2022年11月21日至23日，爱荷华州立大学王信伟教授做客中国科学技术大学“2022工程科学论坛”为工程科学学院师生做系列线上学术报告，系列报告主题为“Energy Transport in Extremely Confined Domains”。报告会由热科学和能源工程系程文龙教授主持。
王信伟教授给与会师生带来了非常精彩的系列学术报告。本系列报告主要围绕基于瞬态电热（TET）思想表征一维结构、二维材料以及范德华晶体中的能量传输进行展开。新兴的纳米材料和热设计在电子和能源收集领域的应用，在极其有限领域的能量传输引起了极大的关注。在首场报告中，王信伟教授首先对材料的导热系数与导电系数的测量方式做了简单介绍，重点阐述了瞬态电热测量法的优势，并列举大量实例说明温度升高与单点接触热阻的关系。王信伟教授指出常规材料、纳米级材料、极性材料及碳材料之间洛伦兹常数的差别，而导致这种现象的原因是不同材料的导电能力与导热能力会随着材料的形态或缺陷等呈现不同程度的增减，当导电能力减弱的程度大于导热能力的程度，洛伦兹数将上升，反之则会下降。
在第二场报告中，王信伟教授重点介绍了拉曼技术探测纳米尺度二维材料的能量运输。拉曼测温技术，是一种超快测温技术，利用光学特性，在时间尺度上可以达到皮秒级。王教授指出，拉曼散射偏移与材料的热物性、温升等因素有关。单位激光能量下拉曼偏移，可以通过光斑大小观测二维材料对激光的吸收，很大程度上减弱了电子迁移对材料导热影响。
在最后一场报告中，王信伟教授介绍了两个传热模型。阻温系数模型解释了缺陷对材料传热的影响，提出了结构尺寸概念，简化了复杂结构传热问题。阐述了基于低动量声子散射的结构的各向异性双温理论，解释范德华晶体中的能量传输，指出石墨烯等片层结构在片层内部与片层之间温度传递的区别。
在系列报告中，与会师生对王信伟教授的讲座内容展开了热烈的讨论，王信伟教授对相关问题进行了详细、耐心的解答。总的来说，整个讲座过程学术氛围非常浓厚，师生们都受益匪浅。
报告人简介
Dr. Xinwei Wang is the Anson Marston Distinguished Professor and Wilkinson Professor in Interdisciplinary Engineering at Iowa State University (http://web.me.iastate.edu/wang). He obtained his Ph.D. from the School of Mechanical Engineering, Purdue University in 2001, M.S. (1996) and B.S. (1994) from the University of Science and Technology of China. Over the past 20 years, he has led his laboratory to develop new techniques for characterizing thermal transport at the micro/nanoscale, including the TET, ET-Raman, TD-Raman, and FR-Raman techniques. His lab reported the first work on distinguishing the optical and acoustic phonon temperatures under intense photon excitation, and determining their energy coupling factor. His work on conjugated phonon and hot carrier transport represents the first accomplishment in distinguishing these two physical processes and quantifying their transport diffusivities. The thermal reffusivity theory developed in his lab provides a novel way to characterizing material’s structure domain size, similar to that measured by x-ray diffraction, but has unique applications for nanomaterials. He received the inaugural Viskanta Fellow Award of Purdue University in recognition of his pioneering and independent work in thermal sciences. He is the recipient of the Mid-career Award for Research (2014) and Award for Outstanding Achievement in Research (2018) from ISU. He is the Fellow of ASME and Associate Fellow of AIAA. He serves as the senior and associate editor of four international journals and is on the editorial board of five journals.
本次报告会为2022年工程科学论坛第26~28期报告，报告由研究生教育创新项目支持。
撰稿人：王敏 李亚慧 胡俊
（热科学和能源工程系）
