Hot pressed SiC ceramics employing polymer-derived SiBCN as sintering aid

Abstract

SiC ceramics were densified with 10wt.% polymer-derived SiBCN additives by hot-pressing under a load of 40MPa at 1850°C for 90min in a vacuum environment. Polyborosilazane was chosen as the SiBCN precursor and pyrolyzed at 1000°C before use. The obvious densification process began at about 1700°C during the sintering. The densification mechanism was different from the SiC ceramics densified by traditional sintering aids. When the temperature was above 1700°C, particle rearrangement was accelerated because deformation and/or viscous flow of the SiBCN occurred under the external pressure. This procedure resulted in rapid increase of density. After particle rearrangement, B and C elements and nano SiC grains separating out from the SiBCN material led to SiC grain growth and further densification. The bending strength and Vickers hardness of the product were 562±36MPa and 22.5GPa at room temperature.