Study Of Crystallization Kinetics Research Articles

Study of thermal behavior and crystallization kinetics of glass microspheres in the Y3Al5O12-Al2O3 system

Five types of glass microspheres with alumina and 40–80 mol.% Y3Al5O12 were prepared using solgel Pechini and flame synthesis techniques. Glass thermal behavior was analyzed using DSC/TG, XRD and SEM, and the JMAK model was applied to study crystallization kinetics and determine prevailing mechanisms. All samples, except the one with 80 mol.% YAG, had two exothermic effects in their DSC curves. The first appeared between 937 and 950 °C, while the second was observed between 958 and 1102 °C. XRD analysis of crystallized microspheres confirmed the presence of YAG and various forms of alumina phases in the samples with lower YAG/higher Al2O3 content (40 and 50 mol.%). The sample with the highest YAG content showed the strongest tendency to crystallize in the kinetics study. The value of apparent activation energy (Eapp) of this sample was 987.3 ± 13.0 kJ mol−1. For the remaining samples, the values of Eapp were higher and ranged from 1215.1 ± 10.6 to 1847.5 ± 9.3 kJ mol−1, indicating the lowest ability of these compositions to crystallization. The growth of three-dimensional (3-D) YAG crystals was predominant in glasses with the highest (80 mol.%) YAG content. One-dimensional (1-D) growth of γ-Al2O3 crystals and 3-D growth of YAG crystals was predominant in glasses with the lowest (40 mol.%) YAG content.

In-situ scattering and calorimetric studies of crystallization pathway and kinetics in a Cu-Zr-Al bulk metallic glass

The crystallization route and kinetics of a Cu-Zr-Al bulk metallic glass (BMG), based on Cu50Zr50, were investigated using in-situ synchrotron small- and wide-angle X-ray scattering (SAXS/WAXS), in-situ high-energy X-ray diffraction (HEXRD), and differential scanning calorimetry (DSC). The acquisition of kinetic diagrams of SAXS/WAXS enables the direct construction of the overall phase transformation route from room temperature to the onset temperature of solid state phase transformation upon heating. It is revealed that the studied alloy undergoes multiple steps (at least five steps) before reaching the high-temperature thermodynamic equilibrium. This is distinct from the commonly believed simple path of glass → Cu10Zr7 + CuZr2 → B2-CuZr predicted by the Cu-Zr equilibrium phase diagram. In addition to thermodynamics, we emphasize that kinetic factors play a prominent role in the phase transformation process of Cu-Zr-Al BMGs. Furthermore, isothermal crystallization kinetics analyses conducted by in-situ HEXRD and DSC indicate that the formation of the initial crystalline phase, specifically the Cu10Zr7, follows an interface-controlled quasi-polymorphic process with an increasing nucleation rate. The findings of this study may provide novel insights into the crystallization mechanism of glass-forming supercooled liquids from a thermophysical perspective.

The Study of Crystallization Kinetics and Chemical Changes in Ge4Sb4Te5 through Transmission Electron Microscope

The Study of Crystallization Kinetics and Chemical Changes in Ge4Sb4Te5 through Transmission Electron Microscope

Unveiling dual crystallization peaks in Zn2P2O7 glass: Insights into stability, nucleation, and growth kinetics

This study reports on the successful synthesis of Zn2P2O7 glass using the conventional melt-quenching method. The state of the material has been investigated using X-ray Diffraction (XRD) and Differential Scanning Calorimetry (DSC), to verify its amorphous and glassy state with the onset of two distinct crystallization peaks. These peaks were indicative of the transition to α-Zn2P2O7 and γ-Zn2P2O7 phases during the annealing process, a finding that was supported by Fourier-transform infrared spectroscopy (FTIR) analysis. This marked the inaugural occasion where the stabilization of both Zn2P2O7 phases from their respective annealed glassy state was achieved. The crystallization kinetics and associated parameters of Zn2P2O7 glass were deeply delved into, with various models including Kissinger, Ozawa, and the Matusita-Sakka approach. The applied models elucidate the mechanisms of growth and nucleation within the glass matrix. This kinetic study provided valuable insights into the crystallization process, revealing that α-Zn2P2O7 is both kinetically and thermally more stable than the γ-phase. However, it is less thermodynamically stable compared to the γ-phase. Besides, the study of phase transformations and crystallization kinetics was enhanced by the analysis of the Avrami index.

Molecular dynamics simulation of the 3-15alkyphenol compatibilizer in highly toughened and robust polyamide 10,12/MWCNT composites.

