Ag-Ni Alloy Research Articles

Low temperature crystalline Ag–Ni alloy formation from silver and nickel nanoparticles entrapped in a fatty acid composite film

Nanoparticles of silver and nickel were grown in thermally evaporated fatty acid (stearic acid) films by immersion of the film sequentially in solutions containing Ag+ ions and Ni2+ ions. Attractive electrostatic interaction between the metal cations and the carboxylate ions in the fatty acid film leads to entrapment of the cations in the film. Thereafter, the metal ions were reduced in situ to yield nanoparticles of Ag and Ni of ∼30 nm diameter within the fatty acid matrix. Thermal treatment of the stearic acid-(silver+nickel) nanocomposite films led to the formation of a Ni–Ag alloy at ∼100 °C. Prolonged heat treatment at this temperature resulted in the phase separation of the alloy and the reformation of individual Ag and Ni nanoparticles.

Synthesis of metastable silver-nickel alloys by a novel laser-liquid-solid interaction technique

Metastable silver-nickel alloys have been synthesized by chemical wetness and laser-liquid-solid interaction techniques from nitrate and acetate precursors of silver and nickel. Ethylene glycol and 2-ethoxyethanol were used as reductants in the synthesis reactions. Rotating niobium substrates immersed in the liquid precursor were irradiated by a continuos wave CO2 and Nd-YAG laser (λ = 1064 nm). The powders were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and high-resolution transmission electron microscopy (HRTEM). Two-phase alloys containing silver, nickel, and oxygen were fabricated, and the shape of the particles was found to be dependent on laser parameters and the chemical composition of the precursor solution. The synthesis mechanism of non-equilibrium Ag-Ni alloy nanoparticles has been proposed to occur primarily at the laser-liquid-solid interface by a nucleation and growth mechanism.

In situ surface Raman study of the phosphorus incorporation mechanism during electrodeposition of Ni–P alloys

Abstract Codeposition of phosphorus with nickel on an Ni–Ag alloy electrode has been investigated by means of in situ surface enhanced Raman spectroscopy (SERS) to obtain information about the phosphorus incorporation mechanism during electrodeposition of Ni–P alloys. The experimental results showed that in the solution without NiSO4, hypophosphite was reduced only to a Ni–phosphine compound, while in the case where NiSO4 coexisted in the solution, the Ni–phosphine compound, as an intermediate, was oxidized by Ni2+ to elemental phosphorus in alloys with nickel acting as the catalyst.

Tantalum powder production by magnesiothermic reduction of TaCl5 through an electronically mediated reaction (EMR)

Tantalum powder production by magnesiothermic reduction of tantalum pentachloride (TaCl5) through an electronically mediated reaction (EMR) has been examined. Feed material, TaCl5, and reductant magnesium alloy were charged into electronically isolated locations in the molten salt (e.g. NaCl–KCl–MgCl2) at 1073 K. After providing external path for electron flow, the current flow between the feed and the reductant locations was monitored. A large current, more than 1 A, was detected during the reaction and tantalum powder with low nickel and silver content was obtained, although liquid Mg–Ag–Ni alloy was used as the reductant. This clearly demonstrates that tantalum powder can be produced by electronically mediated reaction (EMR) without direct physical contact between the feed (TaCl5) and the reductant (magnesium). The feasibility of tantalum reduction using Dy2+ ions dissolved in molten salt has also been demonstrated by utilizing molten salt containing DyCl2 as a reaction mediator. The mechanism of magnesiothermic reduction of TaCl5 in the molten salt is discussed using isothermal chemical potential diagrams.

合金‐セラミックス分散複合化プロセスにおける複合粒子成長シミュレーション

In this paper, a compounding process in which fine WC powder was dispersed in particulate Ag-Ni alloy using a high-speed elliptical-rotor-type mill was investigated. In the process, the growth of the composite particle was observed as the processing time proceeds. A model for the growth phenomenon of the particle was constructed by means of theory of powder grinding using ball mill and dynamics of the plastic deformation of metal particle. In the model, the probability that the composite particle grew was adopted. It was expressed as the product of the probability that the particle was caught between a pair of media (zirconia beads), that it occurred the plastic deformation and the number of the rotor caught them, which included the experimental conditions as parameters. Temporal change in size distribution of the composite particles has been calculated using this method. Comparing calculated value with experimental data of particle median diameter, they were in good agreement. Consequently, it has been indicated that the model is valid and accurate estimation and control of particle size were possible.

Ａｇ‐Ｎｉ粒子とＷＣ微粒子の高速楕円ローター型ミルによる分散複合化過程

Using a high-speed elliptical-rotor-type powder mill, the dispersion and compounding process of particulate Ag-Ni alloy and nano-scale WC powder were investigated. This type of powder mill gives the powders a strong shear force periodically at the narrow clearance between the vessel and the rotor tip. Therefore, controllability of the granule growth with plastic deformation throughout the process was expected. The effects of the operating conditions on the dispersion and compounding processes have been discussed by mean of colorimetric method, X-ray diffraction and Scanning electron microscopy (SEM).

