Abstract
Polytitanasilazanes with Ti/Si ratios ranging from 0.001 to 0.1 were synthesized by chemical modification of commercially available perhydropolysilazane (PHPS) with Ti(N(CH3)2)4. Amorphous Si-Ti-N ceramics were synthesized by pyrolysis of the polytitanasilazanes in Ar. The results of XRD analysis showed that the crystallization of α-Si3N4 from the Si-Ti-N materials with the Ti/Si ratios ranging from 0.001 to 0.01 started at 1273 K. This crystallization temperature was 200 K lower than that of the PHPS-derived Ti-free amorphous Si-N material. FT-IR and 29Si MAS NMR spectroscopic analyses revealed that, during the polymer/ceramics conversion process, the dehydrogenation reactions of the PHPS were apparently accelerated by the small amount of Ti-doping using Ti(N(CH3)2)4. This could lead to enhancing the lower temperature formation of SiN4 tetrahedral units necessary for the crystallization of α-Si3N4 at 1273 K.
