| 摘要 |
PURPOSE:To obtain a stable powdered magnetic material composed or Co modified needle crystal iron oxide fine particles by dispersing and suspending needle crystal iron oxide fine particles surface-coated with silica in a Co ion-contg. ammonia soln. CONSTITUTION:Needle crystal iron oxide fine particles as nuclei are surface-treated with an Si-contg. compound to form silica coats, and then thermal shrinking may be carried out. The silica coated particles are dispersed and suspended in a Co ion- contg. ammonia soln., and Co modified magnetic iron oxide fine particles are obtd. from the suspension under a hot inert gas atmosphere or a reducing atmosphere. The thermal shrinking is preferably carried out at 400-800 deg.C under a nitrogen atmosphere, whereby micropores in Fe3O4 particles are eliminated to enhance the magnetic characteristics and dispersibility. |
