High-temperature microwave bilayer absorber based on lithium aluminum silicate/lithium aluminum silicate-SiC composite

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• 作者：Cheng-Hsiung Peng ; Pang Shiu Chen ; Ching-Chih Chang
• 关键词：Ceramic-matrix composites ; Layered structures ; High-temperature microwave absorption ; Lithium aluminum silicate ; D. SiC
• 刊名：Ceramics International
• 出版年：January, 2014
• 年：2014
• 卷：40
• 期：1_part_PA
• 页码：47-55
• 全文大小：1550 K

文摘

The microwave absorbing properties of lithium aluminum silicate (LAS) and LAS-SiC double layer composite absorbers were investigated within the frequency range of 8.2-12.4 GHz at 300-500 掳C. The composite absorbers for use as high-temperature radar wave-absorbing materials were developed by hot-pressing LAS glass-ceramic and LAS-SiC composite, which were used as the impedance transformer layer and the low-impedance resonator layer, respectively. Nanometer-size 尾-SiC powders were fabricated at the relatively low sintering temperature of 1450 掳C in argon atmosphere. The structure and morphology of the SiC powders were characterized using thermogravimetry-differential scanning calorimetry (TG-DSC), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The electromagnetic absorbing properties of the double layer at different temperatures and SiC contents were measured at normal temperature (27 掳C) and high temperature by a vector network analyzer. The results indicate that the contents of nanometer-size 尾-SiC can increase the relative permittivity and dielectric loss of the double layer microwave absorbers. At high temperatures, the microwave absorber consisting of a 2-mm-thick layer of LAS ceramic and a 2-mm-thick layer of LAS-SiC composite with 10 wt% SiC content exhibited excellent performance with a minimum absorption at 鈭?2.8 dB at 10.5 GHz and the absorption bandwidth (reflection loss less than 鈭?0 dB) of 3.5 GHz in the X-band. The minimum reflection loss measured at 300-500 掳C was less than 鈭?4 dB.