Week 9 - Thermal Analysis DSC DTA (Dr. ASNA) PDF

FACULTY OF MECHANICAL ENGINEERING AND TECHNOLOGY UNIVERSITI MALAYSIA PERLIS (UNIMAP) PERLIS. MMK 43803 – ADVANCED CHARACTERIZATION PROCESS CHAPTER 4: CHARACTERIZATION OF THERMAL ANALYSIS SEMESTER 1 (2024/2025)...

FACULTY OF MECHANICAL ENGINEERING AND TECHNOLOGY UNIVERSITI MALAYSIA PERLIS (UNIMAP) PERLIS. MMK 43803 – ADVANCED CHARACTERIZATION PROCESS CHAPTER 4: CHARACTERIZATION OF THERMAL ANALYSIS SEMESTER 1 (2024/2025) PRESENTER BY: ASNA RASYIDAH BINTI ABDUL HAMID, PhD 019-3425567 Faculty of Mechanical Engineering , Universiti Malaysia Perlis (UniMAP) MMK 10103 – ADVANCED CHARACTERIZATION PROCESS Lesson Plan / Teaching Plan WEEK CHAPTER 9 4.0 CHARACTERIZATION OF THERMAL ANALYSIS Apply and compare the thermal analysis process using Differential Scanning Calorimetry (DSC) and Thermogravimetry Analysis (TGA). Describe application of DSC and TGA. 10 4.0 CHARACTERIZATION OF THERMAL ANALYSIS CON`T 11 5.0 CHARACTERIZATION OF DIFFRACTOMETER (XRD & XRF) Explain and apply X-ray Diffractometer (XRD) and X-ray Fluorescence (XRF) Describe the process and application of XRD and XRF. 12 5.0 CHARACTERIZATION OF DIFFRACTOMETER (XRD & XRF) CON`T 13 6.0 INTRODUCTION OF MECHANICAL PROPERTIES TEST (Surface roughness and Fatique Test) Calculate and select mechanical properties of surface roughness and follow by mechanical analysis; Impact, bending and flexural analytical test. 14 6.0 INTRODUCTION OF MECHANICAL PROPERTIES TEST (Surface roughness and Fatique Test) CON`T. 15 Test 2 MMK 10103 – ADVANCED CHARACTERIZATION PROCESS Lesson Plan / Teaching Plan WEEK CHAPTER 9 10 11 12 13 6.0 INTRODUCTION OF MECHANICAL PROPERTIES TEST (Surface roughness and Fatique Test) Calculate and select mechanical properties of surface roughness and follow by mechanical analysis; Impact, bending and flexural analytical test. 14 6.0 INTRODUCTION OF MECHANICAL PROPERTIES TEST (Surface roughness and Fatique Test) CON`T. 15 Test 2 16 Study week  THERMAL ANALYSIS: DIFFERENTIAL SCANNING CALORIMETRY (DSC)  Types of thermal analysis TG (Thermo Gravimetric) analysis: Weight DTA (Differential Thermal Analysis): Temperature DSC (Differential Scanning Calorimetry): Energy 4 Introduction DSC measure heat absorbed or liberated during heating or cooling. DSC is used to measure: Qualitative analysis (Fingerprinting of minerals, clays, polymers) Thermal transition of samples Sample purity (melting point) Heat capacity, Cp Glass transition temperature, Tg Crystallization temperature, Tc Phase diagrams  Principle of DSC The sample and reference are maintained at the same temperature, even during a thermal event in the sample. The energy required to maintain zero temperature difference between the sample and the reference is measured. During a thermal event in the sample, the system will transfer heat to or from the sample pan to maintain the  Principle During heating two types of reactions can be take place one is the endothermic and the other is the exothermic. Endothermic reaction: If sample absorbs some amount of heat durin phas transition, then reaction is said to be g e endothermic More energy needed to maintain zero temp difference between sample & reference. Exothermic reaction: If sample released some amount of heat during phase transition, then reaction is said to be exothermic. In exothermic reaction, less energy needed to maintain zero temp difference between sample & Instrument Types 2 basic types: power compensation DSC and heat-fl ux DSC Power compensation DSC Heat flux DSC  Instrument Types – Power Compensation DSC Sample holder Aluminum or Platinum individual pans heaters controller P Sensors Platinum resistance thermocouples Separate sensors and heaters sample reference for the pan pan sample and reference Furnace Separate blocks for sample and reference cells inert gas inert gas Temperature vacuum vacuum controller Supply the differential T = 0 thermal power to the thermocouple heaters to maintain the temperature of the sample and reference at the program value  Instrument Types – Heat Flux DSC heating Sample and reference coil holders Al or Pt pans placed on sample reference pan pan constantan disc constantan Sample and reference chromel/alumel wires holders are inert gas thermocouples Chromel connected by a low- vacuum resistance heat flow path Thermocouple is a junction between two different metals that produces a voltage due to a temperature difference  Instrument Types – Heat Flux DSC Furnace heating coil One block for both sample and reference cells sample reference pan pan Temperature constantan controller chromel/alumel wires The temperature difference between the sample and inert gas thermocouples Chromel reference is converted to vacuum differential thermal power, which is supplied to the heaters to maintain the temperature of the sample and reference at the program value Sample Preparation  Accurately-weigh samples (~3-20 mg)  Small sample pans (0.1 mL) of inert or treated metals (Al, Pt, Ni, etc.)  