Thermogravimetry is the technique in which change in the weight is recorded as the function of temperature Or time. The phenomenon is used for qualitative as well as quantitative analysis.
The instrumentation of TGA is consisting of the following components:
1) Balance: It must be highly sensitive analytical balance. It must be precise and accurate at experimental temp. The commonly used balance is "Cahn" electro balance. It functions as null type device by providing an electrical force to restore the beam to a predetermined position. When mass changes, the beam of the balance changes, a shutter fixed to the beam changes the amount of light reaching a photo tube (EMR), which causes a restoring force to be generated by passing a current through an electromagnet, that serves as the pivot for the balance beam. A permanent magnet above and below the pivot provides the magnetic attraction to the electromagnet. The force require to restore the beam is proportional to the current which is recorded.
2) Furnace or Heating Device: Here the sample is heated by resistance heaters, IR-radiations, Microwave radiations or heating can also be done by passing the hot vapors of liquids or solids. The furnace must be design in such a manner that heat produced is directly given to the sample. The rate of increase of temp must be 0.15 to 2 deg per minute. The heating should be done in such a manner so that the weighing system should not be affected.
3) Sample Holder: The sample holder should be made up of glass, quartz, stainless steel or pt. The size and shape depends on the weight and nature of the sample
4) Temperature measurement and control: The temperature measurement is done by thermo couples. It is placed very Close to the sample. The emf generated by thermocouple, when heated is incident and is applied on the X-axis of Data acquisition and Manipulation (computer).
5) Recorder: The electrical current obtained with EMR null detector is plotted on the Y-axis and emf. of the thermocouple on X-axis in data acquisition manipulation (Computer).
6) Control of Atmosphere: The results in tile thermo gravimetry depends on the atmosphere of sample see that the atmosphere should be inert gas called purge gas which may be Ar OR N2.
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