Simulation of segregation at interphase boundaries in Ni-Ag-Cu alloys

Monte Carlo simulation, in conjunction with the embedded atom method, has been used to model the composition and structure of semicoherent (111) and (001) interphase boundaries separating Ni-rich from Ag-rich phases in ternary Ni-Ag-Cu alloys. Cu is found to segregate strongly at both interfaces, although the interfacial excess of Cu is larger at the (001) than at the (111) interface. The results show that the (001) interphase boundary is unstable and tends to break down into truncated pyramidal facets bounded by (111) and (100) faces. The periodicity of the facets is related to the period of the interfacial dislocations lying in the interface. In contrast, the (111) interphase boundary is stable. Comparison of the behaviour of the (001) interface in the ternary alloy with the binary Ni-Ag alloy implies that the segregation of Cu at the (001) interface tends to stabilize (001) facets relative to (111) facets. This latter behaviour is different from that of the (001) interface in Cu-Ag-Au alloys, where weak segregation of Au at the Cu-Ag interface tends to stabilize (111) facets.

Application of a powder coating method to dispersion of fine Ni powders into AgNi alloy matrix

A dry powder coating method has been applied to develop high-performance contact material for the electrical industry. Using a high-speed/high-shear type of mill, fine nickel powder was coated onto coarser particles of silver—nickel alloy. Various operating conditions were used to control the concentration and the state of dispersion of the nickel powder in the composite. The transformation of the particles throughout the process was assessed by the color of the powders, the power consumption curve and by SEM. The contact performance, i.e., fusion and wear resistance, was improved using the product with a 3-dimensional network of fine nickel powders in a silver matrix.

Manufacturing process and material characteristics of Ag-Ni contacts consisting of nickel-compounded particles

Using a high-speed, high-shear mill, particle surfaces of Ag-Ni alloy in which Ni is finely dispersed in the Ag matrix were coated and compounded with Ni powder. Particles thus compounded can be processed into a wire. Post-processing compounded Ni forms a fibrous texture on the wire longitudinal section and a network on the cross-section. This characteristic metallurgical structure improves the contact performance (fusion and wear resistances).

Recovery of hydrogen from hydrogen sulfide with metals or metal sulfides

The following two types of reactions were investigated for the recovery of hydrogen from hydrogen sulfide: Type 1 H 2S → H 2 + S 0, Type 2 H 2S + O 2 → H 2 + SO 2 Each type of reaction is constructed by a two-step cycle, in which H 2S is reacted with metal or metal sulfide and then the resulting sulfide undergoes thermal decomposition or oxidation. Ag 2S, FeS, Co 9S 8, Ni 3S 2, and the double sulfide CuFeS 2 were examined in the former type of reaction, while Ag, Cu, Ni, liquid Pb, and liquid BiAg alloy were used as an intermediate in the latter.

Rolling deformation of two-ductile-phase AgNi alloys

The AgNi alloy system is a model system for the investigation of two-ductile-phase deformation, due to its simplicity. Alloys are composed of ductile Ag and Ni phases. Three AgNi alloys were examined: 25 vol.% Ni phase, 50% Ni, and 75% Ni. These alloys were cold rolled to an 80% reduction in thickness. The 50% Ni alloy was cold rolled to reductions in thickness of 20, 40, 60, 80, and 90%. Phase boundary surface area per unit volume and Ni phase dimensions were measured quantitatively. Using a quantitative microscopy approach, phase strains resultant in the Ni phase were defined and measured as a function of cold rolling reduction and phase volume fraction. Comparison with the overall strain indicated that the harder Ni phase strained less than the overall strain. This is suggestive of the occurrence of phase strain partitioning in the two-ductile-phase alloy.

蒸着法で製造したAg-Ni,Ag-C合金の組織と機械的性質

By applying the vacuum-deposition method, it may be possible to prepare alloys constituted of elements mutually insoluble in the liquid state. From this point of view, Ag-Ni and Ag-C alloys were successfully produced, and their structure and the mechanical properties were investigated. The following results were obtained: (1) The solid solution of silver containing up to 9 at%Ni could be produced. The solid solubility of carbon in silver could not be detected by means of the X-ray method, but the change in the electric resistivity of 1 and 2 at%C-Ag alloys with temperature indicated the decomposition of the solid solution into silver and carbon. (2) By alloying nickel and carbon in silver, the duplex grain structure in silver films as-deposited were normalized and refined. (3) After the tempering of 4 at%Ni-Ag alloy at 400°C and of 1 and 2 at%C-Ag alloys at 200°C, they were hardened by the precipitation of fine nickel and carbon particles. (4) The linear relationship between proof stress vs. (grain diameter)−1⁄2 for bulk silver polycrystals can be applied to vacuum-deposited films up to about 0.1 μ in grain diameter, but the proof stress of ultra-fine grained silver with grain diameters of less than 0.1 μ was smaller than the value expected from the Petch’s relation.