Nucleation Behavior Research Articles

Insights into the structure sustainable evolution and crystallization kinetics of amorphous Mg60Ni30La10 alloy

Nanocrystalline materials have wide potential applications due to the special properties, which can be easily prepared by nanocrystallization of the amorphous alloys. In this work, phase transformations of the melt-spun amorphous Mg60Ni30La10 alloy were characterized by in-situ XRD and TEM. The results showed that during crystallization Mg2Ni first formed from the amorphous matrix followed by LaMg3, LaMg2Ni and LaMgNi4. The phase transformation was completed rapidly, with nucleation progressing more prominently than grain growth. Nucleation and grain growth during crystallization were discussed according to Avrami index n(α) based on Kissinger equation. In addition, the classic Miedema theory was introduced to estimate the crystallization temperature and the nucleation frequency. Nucleation behaviors are closely related to the phase structures formed during the amorphous crystallization from the view of thermodynamics. This work provided a preliminary basis for controlling the evolution of amorphous/nanocrystalline structure of alloys.

Revealing the Heterogeneous Bubble Nucleation at Individual Silica Nanoparticles.

Deep understanding of the bubble nucleation process is universally important in systems, from chemical engineering to materials. However, due to its nanoscale and transient nature, effective probing of nucleation behavior with a high spatiotemporal resolution is prohibitively challenging. We previously reported the measurement of a single nanobubble nucleation at a nanoparticle using scanning electrochemical cell microscopy, where the bubble nucleation and formation were inferred from the voltammetric responses. Here, we continue the study of heterogeneous bubble nucleation at interfaces by regulating the local nanostructures using silica nanoparticles with a distinct surface morphology. It is demonstrated that, compared to the smooth spherical silica nanoparticles, the raspberry-like nanoparticles can further significantly reduce the nucleation energy barrier, with a critical peak current about 23% of the bare carbon surfaces. This study advances our understanding of how surface nanostructures direct the heterogeneous nucleation process and may offer a new strategy for surface engineering in gas involved energy conversion systems.

Cholesteric Tactoids with Tunable Helical Pitch Assembled by Lysozyme Amyloid Fibrils.

Amyloid fibrils are biological rod-like particles showing liquid-liquid crystalline phase separation into cholesteric phases through a complex behavior of nucleation, growth, and order-order transitions. Yet, controlling the self-assembly of amyloids into liquid crystals, and particularly the resulting helical periodicity, remains challenging. Here, a novel cholesteric system is introduced and characterized based on hen egg white lysozyme (HEWL) amyloid fibrils and the results rationalized via a combination of experiments and theoretical scaling arguments. Specifically, the transition behaviors are elucidated from homogenous nematic, bipolar nematic to cholesteric tactoids following the classic Onsager model and the free energy functional model from Frank-Oseen elasticity theory. Additionally, the critical effects of pH and ionic strength on these order-order-transitions, as well as on the shape and helical pitch of the cholesteric tactoids are demonstrated. It is found that a small increase in pH from 2.0 to 2.8 results in a 34% decrease in pitch, while, on the contrary, increasing ionic strength from 0 to 10mm leads to a 39% increase in pitch. The present study provides an approach to obtain controllable chiral nematic structures from HEWL amyloid fibrils, and may contribute further to the application of protein-based liquid crystals in pitch-sensitive biosensors or biomimetic architectures.

Insight into the nucleation behavior of tiamulin hydrogen fumarate methanol solvate in methanol-ethyl acetate binary mixtures

To investigate the nucleation behavior of tiamulin hydrogen fumarate methanol solvate (THFMS), the solubility, induction time, and metastable zone width (MSZW) of THFMS in methanol-ethyl acetate binary mixtures were measured. The nucleation potential model, which is based on the classical nucleation theory and correlates the induction time and MSZW, has been employed to deal with the experimental data and estimate the interfacial energy and the critical nucleation potential. The estimated values determined from the nucleation potential model are in accordance with the experimental values. The interfacial energy and the critical nucleation potential of THFMS steadily decrease with the increasing saturation temperature, whereas those of THFMS initially decrease and subsequently increase as the ethyl acetate content increases. The results demonstrate that an increase in saturation temperature leads to enhanced nucleation favorability, while the difficulty of nucleation initially decreases and then increases with increasing ethyl acetate content. Furthermore, the critical nucleation parameters, including the critical Gibbs free energy, the critical nucleus size, and the critical number of molecules in a nucleus, exhibit the same trend in alterations regarding both saturation temperature and ethyl acetate content.

