Thermal Analysis
TGA / DTA
Linda Fröberg
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Microelectronics circuits, Exams of Electrical Engineering
advanced electronics circuits
Typology: Exams
2018/2019
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Thermal Analysis
TGA / DTALinda Fröberg
Outline
Definitions
What is thermal analysis?
Instrumentation & origin of the TGA-DTA signal.
TGA
DTA
Phase diagrams & Thermal analysis
•^
Thermal analysis,an experimental method to determine phase diagrams.
Basics and applications
Thermal analysis
In practice thermal analysis gives properties like;enthalpy, thermal capacity, mass changes and thecoefficient of heat expansion.
Solid state chemistry uses thermal analysis for studyingreactions in the solid state, thermal degradationreactions, phase transitions and phase diagrams.
^
Thermogravimetric analysis (TGA): mass
^
Differential thermal analysis (DTA): temperature difference
^
Differential scanning calorimetry (DSC): heat difference
^
Pressurized TGA (PTGA): mass changes as function of pressure.
^
Thermo mechanical analysis (TMA): deformations and dimension
^
Dilatometry (DIL): volume
^
Evolved gas analysis (EGA): gaseous decomposition products
Often different properties may be measured at the same time:
TGA-DTA, TGA-EGA
... Includes several different methods. These are distinguished from one another by the property which
is measured.
Thermal analysis
TGA - SDTA
Mettler - Toledo
Leena Hupa & Daniel Lindberg
A modern TGA - DTA
Heat transfer from crucible to recording
microbalance & thermo elements
platinum
Origin of the TGA-DTA signal
Temperature
T
, Tp
r
T
: program temperaturep T
: reference temperaturer = Tc furnace temperatureT
: sample temperatures
Schematic diagram showing the different temperatures in the DTA during a thermal process.
T
s
Time
Peak onset
Reaction temperature
Origin of the TGA-DTA signal
T
: program temperaturep Tc
:^
furnace temperature
T
: sample temperatures
Melting point: Indium
Heating rate 50 K / min
t
T
Time / min
t = Tau lag
T s
Tp
Tc
TGA
Thermo Gravimetric Analyis
TGA;
Phenomena causing mass changes
Physical Gas adsorptionGas desorptionPhase transitions
Vaporization
Sublimation
Chemical^ DecompositionBreak down reactionsGas reactionsChemisorption(adsorption by means of chemicalinstead of physical forces)
TGA: Applications
Characterization of
Thermal stability
Material purity
Determination of humidity
• Examination of
» Corrosion studies
(e.g. oxidation or reactions with reactive
gases)
» Gasification processes» Kinetic processes
TGA
Ex. Decomposition of calcium oxalate monohydrate
Calcium oxalat monohydrat, a standard material oftenused to demonstrate TGA performance.
Exhibits three weight losses with temperature in an inertatmosphere (e.g. N
2
CaC
O
- H
O
→
CaC
O
→
CaCO
→
CaO
- H
2
O
- CO
- CO
2
- H
O 2
- CO
- CO
2
TGA
Ex. Decomposition of calcium oxalat monohydrate
Absolute confirmation of the decomposition process is possible when the gaseousby products are identified as they evolve, eg. by mass spectrometry (MS).
TG DTG