Several pan confi gurations, e.g., open, pinhole, or hermetically- sealed (airtight) pans  The same material and configuration should be used for the sample and the reference  Material should completely cover the bottom of the pan to ensure good thermal contact Sample Preparation Because DSC measures the difference in heat flow between a sample and reference, the baseline stabilizes faster if the difference in heat capacity between the sample and reference is kept small by adding weight (same material as pan) to the reference pan so that it is similar in total weight to the sample pan. Aluminum pans can be used in most experiments, unless the sample reacts with aluminum or the temperature is to exceed 600 °C. Sample Preparation Avoid overfilling the pan to minimize thermal lag from the bulk of the material to the sensor * Small sample masses and low heating rates increase resolution Al P alumin N C quart t a i u z Types of crucible DSC Curve The result of a DSC experiment is a curve of heat flux versus temperature or versus time. This curve can be used to calculate enthalpies of transitions. ΔH = KA Where ΔH is the enthalpy of transition,K is the calorimetric constant and A is the area under the peak. Typical DSC-Traces DSC Curve Area under the peak is directly proportional to heat absorbed or evolved by the reaction Height of the peak is directly proportional to rate of the reaction DSC Curve Heat Suppose a polymer is Capacity being heated. When we start heating two pans, the computer will plot the difference in heat output of the two heaters against temperature that is plot of heat absorbed by the polymer against temperature. The plot will look like this at first. DSC Curve Heat By Capacity heat flow (q/t) by heating dividing rate the (ΔT/t). It ends up with heat supplied divided by the temperature increase, which is called heat capacity. DSC Curve Heat When Capacitya amount of heat is certain transferred to the sample, its temperature increases by a amount, certain and the amount of heat it takes to get a certain temperature increase is called the heat capacity, or C p. DSC Curve Glass Transition Temperature (Tg) On further heating the polymer to a certain temperature, plot will shift downward suddenly. This means there is more heat flow. There is an increase in the heat capacity of the polymer. Take note that this change This happens because the doesn't occur suddenly, but takes place over a polymer has just gone temperature range. This through the glass makes picking one discreet Tg a transition. kind of tricky matter, but we usually just take the middle of the incline to be the Tg. DSC Curve Crystallization (Tc) After glass transition, the polymers have a lot of mobility and never stay in one position for very long time. But, when reaches the right temperature, they will give off enough energy to move into very ordered arrangements, which is called crystals. When polymers fall into these crystalline arrangements, they give off heat. The temperature at the highest point in the peak is DSC Curve Crystallization (Tc) we can measure the area of the peak, which tells us the latent energy of crystallization of the polymer. This peak tells that the polymer can in fact crystallize. A 100% amorphous polymer, e.g. polystyrene, wouldn't get this peak, because such materials don't crystallize. Also, because the polymer gives off heat when it crystallizes, the crystallization is called an exothermic transition. DSC Curve Melting When reaches the polymer's (Tm) melting temperature, Tm, the polymer crystals begin to fall apart, that is they melt. It comes out of their ordered arrangements, and begin to move around freely. When the polymer crystals melt, they must absorb heat in order to do so. Remember melting is a first order transition. This means that at the melting temperature, the polymer's temperature won't rise until DSC Curve Melting (Tm) This means that the little heater under the sample pan has to put a lot of heat into the polymer in order to both melt the crystals and keep the temperature rising at the same rate as that of the reference pan. This extra heat flow during melting shows up as a big dip.  Output of DSC Putting all together - Thermogram From DSC plot, big difference is seen between the glass transition and the other two thermal transitions (crystallization and melting). For the glass transition, there is no dip, and there's no peak, either. This is because there is no latent heat given off, or absorbed, by the polymer during the glass transition. Both melting and crystallization involve giving off or absorbing heat. Advantages of DSC Instruments can be used at very high temperatures Instruments are highly sensitive Flexibility in sample Characteristic transition or reaction can temperatures determined volume/form be High resolution obtained High sensitivity Stability of the Limitation of DSC DSC generally unsuitable for two-phase mixtures Difficulties in test cell preparation in avoiding evaporation of volatile Solvents DSC is generally only used for thermal screening of isolated intermediates and products Does not detect gas generation Uncertainty of heats of fusion and