Abstract:

Thermal radiation behavior in the near-field was first addressed from a theoretical perspective using fluctuation electrodynamics nearly 60 years ago. This process refers to thermal radiation transport over distances between source and sink ranging from ~ nanometers to ~ sub-micrometers. In contrast far-field thermal radiation which is governed by the Stefan-Boltzmann law refers to distances that are greater than many micrometers. It was pointed out at that time that near-field radiation maybe substantially different from what the conventional Stefan-Boltzmann law would suggest. But until recently further advances have been relatively slow primarily due to lack of experimental capability. In fact as late as the mid-nineties attempts to measure thermal radiation over sub-micrometer range was inconclusive. However, recent advances in nanosacle instrumentation have enabled near-field thermal radiation to be characterized in more detail experimentally. This has fueled accelerating interest in this phenomenon driven by the scientific and engineering challenges as well as by the potential technological opportunities ranging from next generation thermal management to energy storage and conversion. In this presentation the physics of near-field thermal radiation would be discussed. A dipole model of nano-scale radiation would be presented. This model would be utilized to highlight the differences between the "conventional" descriptions of thermal radiation in the far field from that of the near-field. Within this model the far field contribution would be correlated to the Stefan-Boltzmann description. Recent experimental findings on near-field thermal radiation would be discussed in terms of this model. A parameter akin to an effective thermal conductivity for near-field process would be extracted. This facilitates comparison to the bulk scale thermal conduction process and enables one to assess quantitatively the relative significance of the near-field heat transfer process. Near-field thermal radiation is non-material specific in the sense that the process would occur for all materials to comparable degree. However, for some categories of materials that are capable of supporting surface polariton resonance in the thermal regime near-field thermal radiation maybe enhanced. A quantitative assessment of this enhancement would be discussed. Technological applications may require judicious choices of materials selection. Potential opportunities and challenges in the application of nanoscale thermal radiation to next generation thermal management, energy storage and conversion would be addressed.

Brief bio:

Shiu-Wing Tam, Ph.D, is a metallurgist/materials scientist at Argonne National Laboratory.  He has over 30 years experience in nuclear materials issues in nuclear technologies including fission, fusion and nuclear waste.  His current research involves the study of nano-scale heat transfer and its applications to thermal management of industrial processing issues and thermal energy storage.  He is actively involved in hydrogen generation issues in storage of nuclear waste and electronic structure calculations of potential new phases of oxides of Pu. He is also engaged in applying nonlinear dynamics to the studies of complex engineering systems (fluidized bed technology and electrical grids).  These activities are supported by DOE/EM, DOE/EERE, and private industry.  Concurrent to his tenure at Argonne he has also held at various times adjunct professorship of Materials Science and Engineering (University of Illinois at Chicago), and Adjunct Professor of Physics (Michigan Technological University).  In those capacities he has taught courses in materials science and engineering (University of Illinois at Chicago) and has been co-thesis advisors for doctoral and master candidates in Physics and Nuclear Engineering (Michigan Technological University and University of Illinois at Urbana/Champaign). He is a member of the American National Standard subcommittee N14.5 on Leakage Tests on Packages for Shipment of Radioactive Materials for the preparation of the American National Standard ANSI N14.5-2011. He has over 40 publications in refereed journals and book chapters and is the author/co-author of many formal technical reports.  He is also the recipient of four US patents.