The mass is a fundamental physical quantity for determining a quantity of substance. In the context of this size, the properties inertia and severity are defined. Inertia means that an external force is required to change the direction or speed of movement of a body. Gravity is the result of mass attraction of bodies (gravitation). The unit of measurement of the mass is kilogram [kg].
The determination of the mass is carried out by weighing. A balance is used to determine the weight of a substance that results from the weight and is proportional to the mass. The unit of measure of weight is Newton [N]. In common usage, this relationship is often neglected and the term weight is used as meaning mass.
The mass change in the thermal analysis
Thermogravimetric analysis determines the mass change of a sample or material during heating or cooling. The result is also referred to a mass change or weight change and is usually given in micrograms [μg]. The determination of the mass change is carried out with a thermobalance.
The thermobalance consists of the oven with precise temperature control, the very accurate electrical balance, supply lines for required gases and evaluation units for the measured value processing.
Linseis thermal analysis instruments allow simultaneous thermal analysis (STA) to simultaneously determine mass changes and release or consumption of heat during the controlled temperature history. The mass change is due to evaporation, sublimation or chemical reactions. Heat is released or consumed in chemical reactions and phase transformations.
The values determined are an important basis for the development of specific materials in the automotive industry, for the investigation of food as well as for product development and quality assurance in the pharmaceutical and chemical industries.
Applications with mass change
Introduction and Application: Talc (Mg3(OH)2[Si2O5]2) is a mineral composed of hydrated magnesium silicate. It is used for the production of steatite bodies used as isolators with high resistance and a low dielectrical loss factor. The impurities (chlorite, carbonates) can be detected with combined TG and DTA signal.
Analysis using STA: The dehydroxilation of chlorite appears at 608°C and 848°C as endothermal DTA signals. At 786°C evolve CO2, the carbonate decomposes to its oxide. The endothermal peak at 937°C is the dehydroxilation of talc. The quantitative measurement of the impurity can be evaluated from the TG signal.
Application: Calciumoxalate standard
The picture shows the measurement of a Calciumoxalate standard. There are three mass loss steps, where the first one is the removal of H2O, the second one is the loss of CO, which is immediately oxidized to CO2 in air atmosphere (this is why the second peak is exotherm instead of endotherm like the others.) The third step is the loss of CO2. The resulting Calciumoxide (CaO) is reacting afterwards with the water from the first step, that is still in the reaction chamber if the atmosphere is static. It shows the formation of Calciumhydroxide (Ca(OH)2) that is formed at around 580°C. This last step is hard to see on a standard STA or TG because of the slow cooling rates. But in this case, a whole measurement cycle can be done within just 20 minutes. In this example the heating and cooling rate was 2K/s, but you can easily go up to 100K/s.