Flynn Wall Ozawa Method Research Articles

Kinetic modeling study on the combustion treatment of cathode from spent lithium-ion batteries.

Thermal treatment offers an alternative method for the separation of aluminum foil and cathode materials during spent lithium-ion batteries recycling. In this work, the combustion kinetic of cathode was studied based on six model-free (isoconversional) methods, namely Flynn-Wall-Ozawa (FWO), Friedman, Kissinger-Akahira-Sunose, Starink, Tang, and Boswell methods. The possible decomposition mechanism was also probed using a master-plots method (Criado method). Thermogravimetric analysis showed that the whole thermal process could be divided into three stages with temperatures of 37-578°C, 578-849°C, and 849-1000°C. The activation energy (Eα) derived from these model-free methods displayed the same trend, gradually increasing with a conversion range of 0.002-0.013, and significantly elevating beyond this range. The coefficients from the FWO method were larger, and the resulted Eα fell into the range of 10.992-40.298 kJ/mol with an average value of 20.228 kJ/mol. Comparing the theoretical master plots with an experimental curve, the thermal decomposition of cathode could be better described by the geometric contraction models.

Preparation of polyarylene ether nitriles/fullerene composites with low dielectric constant by cosolvent evaporation

Fullerenes are widely used to reduce the dielectric constant of composites due to their special hollow cage structure. However, the main challenge for the realization of its material potential application is to improve the interfacial compatibility between the polymer matrix and fullerenes. Here we report a pure physical method of cosolvent evaporation to prepare polyarylene ether nitriles (PEN) composite films with well-defined monodisperse clusters of fullerenes for manufacturing flexible printed circuit boards. The presence of fullerenes is proven to be crucial to decrease the dielectric constant of composite films. The film with 3 wt% fullerenes loading possesses the lowest dielectric constant of 2.65 at 1 MHz, and its service life is detected as 3.3 years by Flynn–Wall–Ozawa method. Additionally, when the composite films used in flexible copper clad laminate (FCCL), the 180° peeling strength between the resin and copper foil is 6.91 N cm−1. Therefore, this PEN/fullerene composite provides potential application for the preparation of FCCL.

Pyrolysis kinetics behavior of solid leather wastes

In the leather industry, considerable amounts of non-recyclable solid leather wastes (SLWs) are produced and accumulated in factories. In this work, the non-isothermal thermochemical analysis (TGA) test was used to analyse the thermal degradation behaviour of chromium-tanned leather shaving, which is one of the main SLWs. The pyrolysis experiments were carried out under nitrogen atmosphere from 30 to 800 °C at different heating rates of 5, 10, 15 and 20 °C/min. Three different kinetic models, including the Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS) and Kissinger methods, were used to calculate the kinetic parameters. The activation energy values calculated by FWO and KAS methods were 391.79 and 348.77 kJ/mol, respectively. In consideration of the high HHV (14.15 MJ/kg) and carbon productivity (10.15%), SLWs could represent a potential candidate material for bioenergy production and carbon preparation. These results could be used for the design of thermochemical conversion processes utilizing SLWs as feedstock.

Experimental Investigation on the Energy Consumption, Physical, and Thermal Properties of a Novel Pellet Fuel Made from Wood Residues with Microalgae as a Binder

