from oxidizing the newly reduced Ag atoms (by ascorbic acid) back to Ag(+), facilitating the further aggregation of Ag atoms to become Ag nanoparticles. The visible colour change was shown to be specific towards Cu(2+) over most other metal ions. The limit of detection was 0.75 μM Cu(2+) by the naked eye and 0.25 μM by spectrometer. Quantitation of Cu(2+) was achieved in a linear range from 0.25 to 2.0 μM. This method was validated by measuring real water and serum samples, giving results agreeing well with the data reported and measured by inductively coupled plasma mass spectrometry. The recovery was 95.6-106% for untreated tap water and 96.0-100% for resin-pre-treated water and serum samples.

  12. Giant magnetic coercivity in CaCu5-type SmNi3TSi (T=Mn-Cu) solid solutions

    NASA Astrophysics Data System (ADS)

    Yao, Jinlei; Yan, Xu; Morozkin, A. V.

    2015-12-01

    The effects of transition metal substitution for Ni on the magnetic properties of the CaCu5-type SmNi3TSi (T=Mn, Fe, Co, Cu) solid solutions have been investigated. SmNi3MnSi, SmNi3FeSi, SmNi3CoSi and SmNi3CuSi show ferromagnetic ordering at 125 K, 190 K, 46 K and 12 K and field induced transitions at 65 K, 110 K, 30 K and 6 K, respectively. The magnetocaloric effects of SmNi3TSi (T=Mn, Fe, Co, Cu) were calculated in terms of isothermal magnetic entropy change (ΔSm). The magnetic entropy ΔSm reaches value of -1.1 J/kg K at 130 K for SmNi3MnSi, -0.4 J/kg K at 180 K for SmNi3FeSi, -0.37 J/kg K at 45 K for SmNi3CoSi and -0.5 J/kg K at 12 K for SmNi3CuSi in field change of 0-50 kOe around the ferromagnetic ordering temperature. They show positive ΔSm of +2.4 J/kg K at 30 K for SmNi3MnSi, -2.6 J/kg K at 65 K for SmNi3FeSi, +0.73 J/kg K at 15 K for SmNi3CoSi and -0.5 J/kg K at 6 K for SmNi3CuSi in field change of 0-50 kOe around the metamagnetic-like transition temperature. Below the field induced transition temperature, SmNi3TSi (T=Mn, Fe, Co, Cu) exhibits giant magnetic coercivity of 80 kOe at 20 K for SmNi3MnSi, 87 kOe at 40 K for SmNi3FeSi, 27 kOe at 20 K for SmNi3CoSi and 54 kOe at 5 K for SmNi3CuSi. Below the field induced transition temperature, SmNi3TSi (T=Mn, Fe, Co, Cu) exhibits giant magnetic coercivity of 80 kOe at 20 K for SmNi3MnSi, 87 kOe at 40 K for SmNi3FeSi, 27 kOe at 20 K for SmNi3CoSi and 54 kOe at 5 K for SmNi3CuSi.

  13. Ni nanoparticle catalyzed growth of MWCNTs on Cu NPs @ a-C:H substrate

    NASA Astrophysics Data System (ADS)

    Ghodselahi, T.; Solaymani, S.; Akbarzadeh Pasha, M.; Vesaghi, M. A.

    2012-11-01

    NiCu NPs @ a-C:H thin films with different Cu content were prepared by co-deposition by RF-sputtering and RF-plasma enhanced chemical vapor deposition (RF-PECVD) from acetylene gas and Cu and Ni targets. The prepared samples were used as catalysts for growing multi-wall carbon nanotubes (MWCNTs) from liquid petroleum gas (LPG) at 825 °C by thermal chemical vapor deposition (TCVD). By addition of Cu NPs @ a-C:H thin layer as substrate for Ni NPs catalyst, the density of the grown CNTs is greatly enhanced in comparison to bare Si substrate. Furthermore the average diameter of the grown CNTs decreases by decreasing of Cu content of Cu NPs @ a-C:H thin layer. However Cu NPs @ a-C:H by itself has no catalytic property in MWCNTs growth. Morphology and electrical and optical properties of Cu NPs @ a-C:H thin layer is affected by Cu content and each of them is effective parameter on growth of MWCNTs based on Ni NPs catalyst. Moreover, adding of a low amount of Ni NPs doesn't vary optical, electrical and morphology properties of Cu NPs @ a-C:H thin layer but it has a profound effect on its catalytic activity. Finally the density and diameter of MWCNTs can be optimized by selection of the Cu NPs @ a-C:H thin layer as substrate of Ni NPs.

  14. Investigations on Cu2+-substituted Ni-Zn ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Amarjeet; Kumar, Vinod

    2016-11-01

    CuxNi(1-x)/2Zn(1-x)/2Fe2O4 (x = 0.1, 0.3 and 0.5) nanoparticles were prepared by chemical co-precipitation method. The developed nanoparticles were characterized for structural properties by powder X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) techniques. Peak position in the X-ray diffraction pattern confirmed the single spinel phase of the developed particles. Infrared (IR) spectroscopy in mid-IR range showed the presence of characteristic absorption bands corresponding to octahedral and tetrahedral bonds in the spinel structure of prepared samples. Thermo-gravimetric analysis (TGA) measurements showed a considerable weight loss in the developed samples above 700∘C. Frequency dependence of the electrical properties of the developed material pellets was studied in the frequency range of 1 kHz-5 MHz. Temperature dependence of the dielectric constant of Cu0.1Ni0.45Zn0.45Fe2O4 was studied at different temperatures, i.e. at 425, 450 and 475 K, in the frequency range of 1 kHz-5 MHz. It was found that the electrical conductivity decreases with increasing Cu2+ ion content while it increases with the increase in temperature.

  15. Catalysis by Nanostructures: Methane, Ethylene Oxide, and Propylene Oxide Synthesis on Ag, Cu or Au Nanoclusters

    DTIC Science & Technology

    2008-02-07

    GRANT NUMBER Propylene Oxide Synthesis on Ag , Cu or Au nanoclusters F49620-01-1-0459 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER Horia...Nanostructures: Methane, Ethylene Oxide, and Propylene Oxide Synthesis on Ag , Cu or Au nanoclusters, F49620-01-1-0459 Final Performance Report (for the period 07...andthe mobility of Ag clusters and Au clusters on TiO 2(1 10) have been published " . We found that Au atoms are very mobile and form large clusters at

  16. Synthesis and anti-bacterial activity of Cu, Ag and Cu-Ag alloy nanoparticles: A green approach

    SciTech Connect

    Valodkar, Mayur; Modi, Shefaly; Pal, Angshuman; Thakore, Sonal

    2011-03-15

    Research highlights: {yields} Synthesis of novel nanosized copper-silver alloys of different compositions. {yields} Completely green approach for synthesis of water soluble bimetallic nanoparticle. {yields} Interesting anti-bacterial activity of as synthesized metal and alloy nanoparticle. -- Abstract: Metallic and bimetallic nanoparticles of copper and silver in various proportions were prepared by microwave assisted chemical reduction in aqueous medium using the biopolymer, starch as a stabilizing agent. Ascorbic acid was used as the reducing agent. The silver and copper nanoparticles exhibited surface plasmon absorption resonance maxima (SPR) at 416 and 584 nm, respectively; while SPR for the Cu-Ag alloys appeared in between depending on the alloy composition. The SPR maxima for bimetallic nanoparticles changes linearly with increasing copper content in the alloy. Transmission electron micrograph (TEM) showed monodispersed particles in the range of 20 {+-} 5 nm size. Both silver and copper nanoparticles exhibited emission band at 485 and 645 nm, respectively. The starch-stabilized nanoparticles exhibited interesting antibacterial activity with both gram positive and gram negative bacteria at micromolar concentrations.

  17. Alloying effects in near-eutectic Sn-Ag-Cu solder alloys for improved microstructural stability

    NASA Astrophysics Data System (ADS)

    Anderson, I. E.; Foley, J. C.; Cook, B. A.; Harringa, J.; Terpstra, R. L.; Unal, O.

    2001-09-01

    This study included a comparison of the baseline Sn-3.5Ag eutectic to one near-eutectic ternary alloy, Sn-3.6 Ag-1.0Cu and two quaternary alloys, Sn-3.6Ag-1.0Cu-0.15Co and Sn-3.6Ag-1.0 Cu-0.45 Co, to increase understanding of the beneficial effects of Co on Sn-Ag-Cu solder joints cooled at 1 3 C/sec, typical of reflow practice. The results indicated that joint microstructure refinement is due to Co-enhanced nucleation of the Cu6Sn5 phase in the solder matrix, as suggested by Auger elemental mapping and calorimetric measurements. The Co also reduced intermetallic interface faceting and improved the ability of the solder joint samples to maintain their shear strength after aging for 72 hr at 150 C. The baseline Sn-3.5Ag joints exhibited significantly reduced strength and coarser microstructures.

  18. Alloy Catalyst in a Reactive Environment: The Example of Ag-Cu Particles for Ethylene Epoxidation

    SciTech Connect

    Piccinin, Simone; Zafeiratos, Spiros; Stampfl, Catherine; Hansen, Thomas W.; Haevecker, Michael; Teschner, Detre; Girgsdies, Frank; Knop-Gericke, Axel; Schloegl, Robert; Scheffler, Matthias; Bukhtiyarov, Valerii I.

    2010-01-22

    Combining first-principles calculations and in situ photoelectron spectroscopy, we show how the composition and structure of the surface of an alloy catalyst is affected by the temperature and pressure of the reagents. The Ag-Cu alloy, recently proposed as an improved catalyst for ethylene epoxidation, forms a thin Cu-O surface oxide, while a Ag-Cu surface alloy is found not to be stable. Several possible surface structures are identified, among which the catalyst surface is likely to dynamically evolve under reaction conditions.

  19. Selective recovery of Cu, Zn, and Ni from acid mine drainage.

    PubMed

    Park, Sang-Min; Yoo, Jong-Chan; Ji, Sang-Woo; Yang, Jung-Seok; Baek, Kitae

    2013-12-01

    In Korea, the heavy metal pollution from about 1,000 abandoned mines has been a serious environmental issue. Especially, the surface waters, groundwaters, and soils around mines have been contaminated by heavy metals originating from acid mine drainage (AMD) and mine tailings. So far, AMD was considered as a waste stream to be treated to prevent environmental pollutions; however, the stream contains mainly Fe and Al and valuable metals such as Ni, Zn, and Cu. In this study, Visual MINTEQ simulation was carried out to investigate the speciation of heavy metals as functions of pH and neutralizing agents. Based on the simulation, selective pH values were determined to form hydroxide or carbonate precipitates of Cu, Zn, and Ni. Experiments based on the simulation results show that the recovery yield of Zn and Cu were 91 and 94 %, respectively, in a binary mixture of Cu and Zn, while 95 % of Cu and 94 % of Ni were recovered in a binary mixture of Cu and Ni. However, the recovery yield and purity of Zn and Ni were very low because of similar characteristics of Zn and Ni. Therefore, the mixture of Cu and Zn or Cu and Ni could be recovered by selective precipitation via pH adjustment; however, it is impossible to recover selectively Zn and Ni in the mixture of them.

  20. Kinetic trapping through coalescence and the formation of patterned Ag-Cu nanoparticles

    NASA Astrophysics Data System (ADS)

    Grammatikopoulos, Panagiotis; Kioseoglou, Joseph; Galea, Antony; Vernieres, Jerome; Benelmekki, Maria; Diaz, Rosa E.; Sowwan, Mukhles

    2016-05-01

    In recent years, due to its inherent flexibility, magnetron-sputtering has been widely used to synthesise bi-metallic nanoparticles (NPs) via subsequent inert-gas cooling and gas-phase condensation of the sputtered atomic vapour. Utilising two separate sputter targets allows for good control over composition. Simultaneously, it involves fast kinetics and non-equilibrium processes, which can trap the nascent NPs into metastable configurations. In this study, we observed such configurations in immiscible, bi-metallic Ag-Cu NPs by scanning transmission electron microscopy (S/TEM) and electron energy-loss spectroscopy (EELS), and noticed a marked difference in the shape of NPs belonging to Ag- and Cu-rich samples. We explained the formation of Janus or Ag@Cu core/shell metastable structures on the grounds of in-flight mixed NP coalescence. We utilised molecular dynamics (MD) and Monte Carlo (MC) computer simulations to demonstrate that such configurations cannot occur as a result of nanoalloy segregation. Instead, sintering at relatively low temperatures can give rise to metastable structures, which eventually can be stabilised by subsequent quenching. Furthermore, we compared the heteroepitaxial diffusivities along various surfaces of both Ag and Cu NPs, and emphasised the differences between the sintering mechanisms of Ag- and Cu-rich NP compositions: small Cu NPs deform as coherent objects on large Ag NPs, whereas small Ag NPs dissolve into large Cu NPs, with their atoms diffusing along specific directions. Taking advantage of this observation, we propose controlled NP coalescence as a method to engineer mixed NPs of a unique, patterned core@partial-shell structure, which we refer to as a ``glass-float'' (ukidama) structure.In recent years, due to its inherent flexibility, magnetron-sputtering has been widely used to synthesise bi-metallic nanoparticles (NPs) via subsequent inert-gas cooling and gas-phase condensation of the sputtered atomic vapour. Utilising two

  1. Effect of rare earth metal Ce addition to Sn-Ag solder on interfacial reactions with Cu substrate

    NASA Astrophysics Data System (ADS)

    Yoon, Jeong-Won; Noh, Bo-In; Jung, Seung-Boo

    2014-05-01

    The effect of adding a small amount of rare earth cerium (Ce) element to low Ag containing Sn-1wt%Ag Pb-free solder on its interfacial reactions with Cu substrate was investigated. The growth of intermetallic compounds (IMCs) between three Sn-1Ag-xCe solders with different Ce contents and a Cu substrate was studied and the results were compared to those obtained for the Ce-free Sn-1Ag/Cu systems. In the solid-state reactions of the Sn-1Ag(-xCe)/Cu solder joints, the two IMC layers, Cu6Sn5 and Cu3Sn, grew as aging time increased. Compared to the Sn-1Ag/Cu joint, the growth of the Cu6Sn5 and Cu3Sn layers was depressed for the Ce-containing Sn-1Ag-xCe/Cu joint. The addition of Ce to the Sn-Ag solder reduced the growth of the interfacial Cu-Sn IMCs and prevented the IMCs from spalling from the interface. The evenly-distributed Ce elements in the solder region blocked the diffusion of Sn atoms to the interface and retarded the growth of the interfacial IMC layer.

  2. Ag- and Cu-doped multifunctional bioactive nanostructured TiCaPCON films

    NASA Astrophysics Data System (ADS)

    Shtansky, D. V.; Batenina, I. V.; Kiryukhantsev-Korneev, Ph. V.; Sheveyko, A. N.; Kuptsov, K. A.; Zhitnyak, I. Y.; Anisimova, N. Yu.; Gloushankova, N. A.

    2013-11-01

    A key property of multicomponent bioactive nanostructured Ti(C,N)-based films doped with Ca, P, and O (TiCaPCON) that can be improved further is their antibacterial effect that should be achieved without compromising the implant bioactivity and biocompatibility. The present work is focused on the study of structure, chemical, mechanical, tribological, and biological properties of Ag- and Cu-doped TiCaPCON films. The films with Ag (0.4-4 at.%) and Cu (13 at.%) contents were obtained by simultaneous sputtering of a TiC0.5-Ca3(PO4)2 target and either an Ag or a Cu target. The film structure was studied using X-ray diffraction, transmission and scanning electron microscopy, energy dispersive X-ray spectroscopy, glow discharge optical emission spectroscopy, and Raman-shift and IR spectroscopy. The films were characterized in terms of their hardness, elastic modulus, dynamic impact resistance, friction coefficient and wear rate (both in air and normal saline), surface wettability, electrochemical behavior and Ag or Cu ion release in normal saline. Particular attention was paid to the influence of inorganic bactericides (Ag and Cu ions) on the bactericidal activity against unicellular yeast fungus Saccharomyces cerevisiae and gram-positive bacteria Lactobacillus acidophilus, as well as on the attachment, spreading, actin cytoskeleton organization, focal adhesions, and early stages of osteoblastic cell differentiation. The obtained results show that the Ag-doped films are more suitable for the protection of metallic surfaces against bacterial infection compared with their Cu-doped counterpart. In particular, an excellent combination of mechanical, tribological, and biological properties makes Ag-doped TiCaPCON film with 1.2 at.% of Ag very attractive material for bioengineering and modification of load-bearing metal implant surfaces.

  3. Grindability of dental cast Ti-Ag and Ti-Cu alloys.

    PubMed

    Kikuchi, Masafumi; Takahashi, Masatoshi; Okabe, Toru; Okuno, Osamu

    2003-06-01

    Experimental Ti-Ag alloys (5, 10, and 20 mass% Ag) and Ti-Cu alloys (2, 5, and 10 mass% Cu) were cast into magnesia molds using a dental casting machine, and their grindability was investigated. At the lowest grinding speed (500 m min(-1)), there were no statistical differences among the grindability values of the titanium and titanium alloys. The grindability of the alloys increased as the grinding speed increased. At the highest grinding speed (1500 m x min(-1)), the grindability of the 20% Ag, 5% Cu, and 10% Cu alloys was significantly higher than that of titanium. It was found that alloying with silver or copper improved the grindability of titanium, particularly at a high speed. It appeared that the decrease in elongation caused by the precipitation of small amounts of intermetallic compounds primarily contributed to the favorable grindability of the experimental alloys.

  4. Fracture of Sn-Ag-Cu Solder Joints on Cu Substrates. II: Fracture Mechanism Map

    NASA Astrophysics Data System (ADS)

    Kumar, P.; Huang, Z.; Dutta, I.; Sidhu, R.; Renavikar, M.; Mahajan, R.

    2012-02-01

    A methodology to construct fracture mechanism maps for Sn-3.8%Ag-0.7%Cu (SAC387) solder joints attached to Cu substrates has been developed. The map, which delineates the operative mechanisms of fracture along with corresponding joint fracture toughness values, is plotted in a space described by two microstructure-dependent parameters, with the abscissa describing the interfacial intermetallic compound (IMC) and the ordinate representing the strain-rate-dependent solder yield strength. The plot space encompasses the three major mechanisms by which joints fail, namely (i) cohesive fracture of solder, (ii) cleavage fracture of interfacial intermetallic compounds (IMC), and (iii) fracture of the solder-IMC interface. Line contours of constant fracture toughness values, as well as constant fraction of each of the above mechanisms, are indicated on the plots. The plots are generated by experimentally quantifying the dependence of the operative fracture mechanism(s) on the two microstructure-dependent parameters (IMC geometry and solder yield strength) as functions of strain rate, reflow parameters, and post-reflow aging. Separate maps are presented for nominally mode I and equi-mixed mode loading conditions (loading angle ϕ = 0° and 45°, respectively). The maps allow rapid assessment of the operative fracture mechanism(s) along with estimation of the expected joint fracture toughness value for a given loading condition (strain rate and loading angle) and joint microstructure without conducting actual tests, and may serve as a tool for both prediction and microstructure design.

  5. Kinetic trapping through coalescence and the formation of patterned Ag-Cu nanoparticles.

    PubMed

    Grammatikopoulos, Panagiotis; Kioseoglou, Joseph; Galea, Antony; Vernieres, Jerome; Benelmekki, Maria; Diaz, Rosa E; Sowwan, Mukhles

    2016-05-14

    In recent years, due to its inherent flexibility, magnetron-sputtering has been widely used to synthesise bi-metallic nanoparticles (NPs) via subsequent inert-gas cooling and gas-phase condensation of the sputtered atomic vapour. Utilising two separate sputter targets allows for good control over composition. Simultaneously, it involves fast kinetics and non-equilibrium processes, which can trap the nascent NPs into metastable configurations. In this study, we observed such configurations in immiscible, bi-metallic Ag-Cu NPs by scanning transmission electron microscopy (S/TEM) and electron energy-loss spectroscopy (EELS), and noticed a marked difference in the shape of NPs belonging to Ag- and Cu-rich samples. We explained the formation of Janus or Ag@Cu core/shell metastable structures on the grounds of in-flight mixed NP coalescence. We utilised molecular dynamics (MD) and Monte Carlo (MC) computer simulations to demonstrate that such configurations cannot occur as a result of nanoalloy segregation. Instead, sintering at relatively low temperatures can give rise to metastable structures, which eventually can be stabilised by subsequent quenching. Furthermore, we compared the heteroepitaxial diffusivities along various surfaces of both Ag and Cu NPs, and emphasised the differences between the sintering mechanisms of Ag- and Cu-rich NP compositions: small Cu NPs deform as coherent objects on large Ag NPs, whereas small Ag NPs dissolve into large Cu NPs, with their atoms diffusing along specific directions. Taking advantage of this observation, we propose controlled NP coalescence as a method to engineer mixed NPs of a unique, patterned core@partial-shell structure, which we refer to as a "glass-float" (ukidama) structure.

  6. Control of Surface Segregation in Bimetallic NiCr Nanoalloys Immersed in Ag Matrix

    PubMed Central

    Bohra, Murtaza; Singh, Vidyadhar; Grammatikopoulos, Panagiotis; Toulkeridou, Evropi; Diaz, Rosa E.; Bobo, Jean-François; Sowwan, Mukhles

    2016-01-01

    Cr-surface segregation is a main roadblock encumbering many magneto-biomedical applications of bimetallic M-Cr nanoalloys (where M = Fe, Co and Ni). To overcome this problem, we developed Ni95Cr5:Ag nanocomposite as a model system, consisting of non-interacting Ni95Cr5 nanoalloys (5 ± 1 nm) immersed in non-magnetic Ag matrix by controlled simultaneous co-sputtering of Ni95Cr5 and Ag. We employed Curie temperature (TC) as an indicator of phase purity check of these nanocomposites, which is estimated to be around the bulk Ni95Cr5 value of 320 K. This confirms prevention of Cr-segregation and also entails effective control of surface oxidation. Compared to Cr-segregated Ni95Cr5 nanoalloy films and nanoclusters, we did not observe any unwanted magnetic effects such as presence Cr-antiferromagnetic transition, large non-saturation, exchange bias behavior (if any) or uncompensated higher TC values. These nanocomposites films also lose their unique magnetic properties only at elevated temperatures beyond application requirements (≥800 K), either by showing Ni-type behavior or by a complete conversion into Ni/Cr-oxides in vacuum and air environment, respectively. PMID:26750659

  7. TEM study on the interfacial reaction between electroless plated Ni-P/Au UBM and Sn-3.5Ag solder

    NASA Astrophysics Data System (ADS)

    Park, Min-Ho; Kwon, Eun-Jung; Kang, Han-Byul; Jung, Seung-Boo; Yang, Cheol-Woong

    2007-06-01

    This study examined the interfacial reaction between electroless plated Ni-P/Au under bump metallization (UBM) and a eutectic Sn-3.5Ag solder using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The chemical and crystallographic analysis using TEM provided important information on the microstructural evolution at the interface. In this study, UBM was prepared by the electroless plating of Au (0.15 μm)/Ni-15 at %P (5 μm) on a bare Cu substrate and was then reacted with a Sn-3.5Ag eutectic solder at 260°C for various amounts of time to examine the different sequential stages of the interfacial reaction TEM analyses confirmed that beside the Ni3Sn4 layer, there were three more IMC layers at the interface: the Ni-Sn-P ternary layer, Ni3P layer, and the layer of phase mixture of the Ni3P and Ni2SnP ternary phases.

  8. Distribution of Ag in Cu-sulfides in Kupferschiefer deposit, SW Poland

    NASA Astrophysics Data System (ADS)

    Kozub, Gabriela A.

    2014-05-01

    The Cu-Ag Kupferschiefer deposit located at the Fore-Sudetic Monocline (SW Poland) is a world class deposit of stratabound type. The Cu-Ag mineralization in the deposit occurs in the Permian sedimentary rocks (Rotliegend and Zechstein) in three lithological types of ore: the dolomite, the black shale and the sandstone. Silver, next to copper, is the most important element in the Kupferschiefer deposit (Salamon 1979; Piestrzyński 2007; Pieczonka 2011). Although occurrence of the Ag-minerals such as native silver, silver amalgams, stromeyerite, jalpaite and mckinstryite, silver is mainly present in the deposit due to isomorphic substitutions in Cu-minerals such as chalcocite, bornite, tennantite, covellite and chalcopyrite. The aim of the study was to define distribution of silver in Cu-minerals and correlate occurrence of Ag-enriched Cu-sulfides with native silver and silver amalgams. Identification of minerals and textural observation were performed using field emission scanning electron microscope. Analyzes of chemical composition of Cu-sulfides were performed utilizing electron microprobe. Silver concentration in Cu sulfides ranges from 0.1 to 10.4 wt.% in chalcocite, 0.2-15.8 wt.% in bornite, 0.1-2.9 wt.% in tennantite, 0.05-0.3 wt.% in chalcopyrite and ca. 0.4 wt.% in covellite. In general, distribution of silver in Cu-minerals is irregular, as indicated by high variations of Ag concentration in each mineral. Content of Ag in Cu-sulphides, in samples where native silver and silver amalgams are not found, is lower than in samples, where native silver and silver amalgams are noted. The chemical analyzes of Ag-bearing Cu-minerals indicate decrease of Cu content in minerals with high Ag concentration. In such case, decrease of Fe content is also noted in bornite. Lack of micro-inclusions of the native silver or silver amalgams in the Cu-minerals indicates that presence of Ag is mainly related to the isomorphic substitutions. This is in agreement with previous

  9. Microstructures and martensitic transformation behavior of superelastic Ti-Ni-Ag scaffolds

    SciTech Connect

    Li, Shuanglei; Kim, Eun-soo; Kim, Yeon-wook; Nam, Tae-hyun

    2016-10-15

    Highlights: • The B2-R-B19′ transformation occurred in 49Ti-50.3Ni-0.7Ag alloy fibers. • Annealing treated alloy fibers showed superelastic recovery ratio of 93%. • Ageing treated scaffold had an elastic modulus of 0.67 GPa. • Ageing treated scaffold exhibited good superelasticity at human body temperature. - Abstract: Ti-Ni-Ag scaffolds were prepared by sintering rapidly solidified alloy fibers. Microstructures and transformation behaviors of alloy fibers and scaffolds were investigated by means of electron probe micro-analyzer (EPMA), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The B2-R-B19′ transformation occurs in alloy fibers. The alloy fibers have good superelasticity with superelastic recovery ratio of 93% after annealing heat treatment. The as-sintered Ti-Ni-Ag scaffolds possess three-dimensional and interconnected pores and have the porosity level of 80%. The heat treated Ti-Ni-Ag scaffolds not only have an elastic modulus of 0.67 GPa, which match well with that of cancellous bone, but also show excellent superelasticity at human body temperature. In terms of the mechanical properties, the Ti-Ni-Ag scaffolds in this study can meet the main requirements of bone scaffold for the purpose of bone replacement applications.

  10. Characterization of Cu buffer layers for growth of L10-FeNi thin films

    NASA Astrophysics Data System (ADS)

    Mizuguchi, M.; Sekiya, S.; Takanashi, K.

    2010-05-01

    A Cu(001) layer was fabricated on a Au(001) layer to investigate the use of Cu as a buffer layer for growing L10-FeNi thin films. The epitaxial growth of a Cu buffer layer was observed using reflection high-energy electron diffraction. The flatness of the layer improved drastically with an increase in the substrate temperature although the layer was an alloy (AuCu3). An FeNi thin film was epitaxially grown on the AuCu3 buffer layer by alternate monatomic layer deposition and the formation of an L10-FeNi ordered alloy was expected. The AuCu3 buffer layer is thus a promising candidate material for the growth of L10-FeNi thin films.

  11. Atomic-scale investigation of interface-facilitated deformation twinning in severely deformed Ag-Cu nanolamellar composites

    SciTech Connect

    An, X. H. E-mail: xiaozhou.liao@sydenye.edu.au; Cao, Y.; Liao, X. Z. E-mail: xiaozhou.liao@sydenye.edu.au; Zhu, S. M.; Nie, J. F.; Kawasaki, M.; Ringer, S. P.; Langdon, T. G.; Zhu, Y. T.

    2015-07-06

    We report an atomic-scale investigation of interface-facilitated deformation twinning behaviour in Ag-Cu nanolamellar composites. Profuse twinning activities in Ag supply partial dislocations to directly transmit across the Ag-Cu lamellar interface that promotes deformation twinning in the neighbouring Cu lamellae although the interface is severely deformed. The trans-interface twin bands change the local structure at the interface. Our analysis suggests that the orientation relationship and interfacial structure between neighbouring Ag-Cu lamellae play a crucial role in such special interface-facilitated twinning behaviour.

  12. First-Principles Study of Substitution of Cu and Au for Ni in Ni3Sn2

    NASA Astrophysics Data System (ADS)

    Tian, Yali; Wu, Ping; Lu, Zhengxiong

    2017-01-01

    The effects of substitution of Cu and Au for Ni on the mechanical, thermodynamic and electronic properties of two different Ni3Sn2 structures are investigated by first-principles calculations. Cu atom at Ni2 site and Au atom at Ni1 site of the η phase lead to the thermodynamic stable structure. For the λ phase, Au atom can only replace the Ni1 site. Substitution causes the decrease of the polycrystalline elastic modulus and the Debye temperature. The degree of anisotropy along Z axis decreases dramatically for η phase, but it increases along Y axis for λ phase after substitution. The Ni3Sn2-based intermetallics are all ductile; the η phase is more ductile than the λ phase. The electronic density of states manifest an energy gap appearing in η phase and the effective mass of the η phase is lower than λ phase.

  13. Carbon encapsulated nanoparticles of Ni, Co, Cu, and Ti

    NASA Astrophysics Data System (ADS)

    Jiao, Jun; Seraphin, Supapan

    1998-03-01

    Despite intensive research on the encapsulation of metal nanoparticles into carbon clusters deposited by arc discharge, the detailed pathways of the formation of these novel forms of materials remain unclear. The growth of a rich variety of morphologies is not well understood. Studies are reported here on the growth phenomena of different metals encapsulated into carbon cages that emphasize the effect of carbon and metal supply on the size of particles. Post-deposition annealing was introduced as a process that induces structural rearrangements, and thus enables changes in morphologies. A set of carbon encapsulated Ni, Co, Cu, and Ti particles were prepared by an arc discharge process modified in the geometry of the anode and flow pattern of helium or methane gas. The samples were then annealed under flowing argon gas. Three annealing temperatures were used (600, 900, and 1100 °C). Samples were characterized by transmission and scanning electron microscopy. Particles made under the same experimental conditions are of roughly the same size. When the supply of metal in the reactor space was increased by using a larger diameter of the metal pool, the average diameter of the particles is bigger than those of produced from the smaller metal pool. The thickness of the carbon cages of Ni and Co particles increased during the annealing. The carbon cages of Cu particles, however, did not change their thickness, while some carbon coatings of Ti particles disappeared under annealing. This suggests that the addition of layers for the Ni and Co cages results from a precipitation of carbon previously dissolved in the metal, while the much lower solubility of C in Cu prevents this possibility. The Ti of high reactivity, on the other hand, may further react with the available carbon under annealing to form TiC. It is suggested that annealing provides additional thermal energy that makes structural re-arrangement possible long after the initial deposition process was terminated

  14. Energetics of the formation of Cu-Ag core–shell nanoparticles

    DOE PAGES

    Chandross, Michael

    2014-10-06

    Our work presents molecular dynamics and Monte Carlo simulations aimed at developing an understanding of the formation of core–shell Cu-Ag nanoparticles. The effects of surface and interfacial energies were considered and used to form a phenomenological model that calculates the energy gained upon the formation of a core–shell structure from two previously distinct, non-interacting nanoparticles. In most cases, the core–shell structure was found to be energetically favored. Specifically, the difference in energy as a function of the radii of the individual Cu and Ag particles was examined, with the assumption that a core–shell structure forms. In general, it was foundmore » that the energetic gain from forming such a structure increased with increasing size of the initial Ag particle. This result was interpreted as a result of the reduction in surface energy. Moreover, for two separate particles, both Cu and Ag contribute to the surface energy; however, for a core–shell structure, the only contribution to the surface energy is from the Ag shell and the Cu contribution is changed to a Cu–Ag interfacial energy, which is always smaller.« less

  15. Energetics of the formation of Cu-Ag core–shell nanoparticles

    SciTech Connect

    Chandross, Michael

    2014-10-06

    Our work presents molecular dynamics and Monte Carlo simulations aimed at developing an understanding of the formation of core–shell Cu-Ag nanoparticles. The effects of surface and interfacial energies were considered and used to form a phenomenological model that calculates the energy gained upon the formation of a core–shell structure from two previously distinct, non-interacting nanoparticles. In most cases, the core–shell structure was found to be energetically favored. Specifically, the difference in energy as a function of the radii of the individual Cu and Ag particles was examined, with the assumption that a core–shell structure forms. In general, it was found that the energetic gain from forming such a structure increased with increasing size of the initial Ag particle. This result was interpreted as a result of the reduction in surface energy. Moreover, for two separate particles, both Cu and Ag contribute to the surface energy; however, for a core–shell structure, the only contribution to the surface energy is from the Ag shell and the Cu contribution is changed to a Cu–Ag interfacial energy, which is always smaller.

  16. The evolution of interface microstructure in a ZrO[sub 2]/Ag-Cu-Al-Ti system

    SciTech Connect

    Lee, Youngmin; Yu, Jin )

    1993-08-01

    Among ceramic/metal (C/M) joining technologies, the active filler metal method has been studied extensively due to the simple brazing process and excellent joint strength. Active metal elements, typically Ti, are intentionally added to braze alloys to enhance the formation of reaction products between the ceramic and the braze metal at the C/M interface. In the brazing of Al[sub 2]O[sub 3] with the Ag-Cu-Ti filler metal, reaction products such as [gamma]-TiO, Cu[sub 2](Ti, Al)[sub 4]O, Ti[sub 3](Cu[sub 0.76]Al[sub 0.18]Sn[sub 0.06])[sub 3]O were found, while products such as Ti[sub 5]Si[sub 3] and TiN formed in the brazing of Si[sub 3]N[sub 4]. The presence of reaction layers at the C/M interface influences the interface strength in a complex way. In Cu/Al[sub 2]O[sub 3], Co/Al[sub 2]O[sub 3], Ni/Al[sub 2]O[sub 3], and Cu/diamond systems, maxima of joint strength were observed at some intermediate Ti addition, while the flexural strength decreased substantially with the thickening of the TiO layer in a ZrO[sub 2]/Ag-Cu-Sn-Ti system. Thus, composition of the braze alloy (particularly, the content of the active metal), process conditions such as brazing temperature and time, microstructure and mechanical properties of reaction products at the C/M interfaces, interfacial chemistry, and residual stress are primary factors to be studied in order to understand the strengths of the C/M interfaces systematically. In the present and the following papers, evolutions of interfacial microstructures at various brazing conditions, and corresponding interface strengths are reported, respectively, for a ZrO[sub 2]/Ag-Cu-Al-Ti system.

  17. Preparation and optical properties of silica Ag-Cu alloy core-shell composite colloids

    SciTech Connect

    Zhang Jianhui Liu Huaiyong; Wang Zhenlin; Ming Naiben

    2007-04-15

    The silica Ag-Cu alloy core-shell composite colloids have been successfully synthesized by an electroless plating approach to explore the possibility of modifying the plasmon resonance at the nanoshell surface by varying the metal nanoshell composition for the first time. The surface plasmon resonance of the composite colloids increases in intensity and shifts towards longer, then shorter wavelengths as the Cu/Ag ratio in the alloy shell is increased. The variations in intensity of the surface plasmon resonance with the Cu/Ag ratio obviously affect the Raman bands of the silica colloid core. The report here may supply a new technique to effectively modify the surface plasmon resonance. - Graphical abstract: The silica Ag-Cu alloy core-shell colloids have been successfully synthesized to explore the possibility of modifying the surface plasmon resonance (SPR) by varying the metal nanoshell composition for the first time. Varying the Cu/Ag ratio of the alloy nanoshell has obvious influences on the SPR of the composite colloids and the Raman bands of the amorphous silica core.

  18. Microstructural stability and mechanical response of Cu-Ag microcomposite wires

    SciTech Connect

    Hong, S.I.; Hill, M.A.

    1998-07-24

    A transmission electron microscope (TEM) was used to study the microstructural and mechanical stability of Cu-24 wt % Ag microcomposites in both the as-drawn and heat-treated condition. Three phase morphologies were observed in the heavily drawn Cu-24 wt % Ag wires: fine silver filaments, thick silver lamellae, and copper-rich {alpha} phase. The microstructure of the Cu-Ag microcomposite was observed on a much finer scale than that reported by previous investigators. The stress-strain responses and fracture behavior of Cu-Ag microcomposite wires were also examined and correlated with the microstructural change caused by thermomechanical treatments. The ratios of yield stresses (0.86) and ultimate tensile strengths (0.83) at 295 and 77 K were quite close to the ratio of Young`s moduli (0.85), suggesting that the strengthening mechanism is predominantly controlled by long-range athermal obstacles. A modified rule of mixtures was used to predict the strength of the Cu-24 wt % Ag microcomposites. The strength of each of the three regions observed by TEM was evaluated or estimated based on the available data. The predictions of the model were in good agreement with experimental data.

  19. Preparation and characterization of dendrimer-templated Ag-Cu bimetallic nanoclusters.

    PubMed

    Li, Guoping; Luo, Yunjun

    2008-01-07

    Ag-Cu bimetallic nanoclusters with different shapes were prepared by a co-complexation method in the presence of PAMAM dendrimers. Small and evenly sized spherical Ag-Cu bimetallic nanoparticles were obtained with N2H4.H2O as the reducing agent, and long rod-shaped bimetallic nanoclusters were prepared with NaBH4 as the reducing agent. The mechanisms of formation of Ag-Cu bimetallic nanolusters with different shapes were discussed. The different shapes of the cluster were likely caused by the differences in the reduction rate of metal ions with NaBH4 and N2H4.H2O. Structure characterization by TEM, UV-vis spectra, EDX, and TGA showed that, in the presence of PAMAM dendrimers, Ag-Cu alloy bimetallic nanorods were obtained with NaBH4 reduction, and Ag-Cu bimetallic nanoparticles were prepared with N2H4.H2O as the reducing agent.

  20. 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.

  1. NMR study of Cu2Se and Cu1.98Ag0.2Se superionic conductors

    NASA Astrophysics Data System (ADS)

    Sirusi Arvij, Ali; Ross, Joseph H., Jr.; Ballikaya, Sedat; Uher, Ctirad

    2015-03-01

    Cu2Se and Cu1.98Ag0.2Se are well known as superionic conductors and recently as thermoelectric materials due to observation of high ZT. We will report NMR of these compounds. Our results include indications of glassy anharmonic behavior at low temperatures, Cu ionic motion which becomes initiated near 90K, and motional narrowing near the phase transition at high temperatures as well as modified dynamics observed in the Ag-doped sample. NMR is particularly well suited to probe low frequency dynamics and at low temperatures the relaxation rate indicates anharmonic rattling behavior similar to what has been observed in other thermoelectric materials. A 90K change in the NMR spectra corresponds to the recently observed transport anomaly and indicates that the slow motion of Cu ions is initiated at this temperature and eventually becomes liquid-like at higher temperatures. We detect fast ionic motion in Cu2Se starting at 140K whereas in the Ag-doped compound this onset shifts to a higher temperature around 300K. At high temperatures the spectra become motionally narrowed, and we will discuss the narrowing and shifts in terms of activated carrier density and ionic motion. This work was supported by the Robert A. Welch Foundation.

  2. Electronic structure of benzene adsorbed on Ni and Cu surfaces

    SciTech Connect

    Weinelt, M.; Nilsson, A.; Wassdahl, N.

    1997-04-01

    Benzene has for a long time served as a prototype adsorption system of large molecules. It adsorbs with the molecular plane parallel to the surface. The bonding of benzene to a transition metal is typically viewed to involve the {pi} system. Benzene adsorbs weakly on Cu and strongly on Ni. It is interesting to study how the adsorption strength is reflected in the electronic structure of the adsorbate-substrate complex. The authors have used X-ray Emission (XE) and X-ray Absorption (XA) spectroscopies to selectively study the electronic states localized on the adsorbed benzene molecule. Using XES the occupied states can be studies and with XAS the unoccupied states. The authors have used beamline 8.0 and the Swedish endstation equipped with a grazing incidence x-ray spectrometer and a partial yield absorption detector. The resolution in the XES and XAS were 0.5 eV and 0.05 eV, respectively.

  3. Oxidation resistance of graphene-coated Cu and Cu/Ni alloy.

    PubMed

    Chen, Shanshan; Brown, Lola; Levendorf, Mark; Cai, Weiwei; Ju, Sang-Yong; Edgeworth, Jonathan; Li, Xuesong; Magnuson, Carl W; Velamakanni, Aruna; Piner, Richard D; Kang, Junyong; Park, Jiwoong; Ruoff, Rodney S

    2011-02-22

    The ability to protect refined metals from reactive environments is vital to many industrial and academic applications. Current solutions, however, typically introduce several negative effects, including increased thickness and changes in the metal physical properties. In this paper, we demonstrate for the first time the ability of graphene films grown by chemical vapor deposition to protect the surface of the metallic growth substrates of Cu and Cu/Ni alloy from air oxidation. In particular, graphene prevents the formation of any oxide on the protected metal surfaces, thus allowing pure metal surfaces only one atom away from reactive environments. SEM, Raman spectroscopy, and XPS studies show that the metal surface is well protected from oxidation even after heating at 200 °C in air for up to 4 h. Our work further shows that graphene provides effective resistance against hydrogen peroxide. This protection method offers significant advantages and can be used on any metal that catalyzes graphene growth.

  4. Interactions of Oxygen and Ethylene with Submonolayer Ag Films Supported on Ni(111)

    SciTech Connect

    Alamgir, F.M.; Senanayake, S.; Rettew, R.E.; Meyer, A.; Chen, T.-L.; Petersburg, C.; Flege, J.I.; Falta, J.

    2011-06-01

    We investigate the oxidation of, and the reaction of ethylene with, Ni(111) with and without sub-monolayer Ag adlayers as a function of temperature. The addition of Ag to Ni(111) is shown to enhance the activity towards the ethylene epoxidation reaction, and increase the temperature at which ethylene oxide is stable on the surface. We present a systematic study of the formation of chemisorbed oxygen on the Ag-Ni(111) surfaces and correlate the presence and absence of O{sup 1-} and O{sup 2-} surface species with the reactivity towards ethylene. By characterizing the samples with low-energy electron microscopy (LEEM) in combination with X-ray photoelectron spectroscopy (XPS), we have identified specific growth of silver on step-edge sites and successfully increased the temperature at which the produced ethylene oxide remains stable, a trait which is desirable for catalysis.

  5. Interactions of Oxygen and Ethylene with Submonolayer Ag Films Supported on Ni(111)

    SciTech Connect

    R Rettew; A Meyer; S Senanayake; T Chen; C Petersburg; J Flege; J Falta; F Alamgir

    2011-12-31

    We investigate the oxidation of, and the reaction of ethylene with, Ni(111) with and without sub-monolayer Ag adlayers as a function of temperature. The addition of Ag to Ni(111) is shown to enhance the activity towards the ethylene epoxidation reaction, and increase the temperature at which ethylene oxide is stable on the surface. We present a systematic study of the formation of chemisorbed oxygen on the Ag-Ni(111) surfaces and correlate the presence and absence of O{sup 1-} and O{sup 2-} surface species with the reactivity towards ethylene. By characterizing the samples with low-energy electron microscopy (LEEM) in combination with X-ray photoelectron spectroscopy (XPS), we have identified specific growth of silver on step-edge sites and successfully increased the temperature at which the produced ethylene oxide remains stable, a trait which is desirable for catalysis.

  6. Thermal Analysis of the Effect of Oxygen Contamination on Undercooling of Zr-Al-Ni-Cu, Cu-Zr-Ti, and Cu-Ni-Zr-Ti Metallic Glasses (Preprint)

    DTIC Science & Technology

    2009-04-01

    been done on systems other than Zr65Al7.5(Cu17.5Ni10). Zr55Al10(Cu30Ni5) was found to be less sensitive to oxygen content than Zr65Al7.5(Cu17.5Ni10...Zr11Ti34 by arc-melting each of the pure elements under a titanium - gettered atmosphere. Starting materials used were: Al pellets, 99.999%; Cu shot...produce 2-6 g alloyed ingots of each composition. Each ingot was flipped typically 4-5 times in a titanium -gettered, high-purity argon atmosphere

  7. Ag/AgO Nanoparticles Grown via Time Dependent Double Mechanism in a 2D Layered Ni-PCP and Their Antibacterial Efficacy

    PubMed Central

    Agarwal, Rashmi A.; Gupta, Neeraj K.; Singh, Rajan; Nigam, Shivansh; Ateeq, Bushra

    2017-01-01

    A simple synthesis route for growth of Ag/AgO nanoparticles (NPs) in large quantitative yields with narrow size distribution from a functional, non-activated, Ni (II) based highly flexible porous coordination polymer (PCP) as a template has been demonstrated. This template is a stable storage media for the NPs larger than the pore diameters of the PCP. From EPR study it was concluded that NPs were synthesized via two mechanisms i.e. acid formation and the redox activity of the framework. Size range of Ag/AgO NPs is sensitive to choice of solvent and reaction time. Direct use of Ag/AgO@Ni-PCP shows influential growth inhibition towards Escherichia coli and the pathogen Salmonella typhimurium at extremely low concentrations. The pristine template shows no cytotoxic activity, even though it contains Ni nodes in the framework. PMID:28322256

  8. Ag/AgO Nanoparticles Grown via Time Dependent Double Mechanism in a 2D Layered Ni-PCP and Their Antibacterial Efficacy

    NASA Astrophysics Data System (ADS)

    Agarwal, Rashmi A.; Gupta, Neeraj K.; Singh, Rajan; Nigam, Shivansh; Ateeq, Bushra

    2017-03-01

    A simple synthesis route for growth of Ag/AgO nanoparticles (NPs) in large quantitative yields with narrow size distribution from a functional, non-activated, Ni (II) based highly flexible porous coordination polymer (PCP) as a template has been demonstrated. This template is a stable storage media for the NPs larger than the pore diameters of the PCP. From EPR study it was concluded that NPs were synthesized via two mechanisms i.e. acid formation and the redox activity of the framework. Size range of Ag/AgO NPs is sensitive to choice of solvent and reaction time. Direct use of Ag/AgO@Ni-PCP shows influential growth inhibition towards Escherichia coli and the pathogen Salmonella typhimurium at extremely low concentrations. The pristine template shows no cytotoxic activity, even though it contains Ni nodes in the framework.

  9. Ag/Ni Metallization Bilayer: A Functional Layer for Highly Efficient Polycrystalline SnSe Thermoelectric Modules

    NASA Astrophysics Data System (ADS)

    Park, Sang Hyun; Jin, Younghwan; Ahn, Kyunghan; Chung, In; Yoo, Chung-Yul

    2017-02-01

    The structural and electrical characteristics of Ag/Ni bilayer metallization on polycrystalline thermoelectric SnSe were investigated. Two difficulties with thermoelectric SnSe metallization were identified for Ag and Ni single layers: Sn diffusion into the Ag metallization layer and unexpected cracks in the Ni metallization layer. The proposed Ag/Ni bilayer was prepared by hot-pressing, demonstrating successful metallization on the SnSe surface without interfacial cracks or elemental penetration into the metallization layer. Structural analysis revealed that the Ni layer reacts with SnSe, forming several crystalline phases during metallization that are beneficial for reducing contact resistance. Detailed investigation of the Ni/SnSe interface layer confirms columnar Ni-Sn intermetallic phases [(Ni3Sn and Ni3Sn2) and Ni5.63SnSe2] that suppress Sn diffusion into the Ag layer. Electrical specific-contact resistivity (5.32 × 10-4 Ω cm2) of the Ag/Ni bilayer requires further modification for development of high-efficiency polycrystalline SnSe thermoelectric modules.

