tga

Belgium February 2009E. Post/NETZSCH1

Principles of TG, DSC, STA and EGA

Ekkehard PostNETZSCH Gerätebau GmbHWittelsbacherstrasse 42D-95100 Selb, Germany


Thermal Analysis

Definition (ICTAC):Thermal analysis (TA) is a group of techniques in which changes of physical or chemical properties of the sample are monitored against time ortemperature, while the temperature of the sample isprogrammed.

The temperature program may involve heating orcooling at a fixed rate, holding the temperatureconstant (isothermal), or any sequence of these.


Differential Scanning

Calorimetry(DSC, DTA)

Thermogravimetry(TG)

Thermomechanical Analysis

(TMA)Dilatometry (DIL)Dynamic-MechanicalAnalysis (DMA)

Physical and chemical processes

related to thermal effects can becharacterized

Mass changes due to evaporation,

decomposition and interaction with the

atmosphere

Dimensional changes, deformations, viscoelastic properties,

transitions, density

Methods of Thermal Analysis (TA)

Evolved Gas Analysis (EGA)


Thermal analysis for the characterizationof solids

Solids

Crystalline Amorphous

Polymorphism

Phase transition

Decomposition

Glass transition

Crystallization Softening

Decomposition

Liquid Crystal Glass-ceramics, polymers

∆∆∆∆H∆∆∆∆L

∆∆∆∆H, ∆∆∆∆Cp∆∆∆∆L

∆∆∆∆m ∆∆∆∆H∆∆∆∆L

∆∆∆∆m ∆∆∆∆H∆∆∆∆L

∆∆∆∆H∆∆∆∆L

∆∆∆∆ L

∆∆∆∆Cp, ∆∆∆∆L


Principle of thermogravimetry (TG)


Thermogravimetry

Top loading Hang downhorizontal

Mass change versus temperature and/or time

Thermobalance types


TG Curve - Principle


DTG Curve - Principle


Equal Volumes Feel Equal Buoyant ForcesSuppose you had equal sized balls of cork, aluminum and lead, with respective specific gravities of 0.2, 2.7, and 11.3. If the volume of each is 10 cubic cm then their masses are 2, 27, and 113 g.

Each would displace 10 grams of water, yielding apparent masses of -8 (the cork would accelerate upward, swim), 17 and 103 g respectively.

Thermogravimetry: Buoyancy effect


Thermogravimetry: Buoyancy effect

Buoyant Force

Buoyant force is also present in gases, but much smallercompared to liquids (density difference)


STA 409PC Luxx

The sample holder „swims“ in the atmosphere. The buoyancy force (Archimedes‘ prin-ciple) is reducedwith increasingtemperature, the balance shows an apparent weightincrease. Thisdepends also on density of the gas.


STA 449 F1: Buouancy Reproducibility

100 200 300 400 500 600 700 800 900Temperatur /°C

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

TG /mg

Difference of the two baselines

Two Baselines

0.000 mg

-> microgram accuracy!


TG of Calcium Oxalate Monohydrate


Bouyancy and Convection

Dependent on� Atmosphere� Type of sample carrier� Heating rate� Crucible size

Fa = g • ρ • VK

∆Fa = g • VK • (ρ1- ρ2)



100 200 300 400 500 600 700 800 900Temperature /°C

-0.30

-0.20

-0.10

-0.0

0.10

0.20

0.30

0.40

TG /mg


20 K/min

2.5 K/min10 K/min


Heating Rate – Atmosphere generated

[#] Instrument [1] TG 209 F3[2] TG 209 F3[3] TG 209 F3

Filexxx-3-08-06.dt6xxx-0-08-4.dt6xxx-3-08-5.dt6

Date2008-08-302008-08-302008-08-30

Identityxxx-3-08-06xxx-0-08-4xxx-3-08-5

Sampledolomitdolomit 2 Kdolomit

Mass/mg41.09239.12937.307

Segment1/11/11/1

Range20/100.0(K/min)/99020/2.0(K/min)/99020/20.0(K/min)/990

AtmosphereN2, 20.0ml/min / N2, 20.0ml/minN2, 20.0ml/min / N2, 20.0ml/minN2, 20.0ml/min / N2, 20.0ml/min