An experimental instrument for solidification and in situ characterization of the nucleation behavior of high-melting metal under a high magnetic field.

A specially designed experimental apparatus suitable for commercial superconductor magnet is used for solidification and in situ characterization of the nucleation behavior of high-melting metals. In order to carry out solidification experiments under a high magnetic field (HMF), the sample cell in the experimental device has two stations for repeated verification experiments of two same samples or comparative experiments of two different samples. Meanwhile, a metal specimen and a reference (α-Al2O3) are placed in the sample cell to characterize the nucleation behavior in situ. Using this experimental device, the nucleation behaviors of Al-7wt. %Si alloy and pure Cu under a HMF were investigated. The results show that the undercoolings of Al-7wt. %Si alloy and pure Cu increase under the HMF. Furthermore, the applied HMF decreases the activation energy of Al-7wt. %Si alloy and increases the nucleation work. Based on the magnetohydrodynamic effect, the change in undercooling and nucleation work could be partly attributed to the restrained thermal convection by the HMF in this study.

Unraveling the concomitant polymorphism phenomenon in crystallization process: A case study on risperidone in ethyl acetate

Concomitant polymorphism is a widespread occurrence in industrial crystallization processes. A thorough understanding of this phenomenon is essential to prevent the emergence of undesirable polymorphs and ensure the production of high-quality products. In this study, the induction time method was employed to investigate the concomitant polymorphism phenomenon of risperidone in ethyl acetate. The impact of crystallization temperature and stirring rate on the concomitant polymorphism region was explored. Additionally, an analysis of the nucleation tendencies of risperidone form I and form II was conducted from both thermodynamic and kinetic perspectives. Based on the induction time theory, the nucleation parameters of form I and form II were calculated. Through an examination of the change in these nucleation parameters with supersaturation, a comprehensive explanation was provided for the reasons behind the occurrence of concomitant polymorphism and the nucleation behavior of form I and form II under varying degrees of supersaturation. Moreover, the concomitant polymorphism phenomenon during the slow-cooling crystallization process was investigated, and the relationship between operational conditions and the concomitant polymorphism region was discussed.

Ultra-stable dendrite-free Na and Li metal anodes enabled by tin selenide host material

Lithium/sodium metal anodes are considered promising candidates to realize high-energy–density batteries because of their high theoretical specific capacity and low potential. However, their cycling stability are hindered by uncontrolled dendrites growth. Herein, SnSe nanoparticles are tightly anchored on the fiber of carbon cloth (CC) to construct SnSe@CC host material in order to control Li/Na nucleation behavior and restrain dendrites growth. It is demonstrated that the alloying product of Li15Sn4/Na15Sn4 with strong metal affinity can provide abundant active nucleation sites, and three-dimensional structure of CC host can significantly decrease the local electric current, thereby guiding homogeneous metal deposition without Li and Na dendrites. Meanwhile, the conversion product of Li2Se/Na2Se will uniformly cover on the surface of metal to serve as ultra-stable solid state interface film. As a result, high-capacity Li metal anode (20 mAh·cm−2) and Na metal anode (10 mAh·cm−2) can work steadily with ultra-long lifespans over 5000 and 6000 h with low overpotentials of 7 mV and 141 mV, respectively. Moreover, the assembled Li and Na metal full batteries exhibit superior electrochemical performances, confirming the practicability of metal anode confined in composite host. Such a strategy of conversion-alloying-type materials as hosts opens up a new path for dendrite-free metal anode electrode.

