CAREER: Investigation of strain and superior functionalization schemes for large enhancement of thermal conductivity in polymer-graphene nanocomposites and binary semiconductors

高导热聚合物和半导体在电子、汽车、航空航天、发电和能源收集等广泛应用中具有显著改善热管理的潜力。本项目的研究目标是探索通过聚合物与石墨烯之间具有更高的界面热传递能力以及通过控制高分子链和石墨烯纳米片的取向来显著提高聚合物-半导体复合材料热导率的方法。该项目的教育目标是通过夏令营计划吸引高中生。为了激发人们对热传输的兴趣，高中生将通过使用红外线成像的彩色温度图可视化来测量不同纳米复合材料的热响应。同时，该计划旨在通过吸引来自俄克拉荷马州不同部落学院的美国原住民学生来增强多样性。参与者将加深对原子模拟的理解，还将进行热传输的实验表征。在聚合物中，沿聚合物链轴的导热系数最高。在这个项目中，通过应变实现了聚合物链和纳米小片的平面方向的同时对准，以沿着两个组分中最有效的方向传导热量。排列通过显微镜和成像来表征。非平衡格林-S函数技术被用来揭示聚合物和石墨烯之间的共价键方案，使得聚合物和石墨烯之间能够实现良好的声子传输。本工作通过实验和原子模拟两种方法对通过这种方案制备的功能化聚合物复合材料进行了热表征。半导体振动光谱中的能隙已被证明能抑制低能声子的散射，导致其寿命和整体材料热导率的大幅提高。应变可以进一步增加能隙，导致更长的声子寿命。在这个项目中，应变效应是通过从密度泛函理论推导出原子间作用力相互作用，并将它们与声子玻尔兹曼输运方程的精确解一起用于预测热导率来量化的。下一代高导热聚合物和半导体的设计将为在各种技术中改善热管理带来巨大的影响机会。该奖项由工程总局的化学、生物工程、环境和运输系统司和综合活动办公室的激励竞争性研究计划共同资助。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。

High thermal conductivity polymers and semiconductors hold potential to significantly improve thermal management in wide range of applications including electronics, automobiles, aerospace, power generation and energy harvesting. The research objective of this project is to investigate ways to significantly enhance thermal conductivity of polymer-semiconductor composite materials, through superior bonding between polymer and graphene with higher interfacial thermal transport and by controlling orientation of polymer chains and graphene nanoplatelets. The educational objectives of the project are to engage high school students through a summer camp program. To stimulate fascination with thermal transport, high school students will measure thermal response in different nanocomposites through colorful visualization of temperatures maps using infra-red imaging. Simultaneously the program will aim to enhance diversity by engaging Native American students from various tribal colleges in Oklahoma. The participants will develop understanding of both atomistic simulations and also perform experimental characterization of thermal transport. Within polymers, thermal conductivity is highest along the polymer chain axis. Simultaneous alignment of polymer chains and planar direction of nanoplatelets, to conduct heat along the most efficient directions in the two components, is achieved in this project through strain. Alignment is characterized through microscopy and imaging. Non-equilibrium Green?s function technique has been used to reveal covalent bonding schemes enabling superior phonon transmission between polymer and graphene. Functionalized polymer composites prepared through such schemes are thermally characterized in this work through both experiments and atomistic simulations. Energy gap in the vibrational spectra of semiconductors has been shown to suppress scattering of low energy phonons, leading to large enhancement in their lifetimes, and overall material thermal conductivity. Strain can further increase energy gap, resulting in higher phonon lifetimes. Strain effects are quantified in this project by deriving interatomic force interactions from density-functional theory and using them with an exact solution of the phonon Boltzmann transport equation to predict thermal conductivity. Design of next generation high thermal conductivity polymers and semiconductors will lead to high impact opportunities for improving thermal management in a wide array of technologies. This award is jointly funded by the Division of Chemical, Bioengineering, Environmental, and Transport Systems in the Directorate of Engineering and the Established Program to Stimulate Competitive Research in the Office of Integrative Activities.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.