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A multi-stage precipitation model is formulated to predict the microstructural evolution and explain the high performance of additive friction stir deposited aluminum alloy 7050 (AA 7050) for hole repair. The first stage is the heating process due to the high-temperature thermomechanical process of the stir. In this process, small η precipitates dissolve as they lose their stability with increasing temperature, and this causes the volume fraction of η precipitates to decrease and the concentration of Mg and Zn in the matrix to increase. The second stage is the cooling process at the end of the repair where material feeding ends and the tool is lifted away. Heterogeneous nucleation of η precipitates may occur and as the temperature cools below 250 °C, Guinier–Preston (GP) zones start to form. The final stage is the natural aging process, where the η ′ precipitate starts to grow. The volume fraction and precipitate radius are predicted for each type of precipitate. Furthermore, the fine η ′ precipitates and GP zones with a decent volume fraction improve the material strength and fatigue life. [ABSTRACT FROM AUTHOR]

Organic matter can initiate heterogeneous ice nucleation in supercooled water droplets, thereby influencing atmospheric cloud glaciation. Predicting the ice nucleation ability of organic matter-containing cloud droplets is challenging due to the unknown mechanism for templating ice. Here, we observed the presence of nanoparticles in aqueous samples of known ice-nucleating biopolymers cellulose and lignin, as well as in newly identified ice-nucleating biopolymers xylan and laminarin. Using our drop Freezing Ice Nuclei Counter (FINC), we measured the median ice nucleation temperature (T50) of xylan and of laminarin droplets of 2 μl to be −14.2 and −20.0 °C, respectively. Next, we characterized these samples using nanoparticle tracking analysis, and we detected and quantified nanoparticles with mean diameters between 132 and 267 nm. Xylan contained the largest nanoparticles and froze at higher temperatures. Xylan also dictated the freezing in a 1:1:1:1 mixture with cellulose, lignin, laminarin, and xylan. Filtration experiments down to 300 kDa with the xylan sample indicated that the presence of nanoparticles triggered freezing. Overall, only samples with mean diameters above 150 nm froze above −20 °C. Furthermore, we determined the ice-active site densities normalized to particle concentrations, surface area, and mass of the nanoparticles to show that the samples' nucleation site densities are similar to sea spray aerosols and nanometer-sized dust. The identification and characterization of xylan and laminarin as nanometer-sized ice-nucleating substances expands the growing list of organic matter capable of impacting cloud formation and thus climate. [ABSTRACT FROM AUTHOR]

The temperature-induced phase and morphology changes of a thin layer sandwiched between two substrates which it partially wets are investigated using transmission electron microscopy, scanning electron microscopy, and x-ray scattering techniques. For this, SiC wafers were bonded with Si layers of various thicknesses and annealed at temperatures below and above the Si melting point. Below the melting point of Si, solid-state dewetting occurs. It starts with the heterogeneous nucleation of pits at the Si/SiC interfaces and progresses to their partial transformation into voids crossing the whole film. The further growth of voids is accompanied with an increase in the Si film thickness. Final equilibrium is shown to be impacted by Si crystallographic state evolution. Above the Si melting temperature, liquid Si drives SiC interfaces step bunching. When high steps and large terraces are formed over the two SiC surfaces, Si is shown to be trapped within quasi-closed pockets. Eventually, the interface locally closes around these Si inclusions with the creation of SiC/SiC direct contacts. The influence of both annealing temperatures and Si film thickness on all these processes is discussed. [ABSTRACT FROM AUTHOR]

FCC-HCP phase transition plays a pivotal role in many intelligent materials, which also occurs in Pb under high pressures. However, its impacts on the spallation of polycrystalline, as well as the effects related to grain size, are still unclear. In this work, spallation behaviors of Pb polycrystals with different grain sizes under various shock loadings are investigated using the quasi-coarse-grained molecular dynamics (QCGD) method based on our recently developed response embedding atom model potential. The QCGD method is rigorously validated for applications in the metals exhibiting solid–solid phase transitions. Due to the restriction of the critical size for the phase transition nucleus, the coarsening level of the QCGD method cannot exceed two times the lattice parameter. Nevertheless, such a method enables us to explore the whole rule of the grain-size-dependence incipient spall strength. Our results suggest that the incipient spall strength exhibits a transition from the Hall–Petch to the inverse Hall–Petch relationship at about 13 nm and the spallation strength converging to that of a single crystal for grain sizes larger than 60 nm. As the grain size decreases, void nucleation becomes more prevalent than void growth, making the material better equipped to prevent the progression of damage into fractures. When the grain size is sufficiently large, voids nucleate and grow in the grain interior, making the spallation behave like in a single crystal. Interestingly, the phase transition from HCP to FCC phase enhances dislocation entanglement, leading to heterogeneous nucleation of voids in the grain interior. [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]

Heterogeneous nucleation is the main path to ice formation on Earth. The ice nucleating ability of a certain substrate is mainly determined by both molecular interactions and the structural mismatch between the ice and the substrate lattices. We focus on the latter factor using molecular simulations of the mW model. Quantifying the effect of structural mismatch alone is challenging due to its coupling with molecular interactions. To disentangle both the factors, we use a substrate composed of water molecules in such a way that any variation on the nucleation temperature can be exclusively ascribed to the structural mismatch. We find that a 1% increase in structural mismatch leads to a decrease of ∼4 K in the nucleation temperature. We also analyze the effect of orientation of the substrate with respect to the liquid. The three main ice orientations (basal, primary prism, and secondary prism) have a similar ice nucleating ability. We finally assess the effect of lattice flexibility by comparing substrates where molecules are immobile to others where a certain freedom to fluctuate around the lattice positions is allowed. Interestingly, we find that the latter type of substrate is more efficient in nucleating ice because it can adapt its structure to that of ice. [ABSTRACT FROM AUTHOR]

Heterogeneous ice nucleation (HIN) has applications in climate science, nanotechnology, and cryopreservation. Ice nucleation on the earth's surface or in the atmosphere usually occurs heterogeneously involving foreign substrates, known as ice nucleating particles (INPs). Experiments identify good INPs but lack sufficient microscopic resolution to answer the basic question: What makes a good INP? We employ molecular dynamics (MD) simulations in combination with machine learning (ML) to address this question. Often, the large amount of computational cost required to cross the nucleation barrier and observe HIN in MD simulations is a practical limitation. We use information obtained from short MD simulations of atomistic surface and water models to predict the likelihood of HIN. We consider 153 atomistic substrates with some surfaces differing in elemental composition and others only in terms of lattice parameters, surface morphology, or surface charges. A range of water features near the surface (local) are extracted from short MD simulations over a time interval (≤ 300 ns) where ice nucleation has not initiated. Three ML classification models, Random Forest (RF), support vector machine, and Gaussian process classification are considered, and the accuracies achieved by all three approaches lie within their statistical uncertainties. Including local water features is essential for accurate prediction. The accuracy of our best RF classification model obtained including both surface and local water features is 0.89 ± 0.05. A similar accuracy can be achieved including only local water features, suggesting that the important surface properties are largely captured by the local water features. Some important features identified by ML analysis are local icelike structures, water density and polarization profiles perpendicular to the surface, and the two-dimensional lattice match to ice. We expect that this work, with its strong focus on realistic surface models, will serve as a guide to the identification or design of substrates that can promote or discourage ice nucleation. [ABSTRACT FROM AUTHOR]

