Abstract
Oxide-boron nitride composites (OXBN) including alumina-boron nitride and mullite-boron nitride composites were prepared by in situ reaction synthesis. The reaction mechanisms, microstructural features and properties of the hot pressed OXBN were investigated. These OXBNs showed very fine, homogeneous and isotropic microstructures and excellent mechanical properties compared to those of conventionally processed ones. For example, an Al2O 3 -13 vol.% BN composite hot pressed at 1600C for 60 min in a nitrogen atmosphere exhibited a mean three-point bending strength of 806 MPa. On the other hand, a mullite-18 vol.% BN composite hot pressed at 1800C for 60 min in an argon atmosphere exhibited a mean three-point bending strength of 540 MPa. In addition, we found that the addition of a small amount of Y2O3 remarkably improved the densification process of the composites and enhanced the crystallization of the in situ formed BN.
