Polycarbosilane (PCS) ceramic precursor fibers were irradiated by a nuclear reactor under inert atmosphere. The chemical structure of the irradiated products and the effect of neutron fluence on curing were studied

and the reaction mechanism was presumed. Results showed that the infusibilization of PCS fibers were achieved when irradiated at the neutron fluence of 2.6×1017cm-2 under N2 atmosphere

and the gel content and ceramic yield were 80% and 94.3%

respectively. The sintered products were still fibrous. The content of oxygen introduced in this process was very low. Bridge structure of Si―CH2―Si was formed by the rupture of Si-H bonds and succeeding radiation cross-linking.