Fabrication and mechanical properties of silicon carbide-aluminum oxynitride nanocomposites

Although aluminum oxynitride (AlON) has been considered as an ideal candidate ceramic material due to high rigidity, good chemical stability, superior corrosion and wear resistance, it has relatively low flexural strength and poor fracture toughness. The aim of this investigation was to develop silicon carbide (SiC) nano-particulate reinforced AlON composites via a change of SiC content. The processing and mechanical behavior of SiC-AlON composites was investigated. The addition of SiC nano-particles resulted in a change of fracture mode from intergranular cracking to combined cracking in the composites due to the pinning effect of SiC nano-particles positioned at grain boundaries or triple junctions of micro-sized AlON particles. With increasing amount of SiC nano-particles up to 8 wt%, a reduction of porosity and grain size was observed in the composite. Meanwhile, the hardness, Young׳s modulus, flexural strength and fracture toughness all increased moderately. When the addition of SiC nano-particles reached up to 12 wt%, however, the agglomerates of SiC nano-particles were occurred and the relative density decreased obviously, resulting in the decrease of the hardness, Young׳s modulus, flexural strength and fracture toughness. By evaluating the effect of the additive concentration, on the mechanical properties of the AlON matrix, it is confirmed that the optimal SiC addition is 8 wt%.