GRANULATED MAGNETITE PARTICLES AND THEIR PRODUCING METHOD

摘要

PROBLEM TO BE SOLVED: To provide magnetite particles superior in oxidation resistance and particularly superior in weather resistance at high temperature and high humidity conditions without adding a component except an iron element and their producing method. SOLUTION: The relationship between an average particle diameter (Xμm) of primary granulated magnetite particles by a TEM projective photo and a crystallite diameter (Yμm) is denoted as the equation, 0.4X<=Y<=0.8X (X=0.05-1). The magnetite particles are produced by mixingα-FeOOH having a short axis diameter of 0.1-0.3μm with ferrous hydroxide at molar ratio of 1.5:1-2:1 and by a hydrothermal synthesis at 100-150 deg.C in the presence of an alkali of 1 equivalent or more to the iron element.