Time-domain and frequency-domain differential calorimetry

Abstract

The heat capacity Cp of a sample can be considered as a frequency dependent quantity; its behaviour can reflect the dynamics of enthalpy fluctuations. In order to take into account the dynamic nature of the measured quantity, calorimetry can mimic experimental methods as those of dieleetrometry, performing experiments in time domain or in frequency domain.In this paper, an instrument is presented which is based on a calorimetric method meeting these requirements, and thus allowing to study sample dynamics of very viscous systems as glasses and some supercooled liquids. Moreover, experimental procedures permitting investigation of samples undergoing chemical and/or physical transformations by simultaneous measurements of enthalpy variation, heat capacity and, under cerf.ain conditions, thermal conductivity, are discussed.