Co-pelletization of waste biomass and microalgae is an attractive option for using bioenergy efficiently. This work investigates the potential of microalgae as a binder to improve the energy consumption and physical and thermal properties of a novel pellet. Wood waste biomass was blended with microalgae in proportions of 15%, 30%, and 50% to investigate its properties using a single pelleting device and thermodynamic analysis. The results showed that, under the conditions of temperature (80–160 °C), pressure (120–200 MPa), and moisture content (6%–14%), blending microalgae can effectively increase the bulk density and mechanical durability of the pellets by 9%–36% and 0.7%–1.6%, respectively, and can significantly reduce the energy consumption of pelleting by 23.5%–40.4%. Blending microalgae can significantly reduce the energy consumption of pelleting by 23.5%–40.4%. Moreover, when the amount of Chlorella vulgaris powder (CVP) is 50%, a maximum bulk density (BD) of 1580.2 kg/m3, a durability (DU) of 98%, and a minimum energy consumption of 25.2 kJ/kg were obtained under the optimum conditions of temperature (120 °C), pressure (120 MPa), and moisture content (10%), respectively. Besides, the interaction between the microalgae and sawdust does exist, and their effect on the co-combustion process is inhibitive (0–300 °C) and accelerative (300–780 °C). When the amount of microalgae was 15%, the average activation energy of the pellet was a minimum value, which was 133.21 kJ/mol and 134.60 kJ/mol calculated by the Kissinger–Akahira–Sunose method and Ozawa–Flynn–Wall method, respectively. Therefore, the energy consumption, physical, and thermal properties of the novel pellet could be improved and meet the ISO standard (International Organization for Standardization of 17225, Geneva, Switzerland, 2016) by blending 15% of microalgae. Overall, the use of microalgae as a binder can indeed improve pellet quality, and it can be considered a significant way to utilize microalgae in the future.

Pyrolysis and kinetic behaviour of black gram straw using thermogravimetric analysis

ABSTRACT The present study aims to investigating the thermal behavior and pyrolysis kinetics of Black Gram Straw (BGS) degradation using thermogravimetric analyzer at three heating rates (20, 30 and 40°C/min). TGA results showed maximum decomposition took place in the temperature range of 180 to 380°C. Three different iso-conversional models Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), and Starink methods were applied on TGA results to calculate the kinetic and thermodynamic parameters. Average activation energies from FWO, KAS, and Starink methods were 172.96, 172.81, and 172.54 kJ/mol and pre-exponential factors ranged from 1010 to 1017 s−1 respectively. Differences between Eα and ∆H*values (~5 kJ/mol) showed the formation of the activation complex is being favored. The values of ∆G* and ΔS*varied from 166.99 to 167.01kJ/mol and −66.61 to 70.13J/mol, respectively. The above kinetics, thermodynamic data can be of massive benefit to modeling, designing and developing a suitable thermochemical conversion system of black gram stalk to energy carrier.

Non-isothermal kinetic analysis of the combustion of argan shell biomass

Abstract Argan shell is one of the main by-products during argan oil production. It is considered as an attractive, cheap and renewable biomass source for sustainable energy utilization. The present paper reports on combustion characteristics of argan shell in order to evaluate their potential for thermochemical conversion. Combustion studies using thermogravimetry (TG) are performed at four different heating rates of 5, 10, 15 and 20 °C·min−1. Kinetic parameters under non-isothermal condition are calculated using FWO (Flynn-Wall-Ozawa method) and KAS (Kissinger-Akahira-Sunose) model free methods. From the results obtained, it was revealed that when the conversion level (α) fluctuates between 0.1 and 0.55, the average activation energy were 154 and 145 KJ/mol for FWO and KAS methods, respectively. Then, it decreases drastically with α ≥ 0.6, reflecting the kinetic complexity of the combustion process characterized by a faster reaction caused by the intense devolatilization stage. Overall, the results highlight the potential use of argan shell as a biomass product for thermal conversion through combustion.

Thermal decomposition and kinetics of electrically controlled solid propellant through thermogravimetric analysis

The thermal decomposition behavior of electrically controlled solid propellant (ECSP) with hydroxyl ammonium nitrate as oxidizer and polyvinyl alcohol as binder was investigated through thermogravimetric analysis and differential scanning calorimetry coupling technology at the heating rates of 15, 20, 25, 30, and 35 K min−1 in nitrogen. Results indicated that the Tinitial and Tmax values of the thermal decomposition of ECSP increase with heating rates. The activation energy Eα from the results of TG data at various heating rates was calculated by model-free isoconversional Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) methods. The activation energies obtained through the FWO method were close to those obtained through the KAS method, and the values for activation energy were located between 42.82 and 48.49 kJ mol−1. An appropriate reaction mechanism conversion model for ECSP was determined by Malek and Coats–Redfern methods. Thermal decomposition kinetics of the ECSP obeyed the random nucleation and subsequent growth model, called Avrami–Erofeev function.

