MAE Seminar – Geoff Wehmeyer – Understanding heat transfer in complex nanostructures: simulations and experiments

Date/Time

02/22/2018
4:00 pm-5:00 pm
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Location

303 MAE-A
939 Sweetwater Drive
Gainesville, FL 32611-6250

Details

Understanding heat transfer in complex nanostructures: simulations and experiments

Geoff Wehmeyer
Ph.D. Candidate, Mechanical Engineering,
University of California Berkeley

Abstract
Thermal management plays a critical role in enabling energy systems and information technologies ranging from light-emitting diodes and thermoelectric generators to data storage devices and microelectronics. Improving the thermal performance of these technologies, however, requires a better fundamental understanding of how energy carriers such as phonons transport heat in complicated nanostructures.

In this talk, I will describe how I develop computational and experimental tools to answer open questions about nanoscale heat transfer mechanisms. First, I will discuss how my phonon ray tracing simulations and my collaborator’s thermal conductivity measurements resolved a controversial debate by showing that thermal phonons behave like incoherent particles rather than like coherent waves in silicon nanomeshes, which are membranes with periodically etched holes. I will then introduce my new experimental techniques for in-situ temperature measurements in the scanning transmission electron microscope (STEM) using thermal diffuse scattering. STEM offers the potential for thermal imaging with single-digit nanometer spatial resolution, which would open pathways to study nanoscale Joule heating and interfacial heat transport. These new numerical and experimental capabilities answer long-standing thermal questions and can be leveraged in the design of energy-efficient lighting technologies and solid-state refrigeration cycles.

Biography
Geoff Wehmeyer is currently a Ph.D. candidate in Mechanical Engineering at the University of California, Berkeley. He received his bachelor’s degree in Mechanical Engineering from the University of Texas at Austin. His Ph.D. thesis focuses on developing electron microscopy nanothermometry experiments and phonon ray tracing simulations to study heat conduction in nanostructures. Geoff is a recipient of a NSF Graduate Research Fellowship and a Berkeley Graduate Fellowship.

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