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1.
A. Y Obaid A. O. Alyoubi A. A. Samarkandy S. A. Al-Thabaiti S. S. Al-Juaid A. A. El-Bellihi El-H. M. Deifallah 《Journal of Thermal Analysis and Calorimetry》2000,61(3):985-994
The thermal decomposition of copper(II) acetate monohydrate was studied in air and nitrogen atmospheres by means of DTA-TG
and SEM measurements. The kinetics of the thermal decomposition steps in air was studied by using isothermal and non-isothermal
thermogravimetric techniques. The results are discussed in terms of various reaction interface models and different techniques
of computational analysis of non-isothermal data. The activation parameters, calculated by using a composite method of integral
analysis of non-isothermal data, revealed not only their independence from the heating rate and fractional reaction, but also
a better correlation and agreement with the results obtained under isothermal conditions.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
Ramis X. Salla J. M. Cadenato A. Morancho J. M. 《Journal of Thermal Analysis and Calorimetry》2003,72(2):707-718
The curing of a thermosetting powder coating was studied by means of differential scanning calorimetry (DSC). The isothermal
cure was simulated by non-isothermal experiments. The results of the simulation were compared with experimental isothermal
data. From non-isothermal isoconversional procedures (free model), it was concluded that these permit simulation of the isothermal
cure but do not enable us to determine the complete kinetic triplet (A preexponential factor, E activation energy, f(a) and/or g(a) function of conversion). Non-isothermal procedures based on a single heating rate or on master curves present difficulties
for determination of all the kinetic parameters, due to the compensation effect between preexponential factor and activation
energy. The kinetic triplet can be determined by a combination of various non-isothermal methods or by using experimental
isothermal data in addition to non-isothermal data.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
A general procedure for deriving the equations that underlie various isoconversional nonlinear methods for evaluating the activation energy is presented. A new integral isoconversional nonlinear method with integration over a given range of conversion is suggested. This method was applied to simulated nonisothermal data as well as to data for the nonisothermal decomposition of ammonium perchlorate. The obtained dependencies of the activation energy on the degree of conversion were compared with those resulting from other nonlinear and linear methods of analysis. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 36: 87–93 2004 相似文献
4.
B. Saha 《Thermochimica Acta》2006,444(1):46-52
Pyrolysis, one possible alternative to recover valuable products from waste plastics, has recently been the subject of renewed interest. In the present study, the isoconversion methods, i.e., Vyazovkin model-free approach is applied to study non-isothermal decomposition kinetics of waste PET samples using various temperature integral approximations such as Coats and Redfern, Gorbachev, and Agrawal and Sivasubramanian approximation and direct integration (recursive adaptive Simpson quadrature scheme) to analyze the decomposition kinetics.The results show that activation energy (Eα) is a weak but increasing function of conversion (α) in case of non-isothermal decomposition and strong and decreasing function of conversion in case of isothermal decomposition. This indicates possible existence of nucleation, nuclei growth and gas diffusion mechanism during non-isothermal pyrolysis and nucleation and gas diffusion mechanism during isothermal pyrolysis. Optimum Eα dependencies on α obtained for non-isothermal data showed similar nature for all the types of temperature integral approximations. 相似文献
5.
Thermal behavior of nitroguanidine (NQ) has been investigated by TG/DSC-MS-FTIR simultaneous analysis performed under both isothermal and nonisothermal conditions. The isothermal test at 230 °C indicated that the release of gas products can be divided into several stages. The processing of the non-isothermal data, namely 5, 10, 15, and 20 K/min, was performed by using Netzsch Thermokinetics. The dependence of the activation energy evaluated by Friedman’s isoconversional method on the conversion degree shows that the investigated process is complex one, and can be divided into three parts. The mechanism of the process and the corresponding kinetic parameters were determined by Multivariate Non-linear Regression Program. The kinetic results was used to simulate the thermal decomposition of NQ under isothermal condition at 210 °C. The simulated curve is in agreement with the tested curve. The obtained results were also used for prediction of the thermal lifetime of NQ corresponding to a certain temperature. 相似文献
6.
Results obtained on the thermooxidative degradations of LDPE (low-density polyethylene) and NBR (nitrile-butadiene rubber)
are presented. The activation energies for the thermooxidations leading to solid products were estimated. For LDPE, the activation
energies obtained from non-isothermal data are in satisfactory agreement with those obtained from isothermal data. For NBR,
the isothermal activation energy is ≉16% higher than the non-isothermal one. This difference is due to the morphological changes
undergone by NBR during its heating at the rather high temperatures at which isothermal measurements were performed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
Vulcanisation of rubber compounds was studied by DSC under isothermal and non-isothermal conditions. The parameters of an
Arrhenius-like equation describing the temperature dependence of induction period have been obtained both from isothermal
and non-isothermal measurements. A new method for obtaining the kinetic parameters from non-isothermal measurements, based
on the dependence of onset temperature of vulcanisation peak on heating rate, is presented. Also, a procedure for the evaluation
of temperature difference between the furnace and sample is proposed. It has been shown that the treatment of non-isothermal
DSC measurements gives the kinetic parameters free of systematic errors. The new method can also be used for studying other
reactions exhibiting the induction period.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
8.
