New Utilization of Nitrogen using Metal Nitrides

本文研究了铁基金属间化合物的吸氮解吸特性。在Fe_3N/Y_2O_3纳米复合材料上，通过结构和电子态的变化制备了微波吸收功能材料。总结如下。研究了稀土-铁金属间化合物R_2Fe_<17>和RFe_7对氮的吸附和解吸特性。RFe_7的吸氮和脱氮性能优于R_2Fe_<17>，这是由于两者晶体结构的差异使氮易于扩散所致。Y_2Fe_<17>通过吸收氮进入其晶格而由晶体转变为非晶态。用DV-Xα簇法计算表明，氮在八面体Y_2Fe_4或四面体Y_2Fe_2单元中插入使氮原子周围的Y-Fe和Fe-Fe键强度不稳定。制备了Fe-Mox （M=Ce, Al, Si, Sr, Zr）复合粉末。Fe-(Ce, Zr)O_2具有较高的氨分解催化活性。这是由于（Ce, Zr）O_2吸附氨的表面积和固体酸度增大，反应概率增大所致。研究了Fe_3N/Y_2O_3纳米复合材料的电磁波吸收性能。Fe_3N/Y_2O_3粉末质量分数为80 wt%的树脂复合材料在0.6 ~ 4.4 GHz频率范围内具有良好的电磁波吸收性能（RL<-20 dB），厚度为3.3 ~ 19.3 mm。

In this study, the nitrogen absorption and desorption properties of the iron based intermetallic compounds were investigated. Furthermore, the fabrication of functional material by the change of structure and electronic state was performed on Fe_3N/Y_2O_3 nanocomposite for the microwave absorption. The summary is as followed.Nitrogen absorption and desorption characteristics on rare earth-iron intermetallic compounds, R_2Fe_<17> and RFe_7, were performed. The nitrogen absorption and desorption properties of RFe_7 was superior to that of R_2Fe_<17> because of the ease of nitrogen diffusion due to the difference of crystal structure between them.Y_2Fe_<17> transforms from crystalline to amorphous state by absorption of nitrogen into its crystal lattice. The calculation by the DV-Xα cluster method revealed that the insertion of nitrogen into the crystal lattice unstabilizes the Y-Fe and Fe-Fe bond strength around the nitrogen atom in octahedral Y_2Fe_4 or tetrahedral Y_2Fe_2 unit.The fine composite powders of Fe-Mox (M=Ce, Al, Si, Sr, and Zr) were prepared. High catalytic activity of ammonia decomposition was observed on Fe-(Ce, Zr)O_2. This result is ascribable to the enhancement of surface area and solid acidity of(Ce, Zr)O_2 to adsorb ammonia and increase the reaction probability.The electromagnetic wave absorption properties of Fe_3N/Y_2O_3 nanocomposites were characterized. The resin composites with 80 wt% Fe_3N/Y_2O_3 powders exhibited excellent electromagnetic wave absorption properties (RL<-20 dB) in a frequency range of 0.6-4.4 GHz, with thickness of 3.3-19.3 mm.