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The transformation of 2 ¯ 01 β - Ga 2 O 3 to h- GaN under exposure to RF nitrogen plasma was monitored in situ by reflection high-energy electron diffraction. Analysis of the reaction kinetics reveals that the nitridation process is initiated by the formation of an oxynitride phase and proceeds via two-dimensional nucleation and growth of wurtzite GaN grains. X-ray photoelectron spectra suggest a Ga − (N x O 1 − x) type configuration dominates the surface early in the nitridation process. The surface restructuring is followed by a diffusion-fed phase transformation, which propagates the wurzite GaN structure into the substrate upon reaching 70 % nitrogen anion site occupation, corresponding to the oxygen solubility in h - GaN. A direct correlation is observed between the nitridated film morphology and the epitaxial film crystallinity, demonstrating control of the residual strain, lateral coherence, and mosaicity in subsequent GaN epitaxy by the nitridation conditions. This study provides mechanistic details of the nitridation reaction of 2 ¯ 01 β - Ga 2 O 3 facilitating the optimization of the nitridation process toward improving GaN - 2 ¯ 01 β - Ga 2 O 3 heterojunctions. [ABSTRACT FROM AUTHOR]

Despite a large amount of work being devoted to study the phase separation in solids, the underlying physical mechanism responsible for such diffusive first-order phase transitions remains difficult to model outside the spinodal regime, i.e., in the nucleation and growth regime. This work presents an alternative of the classical nucleation theory for modeling phase separation in this regime, even for systems far from the solubility limit, i.e., for high degree of meta-stability where the classical nucleation theory does not hold. This method then allows a direct comparison between simulations and experiments always performed in solids with a high degree of meta-stability. [ABSTRACT FROM AUTHOR]

Understanding the nucleation and growth of tungsten (W) is technologically important in spin-to-charge interconversion for realizing energy-efficient spintronic devices. Here, we have systematically investigated the effect of Ar deposition pressure (P A r ) on the nucleation and growth of W. The observed surface topography as a function of P A r reveals a microstructural transition from zone T to zone 1 in the structure zone model. The physical origin for the increasing roughness as a function of P A r correlates with the surface diffusion of adatoms and growth kinetics in the Volmer–Weber growth mechanism. Grazing incidence x-ray diffraction (GIXRD) results show that W exhibits a structural phase transition from a mixed phase of (α + β) - W to a single phase of β - W as a function of P A r . The analysis of the electron diffraction patterns obtained from the films grown on amorphous-SiNx windows also supports these observations. The observed transition is fundamentally correlated with the growth kinetics in zone T and zone I. Thickness-dependent GIXRD results qualitatively prove that the film grown in zone T exhibits compressive strain, whereas that grown in zone I exhibits only tensile strain. The critical thickness for the phase transition is strongly attributed to the strain during nucleation and growth. The increasing resistivity as a function of P A r corroborates the change in structural phases. Thickness-dependent resistivity measurements correlate with the degree of crystallinity via relative intensity observed from the GIXRD results. Our results strongly suggest that W structural phases can be deterministically controlled via P A r for developing low-power spintronic devices. [ABSTRACT FROM AUTHOR]

We studied the nonequilibrium dynamics of a cycling three-state Potts model using simulations and theory. This model can be tuned from thermal-equilibrium to far-from-equilibrium conditions. At low cycling energy, the homogeneous dominant state cycles via nucleation and growth, while spiral waves are formed at high energy. For large systems, a discontinuous transition occurs from these cyclic homogeneous phases to spiral waves, while the opposite transition is absent. Conversely, these two modes can coexist for small systems. The waves can be reproduced by a continuum theory, and the transition can be understood from the competition between nucleation and growth. [ABSTRACT FROM AUTHOR]

Conventional molecular dynamics (MD) simulations struggle when simulating particles with steeply varying interaction potentials due to the need to use a very short time step. Here, we demonstrate that an event-driven Monte Carlo (EDMC) approach was first introduced by Peters and de With [Phys. Rev. E 85, 026703 (2012)] and represents an excellent substitute for MD in the canonical ensemble. In addition to correctly reproducing the static thermodynamic properties of the system, the EDMC method closely mimics the dynamics of systems of particles interacting via the steeply repulsive Weeks–Chandler–Andersen (WCA) potential. In comparison to time-driven MD simulations, EDMC runs faster by over an order of magnitude at sufficiently low temperatures. Moreover, the lack of a finite time step in EDMC circumvents the need to trade accuracy against the simulation speed associated with the choice of time step in MD. We showcase the usefulness of this model to explore the phase behavior of the WCA model at extremely low temperatures and to demonstrate that spontaneous nucleation and growth of the Laves phases are possible at temperatures significantly lower than previously reported. [ABSTRACT FROM AUTHOR]

Droplets are essential for spatially controlling biomolecules in cells. To work properly, cells need to control the emergence and morphology of droplets. On the one hand, driven chemical reactions can affect droplets profoundly. For instance, reactions can control how droplets nucleate and how large they grow. On the other hand, droplets coexist with various organelles and other structures inside cells, which could affect their nucleation and morphology. To understand the interplay of these two aspects, we study a continuous field theory of active phase separation. Our numerical simulations reveal that reactions suppress nucleation while attractive walls enhance it. Intriguingly, these two effects are coupled, leading to shapes that deviate substantially from the spherical caps predicted for passive systems. These distortions result from anisotropic fluxes responding to the boundary conditions dictated by the Young–Dupré equation. Interestingly, an electrostatic analogy of chemical reactions confirms these effects. We thus demonstrate how driven chemical reactions affect the emergence and morphology of droplets, which could be crucial for understanding biological cells and improving technical applications, e.g., in chemical engineering. [ABSTRACT FROM AUTHOR]

Clathrate hydrates are crystals formed by guest molecules that stabilize cages of hydrogen-bonded water molecules. Whereas thermodynamic equilibrium is well described via the van der Waals and Platteeuw approach, the increasing concerns with global warming and energy transition require extending the knowledge to non-equilibrium conditions in multiphase, sheared systems, in a multiscale framework. Potential macro-applications concern the storage of carbon dioxide in the form of clathrates, and the reduction of hydrate inhibition additives currently required in hydrocarbon production. We evidence porous mesomorphologies as key to bridging the molecular scales to macro-applications of low solubility guests. We discuss the coupling of molecular ordering with the mesoscales, including (i) the emergence of porous patterns as a combined factor from the walk over the free energy landscape and 3D competitive nucleation and growth and (ii) the role of molecular attachment rates in crystallization–diffusion models that allow predicting the timescale of pore sealing. This is a perspective study that discusses the use of discrete models (molecular dynamics) to build continuum models (phase field models, crystallization laws, and transport phenomena) to predict multiscale manifestations at a feasible computational cost. Several advances in correlated fields (ice, polymers, alloys, and nanoparticles) are discussed in the scenario of clathrate hydrates, as well as the challenges and necessary developments to push the field forward. [ABSTRACT FROM AUTHOR]

The crystallization of complex, concentrated alloys can result in atomic-level short-range order, composition gradients, and phase separation. These features govern the properties of the resulting alloy. While nucleation and growth in single-element metals are well understood, several open questions remain regarding the crystallization of multi-principal component alloys. We use molecular dynamics to model the crystallization of a five-element, equiatomic alloy modeled after CoCrCuFeNi upon cooling from the melt. Stochastic, homogeneous nucleation results in nuclei with a biased composition distribution, rich in Fe and Co. This deviation from the random sampling of the overall composition is driven by the internal energy and affects nuclei of a wide range of sizes, from tens of atoms all the way to super-critical sizes. This results in short-range order and compositional gradients at nanometer scales. [ABSTRACT FROM AUTHOR]

