Conferences - Seminars

  Friday 16 February 2018 13:15 - 14:15 MED 0 1418

Extraordinary heat transport at the nanoscale

By Dr. BAI SONG, NanoEngineering Group, MIT

Heat carriers such as photons and phonons are ultimately waves, however, the wave nature of heat has remained rather elusive in thermal transport. As some examples, nanoscale thermal radiation and phonon localization will be discussed in this talk. Radiative heat transfer between objects separated by  nanometer-sized gaps is of considerable interest for a variety of novel applications, including energy conversion, thermal logic, lithography, data storage, and scanning thermal microscopy. Although thermal radiation over macroscopic distances is well understood in terms of Planck’s law and the Stefan-Boltzmann law, radiative heat transfer at the nanoscale remains largely unexplored. Here I will address two foundational questions in the field:
1) Can existing  theories accurately describe radiative heat transfer across few-nanometer gaps?
2) Can radiative heat flow exceed the blackbody limit by a few orders of magnitude? To answer these challenging questions, I built novel experimental platforms featuring nanometerprecise positioning mechanisms in conjunction with novel heater/calorimeter microdevices and scanning probes. Further, I performed state-of-the-art calculations and analysis to compare theoretical predictions with experimental observations
I will demonstrate that:
1) Current nanoscale radiation theories can adequately describe radiative heat transfer down to about 1 nm gaps.
2) Radiative heat flow between two parallel planes can exceed the blackbody limit by over 1000 times.
These advances open up many new opportunities in the emerging field of nanoscale thermal radiation. To wrap up, I will briefly discuss whether localization of thermal phonons can take place in 3D materials and be experimentally demonstrated. The departure from diffusive Fourier transport has been widely observed in nanostructures and largely explained with classical size effects on phonon gas, ignoring the wave nature of phonons. I will discuss our recent
work on phonon localization in heat conduction through quantum-dot superlattices, due to multiple scattering and interference of coherent phonon waves. This discovery is surprising given the broadband nature of thermal transport, and suggests a new path for engineering phonon transport. Altogether, I hope to show a glimpse of the beauty and potential of heat transport at the nanoscale.

Dr. Bai Song is a postdoctoral associate at MIT, mentored by Prof. Gang Chen in the Mechanical Engineering Department. He earned his PhD in 2015 at the University of Michigan, Ann Arbor, where he was honored with the Distinguished Dissertation Award.
He obtained his MS and BE at Tsinghua University, Beijing, and was a recipient of the Distinguished Master Thesis Award. His primary research interest is to understand heat transport, conversion, storage and dissipation, in diverse materials, devices and systems, and especially at small spatial and temporal scales. He further aims to leverage such knowledge to develop engineering solutions to real-world challenges such as the global energy and environmental problems, and thermal management of buildings, spacecrafts and microelectronics.

Organization IGM

Contact Prof. François Gallaire IGM - LFMI

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Admittance Free