Arrhenius Plot Method Research Articles

Investigation of electric field effect on defects in GaAsN by admittance spectroscopy

• Electric-field dependent properties of defects in GaAsN. • Temperature dependent properties of defects in GaAsN. • Extraction of defect properties without the Arrhenius plot. We use the Arrhenius transformation and matching (ATM) method to extract activation energy and attempt-to-escape frequency of the nitrogen-related defect (E1) in GaAsN from admittance spectroscopy measurements taken at various temperature and electric field. The ATM method is equivalent to the conventional Arrhenius plot and line-fitting (APL) method for Arrhenius processes with temperature-independent E a and ν 0 (e.g., E1 in a low electric field and at high temperatures) and advantageous for non–Arrhenius processes with temperature-dependent E a and ν 0 , (e.g., E1 in a high electric field and at low temperatures), where the APL method is not reliable. The ATM method enables a detailed account on how E a evolves with the temperature and the electric field in a continuously varying experimental space, which is not possible with the APL method. The evolution of carrier emission behaviors from the E1 defect and a neighboring E2 defect provides experimental evidence of field-induced metastability possibly due to the interaction of two defects with close atomic origins or spatial locations.

Thermogravimetric pyrolysis of onion skins: Determination of kinetic and thermodynamic parameters for devolatilization stages using the combinations of isoconversional and master plot methods

Thermogravimetric pyrolysis of onions skins was studied thoroughly for the first time. Kinetic calculations of devolatilization stages were performed applying direct Arrhenius plot (DAP) method and combinations of isoconversional and Criado’s Z(α) master plot (CZMP) methods. The kinetic parameters calculated using combined methods were utilized successfully to reproduce the experimental kinetic curves whereas those calculated using DAP method failed in this sense. The average Ea values of isoconversional methods were between 164.0 and 172.0 kJ/mol. The CZMP method yielded multiple F-type reaction mechanisms. The simplified kinetic models of combined methods were also developed by using single reaction mechanisms deduced from multiple reaction mechanisms. The Friedman-CZMP combination was the best option for developing simplified/unsimplified kinetic models. Determination of reaction mechanism using DAP method by searching for the highest R2 value of regression equation among several candidates was found unreliable. ΔH, ΔG and ΔS values were calculated for 10 °C/min heating rate.

Type I kerogen-rich oil shale from the Democratic Republic of the Congo: mineralogical description and pyrolysis kinetics

The Democratic Republic of the Congo holds important reserves of oil shale which is still under geological status. Herein, the characterization and pyrolysis kinetics of type I kerogen-rich oil shale of the western Central Kongo (CK) were investigated. X-ray diffraction, Fourier-transform infrared spectroscopy and thermal analysis (TG/DTA) showed that CK oil shale exhibits a siliceous mineral matrix with a consistent organic matter rich in aliphatic chains. The pyrolysis behavior of kerogen revealed the presence of a single mass loss between 300 and 550 °C, estimated at 12.5% and attributed to the oil production stage. Non-isothermal kinetics was performed by determining the activation energy using the iterative isoconversional model-free methods and exhibits a constant value with E = 211.5 ± 4.7 kJ mol−1. The most probable kinetic model describing the kerogen pyrolysis mechanism was obtained using the Coats–Redfern and Arrhenius plot methods. The results showed a unique kinetic triplet confirming the nature of kerogen, predominantly type I and reinforcing the previously reported geochemical characteristics of the CK oil shale. Besides, the calculation of thermodynamic parameters (ΔH*, ΔS* and ΔG*) corresponding to the pyrolysis of type I kerogen revealed that the process is non-spontaneous, in agreement with DTA experiments.

Influence of Light and Temperature on the Extractability of Cerium(IV) as a Surrogate of Plutonium(IV) and its Effect on the Simulation of an Accidental Fire in the PUREX Process.

