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 TGA– Size TMA– Heat Flow DSC– Temp DTA– Gas evolved 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

• Decomposition• Zr5O8(SO4)2*15 H2O (s)

Zr5O8(SO4)2*14 H2O (s) + H2O (v)

• Zr5O8(SO4)2 5 ZrO2

(s) +2 SO2 (v)

15 H2O Water Loss Wt. Loss % loss1 18.0152 1.7215732 36.0304 3.4431463 54.0456 5.1647194 72.0608 6.8862925 90.076 8.6078656 108.0912 10.329447 126.1064 12.051018 144.1216 13.772589 162.1368 15.49416

10 180.152 17.2157311 198.1672 18.937312 216.1824 20.6588713 234.1976 22.3804514 252.2128 24.1020215 270.228 25.82359

SO2 1 64.0588 31.94522 128.1176 38.0668