Cross-scale microstructure design of precursor-derived SiC-AlN nanoceramic composites hybrid with ex-situ ZrB2

ZrB₂/SiC–AlN nanoceramic composites were densified at 1950 ​°C by hot pressing using an organic-precursor-derived SiC and commercially available AlN and ZrB₂. A cross-scale microstructure was constructed by distributing the ZrB₂ secondary phase (∼421 ​nm) within the SiC–AlN solid solution matrix. The substructure of the SiC–AlN matrix was agglomerated by nanograins with an average size of only 62 ​nm. ZrB₂ connected around the majority of pores within the SiC–AlN matrix and contributed to the formation of numerous weak interfacial bonding, resulting in improved strength and toughness. The highest flexural strength and fracture toughness of 579 ​± ​52 ​MPa and 6.7 ​± ​0.1 ​MPa ​m^1/2 were obtained from a 10 ​wt%-ZrB₂/SiC–AlN sample, respectively. The high concentration of grain boundaries of the ZrB₂/SiC–AlN nanoceramic composites resulted in heat insulation characteristic. The thermal diffusivity and conductivity were 3.6 ​mm²⋅s⁻¹ and 14.3 ​W·(m·K)⁻¹ at 1400 ​°C, respectively, while the electrical resistivity was 3.9×10³ ​Ω·cm for the 10 ​wt%-ZrB₂/SiC–AlN sample.