The key difference between TGA DTA and DSC is that TGA measures the weight change of a sample over a temperature range, while DTA measures heat differences between a reference sample and a sample of interest over a temperature range, and DSC measures the heat flow of a sample over a temperature range.
TGA stands for thermogravimetric analysis while DTA stands for differential thermal analysis, and DSC stands for differential scanning calorimetry.
CONTENTS
1. Overview and Key Difference
2. What is TGA
3. What is DTA
4. What is DSC
5. TGA vs DTA vs DSC in Tabular Form
6. Summary – TGA vs DTA vs DSC
What is TGA (Thermogravimetric Analysis)?
The term TGA stands for thermogravimetric analysis. It is a method of analyzing a sample thermally in which the mass of the sample is measured over time when temperature changes subsequently. Measuring the mass in this method provides us with information about physical phenomena, including phase transitions, absorption, adsorption, and desorption. It also provides information about chemical phenomena such as chemisorption, thermal decomposition, and solid-gas reactions like oxidation and reduction.
The instrument that we can use for TGA is a thermogravimetric analyser. It can continuously measure mass while the temperature of the sample is changed over time. In this method, we consider mass, temperature, and time as base measurements, and many additional measures are derived from these three base measurements.
Typically, a TGA analyser contains a precision balance with a sample pan located inside a furnace with a programmable control temperature. Generally, this temperature is increased at a constant rate to incur a thermal reaction. The thermal reaction can take place under a variety of atmospheres, including ambient air, vacuum, inert gas, oxidizing/reducing gases, corrosive gases, carburizing gases, vapours of liquids, or self-generated atmosphere. It can also include a variety of pressures such as high vacuum, high pressure, constant pressure, or controlled pressure.
The data collected from the analyzer can be used to make a plot of mass or percentage of initial mass on the y axis vs. temperature of time on the x axis. We call this plot a TGA curve. The first derivative of the TGA curve can be plotted by determining infection points that are useful for in-depth interpretations and differential thermal analysis.
What is DTA (Differential Thermal Analysis)?
The term DTA stands for differential thermal analysis. It is a thermoanalytical technique similar to differential scanning calorimetry. In this method, the material under study and an inert reference undergo identical thermal cycles, such as the same cooling or same heating programs. Then, we can record any temperature difference between the sample and the reference.
A plot between the differential temperature and time or temperature is called a DTA curve or thermogram. From this, we can detect changes in the sample that are either endothermic or exothermic in relation to the inert reference. Therefore, a DTA curve provides data on the transformations that have taken place, which include glass transitions, crystallization, melting, and sublimation. We can identify the area under the DTA peak as the enthalpy change, and it is not really affected by the heat capacity of the sample.
What is DSC (Differential Scanning Calorimetry)
DSC or differential scanning calorimetry is a thermoanalytical method that measures the difference in the heat required to increase the temperature of a sample and the reference as a function of temperature. In this method, both the sample and the reference are maintained at the same temperature throughout the experiment.
Usually, the temperature used for the DSC method is designed as a temperature program in such a way that the sample holder temperature increases linearly as a function of time. On the other hand, the reference sample should have a well-defined heat capacity over the range of temperatures that we are going to scan.
There are different types of DSC, such as heat-flux DSc and power differential DSC. Heat-reflux DSC measures the difference in heat flux between the sample and a reference, whereas power differential DSC measures the difference in power supplied to the sample and a reference.
What is the Difference Between TGA DTA and DSC?
TGA stands for thermogravimetric analysis while DTA stands for differential thermal analysis, and DSC stands for differential scanning calorimetry. The key difference between TGA DTA and DSC is that TGA measures the weight change of a sample over a temperature range, whereas DTA measures the difference in heat between a reference sample and a sample of interest over a temperature range, and DSC measures the heat flow of a sample over a temperature range.
The below infographic presents the differences between TGA DTA and DSC in tabular form for side-by-side comparison.
Summary – TGA vs DTA vs DSC
The key difference between TGA DTA and DSC is that TGA measures the weight change of a sample over a temperature range, and DTA measures the difference in heat between a reference sample and a sample of interest over a range of temperature, whereas DSC measures the heat flow of a sample over a temperature range.
Reference:
1. “Thermogravimetric Analysis.” An Overview | ScienceDirect Topics.
Image Courtesy:
1. “Thermogravimetric analyser” By Inside_DSC.JPG: Aboalbissderivative work: Walkerma (talk) – Inside_DSC.JPG, (CC BY-SA 3.0) via Commons Wikimedia
2. “Inside DSC small” By Luigi Chiesa – Own work (CC BY 3.0) via Commons Wikimedia