Career: Using High-resolution Piezoelectric Sensing to Investigate Liquid-vapor Phase-change Mechanisms in Nanostructures

蒸发和冷凝过程是海水淡化、发电、供暖、空调和制造的核心。改善和控制汽液相变特性可以提高这些应用的性能和整体效率。增强相变的技术之一是加入纳米材料或纳米结构。然而，到目前为止，这项技术的实施主要是基于试验，通过比较使用和不使用纳米结构的应用程序。这个NSF职业项目的总体目标是围绕纳米工程材料的使用整合研究和教育，以增强和控制蒸发和冷凝。这个项目将确定和量化影响光滑和纹理表面相变的各种因素的作用。该项目的教育目标是让学生和未来的劳动力掌握技术知识和技能，以创新和建立变革性和可持续的发电、能源储存和海水淡化系统。该项目还旨在通过提供更多的研究机会和增强现实教学来激发学生对能量转移机制及其在行业中的应用的兴趣，从而增加学生对科学、技术、工程和数学的参与。虽然宏观尺度上的相变和水蒸气传输已被很好地理解，但它们在纳米结构中显示出独特的特征。了解这些特性对于在工业应用中利用纳米材料至关重要。这项拟议的项目将通过使用一种新的实验技术来阐明纳米级的相变和蒸汽传输，该技术结合了压电质量和面积传感机制、可视化和红外热像技术。这种方法允许以高灵敏度、准确性和重复性检测质量变化。该项目将对纳米结构的几何结构和表面化学如何控制液-汽相变和蒸汽传输产生新的理解。这项研究将解决非理想性对相变的影响。这些非理想状态包括液体中的非挥发性杂质和汽相中的不可凝结气体。尽管这种非理想的现象无处不在，但以前的研究主要集中在纯流体的蒸发和冷凝上。相变的直接测量还将测试用于预测纳米结构内蒸发和冷凝的经典模型的准确性。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Evaporation and condensation processes are central to water desalination, power generation, heating, air-conditioning, and manufacturing. Improving and controlling the characteristics of the liquid-vapor phase-change can enhance the performance and the overall efficiency of these applications. One of the techniques to enhance phase-change is by incorporating nanomaterials or nanostructures. However, implementation of this technique so far has primarily been trial-based, by comparisons of applications with and without nanostructures. The overall goal of this NSF CAREER project is to integrate research and education around the use of nanoengineered materials to enhance and control evaporation and condensation. This project will determine and quantify the role of various factors that affect phase-change on smooth and textured surfaces. The education objectives of this project are to equip students and the future workforce with the technical knowledge and skill sets to innovate and build transformative and sustainable systems for power generation, energy storage, and water desalination. The project also aims to increase the participation of students in science, technology, engineering, and mathematics by providing extended research opportunities and augmented reality instruction to excite students about energy transfer mechanisms and their applications in the industry. Although phase-change and vapor transport at the macroscale are fairly well understood, they show unique characteristics in nanostructures. Understanding these characteristics is essential to leverage nanomaterials in industrial applications. The proposed project will allow elucidating phase-change and vapor transport at the nanoscale by using a novel experimental technique combining a piezoelectric mass and area-sensing mechanism, visualization, and infrared thermography. This approach allows detecting mass changes with high sensitivity, accuracy, and repeatability. The project will generate a new understanding of how geometry and surface chemistry of nanostructures control liquid-vapor phase-change and vapor transport. The research will address the effect of non-idealities on phase-change. These non-idealities include non-volatile impurities in the liquid phase and non-condensable gases in the vapor phase. Although such non-idealities are ubiquitous, prior efforts have primarily focused on evaporation and condensation of pure fluids. Direct measurements of phase-change will also test the accuracy of the classic models used to predict evaporation and condensation within nanostructures.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.