New Utilization of Nitrogen using Metal Nitrides

本文研究了铁基金属间化合物的吸氮和脱氮性能。在此基础上，通过改变Fe_3N/Y_2O_3纳米复合材料的结构和电子态，制备了具有微波吸收功能的功能材料。研究了稀土-铁金属间化合物R_2Fe_3和RFe_7的吸氮和脱氮特性<17>。由于RFe_7和R_2Fe_3晶体结构的差异，使得氮易于扩散，RFe_7的吸氮和脱氮性能上级R_2Fe_3<17>，而Y_2Fe_3<17>则是通过将氮吸附到晶格中而从晶态转变为非晶态。用DV-Xα团簇方法计算表明，氮的插入使八面体Y_2Fe_4或四面体Y_2Fe_2单元中氮原子周围的Y-Fe和Fe-Fe键强度不稳定。结果表明，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的比表面积和固体酸性增大，有利于吸附NH_3，提高了反应几率。当Fe 3 N/Y2 O3粉末含量为80wt%时，复合材料在0.6- 4.4GHz频率范围内具有良好的电磁波吸收性能（RL&lt;-20dB），厚度为3.3- 19.3mm。

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.