Collaborative Research: Cross-plane Heat Conduction in 2D Materials under Large Compressive Strain

合作研究：大压缩应变下二维材料的横向热传导

基本信息

批准号：
2211696
负责人：
Yan Wang
金额：
$ 11.73万
依托单位：
Board of Regents, NSHE, obo University of Nevada, Reno
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2022
资助国家：
美国
起止时间：
2022-06-15 至 2025-05-31
项目状态：
未结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2211696&HistoricalAwards=false
关键词：
Collaborative Research Cross plane Heat

项目摘要

Heat conduction highly depends on the strength of bonding among atoms and molecules. Typical interatomic forces include the weak Van Der Waals forces (e.g., in liquids) and the strong ionic and covalent forces (e.g., in solids). 2D materials, such as graphite, are peculiar in that individual layers are coupled via Van Der Waals forces while within the layer, atoms are bonded via covalent forces. Heat conduction along the in-plane direction could be hundreds of times faster than the cross-plane direction. The strength of the Van Der Waals force across layers can be tuned to a great extent by compressing the material. In graphite, under extreme compression, atoms from different layers could even form strong, covalent-like bonds. 2D materials provide a good model to study how heat conduction is associated with interatomic bonding. A high-pressure diamond anvil cell will be used to apply compressive strain in 2D materials. Pressure produced in the diamond anvil cell can be as high as 100~200 GPa, similar to the pressure inside Earth core, and can reduce the distance between the 2D layers by about 30%, hence increasing the strength of interlayer bonds substantially. Fundamental understanding of heat conduction across 2D layers under compression will facilitate the realization of parallel strain tuning of thermal, structural, and electrical properties of 2D materials for novel functionalities with improved thermal stability and performance. This research will also provide opportunities to improve diversity in science and engineering through research training of underrepresented groups and various outreach activities.Classical kinetic theory predicts that cross-plane phonon mean free paths in 2D materials are extremely short, leading to low thermal conductivity. This paradigm was challenged by several recent studies that suggest phonon mean free paths orders of magnitude longer, which indicates the lack of understanding about the nature of heat conduction across 2D layers. The hypotheses are that long phonon mean free paths across 2D layers require both weak interlayer force and periodicity, and that phonon scattering and heat conduction depend strongly on the strength of interlayer force. In this proposed research, the large compressive strain generated in a high-pressure diamond anvil cell will tune the interlayer force over a wide range of strength. A comprehensive study of cross-plane thermal transport will be conducted with optical spectroscopies (e.g., x-ray diffraction, transient thermoreflectance) and advanced computational techniques (e.g., ab initio, machine learning-enhanced molecular dynamics). Three material systems will be studied: (i) pristine ReS2, which possesses the weakest interlayer force in the transition metal dichalcogenides family at the ambient condition; (ii) twisted ReS2, which has broken periodicity along the cross-plane direction; and (iii) graphite, which could experience interlayer buckling via sp2-sp3 bond transition under high pressure.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.

热传导很大程度上取决于原子和分子之间键合的强度。典型的原子间力包括弱的范德华力（例如，在液体中）和强离子和共价力（例如，在固体中）。 2D材料（例如石墨）是特殊的，因为单个层是通过范德华力耦合的，而在层中，原子通过共价力键合。沿平面方向的热传导可能比跨平面方向快数百倍。可以通过压缩材料来在很大程度上调节范围范围的范德华力的强度。在石墨中，在极端压缩下，来自不同层的原子甚至可以形成强，共价键。 2D材料提供了一个良好的模型，以研究热传导与原子间粘结如何相关的模型。高压钻石砧细胞将用于在2D材料中施加压缩应变。在钻石砧室中产生的压力可以高达100〜200 GPA，类似于地球内部核心内部的压力，并且可以将2D层之间的距离降低约30％，从而大大增加了层中键的强度。在压缩下对2D层的热传导的基本理解将有助于实现2D材料的热，结构和电气性能的平行应变调整，以提高热稳定性和性能的新功能。这项研究还将通过对代表性不足的群体和各种外展活动进行研究培训来改善科学和工程学的多样性。古典动力学理论预测，跨平面声子在2D材料中的平均自由路径的平均自由路径非常短，导致导热率低。该范式受到最近的一些研究的挑战，这些研究表明声子意味着更长的数量级，这表明对跨2D层的热传导性质缺乏理解。假设是，长声子在二维层上的平均自由路径既需要弱的层间力和周期性，又有声子散射和热传导在很大程度上取决于层间力的强度。在这项拟议的研究中，在高压钻石砧细胞中产生的大型压缩应变会在各种强度范围内调整层间力。将对跨平面热运输的综合研究将使用光谱（例如X射线衍射，瞬态热室内）和先进的计算技术（例如，从头开始，机器学习增强分子动力学）进行。将研究三个材料系统：（i）原始RES2，它在环境状况下具有过渡金属二甲构代基元中最弱的层间力；（ii）扭曲的RES2，沿跨平面方向损坏了周期性；（iii）石墨，它可以在高压下通过SP2-SP3债券过渡经历层间屈曲。该奖项反映了NSF的法定任务，并且使用基金会的知识分子优点和更广泛的影响审查标准，被认为是值得通过评估的支持。