THERMOGRAVIMETRIC ANALYSIS (TGA) THERMAL ANALYSIS THERMOGRAVIMETRIC ANALYSIS (TGA)

THERMOGRAVIMETRIC ANALYSIS Thermogravimetric analysis (TGA) is a technique in which the weight changes in a material is measured as a function of temperature (or time) under a controlled atmosphere. TGA is used in the research & development of various substances and engineering materials – solid or liquid – in order to obtain knowledge about their thermal stability and composition.

TYPES OF MEASUREMENT Thermobalance An instrument that measures the change in weight of a sample while it is being heated Thermogravimetric analysis relies on high degree of precision in three measurements: mass change, temperature, and temperature changes. TGA-FTIR/MS The combination of TGA with a mass spectrometer (MS) or a fourier transform infrared spectrometer (FTIR) is allowing the technique of Evolved Gas Analysis (EGA) where as the temperature increases, various components of the sample are decomposed and the volatile products can be measured.

OPERATING PRINCIPLE The sample is heated. The change in the weight of the substance is recorded as a function of temperature or time. The temperature is increased and the changes in weights are recorded as a function of temperature at different interval. This plot of weight change against temperature is called thermogravimetric curve or thermogram.

TGA INSTRUMENTATION AND SPECIFICATION: Sample holder (metallic/ceramic pans) Microbalance Programmable heater (furnace) Gas flow control Temperature control (thermostat) Temperature sensor (thermocouple) Read-out

CALIBRATION: Balance calibration Furnace calibration Temperature calibration

TEST SAMPLE: Sample size - between 2 and 50 mg. Or at least 1 mg. Cover the bottom of the pan with the sample material. The sample pans can accommodate liquids, powders, films, solids or crystals. Use approximately the same sample weight during each experiment. Better to have a large surface area exposed to the sample purge.

TEST RELATED: Analysis of mixtures Oxidation studies Reduction studies Exact chemical identification

INSTRUMENT PROCEDURE:

ADVANTAGES Accurate and precise method of macro quantitative analysis Low detection limit (up to 10-7) Reliable data Easy to use Minimal sample preparation Capable of conducting isothermal experiment and cooling experiment.

DISADVANTAGES Destructive Limited range of samples Required meticulous time consuming Usually not qualitative Mis-step in the procedure can lead to error for the analysis