3. ◼ An Internationally accepted definition of
thermogravimetry is as follows:-
"It is a technique where by weight of substance in an
environment heated or cooled at a controlled rate, is
recorded as a function of time or temperature.”
3
OR
Thermogravimetric analysis or thermal gravimetric
analysis (TGA) is a method of thermal analysis in which
the mass of a sample is measured over time as the
temperature changes.
◆Definition
4. A TGA analysis is performed by gradually raising the
temperature of a sample in a furnace as its weight is
measured on an analytical balance that remains
outside of the furnace. In TGA, mass loss is observed
if a thermal event involves loss of a volatile
component.
4
◆Principle:-
7. The basic requirements of a Balance are accuracy,
sensitivity, reproducibility and capacity.There are 2
types of balances
1) Null type balance which consists of a sensor which
detects the deviation from the null point and restores
the balance to its null point by means of a restoring
force.
2) Deflection balance which converts the deflection
of balance beam deflection into a suitable mass by
means of photographic recording or recording
electrical signals or using an electro-chemical device.
7
1)Thermobalance:-
8. The Furnace provides linear heating over a wide range
of operating temperaures, typically -150 deg. Celsius to
about 2000 deg. Celsius depending on the requirement.
8
2)Furnace:-
9. Temperature measurement and regulation is done with
the help of thermocouples. Usually 2 thermocouples
are used, where one records the temperature change,
the other actuates the control system.
9
3)Furnace tempreture
programmer/controler:-
10. The recording unit makes use of a microprocessor
which allows for digital data acquisition and
processing using a personal computer.
10
4)Recorder:-
11. 1) Furnace heating rate
2) Sensitivity of the sensors
3) Recording speed
4) Amount of sample
5) Particle size
6) Heat of reaction etc.
11
◆The factors affecting the precision and
accuracy of theTG curve are
