Oxide-coated magnetite particle with improved fluidity

摘要

A magnetite particle has each surface covered with a thin iron-zinc oxide film and has a saturation magnetisation of at least 79 emu/g., a blackness (L, measured by differential colorimetry) of max. 19.5 and an oil absorption (measured according to HJIS K 5101) of at least 30 ml/100 g. Also claimed is a similar magnetite particle which has a thin iron-silicon oxide film covering the iron-zinc oxide film and which additionally has a spatula angle of max. 60 deg. Further claimed are magnetite particle prodn. processes.