Non-isothermal Kinetic Study Research Articles

A non-isothermal kinetic study on the extraction of metals from spent lithium iron phosphate batteries using the NH2SO3H roasting process

A non-isothermal kinetic study on the extraction of metals from spent lithium iron phosphate batteries using the NH2SO3H roasting process

Epoxy/Phenolic Nanocomposite based Adhesives: Non-isothermal Cure Kinetic Study

The curing behavior of an epoxy/phenolic-based system containing graphene oxide (GO), and rubber powder as a toughening agent has been studied using differential scanning calorimetry (DSC) under non-isothermal conditions at a temperature from 0 to 200°C. So, to better dispersion of GO nanoplates in the resin media, the surface of the GOs was modified by 1,12-diaminododecane and subsequently aforementioned reaction was confirmed by Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric techniques (TGA). DSC results show that rubber powders despite toughening properties prohibited resin-curing reactions. On the other hand, modified GO led to the promotion of curing reactions. The results of differential and integral iso conversional approaches indicated low activation energy for nanocomposite containing modified GO. Furthermore, thermal stability results reveal that the maximum decomposition temperature and char yield values of samples were increased gradually by the addition of GO and rubber powder to the system.

Synthesis, structure, and AP catalytic performance of two new 1D coordination polymers

Two 1D chain coordination polymers (CPs), [Co(DNDPA)(DMF)2] 1 and [Mn(DNDPA)(DMF)2] 2, were successfully synthesized (4,4′-dinitrodiphenic acid, DNDPA). Their structures were confirmed by single-crystal X-ray diffraction. Differential scanning calorimetry coupled with thermogravimetric analysis revealed that both CPs exhibit commendable thermal stability, with CP 1 and 2 decomposing at 368.9 °C and 375.5 °C, respectively. Non-isothermal kinetic studies confirmed that both CPs displayed significant catalytic activity for the decomposition of ammonium perchlorate (AP). In particular, CP 1 and 2 reduced the activation energy of AP from its intrinsic value to 100.5 kJ/mol and 127.45 kJ/mol, respectively, and its high-temperature decomposition peak to 354.3 °C and 327.7 °C, respectively. These findings underscore the potential of these CPs as effective catalysts for enhancing the combustion properties of AP.

Polymer Crystallization Kinetics and Thermodynamics of Some Industrial Polyamides

A comprehensive non-isothermal kinetics study on polymer crystallization processes taking place in a set of industrial polyamides comprising nylon 6, nylon 6,6, nylon 11 and nylon 12, individually, is reported. The kinetics studies elucidated that the phenomena of nucleation/diffusion underlying the nylons crystallization go to completion in a single-step. Notwithstanding, the nylons diffusion activation energies do not correspond to the universal value of segmental jump activation energy signifying polymer chains diffusion processes. The polymer chain transport phenomenon was probably the slowest one in the case of nylon 6 and nylon 6,6, and the fastest in the case of nylon 12, while intermediate for nylon 11. Furthermore, the nucleation barrier during the course of polymer crystallization was the highest for nylon 6,6, followed by nylon 6, nylon 11 and nylon 12. Our kinetics studies further predict that the crystallization of nylon 12 and nylon 11 follows, respectively, diffusion-controlled 2D growth of spherulites and a somewhat complicated nucleation/growth phenomenon. The thermodynamics of the nylons crystallization suggests that the highest structural orientation of the activated complex was attained in the case of the nylon 12 crystallization process. Interestingly, while the thermodynamics and majority of the kinetic parameters of nylon 6 and nylon 6,6 were similar/comparable, the two follow widely differing crystallization mechanisms. The most probable physical meanings of the obtained kinetics and thermodynamics parameters and their practical significance are given and discussed.

