Woodruff School of Mechanical Engineering
Mechanical Engineering Seminar
Thermal Transport in Nanostructured Materials for Solid State Energy Conversion
Dr. Jonathan Malen
Carnegie Mellon University, Dept. of Mechanical Engineering
Monday, June 16, 2014 at 2:00:00 PM
MRDC Building, Room 4211
Operating temperature, and hence heat dissipation, impact the performance of energy conversion technologies ranging from solar cells to thermoelectric devices. Thermal transport in advanced materials for these conversion technologies cannot be described simply by Fourier¡¦s law when the mean free paths of energy carriers are commensurate to feature sizes. Instead, interfaces and non-diffusive transport can govern macroscopic quantities like thermal conductivity. The objective of my research group is to experimentally measure these effects, to better design and understand these materials. I will begin with an introduction to the nanoscale heat carriers, and I will then present two projects where we collaborated with computational modelers to reveal novel thermal transport properties in new and old materials. (1) Nanocrystal arrays (NCAs) are self assembled organic-inorganic hybrid materials with novel electronic and optical properties. Our measurements reveal that thermal transport in NCAs is mediated by surface chemistry defined interfaces between neighboring nanocrystals. Complementary measurements of self assembled monolayers (SAMs) shed light on phonon transport at the organic-inorganic interface. (2) Deeper understanding of phonon physics in NCAs will be based on a new laser-based technique that can directly measure the mean free path spectra of energy carriers. Our initial studies of silicon reveal that ~40% of its thermal conductivity results from energy carriers with mean free paths longer than 1 İm, in stark contrast to historical predictions.
Jon received his Ph.D in Mechanical Engineering at the University of California, Berkeley under the co-advisory of Professors Arun Majumdar (ME, MSE) and Rachel Segalman (ChemE). He investigated thermoelectricity in single molecule junctions, in an effort to learn more about electronic transport in molecular electronics and organic-inorganic hybrid materials. Jon received his B.S. in Mechanical Engineering (and so much more) at the University of Michigan, Ann Arbor in 2000 and an S.M. in Nuclear Engineering (2003) from MIT, where he studied transport at the macroscopic reactor scale under the advisory of Professor Neil Todreas. He spent one year as an intern at the Lawrence Livermore National Laboratory from 2003-2004, and was an NDSEG Fellow from 2005-2008. Since his arrival at Carnegie Mellon in 2009, Jon has received the AFOSR Young Investigator Award (2011), the ACS PRF Doctoral New Investigator Award (2011), and the NSF CAREER Award (2012).