Differential thermal analysis dta pptx...

Differential thermal analysis

1. DIFFERENTIAL THERMAL ANALYSIS

2. Differential Thermal Analysis Differential Thermal Analysis (DTA) is a laboratory technique used to measure the changes in heat flow of a sample as it's heated at a constant rate. It measures the difference in temperature between the sample and an inert reference material (often alumina) as they are both subjected to the same heating program. DTA can be used to investigate various thermal events occurring in a sample, such as: Phase transitions:  Melting, solidification, boiling, sublimation, etc. Chemical reactions:  Decomposition, oxidation, hydration, etc. Physical changes:  Adsorption, desorption, etc. INTRODUCTION 2

3. PRINCIPLE The basic principle involved in DTA is the temperature difference (AT) between the test sample and an inert reference sample under controlled and identical ( Abes of heating or cooling is recorded continuously as a function of temperature of time thus, the heat absorbed or emitted by a chemical system is determined. 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.) AT = - ve (for the endothermic process). In an exothermic change or process, the sample temperature is higher than that of the reference material (i.e.) AT = + 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 (such as; melting, fusion, etc.) 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. 3

4. DIFFERNTIAL THERMAL ANALYZER Physical changes usually result in Endothermic peak whereas, chemical reactions those of an oxidative nature are exothermic.

Endothermic reaction (absorption of energy) includes; vaporization, sublimation and absorption and gives downward peak.

Exothermic reaction (liberation of energy) includes; oxidation, polymerization and catalytic reaction and gives upward peak. 4

5. INSTRUMENTATION

6. INSTRUMENTATION DTA Apparatus always prefered a tubelar furnace This is constructed with an appropriate material wire or ribbon wound on a refractory tube This is fairly inexpensive Furnance Both metallic as well as nonmetallic are employed for fabrication of sample holders Metallic materials generally include stainless steel platinum and its alloys Non Metallic materials generally include glass vitreous silica sintered ammonia Sample Holder 6 It is used for amplification of signal obtained from thermocouple It gains a low by circuit DC Amplifier

7. INSTRUMENTATION In order to control temperature to three basic elements are required these are sensor control element and heater in this device if the sensor signals indicate the temperature has become greater than the set point the heater is immediately cut off Differential Temperature Detector DTA instruments typically consist of a furnace, two thermocouples, and a voltmeter. One thermocouple is placed in contact with the sample, while the other is placed in contact with an inert reference material. As the furnace heats up, the temperature of the sample and the reference material will increase. However, if the sample undergoes a phase transition, it will absorb or release heat, which will cause its temperature to deviate from that of the reference material. This difference in temperature is measured by the voltmeter and plotted as a function of time or temperature. Furance Temperature Programmer 7 In thermal analytical studies, the signal obtained from the sensor can be recorded in which the signal trace is produced on paper or film hitting stylus electric while writing or optical views There are two types of recording devices similar to T G deflections type and null point type Recorder

8. WORKING Sample and Reference: Two crucibles are placed in the furnace: one containing the sample and another containing an inert reference material (e.g., alumina). Both materials are subjected to the same controlled heating program. 2. Temperature Measurement: Thermocouples are attached to the sample and reference crucibles to measure their respective temperatures. The difference in temperature between the sample and reference (ΔT) is continuously monitored and recorded. 3. Endothermic and Exothermic Events: When an endothermic event (heat absorption) occurs in the sample (e.g., melting), its temperature lags behind the reference, resulting in a negative ΔT peak. Conversely, an exothermic event (heat release) in the sample (e.g., oxidation) causes its temperature to rise faster than the reference, leading to a positive ΔT peak. 4. DTA Curve: The ΔT is plotted against temperature or time, resulting in a DTA curve. The peaks on the curve correspond to the thermal events occurring in the sample, providing qualitative and quantitative information.

9. ADVANTAGES & LIMITATIONS Instruments can be used at very high temperature Instruments are highly sensitive Characteristic transition or reaction temperature can be accurately determined ADVANTAGES 9 LIMITATIONS ΔT Determine by dta is not so accurate (2-3) Celsius Small change in ΔT cannot be determined and qualified Due to heat variation between sample and reference makes it less sensitive

10. APPLICATIONS Qualitative and Quantitative Identification of Minerals : Detection of any minerals in a sample. Polymeric Materials: DTA useful for the characterization of polymeric materials in the light of identification of thermo physical, thermo chemical, thermo mechanical and thermo elastic changes or transitions. Measurement of Crystalline: Measurement of the mass fraction of crystalline material. Analysis of Biological Materials : DTA curves are used to date bone remains or to study archaeological materials.

DTA curves for two substances are not identical. Hence, they serve as finger prints for various substances.

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.

11. PRESENTED BY 11 Firstname Lastname Firstname Lastname Bahalen Gagrai 20BPH015 Firstname Lastname Gungan Shashwat Kerketta 20BPH017 Harsh Kumar Sinha 20BPH019

12. REFERENCE 12 A textbook of advanced Instrumentation techniques by Hitesh Vishwanat Shashare et.al Nirali publication pg no. 3.6-3.10 A textbook of Advanced instrumentation techniques by Shital .S. Patil et.al PV publication pg no. 74-82