Crystallization Kinetic Parameters Research Articles

Eco-friendly zinc-metal-organic framework as a nucleating agent for poly (lactic acid)

Eco-friendly poly(L-lactic acid) (PLA) can be made more versatile, and its crystallization rate is accelerated by adding Zinc-based metal-organic framework (Zn-MOF) particles. Using differential scanning calorimetry (DSC), the non-isothermal melt crystallization behavior of biodegradable PLA nucleated by 0.3 to 3 wt% of Zn-MOF was examined. The non-isothermal melt crystallization kinetics parameters were determined using a modified Avrami model and Mo approach. Zn-MOF dramatically accelerated the crystallization process, as evidenced by several non-isothermal crystallization metrics, including the crystallization half-time and crystallization rate constant. The melt crystallization temperatures of the PLA-Zn-MOF composites, with contents of 0.7 and 1 wt%, were increased by 21 °C compared to the neat PLA. Using the Friedman isoconversional kinetic method, the neat PLA and PLA-Zn-MOF composites' effective activation energy values, ∆E, were determined. The ∆E values of PLA-Zn-MOF from 0.3 to 1 wt% Zn-MOF composites were lower than that of neat PLA. Moreover, polarized optical microscopy revealed the formation of numerous small-sized PLA spherulites upon Zn-MOF addition. The results indicate that the Zn-MOF (at concentrations of 0.7 to 1.0 wt%) can be used as an efficient nucleating agent for PLA, where it increases the melt crystallization temperature, nucleation density, and crystallinity without changing the crystalline structure, while also significantly reduces the effective activation energy and the size of spherulites. Additionally, scanning electron microscopy confirms good dispersion of Zn-MOF (0.3 to 1 wt%) within the PLA matrix.

Crystallization behavior and properties of quartz glass-ceramics synthesized from desert sand

Quartz glass-ceramics were synthesized with desert sand as the main raw material. The effects of pretreatment technology of desert sand and various cations on the glass stability (GS) parameters (KH, KLL,KW, KZW, KLX), crystallization kinetic parameters (crystallization activation energy (Ec), reaction rate (k), the effective frequency factor(ν) and the Avrami parameter (n)), phase transition, microstructure and properties of glass-ceramics were investigated. The results show that the chemical composition of desert sand is greatly changed by sieving and magnetic separation, and the glass stability, phase transition and crystallization ability of glass are controlled by the mixed mobile ion effect (MMIE), in which the ionic field intensity determined by ionic valence and radius plays a major role. Finally, the crystallization of glass is dominated by the surface crystallization mechanism, and the obtained glass-ceramics mainly consist of α-quartz, β-cristobalite and glass phases, which have excellent comprehensive properties.

Elucidation of the crystallization behavior and the thermodynamics property of CuO/Bi12SiO20@ SiO2-B2O3-Bi2O3-CuO glass-ceramics

Glass has good friction, lubricating properties, and great thermal stability, which has already made it to be widely used as excellent friction resistance and high temperature resistance materials for mechanical processing, and many other applications. In this study, SiO2-B2O3-Bi2O3-CuO (SBBC) system glasses were prepared via cooling the high temperature melt. The nucleation and crystal growth kinetics of SBBC system glasses were analyzed by thermogravimetric analysis and X-ray diffraction And then the value obtained was further analyzed by Gaussian fitting to give the temperature–time–transition (T–T–T) curve of SBBC system glasses under non-isothermal heating conditions. The crystallization kinetic parameters including the crystallization apparent activation energy (Ep) and the crystallization index (p) were also measured by the Ozawa and JMA methods (i.e. Ep1 = 116.4 kJ/mol, Ep2 = 50.1 kJ/mol, p1 = 3.7, p2 = 3.2). The effects of time(holding for 60 min), temperature (500 °C) and the phase of the precipitated crystal on the crystallization rate curves of SBBC system glasses were established. Furthermore, the crystal precipitation process of SBBC system glasses was verified by the typical crystal structure presented in scanning electron microscope (SEM) images, which successfully elucidated the working mechanism of the lubricating glass in high-temperature metal devices. The measurement of contact angles of the soften glass as well as the SEM-EDS analysis indicated that the early crystallization of SBBC glass has negative effect on the lubricating properties.

