In differential thermal analysis (DTA), the temperature difference between test sample and reference material (non-reactive generally alumina) is followed, while the two substances are subjected to identical and controlled heating or cooling. The thermal plot is temperature difference Vs the temperature of reference material.
1) Furnace: It is operating from the temp. of 170-2800°C. The temperature varies 0.1-30°C per minute. The heating is done with heater coils or IR-radiations.
2) Two wells of equal size: One for reference and the other well (cavity) is for sample. The reference is usually Alumina. The reference and sample is placed in the wells.
3) Thermo couple: The temp. of reference and sample and the diff. between two temperature is measured with the help of thermocouples, which is combination of two metals
4) Amplifier: If the diff. of temp. is small, it is difficult to measure accurately then it is to be amplified with amplifier.
5) Atmosphere Control: The heating of sample and reference is done in presence of inert (purge) atmosphere. In other case the ref. or sample may react with the gases of atmosphere.
6) Recorder: Very sensitive recorders are used. It may be photographic light beam galvanometer or electronic potentiometer. A two point recorder records both the diff. temp. and reference material temp as a function of time or temp. ref. on the axis. Recorder will give graph, which on analysis we can have quantitative analysis and from the graph we can decide the change whether it is physical or chemical change.
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