原位裂解碳对氮化铝基微波衰减陶瓷性能的影响

碳材料具有优异的吸波性能, 但是难以在陶瓷基体中均匀分散。本研究通过酚醛树脂裂解的方法在氮化铝陶瓷基体中引入碳, 研究了酚醛树脂的添加量对氮化铝陶瓷烧结性能、微观形貌、导热性能和介电性能的影响。研究发现, 酚醛裂解形成的碳能够有效促进氮化铝陶瓷的致密化进程, 降低烧结温度。当酚醛树脂含量为3wt%, 1700℃烧结后陶瓷的致密度达到99.26%。此外, 裂解碳的引入能够显著提高材料的导热性能, 并在材料的气孔中和氮化铝的晶界处形成碳膜, 从而显著提高材料的介电性能。当酚醛树脂含量为6wt%时, 材料热导率达135.1W/(m·K), 在X波段的介电损耗为0.3, 表明材料具有良好的微波衰减能力, 有望应用于大功率的微波电真空器件中。

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

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.