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  • Author or Editor: D. Fatu x
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A model describing the initial step of diffusion-controlled solid-solid reactions is presented. The kinetic equation obtained was used to evaluate the activation energy of the reaction LiCl(s)+NaF(s)=LiF(s)+NaCl(s) from DTA data.

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Abstract  

The object of this work is the quantitative explanation of linear correlation between activation energy (E), initial decomposition temperature (T i) and ionic potential (V i), observed for thermal degradation of some complexes of transitional metals. The proposed model allowed the evaluation of characteristic parameter proportional to the activation free enthalpy and also the variation of effective electrical charge (ΔQ *) of ligand, in the formation process of the activated complex. These results are satisfactory, taking into account that we utilized many simple hypotheses for deduction of Arrhenius equation.

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A modification of the differential method is presented in order to evaluate the kinetic parameters of thermal decomposition reactions of the type As → Bs+ +Cg, using differential thermal analysis (DTA) data. The kinetic parameters calculated for the dehydration and decomposition of calcium oxalate and carbonate agree satisfactorily with those mentioned in the literature.

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Abstract  

A method was devised to evaluate latent heats of vaporization from quasi-isothermal isobaric analysis data. The procedure requires the recording of at least two diagrams: one for the investigated liquid, and the other for a standard liquid with a known latent heat of vaporization. Use of the method to determine the heats of vaporization of some alcohols, with water as standard liquid, led to results close to those previously reported in the literature. The main advantage of the procedure consists in the fact that it requires only small amounts of sample (5–10 mg).

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The kinetics of gypsum dehydration in non-isothermal conditions with constant heating rate as well in quasi-isotherm, quasi-isobar regime, was investigated. The latter ones of these methods allowed putting in evidence the autocatalytic character of the dehydration, as well as the change of the activation energy with the conversion.The activation energy change was explained by the crystal growth and sample compaction observed by optical microscopy.Microscopic observations show that at higher conversions a compaction occur. This process is probably favoured by the accumulation of the water vapour from the dehydration (autogenerate atmosphere). These are the reason for step III characterised by higher activation.

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Thermal investigation has allowed us to show the changes undergone by a sort of nitrile-butadiene rubber (NBR) as a consequence ofγ-radiation-induced ageing. The parameters of the processes, which occur at progressive heating of the investigated samples, were determined. It was shown that for γ-irradiated samples the activation parameters corresponding to the thermo-oxidative process leading to solid products are correlated through the relation of compensation effect. Also, it was shown that, by γ-irradiation, NBR undergoes a relatively rapid change of its thermal behaviour which can be due to structural changes.

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Abstract  

In order to evidence the ligand influence on the thermal stability for Co(II) complex combinations, we have synthesized five complex combinations of this metal with Schiff bases obtained by condensation of ethylenediamine with acetylacetone and benzoylacetone; phenylenediamine with benzoylacetone and also anthranilic acid with benzaldehyde.

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