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ME4331 – DSC Review

ME4331 – DSC Review. APR 29 , 2008. Jeung Hwan Choi. CALORIMETRY. Calorimetry - The science of counting the heat of chemical reactions or physical changes. - In constant-pressure calorimetry, the heat measured represents the enthalpy change. Differential Scanning Calorimetry.

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ME4331 – DSC Review

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  1. ME4331 – DSC Review APR 29 , 2008 Jeung Hwan Choi

  2. CALORIMETRY Calorimetry - The science of counting the heat of chemical reactions or physical changes. - In constant-pressure calorimetry, the heat measured represents the enthalpy change. Differential Scanning Calorimetry Differential Scanning Calorimetry (DSC) is a thermal analysis method in which the difference in the amount of heat applied (or removed) to increase (or decrease) the temperature of a sample material and a reference material are measured as a function of temperature. - Höhne et al. (1996) Differential Scanning Calorimetry - Perkin Elmer, Inc. - Wikipedia.org

  3. DIFFERENTIAL SCANNING CALORIMETER - The DSC will maintain the temperatures of the sample and reference equal during a scan (change of both materials from one temperature to another). - The Pyris1 Differential Scanning Calorimeter allows the user to change the temperature at a prescribed constant rate (linear temperature control). sample furnace reference furnace - Höhne et al. (1996) Differential Scanning Calorimetry - Perkin Elmer, Inc.

  4. DSC – ENDOTHERMIC VS. EXOTHERMIC - When the sample undergoes a physical transformation such as phase transitions, more (or less) heat will need to flow to it than the reference to maintain both at the same temperature. - This noticeable difference results in the appearance of an upper or lower peak, depending on whether the transformation is exothermic or endothermic. - A solid sample melting to a liquid willrequire more heat flowing to the sampleto increase its temperature at the samerate as the reference, and is an exampleof an endothermic process. - If a liquid crystallizes into a solid duringa cooling scan, more heat would have tobe removed compared to the referenceand is an example of an exothermicprocess. - Höhne et al. (1996) Differential Scanning Calorimetry - Perkin Elmer, Inc.

  5. DSC – MELTING POINT • Melting point measurement DSC outline – latent heat heating rate = 5 °C/min - Melting point of a pure substance (i.e. ice) is the onset temperature - Onset is determined from the intersection of the slopes of the base and the rising curve Reference : Höhne et al.Differential Scanning Calorimetry 1996 Perkin Elmer, Inc.

  6. DSC - LATENT HEAT • Latent heat of fusion of ice DSC outline – latent heat Reference : CRC Handbook of Chemistry and Physics 2007

  7. DSC - LATENT HEAT • Latent heat measurement DSC outline – latent heat Possible errors - Weight value - Evolution width - Baseline error (Instrument based) - Baseline error (sample based) heating rate = 5 °C/min Reference : Höhne et al.Differential Scanning Calorimetry 1996 Perkin Elmer, Inc.

  8. DSC - BASELINE • Selecting a baseline DSC outline – latent heat Standard(linear) Sigmoidal Horizontal(from right) Linear baseline suffices for samples that : - are small in weight / volume - have a small specific transition energy - undergo a slow scanning rateOtherwise, sigmoidal baseline gives a good result Horizontal(from left) Reference : Höhne et al.Differential Scanning Calorimetry 1996 Perkin Elmer, Inc.

  9. DSC - SPECIFIC HEAT • Specific heat of ice / water DSC outline – specific heat Reference : CRC Handbook of Chemistry and Physics 2007

  10. DSC - SPECIFIC HEAT • Specific heat measurement DSC outline – specific heat Red :with waterBlue :empty Green :specific heat heating rate = 5 °C/min Reference : Höhne et al.Differential Scanning Calorimetry 1996 Perkin Elmer, Inc.

  11. DSC – PHASE DIAGRAM • System NaCl-H2O Phase Diagram DSC outline – specific heat

  12. DSC – PHASE DIAGRAM • 1xNaCl Thermal Analysis DSC outline – specific heat

  13. DSC – PHASE DIAGRAM • 5xNaCl Thermal Analysis DSC outline – specific heat

  14. DSC – PHASE DIAGRAM • 10xNaCl Thermal Analysis DSC outline – specific heat

  15. DSC – PHASE DIAGRAM • 23.3%(w/w) NaCl Thermal Analysis DSC outline – specific heat

  16. DSC – PHASE DIAGRAM • NaCl+H2O Thermal Analysis DSC outline – specific heat

  17. DSC – PHASE DIAGRAM • NaCl+H2O Thermal Analysis DSC outline – specific heat

  18. CRYOMICROSCOPY • Visualization of freeze-thaw events Cryomicroscopy - layout microscope LN2 dewar video text overlay cooling pump computer interfaced temperature controller cryostage Reference : Linkam Scientific Instruments

  19. CRYOMICROSCOPY • Growth of Primary Ice DSC outline – specific heat Video credits : Bumsoo Han

  20. CRYOMICROSCOPY • Solidification of the Eutectic DSC outline – specific heat Video credits : Bumsoo Han

  21. EUTECTIC SOLIDIFICATION • Phase change behavior in salt solutions (10xPBS) ADD: 10xPBS eutectic (photo) pre-eutectic @ -26°C eutectic @ -26°C(after supercooling) Photo credits : Adam Grovender

  22. DSC CAL • Diamond DSC 5C/min calibrations : - Baseline Curvature Calibrations- Baseline Slope Calibrations- Sample Temperature Calibrations- Furnace Calibrations- Heat Flow Calibrations

  23. DSC CAL • Diamond DSC 5C/min calibrations : Baseline Curvature- minimize amplitude of curve for operating temp. range Factory default Coarse control : + 1 Fine control : + 3

  24. DSC CAL • Diamond DSC 5C/min calibrations : Baseline Curvature- minimize amplitude of curve for operating temp. range Factory default Fine control : + 10 Fine control : + 13 Fine control : + 14 Fine control : + 15 Fine control : + 20

  25. DSC CAL • Diamond DSC 5C/min calibrations : Baseline Slope- minimize slope of curve for operating temp. range Factory default Slope : - 5 Slope : - 4 FSlope : - 3 Slope : + 5

  26. DSC CAL • Diamond DSC 5C/min calibrations : Sample Temp. Cal.- Correctly predict transition temperatures of standards n-Decane : Expected = -29.66 , Measured = -31.73 Scyclohexane : Expected = -87.06 & 6.54 , Measured = -87.1 & 5.2

  27. DSC CAL • Diamond DSC 5C/min calibrations : Furnace Calibration - 9-point temperature calibration between upper and lower temp. range - matches platinum resistance thermometer and programmed temp. -150.04 -125.01 -100.02 -75.02 -50.05 -24.93 -0.002 24.99 49.99 75.01 99.99

  28. DSC CAL • Diamond DSC 5C/min calibrations : Heat Flow Calibration- match enthalpy values with known reference materials n-Decane : H = 202.09 vs 201.19 +/- 0.5, -0.45% T = -29.66 vs -29.66 +/- 0.04

  29. DSC CAL • Diamond DSC 5C/min calibrations : Heat Flow Calibration- match enthalpy values with known reference materials H2O : H = 333.8 vs 338.6 +/- 0.15, +1.07% T = 0 vs -0.43 +/- 0.01

  30. END OF SLIDES

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