The Preparation And The Performance Research Of Fibrous Nickel Oxalate Salt Under The Action Of Pulse Electromagnetic Field

Nickel powder is a kind of indispensible electrode materials. It is necessary for thedevelopment of battery industry to improve the quality of nickel products. The key ofhigh-quality nickel products is how to obtain the fibrous and superfine nickel powder. Basedon the morphology characteristic, nickel powder obtained by thermal decomposition caninherit the morphology of nickel oxalate salt precursor, it is essential to study the morphologyand size of nickel oxalate, which is not only beneficial to the development of new nickelpowder material, but also to the preparation of other metal oxalate system.In this paper, nickel oxalate salt was prepared by oxalate precipitation method usingnickel chloride and ammonium oxalate solution as raw materials. The nickel oxalate salt wascharacterized by XRD, SEM, FTIR, particle size analyzer and conductivity meter techniques.Effects of reactant concentration, reaction temperature, pH value, feeding speed, aging time,and the amount of surfactant addition on the morphology and particle size of nickel oxalatesalt were investigated. The optimum technological parameters are as determined as well.Meanwhile, nickel oxalate salt was prepared at a feeding speed of5mL/min under the actionof pulsed electromagnetic field (PEMF). The PEMF voltage, PEMF frequency and PEMFtreatment time on the morphology and size of nickel oxalate salt were investigated as well.Combined with the powder nucleation and growth mechanism, the mechanism of the pulsedelectromagnetic field was preliminarily discussed.The results show that a large aspect ratio and fine size of fibrous nickel oxalate salt withgood dispersion is obtained at Ni2+concentration of0.6mol/L, the reaction temperature of65℃, pH valueof9.0, the feeding speed of2mL/min, aging time of4h and surfactant additioncontent of0.2(wt)%. In contrast to the sample prepared at a feed speed of5mL/min withoutPEMF treatment, the nickel oxalate salt sample with PEMF posses a relatively large aspectratio of about25:1with no obvious aggregation when the PEMF voltage was600V, PEMFfrequency was4Hz and PEMF treating time was3min. In the reaction system with PEMF, watermolecules under the magnetic repulsion are away from ions and the opportunities ofNi(NH3)n2+complex ions colliding with C2O42-increase, small scale nickel oxalate saltclusters develop in the direction of large scale ones, the number of critical crystal nucleusscale nickel oxalate salt group increases, which results in the enhancement of nucleation ratioand fine grain size. Furthermore, nickel oxalate salt particles are evenly dispersed due to thereduction of secondary nucleation phenomenon. Appropriate pulse energy can improveammonia nickel ratio between0.5to2.5, fibrous morphology of nickel oxalate salt becomeideal.