Carbon elimination by heat-treatment in hydrogen and its effect on thermal stability of polycarbosilane-derived silicon carbide fibers
2004
Shimoo, T. | Katase, Y. | Okamura, K. | Takano, W.
Carbon elimination from EB-cured PCS fibers by H₂-treatment and the thermal stability of resultant SiC fibers were examined through TG, chemical analysis, AES analysis, XRD analysis, resistivity measurements, SEM observation and tensile tests. The C/Si mole ratio from 1.50 to 1.05 could be achieved by H₂-heat treatment at t ≧ 4 h and T = 773–1173 K. There was no difference in XRD patterns, fiber morphology and tensile strength of the fibers in the as-H₂-treated state. H₂-treatment at higher temperature caused the reduction in residue and the increase in resistivity of the fibers. An oxygen-rich layer was formed on the fiber surface after H₂-treatment, resulting in the mass loss, the coarsening of β-SiC grains and a marked degradation of fiber strength after exposure to higher temperature. Prevention of oxygen uptake after H₂-treatment is essential to improve the thermal stability of SiC fibers.
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