Differential Scanning Calorimeters

Specific heat capacity is measured using differential scanning calorimetry (DSC), applying two different techniques:

•Heat Flux

•Power compensation

The heat flux DSC (HF-DSC) can be used from room temperature up to 1500°C.

The power compensation DSC (PC-DSC) can operate from -100°C up to 700°C. Please note that a change of the measurement head is required to cover the full temperature range for the PC-DSC, so it cannot be performed as a single measurement scan.

A DSC measures the specific heat of a sample by heating two identical sample pans, one empty and the other containing the sample.

As the thermal mass of the pan containing the sample is greater than the empty one, the power needed to maintain the sample heating profile for both is different.

In PC-DSC, the pans are in separate furnaces, and the power difference is measured directly by the system.

In HF-DSC the heat flux to both pans is identical and the temperature difference between the pans is measured.

The difference in power or temperature is used to determine the heat capacity of the sample. To achieve this the DSC must perform identical heating/cooling cycles for the sample, for a well characterised sample and for the empty system (baseline).

Using all three data sets the heat capacity of the sample can be determined using the following equations:

C_sample= ((D_sample-D_baseline ))/((D_reference-D_baseline ) ) (m_reference C_reference)/m_sample

Where

•Di = the measured DSC for the ith measurement

•Ci = the specific heat capacity of the sample measured in the ith measurement

•mi = the mass of the ith sample

DSC specific heat measurement uses small samples (typically 1 mm thick and 5-6 mm in diameter), and is excellent for the identification of phase transitions.