III–V colloidal quantum dots (QDs) promise Pb and Hg-free QD compositions with which to build short-wavelength infrared (SWIR) optoelectronic devices. However, their synthesis is limited by the availability of group-V precursors with controllable reactivities to prepare monodisperse, SWIR-absorbing III–V QDs. Here, we report a one-pot heat-up method to synthesize ∼8 nm edge length (∼6.5 nm in height) tetrahedral, SWIR-absorbing InAs QDs by increasing the [In3+]:[As3+] ratio introduced using commercially available InCl3 and AsCl3 precursors and by decreasing the concentration and optimizing the volume of the reducing reagent superhydride to control the concentration of In(0) and As(0) intermediates through QD nucleation and growth. InAs QDs are treated with NOBF4, and their deposited films are exchanged with Na2S to yield n-type InAs QD films. We realize the only colloidal InAs QD photoconductors with responsivity at the technologically important wavelength of 1.55 μm. [ABSTRACT FROM AUTHOR]

Crystal growth is a complex process with far-reaching implications for high-performance materials across various fields. Recent advancements in structural analysis methods such as polyhedral template matching, which allows semiconductor-specific analysis, coupled with simulation technology, have enabled the comprehensive study of crystallization dynamics in semiconductors. However, the exploration of polycrystalline semiconductors created with minimal external intervention of the crystallization processes is relatively uncharted in comparison with metals. In this study, we employ molecular dynamics to simulate the growth of polycrystalline CdTe/CdS with the assumptions of classical mechanics, a Stillinger–Weber potential, an amorphous substrate, and common vapor growth conditions to allow the polycrystalline structures to evolve naturally. Post-simulation, we identify and analyze impactful structures and events, comparing them to theory and experiment to gain insight into various modes of crystallization dynamics. Two research questions guided the study: (1) How realistic are assumption-less simulated polycrystalline semiconductor structures? (2) To what extent can the approach provide insight into crystallization? The simulations, performed with minimal external control, yield polycrystalline structures mirroring experimental findings. The analysis reveals key crystallization insights, such as the role of amorphous atoms in the transition from nucleation to grain growth and the transformative impact of single events, such as dislocations, on crystallization dynamics. The method paves the way for reproducing and analyzing realistic polycrystalline semiconductor structures with minimal simulation assumptions across various growth modes. [ABSTRACT FROM AUTHOR]

This study is concerned with a theory of two-step nucleation and growth of crystals in a metastable liquid. This mechanism is that crystalline nuclei formation occurs in dense liquid clusters suspended in the solution. These clusters contain higher solution concentration and viscosity, leading to a lower surface free energy barrier and faster phase transition route. The theory is based on growth laws of crystals during the two-step bulk phase transformation. At the initial stage, the crystals evolve in a diffusion-limited environment with almost unchanged supersaturation. At the second stage, they become larger, move beyond these clusters, and evolve in accordance with a hyperbolic tangent law. A generalized particle growth law joining the first and second stages is obtained by stitching the diffusion limited and hyperbolic tangent laws. On this basis, an integrodifferential model of the evolution of a polydisperse ensemble of crystals was formulated and solved. The crystal-size distribution function increases and the solution supersaturation remains practically unchanged until the particle size corresponds to a transition in the particle growth rate from a diffusion-limited branch to a hyperbolic tangent branch. This is followed by an increase in the crystal growth rate, a decrease in the distribution function and solution supersaturation. Then the distribution function increases up to the maximum size of crystals grown in the solution. A sufficiently long time interval of almost constant supersaturation and the N-shaped behavior of the distribution function are the consequences of a two-step nucleation and growth mechanisms. [ABSTRACT FROM AUTHOR]

Metal hexafluorides hydrolyze at ambient temperature to deposit compounds having fluorine-to-oxygen ratios that depend upon the identity of the metal. Uranium-hexafluoride hydrolysis, for example, deposits uranyl fluoride (UO2F2), whereas molybdenum hexafluoride (MoF6) and tungsten hexafluoride deposit trioxides. Here, we pursue general strategies enabling the prediction of depositing compounds resulting from multi-step gas-phase reactions. To compare among the three metal-hexafluoride hydrolyses, we first investigate the mechanism of MoF6 hydrolysis using hybrid density functional theory (DFT). Intermediates are then validated by performing anharmonic vibrational simulations and comparing with infrared spectra [McNamara et al., Phys. Chem. Chem. Phys. 25, 2990 (2023)]. Conceptual DFT, which is leveraged here to quantitatively evaluate site-specific electrophilicity and nucleophilicity metrics, is found to reliably predict qualitative deposition propensities for each intermediate. In addition to the nucleophilic potential of the oxygen ligands, several other contributing characteristics are discussed, including amphoterism, polyvalency, fluxionality, steric hindrance, dipolar strength, and solubility. To investigate the structure and composition of pre-nucleation clusters, an automated workflow is presented for the simulation of particle growth. The workflow entails a conformer search at the density functional tight-binding level, structural refinement at the hybrid DFT level, and computation of a composite free-energy profile. Such profiles can be used to estimate particle nucleation kinetics. Droplet formation is also considered, which helps to rationalize the different UO2F2 particle morphologies observed under varying levels of humidity. Development of predictive methods for simulating physical and chemical deposition processes is important for the advancement of material manufacturing involving coatings and thin films. [ABSTRACT FROM AUTHOR]

Metal hexafluorides hydrolyze at ambient temperature to deposit compounds having fluorine-to-oxygen ratios that depend upon the identity of the metal. Uranium-hexafluoride hydrolysis, for example, deposits uranyl fluoride (UO2F2), whereas molybdenum hexafluoride (MoF6) and tungsten hexafluoride deposit trioxides. Here, we pursue general strategies enabling the prediction of depositing compounds resulting from multi-step gas-phase reactions. To compare among the three metal-hexafluoride hydrolyses, we first investigate the mechanism of MoF6 hydrolysis using hybrid density functional theory (DFT). Intermediates are then validated by performing anharmonic vibrational simulations and comparing with infrared spectra [McNamara et al., Phys. Chem. Chem. Phys. 25, 2990 (2023)]. Conceptual DFT, which is leveraged here to quantitatively evaluate site-specific electrophilicity and nucleophilicity metrics, is found to reliably predict qualitative deposition propensities for each intermediate. In addition to the nucleophilic potential of the oxygen ligands, several other contributing characteristics are discussed, including amphoterism, polyvalency, fluxionality, steric hindrance, dipolar strength, and solubility. To investigate the structure and composition of pre-nucleation clusters, an automated workflow is presented for the simulation of particle growth. The workflow entails a conformer search at the density functional tight-binding level, structural refinement at the hybrid DFT level, and computation of a composite free-energy profile. Such profiles can be used to estimate particle nucleation kinetics. Droplet formation is also considered, which helps to rationalize the different UO2F2 particle morphologies observed under varying levels of humidity. Development of predictive methods for simulating physical and chemical deposition processes is important for the advancement of material manufacturing involving coatings and thin films. [ABSTRACT FROM AUTHOR]

