Nucleation Kinetics Research Articles

Facile synthesis of dual-MOF ultrathin nanosheets supported on layered double hydroxides heterostructure: Electron modulation strategy for enhanced electrocatalytic water splitting

In this study, we achieved electron environment modulation of MOF-based electrocatalyst by creating a dual-functional heterostructure using two-dimensional (2D) MOFs and layered double hydroxides (LDH), to enhance its electrocatalytic performance. Through a self-sacrificial template method, ultrathin hybrid dual-MOF (CoBDC and MIL-100(Fe)) nanosheets were grown on LDH, forming DM@CoFeRu-LDH, a 2D heterostructure benefiting from interference co-growth on the 2D scaffold. The thickness of dual-MOF nanosheets can be controlled by regulating the nucleation and reaction kinetics. Specifically, with a thickness ranging from 1–1.5 nm, it effectively exposes more active sites and accelerate electron and mass transfer. Additionally, electron transfer occurred between the dual-MOF and LDH heterostructures, leveraging synergistic effects from multi-metal centers to achieve an optimal electron structure. DM@CoFeRu-LDH exhibited the lowest energy barrier for the rate-determining step in the oxygen evolution reaction, along with a favorable hydrogen adsorption energy for the hydrogen evolution reaction. As a result, the DM@CoFeRu-LDH demonstrated efficient electrocatalytic activity, requiring only a voltage of 1.50 V to achieve a current density of 10 mA cm−2.

In Situ Monitoring the Nucleation and Growth of Nanoscale CaCO3 at the Oil-Water Interface.

Interfaces can actively control the nucleation kinetics, orientations, and polymorphs of calcium carbonate (CaCO3). Prior studies have revealed that CaCO3 formation can be affected by the interplay between chemical functional moieties on solid-liquid or air-liquid interfaces as well as CaCO3's precursors and facets. Yet little is known about the roles of a liquid-liquid interface, specifically an oil-liquid interface, in directing CaCO3 mineralization which are common in natural and engineered systems. Here, by using in situ X-ray scattering techniques to locate a meniscus formed between water and a representative oil, isooctane, we successfully monitored CaCO3 formation at the pliable isooctane-water interface and systematically investigated the pivotal roles of the interface in the formation of CaCO3 (i.e., particle size, its spatial distribution with respect to the interface, and its mineral phase). Different from bulk solution, ∼5 nm CaCO3 nanoparticles form at the isooctane-water interface. They stably exist for a long time (36 h), which can result from interface-stabilized dehydrated prenucleation clusters of CaCO3. There is a clear tendency for enhanced amounts and faster crystallization of CaCO3 at locations closer to isooctane, which is attributed to a higher pH and an easier dehydration environment created by the interface and oil. Our study provides insights into CaCO3 nucleation at an oil-water interface, which can deepen our understanding of pliable interfaces interacting with CaCO3 and benefit mineral scaling control during energy-related subsurface operation.

Study of the Kinetics of Nucleation and Growth of Silver Nanoparticles: UV-Visible Spectroscopy vs. Atomic Force Microscopy and Transmission Electron Microscopy

Silver nanoparticles have been the subjects of research interest because of their unique properties and extensive use in modern-day applications. A variety of preparation techniques have been reported for their synthesis but among them mostly recognized is a modified version of the Turkevich citrate method. In this study, we also chose this method of silver nanoparticle synthesis. The synthesized nanoparticles were characterized first, traditionally with UV-Visible spectroscopy and then their sizes and shapes were identified employing Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM). From the UV-Vis data were extracted the rate constants for the nucleation ($$k_1$$) and growth ($$k_2$$) of the silver nanoparticles, and then these constants were further used to fit those obtained from AFM and TEM. Using the values of $$k_1$$ and $$k_2$$ independently in the two experimental methods validated and supported the well-acknowledged two-step mechanism of slow nucleation and fast autocatalytic surface growth.

