The thermal transformation of Na2C2O4 was studied in N2 atmosphere using thermo gravimetric (TG) analysis and differential thermal analysis (DTA). Na2C2O4 and its decomposed product were characterized using a scanning electron microscope (SEM) and the X-ray diffraction technique (XRD). The non-isothermal kinetic of the decomposition was studied by the mean of Ozawa and Kissinger–Akahira–Sunose (KAS) methods. The activation energies (Eα) of Na2C2O4 decomposition were found to be consistent. Decreasing Eα at increased decomposition temperature indicated the multi-step nature of the process. The possible conversion function estimated through the Liqing–Donghua method was ‘cylindrical symmetry (R2 or F1/2)’ of the phase boundary mechanism. Thermodynamic functions (ΔH*, ΔG* and ΔS*), calculated by the Activated complex theory and kinetic parameters, indicated that the decomposition step is a high energy pathway and revealed a very hard mechanism.
Authors:C. Păcurariu, R. I. Lazău, I. Lazău, D. Tiţa, and A. Dumitrel
values related to a given extent of conversion.
Four of the linear integral isoconversional methods, considered in the literature the most accurate, were used in this article.
crystallization process is obtained using Kissinger–Akahira–Sunosemethod (Eq. 5 ), Flynn–Wall–Ozawa method (Eq. 6 ), Tang method (Eq. 7 ), and Straink method (Eq. 8 ). Straight lines are obtained by plotting ln(β i / T α i ) versus 1000/ T (Eq. 5 ), ln(β i
-known Kissinger–Akahira–Sunosemethod (KAS method hereafter for short) was used [ 20 ]. Kissinger suggested that the activation energy can be estimated from the variation of DTA peak temperatures with different heating rates. The kinetics of most solid state
Authors:Dumitru Tiţa, Adriana Fuliaş, and Bogdan Tiţa
The Flynn–Wall–Ozawa isoconversional diagrams
The Kissinger – Akahira – Sunosemethod , sometimes called the generalized Kissinger method, is one of the best isoconversional methods and it is based on the
The temperature integral p ( x ) can be developed by an alternate series expansion [ 19 ]
The Kissinger–Akahira–Sunosemethod [ 20 , 21 ] is based on Murray’s approximation [ 22 ], which corresponds to the first term, i = 0, of Eq. 9
( E a = 144.9 kJ mol −1 by Kissinger–Akahira–Sunosemethod; E a = 140.1 kJ mol −1 by Flynn–Wall–Ozawa method and E a = 129.9 kJ mol −1 by Friedman method) was investigated with thermogravimetric analysis (TG) at four different heating rates (10