Kissinger Equation Research Articles

Non-isothermal crystallization kinetics of the Zr50Cu34Al8Ag8 amorphous alloy

The crystallization kinetics of Zr50Cu34Al8Ag8 bulk metallic glass, under non-isothermal condition, is investigated using differential scanning calorimetry. The activation energies for crystallization of the alloy are calculated using the Kissinger and Ozawa equations. The crystallization mechanism of amorphous alloy under continuous heating is explored via the improved Johnson-Mehl-Avrami equation. The local avrami index is mainly in the range of 2 to 2.5, which indicates that the crystallization is mainly governed by diffusion-controlled three-dimensional growth with a decreasing nucleation rate.

Preparation and Crystallization of Magnetic Glass-Ceramics from the Residues after Sulfur Release and Iron Recovery from Copper Ore Tailings with Varied CaO Content.

To comprehensively reuse copper ore tailings (COT), the fabrication of glass‐ceramics by the direct sintering method was investigated, where the residues after sulfur release and iron recovery from copper ore tailings were used as raw materials. The effect of the CaO added on the fabrication of glass‐ceramics was emphasized. After analysis of chemical composition and thermodynamics, crystallization kinetics were analyzed by Differential Scanning Calorimetry (DSC) and fitted to the Kissinger equation. The crystal phase and microstructure of sintered glass‐ceramics heated between 1080 °C and 1100 °C were estimated by X‐Ray diffraction analysis (XRD) and Scanning Electron Microscopy (SEM), respectively. Furthermore, the effects of the addition of CaO on the properties of the sintered glass‐ceramics have been discussed. The results showed that the magnetic glass‐ceramics were sintered by the residues successfully, the color of which was lighter than that of glass‐ceramics sintered by raw materials before iron recovery. According to the XRD analysis, hedenbergite, wollastonite and sekaninaite were formed with traces of maghemite and quartz. In terms of crystallization kinetics and sintering results, a decrease in the activation energies of crystallization and in sintering temperature were observed for an increase in the addition of CaO of up to 10 wt.%. Moreover, the properties of the sintered glass‐ceramics, including bulk density, linear shrinkage and flexural strength, were enhanced, while water absorption and true density were reduced with the increase of the amount of CaO added.

Design, synthesis, and water resistance properties of bis(4‐maleimidephenyl) adamantane and hybrid resins

AbstractA novel bismaleimide (BMI) resin, bis(4‐maleimidephenyl) adamantane (BMA), was successfully designed and synthesized by a facile, green, and economic route. Chemical structures were characterized and confirmed by Fourier transform infrared (FT‐IR) and proton nuclear magnetic resonance (1H NMR) spectra. Curing kinetics was investigated by the non‐isothermal curing method, and the apparent activation energy (Ea) and reaction order were further calculated by Kissinger and Ozawa equations. Compared with typical BMI resin, the heat resistance of BMA resin is significantly improved. According to thermogravimetric (TG) analysis, the decomposition temperature of 10% weight loss (T10) is about 504.3°C in N2 and 486.4°C in air atmosphere. Furthermore, BMA resin displays very excellent solubility in some organic solvents. After diamine chain expansion, BMA resin would possess the wider processing window, higher thermal stability, dielectric and water resistance properties, which could be widely applied as an matrix of advanced composites.

Determination of recrystallization temperature of deformed high-purity Al assessed by internal friction technique

