Thermal analysis by_menna_koriam

Thermal analysis

1. Thermal Analysis Presented by MENNA KORIAM

2. Contents Definition Methods of analysis: Thermo Gravimetric Analysis (TGA) Differential Thermal Analysis (DTA) Differential Scanning Calorimetric (DSC) Thermo Mechanical Analysis (TMA) Dynamic Mechanical Analysis Dilatometery Laser Flash Analysis Thermo-stimulated current Thermo- luminensce Evolved Gas Analysis Recently: Micro calorimetry & Nano calorimetry

3. Definition Thermal Analysis is a branch of materials science by which the physical, chemical , and mechanical properties of materials are studied as a function of temperature. This measurement provides information about physical phenomena, such as phase transitions, absorption, adsorption and desorption; as well as chemical phenomena including  thermal decomposition, and solid-gas reactions

4. Methods of Thermal Analysis According to the property measured

5. Thermo-Gravimetric Analysis (TGA)

6. (TGA) principle Upon heating a certain material, its weight increases or decreases due to certain reactions like decomposition, oxidation and dehydration. It measures the change in mass or weight in function with the temperature or time with constant heating rate or constant time. TGA is based on that the sample is continuously weighted as temperature is elevated using an instrument called “ thermo balance ”. Data is recorded in the form of curve called “ thermo gram ”. Instruments which can quantify loss of water, loss of solvent, loss of plasticizer are used and comparing weight loss of material is being followed

7. Types of TGA Dynamic (scanning mode) TGA: this type of analysis the sample is subjected to conditions of continuous increase in temperature usually linear with time. 2) Static (Isothermal ) TGA: this type of analysis the sample is maintained at a constant temperature for a period of time during which any change in weight is noted.

8. TGA Instruments Components of thermo balance: The balance (electronic micro balance) The furnace (heart) The programmer (brain) The recorder (data collector)

9. TGA Curve

10. TGA provides the following useful information: Decomposition temperatures Quantitative weight losses Compositional analysis Long term stabilities Flammability properties Rates of degradation Life time of a product Effect of reactive or corrosive atmospheres Oxidative stability of materials

11. Factors affecting TGA curve Instrumental factors: Furnace heating rate Furnace atmosphere Sample characteristics: Weight of sample Sample particle size

12. TGA Applications Materials characterization through analysis of characteristic decomposition patterns . Can be used to evaluate the  thermal stability  of a material in a desired temperature range. Can determine the inorganic or organic content in the sample.

13. Differential Thermal Analysis

14. DTA Principle Is a thermo-analytic technique in which the material under study and an inert reference non reactive material (alumina ) are made to undergo identical thermal cycles. Thermocouples measuring temperature of sample and reference material is exposed to the same heating and cooling schedule via symmetric arrangement in the same furnace. The difference in the temperature profiles of sample and reference material are recorded as the cycle proceeds.

15. DTA Apparatus 1 ) Sample holder comprising thermocouple (is a sensor used to measure temperature), sample containers and a ceramic or metallic block. 2) Furnace (must have a uniform hot zone and linear heating). 3) Temperature programmer (it’s capable of giving a wide range of heating /cooling rates: usually 1 °c/min to 50 °c/min). 4) Recording system.

16. Identical pair of cavities for the sample and reference material. Whole unit is set in an oven – control pressure. Thermocouple is placed directly in contact with the sample and another in contact with the reference. When Temperature of the block is raised, the temperature of the sample and reference also raised .

17. This differential temperature is then plotted against temperature. If temperature difference between sample and reference material is zero: This means that sample didn’t undergo any chemical or physical change. If there is temperature difference between sample & reference material: This means that there was a chemical or physical change in the sample.

18. DTA Curve

19. DTA Applications Determination of phase diagrams . Qualitative and Quantitative identification of minerals: detection of any minerals in a sample Characterization of polymeric materials in the light of identification of thermal, physical, thermo- chemical, thermo-mechanical and thermo-elastic changes or transitions. Measurement of the mass fraction of crystalline material as in semi- crystalline polymers. Polymers composition. Melting point and glass transition temperature ( Tg ). Polymer degradation at the melting point (Tm). Polymer molecular weight (low grade – low melting point). Measurement of the mass fraction of crystalline material as in semi crystalline polymers.

20. PROS AND CONS PROS: DTA instruments can be used at very high temperatures. DTA Instruments are highly sensitive. Characteristic transition or reaction temperatures can be accurately determined. CONS: Uncertainty of heat of fusion, transition, or reaction estimations is 20-50%.

