2010
DOI: 10.1016/j.carbon.2009.08.041
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Kinetic modeling of surface reactions involved in CVI of pyrocarbon obtained by propane pyrolysis

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Cited by 53 publications
(65 citation statements)
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“…Lédé and coworkers [17] have conducted a kind of "transient" study but in fact they vary the pyrolysis time through successive experiments and analyse the products after the test and not during the test. Lacroix et al [18] did the same for the formation of pyrocarbon. Consequently, no specific device is used but only common HPLC or MS apparatus.…”
Section: Transient Analysis Of Pyrolysis Products Formationmentioning
confidence: 74%
“…Lédé and coworkers [17] have conducted a kind of "transient" study but in fact they vary the pyrolysis time through successive experiments and analyse the products after the test and not during the test. Lacroix et al [18] did the same for the formation of pyrocarbon. Consequently, no specific device is used but only common HPLC or MS apparatus.…”
Section: Transient Analysis Of Pyrolysis Products Formationmentioning
confidence: 74%
“…以 T700 12K 碳纤维无纬布、网胎为原材料, 采 用正交方式在 X-Y 面循环铺设碳纤维无纬布, 无纬 布间铺设面密度为 44 g/m 2 的网胎层, 达到一定厚 度后, 采用接力针刺技术, 以(18~20)针/cm 2 的针刺 密度将网胎层中的纤维垂直刺入到无纬布间, 形成 长度为 15~17 mm 的 Z 向纤维, 使预制体连接成为 整体, 得到密度为 0.48 g/cm 3 的针刺预制体。根据 Z 向纤维含量估算方法 [11] , 计算出 Z 向纤维含量占比 为 7%~8%, 则相应 X-Y 面纤维含量占比为 92%~93%。 以 C 3 H 6 为碳源气, 在 1~5 kPa 炉压、 900~950 ℃ 条件下对尺寸为 200 mm×200 mm×150 mm 针刺预 制 体 进 行 可 控 化 学 气 相 渗 透 (CVI), 使 其 增 密 至 (1.05~1.15) g/cm 3 工艺的实施。研究表明, 在 C/C 复合材料成型过程 中, 沥青碳与碳纤维直接接触将形成较强的界面结 合 [12][13] 。 本研究中通过低损伤 CVI 工艺 [14] 在纤维束 表面制备涂覆热解碳缓冲层后, 能有效调节沥青碳 与碳纤维的界面性能。随后, 在高压作用下使沥青 充满大孔孔隙, 并利用(60~70 MPa)压力条件下 HPIC 工艺高残碳(残碳率≥89%)特性 [15] , 实现对孔隙的 有效填充和使材料获得极高的致密度。此外, 本研 究 HPIC 工艺条件制备针刺 C/C 喉衬材料的沥青碳 主要为"葡萄串状"镶嵌结构(如图 2 虚线及其放大区 域所示), 已有研究表明镶嵌型结构相对于其它结 构沥青碳具有更好的抗烧蚀性能 [16][17][18] , 这为针刺喉 衬材料的可靠工作提供了重要保障。 图 3 为针刺 C/C 喉衬材料 μ-CT 三维结构及内 部孔隙分布情况。由图 3(a)可以看出, 材料内部孔 隙呈离散态均匀分布, 孔隙间没有相互联通, 表明 材料已经接近工艺致密的极限状态。根据图 3(b)计 算出材料的孔隙率为 4%, 其中小于 10 μm 的孔隙占 70%, 10~20 μm 的孔隙占 28%, 针刺 C/C 复合材料 Fig. 4 Ablation rate at different cross sections of the C/C composites 生的热应力会对界面结合产生显著影响, 甚至使界 面形成裂纹、脱粘等缺陷, 而材料内部微裂纹、孔 洞等缺陷会成为烧蚀薄弱区或始发点 [19][20]…”
Section: 实验方法unclassified
“…Here three types of deposition reactions are considered: [20,22,33] have shown that the deposition rate at zero residence time is larger than zero, both indicating that pyrocarbon could be deposited quickly with methane or its dehydrogenation products, i.e., CH x(x≤4) . CH 3 has been successfully considered as a main reactant in deposition simulations with elementary surface reactions [34][35][36]. Meanwhile, the concentration of methane with or without pyrocarbon deposition is quite different, which will be compared in quantity in the next section.…”
Section: Heterogeneous Reactionsmentioning
confidence: 99%