NEEDLE ALPHA-FE2O3 GRAINS WITH NOVEL CRYSTAL ORIENTATION AND ITS PREPARATION

摘要

PURPOSE:A mixture of anhydrous or hydrated ferrous sulfate or ferric sulfate and a halide of an alkali or alkaline earth metal is heated at a specific temperature to produce needle alpha-Fe2O3 grains with high antimagnetic property and wearing resistance. CONSTITUTION:(A) Anhydrous or hydrated ferrous sulfate or ferric sulfate is mixed with (B) 5-100wt%, based on the component A, of at least one selected from halides, sulfates, nitrates and carbonates of alkali and alkaline earth metals such as sodium chloride are mixed, when necessary in the presence of an organic solvent free from water such as methanol and dried. The mixture is heated at 400-1,000 deg.C for 10min-10hrs, washed with water to remove the alkali salt to produce needle alpha-Fe2O3 grains with a needle orientation of[0001]and a plate face of (1-210).