Disproportionation Of Nd₂Fe₁₄B Induced By High Energy Ball Milling In Heptane

The Nd-Fe-B rare earth permanent magnet is the most important materials inpermanent magnetic application. The Hydrogenation disproportionation desorptionrecombination (HDDR) technique, established in1990, has been successfully appliedto the production of Nd2Fe14B or Sm2Fe17Ny magnets. The detailed technologicprocess is as follow. Being heated to about700–900℃in furnace flled withhydrogen of1bar, the Nd2Fe14B phase absorbs hydrogen and disproportionate intomixture of very fne NdH2,-Fe and Fe2B. Subsequent evacuation of the furnace atthe same temperature induces the desorption of H2and restores the original Nd2Fe14Bphase. Undergoing such a HDDR process, the Nd2Fe14B ingot with coarse grains hasbeen changed to polycrystalline powder with submicron grains and coercivity largeenough for permanent magnetic application. By means of dynamic control ofhydrogen pressure and temperature (d-HDDR), the produced powder is anisotropic asresult of the texture memory effect. In this work, being milled in heptanes for acertain time, the Nd2Fe14B phase can disproportionate into NdH2,-Fe and Fe2B also.followed conventional desrption and recombination process, Nd2Fe14B phase withlarger coercivity can be obtained.1.High energy ball milled in heptanes for more than400minutes, Nd2Fe14B phasedisproportionate into into NdH2,-Fe and Fe2B absolutely.2.Heated in vacuum form room temperature to800℃， NdH2release H2andNd2Fe14B phase has been restored along with-Fe。3.Thecoercivity of final Nd2Fe14B phaseis about7kOe. The content of-Fe bust bedecreased from the respective of much better permanent magnetic properties.