China Nonferrous Metallurgy

The α-Fe?O? powder prepared by traditional methods exhibits poor dispersibility, irregular morphology, and imposes high demands on equipment and operational requirements. The precursor of iron oxide was prepared by coprecipitation method using FeCl? and NaOH as raw materials, and spherical α-Fe?O? powder with a particle size of 1 ~ 4 μm was prepared by spray drying and further calcination. The samples were characterized by TG, XRD, SEM and Nitrogen adsorption-desorption. The effects of calcination temperatures, types of precipitants and valence state of iron ions in the raw material solution on the phase, morphology and specific surface area of the products were analyzed in systematically. The results showed that the precursor of iron oxide was amorphous after spray drying, and the total weight loss of the precursor after further calcination was about 15.59%, accompanied by the dehydration of the precursor of iron oxide precursor to produce iron oxide. As the calcination temperature increased, the intensity of the diffraction peak of iron oxide increased, the specific surface area decreased, and the surface of the spherical product changed from many small particles to rod-shaped and then to sheet-like particles, indicating sintering between particles. The reddish brown product changed from light to dark. When the precipitant was ammonium bicarbonate or ammonia water, the product was a mixture of α-Fe?O? and γ-Fe?O?. When the valence state of iron ions in the raw material solution changed from +3 to +2, the prepared product transformed from a single α-Fe?O? phase to a mixture of α-Fe?O? and γ-Fe?O?.