The kinetics of the thermal decomposition of ammonium perchlorate at temperatures between 215 and 260°C is studied, in this
work, by measuring the sample mass loss as a function of time applying the isothermal thermogravimetric method.
From the maximum decomposition rate – temperature dependence two different decomposition stages, corresponding to two different
structural phases of ammonium perchlorate, are identified. For the first region (215–235°C), corresponding to the orthorhombic
phase, the mean value of the activation energy of 146.3 kJ mol–1, and the pre-exponential factor of 3.43⋅1014 min–1 are obtained, whereas for the second region (240–260°C), corresponding to the cubic phase, the mean value of the activation
energy of153.3 kJ mol–1, and the pre-exponential factor of 4.11⋅1014 min–1 are obtained.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
9.
Herdes C Santos MA Medina F Vega LF 《Langmuir : the ACS journal of surfaces and colloids》2005,21(19):8733-8742
We combine here a regularization procedure with individual adsorption isotherms obtained from grand canonical Monte Carlo simulations in order to obtain reliable pore size distributions. The methodology is applied to two hexagonal high-ordered silica materials: SBA-15 and PHTS, synthesized in our laboratory. Feasible pore size distributions are calculated through an adaptable procedure of deconvolution over the adsorption integral equation, with two necessary inputs: the experimental adsorption data and individual adsorption isotherms, assuming the validity of the independent pore model. The application of the deconvolution procedure implies an adequate grid size evaluation (i.e., numbers of pores and relative pressures to be considered for the inversion, or kernel size), the fulfillment of the discret Picard condition, and the appropriate choice of the regularization parameter (L-curve criteria). Assuming cylindrical geometry for both porous materials, the same set of individual adsorption isotherms generated from molecular simulations can be used to construct the kernel to obtain the PSD of SBA-15 and PHTS. The PSD robustness is measured imposing random errors over the experimental data. Excellent agreement is found between the calculated and the experimental global adsorption isotherms for both materials. Molecular simulations provide new insights into the studied systems, pointing out the need of high-resolution isotherms to describe the presence of complementary microporosity in these materials. 相似文献
10.
Some contradictions concerning the classification of the methods to evaluate nonisothermal kinetic parameters into differential and integral ones are analyzed. Using the theorem of media for integrals, the equivalence between the methods that use the integration on low ranges of variables and the differential methods is shown. Concerning the magnitude of the range of change of variables on which the integration of the rate equation is performed, the applicability of the isoconversional methods that use approximate expressions of the temperature integral (Simpson's formula, formula based on the theorem of media for integrals) was analyzed. Our results were verified for simulated data (which are not affected by the experimental errors) as well as for the nonisothermal data for the thermal decomposition of ammonium perchlorate. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 339–344, 2006 相似文献
11.
A simple and precise linear integral method to evaluate the activation energy dependence on the extent of conversion has been proposed. The method leads to consistent results with those from differential and integral non-linear procedure (Vyazovkin method). Moreover, the new procedure yields the pre-exponential factor and the kinetic model. The method was evaluated from isothermal, non-isothermal and non-linear non-isothermal data (CRTA). 相似文献
12.
Chen F. Sørensen O. T. Meng G. Peng D. 《Journal of Thermal Analysis and Calorimetry》1998,53(2):397-410
Thermal decomposition of BaC2O4·0.5H2O in air was studied by a combination of stepwise isothermal analysis (SIA) and non-isothermal
thermogravimetry. The results from both techniques show that the crystal water is released in one step and that anhydrous
barium oxalate is decomposed in one step, while BaCO3 decomposes in three steps to BaO, forming two intermediate compounds
with the formulas of BaCO3·(BaO)2 and (BaCO3)0.5·(BaO)2.5. Reaction mechanism analyses using the data from SIA measurements
show that the controlling mechanism for all the five decomposition steps in isothermal conditions is a two-dimensional phase-boundary
controlled process. Kinetic parameters are obtained for the five decomposition steps from the non-isothermal thermogravimetric
data.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
13.
With on-line coupled thermo-gravimetric analyzer-Fourier transform infrared spectrometer technique, the thermal decomposition of lithium hexafluorophosphate (LiPF6) and its gas evolution at inert environment (H2O<10 ppm) were studied under both non-isothermal and isothermal conditions. The results showed that the LiPF6 decomposition is a single-stage reaction with LiF as final residue and PF5 as gas product. In addition, its decomposi-tion kinetics was determined as 2D phase boundary movement (cylindrical symmetry) under both non-isothermal and isothermal conditions. Furthermore, the activation energy of LiPF6 decomposition was calculated as 104 and 92 kJ/mol for non-isothermal and isothermal con-ditions, respectively. 相似文献
14.
