Compression creep behaviour of precursor-derived Si-C-N ceramics

The creep behaviour of Si-C-N materials derived from polyvinylsilazane (PVS ) and polyhydridomethylsilazane (PHMS) precursors was investigated in the t emperature range between 1200 and 1550 degrees C at compressive stresses be tween 30 and 250 MPa in air. Both materials show very similar creep behavio ur. Decreasing strain rates with time were observed Even after 4x10(6) s cr eep deformation, stationary creep was not observed. Temperature dependence of the creep behaviour of such materials is very low. Dense passivating oxi de layers were found on the surface of creep specimens tested in the temper ature range up to 1500 degrees C. At 1550 degrees C active oxidation was ob served. (C) 1999 Elsevier Science Ltd. All rights reserved.