| 摘要 |
PURPOSE: Provided is a preparation method of soft ferrite powder by mixing metal salt solution with gel-type ammonium hydroxide for slow reaction resulting in high purity and homogeneity ferrite powder, comparing to the conventional reaction using ammonium hydroxide solution. CONSTITUTION: The soft ferrite powder is prepared by the following steps of: (i) preparing a gelling agent by mixing sol of gelatin and agar with sodium alginate solution, wherein the gelling agent, comprising 3.25-5.04wt.% of gelatin, 1.13-2.52wt.% of agar and 1.12-1.40wt.% of sodium alginate, is changed to gel at 10-15deg.C and sol at 45-50deg.C; (ii) mixing gelling agent with ammonium hydroxide, cooling mixtures to 10-15deg.C to form a gel, and extruding the ammonium hydroxide gel to get finger-sized pieces to increase the contact between metal salt solution and ammonium hydroxide; (iii) preparing a metal salt solution by dissolving sulfate or chloride of metals such as Fe, Mn, Zn, Ni and Mg in water; (iv) mixing ammonium hydroxide gel with metal sulfate(or chloride) solution for the metal concentration corresponding to ferrite; (v) heating mixtures under 60deg.C to change an alkaline gel containing ammonium hydroxide to an alkaline sol slowly, which results in homogeneous reaction between metal salt and alkali to form metal hydroxides; (vi) heating metal hydroxides over 70deg.C with air inflow for the oxidation of metal hydroxides; (vii) washing metal oxides, ferrite; (viii) drying and grinding ferrite to a size of 2-4micrometer.
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