Chemorheological Kinetic Modeling of Uncatalyzed Hydroxyl‐Terminated Polybutadiene and Isophorone Diisocyanate

AbstractCatalysts are often employed to enable nonisothermal reaction kinetic studies when tracking cure progression of polyurethane reactions. However, when quickly reacting, catalyzed materials are prepared through mixing followed by the addition of fillers or additives, subsequent processing of the partially reacted material becomes difficult. Here, chemorheology is used to track changes in viscoelastic properties of uncatalyzed polybutadiene‐diisocyanate reactions for multiple days, which quantifies the degree of cure during polymerization. Viscosity profiles are accurately captured by the two‐stage Arrhenius model (r2>0.95), and conversion progress is adequately represented by the Kamal–Sourour model (r2>0.76). Transition state analysis via Wynne–Jones–Eyring–Evans theory (WJEE) reveals the presence of an associative mechanism according to entropic and enthalpic activation energies ΔS# = −96.9 J K−1 and ΔH# = 36.4 kJ, respectively. These rheokinetic modeling results align with Fourier transform infrared spectroscopy findings. To the knowledge, no rheokinetic studies have tracked cure progress of this uncatalyzed system for the extended timeframe presented here. The cure profile also presents unique viscosity growth, representative of molecular weight buildup, compared to catalyzed systems. This finding emphasizes the novelty of applying previously developed chemorheological models to multiday thermosetting reactions within a flow field in a manner that is generalizable to many long‐term curing systems.

Development of Novel Nano-Sized Imine Complexes Using Coriandrum sativum Extract: Structural Elucidation, Non-Isothermal Kinetic Study, Theoretical Investigation and Pharmaceutical Applications.

A new Schiff base (H2L) generated from sulfamethazine (SMT), as well as its novel micro- and nanocomplexes with Ni(II) and Cd(II) metal ions, have been synthesized. The proposed structures of all isolated solid compounds were identified with physicochemical, spectral, and thermal techniques. Molar conductance studies confirmed that the metal complexes are not electrolytic. The molecular geometry located at the central metal ion was found to be square planar for the NiL2 and tetrahedral for the CdL2 complexes. The kinetic and thermal parameters were obtained using the Coats and Redfern approach. Coriandrum sativum (CS) in ethanol was used to create the eco-friendly Ni and Cd nanocomplexes. The size of the obtained nanoparticles was examined using PXRD and TEM, and found to be in the sub-nano range (3.07-4.61 nm). Furthermore, the TEM micrograph demonstrated a uniform and homogeneous surface morphology. The chemistry of the prepared nanocomplexes was studied using TGA and TEM techniques. The effect of temperature on the prepared nanocomplexes' size revealed a decrease in size by heating. Furthermore, the nanocomplexes' antimicrobial and anticancer properties were evaluated. The outcomes demonstrated that the nanocomplexes exhibited better antimicrobial properties. Moreover, the antitumor results showed that after heating, the Ni nanocomplex exhibited a substantial antitumor activity (IC50 = 1.280 g/mL), which was higher than the activity of cis-platin (IC50 = 1.714 g/mL). Finally, molecular-docking studies were performed to understand the evaluated compounds' ability to bind to methionine adenosyl-transferases (PDB ID: 5A19) in liver cancer and COVID-19 main protease (PDB ID: 6lu7) cell-proteins. The findings reveal that [NiL2]·1.5H2O2 has a higher binding energy of -37.5 kcal/mol with (PDB ID: 5A19) cell protein.

Numerical Solution of nth Order DAEM for Kinetic Study of Lignocellulosic Biomass Pyrolysis

The aim of the present study was to explore the most optimal configuration to numerically solve Distributed Activation Energy Models (DAEMs). DAEMs are useful in obtaining the kinetic parameters in non-isothermal kinetic studies using a thermogravimetry analyzer (TGA). Compared to other kinetic models, DAEMs provide an additional kinetic parameter that quantifies the extent of the reaction (σ) for each reaction’s mean activation energy (E ̅). Although DAEMs are efficacious in kinetic studies, solving DAEMs numerically is challenging. The DAEM equation includes double integration with respect to activation energy and temperature, which involves various numerical discretizations. Previously, many researchers utilized a DAEM to explicate complex reactions such as lignocellulosic biomass pyrolysis. However, most of them have yet to propose a numerical approach to solve DAEMs. Therefore, by exploring multiple numerical calculation configurations, here we present a general structure to numerically solve nth order and first-order DAEMs. The exploration includes determining the optimal integration limit of activation energy and the discretization of activation energy and temperature integration. From the investigation, we came up with a configuration that limits the integration of activation energy from E ̅-3σ to E ̅+3σ. Meanwhile, the number of integration points for temperature and activation energy must be 51 and 21, respectively. By using this configuration, DAEM can be utilized optimally in kinetic studies.

