CAREER: Pushing the Lower Limit of Thermal Conductivity in Layered Materials

找出在固态材料中实现极低导热系数的有效策略，可能会将导热推向极端。拟议的项目旨在使无序、分层材料中的新型热控制功能应用于可持续能源基础设施，如通过隔热节省能源、电池储能、热电能量转换以及电子产品的热管理。研究、教育和推广计划的整合旨在提高公众对可持续能源挑战的认识，并激励学生追求通往STEM职业的适当教育途径。将开发电影般的360虚拟现实实验室之旅，将在线的K-12学生“传送”到实验室，可视化热传输研究及其在可持续能源中的应用。将邀请教师合作并试点教育活动，宣传可持续能源基础设施的重要性和挑战。加强学生为STEM职业生涯的准备将通过一个暑期项目实现，该项目特别强调接触女性和非裔美国学生。这个职业项目的研究目标是了解如何通过无序抑制各向异性层状材料中的振动能量传输。通过在层状晶体的范德华带隙中插入离子或分子链的电化学过程，可以精确和可逆地控制无序的程度和不均匀性，从而实现层间距的控制。这些研究将集中在一种模型过渡金属二卤化物晶体上，使用补充的最先进的理论和实验方法。用时间域热反射法测量插入到缝隙中的离子或分子链的数量和类型可控的大块晶体的热导率。然后用晶格动力学和分子动力学相结合的方法分析不同类型的振动模对这些无序晶体中微观热输运的贡献。该项目的成功将使第一组实验和理论研究能够阐明层间距和键合环境在抑制振动能量传输方面的作用，从而促进目前对各向异性无序、层状材料中微观热传输机制的理解。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Identifying effective strategies to achieve exceptionally low thermal conductivity in solid-state materials can potentially push the extremes in heat conduction. The proposed project seeks to enable novel thermal control functionalities in disordered, layered materials to be applied in sustainable energy infrastructure, such as energy savings by thermal insulation, energy storage in batteries, energy conversion in thermoelectrics, and thermal management in electronics. The integration of research, education, and outreach programs aims to raise the public awareness of challenges in sustainable energy, and motivate students to pursue appropriate education pathways to STEM occupations. Cinematic 360 Virtual Reality lab tours will be developed to "teleport" online K-12 students into the lab to visualize thermal transport research and its applications in sustainable energy. Teachers will be invited to collaborate and pilot educational activities promoting the importance and challenges in sustainable energy infrastructure. The enhancement of students' preparation for a STEM career will be achieved by a summer program with a particular emphasis on reaching out to female and African-American students.The research goal of this CAREER project is to understand how to suppress vibrational energy transport in anisotropic layered materials by disorder. Precise and reversible control of the degree and inhomogeneity of disorder and thus interlayer spacing are achieved by an electrochemistry process, which inserts ions or molecular chains into the van der Waals gaps of layered crystals. The investigations will focus on a model transition metal dichalcogenide crystal, using complementary state-of-the-art theoretical and experimental approaches. The thermal conductivity of bulk crystals with a controllable amount and type of ions or molecular chains inserted into the gaps will be measured by the time-domain thermoreflectance method. The contribution from different types of vibrational modes to the microscopic thermal transport in these disordered crystals will then be analyzed using a combination of lattice dynamics and molecular dynamics methods. The success of this project will enable the first set of experimental and theoretical studies to elucidate the roles of interlayer spacing and bonding environment on suppressing vibrational energy transport, thereby advancing the current understanding on the microscopic thermal transport mechanisms in anisotropic disordered, layered materials.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.