Application of Mechanochemical Synthesis to Manufacturing of Permanent Magnets

Synthesis of permanent magnet powders through mechanically and thermally activated reduction of metal oxides with calcium, which allows for the production of fine single crystal particles, may contribute to the ongoing search for alternatives to the Nd-Fe-B magnets. The reviewed efforts demonstrate the possibilities to prepare (1) high-coercivity SmCo5 nanoparticles for anisotropic exchange-coupled nanocomposites, (2) YCo5/LaCo5 powders with the magnetic properties superior to those obtained through other manufacturing methods and (3) submicron Mn-Bi powders with large concentration of the MnBi phase. Also discussed are less successful attempts to prepare Mn-Al, Zr-Co and Hf-Co hard magnetic alloys in which the principal phases are known or likely to be metastable.