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

University Of Oklahoma Norman Campus, Norman OK

Investigators

Abstract

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.