Thermal techniques application

Type of technology Thermal technique Application Type of Biomass / Waste... 

Some scientists describe DSC techniques as a subset of DTA. DTA can be considered a more global term, covering all differential thermal techniques, while DSC is a DTA technique that gives calorimetric (heat transfer) information. This is the reason that DSC has calorimetry as part of its name. Most thermal analysis work is DSC, and Sections 15.3.3 and 15.3.4 provide information about the instrumentation and applications of this technique. 

Thermal Transition Applicable Thermal Analytical Technique... 

Preformed sticks or tubes of solid epoxy may also be applied much as a solder is.6 To apply, the area to be bonded is heated until sufficiently hot to cause the stick solder to flow when drawn across the surface. After application, the adhesive is cured by conventional thermal techniques. If two substrates are to be bonded, both must be preheated prior to... 

Ollivon, M., Loisel, C., Lopez, C., Lesieur, P., Artzner, F., Keller, G. 2001. Simultaneous examination of structural and thermal behaviours of fats by coupled X-ray diffraction and differential scanning calorimetry techniques application to cocoa butter polymorphism. In, Crystallization and Solidification Properties of Lipids (N. Widlak, R. Hartel, S. Narine, eds.), pp. 34-41, AOCS Press, Champaign, IL. 

Another important source of perturbation of a chemical system is light, such as a laser flash. The irradiation can cause a rapid photochemical reaction, such as photohomolysis of a single bond. The reverse, thermal reaction will then regenerate the reactant(s). This method differs from the other relaxation methods mentioned above in that the relaxation process brings the system back to its initial state rather than to a new equilibrium. The amount of energy deposited with a flash is often large enough to temporarily perturb even an irreversible thermal system, which makes this technique applicable to both reversible and irreversible reactions. Flash photo-lytic methods are a subject of a later chapter and will not be dealt with here. 

APPLICATION OF THERMAL TECHNIQUES FOR THE DRUG PRODUCT PREFORMULATION, PROCESSING, AND AGING... 

Thermal FFF (thermal field-flow fractionation) is an elution-type separation technique applicable to the characterization of various synthetic organic polymers with molecular weights higher than about 10 [1], In thermal FFF, a dilute solution of polymer sample is injected into a thin ribbon-shaped flow channel across which an external field (in the form of a temperature gradient) is applied. Under the influence of the temperature gradient, different components of the sample are carried down the channel at different velocities, leading to the elution of different components at different times and separation is achieved. 

Simultaneous Examination of Structural and Thermal Behaviors of Fats by Coupled X-ray Diffraction and Differential Scanning Calorimetry Techniques Application to Cocoa Butter Polymorphism... 

These expensive carbon-carbon fiber composites are used for thermally demanding applications like aircraft and racecar brakes. Typically, both pads and rotors are made of carbon composite. These friction couples have a relatively low friction level, which is insensitive to the high temperatures experienced in operation. Friction couple components are expensive to manufacture as they are fabricated by time-consuming chemical vapor deposition techniques. Carbon-carbon systems suffer from low cold friction and are best suited for hot operation. 

Applications of TMA are in many ways the simplest of the thermal techniques. Only the change in the size or position of a sample is being measured. However, they are also incredibly important in supplying information needed to design and process everything from chips to food products to engines. A sample of ASTM methods for TMA is shown in Table 1. Because of the sensitivity of modern TMA, it is often used to measure Tg s that are difficult to obtain by DSC, for example, those of highly cross-linked thermosets. 

Since each mineral undergoes certain phase changes at a definite temperature (or range of temperatures), it is possible to detect specific minerals in mixtures. A monograph detailing application of various thermal techniques to coal, coal-related materials, and other substances has been prepared by Earnest (59). 

To perform mass spectrometry, one must make ions from neutral molecules. Ionization methods have advanced from the classic electron ionization (El), through chemical ionization, field desorption, fast atom bombardment (FAB), h 62 thermospray to the atmospheric pressure ionization (API) techniques currently favored. El is classic, but its is restricted to thermally stable, volatilizable compounds. Field desorption was always a specialized niche technique applicable to some larger compounds. Fast atom bombardment enjoyed a meteoric rise in use when it was first reported in 1981 but it has all but disappeared now, being replaced by the API tech-... 

Techniques that apply to in situ analysis of the dosage form, its precursor granulations, or powders are discussed. Applications of solid-state NMR, FTIR microspectroscopy, visual and scanning electron microscopy, Raman spectroscopy, NIR analysis, thermal techniques, mass spectrometry, and imaging techniques are presented. 

The increased application of modern thermal techniques and companion techniques must occur if the thermal characterization of organometallic and inorganic polymers is to progress. 

The application of thermogravimetry to a particular problem is possible if a mass-change is observed on the application of heat. If no mass-change is observed, then other thermal techniques such as DTA, DSC, TMA, and so on, may have to be employed. If the mass-change is very small (< 1%), then perhaps other techniques such as evolved-gas analysis (EGA) may be more useful. Mass-changes (generally mass-losses) which can be detected by TG techniques are summarized in Figure 4.1. 

Nordal and Kanstad have derived absorption spectra by photothermal radiometry (PTR), a technique whereby the absorption of amplitude-modulated light causes pulsating surface temperatures and hence a pulsed thermal reradiation. Applications of this technique to biological materials such as blood and leaves have been demonstrated. 

The application of thermal techniques to study the nature of the volatile thermal fragments from petroleum asphaltenes has produced some interesting data relating to the polynuclear aromatic systems (18-22). These thermal techniques have produced strong evidence for the presence of small polynuclear aromatic systems (one to four rings) (14), and application of the techniques to the various functional fractions has confirmed the general, but unequal, distribution of these systems throughout asphaltenes. 

M. Reading, Controlled Rate Thermal Analysis and Beyond , in Thermal Analysis - Techniques Applications, ed. E. L. Charsley and S. B. Warrington, The Royal Society of Chemistry, Cambridge, 1992, p. 127. 

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