Modeling of plutonium(IV) behavior during an accidental fire in a reprocessing plant was considered using various non-radioactive metallic surrogates. Among those elements, cerium(IV) was supposed to be a suitable candidate due to possible formation of a complex with TPB, but its extractability and stability have not been studied previously under representative plutonium uranium reduction extraction (PUREX) conditions. In this work, we investigated the chemical analogy between cerium(IV) and plutonium(IV) in this extractive process and combustion thereof. Distribution ratios are reported for acidities of 1–4 mol L–1 in equal volumes of nitric acid and a 30:70 mixture of tributylphosphate and hydrogenated tetrapropylene. The influences of light, temperature, and extraction time were studied by UV–vis spectroscopy. The results showed that cerium(IV) is extracted quantitatively but is reduced over time to cerium(III) in the organic mixture. Spectrophotometric investigations of this reaction kinetics revealed an apparent rate constant k of 0.021 ± 0.002 mol0.5 L0.5 min–1 at 298 K and an apparent fractional reaction order of 0.5. The activation energy of this reduction was found to be around 82 ± 2 kJ mol–1 by the Arrhenius plot method. The combustion of mono- and biphasic solutions prepared with a cerium(IV) concentration of 10 g L–1 revealed that the extracted complexes, Ce2O·6NO3·3TBP(org) or Ce4O4·8NO3·6TBP(org), are reduced during the combustion. Compositions of the resulting ashes and soot were analyzed and highlighted the presence of pyrophosphates and polycyclic aromatic hydrocarbons, with some traces of cerium. Ce(IV) is not suitable to represent Pu(IV) from a chemical point of view in HNO3/TBP–HTP solutions.

Kinetic Parameters Determination of Biomass Pyrolysis Fuels Using TGA and DTA Techniques

A TG/DTG and DTA measurements are used to determine the kinetics of the thermal decomposition of two Egyptian biomasses (sugarcane bagasse and cotton stalks powders) at three heating rates of 10, 15 and 20 °C/min. Two distinct reaction zones were observed for the two biomasses. The direct Arrhenius plot method and integral method were applied to (TG/DTG) analysis for determination of kinetic parameters: activation energy, pre-exponential factor, and order of reaction. The weight loss curve showed that pyrolysis of sugarcane bagasse and cotton stalks took place mainly in the range of 200–500 °C. Also, the activation energy of a phase transition can be calculated directly from the DTA thermogram of each biomass material. Heating rates had little effect on the pyrolysis process, but the peak of the weight loss rate in the DTG curves shifted towards higher temperature with heating rate. The activation energy of the sugarcane bagasse powder obtained by the direct Arrhenius plot method are 48.25, 57.15 and 45.35 kJ/mol for the heat rate of 10, 15 and 20 °C/min, respectively. On the other side, the integral method shows larger values of the activation energy for sugarcane bagasse (82.5, 78.5 and 56.7 kJ/mol for the heat rate of 10, 15 and 20 °C/min, respectively). The activation energy of the cotton stalks powder obtained by the direct Arrhenius plot method are 100, 80 and 68 kJ/mol for the heat rate 10, 15 and 20 °C/min, respectively, but the integral method shows larger values of activation energy (100, 107 and 101 kJ/mol for the heat rate of 10, 15 and 20 °C/min, respectively). The calculated activation energy by DTA analysis was found to be 81.77 and 84.75 kJ/mol for sugarcane bagasse and cotton stalks, respectively. These values are, to some extent, in agreement with the data obtained by direct and integral methods. The cotton stalks are more reactive than the sugarcane bagasse.

Pyrolysis characteristics and kinetic parameters determination of biomass fuel powders by differential thermal gravimetric analysis (TGA/DTG)

The kinetics of the thermal decomposition of the two biomass materials (sugarcane bagasse and cotton stalks powders) were evaluated using a differential thermo-gravimetric analyzer under a non-isothermal condition. Two distinct reaction zones were observed for the two biomasses. The direct Arrhenius plot method and the integral method were applied for determination of kinetic parameters: activation energy, pre-exponential factor, and order of reaction. The weight loss curve showed that pyrolysis of sugarcane bagasse and cotton stalks took place mainly in the range of 200–500°C. The activation energy of the sugarcane bagasse powder obtained by the direct Arrhenius plot method ranged between 43 and 53.5kJ/mol. On the other side, the integral method shows larger values of activation energy (77–87.7kJ/mol). The activation energy of the cotton stalks powder obtained by the direct Arrhenius plot method was ranged between 98.5 and 100.2kJ/mol, but the integral method shows larger values of activation energy (72.5–127.8kJ/mol).

Measurement of Ionization Energies of Nitrogen in 4H-SiC by Traveling-Wave Method

The impurity bands and corresponding ionization energies of nitrogen atoms in a 4H-SiC crystal with a concentration of 1×1019 cm-3 are measured by a nondestructive and noncontact traveling-wave method. When a SiC sample was placed near the surface of a surface acoustic wave device, its conductivity can be obtained by measuring the attenuation of the piezo-potential traveling-wave grazing along the surface of the sample. Temperature-dependent conductivities corresponding to a freeze-out process of free carriers excited from nitrogen atoms were observed, and the corresponding ionization energies of the nitrogen atoms were estimated by the Arrhenius plot method. The ionization energies in the impurity bands originating from splits of the doping atoms at cubic and hexagonal sites in the carbon sublattice are 72.89 and 47.89 meV, respectively, at room temperature. The ionization energies are in good agreement with the results reported in other theoretical and experimental studies. We also found that the skin depth of the traveling wave in the sample is below 1 mm and that the mobility of the carriers is strongly affected by both ionized dopants and charged surface defects in the depletion region near the surface of the sample. The effects of the sample and traveling wave such as the polarization effects of the crystal and the frequency effects of the traveling wave are discussed.