Preparation of a Transient Thermal Expansion Rock Cracking Agent by Deposition Method and Its Nonisothermal Kinetics Study with Isoconversional Procedure and DAEM.

Cracking agents are indispensable and important products for national energy exploitation and large-scale infrastructure construction. Transient thermal expansion rock cracking agent is a new cracking agent product with excellent performance that has just appeared in recent years. However, it is still prepared by mechanical ball milling, which is considered not the best choice among traditional methods for preparing energetic materials. In this paper, a transient thermal expansion rock splitting agent was prepared by the chemical deposition method using carbon black and calcium peroxide as raw materials. The TG/DTG results show that the mass loss of the sample can be divided into four stages with the increase of temperature. It is worth noting that the mass loss of the TG curve of the sample during the entire thermal decomposition process is 93.385%, and the instantaneous weight loss is 78.07% (β = 15 °C/min). Kinetic analysis of the thermal decomposition process of the samples was performed using an isotransformation program and a distributed activation energy model (DAEM). The activation energy E α of the thermal decomposition of the sample was iteratively calculated. The results show that the a-E a curve of the sample can be divided into two stages. The pyrolysis kinetics of the first stage was successfully analyzed by the DAEM method and its thermal conversion behavior was predicted. The thermal decomposition behavior of the second stage was analyzed by a traditional kinetic analysis method.

Non-isothermal kinetic study by TGA analysis of printed circuit boards and cotton stalk

Waste electrical and electronic equipment (WEEE) consisting of Printed circuit boards (PCBs) is a very hazardous materials with a complex chemical composition, making it difficult to reuse and recycle. Pyrolysis has thus far been demonstrated to be a viable alternative for energy and material recovery in the form of gas, solid char and especially liquid oil. In this study, the pyrolysis of PCB, CS (Cotton Stalk) and its different compositions are examined by thermogravimetric analysis (TGA) using a non-isothermal technique. The thermal degradation was carried out for the temperature range 25–700 °C, in the presence of N2 atmosphere, with 50 ml/min flow rate using three different heating rates 5, 10 and 15° 30 C/min. The kinetic parameters such as apparent activation energy (Eα and lnA)were calculated using the Flynn Wall Ozawa (FWO) model-free method and the degradation mechanism was investigated by the Criado method, using a range from reaction order n = 1 to n = 3 for different samples. Within the two pyrolysis zones, the first zone of CS:PCB composition, showed slower reactions and better thermal stability of char compared to individual samples; whereas, in the second zone decreased activation energy is an indication of a faster reaction rate due to the presence of lignin in CS and alkali metals from the PCB. The experiment was carried out in a lab scale fixed bed reactor and the produced oil has been analysed using gas chromatography-mass spectrometry. Co-pyrolysis facilitated the suppressed phenol, and phenolic compounds and the fixing of bromine in char by almost twice as much.

A Novel Approach to Analysis of Complex Crystallization Behavior in Zr-Based Bulk Metallic Glass by Non-isothermal Kinetics Studies

The complex crystallization behavior of the Zr40Ti15Cu10Ni10Be25 bulk metallic glass (BMG) produced by suction-casting method was studied with the non-isothermal DSC measurements with the heating rate from 5 to 40 K/min. Three exothermic phenomena were observed for the investigated material. The novel evaluation procedure for qualitative and quantitative analysis of intricate crystallization kinetics for Zr-based BMGs is proposed. The unusual deconvolution of the DSC curves based on a Gaussian function and a two-phase exponential decay function allowed for separate, detailed analysis of overlapped peaks. The activation energies for each crystallization stage were studied based on overall (Kissinger) and local (Kissinger–Akahira–Sunose) procedures. The KAS method applied separately for both low and high heating rates showed a significant difference in local activation energies. Finally, the local Avrami exponent evaluation revealed that the first two stages of crystallization are diffusion-controlled with mainly increasing nucleation rate, whereas the third crystallization is more growth-dominated.

