Thermal Analysis Flashcards
Learn basic principles, TGA, DTA, DSC
Basic Principles of Thermal Analysis
Analysing change in property of analyte given a change in T. Sample is heated at a constant rate (temp progr.). Sample is usually a solid therefore changes include: melting, phase transition, sublimation and decomposition.
TGA (Definition)
Thermogravimetric Analysis is where you measure changes in mass upon heating
TGA (Diagram)
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TGA (Components)
Uses a thermobalance: Electronic microbalance, temp programming, furnace and controller.
TGA (Uses)
Ability to measure the thermal stability/composition of the analyte
TGA (Applications)
Oxidative stability and carbon black content
TGA (Pointers)
Mass loss = decomposition/sublimation of analyte.
Mass gain = oxidation
Balance/furnace in a closed system which is therefore a controlled enviornment
DTA (Defintion)
Differential Thermal Analysis is the most common TA method. Temperature of sample monitored against ref. material - both undergo same heating procedure. Sample and ref placed in low thermal conductivity holders. T increases linearly and the plot is diff in T between sample and ref. vs T of furnace
DTA (Diagram)
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DTA (Pointers)
Dehydroxylation dips and crystallisation spikes. In DTA graph, EXO = increase in difference of T, ENDO = decrease in difference of T. Area underneath curves = to enthalpy of thermal event.
DTA vs TGA
Draw the graph that is in the notes and compare
DSC (Definition)
Differential Scanning Calorimetry is when the sample and ref is always at the same temperature, this is done by using separate power supplies. The plot is given by diff in power supply vs T in furnace.
DSC (Diagram)
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DSC (Pointers)
Uses temperature programming therefore temperature increases linearly vs time
DSC (Applications)
Melting, crystallisation and glass transitions
