SiC(N)纳米粉体的吸波性能研究

采用CVD法合成了SiC(N)纳米粉体。在NH3流量为0－480ml/min范围内，合成了氮原子百分含量随NH3流量逐渐增大的一系列SiC(N)纳米粉体。研究了SiC(N)纳米粉体的介电常数和介电损耗角正切与粉体组成的关系，发现介电常数的实部、瞄部和介电损耗角正切均随粉体中氮原子摩尔分数的升高而降低，依据粉体的介电常数设计了双层吸波涂层，涂层的吸波效果随粉体氮含量的升高而降低。N原子取代SiC晶格中C产生的带电缺陷在电磁场作用下的极化驰豫是SiC(N）纳米粉体吸波的主要机理。

Wave-Absorbing Property of SiC(N) Nano Powder

Although SiC is a prospective candidate for high temperature absorbers, some improvements are needed to increase its wave-absorbing ability. One method is to dope SiC with other atoms. In this paper, nano SiC(N) powders are synthesized by chemical vapor deposition (CVD). The as-formed SiC(N) nano powder is considered as SiC nano crystalline doped with nitrogen atoms. The SiC(N) nano powders are spherical and loosely agglomerate into particles with a range of 20-30 nm. The nitrogen content of nano SiC(N) powders can be adjusted by varying the flow rate of NH3 in the preparation process. The microwave permittivity of the mixture of the SiC(N) nano powder with paraffin wax was measured. Figs.2 and 3 show that the permittivity of the mixture changed with the composition of SiC(N) nano powder. Both the permittivity and dielectric loss of the mixture decreased with the increase of N mole content in Figs. 2 and 3. Based on the above measured data, we designed double-layer wave-absorbing materials with3 kinds of SiC(N) nano powders. The thickness of the materials is 3mm. The change of reflectivity with frequency for these 3 kinds of materials is illustrated in Fig. 4. It shows that reflectivity decreases with the increase of N content in SiC(N) nano powders.