| 摘要 |
PURPOSE:To produce ultrafine grains in excellent dispersion properties in even distribution of grain diameter by a method wherein an oxide magnetic body is heat-treated within the range of temperature and specified time not exceeding temperature higher by a specified temperature than the crystallization peak temperature. CONSTITUTION:In the manufacturing process of magnetic powder by glass crystallizing process, the heat treatment temperature for crystal separation is specified within the range not exceeding 80 deg.C higher than the crystallization peak temperature measured by differential thermal analysis of the oxide magnetic body. If the heat treatment temperature exceeds 80 deg.C higher than the crystallization peak temperature, the crystalline grains are deposited progressively into larger size making it unable to produce fine grains of 20nm or less pertinent to magnetic fluid. Furthermore, at the temperature not exceeding the crystallization peak temperature, the crystal separation can be hardly performed within specified time making it requisite to extend the heat treatment time. The heat treatment temperature is related to the time i.e., the higher the temperature is, the shorter the treatment time while the lower the temperature, the longer the treatment time to make the crystal separation is required. The preferable crystallization temperature is plus 20-50 deg.C to be kept for 5-10 hours as the optimum time. |
