mlz 229 materials characterisation techniques: thermal analysis...

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Eskisehir Technical University ‐ Dr. Umut Savacı

MLZ 229 MATERIALS CHARACTERISATION TECHNIQUES:

THERMAL ANALYSIS (TA)



CHARACTERISATION TECHNIQUES

Non-Microscobic Tech.Microscobic Tech.

Light Microscopy

Scanning Electron Micr.

Transmission Electron Micr.

Other Tech.

Thermal Analysis

X-ray Diffraction

Spectroscopic Techniques

Other Tech.


TRUSTING BLACK BOX

Working PrinciplesOperationComments

Why You need to study?

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What do you understand from«THERMAL ANALYSIS» ?

Temperature ?

Sample ?

Heat ?

Melting ?

Furnace ?

Cooling ? Thermometer ?

Thermal Conductivity ?

Bread ???

Chocolate ???

Thermocouple ?

Pyrometer ? Heat capacity?


HEAT AND SPECIMEN INTERACTION

Volume ChangeWeight Change

Specimen

New Products


Any of these events or reactions

DTA/DSC

Phase Transformation


Specimen

New ProductsH2O, CO, CO2, MxOy & etc

Loss

Oxidation

Gain

EvaporationLoss of HumidityLoss of Chemical WaterDecomposition (Carbonates)

Shrinkage Expansion

CrsytallisationGlass Transition

MeltingEndothermic Exothermic

TG Dilatometer

MSTG‐DTA TG‐DSC TG‐MS TG‐DTA‐MS


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CLASSIFICATION &APPLICATION GUIDE


Crystal Structure

Processing

Properties

Performance

Characterisaton

TA-PERFORMANCE-PROPERTIES RELATIONSHIP

Phase Transformation T.Crsytallisation T.

Glass Transition T.Thermal Exp. Coeff.

Decomposition T.Melting T.

Moisture ContentPurity Content

Thermal Stability

Chemical Stability

Reaction T.

Phase ContentGlasses do not melt at a sharply defined temperature, but soften over a temperatureinterval. This softening temperature is called as glass transition temperature


WHAT IS THERMAL ANALYSIS?

A group of techniques measuring the physical andchemical changes of a matter (material properties) asa function of temperature, time & atmosphere undera controlled temperature program

LEARNING OBJECTIVES?Know which TA techniques are appropriate to measure avariety of materials properties.Have some practical knowledge of how TA experiments arecarried out.Be able to interpret TA data in order to calculate sampleproperties.


History

8000 BC 8000 BC

3400 BC

19th CenturyControlled and quantitative analyses

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MATERIALS TO BE STUDIED

TA techniques are used in virtually every area ofmodern science & technologyCeramics & glassesCatalysisPolymeric materialsMetalic materialsBuilding materialsBiological materialsFood IndustryLiquids (limited)


WHERE IS THERMAL ANALYSIS USED?

(i) Research and development of new products:Development and selection of new materials,Performance and evaluation of existing materials

Crystallinity, specific heat, expansion, shrinkage(ii)Quality control & assurance: FingerprintingTroubleshooting, Monitoring, Purity and Certification

(iii) Reverse Engineering; TA results allow toconclude chemical and phase composition andmanufacturing history of Bronze Age pottery


Any of these events or reactions

DTA/DSC



Specimen

New ProductsH2O, CO, CO2, MxOy & etc

Loss

Oxidation

Gain

EvaporationLoss of HumidityLoss of Chemical WaterDecomposition (Carbonates)

Shrinkage Expansion

CrystallisationGlass Transition

MeltingEndothermic Exothermic

TG Dilatometer

MSTG‐DTA TG‐DSC TG‐MS TG‐DTA‐MS



Solid SolidSolid LiquidSolid GasLiquidGas

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PROPERTIES TO BE STUDIED:1.PHASE TRANSFORMATIONS

DISPLACIVE PHASE TRANSFORMATIONSNo chemical bond broken


PROPERTIES TO BE STUDIED:1.PHASE TRANSFORMATIONS

DISPLACIVE PHASE TRANSFORMATIONS


PHASE TRANSFORMATIONSRECONSTRUCTIVE PHASE TRANSFORMATIONS

Chemical bonds are broken and reconstructed


PHASE TRANSFORMATIONS

Diamond (C)