In this study, the recrystallization process in deformed high-purity aluminum was investigated by using the internal friction (IF) and hardness measurement. In the heating process, two IF peaks were detected when the heating rate is 2 °C/min: a sharp peak (P1 peak) at ~139 °C and a wide peak (P2 peak) at ~278 °C (0.5 Hz). In the subsequent cooling process, the P1 peak disappears while the P2 peak remains. The P2 peak shifted towards higher temperatures with increasing frequency and can be ascribed to grain boundary relaxation. For the P1 peak, however, its position did not change with increasing frequency but shifted towards higher temperatures with increasing heating rate in the range of 1–5 °C/min, and the corresponding modulus varied abnormally in the temperature range of 115–160 °C. These facts indicated that the P1 peak is a non-relaxational peak and can be ascribed to the recrystallization process. The recrystallization activation energy deduced via the shift of peak position with heating rate by using the Kissinger equation is 57± 3 kJ/mol, which is as same as that deduced from the classical isothermal recrystallization process as assessed by microhardness measurement. The classical isothermal recrystallization temperature can be deduced from the peak temperature of P1 peak by simply adjusting the heating rate. This provided a method to determine the recrystallization temperature via internal friction measurement in a continuously heating process, which needs only two or three samples.

The Curing Kinetics of E-Glass Fiber/Epoxy Resin Prepreg and the Bending Properties of Its Products.

The curing kinetics can influence the final macroscopic properties, particularly the three-point bending of the fiber-reinforced composite materials. In this research, the curing kinetics of commercially available glass fiber/epoxy resin prepregs were studied by non-isothermal differential scanning calorimetry (DSC). The curing kinetic parameters were obtained by fitting and the apparent activation energy Ea of the prepreg, the pre-exponent factor, and the reaction order value obtained. A phenomenological nth-order curing reaction kinetic model was established according to Kissinger equation and Crane equation. Furthermore, the optimal curing temperature of the prepregs was obtained by the T-β extrapolation method. A vacuum hot pressing technique was applied to prepare composite laminates. The pre-curing, curing, and post-curing temperatures were 116, 130, and 153 °C respectively. In addition, three-point bending was used to test the specimens’ fracture behavior, and the surface morphology was analyzed. The results show that the differences in the mechanical properties of the samples are relatively small, indicating that the process settings are reasonable.

Thermal degradation characteristics and kinetic study of camel manure pyrolysis

An alternate and sustainable utilisation of camel dung waste has been investigated in this study. The pyrolysis degradation characteristics of camel dung have been investigated using a thermogravimetric analyser and the same has been compared with the gasification decomposition behaviour of the dung. The pyrolysis analyses were performed at heating rates of 10, 20, and 50 K/min from room temperature to 1173 K under an inert N2 atmosphere. The pyrolytic kinetics were estimated using different models such as Coats-Redfern, Friedman, Distributed activation energy, Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa, and Starink. The average activation energy values were consistent (162–172 kJ/mol) for all the models. Comparison of pyrolysis kinetics with gasification kinetics indicated that the camel dung requires more activation energy for the pyrolysis decomposition. The estimated activation energy values and the Kissinger equation were used to determine the thermodynamic properties such as Gibbs free energy, enthalpy, and entropy. The Gibbs free energy and enthalpy values of the pyrolysis degradation were lower than in the case of the gasification decomposition. The details of these kinetic parameters and thermodynamic properties are vital for the design and fabrication of pyrolysis reactors.

On the Cr-rich continuous and discontinuous precipitation kinetics in Ni-Cr alloys by microstructural characterization and differential scanning calorimetry analysis

Microstructural dependence of continuous and discontinuous Cr-rich precipitation kinetics in Ni-45%Cr alloys on composition and thermal history was investigated by microstructure characterization and differential scanning calorimetry (DSC). The results indicated that discontinuous precipitation was favored at low temperatures and high Cr contents, while continuous precipitation was favored at high temperatures. Activation energies estimated by Kissinger equation using DSC and microstructural evolution showed that Nb and B suppressed, but Zr promoted discontinuous precipitation. It provided a simple effective method to figure out the effect of additions on precipitation kinetics.

Combining Source Rock Kinetics and Vitrinite Reflectance in Source Rock Evaluation of the Bakken Formation, Williston Basin, USA.