Corr.420420420

550 600 650 700 750 800 850 900 950Temperature /°C

55

60

65

70

75

80

85

90

95

100

TG /%

Main 2008-09-03 10:21 User: Ekkehard.Post dolomit-heizraten.ngb

Dolomite2 K/min

20 K/min

100 K/min

in nitrogen

701.8 °C783.7 °C

861.9 °C


Application – Ferromagnetic MetalsMeasurements in a Static Magnetic Field


200 400 600 800 1000 1200Temperature /°C

-3

-2

-1

0

1

2

3

4

5

DSC /(mW/mg)

94

95

96

97

98

99

100

101

TG /%

Sample: Ironboride

421.2 °C-151 J/g

554.6 °C

1051.1 °C

1153.2 °C

280 J/g!1066.5 °C 3.285 %1188.0 °C 100.000 %

421.0 °C

1.6 J/g

550.0 °C 741.4 °C

660.9 °C

↓ exo

Amorphous Metal: Ironboride (II)

STA 449 JupiterSample: Ironboridemass: 17.74 mg crucible: Pt+Al 2O3 lin.atm.: Ar flow rate: 70 ml/minheating rate: 20 K/min

melting

crystallization

Measurement in magneticfield gradient!

Curie-transition

magnetic reentrancedue to crystallization!


Differential Thermal Analysis (DTA)

Differential Scanning Calorimetry (DSC)


Temperature is one of the most frequently measured quantities.

Measurement with thermocouples or resistance thermometers.

Thermocouples for measuring temperature differences according to the Seebeck effect:

If an electric conductor isexposed to a temperaturegradient, an electron flow isgenerated inside the conductor, which causes an electromagneticforce (EMF, thermocouplevoltage).

EMF = resulting voltage, S – Seebeck Coefficient.; t1 – temperature at the solderingjoint, t2 – reference temperature

Temperature Measurement

solderingjoint

Metal A

Metal B

EMF


Thermocouple type

(+) Leg

(-) Leg

Generated emf change in µV/°C

(reference junction at 0°C)

approx. working temperature range

Notes

at 100°C

at 500°C

at 1000°C

K Ni-Cr (Chromel)

Ni-Al (Alumel)

42 43 39 0 …1100°C most suited for oxidising atmospheres

T Cu CuNi (Constantan)

46 - - -185 … 300°C excellent for low temperatures

J Fe CuNi 54 56 59 20 … 700°C used in reducing atmospheres as an unprotected thermocouple

N NiCrSi

(Nicrosil)

NiSi 30 38 39 0 … 1100°C very stable output signal at high temperatures

E NiCr CuNi 68 81 - -200 … 800°C highest thermal emf per °C

R Pt13Rh Platin-13%Rhodium

Platinum 8 11 13 0 … 1600°C high resistance to oxidation and corrosion

S Pt10Rh Platin-10%Rhodium

Platinum 8 9 11 0 … 1550°C similar characteristics to type R

B Pt30Rh Platin-30%Rhodium

Pt6Rh Platinum-6%Rhodium

1 5 9 0 ... 1600° similar characteristics to type R and S

Thermocouples according toITS 90 and IEC 584-1

Thermocouple type E usually used for low temperature DSC instruments


DTA and DSC Principle

FurnaceRefer.Sample

∆T

QPR

.

During a phase transitiona temperature difference(heat fluxdifference) between thesample and reference canbe measuredby means of a thermocouple.

Difference of heat flowrate between sample and reference


Generation of the DSC Signal

Melting of a metal


Transformation Energetics of a Slag

The DSC 404 C Pegasus® allows examination of nearly all transformation energeticsover a wide temperature range. Glass transitions, crystallization and melting effectscan easily be studied.


