Thermogravimetry

The aim of thermogravimetric analysis (TGA) or thermogravimetry is to characterize materials by directly measuring their mass as a function of temperature and/or time.

This technique for measuring the overall properties of a material sample can also be coupled with other analysis methods carried out simultaneously. The most frequently used complementary techniques are :

• calorimetry (DSC) ;

• differential thermal analysis (DTA);

• separation techniques: mass spectrometry (MS), chromatography.

Most instruments operate at atmospheric pressure or under vacuum, in isothermal or programmed temperature mode. Operation in a controlled atmosphere with a defined composition enables us to understand the behavior of materials at high temperatures. Recently, developments in electronics and nanotechnology have led to the commercialization of piezoelectric balances enabling the study of very small variations in mass for samples deposited in thin layers. Further progress is currently being made in the field of pressure-controlled atmosphere studies.

Since 2004, mass sensors have evolved into new, more compact and powerful versions. This article reviews the various modern sensor technologies and their impact on instrument design, with their strengths and weaknesses. A chapter is devoted to the compatibility of sensor materials with different working atmospheres.

The metrological aspect is covered through vocabulary, as well as an analysis of the main sources of error and the quantities influencing measurement.

To illustrate the many and varied possibilities of thermogravimetric analysis, a series of typical experiments, linked to different sectors of activity, are presented.