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Abstract
When ethylene-vinyl acetate copolymer, EVA, is heated, a two-stage thermal degradation occurs following its melting. The vinyl acetate content of the copolymer was determined to be 43.8% by using TA 2950 and TA 2050 thermogravimetric instruments. TG/FTIR was used to detect the evolved gas. Acetic acid and trans-1-R-4-R'-cyclohexane were the main products evolved from EVA in the first and second stage, respectively. The apparent activation energies were determined for both stages by differential methods.
Abstract
In this work several Fe(Co,Ni) based nanocrystalline alloys were obtained by mechanical alloying. Thermal study was performed by differential scanning calorimetry and thermogravimetry. After 80 h milling, all DSC scans show several reactions on heating. At low temperature, about 400 K, the exothermal process detected is associated to structural relaxation. In all alloys, the main crystallization process begins over 700 K and has apparent activation energy values between 3.7 and 3.1 eV at–1. The Co content increases the thermal stability of this process. Furthermore, thermomagnetic measurements confirm the Co solid solution into Fe. The ferromagnetic–paramagnetic transition occurs at about 900 K.
Abstract
Pb(1,4-BDC)·(DMF)(H2O) (1,4-BDC=1,4-benzenedicarboxylate; DMF=dimethylformamide) has been synthesized and investigated by elemental analysis, FTIR spectroscopy, thermogravimetry (TG), derivative thermogravimetry (DTG). TG-DTG curves show that the thermal decomposition occurs in four stages and the corresponding apparent activation energies were calculated with the Ozawa-Flynn-Wall (OFW) and the Friedman methods. The most probable kinetic model function of the dehydration reaction of the compound has been estimated by the Coats-Redfern integral and the Achar-Bridly-Sharp differential methods in this study.
Abstract
A number of ionic chelate complexes of maltol(A) and hafnium(IV) the type[(η5−C5H5)2HfL]+[MCl3]− (B) [HL=maltol; M=Zn(II), Cd(II), Hg(II), Cu(II)]have been synthesized and characterized by spectral studies (IR, UV, 1H NMR and 13C NMR). The stoichiometry of the complexes has been confirmed by conductance measurements. Thermogravimetric (TG) and differential thermal analytical (DTA) studies have been carried out for these complexes and from TG curves, the order, apparent activation energy and apparent activation entropy of the thermal decomposition reactions have been elucidated .The order in each case has been determined to be one and the degree of spontaneity and lability have been inferred from the apparent activation energy and entropy, respectively. Thermal parameters have been correlated with some structural aspects of the complexes concerned. From differential thermal analysis curves, the heat of reaction has been calculated.
Abstract
The effects of some kinds of metal ions used as chemical modifications on the thermal properties of the modified polyacrylonitrile (PAN) fibers were studied by DTA, TG, GC and cone calorimetry. The apparent activation energies for the decomposition of the unmodified and modified PAN fibers were determined using Kissinger equation and Broido equation.
parameters should be avoided, and the different kinetics analysis techniques are complementary rather than competitive [ 45 ]. Thus, the apparent activation energy should be obtained by combining the obtained results in Tables 3 and 4 . The results
the melt viscosity, which determine hematite proportion and the size of the developing crystals. This article focuses on the kinetics study of the hematite crystallization in an aventurine glaze. The apparent activation energy, as a function of
apparent activation energy is important as it defines the reactor dimensions and energy consumptions. Activation energy values are dependent on the reducing gases, temperature of reduction, heating rates, presence of impurities, structural imperfections etc
HPMo ( 1 ), HPVMo ( 2 ), (NH 4 ) 3 PMo ( 3 ), (NH 4 ) 3 HPVMo ( 4 ), (NH 4 ) 2 KHPVMo ( 5 ), (NH 4 ) 1,5 CsH 1,5 PVMo ( 6 ), Cs 3 HPVMo ( 7 ) By means of the well-known Arrhenius equation, the values of apparent activation energy were determined
