Abstract:A novel precursor of nickel-cobalt alloy powders with an appropriate Ni to Co molar ratio was prepared under selectively synthetic conditions. The composition and morphology of the precursor were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FT-IR) and energy dispersive spectrometry (EDS). The effects of pH value, reaction temperature, metal ion concentrations and surfactant on the morphology and the dispersion of precursor were investigated. The results show that the morphology of precursor depends on ammonia content in the precursor. A fibriform precursor is a complicated ammonia-containing nickel-cobalt oxalate. The uniform shape-controlled fibrous precursor is obtained under the following optimum conditions: ammonia as complex agent as well as pH adjustor, oxalate as coprecipitator, 50−65 °C of reaction temperature, 0.5−0.8 mol/L of total concentration of Ni²⁺ and Co²⁺, PVP as dispersant, and pH 8.0−8.4.

Key words: fibrous precursor; Ni-Co alloy powder; shape-controlled synthesis; composition control; growth mechanism