Transcript Presentation

Centre of Excellence POEMES, IEES (CLEPS), BULGARIAN
ACADEMY OF
Differential
Thermal Analysis
Methods
Sources: http://www.e-thermal.com
http://www.tainst.com, Eric Weisstein
http://scienceworld.wolfram.com
SCIENCES
Centre of Excellence POEMES, IEES (CLEPS), BULGARIAN
ACADEMY OF
SCIENCES
Differential Thermal Analysis Methods
Differential Thermal Analysis DTA
 difference in temperature and heat flows between the sample and a reference.
temperature control program, qualitative analyses of thermal processes.
Differential Scanning Calorimetry (DSC)
 temperatures and heat flows associated with thermal transitions.
 phase transitions/changes, dehydration, gas evolution, melting, crystallization.
 heats of fusion and of reactions, Arrhenius parameters (E, k and n).
 oxidation stability, direct measurement of heat capacity.
Thermogravimetric Analysis (TGA) and DTGA
 weight changes (losses) as a function of temperature under a controlled atmosphere.
 moisture or volatiles, thermal stability and composition, simultaneous DSC / TGA.
Dynamic Mechanical Analysis (DMA)
 mechanical properties as a function of time, temperature, and frequency.
 dimension change measurements as a function of temperature or force.
 stress / strain, stress relaxation, creep.
Sources: http://www.e-thermal.com, http://www.tainst.com, Eric Weisstein, http://scienceworld.wolfram.com
Centre of Excellence POEMES, IEES (CLEPS), BULGARIAN
ACADEMY OF
SCIENCES
Differential Thermal Analysis Methods
Ttmper.
Differential Scanning Calorimetry (DSC)
time
Two designs of DSC instruments produce comparable data .
 endothermic / exothermic processes or changes in heat capacity.
 minimal sample amounts (liquids / solids), 30 min analysis, easy sample preparation.
 wide range of temperatures, hermetically closed or in an atmosphere.
 linear heating ramp, faster heating = higher sensitivity but lower resolution.
Source: http://www.npl.co.uk/npl/cmmt/cog/thermal.html
Centre of Excellence POEMES, IEES (CLEPS), BULGARIAN
ACADEMY OF
SCIENCES
Differential Thermal Analysis Methods
Differential Scanning Calorimetry (DSC)
The two schemes of DSC devices produce comparable data – Power
compensated and Heat flux plate. They comprise two pans with volumes of
some ml which are in contact to heaters and thermo sensors. The sample is
colored in red on the figure, the empty pan is the reference. The sample
weight is measured precisely.
The temperature program is a simple linear rise with time, the maximum
temperatures can exceed 1200oC and sample cooling is possible. Using high
sweep rates, a higher sensitivity, but lower resolution is achieved and vice
versa. The specific heats of the occurring endothermic/exothermic processes
or the changes in heat capacity can be determined for some mg of sample
only.
No special sample preparation is required, the sample can be in a form of
powder, granules, paste or a liquid. The sample pan can be hermetically
closed during the test, or an inert oxidative or reductive atmosphere can be
ensured. A routine analysis takes only about 30 min.
Source: http://www.npl.co.uk/npl/cmmt/cog/thermal.html
Centre of Excellence POEMES, IEES (CLEPS), BULGARIAN
ACADEMY OF
SCIENCES
Differential Thermal Analysis Methods
Temperature modulated DSC (TMDSC)
The Temperature modulated DSC (TMDSC) is a modification of DSC.
A fast sinusoidal modulation is applied over the slower linear heating
ramp. The modulation is of low amplitude (about one degree). The output
signal is processed by FFT analysis. The slow linear sweep ensures a high
resolution combined by the high sensitivity provided by the fast
modulation.
The method is perfect for differentiation of overlapping transitions. It
allows to separate heat capacity related (reversible - crystal melting) from
kinetic (non-reversible – evaporation, decomposition) heat flows. Blends of
two or more materials can be studied. The thermal conductivity of
insulating materials can be determined.
By TMDSC determination of heat capacity along with changes in heat
capacity during transitions is also possible.
Source: http://www.npl.co.uk/npl/cmmt/cog/thermal.html
Centre of Excellence POEMES, IEES (CLEPS), BULGARIAN
ACADEMY OF
SCIENCES
Differential Thermal Analysis Methods
Temper.