  10. BRAZING OF POROUS ALUMINA TO MONOLITHIC ALUMINA WITH Ag-CuO and Ag-V2O5 ALLOYS

    SciTech Connect

    Lamb, M. C.; Camardello, Sam J.; Meier, Alan; Weil, K. Scott; Hardy, John S.

    2005-01-31

    The feasibility of joining porous alumina (Al{sub 2}O{sub 3}) bodies to monolithic Al{sub 2}O{sub 3} using Ag-CuO and Ag-V{sub 2}O{sub 5} alloys via reactive air brazing (RAB) was examined for a nanoporous filter application. Brazing for these systems is complicated by the conflicting requirements of satisfactory wetting to fill the braze gap, while minimizing the infiltration of the porous body. By varying the firing time, temperature, and initial powder size, porous bodies with a range of pore microstructures were fabricated. The wettability was evaluated via sessile drop testing on monolithic substrates and porous body infiltration. Porous Al{sub 2}O{sub 3}/monolithic Al{sub 2}O{sub 3} brazed samples were fabricated, and the microstructures were evaluated. Both systems exhibited satisfactory wetting for brazing, but two unique types of brazing behavior were observed. In the Ag-CuO system, the braze alloy infiltrated a short distance into the porous body. For these systems, the microstructures indicated satisfactory filling of the brazed gap and a sound joint regardless of the processing conditions. The Ag-V{sub 2}O{sub 5} alloys brazed joints exhibited a strong dependence on the amount of V{sub 2}O{sub 5} available. For Ag-V{sub 2}O{sub 5} alloys with large V{sub 2}O{sub 5} additions, the braze alloy aggressively infiltrated the porous body and significantly depleted the Ag from the braze region resulting in poor bonding and large gaps within the joint. With small additions of V{sub 2}O{sub 5}, the Ag infiltrated the porous body until the V{sub 2}O{sub 5} was exhausted and the Ag remaining at the braze interlayer bonded with the Al{sub 2}O{sub 3}. Based on these results, the Ag-CuO alloys have the best potential for brazing porous Al{sub 2}O{sub 3} to monolithic Al{sub 2}O{sub 3}.

  11. Studies on polishing of Ti and Ag-Pd-Cu-Au alloy with five dental abrasives.

    PubMed

    Hirata, T; Nakamura, T; Takashima, F; Maruyama, T; Taira, M; Takahashi, J

    2001-08-01

    Titanium (Ti) and Ag-Pd-Cu-Au alloy were examined for their polishing behaviour by conducting manually controlled polishing tests using five dental abrasives [carborundum point (CR) and silicone points (R1 and R2)] driven by a high torque micromotor with rotational speeds ranging from 2000 to 15 000 r.p.m. Polishing of Ti resulted in less volume of removal upon polishing, a rougher surface and larger loss of abrasives, compared with polishing of Ag-Pd-Cu-Au alloy. Polishing of Ti with a rotational speed of 15 000 r.p.m. led to the largest volume of removal upon polishing, whilst that of 10 000 r.p.m. produced the optimal volume for Ag-Pd-Cu-Au alloy. It was concluded that Ti was much more difficult to polish, requiring special care (e.g. frequent exchange of abrasives). Development of new abrasives for polishing Ti is required.

  12. Microstructure and properties of heavily drawn Cu-Ag-Fe composites

    NASA Astrophysics Data System (ADS)

    Huang, J. S.; Yao, D. W.; Meng, L.

    2013-03-01

    Heavily drawn Cu-6 wt% Ag-2 wt% Fe, Cu-6 wt% Ag-4 wt% Fe and Cu-6 wt% Ag-6 wt% Fe were prepared by melting, homogenizing and cold drawing processes. The homogenizing treatment promotes the precipitation of secondary particles in the matrix, which results in finer and more uniform composite filaments in the drawn microstructure. With the increase of Fe content, the tensile strength increases but the electrical conductivity decreases. The strengthening of the composites and the decrease of the conductivity could be divided into two stages, which is explained by the non-homogeneous deformation model. At η = 5.6, dynamic recovery is thought to occur due to the temperature rise associated with severe deformation, leading to the sudden increase of the conductivity. A dislocation mechanism or an interface obstacle mechanism could be considered to be responsible for the strengthening and conducting behaviors.

  13. Length scale of the dendritic microstructure affecting tensile properties of Al-(Ag)-(Cu) alloys

    NASA Astrophysics Data System (ADS)

    Duarte, Roberto N.; Faria, Jonas D.; Brito, Crystopher; Veríssimo, Nathalia C.; Cheung, Noé; Garcia, Amauri

    2016-12-01

    The dependence of tensile properties on the length scale of the dendritic morphology of Al-Cu, Al-Ag and Al-Ag-Cu alloys is experimentally investigated. These alloys were directionally solidified (DS) under a wide range of cooling rates (Ṫ), permitting extensive microstructural scales to be examined. Experimental growth laws are proposed relating the primary dendritic arm spacing, λ1 to Ṫ and tensile properties to λ1. It is shown that the most significant effect of the scale of λ1 on the tensile properties is that of the ternary alloy, which is attributed to the more homogeneous distribution of the eutectic mixture for smaller λ1 and by the combined reinforcement roles of the intermetallics present in the ternary eutectic: Al2Cu and nonequilibrium Ag3Al.

  14. Microwave Spectroscopy and Structure Determination of H_2S-MI (M=Cu,Ag,Au)

    NASA Astrophysics Data System (ADS)

    Medcraft, Chris; Legon, Anthony; Walker, Nick

    2016-06-01

    A series of hydrogen sulphide-metal iodide complexes (H_2S-MI, M=Cu, Ag and Au) have been measured via chirped pulse Fourier transform microwave spectroscopy between 7.5-18 GHz. The complexes were generated in a supersonic expansion via laser ablation of the metal and decomposition of CF_3I. Experimental structures were obtained by least squares fitting of structural parameters to the rotational constants of deuterium and metal (63Cu / 65Cu and 107Ag / 109Ag) isotopologues. Interestingly K-1=1 transitions were observed in the spectra containing D_2S, these were not observed in previous studies of similar molecules (H_2S-MCl). This allowed for the determination of an extra rotational constant and, consequently, extra structural information could be obtained. The structures are compared to high level coupled cluster theory calculations.

  15. Electromigration Behaviors of Cu Reinforced Sn-3.5Ag Composite Solder Joints

    NASA Astrophysics Data System (ADS)

    Wang, Yan; Han, Jing; Ma, Limin; Zuo, Yong; Guo, Fu

    2016-12-01

    The composite approach, by incorporating small amounts of reinforcement particles in the solder matrix, has proven to be one of the effective ways to improve the reliability of solder joints. The effects of Cu addition on electromigration were investigated in this study by incorporating 2% volume fraction Cu particles into Sn-3.5Ag eutectic solder paste by the in situ process. The one-dimensional solder joints, designed to prevent the current crowding effect, were stressed under a constant current density of 104 A/cm2 at room temperature, and the temperature of the sample could reach 105 ± 5°C due to the Joule heating effect. Doping 2 vol.% Cu was found to retard the electromigration phenomenon effectively. After electric current stressing for 528 h, the growth rate of an interfacial intermetallic compound (IMC) layer at the anode decreased 73% in contrast to that of Sn-3.5Ag solder joints, and the IMC layer at the cathode was almost unchanged. The polarization effect of Cu reinforced composite solder joints was also apparently mitigated. In addition, the surface damage of the composite solder joints was relieved by incorporating 2 vol.% Cu particles. Compared to Sn-3.5Ag solder joints, which had protruded Cu6Sn5 and wrinkles of Sn-solder matrix on the surface, the solder joints with Cu addition had a more even surface.

  16. On the evolution of Cu-Ni-rich bridges of Alnico alloys with tempering

    NASA Astrophysics Data System (ADS)

    Fan, M.; Liu, Y.; Jha, Rajesh; Dulikravich, George S.; Schwartz, J.; Koch, C. C.

    2016-12-01

    Tempering is a critical step in Alnico alloy processing, yet the effects of tempering on microstructure have not been well studied. Here we report these effects, and in particular the effects on the Cu-Ni bridges. Energy-dispersive X-ray spectroscopy (EDS) maps and line scans show that tempering changes the elemental distribution in the Cu-Ni bridges, but not the morphology and distribution of Cu-bridges. The Cu concentration in the Cu-Ni bridges increases after tempering while other element concentrations decrease, especially Ni and Al. Furthermore, tempering sharpens the Cu bridge boundaries. These effects are primarily related to the large 2C44/(C11-C12) ratio for Cu, largest of all elements in Alnico. In addition, the Ni-Cu loops around the α1 phases become inconspicuous with tempering. The diffusion of Fe and Co to the α1 phase during tempering, which increases the difference of saturation magnetization between the α1 and α2 phases, is observed by EDS. In summary, α1, α2 and Cu-bridges are concentrated with their major elements during tempering which improves the magnetic properties. The formation of these features formed through elemental diffusion is discussed via energy theories.

  17. Structural evolution in Ti-Cu-Ni metallic glasses during heating

    SciTech Connect

    Gargarella, P.; Pauly, S.; Stoica, M.; Kühn, U.; Vaughan, G.; Afonso, C. R. M.; Eckert, J.

    2015-01-01

    The structural evolution of Ti{sub 50}Cu{sub 43}Ni{sub 7} and Ti{sub 55}Cu{sub 35}Ni{sub 10} metallic glasses during heating was investigated by in-situ synchrotron X-ray diffraction. The width of the most intense diffraction maximum of the glassy phase decreases slightly during relaxation below the glass transition temperature. Significant structural changes only occur above the glass transition manifesting in a change in the respective peak positions. At even higher temperatures, nanocrystals of the shape memory B2-Ti(Cu,Ni) phase precipitate, and their small size hampers the occurrence of a martensitic transformation.

  18. A 3D porous Ni-Cu alloy film for high-performance hydrazine electrooxidation

    NASA Astrophysics Data System (ADS)

    Sun, Ming; Lu, Zhiyi; Luo, Liang; Chang, Zheng; Sun, Xiaoming

    2016-01-01

    Structural design and catalyst screening are two most important factors for achieving exceptional electrocatalytic performance. Herein we demonstrate that constructing a three-dimensional (3D) porous Ni-Cu alloy film is greatly beneficial for improving the hydrazine oxidation reaction (HzOR) performance. A facile electrodeposition process is employed to synthesize a Ni-Cu alloy film with a 3D hierarchical porous structure. As an integrated electrode for HzOR, the Ni-Cu alloy film exhibits superior catalytic activity and stability to the Ni or Cu counterparts. The synthesis parameters are also systematically tuned for optimizing the HzOR performance. The excellent HzOR performance of the Ni-Cu alloy film is attributed to its high intrinsic activity, large electrochemical specific surface area, and 3D porous architecture which offers a ``superaerophobic'' surface to effectively remove the gas product in a small volume. It is believed that the Ni-Cu alloy film electrode has potential application in direct hydrazine fuel cells as well as other catalytic fields.Structural design and catalyst screening are two most important factors for achieving exceptional electrocatalytic performance. Herein we demonstrate that constructing a three-dimensional (3D) porous Ni-Cu alloy film is greatly beneficial for improving the hydrazine oxidation reaction (HzOR) performance. A facile electrodeposition process is employed to synthesize a Ni-Cu alloy film with a 3D hierarchical porous structure. As an integrated electrode for HzOR, the Ni-Cu alloy film exhibits superior catalytic activity and stability to the Ni or Cu counterparts. The synthesis parameters are also systematically tuned for optimizing the HzOR performance. The excellent HzOR performance of the Ni-Cu alloy film is attributed to its high intrinsic activity, large electrochemical specific surface area, and 3D porous architecture which offers a ``superaerophobic'' surface to effectively remove the gas product in a small

  19. Interface stress development in the Cu/Ag nanostructured multilayered film during the tensile deformation

    SciTech Connect

    Su, R.; Nie, Z. H.; Zhang, Q. H.; Li, X. J.; Li, L. E-mail: ydwang@mail.neu.edu.cn; Zhou, X. T.; Wang, Y. D. E-mail: ydwang@mail.neu.edu.cn; Wu, Y. D.; Hui, X. D.; Wang, M. G.

    2014-12-01

    Cu/Ag nanostructured multilayered films (NMFs) with different stacking sequences were investigated by synchrotron X-ray diffraction during the tensile deformations for interface stress study. The lattice strains were carefully traced and the stress partition, which usually occurs in the multiphase bulk metallic materials during plastic deformations, was first quantitatively analyzed in the NMFs here. The interface stress of the Cu/Ag NMFs was carefully analyzed during the tensile deformation and the results revealed that the interface stress was along the loading direction and exhibited three-stage evolution. This tensile interface stress has a detrimental effect on the deformation, leading to the early fracture of the NMFs.

  20. Effect of Cu addition on the martensitic transformation of powder metallurgy processed Ti–Ni alloys

    SciTech Connect

    Kim, Yeon-wook; Choi, Eunsoo

    2014-10-15

    Highlights: • M{sub s} of Ti{sub 50}Ni{sub 50} powders is 22 °C, while M{sub s} of SPS-sintered porous bulk increases up to 50 °C. • M{sub s} of Ti{sub 50}Ni{sub 40}Cu{sub 20} porous bulk is only 2 °C higher than that of the powders. • Recovered stain of porous TiNi and TiNiCu alloy is more than 1.5%. - Abstract: Ti{sub 50}Ni{sub 50} and Ti{sub 50}Ni{sub 30}Cu{sub 20} powders were prepared by gas atomization and their transformation behaviors were examined by means of differential scanning calorimetry and X-ray diffraction. One-step B2–B19’ transformation occurred in Ti{sub 50}Ni{sub 50} powders, while Ti{sub 50}Ni{sub 30}Cu{sub 20} powders showed B2–B19 transformation behavior. Porous bulks with 24% porosity were fabricated by spark plasma sintering. The martensitic transformation start temperature (50 °C) of Ti{sub 50}Ni{sub 50} porous bulk is much higher than that (22 °C) of the as-solidified powders. However, the martensitic transformation start temperature (35 °C) of Ti{sub 50}Ni{sub 30}Cu{sub 20} porous bulk is almost the same as that (33 °C) of the powders. When the specimens were compressed to the strain of 8% and then unloaded, the residual strains of Ti{sub 50}Ni{sub 50} and Ti{sub 50}Ni{sub 30}Cu{sub 20} alloy bulks were 3.95 and 3.7%, respectively. However, these residual strains were recovered up to 1.7% after heating by the shape memory phenomenon.

  1. Interfacial Microstructure Evolution and Shear Behavior of Au-Sn/Ni- xCu Joints at 350°C

    NASA Astrophysics Data System (ADS)

    Peng, J.; Wang, R. C.; Wang, M.; Liu, H. S.

    2017-04-01

    Interfacial reaction and shear behavior of the joints between Au-29Sn (at.%) solder and Ni- xCu ( x = 20 at.%, 40 at.%, 60 at.%, and 80 at.%) substrate alloys soldered at 350°C for various durations were investigated in this study. The results show that α(Au) is the common reaction product at the solder/substrate interfaces after a short-time reaction regardless of Cu content. As soldering goes on, another new Ni3Sn2 layer forms at the interface company with ordering of the α(Au) phase, AuCu I/Ni3Sn2 bi-layers formed at the Au-Sn/Ni-20Cu interface, or with AuCu III/Ni3Sn2 bi-layers at the Au-Sn/Ni-40Cu interface. If the content of Cu in the substrate is higher than 40 at.%, periodic layered structure and discontinuous Ni3Sn2 layers appear. In the couple of Au-Sn/Ni-60Cu, AuCu I + AuCu III/Ni3Sn2/α(Au) can be observed while AuCu3/Ni3Sn2/α(Au) forms in the couple of Au-Sn/Ni-80Cu. Shear fracture always occurs in the region near the Ni-20Cu substrate in Au-Sn/Ni-20Cu joints, whereas it appears in the reaction layer for the joint of higher Cu content. The shear strength of Au-Sn/Ni-60Cu and Au-Sn/Ni-80Cu joints achieves about 55 MPa as α(Au) phase forms but decreases remarkably due to pore formation after soldering for a long duration. Whereas, the shear strength of Au-Sn/Ni-40Cu joints can reach 62 MPa as the α(Au) phase forms at an early stage, and maintains above 52 MPa even soldered for a long duration because of the adequate thick α(Au) and AuCu III layer adjacent to substrate provides good bonding. The reason why the soldering joint of Au-Sn/Ni-40Cu possesses higher strength and a better stability exists is that high Ni concentration in α(Au) and the continuous Ni3Sn2 layer inhibit formation of Kirkendall pores.

  2. CuNi Nanoparticles Assembled on Graphene for Catalytic Methanolysis of Ammonia Borane and Hydrogenation of Nitro/Nitrile Compounds

    DOE PAGES

    Yu, Chao; Fu, Jiaju; Muzzio, Michelle; ...

    2017-01-12

    Here we report a solution phase synthesis of 16 nm CuNi nanoparticles (NPs) with the Cu/Ni composition control. These NPs are assembled on graphene (G) and show Cu/Ni composition-dependent catalysis for methanolysis of ammonia borane (AB) and hydrogenation of aromatic nitro (nitrile) compounds to primary amines in methanol at room temperature. Among five different CuNi NPs studied, the G-Cu36Ni64 NPs are the best catalyst for both AB methanolysis (TOF = 49.1 molH2 molCuNi-1 min-1 and Ea = 24.4 kJ/mol) and hydrogenation reactions (conversion yield >97%). In conclusion, the G-CuNi represents a unique noble-metal-free catalyst for hydrogenation reactions in a greenmore » environment without using pure hydrogen.« less

  3. Global optimization and oxygen dissociation on polyicosahedral Ag32Cu6 core-shell cluster for alkaline fuel cells

    PubMed Central

    Zhang, N.; Chen, F. Y.; Wu, X.Q.

    2015-01-01

    The structure of 38 atoms Ag-Cu cluster is studied by using a combination of a genetic algorithm global optimization technique and density functional theory (DFT) calculations. It is demonstrated that the truncated octahedral (TO) Ag32Cu6 core-shell cluster is less stable than the polyicosahedral (pIh) Ag32Cu6 core-shell cluster from the atomistic models and the DFT calculation shows an agreeable result, so the newfound pIh Ag32Cu6 core-shell cluster is further investigated for potential application for O2 dissociation in oxygen reduction reaction (ORR). The activation energy barrier for the O2 dissociation on pIh Ag32Cu6 core-shell cluster is 0.715 eV, where the d-band center is −3.395 eV and the density of states at the Fermi energy level is maximal for the favorable absorption site, indicating that the catalytic activity is attributed to a maximal charge transfer between an oxygen molecule and the pIh Ag32Cu6 core-shell cluster. This work revises the earlier idea that Ag32Cu6 core-shell nanoparticles are not suitable as ORR catalysts and confirms that Ag-Cu nanoalloy is a potential candidate to substitute noble Pt-based catalyst in alkaline fuel cells. PMID:26148904

  4. Global optimization and oxygen dissociation on polyicosahedral Ag32Cu6 core-shell cluster for alkaline fuel cells.

    PubMed

    Zhang, N; Chen, F Y; Wu, X Q

    2015-07-07

    The structure of 38 atoms Ag-Cu cluster is studied by using a combination of a genetic algorithm global optimization technique and density functional theory (DFT) calculations. It is demonstrated that the truncated octahedral (TO) Ag32Cu6 core-shell cluster is less stable than the polyicosahedral (pIh) Ag32Cu6 core-shell cluster from the atomistic models and the DFT calculation shows an agreeable result, so the newfound pIh Ag32Cu6 core-shell cluster is further investigated for potential application for O2 dissociation in oxygen reduction reaction (ORR). The activation energy barrier for the O2 dissociation on pIh Ag32Cu6 core-shell cluster is 0.715 eV, where the d-band center is -3.395 eV and the density of states at the Fermi energy level is maximal for the favorable absorption site, indicating that the catalytic activity is attributed to a maximal charge transfer between an oxygen molecule and the pIh Ag32Cu6 core-shell cluster. This work revises the earlier idea that Ag32Cu6 core-shell nanoparticles are not suitable as ORR catalysts and confirms that Ag-Cu nanoalloy is a potential candidate to substitute noble Pt-based catalyst in alkaline fuel cells.

  5. Tribological properties of self-lubricating NiAl/Mo-based composites containing AgVO{sub 3} nanowires

    SciTech Connect

    Liu, Eryong; Gao, Yimin; Bai, Yaping; Yi, Gewen; Wang, Wenzhen; Zeng, Zhixiang; Jia, Junhong

    2014-11-15

    Silver vanadate (AgVO{sub 3}) nanowires were synthesized by hydrothermal method and self-lubricating NiAl/Mo-AgVO{sub 3} composites were fabricated by powder metallurgy technique. The composition and microstructure of NiAl/Mo-based composites were characterized and the tribological properties were investigated from room temperature to 900 °C. The results showed that NiAl/Mo-based composites were consisted of nanocrystalline B2 ordered NiAl matrix, Al{sub 2}O{sub 3}, Mo{sub 2}C, metallic Ag and vanadium oxide phase. The appearance of metallic Ag and vanadium oxide phase can be attributed to the decomposition of AgVO{sub 3} during sintering. Wear testing results confirmed that NiAl/Mo-based composites have excellent tribological properties over a wide temperature range. For example, the friction coefficient and wear rate of NiAl/Mo-based composites containing AgVO{sub 3} were significantly lower than the composites containing only metallic Mo or AgVO{sub 3} lubricant when the temperature is above 300 °C, which can be attributed to the synergistic lubricating action of metallic Mo and AgVO{sub 3} lubricants. Furthermore, Raman results indicated that the composition on the worn surface of NiAl-based composites was self-adjusted after wear testing at different temperatures. For example, Ag{sub 3}VO{sub 4} and Fe{sub 3}O{sub 4} lubricants were responsible for the improvement of tribological properties at 500 °C, AgVO{sub 3}, Ag{sub 3}VO{sub 4} and molybdate for 700 °C, and AgVO{sub 3} and molybdate for 900 °C of NiAl-based composites with the addition of metallic Mo and AgVO{sub 3}. - Highlights: • NiAl/Mo-AgVO{sub 3} nanocomposites were prepared by mechanical alloying and sintering. • AgVO{sub 3} decomposed to metallic Ag and vanadium oxide during the sintering process. • NiAl/Mo-AgVO{sub 3} exhibited superior tribological properties at a board temperature range. • Phase composition on the worn surface was varied with temperatures. • Self-adjusted action

  6. Hardening behavior after high-temperature solution treatment of Ag-20Pd-12Au-xCu alloys with different Cu contents for dental prosthetic restorations.

    PubMed

    Kim, Yonghwan; Niinomi, Mitsuo; Hieda, Junko; Nakai, Masaaki; Cho, Ken; Fukui, Hisao

    2014-07-01

    Ag-Pd-Au-Cu alloys have been used widely for dental prosthetic applications. Significant enhancement of the mechanical properties of the Ag-20Pd-12Au-14.5Cu alloy as a result of the precipitation of the β' phase through high-temperature solution treatment (ST), which is different from conventional aging treatment in these alloys, has been reported. The relationship between the unique hardening behavior and precipitation of the β' phase in Ag-20Pd-12Au-xCu alloys (x=6.5, 13, 14.5, 17, and 20mass%) subjected to the high-temperature ST at 1123K for 3.6ks was investigated in this study. Unique hardening behavior after the high-temperature ST also occurs in Ag-20Pd-12Au-xCu alloys (x=13, 17, and 20) with precipitation of the β' phase. However, hardening is not observed and the β' phase does not precipitate in the Ag-20Pd-12Au-6.5Cu alloy after the same ST. The tensile strength and 0.2% proof stress also increase in Ag-20Pd-12Au-xCu alloys (x=13, 14.5, 17, and 20) after the high-temperature ST. In addition, these values after the high-temperature ST increase with increasing Cu content in Ag-20Pd-12Au-xCu alloys (x=14.5, 17, and 20). The formation process of the β' phase can be explained in terms of diffusion of Ag and Cu atoms and precipitation of the β' phase. Clarification of the relationship between hardening and precipitation of the β' phase via high-temperature ST is expected to help the development of more effective heat treatments for hardening in Ag-20Pd-12Au-xCu alloys.

  7. Strength of Cu-28 wt%Ag composite solidified under high magnetic field followed by cold drawing

    NASA Astrophysics Data System (ADS)

    Zhao, Congcong; Zuo, Xiaowei; Wang, Engang; Han, Ke

    2017-03-01

    Cu-Ag composite is one of the best conductors for high-field magnets. Increasing its strength is crucial for designing newer high-field magnets. Cu-28 wt%Ag samples were solidified with and without a 12-T high magnetic field (HMF), and then cold-drawn. We investigated the influence of HMF on microstructure, hardness and strength of Cu-Ag samples both before and after cold-drawing. The introduction of external HMF during solidification increased both the dendrite arm spacing and the dissolved Ag in Cu, and it reduced the spacing between both the Ag precipitates in proeutectic Cu and the eutectic lamellae. The transversal microstructure after cold-drawing inherited the network solidification structure, but at a refined scale. The Cu dendrite spacing in the 12-T HMF samples at all deformation strain was larger than that without HMF. HMF slightly increased the intensity of <111> fiber texture of Cu, which strengthened proeutectic Cu at the level of 3.5 deformation strain. In samples deformed to strain of 3.5, refined Ag precipitation spacing, increased Ag solubility in Cu matrix, and refined eutectic lamellar spacing by 12-T HMF increased the strength by 5% in the sample compared with that without HMF.

  8. Sensitive and selective detection of Hg2+ and Cu2+ ions by fluorescent Ag nanoclusters synthesized via a hydrothermal method

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Ren, Xiangling; Meng, Xianwei; Fang, Zheng; Tang, Fangqiong

    2013-09-01

    An easily prepared fluorescent Ag nanoclusters (Ag NCs) probe for the sensitive and selective detection of Hg2+ and Cu2+ ions was developed here. The Ag NCs were synthesized by using polymethacrylic acid sodium salt as a template via a convenient hydrothermal process. The as-prepared fluorescent Ag NCs were monodispersed, uniform and less than 2 nm in diameter, and can be quenched in the presence of mercury (Hg2+) or copper (Cu2+) ions. Excellent linear relationships existed between the quenching degree of the Ag NCs and the concentrations of Hg2+ or Cu2+ ions in the range of 10 nM to 20 μM or 10 nM to 30 μM, respectively. By using ethylenediaminetetraacetate (EDTA) as the masking agent of Cu2+, Hg2+ was exclusively detected in coexistence with Cu2+ with high sensitivity (LOD = 10 nM), which also provided a reusable detection method for Cu2+. Furthermore, the different quenching phenomena caused by the two metals ions such as changes in visible colour, shifts of UV absorbance peaks and changes in size of Ag NCs make it easy to distinguish between them. Therefore the easily synthesized fluorescent Ag NCs may have great potential as Hg2+ and Cu2+ ions sensors.An easily prepared fluorescent Ag nanoclusters (Ag NCs) probe for the sensitive and selective detection of Hg2+ and Cu2+ ions was developed here. The Ag NCs were synthesized by using polymethacrylic acid sodium salt as a template via a convenient hydrothermal process. The as-prepared fluorescent Ag NCs were monodispersed, uniform and less than 2 nm in diameter, and can be quenched in the presence of mercury (Hg2+) or copper (Cu2+) ions. Excellent linear relationships existed between the quenching degree of the Ag NCs and the concentrations of Hg2+ or Cu2+ ions in the range of 10 nM to 20 μM or 10 nM to 30 μM, respectively. By using ethylenediaminetetraacetate (EDTA) as the masking agent of Cu2+, Hg2+ was exclusively detected in coexistence with Cu2+ with high sensitivity (LOD = 10 nM), which also provided a

  9. The coupled effect of grain size and solute on work hardening of Cu-Ni alloys

    NASA Astrophysics Data System (ADS)

    Shadkam, A.; Sinclair, C. W.

    2015-12-01

    A modified grain size-dependent model developed to capture the combined effects of solute and grain size on the work hardening behaviour of fine-grained Cu-Ni alloys is provided. This work builds on a recent model that attributes the grain size-dependent work hardening of fine-grained Cu to backstresses. In the case of Cu-Ni alloys, unlike commercially pure Cu, a grain size-dependent separation between the Kocks-Mecking curves develops, this being explained here based on an extra contribution from geometrically necessary dislocations in the solid solution alloy. This is corroborated by strain-rate sensitivity experiments.

  10. Effects on Undercooling and Interfacial Reactions with Cu Substrates of Adding Bi and In to Sn-3Ag Solder

    NASA Astrophysics Data System (ADS)

    Chiang, Yu-Yan; Cheng, Robbin; Wu, Albert T.

    2010-11-01

    This study investigated the effects of adding Bi and In to Sn-3Ag Pb-free solder on undercooling, interfacial reactions with Cu substrates, and the growth kinetics of intermetallic compounds (IMCs). The amount of Sn dominates the undercooling, regardless of the amount or species of further additives. The interfacial IMC that formed in Sn-Ag-Bi-In and Sn-In-Bi solders is Cu6Sn5, while that in Sn-Ag-In solders is Cu6(Sn,In)5, since Bi enhances the solubility of In in Sn matrices. The activation energy for the growth of IMCs in Sn-Ag-Bi-In is nearly double that in Sn-Ag-In solders, because Bi in the solder promotes Cu dissolution. The bright particles that form inside the Sn-Ag-In bulk solders are the ζ-phase.

  11. Preparation of Cu-Ni/YSZ solid oxide fuel cell anodes using microwave irradiation

    NASA Astrophysics Data System (ADS)

    Islam, Shamiul; Hill, Josephine M.

    A microwave irradiation process is used to deposit Cu nanoparticles on the Ni/YSZ anode of an electrolyte-supported solid oxide fuel cell (SOFC). The reaction time in the microwave is only 15 s for the deposition of 6 wt% Cu (with respect to Ni) from a solution of Cu(NO 3) 2·3H 2O and ethylene glycol (HOCH 2CH 2OH). The morphology of the deposited Cu particles is spherical and the average size of the particles is less than 100 nm. The electrochemical performance of the microwave Cu-coated Ni/YSZ anodes is tested in dry H 2 and dry CH 4 at 1073 K, and the anodes are characterized with scanning electron microscopy, electrochemical impedance spectroscopy, and temperature-programmed oxidation. The results indicate that preparation of the anodes by the microwave technique produces similar performance trend as those reported for Cu-Ni/YSZ/CeO 2 anodes prepared by impregnation. Specifically, less carbon is formed on the Cu-Ni/YSZ than on conventional Ni/YSZ anodes when exposed to dry methane and the carbon that does form is more reactive.

  12. Preparation, characterization, and antibacterial activity of NiFe2O4/PAMA/Ag-TiO2 nanocomposite

    NASA Astrophysics Data System (ADS)

    Allafchian, Alireza; Jalali, Seyed Amir Hossein; Bahramian, Hamid; Ahmadvand, Hossein

    2016-04-01

    We have described a facile fabrication of silver deposited on the TiO2, Poly Acrylonitrile Co Maleic Anhydride (PAMA) polymer and nickel ferrite composite (NiFe2O4/PAMA/Ag-TiO2) through a three-step procedure. A pre-synthesized NiFe2O4 was first coated with PAMA polymer and then Ag-TiO2 was deposited on the surface of PAMA polymer shell. After the characterization of this three-component composite by various techniques, such as FTIR, XRD, FESEM, BET, TEM and VSM, it was impregnated in standard antibiotic discs. The antibacterial activity of NiFe2O4/PAMA/Ag-TiO2 nanocomposite was investigated against some gram positive and gram negative bacteria by employing disc diffusion assay and then compared with that of naked NiFe2O4, NiFe2O4/Ag, AgNPs and NiFe2O4/PAMA. The results demonstrated that the AgNPs, when embedded in TiO2 and combined with NiFe2O4/PAMA, became an excellent antibacterial agent. The NiFe2O4/PAMA/Ag-TiO2 nanocomposite could be readily separated from water solution after the disinfection process by applying an external magnetic field.

  13. Electroless deposition of NiCrB diffusion barrier layer film for ULSI-Cu metallization

    NASA Astrophysics Data System (ADS)

    Wang, Yuechun; Chen, Xiuhua; Ma, Wenhui; Shang, Yudong; Lei, Zhengtao; Xiang, Fuwei

    2017-02-01

    NiCrB films were deposited on Si substrates using electroless deposition as a diffusion barrier layer for Cu interconnections. Samples of the prepared NiCrB/SiO2/Si and NiCrB/Cu/NiCrB/SiO2/Si were annealed at temperatures ranging from 500 °C to 900 °C. The reaction mechanism of the electroless deposition of the NiCrB film, the failure temperature and the failure mechanism of the NiCrB diffusion barrier layer were investigated. The prepared samples were subjected to XRD, XPS, FPP and AFM to determine the phases, composition, sheet resistance and surface morphology of samples before and after annealing. The results of these analyses indicated that the failure temperature of the NiCrB barrier film was 900 °C and the failure mechanism led to crystallization and grain growth of the NiCrB barrier layer after high temperature annealing. It was found that this process caused Cu grains to reach Si substrate through the grain boundaries, and then the reaction between Cu and Si resulted in the formation of highly resistive Cu3Si.

  14. Effect of 0.5 wt % Cu addition in Sn-3.5%Ag solder on the dissolution rate of Cu metallization

    NASA Astrophysics Data System (ADS)

    Alam, M. O.; Chan, Y. C.; Tu, K. N.

    2003-12-01

    The dissolution of thin film under-bump-metallization (UBM) by molten solder has been one of the most serious processing problems in electronic packaging technology. Due to a higher melting temperature and a greater Sn content, a molten lead-free solder such as eutectic SnAg has a faster dissolution rate of thin film UBM than the eutectic SnPb. The work presented in this paper focuses on the role of 0.5 wt % Cu in the base Sn-3.5%Ag solder to reduce the dissolution of the Cu bond pad in ball grid array applications. We found that after 0.5 wt % Cu addition, the rate of dissolution of Cu in the molten Sn-3.5%Ag solder slows down dramatically. Systematic experimental work was carried out to understand the dissolution behavior of Cu by the molten Sn-3.5%Ag and Sn-3.5%Ag-0.5%Cu solders at 230-250 °C, for different time periods ranging from 1 to 10 min. From the curves of consumed Cu thickness, it was concluded that 0.5 wt % Cu addition actually reduces the concentration gradient at the Cu metallization/molten solder interface which reduces the driving force of dissolution. During the dissolution, excess Cu was found to precipitate out due to heterogeneous nucleation and growth of Cu6Sn5 at the solder melt/oxide interface. In turn, more Cu can be dissolved again. This process continues with time and leads to more dissolution of Cu from the bond pad than the amount expected from the solubility limit, but it occurs at a slower rate for the molten Sn-3.5%Ag-0.5%Cu solder.

  15. First principles investigation of the diffusion of interstitial Cu, Ag and Au in ZnTe

    NASA Astrophysics Data System (ADS)

    Chen, Li An; Zhu, Xing Feng; Chen, Ling Fu

    2015-07-01

    The diffusion is of great significance in many applications when the impurities are employed to tune the semiconductor's electrical or optical properties. It is necessary to understand how dopant defects diffuse in semiconductors. Using first-principles calculations, we consider interstitial diffusion mechanisms and calculate the migration barrier energies of interstitial Cu, Ag and Au atoms in II-VI compounds ZnTe. We find that the relative size of dopant and bulk atoms is an important factor which affects the diffusion behavior. The high symmetry Tc site, which is tetrahedrally coordinated by four cation atoms, is the global minimum energy location for Ag and Au interstitials. The size of Cu adatom is small, so Cu is more stable when it locates at the Ta site which is tetrahedrally coordinated by four anion atoms. But the global minimum energy location for Cu interstitials is M site which is of smaller space than Ta. Cu adatoms show an asymmetric curve of energy diffusion barrier with two energetically distinct extremum in the pathway. Ag diffuses along nearly straight line paths along [111] or equivalent directions. Diffusion for Cu or Au deviates from the straight line paths along <111> avoiding high symmetric sites.

  16. Lack of dependence between intrinsic magnetic damping and perpendicular magnetic anisotropy in Cu(tCu)/[Ni/Co]N multilayers

    NASA Astrophysics Data System (ADS)

    Tang, Minghong; Li, Wei; Ren, Yang; Zhang, Zongzhi; Jin, Q. Y.

    2017-04-01

    The correlation between magnetic damping and perpendicular magnetic anisotropy has been investigated in Cu(tCu)/[Ni/Co]N multilayers by time-resolved magneto-optical Kerr effect. The uniaxial magnetic anisotropy constant Ku is varied in the range of 3.0-3.6 Merg/cm3 by tuning either multilayer repetition number N or Cu thickness tCu. It is found that the PMA strength Ku increases with the increase of N, while the damping constant α0 keeps nearly a constant of 0.025, implying the intrinsic damping is independent of the Ku tuned by N. In contrast, as tCu increases from 2.5 to 20 nm, the α0 value rises continuously up to 0.040, in spite of the rather weak enhancement in Ku and its non-monotonic variation behavior. We consider the constant α0 with N is due to the unchanged spin-orbit coupling strength at each Co/Ni interface, while the obvious enhancement in α0 with tCu results mainly from the increased degree of spin disordering at the rougher Cu/Ni interface.

  17. Molecular Dynamics Simulation of the Phonon Conductivity in Cu-Ni Binary Alloy

    NASA Astrophysics Data System (ADS)

    Konishi, Yusuke; Fukushima, Tetsuya; Sato, Kazunori; Asai, Yoshihiro; Katayama-Yoshida, Hiroshi

    2014-03-01

    In 2010, a giant Peltier effect was observed in a Cu-Ni/Au junction. It is considered that this giant Peltier effect is caused by nano-scale phase separation formed in the sputtering process. The giant Peltier coefficient in the Cu-Ni/Au junction indicates the great Seebeck coefficient in Cu-Ni alloy. Although this alloy is a prospective thermoelectric material because of its great Seebeck coefficient, the low phonon thermal conductivity is also necessary for a large thermoelectric coefficient ZT. In order to find conditions for the low phonon conductivity, we calculate the thermal conductivity in Cu-Ni Alloy in various shapes with or without nanostructures by using nonequilibrium molecular dynamics simulation. In this simulation, we use a semi-empirical potential and the reverse nonequilibrium molecular dynamics method.

  18. Optimization of conductivity and strength in Cu-Ni-Si alloys by suppressing discontinuous precipitation

    NASA Astrophysics Data System (ADS)

    Han, Seung Zeon; Lee, Jehyun; Lim, Sung Hwan; Ahn, Jee Hyuk; Kim, Kwangho; Kim, Sangshik

    2016-11-01

    Cu-Ni-Si alloys with and without Ti were solution treated at 980 °C for 1 h and cooled by air cooling and water quenching, after which the specimens were aged at 500 °C. The two alloys showed different aging characteristics with different cooling rates during the aging process. The conductivity of all alloys increased during aging; for alloys that were water quenched, hardness increased at the early stage of aging and then drastically decreased. The air-cooled Cu-Ni-Si alloy without Ti also experienced an increase in hardness, which then decreased during aging, but the air-cooled Cu-Ni-Si alloy with Ti did not show a drastic decrease in hardness during prolonged aging. A combination of yield strength and conductivity of 820 MPa and 42% IACS, respectively, was achieved in the air-cooled Cu-Ni-Si-Ti alloy after solution treatment.

  19. Orbital degeneracy removed by charge order in triangular antiferromagnet AgNiO2.

    PubMed

    Wawrzyńska, E; Coldea, R; Wheeler, E M; Mazin, I I; Johannes, M D; Sörgel, T; Jansen, M; Ibberson, R M; Radaelli, P G

    2007-10-12

    We report a high-resolution neutron diffraction study on the orbitally degenerate spin-1/2 hexagonal metallic antiferromagnet AgNiO2. A structural transition to a tripled unit cell with expanded and contracted NiO6 octahedra indicates sqrt[3]xsqrt[3] charge order on the Ni triangular lattice. This suggests charge order as a possible mechanism of lifting the orbital degeneracy in the presence of charge fluctuations, as an alternative to the more usual Jahn-Teller distortions. A novel magnetic ground state is observed at low temperatures with the electron-rich S=1 Ni sites arranged in alternating ferromagnetic rows on a triangular lattice, surrounded by a honeycomb network of nonmagnetic and metallic Ni ions. We also report first-principles band-structure calculations that explain microscopically the origin of these phenomena.

  20. Cast-Replicated NiTiCu Foams with Superelastic Properties

    NASA Astrophysics Data System (ADS)

    Young, Marcus L.; DeFouw, John D.; Frenzel, Jan; Dunand, David C.

    2012-08-01

    Ni40Ti50Cu10 foams were replication cast into a porous SrF2 preform. This space holder is chemically stable in contact with liquid and solid Ni40Ti50Cu10, but can be removed by dissolution in nitric acid. A Ni40Ti50Cu10 foam with 60 pct porosity exhibits low stiffness (1 to 13 GPa) and large recoverable strains (~4 pct) during cyclical compression testing at 311 K (38 °C), within the superelastic range based on calorimetry results. This is the first time that replication casting is used to create an open foam of a NiTi-based shape-memory alloy, due to difficulties associated with the high reactivity and strong contamination tendency of the melt. Casting NiTi-based shape-memory alloy foams enable the economical production of porous actuators, energy absorbers, and biomedical implants with complex shapes.

  1. Calculation and measurement of helium generation and solid transmutations in Cu-Zn-Ni alloys

    SciTech Connect

    Greenwood, L.R.; Oliver, B.M.; Garner, F.A.; Muroga, T.

    1998-03-01

    A method was recently proposed by Garner and Greenwood that would allow the separation of the effects of solid and gaseous transmutation for Cu-Zn-Ni alloys. Pure copper produces zinc and nickel during neutron irradiation. {sup 63}Cu transmutes to {sup 64}Ni and {sup 64}Zn, in about a 2-to-1 ratio, and {sup 65}Cu transmutes to {sup 66}Zn. The {sup 64}Zn further transmutes to {sup 65}Zn which has been shown to have a high thermal neutron (n,{alpha}) cross-section. Since a three-step reaction sequence is required for natural copper, the amount of helium produced is much smaller than would be produced for the two-step, well-known {sup 58}Ni (n,{gamma}) {sup 59}Ni (n,{alpha}) reaction sequence. The addition of natural Zn and Ni to copper leads to greatly increased helium production in neutron spectra with a significant thermal component. Using a suitable Cu-Zn-Ni alloy matrix and comparative irradiation of thermal neutron-shielded and unshielded specimens, it should be possible to distinguish the separate influences of the solid and gaseous transmutants. Whereas helium generation rates have been previously measured for natural nickel and copper, they have not been measured for natural Zn or Cu-Ni-Zn alloys. The (N,{alpha}) cross section for {sup 65}Zn was inferred from helium measurements made with natural copper. By comparing helium production in Cu and Cu-Zn alloys, this cross section can be determined more accurately. In the current study, both the solid and helium transmutants were measured for Cu, Cu-5Ni, Cu-3.5Zn and Cu-5Ni-2Zn, irradiated in each of two positions in the HFIR JP-23 test. Highly accurate helium measurements were performed on these materials by isotope dilution mass spectrometry using a facility that was recently moved from Rockwell International to PNNL. It is shown that both the helium and solid transmutants for Cu-zn-Ni alloys can be calculated with reasonable certainty, allowing the development of a transmutation experiment as proposed by

  2. Oxide/metal interface distance and epitaxial strain in the NiO/Ag(001) system.

    PubMed

    Lamberti, Carlo; Groppo, Elena; Prestipino, Carmelo; Casassa, Silvia; Ferrari, Anna Maria; Pisani, Cesare; Giovanardi, Chiara; Luches, Paola; Valeri, Sergio; Boscherini, Federico

    2003-07-25

    Geometric parameters of NiO films epitaxially grown on Ag(001) were determined using two independent experimental techniques and ab initio simulations. Primary beam diffraction modulated electron emission experiments determined that the NiO films grow with O on top of Ag and that the oxide/metal interface distance is d=2.3+/-0.1 A. Polarization-dependent x-ray absorption, at the Ni-K edge, determined the tetragonal strain (r( parallel )=2.046+/-0.009 A, r( perpendicular )=2.12+/-0.02 A) and d=2.37+/-0.05 A. Periodic slab model results agree with the experiments (d=2.40, r( parallel )=2.07, r( perpendicular )=2.10 A; the O-on-top configuration is the most stable).

  3. Oxide/Metal Interface Distance and Epitaxial Strain in the NiO/Ag(001) System

    NASA Astrophysics Data System (ADS)

    Lamberti, Carlo; Groppo, Elena; Prestipino, Carmelo; Casassa, Silvia; Ferrari, Anna; Pisani, Cesare; Giovanardi, Chiara; Luches, Paola; Valeri, Sergio; Boscherini, Federico

    2003-07-01

    Geometric parameters of NiO films epitaxially grown on Ag(001) were determined using two independent experimental techniques and abinitio simulations. Primary beam diffraction modulated electron emission experiments determined that the NiO films grow with O on top of Ag and that the oxide/metal interface distance is d=2.3±0.1 Å. Polarization-dependent x-ray absorption, at the Ni-K edge, determined the tetragonal strain (r∥=2.046±0.009 Å, r⊥=2.12±0.02 Å) and d=2.37±0.05 Å. Periodic slab model results agree with the experiments (d=2.40, r∥=2.07, r⊥=2.10 Å; the O-on-top configuration is the most stable).

  4. Microstructure, Melting and Wetting Properties of Pd-Ag-CuO Air Braze on Alumina

    SciTech Connect

    Darsell, Jens T.; Hardy, John S.; Kim, Jin Yong Y.; Weil, K. Scott

    2005-03-19

    A reactive air brazing (RAB) technique utilizing silver-copper oxide (Ag-CuO) alloys has previously been developed for joining ceramics components used in high temperature devices ranging from oxygen separation membranes, gas turbines and combustion engines. The application of the Ag-CuO system as a brazing material is limited by its solidus and liquidus temperatures, which are known to be in the range of 935 C and 967 C. Some joined ceramic components may be used in devices, which require further processing steps, or may be used in applications, that exceed these temperatures. It has been found that the addition of palladium to the silver copper oxide system will increase solidus and liquidus temperatures of the resulting alloy. In our work, we are studying the effects of palladium addition on the wetting properties of Ag-CuO braze system on alumina. Quality of brazing is evaluated through microstructural analysis and bending strength of brazed joints created with alumina. The presentation will include processing, and characterization of Ag-CuO brazed system with and without palladium addition on alumina.

  5. Potential energy curves for the ground and low-lying excited states of CuAg

    SciTech Connect

    Alizadeh, Davood; Shayesteh, Alireza E-mail: ashayesteh@ut.ac.ir; Jamshidi, Zahra E-mail: ashayesteh@ut.ac.ir

    2014-10-21

    The ground and low-lying excited states of heteronuclear diatomic CuAg are examined by multi-reference configuration interaction (MRCI) method. Relativistic effects were treated and probed in two steps. Scalar terms were considered using the spin-free DKH Hamiltonian as a priori and spin-orbit coupling was calculated perturbatively via the spin-orbit terms of the Breit-Pauli Hamiltonian based on MRCI wavefunctions. Potential energy curves of the spin-free states and their corresponding Ω components correlating with the separated atom limits {sup 2}S(Cu) + {sup 2}S(Ag) and {sup 2}D(Cu) + {sup 2}S(Ag) are obtained. The results are in fine agreement with the experimental measurements and tentative conclusions for the ion-pair B0{sup +} state are confirmed by our theoretical calculations. Illustrative results are presented to reveal the relative importance and magnitude of the scalar and spin-orbit effects on the spectroscopic properties of this molecule. Time dependent density functional theory calculations, using the LDA, BLYP, B3LYP, and SAOP functionals have been carried out for CuAg and the accuracy of TD-DFT has been compared with ab initio results.

