Department of Interstitial Nitrogen Rare-Earth Magnet Material Through Nitriding under Atmospheric-pressure Plasma

本研究的目的是首次开发一种新型的常压混合离子渗氮装置，该装置有望将许多优点引入到新氮化物的合成和表面改性中。其次是开发新发现的高质量、高性能的Sm_2Fe_(17)&GT；N_x磁性材料。此外，为了确保新研制的常压混合离子渗氮装置的效果，首次尝试了利用该装置在较低的温度下合成Mo氮化物。1994年，我们研究了在1atm N_2气体流量下常规渗氮形成Sm_2Fe_&lt；17&gt；N_X的过程，明确了a-Fe的析出过程，这降低了Sm_2Fe_&lt；17&gt；N_X材料的磁性能。此外，我们还研制了世界上第一台大气压混合离子渗氮装置，它能够提高高压(大气压)等离子体的电离度，并能够提供比热平衡氮气更多的氮气，因为直流和射频辉光电荷混合等离子体。讨论了稳定杂化等离子体的条件。1995年，利用新研制的常压杂化等离子体氮化装置研究了高质量Sm_2Fe_(17)&Gt；N_x材料的制备。因此，与通常的氮气氮化相比，我们在明显较低的温度下成功地合成了材料。此外，利用常压高杂化等离子体氮化装置对氮化钼的合成进行了研究。首次发现，复合离子渗氮的氮化物形成温度明显低于常规氮气渗氮。此外，在混合离子渗氮中发现，在500ﾟC时，在通常的N_2气体渗氮中不会在低温下形成MoN。

The aim of this research is first development of new atmospheric pressure hybrid plasma nitriding apparatus by which a number of advantages are expected to be introduced into synthesis of new nitrides and surface modification. Secondly the aim is development of recently found Sm_2Fe_<17>N_X magnetic materials with high quality and excellent property. Moreover, in order to ensure the effects of the newly developed atmospheric pressure hybrid plasma nitriding apparatus, synthesis of Mo nitrides was first tried at lower temperatures using the newly developed apparatus.In 1994, we studied the formation process of Sm_2Fe_<17>N_X through usual nitriding under 1 atm N_2 gas flow and made clear the precipitation process of a-Fe which degraded the magnetic properties of Sm_2Fe_<17>N_X materials. Furthermore, we developed, first in the world the atmospheric pressure hybrid plasma nitriding apparatus which was enable to increase the degree of ionization due to high presure (atmospheric) plasma and to supply much larger amount of nitrogen than thermal equilibrium one due to hybrid of DC and RF glow charge plasma. The conditions of stable hybrid plasma were discussed.In 1995, the preparation of high quality Sm_2Fe_<17>N_X materials was studied using newly developed atmospheric pressure hybrid plasma nitriding apparatus. As a result we succeeded synthesis of the materials at markedly lower temperatures in comparison with usual N_2 gas nitriding. We also found high quality materials due to suppression of formation of a-Fe.Furthermore, synthesis of Mo nitrides was studied using atmospheric pressure high hybrid plasma nitriding apparatus. We first found that the formation temperature of the Mo nitrides were remarkably lower in hybrid plasma nitriding than in the usual N_2 gas nitriding. In addition, MoN which did not formed at low temperature in the usual N_2 gas nitriding, was found to form at 500ﾟC in hybrid plasma nitriding.