Thermal contact conductance

About: Thermal contact conductance is a research topic. Over the lifetime, 5613 publications have been published within this topic receiving 134106 citations.

Negative differential thermal resistance and thermal transistor

Abstract: We report on the first model of a thermal transistor to control heat flow. Like its electronic counterpart, our thermal transistor is a three-terminal device with the important feature that the current through the two terminals can be controlled by small changes in the temperature or in the current through the third terminal. This control feature allows us to switch the device between “off” (insulating) and “on” (conducting) states or to amplify a small current. The thermal transistor model is possible because of the negative differential thermal resistance.

Role of thermal boundary resistance on the heat flow in carbon-nanotube composites

Abstract: We use classical molecular dynamics simulations to study the interfacial resistance for heat flow between a carbon nanotube and octane liquid. We find a large value of the interfacial resistance associated with weak coupling between the rigid tube structure and the soft organic liquid. Our simulation demonstrates the key role played by the soft vibration modes in the mechanism of the heat flow. These results imply that the thermal conductivity of carbon-nanotube polymer composites and organic suspensions will be limited by the interface thermal resistance and are consistent with recent experiments.

Thermally conducting aluminum nitride polymer-matrix composites

Abstract: Thermally conducting, but electrically insulating, polymer-matrix composites that exhibit low values of the dielectric constant and the coefficient of thermal expansion (CTE) are needed for electronic packaging. For developing such composites, this work used aluminum nitride whiskers (and/or particles) and/or silicon carbide whiskers as fillers(s) and polyvinylidene fluoride (PVDF) or epoxy as matrix. The highest thermal conductivity of 11.5 W/(m K) was attained by using PVDF, AlN whiskers and AlN particles (7 μm), such that the total filler volume fraction was 60% and the AlN whisker–particle ratio was 1:25.7. When AlN particles were used as the sole filler, the thermal conductivity was highest for the largest AlN particle size (115 μm), but the porosity increased with increasing AlN particle size. The thermal conductivity of AlN particle epoxy-matrix composite was increased by up to 97% by silane surface treatment of the particles prior to composite fabrication. The increase in thermal conductivity is due to decrease in the filler–matrix thermal contact resistance through the improvement of the interface between matrix and particles. At 60 vol.% silane-treated AlN particles only, the thermal conductivity of epoxy-matrix composite reached 11.0 W/(m K). The dielectric constant was quite high (up to 10 at 2 MHz) for the PVDF composites. The change of the filler from AlN to SiC greatly increased the dielectric constant. Combined use of whiskers and particles in an appropriate ratio gave composites with higher thermal conductivity and low CTE than the use of whiskers alone or particles alone. However, AlN addition caused the tensile strength, modulus and ductility to decrease from the values of the neat polymer, and caused degradation after water immersion.

Thermal conductance of interfaces between highly dissimilar materials

Abstract: The thermal conductance of interfaces between materials with low Debye temperatures (Pb or Bi) and dielectrics or semiconductors with high Debye temperatures (hydrogen-terminated Si, $\mathrm{Si}{\mathrm{O}}_{2}$, the native oxide of Be, sapphire, or hydrogen-terminated diamond) is measured using time-domain thermoreflectance. The interface thermal conductance $G$ for these combinations of materials falls within a relatively narrow range, $8lGl30\phantom{\rule{0.3em}{0ex}}\mathrm{MW}\phantom{\rule{0.2em}{0ex}}{\mathrm{m}}^{\ensuremath{-}2}\phantom{\rule{0.2em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$, at room temperature. Because the thermal conductance of interfaces with Bi, a semimetal, and interfaces with Pb, a metal, are similar, we conclude that the coupling of electrons in a metal to phonons in a dielectric substrate does not contribute significantly to the thermal transport at interfaces. For Pb or Bi on hydrogen-terminated diamond, the measured conductance greatly exceeds the radiation limit and decreases approximately linearly with decreasing temperature, suggesting that anharmonic processes dominate the transfer of thermal energy across interfaces between materials with highly dissimilar spectra of lattice vibrations.