Using colloids effectively confined in two dimensions by a cell with a thickness comparable to the particle size, we investigate the nucleation and growth of crystallites induced by locally heating the solvent with a near-infrared laser beam. The particles, which are "thermophilic," move towards the laser spot solely because of thermophoresis with no convection effects, forming dense clusters whose structure is monitored using two order parameters that gauge the local density and the orientational ordering. We find that ordering takes place when the cluster reaches an average surface density that is still below the upper equilibrium limit for the fluid phase of hard disks, meaning that we do not detect any sign of a proper "two-stage" nucleation from a glass or a polymorphic crystal structure. The crystal obtained at late growth stage displays a remarkable uniformity with a negligible amount of defects, arguably because the incoming particles diffuse, bounce, and displace other particles before settling at the crystal interface. This "fluidization" of the outer crystal edge may resemble the surface enhanced mobility giving rise to ultra-stable glasses by physical vapor deposition. [ABSTRACT FROM AUTHOR]

Barium Oxyfluoride plays an important role, as a precursor species, in the nucleation and growth of YBa2Cu3O7− δ (YBCO) via the low fluorine metal organic decomposition (MOD low-fluorine) route. In this contribution, we present a study on the thermodynamics of oxyfluoride by processing experimental data on YBCO growth on LaAlO3 (LAO) substrates. The analysis allows one to determine the standard enthalpy and the standard entropy changes for oxyfluoride formation from barium oxide and barium fluoride. To identify the thermodynamically more favorable route to oxyfluoride formation in the MOD low-fluorine process, the free energy change for the formation of the precursor, through reactions involving gas water, has been determined. The free energy of formation via fluoride and water indicates higher stability of oxygen rich oxyfluoride for P HF 2 P H 2 O < 10 − 6 . In the framework of nucleation theory, the present results are needed to study the effect of precursor composition on film orientation. [ABSTRACT FROM AUTHOR]

The evaporation behaviors of ESR slag (CaF 2 -CaO-Al 2 O 3 -MgO-(B 2 O 3)) for B-containing rack steel was laboratorially investigated to improve the stability of ESR process and the quality of ESR ingots. The thermogravimetric measurement, FactSage 8.3, kinetic analysis and molecular dynamics simulation methods were applied in this study. Additionally, the melting characteristic temperatures of the slag was tested by the hemisphere method. The results showed that B 2 O 3 reduced the melting characteristic temperatures and mass loss of slag. Increasing the B 2 O 3 content increased the vapor pressure of AlF 3 , OBF, and BF 3 , consequently promoting their evaporation. The main evaporating product in the slag was found to be CaF 2 , followed by minor amounts of MgF 2 , AlF 3 , OBF, AlOF, and BF 3. Notably, the apparent activation energy for fluoride evaporation was calculated to fall within the range of 189.43–388.24 kJ mol−1, with the evaporation process following a nucleation and growth mechanism. The order of the self-diffusion coefficients of ions in the slag was determined to be F− > Mg2+>Ca2+>O2− ≈ B3+>Al3+. With the increase of B 2 O 3 content in the slag, the self-diffusion coefficient of each ion underwent an initial decrease followed by a significant increase, illustrating that diffusion did not serve as the controlling step of the evaporation reaction. [ABSTRACT FROM AUTHOR]

New particle formation (NPF) often drives cloud condensation nuclei concentrations and the processes governing nucleation of molecular clusters vary substantially in different regions. The growth of these clusters from ∼2 to >10 nm diameters is often driven by the availability of extremely low volatility organic vapors (ELVOCs). Although the pathways to ELVOC formation from the oxidation of biogenic terpenes are better understood, the mechanistic pathways for ELVOC formation from oxidation of anthropogenic organics are less well understood. We integrate measurements and detailed regional model simulations to understand the processes governing NPF and secondary organic aerosol formation at the Southern Great Plain (SGP) observatory in Oklahoma and compare these with a site within the Bankhead National Forest (BNF) in Alabama, southeast USA. During our two simulated NPF event days, nucleation rates are predicted to be at least an order of magnitude higher at SGP compared to BNF largely due to lower sulfuric acid (H2SO4) concentrations at BNF. Among the different nucleation mechanisms in WRF‐Chem, we find that the dimethylamine (DMA) + H2SO4 nucleation mechanism dominates at SGP. We find that anthropogenic ELVOCs are critical for explaining the growth of particles observed at SGP. Treating organic particles as semisolid, with strong diffusion limitations for organic vapor uptake in the particle phase, brings model predictions into closer agreement with observations. We also simulate two non‐NPF event days observed at the SGP site and show that low‐level clouds reduce photochemical activity with corresponding reductions in H2SO4 and anthropogenic ELVOC concentrations, thereby explaining the lack of NPF. Plain Language Summary: In forested regions around the world, biogenic emissions have been reported to be key drivers of new particle formation (NPF), cloud condensation nuclei (CCN). However, at locations in the Midwest USA that are far from forests and influenced by croplands and urban sources, the processes driving NPF and CCN are not well understood. Using detailed regional model simulations, we show that dimethylamines (DMA) and sulfuric acid (H2SO4) are key nucleation drivers at the Southern Great Plain (SGP) site during our two simulated days in the springtime, and condensation of H2SO4 alone is not sufficient to explain the observed growth of molecular clusters from ∼2 nm diameters to >10 nm diameter. We show that anthropogenic extremely low volatility organics (ELVOCs) are critical for explaining the observed particle growth. In contrast, our simulated non‐NPF days at SGP are characterized by low‐level clouds, which reduce photochemical activity, H2SO4, and ELVOC concentrations, thereby explaining the lack of NPF. At the BNF forested site in southeast USA, we show that nucleation rates are limited by availability of H2SO4. Our study highlights the large heterogeneities in nucleation and particle growth mechanisms within the Midwest compared to southeast USA. Key Points: Dimethylamines (DMA) and sulfuric acid drive nucleation over the Southern Great Plain (SGP) region in the Midwest USAAromatic low volatile organic gases govern the growth of molecular clusters to larger sizesNucleation in forested regions of southeast USA is limited by sulfuric acid [ABSTRACT FROM AUTHOR]

Starch retrogradation is important in controlling many properties of starch-rich foods, while many crucial issues remain to be answered in this field. This review for the first time summarized recent understandings on starch retrogradation property, especially from the kinetics and molecular perspectives. Consecutive reaction kinetics (CR) model was recently proposed to help understand nucleation and crystal growth steps, which are critical in determining the overall retrogradation rate. By applying CR model, relations between starch fine molecular structures and retrogradation property have been revealed. Food ingredients, e.g. sugars, salts, proteins, lipids, polyphenols, and various non-starch polysaccharides, all influence starch retrogradation via different mechanisms. These new insights were comprehensively discussed in this review, aiming to help the development of functional foods with both preferable texture and nutrition property, through a better manipulation of starch retrogradation property during food processing. [ABSTRACT FROM AUTHOR]

A novel and green microfluidic approach was employed for the synthesis of undoped and Eu(III)-doped calcium molybdate at room and low temperatures. The controlled formation of nano- and microstructures was successfully achieved by tuning the nucleation and growth stages of particle formation through a systematic variation of the viscosity and dielectric constant of the reaction medium, i.e. water and ethanol in different weight ratios and at different temperatures. Thanks to the inherent advantages of the microfluidic approach in terms of mass transport, mixing and heat exchange, it was possible to carry out the reaction at low temperature (−4 °C) in an effective manner and to further control the reaction conditions to achieve the formation of small and monodisperse nanoparticles. The synthesised nano- and microstructures, displaying different morphologies depending on reaction conditions, were investigated from a structural (XRD), dimensional and morphological (TEM, SEM), compositional (ICP-MS), and functional (photoluminescence) point of view. The remarkable photoluminescence properties of pure and Eu(III)-doped calcium molybdate structures proved that they are promising materials to be employed as phosphors. [ABSTRACT FROM AUTHOR]