Pyrolysis characteristics of oil-field sludge and the comparison of kinetic analysis with two representative methods

The pyrolysis of oil-field sludge (OS) has the appeal of resource recovery for this kind of waste disposal. In this paper, we investigate the pyrolysis kinetics of OS with Coast-Redfern (CR) and Flynn-Wall-Ozawa (FWO) methods in a wide temperature range (305–1223 K). The pyrolysis process of OS mainly includes light organics vaporization (Stage-2), middle and heavy organics and carbonates decomposition (Stage-3), coke reduction and other inorganics decomposition (Stage-4). The kinetic analysis manifests that Stage-2 meets well with the reaction order mechanism, and the reaction order (n) is 2 and in the range of 1.3–1.9 obtained by CR and FWO, respectively. The divergence of the two methods mainly appears in Stage-3, where Ea calculated by FWO method is much higher than that by CR method. CR method gives D1 model for this stage, while FWO method picks D3 model to describe this stage. The simulation plots indicate that the results of CR method are more credible. As for Stage-4, both methods select G(α) = α as the mechanism, but CR method performs better agreement and a smaller discrepancy than FWO method does. Thus, FWO method is considered less accurate for OS analysis.

Pyrolysis and combustion characteristics and kinetics of wood sawdust and wood sawdust hydrochar

AbstractThis study compares the pyrolysis and combustion characteristics with the kinetics of wood sawdust and its hydrochar. Wood sawdust hydrochar was obtained by the hydrothermal treatment of wood sawdust (biomass/water: 1 g/4 mL) at 220°C, where the residence time was set as 90 min. After hydrothermal carbonization, carbon content and heating value were both increased by 14%. Pyrolysis and combustion of wood sawdust and its hydrochar were performed by thermogravimetric analysis at 10, 20, 30, and 40°C/min. Kissinger–Akahira–Sunose (KAS) method, Friedman method, Flynn–Wall–Ozawa (FWO) method, and Kissinger method were used for analyzing the pyrolysis data. For combustion, only KAS and FWO methods were used to determine the kinetic parameters. As compared to wood sawdust pyrolysis, average activation energy of hydrochar pyrolysis was lower (150.36 kJ/mol by using KAS method, 153.05 kJ/mol by using FWO method). Based on mean activation energies, pyrolysis reaction of hydrochar was more favorable than its combustion. In combustion, average activation energy of hydrochar combustion reaction was higher; indicating that combustion of wood sawdust was more favorable.

Spinodal decomposition and martensitic transformation kinetics of the 82.2Mn-15.8Cu-2Al thermosensitive damping alloy

Mn-Cu alloys with a high manganese content are traditional damping alloys. In this study, the effects of cyclic annealing on the spinodal decomposition of the 82.2Mn-15.8Cu-2Al(at%) alloy and the martensitic transformation and reverse martensitic transformation of the manganese-rich phase were investigated using differential scanning calorimetry (DSC) analysis, scanning electron microscopy, energy dispersive X-ray spectroscopy, internal friction analysis, and X-ray diffraction analysis. The apparent activation energy and the logarithm of the pre-exponential factor of the spinodal decomposition of the alloy and reverse martensitic transformation were calculated by the Friedman’s and Ozawa–Flynn–Wall methods. The results showed that the cyclic annealing temperature (Ta) and the cyclic annealing number (C) affect the degree of spinodal decomposition. When Ta and C increased, the heat hysteresis of the alloy became narrow. The DSC results showed that the heat hysteresis was only 0.8 K when Ta =693 K for C = 9.

