New Utilization of Nitrogen using Metal Nitrides

本文研究了铁基金属间化合物对氮气的吸附和解吸性能。在此基础上，利用结构和电子态的变化，制备了用于微波吸收的Fe3N/Y2O_3纳米复合材料。本文研究了稀土-铁金属间化合物R_2Fe_(17)和RFe_7对氮气的吸附和脱附特性。由于R2Fe_17和R_2Fe_(17)的晶体结构不同，易扩散，故RFe_7的吸氮脱附性能优于R_2Fe_(17)。Y_2Fe_(17)和R_2Fe_(17)的氮吸附是由晶态向非晶态转变。用DV-Xα团簇方法计算表明，氮的加入不稳定八面体Y2Fe4或四面体Y2Fe2单元中氮原子周围的Y-Fe和Fe-Fe键强度，得到了Fe-Mox(M=Ce，Al，Si，Sr，Zr)复合微粉。Fe-(Ce，Zr)O2具有较高的氨分解催化活性，这归因于(Ce，Zr)O2比表面积和固体酸度的提高，吸附氨气的能力增强，反应几率增加。含80wt%Fe_3N/Y_2O_3粉末的树脂基复合材料在0.6~4.4 GHz频率范围内具有良好的吸波性能(RL&lt；-20d B)，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.