The elements of Bakken Petroleum System consist of two source rocks with high underlying burial depths for significant hydrocarbon generation. However, this deep hydrocarbon generation process is dependent on its kinetic properties, thermal maturity, and geochemical properties. The statistical compensation effect is a complicating factor in the kinetic analyses of the Bakken Formation. In this study, we experimentally determined the kinetics of the Bakken formation source beds, observed the presence of the residual compensation effect, and numerically established a correlation between the kinetic parameters, thermal maturity indices (Tmax), and the vitrinite reflectance (VRo) and bitumen reflectance (BRo). First, we conducted source rock analysis to determine kinetic properties and the organic geochemical assays of reactive kerogen in the Bakken source beds. Finally, we incorporated previous established studies to generate numerical correlation for Tmax in terms of VRo and BRo reflectance. Our kinetic results show evidence of the residual compensation effect in the Bakken Formation when samples are repeatedly analyzed. The simultaneous linear expression of the residual compensation effect and the regression analysis of the solutions to the Kissinger equation for heating rate, yielded a kinetic parameter solution that correlates with Tmax. Furthermore, recalculated Tmax values established a correlation between the kinetic parameters, Tmax, VRo, and BRo. The application of state-of-the-art numerical correlations to measure subsurface kinetics, source rock richness, and burial-depth temperatures will enhance the accuracy of reservoir exploration and hydrocarbon production within the Bakken Formation.

Non-Isothermal Crystallization Kinetics of Poly(Ethylene Glycol)-Poly(l-Lactide) Diblock Copolymer and Poly(Ethylene Glycol) Homopolymer via Fast-Scan Chip-Calorimeter.

The non-isothermal crystallization kinetics of double-crystallizable poly(ethylene glycol)–poly(l-lactide) diblock copolymer (PEG-PLLA) and poly(ethylene glycol) homopolymer (PEG) were studied using the fast cooling rate provided by a Fast-Scan Chip-Calorimeter (FSC). The experimental data were analyzed by the Ozawa method and the Kissinger equation. Additionally, the total crystallization rate was represented by crystallization half time t1/2. The Ozawa method is a perfect success because secondary crystallization is inhibited by using fast cooling rate. The first crystallized PLLA block provides nucleation sites for the crystallization of PEG block and thus promotes the crystallization of the PEG block, which can be regarded as heterogeneous nucleation to a certain extent, while the method of the PEG block and PLLA block crystallized together corresponds to a one-dimensional growth, which reflects that there is a certain separation between the crystallization regions of the PLLA block and PEG block. Although crystallization of the PLLA block provides heterogeneous nucleation conditions for PEG block to a certain extent, it does not shorten the time of the whole crystallization process because of the complexity of the whole crystallization process including nucleation and growth.

Study on the Al2O3p/Al composites prepared by Al-calcined kaolin system

In this study, in-situ Al2O3p/Al composite was prepared by the exothermic dispersion method from Al-calcined kaolin system. Thermodynamic analysis was carried out by calculating Gibbs free energy. The reaction kinetics of the system was studied by differential scanning calorimetry and Kissinger equation. The effects of heating temperature and holding time on the microstructure of the composites were analysed. The results showed that the reaction activation energy of the system continued to increase with the progress of the reaction. With the extension of the reaction time at 800°C, the particle size of Al2O3 increased slowly. When the holding time was 50 min, the density and hardness of the composite material were 2.7 g cm−3 and 64HV respectively.

Characterization of microstructure, hydrogen storage kinetics and thermodynamics of ball-milled Mg90Y1.5Ce1.5Ni7 alloy

In this work, the Mg90Y1.5Ce1.5Ni7 sample is successfully prepared by combining the vacuum induction melting and the mechanical milling. The phase composition and microstructure characteristics are studied by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy measurements. The hydrogenated sample is composed of MgH2, Mg2NiH4, CeH2.73 phases, whereas only the MgH2 and Mg2NiH4 phases are decomposed during dehydrogenation. The hydrogen storage properties of Mg90Y1.5Ce1.5Ni7 samples are measured by semi-automatic Sievert type apparatus. It is found that the samples could be fully activated within three cycles of absorption and dehydrogenation, with a reversible hydrogen storage capacity of about 5.6 wt%. Also, the “optimal hydrogenation temperature” is reduced to 200 °C, and the dehydrogenation activation energy is calculated to be 68.2 kJ/mol and 65.8 kJ/mol by using the Arrhenius and Kissinger equations, respectively. This work provides a scientific approach to promote the practical application of Mg-based alloy.

