Extremes in Heat Conduction:
Pushing the Boundaries of the Thermal Conductivity of Materials

David G. Cahill
Department of Materials Science and Engineering
Frederick Seitz Materials
Research Laboratory, University of Illinois, Urbana, Illinois 61801

Abstract
Thermal conductivity is a basic and familiar property of materials: silver spoons conduct heat well and plastic does not.  In recent years, an interdisciplinary group of materials scientists, engineers, physicists, and chemists have succeeded in pushing-back long-established limits in the thermal conductivity of materials.  The current champion at the high end of the thermal conductivity spectrum is carbon nanotubes, due to their high sound velocities and relative lack of processes that scatter phonons. Unfortunately, the superlative thermal properties of nanotubes have not found immediate application because of difficulties in making good thermal contact with nanotubes, i.e., the thermal conductance of interfaces with nanotubes is very small.  At the low end of the thermal conductivity spectrum, solids that combine order and disorder in the random stacking of two-dimensional crystalline sheets, so-called “disordered layered crystals” show a thermal conductivity that is only a factor of 2 larger than air; the cause of this low thermal conductivity is not fully understood but may be explained by a large fraction of vibrational modes that are localized and neither propagate as waves (as in crystals) or transport diffusively (as in glasses).

 Thursday, October 4th
Berger Auditorium, Skirkanich Hall
2:00 – 3:00 p.m.