Determination of kinetic properties of polyurethane foam decomposition for pyrolysis modelling

A non-fire-retardant and a fire retardant polyurethane foam are tested under a nitrogen environment using thermogravimetry at different heating rates of 1, 5, 20 and 60 °C min−1 to obtain the foams’ decomposition behaviours. During decomposition, both foams experience two major mass loss reactions with the second reaction consuming most of the fuel. Three graphical techniques applied to calculate the kinetic properties governing each reaction are kinetic analysis, the Arrhenius plot method and the inflection point methods. In general, these methods are compatible with the pyrolysis model within Fire Dynamics Simulator Version 5 and Gpyro. A normalised version of the inflection point methods is also developed to improve the suitability of the kinetic properties with the simplest decomposition scheme of the pyrolysis model. A consistent trend is noted in the calculated kinetic properties of both foams regardless of the calculation techniques applied.

Pyrolysis Characteristics of Rice Husk Using TG-DTG Analysis

The rice husk from China has been non-isothermally pyrolysed on thermogravimetric analyzer(TGA). The analyses were performed at different heating rates (20, 40, 60, 80, 100°C/min) up to 900°C with nitrogen as purge gas. The weight loss curve showed that the main pyrolysis of rice husk took place in the range of 200~500°C. On the basis of experiment data, a pyrolysis kinetic model was proposed. The kinetic parameters of activation energy(E) and frequency factor(A) were obtained by the Direct Arrhenius Plot Method. There was no clear relationship between activation energy and heating rate.

Kinetic Parameter Estimation of Lignite by Thermo-gravimetric Analysis

Abstract TGA studies of lignite have been carried out. Lignite sample from Gujarat, India have been non-isothermally pyrolyzed using thermogravimetric analyzer and kinetics of decomposition of lignite was studied by non-isothermal method. The sample was heated over a range of temperature from room temperature to 1000 °C with seven different heating rates of 5, 7, 10, 15, 20, 30, 50 °C min-1 and non- isothermal weight loss was recorded for all heating rates. The weight loss curve showed that pyrolysis of lignite took place mainly in the range of 200-500 °C. Two non-isothermal methods, namely the direct Arrhenius plot method and the integral method were applied for determination of kinetic parameters-activation energy (Ea) and frequency factor (A). The activation energy obtained by the direct Arrhenius plot method ranged between 60 kJ/mol to 92 kJ/mol. While the result obtained by integral method shows lesser value of activation energy (28 kJ/mol to 50 kJ/mol).

KINETICS OF ISOTHERMAL AND NON-ISOTHERMAL PYROLYSIS OF OIL SHALE

The kinetics of decomposition of Huadian oil shale was studied by non-isothermal and isothermal methods. The non-isothermal weight loss was recorded at different heating rates (2, 5, 10, 15 and 20 K/min) up to 873 K. Two nonisothermal methods were applied for determination of kinetic parameters: the direct Arrhenius plot method and integral method. The isothermal weight loss studies were carried out for one hour at different temperatures 623, 648, 673, 698 and 723 K. Activation energy and frequency factor were calculated. The kinetic parameters evaluated from isothermal and non-isothermal kinetic data were compared with each other. As for the two non-isothermal analysis models, the integral method shows lower deviation and hence provides a better fit of the data. The average results of non-isothermal experiments were similar to kinetic parameters determined by isothermal analysis.

Kinetics of pyrolysis and combustion of oil shale sample from thermogravimetric data

Thermogravimetric (TG) data of oil shale obtained at MI (Waste to Energy laboratory) were studied to evaluate the kinetic parameters for El-Lujjun oil shale samples. Different heating rates were employed simulating pyrolysis reaction using Nitrogen as purging gas up to ∼800°C. The extent of char combustion was found out by relating TG data for pyrolysis and combustion with the ultimate analysis. Due to distinct behavior of oil shale during pyrolysis, TG curves were divided into three separate events: moisture release; devolatization; and evolution of fixed carbon/char, where for each event, kinetic parameters, based on Arrhenius theory, were calculated. Three methods were used and compared: integral method; direct Arrhenius plot method; and temperature integral approximation method. Results showed that integral method is closer to the experiment, while no relationship was observed between activation energy and the heating rate.