The large discrepancy among the nucleation kinetics extracted from experimental measurements and computer simulations and the prediction of the classical nucleation theory (CNT) has stimulated intense arguments about its origin in the past decades, which is crucially relevant to the validity of the CNT. In this paper, we investigate the atomistic mechanism of the nucleation in liquid Al in contact with amorphous substrates with atomic-level smooth/rough surfaces, using molecular dynamics (MD) simulations. This study reveals that the slightly distorted local fcc/hcp structures in amorphous substrates with smooth surfaces can promote heterogeneous nucleation through a structural templating mechanism, and on the other hand, homogeneous nucleation will occur at a larger undercooling through a fluctuation mechanism if the surface is rough. Thus, some impurities, previously thought to be impotent, could be activated in the homogeneous nucleation experiments. We further find that the initial growth of the nucleus on smooth surfaces of amorphous substrates is one order of magnitude faster than that in homogeneous nucleation. Both these factors could significantly contribute to the discrepancy in the nucleation kinetics. This study is also supported by a recent study of the synthesis of high-entropy alloy nanoparticles assisted with the liquid metal Ga [Cao et al., Nature 619, 73 (2023)]. In this study, we established that the boundary existed between homogeneous and heterogeneous nucleation, i.e., the structural templating is a general mechanism for heterogeneous nucleation, and in its absence, homogeneous nucleation will occur through the fluctuation mechanism. This study provides an in-depth understanding of the nucleation theory and experiments. [ABSTRACT FROM AUTHOR]

Water ubiquitously exists with dissolved salt in both natural and engineered porous media, such as soil, rock, concrete, and tissue; therefore, its freezing temperature depression behavior is of particular interest to various scientific communities tackling with mechanics and physics of porous media. To date, it remains elusive which physical mechanism accounts for its freezing temperature depression and how dissolved ions affect it. Herein, a series of pore-scale experiments were designated to investigate the freezing temperature of salt solutions in tubes with varying pore diameters, pore solution volumes, solid–liquid interfacial areas, ion concentrations, and ion types. The results reveal two main findings: (i) the freezing temperature depression of pore solutions is governed by the heterogeneous ice nucleation (HIN) at the water–solid interface, as evidenced by the observation that the freezing temperature decreases with the decreasing solid–liquid interfacial areas, regardless of pore diameter and pore solution volume; (ii) the dissolved salts alter HIN processes via changing the osmotic potential across the ice embryo–liquid water interface, as indicated by the observation that the freezing temperature is mainly determined by the salt concentration irrespective of salt types. Furthermore, the classical nucleation theory model is adapted for the freezing behavior of pore solutions by including an osmotic potential term. The model shows excellent performance in capturing experimental data with various pore solution concentrations, further substantiating the HIN as the physical mechanism governing pore solution freezing. [ABSTRACT FROM AUTHOR]

We investigate the nucleation dynamics of the three-dimensional random field Ising model under an external field. We use umbrella sampling to compute the free-energy cost of a critical nucleus and use forward flux sampling for the direct estimation of nucleation rates. For moderate to strong disorder, our results indicate that the size of the nucleating cluster is not a good reaction coordinate, contrary to the pure Ising model. We rectify this problem by introducing a coordinate that also accounts for the location of the nucleus. Using the free energy barrier to predict the nucleation rate, we find reasonable agreement, although deviations become stronger as disorder increases. We attribute this effect to cluster shape fluctuations. We also discuss finite-size effects on the nucleation rate. [ABSTRACT FROM AUTHOR]

Polypropylene double‐grafted maleic anhydride and bisphenol A epoxy resin (PP‐g‐M‐E) was successfully prepared by a single‐step method and characterized by Fourier‐transform infrared spectroscopy. Subsequently, it was employed as a compatibilizer to fabricate polypropylene (PP)/polyethylene terephthalate (PET) blends via melt extrusion. The content of the PET dispersed phase in the composite varied from 0 to 30 phr. The microstructure and morphology of the composites were characterized using scanning electron microscopy and Raman spectroscopy. The addition of PP‐g‐M‐E increased the interfacial interaction between the two phases and improved the compatibility and thermal stability of the system. In the presence of the compatibilizer, the crystallinity of the matrix phase (PP) increased, while that of the dispersed phase (PET) decreased owing to the heterogeneous nucleation effect of uniformly distributed PET. Double grafting of the PP‐g‐M‐E compatibilizer considerably enhanced the mechanical performance of the PP/PET blend system. The elongation at break of the modified sample exceeded that of the PP/PET blends by 117.55%, and the flexural and impact properties also showed considerable improvement. [ABSTRACT FROM AUTHOR]

The influence of as-cast grain size on recrystallization and the related mechanical properties of Al–Zn–Mg–Cu-based alloys was investigated. Grain sizes ranging from 163 to 26 μm were achieved by adding Ti, Cr and Mn, and ZnO nano-particles, which acted as heterogeneous nucleation sites. A decrease in the as-cast grain size led to a corresponding reduction in the recrystallized grain size from 54 to 13 μm. Notably, as-cast grain sizes below 100 μm provided additional nucleation sites at grain boundaries, allowing for a reasonable prediction of recrystallized grain size. Finer grains also contributed to enhanced mechanical properties, with yield strength increasing as recrystallized grain size decreased without significant loss of elongation. Additional strengthening was observed due to η-precipitates at grain boundaries, further improving the properties of fine-grained sheets. [ABSTRACT FROM AUTHOR]

The cell structure uniformity of microcellular polymers significantly impacts material performance, especially for low-porosity microcellular TPU used in chip polishing. The distribution of the cell structure of polishing pads directly affects the removal rate and process repeatability. Despite its importance, no quantitative method for evaluating cell structure uniformity has been reported in the literature. In this study, a digital image processing method that involves morphological operations of scanning electron microscopy (SEM) images, binarization, and cell localization, and the statistical evaluation of cell structure parameters was established to evaluate cell structure uniformity. A quantitative metric, the cell structure uniformity index (CUI), was calculated based on cell structure indices, incorporating the cell size index (Ud), the cell number index (Un), and the cell local spacing index (Ur). By establishing an ideal model and analyzing representative SEM images, the effectiveness and efficiency of the method for evaluating cell structure uniformity of microcellular TPU were successfully validated. The results demonstrated that low-porosity TPU foams exhibited relatively low cell structure uniformity compared to the ideal model. The heterogeneous nucleation process in TPU caused non-uniform cell structures due to the temporal and spatial non-homogeneities during the early cell nucleation process. As the cells grew, they merged and reduced the distance between them, resulting in improved cell structure uniformity. [ABSTRACT FROM AUTHOR]

Polypropylene (PP) was a very practical and important thermoplastic, which was widely used in various fields due to its low cost, universal, and corrosion resistance. However, the moderate mechanical and heat resistance properties of PP limited its application in some special fields. In this paper, nucleating agents NP‐657 were added to further improve its mechanical and heat resistance performances of PP (300H). Furthermore, the heterogeneous nucleation of NP‐657 reduced the crystal size and increased the crystal density of 300H. With the rise of NP‐657 content, the crystallization rate of different PP systems increased significantly, such as the t1/2 of 300H‐0.2 reduced by 31.9 min in comparison with that of 300H at 140°C. At the same time, the crystallinity of 300H‐0.05 with 0.05 wt.% NP‐657 increased by about 5.96% compared with 300H. In addition, 300H‐0.05 has the highest tensile strength (23.9 ± 0.6 MPa), flexural modulus (1273.3 ± 67.3 MPa), and the highest thermal deformation temperature (88.5 ± 7.7°C) in different PP systems. In general, this paper provided a reference for the fabrication of PP with satisfactory mechanical and heat resistance performances. Highlights: 300H‐0.05 had a maximum crystallinity of 40.8 ± 0.2% in different PP systems.The flexural modulus of 300H‐0.05 was 434 MPa higher than that of 300H.The tensile strength of 300H‐0.05 increased to 23.9 ± 0.6 MPa.300H had the highest thermal deformation temperature of 88.5 ± 7.7°C. [ABSTRACT FROM AUTHOR]

