Investigation on the microwave sintering heating process and mechanism of h-BN/ZrO2/SiC composites

To explore the potential of microwave sintering's application in the preparation of h-BN/ZrO2 based side sealing plate, h-BN/ZrO2/SiC composites were sintered using above technology. The effect of feedstock material composition and input microwave power regulation rate on the microwave sintering process was emphatically analyzed. The phase composition, microstructure and related physical properties of sintered composites were examined. The results indicated that ZrB2 was generated in microwave sintered h-BN/ZrO2/SiC. The fracture strength and apparent porosity were 42 MPa and 11%, respectively, when the composite was sintered at 1550 degrees C for 30 min. Regarding the heating process of sample during microwave sintering, larger input power in the heating stage could increase the heating rate and ensure the sample obtain higher sintering temperature. After reaching the sintering temperature, the highest sintering temperature could be maintained even if the input power was greatly reduced in the holding stage. When the temperature exceeded a critical value, the sintering temperature of the sample would decrease obviously even if the input power greatly increased. The above phenomenon could be attributed to the power redistribution effect of microwave sintering. Based on this effect, the change of SiC content also had a significant impact on the microwave sintering process, which mostly depended on the variations of dielectric loss and electroconductibility of SiC due to the evolution of temperature.