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Sources: http://www.e-thermal.com http://www.tainst.com, Eric Weisstein http://scienceworld.wolfram.com

D ifferential T hermal A nalysis M ethods. Sources: http://www.e-thermal.com http://www.tainst.com, Eric Weisstein http://scienceworld.wolfram.com. D ifferential T hermal A nalysis M ethods. Differential Thermal Analysis DTA

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Sources: http://www.e-thermal.com http://www.tainst.com, Eric Weisstein http://scienceworld.wolfram.com

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  1. Differential Thermal Analysis Methods Sources: http://www.e-thermal.com http://www.tainst.com, Eric Weisstein http://scienceworld.wolfram.com

  2. 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

  3. Ttmper. time Differential Thermal Analysis Methods Differential Scanning Calorimetry (DSC) 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

  4. 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

  5. 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

  6. Temper. time Differential Thermal Analysis Methods Temperature modulated DSC (TMDSC) 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

  7. DSC curves for non cured and cured positive plates cured non cured Pb dehydration 200 – 300oC: dehydration 327oC: metalic Pb melting 360oC: hydrocarbonates 420oC: hydrocarbonates 410oC: hydrocarbonates Source: G. Papazov, M. Matrakova, to be published

  8. 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

  9. CThermogravimetric (TGA) and DTGA analysis non cured 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

  10. 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

  11. 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: dehydration 510oC: 570oC: Source: G. Papazov, M. Matrakova, to be published

  12. 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

  13. 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 b-PbO2 are thermally decomposed to a variety of non stoichiometric lead oxides.

  14. 8 1 7 6 5 7 6 4 1 3 2 6 4 1 6 Thermograms of various PbO2 types obtained by DSC 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)

  15. 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.

  16. 2 1 2 4 2 1 6 4 2 4A 6 4 1 6 1 4B Thermograms of PbO2 samples from PAM sublayers (SGTP) 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)

  17. 1 2 4 2 6 1 4 6 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) Source: B. Monahov, M. Matrakova, to be published

  18. 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 9 6 Source: B. Monahov, M. Matrakova, to be published

  19. Battery knowledge contributed by thermal techniques • Fundamentals of the processes taking place in the plates during production and service life (phase transitions, hydration, dehydtration and their impact on battery performance). • Fundamentals of the processes taking place during the COC and of the processes related to battery thermal runaway. • Rate of temperature changes in the cell and temperature distribution along the plate during charge and discharge. • Dependence of battery temperature changes on cycle life. • Estimation of heating rate, thermal efficiency and thermal capacity of the battery / cell (or its components). • Thermal modeling of batteries in EV and stationary applications.

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