Thermogravimetry microbalance

Thermogravimetry consists of the continual recording of the mass of the sample as it is heated in a furnace, and a schematic diagram of a TG apparatus is given in Fig. 14. The weighing device used in most systems is a microbalance, which permits the accurate determination of milligram changes in the sample mass. The... 

In thermogravimetry (TG or TGA) the change in sample mass is determined as a function of temperature and/or time. The instrument is a thermobalance that permits the continuous weighing of a sample as a function of time. The sample holder and a reference holder are bounded to each side of a microbalance. The sample holder is in a furnace, without direct contact with the sample, the temperature of which is controlled by a temperature programer. The balance part is maintained at a constant temperature. The instrument is able to record the mass loss or gain of the sample as a function of temperature and time [m = /( )]. Most instruments also record the DTG curve, which is the rate of the mass change dm/dt = f(T). 

In thermogravimetry the variation of the mass of a sample with temperature is monitored in a thermobalance comprising a microbalance, a furnace and a temperature controller. This apparatus allows the calculation of the fractional loss of mass and thus the stoichiometry of a solvate by TGA (Caira, 1998) (Figure 10-6). 

Thermogravimetry is the most commonly used method for studying the kinetics of corrosion reactions at high temperatures. The sample is placed in an oven with a controlled atmosphere, where one monitors the variation of its mass by means of a microbalance (Figure 9.3). The precision of the technique is on the order of micrograms. If all corrosion products remain on the surface of the sample, the measured mass increase as a function of time permits to identify the rate law that governs the reaction kinetics. 

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