Preparation Of Highly Crystalline Nickel Nanoparticles With The Isolation Of Salts

Nickel nanoparticles have broad application prospects in the fields of electrode materials,catalysts,magnetic fluids,etc.because they have both good electrical and magnetic properties.Due to the development of base metal multilayer electrode ceramic capacitors（BME-MLCC）,the demands for nickel nanoparticles becomes high,more and more researches have been done on nickel nanoparticles.The nickel nanoparticles prepared by existing methods are usually of large size and have the problem of uneven particle size distribution and low oxidation resistance temperature,etc.The oxidation resistance of nano-nickel powder depends on its crystallinity,and the crystallinity is heavily dependent on the preparation temperature.However,there is always the problem of agglomeration of nanoparticles under high temperature.Because of this,the preparation of nano-nickel particles with high dispersibility and high crystallinity has always been a technical bottleneck and research focus in the field.In this paper,a new technology for preparing nano-nickel powder with high melting point water-soluble inorganic salt as the isolated phase was explored,and high-dispersion nano-nickel powder with good crystallinity and high oxidation temperature was successfully prepared at high temperature.In this paper,the preparation of water-soluble inorganic salt particles and the control of particle morphology were studied.The K₂SO₄ and NaCl salt particles were successfully prepared by anti-solvent method.The parameters like solvent/anti-solvent ratio,initial concentration of inorganic salt,dropping method and dropping speed which can affect the size and morphology of product were studied.It has been found that by introducing a polyacrylic acid（PAA）additive and adjusting the amount thereof,a K₂SO₄ salt having a particle size of from 10 nm to 400 nm can be prepared.On the basis of controlling the size and morphology of water-soluble inorganic salt particles,this paper studied the preparation of nano-nickel powder by water-soluble inorganic salt isolation method.This paper mainly studies two preparation methods:One is a nano-sulfate potassium salt mixed isolation method.In this paper,potassium sulfate salt nanoparticles and nickel precursor nanoparticles were separately prepared,and the two were dispersed and mixed in an organic solvent,and then after the water is removed,they would be calcined at 700℃,After reduction at 550℃,nano-nickel powder with high dispersity,uniform size,good crystallinity and particle size below 100 nm was successfully prepared,and the oxidation resistance temperature could reach 508℃.It is found that when the amount of potassium sulfate is more than 5 times the molar amount of the precursor,the isolation effect is better:by adjusting the precursor raw material concentration,salt/precursor ratio and other parameters,nano-nickel powder with different particle diameters from 30 nm to 300 nm can be obtained.The other is a nickel salt solution impregnated with a sodium chloride method,in which the micro-sodium chloride salt was immersed in excess organic solvent containing Ni²⁺,under the action of capillary force,the active component permeated and adsorbed onto the surface and the gap of the sodium chloride salt support by diffusion,and then the excess liquid was subsequently removed,after drying they were reduced under the H₂ atmosphere at 550℃,finally the nanocrystalline nickel powders with high crystallinity,uniformity and dispersity,and the average particle size of at least 6 nm were successfully prepared,and the oxidation temperature was above 300℃.In this paper,the effects of impregnating liquid raw materials,concentration of impregnation solution and drying method on the particle size and morphology of nickel powder were investigated.Studies have shown that:chloroform,acetone and ethanol can be used as solvent for the impregnation solution;the higher the concentration of the immersion liquid,the larger the nickel particles would be prepared and the particle size distribution would be wider;the 80℃drying and freeze-drying method is superior to vacuum drying after which the uniformity of nickel particle size is better.