炭化ケイ素系繊維の熱分解速度に及ぼす結晶性の影響

概要

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The mechanism of pyrolysis of amorphous silicon carbide fibre has been investigated. Using two types of fibres (Nicalon NL 400 and NL 200), the rate of pyrolysis has been measured with a thermobalance in an argon atmosphere at temperatures from 1673 K to 1973 K. X-ray diffraction patterns showed that the atomic arrangement in NL 400 was disordered in comparison with that in NL 200. The amorphous fibre NL 400 decomposed to β-SiC rapidly. TEM observation showed that the crystallites of SiC grew three-demensionally during pyrolysis. At the same fractional decomposition of fibre, the size of the crystallites of NL 400 was smaller than that of NL 200. The pyrolytic rate was analyzed by means of an Avrami-Erofeev's equation. The mean value of the exponent m in the rate equation was 1.3 for both fibres. Because large amounts of stable nuclei were generated immediately after the onset of pyrolysis of NL 400, its rate constant was about 3 times larger than that of NL 200. The activation energies were 487 kJ/mol for NL 400 and 484 kJ/mol for NL 200. The rate of pyrolysis of amorphous silicon carbide fibre was controlled by the nucleation and growth of SiC crystallites.
社団法人日本セラミックス協会の論文
1990-12-01