Control of Particle Size of Amorphous Ni-P Spherical Powder Produced by Non-Electrolytic Reduction

Abstract

This paper describes the influence of some reaction factors on the particle size control for the production of Ni-P amorphous particles, especially the concentration of the reducing agent and the temperature of the reaction system. Reagents used in this experiment were as follows; NiCl₂·6H₂O as a nickel origin, NaOH as a pH regulator, and NaPH₂O₂·H₂O as a reducing agent and also as a phosphorous origin. The metallic salt solution was composed of a solution of the reducing agent and a pH regulator mixed in the fixed proportion. After completion of the reaction, produced precipitates were analyzed with SEM, TG-DTA, XRD and EPMA. Except for the high concentration of the reducing agent and the high reaction temperature, spherical particles were obtained. The higher the reaction temperature and the concentration of the reducing agent, the smaller became the average particle diameter measured from the SEM images. The smallest average particle diameter was 0.1 μm, and the largest one was 2.5 μm. According to the thermal analysis curves and the XRD patterns, almost all the particles were recognized as amorphous. The chemical composition of the powders confirmed by EPMA was mainly nickel and phosphorus.