Non-Isothermal Crystallization Kinetics of Poly (ɛ-Caprolactone) (PCL) and MgO Incorporated PCL Nanofibers.

The study delves into the kinetics of non-isothermal crystallization of Poly (ɛ-caprolactone) (PCL) and MgO-incorporated PCL nanofibers with varying cooling rates. Differential Scanning Calorimetry (DSC-3) was used to acquire crystallization information and investigate the kinetics behavior of the two types of nanofibers under different cooling rates ranging from 0.5-5 K/min. The results show that the crystallization rate decreases at higher crystallization temperatures. Furthermore, the parameters of non-isothermal crystallization kinetics were investigated via several mathematical models, including Jeziorny and Mo's models. Mo's approach was suitable to describe the nanofibers' overall non-isothermal crystallization process. In addition, the Kissinger and Friedman methods were used to calculate the activation energy of bulk-PCL, PCL, and MgO-PCL nanofibers. The result showed that the activation energy of bulk-PCL was comparatively lower than that of nanofibers. The investigation of the kinetics of crystallization plays a crucial role in optimizing manufacturing processes and enhancing the overall performance of nanofibers.

Effect of support salts on apparent performance of Li metal anode in Ethylene carbonate/Ethyl methyl carbonate solvent and dynamic mechanism analysis

Lithium metal batteries (LMB) have received widespread attention due to their high energy density and potential commercial value. The relationship between the rate performance, cycling performance, microstructure of the deposition layer, and SEI of lithium anodes has not yet been elucidated. Here, we investigated the cycling performance and rate characteristics of metal lithium anodes in classic carbonate electrolytes containing different supporting salts. And the microstructure and chemical information of the lithium anode surface were analyzed. In addition, microelectrode technology was used to study the dynamic behavior and reaction of electroplating/stripping lithium process under different polarization conditions (current density), revealing the apparent performance, microscopic visual information, and dynamic causes and mechanisms of SEI. The results indicate that in carbonate electrolytes containing LiBOB and LiPF6, the cycling performance of lithium anodes, the microstructure of the deposition layer, and SEI can be significantly improved. Microelectrode research has revealed a close causal relationship between the stability and coordination of each basic step, including lithium ion mass transfer, interface charge transfer, and surface crystallization kinetics parameters, and the apparent performance of lithium anodes. This correlation can serve as a dynamic evaluation basis for future selection and optimization of operating and manufacturing conditions.

Multiscale framework for estimation of elastic properties of Poly ethylene terephthalate from the crystallization temperature

A 2D multiscale numerical strategy is presented in this paper. It allows to generate a representative elementary volume (REV) with a spherulitic microstructure used to predict the elastic properties of PET using a 2-scale numerical homogenization scheme. Because of the rapid crystallization kinetics of PET, DSC and optical microscopy were combined with empirical laws to estimate the crystallization kinetic parameters used to generate the REVs. Our framework allows estimating the elastic properties identified by tensile tests for several specimens crystallized at different temperatures. In addition, the comparison with mean-field models from the literature confirms that the Young's modulus of PET does not only depend on the crystallinity volume ratio but also on the crystal organization in the spherulites. The main advantage of this study is to provide a strategy for estimating the elastic properties that can be transposed to many semi-crystalline polymers with a spherulitic microstructure. Nevertheless, the numerical framework presented in the article is limited to semicrystalline polymers with a spherulitic microstructure, which crystallize under isothermal condition.

Non-isothermal crystallization kinetics of CaO-SiO2-B2O3-TiO2 glass studied by differential thermal analysis in the case of “site saturation”