Highly toughened and stiff polyamide 10,12 (PA10,12) composites present a promising alternative to metal products for high-impact environments. However, it is challenging to toughen PA10,12 composites without compromising their robustness. Herein, we report a facile and scalable route to simultaneously develop reinforced and toughened PA10,12 composites via compounding PA10,12, carbon nanotubes (CNTs) and 3-15alkyphenol (PDP). The PDP acted as a compatibilizer to well-disperse MWCNTs since they tended to be adsorbed onto the CNT surface, which was revealed by molecular dynamics simulation. According to the simulation statistics, the vertical PDP conformations (to the CNT surface) were predominant in the ternary composites with ∼78.7% probability. Moreover, the hydrogen bonds (H-bonds) between the PDP and the PA matrix were confirmed using FTIR. A crystallization kinetics study also revealed that the crystallization temperature increased from 166.7 °C for the neat PA10,12 to 168.7 °C for the ternary PA/PDP/CNT composites containing 1.5 wt% CNTs, while the crystallization half-time increased from 0.58 s for the neat PA10,12 to 1.2 s for the ternary composites. It was also found that the notched impact strength of the ternary composites reached 75.2 kJ m-2, which was 970% higher than that of the neat PA10,12 without compromising their tensile strength of 50.5 MPa much. This work provides a new insight into PDP as a compatibilizer to develop simultaneously stiff and toughened nylon composites.

Reactive Crystallization Kinetics Study of Boehmite in Ammonia Solution by Adding Ammonium Aluminum Sulfate

As an important intermediate product in new techniques for extracting alumina from coal fly ash, boehmite is obtained by the reaction between ammonium aluminum sulfate and ammonia. The reactive crystallization kinetics of boehmite is investigated using a continuous steady-state method. The Mydlarz and Jones (MJ3) models are in considerable agreement with the experimental results by a non-linear regression method; furthermore, crystal nucleation and growth rate equations are proposed. The results revealed that the suspension density and agitation rates present considerable influence on nucleation. Additionally, high levels of supersaturation are not conducive for crystal growth, and the supersaturation index for crystal growth was small due to its poor water solubility. Moreover, the maximum d0.5 (average particle size) was 27.968 μm under the agitation condition and the feed rates of 250 r/s and 0.5 g/10 min. Fast crystal growth speed is associated with the crystal structure’s high AlO6-unit and bulk-oxygen content. Our study on crystal nucleation and growth kinetics will be beneficial to the industrial production of boehmite.

Sb induced effect on glass transition, crystallization kinetics and optical properties of Se96Sn4 alloy

Se96-xSn4Sbx (x = 0, 2, 4, 6, and 8) glassy alloys were prepared using the melt quench technique. Thermal measurements were carried out using differential scanning calorimetry (DSC) in non-isothermal mode. Kissinger and Moynihan methods are used for glass transition kinetics, while Kissinger, Takhor, and Augis-Bennet methods are used to study crystallization kinetics. The inclusion of Sb in the alloy increased the glass transition temperature (Tg), activation energy of the glass transition (Et), and activation energy of crystallisation (Ec). The chemical bond approach has been used to explain the results. The rising trend of Ec is explained by the production of SnSe4/2 structural units with energies greater than those of Se–Se and Se–Sb bonds, increasing the degree of cross-linking. The dimensionality of crystal growth changes from one to two with the addition of Sb to the Se-Sn alloy. The criterion for thermal stability was addressed by using the enthalpy emitted during the crystallization process. In addition, Kubelka-Munk transformation and Tauc plots were used to calculate the band gaps. The energy gap (Eg) decreases from 3.72 to 1.60 eV as the Sb concentration increases from 0 to 8 atm%.

Influence of low contents of cellulose nanocrystals on the crystallization behavior of biobased Poly(propylene 2,5-furandicarboxylate)

To address the slow crystallization problem of poly(propylene 2,5-furandicarboxylate) (PPF), fully biobased PPF/cellulose nanocrystals (CNC) composites were prepared via a solution and casting method in this work at low CNC contents. The influence of CNC on the crystallization of PPF was studied in detail under various conditions, including nonisothermal and isothermal melt crystallization as well as nonisothermal and isothermal cold crystallization. The results revealed that the crystallization of PPF was enhanced under various crystallization conditions by CNC due to the heterogeneous nucleating agent role. From the isothermal crystallization kinetics study, the presence of CNC did not alter the crystallization mechanism of PPF. In addition, the thermogravimetric analysis results showed that both PPF and PPF/CNC composites displayed an excellent thermal stability. On the basis of the wide angle X-ray diffraction study, CNC did not change the crystal structure of PPF.

