预氧化聚碳硅烷纤维热分解动力学及其机理  

Kinetics and mechanism of thermal decomposition of pre-oxidized polycarbosilane fibers

作　　者：郑春满[1] 李效东[1] 余煜玺[1] 王浩[1] 冯春祥[1] 

机构地区：[1]国防科技大学新型陶瓷纤维及其复合材料国防科技重点实验室,湖南长沙410073

出　　处：《新型炭材料》2007年第2期171-176,共6页New Carbon Materials

基　　金：国家自然科学基金(59972042)~~

摘　　要：利用动态TGA分析和Coats-Redfern模型研究了预氧化聚碳硅烷(PCS)纤维的热分解动力学,用IR、XRD、SEM和HRTEM等研究了其热分解过程与机理。结果表明,预氧化PCS纤维热分解过程为一级反应,表观活化能为19.826kJ/mol;在初始分解阶段,主要为小分子PCS逸出,≡Si-H键之间以及≡Si-H与≡Si-CH3键发生了脱氢、脱CH4反应,从而导致交联程度的增加;随热分解温度进一步提高,分子的有机侧链急剧热解,分解产物从有机物转变为存在部分微晶的无机结构;热分解温度继续提高,纤维无机化结构进一步完善,β-SiC晶粒尺寸增加,纤维中出现自由碳;1250℃以上,β-SiC晶粒急剧长大,晶粒尺寸增加导致SiC纤维的力学性能下降。The thermal decomposition of pre-oxidized polycarbosilane （PCS） fibers was carded out in a thermogravimetric analyzer under non-isothermal condition. The Coats-Redfem equation was used to estimate the apparent activation energy in thermal decomposition and the mechanism of thermal decomposition was studied by IR, XRD and SEM. It was found that the thermal decomposition of pre-oxidized PCS fibers was a first order reaction and the apparent activation energy was estimated to be 19. 826 kJ/mol. The thermal decomposition process was a dehydrogenation and dehydrocarbonation condensation with the evaporation of low molecular components at low temperature. With increasing temperature the fibers were converted into an inorganic structure by decomposition of the side chains of the polymer. When the temperature was further increased, the crystallite size of SiC increased and the fibers became completely inorganic; above 1 250 ℃. The mechanical properties of the SiC fibers became lower with the rapidly increasing crystallite size of the β-SiC.

关 键 词：聚碳硅烷 热分解 动力学 预氧化 碳化硅纤维 

分 类 号：TQ340.1[化学工程—化纤工业]