Nickel oxalate particles were prepared by mixing aqueous solutions of nickel sulfate and oxalic acid at 25 and 85 °C. Effect of composition of the reacting solutions and pH of the resulting dispersion was evaluated on morphology of the precipitated particles. Besides these parameters, isoelectric point of the nickel oxalate played a major role in the particles build up. On control heating at 340 °C, the nickel oxalate particles converted into nickel oxide particles while preserving their particles' integrity to a maximum extent. Selected batches of the as‐prepared and heat‐treated particles were characterized by various physical methods.
Iron(III) hydroxide was precipitated from the homogeneous solutions, containing variuos amounts of iron(III) nitrate, potassium sulfate, and urea, by heating at 85 °C for different periods of time (5‐30 min). The precipitated solids were either in the form of gel or dispersed particles of different shapes and sizes, depending upon the composition of the reactant mixtures. The as‐prepared solids were amorphous in nature and were formulated as Fe(OH)3.H2O. On calcinations at 800 °C for 1 h, the latter converted into crystalline compound, composed of α‐Fe2O3 (hematite). The calcined particles retained the original features of their precursors to a maximum extent.
The coated system, i.e., nickel basic carbonateshell/copper oxalatecore, were synthesized by heating dispersions, containing various amounts of the cores (copper oxalate particles), urea, and nickel sulfate for different intervals of time at 85 °C. These uniformly coated particles were obtained under narrow set of the experimental conditions. On heat treatment, the shell and core materials transformed independently into their respective oxides and ended up with coated particles composed of nickel oxideshell/copper oxidecore. The above‐mentioned systems of particles were characterized by scanning electron microscopy (SEM), x‐ray diffractometry (XRD), Fourier transform infrared spectrometry (FTIR), and thermogravimetric/differential thermal analysis (TG/DTA).
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