  6. THE TWO-DIMENSIONAL VALENCE ELECTRONIC STRUCTURE OF A MONOLYAER OF Ag ON Cu(00l)

    SciTech Connect

    Tobin, J.G.; Robey, S.W.; Shirley, D.A.

    1985-05-01

    The metal overlayer system c(10x2)Ag/Cu(001) was studied at coverages near one monolayer with angle-resolved photoemission. The observed spectroscopic features indicate a two-dimensional d-band electronic structure that can be interpreted using a model with planar, hexagonal symmetry in which crystal field effects dominate over spin-orbit effects.

  7. Spin-Diffusion Lengths in Ag(4%Sn) and Cu(2%Ge) alloys

    NASA Astrophysics Data System (ADS)

    Sharma, Amit; Richard, Brandon; Fowler, Quinton; Loloee, Reza; Pratt, William, Jr.; Bass, Jack

    2008-03-01

    Alloying Ag with a little Sn, or Cu with a little Ge, greatly increases elastic scattering of electrons---i.e., greatly decreases the electron mean-free-path (mfp), but does not produce much spin-flipping---i.e., leaves the electron spin-diffusion length, l, relatively long. Thus, dilute AgSn and CuGe alloys were used to study effects of changing the mfp on current-perpendicular-to-plane (CPP) magnetoresistance [1] and current-induced magnetization switching (CIMS) [2], while leaving spin-flipping weak. Published transport data in dilute AgSn and CuGe alloys give only lower bounds for l [3-5]. We find l = 34 ± 4 nm for Ag(4%Sn) and l = 125 ± 10 nm for Cu(2%Ge). [1] K. Eid et al., J. Magn. Magn. Mat. 224, L205 (2001). [2] N. Theodoropoulou et al., Phys. Rev. B (rapid comm.) in press. [3] S.-F.Lee et al., J. Magn. Magn. Mat. 118, L1 (993). [4] J. Bass et al, Mat. Sci. and Eng. B31, 77 (1995). [5] J. Bass and W.P. Pratt Jr., J. Phys. Cond. Matt. 19, 183201 (2007).

  8. ZnO-(Cu/Ag)TCNQ heterostructure network over flexible platform for enhanced cold cathode application

    NASA Astrophysics Data System (ADS)

    Pal, Shreyasi; Maiti, Soumen; Narayan Maiti, Uday; Chattopadhyay, Kalyan Kumar

    2016-07-01

    Multistage field emitters consisting of organic/inorganic hybrid nanostructures with branched geometry are designed via a two-step protocol: a simple wet chemical method followed by a vapor-solid-phase technique. (Cu/Ag)TCNQ (copper/silver-7,7,8,8-tetracyanoquinodimethane) nanowires (NWs) were grown hierarchically on zinc oxide (ZnO) nanorods (NRs) to form ZnO-(Cu/Ag)TCNQ heterostructure assemblies. By monitoring the metallic Cu and Ag coating thickness on ZnO NRs, precise control over the morphology and orientations of the secondary organic NWs is achieved. In-depth analysis of electron field emission (FE) behavior of the ZnO-(Cu/Ag)TCNQ-based hierarchy suggests highest emission performance with low turn-on as well as threshold fields of 1.15 and 3.75 V μm-1 respectively from the morphology-optimized hierarchy. Beneficial orientation of the branched organic NWs ensures sequential electric field enhancement in the consecutive stem and branches whereas its low work function eases electron emission; these aspects combined together render an overall enhancement in the emission behavior of the hybrid system. As compared to individual building units, the heterostructures show improved field electron emission. Additionally, successful construction of this novel hybrid over a fabric platform displays great potential in opening up new pathways in the highly-anticipated field of flexible electronics.

  9. Metallic glass alloys of Zr, Ti, Cu and Ni

    DOEpatents

    Lin, Xianghong; Peker, Atakan; Johnson, William L.

    1997-01-01

    At least quaternary alloys form metallic glass upon cooling below the glass transition temperature at a rate less than 10.sup.3 K/s. Such alloys comprise titanium from 19 to 41 atomic percent, an early transition metal (ETM) from 4 to 21 atomic percent and copper plus a late transition metal (LTM) from 49 to 64 atomic percent. The ETM comprises zirconium and/or hafnium. The LTM comprises cobalt and/or nickel. The composition is further constrained such that the product of the copper plus LTM times the atomic proportion of LTM relative to the copper is from 2 to 14. The atomic percentage of ETM is less than 10 when the atomic percentage of titanium is as high as 41, and may be as large as 21 when the atomic percentage of titanium is as low as 24. Furthermore, when the total of copper and LTM are low, the amount of LTM present must be further limited. Another group of glass forming alloys has the formula (ETM.sub.1-x Ti.sub.x).sub.a Cu.sub.b (Ni.sub.1-y Co.sub.y).sub.c wherein x is from 0.1 to 0.3, y.cndot.c is from 0 to 18, a is from 47 to 67, b is from 8 to 42, and c is from 4 to 37. This definition of the alloys has additional constraints on the range of copper content, b.

  10. Dynamics of domain walls in Ti-Ni-Cu alloy

    NASA Astrophysics Data System (ADS)

    Liang, X. L.; Zhang, Z. F.; Liu, Q.; Shen, H. M.; Wang, Y. N.; Shi, P.; Chen, F. X.; Yang, D. Z.

    1999-12-01

    The internal friction for Ti-Ni-Cu shape memory alloys (SMAs) was measured in the Hz and kHz range. The peak temperature in the Hz range is independent of the measuring frequencies. Only in the tens of kHz range does the peak temperature shift with the frequencies, showing a thermally activated progress with icons/Journals/Common/tau" ALT="tau" ALIGN="TOP"/> = icons/Journals/Common/tau" ALT="tau" ALIGN="TOP"/>0e-B/Tc - T, characteristic of viscous motion of domain walls, instead of the Arrhenius relation. Taking into account the change of the density of the domain walls during the phase transformation, we modified the Q-1-formula by using a model of viscous motion of domain walls, obtaining a good result in agreement with the experimental data. Additionally, corresponding parameters, which play a key role in the shape memory effect, such as the viscosity coefficient and the effective pinning force constant, were obtained.

  11. Physically synthesized Ni-Cu nanoparticles for magnetic hyperthermia

    PubMed Central

    Bettge, Martin; Chatterjee, Jhunu; Haik, Yousef

    2004-01-01

    Background In this paper, a physical method to prepare copper-nickel alloy particles in the sub-micron range for possible self controlled magnetic hyperthermia treatment of cancer is described. It is reported that an increase in tumor temperature decreases the tumor resistance to chemo- and radiation therapies. Self controlled heating at the tumor site to avoid spot heating is managed by controlling the Curie temperature of the magnetic particles. The process described in this paper to produce the nanomagnetic particles allows for a large scale production of these particles. Methods The process used here is mainly composed of melting of the Cu-Ni mixture and ball milling of the resulted bulk alloy. Both mechanical abrasion and continuous grinding were used to break down the bulk amount into the desired particle size. Results It was found that the desired alloy is composed of 71% nickel and 29% copper by weight. It was observed that the coarse sand-grinded powder has a Curie temperature of 345 K and the fine ball-milled powder shows a temperature of 319 K – 320 K. Conclusion Self regulating magnetic hyperthermia can be achieved by synthesizing nanomagnetic particles with desired Curie temperature. In this study the desired range of Curie temperatures was obtained by combination of melting and ball milling of nickel-copper alloy. PMID:15132747

  12. [Corrosion of Ag-Pd-Cu alloys in saline solution. Amount of released elements and electrochemical corrosion].

    PubMed

    Kitaoka, M

    1989-03-01

    The effect of the Pd content on corrosion and tarnish resistance in twelve experimental alloys was investigated. The alloys were prepared with a composition of Pd content from 20.1 to 30.1 at %. The composition of the alloys Ag-20% Pd, Ag-25% Pd and Ag-30% Pd was varied by adding Cu 5 wt%, 10 wt% and 15 wt% to each of them. The corrosion resistance was estimated by the amount of the released Ag, Cu and by electrochemical corrosion behavior in 0.86% NaCl solution at 37 degrees C. The tarnish resistance was assessed using a spectrophotometer. The test solutions included 0.86% NaCl solution, 0.1% Na2S solution and a mixture of 1.0% lactic acid and 0.1% Na2S, all at 37 degrees C, in sealed containers. The results are summarized as follows. The larger the amount of Pd in Ag-Pd binary alloys and Ag-Pd-Cu ternary alloys, the more stable was the release and the release rate of Ag, Cu and corrosion resistance increased in 0.86% NaCl solution. The addition of Cu to Ag-Pd binary alloys increased the release and release rate of Ag, but there was a shift of the rest potential in the noble direction. A relationship was found between the amount of Ag and Cu released from Ag-Pd-Cu ternary alloys. In this study, an increase in corrosion resistance was observed when the content of Pd in Ag-Pd binary alloys was 25 wt%. Furthermore, it was also observed that Ag-Pd-Cu ternary alloys need an additional 30 wt% Pd for corrosion resistance. Moreover, the addition of Cu must be kept lower than 10 wt%. The tarnish resistance of the twelve experimental alloys was good in 0.86% NaCl solution but was barely improved with increased in the Pd content in sulfide solution. The correlation between electrochemical corrosion behavior and tarnish resistance was not significant, but the correlation between the amount of Ag, Cu release from Ag-Pd-Cu ternary alloys and tarnish resistance was remarkable.

  13. Monitoring bacterial community shifts in bioleaching of Ni-Cu sulfide.

    PubMed

    He, Zhiguo; Zhao, Jiancun; Gao, Fengling; Hu, Yuehua; Qiu, Guanzhou

    2010-11-01

    The microbial ecology of the bioleaching of Ni-Cu sulfide is poorly understood and little effort has been made to handle the microbiological components of these processes. In this study, denaturing gradient gel electrophoresis (DGGE) analysis of PCR-amplified 16S rRNA genes fragments from bacteria was used to evaluate the changes of the bacterial community in the process of Ni-Cu sulfide bioleaching in a shaken flask system. The results revealed that the bacterial community was disturbed after the addition of Ni-Cu sulfide. Phylogenetic analyses of 16S rRNA fragments revealed that the retrieved sequences clustered together with the genera Acidithiobacillus and Leptospirillum. Multidimensional scaling (MDS) and cluster analysis of DGGE-banding patterns revealed that the process of Ni-Cu sulfide bioleaching in 46days was divided into three stages. During the bioleaching process of Ni-Cu sulfide, Leptospirillum was always dominant. The genera Acidithiobacillus was only detected at early and later stages of the bioleaching process. These results extend our knowledge on microbial dynamics in Ni-Cu sulfide bioleaching, a key issue required to improve commercial applications.

  14. A NiFeCu alloy anode catalyst for direct-methane solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Zhu, Huaiyu; Yang, Guangming; Park, Hee Jung; Jung, Doh Won; Kwak, Chan; Shao, Zongping

    2014-07-01

    In this study, a new anode catalyst based on a NiFeCu alloy is investigated for use in direct-methane solid oxide fuel cells (SOFCs). The influence of the conductive copper introduced into the anode catalyst layer on the performance of the SOFCs is systematically studied. The catalytic activity for partial oxidation of methane and coking resistance tests are proposed with various anode catalyst layer materials prepared using different methods, including glycine nitrate process (GNP), physical mixing (PM) and impregnation (IMP). The surface conductivity tests indicate that the conductivities of the NiFe-ZrO2/Cu (PM) and NiFe-ZrO2/Cu (IMP) catalysts are considerably greater than that of NiFe-ZrO2/Cu (GNP), which is consistent with the SEM results. Among the three preparation methods, the cell containing the NiFe-ZrO2/Cu (IMP) catalyst layer performs best on CH4-O2 fuel, especially under reduced temperatures, because the coking resistance should be considered in real fuel cell conditions. The cell containing the NiFe-ZrO2/Cu (IMP) catalyst layer also delivers an excellent operational stability using CH4-O2 fuel for 100 h without any signs of decay. In summary, this work provides new alternative anode catalytic materials to accelerate the commercialization of SOFC technology.

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  16. Microstructure evolution during annealing of an SPD- processed supersaturated Cu - 3 at.% Ag alloy

    NASA Astrophysics Data System (ADS)

    Gubicza, J.; Hegedüs, Z.; Lábár, J. L.; Subramanya Sarma, V.; Kauffmann, A.; Freudenberger, J.

    2014-08-01

    Supersaturated Cu - 3 at.% Ag alloy was processed by rolling at liquid nitrogen temperature and subsequent annealing at 623 K up to 20 min. It was found that after annealing, an inhomogeneous solute atom distribution developed, since the Ag particles with small size and/or large specific interfacial energy were dissolved due to the Gibbs-Thomson effect. In the region where the solute concentration increased, a high dislocation density was retained in the Cu matrix even after annealing, while in the region where the Ag solute content did not increase, the dislocation density decreased by more than one order of magnitude. Therefore, in the cryorolled and annealed samples, heterogeneous microstructures were developed where both the dislocation density and the solute concentration varied considerably.

  17. Wetting reaction of Sn-Ag based solder systems on Cu substrates plated with Au and/or Pd layer

    NASA Astrophysics Data System (ADS)

    Liu, C. Y.; Li, Jian; Vandentop, G. J.; Choi, W. J.; Tu, K. N.

    2001-05-01

    The wetting behavior of SnAg based Pb-free solders on Cu and Cu substrates plated with Au, Pd, and Au/Pd thin films have been studied. The wetting angle and kinetics of interfacial reaction were measured. The Au-plated substrates exhibit better wetting than the Pd-plated substrates. In the case of SnAg on Pd-plated Cu, SEM observation revealed that the solder cap was surrounded by an innerring of Cu-Sn compound and an outer ring of Pd-Sn compound. This implies that the molten SnAg solder had removed the Pd and wetted the Cu directly in the equilibrium state. The effects of pre-doping Cu in the SnAg solder on wetting behavior were also investigated. We found that wettability decreases with increasing Cu content in the solder. We also observed that the SnAgCu solders have a lower Cu consumption rate than the SnAg solder.

  18. Interfaces in La2NiO4- La2CuO4 superlattices

    NASA Astrophysics Data System (ADS)

    Smadici, S.; Lee, J. C. T.; Wang, S.; Abbamonte, P.; Logvenov, G.; Gozar, A.; Bozovic, I.

    2009-03-01

    Ni substitution on Cu sites in underdoped La2-xSrxCuO4 quickly restores Neel order. This was attributed to strong interaction between the Ni and doped holes. An open question was whether the additional Ni empty orbital or the different spin on Ni sites was at the origin of this strong interaction. We have addressed this problem with resonant soft x-ray scattering on a La2NiO4- La2CuO4 heterostructure. La2NiO4 and La2CuO4 have close lattice structures and electronic configurations. However, the x-ray scattering contrast between superlattice layers is greatly enhanced at soft x-ray resonant energies. Based on our measurements at the O K, La M, Cu L and Ni L edges a model of the charge, orbital and spin structures in these superlattices will be presented with a special emphasis on the interface region. This work was supported by Grants. DE-FG02- 06ER46285, DE-AC02-98CH10886, MA-509-MACA, DE-FG02-07ER46453 and DE-FG02-07ER46471.

  19. Effect of NiO spin orientation on the magnetic anisotropy of the Fe film in epitaxially grown Fe/NiO/Ag(001) and Fe/NiO/MgO(001)

    SciTech Connect

    Kim, W.; Jin, E.; Wu, J.; Park, J.; Arenholz, E.; Scholl, A.; Hwang, C.; Qiu, Z.

    2010-02-10

    Single crystalline Fe/NiO bilayers were epitaxially grown on Ag(001) and on MgO(001), and investigated by Low Energy Electron Diffraction (LEED), Magneto-Optic Kerr Effect (MOKE), and X-ray Magnetic Linear Dichroism (XMLD). We find that while the Fe film has an in-plane magnetization in both Fe/NiO/Ag(001) and Fe/NiO/MgO(001) systems, the NiO spin orientation changes from in-plane direction in Fe/NiO/Ag(001) to out-of-plane direction in Fe/NiO/MgO(001). These two different NiO spin orientations generate remarkable different effects that the NiO induced magnetic anisotropy in the Fe film is much greater in Fe/NiO/Ag(001) than in Fe/NiO/MgO(001). XMLD measurement shows that the much greater magnetic anisotropy in Fe/NiO/Ag(001) is due to a 90{sup o}-coupling between the in-plane NiO spins and the in-plane Fe spins.

  20. Energy loss of 107Ag, 109Ag, and 150Sm in Ni and Au

    NASA Astrophysics Data System (ADS)

    Ribas, R. V.; Seale, W. A.; Roney, W. A.; Szanto, E. M.

    1980-04-01

    The stopping pow´er of 107Ag, 109Ag, and 150Sm in nickel and gold was measured as a preliminary test of a new technique for measuring energy loss based on the γ-ray Doppler shift. The analysis of the data was based on the theories of Lindhard, Scharff, and Schiott for nuclear and electronic stopping. The results are compared with the semiempirical predictions of Northcliffe and Schilling and the Lindhard-Scharff-Schiott theory.

  1. X-ray diffraction study of thermal parameters of Pd, Pd-Ag and Pd-Ag-Cu alloys as hydrogen purification membrane materials

    NASA Astrophysics Data System (ADS)

    Pati, Subhasis; Jat, Ram Avtar; Mukerjee, S. K.; Parida, S. C.

    2016-03-01

    High temperature X-ray diffraction measurements were carried out for pure palladium and palladium-rich alloys of compositions Pd0.77Ag0.23 and Pd0.77Ag0.10Cu0.13 in the temperature range of 298-1023 K at an interval of 50 K. The lattice parameters, coefficient of thermal expansion and X-ray Debye temperature of these materials were calculated as a function of temperature from the XRD data. The lattice parameter of Pd0.77Ag0.23 alloy was found to be higher than that of palladium, whereas the lattice parameter of Pd0.77Ag0.10Cu0.13 was found to be lower than that of palladium in the temperature range of investigation. Further, the lattice parameters of both the palladium alloys show negative deviation from Vegard's law and the deviation was found to increase with increase in temperature. The average value of coefficient of linear thermal expansion was found to follow the trend: αT (Pd)>αT (Pd0.77Ag0.23)>αT (Pd0.77Ag0.10Cu0.13). The X-ray Debye temperatures of Pd0.77Ag0.23 and Pd0.77Ag0.10Cu0.13 alloys were calculated and found to be 225±10 and 165±10 K, respectively.

  2. Thermoelectric properties of molten Bi2Te3, CuI, and AgI

    NASA Astrophysics Data System (ADS)

    Nishikawa, Kazutaka; Takeda, Yasuhiko; Motohiro, Tomoyoshi

    2013-01-01

    To achieve large figure of merit (ZT) and superior thermal durability at high temperatures, we have investigated thermoelectric properties of molten Bi2Te3, CuI, and AgI up to 1173 K. Molten Bi2Te3 was found to have large electrical conductivity between 1800 and 2000 (Ω ṡ cm)-1. Molten CuI and AgI, however, exhibited small electrical conductivity less than 1 (Ω ṡ cm)-1, nevertheless they show very large Seebeck coefficients over 800 μV/K. We estimated thermal conductivity using Wiedemann Franz law and the model established by Regel et al. [Phys. Status Solidi A 5, 13 (1971)]. The evaluated ZT for CuI is over 0.1.

  3. Facile and low-cost fabrication of Ag-Cu substrates via replacement reaction for highly sensitive SERS applications

    NASA Astrophysics Data System (ADS)

    Hu, Litao; Liu, Yan Jun; Xu, Shicai; Li, Zhe; Guo, Jia; Gao, Saisai; Lu, Zhengyi; Si, Haipeng; Jiang, Shouzhen; Wang, Shuyun

    2017-01-01

    In this work, we demonstrated facile and low-cost fabrication of highly sensitive SERS substrates via replacement reaction by immersing Cu foils into a AgNO3 solution. Different morphologies of Ag nanostructures were observed on the substrate surface by controlling the reaction time. The growth mechanism of Ag nanostructures on the Cu substrates was also analyzed based on the nanostructure evolution. The Ag-Cu substrates showed optimum SERS enhancement at certain reaction time, and the minimum detected concentration of Rhodamine 6G is as low as 10-13 M. The easy and low-cost fabrication makes the Ag-Cu SERS substrates promising for rapid, sensitive detection of targeted analytes, such as biomolecules, pollutants, and explosives in the environment.

  4. Electrochemical detection of Cu2+ through Ag nanoparticle assembly regulated by copper-catalyzed oxidation of cysteamine.

    PubMed

    Cui, Lin; Wu, Jie; Li, Jie; Ge, Yanqiu; Ju, Huangxian

    2014-05-15

    A highly sensitive and selective electrochemical sensor was developed for the detection of Cu(2+) by the assembly of Ag nanoparticles (AgNPs) at dithiobis[succinimidylpropionate] encapsulated Au nanoparticles (DSP-AuNPs), which was regulated by copper-catalyzed oxidation of cysteamine (Cys). The electrochemical sensor was constructed by layer-by-layer modification of glassy carbon electrode with carbon nanotubes, poly(amidoamine) dendrimers and DSP-AuNPs. In the absence of Cu(2+), Cys could bind to the surface of citrate-stabilized AgNPs via Ag-S bond, thus AgNPs could be assembled on the sensor surface through the reaction between DSP and Cys. In contrast, the copper-catalyzed oxidation of Cys by dissolved oxygen in the presence of Cu(2+) inhibited the Cys-induced aggregation of AgNPs, leading to the decrease of the electrochemical stripping signal of AgNPs. Under the optimized conditions, this method could detect Cu(2+) in the range of 1.0-1000 nM with a detection limit of 0.48 nM. The proposed Cu(2+) sensor showed good reproducibility, stability and selectivity. It has been satisfactorily applied to determine Cu(2+) in water samples.

  5. A Review of TiNiPdCu Alloy System for High Temperature Shape Memory Applications

    NASA Astrophysics Data System (ADS)

    Khan, M. Imran; Kim, Hee Young; Miyazaki, Shuichi

    2015-06-01

    High temperature shape memory alloys (HTSMAs) are important smart materials and possess a significant potential to improve many engineering systems. Many TiNi-based high temperature ternary alloy systems have been reported in literature including TiNiPd, TiNiPt, TiNiZr, TiNiAu, TiNiHf, etc. Some quaternary additions of certain elements in the above systems have been successful to further improve many important shape memory and mechanical properties. The success criteria for an HTSMA become strict in terms of its cyclic stability, maximum recoverable strain, creep resistance, and corrosion resistance at high temperatures. TiNiPdCu alloy system has been recently proposed as a promising HTSMA. Unique nanoscaled precipitates formed in TiNiPdCu-based HTSMAs are found to be stable at temperatures above 773 K, while keeping the benefits of ease of fabrication. It is expected that this alloy system possesses significant potential especially for the high temperature shape memory applications. Till now many research reports have been published on this alloy system. In the present work, a comprehensive review of the TiNiPdCu system is presented in terms of thermomechanical behavior, nanoscale precipitation mechanism, microstructural features, high temperature shape memory and mechanical properties, and the important parameters to control the high temperature performance of these alloys.

  6. Agglomeration in core-shell structure of CuAg nanoparticles synthesized by the laser ablation of Cu target in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Petrović, S.; Salatić, B.; Milovanović, D.; Lazović, V.; Živković, Lj; Trtica, M.; Jelenković, B.

    2015-02-01

    Metallic copper Cu and bimetallic copper-silver CuAg nanoparticles (NPs) are generated by the ablation of copper bulk target in water and aqueous Ag colloidal solution, respectively. The experiments were performed using nanosecond Nd:YAG laser operating at 1064 nm. The generated NPs are characterized by UV-vis absorption spectroscopy, laser-induced breakdown spectroscopy, dynamic light scattering and scanning electron microscopy. The conducted investigations can be summarized as follows: (i) CuAg NPs colloidal solution possess the absorption in UV-vis spectral region, which can be attributed to the Cu-component; (ii) the primary bimetallic CuAg NPs have near uniform dimensions with diameter of about 15 nm, and as a rule, they are grouped into larger agglomerates without defined morphology; (iii) the obtained Cu NPs have mainly spherical form with average diameters up to 20 nm. Both types of NPs show a tendency towards the formation of large agglomerates with different morphology. Bimetallic NPs show the plasmon resonance in the vicinity of 640 nm with a good coincidence with formation of the colloidal solution of pure Cu NPs. The results also demonstrate that the core-shell structure (Ag-rich core/Cu-rich shell) is important for the formation of the bimetallic NPs, also agreeing very well with theory.

  7. Evaluation of the amalgamation reaction of experimental Ag-Sn-Cu alloys containing Pd using a mercury plating technique.

    PubMed

    Koike, Marie; Ferracane, Jack L; Fujii, Hiroyuki; Okabe, Toru

    2003-09-01

    A mercury plating technique was used to determine the phases forming on experimental Ag-Sn-Cu alloy powders (with and without Pd) exposed to electrolytically deposited mercury. Four series of alloy powders were made: a) 1.5% Pd with 10-14% Cu (CU series); b) 1.0% Pd with 10-14% Cu (1PD series); c) 1.5% Pd with different ratios of Ag3Sn (gamma) to Ag4Sn (beta) with 12% Cu (AGSN series); and d) 9-13% Cu with no Pd (NOPD series). Each powder was pressed on a freshly prepared amalgam specimen made from the same powder and metallographically polished until cross sections appeared; mercury was electroplated on the alloy particles. Alloy powders, amalgams and electroplated specimens were examined using XRD and SEM/EDS. XRD confirmed the presence of gamma2 in amalgams made from alloys with Cu < 13% or with Ag3Sn/Ag4Sn > 0.8. Specimens with moderately plated Hg showed gamma1 (Ag2Hg3) polyhedra and eta' Cu6Sn5, but not gamma2. This method effectively identifies alloys prone to forming gamma2.

  8. Kinetics and thermodynamics associated with Bi adsorption transitions at Cu and Ni grain boundaries

    SciTech Connect

    Tai, Kaiping; Feng, Lin; Dillon, Shen J.

    2013-05-21

    The grain boundary diffusivity of Au in Cu and Cu-Bi, and Cu in Ni and Ni-Bi are characterized by secondary ion mass spectroscopy depth profiling. Samples are equilibrated in a Bi containing atmosphere at temperatures above and below the onset of grain boundary adsorption transitions, sometimes called complexion transitions. A simple thermo-kinetic model is used to estimate the relative entropic contributions to the grain boundary energies. The results indicate that the entropy term plays a major role in promoting thermally and chemically induced grain boundary complexion transition.

  9. Single-Step Production of Nanostructured Copper-Nickel (CuNi) and Copper-Nickel-Indium (CuNiIn) Alloy Particles

    NASA Astrophysics Data System (ADS)

    Apaydın, Ramazan Oğuzhan; Ebin, Burçak; Gürmen, Sebahattin

    2016-07-01

    Nanostructured copper-nickel (CuNi) and copper-nickel-indium (CuNiIn) alloy particles were produced from aqueous solutions of copper, nickel nitrates and indium sulfate by hydrogen reduction-assisted ultrasonic spray pyrolysis. The effects of reduction temperatures, at 973 K, 1073 K, and 1173 K (700 °C, 800 °C, and 900 °C), on the morphology and crystalline structure of the alloy particles were investigated under the conditions of 0.1 M total precursor concentration and 0.5 L/min H2 volumetric flow rate. X-ray diffraction studies were performed to investigate the crystalline structure. Particle size and morphology were investigated by scanning electron microscope and energy-dispersive spectroscopy was applied to determine the chemical composition of the particles. Spherical nanocrystalline binary CuNi alloy particles were prepared in the particle size range from 74 to 455 nm, while ternary CuNiIn alloy particles were obtained in the particle size range from 80 to 570 nm at different precursor solution concentrations and reduction temperatures. Theoretical and experimental chemical compositions of all the particles are nearly the same. Results reveal that the precursor solution and reduction temperature strongly influence the particle size of the produced alloy particles.

  10. Thin-layer chromatographic specification and separation of Cu(1+), Cu(2+), Ni(2+), and Co(2+) cations.

    PubMed

    Savasci, Sahin; Akçay, Mehmet; Ergül, Soner

    2010-07-01

    The M(PyDTC)(2) (M: Cu, Co, or Ni) and CuPyDTC complexes, prepared by reactions of ammonium pyrrolidinedithiocarbamate with metal nitrates, are examined for qualitative analysis, speciation, and mutual separation using thin-layer chromatography systems. These complexes and their mixtures are spotted to the activated and non-activated thin layers of silica gel 60GF(254) (Si-60GF(254)) with a 250-microm thickness. Toluene-dichloromethane mixtures (4:1, 1:1, 1:4 v/v) are used as mobile phases for running of the complexes. All of these chromatographic systems are successfully used for speciation of Cu(2+) and Cu(1+) cations. The best analytical separation for the qualitative analysis of corresponding metal cations and mutual separation of components in M(PyDTC)(2) and CuPyDTC complexes are obtained when using pure toluene-dichloromethane (1:1 v/v) on the activated layer. This study shows that it is possible to qualitatively analyze and satisfactorily separate a mixture of Cu(1+), Cu(2+), Ni(2+), and Co(2+) cations on cited chromatographic systems. These results may be also said for the adaptability or validity on column chromatography.

  11. Enhancement of electric field and Raman scattering by Ag coated Ni nanotips

    NASA Astrophysics Data System (ADS)

    Ye, Dexian; Mutisya, Stephen; Bertino, Massimo

    2011-08-01

    Localization and enhancement of electric field by Ag-coated vertical Ni nanotip arrays were studied by using finite-different time domain calculations. With the 30 nm thick Ag coating, the nanotips can localize and enhance the electric field to more than 103 times under the excitation of TE-polarized light with a 532 nm wavelength. Nanotip-enhanced Raman scattering of cytochrome-c protein was demonstrated in a confocal Raman microscope. Significant enhancement of Raman spectrum was achieved at 1 × 10-9 mol/l concentration of the proteins.

  12. Development of Cu alloy anode and separator coated with Al-Ni intermetallic compound

    SciTech Connect

    Toyokura, K.; Hoshino, K.; Yamamoto, M.

    1996-12-31

    Anode made of Cu alloy and separator coated with Al-Ni intermetallic compound have been developed for VCFC. Anode of Ni alloy is usually used. However, the alternative of cost lower than Ni alloy anode should be needed, because Ni is expensive. Cu is attractive as an anode material for VCFC because it is inexpensive and electrochemically noble. However, the creep resistance of Cu is not sufficient, compared with Ni alloy. In this study, strengthening due to oxide-dispersed microstructure has been developed in Cu-Ni-Al alloy with the two-step sintering process. A wet-seal technique has been widely applied for gas-sealing and supporting of electrolyte in MCFC. Since the wet-seal area is exposed to a severe corrosive environment, corrosion resistance of material for wet sealing is related with the cell performance. Al-Ni plating with post-heat treating for stainless steel has been investigated. Stainless steel substrate was plated with Al after being coated with Ni, then heat-treated at 750 {degrees}C for 1 hour in Ar gas atmosphere. Due to the treatment, Al-Ni intermetallic compound ( mainly Al3Ni2 ) layer is formed on stainless steel surface. The long-term immersion test was carried out till 14,500 hours in 62 mol% Li{sub 2}CO{sub 3}-38 mol% K{sub 2}CO{sub 3} at 650 {degrees}C under air-30%CO{sub 2} atmosphere, for the purpose of evaluating the corrosion resistance and thermal stability of Al-Ni intermetallic compound layer in actual generating with VCFC.

  13. Structure and phonon spectrum of a submonolayer Ni film on the surface of Cu(100)

    NASA Astrophysics Data System (ADS)

    Rusina, G. G.; Borisova, S. D.; Chulkov, E. V.

    2016-02-01

    The equilibrium atomic structure and the phonon spectra of a submonolayer (θ = 0.5 monolayer) Ni film deposited on the surface of Cu(100) are calculated using the potentials obtained by the embedded atom method. We consider atomic relaxation, the vibrational state density distribution on Ni and substrate atoms, and polarization of vibrational modes. Variation of the phonon spectrum upon segregation of Cu atoms on the film surface is considered. It is shown that mixing of vibrations of Ni adatoms with vibrations of substrate atoms occurs in the entire frequency range, leading to a frequency shift of the vibrational modes of the substrate and to the occurrence of new vibrational states atypical of a clean surface. The Cu(100)- c(2 × 2)-Ni structure is dynamically stabler when placed in the subsurface layer of the substrate.

  14. Resistive switching mechanism of Ag/ZrO2:Cu/Pt memory cell

    NASA Astrophysics Data System (ADS)

    Long, Shibing; Liu, Qi; Lv, Hangbing; Li, Yingtao; Wang, Yan; Zhang, Sen; Lian, Wentai; Zhang, Kangwei; Wang, Ming; Xie, Hongwei; Liu, Ming

    2011-03-01

    Resistive switching mechanism of zirconium oxide-based resistive random access memory (RRAM) devices composed of Cu-doped ZrO2 film sandwiched between an oxidizable electrode and an inert electrode was investigated. The Ag/ZrO2:Cu/Pt RRAM devices with crosspoint structure fabricated by e-beam evaporation and e-beam lithography show reproducible bipolar resistive switching. The linear I- V relationship of low resistance state (LRS) and the dependence of LRS resistance ( R ON) and reset current ( I reset) on the set current compliance ( I comp) indicate that the observed resistive switching characteristics of the Ag/ZrO2:Cu/Pt device should be ascribed to the formation and annihilation of localized conductive filaments (CFs). The physical origin of CF was further analyzed by transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). CFs were directly observed by cross-sectional TEM. According to EDS and elemental mapping analysis, the main chemical composition of CF is determined by Ag atoms, coming from the Ag top electrode. On the basis of these experiments, we propose that the set and reset process of the device stem from the electrochemical reactions in the zirconium oxide under different external electrical stimuli.

  15. Metallic glass alloys of Zr, Ti, Cu and Ni

    DOEpatents

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

    1997-04-08

    At least quaternary alloys form metallic glass upon cooling below the glass transition temperature at a rate less than 10{sup 3} K/s. Such alloys comprise titanium from 19 to 41 atomic percent, an early transition metal (ETM) from 4 to 21 atomic percent and copper plus a late transition metal (LTM) from 49 to 64 atomic percent. The ETM comprises zirconium and/or hafnium. The LTM comprises cobalt and/or nickel. The composition is further constrained such that the product of the copper plus LTM times the atomic proportion of LTM relative to the copper is from 2 to 14. The atomic percentage of ETM is less than 10 when the atomic percentage of titanium is as high as 41, and may be as large as 21 when the atomic percentage of titanium is as low as 24. Furthermore, when the total of copper and LTM are low, the amount of LTM present must be further limited. Another group of glass forming alloys has the formula (ETM{sub 1{minus}x}Ti{sub x}){sub a} Cu{sub b} (Ni{sub 1{minus}y}Co{sub y}){sub c} wherein x is from 0.1 to 0.3, y{center_dot}c is from 0 to 18, a is from 47 to 67, b is from 8 to 42, and c is from 4 to 37. This definition of the alloys has additional constraints on the range of copper content, b. 2 figs.

  16. Transition metal interaction and Ni-Fe-Cu-Si phases in silicon

    NASA Astrophysics Data System (ADS)

    Heuer, M.; Buonassisi, T.; Istratov, A. A.; Pickett, M. D.; Marcus, M. A.; Minor, A. M.; Weber, E. R.

    2007-06-01

    In the present article we characterize several intermetallic phases of the Cu-Ni-Fe-Si system found as precipitates in the misfit dislocation layer of intentionally contaminated and slowly cooled Si1-xGex/Si-heterostructures. The clusters showed a characteristic phase speciation into a Cu-rich part similar to Cu3Si and an Fe-Ni-Cu-Si phase similar to NiSi2. It is suggested that the precipitate formation of the investigated intermetallic silicides involves a homogeneous precursor phase at higher temperatures that later decomposes into the observed phases. Our results indicate that chemical reactions between metals and silicon during precipitation may reduce the lattice mismatch compared to single-metal precipitates, rendering mixed-metal-silicide precipitates more stable and energetically favorable.

  17. Vacuum Brazing of WC-8Co Cemented Carbides to Carbon Steel Using Pure Cu and Ag-28Cu as Filler Metal

    NASA Astrophysics Data System (ADS)

    Zhang, X. Z.; Liu, G. W.; Tao, J. N.; Shao, H. C.; Fu, H.; Pan, T. Z.; Qiao, G. J.

    2016-12-01

    The wetting and spreading behavior of commercial pure Cu and Ag-28Cu alloy on WC-8Co cemented carbide were investigated by the sessile drop technique. The contact angle of both systems obviously decreases with moderately increasing the wetting temperature. Vacuum brazing of the WC-8Co cemented carbide to SAE1045 steel using the pure Cu or Ag-28Cu as filler metal was further carried out based on the wetting results. The interfacial interactions and joint mechanical behavior involving microhardness, shear strength and fracture were analyzed and discussed. An obvious Fe-Cu-Co transition layer is detected at the WC-8Co/Cu interface, while no obvious reaction layer is observed at the whole WC-8Co/Ag-28Cu/SAE1045 brazing seam. The microhardness values of the two interlayers and the steel substrate near the two interlayers increase more or less, while those of WC-8Co cemented carbide substrates adjacent to the two interlayers decrease. The WC-8Co/SAE1045 joints using pure Cu and Ag-28Cu alloy as filler metals obtain average shear strength values of about 172 and 136 MPa, and both of the joint fractures occur in the interlayers.

  18. Vacuum Brazing of WC-8Co Cemented Carbides to Carbon Steel Using Pure Cu and Ag-28Cu as Filler Metal

    NASA Astrophysics Data System (ADS)

    Zhang, X. Z.; Liu, G. W.; Tao, J. N.; Shao, H. C.; Fu, H.; Pan, T. Z.; Qiao, G. J.

    2017-02-01

    The wetting and spreading behavior of commercial pure Cu and Ag-28Cu alloy on WC-8Co cemented carbide were investigated by the sessile drop technique. The contact angle of both systems obviously decreases with moderately increasing the wetting temperature. Vacuum brazing of the WC-8Co cemented carbide to SAE1045 steel using the pure Cu or Ag-28Cu as filler metal was further carried out based on the wetting results. The interfacial interactions and joint mechanical behavior involving microhardness, shear strength and fracture were analyzed and discussed. An obvious Fe-Cu-Co transition layer is detected at the WC-8Co/Cu interface, while no obvious reaction layer is observed at the whole WC-8Co/Ag-28Cu/SAE1045 brazing seam. The microhardness values of the two interlayers and the steel substrate near the two interlayers increase more or less, while those of WC-8Co cemented carbide substrates adjacent to the two interlayers decrease. The WC-8Co/SAE1045 joints using pure Cu and Ag-28Cu alloy as filler metals obtain average shear strength values of about 172 and 136 MPa, and both of the joint fractures occur in the interlayers.

  19. Diffusion bonding titanium to stainless steel using Nb/Cu/Ni multi-interlayer

    SciTech Connect

    Li Peng; Li Jinglong; Xiong Jiangtao; Zhang Fusheng; Raza, Syed Hamid

    2012-06-15

    By using Nb/Cu/Ni structure as multi-interlayer, diffusion bonding titanium to austenitic stainless steel has been conducted. The effects of bonding temperature and bonding time on the interfacial microstructure were analyzed by scanning electron microscope equipped with energy dispersive spectroscope, and the joint strength was evaluated by tensile test. The results showed that Ni atoms aggregated at the Cu-Nb interface, which promoted Cu solution in Nb. This phenomenon forms a Cu-Nb solution strengthening effect. However, such effect would decay by using long bonding time that dilutes Ni atom aggregation, or be suppressed by using high bonding temperature that embrittles the Cu-Nb interface due to the formation of large grown intermetallic compounds. The sound joint was obtained by promoted parameters as 850 Degree-Sign C for 30-45 min, under which a bonding strength around 300 MPa could be obtained. - Highlights: Black-Right-Pointing-Pointer Titanium was diffusion bonded to stainless steel using Nb/Cu/Ni multi-interlayer. Black-Right-Pointing-Pointer The effects of bonding parameters on microstructure and joint strength were studied. Black-Right-Pointing-Pointer Nickel aggregation promotes Cu solution in Nb which can strengthen the joint. Black-Right-Pointing-Pointer The sound joint with strength of around 300 MPa was obtained by promoted parameters.

  20. Room temperature nanojoining of Cu-Ag core-shell nanoparticles and nanowires

    NASA Astrophysics Data System (ADS)

    Wang, Jiaqi; Shin, Seungha

    2017-02-01

    Room temperature ( T room, 300 K) nanojoining of Ag has been widely employed in fabrication of microelectronic applications where the shapes and structures of microelectronic components must be maintained. In this research, the joining processes of pure Ag nanoparticles (NPs), Cu-Ag core-shell NPs, and nanowires (NWs) are studied using molecular dynamics simulations at T room. The evolution of densification, potential energy, and structural deformation during joining process are analyzed to identify joining mechanisms. Depending on geometry, different joining mechanisms including crystallization-amorphization, reorientation, Shockley partial dislocation are determined. A three-stage joining scenario is observed in both joining process of NPs and NWs. Besides, the Cu core does not participate in all joining processes, however, it enhances the mobility of Ag shell atoms, contributing to a higher densification and bonding strength at T room, compared with pure Ag nanomaterials. The tensile test shows that the nanojoint bears higher rupture strength than the core-shell NW itself. This study deepens understanding in the underlying joining mechanisms and thus nanojoint with desirable thermal, electrical, and mechanical properties could be potentially achieved.

  1. 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.

  2. Active Brazing of C/C Composite to Copper by AgCuTi Filler Metal

    NASA Astrophysics Data System (ADS)

    Zhang, Kexiang; Xia, Lihong; Zhang, Fuqin; He, Lianlong

    2016-05-01

    Brazing between the carbon-fiber-reinforced carbon composite (C/C composite) and copper has gained increasing interest because of its important application in thermal management systems in nuclear fusion reactors and in the aerospace industry. In order to examine the "interfacial shape effect" on the mechanical properties of the joint, straight and conical interfacial configurations were designed and machined on the surface of C/C composites before joining to copper using an Ag-68.8Cu-4.5Ti (wt pct) alloy. The microstructure and interfacial microchemistry of C/C composite/AgCuTi/Cu brazed joints were comprehensively investigated by using high-resolution transmission electron microscopy. The results indicate that the joint region of both straight and conical joints can be described as a bilayer. Reaction products of Cu3Ti3O and γ-TiO were formed near the copper side in a conical interface joint, while no reaction products were found in the straight case. The effect of Ag on the interfacial reaction was discussed, and the formation mechanism of the joints during brazing was proposed. On the basis of the detailed microstructure presented, the mechanical performance of the brazed joints was discussed in terms of reaction and morphology across the joint.

  3. Valence and spin states in delafossite AgNiO2 and the frustrated Jahn-Teller system ANiO2 (A=Li,Na)

    NASA Astrophysics Data System (ADS)

    Kang, J.-S.; Lee, S. S.; Kim, G.; Lee, H. J.; Song, H. K.; Shin, Y. J.; Han, S. W.; Hwang, C.; Jung, M. C.; Shin, H. J.; Kim, B. H.; Kwon, S. K.; Min, B. I.

    2007-11-01

    Electronic structures of delafossite oxides AgNi1-xCoxO2 and the frustrated Jahn-Teller (JT) system ANiO2 (A=Li,Na) have been investigated by employing soft x-ray absorption spectroscopy and photoemission spectroscopy (PES). It is found that Ni ions are in the Ni2+-Ni3+ mixed-valent states and that the low-spin (LS) Ni3+ component increases from LiNiO2 to AgNiO2 and NaNiO2 , in agreement with the presence of the JT transition in NaNiO2 and the absence of the JT transition in LiNiO2 and AgNiO2 . In AgNi1-xCoxO2 , the Ni3+ component increases with x , while Co ions are in the LS Co3+ states for all x , which is consistent with the metallic nature for low values of x . A good agreement is found between the measured PES spectra and the calculated local spin density approximation (LSDA) electronic structures of AgNiO2 and AgCoO2 , but the pseudogap feature in PES of AgNiO2 is not described by the LSDA.

  4. Highly Active Three-Dimensional NiFe/Cu2 O Nanowires/Cu Foam Electrode for Water Oxidation.

    PubMed

    Chen, Hu; Gao, Yan; Sun, Licheng

    2017-04-10

    Water splitting is of paramount importance for exploiting renewable energy-conversion and -storage systems, but is greatly hindered by the kinetically sluggish oxygen evolution reaction (OER). In this work, a three-dimensional, highly efficient, and durable NiFe/Cu2 O nanowires/Cu foam anode (NiFe/Cu2 O NWs/CF) for water oxidation in 1.0 m KOH was developed. The obtained electrode exhibited a current density of 10 mA cm(-2) at a uniquely low overpotential of η=215 mV. The average specific current density (js ) was estimated, on the basis of the electrocatalytically active surface area, to be 0.163 mA cm(-2) at η=310 mV. The electrode also displayed a low Tafel slope of 42 mV decade(-1) . Moreover, the NiFe/Cu2 O NWs/CF electrode could maintain a steady current density of 100 mA cm(-2) for 50 h at an overpotential of η=260 mV. The outstanding electrochemical performance of the electrode for the OER was attributed to the high conductivity of the Cu foam and the specific structure of the electrode with a large interfacial area.

  5. Surface electronic structure of polar NiO thin film grown on Ag(111)

    SciTech Connect

    Das, Jayanta; Menon, Krishnakumar S. R.

    2015-06-24

    The growth and structure of NiO thin films on top of Ag(111) substrate were studied where the formation of faceted surface was confirmed by Low Energy Electron Diffraction. The electronic structure of polar NiO(111) surface has been probed using photoemission techniques. The core energy levels and the valence band electronic structure were excited by x-ray and ultraviolet photons respectively. The modifications in physical structure and valence band electronic structure of the film under vacuum annealing have also been enlightened.

  6. High temperature phase equilibria studies in the Bi-Sr-Ca-Cu-O-Ag system

    SciTech Connect

    Margulies, Lawrence

    1999-11-08

    A variety of experimental techniques were utilized to examine the high temperature phase equilibria in the Bi-Sr-Ca-Cu-O-Ag system. Quenching studies were used to determine the liquid solubility of Ag in the Bi2Sr2CaCu2O8 (Bi2212) melt and the details of the peritectic decomposition pathway of Bi2212 as a function on Ag content and oxygen partial pressure (PO2). A liquid immiscibility region between oxide and Ag liquids in the 8--98 at% range was found above 900 C. Two eutectics were found in the Bi2212-Ag pseudobinary. On the oxide rich side, a eutectic exists at approximately 4 at% Ag. On the Ag rich side, a eutectic exists at approximately 98 at% Ag at a temperature of 15 C below the melting point of pure Ag. Six distinct solid phases were found to be in equilibrium with the partial melt within the Ag content and PO2 range studied. The stability of these solid phases were found to be highly sensitive to PO2, and to a much lesser extent Ag content. High temperature x-ray diffraction (HTXRD) studies of this system are in conflict with these results. It is suggested that these discrepancies are due to experimental artifacts caused by the significant thermal gradients and lack of full bulk sampling which is inherent in conventional HTXRD designs. In part 2, a new furnace design compatible with synchrotron radiation sources is introduced to address these problems. This design allows for full bulk sampling in a low thermal gradient environment using Debye-Scherrer transmission geometry. Sample spinning is also introduced in the design to eliminate preferred orientation and incomplete powder averaging and allow for quantitative phase analysis and structural refinement. Studies on model systems are presented to demonstrate the capabilities for high resolution structural studies (Al2O3) and time resolved phase transformation studies (SrCO3). Finally, the Bi2212

  7. 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.

