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

Two typical high-temperature dielectric materials, fused silica and BN, hav e been used to form a composite with an attempt to overcome their own drawb acks. In the resultant BN-SiO2 composites, BN platelike grains were prefere ntially orientated by hot pressing and homogeneously distributed in the fus ed silica matrix. An evident co-operative enhancement has been achieved by the combination of the constituents. The sinterability and the thermal shoc k resistance of the BN materials were increased and the ablation surface te mperature was decreased by the involvement of the fused silica. On the othe r 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 abl ated composites, to which attention should be further paid in the developme nt of new elevated temperature dielectric materials. (C) 2000 Elsevier Scie nce Ltd. All rights reserved.