Nucleation and Coarsening Behavior of Aluminum Nitride and Its Effect on Abnormal Grain Growth in High-Temperature Carburizing Process

Nucleation and Coarsening Behavior of Aluminum Nitride and Its Effect on Abnormal Grain Growth in High-Temperature Carburizing Process

Fretting fatigue behavior of metal injection molded stainless steel MIM 316L with small pores and low porosity

The fretting fatigue of metal injection molded stainless steel (MIM 316L) with a mean pore diameter of 3 μm and porosity of 5.1% was investigated both experimentally and numerically. The granular-like wear debris accumulated in pores on the fretted surface of the MIM 316L specimen was the cause of the reduction in the tangential force coefficient, potentially improving fretting fatigue strength. These pores did not significantly influence the location of fretting crack nucleation and crack path due to high stress concentration at the fretting contact edge. Under the large-scale yielding at the crack tip and fretting-contact-induced crack opening/closure, a continuum body finite element model can be applied to estimate crack nucleation and propagation behavior, as well as fretting fatigue life.

Low-temperature ice nucleation of sea spray and secondary marine aerosols under cirrus cloud conditions

Abstract. Sea spray aerosols (SSAs) represent one of the most abundant aerosol types on a global scale and have been observed at all altitudes including the upper troposphere. SSA has been explored in recent years as a source of ice-nucleating particles (INPs) in cirrus clouds due to the ubiquity of cirrus clouds and the uncertainties in their radiative forcing. This study expands upon previous works on low-temperature ice nucleation of SSA by investigating the effects of atmospheric aging of SSA and the ice-nucleating activity of newly formed secondary marine aerosols (SMAs) using an oxidation flow reactor. Polydisperse aerosol distributions were generated from a marine aerosol reference tank (MART) filled with 120 L of real or artificial seawater and were dried to very low relative humidity to crystallize the salt constituents of SSA prior to their subsequent freezing, which was measured using a continuous flow diffusion chamber (CFDC). Results show that for primary SSA (pSSA), as well as aged SSA and SMA (aSSA+SMA) at temperatures >220 K, homogeneous conditions (92 %–97 % relative humidity with respect to water – RHw) were required to freeze 1 % of the particles. However, below 220 K, heterogeneous nucleation occurs for both pSSA and aSSA+SMA at much lower RHw, where up to 1 % of the aerosol population freezes between 75 % and 80 % RHw. Similarities between freezing behaviors of the pSSA and aSSA+SMA at all temperatures suggest that the contributions of condensed organics onto the pSSA or alteration of functional groups in pSSA via atmospheric aging did not hinder the major heterogeneous ice nucleation process at these cirrus temperatures, which have previously been shown to be dominated by the crystalline salts. Occurrence of a 1 % frozen fraction of SMA, generated in the absence of primary SSA, was observed at or near water saturation below 220 K, suggesting it is not an effective INP at cirrus temperatures, similar to findings in the literature on other organic aerosols. Thus, any SMA coatings on the pSSA would only decrease the ice nucleation behavior of pSSA if the organic components were able to significantly delay water uptake of the inorganic salts, and apparently this was not the case. Results from this study demonstrate the ability of lofted primary sea spray particles to remain an effective ice nucleator at cirrus temperatures, even after atmospheric aging has occurred over a period of days in the marine boundary layer prior to lofting. We were not able to address aging processes under upper-tropospheric conditions.

