| Summary: | 碩士 === 國立中正大學 === 物理系 === 87 === This research is to adopt the transition metals and carbon co-substitution in a-Fe/2:14:1 type nanocomposite for improving the magnetic properties and temperature stability. Based on the results of the above ribbons, the alloy ribbons with high magnetic energy product and low coercive force were also explored at the rare earth lean ( <=10 at%) and boron rich (>=10 at %) composition region.
The alloy ribbons were prepared by single roller melt spinning process followed by suitable post annealing in order to obtain the microstructure with a-Fe/2:14:1-type composites. The following conclusions are achieved.
(1) For (Nd1-XLaX)9.5Febal.TiCYB10.5 (x=0, y=0; x=0, y=1; x=0.05, y=0), Ti and C co-substitution in the alloys may not refine the grain size of the ribbons but increase the Ti concentration in the grain boundary, due to the strong chemical affinity between Ti and C. The Ti and C coexisted grain boundary solid solution is presumed to improve the domain wall pinning, which eventually enhanced the coercivity of the ribbons. The best magnetic properties of Br=9.1kG, iHc=10kOe and （BH）max=14.6MGOe were achieved in Nd9.5Febal.TiCB10.5. While the irreversible loss of the ribbons is as low as -1.16 %.
(2) For NdXFebal.TiCB10.5 (x=9-11), the intrinsic coercive force increases with the increase of Nd content (x), but the irreversible loss decreases with it. When x =9, 9.5 and 10, three magnetic phases, namely Nd2Fe14B, Fe3B and a-Fe phases, were coexisted. For x=11, the intrinsic coercive force is dramatically improved, because the volume fraction of hard magnetic phase ( 2:14:1 ) was increased by the diminish of Fe3B phase. The best magnetic properties of Br=9.2kG、iHc=12.1kOe and ( BH)max=16.2MGOe were obtained in Nd10Febal.TiCB10.5.
(3) For Nd10Febal.MCB10.5（M=Ti、Mo、Cr、V and Nb）, three magnetic phases (Nd2Fe14B, Fe3B and a-Fe) were also found to coexist in the ribbons except M=Nb. Because the finer grain size and the increment of the volume fraction of 2:14:1 in the ribbons, the intrinsic coercive force of the ribbons with M=Nb is higher than that of the others. An iHc of 15kOe and a irreversible loss of -1. 28 % were obtained at M=Nb.
(4) To explore the alloy ribbons with high magnetic energy product and low coercive force simultaneously, for the purpose of easy magnetization, it is desirable not to incorporate C with transition metals and to develop a microstructure with the existence of Fe3B. The best magnetic properties combination of Br=8.7kG、iHc=7.6kOe and （BH）max=13.8MGOe was found in Nd9.25Febal.TiB10.25。
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