K. Muraleedharan M. P. Kannan T. Ganga Devi 《Journal of Thermal Analysis and Calorimetry》2011,103(3):943-955
The thermal decomposition of potassium iodate (KIO3) has been studied by both non-isothermal and isothermal thermogravimetry (TG). The non-isothermal simultaneous TG–differential
thermal analysis (DTA) of the thermal decomposition of KIO3 was carried out in nitrogen atmosphere at different heating rates. The isothermal decomposition of KIO3 was studied using TG at different temperatures in the range 790–805 K in nitrogen atmosphere. The theoretical and experimental
mass loss data are in good agreement for the thermal decomposition of KIO3. The non-isothermal decomposition of KIO3 was subjected to kinetic analyses by model-free approach, which is based on the isoconversional principle. The isothermal
decomposition of KIO3 was subjected to both conventional (model fitting) and model-free (isoconversional) methods. It has been observed that the
activation energy values obtained from all these methods agree well. Isothermal model fitting analysis shows that the thermal
decomposition kinetics of KIO3 can be best described by the contracting cube equation. 相似文献
15.
《Thermochimica Acta》2004,414(2):137-143
The kinetics of nanocrystallization in amorphous TiO2 has been studied in non-isothermal conditions by DSC. It was found that this process could be well described by standard Johnson-Mehl-Avrami-Kolmogorov (JMA) model with kinetic exponent m≅1. The kinetic parameters were calculated by simultaneous analysis of experimental data taken at different heating rates. These parameters were used as a basis for prediction of crystallization kinetics in isothermal conditions. The agreement between the JMA model prediction and experimental data depends on the method of preparation of amorphous TiO2. 相似文献
16.
S. N. Basahel M. M. El-Fass A. A. El-Bellihi E. A. Al-Sabban El-H. M. Diefallah 《Radiation Physics and Chemistry》1994,44(6):583-587
The kinetics of the non-isothermal decomposition of potassium nickel(II) oxalate in air were studied for non-irradiated and irradiated crystals using thermogravimetric techniques. Analysis of kinetic data were performed using the direct differential method, the integral methods due to Coats-Redfern, Ozawa and a composite integral method. The results of the kinetic analysis of dynamic data and the effects of radiation were discussed and compared with those obtained under isothermal conditions. 相似文献
17.
The thermal decomposition of ammonium perchlorate (AP) is considerably modified when it is cocrystallized or mixed with small amounts of tetramethyl- ammonium perchlorate. The decomposition is sensitized when tetramethylphosphonium perchlorate is added to AP. The effect on the isothermal decomposition of AP when it is mixed with tetramethylammonium perchlorate, appears to be similar to that of AP-based composite propellant having the same mixed AP composition. 相似文献
18.
Litwinienko G. Kasprzycka-Guttman T. 《Journal of Thermal Analysis and Calorimetry》1998,54(1):211-217
Oxidation of saturated fatty acids ethyl esters: laurate, myristate, palmitate and stearate was investigated by means of DSC
techniques under isothermal and non-isothermal conditions. The activation energies of isothermal oxidation were similar to
each other (112–123 kJ mol−1) and no influence of carbon length on the rate of oxidative decomposition was observed. Results obtained from non-isothermal
experiments were similar only for the first stage of oxidation.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
19.
T. Vlase Gabriela Vlase Nicoleta Birta N. Doca 《Journal of Thermal Analysis and Calorimetry》2007,88(3):631-635
A comparative kinetic analysis on the thermal decomposition of tartaric acid and potassium tartrate under non-isothermal conditions
was performed. The non-isothermal kinetic parameters were determined by the following four methods: integral isoconversional
method suggested by Flynn-Wall-Ozawa (FWO method); differential isoconversional method suggested by Friedman; Budrugeac-Segal
method and Non-Parametric-Kinetic (NKP) method suggested by Sempere and Nomen and modified by Vlase and Doca. The comparison
of the results obtaining by these methods leads to interesting conclusions. The experimental data were obtained in dynamic
nitrogen atmosphere at heating rates of 5, 7, 10, 12 and 15 K min−1. The less speculative kinetic analysis was possible by the NPK method. 相似文献
20.
P. Budrugeac E. Segal E. Stere Alice Luminita Petre 《Journal of Thermal Analysis and Calorimetry》1996,46(5):1313-1324
The isothermal and non-isothermal degradation of a typical styrenated phthalic acid-maleic acid-propylene glycol polyester were measured. Non-isothermal and isothermal kinetic analyses were performed on the various degradation steps observed. The values of the non-isothermal and the isothermal kinetic parameters are in good agreement. 相似文献