Quartz (SiO )2

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QUARTZ PHASE TRANSFORMATIONS



Silica have three different forms:Quartz, trydymite, crystoballite-quartz, -crystobalite and -tridymitetransformations are displacive (atomic positions do notchange much)However, quartz crystobalite tridymitetransformations are reconstructive (new crystal latticewill form and is very slow)Volume changes occur and cracks will form

PROPERTIES TO BE STUDIED




2. POSSIBLE REACTIONS

Physical Water Loss

Clay minerals can contain different ratios of physicalwater. Amount of water and the temperature of losscan give information about the mineral.

Will be lost around 100˚C

The amount of water depends on the particle sizeand mineral type

PROPERTIES TO BE STUDIED

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POSSIBLE REACTIONS

Physical Water Loss

Type of mineral Percentage weight lost (%)

Cornish china clay 1.2Stourbridge fire clay 3.8Brick clay 2.0Ball clay (Dorset) 5.7Bonding clay (Scottish) 7.4Eureka halloysite 6.3Wyoming bentonite (Montmorillonite) 14.2


POSSIBLE REACTIONS

Chemical Water LossAs the temperature rise the crystal water will be lostslowlyFor exam.: kaolinite will loose its crystal water at420˚C but it will take months.However, at 550˚C it will only take half an hrBoth the chemical and physical water requires heatto be lost


POSSIBLE REACTIONSChemical Water Loss

Mineral Chemical Formula Temp. of rapid decomposition (oC)

Percentage water lost

Kaolinite Al2O3.2SiO2.2H2O 585 14.1Halloysite Al2O3.2SiO2.2H2O 558 14.1Montmorillonite Al2O3.4SiO2.H2O (ideal) 678 5.0Muscovite mica K2O.3Al2O3.6SiO2.2H2O 856 4.5Hydrous mica As above but less alkali

& more water550 upwards 6.0-10.0

Gibbsite Al(OH)3 325 34.6Goethite FeO(OH) 350 10.1


POSSIBLE REACTIONS

Decomposition of sulphates and carbonatesIf the clay mineral contains sulphates andcarbonates, they decompose under heatCalcium carbonate (CaCO3, calcite) common mineralfound in clay and @ 880˚C it decomposes with 44 %weight lossMagnesium carbonate (MgCO3) decomposes @ 790˚CDolomite is a mixture of both ((Ca, Mg)CO3) andbehave like two different carbonates

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POSSIBLE REACTIONS

ORGANICSOrganic materials oxidized and lost from the mainmaterials between 200˚C and 1000˚C


Possible ReactionsMaterials may react with the surrounding atmosphere


Why Use Thermal Analysis Techniques?

to measure a property of interest, such as specific heat, latent heat or heat of reactionto fingerprint a particular material or substanceto assess the high-temperature stability ofmaterialsto detect phase transformationsfundamental studies of reaction kinetics


Common Types of Experimental Scans

Temperature scanIsothermal heat treatment

• The isothermal heat treatment is usually best suited to kinetic studies. It is useful to study things that happen far away from the equilibrium temperature and hence occur when we hold the temperature constant

• The temperature scan is generally more useful to examine thermodynamic properties. It is useful to study things that happen near to the equilibrium temperature and hence need us to ramp up from below the equilibrium temperature to above it in order for the transformation to occur.

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Properties Studied by Thermal AnalysisThere are a wide range of properties that may be studied, and each has an associatedtechnique which can be used:

• a) specific heat• b) thermal expansion• c) weight• d) flow stress• e) viscosity• f) elastic modulus and damping• g) evolved gases• h) phase changes and lattice parameter• Of course, you can measure just about any property as a function of temperature, i.e.

Electrical resistivity, magnetic permeability, thermoluminescence. But some techniques (those which have acquired acronyms) are commonly used and have developed specialised commercial instrumentation.


USE INTERNET WISELY!


CLASSIFICATION &APPLICATION GUIDE

mlz 229 materials characterisation techniques: thermal analysis...

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