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 between 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 dehy-drogenation 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 dehydro-genation reaction between P and F species leads to the formation of HT pyrocarbon. The relationship between the types of pyrocar-bons 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 deposi-tion 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 simplifica-tion in constructing the model.
参考文献
| [1] | B. Reznik;M. Guellali;D. Gerthsen.Microstructure and mechanical properties of carbon-carbon composites with multilayered pyrocarbon matrix[J].Materials Letters,20021/2(1/2):14-19. |
| [2] | Benzinger W.;Huttinger KJ.;Becker A..CHEMISTRY AND KINETICS OF CHEMICAL VAPOUR DEPOSITION OF PYROCARBON .1. FUNDAMENTALS OF KINETICS AND CHEMICAL REACTION ENGINEERING[J].Carbon: An International Journal Sponsored by the American Carbon Society,19968(8):957-966. |
| [3] | W. BENZINGER;K. J. HUETTINGER.CHEMICAL VAPOUR INFILTRATION OF PYROCARBON: Ⅰ. SOME KINETIC CONSIDERATIONS[J].Carbon: An International Journal Sponsored by the American Carbon Society,199612(12):1465-1471. |
| [4] | Z.J.Hu;W.G.Zhang;K.J.Huttinger;B.Reznik;D.Gerthsen.Influence of pressure, temperature and surface area/volume ratio on the texture of pyrolytic carbon deposited from methane[J].Carbon: An International Journal Sponsored by the American Carbon Society,20034(4):749-758. |
| [5] | Dong GL.;Huttinger KJ..Consideration of reaction mechanisms leading to pyrolytic carbon of different textures[J].Carbon: An International Journal Sponsored by the American Carbon Society,200214(14):2515-2528. |
| [6] | P.Delhaes.Attempts to chemical vapour infiltrate pyrocarbons:evidence for a spatial bistability ?[J].Carbon: An International Journal Sponsored by the American Carbon Society,20035(5):1093-1095. |
| [7] | R. Lacroix;R. Fournet;I. Ziegler-Devin.Kinetic modeling of surface reactions involved in CVI of pyrocarbon obtained by propane pyrolysis[J].Carbon: An International Journal Sponsored by the American Carbon Society,20101(1):132-144. |
| [8] | 徐伟;张中伟;白瑞成;李爱军;王俊山;孙晋良.丙烷化学气相沉积均相热解反应动力学模拟[J].新型炭材料,2014(1):67-77. |
| [9] | V. De Pauw;A. Collin;W. Send.Deposition rates during the early stages of pyrolytic carbon deposition in a hot-wall reactor and the development of texture[J].Carbon: An International Journal Sponsored by the American Carbon Society,200614(14):3091-3101. |
| [10] | M.Guellali;R.Oberacker;M.J.Hoffmann;W.G.Zhang;K.J.Huttinger.Textures of pyrolytic carbon formed in the chemical vapor infiltration of capillaries[J].Carbon: An International Journal Sponsored by the American Carbon Society,20031(1):97-104. |
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