Dehydration of Al(OH)3, Crystallization of Al2O3 and Melting

500 1000 1500 2000Temperature /°C

-1

0

1

2

3

4

5

6

DSC /(uV/mg)

dehydration

Al(OH)3

crystallization

alpha Al2O3

melting

gamma Al2O3

348 °C

1259 °C

2057 °C

1136 °C

1378 °C

↓ exo

Al(OH)3 42.4 mg, tungsten crucible, 75 K/min, helium static

Al(OH)3�Al2O3

α�γ


Application of DSC

Melting temperatures

Transition enthalpies

Phase transformations, Phase diagrams

Crystallization temperatures

Degree of crystallinity

Glass transition temperatures

Decomposition effects

Reaction kinetics

Purity determinations

SPECIFIC HEAT


Calculation of Specific Heat

ysensitivitrateheatingmasssample

baselinesampleCp

••−=

)( difference signal

The specific heat of a material can be calculated from 3 measurements(baseline, sapphire and sample).

The sensitivity is determined from the sapphire measurement

)(. )(

)(

sapphireCptheoretrateheatingsapphiremass

baselinesapphiredifferencesignalysensitivit

••−=


Calculation of the specific heat (Ratio Method)

Isothermal segment of about 5-10 min. to obtain stable start conditions.


Calculation of specific heat

• All 3 measurements have to be performed with the same cruciblesand the same conditions

• Only sample crucible will be filled, reference crucible stays empty

• The crucibles should have during the 3 measurements the samepositions (for example mark with the tweezers).

• Switch off the STC.

• Cp values are only valid when no weight loss occurs.


Calculation of specific heat

samplesapphire

Specific heat


Specific Heat Capacity of Sapphire

isothermal isothermal

dynamic

10 20 30 40 50Time /min

-0.10

-0.05

0.00

0.05

0.10

0.15

0.20

DSC /(mW/mg)

0

50

100

150

Temp. /°C↓ exo

ASTM E 1269 : Test method for determining specific heat capacity by differential scanning calorimetry


Specific Heat Capacity of Sapphire

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

DSC /(mW/mg)

0 20 40 60 80 100 120 140 160Temperature /°C

0.0

0.5

1.0

1.5

2.0

Cp /(J/(g*K))

DSC signal sapphire 1DSC signal sapphire 2

measured values of the temperature dependent change of the specific heat capacity of sapphire

literature values of the temperature dependent chan ge of the specific heat capacity of sapphire

↓ exo


Specific Heat of stab. Zirconia

Stab. zirconia is a ceramic material often used for industrial applications such as thermal barrier coating or electrolyte material. The specific heat measured with the DSC is close (less than 3% ) to the literature values for such materials.

Sample: Stab. ZirconiaSample weight: 127.07 mgCrucibles Pt + lidsHeating rate: 20 K/minAtmosphere: ArgonSensor: DSC-cp type S

200.0 400.0 600.0 800.0 1000.0 1200.0 1400.0Temperature /°C

0.3000

0.4000

0.5000

0.6000

0.7000

0.8000

0.9000

1.0000

Cp /(J/(g*K))


Simultaneous Thermal Analysis (STA)

FurnaceRefer.Sample

∆T

QPR

.

TG + DSC = STAThermogravimetry Differential Scanning

Calorimetry

TG, DSC applied simultaneously to the same sample.


Advantages of STA

TG and DSC are applied simultaneously to the same sample!

Time effective! Also (expensive) samplematerial can be saved.

Direct comparison of TG and DSC possible(same measurement conditions on exactly the same sample)

Exact determination of enthalpy changes(sample mass continuously monitored)


Double furnace hoist

Automatic Sample Changer (ASC)Exchangable Furnaces

Exchangable SampleCarriers (TG, TG-DSC, ...)

