PROCESS FOR PREPARING SILICA COATED GAMMA FERRITE

摘要

The silica coated gamma-ferrite is prepared by (A) forming iron hydroxide through the solution reaction of aqueous alkaline-added iron salt solution with air, (B) cleaning formed iron hydroxide more than 3 times with water 2 times the amount of the solution, (C) controlling the pH of the iron hydroxide slurry of 6-9.0 and the concentration of the slurry at higher than 2M, (D) pretreating the iron hydroxide slurry by agitating and dispersing for more than 1 hour for silica coating, and (E) coating iron hydroxide with a coating material containing 0.1-1.0 wt% silica with respect to the weight of iron hydroxide, followed by heat-treating the silica coated iron hydroxide.