The quality of heavy rail steel is significantly influenced by the distribution and morphology of MnS inclusions. With the help of experimental methods and thermodynamic predictions, the evolution of inclusions in heavy rail steels with different rare‐earth (RE: La + Ce) additions is investigated, and the relationship between RE inclusions and MnS is better interpreted by the classical two‐dimensional mismatch degree theory. The results show that the deoxidizing ability of RE elements added to the steel is greater than the desulfurizing ability. The best data for physical parameters of inclusions in steel are obtained at a RE addition of 122 ppm. The MnS inclusion particles are roughly spherical around the REAlO3 inclusion particles when the aluminum content in the RE inclusion is high. The MnS inclusion particles are better able to fit flatly around the RE2O2S inclusion particles when the sulfur content of the RE inclusion is high. By computing the two‐dimensional mismatch between the interfaces of different inclusions, it is discovered that the heterogeneous nucleation efficiency is comparatively low between MnS and REAlO3, relatively high between MnS and RE2O2S, and highest between MnS and RE2O3. [ABSTRACT FROM AUTHOR]

During processing in deep convective cloud systems, highly viscous or glassy secondary organic aerosol (SOA) particles can develop a porous structure through a process known as atmospheric freeze‐drying. This structural modification may enhance their heterogeneous ice nucleation ability under cirrus conditions through the pore condensation and freezing mechanism. Pristine, compact SOA particles, on the other hand, are recommended to be treated as ice‐inactive in models. This recommendation also applies to internally mixed particles, where a coating layer of secondary organic matter (SOM) deactivates the intrinsic ice nucleation ability of the core, which may be a mineral dust grain. Ice cloud‐processing may also improve the ice nucleation ability of such a composite particle by inducing structural changes in the coating layer, which can release active sites on the mineral surface. In this work, we investigated the change in the ice nucleation ability of pure SOA particles from the ozonolysis of α‐pinene and two types of internally mixed particles (zeolite and coal fly ash particles coated with SOM) after being subjected to the atmospheric freeze‐drying process simulated in an expansion cloud chamber. For pure α‐pinene SOA, we found only a slight improvement in the ice nucleation ability of the ice cloud‐processed, porous particles compared to their pristine, compact counterparts at 221 and 217 K. In contrast, the zeolite and coal fly ash particles, which were initially deactivated by the organic coating, became significantly more ice‐active after atmospheric freeze‐drying, emphasizing that such composite particles cannot be excluded from model simulations of heterogeneous ice formation. Plain Language Summary: Understanding how ice crystals form in the Earth's atmosphere is important for predicting climate using cloud models. It is believed that certain surface features on atmospheric aerosol particles, such as cracks and pores found on mineral dust grains, can effectively induce ice formation. Ice crystals are formed from small amounts of liquid water that have condensed and frozen in the pores of the particles. As a result, ice formation is less likely to occur on solid particles that lack such pores and have a smooth surface. One type of the latter are particles formed by the condensation of volatile, biogenic and anthropogenic organic compounds. In models of ice formation, such secondary organic aerosol particles are often neglected because of their compact, non‐porous shape. In our work, we simulated a pathway by which such particles can acquire a porous structure through cloud‐processing in the atmosphere, and investigated how this affects their ability to form ice. We also investigated mixed particle types in which the organic compounds condensed on a mineral surface, blocking the pores that allowed efficient ice formation. The aforementioned cloud‐processing partially restructured the organic material on the mineral surface, and the particles became more effective at forming ice again. Key Points: Regardless of particle morphology, pure secondary organic aerosol particles are inefficient at nucleating ice under cirrus conditionsA pristine coating layer of secondary organic matter deactivates efficient ice nucleating particles such as mineral dust and coal fly ashIce cloud‐processing changes the structure of the coating layer and partially restores the ice nucleation ability of such mixed particles [ABSTRACT FROM AUTHOR]

Cirrus clouds are of great importance to the global climate, with their net radiative forcing strongly dependent on the microphysical properties that are related to the ice‐nucleating regime. However, the influence of long‐range transport of dust on primary ice formation in cirrus clouds is limitedly understood, specifically over the clean remote ocean regions. Here, two case studies show that transpacific Asian dust can impact the ice formation of cirrus clouds over the central Pacific based on Cloud‐Aerosol Lidar with Orthogonal Polarization and Cloud Profiling Radar (CPR, CloudSat) observations. One case shows a well‐developed horizontally extended cirrus embedded in a pure dust layer, with an average dust‐related ice‐nucleating particle concentration (INPC) of 7 L−1 and 96 L−1 for an ice saturation ratio Si of 1.15 and 1.25, respectively; ice crystal number concentration (ICNC) with diameters >25 and 100 μm (denoted as nice,25 μm and nice,100 μm) are 64 L−1 and 7 L−1, respectively. Another case shows that cirrus clouds with a much smaller horizontal extent appeared in the vicinity of polluted dust, with an average INPC of 42–310 L−1 for the typical higher Si of 1.25–1.35 by considering a tenfold reduction of the ice nucleation efficiency of ice crystals; nice,25 μm and nice,100 μm are 168 L−1 and 20 L−1, respectively. The estimated INPC and ICNC values suggest the dominance of ice formation by dust‐induced heterogeneous nucleation, proving that the long‐range transport of dust toward the upper troposphere and the potential influence on cirrus formation over the central Pacific should be well considered in atmospheric models. Plain Language Summary: Cirrus clouds are vital to the global radiative balance. Their net radiation effect is very uncertain, depending on the microphysical properties that are mainly determined by the ice nucleation mechanism, that is, heterogeneous and homogeneous ice nucleation. In this work, two dust‐cirrus interaction cases are studied with the combinational observations of space‐borne lidar and radar. Over the remote central Pacific, where is generally very clean, we show that the long‐range transported Asian dust can significantly influence the ice nucleation at cirrus height by acting as efficient ice‐nucleating particles (INPs). The estimated number concentrations of INPs and ice crystals reveal that dust‐induced heterogeneous nucleation is dominant in ice formation, which should thus be better considered in atmospheric and climate models. Key Points: Cloud‐Aerosol Lidar with Orthogonal Polarization (CALIOP)‐CloudSat observations corroborate that dust in the outflow regime of Asia can influence cirrus formation over the central PacificCALIOP observations indicate the strongest dust occurrence in the upper troposphere over the Pacific during the spring seasonDust transport toward the upper troposphere and the potential impact on cirrus formation should be well considered in atmospheric models [ABSTRACT FROM AUTHOR]

Bacterial ice nucleating proteins (INPs) are exceptionally effective in promoting the kinetically hindered transition of water to ice. Their efficiency relies on the assembly of INPs into large functional aggregates, with the size of ice nucleation sites determining activity. Experimental freezing spectra have revealed two distinct, defined aggregate sizes, typically classified as class A and C ice nucleators (INs). Despite the importance of INPs and years of extensive research, the precise number of INPs forming the two aggregate classes, and their assembly mechanism have remained enigmatic. Here, we report that bacterial ice nucleation activity emerges from more than two prevailing aggregate species and identify the specific number of INPs responsible for distinct crystallization temperatures. We find that INP dimers constitute class C INs, tetramers class B INs, and hexamers and larger multimers are responsible for the most efficient class A activity. We propose a hierarchical assembly mechanism based on tyrosine interactions for dimers, and electrostatic interactions between INP dimers to produce larger aggregates. This assembly is membrane-assisted: Increasing the bacterial outer membrane fluidity decreases the population of the larger aggregates, while preserving the dimers. Inversely, Dulbecco’s Phosphate-Buffered Saline buffer increases the population of multimeric class A and B aggregates 200-fold and endows the bacteria with enhanced stability toward repeated freeze-thaw cycles. Our analysis suggests that the enhancement results from the better alignment of dimers in the negatively charged outer membrane, due to screening of their electrostatic repulsion. This demonstrates significant enhancement of the most potent bacterial INs. [ABSTRACT FROM AUTHOR]

