Transcript Thermal Analysis.ppt

Thermal Analysis
Terry A. Ring
Chemical Engineering
University of Utah
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)
Basic Principle
• Sample is heated at a constant heating
rate
• Sample’s Property Measured
– Wt
– Size
– Heat Flow
– Temp
– Gas evolved
TGA
TMA
DSC
DTA
TPD
TGA
• Constant Heating
Rate
– Initial Temp
– Final Temp
– Heating Rate (°C/min)
• Data
– Weight vs Time
– Weight vs Temp.
• Differential This Data
(DTG)
DSC
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
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
DTA + DTG
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
TMA
Polymer with glass transition
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
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
TGA
• Constant Heating
Rate
– Initial Temp
– Final Temp
– Heating Rate (°C/min)
• Data
– Weight vs Time
– Weight vs Temp.
• Differential This Data
(DTG)
TGA – Ca(C204)*xH2O
Different Heating Rates
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
Precipitated Zr5O8(SO4)2*15 H2O
This sample was dried fro 48 hrs at 110C before TGA analysis.
What is going on?
Analysis of Filtrate from
Precipitation
• Precipitation
• 5ZrOCl2 + 2H2SO4 + xH2O 
Zr5O8(SO4)2*15 H2O (s) + 10 HCl
15 H2O
• Decomposition
•
Zr5O8(SO4)2*15 H2O (s) 
Zr5O8(SO4)2*14 H2O (s) + H2O (v)
•
Zr5O8(SO4)2 
ZrO2 (s) +2 SO2 (v)
5
SO2
Water Loss
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
1
2
Wt. Loss
18.0152
36.0304
54.0456
72.0608
90.076
108.0912
126.1064
144.1216
162.1368
180.152
198.1672
216.1824
234.1976
252.2128
270.228
64.0588
128.1176
% loss
1.721573
3.443146
5.164719
6.886292
8.607865
10.32944
12.05101
13.77258
15.49416
17.21573
18.9373
20.65887
22.38045
24.10202
25.82359
31.9452
38.0668