Effect of Hexagonal BN on the Microstructure and Mechanical Properties of Pressureless Sintered Porous Si3N4 Ceramics
Porous silicon nitride ceramics with various amounts (25, 35, and 45 vol %) of hexagonal boron nitride (h-BN) were fabricated at 1800°C for 2h by the pressureless sintering process. With FESEM and TEM, the effects of h-BN on the microstructure and mechanical properties of Si3N4 ceramics were investigated. Results of the microstructure and mechanical properties of Si3N4/BN composites showed that the growth of the elongated β-Si3N4 were hindered by h-BN additive, which resulted in the decrease of fracture toughness of Si3N4/BN ceramics with increasing h-BN content. The morphologies of the fracture surfaces by FESEM revealed the fracture mode for Si3N4/BN composites to be intergranular. However, phase analysis by XRD indicated that the effect of h-BN on the α- to β- Si3N4 phase transformation of Si3N4/BN composites was negligible.
Wei Pan and Jianghong Gong
Y. F. Li et al., "Effect of Hexagonal BN on the Microstructure and Mechanical Properties of Pressureless Sintered Porous Si3N4 Ceramics", Key Engineering Materials, Vols. 434-435, pp. 697-700, 2010