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Contents: ° Introduction ° History ° Principle * Instrumentation * Working * Thermogram * Advantages ¢ Limitations * Applications * Derivative differential thermal analysis Differential Thermal Analysis (DTA): History of Differential Thermal Analysis Roots of DSC: heating curves and twin calorimetry: Imiddle 19‘ century continuous temperature measurement and recording: LeChatelier 1887 Kurnakov DTA: lime — AT recording: 1. photographic T-AT Roberts-Austen 1899 recording classical DTA setup 2. reference ice bath Kurnakov and Saladin 1904 3. DTA furnace Principle: ¢ A Technique in which the temperature difference between a substance and reference material is measured as a function of temperature, while the substance and reference are subjected to a controlled temperature programme. * The Difference in temperature is called as Differential temp(At) is plotted against temp. or a function of time. Cooling jacket Instrumentation: 1. FURNACE 2. SAMPLE HOLDER 3. DC AMPLIFIER 4. DIFFERENTIAL TEMPERATURE DETECTOR 5. FURNACE TEMPERATURE PROGRAMMER 6 7 . RECORDER . CONTROL EQUIPMENT 2.Sample holders: * Both metallic as well as non-metallic are employed for the fabrication of sample holders. * Metallic materials generally include nickel , stainless steel , platinum and its alloys. * Non-metallic material generally includes glass , vitreous silica or sintered alumina. * Metallic holders give rise to sharp exotherms and flat endotherms . On the other hand non-metallic holders yield relatively sharp endotherms and flat exotherms. 10 3.DC Amplifier: * It is used for amplification of signals obtained from (T)ec. * It is gain and low noise circuit. 11 4.Differential temperature detector: * PROPORTIONAL CONTROL- In on-off controllers there occurs fluctuations of temperature around the set value. These can be minimized if the heat input to the system is temperature a ¢ Such a contro progressively reduced as the pproaches the desired value . ler that anticipates the approach to the set value is known as proportional controller. 13 5.Furnace temperature programmer/Sensors: * It provides smooth heating or cooling at a linear rate by changing the voltage through heating component. Modern DTA instruments incorporate electronic temp controller in which the signal from thermocouple in furnace is compared electically against ref.potential which can be programmed to corresponds to a variety of heating modes & heating rates. 14 7.Control Equipment: * For some type of samples the atmosphere must be controlled to suppress and undesirable reaction such as oxidation by flowing an inert gas. 16 Working of DTA: n is C n The sample irectly und This proced and reference standard are placed in the furnace on flat , highly thermally conductive pans and he thermocouples are physically attached to the pans er the sample . ure avoids or reduces any thermal lag resulting from the time required for the heat to transfer to t the thermocouples. he sample and reference materials then to 17 Working of DTA: differential temperature Tp Ts ; Tr - _| ‘ reference —_——— temperature, Tr \ . \ v) (¥)) es panies J (inert) ) rf — ~~ furnace and block 19 Thermogram: * A differential thermogram consists of a record of the difference in sample and reference temperature (AT) plotted as a function of time t , sample temperature (Ts) , reference temperature (Tr) or furnace temperature (Tf). 20 
