Thermogravimetry / Thermogravimetric analysis (TGA)
Thermogravimetric analysis, also known as thermogravimetry, is an analytical technique used to measure the mass change of a sample as it is subjected to a controlled temperature profile. This analysis can involve heating, cooling, or maintaining isothermal conditions. The resulting measurement signal typically provides information on both the absolute mass change in milligrams (mg) and the relative mass change in percentage (%).
The setup for thermogravimetry involves placing the sample into a crucible made of inert material, such as platinum, alumina, or gold. This crucible is then positioned on a sensor within a furnace capable of maintaining controlled atmospheres and temperatures (as shown in scheme 1). The sensor is connected to a high-resolution microbalance, which records the changes in mass throughout the experiment. In many thermogravimetric analyzers, compensation balances are employed for precise mass measurements (as illustrated in scheme 2).
What is thermogravimetric analysis?
Thermogravimetry, or thermogravimetric analysis, is an analytical technique that tracks the changes in the mass of a sample as it is subjected to a controlled temperature profile. This can involve processes such as heating, cooling, or maintaining isothermal conditions. The measurement signal typically provides information about the absolute mass change in milligrams (mg) and the relative mass change in percentage (%).
The setup of thermogravimetry:
In conventional thermogravimetry, a sample is typically placed within a crucible made of an inert material like platinum, alumina, or gold. This crucible is then positioned on a sensor located within a furnace capable of maintaining controlled atmospheres and temperatures (as depicted in scheme 1).
The sensor is linked to a high-resolution microbalance that meticulously documents the changes in mass throughout the experiment. In many thermogravimetric analyzers, compensation balances, as illustrated in scheme 2, are employed for this precise measurement.
A compensation balance is a specialized type of balance that employs an electromagnet to offset the applied mass. In precise terms, the magnet compensates for the force of weight, and mass is determined using the formula:
Since gravity is typically known through calibration or can be accounted for using a counterweight, as is the case in a bar setup, the force of weight can directly yield the mass. It’s worth noting that this principle is not limited to thermogravimetric analyzers; laboratory balances often operate on the same fundamental principle.
During the sample’s exposure to temperature changes, the balance is usually maintained within a static temperature environment, such as a separate chamber or at a designated distance from the sensor.
To ensure precise temperature measurement, thermocouples are employed, leveraging the Seebeck effect for accurate temperature determination. Scheme 3 provides a visual representation of a typical thermogravimetric measurement, depicting relative weight change against temperature.
What is thermogravimetry used for?
Thermogravimetry finds extensive applications in various industries and research fields. It is employed in ceramic, chemical, polymer, construction, energy storage, battery research, and the oil industry. Typical uses include investigating thermal decomposition, determining ash or organic content, conducting gravimetric sorption studies, exploring thermal stability and oxidation behavior, and material analysis, among other applications. Additionally, specialized fields like nuclear research and high-pressure process studies benefit from this technique.
Thermogravimetry plays a vital role in the broader realm of thermal analysis and adheres to international standards such as ASTM D 3850, E 914, E 1131, E 1868, DIN 51006, ISO 7111, and ISO 11358.