Fabrication of SiAlCNO and SiAlC fibers from a photo‐sensitive polyvinylaluminocarbosilane precursor using the ultraviolet curing method

Abstract SiC fiber is a critical structural material for high‐temperature extreme environments and nuclear energy applications. Traditional methods for producing industrial SiC fibers include oxidation and electron irradiation. In this study, a photo‐sensitive nitrogenous polyvinylaluminocarbosilane (PVACNS) is synthesized by uniformly blending polyaluminocarbosilane (PACS) and triallyl isocyanurate (TAIC). This precursor can be melt‐spun into fibers and rapidly UV‐cured at room temperature. After thermal pyrolysis at 1200°C and sintering at 1800°C of the cured fiber, amorphous SiAlCNO fibers with an oxygen content of 9.25 wt%, nitrogen content of 4.42 wt%, and a C/Si ratio of 1.60, and crystalline SiAlC fibers with an oxygen content of 0.02 wt%, nitrogen content of 0.11 wt%, and a C/Si ratio of 1.18 are obtained. The main UV curing mechanism involves homopolymerization of C = C bonds, in addition to minor hydrosilylation reaction between Si–H and C = C bonds. Between 400°C and 600°C, oxygen, nitrogen, and carbon contents decrease significantly due to the decomposition of TAIC. At 1200°C, the amorphous SiAlCNO fiber consists of amorphous SiC x O y , SiC x N y phases, and free carbon, with formation of Al–C and Al–N bonds. β‐SiC begins to form at 1400°C. At higher temperatures above 1400°C, SiC x O y and SiC x N y phases decompose, leading to notable decrease in oxygen and nitrogen content at 1600°C and 1800°C. However, due to the presence of Al–C and Al–N bonds, the formation of voids and defects is inhibited and the coarsening of β‐SiC is suppressed, resulting in a relatively dense structure in the SiAlC fibers at 1600°C and 1800°C.