Various Cruciblesand Accessories

Flexible TemperatureProgram (-150...2000°C)

Coupling withMS and/or FTIR

Different GasAtmospheres


Various Crucibles (I)

Various Crucibles for TG,TG-DTA, TG-DSC (STA)

(also TG-plate, TG-basket)

Volumes: 40µl … 3.4 ml

Materials: Al2O3, Pt/Rh, Pt/Ir, AlAu, Ag, ZrO2, graphite,Cu, Ni, steel


STA Interchangeable Sensors


Schematics (A)

Toploading design!(easy handling, robust)

Chimney effect!(sensor contaminationavoided, less purge gasrequired which is goodfor EGA)

Vacuum tight fordefined atmospheres!


200 400 600 800 1000 1200 1400Temperatur /°C

-4

-2

0

2

4

6

DSC /(mW/mg)

86

88

90

92

94

96

98

100

102

TG /%

Sample: MnO2

619.1 °C

958.2 °C1200.7 °C

179.7 J/g

71.45 J/g

432.1 J/g

-9.20 %

-3.07 %

-0.23 %

1147.8 °C

-71.83 J/g

↓ exo

Inorganic Application: MnO2

STA 449 JupiterSample: MnO 2mass: 32.14 mg crucible: Pt atm.: Synth. air flow rate: 70 ml/minheating rate: 20 K/min

evaporation of humidity

MnO2 -> Mn2O3

Mn2O3 -> Mn3O4

Solid state phase transition

cooling


STA measurement of Fe 2O3

3Fe2O3�2Fe3O4+1/2O2


A very short excourse aboutthe influence of measurement

parameters


Hexatriacontane


Gas atmosphere - Calciumoxalat Monohydrate

-3.0

-2.0

-1.0

0

1.0

2.0

3.0

c-DTA /K

100 200 300 400 500 600 700 800 900Temperature /°C

30

40

50

60

70

80

90

100

TG /%

0

0.05

0.10

0.15

0.20

Gram Schmidt

-6.0

-5.0

-4.0

-3.0

-2.0

-1.0

0

1.0

DTG /(%/min)

-12.05 %

-18.81 %

-29.48 %

↓ exo

Instrument: TG 209 IrisSample mass: 10.12 mgCruciblel: Al2O3

Atmosphere: syn. air, 30 ml/minHeating rate: 10 K/min



100 200 300 400 500 600 700 800 900Temperature /°C

30

40

50

60

70

80

90

100

TG /%

Stickstoff

synthetische Luft

-12.32 %

-18.96 %

-30.06 %

-12.01 %

-18.78 %

-29.47 %

Synthetic air

Nitrogen


-1.0

0

1.0

2.0

3.0

c-DTA /K

100 200 300 400 500 600 700 800 900Temperature /°C

40

50

60

70

80

90

100

TG /%

0

0.02

0.04

0.06

0.08

0.10

Gram Schmidt

-4.0

-3.0

-2.0

-1.0

0

1.0

DTG /(%/min)

-12.32 %

-19.02 %

-30.02 %

↓ exo

Instrument: TG 209 IrisSample mass: 9.84 mgCrucible: Al2O3

Atmosphere: N2, 30 ml/minHeating rate: 10 K/min



2C750

3 CO CaO CaCO + → °≈

2C500

221 CO O CO →+ °≈

CO CaCO OCaC 3C500

42 + → °≈

OH OCaC OH OCaC 242C150

242 + →∗ °≈



Gypsum (CaSO4 - Dihydrate) - Pt-Crucibles

Sample: CaSO104

Sample mass: 38.68 mgCrucibles: Pt+lidsHeating rate: 20 K/minAtmosphere: AirSensor: TG/DSC type S


Gypsum (CaSO4 - Mixture) - Al-Crucibles (with 50 micron hole)

Sample: CaSO4

Sample mass: ≈ 12 mgCrucibles: Closed AlHeating rate: 30 K/minAtmosphere: AirSensor: TG/DSC type S

Self-generated water vapor


Coupling with MS and/or FTIR

STA-FTIR

STA-MS

STA-MS-FTIR


Fe(OH)SO4

-4

-2

0

2

4

6

DSC /(mW/mg)

