Isothermal and non-isothermal kinetics of three dimensional growth processes from nuclei pre-existing on surface of infinite
plate specimen have been derived. Some useful and interesting relations have been found, and methods for kinetic analysis
of experimental data are proposed.
The non-isothermal kinetics of precipitation of an Al-12.6 mass% Mg alloy for different heating rates were studied using thermal
expansion techniques. The structural changes associated with the precipitation of the and b phases were identified. The conversion
degree of each phase was associated with the area under the derivative curve of the thermal expansion with respect to temperature.
Using the Kissinger relation and an iso-conversional method we calculated the apparent activation energies associated with
formation of the precipitated phases. We report an increasing dependence of the activation energy on the conversion degree,
the values obtained being within the range reported in the literature.
The kinetic compensation effect observed in heterogeneous non-isothermal kinetics is only an apparent effect. In general,
the correlation derived between the kinetic parameters E and log A from TG curves can be described by means of a non-linear
compensation law, expressed by Eq. (14). This equation may become approximately linear in certain particular cases, i.e. it
may change into an isokinetic relation. The validity of the non-linear compensation law has been tested by using over 1000
sets of kinetic parameters reported earlier.
Authors:M. Beneš, N. Milanov, G. Matuschek, A. Kettrup, V. Plaček, and V. Balek
Thermogravimetry (TG/DTG) coupled with evolved gas analysis (MS detection) of volatiles was used to characterize the thermal
behavior of commercial PVC cable insulation material during heating in the range 20-800C in air and nitrogen, respectively.
In addition, simultaneous TG/FTIR was used to elucidate chemical processes that caused the thermal degradation of the sample.
A good agreement between results of the methods was found. The thermal degradation of the sample took place in three temperature
ranges, namely 200-340, 360-530 and 530-770C. The degradation of PVC backbone started in the range 200-340C accompanied
by the release of HCl, H2O, CO2 and benzene. The non-isothermal kinetics of thermal degradation of the PVC cable insulation in the temperature range 200-340C
was determined from TG results measured at heating rates of 1.5, 5, 10, 15 and 20 K min-1 in nitrogen and air, respectively. The activation energy values of the thermal degradation process in the range 200-340C
of the PVC cable insulation sample were determined from TG results by ASTM method.
In this research, non-isothermal kinetics and feasibility study of medium grade crude oil is studied in the presence of a
limestone matrix. Experiments were performed at a heating rate of 10°C min−1, whereas the air flow rate was kept constant at 50 mL min−1 in the temperature range of 20 to 600°C (DSC) and 20 to 900°C (TG). In combustion with air, three distinct reaction regions
were identified in all crude oil/limestone mixtures, known as low temperature oxidation (LTO), fuel deposition (FD) and high
temperature oxidation (HTO). The activation energy values were in the order of 5–9 kJ mol−1 in LTO region and 189–229 kJ mol−1 in HTO region. It was concluded that the medium grade crude oil field was not feasible for a self-sustained combustion process.
Authors:Zhong-Suo Liu, Qi Wang, Zong-Shu Zou, and Guang-Lei Tan
kinetic analysis of adsorption and reaction rates, the mechanism of the carbon gasification is proposed and the region where chemisorption exists is determined, thereby providing a basis for the non-isothermalkinetics of carbon gasification
Authors:T. M. Carvalho, A. T. Adorno, A. G. Magdalena, and R. A. G. Silva
or a continuous process of atomic interchange [ 3 ]. Phases in the Cu–Al–Ag ternary system are structurally analog to those present in the binary systems, without intermediate phases [ 4 , 5 ].
In this study, the effect of Ag on the non-isothermal
Authors:A. Cadenato, J. Morancho, X. Fernández-Francos, J. Salla, and X. Ramis
The thermal polymerization kinetics of dimethacrylate monomers was studied by differential calorimetry using non-isothermal
experiments. The kinetic analysis compared the following procedures: isoconversional method (model-free method), reduced master
curves, the isokinetic relationship (IKR), the invariant kinetic parameters (IKP) method, the Coats-Redfern method and composite
integral method I. Although the study focused on the integral methods, we compared them to differential methods. We saw that
even relatively complex processes (in which the variations in the kinetic parameters were only slight) can be described reasonably
well using a single kinetic model, so long as the mean value of the activation energy is known (E). It is also shown the usefulness of isoconversional kinetic methods, which provide with reliable kinetic information suitable
for adequately choosing the kinetic model which best describes the curing process. For the system studied, we obtained the
following kinetic triplet: f(α)=α0.6(1−α)2.4, E=120.9 kJ mol−1 and lnA=38.28 min−1.
For the most common kinetic models used in heterogeneous reactions, the dependencies on xm = E/RTm (E is the activation energy, Tm is the temperature corresponding to maximum process rate, R is the gas constant) on the relative errors (e%) in the determination of the activation energy from the slope of the Kissinger straight line ln(β / Tm2) vs. 1/Tm (β is the heating rate) are evaluated. It is pointed out that, for xm≥10.7 and all kinetic models, ∣e%∣≤5%. Some possible cases exhibiting high values of ∣e%∣, which can be higher than 10%, are put in evidence and discussed.
The paper contains an analysis of the used of Diefallah's composite integral method of kinetic parameters evaluation. It is
shown that the application of this method should be preceded by the application of an isoconversional method through which
the dependence of the activation energy, E, on the conversion degree,a,
should be established. If Edepends ona, Diefallah's composite integral
method leads to erroneous results. If Edoes not depend ona, the
true kinetic model should be comprised in the pre-established set of kinetic models. These observations were checked for two
sets of non-isothermal data, namely: (a) the TG curves corresponding to the dehydration of CaC2O4H2O; (b) the TG curves corresponding to the thermal decomposition of polyvinyl chloride (PVC).