Pyrolysis kinetic study of waste milk packets using thermogravimetric analysis and product characterization

This work deals with the study of kinetic evaluation and pyrolysis of waste milk packets (polyethylene) for oil production. Thermogravimetric analysis (TGA) of waste milk packets was conducted in an inert atmosphere with heating rates of 5, 10 and 20 °C min−1 to analyse its thermal degradation behaviour. Pyrolysis kinetic parameters consist of activation energy and pre-exponentiation factor, and thermodynamic parameters include changes in Gibb’s free energy, enthalpy and entropy which were computed by Kissinger–Akahira–Sunose (KAS), Ozawa–Flynn–Wall (OFW) and Coats–Redfern methods using TGA data. The mean value of activation energy for pyrolysis of waste milk packets computed by KAS and OFW methods was 175.36 and 177.94 kJ mol−1, respectively, and the pre-exponential factors were found to be in the range of 1.37 × 1013–1.54 × 1014 min−1. Thermal pyrolysis of waste milk packets was performed in a semi-batch pyrolysis reactor. The maximum yield of oil was obtained as 45 wt% at pyrolysis temperature of 500 °C. The oil was analysed by ultimate analysis, Fourier transform infrared spectroscopy (FTIR) and gas chromatography–mass spectrometry (GC–MS). Chemical compounds present in oil were mainly paraffins, naphthenes and olefins with carbon number range of C9–C18. The boiling point of oil was found in the range of 63–360 °C.

Determination of activation energy during the thermal degradation of Polyamide 66/glass fiber composites

The objective of this study was to clarify the mechanical properties and the non-isothermal degradation kinetics of Polyamide 66 (PA 66)/glass fiber (GF) composites. The non-isothermal degradation behavior of the samples was studied by thermal gravimetric analysis under nitrogen purge. The perfect compatibility of GFs with polymer matrix in composites was studied by scanning electron microscopy. It was found that with increasing content of GFs in samples due to good distribution of fibers in PA 66, the degradation temperature and calculated activation energy in composites increased in all heating rates. The activation energy was calculated by the Flynn–Wall–Ozawa method (isoconversional method). It was concluded that the model-free methods can be a reliable way to determine the kinetic parameters. Furthermore, the isokinetic relationship was used to estimate a model-independent pre-exponential factor (ln A) corresponding to a given degree of conversion.

Catalytic pyrolysis of Chlorella vulgaris: Kinetic and thermodynamic analysis

In the present study, catalytic pyrolysis of Chlorella vulgaris biomass was conducted to analyse the kinetic and thermodynamic performances through thermogravimetric approach. HZSM-5 zeolite, limestone (LS), bifunctional HZSM-5/LS were used as catalysts and the experiments were heated from 50 to 900 °C at heating rates of 10–100 °C/min. Iso-conversional model-free methods such as Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS), Starink’s, and Vyazovkin (V) were employed to evaluate the kinetic parameters meanwhile the thermodynamic parameters were determined by using FWO and KAS methods. The calculated EA values of non-catalytic and catalytic pyrolysis of HZSM-5 zeolite, LS, and bifunctional HZSM-5/LS were determined to be in the range of 156.16–158.10 kJ/mol, 145.26–147.84 kJ/mol, 138.81–142.06 kJ/mol, and 133.26 kJ/mol respectively. The results have shown that catalytic pyrolysis with the presence of bifunctional HZSM-5/LS resulted to a lower average EA and ΔH compared to HZSM-5, and LS which indicated less energy requirement in the process.

Critical Appraisal of Kinetic Calculation Methods Applied to Overlapping Multistep Reactions.

Thermal decomposition of solids often includes simultaneous occurrence of the overlapping processes with unequal contributions in a specific physical quantity variation during the overall reaction (e.g., the opposite effects of decomposition and evaporation on the caloric signal). Kinetic analysis for such reactions is not a straightforward, while the applicability of common kinetic calculation methods to the particular complex processes has to be justified. This study focused on the critical analysis of the available kinetic calculation methods applied to the mathematically simulated thermogravimetry (TG) and differential scanning calorimetry (DSC) data. Comparing the calculated kinetic parameters with true kinetic parameters (used to simulate the thermoanalytical curves), some caveats in the application of the Kissinger, isoconversional Friedman, Vyazovkin and Flynn–Wall–Ozawa methods, mathematical and kinetic deconvolution approaches and formal kinetic description were highlighted. The model-fitting approach using simultaneously TG and DSC data was found to be the most useful for the complex processes assumed in the study.

