Differential thermal analysis (DTA)presentation.pdf

DTA is a type of thermoanalytical technique that measures the temperature difference between a sample and a reference material as they are exposed to a controlled temperature program, revealing information about thermal events like phase transitions and reactions.
 Application-
1) used to identify the minerals both qualitatively and quantitatively.
2) polymers characteristics can be easily characterized.
3) Degree of crystallinity can be measured.
4) Degree of polymerization can be assessed.
5) many of the biological material can be analyzed.
6) Melting point, Boiling point and temperature of decomposition of organic compound can be determined.

1. Topic –Differential thermal analysis (DTA)
•Guided by –
Dr.Rahul godge
•Presentedby –
Thete Bhakti Sharad
F.Y.M Pharm ( Pharmacognosy).
•Institute -
Pravara Rural College Of Pharmacy, Loni.

2. •DTA is a type of thermoanalytical technique that measures the
temperature difference between a sample and a reference material as
they are exposed to a controlled temperature program, revealing
information about thermal events like phase transitions and reactions.
•Either endothermic or exothermic changes occurs in sample can be
detected relative to the inert reference.
•A plot ( curve/ thermogram) is then plotted between the differential
temperature (△T) and time or temperature (T). Then changes observed in
the sample, due to the absorption or evolution of heat, are detected
relative to the reference.
Introduction

3. •Thus a DTA curve provides data on the transformation that have
occurred such as glass transition, crystallization, Melting and
sublimation.
•The area under DTA peak is the enthalpy change and is not affected by
the heat Capacity of the sample.
•In DTA both the test sample and inert reference material (alumina)
controlled heating or cooling programming.
•If zero temperature difference between the sample and material then
sample does not undergo any chemical and physical changes.
•If any reaction takes place temperature difference will occur between
sample and reference material.

4. History -
•Robert Austen was the first scientist who worked on this technique by
introducing two thermocouple in it’s apparatus in 1899.
•Burgess modified this technique in 1909.
•Scientists who followed this technique later -
•Norton 1939.
•Kerr 1948
•Kauffman 1950
•Grim 1958.
•Robert Austen who suggested the differential thermocouple
arrangement is still widely used in thermal analysis and therefore this
technique known as DTA or thermography .

5. •Principle –
•DTA is a thermal analysis which involves the comparison between the
temperature of sample under investigation and a thermally inert or
reference material (alpha-alumina).
•This comparison is then recorded with the furnace temperature as the
sample I heated or cooled at uniform rate . There is constant difference
between the sample and the reference as they have the different heat
Capacity.
•When sample undergoes the endothermic or exothermic reaction
changes then △T becomes different. The endothermic and exothermic
reaction changes in the sample lead to characterized deviation in
temperature which can be used for qualitative and quantitative analysis.
•The basic principle involves is the measurement in temperature changes
which are associated with the physical changes or chemical changes of
the sample during the gradual heating process.

6. •The difference in the temperature is called as differential
temperature and is plotted against temperature/Time.
•Physical changes usually results in endothermic peaks, whereas
chemical reaction those of an oxidative nature show exothermic
peaks.
•Endothermic reaction (absorption of heat) include sublimation and
gives downwards peak.
•Exothermic reaction (liberation of heat) include oxidation ,
polymerization and gives upward peaks.

7. Instrumentation

9. •Instrumentation–
DTA instrument consist of –
1)Furnace assembly.
2)Sample and reference holders with temperature detector.
3)Furnace temperature Programmer.
4)Amplifier.
5)Read out unit
6)Insulator for furnace and sample holders.
•The key feature is the existenceof two thermocouple connected to a
voltmeter.
•Onethermocouple is placed in an inert material (reference material)
such as Aluminiumoxide, while the second is placed in a sample of
the material.

10. 1) Furnaceassembly–
•It works as a temperature Programmer.
•There are many furnaceswhich are used ,depending upon the sample material and
the rate of heating.
•Eg –i) nichrome furnace made up of nickel and chromium alloy used when rate of
heating is up to 1300°C
ii) Platinum furnace –1750°C
iiii) Molybdenum furnace –2000°C
2)Sample and reference holders with temperature detector –
•InDTA apparatus, two compartments are present, one for the sample and other for
reference material. The holders are designed in a manner that they can
accommodate even a small sample quantity for both material and give maximum
thermal effect.
•Holders are made up of Platinum, stainless steel, nickel, silver and alloy.
•Temperature detector -
•Theholders are connected with the temperature detector which measures the
sample and reference material temperature.

11. •In order to control temperature the three basic elements are required-
Sensor , on/off control and heater.
•In this device the Sensor signal indicates the temperature has become
greater then the set point the heateris immediately get stop.
3) Furnace temperature Programmer –
•Electronic temperature regulators are used to ensure constant rate of
heating of the furnace for temperature regulation.
•It provides smooth heating or a cooling at a linear rate by changing the
voltage through heating components.
•Modern DTA instrument incorporate electronic temperature controller
in which the signal from thermocouple in furnace is compared against
reference potential which can be Programmedto correspondsto a
variety of heating modes and heating rates.
4) Amplifier –
It is used for signal amplifcation. It converts heat signal into electric
signal .

12. 5) Read out unit –
It is used to display the results in the form of thermogram.
Nowadays, the read out devices have microprocessors that delivers
interpretedthermogram or output compatible with computer and
printer thus minimizing the risk of operator errors.
6) Insulator for furnace and sample holders –
It is a block of ceramic or other insulating material enclosing the
furnace and sample holders which does not readily allow the passage
of heat.