Temperature modulated DSC (TMDSC)
time
sinusoidal modulation over the linear heating ramp, differentiation of overlapping transitions
(fast)
(slow)
(FTA)
separates heat capacity related (reversible - crystal melting) and kinetic
(non-reversible – evaporation, decomposition) heat flows.
 blends of two or more materials, determine thermal conductivity of insulating
materials.
 determination of heat capacity along with changes in heat capacity during
transitions.
Source: http://www.npl.co.uk/npl/cmmt/cog/thermal.html
Centre of Excellence POEMES, IEES (CLEPS), BULGARIAN
ACADEMY OF
DSC curves for non cured and cured positive plates
cured
non cured
Pb
dehydration
200 – 300oC:
327oC:
360oC:
420oC:
410oC:
Source: G. Papazov, M. Matrakova, to be published
dehydration
metalic Pb melting
hydrocarbonates
hydrocarbonates
hydrocarbonates
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Centre of Excellence POEMES, IEES (CLEPS), BULGARIAN
ACADEMY OF
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DSC curves for non cured and cured positive plates
Four broad endothermic peaks are observed in the
thermograms along with a sharp endothermic peak due to
metallic lead melting at 327oC.
The couple of overlapping peaks at 200-300oC are related
to the dehydration of the paste and the peaks at 360oC and
above – to the destruction of lead hydrocarbonates.
After curing, the shape of the thermogram changes
significantly. The amount of crystalline water and the type
of its bonds are important for the properties of the paste.
Source: G. Papazov, M. Matrakova, to be published
Centre of Excellence POEMES, IEES (CLEPS), BULGARIAN
non cured
ACADEMY OF SCIENCES
CThermogravimetric
(TGA) and DTGA
analysis
TGA and DTG curves for a non
cured positive plate
up to 200oC: moisture
270oC: dehydration
340oC: hydrocarbonate
370oC: hydrocarbonate
dehydration
cured
TGA and DTG curves for a
cured positive plate
up to 200oC: moisture
260oC: dehydration
340oC: hydrocarbonate
370oC: hydrocarbonate
dehydration
Source: G. Papazov, M. Matrakova, to be published
Centre of Excellence POEMES, IEES (CLEPS), BULGARIAN
ACADEMY OF
SCIENCES
CThermogravimetric (TGA) and DTGA analysis
The presented curves correspond to TGA (weight loss in
% vs temperature) and DTG (rate of loosing weight vs.
temperature).
The samples are the same as for the above DSC curves
(non cured and cured positive plates).
Up to 200oC the moisture from the sample is evolved.
The main weight loss is due to dehydration occurring at
270oC.
Smaller weight losses are observed due to the destruction
of hydrocarbonates at 340oC and 370oC.
Source: G. Papazov, M. Matrakova, to be published
Centre of Excellence POEMES, IEES (CLEPS), BULGARIAN
ACADEMY OF
SCIENCES
TGA and DTG curves for
a positive plate
TGA and DTG curves for a
cured positive plate
260oC: dehydration
340oC: hydrocarbonate
380oC: hydrocarbonate
TGA and DTG curves for a
formed positive plate
Up to 350oC:
510oC:
570oC:
dehydration
Source: G. Papazov, M. Matrakova, to be published
Centre of Excellence POEMES, IEES (CLEPS), BULGARIAN
ACADEMY OF
SCIENCES
TGA and DTG curves for a positive plate
The cured plate (containing 4PbO.PbSO4) looses weight
due to dehydration at about 260oC and due to the
destruction of hydrocarbonates at 340 and 380oC.
The curves for the positive plate after formation
(containing PbO2) are rather different. Weight losses due
to dehydration are observed at 350oC.
Source: G. Papazov, M. Matrakova, to be published
Centre of Excellence POEMES, IEES (CLEPS), BULGARIAN
ACADEMY OF
SCIENCES
Thermograms of various PbO2 types obtained by DSC
DSC is a powerful method to investigate the phase composition and the
properties of PbO2. In combination with XRD and SEM it provides
unique information.
The thermal spectra of four PbO2 samples are shown on the next figure.
The red curve is for chemical b-PbO2 (Merck), the black one for a
mixture of b-PbO2 with few % of a-PbO2, and the green and the blue
curves are for electrochemically prepared PbO2 – freshly prepared PAM
(green) and PAM at the end of cycle life (blue).