Synthesis and curing properties of fluorinated curing agent for epoxy resin based on natural soybean isoflavones

A novel fluorinated diamine curing agent (AFPCO) was synthesized from natural isoflavone daidzein, used to cure hydrogenated epoxy resin (DGEHBPA) and tested against commercially available DGEHBPA cured with 4,4′-diaminodiphenylmethane (DDM). The results show that the non-isothermal curing reaction kinetics study found AFPCO to be less reactive than DDM. Compared to DDM, the AFPCO cured material increases the energy storage modulus, impact strength and flexural strength by 34%, 51% and 12% respectively. The AFPCO cured material performs worse in terms of decomposition temperature, but the residual carbon rate exceeds that of DDM/DGEHBPA by 230% and the flame retardancy reaches VL-94 V-1 level. In contrast to the hydrophilic nature of the material after DDM curing, the introduction of fluorine in AFPCO gives the material a water contact angle of 92.19°, which meets the criteria for hydrophobic materials. In contrast to low dielectric constant resins prepared with conventional fluorinated curing agents, AFPCO/DGEHBPA has a high dielectric constant, but still exhibits a low numerical value of 0.0338 in dielectric loss.

Study of Nonisothermal Crystallization Kinetics of Unstretched and Uniaxially Stretched Electroactive PVDF Composite Films

AbstractIncorporation of graphene‐based fillers such as graphene oxide (GO) and reduced graphene oxide (rGO) into polyvinylidene fluoride (PVDF) followed by uniaxial stretching can significantly improve their electroactive phase content as well as the dielectric properties. In this study, the nonisothermal crystallization kinetics of unstretched and uniaxially stretched PVDF‐GO and PVDF‐rGO composite films are investigated through differential scanning calorimetry (DSC) at different cooling rates. Avrami‐modified Jeziorney's model is used to understand their crystallization behavior which leads to the nucleation of electroactive crystalline phases in PVDF. Avrami's exponent “n” values in the range of 2–4 are obtained for nonisothermal crystallization of PVDF in different samples which reveal both two‐ and three‐dimensional growth of spherulites in the crystalline region. Kissinger's method is used to calculate the activation energy of crystallization and the results reveal accelerated crystallization of PVDF after addition of GO and rGO fillers followed by uniaxial stretching.

Oxidation kinetics of SPS-densified U3Si2 fuels—Microstructure impact

U3Si2 is a potential candidate for accident tolerant fuels because of its high uranium density and excellent thermal conductivity in comparison to UO2. However, U3Si2 suffers from oxidation, steam corrosion, and subsequent disintegration/pulverization. The detailed investigation of kinetics that incorporates fundamental treatment of oxidation of U3Si2 is scarcely reported, and the oxidation mechanisms have not been fully elucidated. In this paper, the oxidation behavior of microcrystalline (mc-) and nanocrystalline (nc-) U3Si2 have been systematically investigated using a thermogravimetric analysis (TGA) apparatus through a series of isothermal and non-isothermal kinetic studies. The isothermal kinetic study with a model-fitting approach indicates oxidation activation energy of 85 kJ/mol for dense mc-U3Si2 and 96.4 kJ/mol for nc-U3Si2 pellets, while the isoconversional approach leads to an activation energy in the range of 70–85 kJ/mol for mc-U3Si2 and 75–86 kJ/mol for nc-U3Si2 with three most common model-free methods, including Kissinger–Akahira–Sunose, Flynn–Wall–Ozawa, and Friedman methods. The derivation of oxidation activation energies using both isothermal and isoconversional methods highlights the approach to evaluate the oxidation resistance of nuclear materials using TGA quantitatively and makes it possible to compare among various nuclear fuels.