Crystallization characteristics of the CaO-SiO2-B2O3-TiO2 glass have been studied using scanning electron microscopy, X-ray diffraction and differential thermal analysis techniques. The crystallization kinetic parameters of this glass were estimated under non-isothermal conditions using the Matusuta-Sakka equation. Glass with fine particles (<74 μm), case referred to as ‘‘site saturation’’, was used to obtain the non-isothermal differential thermal analysis curves. Bulk glass-ceramics with dense and nonporous morphology are obtained after the heating treatment indicating the strong heterogeneous nucleation at the junction of gain boundaries in the case of “site saturation”. As the content of TiO2 exceeds 18%, the predominant crystal phase changes from CaSiO3 to CaTiSiO5, until CaTiSiO5 becomes the only crystal phase of the glass at 26% TiO2. The crystallization activation energies, EG, are in the range of 245–514 kJ/mol. As TiO2 increases from 10% to 18%, crystallization ability of the glass decreases gradually and the crystallization corresponds to one-dimensional growth mechanism or surface crystallization, while as TiO2 further increases from 18% to 26%, not only does the glass show an increasing crystallization ability, but also the crystal growth changes to the two-dimensional growth mechanism. Within the range of 22%–26%, TiO2 plays the role of strengthening the crystallization of the glass by acting as a major component in the glass to form Ti-bearing compound. From the standpoint of glass-ceramics preparation, the glass containing more TiO2 (such as 26%) with CaTiSiO5 as the only crystal phase is favorable in the present study.

Experimental Design for the Efficient Determination of the Crystallization Kinetics of a Polymorphic System in Combined Cooling and Antisolvent Crystallization

In this work, the polymorphic transformation of a dimorphic model compound, ortho-aminobenzoic acid (OABA), is investigated using experimental characterization in combination with population balance modeling. A novel experimental design is proposed to estimate the crystallization kinetic parameters of the polymorphic system in a combined cooling and antisolvent crystallization (CCAC) process with a minimum number of experiments, which can reduce the resources and time required to obtain kinetic information, which is of great importance in the drug substance development stage. The modeling studies revealed that the growth rates of the two polymorphs depend on the solvent composition. At a particular temperature and supersaturation, the form I growth rate increased as the solvent content proportion increased, whereas the form II growth rate decreased as the solvent content increased. The identified kinetic parameters of the nucleation and growth rate expressions of the two polymorphs were validated for different solvent compositions and temperatures. The validated model was then used to perform in silico design of experiments to develop a design space that can be used to identify operating conditions to achieve the desired crystal size and polymorphic form.

Stepwise sulfurization of MoO3 to MoS2 thin films studied by real-time X-ray scattering

Chemical vapor deposition (CVD) is commonly used for the large-scale synthesis of the films of two-dimensional (2D) transition metal dichalcogenide (TMD) materials, including MoS2 thin films, which have potential applications in optoelectronics, catalysis, and nanoelectronics. As far as thin film of MoS2 is concerned, the influence of deposition parameters on the chemical reactions in the growth process via CVD synthesis has not yet been exhaustively studied. Here we present a comprehensive, time-resolved, in-situ study of the growth of MoS2 thin film from MoO3 by sulfurization using the grazing-incidence wide-angle X-ray scattering (GIWAXS) in laboratory conditions. We tracked the basic chemical reactions during the sulfurization process in real time by monitoring the phase transformations of MoO3 to MoO2 and MoO2 to MoS2 via a MoOS2 transient phase, although it was not possible to observe it directly. Preferential crystallographic orientation of MoO3, and MoO2 phases during the growth was confirmed. In addition, their activation energies were determined from the crystallization kinetics parameters. The present work highlights the importance of understanding the basic chemical reactions inside the CVD reactor as a prerequisite for optimizing the properties of the final 2D TMD films.

Kinetics Crystallization and Polymorphism of Cocoa Butter throughout the Spontaneous Fermentation Process.

The spontaneous fermentation process of Criollo cocoa is studied for its importance in the development of chocolate aroma precursors. This research supports the importance of spontaneous fermentation, which was studied through the crystallization behavior and polymorphisms of cocoa butter (CB), the most abundant component of chocolate that is responsible for its quality physical properties. The k-means technique was used with the CB crystallization kinetics parameters to observe the division of the process during the first stage (day 0–3). The experimental crystallization time was 15.78 min and the second stage (day 4–7) was 17.88 min. The Avrami index (1.2–2.94) showed that the CB crystallizes in the form of a rod/needle/fiber or plate throughout the process. CB produced metastable crystals of polyforms and . Three days of fermentation are proposed to generate Criollo cocoa beans with acceptable CB crystallization times.