Calorimetric studies of yttrium doped non-conventional phase-change materials for improved performance

Though phase-change materials (PCMs) are regarded as constituent part of next-generation phase-change memory and other unfolding optoelectronic applications, the kinetics study of glass transition and crystallization, significant property in switching remains obscure in high-temperature region. Hence, this paper reports the investigation of glass transition and crystallization kinetics of Te(1-x) (GeSe0.5)Yx (TGSY) chalcogenide glass using differential scanning calorimetry (DSC) at heating rates 5, 10, 15, 20 °C/min. The effect of increasing Y quantity has been described by connecting structural relaxation kinematics during glass transition phenomena and devitrification while crystallization in chalcogenide glasses with their varied physicochemical characteristics. The inclusion of Y causes a discernible rise in the crystallization rate. The system is compatible with a strong glass-forming liquid, according to the Te(1-x) (GeSe0.5) Yx material fragility index. According to the average values of the kinetic exponent factors, there is heterogeneous nucleation for the investigated composition, which is subsequently followed by a two- or three-dimensional crystal growth phenomenon. Different glass stability criteria have been discussed based on the relationship between the characteristic temperatures. The CZW and CLX criteria were found to be inappropriate for discussing glass stability (GS) for the studied compositions based on the heating rate and composition dependencies of all criteria. The CYL criteria of Yuan et al. is the finest and it demonstrates the optimal ability for evaluating the GS, according to the data that was extracted from several GS criteria and their relative change parameters. By adding Y, thermal stability parameter and enthalpy emitted during the transition of glass and crystalline phases have been found to have an inverse relationship. All studied properties can conclude the application of studied material in phase-change material devices.

Characterization of crystallization kinetics in Polyamide 6 with a focus on modeling the thermoforming process: experiments, modeling, simulations

Thermoforming of continuous fiber-reinforced plastics made of semi-crystalline thermoplastics has gained significant interest due to its potential for producing lightweight and high-strength components for various applications. Before thermoforming, a laminate is heated to a temperature beyond the melting point of the thermoplastic. During the subsequent forming process, the laminate is continuously cooled, which triggers non-isothermal crystallization in the semi-crystalline matrix material. In this context, the study of crystallization kinetics is crucial in identifying phase transition, analyzing exothermic latent heat during crystallization and determining inhomogeneous crystallinity distribution caused by uneven cooling in the laminate’s thickness direction. This contribution primarily deals with experimental investigations, modeling and finite element simulations for characterizing the crystallization kinetics in the matrix material, Polyamide 6 and investigating the aforementioned factors. To model the crystallization kinetics, an extended form of the Avrami model, known as the modified Nakamura–Ziabicki model, is adopted. The parameters for the modified Nakamura–Ziabicki model, which depend on the local cooling rates, are identified based on fitting the model to flash DSC (differential scanning calorimetry with high cooling rates) and standard DSC non-isothermal cooling experiments. Finally, the model is implemented into the commercial FE software COMSOL Multiphysics® and the crystallinity evolution in the laminate is simulated for the process-relevant die and laminate temperatures and laminate thicknesses.

A study of crystallization kinetics, phase formation and magnetic properties of (FeCoNiMn0.25Al0.25)75Si13B12 high-entropy metallic glass

The crystallization kinetics, phase formation and magnetic properties of (FeCoNiMn0.25Al0.25)75Si13B12 high-entropy metallic glass are investigated by thermal analysis, electron microscopic imaging, X-ray and magnetic tests. The results indicate that the alloy combines good glass forming ability and thermal stability. After heat treatment, the alloy precipitates with a feature of three-dimensional growth, while the α-Fe,Co phase first precipitates, and following the lamellar eutectic precipitate as Fe-B and Co2Si. This ultra-fine α-Fe,Co at low temperatures and the solid solution of non-ferromagnetic elements in the α-Fe,Co at high temperatures decrease the saturation magnetization of the alloy. In addition, the change from antiferromagnetic to ferromagnetic of Mn is confirmed through first-principles density functional theory calculations.

