Research Of Liquid Phase Reduction Preparate Ultrafine Nickel Powder And Control Its Morphology

Ultrafine nickel powder materials have characteristics such as high surface activity, large specific surface area,widely used as powder metallurgy additive,electromagnetic shielding materials,magnetic materials,organic catalytic materials, high-energy fuel and conductive paste.The preparation of ultrafine nickel powder technology,performance and application of exploring get more and more attentions from researchers.Liquid chemical reduction method is a very important method of preparating of ultrafine nickel powder material,it is easy to control particle size and morphology of ultrafine nickel.The template method was used,precisely control the morphology of particles,the size of particle and growth direction,etc.Liquid chemical reduction method was adopted to prepare ultrafine nickel powders in this research,the technical parameters, elimination of inorganic ions, and the morphology control in this research.Orthogonal experiment was used to optimize the experimental conditions, nucleating agent was used to control the nickel powder particle size distribution,template agents were used to control morphology is studied, respectively.The main research contents as follows.（1） Ultrafine nickel powder was preparated by conventional hydrazine hydrate reduce nickel sulfate solution.Average particle size as the evaluation index,orthogonal optimization design conditions for the preparation of nickel powder.Poor analysis showed that the average particles size effected by the preparation conditions in the order: the mole ratio of N₂H₄/Ni²⁺,the mole ratio of NaOH/Ni²⁺,the concentration of Ni²⁺ and temperature.it is concluded that the optimal conditions are the concentration of Ni²⁺ is 0.5 mol/L,the mole ratio of Ni²⁺:NaOH:N₂H₄ is 1:7:12,the temperature is 60℃.Under the optimal conditions for preparation of nickel powder,high purity,good dispersion, high degree of crystallization,the particle size distribute 210 nm to 250 nm.（2） It is a regular way that to choose precious metals as nucleating agent control the distribution of particle sizes.Nickel as nucleating agent,using two step reduction method, preparate ultrafine nickel powder in ethanol system was studied in this topic.The first step is nucleation, and the second step is nuclear growth.The results show that adding nucleating agent can control the nucleation rate of nickel effectively,uniform nucleation rate is more stable and narrow particle size distribution can be obtained,good dispersion of ultrafine nickel powder.In addition,in the ethanol system won the particle size is smaller than water system,more smooth surface of ultrafine nickel powder.This shows that the polarity of the solvent effect on the growth of ultrafine nickel particles,but the mechanism needs further research.（3） Ultrafine nickel powders was used in electronical functional materials field generally require a high purity.Ultrafine nickel powders have large adsorption capacity, can adsorb inorganic anions,such as Cl-, SO₄2-,and it is a physical adsorption.Butyl mercaptan can react with ultrafine nickel powder, chemical adsorb at the nickel surface.Research results show that the cleaning process in the nickel powder with butyl mercaptan can make the ultrafine nickel powder in the adsorption of anion content dropped significantly.（4） Surfactants as template agents,the type and concentration of template agents influence the morphology of nickel particles.When the concentration of template agent cetyl trimethyl ammonium bromide（CTAB） is 6 mmol/L,nickel powder was preparated with much more octahedral particles.When the concentration of template agent sodium dodecyl sulfate（SDS） is 7 mmol/L,fibrous nickel powder was preparated.When the concentration of template agent polyvinylpyrrolidone（PVP） is 160 mg/L,stabbing spherical nickel powder was prepared.