What’s DTA?

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Differential thermal analysis (DTA) occurs when two substances are exposed to the same temperatures and the same thermal changes over time. The test typically includes a reference substance, which is known to behave under the applied temperature conditions. Another substance is subject to the same temperatures and rate of change as the reference. The sample can either absorb heat, generally meaning it is colder than the reference, or give off heat when it is hotter than the first material. With the tracked data, researchers can determine how specific materials react at certain temperatures, as well as over time.

Reference materials typically do not melt or freeze; they must remain in a steady state for the experiment to work. A differential thermal analysis technique is often performed by placing each material in a separate container. Each container is usually in a separate cavity in the same space. Instruments called thermocouples are generally used to record the temperature differences between two materials. Thermocouples can detect a phase change, such as melting or vaporization, as a signal.

Another method of differential thermal analysis can be the use of conductive pans, with thermocouples attached to them, inside an oven. Both materials are most often heated equally over time when DTA is performed this way. Test results are typically recorded using a DTA curve. You can track temperature differences between materials or a change in temperature over time. The graph often displays the latent heat of transition that occurs as a substance changes from one state to another; this usually causes the sample temperature to be temporarily lower than the reference.

Differential thermal analysis often involves analyzing samples at higher temperatures than other forms of thermal analysis. It can be conducted with materials such as metal, ceramic, glass and ceramics. Reference materials often used include silicon carbide and aluminum. Liquid reference standards sometimes include silicon oil.

21st century technology has combined differential thermal analysis with the ability to detect material mass loss and temperature change. Software programs can automatically monitor the process and record the measurements. Before a test, instruments for differential thermal analysis generally need to be calibrated. A separate calibration procedure runs materials known to respond in a particular way over certain temperature ranges. Local and regional regulations may guide the calibration process for differential thermal analysis in pharmaceutical, food or environmental applications.

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