Preparation of fiber-like complex nickel oxalate by precipitation-transformation method

The fiber-like complex nickel oxalate precursor powders were prepared by precipitation-transformation method using nickel sulfate hexahydrate as the raw materials, oxalic acid dihydrate as the precipitants, and ethylenediamine as the complexants in this paper. The composition and morphology of the precursors were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric‒differential thermal analysis (TG‒DTA). The effects of preparation process parameters on the size and morphology of the precursors were studied. The results show that, the nickel salt precursors prepared by the precipitation-transformation method contain ethylenediamine, and the crystal morphology are fibrous and dispersed uniformly. The optimum conditions are as follows: the positive feeding mode, initial pH 7.5, Ni²⁺ concentration 0.6 mol·L^‒1, reaction temperature 65 ℃, and surfactant 0.4 g. Under these conditions, the desire fiber-like complex nickel oxalate precursors with good dispersibility can be prepared, and the maximum aspect ratio can reach 55.