Collaborative Research: Wetting of Liquid Metals on Rough Surfaces

1235757 /1234581 PI：Sekulic /Mesarovic液体在固体表面上的铺展在自然界中是普遍存在的，并且是许多工业过程的关键方面，例如低温钎焊、高温钎焊、除冰、有机液体吸收等。例如，在钎焊/钎焊的情况下，与被连接材料的不同润湿性能和铺展过程中温度的可能变化相结合的处理的紧凑时间安排，需要精确控制，这又需要定量预测工具。 预测这种复杂流动的主要困难包括：（1）铺展表面的粗糙度，（2）液体/熔体和基底之间的化学反应，以及（3）三线（固体、液体和蒸汽/气体相遇的点的轨迹）传播的物理机制的模型不足。 该项目将通过以下方式整合实验和建模策略：（i）在具有特征的原始表面和设计表面上进行实验，并对三线运动进行现场监测和测量，（ii）基于扩散界面的理论和建模方面的进展（相场）模型，能够表示相和化学反应前沿的传播，以及三线运动的扩散性质，以及，（三）模型与实验相结合。 真实的原位监测在微尺度上围绕三线的扩散将是关于液体前沿传播的动力学的数据的来源。 为了实现项目目标，反应性和非反应性扩散的相场建模将在一个通用的计算有限元框架内实施，从而能够研究具有不同几何形状的各种问题。 主要的实验挑战与三线的快速演化和反应性底物的存在有关。 所需的时间分辨率将通过开发热台显微镜技术来实现，该技术用于原位监测移动的液体前沿和接触角的动态。 化学反应的抑制将通过在液态金属扩散之前形成金属间化合物来实现。 主要的建模挑战包括：（a）将控制非反应性模型的三线运动的表面扩散动力学实现到有限元框架中以模拟粗糙表面，以及（B）将组合的液-气相场和化学反应相场实现到有限元框架中。与工业和自然过程有关。 该研究的变革性质是，它将导致通过表面改变和液体系统和固体基质的选择来有效控制润湿的能力。 这将使依赖于液体扩散的工业过程和功能依赖于润湿的产品的合理设计成为可能。

1235757 / 1234581PI: Sekulic / MesarovicSpreading of liquids over solid surfaces is ubiquitous in nature and is the key aspect of many industrial processes, such as low temperature soldering, high temperature brazing, de-icing, organic liquid imbibing, etc. For example, in the case of brazing/soldering, the tight time scheduling of the processing combined with dissimilar wetting properties of materials being joined and a possible variability of temperature during spreading, require a precise control, which in turn requires quantitative prediction tools. The major difficulties in predicting such a complex flow include: (1) roughness of the spreading surface, (2) chemical reactions between the liquid/melt and the substrate, and, (3) inadequate models of the physical mechanism by which the triple line (a locus of points where solid, liquid and vapor/gas meet) propagates. This project will integrate experimental and modeling strategy through: (i) experiments on characterized virgin and designed surfaces, with in situ monitoring and measurements of the triple line motion, (ii) advances in theory and modeling based on the diffuse interface (phase-field) models, capable of representing propagation of phase- and chemical reaction fronts, as well as the diffusive nature of the triple line motion, and, (iii) integration of modeling and experiments. Real time in situ monitoring of the spreading at the micro scale around the triple line will be the source of data on kinetics of the liquid front propagation. To achieve projects objectives, the phase-field modeling for reactive and non-reactive spreading will be implemented within a versatile computational finite element framework, thus enabling studies of variety of problems with different geometries. The major experimental challenges are related to the fast evolution of the triple line and the presence of reactive substrates. The required time resolution will be achieved by developing hot stage microscopy techniques for in situ monitoring of the moving liquid front and the dynamics of the contact angle. Suppression of a chemical reaction will be accomplished by formation of intermetallics prior to spreading of a liquid metal. The major modeling challenges include: (a) implementation of the surface diffusion kinetics governing the motion of the triple line for the non-reactive model into the finite element framework to model rough surfaces, and, (b) implementation of the combined liquid-gas phase-field and the chemical reaction phase-field into the finite element framework.The impact of this investigation will be felt in a broad set of applications, related to industrial and natural processes. The transformative nature of the research is that it will results in the ability to effectively control wetting by surface alterations and the selection of liquid system and solid substrates. This will enable rational design of industrial processes which depend on liquid spreading, and products whose function depends on wetting.