  8. Tensile strength and creep resistance in nanocrystalline Cu, Pd and Ag

    SciTech Connect

    Nieman, G.W.; Weertman, J.R. . Dept. of Materials Science and Engineering); Siegel, R.W. )

    1990-12-01

    Measurements of tensile strength and creep resistance have been made on bulk samples of nanocrystalline Cu, Pd and Ag consolidated from powders by cold compaction. Samples of Cu-Cu{sub 2}O have also been tested. Yield strength for samples with mean grains sizes of 5-80 nm and bulk densities on the order of 95% of theoretical density are increased 2--5 times over that measured in pure, annealed samples of the same composition with micrometer grain sizes. Ductility in the nanocrystalline Cu has exceeded 6% true strain, however, nanocrystalline Pd samples were much less ductile. Constant load creep tests performed at room temperature at stresses of >100 MPa indicate logarithmic creep. The mechanical properties results are interpreted to be due to grain size-related strengthening and processing flaw-related weakening. 26 refs., 2 figs.

  9. Effect of Surplus Phase on the Microstructure and Mechanical Properties in Al-Cu-Mg-Ag Alloys with High Cu/Mg Ratio

    NASA Astrophysics Data System (ADS)

    Xu, Xiaofeng; Zhao, Yuguang; Wang, Xudong; Zhang, Ming; Ning, Yuheng

    2015-11-01

    In order to examine the effect of surplus phase on the microstructure and mechanical properties, different compositions with high Cu/Mg ratio of the T6-temper extruded Al-Cu-Mg-Ag alloys were studied in this investigation. The results show that the Al-5.6Cu-0.56Mg-0.4Ag alloy obtains superior mechanical properties at room temperature, while the yield strength of Al-6.3Cu-0.48Mg-0.4Ag alloy is 378 MPa at 200 °C, which is 200 MPa higher than that of Al-5.6Cu-0.56Mg-0.4Ag alloy. Although the excessive Cu content causes the slight strength loss and elongation decrease in the Al-6.3Cu-0.48Mg-0.4Ag alloy at room temperature, the surplus phases and recrystallized microstructure will play an effective role in strengthening the alloy at elevated temperature.

  10. Microstructure analysis of the ferromagnetic Ag-Ni system synthesized by pulsed electrodeposition

    NASA Astrophysics Data System (ADS)

    Santhi, Kalavathy; Karthick, S. N.; Kim, Hee-Je; Nidhin, Marimuthu; Narayanan, V.; Stephen, A.

    2012-01-01

    Nanocrystalline silver-nickel deposits were prepared by pulsed electrolysis at different current densities from nontoxic complex electrolytes of two compositions containing silver nitrate and nickel sulphate. The structural and magnetic properties of these deposits have been analyzed in comparison with those of pure Ag and pure Ni deposited under similar conditions. The morphological and the microstructural studies have been carried out for these samples using SEM and HRTEM. The results suggest that the as deposited materials consist of Ag-Ni in the metastable alloy form. Heating the sample beyond Curie temperature leads to grain growth and long range ordering. The hysteresis curves and the magneto-thermograms reveal that the deposits exhibit room temperature ferromagnetism.

  11. Giant magnetoresistance of Co-Ni-Cu alloys produced by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Zhang, Y. Q.; Zhang, Z. D.; Xiao, Q. F.; Geng, D. Y.; Zhao, X. G.; Zhang, W. S.; You, C. Y.

    2003-05-01

    The structure, magnetic properties and magnetoresistance (MR) effect of Co20NixCu80-x alloys produced by mechanical alloying and subsequent annealing have been investigated. After milling for 5 h, a supersaturated solid solution forms for all the alloys. Co20NixCu80-x alloys annealed at 973 K for 30 min segregated into two-phases of fcc-Co and fcc-Cu. The maximum value for MR ratio, at room temperature is 4.7% at a field of 1.2 T, and at 5 K is 15% at a field of 2 T for Co20Cu80 annealed at 718 K for 30 min. The MR ratio of Co-Ni-Cu alloys decreases monotonically with increasing Ni content. The MR and its dependence on particle size are discussed.

  12. Ion irradiation induced element-enriched and depleted nanostructures in Zr-Al-Cu-Ni metallic glass

    SciTech Connect

    Chen, H. C.; Liu, R. D.; Yan, L. E-mail: zhouxingtai@sinap.ac.cn; Zhou, X. T. E-mail: zhouxingtai@sinap.ac.cn; Cao, G. Q.; Wang, G.

    2015-07-21

    The microstructural evolution of a Zr-Al-Cu-Ni metallic glass induced by irradiation with Ar ions was investigated. Under ion irradiation, the Cu- and Ni-enriched nanostructures (diameter of 30–50 nm) consisted of crystalline and amorphous structures were formed. Further, Cu- and Ni-depleted nanostructures with diameters of 5–20 nm were also observed. The formation of these nanostructures can be ascribed to the migration of Cu and Ni atoms in the irradiated metallic glass.

  13. Colloidal synthesis of Cu-ZnO and Cu@CuNi-ZnO hybrid nanocrystals with controlled morphologies and multifunctional properties.

    PubMed

    Zeng, Deqian; Gong, Pingyun; Chen, Yuanzhi; Zhang, Qinfu; Xie, Qingshui; Peng, Dong-Liang

    2016-06-02

    Metal-semiconductor hybrid nanocrystals have received extensive attention owing to their multiple functionalities which can find wide technological applications. The utilization of low-cost non-noble metals to construct novel metal-semiconductor hybrid nanocrystals is important and meaningful for their large-scale applications. In this study, a facile solution approach is developed for the synthesis of Cu-ZnO hybrid nanocrystals with well-controlled morphologies, including nanomultipods, core-shell nanoparticles, nanopyramids and core-shell nanowires. In the synthetic strategy, Cu nanocrystals formed in situ serve as seeds for the heterogeneous nucleation and growth of ZnO, and it eventually forms various Cu-ZnO hetero-nanostructures under different reaction conditions. These hybrid nanocrystals possess well-defined and stable heterostructure junctions. The ultraviolet-visible-near infrared spectra reveal morphology-dependent surface plasmon resonance absorption of Cu and the band gap absorption of ZnO. Furthermore, we construct a novel Cu@CuNi-ZnO ternary hetero-nanostructure by incorporating the magnetic metal Ni into the pre-synthesized colloidal Cu nanocrystals. Such hybrid nanocrystals possess a magnetic Cu-Ni intermediate layer between the ZnO shell and the Cu core, and exhibit ferromagnetic/superparamagnetic properties which expand their functionalities. Finally, enhanced photocatalytic activities are observed in the as-prepared non-noble metal-ZnO hybrid nanocrystals. This study not only provides an economical way to prepare high-quality morphology-controlled Cu-ZnO hybrid nanocrystals for potential applications in the fields of photocatalysis and photovoltaic devices, but also opens up new opportunities in designing ternary non-noble metal-semiconductor hybrid nanocrystals with multifunctionalities.

  14. Improved Wetting Characteristics in TiO2–Modified Ag-CuO Air Braze Filler Metals

    SciTech Connect

    Weil, K. Scott; Kim, Jin Yong Y.; Hardy, John S.; Darsell, Jens T.

    2006-01-01

    In this paper we report on the results of a series of sessile drop experiments designed to examine the effect of TiO2 on the wetting behavior of Ag-CuO air braze filler metals. It was found that TiO2 concentrations as small as 0.5 mol% can significantly decrease the contact angle of Ag-CuO on alumina over a compositional range of 1 – 34mol% CuO. The effect appears to maximize at a copper oxide concentration of ~4 mol% CuO regardless of the titania content.

  15. Influence of the ARC patterning method and annealing on the contact adhesion of Ni/Cu-plated solar cells

    NASA Astrophysics Data System (ADS)

    Baik, Jong Wook; Lee, Sang Hee; Lee, Doo Won; Lee, Soo Hong

    2016-05-01

    Ni/Cu two-step plating is a promising metallization technique because low contact resistance and improved contact adhesion can be achieved after the Ni annealing process. Also, narrow fingers, which are required for high-efficiency solar cells, can be formed by plating. However, the reliability of contact adhesion is still considered one obstacle to industrializing solar cells with plated metal contacts. In this experiment, the influence of ARC opening methods on plated contact adhesion was investigated because the roughnesses of the Si surfaces produced by using pico-second laser ablation and photolithography may be different. Also, the annealing process was conducted before and after plating Cu/Ag metal stacks. The sequence of the annealing can be significant for efficient production because plating is a wet process while annealing is a dry process. The contact adhesion was measured by using a peel-off test. The test was conducted on a 1.5-mm-wide by a 60 ~ 70- mm-long bus bar area. A 3.2-N/mm adhesion force was recorded as a highest average value along the bus bar.

  16. Impacts of Pristine and Transformed Ag and Cu Engineered Nanomaterials on Surficial Sediment Microbial Communities Appear Short-Lived.

    PubMed

    Moore, Joe D; Stegemeier, John P; Bibby, Kyle; Marinakos, Stella M; Lowry, Gregory V; Gregory, Kelvin B

    2016-03-01

    Laboratory-based studies have shown that many soluble metal and metal oxide engineered nanomaterials (ENM) exert strong toxic effects on microorganisms. However, laboratory-based studies lack the complexity of natural systems and often use "as manufactured" ENMs rather than more environmentally relevant transformed ENMs, leaving open the question of whether natural ligands and seasonal variation will mitigate ENM impacts. Because ENMs will accumulate in subaquatic sediments, we examined the effects of pristine and transformed Ag and Cu ENMs on surficial sediment microbial communities in simulated freshwater wetlands. Five identical mesocosms were dosed through the water column with either Ag(0), Ag2S, CuO or CuS ENMs (nominal sizes of 4.67 ± 1.4, 18.1 ± 3.2, 31.1 ± 12, and 12.4 ± 4.1, respectively) or Cu(2+). Microbial communities were examined at 0, 7, 30, 90, 180, and 300 d using qPCR and high-throughput 16S rRNA gene sequencing. Results suggest differential short-term impacts of Ag(0) and Ag2S, similarities between CuO and CuS, and differences between Cu ENMs and Cu(2+). PICRUSt-predicted metagenomes displayed differential effects of Ag treatments on photosynthesis and of Cu treatments on methane metabolism. By 300 d, all metrics pointed to reconvergence of ENM-dosed mesocosm microbial community structure and composition, suggesting that the long-term microbial community impacts from a pulse of Ag or Cu ENMs are limited.

  17. 63Cu nuclear magnetic resonance study of Pr(1.85)Ce(0.15)Cu(1-x)Ni(x)O(4): Ni-induced spin density oscillation and modification of the low energy spin fluctuations.

    PubMed

    Williams, G V M; Jurkutat, M; Rybicki, D; Haase, J

    2011-02-23

    We report the results from a (63)Cu nuclear magnetic resonance (NMR) study of the electron-doped high temperature superconducting cuprate (HTSC) Pr(1.85)Ce(0.15)Cu(1-x)Ni(x)O(4). We find that Ni induces a magnetic broadening of the (63)Cu NMR spectra that can be interpreted in terms of an induced spin density oscillation about the Ni site, similar to that reported from (63)Cu NMR measurements on the hole-doped HTSCs when Zn is partially substituted for Cu. There is also an additional temperature-dependent contribution to the (63)Cu spin-lattice relaxation rate that can be interpreted in terms of an Ni-induced modification of the low energy spin fluctuations. Furthermore, the spin fluctuations are intrinsically spatially inhomogeneous and additional inhomogeneities are induced by Ni.

  18. Influence of structural parameters on magnetoresistive properties of CuFeNi melt spun ribbons.

    PubMed

    Cazottes, S; Danoix, F; Fnidiki, A; Lemarchand, D; Baricco, M

    2009-04-01

    The microstructure of Cu(80)Fe(10)Ni(10) (at%) granular ribbon was investigated by means of atom probe tomography (APT). A granular system is composed of magnetic precipitates embedded in a non-magnetic matrix. In this ribbon, the magnetic precipitates have a diameter smaller than 5nm in the as-spun state, and their crystallographic structure is very similar to the one of the matrix, which makes it difficult to characterize them using conventional techniques. Those data are of great importance to understand the magnetic and the transport behaviour of these ribbons. Using atom probe tomography, a 3D reconstruction of the microstructure of the as-spun and annealed ribbons was achieved and a precise characterization of the compositions of the two phases and of the composition profile at interfaces was carried out. In the as-spun state the composition of the matrix is Cu(89)Fe(3)Ni(8), the one of the precipitates is Cu(30)Fe(40)Ni(30). Upon annealing, the precipitates get enriched in iron. After annealing at 600 degrees C for 24h, the measured compositions are close to the one predicted by Thermocalc, with Cu(94)Fe(1)Ni(5) for the matrix and Cu(5)Fe(64)Ni(31) for the precipitates.

  19. Cytotoxicity Evaluation and Magnetic Characteristics of Mechano-thermally Synthesized CuNi Nanoparticles for Hyperthermia

    NASA Astrophysics Data System (ADS)

    Amrollahi, P.; Ataie, A.; Nozari, A.; Seyedjafari, E.; Shafiee, A.

    2015-03-01

    CuNi alloys are very well known, both in academia and industry, based on their wide range of applications. In the present investigation, the previously synthesized Cu0.5Ni0.5 nanoparticles (NPs) by mechano-thermal method were studied more extensively. Phase composition and morphology of the samples were studied by employing x-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) techniques. The Curie temperature ( T c) was determined by differential scanning calorimetry (DSC). In vitro cytotoxicity was studied through methyl-thiazolyl-tetrazolium (MTT) assay. XRD and FESEM results indicated the formation of single-phase Cu0.5Ni0.5. TEM micrographs showed that the mean particle size of powders is 20 nm. DSC results revealed that T c of mechano-thermally synthesized Cu0.5Ni0.5 is 44 °C. The MTT assay results confirmed the viability and proliferation of human bone marrow stem cells in contact with Cu0.5Ni0.5 NPs. In summary, the fabricated particles were demonstrated to have potential in low concentrations for cancer treatment applications.

  20. NiCu Alloy Nanoparticle-Loaded Carbon Nanofibers for Phenolic Biosensor Applications.

    PubMed

    Li, Dawei; Lv, Pengfei; Zhu, Jiadeng; Lu, Yao; Chen, Chen; Zhang, Xiangwu; Wei, Qufu

    2015-11-20

    NiCu alloy nanoparticle-loaded carbon nanofibers (NiCuCNFs) were fabricated by a combination of electrospinning and carbonization methods. A series of characterizations, including SEM, TEM and XRD, were employed to study the NiCuCNFs. The as-prepared NiCuCNFs were then mixed with laccase (Lac) and Nafion to form a novel biosensor. NiCuCNFs successfully achieved the direct electron transfer of Lac. Cyclic voltammetry and linear sweep voltammetry were used to study the electrochemical properties of the biosensor. The finally prepared biosensor showed favorable electrocatalytic effects toward hydroquinone. The detection limit was 90 nM (S/N = 3), the sensitivity was 1.5 µA µM(-1), the detection linear range was 4 × 10(-7)-2.37 × 10(-6) M. In addition, this biosensor exhibited satisfactory repeatability, reproducibility, anti-interference properties and stability. Besides, the sensor achieved the detection of hydroquinone in lake water.

  1. Structural and magnetic properties of NiCuZn ferrite/SiO 2 nanocomposites

    NASA Astrophysics Data System (ADS)

    Praveena, K.; Sadhana, K.; Ramana Murthy, S.

    2011-08-01

    Ni0.53Cu0.12Zn0.35Fe2O4/SiO2 nanocomposites with different weight percentages of NiCuZn ferrite dispersed in silica matrix were prepared by microwave-hydrothermal method using tetraethylorthosilicate as a precursor of silica, and metal nitrates as precursors of NiCuZn ferrite. The structure and morphology of the composites were studied using X-ray diffraction and scanning electron microscopy. The structural changes in these samples were characterized using Fourier Transform Infrared Spectrometer in the range of 400-1500 cm-1. The bands in the range of 580-880 cm-1 show a slight increase in intensity, which could be ascribed to the enhanced interactions between the NiCuZnFe2O4 clusters and silica matrix. The effects of silica content and sintering temperature on the magnetic properties of Ni0.53Cu0.12Zn0.35Fe2O4/SiO2 nanocomposites have been studied using electron spin resonance and vibrating sample magnetometer.

  2. Size and alloying induced shift in core and valence bands of Pd-Ag and Pd-Cu nanoparticles

    SciTech Connect

    Sengar, Saurabh K.; Mehta, B. R.; Govind

    2014-03-28

    In this report, X-ray photoelectron spectroscopy studies have been carried out on Pd, Ag, Cu, Pd-Ag, and Pd-Cu nanoparticles having identical sizes corresponding to mobility equivalent diameters of 60, 40, and 20 nm. The nanoparticles were prepared by the gas phase synthesis method. The effect of size on valence and core levels in metal and alloy nanoparticles has been studied by comparing the values to those with the 60 nm nanoparticles. The effect of alloying has been investigated by comparing the valence and core level binding energies of Pd-Cu and Pd-Ag alloy nanoparticles with the corresponding values for Pd, Ag, and Cu nanoparticles of identical sizes. These effects have been explained in terms of size induced lattice contractions, alloying induced charge transfer, and hybridization effects. The observation of alloying and size induced binding energy shifts in bimetallic nanoparticles is important from the point of view of hydrogen reactivity.

  3. Efficient enhancement of hydrogen production by Ag/Cu2O/ZnO tandem triple-junction photoelectrochemical cell

    NASA Astrophysics Data System (ADS)

    Liu, Ying; Ren, Feng; Shen, Shaohua; Fu, Yanming; Chen, Chao; Liu, Chang; Xing, Zhuo; Liu, Dan; Xiao, Xiangheng; Wu, Wei; Zheng, Xudong; Liu, Yichao; Jiang, Changzhong

    2015-03-01

    Highly efficient semiconductor photoelectrodes for solar hydrogen production through photocatalytic water splitting are a promising and challenge solution to solve the energy problems. In this work, Ag/Cu2O/ZnO tandem triple-junction photoelectrode was designed and prepared. An increase of 11 times of photocurrent is achieved in the Ag/Cu2O/ZnO photoelectrode comparing to that of the Cu2O film. The high performance of the Ag/Cu2O/ZnO film is due to the optimized design of the tandem triple-junction structure, where the localized surface Plasmon resonance of Ag and the hetero-junctions efficiently absorb solar energy, produce, and separate electron-hole pairs in the photocathode.

  4. Ag-Cu nanoalloyed film as a high-performance cathode electrocatalytic material for zinc-air battery

    NASA Astrophysics Data System (ADS)

    Lei, Yimin; Chen, Fuyi; Jin, Yachao; Liu, Zongwen

    2015-04-01

    A novel Ag50Cu50 film electrocatalyst for oxygen reduction reaction (ORR) was prepared by pulsed laser deposition (PLD) method. The electrocatalyst actually is Ag-Cu alloyed nanoparticles embedded in amorphous Cu film, based on transmission electron microscopy (TEM) characterization. The rotating disk electrode (RDE) measurements provide evidence that the ORR proceed via a four-electron pathway on the electrocatalysts in alkaline solution. And it is much more efficient than pure Ag catalyst. The catalytic layer has maximum power density of 67 mW cm-2 and an acceptable cell voltage at 0.863 V when current densities increased up to 100 mA cm-2 in the Ag50Cu50-based primary zinc-air battery. The resulting rechargeable zinc-air battery exhibits low charge-discharge voltage polarization of 1.1 V at 20 mAcm-2 and high durability over 100 cycles in natural air.

  5. Magnetic behavior of NiCu nanowire arrays: Compositional, geometry and temperature dependence

    SciTech Connect

    Palmero, E. M. Bran, C.; Real, R. P. del; Vázquez, M.; Magén, C.

    2014-07-21

    Arrays of Ni{sub 100−x}Cu{sub x} nanowires ranging in composition 0 ≤ x ≤ 75, diameter from 35 to 80 nm, and length from 150 nm to 28 μm have been fabricated by electrochemical co-deposition of Ni and Cu into self-ordered anodic aluminum oxide membranes. As determined by X-ray diffraction and Transmission Electron Microscopy, the crystalline structure shows fcc cubic symmetry with [111] preferred texture and preferential Ni or Cu lattice depending on the composition. Their magnetic properties such as coercivity and squareness have been determined as a function of composition and geometry in a Vibrating Sample Magnetometer in the temperature range from 10 to 290 K for applied magnetic fields parallel and perpendicular to the nanowires axis. Addition of Cu into the NiCu alloy up to 50% enhances both parallel coercivity and squareness. For the higher Cu content, these properties decrease and the magnetization easy axis becomes oriented perpendicular to the wires. In addition, coercivity and squareness increase by decreasing the diameter of nanowires which is ascribed to the increase of shape anisotropy. The temperature dependent measurements reflect a complex behavior of the magnetic anisotropy as a result of energy contributions with different evolution with temperature.

  6. Mechanical properties and microstructures of dental cast Ti-Ag and Ti-Cu alloys.

    PubMed

    Takahashi, Masatoshi; Kikuchi, Masafumi; Takada, Yukyo; Okuno, Osamu

    2002-09-01

    In this study, experimental Ti-Ag alloys (5, 10, and 20 mass% Ag) and Ti-Cu alloys (2, 5, and 10 mass% Cu) were made in an argon-arc melting furnace. The alloys were cast into magnesia molds using an argon gas-pressure dental casting machine, and the mechanical properties and microstructures of the castings were investigated. As the concentration of silver or copper in the alloys increased, the tensile strength, yield strength, and hardness of the alloys became higher than those of CP Ti, and the elongation of the alloys became lower than that of CP Ti. Changes in the mechanical properties by alloying were considered to be caused by solid-solution strengthening of the a-phases and by precipitation of intermetallic compounds.

  7. Achieving high strength and high electrical conductivity in Ag/Cu multilayers

    NASA Astrophysics Data System (ADS)

    Wei, M. Z.; Xu, L. J.; Shi, J.; Pan, G. J.; Cao, Z. H.; Meng, X. K.

    2015-01-01

    In this work, we investigated the microstructure evolution of Ag/Cu multilayers and its influences on the hardness and electric resistivity with individual layer thickness (h) ranging from 3 to 50 nm. The hardness increases with the decreasing h in the range of 5-20 nm. The barrier to dislocation transmission by stacking faults, twin boundaries, and interfaces leads to hardness enhancement. Simultaneously, in order to get high conductivity, the strong textures in-layers were induced to form for reducing the amount of grain boundaries. The resistivity keeps low even when h decreases to 10 nm. Furthermore, we developed a facile model to evaluate the comprehensive property of Ag/Cu multilayers—the results indicate that the best combination of strength and conductivity occurs when h = 10 nm.

  8. Green Synthesis of Ag-Cu Nanoalloys Using Opuntia ficus- indica

    NASA Astrophysics Data System (ADS)

    Rocha-Rocha, O.; Cortez-Valadez, M.; Hernández-Martínez, A. R.; Gámez-Corrales, R.; Alvarez, Ramón A. B.; Britto-Hurtado, R.; Delgado-Beleño, Y.; Martinez-Nuñez, C. E.; Pérez-Rodríguez, A.; Arizpe-Chávez, H.; Flores-Acosta, M.

    2017-02-01

    Bimetallic Ag/Cu nanoparticles have been obtained by green synthesis using Opuntia ficus- indica plant extract. Two synthesis methods were applied to obtain nanoparticles with core-shell and Janus morphologies by reversing the order of precursors. Transmission electronic microscopy revealed size of 10 nm and 20 nm for the core-shell and Janus nanoparticles, respectively. Other small particles with size of up to 2 nm were also observed. Absorption bands attributed to surface plasmon resonance were detected at 440 nm and 500 nm for the core-shell and Janus nanoparticles, respectively. Density functional theory predicted a breathing mode type (BMT) located at low wavenumber due to small, low-energy clusters of (AgCu) n with n = 2 to 9, showing a certain correlation with the experimental one (at 220 cm-1). The dependence of the BMT on the number of atoms constituting the cluster is also studied.

  9. Formation of M-C≡C-Cl (m = ag or Cu) and Characterization by Rotational Spectroscopy

    NASA Astrophysics Data System (ADS)

    Zaleski, Daniel P.; Tew, David Peter; Walker, Nick; Legon, Anthony

    2015-06-01

    The new linear molecule Ag-C≡C-Cl has been detected and characterized by means of rotational spectroscopy. It was synthesized by laser ablation of a slver rod in the presence of a gaseous sample containing a low concentration of CCl4 in argon, cooled to a rotational temperature approaching 2 K through supersonic expansion and analyzed by chirped pulse Fourier transform microwave spectroscopy. Substitution coordinates are available for the silver and chlorine positions and will be compared to ab initio calculations at the CCSD(T)/aug-cc-pV5Z level of theory. The Ag-13C≡13C-Cl isotopologue was also observed using a similar gas mixture containing 13CCl4. The Cu analogue Cu-C≡C-Cl was similarly identified and characterized.

  10. Possible Mesozoic age of Ellenville Zn-Pb-Cu(Ag) deposit, Shawangunk Mountains, New York

    USGS Publications Warehouse

    Friedman, J.D.; Conrad, J.E.; McKee, E.H.; Mutschler, F.E.; Zartman, R.E.

    1994-01-01

    Ore textures, epithermal open-space filling of Permian structures of the Alleghanian orogeny, and largely postorogenic mineralization of the Ellenville, New York, composite Zn-Pb-Cu(Ag) vein system, provide permissive evidence for post-Permian mineralization. Isochron ages determined by 40Ar/39Ar laser-fusion techniques for K-bearing liquid inclusions in main-stage quartz from the Ellenville deposit additionally suggest a Mesozoic time of mineralization, associated with extensional formation of the Newark basin. The best 40Ar/39Ar total-fusion age range is 165 ?? 30 to 193 ?? 35 Ma. The Mesozoic 40Ar/39Ar age agrees with that of many other dated northern Appalachian Zn-Pb-Cu(Ag) deposits with near-matching lead isotope ratios, and adds new evidence of Jurassic tectonism and mineralization as an overprint to Late Paleozoic tectonism at least as far north as Ellenville (lat. 41??43???N). ?? 1994 Springer-Verlag.

  11. Molecular Dynamics Study of Surface Anisotropy in Ag_{60} Cu_{40} Alloy at Nanoscale

    NASA Astrophysics Data System (ADS)

    Imran, Muhammad; Hussain, Fayyaz; Rashid, Muhammad; Kousar, Farhana; Javid, M. Arshad; Ullah, Hafeez; Ahmad, Ejaz; Ahmad, S. A.

    2017-03-01

    In the present study, molecular dynamics simulation has been performed to investigate the anisotropic behavior of free standing Ag_{60} Cu_{40} nanorods. We choose different orientations with various cross sections to study the dynamics of thermal behavior of Ag_{60} Cu_{40} nanorods. The system is modeled using embedded atom method potentials. The radial distribution functions are analyzed to reveal the dynamic evolution of the structural behavior of nanorods with different orientations and sample sizes. The total energy and mean square displacement is also calculated to characterize the melting phenomenon of various samples. The melting temperature of the nanorods is found to be significantly size and orientation dependent, and it increases with the increase in cross-sectional area. The nanorods with low-index crystallographic surfaces such as (110) exhibit lowest melting temperature as compared to compact surfaces (111).

  12. Electromigration induced Kirkendall void growth in Sn-3.5Ag/Cu solder joints

    SciTech Connect

    Jung, Yong; Yu, Jin

    2014-02-28

    Effects of electric current flow on the Kirkendall void formation at solder joints were investigated using Sn-3.5Ag/Cu joints specially designed to have localized nucleation of Kirkendall voids at the Cu{sub 3}Sn/Cu interface. Under the current density of 1 × 10{sup 4} A/cm{sup 2}, kinetics of Kirkendall void growth and intermetallic compound thickening were affected by the electromigration (EM), and both showed the polarity effect. Cu{sub 6}Sn{sub 5} showed a strong susceptibility to the polarity effect, while Cu{sub 3}Sn did not. The electromigration force induced additional tensile (or compressive) stress at the cathode (or anode), which accelerated (or decelerated) the void growth. From the measurements of the fraction of void at the Cu{sub 3}Sn/Cu interface on SEM micrographs and analysis of the kinetics of void growth, the magnitude of the local stress induced by EM was estimated to be 9 MPa at the anode and −7 MPa at the cathode.

  13. [Determination of Ag, Cu, Zn and Cd in silver brazing filler metals by ICP-AES].

    PubMed

    Yang, X

    1997-06-01

    A method of simultaneous and direct determination for Ag, Cu, Zn and Cd in silver brazing filler metals by ICP-AES is reported. The spectral interferences and effect of acidity have been investigated. Working conditions were optimized. The method has been applied to the analysis of silver brazing filler metals with RSD of 4-7% and recovery of 94-105%. This method was accurate, simple and rapid.

  14. 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.

  15. Microstructure-property relationships in Al-Cu-Li-Ag-Mg Weldalite (tm) alloys, part 2

    NASA Technical Reports Server (NTRS)

    Langan, T. J.; Pickens, J. R.

    1991-01-01

    The microstructure and mechanical properties of the ultrahigh strength Al-Cu-Li-Ag-Mg alloy, Weldalite (tm) 049, were studied. Specifically, the microstructural features along with tensile strength, weldability, Young's modulus and fracture toughness were studied for Weldalite (tm) 049 type alloys with Li contents ranging from 1.3 to 1.9 wt. pct. The tensile properties of Weldalite 049 and Weldalite 049 reinforced with TiB2 particles fabricated using the XD (tm) process were also evaluated at cryogenic, room, and elevated temperatures. In addition, an experimental alloy, similar in composition to Weldalite 049 but without the Ag+Mg, was fabricated. The microstructure of this alloy was compared with that of Weldalite 049 in the T6 condition to assess the effect of Ag+Mg on nucleation of strengthening phases in the absence of cold work.

  16. Competitive removal of Cu-EDTA and Ni-EDTA via microwave-enhanced Fenton oxidation with hydroxide precipitation.

    PubMed

    Lin, Qintie; Pan, Hanping; Yao, Kun; Pan, Yonggang; Long, Wei

    2015-01-01

    Ethylenediaminetetraacetic acid (EDTA) can form very stable complexes with heavy metal ions, greatly inhibiting conventional metal-removal technologies used in water treatment. Both the oxidation of EDTA and the reduction of metal ions in metal-EDTA systems via the microwave-enhanced Fenton reaction followed by hydroxide precipitation were investigated. The Cu(II)-Ni(II)-EDTA, Cu(II)-EDTA and Ni(II)-EDTA exhibited widely different decomplexation efficiencies under equivalent conditions. When the reaction reached equilibrium, the chemical oxygen demand was reduced by a microwave-enhanced Fenton reaction in different systems and the reduction order from high to low was Cu(II)-Ni(II)-EDTA ≈ Cu(II)-EDTA > Ni(II)-EDTA. The removal efficiencies of both Cu(2+) and Ni(2+) in Cu-Ni-EDTA wastewaters were much higher than those in a single heavy metal system. The degradation efficiency of EDTA in Cu-Ni-EDTA was lower than that in a single metal system. In the Cu-Ni-EDTA system, the microwave thermal degradation and the Fenton-like reaction created by Cu catalyzed H2O2 altered the EDTA degradation pathway and increased the pH of the wastewater system, conversely inhibiting residual EDTA degradation.

  17. Structural evolution of Ag-Cu nano-alloys confined between AlN nano-layers upon fast heating.

    PubMed

    Janczak-Rusch, J; Chiodi, M; Cancellieri, C; Moszner, F; Hauert, R; Pigozzi, G; Jeurgens, L P H

    2015-11-14

    The structural evolution of a Ag-Cu/AlN nano-multilayer (NML), as prepared by magnetron-sputtering on a α-Al2O3 substrate, was monitored during fast heating by real-time in situ XRD analysis (at the synchrotron), as well as by ex situ microstructural analysis using SEM, XPS and in-house XRD. The as-deposited NML is constituted of alternating nano-layers (thickness ≈ 10 nm) of a chemically inert AlN barrier and a eutectic Ag-Cu(40at%) nano-alloy. The nano-alloy in the as-deposited state is composed of a fcc matrix of Ag nano-grains (≈6 nm), which are supersaturated by Cu, and some smaller embedded Cu rich nano-grains (≈4 nm). Heating up to 265 °C activates segregation of Cu out of the supersaturated Ag nano-grains phase, thus initiating phase separation. At T > 265 °C, the phase-separated Cu metal partially migrates to the top NML surface, thereby relaxing thermally-accumulated compressive stresses in the confined alloy nano-layers and facilitating grain coarsening of (still confined) phase-separated nano-crystallites. Further heating and annealing up to 420 °C results in complete phase separation, forming extended Ag and Cu domains with well-defined coherent Ag/AlN interfaces. The observed outflow of Cu well below the eutectic melting point of the bulk Ag-Cu alloy might provide new pathways for designing low-temperature nano-structured brazing materials.

  18. Pressure-Free Bonding of Metallic Plates with Ni Affinity Layers Using Cu Nanoparticles

    NASA Astrophysics Data System (ADS)

    Ishizaki, Toshitaka; Akedo, Kunio; Satoh, Toshikazu; Watanabe, Ryota

    2014-01-01

    This study investigated the pressure-free bonding of metallic plates using Cu nanoparticles capped by fatty acid and amine as the bonding material. The application of Ni layers to Cu plates prior to bonding significantly improved their adhesion to sintered Cu nanoparticles, resulting in higher strengths even without pressure compared to samples bonded using an ordinary Pb-rich solder at a similar temperature. The shear strength could be enhanced if the thickness of Ni layers was larger than 1 nm. The same effect was also observed when Al plates with Ni layers were bonded by Cu nanoparticles. In contrast, Ti, Mn, and Cr layers were found to be ineffective with regard to improving bond strength. Cu plates bonded by Cu nanoparticles capped by fatty acid and amine with different alkyl chain lengths from 6 to 18 showed an optimal strength with a length of 10, where the Cu particles were small enough to sinter effectively but not so small as to oxidize.

  19. Microstructures and Mechanical Properties of NiTiFeAlCu High-Entropy Alloys with Exceptional Nano-precipitates

    NASA Astrophysics Data System (ADS)

    Zhang, Yanqiu; Wang, Sibing; Jiang, Shuyong; Zhu, Xiaoming; Sun, Dong

    2017-01-01

    Three novel NiTiFeAlCu high-entropy alloys, which consist of nano-precipitates with face-centered cubic structure and matrix with body-centered cubic structure, were fabricated to investigate microstructures and mechanical properties. With the increase in Ni and Ti contents, the strength of NiTiFeAlCu alloy is enhanced, while the plasticity of NiTiFeAlCu alloy is lowered. Plenty of dislocations can be observed in the Ni32Ti32Fe12Al12Cu12 high-entropy alloy. The size of nano-precipitates decreases with the increase in Ni and Ti contents, while lattice distortion becomes more and more severe with the increase in Ni and Ti contents. The existence of nano-precipitates, dislocations and lattice distortion is responsible for the increase in the strength of NiTiFeAlCu alloy, but it has an adverse influence on the plasticity of NiTiFeAlCu alloy. Ni20Ti20Fe20Al20Cu20 alloy exhibits the substantial ability of plastic deformation and a characteristic of steady flow at 850 and 1000 °C. This phenomenon is attributed to a competition between the increase in the dislocation density induced by plastic strain and the decrease in the dislocation density due to the dynamic recrystallization.

  20. Microstructures and Mechanical Properties of NiTiFeAlCu High-Entropy Alloys with Exceptional Nano-precipitates

    NASA Astrophysics Data System (ADS)

    Zhang, Yanqiu; Wang, Sibing; Jiang, Shuyong; Zhu, Xiaoming; Sun, Dong

    2016-10-01

    Three novel NiTiFeAlCu high-entropy alloys, which consist of nano-precipitates with face-centered cubic structure and matrix with body-centered cubic structure, were fabricated to investigate microstructures and mechanical properties. With the increase in Ni and Ti contents, the strength of NiTiFeAlCu alloy is enhanced, while the plasticity of NiTiFeAlCu alloy is lowered. Plenty of dislocations can be observed in the Ni32Ti32Fe12Al12Cu12 high-entropy alloy. The size of nano-precipitates decreases with the increase in Ni and Ti contents, while lattice distortion becomes more and more severe with the increase in Ni and Ti contents. The existence of nano-precipitates, dislocations and lattice distortion is responsible for the increase in the strength of NiTiFeAlCu alloy, but it has an adverse influence on the plasticity of NiTiFeAlCu alloy. Ni20Ti20Fe20Al20Cu20 alloy exhibits the substantial ability of plastic deformation and a characteristic of steady flow at 850 and 1000 °C. This phenomenon is attributed to a competition between the increase in the dislocation density induced by plastic strain and the decrease in the dislocation density due to the dynamic recrystallization.

  1. Corrosion properties of Ag-Au-Cu-Pd system alloys containing indium.

    PubMed

    Hattori, Masayuki; Tokizaki, Teruhiko; Matsumoto, Michihiko; Oda, Yutaka

    2010-01-01

    In this study, the corrosion resistance of Ag-Au-Cu-Pd system alloys consisting of 5 or 10 mass% indium was evaluated. Levels of element release and tarnish were determined and electrochemical measurements performed. Results were compared with those for commercial silver-palladium-gold alloy. In terms of electrochemical behavior, the transpassive potential of these experimental alloys was 168-248mV. Experimental alloys with 25 mass% Au showed similar corrosion resistance to control gold-silver-palladium alloy. Amount of released elements was 14-130microg/cm(2) at 7 days, which is in the allowable range for dental alloys. Addition of indium to Ag-Au-Cu-10mass%Pd system alloys was effective in increasing resistance to tarnish and alloys containing 10 mass% of indium showed a minimal decrease in L(*) values after immersion. These findings indicate that 25Au-37.5Ag-15Cu-10Pd-2Zn-10In-0.5Ir alloy is applicable in dental practice.

  2. Combinatorial development of antibacterial Zr-Cu-Al-Ag thin film metallic glasses

    PubMed Central

    Liu, Yanhui; Padmanabhan, Jagannath; Cheung, Bettina; Liu, Jingbei; Chen, Zheng; Scanley, B. Ellen; Wesolowski, Donna; Pressley, Mariyah; Broadbridge, Christine C.; Altman, Sidney; Schwarz, Udo D.; Kyriakides, Themis R.; Schroers, Jan

    2016-01-01

    Metallic alloys are normally composed of multiple constituent elements in order to achieve integration of a plurality of properties required in technological applications. However, conventional alloy development paradigm, by sequential trial-and-error approach, requires completely unrelated strategies to optimize compositions out of a vast phase space, making alloy development time consuming and labor intensive. Here, we challenge the conventional paradigm by proposing a combinatorial strategy that enables parallel screening of a multitude of alloys. Utilizing a typical metallic glass forming alloy system Zr-Cu-Al-Ag as an example, we demonstrate how glass formation and antibacterial activity, two unrelated properties, can be simultaneously characterized and the optimal composition can be efficiently identified. We found that in the Zr-Cu-Al-Ag alloy system fully glassy phase can be obtained in a wide compositional range by co-sputtering, and antibacterial activity is strongly dependent on alloy compositions. Our results indicate that antibacterial activity is sensitive to Cu and Ag while essentially remains unchanged within a wide range of Zr and Al. The proposed strategy not only facilitates development of high-performing alloys, but also provides a tool to unveil the composition dependence of properties in a highly parallel fashion, which helps the development of new materials by design. PMID:27230692

  3. Investigation of Pd-Modified Ag-CuO Air Braze Filler Metals

    SciTech Connect

    Weil, K. Scott; Kim, Jin Yong; Hardy, John S.; Darsell, Jens T.

    2006-01-01

    This paper reports on the effects of palladium on the liquidus/solidus temperatures and wetting behavior of a series of Ag-CuOx air braze filler metals. Currently, the maximum operating temperature of the Ag-CuOx system is limited by its eutectic temperature of ~935°C. One strategy to increase the maximum operational temperature of this family of filler metals is to add a higher melting noble alloying element. In the current study, we examined the effects of palladium additions on the melting characteristics of the Ag-CuO materials and the wetting properties of the resulting air braze filler metals with respect to alumina. It was found that while the addition of Pd causes the anticipated increase in the melting temperature, it does so at a sacrifice in wetting properties. The extent of both effects and therefore the opportunity to trade-off the two properties in order to develop an optimized higher temperature air braze depends on concentrations of both the palladium and copper oxide.

  4. Combinatorial development of antibacterial Zr-Cu-Al-Ag thin film metallic glasses

    NASA Astrophysics Data System (ADS)

    Liu, Yanhui; Padmanabhan, Jagannath; Cheung, Bettina; Liu, Jingbei; Chen, Zheng; Scanley, B. Ellen; Wesolowski, Donna; Pressley, Mariyah; Broadbridge, Christine C.; Altman, Sidney; Schwarz, Udo D.; Kyriakides, Themis R.; Schroers, Jan

    2016-05-01

    Metallic alloys are normally composed of multiple constituent elements in order to achieve integration of a plurality of properties required in technological applications. However, conventional alloy development paradigm, by sequential trial-and-error approach, requires completely unrelated strategies to optimize compositions out of a vast phase space, making alloy development time consuming and labor intensive. Here, we challenge the conventional paradigm by proposing a combinatorial strategy that enables parallel screening of a multitude of alloys. Utilizing a typical metallic glass forming alloy system Zr-Cu-Al-Ag as an example, we demonstrate how glass formation and antibacterial activity, two unrelated properties, can be simultaneously characterized and the optimal composition can be efficiently identified. We found that in the Zr-Cu-Al-Ag alloy system fully glassy phase can be obtained in a wide compositional range by co-sputtering, and antibacterial activity is strongly dependent on alloy compositions. Our results indicate that antibacterial activity is sensitive to Cu and Ag while essentially remains unchanged within a wide range of Zr and Al. The proposed strategy not only facilitates development of high-performing alloys, but also provides a tool to unveil the composition dependence of properties in a highly parallel fashion, which helps the development of new materials by design.

  5. Effect of microstructure on thermal conductivity of Cu, Ag thin films.

    PubMed

    Ryu, Sang; Juhng, Woonam; Kim, Youngman

    2010-05-01

    Thin film type materials are widely used in modern industries, such as semiconductor devices, functional superconductors, machining tools, and so on. The thermal properties of material in semiconductor are very important factors for stable operation because the heat generated during device operation may increase clock frequency. Even though thermal properties of thin films may play a major role in assessing reliability of parts, the measurement methods of thin film thermal properties are generally known to be complex to devise. In this study, a temperature distribution method was applied for the measurement of thermal conductivity of Cu and Ag thin film on borosilicate glass substrate. Cu and Ag thin films were deposited on borosilicate glass using thermal evaporation processes. To measure the thermal conductivity changes according to the microstructure of metallic thin film, the processing variables for the Cu and Ag thin film deposition were changed. To minimize the effect of film thickness, the film thickness was fixed to the thickness of approximately 500 nm throughout experiments. The thermal conductivities of thin films were measured to be much lower than those of bulk materials. Thin film with larger grain size showed higher thermal conductivity probably due to the lower number density of grain boundary. Weidman-Franz law could be applied to thin films produced in this study. Thermal conductivity was also estimated from the resistivity of thin film and Lorenz number of bulk material.

  6. Combinatorial development of antibacterial Zr-Cu-Al-Ag thin film metallic glasses.

    PubMed

    Liu, Yanhui; Padmanabhan, Jagannath; Cheung, Bettina; Liu, Jingbei; Chen, Zheng; Scanley, B Ellen; Wesolowski, Donna; Pressley, Mariyah; Broadbridge, Christine C; Altman, Sidney; Schwarz, Udo D; Kyriakides, Themis R; Schroers, Jan

    2016-05-27

    Metallic alloys are normally composed of multiple constituent elements in order to achieve integration of a plurality of properties required in technological applications. However, conventional alloy development paradigm, by sequential trial-and-error approach, requires completely unrelated strategies to optimize compositions out of a vast phase space, making alloy development time consuming and labor intensive. Here, we challenge the conventional paradigm by proposing a combinatorial strategy that enables parallel screening of a multitude of alloys. Utilizing a typical metallic glass forming alloy system Zr-Cu-Al-Ag as an example, we demonstrate how glass formation and antibacterial activity, two unrelated properties, can be simultaneously characterized and the optimal composition can be efficiently identified. We found that in the Zr-Cu-Al-Ag alloy system fully glassy phase can be obtained in a wide compositional range by co-sputtering, and antibacterial activity is strongly dependent on alloy compositions. Our results indicate that antibacterial activity is sensitive to Cu and Ag while essentially remains unchanged within a wide range of Zr and Al. The proposed strategy not only facilitates development of high-performing alloys, but also provides a tool to unveil the composition dependence of properties in a highly parallel fashion, which helps the development of new materials by design.

  7. Plasmon spectra of binary Ag-Cu mixtures supported in mordenite

    NASA Astrophysics Data System (ADS)

    López-Bastidas, Catalina; Smolentseva, Elena; Petranovskii, Vitalii P.; Machorro, Roberto

    2016-09-01

    Ag and Cu nanoparticles supported in mordenite structure have been formed applying reduction temperatures in the range 100-400 C and varying Ag/Cu atomic ratios. Absorbance spectra of samples exhibit signature features consistent with absorption via localized surface plasmons propagating in metallic nanoparticles. The formation of binary Ag-Cu nanoparticles is inferred. Theoretical calculations within an average field Maxwell-Garnett model modified for a three component composite system are used to interpret resonance shifts and relative intensities of plasmon peaks in the experimental findings. Within the applied model the relative volume occupied by each metallic species can be changed. This permits the simulation of experimental conditions of the samples. It is experimentally found that the simultaneous presence of two metal species during the synthesis affects reduction temperatures, stability and relative concentration of embedded nanoparticles. Furthermore the observed optical spectra of the supported bimetallic nanoparticles is contrasted with that of single metal nanoparticles studied previously. Our study represents a contribution to the possibility of optical monitoring of synthetic pathways in zeolite + metal nanoparticle systems.

  8. Thermal stability and crystallization kinetics of Cu-Zr-Al-Ag BMGs investigated with isothermal electrical resistance measurement

    NASA Astrophysics Data System (ADS)

    Wang, Li-Fang; Cui, Xiao; Zhang, Qi-Dong; Zu, Fang-Qiu

    2014-07-01

    The thermal stability and crystallization kinetics of the Cu x Zr84- x Al8Ag8 ( x = 42, 40, 38, and 36) bulk metallic glasses (BMGs) were studied by measurement of isothermal electrical-resistance. As the composition becomes richer in Zr, the longer incubation time at the same relative annealing temperature, and the larger local activation energy needed to achieve the same crystallized volume-fraction, indicate improved thermal stability, which resists crystallization. The improved thermal stability is attributed to a denser atomic random-stacking structure and larger negative heat-of-mixing. During isothermal annealing processes, the four BMGs exhibited the same nucleation mechanism, which is a decreasing rate of nucleation over time. However, the crystal growth mechanisms of the four BMGs are different. The crystallization of the Cu36Zr48Al8Ag8 and Cu38Zr46Al8Ag8 BMGs is interface-controlled growth, contrasting with diffusion-controlled growth for the Cu40Zr44Al8Ag8 and Cu42Zr42Al8Ag8 alloys. The different growth modes may be caused by fluctuations in composition due to changes in the quantity and distribution of Cu-rich and Ag-rich regions.

