Scanning microcalorimetry at high cooling rate

Heat capacity measurements at fast cooling and heating were realized for linear polyethylene NBS SRM (standard reference material) 1484 sample, ca. 120 ng, in the melting-crystallization region. A commercial vacuum sensor, thermal conductivity gauge TCG-3880, Xensor Integrations, was utilized as a cell for a micro-calorimeter suitable for such measurements. The cell consists of a thin-film Si3Nx membrane with a film-thermopile and a film-heater, which are formed at the membrane center. The current at the heater as well as the signal from the thermopile were monitored in real time during fast scanning of temperature of the central part of the membrane. The measurements were performed in an ambient gas, so that controlled cooling and heating rates up to 5×103 K/s were achieved. As conditions were not adiabatic, the heat leakage from the sample was calibrated and was taken into account for heat capacity measurements. A simple calibration algorithm was developed for such measurements. Thus, a step towards ultra fast cooling scanning calorimetry was made.