The unique coordination configuration of single‐atom materials (SAMs) allows precise reaction control at atomic‐level and a potential of unusual electrochemical reaction. Nevertheless, it is a big challenge to prepare main group element with high loading content. Here, multifield‐regulated synthesis (MRS) technology is utilized to rapidly produce single‐atom antimony (Sb) metal with a high loading of 15 wt.%. Ab initio molecular dynamics simulations reveal the significantly enhanced reaction kinetics of Sb and nitrogen‐doped graphene by multi‐physics field coupling. Compared with common metallic Sb nanoparticles, atomically dispersed Sb displays remarkably improved electrochemical reaction kinetics and stable structure due to the negligible variation of stresses and volume expansion during the pseudocapacitive alloying‐dealloying process. Such extraordinary alloying reaction in well‐dispersed Sb atoms enabling homogeneous ion flow can serve as active nucleation sites for regulating even Na metal nucleation and growth. As a result, copper foil coated with only ≈3 µm thickness of such material exhibits a high Coulombic efficiency of up to 99.99%, an ultra‐low overpotential of 3 mV, and a long lifetime exceeding 2500 h in symmetrical cells. Furthermore, an anode‐free MRS‐SbSA||Na3V2(PO4)3 battery is constructed, which demonstrates exceptionally high energy density (≈362 Wh Kg−1), outstanding rate capability and good cycling stability. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) transition metal chalcogenides (TMDs) have demonstrated immense potential and broad prospects in advancing the fields of next-generation optoelectronics, spintronics, valley electronics, and traditional electronics. In recent years, significant progress has been made in the growth research of TMDs through continuous optimization and innovation of various synthetic strategies. However, precisely controlling the growth conditions of materials, synthesizing high-quality 2D materials with a single domain structure, and achieving the desired shape and performance standards remain complex scientific challenges. Here, we report on the study of MoS2 nucleation and growth habits by precisely controlling the ratio of molybdenum and sulfur sources during the growth process. Using pre-deposited highly oriented MoO2 nanorods as templates, two preferentially oriented (0° or 60°) MoS2 crystal domains were obtained on c-plane sapphire. Characterization using Raman spectroscopy, PL, XPS, and HRTEM reveals that the monolayer MoS2 continuous film, grown using this templating method, possesses superior quality. Our work demonstrates a method for directional growth of 2D MoS2 thin films using highly oriented 1D MoO2 nanorods as templates and precursors, providing new insights into orientation control for epitaxial growth of 2D TMD materials. [ABSTRACT FROM AUTHOR]

The crack formations in AlGaN templates for deep ultraviolet (DUV) light‐emitting diodes (LEDs) are investigated and successfully suppressed. The strain values in AlGaN thick layers on sapphire substrates by in situ wafer curvature measurements and ex situ X‐ray diffraction measurements are evaluated. It is found that the tensile strain during the AlGaN thick layer growth comes from a thermal expansion difference between the AlGaN thick layer and the sapphire substrate as the temperature changes from the AlN nucleation layer growth to the AlGaN thick layer growth. When the temperature change is 100 °C and less, the tensile strain of 0.1% and less is observed during the AlGaN thick layer growth, resulting in no crack formations in the AlGaN thick layer. Furthermore, a DUV LED layer structure grown on such a crack‐free AlGaN template shows no crack formations. Thus, to suppress crack formation in templates fabricated for DUV LEDs, their growth temperature must be optimized by considering thermal expansions caused by the changes in the growth temperature from the nucleation layer to the thick layer. [ABSTRACT FROM AUTHOR]

In this paper, the texture evolution of the Ni-5%W alloy baseband with different strain variables (εvM = 3.9, 4.9, and 5.1) during rolling and annealing was studied using the electron back scattering diffraction (EBSD) technique. The results indicate that after high-temperature annealing at 1150 °C, all three strain levels of the alloy substrates can achieve a strong cubic texture, with a content exceeding 99% (<10°). However, the texture evolution trajectory is significantly influenced by the strain level. When the content of cubic texture in the alloy substrates under strain levels of 3.9 and 5.1 is the same, significant temperature differences exist. Additionally, the different strain levels result in varying nucleation rates and growth rates of cubic texture in the Ni-5%W alloy substrates. The study reveals that in the alloy substrates under strain levels of 3.9 and 4.9, recrystallized cubic grain nuclei grow within a layered structure, resulting in larger grain sizes and lower nucleation rates. In contrast, in the alloy substrates under a strain level of 5.1, recrystallized cubic grain nuclei form from small equiaxed grains, leading to higher nucleation rates but smaller grain sizes, competing with random orientations. In the later stages of nucleation, recrystallized grains in the alloy substrates under a strain level of 5.1 exhibit a significant size advantage, rapidly growing by engulfing randomly oriented grains. Compared to the alloy substrates with lower strain levels, the recrystallized cubic grains in the alloy substrates under a strain level of 5.1 have higher nucleation rates and faster growth rates. [ABSTRACT FROM AUTHOR]

In this study, isothermal annealing experiments were conducted on copper-nickel-silicon alloys containing continuous precipitates (CP) and discontinuous precipitates (DP) to investigate the effects of different types of precipitate phases on the microstructural evolution and softening temperature during annealing, as well as to analyze the differences in softening mechanisms. The experimental results revealed that the softening temperature of the CP alloy, subjected to 75% cold deformation, was 505 °C. In contrast, the DP alloy achieved softening temperatures of 575 °C and 515 °C after 75% and 97.5% cold deformation, respectively. This indicates that the DP alloy exhibits significantly superior softening resistance compared to the CP alloy, attributed to the distinct softening mechanisms of the two alloys. In the CP alloy, softening is primarily influenced by factors such as the coarsening of the precipitate phase, the occurrence of recrystallization, and the reduction in dislocation density. In the DP alloy, the balling phenomenon of the DP phase is more pronounced, and its unique microstructure exerts a stronger hindrance to dislocation and grain boundary motion. This hindrance effect reduces the extent of recrystallization and results in a smaller decrease in dislocation density. In summary, the DP alloy, due to its unique microstructure and softening mechanisms, demonstrates better softening resistance, providing higher durability and stability for high-temperature applications. [ABSTRACT FROM AUTHOR]