  9. Ag-Pd-Cu alloy inserted transparent indium tin oxide electrodes for organic solar cells

    SciTech Connect

    Kim, Hyo-Joong; Seo, Ki-Won; Kim, Han-Ki; Noh, Yong-Jin; Na, Seok-In

    2014-09-01

    The authors report on the characteristics of Ag-Pd-Cu (APC) alloy-inserted indium tin oxide (ITO) films sputtered on a glass substrate at room temperature for application as transparent anodes in organic solar cells (OSCs). The effect of the APC interlayer thickness on the electrical, optical, structural, and morphological properties of the ITO/APC/ITO multilayer were investigated and compared to those of ITO/Ag/ITO multilayer electrodes. At the optimized APC thickness of 8 nm, the ITO/APC/ITO multilayer exhibited a resistivity of 8.55 × 10{sup −5} Ω cm, an optical transmittance of 82.63%, and a figure-of-merit value of 13.54 × 10{sup −3} Ω{sup −1}, comparable to those of the ITO/Ag/ITO multilayer. Unlike the ITO/Ag/ITO multilayer, agglomeration of the metal interlayer was effectively relieved with APC interlayer due to existence of Pd and Cu elements in the thin region of the APC interlayer. The OSCs fabricated on the ITO/APC/ITO multilayer showed higher power conversion efficiency than that of OSCs prepared on the ITO/Ag/ITO multilayer below 10 nm due to the flatness of the APC layer. The improved performance of the OSCs with ITO/APC/ITO multilayer electrodes indicates that the APC alloy interlayer prevents the agglomeration of the Ag-based metal interlayer and can decrease the thickness of the metal interlayer in the oxide-metal-oxide multilayer of high-performance OSCs.

  10. Electromigration-induced cracks in Cu/Sn3.5Ag/Cu solder reaction couple at room temperature

    NASA Astrophysics Data System (ADS)

    Hongwen, He; Guangchen, Xu; Fu, Guo

    2009-03-01

    Electromigration (EM) behavior of Cu/Sn3.5Ag/Cu solder reaction couple was investigated with a high current density of 5 × 103 A/cm2 at room temperature. One dimensional structure, copper wire/solder ball/copper wire SRC was designed and fabricated to dissipate the Joule heating induced by the current flow. In addition, thermomigration effect was excluded due to the symmetrical structure of the SRC. The experimental results indicated that micro-cracks initially appeared near the cathode interface between solder matrix and copper substrate after 474 h current stressing. With current stressing time increased, the cracks propagated and extended along the cathode interface. It should be noted that the continuous Cu6Sn5 intermetallic compounds (IMCs) layer both at the anode and at the cathode remained their sizes. Interestingly, tiny cracks appeared at the root of some long column-type Cu6Sn5 at the cathode interface due to the thermal stress.

  11. Novel high-strength NiCuCoTiTa alloy with plasticity

    NASA Astrophysics Data System (ADS)

    Samal, Sumanta; Biswas, Krishanu

    2013-07-01

    The present investigation reports a novel Ni-Ti-based Ni48Cu10Co2Ti38Ta2 alloy, obtained by arc melting cum suction casting route under ultrahigh-purity Ar atmosphere. X-ray diffractometer, scanning electron microscopy, and transmission electron microscopy (TEM) investigations reveal a microstructure consisting of nanostructured eutectic between cubic NiTi and hexagonal Ni3Ti with micron-scale NiTi and cubic Ti2Ni dendrites. Detailed TEM investigation indicates substantial reduction in the interlamellar spacing as the alloy chemistry changes from binary to quinary. The alloy shows a high compressive strength, 2 GPa, with high plasticity 13 %. Fractography surface of this new alloy reveals mixed mode of fracture. The results are discussed in light of the available literature on deformation of nanostructured eutectic with micron-sized dendrites in the microstructures.

  12. Necklace-like NiO-CuO Heterogeneous Composite Hollow Nanostructure: Preparation, Formation Mechanism and Structure Control.

    PubMed

    Xu, Shao Hui; Fei, Guang Tao; Ouyang, Hao Miao; Shang, Guo Liang; Gao, Xu Dong; Zhang, Li De

    2017-12-01

    Composite hollow nanostructure composed by transition metal oxides are promising materials in electrochemistry, catalyst chemistry and material science. In this contribution, necklace-like NiO-CuO heterogeneous composite hollow nanostructures were synthesized by annealing Ni/Cu superlattice nanowires in air. Two kinds of morphologies including CuO nanotube linked core-shell structures and CuO nanotube linked hollow structures were obtained. The structure can be tuned easily by adjusting the relative length of Cu segments in Ni/Cu superlattice nanowires and the annealing temperature. The relative diffusion amount of Cu to Ni segments was proved to be the key factor to influence the annealed sample morphology. The formation mechanism was discussed in detail based on Kirkendal effect and high temperature oxidation of alloy. We demonstrated that hollow structure or core-shell structure is related to whether the oxidation exists only in external sites or co-exists in external and internal sites during annealing.

  13. The As-Cu-Ni System: A Chemical Thermodynamic Model for Ancient Recycling

    NASA Astrophysics Data System (ADS)

    Sabatini, Benjamin J.

    2015-12-01

    This article is the first thermodynamically reasoned ancient metal system assessment intended for use by archaeologists and archaeometallurgists to aid in the interpretation of remelted/recycled copper alloys composed of arsenic and copper, and arsenic, copper, and nickel. These models are meant to fulfill two main purposes: first, to be applied toward the identification of progressive and regressive temporal changes in artifact chemistry that would have occurred due to recycling, and second, to provide thermodynamic insight into why such metal combinations existed in antiquity. Built on well-established thermodynamics, these models were created using a combination of custom-written software and published binary thermodynamic systems data adjusted to within the boundary conditions of 1200°C and 1 atm. Using these parameters, the behavior of each element and their likelihood of loss in the binaries As-Cu, As-Ni, Cu-Ni, and ternary As-Cu-Ni, systems, under assumed ancient furnace conditions, was determined.

  14. Geochemical partitioning of Cu and Ni in mangrove sediments: relationships with their bioavailability.

    PubMed

    Chakraborty, Parthasarathi; Ramteke, Darwin; Chakraborty, Sucharita

    2015-04-15

    Sequential extraction study was performed to determine the concentrations of non-residual metal-complexes in the mangrove sediments from the Divar Island, (west coast of India). Accumulation of metal in the mangrove roots (from the same location) was determined and used as an indicator of bioavailability of metal. An attempt was made to establish a mechanistic linkage between the non-residual metal complexes and their bioavailability in the mangrove system. The non-residual fractions of Cu and Ni were mainly associated with Fe/Mn oxyhydroxide and organic phases in the sediments. A part of these metal fractions were bioavailable in the system. These two phases were the major controlling factors for Ni speciation and their bioavailability in the studied sediments. However, Cu was found to interact more strongly with the organic phases than Ni in the mangrove sediments. Organic phases in the mangrove sediments acted as buffer to control the speciation and bioavailability of Cu in the system.

  15. Complete oxidation of methane over Ag- and Cu-modified cerium and zirconium oxides

    NASA Astrophysics Data System (ADS)

    Kundakovic, Ljiljana

    Low temperature oxidation of methane is an area in catalysis that, despite the large number of catalytic systems studied, does not yet have an adequate solution. The exhaust gas from natural gas burning devices (gas turbines and natural gas vehicles), contains unconverted methane which is emitted into the atmosphere (currently unregulated). Methane is the most refractory of all hydrocarbons, and its activation requires temperatures higher than the typical exhaust temperatures (350-400sp°C). In this work, ceria- and zirconia-supported Ag and CuO catalysts were studied for the complete oxidation of methane. Catalysts were typically tested under excess oxygen and high space velocity (72,000 hsp{-1}). The reaction kinetics were measured over selected catalysts. Hsb2- and CHsb4- TPR and oxygen uptake measurements were used to characterize the catalyst reduction properties. XRD, STEM/EDX and HRTEM were used to characterize the catalyst structure. The oxidation state of various active species present was identified by XPS and UV-VIS DR spectrometry. Ceria- and zirconia-supported Ag and CuO catalysts are very active and stable catalysts for the complete oxidation of carbon monoxide and methane. When ceria is used as an active catalyst support, its activity depends strongly on its structure. Nanocrystalline ceria, stabilized by dopants such as La or Zr, is highly reducible and structurally defective. Our results indicate that surface oxygen species present under reaction conditions are the active sites for methane activation. Activity in the complete oxidation of methane is related to ceria crystal size and reducibility of surface oxygen species. The addition of a transition metal (Ag) or a metal oxide (CuO) in low amounts increases the low temperature reducibility of ceria and enhances the catalyst oxidation activity. On the other hand, both Ag and CuO are active catalysts for the complete oxidation of methane. These were studied separately on inert zirconia support. A

  16. Characterization of Al-Cu-Mg-Ag Alloy RX226-T8 Plate

    NASA Technical Reports Server (NTRS)

    Lach, Cynthia L.; Domack, Marcia S.

    2003-01-01

    Aluminum-copper-magnesium-silver (Al-Cu-Mg-Ag) alloys that were developed for thermal stability also offer attractive ambient temperature strength-toughness combinations, and therefore, can be considered for a broad range of airframe structural applications. The current study evaluated Al-Cu-Mg-Ag alloy RX226-T8 in plate gages and compared performance with sheet gage alloys of similar composition. Uniaxial tensile properties, plane strain initiation fracture toughness, and plane stress tearing resistance of RX226-T8 were examined at ambient temperature as a function of orientation and thickness location in the plate. Properties were measured near the surface and at the mid-plane of the plate. Tensile strengths were essentially isotropic, with variations in yield and ultimate tensile strengths of less than 2% as a function of orientation and through-thickness location. However, ductility varied by more than 15% with orientation. Fracture toughness was generally higher at the mid-plane and greater for the L-T orientation, although the differences were small near the surface of the plate. Metallurgical analysis indicated that the microstructure was primarily recrystallized with weak texture and was uniform through the plate with the exception of a fine-grained layer near the surface of the plate. Scanning electron microscope analysis revealed Al-Cu-Mg second phase particles which varied in composition and were primarily located on grain boundaries parallel to the rolling direction. Fractography of toughness specimens for both plate locations and orientations revealed that fracture occurred predominantly by transgranular microvoid coalescence. Introduction High-strength, low-density Al-Cu-Mg-Ag alloys were initially developed to replace conventional 2000 (Al-Cu-Mg) and 7000 (Al-Zn-Cu-Mg) series aluminum alloys for aircraft structural applications [1]. During the High Speed Civil Transport (HSCT) program, improvements in thermal stability were demonstrated for candidate

  17. A series of M(II)Cu(II)3 stars (M = Mn, Ni, Cu, Zn) exhibiting unusual magnetic properties.

    PubMed

    Mondal, Suraj; Mandal, Shuvankar; Carrella, Luca; Jana, Arpita; Fleck, Michel; Köhn, Andreas; Rentschler, Eva; Mohanta, Sasankasekhar

    2015-01-05

    The work in this report describes the syntheses, electrospray ionization mass spectromtery, structures, and experimental and density functional theoretical (DFT) magnetic properties of four tetrametallic stars of composition [M(II)(Cu(II)L)3](ClO4)2 (1, M = Mn; 2, M = Ni; 3, M = Cu; 4, M = Zn) derived from a single-compartment Schiff base ligand, N,N'-bis(salicylidene)-1,4-butanediamine (H2L), which is the [2 + 1] condensation product of salicylaldehyde and 1,4-diaminobutane. The central metal ion (Mn(II), Ni(II), Cu(II), or Zn(II)) is linked with two μ2-phenoxo bridges of each of the three [Cu(II)L] moieties, and thus the central metal ion is encapsulated in between three [Cu(II)L] units. The title compounds are rare or sole examples of stars having these metal-ion combinations. In the cases of 1, 3, and 4, the four metal ions form a centered isosceles triangle, while the four metal ions in 2 form a centered equilateral triangle. Both the variable-temperature magnetic susceptibility and variable-field magnetization (at 2-10 K) of 1-3 have been measured and simulated contemporaneously. While the Mn(II)Cu(II)3 compound 1 exhibits ferromagnetic interaction with J = 1.02 cm(-1), the Ni(II)Cu(II)3 compound 2 and Cu(II)Cu(II)3 compound 3 exhibit antiferromagnetic interaction with J = -3.53 and -35.5 cm(-1), respectively. Variable-temperature magnetic susceptibility data of the Zn(II)Cu(II)3 compound 4 indicate very weak antiferromagnetic interaction of -1.4 cm(-1), as expected. On the basis of known correlations, the magnetic properties of 1-3 are unusual; it seems that ferromagnetic interaction in 1 and weak/moderate antiferromagnetic interaction in 2 and 3 are possibly related to the distorted coordination environment of the peripheral copper(II) centers (intermediate between square-planar and tetrahedral). DFT calculations have been done to elucidate the magnetic properties. The DFT-computed J values are quantitatively (for 1) or qualitatively (for 2 and 3) matched

  18. Tensile strength of thermomechanically processed Cu-9Ni-6Sn alloys

    SciTech Connect

    Rhu, J.C.; Kim, S.S.; Jung, Y.C.; Han, S.Z.; Kim, C.J.

    1999-10-01

    The tensile properties of Cu-9Ni-6Sn alloys with different swaging amounts of 64, 77, and 95 pct, either solutionized and aged (S/A), were examined as a function of aging time. It was found that the aging response of Cu-9Ni-6Sn alloys varied greatly depending on the prior solution heat treatment before aging and/or different swaging amounts. The swaged S/A Cu-9Ni-6Sn alloys showed a multistage increase in tensile strength with respect to aging time, probably due to the sequential occurrence of spinodal decomposition, formation of metastable {gamma}{center{underscore}dot} precipitates, and recrystallization. The effect of different swaging amounts, ranging from 64 to 95 pct, was minimal on the aging response of S/A specimens. The prior cold working, however, appeared to favor the spinodal strengthening, comparing unswaged and swaged S/A Cu-9Ni-6Sn alloys. In 95 pct swaged D/A Cu-9Ni-6Sn alloys, the level of hardening was much less sensitive to aging time. A complex interaction between the reduction in dislocation density, the formation of equilibrium precipitates, and the reduction of Sn content in the Sn-rich segregates during an aging process is believed to be responsible for such a lean sensitivity. The increases in tensile strength of 64 and 77 pct swaged D/A Cu-9Ni-6Sn alloys were found to be much steeper than that in the 95 pct counterparts in the early and intermediate stages of aging, which is believed to be related to the relative contribution from work hardening and precipitation hardening to the strength level of D/A specimens.

  19. Effect of Cu doping on the resistive switching of NiO thin films

    SciTech Connect

    Li, Jian-Chang Hou, Xue-Yan; Cao, Qing

    2014-04-28

    Bipolar resistive switching is observed in the GaIn/Cu:NiO film/ITO device with active layer deposited by sol-gel spin-coating. The first-principles calculations indicate that Cu dopants with valence of +1 are located at the substitutional Ni sites rather than the interstitial ones. Cu doping introduces more oxygen vacancies in the film and increases the carrier mobility, however, excessive Cu dopants may assemble at the grain boundary resulting in larger set voltage. Current–voltage measurements indicate that the trap charge limited and space charge limited conduction dominate the high resistance state, while the low resistance state follows the Ohmic mechanism. The switching is attributed to the formation/rupture of oxygen vacancy filaments.

  20. Metal Cyanide Ions Mx(CN)y]+,- in the gas phase: M = Fe, Co, Ni, Zn, Cd, Hg, Fe + Ag, Co + Ag.

    PubMed

    Dance, Ian G; Dean, Philip A W; Fisher, Keith J; Harris, Hugh H

    2002-07-01

    The generation of metal cyanide ions in the gas phase by laser ablation of M(CN)(2) (M = Co, Ni, Zn, Cd, Hg), Fe(III)[Fe(III)(CN)(6)] x xH(2)O, Ag(3)[M(CN)(6)] (M = Fe, Co), and Ag(2)[Fe(CN)(5)(NO)] has been investigated using Fourier transform ion cyclotron resonance mass spectrometry. Irradiation of Zn(CN)(2) and Cd(CN)(2) produced extensive series of anions, [Zn(n)(CN)(2n+1)](-) (1 < or = n < or = 27) and [Cd(n)(CN)(2n+1)](-) (n = 1, 2, 8-27, and possibly 29, 30). Cations Hg(CN)(+) and [Hg(2)(CN)(x)](+) (x = 1-3), and anions [Hg(CN)(x)](-) (x = 2, 3), are produced from Hg(CN)(2). Irradiation of Fe(III)[Fe(III)(CN)(6)] x xH(2)O gives the anions [Fe(CN)(2)](-), [Fe(CN)(3)](-), [Fe(2)(CN)(3)](-), [Fe(2)(CN)(4)](-), and [Fe(2)(CN)(5)](-). When Ag(3)[Fe(CN)(6)] is ablated, [AgFe(CN)(4)](-) and [Ag(2)Fe(CN)(5)](-) are observed together with homoleptic anions of Fe and Ag. The additional heterometallic complexes [AgFe(2)(CN)(6)](-), [AgFe(3)(CN)(8)](-), [Ag(2)Fe(2)(CN)(7)](-), and [Ag(3)Fe(CN)(6)](-) are observed on ablation of Ag(2)[Fe(CN)(5)(NO)]. Homoleptic anions [Co(n)(CN)(n+1)](-) (n = 1-3), [Co(n)(CN)(n+2)](-) (n = 1-3), [Co(2)(CN)(4)](-), and [Co(3)(CN)(5)](-) are formed when anhydrous Co(CN)(2) is the target. Ablation of Ag(3)[Co(CN)(6)] yields cations [Ag(n)(CN)(n-1)](+) (n = 1-4) and [Ag(n)Co(CN)(n)](+) (n = 1, 2) and anions [Ag(n)(CN)(n+1)](-) (n = 1-3), [Co(n)(CN)(n-1)](-) (n = 1, 2), [Ag(n)Co(CN)(n+2)](-) (n = 1, 2), and [Ag(n)Co(CN)(n+3)](-) (n = 0-2). The Ni(I) species [Ni(n)(CN)(n-1)](+) (n = 1-4) and [Ni(n)(CN)(n+1)](-) (n = 1-3) are produced when anhydrous Ni(CN)(2) is irradiated. In all cases, CN(-) and polyatomic carbon nitride ions C(x)N(y)(-) are formed concurrently. On the basis of density functional calculations, probable structures are proposed for most of the newly observed species. General structural features are low coordination numbers, regular trigonal coordination stereochemistry for d(10) metals but distorted trigonal stereochemistry

  1. Equation of State of an AlCoCrCuFeNi High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

    Li, Gong; Xiao, Daihong; Yu, Pengfei; Zhang, Lijun; Liaw, Peter K.; Li, Yanchun; Liu, Riping

    2015-08-01

    The pressure-volume (P-V) relationship of the AlCoCrCuFeNi high-entropy alloy (HEA) at room temperature has been studied using in situ high-pressure energy-dispersive x-ray diffraction with synchrotron radiation at high pressures. The equation of state of the AlCoCrCuFeNi HEA is determined by the calculation of the radial distribution function. The experimental results indicate that the HEA keeps a stable face-centered-cubic + body-centered-cubic structure in the experimental pressure range from 0 GPa to 24 GPa.

  2. First-principles investigation of structural and magnetic disorder in CuNiMnAl and CuNiMnSn Heusler alloys

    NASA Astrophysics Data System (ADS)

    Aron-Dine, S.; Pomrehn, G. S.; Pribram-Jones, A.; Laws, K. J.; Bassman, L.

    2017-01-01

    Two quaternary Heusler alloys, equiatomic CuNiMnAl and CuNiMnSn, are studied using density functional theory to understand their tendency for atomic disorder on the lattice and the magnetic effects of disorder. Disordered structures with antisite defects of atoms of the same and different sublattices are considered, with the level of atomic disorder ranging from 3% to 25%. Formation energies and magnetic moments are calculated relative to the ordered ground state and combined with a simple thermodynamical model to estimate temperature effects. We predict the relative levels of disordering in the two equiatomic alloys with good correlation to experimental x-ray diffraction results. The effect of swaps involving Mn is also discussed.

  3. Microstructure and Corrosion Resistance of Electrodeposited Ni-Cu-Mo Alloy Coatings

    NASA Astrophysics Data System (ADS)

    Meng, Xinjing; Shi, Xi; Zhong, Qingdong; Shu, Mingyong; Xu, Guanquan

    2016-11-01

    This paper deals with the electrodeposition of Ni-Cu-Mo ternary alloy coatings on low-carbon steel substrate from an aqueous citrate sulfate bath. The structures and microstructure of coatings were characterized by scanning electron microscopy and x-ray diffractometry. The corrosion resistance of coatings was investigated by potentiodynamic polarization (Tafel) and electrochemical impedance spectroscopy techniques. The results show that the Ni-Cu-Mo coatings are mainly composed of fcc-Ni phase and a small amount of NiCu phase. Ni-Cu-Mo coatings exhibit a nodular surface morphology, and the roughness of electroplated coating increases with the increasing of Na2MoO4·2H2O in the bath. The corrosion performance of the coatings is significantly affected by the Mo content of the alloy coating and their surface morphology. The coating prepared in bath containing 40 g/L Na2MoO4·2H2O has the highest corrosion resistance in 3.5 wt.% NaCl solution, while that prepared in bath containing 60 g/L (or more) Na2MoO4·2H2O shows a lower corrosion resistance due to the presence of microcracks on the coating surface.

  4. Undercooling Behavior and Intermetallic Compound Coalescence in Microscale Sn-3.0Ag-0.5Cu Solder Balls and Sn-3.0Ag-0.5Cu/Cu Joints

    NASA Astrophysics Data System (ADS)

    Zhou, M. B.; Ma, X.; Zhang, X. P.

    2012-11-01

    The microstructure of microscale solder interconnects and soldering defects have long been known to have a significant influence on the reliability of electronic packaging, and both are directly related to the solidification behavior of the undercooled solder. In this study, the undercooling behavior and solidification microstructural evolution of Sn-3.0Ag-0.5Cu solder balls with different diameters (0.76 mm, 0.50 mm, and 0.30 mm) and the joints formed by soldering these balls on Cu open pads of two diameters (0.48 mm and 0.32 mm) on a printed circuit board (PCB) substrate were characterized by differential scanning calorimetry (DSC) incorporated into the reflow process. Results show that the decrease in diameter of the solder balls leads to an obvious increase in the undercooling of the balls, while the undercooling of the solder joints shows a dependence on both the diameter of the solder balls and the diameter ratio of solder ball to Cu pad (i.e., D s/ D p), and the diameter of the solder balls has a stronger influence on the undercooling of the joints than the dimension of the Cu pad. Coarse primary intermetallic compound (IMC) solidification phases were formed in the smaller solder balls and joints. The bulk Ag3Sn IMC is the primary solidification phase in the as-reflowed solder balls. Due to the interfacial reaction and dissolution of Cu atoms into the solder matrix, the primary Ag3Sn phase can be suppressed and the bulk Cu6Sn5 IMC is the only primary solidification phase in the as-reflowed solder joints.

  5. Bidirectional threshold switching in engineered multilayer (Cu{sub 2}O/Ag:Cu{sub 2}O/Cu{sub 2}O) stack for cross-point selector application

    SciTech Connect

    Song, Jeonghwan; Prakash, Amit; Lee, Daeseok; Woo, Jiyong; Cha, Euijun; Lee, Sangheon; Hwang, Hyunsang

    2015-09-14

    In this study, we achieved bidirectional threshold switching (TS) for selector applications in a Ag-Cu{sub 2}O-based programmable-metallization-cell device by engineering the stack wherein Ag was intentionally incorporated in the oxide (Cu{sub 2}O) layer by a simple approach comprising co-sputtering and subsequent optimized annealing. The distribution of the Ag was directly confirmed by transmission electron microscopy and energy dispersive spectroscopy line profiling. The observed TS occurred because of the spontaneous self-rupturing of the unstable Ag filament that formed in the oxide layer.

  6. Reassessment of Atomic Mobilities in fcc Cu-Ag-Sn System Aiming at Establishment of an Atomic Mobility Database in Sn-Ag-Cu-In-Sb-Bi-Pb Solder Alloys

    NASA Astrophysics Data System (ADS)

    Xu, Huixia; Zhang, Lijun; Cheng, Kaiming; Chen, Weimin; Du, Yong

    2017-04-01

    To establish an accurate atomic mobility database in solder alloys, a reassessment of atomic mobilities in the fcc (face centered cubic) Cu-Ag-Sn system was performed as reported in the present work. The work entailed initial preparation of three fcc Cu-Sn diffusion couples, which were used to determine the composition-dependent interdiffusivities at 873 K, 923 K, and 973 K, to validate the literature data and provide new experimental data at low temperatures. Then, atomic mobilities in three boundary binaries, fcc Cu-Sn, fcc Ag-Sn, and fcc Cu-Ag, were updated based on the data for various experimental diffusivities obtained from the literature and the present work, together with the available thermodynamic database for solder alloys. Finally, based on the large number of interdiffusivities recently measured from the present authors, atomic mobilities in the fcc Cu-Ag-Sn ternary system were carefully evaluated. A comprehensive comparison between various calculated/model-predicted diffusion properties and the experimental data was used to validate the reliability of the obtained atomic mobilities in ternary fcc Cu-Ag-Sn alloys.

  7. Mechanical properties and microstructure investigation of Sn-Ag-Cu lead free solder for electronic package applications

    NASA Astrophysics Data System (ADS)

    Wang, Qing

    While the electronics industry appears to be focusing on Sn-Ag-Cu as the alloy of choice for lead free electronics assembly, the exact composition varies by geographic region, supplier and user. Add to that dissolved copper and silver from the printed circuit board traces and surface finish, and there can be significant variation in the final solder joint composition. A systematic study of the mechanical and microstructural properties of Sn-Ag-Cu alloys with Ag varying from 2wt% to 4wt% and Cu varying from 0.5wt% to 1.5wt%, was investigated in this research study. Different sample preparation techniques (water quenched, oil quenched and water quenched followed by reflow) were explored and the resulting microstructure compared to that of a typical reflowed lead free chip scale package (CSP) solder joint. Tensile properties such as tensile strength, 0.2% yield strength and the ultimate tensile strength and creep behavior of selected alloy compositions (Sn-4Ag-1.5Cu, Sn-4Ag-0.5Cu, Sn-2Ag-1.5Cu, Sn-2Ag-0.5Cu, Sn-3.5Ag-0.8Cu) were performed for three conditions: as-cast; aged for 100 hours at 125°C; and aged for 250 hours at 125°C. The microstructures of these alloys were examined using light and scanning electron microscopy (LM and SEM) respectively and SEM based energy dispersive x-ray spectroscopy (EDS). Fracture surface and cross-section analysis were performed on the specimens after creep testing. The creep testing results and the effect of high temperature aging on mechanical properties will also be presented for the oil quenched samples. A hyperbolic-sine creep model was adopted and used to fit the creep experiment data. The effect of adding the quaternary element bismuth to the Sn-3.5Ag-0.8Cu alloy on the mechanical properties was measured and compared with the mechanical properties of the ternary alloys. The results of this research study provide necessary data for the modeling of solder joint reliability for a range of Sn-Ag-Cu compositions and a baseline

  8. Electrodeposition mechanism and characterization of Ni-Cu alloy coatings from a eutectic-based ionic liquid

    NASA Astrophysics Data System (ADS)

    Wang, Shaohua; Guo, Xingwu; Yang, Haiyan; Dai, JiChun; Zhu, Rongyu; Gong, Jia; Peng, Liming; Ding, Wenjiang

    2014-01-01

    The electrodeposition mechanism, microstructures and corrosion resistances of Ni-Cu alloy coatings on Cu substrate were investigated in a choline chloride-urea (1:2 molar ratio) eutectic-based ionic liquid (1:2 ChCl-urea IL) containing nickel and copper chlorides. Cyclic voltammetry showed that the onset reduction potentials for Cu (∼-0.32 V) and for Ni (∼-0.47 V) were close to each other, indicating that Ni-Cu co-deposition could be easily achieved in the absence of complexing agent which was indispensable in aqueous plating electrolyte. Chronoamperometric investigations revealed that Ni-Cu deposits followed the three-dimensional instantaneous nucleation/growth mechanism, thus producing a solid solution. The compositions, microstructures and corrosion resistances of Ni-Cu alloy coatings were significantly dependent on the deposition current densities. Ni-Cu alloy coatings were α-Ni(Cu) solid solutions, and the coating containing ∼17.6 at.% Cu exhibited the best corrosion resistance because of its dense and crack-free structure.

  9. Quasi-Instantaneous Bacterial Inactivation on Cu-Ag Nanoparticulate 3D Catheters in the Dark and Under Light: Mechanism and Dynamics.

    PubMed

    Rtimi, Sami; Sanjines, Rosendo; Pulgarin, Cesar; Kiwi, John

    2016-01-13

    The first evidence for Cu-Ag (50%/50%) nanoparticulate hybrid coatings is presented leading to a complete and almost instantaneous bacterial inactivation in the dark (≤5 min). Dark bacterial inactivation times on Cu-Ag (50%/50%) were observed to coincide with the times required by actinic light irradiation. This provides the evidence that the bimetal Cu-Ag driven inactivation predominates over a CuO/Cu2O and Ag2O oxides inducing a semiconductor driven behavior. Cu- or Ag-coated polyurethane (PU) catheters led to bacterial inactivation needing about ∼30 min. The accelerated bacterial inactivation by Cu-Ag coated on 3D catheters sputtered was investigated in a detailed way. The release of Cu/Ag ions during bacterial inactivation was followed by inductively coupled plasma mass-spectrometry (ICP-MS) and the amount of Cu and Ag-ions released were below the cytotoxicity levels permitted by the sanitary regulations. By stereomicroscopy the amount of live/dead cells were followed during the bacterial inactivation time. By Fourier transform infrared spectroscopy (FTIR), the systematic shift of the -(CH2) band stretching of the outer lipo-polysaccharide bilayer (LPS) was followed to monitor the changes leading to cell lysis. A hydrophobic to hydrophilic transformation of the Cu-Ag PU catheter surface under light was observed within 30 min followed concomitantly to a longer back transformation to the hydrophobic initial state in the dark. Physical insight is provided for the superior performance of Cu-Ag films compared to Cu or Ag films in view of the drastic acceleration of the bacterial inactivation observed on bimetal Cu-Ag films coating PU catheters. A mechanism of bacterial inactivation is suggested that is consistent with the findings reported in this study.

  10. Design and development of novel antibacterial Ti-Ni-Cu shape memory alloys for biomedical application

    PubMed Central

    Li, H. F.; Qiu, K. J.; Zhou, F. Y.; Li, L.; Zheng, Y. F.

    2016-01-01

    In the case of medical implants, foreign materials are preferential sites for bacterial adhesion and microbial contamination, which can lead to the development of prosthetic infections. Commercially biomedical TiNi shape memory alloys are the most commonly used materials for permanent implants in contact with bone and dental, and the prevention of infections of TiNi biomedical shape memory alloys in clinical cases is therefore a crucial challenge for orthopaedic and dental surgeons. In the present study, copper has been chosen as the alloying element for design and development novel ternary biomedical Ti‒Ni‒Cu shape memory alloys with antibacterial properties. The effects of copper alloying element on the microstructure, mechanical properties, corrosion behaviors, cytocompatibility and antibacterial properties of biomedical Ti‒Ni‒Cu shape memory alloys have been systematically investigated. The results demonstrated that Ti‒Ni‒Cu alloys have good mechanical properties, and remain the excellent shape memory effects after adding copper alloying element. The corrosion behaviors of Ti‒Ni‒Cu alloys are better than the commercial biomedical Ti‒50.8Ni alloys. The Ti‒Ni‒Cu alloys exhibit excellent antibacterial properties while maintaining the good cytocompatibility, which would further guarantee the potential application of Ti‒Ni‒Cu alloys as future biomedical implants and devices without inducing bacterial infections. PMID:27897182

  11. Design and development of novel antibacterial Ti-Ni-Cu shape memory alloys for biomedical application.

    PubMed

    Li, H F; Qiu, K J; Zhou, F Y; Li, L; Zheng, Y F

    2016-11-29

    In the case of medical implants, foreign materials are preferential sites for bacterial adhesion and microbial contamination, which can lead to the development of prosthetic infections. Commercially biomedical TiNi shape memory alloys are the most commonly used materials for permanent implants in contact with bone and dental, and the prevention of infections of TiNi biomedical shape memory alloys in clinical cases is therefore a crucial challenge for orthopaedic and dental surgeons. In the present study, copper has been chosen as the alloying element for design and development novel ternary biomedical Ti‒Ni‒Cu shape memory alloys with antibacterial properties. The effects of copper alloying element on the microstructure, mechanical properties, corrosion behaviors, cytocompatibility and antibacterial properties of biomedical Ti‒Ni‒Cu shape memory alloys have been systematically investigated. The results demonstrated that Ti‒Ni‒Cu alloys have good mechanical properties, and remain the excellent shape memory effects after adding copper alloying element. The corrosion behaviors of Ti‒Ni‒Cu alloys are better than the commercial biomedical Ti‒50.8Ni alloys. The Ti‒Ni‒Cu alloys exhibit excellent antibacterial properties while maintaining the good cytocompatibility, which would further guarantee the potential application of Ti‒Ni‒Cu alloys as future biomedical implants and devices without inducing bacterial infections.

  12. Design and development of novel antibacterial Ti-Ni-Cu shape memory alloys for biomedical application

    NASA Astrophysics Data System (ADS)

    Li, H. F.; Qiu, K. J.; Zhou, F. Y.; Li, L.; Zheng, Y. F.

    2016-11-01

    In the case of medical implants, foreign materials are preferential sites for bacterial adhesion and microbial contamination, which can lead to the development of prosthetic infections. Commercially biomedical TiNi shape memory alloys are the most commonly used materials for permanent implants in contact with bone and dental, and the prevention of infections of TiNi biomedical shape memory alloys in clinical cases is therefore a crucial challenge for orthopaedic and dental surgeons. In the present study, copper has been chosen as the alloying element for design and development novel ternary biomedical Ti‒Ni‒Cu shape memory alloys with antibacterial properties. The effects of copper alloying element on the microstructure, mechanical properties, corrosion behaviors, cytocompatibility and antibacterial properties of biomedical Ti‒Ni‒Cu shape memory alloys have been systematically investigated. The results demonstrated that Ti‒Ni‒Cu alloys have good mechanical properties, and remain the excellent shape memory effects after adding copper alloying element. The corrosion behaviors of Ti‒Ni‒Cu alloys are better than the commercial biomedical Ti‒50.8Ni alloys. The Ti‒Ni‒Cu alloys exhibit excellent antibacterial properties while maintaining the good cytocompatibility, which would further guarantee the potential application of Ti‒Ni‒Cu alloys as future biomedical implants and devices without inducing bacterial infections.

  13. Bonding of Cf/SiC composite to Invar alloy using an active cement, Ag-Cu eutectic and Cu interlayer

    NASA Astrophysics Data System (ADS)

    Lei, Zhao; Xiaohong, Li; Jinbao, Hou; Qiang, Sun; Fuli, Zhang

    2012-10-01

    The interfacial microstructures and mechanical properties of the joints formed by active cement added brazing in vacuum of Cf/SiC composite to Invar alloy, using Ag-Cu eutectic alloy and pure copper foil as braze alloy and interlayer respectively, were investigated. CuTi, Cu4Ti3, Fe2Ti and the reaction layer of TiC and Si were the predominant components at the joint interface. The maximum shear strength of the joint was 77 MPa for brazing at 850 °C for 15 min. The results show that active cement added brazing in vacuum using Ag-Cu eutectic alloy and Cu interlayer can be used successfully for joining Cf/SiC composites to Invar alloy.

  14. Facile synthesis of bimetallic Ag/Ni core/sheath nanowires and their magnetic and electrical properties.

    PubMed

    McKiernan, Maureen; Zeng, Jie; Ferdous, Sunzida; Verhaverbeke, Steven; Leschkies, Kurtis S; Gouk, Roman; Lazik, Christopher; Jin, Miao; Briseno, Alejandro L; Xia, Younan

    2010-09-06

    This paper describes a facile method for coating Ag nanowires with uniform, ferromagnetic sheaths made of polycrystalline Ni. A typical sample of these core/sheath nanowires had a saturation magnetization around 33 emu g(-1). We also demonstrated the use of this magnetic property to align the nanowires by simply placing a suspension of the nanowires on a substrate in a magnetic field and allowing the solvent to evaporate. The electrical conductivity of these core/sheath nanowires (2 × 10(3) S cm(-1)) was two orders of magnitude lower than that of bulk Ag (6.3 × 10(5) S cm(-1)) and Ni (1.4 × 10(5) S cm(-1)). This is likely caused by the transfer of electrons from the Ag core to the Ni sheath due to the difference in work function between the two metals. The electrons are expected to experience an increased resistance due to spin-dependent scattering caused by the randomized magnetic domains in the polycrystalline, ferromagnetic Ni sheath. Studies on the structural changes to the Ni coating over time under different storage conditions show that storage of the nanowires on a substrate under ambient conditions leads to very little Ni oxidation after 6 months. These Ag/Ni core/sheath nanowires show promise in areas such as electronics, spintronics, and displays.

  15. Anodic behavior of carbon supported Cu@Ag core-shell nanocatalysts in direct borohydride fuel cells

    NASA Astrophysics Data System (ADS)

    Duan, Donghong; Liu, Huihong; You, Xiu; Wei, Huikai; Liu, Shibin

    2015-10-01

    Carbon-supported Cu@Ag core-shell nanoparticles are prepared by a successive reduction method in an aqueous solution and are used as an anode electrocatalyst for the direct borohydride-hydrogen peroxide fuel cell (DBHFC). The physical and electrochemical properties of the as-prepared electrocatalysts are investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), cyclic voltammetry (CV), chronopotentiometry (CP), and fuel cell tests. In situ Fourier transform infrared (FTIR) spectroscopy is employed in 2 M NaOH/0.1 M NaBH4 to understand the borohydride oxidation reaction (BOR) mechanism by studying the intermediate reactions occurring on the Cu@Ag/C electrode. The TEM images show that the average size of the Cu1@Ag1/C particles is approximately 18 nm. Among the as-prepared catalysts, the Cu2@Ag1/C catalyst presents the highest catalytic activity. As shown by in situ FTIR, the oxidation reaction mechanism of BH4- is similar to that of Ag/C: BHn(OH)4-n- + 2OH- → BHn-1(OH)5-n- +H2 O + 2e . At 25 °C, the DBHFC with Cu2@Ag1/C as the anode electrocatalyst and Pt mesh (1 cm2) as the cathode electrode exhibits a maximum anodic power density of 17.27 mW mg-1 at a discharge current density of 27.8 mA mg-1.

  16. Effect of thermally stable Cu- and Mg-rich aluminides on the high temperature strength of an AlSi12CuMgNi alloy

    SciTech Connect

    Asghar, Z.

    2014-02-15

    The internal architecture of an AlSi12CuMgNi piston alloy, revealed by synchrotron tomography, consists of three dimensional interconnected hybrid networks of Cu-rich aluminides, Mg-rich aluminides and eutectic/primary Si embedded in an α-Al matrix. The strength at room temperature and at 300°C is studied as a function of solution treatment time at 490°C and compared with results previously reported for an AlSi12Ni alloy. The addition of 1 wt% Cu and 1 wt% Mg to AlSi12CuMgNi increases the room temperature strength by precipitation hardening while the strength at 300°C is similar for both alloys in as-cast condition. The strength of AlSi12CuMgNi decreases with solution treatment time and stabilizes at 4 h solution treatment. The effect of solution treatment time on the strength of the AlSi12CuMgNi alloy is less pronounced than for the AlSi12Ni alloy both at room temperature and at 300°C. - Highlights: • The 3D microstructure of AlSi12CuMgNi is revealed by synchrotron tomography. • An imaging analysis procedure to segment phases with similar contrasts is presented. • 1 wt% Cu and Mg results in the formation of 3D networks of rigid phases. • AlSi12CuMgNi is stronger than AlSi12Ni owing to the stability of the 3D networks.

  17. Resistance to sulfur poisoning of Ni-based alloy with coinage (IB) metals

    NASA Astrophysics Data System (ADS)

    Xu, Xiaopei; Zhang, Yanxing; Yang, Zongxian

    2015-12-01

    The poisoning effects of S atom on the (1 0 0), (1 1 0) and (1 1 1) metal surfaces of pure Ni and Ni-based alloy with IB (coinage) metals (Cu, Ag, Au) are systematically studied. The effects of IB metal dopants on the S poisoning features are analyzed combining the density functional theory (DFT) results with thermodynamics data using the ab initio atomistic thermodynamic method. It is found that introducing IB doping metals into Ni surface can shift the d-band center downward from the Fermi level and weaken the adsorption of S on the (1 0 0) and (1 1 0) surfaces, and the S tolerance ability increases in the order of Ni, Cu/Ni, Ag/Ni and Au/Ni. Nevertheless, on the (1 1 1) surface, the S tolerance ability increases in the order of Ag/Ni (or Cu/Ni), Ni, and Au/Ni. When we increase the coverage of the IB metal dopants, we found that not only Au, but Cu and Ag can increase its S tolerance. We therefore propose that alloying can increase its S tolerance and alloying with Au would be a better way to increase the resistance to sulfur poisoning of the Ni anode as compared with the pure Ni and the Ag- or, Cu-doped Ni materials.

  18. Low-Temperature Sintering and Electromagnetic Properties of NiCuZn/CaTiO3 Composites

    NASA Astrophysics Data System (ADS)

    Yang, Haibo; Yang, Yanyan; Lin, Ying; Zhu, Jianfeng; Wang, Fen

    2012-04-01

    Dense CaTiO3/Ni0.37Cu0.20Zn0.43Fe1.92O3.88 (CTO/NiCuZn) composites were prepared by the conventional solid-state reaction method and sintered at 950°C. The phase compositions and surface morphologies of the composites were investigated using x-ray diffraction and scanning electron microscopy, respectively. The dielectric and magnetic properties of the composites were also investigated. The results show that the CTO/NiCuZn composites possess high dielectric constants and permeabilities, which can be used in high-frequency communications for capacitor-inductor integrating devices such as electromagnetic interference filters and antennas. With increasing NiCuZn concentration, the permeabilities of the CTO/NiCuZn composites increase, while the dielectric constants and cutoff frequencies decrease.

  19. Wetting and interface phenomena in the molten Sn/CuFeNiCoCr high-entropy alloy system

    NASA Astrophysics Data System (ADS)

    Ma, G. F.; Li, Z. K.; Ye, H.; He, C. L.; Zhang, H. F.; Hu, Z. Q.

    2015-11-01

    The wetting behavior and the interfacial characteristics of the molten Sn on a CuFeNiCoCr high-entropy alloy (HEA) substrate were investigated by the sessile drop method. Oxidation of the CuCoNiFeCr HEA surface inhibited the interaction between the molten Sn and the CuCoNiFeCr HEA substrate, leading to a very poor wetting at 573 K, 623 K and 673 K. However, the equilibrium contact angle decreased monotonously with the temperature increasing in the temperature range of 673-923 K. Moreover, the interfacial microstructure depended on temperature. An intermetallic compound existed at the interface between the molten Sn and the CuFeNiCoCr HEA substrate, and the interface thickness varied with the wetting temperature. The wetting process of the molten Sn on the CuFeNiCoCr HEA substrate consisted of three stages according to the wetting temperature.

  20. Optimization of Bulk Thermoelectrics: Influence of Cu Insertion in Ag3.6Mo9Se11

    NASA Astrophysics Data System (ADS)

    Colin, Malika; Zhou, Tong; Lenoir, Bertrand; Dauscher, Anne; Al Rahal Al Orabi, Rabih; Gougeon, Patrick; Potel, Michel; Baranek, Philippe; Semprimoschnig, Christopher

    2012-06-01

    Currently, there is a resurgence of interest in thermoelectric materials with enhanced efficiency. Among investigated classes of bulk thermoelectrics such as partially filled skutterudites, Zn4Sb3-based materials, and clathrates, novel polycrystalline Mo9 cluster-based chalcogenides were reported recently. Among those, Chevrel phase-derived Ag y Mo9Se11 (with 3.4 ≤ y ≤ 3.9) compounds have shown interesting thermoelectric properties, in particular extremely low thermal conductivity allowing improved thermoelectric efficiency compared with reported Chevrel phases. They also possess a complex crystallographic structure where stacked Mo9Se11 units leave channels occupied by Ag atoms. Analysis of the structural determinants of the thermoelectric properties of Ag y Mo9Se11 suggested that performance improvements could result from further Cu insertion. In this paper, we describe the synthesis route we used for preparing quaternary Ag-Cu-Mo-Se compositions by a combination of powder metallurgy and spark plasma sintering techniques. Characterization by x-ray diffraction, scanning electron microscopy, and electrical and thermal measurements has been performed. The results obtained for two compounds (Ag3.6Cu0.2Mo9Se11 and Ag3.6Cu0.4Mo9Se11) are discussed and compared with those of the parent ternary compound Ag3.6Mo9Se11.

  1. Mechanical properties of NiTi and CuNiTi wires used in orthodontic treatment. Part 2: Microscopic surface appraisal and metallurgical characteristics

    PubMed Central

    Gravina, Marco Abdo; Canavarro, Cristiane; Elias, Carlos Nelson; Chaves, Maria das Graças Afonso Miranda; Brunharo, Ione Helena Vieira Portella; Quintão, Cátia Cardoso Abdo

    2014-01-01

    Objective This research aimed at comparing the qualitative chemical compositions and the surface morphology of fracture regions of eight types of Nickel (Ni) Titanium (Ti) conventional wires, superelastic and heat-activated (GAC, TP, Ormco, Masel, Morelli and Unitek), to the wires with addition of copper (CuNiTi 27ºC and 35ºC, Ormco) after traction test. Methods The analyses were performed in a scanning electronic microscope (JEOL, model JSM-5800 LV) with EDS system of microanalysis (energy dispersive spectroscopy). Results The results showed that NiTi wires presented Ni and Ti as the main elements of the alloy with minimum differences in their composition. The CuNiTi wires, however, presented Ni and Ti with a significant percentage of copper (Cu). As for surface morphology, the wires that presented the lowest wire-surface roughness were the superelastic ones by Masel and Morelli, while those that presented the greatest wire-surface roughness were the CuNiTi 27ºC and 35ºC ones by Ormco, due to presence of microcavity formed as a result of pulling out some particles, possibly of NiTi.4 The fracture surfaces presented characteristics of ductile fracture, with presence of microcavities. The superelastic wires by GAC and the CuNiTi 27ºC and the heat-activated ones by Unitek presented the smallest microcavities and the lowest wire-surface roughness with regard to fracture, while the CuNiTi 35ºC wires presented inadequate wire-surface roughness in the fracture region. Conclusion CuNiTi 35ºC wires did not present better morphologic characteristics in comparison to the other wires with regard to surfaces and fracture region. PMID:24713562

  2. Phase constitution and interface structure of nano-sized Ag-Cu/AlN multilayers: Experiment and ab initio modeling

    SciTech Connect

    Pigozzi, Giancarlo; Janczak-Rusch, Jolanta; Passerone, Daniele; Antonio Pignedoli, Carlo; Patscheider, Joerg; Jeurgens, Lars P. H.; Antusek, Andrej; Parlinska-Wojtan, Magdalena; Bissig, Vinzenz

    2012-10-29

    Nano-sized Ag-Cu{sub 8nm}/AlN{sub 10nm} multilayers were deposited by reactive DC sputtering on {alpha}-Al{sub 2}O{sub 3}(0001) substrates. Investigation of the phase constitution and interface structure of the multilayers evidences a phase separation of the alloy sublayers into nanosized grains of Ag and Cu. The interfaces between the Ag grains and the quasi-single-crystalline AlN sublayers are semi-coherent, whereas the corresponding Cu/AlN interfaces are incoherent. The orientation relationship between Ag and AlN is constant throughout the entire multilayer stack. These observations are consistent with atomistic models of the interfaces as obtained by ab initio calculations.

  3. Intermetallic compounds formed at the interface between Cu substrate and an Sn-9Zn-0.5Ag lead-free solder

    SciTech Connect

    Chang, T.-C.; Hon, M.-H.; Wang, M.-C

    2003-04-30

    The intermetallic compounds (IMCs) formed at the interface between Cu substrate and an Sn-9Zn-0.5Ag lead-free solder alloy have been investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and electron diffraction (ED). The XRD patterns show that the main IMCs formed at the interface of Sn-9Zn-0.5Ag/Cu are {gamma}-Cu{sub 5}Zn{sub 8} and {eta}'-Cu{sub 6}Sn{sub 5}. The Ag{sub 3}Sn IMC with orthorhombic structure was also observed at the Sn-9Zn-0.5Ag/Cu interface by TEM and ED analyses. The interfacial adhesion strength between the Cu substrate and Sn-9Zn-0.5Ag lead-free solder alloy is higher than that of the Sn-9Zn alloy due to the formation of Ag{sub 3}Sn IMC at the interface.

