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Abstract: Self-toughening α-SiAlON/6H-SiC composites containing both α-SiAlON and α-SiC elongated grains in the microstructures were previously fabricated by spark plasma sintering (SPS). In this study, the α-SiAlON/6H-SiC composites were heat treated at 1850°C for 3h. The effects of the heat treatment on the phase compositions, microstructures, and mechanical properties were investigated. The results showed M′ phases formed from crystallization of the intergranular glassy films. No polytype transformation for the SiC phase was observed. Both α-SiAlON and α-SiC grains grow anisotropic in the heat treatment, rather than converted into the brittle equiaxed morphologies. The flexural strength and fracture toughness of the post heat-treated composites were further increased and the 40wt% SiC composition reached 907MPa and 8.5MPam1/2, respectively. [Copyright &y& Elsevier]

MWCNTs modified Si 2 BC 3 N ceramics were prepared through SPS sintering mechanically alloyed amorphous Si 2 BC 3 N powder and MWCNTs at 1900 °C in N 2 atmosphere. The phase evolutions, microstructures and mechanical properties of the prepared ceramic were characterized by XRD, SEM and TEM (SAED and HRTEM), as well as the properties testing. The results show that the Si 2 BC 3 N ceramics are mainly composed of β-SiC, α-SiC and BN(C) phases. The introduction of MWCNTs can stimulate the formation of β-SiC in comparison with the pure Si 2 BC 3 N ceramics. Meanwhile, the particle sizes of BN(C) and SiC are reduced with the introduction of MWCNTs. Furthermore, the MWCNTs are mainly embedded in the Si 2 BC 3 N matrixes, contributing to enhanced bonding. Judging from the interfacial characteristic, the strengthening and toughening mechanisms of MWCNTs in Si 2 BC 3 N ceramics can be classified as “crack bridging”, “pull-out” and “crack deflection”. Based on these effects, the 1 vol% MWCNTs incorporated Si 2 BC 3 N ceramics have much higher flexural strength and fracture toughness of 462.1 MPa and 5.54 MPa·m 1/2 , respectively. [ABSTRACT FROM AUTHOR]