碳纤维低温晶化与表面涂层的原位生长研究

One of effective methods by which the performance of carbon fibers and interface between them and matrix can be improved is having them crystallized and/or preparing coating with a good quality on their surface. Here, a new "electrochemical technology" was proposed, where carbon fiber crystallization can be carried out at ambient temperature and pressure. The coating can be grown in-situ on their surface by adjusting such processing parameters as electrolyte, current density, and reaction time. The detailed study focused on inert electrolyte, multi-component electrolyte, additives and electrochemical process so as to effectively control preparing process and ensure the quality of products. The chemical / phase composition and surface chemical state of carbon fibers were characterized by XRD, XPS, and Raman, respectively. AFM, TEM, HRTEM, and SEM images revealed the characteristics of crystallized carbon fibers and their possible crystallizing defects, and indicated the difference between fibers and coating in microstructure. Our study also explained theoretically the real cause of the low temperature crystallization and phase transformation mechanism of carbon fibers, and proposed the growing model for new phases and their substable condition in liquid environment. In addition, the reaction mechanism, thermodynamics and kinetics of coating formation were also analyzed in detail.

碳纤维结晶化以及在其表面制备性能良好的表面涂层，是提升碳纤维综合性能，改善与复合材料基体间界面结合的有效途径。本项目提出了一种新型的"电化学"处理工艺，可在常温常压条件下，使碳纤维结晶化。通过调节电解液组分、电流密度、反应时间等工艺参数，可在碳纤维上原位生成表面涂层。分别针对惰性电解液、多组元电解液、添加剂以及"电化学"过程等进行了详尽研究，可实现工艺过程及产物性能的有效控制。采用XPS，XRD，Raman等分析检测手段，对产物的化学/矿相组成、表面化学状态等进行了分析表征。AFM，TEM，HRTEM，SEM等微观分析结果，揭示了"电化学"条件下低温晶化碳纤维的结晶特点、微结构缺陷特征以及涂层与纤维内部结构的主要差异。从理论上解释了碳纤维"低温晶化"的本质、相转变机制，提出了液相环境下新相生长模型及介稳条件，分析研究了扩散过程及化学反应机制，涂层形成的热力学条件及动力学过程等。

碳纤维结晶化以及在其表面制备性能良好的表面涂层，是提升碳纤维综合性能，改善与复合材料基体间界面结合以及碳纤维功能化的有效途径。本项目提出了一种新型的“电化学”处理工艺，可在常温、常压环境条件下，使碳纤维结晶化。优化工艺参数，可原位生成金刚石微晶，在理论或应用上，均具有重要的科学价值及理论指导意义。通过调节电解液组分、电流密度、反应时间等工艺参数，可在碳纤维上原位生成多种表面涂层（(a) ZnO涂层原位生长，(b) SiO2纳米线原位生长，(c) TiO2 针状微晶原位生长，(d) TiO2 片状微晶原位生长，(e) 3 D 网状结构碳纳米管原位生长）。分别针对单组元电解液、多组元电解液、添加剂以及“电化学”过程等进行了详尽研究，可实现工艺过程及产物性能的有效控制。研究工作具有独创性，揭示了异质涂层原位生长的共性特征以及无金属催化剂添加时碳纳米管的生长机制，具有重要的科学意义。采用XPS，EDS、XRD，Raman等分析检测手段，对产物的化学/矿相组成、表面化学状态等进行了分析表征。TEM，HRTEM，SEM等微观分析结果，揭示了“电化学”条件下低温晶化碳纤维的结晶特点、微结构缺陷特征以及涂层与纤维内部结构的主要差异。研究揭示了碳纤维“低温晶化”的本质，并提出了碳纤维中金刚石相原位形成机制，尤其强调了电解液的淬冷效应；依据该工艺方法特点，提出了碳纤维表面SiO2纳米线及3D网状结构碳纳米管的原位生长机理。