| 摘要 |
A permanent magnet having high coercive force and remanence, is made by the agglomeration of a fine powder obtained by the simultaneous precipitation of iron and cobalt salts from a solution, the decomposition of the salts into oxides by heat at a temperature less than 600 DEG C and their oxidation in contact with an oxidising atmosphere. The magnet or the powder may be reheated to temperatures less than 400 DEG C, if desired, in a magnetic field. To facilitate mixed crystallization, salts, such as formates, acetates and oxalates, are selected in which the iron is in a ferrous condition. To prevent the salts assuming a ferric condition, oxidation is stopped by oxidizing the outer layer before decomposition. In one example a boiling solution of iron and cobalt formates containing iron and cobalt in the ratio 2 : 1 in dilute formic acid, is cooled so that a compound formate is precipitated. It is dried, heated to 400 DEG C to achieve decomposition and the beginning of oxidation and air is passed over first at 1 litre/gm/hr and then at 4 litres/gm/hr and the powder obtained is agglomerated under pressure. In other examples formates having a Fe, Co ratio of 6 : 1, and oxalates and acetates having Fe, Co ratios of 2 : 1 were treated as in the preceding example. Figures of remanence and coercive force before and after heat and magnetic treatment are given. Specification 590,392, [Group XXXV], is referred to. |
