State-of-the-art technology for thermophysical properties

Polycrystalline Graphite
Graphite materials are known to show a maximum thermal conductivity around room temperature, which can easily be analyzed using the low temperature version of the LFA 457 MicroFlash®. The physical explanation for this maximum is the high Debye temperature of this material (> 1000 K). The decrease in thermal diffusivity with increasing temperature dominates the temperature dependence of the thermal conductivity in the high temperature region. The specific heat decreases stronlgy at temperatures below room temperature and dominates the temperature dependence of the thermal conductivity there.

Polycarbonate
Polycarbonate (PC) is a popular polymer material used among other things, for electric tool casings. To optimize the production/molding process by finite element simulations, the thermophysical properties have to be known. The thermal diffusivity can be determined not only in the solid region but also at temperatures above the glass transition (> 140°C) if a molten material cell is employed in the LFA 457 MicroFlash®. Together with the specific heat (measured with a DSC) and density data, the thermal conductivity can be determined. The silght increase in the thermal conductivity versus temperature is typical for 100% amorphous materials. Furthermore, the glass transition is visible in the specific heat curve and in the thermal diffusivity result. In the thermal conductivity result, this second order transition cannot be seen.