Process for producing SiO.sub.2 coated iron oxide powder for use in the preparation of acicular magnetic iron or iron oxide powder
AssigneeTDK Electronics Co., Ltd.
InventorYasumichi Tokuoka
Life of this patent
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Abstract
An SiO.sub.2 coated iron oxide powder used for the preparation of an acicular metallic iron powder or an acicular magnetic iron oxide powder, is produced by forming a slurry of hydrated iron oxide as a starting material or a iron oxide powder having pH of 8 to 14; admixing a water soluble silicate at a ratio of 0.1 to 10 mol % as SiO.sub.2 based on Fe; hydrothermally reacting said mixed slurry at 100.degree. to 250.degree. C. for 5 minutes or longer in a closed reactor, and washing, filtering and drying the product.
Claims3
A process for producing SiO.sub.2 -coated iron oxide powder, for use in the preparation of acicular magnetic iron powder or acicular magnetic iron oxide powder, comprising:
- forming an aqueous slurry of an iron oxide selected from the group consisting of acicular goethite, acicular lepidocrosite and alpha-Fe.sub.2 O.sub.3, having a pH of 8-14;
- admixing a water-soluble silicate in an amount of 0.1-10 mole percent, as SiO.sub.2 based on Fe;
- charging the resultant mixture into an autoclave at 100.degree.-250.degree. C. for at least 5 minutes, to effect hydrothermal reaction at high pressure, the pressure in the autoclave being self-generative;
- and washing, filtering and drying the resulting product.
Dependencies are inferred from the claim text.