【作者】 赵东林； 罗发； 周万城；

【Author】 ZHAO Dong-lin, LUO Fa, ZHOU Wan-cheng( State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xran. Shaanxi, 710072, China; The Key Laboratory of Science and Technology of Controllable Reactions BUCT. Ministry of Education, China; Institute of Carbon Fiber and Composites, Beijing University of Chemical Technology. Beijing 100029. China)

【机构】 西北工业大学凝固技术国家重点实验室；

【摘要】 用激光诱导气相反应法,以六甲基二硅胺烷(Me3Si)2NH)(Me:CH3)为原料,用双反应室激光气相合成纳米粉体装置合成了纳米Si/C/N复相粉体,复相粉体的粒径为20-30 nm,纳米粉体的分散性好,无严重团聚.研究了纳米Si/C/N复相粉体在8.2-12.4 GHz的微波介电特性,纳米Si/C/N复相粉体介电常数的实部(ε’)和虚部(ε”)在8.2-12.4 GHz随频率增大而减小,复合材料的ε’和ε”可以通过纳米粉体的含量进行调整,而且介电损耗(tgδ=ε”/ε’)较高,是较为理想的微波吸收材料,计算结果表明经典的有效媒质公式对含纳米Si/C/N复相粉体的复合材料是不适合的.纳米Si/C/N复相粉体中Si,C、N原子周围的化学环境比纯SiC和Si3N4相的混合体要复杂得多,这是导致其性能变化的主要原因.纳米Si/C/N复相粉体中的SiC微晶固溶了大量的N原子,在纳米Si/C/N复相粉体中形成大量的带电缺陷,在电磁场作用下形成极化耗散电流,极化弛豫是其吸收电磁波的主要原因.更多还原

【Abstract】 The nano Si/C/N composite powders was synthesized from hexamethyldisilazane ((Me3Si)2NH) (Me:CH3) by a laser-induced gas-phase reaction. The particles are spherical, loosely agglomerate with size in a range of 20-30nm. The laser synthesis reactor consists of two reaction zones, which can efficiently increase laser efficiency and production yield. The microwave permittivities of nano Si/C/N composite powder suspended in paraffin wax matrix have been studied at the frequency range of 8.2-l2.4GHz. The dissipation factors of the nano Si/C/N composite powder are high at the microwave frequencies. The microwave permittivity of the mixture of nano Si/C/N composite powder and paraffin wax (or other dielectric materials) can be tailored by the content of this composite powder. The ε’ and ” of the nano Si/C/N composite powder decrease with frequency increase at the frequency range of 8.2-12.4GHz. The difference in the microwave resonance is not sharply peaked but rather smeared out over a large frequency range. It is found that the microwave permittivities of the nano composites can not be predicted using classical effective medium functions. The promising features of nano Si/C/N composite powder would be due to more complicated Si, C, and N atomic chemical environment than that in a mixture of pure SiC and Si3N4 phase. so charged defects and quasi-free electrons move in response to the electric field, diffusion or polarization current . results from the field propagation. The high ε” and tgδ of nano Si/C/N composite powder would be due to the dielectric relaxation. The nano Si/C/N composite powder could be a good candidate for radar absorbing material.更多还原