| 摘要 |
PURPOSE:To prevent deformation of particles and sintering between particles and allow crystal growth to take place uniformly in particles thereby to obtain a magnetic powder excellent in both particle size distribution and acicularity, by growing a goethite containing at least one kind of reduction retardant element on the surface of an acicular goethite as a core crystal. CONSTITUTION:A ferric hydroxide colloidal solution is prepared from a ferric salt solution, and 25g of an acicular alphaFeOOH obtained by aging this mother liquor is dispersed into 1,000ml of distilled water on stirring. Thereafter, 5.63g of ferric sulfate and 2.0g of zirconium sulfate are dissolved into 300ml of distilled water, and the mixed solution is added and mixed into a suspension of core crystal alphaFeOOH on stirring. Subsequently, 150ml of a sodium hydroxide solution of 2.5mol/l is added thereto to attach newly produced ferric hydroxide colloidal particles containing Zr on the surfaces of core crystal alphaFeOOH particles. The pH of this suspension is 13.2. Then, the suspension is subjected to a water heat treatment at 100 deg.C for 20hr to epitaxially grow the colloidal particles on the surfaces of the core crystal alphaFeOOH particles, thereby to produce alphaFeOOH containing Zr through crystal growth. After being rinsed and dried, this alphaFeOOH is reduced in an H2 gas stream at 400 deg.C for three hours to obtain a magnetic alloy powder containing a reduction retardant element on the surface of acicular goethite. |