Two exothermic peaks are observed on the figure at about 200 and
280oC. They are due to crystallization processes occurring in the
partially hydrated zones of their particles. Amorphous PbO2 is observed
mainly in electrochemically obtained PbO2.
Six endothermal peaks are observed at higher temperatures. First,
between 300 and 400 oC chemically bound water contained in the PbO2
PAM particles is evolved. At temperatures above 400oC a-PbO2 and bPbO2 are thermally decomposed to a variety of non stoichiometric lead
oxides.
Centre of Excellence POEMES, IEES (CLEPS), BULGARIAN
ACADEMY OF
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Thermograms of various PbO2 types obtained by DSC
1
78
6
5
7
1
1
3
2
4
4
6
6
6
Peaks 1, 2 (exo) - up to 200oC – crystallization of amorphous PbO2.
Peaks 3, 4 (endo) - 300-380oC - PbO(OH)2  PbO2
Peaks 5, 6, (endo) - 380 - 480oC - b-PbO2  PbOx (A)
Peaks 7, 8 (endo)- above 480oC - PbOx (A)  PbOx (B)
Centre of Excellence POEMES, IEES (CLEPS), BULGARIAN
ACADEMY OF
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Thermograms of PbO2 samples from PAM sublayers
(SGTP)
On the next figure thermal spectra of PbO2 PAM samples from a
SGTP are shown. The samples are taken from one electrode at
different distances from the current collector in the middle.
The area of Peak 6 which is related to b-PbO2 decomposition
decreases slowly from the surface towards the current collector.
On the red curve for the sample in the AMCL a new hump is
observed (in white). The shape of the curve changes completely in
the corrosion layer what is an indication about phase composition
changes.
Centre of Excellence POEMES, IEES (CLEPS), BULGARIAN
ACADEMY OF
SCIENCES
Thermograms of PbO2 samples from PAM sublayers (SGTP)
2 2
1
4
2
1
6
4
2
4A
6
4
1
1
6
4B
Peaks 1, 2 (exo) - up to 200oC – crystallization of amorphous PbO2.
Peak 4 (endo) - 300-380oC - PbO(OH)2  PbO2
Peaks 6 (endo) - 380 - 480oC - b-PbO2  PbOx (A)
Peaks 7, 8 (endo) - above 480oC - PbOx (A)  PbOx (B)
Peaks 4A, 4B (endo) - 385oC and 430oC - PbOx (C)  PbOx (D)
Centre of Excellence POEMES, IEES (CLEPS), BULGARIAN
ACADEMY OF
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DSC of PAM with declined capacity and after capacity recovery
Peaks 1, 2 (exo) - up to 200oC – crystallization of amorphous PbO2.
Peak 4 (endo) - 300-380oC - PbO(OH)2  PbO2
Peak 6 (endo) - 380 - 480oC - b-PbO2  PbOx (A)
1
2
4
2
1
6
4
6
Source: B. Monahov, M. Matrakova, to be published
Centre of Excellence POEMES, IEES (CLEPS), BULGARIAN
ACADEMY OF
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Peak 4 (endo) - 300-380oC - PbO(OH)2  PbO2
Peak 6 (endo) - 380 - 480oC - b-PbO2  PbOx (A)
Peak 9 (endo) - 510oC - PbOx  Pb3O4 + a-PbOy
Peak 10 (endo) - 560oC - PbOx  Pb3O4 + a-PbOy
TGA / DTG, PAM, before and after capacity recovery
4
10
6
9
Source: B. Monahov, M. Matrakova, to be published
Centre of Excellence POEMES, IEES (CLEPS), BULGARIAN
ACADEMY OF
SCIENCES
Battery knowledge contributed by thermal techniques
1. Fundamentals of the processes taking place in the plates during
production and service life (phase transitions, hydration,
dehydtration and their impact on battery performance).
2. Fundamentals of the processes taking place during the COC and of
the processes related to battery thermal runaway.
3. Rate of temperature changes in the cell and temperature
distribution along the plate during charge and discharge.
4. Dependence of battery temperature changes on cycle life.
5. Estimation of heating rate, thermal efficiency and thermal capacity
of the battery / cell (or its components).
6. Thermal modeling of batteries in EV and stationary applications.