fundamentals and applications of thermal analysis
TRANSCRIPT
FUNDAMENTALS AND APPLICATIONS
OF THERMAL ANALYSIS
Objectives:
To explain principle of different types of thermal
techniques.
To describe instrumentation of different types of
thermal techniques
To distinguish between DSC,DTA & TGA
To explain application of thermal method
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Introduction:
Thermal analysis is a branch of material science where the properties of
materials are studied as they change with temperature.
When matter is heated it undergoes certain physical and chemical changes.
These physical and chemical take place over a wide temperature range.
Physical changes such as melting or boiling may occur at widely varying
temperature, depending on material involve.
Chemical changes such as decomposition or reaction may also take place at very
different temperatures.
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Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no-2-701
Definition of Thermal Analysis
A branch of materials science where the properties of materials are studied as they change with temperature.
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Ref-Skoog, Douglas A., F. James Holler and Timothy Nieman (1998). Principles of Instrumental Analysis (5 ed.). New York. pp. 805.
NO
Technique Name
Abbreviation
Instrument Apply
Parameter Measure
Graph
1 Thermogravimetry
TG Thermobalance
Mass mass vs temp
2 Derivative Thermogravimetry
DTG Thermobalance
dm/dt dm/dt vs temp
3 Diff.Thermal Analysis
DTA DTA Appts ∆T ∆T vs temp
4 Diff.Scanning Calorimetry
DSC Calorimeter dH.dt dH/dt vs temp
5 Thermometric Titrimetry
…….. Calorimeter Temp. Temp vs titrant volume
6 Dynamic Reflectance Spectroscopy
DRS Spectrophotometer
Reflectance
%refle.and temp.
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7 Evolved gas detection
EGD Thermal conductivity cell
T.C. T.C. vs temp
8 Dialotometry TMA Dialatometer
Vol.of Length
Vol or length vs temp
9 Electrical conductivity
EC Electrometer or Bridget
Current or resistance
I or R vs temp
10 Emanation Thermal Analysis
ETA ETA appts. Radioactivity
E vs temp
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Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.701-2.702
Thermal Analysis Instrument Manufacturers Perkin Elmer Thermal Analysis Systems
http://www.perkin-elmer.com/thermal/index.html TA Instruments
http://www.tainst.com/ Mettler Toledo Thermal Analysis Systems
http://www.mt.com/ Rheometric Scientific
http://www.rheosci.com/ Haake
http://polysort.com/haake/ NETZSCH Instruments
http://www.netzsch.com/ta/ SETARAM Instruments
http://setaram.com/ Instrument Specialists, Inc.
http://www.instrument-specialists.com/
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Ref-by google search thermal method instrument
Thermogravimetry:
It is a technique whereby the weight of the
substance, in an environment heated or cooled at a
controlled rate, is recorded as a function of time or
temperature.
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Ref-Skoog, Douglas A., F. James Holler and Timothy Nieman (1998). Principles of Instrumental Analysis (5 ed.). New York. pp. 805-806
Types of thermogravimetry:
1. Static thermogravimetry
2. Quasistatic thermogravimetry
3.Dynamic thermogravimetry
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Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.703-2.704
Instrumentation: TGA
TEMPERATURE PROGRAMMER
BALANCE
CONTROLLER
POWER FURNACE TEMP.
SAMPLE TEMP.
WEIGHT INLET
10 Ref-Google image search
1.Balance: 1.Balance:
Requirements:
1. Accurate, sensitive, reproducible
2. Adequate range of automatic weight adjustment.
3. High degree of mechanical & electronic stability.
4. Rapid response to weight changes.
5. Should be unaffected by vibrations, simple to operate
& versatile.
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Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.705
Types of balances:
1.Deflection balance
2.Null point balance
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Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.703-2.704
Types of deflection balance:
1.Beam type
2.Helical or spring type
3.Cantilever type
4.Torsion type
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Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.704-2.705
Types of Deflection Balance:
Fig: Deflection balance
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Null-Point Balance:
Fig: Null-Point Balance
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2. Sample Holders:
Types:
1.Shallow Pans
2.Deep Crucibles
3.Loosely Covered Crucibles
4.Retort Cups
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Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.703-706
3.The Furnace:
For 1100ºC – Nichrome is used
1100 to 1500ºC. – Platinum or an alloy of
platinum and rhodium
Above 1750ºC – tungsten or molybdenum
Nitrogen or argon are usually used to purge the
furnace & prevent oxidation of sample.
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4. Temperature measurement:
Fig: Position of a Thermocouple in a Thermobalance
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5. Recorder:
Time base potentiometric strip chart recorder
X Y recorder
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6.Thermobalance:
1)Continuously the weight changes of the sample as a function of temperature & time.
2) The temperature recorded to an accuracy of better than
±1%.
3) Temperature should, ideally, be the sample Temperature.
4) No chemical attack of volatile products on the apparatus.
5) The balance is protected from furnace.
6) The weight loss should be recorded to an accuracy of ±1%.
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Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.710-11
TGA Applications: Inorganics
Hydrates decomposition, drying phenomena Carbonates and other salts decomposition Kinetics and mechanisms of oxidation, and other solid-gas
reactions Analysis of magnetic materials Automatic TG analysis Evaluation of TG pptet. Test purity Curie point determination
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Ref-M C Ramos-Sanchez, F J Rey, M L Rodríguez, F J Martin-Gil, J Martin-Gil, "DTG and DTA studies on typical sugars", , 134: 55-60
TGA Applications: Organics
Identification of polymers and pharmaceutical agents Thermal stability of synthetic and natural polymers and other
organics Analysis of polymer-matrix composites Kinetics and mechanism of solid organics – gas reactions Residual solvent determinations Building material Glass technology
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Ref-M C Ramos-Sanchez, F J Rey, M L Rodríguez, F J Martin-Gil, J Martin-Gil, "DTG and DTA studies on typical sugars", , 134: 55-60
DTA:
DTA measures temperature difference between a sample and an inert reference (usually Al2O3) while heat flow to the reference and the sample remains the same
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Ref-M C Ramos-Sanchez, F J Rey, M L Rodríguez, F J Martin-Gil, J Martin-Gil, "DTG and DTA studies on typical sugars", , 134: 55-60
Differential Thermal Analysis (DTA)
.
