Mechanical and thermal properties of AlN–BN–SiC ceramics

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2008-10, Vol.494 (1-2), p.239-246
• Main Authors: Buchheit, Andrew A., Hilmas, Greg E., Fahrenholtz, William G., Deason, Douglas M., Wang, Hsin
• Format: Article
• Language: English
• Subjects: Aluminum nitride; Boron nitride; Condensed matter: structure, mechanical and thermal properties; Deformation and plasticity (including yield, ductility, and superplasticity); Exact sciences and technology; Hot pressing; Mechanical and acoustical properties of condensed matter; Mechanical properties; Mechanical properties of solids; Physics; Silicon carbide; Thermal properties
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2008.05.051

Mechanical and thermal properties were characterized for two AlN:BN:SiC composite ceramics produced from BN with different particle sizes. The ceramics were hot pressed at temperatures from 1950 to 2100°C to ∼97% relative density. For both materials, the matrix (90:10vol% SiC:AlN) had a grain size of ∼0.4μm, and the BN grains (10vol%) were crystallographically aligned. Microhardness values were between 20 and 22GPa, while fracture toughness values were between 2.5 and 3.1MPam1/2. Other properties were found to be dependent on testing direction. Elastic moduli were between 260 and 300GPa and strengths were ∼630MPa for small particle BN additions. Thermal conductivity was calculated to be between 25 and 37W/mK at room temperature and 17 and 25W/mK at 900°C. The low values compared to traditional SiC ceramics were attributed to AlN–SiC solid solution formation and sub-micron matrix grain sizes.