Crystallization kinetics and morphology of biochar modified bio-asphalt binder

Crystallization of biochar modified bio-asphalt binder (BMBA) directly affects their intrinsic physicochemical properties, which can significantly impact their processing and application. This research aims to maximize recycling the pyrolysis products of biomass (biochar and bio-oil) and investigate the crystallization kinetics of BMBA to inhibit the second crystallization and phase separation. Specifically, the parameters of crystallization kinetics and free volume were quantified using molecular dynamic simulations (MD). Relative crystallinity was evaluated using dynamic shear rheometer (DSR). Crystallization structure was analyzed using X-ray diffraction (XRD) and Synchrotron radiation small angle scattering (SAXS), and high-temperature-induced crystallization and low-temperature-physical hardening were quantified using hot-table polarizing microscope (HTPM). Crystallization morphology was measured by environmental scanning electron microscope (ESEM) and atomic force microscope (AFM). The parameters of crystallization kinetics show that high temperature and stress could induce the crystallization of BMBA. The low-temperature-physical hardening and aggregation of molecules indicate that the shape of BMBA crystals tends to be spherical under isothermal conditions but lamellar crystals under the non-isothermal conditions. This study provides a better understanding of the mechanism of crystallization kinetics of BMBA and a theoretical basis for the application of sustainable materials in asphalt pavement.

Role of a Nanocomposite Pour Point Depressant on Wax Deposition in Different Flow Patterns from the Perspective of Crystallization Kinetics.

Wax deposition is one of the core issues affecting flow assurance studies of crude oil pipelines, particularly with deep and ultradeep water conditions. Nanocomposite pour point depressants (NPPDs) provide a novel and effective strategy for inhibiting wax deposition and have recently attracted increasing research attention. Although recent advances have been made in understanding the performance and mechanism of NPPDs, the effect of flow pattern remains an open question. In this paper, deposition thicknesses of waxy oils with different flow patterns and NPPD dosages were obtained using a flow loop experimental device. It was found that the NPPD used in the current work can effectively inhibit the formation of wax deposition layers in different flow patterns. The Avrami model-focused beam reflectance measurement and polarizing microscope experiment method were used to characterize crystallization kinetics parameters and mesoscopic structure parameters of wax crystals. The consistency of results from Avrami equation fitting parameters, wax crystal morphology, and particle number supported the validity of crystallization kinetics analysis. The mechanisms of NPPD in different flow regimes were discussed. The inhibition of laminar and turbulent deposition layers by NPPD was attributed to the improvement of wax crystal morphology and the reduction of wax crystal number, respectively. This has important consequences for our understanding of the utilization and mechanism of nanocomposite pour point depressants.

A novel approach for preparing glass ceramic foams from MSWI fly ash: foaming characteristics and hierarchical pore formation mechanism

Powder sintering and in–situ foaming are the primary treatments for the preparation of glass ceramic foams from solid wastes. However, variables such as crystallization and viscosity, which are difficult to regulate at high temperatures. Herein, a novel technology based on alkali activation–crystallization strengthening was developed for the fabrication of glass ceramic foams with hierarchical pores. Vitrified municipal solid waste incineration (MSWI) ashes as the main calcium and aluminum source and secondary aluminum ash (SAA) as a foaming agent were foamed in NaOH solution at room temperature. The effects of solid–liquid ratio and NaOH concentration on the pore structure, individual foam force, phase evolution and physical properties were investigated, including crystallization kinetics and hierarchical pore formation mechanism. The results indicated that the solid–liquid ratio decreased from 60:40 to 40:60, making the pore wall thin and eventually disappear. The pore size in the range of 0–1 mm reaches 99.5% in 3 mol/L NaOH sample, with the lowest mean size of 0.34 mm. The crystallization kinetics parameters of the basic glass at 5–20 K/min showed that grains were primarily precipitated as three–dimensional at 5 K/min, resulting in micropores. The prepared samples exhibit high porosity (79.23–88.35%), adequate compressive strength (0.36–5.55 MPa) and a bulk density of 0.68–0.76 g/cm3. This work develops the function of SAA as a foaming agent at room temperature, as well as a new idea for the preparation of glass ceramic foams from solid waste containing glass phase or needing vitrification.

Crystallization of Lactose-Protein Solutions in the Presence of Flavonoids.