Measuring temperature-dependent activation energy in thermally activated processes: A 2D Arrhenius plot method

Thermally activated processes are characterized by two key quantities, activation energy (E(a)) and pre-exponential factor (nu(0)), which may be temperature dependent. The accurate measurement of E(a), nu(0), and their temperature dependence is critical for understanding the thermal activation mechanisms of non-Arrhenius processes. However, the classic 1D Arrhenius plot-based methods cannot unambiguously measure E(a), nu(0), and their temperature dependence due to the mathematical impossibility of resolving two unknown 1D arrays from one 1D experimental data array. Here, we propose a 2D Arrhenius plot method to solve this fundamental problem. Our approach measures E(a) at any temperature from matching the first and second moments of the data calculated with respect to temperature and rate in the 2D temperature-rate plane, and therefore is able to unambiguously solve E(a), nu(0), and their temperature dependence. The case study of deep level emission in a Cu(In,Ga)Se(2) solar cell using the 2D Arrhenius plot method reveals clear temperature dependent behavior of E(a) and nu(0), which has not been observable by its 1D predecessors.

Decomposition of KMnO4 in different gases as a potential kinetics standard in thermal analysis

The assumption that potassium permanganate may serve as a kinetics standard in solid decomposition kinetics made a priori on the basis of the mechanism of the congruent dissociative vaporization of KMnO4 and its crystal structure was successfully supported experimentally. As expected, the decomposition rate of KMnO4 does not depend on the kind of foreign gas (He, air, CO2 and Ar) and on the measurement technique (isothermal or dynamic). Other requirements for KMnO4 as an ideal kinetics standard are satisfied as well. The use of the third-law method for determining the molar enthalpy of a reaction \( \left( {\Updelta_{\text{r}} H_{\text{T}}^{\text{o}} / \nu } \right) \) provides an excellent reproducibility of results. The mean value of \( \Updelta_{\text{r}} H_{\text{T}}^{\text{o}} / \nu \) from 12 experiments in different gases is 138.3 ± 0.6 kJ mol−1, which coincides with the value of 138.1 kJ mol−1 calculated from the isothermal measurements in different gases by the second-law method. As predicted by theory, the random errors of the second-law and Arrhenius plot methods are 10–20 times greater. In addition, the use of these methods in the case of dynamic measurements is related to large systematic errors caused by an inaccurate selection of the geometrical (contraction) model. The third-law method is practically free of these errors.

Fundamental restrictions of the second-law and Arrhenius plot methods used in the determination of reaction enthalpies in decomposition kinetics

The apparent increase of the reaction enthalpy ΔH with temperature due to the self-cooling and condensation effects is responsible for the fundamental restrictions of the second-law and Arrhenius plot methods related to determination of this parameter. Theoretical analysis and a comparison with the experimental data indicate that the systematic underestimation of ΔH magnitudes determined by the second-law method equals 10–25% for the reactants decomposed to gaseous products and 15–50% for reactants decomposed to solids. Therefore, the use of these methods in decomposition kinetics is hardly acceptable. The replacement of the Arrhenius plot and second-law methods to the much more precise and accurate third-law method is desirable or even obligatory.

Kinetics and mechanism of solid decompositions — From basic discoveries by atomic absorption spectrometry and quadrupole mass spectroscopy to thorough thermogravimetric analysis

This paper sums up the evolution of thermochemical approach to the interpretation of solid decompositions for the past 25 years. This period includes two stages related to decomposition studies by different techniques: by ET AAS and QMS in 1981–2001 and by TG in 2002–2007. As a result of ET AAS and QMS investigations, the method for determination of absolute rates of solid decompositions was developed and the mechanism of decompositions through the congruent dissociative vaporization was discovered. On this basis, in the period from 1997 to 2001, the decomposition mechanisms of several classes of reactants were interpreted and some unusual effects observed in TA were explained. However, the thermochemical approach has not received any support by other TA researchers. One of the potential reasons of this distrust was the unreliability of the E values measured by the traditional Arrhenius plot method. The theoretical analysis and comparison of metrological features of different methods used in the determinations of thermochemical quantities permitted to conclude that in comparison with the Arrhenius plot and second-law methods, the third-law method is to be very much preferred. However, this method cannot be used in the kinetic studies by the Arrhenius approach because its use suggests the measuring of the equilibrium pressures of decomposition products. On the contrary, the method of absolute rates is ideally suitable for this purpose. As a result of much higher precision of the third-law method, some quantitative conclusions that follow from the theory were confirmed, and several new effects, which were invisible in the framework of the Arrhenius approach, have been revealed. In spite of great progress reached in the development of reliable methodology, based on the third-law method, the thermochemical approach remains unclaimed as before.

