CNT纸/SiC对称梯度层状复合材料的高温电磁屏蔽性能和介电性能

High-temperature electromagnetic shielding and dielectric properties of CNT buckypaper/SiC symmetric graded laminated composite

将单层碳纳米管(CNT)纸浸渍酚醛树脂致密化,通过树脂碳层层焊接得到厚度约为2.6 mm的CNT纸/SiC层状梯度复合材料,由13个CNT纸/SiC复合材料结构层和12个膨胀石墨增韧树脂C界面层组成,SiC含量沿厚度方向由中心向两端呈递增的对称梯度分布。CNT纸/SiC层状梯度复合材料的体积密度为1.65 g/cm^3,开气孔率为7.25%,在宏观尺度范围获得在SiC基体中均匀弥散分布的高含量的CNT。在X频段范围,CNT纸/SiC层状梯度复合材料600℃时的平均总屏蔽效率(37.19 dB)高于室温(35.00 dB)。较之室温时的屏蔽性能,CNT纸/SiC层状梯度复合材料600℃时的反射系数略有减小,但吸收系数明显增加,透射系数由0.0003减小至0.0002,展示了良好的在电磁屏蔽领域尤其是高温屏蔽领域的应用前景。在X频段范围,随温度由室温升高至600℃,CNT纸/SiC层状梯度复合材料的虚介电常数平均值由114.6增大至149.1;平均损耗正切值由1.62增大至1.79。

A single-layer carbon nanotube(CNT)buckypaper densified by phenolic resin and then welded by resinderived carbon layer by layer was proposed to obtain a CNT buckypaper/SiC laminated graded composite with a thickness of 2.6 mm in this paper.The CNT buckypaper/SiC laminated graded composite consists of 13 structural layers made of CNT buckypaper/SiC composites and 12 interface layers made of expanded graphite-toughened resinderived carbon,in which the SiC content increases gradually from the center to both ends with symmetrically distribution along thickness.The CNT buckypaper/SiC laminated graded composite has a volume density of 1.65 g/cm^3 and an open porosity of 7.25%.High content CNT with uniform dispersion distribution in SiC matrix was obtained at a macroscopic scale.The average total shielding effectiveness of the CNT buckypaper/SiC laminated graded composite at 600℃(37.19 dB)is higher than that at room temperature(35.00 dB)throughout the X-band.Compared with the shielding performance at room temperature,the reflection coefficient decreases slightly,but the absorption coefficient increases significantly,and the transmission coefficient decreases from 0.0003 to 0.0002 at 600℃,which forecasts a promising prospect of electromagnetic shielding applications,especially of a high-temperature shielding application.The average value throughout the X-band of the imaginary permittivity increases from114.6 to 149.1,and that of the loss tangent increases from 1.62 to 1.79,respectively,with the increase of temperature from room temperature to 600℃.