The convexity of localization forms, strictly required by conventional geometric-probabilistic formalism, is not in agreement with many experimental observations concerning solid-phase chemical reactions. In a discussion of the essence of this requirement, it is shown that it may be weakened for non-convex localization forms consistent with the symmetry of a solid reagent and described within the geometric-probabilistic approach in terms of planigons and Wigner-Seitz cells.
Authors:Ž. D. Živković, D. T. Živković and J. Šesták
Processes which occur during the thermal treatment of system FeSO4·7H2O-MnO2 are of the interest for obtaining MnSO4, which can be easily soluted in water and separated from impurities in manganese slime in zinc metallurgy. Results of the experimental investigations of such processes are given in this paper. Kinetic parameters for the previously defined mechanism were determined using Borchardt and Daniels method.
The methods of preparing the samples for kinetic studies are critically discussed with particular consideration to the effect
of granulometric characteristics and structure of the material, conditions of performing the measurements, and choice of proper
kinetic equation on the reliability of the results obtained.
/DTG curve were qualitatively described [ 2 – 4 ]. The dehydration kinetics of cemetitious materials were usually characterized by the modified Arrhenius equation [ 5 ], where the cemetitious materials were considered as pure substance.
Non-isothermal thermogravimetry was performed in a dynamic nitrogen atmosphere, on a series of poly(di-n-propyl itaconates) (PDnPI) and poly(di-iso-propyl itaconates) (PDiPI) which had been prepared in the presence of various amounts of the chain transfer agentn-dodecyl mercaptan (DDM).
Differential thermogravimetry (DTG) showed that both polymers degraded in two stages. The DTG curve of PDnPI had a large first
peak followed by a smaller shoulder, whereas the DTG curve of PDiPI was composed of two peaks of almost equal heights. The
addition of DDM during the polymerisations in both cases resulted in a similar decrease in the relative area of the first
This paper reports on the results attained in the determination of the mechanism of oxidation of molybdenum sulphide under
non-isothermal conditions in an air atmosphere. The mechanism of the process was determined by simultaneous DTA-TG-DTG, and
the kinetic parameters of the reactions involved were obtained according to the methods of Kissinger and Ozawa.
Differential scanning calorimetry (DSC) was used to indicate the relative extents of the different cure reactions of the 4-glycityloxyl-N,
N-diglycidylaniline (MY0510), polyglycidyl ether of phenol formaldehyde novolac (DEN431) and 3,3 diamino diphenylsulphone
(3,3 DDS) resin systems and how these were affected by the presence of polyethersulphone (PES). The extent of reactions at
any given time decreased with increasing PES concentration and the reaction rate maximum shifted to longer times. The cured
resin systems were examined using dynamic mechanical analysis (DMA). Broader β-transitions of lower intensities were observed
in specimens containing PES, suggesting an increased range of relaxations within the transition.
A study was made on the topochemical processes of hydration-dehydration, ammonation-deammonation, disproportionation and anionic
condensation (certain of which can proceed concurrently) that occur during the production, storage and exploitation of phosphoric
salts and phosphate materials. These processes which can be accompanied by complicated structural transformations and sometimes
by melting were shown to be satisfactorily described by the known kinetic regularities. The detected deviations, that are
associated with the anomalous influence of temperature, the gaseous phase, the size and habit of the crystals and the ageing
of samples on the process rate, were explained in terms of the localization peculiarities of the reactions proceeding on the
surface or in the bulk of the reactant.