Si/C/N纳米微波吸收剂的制备

Preparation of Nano-Sized Si/C/N Microwave Absorber

采用化学气相沉积方法,在1200℃～1600℃温度范围内,于不同的NH3流量条件下,合成了Si/C/N纳米粉体,研究了粉体的制备工艺、成分、相组成与其微波介电性能之间的关系.结果表明：NH3流量增加,粉体中N含量升高,随着合成温度的提高,粉体的晶化程度增强,主要为β-SiC相.在SiC晶格中固溶有N原子,且N原子的固溶量随合成温度升高而减少.Si/C/N纳米粉体中SiC微晶含量,以及SiC微晶中固溶的N原子浓度对粉体的ε＇,ε（＂）和损耗因子tgδ（ε＂/ε＇）起着重要作用.N原子固溶所导致的极化驰豫损耗和漏导损耗是Si/C/N纳米粉体具有吸波性能的主要机理.

Nano-sized Si/C/N powders were prepared by chemical vapor deposition （CVD） at 1200℃-1600℃ with different NH3 flow rates. The effects of preparation technology, N content and phase composition on the microwave permittivity of the powders were investigated. The results show that a higher flow rate of NH3 results＇in a higher N content, the degree of crystallization increases with the synthesizing temperature increasing, and the powders mainly consist of β-SiC. The N atoms dissolved in SiC lattice, and the dissolved amount of N atoms decreases with the increase of synthesizing temperature. The amount of SiC in powders and the dissolved N amount have no influence on the ε′, ε″, and tgδ （ ε″/ ε′）. We believe that the Si/C/N nano-sized powders have the ability of absorbing microwave mainly due to the conductivity losses and the dielectric relaxation induced by the dissolved N atoms.