石墨烯腐蚀促进机制及氟化改性制备高性能导热防腐涂层研究

Graphene with ultrathin 2D structure, superior thermal conductivity and impermeatability displays unique advantages for applications in corrosion protection of heat transfer equipments. However, the corrosion promotion effect of graphene hinders their practical applications in corrosion protection. This work plans to explore a new strategy to enhance the corrosion resistance of graphene coating by combining the molecular modification technique and graphene-polymer composite process. Firstly, the influences of electrical and electrochemical properties on the corrosion promotion effects are systematically investigated in order to elucidate the corrosion promotion mechanism of graphene. Previous work has proved that the corrosion promotion effect is closely related to electrical conductivity and electrochemical reactivity. Consequently, fluorination as a molecular modification strategy is introduced to control the electrical conductivity and electrochemical reactivity of graphene.This work aims to detailedly illustrate the close relationship among the bonding structure, electrochemical reactivity and electrical conductivity of graphene, thus giving the effective measures to inhibit this effect from the molecular aspect. Finally, the coating structure and process parameters are optimized to obtain corrosion resistant composite coating with high thermal conductivity and hydrophobility for enhancing the heat transfer process. It not only provides a theoretical base for developing superior anticorrosive graphene coating with thermal conductivity, but also is of great significance to solve the corrosion problem during heat energy reclaim.

石墨烯超凡的不可渗透性能、优异的热学性质及二维结构，使其在换热设备表面防腐蚀涂层开发中具有得天独厚优势，然而，石墨烯的腐蚀促进效应却极大地限制了其防腐作用的发挥。因此，本课题拟将分子改性技术与石墨烯-高分子复合材料制备方法相结合，探索一条制备高性能导热石墨烯防腐涂层的新途径。首先，通过系统考察石墨烯电学和电化学性质对腐蚀促进效应的影响，揭示石墨烯腐蚀促进机理，前期研究结果已经初步证明了这种影响关系的存在。然后，借助分子改性技术，通过氟化改性调控石墨烯电导率和电化学活性以抑制其腐蚀促进效应，通过深入解析氟化石墨烯键结构与电化学活性及电导性之间的关联机制，从分子层面找到克服石墨烯腐蚀促进效应的措施。最后，优化涂层结构及工艺，赋予其滴状冷凝强化传热功能，制备高性能导热防腐功能涂层。本课题的实施不仅可为高性能导热防腐蚀涂层的开发提供理论依据，并且对能量回收过程中腐蚀难题的解决具有重要实际意义。

石墨烯具有优异的耐分子渗透性能和超高的导热系数，被认为是理想的换热设备防腐涂层填料。本课题针对石墨烯存在腐蚀促进活性这一弊端，研究了石墨烯的构效关系，揭示了石墨烯的腐蚀促进活性机理；通过氟化分子改性手段，开辟了一条抑制石墨烯腐蚀促进活性的新思路；进一步优化涂层的结构，协同提高涂层的防腐、导热及强化冷凝传热性能，突破了烟气余热深度回收中的技术瓶颈，完成了工程示范，具有重要的推广价值和前景。主要研究内容和结论如下：.(1)从石墨烯的表面微结构、载量、表面键结构、分散性等方面研究了石墨烯的屏蔽防腐蚀性能和电化学腐蚀促进活性。研究发现少量石墨烯可以增加涂层缺陷的防腐性能，然而过多的反而促进缺陷处腐蚀；随着改性程度的增加腐蚀促进活性加强，进一步越过“最优值”1.4at%Si，随着改性程度的增加腐蚀促进活性减弱。.(2)提出了全氟改性和部分氟化改性两种策略用于抑制石墨烯的电化学腐蚀促进活性，从电学（能带结构）和电化学（氧还原反应活性）两个方面深刻揭示了石墨烯的腐蚀促进活性机理。氟化石墨烯在继承石墨烯优异的耐渗透性能的同时，可分别通过控制导电性和氧还原反应(ORR)活性两个方面抑制石墨烯的腐蚀促进活性。对于全氟化改性石墨烯，其机理是氟原子的引入，导电性显著下降，抑制了氟化石墨烯与铜之间的电偶腐蚀，进而表现出优越于石墨烯的防腐蚀性能；对于部分氟化石墨烯，氟原子的引入降低了ORR电催化活性，提高了阴极去极化电阻，从而抑制石墨烯的电化学腐蚀促进活性。.(3)通过优化涂层的结构及制备工艺，制备出了多巴胺改性石墨烯/环氧复合涂层，当掺杂3 wt%多巴胺改性石墨烯时，涂层防腐效果最优，热导率由0.18 W/m·K提升至0.52 W/m·K，兼顾了导热和防腐性能。进一步开发了氟化石墨烯多功能复合涂层，具有优异的防腐、导热和疏水性能的同时，强化了冷凝传热性能，冷凝传热系数提高至1.30倍。其中石墨烯导热防腐涂层已初步应用在烟气余热回收换热设备表面防腐工程示范项目中，提高了燃料的利用效率，实现了节能、节水和减排。