  4. Characterization of Cu buffer layers for growth of L1{sub 0}-FeNi thin films

    SciTech Connect

    Mizuguchi, M.; Sekiya, S.; Takanashi, K.

    2010-05-15

    A Cu(001) layer was fabricated on a Au(001) layer to investigate the use of Cu as a buffer layer for growing L1{sub 0}-FeNi thin films. The epitaxial growth of a Cu buffer layer was observed using reflection high-energy electron diffraction. The flatness of the layer improved drastically with an increase in the substrate temperature although the layer was an alloy (AuCu{sub 3}). An FeNi thin film was epitaxially grown on the AuCu{sub 3} buffer layer by alternate monatomic layer deposition and the formation of an L1{sub 0}-FeNi ordered alloy was expected. The AuCu{sub 3} buffer layer is thus a promising candidate material for the growth of L1{sub 0}-FeNi thin films.

  5. Relationship between microstructure, cytotoxicity and corrosion properties of a Cu-Al-Ni shape memory alloy.

    PubMed

    Colić, Miodrag; Rudolf, Rebeka; Stamenković, Dragoslav; Anzel, Ivan; Vucević, Dragana; Jenko, Monika; Lazić, Vojkan; Lojen, Gorazd

    2010-01-01

    Cu-Al-Ni shape memory alloys (SMAs) have been investigated as materials for medical devices, but their biomedical application is still limited. The aim of this work was to compare the microstructure, corrosion and cytotoxicity in vitro of a Cu-Al-Ni SMA. Rapidly solidified (RS) thin ribbons, manufactured via melt spinning, were used for the tests. The control alloy was a permanent mould casting of the same composition, but without shape memory effect. The results show that RS ribbons are significantly more resistant to corrosion compared with the control alloy, as judged by the lesser release of Cu and Ni into the conditioning medium. These results correlate with the finding that RS ribbons were not cytotoxic to L929 mouse fibroblasts and rat thymocytes. In addition, the RS ribbon conditioning medium inhibited cellular proliferation and IL-2 production by activated rat splenocytes to a much lesser extent. The inhibitory effects were almost completely abolished by conditioning the RS ribbons in culture medium for 4 weeks. Microstructural analysis showed that RS ribbons are martensitic, with boron particles as a minor phase. In contrast, the control Cu-Al-Ni alloy had a complex multiphase microstructure. Examination of the alloy surfaces after conditioning by energy dispersive X-ray and Auger electron spectroscopy showed the formation of Cu and Al oxide layers and confirmed that the metals in RS ribbons are less susceptible to oxidation and corrosion compared with the control alloy. In conclusion, these results suggest that rapid solidification significantly improves the corrosion stability and biocompatibility in vitro of Cu-Al-Ni SMA ribbons.

  6. Relationship between morphologies and orientations of Cu{sub 6}Sn{sub 5} grains in Sn3.0Ag0.5Cu solder joints on different Cu pads

    SciTech Connect

    Tian, Yanhong Zhang, Rui; Hang, Chunjin; Niu, Lina; Wang, Chunqing

    2014-02-15

    The morphologies and orientations of Cu{sub 6}Sn{sub 5} intermetallic compounds in the Sn3.0Ag0.5Cu solder joints both on polycrystalline and single crystal Cu pads under different peak reflow temperatures and times above liquids were investigated. The relationship between Cu{sub 6}Sn{sub 5} grain orientations and morphologies was clarified. At the interface of Sn3.0Ag0.5Cu/polycrystalline Cu pad, scalloped Cu{sub 6}Sn{sub 5} intermetallic compounds formed at 250 °C and roof shape Cu{sub 6}Sn{sub 5} formed at 300 °C. Both scalloped Cu{sub 6}Sn{sub 5} and roof shape Cu{sub 6}Sn{sub 5} had a preferred orientation of (0001) plane being parallel to polycrystalline Cu pad surface. Besides, the percentage of large angle grain boundaries increased as the peak reflow temperature rose. At the interface of Sn3.0Ag0.5Cu/(111) single crystal Cu pad, the Cu{sub 6}Sn{sub 5} intermetallic compounds were mainly scallop-type at 250 °C and were prism type at 300 °C. The prismatic Cu{sub 6}Sn{sub 5} grains grew along the three preferred directions with the inter-angles of 60° on (111) single crystal Cu pad while along two perpendicular directions on (100) single crystal Cu pad. The orientation relationship between Cu{sub 6}Sn{sub 5} grains and the single crystal Cu pads was investigated by electron backscatter diffraction technology. In addition, two types of hollowed Cu{sub 6}Sn{sub 5} intermetallic compounds were found inside the joints of polycrystalline Cu pads. The long hexagonal Cu{sub 6}Sn{sub 5} strips were observed in the joints reflowing at 250 °C while the hollowed Cu{sub 6}Sn{sub 5} strips with the ‘▪’ shape cross-sections appeared at 300 °C, which was attributed to the different grain growth rates of different Cu{sub 6}Sn{sub 5} crystal faces. - Highlights: • The orientation of interfacial Cu{sub 6}Sn{sub 5} grains was obtained by EBSD technology. • Two types of hollowed Cu{sub 6}Sn{sub 5} strips were found at different temperatures. • The formation

  7. Synthesis, surface and optical properties of Ag2Cu(VO3)4 and Cu(VO3)2 vanadates

    NASA Astrophysics Data System (ADS)

    Qiao, Xuebin; Wan, Yingpeng; Li, Yuze; Qin, Lin; Seo, Hyo Jin

    2016-04-01

    Ag2Cu(VO3)4 and Cu(VO3)2 were prepared via the sol-gel chemical synthesis. The phase formation was confirmed by X-ray powder polycrystalline diffraction (XRD) measurements. The surface properties were measured with the scanning electron microscope (SEM), energy dispersive spectra (EDS), transmission electron microscopy (TEM), and nitrogen adsorption-desorption isotherms. The optical properties and the band-gap structures were investigated. The vanadates have efficient optical absorption in the UV to visible wavelength region with an indirect allowed transition. Ag2Cu(VO3)4 has smaller band gap (1.85 eV) than that of Cu(VO3)2 (2.03 eV). The narrowed band gap is due to the hybridization between the Ag-4d and O-2p in the valence band. The photocatalysis was investigated by photodegradation of methylene blue (MB) solutions excited by the light with wavelength longer than 420 nm. Correspondingly Ag2Cu(VO3)4 has more efficient photocatalytic activity on MB photodegradation than that of Cu(VO3)2. The photocatalytic mechanisms were suggested according to the band positions and the trapping experiments.

  8. Enhanced photocatalytic, electrochemical and photoelectrochemical properties of TiO2 nanotubes arrays modified with Cu, AgCu and Bi nanoparticles obtained via radiolytic reduction

    NASA Astrophysics Data System (ADS)

    Nischk, Michał; Mazierski, Paweł; Wei, Zhishun; Siuzdak, Katarzyna; Kouame, Natalie Amoin; Kowalska, Ewa; Remita, Hynd; Zaleska-Medynska, Adriana

    2016-11-01

    TiO2 nanotubes arrays (NTs), obtained via electrochemical anodization of Ti foil, were modified with monometallic (Cu, Bi) and bimetallic (AgCu) nanoparticles. Different amounts of metals' precursors were deposited on the surface of NTs by the spin-coating technique, and the reduction of metals was performed via gamma radiolysis. Surface modification of titania was studied by EDS and XPS analysis. The results show that AgCu nanoparticles exist in a Agcore-Cushell form. Photocatalytic activity was examined under UV irradiation and phenol was used as a model pollutant of water. Over 95% of phenol degradation was achieved after 60 min of irradiation for almost all examined samples, but only slight difference in degradation efficiency (about 3%) between modified and bare NTs was observed. However, the initial phenol degradation rate and TOC removal efficiency was significantly enhanced for the samples modified with 0.31 and 0.63 mol% of Bi as well as for all the samples modified with Cu and AgCu nanoparticles in comparison with bare titania nanotubes. The saturated photocurrent, under the influence of simulated solar light irradiation, for the most active Bi- and AgCu-modified samples, was over two times higher than for pristine NTs. All the examined materials were resistant towards photocorrosion processes that enables their application for long term processes induced by light.

  9. Dephasing of conduction electrons by magnetic impurities in Cu/Ni and Cu/Cr samples: Influence of spin-glass transition on the superconducting proximity effect

    NASA Astrophysics Data System (ADS)

    Sosnin, I.; Nugent, P.; Zou, J.; Petrashov, V. T.; Volkov, A. F.

    2006-07-01

    The dependence of the superconducting proximity effect on the amount of magnetic impurities in the normal part of Andreev interferometers has been studied experimentally. The dephasing rates obtained from fitting experimental data to quasiclassical theory of the proximity effect are consistent with the spin flip scattering from Cr impurities forming a local moment in the Cu host. In contrast, Ni impurities do not form a local moment in Cu and as a result there is no extra dephasing from Ni as long as Cu/Ni alloy remain paramagnetic.

  10. AN INVESTIGATION OF WETTABILITY, AND MICROSTRUCTURE IN ALUMINA JOINTS BRAZED WITH Ag-CuO-TiO2

    SciTech Connect

    Darsell, Jens T.; Hardy, John S.; Kim, Jin Yong Y.; Weil, K. Scott

    2004-04-06

    A silver-based joining technique referred to as reactive air brazing (RAB) has been recently developed for joining high temperature structural ceramic components of the type used in gas turbines, combustion engines, heat exchangers, and burners. It was found that additions of CuO to silver have a significant effect on the wettability and joint strength characteristics of the resulting braze on polycrystalline alumina substrates. More recently, it has been found that by adding as little as 0.5 mol% titania to these Ag-CuO brazes, the wettability of the RAB on alumina surfaces is further enhanced. The results of wettabilty measurements of Ag-CuO-TiO2 RAB compositions on alumina will be presented along with the microstructural characterization of Ag-CuO-TiO2 braze joints in alumina.

  11. Improved Wetting Characteristics in TiO2–Modified Ag-CuO Air Braze Filler Metals

    SciTech Connect

    Weil, K. Scott; Kim, Jin Yong; Hardy, John S.; Darsell, Jens T.

    2006-01-04

    A silver-based joining technique referred to as reactive air brazing (RAB) has been recently developed for joining high temperature structural ceramic components of the type used in high-temperature electrochemical devices. In prior work, it was found that additions of CuO to silver have a significant effect on the wettability and joint strength characteristics of the resulting braze on polycrystalline alumina substrates. More recently, it has been found that by adding as little as 0.5 mol % titania to these Ag-CuO brazes, the wettability of the RAB on alumina surfaces is further enhanced. The results of wettabilty measurements of Ag-CuO-TiO2 RAB compositions on alumina will be presented along with the microstructural characterization of Ag-CuO-TiO2 braze joints in alumina.

  12. Electrodeposition of high corrosion resistance Cu/Ni-P coating on AZ91D magnesium alloy

    NASA Astrophysics Data System (ADS)

    Zhang, Shan; Cao, Fahe; Chang, Linrong; Zheng, JunJun; Zhang, Zhao; Zhang, Jianqing; Cao, Chunan

    2011-08-01

    High corrosion resistance Cu/Ni-P coatings were electrodeposited on AZ91D magnesium alloy via suitable pretreatments, such as one-step acid pickling-activation, once zinc immersion and environment-friendly electroplated copper as the protective under-layer, which made Ni-P deposit on AZ91D Mg alloy in acid plating baths successfully. The pH value and current density for Ni-P electrodeposition were optimized to obtain high corrosion resistance. With increasing the phosphorous content of the Ni-P coatings, the deposits were found to gradually transform to amorphous structure and the corrosion resistance increased synchronously. The anticorrosion ability of AZ91D Mg alloy was greatly improved by the amorphous Ni-P deposits, which was investigated by potentiodynamic polarization curve and electrochemical impedance spectroscopy (EIS). The corrosion current density ( Icorr) of the coated Mg alloy substrate is about two orders of magnitude less than that of the uncoated.

  13. Photocatalytic comparison of Cu- and Ag-doped TiO2/GF for bioaerosol disinfection under visible light

    NASA Astrophysics Data System (ADS)

    Pham, Thanh-Dong; Lee, Byeong-Kyu

    2015-12-01

    Photocatalysts, TiO2/glass fiber (TiO2/GF), Cu-doped TiO2/glass fiber (Cu-TiO2/GF) and Ag-doped TiO2/glass fiber (Ag-TiO2/GF), were synthesized by a sol-gel method. They were then used to disinfect Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) in bioaerosols under visible light irradiation. TiO2/GF did not show any significant disinfection effect. Both Cu and Ag acted as intermediate agents to enhance separation efficiency of electron-hole pairs of TiO2, leading to improved photocatalytic activity of Cu-TiO2/GF and Ag-TiO2/GF under visible light. Cu in Cu-TiO2/GF acted as a defective agent, increasing the internal quantum efficiency of TiO2, while Ag in Ag-TiO2/GF acted as a sensitive agent, enhancing the transfer efficiency of the electrons generated. The highest disinfection efficiencies of E. coli and S. aureus by Cu-TiO2/GF were 84.85% and 65.21%, respectively. The highest disinfection efficiencies of E. coli and S. aureus by Ag-TiO2/GF were 94.46% and 73.12%, respectively. Among three humidity conditions - 40±5% (dry), 60±5% (moderate), and 80±5% (humid) - the moderate humidity condition showed the highest disinfection efficiency for both E. coli and S. aureus. This study also showed that a Gram-negative bacterium (E. coli) were more readily disinfected by the photocatalysts than a Gram-positive bacterium (S. aureus).

  14. First Principles Calculations on the Diffusion of Cu, Ag and Au Atoms or Aggregates on the Bulk and Surface of Titania

    DTIC Science & Technology

    2011-04-01

    AFRL-AFOSR-UK-TR-2011-0002 First Principles Calculations on the Diffusion of Cu, Ag and Au Atoms or Aggregates on the Bulk and...SUBTITLE First Principles Calculations on the Diffusion of Cu, Ag and Au Atoms or Aggregates on the Bulk and Surface of Titania 5a. CONTRACT...093072 Final report First principles calculations on the diffusion of Cu, Ag and Au atoms or aggregates on the bulk and surface of titania List

  15. Elevated Temperature Creep Properties of Conventional 50Au-50Cu and 47Au 50Cu-3Ni Braze Alloys

    SciTech Connect

    STEPHENS JR.,JOHN J.; SCHMALE,DAVID T.

    2000-12-18

    The elevated temperature creep properties of the 50Au-50Cu wt% and 47Au-50Cu-3Ni braze alloys have been evaluated over the temperature range 250-850 C. At elevated temperatures, i.e., 450-850 C, both alloys were tested in the annealed condition (2 hrs. 750 C/water quenched). The minimum strain rate properties over this temperature range are well fit by the Garofalo sinh equation. At lower temperatures (250 and 350 C), power law equations were found to characterize the data for both alloys. For samples held long periods of time at 375 C (96 hrs.) and slowly cooled to room temperature, an ordering reaction was observed. For the case of the 50Au-50Cu braze alloy, the stress necessary to reach the same, strain rate increased by about 15% above the baseline data. The limited data for ordered 47Au-50Cu-3Ni alloy reflected a,smaller strength increase. However, the sluggishness of this ordering reaction in both alloys does not appear to pose a problem for braze joints cooled at reasonable rates following brazing.

  16. Transparent ITO/Ag-Pd-Cu/ITO multilayer cathode use in inverted organic solar cells

    SciTech Connect

    Kim, Hyo-Joong; Kim, Han-Ki; Lee, Hyun Hwi; Kal, Jinha; Hahn, Jungseok

    2015-10-15

    The characteristics of transparent ITO/Ag-Pd-Cu (APC)/ITO multilayer cathodes were investigated for use in inverted organic solar cells (IOSCs). The insertion of an APC interlayer into the ITO film effectively led to crystallization of the top ITO layer, unlike that in the Ag interlayer, and resulted in a low sheet resistance of 6.55 Ohm/square and a high optical transmittance of 84.14% without post annealing. In addition, the alloying of the Pd and Cu elements into Ag prevented agglomeration and oxidization of the metal interlayer and led to more stable ITO/APC/ITO films under ambient conditions. The microstructure and interfacial structure of the transparent ITO/APC/ITO cathode in the IOSCs were examined in detail by synchrotron X-ray scattering and high resolution transmission electron microscopy. Furthermore, we suggested a possible mechanism to explain the lower PCE of the IOSCs with an ITO/APC/ITO cathode than that of a reference IOSC with a crystalline ITO cathode using the external quantum efficiency of the IOSCs.

  17. Ag-Cu catalysts for ethylene epoxidation: Selectivity and activity descriptors

    NASA Astrophysics Data System (ADS)

    Nguyen, Ngoc Linh; de Gironcoli, Stefano; Piccinin, Simone

    2013-05-01

    Ag-Cu alloy catalysts for ethylene epoxidation have been shown to yield higher selectivity towards ethylene oxide compared to pure Ag, the unique catalyst employed in the industrial process. Previous studies showed that under oxidizing conditions Cu forms oxide layers on top of Ag. Using first-principles atomistic simulations based on density functional theory, we investigate the reaction mechanism on the thin oxide layer structures and establish the reasons for the improved selectivity. We extend the range of applicability of the selectivity descriptor proposed by Kokalj et al. [J. Catal. 254, 304 (2008)], 10.1016/j.jcat.2008.01.008, based on binding energies of reactants, intermediates, and products, by refitting its parameters so as to include thin oxide layer catalysts. We show that the selectivity is mainly controlled by the relative strength of the metal-carbon vs. metal-oxygen bonds, while the height of the reaction barriers mostly depend on the binding energy of the common oxametallacycle intermediate.

  18. Effect of Processing Scheme on Precipitation Mechanisms and Evolution of Microstructures and Properties of CuAgZr alloy

    NASA Astrophysics Data System (ADS)

    Piyawit, Waraporn

    CuAgZr alloy is a variant of the CuAg alloy that is developed for high strength and high conductivity applications. With Zr addition, the discontinuous precipitation at the grain boundaries is decreased due to slower Ag diffusion rate. Mechanical and electrical properties of copper alloys can be influenced by many factors including alloying elements, mechanical processing, heat treatment and their microstructures. For high strength and high conductivity applications, Cu-Ag alloys are one of the good candidate materials for these used because of their excellent combinations of high strength and high electrical conductivity. The primary strengthening mechanism is precipitation hardening due to the formation of Ag precipitates during the heat treatment process. Its strengthening is accomplished mainly by the precipitation of Ag precipitates, which tend to align on the {111} planes in the Cu matrix. The evolutions of hardness and electrical conductivity of the aged samples showed that the Ag particles precipitated out from the Cu matrix in the early stage of aging. The hardness of the aged samples is significantly increased from 95 HV0.1 to the maximum at 193 HV0.1 after 2 hours of aging. The density of Ag precipitates is increased with increased aging time. Ag precipitation occurs in particular Cu matrix planes due to the minimization of elastic energy. The Ag precipitates were formed by clustering of Ag atoms while maintaining the fcc crystal structure of the matrix. They have faceted {111} interfaces with the matrix. The thickening of the precipitates appears to be by the ledge growth mechanism, which is promoted by misfit dislocation networks on the interface. The ledge movement and growth were compensated with the existence of interfacial misfit dislocations. During diffusional growth, misfit dislocation arrays along the precipitate/matrix interface accommodated the lattice mismatch. Therefore, precipitate growth involves the formation and migration of ledges

  19. Al2O3/SUS304 Brazing via AgCuTi-W Composite as Active Filler

    NASA Astrophysics Data System (ADS)

    Su, Cherng-Yuh; Zhuang, Xie-Zongyang; Pan, Cheng-Tang

    2014-03-01

    Alumina ceramic (α-Al2O3) was brazed to stainless steel (SUS304) using an Ag-Cu-Ti + W composite filler and a traditional active brazing filler alloy (CuSil-ABA). Then, the effects of the presence of W particles and of the brazing parameters on the microstructures and mechanical properties of the brazed joints were investigated. The maximum tensile strength of the joints obtained using Ag-Cu-Ti + W composite filler was 13.2 MPa, which is similar to that obtained using CuSil-ABA filler (13.5 MPa). When the joint was brazed at 930 °C for 30 min, the tensile strengths decreased for both kinds of fillers, although the strength was slightly higher for the Ag-Cu-Ti + W composite filler than for the Ag-Cu-Ti filler. The interfacial microstructure results show that the Ti reacts with W to form a Ti-W-O compound in the brazing alloy. When there are more W particles in the brazing alloy, the thickness of the Ti X O Y reaction layer near the alumina ceramic decreases. Moreover, W particles added to the brazing alloy can reduce the coefficient of thermal expansion of the brazing alloy, which results in lower residual stress between the Al2O3 and SUS304 in the brazing joints and thus yields higher tensile strengths as compared to those obtained using the CuSil-ABA brazing alloy.

  20. Colloidal synthesis of Cu-ZnO and Cu@CuNi-ZnO hybrid nanocrystals with controlled morphologies and multifunctional properties

    NASA Astrophysics Data System (ADS)

    Zeng, Deqian; Gong, Pingyun; Chen, Yuanzhi; Zhang, Qinfu; Xie, Qingshui; Peng, Dong-Liang

    2016-06-01

    Metal-semiconductor hybrid nanocrystals have received extensive attention owing to their multiple functionalities which can find wide technological applications. The utilization of low-cost non-noble metals to construct novel metal-semiconductor hybrid nanocrystals is important and meaningful for their large-scale applications. In this study, a facile solution approach is developed for the synthesis of Cu-ZnO hybrid nanocrystals with well-controlled morphologies, including nanomultipods, core-shell nanoparticles, nanopyramids and core-shell nanowires. In the synthetic strategy, Cu nanocrystals formed in situ serve as seeds for the heterogeneous nucleation and growth of ZnO, and it eventually forms various Cu-ZnO hetero-nanostructures under different reaction conditions. These hybrid nanocrystals possess well-defined and stable heterostructure junctions. The ultraviolet-visible-near infrared spectra reveal morphology-dependent surface plasmon resonance absorption of Cu and the band gap absorption of ZnO. Furthermore, we construct a novel Cu@CuNi-ZnO ternary hetero-nanostructure by incorporating the magnetic metal Ni into the pre-synthesized colloidal Cu nanocrystals. Such hybrid nanocrystals possess a magnetic Cu-Ni intermediate layer between the ZnO shell and the Cu core, and exhibit ferromagnetic/superparamagnetic properties which expand their functionalities. Finally, enhanced photocatalytic activities are observed in the as-prepared non-noble metal-ZnO hybrid nanocrystals. This study not only provides an economical way to prepare high-quality morphology-controlled Cu-ZnO hybrid nanocrystals for potential applications in the fields of photocatalysis and photovoltaic devices, but also opens up new opportunities in designing ternary non-noble metal-semiconductor hybrid nanocrystals with multifunctionalities.Metal-semiconductor hybrid nanocrystals have received extensive attention owing to their multiple functionalities which can find wide technological applications

  1. Preparation of SmNi5 and Sm(Ni,T)5 [T=Co,Fe] ordered alloy thin films on Cu(111) underlayers

    NASA Astrophysics Data System (ADS)

    Ohtake, Mitsuru; Yabuhara, Osamu; Nukaga, Yuri; Kirino, Fumiyoshi; Futamoto, Masaaki

    2010-05-01

    SmNi5 and Sm(Ni,T)5 [T =Co,Fe] epitaxial thin films with the c-axis perpendicular to the substrate surface are successfully prepared on Cu underlayers heteroepitaxially grown on MgO(111) single-crystal substrates. The nucleation behavior of SmNi5 and Sm(Ni,T)5 crystals on Cu(111) underlayers were investigated. The SmNi5 and the Sm(Ni,Co)5 films consist of two types of domains whose orientations are rotated around the film normal by 30° each other, whereas the Sm(Ni,Fe)5 film is a single crystal. The nucleation and the domain volume ratio seem to be controllable by adjusting the kind and the composition of transition metal elements.

  2. Microstructure and Mechanical Properties of Dissimilar Welded Ti3Al/Ni-Based Superalloy Joint Using a Ni-Cu Filler Alloy

    NASA Astrophysics Data System (ADS)

    Chen, Bing-Qing; Xiong, Hua-Ping; Guo, Shao-Qing; Sun, Bing-Bing; Chen, Bo; Tang, Si-Yi

    2015-02-01

    Dissimilar welding of a Ti3Al-based alloy and a Ni-based superalloy (Inconel 718) was successfully carried out using gas tungsten arc welding technology in this study. With a Ni-Cu alloy as filler material, sound joints have been obtained. The microstructure evolution along the cross section of the dissimilar joint has been revealed based on the results of scanning electron microscopy and X-ray energy dispersive spectroscopy as well as X-ray diffractometer. It is found that the weld/Ti3Al interface is composed of Ti2AlNb matrix dissolved with Ni and Cu, Al(Cu, Ni)2Ti, (Cu, Ni)2Ti, (Nb, Ti) solid solution, and so on. The weld and In718/weld interface mainly consist of (Cu, Ni) solid solutions. The weld exhibits higher microhardness than the two base materials. The average room-temperature tensile strength of the joints reaches 242 MPa and up to 73.6 pct of the value can be maintained at 873 K (600 °C). The brittle intermetallic phase of Ti2AlNb matrix dissolved with Ni and Cu at the weld/Ti3Al interface is the weak link of the joint.

  3. Comparative study on hydrogenation of propanal on Ni(111) and Cu(111) from density functional theory

    NASA Astrophysics Data System (ADS)

    An, Wei; Men, Yong; Wang, Jinguo

    2017-02-01

    Using propanal as a probe molecule, we have comparatively investigated hydrogenation of carbonyl (Cdbnd O) in short carbon-chain aldehyde on Ni(111) and Cu(111) by means of periodic density functional theory. Our focus is in particular on the differentiation of reaction route in sequential hydrogenation on Ni(111) and Cu(111) following Langmuir-Hinshelwood mechanism. Strong binding with alkoxy intermediates has great impact on altering reaction pathways on the two surfaces, where hydroxyl route via 1-hydroxyl propyl intermediate is dominant on Ni(111), but alkoxy route via propoxyl intermediate is more likely on Cu(111) due to a higher activiation barrier of initial hydrogenation in hydroxyl route. In comparison, hydrogenation of carbonyl on Ni(111) is kinetically much faster than that on Cu(111) as a result of much lower activation barrier in rate-determining step (i.e., 13.2 vs 26.8 kcal/mol) of most favorable reaction pathways. Furthermore, the discrepancy in calculated and experimental barriers can be well explained by using the concept of H-tunneling effect on bond forming with H atoms during sequential hydrogenation. The different features of electronic structure exhibited by the two metal surfaces provide insight into their catalytic behaviors.

  4. Dendritic Ni(Cu)-polypyrrole hybrid films for a pseudo-capacitor.

    PubMed

    Choi, Bit Na; Chun, Woo Won; Qian, Aniu; Lee, So Jeong; Chung, Chan-Hwa

    2015-11-28

    Dendritic Ni(Cu)-polypyrrole hybrid films are fabricated for a pseudo-capacitor in a unique morphology using two simple methods: electro-deposition and electrochemical de-alloying. Three-dimensional structures of porous dendrites are prepared by electro-deposition within the hydrogen evolution reaction (HER) at a high cathodic potential; the high-surface-area structure provides sufficient redox reactions between the electrodes and the electrolyte. The dependence of the active-layer thickness on the super-capacitor performance is also investigated, and the 60 μm-thick Ni(Cu)PPy hybrid electrode presents the highest performance of 659.52 F g(-1) at the scan rate of 5 mV s(-1). In the thicker layers, the specific capacitance became smaller due to the diffusion limitation of the ions in an electrolyte. The polypyrrole-hybridization on the porous dendritic Ni(Cu) electrode provides superior specific capacitance and excellent cycling stability due to the improvement in electric conductivity by the addition of conducting polypyrrole in the matrices of the dendritic nano-porous Ni(Cu) layer and the synergistic effect of composite materials.

  5. Positron annihilation process in Ni/sub c/Cu/sub 1-c/ alloys

    SciTech Connect

    Szotek, Z.; Gyorffy, B.L.; Stocks, G.M.; Temmerman, W.M.

    1982-01-01

    New, accurate, calculations of the electron momentum distribution function for the Cu/sub 60/Ni/sub 40/ random solid solution are presented and the role played by the positron wavefunction in determining the Angular Correlation of the Annihilation Radiation (ACAR) is discussed in quantitative terms.

  6. The vibrational spectra of the Ni(II) and Cu(II) complexes with oxamic hydrazide

    NASA Astrophysics Data System (ADS)

    Quaeyhaegens, Frank; Hofmans, Hendrik; Desseyn, H. O.

    The infrared-, Raman- and u.v./vis spectra as well as the thermal analysis ofthe Ni(II)and Cu(II) complexes with oxamic hydrazide (H 2NCOCONHNH 2) are discussed. We assume 2/1 planar complexes and a coordination via the four amide nitrogen atoms as visualised in Fig. 1.

  7. Magnetic properties of the Ni-Cu-Zn system doped with magnesium oxide

    NASA Astrophysics Data System (ADS)

    Hemeda, O. M.; Tawfik, A.; Hemeda, D. M.; Elsheekh, A. M.

    2015-09-01

    A series of ferrite samples, Ni0.1Cu0.2MgxZn0.7-x Fe2O4, (x=0.00, 0.15, 0.25, 0.35, 0.45, 0.55 and 0.70) has been prepared by the standard ceramic technique, sintered at 1200 °C for 2 h, and their crystalline structures were investigated by using X-ray diffraction. The IR spectra and the ESR spectra analysis have been studied. DC electrical resistivity, thermoelectric power, charge carriers concentration and charge carrier mobility have been calculated at different temperatures. The value of dc electrical resistivity reach minimum at x=0.35 and above this value the electrical resistivity start to increase. It is noticed that thermoelectric power α for the "Ni-Cu-Zn" system exhibits a positive sign indicating the majority carriers are holes without excluding the presence of electrons. Saturation magnetization Ms for the "Ni-Cu-Zn" system was calculated from M-H loop. It is noted that Ms decreases with Mg content up to x=0.55 and rapidly decrease above x>0.55 for the "Ni-Cu-Zn" system.

  8. The response of macrophages to a Cu-Al-Ni shape memory alloy.

    PubMed

    Colić, Miodrag; Tomić, Sergej; Rudolf, Rebeka; Anzel, Ivan; Lojen, Gorazd

    2010-09-01

    Cu-Al-Ni shape memory alloys (SMAs) have been investigated as materials for medical devices, but little is known about their biocompatibility. The aim of this work was to study the response of rat peritoneal macrophages (PMØ) to a Cu-Al-Ni SMA in vitro, by measuring the functional activity of mitochondria, necrosis, apoptosis, and production of proinflammatory cytokines. Rapidly solidified (RS) thin ribbons were used for the tests. The control alloy was a permanent mold casting of the same composition, but without the shape memory effect. Our results showed that the control alloy was severely cytotoxic, whereas RS ribbons induced neither necrosis nor apoptosis of PMØ. These findings correlated with the data that RS ribbons are significantly more resistant to corrosion compared to the control alloy, as judged by the lesser release of Cu and Ni in the conditioning medium. However, the ribbons generated intracellular reactive oxygen species and upregulated the production of IL-6 by PMØ. These effects were almost completely abolished by conditioning the RS ribbons for 5 weeks. In conclusion, RS significantly improves the corrosion stability and biocompatibility of Cu-Al-Ni SMA. The biocompatibility of this functional material could be additionally enhanced by conditioning the ribbons in cell culture medium.

  9. Dendritic Ni(Cu)-polypyrrole hybrid films for a pseudo-capacitor

    NASA Astrophysics Data System (ADS)

    Choi, Bit Na; Chun, Woo Won; Qian, Aniu; Lee, So Jeong; Chung, Chan-Hwa

    2015-11-01

    Dendritic Ni(Cu)-polypyrrole hybrid films are fabricated for a pseudo-capacitor in a unique morphology using two simple methods: electro-deposition and electrochemical de-alloying. Three-dimensional structures of porous dendrites are prepared by electro-deposition within the hydrogen evolution reaction (HER) at a high cathodic potential; the high-surface-area structure provides sufficient redox reactions between the electrodes and the electrolyte. The dependence of the active-layer thickness on the super-capacitor performance is also investigated, and the 60 μm-thick Ni(Cu)PPy hybrid electrode presents the highest performance of 659.52 F g-1 at the scan rate of 5 mV s-1. In the thicker layers, the specific capacitance became smaller due to the diffusion limitation of the ions in an electrolyte. The polypyrrole-hybridization on the porous dendritic Ni(Cu) electrode provides superior specific capacitance and excellent cycling stability due to the improvement in electric conductivity by the addition of conducting polypyrrole in the matrices of the dendritic nano-porous Ni(Cu) layer and the synergistic effect of composite materials.

  10. Ehrlich-Schwöbel barriers and adsorption of Au, Cu and Ag stepped (100) surfaces

    NASA Astrophysics Data System (ADS)

    Benlattar, M.; Elkoraychy, E.; Sbiaai, K.; Mazroui, M.; Boughaleb, Y.

    2017-02-01

    We use a combination of quenched molecular dynamics and embedded atom method to calculate the activation energy barriers for the hopping and exchange mechanisms of Au, Ag or Cu on Au(100), Ag(100) or Cu(100) stepped surfaces. Our findings show that the Ehrlich-Schwöbel (ES) barriers for an adatom to undergo jump or exchange at a step edge are found to be dependent of the nature of substrate stepped surfaces. We also find that the ES barriers for the hopping processes are too high, except for Cu/Au(100). While for exchange process the Ehrlich-Schwöbel barriers are found to be very low and even negative. These ES barriers can explain the difference in the growth modes for the different systems. On the other hand, we calculated the adsorption energies at the most stable adsorption sites near step edges. In particular, we wish to clarify the relation between the adatom diffusion energy barriers and the adatom adsorption energies. These results may serve as some guiding rules for studying stepped surface morphologies, which are of importance to surface nanoengineering.

  11. Effect of cooling rate on the microstructure and microhardness of the CuZrAgAl alloy

    SciTech Connect

    Liu, Y.; Blandin, J.J.; Suery, M.; Kapelski, G.

    2012-08-15

    The effect of cooling rate on the microstructure and microhardness of the Cu{sub 40}Zr{sub 44}Ag{sub 8}Al{sub 8} (at.%) alloy has been studied. The crystalline phases were characterized by X-ray diffraction, optical microscopy and scanning electron microscopy with energy dispersive X-ray spectroscopy, and identified as AlCu{sub 2}Zr, Cu{sub 10}Zr{sub 7} and CuZr{sub 2}. The solidification sequence was established as following: the Cu{sub 10}Zr{sub 7} phase forms first in the periphery of the rod, then following with AlCu{sub 2}Zr phase in the rod center and finally CuZr{sub 2} crystals in Cu-depleted areas. The effect of crystals on the mechanical properties of the Cu{sub 40}Zr{sub 44}Ag{sub 8}Al{sub 8} alloy was also estimated through the microhardness. According to the value of microhardness, inhomogeneous structure of the amorphous matrix is more easily formed for the alloy in the low cooling rate (i.e., 9 mm) as compared with the alloy with fully amorphous state in the large cooling rate (i.e., 3 mm). This inhomogeneous structure was attributed to the composition change of amorphous matrix arising from the forming of crystalline phases due to the low cooling rate. - Highlights: Black-Right-Pointing-Pointer The crystalline phases in the Cu{sub 40}Zr{sub 44}Ag{sub 8}Al{sub 8} alloy were identified. Black-Right-Pointing-Pointer The solidification sequence of Cu{sub 40}Zr{sub 44}Ag{sub 8}Al{sub 8} alloy was verified. Black-Right-Pointing-Pointer The softening and hardening of alloy could be observed due to the crystallization.

  12. Chemistry of Cu(acac){sub 2} on Ni(110) and Cu(110) surfaces: Implications for atomic layer deposition processes

    SciTech Connect

    Ma Qiang; Zaera, Francisco

    2013-01-15

    The thermal chemistry of copper(II)acetylacetonate, Cu(acac){sub 2}, on Ni(110) and Cu(110) single-crystal surfaces was probed under vacuum by using x-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD). Some data for acetylacetone (Hacac, CH{sub 3}COCH{sub 2}COCH{sub 3}) adsorbed on Ni(110) are also reported as reference. Chemical transformations were identified in several steps covering a temperature range from 150 K to at least 630 K. The desorption of Hacac and a 3-oxobutanal (CH{sub 3}COCH{sub 2}CHO) byproduct was observed first at 150 and 180 K on Ni(110) and at 160 and 185 K on Cu(110), respectively. Partial loss of the acetylacetonate (acac) ligands and a likely change in adsorption geometry are seen next, with the possible production of HCu(acac), which desorbs at 200 and 235 K from the nickel and copper surfaces, respectively. Molecular Cu(acac){sub 2} desorption is observed on both surfaces at approximately 300 K, probably from recombination of Cu(acac) and acac surface species. The remaining copper atoms on the surface lose their remaining acac ligands to the substrate and become reduced directly to metallic copper. At the same time, the organic ligands follow a series of subsequent surface reactions, probably involving several C-C bond-scissions, to produce other fragments, additional Hacac and HCu(acac) in the gas phase in the case of the copper surface, and acetone on nickel. A significant amount of acac must nevertheless survive on the surface to high temperatures, because Hacac peaks are seen in the TPD at about 515 and 590 K and the C 1s XPS split associated with acac is seen up to close to 500 K. In terms of atomic layer deposition processes, this suggests that cycles could be design to run at such temperatures as long as an effective hydrogenation agent is used as the second reactant to remove the surface acac as Hacac. Only a small fraction of carbon is left behind on Ni after heating to 800 K, whereas more carbon

  13. Bioaccessibility of As, Cd, Cu, Ni, Pb, and Sb in toys and low-cost jewelry.

    PubMed

    Guney, Mert; Zagury, Gerald J

    2014-01-21

    Children can be exposed to toxic elements in toys and jewelry following ingestion. As, Cd, Cu, Ni, Pb, and Sb bioavailability was assessed (n = 24) via the in vitro gastrointestinal protocol (IVG), the physiologically based extraction test (PBET), and the European Toy Safety Standard protocol (EN 71-3), and health risks were characterized. Cd, Cu, Ni, and Pb were mobilized from 19 metallic toys and jewelry (MJ) and one crayon set. Bioaccessible Cd, Ni, or Pb exceeded EU migratable concentration limits in four to six MJ, depending on the protocol. Using two-phase (gastric + intestinal) IVG or PBET might be preferable over EN 71-3 since they better represent gastrointestinal physiology. Bioaccessible and total metal concentrations were different and not always correlated, indicating that bioaccessibility measurement may provide more accurate risk characterization. More information on impacts of multiple factors affecting metals mobilization from toys and jewelry is needed before recommending specific tests. Hazard index (HI) for Cd, Ni, or Pb were >1 for all six MJ exceeding the EU limits. For infants (6-12 mo old), 10 MJ had HI > 1 for Cd, Cu, Ni, or Pb (up to 75 for Cd and 43 for Pb). Research on prolonged exposure to MJ and comprehensive risk characterization for toys and jewelry exposure is recommended.

  14. Evaluation of high strength, high conductivity CuNiBe alloys for fusion energy applications

    SciTech Connect

    Zinkle, Steven J

    2014-06-01

    The unirradiated tensile properties for several different heats and thermomechanical treatment conditions of precipitation strengthened Hycon 3HPTM CuNiBe (Cu-2%Ni-0.35%Be in wt.%) have been measured over the temperature range of 20-500 C for longitudinal and long transverse orientations. The room temperature electrical conductivity has also been measured for several heats, and the precipitate microstructure was characterized using transmission electron microscopy. The CuNiBe alloys exhibit very good combination of strength and conductivity at room temperature, with yield strengths of 630-725 MPa and electrical conductivities of 65-72% International Annealed Copper Standard (IACS). The strength remained relatively high at all test temperatures, with yield strengths of 420-520 MPa at 500 C. However, low levels of ductility (<5% uniform elongation) were observed at test temperatures above 200-250 C, due to flow localization near grain boundaries (exacerbated by having only 10-20 grains across the gage thickness of the miniaturized sheet tensile specimens). Scanning electron microscopy observation of the fracture surfaces found a transition from ductile transgranular to ductile intergranular fracture with increasing test temperature. Fission neutron irradiation to a dose of ~0.7 displacements per atom (dpa) at temperatures between 100 and 240 C produced a slight increase in strength and a significant decrease in ductility. The measured tensile elongation increased with increasing irradiation temperature, with a uniform elongation of ~3.3% observed at 240 C. The electrical conductivity decreased slightly following irradiation, due to the presence of defect clusters and Ni, Zn, Co transmutation products. Considering also previously published fracture toughness data, this indicates that CuNiBe alloys have irradiated tensile and electrical properties comparable or superior to CuCrZr and oxide dispersion strengthened copper at temperatures <250 C, and may be an attractive

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

    NASA Astrophysics Data System (ADS)

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

    2009-09-01

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

  16. Tarnish resistance evaluation of experimental Pd-free Ag-Au-Pt-Cu dental alloys.

    PubMed

    Takuma, Yasuko; Shiraishi, Takanobu; Fujita, Takeshi; Hisatsune, Kunihiro

    2010-05-01

    This study evaluated the tarnish resistance of eight experimental Pd-free Ag-Au-Pt-Cu dental alloys in a 0.1% Na(2)S aqueous solution at 37 degrees C. Color measurements of the plate samples were made using a computerized spectrophotometer before and after immersion in the test solution for up to 72 hours. Tarnish discoloration was evaluated using the color difference vector, DeltaE*, in the CIELAB color space. Microstructural observation of each sample through an optical microscope revealed the matrix phase as the major constituent and second-phase small grains in the matrix phase. Selective tarnish discoloration occurred in the matrix, and fractional area of the matrix to the whole surface area was influenced by the sum of Au and Ag concentrations. The DeltaE* value significantly decreased with increasing Au/(Au+Ag) atomic ratio. In conclusion, the Au/(Au+Ag) ratio in an alloy and the fractional area of the matrix were found to be primary and auxiliary factors affecting the tarnish resistance of the experimental alloys.

  17. Preparation and electrical properties of Ni-Cu-Zn system doped with the magnesium oxide

    NASA Astrophysics Data System (ADS)

    Hemeda, O. M.; Tawfik, A.; Hemeda, D. M.; Elsheekh, A. M.

    2014-06-01

    A sery of ferrite samples, Ni0.1Cu0.2MgxZn0.7-xFe2O4, (x = 0.00, 0.15, 0.25, 0.35, 0.45, 0.55 and 0.70) have been prepared by the standard ceramic techniques, sintered at 1200°C for 2 h, and their crystalline structures were investigated by using X-ray diffraction, which confirmed the formation of Ni0.1Cu0.2MgxZn0.7-xFe2O4 phase. The presence of Mg content increases the crystallinity of the given ferrite which is considered as catalyst for the accomplishment of the solid state reaction. The lattice parameter and crystallite size were calculated from XRD. The cationic distribution was estimated from the theoretical values of lattice parameters. The IR spectra analysis has been studied. The dielectric constant for the ferrite system Ni-Cu-Zn gradually increases with temperature up to nearly Curie temperature and then increase sharply beyond the Tc. The Curie temperature obtained from the ´ ǎrepsilon versus T is in agreement with the Curie temperature obtained from other measurements. Dielectric loss tangent (tan δ) has the same behavior as dielectric constant (´ ǎrepsilon). A minimum value of dielectric loss tangent (tan δ) for the system "Ni-Cu-Zn" was observed at x = 0.45. Magnetic permeability has been studied. The dependence of initial permeability on temperature exhibit a peak which is called Hopkinson peak (HP) in the vicinity of Curie temperature and confirmed the phase purity of ferrite sample. The increasing of porosity and decreasing of grain size play an important role in decreasing μi. It is clear that the value of Tc is found to increase by increasing the concentration of diamagnetic substitution Mg for "Ni-Cu-Zn" system.

  18. One-Step Solvothermal Method to Prepare Ag/Cu2O Composite With Enhanced Photocatalytic Properties

    NASA Astrophysics Data System (ADS)

    Deng, Xiaolong; Wang, Chenggang; Zhou, E.; Huang, Jinzhao; Shao, Minghui; Wei, Xianqi; Liu, Xiaojing; Ding, Meng; Xu, Xijin

    2016-01-01

    Ag/Cu2O microstructures with diverse morphologies have been successfully synthesized with different initial reagents of silver nitrate (AgNO3) by a facile one-step solvothermal method. Their structural and morphological characteristics were carefully investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), and the experimental results showed that the morphologies transformed from microcubes for pure Cu2O to microspheres with rough surfaces for Ag/Cu2O. The photocatalytic activities were evaluated by measuring the degradation of methyl orange (MO) aqueous solution under visible light irradiation. The photocatalytic efficiencies of MO firstly increased to a maximum and then decreased with the increased amount of AgNO3. The experimental results revealed that the photocatalytic activities were significantly influenced by the amount of AgNO3 during the preparation process. The possible reasons for the enhanced photocatalytic activities of the as-prepared Ag/Cu2O composites were discussed.

  19. One-Step Solvothermal Method to Prepare Ag/Cu2O Composite With Enhanced Photocatalytic Properties.

    PubMed

    Deng, Xiaolong; Wang, Chenggang; Zhou, E; Huang, Jinzhao; Shao, Minghui; Wei, Xianqi; Liu, Xiaojing; Ding, Meng; Xu, Xijin

    2016-12-01

    Ag/Cu2O microstructures with diverse morphologies have been successfully synthesized with different initial reagents of silver nitrate (AgNO3) by a facile one-step solvothermal method. Their structural and morphological characteristics were carefully investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), and the experimental results showed that the morphologies transformed from microcubes for pure Cu2O to microspheres with rough surfaces for Ag/Cu2O. The photocatalytic activities were evaluated by measuring the degradation of methyl orange (MO) aqueous solution under visible light irradiation. The photocatalytic efficiencies of MO firstly increased to a maximum and then decreased with the increased amount of AgNO3. The experimental results revealed that the photocatalytic activities were significantly influenced by the amount of AgNO3 during the preparation process. The possible reasons for the enhanced photocatalytic activities of the as-prepared Ag/Cu2O composites were discussed.

  20. Microstructure and reactions of SiC{sub w}-reinforced alumina with Ag-Cu-In-Ti

    SciTech Connect

    Park, E.S.; Lannutti, J.J.; Cawley, J.D.

    1995-01-01

    Brazing experiments were performed at 750 C for 2 h between Ag-Cu-In-Ti alloy and SiC{sub w}/Al{sub 2}O{sub 3}. The first clearly nonbraze layer consists of an oxide layer of metallic composition 33Ti-31Al-22Cu-14S. Areas adjacent to the SiC whiskers were of different composition. A thin, continuous layer on the alumina portion of the composite appears to be {gamma}-TiO. The SiC whiskers are preferentially consumed and undergo reductions in diameter of approximately 40%. Observed knobby whisker morphologies may be related to SiC stacking faults. {eta}-type phases detected near the Ag-Cu eutectic portion of the joint appear to consist of Ti-Cu-Al-Si-O and Ti{sub 3}Cu{sub 3}O.

