CAREER: Integrated Approach for Modeling Thermal Energy Transport in Mesoscale Arrays of Nanostructures

jennifer R. lukes宾夕法尼亚大学机械工程与应用力学系，宾夕法尼亚19104摘要物理上有意义但计算上方便的多尺度热建模方法对于用于发电和电子热管理的先进纳米结构材料的从头设计至关重要。这些材料的纳米级构建块，包括量子点、纳米线和超薄固体薄膜，通常被配置成覆盖微米到厘米的阵列，意想不到的热传输现象是由不同长度尺度上不同物理过程的相互作用引起的。在这种阵列中开发建模方法的关键问题是如何将仅适用于特定长度尺度的不同热模型集成到跨越几个数量级的连贯框架中。这里提出的研究计划将通过结合紧密结合量子力学、分子动力学和蒙特卡罗模拟来解决这个问题，以创建一个新的建模工具，该工具使用两个物理上有意义的量：声子散射函数和声子弛豫时间来连接长度尺度。验证和改进建模工具的综合实验研究也将是这项研究工作的重要组成部分。这些研究将包括制造不同构型的新型纳米材料测试样品，表征它们的结构和化学成分，测量它们的热导率，并与相同结构的建模结果进行比较。这个研究项目将在基础和应用方面做出有价值的贡献。在应用方面，建模工具将是实现工程热纳米材料设计的关键一步，实验研究将探索广域（厘米尺度）制造任意图案纳米结构阵列的新技术。在基础方面，本研究创建的声子散射函数、弛豫时间、透射系数和镜面参数数据库将为纳米级热输运界提供重要的新微观信息，这些信息在很大程度上是实验无法获得的。这些信息将是未来解决该领域当前问题的关键，例如Umklapp散射过程的频率依赖性，材料界面上的声子行为以及纳米结构附近声子的相互作用。更广泛的影响这项职业建议概述了一个紧密结合的研究和教育计划。研究生研究活动是该计划的核心，研究成果将通过夏季研究项目直接传达给代表性不足的本科生，通过期刊出版物和自由软件直接传达给公众，通过在课程中引入微纳米主题直接传达给本科生，通过协同教学和研究直接传达给研究生。

CAREER: INTEGRATED APPROACH FOR MODELING THERMAL ENERGY TRANSPORT IN MESOSCALE ARRAYS OF NANOSTRUCTURESCAREER Award: 0547588Jennifer R. LukesDepartment of Mechanical Engineering and Applied MechanicsUniversity of PennsylvaniaPhiladelphia, Pennsylvania 19104ABSTRACTPhysically meaningful yet computationally expedient multiscale thermal modeling methodologies are critical for the de novo design of advanced nanostructured materials for power generation and electronics thermal management. The nanoscale building blocks of these materials, including quantum dots, nanowires, and ultrathin solid films, are typically configured in arrays covering microns to centimeters and unexpected thermal transport phenomena arise from the interplay of different physical processes at the various length scales involved. The key question in developing modeling methodologies in such arrays is how to integrate disparate thermal models appropriate only at certain length scales into a coherent framework spanning several orders of magnitude. The research program proposed here will address this question by combining tight binding quantum mechanics, molecular dynamics, and Monte Carlo simulation to create a new modeling tool that links the length scales using two physically meaningful quantities: phonon scattering functions and phonon relaxation times. Comprehensive experimental studies for validation and improvement of the modeling tool will also be a significant part of this research effort. These studies will involve fabricating novel nanomaterial test samples in various configurations, characterizing their structures and chemical compositions, measuring their thermal conductivities, and comparing to modeling results for the same structures.Intellectual MeritThis research program will make valuable contributions, both fundamental and applied. On the applied side, the modeling tool will be a critical step forward enabling the design of engineered thermal nanomaterials and the experimental studies will explore new techniques for wide-area (centimeter-scale) fabrication of arbitrarily patterned nanostructure arrays. On the fundamental side, the database of phonon scattering functions, relaxation times, transmission coefficients, and specularity parameters created in this study will provide vital new microscopic information to the nanoscale thermal transport community that has been largely inaccessible experimentally. This information will be key for the future resolution of current questions in the field such as the frequency dependence of Umklapp scattering processes, phonon behavior at material interfaces, and phonon interactions in the vicinity of nanostructures.Broader ImpactsThis CAREER proposal outlines a tightly integrated program of research and education. Graduate research activities form the core of the program, and results from the research will be conveyed directly to undergraduates from underrepresented groups through summer research projects, to the public through journal publications and free software, to the undergraduates through the introduction of micro and nano topics into the curriculum, and to the graduate students through synergistic teaching and research.