Investigation of nickel coatings obtained by laser processing on the surface of bronze

The article presents the results of a comprehensive study of the modes of laser processing during the formation of a coating on nickel-aluminum bronze using nickel powders. The coating was obtained in two stages. At the first stage, a precursor coating of the powder material was applied by cold spraying, at the second stage, its surface treatment with a laser was performed. The change in the composition and properties of the coating is shown depending on the processing modes and the thickness of the precursor coating, as well as the modes of laser processing.

Investigation on microstructure and selected properties of aluminum oxide–copper–nickel ceramic–metal composites

A new ternary system of ceramic–metal composites has been fabricated from alumina, copper, and nickel powders by the slip casting method. The research aimed to avoid copper leaking during the sintering process of the formation while processing the CuNi phase. Five different compositions were examined, differing in the ratio of nickel to copper. Stable slurries with good casting properties were prepared for all compositions. The final composites after the sintering process were characterized by a homogeneous distribution of the metallic phase, but they differed in the microstructure characteristics. The addition of nickel limits the outflow of the liquid phase (copper) during sintering but does not eliminate it. This resulted in a reduction in the hardness of the samples compared to the reference material.

ULTRAFINECOPPER AND NICKEL POWDERS INTHE ELECTRO-CATALYTICHYDROGENATIONOF ORGANIC COMPOUNDS

Ultrafine copper and nickel powders are synthesized by a chemical reduction of the metal cations from their salts in an aqueous ethanol solution without and with the addition of a polymer stabilizer (polyvinylpyrrolidone and polyvinyl alcohol). The structure and morphological features of the prepared metal powders were investigated by X-ray phase analysis and electron microscopy. The electrocatalytic properties of the Cu and Ni powders have been studied in the electrohydrogenation of acetophenone, nitrobenzene, p-nitroaniline, and cyclohexanone. A higher electrocatalytic activity of Cu powders, as well as skeletal copper, was established in the electrohydrogenation of the first three of the listed compounds in comparison with nickel powders, which is explained by the ability of copper cations to be reduced from its oxides in the electrochemical system under investigation. It is shown that the use of polymer stabilizers in the synthesis of Cu and Ni powders contributes to reducing metal particle sizes, but does not increase the electrocatalytic activity of the corresponding metal powders.

Effect of high content of nickel and silicon on the microstructure and properties of Cu-Ni-Si alloys

Cu-Ni-Si alloys have been widely applied in electronic and electrical industries.The effect of precipitation on the microstructure and properties of the alloys are still not well understood. In this study, Cu-Ni-Si alloys were prepared by hot-pressed sintering and elemental copper powders, nickel powders and silicon powders as raw materials. The results show that, there were no Ni-Si intermetallic compounds except the δ-Ni2Si phase in the microstructure by hot-pressed sintered preparation of Cu-Ni-Si alloys. And the distribution of the δ-Ni2Si phase in the alloy was more uniform and smaller. After aging treatment, when the mass ratio of Ni and Si were 2:1 and 3:1, the precipitation of δ-Ni2Si phase was significantly less, and when the mass ratio of Ni and Si were 4:1 and 5:1, the precipitation of δ-Ni2Si phase particles increased significantly.The test results by electrical conductivity and vickers hardness show that after ageing treatment, both the electrical conductivity and vickers hardness of the alloys were greatly improved. When the electrical conductivity was 39.33%IACS, the vickers hardness was 230.95HV, and the Cu-Ni-Si alloy had the best comprehensive performance.