电流作用下电子/离子导电系固－液界面的润湿、传质与结构演变

The wetting and atomic interactions at solid-liquid interface at high temperatures are usually met with in the course of materials manufacturing and processing and thus are widely concerned and regarded as a basic scientific issue. The conventional researches pay attentions to the wetting characteristics and interfacial chemistry of the materials or the systems, seldom conceiving of the effect of introduction of an external field or source. In the light of the experimental fact of the changes in the atomic transfer and reaction behavior by applying a direct current (DC) as well as a triune relationship of wetting - mass transfer - microstructural evolution, we proposed in this project an academic thought of the wettability regulation by DC. We intend to use a novel and distinct wettability testing system by passing a DC through a sessile drop during the experiment. By selecting representative material systems with either electronic or ionic conduction, we are to probe into the wetting, mass transfer and reaction behaviors at the solid-liquid interface under the effect of DC and the influences of various factors such as current intensity, polarity, temperature, alloying composition and crystallographic orientation. The purposes are to clarify the atomic interaction laws and the microstructural evolution mechanisms at the solid-liquid interface, to establish the inherent relationships between wetting dynamics, mass transfer dynamics and reaction dynamics, to put forward physical models of the wetting at the solid-liquid interface under the effect of DC, and finally to disclose the wetting mechanisms. The research results are expected to provide new ideas for the design and regulation of the interfaces in the materials manufacturing and processing as well as to provide important guidance and references to the control of the material serving behaviors under the condition of applying a current and the joining of advanced materials.

高温下固－液界面的润湿及原子间的交互作用是材料制备与加工过程中经常涉及、且广受关注的基础科学问题。传统的研究专注于材料或体系本身的润湿特征和界面化学，而很少考虑外场或外源引入的影响。本项目基于通电改变原子传质和反应行为的实验事实以及润湿－传质－结构演变三位一体的构架关系，提出利用电流调控界面润湿的学术思想。实验上，拟采用一种新型独特的电流耦合座滴的润湿测试系统，选择以电子/离子导电的典型材料体系，探索电流作用下固－液界面的润湿，传质和反应行为以及电流强度、极性、温度、合金成分、晶体取向等因素的影响，阐明电流作用下界面原子的交互作用规律和微结构的演化机制，建立润湿动力学与界面传质及反应动力学之间的内在联系，提出电流作用下固－液界面润湿的物理模型，最终揭示润湿机制。研究结果将为材料制备和加工过程中界面的设计和调控提供新思路，并为通电条件下材料服役行为的控制和先进材料的连接提供重要指导和参考。

高温下固－液界面的润湿及原子间的交互作用是材料制备与加工过程中经常涉及、且广受关注的基础科学问题。传统的研究专注于材料或体系本身的润湿特征和界面化学，而很少考虑外场或外源引入的影响。本项目提出利用电流调控界面润湿的学术思想，并通过搭建一种新型独特的电流耦合座滴系统和三明治反应偶系统，深入细致地研究了电流作用下金属/金属和金属/ZrO2界面的润湿、传质和反应行为，以及电流强度、极性、温度、合金成分、晶体取向等因素的影响，阐述了相关机制，形成了如下结论：(1)在金属表面洁净(无氧化膜)的情况下，无论是惰性，还是溶解或反应型的金属体系，电流的施加对润湿性几乎没有影响，但却能够显著促进表面存在氧化膜的金属体系的润湿。 (2)电流显著促进金属体系固液界面的传质。其中，电迁移和热效应引起的Marangoni对流扮演重要角色。发现电流驱动下金属基板的溶解激活能远低于不通电时的激活能。而且，当电流强度达到一定阈值时，界面容易形成一些异常相。(3) 在合金体系中，证实在熔体内存在Marangoni对流的情况下，电迁移力不能通过驱动合金组元的选择性分离来改变合金熔体/金属固体之间的润湿。(4) 在金属/ZrO2(YSZ)体系中，施加微电流可以显著促进润湿。阐述了其主导机制为界面生成非计量比的ZrO2-x和游离出活性的Zr原子。而对于氧溶解度大的Ag, Cu熔体，还存在电流驱动氧在固液界面的富集降低界面能促进润湿的机制。(5) 证实基板晶体取向对电流作用下Al-YSZ的润湿有一定影响，其中(110)晶面的改善作用最显著。(6) 利用微电流轻松实现了Ni-ZrO2，304不锈钢-ZrO2之间的连接，且接合强度高，工艺范围宽；阐述了工艺参数-界面微结构-接头剪切强度之间的内在联系。以上研究成果为材料制备和加工过程中界面的设计和调控提供了新思路，并为通电条件下材料服役行为的控制和先进材料的连接提供了重要指导和参考。