通过聚碳硅烷(PCS)预氧化后在800~1 200 ℃热解制备了SiC陶瓷,采用傅里叶转化红外光谱(FTIR)与拉曼光谱分别对不同温度交联后PCS及裂解产物进行了表征.并用矩形波导法测试了SiC陶瓷在8.2~12.4 GHz(X波段)频段的复介电常数,利用传输线理论计算了试样的反射率.结果表明,氧化交联过程中PCS通过Si-H键和Si-CH3键与氧反应形成Si-OH键.SiC陶瓷中自由碳有序度随着热解温度的升高而增加,导致复介电常数实部及虚部增加.170 ℃交联,1 200 ℃热解,试样厚度为3.5 mm的SiC陶瓷,吸收峰值为-18 dB,X全波段反射率低于-10 dB,呈现出较好的吸波性能.
SiC ceramics were obtained by pyrolyzing oxidation cured polycarbosilane (PCS) from 800 to 1 200 ℃ in vacuum.The oxidation curing PCS powders at different temperature and pyrolysis product were characterized by FT-IR and Raman spectrum, respectively.The dielectric properties of SiC ceramics are investigated by measuring their complex permittivity using rectangle wave guide method in the frequency range of 8.2-12.4 GHz, and the reflection loss of samples were calculated based on the transmission line theory.The results show that Si-H and Si-CH3 groups are oxidized to form Si-OH bonds during the oxidation curing process.The order of free carbon increases with the increase of pyrolysis temperature, which can contribute to the increasing of the real and imaginary parts of permittivity of SiC ceramics.When the sample thickness is 3.5 mm, the peak value of SiC ceramics derived from PCS after cured at 170 ℃ and pyrolyzed at 1 200 ℃ is-18 dB, and the reflection loss exceeded-10 dB in the whole frequency,which exhibits best absorbing performance.
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