Thermal analysis

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Thermal analysis

  1. 1. Thermal Analysis Terry A. RingChemical Engineering University of Utah
  2. 2. Different Techniques• Thermometric Titration (TT) – Heat of mixing• Thermal Mechanical Analysis (TMA) – Thermal Expansion Coefficient• Dynamic Mechanical Analysis (DMA) – Viscoelastic Properties• Differential Scanning Calorimetric (DSC) – Heat flow during Transitions• Thermal Gravimetric Analysis (TGA) – Weight Loss due to decomposition – Derivative Thermogravimetric Analysis (DTG)• Differential Thermal Analysis (DTA) – Heat of Transitions• Temperature Programmed Desorption (TPD) – Temperature at which gas is desorbed from (catalyst) surface – Emission gas Thermoanalysis (EGT)
  3. 3. Basic Principle• Sample is heated at a constant heating rate• Sample’s Property Measured – Wt TGA – Size TMA – Heat Flow DSC – Temp DTA – Gas evolved TPD
  4. 4. TGA• Constant Heating Rate – Initial Temp – Final Temp – Heating Rate (°C/min)• Data – Weight vs Time – Weight vs Temp.• Differential This Data (DTG)
  5. 5. DSC
  6. 6. DSC• Constant Heating Rate – Initial Temp – Final Temp – Heating Rate (°C/min)• Data – Heat flow to sample minus Heat flow to reference vs Time (Temp.)• Measures heat of crystallization Polymer without weight change in this temperature range
  7. 7. DTA• Sample and Reference Placed in Heater• Constant Heating Rate – Initial Temp – Final Temp – Heating Rate (°C/min)• Data – Temp of Sample vs Time (or Temp) – Temp of Reference vs Time (or Temp) – Reference should be inert, e.g. nothing but latent heat• Measures – Heat of crystallization – Glass Transition Temperature
  8. 8. DTA + DTG
  9. 9. TMA• Constant Heating Rate – Initial Temp – Final Temp – Heating Rate (°C/min)• Data – Size of Sample vs Time (or Temp.)• Measures – Thermal Expansion Coefficient – Volume change on crystalization or crystal transformations – Sintering – Glass Transitions in Polymers
  10. 10. TMAPolymer with glass transition
  11. 11. DMA• Constant Heating Rate – Initial Temp – Final Temp – Heating Rate (°C/min)• Data – Force vs Time (or Temp.) – Force delay vs Time (or Temp.) – Viscoelastic Properties • Storage and Loss Modulus• Measures – Glass Transition – Viscoelastic Properties Polymer with Glass Transition
  12. 12. We have TGA - only• Heating a sample of Calcium oxalate• Ca(C204)*xH2O  Ca(C204) *H2O + x-1 H2O• Ca(C204)*H2O Ca(C204) + H2O• Ca(C204)  CaCO3 + CO• CaCO3  CaO + CO2
  13. 13. TGA• Constant Heating Rate – Initial Temp – Final Temp – Heating Rate (°C/min)• Data – Weight vs Time – Weight vs Temp.• Differential This Data (DTG)
  14. 14. TGA – Ca(C204)*xH2O
  15. 15. Different Heating Rates
  16. 16. Heating Rate• Heating Too Fast – Overlaps Transitions• Interpretation Problems• Kinetics of Decomposition – Sample Size – Mass Transfer • Convective Mass Transfer • Pore Diffusion – Heat Transfer • Convective Heat Transfer • Thermal Conductivity – Porous solid
  17. 17. Precipitated Zr5O8(SO4)2*15 H2O This sample was dried fro 48 hrs at 110C before TGA analysis. What is going on?
  18. 18. Analysis of Filtrate from Precipitation• Precipitation• 5ZrOCl2 + 2H2SO4 + xH2O  Zr5O8(SO4)2*15 H2O (s) + 10 HCl• Decomposition• Zr5O8(SO4)2*15 H2O (s)  Zr5O8(SO4)2*14 H2O (s) + H2O (v)• Zr5O8(SO4)2  5 ZrO2 (s) +2 SO2 (v)

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