| 摘要 |
770,838. Magnetic compositions. SOC. ANON. DE TELECOMMUNICATIONS. June 16, 1955 [June 23, 1954; Dec. 9, 1954], No. 17397/55. Class 38 (2). A magnetic composition having relatively uniform loss coefficients and initial permeability comprises Fe 2 O 3 , Cr 2 O 3 , MnO, ZnO, FeO in the following molecular percentages, 44-58, 1.7- 6.0, 19-27, 14-27, 0-10. Suitable proportions of the first four of these oxides are ballmilled with water to a mixture having particles less than 2 microns maximum dimension, compressed at 4 tons/sq. in., dried at 600‹ C., sintered at 1220-1320‹ C. for 3 to 5 hours, cooled slowly to 600‹ C. and then quickly to room temperature, all in air. Impurities such as oxides of Si, Al, Cu and other heavy metals and compounds of alkali metals may be tolerated. |
