液/固晶面润湿性实验与模拟研究方法

Experimental and Simulation Methods on Liquid/Solid Interface Wettability Considering Crystal Surfaces

液/固晶面润湿问题在钎焊、金属基复合材料液相法制备等领域都有着重要研究意义。研究发现,固体晶面结构会显著影响液/固界面润湿性。研究液体在固体特定晶面上的润湿行为,对于深入理解润湿过程及更有针对性地改善材料液/固界面润湿性具有重要意义。目前研究液/固晶面润湿性的实验测量方法主要为座滴法,然而该方法针对强弱界面结合体系的测量结果对实验条件均较敏感,且受限于特定晶面基板是否容易制备,因此仍不能在液/固晶面润湿性的研究中推广采用。微观模拟方法不仅可以建立不同晶面的固体结构,同时有效避免了实验条件的影响,故对预测实验结果具有独特的优势。用于液/固晶面润湿性研究的微观尺度模拟方法包括分子动力学、第一性原理计算以及Ab-initio分子动力学。目前分子动力学方法主要应用于强界面结合的金属/金属体系,通过模拟实际物理条件下的熔化和润湿过程,可研究润湿性、界面反应、铺展动力学以及探究温度对润湿的影响,然而有效势函数的缺乏限制了该方法在其他体系的推广,且势计算结果的准确性与可靠性严重依赖势函数的参数选择。电子尺度的第一性原理计算可探究弱界面结合体系中不同晶面取向下润湿性差异的根本原因、强界面结合体系中界面微观构型对初始润湿性的影响、反应后熔体/反应产物界面成键特点以及平衡润湿性差异,但是该方法的缺点是计算原子个数有限,需要绝对零度的模拟温度。Ab-initio分子动力学是前两种方法的结合,虽然不依赖于势函数的参数选择,但是仍受限于计算原子个数和模拟效率。本文从每种方法的基本原理、实验操作或模型构建及优缺点等三个方面,阐述了弱/强界面结合体系中液/固晶面润湿性研究进展,并对三种微观模拟方法的未来改进方向进行了展望。

Liquid/solid interface wettability plays an important role in brazing,liquid-phase preparation of metal matrix composites and other fields.Some literatures have indicated that the wettability can be affected by crystal surfaces of solid.Therefore,studying the wetting behavior of liquid on different crystal surfaces is of great importance for an in-depth understanding of the wetting process,and also tailoring,improving the wettability more specifically.Experimental measurements for studying the wettability of the liquid/solid interface considering different crystal surfaces are mainly sessile-drop methods,which are limited by availability of the substrate with a specific crystal surface and susceptible to environmental factors for both of weakly-bonding interface and strongly-bonding interface.Thus it has not yet been widely promoted and applied.Micro-scale simulations can not only establish solid models with different crystal surfaces,but also avoid the environmental sensitivity of experimental measurements,and thus they have distinct advantages in predicting experimental results.Micro-scale simulation methods used for liquid/solid interface wettability research include molecular dynamics,first-principles calculations and Ab-initio molecular dynamics.At present,molecular dynamics simulations are mainly applied to strongly-bonding metal/metal system.It can simu-late melting and wetting process at realistic physical conditions to study wettability,interfacial reaction,spreading kinetics,and also investigate effect of temperature on wettability.However,the lack of effective potential function limits its application and the accuracy and reliability of calculation results are dependent on parameter selection of potential funciton.Electronic-scale first-principles calculations can explain the wettability difference under different crystal surface orientation in weakly-bonding systems in depth,and analyze the influence of interfacial microstructure on initial wettability,explore the bonding characteristics of the melt/reaction product interface and explain difference of equilibrium wettability in strongly-bonding systems.However,the obvious drawback of this method are the limited atoms for calculation and simulation temperature of 0 K.Ab-initio molecular dynamics simulation,as a combination of molecular dynamics and first-principles calculations,is independent of potential function,but is still limited by the number of atoms and simulation efficiency.In this paper,the research progress on liquid/solid interface wettability considering crystal surfaces for both of weakly-bonding interface and strongly-bonding interfaces is reviewed from three aspects,including basic principles,experimental methods or model construction,as well as advantages and disadvantages of each method.The outlooks are also proposed.