TIME-DOMAIN AND FREQUENCY-DOMAIN DIFFERENTIAL CALORIMETRY

The heat capacity C-p of a sample can be considered as a frequency dep endent quantity; its behaviour can reflect the dynamics of enthalpy fl uctuations. In order to take into account the dynamic nature of the me asured quantity, calorimetry can mimic experimental methods as those o f dielectrometry, performing experiments in time domain or in frequenc y 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 sup ercooled liquids. Moreover, experimental procedures permitting investi gation of samples undergoing chemical and/or physical transformations by simultaneous measurements of enthalpy variation, heat capacity and, under certain conditions, thermal conductivity, are discussed.