Zeolites are widely used in fields such as separation and catalysis due to their unique pore structure. However, the complexity of its crystallization process and growth mechanism presents challenges for the research and exploitation of novel zeolites. In order to achieve the development of new zeolites with specific structures and properties, this study delves into the key factors in zeolite synthesis and dealumination processes, as well as their impact on zeolite synthesis, from the perspective of changes in silicon and aluminum. It was found that selecting silicon and aluminum sources with high activity and high specific surface area could achieve the best dissolution effect, and the suitable alkalinity could help to enhance the solubility and reactivity of silicon and aluminum sources, which in turn could improve the crystallinity and yield of zeolite. Prolonging the crystallization time and increasing the crystallization temperature can accelerate the nucleation and growth of aluminosilicate gel and reduce the anticrystallization phenomenon. In addition, precise control of the pore structure of zeolite can be achieved by controlling the selection of template agents and the conditions of dealumination treatment, thereby improving the application performance of zeolite. In this study, we reveal the deep connection between influence factors, zeolite synthesis, and silicon-aluminum variations, which provides new perspectives and methods for the exploitation and application of novel zeolites. Meanwhile, through a deep understanding of the mechanism of influence factors on zeolite synthesis, it is able to target and regulate the synthesis conditions to achieve the desired zeolite structure and properties, which not only improves the efficiency and cost effectiveness of the synthesis, but also establishes a solid foundation for the further development and wide application of zeolites. Highlights: Clarified the migration and conversion of silica-aluminum in zeolite synthesis Summarized the dealumination of zeolite by different post-treatment methods Coupled synthesis and post-treatment to construct high-silica zeolite with hierarchical pore [ABSTRACT FROM AUTHOR]

This work reports the preparation by co‐precipitation method of [Zn2Al0.95:Ln0.05(OH)6](HMA)0.21·(H2O)x, where x = 1.0–1.7 and Ln3+: Sm3+, Eu3+, Gd3+, Tb3+ and Dy3+, doped trivalent lanthanide ions (Ln3+) intercalated with mellitate (HMA5−) anions in the interlayer gallery. The results indicate that the Ln3+ ions and the organic anion are effectively introduced into the material without significantly losing the structural properties of the layered double hydroxydes (LDH). In situ measurements reveal slight changes in the luminescent properties assigned to the nucleation and growth processes of the LDH. Ex situ experiments show that the photophysical properties also changed after the drying process, indicating significant interactions of the mellitate anion in the materials. LDH‐HMA:Eu3+ and LDH‐HMA:Tb3+ exhibit high luminescence intensity in the red and green spectral regions due to the 5D0→7F0‐6 and 5D4→7F6‐0 transitions, respectively. The LDH‐HMA doped with different ratios Eu3+/Tb3+ presenting emission colors from red to green are also investigated. Surprisingly, the unexpected afterglow blue luminescence from the LDH‐HMA doped with Gd3+ ion is ascribed to the phosphorescence T→S0 transition. Finally, obtaining three red, green and blue luminophores based on the same type of material represents an effective strategy toward white‐light emission realized by mixing three different LDHs materials based on Ln3+ ions. [ABSTRACT FROM AUTHOR]

High‐aluminum advanced high‐strength steels have received increasing interest due to their excellent combination of strength and ductility. The control of nonmetallic inclusions in steel is among the most important issue for the production of high‐aluminum steel. This study proposes a model for the evolution of size distributions of AlN inclusions during solidification of steel based on the Kampmann–Wagner numerical model and microsegregation calculation. Both homogeneous (pure AlN) and heterogeneous precipitations (AlN+oxide or MnS) are described using homogeneous nucleation and free growth models of Greer et al. respectively. The model is applied to calculate the size distributions of AlN in high‐Al (up to 5%) Fe–Cr–Al steels and high‐ and medium‐manganese steels and validated by the experimental data in the literature. The model correctly describes the influence of cooling rates on the precipitation of AlN in Fe–Cr–Al steels and high‐manganese steels, and the sizes of AlN are reduced and the number densities of AlN inclusions are increased by increasing the cooling rate. The effects of nitrogen and aluminum concentration in medium‐manganese steel on inclusion precipitation are investigated by the model calculation. The increases in nitrogen and aluminum concentration facilitate the homogeneous precipitation of AlN inclusions. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive study on discontinuous precipitation (DP) in Al-22 at.% Zn alloy, leveraging the correlative and synergic effects of advanced microscopy and modelling techniques. The study is structured into three pivotal steps: in-situ scanning electron microscopy combined with an energy backscattered diffraction analysis for real-time monitoring and an analysis of DP reaction kinetics and grain boundary misorientations; transmission electron microscopy and an energy X-ray dispersive microanalysis for detailed observation of solute-depleted α and solute-rich β lamellae, offering insights into the kinetics of the reaction front (RF) and solute concentration profiles; and a sophisticated modelling approach addressing the limitations of direct observation methods by simulating solute concentration changes within αphase lamellae during RF go-and-stop cycles. This multifaceted approach elucidates the nuances of DP mechanisms, from the nucleation and growth of precipitates to the estimation of instantaneous RF velocity and the impact of grain boundary misorientations. The integration of these methodologies enhances our understanding of DP kinetics and morphology at both meso- and nanoscales, highlighting the significant role of correlative microscopy in metallurgical research. The findings not only deepen our grasp of the fundamental mechanisms driving DP reactions but also provide a valuable comparison framework for experimental data, potentially guiding the development and optimization of metallurgical processes. [ABSTRACT FROM AUTHOR]

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 -colony microstructures constituting the "layer bands," while the rest of the build is predominantly basketweave. Additionally, changes in the basketweave α -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. [ABSTRACT FROM AUTHOR]

The blockage of gas transmission pipelines due to gas hydrates poses a significant challenge for the gas industry. Low‐dosage hydrate inhibitors (LDHI) are utilized to influence the kinetics of hydrate formation, including nucleation, growth, and/or agglomeration. In the current study, a series of batch, isochoric, and isothermal tests were carried out to investigate the impacts of two LDHIs, poly N‐vinylpyrrolidone (PVP) and polyvinyl alcohols (PVA). This study examined the influence of these inhibitors on nucleation and growth of ethane+propane mixture in the presence of kaolin nanoparticles. In laboratory studies and using pure constituents, the rate of hydrate formation is low to investigate the inhibitors effect. To enhance the rate of hydrate formation, kaolin nanoparticles were utilized as they serve as a suitable representative for solid minerals commonly found in pipelines. The gas phase's compositional change were measured using a gas chromatograph. The results revealed that the growth stage of mixed‐gas exhibited two distinct steps, attributed to the formation of two different structures known as structure II and structure I. During the first step, structure II was formed, and the cavities were occupied by both gas components. In the second stage, structure I was formed by ethane. The effect of temperature on the induction time (nucleation rate) and the growth rate during the second stage was lower than that at the first stage. The increase in PVA concentration resulted in an increase in the induction time and a decrease in the rate of growth during the first stage. The performance of PVA was found to be affected by temperature. Lower temperatures resulted in the formation of less foam, providing improved performance for PVA at −0.5°C. PVP had a stronger impact on induction time and both growth steps compared to PVA, indicating stronger inhibitory impact of PVP on nucleation of hydrates initiated by propane and the growth of both propane and ethane hydrates. [ABSTRACT FROM AUTHOR]

The high‐temperature oxidation behavior of 444 ferritic stainless steel has been studied in cyclic oxidation experiments using synthetic automotive exhaust gas atmospheres at 950 and 1050 °C. The weight gain per unit area of the 444 ferritic stainless steel following oxidation at 950 °C for 100 h iss 85.7% lower than recorded at 1050 °C. The oxide scale at both temperatures consisted of Fe–Cr and Mn–Cr spinels in the outer layer and Cr2O3 in the inner layer. Nodule formation and spallation of the oxide scale are identified as the main causes of breakaway oxidation. The depth of the internal oxides gradually increases with the oxidation time. The nucleation and growth of internal SiO2 result in the formation of metal protrusions, which are eventually consumed in the formation of a SiO2 layer. The SiO2 layer is formed at the interface between the oxide scale and the substrate at 1050 °C. The nucleation and growth of internal SiO2, in combination with lateral growth of SiO2 at the Cr2O3 layer/substrate interface contributed to the formation of the SiO2 layer. [ABSTRACT FROM AUTHOR]

