Synthesis of Needle-like Metal Fine Particles by Hydroprocess and Size Control

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The usage and characteristics of metallic particles are determined by the size and morphology. Therefore, accurate control of size and morphology and easy process for powder production gives advanced usage and improvement of new properties in the future. In this investigation, metallic particles such as nickel, copper, cobalt can be fabricated from thermal decomposition of the needle-like precursors precipitated in the solution with metal ammine complexes and oxalate salts. The morphology formed in the solution was maintained in thermal decomposition. Nickel particles were 100 micrometer in average length and several 10 nanometer in width, which changed to chain-like shape in higher thermal decomposition temperature. Though metallic particles tended to aggregate each other as smaller, aggregation was inhibited by adding polymer dispersant in the solution in precipitation process for precursors fabrication. Monodispersed Ni precursors with rectangular parallelepiped in shape were obtain … More ed in the solution without ammonia thorough the transformation of nickel hydroxide to nickel oxalate.This process was applied to copper particle synthesis. Copper particles with rod type and sphere type can be obtained by controlling ion type and ion oversaturation to the precipitation reaction in the solution as well as the synthesis of nickel particles.In addition, copper particles in nano size were synthesized by means of polyol process. This method consists of two-step reduction route in polyol process. One is reduction from cupric ion to cuprous ion and following from cuprous to metallic copper. We obtained 80 nm copper nano-particles with narrow size distribution and with satisfied anti-oxidation property. This two-step reduction method compulsively not only disconnects nucleation and nucleation growth, but also weakens conventional eruptible nucleation. PVP preventing the copper particles from aggregation and preventing the copper particles form oxidation are two main roles in this process Less