Understanding the ice nucleation mechanism in the catalyst layers (CLs) of proton exchange membrane (PEM) fuel cells and inhibiting icing by designing the CLs can optimize the cold start strategies, which can enhance the performance of PEM fuel cells. Herein, mitigating the structural matching and templating effects by adjusting the surface morphology and wettability can inhibit icing on the platinum (Pt) catalyst surface effectively. The Pt(211) surface can inhibit icing because the atomic spacing of (211) crystalline surface is much larger than the characteristic distance of ice crystal, thereby mitigating the structural matching effects. A water overlayer on the Pt surface induced by the strong attraction of Pt can act as a template for ice layers and plays an important role in the icing process. Buckling of water overlayer due to the larger atomic spacing of (211) crystalline surface mitigates the templating effect and inhibits icing. Moreover, the water overlayer on the hydrophobic Pt(211) surface with fewer water molecules also mitigates the templating effect, which makes ice nucleation more difficult than homogeneous nucleation. These findings reveal the ice nucleation mechanisms on the Pt catalyst surface from the molecular level and are valuable for catalyst designs to inhibit icing in CL. [ABSTRACT FROM AUTHOR]

Ice formation mechanisms in generating cells near stratiform cloud tops, where mixing and entrainment occurs in the presence of supercooled water droplets, remain poorly understood. Supercooled cloud droplet temperature and lifetime may impact heterogeneous ice nucleation through contact and immersion freezing; however, modeling studies normally assume the droplet temperature to be spatially uniform and equal to the ambient temperature. Here, we present a first-of-its-kind quantitative investigation of the temperature and lifetime of evaporating droplets, considering internal thermal gradients within the droplet, as well as thermal and vapor density gradients in the surrounding air. Our approach employs solving Navier–Stokes and continuity equations, coupled with heat and vapor transport, using an advanced numerical model. For typical ranges of cloud droplet sizes and environmental conditions, the droplet internal thermal gradients dissipate quickly (≤ 0.3 s) when droplets are introduced to new subsaturated environments. However, the magnitude of droplet cooling is much greater than estimated from past studies of droplet evaporation, especially for drier environments. For example, for an environment with 500 hPa pressure, and ambient temperature far from the droplet of - 5 °C , the droplet temperature reduction can be as high as 24, 11, and 5 °C for initial ambient relative humidities of 10 %, 40 %, and 70 %, respectively. Droplet lifetimes are found to be tens of seconds longer compared to previous estimates, due to weaker evaporation rates because of lower droplet surface temperatures. Using these new end-of-lifetime droplet temperatures, the enhancement in the activation of ice-nucleating particles predicted by current ice nucleation parameterization schemes is discussed. [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]

The gelation of crude oil with high wax and asphaltene content at low temperatures often results in the block of transportation pipeline in Africa. In recent years, it was reported that surface hydrophobicmodified nanoparticles have important applications in crude oil flow modification. In this work, four kinds of core-shell hybride nanoparticles by grafting poly (octadecyl, docosyl acrylate) and poly (acrylate-a-olefin) onto the surface of nano-sized SiO2 were synthesized by grafting polymerization method. The chemical structure of nanoparticles was analyzed by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The rheological behaviors of crude oil and precipitation of asphaltenes in the presence of nanoparticles were studied by measuring the viscose-temperature relationship curve, the cumulative wax precipitation amount, and morphology of waxes and asphaltenes. The results indicate that the docosyl polyacrylate@SiO2 nanoparticle (PDA@SiO2) can reduce the cumulative wax precipitation amount of crude oil by 72.8%, decline the viscosity of crude oil by 85.6% at 20 ℃, reduce the average size of wax crystals by 89.7%, and inhibit the agglomeration of asphaltene by 74.8%. Therefore, the nanoparticles not only adjust the crystalline behaviors of waxes, but also inhibit the agglomeration of asphaltenes. Apparently, core-shell hybride nanoparticles provides more heterogeneous nucleation sites for the crystallization of wax molecules, thus inhibiting the formation of three-dimensional network structure. The core-shell polymer@SiO2 hybride nanoparticles are one of promising additives for inhibiting crystallization of waxes and agglomeration of asphaltenes in crude oil. [ABSTRACT FROM AUTHOR]

In this study, the microstructure, hardness, density, viscosity, and surface tension of molten pure Ti with TiC particles were studied via electrostatic levitation experiments, where the electrostatic levitation experiment involved container-less processing, which can suppress heterogeneous nucleation via crucibles. Microstructural observation revealed long needle-shaped α-grains across the whole area in the pure Ti sample. On the other hand, smaller needle-shaped α-grains were found in the samples with TiC particles. However, the detailed microstructural analysis of Ti + 0.7vo l%TiC sample revealed that the fine α-grains observed in the Ti + 0.7vo l%TiC are transformed from single grain of prior β phase. This is because the TiC particles dissolve into the molten Ti during the electrostatic levitation experiment. Instead, Ti–rich TiC precipitates formed by cooling can act as pinning sites rather than heterogeneous nucleation sites, which results in a finer microstructure for the samples with TiC particles during the electrostatic levitation experiment. The density of the samples is linearly related to the temperature, and it decreases with increasing temperature. In addition, a higher density is observed for the samples with TiC particles. Although linear relationships between the surface tension and temperature were found, the addition of TiC particles had no notable effect on the viscosity of the molten pure Ti. [ABSTRACT FROM AUTHOR]

Zinc–nickel coatings based on the zinc-enriched gamma phase exhibit the maximum corrosion resistance and form the basis of the production of highly electrocatalytically active nanoporous nickel by selective dissolution. The electrodeposition of Zn–Ni alloys is the most widely used method of their preparation which proceeds by the mechanism of anomalous codeposition, where the deposition rate of the electropositive component (nickel) is lower as compared with the electronegative component (zinc). To obtain coatings of the particular morphology, chemical and phase composition, it is necessary to know the kinetics of the cathodic deposition of Zn–Ni alloys in the stage of heterogeneous nucleation, which is the goal of this study. The kinetics of this process is studied in non-stirred ammonium chloride electrolytes using the methods of cyclic voltammetry and chronoamperometry. The mechanism of heterogeneous nucleation at the electrodeposition of zinc and nickel is determined using the approach proposed by Palomar-Pardavé et. al which takes into account the contributions to the total cathodic current made by the parallel reaction of hydrogen reduction and the electric double layer charging. The nucleation mechanism for zinc–nickel coatings is described using the model of Scharifker–Hills for the electrodeposition of binary alloys additionally modified by taking into account the experimentally determined dependence of the composition of zinc–nickel coatings on the time in the stage of cathodic nucleation of the deposit. Using the method of energy-dispersive X-ray spectroscopy, the anomalous character of the deposition of Zn–Ni coatings is confirmed, where the ratio of atomic fractions Ni/Zn turns out to be lower than the ratio of concentrations of ions Ni2+/Zn2+ in the electrolyte. It is found that both during the electrodeposition of zinc and nickel from their individual solutions and during their anomalous codeposition, the nucleation rate constant increases with an increase in the cathodic potential but in average does not exceed 3 s–1, which points to the predominantly progressive nucleation. The growth of the new phase, regardless of its chemical composition, is limited by the 3D-diffusion of zinc and nickel ions to the electrode surface. The nucleation site density depends weakly on the deposition potential, decreasing with the transition from zinc to nickel and zinc–nickel alloys. As expected, the contribution of the side reaction of hydrogen reduction is the maximum for nickel electrocrystallization and decreases with the transition to Zn–Ni alloys and zinc, increasing with an increase in the cathodic potential, in agreement with the values of current efficiency. [ABSTRACT FROM AUTHOR]

