This document discusses thermal analysis techniques such as differential thermal analysis (DTA) and thermogravimetry (TGA). It explains that DTA involves measuring the temperature difference between a sample and reference material as they are heated, allowing physical and chemical changes to be identified. TGA measures the mass change of a sample as it is heated to determine information about physical phenomena like phase transitions and chemical phenomena like decomposition. The document provides details on the principles, instrumentation, factors affecting the techniques, and applications of DTA and TGA.

1. JISHANA BASHEER
RESEARCH SCHOLAR
PS&RT
CUSAT

2. INTRODUCTION
THERMAL ANALYSIS TECHNIQUES
DTA & TGA
PRINCIPLE
INSTRUMENTATION
WORKING
THERMOGRAM
FACTORS AFFECTING
ADVANTAGES AND DISADVANTAGES
APPLICATIONS
REFERENCES

3.  Classical meaning of term ‘analysis’: Dissolution,
separation and break up into constituent elements.
 Thermal analysis definition by International
Confederation for Thermal Analysis and
Calorimetry(ICTAC):
A group of techniques in which a property of the
sample is monitored against time or temperature
while the temperature of the sample, in a
specified atmosphere is programmed.

4.  In thermal analysis and calorimetry, a signal is
measured which is a measure of the change of
property.
 The property of the sample means
thermodynamic properties, material properties,
chemical composition or structure.

5. Heating or cooling wave analysis
Differential Scanning Calorimetry (DSC)
Thermo Mechanical Analysis (TMA)
Thermomanometric Analysis
Thermoelctrical Analysis
Thermomagnetic Analysis

6. Thermo Optical Analysis (TOA)
Thermo Acoustic Analysis (TAA)
Thermally stimulated Exchanged
Gas Analysis (EGA)
Thermodiffractometric Analysis
Differential Thermal Analysis (DTA)
Thermogravimetry (TG)

7.  Technique for identifying and quantitatively
analysing the chemical composition of substances
by observing the thermal behaviour of a sample as
it is heated.
 As the substance is heated, it undergoes reactions
and phase changes that involve absorption or
emission of heat.

8.  Temperature difference between sample and
reference is measured as a function of temperature
while the substance and reference are subjected to
a controlled temperature programme.
 Physical changes usually result in endothermic
peak whereas chemical reactions those of an
oxidative nature are exothermic.

9. ENDOTHERMIC REACTIONS
(ABSORPTION OF ENERGY)
Melting
Vaporization
Boiling
Desolvation
Chemical degradation
Sublimation
Absorption
EXOTHERMIC REACTIONS
(LIBERATION OF ENERGY)
Polymerization
Catalytic reactions
Oxidation
Crytallisation

11. 1. FURNACE
 Source of uniform heating
 Nichrome furnace – used upto 13000C
 Platinum and its alloys – used upto 17500C
 Molybdenum – used upto 20000C
 Special type of higher frequency induction
heating for higher temperatures

12. 2. SPECIMEN HOLDER
 Designed to accommodate even a small quantity of
material and to give maximum thermal effect.
 Materials such as silica, alumina, heat resistant
glass, graphite, etc. can be used.
3. TEMPERATURE SENSOR
 Pair of matched thermocouple – one pair is in
contact with sample and other pair is in contact
with the reference.

13.  The sample and reference standard are placed in
the furnace on flat, highly thermally conductive
pans.
 The thermocouples are physically attached to the
pans directly under the sample.
 As the temperature increased, there will be a brief
deflection of the voltage if the sample undergoing
a phase transition.

14. A differential thermogram consists of a record of the
difference in sample and reference temperature (∆T)
plotted as a function of time t, sample temperature (Ts),
reference temperature (Tr) or furnace temperature (Tf).

15. A. ENVIRONMENTAL FACTORS
Static gaseous atmosphere – studies are not precise.
Dynamic gaseous atmosphere – more precise and
accurate.
B. SAMPLE FACTORS
1. Amount of sample: Small sample size gives best
peak which can be easy for resolution.
2. Particle size: Finely powdered sample size give
best peak.
3. Sample packing: Packing density of sample
influences the shape of DTA curve.

