| 简介 |
PROBLEM TO BE SOLVED : To produce a spindle goethite particle powder and a spindle metallic magnetic particle powder obtained by using the spindle goethite particle powder as a starting material. SOLUTION : In the spindle goethite particle powder consisting of the goethite particles being a spindle particle having 0.05-1.0 μm average major axis diameter and in which the particles are composed of a seed crystal part and a surface layer part, and the seed crystal part is incorporated with 0.5-25 atom % Co per total iron and the surface layer part is incorporated with 0.5-15 atom % Al per total iron and 0.5-10 atom % rare earth elements. When the spindle goethite particle powder is formed by aging in a non-oxidizing atmosphere an aq. suspension containing a ferrous salt- containing precipitate obtained by allowing a mixed alkali soln. of an alkali carbonate and an alkali hydroxide to react with a ferrous salt soln., forming spindle goethite seed crystal particles by passing an oxygen-containing gas, adding again the mixed alkali soln. and the ferrous salt soln., mixing the mixture, then subjecting the mixture to growth reaction, 0.5-25 atom % Co compd., 0.5-15 atom % Al compd. and 0.5-10 atom % rare earth elements compd. per total iron are added. |
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