A multi‐technique analysis was used to investigate how the orientation of single‐crystal Si wafer surfaces affects the size, shape and orientation of NiSi2 nanocrystals grown within the wafers through the thermal diffusion of Ni atoms from a nickel‐doped thin film deposited on the surface. Nickel‐doped thin films were prepared on silicon wafers with three distinct crystallographic orientations, [001], [110] and [111]. Three sets of samples were then annealed at 500, 600 and 700°C for 2 h. Regardless of crystallographic orientation or annealing temperature, NiSi2 nanoplates with a nearly hexagonal shape grew close to the external surface of the wafers, aligning their larger surfaces parallel to one of the planes of the Si{111} crystallographic form. The crystallographic orientation and annealing temperature in the 500–700°C range did not significantly affect the final values of the average diameter and thickness of the nanoplates. However, significant differences were noted in the number of nanoplates formed in Si wafers with different crystallographic orientations. The results indicate that these observed differences are correlated with the number of pre‐existing defects in the wafers that influence the heterogeneous nucleation process. In addition, the average size and size dispersion were determined for pores at the surface of the Si wafers formed due to the etching process used for native oxide removal. [ABSTRACT FROM AUTHOR]

Ge‐rich GeSbTe chalcogenide alloys have gained significant attention in the field of phase‐change materials due to their remarkable thermal stability and thus their suitability for integration in nonvolatile memories targeting embedded automotive applications. Herein, the effects of different encapsulating materials on the evolution and on the crystallization kinetic of N‐doped Ge‐rich GeSbTe films are focused on. These films are annealed with temperatures compatible with the back‐end‐of‐line of the complementary metal‐oxide‐semiconductor (CMOS) fabrication. First, it shows how the encapsulation layer thickness should be tuned in order to protect the layer from oxidation and at the same time to avoid delamination phenomena. TaN, C, TiN, SiC, and SiN used as encapsulating layers are compared. The segregation and crystallization of Ge‐rich GeSbTe alloys appear more homogeneous in the case of C, TiN, and SiC. On the contrary, the effects of an interfacial heterogeneous nucleation in the case of TaN and SiN are observed. It results in a different final morphology of the chalcogenide layer after annealing depending on the encapsulation, with different grain sizes and kinetic of phase separation. [ABSTRACT FROM AUTHOR]

In this study, D2 steel (Cr12Mo1V1) with different yttrium (Y) contents was designed, and the effects of Y on the inclusions and eutectic carbides of D2 steel after casting were analyzed by scanning electron microscopy, ASPEX, and electron probe microanalyzer. The results reveal that the inclusions in D2 steel without Y are mainly Al2O3 and MnS, while the inclusions with Y are mainly Y2S3, Y2O2S, and complex inclusions. When the Y content increased from 0 to 0.021%, the quantity of inclusions with an average grain size of 1–2 microns gradually increased from 47.6 to 64.7%. The chain eutectic carbides in D2 were broken and tend to be spheroidized after adding Y, which was attributed to the fact that the submicron Y-rich inclusions help to slow down the segregation of carbon and alloying elements. The inclusion is beneficial to the heterogeneous nucleation of M7C3 eutectic carbides and the decrease in eutectic reaction temperature. [ABSTRACT FROM AUTHOR]

Synergistic micro-alloying with Ti–Zr effectively enhances the mechanical properties of cast Al–Cu–Mn alloys. In this study, the connection between microstructure evolution and mechanical properties of Al–Cu–Mn alloy through gravity casting was investigated with synergistic addition of Ti and Zr elements, aiming to promote the strength and toughness of Al–Cu–Mn alloy. The results showed that synergistic addition of 0.15 wt%Ti and 0.2 wt%Zr refined grains owing to the constitutional supercooling caused by Ti and Zr. A large number of Al3(Ti,Zr)-L12 dispersoids with core–shell structure uniformly precipitated within the grains during the solution process. The Al3(Ti,Zr) dispersoids served as heterogeneous nucleation sites for θ′(Al2Cu) precipitates during aging. As confirmed by quantitative analysis, Ti–Zr-modified alloys (with 0.15 wt%Ti and 0.2 wt%Zr) exhibited finer and more densely populated θ′ precipitates than unmodified alloys, resulting in superior mechanical properties. In the peak-aged state, the ultimate tensile strength, yield strength and elongation of Ti–Zr-modified alloy were 530.5 MPa, 462.8 MPa and 7.6%, respectively, which were mainly ascribed to grain boundaries strengthening, solution strengthening and precipitation strengthening. This work is expected to provide reliable theoretical guidance for the successful preparation of high-strength and high toughness Ti–Zr-modified aluminum alloys. [ABSTRACT FROM AUTHOR]

An Al–8Si–1Cu–0.35Mg casting alloy with (Mn + B) composite addition was prepared via traditional ingot metallurgy. The effects of (Mn + B) composite addition on the α-Al dendrites, AlB2 phase, Fe-rich phase, fluidity, and mechanical properties of the hypoeutectic Al–8Si–1Cu–0.35Mg casting alloy were systematically studied via optical microscopy, scanning electron microscopy, energy–dispersive spectroscopy analysis, and fluidity and mechanical property tests. Results show that (Mn + B) addition refines the α-Al dendrites. The α-Al phase and AlB2 particles function as heterogeneous nucleation particles to promote alloy nucleation, and the coarse dendrites are transformed into fine equiaxed crystals. The best effect is observed when 0.6 wt% Mn and 0.1 wt% B are added. (Mn + B) composite addition improves the morphology of the Fe-rich phase in the alloy and transforms the needle-like β-Fe phase into a dendritic Fe-rich phase and α-Fe phase. Furthermore, the grain refinement of the alloy and the improvement of the Fe-rich phase enhance the fluidity of the alloy. When 0.6 wt% Mn and 0.3 wt% B are added, the fluidity is the best, which is 77.5% higher than that without addition. (Mn + B) composite addition has minimal effect on the hardness of the alloy. The best mechanical properties are obtained upon the addition of 0.6 wt% Mn and 0.2 wt% B. In particular, the tensile strength and elongation are 235 MPa and 8.6%, respectively. These values are 40.1% and 100% higher than those obtained without addition, respectively. The fracture mode of the alloy also changes from ductile–brittle mixed fracture to ductile fracture. [ABSTRACT FROM AUTHOR]

Atmospheric aerosol particles can impact the optical depth of mixed-phase clouds through heterogeneous ice nucleation. Ice nucleating particles (INP) are therefore important contributors to global and local climate but remain under-parameterized in climate models, partially due to the complex interaction between composition and processing conditions. In this article, we study the ice nucleation (IN) activity of montmorillonite bentonite clay which is a common model dust INP, utilizing a 150-well microfluidic device. Refreezing tests are carried out for solutions across a range of salinity and pH to determine the impact of composition and processing on droplet freezing behavior, with and without an intermediate relative humidity (RH) cycling step. It is found that freezing order deviation dramatically increases after droplets undergo RH cycling, and the potential influence on IN activity of delamination of clay when subjected to changing RH conditions is discussed. Freezing order deviation decreases with increasing solution ionic strength, a trend linked to the delamination behavior of bentonite clays, and an overall decrease in IN activity at low pH is observed, possibly due in part to pH-dependent changes in clay aggregate size distribution. The authors conclude that pH changes and RH processing, such as those which naturally occur in the atmosphere, have a marked impact on the IN activity of clay-containing aerosol droplets. Copyright © 2024 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

