Microstructural features and properties of the nano-crystalline SiC/BN(C) composite ceramic prepared from the mechanically alloyed SiBCN powder

Nano SiC/BN(C) ceramic was prepared from the mechanically-alloyed amorphous SiBCN powder, hot pressed at 1900 degrees C under 80 MPa in the nitrogen atmosphere for 30 min. The microstructures and the properties of the prepared ceramic were carefully studied by XRD, TEM (SAED, HRTEM and EFTEM), EELS and property testing. Results show that the ceramic consists of beta-SiC, alpha-SiC and BN(C). SiC has an average grain size of about 78.2 +/- 32.4 nm, most of which have numerous stacking faults. BN(C) has small size, no fixed shape and turbostratic structure with heterogeneously distributed t-carbon layers, t-BN layers and B-doped t-carbon layers. It has uniform distribution in the ceramic, retarding the atomic diffusion and being responsible for the fine grains. The ceramic has room-temperature density, flexural strength, Young's modulus and fracture toughness of 2.6 g/cm(3), 331.1 MPa, 139.4 GPa and 2.8 MPa m(1/2), respectively. The detailed investigation of the hot-pressed SiC/BN(C) ceramic is helpful for the further study of this material and other ceramics, targeted for the high-temperature applications. (C) 2012 Elsevier B.V. All rights reserved.