The hot-press sintering of hexagonal boron nitride is made by sintering raw material powder into a mold according to a specific pressure direction and sintering temperature. The parts prepared by hot pressing sintering have excellent mechanical properties.
The melting point of MAS is about 1450°C. It is an effective liquid phase sintering aid. Different glass ratios can be obtained, for example, cordierite (Mg2Al4Si5O18), spinel (MgAl2O4), mullite (3Al2O32SiO2). MAS can improve the sintering performance of BN ceramics; h-BN can inhibit the crystallization of MAS and increase MAS’s mechanical properties. The combination of the two can make up for the shortcomings of their respective attributes. Delong Cai [10,11] and others prepared BN-MAS composite ceramics by hot pressing at a lower temperature. This system studies the MAS of h-BN composites in the temperature range of 600°C to 1400°C. The material is resistant to thermal shock and oxidation.
Contains 50wt. The bending strength and fracture toughness of the composite ceramic of %MAS are 213±25MPa and 2.49±0.35MPa·m1/2, respectively. 60wt. The %MAS composite ceramic has the highest residual strength, which is 77% higher than the original power. (ΔT=1000℃). The enhancement effect of MAS and the transformation of the composite ceramic surface’s microstructure are the main reasons for improving the thermal shock resistance. During the thermal shock, the surface oxidation of the composite material can self-heal the cracks, generate internal stress, and increase the residual strength. The oxide layer can also act as a thermal barrier, reducing the actual thermal stress by preventing oxygen diffusion and improving the oxidation resistance of the h-BN matrix composite. Short-term surface oxidation during thermal shock is beneficial to improve the thermal shock resistance of BN-MAS composite ceramics.