Thermal stability of polymer derived SiBNC ceramics

To study the thermal stability of polymer derived SiBNC ceramics, a polyborosilazane was pyrolyzed in N-2 and NH3/N-2 atmosphere, respectively. The as-pyrolyzed products were annealed in N-2 atmosphere at 1200-1850 degrees C for 2 h. The chemical composition and phase structure of the as-pyrolyzed and annealed ceramics were investigated by element analysis, XRD and FT-IR. The results show that all the ceramics exhibit excellent high temperature stability. They are fully amorphous to 1700 degrees C, and only partial crystallization, giving a mixture Of Si3N4, BN and SiC phases, is observed upon heating at 1850 degrees C. The N-2 pyrolyzed products show better stability than the NH3/N-2 pyrolyzed products and have less tendency to crystalline at higher temperatures. Better retention of nitrogen at high temperatures is also observed for the N-2 pyrolyzed products. (C) 2009 Elsevier Ltd and Techna Group S.r.l. All rights reserved.