Gas hydrate inhibition by urea and its blends with vinyl lactam polymer: Paving the way to green hybrid inhibitors

Urea is an environmentally benign substance considered a promising gas hydrate inhibitor in flow assurance. Nevertheless, its effect on gas hydrate formation kinetics remains poorly understood. This study investigates the impact of urea and hybrid urea/polymer KHI samples on the nucleation and growth kinetics of sII natural gas hydrates. Hydrate formation was observed at a lower onset temperature with increasing urea and polymer concentration. The nucleation of sII hydrate in aqueous urea solutions occurred at a higher subcooling (7.50 ± 0.58 K at 30 mass%) than in pure water (5.17 ± 0.69 K). These findings indicate that urea acts as a nucleation inhibitor of sII hydrates, although its capacity is not as potent as that of polymer KHI.The analysis of the hydrate nucleation probability distributions revealed that the sII hydrate nucleation rate exhibited a significant decline, approximately one order of magnitude, at subcooling of 5.3–6 K for 20 mass% urea compared to water. A similar behavior was noticed in an aqueous solution of polymer KHI. Urea has succeeded in providing a total benefit of up to 10 K in hydrate onset temperature due to a shift in the hydrate stability zone and nucleation retardation.Consequently, urea is a green dual-acting anti-hydrate chemical that inhibits the formation of sII hydrates by thermodynamic and kinetic mechanisms. Besides, adding 10 mass% urea increases the cloud point temperature of vinyl lactam polymer Luvicap 55W by 14 K. Urea is an additive that considerably augments the stability of the polymer in aqueous solutions at elevated temperatures. These findings make urea an effective and environmentally friendly top-up inhibitor that significantly enhances the anti-hydrate properties of polymer KHI.

Location-Dependent Phase Transformation Kinetics During Laser Wire Deposition Additive Manufacturing of Ti–6Al–4V

This work models the microstructural evolution as a function of position in laser-wire deposited Ti–6Al–4V parts using a classical multi-component JMAK nucleation and growth model with additive isothermal time-steps. Model predictions are compared to experimental observations. The model can be used to interpret nucleation and growth kinetics of various characteristic features of the microstructure that are inaccessible by experiments. It explains the presence of “layer bands” at specific locations unrelated to the weld bead structure. The last re-heating (of multiple thermal cycles) of a solidified layer, and where it peaks, plays a key role in increasing the nucleation density at specific locations, resulting in full α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document}-colony microstructures constituting the “layer bands,” while the rest of the build is predominantly basketweave. Additionally, changes in the basketweave α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document}-lath thickness as a function of the distance from the substrate are studied and compared with an Arrhenius-type function, with results highlighting a more complex relationship than an Arrhenius-type function would suggest.

Experimental evidence of seismic ruptures initiated by aseismic slip

Seismic faults release the stress accumulated during tectonic movement through rapid ruptures or slow-slip events. The role of slow-slip events is crucial as they impact earthquakes occurrence. However, the mechanisms by which slow-slip affects the failure of frictionally locked regions remain elusive. Here, building on laboratory experiments, we establish that a slow-slip region acts as a nucleation center for seismic rupture, enhancing earthquakes’ frequency. We emulate slow-slip regions by introducing a granular material along part of a laboratory fault. Measuring the fault’s response to shear reveals that the heterogeneity serves as an initial rupture, reducing the fault shear resistance. Additionally, the slow-slip region extends beyond the heterogeneity with increasing normal load, demonstrating that fault composition is not the only requirement for slow-slip. Our results show that slow-slip modifies rupture nucleation dynamics, highlighting the importance of accounting for the evolution of the slow-slip region under varying conditions for seismic hazard mitigation.

Metastable zone width and nucleation kinetics of vanillyl alcohol crystallization in various solvents

In this study, linear cooling batch crystallization of vanillyl alcohol using a laser power system was carried out to experimentally measure the metastable zone widths of vanillyl alcohol in selected solvents (ethanol, 2-propanol, and methyl cyanide) at various saturated temperatures (40, 50, and 60 °C), cooling rates (0.5, 1, 1.5, and 2 °C/min), and agitation speeds (300, 400 rpm). Besides, the sonocrystallization of vanillyl alcohol in ethanol was conducted for measuring MSZW at a various ultrasonic amplitudes (0 %, 25 %, 50 %, and 100 %) at a fixed temperature of 40 °C, cooling rate of 1 °C/min, and agitation speed of 300 rpm. For all three solvents, the MSZW decreases with saturation temperature, while it increases with cooling rate, and this trend doesn’t change for different agitation speeds. Three models—the self-consistent Nývlt-like model, the classical 3D nucleation theory model, and the simplified linear integral model based on classical nucleation theory (CNT)—were employed to estimate the nucleation kinetic parameters for vanillyl alcohol in three solvents. The goodness fit of the models were checked by the coefficient of determination (R-squared). The R-squared values reflected a very good fit between the experimental and predicted values and implied that the models are reliable to estimate nucleation kinetic parameters. Additionally, the interfacial energy between vanillyl alcohol and the solvents was observed to decrease with increasing temperature. Overall, the results indicate that a low nucleation order and low interfacial energy suggest weak solute–solvent interactions, making nucleation easier in the following order: methyl cyanide > ethanol > 2-propanol.

