Thermal conductivity and thermal diffusivity of selected oxide single crystals

Values for the thermal conductivity kappa and the thermal diffusivity D of four oxide single crystals were obtained. Near room temperature, the values for kappa (W cm(-1) K-1) and D (cm(2) s(-1)) are as follows: LaAlO3, kappa = 0.115, D = 0.0446; NdGaO3, kappa = 0.068, D = 0.0197 for one structural orientation, and kappa = 0.059, D = 0.0195 for an orthogonal orientation; (LaAlO3)(0.3)-SrAl0.5Ta0.5O3, kappa = 0.051, D = 0.0133; and, ScAlMgO4, kappa = 0.062, D = 0.0229. The relative standard uncertainties in these values are +/-10% (1 sigma). These values allowed us to calculate the specific heat of the materials. The thermal conductivity was measured by a dc heated bar method, and the thermal diffusivity was measured by a modification of Angstroms method

A Thermokinetic approach to radiative heat transfer at the nanoscale

Radiative heat exchange at the nanoscale presents a challenge for several areas due to its scope and nature. Here, we provide a thermokinetic description of microscale radiative energy transfer including phonon-photon coupling manifested through a non-Debye relaxation behavior. We show that a lognormal-like distribution of modes of relaxation accounts for this non-Debye relaxation behavior leading to the thermal conductance. We also discuss the validity of the fluctuation-dissipation theorem. The general expression for the thermal conductance we obtain fits existing experimental results with remarkable accuracy. Accordingly, our approach offers an overall explanation of radiative energy transfer through micrometric gaps regardless of geometrical configurations and distances

Heat Conduction of Air in Nano Spacing

<p>Abstract</p> <p>The scale effect of heat conduction of air in nano spacing (NS) is very important for nanodevices to improve their life and efficiency. By constructing a special technique, the changes of heat conduction of air were studied by means of measuring the heat conduction with heat conduction instrument in NS between the hot plate and the cooling plate. Carbon nanotubes were used to produce the nano spacing. The results show that when the spacing is small down to nanometer scale, heat conduction plays a prominent role in NS. It was found that the thickness of air is a non-linear parameter for demarcating the heat conduction of air in NS and the rate of heat conduction in unit area could be regard as a typical parameter for the heat conduction characterization at nanometer scale.</p