21. Differential Scanning Calorimetry (DSC)

22. DSC Principle The calorimeter measures the difference in heat flow between the sample and a blank reference during a non-isothermal phenomenon, such as polymerization and the melting of metals. During a thermal event in the sample, the system will transfer heat to or from the sample pan to maintain the same temperature in reference and sample pans . Determines series of temperature transitions in materials, such as the Tg and melting temperature (Tm).  

23. The endotherm sudden increase in the number of molecular degrees of freedom at those transitions, which require energy gain from the environment . Dynamic exothermic reactions : e.g. during polymerization, the heat released can be correlated to the amount of reacted vinyl double bonds and the degree of conversion in real time → But not accurate evaluation of the chemical structure as it measures it indirectly.

24. DSC Instrument

25. Types of Disc Power compensation DSC (two separate individual heaters).

26. 2) Heat flux DSC (single heat source).

27. In a power compensating DSC, the endothermic events peak upward as the instrument must supply more power to the sample to both furnaces at the same temperature. In a heat flux DSC, these same events cause the sample to absorb heat and be cooler than the furnace, so they point down.

28. Data (DSC curve)

29. Applications of (DSC) Phase diagrams Endothermic or Exothermic reactions Melting temperature. Glass transition temperature (Tg). Percentage of crystallinity. Additives or impurities. Thermal stability. Specific heat.

30. Thermo Mechanical Analysis

31. TMA principle It is a technique to measure the deformation or the dimensional changes of the sample under non oscillating force at several frequencies over different temperature ranges is monitored against temperature or time . Applications: CTE of polymeric materials Tg of materials

32. TMA Instrument Have a quartz probe which contains a thermocouple for Temperature measurement of sample and connected linear variable differential transformer

33. TMA Probes

34. TMA curve

35. Dynamic Mechanical Analysis

36. DMA Principle A sinusoidal strain (oscillating force) is applied to the material at a given frequency, while the temperature is ramped up or down over a range and deformation is recorded. − 50 and 220° C for polymers, 25 and 600° C for glasses and ceramics 50 and 600° C for metals Sinusoidal motion is the repeated motion in which the dynamic clamp repeated the same movement over and over with maximum and minimum values of forces .

37. DMA Instrument

38. DMA Information Through DMA, some useful properties of materials can be measured, such as the viscoelasticity, dynamic elastic modulus (E’) and the glass transition temperature (Tg) in polymers , damping behavior , creep recovery behavior .

39. Glass transition temperature ( Tg ): The temperature at which the maximum in the tan delta peak is observed. It defines the point at which the material transitions from an elastic to a rubbery state .

40. Dilatometry

41. Principle Dilatometer measures change in volume or length caused by physical or chemical process. It can determine linear coefficient of expansion and contraction of the material . ex Like mercury in glass thermometer with graduated scale.

42. Dilatometer

43. Dilatometry curve

44. Laser Flash Analysis

45. Principle Its used for measuring the thermal diffusivity which is strongly temperature-dependent, at different temperatures The sample can be placed in a furnace at constant temperature.

46. LFA curve

47. Evolved Gas Analysis

48. Principle When the material sample is heated the evolved gases is detected by spectrometry and useful information can be obtained. TGA/STA-MS Mass spectrometry identifies the evolved molecules after their ionization based on the m/z ratio of the main ions and their fragments. TGA/STA-FTIR Chemical functions of the evolved molecules are identified according to their specific absorption of IR light wavelengths.

49. EGA Curve

50. Thermally Stimulated Current

51. Principle Is An Experimental Technique Which Is Used To Study Energy Levels In Semi-conductors Or Insulators. By Measuring Change In The Electric Current With Changing Of Temperature. It Provides Additional Information About Molecular Mobility In The Solid State, And As A Result Characterise Phase Transitions That Are Related To Thermal Transitions In The Crystalline (Polymorphic) And Amorphous Phases.

52. TSC CURVE

53. Thermo-luminescence

54. Principle When a radiation is incident on a material, some of its energy may be absorbed and re-emitted as light of longer wavelength. Its a form of luminance that is exhibited by certain crystalline materials when previously absorbed energy from ionizing radiation (pre excited) and re emit it upon heating as a light. Using a light sensitive detector the data can be recorded . It is mainly used in archaeology dating.

55. TL curve

56. Micro calorimetry - Nano calorimetry

57. Principle: Micro thermal analysis is a technique which combines the thermal analysis principles of differential scanning calorimetry (DSC) with high spatial resolution of scanning probe microscopy. real-time monitoring and dynamic analysis of chemical, physical and biological processes. Over a period of hours or days. determines the onset, rate, extent and energetic of such processes for specimens in small ampoules (e.g. 3–20 ml) at a constant set temperature (c. 15 °C–150 °C). Nano thermal analysis which uses micro fabricated self-heating silicon cantilevers to probe thermo mechanical properties of materials with sub-100 nm spatial resolution

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