MELTING OF INDIUM BY TEMPERATURE-MODULATED DIFFERENTIAL SCANNING CALORIMETRY

The melting and crystallization of a sharply melting standard has been explored for the calibration of temperature-modulated differential sc anning calorimetry, TMDSC. Modulated temperature and heat flow have be en followed during melting and crystallization of indium. It is observ ed that indium does not supercool as long as crystal nuclei remain in the sample when analyzing quasi-isothermally with a small modulation a mplitude. For standard differential scanning calorimetry, DSC, the mel ting and crystallization temperatures of indium are sufficiently diffe rent not to permit its use for calibration on cooling, unless special analysis modes are applied. For TMDSC with an underlying heating rate of 0.2 K min(-1) and a modulation amplitude of 0.5-1.5 K at periods of 30-90 s, the extrapolated onsets of melting and freezing were within 0.1 K of the known melting temperature of indium. Further work is need ed to separate the effects originating from loss of steady state betwe en sample and sensor on the one hand and from supercooling on the othe r.