气液固三相接触线介尺度结构和传递的模型与机制研究

This proposal is in response of the mesoscale issue “material structure or temporal-spatial evolution of surface/interface between the scales of molecules and particles (including discrete units such as bubbles and drops)” published by the Main Research Program (MRP) at NSFC. The gas-liquid-solid three-phase line is the critical region of reaction and diffusive transport in the multiphase reaction systems. It is a mesoscale structure which scale lies in between the molecules/atoms and macroscopic materials. Distinguished by the molecular forces existed in the liquid phase, the mesoscale structure can be divided into three units, namely intrinsic meniscus region, thin liquid film region and adsorption region. The inherent mechanism of formation and transport of the mesoscale structure is mainly controlled by the relationship between disjoining pressure and thickness of the thin film and is influenced by the effects of wall and interface. We propose in this proposal to further investigate the controlling mechanisms and their coupling relations in the mesoscale structure based on our previous researches, and to modify the continuum model for the thin liquid film using the results of molecular simulation and experimental measurement of the disjoining pressure and thickness of the thin film region. A multiscale coupling model of the mesoscale structure will be constructed utilizing the continuity condition for each of the adjacent units. The calculation based on this model is expected to explain the mechanisms of formation and transport of the mesoscale structure. This understanding will help provide theoretical basis and technical support for measurement and controlling of the mesoscale structure during the processes of multiphase reactions.

本申请重点针对“分子尺度到颗粒（包括气泡、液滴等离散单元）尺度间的材料结构或表界面时空尺度”的介尺度问题。气液固三相接触线是多相反应过程中反应和扩散传递的关键区域，是介于分子/原子尺度到宏观材料尺度的介尺度结构，依据液相分子受力机制的不同可划分为本征弯月面区、薄液膜区及吸附膜区等三个单元。介尺度结构的形成和传递机制，受薄液膜区分离压与厚度函数关系的控制，以及壁面效应和界面效应等因素的影响。本申请拟在前期研究基础上，针对这些控制机制及其耦合关系，利用对薄液膜区分离压与厚度函数关系的分子模拟和实验测量，建立适用于薄液膜区的连续介质修正模型。利用各单元的连续性条件，建立介尺度结构的多尺度耦合模型，通过计算阐释其形成机理及其对传递过程的影响，为多相反应过程介尺度结构测量和调控提供理论和技术支撑。

本项目重点针对“分子尺度到颗粒尺度间的材料结构或表界面时空尺度”的介尺度问题。接触线是多相反应过程中介于分子/原子尺度到宏观材料尺度的介尺度结构，可划分为本征弯月面、薄液膜及吸附膜区；其形成和传递机制，受分离压与厚度关系的控制，及壁面效应和界面效应等影响。本项目获得如下重要结果：(1) 针对液滴蒸发、混合及化学反应过程，实验研究了介尺度结构的演变和传递特征；结合Scheludko腔体法，研究了混合体系介尺度结构分离压与液膜厚度关系，为进一步探究混合和化学反应时介尺度结构演变和传递奠定基础。(2) 采用分子模拟，通过混合体系分离压的结果验证，获得介尺度结构分离压与厚度函数关系。(3) 分别对薄液膜和本征弯月面区采用分子力学和连续介质力学的方程描述，依据重叠区边界条件的连续性，实现多尺度耦合模型的建立和求解。(4) 运用多尺度耦合模型，结合分子模拟，研究传递量的主要控制机制，及液相物性、壁面效应、界面效应和组分等因素对介尺度结构的影响，为多相反应过程介尺度结构研究提供理论和技术支撑。项目研究按计划进行，执行结果主要反映在己发表的14 篇期刊论文及参加的5场国际学术会议，培养研究生10名。