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- Author or Editor: Lucia Odochian x
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Abstract
The nature of the crystallization water in MgSO4·7H2O, Mg(NO3)2·6H2O and MgCl2·6H2O has been studied with the nonisothermal methods of thermogravimetry (TG), derived thermogravimetry (DTG) and differential thermal analysis (DTA). Analysis of the characteristic thermogravimetric data (T M,W ∞) and the kinetic parameters (n, E a), together with the DTA results, with CuSO4·5H2O as control sample, provided evidence of the existence of coordinated water and of the nature of the anions in these hydrates. The results are confirmed by the observation of a real compensation effect. For the compensation effect, the following equation is proposed: InA=0.220E-0.8 Structures explaining the presence of the coordinated water and the nature of the anions in these hydrates are also proposed.
Abstract
The study is devoted to the characterization by both TG-DTG analysis and FTIR spectroscopy of beech flour, dyes and the sorbent-dyes products obtained through retention of the dyes from aqueous solution on the beech flour, to the aim of obtaining information on the nature of dyes’ retention, thermal behavior of the sorbent-dye materials as well as on their possible upgrading as fuel. Thermal analysis led to the conclusion that the mechanism of thermo-oxidative degradation is specific and the retention of dyes occurs on cellulose from beech flour. The nature of the bonds involved in dyes’ retention is also investigated by FTIR analysis, which evidences that dyes retention on cellulose is realized through hydrogen bonding between the NH and, respectively, OH groups from dye molecule and the oxygen atoms from cellulose. Involvement of the non-participating electrons of the nitrogen and, respectively, oxygen atoms of these groups in the extended electronic conjugation with aromatic nuclei strongly influences the capacity of the amino and, respectively, hydroxyl groups of forming hydrogen bonds, thus achieving dyes fixation on the sorbent. DTA analysis led to the conclusion that an improvement in the quality of the sorbent-dye materials as fuels is possible, as compared to untreated beach flour, as a result of the modification of the cellulosic fibers in the process of dyes retention.
Abstract
The study on the thermal behavior of some new diazoaminoderivatives was aimed to follow the structure-thermal stability-degradation mechanism correlation by means of the TG-FTIR technique and formation enthalpies. The TG-DTG-DTA curves reveal the thermal degradation in air (30–900 °C) to show two ranges as a function of temperature (time), where the gaseous species resulting by degradation are eliminated: the first, an endothermic one which is identical to that under nitrogen atmosphere and the second, an exothermal one. As made evident by the identification of the individual gaseous species by their characteristic absorbances as well as those obtained by TG-FTIR the compounds C2H2, H2C = NH, SO2, NH3, CO2, H2O, HCl are eliminated in the first domain while CO2, SO2, H2O in the second, which afforded the advancement of the most probable degradation mechanism.
Abstract
The article is devoted to the study on the thermal behaviour of three species of edible mushrooms: Boletus edulis (foot and cap), Pleurotus ostreatus (foot and cap), Lactarius deterrimus (cap) by the TG–FTIR-coupled technique, in air, over the 30–900 °C temperature range. The analysis of the TG–DTG–DTA curves reveals the thermal degradation mechanism to be complex and specific to every species under the recording conditions applied. A similar degradation mechanism is noticed for the foot and cap of Pleurotus ostreatus in comparison with the Boletus edulis and Lactarius deterrimus species where the mechanisms are different. The TG–FTIR analysis, combustion heats and IR spectra of the starting samples also support these results. The initial degradation temperatures from TG–DTG indicate the temperature range where these species are thermally stable and their nutrient features maintained making them proper for food. The TG–FTIR analysis gives information on the gaseous species evolved by the thermal degradation bringing thus a contribution to the elucidation of the changes developing by processing the edible mushrooms (industrialization, conservation, culinary preparations, etc.) at temperatures above the initial degradation temperature. At the same time, the environmental impact, when the mushroom failed cultures are burned, is also important.
Abstract
The paper deals with the characterization of three hydrazinic complexes with Ni, Cu and Cr respectively, by means of non-isothermal thermal methods, TG, DTG and DTA, under nitrogen atmosphere in order to investigate the structure-thermostability-thermal degradation mechanism correlation. The thermal analysis made evident the degradation mechanisms characteristic of every sample in accordance with the chemical structure. The quantitative analysis by TG-DTG afforded the estimation of the metal amount in the complex on the basis of the resulting metallic oxide nature as well as of some aspects of the thermal degradation mechanism supported by mass spectral measurements. The melting points given by DTA and confirmed by the Boetius method and the initial temperatures of thermal degradation from TG-DTG-DTA afforded to ascertain the temperature range proper for using and storing the complexes under study which show potential practical applications as drugs.
Abstract
The study is devoted to the characterization by TG, DTG, DTA, both in air and N2 atmosphere, of three cyclic ylides as well as two spirane derivatives, to the purpose of elucidating the correlation between structure, thermostability and thermal degradation mechanism. Thermal analysis data indicated that the degradation mechanism is characteristic for every sample, and the consequences of structural peculiarities are discussed. The thermostability series of the samples is correlated to their structure. The quantitative TG-DTG-DTA analysis allowed some considerations on the thermal degradation mechanism, subsequently confirmed by mass spectrometry. The melting points obtained by DTA and Boetius measurements along with the initial degradation temperatures from TG-DTG-DTA curves indicates the temperature range for the use and storage of these compounds, considering that some derivatives of cyclic ylides show biological activity and potential medical applications.
Abstract
The article is devoted to a comparative study on the thermal degradation of some new diazoaminoderivatives under both air and nitrogen atmosphere by TG-FTIR analysis. The TG–DTG–DTA curves show the thermal degradation in air to present two temperature domains: an endothermic one identical to the case of the degradation under nitrogen and an exothermic one which is not to be found under nitrogen atmosphere. The identification of the gaseous species released by degradation in air within the endothermic domain made evident the presence of the same components of the degradation in nitrogen atmosphere. In the exothermic domain of the sample degradation in air, the CO2, H2O, SO2 species result by the burning of the molecular residues of the first domain. The obtained results afforded a degradation mechanism to be advanced that coincide for the endothermic domain with that of degradation under nitrogen atmosphere. Due to the importance of these compounds as possible reaction initiators and also as potentially bioactive substances (herbicides, acaricides, fungicides), the study on their thermal degradation could give useful information on the environmental impact of the degradation products resulting by the thermal processing of the plants which could possible retain these compounds, when the initial degradation temperature is exceeded.