Influence of sintering pressure on the crystallization and mechanical properties of BN-MAS composite ceramics

A type of hexagonal boron nitride-magnesium aluminosilicate composite ceramics was fabricated by hot-pressed sintering under different pressures. The relationships between sintering pressure, microstructure, and mechanical properties were investigated. The results indicate that sintering pressure has a great influence not only on the mechanical properties of composite ceramics, but also on crystallization of magnesium aluminosilicate (MAS) and structural order of hexagonal boron nitride. Under the given sintering pressure of 30 MPa, the fracture toughness of composites was greatly improved 66 % (from 2.49 to 4.12 MPa m¹/², with similar densities). It also exhibits the highest bend strength of 245 ± 23 MPa. The fracture behavior of composites and the mechanism of sintering pressure which affect the crystallization of mullite in MAS were also discussed.