Crystallization of an undercooled Zn-based glass forming alloy

Zn-based metallic glasses (Zn40Mg11Ca31+xYb18-x, x = 0 - 4) are strong glass forming alloys with low glass transition temperatures. While the crystallization onset temperature is also low, the nucleation behavior has not been examined and analyzed quantitatively. For a Zn40Mg11Ca31Yb18 metallic glass alloy, the crystallization behavior was determined based on the application of the Flash differential scanning calorimetry (DSC) with ultrafast heating and cooling rates. The critical cooling rate range was measured for glass formation at 1.6(±0.2) × 104K/s. A temperature-time-transformation (TTT) diagram for the nucleation onset in an undercooled liquid was obtained by applying a series of isothermal exposures by fast heating from the glass state or fast cooling from the liquid state to the target temperatures. A heterogeneous nucleation analysis model was developed to interpret the experimental TTT diagram, which provided a further understanding of the nucleation in Zn-based metallic glasses.

In-situ formed Co nano-clusters as separator modifier and catalyst to regulate the film-like growth of Li and promote the cycling stability of lithium metal batteries

Lithium metal batteries (LMBs) are considered a highly prospective next-generation energy storage technology. However, their large-scale commercial application is hampered by the uncontrollable growth of Li dendrites, which accompany the boundless inflation of the battery's volume. In this study, we address this challenge by fabricating a porous structure of the MOF-derived CoP nanocube film (CoP-NC@PP) as a adorned layer for the separator. During the initial cycle, this film facilitates the in situ formation of Li3P with ultrahigh ionic conductivity and a lithiophilic Co, which helps rule the nucleation and deposition behavior of lithium and stabilizes the solid-electrolyte interphase. The symmetric cell incorporating the CoP-NC@PP modified layer exhibits exceptional cycling stability, surpassing 1500 h of continuous operation. The kinetic process of Li interaction with CoP and the structural factors contributing to the high cycling stability and high naminal voltage were investigated by molecular dynamics simulation and density functional theory calculations. Furthermore, full cells employing Li||CoP-NC@PP||LFP (LFP = LiFePO4) configurations demonstrate excellent cycling stability and high capacity, even at a high rate of 5 C (≈5.2 mA cm−2), with the cathode mass loading reaching as high as 10.3 mg cm−2.

Unlocking the Potential of Li–Ag Alloys: Phase Selection and Practical Application

Dendrite formation, contact loss, and continuous formation of the solid electrolyte interphase (SEI) preclude the practical use of the energy-dense lithium (Li) metal. Li–Ag alloys have the potential to address these issues due to their exceptional lithiophilicity, outstanding mechanical stability, and moderate chemical stability. This study evaluates all phases in the Li–Ag phase diagram based on lithiation capacity, Li insertion, mechanical property, and chemical stability. Our findings suggest that Li 4 Ag is the most promising phase, and the Gibbs free energy of nucleation (∆ G nucle ) for Li–Ag alloys is 3 to 5 orders of magnitude smaller compared to pure Li, resulting in uniform nucleation and deposition behavior. We proposed practical applications within the Li 4 Ag phases or from the Li 9 Ag 4 to the Li 4 Ag phases, which may provide a usable capacity of 409 to 696 mAh/g, respectively. Experiments indicate that Li 4 Ag exhibits not only the smallest impedance but also the highest capacity retention compared to Li 9 Ag 4 and pure Li. The study provides valuable guidance for the selection and application of Li-containing alloys in future battery development.

Understanding the nanoscale phenomena of nucleation and crystal growth in electrodeposition.

Electrodeposition is used at the industrial scale to make coatings, membranes, and composites. With better understanding of the nanoscale phenomena associated with the early stage of the process, electrodeposition has potential to be adopted by manufacturers of energy storage devices, advanced electrode materials, fuel cells, carbon dioxide capturing technologies, and advanced sensing electronics. The ability to conduct precise electrochemical measurements using cyclic voltammetry, chronoamperometry, and chronopotentiometry in addition to control of precursor composition and concentration makes electrocrystallization an attractive method to investigate nucleation and early-stage crystal growth. In this article, we review recent findings of nucleation and crystal growth behaviors at the nanoscale, paying close attention to those that deviate from the classical theories in various electrodeposition systems. The review affirms electrodeposition as a valuable method both for gaining new insights into nucleation and crystallization on surfaces and as a low-cost scalable technology for the manufacturing of advanced materials and devices.

