Toda Kogyo Corporation

Tokihiro Kurata

Tsutomu Katamoto

Tosiharu Harada

Masaru Isoai

Kazushi Takama

Kazuhiro Fujita

Shigekazu Jikuhara

Nanao Horiishi

Masao Kiyama

Akio Mishima

Hiroshi Sumita

Akira Mukaizaka

Yosiro Okuda

Yoshitaka Yoshinaga

Nanao Hiriishi

Disclosed herein are a process for producing acicular goethite particles comprising the step off: blowing an oxygen-containing gas into a ferrous salt reaction solution containing colloidal ferrous hydroxide or iron-containing colloidal precipitates which is obtained by reacting an aqueous ferrous salt solution with less than one equivalent of an aqueous alkali hydroxide solution, an aqueous alkali carbonate solution, or an aqueous alkali hydroxide and alkali carbonate solution based on Fe.sup.2+ in said aqueous ferrous salt solution, in the presence of ascorbic acid or a salt thereof so as to oxidize said colloidal ferrous hydroxide or iron-containing colloidal precipitates and to produce acicular goethite particles throught green rust; and a process for producing acicular magnetic iron oxide particles by reducing the acicular goethite particles obtained in the above process to produce acicular magnetite particles, and if necessary, oxidizing the acicular magnetite particles to obtain acicular maghemite particles, and if necessary, modifying the acicular magnetite or maghemite particles with Co or Co and Fe.sup.2+.

Process for producing acicular goethite particles and acicular magnetic

Disclosed herein are a process for producing acicular goethite particles comprising the step of: blowing an oxygen-containing gas into a ferrous salt reaction solution containing colloidal ferrous hydroxide or iron-containing colloidal precipitates which is obtained by reacting an aqueous ferrous salt solution with less than one equivalent of an aqueous alkali hydroxide solution, an aqueous alkali carbonate solution, or an aqueous alkali hydroxide and alkali carbonate solution based on Fe.sup.2+ in said aqueous ferrous salt solution, in the presence of ascorbic acid or a salt thereof so as to oxidize said colloidal ferrous hydroxide or iron-containing colloidal precipitates and to produce acicular goethite particles throught green rust; and a process for producing acicular magnetic iron oxide particles by reducing the acicular goethite particles obtained in the above process to produce acicular magnetite particles, and if necessary, oxidizing the acicular magnetite particles to obtain acicular maghemite particles, and if necessary, modifying the acicular magnetite or maghemite particles with Co or Co and Fe.sup.2+.

Process for producing acicular geothite particles and acicular magnetic

Disclosed herein are plate-like hematite particles having an average particle diameter of 0.5 to 5.0 .mu.m, a lamellar thickness of 50 to 500.ANG. and a plate ratio (the ratio of the average particle diameter to the lamellar thickness) of 50:1 to 500:1, an iron oxide pigment showing a golden color and comprising the plate-like hematite particles, and a process for producing the plate-like hematite particles.

Plate-like hematite particles, a pigment comprising the same and showing

Disclosed herein are electroconductive iron oxide particles having a volume resistivity less than 5.times.10.sup.6 .OMEGA.-cm, and comprising iron oxide particles selected from hematite and maghemite, and SnO.sub.2 particles containing Sb as a solid solution deposited on the surfaces of the iron oxide particles, and a process for producing the same.

Electroconductive iron oxide particles

Disclosed herein is spindle ferromagnetic alloy particles having the aspect ratio (major:minor) of less than 3:1 and the coercive force of 500 to 100 Oe, and containing 0.1 to 13 atomic % of Si to Fe, and a process for producing the same.

Spindle ferromagnetic alloy particles

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Hiroshima, Japan

Tokihiro Kurata