Mechanical and Thermal Properties of AlN-SiC Composite Ceramics Fabricated by In Situ Reaction Hot-Pressing Sintering

Simultaneously achieving high densification, excellent mechanical properties, and high thermal conductivity remains challenging for aluminum nitride–silicon carbide (AlN-SiC) composites. In this study, fine-grained AlN-SiC composite ceramics were fabricated via in situ reaction hot pressing with the addition of small amounts of silicon (Si) and carbon (C). At an optimal sintering temperature of 1800 °C, the primary phase composition consisted of AlN, SiC and residual graphite, with an average AlN grain size of 0.94 μm. The Si additive melted and wetted the AlN matrix via capillary action, thereby providing sufficient kinetic driving force for densification. Meanwhile, the C additive not only removed oxygen impurities and purified grain boundaries but also reacted in situ with liquid Si to form SiC. The uniformly dispersed SiC particles inhibited the abnormal growth of AlN grains via the grain boundary pinning effect. Consequently, the relative density, flexural strength, and Vickers hardness of the obtained AlN-SiC ceramics reached 99.08%, 365 MPa and 22.58 GPa, respectively. At room temperature, the composite exhibited a thermal conductivity of 66 W/(m·K) and a thermal diffusivity of 32.6 mm2/s. This superior thermal performance is attributed to the purified grain boundaries, uniform SiC distribution, high densification, and tightly bonded SiC/AlN interfaces, which result in weak phonon interfacial scattering.