Differential Scanning Calorimetry

Differential Scanning Calorimetry

The Differential Scanning Calorimeter (DSC) is an instrument used frequently by our group to measure the thermal characteristics of the phase change materials (PCM). For every sample, heat flow in mW versus temperature was collected in the following manner. A sample of PCM of known mass is placed in a closed pan with a volume of 50m L. This sample pan and an empty reference pan of the same volume are placed inside the DSC. As the temperature is raised at a steady rate, i.e. 5K/min, the DSC measures how much extra heat is put into the sample pan in order to maintain its temperature the same as the empty reference pan. The melting point of the PCM should be reached as the temperature is raised. The melting phase transition is an endothermic process and appears as a peak in the heat flow versus temperature plot, indicating that an added amount of heat is necessary to melt the PCM (in comparison to the empty reference pan). This added heat is called the latent heat of melting and is stored by the PCM. Crystallization of the PCM (for crystalline PCM) occurs as the temperature is lowered at a steady rate. This phase transition appears as a dip in the heat flow versus temperature plot. Crystallization is an exothermic process in which heat is released by the PCM, this is called the latent heat of crystallization.

The latent heats of melting and crystallization can be quantified from the area of the peak and dip in the heat flow versus temperature plot, respectively. Latent heat in Joules/gram calculated by dividing the area by heating rate x sample mass.

                     (1)

To see the results of our DSC measurements, click here.