Thermogravimetric (TG) analysis measures changes in the mass of the sample as a function of temperature and/or time. TG provides characteristic information about the composition of the specimen, specifically the amounts of its various components and their thermal behavior. Other measurements, such as the kinetic analysis of thermal decomposition, are also possible. However, by itself TG does not allow the direct identification of the gases released from the sample during the thermal treatment. For this purpose, coupling TG to a spectroscopic interrogation method, such as Fourier- Transform- Infrared (FT-IR) spectroscopy, is an excellent solution.
IR spectroscopy gives, with the exception of homonuclear diatomics and noble gases, the characteristic spectrum of each substance. It is a standard technique, which exploits the interaction of infrared radiation with the vibrating dipole moments of molecules.
TG-FTIR Coupled System
Netzsch Thermal Analysis and Bruker Optics offer the integrated TG-FTIR coupled system.
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Figure 1. Internal view of TG-209 IRIS
A 588 TG-FTIR module comprises a stainless steel gas cell, which has been designed for optimal IR beam geometry. It has an optical path length of 123 mm. The instrument is optimised for low volume analysis. The small active volumes of the thermal micro balance (2.4 ml), of the transfer line (4.5 ml) and of the gas cell (8.7 ml) in fact, allow a very low usage of transfer gas flow. This leads to an increased concentration of the evolved gases transported into the gas cell. Thanks to the vacuum-tight construction of the thermal micro balance and the gas cell, shown in Figure 2, both systems can be evacuated together. Due to the small amount of residual gases reduces the possible and undesired influence of the released gases on the decomposition process.
The features of the TG-FTIR Coupled System are listed below:
- Easy-to-use, powerful, integrated software
- Optimized low volume design
- Vacuum compatible, to remove oxygen, eliminate carryover, and lower boiling points
- Easy-to-maintain gas cell and transfer line
- Optional 64 position automatic sample changer
Optimized TG-FTIR Gas Cell
The TG-FTIR interface has been specifically designed (Figure 2) so that cleaning is no longer a time consuming operation requiring great expertise. The cell features removable ends which can be easily unscrewed for maintenance purposes. The transfer line is a disposable and easy-to-replace Teflon tube. IR spectroscopy is a non-destructive method. It allows the spectral analysis of single components from gas mixtures. The analysis of the gas phase IR spectra is simplified due to minimal molecular interaction. This also means that the IR spectra of gas mixtures can be resolved into their single components, simply by subtracting specific library spectra relevant to the corresponding pure compounds. Large libraries of infrared spectra are available for the identification of most gases and vapors.
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Figure 2. TG-FTIR gas cell schematic
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Figure 3. Beam path in the TENSOR 27
TG-FTIR Application Areas
The TG-FTIR range of applications include:
- Outgassing of Materials
- Detection of Residues
- Analysis of Additives
- Analysis of Aging Processes
- Competitive Analysis
- Characterization of Natural and Raw Materials
- Desorption Behavior
- Analysis of Synthesis Processes
- Analysis of Decomposition Processes
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This information has been sourced, reviewed and adapted from materials provided by Bruker Optics.
For more information on this source, please visit Bruker Optics.