Polymer(Korea), Vol.25, No.6, 866-875, November, 2001
산화억제제를 첨가한 탄소/탄소 복합재료의 물성에 관한 연구: 8. TEOS 를 함유한 복합재료의 열분해 메카니즘 및 열안정성 연구
Influence of Oxidation Inhibitor on Carbon-Carbon Composites: 8. Studies on Thermal Decomposition Mechanism and Thermal Stability of Composites Impregnated with TEOS
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초록
본 연구에서는 고온 산화분위기 하에서 탄소/탄소 복합재료의 열적 향상을 위해 사용된 tetraethylorthosilicate(TEOS)의 첨가량에 따른 복합재료의 kinetic parameter에 기초한 열분해 메카니즘 및 열안정성을 열중량분석기(TGA)를 사용하여 고찰하였다. TEOS를 함유한 탄소/탄소 복합재료의 kinetic parameter, 즉 열분해 활성화 에너지 (Ed), 반응차수(n), 지수앞 인자 (A)는 각각 136 kJ/mol, 0차, 및 2.3×109 s-1을 나타내었으며, 특히 IPDT 및 Ed로부터 살펴본 복합재료의 열안정성은 탄소/탄소 복합재료에 TEOS가 첨가되면 크게 향상되었는데, 이는 산소에 대한 산화 방지막, 즉 SiO2의 형성으로 인한 복합재료 표면에서의 카본 활성종에 산소의 침투를 방해하여 TEOS를 함유한 복합재료가 이를 함유하지 않은 것에 비하여 표면 산화 속도가 감소되어 열안정성이 증가하였다고 사료된다.
ABSTRACT:In this work, thermal decomposition mechanism based on kinetic parameters and thermal stability of carbon fiber-reinforced carbon matrix
composites(C/C composites), have been studied under high temperature oxidative conditions with addition of tetraethylorthosilicate(TEOS) as an oxidation inhibitor. Thermogravimetric analysis(TGA) was executed to evaluate the thermal decomposition mechanism and thermal stability of C/C composites in the temperature range of 30∼850 ℃. As a result, the kinetic parameters of the composites impregnated with TEOS, i.e., activation energy for thermal decomposition (E(d)), order of reaction (n), and pre.exponential factor (A) were evaluated as 136 kJ/mol, 0, and 2.3×10(9) s(-1), respectively. Especially, the IPDT and Ed of C/C composites impregnated with TEOS were improved largely compared with the composites impregnated without TEOS, due to the formation of SiO2 on composite surfaces, resulting in interrupting the oxygen attack to carbon active site in the composites.
Keywords:oxidation inhibitor;thermal decomposition mechanism;thermal stability;C/C composites;tetraethylorthosilicate (TEOS)
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