Heterogeneous Nucleation Regulation Amends Unfavorable Crystallization Orientation and Defect Features of Antimony Selenosulfide Film for High-Efficient Planar Solar Cells.

Antimony selenosulfide (Sb2(S,Se)3) has obtained widespread concern for photovoltaic applications as a light absorber due to superior photoelectric features. Accordingly, various deposition technologies have been developed in recent years, especially hydrothermal deposition method, which has achieved a great success. However, device performances are limited with severe carrier recombination, relating to the quality of absorber and interfaces. Herein, bulk and interface defects are simultaneously suppressed by regulating heterogeneous nucleation kinetics with barium dibromide (BaBr2) introduction. In details, the Br adsorbs and dopes on the polar planes of cadmium sulfide (CdS) buffer layer, promoting the exposure of nonpolar planes of CdS, which facilitates the favorable growth of [hk1]-Sb2(S,Se)3 films possessing superior crystallinity and small interface defects. Additionally, the Se/S ratio is increased due to the replacement of S/Se by Br, causing a downshift of the Fermi levels with a benign band alignment and a shallow-level defect. Moreover, Ba2+ is located at grain boundaries by coordination with S and Se ions, passivating grain boundary defects. Consequently, the efficiency is increased from 7.70% to 10.12%. This work opens an avenue towards regulating the heterogeneous nucleation kinetics of Sb2(S,Se)3 film deposited via hydrothermal deposition approach to optimize its crystalline orientation and defect features.

Interplay Between Nucleation and Kinetics in Dynamic Twinning

Abstract In this work, we apply a phase-field modeling framework to elucidate the interplay between nucleation and kinetics in the dynamic evolution of twinning interfaces. The key feature of this phase-field approach is the ability to transparently and explicitly specify nucleation and kinetic behavior in the model, in contrast to other regularized interface models. We use this to study two distinct problems where it is essential to explicitly specify the kinetic and nucleation behavior governing twin evolution. First, we study twinning interfaces in 2D. When these interfaces are driven to move, we find that significant levels of twin nucleation occur ahead of the moving interface. Essentially, the finite interface velocity and the relaxation time of the stresses ahead of the interface allow for nucleation to occur before the interface is able to propagate to that point. Second, we study the growth of needle twins in antiplane elasticity. We show that both nucleation and anisotropic kinetics are essential to obtain predictions of needle twins. While standard regularized interface approaches do not permit the transparent specification of anisotropic kinetics, this is readily possible with the phase-field approach that we have used here.

Resolving intermediates during the growth of aluminum deuteroxide (Hydroxide) polymorphs in high chemical potential solutions

Aluminum hydroxide polymorphs are of widespread importance yet their kinetics of nucleation and growth remain beyond the reach of current models. Here we attempt to unveil the reaction processes underlying the polymorphs formation at high chemical potential. We examine their formation in-situ from supersaturated alkaline sodium aluminate solutions using deuteration and time-resolved neutron pair distribution function analyses, which indicate the formation of individual Al(OD)3 layers as an intermediate particle phase. These layers ultimately stack to form gibbsite- or bayerite-like layered heterostructures. Ex-situ characterization of the recovered precipitates using 27Al magic angle spinning nuclear magnetic resonance spectroscopy, Raman, X-ray diffraction, and scanning electron microscopy, suggests the presence of additional intermediate states, an amorphous compound bearing both tetrahededrally- and penta-coordinated Al3+. These observations reveal the complex pathways to form Al(OD)3 monolayers via either transient pentacoordinate species or amorphous-to-ordered transitions. The subsequent crystallization of admixed gibbsite/bayerite is followed by an Al(OD)3 monolayer attachment process.

