An experimental study of some thermophysical properties of solid materials

The study of thermophysical properties of materials is of considerable interest in many areas of science and engineering. In the present work, three of these properties, i.e., specific heat, thermal diffusivity and thermal conductivity, were measured on some solid materials over a wide temperature range. Two experimental techniques i.e., ac calorimetry and photoacoustic photothermal microscopy, were developed for these measurements. The materials studied included carbon-carbon composites and amorphous solids (glasses). The measured results on one glass sample were compared with theoretical predictions for such materials.; In the ac calorimetry technique, a sinusoidal voltage is applied to a resistor that is in good thermal contact with the sample. The applied voltage produces an oscillation in the temperature of the sample. From the amplitude and phase of this temperature oscillation, which is measured by a thermometer attached to the sample, the specific heat and the thermal diffusivity of the sample can be determined. The thermal conductivity of the sample can then be obtained from the measured values of the specific heat and thermal diffusivity. This system is unique in that it incorporates two separate methods for determining the thermal diffusivity in the same apparatus. This approach provides a self-consistency test for the measured results.; In the photoacoustic microscopy technique, modulated light is absorbed by a sample and the resulting acoustic wave in the gas around the sample is measured. In the photothermal measurements, the temperature oscillation of the sample due to the absorbed light is measured. These techniques were used to perform in-situ measurements of the thermal diffusivity of a material at room temperature. With these techniques, the thermal diffusivity of the single fiber bundles of a carbon-carbon composite was measured.