  1. Reactions of Ni-B on printed Ag pattern by using nearly neutral electroless bath.

    PubMed

    Rha, Sa-Kyun; Kim, Hyung Chul; Lee, Youn-Seoung

    2014-11-01

    In this study, we investigated the characteristics of a nearly neutral Ni source solution including dimethylamine borane (DMAB) used to develop the metal PCB (printed circuit board) of high power LED (light-emitting diode) package. In accordance with the bath temperature ranging from 50 degrees C to 75 degrees C, an electroless Ni-B plating on a screen-printed Ag pattern with an anodized Al substrate was carried out. The depositon rate of the electroless plated Ni-B film at bath temperature ranging from 50 degrees C to 75 degrees C was estimated by measurements of the thickness and the mass. The deposition rates by change of thickness and mass of the electroless plated Ni-B film at 50 degrees C were - 58 nm/min and 0.113 mg/min respectively. The activation energy obtained from slope of Arrhenius plot using these deposition rates was - 59 kJ/mol. Finally, selectively the film growth was achieved at all plating temperatures, without a damage of anodized Al substrate.

  2. The effects of deposition time on surface morphology, structural, electrical and optical properties of sputtered Ag-Cu thin films

    NASA Astrophysics Data System (ADS)

    Ahmadpourian, Azin; Luna, Carlos; Boochani, Arash; Arman, Ali; Achour, Amine; Rezaee, Sahare; Naderi, Sirvan

    2016-10-01

    The preparation of designed nanostructured thin films combining nano grains of different compositions and physical properties represents a promising avenue for the exploration of novel collective behaviors with technological potentials. Herein, nanostructured Ag-Cu thin films with different surface morphology properties were grown by magnetron sputtering varying the deposition time (4-24 min) and fixing the other deposition conditions. X-ray diffraction studies corroborated that Cu and Ag tend to appear as separated phases with nanometric sizes due to the fact that these elements are rather immiscible. The deposited Cu tended to be partially oxidized with crystal sizes of several tens of nm, whereas the deposited Ag phase displayed a poor crystallinity with an average crystal size of around 3nm. However, at deposition time of few minutes, the formation of Ag-Cu crystals with a preferable crystallization orientation along the [111] direction was detected. The surface morphology of the obtained thin films was studied by atomic force microscopy determining the surface roughness and average particle sizes of the samples. These parameters were correlated with the plasmon resonance extinction bands of the different Ag-Cu films and their electrical properties, providing a reproducible route to obtain thin films with tuned electrical resistances and optical properties.

  3. Antimicrobial effect of TiO2 doped with Ag and Cu on Escherichia coli and Pseudomonas putida

    NASA Astrophysics Data System (ADS)

    Angelov, O.; Stoyanova, D.; Ivanova, I.

    2016-10-01

    Antimicrobial effect of TiO2 doped with Ag and Cu on Gram-negative bacteria Escherichia coli and Pseudomonas putida is studied. The thin films are deposited on glass substrates without heating during the deposition by r.f. magnetron co-sputtering of TiO2 target and pieces of Ag and Cu. The studied films, thickness about 65 nm, were as deposited and annealed (5200C, 4h, N2+5%H2, 4Pa). The as deposited thin films TiO2:Ag:Cu have band gap energy of 3.56 eV little higher than the band gap of crystalline anatase TiO2 which can be explained with the quantum effect of the granular structure of r.f. magnetron sputtered films. The annealed samples have band gap of 2.52 eV due to formation of donor levels from Ag and Cu atoms near the bottom of the conduction band. The toxic effect was determined through the classical Koch's method and the optical density measurements at λ=610 nm. The as deposited TiO2:Ag:Cu thin films demonstrate stronger inhibition effect - bactericidal for P. putida and bacteriostatic for E. coli (up to the 6th hour) in comparison with the annealed samples. The both methods of study show the same trends of the bacterial growth independently of their different sensitivity which confirms the observed effect.

  4. Element-specific study of epitaxial NiO/Ag/CoO/Fe films grown on vicinal Ag(001) using photoemission electron microscopy

    SciTech Connect

    Meng, Y.; Li, J.; Tan, A.; Jin, E.; Son, J.; Park, J. S.; Doran, A.; Young, A. T.; Scholl, A.; Arenholz, E.; Wu, J.; Hwang, C.; Zhao, H. W.; Qiu, Z. Q.

    2011-01-10

    NiO/Ag/CoO/Fe single crystalline films are grown epitaxially on a vicinal Ag(001) substrate using molecular beam epitaxy and investigated by photoemission electron microscopy. We find that after zero-field cooling, the in-plane Fe magnetization switches from parallel to perpendicular direction of the atomic steps of the vicinal surface at thinner CoO thickness but remains in its original direction parallel to the steps at thicker CoO thickness. CoO and NiO domain imaging result shows that both CoO/Fe and NiO/CoO spins are perpendicularly coupled, suggesting that the Fe magnetization switching may be associated with the rotatable-frozen spin transition of the CoO film.

  5. Interfacial structure of Si3N4 brazed with an Ag-Cu-Ti alloy

    NASA Astrophysics Data System (ADS)

    Suematsu, H.; Petrovic, J. J.; Mitchell, T. E.; Yano, T.

    Single crystal Si3N4 was brazed using a Ag-Cu eutectic alloy containing 2 percent Ti at 950 C for 30 min and the interface was observed by high resolution electron microscopy. A layer of reaction products is formed between the Si3N4 and the brazed metal. TiN and Ti2N are formed near the interface; however, only TiN is found at the interface in contact with the Si3N4. A crystallographic orientation relationship was found between the TiN and Si3N4 in which the N atoms are shared between the two structures with little distortion.

  6. Carboxylation of 2-methylbutyn-3-ol-2 on Ag- and Cu-containing catalysts

    NASA Astrophysics Data System (ADS)

    Finashina, E. D.; Kustov, L. M.; Krasovskii, V. G.; Formenova, E. I.

    2016-09-01

    The analysis of the products of direct carboxylation of 2-methylbutyn-3-ol-2 with carbon dioxide on Ag- and Cu-containing catalysts by 1H and 13C NMR and FTIR spectroscopy showed that the desired 4-hydroxy-4-methylpent-2-ynoic acid did not form under the given conditions; instead, the triple bond of the substrate decomposed, and two polyfunctional acids formed: 4-hydroxy-4-methyl-3-oxopentanoic and 3,4-dihydroxy-4-methylpent-2-enic (the latter is the result of the keto-enol rearrangement of the former keto acid).

  7. Spasmodic growth during the rapid solidification of undercooled Ag-Cu eutectic melts

    NASA Astrophysics Data System (ADS)

    Clopet, C. R.; Cochrane, R. F.; Mullis, A. M.

    2013-01-01

    A melt fluxing technique has been used to undercool Ag-Cu eutectic alloy by 10-70 K and the subsequent recalescence has been studied using high speed imaging. Spasmodic growth of the solidification front was observed, in which the growth front would make a series of quasi-periodic jumps separated by extended periods during which time growth appeared to arrest. Evidence of this previously unreported mode of growth is presented. The high speed images and microstructural evidence support the theory that anomalous eutectics form by the growth and subsequent remelting of eutectic dendrites.

  8. New analysis of He scattering data from Ag(110) and Cu(110)

    NASA Astrophysics Data System (ADS)

    Cortona, P.; Dondi, M. G.; Lausi, A.; Tommasini, F.

    1992-10-01

    A method for the analysis of the He-surface scattering data using a model potential based on the superposition of pseudo-pairwise anisotropic terms and degenaracy-dependent self-interaction-corrected (D-SIC) calculations of the atomic electron densities is presented and applied to the study of the electron density of Ag(110) and Cu(110). Rearrangements of the electron clouds around the surface atoms with respect to those of the free atoms, leaving unchanged the lateral average, are observed in both cases.

  9. Sulfides from Martian and Lunar Basalts: Comparative Chemistry for Ni Co Cu and Se

    SciTech Connect

    J Papike; P Burger; C Shearer; S Sutton; M Newville; Y Choi; A Lanzirotti

    2011-12-31

    Here Mars and Moon are used as 'natural laboratories' with Moon displaying lower oxygen fugacities ({approx}IW-1) than Mars ({approx}IW to FMQ). Moon has lower concentrations of Ni and Co in basaltic melts than does Mars. The major sulfides are troilite (FeS) in lunar basalts and pyrrhotite (Fe{sub 1-x}S) in martian basalts. This study focuses on the concentrations of Ni, Co, Cu, and Se. We chose these elements because of their geochemical importance and the feasibility of analyzing them with a combination of synchrotron X-ray fluorescence (SXRF) and electron microprobe (EPMA) techniques. The selenium concentrations could only be analyzed, at high precision, with SXRF techniques as they are <150 ppm, similar to concentrations seen in carbonaceous chondrites and interplanetary dust particles (IDPs). Nickel and Co are in higher concentrations in martian sulfides than lunar and are higher in martian olivine-bearing lithologies than olivine-free varieties. The sulfides in individual samples show very large ranges in concentration (e.g., Ni ranges from 50 000 ppm to <5 ppm). These large ranges are mainly due to compositional heterogeneities within individual grains due to diffusion and phase separation. Electron microprobe wavelength-dispersive (WDS) mapping of Ni, Co, and Cu show the diffusion trajectories. Nickel and Co have almost identical diffusion trajectories leading to the likely nucleation of pentlandite (Ni,Co,Fe){sub 9}S{sub 8}, and copper diffuses along separate pathways likely toward chalcopyrite nucleation sites (CuFeS{sub 2}). The systematics of Ni and Co in lunar and martian sulfides clearly distinguish the two parent bodies, with martian sulfides displaced to higher Ni and Co values.

  10. Influence of the Ag concentration on the medium-range order in a CuZrAlAg bulk metallic glass

    PubMed Central

    Gammer, C.; Escher, B.; Ebner, C.; Minor, A. M.; Karnthaler, H. P.; Eckert, J.; Pauly, S.; Rentenberger, C.

    2017-01-01

    Fluctuation electron microscopy of bulk metallic glasses of CuZrAl(Ag) demonstrates that medium-range order is sensitive to minor compositional changes. By analyzing nanodiffraction patterns medium-range order is detected with crystal-like motifs based on the B2 CuZr structure and its distorted structures resembling the martensitic ones. This result demonstrates some structural homology between the metallic glass and its high temperature crystalline phase. The amount of medium-range order seems slightly affected with increasing Ag concentration (0, 2, 5 at.%) but the structural motifs of the medium-range ordered clusters become more diverse at the highest Ag concentration. The decrease of dominant clusters is consistent with the destabilization of the B2 structure measured by calorimetry and accounts for the increased glass-forming ability. PMID:28322304

  11. Influence of the Ag concentration on the medium-range order in a CuZrAlAg bulk metallic glass

    NASA Astrophysics Data System (ADS)

    Gammer, C.; Escher, B.; Ebner, C.; Minor, A. M.; Karnthaler, H. P.; Eckert, J.; Pauly, S.; Rentenberger, C.

    2017-03-01

    Fluctuation electron microscopy of bulk metallic glasses of CuZrAl(Ag) demonstrates that medium-range order is sensitive to minor compositional changes. By analyzing nanodiffraction patterns medium-range order is detected with crystal-like motifs based on the B2 CuZr structure and its distorted structures resembling the martensitic ones. This result demonstrates some structural homology between the metallic glass and its high temperature crystalline phase. The amount of medium-range order seems slightly affected with increasing Ag concentration (0, 2, 5 at.%) but the structural motifs of the medium-range ordered clusters become more diverse at the highest Ag concentration. The decrease of dominant clusters is consistent with the destabilization of the B2 structure measured by calorimetry and accounts for the increased glass-forming ability.

  12. Performance of the nano-structured Cu-Ni (alloy) -CeO2 anode for solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Liu, Minquan; Wang, Shaolan; Chen, Ting; Yuan, Chun; Zhou, Yucun; Wang, Shaorong; Huang, Jun

    2015-01-01

    In this work, copper and nickel oxides (CuO-NiO) powders with various mole ratios were synthesized by the glycine nitrate process (GNP) and the Cu-Ni alloy was obtained by reducing the CuO-NiO powders at 600 °C for 0.75 h. Furthermore, Cu1-xNix (alloy) -CeO2 impregnated YSZ anodes were fabricated by the impregnation method and the optimized anode composition was evaluated. It was found that the optimized mole ratio of Cu:Ni was 5:5, while the weight ratio of Cu-Ni alloy to CeO2 was 3:1. Additionally, impregnated anode with 40 wt % loading of Cu0.5Ni0.5 (alloy)-CeO2 exhibited the best performance and the polarization resistance of such anode was only 0.097, 0.115, 0.145 and 0.212 Ω cm2 at 750, 700, 650 and 600 °C, respectively. Finally, the performance of the optimized anode in methane (CH4) was investigated and the carbon deposition is greatly suppressed compared to the Ni-based anode.

  13. Contact angle measurements of Sn-Ag and Sn-Cu lead-free solders on copper substrates

    NASA Astrophysics Data System (ADS)

    Arenas, Mario F.; Acoff, Viola L.

    2004-12-01

    In this study, the contact angles of four lead-free solders, namely, Sn-3.5Ag, Sn-3.5Ag-4.8Bi, Sn-3.8Ag-0.7Cu, and Sn-0.7Cu (wt.%), were measured on copper substrates at different temperatures. Measurements were performed using the sessile-drop method. Contact angles ranging from 30° to 40° after wetting under vacuum with no fluxes and between 10° and 30° with rosin mildly activated (RMA) and rosin activated (RA) fluxes were obtained. The Sn-3.5Ag-4.8Bi exhibited the lowest contact angles, indicating improved wettability with the addition of bismuth. For all soldering alloys, lower contact angles were observed using RMA flux. Intermetallics formed at the solder/Cu interface were identified as Cu6Sn5 adjacent to the solder and Cu3Sn adjacent to the copper substrate. The Cu3Sn intermetallic phase was generally not observed when RMA flux was used. The effect of temperature on contact angle was dependent on the type of flux used.

  14. M atom (M = Cu, Ag and Au) interaction with Ag and Au substrates: a first-principles study using cluster and slab models.

    PubMed

    Nigam, Sandeep; Majumder, Chiranjib

    2010-11-03

    Using state-of-the-art first-principles calculations we report the interaction of M atoms (M = Cu, Ag and Au) with small Ag(n), Au(n) clusters (n = 3 and 6) and periodic Ag(111) and Au(111) surfaces. All calculations were performed using the plane wave pseudo-potential approach under the spin polarized version of the generalized gradient approximation scheme. The result shows that the equilibrium geometry of all MAg(3) and MAu(3) clusters favor a planar rhombus structure. From the charge distribution analysis of MAg(n)/MAu(n) clusters it is found that, while Cu and Ag donates electronic charge towards the host clusters, the Au atom acts as an acceptor, thus creating charge polarization in the system. The difference in orbital decomposed charges before and after the M interaction reveals that enhanced s-d hybridization is responsible for keeping the MAu(6) cluster planar, and increased p-orbital participation induces three-dimensional configurations in MAg(6) clusters. The optimization of M atom deposition on the Ag(111) and Au(111) surfaces shows that M atoms prefer to adsorb on the threefold fcc site over other well-defined sites. From the orbital decomposed charge analysis it is inferred that, although there is significant difference in the absolute magnitude of the interaction energy between M atoms and the Ag or Au substrates, the nature of chemical bonding is similar for the finite size clusters as well as in slab models.

  15. Tren centered tris-macrocycles as polytopic ligands for Cu(II) and Ni(II).

    PubMed

    Siegfried, Liselotte; McMahon, C Niamh; Kaden, Thomas A; Palivan, Cornelia; Gescheidt, Georg

    2004-07-21

    Two novel symmetric polytopic ligands L(1) and L(2) have been synthesized. They are composed of three 1,4,8,11-tetraazacyclotetradecane macrocycles which are connected to a central tren moiety via an ethylene and a trimethylene bridge, respectively. The complexation potential and the speciation diagrams of L(1) and L(2) towards Cu(2+) and Ni(2+) were determined by spectrophotometric and potentiometric titrations. Insight into the geometry of the Cu(2+) complexes is provided by UV-VIS and EPR spectroscopy. The simplified ligands L(3) and L(4) are utilized as references for an aminoethyl- and a tren-substituted tetraaza macrocycle to help assign the EPR spectra of the polytopic ligands L(1) and L(2). At a metal-to-ligand ratio of 3 : 1, the metal cations are preferentially bound to the tetraaza macrocycles of L(1) and L(2) in a square planar geometry. At high pH values, a nitrogen atom of the tren moiety in L(1) serves as an additional ligand in an axial position leading to a square pyramidal coordination around Cu(2+), whereas in L(2) no such geometry change is observed. At a metal-to-ligand ratio of 4 : 1, the additional metal cation resides in the central tren moiety of L(1) and L(2). However, in contrast to the typical trigonal bipyramidal geometry found in the [Cutren](2+) complex, the fourth Cu(2+) has a square pyramidal coordination caused by the interaction with the Cu(2+) cations in the macrocycles (as evidenced by EPR spectra). Since the sequence of metal complexation is such that the first three metal ions always bind to the three macrocycles of L(1) and L(2) and the fourth to the tren unit, it is possible to prepare heteronuclear complexes such as [Cu(3)NiL](8+) or [Ni(3)CuL](8+), which can be unambiguously identified by their spectral properties.

  16. Efficient and selective recovery of Ni, Cu, and Co from low-nickel matte via a hydrometallurgical process

    NASA Astrophysics Data System (ADS)

    Chen, Guang-ju; Gao, Jian-ming; Zhang, Mei; Guo, Min

    2017-03-01

    Low-nickel matte was intensively characterized, and Ni, Cu, and Co were determined to exist mainly as (Fe,Ni)9S8 and FeNi3, Cu5FeS4, and (Fe,Ni)9S8 and Fe3O4 (in isomorphic form), respectively. The efficient and selective extraction of Ni, Cu, and Co from the low-nickel matte in an (NH4)2S2O8/NH3·H2O solution system was studied. The effects of (NH4)2S2O8 and NH3·H2O concentrations, leaching time, and leaching temperature on the metal extraction efficiency were systematically investigated. During the oxidative ammonia leaching process, the metal extraction efficiencies of Ni 81.07%, Cu 93.81%, and Co 71.74% were obtained under the optimal conditions. The relatively low leaching efficiency of Ni was mainly ascribed to NiFe alloy deactivation in ammonia solution. By introducing an acid pre-leaching process into the oxidative ammonia leaching process, we achieved the high extraction efficiencies of 98.03%, 99.13%, and 85.60% for the valuable metals Ni, Cu, and Co, respectively, from the low-nickel matte.

  17. Evolution of Microstructure in Brazed Joints of Austenitic-Martensitic Stainless Steel with Pure Silver Obtained with Ag-27Cu-5Sn Brazing Filler Material

    NASA Astrophysics Data System (ADS)

    Gangadharan, S.; Sivakumar, D.; Venkateswaran, T.; Kulkarni, Kaustubh

    2016-12-01

    Brazing of an austenitic-martensitic stainless steel (AMSS) with pure silver was carried out at 1053 K, 1073 K, and 1093 K (780 °C, 800 °C, and 820 °C) with Ag-27Cu-5Sn (wt pct) as brazing filler material (BFM). Wettability of the liquid BFM over base AMSS surface was found to be poor. Application of nickel coating to the steel was observed to enhance the wettability and to enable the formation of a good bond between BFM and the steel. The mechanism responsible for enhanced metallurgical bonding of the BFM with AMSS in the presence of nickel coating was explained based on diffusional interactions and uphill diffusion of iron, chromium and nickel observed in the brazed microstructure. Good diffusion-assisted zone was observed to form on silver side at all three temperatures. Four phases were encountered within the joint including silver solid solution, copper solid solution, Cu3Sn intermetallic and Ni-Fe solid solution. The Cu3Sn intermetallic was present in small amounts in the joints brazed at 1053 K and 1073 K (780 °C and 800 °C). The joint formed at 1093 K (820 °C) exhibited the absence of Cu3Sn, fewer defects and larger diffusion-assisted zone. Hardness of base AMSS was found to reduce during brazing due to austenite reversion and post-brazing sub-zero treatment for 2.5 hours was found suitable to recover the hardness.

  18. Electrical transport and structural investigations in Cu2O substituted AgI-Ag2O-V2O5 glass-ceramic nanocomposites

    NASA Astrophysics Data System (ADS)

    Gupta, Neha; Dalvi, Anshuman; Awasthi, Barkha; Deva, Dinesh

    2012-06-01

    Glass-ceramic nanocomposites in Cu2O substituted AgI-(Ag2O)1-x-(Cu2O)x-V2O5 superionic system are prepared by annealing the melt-quenched glasses above the crystallization temperatures. Structural and electrical properties have been investigated. Scanning electron microscopy suggests the existence of fine particles of size 20-200 nm dispersed in the annealed glass matrix. Samples are essentially ionic and stable under conductivity-temperature cycles upto ˜ 160 °C. It is found that the conductivity in the nanocomposites increases with Cu2O substitution and highest conductivity is found to be ˜ 2 × 10-3 Ω-1cm-1 for x = 0.3 at room temperature. Differential scanning calorimetry scans confirm the existence of silver iodide crystallites in all the glass-ceramic compositions.

  19. Spatial statistical and structural modeling of the Keivitsa Ni-Cu-PGE deposit, northern Finland

    NASA Astrophysics Data System (ADS)

    Parkkinen, J.

    2003-04-01

    The Keivitsa Ni-Cu-PGE deposit, located in the central Finnish Lapland, has been studied using Gemcom’s software to analyze and model Cu, S, Ni, and PGE (+Au) grade structures. Input data includes whole rock geochemistry, base metal geochemistry (Cu, Ni, S, 13102 assays averaging 0.15 %, 0.13 %, and 0.82 % correspondingly) and Platinum Group Element (PGE) and gold geochemistry (Pt, Pd, and Au, 4297 assays averaging 242 ppb, 159 ppb, and 81 ppb, correspondingly). Additionally, core geophysical data (specific gravity, 22098 determinations averaging 3.157) has been used in modeling. In the first phase Inverse Distance (ID2) was used for the interpolation of above assays as well as for specific gravity measurements, taken from core samples at 1m intervals. This occurred on horizontal planes and on N-S, E-W, and diagonally oriented vertical sections where also grade structures for PGE, Ni, Cu and S were outlined while making use of above interpolations and block models. Interpretation of geophysical data suggests sub-horizontal layering of the Keivitsa intrusion. Geochemical correlation modeling shows that the PGE have good spatial correlation with Ni and S, whereas Cu peaks are slightly shifted from the PGE maximum. A high PGE zone is trending almost S-N, with grade structures indicating pipe-like vertical bodies. The PGE-rich pipes, delimited by a cutoff grade 1 ppm PGE+Au, are about 30-50 m long and 10-30 m wide with a vertical depth of more than 400 m at most. The Pt/Pd ratio is 1.76 on an average and the average PGE + Au is 2.1 ppm within the pipes delineated with an one ppm cutoff grade. The PGE-rich zone may be a deep fault zone, having split the Ni-Cu deposit hosted by the Keivitsa olivine clino-pyroxenite into two segments plunging to the SE. The low grade Cu-Ni-sulfide dissemination extends approximately 1.0 km in the E-W direction and 0.6 km in the N-S direction with a thickness of about 500 m. The total resources at Keivitsa to a depth of 300 m are 112 Mt

  20. Incommensurate magnetic order in Ag2NiO2 studied with muon-spin-rotation and relaxation spectroscopy

    NASA Astrophysics Data System (ADS)

    Sugiyama, J.; Ikedo, Y.; Mukai, K.; Brewer, J. H.; Ansaldo, E. J.; Morris, G. D.; Chow, K. H.; Yoshida, H.; Hiroi, Z.

    2006-06-01

    The nature of the magnetic transition of the half-filled triangular antiferromagnet Ag2NiO2 with TN=56K was studied with positive muon-spin-rotation and relaxation (μ+SR) spectroscopy. Zero field μ+SR measurements indicate the existence of a static internal magnetic field at temperatures below TN . Two components with slightly different precession frequencies and wide internal-field distributions suggest the formation of an incommensurate antiferromagnetic order below 56K . This implies that the antiferromagnetic interaction is predominant in the NiO2 plane in contrast to the case of the related compound NaNiO2 . An additional transition was found at ˜22K by both μ+SR and susceptibility measurements. It was also clarified that the transition at ˜260K observed in the susceptibility of Ag2NiO2 is induced by a purely structural transition.

  1. Enhanced hydrogenation and reduced lattice distortion in size selected Pd-Ag and Pd-Cu alloy nanoparticles

    SciTech Connect

    Sengar, Saurabh K.; Mehta, B. R.; Kulriya, P. K.; Khan, S. A.

    2013-10-21

    Important correlation between valence band spectra and hydrogenation properties in Pd alloy nanoparticles is established by studying the properties of size selected and monocrystalline Pd, Ag, Cu, Pd-Ag, and Pd-Cu nanoparticles. The X-ray photoelectron spectroscopy and elastic recoil detection analysis show that size induced Pd4d centroid shift is related to enhanced hydrogenation with H/Pd ratio of 0.57 and 0.49 in Pd-Ag and Pd-Cu nanoparticles in comparison to reported bulk values of 0.2 and 0.1, respectively. Pd-alloy nanoparticles show lower hydrogen induced lattice distortion. The reduced distortion and higher hydrogen reactivity of Pd-alloy nanoparticles is important for numerous hydrogen related applications.

  2. Mechanical, structural and thermal properties of Ag-Cu and ZnO reinforced polylactide nanocomposite films.

    PubMed

    Ahmed, Jasim; Arfat, Yasir Ali; Castro-Aguirre, Edgar; Auras, Rafael

    2016-05-01

    Plasticized polylactic acid (PLA) based nanocomposite films were prepared by incorporating polyethylene glycol (PEG) and two selected nanoparticles (NPs) [silver-copper (Ag-Cu) alloy (<100 nm) and zinc oxide (ZnO) (<50 and <100 nm)] through solvent casting method. Incorporation of Ag-Cu alloy into the PLA/PEG matrix increased the glass transition temperature (Tg) significantly. The crystallinity of the nanocomposites (NCs) was significantly influenced by NP incorporation as evidenced from differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analysis. The PLA nanocomposite reinforced with NPs exhibited much higher tensile strength than that of PLA/PEG blend. Melt rheology of NCs exhibited a shear-thinning behavior. The mechanical property drastically reduced with a loading of NPs, which is associated with degradation of PLA. SEM micrographs exhibited that both Ag-Cu alloy and ZnO NPs were dispersed well in the PLA film matrix.

  3. Effect of filler metal composition on the strength of yttria stabilized zirconia joints brazed with Pd-Ag-CuOx

    SciTech Connect

    Darsell, Jens T.; Weil, K. Scott

    2008-09-08

    The Ag-CuOx system is of interest to be used to be used as an air braze filler metal for joining high temperature electrochemical devices. Previous work has shown that the melting temperatures can be increased by adding palladium to Ag-CuOx and it is expected that this may aid high temperature stability. This work compares the room temperature bend strength of joints made between yttria-stabilized zirconia (YSZ) air brazed using Ag-CuOx without palladium and with 5 and 15mol% palladium additions. It has been found that in general palladium decreases joint strength, especially in low copper oxide compositions filler metals. At high copper oxide contents, brittle fracture through both copper oxide rich phases and the YSZ limits joint strength.

  4. Enhancement of photocurrent in GaInNAs solar cells using Ag/Cu double-layer back reflector

    NASA Astrophysics Data System (ADS)

    Aho, Timo; Aho, Arto; Tukiainen, Antti; Polojärvi, Ville; Salminen, Turkka; Raappana, Marianna; Guina, Mircea

    2016-12-01

    The effect of a Ag/Cu-based double-layer back reflector on current generation in GaInNAs single-junction solar cell is reported. Compared to Ti/Au reflector, the use of Ag/Cu led to a 28% enhancement of short-circuit current density, attaining a value of ˜14 mA/cm2 at AM1.5D (1000 W/m2) under a GaAs filter. The enhanced current generation is in line with requirements for current-matching in GaInP/GaAs/GaInNAs triple-junction solar cells. The Ag/Cu reflectors also had a low contact resistivity of the order of 10-6 Ω.cm2 and none of the samples exhibited notable peeling of metals in the adhesion tests. Moreover, no discernible diffusion of the metals into the semiconductor was observed after thermal annealing at 200 °C.

  5. Lattice Dynamical Properties and Elastic Constants of the Ternary Chalcopyrite Compounds CuAlS2, CuGaS2, CuInS2, and AgGaS2

    NASA Astrophysics Data System (ADS)

    Kushwaha, A. K.; Khenata, R.; Bouhemadou, A.; Bin-Omran, S.; Haddadi, K.

    2017-02-01

    Lattice dynamics calculations have been performed for ternary chalcopyrite compounds CuAlS2, CuGaS2, CuInS2, and AgGaS2 using the proposed theoretical model. This model is applied to study the zone-centre (GAMMA = 0) phonon frequencies of CuAlS2, CuGaS2, CuInS2, and AgGaS2. The interatomic interactions up to third nearest neighbours were calculated. The calculated zone-centre phonon frequencies are found to be in very good agreement with observed and previous calculated data available in the literature. Single crystal elastic constants and related properties for these materials were also calculated and compared with the available data in the scientific literature.

  6. A study on the inhibition kinetics of bioaccumulation of Cu(II) and Ni(II) ions using Rhizopus delemar.

    PubMed

    Açikel, Unsal; Alp, Tuğba

    2009-09-15

    The microbial growth and simultaneous bioaccumulation of Cu(II) and Ni(II) ions during the growth of Rhizopus delemar in molasses medium was investigated in a batch system. The level of Cu(II) and Ni(II) bioaccumulation and microbial growth was dependent on pH, molasses sucrose concentration and initial Cu(II) and Ni(II) ion concentrations. An increase in initial total metal ion concentration inhibited both the growth rate of fungus and the bioaccumulation capacity. Lineweaver-Burk plot of Monod equation was used to study the inhibition kinetics of bioaccumulation of Cu(II) and Ni(II) and the intrinsic and apparent model parameters were evaluated in metals-free and metals-contaminated fermentation media. The maximum specific growth rate (micro(m)) and the Monod constant (K(s)) of microorganism in metals-free media were found as 0.405 L/h and 3.977 g/L, respectively. As micro(m) remained constant in the presence of increasing concentrations of Cu(II) and Ni(II) ions, the combined inhibition of Cu(II) and Ni(II) ions on the growth rate of R. delemar was found to be a competitive inhibition. The inhibition constants for Cu(II) and Ni(II) ions were determined as 56.71 mg Cu(II)/L and 47.44 mg Ni(II)/L. As the bioaccumulation of Cu(II) and Ni(II) ions was reduced by the presence of increasing concentrations of the other metal ion, compared with the single-metal systems, the individual action of Cu(II) and Ni(II) ions on the bioaccumulation of R. delemar was generally found to be antagonistic. On the other hand, the total combined effects of Cu(II) and Ni(II) ions on the bioaccumulation of R. delemar are thought to be synergistic since the total bioaccumulated metal ion quantities per unit mass of biomass were higher than those obtained in the growth media containing Cu(II) and Ni(II) ions alone at the same concentrations.

  7. Giant Peltier Effect in a Submicron-Sized Cu-Ni/Au Junction with Nanometer-Scale Phase Separation

    NASA Astrophysics Data System (ADS)

    Sugihara, Atsushi; Kodzuka, Masaya; Yakushiji, Kay; Kubota, Hitoshi; Yuasa, Shinji; Yamamoto, Atsushi; Ando, Koji; Takanashi, Koki; Ohkubo, Tadakatsu; Hono, Kazuhiro; Fukushima, Akio

    2010-06-01

    We observed a giant Peltier effect in a submicron Cu-Ni/Au junction. The Peltier coefficient was evaluated to be 480 mV at room temperature from the balance between Joule heating and the Peltier cooling effect in the junction, which is 40 times that expected from the Seebeck coefficients of bulk Au and Cu-Ni alloy. This giant cooling effect lowered the inner temperature of the junction by 160 K. Microstructure analysis with a three-dimensional atom probe suggested that the giant Peltier effect possibly originated from nanometer-scale phase separation in the Cu-Ni layer.

  8. Cu-Al-Ni Shape Memory Single Crystal Wires with High Transformation Temperature

    NASA Technical Reports Server (NTRS)

    Hautcoeur, Alain; Fouché, Florian; Sicre, Jacques

    2016-01-01

    CN-250X is a new material with higher performance than Nickel-Titanium Shape Memory Alloy (SMA). For space mechanisms, the main disadvantage of Nickel-Titanium Shape Memory Alloy is the limited transformation temperature. The new CN-250X Nimesis alloy is a Cu-Al-Ni single crystal wire available in large quantity because of a new industrial process. The triggering of actuators made with this Cu-Al-Ni single crystal wire can range from ambient temperature to 200 C in cycling and even to 250 C in one-shot mode. Another advantage of CN-250X is a better shape recovery (8 to 10%) than Ni-Ti (6 to 7%). Nimesis is the first company able to produce this type of material with its new special industrial process. A characterization study is presented in this work, including the two main solicitation modes for this material: tensile and torsion. Different tests measure the shape recovery of Cu-Al-Ni single crystals wires during heating from room temperature to a temperature higher than temperature of end of martensitic transformation.

  9. Microstructure and Precipitate's Characterization of the Cu-Ni-Si-P Alloy

    NASA Astrophysics Data System (ADS)

    Zhang, Yi; Tian, Baohong; Volinsky, Alex A.; Sun, Huili; Chai, Zhe; Liu, Ping; Chen, Xiaohong; Liu, Yong

    2016-04-01

    Microstructure of the Cu-Ni-Si-P alloy was investigated by transmission electron microscopy (TEM). The alloy had 551 MPa tensile strength, 226 HV hardness, and 36% IACS electrical conductivity after 80% cold rolling and aging at 450 °C for 2 h. Under the same aging conditions, but without the cold rolling, the strength, hardness, and electrical conductivity were 379 MPa, 216 HV, and 32% IACS, respectively. The precipitates identified by TEM characterization were δ-Ni2Si. Some semi-coherent spherical precipitates with a typical coffee bean contrast were found after aging for 48 h at 450 °C. The average diameter of the observed semi-coherent precipitates is about 5 nm. The morphology of the fracture surface was observed by scanning electron microscopy. All samples showed typical ductile fracture. The addition of P refined the grain size and increased the nucleation rate of the precipitates. The precipitated phase coarsening was inhibited by the small additions of P. After aging, the Cu-Ni-Si-P alloy can gain excellent mechanical properties with 804 MPa strength and 49% IACS conductivity. This study aimed to optimize processing conditions of the Cu-Ni-Si-P alloys.

  10. Development of Ag-Pd-Au-Cu alloys for multiple dental applications. Part 2. Mechanical properties of experimental Ag-Pd-Au-Cu alloys containing Sn or Ga for ceramic-metal restorations.

    PubMed

    Goto, S; Nakai, A; Miyagawa, Y; Ogura, H

    2001-06-01

    Eighteen Ag-Pd-Au-Cu alloys, consisting of nine Ag-Pd-Au-Cu mother compositions (Pd: 20, 30 or 40%, Au: 20%, Cu: 10, 15 or 20%, Ag: balance) containing either 5% Sn or 5% Ga as an additive metal, were experimentally prepared. Tensile strength, proof stress, elongation, elastic modulus, and Vickers hardness of these alloys were evaluated to clarify the potential of these alloys for use as ceramic-metal restorations as well as the effects of the Pd and Cu contents on their mechanical properties. The tensile strength, proof stress, elongation, elastic modulus and Vickers hardness of the 18 experimental alloys were in the range of 410.0-984.0 MPa, 289.7-774.3 MPa, 2.2-23.7%, 81.3-123.0 GPa and 135.7-332.3 HV1, respectively. Ten of the 18 experimental alloys can be used for ultra-low fusing ceramics based on their proof stress, elastic modulus, elongation and hardness. Between the Ga- and Sn-added alloys, differences in tensile strength, proof stress, elongation and hardness were found at several Ag-Pd-Au-Cu compositions.

  11. Structural transformations in Cu1.95Ni0.05S crystals

    NASA Astrophysics Data System (ADS)

    Nasirov, V. I.; Rzaeva, A. G.; Ibragimov, G. B.

    2016-12-01

    A solid solution of the Cu1.95Ni0.05S composition has been synthesized for the first time due to the partial replacement of Cu with Ni atoms in Cu2S. The polymorphic transformations in the polycrystalline samples in the temperature range of 300-1400 K have been investigated by X-ray diffraction and differential thermal analysis. It is established that, at room temperature, the synthesized Cu1.95Ni0.05S samples have an orthorhombic lattice with unit-cell parameters a = 26.50 Å, b = 15.39 Å, and c = 13.85 Å (sp. gr. Abm2). Heating to T = 379 ± 2 K leads to its transformation into a hexagonal lattice with parameters a = 3.960 Å and c = 6.78 Å (sp. gr. P63/ mmc). At 750 ± 2 K, the hexagonal modification is transformed into a cubic one with period a = 5.788 Å (sp. gr. Fm bar 3 m). The phase transition in this crystal is enantiotropic.

  12. Structural and magnetic phase transitions in CeCu6-xTx (T = Ag,Pd)

    DOE PAGES

    Poudel, Lekhanath N.; De la cruz, Clarina; Payzant, E. Andrew; ...

    2015-12-15

    The structural and the magnetic properties of CeCu6-xAgx (0 ≤ x ≤ 0.85) and CeCu6-xPdx (0 ≤ x ≤ 0.4) have been studied using neutron diffraction, resonant ultrasound spectroscopy (RUS), x-ray diffraction measurements, and first principles calculations. The structural and magnetic phase diagrams of CeCu6-xAgx and CeCu6-xPdx as a function of Ag/Pd composition are reported. The end member, CeCu6, undergoes a structural phase transition from an orthorhombic (Pnma) to a monoclinic (P21/c) phase at 240 K. In CeCu6-xAgx, the structural phase transition temperature (Ts) decreases linearly with Ag concentration and extrapolates to zero at xS ≈ 0.1. The structural transitionmore » in CeCu6-xPdx remains unperturbed with Pd substitution within the range of our study. The lattice constant b slightly decreases with Ag/Pd doping, whereas a and c increase with an overall increase in the unit cell volume. Both systems, CeCu6-xAgx and CeCu6-xPdx, exhibit a magnetic quantum critical point (QCP), at x ≈ 0.2 and x ≈ 0.05, respectively. Near the QCP, long range antiferromagnetic ordering takes place at an incommensurate wave vector (δ1 0 δ2), where δ1 ~ 0.62, δ2 ~ 0.25, x = 0.125 for CeCu6-xPdx and δ1 ~ 0.64, δ2 ~ 0.3, x = 0.3 for CeCu6-xAgx. As a result, the magnetic structure consists of an amplitude modulation of the Ce moments which are aligned along the c axis of the orthorhombic unit cell.« less

  13. Joint effect of ferromagnetic and non-ferromagnetic cations for adjusting room temperature ferromagnetism of highly luminescent CuNiInS quaternary nanocrystals

    NASA Astrophysics Data System (ADS)

    Shen, Jin; Wang, Chunlei; Xu, Shuhong; Lv, Changgui; Zhang, Ruohu; Cui, Yiping

    2017-01-01

    In this work, highly luminescent quaternary CuNiInS nanocrystals (NCs) are put forward as a good prototype for investigating defect-induced room temperature ferromagnetism. A ferromagnetic Ni cation can preserve the strong luminescence of NCs without introducing intermediate energy levels in the center of the forbidden band. The strong luminescence of NCs is used as an indicator for monitoring the concentration of vacancy defects inside them, facilitating the investigation of the origin of room temperature ferromagnetism in CuNiInS NCs. Our results reveal that the patching of Cu vacancies ({{{{V}}}{{Cu}}}-) with Ni will result in bound magnetic polarons composed of both {{{{V}}}{{Cu}}}- and a substitution of Cu by Ni ({{{{Ni}}}{{Cu}}}+), giving rise to the room temperature ferromagnetism of CuNiInS NCs. Either the ferromagnetic Ni or the non-ferromagnetic Cu cation can tune the magnetism of CuNiInS NCs because of the change of bound magnetic polaron concentration at the altered concentration ratio of {{{{V}}}{{Cu}}}- and {{{{Ni}}}{{Cu}}}+.

  14. Modification of ZnO Thin Films by Ni, Cu, and Cd Doping*1

    NASA Astrophysics Data System (ADS)

    Jiménez-González, A. E.

    1997-02-01

    With the propose of investigating the effect of transition elements in ZnO thin films prepared by the Successive Ion Layer Adsorption and Reaction (SILAR) technique, the deposition solutions were chemically impurified with Ni, Cu, and Cd, as elements of the Ib, IIb, and VIIIa groups. X-ray fluorescence (XRF) analyses confirm that the impurification with Ni and Cu in fact took place but the impurification with Cd did not, while the XRD analyses show that foras preparedand Ni-impurified annealed films, the crystallites are almost oriented along thecaxis. The electrical properties of the ZnO films were also modified with the impurification. After annealing in air (450°C) the dark conductivity of the films was increased in the case of Ni and Cd impurification up to 1.80×10-3and 1.86×10-2[Ω cm]-1, respectively, but it decreased drastically in the case of Cu to 5.51×10-7[Ω cm]-1, as referred to the dark conductivity (1.86×10-4[Ω cm]-1) of the pure ZnO sample. The measured activation energy for the electrical conductivity of the modified ZnO thin films is 55 meV for the Ni modification, indicating the existence of donor levels. On the other hand, the Cu modification increases the activation energy up to 132 meV, which is higher than the activation energy for pure ZnO thin films (98 meV).

  15. Solid-state growth kinetics of Ni{sub 3}Sn{sub 4} at the Sn-3.5Ag solder/Ni interface

    SciTech Connect

    Alam, M.O.; Chan, Y.C.

    2005-12-15

    Systematic experimental work was carried out to understand the growth kinetics of Ni{sub 3}Sn{sub 4} at the Sn-3.5Ag solder/Ni interface. Sn-3.5%Ag solder was reflowed over Ni metallization at 240 deg. C for 0.5 min and solid-state aging was carried out at 150-200 deg. C, for different times ranging from 0 to 400 h. Cross-sectional studies of interfaces have been conducted by scanning electron microscopy and energy dispersive x ray. The growth exponent n for Ni{sub 3}Sn{sub 4} was found to be about 0.5, which indicates that it grows by a diffusion-controlled process even at a very high temperature near to the melting point of the SnAg solder. The activation energy for the growth of Ni{sub 3}Sn{sub 4} was determined to be 16 kJ/mol.

  16. Magnetoimpedance of NiFe/Ag multilayers in the 100 kHz-1.8 GHz range

    NASA Astrophysics Data System (ADS)

    de Andrade, A. M. H.; da Silva, R. B.; Correa, M. A.; Viegas, A. D. C.; Severino, A. M.; Sommer, R. L.

    2004-05-01

    Magnetoimpedance curves at frequencies up to 1.8 GHz for (Ni 81Fe 19/Ag) n multilayers with n=15, 50 and 100, and thickness ratio tPy/ tAg: {100}/{7}, {100}/{25}, {100}/{100}, {200}/{14}, {200}/{50} and {200}/{200} Å are presented. Evidences of FMR are observed in most samples studied. Samples with 15, 50 and 100 bilayers exhibited a maximum MI ratio of about 100%, 175% and 250%, respectively. For samples with tPy=4t Ag, peculiar impedance spectra with 4 peaks were observed.

  17. 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.

  18. Phase Evolution in the Pd-Ag-CuO Air Braze Filler Metal Alloy System

    SciTech Connect

    Darsell, Jens T.; Weil, K. Scott

    2006-08-01

    Palladium was added as a ternary component to a series of copper oxide-silver alloys in an effort to increase the use temperature of these materials for potential ceramic air brazing applications. Phase equilibria in the ternary Pd-Ag-CuO system were investigated via differential scanning calorimetry (DSC) and a series of quenching experiments. Presented here are the latest findings on this system and a construction of the corresponding ternary phase diagram for low-to-moderate additions of palladium. The analysis included samples with higher palladium additions than were studied in the past, as well as an analysis of the composition-temperature trends in the Ag-CuO miscibility gap with palladium addition. It was found that the addition of palladium increases the solidus and liquidus and caused three phase zones to appear as expected by the phase rule. Furthermore, the palladium additions cause the miscibility gap boundary extending from the former binary eutectic to shift to lower silver-to-copper ratios.

  19. Adsorption of Ag, Cu and Hg from aqueous solutions using expanded perlite.

    PubMed

    Ghassabzadeh, Hamid; Mohadespour, Ahmad; Torab-Mostaedi, Meisam; Zaheri, Parisa; Maragheh, Mohammad Ghannadi; Taheri, Hossein

    2010-05-15

    The aim of the present work was to investigate the ability of expanded perlite (EP) to remove of silver, copper and mercury ions from aqueous solutions. Batch adsorption experiments were carried out and the effect of pH, adsorbent dosage, contact time and temperature of solution on the removal process has been investigated. The optimum pH for the adsorption was found to be 6.5. Adsorption of these metal ions reached their equilibrium concentration in 120, 240 and 180 min for Ag (I), Cu (II) and Hg (II) ions, respectively. Experimental data were also evaluated in terms of kinetic characteristics of adsorption and it was found that adsorption process for these metal ions followed well pseudo-second-order kinetics. Using Langmuir isotherm model, maximum adsorption capacity of EP was found to be 8.46, 1.95 and 0.35 mg/g for Ag (I), Cu (II) and Hg (II) ions, respectively. Finally, the thermodynamic parameters including, the change of free energy (DeltaG degrees ), enthalpy (DeltaH degrees ) and entropy (DeltaS degrees ) of adsorption were calculated for each metal ion. The results showed that the adsorption of these metal ions on EP was feasible and exothermic at 20-50 degrees C.

  20. Electrochemical depositions of fluorohydroxyapatite doped by Cu2+, Zn2+, Ag+ on stainless steel substrates

    NASA Astrophysics Data System (ADS)

    Bir, F.; Khireddine, H.; Touati, A.; Sidane, D.; Yala, S.; Oudadesse, H.

    2012-07-01

    Fluoridated hydroxyapatite (FHA, Ca10(PO4)6(OH)2-xFx where 0 < x < 2 is the degree of fluoridation) and inorganic ions (Zn2+, Cu2+, Ag+) substituted fluoridated hydroxyapatite coatings (M-FHA) were deposited on the surface of medical grade 316L stainless steel samples by electrochemical deposition technique. The FHA coatings were co-substituted with antibacterial ions (Zn2+, Cu2+ or Ag+) by co-precipitation and ion-exchange methods. Characterization studies of coatings from X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Energy dispersive X-ray spectroscopy (EDX) showed that the obtained layers are monophase crystals FHA and did not contain any discernible crystalline impurity. The particles of all samples are of nano size that gives thin layers. The surface morphology, microstructure and Ca/P atomic ratio of the FHA coatings can be regulated by varying electrolyte temperature. This later affects the porosity of the coating surface and the chemical compositions of the deposits. Quantitative elemental analysis indicates that the copper, zinc and silver ions are incorporated into the Fluorohydroxyapatite. The antimicrobial effects of doped fluorohydroxyapatite coatings against pathogen bacterial strains Staphylococcus aureus were tested in liquid media. The results are promising and demonstrated that all doped FHA samples exhibit excellent antimicrobial activity "in vitro" against the microorganism, so the antimicrobial properties of the coatings developed are improved.

  1. Atomic structure of water/Au, Ag, Cu and Pt atomic junctions.

    PubMed

    Li, Yu; Kaneko, Satoshi; Fujii, Shintaro; Nishino, Tomoaki; Kiguchi, Manabu

    2017-02-08

    Much progress has been made in understanding the transport properties of atomic-scale conductors. We prepared atomic-scale metal contacts of Cu, Ag, Au and Pt using a mechanically controllable break junction method at 10 K in a cryogenic vacuum. Water molecules were exposed to the metal atomic contacts and the effect of molecular adsorption was investigated by electronic conductance measurements. Statistical analysis of the electronic conductance showed that the water molecule(s) interacted with the surface of the inert Au contact and the reactive Cu ant Pt contacts, where molecular adsorption decreased the electronic conductance. A clear conductance signature of water adsorption was not apparent at the Ag contact. Detailed analysis of the conductance behaviour during a contact-stretching process indicated that metal atomic wires were formed for the Au and Pt contacts. The formation of an Au atomic wire consisting of low coordination number atoms leads to increased reactivity of the inert Au surface towards the adsorption of water.

