Synthesis of Silicon Carbide Fiber Containing Beryllium from Polyberylliumocarbosilane Using Electron Beam Irradiation

Abstract

Polyberylliumocarbosilane(PBeCS) precursor fibers were irradiated using electron beam in an atmosphere with N2:O2 rate of 200:1,They were then pyrolyzed at high temperature under nitrogen to give silicon carbide fiber containing beryllium(SiC(Be)).The effect of irradiation dose on the chemical structure,gel content,oxygen content,and tensile strength was studied.The results show that Si-H bonds in the molecular structure of PBeCS react with oxygen in the electron beam irradiation under low oxygen partial pressure bombarding to get Si-OH groups,and then Si-OH groups undergo dehydration condensation reactions to produce Si-O-Si linkage,Si-H and Si-CH3 decompose and polymerize to produce Si-CH2-Si linkage,resulting in cross-linking.SiC(Be) fibers prepared at 1250℃ have smooth and dense surface.XRD curve reveals that β-SiC microcrystals are formed in the fibers.The atom fraction of oxygen of the fiber is less than 5%,and the molar ratio of C to Si is close to 1:1,and the average tensile strength and tensile modulus are 1.8 GPa and 179 GPa,respectively.

Keywords

• polyberylliumocarbosilane
• electron beam irradiation
• curing
• silicon carbide fiber containing beryllium