EFFECT OF TEMPERATURE SCHEDULE ON THE PARTICLE SIZE OF NiFe_2O_4 SPINEL NANOPOWDER DURING SOLID-STATE REACTIONS

摘要

NiFe_2O_4 spinel nanopowder was synthesized by solid-state reactions in air using a two-step heat treatment process. The dependence of the particle size and morphology of nanopowder on the temperature schedule was investigated emphatically. The temperature was held for 5h at an intermediate temperature before heating to the target temperature of 800°C for 1.5h. Although more heat was consumed and the technological process was more complicated, the powders synthesized by the two-step heat treatment method showed a smaller particle size with better dispersity than those produced by direct heating. Scanning electron microscopy (SEM) and laser particle analyzer indicated that the powder prepared at the intermediate temperature of 500°C for 5h was spherical and well-dispersed with the average particle size of 50 nm, while it was more than 80nm with particle agglomeration for direct heating to the same target temperature of 800°C.