Nickel stanogermanides thin films: Phases formation, kinetics, and Sn segregation

Ge1−xSnx thin films with a Sn content of x ≥ 0.1 present a direct bandgap, which is very interesting for the fabrication of efficient photonic devices. The monostanogermanide phase, Ni(GeSn), is promising to form ohmic contact in GeSn-based Si photonic devices. However, the formation kinetics of Ni stanogermanides and the incorporation of Sn in Ni–GeSn phases are not fully understood. In this work, Ni thin films were deposited on Ge and Ge0.9Sn0.1 layers grown in epitaxy on an Si(100) substrate using magnetron sputtering technique. In situ x-ray diffraction measurements were performed during the solid-state reaction of Ni/Ge and Ni/Ge0.9Sn0.1. 1D finite difference simulations based on the linear parabolic model were performed to determine the kinetics parameters for phase growth. The nucleation and growth kinetics of Ni germanides are modified by the addition of Sn. A delay in the formation of Ni(GeSn) was observed and is probably due to the stress relaxation in the Ni-rich phase. In addition, the thermal stability of the Ni(GeSn) phase is highly affected by Sn segregation. A model was developed to determine the kinetic parameters of Sn segregation in Ni(GeSn).

Model predicted optimization of experimental set-up and process conditions for microwave-assisted synthesis of silver nanowires

This work presents simulations led optimization of choice of a reactor for an experimental set-up for the continuous production of silver nanowires with certain constraints in terms of yield, reaction time, and dimensions of nanowires. The choice of reactors based on the simulations of reaction kinetics for nucleation and growth phases of driving the optimization of an experimental set-up and subsequent optimization of process conditions to maximize the yield of nanowires of desired dimensions. The optimized reactor configuration is dictated by the reaction kinetics and using a microwave in continuous mode becomes unavoidable. This makes the approach highly reproducible as well as scalable. The integration of conventional and microwave heating is simulated and subsequently optimized experimentally to attain a significant increase in nanowire yield under steady-state conditions with less than 15 min of residence time. The precise control over the rate in different reactor configurations governing nucleation, accelerated growth followed by slow growth to complete the conversion of precursor enables higher selectivity of nanowires with controllable dimensions resulting in 100 gm production per day using simple set-up. We systematically examined key reaction parameters, including the concentration of metal ions, residence time, and different reactor configurations. Our approach successfully yielded AgNWs with 40–60 nm diameter and 15 µm length. The cost associated with this process for synthesizing AgNWs is less than 10$ per gram. This study highlights the potential of continuous, high-throughput processes for controlling nanowire size and yield through advanced reactor engineering.

The effect of cobalt alloying on the phase transformation kinetics of Ni-Ti alloys

This study investigates the influence of cobalt (Co) alloying addition and heat treatment temperature on the phase transformation behaviour controlling the superelasticity and shape memory effect (SME) of Nickel-Titanium (Ni-Ti) alloys, commonly known as nitinol. The microstructural evolution upon heat treatment conducted at a temperature ranging from 440 to 560 °C was thoroughly analyzed via Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), and Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS). Increase in heat treatment temperatures from 470 °C up to 530 °C led to the dissolution of particles present in as-received (cold-worked) condition. It was determined that Co addition into the Ni-Ti alloy system resulted in a change in the nucleation and growth kinetics of Ti-rich precipitates, leading to the formation of larger and fewer particles during processing. Both binary and ternary alloys showed a decrease in austenite finish temperature (Af) with increasing heat treatment temperatures, however, the rate of decrease was found to be higher for Co containing ternary alloys. This is linked with faster structural relaxation when Co is present and evidenced by lattice size variation during heat treatment. It is highlighted that heat treatment methodology needs to be tailored to the specific alloy composition for controlling superelasticity and SME via alloy design.

Capture zone scaling in 2D Ge island nucleation on Si(111)-(7 × 7) at elevated temperatures

Recently we have studied the concentration N2D of 2D Ge island nucleated on large-scale Si(111)-(7 × 7) terraces at 550 − 650 °C as function of the substrate temperature T and Ge deposition rate R [J. Cryst. Growth. 531 (2020) 125347], where we have shown that N2D(R) dependence is characterized by a power law with scaling exponent χ = 1 ± 0.1. However, in the frames of classical Venables rate-equation approach, the obtained range of χ values do not allow one to unambiguously determine the critical nucleus size i, since χ = 1 ± 0.1 can be attributed to both diffusion limited (DL) and attachment limited (AL) growth regimes. In order to determine an exact i size and growth kinetics, in this work, we have investigated the scaled capture-zone distribution (CZD) of nucleated 2D Ge islands on the same Ge/Si(111)-(7 × 7) samples and described it by the generalized Wigner distribution Pβ=aβAβexp-bβA2, where Pβ is the probability density of getting into some region of capture zone values, A is normalized Voronoi cell area for 2D island, β=iχ is scaling parameter directly related to the critical nucleus size i. It has been shown that the kinetics of 2D Ge island nucleation on the wide Si(111)-(7 × 7) terraces at elevated temperatures should procced under AL growth kinetics with i = 3–5 particles.