Improvement of the cooling control during electrofusion welding of polyethylene pipes at low temperatures

A method has been developed for determining the heater power at the cooling stage when welding polyethylene pipes for gas pipelines at low ambient temperatures (below those recommended by regulatory documents). Efficiency of the method is verified by studies of materials crystallization kinetics in the heataffected zones of welded joints

A simple strategy for synthesis of b-axis-oriented MFI zeolite macro-nanosheets

Zeolite nanosheets with shortened diffusion paths and high external surface areas have drawn significant attention. This unique morphology of zeolites can endow them with reduced diffusion resistance and high accessibility of active sites, and thereby good catalytic performance. Exploring simple synthesis strategies for zeolite nanosheets is mostly desired in zeolite chemistry. Herein, MFI zeolite nanosheets with a thickness of 50-100 nm along the b -axis and a length of 1 μm along the c -axis, namely zeolite macro-nanosheets, have been successfully synthesized via the strategy of combining pre-aging and pH regulation without the use of complex templates/additives and fluorine media. Pre-aging at a relatively high temperature of 90 °C and low alkalinity for crystallization (pH = 7.0~8.5) are found to play key roles in controlling macro-nanosheet synthesis, which can promote the formation of MFI zeolite precursors and then dissociate them into smaller ones for the following oriented aggregation during hydrothermal treatment. Crystallization kinetic studies suggest that the two-dimensional crystal growth is the intrinsic behavior of zeolite crystallization under employed conditions. This synthesis strategy can be easily extended to the synthesis of heteroatom-containing MFI macro-nanosheets, such as ZSM-5 and TS-1.

Study of Glass Formation and Crystallization Kinetics in a 2D Metal Halide Perovskite Using Ultrafast Calorimetry.

While crystalline 2D metal halide perovskites (MHPs) represent a well-celebrated semiconductor class, supporting applications in the fields of photovoltaics, emitters, and sensors, the recent discovery of glass formation in an MHP opens many new opportunities associated with reversible glass-crystalline switching, with each state offering distinct optoelectronic properties. However, the previously reported [S-(-)-1-(1-naphthyl)ethylammonium]2PbBr4 perovskite is a strong glass former with sluggish glass-crystal transformation time scales, pointing to a need for glassy MHPs with a broader range of compositions and crystallization kinetics. Herein we report glass formation for low-melting-temperature 1-MeHa2PbI4 (1-MeHa = 1-methyl-hexylammonium) using ultrafast calorimetry, thereby extending the range of MHP glass formation across a broader range of organic (fused ring to branched aliphatic) and halide (bromide to iodide) compositions. The importance of a slight loss of organic and hydrogen iodide components from the MHP in stabilizing the glassy state is elucidated. Furthermore, the underlying kinetics of glass-crystal transformation, including activation energies, crystal growth rate, Angell plot, and fragility index, is studied using a combination of kinetic, thermodynamic, and rheological modeling techniques. An inferred fast crystal growth rate of 0.21 m/s for 1-MeHa2PbI4 shows promise toward suitability in extended application spaces, for example, in metamaterials, nonvolatile memory, and optical and neuromorphic computing devices.

Study of Crystallization Kinetics of (Fe50Ni50)73.5Si13.5B9Nb3Cu1 Ribbons Prepared by Rapid Cooling Technique

Amorphous alloy ribbons of (Fe50Ni50)73.5Si13.5B9Nb3Cu1 were fabricated by rapid cooling technique on single copper wheel. After fabrication, the crystalline structure of the ribbons were examined by X-ray diffraction method. The results show that the samples possess a complete amorphous state. The crystallization process was studied by using a differential thermal analyzer (DSC). The DSC analysis show that there are two exothermic peaks corresponding to two crystalline phases appeared in the alloy ribbons. By changing the heating rate (i.e. 5, 10, 15, 20 and 25 oC/min) and by using the Kissinger method, The activation energy of crystallization of the crystalline phases determined for one phase was found to be E1 = 350 kJ/mol and for other one, E2 = 375 kJ/mol. Based on these results, we have chosen the appropriate annealing mode for the alloy ribbons. After annealing, the alloy ribbons were achieved nanocrystalline states of FeNi and α-Fe nano-particles with the grain size ranging from 5 to 15 nm and the fraction of crystallization between the crystalline and amorphous phases of 46, 67, 85 and 96 % respectively for the annealing regimes at 500 oC for 20, 30, 50 and 60 minutes.

Compact sample environment for in situ X-ray scattering during spin-coating.

