Thermal analysis techniques such as differential thermal analysis (DTA) measure the temperature difference between a sample and an inert reference material as they are heated or cooled. DTA can identify physical and chemical changes in materials through endothermic or exothermic peaks on a thermogram. The DTA instrument contains sample and reference holders connected to thermocouples which are heated in a furnace and temperature differences are amplified, detected and recorded. DTA has applications in determining melting points, phase changes, and reactions, as well as characterizing materials like polymers, pharmaceuticals, soils and catalysts. It can also provide information on purity, thermal stability and kinetic parameters of organic materials.

1. S.N.PATEL INSTITUTE OF TECHNOLOGY
AND RESEARCH CENTRE,UMRAKH
THERMAL ANALYSIS (DTA) AND
THEIR APPLICATION
Subject : P& IC(2140501)
Guided by:

2. Contents
Thermal analysis
 Classification of thermal analysis
 Differential thermal analysis(DTA)
 Principle
 Instrumentation
Advantage and Disadvantage
 Application

3.  Thermal analysis is defined as technique for measuring the difference in
temperature between a substance and a reference material (inert substance) with
respect to temperature and time.
 substance is heated it undergoes physical and chemical changes occur.
 physical change: melting or boiling ,weight loss, gas evolution.
 chemical change : decomposition or reaction take place.

4. Sr no Technique Parameter
measured
Instrument used Graph
1 Thermogravimetry mass thermobalance Mass vs. temp
or time
2 Derivative
Thermogravimetry
dm/dt thermobalance dm/dt vs.
temp.
3 Differential thermal
analysis
Delta T DTA apparatus Delta T vs.
temp.
4 Differential scanning
calorimetry
dH.dt calorimeter dh/dt vs. temp.
5 Thermometric
titrimetry
temperature calorimeter Temp vs.
titrant volume

5. 6 Dynamic
Reflectance
spectroscopy
Reflectance Spectrophotometer % reflectance and
temp
7 Evolved gas
detection
Thermal
conductivity
Thermal
conductivity cell
T.C vs. temp.
8 Thermo mechanical
analysis
Volume or length dilatometer Volume or length
vs. temp.
9 Electrical
conductivity
Current or
resistance
electrometer I or R vs. temp.
10 Emanation thermal
analysis
Radioactivity ETA apparatus E vs. temp.

6.  TG/DTA
Simultaneous
Measuring
Instrument
 Simultaneous
TG/DTA
improves ease
of operation,
sensitivity and
analytical
accuracy

7. Principle :
The principle of (DTA) analysis is that sample and
reference (inert substance) materials is heating
or cooling at desirable rate simultaneously and they under
go chemical and physical change which is measured by
recorder.
Differential thermal analysis

8. Instrumental detail
• This instrument comprises a sample holder with thermocouple assembly ,furnaces, flow
rate control assembly ,amplifier, detector ,recorder and furnace temperature controller
as mentioned in fig
• Briefly sample and references are kept in small crucible called sample holder which it
connected with thermocouple each.
• This crucible made of refractory materials like silica Pyrex nickel or platinum .
depending upon the nature of the of the test involved the thermocouple is direct contact
with the sample and reference to avoid contamination and degradation .
• The function of thermo couple is to ensure that heating or cooling is equally distributed
in the sample and reference

9. • These holders are kept in furnace in which heating is carried out for continuous and
desirable heating or cooling furnace .
• Temperature Control is attached with furnace with furnace now thermocouple is
attached with amplifier detector and recorder which is measures the
• Chemical and physical on heating or cooling the sample and reference .
• Now the sample which is to be analyzed and reference are kept in sample holder and
heating or cooling is started at desirable flow rate the chemical and physical change
during temperature difference with respect to time is measured and recorded which is
represented as thermogram the thermogram of calcium acetate is illustrated below

10. Microprocessor controlled
power source
Reference sample
Environment
Control
Equipment
Thermocouple 1
Amplifier
Thermocouple 2 Amplifier
Recorder
Ice box
Block diagram of DTA instrument

11.  SAMPLE HOLDER
a) METALIC : nickel,stainless steel,platinum
sharp endothermic peak.
a) NON METALIC : glass,silica,sintered alumina
sharp exothermic peak.
 FURNACE
For heating the sample.
Material used wire or ribbon wound on refractory tube.

12. TEMPERATURE CONTROLLER
1) SENSOR
2) CONTROL ELEMENT
3) HEATER
RECORDER
1) DEFLECTION TYPE: Recording pen is
moved directly by the input signal.
2) NULL TYPE: Input signal is compared
with a reference or standard signal and
difference is amplified.

13. ADVANTAGE
High resolution and a robust easy to
use.
DISADVANTAGE
Less satisfactory with regard to
resolution of thermal traces and
quantitative data.
 Unable to measure the energy
associated with each event.

14. Application
1. DTA techniques are useful for providing many basic
transformations,dehydration,decomposition,oxidation,reduction,heat of reaction,
specific heat, thermal diffusivity , etc.
2. Melting point and boiling point of any organic compound are easily determined
using this techniques .
3. DTA techniques is widely used for characterization of polymer one of the
thermogram of polymer as mentioned .

15. decompositionmelting
oxidation
Glass
transition
crystallization
Temperature
T
No oxidation

16. 4. Qualitative analysis of the material when two or more substance or polymer
are mixed together then mixture undergoes DTA analysis to give characteristic
melting point peak of each substance or polymer
5.DTA technique has been widely used for the quality control of large number of
substance like cement, glass, soil, catalyst, textiles, explosives, resins,etc

17. 6.It is also utilized for analyze the thermal stability of large no of
inorganic compounds and complexes.
7. It is widely used for purity determination and also evaluation of
kinetic parameters of polymer, explosives ,pharmaceuticals oils fat
and other organic materials.