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

2. CALORIMETRY Calorimetry Differential Scanning 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 will require more heat flowing to the sample to increase its temperature at the same rate as the reference, and is an example of an endothermic process.
- If a liquid crystallizes into a solid during a cooling scan, more heat would have to be removed compared to the reference and is an example of an exothermic process.
- Höhne et al. (1996) Differential Scanning Calorimetry
- Perkin Elmer, Inc.

5. DSC outline – latent heat
DSC – MELTING POINT
Melting point measurement
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 Perkin Elmer, Inc.
DSC outline – latent heat

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

7. DSC outline – latent heat
DSC - LATENT HEAT
Latent heat measurement
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 Perkin Elmer, Inc.
DSC outline – latent heat

8. DSC outline – latent heat
DSC - BASELINE
Selecting a baseline
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 rate Otherwise, sigmoidal baseline gives a good result
Horizontal (from left)
Reference : Höhne et al. Differential Scanning Calorimetry Perkin Elmer, Inc.
DSC outline – latent heat

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

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

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

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

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

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

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

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

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

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

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

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

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

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 = , Measured =
Scyclohexane : Expected = & 6.54 , Measured = & 5.2

27. DSC CAL
Diamond DSC 5C/min calibrations : Furnace Calibration point temperature calibration between upper and lower temp. range - matches platinum resistance thermometer and programmed temp.

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

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

30. END OF SLIDES