Anisotropic properties of textured h-BN matrix ceramics prepared using 3Y(2)O(3)-5Al(2)O(3)(-4MgO) as sintering additives

摘要

Textured hexagonal boron nitride (h-BN) matrix composite ceramics were prepared by hot pressing using 3Y(2)O(3)-5Al(2)O(3) (mole ratio of 3:5) and 3Y(2)O(3)-5Al(2)O(3)-4MgO (mole ratio of 3:5:4) as liquid phase sintering additives, respectively. During the sintering process with liquid phase environments, platelike h-BN grains were rotated to be perpendicular to the sintering pressure, forming the preferred orientation with the c-axis parallel to the sintering pressure. Both h-BN matrix ceramic specimens show significant texture microstructures and anisotropic mechanical and thermal properties. The h-BN matrix ceramics prepared with 3Y(2)O(3)-5Al(2)O(3)-4MgO possess higher texture degree and better mechanical properties. While the anisotropy of thermal conductivities of that prepared with 3Y(2)O(3)-5Al(2)O(3) is more significant. The phase compositions and degree of grain orientation are the key factors that affect their anisotropic properties.