为获得性能优异的耐高温结构吸波材料,以纳米SiO2颗粒为填料,采用有机先驱体浸渍裂解法(precursor infiltration and pyrolysis,PIP)制备SiCf/SiC复合材料,研究填料对复合材料力学性能和高温介电性能的影响.结果表明:随着SiO2含量从3%(质量分数,下同)增加至15%,SiCf/SiC复合材料的弯曲强度先增加后减小,最高可达275 MPa;低介电常数SiO2填料的引入使得复合材料的复介电常数逐渐减小,室温吸波性能得到有效改善,15% SiO2含量的复合材料厚度为3.2~4.0 mm时,室温反射率在整个X波段均达到–8 dB以下;复合材料的复介电常数随着温度的升高逐渐增大,而SiO2能显著降低高温复介电常数及其增幅,700 ℃时15% SiO2含量复合材料在2.7~3.0 mm厚度范围具有优异的吸波性能.%The mechanical and high-temperature dielectric properties of SiCf/SiC composites with nano-SiO2filler were investigated in the present work for the development of high-temperature structural microwave absorbing materials. The results reveal that the flexural strength of SiCf/SiC composites is increased firstly and then is degraded with the filler content increased from 3% to 15%, and the maximum strength can be up to 275 MPa, meanwhile all of which show favourable fracture toughness. Owing to the high specific surface area and low permittivity of SiO2filler, the complex permittivity of the composites decreases and the room-temperature reflection loss (RL) is promoted with the increase of filler content. When the composites possess 15% SiO2filler, the room-temperature RL values can be reached to –8 dB in the whole X band with the thickness of 3.2-4.0 mm. The complex permittivity of the composites increases with the rising temperatures, while the specific values and increasing range of the high-temperature complex permittivity can be significantly reduced by introducing the SiO2filler, and the composites can obtain excellent microwave absorbing property at 700 ℃ with the thickness range of 2.7-3.0 mm.
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