微小纳米流体液滴蒸发特性及其颗粒堆叠沉积微观机理研究

The evaporation and particle stack deposition pattern of small nanofluid droplets have great application potential in many micro/nano systems, such as cooling of microelectronics devices and micro fabrication. With the combined use of theoretical analysis, numerical simulation and experimental exploration, a thorough and systematic investigation will be carried out in this project on the evaporation characteristics of small nanofluid droplets and the microscope mechanism of stack deposition behavior of particles. The main work includes:1) systematically analyzing the influence rules of nanoparticle on the properties of liquid, liquid-gas interface and liquid-solid interface, and revealing the physical mechanism of the influence of nanoparticle on the evaporation characteristics of droplets; 2)on the above basis, constructing the multi-physics coupling numerical model for the evaporation of nanofluid droplets, then exploring the micro-flow rule of evaporating nanofluid droplets and describing the characteristics of the topological structure of micro-flow filed; 3)further focusing on the characteristics of stack deposition pattern of nanofluid droplets, revealing the acting forces and physical mechanism of the deposition behavior of nanoparticles. Based on the above investigation, the evaporation characteristics of small nanofluid droplets and the microscopic mechanism of stack deposition behavior of nanoparticles will be exactly revealed, which will provide basic theory support and scientific guide for the emerging applications building on the evaporation and deposition of nanofluid droplets.

微小纳米流体液滴蒸发及其颗粒堆叠沉积构型在微电子器件冷却、微制造等诸多微纳系统领域具有重大应用潜力。本项目拟采用理论分析、数值模拟和实验研究相结合的方法，围绕微小纳米流体液滴蒸发特性及其颗粒堆叠沉积微观机理开展深入系统研究，内容包括：1）首先从系统分析纳米颗粒对液滴流体物性、气液界面以及固液界面属性的影响规律入手，深层次揭示纳米颗粒对液滴蒸发特性影响的物理机制；2）在此基础上，通过构建纳米流体液滴蒸发的多物理场耦合模型，揭示纳米流体液滴蒸发过程中内部微流动规律，重点刻画液滴内部涡流场拓扑结构特征；3）进一步聚焦纳米颗粒堆叠沉积特性，从颗粒沉积行为的微观作用力视角揭示纳米流体液滴蒸发过程中内部颗粒堆叠沉积的物理机理。项目旨在准确揭示纳米流体液滴蒸发特性及其颗粒堆叠沉积的微观机理，为基于纳米流体液滴蒸发沉积涌现的新型应用提供基础理论支持和科学技术指导。

微小纳米流体液滴蒸发及其颗粒沉积现象在新型光电材料制备、新型纳米涂层、环境颗粒物检测等方面有重要应用。本项目围绕微小纳米流体液滴蒸发及其颗粒沉积特性，研究了纳米流体液滴蒸发特性及热质输运机制、液滴内部微流动规律、液滴蒸发颗粒堆叠沉积特性及机理。基于最小表面能原理分析了重力对液滴形貌的影响，提出了重力场下液滴形状的预测关系式，进一步数值模拟研究了Al2O3纳米颗粒体积分数、惯性力和液滴直径大小对撞击后液滴铺展回缩过程的影响规律，发现一定体积分数的纳米颗粒使流体表现出明显的剪切稀化特性，抑制了液滴的铺展回缩过程，减少其不稳定振荡。采用可视化方法实验研究了Al2O3纳米流体液滴瞬态蒸发速率，发现纳米颗粒的加入有利于提升液滴蒸发速率，且与纯水不同，2%质量分数的纳米流体液滴的瞬态蒸发速率随时间呈现先降低后升高的变化关系。建立了基于拉格朗日-欧拉（ALE）法的瞬态液滴蒸发模型，考虑了纳米颗粒在液滴内部的输运行为和纳米颗粒浓度对流体物性参数的影响，研究了Al2O3纳米流体液滴的蒸发与沉积特性，发现当基液为纯水时，大部分颗粒由于毛细补偿流的作用聚集在三相接触线处，当基液为乙醇时，由于毛细补偿流和Marangoni流的共同作用，基板表面沉积高度存在两个峰值。本项目的研究成果将可为基于纳米流体液滴蒸发沉积涌现的新型应用提供理论和技术指导。