Interaction of D2 with H2O amorphous ice studied by temperature-programed desorption experiments

The gas-surface interaction of molecular hydrogen D2 with a thin film of porous amorphous solid water (ASW) grown at 10 K by slow vapor deposition has been studied by temperature-programmed-desorption (TPD) experiments. Molecular hydrogen diffuses rapidly into the porous network of the ice. The D2 desorption occurring between 10 and 30 K is considered here as a good probe of the effective surface of ASW interacting with the gas. The desorption kinetics have been systematically measured at various coverages. A careful analysis based on the Arrhenius plot method has provided the D2 binding energies as a function of the coverage. Asymmetric and broad distributions of binding energies were found, with a maximum population peaking at low energy. We propose a model for the desorption kinetics that assumes a complete thermal equilibrium of the molecules with the ice film. The sample is characterized by a distribution of adsorption sites that are filled according to a Fermi-Dirac statistic law. The TPD curves can be simulated and fitted to provide the parameters describing the distribution of the molecules as a function of their binding energy. This approach contributes to a correct description of the interaction of molecular hydrogen with the surface of possibly porous grain mantles in the interstellar medium.

Thermal stability evaluation of palm oil as energy transport media

The thermal stability of palm oil as energy transport media in a hydraulic system was studied. The oils were aged by circulating the oil in an open loop hydraulic system at an isothermal condition of 55 °C for 600 h. The thermal behavior and kinetic parameters of fresh and degraded palm oil, with and without oxidation inhibitor, were studied using the dynamic heating rate mode of a thermogravimetric analyser (TGA). Viscometric properties, total acid number and iodine value analyses were used to complement the TGA data. The thermodynamic parameter of activation energy of the samples was determined by direct Arrhenius plot and integral methods. The results may have important applications in the development of palm oil based hydraulic fluid. The results were compared with commercial vegetable based hydraulic fluid. The use of F10 and L135 additives was found to suppress significantly the increase of acid level and viscosity of the fluid.

Thermo-oxidative reactions of Nigerian oil sand bitumen

The thermal behavior of the Nigerian oil sand bitumen in an oxidizing environment was studied using non-isothermal thermogravimetric analysis (TGA) and differential thermal analysis (DTA). This condition can occur during in situ thermal recovery. The kinetics of the reactions was also determined by Arrhenius plot method. Three regions of weight loss corresponding to low-temperature oxidation, fuel deposition and high temperature oxidation were identified. Increasing the heating rate caused a shift in the reaction regions and peak temperatures to higher temperatures. No effect of gas flow rate was observed on the reactions. The oil sands have lower peak temperatures and activation energies compared with their corresponding bitumen extracts, suggesting a catalytic effect of sand on the reactions. The DTA revealed the exothermic nature of the reactions. The exothermicity increased with increasing heating rate. The results of this study showed that the heating rate and the presence of sand have significant effect on the thermo-oxidative reactions of the bitumen.

Kinetics of the thermal decomposition of oil shale from Puertollano (Spain)

The kinetics of the thermal decomposition of Spanish oil shale was studied using isothermal and non-isothermal thermogravimetric analyses (TGA). The isothermal TG data were studied at different particle sizes (0.250×10 −3, 0.505×10 −3 and 0.925×10 −3 m) and three temperature plateaux (703, 688 and 673 K). For the kinetic analysis, the Integral Method was used. The non-isothermal weight-loss data was analysed at different heating rates (5, 10, 15, 20 and 50 K/min) up to 1173 K and for a particle size of 0.250×10 −3 m. Three methods were applied for the determination of the kinetic parameters: the Direct Arrhenius Plot Method, the Integral Method and the Differential Method. From an engineering point of view, the rate of the thermal decomposition of Spanish oil shale can be suitably described by overall first-order kinetics. We also found that transport effect problems affected the observed rate when the heating rates were higher than 10 K/min; additionally, no mass and heat transfer resistance was observed for the different particle sizes studied. The results obtained from the isothermal method give an apparent activation energy of 150 kJ/mol and a frequency factor of 2.11×10 8 s −1, while for the non-isothermal method these results were: E=167 kJ/mol and A=2.16×10 9 s −1. The pyrolysis rates of Spanish shale are compared with those of Anvil Points, Clear Creek and Moroccan shale.