Influences of deposition conditions on atomic layer deposition films for enhanced performance in perovskite solar cells

Atomic layer deposition (ALD) is a key technology for fabricating functional layers in perovskite solar cells, as it can deposit pinhole-free films with atomic-level thickness and tunable composition on high-aspect-ratio surfaces. Various deposition conditions have significant effects on the growth, physical, and chemical properties of ALD films, which, in turn, critically influences the performance of associated devices. Here, we review the reaction mechanisms underlying ALD and summarize how variables, such as precursors, deposition temperatures, and substrates, impinge upon the quality of ALD films and the related devices. We emphasize the role of substrate in determining the nucleation and growth behavior of ALD films, which has been overlooked in previous reviews. Finally, we highlight the potential application of ALD in efficient perovskite solar cells in terms of carrier transport, encapsulated, and buffer layers, especially for tandem cells.

Phase-field simulation on fission gas release behavior of large grain UO<sub>2</sub> fuel

In order to predict the release behavior of fission gas in large grain UO<sub>2</sub> fuel and provide support for the development of accident tolerant fuel, a phase-field model is used to simulate the release behavior of fission gas in the microstructure of UO<sub>2</sub> polycrystalline in this work. This model adopts a set of coupled Cahn-Hilliard equations and Allen-Cahn equations, using conserved field variables to represent the distribution of fission gas and vacancies, and distinguishing bubble phase from matrix phase by using order parameters. This model focuses on investigating the effects of different grain sizes, temperature conditions, and diffusion coefficients on the release behavior of fission gas, demonstrating the nucleation, growth, and fusion behavior of bubbles. Simulation results are obtained for fuel porosity, bubble coverage on grain boundaries, and average bubble radius at a certain degree of burnup. The results show that temperature and diffusion coefficient have a significant influence on porosity and bubble coverage on grain boundaries. When the diffusion coefficient is high, grain size also has a significant influence on fission gas release behavior. And when the diffusion coefficient is low, the influence of grain size is not significant. In addition, the distribution of fission gas bubbles under high burnup obtained through this model is also in good agreement with experimental result. The model can predict the behavior of fission gas release in large grain UO<sub>2</sub> fuel.

Key Roles of Nucleation and Impurity Migration Behavior in Layer Melt Crystallization: Case Study of 4,5-Dimethyl-1,3-dioxol-2-one

Key Roles of Nucleation and Impurity Migration Behavior in Layer Melt Crystallization: Case Study of 4,5-Dimethyl-1,3-dioxol-2-one

Development of a multi-stage model for freezing of a suspended binary solution droplet

The importance of developing spray freeze-drying technology for extending the shelf life of biological and pharmaceutical materials has never been greater, given the increasing food shortage and the strong demand for pharma processes. In particular, the optimal thermal design and application of spray freeze-drying technologies now depend on the estimation of nucleation behavior for droplet solidification (especially the droplets of binary mixtures). Although earlier nucleation models could estimate the nucleation rate and temperature of solidifying droplets, few considered extreme environmental factors, such as extremely low ambient temperatures below −60C∘. To ensure the preservation and storage of biological and pharmaceutical products, such as vaccines and protein drugs, these conditions are essential. Hence, developing an accurate and trustworthy mathematical framework for simulating nucleation is paramount. In this study, a multi-stage, hybrid analytical-numerical model for droplet solidification is developed while coupled with a gradient-based optimization algorithm. Specifically, the five-stage solidification of binary mixtures is simulated (including supercooling of liquid, nucleation, recalescence, equilibrium freezing, and subcooling of solid), which captures the dynamic behaviors of temperature and composition or solute concentration during phase change. The heterogeneous nucleation of a binary-mixture droplet in a frigid environment is predicted and validated against a series of experiments on single suspended droplets at a wide range of ambient temperatures between −20 and −160C∘. The freezing curves of different solute concentrations are also validated against experimental data. It is found that significant variations in interfacial tension lead to abrupt changes in nucleation temperature for extremely cold environments. Further, the effects of the concentration, contact angle, droplet size, and heat transfer coefficient are investigated.

