D.T.A. - differential thermal

Figure 9. Thermal analysis of levoglucosenone samples (a) neat, (b) +5% zinc chloride, (c) +5% diammonium phosphate, and (d) +5% diphenyl phosphate (D.t.a., differential thermal analysis T.g., thermo gravimetry D.t.g., derivative of thermogravimetry)...

Keywords D.T.A.-Differential Thermal analysis magnetic susceptibility, Mossbauer... 

It has been determined by differential thermal analyses (D.T.A.) that tungsten(V) trichloride oxide decomposes above 290°C. without a sharp transition point. On cooling, a transition is observed at 210°C., the melting point of tungsten(VI) tetrachloride oxide. Therefore the decomposition of tungsten(V) trichloride oxide seems to take place by the following reaction ... 

The technique of differential thermal analysis (D.T.A.) has been applied to the study of the systems CraOa, FeaOs, and CrjOa-FejOj. 

The technique of differential thermal analysis (D.T.A.) has been extensively employed in the study of clay and other minerals for elucidating their structures for more than three decades. The application of D.T.A. as a tool has not been widely made to the systematic study of solid catalysts. Only a few references on the subject could be foimd 1-6). In the present article, differential thermal studies of a number of solid catalysts like chromic oxide gels, ferric oxide gels, and chromic oxide-ferric oxide are reported. An attempt has also been made to correlate the data with x-ray... 

The kinetics and mechanism of the transfonnation of aragonite, CaCOs, (containing 0.025 % Na) into caldte have been investigated using d.t.a., X-my diffraction, and i.r. spectrophotometry. The transformation temperature (476 C) and the energetics of the transformation (AH = 85 kcal mol and = 98 kcal mol ), as determined from the differential thermal curves, are in approximate agreement with previously reported values. A complementary... 

The form of equation (21) is interesting. It shows that the uptake curve for a system controlled by heat transfer within the adsorbent mass has an equivalent mathematical form to that of the isothermal uptake by the Fickian diffusion model for mass transfer [26]. The isothermal model hag mass diffusivity (D/R ) instead of thermal diffusivity (a/R ) in the exponential terms of equation (21). According to equation (21), uptake will be proportional to at the early stages of the process which is usually accepted as evidence of intraparticle diffusion [27]. This study shows that such behavior may also be caused by heat transfer resistance inside the adsorbent mass. Equation (22) shows that the surface temperature of the adsorbent particle will remain at T at all t and the maximum temperature rise of the adsorbent is T at the center of the particle at t = 0. The magnitude of T depends on (n -n ), q, c and (3, and can be very small in a differential test. 

However, as with the penetration theory analysis, the difference in magnitude of the mass and thermal diffusivities with cx 100 D, means that the heat transfer film is an order of magnitude thicker than the mass transfer film. This is depicted schematically in Fig. 8, The fall in temperature from T over the distance x is (if a = 100 D) about 0% of the overall interface excess temperature above the datum temperature T.. Furthermore, in considering the location of heat release oue to reaction in the mass transfer film, this is bound to be greatest closest to the interface, and this is especially the case when the reaction becomes fast. Therefore, two simplifications can be introduced as a result of this (i) the release of heat of reaction can be treated as am interfacial heat flux and (ii) the reaction can be assumed to take place at the interfacial temperature T. The differential equation for diffusion and reaction can therefore be written... 

Fig. 2 Schematic five types of SMPs depicted as a function of their thermal behavior. Plotted is the heat flow vs temperature as measured in a differential scanning calorimetry (DSC) experiment (a) Cat. A-1, chemically crosslinked tunorphous polymer network (Tirans = 7g) (b) Cat. A-11, chemically ciossfinked semicrystaUine polymer networks (Taims = 7m)> ( ) Cat. B-1, physically crosslinked thermoplastic with Tirans = T (d) Cat. B-11, physically crosslinked thermoplastic (Tams = I m) and (e) liquid crystalline polymer (Tlrans = T -n)...

A number of other processes for separating isotopes are documented. A partial list includes membrane pervaporation, thermal diffusion of liquids, mass diffusion, electrolysis and electro migration, differential precipitation, solvent extraction, biological microbial enrichment, and more. Although not discussed in this chapter, some are suitable for small-scale laboratory separations, and others have been applied on reasonably large scale to D/T, H/T, and i/ Li and presumably to other pairs of isotopes. 

MHz H-NMR spectra were recorded on a Varian XL-200 spectrometer from CDCl or C D NO solutions and with TMS as internal standard. IR spectra were recorded on a Perkin-Elmer Model 1310 infrared spectrophotometer from KBr pellets. Perkin-Elmer DSC-2 and DSC-4 Differential Scanning Calorimeters were used to determine the thermal transitions. Glass transition (Tg), melting (T ), crystallization (T ), smectic-nematic >... 

Reading, M., Price, D. M., and Orliac, H. (2001), Measurement of crystallinity in polymer using modulated temperature differential scanning calorimetry, in Material Characterization by Dynamic and Modulated Thermal Analysis Techniques, American Society for Testing and Materials, Riga, A. T. and Judovits, L. H., eds ASTM, STP 1402. 

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