Thermal characterization and kinetic analysis of polyvinyl chloride containing Sn and Zn

Polyvinyl chloride (PVC) films containing the mercaptan methyltin (S), zinc stearate (Z) and dipentaerythritol (D) additives were prepared. The thermal degradation kinetics of the films were investigated by nonisothermal thermogravimetry and TG–FTIR techniques. Using the nonmodel method and the Kissinger, the Friedman, the Kissinger–Akahira–Sunose and the Flynn–Wall–Ozawa methods, the average apparent activation energies of the PVC–SZD films in the first and second thermal decomposition stages obtained were 127.5 and 261.6 kJ mol−1, respectively. Compared with the experimental master plot by the generalized master plot, the experimental and theoretical master plots on the master plot of θ/θ0.5 versus α show that the thermal degradation of PVC-SZD film conforms to the chemical reaction F1.5 mechanism model. TG–FTIR analysis showed that the infrared vibration peaks ordered from strong to weak after adding SZD components were: νCO2 (638 °C) > ν(–COOR) (275 °C) > νHCl (299 °C). The thermal degradation of the film did not show hydroxyl or moisture formation compared to the blank. The removal of carboxyl groups of plasticizer dioctyl terephthalate (DOTP) in PVC was significantly inhibited, and the CO2 gas released by thermal degradation was reduced by 85.2%. This suggests that SZD has a strong interaction with the ester groups in DOTP, and there is the possibility of generating a more stable carboxyl group-containing metal complex, which creates favorable conditions for the recovery of DOTP. When the heating rates were 2.5, 5.0, 10 and 20 °C min−1, the lowest temperatures at which the conversions reached 5 and 10% were 226.1 °C and 239.1 °C, respectively.

Investigation of water influence on coal based on thermal oxidative degradation kinetics

In order to further understand the effect of the water content on spontaneous combustion of coal, the thermal oxidative degradation kinetics of coals with different water contents were studied by Kissinger method, Flynn–Wall–Ozawa method, and Starink method. The results show that the water has no substantial effect on the thermal decomposition mechanism of the coal, and reaction orders are similar (n = 1) with different water contents. However, the activation energy Ea of coals has a certain relationship with the water content. When the water content of the coal is less than 6.0 mass%, with the increase of the water content, the activation energy Ea decreases. With the water content of coal exceeding 6.0 mass%, the activation energy Ea is increased with the increase of the water content. The change tendency of activation energy Ea is consistent with the mass increase of coals in the coal oxidation stage, which means that lower activation energy Ea is easier to make spontaneous combustion of coal. From this study, we hope to provide an efficient method for further understanding the mechanism of the water influence on spontaneous combustion of coal.

Thermal and kinetic analyses of silicide formation at nanostructured Si/Ni interface

The problem of the manifestation of nanostructures properties that are not typical for similar macrosystems is still relevant. First of all, this concerns the stability of the thermodynamic properties of nanomaterials, which determines the operational reliability of devices based on them. In this paper, the influence of the nanostructured Si/Ni interface on the mechanism of silicide formation is studied. For this purpose, nickel/porous silicon nanocomposites have been electrochemically synthesized and analyzed using the scanning electron microscopy and the phase X-ray diffraction analysis. The solid-state interaction during heating the nanocomposites has been investigated using differential scanning calorimetry. The evolution of phase composition in the temperature range 25–500 °C has been studied. The temperature characteristics of silicide formation processes have been estimated. Kinetic analysis of the solid-state interaction has been performed using the isoconversional Ozawa–Flynn–Wall method. The dependence of effective activation energy on conversion has been calculated from the calorimetric data. The mechanism of silicide formation in the nickel/porous silicon nanocomposite is shown to be significantly different from the bulk Ni–Si diffusion couple. At the same time, it has similarities with, but also some differences from, the silicide formation in thin-film Ni–Si systems and individual Si nanowires. Methodical aspects of the characterization of the thermal behavior of nanocomposites taking into account the nanorelief of the Si–Ni interphase boundary are discussed.