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Ref-Mansfield, E.; Kar, A.; Quinn, T. P.; Hooker, S. A. (2010). ". Analytical Chemistry 82
Principle:
The principle of method consists of measuring the change in
temperature associated with physical or chemical changes during the
gradual heating of the substance.
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Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.720-22
Differential Thermal Analysis
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%.
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Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.722-23
Applications –
Physical chemistry Analytical chemistry Quality control Inorganic chemistry Organic chemistry
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Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.735-38
Differential Scanning Calorimetry (DSC)
Differential Scanning Calorimetry technique is a thermal
technique in which the difference in the amount of heat required to
increase the temperature of a sample & reference is measured as a
function of temperature.
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Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.720-30
Differential Scanning Calorimetry (DSC)29
DSC measures differences in the amount of heat required to increase the temperature of a sample and a reference as a function of temperature
Differential Scanning Calorimeter
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Differential Scanning CalorimeterPerkin Elmer DSC 731
Platinum sensors
Sample heater Reference heater
Temperature range 110 – 1000 K Heating rate 0.1 – 500 K/min
(normally 0.5 – 50 K/min) Noise ± 4 W Sample volume up to 75 mm3
Applications-
Physical chemistry Analytical chemistry Quality control Inorganic chemistry Organic chemistry
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Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.720-30
DSC in Polymer Analysis
Main transitions which can be studied by DSC:
Melting Freezing Glass transition
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Difference Between:
TGA DTA DSC
Measures thermo-chemical effect.
Measures thermo-physical, thermo-chemical effect.
Measures thermo-physical, chemical effect with more sensitivity.
Provide range: Thermal Chemical stability of materials.
Provide range: Thermal, Physical and Chemical stability of materials.
Provide range: Thermal, Physical and Chemical stability and also transition time. E.g. Curie Temperature
Contains: Thermobalance.
Contains: Thermocouple for measuring ∆T.
Contains: Secondary heater for measure ∆H.
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Thermo mechanical analysis:
Thermo mechanical analysis (TMA) is the technique in
which a physical dimensions of a material is monitored
as a function of temperature. With the other methods a
thermocouple is used to monitor the temperature of the
sample in an oven through which a purge gas flow.
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Ref- introduction to thermal method by brown m.e. p.no-149
Thermo mechanical Analysis: Instrumentation
Consist of Transducer(Linear Variable Displacement Transducer) Probe (made up of quartz glass) Thermocouple Furnace
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Ref-www.google.com
Principle-
Measurement of effect of heat on mechanical property of sample eg. Expansion,Compression,Penetration and Extension.
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Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.754
Applications-
Polymer study Quality control
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Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.754
Dielectric thermal analysis:
Dielectric thermal analysis (DETA) or Dielectric
Analysis (DEA), is a material science technique similar
to dynamic mechanical analysis except that an oscillating
electrical field is used instead of a mechanical force.
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Ref- vogel textbook of chemical analysis p.no.-474-576
Dielectric thermal analysis: Principle
In a typical test, the sample is placed in contact with two electrodes(the
dielectric sensor) and a sinusoidal voltage (the excitation) is applied to one
electrode. The resulting sinusoidal current (the response) is measured at the
second electrode. The response signal is attenuated in amplitude and shifted
in phase in relation to the mobility of the ions and the alignment of the
dipoles.
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Ref- vogel textbook of chemical analysis p.no.-474-576
Evolved gas analysis:
Evolved gas analysis (EGA) is a method used to study
the gas evolved from a heated sample that undergoes
decomposition or desorption.
It is possible to detect which gas is evolved using
(EGD) Evolved gas detection..
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Thermometric titrations:
Definition:
A Titration in which the temperature of the titrant is
monitored as a function of added titrant volume is a
thermometric titration.
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Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.739
Principle:
Thermometric Titrations is based on the change in temperature
with theaddition of titrant & determine the end point from a
plot of temperature vs. volume of titrant. In thermometric
titration change in temperature occurs only when titration is in
progress & sample reactant is present.
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Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.739
Theory-
A titration reaction follow chemical equation
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In this method there should be change in free energy at end point.
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A(sample)+B(titrant)C(product)+heat
∆H=∆G+T∆S
Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.739
Instrumentation:
It consist of Delivery pump fig: thermometric titration assembly
Adiabatic cell (Dewar cell) Calibration unit Temperature sensing system Amplification & Recording
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Enthalpimetry:Enthalpimetry:
Quantitative analysis of a sample can be sometimes be performed by measurement of the change in enthalpy that is associated with the addition of excess of a chemical reactant to the sample.
When a chemical reaction takes place heat is liberated or absorbed. This is known as heat of reaction or enthalpy.
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Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.759
Methods:
1.Direct injection enthalpimetric titration (DIE): In this technique in which a single portion of an excess of one
chemical reactant is added to a fixed volume of a sample that contains other reactant.
2. Continuous flow enthalpimetry: Similar to DIE except that an excess of one reactant is
continuously to flowing stream of sample added.
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Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.759
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