The development of an artificial solid‐electrolyte interphase (SEI) has been recognized as the most efficient strategy to overcome the safety concerns associated with the lithium metal anode (LMA). Inorganic‐rich SEIs on the LMA are crucial for suppressing Li dendrites. Among the prevalent SEI inorganic compounds observed for LMA, lithium nitride (Li3N) is often found in the SEIs of high‐performance LMA. Herein, the Li3N nanowire array is successfully synthesized and the catalytic base‐growth mechanism is thoroughly investigated. The fast ionic conductor Li3N nanowires act as pillars to control the nucleation and growth of lithium metal along the vertical direction of the nanowire by bottom‐up self‐lubrication, which fundamentally prevents the dendrite growth. The Li3N is characterized by abundant lithiophilic nucleation sites, which effectively reduces the local current density, and facilitates homogeneous Li+ flux. Symmetric cells utilizing the Li3N@Li anode have demonstrated excellent stability, featuring uniform deposition without dendrite formation. Additionally, high‐capacity retentions of 98% at 0.5 C after 400 cycles and impressive high‐rate performance at 31.1 mA cm−2 have been realized in high‐loading Li3N@Li||LFP cells. The universal preparation of the Li3N nanowires with various precursors and substrates is further explored, which is expected to be applied in solid‐state batteries and hydrogen storage. [ABSTRACT FROM AUTHOR]

Perovskite quantum dots (PQDs) show high potential for new‐generation light‐emitting diodes (LEDs) due to their outstanding optoelectronic properties. Even though the red PQD‐LEDs can be realized through mixing halide in the PQDs to tune their spectroscopies, the PQDs may suffer from phase separation under a high electric field, predominantly affecting LED applications. Herein, a ligand‐pinning‐assisted approach is reported to tune the spectroscopies of CsPbI3 PQDs, in which vinyl phosphonic acid (VPA) is applied as function ligands to regulate the nucleation and growth of PQDs during the synthesis. Systematically experimental studies and theoretical calculations are conducted to comprehensively understand the functions of the VPA ligands during the PQD synthesis, which reveals that the VPA ligands with high binding energy with Pb2+ cations could firmly anchor on the surface matrix of PQDs without desorption, regulating the growth of PQDs and thus resulting in tunable spectroscopies being realized. Meanwhile, VPA could also renovate the defective surface matrix of PQDs, substantially diminishing trap‐induced nonradiative recombination. Consequently, red PQD‐LEDs deliver a high external quantum efficiency of 22.83%, which is significantly improved compared with the control devices. This work provides a new avenue to tune the spectroscopies of PQDs toward high‐performing LEDs. [ABSTRACT FROM AUTHOR]

Lithium (Li) metal anodes have received sustained attention due to their remarkable theoretical specific capacities and low electrochemical potentials. However, the nucleation and growth of Li dendrites during cycling have hindered their application in Li metal batteries (LMBs). As an indispensable battery component, separators offer an ideal platform for mitigating Li dendrites. Herein, an ion‐management membrane (IMM) concept utilizing polydopamine (PDA)‐modified polyetherimide track‐etched membranes (PEITEMs) is proposed. The PDA@PEITEM‐based IMM features vertically aligned uniform electronegative nanochannels, serving as ion distributors and "Li‐ion guides" to simultaneously smooth ion concentration fluctuations and accelerate Li+ selective conduction. The IMM's unique structural and chemical properties yield exceptional ionic conductivity (0.73 mS cm−1) and high Li+ transfer number (0.80) while minimizing Li+ concentration fluctuations. When employed in Li/Cu cells, the IMM facilitates a Coulombic efficiency exceeding 96% over 100 cycles at 0.5 mA cm−2. Moreover, it extends the cycle lifespan of Li/Li cells to 1 200 h at 1.0 mA cm−2. For Li/LiFePO4 cells, this approach enables a specific capacity of 146 mAh g−1, maintaining capacity retention of 79.84% after 1 000 cycles. This novel strategy for constructing free‐standing functional separators is convenient, efficient, and scalable, providing valuable insights into multifunctional separators for dendrite‐free LMBs. [ABSTRACT FROM AUTHOR]

Solid‐state electrolytes (SSEs) offer enhanced safety, extended cycle life, and increased energy density when replacing flammable liquid electrolytes in lithium‐ion batteries. Poly(ethylene oxide) (PEO)‐based SSE is the only candidate that has been commercially implemented in electric vehicles. However, the equipped battery needs to operate at temperatures above 50 °C, and its phase transitions at room temperature are still unclear. Herein, the solidification of the PEO‐lithium bis(trifluoromethanesulfonyl)imide (PEOn‐LiTFSI) system is revisited. Contrary to the prevailing view of forming PEO(6)‐LiTFSI spherulites, the presence of crystalline PEO(8)‐LiTFSI complexes is quantitatively confirmed. The nucleation and growth processes of crystalline PEO and PEO(8)‐LiTFSI spherulites are also visually elucidated, and phase transitions with the impedance change are correlated. In addition, it is demonstrated that the crystalline PEO shell surrounding the PEO(8)‐LiTFSI spherulites hinders the kinetics of crystal growth, thereby enabling the highest ionic conductivity at n = 10. Importantly, it is pointed out that instead of the poor ionic conductivity of the electrolyte layer, the heterogeneous nucleation of PEO(8)‐LiTFSI within the electrodes is the limiting factor in constructing room‐temperature all‐solid‐state batteries. [ABSTRACT FROM AUTHOR]

Based on the analysis of thermodynamic driving force and solidification kinetics under pressure, the influence mechanism of solidification pressure on columnar‐to‐equiaxed transition (CET) of high‐nitrogen steel is clarified. It is observed that increasing the solidification pressure from 0.5 to 2 MPa results in a shift of the CET positions toward the center. This is attributed to the fact that higher solidification pressure can promote the growth of columnar dendrites by increasing the solidification rate, temperature gradient, and cooling rate. Meanwhile, increasing the solidification pressure shortens the length of the diffusion zone ahead of the advancing columnar front and reduces the supercooling. As a result, it becomes more difficult for equiaxed dendrites to nucleate ahead of the advancing columnar front, leading to CET positions closer to the center. This indicates that the main influencing factor for the change in CET caused by changing solidification pressure is solidification kinetics, that is, changes in the nucleation and growth environment of equiaxed dendrites, while thermodynamic driving forces are not the primary factor causing CET position changes. [ABSTRACT FROM AUTHOR]

Long-term stability and power conversion efficiency of perovskite solar cells are strongly affected by their precursor compositions and intermediate phases during the fabrication process. In general, complex chemical reactions happen in a short time scale during the nucleation and crystal growth steps. However, the ex-situ characterization probes cannot capture the dynamics of perovskite film formation and degradation. In this review, we discussed the ambient air-compatible in-situ characterization probes that are used to monitor the evolution of the structural, morphological, and optoelectronic properties of perovskite films, which provides a deep understanding of the perovskite crystal formation process. [ABSTRACT FROM AUTHOR]