Bioaerosols influence the climate processes, human health and overall ecosystem. Their type, concentration and diversity have important implications on various atmospheric processes however the limited understanding of bioaerosols-cloud-climate connection has resulted in existing uncertainty in climate models. Bioaerosols as ice nucleating particles (INPs) and cloud condensation nuclei (CCN) govern precipitation initiation, cloud formation and thus the complex hydrological cycle. Homogeneous nucleation takes place at colder temperatures (< − 38 ℃), while owing to their unique properties, certain ice nucleating bioaerosols can initiate freezing at much warmer temperatures (≧ − 10 °C) and thus are important for precipitation initiation through heterogenous nucleation mechanism. Flux of bioaerosols from diverse terrestrial and marine sources lead to their build-up in the atmosphere but rare bioaerosols act as CCN and INP. These rare characteristics of bioaerosols remain largely unexplored and need further attention and research. This work presents fundamental insights on the role of bioaerosols in cloud formation and ice nucleation mechanism along with an overview on the types, diversity and sources of bioaerosols. Most studies reviewed here on bioaerosol-cloud-climate connections are restricted to from specific research groups. Bioaerosol research is still in evolving stage and limited usage of advanced techniques of sampling and characterization is noticed particularly in developing countries. Lack of even baseline database on bioaerosols has resulted in poor understanding of their implications. The discussion presented here on species level information of cloud forming and ice nucleating bioaerosols will help researchers in developing fundamental understanding on characteristics and implications of bioaerosols. Bioaerosol research is expensive and thus joint campaigns by researchers from interdisciplinary areas should be encouraged. Application of high-throughput sequencing allows rapid taxonomic identification and such modern molecular methods should be routinely used for understanding implications of bioaerosols on climate as well as human health.Highlights: Overview of the types, diversity and sources of bioaerosols is presented. Bioaerosols initiate heterogeneous nucleation at much warmer temperatures than other classes of aerosols. Specific properties of bioaerosols are responsible for their cloud forming and ice nucleating potential. Species level information of bioaerosols is necessary to understand indirect climate implications. [ABSTRACT FROM AUTHOR]

The present study speaks of development of a two-dimensional phase field (PF) model to simulate the cooling slope rheoprocessing of the novel Al-15Mg2Si-4.5Si composite, in view of process optimization and investigation of physics of microstructure formation. In case of cooling slope rheoprocessing, the composite melt starts losing its superheat once it impinges over the slope and transforms into semi-solid slurry during its length of travel over the slope. After experiencing shear flow over the slope, the melt fills an isothermal slurry holding furnace where it undergoes coarsening for a certain length of time. The present PF model simulates how heterogeneous nucleation of solid grains is supposed to happen within the melt, during cooling slope processing, adopting a seed undercooling-based nucleation model. Moreover, the PF model implements a grain coarsening model to simulate the isothermal globularization process of the evolving solid grains of primary Mg2Si and primary Al phases. The interfacial free energy of Al–melt interface is taken from literature, whereas a molecular dynamics (MD) model is employed to estimate the interfacial energy value of the Mg2Si–melt interface. The cooling rate values employed in the present PF model for different melt pouring temperatures are determined experimentally from initial trial experiments, whereas the validation experiments are performed to collect the slurry samples from chosen locations of the melt flow front over the slope and from isothermally kept slurry holding furnace. Micrographs obtained from the above samples confirm the accuracy of the developed 2D PF model to capture microstructural morphology of the composite slurry. Moreover, the model predictions of quantitative parameters such as grain diameter, shape factor/sphericity, and solid fraction are found to be close to the experimental measurements. For example, a representative simulated value of grain size and sphericity of primary Mg2Si grains, after 8 minutes of slurry holding, are as follows: 24.01 and 0.834 μm, whereas the corresponding experimental values are 29.0 and 0.885 μm, respectively. [ABSTRACT FROM AUTHOR]

Complex oxide–carbonitrides (MgO-Ti(CN), Al2O3-Ti(CN), and MgO·Al2O3-Ti(CN)) are the most common non-metallic inclusions presented in cast and wrought superalloys. In this work, a coupled kinetics model was proposed to predict the complex oxide–carbonitride inclusion's precipitation behavior during the solidification of superalloys. This model takes into account thermodynamics, micro-segregation, heterogeneous nucleation in the inter-dendritic liquid, and growth controlled by the diffusion of solute elements and kinetics of interfacial reaction. The results demonstrated that both the cooling rate and nitrogen content take significant effects on the final size of complex oxide–carbonitride inclusions, as the former controls the total growth time and the latter determines the initial precipitation temperature. In comparison, the particle size of primary oxides shows a negligible impact on the final size of complex inclusions. The practice of an industrial vacuum arc remelting confirmed that the inclusion size variation predicted by the present model is reasonably consistent with the experimental results. [ABSTRACT FROM AUTHOR]

Highlights Polymer nanocomposites boast complex microstructures with instant control of final performance, including mechanical strength, thermal stability, and crystallinity. Although tremendous studies have been devoted to understanding the structure–property relation of polymer nanocomposites, the effect of simultaneous nanomaterial contents on binary polymers remains unclear. Here, we report how the microstructure and rheological characteristics are subject to change upon adding a hybrid multi‐walled carbon nanotube (CNT) and graphene nanoplatelet (GNP). We choose a refined binary system based on polypropylene (PP) as a commodity polymer with proven long‐standing applications, alongside ethylene‐butylene copolymer (EBC) with a random ethylene and butylene monomers orientation for better impact strength acquisition. Rheology and microscopy imaging support an adequate dispersion of both materials across the PP/EBC blend, similar to when a single‐particle nanocomposite is examined. Beyond investigating the heterogeneous nucleation role of CNT and GNP, the crystallinity rate and the half‐time parameter for completing the ordered transformation are calculated using the Avrami equations. The thermal stability as well as the mechanical properties of all nanocomposites reveal improved resilience under heat and external stress, leading to a rising trend in decomposition temperature, tensile strength, and modulus. Synergistic effect of hybrid CNT and GNP on the thermal stability of PP/EBC. The impact of hybrid CNT and GNP on crystallization kinetics. Improvement of the mechanical performance with CNT/GNP loading. Role of PP‐g‐MA on the dispersion and distribution of CNT and GNP. [ABSTRACT FROM AUTHOR]

This work demonstrates a mechanism of heterogeneous nucleation for the synthesis of BaTiO 3 nanowires utilizing K 2 Ti 4 O 9 as template by manipulating alkalinity, temperature and reaction time. Results suggest that the synthesis of BaTiO 3 does not occur through a hydrothermal ion-exchange, instead, the predominant mechanism observed is the heterogeneous of dissolution-crystallization. The consistency of crystallographic orientation for BaTiO 3 nanowires is affected by the hydrothermal conditions. BaTiO 3 nanowires synthesized at 190 °C/0.2 M exhibit a uniform (100)/(001) crystallographic orientation, albeit not consistently along the length of the nanowires, while BaTiO 3 crystal grains no longer have the same crystallographic orientation at 190 °C/0.8 M. By investigating the reaction mechanism of BaTiO 3 , this work may have great significance for the synthesis of perovskite-type MTiO 3 (M = Ba,Ca, Sr, Pb) utilizing layered titanates. [ABSTRACT FROM AUTHOR]

Highlights For traditional materials, a polymer composite with high performance and large‐scale production is still the goal pursued by researchers. In our work, polyamide 6/calcium sulfate whiskers (PA6/SCW) composites were fabricated via melt‐compouding method. The calcium sulfate whisker based on gypsum mineral was used as reinforcement. After grafting silane coupling agent on the whisker surface, the whiskers showed a significant reinforcing effect in polyamide. The mechanics and tribology performance of the samples had been significantly inhanced. Based on the nucleation mechanism of lattice matching, calcium sulfate whiskers have obvious heterogeneous nucleation effect in PA6 matrix, while the crystallization period was slightly prolonged. This was caused by the network structure formed by the whiskers in the matrix, which impeded the free movement of polymer chain segments. In combination with the orientation degree of the molecular chains measured by the interdigital electrode, the reinforcing effect of the oriented PA6 specimens was derived from the orientation arrangement of the whiskers and the efficient load transfer. Mechanical and tribological properties of composite were significantly improved. The composite could achieved large‐scale production due to simple preparation. The whiskers had obvious heterogeneous nucleation effect in matrix. The reinforcing effect was derived from efficient load transfer from whiskers. [ABSTRACT FROM AUTHOR]