Identification of carbon nanomaterials by deconvolution of thermogravimetric analysis signals

In order to link fundamental properties to performance in real-world applications, carbon nanomaterials, especially carbon nanotubes, require detailed compositional information such as the number of distinct species, their relative amounts, and thermochemical data such as kinetic prefactors and activation energies for combustion. Thermogravimetric analysis (TGA) is used widely to measure these values, but the signals can be deceptive, especially with respect to the number of different nanomaterial types. In this work, the Fraser-Suzuki equation is used as the basis of a nonlinear least squares technique to deconvolute the mass loss curves of carbon nanotubes, confirming through subsequent use of the Kissinger equation that there are indeed multiple species present in the sample and they differ in their activation energies for combustion.

Preparation and curing behavior of latent 2‐PhIm‐PS microcapsule curing agent for epoxy resin

AbstractA core–shell microcapsule latent epoxy curing agent (2‐PhIm‐PS) is obtained by solvent evaporation method with 2‐phenyl imidazole (2‐PhIm) as the core material and polystyrene (PS) as the wall material. The microcapsule parameters, morphology, structure, curing behavior, and the mechanic properties of cured epoxy resin with this microcapsule latent curing agent were characterized through comparing with 2‐PhIm. The particle size distribution of the microcapsule is narrow, the average particle size is about 10.56 μm, and the core material content is 23%. The prepared 2‐PhIm‐PS microcapsule curing agent has excellent latent curing properties. It can completely cure epoxy resin E‐51 within 10 min at 130°C, and its latent period can be more than 40 days at room temperature. In addition, the curing kinetics of one‐component epoxy resin curing system (E‐51/2‐PhIm‐PS) composed of 2‐PhIm‐PS microcapsules and epoxy resin E‐51 is also studied by using Kissinger equation, Flynn–Wall–Ozawa and Crane formula. The results provide an outline for the evaluation on the applicability of the microcapsule curing agent of 2‐PhIm‐PS for epoxy resin.

Kinetics of non-isothermal cold crystallization in the antiferroelectric smectic phase of 3F5BFBiHex as seen by differential scanning calorimetry and broadband dielectric spectroscopy

The non-isothermal cold crystallization process from the antiferroelectric SmC*A phase of 3F5BFBiHex was studied by differential scanning calorimetry (DSC) and broadband dielectric spectroscopy (BDS) experiments in detail with various heating rates. DSC studies have revealed the complexity of the crystallization process. The use of the dielectric spectroscopy method allowed to describe the behavior of molecular l-process (reorientation molecules around the long axis) and collective (anti-phase phason) relaxation processes during cold crystallization. The amplitude of l-process decreases faster than the intensity of anti-phase phason process. The kinetics of non-isothermal crystallization process was analyzed in terms of Ozawa and Mo models. The use of the Ozawa model allowed to obtain the dimensionality parameter m and the crystallization constant rate Z. The energy barrier obtained using the Kissinger equation is almost the same in both DSC and BDS methods (51 kJ/mol). Energy barriers obtained by means of Augis-Bennett model for DSC data are around 10–20 kJ/mol smaller than those determined based on dielectric data.

