Abstract:C/ C-SiC composites were prepared by CVD ꎬimpregnation and pyrolysis method using polycarbosilane
(PCS) with four number average molecular weight as impregnant.The molecular weightꎬ softening pointꎬ molecular struc ̄
ture and thermogravimetic performance of PCS were determinedꎬ and the distribution of pores were analyzed by means of
mercury intrusion method .The results showed that the softening point and rate of conversion at 800℃ of PCS increased with
increasing molecular weight of PCS. The pyrolysis process of PCS with four molecular weight grade were identicalꎬ and
branch degree did not have significant difference. The integral densification efficiency of PCS with molecular weight 1 178
and 1 333 was higher than that of PCS with molecular weight 1 550. The cumulative pore content of sample densified by PCS
with molecular weight 1 178 was maximum after seven densification cyclesꎬ and that of sample densified by PCS with molec ̄
ular weight 1 550 was minimum.When PCS with molecular weight 1 178 and 1 333 was used in previous five ̄cycles and mo ̄
lecular weight 1 550 was used in other cyclesꎬ the material could be densified more efficiently.