13. Working of DTA

15. •Sample preparation (2-sampleand reference material)
•Load in container or holders
•Later holders placed in a compartment.
•Place thermocouple in this 2 sample.
•Heat the sample and reference material.
•The metal block which surrouds compartment act as heat sink contain
internal heater which is increase temperature and heat the sample.
•Thermocouple attachedwith the amplifier which converts the heat signal
into electric signal send this results to read out unit which display the
results as thermogram.
•Eg –Metal oxide decomposed and produce carbon dioxide which is a
endothermic reaction where heat absorbed and the sample temperature
decreased. Now the sample temperature is less than the reference
temperature. This temperature difference between both material
producesnet signal, which is then recorded.

16. DTA CURVE

17. •The DTA curve or thermogram is a plot between differential
temperature (△T) andthe temperature of reference (T).
•There Two reaction occurs which are exothermic reaction and
endothermic reaction due to that two reaction curves we get – 1)
Endo-thermogram and 2) Exo-thermogram.
•Exo-thermogram =
1)Upward plot.
2)Sample temperature is high than that of the reference .
•Endo-thermogram =
1)Downward plot.
2)sample temperature is less than that of the reference .
•If there is no reaction happening in the sample material, then the
sample temperature remains the same as that of the reference
material.

19. •Curve explanation-
•The value of △T is zero along the line AB which indicates no reaction in
the sample material.
•AB – baseline of peak.
•B – curve rises due to exothermic reaction and it forms a peak BCD with
maximum temperature.
•C - at this point the heat rate is almost same to sample and reference
material.
•D – after process of heat is completed and then it decreases at point D.
•Peak BCD – this area has direct relation with the amount of reacting
material.
•Identification of the sample material, heat of reaction, sample mass
(m),
•Sample geometry, and thermal conductivity are the prospects which
can be determined using DTA curves.

20. Factors affecting on DTA curve .

21. •Differential thermal analysis is not a dynamic thermal analytical technique due to that it’s value
can derivate because of many factors which can be divided into four major groups.
A)Sample factor
B)Instrumental factors
C)Physical factors
D)Chemical factors
•A) Sample factor
•Amount of the sample
•Packing density
•Particle size of the sample material.
•Degree of crystallinity.
•Heat capacity .
•Thermal conductivity.
•Dilutes of the diluent .
•Swelling of the sample.
•Shrinkage of the sample.

22. •B) Instrumental factors –
•Size or shape of the sample holders.
•Material of the sample holders.
•Recording system sensitivity.
•Rate of heating of the sample.
•Atmosphere around the sample.
•Thermocouple location in the sample.
•Instrumental design.
C) Physical factors – They further divided into two groups. Some will affect the endo-
thermogram curve and some will affect exo-thermogram curve.
1) Exo-thermogram factors –
• Adsorption
•Change in crystal structure
•Crystallization.

23. 2) Endo-thermogram factors –
•Desorption.
•Change in crystal structure.
•Melting.
•Vaporization.
•Sublimation.
D) Chemical factors – They further divided into two groups. Some will affect the endothermic reaction
and some will affect exothermic reaction.
1) Exothermic reaction factors –
•Oxidation
•Break down reaction
•Chemisorption.
•Solid state reaction.
2) Endothermic reaction factors –
•Reduction.
•Break down reaction.
•Solid state reaction.

25. 1) used to identify the minerals both qualitatively and quantitatively.
2) polymers characteristics can be easily characterized.
3) Degree of crystallinity can be measured.
4) Degree of polymerization can be assessed.
5) many of the biological material can be analyzed.
6) Melting point, Boiling point and temperature of decomposition of
organic compound can be determined.
7) Have wide application for the quality Control of many substances such
as soil ,glass ,cement etc.
8) used to determine the thermal stability of many inorganic compound
and complexes.
Applications of DTA.

26. •Advantages –
1)DTA apparatus can be operated at very high temperature ranges.
2)Highly sensitive technique .
3)Both exothermic and endothermic reaction can be determined
accurately.
•Disadvantages -
1)There is a lot of uncertainty in transition reaction and heat of fusions.
2)Due to heat variation between sample and reference material makes
it less sensitive.
•Limitations –
1) △T determinedby DTA is not so accurate (2-3°C).
2) Small change in △T cannot be determined and quantified.

27. •DDTA –A methodbased on the used of the two temperature of the
inflection determined on a single derivative differential thermal analysis
curve and of the temperature the extremely determined on the
differential thermal analysis curve is Proposed for computing the
activation energy and the order of reaction of a chemical process.
•Derivative Differential Thermal Analysis (DDTA) is a thermoanalytical
technique that measures the rate of change of the temperature
difference between a sample and a reference material as they are
heated or cooled. It’s derived from Differential Thermal Analysis (DTA)
and provides more detailed information about thermal events.
•The obtained formulaedo not contain heatingrate. If the conversion
degree corressponding to the three temperature required by the
formulaeare known, the third kinetic parameter may be also computed.
Theformulaeare fitted to the reaction order model.
Derivative differential thermal analysis (DDTA)

28. •References–
1)Dr. ChandanR.S., Dr. Sanjay G.W., Dr. Vinod M.T., Pharmaceutical
analysis, Nirali Prakashan, T.Y.Pharm.Dbook.
2)Andrew J Pasztor , the dow chemical company, Handbook of
Instrumentaltechnique for analytical chemistry.
3)Willard merritt dean settle , Instrumental method of analysis, Seventh
Edition.
4)Gurdeep R Chatwal,Instrumental method of chemical analysis .

29. Thank you