DIFFRENTIAL THERMAL ANALYSIS POWERPOINT PRESENTATION

Differential Thermal Analysis (DTA) is a thermal analysis technique used to investigate phase transitions, chemical reactions, and thermal stability of materials by measuring temperature differences between a sample and a reference material as they undergo controlled heating or cooling.
Key points about Differential Thermal Analysis include:

Principle: DTA works on the principle that when a sample undergoes a physical or chemical change, such as melting, crystallization, decomposition, or reaction with gases, it either absorbs or releases heat. This heat flow causes a temperature difference between the sample and a reference material (often an inert substance).

Instrumentation: DTA instruments consist of a sample holder (often a crucible), a reference holder, and a furnace capable of controlled heating or cooling rates. Both sample and reference are subjected to the same temperature program, and the temperature difference (∆T) between them is continuously recorded.

Output: The DTA curve plots the temperature difference (∆T) against temperature, showing peaks and troughs corresponding to exothermic (heat-releasing) and endothermic (heat-absorbing) processes in the sample.
Applications:

Phase Transitions: Determination of melting points, crystallization temperatures, and glass transition temperatures.
Reaction Kinetics: Studying chemical reactions by observing the heat changes associated with them.
Thermal Stability: Assessing the stability of materials under different thermal conditions.
Quality Control: Used in industries such as pharmaceuticals, polymers, and ceramics to ensure product consistency and quality.
Advantages: DTA provides quantitative information about the heat flow associated with physical and chemical changes in materials. It is sensitive to small changes in heat capacity and can distinguish between overlapping thermal events.

Limitations: DTA requires a reference material and cannot directly measure heat capacity or enthalpy changes. Interpretation of DTA curves often requires complementary techniques for full understanding

1. CENTRAL UNIVERSITY OF RAJASTHAN TOPIC- DIFFRENTIAL THERMAL ANALYSIS AAKRITI TRIPATHI (PHARMACEUTICAL CHEMISTRY)

2. THERMAL ANALYSIS TECHNIQUES A group of techniques in which a physical property is measured as a function of temperature The sample is subjected to a predefined heating or cooling program

3. TYPES OF THERMAL ANALYSIS TG (Thermo-gravimetry) analysis: Weight DTA( Differential thermal analysis): Temperature DSC(Differential scanning Calorimetry): Temperature

4. DIFFRENTIAL THERMAL ANALYSIS LE- CHATELIAR studied clay and minerals by an examination of temperature-time curve. Later ROBERT AUSTEN improved technique by introducing thermocouple. DEFINATION- DTA is a technique in which the temperature between sample and thermally inert reference substance is continuously recorded as a function of temperature/time. In DTA both test sample and an inert reference material (ALUMINA)- controlled heating or cooling programming. If zero temperature difference between sample and reference material- sample does not undergo any chemical or physical change. If any reaction take place temperature difference (delta temperature) will occur between sample and reference material.

5. DTA PRINCIPLE The basic principle in DTA is the temperature difference ( DELTA TEMPERATURE ) 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. If any reaction take 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 a sample is lower than that of the reference material (i.e.) DELTA TEMPERATURE is –VE ( for endothermic process). In an exothermic change or process the sample temperature is higher than that of reference material that is DELTA TEMPERATURE=+VE (Exothermic process).

6. DTA INSTRUMENTATION

7. INSTRUMENTATION FURANCE SAMPLE HOLDER DC AMPLIFIER DIFFRENTIAL TEMPERATURE DETECTOR FURANCE TEMPERATURE PROGRAMMER RECORDER CONTROL EQUIPMENT

8. 1-FURANCE In DTA apparatus, one always prefer a tubular furance . This is constructed with an appropriate material (WIRE or RIBBON) wound on a refractory tube. These are fairly inexpensive. Generally choice of the resistance material as well that of refractory is decided from the internal maximum temperature of operation of and gaseous environment.

9. 2- SAMPLE-HOLDER Both metallic as well as non metallic are employed for the fabrication of sample holders. Metallic material include NICKEL,STAINLESS STEEL,PLATINIUM and its ALLOY. Non metallic material generally include GLASS,VITREOUS SILICA OR SINTERED ALUMINA. Metallic holder give rise to sharper exotherms and flat endotherms. on the other hand non metallic holder yield relatively sharper endotherms and flat exothermal.

10. 3- DC AMPLIFIER It is used for amplification of signal obtained from (T)c. It is gain a low noise circuit.

11. 4- DIFFRENTIAL TEMPERATURE DETECTOR In order to control temperature, the basic elements is required- these are sensor,control element and heater. ON-OFF CONTROL- in this device,if the sensor signal indicate the temperature has become greater than the set point,the heater is immediately cutoff not used in DTA. PROPORTIONAL CONTROL- in on/off controllers the occur fluctuations of temperature around the set value. These can be minimized if the heat input to the system is progressively reducded as the temperature approaches the desired value. Such a controller anticipate the approach to the set value is known as PROPORTIONAL CONTROLLER.

12. 5- FURANCE TEMPERATURE PROGRAMMER/SENSOR It provides smooth heating or cooling at a linear rate by changing the voltage through heating component. Modern DTA instruments incorporates electronic temp controller in which the signal from thermocouple in furnace is compared electically against reference potential which can be programmed to corresponds to a variety of heating modes and heating rates.

13. 6-RECORDER In thermos analytical studies ,the the signal obtained from the sensors can be recorded in which the signals traces is produced or film ,heating stylus ,electrical writing or optical beam. There are two types of recording device similar to TG DEFLECTION TYPE NULL-POINT TYPE

14. 7-CONTROL EQUIPMENT For some types of sample the atmosphere must be controlled to suppress an undesirable reaction such as oxidation by flowing an inert gas.

15. ADVANTAGES OF DTA Instruments can be used at high temperatures. Instruments are highly sensitive. Characteristic transition or reaction temperature can be accurately determined .

16. DISADVANTAGES OF DTA Delta temperature determined by DTA is not so accurate. Small change in delta temperature cannot be determined and quantified. Due to heat variation between sample and reference make it less sensitive.

17. APPLICATIONS OF DTA Use for the study of characteristics of polymeric materials. Use for the testing of purity of drug samples and also for test quality control of number of substance like cement ,soil, glass. Determination of heat reaction specific heat and energy change during melting. Trend in ligand stability gives the information about ligands in coordination sphere. DTA curve for two substance are not identical hence they serves as finger print for various substance.

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