Differential thermal analysis

Differential Thermal Analysis
Differential Thermal Analysis – (Also DTA) – One of the methods used to study the thermal properties of energetic materials. DTA is a technique in which the difference in temperature between a sample and an inert reference substance is measured, as the two specimens are subjected to an identical temperature program. If the test sample generates heat, its temperature will be higher than the reference sample. If the sample absorbs heat, its temperature will be lower than the reference sample. During the temperature program, the specimens are most often heated at a constant rate (typically ranging from 2 to 20°C per minute) or held at constant temperature (isothermal). One of the advantages of the DTA technique is that the instrument design can be made relatively robust so that much higher temperature than that achievable in differential scanning calorimetry can be attained (typically 1400-1500°C). A schematic diagram of a typical DTA apparatus is shown in Fig. 1, below.

What is Differential Thermal Analysis?

Difference in temperature, DT, between a sample and a reference material is measured when they are
subjected to a controlled temperature program (usually T increases linearly with time).

<10 mg of sample (s) and inert reference (r) are contained in Al pans each with thermocouple, held in
heating block, with thermocouple.

Both sample and reference material must be heated under carefully controlled conditions. If the sample
undergoes a physical change or a chemical reaction, its temperature will change while the temperature of
the reference material remains the same. That is because physical changes in a material such as phase
changes and chemical reactions usually involve changes in enthalpy, the heat content of the material.

There is a constant temperature difference DT between s and r since they have different heat capacities.
But when the sample undergoes an endo (exo) thermic change DT becomes different.