Microstructure and property enhancement of silicon nitride-barium aluminum silicate composites with β-Si₃N₄ seed addition

摘要

Si₃N₄-barium aluminum silicate (BAS) self-reinforced composites have been prepared by pressureless sintering at 1800 °C for 2 h. The β-Si₃N₄ seeds incorporated in the starting α-Si₃N₄ powders encouraged the α- to β-Si₃N₄ phase transformation, and the final bimodal microstructure with large grains, consequently, led to the improvement of the fracture toughness, from 7.74 to 8.34 MPa m1/2. The almost-complete crystallized BAS benefited the high-temperature mechanical properties. The residual stress, crack deflection, grain bridging, and pullout were considered as the major toughening mechanisms in this composite.