Thermal characterization techniques thermogravimetric analysis

Thermogravimetric analysis (TGA) is a successful and widely employed technique of measuring the change of weight of a sample as a function of the temperature whereas IR spectroscopy has been successfully employed to identify gaseous samples. Recent publications (Wieboldt et al. (1988) Belz (1989) demonstrate that a combination of these two techniques allows complete characterization of materials in terms of thermal stability and decomposition mechanisms. 

Thermal Analyses. Thermal techniques such as differential thermal analysis, thermal gravimetric analysis, and derivative thermogravimetric analysis have been successfully applied to characterizing various minerals in coal (58). The methods are based on measurements of weight loss or heat transfer during phase changes at temperatures from ambient to over 1000° C. 

A combination of techniques, such as powder X-ray diffraction (XRD) [56, 58], thermogravimetric analysis (TGA) [57], differential thermal analysis (DTA) [57], X-ray photoelectron spectroscopy (XPS) [56, 58], scanning electron microscopy (SEM) [26, 57], Fourier transform infrared (FT-IR) spectroscopy [57, 58] and BET N2 adsorption measurements [67], was used for structural characterization of the enzyme-clay conjugates. 

In addition, there are some other characterization techniques that can be used to examine the carbon-Ti02 composites, including Raman spectroscopy [40,123], atomic force microscopy (AFM) [106,123], thermogravimetric and differential thermal analysis (TGA-DTA) [26,125], determination of pHpzc [19,29], and electron paramagnetic resonance (EPR) [126,127],... 

While methods for studying these and other types of changes in the sample have become widely used, the most widely used methods are thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). As a group, thermal methods of analysis now constitute the most widely used experimental techniques in the chemical industry. A major reason for this widespread use is that determination of bulk properties, thermal stabdity, and characterization of materials are as important in industrial appHcations as are the determination of molecular properties. 

SSNMR spectroscopy. However, FTIR and Raman spectroscopy, thermal microscopy, variable-temperature x-ray diffractometry (VTXRD), and DSC may also be used to identify polymorphs. Solvates may be similarly characterized by the techniques mentioned above. In addition, the stoichiometric number of the solvent molecules in the crystal lattice of solvates may be determined by thermogravimetric analysis (TGA), gas chromatography, or, in the case of a hydrate, by Karl Fiseher titrimetry [37]. 

Thermogravimetrical analysis (TGA) This technique is widely employed and it measures the amount and rate of change in the weight of a material as a function of temperature under a controlled atmosphere. The measurements are used primarily to evaluate the thermal stability. The technique can characterize materials that exhibit weight loss or gain dne to decomposition, oxidation, or dehydration. As an example, Zhang et al." evaluated the step thermal degradation and the thermal reliability of a silica/n-octadecane MPCM. 

The technique can also be used for studying the kinetics of chemical reactions, e.g., oxidation and decomposition. The conversion of a measured heat of fusion can be converted to a % crystallinity provided, of course, the heat of fusion for the 100% crystalline polymer is known. An example of a thermogram is shown in Figure 1. Refer to Thermal Analysis and Thermogravimetric Analysis. (Source Cheremisinoff, N.P. Polymer Characterization Laboratory Techniques and Analysis Noyes Publishers, New Jersey, 1996). 

Thermal analysis is well suited for characterizing and identifying plastics, as their properties are temperature dependent. It involves methods in which the substance is subjected to a controlled temperature program and the changes in the physical and chemical properties are measured as a function of temperature or time. The ambient atmosphere also influences the properties of plastic. Thermal analysis comprises traditional techniques differential scanning calorimetry (DSC), differential thermal analysis, thermogravimetric analysis, thermomechanical analysis, and more recent methods pressure differential scanning calorimetry, dynamic mechanical analysis, and differential photocalorimetry. 

Thermogravimetric analysis (TGA) is one of the most commonly used techniques to study the primary reactions of the decomposition of polymers and other materials. TGA is also useful for the characterization and evaluation of polymer thermal stability. Although synthetic mbber nano composites have excellent mechanical properties, these properties may interfere with its low thermal stability. This may cause the polymer chain to be more susceptible to degradation. Degradation usually starts from a head-to-head stmcture, a site of unsaturation or a tertiary carbon atom [77]. 

Adsorbent materials have been characterized and tested using a range of techniques. Characterisation of materials has focused on deteiming the physical and chemical properties of the sold sorbent materials. This has heen conducted using a range of techniques, for example, elemental analysis, power x-ray diffraction (XRD), diffuse reflectance infrared Fourier transform spectra (DRIFTS), textural properties have been determined by BET N2 adsorption analysis. Thermogravimetric analysis (TGA) has been used to determine the thermal stability of the materials as well as measure CO2 adsorption capacity and cyclic capacity [14]. 

Thermal analysis A group of analytical techniques used to characterize solid materials. Most commonly used thermal techniques include differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), hot-stage microscopy (HSM), and differential thermal analysis (DTA). 

Thermogravimetric analysis enables one to continuously monitor the mass of a sample as a function of temperature and/or time. Unfortunately, the instrument cannot identify the volatile products that are evolving as temperature is increased unless it is coupled to another analytical tool such as a mass spectrometer (MS) or Fourier transform infrared spectrometer (FTIR), as discussed in Section 3.2.5. For standalone TGA it is important to gather as much information as possible about a sample from prior work, from the suppher, or from the open literature. In some instances, a more complete characterization of a sample may be possible using complementary experiments, including other thermal or analytical techniques. 

Thermogravimetric analysis is one of the thermal analysis techniques used to characterize a variety of polymers and provides complementary and supplementary characterization information to DSC technique. TGA measures the amount and rate (velocity) of change in the mass of a sample as a function of temperature or time in a controlled... 

An understanding of the complex physico-chemical phenomena associated with the formation and behavior of cementitious compounds is facilitated through the application of many different types of investigative methods. Techniques such as NMR, XRD, neutron activation analysis, atomic absorption spectroscopy, IR/UV spectroscopy, electron microscopy, surface area techniques, pore characterization, zeta potential, vis-cometry, thermal analysis, etc., have been used with some success. Of the thermal analysis techniques the Differential Thermal Analysis (DTA), Thermogravimetric Analysis (TG), Differential Scanning Calorimetry (DSC), and Conduction Calorimetric methods are more popularly used than others. They are more adaptable, easier to use, and yield important results in a short span of time. In this chapter the application of these techniques will be highlighted and some of the work reported utilizing other related methods will also be mentioned with typical examples. 

Among the various methods used for studying thermal and thermo-oxidative degradation of PES, thermogravimetric analysis (TGA) and pyrolysis gas chromatography-mass spectroscopy (PGC-MS) have been used most frequently. These instruments enable comparisons of the relative thermal stability and thermal decomposition temperature, and give information about the degradation mechanism [9,24]. TGA also is an excellent technique for product characterization and quality control. 

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