炭/炭复合材料热解炭基体微观结构转变动力学  

Simulation of the kinetics of pyrolytic carbon deposition in C/C composites

作　　者：黄清波[1] 张丹[2] 白瑞成[1] 李爱军[1] 孙晋良[1] 

机构地区：[1]上海大学材料复合及先进分散技术教育部工程中心,上海200072 [2]上海大学上海市应用数学及力学研究所,上海200072

出　　处：《新型炭材料》2016年第2期167-175,共9页New Carbon Materials

基　　金：教育部博士点基金(20113108120019);国家自然科学基金(11202124);航空科学基金(2013ZF6001);上海市科委基金(13521101202)~~

摘　　要：对热解炭沉积和织构形成过程进行动力学建模,重点分析C/C复合材料CVI制备工艺中基体炭形成时中织构/高织构(MT/HT)热解炭之间轮廓分明的急剧转变现象。基于Langmuir-Hinshelwood(L-H)理论和Particle-filler(P-F)概念模型,将MT和HT热解炭作为炭的两种亚稳相,以气相中占优的两种中间组分作为基体炭前驱体(线性小分子烃和小分子芳香烃),考虑基体表面单分子沉积形成MT热解炭和P-F双分子反应形成HT热解炭的过程,建立包含吸附/解吸附/脱氢的多步非均相热解炭沉积和织构形成反应动力学模型,研究该动力学系统达到稳态时热解炭随气相组成变化的情况。结果表明,热解炭沉积和织构形成过程曲线呈现"S"型特征,该曲线的线性稳定性分析表明热解炭沉积中的织构转变是一个包含迟滞区间的双稳态过程,进一步的计算表明此迟滞区间的大小明显受初始直链烃浓度以及沉积温度的影响。A multistep heterogeneous reaction kinetic model for pyrocarbon deposition is proposed to investigate the sharp and clear transition betw een the high-texture（HT） and medium-texture（MT） pyrocarbons in C/C composites synthesized by chemical vapor infiltration（CVI）. The model is based on the Langmuir-Hinshelwood mechanism and a particle-filler conceptual model,which models both the pyrocarbon deposition and the texture formation. The model assumes that adsorption,desorption and dehydrogenation reactions are involved. Unimolecular dehydrogenation reactions of either light linear hydrocarbons as the source of fillers（F） or light aromatic species as the source of particles（P） result in the formation of MT pyrocarbon,while a bimolecular dehydrogenation reaction between P and F species leads to the formation of HT pyrocarbon. The relationship between the types of pyrocarbons and gas-phase compositions is simulated under steady state. It is found that MT and HT pyrocarbon formation are two dominant stable processes with a hysteresis interzone that is affected by gas composition,initial linear hydrocarbon concentration and deposition temperature.Simulated results account for the sharp and clear transition between MT and HT pyrocarbon,and agree well with most pyrocarbon evolution studies under various conditions during CVI with only a few exceptions that may be caused by simplification in constructing the model.

关 键 词：炭/炭复合材料 热解炭 微观结构 动力学 

分 类 号：TB332[一般工业技术—材料科学与工程] TQ127.11[化学工程—无机化工]