| 摘要 |
PURPOSE:To obtain the titled powder having uniform particle size and free from resinous particles by reacting an aqueous alkali soln. contg. water soluble silicate with an aqueous ferrous salt soln. and an aqueous soln. of water soluble Co salt, oxidizing the reaction product, and heat treating the resulting particles. CONSTITUTION:Water soluble silicate is previously added to an aqueous alkali soln. used to prepare an aqueous soln. of >=12pH contg. Fe(OH)2 and Co(OH)2. This alkali soln. is reacted with an aqueous ferrous slat soln. and an aqueous aoln. of water soluble Co salt to prepare a mixed aqueous soln. of >=12pH contg. fine uniform Fe(OH)2 and Co(OH)2. By blowing oxygen-contg. gas into the soln., Co-contg. needle crystal goethite particles are formed. The particles are then separated by filtration, washed, dried, heat dehydrated, heat calcined under an atmosphere of heated steam and nonreducing gas, and heat reduced to obtain Co- contg. needle crystal magnetite particles, which may further be oxidized to give Co- contg. needle crystal maghemite particles. |
