比表面积与入口气体分压对热解炭微观结构影响的数值模拟研究

doi:10.15541/jim20150528

无机材料学报 ›› 2016, Vol. 31 ›› Issue (12): 1327-1334.DOI: 10.15541/jim20150528

比表面积与入口气体分压对热解炭微观结构影响的数值模拟研究

许健¹, 汤哲鹏², 彭雨晴², 顾传青¹, Koyo Norinaga³, 李爱军²

(1. 上海大学理学院, 数学系, 上海 200444; 2. 上海大学材料复合及先进分散技术教育部工程中心, 上海 200444; 3. 九州大学材料化学与工程学院, 日本福冈 816-8580)

收稿日期:2015-10-26 修回日期:2016-03-22 出版日期:2016-12-16 网络出版日期:2016-11-23
作者简介:许健(1991–), 男, 硕士研究生. E-mail: sky3273626@163.com
基金资助:
基金项目:国家自然科学基金(11371243);上海市教委重点创新项目(13ZZ068);上海市科委重点项目(S30104);教育部博士点基金(20113108120019);航空基金(2013ZFS6001);上海市科委项目(13521101202)

Numerical Simulation for Influence of Surface Area/Volume Ratio and Inlet Gas Pressure on Pyrolytic Carbon Texture

XU Jian¹, TANG Zhe-Peng², PENG Yu-Qing², GU Chuan-Qing¹, KOYO Norinaga³, LI Ai-Jun²

(1. Department of Mathematics, College of Sciences, Shanghai University, Shanghai, 200444, China; 2. Research Center for Composite Materials, Shanghai University, Shanghai, 200444, China; 3. Kyushu University, Institute for Materials Chemistry and Engineering, Fukuoka, Fukuoka-ken, 816-8580, Japan)

Received:2015-10-26 Revised:2016-03-22 Published:2016-12-16 Online:2016-11-23
About author:XU Jian. E-mail: sky3273626@163.com
Supported by:
National Natural Science Foundation of China (11371243);Innovation Major Project of Shanghai Municipal Education Commission (13ZZ068);Key Disciplines of Shanghai Municipality (S30104);Doctoral Fund of Ministry of Education(20113108120019);ARF(2013ZFS6001);SSTC (13521101202)

摘要/Abstract

摘要：

本研究在炭/炭复合材料热解炭基体织构形成与转化的模型基础上, 基于石墨微晶片层的表面结构特点, 建立了蜂窝结构的热解炭沉积表面几何模型, 并运用Monte Carlo方法模拟了在等温等压化学气相渗透(CVI)过程中热解炭基体沉积的动力学过程, 研究了预制体比表面积(A_S/V_R)和入口气体分压对热解炭微观结构的影响。通过数值模拟并结合已公开发表的实验结果发现, 在CVI工艺过程中一定的压力条件下, 通过控制A_S/V_R可以获得不同织构的热解炭, 预制体的A_S/V_R存在两个临界值, 靠近反应器入口处的临界值为1.45 m^-1和8.9 mm^-1, 靠近反应器出口处的临界值为0.3 mm^-1, 当A_S/V_R处于这两个临界值之间时, 系统主要沉积高织构热解炭; 在同一A_S/V_R且压强小于30 kPa的条件下, 通过控制反应气体压强的值也可以得到不同织构的热解炭, 并且压强也存在一个临界值, 当压强大于这个临界值时, 系统主要沉积高织构热解炭。

关键词: Monte Carlo模拟, 炭/炭复合材料, 热解炭, 蜂窝结构, 比表面积, 入口气体分压

Abstract:

Based on the model of pyrolytic carbon matrix texture formation and transformation in CVI for densification of carbon/carbon composites, a new model was constructed to describe the surface of pyrolytic carbon deposited in a honeycomb structure pores. This new model is related with structure characteristics of graphite microchip. The Monte Carlo method is applied to simulate the pyrocarbon deposition kinetics and to analyze the influence of surface area/volume (A_S/V_R) and gas pressure on the texture of pyrocarbon in the process of isothermal-isobaric chemical vapor infiltration (ICVI). According to the numerical simulation results, under certain conditions of pressure, various textured carbon were obtained by controlling A_S/V_R in CVI process. Between two critical values (1.45 mm^-1and 8.9 mm^-1near the inlet, 0.3 mm^-1near the outlet) of A_S/V_R, the high-textured carbon can be obtained. Moreover, if A_S/V_R is certain value and pressure is less than 30 kPa, pyrolytic medium and high textured carbon texture can be obtained as a result of different pressure in CVI process. There is also a critical pressure value and the high-textured carbon can be obtained if the pressure is greater than the critical value.

Key words: Monte Carlo simulation, carbon/carbon composites, pyrolytic carbon, honeycomb structure, surface area/volume, inlet gas pressure

中图分类号:

TQ174

许健, 汤哲鹏, 彭雨晴, 顾传青, Koyo Norinaga, 李爱军. 比表面积与入口气体分压对热解炭微观结构影响的数值模拟研究[J]. 无机材料学报, 2016, 31(12): 1327-1334.

