Preparation of hollow SiC ceramic fibre from polycarbosilane fibre by diffusion-controlled cross-linking method

Abstract

Cross-linking is favourable for increasing ceramic yield and avoiding melting or deformation of SiC ceramic precursor polycarbosilane (PCS) during pyrolysis. In order to achieve hollow SiC fibre, PCS fibre with a limited cross-linking depth was prepared by chlorinating the Si-H group in the outer layer of PCS fibre followed by hydrolysis and condensation of the formed Si-Cl group. The chlorination was implemented through a gas-solid reaction between Cl 2 and PCS fibre. Based on the results of energy-dispersive spectrometer and attenuated total reflectance-Fourier transform infrared spectroscopy, the diffusion-controlled chlorination reaction was confirmed. During hydrolysis, the catalysis of ammonia gas was necessary. According to the results of dissolution and degradation experiments, cross-linked PCS outer layer formed after chlorination, hydrolysis and condensation, and the outer layer had higher ceramic yield than the core part. After pyrolysis, SiC fibre with hollow morphology was formed. By adjusting the chlorination degree, the morphology of resulting hollow SiC fibre could be modified.

Preparation of liquid polycarbosilane containing vinyl ether group and its rapid curing through thiol‐ene click reaction

“…After the chlorination of LHBPCS, a new absorption peak corresponding to Si-Cl group appeared at 460-490 cm −1 . [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] After incorporating the 2-HEVE, the absorption peak corresponding to Si-Cl group disappeared, and the absorption peaks corresponding to vinyl ether group appeared at 3116 cm −1 (=C-H stretching), 1616 cm −1 (C=C stretching), and 1219 cm −1 (=C-O stretching). 31,32 In addition, compared with the raw LHBPCS, the intensity of peaks at 2930 and 2880 cm −1 (C-H stretching of linkage structure -CH 2 -CH 2 -O-) increased significantly.…”

“…In the studies of Pei et al, diffusioncontrolled cross-linking methods were adopted, and continuous hollow SiC fibers were obtained. 15,16 Moreover, cross-linking agent divinylbenzene was also used to crosslink the solid polycarbosilane through hydrosilylation reaction. 17 For liquid polycarbosilane (LHBPCS) with the approximate formula of [SiH 2 CH 2 ] n , latent reactive functional groups (vinyl, allyl, or ethynyl) that could promote crosslinking reaction were always introduced.…”

“…At present, air oxidation and e‐beam radiation are widely used in the preparation of SiC fiber. In the studies of Pei et al., diffusion‐controlled cross‐linking methods were adopted, and continuous hollow SiC fibers were obtained 15,16 . Moreover, cross‐linking agent divinylbenzene was also used to cross‐link the solid polycarbosilane through hydrosilylation reaction 17 …”