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5/17/2017  |   2:00 PM - 2:25 PM   |  3

Thermal Reffusivity of Materials: 0 K-limit and uncovered structure grain size

Electrical resistivity of metals and its variation against temperature directly reflects the phonon scattering behavior, and is dependent on the phonon structure. On the other hand, the thermal resistivity concept in heat conduction cannot be used directly to capture the same phonon behavior. This talk will introduce a new concept: thermal reffusivity, which is the inverse of thermal diffusivity, and present the studies we have conducted for various metallic, polymer, and semiconductor materials. The material size spans from tens of micrometer to a few nm. The variation of the thermal reffusivity against temperature, in comparison with that of bulk counter part, directly uncovers the contribution of defects. Also the Debye temperature of materials can be directly determined from the thermal reffusivity-temperature curve, similar to the electrical resistivity-temperature curve. The 0 K-limit of the thermal reffusivity, termed residual thermal reffusivity, is directly used to determine the grain size uncovered by low-momentum phonon scattering. This size is very close to that determined by x-ray diffraction. In summary, the thermal reffusivity sheds new light into the structure effect on heat conduction, and provides great potential to look into material’s structure from the heat conduction respect.

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Xinwei Wang (POC,Primary Presenter,Author), Iowa State University, ;

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