Fundamentals And applications Of Thermal Analysis

Objectives: To explain principle of different types of thermal techniques. To describe instrumentation of different types of thermal techniques To distinguish between DSC,DTA & TGA To explain application of thermal method

Introduction: Thermal analysis is a branch of material science where the properties of materials are studied as they change with temperature. When matter is heated it undergoes certain physical and chemical changes. These physical and chemical take place over a wide temperature range. Physical changes such as melting or boiling may occur at widely varying temperature, depending on material involve. Chemical changes such as decomposition or reaction may also take place at very different temperatures. Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no-2-701

Definition of Thermal Analysis A branch of materials science where the properties of materials are studied as they change with temperature. Ref-Skoog, Douglas A., F. James Holler and Timothy Nieman (1998). Principles of Instrumental Analysis (5 ed.). New York. pp. 805.

NO Technique Name Abbreviation Instrument Apply Parameter Measure Graph 1 Thermogravimetry TG Thermobalance Mass mass vs temp 2 Derivative Thermogravimetry DTG dm/dt dm/dt vs temp 3 Diff.Thermal Analysis DTA DTA Appts ∆T ∆T vs temp 4 Diff.Scanning Calorimetry DSC Calorimeter dH.dt dH/dt vs temp 5 Thermometric Titrimetry …….. Temp. Temp vs titrant volume 6 Dynamic Reflectance Spectroscopy DRS Spectrophotometer Reflectance %refle.and temp.

7 Evolved gas detection EGD Thermal conductivity cell T.C. T.C. vs temp 8 Dialotometry TMA Dialatometer Vol.of Length Vol or length vs temp 9 Electrical conductivity EC Electrometer or Bridget Current or resistance I or R vs temp 10 Emanation Thermal Analysis ETA ETA appts. Radioactivity E vs temp Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.701-2.702

Thermal Analysis Instrument Manufacturers Perkin Elmer Thermal Analysis Systems http://www.perkin-elmer.com/thermal/index.html TA Instruments http://www.tainst.com/ Mettler Toledo Thermal Analysis Systems http://www.mt.com/ Rheometric Scientific http://www.rheosci.com/ Haake http://polysort.com/haake/ NETZSCH Instruments http://www.netzsch.com/ta/ SETARAM Instruments http://setaram.com/ Instrument Specialists, Inc. http://www.instrument-specialists.com/ Ref-by google search thermal method instrument

Thermogravimetry: It is a technique whereby the weight of the substance, in an environment heated or cooled at a controlled rate, is recorded as a function of time or temperature. Ref-Skoog, Douglas A., F. James Holler and Timothy Nieman (1998). Principles of Instrumental Analysis (5 ed.). New York. pp. 805-806

Types of thermogravimetry: 1. Static thermogravimetry 2. Quasistatic thermogravimetry 3.Dynamic thermogravimetry Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.703-2.704

Instrumentation: TGA Ref-Google image search BALANCE CONTROLLER TEMPERATURE PROGRAMMER BALANCE CONTROLLER POWER FURNACE TEMP. SAMPLE TEMP. WEIGHT INLET Ref-Google image search

1.Balance: Requirements: Accurate, sensitive, reproducible Adequate range of automatic weight adjustment. High degree of mechanical & electronic stability. Rapid response to weight changes. Should be unaffected by vibrations, simple to operate & versatile. Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.705

Types of balances: 1.Deflection balance 2.Null point balance Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.703-2.704

Types of deflection balance: 1.Beam type 2.Helical or spring type 3.Cantilever type 4.Torsion type Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.704-2.705

Types of Deflection Balance: Fig: Deflection balance

Null-Point Balance: Fig: Null-Point Balance

2. Sample Holders: Types: 1.Shallow Pans 2.Deep Crucibles 3.Loosely Covered Crucibles 4.Retort Cups Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.703-706

3.The Furnace: For 1100ºC – Nichrome is used 1100 to 1500ºC. – Platinum or an alloy of platinum and rhodium Above 1750ºC – tungsten or molybdenum Nitrogen or argon are usually used to purge the furnace & prevent oxidation of sample.

4. Temperature measurement: Fig: Position of a Thermocouple in a Thermobalance

5. Recorder: Time base potentiometric strip chart recorder X Y recorder

6.Thermobalance: 1)Continuously the weight changes of the sample as a function of temperature & time. 2) The temperature recorded to an accuracy of better than ±1%. 3) Temperature should, ideally, be the sample Temperature. 4) No chemical attack of volatile products on the apparatus. 5) The balance is protected from furnace. 6) The weight loss should be recorded to an accuracy of ±1%. Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.710-11

TGA Applications: Inorganics Hydrates decomposition, drying phenomena Carbonates and other salts decomposition Kinetics and mechanisms of oxidation, and other solid-gas reactions Analysis of magnetic materials Automatic TG analysis Evaluation of TG pptet. Test purity Curie point determination Ref-M C Ramos-Sanchez, F J Rey, M L Rodríguez, F J Martin-Gil, J Martin-Gil, "DTG and DTA studies on typical sugars", , 134: 55-60

TGA Applications: Organics Identification of polymers and pharmaceutical agents Thermal stability of synthetic and natural polymers and other organics Analysis of polymer-matrix composites Kinetics and mechanism of solid organics – gas reactions Residual solvent determinations Building material Glass technology Ref-M C Ramos-Sanchez, F J Rey, M L Rodríguez, F J Martin-Gil, J Martin-Gil, "DTG and DTA studies on typical sugars", , 134: 55-60

DTA: DTA measures temperature difference between a sample and an inert reference (usually Al2O3) while heat flow to the reference and the sample remains the same Ref-M C Ramos-Sanchez, F J Rey, M L Rodríguez, F J Martin-Gil, J Martin-Gil, "DTG and DTA studies on typical sugars", , 134: 55-60

Differential Thermal Analysis (DTA) Ref-Mansfield, E.; Kar, A.; Quinn, T. P.; Hooker, S. A. (2010). ". Analytical Chemistry 82 .