A new type of SiCf/TiC-Ti3SiC2 composite was prepared by the Spark Plasma Sintering (SPS) method in this work. The phase transformation and interface cracking of this composite under ion irradiation (single Xe, Xe + He, and Xe + He + H ions) and subsequent annealing were analyzed using transmission electron microscopy (TEM), mainly focusing on the interface regions. Xe ion irradiation resulted in the formation of high-density stacking faults in the TiC coatings and the complete amorphization of SiC fibers. The implanted H ions exacerbated interface coarsening. After annealing at 900 °C for 2 h, the interface in the Xe + He + H ion-irradiated samples was seriously damaged, resulting in the formation of large bubbles and cracks. This damage occurred because the H atoms reduced the surface free energy, thereby promoting the nucleation and growth of bubbles. Due to the absorption effect of the SiCf/TiC interface on defects, the SiC fiber areas near the interface recovered back to the initial nano-polycrystalline structure after annealing. [ABSTRACT FROM AUTHOR]

This study investigates the influence of super-fast heating rate and holding time on the microstructure and mechanical properties of dual-phase (DP) Fe-0.16C-1.4Mn sheet steel. Super-fast heating and cooling rates were achieved via induction heating and gas quenching. The results were also compared with those for a conventional low-speed heat treatment. The microstructures were characterized in detail using X-ray diffraction, scanning electron microscopy, electron backscatter diffraction, and electron probe microanalysis. The results showed that the layered structure of the DP Fe-0.16C-1.4Mn steel after super-fast heating was mainly composed of recrystallized ferrite, martensite clusters, and a small amount of residual austenite. Compared with the conventional method, super-fast heating significantly refined the grains and improved yield and tensile strength, but it slightly reduced the elongation. The fraction of martensite, which depends on the nucleation and growth behavior of austenite, was significantly affected by the heating rate and holding time. The DP structure of Fe-0.16C-1.4Mn steel had an atypical layered heterogeneous structure, with an uneven plastic strain between the two phases occurring during the deformation process, which is something that can improve fracture elongation. [ABSTRACT FROM AUTHOR]

Novel three-dimensional mesh porous gallium nitride (GaN) substrates were prepared by a two-step method combining electrochemical etching and molten alkali etching. The porous GaN substrate facilitated the successful growth of self-separated GaN crystals via hydride vapor phase epitaxy (HVPE), achieving a thickness of around 1.5 mm. The nucleation and growth process on a three-dimensional mesh porous substrate was demonstrated. High-resolution X-ray diffraction full width at half maximum (FWHM) highlighted the superior quality of the GaN crystals grown on porous substrates. Cathodoluminescence (CL) testing showed a significant reduction in the dislocation density, and transmission electron microscopy (TEM) cross-sectional analysis revealed that the porous structure can effectively impede dislocation propagation. Our work provides a new technological route for the growth of high-quality self-separated GaN crystals. [ABSTRACT FROM AUTHOR]

Insufficient selenization and uneven distribution of elements caused by the poor diffusion and reaction activity of selenium clusters is one of the main issues limiting the efficiency of Cu2ZnSn(S,Se)4 (CZTSSe) solar cells. Here, this work designs a simple and feasible strategy to improve the activity of selenium (Se) by implementing high‐temperature treatment on graphite boxes loaded with Se pellets. The rapid adsorption/desorption characteristics of graphite on active gaseous small‐molecule selenium have successfully introduced hyperactive Se4, Se3, and Se2 into the selenization process. The results indicate that the adsorbed non‐toxic gaseous active Se3 and Se4 can quickly and uniformly diffuse into the precursor film at low temperatures, thereby inducing nucleation and grain growth at both surface and back interface simultaneously, which inhibits the upward migration and aggregation of cations, especially Cu, and promotes the homogenization of elements. The overall relatively Cu‐poor chemical environment suppresses the formation of CuZn defects and [2CuZn+SnZn] defect clusters, and also promotes the generation of favorable VCu. The band tail states and non‐radiative recombination are then optimized. Finally, the CZTSSe solar cells achieve a power conversion efficiency (PCE) of 14.5%, with VOC/VOCSQ of 67% being one of the highest in the literature. [ABSTRACT FROM AUTHOR]

Quasicrystals are of interest because of their unique nonperiodic structures and physical properties. Motivated by naturally occurring icosahedral AlCuFe- and decagonal AlNiFe-phases hosted in a shocked meteorite, different laboratories have undertaken a series of shock recovery experiments to understand their formation mechanism. Shock experiments generate a complex series of processes and conditions, including a near-instantaneous excursion to high pressure and high temperature, large shear stresses, local melting, rapid decompression, fast quenching and post-shock annealing. This highly dynamic scenario offers a very useful but imperfect tool for exploring the stability of novel alloys, such as quasicrystals. So far, all the shock-synthesized quasicrystals differ considerably in composition from any thermodynamically stable or metastable quasicrystals synthesized by metallurgical techniques at low pressure, leaving plenty of questions to be answered about their formation conditions and their nucleation and growth mechanisms occurring during shock experiments. In this Perspective, we summarize the previous studies of shock-synthesized quasicrystals and discuss the advantages and difficulties caused by the experimental complexity. We also propose a few directions for future experiments to better control the shock conditions and understand the properties of quasicrystals. Shock compression is a highly dynamic, useful tool for exploring the stability of novel alloys such as quasicrystals, but their formation conditions and the nucleation-growth mechanisms occurring during shock experiments remain largely elusive. Here, the authors provide a summary of quasicrystal shock-syntheses and discuss the advantages and difficulties caused by the experimental complexity. [ABSTRACT FROM AUTHOR]

Open nanoshells such as nanobowls or nanocups collectively described as 'semi shells' have unique plasmonic properties due to their lack of symmetry. So far, their fabrication was based on multistep and laborious methods such as solid state sputter coating or selective deposition/etching using sacrificial templates. In this work, we report a rapid one step colloidal synthetic protocol for PEGylated semi-shell (SS) fabrication by simultaneous facet specific anisotropic chemical etching of rhombic dodecahedral ZIF-8 and heterogenous nucleation & growth of gold. The SS possesses a strong localized surface plasmon resonance in the near-infrared region, which is retained after surface passivation with polyethylene glycol and subsequent cryopreservation for extended shelf-life. Freshly reconstituted PEGylated SS was found to be safe & non-toxic in healthy C57BL/6 mice post intravenous administration. The PEGylated SS displayed significant photothermal efficiency of ~37% with 808 nm laser irradiation. Preclinical assessment of intra-tumoral photothermal efficacy indicated complete remission of primary breast tumor mass with insignificant metastasis to vital organs in 4T1 FL2 tumor bearing CD1 nude mice. Further, PEGylated SS mediated photothermal therapy also yielded morbidity free survivael of 75% for up to 90 days, indicating their potential to significantly improve outcomes in advanced breast tumors. Anisotropic gold-based colloidal nanoparticles such as semi shells have unique optical properties and widespread applications such as in bioimaging, biosensing and therapy, however, the fabrication process of semi shells remains a challenge due to laborious multistep solid state and colloidal procedures. In this study, the authors develop a rapid one-pot colloidal synthetic route for the fabrication of semi shells using ZIF-8 as a sacrificial template, and demonstrate their promise for photothermal therapy. [ABSTRACT FROM AUTHOR]

