SI-29 MAS-NMR INVESTIGATION OF THE CONVERSION PROCESS OF A POLYTITANOCARBOSILANE INTO SIC-TIC CERAMICS

A polytitanocarbosilane has been prepared from polycarbosilane and titanium n-butoxide.29Si MAS-NMR was used to characterize the various steps of the conversion process of the polymer into the final ceramic. The reaction of titanium butoxide with polycarbosilane introduces oxygen into the polymer that seems to play an important role in the pyrolysis process. In the first stage up to 1000 ° C, the study reveals the cleavage of Si-C bonds and the formation of SiC4-xOx units. In the second stage, above 1000 ° C, the number of Si-O bonds decreases, probably due to a carbothermal reduction process. At 1500 ° C, the product can be described as a mixture of crystalline SiC and TiC with no excess carbon. © 1990 Chapman and Hall Ltd.