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

Microwave heating provides a rapid method for the heterogeneous nucleation of noble metal particles on perovskite support materials for electrocatalytic purposes. To succeed, dielectric tuning of perovskite materials becomes fundamental. Herein, the dielectric engineering of the BaMnO3 perovskite system is carried out through the use of B‐site doping to give BaTi0.5Mn0.5O3. Using a combination of atomic‐scale imaging and electron energy loss spectroscopy (EELS), the preferential filling of the M1 and M3 B‐sites with Mn and Ti ions in the 12R‐rhombohedral perovskite structure is established. While the addition of Ti in the BaMnO3 system has no detrimental effects on the presence of the oxygen reduction reaction (ORR) active Mn3+ states at the surface, it does alter the dielectric constant and loss tangent, thus facilitating the heterogeneous nucleation of Pt nanoparticles on BaTi0.5Mn0.5O3 via rapid microwave heating. Higher Pt loading regimes are found to increase the size and aggregation of the nucleated particles, thus reducing their ORR activity. Therefore, lower Pt loading not only reduces costs but improves overall activity. This work represents future possibilities for the dielectric engineering of perovskite and similar support materials to aid in the quick and easy formation of stable noble metal‐support catalytic systems. [ABSTRACT FROM AUTHOR]

Lithiophilic modification of Li hosts is regarded as an effective strategy to address the uncontrollable Li dendrite issue for stably cycling lithium metal anode (LMA). Precise construction of stable and lightweight Li hosts with homogeneously distributed lithiophilic sites is vital to promoting uniform Li deposition but remains highly challenging, and the lithiophilic mechanism is still unrevealed. Herein, atomically dispersed single-, double-, and triple- Znn-anchored C2N matrixes (denoted as Znn@C2N, n = 1, 2, and 3) are proposed as potential lithiophilic hosts with well-defined and homogeneously distributed multilithiophilic sites to regulate Li metal deposition by means of DFT calculations and ab initio molecular dynamics simulations. The results demonstrate that Zn2 dimer-anchored C2N (Zn2@C2N) exhibits the highest thermodynamic stability and excellent electronic conductivity among the three atomically dispersed Znn single-atom/clusters anchored C2N hosts. The chemical essence of lithiophilic activity and the exact mechanism of Zn2@C2N as a promising Li host are systematically explored by in-depth analysis of the electron structure, local dipole, and chemical bonding at the atomical level. It is found that the lithiophilicity of Zn2@C2N is co-contributed by Zn2-anchoring and N-containing functional groups, which facilitate the uniform Li deposition by inducing heterogeneous nucleation at uniform and multiple lithiophilic sites. The moderate adsorption strength, low diffusion energy barrier, and stable atomic structure of these lithiophilic sites endow Zn2@C2N with low Li nucleation overpotential, smooth Li deposition morphology, and thus a long cycle life. This work sheds new light on the precise design of ideal lithiophilic hosts for dendrite-free LMA. [ABSTRACT FROM AUTHOR]

The effect of the cerium addition on the microstructure and properties of the ductile iron is investigated. The ferrocerium is added to obtain ductile iron samples with cerium contents of 10–750 ppm. In the ductile iron with a cerium content of 60 ppm, the amount and the spheroidization rate of graphites are the highest. The tensile strength of the ductile iron is 488 MPa and the elongation rate reaches 20.17%. For the ductile iron with a high toughness demand, it is necessary to add 60 ppm Ce in the ductile iron to increase the number density and spheroidization rate of graphites. The formation of CeS inclusions effectively promotes the heterogeneous nucleation of graphites, increasing the amount of graphites. The stronger carbon diffusion during the eutectic process increases the ferrite formation in the ductile iron, leading to a lower tensile strength and a higher elongation rate. When the cerium content exceeds 460 ppm, the precipitated Ce2C3 significantly reduces the performance of the ductile iron. [ABSTRACT FROM AUTHOR]

Poly(vinylidene fluoride) (PVDF) has been widely studied because of its various crystal phase transformations as well as its special dielectric, piezoelectric, and other electrical properties. In this study, a temperature gradient (T-gradient) was constructed for studying the temperature dependence of the crystallization behavior of PVDF and the heterogeneous nucleation effect of multiwall carbon nanotubes (MWCNTs). The nanoscale structure of PVDF was investigated through three different dimensions using FTIR for the surface, WAXD/SAXS for the bulk and AFM for the cross-section. The results showed that low temperature and a heterogeneous nucleating agent were both conducive to the formation of the γ phase of PVDF. The distance of MWCNT nucleation effect is about 15 μm, and it is more significant in 0–5 μm. The content of the γ phase reached 77% when Tc was lower than 61 °C. The higher content and lower crystallite size of the γ phase lead to a higher dielectric constant, which can lay a foundation for its future application in the field of dielectrics. [ABSTRACT FROM AUTHOR]

FeCrAl alloy is considered a promising material for light water reactor fuel cladding due to its excellent elevated temperature oxidation resistance and radiation performance. The effects of 0.21 wt% Nb or 0.23 wt% La additions on the microstructure, second phase, yield strength and toughness of FeCrAl alloy are studied. The morphology and number fraction of inclusions in FeCrAl alloys are analyzed. The addition of 0.21 wt% Nb in FeCrAl alloy promotes the precipitation of nanoscale (Fe,Cr)2(Nb,Ti) Laves phase and refining grain size. The addition of La‐modified Al2O3 and MgO·Al2O3 inclusions to La2O3 and LaS, and La2O3 is favorable to promote the heterogeneous nucleation of α‐Fe. The fracture mode of the FeCrAl alloy with 0.21 wt% Nb or 0.23 wt% La transitions from dimple fracture and quasi‐cleavage fracture to dimple fracture, in comparison with Nb‐free or La‐free FeCrAl alloy. Nb and La additions improve the yield strength and toughness of FeCrAl alloy. The addition of Nb exhibits a more pronounced strengthening effect on FeCrAl alloy compared with the addition of La. [ABSTRACT FROM AUTHOR]

Metastable phases such as supersaturated solid solutions, supercooling, and amorphous phases are well-known in metallurgy. They are often composed in non-equilibrium states and can be transformed into a stable phase by overcoming an energy barrier with driving forces. Particularly, it has been widely used for material strengthening and heterogeneous nucleation of precipitates in solids is mainly induced by heat treatments for supersaturated solid solutions. However, little is known about the metastable phases of the Ag–Si alloy, although it is a well-known simple binary eutectic alloy. Here, we show that the metastable phases composed of amorphous Si and supersaturated Ag solid solution are induced by the eutectic reaction under rapid cooling of Ag–Si. Furthermore, the solute Si in the Ag matrix reacts with oxygen to precipitate Ag by-products, which grow as nodules. The Ag nodules have high crystallinity and robust interfacial structures, and the nodule growth leads to the formation of cross-links between the Ag–Si particles. We also demonstrate the Ag nodule-mediated bonding where the rapidly cooled Ag–Si ribbon is directly used as a bonding medium, indicating the possibility of using it as a high-temperature bonding material with low-temperature processes. [ABSTRACT FROM AUTHOR]

The two‐step sequential deposition method is considered a potential way for the large‐scale manufacture of perovskite solar cells (PSCs) with high power conversion efficiency and reproducibility. However, the dense lead iodide (PbI2) film interferes with its full contact with organic solutions, resulting in an inadequate reaction at the interface. Herein, 2 kinds of metal‐organic framework (MOF) are introduced, amorphous Ni‐MOF‐74 (amNi‐MOF‐74) and crystalline Zn‐MOF‐74 (crZn‐MOF‐74), into PbI2 for regulating crystallization. Compared to crZn‐MOF‐74, the incorporation of amNi‐MOF‐74 exhibited rapid nucleation, resulting in high‐quality perovskite films with large grain size, low trap density, and enhanced charge transfer between the perovskite and charge transfer layers. Meanwhile, the content of unstable phase PbI2 left in perovskite films due to insufficient reaction is also reduced. The amNi‐MOF‐74 modified PSCs exhibited a champion power conversion efficiency of 24.17% with good humidity and thermal stability. The unencapsulated device maintains 90% of its initial efficiency after 1000 h storage in dark ambient conditions with ≈30% relative humidity. This strategy provides an effective approach for promoting the crystallization process of perovskite and fabricating efficient and stable PSCs. [ABSTRACT FROM AUTHOR]

