High‐Performance Al ₂ O ₃ –C Composite Ceramics With Micron‐Scale Layered Structure via Foam Ceramic Precursor Method

ABSTRACT We proposed a simple strategy for designing micron‐scale layered structures in Al 2 O 3 –C composite ceramics by foam ceramic precursor method. The effects of lamellar Al 2 O 3 foam ceramic precursor and in situ formed SiC whiskers on their microstructure, fracture behavior, and overall properties were investigated. The lamellar Al 2 O 3 foam ceramic precursor achieved the formation of micron‐scale layered Al 2 O 3 /C structures in the Al 2 O 3 –C composite ceramics, and thus improved the Al 2 O 3 /C interface bonding. The lamellar Al 2 O 3 also promoted to the distribution of SiC whiskers via vapor–solid reaction mechanism between the Al 2 O 3 /C interface, resulting in more tightly interlocked interfacial structures. The layered Al 2 O 3 /C interface structure reinforced by SiC whiskers impeded crack propagation and further oxygen diffusion along the interface, thereby enhancing their mechanical properties, fracture energy and oxidation resistance. According to the traditional concept, the denser the ceramics, the higher the strength of ceramics. Interestingly, the bulk density of novel Al 2 O 3 –C composite ceramics was reduced from 2.38 to 2.20 g/cm 3 , but the cold modulus of rupture increased by nearly 70.3% from 23.61 to 40.20 MPa when lamellar Al 2 O 3 replaced spherical Al 2 O 3 particles. Therefore, the synergistic effect of micron‐scale layered Al 2 O 3 /C interface structure and SiC whiskers demonstrated a significant strengthening impact for the novel Al 2 O 3 –C composite ceramics.