Principle: The principle of method consists of measuring the change in temperature associated with physical or chemical changes during the gradual heating of the substance. Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.720-22

Differential Thermal Analysis Advantages: Instruments can be used at very high temperatures Instruments are highly sensitive Characteristic transition or reaction temperatures can be accurately determined Disadvantages: Uncertainty of heats of fusion, transition, or reaction estimations is 20-50%. Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.722-23

Applications – Physical chemistry Analytical chemistry Quality control Inorganic chemistry Organic chemistry Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.735-38

Differential Scanning Calorimetry (DSC) 4/26/2017 Differential Scanning Calorimetry (DSC) Differential Scanning Calorimetry technique is a thermal technique in which the difference in the amount of heat required to increase the temperature of a sample & reference is measured as a function of temperature. Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.720-30

Differential Scanning Calorimetry (DSC) DSC measures differences in the amount of heat required to increase the temperature of a sample and a reference as a function of temperature

Differential Scanning Calorimeter

Differential Scanning Calorimeter Perkin Elmer DSC 7 Platinum sensors Sample heater Reference heater Temperature range 110 – 1000 K Heating rate 0.1 – 500 K/min (normally 0.5 – 50 K/min) Noise ± 4 mW Sample volume up to 75 mm3

Applications- Physical chemistry Analytical chemistry Quality control Inorganic chemistry Organic chemistry Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.720-30

DSC in Polymer Analysis Main transitions which can be studied by DSC: Melting Freezing Glass transition

Difference Between: TGA DTA DSC Measures thermo-chemical effect. Measures thermo-physical, thermo-chemical effect. Measures thermo-physical, chemical effect with more sensitivity. Provide range: Thermal Chemical stability of materials. Provide range: Thermal, Physical and Chemical stability of materials. Provide range: Thermal, Physical and Chemical stability and also transition time. E.g. Curie Temperature Contains: Thermobalance. Contains: Thermocouple for measuring ∆T. Contains: Secondary heater for measure ∆H.

Thermo mechanical analysis: Thermo mechanical analysis (TMA) is the technique in which a physical dimensions of a material is monitored as a function of temperature. With the other methods a thermocouple is used to monitor the temperature of the sample in an oven through which a purge gas flow. Ref- introduction to thermal method by brown m.e. p.no-149

Thermo mechanical Analysis: Instrumentation Consist of Transducer(Linear Variable Displacement Transducer) Probe (made up of quartz glass) Thermocouple Furnace Ref-www.google.com

Principle- Measurement of effect of heat on mechanical property of sample eg. Expansion,Compression,Penetration and Extension. Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.754

Applications- Polymer study Quality control Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.754

Dielectric thermal analysis: Dielectric thermal analysis (DETA) or Dielectric Analysis (DEA), is a material science technique similar to dynamic mechanical analysis except that an oscillating electrical field is used instead of a mechanical force. Ref- vogel textbook of chemical analysis p.no.-474-576

Dielectric thermal analysis: Principle In a typical test, the sample is placed in contact with two electrodes(the dielectric sensor) and a sinusoidal voltage (the excitation) is applied to one electrode. The resulting sinusoidal current (the response) is measured at the second electrode. The response signal is attenuated in amplitude and shifted in phase in relation to the mobility of the ions and the alignment of the dipoles. Ref- vogel textbook of chemical analysis p.no.-474-576

Evolved gas analysis: Evolved gas analysis (EGA) is a method used to study the gas evolved from a heated sample that undergoes decomposition or desorption. It is possible to detect which gas is evolved using (EGD) Evolved gas detection..

Thermometric titrations: Definition: A Titration in which the temperature of the titrant is monitored as a function of added titrant volume is a thermometric titration. Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.739

Principle: Thermometric Titrations is based on the change in temperature with theaddition of titrant & determine the end point from a plot of temperature vs. volume of titrant. In thermometric titration change in temperature occurs only when titration is in progress & sample reactant is present. Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.739

Theory- A titration reaction follow chemical equation aaaaaaaaaaaaaaaaaaaaaaaaa In this method there should be change in free energy at end point. A(sample)+B(titrant)C(product)+heat ∆H=∆G+T∆S Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.739

Instrumentation: It consist of Delivery pump fig: thermometric titration assembly Adiabatic cell (Dewar cell) Calibration unit Temperature sensing system Amplification & Recording

4/26/2017 Enthalpimetry: Quantitative analysis of a sample can be sometimes be performed by measurement of the change in enthalpy that is associated with the addition of excess of a chemical reactant to the sample. When a chemical reaction takes place heat is liberated or absorbed. This is known as heat of reaction or enthalpy. Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.759

Methods: 1.Direct injection enthalpimetric titration (DIE): In this technique in which a single portion of an excess of one chemical reactant is added to a fixed volume of a sample that contains other reactant. 2. Continuous flow enthalpimetry: Similar to DIE except that an excess of one reactant is continuously to flowing stream of sample added. Ref-Instrumental methods of chemical analysis by Gurdeep Chatwal and shyam anand, himalaya publication thermal method,p no 2.759

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