We demonstrate a compact sample environment for the in situ study of crystallization kinetics of thin films on synchrotron beamlines, featuring atmospheric control, automated deposition, spin-coating, and annealing stages. The setup is suitable for studying thin film growth in real time using grazing-incidence X-ray diffraction techniques. Humidity and oxygen levels are being detected by sensors. The spinning stage exhibits low vertical oscillation amplitude (∼3μm at speeds up to 10 000 rpm) and can optionally be employed for antisolvent application or gas quenching to investigate the impact of these techniques, which are often used to assist thin film growth. Differential reflectance spectroscopy is implemented in the spin-coater environment for inspecting thin film thickness and optical properties. The infrared radiation-based annealing system consists of a halogen lamp and a holder with an adjustable lamp-to-sample distance, while the sample surface temperature is monitored by a pyrometer. All features of the sample environment can be controlled remotely by the control software at synchrotron beamlines. In order to test and demonstrate the performance, the crystallization pathway of the antisolvent-assisted MAPbI3 (MA = methylammonium) perovskite thin film during the spinning and annealing stages is monitored and discussed.

Study on the regulation mechanism of effective glass transition temperature on the crystallization of crystalline solid dispersion.

The focus of this investigation was to determine the mechanism of effective glass transition temperature (TgE) on the crystallization behavior and microstructure of drugs in crystalline solid dispersion (CSD). CSDs were prepared by rotary evaporation using ketoconazole (KET) as a model drug and the triblock copolymer poloxamer 188 as a carrier. The pharmaceutical properties of CSDs, such as crystallite size, crystallization kinetics, and dissolution behavior, were investigated to provide a foundation for studying the crystallization behavior and the microstructure of drugs in CSDs. According to classical nucleation theory, the relationship of treatment temperature-drug crystallite size-TgE of CSD was investigated. Voriconazole, a compound that is structurally similar to KET but with different physicochemical properties, was used to verify the conclusions. The dissolution behavior of KET was significantly enhanced compared to the raw drug due to smaller crystallite size. Crystallization kinetic studies revealed a two-step crystallization mechanism for KET-P188-CSD, in which P188 crystallized first and KET crystallized later. When the treatment temperature was near TgE, the drug crystallite size was smaller and more numerous, which suggests nucleation and slow growth. With the increase of temperature, the drug changed from nucleation to growth, and the number of crystallites decreased and the size of the drug increased. This result suggests it is possible to prepare CSDs with higher drug loading and smaller crystallite size by adjusting the treatment temperature and TgE, so as to maximize the drug dissolution rate. The VOR-P188-CSD maintained a relationship between treatment temperature, drug crystallite size, and TgE. The findings of our study demonstrate that TgE and the treatment temperature can be used to regulate the drug crystallite size and improve the drug solubility and dissolution rate.

Shape-stable erythritol composite phase change materials with controlled latent heat release for spatiotemporally thermal energy utilization

Phase change materials (PCMs) have been extensively concerned recently as suitable medium for thermal energy storage due to their absorbing or releasing a large amount of latent heat in the phase change process. However, traditional PCMs usually crystallize spontaneously to release their latent heat in the cooling process, which greatly limits their practical application in thermal energy long-term storage and controllable release. Herein, we designed and synthesized a shape-stable erythritol (ERY)-based composite PCM with attractive performance of latent heat controlled storage and release using a facile aqueous fabrication route. In this composite, calcium ions cross-linked with sodium alginate is introduced to construct strong hydrogen bonding with ERY to increase the activation energy barrier for stabilizing supercooling, thus realizing long-term latent heat stored in supercooling state. The supercooled ERY composite can be maintained at room temperature for 50 days and subsequently controllably releases latent heat by thermal or mechanical trigger method. Meanwhile, the ERY composite exhibits excellent shape stability without any leakage over the phase change temperature. In addition, the crystallization enthalpy can reach 181.2 J/g, which can be maintained even after 80 thermal cycles, showing superior thermal energy storage capacity and repeatability. The crystallization kinetics study reveals that the crystallization mode of the ERY composite is three-dimensional growth spherical diffusion. This work provides an important strategy for the design and synthesis of shape-stable PCMs with controllable latent heat storage and release performance, which is of great prospect for the development of spatiotemporally thermal energy storage technology.

Calorimetric studies of crystallization in Se76Te20Sn2Ge2 glass under heating/cooling mode

In the liquid-solid phase transition analysis, it was observed that two phenomena namely crystallization and glass transition take place, whenever we cool a liquid or melt a solid. In the present endeavor, we have tried to analyze the comparative study of crystallization kinetics using comprehensive iso-conversional methods in both heating/cooling modes of quaternary Se76Te20Sn2Ge2 glassy material synthesized by a very simple and famous melt quenching technique. Differential Scanning Calorimetry (DSC) was employed for this analysis. The effect of heating, as well as cooling rates on the crystallization kinetics, was investigated. Various kinetic parameters like activation energy using the iso-conversional approach, the reaction rate constant, the Avrami index, Meyer-Neldel energy, etc have been calculated for both heating and cooling modes.

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.