Templated Nucleation of Clotrimazole and Ketoprofen on Polymer Substrates.

The use of different template surfaces in crystallization experiments can directly influence the nucleation kinetics, crystal growth, and morphology of active pharmaceutical ingredients (APIs). Consequently, templated nucleation is an attractive approach to enhance crystal nucleation kinetics and preferentially nucleate desired crystal polymorphs for solid-form drug molecules, particularly large and flexible molecules that are difficult to crystallize. Herein, we investigate the effect of polymer templates on the crystal nucleation of clotrimazole and ketoprofen with both experiments and computational methods. Crystallization was carried out in toluene solvent for both APIs with a template library consisting of 12 different polymers. In complement to the experimental studies, we developed a computational workflow based on molecular dynamics (MD) and derived descriptors from the simulations to score and rank API-polymer interactions. The descriptors were used to measure the energy of interaction (EOI), hydrogen bonding, and rugosity (surface roughness) similarity between the APIs and polymer templates. We used a variety of machine learning models (14 in total) along with these descriptors to predict the crystallization outcome of the polymer templates. We found that simply rank-ordering the polymers by their API-polymer interaction energy descriptors yielded 92% accuracy in predicting the experimental outcome for clotrimazole and ketoprofen. The most accurate machine learning model for both APIs was found to be a random forest model. Using these models, we were able to predict the crystallization outcomes for all polymers. Additionally, we have performed a feature importance analysis using the trained models and found that the most predictive features are the energy descriptors. These results demonstrate that API-polymer interaction energies are correlated with heterogeneous crystallization outcomes.

Free Energy Evaluation of Cavity Formation in Metastable Liquid Based on Stochastic Thermodynamics.

Nucleation is a fundamental and general process at the initial stage of first-order phase transition. Although various models based on the classical nucleation theory (CNT) have been proposed to explain the energetics and kinetics of nucleation, detailed understanding at nanoscale is still required. Here, in view of the homogeneous bubble nucleation, we focus on cavity formation, in which evaluation of the size dependence of free energy change is the key issue. We propose the application of a formula in stochastic thermodynamics, the Jarzynski equality, for data analysis of molecular dynamics (MD) simulation to evaluate the free energy of cavity formation. As a test case, we performed a series of MD simulations with a Lennard-Jones (LJ) fluid system. By applying an external spherical force field to equilibrated LJ liquid, we evaluated the free energy change during cavity growth as the Jarzynski's ensemble average of required works. A fairly smooth free energy curve was obtained as a function of bubble radius in metastable liquid of mildly negative pressure conditions.

Solid-liquid interfacial nanobubble nucleation dynamics influenced by surface hydrophobicity and gas oversaturation

Over the past two decades, extensive research efforts have been devoted to exploring the existence, stability, and applications of interfacial nanobubbles (INBs). However, investigations into the microscopic nucleation process of INBs have been relatively limited. In this study, we utilized molecular dynamics simulations to elucidate the nucleation dynamics of INBs, with a particular focus on examining the influence of surface hydrophobicity and gas oversaturation. Our findings revealed a distinct preference for INBs to form on hydrophobic surfaces compared to hydrophilic ones, which agrees well with the experimental results. Temporal evolution analysis of the interfacial density of gas and liquid near the solid–liquid interface indicated a gradual enrichment of gas molecules at the hydrophobic surface, accompanied by a gradual disruption of the hydration layer, phenomena not observed on hydrophilic surfaces. The affinity of gas molecules towards the hydrophobic surface was further confirmed by potential of mean force (PMF) analysis, which demonstrated a decrease in the energy barrier and an increase in the potential well with increasing surface hydrophobicity. Moreover, increasing bulk gas supersaturation and surface hydrophobicity both contribute to shortening the INB nucleation time, primarily due to the enhanced gas enrichment rate. Further studies indicated that the gas enrichment rate had a directly proportional linear relationship with the bulk gas concentration. However, as the surface hydrophobicity increased, the gas enrichment rate initially rose rapidly and then entered a plateau phase. This may be because, when surface hydrophobicity is strong, the gas enrichment rate becomes limited by the diffusion of gas molecules in the liquid. These findings offer valuable insights into the nucleation mechanism of INBs on hydrophobic surfaces under gas oversaturation, contributing to a deeper understanding of their behavior and potential applications.

