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

本课题致力于晶格中热传导反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质，主要与介质原子结构的离散性有关。在这一层次上理解热传导的能量传递对于获得固体的微观描述和宏观描述之间的联系是至关重要的。技术的最新发展使研究低维物体的性质成为可能，如纳米管、石墨烯或富勒烯。在过去的几十年中，研究表明，在声子平均自由程与结构尺寸相比较小的低维结构中，热传播的性质是弹道性质而不是扩散性质。在过去的几十年里，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质引起了人们的兴趣。由于冷却和设计创新的热设备的问题，热传导的能量传输问题是非常重要的。电子器件和电路的小型化导致了自热的出现，成为新开发的微电子电路和系统的性能和可靠性的关键瓶颈。为了解决单个器件水平上的热传递物理问题，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研究石墨烯和碳纳米管等结构的热性质的兴趣，在这些结构中，这种反常现象最为突出。这项建议的目的是利用分析方法和模拟研究低维结构中通过热传导进行的反常能量传输，这将有助于设计和解释为验证理论模型预测而进行的实验。以下将被研究：-一维和准一维晶体材料中反常能量传输的离散和连续模型的建立。-对简单结构的二维材料中反常能量传输的描述。-2D晶格和连续模型的发展。-使用离散和连续方法模拟此类系统中的热传导能量传递。-针对瞬变情况进行类似的实验。-使用拉曼光谱和原子力显微镜温度传感器进行实验，确定非稳态区域纳米结构(石墨烯)的热参数。-将实验数据与模拟和分析研究的结果进行比较和解释。我们的主要目标：-根据第一原理建立晶体中热传导能量传播的理论。-研究其与扩展热力学和唯象理论的一致性。-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