Effect of Ge Addition on Magnetic Properties and Crystallization Mechanism of FeSiBPNbCu Nanocrystalline Alloy with High Fe Content

In this work, new Ge-containing Fe-based nanocrystalline alloys with the composition of Fe80.2Si3B12-xP2Nb2Cu0.8Gex (x = 0, 1, 2 at.%) were developed, and the effects of Ge content on the magnetic and crystallization processes of the alloys were investigated. The addition of Ge extends the annealing window of the present Fe-based alloys, which reaches 173.6 K for the alloy of x = 2. The nanocrystalline alloy of x = 2, composed of dense and uniformly distributed α-Fe grains with an average grain size of 15.7 nm precipitated in the amorphous matrix, was obtained by conventional annealing treatment at a temperature of 843 K for 10 min, and this nanocrystalline alloy exhibited excellent magnetic properties with the Hc of 3 A/m and Bs of 1.65 T, which has great potential for industrial application. Non-isothermal crystallization kinetics studies show that the nucleation activation energy of the alloys gradually decreases with the increase in Ge content. The primary crystallization process is dominated by the direct growth of pre-existing nuclei in the as-spun alloy ribbons, and these pre-existing nuclei provide numerous heterogeneous nucleation sites to form dense and uniform α-Fe nanocrystals with a fine grain size, which leads to the excellent magnetic properties of the present Ge-containing Fe-based nanocrystalline alloys.

Non-Isothermal Kinetics Study of Thermal Decomposition of Transient Thermal Expansion Rock Cracking Agent with Isoconversional Procedure and Daem and Preparation

Non-Isothermal Kinetics Study of Thermal Decomposition of Transient Thermal Expansion Rock Cracking Agent with Isoconversional Procedure and Daem and Preparation

Crystallization kinetics and photoluminescence studies on SiO2‐ZnGa2O4:Cr3+ glass ceramics

AbstractSiO2‐ZnGa2O4:Cr3+ glass ceramics were prepared by a sol‐gel method. The influence of TiO2 addition on the crystallization behavior and photoluminescence properties were investigated in detail. The nonisothermal crystallization kinetic studies based on Kissinger, Ozawa, and Matusita models were performed on the SiO2‐ZnGa2O4:Cr3+ glasses with different amount of TiO2. The introducing of TiO2 component as nucleant in the glasses can significantly reduce the crystallization activation energy. The results of the crystallization kinetic calculation and scanning electronic microscope observations indicated that the crystallization of ZnGa2O4:Cr3+ from the glass possessed a surface nucleation and growth mechanism. Near infrared emission of the glass ceramics was obtained under the excitation at 414 nm. The crystal field parameters around Cr3+ and excited state dynamics of Cr3+ were studied in detailed.

Effect of heating rate on structure, morphology and photocatalytic properties of TiO2 particles: thermal kinetic and thermodynamic studies

In this study, TiO2 powders were produced via sol–gel route at 500 °C for 2 h with distinct heating rates. TGA-DTA, XRD, SEM, Raman spectroscopy, XPS, UV–vis spectroscopy and photoluminescence characterization techniques were carried out for TiO2 powders. Photocatalytic efficiency of TiO2 powders on degradation of methylene blue (MB) solution was examined in terms of different heating rates. Thermodynamic and non-isothermal kinetic study of TiO2 powders were estimated. TiO2 powders showed anatase phase based on XRD results. Surface morphology of TiO2 powders did not change with different heating rates. It can be concluded that heating rate played important role on band gap and photocatalytic activity. The band gap of the TiO2 particles decreased from 3.25 to 2.95 with increasing heating rate. The photocatalytic activity results exhibit that T1 powders have the highest photocatalytic performances. The kinetic constant and photocatalytic degradation rate were 0.00678 min−1 and 83.48%, respectively. This could be attributed to high crystalline structure and low bulk vacancies or defects. Furthermore, TiO2 powders showed good stability. This study exhibited a new way to enhance the photocatalytic performances of pure TiO2 powders.

Functionality of Cellulose Nanofiber as Bio-Based Nucleating Agent and Nano-Reinforcement Material to Enhance Crystallization and Mechanical Properties of Polylactic Acid Nanocomposite.