Eriobotrya japonica Lindl. Kernels: Kinetics of Thermal Degradation under Inert Atmosphere Using Model-Free and Fitting Methods

A kinetic study of the pyrolysis process of raw Eriobotrya japonica Lindl. Kernels (RLK) was investigated using a thermogravimetric analyzer. The weight loss was measured in a nitrogen atmosphere. The samples were heated over a range of temperature from 298 K to 873 K with four different heating rates of 5, 10, 15, 20 K min-1. Mass loss (TGA) and derivative mass loss (DTG) measurements indicate that the increase in heating rate has no noticeable effect on the thermal degradation of the RLK. The results obtained from the thermal decomposition process indicate that there are three main stages such as dehydration, active, and passive pyrolysis. TGA curves indicate that active pyrolysis of RLK is between 160 and 450 °C. In this interval, a shoulder followed by a peak exists on the DTG plots. The shoulder corresponds to the decomposition of hemicelluloses, the first peak to that of cellulose. Lignin decomposes through all temperature range. The kinetic parameters such as activation energy and pre-exponential factor were obtained for two degradation steps by isoconversional model-free methods proposed by FWO, KAS, Kissinger, Tang, MKN, and FR, with degradation mode being: f(α)=(1-α)n with n = 1 for FR and g(α)=-Ln(1- α) for the other methods. The activation energy and pre-exponential factor obtained by the Kissinger method are 173 kJ/mol and 1.9×1016 min-1. While for free model methods, the average kinetic parameters calculated are 172-248 kJ.mol-1 and 5,30×1020 for integral methods (FWO, KAS, Tang and MKN) and 190-271 kJ.mol-1 and 1.77×1022 min-1 for differential Fr method. The activation energy decreases in the final stages of the process. The energy required for hemicellulose degradation is lower than that of cellulose. The most probable reaction functions have thus been determined for these two stages by Coats-Redfern and Criado method, leading to greatly improved calculation performance over the entire conversion range. The reaction, second-order F2, describes the pyrolysis reaction models of RLK. With the Arrhenius parameters obtained from the fitting model of CR, we attempt to reconstruct the temperature-dependent mass conversion curves and have resulted in generally acceptable results. Based on the Arrhenius parameter values obtained by Kissinger equation, the changes in entropy, enthalpy and Gibbs free energy, and lifetime predictions have been estimated concerning the thermal degradation processes of RLK.

Thermal Degradation, Kinetic Analysis and Char Formation in the Pyrolysis of Poly(melamine-co-phenolic resin) Copolymer

Understanding the mechanism of thermal degradation of a material may suggest a promising way for further improving its thermal properties. poly(melamine-co-phenolic resin) (P(M-co-PR)) has been widely used in flame resistant and fire-proof materials. Our characterization of the thermal degradation of P(M-co-PR) is described in this work. Fourier-transform infrared (FTIR) and X-ray photo-electron spectroscopy (XPS) analyses were used to investigate the structural evolution during the thermal degradation of the copolymer. The evolutions of C = N and C-N bonding in heteroaromatic rings were monitored during the degradation process by C1s and N1s XPS spectra. The degradation processes of P(M-co-PR) is divided into three stages. The degradation kinetics of P(M-co-PR) was researched by using the Ozawa and Kissinger activation energy equation methods. The conclusion is that the Kissinger equation applied to the first stage, and the Ozawa equation applied to the second and third stages.

On thermal decomposition kinetics of poly(ethylene-alt- tetrafluoroethylene) using an autocatalytic model

The thermal decomposition of a commercial poly(ethylene-alt-tetrafluoroethylene) (ETFE) Fluon®C-88AXP, in nitrogen atmosphere has been carried out using thermogravimetric analysis (TG) with dynamic method at different heating rates. The widely used Kissinger equation, Friedman's and Ozawa analysis are used to estimate the activation energy of the degradation reaction. Method of fitting the dynamic derivative thermogram (DTG) data directly using isothermal kinetic model is adopted and the model parameters have been obtained which could not be acquired by using the conventional methods. The TG data of Fluon®C-88AXP could not be described properly using n-order kinetic model but the autocatalytic Kamal model fits the data perfectly. The standard deviations of the calculated mass loss rates from the experimental results decrease from 1.497 × 10−6 to 0.138 × 10−6, with a decrease of 91 %, when Kamal model was used instead of n-order kinetics. This indicates that the thermal decomposition of ETFE in nitrogen atmosphere obeys an autocatalytic kinetics.

