Co-enhanced SiO2-BN ceramics for high-temperature dielectric applications

Two typical high-temperature dielectric materials, fused silica and BN, were used to form a composite with an attempt to overcome their own drawbacks. In the resultant BN-SiO2 composites, BN platelike grains were preferentially orientated by hot pressing and homogeneously distributed in the fused silica matrix. An evident co-operative enhancement was achieved by the combination of the constituents. The sinterability and the thermal shock resistance of the BN materials were increased and the ablation surface temperature was decreased by the involvement of the fused silica. On the other hand, the strength, fracture toughness, and flame ablation resistance of the fused silica were increased due to the addition of BN. Furthermore, an amorphous Si-B-O-N structure was identified in the surface layer of the ablated composites, to which attention should be further paid in the development of new elevated temperature dielectric materials. 8 refs.