Polylactic acid (PLA), a potential alternative material for single use plastics, generally portrays a slow crystallization rate during melt-processing. The use of a nanomaterial such as cellulose nanofibers (CNF) may affect the crystallization rate by acting as a nucleating agent. CNF at a certain wt.% has been evidenced as a good reinforcement material for PLA; nevertheless, there is a lack of information on the correlation between the amount of CNF in PLA that promotes its functionality as reinforcement material, and its effect on PLA nucleation for improving the crystallization rate. This work investigated the nucleation effect of PLA incorporated with CNF at different fiber loading (1–6 wt.%) through an isothermal and non-isothermal crystallization kinetics study using differential scanning calorimetry (DSC) analysis. Mechanical properties of the PLA/CNF nanocomposites were also investigated. PLA/CNF3 exhibited the highest crystallization onset temperature and enthalpy among all the PLA/CNF nanocomposites. PLA/CNF3 also had the highest crystallinity of 44.2% with an almost 95% increment compared to neat PLA. The highest crystallization rate of 0.716 min–1 was achieved when PLA/CNF3 was isothermally melt crystallized at 100 °C. The crystallization rate was 65-fold higher as compared to the neat PLA (0.011 min–1). At CNF content higher than 3 wt.%, the crystallization rate decreased, suggesting the occurrence of agglomeration at higher CNF loading as evidenced by the FESEM micrographs. In contrast to the tensile properties, the highest tensile strength and Young’s modulus were recorded by PLA/CNF4 at 76.1 MPa and 3.3 GPa, respectively. These values were, however, not much different compared to PLA/CNF3 (74.1 MPa and 3.3 GPa), suggesting that CNF at 3 wt.% can be used to improve both the crystallization rate and the mechanical properties. Results obtained from this study revealed the dual function of CNF in PLA nanocomposite, namely as nucleating agent and reinforcement material. Being an organic and biodegradable material, CNF has an increased advantage for use in PLA as compared to non-biodegradable material and is foreseen to enhance the potential use of PLA in single use plastics applications.

Compatibility by a Nonisothermal Kinetic Study of Azathioprine Associated with Usual Excipients in the Product Quality Review Process

Azathioprine is an immunosuppressive drug for several inflammatory disorders. Due to its clinical relevance, to explore the solid-state properties for excipient compatibility in the product quality review process is essential. Fourier transform infrared spectroscopy, powder X-ray diffraction and thermal analysis (thermogravimetry/derivative thermogravimetry (TG/DTG), differential thermal analysis (DTA), and differential scanning calorimetry (DSC)) were applied. The compatibility studies evidenced that starch pregelatinized, colloidal silicon dioxide, and talc are fully compatible with azathioprine. However, stearic acid, magnesium stearate, and mannitol are incompatible after heat supply at temperatures easily reached by industrial processing. The nonlinear Vyazovkin isoconversional treatment performed the kinetic study of the thermal degradation. The activation energies were determined to clarify the influence of each excipient on the thermal drug stability, an essential procedure in the pharmaceutical development, and all over the commercial live span, in Good Manufacturing Practices.

Tailoring poly(ether-imide) films features towards high performance flexible substrates

A series of films prepared from poly(ether-imide)s (PEI) containing a hydroxyl group and various flexible bridges has been investigated to survey the applicative potential. The structure-property correlations were studied to explore the influence of the structural design on the overall physico-chemical properties. FTIR spectra confirmed the complete imidization of polyamidic acid precursors used for films preparation. These films exhibited high glass transition temperatures, and two stages of decomposition, being thermally stable up to 400°C, with a char residue up to 68.97 %. A systematic non-isothermal kinetic study was accomplished to evaluate the kinetic parameters of the thermogravimetric curves. The dielectric behaviour of the PEI films was assessed on the bases of dielectric constant, dielectric loss, secondary relaxations, dielectric loss processing by Havriliak-Negami model and conductivity studies. Beside the mechanical behaviour evaluation, these polymer films were subjected to chemical resistance tests in the presence of methyl ethyl ketone and an alkaline solution. To prove their suitability for use as flexible electrodes, e.g. electrochemical storage devices, the films were coated with a graphite-containing paint and analysed in comparison with indium tin oxide-coated glass with respect to the electrical response in a standard electrochemical cell.