Lactose is commonly crystallized in the presence of whey proteins, forming co-crystals of lactose and proteins. This work hypothesized that flavonoids such as rutin or epigallocatechin-3-gallate (EGCG) could be incorporated into the lactose and protein co-crystal structure since flavonoids may interact with both lactose and proteins. The interactions between whey proteins and flavonoids were first studied. Then, lactose-protein solutions were crystallized with and without flavonoids, measuring the kinetic parameters of crystallization and characterizing the resulting crystals. The incorporation of flavonoids in lactose-protein co-crystals depended on the hydrophilic nature of flavonoids. The hydrophilic EGCG was scarcely enclosed in the crystal lattice of lactose and avoided the inclusion of whey proteins in the crystals. In contrast, the less water-soluble rutin interacted with whey proteins and lactose, leading to the formation of co-crystals containing lactose, protein, and a large concentration of rutin (3.468 ± 0.392 mg per 100 mg of crystals).

Influence of isotactic polypropylene grafted with styryl-group on the polymer crystallization behavior

4-Furfuryloxymethylstyrene (Sf) grafted isotactic polypropylene (iPP-g-Sf) was prepared by melt grafting reaction. The crystallization temperature of iPP after grafting increased to ∼130 °C. The isothermal and non-isothermal crystallization kinetics of iPP-g-Sf containing up to 1.50 mol% grafted Sf groups were compared with that of virgin iPP, and the isothermal and non-isothermal crystallization kinetics parameters of the polymers, including the fold surface free energy σe, the chain folding work q, and the crystallization activation energy ΔE, were calculated by Lauritzen-Hoffman theory and Kissinger method respectively. The results showed that iPP-g-Sf exhibited a unique self-nucleation phenomenon, which accelerating the crystallization rate of iPP and produced tiny crystal morphology than that for iPP. The introduction of only 0.23–1.50 mol% grafted Sf groups reduced the σe of the crystals by 44–57%. This might provide guidance for the design of polymer crystallization rate by controlling the molecular structures.

Phase formation and crystallization kinetics of CuIn-=SUB=-5-=/SUB=-S-=SUB=-8-=/SUB=- amorphous films

The processes of interaction and formation of phases in the Cu2S-In2S3 system obtained by sequential and simultaneous deposition of Cu2S and In2S3 binary compounds in vacuum have been investigated. Using the kinematic electron diffraction method, the kinetic crystallization parameters of CuIn5S8 amorphous films formed as a result of vacuum condensation of the above binary compounds, both under normal conditions and under the influence of an external electric field, have been established. Keywords: kinematic electron diffraction, nanosized films, condensation plane.

Nonisothermal Crystallization Kinetics: Studying the Validity of Different Johnson–Mehl–Avrami–Erofeev–Kolmogorov (JMAEK) Based Equations

The Johnson–Mehl–Avrami–Erofeev–Kolmogorov (JMAEK) equation modifications proposed by Jeziorny, by Atiqullah and by Ruitenberg and Woldt were applied on the nonisothermal crystallization data of Poly(ethylene 2,5-furandicarboxylate)/2.5 wt. % Carbon Nanotubes (PEF/2.5 CNTs) nanocomposite. The classic JMAEK equation and the JMAEK model using the multivariate nonlinear regression method were also used to evaluate the cold crystallization's kinetic parameters of PEF/2.5 CNTs. Differential Scanning Calorimetry (DSC) measurements were carried out at heating rates of 1, 2.5, 5, 10 and 15 K/min. The effective activation energy (Eα) of the process was calculated using the isoconversional method of Vyazovkin. The Eα values indicate a nonlinear Arrhenian behavior and a complex process. The multivariate nonlinear regression method suggested a consecutive two-mechanism reaction model described by the JMAEK equation for both mechanisms. This method provided better fitting results of the experimental data for all the heating rates simultaneously and kinetic parameters' values within the limits of physical meaning. In any case, Jeziorny's modification of the JMAEK model was the most inadequate since the extracted Avrami exponents exceed in value those with a physical meaning.

