| 摘要 |
PURPOSE:To inexpensively manufacture a corrosion-resisting permanent magnet having stable and high magnetic properties, by making noble-metal colloid to be adsorbed by the surface of a sintered permanent-magnet body having a specific composition composed principally of rare-earth elements, B, and Fe and then by applying the electroless plating of base metals. CONSTITUTION:A sintered permanent-magnet body which has a composition composed principally of, by atom., 10-30% R (where R means at least one element among Nd, Pr, Dy, Ho, and Tb, or further, at least one element among La, Ce, Sm, Gd, Er, Eu, Tm, Yb, Lu, and Y), 2-28% B, and 65-80% Fe and in which main phase is composed of tetragonal phase is prepared. The colloid of at least one noble metal among Pd, Ag, Pt, Au, etc., is allowed to be adsorbed to about 10-100Angstrom thickness by the surface of the porous sintered permanent-magnet body in a neutral liquid medium of pH 6.0-9.0. Then, the electroless plating of at least one base metal among Ni, Cu, Sn, Co, etc., is further applied to the above-mentioned adsorption layer to <=about 25mum thickness. In this way, an Fe-B-R-type permanent magnet having stable and high magnetic properties free from deterioration for a long period under the atmospheric conditions of about 80 deg.C temp. and >=about 90% relative humidity can be obtained. |