XU Jian, TANG Zhe-Peng, PENG Yu-Qing, GU Chuan-Qing, KOYO Norinaga, LI Ai-Jun. Numerical Simulation for Influence of Surface Area/Volume Ratio and Inlet Gas Pressure on Pyrolytic Carbon Texture[J]. Journal of Inorganic Materials, 2016, 31(12): 1327-1334.

图/表 12

图1 热解炭沉积反应简图

Fig. 1 Simplified reaction scheme for pyrocarbon deposition. GP: gaseous precursors; L: linear small molecule hydrocarbons; A: small aromatic hydrocarbons; PAHs: polycyclic aromatic hydrocarbons

表1 热解炭沉积和织构形成非均相表面反应动力学模型参数设定

Table1 Kinetic parameters of the heterogeneous surface reaction mechanism for carbon deposition and texture formation

k₁/(mol^-1·m³·s^-1)	k₂/s^-1	k₃/(mol^-6·m¹⁸·s^-6)	k₄/s^-1	k₅/s^-1	k₆/s^-1	k₇/(mol^-1·m³·s^-1)
1×10	5×10^-2	4.81×10⁴	2×10^-1	3.86×10^-2	6.57×10^-2	8.96×10

图2 热解炭微观结构的蜂窝结构几何模型点阵图

Fig. 2 Hexagon geometry model diagrammatic sketch for the microstru cture of pyrocarbon

图3 基体表面主要反应物在单位MCS时间内的发生速率 (次/MCS)

Fig. 3 Rates of events happened per MCS on the surface of carbon matrix (times/MCS)

表2 靠近进气口 (No.2) 不同AS/VR值下反应器中C2和Cb的摩尔分数

Table 2 Mole fraction profiles of C2 and C6 in the reactor near the intlet (No.2) with variation of AS/VR

A_S/V_R	0.31	0.79	1.6	2	3.2	4	5	6	7.4
C₂	0.094	0.065	0.033	0.034	0.031	0.025	0.022	0.015	0.015
C₆×100	0.28	0.32	0.41	0.45	0.51	0.50	0.43	0.37	0.31

表3 靠近出气口处 (No.8) 不同AS/VR值下反应器中C2和Cb的摩尔分数

Table 3 Mole fraction profiles of C2 and C6 in the reactor near the outlet (No.8) with variation of AS/VR

A_S/V_R	0.31	0.79	1.6	2	3.2	4	5	6	7.4
C₂	0.12	0.083	0.065	0.062	0.062	0.061	0.061	0.06	0.059
C₆×100	1.12	0.85	0.79	0.78	0.78	0.78	0.77	0.76	0.71

图4 靠近进气口处(No.2)和靠近进气口处(No.8)采样区域归一化C2浓度随AS/VR变化曲线(a)和这两处R值随AS/VR变化曲线

Fig. 4 C2 normalized concentration profiles (a) and R (b) as a function of [AS/VR] ratio at the No.2 sampling area (near the inlet) and the No.8 sampling area (near the outlet)

表4 靠近进气口的No.2采样区域C2归一化浓度a和对应的实验模拟突变点r0

Table 4 Values of C2 normalized and the relative simulated catastrophe points at No.2 sampling area (near the inlet)

a	1	0.691	0.564	0.543	0.479	0.468	0.404	0.372	0.372
r₀	0.156	0.086	0.062	0.058	0.049	0.047	0.046	0.041	0.041

表5 靠近出气口的No.8采样区域C2归一化浓度a和对应的实验模拟突变点r0

Table 5 Values of C2 normalized and the relative simulated catastrophe points at No.8 sampling area (near the outlet)

a	1	0.692	0.525	0.517	0.517	0.508	0.508	0.500	0.492
r₀	0.156	0.086	0.057	0.056	0.056	0.055	0.055	0.054	0.053

图5 靠近进气口的No.2采样区域和靠近出气口的No.8采样区域R和r0随AS/VR值的变化

Fig. 5 R and r0 profiles as a function of [AS/VR] ratio^(a) No.2 sampling area (inlet); (b) No.8 sampling area (outlet)

图6 AS/VR为0.79 mm-1时, No.2和No.8采样区R和r0随压强的变化

Fig. 6 R and r0 profiles as a function of pressure^(a) No.2 sampling area (inlet); (b) No.8 sampling area (outlet); [AS/VR]=0.79 mm-1

图7 AS/VR为3.2 mm-1时, No.2和No.8采样区域R和r0随压强的变化

Fig. 7 R and r0 profiles as a function of pressure^(a) No.2 sampling area (inlet); (b) No.8 sampling area (outlet). [AS/VR]=3.2 mm-1

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比表面积与入口气体分压对热解炭微观结构影响的数值模拟研究

Numerical Simulation for Influence of Surface Area/Volume Ratio and Inlet Gas Pressure on Pyrolytic Carbon Texture

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