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Abstract
The thermal behavior of rutin extracted from the buds of Sophora japonica L. by different methods and conditions have been investigated using TG and DTG. The results showed that every sample had different mass loss, curve shape, and peak location related to varied extraction technology. The TG-DTG characteristics of the rutin sample extracted by alkali-dissolution and acid-sedimentation with the solution adjusted to pH 9 and simply borax as stabilizer were highly similar to that of standard rutin, with the maximal purity determined by spectrophotometry. Therefore, the TG-DTG patterns could be served to characterize rutin extracted from the buds of Sophora japonica L.
the simultaneous TG/DTG–DTA technique in inert and oxidative atmospheres. Simultaneous TG-DTA coupled with MS was used for the analysis of the gaseous decomposition products in argon atmosphere, while Powder XRD was used for the verification of the
Thermal studies of isoxazolylnaphthoquinones by simultaneous DTA-TG-DTG
II. Solid-state studies on a ketoenol system
The tautomeric binary system consisting of N-(3,4-dimethyl-5-isoxazolyl)-4-amino-1,2-naphthoquinone (1),m.p. 156‡C, and 2-hydroxy-N-(3,4-dimethyl-5-isoxazolyl)-1,4-naphthoquinon-4-imine (2),m.p. 218‡C, was studied by DTA-TG-DTG and IR spectrometry. Crystals of 1, left in contact with their mother liquor during 4 months, exhibited thermal behaviour similar to that of physical mixtures of 1 and 2, which reveal the presence of a eutectic at about 146‡C.
Abstract
Dental composites can be improved by heat treatment, as a possible way to increase mechanical properties due to additional cure (post-cure). Direct dental composites are essentially similar to the indirect ones, supposing they have the same indication. Therefore, to establish a heat treatment protocol for direct composites, using as indirect (photoactivated by continuous and pulse-delay techniques), a characterization (TG/DTG and DSC) is necessary to determine parameters, such as mass loss by thermal decomposition, heat of reaction and glass transition temperature (T g). By the results of this study, a heat treatment could be carried out above 160 °C (above T g, and even higher than the endset exothermic event) and under 180 °C (temperature of significant initial mass loss).
.0 ± 0.2 mg for thermal analysis and l.0 ± 0.1 mg for XRD. Simultaneous TG–DTG–DTA analyses were carried out using a thermal analyser STA 780, Stanton Redcroft (England). The samples were heated from 20 to 1,000 °C at a constant rate of 10 °C
Abstract
The effect of ammoxidation on thermal stability of carbonaceous materials characterised by degree of coalification other than that of brown coal (Konin mine, Poland) or sub-bituminous coal (Sośnica mine, Poland) was studied by thermogravimetric (TG-DTG) method. Analysis of TG-DTG curves has shown that coal samples ammoxidised at the higher temperature show slightly lower thermal stability. It has been established the importance of the sequence in the processes of carbonisation and ammoxidation. Both the amount of nitrogen introduced on the surface of studied carbonaceous materials and the thermal stability of nitrogen groups were affected.
Abstract
In this research, the relationship between particle size and combustion kinetics and combustion properties of lignite samples was examined by utilizing the thermogravimetric (TG/DTG) and differential thermal analysis (DTA) techniques. The lignite samples separated into different size fractions were subjected to non-isothermal thermogravimetric analysis between ambient and 900�C in the presence of 50 mL min−1 air flow rate. Activation energy (E) and Arrhenius constant (A r) of combustion reaction of each size was evaluated by applying Arrhenius kinetic model to the resulting data. Combustion properties of the samples were interpreted by careful examination of the curves. The apparent activation energies in major combustion region were calculated as 41.03 and 53.11 kJ mol−1 for the largest size (−2360+2000 μm) and the finest size (−38 μm), respectively.
The effect of procedural variables, including sample mass, heating rate, particle size and partial pressure of carbon dioxide, on TG, DTG and DTA curves for the decomposition of A. R. calcium carbonate and limestone has been studied. Such variables have a marked effect, similar in magnitude for both DTG and DTA. The effect of sample mass, or depth of undiluted sample, is shown to be due to an increase in the partial pressure of carbon dioxide within the reacting powder and has been called the bed-depth effect. This effect is most pronounced in nitrogen but is much reduced in carbon dioxide. Inert diluents have little effect on the TG curves but changing the composition of the inert carrier gas causes variations which are correlated with the thermal conductivity of the gas. Water vapour causes a lowering of the DTG and DTA peak temperatures.
TG, DTG and DTA curves of magnesite are dependent on procedural variables, especially sample mass, heating rate and partial pressure of carbon dioxide, in a similar manner to those of calcite [1], although the magnitude of the effect is less for magnesite. The first stage of the decomposition of dolomite varies with increasing partial pressure of carbon dioxide in an anomalous manner and hence the effects of these procedural variables (except heating rate) are not similar to those observed for magnesite and calcite. The second stage of the decomposition of dolomite is, however, strongly dependent on these procedural variables and behaves in a manner that would be predicted for a sample of calcite diluted with magnesia. A 1∶1 molar mixture of magnesite and calcite also behaves as would be predicted from the behaviour of the single carbonates but differently from that of dolomite.
Introduction TG/DTG curves can be used to estimate alimentary fats quality by determining the kinetic parameters and induction period of oxidation. Also, since the thermal decomposition reactions imply oxidative exothermic and