Synthesis and characterization of sol-gel derived monophasic mullite powder

Abstract High-purity microfine mullite precursor powder of stoichiometric chemical composition, 3Al2O3.2SiO2, was synthesized through the sol-gel route using aluminum isopropoxide and tetraethyl orthosilicate. The derived mullite precursor powder was characterized by BET surface area, particle size distribution, Fourier-transform infrared spectroscopy, thermogravimetry-differential thermal analysis (TG-DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy. Phase analysis of the precursor powder and calcined samples at different temperatures was done by XRD. Non-isothermal crystallization kinetics of mullite precursor was studied by TG-DTA in static air using heating rates of 5.0, 7.5, 10.0, 12.5, and 15 K.min-1. Grain morphology was studied by SEM. The results showed that synthesized mullite precursor powder possessed homogeneity of Al and Si components, and the amorphous precursor powder was converted to monophasic mullite crystal when heat-treated at 970 °C. Based on Flynn-Wall-Ozawa and Kissinger equations, the activation energy associated with the crystallization of mullite was determined to be 1189.8 and 1189.0 kJ.mol-1, respectively.

The Crystallization Mechanism of Zr-Based Bulk Metallic Glass during Electron Beam Remelting.

Bulk metallic glasses (BMGs) are promising for multifunctional and structural application in different industries. However, the limited size of BMGs hinders their further application. The welding of BMGs has shown the possibility of getting rid of the casting size limitation. The heat-affected zone (HAZ) and fusion zone (FZ) often undergo severe crystallization during the welding process. It is still unclear whether the crystallization occurs during the heating process or the cooling process. To figure out the crystallization mechanisms of Zr-based BMGs during the electron beam welding process, the Zr-based BMGs with the composition of Zr41.2Ti13.8Cu12.5Ni10Be22.5 were remelted by electron beam. The microstructures of the HAZ and the remelting zone (RZ) were analyzed. The thermal field of the electron beam welding was obtained by the finite element method (FEM). The critical conditions for crystallization during the heating and cooling processes were obtained by differential scanning calorimetry (DSC) and the Kissinger equation. The results show that the Zr41.2Ti13.8Cu12.5Ni10Be22.5 in the HAZ undergoes severe crystallization, while the Zr41.2Ti13.8Cu12.5Ni10Be22.5 in RZ keeps amorphous state after the remelting process. The low cooling rate in the HAZ is responsible for its crystallization.

Thermal Behavior Analysis of Melamine Modified Urea-Formaldehyde Resin with Different Molar Ratios

In this study, Thermogravimetry (TG) were used to analyze thermal degradation properties of two kinds of low-molar ratio of the melamine-modified urea-formaldehyde resin (MUF). The MUF was calculated using Kissinger equation and Flynn-Wall-Ozawa equation Resin pyrolysis activation energy. The results showed that the curing time of low mole was longer than that of MUF resin (muf-b), the content of free formaldehyde was lower, and the formaldehyde emission and wet bonding strength of plywood were reduced by 65.79% and 21.90%, respectively. TG test showed that the pyrolysis process of MUF resins with different molar ratios can be divided into three stages: dehydration, rapid pyrolysis and carbonization. At the same heating rate, the weight loss rate, peak conversion rate and carbon residue of the high molar ratio MUF resin (MUF-a) in the fast pyrolysis stage are larger than those of the MUF-b resin. The MUF-a resin pyrolysis activation energy is 166.76 kJ/mol, and the MUF-b resin pyrolysis activation energy is 95.30 kJ/mol. High molar ratio resin has higher pyrolysis activation energy and better thermal stability.