C涂层对SiC纤维介电性能的影响

以丙烯(C3H6)和氮气(N2)为反应气,用低压化学气相沉积(LPCVD)法在SiC纤维表面制备了热解碳层。考察了碳层厚度对纤维介电性能、反应气中C3H6体积分数对碳层微观结构及纤维介电性能的影响。结果表明,沉积100nm厚碳层后,纤维复介电常数实部由76.4～73.8增加到176.9～174.3,虚部由67.5～66.0增加到214.7～210.2。但碳层厚度进一步增大到200nm后,介电常数的增加不多。当C3H6体积分数由0.6降为0.45时,碳层结构有序化程度降低,晶粒变粗大,纤维介电常数实部由176.9～174.3降为156.4～153.7,虚部由214.7～210.2降为194.5～189.6。

Effects of Pyrocarbon Coating on Dielectric Properties of Silicon Carbide Fibers

Pyrocarbon coating was prepared on the surface of silicon carbide fiber by low pressure chemical vapor deposition(LPCVD) method using propylene and nitrogen as reactant gas.Effects of thickness of carbon coating on permittivity of fibers and volume fraction of propylene on microstructures of carbon coating and permittivity of fibers were investigated.The results show that a carbon coating of 100 nm thick could lead to an increase of the real part(ε') and imaginary part(ε″) of the complex permittivity from 76.4～73.8 to 176.9～174.3 and from 67.5～66.0 to 214.7～210.2,respectively.When the coating thickness reaches 200 nm,the complex permittivity does not show obvious change.When the volume fraction of propylene in the reactant gas decreases from 0.6 to 0.45,the disorder degree and the grain size of carbon coating increase,while ε' and ε″ decrease from 176.9～174.3 to 156.4～153.7 and from 214.7～210.2 to 194.5～189.6 respectively.