Passivation of Lead-Acid Batteries Lead Negative Electrodes by PbSO4 Crystals: Analysis from Modeling Cyclic Voltammetry Responses

Lead-acid batteries (LABs) play a pivotal role in the energy storage sector with applications spanning from starting-ignition-lightning batteries to grid energy storage. Passivation of lead negative electrodes by PbSO4 crystals is a one fundamental mechanism limiting the performance of LAB. In this regard, we developed an electrochemical mathematical model that simulates the nucleation and growth dynamics of PbSO4 crystals on a flat lead electrode, responsible for its passivation. The model considers the electrochemical dissolution of Pb2+ from lead electrode and the ternary transport of lead, bisulfate, and hydrogen ions in H2SO4 electrolyte. We have validated the model with a rich dataset of cyclic voltammetry (CV) responses collected at several scan rates and several concentrations of H2SO4. The model shows remarkable qualitative and quantitative agreement with the experimental data including the onset potential, center, height, and width of the CV peaks, discharge capacity, and particle size. The model is used to give insights on how different physical and operational parameters can influence the electrochemical response of lead negative electrodes. Keywords: lead-acid battery, nucleation and growth, passivation, cyclic voltammetry

Influence of Temperature on the Nucleation and Adsorption Kinetic Mechanisms for Copper Corrosion

Copper is a valuable catalyst that is widely used in electrochemical devices, particularly in the generation of clean, renewable energy and the CO2 reduction reaction (CO2RR). Gaining insight into the fundamentals of corrosion/deposition of Cu in an electrochemical cell can aid in the design of more durable and efficient devices. To take advantage of the capabilities of Cu and comprehend the broader impacts, it is crucial to understand the kinetics of nucleation and adsorption mechanisms and conduct a thorough investigation of the underlying principles. Here, we utilize a model system with Cu underpotential deposition (UPD) on an Au(111) electrode surface in sulfuric acid electrolyte and investigate the impact of temperature change on the kinetics of Cu corrosion/deposition. The Transient technique, chronoamperometry, is employed to differentiate and illustrate the effects of the nucleation process and adsorption of ions. At temperatures below 20°C, peaks indicate the nucleation and adsorption processes can be identified individually. At temperatures 20°C and above, more adsorption characteristics are seen which may be due to the interactions between less-ordered monolayers at the interface, further demonstrated by the loss of nucleation characteristics. Electrochemical devices operate across a wider temperature range in practical uses. The aim of this study is to examine and quantify the influence of temperature on the nucleation and adsorption mechanisms for the kinetics of Cu in order to optimize the durability of Cu-containing electrochemical devices.

Operando study of the dynamic evolution of multiple Fe-rich intermetallics of an Al recycled alloy in solidification by synchrotron X-ray and machine learning

Using synchrotron X-ray diffraction, tomography and machine-learning enabled phase segmentation strategy, we have studied under operando conditions the nucleation, co-growth and dynamic interplays among the dendritic and multiple intermetallic phases of a typical recycled Al alloy (Al5Cu1.5Fe1Si, wt.%) in solidification with and without ultrasound. The research has revealed and elucidated the underlying mechanisms that drive the formation of the very complex and convoluted Fe-rich phases with rhombic dodecahedron and 3D skeleton networks (the so-called Chinese-script type morphology). Through statistical microstructural analyses and numerical modelling of the ultrasound melt processing, the research has demonstrated that a short period of ultrasound processing of just 7 s in the liquid state is able to reduce the average size of the α-Al dendrites and the Fe-containing intermetallic phases by ∼5 times compared to the cases without ultrasound. For the first time, this work has revealed fully the nucleation and growth dynamics of the convoluted morphology of the Fe-containing intermetallic phases in 4D domain. The research has also demonstrated clearly the beneficial effects of applying ultrasound to control the Fe phases' morphology in recycled Al alloys and it is one of the most effective and green processing strategies.