Insights on  Differential Thermal Analysis (DTA) And Differential Scanning  Calorimetry

Differential Thermal Analysis (DTA) And Differential Scanning  Calorimetry

Differential thermal analysis (DTA) involves gradually increasing the sample’s temperature while recording the Tref – Tsamp temperature difference as a function of the sample’s temperature. Similar to differential scanning calorimetry (DSC), differential thermal analysis (DTA) measures the thermal expansion and contraction of a sample in order to draw conclusions about the sample’s properties.

Differential Thermal Analysis (DTA) is a fundamental principle that measures the temperature difference between a sample and a reference material as they both undergo controlled heating or cooling. When a sample undergoes a phase change or chemical reaction, it either absorbs or releases heat energy, leading to a temperature difference (ΔT) between the sample and the reference. DTA measures this temperature difference as a function of temperature (T) while subjecting both the sample and the reference to the same controlled heating or cooling rate. The resulting curve provides information about the heat effects associated with phase transitions, reactions, and other thermal events in the sample.

Detailed instrumentation for DTA includes sample and reference crucibles, furnaces, thermocouples, temperature controllers, differential temperature detectors, and data acquisition systems. DTA is used in various applications such as phase transition characterization, reaction kinetics, quality control, material development, geological studies, polymer characterization, pharmaceuticals, and environmental science. It provides critical insights into phase transitions, reactions, and thermal stability, aiding in material characterization, quality control, and product development.

ΔT=Tref−Tsamp

The value of T becomes more negative when the sample temperature rises higher than the reference temperature during an exothermic process like crystallization or a chemical reaction. The sample’s temperature is lower than the reference materials’ temperature because of an endothermic process, such as melting a crystalline substance or losing water from hydration. In DSC, the sample temperature is raised linearly, and the difference in the amount of heat required to keep the sample and the reference at the same temperature is calculated. For an endothermic process, heat is added to the sample, while for an exothermic process, heat is removed. The resulting DSC curve resembles a DTA curve.

Differential Scanning Calorimetry (DSC) is another closely related thermal analysis technique used to study the thermal properties of materials, including phase transitions, reactions, and heat capacity changes. DTA measures the temperature difference (ΔT) between a sample and a reference material as they both undergo controlled heating or cooling. DSC measures the heat flow (either absorbed or released) between a sample and a reference material as they are subjected to controlled heating or cooling.

Small metal pans containing the sample and the standard are put on different levels of the sample chamber. To keep the T constant between the sample and the reference, a metal disk connects the two platforms and acts as a low-resistance heat conduit. By placing the sample and the reference in separate heating chambers and measuring the difference in power provided to the two chambers necessary to maintain a T of zero, power compensation DSC is another instrument design for differential scanning calorimetry.

Differential scanning calorimetry (DSC) apparatus elements : The procedure entails (a) placing the sample and the standard in separate tiny aluminum pans and (b) crimping the lids and pans together. The sample and the reference can be heated in the chamber’s central well (c), where the sample is also located. In this up-close view of the sample chamber (d), you can see the two platforms used to hold the sample and the reference. The sample chamber is covered with an insulated lid. Even though this is a DSC setup, the instruments used for differential thermal analysis are very comparable. The pan in (a) is about 5 mm in diameter and 1 mm in depth, and the platforms in (d) are similarly around 5 mm in diameter to give you an idea of size.

Applications

When the area, A, of a peak is integrated in DSC or DTA, the resulting signal is proportional to heat capacity, H.

ΔH=K×A

where the constant of calibration, k, is calculated from a known standard. DSC and DTA are both useful tools for researchers interested in studying liquid crystals, pharmaceuticals, and polymers.

DTA provides a temperature difference curve (ΔT vs. temperature), while DSC directly measures heat flow. The choice between the two techniques depends on the specific research or analysis requirements.

DTA and DSC are complementary thermal analysis techniques that provide valuable insights into the thermal behavior of materials. DTA focuses on temperature differences, while DSC directly measures heat flow. The choice between the two techniques depends on the specific research or analysis requirements. Both the heat flow (DSC) and temperature gradient (DTA) are quantified in these analyses.