Differential Thermal Analysis.pptx

Presentation describes principle, instrumentation, advantages, disadvantages, working as well as factors affecting on the differential thermal analysis.

1. DIFFERENTIAL THERMAL ANALYSIS Presented by - Miss. Rubina U. Watangi. M. Pharm Department - Pharmacology

2. CONTENTS Principle Instrumentation Factors affecting on DTA Advantages Disadvantages References Miss. Rubina U. Watangi. (M. Pharm) 2

3. Differential thermal analysis (DTA) was constructed soon after the development of the thermocouple ( Le Chatelier) Miss. Rubina U. Watangi. (M. Pharm) 3

4. Differential thermal analysis In Differential Thermal Analysis, the temperature difference that develops between a sample and an in reference material is measured, when both are subjected to identical heat treatments Miss. Rubina U. Watangi. (M. Pharm) 4

5. This is a comparison method In the thermogram the change in temperature and time or temperature of furnance is plotted Any transformation – change in specific heat or an enthalpy of transition can be detected by DTA In DTA both test sample and an inert reference material ( alumina) are under controlled heating or cooling programming Miss. Rubina U. Watangi. (M. Pharm) 5

6. If zero temperature difference between sample and reference material – sample does not undergo any chemical or physical change. If any reaction takes place temperature difference (∆T) will occur between sample and reference material Miss. Rubina U. Watangi. (M. Pharm) 6

7. Sharp Endothermic - changes in crystallinity or fusion Broad Endothermic – dehydration reaction Physical changes usually result in endothermic curves Chemical reactions are exothermic Miss. Rubina U. Watangi. (M. Pharm) 7

8. The temperature should be the same until thermal event occurs, such as melting, decomposition or change in the crystal structure. In an endothermic event takes place within the sample, the temperature of the sample will lag behind that of the reference and a minimum will be observed on the curve. On the contrary, if an exothermal event takes place, then the temperature of the sample will exceed that of the reference and a maximum will be observed on the curve. The area under the endotherm or exotherm is related to the enthalpy of the thermal event, ΔH. Miss. Rubina U. Watangi. (M. Pharm) 8

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10. What kind of reference materials is used in DTA ? The ideal reference material is a substance with the same thermal mass as the sample, but with no thermal events over the temperature range of interest. In DTA is usually used alumina (Al2O3), carborundum (SiC) or magnesium oxide(MgO) powder as the reference material for the analysis of inorganic compounds Miss. Rubina U. Watangi. (M. Pharm) 10

11. ISTRUMENTATION The key features of a differential thermal analysis are as follows 1. Sample holder comprising thermocouples , sample containers and a ceramic or metallic block. 2. Furnace. 3. Temperature programmer 4. Recording system Miss. Rubina U. Watangi. (M. Pharm) 11

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13. SAMPLE HOLDER Both metallic and non-metallic materials are employed for fabrication of sample holder metallic holders give rise to sharp exothermic peak and flat endothermic peak Non-metallic holders gives flat exothermic and sharp endothermic peak Miss. Rubina U. Watangi. (M. Pharm) 13

14. FURNANCE Always prefers a tubular furnace This is constructed with an appropriate material ( wire or ribbon ) wound on a refractory tube Such furnaces possesses the desired characteristics for good temperature regulation and programming These are fairly inexpensive Miss. Rubina U. Watangi. (M. Pharm) 14

15. It is operating at temperature 170-2008 degree Celsius and temperature varies from 0.1-30 degree Celsius per min Heating is done with heating coil or IR radiation Consist of two wells of equal size for reference and sample Miss. Rubina U. Watangi. (M. Pharm) 15

16. TEMPERATURE CONTROLLER To control temperature three basic elements are required Sensor Control element Heater On off control In this device , if the sensor signal indicates the temperature has become greater than set point , the heater is immediately cut off Miss. Rubina U. Watangi. (M. Pharm) 16

17. Proportional control In on off controllers there occurs fluctuations of temperature around set value This can be minimized if the heat input to the system is progressively reduced as temperature approaches desired value Miss. Rubina U. Watangi. (M. Pharm) 17

18. RECORDER The signal obtained from the sensors can be recorded Photographic light beam , Galvanometer Electronic potentiometer A two point recorder records temperature difference and temperature of reference material as a function of time and temperature Miss. Rubina U. Watangi. (M. Pharm) 18

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21. Advantages Instrument can be used at very high temperature It is highly sensitive Characteristic transition or reaction temperatures can be accurately determined Disadvantage Uncertainty of heat of fusion ,transition , or reaction estimation is 20-50% Miss. Rubina U. Watangi. (M. Pharm) 21

22. REFERENCES https://www.hitachi-hightech.com/global/products/science/tech/ana/thermal/descriptions/dta.html Miss. Rubina U. Watangi. (M. Pharm) 22

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