30

40

50

60

70

80

90

100

TG /%

100 200 300 400 500 600 700 800 900 1000Temperature /°C

0

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

Ion Current *10-9 /A

amu 18amu 32amu 64

Probe: Fe(OH)SO4

562.9 °C

750.3 °C

246 J/g 1170 J/g

-4.31 %

-45.48 %

-2.46 %

567.9 °C

759.7 °C

↓ exo

STA 449 JupiterSample: Fe(OH)SO 4mass: 30.58 mg crucible: Pt atm.: N 2flow rate: 70 ml/minheating rate: 20 K/min

Ferrofluid

This material is a possibleprecursor for the productionof iron oxide particles.

H2OO2SO2


EGA methods combined with TGA

MS Mass SpectrometryFTIR Fourier Transform Infrared

SpectroscopyGC-MS Gas Chromatography with

MSGC-FTIR GC with FTIR


Mass Spectrometer Couplings

Most common mass spectrometer types which are used for TGA coupling are Quadrupol Mass Spectrometer


Quadrupol Mass Spectrometer (QMS)

cathode

--+

evolved gas inlet

electrons

ion source detector

Principle of Function


Ionization (II)

ABC + e- ABC+ + 2e-

AB+C+ + 2e-

AB+ + C + 2e-

A + BC+ + 2e-

A+ + BC + 2e-

AC+ + B + 2e-

AC + B+ + 2e-

Molecule fragments

red = ionized

blue = neutral


Natural

Abundancies

18O = 0.2%

13C = 1.1%

CO2 spectra of the 11 most intensefragments

Ionization (III)


Gas flow in the STA furnace


Hydromagnesite(STA-MS Capillary)

mass 25.98 mgtemp. 25 ... 960°CHR 10 K/minAir, 80 ml/min


STA 409 C/5 Skimmer

RT....2000° C (1550° C)


Skimmer Pressure Reduction Steps

Sample chamber

divergent nozzle

molecule cloud


Skimmer Coupling

10 mbar-1

Sample

Heater

Sample carrier

Gas overflow

Quadrupol analyzerIon source

SkimmerOrifice

1013

mba

r

10 mbar-5


I2

STA-MS Skimmer: CuGaSe 2

mass 333.08 mgtemp. 10 ... 1170°CHR 10 K/minHe, 75 ml/min

Impurities: Selenium excess, Iodine


STA 449 C STA 449 C JupiterJupiter®®

BRUKER BRUKER TensorTensorTMTM 2727

STA – FTIR Coupling


TG-FTIR Coupling

IR spectra Wave lengths 2.5 to approx. 15 micronWave numbers 4000 to 600 cm-1

Change in DipolmomentNonsymmetrical Molecules

Bending StrechingChange of Bonding Length Change of Bonding Angle


DetectorInterfero-gram

Spectra

Globar

FTIR Principle

Sample

Fixed Mirror

Movable Mirror

BeamsplitterMichelson Interferometer Principle


Thermo-couple

TG

FTIR gas cell (230°C)

Transferline (230°C)

Adapter

Outlet

MicrofurnaceSample

Sample carrier

Thermocouple

Thermocouple

FTIR Coupling System


Pyrolysis of PVC


Y:\Commissions\823-xxx-06\006-3-06-TG209F1-FTIR-MS\006-3-06-12_PVC\006-3-06-12_PVC_308.0 PVC 10.060 | NETZSCH TG 209 F1 | Z:\Commissions\823-xxx-06\006-3-06-TG209F1-FTIR-MS\006-3-06-12_PVC\006-3-06-12.dt3

P:\measurement\0_libspectra\HCl.0

1000150020002500300035004000

Wavenumber cm-1

0.0

0.1

0.2

0.3

0.4

0.5

Abs

orba

nce

Uni

ts

HCl emission during PVC pyrolysis


Thank you for your attention

tga

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