Failure initiation and subsequent crack trajectory in heterogeneous materials, such as functionally graded materials and bones, are yet insufficiently addressed. The AT1 phase field model (PFM) is investigated herein in a 1D setting, imposing challenges and opportunities when discretized by h- and p-finite element (FE) methods. We derive explicit PFM solutions to a heterogeneous bar in tension considering heterogeneous E(x) and G Ic (x) , necessary for verification of the FE approximations. G Ic (x) corrections accounting for the element size at the damage zone in h-FEMs are suggested to account for the peak stress underestimation. p-FEMs do not require any such corrections. We also derive and validate penalty coefficient for heterogeneous domains to enforce damage positivity and irreversibility via penalization. Numerical examples are provided, demonstrating that p-FEMs exhibit faster convergence rates comparing to classical h-FEMs. The new insights are encouraging towards p-FEM discretization in a 3D setting to allow an accurate prediction of failure initiation in human bones. [ABSTRACT FROM AUTHOR]

The inefficiency of grain refinement processes has traditionally been attributed to the limited utilization of heterogeneous nucleation particles within master alloy systems, resulting in the formation of abundant inactive particles. This study aims to investigate the alternative influences of particles by incorporating external micrometer-sized TiB2 particles into the grain refinement process. Through a series of experiments, the refinement efficiency, grain refinement mechanism, and resultant microstructure of TiB2 particle-induced grain refinement specimens are comprehensively examined using various microscopy and analytical techniques, including polarization microscopy (OM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). Our findings demonstrate a direct correlation between increased levels of TiB2 particles and enhanced grain refinement efficiency. Moreover, the microstructure analysis reveals the distribution of TiB2 particles along grain boundaries, forming a coating due to self-assembly phenomena, while regions with a lower particle content may exhibit irregular grain structures. DSC analysis further confirms reduced undercooling, indicating the occurrence of heterogeneous nucleation events. However, TEM observations suggest that heterogeneous nucleation is not significantly influenced by the growth restriction factor attributed to TiAl3 2DC compounds. The grain refinement mechanism involving TiB2 particles is elucidated to entail both heterogeneous nucleation and physical growth restriction effects. Specifically, a reduction in average grain size is attributed not only to heterogeneous nucleation but also to the physical growth restriction effect facilitated by the TiB2 particle coating. This study offers insights into leveraging particles that do not participate in heterogeneous nucleation within master alloy-based grain refinement systems. [ABSTRACT FROM AUTHOR]

Herein, the effect of nonmetallic inclusions (NMIs) on the microstructure and dynamic recrystallization (DRX) of Fe–23Mn–6Al–0.7C low‐density steel is studied. The specimens are separately added sulfur (S) and nitrogen (N) to change the characteristics of NMIs. As a result, the addition of S significantly increases the number of MnS inclusions and AlN–MnS complex inclusions in low‐density steel. The addition of N results in a significant increase in the size of NMIs. In the results, NMIs act as the heterogeneous nucleation sites for austenite and refine the as‐cast grains in low‐density steel. In addition, the treated specimens are subjected to a thermal compression simulation experiment. During the thermal compression process, discontinuous DRX is considered to be the main recrystallization method in the experimental low‐density steels. Meanwhile, the typical NMIs significantly accelerate the DRX within grains in low‐density steel through the mechanism of particle‐stimulated nucleation and continuous DRX. [ABSTRACT FROM AUTHOR]

The linkage between the variation of the seawater Mg budget and the long-term carbon cycle can be elucidated by seawater Mg isotope composition (δ26Mg). However, obtaining primary seawater δ26Mg signatures from marine archives is challenging due to the widespread alteration of diagenesis. Aragonite, a common primary marine carbonate, can effectively record seawater δ26Mg but is prone to alteration and transformation into calcite during early diagenesis. Therefore, a comprehensive understanding of Mg isotope behavior during the aragonite–calcite transition is essential to enhance the applicability of aragonite δ26Mg. In this study, we investigate the variation of aragonite δ26Mg during diagenesis with a limited supply of Mg by conducting a series of well-controlled aragonite–calcite transition experiments in a closed system. The experimental conditions encompass temperatures of 60 and 90 °C, the presence of Ca and Na in the solution, varying Na concentrations, as well as the presence of calcite seed. Results demonstrate that the significant decrease of bulk carbonate δ26Mg is accompanied by a substantial amount of Mg released into the solution during the aragonite–calcite transition, and the amount of released Mg is controlled by fluid chemistry via altering Mg partitioning in calcite. Furthermore, Mg isotope fractionation during calcite precipitation is influenced by temperature, ionic strength, and the presence of calcite seed, while kinetics played a negligible role in our experiments. Combined with previous experiments, the temperature-dependent Mg isotope fractionation during calcite precipitation in unseeded experiments is Δ26Mg cal-sol = (−0.13 ± 0.06) × 106/T2 – (0.47 ± 0.68). This fractionation is systematically higher than that of seeded experiments by 0.3–0.6 ‰ from 15 to 90 °C and can mainly be attributed to differences in surface free energy between homogeneous and heterogeneous calcite nucleation. These findings offer fundamental understandings of the Mg isotope behavior during the aragonite–calcite transformation, providing useful insights for interpreting the variation of δ26Mg in experimental and natural carbonates and facilitating ancient seawater δ26Mg reconstruction. [ABSTRACT FROM AUTHOR]

Two kinds of Cr 2 AlC coatings with different microstructures were prepared by direct crystallization during oxidation at 1000 ℃ and conventional crystallization at 700 ℃ for 1 h for amorphous Cr-Al-C coatings prepared by magnetron sputtering, respectively. The effect of microstructure on the oxidation behavior of the coatings at 1000 ℃ was investigated. The grain boundary density and dislocation density of the Cr 2 AlC coatings crystallized directly during oxidation were much higher, which provided much more sites for heterogeneous nucleation of α-Al 2 O 3 and fast diffusion paths for Al. Therefore, the coating formed complete pure α-Al 2 O 3 scales earlier with better antioxidant properties. More importantly, the present work demonstrates feasibility and advantages of directly applying amorphous Cr-Al-C coatings at high temperatures without additional crystallization treatments, which simplifies preparation process of Cr 2 AlC coatings, facilitates their industrial applications, and provides a new method for rapid preparation of MAX-phase coatings. [ABSTRACT FROM AUTHOR]

Zr has been widely used in high-quality steel due to its strong deoxidizing capacity and ability of improve performance of steel. ZrO2–Al2O3 inclusions with core-shell structure were observed in this study. The structure, electronic properties, and energy changes of ZrO2 and ZrO2–Al2O3 systems were studied based on first principles calculation. It indicates that ZrO2 can be used as the heterogeneous nucleation core of Al2O3. Al atoms were preferentially adsorbed on the bridge site of ZrO2 (001) and then form the ZrO2–Al2O3 interface. The template effect of ZrO2 was nine adsorption atomic layers, among which layers 1–5 was a coherent epitaxial layer, layers 5–9 was the transition layer, and the atomic ratio was 3:2. The growth mechanism of Al2O3 on ZrO2 surface was discussed. The results help understand the formation of inclusion at atomic scale and find ways to control the characteristics of inclusion in steel with Zr treatment. [ABSTRACT FROM AUTHOR]