transition temperatures  THERMAL ANALYSIS: DIFFERENTIAL THERMAL ANALYSIS (DTA) Types of thermal analysis TG (Thermo Gravimetric) analysis: Weight DTA (Differential Thermal Analysis): Temperature DSC (Differential Scanning Calorimetry): Energy 39 Thermogravimetry (TG) Thermogravimetry is the measurement of the mass of a sample as the temperature increases. This method is useful for determining sample purity and water, carbonate, and organic content; and for studying decomposition reactions. This is a comparison method Analytical method for recording the difference in temperature (∆T) between a substance and an inert reference material as a function of temperature or time Any transformation – change in specific heat or an enthaply of transition can be detected by DTA In DTA both test sample & an inert reference material (alumina) – controlled heating or cooling programming If zero temperature difference between sample & reference material – sample does not undergo any chemical or physical If any change reaction takes place difference (∆T) will temperature occur between sample reference material & A DTA curve can be used as a fingerprint for identification purposes  ∆T VS Temp. Sharp Endothermic – changes in crystallinity or fusion (join together) Broad endotherms - dehydration reaction Physical changes usually result in endothermic curves Chemical reactions are exothermic. Differential Thermal Analysis (DTA) Principle: The basic principle involved in DTA is the temperature difference (∆T) between the test sample and an inert reference sample under controlled and identical conditions of heating or cooling is recorded continuously as a function of temperature or time, thus the heat absorbed or emitted by a chemical system is determined. Differential Thermal Analysis (DTA) If any reaction takes place in the sample, then the temperature difference will occur between the sample and the reference material. In an endothermic change (such as melting or dehydration of the sample) the temperature of the sample is lower than that of the reference material) (i.e) ∆T = ‒ ve (for endothermic process) In an exothermic change or process the sample temperature is higher than that of the reference material. (i.e) ∆T = + ve (exothermic process) The shape and the size of the peak give information about the nature of the test sample. 1. Sharp endothermic peaks indicate phase changes (melting, fusion) transition from one crystalline form to another crystalline form. 2. Broad endothermic peaks are obtained from dehydration reactions 3. Chemical reactions like oxidative reactions are exothermic reactions. Instrumentation for DTA/Block Diagram Differenti temperature measure al sensor (to reference difference temperat material) between the sample the and reference holder ure the are kept inside samplethe furnace and the temperature of and the furnace and sample holder is controlled by using furnace controller.  Apparatus The key features of a differential thermal analysis kit are as follows 1. Sample holder comprising sample containers and a thermocouples, or ceramic block. metallic 2. Furnace. 3. Temperature programmer. 4. Recording system. Thermal Analysis Techniques When a material is heated, its and chemical composition can structural changes such as fusion, undergo crystallization, oxidation, melting, transition, decomposition, expansion and sintering. Using Thermal Analysis, such changes can be monitored in every atmosphere of interest.  Phenomena causing changes in temperature Physical: Chemical : Oxidation Adsorption (exothermic) (exothermic) Desorption Reduction (endothermic) (endothermi A change in c) crystal structure Break down (endo – or reactions (endo – exothermic) or Crystallizati exothermic) on Chemisorpti (exothermic) on Melting (exothermic) (endothermic Solid state 53 54  Differential Thermal Analysis Advantages: instruments can be used at very high temperatures instruments are highly sensitive characteristic transition or reaction Disadvantage DTA temperatures can be accurately s:determined uncertainty of heats of fusion, transition, or reaction estimations is 20-50% Factors affecting the DTA Curve Instrumental Factors: Size and shape of the sample and furnace holder. Material from which sample holder is made and its corrosive attack. Heating rate (furnace heating rate) Sample characteristics: Amount of the sample (sample weight) Particle size of the sample  Applications of DTA DTA curves for substances are not identical. Hence, they serve as fingerprints for various substances. Used to study the characteristic of polymeric material. This technique is used for testing the purity of the drug sample and also to test the quality control of number of substances like cement, soil, glass etc. Used for the determination of heat of reaction, specific heat and energy change occurring during melting etc. Trend in ligand stability (thermal stability of the ligands) gives the information about the ligands in the coordination sphere. Quantitative identification and purity  What is the difference principle between DSC and DTA?