In situ Pyrolyzed Carbon on the Property of AlN-based Microwave Attenuation Ceramics

doi:10.15541/jim20170203

Abstract

Abstract:

Carbon materials exhibit excellent microwave absorbing properties. However, it is difficult to disperse carbon homogeneously in the ceramic substrate. In this study, carbon was introduced into AlN matrix by addition of phenolic resin followed by pyrolysis process. The effects of phenolic resin content on sintering behavior, microstructure, thermal conductivity and dielectric properties of AlN ceramics were investigated. It was found that phenolic resin derived carbon could effectively promote the densification of AlN ceramics and reduce the sintering temperature. Relative density of the AlN ceramics reached 99.26% after sintering at 1700℃ with addition of 3wt% phenolic resin. In addition, it was found that the presence of phenolic resin derived carbon can effectively improve the thermal conductivity of the ceramics. The dielectric properties were also improved due to the carbon films formed in the pores and at AlN grain boundaries. With addition of 6wt% phenolic resin, AlN ceramics showed high thermal conductivity of 135.1 W/(m•K) and excellent microwave attenuation properties (the dielectric loss was 0.3 at X-band), which were perspective candidates for possible applications in high power microwave vacuum electron devices.

Key words: phenolic resin, AlN, thermal conductivity, dielectric loss

CLC Number:

TQ174

HE Yong-Qin, LI Xiao-Yun, ZHANG Jing-Xian, LI Xiao-Guang. In situ Pyrolyzed Carbon on the Property of AlN-based Microwave Attenuation Ceramics[J]. Journal of Inorganic Materials, 2018, 33(4): 421-426.

Figures/Tables 7

Fig. 1 Pyrolysis process of phenolic resin

Fig. 2 Effects of phenolic resin content on the relative densities of composites sintered at different temperatures

Fig. 3 XRD patterns of composites with different phenolic resin contents sintered at 1800℃

Fig. 4 SEM images and EDS analysis of composites with different phenolic resin content sintered at 1800℃

Fig. 5 SEM image (a) and EDS analysis (b, c) of the composite with 6wt% phenolic resin

Fig. 6 Thermal properties of composites with different phenolic resin contents sintered at 1800℃

Fig. 7 Dielectric properties at X-band of composites with different phenolic resin contents sintered at 1800℃

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