On February 7, Assistant Professor Jivtesh Garg was awarded the CAREER grant from the National Science Foundation. He will be working on the investigation of strain and superior functionalization schemes for large enhancement of thermal conductivity in polymer-graphene nanocomposites and binary semiconductors. The NSF grant award for this project is a total of $500,000.

The NSF CAREER project targets large enhancement in thermal conductivity of polymer-graphene nanocomposites and group III-V semiconductors. Such high thermal conductivity polymers and semiconductors will significantly improve thermal management in electronics, automotive, aerospace, power generation, and energy harvesting applications. The approach involves simultaneously aligning the most thermally conductive paths in polymer and graphene particles and also covalently bonding the two to enhance thermal conductance at the polymer-graphene interface. Promising results have been achieved by our group in preliminary work. The thermal conductivity of semiconductor materials will be enhanced through phonon lifetime engineering.

The project also aims to enhance the participation of high school students through a summer camp program. To stimulate fascination with thermal transport, high school students will measure thermal response through colorful visualization of temperatures maps using infra-red imaging. Simultaneously the program will aim to enhance diversity by engaging American Indian students from various colleges in Oklahoma. The participants will develop an understanding of both atomistic simulations and perform experimental characterization of thermal transport.

Within polymers, thermal conductivity is highest along the polymer chain axis. Similarly, graphene nanoplatelets have dramatically higher in-plane compared to through-plane thermal conductivity. Simultaneous alignment of polymer chains and planar direction of nanoplatelets is achieved in this project through strain. Alignment is characterized through microscopy and imaging. As a second aspect, non-equilibrium Green’s function computations are used to achieve understanding of covalent bonding schemes enabling superior interfacial thermal conductance between polymer and graphene. Functionalized polymer composites will be prepared through such efficient schemes and thermally characterized in this work both experimentally and via atomistic simulations.

Finally, energy gap in the vibrational spectra of certain group III-V semiconductors has been shown to dramatically suppress scattering of low energy phonons, leading to large enhancement in phonon lifetimes, thus increasing overall material thermal conductivity. We have demonstrated this effect in ideal short-period superlattices and more recently in Gallium Nitride. This project will computationally explore strain engineering to further increase energy gap, resulting in higher phonon lifetimes. Strain effects will be quantified accurately through a first-principles approach based on deriving interatomic force interactions from density-functional theory and using them in an exact solution of the phonon Boltzmann transport equation.

Dr. Garg says that he is very thankful to National Science Foundation (NSF) for awarding him this grant. It will allow him to significantly enhance research, in his group, related to thermal transport at the atomistic scale for design of advanced materials for thermal management and energy conversion applications.

Congratulations Dr. Garg!