It is shown that the total differential of the function of the amount of conversion versus temperature and time (α=f(T, t)) is equal to zero non-isothermal kinetics at constant heating rate. Hence, the mathematical expression used in the literature for the rate of the non-isothermal transformation,
, is not valid.
Authors:V. Kolarik, M. Juez-Lorenzo, N. Eisenreich, and W. Engel
Temperature resolved X-ray diffraction using a diffractometer equipped with a high temperature device was applied to the study of the oxidation of Fe-ARMCO below 570°C. The oxidation products are identified in situ and the difference method yields curvesY(T) showing the global changes. These curves were calibrated to the microscopically measured end thickness of the oxide layer obtaining the growthx(T). A calculated curve including the Arrhenius relation was fitted to thex(T) curve yielding activation energy and values of the oxidation rate constant as a function of temperature.
The thermal behavior of[Eu2(BA)6(dmbpy)2] (BA=C7H5O
, benzoate; dmbpy=C12H12N2, 4,4-dimethyl-2,2-bipyridine) and its kinetics were studied under the non-isothermal condition in a static air atmosphere by TG-DTG, IR and SEM methods. Thermal decomposition of [Eu2(BA)6(dmbpy)2] occurred in four consecutive stages at TP 232, 360, 455 and 495°C. The kinetic parameters were obtained from analysis of the TG-DTG curves by Achar and Madhusudanan—Krishnan—Ninan (MKN) methods. The most probable mechanisms for the first stage was suggested by comparing the kinetics parameters.
Authors:B. Janković, B. Adnađević, and J. Jovanović
Kinetics of dehydration of equilibrium swollen poly(acrylic acid) hydrogel was investigated using methods of non-isothermal
thermal analysis. Methods of Kissinger, Coats-Redfern, Van Krevelen and Horowitz-Metzger were applied for determination the
kinetics parameters: activation energy (E), pre-exponent (lnA) as well as the kinetics model ƒ(69) for the process of hydrogel dehydration under different heating rates. An existence
of good agreement between determined values of kinetic parameters (Eand A), which were obtained applying different methods under the same heating rate. Functional relationship between changes of
kinetic parameters of dehydration and changes of heating rate was established. An existence of compensation effect is accepted
and explanation of compensation effect appearance during the hydrogel dehydration is suggested.
As a numerical characteristic of the sensitivity of the kinetic parameter calculation method to the form of the kinetic function in non-isothermal kinetics, the value of the curvature of the line plotting residual dispersionvs. formal reaction order at the minimum point is suggested. The efficiency of this characteristic is exemplified.
This work reports a non-isothermal kinetics of the melting and the nematic to isotropic (N–I) phase transitions of the pentylcyanobiphenyl
(5CB) liquid crystal compared with octylcyanobiphenyl (8CB) liquid crystal using calorimetric technique. Temperature scans
and heating rate scans were performed for 5CB and 8CB from 280 to 333 K at various rates using differential scanning calorimetry
from 0.5 to 20 K min−1. Double activation was observed for 5CB for two heating rate regimes whereas 8CB indicated single activation only. The 5CB
has smaller enthalpy and entropy of the transitions and needs larger activation than 8CB. This kinetic change can be explained
in terms of the length scale and mobility of the liquid crystal molecules.
for more than a century [ 8 ]. Decomposition and its non-isothermalkinetics, belonging to some of the oxalates (Ag 2 C 2 O 4 , NiC 2 O 4 , MnC 2 O 4 , HgC 2 O 4 , PbC 2 O 4 , and SrTiO(C 2 O 4 ) 2 ·4H 2 O), were reported later [ 3 , 8 – 10 ]. The
Authors:Wenwei Wu, Xuehang Wu, Shuibin Lai, and Sen Liao
potential [ 11 – 13 ]. In this article, the mechanisms and kinetics of the decomposition of NH 4 ZrH(PO 4 ) 2 ·H 2 O were studied using TG–DTA technique. Non-isothermalkinetics of the decomposition process of NH 4 ZrH(PO 4 ) 2 ·H 2 O were interpreted by