以丙烯为气源的热解炭的化学气相沉积
文献类型：学位论文
| 作者 | 吴文军 |
| 学位类别 | 硕士 |
| 答辩日期 | 2007-06-04 |
| 授予单位 | 中国科学院过程工程研究所 |
| 授予地点 | 过程工程研究所 |
| 导师 | 张伟刚 |
| 关键词 | 化学气相沉积 化学气相渗透 热解炭 动力学 微观结构 |
| 其他题名 | Chemical vapor deposition of pyrolytic carbon from propylene |
| 学位专业 | 化学工程 |
| 中文摘要 | 在利用化学气相沉积技术制备炭/炭复合材料的工艺中，如何缩短致密化时间以及实现对热解炭基体微观结构的精确控制，一直是从事相关研究和生产的科技人员十分关注的热点课题。本文对丙烯热解炭的化学气相沉积及化学气相渗透过程开展研究，致力于深化对化学气相沉积过程动力学与热解炭显微结构形成规律的认识，为优化工艺，提高产品性能提供依据。 热解炭在堇青石表面的化学气相沉积实验表明：丙烯在850~950℃之间CVD的表观活化能ΔEa大约为345kJ/mol。氢气对动力学的影响有两方面：在气相反应中，少量的(5kPa)氢气加速了丙烯的裂解，大量(15kPa)氢气则又有效抑制芳香化合物的生成，降低沉积速率；在表面反应中，氢原子能够在芳香碳平面边缘形成断裂能很高的C-H键，强烈抑制热解炭的生成。沉积速率的倒数与氢气分压呈线性关系。 丙烯加氢的化学气相渗透过程研究则表明：氢气对渗透过程的影响是其对气相反应和气体扩散共同作用的结果。添加5kPa氢气会加速外层热解炭的沉积；大量氢气虽可有效抑制芳香化合物的生成，但是同时造成总压增大，提高了Thiele模数，阻碍气体向预制体内部的扩散，总体来说对内外一致的化学气相渗透不利。氢气未对热解炭的结构产生明显的影响，各条件下均获得单一的中等织构热解炭。 通过在铁黄表面沉积热解炭并用氢气还原的研究发现催化表面会增大热解炭的沉积速率，降低沉积温度；随着温度的升高，铁黄在CVD过程中逐渐被还原为Fe2O3、Fe3O4、FeO和Fe3C；形貌上也逐渐从针状变为哑铃状和片状。最终在此方法下获得了分散性良好的高纯纳米针状铁粉。 |
| 英文摘要 | In the process of chemical vapor deposition (CVD) for producing carbon/carbon composites, how to achieve a rapid infiltration, to design and control the microstructure of pyrolytic carbon were always the research hotspots concerned. Chemical vapor deposition and infiltration (CVI) of pyrolytic carbon from propylene were studied to understand more details on the kinetics and the microstructures of pyrolytic carbon, which is important to optimize the densification process of C/C composite materials. The results of CVD on the surface of cordierite using argon and hydrogen as carrier gases indicated that the overall activation energy of carbon deposition from propylene at temperatures ranging from 850~950℃ amounts to 345kJ/mol. The influence of hydrogen on the kinetics of CVD was analyzed either: (1) On the gas phase reactions, decomposition of C3H6 was enhanced by a small amount of hydrogen, and the aromatic hydrocarbons were inhibited with increasing hydrogen initial partial pressure; (2) On the surface reactions, carbon deposition was strongly inhibited by the stable carbon-hydrogen surface complexes at the edge atoms of the graphene layers. Reciprocal deposition rates as a function of hydrogen initial partial pressure were obtained. The influence of hydrogen on the kinetics of CVI was studied: (1) Similar effect on the gas phase reactions as to the case of CVD. (2) An increase of total pressure with increasing hydrogen initial partial pressure leads to an increase of “Thiele modulus”, which was unambiguously disadvantageous for a homogeneous infiltration. Hydrogen exhibits ignorable influence on the microstructure of pyrocarbon, all of which show a single layer of medium-textured. CVD of pyrocarbon on the surface of needle-like goethite (FeOOH) was also investigated to obtain a kind of nano sized iron. It was found that pyrocarbon deposited from propylene was formed on the catalytic surface at very low temperature but with a higher deposition rates, goethite was gradually reduced to Fe2O3, Fe3O4, FeO and finally Fe3C with increasing the temperature progressively. The shape of these particles varies from needle-liked to dumbbell and sheet. Pure iron with high aspect ratios and excellent dispersivity was produced after reduction. |
| 语种 | 中文 |
| 公开日期 | 2013-09-13 |
| 页码 | 81 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/1134]  |
| 专题 | 过程工程研究所_研究所（批量导入） |
| 推荐引用方式 GB/T 7714 | 吴文军. 以丙烯为气源的热解炭的化学气相沉积[D]. 过程工程研究所. 中国科学院过程工程研究所. 2007. |
入库方式： OAI收割
来源：过程工程研究所
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