Crosslinking kinetics of polycarbosilane precursor in ozone atmosphere and the formation mechanism of continuous hollow SiC fiber

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

“…Considering that cross-linking is favourable for increasing the ceramic yield of PCS, we thought PCS fibre with cross-linked outer layer–uncross-linked core structure may contribute to the formation of hollow SiC fibre. In our previous study, PCS fibre with cross-linked outer layer–uncross-linked core structure was obtained via diffusion-controlled ozone oxidation cross-linking reaction, and as expected, the much lower ceramic yield of uncross-linked core part contributed to the formation of hollow structure during pyrolysis [13]. We also found that a lot of micropores and mesopores along fibre formed during pyrolysis and then disappeared after treatment at high temperature, providing very good escape paths for degradation product of uncross-linked core part and guaranting the formation of continuous hollow SiC fibre with dense wall.…”

“…The air cross-linking process is usually conducted at about ∼200°C for several hours in air atmosphere furnace, and the main cross-linking mechanism is oxidisation of the Si–H group in PCS and then condensation of the formed Si–OH group [15,16]. In our previous report, we had confirmed that oxygen reaction control was the dominant factor during the air oxidation cross-linking process and led to uniformly distributed oxygen element in the cross-section of PCS fibre [13]. The electron irradiation cross-linking process is conducted in an electron accelerator [17,18].…”

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

“…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 …”