Thermogravimetric curve

Fig. 12. Portion of dynamic thermogravimetric curves between 130 and 400°C, with temperature rising 6°C per minute for wood, lignin, and a-ceUulose.

Phase relationships ia the system K O—B2O2—H2O have been described and a portion of the phase diagram is given ia Figure 8. The tetrahydrate, which can be dried at 65°C without loss of water of crystallisation, begias to dehydrate between 85 and 111°C, depending on the partial pressure of water vapor ia the atmosphere. This conversion is reversible and has a heat of dehydration of 86.6 kj/mol (20.7 kcal/mol) of H2O. Thermogravimetric curves iadicate that two moles of water are lost between 112 and 140°C, one more between 200 and 230°C and the last between 250 and 290°C (121). 

Figure 7 Thermogravimetric and differential thermogravimetric curves of NBR and HNBR. Source Ref. 134.

A typical thermogravimetric curve, for copper sulphate pentahydrate CuS04,5H20, is given in Fig. 11.2. 

The heating rate has only a small effect when a fast reversible reaction is considered. The points of inflexion B and C obtained on the thermogravimetric curve for copper sulphate pentahydrate (Fig. 11.2) may be resolved into a plateau if a slower heating rate is used. Hence the detection of intermediate compounds by thermogravimetry is very dependent upon the heating rate employed. 

Crucible geometry. The geometry of the crucible can alter the slope of the thermogravimetric curve. Generally, a flat, plate-shaped crucible is preferred to a high-form cone shape because the diffusion of any evolved gases is easier with the former type. 

Figure 6. Thermogravimetric curves for I l08,Li0 ]5NiOi in air. The heating and cooling rates were 5 °Cmin 1. The sample was prepared by electrochemical oxidation of LiNi02 without addition of conductive binder to 4.8V using an Li/LiNiO, cell, washed with DME and THF, and dried under vacuum at room temperature.

The area under a thermogravimetric curve can also be used [535,544], since... 

Decomposition of the rare earth nitrates proceeded [821] through the intermediate formation of oxysalts of the form MON03 and E values were low Nd(N03)3, 33 kJ mole 1, 663-703 K Dy(N03)3, 23 kJ mole 1, 583—633 K Yb(N03)3, 46 kJ mole 1, 563—598 K. Thermogravimetric curves showed that the formation of anhydrous salts was possible, in contrast to observations by Wendlandt and Bear [826]. In a similar study [827] of the reaction of Pr(N03)3 at 558—758 K, the intermediate formation of a nitrite is postulated during decomposition to a non-stoichiometric residual oxide, Pr0li83 (the actual composition depends on temperature). 

Figure 2. Thermogravimetric and differential thermogravimetric curves (TG and DTG) of melamine, heating rate 10 C/min nitrogen, 60 cm3/min.

A sample of white plastic tape was placed in a thermobalance and heated at 10°C min-1 in nitrogen to give the thermogravimetric curve below. By careful measurement identify... 

Part of the difficulty in interpretation of the PTA XPS data is uncertainty in the extent of hydration of some of the samples. The commercial samples are typically marked nl FO." making no commitment as to its true water content. Consequently, it was necessary to investigate water content on our own. In Figure 3, the thermogravimetric curve associated with Sigma PTA is shown. Two endothermic transitions are shown at 45 and 160 °C. The mass loss during the scan out to 210 C was 7% of the original amount. This corresponds to -13 waters of hydration. 

Figure 3. Thermogravimetric curves for hydrated phosphotungstic acid.

Figure 20.1 show as an example the thermogravimetric crave (TG) obtained for the natural ilhte. A continuous weight loss can be seen between 150°C and 980°C the differential thermogravimetric curve (DTG) showing two endothermic effects. The first one is centered at 150°C which corresponds to loss of ilhte water. The second one is centered about 580°C and is mainly associated to the loss of stractural water. 

Typical thermogravimetric curves for black powder and its ingredients have been obtained as shown in Figure 2.7, and the main events depicted by the curves can be presented as in Table 2.1. 

Figure 2.7 Thermogravimetric curves for black powder and its ingredients.

Figure 1 Thermogravimetric curves for the unrefined and milled kaolins...

Figure 11 Thermogravimetric curves for Pb2Sr2YCu308 00 at 2°CminT1 in various atmospheres (82).

Amount of deposited material - The thermogravimetric curves of uncoated sulfur and sulfur encapsulated with different plasma polymers are given in Fig. 12. The weight losses in the TGA curves of the different encapsulated sulfur powders are all shifted to a higher temperature compared to uncoated sulfur. The... 

Figure 27-3 Thermogravimetric curve for calcium salicylate. [From G. Liptay ed., Atlas of Thermoanalytical Curves (London Heyden and Son, 1976).]...

Fig. 12. Thermogravimetric curves of various homopolyisocyanides polymers of / (ot-carboxymethyl)ethyl, 2 n-butyl, 3 sec-butyl, 4 a-phenylethyl, 5 cyclohexyl, 6 isopropyl, 7 jS-phenylethyl, 8 and 9 rr-toluyl isocyanides (5)...

A good-quality CeMCM-41 material with Si/Ce=50 was synthesized by hydrothermal method. For the purpose of comparison a pure siliceous MCM-41 was prepared using the same composition without cerium. Thermogravimetric curves for the synthesized uncalcined samples exhibit shape characteristic for the MCM-41-type materials. The specific surface area of CeMCM-41 evaluated from nitrogen adsorption was equal to 850 m2/g, whereas the pore width and mesopore volume of this material were equal to 3.8 nm and 0.8 cm3/g, respectively. In contrast to the pure silica MCM-41, the CeMCM-41 material exhibits medium and strong acid sites as revealed by thermogravimetric studies of n-butylamine thermodesorption. 

The evaluation of the acid properties of calcined materials was based on the assumption that n-butylamine molecules interact with all acid sites, and the total acidity of the sample studied can be determined from the maximum amount adsorbed. Shown in Fig. 2 are thermogravimetric curves for n-butylamine thermodesorption, which were used to evaluate the amount of medium and strong acid sites for both samples. Thermodesorption of n-butylamine from CeMCM-41 exhibits three distinct ranges (i) desorption of physically adsorbed amine bellow 230 °C (ii) desorption of n-butylamine from medium acid sites at 230 - 410 °C (0.25 mmol/g), and (iii) its desorption from strong acid sites at 410 - 590 °C (0.21 mmol/g). However, only one weight loss was observed for pure silica MCM-41 due to thermodesorption of physically adsorbed amine, indicating negligible acidity of this material. 

The thermogravimetric curves for cimetidine and cimetidine hydrochloride are shown in Figure 13 and 14, respectively. The curves show that the compounds are stable up to a temperature of approximately 175-185°C and then decompose. The thermograms were obtained at a heating rate of 10°C/minute. 

The structure proposed by Bradley (1940) has three forms of water a zeolitic water, bound water (at the edges of the octahedral sheet), and structural hydroxyls. Using thermogravimetric curves, Caillere and Henin (1961a) attempted to measure the amount of these three types of water for several attapulgites (Table LV). The amount of bound water and hydroxyls differs considerably from that calculated on the basis of the ideal structure (column 5) and suggests there are more structural hydroxyls than proposed for the ideal structure. 

The thermogravimetric curves obtained indicate that the modified and un-modified resins begin to decompose at 300°C. 

Fig. 2. Thermogravimetric curves obtained for purified and nonpurified EPS produced by Rhizobium sp. EQ1 (experiment 1).

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