Prediction of crystal nucleation and growth behavior of Fe/Ni-based multi-materials deposited by laser directed energy deposition using a multi-area, multi-layer, and multi-scale phase field calculation (M3-PFC)

Laser directed energy deposition (LDED), based on the powder feeding technology, possesses the capability to fabricate complex structures within hollow structures. The arbitrary Lagrangian-Eulerian (ALE) method was innovatively applied to derive temporal interpolation functions for the free surface contour F (x, y, t) and the temperature distribution T (x, y, t) of the melt pool from a mesoscopic computational fluid dynamics (CFD) thermal model. These interpolation functions were not simply integrated but specifically designed to impart a quantified impetus for the growth of crystalline solidification within the microstructural phase field, effecting real-time adjustments to the computational domain of the phase field model. The multi-area, multi-layer and multi-scale phase field calculation (M3-PFC), which takes into account the bi-directional coupling of Marangoni flow and the phase field, was established to incorporate the transportation of elements within the multi-layer deposition and previously solidified material. Thermodynamics of multi-layer deposition was integrated into M3-PFC, enabling the prediction of multi-layer dendritic evolution using LDED process. Influence of Marangoni flow on microstructure evolution of multi-layer C276 deposited on 316 L-substrate utilizing M3-PFC was investigated during LDED process. It was observed that the nucleation of equiaxed and columnar crystals occurred at the top and bottom-middle of the melt pool. Both columnar and equiaxed crystals were preferentially produced along the opposite direction of Marangoni flow, impeding the apparent dendrite-growth in the counter direction. Partial remelting of the (N + 1)th layer was induced by the thermodynamics generated in the (N + 2)th deposition layer, promoting re-solidification of the liquid phase in the (N + 1)th layer. However, no liquid-solid transformation occurred in the Nth layer subjected to periodic heating. The partially remelted tissue in the (N + 1)th layer was shown in wider columnar crystals generated through the competitive growth, which were transformed into planar crystals and identified as the initial solidification conditions for the nucleation of the (N + 2)th layer. The columnar crystal growth, nucleated at the planar crystals of the (N + 1)th layer, was dominated in the (N + 2)th layer. Micropillar compression tests revealed that the columnar crystal had a compressive strength of 1102.78 MPa, while the equiaxed crystals displayed a higher compressive strength of 1464.34 MPa.

Effect of substrate roughness on the nucleation and growth behaviour of microwave plasma enhanced CVD diamond films – a case study

The influence of substrate surface roughness on the nucleation and growth of diamond films by chemical vapour deposition (CVD) is investigated. Silicon substrates were grinded with six different grit sizes of abrasive papers with a rotating wheel. Si was also etched by Ar+ ions to produce average surface roughness Ra = 11.29 nm on the mirror polished side (Ra = 1.17 nm). A comparison of the results of the effect of substrate roughness, on the growth behaviour of nanocrystalline diamond (NCD) films, by using both the resonant cavity and the linear antenna CVD systems, are presented here. Scanning electron microscopy (SEM) images and Raman spectroscopy reveal that under both the linear antenna and the resonant cavity microwave plasma CVD conditions, grown films are NCD. The diamond nanocrystals sizes vary from 80 to 180 nm, grown by both the reactors after few hours of deposition, irrespective of the substrate roughness, whereas their quality (defined by the relative percentage ratios of the Raman sp3 peak intensity to the non-sp3 peak intensity) varies from 33% to 45%, depending on the substrate surface roughness. Such nanocrystals grew into plate-like flat 1–6 μm size diamond grains after prolonged hours (64–69 h) of CVD growth. It is found specifically that the roughness created by the argon plasma treatment of the silicon substrate surfaces effectively enhances the nucleation and growth behaviour of the diamond films.