Authors:R. Issa, S. Amer, I. Mansour, and A. Abdel-Monsef
The thermal stabilities of bis salicylidene adipic dihydrazone derivatives and their complexes with divalent Mn, Co, Ni, Cu
and Zn were studied and discussed in terms of structure and type of metal ions. TG curves display mostly four steps of thermal
decomposition. The first step is due to dehydration, then the elimination of the acetate anions followed by the decomposition
of the ligand in two interacting steps. The activation energies Ea were evaluated and discussed in accordance with the structure of the complexes which have been previously characterized by
elemental analysis and IR spectra. It was found that the activation energies of the complexes based on bis salicylidene adipic
dihydrazone were higher than those of the dihydroxy derivative.
In this study, four oil-shale samples (Niğde-Ulukışla) excavated from Central Anatolia Turkey were analyzed where this region
is believed to have a high potential of oil in its shale rich outcrops. The samples (∼40 g) were combusted at 50 psi gas injection
pressure, at an air injection rate of 1.5 L min−1 in a combustion-reaction cell. All the experiments were conducted up to 600°C. The percentages of oxygen consumption and
carbon monoxide and carbon dioxide production were obtained instantaneously with respect to time. The combustion periods and
relative reaction rates were determined by examining the effluent gas concentration peaks. Activation energies of the samples
were determined using Weijdema’s approach. It was observed that the activation energies of the samples are varied between
22–103 kJ mol−1.
The influence of aliovalent ions such as Mn, Cr, Fe, Mo, and V on the temperature and kinetics of anatase to rutile phase
transformation in TiO2 heated in microwave field was studied in this work. The results indicated that heat treatment method and dopants considerably
affected the anatase-to-rutile phase transition temperature and kinetics of transformation. The activation energy for anatase
to rutile transformation of TiO2 derived from the isothermal data was found to be 328.4 kJ mol-1, which was considerably reduced by the addition of dopants in TiO2 matrix. The activation energy for Mo, Mn and V doped samples was 252.0, 101.3 and 96.4 kJ mol-1, respectively.
Authors:F. Doǧan, S. Gülcemal, M. Yürekli, and B. Çetinkaya
The imidazolinium and benzimidazolium bromide salts with pentafluor substituents on N atom were synthesized. The structures
of imidazolinium and benzimidazolium bromide salts obtained were conformed by 1H and 13C NMR, 19F NMR and elemental analysis. It was found that pyrolytic decomposition occurs with melting in salts. The imidazolinium and
benzimidazolium bromide salts were studied by TG-DTG and DTA from ambient temperature to 1000°C in nitrogen atmosphere. The
decomposition occurred mainly in one stage and the values of activation energy E, frequency factor A, reaction order n, enthalpy change ΔH#, entropy change ΔS# and Gibbs free energy ΔG#, of the thermal decomposition were calculated by means of Coats-Redfern (CR), MacCallum-Tanner (MC) and van Krevelen (vK)
methods. The activation energy value obtained by CR and MC methods were in good agreement with each other while those obtained
by vK were found to be 10–12 kJ mol−1 larger.
and the steady-state approximation are used to present a demonstration of the fact that the evolution of the reaction rates
under non-isothermal conditions depends on the ratio of the activation energies and on the heating rate. At the same time,
it is shown that, under isothermal conditions, the ratio of the activation energies plays no role.
Authors:M. Ginic-Markovic, N. Choudhury, J. Matisons, and D. Williams
A two-pack polyurethane coating was analyzed using thermoanalytical techniques. The curing reaction, monitored using pressure differential calorimetry (PDSC), rheometry and dynamic mechanical analysis (DMA) shows the temperature dependency of activation energy and hence rate of curing. In-situ ATR-FTIR shows the formation of urethane linkage over time. The decomposition behavior carried out under non-isothermal mode using thermogravimetric analysis (TGA) shows bimodal behavior. The activation energies of the initial step (10% decomposition) from both iso and non-isothermal experiments are in very good agreement with each other. The use of dynamic mechanical analysis (DMA) shows the difference in glass transition behavior (Tg) and elastic modulus (E') due to the different state of cure. Also the coating exhibits a very broad loss modulus peak (E'') indicating higher energy dissipation with deformation.
Authors:P. Lavrenko, O. Okatova, K. Andreeva, and B. Schulz
Translational diffusion of poly-2,5-(1,3-phenylene)-1,3,4-oxadiazole (PMOD) in solution in 96% sulphuric acid was studied,
and intrinsic viscosity was measured at different stages of thermal degradation. Polymer solution has previously been subjected
to heating at temperature ranging from 75 to 104C and then investigated at 26C. A monotonic decrease in intrinsic viscosity
and the molecular mass, M, of degraded products with increasing degradation temperature was detected. The rate constant of the degradation process
has been obtained from the change in M of the degradation products with time at a fixed solution temperature, and the activation energy of the process was calculated
by using the temperature dependence of the rate constant. The activation energy (E =1028 kJ–1 ) is close to that obtained previously for the hydrolysis of poly-2,5-(1,4-phenylene)-1,3,4-oxadiazole (PPOD) in sulphuric
acid (106 kJ–1 ), the rate constant being approximately twice in the value.
this research, thermal characterization and kinetics of Karakus crude oil
in the presence of limestone matrix is investigated. Thermogravimetry (TG/DTG)
is used to characterize the crude oil in the temperature range of 20-900C,
at 10C min -1 heating rate using air
flow rate of 20 mL min -1. In combustion
with air, three distinct reaction regions were identified known as low temperature
oxidation (LTO), fuel deposition (FD) and high temperature oxidation (HTO).
Five different kinetic methods used to analyze the TG/DTG data to identify
reaction parameters as activation energy and Arrhenius constant. On the other
hand different f(α) models from literature
were also applied to make comparison. It was observed that high temperature
oxidation temperature (HTO) activation energy of Karakus crude oil is varied
between 54.1 and 86.1 kJ mol -1, while low
temperature oxidation temperature (LTO) is varied between 6.9 and 8.9 kJ mol -1.
The thermal stability of push-pull 5-substituted-4-oxothiazolidines was studied by DSC, IC and X-ray diffraction techniques.
It was shown that the compounds are stable in the temperature range from room temperature to melting point. The melting is
combined with breaking crystal structure and forming glass material as a new phase that forms crystals by cooling it very
slowly. The rate constant, activation energy as well as activation parameters of process were determined.
Authors:C. Soykan, R. Sahingoz, and F. Yakuphanoglu
The influence of pressure on the polyphenacylmethacrylate [poly(PAMA)] was investigated using thermal and scanning electron microscopical (SEM) methods. It is observed that the application of pressure reduces 10% of the initial glass transition temperature. A part from each of the sample was taken for thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). The activation energies were calculated by Ozawa method and significant changing was observed due to this calculation justified the effect of applying pressure.