Thermoplastic polyurethane/polytetrafluoroethylene/bridged dopo derivative composites: Flammability, thermal stability, and mechanical properties

A phenethyl‐bridged DOPO derivative (DiDOPO) is combined with polytetrafluoroethylene (PTFE) in thermoplastic polyurethane (TPU). The flame retardancy and thermal stability of TPU/PTFE/DiDOPO composites with different weight percentages of DiDOPO are investigated by using limiting oxygen index (LOI), UL‐94 test, cone calorimetry test (CCT), scanning electronic microscopy (SEM), energy‐dispersive spectrometry, and thermogravimetric analysis (TGA). With the incorporation of 8 wt% DiDOPO, the LOI value of TPU/PTFE/DiDOPO composites increases to 34.0% from 25.4% of TPU, and the V‐0 rating level is achieved. The CCT results indicate that the peak heat release rate and total heat release of TPU/PTFE/DiDOPO composites decrease due to the addition of DiDOPO and PTFE. The thermal decomposition process of TPU is changed due to the present of DiDOPO and PTFE. Based on this, the Flynn–Wall–Ozawa method for the determination of characteristic degradation kinetics parameters is evaluated. SEM results and residues from TGA curves show that the addition of DiDOPO promotes the increase in the char layer and a crosslinked char coating exists after burning. The flame‐retardant mechanism is flame inhibition. Overall, these findings indicate that the combination of DiDOPO with PTFE in TPU is an effective way in developing high‐performance resins with attractive flame retardancy. POLYM. ENG. SCI., 59:1593–1602 2019. © 2019 Society of Plastics Engineers

Effects of acetylation on the thermal decomposition kinetics of makino bamboo fibers

In this study, makino bamboo (Phyllostachys makinoi) fibers were acetylated with different solution ratios of acetic anhydride/dimethylformamide using a liquid phase reaction. This reaction resulted in the production of acetylated bamboo fibers (BFs) with the following weight percent gains (WPGs): 2, 6, 9, 13, and 19%. The effects of the acetylation level on the thermal decomposition kinetics of bamboo fibers were evaluated by thermogravimetric analysis. The results revealed that as the acetylation level increased, both the onset and maximum decomposition temperatures increased. In addition, four model-free iso-conversional methods, the Friedman method, Flynn–Wall–Ozawa method, the Starink method, and the modified Coats–Redfern method, were used to determine the thermal decomposition kinetics. Accordingly, the activation energies of thermal decomposition with conversion rates ranging between 10% and 70% were 191–196, 190–191, 192–194, 182–186, 186–191, and 189–201 kJ/mol for unmodified BFs and acetylated BFs with WPGs of 2, 6, 9, 13, and 19%, respectively. There were no significant dependencies among them. Furthermore, the Avrami method was used to determine the reaction order of unmodified BFs (0.47), which was lower than those of acetylated BFs (0.55–0.74).

Aloe vera leaf extract-assisted facile green synthesis of amorphous Fe2O3 for catalytic thermal decomposition of ammonium perchlorate

Fe2O3 is a well-known catalyst for thermal decomposition of ammonium perchlorate (AP). Amorphous Fe2O3 nanoflakes were biosynthesised by a novel sol–gel method using Aloe vera leaf extract, and its catalytic effect on thermal decomposition of AP was investigated. The precursor ferric nitrate–Aloe vera gel was calcined at three different temperatures. The oxides were characterised by Fourier-transform infrared spectroscopy, X-ray powder diffraction, atomic force microscopy, field emission scanning electron microscopy and transmission electron microscopy. Microscopy analyses revealed that Fe2O3-250 consists of a porous structure as aggregates of many nanoflakes of ~ 2 nm diameter. The catalytic activity of the synthesised products on thermal decomposition of AP was evaluated using thermogravimetry–differential scanning calorimetry. The presence of 2.0% of mesoporous Fe2O3-250 catalyst (surface area of 208 m2 g−1) enhanced the rate of high-temperature decomposition of AP by decreasing the peak decomposition temperature from 367 to 337 °C. Average activation energy of thermal decomposition of AP was calculated using Flynn–Wall–Ozawa method reduced from 145 to 128 kJ mol−1 in the presence of the catalyst. The high surface area of mesoporous Fe2O3-250 originated from its amorphous nature makes it a potential catalyst for thermal decomposition of AP.