16. C. INSTRUMENTAL FACTORS
1. Sample holders: Made up from high thermal
conducting material gives sharp exothermic peak
but relatively flat endothermic peak.
2. Thermocouples: Position of thermocouples affect
on DTA curve.
3. Furnace characteristics: The type of winding on
furnace shows direct effect on DTA curve.
Uniformity in windings is preferred.
4. Heating rate: 100C – 200C is preferred for sharper
peak

17. ADVANTAGES
 Instruments can be used at very high temperatures.
 Instruments are highly sensitive.
 Characteristic transition or reaction temperatures can
be accurately determined.
DISADVANTAGES
 Uncertainty of heats of fusion, transition, or reaction
estimations is 20 – 50%

18.  They serve as fingerprints for various substances.
 To study the characteristic of polymeric material.
 Determination of heat of reaction, specific heat and
energy change occuring during melting.
 Analysis of characteristic decomposition pattern.
 Thermal stability of inorganic compounds and
complexes.

19.  By ICTAC, it is a technique in which the mass of
the sample is monitored against time or temperature
while the temperature of the sample, in a specified
atmosphere, is programmed.
 This measurement provides information about
physical phenomena, such as phase transitions,
absorption and desorption as well as chemical
phenomena including chemisorptions, thermal
decomposition, etc.

20. Isothermal or
Static
Thermogravimetry
The sample
weight is
recorded as
function of
time at
constant
temperature.
Quasistatic
Thermogravimetry
The sample is
heated to
constant
weight at each
of series of
increasing
temperature.
Dynamic
Thermogravimetry
The sample is
heated in an
environment
whose
temperature is
changing in a
predetermined
manner
generally at
linear rate.

21.  The sample is heated in a given environment at
controlled rate.
 The temperature is increased at a constant rate
for a known initial weight of the substance and
the changes in weights are recorded as a
function of temperature at different time
interval.

23.  A known weight of the sample is taken in a
crucible which is closed by a furnace.
 The furnace temperature is raised slowly, the
temperature of the sample and the corresponding
weights are taken.
 A platinum/platinum rhodium thermocouple is
used to measure the sample temperature.

24. • The change in weights are found out by finding the
beam deflection on adding a known weight to the pan.
• Recorder records the change in weight in y – axis w.r.t
temperature on the x – axis - THERMOGRAM

25. A. SAMPLE FACTORS
1. Weight of the sample: Small sample weight is
recommended as it eliminates the existence of
temperature gradient through the sample.
2. Particle size of the sample: Should be small and
uniform. Large particle may result in apparent,
very rapid weight loss during heating.

26. B. INSTRUMENTAL FACTORS
1. Furnace heating rate: A heating rate of 3.50C per
minute is usually recommended for reliable and
reproducible TGA.
2. Furnace atmosphere: The atmosphere inside the
furnace surrounding the sample has a profound
effect on the decomposition temperature of the
sample.

27.  Continuous recording of weight loss as a function
of temperature ensures equal weightage to
examination over the whole range of study.
 Fast heating rate with good resolution can be
maintained.
 Easy sample changing and easy change of sample
holder.

28.  The chemical or physical changes which are not
accompanied by the change in mass on heating are
not indicated in TGA.
 Pure fusion reaction, crystalline transition, glass
transition, crystallisation and solid state reaction
with no volatile product would not be indicated
because they provide no change in mass of the
specimen.

29.  Determining purity and thermal stability.
 Oxidative and reductive stability.
 Determining moisture, volatile and ash contents.
 Determining composition of the mixture.
 Reaction kinetic studies.

30.  Macdonald, A. M. G. (1965). Clement Duval,
Inorganic Thermogravimetric Analysis: Elsevier
Publishing Company, Amsterdam, 1963, xv+ 722
pp., price 120 s (D. fl. 60.—, DM 67.—).
 Wagner, M. (Ed.). (2013). Thermal Analysis in
Practice: Collected Applications. Mettler-Toledo.
 Gallagher, P. K., & Brown, M. E. (2003).
Handbook of thermal analysis and calorimetry.
 https://egyankosh.ac.in/bitstream/123456789/4333
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