Anomalous energy transfer in crystalline materials from the viewpoints of discrete mechanics and continuum theory

本课题着重于晶体晶格中热传导的异常能量传递的理论和实验研究。在纳米尺度上，材料表现出特殊的热机械性能，这主要与介质原子结构的离散性有关。在这个水平上通过热传导的能量传递的理解对于获得固体的微观和宏观描述之间的联系是必不可少的。技术的最新发展使得研究低维物体的性质成为可能，如纳米管、石墨烯或富勒烯。在过去的几十年里，研究表明，在低维结构中，声子的平均自由程比结构尺寸小，热传播的性质是弹道而不是扩散。近几十年来，由于在微电子器件中的应用，低维晶体结构的电学和力学性能引起了人们的兴趣。由于冷却和设计创新热装置的问题，热传导能量传输问题具有重要意义。电子器件和电路的小型化导致了自热的出现，这是新开发的微电子电路和系统的性能和可靠性的关键瓶颈。为了解决单器件水平的传热物理问题，应该考虑更先进的热传导能量传输模型。这激发了人们最近对石墨烯和碳纳米管等结构的热性能的研究兴趣，这些结构的热性能异常最为突出。本提案的目的是利用分析方法和模拟来研究低维结构中热传导的异常能量输运，这将有助于设计和解释将要进行的实验，以验证理论模型的预测。-一维和准一维晶体材料中异常能量传递的离散和连续模型的公式。-描述简单结构二维材料中的异常能量传递。-开发二维点阵和连续体模型。-用离散和连续方法模拟这类系统中热传导的能量传递。-瞬态情况的类似实验。-利用拉曼光谱和原子力显微镜热传感器进行实验，确定纳米结构（石墨烯）在非稳态状态下的热参数。-将实验数据与模拟和分析研究结果进行比较和解释。我们的主要目标：-建立基于第一原理的晶体热传导能量传播理论。-研究其与扩展热力学和现象学理论的一致性。-在定制设计的实验中测试模型

This project focuses on theoretical and experimental studies of anomalous energy transfer by heat conduction in crystalline lattices. At the nanoscale materials exhibit special thermomechanical properties mostly related to the discreteness of the atomic structure of the medium. An understanding of the energy transfer by heat conduction at that level is essential to obtain a link between the microscopic and the macroscopic descriptions of solids. Latest developments in technology made it possible to investigate properties of low dimensional objects, such as nanotubes, graphene, or fullerenes. During the last decades it was shown that in low dimensional structures, where the phonon mean free path is small compared to the structural size, the nature of heat propagation is ballistic rather than diffusive. Electrical and mechanical properties of low dimensional crystalline structures became of interest during the last decades due to applications in microelectronic devices. Problems of energy transport by heat conduction are of great importance due to problems of cooling and designing innovative thermal devices. Miniaturization of electronic devices and circuits has led to the emergence of self-heating as a critical bottleneck to the performance and reliability of newly developed microelectronic circuits and systems. In order to address heat transfer physics at the single device level, more advanced models of energy transport by heat conduction should be considered. This motivates recent interest in investigating thermal properties of the structures, such as graphene and carbon nanotubes, where such anomalies are most prominent. The aim of this proposal is to investigate anomalous energy transport by heat conduction in low dimensional structures using analytical approaches and simulations, which will help to design and interpret experiments to be performed in order to validate theoretical model predictions.The following will be investigated:- Formulation of discrete and continuous models of anomalous energy transfer in 1D and quasi-1D crystalline materials.- Description of anomalous energy transfer in 2D materials of simple structure.- Development of 2D lattice and continuum models. - Simulation of the energy transfer by heat conduction in such systems using discrete and continuum approaches.- Analogous experiments for the transient case.- Performing experiments determining thermal parameters of nano-structures (graphene) in the non-steady regime using Raman spectroscopy and AFM thermosensors.- Comparison and interpretation of experimental data with results of simulation and analytical studies.Our main objectives:- Create a theory of energy propagation by heat conduction in crystals based on first principles.- Investigate its consistency with extended thermodynamics and phenomenological theories. - Test the models in custom designed experiments