Lithium niobate and lithium tantalate are among the most widespread materials for nonlinear, integrated photonics. Mixed crystals with arbitrary Nb–Ta ratios provide an additional degree of freedom to not only tune materials properties, such as the birefringence but also leverage the advantages of the singular compounds, for example, by combining the thermal stability of lithium tantalate with the larger nonlinear or piezoelectric constants of lithium niobate. Periodic poling allows to achieve phase-matching independent of waveguide geometry and is, therefore, one of the commonly used methods in integrated nonlinear optics. For mixed crystals, periodic poling has been challenging so far due to the lack of homogeneous, mono-domain crystals, which severely inhibit domain growth and nucleation. In this work, we investigate surface-near (< 1 μ m depth) domain inversion on x-cut lithium niobate tantalate mixed crystals via electric field poling and lithographically structured electrodes. We find that naturally occurring head-to-head or tail-to-tail domain walls in the as-grown crystal inhibit domain inversion at a larger scale. However, periodic poling is possible if the gap size between the poling electrodes is of the same order of magnitude or smaller than the average size of naturally occurring domains. This work provides the basis for the nonlinear optical application of lithium niobate tantalate mixed crystals. [ABSTRACT FROM AUTHOR]

Shape control has been a major theme of nanocrystal research in terms of synthesis, property tailoring, and optimization of performance in a variety of applications. Among the possible shapes, bipyramids are unique owing to their symmetry, planar defects, and exposed facets. In this article, we focus on the colloidal synthesis of noble‐metal nanocrystals featuring a triangular bipyramidal shape, together with highlights of their properties and applications. We start with a brief discussion of the general classification and requirements for the nucleation and growth of bipyramidal nanocrystals, followed by specific aspects regarding the synthetic methods with a focus on the roles of reduction, etching, and capping, as well as controls of facet, size, aspect ratio, and corner truncation. In the end, we illustrate how these aspects affect the properties of bipyramidal nanocrystals for plasmonic and catalytic applications, together with future perspectives. [ABSTRACT FROM AUTHOR]

This study involved a numerical investigation of the homogeneous nucleation of CO2 from a CO2–Ar gas mixture in a supersonic nozzle with a throat size of 2.11 mm, a total pressure of 61.15 kPa, and a total temperature of 293.15 K. The flow conditions covered the cryogenic temperature range (∼75 K). Therefore, the surface tension of the clusters was calculated using the Tolman–Tanaka correction, and nucleation growth was evaluated considering both free molecular and continuum regimes. Numerical simulations were conducted for a wide range of CO2 mole fractions (3%–39%). In particular, the effect of the CO2 mole fraction on the condensation-shock position—approximately the Wilson point—was investigated. For 3%, 12%, 24%, and 39%, the condensation shock occurred at 0.048, 0.043, 0.046, and 0.054 m from the throat, respectively. When the mole fraction was low (≤10%), the condensation-shock position moved downstream as the mole fraction decreased. This trend was attributed to a lower nucleation rate. In contrast, when the mole fraction was high (≥10%), the condensation-shock position moved downstream as the mole fraction increased. This was because the CO2 equilibrium pressure rose more rapidly than the CO2 vapor pressure as the mole fraction increases. [ABSTRACT FROM AUTHOR]

Creep damage assessment is crucial for ensuring the long‐term reliability of key components operating at high temperatures. However, the existing studies on creep damage are mainly focused on constant loading conditions, while the effect of cyclic loading, which is a common loading mode in practice, remains unclear. In this paper, a series of stress‐controlled cyclic creep tests on the Inconel 718 superalloy were performed to investigate the influence of cyclic loading on creep damage evolution. The ex‐situ microstructural analyses, including fracture surface observations and EBSD measurements, were conducted to reveal the damage mechanisms under cyclic creep conditions. Furthermore, a cavity nucleation and growth model that accounts for the additional cavity closure was developed for the healing effect of cyclic creep damage evolution. The prediction results were consistent with the experimental data of cavity nucleation life and experimental life within a factor of 2. Performing cyclic creep tests under various holding time and stresses.Establishing a cavity nucleation and growth model considering cavity closure.Considering the effect of cyclic loading on creep damage evolution.Revealing the microscopic interactions under cyclic creep conditions. [ABSTRACT FROM AUTHOR]

Characterization of crystallization processes in situ is of great importance to furthering knowledge of how nucleation and growth processes direct the assembly of organic and inorganic materials in solution and, critically, understanding the influence that these processes have on the final physico‐chemical properties of the resulting solid form. With careful specification and design, as demonstrated here, it is now possible to bring combined X‐ray diffraction and Raman spectroscopy, coupled to a range of fully integrated segmented and continuous flow platforms, to the laboratory environment for in situ data acquisition for timescales of the order of seconds. The facility used here (Flow‐Xl) houses a diffractometer with a micro‐focus Cu Kα rotating anode X‐ray source and a 2D hybrid photon‐counting detector, together with a Raman spectrometer with 532 and 785 nm lasers. An overview of the diffractometer and spectrometer setup is given, and current sample environments for flow crystallization are described. Commissioning experiments highlight the sensitivity of the two instruments for time‐resolved in situ data collection of samples in flow. Finally, an example case study to monitor the batch crystallization of sodium sulfate from aqueous solution, by tracking both the solute and solution phase species as a function of time, highlights the applicability of such measurements in determining the kinetics associated with crystallization processes. This work illustrates that the Flow‐Xl facility provides high‐resolution time‐resolved in situ structural phase information through diffraction data together with molecular‐scale solution data through spectroscopy, which allows crystallization mechanisms and their associated kinetics to be analysed in a laboratory setting. [ABSTRACT FROM AUTHOR]

Formation kinetics of metal nanoparticles are generally described via mass transport and thermodynamics‐based models, such as diffusion‐limited growth and classical nucleation theory (CNT). However, metal monomers are commonly assumed as precursors, leaving the identity of molecular intermediates and their contribution to nanoparticle formation unclear. Herein, liquid phase transmission electron microscopy (LPTEM) and reaction kinetic modeling are utilized to establish the nucleation and growth mechanisms and discover molecular intermediates during silver nanoparticle formation. Quantitative LPTEM measurements show that their nucleation rate decreases while growth rate is nearly invariant with electron dose rate. Reaction kinetic simulations show that Ag4 and Ag− follow a statistically similar dose rate dependence as the experimentally determined growth rate. We show that experimental growth rates are consistent with diffusion‐limited growth via the attachment of these species to nanoparticles. The dose rate dependence of nucleation rate is inconsistent with CNT. A reaction‐limited nucleation mechanism is proposed and it is demonstrated that experimental nucleation kinetics are consistent with Ag42+ aggregation rates at millisecond time scales. Reaction throughput analysis of the kinetic simulations uncovered formation and decay pathways mediating intermediate concentrations. We demonstrate the power of quantitative LPTEM combined with kinetic modeling for establishing nanoparticle formation mechanisms and principal intermediates. [ABSTRACT FROM AUTHOR]

Phase transitions and critical phenomena are among the most intriguing phenomena in nature and society. They are classified into first-order phase transitions (FOPTs) and continuous ones. While the latter shows marvelous phenomena of scaling and universality, whether the former behaves similarly is a long-standing controversial issue. Here we definitely demonstrate complete universal scaling in field driven FOPTs for Langevin equations in both zero and two spatial dimensions by rescaling all parameters and subtracting nonuniversal contributions with singular dimensions from an effective temperature and a special field according to an effective theory. This offers a perspective different from the usual nucleation and growth but conforming to continuous phase transitions to study FOPTs. [ABSTRACT FROM AUTHOR]