  2. Graphitic carbon nitride solid nanofilms for selective and recyclable sensing of Cu2+ and Ag+ in water and serum.

    PubMed

    Huang, Heqin; Chen, Rui; Ma, Jiale; Yan, Li; Zhao, Yingqi; Wang, Yu; Zhang, Wenjun; Fan, Jun; Chen, Xianfeng

    2014-12-18

    Herein we report the fabrication of g-C3N4 nanofilms and their application as a solid fluorescence sensor. The as-prepared films are capable of convenient, sensitive, selective, rapid and recyclable sensing of Cu(2+) and Ag(+) in water and serum, indicating the sensor's potential application in disease diagnosis. Attractively, our sensor is able to differentiate Cu(2+) and Ag(+) by making use of their different adsorption and desorption kinetics during the interaction with g-C3N4 nanofilms.

  3. Variability in the fractionation of Cu, Ag, and Zn among cytosolic proteins in the bivalve Macoma balthica

    USGS Publications Warehouse

    Johansson, C.; Cain, Daniel J.; Luoma, Samuel N.

    1986-01-01

    Gel filtration chromatographs of cytosols from the clam Macorna balthica analysed from both field and laboratory treated specimens showed that uptake of Cu, Ag, and Zn in the metallothionein-like protein (MLP) pool follows exposure both in nature and in the laboratory. Specimens collected from San Francisco Bay over 18 mo showed strong temporal variability in the fractionation of the metals among cytosolic proteins. A marked increase in Cu, Ag, and Zn in a very low molecular weight pool occurred when concentrations were highest In the MLP pool. The correlation between total cytosollc metal and MLP-metal also appeared to approach a hyperbolic character at the highest concentrations.

  4. A grazing incidence surface X-ray absorption fine structure (GIXAFS) study of alkanethiols adsorbed on Au, Ag, and Cu

    NASA Astrophysics Data System (ADS)

    Floriano, Pierre N.; Schlieben, Olaf; Doomes, Edward E.; Klein, Ingo; Janssen, J.; Hormes, Josef; Poliakoff, E. D.; McCarley, Robin L.

    2000-04-01

    Self-assembled monolayers of n-alkanethiols, CH 3-(CH 2) x-SH, on Au, Ag, and Cu have been studied with GIXAFS at the sulfur K-edge. For both pentanethiol and decanethiol monolayers on Ag and Cu, the three-fold hollow site is found to be the most probable sulfur binding site. However, observations for octadecanethiol indicate that the three-fold hollow site is not the exclusive binding site. In addition, the possible existence of disulfide bonds on the metal surface (adsorbed dialkyldisulfides) is not supported by the data. Preliminary results from monolayers on Au are also reported.

  5. Structural and optical properties of (Ag,Cu)(In,Ga)Se{sub 2} polycrystalline thin film alloys

    SciTech Connect

    Boyle, J. H.; Shafarman, W. N.; Birkmire, R. W.; McCandless, B. E.

    2014-06-14

    The structural and optical properties of pentenary alloy (Ag,Cu)(In,Ga)Se{sub 2} polycrystalline thin films were characterized over the entire compositional range at a fixed (Cu + Ag)/(In + Ga) ratio. Films deposited at 550 °C on bare and molybdenum coated soda-lime glass by elemental co-evaporation in a single-stage process with constant incident fluxes exhibit single phase chalcopyrite structure, corresponding to 122 spacegroup (I-42d) over the entire compositional space. Unit cell refinement of the diffraction patterns show that increasing Ag substitution for Cu, the refined a{sub o} lattice constant, (Ag,Cu)-Se bond length, and anion displacement increase in accordance with the theoretical model proposed by Jaffe, Wei, and Zunger. However, the refined c{sub o} lattice constant and (In,Ga)-Se bond length deviated from theoretical expectations for films with mid-range Ag and Ga compositions and are attributed to influences from crystallographic bond chain ordering or cation electronegativity. The optical band gap, derived from transmission and reflection measurements, widened with increasing Ag and Ga content, due to influences from anion displacement and cation electronegativity, as expected from theoretical considerations for pseudo-binary chalcopyrite compounds.

  6. Valorization of biosorbent obtained from a forestry waste: Competitive adsorption, desorption and transport of Cd, Cu, Ni, Pb and Zn.

    PubMed

    Cutillas-Barreiro, Laura; Paradelo, Remigio; Igrexas-Soto, Alba; Núñez-Delgado, Avelino; Fernández-Sanjurjo, María José; Álvarez-Rodriguez, Esperanza; Garrote, Gil; Nóvoa-Muñoz, Juan Carlos; Arias-Estévez, Manuel

    2016-09-01

    Bark from Pinus pinaster is one of the most abundant forestry wastes in Europe, and among the proposed technologies for its reutilization, the removal of heavy metals from wastewater has been gaining increasing attention. In this work, we have studied the performance of pine bark for heavy metal biosorption on competitive systems. Pb, Cu, Ni, Zn and Cd sorption and desorption at equilibrium were studied in batch experiments, whereas transport was studied in column experiments. Batch experiments were performed adding simultaneously different concentrations (0.08-3.15mM) of two or more metals in solution to pine bark samples. Column experiments were performed with 10mM solutions of two metals or a 5mM solution of the five metals. In general, the results under competitive conditions were different to those obtained in monoelemental experiments. The multi-metal batch experiments showed the adsorption sequence Pb≈Cu>Cd>Zn>Ni for lower metal doses, Pb>Cu>Cd>Zn>Ni for intermediate doses, and Pb>Cu>Cd≈Zn≈Ni for high metal doses. Desorption followed the sequence PbCu for the lowest metal doses, and Pb<Cu for the highest ones. The bi-metal batch experiments indicated that Cu and Pb suffered the highest retention, with high capacity to displace Cd, Ni and Zn from adsorption sites on pine bark. The transport experiments produced comparable results to those obtained in the batch experiments, with pine bark retention capacity following the sequence Pb>Cu>Zn>Cd>Ni. The presence of a second metal affected the transport of all the elements studied except Pb, and confirmed the strong influence of Pb and Cu on the retention of the other metals. These results can help to appropriately design decontamination systems using this forestry waste.

  7. Silver tracer diffusion in oriented Ag/Cu interphase boundaries and correlation to the boundary structure

    SciTech Connect

    Sommer, J.; Herzig, C.; Muschik, T.; Gust, W.

    1996-01-01

    Radiotracer experiments were performed on oriented Ag/Cu bicrystals to study the influence of the interphase boundary (IB) structure on the material transport along the interfaces. Tracer diffusion of {sup 110m}Ag was measured along (011) IBs in the [100] and [01{bar 1}] directions and along (111) IBs in the [01{bar 1}] and [{bar 2}11] directions in the temperature range 593--882 K. It is demonstrated for cube-on-cube orientations how the interfacial structure is reflected in the diffusion behavior. It was found that the Ag diffusion along anisotropic misfit dislocation arrays in (011) IBs is anisotropic and fastest along channels of rapid diffusion. A scatter in the diffusion data for (011) IBs indicates that their structure, quite in contrast to morphologically stable (111) interfaces, depends on the thermal history of the specimens. This is interpreted as a result of microfaceting of the morphologically unstable (011) IBs. Furthermore, the influence of interdiffusion across the interface on the diffusion along the interface is discussed.

  8. Connectivity and limitation of critical current in Bi-Pb-Sr-Ca-Cu/Ag tapes

    NASA Astrophysics Data System (ADS)

    Müller, K.-H.; Andrikidis, C.; Du, J.; Leslie, K. E.; Foley, C. P.

    1999-07-01

    We have shown experimentally that the remanent magnetic moments of Y-Ba-Cu-O thin-film networks and of Bi-2223/Ag monofilamentary tapes show remarkable similarities, as their magnetic moments are both composed of intersquare (intergrain) and intrasquare (intragrain) magnetic moments. Starting from the geometrical definition of connectivity in a thin-film network, we show that connectivity in a Bi-2223/Ag monofilamentary tape is solely defined by the ratio of the average grain size to the width of the superconducting core and by the ratio of the intergrain to intragrain remanent magnetic moments at saturation. The measured upper limit for the connectivities ranged from 4.2×10-3 in a tape with low critical current density Jc to 2.9×10-2 in a tape with Jc(77 K,0 T)~=2×108 A m-2. Our study reveals that even good Bi-2223/Ag tapes suffer from very low grain connectivity. We estimate that in the case of perfect connectivity a Jc(77 K,0 T) between 8×109 and 6×1010 A m-2 would be achievable.

  9. Processing and fabrication of YBa2Cu3O(x)/Ag composite wires and coils

    NASA Astrophysics Data System (ADS)

    Ferrando, W. A.; Divecha, A. P.; Mansour, A. N.; Karmarkar, S. D.; Balachandran, U.; Dorris, S. E.; Dusek, J. T.; Picciolo, J. J.; Singh, J. P.; Poeppel, R. B.

    1990-11-01

    Silver was added to YBa2Cu3O(x) (123) powder by a melt technique using AgNO3 and heated to approx. 600 C to decompose the nitrate. This process yields 123 powder that is uniformly coated with Ag, as indicated by optical and scanning electron microscopy (SEM). The composite power is formed into rods (approx. 4 mm diameter) via drawing and swaging through conical converging dies. Wires of finer diameter (approx. 1 mm) and substantially greater linear uniformity were produced by slurry extrusion of the composite powder in a polymeric vehicle. Transport critical current density, J sub c, of these wires at present is about 750 A/sq cm. This value may be expected to rise due to further reduction of second phase impurities localized at grain boundaries and better understanding of the Ag/superconductor interface. The wire fabrication is described in some detail and discusses the results of microscopic analyses by scanning electron microscopy (SEM), x ray photoemission spectroscopy (XPS), and x ray diffraction (XRD).

  10. Exponentially decaying magnetic coupling in sputtered thin film FeNi/Cu/FeCo trilayers

    NASA Astrophysics Data System (ADS)

    Wei, Yajun; Akansel, Serkan; Thersleff, Thomas; Harward, Ian; Brucas, Rimantas; Ranjbar, Mojtaba; Jana, Somnath; Lansaker, Pia; Pogoryelov, Yevgen; Dumas, Randy K.; Leifer, Klaus; Karis, Olof; Åkerman, Johan; Celinski, Zbigniew; Svedlindh, Peter

    2015-01-01

    Magnetic coupling in trilayer films of FeNi/Cu/FeCo deposited on Si/SiO2 substrates have been studied. While the thicknesses of the FeNi and FeCo layers were kept constant at 100 Å, the thickness of the Cu spacer was varied from 5 to 50 Å. Both hysteresis loop and ferromagnetic resonance results indicate that all films are ferromagnetically coupled. Micromagnetic simulations well reproduce the ferromagnetic resonance mode positions measured by experiments, enabling the extraction of the coupling constants. Films with a thin Cu spacer are found to be strongly coupled, with an effective coupling constant of 3 erg/cm2 for the sample with a 5 Å Cu spacer. The strong coupling strength is qualitatively understood within the framework of a combined effect of Ruderman-Kittel-Kasuya-Yosida and pinhole coupling, which is evidenced by transmission electron microscopy analysis. The magnetic coupling constant surprisingly decreases exponentially with increasing Cu spacer thickness, without showing an oscillatory thickness dependence. This is partially connected to the substantial interfacial roughness that washes away the oscillation. The results have implications on the design of multilayers for spintronic applications.

  11. Exponentially decaying magnetic coupling in sputtered thin film FeNi/Cu/FeCo trilayers

    SciTech Connect

    Wei, Yajun Akansel, Serkan; Thersleff, Thomas; Brucas, Rimantas; Lansaker, Pia; Leifer, Klaus; Svedlindh, Peter; Harward, Ian; Celinski, Zbigniew; Ranjbar, Mojtaba; Dumas, Randy K.; Jana, Somnath; Pogoryelov, Yevgen; Karis, Olof; Åkerman, Johan

    2015-01-26

    Magnetic coupling in trilayer films of FeNi/Cu/FeCo deposited on Si/SiO{sub 2} substrates have been studied. While the thicknesses of the FeNi and FeCo layers were kept constant at 100 Å, the thickness of the Cu spacer was varied from 5 to 50 Å. Both hysteresis loop and ferromagnetic resonance results indicate that all films are ferromagnetically coupled. Micromagnetic simulations well reproduce the ferromagnetic resonance mode positions measured by experiments, enabling the extraction of the coupling constants. Films with a thin Cu spacer are found to be strongly coupled, with an effective coupling constant of 3 erg/cm{sup 2} for the sample with a 5 Å Cu spacer. The strong coupling strength is qualitatively understood within the framework of a combined effect of Ruderman-Kittel-Kasuya-Yosida and pinhole coupling, which is evidenced by transmission electron microscopy analysis. The magnetic coupling constant surprisingly decreases exponentially with increasing Cu spacer thickness, without showing an oscillatory thickness dependence. This is partially connected to the substantial interfacial roughness that washes away the oscillation. The results have implications on the design of multilayers for spintronic applications.

  12. Microstructural changes to AlCu6Ni1 alloy after prolonged annealing at elevated temperature.

    PubMed

    Wierzbińska, M; Sieniawski, J

    2010-03-01

    This work presents results of microstructure examination of AlCu(6)Ni(1) aluminium alloy. The commercial AlCu(4)Ni(2)Mg(2) (M-309) alloy is widely used for elements of aircraft and automotive engines. Modification its chemical composition was aimed at improving the stability of mechanical properties of the alloy subjected to long-term exposure to high temperature. The alloy after standard T6 heat treatment (solution heat treated at 818 K/10 h/water quenched followed by ageing at 498 K/8 h/air cooled) was annealed for 150 h at elevated temperature of 573 K corresponding to the maximum value at which structural elements of jet piston engines made of aluminium alloys operate. It was found that applied heat treatment caused an increasing in the particles of hardening phase (theta'-Al(2)Cu) size. The significant growth of the length of theta'-Al(2)Cu precipitations was observed in particularly. Nevertheless, it did not strongly result in change of its shape - the 'crystallites' and 'rods' were still characteristic of hardening phase morphology. The phenomena of the growth of theta'-Al(2)Cu precipitates caused decreasing the mechanical properties of the alloy, what is the subject of further investigations by the authors.

  13. Chemical synthesis, structural, optical, magnetic characteristics and enhanced visible light active photocatalysis of Ni doped CuS nanoparticles

    NASA Astrophysics Data System (ADS)

    Subramanyam, K.; Sreelekha, N.; Amaranatha Reddy, D.; Murali, G.; Rahul Varma, K.; Vijayalakshmi, R. P.

    2017-03-01

    In this paper, we report systematic investigations on the effects of Ni doping on the structural, optical, magnetic and photocatalytic characteristics of CuS nanoparticles synthesized by simplistic wet chemical co-precipitation route via EDTA molecules as templates. XRD studies confirmed that accurate phase formation of synthesized nanoparticles and chemical composition were obtained by EDX. Magnetic measurements revealed that 3% Ni doped CuS nanoparticles show signs of good ferromagnetism at room temperature and transition of magnetic signs from ferromagnetic to paramagnetic nature by increasing the Ni dopant concentration in CuS host matrix. The photocatalytic degradation efficiency of the prepared pure and Ni doped CuS nanoparticles were evaluated as a function of simulated sunlight irradiation via RhB organic dye pollutant as a test molecule. Particularly, in the presence of 3% Ni doped CuS nanoparticles in pollutant solution 98.46% degradation efficiency was achieved within 60 min of sunlight irradiation; meanwhile bare CuS attained only 83.22%. Further, after five cycles 3% Ni doping CuS nanoparticles exhibit good photocatalytic stability with very negligible catalyst loss. We believe that the investigations in this study provides adaptable pathway for the synthesizing of various diluted magnetic semiconductor nanoparticles and their applications in spintronic devices as well as sunlight-driven photocatalysts intended for wastewater purification.

  14. Comparison of Extensive Thermal Cycling Effects on Microstructure Development in Micro-alloyed Sn-Ag-Cu Solder Joints

    SciTech Connect

    Anderson, Iver E.; Boesenberg, Adam; Harringa, Joel; Riegner, David; Steinmetz, Andrew; Hillman, David

    2011-09-28

    Pb-free solder alloys based on the Sn-Ag-Cu (SAC) ternary eutectic have promise for widespread adoption across assembly conditions and operating environments, but enhanced microstructural control is needed. Micro-alloying with elements such as Zn was demonstrated for promoting a preferred solidification path and joint microstructure earlier in simple (Cu/Cu) solder joints studies for different cooling rates. This beneficial behavior now has been verified in reworked ball grid array (BGA) joints, using dissimilar SAC305 (Sn-3.0Ag-0.5Cu, wt.%) solder paste. After industrial assembly, BGA components joined with Sn-3.5Ag-0.74Cu-0.21Zn solder were tested in thermal cycling (-55 C/+125 C) along with baseline SAC305 BGA joints beyond 3000 cycles with continuous failure monitoring. Weibull analysis of the results demonstrated that BGA components joined with SAC + Zn/SAC305 have less joint integrity than SAC305 joints, but their lifetime is sufficient for severe applications in consumer, defense, and avionics electronic product field environments. Failure analysis of the BGA joints revealed that cracking did not deviate from the typical top area (BGA component side) of each joint, in spite of different Ag3Sn blade content. Thus, SAC + Zn solder has not shown any advantage over SAC305 solder in these thermal cycling trials, but other characteristics of SAC + Zn solder may make it more attractive for use across the full range of harsh conditions of avionics or defense applications.

  15. Effect of ultrasonic vibration time on the Cu/Sn-Ag-Cu/Cu joint soldered by low-power-high-frequency ultrasonic-assisted reflow soldering.

    PubMed

    Tan, Ai Ting; Tan, Ai Wen; Yusof, Farazila

    2017-01-01

    Techniques to improve solder joint reliability have been the recent research focus in the electronic packaging industry. In this study, Cu/SAC305/Cu solder joints were fabricated using a low-power high-frequency ultrasonic-assisted reflow soldering approach where non-ultrasonic-treated samples were served as control sample. The effect of ultrasonic vibration (USV) time (within 6s) on the solder joint properties was characterized systematically. Results showed that the solder matrix microstructure was refined at 1.5s of USV, but coarsen when the USV time reached 3s and above. The solder matrix hardness increased when the solder matrix was refined, but decreased when the solder matrix coarsened. The interfacial intermetallic compound (IMC) layer thickness was found to decrease with increasing USV time, except for the USV-treated sample with 1.5s. This is attributed to the insufficient USV time during the reflow stage and consequently accelerated the Cu dissolution at the joint interface during the post-ultrasonic reflow stage. All the USV-treated samples possessed higher shear strength than the control sample due to the USV-induced-degassing effect. The shear strength of the USV-treated sample with 6s was the lowest among the USV-treated samples due to the formation of plate-like Ag3Sn that may act as the crack initiation site.

  16. NiFe/CoFe/Cu/CoFe/MnIr spin valves studied by ferromagnetic resonance

    NASA Astrophysics Data System (ADS)

    Timopheev, A. A.; Sobolev, N. A.; Pogorelov, Y. G.; Bunyaev, S. A.; Teixeira, J. M.; Cardoso, S.; Freitas, P. P.; Kakazei, G. N.

    2013-05-01

    Ion-beam deposited (Glass/Ta/NiFe/CoFe/Cu/CoFe/MnIr/Ta) spin valves (SVs) with a Cu-spacer thickness (tCu) varying from 14 to 28 Å have been studied by ferromagnetic resonance (FMR) and magnetoresistance (MR) measurements. With respect to the interlayer coupling strength between the free and fixed ferromagnetic layers, the samples have been divided in those with a weak coupling (for tCu > 16 Å) and a strong coupling regimes (for tCu ≤ 16 Å). The FMR behavior in these two regimes is quite different. For the weakly coupled series, there are two well-defined FMR peaks stemming from the free and fixed layers. Their in-plane angular dependences exhibit 180° and 360° symmetries, respectively. For the strongly coupled SVs, the resonance modes are hybridized and possess features of both layers simultaneously. The main coupling mechanism between the two layers, as concluded from the FMR and MR measurements, is the Néel "orange-peel" magnetostatic interaction, accompanied by a direct exchange due to pinholes in the Cu spacer for tCu < 17 Å.

  17. Superelasticity of Cu-Ni-Al shape-memory fibers prepared by melt extraction technique

    NASA Astrophysics Data System (ADS)

    Li, Dong-yue; Zhang, Shu-ling; Liao, Wei-bing; Geng, Gui-hong; Zhang, Yong

    2016-08-01

    In the paper, a melt extraction method was used to fabricate Cu-4Ni-14Al (wt%) fiber materials with diameters between 50 and 200 μm. The fibers exhibited superelasticity and temperature-induced martensitic transformation. The microstructures and superelasticity behavior of the fibers were studied via scanning electron microscopy (SEM) and a dynamic mechanical analyzer (DMA), respectively. Appropriate heat treatment further improves the plasticity of Cu-based alloys. The serration behavior observed during the loading process is due to the multiple martensite phase transformation.

  18. Aqueous synthesis of nontoxic Ag2Se/ZnSe quantum dots designing as fluorescence sensors for detection of Ag(I) and Cu(II) ions.

    PubMed

    Wang, Chunlei; Xu, Shuhong; Zhao, Zengxia; Wang, Zhuyuan; Cui, Yiping

    2015-01-01

    We reported the synthesis of water-soluble and nontoxic Ag(2)Se/ZnSe Quantum Dots (QDs) using for fluorescence sensors. The influences of various experimental conditions including the synthesis pH, types of ligand, feed ratios, and the refluxed time on the growth process and fluorescence of QDs were investigated in detail. Under optimal conditions, Ag(2)Se/ZnSe QDs show a single emission peak around 490 nm with the maximal photoluminescence (PL) quantum yield (QYs) of 13.7 %. As-prepared Ag(2)Se/ZnSe QDs can be used for detection of Ag(II) and Cu(II). The detection limits are 1 × 10(-6) mol/L to 5 × 10(-5) mol/L for Ag (I), and 2 × 10(-6) mol/L to 1.10 × 10(-4) mol/L for Cu(II).

  19. Measurement and prediction of contact angles of Pb-free Sn-Ag solder alloys on Cu substrate

    NASA Astrophysics Data System (ADS)

    Erer, A. M.; Candan, E.; Güven, M. H.; Turen, Y.

    2011-04-01

    The contact angle (Θ) of molten Sn and Sn-Ag alloys (0.5, 1.5, 3.5, 6 wt.% Ag) on Cu substrates have been studied by using sessile drop method at various temperatures (230, 250, 275 and 300 °C). Experimental results showed that additions of Ag to Sn resulted in a continuous decrease in the Θ up to 3.5 wt.% above which the Θ value was increased. Increasing alloy temperature also decreased the Θ proportionally. Experimental results revealed that a correlation between the Θ, alloy composition and the alloy temperature exists which yielded an empirical model to predict the Θ at a given Ag content and temperature for a given Sn-Ag alloy. The empirical model predicts the Θ reasonably well with the present work and the other published works.

  20. Synthesis of highly fluorescent metal (Ag, Au, Pt, and Cu) nanoclusters by electrostatically induced reversible phase transfer.

    PubMed

    Yuan, Xun; Luo, Zhentao; Zhang, Qingbo; Zhang, Xinhai; Zheng, Yuangang; Lee, Jim Yang; Xie, Jianping

    2011-11-22

    This paper reports a simple and scalable method for the synthesis of highly fluorescent Ag, Au, Pt, and Cu nanoclusters (NCs) based on a mild etching environment made possible by phase transfer via electrostatic interactions. Using Ag as a model metal, a simple and fast (total synthesis time < 3 h) phase transfer cycle (aqueous → organic (2 h incubation) → aqueous) has been developed to process originally polydisperse, nonfluorescent, and unstable Ag NCs into monodisperse, highly fluorescent, and extremely stable Ag NCs in the same phase (aqueous) and protected by the same thiol ligand. The synthetic protocol was successfully extended to fabricate highly fluorescent Ag NCs protected by custom-designed peptides with desired functionalities (e.g., carboxyl, hydroxyl, and amine). The facile synthetic method developed in this study should largely contribute to the practical applications of this new class of fluorescence probes.

  1. Hydrogen production by thermocatalytic decomposition of methane over Ni-Al and Ni-Cu-Al catalysts: Effect of calcination temperature

    NASA Astrophysics Data System (ADS)

    Echegoyen, Y.; Suelves, I.; Lázaro, M. J.; Moliner, R.; Palacios, J. M.

    Thermo catalytic decomposition of methane using Ni-Al and Ni-Cu-Al catalyst prepared by fusion of the corresponding nitrates is studied. The effects of catalyst calcination temperature on the hydrogen yields and the characteristics of the carbon obtained are studied. The role of copper has been also analyzed. Whatever the calcination temperature, all the catalysts show a high and almost constant hydrogen yield without catalyst deactivation after 8 h on stream, which confirms the good performance of this kind of catalysts. The presence of copper enhances the hydrogen production and the best results were obtained using catalysts calcined at 600 °C. Cu has a strong influence on the dispersion of Ni in the catalysts and inhibits NiO from the formation of nickel aluminate even at high calcinations temperatures, which facilitates the formation of the metallic Ni active phase during the subsequent catalyst reduction step. All catalysts tested promote the formation of very long filaments of carbon a few tens of nanometers in diameter and some micrometers long. The structural properties of these carbon filaments highly depend on the presence of Cu:Ni-Cu-Al catalysts promote the formation of a well-ordered graphitic carbon while Ni-Al catalysts enhance the formation of a rather turbostratic carbon.

  2. Improvement of mechanical and biological properties of TiNi alloys by addition of Cu and Co to orthodontic archwires.

    PubMed

    Phukaoluan, Aphinan; Khantachawana, Anak; Kaewtatip, Pongpan; Dechkunakorn, Surachai; Kajornchaiyakul, Julathep

    2016-09-01

    The purpose of this study was to investigate improved performances of TiNi in order to promote tooth movement. Special attention was paid to the effect on the clinical properties of TiNi of adding Cu and Co to this alloy. Ti49.4Ni50.6, Ti49Ni46Cu5 and Ti50Ni47Co3 (at %) alloys were prepared. Specimens were cold-rolled at 30% reduction and heat-treated at 400°C for 60min. Then, the test results were compared with two types of commercial archwires. The findings showed that superelasticity properties were confirmed in the manufactured commercial alloys at mouth temperature. The difference of stress plateau in TiNi, TiNiCo and commercial wires B at 25°C changed significantly at various testing temperatures due to the combination of martensite and austenite phases. At certain temperatures the alloys exhibited zero recovery stress at 2% strain and consequently produced zero activation force for moving teeth. The corrosion test showed that the addition of Cu and Co to TiNi alloys generates an increase in corrosion potential (Ecorr) and corrosion current densities (Icorr). Finally, we observed that addition of Cu and Co improved cell viability. We conclude that addition of an appropriate amount of a third alloying element can help enhance the performances of TiNi orthodontic archwires.

  3. Sn-Ag-Cu to Cu joint current aging test and evolution of resistance and microstructure

    NASA Astrophysics Data System (ADS)

    Xu, Di Erick; Chow, Jasper; Mayer, Michael; Jung, Jae Pil; Yoon, Jong Hyun

    2015-11-01

    SAC 305 solder bump with 800 μm diameter were produced and soldered to a custom substrate with Cu lines as leads that allow for resistance measurement during current aging. The measured joint resistance values (leads plus solder bump) before aging are 7.7 ± 1.8 mΩ and 11.8 ± 2.8 mΩ at room temperature and 160°C, respectively. In general, the resistance of the solder joint increases instantly by about 1 mΩ, when subjected to a 2.2 A aging current at 160°C. The increase is gradual in the following hours of aging and more drastic as it approaches the final failure. Four stages are identified in the resistance signal curve and compared with observations from cross sections. The stages are IMC growth, crack formation and propagation, intermittent crack healing-forming, and final failure resulting in an open connection at the cathode. Recently a periodical drop and rise behavior was reported for the resistance signal. This behavior is reproduced and attributed to the intermittent crack healing-forming stage. The healing events observed are faster than the sampling time. Possibly, as current is concentrated when bypassing interfacial cracks, local melting occurs partially filling cracks before resolidifying. [Figure not available: see fulltext.

  4. Structure and magnetism of S = 1/2 kagome antiferromagnets NiCu3(OH)6Cl2 and CoCu3(OH)6Cl2.

    PubMed

    Li, Yue-sheng; Zhang, Qing-ming

    2013-01-16

    We have successfully synthesized S = 1/2 kagome antiferromagnets MCu(3)(OH)(6)Cl(2) (M = Ni and Co) by a hydrothermal method with a rotating pressure vessel. Structural characterization shows that both compounds have similar crystal structure to ZnCu(3)(OH)(6)Cl(2) with R3m symmetry. As with ZnCu(3)(OH)(6)Cl(2), the compounds show no obvious hysteresis at 2 K. A spin-glass transition is found in both NiCu(3)(OH)(6)Cl(2) and CoCu(3)(OH)(6)Cl(2) at low temperatures (6.0 and 3.5 K respectively) by AC susceptibility measurements. This indicates no long-range magnetic order and a strong spin frustration. The substitution of Zn(2+) by magnetic ions Ni(2+) or Co(2+) effectively enhances the interlayer exchange coupling and changes the ground state of the kagome spin system.

  5. Mean-time-to-failure study of flip chip solder joints on Cu/Ni(V)/Al thin-film under-bump-metallization

    NASA Astrophysics Data System (ADS)

    Choi, W. J.; Yeh, E. C. C.; Tu, K. N.

    2003-11-01

    Electromigration of eutectic SnPb flip chip solder joints and their mean-time-to-failure (MTTF) have been studied in the temperature range of 100 to 140 °C with current densities of 1.9 to 2.75×104 A/cm2. In these joints, the under-bump-metallization (UBM) on the chip side is a multilayer thin film of Al/Ni(V)/Cu, and the metallic bond-pad on the substrate side is a very thick, electroless Ni layer covered with 30 nm of Au. When stressed at the higher current densities, the MTTF was found to decrease much faster than what is expected from the published Black's equation. The failure occurred by interfacial void propagation at the cathode side, and it is due to current crowding near the contact interface between the solder bump and the thin-film UBM. The current crowding is confirmed by a simulation of current distribution in the solder joint. Besides the interfacial void formation, the intermetallic compounds formed on the UBM as well as the Ni(V) film in the UBM have been found to dissolve completely into the solder bump during electromigration. Therefore, the electromigation failure is a combination of the interfacial void formation and the loss of UBM. Similar findings in eutectic SnAgCu flip chip solder joints have also been obtained and compared.

  6. Analysis of the applicability of Ni, Cu, Au, Pt, and Pd nanoclusters for data recording

    NASA Astrophysics Data System (ADS)

    Redel', L. V.; Gafner, S. L.; Gafner, Yu. Ya.; Zamulin, I. S.; Goloven'ko, Zh. V.

    2017-02-01

    The applicability of individual Ni, Cu, Au, Pt, and Pd nanoclusters as data bits in next generation memory devices constructed on the phase-change carrier principle is studied. To this end, based on the modified tight-binding potential (TB-SMA), structure formation from the melt of nanoparticles of these metals to 10 nm in diameter was simulated by the molecular dynamics method. The effect of various crystallization conditions on the formation of the internal structures of Ni, Cu, Au, Pt, and Pd nanoclusters is studied. The stability boundaries of various crystalline isomers are analyzed. The obtained systematic features are compared for nanoparticles of copper, nickel, gold, platinum, and palladium of identical sizes. It is concluded that platinum nanoclusters of diameter D > 8 nm are the best materials among studied metals for producing memory elements based on phase transitions.

  7. Characterization of ultrafine grained Cu-Ni-Si alloys by electron backscatter diffraction

    NASA Astrophysics Data System (ADS)

    Altenberger, I.; Kuhn, H. A.; Gholami, M.; Mhaede, M.; Wagner, L.

    2014-08-01

    A combination of rotary swaging and optimized precipitation hardening was applied to generate ultra fine grained (UFG) microstructures in low alloyed high performance Cu-based alloy CuNi3Si1Mg. As a result, ultrafine grained (UFG) microstructures with nanoscopically small Ni2Si-precipitates exhibiting high strength, ductility and electrical conductivity can be obtained. Grain boundary pinning by nano-precipitates enhances the thermal stability. Electron channeling contrast imaging (ECCI) and especially electron backscattering diffraction (EBSD) are predestined to characterize the evolving microstructures due to excellent resolution and vast crystallographic information. The following study summarizes the microstructure after different processing steps and points out the consequences for the most important mechanical and physical properties such as strength, ductility and conductivity.

  8. Calculation of Phonon Conductivity and Seebeck Coefficient in Cu-Ni Alloy

    NASA Astrophysics Data System (ADS)

    Konishi, Yusuke; Asai, Yoshihiro

    2015-03-01

    In recent years, thermoelectric materials have been attracting a lot of attention because they are expected to be applied for utilization of waste heat. Many kinds of materials are studied for this purpose; semiconductors, alloys, organic materials, etc. In 2010, a giant Peltier effect was observed in a Cu-Ni/Au junction. It is considered that this giant Peltier effect is caused by nano-scale phase separation formed in the sputtering process. Although this material is a great candidate for a thermoelectric material, we need to find the condition for a large thermoelectric coefficient that requires a large Seebeck coefficient, large electric conductivity, and small phonon conductivity. We calculated phonon conductivity in Cu-Ni alloy by using nonequilibrium molecular dynamics simulation and calculated Seebeck coefficients via ab-initio methods.

  9. Microstructural characterization of irradiated Fe-Cu-Ni-P model steels

    SciTech Connect

    Miller, M.K.; Hoelzer, D.T.; Ebrahimi, F.; Hawthorne, J.R.; Burke, M.G.

    1987-01-01

    The microstructure of Fe-Cu-Ni-P model pressure vessel steels after neutron irradiation and thermal aging has been characterized by atom probe field-ion microscopy and augmented by transmission electron microscopy. High densities of small, roughly spherical or disc shaped copper clusters/precipitates were observed in the neutron irradiated alloys that contained copper. Small spherical phosphorus clusters were observed in the irradiated copper-free alloys, and copper phosphides were observed in a high phosphorus Fe-Cu-Ni-P alloy. None of these clusters/precipitates were observed in the thermally aged materials. The increases in the tensile and yield strengths that were observed after neutron irradiation resulted from these clusters and other lattice defects. 14 refs., 8 figs., 2 tabs.

  10. Investigation on compressive behavior of Cu-35Ni-15Al alloy at high temperatures

    NASA Astrophysics Data System (ADS)

    Li, Cong; Chen, Jian; Li, Wei; Hu, Yongle; Ren, Yanjie; Qiu, Wei; He, Jianjun; Chen, Jianlin

    2014-09-01

    Microstructures and mechanical properties of Cu-35Ni-15Al alloy in cast and porous states were studied by scanning electron microscopy and compression tests. The influence of porosity, deformation temperature and loading rate on mechanical properties of the two kinds of alloys was investigated. The results show that the as cast alloy and porous alloys have almost the same phase constitution: Cu rich phase, Ni rich phase and K intermetallics. The yield strength of porous alloys increases continuously with decreasing porosity, the relationship between porosity and yield stress follows Gibson-Ashby equation. With decreasing deformation temperature, the yield strength of as cast alloy and porous alloy increase. With the increase of loading rate, the yield strength of these alloys shows an increasing trend. After compression, the microstructure of as cast alloy is more uniform, and porous alloys are more prone to have localized deformations.

  11. Deformation behavior of Nb nanowires in TiNiCu shape memory alloy matrix

    DOE PAGES

    Jiang, Daqiang; Liu, Yinong; Yu, Cun; ...

    2015-08-18

    An in-situ nanowire Nb/TiNiCu composite is fabricated based on the concept of strain under-matching between a phase transforming matrix and high strength nanomaterials. The deformation behavior of the Nb nanowire was investigated by means of in-situ synchrotron X-ray diffraction when the TiNiCu matrix underwent different deformation modes. The maximum lattice strain of the Nb nanowires was about 5% when the matrix deformed via martensitic transformation or 1% when deforming plastically by dislocation slip. As a result, the Nb nanowires showed a lattice strain of 3.5% when the matrix deformed in the mixed mode of plastic deformation and martensitic transformation, whichmore » means that the occurrence of plastic deformation does not impede load transfer from the matrix to the nanowires.« less

  12. Deformation behavior of Nb nanowires in TiNiCu shape memory alloy matrix

    SciTech Connect

    Jiang, Daqiang; Liu, Yinong; Yu, Cun; Liu, Weilong; Yang, Hong; Jiang, Xiaohua; Ren, Yang; Cui, Lishan

    2015-08-18

    An in-situ nanowire Nb/TiNiCu composite is fabricated based on the concept of strain under-matching between a phase transforming matrix and high strength nanomaterials. The deformation behavior of the Nb nanowire was investigated by means of in-situ synchrotron X-ray diffraction when the TiNiCu matrix underwent different deformation modes. The maximum lattice strain of the Nb nanowires was about 5% when the matrix deformed via martensitic transformation or 1% when deforming plastically by dislocation slip. As a result, the Nb nanowires showed a lattice strain of 3.5% when the matrix deformed in the mixed mode of plastic deformation and martensitic transformation, which means that the occurrence of plastic deformation does not impede load transfer from the matrix to the nanowires.

  13. Structural, magnetic and dielectric study of Cu substituted NiZn ferrite nanorod

    NASA Astrophysics Data System (ADS)

    Das, Partha Sarathi; Singh, Gajendra Prasad

    2016-03-01

    The Cu2+ doped Ni0.5-xCuxZn0.5Fe2O4 (with x=0, 0.1, 0.2 and 0.3) ferrites of nanorods morphology was synthesized by glycine-nitrate auto-combustion method. The samples presents the diffraction peaks of cubic spinel crystal structure with Fd 3 ̅m space group. An average crystallite size of 47 nm is obtained for undoped Ni0.5Zn0.5Fe2O4. The Cu (x=0.1) doping is increased the crystallite size to 50 nm, thereafter, it is decreased to 42 and 38 nm at x=0.2 and 0.3 respectively. The lattice parameter is found to increase from 8.354 Å to 8.408 Å with increasing the Cu2+ content. The formation of ferrite phase is further confirmed by obtaining the active Raman mode peaks of A1g+Eg+3T2g bands in all samples. The bands are linked with the symmetric and asymmetric stretching as well as the symmetric bending. The Cu (x=0.1) doping showed 20% enhancement in coercivity, i.e. 105 Oe and 16% enhancement in saturation magnetization 87.16 emu/g compared to 87 Oe and 73.13 emu/g at x=0. The dielectric constant of 450 for the Cu (x=0) and 50 for Cu (x=0.1) is obtained at a constant frequency of 100 Hz. The dielectric loss as low as 0.05 is measured for Cu (x=0.1) at 1 MHz.

  14. The Melting Characteristics and Interfacial Reactions of Sn-ball/Sn-3.0Ag-0.5Cu-paste/Cu Joints During Reflow Soldering

    NASA Astrophysics Data System (ADS)

    Huang, J. Q.; Zhou, M. B.; Zhang, X. P.

    2017-03-01

    In this work, the melting characteristics and interfacial reactions of Sn-ball/Sn-3.0Ag-0.5Cu-paste/Cu (Sn/SAC305-paste/Cu) structure joints were studied using differential scanning calorimetry, in order to gain a deeper and broader understanding of the interfacial behavior and metallurgical combination among the substrate (under-bump metallization), solder ball and solder paste in a board-level ball grid array (BGA) assembly process, which is often seen as a mixed assembly using solder balls and solder pastes. Results show that at the SAC305 melting temperature of 217°C, neither the SAC305-paste nor the Sn-ball coalesce, while an interfacial reaction occurs between the SAC305-paste and Cu. A slight increase in reflow temperature (from 217°C to 218°C) results in the coalescence of the SAC305-paste with the Sn-ball. The Sn-ball exhibits premelting behavior at reflow temperatures below its melting temperature, and the premelting direction is from the bottom to the top of the Sn-ball. Remarkably, at 227°C, which is nearly 5°C lower than the melting point of pure Sn, the Sn-ball melts completely, resulting from two eutectic reactions, i.e., the reaction between Sn and Cu and that between Sn and Ag. Furthermore, a large amount of bulk Cu6Sn5 phase forms in the solder due to the quick dissolution of Cu substrate when the reflow temperature is increased to 245°C. In addition, the growth of the interfacial Cu6Sn5 layer at the SAC305-paste/Cu interface is controlled mainly by grain boundary diffusion, while the growth of the interfacial Cu3Sn layer is controlled mainly by bulk diffusion.

  15. The Melting Characteristics and Interfacial Reactions of Sn-ball/Sn-3.0Ag-0.5Cu-paste/Cu Joints During Reflow Soldering

    NASA Astrophysics Data System (ADS)

    Huang, J. Q.; Zhou, M. B.; Zhang, X. P.

    2016-12-01

    In this work, the melting characteristics and interfacial reactions of Sn-ball/Sn-3.0Ag-0.5Cu-paste/Cu (Sn/SAC305-paste/Cu) structure joints were studied using differential scanning calorimetry, in order to gain a deeper and broader understanding of the interfacial behavior and metallurgical combination among the substrate (under-bump metallization), solder ball and solder paste in a board-level ball grid array (BGA) assembly process, which is often seen as a mixed assembly using solder balls and solder pastes. Results show that at the SAC305 melting temperature of 217°C, neither the SAC305-paste nor the Sn-ball coalesce, while an interfacial reaction occurs between the SAC305-paste and Cu. A slight increase in reflow temperature (from 217°C to 218°C) results in the coalescence of the SAC305-paste with the Sn-ball. The Sn-ball exhibits premelting behavior at reflow temperatures below its melting temperature, and the premelting direction is from the bottom to the top of the Sn-ball. Remarkably, at 227°C, which is nearly 5°C lower than the melting point of pure Sn, the Sn-ball melts completely, resulting from two eutectic reactions, i.e., the reaction between Sn and Cu and that between Sn and Ag. Furthermore, a large amount of bulk Cu6Sn5 phase forms in the solder due to the quick dissolution of Cu substrate when the reflow temperature is increased to 245°C. In addition, the growth of the interfacial Cu6Sn5 layer at the SAC305-paste/Cu interface is controlled mainly by grain boundary diffusion, while the growth of the interfacial Cu3Sn layer is controlled mainly by bulk diffusion.

  16. Vibrational states on vicinal surfaces of Al, Ag, Cu and Pd

    NASA Astrophysics Data System (ADS)

    Sklyadneva, I. Yu.; Rusina, G. G.; Chulkov, E. V.

    1998-10-01

    We present the calculation of vibrational modes and lattice relaxation for the (110), (211), (311), (511), (331) and (221) surfaces of Al, Ag, Cu and Pd. The surface phonon frequencies and polarizations are obtained for relaxed and unrelaxed surfaces using embedded atom model potentials. On all surfaces studied step-localized vibrational modes and surface states localized on terrace atoms are found. It is shown that as the terrace width increases so does the number of surface phonons. It is found that interlayer relaxation leads to a shift in the frequencies of the surface states and to a change in the number and localization. In particular, it may cause the appearance or disappearance of step modes. It is shown that the character of relaxation on vicinal surfaces is determined by the number of atoms on a terrace. A comparison of the results with the available experimental data for the Al(221), Cu(211), and Cu(511) surfaces indicates that there is a good agreement with the experimental data.

  17. Microstructural evolution during aging of an Al-Cu-Li-Ag-Mg-Zr alloy

    NASA Technical Reports Server (NTRS)

    Kumar, K. S.; Brown, S. A.; Pickens, Joseph R.

    1991-01-01

    Alloys in the Al-Cu-Li Ag-Mg subsystem were developed that exhibit desirable combinations of strength and ductility. These Weldalite (trademark) alloys, are unique for Al-Cu-Li alloys in that with or without a prior cold stretching operation, they obtain excellent strength-ductility combinations upon natural and artificial aging. This is significant because it enables complex, near-net shape products such as forgings and super plastically formed parts to be heat treated to ultra-high strengths. On the other hand, commercial extrusions, rolled plates and sheets of other Al-Cu-Li alloys are typically subjected to a cold stretching operation before artificial aging to the highest strength tempers to introduce dislocations that provide low-energy nucleation sites for strengthening precipitates such as the T(sub 1) phase. The variation in yield strength (YS) with Li content in the near-peak aged condition for these Weldalite (trademark) alloys and the associated microstructures were examined, and the results are discussed.

  18. Chemical Stability of (Ag,Cu)2Se: a Historical Overview

    NASA Astrophysics Data System (ADS)

    Brown, David R.; Day, Tristan; Caillat, Thierry; Snyder, G. JeffREY

    2013-07-01

    Recent work on Cu2- x Se has caused strong interest in this material due to its high reported peak zT (1.5) and the reduction of thermal conductivity through the mechanism of liquid-like suppression of heat capacity. In the 1960s, 3M patented Cu1.97Ag0.03Se as "TPM-217." Over the following decade it was tested and developed by the 3M Corporation, at the National Aeronautics and Space Administration (NASA) Jet Propulsion Laboratory, Teledyne Energy Systems, and the General Atomics Corporation for use as a next-generation thermoelectric material. During these tests, extreme problems with material loss through Se vaporization and chemical reactions between the material and the device contacts were found. These problems were especially severe while operating under conditions of high iL/A. As a result, the material system was abandoned. The results of these reports are discussed. A simple test of degradation of Cu2Se under conditions of applied current and thermal gradient was performed and showed results compatible with the work done by General Atomics.

  19. Fabrication and shear strength analysis of Sn-3.5Ag/Cu-filled TSV for 3D microelectronic packaging

    NASA Astrophysics Data System (ADS)

    Sharma, Ashutosh; Jung, Do-Hyun; Roh, Myong-Hoon; Jung, Jae Pil

    2016-09-01

    In this study, lead free Sn-3.5Ag solder bumps have been deposited on Cu-filled through-silicon via (TSV) by electroplating method. The solder bumps are plated using an acidic solution composed of SnSO4, H2SO4, Ag2SO4, thiourea and an additive. The current density is varied from -30 to -60 mA/cm2 to obtain the eutectic Sn-3.5Ag solder. The copper is electroplated in TSV using an acidic solution of CuSO4·5H2O, H2SO4, HCl, and an inhibitor. The bottom-up Cu-filling in TSV is achieved by a 3-step pulse periodic reverse (PPR) electroplating. It has been observed that the eutectic Sn-3.5Ag solder is achieved at a current density of -55 mA/cm2. The solder bumps are further reflowed onto TSV at 260 °C for 20 seconds, and shear strength of the formed Sn-3.5Ag/Cu-filled TSV joint is investigated. The results indicate the formation of Cu6Sn5 and Ag3Sn intermetallic compounds (IMCs) at the joint interface. It is found that with an increase of shear speed from 0.5-10 mm/s, the shear stress initially increases to a maximum, and then decreases beyond shear speed of 10 mm/s through 500 mm/s. It is shown that the ductile fracture mode gradually decreases beyond shear speed of 10 mm/s and disappears completely at 500 mm/s.

  20. Porphyrin-based mixed-valent Ag(i)/Ag(ii) and Cu(i)/Cu(ii) networks as efficient heterogeneous catalysts for the azide-alkyne "click" reaction and promising oxidation of ethylbenzene.

    PubMed

    Jiang, Wei; Yang, Jin; Liu, Ying-Ying; Ma, Jian-Fang

    2016-01-25

    By using a new porphyrin-based linker, two unusual mixed-valent Ag(i,ii)- and Cu(i,ii)-organic networks were synthesized. Most strikingly, 1 and 2 exhibit highly efficient catalytic activities for the azide-alkyne "click" reaction and oxidation of ethylbenzene.