Papers by Author: R. Hesse

Abstract: The sintering of Sm2Fe17 compound prior to the nitrogenation process is studied as an alternative process to produce dense Sm2Fe17N3 hard magnets with higher maximum energy products (BH)max than conventional polymer bonded magnets. In order to optimize sintering and nitrogenation processes, powders made from alloys, with different compositions, in the as-cast as well in the as-homogenized state were used. It could be shown that the amount of α-Fe, formed in the casting process, was reduced during sintering and that Sm selective loss is restricted to the surface up to a depth of 100 +m. Moreover the density of the sintered samples was not much affected by the initial composition or by the prior homogenization of the alloys. Although the nitrogenation process was successful in producing the Sm2Fe17N3 as proved by the mass gain, magnetic properties measurements and X-Ray diffraction, the hard magnetic properties were much lower than expected, indicating that other variables, which are discussed in the text, must be considered.

Abstract: This paper compares the effect of using different types of iron powders for the preparation of Sm2Fe17 by calciothermic reduction-diffusion (CRD). Three types of iron powder were used: carbonyl, sponge and water atomized. The results show that, when immediately nitrogenated after the CRD process, Sm2Fe17 prepared from sponge and water atomized iron powders yield Sm2Fe17N3-magnets with a high degree of texture. However, after a suitable treatment with hydrogen followed by nitrogenation, Sm2Fe17-powders made from Carbonyl iron produce magnets with the best quality regarding coercivity, remanence and degree of texture.