Pre-Crystallization Criteria and Triple Crystallization Kinetic Parameters of Amorphous–Crystalline Phase Transition of As40S45Se15 Alloy

This framework focuses mainly on a detailed study of the pre-crystallization criteria that characterize the As40S45Se15 glassy alloy in various heating rates ranging from 5 to 40 (K/min) by Differential Scanning Calorimetry (DSC). These criteria aim to clarify the relationship of the tendency of glass-forming by the heating rate for the investigated glassy alloy. The crystallization parameters were calculated using different methods.The activation energy of crystallization Ec(χ) as a function of conversion (χ) was obtained using the iso-conversional models of Flynn–Wall–Ozawa (FWO), Starink and Kissinger–Akahira–Sunose (KAS). The results show a slight increase of Ec(χ) with conversion (χ) which accounts for a single-step mechanism controlling the crystallization process. Moreever, the conversion dependence of the Avrami exponent n(χ) show an increase with conversion (χ), average values of n(χ) can be accounted for two and three-dimensional crystal growth with heterogeneous nucleation. On the other hand, the fitting of the experimental DSC data to the calculated DSC curves indicated that the crystallization process of the studied glasses cannot be satisfactorily described by the Johnson–Mehl–Avrami (JMA) model. On the contrary (SB) model is more suitable to describe the crystallization process for the studied of As40S45Se15 Alloy. Finally, the crystalline structure of the study sample was recognized by X-ray diffraction (XRD) and electron scanning microscope (SEM).

Crystallization kinetics and glass-forming ability of rapidly crystallizing drugs studied by Fast Scanning Calorimetry

The use of the amorphous forms of drugs is a modern approach for the enhancement of bioavailability. At the same time, the high cooling rate needed to obtain the metastable amorphous state often prevents its investigation using conventional laboratory methods such as differential scanning calorimetry, X-ray powder diffractometry. One of the ways to overcome this problem may be the application of Fast Scanning Calorimetry. This method allows direct determination of the critical cooling rate of the melt and kinetic parameters of the crystallization for bad glass formers. In the present work, the amorphous states of dopamine hydrochloride and atenolol were created using Fast Scanning Calorimetry for the first time. Critical cooling rates and glass transition temperatures of these drugs were determined. Based on the values of the kinetic fragility parameter, dopamine hydrochloride glass can be considered strong, while atenolol glass is moderately strong. Both model-based and model-free approaches were employed to determine the kinetic parameters of cold crystallization of dopamine and atenolol. The results were compared with the data from isothermal crystallization experiments. The Nakamura crystallization model provides the best description of the crystallization process and can be used to predict the long term stability of the amorphous forms of the drugs. The presented approaches may find applications in predicting the storage time and choosing the optimal storage conditions of the amorphous drugs prone to crystallization.

Nanofibrous Foams of Poly(3-hydroxybutyrate)/Cellulose Nanocrystal Composite Fabricated Using Nonsolvent-Induced Phase Separation.

In this study, we fabricated nanofibrous foams of neat poly(3-hydroxybutyrate) (PHB) and PHB/cellulose nanocrystal (CNC) nanocomposite using nonsolvent-induced phase separation (NIPS) followed by solvent extraction. Two different nonsolvents, tetrahydrofuran (THF) and 1,4-dioxane (Diox), in combination with the solvent, chloroform (CF), were used for NIPS. The parameters of NIPS-derived crystallization kinetics were calculated using Avrami analysis of time-dependent infrared spectral measurements. The lower viscosity and poorer PHB affinity of THF than those of Diox resulted in rapid crystallization and gelation rate, which in turn resulted in higher strength of the foam. The mechanical reinforcement by the incorporation of CNCs was achieved for the composite foam prepared in Diox/CF but not in THF/CF, owing to the relatively better dispersion of the CNCs in Diox than that in THF. A rapid rate of NIPS-derived crystallization and gelation was achieved in THF/CF with the incorporation of CNCs, indicating the effective crystal nucleation of CNCs. However, the presence of CNCs deaccelerated the crystallization in Diox/CF, indicating that the inhibition effect of PHB mobility became more dominant than the nucleation effect of CNCs; this was because the CNC dispersion became more homogeneous in Diox/CF. In vitro cell viability assays exhibited excellent cytocompatibility of the foams, thereby showing potential for use in biomedical applications.