铝电解用TiB2基复合阴极抗渗透机制及微结构调控研究

TiB2 based wettable composite cathodes can help to decrease the energy and resources consumption as well as environmental load, so they have become one of the key materials using for the inert aluminum electrolysis system. However, some problems such as easy breakage and short service life make the development of these types of materials encounter bottlenecks. Thus, basic research about the mechanisms of penetration resistance and the strengthening mechanisms of the microstructure need to be carried out necessarily. Through quantified characterization for the formation process of microstructure referring to the binder and TiB2 based cathode, this project will establish the relationship among coking carbon of binder(coking binder), microstructure of composite cathode(interface structure) and corrosion resistance of cathode; Through the research about the migration and penetration behavior of the alkali metals and alkaline-earth metal, scientific character of the interaction between cathode and alkali metals(alkaline-earth metal) under the condition of electrolysis will be known and the relationship between the penetration of alkali metals(alkaline-earth metal) and microstructure as well as corrosion resistance of cathode(interface structure) will be indicated. Subsequently, basic principle about integrated design of TiB2 based cathode referring to corrosion-resistant structure and performance will also be put forward. On this basis, the components and the microstructure(interface structure) will be optimized and the targeted design of corrosion-resistant structure of TiB2 based wettable composite cathodes will be achieved through the regulation and control of the microstructure of coking binder and composite cathode as well as the synergistic effect of adulterant.

TiB2基可润湿性阴极有助于降低电解铝工业的能源消耗、资源消费及环境负荷，成为惰性铝电解系统的关键材料之一，然而易破损、使用寿命短等问题使该材料的发展遭遇瓶颈，因此，针对该材料开展抗渗透机理及微结构增强机制的基础研究十分必要。本项目通过对粘结剂及TiB2基阴极微结构形成过程的量化表征及微结构特性的分析，建立粘结剂结焦（粘结焦）结构，复合阴极微结构（界面结构）及阴极耐腐蚀性能之间的关系；通过研究碱金属及碱土金属在阴极中的渗透迁移行为，认识电解条件下碱金属及碱土金属与阴极相互作用的科学特征，揭示碱金属及碱土金属的渗透与阴极微结构（界面结构）及其耐腐蚀性能之间的关系，提出TiB2基阴极抗渗透耐腐蚀结构与性能一体化设计的依据。在此基础上，优化设计材料的组分，组织及其微结构（界面结构），通过对粘结焦和复合阴极微观结构的调控及掺杂物的协同作用，实现TiB2基可润湿性阴极抗渗透耐腐蚀结构的设计。

TiB2基可润湿性阴极是惰性铝电解系统的重要组成部分，同时也是实现铝电解技术“二次革命”的关键材料。本项目采用微观与宏观相结合的思路，通过对黏结剂及复合阴极微结构形成过程的表征以及微结构特性的分析，结合碱金属及碱土金属在阴极中的渗透迁移行为，建立结构与性能之间的关系，提出TiB2基可润湿性复合阴极抗渗透耐腐蚀结构与性能一体化设计的依据。在此基础上，通过黏结焦和复合阴极微观结构的调控及掺杂物的协同作用，实现TiB2基可润湿性阴极抗渗透耐腐蚀结构的设计。项目的研究取得了以下研究结果：（1）TiB2基复合阴极微结构及抗渗透耐腐蚀性能与所使用的黏结剂碳化后的微结构及性能密切相关，同时也受服役环境的影响。黏结剂为熔盐电解质及碱金属的渗透提供了通道，并首先遭受侵蚀并引起阴极的失效。（2）碱金属电极行为的研究表明，电解过程中，由于极化的作用，部分K、Na会与Al发生共析出，但所生成的插层化合物，其氧化电势差异较大，C-Na插层化合物会被优先氧化，客观上使得C-K插层化合物表现出了较强的稳定性，并引起阴极的腐蚀破损。（3）掺杂物对于改善黏结剂的微结构，提高黏结剂的抗渗透耐腐蚀性能作用明显。其主要是通过优化黏结剂结焦碳的孔径分布，降低孔隙率以及阻挡电解质渗透来实现，并最终提高TiB2基复合阴极的性能。（4）复合阴极中骨料组分对于TiB2基复合阴极的抗渗透耐腐蚀性能有影响。这主要与骨料内部层状结构的完好程度有关，即受材料热解活化能高低的影响。乱层石墨结构成分越多，阴极的抗渗透耐腐蚀性能便会越差。