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Microelectronics circuits, Exams of Electrical Engineering

advanced electronics circuits

Typology: Exams

2018/2019

Uploaded on 01/22/2019

Wajih98
Wajih98 🇺🇸

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Thermal Analysis
TGA / DTA
Linda Fröberg
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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.

ƒ^

Thermogravimetric analysis (TGA): mass

ƒ^

Differential thermal analysis (DTA): temperature difference

ƒ^

Differential scanning calorimetry (DSC): heat difference

ƒ^

Pressurized TGA (PTGA): mass changes as function of pressure.

ƒ^

Thermo mechanical analysis (TMA): deformations and dimension

ƒ^

Dilatometry (DIL): volume

ƒ^

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