| 摘要 |
PURPOSE:To form a strong covering by film and to suppress the change in magnetic properties by the elapse of time by a method wherein a fine ferromagnetic metal powder or its surface is covered with an oxide film and then is brought into contact with sulfur dioxide. CONSTITUTION:This process uses a ferromagnetic metal powder such as one obtained by reduction with hydrolyzing an organic salt of a ferromagnetic metal, reduction products of water-containing metal oxide or its mixture with other metals, a vacuum evaporated product, or a pyrolysis product of a metal carbonyl cpd. The powder is brought into contact with a gas containing about 100ppm of sulfur dioxide at temperatures of 100-400 deg.C, for example, for 30min-50hur, for example. Thus, the process enables to achieve stabilization by using a gas phase and therefore is valuable from practical point of view. This effect can be enhanced by covering the above powder with an oxide in advance. |
